关于电子质量的发散疑难

从电子结构的特点、经典电动力学的局限性以及电磁质量的特性等三个方面对电子质量发散疑难进行了分析和讨论,结果表明,导致电子质量发散是因为：把电子简单地视为无限度的几何点;经典电动力学的局限性;混淆了电子总质量与电磁质量的概念。     

试论中国社会保险立法的难点与突破

我国现有的零乱的、分散的社会保险制度在一定程度上阻碍了我国社会保障事业的发展;《社会保险法》的难产有着深刻的社会原因和制度缺陷;《社会保险法》的立法工作存在诸多难点;可以利用此次立法的时机重组现行散乱制度、突破思想障碍和体制痼疾,力争一次性解决我国社会保险法律制度和运行体系的设计问题。     

大学物理演示实验课的新探索

随着素质教育的逐步深入，传统的大学物理演示实验的教学模式已逐步显露出缺点和弊端，结合实际教学，总结出一套大学物理演示实验选修课行之有效的教学方法，为探索新的物理演示实验教学模式提供了全新的途径。     

Education policy and the heritability of educational attainment

Many workers assume that genetically determined differences in intellectual ability will be influenced little by changes in educational policy or other environmental interventions. Others, however, have suggested that increasing equality of educational opportunity will lead to an increase in the heritability of educational attainment. The resolution of this issue has been delayed until now because of the extremely large sample sizes which would be required. Education data on twins and their parents, from the Norwegian twin panel, provide a unique opportunity to determine the impact on the heritability of educational attainment of the more liberal social and educational policies introduced in Norway after the Second World War. As reported here, for individuals born before 1940 there is a strong effect of family background on educational attainment, accounting for 47% of the variance, though genetic factors account for an additional 41% of the variance. For females born after 1940 and before 1961, the relative importance of genetic (38-45%) and familial environmental (41-50%) differences changes very little. For males born during the same period, the broad heritability of educational attainment has increased substantially (67-74%), and the environmental impact of family background has correspondingly decreased (8-10%). For males, at least, having well-educated parents no longer predicts educational success, as measured by duration of education, independent of the individual's own innate abilities.     

On the difficulty of increasing dental complexity

One of the fascinating aspects of the history of life is the apparent increase in morphological complexity through time, a well known example being mammalian cheek tooth evolution. In contrast, experimental studies of development more readily show a decrease in complexity, again well exemplified by mammalian teeth, in which tooth crown features called cusps are frequently lost in mutant and transgenic mice. Here we report that mouse tooth complexity can be increased substantially by adjusting multiple signalling pathways simultaneously. We cultured teeth in vitro and adjusted ectodysplasin (EDA), activin A and sonic hedgehog (SHH) pathways, all of which are individually required for normal tooth development. We quantified tooth complexity using the number of cusps and a topographic measure of surface complexity. The results show that whereas activation of EDA and activin A signalling, and inhibition of SHH signalling, individually cause subtle to moderate increases in complexity, cusp number is doubled when all three pathways are adjusted in unison. Furthermore, the increase in cusp number does not result from an increase in tooth size, but from an altered primary patterning phase of development. The combination of a lack of complex mutants, the paucity of natural variants with complex phenotypes, and our results of greatly increased dental complexity using multiple pathways, suggests that an increase may be inherently different from a decrease in phenotypic complexity.     

实战武艺之散打难度的探讨

本文对实战武艺之散打,散打之难度及难度中的“知当”进行了概念明晰的解释,对如何提高散打实战中步法及技法的“知当”水平进行了辩证描述。     

高校毕业生就业难对策研究

论述了由于高等教育不能适应当代经济和社会的发展,以及毕业生择业观的不正确,导致了高校毕业生就业难的原因。提出了树立正确的职业理念,更新就业观念,高等教育改革和创新等解决就业难的对策。     

歌唱中的喉音问题及解决方法

喉音是由于声音失去呼吸支持、喉部紧缩、喉头提起或用力挤压舌根所造成。喉音对歌唱很有害：喉音生硬、沉重，缺乏音色变化，声音表现力弱。克服喉音的方法主要有打开喉咙和进行哼鸣训练。     

Information-Theoretic Analysis for the Difficulty of Extracting Hidden Information

The difficulty of extracting hidden information, which is essentially a kind of secrecy, is analyzed by information-theoretic method, The relations between key rate, message rate, hiding capacity and difficulty of extraction are studied in the terms of unicity distance of stego-key, and the theoretic conclusion is used to analyze the actual extracting attack on Least Significant Bit(LSB) steganographic algorithms.     

物业管理收费"难"原因探究

物业管理收费难是物业管理行业普遍存在的问题.这就要求法制健全,司法程序方面要简化现行物业管理欠费的处理程序,媒体要加强宣传、引导,同时物业管理企业自身也要增加透明度,加强自身管理.     

无粒子损失的W态融合研究综述

纠缠W态是量子通信的关键资源,而融合技术已被证明是制备大规模纠缠W态的有效方法.简要综述几类重要的有粒子损失的W态融合方案及相互关系,并着重阐述无粒子损失的W态融合方案及其物理原理,最后给出总结与展望.     

An ERP study for the degrees of the difficulty in visual search

The present study mainly probed the relationships between ERP components and the degrees of difficulty in visual search. Three experimental and one controlled conditions were randomly selected. Results showed that the P1, N1, and P2 amplitudes and latencies had no significant differences among the three experimental and one controlled conditions, and the ERP waveforms of low perceptual load of visual search were different from that of high perceptual load. These results might indicate that the latencies and amplitudes of initial P1, N1 and P2 in high and low perceptual load conditions were almost the same. The ERP waveforms of parallel search were very different from that of serial search, and the ERP waveforms of serial search were very similar. The P3 amplitudes increased as the degrees of the difficulty in visual search decreased.     

An ERP study for the degrees of the difficulty in visual search

The present study mainly probed the relationships between ERP components and the degrees of difficulty in visual search. Three experimental and one controlled conditions were randomly selected. Results showed that the P1, N1, and P2 amplitudes and latencies had no significant differences among the three experimental and one controlled conditions, and the ERP waveforms of low perceptual load of visual search were different from that of high perceptual load. These results might indicate that the latencies and amplitudes of initial P1, N1 and P2 in high and low perceptual load conditions were almost the same. The ERP waveforms of parallel search were very different from that of serial search, and the ERP waveforms of serial search were very similar. The P3 amplitudes increased as the degrees of the difficulty in visual search decreased.     

二棱大麦数量性状相关遗传力和选择指数分析

以15个二棱大麦品种(系)为材料,用相关遗传力研究大麦数量性状的相关遗传,并计算分析籽粒产量和产量构成性状所组合的各种选择指数。结果表明:各性状与单株粒重的相关遗传力均低于单株粒重的遗传力,因而仅利用一个性状作间接选择的效率比对单株粒重作直接选择的效率低,在构成大麦产量的三要素中,着重提高单株穗数对产量的选择效率为最大;高产育种同时考虑与产量显著相关的性状比单纯对产量选择的效果好,其中以单株穗数、每穗粒数和籽粒产量结合起来选择的效果最佳。本文并对相关遗传力在相关遗传变异分析中的应用进行了讨论。