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
2019–2020 Vaping Lung Illness Outbreak
Template:Infobox outbreak An outbreak of severe vaping-associated lung illness starting in 2019 is ongoing among users of cannabis vaping products, almost exclusively in the United States. The first cases were identified in Illinois and Wisconsin in April 2019; as of January 21, 2020, a total of 2,711 hospitalized cases, including 60 deaths have been confirmed by the U.S. Centers for Disease Control. Cases peaked in September 2019, and have been slowly declining since. CDC investigators identified direct exposure to chemicals present in vaping products as responsible for the outbreak. Vitamin E acetate is a very strong culprit of concern in the lung illnesses related to THC-based vaping products, but the CDC did not rule out other chemicals as possible causes. Though patients have reported using vaping products containing THC, nicotine, or both types, about 86% of patients studied by the CDC admitted THC use. The majority of those affected were young adults 18-34, which is the group with the greatest prevalence of cannabis use in the US. Nicotine-containing products are regulated in the U.S. by the Food and Drug Administration; THC products are illegal under federal law, but allowed and regulated by some states. Prior to the outbreak, vitamin E acetate was used in low concentrations, or lower than 20% of the formula in vape cartridges, as a thickening agent. As a result of a limited availability of cannabis in California as well as high demand, illicit sellers had used about 50% or higher of diluent thickeners in their formulas to bulk up tiny potency vape cartridges, and vitamin E acetate is a common choice because it resembles THC oil. Some jurisdictions took action to restrict the sale of products containing vitamin E acetate and other chemicals in response to the outbreak, but THC products in states where it is illegal and some nictotine-containing products are produced illegally (and sometimes obtained illegally in jurisdictions where legal, by underage consumers).
  • 1.7K
  • 30 Sep 2022
Topic Review
Reduction (Complexity)
In computability theory and computational complexity theory, a reduction is an algorithm for transforming one problem into another problem. A reduction from one problem to another may be used to show that the second problem is at least as difficult as the first. Intuitively, problem A is reducible to problem B if an algorithm for solving problem B efficiently (if it existed) could also be used as a subroutine to solve problem A efficiently. When this is true, solving A cannot be harder than solving B. "Harder" means having a higher estimate of the required computational resources in a given context (e.g., higher time complexity, greater memory requirement, expensive need for extra hardware processor cores for a parallel solution compared to a single-threaded solution, etc.). We write A ≤m B, usually with a subscript on the ≤ to indicate the type of reduction being used (m : mapping reduction, p : polynomial reduction). The mathematical structure generated on a set of problems by the reductions of a particular type generally forms a preorder, whose equivalence classes may be used to define degrees of unsolvability and complexity classes.
  • 1.8K
  • 30 Sep 2022
Topic Review
BioMA
Modelling frameworks are used in modelling and simulation and can consist of a software infrastructure to develop and run mathematical models. They have provided a substantial step forward in the area of biophysical modelling with respect to monolithic implementations. The separation of algorithms from data, the reusability of I/O procedures and integration services, and the isolation of modelling solutions in discrete units has brought a solid advantage in the development of simulation systems. Modelling frameworks for agriculture have evolved over time, with different approaches and targets BioMA is a software framework developed focusing on platform-independent, re-usable components, including multi-model implementations at fine granularity.
  • 1.3K
  • 30 Sep 2022
Topic Review
Seagate Barracuda
The Seagate Barracuda is a series of hard disk drives and later solid state drives produced by Seagate Technology that was first introduced in 1993. The line initially focused on high-capacity, high-performance SCSI hard drives until introducing ATA models in 1999 and SATA models in 2002. Since 2001, the Barracuda is Seagate's most popular product line as the hard disk drive industry started to move to a 7200 RPM spindle speed.
  • 2.7K
  • 30 Sep 2022
Topic Review
New Austrian Tunnelling Method
The New Austrian tunneling method (NATM), also known as the sequential excavation method (SEM) or sprayed concrete lining method (SCL), is a method of modern tunnel design and construction employing sophisticated monitoring to optimize various wall reinforcement techniques based on the type of rock encountered as tunneling progresses. This technique first gained attention in the 1960s based on the work of Ladislaus von Rabcewicz, Leopold Müller, and Franz Pacher between 1957 and 1965 in Austria. The name NATM was intended to distinguish it from earlier methods, with its economic advantage of employing inherent geological strength available in the surrounding rock mass to stabilize the tunnel wherever possible rather than reinforcing the entire tunnel. NATM/SEM is generally thought to have helped revolutionise the modern tunneling industry. Many modern tunnels have used this excavation technique. The works built by the Sequential Excavation Method are very attractive from the economic point of view and reasonable in karst conditions.
  • 1.3K
  • 30 Sep 2022
Topic Review
Declaration of War
A declaration of war is a formal act by which one state goes to war against another. The declaration is a performative speech act (or the signing of a document) by an authorized party of a national government, in order to create a state of war between two or more states. The legality of who is competent to declare war varies between nations and forms of government. In many nations, that power is given to the head of state or sovereign. In other cases, something short of a full declaration of war, such as a letter of marque or a covert operation, may authorise war-like acts by privateers or mercenaries. The official international protocol for declaring war was defined in the Hague Convention (III) of 1907 on the Opening of Hostilities. Since 1945, developments in international law such as the United Nations Charter, which prohibits both the threat and the use of force in international conflicts, have made declarations of war largely obsolete in international relations. The UN Security Council, under powers granted in articles 24 and 25, and Chapter VII of the Charter, may authorize collective action to maintain or enforce international peace and security. Article 51 of the United Nations (UN) Charter also states that: "Nothing in the present Charter shall impair the inherent right to individual or collective self-defence if an armed attack occurs against a state." Few nations have formally declared war upon another since then. In addition to this, non-state or terrorist organizations may claim to or be described as "declaring war" when engaging in violent acts. These declarations may have no legal standing in themselves, but they may still act as a call to arms for supporters of these organizations.
  • 9.9K
  • 11 Dec 2025
Topic Review
Scroll Lock
Scroll lock (⤓ or ⇳) is a lock key (typically with an associated status light) on most IBM-compatible computer keyboards. Depending on the operating system, it may be used for different purposes and applications may assign functions to the key or change their behaviour depending on its toggling state. The key is not frequently used, and therefore some reduced or specialized keyboards lack altogether. Pressing performs the same function as pressing . This behavior is a remnant of the original IBM PC keyboards, which did not have a dedicated key. Instead, they assigned the Pause function to and the Break function to .
  • 1.5K
  • 09 Oct 2022
Topic Review
Flowering Plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (/ˌændʒiəˈspɜːrmiː/), commonly called angiosperms. The term "angiosperm" is derived from the Greek words angeion ('container, vessel') and sperma ('seed'), and refers to those plants that produce their seeds enclosed within a fruit. They are by far the most diverse group of land plants with 64 orders, 416 families, approximately 13,000 known genera and 300,000 known species. Angiosperms were formerly called Magnoliophyta (/mæɡˌnoʊliˈɒfətə, -əˈfaɪtə/). Like gymnosperms, angiosperms are seed-producing plants. They are distinguished from gymnosperms by characteristics including flowers, endosperm within their seeds, and the production of fruits that contain the seeds. The ancestors of flowering plants diverged from the common ancestor of all living gymnosperms during the Carboniferous, over 300 million years ago, according to some genetic analyses but there is no fossil evidence for this. The closest fossil relatives of flowering plants are uncertain and contentious. The earliest angiosperm fossils are in the form of pollen around 134 million years ago during the Early Cretaceous. Over the course of the Cretaceous, angiosperms explosively diversified, becoming the dominant group of plants across the planet by the end of the period, corresponding with the decline and extinction of previously widespread gymnosperm groups. The origin and diversification of the angiosperms is often known as "Darwin's abominable mystery".
  • 2.9K
  • 09 Oct 2022
Topic Review
Conversion of Units of Temperature
This is a collection of temperature conversion formulas and comparisons among eight different temperature scales, several of which have long been obsolete.
  • 565
  • 30 Sep 2022
Topic Review
Alternatives to Evolution by Natural Selection
Alternatives to evolution by natural selection, also described as non-Darwinian mechanisms of evolution, have been proposed by scholars investigating biology since classical times to explain signs of evolution and the relatedness of different groups of living things. The alternatives in question do not deny that evolutionary changes over time are the origin of the diversity of life, nor deny that the organisms alive today share a common ancestor from the distant past (or ancestors, in some proposals); rather, they propose alternative mechanisms of evolutionary change over time, arguing against mutations acted on by natural selection as the most important driver of evolutionary change. (In most cases, they do not deny that mutations or natural selection occur, or that they play a role in evolutionary change, but instead deny that they are fully sufficient primary causes for the evidence of evolutionary change that is observed in the natural world.) This distinguishes them from certain other kinds of arguments that deny that large scale evolution of any sort has taken place, as in some forms of creationism, which do not propose alternative mechanisms of evolutionary change but instead deny that evolutionary change has taken place at all. Not all forms of creationism deny that evolutionary change takes places; notably, proponents of theistic evolution, such as the biologist Asa Gray, assert that evolutionary change does occur and is responsible for the history of life on Earth, with the proviso that this process has been influenced by a god or gods in some meaningful sense. Where the fact of evolutionary change was accepted but the mechanism proposed by Charles Darwin, natural selection, was denied, explanations of evolution such as Lamarckism, catastrophism, orthogenesis, vitalism, structuralism and mutationism (called saltationism before 1900) were entertained. Different factors motivated people to propose non-Darwinian mechanisms of evolution. Natural selection, with its emphasis on death and competition, did not appeal to some naturalists because they felt it immoral, leaving little room for teleology or the concept of progress in the development of life. Some who came to accept evolution, but disliked natural selection, raised religious objections. Others felt that evolution was an inherently progressive process that natural selection alone was insufficient to explain. Still others felt that nature, including the development of life, followed orderly patterns that natural selection could not explain. By the start of the 20th century, evolution was generally accepted by biologists but natural selection was in eclipse. Many alternative theories were proposed, but biologists were quick to discount theories such as orthogenesis, vitalism and Lamarckism which offered no mechanism for evolution. Mutationism did propose a mechanism, but it was not generally accepted. The modern synthesis a generation later claimed to sweep away all the alternatives to Darwinian evolution, though some have been revived as molecular mechanisms for them have been discovered.
  • 4.3K
  • 09 Oct 2022
  • Page
  • of
  • 863

Other Entry Collections

>>