Summary

HandWiki is the world's largest wiki-style encyclopedia dedicated to science, technology and computing. It allows you to create and edit articles as long as you have external citations and login account. In addition, this is a content management environment that can be used for collaborative editing of original scholarly content, such as books, manuals, monographs and tutorials.

Expand All
Entries
Topic Review
Englert–Greenberger–Yasin Duality Relation
The Englert–Greenberger–Yasin duality relation, often called the Englert–Greenberger relation, relates the visibility, [math]\displaystyle{ V }[/math], of interference fringes with the definiteness, or distinguishability, [math]\displaystyle{ D }[/math], of the photons' paths in quantum optics. As an inequality: Although it is treated as a single relation, it actually involves two separate relations, which mathematically look very similar. The first relationship was first experimentally shown by Greenberger and Yasin in 1988. It was later theoretically derived by Jaeger, Shimony, and Vaidman in 1995. This relation involves correctly guessing which of the two paths the particle would have taken, based on the initial preparation. Here [math]\displaystyle{ D }[/math] can be called the predictability, and is sometimes denoted by [math]\displaystyle{ P }[/math]. A year later Englert, in 1996, apparently unaware of this result, derived a related relation which dealt with knowledge of the two paths using an apparatus. Here [math]\displaystyle{ D }[/math] is called the distinguishability. The significance of the relation is that it expresses quantitatively the complementarity of wave and particle viewpoints in double slit experiments. The complementarity principle in quantum mechanics, formulated by Niels Bohr, says that the wave and particle aspects of quantum objects cannot be observed at the same time. The Englert–Greenberger relation makes this more precise; an experiment can yield partial information about the wave and particle aspects of a photon simultaneously, but the more information a particular experiment gives about one, the less it will give about the other. The distinguishability [math]\displaystyle{ D }[/math] which expresses the degree of probability with which path of the particle is known, is a measure of the particle information, while the visibility of the fringes [math]\displaystyle{ V }[/math] is a measure of the wave information. The relation shows that they are inversely related, as one goes up, the other goes down.
  • 915
  • 18 Oct 2022
Topic Review
Duck
Duck is the common name for numerous species in the waterfowl family Anatidae which also includes swans and geese. Ducks are divided among several subfamilies in the family Anatidae; they do not represent a monophyletic group (the group of all descendants of a single common ancestral species) but a form taxon, since swans and geese are not considered ducks. Ducks are mostly aquatic birds, mostly smaller than the swans and geese, and may be found in both fresh water and sea water. Ducks are sometimes confused with several types of unrelated water birds with similar forms, such as loons or divers, grebes, gallinules and coots.
  • 3.1K
  • 18 Oct 2022
Topic Review
Biochemical Oxygen Demand
Biochemical oxygen demand (BOD) is the amount of dissolved oxygen (DO) needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C and is often used as a surrogate of the degree of organic pollution of water. BOD reduction is used as a gauge of the effectiveness of wastewater treatment plants. BOD of wastewater effluents is used to indicate the short-term impact on the oxygen levels of the receiving water. BOD analysis is similar in function to chemical oxygen demand (COD) analysis, in that both measure the amount of organic compounds in water. However, COD analysis is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically oxidized organic matter.
  • 3.3K
  • 18 Oct 2022
Topic Review
Internet Archive
Coordinates: 37°46′56″N 122°28′18″W / 37.782321°N 122.47161137°W / 37.782321; -122.47161137 The Internet Archive is an American digital library with the stated mission of "universal access to all knowledge".[notes 2][notes 3] It provides free public access to collections of digitized materials, including websites, software applications/games, music, movies/videos, moving images, and millions of books. In addition to its archiving function, the Archive is an activist organization, advocating a free and open Internet. As of April 2021, the Internet Archive holds over 30 million books and texts, 8.9 million movies, videos and TV shows, 649,000 software programs, 13,225,000 audio files, 3.8 million images, and 580 billion web pages in the Wayback Machine. The Internet Archive allows the public to upload and download digital material to its data cluster, but the bulk of its data is collected automatically by its web crawlers, which work to preserve as much of the public web as possible. Its web archive, the Wayback Machine, contains hundreds of billions of web captures.[notes 4] The Archive also oversees one of the world's largest book digitization projects.
  • 13.3K
  • 18 Oct 2022
Topic Review
Eos (Genus)
Eos is a genus of parrots belonging to the lories and lorikeets tribe of the family Psittaculidae. There are six species which are all endemic to islands of eastern Indonesia, most within very restricted ranges. They have predominantly red plumage with blue, purple or black markings. Males and females are similar in appearance. Their habitats include forest, coconut plantations and mangroves. They gather in flowering trees to feed on nectar and pollen with their brush-tipped tongues. Fruit and insects are also eaten. They make nests in tree hollows generally high in old large trees. Threats to these parrots include habitat loss and trapping for the cagebird trade, and one species, the red-and-blue lory, is classified as endangered.
  • 811
  • 18 Oct 2022
Topic Review
1860 Oxford Evolution Debate
The 1860 Oxford evolution debate took place at the Oxford University Museum in Oxford, England , on 30 June 1860, seven months after the publication of Charles Darwin's On the Origin of Species. Several prominent British scientists and philosophers participated, including Thomas Henry Huxley, Bishop Samuel Wilberforce, Benjamin Brodie, Joseph Dalton Hooker and Robert FitzRoy. The debate is best remembered today for a heated exchange in which Wilberforce supposedly asked Huxley whether it was through his grandfather or his grandmother that he claimed his descent from a monkey. Huxley is said to have replied that he would not be ashamed to have a monkey for his ancestor, but he would be ashamed to be connected with a man who used his great gifts to obscure the truth. One eyewitness suggests that Wilberforce's question to Huxley may have been "whether, in the vast shaky state of the law of development, as laid down by Darwin, any one can be so enamoured of this so-called law, or hypothesis, as to go into jubilation for his great great grandfather having been an ape or a gorilla?", whereas another suggests he may have said that "it was of little consequence to himself whether or not his grandfather might be called a monkey or not." The encounter is often known as the Huxley–Wilberforce debate or the Wilberforce–Huxley debate, although this description is somewhat misleading. Rather than being a formal debate between the two, it was actually an animated discussion that occurred after the presentation of a paper by John William Draper of New York University, on the intellectual development of Europe with relation to Darwin's theory (one of a number of scientific papers presented during the week as part of the British Association's annual meeting). Although Huxley and Wilberforce were not the only participants in the discussion, they were reported to be the two dominant parties. No verbatim account of the debate exists, and there is considerable uncertainty regarding what Huxley and Wilberforce actually said.
  • 2.9K
  • 18 Oct 2022
Topic Review
List of Aircraft (P)
This is a list of aircraft in alphabetical order beginning with 'P'.
  • 5.7K
  • 19 Oct 2022
Topic Review
SHIFT (DOS Command)
This research presents a list of commands used by DOS operating systems, especially as used on x86-based IBM PC compatibles (PCs). Other DOS operating systems are not part of the scope of this list. In DOS, many standard system commands were provided for common tasks such as listing files on a disk or moving files. Some commands were built into the command interpreter, others existed as external commands on disk. Over the several generations of DOS, commands were added for the additional functions of the operating system. In the current Microsoft Windows operating system, a text-mode command prompt window, cmd.exe, can still be used.
  • 1.1K
  • 19 Oct 2022
Topic Review
Kissing Number Problem
In geometry, a kissing number is defined as the number of non-overlapping unit spheres that can be arranged such that they each touch a common unit sphere. For a lattice packing the kissing number is the same for every sphere, but for an arbitrary sphere packing the kissing number may vary from one sphere to another. Other names for kissing number that have been used are Newton number (after the originator of the problem), and contact number. In general, the kissing number problem seeks the maximum possible kissing number for n-dimensional spheres in (n + 1)-dimensional Euclidean space. Ordinary spheres correspond to two-dimensional closed surfaces in three-dimensional space. Finding the kissing number when centers of spheres are confined to a line (the one-dimensional case) or a plane (two-dimensional case) is trivial. Proving a solution to the three-dimensional case, despite being easy to conceptualise and model in the physical world, eluded mathematicians until the mid-20th century. Solutions in higher dimensions are considerably more challenging, and only a handful of cases have been solved exactly. For others investigations have determined upper and lower bounds, but not exact solutions.
  • 1.6K
  • 19 Oct 2022
Topic Review
Chemical Bonding of H2O
Water (H2O) is a simple triatomic bent molecule with C2v molecular symmetry and bond angle of 104.5° between the central oxygen atom and the hydrogen atoms. Despite being one of the simplest triatomic molecules, its chemical bonding scheme is nonetheless complex as many of its bonding properties such as bond angle, ionization energy, and electronic state energy cannot be explained by one unified bonding model. Instead, several traditional and advanced bonding models such as simple Lewis and VESPR structure, valence bond theory, molecular orbital theory, isovalent hybridization, and Bent's rule are discussed below to provide a comprehensive bonding model for H2O, explaining and rationalizing the various electronic and physical properties and features manifested by its peculiar bonding arrangements.
  • 12.1K
  • 18 Oct 2022
  • Page
  • of
  • 863

Other Entry Collections

>>