排序方式: 共有38条查询结果,搜索用时 312 毫秒
31.
以开源GIS软件GRASS为平台,首次通过辐射过程模型r.sun和编程语言Shell实现长江流域500 m分辨率的晴日辐射反演(包括直接辐射、散射辐射和反射辐射),为了解长江流域辐射时空分布规律和相关宏观气候、生态建模奠定基础。结论如下:(1)精度验证表明,晴日辐射反演结果较理想;相关晴日指数的误差指标MPE、MAPE和RMSE分别为37%、75%和64%,r.sun模型可进一步用于中国其它区域;(2)长江流域晴日辐射年均日值为2424±245 MJ/(m2·d),其各组分差异显著,直接、散射、反射辐射分别占总辐射的842%、156%和02%;(3)晴日辐射空间分布梯度明显,沿三级地形阶梯向东辐射值及变异逐渐减小,海拔变化引起的大气衰减因素在决定晴日辐射分布时起重要作用;(4)晴日辐射季节分布不对称,月际变化总体呈倒“U”形分布;直接辐射和散射辐射变化趋势基本一致,但二者比例随大气浑浊度的变化波动剧烈。 相似文献
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A. Dewan S.K. Gupta J.P. Jani S.K. Kashyap 《Journal of environmental science and health. Part. B》2013,48(4):395-402
Abstract The immunosuppressive effect of lindane was assessed in weanling rats over a period of 5 weeks. Agglutinin titres against S. typhi ‘O’ and ‘H’, S. paratyphi ‘AH’ and ‘BR’ antigens were determined following TAB vaccination in control and lindane‐fed animals. The titres attained in non‐treated controls were higher significantly than those in treated animals indicating a suppressive effect of lindane on humoral immune responses. 相似文献
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The resistance pattern and mechanisms of bacterial isolates obtained from clinical origin, soil, industrial effluent, orange juice products and drinking water were studied using commonly used antibiotics. The microbial load of the water samples, industrial effluent and orange juice products were 1.0 × 101–2.25 × 106, 2.15 × 105, and 3.5 × 104–2.15 × 105 cfu mL–1, respectively. The faecal coliform test revealed that only two out of twenty orange juice products had MPN of 2 and 20, the MPN of water ranged from 1–rc="/content/r701696m91q111g6/xxlarge8805.gif" alt="ge" align="MIDDLE" BORDER="0">1800, while the effluent had MPN of rc="/content/r701696m91q111g6/xxlarge8805.gif" alt="ge" align="MIDDLE" BORDER="0">1800. The bacterial isolates that were isolated include E. coli, S. aureus, P. vulgaris, S. marcescens, S. pyogenes, B. cereus, B. subtilis, Micrococcus sp., Klebsiella sp., P. aeruginosa, and Enterobacter sp. Also, clinical and soil isolates of P. aeruginosa were used in the study. Among the eight antibiotics tested for resistance on five strains of each bacterium, seven different resistance patterns were observed among the bacterial isolates obtained from water, effluent and orange juice products. Among the clinical and soil isolates of P. aeruginosa, four multiple-drug resistance patterns were obtained. Thirty strains of E. coli and S. aureus were tested for rc="/content/r701696m91q111g6/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-lactamase production and fourteen strains, seven each of E. coli and S. aureus that had high Minimum Inhibitory Concentration values (MIC) for both Amoxycillin and Cloxacillin were positive. 相似文献
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Bruce A. Ramsay Ilie Saracovan Juliana A. Ramsay Robert H. Marchessault 《Journal of Polymers and the Environment》1994,2(1):1-7
A simple method was developed for the preparation of an autoclavable, long-side-chain poly (rc="/content/r684424264857477/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-hydroxyalkanoate) (LSC-PHA) colloidal suspension, which was used as a substrate for enzymatic degradation and to prepare agar overlay plates for the isolation of microorganisms producing extracellular LSC-PHA depolymerase. Six cultures producing extracellular LSC-PHA depolymerase were isolated from a composted hydrocarbon-contaminated soil. All were pseudomonads or related bacteria. All (with the possible exception ofXanthomonas maltophilia) could produce LSC PHA. Except forX. maltophilia none could hydrolyze poly (rc="/content/r684424264857477/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-hydroxybutyrate). Screening of sevenPseudomonas strains known to accumulate LSC PHA showed that all were negative for extracellular LSC-PHA depolymerase production. It was concluded that extracellular LSC-PHA depolymerase producers are found mostly in the genusPseudomonas but that they are relatively uncommon. 相似文献
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Summary Feeding by the homopteranPsylla pyricola on leaves of pear trees induces the production of volatile compounds, such as (E,E)-rc="/content/r26g4585p7500x79/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-farnesene and methyl-salicylate, as well as the production of polyphenols. The inference on induction is based on GC-MS and HPLC chromatograms from the same samples ofPsylla infested leaves, leaves from the same pear tree beforePsylla infestation and uninfested leaves from other pear trees.Psylla infestation greatly enhanced the production of volatiles ((E,E)-rc="/content/r26g4585p7500x79/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-farnesene, methyl-salicylate and others) and triggered the production of new polyphenols, characterized by much longer retention times.However, the responses to infestation depend critically on leaf age (defined by leaf distance to apex). With respect to the leaf volatiles it appears that infested, old leaves produce fewer compounds and lower amounts of the volatiles than infested, young leaves. Moreover, there seem to be differences in pattern. Relative to (E,E)-rc="/content/r26g4585p7500x79/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-farnesene, methyl-salicylate was found in much lower amounts in heavily infested, old leaves. With respect to polyphenols it was found that infested old leaves collected in August have polyphenols with the same retention times, but more or less equal amounts as uninfested young leaves collected in May. This shows thatPsylla infestation causes the induced response mostly in young leaves.The induced leaf volatiles may act as synomones to heteropteran bugs. As shown elsewhere,Anthocoris nemoralis responds significantly to (E,E)-rc="/content/r26g4585p7500x79/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-farnesene and methyl-salicylate when offered in pure form against clean air in a Y-tube olfactometer. The effect of polyphenols on the performance ofP. pyricola is not yet known. Hence, a role in direct defence is still to be investigated. 相似文献
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Udo Kastenholz 《Umweltwissenschaften und Schadstoff-Forschung》2000,12(3):131-136
Zusammenfassung
Ziel und Schwerpunkte Um das Verhalten des künstlichen Radionuklids137Cs im Landschaftshaushalt der Saar-Lor-Lux Region zu klaren, wurdend die r?umliche Verteilung sowie das deszendente Migrationsverhalten
und die Tiefenfunktionen des Radioisotops in den wichtigsten Bodensubstraten saarl?ndischer Wald?kosysteme untersucht.
Ergebnisse Demnach finden sich die h?chsten137Cs-Aktivit?ten im Norden des Landes, w?hrend die Gebiete im Süden und Südosten deutlich geringere Konzentrationen aufweisen.
Es konnten deszendente Migrationsraten zwischen 0,25 cm/a und 1,0 cm/a festgestellt werden. Durchschnittlich treten die h?chsten
Migrationsraten in den tonig-schluffigen Substraten des Muschelkalks auf (0,66 cm/a), gefolgt von den lehmig ausgepr?gten
Substraten des Unterrotliegenden (0,53 cm/a) und den sandigen Substraten des Buntsandsteins (0,41 cm/a). In den tonarmen Bodensubstraten
des Unterrotliegenden und des Buntsandsteins lassen sich 90–95% der Aktivit?ten in den oberen 10 cm der humusreichen Oberb?den
nachweisen, wohingegen in den tonreichen Substraten des Muschelkalks bis zur gleichen Tiefe nur etwa 70–76% zu finden sind.
Schlussfolgerungen Mit einem Abnehmen der als Leitbahnen fungierenden Prim?r-und Sekund?rporen in zunehmender Tiefe ist künftig mit einer deutlichen
Reduzierung der Verlagerungsgeschwindigkeit von137Cs in den Substraten des Muschelkalks zu rechnen. Insbesondere bei geringm?chtigen B?den auf kluftreichem Ausgangsgestein
impliziert die maximale Eindringtiefe des Isorops von 40 cm in den Unterboden jedoch eine m?gliche Kontamination des oberfl?chennahen
Grundwassers, ebenso wie an Standorten mit hohem Grundwasserstand.
Ausblick Aufgrund der hier vorgestellten Ergebnisse wurde ein137Cs-Monitoring in das Boden-Dauerbeobachtungsprogramm des Landesamts für Umweltschutz des Saarlandes aufgenommen
Online-First: 25. April 2000 相似文献