In vitro activity of chloramphenicol,florfenicol and enrofloxacin against Chlamydia pecorum isolated from koalas (Phascolarctos cinereus)          下载免费PDF全文

LA Black  DP Higgins  M Govendir 《Australian veterinary journal》2015,93(11):420-423

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Defensive Metabolites from Antarctic Invertebrates: Does Energetic Content Interfere with Feeding Repellence?     

Laura Nú?ez-Pons  Conxita Avila 《Marine drugs》2014,12(6):3770-3791

Many bioactive products from benthic invertebrates mediating ecological interactions have proved to reduce predation, but their mechanisms of action, and their molecular identities, are usually unknown. It was suggested, yet scarcely investigated, that nutritional quality interferes with defensive metabolites. This means that antifeedants would be less effective when combined with energetically rich prey, and that higher amounts of defensive compounds would be needed for predator avoidance. We evaluated the effects of five types of repellents obtained from Antarctic invertebrates, in combination with diets of different energetic values. The compounds came from soft corals, ascidians and hexactinellid sponges; they included wax esters, alkaloids, a meroterpenoid, a steroid, and the recently described organic acid, glassponsine. Feeding repellency was tested through preference assays by preparing diets (alginate pearls) combining different energetic content and inorganic material. Experimental diets contained various concentrations of each repellent product, and were offered along with control compound-free pearls, to the Antarctic omnivore amphipod Cheirimedon femoratus. Meridianin alkaloids were the most active repellents, and wax esters were the least active when combined with foods of distinct energetic content. Our data show that levels of repellency vary for each compound, and that they perform differently when mixed with distinct assay foods. The natural products that interacted the most with energetic content were those occurring in nature at higher concentrations. The bioactivity of the remaining metabolites tested was found to depend on a threshold concentration, enough to elicit feeding repellence, independently from nutritional quality.  相似文献   

干旱条件下墨西哥中部高地不同耕作措施和农作物残留物管理对玉米产量和净收益的影响     

R. ROMERO-PEREZGROVAS  N. VERHULST  D. DE LA ROSA  V. HERNÁNDEZ  M. MAERTENS  J. DECKERS  B. GOVAERTS 《土壤圈》2014,24(4):476-486

In the subtropical highlands of Central Mexico, where the main crop is maize （Zea mays）, the conventional practice （CP） involves tillage, monoculture and residue removal, leading to soil degradation and unsustainable use of natural resources and agricultural inputs. Conservation agriculture （CA） has been proposed as a viable alternative in the region, based on reduction in tillage, retention of adequate levels of crop residues and soil surface cover and use of crop rotation. This study began in 2009 when the highlands of Central Mexico suffered from a prolonged drought during vegetative maize growth in July-August, providing an opportunity for the on-farm comparison of CA with CP under severe drought conditions which 21 climate change models projected to become more frequent. Under dry conditions, CA resulted in higher yields and net returns per hectare as early as the first and second years after adoption by farmers. As an average of 27 plots under farmers＇ management in 2009, the maize yields were 26% higher under CA （6.3 t ha-1） than under CP （5.0 t ha-l）. 2010 was close to a normal year in terms of rainfall so yields were higher than in 2009 for both practices; in addition, the yield difference between the practices was reduced to 19% （6.8 t ha-1 for CA vs. 5.7 t ha-1 for CP）. When all the 2009 and 2010 observations were analyzed in a modified stability analysis, CA had an overall positive effect of 3 838 Mexican Pesos ha-1 （320 $US ha-1） on net return and 1.3 t ha-1 on yield. After only one to two years of adoption by farmers on their fields, CA had higher yields and net returns under dry conditions that were even drier than those predicted by the analyzed 21 climate change models under a climate change scenario, emission scenario A2.  相似文献   

Correlation of the highest-energy cosmic rays with nearby extragalactic objects     

Pierre Auger Collaboration  Abraham J  Abreu P  Aglietta M  Aguirre C  Allard D  Allekotte I  Allen J  Allison P  Alvarez C  Alvarez-Muñiz J  Ambrosio M  Anchordoqui L  Andringa S  Anzalone A  Aramo C  Argirò S  Arisaka K  Armengaud E  Arneodo F  Arqueros F  Asch T  Asorey H  Assis P  Atulugama BS  Aublin J  Ave M  Avila G  Bäcker T  Badagnani D  Barbosa AF  Barnhill D  Barroso SL  Bauleo P  Beatty J  Beau T  Becker BR  Becker KH  Bellido JA  Benzvi S  Berat C  Bergmann T  Bernardini P  Bertou X  Biermann PL  Billoir P  Blanch-Bigas O 《Science (New York, N.Y.)》2007,318(5852):938-943

Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources.  相似文献   

Flash X-ray Microscopy     

McCorkle R  Angilello J  Coleman G  Feder R  LA Placa SJ 《Science (New York, N.Y.)》1979,205(4404):401-402

Soft x-ray contact microscopy, utilizing single-shot exposures of approximately 60 nanoseconds duration in polymethyl methacrylate, has been realized with a resolution of 300 angstroms. The radiation spectrum is intense in the "window" between 23 and 44 angstroms where water is transparent compared to biological materials, and therefore permits viewing of wet samples.  相似文献   

SOIL TRANSECT CORRELOGRAMS OF NORTH OXFORDSHIRE AND THEIR INTERPRETATION   总被引：2，自引：1，他引：2  

R. WEBSTER  H. E. CUANALO DE LA C 《European Journal of Soil Science》1975,26(2):176-194

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Frequency of a FAS ligand gene variant associated with inherited feline autoimmune lymphoproliferative syndrome in British shorthair cats in New Zealand     

D Aberdein  JS Munday  KE Dittmer  RW Heathcott  LA Lyons 《New Zealand veterinary journal》2013,61(6):327-331

Abstract