231 resultados para differential item functioning

em QUB Research Portal - Research Directory and Institutional Repository for Queen's University Belfast


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Post-traumatic stress, depression and anxiety symptoms are common outcomes following earthquakes, and may persist for months and years. This study systematically examined the impact of neighbourhood damage exposure and average household income on psychological distress and functioning in 600 residents of Christchurch, New Zealand, 4–6 months after the fatal February, 2011 earthquake. Participants were from highly affected and relatively unaffected suburbs in low, medium and high average household income areas. The assessment battery included the Acute Stress Disorder Scale, the depression module of the Patient Health Questionnaire (PHQ-9), and the Generalized Anxiety Disorder Scale (GAD-7), along with single item measures of substance use, earthquake damage and impact, and disruptions in daily life and relationship functioning. Controlling for age, gender and social isolation, participants from low income areas were more likely to meet diagnostic cut-offs for depression and anxiety, and have more severe anxiety symptoms. Higher probabilities of acute stress, depression and anxiety diagnoses were evident in affected versus unaffected areas, and those in affected areas had more severe acute stress, depression and anxiety symptoms. An interaction between income and earthquake effect was found for depression, with those from the low and medium income affected suburbs more depressed. Those from low income areas were more likely, post-earthquake, to start psychiatric medication and increase smoking. There was a uniform increase in alcohol use across participants. Those from the low income affected suburb had greater general and relationship disruption post-quake. Average household income and damage exposure made unique contributions to earthquake-related distress and dysfunction.

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The subambient behavior of aqueous mannitol solutions is of considerable relevance to the preparation of freeze dried formulations. In this investigation the properties of 3% w/v mannitol solutions were investigated using differential scanning calorimetry (DSC), cold stage microscopy (CSM), and X-ray diffraction (XRD) to identify the thermal transitions and structural transformations undergone by this system. It was found that on cooling from ambient the system formed ice at circa -20°C while a further exotherm was seen at approximately -30°C. Upon reheating an endotherm was seen at circa -30°C followed immediately by an exotherm at circa -25°C. Temperature cycling indicated that the thermal transitions observed upon reheating were not reversible. Modulated temperature DSC (MTDSC) indicated that the transitions observed upon reheating corresponded to a glass transition immediately followed by recrystallization, XRD data showed that recrystallization was into the ß form. Annealing at -35°C for 40 min prior to cooling and reheating resulted in a maximum enthalpy being observed for the reheating exotherm. It is concluded that on cooling 3% w/v aqueous mannitol solutions an amorphous phase is formed that subsequently recrystallises into the ß form. The study has also shown that DSC, CSM, and XRD are useful complementary techniques for the study of frozen systems

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The lifetime success and performance characteristics of communally reared offspring of wild native Burrishoole (native), ranched native (ranched) and non-native (non-native) Atlantic salmon Salmo salar from the adjacent Owenmore River were compared. Non-native year parr showed a substantial downstream migration, which was not shown by native and ranched parr. This appears to have been an active migration rather than competitive displacement and may reflect an adaptation to environmental or physiographic conditions within the Owenmore River catchment where the main nursery habitat is downstream of the spawning area. There were no differences between native and ranched in smolt output or adult return. Both of these measures, however, were significantly lower for the non-native group. A greater proportion of the non-native Atlantic salmon was taken in the coastal drift nets compared to the return to the Burrishoole system, probably as a result of the greater size of the non-native fish. The overall lifetime success of the non-native group, from fertilized egg to returning adult, was some 35% of native and ranched. The ranched group showed a significantly greater male parr maturity, a greater proportion of 1+ year smolts, and differences in sex ratio and timing of freshwater entry of returning adults compared to native, which may have fitness implications under specific conditions.

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The relationship between heat-treatment parameters and microstructure in titanium alloys has so far been mainly studied empirically, using characterization techniques such as microscopy. Calculation and modeling of the kinetics of phase transformation have not yet been widely used for these alloys. Differential scanning calorimetry (DSC) has been widely used for the study of a variety of phase transformations. There has been much work done on the calculation and modeling of the kinetics of phase transformations for different systems based on the results from DSC study. In the present work, the kinetics of the transformation in a Ti-6Al-4V titanium alloy were studied using DSC, at continuous cooling conditions with constant cooling rates of 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C/min. The results from calorimetry were then used to trace and model the transformation kinetics in continuous cooling conditions. Based on suitably interpreted DSC results, continuous cooling–transformation (CCT) diagrams were calculated with lines of isotransformed fraction. The kinetics of transformation were modeled using the Johnson–Mehl–Avrami (JMA) theory and by applying the "concept of additivity." The JMA kinetic parameters were derived. Good agreement between the calculated and experimental transformed fractions is demonstrated. Using the derived kinetic parameters, the transformation in a Ti-6Al-4V alloy can be described for any cooling path and condition. An interpretation of the results from the point of view of activation energy for nucleation is also presented.

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BACKGROUND: Methylenetetrahydrofolate reductase (MTHFR; EC 1.7.99.5) supplies the folate needed for the metabolism of homocysteine. A reduction in MTHFR activity, as occurs in the homozygous state for the 677C-->T (so-called thermolabile) enzyme variant (TT genotype), is associated with an increase in plasma total homocysteine (tHcy). OBJECTIVE: In vitro studies suggest that the reduced activity of thermolabile MTHFR is due to the inappropriate loss of its riboflavin cofactor. We investigated the hypothesis that MTHFR activity in the TT genotype group is particularly sensitive to riboflavin status. DESIGN: We studied tHcy and relevant B-vitamin status by MTHFR genotype in a cross-sectional study of 286 healthy subjects aged 19-63 y (median: 27 y). The effect of riboflavin status was examined by dividing the sample into tertiles of erythrocyte glutathionine reductase activation coefficient, a functional index of riboflavin status. RESULTS: Lower red blood cell folate (P = 0.0001) and higher tHcy (P = 0.0082) concentrations were found in the TT group than in the heterozygous (CT) or wild-type (CC) groups. However, these expected relations in the total sample were driven by the TT group with the lowest riboflavin status, whose mean tHcy concentration (18.09 micromol/L) was almost twice that of the CC or CT group. By contrast, adequate riboflavin status rendered the TT group neutral with respect to tHcy metabolism. CONCLUSIONS: The high tHcy concentration typically associated with homozygosity for the 677C-->T variant of MTHFR occurs only with poor riboflavin status. This may have important implications for governments considering new fortification policies aimed at the prevention of diseases for which this genotype is associated with increased risk.