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991.
借助TGA-MS技术研究了煤中的氯含量(高氯、中氯、低氯煤)对煤在燃烧时氯的析出特征的影响.MS的结果表明,HCl第一个析出峰是一个热作用过程,这部分氯是以离子状态存在于煤的内表面上,第二个HCl析出峰与煤的变质程度有关,而氯则是与煤的有机结构相连,当煤燃烧时,以HCl形式与CO2、SO2、H2O一起析出.第三个HCl析出峰是由于煤中无机氯化物而导致的. 相似文献
992.
Neurotransmitter release at many central synapses is initiated by an influx of calcium ions through P/Q-type calcium channels, which are densely localized in nerve terminals. Because neurotransmitter release is proportional to the fourth power of calcium concentration, regulation of its entry can profoundly influence neurotransmission. N- and P/Q-type calcium channels are inhibited by G proteins, and recent evidence indicates feedback regulation of P/Q-type channels by calcium. Although calcium-dependent inactivation of L-type channels is well documented, little is known about how calcium modulates P/Q-type channels. Here we report a calcium-dependent interaction between calmodulin and a novel site in the carboxy-terminal domain of the alpha1A subunit of P/Q-type channels. In the presence of low concentrations of intracellular calcium chelators, calcium influx through P/Q-type channels enhances channel inactivation, increases recovery from inactivation and produces a long-lasting facilitation of the calcium current. These effects are prevented by overexpression of a calmodulin-binding inhibitor peptide and by deletion of the calmodulin-binding domain. Our results reveal an unexpected association of Ca2+/calmodulin with P/Q-type calcium channels that may contribute to calcium-dependent synaptic plasticity. 相似文献
993.
<正>建立了一种用带有能谱仪的扫描电子显微镜(SEM-EDXA) 测定麦草细胞壁木素分布的方法。讨论了溴化、切片厚度和样品座对定量测定的影响。结果表明,溴对木素的化合不但是专一的,而且也是稳定的;利用薄切片背散射,吸收和荧光对定量测定的影响可以忽略,空间分辩力也可得到弥补。因此,SEM-EDXA技术以较高的准确度提供了定量测定木素分布的信息。 相似文献
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The primary aim of this paper is to select an appropriate power transformation when we use ARMA models for a given time series. We propose a Bayesian procedure for estimating the power transformation as well as other parameters in time series models. The posterior distributions of interest are obtained utilizing the Gibbs sampler, a Markov Chain Monte Carlo (MCMC) method. The proposed methodology is illustrated with two real data sets. The performance of the proposed procedure is compared with other competing procedures. © 1997 John Wiley & Sons, Ltd. 相似文献
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Eunah Kim Joon Hyun Kim Keunhee Seo Ka Young Hong Seon Woo A. An Junyoung Kwon Seung-Jae V. Lee Sung Key Jang 《Cellular and molecular life sciences : CMLS》2018,75(23):4287-4300
The initiator tRNA (Met-tRNA i Met ) at the P site of the small ribosomal subunit plays an important role in the recognition of an mRNA start codon. In bacteria, the initiator tRNA carrier, IF2, facilitates the positioning of Met-tRNA i Met on the small ribosomal subunit. Eukarya contain the Met-tRNA i Met carrier, eIF2 (unrelated to IF2), whose carrier activity is inhibited under stress conditions by the phosphorylation of its α-subunit by stress-activated eIF2α kinases. The stress-resistant initiator tRNA carrier, eIF2A, was recently uncovered and shown to load Met-tRNA i Met on the 40S ribosomal subunit associated with a stress-resistant mRNA under stress conditions. Here, we report that eIF2A interacts and functionally cooperates with eIF5B (a homolog of IF2), and we describe the functional domains of eIF2A that are required for its binding of Met-tRNA i Met , eIF5B, and a stress-resistant mRNA. The results indicate that the eukaryotic eIF5B–eIF2A complex functionally mimics the bacterial IF2 containing ribosome-, GTP-, and initiator tRNA-binding domains in a single polypeptide. 相似文献
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999.
Serdar Neslihanoglu Vasilios Sogiakas John H. McColl Duncan Lee 《Journal of forecasting》2017,36(8):867-897
This paper examines the forecasting ability of the nonlinear specifications of the market model. We propose a conditional two‐moment market model with a time‐varying systematic covariance (beta) risk in the form of a mean reverting process of the state‐space model via the Kalman filter algorithm. In addition, we account for the systematic component of co‐skewness and co‐kurtosis by considering higher moments. The analysis is implemented using data from the stock indices of several developed and emerging stock markets. The empirical findings favour the time‐varying market model approaches, which outperform linear model specifications both in terms of model fit and predictability. Precisely, higher moments are necessary for datasets that involve structural changes and/or market inefficiencies which are common in most of the emerging stock markets. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
1000.