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At least 1,297 records · Page 72Linked to original sources
PubMed1991

Endometrial cancer, obesity, and body fat distribution.

A case-control study was undertaken to evaluate the roles of obesity and body fat distribution in the etiology of endometrial cancer. The study also included an evaluation of the associations of serum estrone, estradiol, and androstenedione with obesity, body fat distribution, and endometrial cancer risk. The study included 168 cases and 334 control subjects identified at an optometry clinic. A strong, positive relationship between overall obesity and endometrial cancer was found. The relative rate of endometrial cancer for women in the upper 90th percentile of a body mass index compared to those below the median was estimated as 5.5 with 95% confidence limits of 3.2-9.6. There was no association between endometrial cancer and the waist to hip ratio, an index of upper versus lower body fat distribution. A statistical test of trend across the four quartiles of the waist to hip ratio yielded a P value of 0.45 after adjustment for confounding by the body mass index. On the other hand, there was a statistically significant, independent positive effect of a high subscapular to tricep skinfold ratio, a measure of central versus peripheral obesity, on endometrial cancer risk. The relative rates of endometrial cancer for the second, third, or fourth quartile compared to the first quartile of this index were 1.5, 1.9, and 2.7, respectively (P = 0.007), after adjustment for the body mass index. Serum estrone and estradiol, but not androstenedione, were statistically significantly correlated with the body mass index among control subjects (r = 0.37 and 0.40 for estrone and estradiol, respectively). On the other hand, each of the sex hormones was uncorrelated with the waist to hip ratio after adjustment for body mass. The correlations between each of the three hormones and the subscapular to tricep skinfold ratio among controls were weak and were not statistically significant (0.10, 0.10, and 0.14 for estrone, estradiol and androstenedione, respectively). Cases had statistically significantly higher mean serum estrogen and androstenedione levels than did controls and these elevations did not simply reflect a higher prevalence of obesity among them. The findings are equivocal with respect to fat patterns and endometrial cancer. We suggest that future epidemiological studies of cancer and body fat distribution more carefully distinguish among the various types of fat patterns.

Adipose Tissue↗
PubMed1989

[Family clustering analysis of HBV infection].

A family clustering analysis of HBsAg, anti-HBs, anti-HBc positive and total infected persons in 148 families on a farm was carried out by the methods of G statistic, binomial distribution and negative binomial distribution. The results consistently showed that there was significant clustering of HBsAg carriers in families, whereas there were not clustering was seen an overall HBV infected persons in families. The clustering of HBsAg carriers in families is due probably to the effect of some genetic factors. The results of G statistic analysis indicate that anti-HBc also have significant clustering in families.

Carrier State↗
PubMedDate not supplied

[Correlation of fine structures of distributions of amplitudes of a photomultiplier dark current fluctuations with the Earth rotations about its axis].

The fine structures of distributions of photomultiplier dark current fluctuations measured in two laboratories 2000 km distant from other: in the international Institute of Biophysics (Neuss, Germany) and in the Moscow State University (Moscow, Russia) were compared. It is shown that similar forms of appropriate histograms are apparently more often realized at both locations at the same local time. This confirms the previous conclusion that the fine structure of distributions correlates with rotation of the Earth about its axis.

Earth, Planet↗
PubMed2003

Differences in spiking patterns among cortical neurons.

Spike sequences recorded from four cortical areas of an awake behaving monkey were examined to explore characteristics that vary among neurons. We found that a measure of the local variation of interspike intervals, L(V), is nearly the same for every spike sequence for any given neuron, while it varies significantly among neurons. The distributions of L(V) values for neuron ensembles in three of the four areas were found to be distinctly bimodal. Two groups of neurons classified according to the spiking irregularity exhibit different responses to the same stimulus. This suggests that neurons in each area can be classified into different groups possessing unique spiking statistics and corresponding functional properties.

Action Potentials↗
PubMed1993

Physiological pharmacokinetics of solutes in the isolated perfused rat hindlimb: characterization of the physiology with changing perfusate flow, protein content, and temperature using statistical moment analysis.

Distribution of Evans Blue (EB), sucrose, and water into the isolated perfused rat hindlimb was studied under various conditions using the multiple indicator dilution (MID) technique. Statistical moment analysis of the outflow profiles for the EB, sucrose, and water were used to define the vascular, extravascular, and total water spaces, respectively. The varied perfusion conditions included albumin content (2, 4.7, and 7%), temperature (25, 37, and 42 C), perfusate flow rate (2, 4, 8, and 12 ml/min) and the presence/absence of red blood cells. The range of studies undertaken were chosen to represent the variety of conditions used in the preparation of both isolated animal and human limbs, the latter being particularly important in cytotoxic therapy for recurrent malignant melanoma. The distribution volumes of EB, sucrose, and water were dependent on the flow rate and the albumin content of perfusate. The normalized variances (CV2) of the markers were of the following order: sucrose (2.18) > water (1.58) > EB (0.68), indicating that some disequilibrium occurs during the capillary exchange of water and sucrose. It is suggested that a Krebs-Henseleit buffer containing 2% BSA is a suitable perfusate for most studies of the isolated rat hindlimb perfusion. The effect of albumin concentration manifests itself only at higher flows.

Animals↗
PubMed2000

Weight characteristics of the parathyroid glands in renal hyperparathyroidism.

BACKGROUND: Although the mean weight of normal parathyroid glands is known, reports concerning the weight of hyperplastic glands in renal hyperparathyroidism are rare. The aim was to collect data about the weight of such glands and also to study the intraindividual distribution. METHODS: Statistical results are presented about the weight of 60 parathyroid glands that were removed in 20 patients with renal hyperparathyroidism (the fourth gland was subtotally removed and therefore not included in the study). RESULTS: The median weight was 1.005 g, with a range from 0.10 to 7.15 g. All removed glands were enlarged, but the most salient finding was the wide distribution of weights. Also, the intra-individual variation was great. The largest gland of each patient weighed, on average, three to four times more than the smallest gland of the same subject. CONCLUSION: The weight of the superior glands tended to be somewhat greater in comparison with the inferior glands.

Adult↗
PubMed2006

Stochastic inequality probabilities for adaptively randomized clinical trials.

We examine stochastic inequality probabilities of the form P (X > Y) and P (X > max (Y, Z)) where X, Y, and Z are random variables with beta, gamma, or inverse gamma distributions. We discuss the applications of such inequality probabilities to adaptively randomized clinical trials as well as methods for calculating their values.

Artificial Intelligence↗
PubMed2005

Model inference or model selection: discussion of Klugkist, Laudy, and Hoijtink (2005).

I. Klugkist, O. Laudy, and H. Hoijtink (2005) presented a Bayesian approach to analysis of variance models with inequality constraints. Constraints may play 2 distinct roles in data analysis. They may represent prior information that allows more precise inferences regarding parameter values, or they may describe a theory to be judged against the data. In the latter case, the authors emphasized the use of Bayes factors and posterior model probabilities to select the best theory. One difficulty is that interpretation of the posterior model probabilities depends on which other theories are included in the comparison. The posterior distribution of the parameters under an unconstrained model allows one to quantify the support provided by the data for inequality constraints without requiring the model selection framework.

Analysis of Variance↗
PubMed1998

Population change in the Great Plains since 1950 and the consequences of selective migration.

This "study was initiated to explore the causes and consequences of persistent population loss in the Great Plains region [of the United States]. After classifying all counties by their growth patterns over the past five decades, we developed a typology that categorized counties based on the direction and magnitude of their population change.... We use this typology to explore the correlates of residential population change, and to examine the explanatory power of the variables found to be statistically significant."

Americas↗
PubMed2000

Approximating the distribution of maximally selected McNemar's statistics.

It is common in epidemiologic analyses to summarize continuous outcomes as falling above or below a threshold. With paired data and with a threshold chosen without reference to the outcomes, McNemar's test of marginal homogeneity may be applied to the resulting dichotomous pairs when testing for equality of the marginal distributions of the underlying continuous outcomes. If the threshold is chosen to maximize the test statistic, however, referring the resulting test statistic to the nominal chi 2 distribution is incorrect; instead, the p-value must be adjusted for the multiple comparisons. Here the distribution of a maximally selected McNemar's statistic is derived, and it is shown that an approximation due to Durbin (1985, Journal of Applied Probability 22, 99-122) may be used to estimate approximate p-values. The methodology is illustrated by an application to measurements of insulin-like growth factor-I (IGF-I) in matched prostate cancer cases and controls from the Physicians' Health Study. The results of simulation experiments that assess the accuracy of the approximation in moderate sample sizes are reported.

Case-Control Studies↗
PubMed2005

Bayesian statistical studies of the Ramachandran distribution.

We describe a method for the generation of knowledge-based potentials and apply it to the observed torsional angles of known protein structures. The potential is derived using Bayesian reasoning, and is useful as a prior for further such reasoning in the presence of additional data. The potential takes the form of a probability density function, which is described by a small number of coefficients with the number of necessary coefficients determined by tests based on statistical significance and entropy. We demonstrate the methods in deriving one such potential corresponding to two dimensions, the Ramachandran plot. In contrast to traditional histogram-based methods, the function is continuous and differentiable. These properties allow us to use the function as a force term in the energy minimization of appropriately described structures. The method can easily be extended to other observable angles and higher dimensions, or to include sequence dependence and should find applications in structure determination and validation.

Journal Article↗
PubMed2006

Gamma histograms for radiotherapy plan evaluation.

BACKGROUND AND PURPOSE: The technique known as the 'gamma evaluation method' incorporates pass-fail criteria for both distance-to-agreement and dose difference analysis of 3D dose distributions and provides a numerical index (gamma) as a measure of the agreement between two datasets. As the gamma evaluation index is being adopted in more centres as part of treatment plan verification procedures for 2D and 3D dose maps, the development of methods capable of encapsulating the information provided by this technique is recommended. PATIENTS AND METHODS: In this work the concept of gamma index was extended to create gamma histograms (GH) in order to provide a measure of the agreement between two datasets in two or three dimensions. Gamma area histogram (GAH) and gamma volume histogram (GVH) graphs were produced using one or more 2D gamma maps generated for each slice of the irradiated volume. GHs were calculated for IMRT plans, evaluating the 3D dose distribution from a commercial treatment planning system (TPS) compared to a Monte Carlo (MC) calculation used as reference dataset. RESULTS: The extent of local anatomical inhomogenities in the plans under consideration was strongly correlated with the level of difference between reference and evaluated calculations. GHs provided an immediate visual representation of the proportion of the treated volume that fulfilled the gamma criterion and offered a concise method for comparative numerical evaluation of dose distributions. CONCLUSIONS: We have introduced the concept of GHs and investigated its applications to the evaluation and verification of IMRT plans. The gamma histogram concept set out in this paper can provide a valuable technique for quantitative comparison of dose distributions and could be applied as a tool for the quality assurance of treatment planning systems.

Head and Neck Neoplasms↗
PubMed2000

Graphing the death of Escherichia coli.

The graphical presentation of measurements of the progress over time of bacterial death or inactivation is discussed. Specifically, the Weibull distribution may be a useful generalisation of the exponential distribution. Data from experiments on the non-thermal death of Escherichia coli reported by Shadbolt et al. [Int. J. Food Microbiol. 49 (1999) 129] are reexamined to support this claim.

Escherichia coli↗
PubMed2007

Bayesian reconstruction of nanodosimetric cluster distributions at 100% detection efficiency.

Ionisation spectra in nanometric volumes at a given distance from a charged particle track are obtained by using electron (or ion) gas detectors, having non-uniformly distributed detection efficiency. Therefore, such spectra should be properly processed in order to reconstruct the frequency distribution of clusters really produced in the detector gas. A Bayesian unfolding has been applied to ionisation distributions due to 5.4 MeV alpha particles in a 20-nm site obtained by Monte Carlo simulations, taking into account different detection efficiency conditions. It will be shown that Bayesian analysis provides a valid tool for reconstructing the true ionisation distributions, well beyond the maximum measured cluster size.

Bayes Theorem↗
PubMedDate not supplied

Unidentifiable divergence times in rates-across-sites models.

The rates-across-sites assumption in phylogenetic inference posits that the rate matrix governing the Markovian evolution of a character on an edge of the putative phylogenetic tree is the product of a character-specific scale factor and a rate matrix that is particular to that edge. Thus, evolution follows basically the same process for all characters, except that it occurs faster for some characters than others. To allow estimation of tree topologies and edge lengths for such models, it is commonly assumed that the scale factors are not arbitrary unknown constants, but rather unobserved, independent, identically distributed draws from a member of some parametric family of distributions. A popular choice is the gamma family. We consider an example of a clock-like tree with three taxa, one unknown edge length, a known root state, and a parametric family of scale factor distributions that contains the gamma family. This model has the property that, for a generic choice of unknown edge length and scale factor distribution, there is another edge length and scale factor distribution which generates data with exactly the same distribution, so that even with infinitely many data it will be typically impossible to make correct inferences about the unknown edge length.

Algorithms↗
PubMed2006

Association of the GSTP1 and NQO1 polymorphisms and head and neck squamous cell carcinoma risk.

The GSTP1 and NQO1 have been reported to be associated with an increased risk for smoking related head and neck squamous cell carcinoma (HNSCC). The purpose of this study was to determine the effect of these metabolic gene polymorphisms on the risk of HNSCC. The study population included 294 histologically confirmed HNSCC cases and 333 controls without cancer. Genotyping analysis of the GSTP1 Ile105Val and NQO1 Trp139Arg genes was performed by polymerase chain reaction-based techniques on DNA prepared from peripheral blood. The Mantel-Haenszel chi2 test was used for statistical analysis. The allele frequencies of the GSTP1 and NQO1 polymorphisms were not statistically significant between cases and controls. In analyzing the association between smoking amounts and genetic polymorphisms, GSTP1 and NQO1 polymorphisms were associated with cigarette smoking amounts in cases. G allele containing genotypes in GSTP1 and T allele containing genotypes in NQO1 were associated with a tobacco dose-dependent increase in risk of HNSCC and these genotype distributions were statistically significant (p<0.05). We found that the GSTP1 105Val allele and NQO1 139Arg allele were associated with tobacco dose-dependent increase in risk of HNSCC. GSTP1 and NQO1 genotype polymorphisms may play an important role in the development of smoking related HNSCC.

Adult↗