Nanocrystallization induced by quasi-static fracture of metallic glasses at room temperature

Nanoparticles on the fracture surfaces of Co- and Fe-based metallic glasses during quasi-static compression at room temperature have been observed using a high-resolution scanning electron microscope. In terms of the differential scanning calorimeter, those nanoparticles were identified to be a result of nanocrystallization induced by the rapid fracture. Finally, the nanocrystallization behavior was evaluated by taking into account the super-high crack propagation rate and high elastic energy, which contributed to the local temperature rise up to the onset of crystallization, T _x.     

Comparison of quasicrystalline (T2) and crystalline (R) structures in AlCuLi using high-resolution X-ray diffraction

Abstract

A high-resolution X-ray scattering experiment has been performed on quasicrystalline (T2) and crystalline (R) phases of AlCuLi alloys. Peak widths determined from the diffraction profile of the R phase are found to scale with momentum transfer G, similar to the strain-broadening effect seen in conventional crystals with small unit cells. A narrowing of peak widths on annealing is also observed. On the other hand, diffraction peak widths in I-phase samples obtained by rapid solidification are found to scale with phason momentum G ₁, similar to that observed in large faceted crystals. Thermal annealing of the I phase is found to have no effect on peak widths. Our findings are discussed in the light of models for crystals and quasicrystals.     

伍连德与早期中俄陆路口岸出入境动物检疫

从档案资料中发现,伍连德在东三省防疫总处工作期间,对我国出入境动物检疫的发展起到了积极的促进作用.在他的大力推动下,黑河道立兽疫检验所和满洲里、海拉尔獭皮消毒检验所得以建立,使得黑龙江省成立了第一个由中国政府掌管的出入境动物检验机构,并且将旱獭的捕猎和贸易引入了科学规范的监管道路.通过对一手资料的挖掘和梳理,论述了伍连德先生在中国出入境动物检疫机构和制度的建立以及人才引进方面所做出的努力,进一步拓展和丰富了对伍连德先生的研究成果.     

凋亡--一个令人困惑的名称

就"细胞凋亡"这个热点名称进行探讨,从凋亡的起因及定义、由凋亡定义引起的哲学思考及就定义所做的建议进行分别论述.凋亡最初提出的是一种形态学特点,描述与坏死相对应的细胞解体的主动过程,之后大多数文章把凋亡定义为程序性的细胞死亡,并逐步演绎把死亡之前的细胞内生化变化称为凋亡.由此引起凋亡判断标准的混乱,并产生相关的药理学问题.细胞凋亡的实际情况与人类冠以的定义产生矛盾,其根本原因是真正实体与人为定义概念的哲学思维的混淆.提出应用直接描述真正实体的名称较凋亡更为可取.     

Event-related brain potentials: report order and task switch on multidimensional stimuli identification

An experiment was conducted to evaluate the effect of order of reporting stimulus dimension in multidimensional stimulus identification using a switch-task paradigm. Participants were required to identify each two-dimensional symbol by pushing the corresponding buttons on the keypad on which there were two columns representing the two dimensions, part and shape. The two orders of report were Order Part/Shape and Order Shape/Part. There was a task cue prior to each presentation of a symbol indicating the particular report order the participants should perform. The cue changed randomly. Both behavioral data and event-related potentials were recorded from 12 college students. Analysis of behavioral data showed switch cost indicated by increase in response time was greater for Order Shape/Part, a less appropriate order of reporting dimensional values, than Order Part/Shape (88 msec. vs 9 msec. for response time for the first stimulus dimension; 96 msec. vs -1 msec. for response time total). Neural activities under Order Shape/Part and Order Part/Shape were different, and it seems plausible that participants put more effort into selection and showed more related semantic activation in Order Shape/Part than in Order Part/ Shape which fits the Chinese adjective-then-noun language habit.     

Response to commentary on the multimodal treatment study of ADHD (MTA): mining the meaning of the MTA

In the December 2000 issue of the Journal of Abnormal Child Psychology, we published a set of papers presenting secondary analyses of the Multimodal Treatment Study of ADHD (MTA), and R. A. Barkley (2000) provided a commentary. A critique of the design of the study (MTA Cooperative Group, 1999) was presented based on a theoretical perspective of a behavioral inhibition deficit that has been hypothesized as the core deficit of ADHD (R. A. Barkley, 1997). The commentary questioned the design and analysis of the MTA in terms of (1) the empirical criteria for selection of components of behavioral (Beh) intervention, (2) the effectiveness of the Beh intervention, (3) the methods for analyses at the group and individual level, (4) implications of the MTA findings for clinical practice, (5) the role of genetics in response to treatment, and (6) the lack of a nontreatment control group. In this response, we relate the content of the papers to the commentary, (1) by reviewing the selection criteria for the Beh treatment, as outlined by K. C. Wells, W. E. Pelham, et al. (2000), (2) by addressing the myth that the MTA Beh treatment was ineffective (Pelham, 1999), (3) by describing the use of analyses at the level of the individual participant, as presented by J. S. March et al. (2000) and W. E. Pelham et al. (2000) as well as elsewhere by J. M. Swanson et al. (2001) and C. K. Conners et al. (2001), (4) by relating some of the suggestions from the secondary analyses about clinically relevant factors such as comorbidity (as presented by J. S. March et al., 2000) and family and parental characteristics (as presented by B. Hoza et al., 2000, S. P. Hinshaw et al., 2000, and K. C. Wells, J. N. Epstein, et al., 2000), (5) by discussing the statistical concept of heritability and the lack of a significant difference in the presence of ADHD symptoms in parents of the MTA families compared to parents in the classmate-control families (as presented by J. N. Epstein, et al., 2000), and (6) by acknowledging that an ethically necessary weakness of the MTA design is that it did not include a no-treatment control group. We discuss the use of secondary analyses to suggest how, when, and for what subgroups effectiveness of the Beh treatment may have been manifested. Finally, we invite others to use the large and rich data set that will soon be available in the public domain, to perform secondary analyses to mine the meaning of the MTA and to evaluate theories of ADHD and response to treatments.     

从儿童赌博任务看热执行功能的发展

为考察热执行功能的发展,本研究通过儿童赌博任务检测了60名3～4岁儿童(男女各半)的情感决策。实验结果表明,3岁和4岁儿童在此任务上存在显著的年龄差异,4岁组在各试验组的分数呈上升趋势,他们在试验组2、尤其在试验组4和5中选择有利纸牌的次数显著多于3岁儿童,这反映出情感决策在3～4岁期间发展迅速。此外,儿童在此任务上的成绩存在很多可变性,可能掩盖了性别差异,因而,尽管男孩在最后两个试验组的成绩优于女孩,但性别差异在统计上并不显著。     

Hemispheric competition in left-handers on bimanual reaction time tasks

The authors examined possible differences in left- and right-handers on bimanual reaction times to centralized visual stimuli. Eighty participants (n = 40 in each group of left- and right-handers) were tested on unimanual and bimanual reaction time (RT) tasks. Consistently across the 2 groups, the dominant-hand RT was faster, on average, than the nondominant-hand RT, and unimanual RTs were faster than bimanual RTs. However, RT differences between hands revealed a higher percentage of dominant-hand-led trials in right-handers than in left-handers, despite similar absolute RT differences in the 2 groups. On the basis of those findings, the authors conclude that hand dominance does not generally determine which hand leads in a bimanual task and that left-handers have stronger between-hemisphere competition than right-handers do.     

A structural model of acculturation and mental health status among Chinese Americans

This study examined the role of acculturation and its direct and indirect impact on depressive symptom severity through various correlates, including socioeconomic status (SES), stress, social support, personality negativity, and physical health perception. Using structural equation modeling, the proposed model was tested with 983 employed Chinese Americans from a representative community sample, the majority of whom were immigrants. The results demonstrated that acculturation, correlated with SES, contributed to depressive symptom severity only through indirect pathways. Higher acculturation was found associated with higher stress that in turn contributed to more elevated depressive symptoms. On the other hand, higher acculturation was also found strongly correlated with higher SES, which was associated with lower depressive symptoms directly or indirectly through several mediators. Better support, lower personality negativity, better health perception, and lower stress were found mediating the relationship between higher SES and lower depressive symptom severity. The simultaneous multigroup analysis showed that the final model was comparable for both men and women with very few differences.