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1.
The RAINFOR database: monitoring forest biomass and dynamics   总被引:1,自引:0,他引:1  
Problem: Data from over 100 permanent sample plots which have been studied for 10–20 years need a suitable system for storage which allows simple data manipulation and retrieval for analysis. Methods: A relational database linking tree records, taxonomic nomenclature and corresponding environmental data has been built in MS Access as part of the RAINFOR project. Conclusion: The database allows flexible and long‐term use of a large amount of data: more than 100 tree plots across Amazonia, incorporating over 80 000 records of individual trees and over 300 000 total records of tree diameter measurements from successive censuses. The database is designed to enable linkages to existing soil, floristic or plant‐trait databases. This database will be a useful tool for exploring the impact of environmental factors on forest structure and dynamics at local to continental scales, and long term changes in forest ecology. As an early example of its potential, we explore the impact of different methodological assumptions on estimates of tropical forest biomass and carbon storage.  相似文献   
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The concentrations of Legionella pneumophila in cooling towers may vary considerably over short periods of time, producing significant fluctuations throughout the year. Despite genetic variability, in small geographical areas the same indistinguishable pulsed-field gel electrophoresis patterns may be shared among different cooling towers and persist over time.  相似文献   
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Contents of individual carotenoids in the fruits of Ramillete cultivar ofCapsicum annuum L. changed during ripening of recently harvested fruits or fruits stored 15 d in a dark and cool room. β-carotene and β-cryptoxanthin contents rose to a maximum and then declined, while the contents of other earotenoids rose to a rather steady level. Capsanthin was the main carotenoid which together with capsorubin were responsihle for the ripening colour.  相似文献   
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Glioblastomas (GBMs) are the most lethal primary brain tumours. Increasing evidence shows that brain tumours contain the population of stem cells, so‐called cancer stem cells (CSCs). Stem cell marker CD133 was reported to identify CSC population in GBM. Further studies have indicated that CD133 negative cells exhibiting similar properties and are able to initiate the tumour, self‐renew and undergo multilineage differentiation. GBM is a highly heterogeneous tumour and may contain different stem cell populations with different functional properties. We characterized five GBM cell lines, established from surgical samples, according to the marker expression, proliferation and differentiation potential. CD133 positive cell lines showed increased proliferation rate in neurosphere condition and marked differentiation potential towards neuronal lineages. Whereas two cell lines low‐expressing CD133 marker showed mesenchymal properties in vitro, that is high proliferation rate in serum condition and differentiation in mesenchymal cell types. Further, we compared therapy resistance capacity of GBM cell lines treated with hydroxyurea. Our results suggest that CSC concept is more complex than it was believed before, and CD133 could not define entire stem cell population within GBM. At least two different subtypes of GBM CSCs exist, which may have different biological characteristics and imply different therapeutic strategies. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
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Abstract. The ecological roles of small (1–1000 mg) predators in benthic marine systems are poorly understood. We investigated the natural history and predatory impact of one group of such mesopredators—larvae of dipteran flies in the genus Oedoparena —which prey on intertidal barnacles. We 1) quantified patterns of larval Oedoparena distribution and abundance in the Northwest Straits of Washington State, USA, 2) determined larval physiological tolerance limits in the laboratory, and 3) conducted a manipulative field experiment to assess the role of microhabitat temperature on predation rates in Oedoparena . Members of Oedoparena in Washington are univoltine, with peak larval abundance in late spring and early summer. Infestation frequencies in the barnacles Balanus glandula and Chthamalus dalli were as high as 22% and 35%, respectively. In laboratory studies, larvae of O . glauca were able to tolerate temperatures up to 37°C; however, this temperature is often exceeded in high intertidal habitats. In a field manipulation using experimental shades, we demonstrate that the alleviation of physiological stress greatly increased the abundance of larvae of Oedoparena spp. As a result of increased larval densities under shades, adult B. glandula mortality increased from 5% to nearly 30%, and C. dalli mortality increased from less than 20% to over 60%. Because high intertidal barnacles serve as food and habitat for a diverse array of species, Oedoparena spp. have the potential to play a major role in structuring high intertidal communities, particularly in cooler microhabitats.  相似文献   
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Plant transformation has had a deep impact on several aspects of basic and applied research. Genetic transformation has offered new opportunities compared to traditional breeding practises since it allows the integration into a host genome of specific sequences leading to a strong reduction of the casualness of gene transfer. One of the first target areas was plant protection against pests, pathogens and environmental stresses while the recent plant engineering programs are aimed at increasing food quality, in particular at increasing nutritional characteristics of food crops. Moreover, transgenic plants, tissue or cell cultures represent an attractive biological system for producing heterologous proteins since they offer economic and qualitative benefits. High yield production can be obtained and large-scale commercial production will take advantage of the existing infrastructure for crop cultivation, processing and storage. There are also qualitative benefits since protein synthesis secretion and post-translational modifications are similar in plants and animal cells. There are no human viral pathogens harboured by plants: thus, especially for pharmaceuticals, plants represent the safer production system. Plant transformation has become an essential instrument also for basic research, in particular for the functional characterisation of genes identified by sequencing of whole genomes. Large collections of insertion mutants have been obtained in the model plant Arabidopsis to provide a high level of genome saturation that means 95% chance of inactivating any gene at least once. To instil greater public confidence in modern plant biotechnology recent advances have already been made to overcome the potential risks for human health and environment.  相似文献   
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Summer dynamics of the deep chlorophyll maximum in Lake Tahoe   总被引:3,自引:0,他引:3  
Vertical profiles of chlorophyll and phytoplankton biomass weremeasured in Lake Tahoe from July 1976 through April 1977. Adeep chlorophyll maximum (DCM) persisted during summer and earlyautumn (July—October) near 100 m, well below the mixedlayer and at the upper surface of the nitracline. The DCM coincidedwith the phytoplankton biomass maximum as determined from cellcounts. In addition, the composition of the phytoplankton assemblagewas highly differentiated with respect to depth. Cyclotellastelligera was the predominant species in the mixed layer whilethe major species in the DCM layer included C. ocellata andseveral green ultraplanktonic species. In situ cell growth playsa substantial role in maintaining the DCM, but sinking of cellsfrom shallower depths and zooplankton grazing above the DCMmay contribute to the maintenance of the DCM. Calculations supportthe interpretation that the summer DCM persists at the boundarybetween an upper, nutrient-limited phytoplankton assemblageand a deeper, light-limited assemblage.  相似文献   
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The present report deals with the alterations produced by cis-diamminedichloroplatinum (II) (DDP), and 2 of its analogs: cis-Pt(II)(tranylcypromine)2Cl2 and cis-Pt(II)(benzothiazole)2Cl2 in cultured epimastigote forms of Trypanosoma cruzi. Studies have been performed at the ultrastructural level and the inhibitory effect of these complexes on macromolecule synthesis, evaluated by 3H-thymidine, 3H-uridine, and 3H-leucine incorporation, has been investigated. DDP at concentrations of 50 and 100 micrograms/ml does not inhibit significantly the incorporation of radioactive precursors, but a clear decrease was observed with the 2 analogs. Eight hours of treatment at a concentration of 10 micrograms/ml rendered in all 3 cases an increase in autophagic vacuoles and lipids as well as an abnormal condensation of the nucleus chromatin.  相似文献   
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