A freely diffusible form of Sonic hedgehog mediates long-range signalling

The secreted protein Sonic hedgehog (Shh) exerts many of its patterning effects through a combination of short- and long-range signalling. Three distinct mechanisms, which are not necessarily mutually exclusive, have been proposed to account for the long-range effects of Shh: simple diffusion of Shh, a relay mechanism in which Shh activates secondary signals, and direct delivery of Shh through cytoplasmic extensions, termed cytonemes. Although there is much data (using soluble recombinant Shh (ShhN)) to support the simple diffusion model of long-range Shh signalling, there has been little evidence to date for a native form of Shh that is freely diffusible and not membrane-associated. Here we provide evidence for a freely diffusible form of Shh (s-ShhNp) that is cholesterol modified, multimeric and biologically potent. We further demonstrate that the availability of s-ShhNp is regulated by two functional antagonists of the Shh pathway, Patched (Ptc) and Hedgehog-interacting protein (Hip). Finally, we show a gradient of s-ShhNp across the anterior-posterior axis of the chick limb, demonstrating the physiological relevance of s-ShhNp.     

关于提高高新技术企业人力资本投资绩效的理论思考

本文运用人力资本理论试分析了高新技术企业人力资本的产权与制度特征 ,分析了人力资本投资与知识管理的作用机制对高新技术企业绩效的影响 ;运用制度理论试分析了高新技术企业人力资本有效性配置的制度化过程 ;运用博弈论试分析了高科技员工在知识共享与合作中的行为选择问题 ;运用代理理论试分析了企业与高科技员工之间存在的“代理成本” ;运用利益相关者理论试分析了企业与高科技员工“双边治理”的可行性。最后 ,提出了关于提高高新技术绩效有待于进一步研究的问题     

论《西游记》的用人理念及其结果

在《西游记》中,孙悟空是一个天才型人才。但是,这个天才型人才却在两种不同的用人制度下经历了两种不同的命运。《西游记》就是通过对孙悟空等人物形象的塑造,通过对玉皇大帝和观音菩萨两种不同用人方式以及产生的不同结果的对照,抒发了对封建时代的不合理的用人制度的不满,表达了一种对理想的用人制度的憧憬。     

竖向弹簧-钢球隔震系统的隔离水平地震作用

提出一种新的竖向弹簧—钢球隔震系统隔离水平地震作用的隔震方法,用势能不变值原理与“对号入座”法则建立该隔震系统的振动方程,分析各控制参数对该隔震系统地震反应的影响．研究结果表明,该隔震系统结构简单,隔离水平地震作用效果显著．     

Observation of contrast variations of a copper (Ⅱ) complex by scanning tunneling microscopy

This report presents experimental observations of dramatic variations in STM images of bis [1,3-DI(p-n-tetradecyloxyphenyl)propane-1,3-dionato]copper( Ⅱ） (abbreviated to C14O-Cu)physisorbed on HOPG as the bias voltage is changed .Several representative image patterns were obtained for the rich changes of the internal contrast of the molecule .Submolecular features of the molecular cores and the interdigitated alkyl parts are clearly visible.     

2D self-assembling of 4, 5-didodecylthiolphthalonitrile on graphite surface

An important precursor 4,5-didodecylthiolphthalonitrile (DCP) for synthesis of phthalocyanines (Pcs) and subphthalocyanines (SubPcs) was synthesized and the assembling structure of this molecule on the basal plane of highly oriented pyrolytic graphite (HOPG) surface was characterized using the scanning tunneling microscopy (STM) in ambient conditions. In high-resolution images of the molecules, we found that the arrangement of the cyano groups forms a “head-to-head” configuration to keep the stability of the entire system. The mismatch of the DCP molecules with the substrate lattice has also been observed in the experiment.     

ENTROPY,INFORMATION,NOISE—STUDIES ON SYSTEM EVOLUTION

Universe, ecosystem, social system, etc. are evolving systems. The evolving processes of thesesystems have gradual small changes and rapid drastic changes with uncertainties under the constraintsof environment. Systems, as a whole, are evolving toward complexity, diversity and variety withfluctuations and jumps. New order emerges from "mutations". The evolution is bothchance-dependent and path-dependent. In this paper three basics: entropy, information and noise areemphasized with regard to system evolution which is a field that can give people wisdom to solvesystem problems with domain knowledge.     

Burger''s方程的若干AGE方法

以求解Ｂｕｒｇｅｒ‘ｓ方程的中心差分格式,显示逆风格式,Ｓａｍａｒｓｋｉｉ格式及修正Ｄｅｎｎｉｓ格式为基础,构造了若干新的ＡＧＥ方法,讨论了方法的线性化稳定性数值结果表明,对于求解Ｂｕｒｇｅｒ’ｓ方程大Ｒｅｙｎｏｌｄ数问题,除了Ｃ－ＡＧＥ方法外,文中所构造的其他ＡＧＥ方法明显优于Ｅｖａｎｓ的分组显式方法。     

Separating Latent Classes by Information Criteria

This study evaluates performance of information criteria used to separate latent classes. In the evaluations, various numbers of latent classes, sample sizes, parameter structures and latent-class complexities were designed to simulate datasets. The average accuracy rates of information criteria in selecting the designed numbers of latent classes were the core results in this experiment. The study revealed that widely used information criteria, e.g., AIC, BIC, CAIC, could perform poorly under some circumstances. By including a sample size adjustment (Rissanen, 1978), the unsatis-factory performances could be improved considerably. The sample size adjustment provides a plausible solution for separating latent classes. Guidelines are provided to help achieve optimum use of the model fit indices.