排序方式： 共有41条查询结果，搜索用时 484 毫秒
1.
2.
3.
Experimental infection of normal and immunosuppressed pigs with Pseudomonas pseudomallei 总被引：1，自引：0，他引：1
AD THOMAS JC FORBES-FAULKNER TL D''ARCY JH NORTON D HOFFMANN 《Australian veterinary journal》1990,67(2):43-46
A single dose of 5 x 10(8) bacilli of Pseudomonas pseudomallei by intratracheal injection resulted in acute (21 cases) or chronic (19 cases) melioidosis in 40 of 48 pigs. Fifteen (10 acute and 5 chronic) had been immunosuppressed by cyclophosphamide before inoculation. The major clinical signs were initial fever, marked neutrophilia and, in the acute cases, respiratory distress. There were no signs of the nasal and ocular discharge, paresis or diarrhoea seen in acute cases in south-east Asia. The cyclophosphamide treatment caused a significant decrease in the neutrophil count by 7 d after inoculation in all 15 immunosuppressed pigs, and all were culture positive at necropsy. Eight of the 33 non-treated pigs were culture negative at necropsy. Pigs overcoming the initial phase of infection had more abscess-like nodules that were bacteriologically sterile at necropsy than the pigs with acute cases of melioidosis. P. pseudomallei was isolated predominantly from the spleen, lungs and the injection site. Although only one strain was used in this study, it is likely that Australian strains of P. pseudomallei are not as virulent as the south-east Asian isolates. 相似文献
4.
1. Six major river systems flow west to east across the Kruger National Park (South Africa). All arise outside the western boundary of the KNP, and are outside the jurisdiction of the Park authorities. 2. Growing human populations to the west of the Park are placing increasing demands on the water resources of these rivers, and a variety of artificial changes threaten the ecological integrity of the rivers. 3. As a result, the Luvuvhu and Letaba Rivers to the north no longer have a perennial flow, while the flow of the Crocodile River on the southern boundary of the Park has been regulated to a more constant regime due to irrigation demands. The Letaba, Olifants, and Crocodile Rivers all receive diverse pollutants. The Sabie River, at present the least disturbed system, and biologically the most diverse in South Africa, is threatened with multiple regulation within the next five years. 4. The paper describes the development of initial protocols for the assessment of instream flow needs for the Luvuvhu and Sabie Rivers. These methods require an extension of existing methods developed in the USA to ensure the maintenance of ecological processes, rather than the maintenance of single target species. 5. Two methods are described: one that identifies the consumptive and non-consumptive water requirements of the rivers, adding all consumptive to the limiting non-consumptive quantity to give a base-flow requirement. 6. A second method uses a conservation status model to assess the ecological consequences of flow reductions generated through a hydrological model, in response to different impoundment conditions. 7. Both methods are successful in appropriate circumstances, but we conclude that the proposed impoundment and agricultural development of the Sabie River, in particular, is an inappropriate use of this unique resource, and that the catchment would be more advantageously developed for tourism, recreation, and nature conservation. 相似文献
5.
Côté AP Benin AI Ockwig NW O'Keeffe M Matzger AJ Yaghi OM 《Science (New York, N.Y.)》2005,310(5751):1166-1170
Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid {C6H4[B(OH)2]2} and hexahydroxytriphenylene [C18H6(OH)6]. Powder x-ray diffraction studies of the highly crystalline products (C3H2BO)6.(C9H12)1 (COF-1) and C9H4BO2 (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P6(3)/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500 degrees to 600 degrees C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively). 相似文献
6.
Interpenetration (catenation) has long been considered a major impediment in the achievement of stable and porous crystalline structures. A strategy for the design of highly porous and structurally stable networks makes use of metal-organic building blocks that can be assembled on a triply periodic P-minimal geometric surface to produce structures that are interpenetrating-more accurately considered as interwoven. We used 4,4',4"-benzene-1,3,5-triyl-tribenzoic acid (H(3)BTB), copper(II) nitrate, and N,N'-dimethylformamide (DMF) to prepare Cu(3)(BTB)(2)(H(2)O)(3).(DMF)(9)(H(2)O)(2) (MOF-14), whose structure reveals a pair of interwoven metal-organic frameworks that are mutually reinforced. The structure contains remarkably large pores, 16.4 angstroms in diameter, in which voluminous amounts of gases and organic solvents can be reversibly sorbed. 相似文献
7.
A global view of gene activity and alternative splicing by deep sequencing of the human transcriptome 总被引：6，自引：0，他引：6
8.
9.
RL Westemeier JD Brawn SA Simpson TL Esker RW Jansen JW Walk EL Kershner JL Bouzat KN Paige 《Science (New York, N.Y.)》1998,282(5394):1695-1698
Effects of small population size and reduced genetic variation on the viability of wild animal populations remain controversial. During a 35-year study of a remnant population of greater prairie chickens, population size decreased from 2000 individuals in 1962 to fewer than 50 by 1994. Concurrently, both fitness, as measured by fertility and hatching rates of eggs, and genetic diversity declined significantly. Conservation measures initiated in 1992 with translocations of birds from large, genetically diverse populations restored egg viability. Thus, sufficient genetic resources appear to be critical for maintaining populations of greater prairie chickens. 相似文献
10.