Anomalous properties in ferroelectrics induced by atomic ordering.

Complex insulating perovskite alloys are of considerable technological interest because of their large dielectric and piezoelectric responses. Examples of such alloys include (Ba1-xSrx)TiO3, which has emerged as a leading candidate dielectric material for the memory-cell capacitors in dynamic random access memories; and Pb(Zr1-xTix)O3 (PZT), which is widely used in transducers and actuators. The rich variety of structural phases that these alloys can exhibit, and the challenge of relating their anomalous properties to the microscopic structure, make them attractive from a fundamental point of view. Theoretical investigations of modifications to the atomic ordering of these alloys suggest the existence of further unexpected structural properties and hold promise for the development of new functional materials with improved electromechanical properties. Here we report ab initio calculations that show that a certain class of atomic rearrangement should lead simultaneously to large electromechanical responses and to unusual structural phases in a given class of perovskite alloys. Our simulations also reveal the microscopic mechanism responsible for these anomalies.     

An experiment to evaluate methods for estimating fossil fuel resources

Estimates of petroleum and natural gas resources vary substantially, both over time and across estimation methods. This paper develops a simulation model of global oil resources to evaluate different resource estimation techniques. Protocols for the Hubbert life cycle and USGS geological analogy methods are developed and applied to synthetic data generated by the model. It is shown that the Hubbert method can generate an accurate estimate as early as twenty years before the peak of global production, but the geological analogy approach overestimates the true resource base over the life cycle of the resource. The results show the applicability of simulation and the synthetic data approach to the problem of evaluating forecasting methods.     

Length of the year in pre-epicyclic planetary theory

An estimate is made of the length of the year implied in the pre-epicyclic planetary theory of the Pañcasiddhntik. It is shown that this could be the same as the year-length of the corresponding Babylonian theory.     

Pilling Segmentation for Objective Pilling Evaluation

IntroductionPillingonfabricsisaquiteunpleasantfeaturewhichaffectsthevisualquality.Pillingisgenerallyformedinfourstages:fuzz,entanglement,growthandwearoff[1].Dailywashingandwearingarethecommonsourcefortheformation.Thedurabilityofagarmentisthereforedeterminedbythetimeusedtoformsuchsmallfuzzballsonsurface.Inthelaboratory,fabricsarecutintosizeandplacedintopillingtesterstosimulatethesituation.ASTMprovidedseveralguidelines[2—5]fortheinspectionwhileAATCCgaveageneraltestingprocedure[6]onpillingre…     

Synthesis and Electrochemical Studies on LiCoVO_4 Surface Modified with La_2O_3 for Lithium-ion Cells

1 Results An inverse spinel LiCoVO4 cathode material was synthesized by a citric acid-urea polymeric method, calcined at 773 K for 5 h. The synthesized LiCoVO4 sample was surface modified with various wt.% of La2O3 by a polymeric process, calcined at 873 K for 2 h. The samples were characterized by XRD, FTIR, SEM, and TEM techniques. XRD patterns exposed that single-phase crystallinity occurred when they were heated at 773 K for 5 h in air. For the La2O3 coated samples, there was no evident signal corre...     

平淡世界里的精彩--评2005年诺贝尔生理学与医学奖

2005年诺贝尔生理学或医学奖授予澳大利亚科学家巴里·马歇尔(Barry Marshall)和罗宾·沃伦(Robin Warren),以表彰他们发现了导致人类罹患胃炎、胃溃疡和十二指肠溃疡的罪魁--幽门螺杆菌(Helicobacter pylori,Hp).这项近乎"平民化"的研究成果相对于当今发展飞快的分子生物学、神经科学以及干细胞研究等领域而言,无疑是一个震撼性的消息.它提示了传统的病原微生物研究并没有退出历史的舞台,恰恰相反,证实了科学研究在平淡中见"奇"之特点.时下包括禽流感等在内的高危传染性疾病近乎是愈演愈烈,也表明对病原微生物深入地开展全方位系统研究的紧迫性和必要性.     

离子液体在热致变色材料中的应用

 含有大量羟基的离子液体可以与镍(II)金属配合物发生配位反应,含有二者的溶液具有热致变色性质。这种新型的热致变色体系,只需要普通太阳光的热量就能驱动变色,具有变色灵敏、环境友好等特点。这种热致变色体系在与高分子材料聚偏氟乙烯(PVDF)形成复合物后,仍然具有优良的热致变色特性,且这种复合物可以由不同的镍(II)金属配合物组成。另外,这种热致变色体系还可以通过引入额外的氯离子,使体系在温度低于0℃以下时有颜色变化响应,体系转变为冷致变色体系。本文介绍几种基于羟烷基咪唑类和基于季铵盐的深共熔溶剂类离子液体,分别与镍(II)金属配合物所组成的热致/冷致变色体系及相关基础研究和复合膜应用研究工作。     

Outer-core compositional stratification from observed core wave speed profiles

Light elements must be present in the nearly pure iron core of the Earth to match the remotely observed properties of the outer and inner cores. Crystallization of the inner core excludes light elements from the solid, concentrating them in liquid near the inner-core boundary that potentially rises and collects at the top of the core, and this may have a seismically observable signal. Here we present array-based observations of seismic waves sensitive to this part of the core whose wave speeds require there to be radial compositional variation in the topmost 300?km of the outer core. The velocity profile significantly departs from that of compression of a homogeneous liquid. Total light-element enrichment is up to five weight per cent at the top of the core if modelled in the Fe-O-S system. The stratification suggests the existence of a subadiabatic temperature gradient at the top of the outer core.     

Mutation of TBCE causes hypoparathyroidism-retardation-dysmorphism and autosomal recessive Kenny-Caffey syndrome

The syndrome of congenital hypoparathyroidism, mental retardation, facial dysmorphism and extreme growth failure (HRD or Sanjad-Sakati syndrome; OMIM 241410) is an autosomal recessive disorder reported almost exclusively in Middle Eastern populations. A similar syndrome with the additional features of osteosclerosis and recurrent bacterial infections has been classified as autosomal recessive Kenny-Caffey syndrome (AR-KCS; OMIM 244460). Both traits have previously been mapped to chromosome 1q43-44 (refs 5,6) and, despite the observed clinical variability, share an ancestral haplotype, suggesting a common founder mutation. We describe refinement of the critical region to an interval of roughly 230 kb and identification of deletion and truncation mutations of TBCE in affected individuals. The gene TBCE encodes one of several chaperone proteins required for the proper folding of alpha-tubulin subunits and the formation of alpha-beta-tubulin heterodimers. Analysis of diseased fibroblasts and lymphoblastoid cells showed lower microtubule density at the microtubule-organizing center (MTOC) and perturbed microtubule polarity in diseased cells. Immunofluorescence and ultrastructural studies showed disturbances in subcellular organelles that require microtubules for membrane trafficking, such as the Golgi and late endosomal compartments. These findings demonstrate that HRD and AR-KCS are chaperone diseases caused by a genetic defect in the tubulin assembly pathway, and establish a potential connection between tubulin physiology and the development of the parathyroid.