Postural coordination patterns as a function of dynamics of the support surface

The present study investigated the compensatory postural coordination patterns that emerge in the face of dynamic changes in the surface of support. Adult subjects stood on a moving platform that was sinusoidally translated in the anterior-posterior direction. The frequency and amplitude of the support surface translation were manipulated over a wide range of parameter values. The results revealed that as the frequency of platform motion increased, the postural system systematically exploited the available joint-space degrees of freedom and generated four distinct postural coordination modes (a rigid mode --> ankle mode --> ankle-hip mode --> ankle-hip-knee mode). It appears that upright standing posture has a small set of coordination patterns that are particular to the dynamics of the surface of support.     

任务图式对文章修改的影响研究

本研究探讨任务图式对文章修改的影响。高低水平的作者先完成一个写作任务,再修改文章的初稿。修改时,实验组学生先接受关于正确修改的任务图式指导,控制组学生则直接进行修改。实验结果表明,任务图式指导有明显的主效应,高低水平作者均提高了对字面错误与意义错误的正确修改,而水平间的差异主要表现在意义错误的修改上。本研究还分析了任务图式指导对修改的字数(包括改变意义与保留意义的字数)、修改的句法水平(包括字、词和句子)以及修改的方式(包括插入、替换、删除和移动句子)的影响。     

Tonic postural lean after-effects influenced by support surface stability and dynamics

Tonic neuromuscular processes are evident during lean after-effects, which occur after prolonged standing on a fixed ramp. Postural processes underlying lean after-effects were examined here using dynamic surface conditions. Three tilt adaptation conditions were tested with eyes-closed (n = 11). Tilt adaptation conditions involved standing for 120 s on a fixed toes-up ramp (7°) or on a toes-up sinusoidally tilted surface (7° ± 3°), which was followed by 120 s of standing on either a fixed horizontal surface or sway-referenced surface. All participants showed postural after-effects (p < .003). Specifically, standing on a fixed horizontal surface after sine-tilt adaptation, resulted in forward leaning which decayed over 120 s back to baseline. Standing on a sway-referenced surface after tilt-adaptation, initially showed no lean after-effect, however over the course of the trial the center-of-pressure shifted backward (p < .02). This after-effect during sway-reference conditions was also evident in the sway-induced surface tilt, which increased in dorsiflexion (p < .002), rather than decaying back to baseline. Thus, adaptation occurs on a dynamically tilted surface, while reliability of the surface as a stable reference affects the return of the center-of-pressure and surface tilt to baseline. These findings relate to changes in flexor/extensor muscle tonic set-point which also occur following a prolonged voluntary isometric contraction.     

Transverse shear surface wave in a functionally graded material infinite half space

The variable substitution and power-series techniques are used for the asymptotic analytical derivation of the governing equation of a transverse surface wave. The results reveal that the transverse wave can propagate along the surface of a functionally graded infinite half space in various modes, and that their dispersion relations are normal. For certain cases, energy is concentrated on the surface region to a depth of several wavelengths. A new theoretical foundation based on the transverse surface wave can be provided for graded-material characterization by experimental measurement. Some phenomena of seismic wave propagation may also be explained.     

Long-range interaction of radiation-generated self-interstitial atoms and adatoms on tungsten surface

ABSTRACT

The morphological modification of the W surface induced by specimen irradiation with 5?keV He atoms was studied at the atomic level using low-temperature ?eld ion microscope techniques. The major impact-induced damage mode on W {110} surface was found to be the formation of adatom sets produced by radiation-generated self-interstitial atoms emerging at the surface. The long-range interaction was revealed by evaluating the experimental probability density of finding two radiation-generated adatoms at a given separation in comparison with the probability density corresponding to a random distribution of adatoms. The statistically significant difference of these distributions consists of the absence or severe reduction of observed adatom pairs with separations in the range 5–11?Å. The experimental distribution was characterised by a relatively open arrangement of adatoms with the closest separation of about 11?Å. Our field ion microscope observations also reveal the self-organisation of radiation-generated W adatoms into atomic chains with the lateral interatomic separation substantially larger than the nearest-neighbor distance. These effects indicate the existence of long-range interactions between radiation-generated adatoms and radiation-generated self-interstitial atoms in the subsurface region.     

Shear horizontal surface waves in piezoelectric materials with surface stress

ABSTRACT

The propagation of shear horizontal (SH) surface waves in piezoelectric semi-infinite bodies is investigated theoretically. The surface stress exerting on the boundary is taken into account through surface piezoelectricity theory, and the velocity ranges and existence conditions of such surface waves for both electrically open and shorted cases are derived in detail. Analysis results show that the SH surface waves occurring with surface stress are dispersive in contrast to the classical situation, and the propagation characteristics strongly depend on the relative value of surface elasticity, surface piezoelectricity and surface density.     

Surface tension measurement of undercooled liquid Ni-based multicomponent alloys

The surface tensions of liquid ternary Ni–5%Cu–5%Fe, quaternary Ni–5%Cu–5%Fe–5%Sn and quinary Ni–5%Cu–5%Fe–5%Sn–5%Ge alloys were determined as a function of temperature by the electromagnetic levitation oscillating drop method. The maximum undercoolings obtained in the experiments are 272 (0.15T _L), 349 (0.21T _L) and 363?K (0.22T _L), respectively. For all the three alloys, the surface tension decreases linearly with the rise of temperature. The surface tension values are 1.799, 1.546 and 1.357?N/m at their liquidus temperatures of 1719, 1644 and 1641?K. Their temperature coefficients are ?4.972?×?10^–4, ?5.057?×?10^?4 and ?5.385?×?10^?4?N/m/K. It is revealed that Sn and Ge are much more efficient than Cu and Fe in reducing the surface tension of Ni-based alloys. The addition of Sn can significantly enlarge the maximum undercooling at the same experimental condition. The viscosity of the three undercooled liquid alloys was also derived from the surface tension data.     

不同表面特征图片对内隐记忆和外显记忆的影响

该研究选取30名被试,采用任务分离实验研究范式探讨不同表面特征图片对内隐记忆和外显记忆的影响。以32张动物图片为实验材料,其中鱼类和鸟类图片各半。两类图片中一半为黑白图片,另一半为彩色图片,所有实验材料用E—Prime软件呈现在电脑上。结果表明：（1）不同表面特征图片的再认成绩（外显记忆）显著好于偏好再认成绩（内隐记忆）,即外显记忆成绩好于内隐记忆;（2）在再认测验和偏好判断测验中,再认成绩和偏好再认成绩在图片表面特征的两个水平上存在显著差异;（3）控制组的偏好再认成绩显著好于实验组的偏好再认成绩,即控制组的内隐记忆好于实验组。结论：刺激材料的表面特征既是外显记忆的内容,也是影响外显记忆的重要因素;内隐记忆的作业成绩高度依赖于刺激材料的表面特征,刺激材料的表面特征是影响两种记忆的重要因素。     

Integrated memory for objects, places, and temporal order: evidence for episodic-like memory in mice

Human episodic memory refers to the recollection of an unique past experience in terms of what happened, and where and when it happened. Factoring out the issue of conscious recollection, episodic memory, even at the behavioral level, has been difficult to demonstrate in non-human mammals. Although, it was previously shown that rodents can associate what and when or what and where information given on unique trials, it proved to be difficult to demonstrate memory for what, where, and when simultaneously in mammals, without using extensive training procedures, which might induce semantic rather than episodic memory recall. Towards the goal of an animal model of human episodic memory we designed an three-trial object exploration task in which different versions of the novelty-preference paradigm were combined to subsume (a) object recognition memory, (b) the memory for locations in which objects were explored, and (c) the temporal order memory for object presented at distinct time points. We found that mice spent more time exploring two "old familiar" objects relative to two "recent familiar" objects, reflecting memory for what and when and concomitantly directed more exploration at a spatially displaced "old familiar" object relative to a stationary "old familiar" object, reflecting memory for what and where. These results suggest that during a single test trial the mice were able to (a) recognize previously explored objects, (b) remember the location in which particular objects were previously encountered, and (c) to discriminate the relative recency in which different objects were presented. According to the currently discussed behavioral criteria for episodic-like memory in animals, our results suggest that mice are capable to form such higher order memories.     

亲子关系和父母教育卷入对青少年抑郁、自伤和自杀意念的影响：挫败感和人生意义感的作用

基于生态系统理论和动机-意志整合模型,采用问卷法以930名青少年(年龄=15.24±1.66岁)及其父母为研究对象,构建一个有调节的中介模型,从家长与孩子双视角分析孩子体验到的亲子关系和父母教育卷入对青少年抑郁、自伤和自杀意念的影响路径。结果显示：(1)相比低亲子关系-低教育卷入一致的个体,高亲子关系-高教育卷入的青少年有着更低水平的挫败感,且相比于低亲子关系-高教育卷入的青少年,有着高亲子关系-低教育卷入的个体表现出更低水平的挫败感;(2)挫败感在亲子关系-教育卷入与青少年抑郁、自伤和自杀意念之间起部分中介作用;(3)人生意义感调节该中介模型后半段,即挫败感对青少年抑郁、自伤和自杀意念的影响,具体表现为随着人生意义感的增加,挫败感对抑郁、自伤和自杀意念的影响逐渐减小。研究从家庭关系中家长与孩子双视角,揭示了挫败感和人生意义感的中介与调节作用,为青少年抑郁、自伤和自杀意念的发生机制提供更多解释路径。