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81.
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   
82.
83.
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   
84.
There is no agreed level of safety that is ‘acceptable’. Those responsible for managing and regulating safety believe that they can establish adequate parameters, but they recognize that those standards must meet with ‘public approval’. This paper examines one way in which that approval is sought, namely the quasijudicial examination of the merits of a proposal to construct Britain's first pressurized water reactor at the Sizewell B site on the Suffolk coast. The authors argue that the Sizewell B Inquiry appears to operate on the assumption that acceptable risk levels can be determined through argument and cross-examination. In its approach to the determination of acceptable risk the Inquiry seems dependent on professional judgement and expertise as assessed by legal minds trained to sift evidence. To ensure that all the necessary evidence comes before it, the Inquiry has established procedures to initiate the preparation and examination of expert viewpoints. The authors examine how far this approach is likely to command public confidence, and the extent to which the Inquiry pinned down the elusive concept of acceptable risk.  相似文献   
85.
Ball lightning     
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   
86.
87.
Metal-contaminated soil may be remediated in situ by the formation of highly insoluble metal phosphates if an appropriate phosphorus (P) source can be found. Leaching column experiments have been carried out to assess the suitability of bone meal as such a source. Bone meal additions reduced metal release from a contaminated soil, increased soil and leachate pH and decreased soil leachate toxicity. Minimal P leaching occurred from the soil. The data are consistent with a proton consuming bone meal (calcium phosphate) dissolution reaction followed by the formation of metal phosphates. Although, no metal phosphates were observed to form using X-ray diffraction of scanning electron microscopy this could be due to their low concentration. Relatively low (1:50 bone meal:soil) concentrations of fine (90-500 microns) bone meal would appear to be an effective treatment for metal-contaminated soils.  相似文献   
88.
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   
89.
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   
90.
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   
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