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Minimum P (minimum + p)

Distribution by Scientific Domains

Medical Sciences	40%
Life Sciences	40%

Selected Abstracts

A counter-clockwise P,T path for the Voltri Massif eclogites (Ligurian Alps, Italy)

JOURNAL OF METAMORPHIC GEOLOGY, Issue 7 2005
G. VIGNAROLI
Abstract Integrated petrological and structural investigations of eclogites from the eclogite zone of the Voltri Massif (Ligurian Alps) have been used to reconstruct a complete Alpine P,T deformation path from burial by subduction to subsequent exhumation. The early metamorphic evolution of the eclogites has been unravelled by correlating garnet zonation trends with the chemical variations in inclusions found in the different garnet domains. Garnet in massive eclogites displays typical growth zoning, whereas garnet in foliated eclogites shows rim-ward resorption, likely related to re-equilibration during retrogressive evolution. Garnet inclusions are distinctly different from core to rim, consisting primarily of Ca-, Na/Ca-amphibole, epidote, paragonite and talc in garnet cores and of clinopyroxene ± talc in the outer garnet domains. Quantitative thermobarometry on the inclusion assemblages in the garnet cores defines an initial greenschist-to-amphibolite facies metamorphic stage (M1 stage) at c. 450,500 °C and 5,8 kbar. Coexistence of omphacite + talc + katophorite inclusion assemblage in the outer garnet domains indicate c. 550 °C and 20 kbar, conditions which were considered as minimum P,T estimates for the M2 eclogitic stage. The early phase of retrograde reactions is polyphase and equilibrated under epidote,blueschist facies (M3 stage), characterized by the development of composite reaction textures (garnet necklaces and fluid-assisted Na-amphibole-bearing symplectites) produced at the expense of the primary M2 garnet-clinopyroxene assemblage. The blueschist retrogression is contemporaneous with the development of a penetrative deformation (D3) that resulted in a non-coaxial fabric, with dominant top-to-the-N sense of shear during rock exhumation. All of that is overprinted by a texturally late amphibolite/greenschist facies assemblages (M4 & M5 stages), which are not associated with a penetrative structural fabric. The combined P,T deformation data are consistent with an overall counter-clockwise path, from the greenschist/amphibolite, through the eclogite, the blueschist to the greenschist facies. These new results provide insights into the dynamic evolution of the Tertiary oceanic subduction processes leading to the building up of the Alpine orogen and the mechanisms involved in the exhumation of its high-pressure roots. [source]

Power and sample size for nested analysis of molecular variance

MOLECULAR ECOLOGY, Issue 19 2009
BENJAMIN M. FITZPATRICK
Abstract Analysis of molecular variance (amova) is a widely used tool for quantifying the contribution of various levels of population structure to patterns of genetic variation. Implementations of amova use permutation tests to evaluate null hypotheses of no population structure within groups and between groups. With few populations per group, between-group structure might be impossible to detect because only a few permutations of the sampled populations are possible. In fact, with fewer than six total populations, permutation tests will never result in P -values <0.05 for higher-level population structure. I present minimum numbers of replicates calculated from multinomial coefficients and an r script that can be used to evaluate the minimum P -value for any sampling scheme. While it might seem counterintuitive that a large sample of individuals is uninformative about hierarchical structure, the power to detect between-group differences depends on the number of populations per group and investigators should sample appropriately. [source]

Anti,interleukin-6 receptor antibody therapy favors adrenal androgen secretion in patients with rheumatoid arthritis: A randomized, double-blind, placebo-controlled study

ARTHRITIS & RHEUMATISM, Issue 6 2006
Rainer H. Straub
Objective Proinflammatory cytokines such as tumor necrosis factor (TNF) were demonstrated to inhibit adrenal steroidogenesis in patients with rheumatoid arthritis (RA), and this was particularly evident in the increase in adrenal androgen levels during anti-TNF therapy. This study investigated the influence on steroidogenesis of an interleukin-6 (IL-6),neutralizing strategy using IL-6 receptor monoclonal antibodies (referred to as MRA). Methods In a placebo-controlled, double-blind, randomized study over 12 weeks in 29 patients with RA being treated with prednisolone, 13 of whom received placebo and 16 of whom received 8 mg MRA/kg body weight, the effects of MRA on serum levels of adrenocorticotropic hormone (ACTH), cortisol, 17-hydroxyprogesterone (17OHP), dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), androstenedione (ASD), estrone, and 17,-estradiol, as well as their respective molar ratios, were determined. Results MRA therapy markedly improved clinical signs of inflammation (the erythrocyte sedimentation rate, swollen joint score, and Disease Activity Score in 28 joints). Serum levels of ACTH and cortisol and the molar ratio of cortisol to ACTH did not change. Although serum levels of DHEA and DHEAS remained stable during therapy, the DHEAS:DHEA molar ratio significantly decreased in treated patients (P = 0.048). Serum levels of ASD as well as the ASD:cortisol and ASD:17OHP molar ratios increased in MRA-treated patients (minimum P < 0.004). Serum levels of estrone and 17,-estradiol did not change. but the estrone:ASD molar ratio (an indicator of aromatization) decreased during 12 weeks of MRA treatment (P = 0.001). Conclusion Neutralization of IL-6 increases secretion of biologically active adrenal androgens in relation to that of precursor hormones and estrogens. This is another important indication that proinflammatory cytokines interfere with adrenal androgen steroidogenesis in patients with RA. [source]

Tonsil size as a predictor of cardiac complications in children with sleep-disordered breathing,

THE LARYNGOSCOPE, Issue 6 2010
Eduardo Homrich Granzotto MD
Abstract Objectives/Hypothesis: The primary objective was to evaluate the association of palatine (T/P) tonsil size determined by radiography with pulmonary artery pressure (PAP) measured by Doppler echocardiography in children with surgical indication for adenotonsillar hypertrophy. The secondary objective was to evaluate if tonsil size could help to identify children at higher risk of pulmonary artery hypertension (PAH). Study Design: Cross-sectional study. Methods: The study was conducted with a consecutive sample of children with indication of adenotonsillectomy for sleep-disordered breathing. T/P was measured by lateral neck radiography, PAP by echodopplercardiography, and symptoms and quality of life by the Obstructive Sleep Apnea (OSA)-18 questionnaire. T/P was plotted in a receiver operating characteristic (ROC) curve to determine the best cut-off point to identify children with PAH. Results: A total of 45 children participated in the study. The mean age was 72.0 ± 32.3 months, and six (13%) patients had PAH. Correlation between systolic PAP and T/P was strong (r = 0.624; P < .0001). T/P was significantly higher in patients with PAH (P < .001). OSA-18 score did not significantly correlate with the variables. The cut-off point identified in the ROC was 0.66, which was the minimum T/P where sensitivity was still 100%. Mean systolic pulmonary artery pressure in children with T/P >0.66 was significantly higher than in those with T/P <0.66 (P < .001). Conclusions: T/P showed a good correlation with PAP in children with adenotonsillar hypertrophy and surgical indication for sleep-disordered breathing. Children with T/P >0.66 can be at greater risk for cardiac complications and should be submitted to complementary studies with echodopplercardiography or given preference for surgery. [source]

Resampling-based multiple hypothesis testing procedures for genetic case-control association studies,

GENETIC EPIDEMIOLOGY, Issue 6 2006
Bingshu E. Chen
Abstract In case-control studies of unrelated subjects, gene-based hypothesis tests consider whether any tested feature in a candidate gene,single nucleotide polymorphisms (SNPs), haplotypes, or both,are associated with disease. Standard statistical tests are available that control the false-positive rate at the nominal level over all polymorphisms considered. However, more powerful tests can be constructed that use permutation resampling to account for correlations between polymorphisms and test statistics. A key question is whether the gain in power is large enough to justify the computational burden. We compared the computationally simple Simes Global Test to the min,P test, which considers the permutation distribution of the minimum p -value from marginal tests of each SNP. In simulation studies incorporating empirical haplotype structures in 15 genes, the min,P test controlled the type I error, and was modestly more powerful than the Simes test, by 2.1 percentage points on average. When disease susceptibility was conferred by a haplotype, the min,P test sometimes, but not always, under-performed haplotype analysis. A resampling-based omnibus test combining the min,P and haplotype frequency test controlled the type I error, and closely tracked the more powerful of the two component tests. This test achieved consistent gains in power (5.7 percentage points on average), compared to a simple Bonferroni test of Simes and haplotype analysis. Using data from the Shanghai Biliary Tract Cancer Study, the advantages of the newly proposed omnibus test were apparent in a population-based study of bile duct cancer and polymorphisms in the prostaglandin-endoperoxide synthase 2 (PTGS2) gene. Genet. Epidemiol. 2006. Published 2006 Wiley-Liss, Inc. [source]