Crystal growth velocity in deeply undercooled Ni–Si alloys

The crystal growth velocity of Ni₉₅Si₅ and Ni₉₀Si₁₀ alloys as a function of undercooling is investigated using molecular dynamics simulations. The modified imbedded atom method potential yields the equilibrium liquidus temperatures T _L?≈?1505 and 1387?K for Ni₉₅Si₅ and Ni₉₀Si₁₀ alloys, respectively. From the liquidus temperatures down to the deeply undercooled region, the crystal growth velocities of both the alloys rise to the maximum with increasing undercooling and then drop slowly, whereas the athermal growth process presented in elemental Ni is not observed in Ni–Si alloys. Instead, the undercooling dependence of the growth velocity can be well-described by the diffusion-limited model, furthermore, the activation energy associated with the diffusion from melt to interface increases as the concentration increases from 5 to 10?at.% Si, resulting in the remarkable decrease of growth velocity.     

An atomistic modelling and statistical analysis study of crack–void interaction in Aluminum

The interaction between a brittle crack and pre-existing void in front of the crack tip was studied in the realm of molecular dynamics simulations at the nanoscale in face centred cubic Al within the framework of embedded-atom method. The results provide corroborative evidence of the fact that presence of a void in front of a running crack deters further crack growth. By performing an extensive series of simulations with different void sizes and crack-void distances coupled with statistical analysis, it has been found that (1) major role of voids is to decrease the fracture stress with increasing void size, in addition to slight increase in strain at which the crack growth occurs and the consequent strain to fracture, (2) fracture stress for a constant void size follows a sinusoidal distribution by varying the crack-void distance and (3) it is the void size that is most crucial in dictating the fracture properties of the material, rather than the void placement.     

Scientific Peer Review: A Case Study From Local And Global Analyses.

The dialog between Staddon (2001, 2004) and Baum (2004) raises general questions about the nature of scientific peer review. Their dialog displays effects on peer review of differences of opinion about the relative merits of local and global analyses. Baum (1995, 1997, 2001, 2002) favors global analyses as a paradigm different, newer, and better than the local, dynamic, real‐time approach that plays a significant role in Staddon (2001). According to the Kuhnian perspective (Kuhn, 1996) Baum advocates, we can better understand his review of Staddon (2001) by considering the implications for it of his commitment to the idea that a global analysis is a superior scientific paradigm. This commentary examines some characteristics of local and global analyses, as well as some of their possible implications for peer review in the context of a reviewer's belief in the Kuhnian idea of incommensurability: According to this idea, a reviewer who either is, or who believes he is, from one paradigm is unlikely, for better or worse, to understand or perhaps even tolerate work from a different paradigm. It is recommended that a process be developed to encourage “truth in peer reviewing” to reduce possible conflicts of interest embedded in the current conception of scientific peer review.     

结核病诊治进展与科技革命

现代科技革命极大地促进了结核病各方面的发展.微生物学和免疫学的发展,揭示了结核病的病因、发病机制、病理生理的本质,分子生物学技术使结核病的基础研究不仅停留在器官、细胞水平,而是深入到蛋白质、核酸、基因的水平;基因治疗的方法可望从根本上治疗结核病.高新技术的产物如X线照片、电子计算机断层扫描、纤维支气管镜检查和新药的出现等极大地提高了临床诊治的能力.借助于各种先进的医疗设备而进行精确的诊断,基因治疗将成为一种崭新的治疗手段.     

Why are maximizers less happy than satisficers? Because they maximize positive and negative outcomes

Although extant research suggests maximizing is related to objectively positive outcomes (e.g., job offers), I propose maximizing may be simultaneously and positively related to objectively negative outcomes (e.g., job rejections). Specifically, I argue maximizers bear more instances of positive and negative outcomes than satisficers, and that in spite of their positive outcomes—yet because of their negative outcomes—maximizers are less happy than satisficers. In Study 1, participants took the alternate uses test; as expected, maximizing was related to seeking alternatives, yet, maximizing was also related to seeking low‐quality alternatives. Moreover, the number of low‐quality alternatives partially mediated the relationship between maximizing and negative affect. In Study 2, the impact of maximizing on experiencing negative affect was further assessed by examining whether maximizing is related to seeking and choosing low‐quality alternatives. Participants played the Iowa Gambling Task; it was found maximizing was related to alternating among decks, and in particular, sampling bad decks; ultimately, maximizing was related to winning less money, and experiencing more negative affect. Finally, in Study 3, participants responded to questionnaires about positive and negative life outcomes; it was found that maximizing was simultaneously related to experiencing more positive and more negative outcomes, and that negative outcomes predicted happiness to a greater degree than positive outcomes. These findings suggest an irony of maximizing: It produces both positive and negative outcomes, contributing to literature explaining why maximizers are less happy than satisficers, and ultimately whether happiness is a matter of choice. Copyright © 2009 John Wiley & Sons, Ltd.     

反社会行为潜在遗传因素的全基因组关联分析

反社会行为是一种受基因和环境共同影响的复杂性行为, 但单个基因如单胺氧化酶基因(MAOA)、5-羟色胺转运体启动因子基因(5-HTT)、儿茶酚-o-甲基转移酶(COMT)基因的影响并不能全面解释其产生的分子遗传机制。来自分子遗传学研究取向的方法—— 全基因组关联分析(genome-wide association study, GWAS), 把人类基因组中数以百万计的单核苷酸(SNPs)和复制数变异(CNVs)作为遗传标记, 在全基因组层面上, 开展多中心、大样本的关联研究, 经过反复验证来发现与外在表型相关的基因位点, 为进一步了解反社会行为复杂分子遗传机制提供了重要的线索。未来的研究应该通过科学的实验设计将精确的基因分型技术与心理、环境因素相结合, 实现对复杂性行为或特质的基因-心理-环境模型的成因性分析。     

精子介导转基因技术的进展与争论

随着生物医学的不断发展,精子介导转基因技术正成为有希望的转基因方法。与其他基因转移方法相比,精子介导具有简单、高效、低廉、安全的特点。我们探讨精子结合外源DNA和DNA内化的分子模型,介绍精子介导转基因技术的改进方法,并指出存在的问题和伦理学争论,旨在推动该技术在生物技术领域的进一步发展。     

肿瘤分子生物学行为与其影像表现关系的探讨

肿瘤基因表达与其影像表现有一定的相关性,为我们用无创的影像学方法显示肿瘤的生物学特征提供了可能。探寻肿瘤分子生物学特性与其影像表现的内在联系,以期对肿瘤浸润和转移做出正确的诊断,从而为临床选择治疗方案、判断疗效和评估预后等提供更多、更有价值的信息。     

Stock optimizing in choice when a token deposit is the operant.

Each of 2 monkeys typically earned their daily food ration by depositing tokens in one of two slots. Tokens deposited in one slot dropped into a bin where they were kept (token kept). Deposits to a second slot dropped into a bin where they could be obtained again (token returned). In Experiment 1, a fixed-ratio (FR) 5 schedule that provided two food pellets was associated with each slot. Both monkeys preferred the token-returned slot. In Experiment 2, both subjects chose between unequal FR schedules with the token-returned slot always associated with the leaner schedule. When the FRs were 2 versus 3 and 2 versus 6, preferences were maintained for the token-returned slot; however, when the ratios were 2 versus 12, preference shifted to the token-kept slot. In Experiment 3, both monkeys chose between equal-valued concurrent variable-interval variable-interval schedules. Both monkeys preferred the slot that returned tokens. In Experiment 4, both monkeys chose between FRs that typically differed in size by a factor of 10. Both monkeys preferred the FR schedule that provided more food per trial. These data show that monkeys will choose so as to increase the number of reinforcers earned (stock optimizing) even when this preference reduces the rate of reinforcement (all reinforcers divided by session time).