896 resultados para Diameter-dependence


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There is no specific self-efficacy measure that has been developed primarily for problem drinkers seeking a moderation drinking goal. In this article, we report the factor structure of a 20-item Controlled Drinking Self-Efficacy Scale (CDSES Sitharthan et al., 1996; Sitharthan et al., 1997). The results indicate that the CDSES is highly reliable, and the factor analysis using the full sample identified four factors: negative affect, positive mood/social context, frequency of drinking, and consumption quantity. A similar factor structure was obtained for the subsample of men. In contrast, only three factors emerged in the analysis of data on female participants. Compared to women, men had low self-efficacy to control their drinking in situations relating to positive mood/social context, and subjects with high alcohol dependence had low self-efficacy for situations relating to negative affect, social situations, and drinking less frequently. The CDSES can be a useful measure in treatment programs providing a moderation drinking goal. (C) 2003 Wiley Periodicals, Inc.

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Background: Because alcohol has multiple dose-dependent consequences, it is important to understand the causes of individual variation in the amount of alcohol used. The aims of this study were to assess the long-term repeatability and genetic or environmental causes of variation in alcohol intake and to estimate the degree of overlap with causes of susceptibility to alcohol dependence. Methods: Data were used from three studies conducted between 1980 and 1995 on volunteer adult male and female Australian twin subjects. In each study, alcohol intake was reported both as quantity X frequency and as past-week data. Repeatability was calculated as correlations between occasions and between measures, and the effects of genes and environment were estimated by multivariate model fitting to the twin pair repeated measures of alcohol use. Relationships between mean alcohol use and the lifetime history of DSM-III-R alcohol dependence were tested by bivariate model fitting. Results: Repeatability of the alcohol intake measures was between 0.54 and 0.85, with the highest repeatability between measures within study and the lowest repeatability between the first and last studies. Reported alcohol consumption was mainly affected by genetic factors affecting all times of study and by nonshared environmental factors (including measurement error) unique to each time of study. Genes that affect alcohol intake do affect alcohol dependence, but genetic effects unique to dependence are also significant; environmental effects are largely unique to either intake and dependence. Conclusions: Nearly all the repeatable component of variation in alcohol intake is due to genetic effects. Genes affecting intake also affect dependence risk, but there are other genes that affect dependence alone. Studies aiming to identify genes that affect alcohol use disorders need to test loci and candidate genes against both phenotypes.

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In this study, we investigated the size, submicrometer-scale structure, and aggregation state of ZnS formed by sulfate-reducing bacteria (SRB) in a SRB-dominated biofilm growing on degraded wood in cold (Tsimilar to8degreesC), circumneutral-pH (7.2-8.5) waters draining from an abandoned, carbonate-hosted Pb-Zn mine. High-resolution transmission electron microscope (HRTEM) data reveal that the earliest biologically induced precipitates are crystalline ZnS nanoparticles 1-5 nm in diameter. Although most nanocrystals have the sphalerite structure, nanocrystals of wurtzite are also present, consistent with a predicted size dependence for ZnS phase stability. Nearly all the nanocrystals are concentrated into 1-5 mum diameter spheroidal aggregates that display concentric banding patterns indicative of episodic precipitation and flocculation. Abundant disordered stacking sequences and faceted, porous crystal-aggregate morphologies are consistent with aggregation-driven growth of ZnS nanocrystals prior to and/or during spheroid formation. Spheroids are typically coated by organic polymers or associated with microbial cellular surfaces, and are concentrated roughly into layers within the biofilm. Size, shape, structure, degree of crystallinity, and polymer associations will all impact ZnS solubility, aggregation and coarsening behavior, transport in groundwater, and potential for deposition by sedimentation. Results presented here reveal nanometer- to micrometer-scale attributes of biologically induced ZnS formation likely to be relevant to sequestration via bacterial sulfate reduction (BSR) of other potential contaminant metal(loid)s, such as Pb2+, Cd2+, As3+ and Hg2+, into metal sulfides. The results highlight the importance of basic mineralogical information for accurate prediction and monitoring of long-term contaminant metal mobility and bioavailability in natural and constructed bioremediation systems. Our observations also provoke interesting questions regarding the role of size-dependent phase stability in biomineralization and provide new insights into the origin of submicrometer- to millimeter-scale petrographic features observed in low-temperature sedimentary sulfide ore deposits.

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Aim. Numerous studies report an association between muscle strength and bone mineral density (BMD) in young and older women. However, the participants are generally non-athletes, thus it is unclear if the relationship varies by exercise status. Therefore, the purpose was to examine the relationships between BMD and muscle strength in young women with markedly different exercise levels. Methods. Experimental design: cross-sectional. Setting: a University research laboratory. Participants: 18 collegiate gymnasts and 22 age- and weight-matched recreationally active control women. Measures: lumbar spine, femoral neck, arm, leg and whole body BMD (g/cm(2)) were assessed by dual X-ray absorptiometry. In addition, lumbar spine and femoral neck bone mineral apparent density (BMAD, g/cm(3)) was calculated. Handgrip strength and knee extensor and flexor torque (60degrees/s) were determined by dynamometry, and bench press and leg press strength (1-RM) using isotonic equipment. Results. BMD at all sites and bench press, leg press and knee flexor strength were greater in gymnasts than controls (p

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Background. Whether current criteria used to define nicotine dependence are informative for genetic research is an important empirical question. The authors used items of the DSM-IV and of the Heaviness of Smoking Index to characterize the nicotine dependence phenotype and to identify salient symptoms in a genetically informative community sample of Australian young adult female and mate twins. Method. Phenotypic and genetic factor analyses were performed on nine dependence symptoms (the seven DSM-IV substance dependence criteria and the two Heaviness of Smoking Index (HSI) items derived from the Fagerstrom Tolerance Questionnaire, time to first cigarette in the morning and number of cigarettes smoked per day). Phenotypic and genetic analyses were restricted to ever smokers. Results. Phenotypic nicotine dependence symptom covariation was best captured by two factors with a similar pattern of factor loadings for women and men. In genetic factor analysis item covariation was best captured by two genetic but one shared environmental factor for both women and men; however, item factor loadings differed by gender. All nicotine dependence symptoms were substantially heritable, except for the DSM-IV criterion of 'giving up or reducing important activities in order to smoke', which was weakly familial. Conclusions. The salient behavioral indices of nicotine dependence are similar for women and men. DSM-IV criteria of tolerance, withdrawal, and experiencing difficulty quitting and HSI items time to first cigarette in the morning and number of cigarettes smoked per day may represent the most highly heritable symptoms of nicotine dependence for both women and men.

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Background: Previous research has reported both a moderate degree of comorbidity between cannabis dependence and major depressive disorder (MDD) and that early-onset cannabis use is associated with increased risks for MDD. Objective: To examine whether associations between both lifetime cannabis dependence and early cannabis use and measures of MDD, suicidal ideation, and suicide attempt persist after controlling for genetic and/or shared environmental influences. Design: Cross-sectional survey of twin pairs discordant for lifetime cannabis dependence and those discordant for early cannabis use. Setting: General population sample of twins (median age, 30 years). Participants: Two hundred seventy-seven same-sex twin pairs discordant for cannabis dependence and 311 pairs discordant for early-onset cannabis use (before age 17 years). Main Outcome Measures: Self-report measures of DSM-IV-defined lifetime MDD, suicidal ideation, and suicide attempt. Results: Individuals who were cannabis dependent had odds of suicidal ideation and suicide attempt that were 2.5 to 2.9 times higher than those of their non-cannabis-dependent co-twin. Additionally, cannabis dependence was associated with elevated risks of MDD in dizygotic but not in monozygotic twins. Those who initiated cannabis use before age 17 years had elevated rates of subsequent suicide attempt (odds ratio, 3.5 [95% confidence interval, 1.4-8.6]) but not of MDD or suicidal ideation. Early MDD and suicidal ideation were significantly associated with subsequent risks of cannabis dependence in discordant dizygotic pairs but not in discordant monozygotic pairs. Conclusions: Comorbidity between cannabis dependence and MDD likely arises through shared genetic and environmental vulnerabilities predisposing to both outcomes. In contrast, associations between cannabis dependence and suicidal behaviors cannot be entirely explained by common predisposing genetic and/or shared environmental predispositions. Previously reported associations between early-onset cannabis use and subsequent MDD likely reflect shared genetic and environmental vulnerabilities, although it remains possible that early-onset cannabis use may predispose to suicide attempt.

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Measurement of the temperature-dependence of thrombin-catalyzed cleavage of the Arg(155)-Ser(156) and Arg(284)-Thr(285) peptide bonds in prothrombin and prothrombin-derived substrates has yielded Arrhenius parameters that are far too large for classical mechanistic interpretation in terms of a simple hydrolytic reaction. Such a difference from the kinetic behavior exhibited in trypsin- and chymotrypsin-catalyzed proteolysis of peptide bonds is attributed to contributions by enzyme exosite interactions as well as enzyme conformational equilibria to the magnitudes of the experimentally determined Arrhenius parameters. Although the pre-exponential factor and the energy of activation deduced from the temperature-dependence of rate constants for proteolysis by thrombin cannot be accorded the usual mechanistic significance, their evaluation serves a valuable role by highlighting the existence of contributions other than those emanating from simple peptide hydrolysis to the kinetics of proteolysis by thrombin and presumably other enzymes of the blood coagulation system. (C) 2004 Elsevier B.V. All rights reserved.

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Background. Genetic influences have been shown to play a major role in determining the risk of alcohol dependence (AD) in both women and men; however, little attention has been directed to identifying the major sources of genetic variation in AD risk. Method. Diagnostic telephone interview data from young adult Australian twin pairs born between 1964 and 1971 were analyzed. Cox regression models were fitted to interview data from a total of 2708 complete twin pairs (690 MZ female, 485 MZ male, 500 DZ female, 384 DZ male, and 649 DZ female/male pairs). Structural equation models were fitted to determine the extent of residual genetic and environmental influences on AD risk while controlling for effects of sociodemographic and psychiatric predictors on risk. Results. Risk of AD was increased in males, in Roman Catholics, in those reporting a history of major depression, social anxiety problems, and conduct disorder, or (in females only) a history of suicide attempt and childhood sexual abuse; but was decreased in those reporting Baptist, Methodist, or Orthodox religion, in those who reported weekly church attendance, and in university-educated males. After allowing for the effects of sociodemographic and psychiatric predictors, 47 % (95 % CI 28-55) of the residual variance in alcoholism risk was attributable to additive genetic effects, 0 % (95 % CI 0-14) to shared environmental factors, and 53 % (95 % CI 45-63) to non-shared environmental influences. Conclusions. Controlling for other risk factors, substantial residual heritability of AD was observed, suggesting that psychiatric and other risk factors play a minor role in the inheritance of AD.