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1.
I. A. Ovid’ko † 《Philosophical Magazine Letters》2013,93(10):655-663
A theoretical model is proposed to describe the generation and evolution of nanoscale cracks (nanocracks) in strained nanocrystalline materials. In the framework of the model, the nanocracks are nucleated and grow along grain boundaries, changing the direction of their growth at triple junctions. 相似文献
2.
A new density matrix renormalization group (DMRG) algorithm is presented which conserves the total spin. This is the first time that standard DMRG is extended to exploit fully the symmetries of the Hamiltonian. The obtained general procedure works for any operator, even operators that do not commute with the Hamiltonian. The new method gives substantial improvements over the standard DMRG. 相似文献
3.
对比不同手术方法对桡骨远端骨折的疗效.收集我院自2008年10月到2012年12月桡骨远端骨折患者86例,双盲随机分成试验组和对照组,试验组采用无头加压空心钉内固定,对照组采用锁定钢板内固定,比较两组的平均手术时间和平均术中出血量.术后12个月采用Jakim标准进行腕关节功能评定,同时对随访患者的腕关节功能进行临床评分.试验组平均手术时间为（30.45±5.14）min,显著低于对照组的（63.42±8.14）min（P＜0.05）,而试验组平均术中出血量为（23.67±6.14）ml,少于对照组的（83.12±10.47）ml（P＜0.05）.术后随访试验组腕关节功能优良率为87.5%;对照组则为87.1% （P＞0.05）,试验组和对照组腕关节在功能、握力活动范围等方面评分存在显著差异,在疼痛评分上两组无明显差异.采用无头加压空心钉治疗桡骨远端骨折可以显著减少手术时间及术中出血,提高腕关节功能而且在疗效上与传统锁定钢板治疗桡骨远端骨折相比无明显差异. 相似文献
4.
Athletes use compression garments (CGs) to improve sport performance, accelerate rehabilitation from knee injuries or to enhance joint position sense (JPS). The position of CGs around the knee may affect knee JPS but the data is inconsistent. The purpose of the present study was to determine the effects of CG position on healthy adults’ knee joint position sense acuity. In a counterbalanced, single-blinded study, 16 healthy young adults (8 female, age: 25.5 y) performed an active knee joint position-matching task with and without (CON) a below-knee (BK), above-knee (AK), or whole-knee (WK) CG in a randomized order on the dominant (CompDom) or the non-dominant leg (CompNon-Dom). We also determined the magnitude of tissue compression by measuring anatomical thigh and calf cross sectional area (CSA) in standing using magnetic resonance imaging (MRI). Subjects had less absolute repositioning error (magnitude of error) in BK compared with CON condition. On the other hand, the analysis of the direction of error (constant error) revealed that in each condition subjects tended to underestimate the target position (AK, BK and CON: 75%; WK: 94%). In WK condition there was a significantly larger negative error (−2.7 ± 3.4) as compared with CON (−1.6 ± 3.7) condition. There also was less variable error, in WK compared to BK and CON conditions, indicating less variability in their position sense using a WK CG, regardless of the underestimation. CG reduced thigh CSA by 4.5 cm2 or 3% and calf CSA by Δ1.3 cm2 or 1%. The position of CG relative to the knee modifies knee JPS. The findings helps us better understand how the application of a WK CG may support athletic activities. 相似文献
5.
A.S. Schneider B.G. Clark C.P. Frick P.A. Gruber E. Arzt 《Philosophical Magazine Letters》2013,93(11):841-849
The effect of prior deformation on mechanical behavior as a function of size is investigated for body-centered cubic (bcc) molybdenum (Mo) pillars. Experiments were performed using focused ion beam (FIB) manufactured [0 0 1] and [2 3 5] Mo micro/nanopillars, which were compressed, re-FIB machined, and compressed again. Unlike in bulk materials, pre-straining has a negligible effect on stress–strain behavior of the pillars, suggesting that dislocation storage does not occur in small-scale bcc specimens. The prevailing mechanism behind the size effect is attributed to dislocation nucleation mechanisms. 相似文献
6.
市场机制、政府调节与医疗管制制度框架的构建 总被引：5，自引：2，他引：5
郑大喜 《医学与哲学(人文社会医学版)》2004,25(9):33-34,37
在现代经济学的框架中,公共产品、外部性、自然垄断和信息不对称的存在会导致市场失灵.我国医疗服务市场也存在市场失灵,使政府管制的产生与存在成为必要,以弥补与矫正市场缺陷. 相似文献
7.
在人工语法范式、序列反应时任务范式以及复杂系统控制任务范式中,内隐学习对学习材料的难度及复杂度、材料性质、材料呈现方式等较为敏感。具体表现为难度和复杂程度较高的学习材料,以及形象性较突出的学习材料,更适合内隐学习,而使材料结构特点变得明显的呈现方式不利于内隐学习。然而,内隐学习的材料敏感性在其它范式上的普遍性有待进一步的实验研究。 相似文献
8.
Vivek Venkatesh Jeffrey S. Podoshen Kathryn Urbaniak Jason J. Wallin 《Journal of community & applied social psychology》2015,25(1):66-81
There is a great deal of literature that examines community orientations, in particular consumption‐based subcultures rooted in the appreciation of music scenes such as heavy metal and its subgenres. Much of this literature focuses on aspects of community maintenance, reaffirmation of shared identities and building of social bonds. In the present article, we report a study in which consumption of, and fandom in a specific scene in extreme metal, namely black metal, may lead to very unique consumer cultural orientations. Our analyses reveal that black metal fans' identities reside in a realm outside of a desired collective identification and tightly knit community, but rather one that uses signification, or representational means to convey meaning and belonging, as a way to signal repugnance with society and a reverence of individuality. The study engages a mixed qualitative approach utilizing interviews, observational research and content analysis to demonstrate how self‐identity related to the black metal music scene can thrive through an ideological and semiotic rejection of traditional community orientations seen in the majority of other extreme metal music scenes. This paper challenges traditional conceptualizations of group identity in music scenes by closely examining aspects of signification and fandom in black metal that represent a unique system of shared identities devoid of community building. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
Manu Kapur 《Cognitive Science》2014,38(5):1008-1022
When learning a new math concept, should learners be first taught the concept and its associated procedures and then solve problems, or solve problems first even if it leads to failure and then be taught the concept and the procedures? Two randomized‐controlled studies found that both methods lead to high levels of procedural knowledge. However, students who engaged in problem solving before being taught demonstrated significantly greater conceptual understanding and ability to transfer to novel problems than those who were taught first. The second study further showed that when given an opportunity to learn from the failed problem‐solving attempts of their peers, students outperformed those who were taught first, but not those who engaged in problem solving first. Process findings showed that the number of student‐generated solutions significantly predicted learning outcomes. These results challenge the conventional practice of direct instruction to teach new math concepts and procedures, and propose the possibility of learning from one's own failed problem‐solving attempts or those of others before receiving instruction as alternatives for better math learning. 相似文献
10.
Lauren L. Saling Natasha Laroo Michael M. Saling 《Neuropsychology, development, and cognition. Section B, Aging, neuropsychology and cognition》2017,24(6):649-661
When older adults retell an impersonal story, the resulting narratives are typically characterized by more prolixity and less coherence than those produced by younger adults. We aimed to determine whether this pattern is also observed when retelling a personal narrative. Younger and older participants told a personal story three consecutive times. With retelling, no evidence of increased coherence or fluency or reduction in hesitancy was observed for either age group. The nature of autobiographical narrative construction explains why such stories are not subject to automatization. A failure to automatize personal narratives is not, therefore, a symptom of aging. 相似文献
11.
Ekhard K.H. Salje Daniel Enrique Soto-Parra Antoni Planes Eduard Vives Marius Reinecker Wilfried Schranz 《Philosophical Magazine Letters》2013,93(8):554-560
The failure mechanism of porous materials under uniaxial stress has been investigated experimentally. Microporous SiO2, Vycor, has been subjected to slowly increasing compressive uniaxial stress with stress rates between 0.2 and 12.2?kPa/s. With increasing stress the strain changes stepwise with acoustic emission correlated with each volume collapse. The acoustic emission followed the characteristics of ‘crackling noise’ with a power law distribution over an exceptionally large interval of 6 decades at the slowest stress rate. The power law exponent is ?1.39. Possible applications in mining industry and others are discussed. 相似文献
12.
Using density functional theory (DFT), we found that high pressures intrinsically favor twinning in niobium by reducing the thickness of a stable twin. Five empirical interatomic potentials for niobium were considered in molecular dynamics (MD) shock simulations. The results show that two potentials exhibit the experimentally observed twinning behavior. Comparing with DFT under high pressure, we found that these two potentials are capable of reproducing the generalized stacking fault (GSF) curve, but the others predict several artificial metastable states along the GSF curve resulting in an artificial structural transformation. 相似文献
13.
为对比分析椎体成形术（PVP）与球囊扩张椎体后凸成形术（PKP）治疗骨质疏松性椎体压缩骨折的临床疗效。共治疗患者45例。PVP25例,PKP20例。所有患者术后疼痛均明显减轻或消失,PVP组与PKP组两组相比,术后的伤椎及相邻椎间隙高度、脊柱后凸Cobb角及ODI评分差异有统计学意义（P〈0．05）。PKP能够更好的恢复骨折椎体的高度,矫正脊柱后凸畸形,改善脊柱功能,明显减少骨水泥渗漏,临床效果较PVP更为满意。 相似文献
14.
A. Revesz P. Ochin P. Donnadieu J. P. Simon P. Guyot 《Philosophical Magazine Letters》2013,93(11):767-775
The first stages of thermal relaxation towards equilibrium in a Zr 57 Ti 5 Cu 20 Al 10 Ni 8 bulk metallic glass have been studied by differential scanning calorimetry, X-ray diffraction, transmission electron microscopy and high-resolution electron microscopy. These coupled experiments rule out for this glass the existence of a phase separation on the nanometric scale preceding the onset of crystallization. The first step of crystallization is of the primary type, that is it consists of the nucleation of nanocrystallites in the amorphous matrix with which they coexist in metastable equilibrium. The very high nucleation rate leads to a nanometric composite structure with a number density of about 7 2 10 24 m -3 of 3-4nm crystallites, occupying a volume fraction of about 15%. These features, as well as the crystallization kinetics observed during isochronal or isothermal heating, are discussed. 相似文献
15.
知觉加工中存在颜色类别知觉效应的证据 总被引：1，自引：0，他引：1
对于颜色的辨别具有类别知觉效应：类间两种颜色的辨别能力比同等颜色空间距离的类内两种颜色的辨别能力更高。对于类别知觉效应的产生机制存在两种观点：知觉特性假设、语言标签假设。以往的研究范式由于实验任务涉及到工作记忆成分,被试在完成任务时会自动地对颜色命名以利于记忆,因此所得证据大多支持语言标签假设,而对知觉特性假设的支持证据则很少。本文利用目标觉察范式最大限度去掉了工作记忆成分,通过测量被试辨别两种颜色的反应时,得到了类别知觉效应。并通过语言干扰任务进一步证实在该实验范式下类别知觉效应与语言的无关性。从而,为知觉特性假设提供了证据 相似文献
16.
Developing synchronised player movements for fluent competitive match play is a common goal for coaches of team games. An ecological dynamics approach advocates that intra-team synchronization is governed by locally created information, which specifies shared affordances responsible for synergy formation. To verify this claim we evaluated coordination tendencies in two newly-formed teams of recreational players during association football practice games, weekly, for fifteen weeks (thirteen matches). We investigated practice effects on two central features of synergies in sports teams – dimensional compression and reciprocal compensation here captured through near in-phase modes of coordination and time delays between coupled players during forward and backwards movements on field while attacking and defending. Results verified that synergies were formed and dissolved rapidly as a result of the dynamic creation of informational properties, perceived as shared affordances among performers. Practising once a week led to small improvements in the readjustment delays between co-positioning team members, enabling faster regulation of coordinated team actions. Mean values of the number of player and team synergies displayed only limited improvements, possibly due to the timescales of practice. No relationship between improvements in dimensional compression and reciprocal compensation were found for number of shots, amount of ball possession and number of ball recoveries made. Findings open up new perspectives for monitoring team coordination processes in sport. 相似文献
17.
临床依据患者外在表征推断心衰的特异性低,缘于传统诊疗难以实测心功能。仅指患者耐受体力活动差异的心功能I级~IV级分级标准缺乏心脏实情的印证。用外在的,多歧义的,存在大量主观虚拟的推论诊治心衰,有悖医道的客观真实属性。对疑似心衰者,临床应优先用超声把握心脏形态与功能证据并判明病因,也是临床干预心衰的必要逻辑前提。 相似文献
18.
尽管近年来在慢性心力衰竭(CHF)的治疗方面取得了较大的进展,但CHF患者仍有较高的住院率及病死率.CHF临床实践指南的发布促进了规范化治疗.为了取得良好的医疗效果,临床医生必须对心力衰竭患者提供一系列复杂的药物治疗及严格的自我控制措施.随着医学的不断发展,出现了包括心脏再同步化起搏、左心室辅助装置或心脏移植等治疗,而这些手段常需要在对患者进行危险性评估的基础上进行.严格遵循指南并使CHF患者出院后的教育与各种支持项目相结合才能够在一定程度上减低患者的再住院率及病死率. 相似文献
19.
Monica Kurylo Timothy R. Elliott Lisa DeVivo Laura E. Dreer 《Journal of clinical psychology in medical settings》2004,11(3):151-157
Family members have a considerable impact on the health and well-being of others in the family. The characteristics of family caregivers that relate to care recipients' positive and negative outcomes associated with chronic disease have received scant empirical attention. We reasoned that family caregiver social problem solving abilities would be associated with depression and life satisfaction reported by persons with congestive heart failure (CHF). Correlational analyses found that caregiver negative orientation toward solving problems was significantly predictive of higher depression and with decreased life satisfaction of persons with CHF. These findings indicate that family caregiver problem solving abilities are important factors in adjustment following CHF. Implications for clinical interventions and theoretical models of problem solving are discussed. 相似文献
20.
David E. Conroy 《Anxiety, stress, and coping》2013,26(4):431-452
Abstract Measuring fear of failure (FF) is a tremendous challenge for researchers and practitioners because (a) existing measures have demonstrated limited support for the validity of their score interpretations, and (b) existing measures are unidimensional while accumulating evidence suggests that FF is multidimensional. The Performance Failure Appraisal Inventory (PFAI) was developed to measures a set of empirically-derived congnitive-motivational-relational appraisals associated with FF. Results indicated that PFAI scores represented fears of (a) experiencing shame and embarrassment, (b) devaluing one's self-estimate, (c) losing social influence, (d) having an uncertain future, and (e) upsetting important others. Correlations with external measures of achievement goal orientations, trait anxiety, and social desirability were consistent with theoretical predictions. PFAI scores correctly classified 76.5% of participants' perceptions of underachievement. 相似文献