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排序方式: 共有167条查询结果,搜索用时 258 毫秒
91.
92.
Children with a genetic absence of transcobalarnin 2 (TC2) are clinically asymptomatic at birth but develop severe megaloblastic anemia early in life. We have examined the incorporation of [57Co]-CN-B12 in the absence of any exogenous source of TC2 in control amniotic fluid derived cells and cultured diploid fibroblasts, and in fibroblasts from a patient with TC2 deficiency. Both control fibroblasts and arnniocytes incorporated labelled B12, into TC2-B12, and the proportion of labelled TC2-B12 could be increased by growing cells in the presence of chloroquine which prevents intralysosomal hydrolysis of the TC2-B12 complex. In contrast, fibroblasts from the patient with TC2 deficiency incorporated almost no label as TC2-B12. These studies suggest that TC2 deficiency either due to aberrant production of TC2 or because of the production of an abnormal TC2 which does not bind B12 can be diagnosed before birth. 相似文献
93.
Emmanuel Delbart Grégory Mahy Bernard Weickmans Fran?ois Henriet Sébastien Crémer Nora Pieret Sonia Vanderhoeven Arnaud Monty 《Environmental management》2012,50(6):1089-1097
Japanese knotweed Fallopia japonica is an extremely abundant invasive plant in Belgium and surrounding countries. To date, no eradication method is available for land managers facing the invasion of this rhizomatous plant. We tested different chemical herbicides with two application methods (spraying and stem injection), as well as mechanical treatments, on knotweed clones throughout southern Belgium. The tested control methods were selected to be potentially usable by managers, e.g., using legally accepted rates for herbicides. Stem volume, height and density reduction were assessed after one or two years, depending on the control method. Labor estimations were made for each control method. No tested control method completely eradicated the clones. Stem injection with glyphosate-based herbicide (3.6?kg?ha?1 of acid equivalent glyphosate) caused the most damage, i.e., no sprouting shoots were observed the year following the injection. The following year, though, stunted shoots appeared. Among the mechanical control methods, repeated cuts combined with native tree transplanting most appreciably reduced knotweed development. The most efficient methods we tested could curb knotweed invasion, but are not likely to be effective in eradicating the species. As such, they should be included in a more integrated restoration strategy, together with prevention and public awareness campaigns. 相似文献
94.
Kávási N Vigh T Kovács T Vaupotič J Jobbágy V Ishikawa T Yonehara H 《Journal of environmental radioactivity》2011,102(9):806-812
One of the essential parameters influencing of the dose conversion factor is the ratio of unattached short-lived radon progeny. This may differ from the value identified for indoor conditions when considering special workplaces such as mines. Inevitably, application of the dose conversion factors used in surface workplaces considerably reduces the reliability of dose estimation in the case of mines.This paper surveyed the concentration of radon and its short-lived radon progeny and identified the unattached fraction of short-lived radon progeny. As well equilibrium factor during the month of August was calculated simultaneously at two extraction faces in a manganese ore mine.During working hours the average radon concentrations were 220 Bq m−3 and 530 Bq m−3 at Faces 1 and 2; the average short-lived progeny concentration was 90 Bq m−3 and 190 Bq m−3, the average equilibrium factors were 0.46 and 0.36, and the average unattached fractions were 0.21 and 0.17, respectively. The calculated dose conversion factor was between 9 and 27 mSv WLM−1, but higher values could also be possible. 相似文献
95.
Chai Minwei Li Ruili Tam Nora Fung Yee Zan Qijie 《Environmental geochemistry and health》2019,41(1):175-189
Environmental Geochemistry and Health - The present study compared accumulation of heavy metals in a mangrove swamp dominated by Kandelia obovata with that by Sonneratia apetala in Pearl River... 相似文献
96.
René E. van Dijk Lidia A. Mészáros Marco van der Velde Tamás Székely Ákos Pogány János Szabad Jan Komdeur 《Behavioral ecology and sociobiology》2010,64(9):1425-1435
Engagement in extra-pair copulations is an example of the abundant conflicting interests between males and females over reproduction.
Potential benefits for females and the risk of cuckoldry for males are expected to have important implications on the evolution
of parental care. However, whether parents adjust parental care in response to parentage remains unclear. In Eurasian penduline
tits Remiz pendulinus, which are small polygamous songbirds, parental care is carried out either by the male or by the female. In addition, one
third of clutches is deserted by both male and female. Desertion takes place during the egg-laying phase. Using genotypes
of nine microsatellite loci of 443 offspring and 211 adults, we test whether extra-pair paternity predicts parental care.
We expect males to be more likely to desert cuckolded broods, whereas we expect females, if they obtain benefits from having
multiple sires, to be more likely to care for broods with multiple paternity. Our results suggest that parental care is not
adjusted to parentage on an ecological timescale. Furthermore, we found that male attractiveness does not predict cuckoldry,
and we found no evidence for indirect benefits for females (i.e., increased growth rates or heterozygosity of extra-pair offspring).
We argue that male Eurasian penduline tits may not be able to assess the risk of cuckoldry; thus, a direct association with
parental care is unlikely to evolve. However, timing of desertion (i.e., when to desert during the egg-laying phase) may be
influenced by the risk of cuckoldry. Future work applying extensive gene sequencing and quantitative genetics is likely to
further our understanding of how selection may influence the association between parentage and parental care. 相似文献
97.
The Science of Nature - 相似文献
98.
99.
Deciding how to remediate and redevelop contaminated lands should involve more than just selecting remediation techniques to clean a site to meet regulations for a predetermined site use. Owners and their consultants also need to understand aspects such as alternative site uses and liability, and how issues such as uncertainty can affect them. A methodology has been developed that provides a framework for current site owners when making decisions. It clarifies the above issues and details the type of information that is needed. It offers a step-by-step approach to improve decision making when contemplating remediation of contaminated sites by identifying the site use and remedial action combination that maximizes the current owner's net benefits. It examines various factors in decision making--with special emphasis on the timely issues of liability and uncertainty--and how expert opinion can be used to address diverse or incomplete data. Future research should include developing a complementary methodology that incorporates community and ecological objectives, resulting in a unified decision framework. 相似文献
100.
The Sequencing Batch Reactor (SBR) system employing activated sludge process is an alternative wastewater treatment technology. A cycle of the conventional SBR system generally consists of five periods, with complete aeration during the React period to oxidize the organic matter and nitrify the ammonium-nitrogen of wastewater. Laboratory-scale reactors were used to evaluate the feasibility of incorporating alternative aerobic-anoxic-aerobic stages within the React period for simultaneous removal of organic matter, N and P. Two cycles of SBR process per day were maintained.Under the operation strategy of 0.75-h fill, 8-h react (with continuous aeration), 3.25-h settle, draw and idle periods, the treatment performance became consistent after running the system for two to four cycles (1–2 days). The percentages of both BOD5 and COD removal were around 94% from Cycle 2 onwards, the BOD5 content dropped from initial 251 mg L−1 to less than 14 mg L−1 in the final effluent. A steady nitrification (about 97%) was obtained from Cycle 4 onwards, with 1 mg NH4+-N L−1 and 25 mg NO3−-N L−1 present in the final effluent. This suggested that the time required for SBR system to acclimate and reach an equilibrium state was relatively short when compared with the time needed for continuous flow activated sludge system. The findings also show that 4-h aeration during the react period was long enough to achieve more than 90% nitrification. With the incorporation of a 3-h anoxic stage after the initial 4-h aeration of the react period, a satisfactory denitrification process was observed, with nitrate level dropped from 27 to around 8 mg L−1 within 3 h. The second aeration stage did not cause significant change in wastewater nitrogen content. The wastewater phosphate content declined rapidly during the initial 4-h aeration and P-release was not observed during the anoxic stage. A slight reduction of P was found in the second aeration stage suggesting that more P-uptake occurred in this stage. A 12-h cyclic SBR system with the incorporation of 4-h aerobic, 3-h anoxic and final 1-h aerobic stages into the 8-h react period was demonstrated to be able to remove C, N and P simultaneously. 相似文献