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661.
Adam Sobkowiak Tore Ericsson Kristina Edström Torbjörn Gustafsson Fredrik Björefors Lennart Häggström 《Hyperfine Interactions》2014,226(1-3):229-236
The tavorite polymorph of LiFeSO4F has attracted considerable attention as a cathode material for lithium ion batteries due to interesting structural and electrochemical characteristics. For the analysis of such iron-based electrode materials, Mössbauer spectroscopy has become an important and highly useful tool. In this work, we perform a detailed Mössbauer study of pristine tavorite LiFeSO4F prepared by an optimized synthesis in tetraethylene glycol as reaction media. In contrast to many reported results, we demonstrate the use of an asymmetric fitting model for the inner doublet of the spectrum, which is coupled to the structural properties of the compound. Moreover, we discuss a new approach of ascribing the Fe2?+?-doublets to the two distinct crystallographic iron sites of tavorite LiFeSO4F by comparing the Mössbauer signal intensities with the expected f-factors for the corresponding iron atom. 相似文献
662.
Nikola Burić Ines Grozdanović Kristina Todorović Nebojša Vasović 《Journal of statistical physics》2011,145(1):175-186
Influence of small time-delays in coupling between noisy excitable systems on the coherence resonance and self-induced stochastic
resonance is studied. Parameters of delayed coupled deterministic excitable units are chosen such that the system has only
one attractor, namely the stationary state, for any value of the coupling and the time-lag. Addition of white noise induces
qualitatively different types of coherent oscillations, and we analyzed the influence of coupling time-delay on the properties
of these coherent oscillations. The main conclusion is that time-lag τ≥1, but still smaller than the refractory period, and sufficiently strong coupling drastically change signal to noise ratio
in the quantitative and qualitative way. An interval of noise values implies quite large signal to noise ratio and different
types of noise induced coherence are greatly enhanced. We also observed coincident spiking for small noise intensity and time-lag
proportional to the inter-spike interval of the coherent spike trains. On the other hand, time-lags τ<1 and/or weak coupling induce negligible changes in the properties of the stochastic coherence. 相似文献
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664.
An approximate mean field model of an ensemble of delayed coupled stochastic Hindmarsh-Rose bursting neurons is constructed and analyzed. Bifurcation analysis of the approximate system is performed using numerical continuation. It is demonstrated that the stability domains in the parameter space of the large exact systems are correctly estimated using the much simpler approximate model. 相似文献
665.
Williams KM 《Journal of AOAC International》2004,87(6):1380-1382
666.
The readily available N-Boc-protected delta-amino alpha,beta-unsaturated gamma-keto ester 1 was diastereoselectively reduced to the corresponding alcohols 2 and 3, using boron- and aluminum-based reducing reagents. Reduction reactions were successful and resulted in anti/syn ratios of alcohols of >95:5 (80% yield), using LiAlH(O-t-Bu)(3) in EtOH at -78 degrees C under chelation control, and 5:95 (98% yield), using NB-Enantride in THF at -78 degrees C under Felkin-Anh control. 相似文献
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670.
Ma S Caprioli RM Hill KE Burk RF 《Journal of the American Society for Mass Spectrometry》2003,14(6):593-600
Characterization of reduced and alkylated rat selenoprotein P by mass spectrometry yielded selenopeptides from which one or more selenium atoms were missing. Predicted selenopeptide mass peaks were accompanied by peaks corresponding to the conversion of one or more selenocysteine residues to dehydroalanine(s). Experiments were carried out to determine whether this loss of selenium occurred in vitro. A selenopeptide was isolated that contained two selenocysteine residues that were both in selenide-sulfide linkages with cysteine residues. After the peptide had been reduced and alkylated, in addition to the predicted mass peak with both selenocysteine residues present, two mass peaks were detected at positions expected for conversion of one and two selenocysteine residues of this selenopeptide to dehydroalanine residues, which was confirmed by tandem mass spectrometry. Similar findings were obtained from a study of another selenoprotein, rat plasma glutathione peroxidase. These results indicate that selenium atoms are lost from selenoproteins during purification and characterization. The loss of selenium from selenoproteins is probably through the mechanism of oxidation of selenocysteine residue to selenoxide followed by syn-beta-elimination of selenenic acid during sample processing. 相似文献