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Topic Review
History and Development of Nanomaterial Research
Scientists think that nanoparticles and nanostructured materials originated during the Big Bang process from meteorites leading to the formation of the universe and Earth. Since 1990, the term nanotechnology became very popular due to advances in imaging technologies that paved the way to specific industrial applications. 
  • 14.2K
  • 09 Feb 2022
Topic Review
State-Dependent Memory
State-dependent memory or state-dependent learning is the phenomenon through which memory retrieval is most efficient when an individual is in the same state of consciousness as they were when the memory was formed. The term is often used to describe memory retrieval while in states of consciousness produced by psychoactive drugs – most commonly, alcohol, but has implications for mood or non-substance induced states of consciousness as well. Unlike context-dependent memory, which involves an individual's external environment and conditions, state-dependent memory applies to the individual's internal conditions. For example, while context-dependent memory might refer to the idea that taking a test in the same room that an individual studied in will make it easier to retrieve those memories, state-dependent learning refers to the idea that if an individual always studied for a test while slightly caffeinated, it will most likely be easiest to recall what they studied during the test if they are at a similar level of caffeination.
  • 14.1K
  • 24 Oct 2022
Topic Review
Burnout and Personal Accomplishment
Research on burnout has traditionally focused on job demands, with less attention paid to protective factors. From the emerging and innovative area of psychology of sustainability and sustainable development, the relationship that job demands (workload), and personal resources (psychological capital) have with burnout was analyzed. Results show that (1) psychological capital and workload are related to burnout, and (2) personal accomplishment is more a personal resource than burnout dimension. The results confirm the role of psychological capital as a protective factor for burnout.
  • 14.1K
  • 27 Oct 2020
Topic Review
Germplasm Conservation
Germplasm is a valuable natural resource that provides knowledge about the genetic composition of a species and is crucial for conserving plant diversity. Germplasm protection strategies not only involve rescuing plant species threatened with extinction, but also help preserve all essential plants, on which rests the survival of all organisms. The successful use of genetic resources necessitates their diligent collection, storage, analysis, documentation, and exchange. Slow growth cultures, cryopreservation, pollen and DNA banks, botanical gardens, genetic reserves, and farmers’ fields are a few germplasm conservation techniques being employed. However, the adoption of in-vitro techniques with any chance of genetic instability could lead to the destruction of the entire substance, but the improved understanding of basic regeneration biology would, in turn, undoubtedly increase the capacity to regenerate new plants, thus expanding selection possibilities. Germplasm conservation seeks to conserve endangered and vulnerable plant species worldwide for future proliferation and development; it is also the bedrock of agricultural production. 
  • 14.1K
  • 25 Jun 2021
Topic Review
Flood Prediction Using ML Models
Floods are among the most destructive natural disasters, which are highly complex to model. The research on the advancement of flood prediction models contributed to risk reduction, policy suggestion, minimization of the loss of human life, and reduction of the property damage associated with floods. To mimic the complex mathematical expressions of physical processes of floods, during the past two decades, machine learning (ML) methods contributed highly in the advancement of prediction systems providing better performance and cost-effective solutions. Due to the vast benefits and potential of ML, its popularity dramatically increased among hydrologists.Researchers through introducing novel ML methods and hybridizing of the existing ones aim at discovering more accurate and efficient prediction models. The main contribution of this paper is to demonstrate the state of the art of ML models in flood prediction and to give insight into the most suitable models. In this paper, the literature where ML models were benchmarked through a qualitative analysis of robustness, accuracy, effectiveness, and speed are particularly investigated to provide an extensive overview on the various ML algorithms used in the field. The performance comparison of ML models presents an in-depth understanding of the different techniques within the framework of a comprehensive evaluation and discussion. As a result, this paper introduces the most promising prediction methods for both long-term and short-term floods. Furthermore, the major trends in improving the quality of flood prediction models are investigated. Among them, hybridization, data decomposition, algorithm ensemble, and model optimization are reported as the most effective strategies for the improvement of ML methods. This survey can be used as a guideline for hydrologists as well as climate scientists in choosing the proper ML method according to the prediction task.
  • 14.1K
  • 04 Jan 2023
Topic Review
Voltaire
François-Marie Arouet (French: [fʁɑ̃swa maʁi aʁwɛ]; 21 November 1694 – 30 May 1778), known by his nom de plume Voltaire (/vɒlˈtɛər, voʊl-/; also US: /vɔːl-/, French: [vɔltɛːʁ]), was a French Enlightenment writer, historian, and philosopher famous for his wit, his criticism of Christianity—especially the Roman Catholic Church—as well as his advocacy of freedom of speech, freedom of religion, and separation of church and state. Voltaire was a versatile and prolific writer, producing works in almost every literary form, including plays, poems, novels, essays, histories, and scientific expositions. He wrote more than 20,000 letters and 2,000 books and pamphlets. He was an outspoken advocate of civil liberties, and was at constant risk from the strict censorship laws of the Catholic French monarchy. His polemics witheringly satirized intolerance, religious dogma, and the French institutions of his day.
  • 14.1K
  • 17 Oct 2022
Topic Review
Gadsden Flag
The Gadsden flag is a historical American flag with a yellow field depicting a timber rattlesnake coiled and ready to strike. Beneath the rattlesnake are the words: "Dont Tread on Me". Some modern versions of the flag include an apostrophe. The flag is named after politician Christopher Gadsden (1724–1805), who designed it in 1775 during the American Revolution. It was used by the Continental Marines as an early motto flag, along with the Moultrie flag. It is often used in the United States as a symbol for gun rights and limited government. There are Americans today that still display the Gadsden flag in support of freedom, independence, and for the United States military.
  • 14.1K
  • 22 Nov 2022
Topic Review
Polygyny
Polygyny (/pəˈlɪdʒɪni/; from Neoclassical Greek πολυγυνία; from grc πολύ 'many', and γυνή 'woman, wife') is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women.
  • 14.0K
  • 17 Oct 2022
Topic Review
Guava Leaves
Psidium guajava (L.) belongs to the Myrtaceae family and it is an important fruit in tropical areas like India, Indonesia, Pakistan, Bangladesh, and South America. The leaves of the guava plant have been studied for their health benefits which are attributed to their plethora of phytochemicals, such as quercetin, avicularin, apigenin, guaijaverin, kaempferol, hyperin, myricetin, gallic acid, catechin, epicatechin, chlorogenic acid, epigallocatechin gallate, and caffeic acid. Extracts from guava leaves (GLs) have been studied for their biological activities, including anticancer, antidiabetic, antioxidant, antidiarrheal, antimicrobial, lipid-lowering, and hepatoprotection activities.
  • 14.0K
  • 14 Apr 2021
Topic Review
Physical Properties of Food Materials
The physical properties of food materials have defined those properties that can only be measured by physical means rather than chemical means. Food materials are basically naturally occurring biological-originated raw materials that have their own exclusive physical identity that makes them unique in nature. Due to the uniqueness of their physical properties, to properly measure the different physical characteristics of any food materials to get control and understand about the changes in their native physical characteristics with the influence of time-temperature-processing-treatment-exposure, proper measurement techniques for various physical properties of food materials are required with numerous desired outputs.
  • 14.0K
  • 25 Feb 2022
Topic Review
Agricultural Production in Qatar
Starting in the 1970s, Qatar had almost entirely based its economic growth on resource exploitation of the hydrocarbon sector, with agriculture being considered only as a ‘’hobby’’, rather than an important economic activity. The real driver of change affecting Qatar’s agricultural sector is the issue of food security, after the 2017 embargo (imposed by neighboring countries that made Qatar’s government critically aware that it cannot rely on other countries to secure its food basket), and thus highlighted the need to produce in the country.The factor that has most hindered the development of productive agricultural and horticultural systems in the past has been the availability of land, with suitable soils. This is a consequence of Qatar’s harsh climate; it is in a hot arid zone characterized by sparse precipitation; high summer temperatures; together with high humidity in the late summer months that makes working outside very difficult; very high solar radiation; strong winds; and limited freshwater availability for irrigation causing dependency on desalinated abstracted groundwater, and/or (more recently) on desalinated sea-water.
  • 14.0K
  • 24 Apr 2021
Topic Review
Water Quality Index
A critical water quality index (WQI) method has been used to determine the overall water quality status of surface water and groundwater systems globally since the 1960s. WQI follows four steps: parameter selection, sub-indices, establishing weights, and final index aggregation.
  • 14.0K
  • 09 Apr 2021
Topic Review
Gravity Well
A gravity well or gravitational well is a conceptual model of the gravitational field surrounding a body in space – the more massive the body, the deeper and more extensive the gravity well associated with it. The Sun is very massive, relative to other bodies in the Solar System, so the corresponding gravity well that surrounds it appears "deep" and far-reaching. The gravity wells of asteroids and small moons, conversely, are often depicted as very shallow. Anything at the center of mass of a planet or moon is considered to be at the bottom of that celestial body's gravity well, and so escaping the effects of gravity from such a planet or moon (to enter outer space) can be likened to "climbing out of the gravity well". The deeper a gravity well is, the more energy any space-bound "climber" must use to escape it. In astrophysics, a gravity well is specifically the gravitational potential field around a massive body. Other types of potential wells include electrical and magnetic potential wells. Physical models of gravity wells are sometimes used to illustrate orbital mechanics. Gravity wells are frequently confused with embedding diagrams used in general relativity theory, but the two concepts are distinctly separate and not directly related.
  • 14.0K
  • 12 Oct 2022
Topic Review
Extended Shelf-Life Milk Thermal Processing
Extended shelf-life (ESL) or ultra-pasteurized milk is produced by thermal processing using conditions between those used for traditional high-temperature, short-time (HTST) pasteurization and those used for ultra-high-temperature (UHT) sterilization. 
  • 14.0K
  • 16 Jul 2021
Topic Review
Melanogenesis
Melanogenesis is the biological and biochemical process of melanin and melanosome biosynthesis. Melanin is formed by enzymic reactions of tyrosinase family proteins that convert tyrosine to form brown-black eumelanin and yellow-red pheomelanin within melanosomal compartments in melanocytes, following the cascades of events interacting with a series of autocrine and paracrine signals. Fully melanized melanosomes are delivered to keratinocytes of the skin and hair. In humans, eumelanin and pheomelanin are mixed together regardless of the pigmentary phenotype. The ratio of the two melanin pigments is determined by race and/or specific genetic variations. On the other hand, many mammals have various patterns of hair coat color that can be changed temporally. Wild type mice have agouti pattern hair caused by a mechanism, called pigment-type switching.
  • 13.9K
  • 27 Oct 2020
Topic Review
Information Seeking Behavior
Information seeking behavior refers to the way people search for and utilize information. The term was coined by Thomas D. Wilson in his 1981 paper, on the grounds that the current 'information needs' was unhelpful as a basis for a research agenda, since 'need' could not be directly observed, while how people behaved in seeking information could be observed and investigated. However, there is increasing work in the information searching field that is relating behaviors to underlying needs. In 2000, Wilson described information behavior as the totality of human behavior in relation to sources and channels of information, including both active and passive information-seeking, and information use. He described information seeking behavior as purposive seeking of information as a consequence of a need to satisfy some goal. Information seeking behavior is the micro-level of behavior employed by the searcher in interacting with information systems of all kinds, be it between the seeker and the system, or the pure method of creating and following up on a search. A variety of theories of information behavior – e.g. Zipf's principle of least effort, Brenda Dervin's sensemaking, Elfreda Chatman's life in the round – seek to understand the processes that surround information seeking. The analysis of the most cited publications on information behavior during the first years of this century shows its theoretical nature. Together with some works that have a constructivist focus, using references to Dewey, Kelly, Bruner and Vygotsky, others mention sociological concepts, such as Bourdieu's habitus. Several adopt a constructionist-discursive focus, whereas some, such as Chatman, who can in general be described as using an ethnographic perspective, stand out for the quantity and diversity of references to social research. The term 'information behaviour' was also coined by Wilson and occasioned some controversy on its introduction, but now seems to have been adopted, not only by researchers in information science but also in other disciplines. The digital world is changing human information behavior and process. Focused almost exclusively on information seeking and using, information receiving, a central modality of the process is generally overlooked. As information seeking continues to migrate to the Internet, and artificial intelligence continues to advance the analysis of user behavior on the Internet across a range of user interactions, information receiving moves to the heart of the process, as systems "learn" what users like, want and need, as well as their search habits.
  • 13.9K
  • 24 Apr 2026
Topic Review
Paschen's Law
Paschen's law is an equation that gives the breakdown voltage, that is, the voltage necessary to start a discharge or electric arc, between two electrodes in a gas as a function of pressure and gap length. It is named after Friedrich Paschen who discovered it empirically in 1889. Paschen studied the breakdown voltage of various gases between parallel metal plates as the gas pressure and gap distance were varied: For a given gas, the voltage is a function only of the product of the pressure and gap length. The curve he found of voltage versus the pressure-gap length product (right) is called Paschen's curve. He found an equation that fit these curves, which is now called Paschen's law. At higher pressures and gap lengths, the breakdown voltage is approximately proportional to the product of pressure and gap length, and the term Paschen's law is sometimes used to refer to this simpler relation. However, this is only roughly true, over a limited range of the curve.
  • 13.9K
  • 09 Nov 2022
Topic Review
Pathophysiology of Obesity
Obesity is a challenging condition of excess body fat, caused by an imbalance in energy consumption and expenditure.
  • 13.9K
  • 18 Mar 2021
Topic Review
Allegory of the Cave
The Allegory of the Cave, or Plato's Cave, was presented by the Ancient Greece philosopher Plato in his work Republic (514a–520a) to compare "the effect of education (παιδεία) and the lack of it on our nature". It is written as a dialogue between Plato's brother Glaucon and his mentor Socrates, narrated by the latter. The allegory is presented after the analogy of the sun (508b–509c) and the analogy of the divided line (509d–511e). All three are characterized in relation to dialectic at the end of Books VII and VIII (531d–534e). Plato has Socrates describe a group of people who have lived chained to the wall of a cave all of their lives, facing a blank wall. The people watch shadows projected on the wall from objects passing in front of a fire behind them, and give names to these shadows. The shadows are the prisoners' reality. Socrates explains how the philosopher is like a prisoner who is freed from the cave and comes to understand that the shadows on the wall are not reality at all, for he can perceive the true form of reality rather than the manufactured reality that is the shadows seen by the prisoners. The inmates of this place do not even desire to leave their prison, for they know no better life. The prisoners manage to break their bonds one day, and discover that their reality was not what they thought it was. They discovered the sun, which Plato uses as an analogy for the fire that man cannot see behind. Like the fire that cast light on the walls of the cave, the human condition is forever bound to the impressions that are received through the senses. Even if these interpretations (or, in Kantian terminology, intuitions) are an absurd misrepresentation of reality, we cannot somehow break free from the bonds of our human condition—we cannot free ourselves from phenomenal state just as the prisoners could not free themselves from their chains. If, however, we were to miraculously escape our bondage, we would find a world that we could not understand—the sun is incomprehensible for someone who has never seen it. In other words, we would encounter another "realm", a place incomprehensible because, theoretically, it is the source of a higher reality than the one we have always known; it is the realm of pure Form, pure fact. Socrates remarks that this allegory can be paired with previous writings, namely the analogy of the sun and the analogy of the divided line.
  • 13.9K
  • 15 Nov 2022
Topic Review
V-twin Engine
A V-twin engine, also called a V2 engine, is a two-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration. Although widely associated with motorcycles (installed either transversely or longitudinally), V-twin engines have also been used for industrial engines and in several small cars. The V-twin design dates back to the late 1880s.
  • 13.8K
  • 21 Oct 2022
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