首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6篇
  免费   0篇
海洋学   3篇
天文学   2篇
自然地理   1篇
  2018年   1篇
  2011年   1篇
  2008年   2篇
  2007年   1篇
  1998年   1篇
排序方式: 共有6条查询结果,搜索用时 31 毫秒
1
1.
Successful scaling of agricultural development strategies is fundamental to increased production and yields, yet targeting efforts frequently fail to fully consider the underlying biophysical drivers of agricultural marginality, particularly at fine spatial resolutions. We present a heuristic for intelligent targeting, utilizing remotely sensed information to identify the intersection between marginal conditions for performance of a staple crop and the optimal niche for technologies that improve crop performance. Here, we explore the geographic potential of maize diversification with pigeonpea, a crop with soil productivity enhancing properties. Overall, 79 percent of agricultural land in Malawi exhibits climate conditions optimal for pigeonpea cultivation and, in total, approximately 51 percent of Malawian maize-based farming is expected to receive some benefit from pigeonpea integration, with 9 percent receiving predictable and substantial benefits. These findings illustrate the geographic scaling potential of pigeonpea in Malawi and provide direction for informed pigeonpea deployment and market development across the country.  相似文献   
2.
Abstract– Shock recovery experiments were performed with an explosive set‐up in which three types of microorganisms embedded in various types of host rocks were exposed to strong shock waves with pressure pulse lengths of lower than 0.5 μs: spores of the bacterium Bacillus subtilis, Xanthoria elegans lichens, and cells of the cyanobacterium Chroococcidiopsis sp. 029. In these experiments, three fundamental parameters were systematically varied (1) shock pressures ranging from 5 to 50 GPa, (2) preshock ambient temperature of 293, 233 and 193 K, and (3) the type of host rock, including nonporous igneous rocks (gabbro and dunite as analogs for the Martian shergottites and chassignites, respectively), porous sandstone, rock salt (halite), and a clay‐rich mineral mixture as porous analogs for dry and water‐saturated Martian regolith. The results show that the three parameters have a strong influence on the survival rates of the microorganisms. The most favorable conditions for the impact ejection from Mars for microorganisms would be (1) low porosity host rocks, (2) pressures <10–20 GPa, and (3) low ambient temperature of target rocks during impact. All tested microorganisms were capable of surviving to a certain extent impact ejection in different geological materials under distinct conditions.  相似文献   
3.
Corkwing wrasse (Symphodus melops L.), a protogynous, non-migratory lipfish species, living close to rocky shores was chosen as an indicator species for the monitoring of biological effects of contaminants. Fish were caught by local fisherman at the Norwegian west coast in fjord sites within the framework of the EU BEEP project. The sites represented different point source impacts of (I) copper (a former copper mine), (II) polycyclic aromatic hydrocarbons (PAHs, aluminium smelter discharge), (III) formaldehyde plus PAHs (kelp-factory and influence of the aluminium smelter). Livers of wrasse were studied for histopathological alterations and compared to healthy livers of fish from a reference location. Besides liver morphology, different functional and metabolic parameters were measured to link pathological alterations to functional disorders. The integrity of the lysosomal compartment was tested by the assessment of lysosomal membrane stability (lys), and the accumulation of neutral lipids and lipofuscin. Activity and intracellular localisation of the NADPH-producing enzymes in the liver were assessed histochemically and measured by computer-assisted image analysis. Histopathological alterations were most severe at the site impacted by formaldehyde and PAHs. These findings were associated with highest tumor prevalence, lowest membrane stabilities in hepatocytes and highest accumulation rates of lipofuscin in the liver. The activities of the NADPH-producing enzymes phosphogluconate dehydrogenase (PGDH) and glucose-6-phosphate dehydrogenase (G6PDH) were significantly lower compared to unimpacted reference fish. Histopathological alterations showed clear differences dependent on the input source. Potential links between specific contaminant impact and functional and morphological disorders are discussed.  相似文献   
4.
Bacterial spores (Bacillus subtilis), cyanobacteria (Chroococcidiopsis sp.), and lichen (Xanthoria elegans) embedded in martian analogue rock (gabbro) were exposed to shock pressures between 5 and 50 GPa which is the range of pressures observed in martian meteorites. The survival of Bacillus subtilis and Xanthoria elegans up to 45 GPa and of Chroococcidiopsis sp. up to 10 GPa supports the possibility of transfer of life inside meteoroids between Mars and Earth and it implies the potential for the transfer of life from any Mars-like planet to other habitable planets in the same stellar system.  相似文献   
5.
Aldehyde dehydrogenases (ALDHs) oxidize endogeneous reactive aldehydes including lipid peroxidation products (propionaldehyde, malondialdehyde) and are also inducible by xenobiotics like DDT and TCDD. ALDHs are found in injured livers and cancers of contaminant-exposed flounder (Platichthys flesus L.) and showed identical characteristics as in hepatocellular carcinomas of rats by its cytosolic localisation, the preferential oxidation of aromatic compounds (benzaldehyde), dependency on NADP as coenzyme and sensitivity to the specific inhibitor disulfiram. Image analysis showed increased activity of NADP-dependent benzaldehyde dehydrogenase localised in a few cells of early eosinophilic foci and in basophilic adenomas, carcinomas and their invasively growing protrusions (satellites). Disulfiram sensitivity to differentiate between the xenobiotic-inducible isozyme and the tumor-specific isozyme in rats was highest in the early stages of carcinogenesis in the liver of fish. Moderate disulfiram inhibition was observed in non-neoplastic and extrafocal tissue. In neoplastic livers of flounder from contaminated areas (Elbe estuary), hepatocytes in early stages of carcinogenesis were best protected against accumulation of toxic aldehydes by increased activity of the specific tumor-associated isozyme.  相似文献   
6.
Every day new extraordinary properties of nanoparticles (a billionth of a meter) are discovered and worldwide millions are invested into nanotechnology and nanomaterials. Risks to marine organisms are still not fully understood and biomarkers to detect health effects are not implemented, yet. We used the filter feeding blue mussel as a model to analyse uptake and effects of nanoparticles from glass wool, a new absorbent material suggested for use in floating oil spill barriers. In both, gills and hepatopancreas we analysed uptake of nanomaterials by transmission electronmicroscopy (TEM) in unstained ultrathin sections over a period of up to 16 days. Lysosomal stability and lipofuscin content as general indicators of cellular pathology and oxidative stress were also measured. As portals of uptake, diffusion and endocytosis were identified resulting in nanoparticle accumulation in endocytotic vesicles, lysosomes, mitochondria and nuclei. Dramatic decrease of lysosomal membrane stability occurred after 12h of exposure. Lysosomal damage was followed by excessive lipofuscin accumulation indicative of severe oxidative stress. Increased phagocytosis by granulocytes, autophagy and finally apoptosis of epithelial cells of gills and primary and secondary digestive tubules epithelial cells indicated progressive cell death. These pathological responses are regarded as general indices of toxic cell injury and oxidative stress. By the combinational use of biomakers with the ultrastructural localisation of nanoparticle deposition, final evidence of cause-effect relationships is delivered.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号