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811.
GuangLi Wang NingXi Li Bo Gao XianQing Li ShengBao Shi TieGuan Wang 《科学通报(英文版)》2013,58(28-29):3588-3594
The main reservoirs of Majiang fossil deposits consist of the Silurian Wengxiang group, dominantly sandstones, and the Ordovician Honghuayuan formation, dominantly carbonate rocks, and the Lower Cambrian Niutitang Formation mudstones serve as the major source rocks. Thermochemical sulfate reduction (TSR) might have taken place in the Paleozoic marine carbonate oil pools, as indicated by high concentrations of dibenzothiophenes in the extracts (MDBT=0.27–4.32 μg/g extract, and MDBT/MPH= 0.71–1.38). Hydrocarbons in the Pojiaozhai Ordovician carbonate reservoirs have undergone severe TSR and are characterized by higher quantities of diamondoids and MDBT and heavier isotopic values (δ 13C=?28.4‰). The very large amounts of dibenzothiophenes might be products of reactions between biphenyls and sulfur species associated with TSR. 相似文献
812.
L.J.M. Coleby M.A. M.Sc. Ph.D. 《Annals of science》2013,70(2):101-123
The development of the circular dividing engine in England is traced from Henry Hindley and Jesse Ramsden through the improvements introduced by Ramsden's successors to the self-acting engine of William Simms. Particular emphasis is given to the invention, evolution and transmission of the methods used to achieve accuracy in: dividing the wheel; ratching the teeth and matching them to the endless screw; and mounting the cutter. The procedures adopted by Ramsden and Troughton for correcting initial dividing marks are also described. 相似文献
813.
814.
随着我国天然气进口量的大幅增长,绿色环保的伴生型能源LNG冷能利用引起了广泛重视.文章从阐述LNG冷能及能源价值入手,对LNG冷能的主要利用技术进行了分析,对LNG冷能在国内的利用途径进行了探讨,提出了冷能发电的实际可行性及大规模利用的方法. 相似文献
815.
Stephen L. Clark 《西北部美国博物学家》2011,35(4)
Field and herbarium studies of Penstemon cyananthus Hook. ssp. longiflorus Pennell suggest that this taxon be elevated to species rank. 相似文献
816.
Small mammal populations inhabiting radioactive waste disposal areas could be important vectors of contaminant redistribution, given sufficiently high numbers. Earlier studies conducted at the Subsurface Disposal Area (SDA) in southeastern Idaho found small mammal densities equaling or exceeding densities in native habitat. Our live-trapping study was conducted in 1988 and 1989 to assess the role of edge habitat (where SDA crested wheatgrass [ Agropyron cristatum ] plantings and native sagebrush habitat are separated by an earthen dike) in facilitating use of this highly modified site by small mammals. Small mammals had a significantly greater density in SDA edge habitat than in the interior. Total density of small mammals and immediately around the SDA appeared to be less variable over time than density in native sagebrush habitat for years when data were available. This phenomenon was largely attributable to steady or increasing SDA population densities of the most common species, Peromyscus maniculatus and Perognathus parvus , during 1988-89, when most small mammal species had below-average densities in surrounding areas. The variety of foraging options in edge habitat may have allowed these relatively opportunistic species to avoid widespread population declines associated with drought years in 1988-89. Movements by P. manicualtus across the boundary were common, suggesting that this species did indeed utilize both habitat types. Preferences for edge habitat could potentially be used to formulate strategies that reduce use of waste site by small mammals. 相似文献
817.
We examined attributes of pi?on pine ( Pinus edulis ) associated with the probability of infestation by pi?on ips ( Ips confuses ) in an outbreak in the Coconino National Forest, Arizona. We used data collected from 87 plots, 59 infested and 28 uninfested, and a logistic regression approach to estimate the probability of infestation based on plot and tree-level attributes. Pi?on pine stand density index was a good predictor of the likelihood of infestation by pi?on ips at the plot level, and a cross-validation analysis confirmed that the model correctly classified 82% of the cases. Diameter at root collar and pi?on dwarf mistletoe infestation level were good predictors of individual tree infestation, and a cross-validation analysis indicated that the model correctly classified 72% of the cases. Results suggest that the occurrence of pi?on ips infestations may be related to stress factors associated with increased stocking and pi?on dwarf mistletoe infestations. 相似文献
818.
Five additional species of wood rotting basidiomycetes on Arizona junipers are described and illustrated. All cause a white rot of dead, fallen trees. Leptosporomyces juniperinus is proposed as a new species. Vararia fibra is reported from the United States for the first time. 相似文献
819.
Lewisia kelloggii has been understood as a rare plant with a disjunct range in California and Idaho. Examination of herbarium specimens and analysis of isozymes in 6 Idaho and 7 California populations revealed consistent differences between plants of the 2 states. Fixed differences in alleles at 2 loci (AAT2 and PGI1) distinguished Idaho from California plants. Genetic identities based on isozymes between Idaho and California populations averaged 0.58, lower than the average for congeneric plant species. Idaho plants were smaller than most California plants, but California plants were variable. The most consistent morphological difference between Idaho and California specimens was the difference in the number of glands on the margins of bracts and sepals. Idaho plants had 0 (-5) pink glands on each margin of these organs, all on teeth near the tips. In California plants these organs had 12-25 glands on each margin, the distal ones elevated on teeth and the proximal ones sessile. We recognize the Idaho plants as a new species, L. sacajaweana , and retain the name L. kelloggii for the California populations. 相似文献
820.
给出了非参数Bayesian 中的Beta 过程的2个性质,并证明了在考虑非参数Bayesian 时,用Beta 过程和Beta-Stacy 过程作先验是等价的. 相似文献