Longitudinal Dynamic Analyses of Depression and Academic Achievement in the Hawaiian High Schools Health Survey Using Contemporary Latent Variable Change Models

The scientific literature consistently supports a negative relationship between adolescent depression and educational achievement, but we are certainly less sure on the causal determinants for this robust association. In this article we present multivariate data from a longitudinal cohort-sequential study of high school students in Hawai‘i (following McArdle, 2008; McArdle, Johnson, Hishinuma, Miyamoto, & Andrade, 2001). We first describe the full set of data on academic achievements and self-reported depression. We then carry out and present a progression of analyses in an effort to determine the accuracy, size, and direction of the dynamic relationships among depression and academic achievement, including gender and ethnic group differences. We apply 3 recently available forms of longitudinal data analysis: (a) Dealing with incomplete data—We apply these methods to cohort-sequential data with relatively large blocks of data that are incomplete for a variety of reasons (Little & Rubin, 1987; McArdle & Hamagami, 1992). (b) Ordinal measurement models (Muthén & Muthén, 2006)—We use a variety of statistical and psychometric measurement models, including ordinal measurement models, to help clarify the strongest patterns of influence. (c) Dynamic structural equation models (DSEMs; McArdle, 2008). We found the DSEM approach taken here was viable for a large amount of data, the assumption of an invariant metric over time was reasonable for ordinal estimates, and there were very few group differences in dynamic systems. We conclude that our dynamic evidence suggests that depression affects academic achievement, and not the other way around. We further discuss the methodological implications of the study.     

Relating Latent Change Score and Continuous Time Models

The primary goal of this article is to demonstrate the close relationship between 2 classes of dynamic models in psychological research: latent change score models and continuous time models. The secondary goal is to point out some differences. We begin with a brief review of both approaches, before demonstrating how the 2 methods are mathematically and conceptually related. It will be shown that most commonly used latent change score models are related to continuous time models by the difference equation approximation to the differential equation. One way in which the 2 approaches differ is the treatment of time. Whereas there are theoretical and practical restrictions regarding observation time points and intervals in latent change score models, no such limitations exist in continuous time models. We illustrate our arguments with three simulated data sets using a univariate and bivariate model with equal and unequal time intervals. As a by-product of this comparison, we discuss the use of phantom and definition variables to account for varying time intervals in latent change score models. We end with a reanalysis of the Bradway–McArdle longitudinal study on intellectual abilities (used before by McArdle & Hamagami, 2004) by means of the proportional change score model and the dual change score model in discrete and continuous time.     

三阶非线性泛函微分方程的振动性和渐近性

利用广义Riccati变换和平均不等式技巧,研究了一类三阶非线性泛函微分方程的振动性和渐近性,建立了所述方程一切解振动或者收敛于零的两个新的充分条件,推广和改进了一些文献中的结果．     

一类不定方程的非负整数解

定义k～1型广义Fibonacci数列,研究其通项与性质;结合相关文献方程和解的特点,猜想并证明了x^2＋麟y—y^2＋1=0（k∈N＊）这一类不定方程有且只有k～1型广义Fibonacci数列形式的非负整数解．     

基于Maxplus II的QDPSK的调制电路的设计

本设计利用QDPSK和差分编码技术,实现了数字信号的传输。在模块正确性的验证中,不但进行软件仿真,还做了电路调试。在FPGA芯片下载程序并运行后,验证了此QDPSK是可以正确工作的。     

A correlation-based computational model for synthesizing long-range dependent data

The authors present a computation model to generate long-range dependent (LRD) data according to a given correlation structure by filtering white noise. The simulation procedure of LRD data according to a given correlation structure is explained. A case study is illustrated with real LRD data series in the Internet.     

Body fat measurement in elite sport climbers: Comparison of skinfold thickness equations with dual energy X-ray absorptiometry

Abstract

The aim of this study was to compare equations for estimating percentage body fat from skinfold thickness in elite sport climbers by assessing their agreement with percentage body fat measured using dual-energy X-ray absorptiometry (DXA). Skinfold thickness was measured in a convenience sample of 19 elite sport climbers [9 women and 10 men; mean age 31.2 years (s = 5.0) and 28.6 years (s = 3.6), respectively]. Percentage body fat was estimated using 17 different equations, and it was also measured by DXA. A significant inter-methods difference was observed for all equations, except for Durnin's equation in men (inter-methods difference: ?0.57% and ?0.29%; 1.96 s: 5.56 and 5.23 for Siri's and Brozek's equation, respectively) and women (inter-methods difference: ?0.67% and ?1.29% for Siri's and Brozek's equation, respectively), and for Wilmore's equation using Siri's body fat equation in women (inter-methods difference: ?1.86%). In women, the limits of agreement were lower when using Durnin's equation compared with Wilmore's equation (1.96 s: 3.86% and 5.13%, respectively). In conclusion, of the 17 studied equations, Durnin's equation was the most accurate in estimating percentage body fat in both male and female elite climbers. Therefore, Durnin's equation could be used to assess percentage body fat in elite sport climbers if more accurate methods are not available. The generalizability of the results is limited by the fact that the sample was not selected at random.     

Morphology of polyethylene ski base materials

Abstract

We used high-resolution Raman spectroscopy and differential scanning calorimetry for a comprehensive analysis of carbon black-filled polyethylene ski base grades at processing stages from the raw material to the structured ski base. Based on Raman mapping, we assessed the applicability of an advanced evaluation procedure for amorphous, disordered, and crystalline phase fractions of polyethylene for polyethylene extrusion and sinter grades. For sinter grades, a sufficient segregation between carbon black and polyethylene was confirmed, allowing for a comprehensive Raman spectroscopic morphological analysis. Significant morphological changes in polyethylene due to processing from the raw material to the semi-finished film and to the structured ski base were identified. Throughout the processing chain, we observed a decrease in crystallinity and an increase in the amorphous phase fraction. Although the raw material and the sintered semi-finished film exhibited a different but uniform polyethylene morphology, the morphological changes due to structuring of the ski base are limited to the top surface layer. The highest amorphous phase fractions were detected in the surface of the structured ski bases.     

Fair Pairs and Three Part Praise – developing the sustained use of differential reinforcement of alternative behaviour

A training course of two after-school sessions was run for teaching assistants (TAs) in a UK inner city primary school. The subject of the training was classroom use of a version of differential reinforcement of alternative behaviours (DRAs) known as Fair Pairs. The training introduced the concept of “Three Part Praise” within Fair Pairs. The method of introduction involved training sessions, with the TAs explaining the process to their class teacher colleagues following each session. The TAs and class teachers were then asked to try the methodology in their classrooms. A follow-up session was held after six months for the TAs to feedback on their experiences. Results showed that most of the TA/class teacher “teams” were still using the approach after six months. Of those who responded most reported improvement in behaviour in the class. The implications of the methodology for training and the effectiveness of the approach being taught are discussed with suggestions for future research.     

利用微分法证明不等式

在理工科的《数学分析》中,不等式的证明是至关重要的。本文结合教学案例从利用函数的单调性、利用极值方法、利用拉格朗日中值定理、利用泰勒公式等方面给出了用微分法证明不等式的几种常用方法和技巧。