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Topic Review

Late Devonian Extinction

The Late Devonian extinction was one of five major extinction events in the history of life on Earth. A major extinction, the Kellwasser event, occurred at the boundary that marks the beginning of the last phase of the Devonian period, the Famennian faunal stage (the Frasnian–Famennian boundary), about 376–360 million years ago. Overall, 19% of all families and 50% of all genera became extinct. A second, distinct mass extinction, the Hangenberg event, closed the Devonian period. Although it is clear that there was a massive loss of biodiversity in the Late Devonian, the timespan of this event is uncertain, with estimates ranging from 500,000 to 25 million years, extending from the mid-Givetian to the end-Famennian. Nor is it clear whether there were two sharp mass extinctions or a series of smaller extinctions, though the latest research suggests multiple causes and a series of distinct extinction pulses during an interval of some three million years. Some consider the extinction to be as many as seven distinct events, spread over about 25 million years, with notable extinctions at the ends of the Givetian, Frasnian, and Famennian stages. By the Late Devonian, the land had been colonized by plants and insects. In the oceans were massive reefs built by corals and stromatoporoids. Euramerica and Gondwana were beginning to converge into what would become Pangaea. The extinction seems to have only affected marine life. Hard-hit groups include brachiopods, trilobites, and reef-building organisms; the reef-building organisms almost completely disappeared. The causes of these extinctions are unclear. Leading hypotheses include changes in sea level and ocean anoxia, possibly triggered by global cooling or oceanic volcanism. The impact of a comet or another extraterrestrial body has also been suggested, such as the Siljan Ring event in Sweden. Some statistical analysis suggests that the decrease in diversity was caused more by a decrease in speciation than by an increase in extinctions. This might have been caused by invasions of cosmopolitan species, rather than by any single event. Surprisingly, jawed vertebrates seem to have been unaffected by the loss of reefs or other aspects of the Kellwasser event, while agnathans were in decline long before the end of the Frasnian.

5.4K
30 Nov 2022

Topic Review

DNA barcoding is a method of species identification using a short section of DNA from a specific gene or genes. The premise of DNA barcoding is that, by comparison with a reference library of such DNA sections (also called "sequences"), an individual sequence can be used to uniquely identify an organism to species, in the same way that a supermarket scanner uses the familiar black stripes of the UPC barcode to identify an item in its stock against its reference database. These "barcodes" are sometimes used in an effort to identify unknown species, parts of an organism, or simply to catalog as many taxa as possible, or to compare with traditional taxonomy in an effort to determine species boundaries. Different gene regions are used to identify the different organismal groups using barcoding. The most commonly used barcode region for animals and some protists is a portion of the cytochrome c oxidase I (COI or COX1) gene, found in mitochondrial DNA. Other genes suitable for DNA barcoding are the internal transcribed spacer (ITS) rRNA often used for fungi and RuBisCO used for plants. Microorganisms are detected using different gene regions. The 16S rRNA gene for example is widely used in identification of prokaryotes, whereas the 18S rRNA gene is mostly used for detecting microbial eukaryotes. These gene regions are chosen because they have less intraspecific (within species) variation than interspecific (between species) variation, which is known as the "Barcoding Gap". Some applications of DNA barcoding include: identifying plant leaves even when flowers or fruits are not available; identifying pollen collected on the bodies of pollinating animals; identifying insect larvae which may have fewer diagnostic characters than adults; or investigating the diet of an animal based on its stomach content, saliva or feces. When barcoding is used to identify organisms from a sample containing DNA from more than one organism, the term DNA metabarcoding is used, e.g. DNA metabarcoding of diatom communities in rivers and streams, which is used to assess water quality.

5.4K
16 Nov 2022

Topic Review Peer Reviewed

Japanese Prefabricated Housing Manufacturers

Japanese prefabricated housing manufacturers have gained international recognition for their innovative approaches to the whole design process, ranging from initial design to innovative cutting-edge technologies, state-of-the-art automated production lines, meticulous workmanship, and mass customisation. In this entry, three manufacturers (Daiwa House, Sekisui House, and Misawa Homes) were selected as case studies for close examination. By studying these leading companies, researchers and industry professionals can gain valuable insights into best practices, challenges, and innovations within the Japanese prefabricated housing sector. The research methods involved a desktop study of available information on websites, articles, and reports, as well as undertaking two study tours on residential sustainable design in Japan in 2022 and 2023. These three manufacturers were discussed and compared with respect to their development trajectories, design customisation, research capabilities and technological advancements, sustainable initiatives and procurement, as well as their after-sale services. They have demonstrated their adaptability and flexibility in response to natural disasters and the transformation of the needs in society. They are all keen on reducing the environmental impacts of their work towards zero carbon emissions and a sustainable future.

5.4K
12 Jul 2024

Topic Review

Transtheoretical Model

The transtheoretical model of behavior change is an integrative theory of therapy that assesses an individual's readiness to act on a new healthier behavior, and provides strategies, or processes of change to guide the individual. The model is composed of constructs such as: stages of change, processes of change, levels of change, self-efficacy, and decisional balance. The transtheoretical model is also known by the abbreviation "TTM" and sometimes by the term "stages of change", although this latter term is a synecdoche since the stages of change are only one part of the model along with processes of change, levels of change, etc. Several self-help books—Changing for Good (1994), Changeology (2012), and Changing to Thrive (2016)—and articles in the news media have discussed the model. It has been called "arguably the dominant model of health behaviour change, having received unprecedented research attention, yet it has simultaneously attracted criticism".

5.4K
21 Oct 2022

Topic Review

Applications of Nanostructured Materials

In the last few decades, the vast potential of nanomaterials for biomedical and healthcare applications has been extensively investigated. Several case studies demonstrated that nanomaterials can offer solutions to the current challenges of raw materials in the biomedical and healthcare fields. The different nanoparticles and nanostructured material synthesis approaches were described.

5.4K
11 Apr 2022

Topic Review

The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100 and their standard deviation is set to 15 or 16 IQ points. When IQ tests are revised, they are again standardized using a new sample of test-takers, usually born more recently than the first. Again, the average result is set to 100. However, when the new test subjects take the older tests, in almost every case their average scores are significantly above 100. Test score increases have been continuous and approximately linear from the earliest years of testing to the present. For example, a study published in the year 2009 found that British children's average scores on the Raven's Progressive Matrices test rose by 14 IQ points from 1942 to 2008. Similar gains have been observed in many other countries in which IQ testing has long been widely used, including other Western European countries, Japan, and South Korea. There are numerous proposed explanations of the Flynn effect, as well as some skepticism about its implications. Similar improvements have been reported for semantic and episodic memory. Some research suggests that there may be an ongoing reversed Flynn effect, i.e. a decline in IQ scores, in Norway, Denmark, Australia, Britain, the Netherlands, Sweden, Finland, and German-speaking countries, a development which appears to have started in the 1990s, but in certain cases an apparent reversal is due to cultural changes making parts of intelligence tests obsolete. Meta-analyses indicate that overall, the Flynn effect continues either at the same rate or at a slower rate in developed countries.

5.4K
03 Nov 2022

Topic Review

Solar PV-Hydrogen-PEM Fuel Cell System

The results obtained from the design and analysis of a photovoltaic-hydrogen-PEM fuel cell (PVHPEMFC) hybrid system for Najaf City in Iraq has been presented. The hybrid system consists of photovoltaic arrays coupled with an electrolyzer to produce hydrogen, a PEM fuel cell that converts chemical energy (H2) to electricity, hydrogen storage, a battery storage system, and the load. In this kind of system, all components can be connected electrically in parallel. The voltage of the PV arrays and fuel cell must be high enough to charge the battery, and the voltage of the electrolyzer must be low enough for the battery to power it during periods of low insolation. The designed system model is based on the electrical component models and variable solar radiation data depending on the location.

5.4K
29 Oct 2020

Topic Review

List of SpaceX Starship Launches

Prototypes of the upper stage of the SpaceX Starship have been flown nine times.[lower-alpha 1] Designed and operated by private manufacturer SpaceX, the flown prototypes of Starship have been Starhopper, SN5, SN6, SN8, SN9, SN10, SN11, and SN15. Starship is planned to be a fully-reusable two-stage super heavy-lift launch vehicle and unusual for previous launch vehicle and spacecraft designs, the upper stage of Starship is intended to function both as a second stage to reach orbital velocity on launches from Earth, and also eventually be used in outer space as an on-orbit long-duration spacecraft. It is being designed to take people to Mars and beyond into the Solar System.

5.4K
20 Oct 2022

Topic Review

Trailer Connectors in North America

A number of standards prevail in North America, or parts of it, for trailer connectors, the electrical connectors between vehicles and the trailers they tow that provide a means of control for the trailers.

5.4K
28 Oct 2022

Topic Review

Impact of Automobility on Urban Sprawl

Urban sprawl has become a controversial issue. Lines of thought among academics, practitioners, and local authorities have been diverse. Some academics advocate the compact city as an antidote to urban sprawl, some scholars doubt the ability of conventional notions of containments to create sustainability, and others are fascinated by urban technologies and believe in the feasibility of these technologies, whereas local authorities impose policies, one after the other, without effective results.

5.4K
29 Sep 2022

Topic Review

The phenomenon of heterosis has fascinated plant breeders ever since it was first described by Charles Darwin in 1876 in the vegetable kingdom and later elaborated by George H Shull and Edward M East in maize during 1908. Heterosis is the phenotypic and functional superiority manifested in the F1 crosses over the parents. Various classical complementation mechanisms gave way to the study of the underlying potential cellular and molecular mechanisms responsible for heterosis. In cereals, such as maize, heterosis has been exploited very well, with the development of many single-cross hybrids that revolutionized the yield and productivity enhancements.

5.4K
29 Oct 2020

Topic Review

Bacha bāzī (Dari: بچه بازی‎, lit. "boy play"; from بچه bacheh, "boy", and بازی bazi "play, game") is a slang term in some parts of Afghanistan for a wide variety of activities involving sexual relations between younger adolescent men or boys, who are called dancing boys, and older men. The custom is connected to sexual slavery and child prostitution. In the 21st century, Bacha bazi is reportedly practiced in various parts of Afghanistan. Force and coercion are common, and security officials state they are unable to end such practices because many of the men involved in bacha bazi-related activities are powerful and well-armed warlords. During the Afghan Civil War (1996–2001), bacha bazi carried the death penalty under Taliban law. The practice of dancing boys is illegal under Afghan law, but the laws are seldom enforced against powerful offenders and police have reportedly been complicit in related crimes. A controversy arose after allegations surfaced that U.S. government forces in Afghanistan after the invasion of the country deliberately ignored bacha bazi. The U.S. military responded by claiming the abuse was largely the responsibility of the "local Afghan government". As of 2020, despite international concern, the practice continues.

5.4K
18 Oct 2022

Topic Review

The purple economy is that part of the economy which contributes to sustainable development by promoting the cultural potential of goods and services. “The purple economy refers to taking account of cultural aspects in economics. It designates an economy that adapts to the human diversity in globalization and that relies on the cultural dimension to give value to goods and services.”

5.4K
18 Oct 2022

Topic Review

Time Management

Time management is the process of planning and exercising conscious control of time spent on specific activities, especially to increase effectiveness, efficiency, and productivity. It involves a juggling act of various demands upon a person relating to work, social life, family, hobbies, personal interests and commitments with the finiteness of time. Using time effectively gives the person "choice" on spending/managing activities at their own time and expediency. Time management may be aided by a range of skills, tools, and techniques used to manage time when accomplishing specific tasks, projects, and goals complying with a due date. Initially, time management referred to just business or work activities, but eventually the term broadened to include personal activities as well. A time management system is a designed combination of processes, tools, techniques, and methods. Time management is usually a necessity in any project development as it determines the project completion time and scope. It is also important to understand that both technical and structural differences in time management exist due to variations in cultural concepts of time. The major themes arising from the literature on time management include the following:

5.4K
04 Nov 2022

Topic Review

Thalidomide Scandal

In the late 1950s and early 1960s, the use of thalidomide in pregnant women in 46 countries resulted in the "biggest man‐made medical disaster ever," with over 10,000 children born with a range of severe deformities, such as phocomelia, and thousands of miscarriages. Thalidomide was introduced in 1956 and was aggressively marketed by the German pharmaceutical company Chemie Grünenthal as a medication for anxiety, trouble sleeping, "tension", and morning sickness. It was introduced as a sedative and medication for morning sickness without having been tested on pregnant women. While initially deemed to be safe in pregnancy, concerns regarding birth defects were noted in 1961, and the medication was removed from the market in Europe that year.

5.4K
09 Nov 2022

Topic Review

Newspeak is the language of Oceania, a fictional totalitarian state and the setting of the dystopian novel Nineteen Eighty-Four (1949), by George Orwell. To meet the ideological requirements of English Socialism (Ingsoc) in Oceania, the ruling Party created Newspeak, a controlled language of restricted grammar and limited vocabulary, meant to limit the freedom of thought—personal identity, self-expression, free will—that threatens the ideology of the régime of Big Brother and the Party, who have criminalized such concepts into thoughtcrime, as contradictions of Ingsoc orthodoxy. In "The Principles of Newspeak", the appendix to the novel, George Orwell explains that Newspeak usage follows most of the English grammar, yet is a language characterised by a continually diminishing vocabulary; complete thoughts reduced to simple terms of simplistic meaning. Linguistically, the contractions of Newspeak—Ingsoc (English Socialism), Minitrue (Ministry of Truth), etc.—derive from the syllabic abbreviations of Russian, which identify the government and social institutions of the Soviet Union, such as politburo (Politburo of the Central Committee of the Communist Party of the Soviet Union), Comintern (Communist International), kolkhoz (collective farm), and Komsomol (Young Communists' League). The long-term political purpose of the new language is for every member of the Party and society, except the Proles—the working-class of Oceania—to exclusively communicate in Newspeak, by A.D. 2050; during that 66-year transition, the usage of Oldspeak (Standard English) shall remain interspersed among Newspeak conversations. Newspeak is also a constructed language, of planned phonology, grammar, and vocabulary, like Basic English, which Orwell promoted (1942–44) during the Second World War (1939–45), and later rejected in the essay "Politics and the English Language" (1946), wherein he criticizes the bad usage of English in his day: dying metaphors, pretentious diction, and high-flown rhetoric, which produce the meaningless words of doublespeak, the product of unclear reasoning. Orwell's conclusion thematically reiterates linguistic decline: "I said earlier that the decadence of our language is probably curable. Those who deny this may argue that language merely reflects existing social conditions, and that we cannot influence its development, by any direct tinkering with words or constructions."

5.4K
08 Nov 2022

Topic Review

In astronomy, air mass or airmass is a measure of the amount of air along the line of sight when observing a star or other celestial source from below Earth's atmosphere (Green 1992). It is formulated as the integral of air density along the light ray. As it penetrates the atmosphere, light is attenuated by scattering and absorption; the thicker atmosphere through which it passes, the greater the attenuation. Consequently, celestial bodies when nearer the horizon appear less bright than when nearer the zenith. This attenuation, known as atmospheric extinction, is described quantitatively by the Beer–Lambert law. "Air mass" normally indicates relative air mass, the ratio of absolute air masses (as defined above) at oblique incidence relative to that at zenith. So, by definition, the relative air mass at the zenith is 1. Air mass increases as the angle between the source and the zenith increases, reaching a value of approximately 38 at the horizon. Air mass can be less than one at an elevation greater than sea level; however, most closed-form expressions for air mass do not include the effects of the observer's elevation, so adjustment must usually be accomplished by other means. Tables of air mass have been published by numerous authors, including Bemporad (1904), Allen (1976), and Kasten and Young (1989).

5.4K
11 Oct 2022

Topic Review

CRISPR-Cas Genome Editing Components in C. elegans

CRISPR-Cas allows us to introduce desired genome editing, including mutations, epitopes, and deletions, with unprecedented efficiency. The development of CRISPR-Cas has progressed to such an extent that it is now applicable in various fields, with the help of model organisms. C. elegans is one of the pioneering animals in which numerous CRISPR-Cas strategies have been rapidly established. Ironically, the emergence of numerous methods makes the choice of the correct method difficult. Choosing an appropriate selection or screening approach is the first step in planning a genome modification.

5.4K
30 Dec 2022

Topic Review

Spiking Neural Networks

Spiking neural networks (SNNs) are artificial neural network models that more closely mimic natural neural networks. In addition to neuronal and synaptic state, SNNs also incorporate the concept of time into their operating model. The idea is that neurons in the SNN do not fire at each propagation cycle (as it happens with typical multi-layer perceptron networks), but rather fire only when a membrane potential – an intrinsic quality of the neuron related to its membrane electrical charge – reaches a specific value. When a neuron fires, it generates a signal which travels to other neurons which, in turn, increase or decrease their potentials in accordance with this signal (ref).

5.4K
13 Oct 2021

Topic Review Peer Reviewed

Stefan Uroš II Milutin Nemanjić (1282–1321)

King Stefan Uroš II Milutin Nemanjić (1282—Donje Nerodimlje, October 29, 1321) was a Serbian medieval king, the seventh ruler of the Serbian Nemanide dynasty, the son of King Stefan Uroš I (r. 1243–1276) and Queen Helen Nemanjić (see), the brother of the King Stefan Dragutin (r. 1276–1282) and the father of King Stefan Dečanski (r. 1322–1331). Together with his great grandfather Stefan Nemanja, the founder of the Nemanide dynasty, and his grandson, Emperor Stefan Uroš IV Dušan, King Milutin is considered the most powerful ruler of the Nemanide dynasty. The long and successful military breach of King Milutin, down the Vardar River Valley and deep into the Byzantine territories, represents the beginning of Serbian expansion into southeastern Europe, making it the dominant political power in the Balkan region in the 14th century. During that period, Serbian economic power grew rapidly, mostly because of the development of trading and mining. King Milutin founded Novo Brdo, an internationally important silver mining site. He started minting his own money, producing imitations of Venetian coins (grosso), which gradually diminished in value. This led to the ban of these coins by the Republic of Venice and provided King Milutin a place in Dante’s Divina Commedia. King Milutin had a specific philoktesia fervor: He built or renovated over three dozen Serbian Orthodox churches and monasteries not only in Serbia but also in Thessaloniki, Mt. Athos, Constantinople and The Holy Land. Over fifteen of his portraits can be found in the monumental painting ensembles of Serbian medieval monasteries as well as on two icons.

5.4K
13 Apr 2022

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