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排序方式: 共有380条查询结果,搜索用时 15 毫秒
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Physiological functions of mineral macronutrients 总被引:6,自引:0,他引:6
Frans JM Maathuis 《Current opinion in plant biology》2009,12(3):250-258
94.
The realized species richness of tropical forests cannot yet be reliably mapped at a regional scale due to lack of systematically collected data. An estimate of the potential species richness (PSR), however, can be produced through the use of species distribution modelling. PSR is interpretable as a climatically determined upper limit to observed species richness. We mapped current PSR and future PSR under climate change scenarios for Mesoamerica by combining the spatial distributions of 2000 tree species as predicted by generalized additive models built from herbaria records and climate layers. An explanatory regression tree was used to extract conditional rules describing the relationship between PSR and climate. The results were summarized by country, ecoregion and protected area status in order to investigate current and possible future variability in PSR in the context of regional biodiversity conservation. Length of the dry season was found to be the key determinant of PSR. Protected areas were found to have higher median PSR values than unprotected areas in most of the countries within the study area. Areas with exceptionally high PSR, however, remain unprotected throughout the region. Neither changes in realized species richness nor extinctions will necessarily follow changes in modelled PSR under climate change. However model output suggests that an increase in temperature of around 3°C, combined with a 20 percent decrease in rainfall could lead to a widespread reduction of around 15 percent of current PSR, with values of up to 40 percent in some moist lower montane tropical forests. The modelled PSR of dry forest ecoregions was found to be relatively stable. Some cooler upper montane forests in northern Mesoamerica, where few species of tropical origin are currently found, may gain PSR if species are free to migrate. 相似文献
95.
Andrew RJ Mitchell Philip Roberts Jonas Eichhöfer Jonathan Timperley Oliver JM Ormerod 《Cardiovascular ultrasound》2004,2(1):1-4
Percutaneous coronary intervention can be associated with distal embolization of thrombotic material causing myocardial necrosis and infarction. We discuss the role of intravascular imaging to guide the use of a distal protection device by describing the outcome of a young woman presenting with non-ST elevation myocardial infarction. Coronary angiography demonstrated an isolated minor stenosis in the proximal left anterior descending coronary artery with slight haziness beyond the lesion. Intravascular ultrasound confirmed an extensive thrombus overlying a bulky atherosclerotic plaque. A distal filter wire was therefore successfully used to reduce the risk of distal embolization. The use of intravascular ultrasound in patients presenting with acute coronary syndrome may reveal large thrombi that are difficult to image using conventional angiographic techniques. Intravascular ultrasound can therefore be used as a tool to select lesions requiring distal protection. 相似文献
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Juan Hou Anita M Charters Sam C Lee Yongjun Zhao Mona K Wu Steven JM Jones Marco A Marra Pamela A Hoodless 《BMC developmental biology》2007,7(1):92
Background
The embryonic definitive endoderm (DE) gives rise to organs of the gastrointestinal and respiratory tract including the liver, pancreas and epithelia of the lung and colon. Understanding how DE progenitor cells generate these tissues is critical to understanding the cause of visceral organ disorders and cancers, and will ultimately lead to novel therapies including tissue and organ regeneration. However, investigation into the molecular mechanisms of DE differentiation has been hindered by the lack of early DE-specific markers. 相似文献98.
Accurate prediction of protein secondary structure and solvent accessibility by consensus combiners of sequence and structure information 总被引:1,自引:0,他引:1
Gianluca Pollastri Alberto JM Martin Catherine Mooney Alessandro Vullo 《BMC bioinformatics》2007,8(1):201
Background
Structural properties of proteins such as secondary structure and solvent accessibility contribute to three-dimensional structure prediction, not only in the ab initio case but also when homology information to known structures is available. Structural properties are also routinely used in protein analysis even when homology is available, largely because homology modelling is lower throughput than, say, secondary structure prediction. Nonetheless, predictors of secondary structure and solvent accessibility are virtually always ab initio. 相似文献99.
Jian Liu Alexander W Bell John JM Bergeron Corey M Yanofsky Brian Carrillo Christian EH Beaudrie Robert E Kearney 《Proteome science》2007,5(1):3-12
Background
Tandem mass spectrometry followed by database search is currently the predominant technology for peptide sequencing in shotgun proteomics experiments. Most methods compare experimentally observed spectra to the theoretical spectra predicted from the sequences in protein databases. There is a growing interest, however, in comparing unknown experimental spectra to a library of previously identified spectra. This approach has the advantage of taking into account instrument-dependent factors and peptide-specific differences in fragmentation probabilities. It is also computationally more efficient for high-throughput proteomics studies. 相似文献100.
Oliva J Cayuela M Paya P Martinez-Cacha A Cámara MA Barba A 《Communications in agricultural and applied biological sciences》2007,72(2):181-189
The influence of six fungicides (famoxadone, fenhexamid, fluquinconazole, kresoxim-methyl, quinoxyfen, trifloxystrobin) on the yeast content in harvested grapes has been studied along with their effect on it during the wine-making process. Two treatments were carried out with authorized formulates at the manufacturer doses. The first was carried out under good agricultural practices, obeying the security times, and the second one under critical conditions, applied on the day of harvesting. The grapes were harvested two hours after the application. During the wine-making process, samples were taken at 1, 5, 12 and 20 days after the start. The levels observed in the control sample (1.9 log CFU/cm2) were similar to previous studies. The counts in all treated samples were higher than the control sample, without adverse effect of the pesticides on the yeast count even in the grapes treated on the day of harvest. As with the observations on grapes, no effect of the pesticides on the fermentation count was observed. All counts on the treated samples were higher than the control sample. The treatment on the day of harvest did not have any effect on the fermentation count, with superior results being obtained for all the pesticides. 相似文献