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911.
David Wesch John R. Lutzker Larry Frisch Michelle M. Dillon 《Journal of behavioral medicine》1987,10(1):91-101
This paper addresses an evaluation of an administrative decision to change the manner in which services were paid for at a Student Health Center (SHC). The impact of the change in payment was observed through monitoring the number of scheduled appointments at the SHC which the patient failed to attend, reschedule, or cancel. The impact was assessed through a comparison of the weekly no-show rates from the year prior to the change in payment practices through the year following the change. A time-series statistical package was used to analyze the no-show data. Collateral measures on the number of students attending the university, staff opinions, and usage of the SHC by different student groups were collected. Evaluations of the impact of administrative decisions on health-related behavior were discussed, in addition to a discussion of the usefulness of time-series models for this type of evaluation. 相似文献
912.
The effects of a 3-day tail suspension on central and peripheral sympathetic activity were studied in rats by determining the in vivo noradrenaline (NA) turnover in the brain cell groups involved in central blood pressure control (A1, A2, A5 and A6) and in two peripheral organs, heart and kidneys. In addition, cardiovascular parameters and their variabilities were investigated by recording blood pressure (BP) and heart rate (HR) before and after suspension. These measurements were processed by spectrum analysis to assess the influence of tail suspension on autonomic balance. The NA turnover in the suspended rats was markedly reduced in A2 (–49%, P<0.01) and A5 (–38%, P<0.01) nuclei but unchanged in A1 and A6 cell groups compared with the control rats. Peripheral NA turnover was decreased in cardiac atria (–44%, P<0.001) and ventricles (–27%, P<0.01) while it was unchanged in kidneys after suspension. The BP, HR and their variabilities were similar in both groups of animals and showed no changes after suspension compared with baseline values. Spectrum analysis of BP and HR in our conscious suspended rats revealed no changes in power spectrum density or in peak frequencies. The discrepancy between the decrease in central sympathetic activity and the absence of changes in cardiovascular parameters after tail suspension raises the question of the validity of the tail suspended rat model when studying the cardiovascular deconditioning observed in humans after an exposure to actual or simulated weightlessness. 相似文献
913.
Summary: The flame retardant mechanisms of red phosphorus, magnesium hydroxide and red phosphorus combined with magnesium hydroxide were studied in high impact polystyrene by means of comprehensive decomposition studies and combustion tests. The study is intended to illuminate prerequisites and the potential of red phosphorus as a fire retardant for hydrocarbon polymers in the condensed phase and in the gas phase. Thermal and thermo‐oxidative decomposition, decomposition kinetics and the product gases evolved were characterized using thermogravimetry coupled with Fourier transform infrared spectroscopy and mass spectroscopy, respectively. Fire behaviour was investigated with a cone calorimeter using different external heat fluxes, whereas the flammability was determined by limited oxygen indices. The combustion residues were analysed using XPS. Red phosphorus reduced the heat release in HIPS due to radical trapping in the gas phase. Magnesium hydroxide influenced fire behaviour by heat sink mechanisms, release of water and the formation of a magnesia layer acting as a barrier. The combination of both flame retardants in HIPS nearly resulted in a superposition. A slight synergy in barrier characteristics was due to the formation of magnesium phosphate, whereas a slight anti‐synergism occurred in flammability and in the gas phase action. The latter effect is controlled by a decreased fuel rate due to the barrier layer rather than by an initiation of red phosphorus oxidation in the condensed phase.
914.
基因表达系列分析及其应用前景 总被引:6,自引:0,他引:6
基因表达系列分析(Serial analysis of gene expression,SAGE)是一种研究真核细胞表达基因信息的高通量检测技术,它能对细胞内所有表达基因进行定性与定量分析。近年来此技术广泛应用于获得表达基因谱的研究,并且可以发现新基因信息,还可发现基因的靶向定位以及对其它基因的影响,明确表达基因的功能。本文就SAGE的原理、实验方案、技术发展与演变及其应用前景进行详细介绍。 相似文献
915.
A common approach to the analysis of gene expression data is to define clusters of genes that have similar expression. A critical step in cluster analysis is the determination of similarity between the expression levels of two genes. We introduce a neural network-based similarity index as a non-linear similarity index and compare the results with other proximity measures for Saccharomyces cerevisiae gene expression data. We show that the clusters obtained using Euclidean distance, correlation coefficients, and mutual information were not significantly different. The clusters formed with the neural network-based index were more in agreement with those defined by functional categories and common regulatory motifs. 相似文献
916.
Muscle synergies involved in shifting the center of pressure while making a first step 总被引:4,自引:0,他引:4
Wang Y Zatsiorsky VM Latash ML 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2005,167(2):196-210
We used the framework of the uncontrolled manifold (UCM) hypothesis to analyze multi-muscle synergies involved in making a
step by a standing person. We hypothesized that leg and trunk muscles are organized into stable groups (muscle modes, M-modes)
related to shifts of the center of pressure (COP) in the anterior-posterior and medio-lateral directions. Another hypothesis
was that the magnitudes of the modes co-vary across repetitive trials to stabilize a certain magnitude of the COP shift in
both directions. M-modes were defined using principal component analysis applied to indices of changes in the electromyographic
(EMG) activity prior to releasing variable loads that were held by the subject using a pulley system. For the task of releasing
the load behind the body three M-modes associated with a backward COP shift were defined. Four M-modes were defined for the
task of releasing the load at the body side associated with a lateral COP shift. Multiple regression analysis was used to
relate changes in the M-mode magnitudes to COP shifts. EMG changes prior to making a step were quantified over five 100 ms
time windows before the lift-off of the stepping leg. Two components of the variance in the M-mode space computed across repetitions
of a stepping task were quantified—a component that did not affect the average COP shift in a particular direction (variance
within the UCM, V
UCM), and a component that affected the COP shift (variance orthogonal to the UCM, V
ORT). V
UCM was significantly higher than V
ORT for both directions of the COP shifts. This relation was observed for the M-modes in the stepping leg as well as in the support
leg. The stepping leg showed a different time evolution of the ratio V
UCM/V
ORT such that the difference between the two variance components disappeared closer to the time of the lift-off. The findings
corroborate both main hypotheses. The study supports a view that control of whole-body actions involves grouping the muscles,
using fewer elemental variables to scale the muscle activity, and forming synergies in the space of the elemental variables
that stabilize time profiles of important performance variables. 相似文献
917.
In prior research we have shown how linear structural equation models and computer programs (e.g., LISREL) may be simply and directly used to provide alternatives for the traditional biometric twin design. We use structural equations and path models to define biometric group differences, we write traditional common-factor models in the same way, and then we take a detailed look at some alternative multivariate and biometric models. We contrast the biometricfactors covariance structure approach used by Loehlin and Vandenberg (1968), Martin and Eaves (1977), and others with the psychometric-factors approach used by McArdle et al. (1980) and others. We use the multivariate primary mental abilities data on monozygotic (MZ) and dizygotic (DZ) twins from Loehlin and Vandenberg (1968) to detail fundamental differences in model specification and results. We extend both multivariate biometric approaches using exploratory and confirmatory multiple-factor models. These comparisons show that each alternative multivariate methodology has useful features for empirical applications.This research has been supported by grants from the National Institute on Aging (AG02695, AG04704, and AG07137) to McArdle, and a Research Career Development Award (HD00694) to Goldsmith. 相似文献
918.
T. I. Farag S. A. Al-Awadi S. A. Al-Othman T. S. Sundareshan D. S. Krishna Murthy R. Usha S. A. Mady R. Uma James F. Reynolds 《American journal of medical genetics. Part A》1988,29(4):943-944
Direct chromosome preparations of neonatal cord blood provides the unique opportunity for rapid chromosome analysis (turnaround time; 6 hr), without the necessity of bone marrow aspiration. Based on 42 samples we confirm the finding of Garnham and Sutherland [1987] for suitability of cord blood for direct chromosome preparation. Procedural modifications are provided for higher yield of cells for chromosome analysis. The procedure may well be of major significance for rapid diagnosis of neonates who suffer from aneusomy. 相似文献
919.
Dr. O. Benoit C. Chataignier 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1973,17(4):348-363
Summary Influences of the wake-sleep states on spontaneous activity of thalamic ventro-basal neurons have been studied in the chronic cat using the following analyses for cell discharges: mean firing rate, interspike histogram and joint interval histogram (J.I.H.). While slow wave sleep is accompagnied by a characteristic firing pattern it is more difficult to compare spontaneous unit activity during wakefulness (W) and desynchronised sleep (D).A detailed analysis (especially of the J.I.H.) of the same neuron during the three states indicates marked differences between W and D; on the contrary, the intraburst pattern shows definite similarities between D and S. The greatest stability in the firing pattern of a given neuron is found during S on long recording. During D the variability in the firing pattern is mainly due to phasic activity but may also be related to tonic changes. 相似文献
920.