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Topic Review
The Application of Food-Grade Emulsions
Briefly, an emulsion is simply a mixture of two (or more) liquids that are otherwise immiscible. The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance people's understanding of these dispersion systems and to expand their application scope. 
  • 1.7K
  • 30 Sep 2022
Topic Review
Polylactic Acid and Its Synthesis
Biomaterials are natural or engineered substances that interact with components of living systems that can be exploited for a medical purpose, either as therapeutic or diagnostic agents.  Poly-(lactic Acid) (PLA) is a compostable polymer derived from corn sugar, potato, and sugar cane whose promising physicochemical properties are comparable to those of petroleum-based polymers, such as polyethylene, polypropylene, polystyrene, polycarbonate, and polyethylene terephthalate. PLA is a semicrystalline polymer that hydrolyses in physiological media, yielding lactic acid, a non-toxic component that is eliminated via the Krebs cycle as water and carbon dioxide. The biocompatibility, biodegradability, and resorbability characteristics of PLA have promoted its use in the biomedical field for a wide range of applications (suture threads, bone fixation screws, drug delivery systems, etc.), offering an alternative to conventional biocompatible materials such as metals and ceramics.
  • 2.1K
  • 30 Sep 2022
Topic Review
Solid Phase Extraction
Solid-phase extraction (SPE) is an extractive technique by which compounds that are dissolved or suspended in a liquid mixture are separated from other compounds in the mixture according to their physical and chemical properties. Analytical laboratories use solid phase extraction to concentrate and purify samples for analysis. Solid phase extraction can be used to isolate analytes of interest from a wide variety of matrices, including urine, blood, water, beverages, soil, and animal tissue. SPE uses the affinity of solutes dissolved or suspended in a liquid (known as the mobile phase) for a solid through which the sample is passed (known as the stationary phase) to separate a mixture into desired and undesired components. The result is that either the desired analytes of interest or undesired impurities in the sample are retained on the stationary phase. The portion that passes through the stationary phase is collected or discarded, depending on whether it contains the desired analytes or undesired impurities. If the portion retained on the stationary phase includes the desired analytes, they can then be removed from the stationary phase for collection in an additional step, in which the stationary phase is rinsed with an appropriate eluent. Many of the adsorbents/materials are the same as in chromatographic methods, but SPE is distinctive, with aims separate from chromatography, and so has a unique niche in modern chemical science.
  • 1.3K
  • 29 Sep 2022
Topic Review
Opioid Epidemic
The opioid epidemic or opioids crisis is the rapid increase in the use of prescription and non-prescription opioid drugs in the United States and Canada beginning in the late 1990s and continuing throughout the next two decades. The increase in opioid overdose deaths has been dramatic, and opioids are now responsible for 49,000 of the 72,000 drug overdose deaths overall in the US in 2017. A recent report indicated that the rate of prolong opioid use is increasing globally. Opioids are a diverse class of moderately strong painkillers, including oxycodone (commonly sold under the trade names OxyContin and Percocet), hydrocodone (Vicodin, Norco), and a very strong painkiller, fentanyl, which is synthesized to resemble other opiates such as opium-derived morphine and heroin. The potency and availability of these substances, despite their high risk of addiction and overdose, have made them popular both as medical treatments and as recreational drugs. Due to their sedative effects on the part of the brain which regulates breathing, the respiratory center of the medulla oblongata, opioids in high doses present the potential for respiratory depression, and may cause respiratory failure and death. In a 2015 report, the U.S. Drug Enforcement Administration stated that "overdose deaths, particularly from prescription drugs and heroin, have reached epidemic levels.":iii Nearly half of all opioid overdose deaths in 2016 involved prescription opioids. From 1999 to 2008, overdose death rates, sales, and substance abuse treatment admissions related to opioid pain relievers all increased substantially. By 2015, there were more than 50,000 annual deaths from drug overdose, causing more deaths than either car accidents or guns. Drug overdoses have since become the leading cause of death of Americans under 50, with two-thirds of those deaths from opioids. In 2016, the crisis decreased overall life expectancy of Americans for the second consecutive year. Overall life expectancy fell from 78.7 to 78.6 years. Men were disproportionately more affected due to higher overdose death rates, with life expectancy declining from 76.3 to 76.1 years. Women's life expectancy remained stable at 81.1 years. In 2016, over 64,000 Americans died from overdoses, 21 percent more than the almost 53,000 in 2015. By comparison, the figure was 16,000 in 2010, and 4,000 in 1999. While death rates varied by state, public health experts estimate that nationwide over 500,000 people could die from the epidemic over the next 10 years. In Canada , half of the overdoses were accidental, while a third were intentional. The remainder were unknown. Many of the deaths are from an extremely potent opioid, fentanyl, which is trafficked from Mexico. The epidemic cost the United States an estimated $504 billion in 2015. CDC former director Thomas Frieden said that "America is awash in opioids; urgent action is critical." The crisis has changed moral, social, and cultural resistance to street drug alternatives such as heroin. Many state governors have declared a "state of emergency" to combat the opioid epidemic or undertook other major efforts against it. In July 2017, opioid addiction was cited as the "FDA's biggest crisis". In October 2017, President Donald Trump concurred with his Commission's report and declared the country's opioid crisis a "public health emergency". Federal and state interventions are working on employing health information technology in order to expand the impact of existing drug monitoring programs. Recent research shows promising results in mortality and morbidity reductions when a state integrates drug monitoring programs with health information technologies and shares data through centralized platform.
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  • 29 Sep 2022
Topic Review
Base
In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances which react with acids as originally proposed by G.-F. Rouelle in the mid-18th century. In 1884, Svante Arrhenius proposed that a base is a substance which dissociates in aqueous solution to form Hydroxide ions OH−. These ions can react with hydrogen ions (H+ according to Arrhenius) from the dissociation of acids to form water in an acid–base reaction. A base was therefore a metal hydroxide such as NaOH or Ca(OH)2. Such aqueous hydroxide solutions were also described by certain characteristic properties. They are slippery to the touch, can taste bitter and change the color of pH indicators (e.g., turn red litmus paper blue). In water, by altering the autoionization equilibrium, bases yield solutions in which the hydrogen ion activity is lower than it is in pure water, i.e., the water has a pH higher than 7.0 at standard conditions. A soluble base is called an alkali if it contains and releases OH− ions quantitatively. Metal oxides, hydroxides, and especially alkoxides are basic, and conjugate bases of weak acids are weak bases. Bases and acids are seen as chemical opposites because the effect of an acid is to increase the hydronium (H3O+) concentration in water, whereas bases reduce this concentration. A reaction between aqueous solutions of an acid and a base is called neutralization, producing a solution of water and a salt in which the salt separates into its component ions. If the aqueous solution is saturated with a given salt solute, any additional such salt precipitates out of the solution. In the more general Brønsted–Lowry acid–base theory (1923), a base is a substance that can accept hydrogen cations (H+)—otherwise known as protons. This does include aqueous hydroxides since OH− does react with H+ to form water, so that Arrhenius bases are a subset of Brønsted bases. However, there are also other Brønsted bases which accept protons, such as aqueous solutions of ammonia (NH3) or its organic derivatives (amines). These bases do not contain a hydroxide ion but nevertheless react with water, resulting in an increase in the concentration of hydroxide ion. Also, some non-aqueous solvents contain Brønsted bases which react with solvated protons. For example in liquid ammonia, NH2− is the basic ion species which accepts protons from NH4+, the acidic species in this solvent. G. N. Lewis realized that water, ammonia, and other bases can form a bond with a proton due to the unshared pair of electrons that the bases possess. In the Lewis theory, a base is an electron pair donor which can share a pair of electrons with an electron acceptor which is described as a Lewis acid. The Lewis theory is more general than the Brønsted model because the Lewis acid is not necessarily a proton, but can be another molecule (or ion) with a vacant low-lying orbital which can accept a pair of electrons. One notable example is boron trifluoride (BF3). Some other definitions of both bases and acids have been proposed in the past, but are not commonly used today.
  • 1.7K
  • 29 Sep 2022
Topic Review
Solar Energy Systems into Seawater Desalination
Solar energy, amongst all renewable energies, has attracted inexhaustible attention all over the world as a supplier of sustainable energy. The energy requirement of major seawater desalination processes such as multistage flash (MSF), multi-effect distillation (MED) and reverse osmosis (RO) are fulfilled by burning fossil fuels, which impact the environment significantly due to the emission of greenhouse gases. The integration of solar energy systems into seawater desalination processes is an attractive and alternative solution to fossil fuels. 
  • 1.3K
  • 29 Sep 2022
Topic Review
Carbon Nanotube Metal Matrix Composites
Carbon nanotube metal matrix composites (CNT-MMC) are an emerging class of new materials that are being developed to take advantage of the high tensile strength and electrical conductivity of carbon nanotube materials. Critical to the realization of CNT-MMC possessing optimal properties in these areas are the development of synthetic techniques that are (a) economically producible, (b) provide for a homogeneous dispersion of nanotubes in the metallic matrix, and (c) lead to strong interfacial adhesion between the metallic matrix and the carbon nanotubes. Since the development of CNT-MMC is still in the research phase, the current focus is primarily on improving these latter two areas.
  • 1.1K
  • 29 Sep 2022
Topic Review
Indane-1,3-Dione: From Synthetic Strategies to Applications
Indane-1,3-dione is a versatile building block used in numerous applications ranging from biosensing, bioactivity, bioimaging to electronics or photopolymerization. Indane-1-3-dione is among one of the most privileged scaffolds in chemistry, as the derivatives of this structure can find applications in various research fields ranging from medicinal chemistry, organic electronics, photopolymerization, to optical sensing and non-linear optical (NLO) applications. 
  • 1.3K
  • 29 Sep 2022
Topic Review
Mechanism of Abrasive-Based Finishing Processes
Various manufacturing industries have been using conventional procedures for finishing the components, such as grinding, honing, lapping, etc., to get the machining components’ desired finishing. However, these conventional procedures of finishing are restricted to very few geometries and cannot work on complex and intricate geometries as well as complicated profiles for finishing of high level, which is required while the operation of the component is in process. These limitations and restrictions in the finishing process have led the industries to develop advanced finishing procedures, known as “Abrasive flow machining (AFM)”. Advances in technology and refinement of available computational resources paved the way for the extensive use of computers to model and simulate complex real-world problems difficult to solve analytically. The appeal of simulations lies in the ability to predict the significance of a change to the system under study. The simulated results can be of great benefit in predicting various behaviors, such as the wind pattern in a particular region, the ability of a material to withstand a dynamic load, or even the behavior of a workpiece under a particular type of machining. 
  • 794
  • 29 Sep 2022
Topic Review
Atomic Carbon
Atomic carbon, systematically named carbon and λ0-methane, also called monocarbon, is a colourless gaseous inorganic chemical with the chemical formula C (also written [C]). It is kinetically unstable at ambient temperature and pressure, being removed through autopolymerisation. Atomic carbon is the simplest form of carbon, and is also the progenitor of carbon clusters. In addition, it may be considered to be the monomer of all (condensed) carbon allotropes like graphite and diamond.
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  • 28 Sep 2022
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