排序方式： 共有28条查询结果，搜索用时 187 毫秒
1.
2.
A gap analysis of terrestrial protected areas in England and its implications for conservation policy 总被引：1，自引：0，他引：1
Thomasina E.E Oldfield Stuart R Harrop Nigel Leader-Williams 《Biological conservation》2004,120(3):303-309
Many protected area (PA) systems have developed in response to socio-economic and aesthetic criteria and need to be modified to increase their conservation value. National gap analyses are an important step in describing and addressing this problem, so we sought to determine the representativeness of English PAs devoted to biodiversity conservation by using Natural Areas (NAs), elevation and PA boundary data. We found that National Nature Reserves (NNRs) and Sites of Special Scientific Interests (SSSIs) cover only 6.3% of England and are generally small, with respective median areas of 1.1 and 0.2 km2. The English PA system under-represents lowland areas and provides a median level of 2.5% protection for the NA types, with seventy nine per cent of NA types having less than 10% protection. Therefore, we suggest that England's PA system needs to be expanded, although this would probably entail modification of existing legislation to increase involvement by landowners. We also compare our results with previous appraisals that used species distribution record data and suggest that landscape-level analyses may give a more accurate and less positive assessment. 相似文献
3.
Relationships Between Radionuclide Content and Textural Properties in Irish Sea Intertidal Sediments
Intertidal sediments from a range of depositional environments in the eastern Irish Sea have been analysed with regard to their radionuclide content, particle size distribution and magnetic properties. Concentrations of241Am and137Cs are highly influenced by the abundance of sediment finer than 32μm in fine-grained sedimentary environments, whilst radionuclide activity in coarser sediments is less dependent on particle size. Investigation of the magnetic properties of these sediments highlights a similar association between this size fraction and magnetic remanence, the latter being shown to offer strong potential as a grain size proxy in monitoring137Cs concentrations in fine-grained sediments. Analysis of particle size fractions indicates the extent to which137Cs may be enriched in the clay size fractions of both tine and coarse sediments. 相似文献
4.
Lymphoid cell-glioma cell interaction enhances cell coat production by human gliomas: novel suppressor mechanism 总被引：1，自引：0，他引：1
S J Dick B Macchi S Papazoglou E H Oldfield P L Kornblith B H Smith M K Gately 《Science (New York, N.Y.)》1983,220(4598):739-742
Certain human glioma lines produce mucopolysaccharide coats that impair the generation of cytolytic lymphocytes in response to these lines in vitro. Coat production is substantially enhanced by the interaction of glioma cells with a macromolecular factor released by human peripheral blood mononuclear cells in culture. This interaction thus constitutes an unusual mechanism by which inflammatory cells may nonspecifically suppress the cellular immune response to at least one class of solid tumors in humans. 相似文献
5.
Yang Handong He Baoyin Cai Shuming Oldfield Frank Yu Lizhong 《Water, air, and soil pollution》1997,98(1-2):187-195
Mineral magnetic measurements have been made on three sediment cores from Lake Donghu, Wuhan, which reveal evidence for changes in magnetic properties of the sediments. It is suggested that the recent lake sediment profiles contain deposited magnetic minerals and atmospherically derived fly ash from industrial processes. In the cores, the record of ‘magnetite’ deposition shows that the environment of the lake has been affected by heavy industrial processes in intensity and range beginning from the 1950's onwards and remaining relatively uniform in the last decades. In Core I the record of ‘hematite’ deposition parallels that for influence of urban waste water input. 相似文献
6.
7.
8.
Effect of feeding selenium-deficient ration to the subhuman primate (Saimiri sciureus) 总被引：1，自引：0，他引：1
O H Muth P H Weswig P D Whanger J E Oldfield 《American journal of veterinary research》1971,32(10):1603-1605
9.
10.
S.E. Abdelgadir J.R. Jaeger J.E. Oldfield L.H. Appell F. Stormshak 《Domestic animal endocrinology》1994,11(4):349-354
Two experiments were conducted to study the effects of cycloheximide and colchicine on prostaglandin F2 (PGF2)-induced secretion and synthesis of oxytocin in bovine luteal tissue in vitro. Corpora lutea were collected from beef heifers on Day 8 of the estrous cycle. In Experiment 1, incorporation of [14C]-leucine into oxytocin synthesized and secreted by luteal slices after exposure to PGF2, cycloheximide and cycloheximide plus PGF2 was examined. In Experiment 2, synthesis and secretion of oxytocin were evaluated in luteal slices incubated with colchicine and PGF2 alone and in combination. Cycloheximide inhibited incorporation of labeled leucine into luteal proteins by more than 90% and no labeled oxytocin was detected in the media or tissue. Prostaglandin F2 induced significant secretion of oxytocin that was not inhibited by cycloheximide. Tissue levels of oxytocin after incubation with cycloheximide and/or PGF2 did not differ and were similar to those of the incubated control. Colchicine alone did not suppress oxytocin secretion and did not alter the ability of PGF2 to induce significant secretion of this nonapeptide. Tissue concentrations of oxytocin after incubation with colchicine and/or PGF2 did not differ. These studies indicate that secretion and replenishment of luteal oxytocin in vitro is not contingent upon de novo protein synthesis. Inability of colchicine to suppress oxytocin secretion and synthesis may have been due to the short duration of exposure of luteal tissue to the drug. 相似文献