Estimating Gait Stability: Asymmetrical Loading Effects Measured Using Margin of Stability and Local Dynamic Stability

Changes to intersegmental locomotor control patterns may affect body stability. Our study aimed to (a) characterize upper body dynamic stability in response to the unilateral addition of mass to the lower extremity and (b) evaluate the efficacy of 2 different stability measures commonly used in the literature to detect resulting symmetrical step pattern modifications across the weighted segments (spatial) and between epochs of the gait cycle (temporal). Young adults walked on a treadmill while unloaded or with weights applied unilaterally to their foot, shank, or thigh. Both margin of stability and local dynamic stability (LDS) estimates detected similar trends of distal segment weighting resulting in more unstable upper body movement compared to proximal weighting; however only LDS detected anteroposterior changes in upper body stability over time.     

On the glass transition temperature and the elastic properties in Zr-based bulk metallic glasses

The temperature dependence of the elastic moduli was estimated from ultrasound time of flight measurements performed on bulk metallic glasses of composition Zr_{63? x} Cu₂₄Al _x Ni₁₀Co₃. Using the corresponding values at the glass transition temperature, the local atomic strain was determined. The obtained values for the critical atomic strain calculated for 8 at%?<?x?<?15 at% are close to the predicted universal criterion derived from a topological model, but may also reflect the difference in the chemical interaction that are not accounted by a topological approach.     

The effect of body and part-based motion on the recognition of unfamiliar objects

We investigated the role of global (body) and local (parts) motion on the recognition of unfamiliar objects. Participants were trained to categorise moving objects and were then tested on their recognition of static images of these targets using a priming paradigm. Each static target shape was primed by a moving object that comprised either the same body and parts motion; same body, different parts motion; different body, same part motion as the learned target or was non-moving. Only the same body but not the same part motion facilitated shape recognition (Experiment 1), even when either motion was diagnostic of object identity (Experiment 2). When parts motion was more related to the object's body motion then it facilitated the recognition of the static target (Experiment 3). Our results suggest that global and local motions are independently accessed during object recognition and have important implications for how objects are represented in memory.     

胃癌辅助化疗的选择和应用

局部进展期胃癌手术后是否给予全身辅助化疗以及关于标准方案的临床研究,一直是临床关注的热点问题,对ⅡB期以上的进展期胃癌术后给予辅助治疗已经成为共识,但对于采用何种方案作为标准方案尚缺乏循证学依据,而且东西方医学界的意见存在较大的争议,我们一方面期待具有更高级别证据的临床研究结果,另一方面在现有证据下对胃癌术后进行最大程...     

Contingent Stimuli Signal Subsequent Reinforcer Ratios

Conditioned reinforcer effects may be due to the stimulus' discriminative rather than its strengthening properties. While this was demonstrated in a frequently‐changing choice procedure, a single attempt to replicate in a relatively static choice environment failed. We contend that this was because the information provided by the stimuli was nonredundant in the frequently‐changing preparation, and redundant in the steady‐state arrangement. In the present experiments, 6 pigeons worked in a steady‐state concurrent schedule procedure with nonredundant informative stimuli (red keylight illuminations). When a response‐contingent red keylight signaled that the next food delivery was more likely on one of the two alternatives, postkeylight choice responding was reliably for that alternative. This effect was enhanced after a history of extended informative red keylight presentation (Experiment 2). These results lend support to recent characterizations of conditioned reinforcer effects as reflective of a discriminative, rather than a reinforcing, property of the stimulus.     

Rudolph Hermann Lotze's philosophically informed psychology

This essay deals with four main topics: the notion of philosophical psychology; the idea that physical events and mental events cannot be compared to one another; psychophysical mechanism; and the theory of local signs. These are all key elements in the Medicinische Psychologie of Rudolph Hermann Lotze (1817‒1881). By philosophical psychology, Lotze understands not only the collection of experimental data regarding physiological and mental states but also their philosophical processing outlining an interpretation of the real nature of the mind‒body connection. Within this framework, Lotze introduces the psychophysical mechanism as based on a key philosophical idea: mind and body are incomparable, but, nevertheless, they are in reciprocal relation (Wechselwirkung). In virtue of said special relation, movements that take place in the mental sphere of reality are transferred or translated in the bodily sphere and vice versa. This rearrangement (Umgestaltung) from one sphere of reality to the other is termed by Lotze “transformation to equivalent.” Through the concept of equivalence, Lotze supports the idea that the mind and the body form an organic whole. However, psychophysical mechanisms should not be seen as not a fixed series of physical changes followed by an equally fixed series of mental changes: physical changes are “read,” organized, and then transformed by the mind into something purely mental. This, in turn, produces new mechanical force and more physical changes. Lotze's legacy and long-term impact is finally read against the background of his contributions.     

A general Bayesian multilevel multidimensional IRT model for locally dependent data

Many item response theory (IRT) models take a multidimensional perspective to deal with sources that induce local item dependence (LID), with these models often making an orthogonal assumption about the dimensional structure of the data. One reason for this assumption is because of the indeterminacy issue in estimating the correlations among the dimensions in structures often specified to deal with sources of LID (e.g., bifactor and two-tier structures), and the assumption usually goes untested. Unfortunately, the mere fact that assessing these correlations is a challenge for some estimation methods does not mean that data seen in practice support such orthogonal structure. In this paper, a Bayesian multilevel multidimensional IRT model for locally dependent data is presented. This model can test whether item response data violate the orthogonal assumption that many IRT models make about the dimensional structure of the data when addressing sources of LID, and this test is carried out at the dimensional level while accounting for sampling clusters. Simulations show that the model presented is effective at carrying out this task. The utility of the model is also illustrated on an empirical data set.     

语篇阅读理解中人物性格模型的建构

采用实时窗口阅读技术,通过操纵特征段落性质和屏蔽段落长度两个变量,探讨人物性格模型在语篇阅读中的建构和影响因素。在研究所用材料中,特征段落描述能反映主人公性格的典型行为或不能反映其性格的一般行为,使其与目标句分别形成冲突或无关关系,考察读者能否利用这些内隐式的行为描述建构人物的性格模型。同时,改变屏蔽段落长度,形成局部或整体联贯两种条件,考察不同联贯类型的影响作用。结果发现：在不论整体还是局部联贯条件下,读者均能利用内隐的行为描述建构人物性格模型,并能应用该模型预期人物的后续行为。     

A latent trait theory via a stochastic learning theory for a knowledge space

To capture the cognitive organization of a set of questions or problems pertaining to a body of information, Doignon and Falmagne have proposed, and analyzed in a number of papers, the concept of aknowledge space, that is, a distinguished collection of subsets of questions, representing the possibleknowledge states. This collection of sets is assumed to satisfy a number of conditions. Since this concept is a deterministic one, the problem of empirical testing arises. A stochastic version of a knowledge space is developed in this paper, in which the knowledge states are considered as possible epochs in a subject's learning history. The knowledge space is decomposed as a union of a number of possible learning paths, calledgradations. The model specifies how a subject is channelled through and progresses along a gradation. A probabilistic axiom of the local indepencence type relates the knowledge states to the observable responses. The predictions of this model are worked out in details in the case of parametric assumptions involving gamma distributions. An application of the model to artificial data is described, based on maximum likelihood methods. The statistical analysis is shown to be capable of revealing the combinatoric core of the model.This work was supported by NSF grant IST-8418860 and ARI grant DAAG29-84-G-0083 to New York University. I am grateful to Jean-Paul Doignon, Mathieu Koppen, Geoff Iverson and Michael Landy for their reactions to previous drafts of this paper, to Michael Villano for carrying out the computer simulation and the analysis of the simulated data, and especially to one referee for his very useful comments.     

The generalized matching law as a description of multiple-schedule responding

The literature was examined to determine how well the generalized matching law (Baum, 1974) describes multiple-schedule responding. In general, it describes the data well, accounting for a median of 91% of the variance. The median size of the undermatching parameter was 0.46; the median bias parameter was 1.00. The size of the undermatching parameter, and the proportion of the variance accounted for by the equation, varied inversely with the number of schedules conducted, with the number of sessions conducted per schedule, and with the time within a component. The undermatching parameter also varied with the operanda used to produce reinforcers and with the reinforcer used. The undermatching parameter did not vary consistently with component duration or with several other variables. Bias was greater when fewer rather than more schedules were conducted, when two rather than one operanda were used, and when White Carneaux rather than homing pigeons served as subjects. These results imply that the generalized matching law may describe both concurrent and multiple-schedule responding, but that the same variables do not always influence the bias and undermatching parameters in the same way for the two types of schedules.