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Topic Review
Electrocommunication
Electrocommunication is the communication method used by weakly-electric fish. Weakly-electric fish are a group of animals that utilize a communicating channel that is "invisible" to most other animals: electric signaling. Electric fish communicate by generating an electric field that a second individual receives with its electroreceptors. The fish interprets the message using the signal's frequencies, waveforms, delay, etc. The best studied species are two freshwater lineages- the African Mormyridae and the South American Gymnotiformes. While weakly-electric fish are the only group that have been identified to carry out both generation and reception of electric fields, other species either generate signals or receive them, but not both. Animals that either generate or receive electric fields are found only in wet or aquatic environments due to water's relatively low electrical resistance, compared to other substances (e.g. air). So far, communication between electric fish has been identified mainly to serve the purpose of conveying information such as: species courtship and biological sex motivational status (e.g. attack warning, submission, etc.) environmental conditions
  • 6.2K
  • 31 Oct 2022
Topic Review
Independent Legal Reasoning in Islamic Law
Ijtihad (Arabic: اجتهاد ijtihād, [ʔidʒ.tihaːd]; lit. physical or mental effort) is an Islamic legal term referring to independent reasoning by an expert in Islamic law, or the thorough exertion of a jurist's mental faculty in finding a solution to a legal question. It is contrasted with taqlid (imitation, conformity to legal precedent). According to classical Sunni theory, ijtihad requires expertise in the Arabic language, theology, revealed texts, and principles of jurisprudence (usul al-fiqh), and is not employed where authentic and authoritative texts (Qur'an and Hadith) are considered unambiguous with regard to the question, or where there is an existing scholarly consensus (ijma). Ijtihad is considered to be a religious duty for those qualified to perform it. An Islamic scholar who is qualified to perform ijtihad is called a mujtahid. Throughout the first five Islamic centuries, the practice of ijtihad continued both theoretically and practically amongst Sunni Muslims. The controversy surrounding ijtihad and the existence of mujtahids started, in its primitive form, around the beginning of the sixth/twelfth century. By the 14th century, development of Sunni jurisprudence prompted leading Sunni jurists to state that the main legal questions had been addressed and the scope of ijtihad was gradually restricted. In the modern era, this gave rise to a perception among Western scholars and lay Muslim public that the so-called "gate of ijtihad" was closed at the start of the classical era. While recent scholarship established that the practice of Ijtihad had never ceased in Islamic history, the extent and mechanisms of legal change in the post-formative period remain a subject of debate. Differences amongst the jurists prevented Muslims from reaching any consensus(Ijma) on the issues of continuity of Ijtihad and existence of Mujtahids. Thus, Ijtihad remained a key aspect of Islamic jurisprudence throughout the centuries. Ijtihad was practiced throughout the Early modern period and claims for ijtihad and its superiority over taqlid were voiced unremittingly. Starting from the 18th century, Islamic reformers began calling for abandonment of taqlid and emphasis on ijtihad, which they saw as a return to Islamic origins. Public debates in the Muslim world surrounding ijtihad continue to the present day. The advocacy of ijtihad has been particularly associated with Islamic modernist and Salafiyya movements. Among contemporary Muslims in the West there have emerged new visions of ijtihad which emphasize substantive moral values over traditional juridical methodology. Shia jurists did not use the term ijtihad until the 12th century. With the exception of Zaydi jurisprudence, the early Imami Shia were unanimous in censuring Ijtihad in the field of law (Ahkam). After the Shiite embracal of various doctrines of Mu'tazila and classical Sunnite Fiqh (jurisprudence), this led to a change. After the victory of the Usulis who based law on principles (usul) over the Akhbaris ("traditionalists") who emphasized on reports or traditions (khabar) by the 19th century, Ijtihad would become a mainstream Shia practice.
  • 6.2K
  • 22 Nov 2022
Topic Review
Evolution of Dinosaurs
Dinosaurs evolved within a single lineage of archosaurs 243-233 Ma (million years ago) from the Anisian to the Carnian ages, the latter part of the middle Triassic. Dinosauria is a well-supported clade, present in 98% of bootstraps. It is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus. In March 2017, scientists reported a new way of classifying the dinosaur family tree, based on newer and more evidence than available earlier. According to the new classification, the original dinosaurs, arising 200 million years ago, were small, two-footed omnivorous animals with large grasping hands. Descendants (for the non-avian dinosaurs) lasted until 66 million years ago.
  • 6.2K
  • 14 Oct 2022
Topic Review
IBM Cloud Computing
IBM cloud computing is a set of cloud computing services for business offered by the information technology company IBM. IBM Cloud includes infrastructure as a service (IaaS), software as a service (SaaS) and platform as a service (PaaS) offered through public, private and hybrid cloud delivery models, in addition to the components that make up those clouds.
  • 6.2K
  • 20 Oct 2022
Topic Review
Combinatorial Peptide Library
Completely randomizing even relatively short peptides would require a library size surpassing the capacities of most platforms. Sampling the complete mutational space for peptides exceeding 8–9 residues is therefore practically impossible, and gene diversification strategies only allow for generation and subsequent interrogation of a limited subset of the entire theoretical peptide population. Directed evolution of peptides therefore strives to ascend towards peak activity through mutational steps, accumulating beneficial mutational over several generations, resulting in improved phenotype. We briefly discuss combinatorial library platforms and take an in-depth look at diversification techniques for random and focused mutagenesis. 
  • 6.1K
  • 30 Oct 2020
Topic Review
Independent Video Game Development
Independent video game development, or indie game development, is the video game development process of creating indie games; these are video games, commonly created by individual or small teams of video game developers and usually without significant financial support of a video game publisher or other outside source. These games may take years to be built from the ground up or can be completed in a matter of days or even hours depending on complexity, participants, and design goal. Driven by digital distribution, the concept of independent video game development has spawned an "indie" movement. The increase in popularity of independent games has allowed increased distribution on popular gaming platforms such as the PlayStation Network, Nintendo eShop, Xbox Live and Steam.
  • 6.1K
  • 21 Nov 2022
Topic Review
G-Protein-Coupled Receptors
G-protein-coupled receptors (GPCRs), which make up the largest superfamily of human membrane proteins, play pivotal roles in mediating intracellular signaling and inducing cell proliferation, cell growth, and cell motility through the association and subsequent dissociation of G-proteins in response to external stimuli.
  • 6.1K
  • 05 Feb 2021
Topic Review
Hydrometallurgy of Lithium Batteries
Spent lithium batteries can cause pollution to the soil and seriously threaten the safety and property of people. They contain valuable metals, such as cobalt and lithium, which are nonrenewable resources, and their recycling and treatment have important economic, strategic, and environmental benefits. The hydrometallurgy process uses reagents such as hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), phosphoric acid (H3PO4), organic acids, and hydrogen peroxide (H2O2) to extract and separate the cathode metals, usually operating below 100 °C, and can recover lithium in addition to the other transition metals.
  • 6.1K
  • 15 Mar 2022
Topic Review
Dracorex
Dracorex is a controversial dinosaur genus of the family Pachycephalosauridae, from the Late Cretaceous of North America. The type (and only known) species is Dracorex hogwartsia, meaning "dragon king of Hogwarts". This dinosaur is named for the wizard school in Harry Potter books. It is known from one nearly complete skull (the holotype TCMI 2004.17.1), as well as four cervical vertebrae: the atlas, third, eighth and ninth. These were discovered in the Hell Creek Formation in South Dakota by three amateur paleontologists from Sioux City, in the U.S. state of Iowa. The skull was subsequently donated to the Children's Museum of Indianapolis for study in 2004, and was formally described by Bob Bakker and Robert Sullivan in 2006. However, Jack Horner et al. suspect that it is a juvenile Pachycephalosaurus and an analysis of pachycephalosaur fossils by a joint team from the University of California, Berkeley and the Museum of the Rockies has questioned the validity of two named genera of pachycephalosaur, Dracorex and Stygimoloch. According to the team, specimens of Dracorex and Stygimoloch might actually represent earlier growth stages of Pachycephalosaurus. This has been supported in a 2016 analysis of the youngest Pachycephalosaurus material known, which indicates that the unique features of Dracorex represent instead ontogenetically variant features on a Pachycephalosaurus growth curve.
  • 6.1K
  • 03 Nov 2022
Topic Review
Psychoanalysis
Psychoanalysis (from Greek: Ancient Greek: + Ancient Greek:) is a set of theories and therapeutic techniques that deal in part with the unconscious mind, and which together form a method of treatment for mental disorders. The discipline was established in the early 1890s by Austrian neurologist Sigmund Freud, who retained the term psychoanalysis for his own school of thought. Freud's work stems partly from the clinical work of Josef Breuer and others. Psychoanalysis was later developed in different directions, mostly by students of Freud, such as Alfred Adler and his collaborator, Carl Gustav Jung, as well as by neo-Freudian thinkers, such as Erich Fromm, Karen Horney, and Harry Stack Sullivan. Psychoanalysis is a controversial discipline, and its effectiveness as a treatment has been contested. It has been largely replaced by the similar but broader psychodynamic psychotherapy in the mid-20th century. although it retains a salient influence within psychiatry. Psychoanalytic concepts are also widely used outside the therapeutic arena, in areas such as psychoanalytic literary criticism, as well as in the analysis of film, fairy tales, philosophical perspectives as Freudo-Marxism and other cultural phenomena.
  • 6.1K
  • 09 Nov 2022
Topic Review
Battery Energy Storage Systems Ancillary Services
The battery energy storage system (BESS) is significant in providing ancillary services to the grid. The BESS plays a crucial role in facilitating the integration of renewable energy sources (RESs) into the grid by compensating for the fluctuations produced by RESs as intermittent resources. Ancillary services encompass all the services necessary for the grid operator (transmission and distribution operator) to maintain the system’s integrity, stability, and power quality. Grid operators ensure a reliable power supply, frequency, voltage, and power load within certain limits. 
  • 6.1K
  • 28 Feb 2024
Topic Review
Polylactic Acid
As a degradable and environmentally friendly polymer, polylactic acid, also known as polylactide, is favored by researchers and has been used as a commercial material in various studies. Lactic acid, as a synthetic raw material of polylactic acid, can only be obtained by sugar fermentation. Good biocompatibility and biodegradability have led it to be approved by the U.S. Food and Drug Administration (FDA) as a biomedical material. Polylactic acid has good physical properties, and its modification can optimize its properties to a certain extent. Polylactic acid blocks and blends play significant roles in drug delivery, implants, and tissue engineering to great effect.  This entry introduces synthesis and biological application of polylactic acid.
  • 6.1K
  • 17 Nov 2020
Topic Review
Taro in West Africa
Taro [Colocasia esculenta (L.) Schott] is the most commonly cultivated species in genus Colocasia and is the fourth most consumed tuber crop globally. It is a member of family Araceae, sub-family Aroideae, and is a tropical monocotyledonous, vegetatively propagated, perennial crop grown primarily for its starchy corm or underground stem. Taro is one of the world’s oldest food crops, with its domestication dating back over 9000 years. It was probably first domesticated in Southeast Asia and thereafter spread across the world, to become one of the most important staple food crops in the Pacific Islands. It is widely distributed across Africa, Oceania, Asia, and the Americas. The crop has been largely maintained by smallholder farmers, and the species’ genetic resources have remained largely within local communities. In many societies, taro is considered a sacred plant of strong cultural importance and is used in religious festivals, domestic and agricultural rituals, and as bride price.
  • 6.1K
  • 19 Sep 2022
Topic Review
Fuel Dispenser
A fuel dispenser is a machine at a filling station that is used to pump gasoline, petrol, diesel, CNG, CGH2, HCNG, LPG, LH2, ethanol fuel, biofuels like biodiesel, kerosene, or other types of fuel into vehicles. Fuel dispensers are also known as bowsers (in Australia ), petrol pumps (in Commonwealth countries), or gas pumps (in North America).
  • 6.1K
  • 19 May 2025
Topic Review
Direct Democracy
Direct democracy or pure democracy is a form of democracy in which people decide on policy initiatives directly. This differs from the majority of most currently established democracies, which are representative democracies.
  • 6.1K
  • 26 Oct 2022
Topic Review
KIC 8462852
KIC 8462852 (also Tabby's Star or Boyajian's Star) is an F-type main-sequence star located in the constellation Cygnus approximately 1,470 light-years (450 pc) from Earth. Unusual light fluctuations of the star, including up to a 22% dimming in brightness, were discovered by citizen scientists as part of the Planet Hunters project. In September 2015, astronomers and citizen scientists associated with the project posted a preprint of an article describing the data and possible interpretations. The discovery was made from data collected by the Kepler space telescope, which observes changes in the brightness of distant stars to detect exoplanets. Several hypotheses have been proposed to explain the star's large irregular changes in brightness as measured by its light curve, but none to date fully explain all aspects of the curve. One explanation is that an "uneven ring of dust" orbits KIC 8462852. In another explanation, the star's luminosity is modulated by changes in the efficiency of heat transport to its photosphere, so no external obscuration is required. A third hypothesis, based on a lack of observed infrared light, posits a swarm of cold, dusty comet fragments in a highly eccentric orbit, however, the notion that disturbed comets from such a cloud could exist in high enough numbers to obscure 22% of the star's observed luminosity has been doubted. Another hypothesis is that a large number of small masses in "tight formation" are orbiting the star. Furthermore, spectroscopic study of the system has found no evidence for coalescing material or hot close-in dust or circumstellar matter from an evaporating or exploding planet within a few astronomical units of the mature central star. It has also been hypothesized that the changes in brightness could be signs of activity associated with intelligent extraterrestrial life constructing a Dyson swarm. The scientists involved are very skeptical, however, with others describing it as implausible. KIC 8462852 is not the only star that has large irregular dimmings, but all other such stars are young stellar objects called YSO dippers, which have different dimming patterns. An example of such an object is EPIC 204278916. New light fluctuation events of KIC 8462852 began in the middle of May 2017. Except for a period between late-December 2017 and mid-February 2018 when the star was obscured by the Sun, the fluctuations have continued (As of July 2018).
  • 6.1K
  • 15 Nov 2022
Topic Review
Early Chinese Cartography
Early Chinese cartography began in the 5th century BC during the Warring States period when cartographers started to make maps of the Earth's surface. Its scope extended beyond China's borders with the expansion of the Chinese Empire under the Han dynasty. It entered its golden age with the invention of the compass in the 11th century during the Song dynasty, and reached its peak in the 15th century when the Ming dynasty admiral Zheng He went on a series of voyages to the South China Sea, Indian Ocean, and beyond.
  • 6.1K
  • 10 Oct 2022
Topic Review
Effects of Exercise on the Autonomic Nervous System
The autonomic nervous system (ANS) has an important impact on health in general. In response to environmental demands, homeostatic processes are often compromised, therefore determining an increase in the sympathetic nervous system (SNS)’s functions and a decrease in the parasympathetic nervous system (PNS)’s functions.
  • 6.1K
  • 21 Feb 2022
Topic Review
Socially Responsible Human Resource Management
At the intersection of corporate social responsibility (CSR) and human resource management (HRM), a specific research strand has been forming and considerably flourishing over the past years, contributing to the burgeoning academic debate of what has been called “socially responsible human resource management” (SRHRM). The SRHRM debate seeks to proactively enhance employees’ work experiences and meet their personal and social expectations in ethical and socially responsible ways.
  • 6.1K
  • 16 Feb 2022
Topic Review
Binary Fission
Fission, in biology, is the division of a single entity into two or more parts and the regeneration of those parts to separate entities resembling the original. The object experiencing fission is usually a cell, but the term may also refer to how organisms, bodies, populations, or species split into discrete parts. The fission may be binary fission, in which a single organism produces two parts, or multiple fission, in which a single entity produces multiple parts.
  • 6.1K
  • 31 Oct 2022
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