An aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. Aerosols can be anthropogenic. Examples of natural aerosols are fog, forest exudates and geyser steam. Examples of anthropogenic aerosols are haze, particulate air pollutants and smoke; the liquid or solid particles have diameters <1 μm. In general conversation, aerosol refers to an aerosol spray that delivers a consumer product from a can or similar container. Other technological applications of aerosols include dispersal of pesticides, medical treatment of respiratory illnesses, convincing technology. Diseases can spread by means of small droplets in the breath called aerosols. Aerosol science covers generation and removal of aerosols, technological application of aerosols, effects of aerosols on the environment and people, other topics. An aerosol is defined as a suspension system of liquid particles in a gas. An aerosol includes both the particles and the suspending gas, air. Frederick G. Donnan first used the term aerosol during World War I to describe an aero-solution, clouds of microscopic particles in air.
This term developed analogously to the term hydrosol, a colloid system with water as the dispersed medium. Primary aerosols contain. Various types of aerosol, classified according to physical form and how they were generated, include dust, mist and fog. There are several measures of aerosol concentration. Environmental science and health uses the mass concentration, defined as the mass of particulate matter per unit volume with units such as μg/m3. Used is the number concentration, the number of particles per unit volume with units such as number/m3 or number/cm3; the size of particles has a major influence on their properties, the aerosol particle radius or diameter is a key property used to characterise aerosols. Aerosols vary in their dispersity. A monodisperse aerosol, producible in the laboratory, contains particles of uniform size. Most aerosols, however, as polydisperse colloidal systems, exhibit a range of particle sizes. Liquid droplets are always nearly spherical, but scientists use an equivalent diameter to characterize the properities of various shapes of solid particles, some irregular.
The equivalent diameter is the diameter of a spherical particle with the same value of some physical property as the irregular particle. The equivalent volume diameter is defined as the diameter of a sphere of the same volume as that of the irregular particle. Used is the aerodynamic diameter. For a monodisperse aerosol, a single number—the particle diameter—suffices to describe the size of the particles. However, more complicated particle-size distributions describe the sizes of the particles in a polydisperse aerosol; this distribution defines the relative amounts of particles, sorted according to size. One approach to defining the particle size distribution uses a list of the sizes of every particle in a sample. However, this approach proves tedious to ascertain in aerosols with millions of particles and awkward to use. Another approach splits the complete size range into intervals and finds the number of particles in each interval. One can visualize these data in a histogram with the area of each bar representing the proportion of particles in that size bin normalised by dividing the number of particles in a bin by the width of the interval so that the area of each bar is proportionate to the number of particles in the size range that it represents.
If the width of the bins tends to zero, one gets the frequency function: d f = f d d p where d p is the diameter of the particles d f is the fraction of particles having diameters between d p and d p + d d p f is the frequency functionTherefore, the area under the frequency curve between two sizes a and b represents the total fraction of the particles in that size range: f a b = ∫ a b f d d p It can be formulated in terms of the total number density N: d N = N d d p Assuming spherical aerosol particles, the aerosol surface area per unit volume is given by the second moment: S = π / 2 ∫ 0 ∞ N d p 2 d d p And the third moment gives the total volume concentration of the particles: V = π / 6 ∫ 0 ∞ N (
Hue is one of the main properties of a color, defined technically, as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, green and yellow". Hue can be represented quantitatively by a single number corresponding to an angular position around a central or neutral point or axis on a colorspace coordinate diagram or color wheel, or by its dominant wavelength or that of its complementary color; the other color appearance parameters are colorfulness, saturation and brightness. Colors with the same hue are distinguished with adjectives referring to their lightness or colorfulness, such as with "light blue", "pastel blue", "vivid blue". Exceptions include brown, a dark orange. In painting color theory, a hue is a pure pigment -- one without shade. Hues are first processed in the brain in areas in the extended V4 called globs. In opponent color spaces in which two of the axes are perceptually orthogonal to lightness, such as the CIE 1976 and 1976 color spaces, hue may be computed together with chroma by converting these coordinates from rectangular form to polar form.
Hue is the angular component of the polar representation. In CIELAB h a b = a t a n 2, analogously, in CIELUV h u v = a t a n 2 = a t a n 2, atan2 is a two-argument inverse tangent. Preucil describes a color hexagon, similar to a trilinear plot described by Evans and Brewer, which may be used to compute hue from RGB. To place red at 0°, green at 120°, blue at 240°, h r g b = a t a n 2. Equivalently, one may solve tan = 3 ⋅ 2 ⋅ R − G − B. Preucil used a polar plot. Using R, G, B, one may compute hue angle using the following scheme: determine which of the six possible orderings of R, G, B prevail apply the formula given in the table below. Note that in each case the formula contains the fraction M − L H − L, where H is the highest of R, G, B; this is referred to as the "Preucil hue error" and was used in the computation of mask strength in photomechanical color reproduction. Hue angles computed for the Preucil circle agree with the hue angle computed for the Preucil hexagon at integer multiples of 30° and differ by 1.2° at odd integer multiples of 15°, the maximal divergence between the two.
The process of converting an RGB color into an HSL color space or HSV color space is based on a 6-piece piecewise mapping, treating the HSV cone as a hexacone, or the HSL double cone as a double hexacone. The formulae used are those in the table above; the hues exhibited by caramel colorings and beers are limited in range. The Linner hue index is used to quantify the hue of such products. Manufacturers of pigments use the word hue, for example, "cadmium yellow" to indicate that the original pigmentation ingredient toxic, has been replaced by safer alternatives whilst retaining the hue of the original. Replacements are used for chromium and alizarin. Dominant wavelength is a physical analog to the perceptual attribute hue. On a chromaticity diagram, a line is drawn from a white point through the coordinates of the color in question, until it intersects the spectral locus; the wavelength at which the line intersects the spectrum locus is identified as the color's dominant wavelength if the point is on the same side of the white point as the spectral locus, as the color's complementary wavelength if the point is on the opposite side.
Δ h or Δ H ∗? There are two main ways; the first is the si
The Mie solution to Maxwell's equations describes the scattering of an electromagnetic plane wave by a homogeneous sphere. The solution takes the form of an infinite series of spherical multipole partial waves, it is named after Gustav Mie. The term Mie solution is used for solutions of Maxwell's equations for scattering by stratified spheres or by infinite cylinders, or other geometries where one can write separate equations for the radial and angular dependence of solutions; the term Mie theory is sometimes used for this collection of methods. More broadly, "Mie scattering" suggests situations where the size of the scattering particles is comparable to the wavelength of the light, rather than much smaller or much larger. Mie scattering takes place in the lower 4.5 km of the atmosphere, where there may be many spherical particles present with diameters equal to the size of the wavelength of the incident energy. Mie scattering theory has no upper size limitation, converges to the limit of geometric optics for large particles.
A modern formulation of the Mie solution to the scattering problem on a sphere can be found in many books, e.g. J. A. Stratton's Electromagnetic Theory. In this formulation, the incident plane wave, as well as the scattering field, is expanded into radiating spherical vector wave functions; the internal field is expanded into regular spherical vector wave functions. By enforcing the boundary condition on the spherical surface, the expansion coefficients of the scattered field can be computed. For particles much larger or much smaller than the wavelength of the scattered light there are simple and excellent approximations that suffice to describe the behaviour of the system, but for objects whose size is similar to the wavelength, e.g. water droplets in the atmosphere, latex particles in paint, droplets in emulsions, including milk, biological cells and cellular components, a more exact approach is necessary. The Mie solution is named after German physicist Gustav Mie. Danish physicist Ludvig Lorenz and others independently developed the theory of electromagnetic plane wave scattering by a dielectric sphere.
The formalism allows the calculation of the electric and magnetic fields inside and outside a spherical object and is used to calculate either how much light is scattered, the total optical cross section, or where it goes, the form factor. The notable features of these results are the Mie resonances, sizes that scatter strongly or weakly; this is in contrast to Rayleigh scattering for small particles and Rayleigh–Gans–Debye scattering for large particles. The existence of resonances and other features of Mie scattering make it a useful formalism when using scattered light to measure particle size. Mie solutions are implemented in a number of programs written in different computer languages such as Fortran, MATLAB, Mathematica; these solutions are in terms of infinite series and include calculation of scattering phase function, extinction and absorption efficiencies, other parameters such as asymmetry parameter or radiation torque. Current usage of a "Mie solution" indicates a series approximation to a solution of Maxwell's equations.
There are several known objects that allow such a solution: spheres, concentric spheres, infinite cylinders, cluster of spheres and cluster of cylinders. There are known series solutions for scattering on ellipsoidal particles. For a list of these specialized codes, examine these articles: Codes for electromagnetic scattering by spheres – solutions for a single sphere, coated spheres, multilayer sphere, cluster of spheres. A generalization that allows a treatment of more shaped particles is the T-matrix method, which relies on the series approximation to solutions of Maxwell's equations. Rayleigh scattering describes the elastic scattering of light by spheres that are much smaller than the wavelength of light; the intensity I of the scattered radiation is given by I = I 0 4 2 6, where I0 is the light intensity before the interaction with the particle, R is the distance between the particle and the observer, θ is the scattering angle, n is the refractive index of the particle, d is the diameter of the particle.
It can be seen from the above equation that Rayleigh scattering is dependent upon the size of the particle and the wavelengths. The intensity of the Rayleigh scattered radiation increases as the ratio of particle size to wavelength increases. Furthermore, the intensity of Rayleigh scattered radiation is identical in the forward and reverse directio
Richard Buckminster Fuller was an American architect, systems theorist, designer and futurist. Fuller published more than 30 books, coining or popularizing terms such as "Spaceship Earth", "Dymaxion" house/car, synergetic, "tensegrity", he developed numerous inventions architectural designs, popularized the known geodesic dome. Carbon molecules known as fullerenes were named by scientists for their structural and mathematical resemblance to geodesic spheres. Fuller was the second World President of Mensa from 1974 to 1983. Fuller was born on July 12, 1895, in Milton, the son of Richard Buckminster Fuller and Caroline Wolcott Andrews, grand-nephew of Margaret Fuller, an American journalist and women's rights advocate associated with the American transcendentalism movement; the unusual middle name, was an ancestral family name. As a child, Richard Buckminster Fuller tried numerous variations of his name, he used to sign his name differently each year in the guest register of his family summer vacation home at Bear Island, Maine.
He settled on R. Buckminster Fuller. Fuller spent much of his youth in Penobscot Bay off the coast of Maine, he attended Froebelian Kindergarten. He disagreed with the way geometry was taught in school, being unable to experience for himself that a chalk dot on the blackboard represented an "empty" mathematical point, or that a line could stretch off to infinity. To him these were illogical, led to his work on synergetics, he made items from materials he found in the woods, sometimes made his own tools. He experimented with designing a new apparatus for human propulsion of small boats. By age 12, he had invented a'push pull' system for propelling a rowboat by use of an inverted umbrella connected to the transom with a simple oar lock which allowed the user to face forward to point the boat toward its destination. In life, Fuller took exception to the term "invention". Years he decided that this sort of experience had provided him with not only an interest in design, but a habit of being familiar with and knowledgeable about the materials that his projects would require.
Fuller earned a machinist's certification, knew how to use the press brake, stretch press, other tools and equipment used in the sheet metal trade. Fuller attended Milton Academy in Massachusetts, after that began studying at Harvard College, where he was affiliated with Adams House, he was expelled from Harvard twice: first for spending all his money partying with a vaudeville troupe, after having been readmitted, for his "irresponsibility and lack of interest". By his own appraisal, he was a non-conforming misfit in the fraternity environment. Between his sessions at Harvard, Fuller worked in Canada as a mechanic in a textile mill, as a laborer in the meat-packing industry, he served in the U. S. Navy in World War I, as a shipboard radio operator, as an editor of a publication, as a crash rescue boat commander. After discharge, he worked again in the meat packing industry. In 1917, he married Anne Hewlett. During the early 1920s, he and his father-in-law developed the Stockade Building System for producing light-weight and fireproof housing—although the company would fail in 1927.
Buckminster Fuller recalled 1927 as a pivotal year of his life. His daughter Alexandra had died in 1922 of complications from polio and spinal meningitis just before her fourth birthday. Stanford historian, Barry Katz, found signs that around this time in his life Fuller was suffering from depression and anxiety. Fuller dwelled on his daughter's death, suspecting that it was connected with the Fullers' damp and drafty living conditions; this provided motivation for Fuller's involvement in Stockade Building Systems, a business which aimed to provide affordable, efficient housing. In 1927, at age 32, Fuller lost his job as president of Stockade; the Fuller family had no savings, the birth of their daughter Allegra in 1927 added to the financial challenges. Fuller drank and reflected upon the solution to his family's struggles on long walks around Chicago. During the autumn of 1927, Fuller contemplated suicide by drowning in Lake Michigan, so that his family could benefit from a life insurance payment.
Fuller said that he had experienced a profound incident which would provide direction and purpose for his life. He felt as though he was suspended several feet above the ground enclosed in a white sphere of light. A voice spoke directly to Fuller, declared: From now on you need never await temporal attestation to your thought. You think the truth. You do not have the right to eliminate yourself. You do not belong to you. You belong to Universe. Your significance will remain forever obscure to you, but you may assume that you are fulfilling your role if you apply yourself to converting your experiences to the highest advantage of others. Fuller stated, he chose to embark on "an experiment, to find what a single individual could contribute to changing the world and benefiting all humanity". Speaking to audiences in life, Fuller would recount the story of his Lake Michigan experience, its transformative impact on his life. Historians have been unable to identify direct evidence for this experience within the 1927 papers of Fuller's Chronofile archives, housed at Stanford University.
Stanford historian Barry Katz suggests that the suicide story may be a myth which Fuller constructed in life, to summarize this formative period of his career. In 1927 Fuller resolved to think independently which included a commitment
An afterglow is a broad arch of whitish or pinkish sunlight in the sky, scattered by fine particulates like dust suspended in the atmosphere. An afterglow may appear above the highest clouds in the hour of fading twilight, or be reflected off high snowfields in mountain regions long after sunset; the particles produce a scattering effect upon the component parts of white light. True alpenglow, which occurs long after sunset or long before sunrise, is caused by the backscattering of red sunlight by aerosols and fine dust particles low in the atmosphere. After sunset, alpenglow is an afterglow caused by the illumination of atmospheric particles by sunlight as it gets refracted and scattered through the Earth's atmosphere; the high-energy and high-frequency light is scattered out the most, while the remaining low-energy and -frequency light reaches the observer on the horizon at twilight. The backscattering of this light further turns; this period of time is referred to as blue hour and is treasured by photographers and painters, as it offers breathtaking views.
The afterglow persists until the Earth's shadow overtakes the sky above the observer as night falls and the stars appear, with Venus visible above the horizon opposite of the Belt of Venus around the antisolar point. After the 1883 eruption of the volcano Krakatoa, a remarkable series of red sunsets appeared worldwide. An enormous amount of exceedingly fine dust were blown to a great height by the volcano's explosion, globally diffused by the high atmospheric winds. Edvard Munch's painting The Scream depicts an afterglow during this period. Belt of Venus Earth's shadow Gegenschein Red sky at morning Sunset
Halo (optical phenomenon)
Halo is the name for a family of optical phenomena produced by sunlight interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from white rings to arcs and spots in the sky. Many of these appear near the Sun or Moon, but others occur elsewhere or in the opposite part of the sky. Among the best known halo types are the circular halo, light pillars, sun dogs, but many others occur; the ice crystals responsible for halos are suspended in cirrus or cirrostratus clouds in the upper troposphere, but in cold weather they can float near the ground, in which case they are referred to as diamond dust. The particular shape and orientation of the crystals are responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split into colors because of dispersion; the crystals behave like prisms and mirrors and reflecting light between their faces, sending shafts of light in particular directions. Atmospheric optical phenomena like halos were used as part of weather lore, an empirical means of weather forecasting before meteorology was developed.
They do indicate that rain will fall within the next 24 hours, since the cirrostratus clouds that cause them can signify an approaching frontal system. Other common types of optical phenomena involving water droplets rather than ice crystals include the glory and rainbow. While Aristotle had mentioned halos and parhelia, in antiquity, the first European descriptions of complex displays were those of Christoph Scheiner in Rome, Hevelius in Danzig, Tobias Lowitz in St Petersburg. Chinese observers had recorded these for centuries, the first reference being a section of the "Official History of the Chin Dynasty" in 637, on the "Ten Haloes", giving technical terms for 26 solar halo phenomena. While known and quoted for being the oldest color depiction of the city of Stockholm, Vädersolstavlan is arguably one of the oldest known depictions of a halo display, including a pair of sun dogs. For two hours in the morning of 20 April 1535, the skies over the city were filled with white circles and arcs crossing the sky, while additional suns appeared around the sun.
A light pillar, or sun pillar, appears as a vertical pillar or column of light rising from the sun near sunset or sunrise, though it can appear below the sun if the observer is at a high elevation or altitude. Hexagonal plate- and column-shaped ice crystals cause the phenomenon. Plate crystals cause pillars only when the sun is within 6 degrees of the horizon; the crystals tend to orient themselves near-horizontally as they fall or float through the air, the width and visibility of a sun pillar depend on crystal alignment. Light pillars can form around the moon, around street lights or other bright lights. Pillars forming from ground-based light sources may appear much taller than those associated with the sun or moon. Since the observer is closer to the light source, crystal orientation matters less in the formation of these pillars. Among the best-known halos is the 22° halo just called "halo", which appears as a large ring around the Sun or Moon with a radius of about 22°; the ice crystals that cause the 22° halo are oriented semi-randomly in the atmosphere, in contrast to the horizontal orientation required for some other halos such as sun dogs and light pillars.
As a result of the optical properties of the ice crystals involved, no light is reflected towards the inside of the ring, leaving the sky noticeably darker than the sky around it, giving it the impression of a "hole in the sky". The 22° halo is not to be confused with the corona, a different optical phenomenon caused by water droplets rather than ice crystals, which has the appearance of a multicolored disk rather than a ring. Other haloes can form at 46° to the sun, or at the horizon, or around the zenith, can appear as full haloes or incomplete arcs. A Bottlinger's ring is a rare type of halo, elliptical instead of circular, it has a small diameter, which makes it difficult to see in the Sun's glare and more to be spotted around the dimmer Subsun seen from mountain tops or airplanes. Bottlinger's rings are not well understood yet, it is suggested that they are formed by flat pyramidal ice crystals with faces at uncommonly low angles, suspended horizontally in the atmosphere. These precise and physically problematic requirements would explain why the halo is rare.
In the Anglo-Cornish dialect of English, a halo round the sun or the moon is called a cock's eye and is a token of bad weather. The term is related to the Breton word kog-heol. In Nepal, the halo round the sun is called Indrasabha with a connotation of the assembly court of Lord Indra – the Hindu god of lightning and rain; the natural phenomena may be reproduced artificially by several means. Firstly, by computer simulations, or secondly by experimental means. Regarding the latter, one may either take a single crystal and rotate it around the appropriate axis/axes, or take a chemical approach. A still further and more indirect experimental approach is to find analogous refraction geometries; this approach employs the fact that in some cases the average geometry of refraction through an ice crystal may be imitated / mimicked via the refraction through another geo