967 resultados para Coal Tar


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Domestic coal combustion has had profound adverse effects on the health of millions of people worldwide. In China alone several hundred million people commonly burn raw coal in unvented stoves that permeate their homes with high levels of toxic metals and organic compounds. At least 3,000 people in Guizhou Province in southwest China are suffering from severe arsenic poisoning. The primary source of the arsenic appears to be consumption of chili peppers dried over fires fueled with high-arsenic coal. Coal samples in the region were found to contain up to 35,000 ppm arsenic. Chili peppers dried over high-arsenic coal fires adsorb 500 ppm arsenic on average. More than 10 million people in Guizhou Province and surrounding areas suffer from dental and skeletal fluorosis. The excess fluorine is caused by eating corn dried over burning briquettes made from high-fluorine coals and high-fluorine clay binders. Polycyclic aromatic hydrocarbons formed during coal combustion are believed to cause or contribute to the high incidence of esophageal and lung cancers in parts of China. Domestic coal combustion also has caused selenium poisoning and possibly mercury poisoning. Better knowledge of coal quality parameters may help to reduce some of these health problems. For example, information on concentrations and distributions of potentially toxic elements in coal may help delineate areas of a coal deposit to be avoided. Information on the modes of occurrence of these elements and the textural relations of the minerals and macerals in coal may help predict the behavior of the potentially toxic components during coal combustion.

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The yeast two-hybrid system and far-Western protein blot analysis were used to demonstrate dimerization of human double-stranded RNA (dsRNA)-dependent protein kinase (PKR) in vivo and in vitro. A catalytically inactive mutant of PKR with a single amino acid substitution (K296R) was found to dimerize in vivo, and a mutant with a deletion of the catalytic domain of PKR retained the ability to dimerize. In contrast, deletion of the two dsRNA-binding motifs in the N-terminal regulatory domain of PKR abolished dimerization. In vitro dimerization of the dsRNA-binding domain required the presence of dsRNA. These results suggest that the binding of dsRNA by PKR is necessary for dimerization. The mammalian dsRNA-binding protein TRBP, originally identified on the basis of its ability to bind the transactivation region (TAR) of human immunodeficiency virus RNA, also dimerized with itself and with PKR in the yeast assay. Taken together, these results suggest that complexes consisting of different combinations of dsRNA-binding proteins may exist in vivo. Such complexes could mediate differential effects on gene expression and control of cell growth.

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Mountaintop removal (MTR) coal mining has had a significant influence on the water sources within the Coal River watershed of West Virginia. Using an approach such as Integrated Water Resources Management (IWRM) may improve management for the long-term protection and sustainability of the Coal River watershed‰Ûªs water resources. This Capstone project analyzes current site-specific information related to water quality and quantity and the impacts of MTR in the region, reviews current management challenges, and identifies key stakeholders to be included in IWRM planning. This information provided a foundation for the development of a preliminary IWRM coordination plan for the Coal River watershed based on IWRM principles and guidelines. It is hoped that this preliminary plan will contribute to the development of a final coordinated IWRM plan.

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A complete study of the importance of the pyrolysis temperature (up to 1500 °C) of a petroleum residue (ethylene tar) in the activation with KOH of the resultant pyrolysis products (covering from the own ethylene tar to pitches and well developed cokes) has been carried out. The trend in the porosity found for activated carbons is as follows: the pore volume increases with the pyrolysis temperature reaching a maximum value (1.39 cm3/g) at about 460 °C, just at the transition temperature between a fluid pitch and a solid coke. It is the pitch with highest mesophase content that develops the maximum porosity when activated with KOH. The amount of H2, CO and CO2 produced during the reaction of the mesophase pitch and coke with KOH has been quantified, and a trend as described for the pore volume was found with the pyrolysis temperature. Therefore, there is a relationship between the reactivity of the precursor with KOH and the porosity developed by the activated carbon. Since the reactions that produce H2 initiate at temperatures as low as 300 °C, it seems that KOH is modifying the conditions under which the pyrolysis occurs, and this fact is critical in the development of porosity.

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tartīb Maḥmūd ibn Ḥamzah.