Do the laws of physics forbid the operation of time machines?

We address the question of whether it is possible to operate a time machine by manipulating matter and energy so as to manufacture closed timelike curves. This question has received a great deal of attention in the physics literature, with attempts to prove no-go theorems based on classical general relativity and various hybrid theories serving as steps along the way towards quantum gravity. Despite the effort put into these no-go theorems, there is no widely accepted definition of a time machine. We explain the conundrum that must be faced in providing a satisfactory definition and propose a resolution. Roughly, we require that all extensions of the time machine region contain closed timelike curves; the actions of the time machine operator are then sufficiently “potent” to guarantee that closed timelike curves appear. We then review no-go theorems based on classical general relativity, semi-classical quantum gravity, quantum field theory on curved spacetime, and Euclidean quantum gravity. Our verdict on the question of our title is that no result of sufficient generality to underwrite a confident “yes” has been proven. Our review of the no-go results does, however, highlight several foundational problems at the intersection of general relativity and quantum physics that lend substance to the search for an answer.     

PTEN、p53和BAG-1在三阴乳腺癌中的表达及意义

为了研究PTEN、p53和BAG-1在三阴乳腺癌中的表达情况及临床病理意义,并讨论三者之间的关系.采用免疫组织化学SP法检测89例三阴乳腺癌中PTEN、p53、BAG-1的表达,其阳性表达率分别为44.9％、47.2％、73.0％,三者的表达均与患者的病理组织学分级、淋巴结转移情况有关（P＜0.05）.PTEN的表达与p53、BAG-1表达呈负相关;BAG-1与p53的表达呈正相关,提示三者在三阴乳腺癌中的表达存在一定关联性,临床上联合检测三者可能为TNBC预后评估、患者的个体化治疗提供一定的参考.     

Mnemonic convergence in a social network: Collective memory and extended influence

Research on the social influences on remembering has focused on how people influence one another's memory through direct conversation. This project examined indirect influence, that is, the influence of those to whom one may be connected through a social network. We extend Christakis and Fowler's (2007. The spread of obesity in a large social network over 32 years. The New England Journal of Medicine, 357(4), 370–379) discovery that factors may propagate across several degrees of influence; influences of social remembering may also propagate. In a naturalistic study, we tracked weekly recollections of a narrative in a small social network. Two individuals’ mnemonic convergence could be predicted by their degree of separation. Directly and indirectly connected pairs show more convergent remembering than unconnected pairs, indicating that conversation is not the only route by which two individuals may come to hold a shared representation of the past. This propagation of memories across the links of a social network is an important means by which a group converges on a collective memory.     

评述基于认知加工的第二语言习得研究

认知加工研究范式是第二语言习得内在因素研究的一个重要方法,它代表第二语言习得向计量研究发展的方向。这一范式注重研究习得动态过程,不仅关注学习者习得什么和为什么能习得,更关注学习者是怎样掌握目标语规则的过程。除了计量研究特点外,该范式还从语言本体研究范式合理吸收了有关理论和方法,这些对汉语作为第二语言习得研究都具有借鉴意义。     

Evaluation of the Delayed Discovery Case

Summary

In this chapter, practicing lawyer Michael S. Morey guides the reader through the complex legal and non-legal issues involved in evaluating whether legal action should be pursued on behalf of an adult survivor of childhood sexual abuse. After analyzing how evaluation of sexual abuse cases differs from that in most other personal injury cases, he presents a model for non-suggestive yet thorough client interviewing and case evaluation to help both survivor and lawyer decide whether to pursue litigation. Viability of a case, determined by three critical legal issues, does not necessarily mean litigation ought to be pursued, and he explores how to make the initial interview a valuable resource to survivors, whether or not legal action is ultimately sought, with practical tips and a reproducible intake form.     

清代词学与易学

易学是清代词学重要的理论源泉,在清代词学理论的构建中,无论是词的创作心态、技法,还是词学审美观、词学诠释学,乃至词学的发展史论等,均受到易学不同程度的影响.易学中的“修辞立其诚”、取“象”、“阴阳刚柔”、“仁者见仁,智者见智”、本色自然、变通发展的理论均渗透到词学领域,滋润灌溉了清代词学.     

尚秉和易学思想考

尚秉和是我国上世纪易学泰斗,其身后留下的《焦氏易林注》、《焦氏易诂》、《周易尚氏学》等系列易著,至今仍是学人治易的重要参考书。为了帮助今人了解尚氏其人其作,本文对尚氏生平行状及其易学思想作一番全面、深入的探考。     

Recognition memory in older adults: adjustment to changing contingencies.

Four older and 4 younger men were given extended exposure to a continuous-recognition memory procedure. Experimental variables included the type of stimulus (alphanumeric strings, words, or sentences), the intervals separating repeated items, gains and losses for correct and incorrect recognitions, and the extent of practice with the memory task. Signal detection analyses indicated that the older men generally were less accurate (sensitivity), particularly when the stimuli were strings, but that age differences decreased with practice. Under conditions in which the payoff matrix was neutral, the older and younger men showed equivalent rates of hits and false alarms (bias). Alteration of the matrix to require more liberal or more conservative patterns of recognition responding led to corresponding changes for men of both ages. Adjustments by the older men, however, were not as close to the bias values called for by the new matrices.