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Semipermeable Membrane Devices
Semipermeable membrane devices (SPMD) are passive sampling devices used to monitor trace levels of organic compounds with a log Kow > 3. SPMDs are an effective way of monitoring the concentrations of chemicals from anthropogenic runoff and pollution in the marine environment because of their ability to detect minuscule levels of chemical. The data collected from a passive sampler is important for examining the amount of chemical in the environment and can therefore be used to formulate other scientific research about the effects of those chemicals on the organisms as well as the environment. Examples of chemicals commonly measured using SPMDs include: PAHs (Polycyclic aromatic hydrocarbons), PCBs (polychlorinated biphenyls), PBDEs (polybrominated diphenyl ethers), dioxins and furans as well as hydrophobic waste-water effluents like fragrances, triclosan, and phthalates. Passive samplers may be used to monitor and record short-lived pulses of contaminants found in surface water t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semipermeable Membrane
Semipermeable membrane is a type of biological or synthetic, polymeric membrane that will allow certain molecules or ions to pass through it by osmosis. The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry. How the membrane is constructed to be selective in its permeability will determine the rate and the permeability. Many natural and synthetic materials which are rather thick are also semipermeable. One example of this is the thin film on the inside of the egg. Biological membranes are selectively permeable, with the passage of molecules controlled by facilitated diffusion, passive transport or active transport regulated by proteins embedded in the membrane. Biological membranes An example of a biological semi-permeable membrane is t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triclosan
Triclosan (sometimes abbreviated as TCS) is an antibiotic, antibacterial and fungus, antifungal agent present in some consumer products, including toothpaste, soaps, detergents, toys, and surgical cleaning treatments. It is similar in its uses and mechanism of action to triclocarban. Its efficacy as an antimicrobial agent, the risk of antimicrobial resistance, and its possible role in endocrine disruptor, disrupted hormonal development remains controversial. Additional research seeks to understand its potential effects on organisms and environmental health. Triclosan was developed in 1966. A 2006 study recommended showering with 2% triclosan as a regimen in surgical units Decolonization (medicine), to rid patients' skin of methicillin-resistant Staphylococcus aureus, methicillin-resistant ''Staphylococcus aureus'' (MRSA). While finding benefit for consumers and no proven risk to human health, but assumed risk of antibiotic resistance, in December 2017, the FDA announced that "co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on December 2, 1970, after Nixon signed an executive order. The order establishing the EPA was ratified by committee hearings in the House and Senate. The agency is led by its administrator, who is appointed by the president and approved by the Senate. The current administrator is Michael S. Regan. The EPA is not a Cabinet department, but the administrator is normally given cabinet rank. The EPA has its headquarters in Washington, D.C., regional offices for each of the agency's ten regions and 27 laboratories. The agency conducts environmental assessment, research, and education. It has the responsibility of maintaining and enforcing national standards under a variety of environmental laws, in consultation with state, tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polar Organic Chemical Integrative Sampler
A polar organic chemical integrative sampler (POCIS) is a passive sampling device which allows for the in situ collection of a time-integrated average of hydrophilic organic contaminants developed by researchers with the United States Geological Survey in Columbia, Missouri. POCIS provides a means for estimating the toxicological significance of waterborne contaminants. The POCIS sampler mimics the respiratory exposure of organisms living in the aquatic environment and can provide an understanding of bioavailable contaminants present in the system. POCIS can be deployed in a wide range of aquatic environments and is commonly used to assist in environmental monitoring studies. __TOC__ Background The first passive sampling devices were developed in the 1970s to determine concentrations of contaminants in the air. In 1980 this technology was first adapted for the monitoring of organic contaminants in water. The initial type of passive sampler developed for aquatic monitoring purposes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Area
The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra (i.e., objects with flat polygonal faces), for which the surface area is the sum of the areas of its faces. Smooth surfaces, such as a sphere, are assigned surface area using their representation as parametric surfaces. This definition of surface area is based on methods of infinitesimal calculus and involves partial derivatives and double integration. A general definition of surface area was sought by Henri Lebesgue and Hermann Minkowski at the turn of the twentieth century. Their work led to the development of geometric measure theory, which studies various notions of surface area for irregular objects of any dimension. An important example is the Minkowski cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triolein
Triolein is a symmetrical triglyceride derived from glycerol and three units of the unsaturated fatty acid oleic acid. Most triglycerides are unsymmetrical, being derived from mixtures of fatty acids. Triolein represents 4–30% of olive oil. Triolein is also known as glyceryl trioleate and is one of the two components of Lorenzo's oil ''Lorenzo's Oil'' is a 1992 American drama film directed and co-written by George Miller. It is based on the true story of Augusto and Michaela Odone, parents who search for a cure for their son Lorenzo's adrenoleukodystrophy (ALD), leading t .... The oxidation of triolein is according to the formula: : + 80 → 57 + 52 This gives a respiratory quotient of 57/80 or 0.7125. The heat of combustion is per mole or per gram. Per mole of oxygen it is . References Triglycerides {{ester-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Column
A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-Duluth. Retrieved 27 May 2014. Descriptively, the deep sea water column is divided into five parts—'' pelagic zones'' (from Greek πέλαγος (pélagos), 'open sea')—from the surface to below the floor, as follows: ''epipelagic'', from the surface to 200 meters below the surface; ''mesopelagic'', from 200 to 1000 meters below the surface; '' bathypelagic'', from 1000 to 4000 meters below the surface; ''abyssopelagic'', from 4000 meters below the surface to the level sea floor; ''hadopelagic'', depressions and crevices below the level sea floor. The concept of water column is useful since many aquatic phenomena are explained by the incomplete vertical mixing of waters with discrete chemical, physical or biological characteristics. Fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phthalate
Phthalates (, ), or phthalate esters, are esters of phthalic acid. They are mainly used as plasticizers, i.e., substances added to plastics to increase their flexibility, transparency, durability, and longevity. They are used primarily to soften polyvinyl chloride (PVC). Note that while phthalates are usually plasticizers, not all plasticizers are phthalates. The two terms are specific and unique and cannot be used interchangeably. Lower-molecular-weight phthalates, those derived from C3-C6 alcohols, are being gradually replaced in many products in the United States, Canada, and European Union over health concerns. They are being replaced by high-molecular-weight phthalates (those with more than six carbons in their backbone, which gives them increased permanency and durability), as well as alternative plasticizers not based on phthalic anhydride. In 2010, the market was still dominated by high-phthalate plasticizers; however, due to legal provisions and growing environmental a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aroma Compound
An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently volatile for transmission via the air to the olfactory system in the upper part of the nose. As examples, various fragrant fruits have diverse aroma compounds, particularly strawberries which are commercially cultivated to have appealing aromas, and contain several hundred aroma compounds. Generally, molecules meeting this specification have molecular weights of less than 310. Flavors affect both the sense of taste and smell, whereas fragrances affect only smell. Flavors tend to be naturally occurring, and the term ''fragrances'' may also apply to synthetic compounds, such as those used in cosmetics. Aroma compounds can naturally be found in various foods, such as fruits and their peels, wine, spices, floral scent, perfumes, fragrance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Partition Coefficient
In the physical sciences, a partition coefficient (''P'') or distribution coefficient (''D'') is the ratio of concentrations of a compound in a mixture of two immiscible solvents at equilibrium. This ratio is therefore a comparison of the solubilities of the solute in these two liquids. The partition coefficient generally refers to the concentration ratio of un-ionized species of compound, whereas the distribution coefficient refers to the concentration ratio of all species of the compound (ionized plus un-ionized). In the chemical and pharmaceutical sciences, both phases usually are solvents. Most commonly, one of the solvents is water, while the second is hydrophobic, such as 1-octanol. Hence the partition coefficient measures how hydrophilic ("water-loving") or hydrophobic ("water-fearing") a chemical substance is. Partition coefficients are useful in estimating the distribution of drugs within the body. Hydrophobic drugs with high octanol-water partition coefficients are m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobe
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds. Hydrophobic is often used interchangeably with lipophilic, "fat-loving". However, the two terms are not synonymous. While hydrophobic substances are usually lipophilic, there are exceptions, suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Furan
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans. Furan is a colorless, flammable, highly volatile liquid with a boiling point close to room temperature. It is soluble in common organic solvents, including alcohol, ether, and acetone, and is slightly soluble in water. Its odor is "strong, ethereal; chloroform-like". It is toxic and may be carcinogenic in humans. Furan is used as a starting point for other speciality chemicals. History The name "furan" comes from the Latin ''furfur'', which means bran. ( Furfural is produced from bran.) The first furan derivative to be described was 2-furoic acid, by Carl Wilhelm Scheele in 1780. Another important derivative, furfural, was reported by Johann Wolfgang Döbereiner in 1831 and characterised nine years later by John Stenhouse. Furan itself was first prepared by Heinrich Lim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
