Duration of tick activity     

K Webster  G B Mitchell  C L Wright 《The Veterinary record》1985,116(14):378-379

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GALILEO AND WOOD     

Webster AG 《Science (New York, N.Y.)》1921,53(1366):212-213

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EFFICIENCY IN THERMAL CALCULATIONS     

Forbes AW  Webster AG 《Science (New York, N.Y.)》1920,52(1338):175-176

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Introduction     

Peter Webster 《Asia Pacific viewpoint》1988,29(2):91-98

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Experimental acidification of Little Rock Lake,Wisconsin: The first four years of chemical and biological recovery     

C. J. Sampson  P. L. Brezonk  T. M. Frost  K. E. Webster  T. D. Simonson 《Water, air, and soil pollution》1995,85(3):1713-1719

Little Rock Lake was experimentally acidified in 1984–1990 during which sulfuric acid was added to one basin, decreasing pH from 6.1 to 5.6, 5.1 and 4.7. The lake has been allowed to recover without manipulation since autumn 1990. By the third year of recovery, ～40% of the change necessary to return to pre-acidification values of pH, acid neutralizing capacity (ANC), sulfate (SO₄ ^2?) and calcium (Ca²⁺) had occurred. During recovery years 1–2, ANC was closely predicted by models based on acidification phase observations, but recovery during years 3–4 was slower than predicted. A possible explanation for the slowed recovery is acidification of the upper 0–5 cm of sediment, which acts as a sink for the ANC generated via SO₄ ^2? reduction, the primary recovery mechanism. Trends for Zooplankton did not follow pH recovery very closely. Species diminished by acidification (e.g. Keralella cochlearis, Daphnia dubia) have not recovered, but species that dominated the community at pH 4.7 (e.g. K. taurocephala, D. catawba) have not maintained high populations. The time required for the Zooplankton community to recover to pre-manipulation conditions is uncertain. Delays also have been observed for the mayfly species Caenis, which had disappeared at pH 4.7. In contrast, reproductive success of largemouth bass (Micropterus salmonides) mirrored that observed during acidification; egg hatch and survival of young-of-the-year to autumn recurred when pH exceeded response levels documented during acidification. Overall, recovery has not closely followed the pattern predicted by acidification responses.  相似文献   

Crop and soil response to subsoil loosening, deep incorporation of phosphorus and potassium fertilizer and subsequent soil management on a range of soil types.: Part 2: Soil structural conditions   总被引：2，自引：0，他引：2  

G.C. Soane  R.J. Godwin  MJ. Marks  G. Spoor 《Soil Use and Management》1987,3(3):123-130

Abstract. In a series of experiments on 16 sites both a power-driven rotary-tine Wye Double Digger and a rigid tine winged subsoiler produced significant subsoil loosening and fissuring. The Double Digger consistently produced the greatest clod breakdown together with the least soil bulk densities and cone penetration resistances. Management strategies after loosening had an important influence on the longevity of the loosening effect. The rate of recompaction was least with controlled traffic and bed systems and increased with random traffic and with the growing of root crops. No significant differences in crop response were monitored between the two loosening treatments, yield response depending largely on the extent of moisture stress experienced by the crop. Loosening on silty soils reduced yields in wet seasons and this was associated with soil structural instability. Visual soil profile examination is necessary to support bulk density and cone penetration resistance measurements when assessing soil compaction.  相似文献   

果胶细菌诱导油菜结瘤与固氮研究     

胡小加 Cock.  EC 《植物营养与肥料学报》1997,3(3):275-279

果胶细菌处理油菜幼根（2天苗龄、根长3cm），同时接种紫云英根瘤菌突变菌株（Rhizobiumhuakuii），诱发类根瘤的结瘤率为96.80％。从这些类根瘤中分离的菌株能回接到原寄主。类根瘤的电镜观察可以明显地见到细胞内充满了细菌。乙炔还原法测定的固氨酶活性（C2H4）为76.80nmol／（planth）。  相似文献   

What predicts nitrous oxide emissions and denitrification N-loss from European soils?     

E.-A. Kaiser  F. Eiland  J. C. Germon  M. A. Gispert  O. Heinemeyer  C. Henault  A. M. Lind  M. Maag  E. Saguer  O. Van Cleemput  A. Vermoesen  C. Webster 《植物养料与土壤学杂志》1996,159(6):541-547

N₂0 emissions and denitrification N-losses. precipitation, air temperature, soil moisture, bulk density and content of mineral N were monitored in 9 different agricultural soils in 6 European countries throughout the vegetation period (April to September) 1992 and 1993. N₂O emissions and denitrification N-losses were log-normal distributed, reflecting high temporal changes. While small flux rates (< 2 g N ha^?1 d^?1) were detectable every day, high rates (> 10 g N ha^?1 d^?1) were measured after fertilization. An attempt to relate the emission variables to climate and soil variables was made through the use of correlation analysis. The mean N₂0 emissions from soil were significantly correlated with the soil properties clay, organic C and mineral N content and the amount of applied mineral N fertilizer. The best prediction of the N₂O emission rates (r² = 0.734) was achieved by multiple linear regression using the soil parameter clay and mineral N. Only 50% of the observed variation could be explained by the factors C_org and mineral N, which describe the substrate availability for microbial processes. No successful statistical model was found for the prediction of denitrification N-losses.  相似文献   

Extinction following intracranial reward: the effect of delay between acquisition and extinction     

D Quartermain  D Webster 《Science (New York, N.Y.)》1968,159(820):1259-1260

Rats trained to press a bar for intracranial reinforcement gave as many responses during extinction as did water-reinforced controls, when extinction came immediately after an acquisition session. However, the experimental animals gave fewer responses in extinction than water-reinforced animals when extinction was delayed for 1 hour after acquisition. The activity level of the experimental animals was high immediately after acquisition but declined markedly over the delay period, which suggests that resistance to extinction after intracranial reinforcement is primarily a function of activity level.  相似文献   

Russia. Putin aims to turn science cities into silicon steppes     

Webster P 《Science (New York, N.Y.)》2003,299(5606):493

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