Time response of the thin layer electrochemical cell used for in situ X-ray diffraction

As the potential applied to the bromide on Ag(001) thin layer electrochemical cell increases past a critical level, the bromide adlayer undergoes a second order phase transition from a disordered state to an ordered state. Using surface X-ray diffraction we measured the time response of this phase transition due to an applied step potential. We find that the time response of the phase transition is limited by the properties of the thin layer geometry. By modeling the electrochemical cell as a RC circuit, we argue that the observed time delay is primarily due to the slow diffusion of charge into the central region of the electrode surface.     

沧州南部典型区近30年来气温演变特征分析

文中主要分析了沧州南部典型区近30年来气温演变情势,分析了其统计特征、年内变化趋势性和年代际变化、持续性、突变性和周期性,得出了一定的规律性,为深入研究本区域与气温有关的课题打下了基础。     

Ultraviolet Lamp Output Measurement: A Concise Derivation of the Keitz Equation

An equation relating the measured irradiance and the output power of a fluorescent lamp was derived by Keitz. The equation forms the basis for a new protocol that has been proposed for quantifying the total flux from an ultraviolet lamp. There has been confusion in the literature regarding the spatial distribution of flux from lamp emitters, which has led to emission models that are similar to the Keitz model but are incorrect. The Keitz equation is derived here from first principles in an effort to eliminate the confusion and present a correct method of calculating total flux.     

腐植酸物质在商业中的应用——现今世界文献综评

连续查阅现今世界文献,关于“腐植酸”文章已经发表了八千篇之多,查阅工作是在美国康乃迪克州内瑞克斯多斯进行的,这项工作可以追朔到七十年代,查阅了二十七种基础资料,包括美国和全世界的专利文件,化学文摘服务社材料,农业,生物文摘,水资源文摘,工程索引和生物科学集录等,收集到的参考文献其数量之多,各地生产的腐植酸物质的明显差异性及全球资源的广泛分布亦给人留下深刻印象。     

Exploiting Peptidomimetics to Synthesize Compounds That Activate Ryanodine Receptor Calcium Release Channels

Ryanodine receptor (RyR) Ca²⁺‐release channels are essential for contraction in skeletal and cardiac muscle and are prime targets for modification of contraction in disorders that affect either the skeletal or heart musculature. We designed and synthesized a number of compounds with structures based on a naturally occurring peptide ( A peptides) that modifies the activity of RyRs. In total, 34 compounds belonging to eight different classes were prepared. The compounds were screened for their ability to enhance Ca²⁺ release from isolated cardiac sarcoplasmic reticulum (SR) vesicles, with 25 displaying enhanced Ca²⁺ release. Competition studies with the parent peptides indicated that the synthetic compounds act at a competing site. The activity of the most effective of the compounds, BIT 180, was further explored using Ca²⁺ release from skeletal SR vesicles and contraction in intact skeletal muscle fibers. The compounds did not alter tension in intact fibers, indicating that (as expected) they are not membrane permeable, but importantly, that they are not toxic to the intact cells. Proof in principal that the compounds would be effective in intact muscle fibers if rendered membrane permeable was obtained with a structurally related membrane‐permeable scorpion toxin (imperatoxin A), which was found to enhance contraction.     

国内外稠油和沥青VAPEX技术发展现状与分析

自1991年Roger Butler提出稠油和沥青的蒸汽萃取（VAPEX）技术以来,VAPEX已经成为一个非常有前途的开采工艺。最主要的原因是,相对于其它的采油工艺,VAPEX具有环境友好、成本低的特点。本文详细综述了国内外VAPEX技术最新发展现状,探讨了VAPEX开采稠油技术机理,评述了VAPEX技术优点及技术局限性,展望了VAPEX技术应用前景,提出了今后发展方向。     

Observations of Membrane Domain Reorganization in Mechanically Compressed Artificial Cells

Giant unilamellar vesicles (GUVs) are considered to be the gold standard for assembling artificial cells from the bottom up. In this study, we investigated the behavior of such biomimetic vesicles as they were subjected to mechanical compression. A microfluidic device is presented that comprises a trap to capture GUVs and a microstamp that is deflected downwards to mechanically compress the trapped vesicle. After characterization of the device, we show that single-phase GUVs can be controllably compressed to a high degree of deformation (D=0.40) depending on the pressure applied to the microstamp. A permeation assay was implemented to show that vesicle bursting is prevented by water efflux. Next, we mechanically compressed GUVs with co-existing liquid-ordered and liquid-disordered membrane phases. Upon compression, we observed that the normally stable lipid domains reorganized themselves across the surface and fused into larger domains. This phenomenon, observed here in a model membrane system, not only gives us insights into how the multicomponent membranes of artificial cells behave, but might also have interesting consequences for the role of lipid rafts in biological cells that are subjected to compressive forces in a natural environment.     

Finite-element thermal modeling of casting microstructures and defects

Finite-element thermal modeling offers the capability of simulating casting solidification conditions. By combining thermal modeling and inspection, a defect map can be established to enable prediction of casting microstructures and defects. Gamma-prime size, dendrite-arm spacing, equiaxed grain size, shrink, hot tearing, misrun, and other features can all be predicted.     

Testing for a break in persistence under long-range dependencies

Abstract.  We show that tests for a break in the persistence of a time series in the classical I (0)/ I (1) framework have serious size distortions when the actual data-generating process (DGP) exhibits long-range dependencies. We prove that the limiting distribution of a CUSUM of squares-based test depends on the true memory parameter if the DGP exhibits long memory. We propose adjusted critical values for the test and give finite sample response curves that allow easy implementation of the test by the practitioner and also ease in computing the relevant critical values. We furthermore prove the consistency of the test for a simple breakpoint estimator also under long memory. We show that the test has satisfying power properties when the correct critical values are used.     

保险粉的盐母液制备硫代硫酸钠

研究了以保险粉的盐母液为原料 ,经加热、加硫、空气氧化、浓缩结晶 ,制备硫代硫酸钠并回收氯化钠的新工艺 ,具有较好的经济和社会效益