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排序方式: 共有1182条查询结果,搜索用时 62 毫秒
981.
Andres M. Gomez Anthony C. Yannarell Gloria Cadavid-Restrepo 《Soil biology & biochemistry》2011,43(6):1275-1284
A combination of culture-dependent and culture-independent methods was used to assess bacterial diversity at different depths within a former solid waste dump in Medellín, Colombia. Sampling sites included a densely populated area, which is built upon 40 m of solid waste (domestic, industrial, agricultural, and medical). The soil and leachate contain high levels of contaminants and the natural soil is highly disturbed with solid anthropogenic materials, disrupting natural aggregation and resulting in a loose, porous matrix with irregular aggregate structure. The unusual physical structure and contaminant levels at the site made it unclear if the indigenous bacterial community would possess the complexity commonly observed for natural soils, and thus may limit potential for remediating the site using monitored natural attenuation. Bacterial diversity patterns were determined through 16S-TTGE and T-RFLP at depths of 0, 10, 20 and 30 m. Abundance and diversity patterns, as estimated by number and intensity of terminal restriction fragments and TTGE bands, varied among the 4 different depths, showing more complex patterns in deeper samples (20 and 30 m), which also contained greater concentrations of organic carbon. General diversity patterns were dominated by the phylum Proteobacteria (λ, β, and α divisions). These findings were reinforced by analysis of the culturable fraction able to use n-hexadecane as sole carbon source, in which the genera Acinetobacter sp. (λ-Proteobacteria) was dominant. This research offers new clues regarding bacterial diversity patterns through different depths in polluted environments with unique physicochemical conditions, suggesting that bacterial diversity profiles may be highly influenced by the nature of pollutants present. Additionally, results imply that the culturable fraction at the site has a very important role in the community. 相似文献
982.
De Lucca AJ Heden LO Ingber B Bhatnagar D 《Journal of agricultural and food chemistry》2011,59(13):6933-6939
Wheat ( Triticum spp.) histones H1, H2, H3, and H4 were extracted, and H1 was further purified. The effect of these histones on specific fungi that may or may not be pathogenic to wheat was determined. These fungi included Aspergillus flavus , Aspergillus fumigatus , Aspergillus niger , Fusarium oxysporum , Fusarium verticillioides , Fusarium solani , Fusarium graminearum , Penicillium digitatum , Penicillium italicum , and Greeneria uvicola . Non-germinated and germinating conidia of these fungi were bioassayed separately. The non-germinated and germinating conidia of all Fusarium species were highly susceptible to the mixture (H1-H4) as well as pure H1, with viability losses of 99-100% found to be significant (p < 0.001) at ≤10 μM or less for the histone mixture and pure H1. F. graminearum was the most sensitive to histone activity. The histones were inactive against all of the non-germinated Penicillium spp. conidia. However, they significantly reduced the viability of the germinating conidia of the Penicillium spp. conidia, with 95% loss at 2.5 μM. Non-germinated and germinating conidia viability of the Aspergillus spp. and G. uvicola were unaffected when exposed to histones up to 10 μM. Results indicate that Fusarium spp. pathogenic to wheat are susceptible to wheat histones, indicating that these proteins may be a resistance mechanism in wheat against fungal infection. 相似文献
983.
A variety of thermal approaches are used to estimate sap flux density in stems of woody plants. Models have proved valuable tools for interpreting the behavior of heat pulse, heat balance and heat field deformation techniques, but have seldom been used to describe heat transfer dynamics for the heat dissipation method. Therefore, to better understand the behavior of heat dissipation probes, a model was developed that takes into account the thermal properties of wood, the physical dimensions and thermal characteristics of the probes, and the conductive and convective heat transfer that occurs due to water flow in the sapwood. Probes were simulated as aluminum tubes 20 mm in length and 2 mm in diameter, whereas sapwood, heartwood and bark each had a density and water fraction that determined their thermal properties. Base simulations assumed a constant sap flux density with sapwood depth and no wounding or physical disruption of xylem beyond the 2 mm diameter hole drilled for probe installation. Simulations across a range of sap flux densities showed that the dimensionless quantity k [defined as (ΔT(m) -ΔT)/ΔT, where ΔT(m) is the temperature differential (ΔT) between the heated and unheated probe under zero-flow conditions] was dependent on the thermal conductivity of the sapwood. The relationship between sap flux density and k was also sensitive to radial gradients in sap flux density and to xylem disruption near the probe. Monte Carlo analysis in which 1000 simulations were conducted while simultaneously varying thermal conductivity and wound diameter revealed that sap flux density and k showed considerable departure from the original calibration equation used with this technique. The departure was greatest for variation in sap flux density typical of ring-porous species. Depending on the specific combination of thermal conductivity and wound diameter, use of the original calibration equation resulted in an 81% under- to 48% overestimation of sap flux density at modest flux rates. Future studies should verify these simulations and assess their utility in estimating sap flux density for this widely used technique. 相似文献
984.
Recurrent constipation is a common problem in cats. Laxatives often are the cornerstone for management of recurrent constipation; however, there is a paucity of published research on laxative use in cats. This study investigated the safety and palatability of polyethylene glycol (PEG3350) in normal cats. All cats consumed the PEG3350 laxative for 4 weeks without changes in weight or food intake. In all cats soft stools were achieved. Effective doses varied widely in experimental cats, so individualized dosing is important. Mild, non-clinical hyperkalemia was noted although the cause is unknown. 相似文献
985.
Arendt AA 《Science (New York, N.Y.)》2011,332(6033):1044-1045
986.
Dueber EC Schoeffler AJ Lingel A Elliott JM Fedorova AV Giannetti AM Zobel K Maurer B Varfolomeev E Wu P Wallweber HJ Hymowitz SG Deshayes K Vucic D Fairbrother WJ 《Science (New York, N.Y.)》2011,334(6054):376-380
Inhibitor of apoptosis (IAP) proteins are negative regulators of cell death. IAP family members contain RING domains that impart E3 ubiquitin ligase activity. Binding of endogenous or small-molecule antagonists to select baculovirus IAP repeat (BIR) domains within cellular IAP (cIAP) proteins promotes autoubiquitination and proteasomal degradation and so releases inhibition of apoptosis mediated by cIAP. Although the molecular details of antagonist-BIR domain interactions are well understood, it is not clear how this binding event influences the activity of the RING domain. Here biochemical and structural studies reveal that the unliganded, multidomain cIAP1 sequesters the RING domain within a compact, monomeric structure that prevents RING dimerization. Antagonist binding induces conformational rearrangements that enable RING dimerization and formation of the active E3 ligase. 相似文献
987.
988.
989.
Gaunt MC Carr AP 《The Canadian veterinary journal. La revue veterinaire canadienne》2011,52(5):497-500
Fresh fecal samples from 124 apparently healthy dogs and 333 random source canine fecal samples from dog walking areas were analyzed by centrifuged flotation in Sheather's solution to determine the prevalence of gastrointestinal parasites in dogs from Saskatoon, Saskatchewan. Fecal flotation was positive in 4.4% of samples. Roundworm species were found in 1.5% of samples, hookworm species were found in 0.4% of samples, whipworm species were found in 0.7%, Strongyloides spp. were found in 0.6%, Giardia spp., Cystoisospora spp., and Alaria spp. were found in 0.4% of samples. 相似文献
990.
The risk of individuals becoming infected during an epidemic of infectious disease can vary as the disease progresses. Monitoring this risk may provide information about the dynamics of transmission. This study describes the epidemic curve for an epidemic of equine influenza (EI) in a closed population of horses predominantly immunologically na?ve to EI at a 3-day event at Morgan Park in southern Queensland, Australia. The hazard function suggested that a subset of horses were at reduced risk of becoming infected. This highlights the importance, when modelling infectious disease in populations, of considering possible differences in the risk of infection among subgroups in the population. 相似文献