Xem 1-20 trên 346 kết quả Chemical effects
  • Ecotoxicological models have been applied increasingly to perform chemical risk assessments since the first models of this kind emerged about 25 years ago. The first ecotoxicological models were applied to very specific cases — for instance, cadmium contamination of Lake Erie or mercury contamination of Mex Bay, Alexandria. The models were inspired by the experience gained in ecological modeling and therefore contained good descriptions of ecological processes. Slightly later, the so-called fate models emerged, which were first developed by McKay and others.

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  • C effects are generally stronger than I effects. C effects can be effective over much longer distances than I effects – provided that conjugation is present. I effects are determined by distance, C effects are determined by relative positions.

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  • .FOOD PROTEIN ANALYSIS Quantitative Ideal for planning, performing, and interpreting food protein analyses, especially as it relates to the effect of food processing on protei investigation results. Delineates basic research principles, practices, and anticipated outcomes in each of the illustrated protein assays.Effects on Processing R. K. Owusu-Apenten The Pennsylvania State University University Park, Pennsylvania Marcel Dekker, Inc. TM New York • Basel Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved. .ISBN: 0-8247-0684-6 This book is printed on acid-free paper.

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  • Preparations derived from Lentinula edodes (Berk.) Pegl. mycelium are worldwide used as dietary supplements containing compounds active as immune system enhancers, demonstrating chemopreventive and anticancer activity. L. edodes mycelium enriched with organic forms of selenium like selenized yeast possess putative, higher cancer preventive properties. The objective of this study was to test the effect of enrichment in selenium on antioxidant, reducing and free radical scavenging activity of water and alcohol extracts from mycelium of L. edodes (Berk.).

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  • The EU Water Framework Directive (2000/60/EC) is probably the most significant legislative instrument in the water field that was introduced on an international basis for many years. It moves towards integrated environmental management with key objectives to prevent any further deterioration of water bodies, and protect and enhance the status of aquatic ecosystems and associated wetlands. It aims to promote sustainable water consumption and will contribute to mitigating the effects of floods and droughts.

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  • This study investigated the effects of Na 2 SO4 additive in the positive electrode on the performance of sealed lead-acid cells. The additive Na 2 SO4 in the cured plates can reduce the 4BS crystal size, which produces a smaller a-PbO 2 and b-PbO 2 crystal size in the formed plates, which will have a larger surface area. The plate’s chemical composition is independent of the amount of Na 2 SO4 additive in the positive electrodes. Plate composition relies only on the cure temperature conditions. ...

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  • Cerium, an element in the lanthanide series, has a number of radioactive isotopes. Several of these are produced in abundance in nuclear fission reactions associated with nuclear industry operations or detonation of nuclear devices. This report summarizes our present knowledge of the relevant physical, chemical, and biological properties of radiocerium as a basis for establishing radiation protection guidelines.

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  • Plants defend themselves from other organisms by elaborating bioactive chemical defences. This is the essential basis of the use of herbal medicines that still represents a major therapeutic resort for much of humanity However, at the outset, it must be stated that any plant that is not part of our evolved dietary cultures is potentially dangerous. Commercial herbal medicinal preparations approved by expert regulatory authorities have a significant place in mainstream conventional medicine and in complementary medicine.

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  • This Acid rain and its effects presents: Definition Acid rain, Emissions of chemicals leading to acidification, Natural phenomena, Human activity, Chemical processes to form acid rain, Measuring Acid Rain, Adverse effects,..

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  • Sewage sludge has been used in agriculture over a long time. Since 1986 the utilization of sewage sludge has been subject to provisions stipulated in the EU Directive (86/278/EEC). The Directive sets out requirements with respect to the quality of sludge, the soil on which it is to be used, the loading rate, and the crops that may be grown on treated land. The European Commission considers that 86/278/EEC has been a success because there have been no reports of adverse effects wherever it has been applied.

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  • Despite the advances in the development of new drugs, a drug may never reach the target organ, or it may be difficult to achieve the necessary level of drug in the body. Large doses can result in serious side effects, and can harm normal cells and organs as well as diseased cells. Hence controlled release and the targeting of delivery systems must evolve in parallel to drug research.

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  • This Letter reports a preparation of Ni(OH)2/CNTs nanoflake composites for supercapacitor applications. The composites were synthesized using a facile and cost-effective chemical precipitation method.

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  • For millennia, advances in human progress have been tied to our ability to protect ourselves from the harmful effects of the wastes we produce—ranging from human waste to the organic and inorganic by-products of everyday living. Across the world, cultures learned to bury their dead away from their homes and to burn their waste or make certain that it was carried away by streams and rivers flowing downstream from their homes. Those cultures that learned this most effectively thrived. When the industrial revolution took place in the nineteenth century, rivers again enabled progress.

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  • Analysis of streambed sediments in the Salem, Oregon, area showed anomalously large concentrations of some elements and organic chemicals, indicating contamination from anthropogenic and/or geologic sources. The streambed sediment sample from Clark Creek, an urban basin, had large concentrations of polycyclic aromatic hyrdocarbons (PAHs), organochlorines, cadmium, lead, and zinc. The sample from the East Fork of Pringle Creek, which is a mostly urban basin, had the highest concentrations of DDD, DDE, and DDT compounds.

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  • Two samples were also analysed for polychlorinated dioxins and furans (PCDD/Fs), a class of chemical that can be formed during the combustion of materials present in e-waste. Soil from an open burning site was moderately contaminated, while sediment from the Agbogbloshie lagoon contained a very high level of these highly toxic, highly persistent and bioaccumulative chemicals, at a level just below the threshold defined as being indicative of serious contamination for sediments in the Netherlands.

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  • Inhibition of the mitochondrial adenine nucleotide translocator (ANT) by long-chain acyl-CoA esters has been proposed to contribute to cellular dys-function in obesity and type 2 diabetes by increasing formation of reactive oxygen species and adenosine via effects on the coenzyme Q redox state, mitochondrial membrane potential (Dw) and cytosolic ATP concentrations.

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  • G-rich GT oligonucleotides with a different content of G clusters have been evaluated for their ability to exert cytotoxicity and to bind to nuclear-associated proteins in T-lymphoblast CCRF-CEM cells. Only the oligomers that did not form G-based structures or had a poor structure, under physiological conditions, were able to exert significant cellular growth inhibition effect.

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  • This study on human cytochrome P450 reductase (CPR) presents a com-prehensive analysis of the thermodynamic and kinetic effects of pH and solvent on two- and four-electron reduction in this diflavin enzyme. pH-dependent redox potentiometry revealed that the thermodynamic equilibrium between various two-electron reduced enzyme species (FMNH • ,FADH • ; FMN,FADH2; FMNH2 ,FAD) is independent of pH.

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  • Information on the regulation and structure–function rela-tion of enzymes involved in DNA precursor synthesis is pivotal, as defects in several of these enzymes have been found to cause depletion or deletion of mitochondrial DNA resulting in severediseases.Here, the effect of aminoacid106 on the enzymatic properties of the cell-cycle-regulated human cytosolic thymidine kinase 1(TK1) is investigated.

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  • Substitution oftrans-proline at three positions in ubiquitin (residues 19, 37 and 38) produces significant context-dependent effects on protein stability (both stabilizing and destabilizing) that reflect changes to a combination of parameters including backbone flexibility, hydrophobic interactions, solvent accessibility to polar groups and intrinsic backbone conformational preferences. Kinetic analysis of thewild-type yeast protein reveals a predominant fast-folding phase which conforms to an apparent two-state folding model. ...

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