Comparative degradation of ZnO- and SnO(2)-based polycrystalline non-ohmic devices by current pulse stress

The degradation behaviour of SnO(2)-based varistors (SCNCr) due to current pulses (8/20 mu s) is reported here for the first time in comparison with the ZnO-based commercial varistors (ZnO). Puncturing and/or cracking failures were observed in ZnO-based varistors possessing inferior thermo-mechanical properties in comparison with that found in a SCNCr system free of failures. Both systems presented electric degradation related to the increase in the leakage current and decrease in the electric breakdown field, non-linear coefficient and average value of the potential barrier height. However, it was found that a more severe degradation occurred in the ZnO-based varistors concerning their non-ohmic behaviour, while in the SCNCr system, a strong non-ohmic behaviour remained after the degradation. These results indicate that the degradation in the metal oxide varistors is controlled by a defect diffusion process whose rate depends on the mobility, the concentration of meta-stable defects and the amount of electrically active interfaces. The improved behaviour of the SCNCr system is then inferred to be associated with the higher amount of electrically active interfaces (85%) and to a higher energy necessary to activate the diffusion of the specific defects.

Momentary stress moderates procoagulant reactivity to a trauma-specific interview in patients with posttraumatic stress disorder caused by myocardial infarction

Hypercoagulability of the blood might partially explain the increased cardiovascular disease risk in posttraumatic stress disorder (PTSD) and is also triggered by anticipatory stress. We hypothesized exaggerated procoagulant reactivity in patients with PTSD in response to a trauma-specific interview that would be moderated by momentary stress levels. We examined 23 patients with interviewer-diagnosed PTSD caused by myocardial infarction (MI) and 21 post-MI patients without PTSD. A second diagnostic (i.e., trauma-specific) interview to assess posttraumatic stress severity was performed after a median follow-up of 26 months (range 12-36). Before that interview patients rated levels of momentary stress (Likert scale 0-10) and had blood collected before and after the interview. The interaction between PTSD diagnostic status at study entry and level of momentary stress before the follow-up interview predicted reactivity of fibrinogen (P=0.036) and d-dimer (P=0.002) to the PTSD interview. Among patients with high momentary stress levels, PTSD patients had greater fibrinogen (P=0.023) and d-dimer (P=0.035) reactivity than non-PTSD patients. Among patients with low momentary stress levels, PTSD patients had less d-dimer reactivity than non-PTSD patients (P=0.024); fibrinogen reactivity did not significantly differ between groups. Momentary stress levels, but not severity of posttraumatic stress, correlated with d-dimer reactivity in PTSD patients (r=0.46, P=0.029). We conclude that momentary stress levels moderated the relationship between PTSD and procoagulant reactivity to a trauma-specific interview. Procoagulant reactivity in post-MI patients with PTSD confronted with their traumatically experienced MI was observed if patients perceived high levels of momentary stress before the interview.

Controlling for culture-specific response bias using ipsatization and response style indicators: Family orientation in seventeen cultures and two generations

Within-subject standardization (ipsatization) has been advocated as a possible means to control for culture-specific responding (e.g., Fisher, 2004). However, the consequences of different kinds of ipsatization procedures for the interpretation of mean differences remain unclear. The current study compared several ipsatization procedures with ANCOVA-style procedures using response style indicators for the construct of family orientation with data from 14 cultures and two generations from the Value-of-Children-(VOC)-Study (4135 dyads). Results showed that within-subject centering/standardizing across all Likert-scale items of the comprehensive VOC-questionnaire removed most of the original cross-cultural variation in family orientation and lead to a non-interpretable pattern of means in both generations. Within-subject centering/standardizing using a subset of 19 unrelated items lead to a decrease to about half of the original effect size and produced a theoretically meaningful pattern of means. A similar effect size and similar mean differences were obtained when using a measure of acquiescent responding based on the same set of items in an ANCOVA-style analysis. Additional models controlling for extremity and modesty performed worse, and combinations did not differ from the acquiescence-only model. The usefulness of different approaches to control for uniform response styles (scalar equivalence not given) in cross- cultural comparisons is discussed.

In situ characterization of sediment oxygen demand across the spectrum of non-resuspension to full resuspension with varying bed shear stress

Sediment oxygen demand (SOD) can be a significant oxygen sink in various types of water bodies, particularly slow-moving waters with substantial organic sediment accumulation. In most settings where SOD is a concern, the prevailing hydraulic conditions are such that the impact of sediment resuspension on SOD is not considered. However, in the case of Bubbly Creek in Chicago, Illinois, the prevailing slack water conditions are interrupted by infrequent intervals of very high flow rates associated with pumped combined sewer overflow (CSO) during intense hydrologic events. These events can cause resuspension of the highly organic, nutrient-rich bottom sediments, resulting in precipitous drawdown of dissolved oxygen (DO) in the water column. While many past studies have addressed the dependence of SOD on near-bed velocity and bed shear stress prior to the point of sediment resuspension, there has been limited research that has attempted to characterize the complex and dynamic phenomenon of resuspended-sediment oxygen demand. To address this issue, a new in situ experimental apparatus referred to as the U of I Hydrodynamic SOD Sampler was designed to achieve a broad range of velocities and associated bed shear stresses. This allowed SOD to be analyzed across the spectrum of no sediment resuspension associated with low velocity/ bed shear stress through full sediment resuspension associated with high velocity / bed shear stress. The current study split SOD into two separate components: (1) SODNR is the sediment oxygen demand associated with non-resuspension conditions and is a surface sink calculated using traditional methods to yield a value with units (g/m2/day); and (2) SODR is the oxygen demand associated with resuspension conditions, which is a volumetric sink most accurately characterized using non-traditional methods and units that reflect suspension in the water column (mg/L/day). In the case of resuspension, the suspended sediment concentration was analyzed as a function of bed shear stress, and a formulation was developed to characterize SODR as a function of suspended sediment concentration in a form similar to first-order biochemical oxygen demand (BOD) kinetics with Monod DO term. The results obtained are intended to be implemented into a numerical model containing hydrodynamic, sediment transport, and water quality components to yield oxygen demand varying in both space and time for specific flow events. Such implementation will allow evaluation of proposed Bubbly Creek water quality improvement alternatives which take into account the impact of SOD under various flow conditions. Although the findings were based on experiments specific to the conditions in Bubbly Creek, the techniques and formulations developed in this study should be applicable to similar sites.

Water Stress Reveals Differential Antioxidant Responses Of Tolerant And Non-tolerant Sugarcane Genotypes.

The biochemical responses of the enzymatic antioxidant system of a drought-tolerant cultivar (IACSP 94-2094) and a commercial cultivar in Brazil (IACSP 95-5000) grown under two levels of soil water restriction (70% and 30% Soil Available Water Content) were investigated. IACSP 94-2094 exhibited one additional active superoxide dismutase (Cu/Zn-SOD VI) isoenzyme in comparison to IACSP 95-5000, possibly contributing to the heightened response of IACSP 94-2094 to the induced stress. The total glutathione reductase (GR) activity increased substantially in IACSP 94-2094 under conditions of severe water stress; however, the appearance of a new GR isoenzyme and the disappearance of another isoenzyme were found not to be related to the stress response because the cultivars from both treatment groups (control and water restrictions) exhibited identical changes. Catalase (CAT) activity seems to have a more direct role in H2O2 detoxification under water stress condition and the shift in isoenzymes in the tolerant cultivar might have contributed to this response, which may be dependent upon the location where the excessive H2O2 is being produced under stress. The improved performance of IACSP 94-2094 under drought stress was associated with a more efficient antioxidant system response, particularly under conditions of mild stress.

A positional FEM Formulation for geometrical non-linear analysis of shells

This work presents a fully non-linear finite element formulation for shell analysis comprising linear strain variation along the thickness of the shell and geometrically exact description for curved triangular elements. The developed formulation assumes positions and generalized unconstrained vectors as the variables of the problem, not displacements and finite rotations. The full 3D Saint-Venant-Kirchhoff constitutive relation is adopted and, to avoid locking, the rate of thickness variation enhancement is introduced. As a consequence, the second Piola-Kirchhoff stress tensor and the Green strain measure are employed to derive the specific strain energy potential. Curved triangular elements with cubic approximation are adopted using simple notation. Selected numerical simulations illustrate and confirm the objectivity, accuracy, path independence and applicability of the proposed technique.

Phosphorylation of the C-terminal sites of human p53 reduces non-sequence-specific DNA binding as modeled with synthetic peptides

Phosphorylation of the tumor suppressor p53 is generally thought to modify the properties of the protein in four of its five independent domains. We used synthetic peptides to directly study the effects of phosphorylation on the non-sequence-specific DNA binding and conformation of the C-terminal, basic domain. The peptides corresponded to amino acids 361-393 and were either nonphosphorylated or phosphorylated at the protein kinase C (PKC) site, Ser378, or the casein kinase II (CKII) site, Ser392, or bis-phosphorylated on both the PKC and the CKII sites. A fluorescence polarization analysis revealed that either the recombinant p53 protein or the synthetic peptides bound to two unrelated target DNA fragments. Phosphorylation of the peptide at the PKC or the CKII sites clearly decreased DNA binding, and addition of a second phosphate group almost completely abolished binding. Circular dichroism spectroscopy showed that the peptides assumed identical unordered structures in aqueous solutions. The unmodified peptide, unlike the Ser378 phosphorylated peptide, changed conformation in the presence of DNA. The inherent ability of the peptides to form an alpha-helix could be detected when circular dichroism and nuclear magnetic resonance spectra were: taken in trifluoroethanol-water mixtures. A single or double phosphorylation destabilized the helix around the phosphorylated Ser378 residue but stabilized the helix downstream in the sequence.

The impact of trauma and post-traumatic stress disorder on the treatment response of patients with obsessive-compulsive disorder

Few case series studies have addressed the issue of treatment response in patients with obsessive-compulsive disorder (OCD) and comorbid post-traumatic stress disorder (PTSD), and there are no prospective studies addressing response to conventional treatment in OCD patients with a history of trauma (HT). The present study aimed to investigate, prospectively, the impact of HT or PTSD on two systematic, first-line treatments for OCD. Two hundred and nineteen non-treatment-resistant OCD outpatients were treated with either group cognitive-behavioral therapy (GCBT n = 147) or monotherapy with a selective serotonin reuptake inhibitor (SSRI n = 72). Presence of HT and PTSD were assessed at intake, as part of a broader clinical and demographical baseline characterization of the sample. Severity and types of OCD symptoms were assessed with the Yale-Brown Obsessive-Compulsive Scale (YBOCS) and the Dimensional YBOCS (DYBOCS), respectively. Depression and anxiety symptoms were measured with the Beck Depression Inventory (BDI) and the Beck Anxiety Inventory (BAI). Both treatments had 12-week duration. Treatment response was considered as a categorical [35% or greater reduction in baseline YBOCS scores plus a Clinical Global Impression-Improvement rating of better (2) or much better (1)] and continuous variable (absolute number reduction in baseline YBOCS scores). Treatment response was compared between the OCD + HT group versus the OCD without HT group and between the OCD + PTSD group versus the OCD without PTSD group. Parametric and non-parametric tests were used when indicated. Data on HT and PTSD were available for 215 subjects. Thirty-eight subjects (17.67% of the whole sample) had a positive HT (OCD + HT group) and 22 subjects (57.89% of the OCD + HT group and 10.23% of the whole sample) met full DSM-IV criteria for PTSD. The OCD + HT and OCD without HT groups presented similar response to GCBT (60% of responders in the first group and 63% of responders in the second group, p = 1.00). Regarding SSRI treatment, the difference between the response of the OCD + HT (47.4%) and OCD without HT (22.2%) groups was marginally significant (p = 0.07). In addition, the OCD + PTSD group presented a greater treatment response than the OCD without PTSD group when treatment response was considered as a continuous variable (p = 0.01). The age when the first trauma occurred had no impact on treatment response. In terms of specific OCD symptom dimensions, as measured by the DYBOCS, OCD treatment fostered greater reductions for the OCD + PTSD group than for the OCD without PTSD group in the scores of contamination obsessions and cleaning compulsions, collecting and hoarding and miscellaneous obsessions and related compulsions (including illness concerns and mental rituals, among others). The OCD + PTSD group also presented a greater reduction in anxiety scores than the OCD without PTSD group (p = 0.003). The presence of HT or PTSD was not related to a poorer treatment response in this sample of non-treatment-resistant OCD patients. Unexpectedly, OCD patients with PTSD presented a greater magnitude of response when compared with OCD without PTSD patients in specific OCD symptom dimensions. Future studies are needed to clarify if trauma and PTSD have a more significant impact on the onset and clinical expression of OCD than on the conventional treatment for this condition, and whether OCD stemming from trauma would constitute a subtype of OCD with a distinct response to conventional treatment.

Appropriate indicators for injury control?

Indicators are valuable tools used to measure progress towards a desired health outcome. Increased awareness of the public health burden due to injury has lead to a concomitant interest in monitoring the impact of national initiatives that aim to reduce the size of the burden. Several injury indicators have now been proposed. This study examines the ability of each of the suggested indicators to reflect the nature and extent of the burden of non-fatal injury. A criterion validity, population-based, prospective cohort study was conducted in Brisbane, a sub-tropical Metropolitan City on the eastern seaboard of Australia, over a 12-month period between 1 January and 31 December 1998. Neither the presence of a long bone fracture nor the need for hospitalisation for 4 or more days were sensitive or specific indicators for 'serious' or major injury as defined by the 'Gold Standard' Injury Severity Score (ISS). Subsequent analysis, using other public health outcome measures demonstrated that the major component of the illness burden of injury was in fact due to 'minor' not serious injury. However, the suggested indicators demonstrated low sensitivity and specificity for these outcomes as well. The results of the study support the need to include at least all hospitalisations in any population-based measure of injury and not attempt to simplify the indicator to a more convenient measure aimed at identifying just those cases of,serious' injury.

Relative importance of female-specific and non-female-specific effects on variation in iron stores between women

Women have lower iron stores than men because of iron loss during their reproductive years. However, variation between women could result from differences in iron loss, aspects of iron homeostasis common to men and women, or a combination of both. We compared the effects of age, menopause, menstrual blood loss and the number of pregnancies (sex-specific factors), and the effects of genetic variation, on markers of iron stores. We assessed how much the same genes or other familial factors influence iron status in both men and women. Data from 2039 female twins who participated in studies of reproductive health and iron status were used to estimate the proportions of variation that could be ascribed to genes, environment and measured factors. Significant effects of age, menopausal status and magnitude of menstrual blood loss were demonstrated, accounting for up to 18% of variance in serum ferritin in this sample, but number of children had no significant effect. Genetic effects were more than twice as great as sex-specific effects. The within-pair similarity of ferritin values in dizygotic female twin pairs was greater than for dizygotic opposite-sex pairs, but this difference was not quite significant, consistent with a minor role for sex-specific factors; and the opposite-sex within-pair differences did not diminish significantly with age. We conclude that the contribution of genetic differences between women to variation in iron stores outweighs the comparatively small effects of interindividual variation in iron loss through variation in menstruation and number of pregnancies.

Functional and molecular characterization of SR45, a plant-specific factor involved in sugar and stress signaling in Arabidopsis thaliana

Dissertation presented to obtain the Ph.D degree in Molecular Biology

Sertraline accumulation and effects in the estuarine decapod Carcinusmaenas: Importance of the history of exposure to chemical stress

Sertraline is widely prescribed worldwide and frequently detected in aquatic systems. There is, however, a remarkable gap of information on its potential impact on estuarine and coastal invertebrates. This study investigated sertraline accumulation and effects in Carcinus maenas. Crabs from a moderately contaminated (Lima) and a low-impacted (Minho) estuary were exposed to environmental and high levels of sertraline (0.05, 5, 500 μg L−1). A battery of biomarkers related to sertraline mode of action was employed to assess neurotransmission, energy metabolism, biotransformation and oxidative stress pathways. After a seven-day exposure, sertraline accumulation in crabs’ soft tissues was found in Lima (5 μg L−1: 15.3 ng L−1 ww; 500 μg L−1: 1010 ng L−1 ww) and Minho (500 μg L−1: 605 ng L−1 ww) animals. Lima crabs were also more sensitive to sertraline than those from Minho, exhibiting decreased acetylcholinesterase activity, indicative of ventilatory and locomotory dysfunction, inhibition of anti-oxidant enzymes and increased oxidative damage at ≥0.05 μg L−1. The Integrated Biomarker Response (IBR) index indicated their low health status. In addition, Minho crabs showed non-monotonic responses of acetylcholinesterase suggestive of hormesis. The results pointed an influence of the exposure history on differential sensitivity to sertraline and the need to perform evaluations with site-specific ecological receptors to increase relevance of risk estimations when extrapolating from laboratory to field conditions.

High prevalence and association of HIV-1 non-B subtype with specific sexual transmission risk among antiretroviral naïve patients in Porto Alegre, RS, Brazil

In South Brazil the circulation of two HIV-1 subtypes with different characteristics represents an important scenario for the study of the impact of HIV-1 diversity on the evolution of the HIV-1 epidemic and AIDS disease. HIV-1 B, the predominant variant in industrialized countries and HIV-1 C, the most prevalent subtype in areas with rapid epidemic growth, are implicated in most infections. We evaluated blood samples from 128 antiretroviral (ARV) naïve patients recruited at entry to the largest HIV outpatient service in Porto Alegre. Based on partial pol region sequencing, HIV-1 C was observed in 29%, HIV-1 B in 22.6% and, the recently identified CRF31_BC, in 23.4% of 128 volunteers. Other variants were HIV-1 F in 10% and other mosaics in 5.5%. In order to evaluate the association of socio-behavioral characteristics and HIV-1 subtypes, interviews and laboratory evaluation were performed at entry. Our data suggest an established epidemic of the three major variants, without any evidence of partitioning in either of the subgroups analyzed. However, anal sex practices were associated with subtype B, which could indicate a greater transmissibility of non-B variants by vaginal intercourse. This study provides baseline information for epidemiologic surveillance of the changes of the molecular characteristics of HIV-1 epidemics in this region.

Glutathione levels in and total antioxidant capacity of Candida sp. cells exposed to oxidative stress caused by hydrogen peroxide

INTRODUCTION: The capacity to overcome the oxidative stress imposed by phagocytes seems to be critical for Candida species to cause invasive candidiasis. METHODS: To better characterize the oxidative stress response (OSR) of 8 clinically relevant Candida sp., glutathione, a vital component of the intracellular redox balance, was measured using the 5,5'-dithiobis-(2-nitrobenzoic acid (DTNB)-glutathione disulfide (GSSG) reductase reconversion method; the total antioxidant capacity (TAC) was measured using a modified method based on the decolorization of the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic) acid radical cation (ABTS*+). Both methods were used with cellular Candida sp. extracts treated or not with hydrogen peroxide (0.5 mM). RESULTS: Oxidative stress induced by hydrogen peroxide clearly reduced intracellular glutathione levels. This depletion was stronger in Candida albicans and the levels of glutathione in untreated cells were also higher in this species. The TAC demonstrated intra-specific variation. CONCLUSIONS: Glutathione levels did not correlate with the measured TAC values, despite this being the most important non-enzymatic intracellular antioxidant molecule. The results indicate that the isolated measurement of TAC does not give a clear picture of the ability of a given Candida sp. to respond to oxidative stress.