Latent structure and factorial invariance of a neuropsychological test battery for the study of preclinical Alzheimer's disease.

Objective: To examine the latent structure of a test battery currently being used in a longitudinal study of asymptomatic middle-aged adults with a parental history of Alzheimer's disease (AD) and test the invariance of the factor solution across subgroups defined by selected demographic variables and known genetic risk factors for AD. Method: An exploratory factor analysis (EFA) and a sequence of confirmatory factor analyses (CFA) were conducted on 24 neuropsychological measures selected to provide a comprehensive estimate of cognitive abilities most likely to be affected in preclinical AD. Once the underlying latent model was defined and the structural validity established through model comparisons, a multigroup confirmatory factor analysis model was used to test for factorial invariance across groups. Results: The EFA solution revealed a factor structure consisting of five constructs: verbal ability, visuospatial ability, speed & executive function, working memory, and verbal learning & memory. The CFA models provided support for the hypothesized 5-factor structure. Results indicated factorial invariance of the model across all groups examined. Conclusions: Collectively, the results suggested a relatively strong psychometric basis for using the factor structure in clinical samples that match the characteristics of this cohort. This confirmed an invariant factor structure should prove useful in research aimed to detect the earliest cognitive signature of preclinical AD in similar middle aged cohorts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anaerobic threshold and maximal aerobic power for three modes of exercise

Alterations in selected respiratory gas exchange parameters have been proposed as sensitive, noninvasive indices of the onset of metabolic acidosis (anaerobic threshold (AT) during incremental exercise. Our purposes were to investigate the validity and feasibility of AT detection using routine laboratory measures of gas exchange, i.e., nonlinear increases in VE and VCO2 and abrupt increases in FEO2. Additionally, we examined the comparability of the AT and VO2 max among three modes of exercise (arm cranking, leg cycling, and treadmill walk-running) with double determinations obtained from 30 college-age, male volunteer subjects. The AT's for arm cranking, leg cycling, and treadmill walk-running occurred at 46.5 +/- 8.9 (means +/- SD), 63.8 +/- 9.0, and 58.6 +/- 5.8% of VO2 max, respectively. No significant difference was found between the leg exercise modes (cycling and walk-running) for the AT while all pairwise arm versus leg comparisons were significantly different. Using nine additional subjects performing leg cycling tests, a significant correlation of r = 0.95 was found between gas exchange AT measurements (expressed as % VO2 max) and venous blood lactate AT measurements (% VO2 max). We conclude that the gas exchange AT is a valid and valuable indirect method for the detection of the development of lactic acidosis during incremental exercise.     

Comparison of a mathematical model to predict 10-km performance from the Conconi test and ventilatory threshold measurements

The purpose of this study was to validate a mathematical model (MM) that evaluates the Conconi test and predicts 10-km race time. In addition, the relationship between ventilatory threshold (Tvent) determined from a laboratory test and heart rate deflection (HRd) from the Conconi test were examined. Seventeen trained runners performed the Conconi test, and performance times were predicted using a MM based on a logistics function. A correlational analysis indicated a highly significant relationship (r = .98, p < .01) between MM predicted time and actual time. Significant relationships were found between velocity at Tvent and HRd (r = .95, p < .01), and predicted times from each method (r = .96, p < .01). Heart rates from Tvent and HRd were also related (r = .79, p < .01). These results suggest that a MM of the Conconi test is a valid method of predicting 10-km performance and is closely related to traditional laboratory measures.     

金属硅矿热炉供电系统电能测试与分析

针对某一典型的具备矿热炉的金属硅生产企业的工业供电系统,进行诸如谐波、功率因数以及三相电压平衡性等电能质量方面的测试,并结合理论分析揭示所存在的电能质量问题,最后提出相应的改善电能质量的技术改进方案,对于节能降耗具有一定的理论指导与实践参考意义.     

Regional localization of two genes for nonspecific X-linked mental retardation to Xp22.3-p22.2 (MRX49) and Xp11.3-p11.21 (MRX50)

Nine human ovarian cancer cell lines that express wild-type (wt) or mutated (mut) p53 were used to evaluate the cytotoxicity induced by cisplatin (DDP). The concentrations inhibiting the growth by 50% (IC50) were calculated for each cell line, and no differences were found between cells expressing wt p53 and mut p53. Using, for each cell line, the DDP IC50, we found that these concentrations were able to induce an increase in p53 levels in all four wt-p53-expressing cell lines and in one out of five mut-p53-expressing cell lines. WAF1 and GADD45 mRNAs were also increased by DDP treatment, independently of the presence of a wt p53. Bax levels were only marginally affected by DDP, and this was observed in both wt-p53- and mut-p53-expressing cells. DDP-induced apoptosis was evident 72 h after treatment, and the percentage of cells undergoing apoptosis was slightly higher for wt-p53-expressing cells. However, at doses near the IC50, the percentage of apoptotic cells was less than 20% in all the cell lines investigated. We conclude that the presence of wt p53 is not a determinant for the cytotoxicity induced by DDP in human ovarian cancer cell lines.     

Justifying the use and increasing the power of a t test for a randomized experiment with a convenience sample.

The standard error in an independent-groups t test is usually derived assuming that individuals are randomly sampled from populations of infinite size. However, t tests are routinely used in randomized experiments with individuals obtained from convenience samples. In such cases, the use of a t test is most often justified by supposing (a) that the convenience sample was a random sample from a hypothetical infinite population and (b) that it is this hypothetical population to which inference is being drawn. It is shown how the use of a t test with a convenience sample can be justified without reference to a hypothetical infinite population and how it may be possible to modify the t test to increase its power for drawing inferences in randomized experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

网络监督开辟了权利"联合"权力监督的反腐新路径

监督分为基于权力的监督和基于权利的监督两种.随着网络的发展,网络舆论监督日益成为人民群众进行监督的手段之一.本文在对权力监督和网络舆论监督的分析之上,探讨把二者结合进行监督,开辟反腐新路径.     

Metabolic and cardiorespiratory responses in young oarsmen during prolonged exercise tests on a rowing ergometer at power outputs corresponding to two concepts of anaerobic threshold

A group of ten young experienced oarsmen [mean age 17.5 (SD 1.7) years, height 182.5 (SD 5.9) cm, body mass 77.0 (SEM 10.6) kg] exercised in a progressive incremental test (PIE: 50W x 3 min[-1]) on a rowing ergometer to determine the power output corresponding to the 4 mmol lactate x l(-1) anaerobic threshold (AT4) and the individual anaerobic threshold (IAT). Within 10 days they performed at random two 30-min prolonged exercise tests (PET) at power outputs corresponding to AT4 and IAT to demonstrate whether or not a steady-state blood lactate concentration [La-]b could be maintained. Oxygen uptake (VO2), heart rate (HR) and [La-]b were measured. The PIE revealed significant lower values at IAT compared to AT4 for power output (P < 0.01), HR (P < 0.01) and VO2 (P < 0.01). Coefficients of correlation between AT4 and IAT were 0.68 for power output, 0.79 for HR and 0.70 for VO2. All the subjects could complete the PET at IAT and only six out of the ten at AT4. The [La-]b at the end of PET was significantly higher at AT4 compared to IAT (P < 0.01). Similar results were found for VO2 (P < 0.01) and for HR (P < 0.01). A steady state of mean blood lactate concentration ([La-]ss was found only for the power output at IAT. From the results of this study, we concluded that both concepts of anaerobic threshold gave different information about submaximal endurance capacity. Only IAT represented on average [La-]ss. It is suggested that more research is needed to elicit optimal guidelines for the intensity of endurance training.     

铁合金矿热炉放大设计模型的讨论

目前常用的矿热炉设计理论公式都是从生产实践数据中得来的统计规律。从矿热炉冶炼工艺角度对4个传统设计公式重新进行了理论分析,得出统计模型的物理本质是描述矿热炉的功率密度随其容量提高的变化规律。根据本设计模型的研究,安德里公式与威斯特里公式认为功率密度恒定不变,凯里和柏森所得统计规律则给出了功率密度随矿热炉容量增加而减小的定量关系。     

Rank transformations and the power of the Student t test and Welch t' test for non-normal populations with unequal variances.

In the present computer simulation study, the Student t test and the Welch version of the t test (the t′ test) were performed first on the initial sample values and then on ranks of the sample values. Unequal variances together with unequal group sizes markedly altered the probability of Type 1 and Type 2 errors for normal and for 8 kinds of nonnormal distributions, including mixed-normal, exponential, lognormal, and Cauchy distributions. Substitution of the Welch t′ test for the Student t test eliminated effects of unequal variances, but not effects of non-normality. The t test on ranks, which is equivalent to the Mann-Whitney-Wilcoxon test, was more powerful than the Student t test for several nonnormal distributions, but exhibited a substantial power loss when variances were unequal. The Welch t′ test in conjunction with the rank transformation simultaneously counteracted effects of both nonnormality and unequal variance. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)