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Ethylidene Difluoride
1,1-Difluoroethane, or DFE, is an organofluorine compound with the chemical formula CHF. This colorless gas is used as a refrigerant, where it is often listed as R-152a (refrigerant-152a) or HFC-152a (hydrofluorocarbon-152a). It is also used as a propellant for aerosol sprays and in gas duster products. As an alternative to chlorofluorocarbons, it has an ozone depletion potential of zero, a lower global warming potential (124) and a shorter atmospheric lifetime (1.4 years). Production 1,1-Difluoroethane is a synthetic substance that is produced by the mercury-catalyzed addition of hydrogen fluoride to acetylene: :HCCH + 2 HF → CHCHF The intermediate in this process is vinyl fluoride (C2H3F), the monomeric precursor to polyvinyl fluoride. Uses With a relatively low global warming potential (GWP) index of 124 and favorable thermophysical properties, 1,1-difluoroethane has been proposed as an environmentally friendly alternative to R134a. Despite its flammability, R152a als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sigma-Aldrich
Sigma-Aldrich (formally MilliporeSigma) is an American chemical, life science, and biotechnology company that is owned by the German chemical conglomerate Merck Group. Sigma-Aldrich was created in 1975 by the merger of Sigma Chemical Company and Aldrich Chemical Company. It grew through various acquisitions until it had over 9,600 employees and was listed on the Fortune 1000. The company is headquartered in St. Louis and has operations in approximately 40 countries. In 2015, the German chemical conglomerate Merck Group acquired Sigma-Aldrich for $17 billion. The company is currently a part of Merck's life science business and in combination with Merck's earlier acquired Millipore Corporation, Millipore, operates as MilliporeSigma. History Sigma Chemical Company of St. Louis and Aldrich Chemical Company of Milwaukee were both American specialty chemical companies when they merged in August 1975. The company grew throughout the 1980s and 1990s, with significant expansion in fac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Chromatography–mass Spectrometry
Gas chromatography–mass spectrometry (GC-MS) is an analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample. Applications of GC-MS include drug detection, fire investigation, environmental analysis, explosives investigation, and identification of unknown samples, including that of material samples obtained from planet Mars during probe missions as early as the 1970s. GC-MS can also be used in airport security to detect substances in luggage or on human beings. Additionally, it can identify trace elements in materials that were previously thought to have disintegrated beyond identification. Like liquid chromatography–mass spectrometry, it allows analysis and detection even of tiny amounts of a substance. GC-MS has been regarded as a "gold standard" for forensic substance identification because it is used to perform a 100% specific test, which positively identifies the presence of a particula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Refrigerants
This is a list of refrigerants, sorted by their ASHRAE-designated numbers, commonly known as R numbers. Many modern refrigerants are man-made halogenated gases, especially fluorinated gases and chlorinated gases, that are frequently referred to as Freon (a registered trademark of Chemours). The R number of a chemical refrigerant is assigned systematically according to molecular structure. First ASHRAE digit is the number of carbon atoms minus 1 (C-1); the second digit is the number of hydrogen atoms plus 1 (H+1); the third digit is the number of fluorine atoms; any remaining spaces are chlorine atoms. Eg.: R-22 aka R-022, which is chlorodifluoromethane. C=1 i.e. 1-1=0; H=1 i.e. 1+1=2; F=2 i.e 2; 1 remaining space 1=Cl. A "B" number means that one of the chlorine atoms is replaced by bromine (Br). This formula does not work with zeotropic or azeotropic blends. The table is sortable by each of the following refrigerant properties (scroll right or reduce magnification to view ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenhouse Gas
A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (), carbon dioxide (), methane (), nitrous oxide (), and ozone (). Without greenhouse gases, the average temperature of Earth's surface would be about , rather than the present average of . The atmospheres of Venus, Mars and Titan also contain greenhouse gases. Human activities since the beginning of the Industrial Revolution (around 1750) have increased the atmospheric concentration of carbon dioxide by over 50%, from 280 ppm in 1750 to 421 ppm in 2022. The last time the atmospheric concentration of carbon dioxide was this high was over 3 million years ago. This increase has occurred despite the absorption of more than half of the emissions by various natural carbon sinks in the carbon cycle. At current greenhouse gas emission rates, temperatures co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Troposphere
The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From the planetary surface of the Earth, the average height of the troposphere is in the tropics; in the middle latitudes; and in the high latitudes of the polar regions in winter; thus the average height of the troposphere is . The term ''troposphere'' derives from the Greek words ''tropos'' (rotating) and '' sphaira'' (sphere) indicating that rotational turbulence mixes the layers of air and so determines the structure and the phenomena of the troposphere. The rotational friction of the troposphere against the planetary surface affects the flow of the air, and so forms the planetary boundary layer (PBL) that varies in height from hundreds of meters up to . The measures of the PBL vary according to the latitude, the landform, and t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angina
Angina, also known as angina pectoris, is chest pain or pressure, usually caused by insufficient blood flow to the heart muscle (myocardium). It is most commonly a symptom of coronary artery disease. Angina is typically the result of obstruction or spasm of the arteries that supply blood to the heart muscle. The main mechanism of coronary artery obstruction is atherosclerosis as part of coronary artery disease. Other causes of angina include abnormal heart rhythms, heart failure and, less commonly, anemia. The term derives from the Latin ''angere'' ("to strangle") and ''pectus'' ("chest"), and can therefore be translated as "a strangling feeling in the chest". There is a weak relationship between severity of angina and degree of oxygen deprivation in the heart muscle, however, the severity of angina does not always match the degree of oxygen deprivation to the heart or the risk of a myocardial infarction (heart attack). Some people may experience severe pain even though t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coronary Disease
Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the heart muscle due to build-up of atherosclerotic plaque in the arteries of the heart. It is the most common of the cardiovascular diseases. Types include stable angina, unstable angina, myocardial infarction, and sudden cardiac death. A common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck, or jaw. Occasionally it may feel like heartburn. Usually symptoms occur with exercise or emotional stress, last less than a few minutes, and improve with rest. Shortness of breath may also occur and sometimes no symptoms are present. In many cases, the first sign is a heart attack. Other complications include heart failure or an abnormal heartbeat. Risk factors include high blood pressure, smoking, diabetes, lack of exercise, obesity, high blood cholesterol, po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
No-observed-adverse-effect Level
The no-observed-adverse-effect level (NOAEL) denotes the level of exposure of an organism, found by experiment or observation, at which there is no biologically or statistically significant increase in the frequency or severity of any adverse effects of the tested protocol. In drug development, the NOAEL of a new drug is assessed in laboratory animals, such as mice, prior to initiation of human trials in order to establish a safe clinical starting dose in humans. The OECD publishes guidelines for Preclinical Safety Assessments, in order to help scientists discover the NOAEL. Synopsis Some adverse effects in the exposed population when compared to its appropriate control might include alteration of morphology, functional capacity, growth, development or life span. The NOAEL is determined or proposed by qualified personnel, often a pharmacologist or a toxicologist. The NOAEL could be defined as "the highest experimental point that is without adverse effect," meaning that under ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DuPont
DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in the development of Delaware and first arose as a major supplier of gunpowder. DuPont developed many polymers such as Vespel, neoprene, nylon, Corian, Polytetrafluoroethylene, Teflon, Mylar, Kapton, Kevlar, Zemdrain, M5 fiber, Nomex, Tyvek, Sorona, Artificial Leather#Corfam, Corfam and Lycra in the 20th century, and its scientists developed many chemicals, most notably Freon (chlorofluorocarbons), for the refrigerant industry. It also developed synthetic pigments and paints including ChromaFlair. In 2015, DuPont and the Dow Chemical Company agreed to a reorganization plan in which the two companies would merge and split into three. As a merged entity, DuPont simultaneously acquired Dow and renamed itself to DowDuPont on August 31, 2017, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bitterant
A bitterant (or bittering agent) is a chemical that is added to a product to make it smell or taste bitter. Bitterants are commonly used as aversive agents to discourage the inhalation or ingestion of toxic substances. Examples of use *The addition of a bitterant to ethanol denatures the product. *Bitterants are used in antifreeze to prevent pet and child poisonings. It is required by law in some places (France, Oregon, etc.). * Gas dusters often use a bitterant to discourage inhalant abuse, although this can cause problems for legitimate users. The bitterant not only leaves a bitter flavor in the air, but also leaves a bitter residue on objects, like screens and keyboards, that may transfer to hands and cause problems (such as when eating). * Game cartridges for the Nintendo Switch are coated with denatonium as a safety feature to deter small children from ingesting them. *Some button cell batteries manufactured by Duracell are coated with a bitterant to discourage accidenta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skye McCole Bartusiak
Skye McCole Bartusiak (September 28, 1992 – July 19, 2014) was an American child actress and child model. She appeared in '' The Patriot'' (2000), '' Don't Say a Word'' (2001), as Rose Wilder in '' Beyond the Prairie: The True Story of Laura Ingalls Wilder'' (2002), as Megan Matheson on season 2 of '' 24'' (2002–03), '' Boogeyman'' (2005), and '' Kill Your Darlings'' (2006). Bartusiak died at the age of 21 in her apartment behind her parents' home. While her mother, shortly after Bartusiak's death, stated she believed that her daughter's history of epileptic seizures may have had a role in her death, the coroner ruled the death resulted from an accidental drug overdose. Early life Skye McCole Bartusiak was born in Houston, Texas, where she lived with her parents, Helen (née McCole) and Donald Bartusiak, until her death. She attended St. Thomas Episcopal Academy and Lutheran South High School in Houston, and graduated from Laurel Springs High School in Ojai, California in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
