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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.
  • 15.0K
  • 21 Oct 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.
  • 15.0K
  • 24 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.
  • 15.0K
  • 06 Oct 2022
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.
  • 14.9K
  • 16 Nov 2022
Topic Review
Hindu Views on Evolution
Hinduism includes a range of viewpoints about the origin of life, creationism and evolution. There is no single story of creation, due to dynamic diversity of Hinduism, and these are derived from various sources like Vedas, some from the Brahmanas, some from Puranas; some are philosophical, based on concepts, and others are narratives. The Rigveda mentions the Hiranyagarbha ("golden embryo") as the source of the creation of the Universe, similar to the world egg motif found in the creation myths of many other civilizations. It also contains a myth of proto-Indo-European origin, in which the creation arises out of the dismemberment of a cosmic being (the Purusha) who is sacrificed by the gods. As for the creation of the primordial gods themselves, the Nasadiya Sukta of Rigveda takes a near-agnostic stand, stating that the Gods came into being after the world's creation, and nobody knows when the world first came into being. In the later Puranic texts, the creator god Brahma is described as performing the act of 'creation', or more specifically of 'propagating life within the universe'. Some texts consider him equivalent to the Hiranyagarbha or the Purusha, while others state that he arose out of these. Brahma is a part of the trinity of gods that also includes Vishnu and Shiva, who are responsible for 'preservation' and 'destruction' (of the universe) respectively. Many Hindu texts mention the cycle of creation and destruction. The Shatapatha Brahmana states that the current human generation descends from Manu, the only man who survived a great deluge after being warned by the God. This legend is comparable to the other flood legends, such as the story of the Noah's Ark mentioned in the Bible and the Quran. Hindus find support for, or foreshadowing of evolutionary ideas in scriptures. For example, the concept of Dashavatara can be seen as having some similarities to Charles Darwin's theory of evolution.The first incarnation of Vishnu in the form of a fish resembles the evolutionary origin of fish in the Silurian Period. In a survey of 909 people, 77% of its respondents in India agreed that enough scientific evidence exists to support Charles Darwin’s Theory of Evolution, and 85% of God-believing people said they agree with evolution as well. According to the survey conducted by Pew Forum in the United States , 80% of Hindus agree that evolution is the best explanation for the origin of human life on earth. However, in India, there were minimal references to Darwinism in the 1800s. Elements of Victorian England opposed the idea of Darwinism. Hindus already had present notion of common ancestry between humans and animals. The Hindu dharma believes that the gods have animal features, showing a theory that humans can be reborn again as animals or with their features.
  • 14.9K
  • 21 Oct 2022
Topic Review
Elephant in the Room
Elephant in the room is an English-language metaphorical idiom for an obvious problem or risk that no one wants to discuss. It is based on the idea/thought that something as conspicuous as an elephant can appear to be overlooked in codified social interactions, and that the sociology/psychology of repression also operates on the macro scale.
  • 14.9K
  • 28 Oct 2022
Topic Review
Ionic Liquid
Ionic Liquids (ILs) are organic salts that melt commonly below 100 °C, constituted entirely by charged species. The tunability and versatility of ILs have given rise to several applications at the academic and industrial levels. Here the following topics are highlighted: chemical structure; ILs classification according to the possibility of proton transfer, and the historical generations of ILs.
  • 14.8K
  • 01 Dec 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.
  • 14.8K
  • 15 Nov 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.
  • 14.8K
  • 23 Jan 2024
Topic Review
Malignant Brain Tumors
A discussion of malignant brain tumors including both primary tumors (gliomas, embryonal CNS tumors) and secondary tumors (brain metastasis).
  • 14.8K
  • 18 Jun 2021
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 ).
  • 14.8K
  • 14 Oct 2022
Topic Review
GNU C Library
The GNU C Library, commonly known as glibc, is the GNU Project's implementation of the C standard library. Despite its name, it now also directly supports C++ (and, indirectly, other programming languages). It was started in the 1980s by the Free Software Foundation (FSF) for the GNU operating system. Released under the GNU Lesser General Public License, glibc is free software. The GNU C Library project provides the core libraries for the GNU system, as well as many systems that use Linux as the kernel. These libraries provide critical APIs including ISO C11, POSIX.1-2008, BSD, OS-specific APIs and more. These APIs include such foundational facilities as open, read, write, malloc, printf, getaddrinfo, dlopen, pthread create, crypt, login, exit and more.
  • 14.8K
  • 21 Nov 2022
Topic Review
Ge'ez
Ge'ez (/ˈɡiːɛz/; ግዕዝ, Gəʿəz Template:IPA-gez; also transliterated Gi'iz) is an ancient South Semitic language of the Ethiosemitic branch. The language originates from the region encompassing northern Ethiopia and southern Eritrea in the Horn of Africa. Today, Ge'ez is used only as the main language of liturgy of the Ethiopian Orthodox Tewahedo and Eritrean Orthodox Tewahedo churches, the Ethiopian and Eritrean Catholic churches, and the Beta Israel Jewish community. However, in Ethiopia, Amharic or other local languages, and in Eritrea and Ethiopia's Tigray Region, Tigrinya may be used for sermons. Amharic, Tigrinya, and Tigre are closely related to Ge'ez. The closest living languages to Ge'ez are Tigre and Tigrinya with lexical similarity at 71% and 68%, respectively. Some linguists do not believe that Ge'ez constitutes a common ancestor of modern Ethiosemitic languages, but that Ge'ez became a separate language early on from another hypothetical unattested language, which can be seen as an extinct sister language of Amharic, Tigre and Tigrinya. The foremost Ethiopian experts such as Amsalu Aklilu point to the vast proportion of inherited nouns that are unchanged, and even spelled identically in both Ge'ez and Amharic (and to a lesser degree, Tigrinya).
  • 14.8K
  • 17 Nov 2022
Topic Review
Fairy Tale
A fairy tale, fairytale, wonder tale, magic tale, or Märchen is an instance of a folklore genre that takes the form of a short story. Such stories typically feature entities such as dwarfs, dragons, elves, fairies, giants, gnomes, goblins, griffins, mermaids, talking animals, trolls, unicorns, or witches, and usually magic or enchantments. In most cultures, there is no clear line separating myth from folk or fairy tale; all these together form the literature of preliterate societies. Fairy tales may be distinguished from other folk narratives such as legends (which generally involve belief in the veracity of the events described) and explicit moral tales, including beast fables. In less technical contexts, the term is also used to describe something blessed with unusual happiness, as in "fairy-tale ending" (a happy ending) or "fairy-tale romance". Colloquially, the term "fairy tale" or "fairy story" can also mean any far-fetched story or tall tale; it is used especially of any story that not only is not true, but could not possibly be true. Legends are perceived as real; fairy tales may merge into legends, where the narrative is perceived both by teller and hearers as being grounded in historical truth. However, unlike legends and epics, fairy tales usually do not contain more than superficial references to religion and to actual places, people, and events; they take place "once upon a time" rather than in actual times. Fairy tales occur both in oral and in literary form; the name "fairy tale" ("conte de fées" in French) was first ascribed to them by Madame d'Aulnoy in the late 17th century. Many of today's fairy tales have evolved from centuries-old stories that have appeared, with variations, in multiple cultures around the world. The history of the fairy tale is particularly difficult to trace because only the literary forms can survive. Still, according to researchers at universities in Durham and Lisbon, such stories may date back thousands of years, some to the Bronze Age more than 6,500 years ago. Fairy tales, and works derived from fairy tales, are still written today. Folklorists have classified fairy tales in various ways. The Aarne-Thompson classification system and the morphological analysis of Vladimir Propp are among the most notable. Other folklorists have interpreted the tales' significance, but no school has been definitively established for the meaning of the tales.
  • 14.7K
  • 17 Nov 2022
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).
  • 14.7K
  • 08 Oct 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.
  • 14.7K
  • 31 Oct 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.
  • 14.7K
  • 04 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. 
  • 14.7K
  • 06 Nov 2020
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.
  • 14.7K
  • 29 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
  • 14.6K
  • 10 May 2021
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