diff --git a/_index.db b/_index.db index 90be8d0a0..4a55ae80b 100644 Binary files a/_index.db and b/_index.db differ diff --git a/data/en.wikipedia.org/wiki/Birds_in_a_truck_riddle-0.md b/data/en.wikipedia.org/wiki/Birds_in_a_truck_riddle-0.md new file mode 100644 index 000000000..ff14d99cc --- /dev/null +++ b/data/en.wikipedia.org/wiki/Birds_in_a_truck_riddle-0.md @@ -0,0 +1,16 @@ +--- +title: "Birds in a truck riddle" +chunk: 1/1 +source: "https://en.wikipedia.org/wiki/Birds_in_a_truck_riddle" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:57.867658+00:00" +instance: "kb-cron" +--- + +The birds in a truck riddle is a riddle that asks whether a container or a truck carrying birds changes in weight when the birds inside are flying. +The television series MythBusters investigated the question in a 2007 episode, testing it both with a box of pigeons and again with a model helicopter. They concluded that the contents being in flight made no difference to the weight, and theorised that the downdraft of air from the wings or rotors pressed down against the base of the box with the same force as the resting bird or helicopter. +A drone research team from Stanford University measured the forces involved in a bird's hovering and found that it created "double the lift during the downstroke [of the wings] so that the birds did not have to lift their weight during the upstroke", with the amount of lift on the upstroke being "almost none". They concluded that a truck containing a few birds would fluctuate in weight over time, but a larger flock flapping at random would cancel one another and leave the truck's weight unaffected. + + +== References == \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/Intrinsic_and_extrinsic_properties-0.md b/data/en.wikipedia.org/wiki/Intrinsic_and_extrinsic_properties-0.md new file mode 100644 index 000000000..8ad573bfd --- /dev/null +++ b/data/en.wikipedia.org/wiki/Intrinsic_and_extrinsic_properties-0.md @@ -0,0 +1,26 @@ +--- +title: "Intrinsic and extrinsic properties" +chunk: 1/1 +source: "https://en.wikipedia.org/wiki/Intrinsic_and_extrinsic_properties" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:49.612401+00:00" +instance: "kb-cron" +--- + +In science and engineering, an intrinsic property is a property of a specified subject that exists itself or within the subject. An extrinsic property is not essential or inherent to the subject that is being characterized. For example, mass is an intrinsic property of any physical object, whereas weight is an extrinsic property that depends on the strength of the gravitational field in which the object is placed. + + +== Applications == +In materials science, an intrinsic property is independent of how much of a material is present and is independent of the form of the material, e.g., one large piece or a collection of small particles. Intrinsic properties are dependent mainly on the fundamental chemical composition and structure of the material. Extrinsic properties are differentiated as being dependent on the presence of avoidable chemical contaminants or structural defects. +In biology, intrinsic effects originate from inside an organism or cell, such as an autoimmune disease or intrinsic immunity. +In electronics and optics, intrinsic properties of devices (or systems of devices) are generally those that are free from the influence of various types of non-essential defects. Such defects may arise as a consequence of design imperfections, manufacturing errors, or operational extremes and can produce distinctive and often undesirable extrinsic properties. The identification, optimization, and control of both intrinsic and extrinsic properties are among the engineering tasks necessary to achieve the high performance and reliability of modern electrical and optical systems. + + +== See also == +All pages with titles beginning with Intrinsic and extrinsic +Intensive and extensive properties +Intrinsic and extrinsic motivation + + +== References == \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/José_Miguel_Camacho_González-0.md b/data/en.wikipedia.org/wiki/José_Miguel_Camacho_González-0.md new file mode 100644 index 000000000..d13286a9c --- /dev/null +++ b/data/en.wikipedia.org/wiki/José_Miguel_Camacho_González-0.md @@ -0,0 +1,23 @@ +--- +title: "José Miguel Camacho González" +chunk: 1/1 +source: "https://en.wikipedia.org/wiki/José_Miguel_Camacho_González" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:55.160998+00:00" +instance: "kb-cron" +--- + +José Miguel Camacho González (born 17 January 1951) is a Spanish ophthalmologist, medical director, and pioneer on intraocular lens. +He was born in Cúllar, Granada. He studied at Universidad de Granada, in 1976 he got a bachelor's degree in Medicine and in 1979 he specialized on Surgery. In 1970s he worked as ophthalmologist at Bola Azul and Hospital Torrecárdenas in Almería, and he cooperated with Instituto de Oftalmología Barraquer. +He opened Vista Camacho, which works with the latest and innovated ophthalmological technologies, including VisX STAR S4 IR CustomVue laser with the Wave Scan aberrometer, and the Spectralis(R) platform, which is a tomograph to make micro-thousandth eye studies. +He is one of the most rated ophthalmologist in the province of Almería by Doctoralia. Manuel Camacho Sampelayo, his son, who followed his steps and also studied at Universidad de Granada and Instituto de Oftalmología Barraquer, holds the eighth place in the ranking, and his brother José Miguel holds the ninth place. In 2010 he got the 3rd Videofestival Secoir Cádiz Award alongside Jaime Campello Lluch and José Miguel Camacho Sampelayo. In March 2022 he provided free services to Ukrainian refugees in Almería due to the Russian invasion of Ukraine, and he was awarded in the same year as "Colegiado Honorífico" by the Colegio de Médicos de Almería. + + +== References == + + +== External links == +Official website +Vista Camacho on Facebook +VistaCamacho on YouTube \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/List_of_effects-0.md b/data/en.wikipedia.org/wiki/List_of_effects-0.md index df4a91839..0dca65b4e 100644 --- a/data/en.wikipedia.org/wiki/List_of_effects-0.md +++ b/data/en.wikipedia.org/wiki/List_of_effects-0.md @@ -4,7 +4,7 @@ chunk: 1/4 source: "https://en.wikipedia.org/wiki/List_of_effects" category: "reference" tags: "science, encyclopedia" -date_saved: "2026-05-05T03:28:36.370706+00:00" +date_saved: "2026-05-05T03:50:48.360559+00:00" instance: "kb-cron" --- diff --git a/data/en.wikipedia.org/wiki/List_of_effects-1.md b/data/en.wikipedia.org/wiki/List_of_effects-1.md index c427c03c4..7bd6b9567 100644 --- a/data/en.wikipedia.org/wiki/List_of_effects-1.md +++ b/data/en.wikipedia.org/wiki/List_of_effects-1.md @@ -4,7 +4,7 @@ chunk: 2/4 source: "https://en.wikipedia.org/wiki/List_of_effects" category: "reference" tags: "science, encyclopedia" -date_saved: "2026-05-05T03:28:36.370706+00:00" +date_saved: "2026-05-05T03:50:48.360559+00:00" instance: "kb-cron" --- diff --git a/data/en.wikipedia.org/wiki/List_of_effects-2.md b/data/en.wikipedia.org/wiki/List_of_effects-2.md index d6af72cdb..e2638de31 100644 --- a/data/en.wikipedia.org/wiki/List_of_effects-2.md +++ b/data/en.wikipedia.org/wiki/List_of_effects-2.md @@ -4,7 +4,7 @@ chunk: 3/4 source: "https://en.wikipedia.org/wiki/List_of_effects" category: "reference" tags: "science, encyclopedia" -date_saved: "2026-05-05T03:28:36.370706+00:00" +date_saved: "2026-05-05T03:50:48.360559+00:00" instance: "kb-cron" --- diff --git a/data/en.wikipedia.org/wiki/List_of_effects-3.md b/data/en.wikipedia.org/wiki/List_of_effects-3.md index 800da864d..0af14e298 100644 --- a/data/en.wikipedia.org/wiki/List_of_effects-3.md +++ b/data/en.wikipedia.org/wiki/List_of_effects-3.md @@ -4,7 +4,7 @@ chunk: 4/4 source: "https://en.wikipedia.org/wiki/List_of_effects" category: "reference" tags: "science, encyclopedia" -date_saved: "2026-05-05T03:28:36.370706+00:00" +date_saved: "2026-05-05T03:50:48.360559+00:00" instance: "kb-cron" --- diff --git a/data/en.wikipedia.org/wiki/List_of_people_considered_father_or_mother_of_a_scientific_field-0.md b/data/en.wikipedia.org/wiki/List_of_people_considered_father_or_mother_of_a_scientific_field-0.md new file mode 100644 index 000000000..b99d3b87d --- /dev/null +++ b/data/en.wikipedia.org/wiki/List_of_people_considered_father_or_mother_of_a_scientific_field-0.md @@ -0,0 +1,63 @@ +--- +title: "List of people considered father or mother of a scientific field" +chunk: 1/1 +source: "https://en.wikipedia.org/wiki/List_of_people_considered_father_or_mother_of_a_scientific_field" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:53.831223+00:00" +instance: "kb-cron" +--- + +The following is a list of people who are considered a "father" or "mother" (or "founding father" or "founding mother") of a scientific field. Such people are generally regarded to have made the first significant contributions to and/or delineation of that field; they may also be seen as "a" rather than "the" father or mother of the field. Debate over who merits the title can be perennial. + + +== Science as a whole == + + +== Natural sciences == + + +=== Biology === + + +=== Chemistry === + + +=== Earth sciences === + + +=== Medicine and physiology === + + +=== Physics and astronomy === + + +== Formal sciences == + + +=== Mathematics === + + +=== Systems theory === + + +== Social sciences == + + +=== Economics === + + +==== Schools of thought ==== + + +==== Theories ==== + + +== See also == +Founders of statistics + + +== Notes == + + +== References == \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/List_of_pioneers_in_computer_science-0.md b/data/en.wikipedia.org/wiki/List_of_pioneers_in_computer_science-0.md new file mode 100644 index 000000000..cfb86a481 --- /dev/null +++ b/data/en.wikipedia.org/wiki/List_of_pioneers_in_computer_science-0.md @@ -0,0 +1,53 @@ +--- +title: "List of pioneers in computer science" +chunk: 1/1 +source: "https://en.wikipedia.org/wiki/List_of_pioneers_in_computer_science" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:56.325384+00:00" +instance: "kb-cron" +--- + +This is a list of people who made transformative breakthroughs in the creation, development and imagining of what computers could do. + + +== Pioneers == + +~ Items marked with a tilde are circa dates. + + +== See also == + +Computer Pioneer Award +IEEE John von Neumann Medal +Grace Murray Hopper Award +History of computing +History of computing hardware +History of computing hardware (1960s–present) +History of software +List of computer science awards +List of computer science journals +List of computer scientists +List of Internet pioneers +List of pioneers in computer science +List of people considered father or mother of a field § Computing +The Man Who Invented the Computer (2010 book) +List of Russian IT developers +List of Women in Technology International Hall of Fame inductees +Timeline of computing +Turing Award +Women in computing + + +== References == + + +=== Sources === +Hamming, Richard W. (1950). "Error detecting and error correcting codes" (PDF). Bell System Technical Journal. 29 (2): 147–160. Bibcode:1950BSTJ...29..147H. doi:10.1002/j.1538-7305.1950.tb00463.x. hdl:10945/46756. MR 0035935. S2CID 61141773. Archived from the original (PDF) on 2006-05-25. +Ling, San; Xing, Chaoping (2004). Coding Theory: a First Course. Cambridge: Cambridge University Press. ISBN 978-0-521-82191-9. +Pless, Vera (1982). Introduction to the Theory of Error-Correcting Codes. New York: Wiley. ISBN 978-0-471-08684-0. +Morgan, Samuel P. (September 1998). "Richard Wesley Hamming (1915–1998)" (PDF). Notices of the AMS. 45 (8): 972–977. ISSN 0002-9920. Retrieved 2014-08-30. + + +== External links == +Internet pioneers \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_chemistry-0.md b/data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_chemistry-0.md new file mode 100644 index 000000000..00a75f902 --- /dev/null +++ b/data/en.wikipedia.org/wiki/List_of_unsolved_problems_in_chemistry-0.md @@ -0,0 +1,61 @@ +--- +title: "List of unsolved problems in chemistry" +chunk: 1/1 +source: "https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_chemistry" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:59.139871+00:00" +instance: "kb-cron" +--- + +This is a list of unsolved problems in chemistry. Problems in chemistry are considered unsolved when an expert in the field considers it unsolved or when several experts in the field disagree about a solution to a problem. + + +== Physical chemistry problems == + +Can the transition temperature of high-temperature superconductors be brought up to room temperature? +How do the spin–orbit coupling, other relativistic corrections, and inter-electron effects modify the chemistry of the trans-actinides? +Is it possible to create a practically useful lithium–air battery? + + +== Organic chemistry problems == + +What is the origin of homochirality in biomolecules? +Why are accelerated kinetics observed for some organic reactions at the water-organic interface? +Do replacement reactions of aryl diazonium salts (dediazotizations) predominantly undergo SN1 or a radical mechanism? +Can an electrochemical cell reliably perform organic redox reactions? +Which "classic organic chemistry" reactions admit chiral catalysts? +Is it possible to construct a quaternary carbon atom with arbitrary (distinguishable) substituents and stereochemistry? +Can artificial enzymes replace the need for protecting groups when modifying sensitive compounds? + + +== Inorganic chemistry problems == + +Are there any molecules that certainly contain a phi bond? +Is there a less labor- or energy-intensive technique for titanium refinement than the Kroll process? +Does nitrogen admit metastable allotropes under standard conditions? +Can new solvents or other techniques make direct carbon capture economical? +Can artificial photosynthesis make any common fuels? +What is a reliable synthesis and stabilization method for catenary allotropes of sulfur and carbon? + + +== Biochemistry problems == + +Enzyme kinetics: Why do some enzymes exhibit faster-than-diffusion kinetics? +Protein folding problem: Is it possible to predict the secondary, tertiary and quaternary structure of a polypeptide sequence based solely on the sequence and environmental information? Inverse protein-folding problem: Is it possible to design a polypeptide sequence which will adopt a given structure under certain environmental conditions? This has been achieved for several small globular proteins in recent years. In 2020, it was announced that Google's AlphaFold, a neural network based on DeepMind artificial intelligence, is capable of predicting a protein's final shape based solely on its amino-acid chain with an accuracy of around 90% on a test sample of proteins used by the team. +RNA folding problem: Is it possible to accurately predict the secondary, tertiary and quaternary structure of a polyribonucleic acid sequence based on its sequence and environment? +Protein design: Is it possible to design highly active enzymes de novo for any desired reaction? +Biosynthesis: Can desired molecules, natural products or otherwise, be produced in high yield through biosynthetic pathway manipulation? + + +== See also == +Lists of unsolved problems +Outline of chemistry + + +== References == + + +== External links == +"First 25 of 125 big questions that face scientific inquiry over the next quarter-century". Science. 309 (125th Anniversary). 1 July 2005. +Unsolved Problems in Nanotechnology: Chemical Processing by Self-Assembly - Matthew Tirrell - Departments of Chemical Engineering and Materials, Materials Research Laboratory, California NanoSystems Institute, University of California, Santa Barbara [No doc at link, 20 Aug 2016] \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/Rayleigh_scattering-0.md b/data/en.wikipedia.org/wiki/Rayleigh_scattering-0.md new file mode 100644 index 000000000..aa0a73cdb --- /dev/null +++ b/data/en.wikipedia.org/wiki/Rayleigh_scattering-0.md @@ -0,0 +1,307 @@ +--- +title: "Rayleigh scattering" +chunk: 1/2 +source: "https://en.wikipedia.org/wiki/Rayleigh_scattering" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:50.823381+00:00" +instance: "kb-cron" +--- + +Rayleigh scattering ( RAY-lee) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scattering medium (normal dispersion regime), the amount of scattering is inversely proportional to the fourth power of the wavelength (e.g., a blue color is scattered much more than a red color as light propagates through air). The phenomenon is named after the 19th-century British physicist Lord Rayleigh (John William Strutt). + +Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle, therefore, becomes a small radiating dipole whose radiation we see as scattered light. The particles may be individual atoms or molecules; it can occur when light travels through transparent solids and liquids, but is most prominently seen in gases. +Rayleigh scattering of sunlight in Earth's atmosphere causes diffuse sky radiation. Since blue light wavelengths scatter more, the diffuse sky seen in daytime is blue. At twilight the sunlight on the horizon is missing the scattered blue light wavelengths giving a yellowish to reddish hue to the low Sun. +Scattering by particles with a size comparable to, or larger than, the wavelength of the light is typically treated by the Mie theory, the discrete dipole approximation and other computational techniques. Rayleigh scattering applies to particles that are small with respect to wavelengths of light, and that are optically "soft" (i.e., with a refractive index close to 1). Anomalous diffraction theory applies to optically soft but larger particles. + +== History == +In 1869, while attempting to determine whether any contaminants remained in the purified air he used for infrared experiments, John Tyndall discovered that bright light scattering off nanoscopic particulates was faintly blue-tinted. He conjectured that a similar scattering of sunlight gave the sky its blue hue, but he could not explain the preference for blue light, nor could atmospheric dust explain the intensity of the sky's color. +In 1871, Lord Rayleigh published two papers on the color and polarization of skylight to quantify Tyndall's effect in water droplets in terms of the tiny particulates' volumes and refractive indices. In 1881, with the benefit of James Clerk Maxwell's 1865 proof of the electromagnetic nature of light, he showed that his equations followed from electromagnetism. In 1899, he showed that they applied to individual molecules, with terms containing particulate volumes and refractive indices replaced with terms for molecular polarizability. +It was this paper that established the basic scientific model for the color of the sky. + +== Small size parameter approximation == +The size of a scattering particle is often parameterized by the ratio + + + + + x + = + + + + 2 + π + r + + λ + + + + + {\displaystyle x={\frac {2\pi r}{\lambda }}} + + +where r is the particle's radius, λ is the wavelength of the light and x is a dimensionless parameter that characterizes the particle's interaction with the incident radiation such that: Objects with x ≫ 1 act as geometric shapes, scattering light according to their projected area. At the intermediate x ≃ 1 of Mie scattering, interference effects develop through phase variations over the object's surface. Rayleigh scattering applies to the case when the scattering particle is very small (x ≪ 1, with a particle size < 1/10 of wavelength) and the whole surface re-radiates with the same phase. Because the particles are randomly positioned, the scattered light arrives at a particular point with a random collection of phases; it is incoherent and the resulting intensity is just the sum of the squares of the amplitudes from each particle and therefore proportional to the inverse fourth power of the wavelength and the sixth power of its size. The wavelength dependence is characteristic of dipole scattering and the volume dependence will apply to any scattering mechanism. In detail, the intensity of light scattered by any one of the small spheres of radius r and refractive index n from a beam of unpolarized light of wavelength λ and intensity I0 is given by + + + + + + I + + s + + + = + + I + + 0 + + + + + + 1 + + + + cos + + 2 + + + ⁡ + θ + + + 2 + + R + + 2 + + + + + + + + ( + + + + 2 + π + + λ + + + ) + + + 4 + + + + + ( + + + + + n + + 2 + + + − + 1 + + + + n + + 2 + + + + + 2 + + + + ) + + + 2 + + + + r + + 6 + + + + + {\displaystyle I_{s}=I_{0}{\frac {1+\cos ^{2}\theta }{2R^{2}}}\left({\frac {2\pi }{\lambda }}\right)^{4}\left({\frac {n^{2}-1}{n^{2}+2}}\right)^{2}r^{6}} + + +where R is the observer's distance to the particle and θ is the scattering angle. Averaging this over all angles gives the Rayleigh scattering cross-section of the particles in air: + + + + + + σ + + s + + + = + + + + 8 + π + + 3 + + + + + ( + + + + 2 + π + + λ + + + ) + + + 4 + + + + + ( + + + + + n + + 2 + + + − + 1 + + + + n + + 2 + + + + + 2 + + + + ) + + + 2 + + + + r + + 6 + + + . + + + {\displaystyle \sigma _{\text{s}}={\frac {8\pi }{3}}\left({\frac {2\pi }{\lambda }}\right)^{4}\left({\frac {n^{2}-1}{n^{2}+2}}\right)^{2}r^{6}.} + + +Here n is the refractive index of the spheres that approximate the molecules of the gas; the index of the gas surrounding the spheres is neglected, an approximation that introduces an error of less than 0.05%. +The major constituent of the atmosphere, nitrogen, has Rayleigh cross section of 5.1×10−31 m2 at a wavelength of 532 nm (green light). Over the length of one meter the fraction of light scattered can be approximated from the product of the cross-section and the particle density, that is number of particles per unit volume. For air at atmospheric pressure there are about 2×1025 molecules per cubic meter, and the fraction scattered will be 10−5 for every meter of travel. + +== From molecules == + +The expression above can also be written in terms of individual molecules by expressing the dependence on refractive index in terms of the molecular polarizability α, proportional to the dipole moment induced by the electric field of the light. In this case, the Rayleigh scattering intensity for a single particle is given in CGS-units by + + + + + + I + + s + + + = + + I + + 0 + + + + + + 8 + + π + + 4 + + + + α + + 2 + + + + + + λ + + 4 + + + + R + + 2 + + + + + + ( + 1 + + + + cos + + 2 + + + ⁡ + θ + ) + + + {\displaystyle I_{s}=I_{0}{\frac {8\pi ^{4}\alpha ^{2}}{\lambda ^{4}R^{2}}}(1+\cos ^{2}\theta )} + + +and in SI-units by \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/Rayleigh_scattering-1.md b/data/en.wikipedia.org/wiki/Rayleigh_scattering-1.md new file mode 100644 index 000000000..cd87fc580 --- /dev/null +++ b/data/en.wikipedia.org/wiki/Rayleigh_scattering-1.md @@ -0,0 +1,345 @@ +--- +title: "Rayleigh scattering" +chunk: 2/2 +source: "https://en.wikipedia.org/wiki/Rayleigh_scattering" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:50.823381+00:00" +instance: "kb-cron" +--- + + + + + + I + + s + + + = + + I + + 0 + + + + + + + π + + 2 + + + + α + + 2 + + + + + + + + ε + + 0 + + + + + 2 + + + + λ + + 4 + + + + R + + 2 + + + + + + + + + 1 + + + + cos + + 2 + + + ⁡ + θ + + 2 + + + . + + + {\displaystyle I_{s}=I_{0}{\frac {\pi ^{2}\alpha ^{2}}{{\varepsilon _{0}}^{2}\lambda ^{4}R^{2}}}{\frac {1+\cos ^{2}\theta }{2}}.} + + +== Effect of fluctuations == +When the dielectric constant + + + + ϵ + + + {\displaystyle \epsilon } + + of a certain region of volume + + + + V + + + {\displaystyle V} + + is different from the average dielectric constant of the medium + + + + + + + ϵ + ¯ + + + + + + {\displaystyle {\bar {\epsilon }}} + +, then any incident light will be scattered according to the following equation + + + + + I + = + + I + + 0 + + + + + + + π + + 2 + + + + V + + 2 + + + + σ + + ϵ + + + 2 + + + + + 2 + + λ + + 4 + + + + R + + 2 + + + + + + + + ( + + 1 + + + + cos + + 2 + + + ⁡ + θ + + ) + + + + + {\displaystyle I=I_{0}{\frac {\pi ^{2}V^{2}\sigma _{\epsilon }^{2}}{2\lambda ^{4}R^{2}}}{\left(1+\cos ^{2}\theta \right)}} + +where + + + + + σ + + ϵ + + + 2 + + + + + {\displaystyle \sigma _{\epsilon }^{2}} + + represents the variance of the fluctuation in the dielectric constant + + + + ϵ + + + {\displaystyle \epsilon } + +. + +== Cause of the blue color of the sky == + +The blue color of the sky is a consequence of three factors: + +the blackbody spectrum of sunlight coming into the Earth's atmosphere, +Rayleigh scattering of that light off oxygen and nitrogen molecules, and +the response of the human visual system. +The strong wavelength dependence of the Rayleigh scattering (~λ−4) means that shorter (blue) wavelengths are scattered more strongly than longer (red) wavelengths. This results in the indirect blue and violet light coming from all regions of the sky. The human eye responds to this wavelength combination as if it were a combination of blue and white light. +Some of the scattering can also be from sulfate particles. For years after large Plinian eruptions, the blue cast of the sky is notably brightened by the persistent sulfate load of the stratospheric gases. Some works of the artist J. M. W. Turner may owe their vivid red colours to the eruption of Mount Tambora in his lifetime. +In locations with little light pollution, the moonlit night sky is also blue, because moonlight is reflected sunlight, with a slightly lower color temperature due to the brownish color of the Moon. The moonlit sky is not perceived as blue, however, because at low light levels human vision comes mainly from rod cells that do not produce any color perception (Purkinje effect). + +== Of sound in amorphous solids == +Rayleigh scattering is also an important mechanism of wave scattering in amorphous solids such as glass, and is responsible for acoustic wave damping and phonon damping in glasses and granular matter at low or not too high temperatures. This is because in glasses at higher temperatures the Rayleigh-type scattering regime is obscured by the anharmonic damping (typically with a ~λ−2 dependence on wavelength), which becomes increasingly more important as the temperature rises. + +== In amorphous solids – glasses – optical fibers == +Rayleigh scattering is an important component of the scattering of optical signals in optical fibers. Silica fibers are glasses, disordered materials with microscopic variations of density and refractive index. These give rise to energy losses due to the scattered light, with the following coefficient: + + + + + + α + + scat + + + = + + + + 8 + + π + + 3 + + + + + 3 + + λ + + 4 + + + + + + + n + + 8 + + + + p + + 2 + + + k + + T + + f + + + β + + + {\displaystyle \alpha _{\text{scat}}={\frac {8\pi ^{3}}{3\lambda ^{4}}}n^{8}p^{2}kT_{\text{f}}\beta } + + +where n is the refraction index, p is the photoelastic coefficient of the glass, k is the Boltzmann constant, and β is the isothermal compressibility. Tf is a fictive temperature, representing the temperature at which the density fluctuations are "frozen" in the material. + +== In porous materials == + +Rayleigh-type λ−4 scattering can also be exhibited by porous materials. An example is the strong optical scattering by nanoporous materials. The strong contrast in refractive index between pores and solid parts of sintered alumina results in very strong scattering, with light completely changing direction each five micrometers on average. The λ−4-type scattering is caused by the nanoporous structure (a narrow pore size distribution around ~70 nm) obtained by sintering monodispersive alumina powder. + +== See also == +Rayleigh sky model – Polarization pattern of the daytime sky +Rician fading – Radio signal statistical model +Optical phenomena – Observable events that result from the interaction of light and matterPages displaying short descriptions of redirect targets +Dynamic light scattering – Technique for determining size distribution of particles +Raman scattering – Inelastic scattering of photons by matter +Rayleigh–Gans approximation +Tyndall effect – Scattering of light by tiny particles in a colloidal suspension +Critical opalescence – Increase in photonic scattering during a phase transition +HRS Computing – scientific simulation software +Marian Smoluchowski – Polish physicist (1872–1917) +Rayleigh criterion – Ability of any image-forming device to distinguish small details of an object +Aerial perspective – Atmospheric effects on the appearance of a distant object +Parametric process – Interacting phenomenon between light and matter +Bragg's law – Physical law regarding scattering angles of radiation through a medium + +== Works == +Strutt, J.W (1871). "XV. On the light from the sky, its polarization and colour". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 41 (271): 107–120. doi:10.1080/14786447108640452. +Strutt, J.W (1871). "XXXVI. On the light from the sky, its polarization and colour". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 41 (273): 274–279. doi:10.1080/14786447108640479. +Strutt, J.W (1871). "LVIII. On the scattering of light by small particles". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 41 (275): 447–454. doi:10.1080/14786447108640507. +Rayleigh, Lord (1881). "X. On the electromagnetic theory of light". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 12 (73): 81–101. doi:10.1080/14786448108627074. +Rayleigh, Lord (1899). "XXXIV. On the transmission of light through an atmosphere containing small particles in suspension, and on the origin of the blue of the sky". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 47 (287): 375–384. doi:10.1080/14786449908621276. + +== References == + +== Further reading == + +== External links == + +HyperPhysics description of Rayleigh scattering +Full physical explanation of sky color, in simple terms \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/Recovery_effect-0.md b/data/en.wikipedia.org/wiki/Recovery_effect-0.md new file mode 100644 index 000000000..3f83e074c --- /dev/null +++ b/data/en.wikipedia.org/wiki/Recovery_effect-0.md @@ -0,0 +1,32 @@ +--- +title: "Recovery effect" +chunk: 1/1 +source: "https://en.wikipedia.org/wiki/Recovery_effect" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:52.101449+00:00" +instance: "kb-cron" +--- + +The recovery effect is a phenomenon observed in battery usage where the available energy is less than the difference between energy charged and energy consumed. + + +== Mechanism == +Intuitively, this is because the energy has been consumed from the edge of the battery and the charge has not yet diffused evenly around the battery. +When power is extracted continuously voltage decreases in a smooth curve, but the recovery effect can result in the voltage partially increasing if the current is interrupted. + + +== In non-lead-acid batteries == +The KiBaM battery model describes the recovery effect for lead-acid batteries and is also a good approximation to the observed effects in Li-ion batteries. In some batteries, the gains from the recovery life can extend battery life by up to 45% by alternating discharging and inactive periods rather than constantly discharging. The size of the recovery effect depends on the battery load, recovery time and depth of discharge. +Even though the recovery effect phenomenon is prominent in the lead acid battery chemistry, its existence in alkaline, Ni-MH and Li-Ion batteries is still questionable. For instance, a systematic experimental case study shows that an intermittent discharge current in case of alkaline, Ni-MH and Li-ion batteries results in a decreased usable energy output compared to a continuous discharge current of the same average value. This is primarily due to the increased overpotential experienced due to the high peak currents of the intermittent discharge over the continuous discharge current of same average value. + + +== See also == +Capacity fading +State of health +State of charge +Smart battery +Battery management system + + +== References == \ No newline at end of file diff --git a/data/en.wikipedia.org/wiki/Virtual_scientific_community-0.md b/data/en.wikipedia.org/wiki/Virtual_scientific_community-0.md new file mode 100644 index 000000000..d32224cc3 --- /dev/null +++ b/data/en.wikipedia.org/wiki/Virtual_scientific_community-0.md @@ -0,0 +1,30 @@ +--- +title: "Virtual scientific community" +chunk: 1/1 +source: "https://en.wikipedia.org/wiki/Virtual_scientific_community" +category: "reference" +tags: "science, encyclopedia" +date_saved: "2026-05-05T03:50:46.134380+00:00" +instance: "kb-cron" +--- + +A virtual scientific community is a group of people, often researchers and students, who share multiple resources related to the scientific field, and whose main medium of communication is the internet. Examples of such communities include the Computational Intelligence and Machine Learning Portal or the Biomedical Informatics Research Network. +There are numerous scientific repositories and websites in existence that, while useful, do not meet the definition of a virtual scientific community. Examples of such are data and scientific literature repositories as well as open access journals. + + +== Further reading == +Jacek M. Zurada, Janusz Wojtusiak, Maciej A. Mazurowski, Devendra Mehta, Khalid Moidu, Steve Margolis, Toward Multidisciplinary Collaboration in the CIML Virtual Community, Proceedings of the 2008 Workshop on Building Computational Intelligence and Machine Learning Virtual Organizations, pp. 62–66 + + +== See also == +Science +Community +CIML community portal + + +== External links == +The Computational Intelligence and Machine Learning Virtual Community Archived 2009-10-04 at the Wayback Machine +What is BIRN? + + +== References == \ No newline at end of file