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Topic Review
Proton–Proton Chain Reaction
The proton–proton chain reaction is one of two known sets of nuclear fusion reactions by which stars convert hydrogen to helium. It dominates in stars with masses less than or equal to that of the Sun, whereas the CNO cycle, the other known reaction, is suggested by theoretical models to dominate in stars with masses greater than about 1.3 times that of the Sun. In general, proton–proton fusion can occur only if the kinetic energy (i.e. temperature) of the protons is high enough to overcome their mutual electrostatic repulsion. In the Sun, deuterium-producing events are rare. Diprotons are the much more common result of proton–proton reactions within the star, and diprotons almost immediately decay back into two protons. Since the conversion of hydrogen to helium is slow, the complete conversion of the hydrogen in the core of the Sun is calculated to take more than ten billion years. Although called the "proton–proton chain reaction", it is not a chain reaction in the normal sense. In most nuclear reactions, a chain reaction designates a reaction that produces a product, such as neutrons given off during fission, that quickly induces another such reaction. The proton-proton chain is, like a decay chain, a series of reactions. The product of one reaction is the starting material of the next reaction. There are two such chains leading from Hydrogen to Helium in the Sun. One chain has five reactions, the other chain has six.
  • 15.4K
  • 21 Oct 2022
Topic Review
Applications of Fibre Reinforced Polymer
Three FRP shapes are used in Structural Engineering applications: FRP profiles for new construction, FRP rebars and FRP strengthening systems. Applications in bridges, buildings, railway platforms, cooling towers and repair and rehabilitation of existing structures are presented. FRP is a strong and lightweight sustainable material with lower carbon footprint than traditional materials. However, FRPs are not as widely used as expected. FRP use in repair and rehabilitation has seen significant growth, though, over last two decades. The major challenges have been steel-like FRP elements, lack of ductility, almost no legal design guidelines and inadequate knowledge about fire and durability performance. The future of FRPs can be promising if engineers use this material more for net-zero carbon construction, and to effectively deal with climate emergency.
  • 15.4K
  • 28 Mar 2022
Topic Review
Georgism
Georgism, also called in modern times geoism and known historically as the single tax movement, is an economic ideology holding that, although people should own the value they produce themselves, the economic rent derived from land – including from all natural resources, the commons, and urban locations – should belong equally to all members of society. Developed from the writings of American economist and social reformer Henry George, the Georgist paradigm seeks solutions to social and ecological problems, based on principles of land rights and public finance which attempt to integrate economic efficiency with social justice. Georgism is concerned with the distribution of economic rent caused by land ownership, natural monopolies, pollution and the control of commons, including title of ownership for natural resources and other contrived privileges (e.g. intellectual property). Any natural resource which is inherently limited in supply can generate economic rent, but the classical and most significant example of land monopoly involves the extraction of common ground rent from valuable urban locations. Georgists argue that taxing economic rent is efficient, fair and equitable. The main Georgist policy recommendation is a tax assessed on land value, arguing that revenues from a land value tax (LVT) can be used to reduce or eliminate existing taxes (such as on income, trade, or purchases) that are unfair and inefficient. Some Georgists also advocate for the return of surplus public revenue to the people by means of a basic income or citizen's dividend. The concept of gaining public revenues mainly from land and natural resource privileges was widely popularized by Henry George through his first book, Progress and Poverty (1879). The philosophical basis of Georgism dates back to several early thinkers such as John Locke, Baruch Spinoza and Thomas Paine. Economists since Adam Smith and David Ricardo have observed that a public levy on land value does not cause economic inefficiency, unlike other taxes. A land value tax also has progressive tax effects. Advocates of land value taxes argue that they would reduce economic inequality, increase economic efficiency, remove incentives to underutilize urban land and reduce property speculation. Georgist ideas were popular and influential during the late 19th and early 20th century. Political parties, institutions and communities were founded based on Georgist principles during that time. Early devotees of Henry George's economic philosophy were often termed Single Taxers for their political goal of raising public revenue mainly or only from a land value tax, although Georgists endorsed multiple forms of rent capture (e.g. seigniorage) as legitimate. The term Georgism was invented later, and some prefer the term geoism as more generic.
  • 15.3K
  • 08 Nov 2022
Topic Review
2020–2021 Taal Volcano Eruptions
Taal Volcano in Batangas, Philippines began to erupt on January 12, 2020, when a phreatomagmatic eruption from its main crater spewed ashes over Calabarzon, Metro Manila, and some parts of Central Luzon and Ilocos Region, resulting in the suspension of school classes, work schedules, and flights in the area. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) subsequently issued an Alert Level 4, indicating "that a hazardous explosive eruption is possible within hours to days." Volcanic activity continued into 2021, when smaller eruptions occurred in July 2021.
  • 15.3K
  • 24 Nov 2022
Topic Review
Self-Discrepancy Theory
The self-discrepancy theory states that individuals compare their “actual” self to internalized standards or the “ideal/ought self”. Inconsistencies between “actual”, “ideal” (idealized version of yourself created from life experiences) and “ought” (who persons feel they should be or should become) are associated with emotional discomforts (e.g., fear, threat, restlessness). Self-discrepancy is the gap between two of these self-representations that leads to negative emotions. Developed by Edward Tory Higgins in 1987, the theory provides a platform for understanding how different types of discrepancies between representations of the self are related to different kinds of emotional vulnerabilities. Higgins sought to illustrate that internal disagreement causes emotional and psychological turmoil. There were several previous theories proving this concept such as the self-inconsistency theory, the cognitive dissonance theory, and the imbalance theory (e.g., Heider, 1958); however, Higgins wanted to take it one step further by determining the specific emotions that surfaced as a result of these internal disagreements. Previous self-imbalance theories had recognized only positive or negative emotions. The self-discrepancy theory was the first to assign specific emotions and affects to the disparity. The theory proposes how a variety of self-discrepancies represents a variety of types of negative psychological situations that are associated with different kinds of discomfort. A primary goal of the self-discrepancy theory is to create an understanding of which types of contrasting ideas will cause such individuals to feel different kinds of negative emotions. The structure of the theory was built based on three ideas. First classify the different kinds of discomfort felt by those people holding contrasting ideals experienced, as well as the various types of emotional vulnerabilities felt by the different types of discrepancies. Lastly, to consider the role of the different discrepancies in influencing the kind and type of discomfort individuals are most likely to experience.
  • 15.3K
  • 31 Oct 2022
Topic Review
Solar Symbol
A solar symbol is a symbol representing the Sun. Common solar symbols include circles (with or without rays), crosses, and spirals. In religious iconography, personifications of the Sun or solar attributes are often indicated by means of a halo or a radiate crown. When the systematic study of comparative mythology first became popular in the 19th century, scholarly opinion tended to over-interpret historical myths and iconography in terms of "solar symbolism". This was especially the case with Max Müller and his followers beginning in the 1860s in the context of Indo-European studies. Many "solar symbols" claimed in the 19th century, such as the swastika, triskele, Sun cross, etc. have tended to be interpreted more conservatively in scholarship since the later 20th century.
  • 15.2K
  • 25 Oct 2022
Topic Review
Muhajir (Pakistani)
The Muhajir (Urdu: مہاجر‎, also spelled Mahajir and Mohajir) are Muslim immigrants, of multi-ethnic origin, and their descendants, who migrated from various regions of India after the Partition of India to settle in the newly independent state of Pakistan . The term Muhajirs refers to those Muslim migrants from India who mostly settled in urban Sindh.
  • 15.2K
  • 23 Jan 2024
Topic Review
Subject–Verb–Object
In linguistic typology, subject–verb–object (SVO) is a sentence structure where the subject comes first, the verb second, and the object third. Languages may be classified according to the dominant sequence of these elements in unmarked sentences (i.e., sentences in which an unusual word order is not used for emphasis). English is included in this group. An example is "Sam ate oranges." The label often includes ergative languages that do not have subjects, but have an agent–verb–object (AVO) order. SVO is the second-most common order by number of known languages, after SOV. Together, SVO and SOV account for more than 75% of the world's languages. It is also the most common order developed in Creole languages, suggesting that it may be somehow more initially "obvious" to human psychology. Languages regarded as SVO include: All Bantu languages, Albanian, Arabic dialects, Assyrian, Bosnian, Bulgarian,[a 1] Chinese, English, Estonian, Finnish (but see below), French, Greek, Hausa, Icelandic (with the V2 restriction), Igbo, Italian, Javanese, Khmer, Latvian, Macedonian, Malay (Indonesian, Malaysian), Modern Hebrew, Norwegian (with the V2 restriction), Polish, Portuguese, Quiché, Reo Rapa, Romanian, Russian (but see below), Slovene, Spanish, Swedish (with the V2 restriction), Thai and Lao, Ukrainian (but see below), Vietnamese and Yoruba. Ancient Greek has free syntactic order, though Classical Greeks tended to favor SOV. Many famous phrases are SVO, however.
  • 15.2K
  • 29 Nov 2022
Topic Review
Value (Ethics)
In ethics, value denotes the degree of importance of some thing or action, with the aim of determining what actions are best to do or what way is best to live (normative ethics), or to describe the significance of different actions. Value systems are prospective and prescriptive beliefs; they affect ethical behavior of a person or are the basis of their intentional activities. Often primary values are strong and secondary values are suitable for changes. What makes an action valuable may in turn depend on the ethical values of the objects it increases, decreases or alters. An object with "ethic value" may be termed an "ethic or philosophic good" (noun sense). Values can be defined as broad preferences concerning appropriate courses of actions or outcomes. As such, values reflect a person's sense of right and wrong or what "ought" to be. "Equal rights for all", "Excellence deserves admiration", and "People should be treated with respect and dignity" are representatives of values. Values tend to influence attitudes and behavior and these types include ethical/moral values, doctrinal/ideological (religious, political) values, social values, and aesthetic values. It is debated whether some values that are not clearly physiologically determined, such as altruism, are intrinsic, and whether some, such as acquisitiveness, should be classified as vices or virtues.
  • 15.2K
  • 06 Oct 2022
Topic Review
Examination of Apollo Moon Photographs
The examination of Apollo Moon photographs is an endeavour undertaken by certain people engaged in the debate as to the merits of Moon landing conspiracy theories, despite the abundance of third-party evidence for Apollo Moon landings. A number of allegations and refutations with a variable degree of notability are put forward due to this examination.
  • 15.2K
  • 02 Dec 2022
Topic Review
4.2 Kiloyear Event
The 4.2-kiloyear BP aridification event was one of the most severe climatic events of the Holocene epoch. It defines the beginning of the current Meghalayan age in the Holocene epoch. Starting around 2200 BC, it probably lasted the entire 22nd century BC. It has been hypothesised to have caused the collapse of the Old Kingdom in Egypt as well as the Akkadian Empire in Mesopotamia, and the Liangzhu culture in the lower Yangtze River area. The drought may also have initiated the collapse of the Indus Valley Civilisation, with some of its population moving southeastward to follow the movement of their desired habitat, as well as the migration of Indo-European-speaking people into India. Some scientists disagree with this conclusion and point out that the event was neither a global drought nor did it happen in a clear timeline.
  • 15.1K
  • 04 Nov 2022
Topic Review
Criticism of Jehovah's Witnesses
Jehovah's Witnesses have received criticism from mainstream Christianity, members of the medical community, former members, and commentators regarding their beliefs and practices. The movement has been accused of doctrinal inconsistency and reversals, failed predictions, mistranslation of the Bible, harsh treatment of former members and autocratic and coercive leadership. Criticism has also focused on their rejection of blood transfusions, particularly in life-threatening medical situations, and claims that they have failed to report cases of sexual abuse to the authorities. Many of the claims are denied by Jehovah's Witnesses and some have also been disputed by courts and religious scholars.
  • 15.1K
  • 18 Nov 2022
Topic Review
Methanol Mitigation during Fruit-Spirits Manufacturing
Methanol is a natural ingredient with major occurrence in fruit spirits, such as apple, pear, plum or cherry spirits, but also in spirits made from coffee pulp. The compound is formed during fermentation and the following mash storage by enzymatic hydrolysis of naturally present pectins. Methanol is toxic above certain threshold levels and legal limits have been set in most jurisdictions. Therefore, the methanol content needs to be mitigated and its level must be controlled. This article will review the several factors that influence the methanol content including the pH value of the mash, the addition of various yeast and enzyme preparations, fermentation temperature, mash storage, and most importantly the raw material quality and hygiene
  • 15.1K
  • 10 May 2021
Topic Review
Outline of Heresies in the Catholic Church
The following outline is provided as an overview of and topical guide to heresies (as regarded by the Roman Catholic Church): Heresy, in Catholicism, is defined as belief that conflicts with established Catholic dogma.
  • 15.1K
  • 16 Nov 2022
Topic Review
Biomechanics of Table Tennis
Table tennis is a popular recreational and competitive sports at all levels. Recent research on table tennis maneuvers identified the differences between playing levels and between maneuvers using parameters which included ball and racket speed, joint kinematics and kinetics, electromyography, and plantar pressure distribution. Different maneuvers underlined changes on body posture and lines of movement which were accommodated particularly by the racket face angle, trunk rotation, knee and elbow joint movements, and thus different contributions of muscles. Higher-level players produced ball and strike at higher accuracy and repeatability but not necessarily lead to higher speed. In addition, higher-level players utilize superior whole-body coordination and footwork to compromise between agility and stability for a quality strike. Strengthening shoulder and wrist muscles could enhance the speed of the strike while personalized training shall be considered since motor coordination and adaptation vary among individuals.
  • 15.1K
  • 29 Oct 2020
Topic Review
The Emergency (India)
The Emergency in India was a 21-month period from 1975 to 1977 when Prime Minister Indira Gandhi had a state of emergency declared across the country. Officially issued by President Fakhruddin Ali Ahmed under Article 352 of the Constitution because of the prevailing "internal disturbance", the Emergency was in effect from 25 June 1975 until its withdrawal on 21 March 1977. The order bestowed upon the Prime Minister the authority to rule by decree, allowing elections to be cancelled and civil liberties to be suspended. For much of the Emergency, most of Indira Gandhi's political opponents were imprisoned and the press was censored. Several other human rights violations were reported from the time, including a mass forced sterilization campaign spearheaded by Sanjay Gandhi, the Prime Minister's son. The Emergency is one of the most controversial periods of independent India's history. The final decision to impose an emergency was proposed by Indira Gandhi, agreed upon by the president of India, and thereafter ratified by the cabinet and the parliament (from July to August 1975), based on the rationale that there were imminent internal and external threats to the Indian state.
  • 15.1K
  • 15 Nov 2022
Topic Review
List of Island Countries
This is a list of island countries. An island is a landmass (smaller than a continent) that is surrounded by water. Many island countries are spread over an archipelago, as is the case with the Federated States of Micronesia and Indonesia (both of which consist of thousands of islands). Others consist of a single island, such as Barbados or Nauru, or part of an island, such as the Dominican Republic or Brunei. Australia is a continent, although it has historically been referred to as an island, due to it having no land borders. The list also includes states with limited diplomatic recognition which have de facto control over territories entirely on the islands, such as Taiwan.[n 1] Indonesia is the world's largest island country by area (1,904,569 km2), and by total number of islands (more than 18,307), and is also the world's most populous island country, with a population of over 270 million (the fourth-largest population in the world, after China , India , and the United States ).
  • 15.0K
  • 14 Oct 2022
Topic Review
2015–16 Stock Market Selloff
The 2015–16 stock market selloff, also known as The Great Fall of China, was the period of decline in the value of stock prices globally that occurred between June 2015 to June 2016. It included the 2015–16 Chinese stock market turbulence, in which the SSE Composite Index fell 43% in just over 2 months between June 2015 and August 2015, which culminated in the devaluation of the yuan. Investors sold shares globally as a result of slowing growth in the GDP of China, a fall in petroleum prices, the Greek debt default in June 2015, the effects of the end of quantitative easing in the United States in October 2014, a sharp rise in bond yields in early 2016, and finally, in June 2016, the 2016 United Kingdom European Union membership referendum, in which Brexit was voted upon. By July 2016, the Dow Jones Industrial Average (DJIA) recovered and achieved record highs. The FTSE 100 Index did not do so until later in 2016.
  • 15.0K
  • 29 Nov 2022
Topic Review
G protein-coupled receptor in hepatocytes
G protein-coupled receptors (GPCRs) are cell surface receptors that mediate the function of extracellular ligands. Understanding how GPCRs work at the molecular level has important therapeutic implications, as 30-40% of the drugs currently in clinical use mediate therapeutic effects by acting on GPCRs. Like many other cell types, hepatocyte's function is regulated by GPCRs. A better understanding of the metabolic role of GPCRs in hepatocytes, the dominant constituent cells of the liver, could lead to the development of novel drugs that are clinically useful for the treatment of various metabolic diseases, including Type 2 diabetes, NAFLD, and NASH. 
  • 15.0K
  • 06 Nov 2020
Topic Review
Carboniferous Rainforest Collapse
The Carboniferous rainforest collapse (CRC) was a minor extinction event that occurred around 305 million years ago in the Carboniferous period. It altered the vast coal forests that covered the equatorial region of Euramerica (Europe and America). This event may have fragmented the forests into isolated 'islands', which in turn caused dwarfism and, shortly after, extinction of many plant and animal species. Following the event, coal-forming tropical forests continued in large areas of the Earth, but their extent and composition were changed. The event occurred at the end of the Moscovian and continued into the early Kasimovian stages of the Pennsylvanian (Upper Carboniferous).
  • 15.0K
  • 08 Oct 2022
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