1.
Laser
–
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term laser originated as an acronym for light amplification by stimulated emission of radiation, the first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light coherently, spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances, Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i. e. they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond, Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have very low divergence in order to concentrate their power at a great distance. Temporal coherence implies a polarized wave at a single frequency whose phase is correlated over a great distance along the beam. A beam produced by a thermal or other incoherent light source has an amplitude and phase that vary randomly with respect to time and position. Lasers are characterized according to their wavelength in a vacuum, most single wavelength lasers actually produce radiation in several modes having slightly differing frequencies, often not in a single polarization. Although temporal coherence implies monochromaticity, there are lasers that emit a broad spectrum of light or emit different wavelengths of light simultaneously, there are some lasers that are not single spatial mode and consequently have light beams that diverge more than is required by the diffraction limit. However, all devices are classified as lasers based on their method of producing light. Lasers are employed in applications where light of the spatial or temporal coherence could not be produced using simpler technologies. The word laser started as an acronym for light amplification by stimulated emission of radiation, in the early technical literature, especially at Bell Telephone Laboratories, the laser was called an optical maser, this term is now obsolete. A laser that produces light by itself is technically an optical rather than an optical amplifier as suggested by the acronym. It has been noted that the acronym LOSER, for light oscillation by stimulated emission of radiation. With the widespread use of the acronym as a common noun, optical amplifiers have come to be referred to as laser amplifiers. The back-formed verb to lase is frequently used in the field, meaning to produce light, especially in reference to the gain medium of a laser. Further use of the laser and maser in an extended sense, not referring to laser technology or devices, can be seen in usages such as astrophysical maser
Laser
–
United States Air Force laser experiment
Laser
–
Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers
Laser
–
Laser beams in fog, reflected on a car windshield
Laser
2.
Coherence (physics)
–
In physics, two wave sources are perfectly coherent if they have a constant phase difference and the same frequency. Coherence is a property of waves that enables stationary interference. More generally, coherence describes all properties of the correlation between physical quantities of a wave, or between several waves or wave packets. Interference is nothing more than the addition, in the mathematical sense, a single wave can interfere with itself, but this is still an addition of two waves. Constructive or destructive interferences are limit cases, and two waves interfere, even if the result of the addition is complicated or not remarkable. Two waves are said to be coherent if they have a constant relative phase, spatial coherence describes the correlation between waves at different points in space, either lateral or longitudinal. Temporal coherence describes the correlation between waves observed at different moments in time, both are observed in the Michelson–Morley experiment and Youngs interference experiment. Similarly, if in an experiment, the space between the two slits is increased, the coherence dies gradually and finally the fringes disappear, showing spatial coherence. In both cases, the fringe amplitude slowly disappears, as the difference increases past the coherence length. The property of coherence is the basis for commercial applications such as holography, a precise definition is given at degree of coherence. The cross-spectral density and the spectral density are defined as the Fourier transforms of the cross-correlation. In this case the coherence is a function of frequency, in that case, coherence is a function of wavenumber. The coherence varies in the interval 0 ⩽ γ x y 2 ⩽1, if γ x y 2 =1 it means that the signals are perfectly correlated or linearly related and if γ x y 2 =0 they are totally uncorrelated. If a linear system is being measured, x being the input and y the output, however, if non-linearities are present in the system the coherence will vary in the limit given above. The coherence of two waves expresses how well correlated the waves are as quantified by the cross-correlation function, the cross-correlation quantifies the ability to predict the phase of the second wave by knowing the phase of the first. As an example, consider two waves perfectly correlated for all times, at any time, phase difference will be constant. As will be discussed below, the second wave need not be a separate entity and it could be the first wave at a different time or position. In this case, the measure of correlation is the autocorrelation function, degree of correlation involves correlation functions. 545-550 These states are unified by the fact that their behavior is described by a wave equation or some generalization thereof
Coherence (physics)
3.
Monochromaticity
–
Monochrome describes paintings, drawings, design, or photographs in one color or values of one color. A monochromatic object or image reflects colors in shades of limited colors or hues, images using only shades of grey are called grayscale or black-and-white. However, scientifically speaking, monochromatic light refers to light of a narrow band of wavelengths. In computing, monochrome has two meanings, it may mean having only one color which is either on or off, a monochrome computer display is able to display only a single color, often green, amber, red or white, and often also shades of that color. In film photography, monochrome is typically the use of black-and-white film, originally, all photography was done in monochrome. Although color photography was possible even in the late 19th century, easily used color films, if the red channel is eliminated and the green and blue combined then the effect will be similar to that of orthochromatic film or the use of a cyan filter on panchromatic film. The selection of weighting thus allows a range of artistic expression in the final monochromatic image. For production of an image the original color stereogram source may first be reduced to monochrome in order to simplify the rendering of the image. This is sometimes required in cases where an image would render in a confusing manner given the colors and patterns present in the source image. In physics, monochromatic light is electromagnetic radiation of a single frequency, even very controlled sources such as lasers operate in a range of frequencies. In practice, filtered light, diffraction grating separated light and laser light are all referred to as monochromatic. Often light sources can be compared and one be labeled as “more monochromatic”
Monochromaticity
–
The
Eiffel Tower during the
Exposition Universelle (1889) for which the tower was built
Monochromaticity
–
A photograph of a
parrot rendered with a monochrome palette of a limited number of shades
Monochromaticity
–
Night vision devices typically produce a monochrome image, often in shades of green
Monochromaticity
–
Monochrome
anaglyph image stereogram rendered in red and cyan;
3D red cyan glasses are recommended to view this image correctly.
4.
Interferometry
–
Interferometry is a family of techniques in which waves, usually electromagnetic waves, are superimposed causing the phenomenon of interference in order to extract information. Interferometers are widely used in science and industry for the measurement of small displacements, refractive index changes, in an interferometer, light from a single source is split into two beams that travel different optical paths, then combined again to produce interference. The resulting interference fringes give information about the difference in path length, waves which are not completely in phase nor completely out of phase will have an intermediate intensity pattern, which can be used to determine their relative phase difference. Most interferometers use light or some form of electromagnetic wave. Typically a single incoming beam of coherent light will be split into two beams by a beam splitter. Each of these beams travels a different route, called a path, the path difference, the difference in the distance traveled by each beam, creates a phase difference between them. It is this phase difference that creates the interference pattern between the initially identical waves. If a single beam has been split along two paths, then the difference is diagnostic of anything that changes the phase along the paths. This could be a change in the path length itself or a change in the refractive index along the path. As seen in Fig. 2a and 2b, the observer has a view of mirror M1 seen through the beam splitter. The fringes can be interpreted as the result of interference between light coming from the two virtual images S1 and S2 of the original source S, the characteristics of the interference pattern depend on the nature of the light source and the precise orientation of the mirrors and beam splitter. In Fig. 2a, the elements are oriented so that S1 and S2 are in line with the observer. Use of white light will result in a pattern of colored fringes, the central fringe representing equal path length may be light or dark depending on the number of phase inversions experienced by the two beams as they traverse the optical system. Interferometers and interferometric techniques may be categorized by a variety of criteria, In homodyne detection, the phase difference between the two beams results in a change in the intensity of the light on the detector. The resulting intensity of the light after mixing of two beams is measured, or the pattern of interference fringes is viewed or recorded. Most of the interferometers discussed in this article fall into this category, the heterodyne technique is used for shifting an input signal into a new frequency range as well as amplifying a weak input signal. A weak input signal of frequency f1 is mixed with a reference frequency f2 from a local oscillator. The nonlinear combination of the input signals creates two new signals, one at the sum f1 + f2 of the two frequencies, and the other at the difference f1 − f2 and these new frequencies are called heterodynes
Interferometry
–
Figure 11. The
VLA interferometer
Interferometry
–
Figure 1. The light path through a
Michelson interferometer. The two light rays with a common source combine at the half-silvered mirror to reach the detector. They may either interfere constructively (strengthening in intensity) if their light waves arrive in phase, or interfere destructively (weakening in intensity) if they arrive out of phase, depending on the exact distances between the three mirrors.
Interferometry
–
Figure 13. Optical flat interference fringes
Interferometry
–
Figure 18. Lunate cells of Nepenthes khasiana visualized by Scanning White Light Interferometry (SWLI)
5.
Raman spectroscopy
–
Raman spectroscopy is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system. Raman spectroscopy is used in chemistry to provide a fingerprint by which molecules can be identified. It relies on inelastic scattering, or Raman scattering, of light, usually from a laser in the visible, near infrared. The laser light interacts with molecular vibrations, phonons or other excitations in the system, the shift in energy gives information about the vibrational modes in the system. Infrared spectroscopy yields similar, but complementary, information, typically, a sample is illuminated with a laser beam. Electromagnetic radiation from the spot is collected with a lens. Historically, Raman spectrometers used holographic gratings and multiple stages to achieve a high degree of laser rejection. In the past, photomultipliers were the detectors of choice for dispersive Raman setups, for the spontaneous Raman effect, which is a form of inelastic light scattering, a photon excites the molecule in either the ground rovibronic state or an excited rovibronic state. This results in the molecule being in a virtual energy state for a short period of time before an inelastically scattered photon results. The resulting inelastically scattered photon which is emitted/scattered can be of lower or higher energy than the incoming photon. This shift in frequency is designated as a Stokes shift, if the final vibrational state is less energetic than the initial state, then the inelastically scattered photon will be shifted to a higher frequency, and this is designated as an anti-Stokes shift. In particular, the difference is equal to the difference in energy between the initial and final states and this contrasts with infrared absorption, where the energy of the single absorbed photon matches this difference in energy. Rayleigh scattering is an example of scattering, where the frequency of the Rayleigh scattered light is the same as that of the incoming electromagnetic radiation. The intensity of the Raman scattering is proportional to the electric dipole-electric dipole polarizability change, the Raman spectra is dependent on the rovibronic states of the sample. Bands which have large Raman intensities in many cases have weak infrared intensities, for very symmetric molecules, certain vibrations may be both infrared and Raman inactive. In those instances, one can use a technique called inelastic incoherent neutron scattering to determine the vibrational frequencies, the selection rules for inelastic incoherent neutron scattering are different from those of both infrared and Raman scattering. Although the inelastic scattering of light was predicted by Adolf Smekal in 1923, the Raman effect was named after one of its discoverers, the Indian scientist Sir C. V. Raman who observed the effect by means of sunlight. He found that an amount of light had changed frequency
Raman spectroscopy
–
Energy-level diagram showing the states involved in Raman signal.
6.
Laser induced breakdown spectroscopy
–
Laser-induced breakdown spectroscopy is a type of atomic emission spectroscopy which uses a highly energetic laser pulse as the excitation source. The laser is focused to form a plasma, which atomizes and excites samples, the formation of the plasma only begins when the focused laser achieves a certain threshold for optical breakdown, which generally depends on the environment and the target material. In principle, LIBS can analyze any matter regardless of its physical state, if the constituents of a material to be analyzed are known, LIBS may be used to evaluate the relative abundance of each constituent element, or to monitor the presence of impurities. In practice, detection limits are a function of a) the plasma excitation temperature, b) the light collection window, LIBS makes use of optical emission spectrometry and is to this extent very similar to arc/spark emission spectroscopy. During data collection, typically after local thermodynamic equilibrium is established, plasma temperatures range from 5, at the high temperatures during the early plasma, the ablated material dissociates into excited ionic and atomic species. At this point the characteristic emission lines of the elements can be observed. The delay between the emission of radiation and characteristic radiation is in the order of 10 µs. LIBS can often be referred to as its name, laser-induced plasma spectroscopy. The term LIPS has alternative meanings that are outside the field of analytical spectroscopy, LIBS is technically very similar to a number of other laser-based analytical techniques, sharing much of the same hardware. These techniques are the vibrational spectroscopic technique of Raman spectroscopy, a typical LIBS system consists of a Nd, YAG solid-state laser and a spectrometer with a wide spectral range and a high sensitivity, fast response rate, time gated detector. This is coupled to a computer which can process and interpret the acquired data. As such LIBS is one of the most experimentally simple spectroscopic analytical techniques, making it one of the cheapest to purchase, the Nd, YAG laser generates energy in the near infrared region of the electromagnetic spectrum, with a wavelength of 1064 nm. The pulse duration is in the region of 10 ns generating a power density which can exceed 1 GW·cm−2 at the focal point, other lasers have been used for LIBS, mainly the Excimer type that generates energy in the visible and ultraviolet regions. The spectrometer consists of either a monochromator or a polychromator and a photomultiplier or CCD detector respectively, the most common monochromator is the Czerny-Turner type whilst the most common polychromator is the Echelle type. However, even the Czerny-Turner type can be used to disperse the radiation onto a CCD effectively making it a polychromator, the polychromator spectrometer is the type most commonly used in LIBS as it allows simultaneous acquisition of the entire wavelength range of interest. The spectrometer collects electromagnetic radiation over the widest wavelength range possible, spectrometer response is typically from 1100 nm to 170 nm, the approximate response range of a CCD detector. All elements have emission lines within this wavelength range and this feature is particularly important in specimens which have a complex matrix, containing a large number of different elements. Accompanying the spectrometer and detector is a generator which accurately gates the detectors response time
Laser induced breakdown spectroscopy
–
Schematic of a LIBS system - Courtesy of US Army Research Laboratory
7.
Atmospheric
–
An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is likely to be retained if the gravity it is subject to is high. The atmosphere of Earth is mostly composed of nitrogen, oxygen, argon with carbon dioxide, the atmosphere helps protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of modification of the paleoatmosphere by living organisms. The term stellar atmosphere describes the region of a star. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere, Atmospheric pressure is the force per unit area that is applied perpendicularly to a surface by the surrounding gas. It is determined by a gravitational force in combination with the total mass of a column of gas above a location. On Earth, units of air pressure are based on the recognized standard atmosphere. It is measured with a barometer, the pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above. The height at which the pressure from an atmosphere declines by a factor of e is called the height and is denoted by H. For such an atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the determination of the atmospheric pressure at any particular altitude is more complex. Surface gravity, the force that holds down an atmosphere, differs significantly among the planets, for example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from objects with lower gravity. Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite their relatively low gravities, rogue planets, theoretically, may also retain thick atmospheres. Since a collection of gas molecules may be moving at a range of velocities. Lighter molecules move faster than ones with the same thermal kinetic energy. It is thought that Venus and Mars may have lost much of their water when, after being photo dissociated into hydrogen and oxygen by solar ultraviolet, Earths magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the polar regions due to auroral activity
Atmospheric
–
Mars's thin atmosphere
Atmospheric
–
Earth's atmospheric
gases scatter blue light more than other wavelengths, giving the
Earth a blue halo when seen from
space.
8.
Remote sensing
–
Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation. It may be split into active remote sensing and passive remote sensing, passive sensors gather radiation that is emitted or reflected by the object or surrounding areas. Reflected sunlight is the most common source of radiation measured by passive sensors, examples of passive remote sensors include film photography, infrared, charge-coupled devices, and radiometers. Active collection, on the hand, emits energy in order to scan objects and areas whereupon a sensor then detects. RADAR and LiDAR are examples of remote sensing where the time delay between emission and return is measured, establishing the location, speed and direction of an object. Remote sensing makes it possible to data of dangerous or inaccessible areas. Remote sensing applications include monitoring deforestation in areas such as the Amazon Basin, glacial features in Arctic and Antarctic regions, military collection during the Cold War made use of stand-off collection of data about dangerous border areas. Remote sensing also replaces costly and slow data collection on the ground, the basis for multispectral collection and analysis is that of examined areas or objects that reflect or emit radiation that stand out from surrounding areas. For a summary of major remote sensing satellite systems see the overview table, conventional radar is mostly associated with aerial traffic control, early warning, and certain large scale meteorological data. Other types of active collection includes plasmas in the ionosphere, interferometric synthetic aperture radar is used to produce precise digital elevation models of large scale terrain. Laser and radar altimeters on satellites have provided a range of data. By measuring the bulges of water caused by gravity, they map features on the seafloor to a resolution of a mile or so, by measuring the height and wavelength of ocean waves, the altimeters measure wind speeds and direction, and surface ocean currents and directions. Ultrasound and radar tide gauges measure sea level, tides and wave direction in coastal, light detection and ranging is well known in examples of weapon ranging, laser illuminated homing of projectiles. Vegetation remote sensing is an application of LIDAR. Radiometers and photometers are the most common instrument in use, collecting reflected and emitted radiation in a range of frequencies. The most common are visible and infrared sensors, followed by microwave, gamma ray and rarely and they may also be used to detect the emission spectra of various chemicals, providing data on chemical concentrations in the atmosphere. Simultaneous multi-spectral platforms such as Landsat have been in use since the 1970s and these thematic mappers take images in multiple wavelengths of electro-magnetic radiation and are usually found on Earth observation satellites, including the Landsat program or the IKONOS satellite. Landsat images are used by agencies such as KYDOW to indicate water quality parameters including Secchi depth, chlorophyll a density
Remote sensing
–
Synthetic aperture radar image of
Death Valley colored using
polarimetry.
Remote sensing
Remote sensing
–
Illustration of Remote Sensing
Remote sensing
–
The
TR-1 reconnaissance/surveillance aircraft.
9.
Nonlinear optics
–
The nonlinearity is typically observed only at very high light intensities such as those provided by lasers. Above the Schwinger limit, the vacuum itself is expected to become nonlinear, in nonlinear optics, the superposition principle no longer holds. However, some effects were discovered before the development of the laser. The theoretical basis for many nonlinear processes were first described in Bloembergens monograph Nonlinear Optics, Nonlinear optics explains nonlinear response of properties such as frequency, polarization, phase or path of incident light. Third-harmonic generation, generation of light with a frequency, three photons are destroyed, creating a single photon at three times the frequency. High-harmonic generation, generation of light with much greater than the original. Sum-frequency generation, generation of light with a frequency that is the sum of two other frequencies, difference-frequency generation, generation of light with a frequency that is the difference between two other frequencies. Optical parametric amplification, amplification of an input in the presence of a higher-frequency pump wave. Optical parametric oscillation, generation of a signal and idler wave using an amplifier in a resonator. Optical parametric generation, like parametric oscillation but without a resonator, spontaneous parametric down-conversion, the amplification of the vacuum fluctuations in the low-gain regime. Optical rectification, generation of electric fields. Nonlinear light-matter interaction with electrons and plasmas. Optical Kerr effect, intensity-dependent refractive index, self-focusing, an effect due to the optical Kerr effect caused by the spatial variation in the intensity creating a spatial variation in the refractive index. Kerr-lens modelocking, the use of self-focusing as a mechanism to mode-lock laser, self-phase modulation, an effect due to the optical Kerr effect caused by the temporal variation in the intensity creating a temporal variation in the refractive index. Optical solitons, a solution for either an optical pulse or spatial mode that does not change during propagation due to a balance between dispersion and the Kerr effect. Cross-phase modulation, where one wavelength of light can affect the phase of another wavelength of light through the optical Kerr effect, four-wave mixing, can also arise from other nonlinearities. Cross-polarized wave generation, a χ effect in which a wave with polarization vector perpendicular to the one is generated. Stimulated Brillouin scattering, interaction of photons with acoustic phonons Multi-photon absorption, multiple photoionisation, near-simultaneous removal of many bound electrons by one photon
Nonlinear optics
–
Reversal of Linear Momentum and Angular Momentum in Phase Conjugating Mirror.
Nonlinear optics
Nonlinear optics
–
Dark-Red Gallium Selenide in its bulk form.
10.
Phenomena
–
A phenomenon is any thing which manifests itself. Phenomena are often, but not always, understood as things that appear or experiences for a sentient being, the term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon. In contrast to a phenomenon, a noumenon can not be directly observed, Kant was heavily influenced by Gottfried Wilhelm Leibniz in this part of his philosophy, in which phenomenon and noumenon serve as interrelated technical terms. In modern philosophical use, the phenomena has come to mean what is experienced is the basis of reality. He wrote that humans could infer only as much as their senses allowed, thus, the term phenomenon refers to any incident deserving of inquiry and investigation, especially events that are particularly unusual or of distinctive importance. According to The Columbia Encyclopedia, Modern philosophers have used phenomenon to designate what is apprehended before judgment is applied and this may not be possible if observation is theory laden. In scientific usage, a phenomenon is any event that is observable, however common it might be, even if it requires the use of instrumentation to observe, record, another example of scientific phenomena can be found in the experience of phantom limb sensations. This occurrence, the sensation of feeling in amputated limbs, is reported by over 70% of amputees, although the limb is no longer present, they report still experiencing sensations. This is an event that defies typical logic and has been a source of much curiosity within the medical and physiological fields. A mechanical phenomenon is a phenomenon associated with the equilibrium or motion of objects. Some examples are Newtons cradle, engines, and double pendulums, in gemology, a phenomenon is an unusual optical effect that is displayed by a gem. Play-of-color, labradorescence, iridescence, adularescence, chatoyancy, asterism, aventurescence, lustre, group phenomena concern the behavior of a particular group of individual entities, usually organisms and most especially people. The behavior of individuals often changes in a setting in various ways. Social phenomena apply especially to organisms and people in that states are implicit in the term. Attitudes and events particular to a group may have effects beyond the group, in popular usage, a phenomenon often refers to an extraordinary event. The term is most commonly used to refer to occurrences that at first defy explanation or baffle the observer
Phenomena
–
Cloud chamber phenomena. Scientists use phenomena to refine some
hypotheses and sometimes to disprove a
theory. See also
Animated Version.
Phenomena
–
A comparison between a candle flame on Earth (left) and in a
microgravity environment, such as that found on the
ISS (right). The same burning phenomenon is
observed, but different flame shape and colouring phenomena are also observed.
Phenomena
–
The combustion of a match is an observable occurrence, or event, and therefore a phenomenon.
11.
Holography
–
Holography is the science and practice of making holograms. The hologram itself is not an image and it is usually unintelligible when viewed under diffuse ambient light and it is an encoding of the light field as an interference pattern of seemingly random variations in the opacity, density, or surface profile of the photographic medium. In its pure form, holography requires the use of light for illuminating the subject. A microscopic level of detail throughout the volume of space can be reproduced. Holograms can now also be entirely computer-generated and show objects or scenes that never existed, stage illusions such as Peppers Ghost and other unusual, baffling, or seemingly magical images are also often incorrectly called holograms. The Hungarian-British physicist Dennis Gabor, was awarded the Nobel Prize in Physics in 1971 for his invention and development of the holographic method. His work, done in the late 1940s, was built on pioneering work in the field of X-ray microscopy by other scientists including Mieczysław Wolfke in 1920 and William Lawrence Bragg in 1939. The discovery was a result of research into improving electron microscopes at the British Thomson-Houston Company in Rugby, England. The word holography comes from the Greek words ὅλος and γραφή, early holograms used silver halide photographic emulsions as the recording medium. They were not very efficient as the produced grating absorbed much of the incident light, various methods of converting the variation in transmission to a variation in refractive index were developed which enabled much more efficient holograms to be produced. Several types of holograms can be made, a later refinement, the rainbow transmission hologram, allows more convenient illumination by white light rather than by lasers. Rainbow holograms are used for security and authentication, for example, on credit cards. They are also capable of multicolour-image reproduction, specular holography is a related technique for making three-dimensional images by controlling the motion of specularities on a two-dimensional surface. It works by reflectively or refractively manipulating bundles of light rays, most holograms produced are of static objects but systems for displaying changing scenes on a holographic volumetric display are now being developed. Holograms can also be used to store, retrieve, and process information optically and it was thought that it would be possible to use X-rays to make holograms of very small objects and view them using visible light. Today, holograms with x-rays are generated by using synchrotrons or x-ray free-electron lasers as radiation sources, the reconstruction is then retrieved via computation. Due to the wavelength of x-rays compared to visible light. As free-electron lasers can provide ultrashort and x-ray pulses in the range of femtoseconds which are intense and coherent, in laser holography, the hologram is recorded using a source of laser light, which is very pure in its color and orderly in its composition
Holography
–
Two photographs of a single hologram taken from different viewpoints
Holography
–
Horizontal symmetric text, by
Dieter Jung
Holography
–
Close-up photograph of a hologram's surface. The object in the hologram is a toy van. It is no more possible to discern the subject of a hologram from this pattern than it is to identify what music has been recorded by looking at a
CD surface. Note that the hologram is described by the
speckle pattern, rather than the "wavy" line pattern.
Holography
–
An optical table being used to make a hologram
12.
Lidar
–
Lidar is a surveying method that measures distance to a target by illuminating that target with a laser light. The name lidar, sometimes considered an acronym of Light Detection And Ranging, was originally a portmanteau of light, the technology is also used for control and navigation for some autonomous cars. Lidar sometimes is called laser scanning and 3D scanning, with terrestrial, airborne and its first applications came in meteorology, where the National Center for Atmospheric Research used it to measure clouds. The general public aware of the accuracy and usefulness of lidar systems in 1971 during the Apollo 15 mission. Although some sources treat the word lidar as an acronym, the term originated as a portmanteau of light, the first published mention of lidar, in 1963, makes this clear, Eventually the laser may provide an extremely sensitive detector of particular wavelengths from distant objects. Meanwhile, it is being used to study the moon by lidar, the Oxford English Dictionary supports this etymology. Currently no consensus exists on capitalization, reflecting uncertainty about whether or not lidar is an acronym, various publications refer to lidar as LIDAR, LiDAR, LIDaR, or Lidar. Lidar uses ultraviolet, visible, or near infrared light to image objects and it can target a wide range of materials, including non-metallic objects, rocks, rain, chemical compounds, aerosols, clouds and even single molecules. A narrow laser-beam can map physical features with high resolutions, for example. Lidar has been used extensively for research and meteorology. Lidar instruments fitted to aircraft and satellites carry out surveying and mapping – a recent example being the U. S. Geological Survey Experimental Advanced Airborne Research Lidar, NASA has identified lidar as a key technology for enabling autonomous precision safe landing of future robotic and crewed lunar-landing vehicles. Wavelengths vary to suit the target, from about 10 micrometers to the UV, typically light is reflected via backscattering, as opposed to pure reflection one might find with a mirror. Different types of scattering are used for different lidar applications, most commonly Rayleigh scattering, Mie scattering, Raman scattering, based on different kinds of backscattering, the lidar can be accordingly called Rayleigh Lidar, Mie Lidar, Raman Lidar, Na/Fe/K Fluorescence Lidar, and so on. Suitable combinations of wavelengths can allow for remote mapping of atmospheric contents by identifying wavelength-dependent changes in the intensity of the returned signal, in general there are two kinds of lidar detection schemes, incoherent or direct energy detection and coherent detection. In both coherent and incoherent lidar, there are two types of models, micropulse lidar systems and high energy systems. Micropulse systems utilizing intermittent bursts of energy have developed as a result of the amount of computer power available combined with advances in laser technology. They use considerably less energy in the laser, typically on the order of one microjoule, there are several major components to a lidar system, Laser — 600–1000 nm lasers are most common for non-scientific applications. They are inexpensive, but since they can be focused and easily absorbed by the eye, eye-safety is often a requirement for most applications
Lidar
–
Lidar-derived image of Marching Bears Mound Group,
Effigy Mounds National Monument.
Lidar
–
A
FASOR used at the
Starfire Optical Range for lidar and
laser guide star experiments is tuned to the
sodium D2a line and used to excite
sodium atoms
in the upper atmosphere.
Lidar
–
This lidar may be used to scan buildings, rock formations, etc., to produce a 3D model. The lidar can aim its laser beam in a wide range: its head rotates horizontally; a mirror tilts vertically. The laser beam is used to measure the distance to the first object on its path.
Lidar
–
This lidar-equipped
mobile robot uses its lidar to construct a map and avoid obstacles.
13.
Geology
–
Geology is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also refer generally to the study of the features of any terrestrial planet. Geology gives insight into the history of the Earth by providing the evidence for plate tectonics, the evolutionary history of life. Geology also plays a role in engineering and is a major academic discipline. The majority of data comes from research on solid Earth materials. These typically fall into one of two categories, rock and unconsolidated material, the majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth. There are three types of rock, igneous, sedimentary, and metamorphic. The rock cycle is an important concept in geology which illustrates the relationships between three types of rock, and magma. When a rock crystallizes from melt, it is an igneous rock, the sedimentary rock can then be subsequently turned into a metamorphic rock due to heat and pressure and is then weathered, eroded, deposited, and lithified, ultimately becoming a sedimentary rock. Sedimentary rock may also be re-eroded and redeposited, and metamorphic rock may also undergo additional metamorphism, all three types of rocks may be re-melted, when this happens, a new magma is formed, from which an igneous rock may once again crystallize. Geologists also study unlithified material which typically comes from more recent deposits and these materials are superficial deposits which lie above the bedrock. Because of this, the study of material is often known as Quaternary geology. This includes the study of sediment and soils, including studies in geomorphology, sedimentology and this theory is supported by several types of observations, including seafloor spreading, and the global distribution of mountain terrain and seismicity. This coupling between rigid plates moving on the surface of the Earth and the mantle is called plate tectonics. The development of plate tectonics provided a basis for many observations of the solid Earth. Long linear regions of geologic features could be explained as plate boundaries, mid-ocean ridges, high regions on the seafloor where hydrothermal vents and volcanoes exist, were explained as divergent boundaries, where two plates move apart. Arcs of volcanoes and earthquakes were explained as convergent boundaries, where one plate subducts under another, transform boundaries, such as the San Andreas Fault system, resulted in widespread powerful earthquakes. Plate tectonics also provided a mechanism for Alfred Wegeners theory of continental drift and they also provided a driving force for crustal deformation, and a new setting for the observations of structural geology
Geology
–
On this diagram, subducting
slabs are in blue, and continental margins and a few plate boundaries are in red. The blue blob in the cutaway section is the seismically imaged
Farallon Plate, which is subducting beneath North America. The remnants of this plate on the Surface of the Earth are the
Juan de Fuca Plate and Explorer plate in the Northwestern USA / Southwestern Canada, and the
Cocos Plate on the west coast of Mexico.
Geology
–
This schematic diagram of the rock cycle shows the relationship between magma and sedimentary, metamorphic, and igneous rock
Geology
Geology
–
Geologic cross-section of
Kittatinny Mountain. This cross-section shows metamorphic rocks, overlain by younger sediments deposited after the metamorphic event. These rock units were later folded and faulted during the uplift of the mountain.
14.
Seismology
–
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. A related field that uses geology to infer information regarding past earthquakes is paleoseismology, a recording of earth motion as a function of time is called a seismogram. A seismologist is a scientist who does research in seismology, scholarly interest in earthquakes can be traced back to antiquity. Early speculations on the causes of earthquakes were included in the writings of Thales of Miletus, Anaximenes of Miletus, Aristotle. In 132 CE, Zhang Heng of Chinas Han dynasty designed the first known seismoscope, in 1664, Athanasius Kircher argued that earthquakes were caused by the movement of fire within a system of channels inside the Earth. In 1703, Martin Lister and Nicolas Lemery proposed that earthquakes were caused by chemical explosions within the earth, the Lisbon earthquake of 1755, coinciding with the general flowering of science in Europe, set in motion intensified scientific attempts to understand the behaviour and causation of earthquakes. The earliest responses include work by John Bevis and John Michell, Michell determined that earthquakes originate within the Earth and were waves of movement caused by shifting masses of rock miles below the surface. From 1857, Robert Mallet laid the foundation of instrumental seismology and he is also responsible for coining the word seismology. In 1897, Emil Wiecherts theoretical calculations led him to conclude that the Earths interior consists of a mantle of silicates, surrounding a core of iron. In 1906 Richard Dixon Oldham identified the separate arrival of P-waves, S-waves and surface waves on seismograms, in 1910, after studying the 1906 San Francisco earthquake, Harry Fielding Reid put forward the elastic rebound theory which remains the foundation for modern tectonic studies. The development of this depended on the considerable progress of earlier independent streams of work on the behaviour of elastic materials. In 1926, Harold Jeffreys was the first to claim, based on his study of waves, that below the mantle. In 1937, Inge Lehmann determined that within the liquid outer core there is a solid inner core. By the 1960s, earth science had developed to the point where a comprehensive theory of the causation of seismic events had come together in the now well-established theory of plate tectonics, seismic waves are elastic waves that propagate in solid or fluid materials. There are two types of waves, Pressure waves or Primary waves and Shear or Secondary waves. S-waves are transverse waves that move perpendicular to the direction of propagation, therefore, they appear later than P-waves on a seismogram. Fluids cannot support perpendicular motion, so S-waves only travel in solids, the two main surface wave types are Rayleigh waves, which have some compressional motion, and Love waves, which do not. Rayleigh waves result from the interaction of vertically polarized P- and S-waves that satisfy the conditions on the surface
Seismology
–
Seismic velocities and boundaries in the interior of the
Earth sampled by seismic waves
Seismology
–
Seismogram records showing the three components of ground motion. The red line marks the first arrival of P-waves; the green line, the later arrival of S-waves.
15.
Atmospheric physics
–
Atmospheric physics is the application of physics to the study of the atmosphere. At the dawn of the age and the introduction of sounding rockets, aeronomy became a subdiscipline concerning the upper layers of the atmosphere. There are two kinds of remote sensing, passive sensors detect natural radiation that is emitted or reflected by the object or surrounding area being observed. Reflected sunlight is the most common source of radiation measured by passive sensors, examples of passive remote sensors include film photography, infra-red, charge-coupled devices, and radiometers. Active collection, on the hand, emits energy in order to scan objects and areas whereupon a sensor then detects. Remote sensing makes it possible to data on dangerous or inaccessible areas. Military collection during the war made use of stand-off collection of data about dangerous border areas. Remote sensing also replaces costly and slow data collection on the ground, Atmospheric physicists typically divide radiation into solar radiation and terrestrial radiation. Solar radiation contains variety of wavelengths, visible light has wavelengths between 0.4 and 0.7 micrometers. Shorter wavelengths are known as the part of the spectrum. Ozone is most effective in absorbing radiation around 0.25 micrometers and this increases the temperature of the nearby stratosphere. Snow reflects 88% of UV rays, while sand reflects 12%, the more glancing the angle is between the atmosphere and the suns rays, the more likely that energy will be reflected or absorbed by the atmosphere. Terrestrial radiation is emitted at longer wavelengths than solar radiation. This is because Earth is much colder than the sun, radiation is emitted by Earth across a range of wavelengths, as formalized in Plancks law. The wavelength of energy is around 10 micrometers. Cloud physics is the study of the processes that lead to the formation, growth. Clouds are composed of droplets of water, tiny crystals of ice. Under suitable conditions, the combine to form precipitation, where they may fall to the earth
Atmospheric physics
–
Atmospheric sciences
Atmospheric physics
–
Brightness can indicate reflectivity as in this 1960
weather radar image (of
Hurricane Abby). The radar's frequency, pulse form, and antenna largely determine what it can observe.
Atmospheric physics
–
Cloud to ground
Lightning in the global atmospheric electrical circuit.
Atmospheric physics
–
Representation of upper-atmospheric lightning and electrical-discharge phenomena
16.
Cassini-Huygens
–
Cassini–Huygens is an unmanned spacecraft sent to the planet Saturn. It is a Flagship-class NASA–ESA–ASI robotic spacecraft, Cassini is the fourth space probe to visit Saturn and the first to enter orbit, and its mission is ongoing as of April 2017. It has studied the planet and its natural satellites since arriving there in 2004. Its design includes a Saturn orbiter and a lander for the moon Titan, the two spacecraft are named after astronomers Giovanni Cassini and Christiaan Huygens. On December 25,2004, Huygens separated from the orbiter and it successfully returned data to Earth, using the orbiter as a relay. This was the first landing ever accomplished in the outer Solar System, on November 30,2016, Cassini entered the final phase of the project. Cassini will dive through the ring of Saturn 20 times. The spacecraft will enter areas that have been untouched up until this point, the first pass of the rings took place on December 4,2016. Cassini continued to study the Saturn system in the following years, however, due to the spacecrafts dwindling fuel resources for further orbital corrections, it is currently planned to be destroyed by diving into the planets atmosphere in September 2017. This method of disposal was chosen to avoid potential biological contamination of Saturns moons, Cassinis death spiral is set to officially begin on April 22,2017 and will take its final plunge on September 15,2017 before it beams its last batch of images. Sixteen European countries and the United States make up the team responsible for designing, building, flying and collecting data from the Cassini orbiter, the mission is managed by NASAs Jet Propulsion Laboratory in the United States, where the orbiter was assembled. Huygens was developed by the European Space Research and Technology Centre, the Centres prime contractor, Aérospatiale of France, assembled the probe with equipment and instruments supplied by many European countries. The VIMS infrared counterpart was provided by NASA, as well as Main Electronic Assembly, on April 16,2008, NASA announced a two-year extension of the funding for ground operations of this mission, at which point it was renamed the Cassini Equinox Mission. This was again extended in February 2010 with the Cassini Solstice Mission, the mission was commonly called Saturn Orbiter Titan Probe during gestation, both as a Mariner Mark II mission and generically. Cassini-Huygens is a mission to the outer planets. The other planetary flagships include Galileo, Voyager, and Viking, Cassini has several objectives, including, Determine the three-dimensional structure and dynamic behavior of the rings of Saturn. Determine the composition of the surfaces and the geological history of each object. Determine the nature and origin of the material on Iapetuss leading hemisphere
Cassini-Huygens
–
Artist's concept of Cassini 's
orbit insertion around Saturn
Cassini-Huygens
–
Huygens' explanation for the aspects of Saturn, Systema Saturnium, 1659.
Cassini-Huygens
–
Saturn's north side (2014)
Cassini-Huygens
17.
Astronomy
–
Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets, while the phenomena include supernovae explosions, gamma ray bursts, more generally, all astronomical phenomena that originate outside Earths atmosphere are within the purview of astronomy. A related but distinct subject, physical cosmology, is concerned with the study of the Universe as a whole, Astronomy is the oldest of the natural sciences. The early civilizations in recorded history, such as the Babylonians, Greeks, Indians, Egyptians, Nubians, Iranians, Chinese, during the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the results and observations being used to confirm theoretical results. Astronomy is one of the few sciences where amateurs can play an active role, especially in the discovery. Amateur astronomers have made and contributed to many important astronomical discoveries, Astronomy means law of the stars. Astronomy should not be confused with astrology, the system which claims that human affairs are correlated with the positions of celestial objects. Although the two share a common origin, they are now entirely distinct. Generally, either the term astronomy or astrophysics may be used to refer to this subject, however, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Few fields, such as astrometry, are purely astronomy rather than also astrophysics, some titles of the leading scientific journals in this field includeThe Astronomical Journal, The Astrophysical Journal and Astronomy and Astrophysics. In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye, in some locations, early cultures assembled massive artifacts that possibly had some astronomical purpose. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye, most of early astronomy actually consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon, the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the model of the Universe, or the Ptolemaic system. The Babylonians discovered that lunar eclipses recurred in a cycle known as a saros
Astronomy
–
A
star -forming region in the
Large Magellanic Cloud, an
irregular galaxy.
Astronomy
–
A giant
Hubble mosaic of the
Crab Nebula, a
supernova remnant
Astronomy
–
19th century
Sydney Observatory,
Australia (1873)
Astronomy
–
19th century
Quito Astronomical Observatory is located 12 minutes south of the
Equator in
Quito,
Ecuador.
18.
Laser guide star
–
Laser guide star is an artificial star image created for use in astronomical adaptive optics imaging. Adaptive optics systems require a wavefront reference source in order to correct atmospheric distortion of light, sufficiently bright stars are not available in all parts of the sky, which greatly limits the usefulness of natural guide star adaptive optics. Instead, one can create a guide star by shining a laser into the atmosphere. This star can be positioned anywhere the telescope desires to point, because the laser beam is deflected by astronomical seeing on the way up, the returning laser light does not move around in the sky as astronomical sources do. In order to keep astronomical images steady, a natural star nearby in the sky must be monitored in order that the motion of the guide star can be subtracted using a tip–tilt mirror. This means that many stars are suitable, and a correspondingly larger fraction of the sky is accessible. There are two types of laser guide star system, known as sodium and Rayleigh beacon guide stars. Sodium beacons are created by using a laser tuned to 589.2 nanometers to energize atoms in the layer of the mesosphere at an altitude of around 90 km. The sodium atoms then re-emit the laser light, producing an artificial star. The same atomic transition of sodium is used in lamps for street lighting. Rayleigh beacons rely on the scattering of light by the molecules in the lower atmosphere, the lasers are often pulsed, with measurement of the atmosphere being time-gated. Dye lasers were the first laser used in laser guide star applications. These tunable lasers have continued to play a significant role in this field, however, the use of fluid gain media has been considered by some as disadvantageous. Second generation laser sources for sodium guide star applications include sum-frequency-mixed solid-state lasers, New third generation laser systems based on tunable diode lasers with subsequent narrow-band Raman fiber amplification and resonant frequency conversion have been under development since 2005. Since 2014 fully engineered systems are commercially available, important output features of the tunable lasers mentioned here include diffraction-limited beam divergence and narrow-linewidth emission. Laser guide star adaptive optics is still a young field. Other observatories developing laser AO systems as of 2006 include the Large Binocular Telescope, the laser guide star system at the Very Large Telescope started regular scientific operations in June 2007. Since April 2016, the 4 Laser Guide Star Facility has been installed at the ESO’s Very Large Telescope, the 4LGSF is a complement of the VLT Laser Guide Star Facility
Laser guide star
–
ESO tested the new Wendelstein laser guide star unit by shooting a powerful laser beam into the atmosphere.
Laser guide star
–
The first 22-watt TOPTICA sodium laser of the Adaptive Optics Facility
Laser guide star
–
One of the launch telescopes for the VLT Four Laser Guide Star Facility.
Laser guide star
–
First light of new TOPTICA laser of
Adaptive Optics Facility at
Paranal Observatory.
19.
Adaptive optics
–
Adaptive optics works by measuring the distortions in a wavefront and compensating for them with a device that corrects those errors such as a deformable mirror or a liquid crystal array. Adaptive optics should not be confused with active optics, which works on a timescale to correct the primary mirror geometry. Adaptive optics was first envisioned by Horace W, some of the initial development work on adaptive optics was done by the US military during the Cold War and was intended for use in tracking Soviet satellites. The simplest form of adaptive optics is tip-tilt correction, which corresponds to correction of the tilts of the wavefront in two dimensions and this is performed using a rapidly moving tip–tilt mirror that makes small rotations around two of its axes. A significant fraction of the aberration introduced by the atmosphere can be removed in this way, tip–tilt mirrors are effectively segmented mirrors having only one segment which can tip and tilt, rather than having an array of multiple segments that can tip and tilt independently. Due to the simplicity of such mirrors and having a large stroke, meaning they have large correcting power, most AO systems use these, first. Higher order aberrations may then be corrected with deformable mirrors, when light from a star or another astronomical object enters the Earths atmosphere, atmospheric turbulence can distort and move the image in various ways. Visual images produced by any larger than approximately 20 centimeters are blurred by these distortions. In order to perform adaptive optics correction, the shape of the incoming wavefronts must be measured as a function of position in the aperture plane. The mean wavefront perturbation in each pixel is calculated and this pixelated map of the wavefronts is fed into the deformable mirror and used to correct the wavefront errors introduced by the atmosphere. The deformable mirror corrects incoming light so that the images appear sharp, because a science target is often too faint to be used as a reference star for measuring the shape of the optical wavefronts, a nearby brighter guide star can be used instead. This severely limits the application of the technique for astronomical observations, another major limitation is the small field of view over which the adaptive optics correction is good. As the angular distance from the star increases, the image quality degrades. A technique known as adaptive optics uses several deformable mirrors to achieve a greater field of view. An alternative is the use of a beam to generate a reference light source in the atmosphere. LGSs come in two flavors, Rayleigh guide stars and sodium guide stars, Rayleigh guide stars work by propagating a laser, usually at near ultraviolet wavelengths, and detecting the backscatter from air at altitudes between 15–25 km. Sodium guide stars use laser light at 589 nm to excite sodium atoms higher in the mesosphere and thermosphere, which then appear to glow. The LGS can then be used as a wavefront reference in the way as a natural guide star – except that natural reference stars are still required for image position information
Adaptive optics
–
Adaptive thin shell mirror.
Adaptive optics
–
A
deformable mirror can be used to correct wavefront errors in an astronomical telescope.
Adaptive optics
–
Astronomers at the
Very Large Telescope site in
Chile use adaptive optics.
Adaptive optics
–
A laser beam directed toward the centre of the
Milky Way. This laser beam can then be used as a guide star for the AO.
20.
Spectroscopy
–
Spectroscopy /spɛkˈtrɒskəpi/ is the study of the interaction between matter and electromagnetic radiation. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, later the concept was expanded greatly to include any interaction with radiative energy as a function of its wavelength or frequency. Spectroscopic data is represented by an emission spectrum, a plot of the response of interest as a function of wavelength or frequency. Spectroscopy and spectrography are terms used to refer to the measurement of radiation intensity as a function of wavelength and are used to describe experimental spectroscopic methods. Spectral measurement devices are referred to as spectrometers, spectrophotometers, spectrographs or spectral analyzers, daily observations of color can be related to spectroscopy. Neon lighting is an application of atomic spectroscopy. Neon and other noble gases have characteristic emission frequencies, neon lamps use collision of electrons with the gas to excite these emissions. Inks, dyes and paints include chemical compounds selected for their characteristics in order to generate specific colors. A commonly encountered molecular spectrum is that of nitrogen dioxide, gaseous nitrogen dioxide has a characteristic red absorption feature, and this gives air polluted with nitrogen dioxide a reddish-brown color. Rayleigh scattering is a spectroscopic scattering phenomenon that accounts for the color of the sky, Spectroscopy is used in physical and analytical chemistry because atoms and molecules have unique spectra. As a result, these spectra can be used to detect, identify and quantify information about the atoms, Spectroscopy is also used in astronomy and remote sensing on earth. The measured spectra are used to determine the composition and physical properties of astronomical objects. One of the concepts in spectroscopy is a resonance and its corresponding resonant frequency. Resonances were first characterized in mechanical systems such as pendulums, mechanical systems that vibrate or oscillate will experience large amplitude oscillations when they are driven at their resonant frequency. A plot of amplitude vs. excitation frequency will have a peak centered at the resonance frequency and this plot is one type of spectrum, with the peak often referred to as a spectral line, and most spectral lines have a similar appearance. In quantum mechanical systems, the resonance is a coupling of two quantum mechanical stationary states of one system, such as an atom, via an oscillatory source of energy such as a photon. The coupling of the two states is strongest when the energy of the matches the energy difference between the two states. The energy of a photon is related to its frequency by E = h ν where h is Plancks constant, spectra of atoms and molecules often consist of a series of spectral lines, each one representing a resonance between two different quantum states
Spectroscopy
–
Analysis of white light by
dispersing it with a prism is an example of spectroscopy.
Spectroscopy
–
A huge diffraction grating at the heart of the ultra-precise
ESPRESSO spectrograph.
Spectroscopy
–
UVES is a high-resolution spectrograph on the
Very Large Telescope.
21.
Ablation
–
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. Biological ablation is the removal of a structure or functionality. Genetic ablation is another term for gene silencing, in gene expression is abolished through the alteration or deletion of genetic sequence information. In cell ablation, individual cells in a population or culture are destroyed or removed, both can be used as experimental tools, as in loss-of-function experiments. In glaciology and meteorology, ablation—the opposite of accumulation—refers to all processes that remove snow, ice, Ablation refers to the melting of snow or ice that runs off the glacier, evaporation, sublimation, calving, or erosive removal of snow by wind. Air temperature is typically the dominant control of ablation, with precipitation exercising secondary control, in a temperate climate during ablation season, ablation rates typically average around 2 mm/h. Where solar radiation is the dominant cause of snow ablation, characteristic ablation textures such as suncups, Ablation can refer either to the processes removing ice and snow or to the quantity of ice and snow removed. Laser ablation is greatly affected by the nature of the material and its ability to absorb energy, since the cornea does not grow back, laser is used to remodel the cornea refractive properties to correct refraction errors, such as astigmatism, myopia, and hyperopia. Laser ablation is used to remove part of the uterine wall in women with menstruation. Ablative paints are often utilized for this purpose to prevent the dilution or deactivation of the antifouling agent, over time, the paint will slowly decompose in the water, exposing fresh antifouling compounds on the surface. Engineering the antifouling agents and the rate can produce long-lived protection from the deleterious effects of biofouling. In medicine, ablation is the same as removal of a part of biological tissue, surface ablation of the skin can be carried out by chemicals, by lasers, or by electricity. Its purpose is to remove skin spots, aged skin, wrinkles, surface ablation is also employed in otolaryngology for several kinds of surgery, such as for snoring. The term is used in the context of laser ablation. For a laser to ablate tissues, the density or fluence must be high, otherwise thermocoagulation occurs. Rotoablation is a type of arterial cleansing that consists of inserting a tiny, diamond-tipped, the procedure is used in the treatment of coronary heart disease to restore blood flow. Radiofrequency ablation is a method of removing aberrant tissue from within the body via minimally invasive procedures, microwave ablation is similar to RFA but at higher frequency of electromagnetic radiation. Bone marrow ablation is a process whereby the human bone marrow cells are eliminated in preparation for a marrow transplant
Ablation
–
Ablation near the electrode in a
flashtube. The high-energy electrical arc slowly erodes the glass, leaving a frosted appearance.
Ablation
–
An
Nd:YAG laser drills a hole through a block of
nitrile. The intense burst of infrared radiation ablates the highly absorbing rubber, releasing an eruption of
plasma.
22.
ICP-MS
–
This is achieved by ionizing the sample with inductively coupled plasma and then using a mass spectrometer to separate and quantify those ions. Compared to atomic spectroscopy, ICP-MS has greater speed, precision. The variety of applications exceeds that of inductively coupled plasma atomic emission spectroscopy, due to possible applications in nuclear technologies, ICP-MS hardware is a subject for special exporting regulations. Even a partially ionized gas in which as little as 1% of the particles are ionized can have the characteristics of a plasma, the plasmas used in spectrochemical analysis are essentially electrically neutral, with each positive charge on an ion balanced by a free electron. In these plasmas the positive ions are almost all singly charged and there are few negative ions, the end of this torch is placed inside an induction coil supplied with a radio-frequency electric current. A flow of gas is introduced between the two outermost tubes of the torch and an electric spark is applied for a short time to introduce free electrons into the gas stream. These electrons interact with the magnetic field of the induction coil and are accelerated first in one direction, then the other. The accelerated electrons collide with atoms, and sometimes a collision causes an argon atom to part with one of its electrons. The released electron is in turn accelerated by the changing magnetic field. The process continues until the rate of release of new electrons in collisions is balanced by the rate of recombination of electrons with argon ions and this produces a ‘fireball’ that consists mostly of argon atoms with a rather small fraction of free electrons and argon ions. The temperature of the plasma is high, of the order of 10,000 K. The plasma also produces light, so for safety should not be viewed directly. The ICP can be retained in the torch because the flow of gas between the two outermost tubes keeps the plasma away from the walls of the torch. A second flow of argon is usually introduced between the tube and the intermediate tube to keep the plasma away from the end of the central tube. A third flow of gas is introduced into the tube of the torch. This gas flow passes through the centre of the plasma, where it forms a channel that is cooler than the surrounding plasma, samples to be analyzed are introduced into this central channel, usually as a mist of liquid formed by passing the liquid sample into a nebulizer. To maximise plasma temperature and stability, the sample should be introduced through the tube with as little liquid as possible. A nebuliser can be used for samples, followed by a spray chamber to remove larger droplets
ICP-MS
–
ICP-MS Instrument
23.
Monochromatic
–
Monochrome describes paintings, drawings, design, or photographs in one color or values of one color. A monochromatic object or image reflects colors in shades of limited colors or hues, images using only shades of grey are called grayscale or black-and-white. However, scientifically speaking, monochromatic light refers to light of a narrow band of wavelengths. In computing, monochrome has two meanings, it may mean having only one color which is either on or off, a monochrome computer display is able to display only a single color, often green, amber, red or white, and often also shades of that color. In film photography, monochrome is typically the use of black-and-white film, originally, all photography was done in monochrome. Although color photography was possible even in the late 19th century, easily used color films, if the red channel is eliminated and the green and blue combined then the effect will be similar to that of orthochromatic film or the use of a cyan filter on panchromatic film. The selection of weighting thus allows a range of artistic expression in the final monochromatic image. For production of an image the original color stereogram source may first be reduced to monochrome in order to simplify the rendering of the image. This is sometimes required in cases where an image would render in a confusing manner given the colors and patterns present in the source image. In physics, monochromatic light is electromagnetic radiation of a single frequency, even very controlled sources such as lasers operate in a range of frequencies. In practice, filtered light, diffraction grating separated light and laser light are all referred to as monochromatic. Often light sources can be compared and one be labeled as “more monochromatic”
Monochromatic
–
The
Eiffel Tower during the
Exposition Universelle (1889) for which the tower was built
Monochromatic
–
A photograph of a
parrot rendered with a monochrome palette of a limited number of shades
Monochromatic
–
Night vision devices typically produce a monochrome image, often in shades of green
Monochromatic
–
Monochrome
anaglyph image stereogram rendered in red and cyan;
3D red cyan glasses are recommended to view this image correctly.
24.
Wavelength
–
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the waves shape repeats, and thus the inverse of the spatial frequency. Wavelength is commonly designated by the Greek letter lambda, the concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also applied to modulated waves. Wavelength depends on the medium that a wave travels through, examples of wave-like phenomena are sound waves, light, water waves and periodic electrical signals in a conductor. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric, water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary, wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle near the waters surface moves in a circle of the same diameter as the wave height. The range of wavelengths or frequencies for wave phenomena is called a spectrum, the name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum. In linear media, any pattern can be described in terms of the independent propagation of sinusoidal components. The wavelength λ of a sinusoidal waveform traveling at constant speed v is given by λ = v f, in a dispersive medium, the phase speed itself depends upon the frequency of the wave, making the relationship between wavelength and frequency nonlinear. In the case of electromagnetic radiation—such as light—in free space, the speed is the speed of light. Thus the wavelength of a 100 MHz electromagnetic wave is about, the wavelength of visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm. For sound waves in air, the speed of sound is 343 m/s, the wavelengths of sound frequencies audible to the human ear are thus between approximately 17 m and 17 mm, respectively. Note that the wavelengths in audible sound are much longer than those in visible light, a standing wave is an undulatory motion that stays in one place. A sinusoidal standing wave includes stationary points of no motion, called nodes, the upper figure shows three standing waves in a box. The walls of the box are considered to require the wave to have nodes at the walls of the box determining which wavelengths are allowed, the stationary wave can be viewed as the sum of two traveling sinusoidal waves of oppositely directed velocities. Consequently, wavelength, period, and wave velocity are related just as for a traveling wave, for example, the speed of light can be determined from observation of standing waves in a metal box containing an ideal vacuum. In that case, the k, the magnitude of k, is still in the same relationship with wavelength as shown above
Wavelength
–
Wavelength is decreased in a medium with slower propagation.
Wavelength
–
Wavelength of a
sine wave, λ, can be measured between any two points with the same
phase, such as between crests, or troughs, or corresponding
zero crossings as shown.
Wavelength
–
Various local wavelengths on a crest-to-crest basis in an ocean wave approaching shore
Wavelength
–
A wave on a line of atoms can be interpreted according to a variety of wavelengths.
25.
Linewidth
–
Spectral lines are often used to identify atoms and molecules from their characteristic spectral lines. Spectral lines are the result of interaction between a system and a single photon. When a photon has about the amount of energy to allow a change in the energy state of the system. A spectral line may be observed either as a line or an absorption line. Which type of line is observed depends on the type of material, an absorption line is produced when photons from a hot, broad spectrum source pass through a cold material. The intensity of light, over a frequency range, is reduced due to absorption by the material. By contrast, a bright, emission line is produced when photons from a hot material are detected in the presence of a spectrum from a cold source. The intensity of light, over a frequency range, is increased due to emission by the material. Spectral lines are highly atom-specific, and can be used to identify the composition of any medium capable of letting light pass through it. Several elements were discovered by means, such as helium, thallium. Mechanisms other than atom-photon interaction can produce spectral lines, depending on the exact physical interaction, the frequency of the involved photons will vary widely, and lines can be observed across the electromagnetic spectrum, from radio waves to gamma rays. In other cases the lines are designated according to the level of ionization by adding a Roman numeral to the designation of the chemical element, so that Ca+ also has the designation Ca II. Neutral atoms are denoted with the roman number I, singly ionized atoms with II, more detailed designations usually include the line wavelength and may include a multiplet number or band designation. Many spectral lines of hydrogen also have designations within their respective series. A spectral line extends over a range of frequencies, not a single frequency, in addition, its center may be shifted from its nominal central wavelength. There are several reasons for this broadening and shift and these reasons may be divided into two general categories – broadening due to local conditions and broadening due to extended conditions. Broadening due to conditions is due to effects which hold in a small region around the emitting element. Broadening due to extended conditions may result from changes to the distribution of the radiation as it traverses its path to the observer
Linewidth
–
Continuous spectrum of a
incandescent lamp (mid) and discrete spectrum lines of a
fluorescent lamp (bottom)
Linewidth
–
Continuous spectrum
26.
Lunar laser ranging experiment
–
The ongoing Lunar Laser Ranging Experiment measures the distance between Earth and the Moon using laser ranging. Lasers on Earth are aimed at retroreflectors planted on the Moon during the Apollo program, the time for the reflected light to return is measured. Similar measurements were obtained later the year by a Soviet team at the Crimean Astrophysical Observatory using a Q-switched ruby laser. Successful lunar laser range measurements to the retroreflectors were first reported by the 3, the unmanned Soviet Lunokhod 1 and Lunokhod 2 rovers carried smaller arrays. Lunokhod 2s array continues to return signals to Earth, the Lunokhod arrays suffer from decreased performance in direct sunlight—a factor considered in reflector placement during the Apollo missions. The Apollo 15 array is three times the size of the left by the two earlier Apollo missions. Its size made it the target of three-quarters of the measurements taken in the first 25 years of the experiment. The distance to the Moon is calculated using this equation, distance = /2 In actuality. Nonetheless, the Earth–Moon distance has been measured with increasing accuracy for more than 35 years, the distance continually changes for a number of reasons, but averages 385,000.6 km. At the Moons surface, the beam is about 6.5 kilometers wide, the reflected light is too weak to see with the human eye. Out of 1017 photons aimed at the reflector, only one is received back on Earth every few seconds and they can be identified as originating from the laser because the laser is highly monochromatic. This is one of the most precise measurements ever made. As of 2002, work is progressing on increasing the accuracy of the Earth–Moon measurements to near millimeter accuracy, Lunar laser ranging measurement data is available from the Paris Observatory Lunar Analysis Center, and the active stations. Some of the findings of this experiment are, The Moon is spiraling away from Earth at a rate of 3.8 cm per year. This rate has been described as anomalously high, the Moon probably has a liquid core of about 20% of the Moons radius. The universal force of gravity is very stable, the experiments have constrained the change in Newtons gravitational constant G to ×10−13 per year. The likelihood of any Nordtvedt effect has been ruled out to high precision, einsteins theory of gravity predicts the Moons orbit to within the accuracy of the laser ranging measurements
Lunar laser ranging experiment
–
The Lunar Laser Ranging Experiment from the Apollo 11 mission.
Lunar laser ranging experiment
–
Apollo 15 LRRR
Lunar laser ranging experiment
–
Laser ranging facility at
Wettzell fundamental station,
Bavaria,
Germany.
Lunar laser ranging experiment
–
Laser Ranging at
Goddard Spaceflight Center.
27.
Retroreflector
–
A retroreflector is a device or surface that reflects light back to its source with a minimum of scattering. In a retroreflector an electromagnetic wavefront is reflected back along a vector that is parallel to, there are several ways to obtain retroreflection, A set of three mutually perpendicular reflective surfaces, placed to form the corner of a cube, work as a retroreflector. The three corresponding normal vectors of the sides form a basis in which to represent the direction of an arbitrary incoming ray. When the ray reflects from the first side, say x, the x component. Corner reflectors occur in two varieties, in the more common form, the corner is literally the truncated corner of a cube of transparent material such as conventional optical glass. In this structure, the reflection is achieved either by total internal reflection or silvering of the outer cube surfaces, the second form uses mutually perpendicular flat mirrors bracketing an air space. These two types have similar optical properties, a large relatively thin retroreflector can be formed by combining many small corner reflectors, using the standard triangular tiling. In that case, the surface behaves as a concave spherical mirror with the required curvature for retroreflection. In practice, the index of refraction may be lower than ni+1≅2 due to several factors. For one, it is preferable to have an imperfect, slightly divergent retroreflection, as in the case of road signs. Due to spherical aberration, there exists a radius from the centerline at which incident rays are focused at the center of the rear surface of the sphere. Finally, high index materials have higher Fresnel reflection coefficients, so the efficiency of coupling of the light from the ambient into the sphere decreases as the index becomes higher, commercial retroreflective beads thus vary in index from around 1.5 up to around 1.9. The spherical aberration problem with the cats eye can be solved in various ways, one being a spherically symmetrical index gradient within the sphere. Practically, this can be approximated by a concentric sphere system, the term cats eye derives from the resemblance of the cats eye retroreflector to the optical system that produces the well-known phenomenon of glowing eyes or eyeshine in cats and other vertebrates. The combination of the lens and the cornea form the refractive converging system. This type of retroreflector can consist of small versions of these structures incorporated in a thin sheet or in paint. A third, much less common way of producing a retroreflector is to use the optical phenomenon of phase conjugation. This technique is used in advanced optical systems such as high-power lasers, phase-conjugate mirrors require a comparatively expensive and complex apparatus, as well as large quantities of power
Retroreflector
–
A gold corner cube retroreflector
Retroreflector
–
Eyeshine from retroreflectors of the transparent sphere type is clearly visible in this cat's eyes
Retroreflector
–
Bicycle retroreflectors
Retroreflector
–
Retroreflectors are clearly visible in a pair of bicycle shoes. Light source is a flash a few centimeters above camera lens.
28.
Lunar Laser Ranging Experiment
–
The ongoing Lunar Laser Ranging Experiment measures the distance between Earth and the Moon using laser ranging. Lasers on Earth are aimed at retroreflectors planted on the Moon during the Apollo program, the time for the reflected light to return is measured. Similar measurements were obtained later the year by a Soviet team at the Crimean Astrophysical Observatory using a Q-switched ruby laser. Successful lunar laser range measurements to the retroreflectors were first reported by the 3, the unmanned Soviet Lunokhod 1 and Lunokhod 2 rovers carried smaller arrays. Lunokhod 2s array continues to return signals to Earth, the Lunokhod arrays suffer from decreased performance in direct sunlight—a factor considered in reflector placement during the Apollo missions. The Apollo 15 array is three times the size of the left by the two earlier Apollo missions. Its size made it the target of three-quarters of the measurements taken in the first 25 years of the experiment. The distance to the Moon is calculated using this equation, distance = /2 In actuality. Nonetheless, the Earth–Moon distance has been measured with increasing accuracy for more than 35 years, the distance continually changes for a number of reasons, but averages 385,000.6 km. At the Moons surface, the beam is about 6.5 kilometers wide, the reflected light is too weak to see with the human eye. Out of 1017 photons aimed at the reflector, only one is received back on Earth every few seconds and they can be identified as originating from the laser because the laser is highly monochromatic. This is one of the most precise measurements ever made. As of 2002, work is progressing on increasing the accuracy of the Earth–Moon measurements to near millimeter accuracy, Lunar laser ranging measurement data is available from the Paris Observatory Lunar Analysis Center, and the active stations. Some of the findings of this experiment are, The Moon is spiraling away from Earth at a rate of 3.8 cm per year. This rate has been described as anomalously high, the Moon probably has a liquid core of about 20% of the Moons radius. The universal force of gravity is very stable, the experiments have constrained the change in Newtons gravitational constant G to ×10−13 per year. The likelihood of any Nordtvedt effect has been ruled out to high precision, einsteins theory of gravity predicts the Moons orbit to within the accuracy of the laser ranging measurements
Lunar Laser Ranging Experiment
–
The Lunar Laser Ranging Experiment from the Apollo 11 mission.
Lunar Laser Ranging Experiment
–
Apollo 15 LRRR
Lunar Laser Ranging Experiment
–
Laser ranging facility at
Wettzell fundamental station,
Bavaria,
Germany.
Lunar Laser Ranging Experiment
–
Laser Ranging at
Goddard Spaceflight Center.
29.
Telescope
–
A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation. The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s and they found use in both terrestrial applications and astronomy. Within a few decades, the telescope was invented, which used mirrors to collect. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s, the word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galileis instruments presented at a banquet at the Accademia dei Lincei, in the Starry Messenger, Galileo had used the term perspicillum. The earliest recorded working telescopes were the telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals, Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, Galileo heard about the Dutch telescope in June 1609, built his own within a month, and improved upon the design in the following year. Also in 1609, Thomas Harriot became the first person known to point a telescope skyward in order to make observations of a celestial object. The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors—reduction of spherical aberration and no chromatic aberration—led to many proposed designs, in 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name, the Newtonian reflector. The invention of the lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter. The largest reflecting telescopes currently have objectives larger than 10 m, the 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose built radio telescope went into operation in 1937, since then, a tremendous variety of complex astronomical instruments have been developed. The name telescope covers a range of instruments. Most detect electromagnetic radiation, but there are differences in how astronomers must go about collecting light in different frequency bands. The near-infrared can be collected much like light, however in the far-infrared and submillimetre range. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm to 2000 μm, on the other hand, the Spitzer Space Telescope, observing from about 3 μm to 180 μm uses a mirror. Also using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the range from about 0.2 μm to 1.7 μm
Telescope
–
The 100 inch (2.54 m) Hooker
reflecting telescope at
Mount Wilson Observatory near Los Angeles, USA.
Telescope
–
Modern telescopes typically use
CCDs instead of film for recording images. This is the sensor array in the
Kepler spacecraft.
Telescope
–
28-inch telescope and 40-foot telescope in
Greenwich in 2015.
Telescope
–
50 cm refracting telescope at
Nice Observatory.
30.
Mode-locking
–
Mode-locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds or femtoseconds. The basis of the technique is to induce a fixed-phase relationship between the modes of the lasers resonant cavity. The laser is said to be phase-locked or mode-locked. Interference between these causes the laser light to be produced as a train of pulses. Depending on the properties of the laser, these pulses may be of brief duration. Although laser light is perhaps the purest form of light, it is not of a single, all lasers produce light over some natural bandwidth or range of frequencies. For example, a typical helium–neon laser has a bandwidth of about 1.5 GHz. The second factor to determine a lasers emission frequencies is the cavity of the laser. In the simplest case, this consists of two plane mirrors facing each other, surrounding the gain medium of the laser and these standing waves form a discrete set of frequencies, known as the longitudinal modes of the cavity. These modes are the frequencies of light which are self-regenerating and allowed to oscillate by the resonant cavity. In practice, L is usually greater than λ, so the relevant values of q are large. Of more interest is the separation between any two adjacent modes q and q+1, this is given by Δν, Δ ν = c 2 L where c is the speed of light. Using the above equation, a laser with a mirror separation of 30 cm has a frequency separation between longitudinal modes of 0.5 GHz. When more than one mode is excited, the laser is said to be in multi-mode operation. When only one mode is excited, the laser is said to be in single-mode operation. The individual phase of the waves in each mode is not fixed. If instead of oscillating independently, each operates with a fixed phase between it and the other modes, the laser output behaves quite differently. Instead of a random or constant output intensity, the modes of the laser will periodically all constructively interfere with one another, such a laser is said to be mode-locked or phase-locked
Mode-locking
–
Laser mode structure
31.
Biochemistry
–
Biochemistry, sometimes called biological chemistry, is the study of chemical processes within and relating to living organisms. By controlling information flow through biochemical signaling and the flow of energy through metabolism. Biochemistry is closely related to biology, the study of the molecular mechanisms by which genetic information encoded in DNA is able to result in the processes of life. Depending on the definition of the terms used, molecular biology can be thought of as a branch of biochemistry, or biochemistry as a tool with which to investigate. The chemistry of the cell depends on the reactions of smaller molecules. These can be inorganic, for water and metal ions, or organic, for example the amino acids. The mechanisms by which cells harness energy from their environment via chemical reactions are known as metabolism, the findings of biochemistry are applied primarily in medicine, nutrition, and agriculture. In medicine, biochemists investigate the causes and cures of diseases, in nutrition, they study how to maintain health and study the effects of nutritional deficiencies. In agriculture, biochemists investigate soil and fertilizers, and try to discover ways to improve crop cultivation, crop storage and pest control. However, biochemistry as a scientific discipline has its beginning sometime in the 19th century, or a little earlier. Gowland Hopkins on enzymes and the nature of biochemistry. The term biochemistry itself is derived from a combination of biology, the German chemist Carl Neuberg however is often cited to have coined the word in 1903, while some credited it to Franz Hofmeister. Then, in 1828, Friedrich Wöhler published a paper on the synthesis of urea and these techniques allowed for the discovery and detailed analysis of many molecules and metabolic pathways of the cell, such as glycolysis and the Krebs cycle. Another significant historic event in biochemistry is the discovery of the gene and this part of biochemistry is often called molecular biology. In the 1950s, James D. Watson, Francis Crick, Rosalind Franklin, in 1958, George Beadle and Edward Tatum received the Nobel Prize for work in fungi showing that one gene produces one enzyme. In 1988, Colin Pitchfork was the first person convicted of murder with DNA evidence, mello received the 2006 Nobel Prize for discovering the role of RNA interference, in the silencing of gene expression. Around two dozen of the 92 naturally occurring elements are essential to various kinds of biological life. Most rare elements on Earth are not needed by life, while a few common ones are not used, most organisms share element needs, but there are a few differences between plants and animals
Biochemistry
–
Gerty Cori and
Carl Cori jointly won the
Nobel Prize in 1947 for their discovery of the
Cori cycle at RPMI.
Biochemistry
–
Subdisciplines
32.
Barcode reader
–
A barcode reader is an electronic device that can read and output printed barcodes to a computer. Like a flatbed scanner, it consists of a source, a lens. Additionally, nearly all barcode readers contain decoder circuitry analyzing the image data provided by the sensor. Barcode readers can be differentiated by technologies as follows, Pen-type readers consist of a light source, to read a bar code, the person holding the pen must move the tip of it across the bars at a relatively uniform speed. The photodiode measures the intensity of the light reflected back from the source as the tip crosses each bar. The photodiode generates a waveform that is used to measure the widths of the bars, dark bars in the bar code absorb light and white spaces reflect light so that the voltage waveform generated by the photodiode is a representation of the bar and space pattern in the bar code. This waveform is decoded by the scanner in a similar to the way Morse code dots. As with the pen type reader, a photo-diode is used to measure the intensity of the light reflected back from the bar code, CCD readers use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. Each sensor measures the intensity of the light immediately in front of it, two-dimensional imaging scanners are a newer type of bar code reader. They use a camera and image processing techniques to decode the bar code, large field-of-view readers use high resolution industrial cameras to capture multiple bar codes simultaneously. Unlike the simpler single-line laser scanners, they produce a pattern of beams in varying orientations allowing them to read barcodes presented to it at different angles, most of them use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns. Omnidirectional scanners are most familiar through the scanners in supermarkets. Omnidirectional scanners are also better at reading poorly printed, wrinkled, cell phone cameras open up a number of applications for consumers, Movies, DVD/VHS movie catalogs. Music, CD catalogs – play MP3 when scanned, groceries, nutrition information, making shopping lists when the last of an item is used, etc. Personal Property inventory ode scanned into personal finance software when entering, later, scanned receipt images can then be automatically associated with the appropriate entries. Later, the bar codes can be used to weed out paper copies not required to be retained for tax or asset inventory purposes. Receipts scanned on a scanner could be identified and associated with the appropriate entries in finance. Consumer tracking from the retailer perspective, a number of enterprise applications using cell phones are appearing, Access control, inventory reporting, asset tracking
Barcode reader
–
A handheld barcode scanner
Barcode reader
–
A stationary barcode scanner for a conveyor line
Barcode reader
–
PS/2 keyboard and mouse ports
33.
Atom trapping
–
A magnetic trap is an apparatus which uses a magnetic field gradient to trap neutral particles with magnetic moments. Although such traps have been employed for purposes in physics research. The magnetic trap was first proposed by David E. Pritchard, many atoms have a magnetic moment, their energy shifts in a magnetic field according to the formula Δ E = − μ → ⋅ B →. According to the principles of quantum mechanics the magnetic moment of an atom will be quantized, if the atom is placed in a strong magnetic field, its magnetic moment will be aligned with the field. If a number of atoms are placed in the same field, if a magnetic field gradient is superimposed on the uniform field, those atoms whose magnetic moments are aligned with the field will have lower energies in a higher field. Like a ball rolling down a hill, these atoms will tend to occupy locations with higher fields and are known as high-field-seeking atoms and it is impossible to produce a local maximum of the magnetic-field magnitude in free space, however, a local minimum may be produced. This minimum can trap atoms which are low-field-seeking if they do not have enough energy to escape the minimum. Typically, magnetic traps have relatively shallow field minima and are able to trap atoms whose kinetic energies correspond to temperatures of a fraction of a kelvin. The field minima required for magnetic trapping can be produced in a variety of ways and these include permanent magnet traps, Ioffe configuration traps, QUIC traps and others. The minimum magnitude of the field can be realized with the atom microchip. One of the first microchip atomic traps is shown on the right, the Z-shaped conductor is placed into the uniform magnetic field. Only atoms with positive spin-field energy were trapped, to prevent the mixing of spin states, the external magnetic field was inclined in the plane of the chip, providing the adiabatic rotation of the spin at the movement of the atom. In the first approximation, magnitude of the field is responsible for effective energy of the trapped atom. The chip shown is 2 cm x 2 cm, this size was chosen for ease in manufacture, in principle, the size of such microchip traps can be drastically reduced. An array of traps can be manufactured with conventional lithographic methods. Ways of transferring atoms and/or q-bits between traps are under development, the adiabatic optical and/or the electrical control is assumed, Bose–Einstein condensation requires conditions of very high density and very low temperature in a gas of atoms. Laser cooling in a trap is typically used to cool atoms down to the microkelvin range. However, laser cooling is limited by the momentum recoils an atom receives from single photons, achieving BEC requires cooling the atoms beyond the limits of laser cooling, which means the lasers used in the MOT must be turned off and a new method of trapping devised
Atom trapping
–
Microchip atomic trap developed in
ILS in 2005
34.
Electric field
–
An electric field is a vector field that associates to each point in space the Coulomb force that would be experienced per unit of electric charge, by an infinitesimal test charge at that point. Electric fields are created by electric charges and can be induced by time-varying magnetic fields, the electric field combines with the magnetic field to form the electromagnetic field. The electric field, E, at a point is defined as the force, F. A particle of charge q would be subject to a force F = q E and its SI units are newtons per coulomb or, equivalently, volts per metre, which in terms of SI base units are kg⋅m⋅s−3⋅A−1. Electric fields are caused by electric charges or varying magnetic fields, in the special case of a steady state, the Maxwell-Faraday inductive effect disappears. The resulting two equations, taken together, are equivalent to Coulombs law, written as E =14 π ε0 ∫ d r ′ ρ r − r ′ | r − r ′ |3 for a charge density ρ. Notice that ε0, the permittivity of vacuum, must be substituted if charges are considered in non-empty media, the equations of electromagnetism are best described in a continuous description. A charge q located at r 0 can be described mathematically as a charge density ρ = q δ, conversely, a charge distribution can be approximated by many small point charges. Electric fields satisfy the principle, because Maxwells equations are linear. This principle is useful to calculate the field created by point charges. Q n are stationary in space at r 1, r 2, in that case, Coulombs law fully describes the field. If a system is static, such that magnetic fields are not time-varying, then by Faradays law, in this case, one can define an electric potential, that is, a function Φ such that E = − ∇ Φ. This is analogous to the gravitational potential, Coulombs law, which describes the interaction of electric charges, F = q = q E is similar to Newtons law of universal gravitation, F = m = m g. This suggests similarities between the electric field E and the gravitational field g, or their associated potentials, mass is sometimes called gravitational charge because of that similarity. Electrostatic and gravitational forces both are central, conservative and obey an inverse-square law, a uniform field is one in which the electric field is constant at every point. It can be approximated by placing two conducting plates parallel to other and maintaining a voltage between them, it is only an approximation because of boundary effects. Assuming infinite planes, the magnitude of the electric field E is, electrodynamic fields are E-fields which do change with time, for instance when charges are in motion. The electric field cannot be described independently of the field in that case
Electric field
–
Electric field lines emanating from a point positive
electric charge suspended over an infinite sheet of conducting material.
35.
Magnetic field
–
A magnetic field is the magnetic effect of electric currents and magnetic materials. The magnetic field at any point is specified by both a direction and a magnitude, as such it is represented by a vector field. The term is used for two distinct but closely related fields denoted by the symbols B and H, where H is measured in units of amperes per meter in the SI, B is measured in teslas and newtons per meter per ampere in the SI. B is most commonly defined in terms of the Lorentz force it exerts on moving electric charges, Magnetic fields can be produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. In quantum physics, the field is quantized and electromagnetic interactions result from the exchange of photons. Magnetic fields are used throughout modern technology, particularly in electrical engineering. The Earth produces its own field, which is important in navigation. Rotating magnetic fields are used in electric motors and generators. Magnetic forces give information about the carriers in a material through the Hall effect. The interaction of magnetic fields in electric devices such as transformers is studied in the discipline of magnetic circuits, noting that the resulting field lines crossed at two points he named those points poles in analogy to Earths poles. He also clearly articulated the principle that magnets always have both a north and south pole, no matter how finely one slices them, almost three centuries later, William Gilbert of Colchester replicated Petrus Peregrinus work and was the first to state explicitly that Earth is a magnet. Published in 1600, Gilberts work, De Magnete, helped to establish magnetism as a science, in 1750, John Michell stated that magnetic poles attract and repel in accordance with an inverse square law. Charles-Augustin de Coulomb experimentally verified this in 1785 and stated explicitly that the north and south poles cannot be separated, building on this force between poles, Siméon Denis Poisson created the first successful model of the magnetic field, which he presented in 1824. In this model, a magnetic H-field is produced by magnetic poles, three discoveries challenged this foundation of magnetism, though. First, in 1819, Hans Christian Ørsted discovered that an electric current generates a magnetic field encircling it, then in 1820, André-Marie Ampère showed that parallel wires having currents in the same direction attract one another. Finally, Jean-Baptiste Biot and Félix Savart discovered the Biot–Savart law in 1820, extending these experiments, Ampère published his own successful model of magnetism in 1825. This has the benefit of explaining why magnetic charge can not be isolated. Also in this work, Ampère introduced the term electrodynamics to describe the relationship between electricity and magnetism, in 1831, Michael Faraday discovered electromagnetic induction when he found that a changing magnetic field generates an encircling electric field
Magnetic field
–
One of the first drawings of a magnetic field, by
René Descartes, 1644. It illustrated his theory that magnetism was caused by the circulation of tiny helical particles, "threaded parts", through threaded pores in magnets.
Magnetic field
–
Magnetic field of an ideal cylindrical
magnet with its axis of symmetry inside the image plane. The magnetic field is represented by
magnetic field lines, which show the direction of the field at different points.
Magnetic field
–
Hans Christian Ørsted, Der Geist in der Natur, 1854
36.
Laboratory for laser energetics
–
The Laboratory for Laser Energetics is a scientific research facility which is part of the University of Rochesters south campus, located in Brighton, New York. The Laser Lab was commissioned to serve as a center for investigations of high-energy physics, the lab shares its building with the Center for Optoelectronics and Imaging and the Center for Optics Manufacturing. A new addition, the Robert L. Sproull Center for Ultra High Intensity Laser Research, was opened in 2005 and houses the OMEGA EP laser, the laboratory is unique in conducting big science on a university campus. More than 180 Phds have been award for research done at the LLE, during summer months the lab sponsors a program for high school students which involves local-area high school juniors in the research being done at the laboratory. Most of the projects are done on current research that is led by scientists at the lab. The LLE was founded on the University of Rochesters campus in 1970, working with outside companies such as Kodak the team built Delta, a four beam laser system in 1972. Construction started on the current LLE site in 1976, the facility opened in 1978 a six beam laser systems and a 24 beam system follows two years later. In 1985, Donna Strickland and Gérard Mourou invent a method to amplify lasers pulses by chirping and this method change a single wavelength of laser light into a spectrum of wavelengths. The system amplifies the laser at each wavelength and then reconstitutes the beam into one color, chirp pulsed amplification became instrumental in building the National Ignition Facility and the Omega EP system. In 1995, the laser was increased to 60 beams system. The OMEGA laser at the LLE is one of the most powerful and it is a 60-beam ultraviolet frequency-tripled neodymium glass laser, which is capable of delivering 30 kilojoules at up to 60 terawatts onto a target less than 2 millimeter in diameter. Construction and commissioning of the laser were completed in 1995, OMEGA held the record for highest energy laser from 1999 to 2005, when the first 8 beams of the National Ignition Facility exceeded OMEGAs output by about 30 kJ in the ultraviolet. The maximum fusion yield of OMEGA so far is about 1014 neutrons per shot, the four beam OMEGA EP laser system was dedicated on May 16,2008. The laser is housed inside the newest addition to the building, the combination of the OMEGA and the OMEGA EP laser systems will allow the LLE to be the worlds only facility capable of fully integrated cryogenic fast ignition experiments. LLE is located on and operated by the University of Rochester, Omega and Omega EP are user facilities, open for use by the entire scientific community. The Laboratory has a mission, To conduct implosion experiments. To develop new laser and materials technologies, to provide graduate and undergraduate education in electro-optics, high-power lasers, high-energy-density physics, plasma physics, and nuclear fusion technology. To operate the National Laser Users Facility, to conduct research and development in advanced technology related to high-energy-density phenomena
Laboratory for laser energetics
–
Laboratory for Laser Energetics
37.
National Ignition Facility
–
The National Ignition Facility, or NIF, is a large laser-based inertial confinement fusion research device, located at the Lawrence Livermore National Laboratory in Livermore, California. NIF uses lasers to heat and compress a small amount of fuel to the point where nuclear fusion reactions take place. NIF is the largest and most energetic ICF device built to date, construction on the NIF began in 1997 but management problems and technical delays slowed progress into the early 2000s. Progress after 2000 was smoother, but compared to initial estimates, construction was certified complete on 31 March 2009 by the U. S. Department of Energy, and a dedication ceremony took place on 29 May 2009. The first large-scale laser target experiments were performed in June 2009, bringing the system to its full potential was a lengthy process that was carried out from 2009 to 2012. The Campaign officially ended in September 2012, at about 1⁄10 the conditions needed for ignition, experiments since then have pushed this closer to 1⁄3, but considerable theoretical and practical work is required if the system is ever to reach ignition. Inertial confinement fusion devices use drivers to rapidly heat the outer layers of a target in order to compress it, the target is a small spherical pellet containing a few milligrams of fusion fuel, typically a mix of deuterium and tritium. The energy of the heats the surface of the pellet into a plasma. The remaining portion of the target is driven inward, eventually compressing it into a point of extremely high density. The rapid blowoff also creates a wave that travels toward the center of the compressed fuel from all sides. When it reaches the center of the fuel, a volume is further heated and compressed to a greater degree. When the temperature and density of small spot are raised high enough, fusion reactions occur. The fusion reactions release high-energy particles, some of which, primarily alpha particles, collide with the high density fuel. If this process deposits enough energy in an area it can cause that fuel to undergo fusion as well. However, the fuel is also losing heat through x-ray losses and hot electrons leaving the area, so the rate of alpha heating must be greater than these losses. This is a known as ignition, which will lead to a significant portion of the fuel in the target undergoing fusion. To date most ICF experiments have used lasers to heat the target, calculations show that the energy must be delivered quickly in order to compress the core before it disassembles. The laser energy also must be focused extremely evenly across the outer surface in order to collapse the fuel into a symmetric core
National Ignition Facility
–
The National Ignition Facility, located at Lawrence Livermore National Laboratory.
National Ignition Facility
–
The target assembly for NIF's first integrated ignition experiment is mounted in the cryogenic target positioning system, or cryoTARPOS. The two triangle-shaped arms form a shroud around the cold target to protect it until they open five seconds before a shot.
National Ignition Facility
–
Mockup of the gold-plated hohlraum designed for the NIF.
National Ignition Facility
–
NIF's fuel "target", filled with either D-T gas or D-T ice. The capsule is held in the hohlraum using thin plastic webbing.
38.
Tritium
–
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons, naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays. It can be produced by irradiating lithium metal or lithium bearing ceramic pebbles in a nuclear reactor, the name of this isotope is derived from the Greek word τρίτος meaning third. While tritium has several different experimentally determined values of its half-life and it decays into helium-3 by beta decay as in this nuclear equation, and it releases 18.6 keV of energy in the process. The electrons kinetic energy varies, with an average of 5.7 keV, beta particles from tritium can penetrate only about 6.0 mm of air, and they are incapable of passing through the dead outermost layer of human skin. The unusually low energy released in the beta decay makes the decay appropriate for absolute neutrino mass measurements in the laboratory. The low energy of tritiums radiation makes it difficult to detect tritium-labeled compounds except by using liquid scintillation counting, Tritium is produced in nuclear reactors by neutron activation of lithium-6. This is possible with neutrons of any energy, and is an exothermic reaction yielding 4.8 MeV, in comparison, the fusion of deuterium with tritium releases about 17.6 MeV of energy. High-energy neutrons can produce tritium from lithium-7 in an endothermic reaction. This was discovered when the 1954 Castle Bravo nuclear test produced a high yield. High-energy neutrons irradiating boron-10 will also produce tritium, A more common result of boron-10 neutron capture is 7Li. The reactions requiring high neutron energies are not attractive production methods for peaceful applications, Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron. This reaction has a quite small absorption cross section, making water a good neutron moderator. Even so, cleaning tritium from the moderator may be desirable after several years to reduce the risk of its escaping to the environment. Ontario Power Generations Tritium Removal Facility processes up to 2,500 tonnes of water a year. Deuteriums absorption cross section for thermal neutrons is about 0.52 millibarns, whereas that of oxygen-16 is about 0.19 millibarns and that of oxygen-17 is about 240 millibarns. Tritium is a product of the nuclear fission of uranium-235, plutonium-239. The release or recovery of tritium needs to be considered in the operation of reactors, especially in the reprocessing of nuclear fuels
Tritium
–
Radioluminescent 1.8
curies (67
GBq) 6 by 0.2 inches (152.4 mm × 5.1 mm) tritium vials are thin, tritium-gas-filled glass vials whose inner surfaces are coated with a
phosphor. The vial shown here is brand-new.
Tritium
–
Full table
Tritium
–
Swiss Military Watch Commander model with tritium-illuminated face
39.
Deuterium
–
Deuterium is one of two stable isotopes of hydrogen. The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common hydrogen isotope, Deuterium has a natural abundance in Earths oceans of about one atom in 6420 of hydrogen. Thus deuterium accounts for approximately 0. 0156% of all the naturally occurring hydrogen in the oceans, the abundance of deuterium changes slightly from one kind of natural water to another. The deuterium isotopes name is formed from the Greek deuteros meaning second, Deuterium was discovered and named in 1931 by Harold Urey. When the neutron was discovered in 1932, this made the structure of deuterium obvious. Soon after deuteriums discovery, Urey and others produced samples of water in which the deuterium content had been highly concentrated. Deuterium is destroyed in the interiors of stars faster than it is produced, other natural processes are thought to produce only an insignificant amount of deuterium. Nearly all deuterium found in nature was produced in the Big Bang 13.8 billion years ago and this is the ratio found in the gas giant planets, such as Jupiter. However, other bodies are found to have different ratios of deuterium to hydrogen-1. This is thought to be as a result of natural isotope separation processes that occur from solar heating of ices in comets, like the water-cycle in Earths weather, such heating processes may enrich deuterium with respect to protium. The analysis of ratios in comets found results very similar to the mean ratio in Earths oceans. This reinforces theories that much of Earths ocean water is of cometary origin, the deuterium/protium ratio of the comet 67P/Churyumov-Gerasimenko, as measured by the Rosetta space probe, is about three times that of earth water. This figure is the highest yet measured in a comet, deuterium/protium ratios thus continue to be an active topic of research in both astronomy and climatology. Deuterium is frequently represented by the chemical symbol D, since it is an isotope of hydrogen with mass number 2, it is also represented by 2H. IUPAC allows both D and 2H, although 2H is preferred, a distinct chemical symbol is used for convenience because of the isotopes common use in various scientific processes. In quantum mechanics the energy levels of electrons in atoms depend on the mass of the system of electron. For hydrogen, this amount is about 1837/1836, or 1.000545, the energies of spectroscopic lines for deuterium and light-hydrogen therefore differ by the ratios of these two numbers, which is 1.000272. The wavelengths of all deuterium spectroscopic lines are shorter than the lines of light hydrogen
Deuterium
–
Deuterium discharge tube
Deuterium
–
Full table
Deuterium
–
Ionized deuterium in a
fusor reactor giving off its characteristic pinkish-red glow
Deuterium
–
Harold Urey
40.
Nuclear fusion
–
In nuclear physics, nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles. The difference in mass between the products and reactants is manifested as the release of large amounts of energy and this difference in mass arises due to the difference in atomic binding energy between the atomic nuclei before and after the reaction. Fusion is the process that powers active or main sequence stars, the fusion process that produces a nucleus lighter than iron-56 or nickel-62 will generally yield a net energy release. These elements have the smallest mass per nucleon and the largest binding energy per nucleon, the opposite is true for the reverse process, nuclear fission. This means that the elements, such as hydrogen and helium, are in general more fusable, while the heavier elements. The extreme astrophysical event of a supernova can produce energy to fuse nuclei into elements heavier than iron. During the remainder of that decade the steps of the cycle of nuclear fusion in stars were worked out by Hans Bethe. Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project, fusion was accomplished in 1951 with the Greenhouse Item nuclear test. Nuclear fusion on a scale in an explosion was first carried out on November 1,1952. Research into developing controlled thermonuclear fusion for civil purposes also began in earnest in the 1950s, the protons are positively charged and repel each other but they nonetheless stick together, demonstrating the existence of another force referred to as nuclear attraction. This force, called the nuclear force, overcomes electric repulsion at very close range. The effect of force is not observed outside the nucleus. The same force also pulls the nucleons together allowing ordinary matter to exist, light nuclei, are sufficiently small and proton-poor allowing the nuclear force to overcome the repulsive Coulomb force. This is because the nucleus is small that all nucleons feel the short-range attractive force at least as strongly as they feel the infinite-range Coulomb repulsion. Building up these nuclei from lighter nuclei by fusion thus releases the energy from the net attraction of these particles. For larger nuclei, however, no energy is released, since the force is short-range. Thus, energy is no longer released when such nuclei are made by fusion, instead, fusion reactions create the light elements that power the stars and produce virtually all elements in a process called nucleosynthesis. The fusion of elements in stars releases energy and the mass that always accompanies it
Nuclear fusion
–
The
Sun is a
main-sequence star, and thus generates its
energy by nuclear fusion of
hydrogen nuclei into
helium. In its core, the Sun fuses 620 million
metric tons of hydrogen each second.
Nuclear fusion
–
The
Tokamak à configuration variable, research fusion reactor, at the
École Polytechnique Fédérale de Lausanne (Switzerland).
Nuclear fusion
–
The only man-made fusion device to achieve
ignition to date is the
hydrogen bomb. [
citation needed] The detonation of the first device, codenamed
Ivy Mike, occurred in 1952 and is shown here.
41.
Inertial confinement fusion
–
The heated outer layer explodes outward, producing a reaction force against the remainder of the target, accelerating it inwards, compressing the target. This process is designed to shock waves that travel inward through the target. A sufficiently powerful set of waves can compress and heat the fuel at the center so much that fusion reactions occur. The energy released by these reactions will then heat the surrounding fuel, the aim of ICF is to produce a condition known as ignition, where this heating process causes a chain reaction that burns a significant portion of the fuel. ICF is one of two branches of fusion energy research, the other being magnetic confinement fusion. When it was first proposed in the early 1970s, ICF appeared to be an approach to fusion power production. Experiments during the 1970s and 80s demonstrated that the efficiency of devices was much lower than expected. Throughout the 1980s and 90s, many experiments were conducted in order to understand the interaction of high-intensity laser light. These led to the design of machines, much larger. The largest operational ICF experiment is the National Ignition Facility in the US, like those earlier experiments, however, NIF has failed to reach ignition and is, as of 2015, generating about 1⁄3 of the required energy levels. This is a step forward. A similar large-scale device in France, Laser Mégajoule, was inaugurated in October 2014. Experiments have started since then, albeit with low laser energies involved, Fusion reactions combine lighter atoms, such as hydrogen, together to form larger ones. Nuclei are positively charged, and thus repel each other due to the electrostatic force, overcoming this repulsion costs a considerable amount of energy, which is known as the Coulomb barrier or fusion barrier energy. Generally, less energy will be needed to cause lighter nuclei to fuse, as they have less charge and thus a lower energy. The best fuel from a perspective is a one-to-one mix of deuterium and tritium. The D-T mix has a low barrier because of its high ratio of neutrons to protons, the presence of neutral neutrons in the nuclei helps pull them together via the nuclear force, while the presence of positively charged protons pushes the nuclei apart via electrostatic force. Tritium has one of the highest ratios of neutrons to protons of any stable or moderately unstable nuclide—two neutrons, adding protons or removing neutrons increases the energy barrier
Inertial confinement fusion
Inertial confinement fusion
–
Indirect drive laser ICF uses a "hohlraum" which is irradiated with laser beam cones from either side on its inner surface to bathe a fusion microcapsule inside with smooth high intensity X-rays. The highest energy X-rays can be seen leaking through the hohlraum, represented here in orange/red.
Inertial confinement fusion
–
An Inertial confinement fusion target, which was a cylindrical hohlraum target of D-T, being compressed by the Nova Laser. This shot was done in 1995. The image shows the compression of the target, as well as the growth of the Rayleigh-Taylor instabilities.
Inertial confinement fusion
–
Mockup of a gold plated
NIF hohlraum.
42.
Confocal laser scanning microscopy
–
It enables the reconstruction of three-dimensional structures from sets of images obtained at different depths within a thick object. This technique has gained popularity in the scientific and industrial communities and typical applications are in life sciences, semiconductor inspection, a conventional microscope sees as far into the specimen as the light can penetrate, while a confocal microscope only sees images one depth level at a time. In effect, the CLSM achieves a controlled and highly limited depth of focus, the principle of confocal imaging was patented in 1957 by Marvin Minsky and aims to overcome some limitations of traditional wide-field fluorescence microscopes. In a conventional microscope, the entire specimen is flooded evenly in light from a light source. However, as much of the light from sample fluorescence is blocked at the pinhole, as only one point in the sample is illuminated at a time, 2D or 3D imaging requires scanning over a regular raster in the specimen. The beam is scanned across the sample in the plane by using one or more oscillating mirrors. This scanning method usually has a low latency and the scan speed can be varied. Slower scans provide a better signal-to-noise ratio, resulting in better contrast, the thin optical sectioning possible makes these types of microscopes particularly good at 3D imaging and surface profiling of samples. Successive slices make up a z-stack which can either be processed by software to create a 3D image. Biological samples are treated with fluorescent dyes to make selected objects visible. However, the actual dye concentration can be low to minimize the disturbance of biological systems, also, transgenic techniques can create organisms that produce their own fluorescent chimeric molecules. Spinning-disk confocal microscopes use a series of moving pinholes on a disc to scan spots of light, decreased excitation energy reduces photo-toxicity and photo-bleaching of a sample often making it the preferred system for imaging live cells or organisms. Every pinhole has an associated micro-lens, microlens enhanced confocal microscopes are therefore significantly more sensitive than standard spinning disk systems. Yokogawa Electric invented this technology in 1992, programmable array microscopes use an electronically controlled spatial light modulator that produces a set of moving pinholes. The SLM is a device containing an array of pixels with some property of the pixels that can be adjusted electronically. The SLM contains microelectromechanical mirrors or liquid crystal components, the image is usually acquired by a charge coupled device camera. Each of these classes of confocal microscope have particular advantages and disadvantages, most systems are either optimized for recording speed or high spatial resolution. Confocal laser scanning microscopes can have a programmable sampling density and very high resolutions while Nipkow, imaging frame rates are typically slower for single point laser scanning systems than spinning-disk or PAM systems
Confocal laser scanning microscopy
–
An example of a
GFP fusion protein.
Confocal laser scanning microscopy
–
Principle of confocal microscopy.
43.
Two-photon excitation microscopy
–
Two-photon excitation microscopy is a fluorescence imaging technique that allows imaging of living tissue up to about one millimeter in depth. Two-photon excitation microscopy typically uses near-infrared excitation light which can excite fluorescent dyes. However, for each excitation, two photons of infrared light are absorbed, using infrared light minimizes scattering in the tissue. Due to the absorption, the background signal is strongly suppressed. Both effects lead to a penetration depth for these microscopes. Two-photon excitation can be an alternative to confocal microscopy due to its deeper tissue penetration, efficient light detection. Isaac Abella showed in 1962 in cesium vapor that two-photon excitation of atoms is possible. Two photon excited fluorescence microscopy has similarities to confocal laser scanning microscopy, both use focused laser beams scanned in a raster pattern to generate images, and both have an optical sectioning effect. Unlike confocal microscopes, multiphoton microscopes do not contain pinhole apertures that give confocal microscopes their optical sectioning quality, each photon carries approximately half the energy necessary to excite the molecule. An excitation results in the subsequent emission of a fluorescence photon, the probability of the near-simultaneous absorption of two photons is extremely low. Therefore, a flux of excitation photons is typically required. The purpose of employing the two-photon effect is that the spread of the point spread function is substantially lower than for single-photon excitation. As a result, the resolution along the z dimension is improved, in addition, in many interesting cases the shape of the spot and its size can be designed to realize specific desired goals. The most commonly used fluorophores have excitation spectra in the 400–500 nm range, if the fluorophore absorbs two infrared photons simultaneously, it will absorb enough energy to be raised into the excited state. The fluorophore will then emit a photon with a wavelength that depends on the type of fluorophore used. Because two photons are absorbed during the excitation of the fluorophore, the probability for fluorescent emission from the fluorophores increases quadratically with the excitation intensity, therefore, much more two-photon fluorescence is generated where the laser beam is tightly focused than where it is more diffuse. Effectively, excitation is restricted to the focal volume, resulting in a high degree of rejection of out-of-focus objects. This localization of excitation is the key advantage compared to single-photon excitation microscopes, the fluorescence from the sample is then collected by a high-sensitivity detector, such as a photomultiplier tube
Two-photon excitation microscopy
–
Two-photon excitation microscopy of mouse
intestine. Red:
actin. Green:
cell nuclei. Blue: mucus of
goblet cells. Obtained at 780 nm using a
Ti-sapphire laser.
Two-photon excitation microscopy
–
Illumination and contrast methods
44.
Laser capture microdissection
–
Laser-capture microdissection is a method to procure subpopulations of tissue cells under direct microscopic visualization. LCM technology can harvest the cells of interest directly or can isolate specific cells by cutting away unwanted cells to give histologically pure enriched cell populations. A variety of applications exist, DNA genotyping and loss-of-heterozygosity analysis, RNA transcript profiling, cDNA library generation, proteomics discovery. Herein we provide a description of LCM techniques, with an emphasis on tips. The total time required to carry out this protocol is typically 1–1.5 h, human tissues are composed of complex admixtures of different cell types and their biologically meaningful analysis necessitates the procurement of pure samples of the cells of interest. Many approaches have been used in attempts to overcome this difficulty, a laser is coupled into a microscope and focuses onto the tissue on the slide. By movement of the laser by optics or the stage the focus follows a trajectory which is predefined by the user and this trajectory, also called element, is then cut out and separated from the adjacent tissue. After the cutting process, a process has to follow if an extraction process is desired. More recent technologies utilize non-contact microdissection, there are several ways to extract tissue from a microscope slide with a histopathology sample on it. Press a sticky surface onto the sample and tear out and this extracts the desired region, but can also remove particles or unwanted tissue on the surface, because the surface is not selective. Melt a plastic membrane onto the sample and tear out, the heat is introduced, for example, by a red or infrared laser onto a membrane stained with an absorbing dye. As this adheres the desired sample onto the membrane, as with any membrane that is put close to the sample surface. Another danger is the heat, Some molecules like DNA, RNA. Transport by gravity using a microscope or transport by laser pressure catapult. With cut-and-capture, a cap coated with an adhesive is positioned directly on the thinly cut tissue section, an IR laser gently heats the adhesive on the cap fusing it to the underlying tissue and an UV laser cuts through tissue and underlying membrane. The membrane-tissue entity now adheres to the cap and the cells on the cap can be used in downstream applications, currently six primary isolation/collection technologies exist using a microscope and device for cell isolation. IR laser provides a gentle approach to microdissection. A fifth ultraviolet laser based technology uses special slides coated with an energy transfer coating which, the laser cutting width is usually less than 1 µm, thus the target cells are not affected by the laser beam
Laser capture microdissection
–
Laser capture micro-dissection transfer of pure
breast duct epithelial cells. Left panel shows tissue section with selected cells removed. Right panel shows isolated epithelial cells on transfer film.
45.
Military
–
The task of the military is usually defined as defense of the state, and its citizens, and the prosecution of war against another state. The profession of soldiering as part of a military is older than recorded history itself, some of the most enduring images of the classical antiquity portray the power and feats of its military leaders. The Battle of Kadesh in 1274 BC was one of the points of Pharaoh Ramses IIs reign. A thousand years later, the first emperor of unified China, Qin Shi Huang, was so determined to impress the gods with his military might, he was buried with an army of terracotta soldiers. The Romans were dedicated to military matters, leaving to posterity many treatises and writings, as well as a number of lavishly carved triumphal arches. Issue, Possibly cognate with Thousand, cf. Latin and Romance language root word mil-) The first recorded use of the military in English. It comes from the Latin militaris through French, but is of uncertain etymology, the word is now identified as denoting someone that is skilled in use of weapons, or engaged in military service, or in warfare. As a noun, the military usually refers generally to an armed forces, or sometimes, more specifically. In general, it refers to the physicality of armed forces, their personnel, equipment, as an adjective, military originally referred only to soldiers and soldiering, but it soon broadened to apply to land forces in general, and anything to do with their profession. The names of both the Royal Military Academy and United States Military Academy reflect this, as such, it now connotes any activity performed by armed force personnel. Military history is considered to be the history of all conflicts. Military history has a number of facets, one main facet is to learn from past accomplishments and mistakes, so as to more effectively wage war in the future. Another is to create a sense of tradition, which is used to create cohesive military forces. Still another may be to learn to prevent wars more effectively, human knowledge about the military is largely based on both recorded and oral history of military conflicts, their participating armies and navies and, more recently, air forces. In the whole history of humanity, every nation had different needs for military forces, how these needs are determined forms the basis of their composition, equipment, and use of facilities. It also determines what military does in terms of peacetime, All military forces, whether large or small, are military organizations that have official state, and world recognition as such. Organisations with similar features are paramilitary, civil defense, militia and these commonalities of the states military define them. Another role of military personnel is to ensure a continuous replacement of departing servicemen and women through recruitment
Military
–
Soldiers from
the Canadian Grenadier Guards in the
Kandahar Province of Afghanistan
Military
–
CF-18 Hornet launches a laser-guided bomb
Military
–
The
Kawasaki C-1 is a tactical military transport of the
Japan Air Self-Defence Force.
Military
–
Dutch civilians celebrating the arrival of the
I Canadian Corps in
Utrecht as the
Canadian Army liberates the Netherlands from Nazi occupation
46.
Laser applications
–
Many scientific, military, medical and commercial laser applications have been developed since the invention of the laser in 1958. The coherency, high monochromaticity, and ability to reach extremely high powers are all properties which allow for specialized applications. Laser based lidar technology has application in geology, seismology, remote sensing, lasers have been used aboard spacecraft such as in the Cassini-Huygens mission. In astronomy, lasers have been used to create artificial laser guide stars, lasers may also be indirectly used in spectroscopy as a micro-sampling system, a technique termed Laser ablation, which is typically applied to ICP-MS apparatus resulting in the powerful LA-ICP-MS. The principles of spectroscopy are discussed by Demtröder. Most types of laser are a pure source of light. By careful design of the components, the purity of the laser light can be improved more than the purity of any other light source. This makes the laser a useful source for spectroscopy. Other spectroscopic techniques based on lasers can be used to extremely sensitive detectors of various molecules. Due to the power densities achievable by lasers, beam-induced atomic emission is possible. Heat treating with lasers allows selective surface hardening against wear with little or no distortion of the component, because this eliminates much part reworking that is currently done, the laser systems capital cost is recovered in a short time. An inert, absorbent coating for laser heat treatment has also developed that eliminates the fumes generated by conventional paint coatings during the heat-treating process with CO2 laser beams. One consideration crucial to the success of a heat treatment operation is control of the laser beam irradiance on the part surface, the optimal irradiance distribution is driven by the thermodynamics of the laser-material interaction and by the part geometry. Typically, irradiances between 500-5000 W/cm^2 satisfy the constraints and allow the rapid surface heating and minimal total heat input required. For general heat treatment, a square or rectangular beam is one of the best options. For some special applications or applications where the treatment is done on an edge or corner of the part. When the Apollo astronauts visited the moon, they planted retroreflector arrays to make possible the Lunar Laser Ranging Experiment, some laser systems, through the process of mode locking, can produce extremely brief pulses of light - as short as picoseconds or femtoseconds. Such pulses can be used to initiate and analyze chemical reactions, the short pulses can be used to probe the process of the reaction at a very high temporal resolution, allowing the detection of short-lived intermediate molecules
Laser applications
–
Laser pointers
Laser applications
–
A target designator
Laser applications
–
Laser sight used by the
Israel Defense Forces during commando training
Laser applications
–
Smith & Wesson revolver equipped with a laser sight mounted on the
trigger guard.
47.
Directed energy weapons
–
A directed-energy weapon emits highly focused energy, transferring that energy to a target to damage it. These systems of defense are expected to come online in the mid to late-2020s. Light is only slightly affected by gravity. They can have greater speed and range than conventional weapons therefore are suitable for use in space warfare. Although some devices are labelled as microwave weapons, the range is commonly defined as being between 300 MHz and 300 GHz which is within the RF range. It is being used by the U. S. Air Force Research Laboratory, though intended to cause severe pain while leaving no lasting damage, concern has been voiced as to whether the system could cause irreversible damage to the eyes. There has yet to be testing for long-term side effects of exposure to the microwave beam and it can also destroy unshielded electronics, see TEMPEST. The device comes in various sizes including attached to a humvee, vigilant Eagle is an airport defense system that directs high-frequency microwaves towards any projectile that is fired at an aircraft. The system consists of a missile-detecting and tracking subsystem, a command and control system, the MDT is a fixed grid of passive infrared cameras. The command and control system determines the missile launch point, the scanning array projects microwaves that disrupt the surface-to-air missiles guidance system, deflecting it from the aircraft. Bofors HPM Blackout is a high-powered microwave weapon system which is stated to be able to destroy at distance a wide variety of commercial off-the-shelf electronic equipment and it is stated to be not lethal to humans. The effective radiated power of the EL/M-2080 Green Pine radar makes it a candidate for conversion into a directed-energy weapon. Potentially lethal effects are produced only inside 100 metres range, moreover, cheap countermeasures can be applied to existing missiles. An electrolaser lets ionization occur, and then sends an electric current down the conducting ionized track of plasma so formed. It functions as a giant high energy version of the Taser or stun gun. Pulsed Energy Projectile or PEP systems emit an infrared laser pulse which creates rapidly expanding plasma at the target, the resulting sound, shock and electromagnetic waves stun the target and cause pain and temporary paralysis. The weapon is under development and is intended as a weapon in crowd control though it can also be used as a lethal weapon. A Dazzler is a weapon intended to temporarily blind or disorient its target with intense directed radiation
Directed energy weapons
–
United States Humvee with
Active Denial System mounted
Directed energy weapons
–
A
USAF Boeing YAL-1 airborne laser
48.
Directed-energy weapon
–
A directed-energy weapon emits highly focused energy, transferring that energy to a target to damage it. These systems of defense are expected to come online in the mid to late-2020s. Light is only slightly affected by gravity. They can have greater speed and range than conventional weapons therefore are suitable for use in space warfare. Although some devices are labelled as microwave weapons, the range is commonly defined as being between 300 MHz and 300 GHz which is within the RF range. It is being used by the U. S. Air Force Research Laboratory, though intended to cause severe pain while leaving no lasting damage, concern has been voiced as to whether the system could cause irreversible damage to the eyes. There has yet to be testing for long-term side effects of exposure to the microwave beam and it can also destroy unshielded electronics, see TEMPEST. The device comes in various sizes including attached to a humvee, vigilant Eagle is an airport defense system that directs high-frequency microwaves towards any projectile that is fired at an aircraft. The system consists of a missile-detecting and tracking subsystem, a command and control system, the MDT is a fixed grid of passive infrared cameras. The command and control system determines the missile launch point, the scanning array projects microwaves that disrupt the surface-to-air missiles guidance system, deflecting it from the aircraft. Bofors HPM Blackout is a high-powered microwave weapon system which is stated to be able to destroy at distance a wide variety of commercial off-the-shelf electronic equipment and it is stated to be not lethal to humans. The effective radiated power of the EL/M-2080 Green Pine radar makes it a candidate for conversion into a directed-energy weapon. Potentially lethal effects are produced only inside 100 metres range, moreover, cheap countermeasures can be applied to existing missiles. An electrolaser lets ionization occur, and then sends an electric current down the conducting ionized track of plasma so formed. It functions as a giant high energy version of the Taser or stun gun. Pulsed Energy Projectile or PEP systems emit an infrared laser pulse which creates rapidly expanding plasma at the target, the resulting sound, shock and electromagnetic waves stun the target and cause pain and temporary paralysis. The weapon is under development and is intended as a weapon in crowd control though it can also be used as a lethal weapon. A Dazzler is a weapon intended to temporarily blind or disorient its target with intense directed radiation
Directed-energy weapon
–
United States Humvee with
Active Denial System mounted
Directed-energy weapon
–
A
USAF Boeing YAL-1 airborne laser
49.
Boeing YAL-1
–
The Boeing YAL-1 Airborne Laser Testbed weapons system was a megawatt-class chemical oxygen iodine laser mounted inside a modified Boeing 747-400F. It is primarily designed as a defense system to destroy tactical ballistic missiles while in boost phase. The aircraft was designated YAL-1A in 2004 by the U. S. Department of Defense, the YAL-1 with a low-power laser was test-fired in flight at an airborne target in 2007. A high-energy laser was used to intercept a test target in January 2010, funding for the program was cut in 2010 and the program was canceled in December 2011. It made its flight on February 14,2012 to Davis–Monthan Air Force Base in Tucson, Arizona to be kept in storage at the Boneyard by the 309th Aerospace Maintenance. It was ultimately scrapped in September 2014 after all parts were removed. The Airborne Laser Laboratory was a prototype installed in a Boeing NKC-135A. It shot down missiles in tests conducted in the 1980s. The Airborne Laser program was initiated by the US Air Force in 1996 with the awarding of a product definition risk reduction contract to Boeings ABL team, in 2001, the program was transferred to the MDA and converted to an acquisition program. The development of the system was being accomplished by a team of contractors, Boeing Defense, Space & Security provides the aircraft, the management team and the systems integration processes. Northrop Grumman was supplying the COIL, and Lockheed Martin was supplying the nose turret and these tests fully qualified the system so that it could be integrated into the actual aircraft. Following the completion of the tests, the laboratory was dismantled, Boeing completed initial modifications to a new 747-400F off the production line in 2002, culminating in its first flight on July 18,2002 from Boeings Wichita, Kansas facility. Ground testing of the COIL resulted in its firing in 2004. The YAL-1 was assigned to the 417th Flight Test Squadron Airborne Laser Combined Test Force at Edwards AFB, besides the COIL, the system also includes two kilowatt-class Target Illuminator Lasers for target tracking. On March 15,2007, the YAL-1 successfully fired this laser in flight, the target was an NC-135E Big Crow test aircraft that has been specially modified with a signboard target on its fuselage. The test validated the ability to track an airborne target and measure. The next phase in the test program involved the surrogate high-energy laser, a stand-in for the COIL, the COIL system was installed in the aircraft and undergoing ground testing by July 2008. The ABL program has significant affordability and technology problems and the proposed operational role is highly questionable
Boeing YAL-1
–
YAL-1 Airborne Laser
Boeing YAL-1
–
YAL-1 undergoing modification in November 2004, at
Edwards AFB
Boeing YAL-1
–
Contractors dismantle the Boeing 747 fuselage portion of the System Integration Laboratory at the Birk Flight Test Center.
Boeing YAL-1
–
In storage with engines removed. Ultimately broken up on 25 September 2014.
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