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Topic Review
Post-transition Metal
Post-transition metals are a set of metallic elements in the periodic table located between the transition metals to their left, and the metalloids to their right. Depending on where these adjacent groups are judged to begin and end, there are at least five competing proposals for which elements to include: the three most common contain six, ten and thirteen elements, respectively (see image). All proposals include gallium, indium, tin, thallium, lead, and bismuth. Physically, post-transition metals are soft (or brittle), have poor mechanical strength, and have melting points lower than those of the transition metals. Being close to the metal-nonmetal border, their crystalline structures tend to show covalent or directional bonding effects, having generally greater complexity or fewer nearest neighbours than other metallic elements. Chemically, they are characterised—to varying degrees—by covalent bonding tendencies, acid-base amphoterism and the formation of anionic species such as aluminates, stannates, and bismuthates (in the case of aluminium, tin, and bismuth, respectively). They can also form Zintl phases (half-metallic compounds formed between highly electropositive metals and moderately electronegative metals or metalloids). The name is universally used, but not officially sanctioned by any organization such as the IUPAC. The origin of the term is unclear: one early use was in 1940 in a chemistry text. Alternate names for this group are B-subgroup metals, other metals, and p-block metals; and at least thirteen other labels.
  • 8.7K
  • 21 Nov 2022
Topic Review
Mass Transfer in Packed-Bed Columns
This review provides a thorough analysis of the most famous mass transfer models for random and structured packed-bed columns used in absorption/stripping and distillation processes, providing an overview of the equations to calculate the mass transfer parameters, i.e.: gas-side coefficient per unit surface ky [kmol·m-2·s-1], liquid-side coefficient per unit surface kx [kmol·m-2·s-1], interfacial packing area ae [m2·m-3], which constitute the ingredients to assess the mass transfer rate of packed-bed columns. This work also provides the ranges of model validity and applicability together with their main pros and cons and the criticalities behind these models, which mostly rely on the assessment of fluid-dynamics parameters such as liquid film thickness, liquid hold-up and interfacial area, or the real liquid paths or any mal-distributions flow. 
  • 8.7K
  • 01 Sep 2021
Topic Review
Nature Sports
Nature sports comprise a group of sporting activities that are developed and experienced in natural or rural areas, ranging from formal to informal practices. These practices are performed in a variety of natural contexts including on land (mountain biking, rock-climbing, trekking, etc.), in water (kayaking, sailing, surfing, windsurfing, etc.), and in the air (paragliding and hang-gliding, etc.). Nature sports have a spontaneous, playful nature, "with participation predominantly taking place in informal settings, often without governing bodies or clubs or other forms of external regulation". They are generally autonomous activities, even if some nature sports are practiced collectively, such as kayaking, or those which create sporting sub-cultures, such as in surfing.
  • 8.7K
  • 06 Sep 2021
Topic Review
Democratic Socialism
Democratic socialism is a political philosophy that supports political democracy and some form of a socially owned economy,({{{1}}}, {{{2}}}) with a particular emphasis on economic democracy, workplace democracy, and workers' self-management within a market socialist economy, or an alternative form of decentralised planned socialist economy. Democratic socialists argue that capitalism is inherently incompatible with the values of freedom, equality, and solidarity and that these ideals can only be achieved through the realisation of a socialist society. Although most democratic socialists seek a gradual transition to socialism,({{{1}}}, {{{2}}}) democratic socialism can support either revolutionary or reformist politics as means to establish socialism.({{{1}}}, {{{2}}}) Democratic socialism was popularized by socialists who were opposed to the backsliding towards a one-party state in the Soviet Union and other nations during the 20th century.({{{1}}}, {{{2}}}) The history of democratic socialism can be traced back to 19th-century socialist thinkers across Europe and the Chartist movement in Britain, which somewhat differed in their goals but shared a common demand of democratic decision making and public ownership of the means of production, and viewed these as fundamental characteristics of the society they advocated for. In the late 19th to the early 20th century, democratic socialism was also heavily influenced by the gradualist form of socialism promoted by the British Fabian Society and Eduard Bernstein's evolutionary socialism in Germany.({{{1}}}, {{{2}}}) Democratic socialism is what most socialists understand by the concept of socialism;({{{1}}}, {{{2}}}) it may be a very broad (socialists who reject a one-party Marxist–Leninist state)({{{1}}}, {{{2}}}) or more limited concept (post-war social democracy).({{{1}}}, {{{2}}}) As a broad movement, it includes forms of libertarian socialism,({{{1}}}, {{{2}}}) market socialism,({{{1}}}, {{{2}}}) reformist socialism, and revolutionary socialism,({{{1}}}, {{{2}}}) as well as ethical socialism,({{{1}}}, {{{2}}}) liberal socialism,({{{1}}}, {{{2}}}) social democracy,({{{1}}}, {{{2}}}) and some forms of state socialism and utopian socialism, all of which share commitment to democracy.({{{1}}}, {{{2}}}) Democratic socialism is contrasted with Marxism–Leninism, which opponents often perceive as being authoritarian and undemocratic in practice.({{{1}}}, {{{2}}}) Democratic socialists oppose the Stalinist political system and the Soviet-type economic planning system, rejecting as their form of governance the administrative-command system that formed in the Soviet Union and other Marxist–Leninist states during the 20th century. Democratic socialism is also distinguished from Third Way social democracy[nb 1] on the basis that democratic socialists are committed to systemic transformation of the economy from capitalism to socialism.[nb 2] While having socialism as a long-term goal,({{{1}}}, {{{2}}}) some moderate democratic socialists are more concerned about curbing capitalism's excesses, and are supportive of progressive reforms to humanise it in the present day,({{{1}}}, {{{2}}}) while other democratic socialists believe that economic interventionism and similar policy reforms aimed at addressing social inequalities and suppressing the economic contradictions of capitalism would only exacerbate the contradictions,({{{1}}}, {{{2}}}) causing them to emerge elsewhere under a different guise.({{{1}}}, {{{2}}}) Those democratic socialists believe that the fundamental issues with capitalism are systemic in nature, and can only be resolved by replacing the capitalist mode of production with the socialist mode of production through the replacement of private ownership with collective ownership of the means of production, and extending democracy to the economic sphere in the form of industrial democracy.({{{1}}}, {{{2}}}) The main criticism of democratic socialism is focused on the compatibility of democracy and socialism. Several academics and political commentators tend to distinguish between authoritarian socialism and democratic socialism as a political ideology, with the first representing the Soviet Bloc, and the latter representing the democratic socialist parties in the Western Bloc countries that have been democratically elected in countries such as Britain, France, and Sweden, among others.({{{1}}}, {{{2}}}) However, following the end of the Cold War, many of these countries have moved away from socialism as a neoliberal consensus replaced the social democratic consensus in the advanced capitalist world.
  • 8.7K
  • 17 Oct 2022
Topic Review
Ego-Dystonic Sexual Orientation
Ego-dystonic sexual orientation is an ego-dystonic mental disorder characterized by having a sexual orientation or an attraction that is at odds with one's idealized self-image, causing anxiety and a desire to change one's orientation or become more comfortable with one's sexual orientation. It describes not innate sexual orientation itself, but a conflict between the sexual orientation one wishes to have and the sexual orientation one actually possesses.
  • 8.7K
  • 14 Oct 2022
Topic Review
Applications of Cyclodextrins
Due to their unique structural, physical and chemical properties, cyclodextrins and their derivatives have been of great interest to scientists and researchers in both academia and industry for over a century. Many of the industrial applications of cyclodextrins have arisen from their ability to encapsulate, either partially or fully, other molecules, especially organic compounds. Cyclodextrins are non-toxic oligopolymers of glucose that help to increase the solubility of organic compounds with poor aqueous solubility, can mask odors from foul-smelling compounds, and have been widely studied in the area of drug delivery. 
  • 8.7K
  • 29 Mar 2022
Topic Review
Mediterranean Climate
A Mediterranean climate /ˌmɛdɪtəˈreɪniən/ or dry summer climate is characterized by dry summers and mild, wet winters. The climate receives its name from the Mediterranean Basin, where this climate type is most common. Mediterranean climate zones are typically located along the western sides of continents, between roughly 30 and 45 degrees north and south of the equator. The main cause of Mediterranean, or dry summer climate, is the subtropical ridge which extends northwards during the summer and migrates south during the winter due to increasing north-south temperature differences. The resulting vegetation of Mediterranean climates are the garrigue or maquis in the Mediterranean Basin, the chaparral in California, the fynbos in South Africa, the mallee in Australia, and the matorral in Chile. Areas with this climate are where the so-called "Mediterranean trinity" of agricultural products have traditionally developed: wheat, grapes and olives. Most historic cities of the Mediterranean basin lie within Mediterranean climatic zones, including Algiers, Athens, Barcelona, Beirut, İzmir, Jerusalem, Marseille, Naples, Rome, Tunis, Valencia, and Valletta. Major cities with Mediterranean climates outside of the Mediterranean basin include Adelaide, Cape Town, Casablanca, Dushanbe, Lisbon, Los Angeles , Perth, Porto, Sacramento, San Diego, San Francisco , San Jose, CA, Santiago, Tashkent and Victoria.
  • 8.6K
  • 07 Nov 2022
Topic Review
Design Considerations of Fixed and Floating Offshore Structures
Offshore structures exist in a variety of forms, and they are used for a variety of functions in varied sea depths. These structures are tailored for certain environments and sea depths and other design considerations. 
  • 8.6K
  • 29 Jul 2022
Biography
Niccolò Machiavelli
Niccolò di Bernardo dei Machiavelli (/ˌmækiəˈvɛli/, also US: /ˌmɑːk-/; Italian: [nikkoˈlɔ mmakjaˈvɛlli]; 3 May 1469 – 21 June 1527) was an Italian diplomat, philosopher, politician, historian and writer who lived during the Renaissance. He is best known for The Prince (Il Principe), written about 1513.[1] He has often been called the father of modern political philosophy and poli
  • 8.6K
  • 23 Nov 2022
Topic Review
College Students Career Decision-Making Difficulties
College students suffer from various difficulties due to their own and environmental reasons in the process of career decision-making, which may affect their individual psychological state and social functions over time. One of the main difficulties is career decision-making. Career decision-making difficulties refer to various difficulties or problems faced by individuals in the process of career decision-making, including lack of readiness (LR), lack of information (LI), and inconsistent information (II). College students have certain career decision-making difficulties due to the lack of occupational information and self-information. The career decision-making difficulties not only affect college students’ employment, but also affect their solutions to the problems in career development.
  • 8.6K
  • 02 Jul 2021
Topic Review
History of Virology
The history of virology — the scientific study of viruses and the infections they cause – began in the closing years of the 19th century. Although Louis Pasteur and Edward Jenner developed the first vaccines to protect against viral infections, they did not know that viruses existed. The first evidence of the existence of viruses came from experiments with filters that had pores small enough to retain bacteria. In 1892, Dmitry Ivanovsky used one of these filters to show that sap from a diseased tobacco plant remained infectious to healthy tobacco plants despite having been filtered. Martinus Beijerinck called the filtered, infectious substance a "virus" and this discovery is considered to be the beginning of virology. The subsequent discovery and partial characterization of bacteriophages by Frederick Twort and Félix d'Herelle further catalyzed the field, and by the early 20th century many viruses had been discovered. In 1926, Thomas Milton Rivers defined viruses as obligate parasites. Viruses were demonstrated to be particles, rather than a fluid, by Wendell Meredith Stanley, and the invention of the electron microscope in 1931 allowed their complex structures to be visualised.
  • 8.6K
  • 31 Oct 2022
Topic Review
Agrivoltaic System
Agrivoltaic systems (AVS) offer a symbiotic strategy for co-location sustainable renewable energy and agricultural production. This is particularly important in densely populated developing and developed countries, where renewable energy development is becoming more important; however, profitable farmland must be preserved. As emphasized in the Food-Energy-Water (FEW) nexus, AVS advancements should not only focus on energy management, but also agronomic management (crop and water management). 
  • 8.6K
  • 05 Sep 2021
Topic Review
Olfaction and Ligand–Receptor Interaction
Odorant or olfactory receptors (ORs) are located in the human nose, in the olfactory epithelium. The olfactory receptors can recognize many different odor molecules of a diverse protein sequence, and OR genes constitute the most abundant family of G protein-coupled receptors (GPCRs). The human receptor gene family comprises 339 receptor genes and 297 receptor pseudogenes, unequally dispersed in 51 distinct loci on 21 human chromosomes. Humans have a compassionate sense of smell, which is essential for discovering odors necessary for maintaining a healthy life, such as the smell of smoke (detection of fire) and rotten food (to avoid ingestion).
  • 8.6K
  • 25 Sep 2023
Topic Review
Natural Biopolymers
Natural biopolymers are an interesting resource for edible films production, as they are environmentally friendly packaging materials.
  • 8.6K
  • 23 Jun 2021
Topic Review
Woodward Effect
The Woodward effect, also referred to as a Mach effect, is part of a hypothesis proposed by James F. Woodward in 1990. The hypothesis states that transient mass fluctuations arise in any object that absorbs internal energy while undergoing a proper acceleration. Harnessing this effect could generate a reactionless thrust, which Woodward and others claim to measure in various experiments. Hypothetically, the Woodward effect would allow for field propulsion spacecraft engines that would not have to expel matter. Such a proposed engine is sometimes called a Mach effect thruster (MET) or a Mach Effect Gravitational Assist (MEGA) drive. So far, experimental results have not strongly supported this hypothesis, but experimental research on this effect, and its potential applications, continues. The Space Studies Institute was selected as part of NASA's Innovative Advanced Concepts program as a Phase I proposal in April 2017 for Mach Effect research. The year after, NASA awarded a NIAC Phase II grant to the SSI to further develop these propellantless thrusters. The effect is controversial within mainstream physics because the underlying model proposed for it appears to be faulty, resulting in violations of energy conservation as well as momentum conservation.
  • 8.6K
  • 16 Nov 2022
Topic Review
Prehistoric Paintings in Magura Cave
The paintings are made of bat guano applied over limestone, therefore two sets of laboratory specimens were considered: stone specimens and stone specimens covered with a layer of sterilized bat guano. The two investigated treatments were a commercial product based on ethyl silicate (“ES”) and a solution of diammonium hydrogen phosphate (“DAP”), aimed at forming calcium phosphates. The results of the study indicate that both treatments were able to increase mechanical properties of stone, the increase being higher for “DAP”. Both consolidants caused acceptable color changes, but the “ES” treatment significantly decreased stone wettability, water absorption and water vapor permeability, while the “DAP” treatment slightly affected those properties. In the stone+guano specimens, the presence of the guano layer affected the penetration of the consolidants, thus partly reducing their effectiveness. Compared to the stone samples, the guano layer experienced a more intense color change, alongside visible cracking. However, the adopted methodology to replicate the cave paintings was not completely successful, as the so-deposited guano layer was very prone to detachment when dry, unlike cave paintings. Future work will be dedicated to assess the consolidant performance onto samples that resemble even more closely the conditions of the cave paintings, by improving the methodology for the guano layer deposition and by contaminating specimens with soluble salts before consolidant application.
  • 8.6K
  • 02 Nov 2020
Topic Review
Kilowatt Hour
The kilowatt hour (symbol: kW⋅h, kW h, or kWh) is a unit of energy equal to 3.6 megajoules. If energy is transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt hours is equal to the power in kilowatts multiplied by the time in hours. The kilowatt hour is commonly used as a billing unit for energy delivered to consumers by electric utilities.
  • 8.6K
  • 14 Nov 2022
Topic Review
Melatonin Protects Mitochondria and Adenosine Triphosphate Production
Melatonin (N-acetyl-5-methoxytryptamine) is a ubiquitous, mitochondria-targeted molecule present in all tested eukarya and bacteria. In March 2022, the first discovery of the serotonin N-acetyltransferase (SNAT) gene—responsible for the penultimate formation of N-acetylserotonin (NAS) before its final conversion into melatonin — in archaea further consolidates the status of melatonin as a regulator of biomolecular condensates in all three domains of life in the cellular empire. RNA viruses including SARS-CoV-2 contain proteins with intrinsically disordered regions that undergo liquid-liquid phase separation (LLPS). Liquid-liquid phase separation (LLPS) of these proteins form membraneless condensates that act as “viral factories” to facilitate and enhance replication. Phase separation of the SARS-CoV-2 nucleocapsid (N) protein is associated with mitochondrial dysfunction and rewiring of energy production away from oxidative phosphorylation (OXPHOS) to favor aerobic glycolysis in cytoplasm. Increased adenosine triphosphate (ATP) in cytoplasm supports viral replication. Melatonin protects mitochondria from damage, maintains adequate levels to disassemble “viral factories”, and prevents suppression of host antiviral immune responses by inhibiting nucleocapsid phase separation via antioxidant-dependent and -independent means.
  • 8.6K
  • 05 Sep 2022
Topic Review
Biomass Gasification
Lignocellulosic gasification is a valid thermochemical approach for the conversion of organic solid matter into a gaseous mixture that is constituted of hydrogen, carbon monoxide, carbon dioxide and methane, named synthetic gas or syngas. Although about 55% of syngas is still produced from coal, biomass utilization, especially lignocellulose, is constantly growing. Indeed, gasification could be potentially applied to all different kinds of lignocellulosic biomass, unlike other conversion technologies. Moreover, in the last few decades, a wide range of applications of syngas have been intensively studied. Syngas can be directly used as a combustible substance in power plants for heat and power production (steam cycle, co-combustion, combustion in gas turbines or internal combustion engines, high temperature fuel cells), which represents the most common use of biomass-derived syngas. However, syngas also represents a platform that can be employed in a broad range of chemical and microbial processes, leading to gaseous and liquid fuels, as well as to chemicals. Chemical process research has mainly focused on transportation fuel production from syngas, such as Fischer–Tropsch liquid fuels, hydrogen, methanol, dimethyl ether (DME), mixed alcohols, and synthetic natural gas (SNG). Instead, the biochemical conversion route consists of syngas fermentation in which obligate anaerobic microorganisms convert syngas into organic acids, alcohols, and other chemicals. The most commonly used microorganisms are acetogens, which use the Wood–Ljungdahl metabolic pathway. Syngas fermentation is defined as an indirect fermentation process because biomass is not fed directly into the fermenter, but it is previously converted into syngas through gasification. 
  • 8.6K
  • 17 Dec 2020
Topic Review
Tandem Mass Spectrometry
Tandem mass spectrometry, also known as MS/MS or MS2, involves multiple steps of mass spectrometry selection, with some form of fragmentation occurring in between the stages. In a tandem mass spectrometer, ions are formed in the ion source and separated by mass-to-charge ratio in the first stage of mass spectrometry (MS1). Ions of a particular mass-to-charge ratio (precursor ions) are selected and fragment ions (product ions) are created by collision-induced dissociation, ion-molecule reaction, photodissociation, or other process. The resulting ions are then separated and detected in a second stage of mass spectrometry (MS2).
  • 8.6K
  • 19 Oct 2022
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