Determining a 'safe' high-mass limit in matrix-assisted laser desorption/ionisation time-of-flight mass spectra of coal derived materials with reference to instrument noise

Three methods for determining a 'safe' estimate for high-mass limits of MALDI spectra of coal derived liquids were explored, using a sample of coal-tar pitch and its pyridine-insoluble fraction. Co-addition of increasing numbers of single-shot spectra (10, 30, 50 and 100 pulses) showed visually observable reductions in noise levels, consistent with robust and statistically meaningful signals. Three separate types of post-acquisition calculation were used to identify high-mass limits of the spectra. (i) A literature method indicated high-mass limits similar to those observed visually-as a shift from baseline at the highest masses, nearly 350 000 u for the coal tar pitch and about 390 000 u for its pyridine insoluble fraction. (ii) Comparing instrument signal with pre-selected multiples of the standard deviation, upper mass estimates of between 40-60 000 u for the coal-tar pitch and about 95 000 u for its pyridine-insoluble fraction were found. (iii) Calculation of the slope was used to identify 'lift-off' of the spectrum from baseline. The angle between the smoothed spectrum and the baseline was matched to a pre-selected value (e.g. 0.5 degrees and 1 degrees ). However, the arbitrary specification of the key parameter did not establish this last method on a firm basis. The choice of a criterion for estimating high-mass limits of MALDI spectra remains a semi-quantitative procedure; a reasonably conservative high-mass limit may be estimated by comparison of signal with five times the standard deviation. However, evaluation of size exclusion chromatograms of the present samples using polystyrene standards suggests that molecular mass distributions of pitch samples arrived at by MALDI mass spectrometry are, at least partly, determined by the limitations of available instruments. Copyright 1999 John Wiley & Sons, Ltd.     

用于边缘检测的Laplace——样条(▽2S)算子

根据数据平滑理论,提出了一种图象边缘检测的方法:把二维四阶B样条函数与Laplacian算子相结合组合成▽²S算子,对图象卷积之后,根据过零点(ZeroCrossing)确定图象边缘。文中证明了它在图象平滑和边缘检测效果上,优于Marr和Hildreth提出的▽²G算子,且计算量较小。而▽²G算子可用高阶▽²S算子近似。文中给出了一些实验结果。     

非线性回旋动力方程

非线性回旋动力方程是处理等离子体中非线性电磁现象及相关输运现象的有力工具.在任意磁场位形、任意频率下,建立了一套适于描述非线性电磁现象、保留有限Larmor半径(FLR)效应的、自洽的非线性回旋动力的Vlasov-Maxwell方程.     

叶绿体结构和功能的研究——叶绿体残缺膜与线粒体嵴膜组合光合磷酸化活力的重建

本文证明了类囊体残缺膜可以与线粒体嵴膜组合而成为新囊膜。这种膜组织可以通过嵴膜的偶联因子借光能来进行光合磷酸化。电子显微镜图谱显示,这种膜组织是介乎残缺膜与嵴膜之间一种膜组织。 试验结果支持了这样一种观点,即:叶绿体内光合磷酸化与线粒体内氧化磷酸化的磷酸化机构是一致的,其细胞器可能是有着共同的来源。     

关于平面二次系统的极限环

关于常微分方程二次系统的极限环及分布结构,本文得到下述定理: 设有一个三阶细焦点,并且无限远奇点是唯一的简单的奇点,则必存在另外一个粗焦点。在粗焦点外有奇数个极限环,无限远奇点为鞍点,全局结构已定。 在上述的基础上对方程作参数的微小变化,使三阶细焦点跳出三个极限环,则得二个粗焦点,每个外面有奇数个极限环,总极限环数为偶数个,并至少为4个,全局结构已定。     

The effect of topical anesthesia on vocal fold motion

The objective of this study was to determine if topical anesthesia to the larynx and pharynx affects vocal fold motion during dynamic voice evaluation with transnasal flexible endoscopy. Transnasal dynamic laryngeal examinations of 10 patients with no voice complaints were evaluated by five blinded fellowship-trained laryngologists. Each patient was examined before and after application of topical anesthetic. Reviewers rated briskness of right and left vocal fold movement and longitudinal tension on a visual analogue scale. Statistical comparisons were made between individual subject scores before and after anesthetic application. Inter-rater reliability was also assessed. No statistical difference was observed between subject scores before and after anesthetic application. Average intraclass correlation coefficients were 0.643 and 0.591 for pre- and postanesthesia scores, respectively. Application of topical anesthesia to the larynx and pharynx does not affect vocal fold motion.     

甲氧羰基亚甲基三苯基胂与氟代烯烃的反应

本文报道甲氧羰基亚甲基三苯基胂(Ⅰ)与氟代烯烃反应生成加成物,Ⅰ与4,4-二氯六氟丁烯-[1]反应,生成甲氧羰基-[4,4-二氯五氟丁烯-1]-基亚甲基三苯基胂(Ⅲ)和甲氧羰基4,4-二氯2,3,3,4-四氟丁酰基亚甲基三苯基肿(Ⅳ),Ⅲ通过氧化铝柱或经湿苯回流都转化为Ⅳ,Ⅰ与四氟乙烯和六氟丙烯都能发生反应,粗产物通过氧化铝柱后,分离得到相应的羰基化合物Ⅶ和Ⅷ,所有产物的结构都经元素分析、红外光谱、核磁共振谱和质谱分析证明。     

论Ore图的泛连通性

符合Ore条件的简单图称为Ore图,Ore条件指图的两个不相邻的顶点的度数之和不小于图的顶点数。本文搞清了Ore图的泛连通性,同时得到了Ore图的点(边)泛圈性的结果,推广了Bondy的一个结论。     

Langevin equation for self-organized morphologies of thin heteroepitaxial films

The self-organization of nanostructures on strained epitaxial films is expressed as a Langevin equation obtained from an atomistic model of the growth kinetics. The transition rules are based on the incorporation of strain effects into environment-dependent detachment barriers. Comparisons are made with a previous approach based on continuum elasticity to provide an atomistic interpretation of the governing equation for the morphological evolution of strained films.