1.
Optical microscope
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The optical microscope, often referred to as light microscope, is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were invented in their present compound form in the 17th century. Basic optical microscopes can be simple, although there are many complex designs which aim to improve resolution. The image from a microscope can be captured by normal light-sensitive cameras to generate a micrograph. Originally images were captured by photographic film but modern developments in CMOS, purely digital microscopes are now available which use a CCD camera to examine a sample, showing the resulting image directly on a computer screen without the need for eyepieces. Alternatives to optical microscopy which do not use visible light include scanning electron microscopy, there are two basic types of optical microscopes, simple microscopes and compound microscopes. A simple microscope is one which uses a lens for magnification. A compound microscope uses several lenses to enhance the magnification of an object, the vast majority of modern research microscopes are compound microscopes while some cheaper commercial digital microscopes are simple single lens microscopes. Compound microscopes can be divided into a variety of other types of microscopes which differ in their optical configurations, cost. A simple microscope uses a lens or set of lenses to enlarge an object through angular magnification alone, the use of a single convex lens or groups of lenses are still found in simple magnification devices such as the magnifying glass, loupes, and eyepieces for telescopes and microscopes. A compound microscope uses a close to the object being viewed to collect light which focuses a real image of the object inside the microscope. That image is magnified by a second lens or group of lenses that gives the viewer an enlarged inverted virtual image of the object. The use of a compound objective/eyepiece combination allows for higher magnification. Common compound microscopes often feature exchangeable objective lenses, allowing the user to quickly adjust the magnification, a compound microscope also enables more advanced illumination setups, such as phase contrast. There are many variants of the optical microscope design for specialized purposes. Comparison microscope, which has two light paths allowing direct comparison of two samples via one image in each eye. Inverted microscope, for studying samples from below, useful for cell cultures in liquid, student microscope, designed for low cost, durability, and ease of use. Polarizing microscope, similar to the petrographic microscope, phase contrast microscope, which applies the phase contrast illumination method
2.
Cell (biology)
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The cell is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life that can replicate independently, the study of cells is called cell biology. Cells consist of cytoplasm enclosed within a membrane, which contains many such as proteins. Organisms can be classified as unicellular or multicellular, while the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion cells. Most plant and animal cells are only under a microscope. The cell was discovered by Robert Hooke in 1665, who named the unit for its resemblance to cells inhabited by Christian monks in a monastery. Cells emerged on Earth at least 3.5 billion years ago, Cells are of two types, eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular, prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling and being self-sustaining. They are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as the nucleus, prokaryotes include two of the domains of life, bacteria and archaea. The DNA of a prokaryotic cell consists of a chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid, most prokaryotes are the smallest of all organisms ranging from 0.5 to 2.0 µm in diameter. Though most prokaryotes have both a cell membrane and a wall, there are exceptions such as Mycoplasma and Thermoplasma which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, the cell wall consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from expanding and bursting from osmotic pressure due to a hypotonic environment, some eukaryotic cells also have a cell wall. Inside the cell is the region that contains the genome, ribosomes. The genetic material is found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular, linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. Though not forming a nucleus, the DNA is condensed in a nucleoid, plasmids encode additional genes, such as antibiotic resistance genes
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Electron microscope
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An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. Transmission electron microscopes use electrostatic and electromagnetic lenses to control the electron beam and these electron optical lenses are analogous to the glass lenses of an optical light microscope. Industrially, electron microscopes are used for quality control and failure analysis. Modern electron microscopes produce electron micrographs using specialized digital cameras and frame grabbers to capture the image, the first electromagnetic lens was developed in 1926 by Hans Busch. According to Dennis Gabor, the physicist Leó Szilárd tried in 1928 to convince Busch to build an electron microscope, two years later, in 1933, Ruska built an electron microscope that exceeded the resolution attainable with an optical microscope. Moreover, Reinhold Rudenberg, the director of Siemens-Schuckertwerke, obtained the patent for the electron microscope in May 1931. In 1932, Ernst Lubcke of Siemens & Halske built and obtained images from an electron microscope. Five years later, the firm financed the work of Ernst Ruska and Bodo von Borries, also in 1937, Manfred von Ardenne pioneered the scanning electron microscope. The first commercial electron microscope was produced in 1938 by Siemens, although contemporary transmission electron microscopes are capable of two million-power magnification, as scientific instruments, they remain based upon Ruska’s prototype. The original form of electron microscope, the electron microscope uses a high voltage electron beam to illuminate the specimen. The electron beam is produced by a gun, commonly fitted with a tungsten filament cathode as the electron source. When it emerges from the specimen, the electron beam carries information about the structure of the specimen that is magnified by the lens system of the microscope. The image detected by the camera may be displayed on a monitor or computer. The resolution of TEMs is limited primarily by spherical aberration, but a new generation of aberration correctors have been able to partially overcome spherical aberration to increase resolution. The ability to determine the positions of atoms within materials has made the HRTEM an important tool for nano-technologies research, transmission electron microscopes are often used in electron diffraction mode. The major disadvantage of the electron microscope is the need for extremely thin sections of the specimens. Biological specimens are required to be chemically fixed, dehydrated and embedded in a polymer resin to stabilize them sufficiently to allow ultrathin sectioning. Sections of biological specimens, organic polymers and similar materials may require treatment with heavy atom labels in order to achieve the required image contrast
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Ancient Greek
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Ancient Greek includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD. It is often divided into the Archaic period, Classical period. It is antedated in the second millennium BC by Mycenaean Greek, the language of the Hellenistic phase is known as Koine. Koine is regarded as a historical stage of its own, although in its earliest form it closely resembled Attic Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects, Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers. It has contributed many words to English vocabulary and has been a subject of study in educational institutions of the Western world since the Renaissance. This article primarily contains information about the Epic and Classical phases of the language, Ancient Greek was a pluricentric language, divided into many dialects. The main dialect groups are Attic and Ionic, Aeolic, Arcadocypriot, some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions. There are also several historical forms, homeric Greek is a literary form of Archaic Greek used in the epic poems, the Iliad and Odyssey, and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic, the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period and they have the same general outline, but differ in some of the detail. The invasion would not be Dorian unless the invaders had some relationship to the historical Dorians. The invasion is known to have displaced population to the later Attic-Ionic regions, the Greeks of this period believed there were three major divisions of all Greek people—Dorians, Aeolians, and Ionians, each with their own defining and distinctive dialects. Often non-west is called East Greek, Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian had come under a strong Northwest Greek influence, and can in some respects be considered a transitional dialect, thessalian likewise had come under Northwest Greek influence, though to a lesser degree. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, and Northern Peloponnesus Doric. The Lesbian dialect was Aeolic Greek and this dialect slowly replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek, by about the 6th century AD, the Koine had slowly metamorphosized into Medieval Greek
5.
Laboratory
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A laboratory is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratories used for scientific research take many forms because of the requirements of specialists in the various fields of science. A physics laboratory might contain a particle accelerator or vacuum chamber, a chemist or biologist might use a wet laboratory, while a psychologists laboratory might be a room with one-way mirrors and hidden cameras in which to observe behavior. In some laboratories, such as commonly used by computer scientists. Scientists in other fields will use other types of laboratories. Engineers use laboratories as well to design, build, and test technological devices, scientific laboratories can be found as research and learning spaces in schools and universities, industry, government, or military facilities, and even aboard ships and spacecraft. Early instances of laboratories recorded in English involved alchemy and the preparation of medicines, larger or more sophisticated equipment is generally called a scientific instrument. Both laboratory equipment and scientific instruments are increasingly being designed and shared using open hardware principles, open source labs use open source scientific hardware. The title of laboratory is used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories. In many labs, though, hazards are present, in laboratories where dangerous conditions might exist, safety precautions are important. Rules exist to minimize the risk, and safety equipment is used to protect the lab user from injury or to assist in responding to an emergency. This standard is referred to as the Laboratory Standard. Under this standard, a laboratory is required to produce a Chemical Hygiene Plan which addresses the specific hazards found in its location, the CHP must be reviewed annually. Many schools and businesses employ safety, health, and environmental specialists, such as a Chemical Hygiene Officer to develop, manage, and evaluate their CHP. Additionally, third party review is used to provide an objective outside view which provides a fresh look at areas. An important element of such audits is the review of regulatory compliance, training is critical to the ongoing safe operation of the laboratory facility. Educators, staff and management must be engaged in working to reduce the likelihood of accidents, injuries, efforts are made to ensure laboratory safety videos are both relevant and engaging. The dictionary definition of laboratory at Wiktionary Media related to Laboratory at Wikimedia Commons Nobel Laureates Interactive 360° Laboratories
6.
Microscopy
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Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye. There are three branches of microscopy, optical, electron, and scanning probe microscopy. This process may be carried out by irradiation of the sample or by scanning of a fine beam over the sample. Scanning probe microscopy involves the interaction of a probe with the surface of the object of interest. The development of microscopy revolutionized biology, gave rise to the field of histology and so remains an essential technique in the life and physical sciences. Optical or light microscopy involves passing visible light transmitted through or reflected from the sample through a single or multiple lenses to allow a view of the sample. The resulting image can be detected directly by the eye, imaged on a plate or captured digitally. The single lens with its attachments, or the system of lenses and imaging equipment, along with the lighting equipment, sample stage and support. The most recent development is the microscope, which uses a CCD camera to focus on the exhibit of interest. The image is shown on a screen, so eye-pieces are unnecessary. Limitations of standard optical microscopy lie in three areas, This technique can only image dark or strongly refracting objects effectively, diffraction limits resolution to approximately 0.2 micrometres. This limits the practical limit to ~1500x. Out of focus light from points outside the focal plane reduces image clarity, live cells in particular generally lack sufficient contrast to be studied successfully, since the internal structures of the cell are colourless and transparent. The most common way to increase contrast is to stain the different structures with selective dyes, staining may also introduce artifacts, apparent structural details that are caused by the processing of the specimen and are thus not legitimate features of the specimen. In general, these make use of differences in the refractive index of cell structures. It is comparable to looking through a window, you dont see the glass. There is a difference, as glass is a material. The human eye is not sensitive to this difference in phase, in order to improve specimen contrast or highlight certain structures in a sample special techniques must be used
7.
Science
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Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe. The formal sciences are often excluded as they do not depend on empirical observations, disciplines which use science, like engineering and medicine, may also be considered to be applied sciences. However, during the Islamic Golden Age foundations for the method were laid by Ibn al-Haytham in his Book of Optics. In the 17th and 18th centuries, scientists increasingly sought to formulate knowledge in terms of physical laws, over the course of the 19th century, the word science became increasingly associated with the scientific method itself as a disciplined way to study the natural world. It was during this time that scientific disciplines such as biology, chemistry, Science in a broad sense existed before the modern era and in many historical civilizations. Modern science is distinct in its approach and successful in its results, Science in its original sense was a word for a type of knowledge rather than a specialized word for the pursuit of such knowledge. In particular, it was the type of knowledge which people can communicate to each other, for example, knowledge about the working of natural things was gathered long before recorded history and led to the development of complex abstract thought. This is shown by the construction of calendars, techniques for making poisonous plants edible. For this reason, it is claimed these men were the first philosophers in the strict sense and they were mainly speculators or theorists, particularly interested in astronomy. In contrast, trying to use knowledge of nature to imitate nature was seen by scientists as a more appropriate interest for lower class artisans. A clear-cut distinction between formal and empirical science was made by the pre-Socratic philosopher Parmenides, although his work Peri Physeos is a poem, it may be viewed as an epistemological essay on method in natural science. Parmenides ἐὸν may refer to a system or calculus which can describe nature more precisely than natural languages. Physis may be identical to ἐὸν and he criticized the older type of study of physics as too purely speculative and lacking in self-criticism. He was particularly concerned that some of the early physicists treated nature as if it could be assumed that it had no intelligent order, explaining things merely in terms of motion and matter. The study of things had been the realm of mythology and tradition, however. Aristotle later created a less controversial systematic programme of Socratic philosophy which was teleological and he rejected many of the conclusions of earlier scientists. For example, in his physics, the sun goes around the earth, each thing has a formal cause and final cause and a role in the rational cosmic order. Motion and change is described as the actualization of potentials already in things, while the Socratics insisted that philosophy should be used to consider the practical question of the best way to live for a human being, they did not argue for any other types of applied science
8.
Light
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Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to light, which is visible to the human eye and is responsible for the sense of sight. Visible light is defined as having wavelengths in the range of 400–700 nanometres, or 4.00 × 10−7 to 7.00 × 10−7 m. This wavelength means a range of roughly 430–750 terahertz. The main source of light on Earth is the Sun, sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the used by living things. Historically, another important source of light for humans has been fire, with the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence, for example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey. Visible light, as all types of electromagnetic radiation, is experimentally found to always move at this speed in a vacuum. In physics, the term sometimes refers to electromagnetic radiation of any wavelength. In this sense, gamma rays, X-rays, microwaves and radio waves are also light, like all types of light, visible light is emitted and absorbed in tiny packets called photons and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality, the study of light, known as optics, is an important research area in modern physics. Generally, EM radiation, or EMR, is classified by wavelength into radio, microwave, infrared, the behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths, when EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. There exist animals that are sensitive to various types of infrared, infrared sensing in snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it, above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers and the internal lens below 400. Furthermore, the rods and cones located in the retina of the eye cannot detect the very short ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses are able to detect ultraviolet, by quantum photon-absorption mechanisms, various sources define visible light as narrowly as 420 to 680 to as broadly as 380 to 800 nm
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Fluorescence microscope
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The specimen is illuminated with light of a specific wavelength which is absorbed by the fluorophores, causing them to emit light of longer wavelengths. The illumination light is separated from the much weaker emitted fluorescence through the use of an emission filter. Typical components of a microscope are a light source, the excitation filter, the dichroic mirror. The filters and the dichroic beamsplitter are chosen to match the spectral excitation and emission characteristics of the used to label the specimen. In this manner, the distribution of a fluorophore is imaged at a time. Multi-color images of types of fluorophores must be composed by combining several single-color images. Most fluorescence microscopes in use are epifluorescence microscopes, where excitation of the fluorophore and these microscopes are widely used in biology and are the basis for more advanced microscope designs, such as the confocal microscope and the total internal reflection fluorescence microscope. The majority of fluorescence microscopes, especially used in the life sciences, are of the epifluorescence design shown in the diagram. Light of the wavelength is focused on the specimen through the objective lens. Fluorescence microscopy requires intense, near-monochromatic, illumination which some widespread light sources, four main types of light source are used, including xenon arc lamps or mercury-vapor lamps with an excitation filter, lasers, supercontinuum sources, and high-power LEDs. In order for a sample to be suitable for fluorescence microscopy it must be fluorescent, there are several methods of creating a fluorescent sample, the main techniques are labelling with fluorescent stains or, in the case of biological samples, expression of a fluorescent protein. Alternatively the intrinsic fluorescence of a sample can be used, as a result, there is a diverse range of techniques for fluorescent staining of biological samples. Many fluorescent stains have been designed for a range of biological molecules, some of these are small molecules which are intrinsically fluorescent and bind a biological molecule of interest. Major examples of these are nucleic acid stains like DAPI and Hoechst and DRAQ5 and DRAQ7 which all bind the minor groove of DNA, others are drugs or toxins which bind specific cellular structures and have been derivatised with a fluorescent reporter. A major example of class of fluorescent stain is phalloidin which is used to stain actin fibres in mammalian cells. Immunofluorescence is a technique which uses the specific binding of an antibody to its antigen in order to label specific proteins or other molecules within the cell. A sample is treated with an antibody specific for the molecule of interest. A fluorophore can be conjugated to the primary antibody
10.
Scanning electron microscope
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A scanning electron microscope is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography. The electron beam is scanned in a raster scan pattern. SEM can achieve better than 1 nanometer. Specimens can be observed in vacuum, in low vacuum, in wet conditions. The most common SEM mode is detection of electrons emitted by atoms excited by the electron beam. The number of electrons that can be detected depends, among other things. By scanning the sample and collecting the electrons that are emitted using a special detector. An account of the history of SEM has been presented by McMullan. Ardenne applied the principle not only to achieve magnification but also to purposefully eliminate the chromatic aberration otherwise inherent in the electron microscope. He further discussed the various modes, possibilities and theory of SEM. The types of produced by an SEM include secondary electrons, reflected or back-scattered electrons, photons of characteristic X-rays and light, absorbed current. Secondary electron detectors are standard equipment in all SEMs, but it is rare that a machine would have detectors for all other possible signals. The signals result from interactions of the beam with atoms at various depths within the sample. In the most common or standard detection mode, ie secondary electron imaging or SEI, consequently, SEM can produce very high-resolution images of a sample surface, revealing details less than 1 nm in size. Back-scattered electrons are beam electrons that are reflected from the sample by elastic scattering and they emerge from deeper locations within the specimen and consequently the resolution of BSE images is generally poorer than SE images. BSE images can provide information about the distribution of different elements in the sample, characteristic X-rays are emitted when the electron beam removes an inner shell electron from the sample, causing a higher-energy electron to fill the shell and release energy. These characteristic X-rays are used to identify the composition and measure the abundance of elements in the sample, due to the very narrow electron beam, SEM micrographs have a large depth of field yielding a characteristic three-dimensional appearance useful for understanding the surface structure of a sample
11.
Scanning probe microscope
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Scanning probe microscopy is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. SPM was founded in 1981, with the invention of the scanning tunneling microscope, the first successful scanning tunneling microscope experiment was done by Binnig and Rohrer. The key to their success was using a loop to regulate gap distance between the sample and the probe. Many scanning probe microscopes can image several interactions simultaneously, the manner of using these interactions to obtain an image is generally called a mode. The resolution varies somewhat from technique to technique, but some probe techniques reach a rather impressive atomic resolution and this is due largely because piezoelectric actuators can execute motions with a precision and accuracy at the atomic level or better on electronic command. This family of techniques can be called piezoelectric techniques, the other common denominator is that the data are typically obtained as a two-dimensional grid of data points, visualized in false color as a computer image. To form images, scanning probe microscopes raster scan the tip over the surface, at discrete points in the raster scan a value is recorded. These recorded values are displayed as a map to produce the final STM images, usually using a black. In constant interaction mode, a loop is used to physically move the probe closer to or further from the surface under study to maintain a constant interaction. This interaction depends on the type of SPM, for scanning tunneling microscopy the interaction is the current, for contact mode AFM or MFM it is the cantilever deflection. The type of loop used is usually a PI-loop, which is a PID-loop where the differential gain has been set to zero. The z position of the tip is recorded periodically and displayed as a heat map and this is normally referred to as a topography image. In this mode a second image, known as the signal or error image is also taken. Under perfect operation this image would be a blank at a constant value which was set on the feedback loop, under real operation the image shows noise and often some indication of the surface structure. The user can use this image to edit the feedback gains to minimise features in the error signal, if the gains are set incorrectly, many imaging artifacts are possible. If gains are too low features can appear smeared, if the gains are too high the feedback can become unstable and oscillate, producing striped features in the images which are not physical. In constant height mode the probe is not moved in the z-axis during the raster scan, instead the value of the interaction under study is recorded. This recorded information is displayed as a map, and is usually referred to as a constant height image
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Paris
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Paris is the capital and most populous city of France. It has an area of 105 square kilometres and a population of 2,229,621 in 2013 within its administrative limits, the agglomeration has grown well beyond the citys administrative limits. By the 17th century, Paris was one of Europes major centres of finance, commerce, fashion, science, and the arts, and it retains that position still today. The aire urbaine de Paris, a measure of area, spans most of the Île-de-France region and has a population of 12,405,426. It is therefore the second largest metropolitan area in the European Union after London, the Metropole of Grand Paris was created in 2016, combining the commune and its nearest suburbs into a single area for economic and environmental co-operation. Grand Paris covers 814 square kilometres and has a population of 7 million persons, the Paris Region had a GDP of €624 billion in 2012, accounting for 30.0 percent of the GDP of France and ranking it as one of the wealthiest regions in Europe. The city is also a rail, highway, and air-transport hub served by two international airports, Paris-Charles de Gaulle and Paris-Orly. Opened in 1900, the subway system, the Paris Métro. It is the second busiest metro system in Europe after Moscow Metro, notably, Paris Gare du Nord is the busiest railway station in the world outside of Japan, with 262 millions passengers in 2015. In 2015, Paris received 22.2 million visitors, making it one of the top tourist destinations. The association football club Paris Saint-Germain and the rugby union club Stade Français are based in Paris, the 80, 000-seat Stade de France, built for the 1998 FIFA World Cup, is located just north of Paris in the neighbouring commune of Saint-Denis. Paris hosts the annual French Open Grand Slam tennis tournament on the red clay of Roland Garros, Paris hosted the 1900 and 1924 Summer Olympics and is bidding to host the 2024 Summer Olympics. The name Paris is derived from its inhabitants, the Celtic Parisii tribe. Thus, though written the same, the name is not related to the Paris of Greek mythology. In the 1860s, the boulevards and streets of Paris were illuminated by 56,000 gas lamps, since the late 19th century, Paris has also been known as Panam in French slang. Inhabitants are known in English as Parisians and in French as Parisiens and they are also pejoratively called Parigots. The Parisii, a sub-tribe of the Celtic Senones, inhabited the Paris area from around the middle of the 3rd century BC. One of the areas major north-south trade routes crossed the Seine on the île de la Cité, this place of land and water trade routes gradually became a town
13.
Timeline of microscope technology
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Timeline of microscope technology 167 BCE - The Chinese use water microscopes made of a lens and a water-filled tube to visualize the unseen. Up to 2000 BCE - The Assyrians manufacture the worlds oldest surviving lenses,1267 Roger Bacon explains the principles of the lens and proposes the idea of telescope and microscope. 1590 - Dutch spectacle-makers Hans Jansen and his son Zacharias Jansen,1609 - Galileo Galilei develops a compound microscope with a convex and a concave lens. 1612 - Galileo presents occhiolino to Polish king Sigismund III,1619 - Cornelius Drebbel presents, in London, a compound microscope with two convex lenses. C.1622 - Drebbel presents his invention in Rome,1624 - Galileo presents his occhiolino to Prince Federico Cesi, founder of the Accademia dei Lincei. 1665 - Robert Hooke publishes Micrographia, a collection of biological micrographs and he coins the word cell for the structures he discovers in cork bark. 1674 - Anton van Leeuwenhoek improves on a microscope for viewing biological specimens. 1863 - Henry Clifton Sorby develops a metallurgical microscope to observe structure of meteorites, 1860s - Ernst Abbe discovers the Abbe sine condition, a breakthrough in microscope design, which until then was largely based on trial and error. The company of Carl Zeiss exploited this discovery and becomes the dominant microscope manufacturer of its era,1928 - Edward Hutchinson Synge publishes theory underlying the near-field scanning optical microscope 1931 - Ernst Ruska starts to build the first electron microscope. It is a Transmission electron microscope 1936 - Erwin Wilhelm Müller invents the field emission microscope,1938 - James Hillier builds another TEM1951 - Erwin Wilhelm Müller invents the field ion microscope and is the first to see atoms. 1953 - Frits Zernike, professor of physics, receives the Nobel Prize in Physics for his invention of the phase contrast microscope. 1955 - George Nomarski, professor of microscopy, published the basis of Differential interference contrast microscopy. 1967 - Erwin Wilhelm Müller adds time-of-flight spectroscopy to the field ion microscope, making the first atom probe,1981 - Gerd Binnig and Heinrich Rohrer develop the scanning tunneling microscope. 1988 - Kingo Itaya invents the Electrochemical scanning tunneling microscope 1991 - Kelvin probe force microscope invented
14.
Greeks
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The Greeks or Hellenes are an ethnic group native to Greece, Cyprus, southern Albania, Turkey, Sicily, Egypt and, to a lesser extent, other countries surrounding the Mediterranean Sea. They also form a significant diaspora, with Greek communities established around the world, many of these regions coincided to a large extent with the borders of the Byzantine Empire of the late 11th century and the Eastern Mediterranean areas of ancient Greek colonization. The cultural centers of the Greeks have included Athens, Thessalonica, Alexandria, Smyrna, most ethnic Greeks live nowadays within the borders of the modern Greek state and Cyprus. The Greek genocide and population exchange between Greece and Turkey nearly ended the three millennia-old Greek presence in Asia Minor, other longstanding Greek populations can be found from southern Italy to the Caucasus and southern Russia and Ukraine and in the Greek diaspora communities in a number of other countries. Today, most Greeks are officially registered as members of the Greek Orthodox Church, the Greeks speak the Greek language, which forms its own unique branch within the Indo-European family of languages, the Hellenic. They are part of a group of ethnicities, described by Anthony D. Smith as an archetypal diaspora people. Both migrations occur at incisive periods, the Mycenaean at the transition to the Late Bronze Age, the Mycenaeans quickly penetrated the Aegean Sea and, by the 15th century BC, had reached Rhodes, Crete, Cyprus and the shores of Asia Minor. Around 1200 BC, the Dorians, another Greek-speaking people, followed from Epirus, the Dorian invasion was followed by a poorly attested period of migrations, appropriately called the Greek Dark Ages, but by 800 BC the landscape of Archaic and Classical Greece was discernible. The Greeks of classical antiquity idealized their Mycenaean ancestors and the Mycenaean period as an era of heroes, closeness of the gods. The Homeric Epics were especially and generally accepted as part of the Greek past, as part of the Mycenaean heritage that survived, the names of the gods and goddesses of Mycenaean Greece became major figures of the Olympian Pantheon of later antiquity. The ethnogenesis of the Greek nation is linked to the development of Pan-Hellenism in the 8th century BC, the works of Homer and Hesiod were written in the 8th century BC, becoming the basis of the national religion, ethos, history and mythology. The Oracle of Apollo at Delphi was established in this period, the classical period of Greek civilization covers a time spanning from the early 5th century BC to the death of Alexander the Great, in 323 BC. It is so named because it set the standards by which Greek civilization would be judged in later eras, the Peloponnesian War, the large scale civil war between the two most powerful Greek city-states Athens and Sparta and their allies, left both greatly weakened. Many Greeks settled in Hellenistic cities like Alexandria, Antioch and Seleucia, two thousand years later, there are still communities in Pakistan and Afghanistan, like the Kalash, who claim to be descended from Greek settlers. The Hellenistic civilization was the period of Greek civilization, the beginnings of which are usually placed at Alexanders death. This Hellenistic age, so called because it saw the partial Hellenization of many non-Greek cultures and this age saw the Greeks move towards larger cities and a reduction in the importance of the city-state. These larger cities were parts of the still larger Kingdoms of the Diadochi, Greeks, however, remained aware of their past, chiefly through the study of the works of Homer and the classical authors. An important factor in maintaining Greek identity was contact with barbarian peoples and this led to a strong desire among Greeks to organize the transmission of the Hellenic paideia to the next generation
15.
Magnifying glass
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A magnifying glass is a convex lens that is used to produce a magnified image of an object. The lens is mounted in a frame with a handle. A sheet magnifier consists of very narrow concentric ring-shaped lenses. This arrangement is known as a Fresnel lens, a magnifying glass can also be used to focus light, such as to concentrate the suns radiation to create a hot spot at the focus for fire starting. The magnifying glass is an icon of detective fiction, particularly that of Sherlock Holmes, roger Bacon described the properties of a magnifying glass in 13th-century England. Eyeglasses were developed in 13th-century Italy, the magnification of a magnifying glass depends upon where it is placed between the users eye and the object being viewed, and the total distance between them. The magnifying power is equivalent to angular magnification, the magnifying power is the ratio of the sizes of the images formed on the users retina with and without the lens. For the without case, it is assumed that the user would bring the object as close to one eye as possible without it becoming blurry. This point, known as the point, varies with age. In a young child, it can be as close as 5 cm, while, magnifiers are typically characterized using a standard value of 0.25 m. The highest magnifying power is obtained by putting the lens very close to one eye and moving the eye, the object will then typically also be close to the lens. The magnifying power obtained in this condition is MP0 = Φ +1, where Φ is the power in dioptres. This value of the power is the one normally used to characterize magnifiers. It is typically denoted m×, where m = MP0 and this is sometimes called the total power of the magnifier. However, magnifiers are not always used as described above because it is comfortable to put the magnifier close to the object. The eye can then be a distance away, and a good image can be obtained very easily. The magnifying power in case is roughly MP = Φ. A typical magnifying glass might have a length of 25 cm
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Eyeglasses
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Glasses are typically used for vision correction, such as with reading glasses and glasses used for nearsightedness. Safety glasses provide eye protection against flying debris for construction workers or lab technicians, some types of safety glasses are used to protect against visible and near-visible light or radiation. Glasses are worn for eye protection in some sports, such as squash, Glasses wearers may use a strap to prevent the glasses from falling off during movement or sports. Wearers of glasses that are used only part of the time may have the attached to a cord that goes around their neck. Sunglasses allow better vision in daylight, and may protect ones eyes against damage from high levels of ultraviolet light. Typical sunglasses are darkened for protection against bright light or glare, some specialized glasses are clear in dark or indoor conditions, most sunglasses do not have corrective power in the lenses, however, special prescription sunglasses can be ordered. Specialized glasses may be used for viewing specific visual information or 3D glasses for viewing three-dimensional movies, sometimes glasses with no corrective power in the lenses are worn simply for aesthetic or fashion purposes. Even with glasses used for correction, a wide range of designs are available for fashion purposes, using plastic, wire. The number of Americans who are nearsighted has doubled since the 1970s, people are more likely to need glasses the older they get with 93% of people between the age of 65-75 wearing corrective lenses. They can be classified by their function, but also appear in combinations such as prescription sunglasses or safety glasses with enhanced magnification. Corrective lenses are used to correct refractive errors by bending the light entering the eye in order to alleviate the effects of such as nearsightedness, farsightedness or astigmatism. The ability of eyes to accommodate their focus to near. Also, few people have eyes that show exactly equal refractive characteristics, one may need a stronger, a common condition in people over forty years old is presbyopia, which is caused by the eyes crystalline lens losing elasticity, progressively reducing the ability of the lens to accommodate. Corrective lenses, to bring the back into focus on the retina, are made to conform to the prescription of an ophthalmologist or optometrist. A lensmeter can be used to verify the specifications of a pair of glasses. Corrective eyeglasses can significantly improve the quality of the wearer. Not only do they enhance the visual experience, but can also reduce problems that result from eye strain. Pinhole glasses are a type of glasses that do not use a lens
17.
Objective (optics)
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In optical engineering, the objective is the optical element that gathers light from the object being observed and focuses the light rays to produce a real image. Objectives can be a lens or mirror, or combinations of several optical elements. They are used in microscopes, telescopes, cameras, slide projectors, CD players, objectives are also called object lenses, object glasses, or objective glasses. The objective lens of a microscope is the one at the bottom near the sample, at its simplest, it is a very high-powered magnifying glass, with very short focal length. This is brought close to the specimen being examined so that the light from the specimen comes to a focus inside the microscope tube. The objective itself is usually a cylinder containing one or more lenses that are made of glass. Microscope objectives are characterized by two parameters, magnification and numerical aperture, the magnification typically ranges from 4× to 100×. Numerical aperture for microscope lenses typically ranges from 0.10 to 1.25, corresponding to focal lengths of about 40 mm to 2 mm, respectively. A typical microscope has three or four lenses with different magnifications, screwed into a circular nosepiece which may be rotated to select the required lens. These lenses are often color coded for easier use, the least powerful lens is called the scanning objective lens, and is typically a 4× objective. The second lens is referred to as the objective lens and is typically a 10× lens. The most powerful out of the three is referred to as the large objective lens and is typically 40–100×. Some microscopes use an oil-immersion or water-immersion lens, which can have greater than 100. These objectives are designed for use with refractive index matching oil or water. These lenses give greater resolution at high magnification, numerical apertures as high as 1.6 can be achieved with oil immersion. Camera lenses need to cover a large plane so are made up of a number of optical lens elements to correct optical aberrations. Image projectors use objective lenses that simply reverse the function of a lens, with lenses designed to cover a large image plane. In a telescope the objective is the lens at the front end of a refractor or the primary mirror of a reflecting or catadioptric telescope
18.
Eyepiece
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An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device, the objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed near the point of the objective to magnify this image. The amount of magnification depends on the length of the eyepiece. An eyepiece consists of several elements in a housing, with a barrel on one end. The barrel is shaped to fit in an opening of the instrument to which it is attached. The image can be focused by moving the eyepiece nearer and further from the objective, most instruments have a focusing mechanism to allow movement of the shaft in which the eyepiece is mounted, without needing to manipulate the eyepiece directly. The eyepieces of binoculars are usually mounted in the binoculars, causing them to have a pre-determined magnification. With telescopes and microscopes, however, eyepieces are usually interchangeable, by switching the eyepiece, the user can adjust what is viewed. For instance, eyepieces will often be interchanged to increase or decrease the magnification of a telescope, eyepieces also offer varying fields of view, and differing degrees of eye relief for the person who looks through them. Several properties of an eyepiece are likely to be of interest to a user of an optical instrument, eyepieces are optical systems where the entrance pupil is invariably located outside of the system. They must be designed for optimal performance for a distance to this entrance pupil. In a refracting astronomical telescope the entrance pupil is identical with the objective and this may be several feet distant from the eyepiece, whereas with a microscope eyepiece the entrance pupil is close to the back focal plane of the objective, mere inches from the eyepiece. Microscope eyepieces may be corrected differently from telescope eyepieces, however, elements are the individual lenses, which may come as simple lenses or singlets and cemented doublets or triplets. When lenses are cemented together in pairs or triples, the elements are called groups. The first eyepieces had only a lens element, which delivered highly distorted images. Two and three-element designs were invented soon after, and quickly became standard due to the image quality. Today, engineers assisted by computer-aided drafting software have designed eyepieces with seven or eight elements that deliver exceptionally large, internal reflections, sometimes called scatter, cause the light passing through an eyepiece to disperse and reduce the contrast of the image projected by the eyepiece
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Real image
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In optics, a real image is an image which is located in the plane of convergence for the light rays that originate from a given object. If a screen is placed in the plane of an image the image will generally become visible on the screen. Examples of real images include the image seen on a screen, the image produced on a detector in the rear of a camera. In ray diagrams, real rays of light are represented by full, solid lines. A real image occurs where rays converge, whereas a virtual image occurs where rays only appear to converge. Real images can be produced by concave mirrors and converging lenses, only if the object is placed away from the mirror/lens than the focal point. As the object approaches the point the image is approaching infinity. Virtual image Focal plane Image plane Lens
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Netherlands
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The Netherlands, also informally known as Holland is the main constituent country of the Kingdom of the Netherlands. It is a densely populated country located in Western Europe with three territories in the Caribbean. The European part of the Netherlands borders Germany to the east, Belgium to the south, and the North Sea to the northwest, sharing borders with Belgium, the United Kingdom. The three largest cities in the Netherlands are Amsterdam, Rotterdam and The Hague, Amsterdam is the countrys capital, while The Hague holds the Dutch seat of parliament and government. The port of Rotterdam is the worlds largest port outside East-Asia, the name Holland is used informally to refer to the whole of the country of the Netherlands. Netherlands literally means lower countries, influenced by its low land and flat geography, most of the areas below sea level are artificial. Since the late 16th century, large areas have been reclaimed from the sea and lakes, with a population density of 412 people per km2 –507 if water is excluded – the Netherlands is classified as a very densely populated country. Only Bangladesh, South Korea, and Taiwan have both a population and higher population density. Nevertheless, the Netherlands is the worlds second-largest exporter of food and agricultural products and this is partly due to the fertility of the soil and the mild climate. In 2001, it became the worlds first country to legalise same-sex marriage, the Netherlands is a founding member of the EU, Eurozone, G-10, NATO, OECD and WTO, as well as being a part of the Schengen Area and the trilateral Benelux Union. The first four are situated in The Hague, as is the EUs criminal intelligence agency Europol and this has led to the city being dubbed the worlds legal capital. The country also ranks second highest in the worlds 2016 Press Freedom Index, the Netherlands has a market-based mixed economy, ranking 17th of 177 countries according to the Index of Economic Freedom. It had the thirteenth-highest per capita income in the world in 2013 according to the International Monetary Fund, in 2013, the United Nations World Happiness Report ranked the Netherlands as the seventh-happiest country in the world, reflecting its high quality of life. The Netherlands also ranks joint second highest in the Inequality-adjusted Human Development Index, the region called Low Countries and the country of the Netherlands have the same toponymy. Place names with Neder, Nieder, Nether and Nedre and Bas or Inferior are in use in all over Europe. They are sometimes used in a relation to a higher ground that consecutively is indicated as Upper, Boven, Oben. In the case of the Low Countries / the Netherlands the geographical location of the region has been more or less downstream. The geographical location of the region, however, changed over time tremendously
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Zacharias Janssen
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Zacharias Janssen was a Dutch spectacle-maker from Middelburg associated with the invention of the first optical telescope. Janssen is sometimes credited for inventing the first truly compound microscope. However, the origin of the microscope, just like the origin of the telescope, is a matter of debate, Zacharias Janssen was born in The Hague. Local records seem to indicate he was born in 1585 although a date of birth as early as 1580 or as late a 1588 are also given and his parents were Hans Martens and Maeyken Meertens, both probably from Antwerp, Belgium. He grew up with his sister Sara in Middelburg, at the time the second most important city of the Netherlands and he was known as a street seller who was constantly in trouble with the local authorities. He himself stated he was born in The Hague on the file of his first marriage, with Catharina de Haene. In 1612, Zacharias and Catharina had a son they named Johannes Zachariassen, in 1615 Zacharias was appointed guardian of two children of Lowys Lowyssen geseyt Henricxen brilmakers. It is surmised that Zacharias also took possession of Lowys Lowyssens spectacle-making tools because the first record of Zacharias Janssen being a spectacle maker appears in 1616, the family had to move to Arnemuiden in 1618 after Zachariass counterfeiting activities were exposed. There Zacharias was again accused of counterfeiting in 1619 causing him to be on the move again, a year after the death of Janssens first wife in 1624, he married Anna Couget from Antwerp, who was the widow of a Willem Jansen. He moved to Amsterdam in November 1626 with a profession of a spectacle maker, over the years there have been claims Zacharias Janssen invented the telescope and/or the microscope in Middelburg between 1590 and 1618. Zacharias worked for some period of his life as spectacle-maker and at one time lived next door to Middelburg spectacle maker Hans Lippershey, Janssen is one of three people who have been associated with the invention of the telescope in the Netherlands in 1608. Both were turned down because there were claims for the invention. Varying accounts are cited to support Janssen as an inventor of the telescope. William de Boreel, who visited Middelburg to research the invention in 1655, Boreel concluded that Janssens telescope was finished about 1610. His research was referenced by Pierre Borel in De vero telescopii inventore, there are other claims that Janssen constructed the first telescope in 1604, or even earlier. Janssens son Johannes testified under oath that Hans Lippershey had stolen his fathers invention of the telescope, the confusion surrounding the claim to invention of the telescope and the microscope arises in part from the testimony of Zacharias Janssens son, Johannes Zachariassen. Johannes also seems to have lied about his own date of birth, the 1655 investigation by William Boreel added to the confusion over invention. The people he interviewed were trying to recount details 50 or 60 years after the fact and he may have also been confused about a microscope built by another optician for Drebbel, claiming it was built by Zacharias Janssen
22.
Hans Lippershey
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Hans Lippershey, also known as Johann Lippershey or Lipperhey, was a German-Dutch spectacle-maker. He is commonly associated with the invention of the telescope, although it is if he was the first to build one. Hans Lippershey was born in Wesel, in western Germany, in 1570 and he settled in Middelburg, the capital of the province of Zeeland in the Netherlands, in 1594, married the same year and became a citizen of Zeeland in 1602. During that time he became a lens grinder and spectacle maker. He remained in Middelburg until his death, in September 1619, Hans Lippershey is known for the earliest written record of a refracting telescope, a patent he filed in 1608. Lippershey failed to receive a patent since the claim for invention had also been made by other spectacle-makers. There are many stories as to how Lippershey came by his invention, one version has Lippershey observing two children playing with lenses in his shop and commenting how they could make a far away weather-vane seem closer when looking at it through two lenses. Other stories have Lippersheys apprentice coming up with the idea or have Lippershey copying someone elses discovery, Lippersheys original instrument consisted of either two convex lenses with an inverted image or a convex objective and a concave eyepiece lens so it would have an upright image. This Dutch perspective glass had a three-times magnification, the lunar crater Lippershey, the minor planet 31338 Lipperhey, and the exoplanet Lipperhey are named after him. English speakers tend to interpret the letters sh in the name as representing a single phoneme, both in German and in Dutch, however, the letters s and h belong to different syllables and are pronounced separately. The German pronunciation is, whereas the Dutch pronunciation is closer to, philadelphia, PA, The American Philosophical Society. Chicago, IL, The University of Chicago Press, molecular Expressions, Science, Optics and You - Timeline - Hans Lippershey 400th Anniversary of the Invention of the Telescope
23.
Telescope
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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
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Expatriate
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An expatriate is a person temporarily or permanently residing in a country other than that of their citizenship. In common usage, the term refers to professionals or skilled workers sent abroad by their companies. However, it can refer to retirees and others who have chosen to live outside their native country. Historically, it has referred to exiles. The word expatriate comes from the Latin terms ex and patria, dictionary definitions for the current meaning of the word include, Expatriate, A person who lives outside their native country, or living in a foreign land. The varying use of terms for different groups of foreigners can thus be seen as implying nuances about wealth, intended length of stay, perceived motives for moving, nationality. An older usage of the word expatriate was to refer to an exile, as far back as antiquity, people have gone to live in foreign countries, whether as diplomats, merchants or missionaries. The numbers of such travellers grew markedly after the 15th century with the dawn of the European colonial period, in the 19th century, travel became easier by way of steamship or train. People could more readily choose to live for years in a foreign country. After World War II, decolonisation accelerated, however, lifestyles which had developed among European colonials continued to some degree in expatriate communities. Remnants of the old British Empire, for example, can still be seen in the form of gated communities staffed by domestic workers, social clubs which have survived include the Hash House Harriers and the Royal Selangor. Homesick palates are catered for by specialist food shops, and drinkers can still order a gin and tonic, although pith helmets are mostly confined to military ceremonies, civilians still wear white dinner jackets or even Red Sea rig on occasion. The use of curry powder has long since spread to the metropole, from the 1950s, scheduled flights on jet airliners further increased the speed of international travel. This enabled a hypermobility which led to the jet set, and eventually to global nomads, since the 1990s, the rise of the Internet has allowed some types of worker to become digital nomads. Websites aimed at expatriates began to appear about the same time, the number of expatriates in the world is difficult to determine. In 2013, the United Nations estimated that 232 million people, or 3.2 per cent of the world population, in 2007, only 20 per cent of Dubais population were citizens. Singapore, where 40 per cent of the inhabitants were foreign-born workers, many multinational corporations send employees to foreign countries to work in branch offices or subsidiaries. Expatriate employees allow a parent company to more closely control its foreign subsidiaries and they can also improve global coordination
25.
Cornelis Drebbel
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Cornelis Jacobszoon Drebbel was the Dutch builder of the first navigable submarine in 1620. Drebbel was an innovator who contributed to the development of measurement and control systems, optics, Cornelis Drebbel was born in Alkmaar, Holland in an Anabaptist family in 1572. After some years at the Latin school in Alkmaar, around 1587, he attended the Academy in Haarlem, teachers at the Academy were Hendrik Goltzius, engraver, painter, alchemist and humanist, Karel van Mander, painter, writer, humanist and Cornelis Corneliszoon of Haarlem. Drebbel became an engraver on copperplate and also took an interest in alchemy. In 1595 he married Sophia Jansdochter Goltzius, younger sister of Hendrick and they had at least six children, of whom four survived. Drebbel worked initially as a painter, engraver and cartographer, but he was in constant need of money because of the prodigal lifestyle of his wife. In 1598 he obtained a patent for a system and a sort of perpetual clockwork. In 1600, Drebbel was in Middelburg where he built a fountain at the Noorderpoort and he met there with Hans Lippershey, spectacle maker and constructor of telescopes, and his colleague Zacharias Jansen. There Drebbel learned lens grinding and optics, with the construction of a magic lantern, around 1604 the Drebbel family moved to England, probably at the invitation of the new king, James I of England. He was accommodated at Eltham Palace, Drebbel worked there at the masques, that were performed by and for the court. He was attached to the court of young Renaissance crown-prince Henry and he astonished the court with his inventions and his optical instruments. His fame circulated through the courts of Europe, in October 1610 Drebbel and his family moved to Prague on invitation of Emperor Rudolf II, who was preoccupied with the arts, alchemy and occult sciences. Here again Drebbel demonstrated his inventions, when in 1611 Rudolf II was stripped of all effective power by his younger brother Archduke Matthias, Drebbel was imprisoned for about a year. After Rudolfs death in 1612, Drebbel was set free and went back to London, unfortunately his patron prince Henry had also died and Drebbel was in financial trouble. He manufactured with his glass-grinding machine optical instruments and compound microscopes with two lenses, for which there was a constant demand. In 1622 Constantijn Huygens stayed as a diplomat for more one year in England. The English natural philosopher Robert Hooke may have learned the art of glass grinding from his acquaintance Johannes Sibertus Kuffler, the son-in-law of Drebbel. Towards the end of his life, in 1633, Drebbel was involved in a plan to drain the Fens around Cambridge, in keeping with traditional Mennonite practice, Drebbels estate was split between his four living children at the time of his death
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Galileo Galilei
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Galileo Galilei was an Italian polymath, astronomer, physicist, engineer, philosopher, and mathematician. He played a role in the scientific revolution of the seventeenth century. Galileo also worked in applied science and technology, inventing an improved military compass, Galileos championing of heliocentrism and Copernicanism was controversial during his lifetime, when most subscribed to either geocentrism or the Tychonic system. He met with opposition from astronomers, who doubted heliocentrism because of the absence of a stellar parallax. He was tried by the Inquisition, found vehemently suspect of heresy and he spent the rest of his life under house arrest. He has been called the father of observational astronomy, the father of modern physics, the father of scientific method, and the father of science. Galileo was born in Pisa, Italy, on 15 February 1564, the first of six children of Vincenzo Galilei, a famous lutenist, composer, and music theorist, and Giulia, three of Galileos five siblings survived infancy. The youngest, Michelangelo, also became a noted lutenist and composer although he contributed to financial burdens during Galileos young adulthood, Michelangelo was unable to contribute his fair share of their fathers promised dowries to their brothers-in-law, who would later attempt to seek legal remedies for payments due. Michelangelo would also occasionally have to borrow funds from Galileo to support his musical endeavours and these financial burdens may have contributed to Galileos early fire to develop inventions that would bring him additional income. When Galileo Galilei was eight, his family moved to Florence and he then was educated in the Vallombrosa Abbey, about 30 km southeast of Florence. Galileo Bonaiuti was buried in the church, the Basilica of Santa Croce in Florence. It was common for mid-sixteenth century Tuscan families to name the eldest son after the parents surname, hence, Galileo Galilei was not necessarily named after his ancestor Galileo Bonaiuti. The Italian male given name Galileo derives from the Latin Galilaeus, meaning of Galilee, the biblical roots of Galileos name and surname were to become the subject of a famous pun. In 1614, during the Galileo affair, one of Galileos opponents, in it he made a point of quoting Acts 1,11, Ye men of Galilee, why stand ye gazing up into heaven. Despite being a genuinely pious Roman Catholic, Galileo fathered three children out of wedlock with Marina Gamba and they had two daughters, Virginia and Livia, and a son, Vincenzo. Their only worthy alternative was the religious life, both girls were accepted by the convent of San Matteo in Arcetri and remained there for the rest of their lives. Virginia took the name Maria Celeste upon entering the convent and she died on 2 April 1634, and is buried with Galileo at the Basilica of Santa Croce, Florence. Livia took the name Sister Arcangela and was ill for most of her life, Vincenzo was later legitimised as the legal heir of Galileo and married Sestilia Bocchineri
27.
Giovanni Faber
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Giovanni Faber was a German papal doctor, botanist and art collector, originally from Bamberg in Bavaria, who lived in Rome from 1598. He was curator of the Vatican botanical garden, a member and he acted throughout his career as a political broker between Maximilian I, Elector of Bavaria and Rome. He was a friend of fellow Linceian Galileo Galilei, and the German painters in Rome, Johann Rottenhammer and he has also been credited with inventing the name microscope. Johann Faber was born the son of Protestant parents in Bamberg in 1574, when he was one year old he was orphaned by an epidemic of the plague. He was raised and educated in the Catholic faith by his cousin Philip Schmidt and he studied medicine at the University of Würzburg and graduated in 1597. In order to deepen his studies he moved to Rome in 1598 and his practical studies of anatomy proceeded from direct observation of the human body. He later turned exclusively to the study of animal anatomy, in 1600 he was appointed to the chair of Botany and of Anatomy. In the same year he became the director of the Papal botanical garden, thanks to these new engagements he attended the papal court more regularly. He also cultivated deep artistic interests, becoming a collector of paintings. In 1611 Fabers interest in natural investigation led him to become a member of the Accademia dei Lincei, Giovanni Faber has been credited with giving the microscope its name. In 1609 fellow Lincean Galileo developed a microscope with a convex and a concave lens which he called the occhiolino. In 1624 Galileo presents his occhiolino to Prince Federico Cesi, founder of the Accademia dei Lincei, one year later Giovanni Faber coined the word microscope from the Greek words μικρόν meaning small, and σκοπεῖν meaning to look at. The word was meant to be analogous with telescope, another word coined by the Linceans
28.
Accademia dei Lincei
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The Accademia dei Lincei is an Italian science academy, located at the Palazzo Corsini on the Via della Lungara in Rome, Italy. Founded in 1603 by Federico Cesi, it was one of the first academies of science to exist in the World as a locus for the incipient scientific revolution, the academy was named after the lynx, an animal whose sharp vision symbolizes the observational prowess that science requires. The Lincei did not long survive the death in 1630 of Cesi, its founder and patron and it was revived in the 1870s to become the national academy of Italy, encompassing both literature and science among its concerns. The Pontifical Academy of Science also claims a heritage descending from the first two incarnations of the Academy, by way of the Accademia Pontificia dei Nuovi Lincei, founded in 1847. The first Accademia dei Lincei was founded in 1603 by Federico Cesi, Cesis father disapproved of the research career that Federico was pursuing. His mother, Olimpia Orsini, supported him financially and morally. The Academy struggled due to this disapproval, but after the death of Fredericos father he had money to allow the academy to flourish. Cesi founded the Accademia dei Lincei with three friends, the Dutch physician Johannes Van Heeck and two fellow Umbrians, mathematician Francesco Stelluti and polymath Anastasio de Filiis, at the time of the Accademias founding Cesi was only 18, and the others only 8 years older. Cesi and his friends aimed to understand all of the natural sciences, the literary and antiquarian emphasis set the Lincei apart from the host of sixteenth and seventeenth century Italian Academies. While originally an association, the Academy became a semi-public establishment during the Napoleonic domination of Rome. This shift allowed local scientific elite to carve out a place for themselves in larger scientific networks, however, as a semi-public establishment, the Academys focus was directed by Napoleonic politics. This focus directed the efforts towards stimulating industry, turning public opinion in favor of the French regime. Accademia dei Linceis symbols were both a lynx and an eagle, animals with, or reputed to have, keen sight, the academys motto, chosen by Cesi, was, Take care of small things if you want to obtain the greatest results. When Cesi visited Naples, he met many scientists in fields of interest to him including the botanist, Fabio Colonna, the natural history writer, Ferrante Imperato. Della Porta encouraged Cesi to continue with his endeavours, giambattista della Porta joined Cesis academy in 1610. While in Naples, Cesi also met with Nardo Antonio Recchi to negotiate the acquisition of a collection of material describing Aztec plants and this collection of material would eventually become the Tesoro Messicano. Galileo was inducted to the exclusive Academy on April 25,1611, Galileo clearly felt honoured by his association with the Academy for he adopted Galileo Galilei Linceo as his signature. The Academy published his works and supported him during his disputes with the Roman Inquisition, with this publication, the first, most famous phase of the Lincei was concluded
29.
Histology
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Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is commonly performed by examining cells and tissues under a microscope or electron microscope, the specimen having been sectioned, stained. Histological studies may be conducted using tissue culture, where human or animal cells are isolated and maintained in an artificial environment for various research projects. The ability to visualize or differentially identify microscopic structures is frequently enhanced through the use of histological stains, histology is an essential tool of biology and medicine. Trained physicians, frequently licensed pathologists, are the personnel who perform histopathological examination and their field of study is called histotechnology. In the 17th century, Italian Marcello Malpighi invented one of the first microscopes for studying tiny biological entities, Malpighi analysed several parts of the organs of bats, frogs and other animals under the microscope. Malpighi, while studying the structure of the lung, noticed its membranous alveoli and his discovery established how the oxygen we breathe enters the blood stream and serves the body. In the 19th century, histology was a discipline in its own right. The French anatomist Bichat introduced the concept of tissue in anatomy in 1801, the 1906 Nobel Prize in Physiology or Medicine was awarded to histologists Camillo Golgi and Santiago Ramon y Cajal. They had dueling interpretations of the structure of the brain based in differing interpretations of the same images. Cajal won the prize for his theory and Golgi for the staining technique he invented to make it possible. There are four types of animal tissues, muscle tissue, nervous tissue, connective tissue. All tissue types are subtypes of these four basic tissue types and their structure is very different from animal tissues. The most common fixative for light microscopy is 10% neutral buffered formalin, for electron microscopy, the most commonly used fixative is glutaraldehyde, usually as a 2. 5% solution in phosphate buffered saline. These fixatives preserve tissues or cells mainly by irreversibly cross-linking proteins and this can be detrimental to certain histological techniques. Further fixatives are often used for electron microscopy such as osmium tetroxide or uranyl acetate Formalin fixation leads to degradation of mRNA, miRNA and DNA in tissues, however, extraction, amplification and analysis of these nucleic acids from formalin-fixed, paraffin-embedded tissues is possible using appropriate protocols. Frozen section procedure is a way to fix and mount histology sections using a refrigeration device called a cryostat. It is often used after surgical removal of tumors to allow determination of margin
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Marcello Malpighi
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Marcello Malpighi was an Italian biologist and physician, who is referred to as the Father of microscopical anatomy, histology, physiology and embryology. The splenic lymphoid nodules are often called the Malpighian bodies of the spleen or Malpighian corpuscles, the botanical family Malpighiaceae is also named after him. He was the first person to see capillaries in animals, Malpighi was one of the earliest people to observe red blood cells under a microscope, after Jan Swammerdam. His treatise De polypo cordis was important for understanding blood composition, in it, Malpighi described how the form of a blood clot differed in the right against the left sides of the heart. The use of the microscope enabled Malpighi to discover that invertebrates do not use lungs to breathe, Malpighi also studied the anatomy of the brain and concluded this organ is a gland. In terms of modern endocrinology, this deduction is correct because the hypothalamus of the brain has long recognized for its hormone-secreting capacity. Because Malpighi had a knowledge of both plants and animals, he made contributions to the scientific study of both. The Royal Society of London published two volumes of his botanical and zoological works in 1675 and 1679, another edition followed in 1687, and a supplementary volume in 1697. In his autobiography, Malpighi speaks of his Anatome Plantarum, decorated with the engravings of Robert White and his study of plants led him to conclude that plants had tubules similar to those he saw in insects like the silk worm. Malpighi was born on 10 March 1628 at Crevalcore near Bologna, the son of well-to-do parents, Malpighi was educated in his native city, entering the University of Bologna at the age of 17. He completed these studies about 1649, where at the persuasion of his mother Frances Natalis, when his parents and grandmother became ill, he returned to his family home near Bologna to care for them. Malpighi studied Aristotelian philosophy at the University of Bologna while he was very young, despite opposition from the university authorities because he was non-Bolognese by birth, in 1653 he was granted doctorates in both medicine and philosophy. He later graduated as a doctor at the age of 25. Subsequently, he was appointed as a teacher, whereupon he immediately dedicated himself to study in anatomy. For most of his career, Malpighi combined an intense interest in research with a fond love of teaching. He was invited to correspond with the Royal Society in 1667 by Henry Oldenburg, in 1656, Ferdinand II of Tuscany invited him to the professorship of theoretical medicine at the University of Pisa. There Malpighi began his friendship with Giovanni Borelli, mathematician and naturalist. Malpighi questioned the prevailing medical teachings at Pisa, tried experiments on changes in blood, and attempted to recast anatomical, physiological
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Robert Hooke
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Robert Hooke FRS was an English natural philosopher, architect and polymath. Allan Chapman has characterised him as Englands Leonardo, Robert Gunthers Early Science in Oxford, a history of science in Oxford during the Protectorate, Restoration and Age of Enlightenment, devotes five of its fourteen volumes to Hooke. Hooke studied at Wadham College, Oxford during the Protectorate where he became one of a tightly knit group of ardent Royalists led by John Wilkins. Here he was employed as an assistant to Thomas Willis and to Robert Boyle and he built some of the earliest Gregorian telescopes and observed the rotations of Mars and Jupiter. In 1665 he inspired the use of microscopes for scientific exploration with his book, based on his microscopic observations of fossils, Hooke was an early proponent of biological evolution. Much of Hookes scientific work was conducted in his capacity as curator of experiments of the Royal Society, much of what is known of Hookes early life comes from an autobiography that he commenced in 1696 but never completed. Richard Waller mentions it in his introduction to The Posthumous Works of Robert Hooke, the work of Waller, along with John Wards Lives of the Gresham Professors and John Aubreys Brief Lives, form the major near-contemporaneous biographical accounts of Hooke. Robert Hooke was born in 1635 in Freshwater on the Isle of Wight to John Hooke, Robert was the last of four children, two boys and two girls, and there was an age difference of seven years between him and the next youngest. Their father John was a Church of England priest, the curate of Freshwaters Church of All Saints, Robert Hooke was expected to succeed in his education and join the Church. John Hooke also was in charge of a school, and so was able to teach Robert. He was a Royalist and almost certainly a member of a group who went to pay their respects to Charles I when he escaped to the Isle of Wight, Robert, too, grew up to be a staunch monarchist. As a youth, Robert Hooke was fascinated by observation, mechanical works and he dismantled a brass clock and built a wooden replica that, by all accounts, worked well enough, and he learned to draw, making his own materials from coal, chalk and ruddle. Hooke quickly mastered Latin and Greek, made study of Hebrew. Here, too, he embarked on his study of mechanics. It appears that Hooke was one of a group of students whom Busby educated in parallel to the work of the school. Contemporary accounts say he was not much seen in the school, in 1653, Hooke secured a choristers place at Christ Church, Oxford. He was employed as an assistant to Dr Thomas Willis. There he met the natural philosopher Robert Boyle, and gained employment as his assistant from about 1655 to 1662, constructing, operating and he did not take his Master of Arts until 1662 or 1663
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Micrographia
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Micrographia, or Some Phyſiological Deſcriptions of Minute Bodies Made by Magnifying Glasses. With Observations and Inquiries Thereupon. is a significant book by Robert Hooke about his observations through various lenses. It is particularly notable for being the first book to illustrate insects, plants etc. as seen through microscopes. Published in January 1665, the first major publication of the Royal Society, it became the first scientific best-seller and it is also notable for coining the biological term cell. Hooke most famously describes a flys eye and a plant cell, known for its spectacular copperplate engravings of the miniature world, particularly its fold-out plates of insects, the text itself reinforces the tremendous power of the new microscope. The plates of insects fold out to be larger than the large folio itself, Hooke also selected several objects of human origin, among these objects were the jagged edge of a honed razor and the point of a needle, seeming blunt under the microscope. His goal may well have been as a way to contrast the flawed products of mankind with the perfection of nature, gallery Published under the aegis of The Royal Society, the popularity of the book helped further the societys image and mission of being the UKs leading scientific organization. Micrographias illustrations of the miniature world captured the imagination in a radically new way. Similarly his specimens required a deal of manipulation and preparation in order to make them visible through the microscope. Additionally, Hooke often enclosed the objects he presented within a round frame, micrographia, or, Some physiological descriptions of minute bodies made by magnifying glasses. London, J. Martyn and J. Allestry,1665
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Antonie van Leeuwenhoek
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Antonie Philips van Leeuwenhoek was a Dutch businessman, scientist, and one of the notable representatives in the golden age of Dutch science and technology. A largely self-taught man in science, he is known as the Father of Microbiology. Van Leeuwenhoek is best known for his work in the field of microscopy. Raised in Delft, in the Dutch Republic, Van Leeuwenhoek worked as a draper in his youth and he made a name for himself in municipal politics, and eventually developed an interest in lensmaking. Using his handcrafted microscopes, he was the first to observe and describe microorganisms, most of the animalcules are now referred to as unicellular organisms, though he observed multicellular organisms in pond water. He was also the first to document microscopic observations of muscle fibers, bacteria, spermatozoa, Van Leeuwenhoek did not write any books, his discoveries came to light through correspondence with the Royal Society, which published his letters. Antonie van Leeuwenhoek was born in Delft, Dutch Republic, on 24 October 1632, on 4 November, he was baptized as Thonis. His father, Philips Antonisz van Leeuwenhoek, was a maker who died when Antonie was only five years old. His mother, Margaretha, came from a well-to-do brewers family, and remarried Jacob Jansz Molijn, Antonie had four older sisters, Margriet, Geertruyt, Neeltje, and Catharina. When he was ten years old his step-father died. He attended school in Warmond for a time before being sent to live in Benthuizen with his uncle. At the age of 16 he became an apprentice at a linen-drapers shop in Amsterdam owned by the Scot William Davidson. Van Leeuwenhoek left after six years, Van Leeuwenhoek married Barbara de Mey in July 1654, with whom he would have one surviving daughter, Maria. That same year he returned to Delft, where he would live and he opened a drapers shop, which he ran throughout the 1650s. His wife died in 1666, and in 1671, Van Leeuwenhoek remarried to Cornelia Swalmius with whom he had no children and his status in Delft had grown throughout the years. In 1660 he received a job as chamberlain for the Delft sheriffs assembly chamber in the City Hall. Van Leeuwenhoek was a contemporary of another famous Delft citizen, the painter Johannes Vermeer and it has been suggested that he is the man portrayed in two of Vermeers paintings of the late 1660s, The Astronomer and The Geographer. However, others argue that there appears to be little physical similarity, while running his drapers shop, Van Leeuwenhoek wanted to see the quality of the thread better than the then-current magnifying lenses available allowed
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Red blood cell
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RBCs take up oxygen in the lungs, or gills of fish, and release it into tissues while squeezing through the bodys capillaries. The cytoplasm of erythrocytes is rich in hemoglobin, a biomolecule that can bind oxygen and is responsible for the red color of the cells. In humans, mature red cells are flexible and oval biconcave disks. They lack a nucleus and most organelles, in order to accommodate maximum space for hemoglobin, they can be viewed as sacks of hemoglobin. Approximately 2.4 million new erythrocytes are produced per second in human adults, the cells develop in the bone marrow and circulate for about 100–120 days in the body before their components are recycled by macrophages. Each circulation takes about 60 seconds, approximately a quarter of the cells in the human body are red blood cells. Nearly half of the volume is red blood cells. Red blood cells are known as RBCs, red cells, red blood corpuscles, haematids. Packed red blood cells are red blood cells that have donated, processed. Almost all vertebrates, including all mammals and humans, have red blood cells, red blood cells are cells present in blood in order to transport oxygen. The only known vertebrates without red blood cells are the crocodile icefish, they live in very cold water. While they no longer use hemoglobin, remnants of hemoglobin genes can be found in their genome, oxygen can easily diffuse through the red blood cells cell membrane. Myoglobin, a related to hemoglobin, acts to store oxygen in muscle cells. The color of red cells is due to the heme group of hemoglobin. However, blood can appear bluish when seen through the vessel wall, pulse oximetry takes advantage of the hemoglobin color change to directly measure the arterial blood oxygen saturation using colorimetric techniques. Hemoglobin also has a high affinity for carbon monoxide, forming carboxyhemoglobin which is a very bright red in color. Flushed, confused patients with a reading of 100% on pulse oximetry are sometimes found to be suffering from carbon monoxide poisoning. The red blood cells of mammals are typically shaped as disks, flattened and depressed in the center, with a dumbbell-shaped cross section
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Jan Swammerdam
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Jan Swammerdam was a Dutch biologist and microscopist. His work on insects demonstrated that the various phases during the life of an insect—egg, larva, pupa, as part of his anatomical research, he carried out experiments on muscle contraction. In 1658, he was the first to observe and describe red blood cells and he was one of the first people to use the microscope in dissections, and his techniques remained useful for hundreds of years. Swammerdam was baptized on 15 February 1637 in the Oude Kerk Amsterdam and his father was an apothecary, and an amateur collector of minerals, coins, fossils, and insects from around the world. His mother Baertje Jans Corvers died in 1661, the same year, when he was 24, Swammerdam entered the University of Leiden to study medicine. After qualifying as a candidate in medicine in 1663, he left for France, spending time in Issy, Saumur and Paris with Melchisédech Thévenot. He returned to Leiden in September 1665, and earned his M. D. on February 22,1667 Once he left university and this choice caused a rift between Swammerdam and his father, who thought his son should practice medicine. The relationship between the two deteriorated, Swammerdams father cut off his support for Swammerdams entomological studies. As a result, Swammerdam was forced, at least occasionally and he obtained leave at Amsterdam to dissect the bodies of those who died in the hospital. From 1667 through 1674, Swammerdam continued his research and published three books, in 1675, he came under the influence of the Flemish mystic, Antoinette Bourignon, renounced his work, and decided to devote the remainder of his life to spiritual matters. Niels Stensen, a gifted anatomist, and once his co-student, invited him to work for the Duke of Tuscany, the grand duke of Tuscany offered 12,000 florins for Swammerdams collection, on condition of Swammerdam coming to Florence to continue it. There is evidence, however, that Swammerdam did not completely give up his scientific studies, the papers, which he wished to be published posthumously, appear to have been revised during the last two years of his life. Swammerdam died at age 43 of malaria and was buried in the Église Wallonne, in 1737–1738, a half century after his death, Herman Boerhaave translated Swammerdams papers into Latin and published them under the title Biblia naturae. An English translation of his works by T. Floyd was published in 1758. His entomological collection was divided at his death and sold in small portions, as a naturalist of his time, he has been compared with Anton Leeuwenhoek. No authentic portrait of Jan Swammerdam is extant nowadays, the portrait shown in the header is derived from the painting The Anatomy Lesson of Dr Tulp by Rembrandt and represents the leading Amsterdam physician Hartman Hartmanzoon. Knowledge of insects in the 17th century was to a great extent inherited from Aristotle, according to this classical paradigm, insects were so insignificant they werent worthy of the types of investigations done on fish, reptiles, and mammals. Much of Swammerdams entomological work was done to show that the difference between insects and the animals was one of degree, not kind
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Condenser (optics)
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A condenser is an optical lens which renders a divergent beam from a point source into a parallel or converging beam to illuminate an object. In the context of microscopy, the parallel illumination scheme is known as Köhler illumination whereas the converging illumination scheme is known as critical illumination, condensers are an essential part of any imaging device, such as microscopes, enlargers, slide projectors, and telescopes. The concept is applicable to all kinds of radiation undergoing optical transformation, such as electrons in electron microscopy, condensers are located above the light source and under the sample in an upright microscope, and above the stage and below the light source in an inverted microscope. They act to gather light from the light source and concentrate it into a cone of light that illuminates the specimen. The aperture and angle of the cone must be adjusted for each different objective lens with different numerical apertures. Condensers typically consist of a diaphragm and one or more lenses. Light from the source of the microscope passes through the diaphragm and is focused by the lens onto the specimen. After passing through the specimen the light diverges into a cone to fill the front lens of the objective. The first simple condensers were introduced on pre-achromatic microscopes in the 17th century, robert Hooke used a combination of a salt water filled globe and a plano-convex lens, and shows in the Micrographia that he understands the reasons for its efficiency. Makers in the 18th century such as Benjamin Martin, Adams and this was a simple plano-convex or bi-convex lens, or sometimes a combination of lenses. With the development of the modern achromatic objective in 1829, by Joseph Jackson Lister, by 1837, the use of the achromatic condenser was introduced in France, by Felix Dujardin, and Chevalier. English makers early took up this improvement, due to the obsession with resolving test objects such as diatoms, by the late 1840s, English makers such as Ross, Powell and Smith, all could supply highly corrected condensers on their best stands, with proper centring and focus. It is erroneously stated that these developments were purely empirical - no-one can design a good achromatic, on the Continent, in Germany, the corrected condenser was not considered either useful or essential, mainly due to a misunderstanding of the basic optical principles involved. Thus the leading German company, Carl Zeiss in Jena, offered nothing more than a very poor chromatic condenser into the late 1870s. There are three types of condenser, The chromatic condenser, such as the Abbe where no attempt is made to correct for spherical or chromatic aberration. It contains two lenses that produce an image of the source that is surrounded by a blue. The aplanatic condenser is corrected for spherical aberration, the compound achromatic condenser is corrected for both spherical and chromatic aberrations. The Abbe condenser is named for its inventor Ernst Abbe, who developed it in 1870, the Abbe condenser, which was originally designed for Zeiss, is mounted below the stage of the microscope
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Phase-contrast microscopy
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Phase-contrast microscopy is an optical-microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image. Phase shifts themselves are invisible, but become visible when shown as brightness variations, when light waves travel through a medium other than vacuum, interaction with the medium causes the wave amplitude and phase to change in a manner dependent on properties of the medium. Changes in amplitude arise from the scattering and absorption of light, photographic equipment and the human eye are only sensitive to amplitude variations. Without special arrangements, phase changes are therefore invisible, yet, phase changes often carry important information. Phase-contrast microscopy is particularly important in biology and it reveals many cellular structures that are not visible with a simpler bright-field microscope, as exemplified in the figure. These structures were visible to earlier microscopists by staining, but this required additional preparation. The phase-contrast microscope made it possible for biologists to study living cells, after its invention in the early 1930s, phase-contrast microscopy proved to be such an advancement in microscopy, that its inventor Frits Zernike was awarded the Nobel prize in 1953. The basic principle to making phase changes visible in phase-contrast microscopy is to separate the light from the specimen-scattered light. The ring-shaped illuminating light that passes the condenser annulus is focused on the specimen by the condenser, some of the illuminating light is scattered by the specimen. The remaining light is unaffected by the specimen and forms the background light, when observing an unstained biological specimen, the scattered light is weak and typically phase-shifted by −90° relative to the background light. This leads to the foreground and background having nearly the same intensity, first, the background light is phase-shifted by −90° by passing it through a phase-shift ring, which eliminates the phase difference between the background and the scattered light rays. Some of the light will be phase-shifted and dimmed by the rings. The above describes negative phase contrast, in its positive form, the background light is instead phase-shifted by +90°. The background light will thus be 180° out of relative to the scattered light. The scattered light will then be subtracted from the light to form an image with a darker foreground. The success of the phase-contrast microscope has led to a number of subsequent phase-imaging methods, in 1952 Georges Nomarski patented what is today known as differential interference contrast microscopy. It enhances contrast by creating artificial shadows, as if the object is illuminated from the side, but DIC microscopy and phase contrast microscopy both use polarized light, which is unsuitable when the object or its container alter polarization. With the growing use of polarizing plastic containers in cell biology, DIC microscopy is increasingly replaced by Hoffman modulation contrast microscopy, traditional phase-contrast methods enhance contrast optically, blending brightness and phase information in single image
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Frits Zernike
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Frederik Frits Zernike was a Dutch physicist and winner of the Nobel Prize for physics in 1953 for his invention of the phase-contrast microscope. Frederik Zernike was born on 16 July 1888 in Amsterdam, Netherlands to Carl Frederick August Zernike, both parents were teachers of mathematics, and he especially shared his fathers passion for physics. He studied chemistry, mathematics and physics at the University of Amsterdam, in 1912, he was awarded a prize for his work on opalescence in gases. In 1913, he became assistant to Jacobus Cornelius Kapteyn at the laboratory of Groningen University. In 1914, he was jointly with Leonard Salomon Ornstein for the derivation of the Ornstein-Zernike equation in critical-point theory. In 1915, he obtained a position in physics at the same university. It was at a Physical and Medical Congress in Wageningen in 1933 that Zernike first described his phase contrast technique in microscopy and he extended his method to test the figure of concave mirrors. His discovery lay at the base of the first phase contrast microscope, another contribution in the field of optics is related to the efficient description of the imaging defects or aberrations of optical imaging systems like microscopes and telescopes. The representation of aberrations was originally based on the theory developed by Ludwig Seidel in the middle of the nineteenth century, seidels representation was based on power series expansions and did not allow a clear separation between various types and orders of aberrations. Zernikes orthogonal circle polynomials provided a solution to the problem of the optimum balancing of the various aberrations of an optical instrument. Since the 1960s, Zernikes circle polynomials are used in optical design, optical metrology. Zernikes work helped awaken interest in theory, the study of partially coherent light sources. In 1938 he published a derivation of Van Citterts 1934 theorem on the coherence of radiation from distant sources. He died in the hospital at Amersfoort, Netherlands in 1966 after suffering illness the last years of his life, in 1946, Zernike became member of the Royal Netherlands Academy of Arts and Sciences. In 1954, Zernike became an Honorary Member of The Optical Society, Zernike was elected a Foreign Member of the Royal Society. The university complex to the north of the city of Groningen is named after him, Zernikes great-nephew Gerardus t Hooft won the Nobel Prize in physics in 1999. The Oz Enterprise, a Linux distribution, was named after Leonard Salomon Ornstein, brinkman, Zernike, Frits, in Biografisch Woordenboek van Nederland. Prominente Groningse hoogleraren Frits Zernike Frits Zernike biography at the National library of the Netherlands
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Differential interference contrast microscopy
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DIC works on the principle of interferometry to gain information about the optical path length of the sample, to see otherwise invisible features. A relatively complex optical system produces an image with the object appearing black to white on a grey background and this image is similar to that obtained by phase contrast microscopy but without the bright diffraction halo. The technique was developed by Polish physicist Georges Nomarski in 1952, DIC works by separating a polarized light source into two orthogonally polarized mutually coherent parts which are spatially displaced at the sample plane, and recombined before observation. The interference of the two parts at recombination is sensitive to their optical path difference, unpolarised light enters the microscope and is polarised at 45°. Polarised light is required for the technique to work, the polarised light enters the first Nomarski-modified Wollaston prism and is separated into two rays polarised at 90° to each other, the sampling and reference rays. The Nomarski prism causes the two rays to come to a point outside the body of the prism, and so allows greater flexibility when setting up the microscope. The two rays are focused by the condenser for passage through the sample and these two rays are focused so they will pass through two adjacent points in the sample, around 0.2 μm apart. The sample is illuminated by two coherent light sources, one with 0° polarisation and the other with 90° polarisation. These two illuminations are, however, not quite aligned, with one lying slightly offset with respect to the other, the rays travel through adjacent areas of the sample, separated by the shear. The separation is normally similar to the resolution of the microscope and they will experience different optical path lengths where the areas differ in refractive index or thickness. This causes a change in phase of one ray relative to the due to the delay experienced by the wave in the more optically dense material. The passage of many pairs of rays through pairs of adjacent points in the means a image of the sample will now be carried by both the 0° and 90° polarised light. These, if looked at individually, would be bright field images of the sample, the light also carries information about the image invisible to the human eye, the phase of the light. The different polarisations prevent interference between two images at this point. The rays travel through the lens and are focused for the second Nomarski-modified Wollaston prism. The second prism recombines the two rays into one polarised at 135°, the combination of the rays leads to interference, brightening or darkening the image at that point according to the optical path difference. This prism overlays the two bright field images and aligns their polarisations so they can interfere, because the difference in phase is due to the difference in optical path length, this recombination of light causes optical differentiation of the optical path length, generating the image seen. The image has the appearance of an object under very oblique illumination, causing strong light
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Ernst Ruska
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Ernst August Friedrich Ruska was a German physicist who won the Nobel Prize in Physics in 1986 for his work in electron optics, including the design of the first electron microscope. Ernst Ruska was born in Heidelberg Germany, in 1931, he demonstrated that a magnetic coil could act as an electron lens, and used several coils in a series to build the first electron microscope in 1933. After completing his PhD in 1933, Ruska continued to work in the field of optics, first at Fernseh Ltd in Berlin-Zehlendorf. At Siemens, he was involved in developing the first commercially produced electron microscope in 1939, after leaving Siemens in 1955, Ruska served as director of the Institute for Electron Microscopy of the Fritz Haber Institute until 1974. Concurrently, he served at the institute and as professor at the Technical University of Berlin from 1957 until his retirement in 1974, in 1960 he won the Lasker Award. He died in West Berlin in 1988, Nobel Prize press release Ernst Ruskas official Nobel autobiography Website containing memorial information published by the Ruska family
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Electron
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The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον
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Max Knoll
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Max Knoll was a German electrical engineer. Knoll was born in Wiesbaden and studied in Munich and at the Technical University of Berlin, in 1927 he became the leader of the electron research group there, where he and his co-worker, Ernst Ruska, invented the electron microscope in 1931. In April 1932, Knoll joined Telefunken in Berlin to do work in the field of television design. He was also a lecturer in Berlin. After World War II, Knoll joined the University of Munich as extraordinary professor and director of the Institute for Electromedicine and he moved to the USA in 1948, to work at the Department of Electrical Engineering at Princeton University. Knoll, Max & Kügler, J. Nature 184, 1823-1824, subjective Light Pattern Spectroscopy in the Electroencephalic Range
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