Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Statistical Distributions”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,243 records · Page 69Linked to original sources
PubMed1995

"Silent" patent ductus arteriosus and bronchopulmonary dysplasia in low birth weight infants.

We conducted a clinical study on the antecedents of bronchopulmonary dysplasia (BPD) in 290 premature RDS infants with < or = 1.75 kg birth weight (BW). They were enrolled in a prospective trial of indomethacin treatment for "silent" patent ductus arteriosus (PDA), screened by 2-D echocardiographic and pulsed Doppler evaluation on the third day of life. The trial took place at the NICU of the Pediatric Department of Padua University between January 1987 and December 1991. Out of 290 infants screened, 96 had evidence of "silent" PDA (33%) and 77 responded to indomethacin treatment (80%). Comprehensively 79 (27%) developed BPD, and from these the incidence of BPD was statistically increased in infants with "silent" PDA, 47 out of 96 (49 +/- 9%), with respect to 32 out of 194 (16 +/- 3%) preterm infants without PDA. Statistical analysis showed that in preterm infants with "silent" PDA the development of BPD was correlated at 99% C.L. to their low BWs (mean BW = 1.13 kg): in fact the mean and the mode of BW distributions were statistically lower in the presence of BPD, 1.03 kg versus 1.24 kg, and 0.88 kg versus 1.65 kg respectively. Moreover, the preterm infants with "silent" PDA unresponsive to the first course of indomethacin and/or submitted later to surgical closure, presented a statistically lower BW with respect to the early responders, 1.06 kg versus 1.18 kg, and at the same time a statistically higher incidence of BPD (63 +/- 20% versus 43 +/- 9%). From these data we conclude that, although "silent", PDA increase per se the incidence of BPD, even if benefits from an early induced closure. Furthermore, a lower BW of infants affected by "silent" PDA represents a contributing factor to the development of BPD.

Bronchopulmonary Dysplasia↗
PubMed2003

[Geographical inequalities in the distribution of general practitioners in Sweden].

AIM: To estimate trends in the inequalities in the distribution of general practitioners in Sweden during the past fifteen years. METHODS: Relative inequality indicators. We plotted the Lorenz curves and calculated the Gini coefficients for the entire country during 1986, 1991, 1996 and 2001. RESULTS: During the past 15 years in all a declining trend was noted in the inequalities in the geographical distribution of general practitioners in Sweden, with the lowest level in 1996. CONCLUSIONS: The degree of inequality in the geographical distribution of general practitioners appeared rather stable during the period, although with some increase in the final year studied. Since equality is part of quality, policy makers in all levels--national, regional and local--should pay attention as to how human resources are distributed.

Family Practice↗
PubMed1986

[Sonographically detectable changes in placental structures in pregnancy. 5. Statistical comparison of the frequency distribution of placental stages 0-3 in newborn infants in a pregnancy of less than 37 weeks duration].

The analysis of sonographically provable changes of placental structures in 97 pregnant women (202 examination) shows in cases with a duration of pregnancy less than 37 gestational weeks that stage 0 could be found statistically significant more frequent until the 32nd week of pregnancy, stage 1 in the whole pregnancy, stage 2 and 3 between the 29. and 36. gestational week. Stage 0 and 1 don't effect prematurity; however stages 2 and 3 could be proved before the 32nd or 34th week of pregnancy in 41 or 100% of examination respectively and effect a premature birth. Stage 2 could be proved 2,8 times more frequent and stage 3 4 times more frequent in premature babies than in newborns with a normal duration of pregnancy.

Birth Weight↗
PubMed2006

Assessing sites contaminated with unexploded ordnance: statistical modeling of ordnance spatial distribution.

More than 40,000 km2 of former military land in the United States are contaminated with unexploded ordnance (UXO). Cleanup costs are estimated to total as much as 140 billion dollars. The amount of contaminated acreage and total costs are likely to increase as the U.S. Department of Defense (DOD) follows through on recently announced plans to close an additional 22 domestic military bases. The U.S. Environmental Protection Agency(EPA) and DOD disagree on how these sites should be characterized to assess their risks and plan for cleanup. As a result, much potentially valuable land remains idle while remediation decisions are pending. One of the sources of disagreement is how the locations of UXO should be characterized, given that the exact spatial distribution of UXO is unknown in advance of cleanup. In this paper, we propose and test a new model to represent the spatial distribution of UXO. Unlike existing DOD models, the new model accounts for the tendency of UXO to cluster, presumably around targets at which soldiers aimed during training. We fit the cluster model to geographic data on UXO locations at two former military installations and show that it describes key characteristics of the data more accuratelythan the existing DOD model. We discuss how the choice of a UXO spatial distribution model could affect important decisions about cleaning up and reusing UXO-affected property.

Environmental Monitoring↗
PubMed2002

A note on estimating the posterior density of a quantitative trait locus from a Markov chain Monte Carlo sample.

We provide an overview of the use of kernel smoothing to summarize the quantitative trait locus posterior distribution from a Markov chain Monte Carlo sample. More traditional distributional summary statistics based on the histogram depend both on the bin width and on the sideway shift of the bin grid used. These factors influence both the overall mapping accuracy and the estimated location of the mode of the distribution. Replacing the histogram by kernel smoothing helps to alleviate these problems. Using simulated data, we performed numerical comparisons between the two approaches. The results clearly illustrate the superiority of the kernel method. The kernel approach is particularly efficient when one needs to point out the best putative quantitative trait locus position on the marker map. In such situations, the smoothness of the posterior estimate is especially important because rough posterior estimates easily produce biased mode estimates. Different kernel implementations are available from Rolf Nevanlinna Institute's web page (http://www.rni.helsinki.fi/;fjh).

Bayes Theorem↗
PubMed1997

Explaining hierarchical and interprovincial migrations of Chinese young adults by personal factors and place attributes: a nested logit analysis.

"This paper uses a two-level nested logit model to explain the inter-stratum (city, town and rural county) and interprovincial migration behaviors of the young adults (aged 17-29) in China during a three-year period (1985-87), based on the micro data of the 1987 National Population Survey. The migration propensity of each person is represented by a departure probability and a destination choice probability. These probabilities are then expressed as functions of personal factors and place attributes. The main findings are that personal factors are of paramount importance in explaining the departure behaviors, and that both departure and destination behaviors responded to market forces in a sensible way, despite government control on territorial movements."

Asia↗
PubMed1997

Kinetochore fiber maturation in PtK1 cells and its implications for the mechanisms of chromosome congression and anaphase onset.

Kinetochore microtubules (kMts) are a subset of spindle microtubules that bind directly to the kinetochore to form the kinetochore fiber (K-fiber). The K-fiber in turn interacts with the kinetochore to produce chromosome motion toward the attached spindle pole. We have examined K-fiber maturation in PtK1 cells using same-cell video light microscopy/serial section EM. During congression, the kinetochore moving away from its spindle pole (i.e., the trailing kinetochore) and its leading, poleward moving sister both have variable numbers of kMts, but the trailing kinetochore always has at least twice as many kMts as the leading kinetochore. A comparison of Mt numbers on sister kinetochores of congressing chromosomes with their direction of motion, as well as distance from their associated spindle poles, reveals that the direction of motion is not determined by kMt number or total kMt length. The same result was observed for oscillating metaphase chromosomes. These data demonstrate that the tendency of a kinetochore to move poleward is not positively correlated with the kMt number. At late prometaphase, the average number of Mts on fully congressed kinetochores is 19.7 +/- 6.7 (n = 94), at late metaphase 24.3 +/- 4.9 (n = 62), and at early anaphase 27.8 +/- 6.3 (n = 65). Differences between these distributions are statistically significant. The increased kMt number during early anaphase, relative to late metaphase, reflects the increased kMt stability at anaphase onset. Treatment of late metaphase cells with 1 microM taxol inhibits anaphase onset, but produces the same kMt distribution as in early anaphase: 28.7 +/- 7. 4 (n = 54). Thus, a full complement of kMts is not sufficient to induce anaphase onset. We also measured the time course for kMt acquisition and determined an initial rate of 1.9 kMts/min. This rate accelerates up to 10-fold during the course of K-fiber maturation, suggesting an increased concentration of Mt plus ends in the vicinity of the kinetochore at late metaphase and/or cooperativity for kMt acquisition.

Anaphase↗
PubMed1999

Multiscale analysis of blood pressure signals.

We describe the multiresolution wavelet analysis of blood pressure waves in vasovagal syncope-affected patients compared with those in healthy people, using Haar and Gaussian bases. A comparison between scale-dependent and scale-independent measures discriminating the two classes of subjects is made. What emerges is a sort of equivalence between these two methodological approaches, that is, both methods reach the same statistical significance of separation between the two classes.

Biophysical Phenomena↗
PubMedDate not supplied

Meta-analysis by random effect modelling in generalized linear models.

The meta-analysis of multi-centre trials can be based on either fixed or random effect models. This paper argues for the general use of random effect models, and illustrates the value of non-parametric maximum likelihood (NPML) analysis of such trials. The same general approach unifies administrative 'league table' analyses in epidemiological and other studies. Several examples of the NPML analysis are given, including a 70-centre trial.

Adrenergic beta-Antagonists↗
PubMed1998

Predictive value of interleukin 6 (IL-6), interleukin 8 (IL-8) and gastric intramucosal pH (pH-i) in major abdominal surgery.

OBJECTIVE: To study plasma concentrations of interleukin 6 (IL-6) and interleukin 8 (IL-8) in patients with splanchnic hypoxia, as documented by gastric intramucosal measurements (pH-i), during major abdominal surgery and the relationship between IL-6 and IL-8 concentrations and postoperative complications as well as clinical outcome. DESIGN: A prospective study. PATIENTS: Twelve patients scheduled for major abdominal surgery with no evidence of coexisting infectious disease. RESULTS: Six out of seven samples from patients with postoperative complications showed intraoperative pH-i levels lower than 7.32 and IL-6 levels higher than 300 pg/ml. Seven out of nine samples from patients without complications showed pH-i levels higher than 7.32 and IL-6 levels lower than 300 pg/ml. The difference in the pattern of distribution was statistically significant (p < 0.01). Only two out of seven samples of patients with postoperative complications showed intraoperative pH-i levels lower than 7.32 and IL-8 levels higher than 60 pg/ml. It was not possible to identify a clear distribution pattern of data points for IL-6 and IL-8 during the postoperative period. CONCLUSIONS: Intraoperative splanchnic ischemia, as documented by gastric intramucosal pH-i, is directly correlated to the increase of IL-6 plasma levels and to the incidence of postoperative complications, while IL-8 levels showed no correlation with surgical complications.

Adult↗
PubMedDate not supplied

Bayesian QTL mapping using skewed Student-t distributions.

In most QTL mapping studies, phenotypes are assumed to follow normal distributions. Deviations from this assumption may lead to detection of false positive QTL. To improve the robustness of Bayesian QTL mapping methods, the normal distribution for residuals is replaced with a skewed Student-t distribution. The latter distribution is able to account for both heavy tails and skewness, and both components are each controlled by a single parameter. The Bayesian QTL mapping method using a skewed Student-t distribution is evaluated with simulated data sets under five different scenarios of residual error distributions and QTL effects.

Algorithms↗
PubMed2004

The phylogeny of persistence in DNA.

We continue our study, Poland [Biophysical Chemistry 110 (2004) 59-2], of the distribution of C or G (C-G for short) in the DNA of select organisms, in particular, the tendency for C-G to cluster on all scales with respect to the number of bases considered. We previously found that if we counted the number of C-G bases in consecutive, nonoverlapping boxes containing a total of m bases, then the width of the distribution function describing how many C-G bases are in a box increases with respect to m dramatically relative to the width expected for a random distribution. The relative width of the C-G composition distribution function was found to vary accurately as a power law with respect to m, the size of the box, over a very wide range of m values. We express the power law in terms of a characteristic exponent gamma, that is, the relative widths of the distributions vary as m(gamma). The enhanced relative width of the distribution functions is a direct consequence of the tendency for boxes of similar composition to follow one another. This tendency represents persistence in composition from box to box and hence we refer to gamma as the persistence exponent. The occurrence of a power law means that the tendency for C-G to cluster is present on all scales of sequence length (box size) up to the total length of the chromosome which for bacteria is the entire genome. The persistence exponent gamma that characterizes the power law is thus an important parameter describing the distribution of C-G on all scales from individual base pairs up to the total length of the DNA sample considered. In the present paper, we determine the characteristic exponent gamma and the associated fractal dimension of DNA samples for a selection of species representing all of the major types of organism, that is, we explore the phylogeny of the exponent gamma. Here we treat six prokaryotes and six eukaryotes which, together with the species we have previously treated, brings the total number of species we have examined to 15. We find the power law form for the C-G distribution for all of the species treated and hence this behavior seems to be ubiquitous. The values of the characteristic exponent gamma that we find tend to cluster around the value gamma=0.20 with no obvious pattern with respect to phylogeny. The extreme values that we obtain are gamma=0.057 (yeast) and gamma=0.386 (human). We conclude by showing that the persistence of C-G clustering on the scale of the length of a chromosome is dramatically illustrated by interpreting the C-G distribution as a random walk.

Animals↗
PubMed1982

Dosimetry and preliminary human studies of 18F-5-fluorouracil.

The relative distribution, metabolism and kinetics of 18F containing compounds, following administration of 18F-5-fluorouracil, has been proposed as a prognostic aid in predicting response to 5-fluorouracil chemotherapy. Because 18F has a relatively short physical half-life (t1/2 = 110 min), and the distribution and kinetics of the radiolabeled 5-fluorouracil need to be studied over periods of time that range over several half-lives of the radionuclide, significant quantities of the labeled drug must be administered in order to obtain good counting statistics. The distribution of 18F, following injection of 18F-5-fluorouracil to rats and mice, has been well documented in our previous work. It appears that the distribution of 18F in humans, following administration of 18F-5-fluorouracil is similar to that in rats. We calculated the radiation dose according to the MIRD technique for the eleven main target organs for a reference man. The critical organs, according to these calculations, are the bladder wall, the kidney and the liver, receiving a radiation dose of 729, 184 and 114 mrad per mCi injected, respectively.

Animals↗