Mechanisms underlying celiac disease and its neurologic manifestations

The extra-intestinal manifestations of celiac disease (CD), including ataxia and peripheral neuropathy, are increasingly being recognized as the presenting symptoms of this autoimmune disease. Although there is a greater understanding of the pathogenesis of the intestinal lesions in CD the mechanisms behind the neurologic manifestations of CD have not been elucidated. In this article, the authors review the cellular and molecular mechanisms behind the histopathologic changes in the intestine, discuss the presentation and characteristics of neurologic manifestations of CD, review the data on the mechanisms behind these manifestations, and discuss the diagnosis and treatment of CD. Molecular mimicry and intermolecular help may play a role in the development of neurologic complications.Received 11 March 2004; received after revision 29 October 2004; accepted 12 November 2004     

Modeling the MHC class I pathway by combining predictions of proteasomal cleavage,TAP transport and MHC class I binding

Epitopes presented by major histocompatibility complex (MHC) class I molecules are selected by a multi-step process. Here we present the first computational prediction of this process based on in vitro experiments characterizing proteasomal cleavage, transport by the transporter associated with antigen processing (TAP) and MHC class I binding. Our novel prediction method for proteasomal cleavages outperforms existing methods when tested on in vitro cleavage data. The analysis of our predictions for a new dataset consisting of 390 endogenously processed MHC class I ligands from cells with known proteasome composition shows that the immunological advantage of switching from constitutive to immunoproteasomes is mainly to suppress the creation of peptides in the cytosol that TAP cannot transport. Furthermore, we show that proteasomes are unlikely to generate MHC class I ligands with a C-terminal lysine residue, suggesting processing of these ligands by a different protease that may be tripeptidyl-peptidase II (TPPII).Received 26 November 2004; received after revision 4 February 2005; accepted 4 March 2005S. Tenzer and B. Peters contributed equally to this work.     

单乙醇胺(MEA)捕获二氧化碳过程解吸能耗的模拟

采用ProMax2.0模拟了30% (质量分数)单乙醇胺填料塔吸收 - 解吸CO2的传统流程,考察了贫吸收液CO2负载(CLL)和溶液循环流速(SCR)对解吸用再沸器热负荷(Qreb)的影响.全系统模拟结果表明,当CO2 移除效率为90%时,CLL增加导致Qreb显著下降后再缓慢上升,其最佳值为0.20 mol CO2/mol MEA (MCPM),此时Qreb达最小值3.24 GJ/t CO2.单独的解吸系统模拟结果显示,当CLL 和富吸收液CO2负载(CRL)不变时,解吸塔中富胺进料流量的变化不影响热负荷.然而,由于全吸收 - 解吸系统CLL和CRL的变化则直接导致解吸塔富胺进料流量和热负荷的变化.     

南海北部近代沉积物钕同位素分布及意义

南海北部及周边地区近代陆源沉积物稀土元素配分模式总体相似, 接近上地壳平均成分(PAAS), 在重稀土含量上则略为偏高, LaN/LuN比值明显小于PAAS. 但是珠江主要支流西江沉积物的稀土元素含量略高于PAAS, 在重稀土分布态势上明显偏轻, LaN/LuN比值明显大于PAAS. 南海北部地区近代沉积物钕同位素分布具有明显的区域性, 主要受控于珠江源区和闽粤沿海源区以及台湾岛源区. 闽粤沿海地区ε_Nd(0)值最大, 西江沉积物最小, 台湾岛以及海域中沉积物ε_Nd(0)值介于两者之间. 沿伶仃洋-东沙岛连线, 在该线东北区域钕同位素值相对偏高, 西南区域相对偏低. 珠江源沉积物主要影响该线西南区域, 源区母岩以发育大量古生代碳酸盐岩为特征. 闽粤沿海源区以及台湾岛源区, 主要影响该线东北区域, 闽粤沿海源区母岩以发育大量中新生代花岗岩为特征. 由于源区母岩成分上的不同, 造成沉积物在重稀土含量、Sc/Ti比值以及ε_Nd(0)值上存在明显差异. 发育在东沙群岛东南侧高沉积速率堆积体的陆源物质超过80%来自南海北部源区即闽粤沿海源区以及台湾岛源区, 来自珠江源的陆源沉积物不超过20%.     

珠穆朗玛峰东绒布冰芯1800 AD以来的火山活动记录

通过元素Bi的含量, 研究了珠穆朗玛峰东绒布冰芯记录的1800 AD以来的9次强火山活动的信号. 结果表明, 东绒布冰芯中Bi含量的变化对关键区域的强火山活动有很好的记录, 这为山地冰芯定年提供了很好的标志层, 并为开展更长时间序列的山地冰芯火山记录研究提供了基础.     

全球植被分布对陆面气温影响的半解析分析

植被分布对全球环流及其温度分布有极其重要的影响, 对于自由大气的无黏性绝热、斜压、大尺度定常有限扰动, 通过三维环流控制方程来描述, 再结合P坐标下的静力方程得到温度的控制方程, 化成到地形坐标系下, 得到环流温度的三维控制方程. 结合下边界辐射平衡条件与常数上边界条件, 可以给出全球环流温度的半解析解. 本文只讨论了陆面气温的分布, 可以看到该模型能够较好地反映全球陆面气温的分布, 而且当考虑到植被反照率对温度的反馈时计算的结果更加符合观测值. 对于敏感性试验, 考虑到全球陆面为冰雪覆盖时陆面气温有较大的降低, 全球陆面为森林覆盖时陆面气温偏高. 所以本模型能够从理论上半解析地给出陆面气温随植被分布的变化, 是研究陆面生态分布对陆面气温变化的一个较好的工具.     

Liquid marbles.

The transport of a small amount of liquid on a solid is not a simple process, owing to the nature of the contact between the two phases. Setting a liquid droplet in motion requires non-negligible forces (because the contact-angle hysteresis generates a force opposing the motion), and often results in the deposition of liquid behind the drop. Different methods of levitation-electrostatic, electromagnetic, acoustic, or even simpler aerodynamic techniques-have been proposed to avoid this wetting problem, but all have proved to be rather cumbersome. Here we propose a simple alternative, which consists of encapsulating an aqueous liquid droplet with a hydrophobic powder. The resulting 'liquid marbles' are found to behave like a soft solid, and show dramatically reduced adhesion to a solid surface. As a result, motion can be generated using gravitational, electrical and magnetic fields. Moreover, because the viscous friction associated with motion is very small, we can achieve quick displacements of the droplets without any leaks. All of these features are of potential benefit in microfluidic applications, and also permit the study of a drop in a non-wetting situation-an issue of renewed interest following the recent achievement of super-hydrophobic substrates.     

How 'spin ice' freezes.

The large degeneracy of states resulting from the geometrical frustration of competing interactions is an essential ingredient of important problems in fields as diverse as magnetism, protein folding and neural networks. As first explained by Pauling, geometrical frustration of proton positions is also responsible for the unusual low-temperature thermodynamics of ice and its measured 'ground state' entropy. Recent work has shown that the geometrical frustration of ice is mimicked by Dy2Ti2O7, a site-ordered magnetic material in which the spins reside on a lattice of corner-sharing tetrahedra where they form an unusual magnetic ground state known as 'spin ice'. Here we identify a cooperative spin-freezing transition leading to the spin-ice ground state in Dy2Ti2O7. This transition is associated with a very narrow range of relaxation times, and represents a new form of spin-freezing. The dynamics are analogous to those associated with the freezing of protons in ice, and they provide a means through which to study glass-like behaviour and the consequences of frustration in the limit of low disorder.