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Topic Review
Keto–Enol Tautomerism
In organic chemistry, keto–enol tautomerism refers to a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol (an alcohol). The keto and enol forms are said to be tautomers of each other. The interconversion of the two forms involves the movement of an alpha hydrogen atom and the reorganisation of bonding electrons; hence, the isomerism qualifies as tautomerism. A compound containing a carbonyl group (C=O) is normally in rapid equilibrium with an enol tautomer, which contains a pair of doubly bonded carbon atoms adjacent to a hydroxyl (−OH) group, C=C-OH. The keto form predominates at equilibrium for most ketones. Nonetheless, the enol form is important for some reactions. The deprotonated intermediate in the interconversion of the two forms, referred to as an enolate anion, is important in carbonyl chemistry, in large part because it is a strong nucleophile. Normally, the keto–enol tautomerization chemical equilibrium is highly thermodynamically driven, and at room temperature the equilibrium heavily favors the formation of the keto form. A classic example for favoring the keto form can be seen in the equilibrium between vinyl alcohol and acetaldehyde (K = [enol]/[keto] ≈ 3 × 10−7). However, it is reported that in the case of vinyl alcohol, formation of a stabilized enol form can be accomplished by controlling the water concentration in the system and utilizing the kinetic favorability of the deuterium-produced kinetic isotope effect (kH+/kD+ = 4.75, kH2O/kD2O = 12). Deuterium stabilization can be accomplished through hydrolysis of a ketene precursor in the presence of a slight stoichiometric excess of heavy water (D2O). Studies show that the tautomerization process is significantly inhibited at ambient temperatures ( kt ≈ 10−6 M/s), and the half-life of the enol form can easily be increased to t1/2 = 42 minutes for first-order hydrolysis kinetics. Another exception is the 1,3-diketones, such as acetylacetone (2,4-pentanedione), which favor the enol form.
  • 6.6K
  • 24 Oct 2022
Topic Review
Design Challenges and Limitations of Injectable Hydrogels
Injectable hydrogels (IHs) are smart biomaterials and are the most widely investigated and versatile technologies, which can be either implanted or inserted into living bodies with minimal invasion. Their unique features, tunable structure and stimuli-responsive biodegradation properties make these IHs promising in many biomedical applications, including tissue engineering, regenerative medicines, implants, drug/protein/gene delivery, cancer treatment, aesthetic corrections and spinal fusions. Regarding their current prospective and ongoing research, hydrogel formulations have some limitations in their applications, clinical practices and sustainability. Many hydrogel systems (natural/synthetic), such as thermosensitive hydrogels, are free-flowing sols at a low temperature, while upon raising to body temperature (physiological temperature), they are converted to a stable visco-elastic gel phase, such as poly (phosphazene), pluronic and poly (N-isopropyl acrylamide). 
  • 6.6K
  • 08 Apr 2022
Topic Review
Cigarette Filter
A cigarette filter is a component of a cigarette, along with cigarette paper, capsules and adhesives. It does not make cigarettes less unhealthy. The filter may be made from cellulose acetate fibre, paper or activated charcoal (either as a cavity filter or embedded into the cellulose acetate). Macroporous phenol-formaldehyde resins and asbestos have also been used in cigarette filters. The acetate and paper modify the particulate smoke phase by particle retention (filtration), and finely divided carbon modifies the gaseous phase (adsorption). Filters can reduce "tar" and nicotine smoke yields up to 50%, with a greater removal rate for other classes of compounds (e.g., phenols), but are ineffective in filtering toxins such as carbon monoxide. Most of these measured reductions occur only when the cigarette is smoked on a smoking machine; when a human smokes them, deliveries remain similar with or without a filter. Most factory-made cigarettes are equipped with a filter; those who roll their own can buy them from a tobacconist. The near-universal adoption of filters on cigarettes has not reduced harms to smokers; for instance, lung cancer rates have not declined. Filling a given length of cigarette with filter is cheaper than filling it with tobacco.
  • 6.6K
  • 10 Nov 2022
Topic Review
Technology and Society
Technology society and life or technology and culture refers to the inter-dependency, co-dependence, co-influence, and co-production of technology and society upon one another. Evidence for this synergy has been found since humanity first started using simple tools. The inter-relationship has continued as modern technologies such as the printing press and computers have helped shape society. The first scientific approach to this relationship occurred with the development of tektology, the "science of organization", in early twentieth century Imperial Russia. In modern academia, the interdisciplinary study of the mutual impacts of science, technology, and society, is called science and technology studies. The simplest form of technology is the development and use of basic tools. The prehistoric discovery of how to control fire and the later Neolithic Revolution increased the available sources of food, and the invention of the wheel helped humans to travel in and control their environment. Developments in historic times have lessened physical barriers to communication and allowed humans to interact freely on a global scale, such as the printing press, telephone, and Internet. Technology has developed advanced economies, such as the modern global economy, and has led to the rise of a leisure class. Many technological processes produce by-products known as pollution, and deplete natural resources to the detriment of Earth's environment. Innovations influence the values of society and raise new questions in the ethics of technology. Examples include the rise of the notion of efficiency in terms of human productivity, and the challenges of bioethics. Philosophical debates have arisen over the use of technology, with disagreements over whether technology improves the human condition or worsens it. Neo-Luddism, anarcho-primitivism, and similar reactionary movements criticize the pervasiveness of technology, arguing that it harms the environment and alienates people. However, proponents of ideologies such as transhumanism and techno-progressivism view continued technological progress as beneficial to society and the human condition.
  • 6.6K
  • 24 Nov 2022
Topic Review
Material Extrusion Additive Manufacturing of Metal
Material extrusion additive manufacturing of metal (metal MEX), which is one of the 3D printing processes, has gained more interests because of its simplicity and economics. Metal MEX process is similar to the conventional metal injection moulding (MIM) process, consisting of feedstock preparation of metal powder and polymer binders, layer-by-layer 3D printing (metal MEX) or injection (MIM) to create green parts, debinding to remove the binders and sintering to create the consolidated metallic parts.
  • 6.6K
  • 02 Jun 2022
Topic Review
Yao's Millionaires' Problem
Yao's Millionaires' problem is a secure multi-party computation problem which was introduced in 1982 by computer scientist and computational theorist Andrew Yao. The problem discusses two millionaires, Alice and Bob, who are interested in knowing which of them is richer without revealing their actual wealth. This problem is analogous to a more general problem where there are two numbers [math]\displaystyle{ a }[/math] and [math]\displaystyle{ b }[/math] and the goal is to determine whether the inequality [math]\displaystyle{ a \geq b }[/math] is true or false without revealing the actual values of [math]\displaystyle{ a }[/math] and [math]\displaystyle{ b }[/math]. The Millionaires' Problem is an important problem in cryptography, the solution of which is used in e-commerce and data mining. Commercial applications sometimes have to compare numbers which are confidential and whose security is important. Many solutions have been introduced for the problem, among which the first solution, presented by Yao himself, was exponential in time and space.
  • 6.5K
  • 15 Nov 2022
Topic Review
Iridology
Iridology (also known as iridodiagnosis or iridiagnosis) is an alternative medicine technique whose proponents claim that patterns, colors, and other characteristics of the iris can be examined to determine information about a patient's systemic health. Practitioners match their observations to iris charts, which divide the iris into zones that correspond to specific parts of the human body. Iridologists see the eyes as "windows" into the body's state of health. Iridologists claim they can use the charts to distinguish between healthy systems and organs in the body and those that are overactive, inflamed, or distressed. Iridologists claim this information demonstrates a patient's susceptibility towards certain illnesses, reflects past medical problems, or predicts later health problems. As opposed to evidence-based medicine, iridology is not supported by quality research studies and is widely considered pseudoscience. The features of the iris are one of the most stable features on the human body throughout life. The stability of iris structures is the foundation of the biometric technology which uses iris recognition for identification purposes. In 1979, Bernard Jensen, a leading American iridologist, and two other iridology proponents failed to establish the basis of their practice when they examined photographs of the eyes of 143 patients in an attempt to determine which ones had kidney impairments. Of the patients, forty-eight had been diagnosed with kidney disease, and the rest had normal kidney function. Based on their analysis of the patients' irises, the three iridologists could not detect which patients had kidney disease and which did not.
  • 6.5K
  • 04 Nov 2022
Topic Review
Rock–Paper–Scissors
Rock–paper–scissors (also known as paper-scissors-rock or other variants) is a hand game usually played between two people, in which each player simultaneously forms one of three shapes with an outstretched hand. These shapes are "rock" (a closed fist), "paper" (a flat hand), and "scissors" (a fist with the index finger and middle finger extended, forming a V). "Scissors" is identical to the two-fingered V sign (also indicating "victory" or "peace") except that it is pointed horizontally instead of being held upright in the air. A simultaneous, zero-sum game, it has only two possible outcomes: a draw, or a win for one player and a loss for the other. A player who decides to play rock will beat another player who has chosen scissors ("rock crushes scissors" or sometimes "blunts scissors"), but will lose to one who has played paper ("paper covers rock"); a play of paper will lose to a play of scissors ("scissors cuts paper"). If both players choose the same shape, the game is tied and is usually immediately replayed to break the tie. The type of game originated in China and spread with increased contact with East Asia, while developing different variants in signs over time. Other names for the game in the English-speaking world include roshambo and other orderings of the three items, with "rock" sometimes being called "stone". Rock–paper–scissors is often used as a fair choosing method between two people, similar to coin flipping, drawing straws, or throwing dice in order to settle a dispute or make an unbiased group decision. Unlike truly random selection methods, however, rock–paper–scissors can be played with a degree of skill by recognizing and exploiting non-random behavior in opponents.
  • 6.5K
  • 25 Oct 2022
Topic Review
Biorhythm
A biorhythm (from Greek βίος – bios, "life" and ῥυθμός – rhuthmos, "any regular recurring motion, rhythm") is an attempt to predict various aspects of a person's life through simple mathematical cycles. The theory was developed by Wilhelm Fliess in the late 19th century, and was popularized in the United States in late 1970s. Scientific analysis shows that biorhythms have no more predictive power than chance, providing no evidence for their existence. "The theory of biorhythms is a theory that claims our daily lives are significantly affected by rhythmic cycles."
  • 6.5K
  • 01 Dec 2022
Topic Review
Sesquiterpene Lactones
Sesquiterpene lactones, a vast group of terpenoids isolated from Asteraceae family species, exhibit a wide variety of biological activities and several of them are already available on the medicines market, such as artemisinin. Here are presented and discussed the most recent and impactful results in vivo, preclinical and clinical studies, involving a selection of ten sesquiterpene lactones (alantolactone, arglabin, costunolide, cynaropicrin, helenalin, inuviscolide, lactucin, parthenolide, thapsigargin and tomentosin) and some of their derivatives.
  • 6.5K
  • 28 Oct 2020
Topic Review
Buddhist Ethics
Buddhist ethics are traditionally based on what Buddhists view as the enlightened perspective of the Buddha, or other enlightened beings such as Bodhisattvas. The Indian term for ethics or morality used in Buddhism is Śīla or sīla (Pāli). Śīla in Buddhism is one of three sections of the Noble Eightfold Path, and is a code of conduct that embraces a commitment to harmony and self-restraint with the principal motivation being nonviolence, or freedom from causing harm. It has been variously described as virtue, moral discipline and precept. Sīla is an internal, aware, and intentional ethical behavior, according to one's commitment to the path of liberation. It is an ethical compass within self and relationships, rather than what is associated with the English word "morality" (i.e., obedience, a sense of obligation, and external constraint). Sīla is one of the three practices foundational to Buddhism and the non-sectarian Vipassana movement — sīla, samādhi, and paññā as well as the Theravadin foundations of sīla, Dāna, and Bhavana. It is also the second pāramitā. Sīla is also wholehearted commitment to what is wholesome. Two aspects of sīla are essential to the training: right "performance" (caritta), and right "avoidance" (varitta). Honoring the precepts of sīla is considered a "great gift" (mahadana) to others, because it creates an atmosphere of trust, respect, and security. It means the practitioner poses no threat to another person's life, property, family, rights, or well-being. Moral instructions are included in Buddhist scriptures or handed down through tradition. Most scholars of Buddhist ethics thus rely on the examination of Buddhist scriptures, and the use of anthropological evidence from traditional Buddhist societies, to justify claims about the nature of Buddhist ethics.
  • 6.5K
  • 27 Nov 2022
Topic Review
Artificial Flower
Artificial flowers are imitations of natural flowering plants used for commercial or residential decoration. They are sometimes made for scientific purposes (the collection of glass flowers at Harvard University, for example, illustrates the flora of the United States). Artificial plants vary widely from mass-produced varieties that are distinguishable from real plants by casual observation to highly detailed botanical or artistic specimens. Materials used in their manufacture have included painted linen and shavings of stained horn in ancient Egypt, gold and silver in ancient Rome, rice-paper in China , silkworm cocoons in Italy, colored feathers in South America, and wax and tinted shells. Modern techniques involve carved or formed soap, nylon netting stretched over wire frames, ground clay, and mass-produced injection plastic mouldings. Polyester has been the main material for manufacturing artificial flowers since the 1970s. Most artificial flowers in the market nowadays are made of polyester fabric.
  • 6.5K
  • 05 Sep 2025
Topic Review
Flocculus (Cerebellar)
The flocculus (Latin: tuft of wool, diminutive) is a small lobe of the cerebellum at the posterior border of the middle cerebellar peduncle anterior to the biventer lobule. Like other parts of the cerebellum, the flocculus is involved in motor control. It is an essential part of the vestibulo-ocular reflex, and aids in the learning of basic motor skills in the brain. It is associated with the nodulus of the vermis; together, these two structures compose the vestibular part of the cerebellum. At its base, the flocculus receives input from the inner ear's vestibular system and regulates balance. Many floccular projections connect to the motor nuclei involved in control of eye movement.
  • 6.5K
  • 02 Nov 2022
Topic Review
Serendipity
Serendipity is defined as an ability to notice, evaluate, and take advantage of unexpected information for survival purposes (both natural and social). The concept has been discussed for centuries. Still, it has only caught the attention of academia quite recently due to its strategic advantage in all aspects of life, such as daily life activities, science and technology, business and entrepreneurship, politics and economics, education administration, career choice and development, etc.
  • 6.5K
  • 01 Sep 2022
Topic Review
Plant-Mediated Nanoparticle Synthesis
The green synthesis of nanoparticles(NPs) is gaining attention owing to its facilitation of the development of alternative, sustainable, safer, less toxic and environment-friendly approaches. Thus, green nanotechnology using plant extract opens up new possibilities for the synthesis of novel nanoparticles with the desirable characteristics required for developing biosensors, biomedicine, cosmetics and nano-biotechnology, and in electrochemical, catalytic, antibacterial, electronics, sensing and other applications. 
  • 6.5K
  • 02 Mar 2022
Topic Review
Soil Erosion Hazards
Soil erosion is a severe threat to food production systems globally. Food production in farming systems decreases with increasing soil erosion hazards. Hazard is a situation or potential condition to harm or threat to life, health or damage to property or environment, social and economic disruption. The mass movement of soil is an indicator of a soil erosion hazard. This includes gully erosion, riverbank erosion, rock-falls, debris-falls and landslides that can create damage to the environment and livelihoods.
  • 6.5K
  • 22 Dec 2020
Topic Review
β-Adrenergic Stimulation
β-adrenergic receptor stimulation (β-ARS) is a physiological mechanism that regulates cardiovascular function under stress conditions or physical exercise, producing a positive inotropic (enhanced contraction), lusitropic (faster relaxation), and chronotropic (increased heart rate) effect. 
  • 6.5K
  • 04 Aug 2021
Topic Review
LGBT Social Movements
Lesbian, gay, bisexual, and transgender (LGBT) social movements are social movements that advocate for LGBT people in society. Social movements may focus on equal rights, such as the 2000s movement for same-sex marriage, or they may focus on liberation, as in the gay liberation movement of the 1960s and 1970s. Earlier movements focused on self-help and self-acceptance, such as the homophile movement of the 1950s. Although there is not a primary or an overarching central organization that represents all LGBT people and their interests, numerous LGBT rights organizations are active worldwide. The earliest organizations to support LGBT rights were formed in the early 20th century. A commonly stated goal among these movements is social equality for LGBT people, but there is still denial of full LGBT rights. Some have also focused on building LGBT communities or worked towards liberation for the broader society from biphobia, homophobia, and transphobia. There is a struggle for LGBT rights today. LGBT movements organized today are made up of a wide range of political activism and cultural activity, including lobbying, street marches, social groups, media, art, and research.
  • 6.5K
  • 11 Nov 2022
Topic Review
The Diachronic Heritage Management and Development of At-Turaif
The At-Turaif District in ad-Dir’iyah (often known and referred to as ‘Historic Diriyah’) has always been the heart and symbol of Saudi Arabian cultural heritage due to its historic values and significance that date back to earlier Saudi states. Historic Diriyah is a World Heritage Site (WHS), and it can still project a successful massive makeover development if a sustainable development approach is used, and visual integrity and site authenticity are preserved. The site of Historic Diriyah and its surroundings were critical in promoting the site as a national identity, an international destination, and presenting a new development agenda for the entire kingdom of Saudi Arabia. It has a significant impact on policymakers who are interested in how heritage sites can be integrated into a larger vision.
  • 6.5K
  • 13 Sep 2022
Topic Review
Early Flood Warning System
The early-warning model for flash floods is based on a hydrological and geomorphological concept connected to the river basin, with the principle that flash floods will only occur where there is a high potential risk and when rainfall exceeds the threshold. In the model used to build flash-floods risk maps, the parameters of the basin are analyzed and evaluated and the weight is determined using Thomas Saaty’s analytic hierarchy process (AHP). The flash-floods early-warning software is built using open source programming tools. With the spatial module and online processing, a predicted precipitation of one to six days in advance for iMETOS (AgriMedia—Vietnam) automatic meteorological stations is interpolated and then processed with the potential risk maps (iMETOS is a weather-environment monitoring system comprising a wide range of equipment and an online platform and can be used in various fields such as agriculture, tourism and services). The results determine the locations of flash floods at several risk levels corresponding to the predicted rainfall values at the meteorological stations. The system was constructed and applied to flash floods disaster early warning for Thuan Chau in Son La province when the rainfall exceeded the 150 mm/d threshold. The system initially supported positive decision-making to prevent and minimize damage caused by flash floods.
  • 6.5K
  • 27 Jan 2022
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