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排序方式: 共有117条查询结果,搜索用时 203 毫秒
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许多实验对用CsI(Tl)闪烁晶体作为探测器来寻找和探测暗物质的可行性进行了研究.本工作利用8MeV单能中子轰击CsI(Tl)晶体探测器来研究Cs核和I核的QuenchingFactor.在数据处理中,运用脉冲形状甄别(PSD)方法来分辨反冲核信号和本底信号.实验结果表明,在7keV到132keV的能区中,Quench ingFactor随着反冲核能量的减少而增加.在探测暗物质的实验中,这一性质对于CsI(Tl)晶体探测器获得较低的能量阈值是很有利的. 相似文献
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An asymptotic expansion is constructed for the double integral
as +, where f(x, y) hasa curve of stationary points in D. The first two coefficientsof the expansion are explicitly calculated. 相似文献
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WONG Henry N. C. 《中国化学》2005,23(8):1106-1108
Trimethylsilyl groups have been used in our research as a director as well as a bulky and lipophilic group in our quest for natural and non-natural molecules. 相似文献
6.
A Minor New Flavone from Scutellaria baicalensis Georgi 总被引:1,自引:0,他引:1
A new flavone,6,2′-dihydroxy-5,7,8,6′-tetramethoxyflavone,was isolated from the roots of Scutellaria baicalensis. Its structure was established on the basis of spectral evidences. 相似文献
7.
LigandscontainingelectrochemicallyresponsivecentrearegoodsubjectsforthestUdyofintfamolecularandhost-guestillteraction.Forthisreason,tYemendousamoulltsofsuchligandsandtheircomplexeshavebeensynthesized.'-'AnobservationfromthestudiesofthesecomPlexesisthattheguestionhasapermrbationonthehostcelltre.2'7-9Forexample,itwasdocumelltedthatintroductionofCo(II)ionontoN-ferrocenylmethyl-l,4,7-triazacyclononane(fcmtacn)causesapositiveshiftintheredoxpotentialofferrocenylgroupfromthatofferrocenegroupinfree… 相似文献
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H. K. WONG 《Photochemistry and photobiology》1968,7(4):377-389
Abstract— Flash-photolysis of safranine in deoxygenated 5 per cent aqueous pyridine produces a transient bleaching, which disappears by a second order process. Very probably this transient species consists of a pair of radicals or radical ions and not of the safranine in the triplet state. These radicals are also produced in chlorophyll sensitized reactions. Present results combined with previous work by us[I] indicate that the chlorophyll sensitization of safranine bleaching involves the formation of these radicals.
The direct photochemical reduction of safranine to its leuco form occurs through the intermediate formation of the radicals. The appearance and disappearance of these radicals is fast compared to the role of photochemical formation and thermal disappearance of leuco safranine. Ascorbic acid influences but is not essential to the photo-bleaching of safranine in 5 per cent aqueous pyridine. An increase in ascorbic acid concentration increases the steady-state yield of the radicals but decreases the steady-state yield of the leuco safranine. In the absence of ascorbic acid or other added substance, safranine photobleaches irreversibly in deoxygenated 5 per cent aqueous pyridine. A plausible mechanism is proposed in explanation of the direct photochemical reduction of safranine. 相似文献
The direct photochemical reduction of safranine to its leuco form occurs through the intermediate formation of the radicals. The appearance and disappearance of these radicals is fast compared to the role of photochemical formation and thermal disappearance of leuco safranine. Ascorbic acid influences but is not essential to the photo-bleaching of safranine in 5 per cent aqueous pyridine. An increase in ascorbic acid concentration increases the steady-state yield of the radicals but decreases the steady-state yield of the leuco safranine. In the absence of ascorbic acid or other added substance, safranine photobleaches irreversibly in deoxygenated 5 per cent aqueous pyridine. A plausible mechanism is proposed in explanation of the direct photochemical reduction of safranine. 相似文献
9.
过氧化物模拟酶生物传感器—二茂铁衍生物为介体 总被引:3,自引:0,他引:3
本文用三种二茂铁衍生物-双羟基乙基二茂铁、单羟基乙基二茂铁和羧基二茂铁为介体,在过氧化物模拟酶-meso-四(4-磺基苯)卟啉锰存在下,检测过氧化氢,以双羟基,单羟基乙基二茂铁为介体时,获得了良好的结果。 相似文献
10.
Saipeng?Huang Zhao?Chen Libo?Du Qiu?Tian Yangping?Liu Yuansuo?Zheng Yang?LiuEmail author 《Applied magnetic resonance》2015,46(5):489-504
The detection of free radicals and related species has attracted considerable attention in recent years due to their critical roles in physiological and pathological processes. Among the various methods for the detection of free radicals, electron spin resonance coupled with spin-trapping technique has been an effective approach for the characterization and quantification of free radicals due to its high specificity. In this study, we designed and synthesized a novel amphiphilic spin trap, 2-(diethoxyphosphoryl)-2-heptadecanyl-3,4-dihydro-2H-pyrrole-1-oxide (DEPHdPO), from 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide with a long hydrocarbon chain at the C-5 position of the pyrroline ring, providing the amphiphilic character. The free-radical-trapping ability of DEPHdPO was evaluated by capturing hydroxyl radicals (·OH), superoxide anions (\( {\text{O}}_{2}^{ \cdot - } \)), and carbon-centered free radicals in a model membrane prepared from sodium dodecyl sulfate (SDS). The results indicate that the hydrophobic hydrocarbon chain of DEPHdPO can be inserted into the inner core of SDS micelles, and the hydrophilic nitronyl functional moiety is located on the surface layer. Thus, various free radicals, including ·OH radicals, \( {\text{O}}_{2}^{ \cdot - } \) anions, and carbon-centered radicals could be site-specifically detected near the membrane surface. Moreover, DEPHdPO could be successfully located on the surface of thylakoid membranes, and the nearby photo-initiated \( {\text{O}}_{2}^{ \cdot - } \) anions could be trapped site-specifically. 相似文献