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791.
Bolesław Zagalak 《Die Naturwissenschaften》1982,69(2):63-74
A critical review on corrinoid biochemistry and physiology is presented. This includes: chemical synthesis of biologically important organocorrinoids and the correlation between their structures and coenzymatic activity; forms, distribution and transport of physiologically active corrinoids; methylcobalamin- and adenosylcobalamin-dependent enzymatic reactions and their physiological functions; and steric course of the adenosylcobalamin-dependent enzymatic rearrangements. Special attention is paid to the mechanisms of adenosylcobalamin-dependent enzymatic reactions. 相似文献
792.
Maria Nowakowska Monika Sterzel Krzysztof Szczubiałka 《Journal of Polymers and the Environment》2006,14(1):59-64
Novel water-soluble polymeric photosensitizers based on a natural polymer, naphthalene-modified hydroxyethylcellulose (HENC),
were obtained and used for the photooxidation of cyanide. The reaction leads to the formation of cyanate. The process occurs
via photoinduced electron transfer from CN− to the naphthalene or naphthoquinone polymeric chromophores. The kinetics of the reaction depend on the degree of substitution
of HENC, its concentration, and pH of the solution. The polymers can be easily removed after reaction as prolonged irradiation
leads to their photodegradation. 相似文献
793.
794.
795.
Mikael Hult María Jos Martínez Canet Peter N. Johnston Kazuhisa Komura 《Journal of environmental radioactivity》2002,60(3)
During the JCO-accident in Tokai-mura in 1999, the surrounding village was irradiated by an uncontrolled neutron flux. At some locations in that village, the thermal neutron flux was determined retrospectively by measurement of the very low activity of 51Cr and 60Co in stainless-steel spoons using γ-ray spectrometry in underground laboratories. Activities determined in the HADES underground facility are presented here, together with calibrations performed using a well-defined thermal neutron flux to directly estimate the fluence of thermal neutrons independent of most assumptions. The results show measurable 51Cr in three samples and 60Co in four samples taken from locations at distances of up to 430 m from the accident location despite the elapse of 4 half-lives of 51Cr before measurement. Effects of air transport of the samples were considered and shown to be negligible. 相似文献
796.
Jazm&#;n Caballero Garc&#;a David G.Ricalde 《生态毒理学报》2002,(4):58-61
作者们介绍了有关恰拉兰生态旅馆发展的最新信息 , 它是玻利维亚亚马孙地区马迪迪国家公 园综合管理自然区的一个社区项目 .能力建设的最初阶段 (1997- 98)对于巩固恰拉兰 (马迪迪 )生态旅馆的新旅游胜地地位和确保社区在可持续发展自行管理项目中独立自主地进行决策是 最根本的 .作者们把这个项目看作是玻利维亚和亚马孙地区生态旅游发展的模范 . 相似文献
797.
Pablo del Río Javier Carrillo-Hermosilla Totti Könnölä Carlos García Suárez 《Mitigation and Adaptation Strategies for Global Change》2008,13(8):863-885
This paper empirically shows how the uncertainty associated to the absence of a mitigation regime which follows the United
Nations Framework Convention on Climate Change Kyoto Protocol (UN FCCC Kyoto Protocol) is affecting investments in abatement
activities in the EU electricity sector and, thus, future emissions levels. Based on a survey of EU electric utilities, it
identifies the most likely post-Kyoto scenarios considered by them and how they are coping with such uncertainty in their
investment decisions. It is found that firms react differently to such uncertainty and adopt different strategies to cope
with it, diversifying their emissions control activities. Although most companies foresee post-Kyoto compliance regimes with
emissions trading systems, they differ in their perceptions of the form that a post-Kyoto regime could take and are, thus,
positioning differently to face such regime. The particular features of each company and the country where they operate affect
their perception of the uncertainties, their position regarding a possible post-Kyoto regime and their inclination to carry
out mitigation activities. Complying with Kyoto (and, eventually, post-Kyoto) targets significantly influences the investment
decisions of European electricity companies. Uncertainty about a post-Kyoto regime may already be affecting investments in
mitigation activities in the electricity sector. Therefore, significant progress has to be made in the definition of a post-Kyoto
regime. It is urgent to define and agree internationally the emissions reduction objectives and the mitigation instruments
that will be accepted for compliance, ensuring continuity of the international emissions trading system foreseen in the Kyoto
Protocol.
相似文献
Pablo del RíoEmail: |
798.
Małgorzata Matejko Anthony J. Dore Jane Hall Christopher J. Dore Marek Błaś Maciej Kryza Rognvald Smith David Fowler 《Environmental Science & Policy》2009,12(7):882-896
In the United Kingdom, as with other European countries, land-based emissions of NOx and SO2 have fallen significantly over the last few decades. SO2 emissions fell from a peak of 3185 Gg S in 1970 to 344 Gg S in 2005 and are forecast by business-as-usual emissions scenarios to fall to 172 Gg by 2020. NOx emissions were at a maximum of 951 Gg N in 1970 and fell to 378 by 2005 with a further decrease to 243 Gg N forecast by 2020. These large changes in emissions have not been matched by emissions changes for NH3 which decreased from 315 Gg N in 1990 to 259 in 2005 and are forecast to fall to 222 by 2020. The Fine Resolution Atmospheric Multi-pollutant Exchange model (FRAME) has been applied to model the spatial distribution of sulphur and nitrogen deposition over the United Kingdom during a 15-year time period (1990–2005) and compared with measured deposition of sulphate, nitrate and ammonium from the national monitoring network. Wet deposition of nitrogen and sulphur was found to decrease more slowly than the emissions reductions rate. This is attributed to a number of factors including increases in emissions from international shipping and changing rates of atmospheric oxidation. The modelled time series was extended to a 50-year period from 1970 to 2020. The modelled deposition of SOx, NOy and NHx to the UK was found to fall by 87%, 52% and 25% during this period. The percentage area of sensitive habitats in the United Kingdom for which critical loads are exceeded is estimated to fall from 85% in 1970 to 37% in 2020 for acidic deposition and from 73% to 49% for nutrient nitrogen deposition. The significant reduction in land emissions of SO2 and NOx focuses further attention in controlling emissions from international shipping. Future policies to control emissions of ammonia from agriculture will be required to effect further significant reductions in nitrogen deposition. 相似文献
799.
Biomarkers are widely known to occur in the fossil record, but the unaltered biomolecules are rarely reported from sediments
older than Paleogene. Polar terpenoids, the natural products most resistant to degradation processes, were reported mainly
from the Tertiary conifers, and the oldest known are Cretaceous in age. In this paper, we report the occurrence of relatively
high concentrations of ferruginol derivatives and other polar diterpenoids, as well as their diagenetic products, in a conifer
wood Protopodocarpoxylon from the Middle Jurassic of Poland. Thus, the natural product terpenoids reported in this paper are definitely the oldest
polar biomolecules detected in geological samples. The extracted phenolic abietanes like ferruginol and its derivatives (6,7-dehydroferruginol,
sugiol, 11,14-dioxopisiferic acid) are produced only by distinct conifer families (Cupressaceae s. l., Podocarpaceae and Araucariaceae),
to which Protopodocarpoxylon could belong based on anatomical characteristics. Therefore, the natural product terpenoids are of great advantage in systematics
of fossil plant remains older than Paleogene and lacking suitable anatomical preservation. 相似文献
800.
Metallothionein and metal content (Cd, Zn, Hg, Cu, Fe, Pb and Mn) were determined in various organs of commercially available eel (Anguilla anguilla) of similar size obtained from a local farm and from The Albufera Lake in Valencia (Spain). Farmed fish showed statistically significant higher Cd concentrations in liver and kidney whereas wild individuals had higher levels of Pb in blood and Zn in kidney. Significant positive correlations were found between metallothionein and Cd in kidney of farmed eel and between metallothionein and Cu in liver of wild ones. No statistically significant differences were found between the two populations in the concentration of any of the metals analyzed in muscle and in all instances these levels were lower than the limits established by the Spanish legislation for fish destined for human consumption. 相似文献