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At least 1,315 records · Page 73Linked to original sources
PubMed1990

Unemployment and marital dissolution.

"This paper analyses the effects of unemployment on the probability of marital dissolution. Based on panel data for a sample of Danish married couples, we estimate a dynamic model for the probability of marital dissolution where we take into account the possible effects of unemployment for both spouses. We also control for other factors such as education, age, presence of children, place of residence, health and economic factors. The empirical results show that unemployment seems to be an important factor behind marital instability. However, only unemployment of the husband has an effect, and this effect is immediate."

Age Factors↗
PubMed1999

Lipids, lipoproteins and apolipoprotein (a) isoforms in type 2 diabetic patients.

BACKGROUND: Patients with type 2 diabetes mellitus have a greater than normal risk of developing atherosclerotic vascular diseases. Higher than normal plasma concentrations of lipoprotein (a) [Lp(a)] have been associated with premature atherosclerosis in several studies. OBJECTIVE: To determine the concentrations of lipids, lipoproteins, and Lp(a) in 107 type 2 diabetic patients, and the distribution of apolipoprotein (a) [apo(a)] phenotypes for this group, and to compare the results found with results for healthy subjects. RESULTS: Plasma concentrations of cholesterol, triglycerides, and apolipoprotein B in the diabetics were significantly higher than those in control subjects. Diabetic patients had slightly lower Lp(a) concentrations than did nondiabetic subjects, but these differences were not statistically significant. Distributions of Lp(a) concentrations both in type 2 diabetic patients and in control subjects were markedly skewed, the highest prevalences being of low values. CONCLUSION: Distributions of apo(a) phenotypes for patients with type 2 diabetes mellitus and controls were remarkably alike. Smaller isoforms were similarly prevalent for the two populations, as were the null, single-band and double-band apo(a) phenotypes.

Adult↗
PubMed2006

Estimation of distribution function in bivariate competing risk models.

We consider lifetime data involving pairs of study individuals with more than one possible cause of failure for each individual. Non-parametric estimation of cause-specific distribution functions is considered under independent censoring. Properties of the estimators are discussed and an illustration of their application is given.

Biometry↗
PubMedDate not supplied

[Macroscopic fluctuations of discrete distribution forms as a consequence of the arithmetic and cosmophysical causes].

The recent investigations are reviewed of the "macsroscopic fluctuations", i.e. synchronous on local time changes in probability of the appearance of the same detailed structure of distribution (histograms) of the rates of different processes, at the same or at different geographic points. Gravitation nonhomogeneousity is considered as a probable cause of these phenomena.

Earth, Planet↗
PubMed2000

Assessing accurate sizes of synaptic vesicles in nerve terminals.

Chemical synaptic transmission occurs when vesicles within a presynaptic neuron fuse to the membrane and release their neurotransmitter content into the synaptic cleft, eliciting a response in the postsynaptic cell. If concentration of neurotransmitter is the same in all synaptic vesicles, the volume of the vesicle determines how much transmitter is released. Thus, variation in vesicular volume may contribute to observed variance of synaptic quantal unit size. The present study provides an approach to more fully and accurately characterize the dimensions of synaptic vesicles within a population containing varied sizes of vesicles. The methodology can be applied in a wide range of stereological problems. The approach characterizes the distribution of vesicle sizes within a population and provides a means to assess effects of experimental manipulations on vesicle dimensions. The mathematical treatments to obtain the true distribution of vesicle sizes involve extraction of the observed distribution from an enlarged population containing smaller vesicle diameters produced by sectioning of the specimens. A FORTRAN program is provided.

Algorithms↗
PubMed2004

Likelihood-based inference for the shape parameter of a two parameter Weibull distribution.

Based on a Type 2 censored sample, we use the likelihood-based approach to draw likelihood inference on the shape parameter gamma of a two-parameter Weibull distribution. In particular, we derive the profile, conditional and marginal likelihoods of gamma. Numerical results along with some concluding remarks regarding the use of likelihood-based methods for inference are provided.

Humans↗
PubMed2004

A method for analyzing longitudinal outcomes with many zeros.

Health care utilization and cost data have challenged analysts because they are often correlated over time, highly skewed, and clumped at 0. Traditional approaches do not address all these problems, and evaluators of mental health and substance abuse interventions often grapple with the problem of how to analyze these data in a way that accurately represents program impact. Recently, the traditional 2-part model has been extended to mixed-effects mixed-distribution model with correlated random effects to deal simultaneously with excess zeros, skewness, and correlated observations. We introduce and demonstrate this new method to mental health services researchers and evaluators by analyzing the data from a study of assertive community treatment (ACT). The response variable is the number of days of hospitalization, collected every 6 months over 3 years. The explanatory variable is group: ACT vs. standard case management. Diagnosis (schizophrenia vs. bipolar disorder), time, and the baseline values of hospital days are covariates. Results indicate that clients in the ACT group have a higher probability of hospital admission, but tend to have shorter lengths of stay. The mixed-distribution model provides greater specification of a model to fit these data and leads to more refined interpretation of the results.

Adult↗
PubMed2002

Human group choice: discrete-trial and free-operant tests of the ideal free distribution.

Ideal free distribution theory predicts that foragers will form groups proportional in number to the resources available in alternative resource sites or patches, a phenomenon termed habitat matching. Three experiments tested this prediction with college students in discrete-trial simulations and a free-operant simulation. Sensitivity to differences in programmed reinforcement rates was quantified by using the sensitivity parameter of the generalized matching law (s). The first experiment, replicating prior published experiments, produced a greater degree of undermatching for the initial choice (s = 0.59) compared to final choices (s = 0.86). The second experiment, which extended prior findings by allowing only one choice per trial, produced comparable undermatching (s = 0.82). The third experiment used free-operant procedures more typical of laboratory studies of habitat matching with other species and produced the most undermatching (s = 0.71). The results of these experiments replicated previous results with human groups, supported predictions of the ideal free distribution, and suggested that undermatching represents a systematic deviation from the ideal free distribution. These results are consistent with a melioration account of individual behavior as the basis for group choice.

Adolescent↗
PubMed1979

[Some remarks about the spatial differentiation of fertility in Poland].

"Some problems are discussed in connection with the estimation and interpretation of regression equations. Stability in time is suggested as one of the criteria of goodness of fit.... Several regression equations are estimated giving the gross reproduction rate as a linear function of the proportion of economically active females outside agriculture (SUMMARY IN ENG, RUS)

Birth Rate↗
PubMed1990

A distribution-free procedure for the statistical analysis of bioequivalence studies.

In bioequivalence assessment, the consumer risk of erroneously accepting bioequivalence is of primary concern. In order to control the consumer risk, the decision problem is formulated with bioinequivalence as hypothesis and bioequivalence as alternative. In the parametric approach, a split into two one-sided test problems and application of two-sample t-tests have been suggested. Rejection of both hypotheses at nominal alpha-level is equivalent to the inclusion of the classical (shortest) (1-2 alpha) 100%-confidence interval in the bioequivalence range. This paper demonstrates that the rejection of the two one-sided hypotheses at nominal alpha-level by means of nonparametric Mann-Whitney-Wilcoxon tests is equivalent to the inclusion of the corresponding distribution-free (1-2 alpha) 100%-confidence interval in the bioequivalence range. This distribution-free (nonparametric) approach needs weaker model assumptions and hence presents an alternative to the parametric approach.

Adult↗
PubMed2006

Unsupervised variational image segmentation/classification using a Weibull observation model.

Studies have shown that the Weibull distribution can model accurately a wide variety of images. Its parameters index a family of distributions which includes the exponential and approximations of the Gaussian and the Raleigh models widely used in image segmentation. This study investigates the Weibull distribution in unsupervised image segmentation and classification by a variational method. The data term of the segmentation functional measures the conformity of the image intensity in each region to a Weibull distribution whose parameters are determined jointly with the segmentation. Minimization of the functional is implemented by active curves via level sets and consists of iterations of two consecutive steps: curve evolution via Euler-Lagrange descent equations and evaluation of the Weibull distribution parameters. Experiments with synthetic and real images are described which verify the validity of method and its implementation.

Algorithms↗
PubMed2006

The amplitude distribution of release events through a fusion pore.

Neurotransmitters, hormones, or dyes may be released from vesicles via a fusion pore, rather than by full fusion of the vesicle with the plasma membrane. If the lifetime of the fusion pore is comparable to the time required for the substance to exit the vesicle, only a fraction of the total vesicle content may be released during a single pore opening. Assuming 1), fusion pore lifetimes are exponentially distributed (tauP), as expected for simple single channel openings, and 2), vesicle contents are lost through the fusion pore with an exponential time course (tauD), we derive an analytical expression for the probability density function of the fraction of vesicle content released (F): dP/dF=A (1-F)(A-1), where A=tauD/tauP. If A>1, the maximum of the distribution is at F=0; if A<1, the maximum is at F=1; if A=1, the distribution is perfectly flat. Thus, the distribution never has a peak in the middle (0<F<1). This should be considered when interpreting the distribution of miniature synaptic currents, or the fraction of FM dye molecules lost during a single fusion pore opening event.

Cell Membrane Permeability↗
PubMed2002

Quality of removable partial dentures worn by the adult U.S. population.

STATEMENT OF PROBLEMS: Research-based assessments of the quality of removable partial dentures (RPDs), especially within a large patient population, are lacking. PURPOSE: This study evaluated the prevalence and quality of RPDs by use of the National Health and Nutrition Survey (NHANES III) data set. MATERIAL AND METHODS: Estimates of the health and nutritional status of the American population were obtained from the NHANES III data set (1988-1994). Calibrated dentists performed dental examinations on 17,884 adults. If the subject wore an RPD, its quality was assessed with 5 criteria: integrity, tooth wear, the presence of temporary reline material or adhesive, stability, and retention. In this study, the data on RPD defects were used to assess the prevalence of problems. The original population was divided into 4 subgroups: paired RPD data = subjects wearing both maxillary and mandibular RPDs (n = 600 prostheses, 300 maxillary and 300 mandibular); single RPD data = subjects with only one RPD (n = 1003 prostheses, 511 maxillary and 492 mandibular); maxillary versus mandibular RPD data = all subjects with all RPDs (n = 1603 prostheses, 811 maxillary and 792 mandibular); and pooled RPD data = all subjects with a single RPD plus subjects with 2 RPDs, counting only the RPD with the most defects (n = 1303 prostheses, 674 maxillary and 629 mandibular). The subjects were analyzed with descriptive statistics. The distribution of defects in the RPDs was examined for possible associations with chi(2) tests. The paired data for patients with both maxillary and mandibular RPDs were analyzed with Wilcoxon signed rank tests. The prevalence of RPDs as a function of patient age and the association between RPD defects and patient age were analyzed with chi(2) tests. The results were considered highly significant at P<.0001 and significant at P<.05. RESULTS: Of the 17,884 adults who underwent a dental examination, 1306 had RPDs. Three patients were excluded because their records were incomplete, leaving 1303 patients available for analysis. Most of the prostheses examined (65%) had at least 1 defect. Lack of stability was the most prevalent single defect. Distinctions in the type and prevalence of defects were observed between mandibular and maxillary RPDs. Mandibular RPDs had significantly more problems related to retention, whereas maxillary RPDs had significantly more problems related to the presence of reline material and to integrity defects. Tooth wear defects were significantly associated with patient age (P<.0001). Only one third of the RPDs were considered satisfactory according to NHANES III criteria. CONCLUSION: A review of the database used in this study indicated that, in spite of a decline in tooth loss, RPDs are still used in all age cohorts, including young adults. A large number of RPDs were found to have defects.

Adhesives↗
PubMed1992

A distribution-free procedure for the statistical analysis of bioequivalence studies.

In bioequivalence assessment, the consumer risk of erroneously accepting bioequivalence is of primary concern. In order to control the consumer risk, the decision problem is formulated with bioinequivalence as hypothesis and bioequivalence as alternative. In the parametric approach, a split into two one-sided test problems and application of two-sample t-tests have been suggested. Rejection of both hypotheses at nominal alpha-level is equivalent to the inclusion of the classical (shortest) (1-2 alpha) 100%-confidence interval in the bioequivalence range. This paper demonstrates that the rejection of the two one-sided hypotheses at nominal alpha-level by means of nonparametric Mann-Whitney-Wilcoxon tests is equivalent to the inclusion of the corresponding distribution-free (1-2 alpha) 100%-confidence interval in the bioequivalence range. This distribution-free (nonparametric) approach needs weaker model assumptions and hence presents an alternative to the parametric approach.

Adult↗
PubMed1975

Modulation of cortical and pyramidal tract induced motor responses by electrical stimulation of the basal ganglia.

Two general mechanisms based on anatomical studies are possible for modulation of motor activity by the caudate nucleus and globus pallidus. These mechanisms are: (1) modulation of the output of cortical neurons that exert motor influences; and (2) modulation of subcortical neurons that exert motor influences. Differentiation between these two mechanisms was accomplished in the present study by two experimental approaches, both of which employed the conditioning-test paradigm. The first approach was an investigation of caudate nucleus or globus pallidus modulation (conditioning stimulus) of flexor responses of the anterior tibialis muscle elicited by electrical stimulation of the sensorimotor cortex (test stimulus) or pyramidal tract (test stimulus). These investigations were carried out in the intact and in decorticate cats. The second approach was an analysis of modulation or cortically induced pyramidal tract responses (direct and indirect, D-I potentials) by conditioning shock trains delivered to various loci within the caudate nucleus or globus pallidus. Both approaches were designed to determine whixh inhibitory and facilitatory motor influences of the basal ganglia occurred at a cortical or subcortical level. Simultaneous stimulation of a locus within the caudate nucleus and the sensorimotor cortex evoked either an enhancement, reduction or no alteration of the cortically induced increase in flexor responses (measured by Ia afferent activity, EMG, myogram). In contrast, no inhibitory influences occurred from caudate nucleus stimulation upon pyramidal tract induced flexor responses in either the intact or decorticate preparation. Inhibitory loci were distributed toward the rostral portion of the caudate nucleus, whereas facilitatory loci were distributed throughout; this distribution was statistically significant (chi2; P less than 0.01). Only enhancement or no influence upon cortical induced or pyramidal tract induced responses were obtained by conditioning stimuli to the globus pallidus. In the unanesthetized but immobilized cat, trains of shocks delivered to the caudate nucleus enhanced, reduced or had no influence upon the cortically evoked direct (D) and indirect (I) potentials recorded in the bulbar pyramidal tract. The distribution of facilitatory and inhibitory loci was organized in a similar fashion as in theanesthetized preparation. From these observations, a model was proposed in which the output of the caudate nucleus exerts both facilitatory or inhibitory modulation of the tonically active globus pallidus cells. The latter in turn predominantly or exclusively facilitate output of pyramidal tract neurons as well as the output of subcortical structures; both effects facilitate motor responses at the spinal level.

Animals↗