用ROC评价AFP、VEGF和瘦素对HCC的诊断价值

用受试者工作特性曲线（ROC）对184例HCC患者和73例健康对照者的血清AFP、VEGF、Lep及三者联合检测结果进行评价。结果显示：AFP、VEGF、Lep测定结果在两组资料间比较均有统计学意义（P〈0．01）。HCC患者的AFP、VEGF、Lep与三者联合检测在ROC曲线下面积分别为0．902、0．841、0．712和0．952。AFP、VEGF、Lep对HCC的临床诊断临界点分别为25ug／L、25lng／L和15ug／L。因此,AFP、VEGF、Lep三者联合检测可显著提高对HCC诊断的灵敏度和有效性,优于AFP、VEGF、Lep的单项检测。     

Perceived fit with an academic environment: Attitudinal and behavioral outcomes

Because person–organization fit relates to important outcomes, and because fit is a time-dependent process, there exists a need to model longitudinal data related to fit. In a multi-university sample (N = 1174), we tested hypotheses concerning person–organization fit and various behavioral and attitudinal outcomes; correlations between changes in these variables over time, and the correlates of these changes. Using autoregressive modeling and latent growth curve modeling, results indicated that academic fit leads to academic satisfaction, which in turn leads to turnover intent, and to a lesser extent GPA and class absenteeism. Changes in academic fit correlated highly with similar changes in satisfaction and GPA and with opposite changes in turnover intent. Academic satisfaction did not correlate with subsequent organizational citizenship behavior (OCB) as predicted; changes across these domains were significantly related, but were small. Consistent with our hypotheses, Realistic interests correlated negatively with changes in academic fit and satisfaction. Investigative interests were correlated positively with changes in fit and initial satisfaction levels. We conclude by discussing implications, limitations, and future research concerning the longitudinal analysis of person–organization fit.     

Regularized Finite Mixture Models for Probability Trajectories

Finite mixture models are widely used in the analysis of growth trajectory data to discover subgroups of individuals exhibiting similar patterns of behavior over time. In practice, trajectories are usually modeled as polynomials, which may fail to capture important features of the longitudinal pattern. Focusing on dichotomous response measures, we propose a likelihood penalization approach for parameter estimation that is able to capture a variety of nonlinear class mean trajectory shapes with higher precision than maximum likelihood estimates. We show how parameter estimation and inference for whether trajectories are time-invariant, linear time-varying, or nonlinear time-varying can be carried out for such models. To illustrate the method, we use simulation studies and data from a long-term longitudinal study of children at high risk for substance abuse. This work was supported in part by NIAAA grants R37 AA07065 and R01 AA12217 to RAZ.     

Graded response model based on the logistic positive exponent family of models for dichotomous responses

Samejima (Psychometrika 65:319–335, 2000) proposed the logistic positive exponent family of models (LPEF) for dichotomous responses in the unidimensional latent space. The objective of the present paper is to propose and discuss a graded response model that is expanded from the LPEF, in the context of item response theory (IRT). This specific graded response model belongs to the general framework of graded response model (Samejima, Psychometrika Monograph, No. 17, 1969 and No. 18, 1972; Handbook of modern item response theory, Springer, New York, 1997; Encyclopedia of Social Measurement, Academic Press, San Diego, 2004), and, in particular to the heterogeneous case (Samejima, Psychometrika Monograph, No. 18, 1972). Thus, the model can deal with any number of ordered polytomous responses, such as letter grades (e.g., A, B, C, D, F), etc. For brevity, hereafter, the model will be called the LPEF graded response model, or LPEFG. This model reflects the opposing two principles contained in the LPEF for dichotomous responses, with the logistic model (Birnbaum, Statistical theories of mental test scores, Addison Wesley, Reading, 1968) as their transition, which provide a reasonable rationale for partial credits in LPEFG, among others.     

Context effects in a temporal discrimination task" further tests of the Scalar Expectancy Theory and Learning-to-Time models

Pigeons were trained on two temporal bisection tasks, which alternated every two sessions. In the first task, they learned to choose a red key after a 1-s signal and a green key after a 4-s signal; in the second task, they learned to choose a blue key after a 4-s signal and a yellow key after a 16-s signal. Then the pigeons were exposed to a series of test trials in order to contrast two timing models, Learning-to-Time (LeT) and Scalar Expectancy Theory (SET). The models made substantially different predictions particularly for the test trials in which the sample duration ranged from 1 s to 16 s and the choice keys were Green and Blue, the keys associated with the same 4-s samples: LeT predicted that preference for Green should increase with sample duration, a context effect, but SET predicted that preference for Green should not vary with sample duration. The results were consistent with LeT. The present study adds to the literature the finding that the context effect occurs even when the two basic discriminations are never combined in the same session.     

The longitudinal relations between parenting and toddlers' attention problems and aggressive behaviors

The aim of the present study was to examine the normative developmental trajectories of toddlers’ externalizing behaviors and several maternal and paternal parenting dimensions. Latent growth models were used to determine intraindividual changes and interindividual differences in these changes. One hundred and eight boys were followed from 17 months of age to 35 months of age. A significant linear decrease in attention problems and a significant linear increase in aggressive behaviors were found. Additionally, multivariate models were tested that related the developmental trajectories of externalizing behaviors to the trajectories of the parenting dimensions. The results showed meaningful contemporary relations and relations between over-time trajectories of parenting dimensions and children's externalizing behaviors.     

Hints of beauty in social cognition: Broken symmetries in mental dynamics

It is a widely held assumption that social cognition is wholly the result of natural selection and learning, debates arising over how much was naturally selected versus how much is learned. I argue here, however, for there being a third factor, namely physics, specifically symmetries and symmetry breakings in neural dynamics. These symmetries manifest themselves in social judgments in a fairly direct way as descending chains of subgroup types in mental social schemata. These schemata are the four models of Alan Page Fiske's relational-models typology. Descending chains of subgroup types are a phenomenon widely observed in nature; their presence in social cognition is consistent with there being a relevant neural network, the activity of which can undergo symmetry breakings. This would be analogous to the neural activity that has been computer modeled in an attempt to explain animal locomotion. This should encourage work towards specifying the particular symmetry groups in social cognition as a step towards devising computer models of the relevant neural mechanism. Approaches to animal locomotion suggest at least the broad outlines of how to proceed. Evidence of symmetry groups in social schemata also supports the view that the innate aspects of social cognition are at least partly structured by dynamics without being encoded in genes, just as the shape of the protective shell of some viruses results from dynamics without being genetically encoded.     

The Thought Experiment of Maxwell’s Demon and the Origin of Irreversibility

The problem of the irreversibility’s origin in thermodynamic processes occupies a distinguished place among many and lasting attempts by researchers to derive irreversibility from molecular-mechanical principles. However, this problem is still open and no universally accepted solution may be given during any course. In this paper, I shall try to show that the examining of Maxwell’s demon thought experiment may provide insight into the difficulties that emerge, looking for this origin because: (i) it is connected with the notion of irreversibility, and (ii) one of its functions is that of the “reversibility objection.” In order to illustrate this point, I study Boltzmann’s approach to the problem of a molecular-mechanical interpretation of irreversibility and I show that an auxiliary assumption (the selected direction of time) is responsible for producing irreversibility. But this result is accordant with the predictions of Maxwell’s demon thought experiment: the assumptions of this kind are not dictated by molecular-mechanical principles but are separate input in the model-systems used.