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排序方式: 共有93条查询结果,搜索用时 31 毫秒
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LoSecco JM Bionta RM Biewitt G Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(21):2299-2301
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Abstract— De-etiolation of maize seedlings reduces their sensitivity for red light potentiation of rapid chlorophyll accumulation in white light. An earlier proposal (Raven and Spruit, 1973) attributes this to migration of the far-red absorbing form of phytochrome (Pfr) to receptors essential for chlorophyll synthesis, thereby increasing the local Pfr/total phytochrome (Ptot)ratio. We have studied etioplasts as possible loci for such P(r receptors. The level of spectrophotometric phytochrome in purified etioplasts isolated from red preirradiated maize seedlings was higher than that of dark grown plants. The difference was marginally significant, however. We argue that migration of a fraction of cytoplasmic Pfr to the etioplasts, too small to be spectrophotometically demonstrable, could still meet the requirements of the model. Dark destruction of bulk spectrophotometric Pfr following saturating red irradiation of seedlings is not paralleled by a decrease of etioplast phytochrome. the latter remaining essentially constant over long periods. On the other hand, the potentiating effect of red light in intact seedlings is still partially reversible by far red light even after 24 h of darkness when destruction of bulk Pfr is complete. Since this demonstrates persistent presence of Pfr active in potentiation, we propose that at least part of this Pfr is associated with the etioplasts. 相似文献
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C. H. Gast J. C. Kraak 《International journal of environmental analytical chemistry》2013,93(4):297-312
Abstract The suitability of HPLC (normal and reversed phase adsorption) with UV or post-column reaction detection for the analysis of organomercurials was investigated systematically. The separation of organomercurials is best carried out on a reversed phase system with a C-8 bonded phase material as the stationary phase and acetonitrile-aqueous sodium bromide mixtures as the mobile phase. The precision and detection limit of the method and the efficiency of the extraction procedure were established. For the alkylmercury compounds the lowest limit of detection (80ppb) was obtained with the dithizone reaction detection and for the phenylmercury compounds with UV detection (60ppb). A chromatogram of a spiked fish (2ppmHg) and a river water sample (50ppbHg) is shown. 相似文献
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Thermally activated negative photoconductivity is observed in p-GaAs/Al0.5Ga0.5As:Be heterostructures under illumination with red light at temperatures below 6 K. As the temperature decreases, the concentration and mobility of 2D holes in the quantum well drop sharply, particularly under uniaxial compression. The phenomenon is quantitatively described under the assumption that a layer of deep donor-like traps with a low thermal activation barrier EB = 3.0 ± 0.5 meV exists at a distance of about 7 nm from the heterojunction and that this barrier does not change with strain. Presumably, the traps may be the p-type dopant Be atoms diffusing from the active layer and occupying interstitial positions. 相似文献
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John?F?StinsEmail author G?Caroline?M?van Baal Tinca?JC?Polderman Frank?C?Verhulst Dorret?I?Boomsma 《BMC neuroscience》2004,5(1):49
Background
There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function, such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task. Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks. 相似文献10.
Sakari Leino Patrick JC May Paavo Alku Lassi A Liikkanen Hannu Tiitinen 《BMC neuroscience》2007,8(1):78