Nonlinear Manner (nonlinear + manner)

Distribution by Scientific Domains

Selected Abstracts

Sublethal effects of methylmercury on fecal metabolites of testosterone, estradiol, and corticosterone in captive juvenile white ibises (Eudocimus albus),

Evan M. Adams
Abstract Methylmercury (MeHg) is a globally distributed neurotoxin, endocrine disruptor, and teratogen, and its effects on birds are poorly understood, especially within an environmentally relevant exposure range. In an effort to understand the potential causal relationship between MeHg exposure and endocrine development, we established four dietary exposure groups (0 [control], 0.05, 0.1, and 0.3 mg/kg wet wt/d of MeHg) of postfledging white ibises (Eudocimus albus) in a divided, free-flight aviary that spanned the estimated range of environmental exposure for this species. Fecal samples were collected from individually identified ibises over six months in 2005 and processed for hormone evaluation. Significant sex-related differences in fecal estradiol concentrations, though unpredicted in direction, suggest that this steroid could be related to juvenile development in this species. Using repeated-measures general linear models, we tested a set of candidate models to explain variation in endocrine expression. We found that MeHg exposure led to significant differences in fecal estradiol concentrations between the control and medium-dose groups, whereas differences in fecal corticosterone concentrations were observed between the control and both the low- and high-dose groups. These results suggest highly nonlinear dose-response patterns for MeHg. Many endocrine-disrupting contaminants are theorized to affect multiple endpoints in a nonlinear manner, making results difficult to interpret using a traditional toxicological approach. The evidence presented here suggests that endocrine effects of MeHg exposure could behave similarly. [source]

Emotional arousal and gender differences in aggression: A meta-analysis

George P. Knight
Abstract This meta-analysis investigated the possibility that gender differences in aggression, and the variability in these differences, are a function of gender differences in the regulation of arousal generated in emotionally evocative contexts. The sample of studies for this analysis was based on an exhaustive search of the relevant research reports from 1965,1999. Studies were excluded from the sample if they were case studies; investigated spousal/familial or societal violence, war, suicide, or political violence; involved clinical or deviant participants; included fewer than 10 participants; included all male, all female, all non-Caucasian, or non-US/non-Canadian participants. Based on previous evidence that males may be more easily aroused by aggressive-relevant emotional stimuli than females, and that males may have more difficulty regulating emotionally arousing states than females, we hypothesized that the magnitude of the gender differences in aggression would covary, in a nonlinear manner, with the emotional evocativeness of the study context. Consistent with our hypothesis, the magnitude of gender differences in aggression was relatively small in research contexts that appeared to produce no or large increments in emotional arousal and larger (favoring males) in contexts that appeared to produce small or medium increments in emotional arousal. Aggr. Behav. 28:366,393, 2002. © 2002 Wiley-Liss, Inc. [source]

Scheduled announcements and volatility patterns: The effects of monetary policy committee announcements on LIBOR and short sterling futures and options

Peng Sun
Both the UK spot and futures markets in short-term interest rates are found to react strongly to surprises in the scheduled announcements of the repo rate and RPI. Therefore, these announcements should also affect the market for options on short-term interest rate futures. Because the repo rate and RPI announcements are scheduled, the options market can predict the days on which announcement shocks may hit, and build this information into its volatility expectations. It is argued that the volatility used in pricing options should alter over time in a predictable nonlinear manner that varies with contract maturity and the number of forthcoming announcements; but is independent of announcement content. The empirical results support this hypothesis. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark 23:773,797, 2003 [source]

Längskraftbeanspruchung von durchgehend geschweißten Schienen auf Brücken für Lastkombinationen

BAUTECHNIK, Issue 7 2004
Peter Ruge Prof. Dr.-Ing. habil.
Die Längskraftbeanspruchung von durchgehend geschweißten Schienen auf Brücken für Lastkombinationen wird im DIN -Fachbericht 101, K.3.5, geregelt. Die Lastfälle werden jeweils einzeln für sich nichtlinear analysiert und anschließend durch Summation der Teil ergebnisse zur Gesamtlösung zusammengefaßt. Diese Näherung wird hier durch eine korrekte Kombination zunächst der Lastfälle Temperaturdehnung plus Bremsen ersetzt. Dabei erweist sich der Wechsel des Längsverschiebewiderstandes von unbelastetem zu belastetem Gleis infolge Zugüberfahrt als zusätzlicher Lastfall. Longitudinal forces in continuously welded rails on bridges for coupled loads. The calculation of longitudinal forces in rails on bridges for coupled loads is treated in DIN-Fachbericht 101, K.3.5. Each loadcase is analysed separately in a nonlinear manner and finally all separate parts are summarized. In this paper, this approximation is replaced by correctly coupling two loadcases: temperature difference between tracks and girders and braking. [source]

Population modelling of the effect of inogatran, at thrombin inhibitor, on ex vivo coagulation time (APTT) in healthy subjects and patients with coronary artery disease

Marie Cullberg
Aims, The purpose of this study was to characterize the relationship between the degree of anticoagulation, assessed by APTT, and the plasma concentration of inogatran in healthy subjects and in patients with coronary artery disease. Methods, Data from five phase I studies in 78 healthy males and two phase II multicentre studies in 948 patients of both sexes with unstable angina pectoris or non-Q-wave myocardial infarction were evaluated. A total of 3296 pairs of concentration-APTT samples were obtained before, during, and after intravenous infusions of inogatran. Mixed effects modelling was used for population pharmacodynamic analysis of the drug effect and for describing the variability in baseline APTT. Results, The population mean baseline APTT was 29 s, but large variations between individuals (s.d. 3.6 s) were observed. The variability between studies (1.3 s) and centres (1.8 s) were of less importance, though statistically significant. APTT increased in a nonlinear manner with increasing inogatran concentration and the relationship was well described by a combined linear and Emax model. A significant part of the overall variability could be ascribed to the APTT reagent and equipment used at the different study centres. These method-dependent differences were compensated for by including the lower limit of the normal reference range as a covariate, affecting both baseline and Emax, in the model. For the typical healthy subject and patient, the method-corrected population mean parameters were: APTTbaseline 35 and 31 s, slope 8.0 and 5.8 s l µmol,1, Emax 36 and 34 s, and EC50 0.54 and 0.72 µmol l,1, respectively. The model predicted plasma concentration needed to double the APTT from the baseline value was 1.25 and 1.45 µmol l,1 in the healthy volunteer and patient, respectively. Conclusions, The nonlinear relationship between APTT and inogatran concentration in plasma was well described by a combined linear and Emax model. Pooling of data was made possible by incorporating a centre-specific characteristic of the assay method in the model. Patients had lower baseline APTT and appeared to have less pronounced effect of inogatran than young healthy subjects. [source]

Distinct Brain Volume Changes Correlating with Clinical Stage, Disease Progression Rate, Mutation Size, and Age at Onset Prediction as Early Biomarkers of Brain Atrophy in Huntington's Disease

Ferdinando Squitieri
Searching brain and peripheral biomarkers is a requisite to cure Huntington's disease (HD). To search for markers indicating the rate of brain neurodegenerative changes in the various disease stages, we quantified changes in brain atrophy in subjects with HD. We analyzed the cross-sectional and longitudinal rate of brain atrophy, quantitatively measured by fully-automated multiparametric magnetic resonance imaging, as fractional gray matter (GM, determining brain cortex volume), white matter (WM, measuring the volume of axonal fibers), and corresponding cerebral spinal fluid (CSF, a measure of global brain atrophy), in 94 gene-positive subjects with presymptomatic to advanced HD, and age-matched healthy controls. Each of the three brain compartments we studied (WM, GM, and CSF) had a diverse role and their time courses differed in the development of HD. GM volume decreased early in life. Its decrease was associated with decreased serum brain-derived-neurotrophic-factor and started even many years before onset symptoms, then decreased slowly in a nonlinear manner during the various symptomatic HD stages. WM volume loss also began in the presymptomatic stage of HD a few years before manifest symptoms appear, rapidly decreasing near to the zone-of-onset. Finally, the CSF volume increase began many years before age at onset. Its volume measured in presymptomatic subjects contributed to improve the CAG-based model of age at onset prediction. The progressive CSF increase depended on CAG mutation size and continued linearly until the last stages of HD, perhaps representing the best marker of progression rate and severity in HD (R2= 0.25, P < 0.0001). [source]