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991.
William O. Rasmussen 《Environmental management》1992,16(3):389-396
Several approaches can be used to define and construct visual buffer strips around proposed new facility sites in a forested
environment. A visual buffer strip of a given value, defines a region around an object within which the probability of an
unblocked view of all or portions of it by an observer are less than the buffer strip probability value. Two primary approaches
are used to define visual buffer strips that take into account the size of the vegetative elements and their individual effects
on visibility. Several variations and combinations of the approaches are possible. One approach defines a visual buffer strip
based on the average probability of a clear view of points along the object by an observer; the other approach is based on
the visibility of the feature as a whole. The computation and construction of visual buffer strips based on these two concepts
are presented. Comparisons of the two approaches for specific feature shapes are also described. 相似文献
992.
Robert O. Briggs 《Journal of the American Water Resources Association》1991,27(6):991-999
ABSTRACT: Waddell Creek is a perennial stream near Santa Cruz, California, which discharges into the Pacific Ocean about 38 km from the epicenter of the Loma Prieta earthquake (October 17, 1989, M 7.1). The earthquake caused no significant changes or damage to structures or surface features in the area, but was followed by an order of magnitude transient increase in discharge of Waddell Creek and nearby springs. The transients approximate a step rise followed by an exponential recession with time constants of from 37 to 59 days. The flow recession pattern of Waddell Creek was obscured by heavy rains after about 50 days; however, the springs maintained an exponential recession with minimal rain interference for periods of several time constants, then abruptly ceased flowing. A comparison of the pre-quake and post-quake chemical signature of one of the springs shows only minor changes in water chemistry indicating a common source for pre- and post-quake waters. Increased permeability of the subsurface ground material appears to be the most probable cause of the hydrologic changes. Post-seismic reduction of permeability has not been observed or inferred. 相似文献
993.
In the search for a cheaper material to effectively condition sludge, oil-free moringa seed was prepared and tested. A Soxhlet
apparatus was used to extract the oil from moringa seed (Moringa oleifera). The oil-free seed (marc) has been found to have higher conditioning potential than the ordinary moringa seed. However,
the traditional ferric chloride is still a better sludge conditioner than moringa seed marc. For the digested domestic sludge
used, optimum conditioning dosages were found to be 0.6, 0.80, and 1.10% of the total solids for ferric chloride, marc of
the moringa seed, and ordinary moringa seed, respectively. Since little or no operational material is lost in the extraction
process, the moringa seed marc is a promising conditioner in place of the ordinary seed. 相似文献
994.
Pérez-Coll CS Herkovits J Fridman O Daniel P D'Eramo JL 《Environmental pollution (Barking, Essex : 1987)》1997,97(3):311-315
Bufo arenarum females were treated daily with 0.5 mg Cd kg(-1) during 10 days to evaluate the uptake of this heavy metal and the induction of metallothionein synthesis in the liver. The liver incorporated 26% of the Cd administered, about 6.5 times higher than the average uptake of the other tissues of B. arenarum. Three protein fractions from the B. arenarum liver bound Cd, and were induced by this xenobiotic up to approx. 24 times above the basal level of these proteins. 相似文献
995.
Influences of organic matters of soil and water on speciation and biological utilization of selenium are discussed. Humic acid is found to be the main pool of selenium in soil and affects the bio-availability of the element in soil-plant system. Fulvic acid from drinking water inhibits the absorption of selenium taken from diet. The relationship between high content of organic matters of water and selenium deficiency on the causes of KBD could be reflected in the limited synthesis of glutathione peroxidase, which is generally stimulated by fulvic acid from drinking water. 相似文献
996.
997.
Salomao O.Bandeira Rui Paula e Silva Jose Paula Adriano Macia Lars Hernroth Almeida T.Guissamulo 《Ambio-人类环境杂志》2002,31(8)
本文概述了莫桑比克包括渔业在内的海洋生物学研究的发展情况.莫桑比克的海岸线约为3000km,海洋的生物资源在莫桑比克的社会中起着重要的作用,主要是作为人们的蛋白质来源以及收入和出口创汇的来源. 相似文献
998.
999.
1000.
R. W. Pohl E. Schmidt G. C. Hirsch H. Marquardt O. Harnisch 《Die Naturwissenschaften》1959,46(11):387-388