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
Plus-Minus Sign
The plus-minus sign (±) is a mathematical symbol with multiple meanings. The sign is normally pronounced "plus or minus". In mathematics, it generally indicates a choice of exactly two possible values, one of which is the negation of the other. In experimental sciences, the sign commonly indicates the confidence interval or error in a measurement, often the standard deviation or standard error. The sign may also represent an inclusive range of values that a reading might have. In engineering the sign indicates the tolerance, which is the range of values that are considered to be acceptable, safe, or which comply with some standard, or with a contract. In botany it is used in morphological descriptions to notate "more or less". In chemistry the sign is used to indicate a racemic mixture. In chess, the sign indicates a clear advantage for the white player; the complementary sign ∓ indicates the same advantage for the black player.
  • 171.9K
  • 23 Apr 2023
Topic Review
Sleep Medicine
Sleep medicine is a medical specialty or subspecialty devoted to the diagnosis and therapy of sleep disturbances and disorders. From the middle of the 20th century, research has provided increasing knowledge and answered many questions about sleep-wake functioning. The rapidly evolving field has become a recognized medical subspecialty in some countries. Dental sleep medicine also qualifies for board certification in some countries. Properly organized, minimum 12-month, postgraduate training programs are still being defined in the United States. In some countries, the sleep researchers and the physicians who treat patients may be the same people. The first sleep clinics in the United States were established in the 1970s by interested physicians and technicians; the study, diagnosis and treatment of obstructive sleep apnea were their first tasks. As late as 1999, virtually any American physician, with no specific training in sleep medicine, could open a sleep laboratory. Disorders and disturbances of sleep are widespread and can have significant consequences for affected individuals as well as economic and other consequences for society. The US National Transportation Safety Board has, according to Charles Czeisler, member of the Institute of Medicine and Director of the Harvard University Medical School Division of Sleep Medicine at Brigham and Women's Hospital, discovered that the leading cause (31%) of fatal-to-the-driver heavy truck crashes is fatigue related (though rarely associated directly with sleep disorders, such as sleep apnea), with drugs and alcohol as the number two cause (29%). Sleep deprivation has also been a significant factor in dramatic accidents, such as the Exxon Valdez oil spill, the nuclear incidents at Chernobyl and Three Mile Island and the explosion of the space shuttle Challenger.
  • 1.6K
  • 27 Sep 2022
Topic Review
Cerium Nitrate
Cerium nitrate refers to a family of nitrates of cerium in the three or four oxidation state. Often these compounds contain water, hydroxide, or hydronium ions in addition to cerium and nitrate. Double nitrates of cerium also exist.
  • 3.7K
  • 27 Sep 2022
Topic Review
Wave-particle Duality Relation
The Wave–particle duality relation, often loosely referred to as the Englert–Greenberger–Yasin duality relation, or 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 relation, derived by Greenberger and Yasin in 1988, is expressed as [math]\displaystyle{ P^2+ V^2\le 1 \, }[/math]. It was later extended 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{ P }[/math] can be called the predictability. An year later Englert, in 1996, derived a related relation which dealt with experimentally acquiring knowledge of the two paths using an apparatus, as opposed to predicting the path based on initial preparation This relation is [math]\displaystyle{ D^2+ V^2\le 1 \, }[/math]. Here [math]\displaystyle{ D }[/math] is called the distinguishability. The significance of the relations is that they express 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 wave–particle duality relations makes Bohr's statement more quantitative – 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 predictability [math]\displaystyle{ P }[/math] which expresses the degree of probability with which path of the particle can be correctly guessed, and the distinguishability [math]\displaystyle{ D }[/math] which is the degree to which one can experimentally acquire information about the path of the particle, are measures of the particle information, while the visibility of the fringes [math]\displaystyle{ V }[/math] is a measure of the wave information. The relations shows that they are inversely related, as one goes up, the other goes down.
  • 861
  • 27 Sep 2022
Topic Review
Dickeya dadantii
Dickeya dadantii is a gram-negative bacillus that belongs to the family Enterobacteriaceae. It was formerly known as Erwinia chrysanthemi but was reassigned as Dickeya dadantii in 2005. Members of this family are facultative anaerobes, able to ferment sugars to lactic acid, have nitrate reductase, but lack oxidases. Even though many clinical pathogens are part of the Enterobacteriaceae family, most members of this family are plant pathogens. D. dadantii is a motile, nonsporing, straight rod-shaped cell with rounded ends. Cells range in size from 0.8 to 3.2 μm by 0.5 to 0.8 μm and are surrounded by numerous flagella (peritrichous). In the natural plant environment, D. dadantii causes plant maladies such as necrosis, blight and “soft rot,” which is a progressive tissue maceration. D. dadantii contains many pectinases that are able to macerate and break down the plant cell wall material. This exposed part of the plant releases nutrients that can facilitate bacterial growth. Commonly infected plants include potato tubers, bulbs of vegetables, and ornamental crops.
  • 1.9K
  • 11 Oct 2022
Topic Review
Atlantic Multidecadal Oscillation
The Atlantic Multidecadal Oscillation (AMO), also known as Atlantic Multidecadal Variability (AMV), is a climate cycle that affects the sea surface temperature (SST) of the North Atlantic Ocean based on different modes on multidecadal timescales. While there is some support for this mode in models and in historical observations, controversy exists with regard to its amplitude, and in particular, the attribution of sea surface temperature change to natural or anthropogenic causes, especially in tropical Atlantic areas important for hurricane development. The Atlantic multidecadal oscillation is also connected with shifts in hurricane activity, rainfall patterns and intensity, and changes in fish populations.
  • 1.8K
  • 27 Sep 2022
Topic Review
Low Intensity Conflict
A low-intensity conflict (LIC) is a military conflict, usually localised, between two or more state or non-state groups which is below the intensity of conventional war. It involves the state's use of military forces applied selectively and with restraint to enforce compliance with its policies or objectives. The term can be used to describe conflicts where at least one or both of the opposing parties operate along such lines.
  • 5.9K
  • 27 Sep 2022
Topic Review
Open Software License
The Open Software License (OSL) is a software license created by Lawrence Rosen. The Open Source Initiative (OSI) has certified it as an open-source license, but the Debian project judged version 1.1 to be incompatible with the DFSG. The OSL is a copyleft license, with a termination clause triggered by filing a lawsuit alleging patent infringement. Many people in the free software and open-source community feel that software patents are harmful to software, and are particularly harmful to open-source software. The OSL attempts to counteract that by creating a pool of software which a user can use if that user does not harm it by attacking it with a patent lawsuit.
  • 1.4K
  • 27 Sep 2022
Topic Review
Jyotisha
Jyotisha (Sanskrit: ज्योतिष, IAST: Jyotiṣa), now the term for traditional Hindu astrology, historically was the branch of knowledge dedicated to the observation of astronomical bodies in order to keep the right time for the Vedic sacrifices. It is one of the six Vedangas, or ancillary science connected with the Vedas that developed . This field of study was concerned with fixing the days and hours of Vedic rituals. Hindu astrology from the 3rd century BCE was greatly influenced by Greek tradition,. But the concept of Vedanga predates Greek contact, and there have also been later independent developments. Hindu astrology as it stands today is inherently a study of karma, which gives it a very different foundation compared to Greek astrology. In addition to this, the predictive techniques such as Dashas (planetary and sign-based time periods), Vargas (harmonic divisions of the horoscope) are not that evolved in Greek astrology.
  • 2.7K
  • 27 Sep 2022
Topic Review
Combat History of the T-26
Though nearly obsolete by the beginning of World War II, the T-26 was the most important tank of the Spanish Civil War and played a significant role during the Battle of Lake Khasan in 1938 as well as in the Winter War. The T-26 was the most numerous tank in the Red Army's armoured force during the German invasion of the Soviet Union in June 1941. The Soviet T-26 light tanks last saw combat in August 1945, in Manchuria. The T-26 was used extensively in the armies of Spain, China and Turkey. In addition, captured T-26 light tanks were used by the Finnish, German, Romanian and Hungarian armies.
  • 4.2K
  • 29 Sep 2022
  • Page
  • of
  • 863

Other Entry Collections

>>