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531.
532.
Ohne Zusammenfassung 相似文献
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We consider in this paper the origin and effect of those sources of noise present in optical fibre backscatter systems which employ large-area semiconductor laser diodes and avalanche photodetectors. Source noise due to the filamentary lasing action of the photodiodes is shown to dominate the near-end performance. The clear superiority of two-point processing over boxcar integration in the presence of source noise is demonstrated. 相似文献
535.
P Begley B E Foulger P D Jeffery R M Black R W Read 《Journal of chromatography. A》1986,367(1):87-101
A sensitive and selective method has been developed for the simultaneous detection in blood of eleven trichothecenes of widely varying polarity. The procedure involved precipitation of blood proteins with acetone followed by a clean-up using reversed-phase Sep-Pak C18 cartridges. The extracted trichothecenes were derivatised as their pentafluoropropionyl esters, separated using capillary gas chromatography and detected using electron-capture negative ion chemical ionisation with methane reagent gas and selected-ion monitoring. Optimum sensitivity and selectivity were obtained using low source temperatures (60 degrees C indicated) and high source pressures (1 Torr indicated). Detection limits on 1-ml blood samples were in the range 0.1-5 ppb. The method was readily adaptable to the detection of other trichothecenes. A protocol was used which minimised the risk of cross-contamination. The method was validated in collaborative studies by the successful analysis of 42 blood samples spiked and submitted blind by two independent laboratories for analysis. 相似文献
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537.
In this work, the conditions required to transform quantum-confined cadmium sulfide (Q-CdS) nanoparticles stabilized by calf thymus deoxyribonucleic acid from deep trap photoluminescent states to band edge-type luminescence are probed. The presence of fivefold excess sulfide relative to cadmium concentration during cluster synthesis, followed by mild heating at 80°C, results in the desired transformation of the Q-CdS emission spectrum. We also indirectly analyze the accompanying structural changes in the polymeric stabilizer, accomplished in this case by use of well-known spectrofluorometric methods with the dyes ethidium bromide and trisphenanthroline ruthenium(II). 相似文献
538.
Background
Clinical spinal cord injury in domestic dogs provides a model population in which to test the efficacy of putative therapeutic interventions for human spinal cord injury. To achieve this potential a robust method of functional analysis is required so that statistical comparison of numerical data derived from treated and control animals can be achieved. 相似文献539.
Michael P. Crockett Alexander S. Wong Bo Li Jeffery A. Byers 《Angewandte Chemie (International ed. in English)》2020,59(13):5392-5397
Suzuki–Miyaura cross‐coupling reactions between a variety of alkyl halides and unactivated aryl boronic esters using a rationally designed iron‐based catalyst supported by β‐diketiminate ligands are described. High catalyst activity resulted in a broad substrate scope that included tertiary alkyl halides and heteroaromatic boronic esters. Mechanistic experiments revealed that the iron‐based catalyst benefited from the propensity for β‐diketiminate ligands to support low‐coordinate and highly reducing iron amide intermediates, which are very efficient for effecting the transmetalation step required for the Suzuki–Miyaura cross‐coupling reaction. 相似文献
540.
Valiallah Hosseininasab Dr. Alison C. McQuilken Dr. Abolghasem Bakhoda Dr. Jeffery A. Bertke Prof. Dr. Qadir K. Timerghazin Prof. Dr. Timothy H. Warren 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):10946-10950
S-Nitrosothiols (RSNOs) serve as air-stable reservoirs for nitric oxide in biology. While copper enzymes promote NO release from RSNOs by serving as Lewis acids for intramolecular electron-transfer, redox-innocent Lewis acids separate these two functions to reveal the effect of coordination on structure and reactivity. The synthetic Lewis acid B(C6F5)3 coordinates to the RSNO oxygen atom, leading to profound changes in the RSNO electronic structure and reactivity. Although RSNOs possess relatively negative reduction potentials, B(C6F5)3 coordination increases their reduction potential by over 1 V into the physiologically accessible +0.1 V vs. NHE. Outer-sphere chemical reduction gives the Lewis acid stabilized hyponitrite dianion trans-[LA-O-N=N-O-LA]2− [LA=B(C6F5)3], which releases N2O upon acidification. Mechanistic and computational studies support initial reduction to the [RSNO-B(C6F5)3] radical anion, which is susceptible to N−N coupling prior to loss of RSSR. 相似文献