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排序方式: 共有209条查询结果,搜索用时 31 毫秒
61.
62.
John S. Stanley Kathy E. Boggess Jon Onstot Thomas M. Sack Janet C. Remmers Joseph Breen Frederick W. Kutz Joseph Carra Philip Robinson Gregory A. Mack 《Chemosphere》1986,15(9-12):1605-1612
Analysis for tetra- through octachloro-PCDDs and PCDFs was completed for 46 tissue samples prepared from the U.S. Environmental Protection Agency (EPA) National Human Adipose Tissue Survey (NHATS). The samples were prepared as composites from over 900 specimens to represent the nine U.S. census divisions and three age groups (0–14, 15–44, and 45 plus years). The data demonstrate that PCDDs and PCDFs are prevalent in the general U.S. population and that differences exist with age. 相似文献
63.
64.
Kumar T Stanley VA Lal AA Balasubramanian M Pillai KS 《Journal of environmental biology / Academy of Environmental Biology, India》2002,23(4):407-410
Alloxan-induced diabetic rats were treated with multiple herbal preparation besides a control group receiving distilled water. The levels of glucose and alkaline phosphatase (ALP) increased abnormally in the alloxan treated group and the same were normalized upon treatment with the herbal preparation. The levels of blood urea nitrogen (BUN), alanine aminotransferase (ALT), protein and albumin in all groups remained unaltered. However, weekly body weight gain which got significantly altered in the alloxan-treated group was normalized by treatment with the herbal preparation. On the whole, a profound hypoglycemic effect was observed by the multiple herbal treatment in the diabetic rats. 相似文献
65.
Stanley Singer 《Die Naturwissenschaften》1980,67(7):332-337
Ball lightning remains a mystery despite consideration extending over one and one-half centuries by a number of distinguished scientists. The fireball is observed in thunderstorms with intense electrical activity. The theoretical problem is that of accounting for a spherical structure which maintains its identity while moving freely in the air for some seconds and for a radiation process which continues over the same length of time. None of the theories presented has yet been conclusive. However, three types of glowing spheres which exhibit some of the properties of the natural globe have been observed experimentally: 1) glowing spheres produced by electric discharges in metal; 2) fireballs ignited in very dilute mixtures of fuel gases in air; 3) certain electric discharges in gases. 相似文献
66.
67.
In recent studies, we developed a combined nutrient removal-marine aquaculture process for the tertiary treatment of wastewater and the production of commercially important shellfish. Part of this process consists of an outdoor mass cultivation system for marine algae. During our previous experiments we observed that marine diatoms almost exclusively are the dominant algal species in our outdoor cultures. To better understand this phenomenon of diatom dominance we grew 16 species of marine algae in continuous monoculture under laboratory conditions simulating to some degree the conditions prevailing in our outdoor experiments. Species such as Skeletonema costatum, Monochrysis lutheri and Tetraselmis sp., which were never dominant in our outdoor cultures, grew as well in monoculture, as Phaeodactylum tricornutum, frequently, the prevalent species outdoors. However, when monocultures of Dunaliella tertiolecta and Thalassiosira pseudonana (3H) were purposely contaminated with P. tricornutum, the latter species quickly became dominant. It is suggested that a complex interaction of environmental factors is usually responsible for the dominance of a particular species; one such factor may be the nitrogen source in the growth media. Under conditions of virtually, complete nitrogen assimilation, the carbon: nitrogen ratio in the algae was high (7 to 8) when NO
3
-
–N was the source of nitrogen, and low (4 to 6) when NH
4
+
–N was the prime form of nitrogen. When algal growth was low, resulting in a large inorganic nitrogen residue, the carbon:nitrogen ratio was low regardless of whether NO
3
-
–N or NH
4
+
–N was the main nitrogen source.Contribution No. 3297 from the Woods Hole Oceanographic Institution. 相似文献
68.
The mid-Atlantic region of the United States has a wide diversity of natural resources. Human pressures on these natural resources are intense. These factors have resulted in the collection of substantial amounts of environmental information about the region by EPA (both Regional and Research Offices), other governmental agencies, industry, and environmental groups. EPA Regional Offices comprehend first hand the importance of environmental data and are extremely supportive of investments in these data. Environmental data are used prominently in a variety of strategic planning and resource management initiatives. In EPA Region 3, the use of scientifically-sound environmental data is, in fact, one of our strategic programmatic goals. Environmental information is captured and assessed continuously by Regional staff, sometimes working in partnership with other Federal and State agencies, to derive relevant resource management conclusions. The restoration goals for the Chesapeake Bay are based on environmental indicators and resulting data. Attainment of the water quality objectives for streams and coastal estuaries are predicted on monitoring data. Our initiative in the Mid-Atlantic Highlands area uses environmental indicators to measure the condition of forests and streams. Landscape-level indicators will provide unique opportunities for the use of data in planning and management activities in support of the principles of community-based activism and sustainable development. Significant value is added to these data during their use by Regional managers. Regional programs, such as the Chesapeake Bay Program and several National Estuary Programs, are founded in environmental data. Environmental information is used by the Regional program managers to ascertain whether programs are accomplishing their intended objectives. Finally, Regional programs provide a crucial means for disseminating this information to broad segments of the public, so that a better informed and educated client base for effective environmental protection will develop. 相似文献
69.
Robert R. Carlton Peter G. Waterman Alexander I. Gray Stanley G. Deans 《Chemoecology》1992,3(1):55-59
Summary The antifungal activity of volatile oil obtained from the leaves of sweet gale (Myrica gale) has been investigated. Fungi, isolated from the leaves ofM. gale, were grown in liquid medium containing the oil and its effect on biomass production was gauged. The oil inhibited growth of all species of fungi to greater or lesser extent. Sesquiterpenes were more active than monoterpenes, and among the sesquiterpenes germacrone was marginally more active than -elemenone. These results support the proposition that the volatile oil ofM. gale has a role in resistance to fungal pathogens. 相似文献
70.
Guided group discussion (
[Lewin et?al., 1952]
,
[Werner, 2003]
and
[Werner and Adams, 2001]
) was used to persuade groups to replace their toxic home and garden chemicals with nontoxic alternatives. We hypothesized that discussion would allow participants to hear others endorse the new information, and this normative information would facilitate persuasion. Approximately two months after the group discussion, we obtained questionnaires from the organizer of the meeting and a member of the group who had missed the meeting because of another obligation (i.e., not because of disinterest in the topic). Most organizers were female and analyses were limited to females. This quasi-experimental matched control group design indicated that those who attended the meeting were more favorable towards using nontoxics and more interested in sharing leftover toxic products with friends (instead of discarding them). Path and mediation analyses showed that the organizer’s evaluation of the meeting predicted her final attitude, and perceptions that the group endorsed the material (perceived group norm) partially mediated this relationship. A second mediation analysis showed that evaluation of the meeting predicted intention to share leftover toxics and this relationship was fully mediated by the organizer’s impression that the group would also share leftovers. The results support the idea that persuasion is based both on individual evaluation and normative influence, especially when people are not confident others will accept the behavior, such as sharing leftover toxic products. 相似文献