Challenges and Barriers to Resistance Training in Middle-Aged Women

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Defect chemistry and transport properties of BaxCe0.85M0.15O3-d

The site-incorporation mechanism of M3+ dopants into A2+B4+O3 perovskites controls the overall defect chemistry and thus their transport properties. For charge-balance reasons, incorporation onto the A2+-site would require the creation of negatively charged point defects (such as cation vacancies), whereas incorporation onto the B4+-site is accompanied by the generation of positively charged defects, typically oxygen vacancies. Oxygen-vacancy content, in turn, is relevant to proton-conducting oxides in which protons are introduced via the dissolution of hydroxyl ions at vacant oxygen sites. We propose here, on the basis of x-ray powder diffraction studies, electron microscopy, chemical analysis, thermal gravimetric analysis, and alternating current impedance spectroscopy, that nominally B-site doped barium cerate can exhibit dopant partitioning as a consequence of barium evaporation at elevated temperatures. Such partitioning and the presence of significant dopant concentrations on the A-site negatively impact proton conductivity. Specific materials examined are BaxCe0.85M0.15O3-d (x = 0.85 - 1.20; M = Nd, Gd, Yb). The compositional limits for the maximum A-site incorporation are experimentally determined to be: (Ba0.919Nd0.081)(Ce0.919Nd0.081)O3, (Ba0.974Gd0.026)(Ce0.872Gd0.128)O2.875, and Ba(Ce0.85Yb0.15)O2.925. As a consequence of the greater ability of larger cations to exist on the Ba site, the H2O adsorption and proton conductivities of large-cation doped barium cerates are lower than those of small-cation doped analogs

Hydrothermal synthesis of perovskite and pyrochlore powders of potassium tantalate

Potassium tantalate powders were hydrothermally synthesized at 100 to 200 °C in 4 to 15 M aqueous KOH solutions. A defect pyrochlore, Kta_(2)O_(5)(OH). nH2O (n ≈ 1.4), was obtained at 4 M KOH, but at 7–12 M KOH, this pyrochlore was gradually replaced by a defect perovskite as the stable phase. At 15 M KOH, there was no intermediate pyrochlore, only a defect perovskite, K_(0.85)Ta_(0.92)O_(2.43)(OH)_(0.57) 0.15H_(2)O. Synthesis at higher KOH concentrations led to greater incorporation of protons in the perovskite structures. The potassium vacancies required for charge compensation of incorporated protons could accommodate water molecules in the perovskite structure

Hydrothermal synthesis of KNbO_3 and NaNbO_3 powders

Orthorhombic KNbO_3 and NaNbO_3 powders were hydrothermally synthesized in KOH and NaOH solutions (6.7–15 M) at 150 and 200 °C. An intermediate hexaniobate species formed first before eventually converting to the perovskite phase. For synthesis in KOH solutions, the stability of the intermediate hexaniobate ion increased with decreasing KOH concentrations and temperatures. This led to significant variations in the induction periods and accounted for the large disparity in the mass of recovered powder for different processing parameters. It is also believed that protons were incorporated in the lattice of the as-synthesized KNbO_3 powders as water molecules and hydroxyl ions

The value of preventing malaria in Tembien, Ethiopia

The authors measure the monetary value households place on preventing malaria in Tembien, Tigray Region, Ethiopia. They estimate a household demand function for a hypothetical malaria vaccine and compute the value of preventing malaria as the household's maximum willingness to pay to provide vaccines for all family members. They contrast willingness to pay with the traditional costs of illness (medical costs and time lost because of malaria). Their results indicate that the value of preventing malaria with vaccines is about US$36 a household a year, or about 15 percent of imputed annual household income. This is, on average, about two or three times the expected household cost of illness. Despite the great benefits from preventing malaria, the fact that vaccine demand is price inelastic suggests that it will be difficult to achieve significant market penetration unless the vaccine is subsidized. The authors obtain similar results for insecticide-treated bed nets. Their estimates of household demand functions for bed nets suggest that at a price that might permit cost recovery (US$6 a bed net), only a third of the population of a 200-person village would sleep under bed nets.Early Child and Children's Health,Public Health Promotion,Disease Control&Prevention,Health Monitoring&Evaluation,Economic Theory&Research,Health Monitoring&Evaluation,Economic Theory&Research,Climate Change,Environmental Economics&Policies,Early Child and Children's Health

Session, Segmented Session, and Acute RPE and Affective Responses to Self-selected Treadmill Exercise

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Risk Factors of Deep Venous Thrombosis in Duplex and Colour Doppler Ultrasound at Tikur Anbessa Specialized Hospital, Addis Ababa, Ethiopia

Background: Deep venous thrombosis is a major health problem with high morbidity and mortality worldwide. Thus early, correct and definitive diagnosis is crucial in assessing thromboembolic risk and initiating therapy. In this regard Patients at risk must be identified and given appropriate prophylaxis to reduce Venous Thromboembolism related morbidity and mortality.The main objective of this study was to determine common risk factors of deep venous thrombosis (DVT) and the common sites involved by DVT in ultrasound proven cases.Methods: This was a prospective cross-sectional study which included all patients who had proven deep venous thrombosis by Dopper and duplex ultrasound at Tikur Anbessa Specialized Hospital (TASH). Senior radiology residents collected the data after getting approval from consultant radiologists. Analysis was under taken by principal investigator.Results: There were a total 81 ultrasound proven cases of DVT involving the extremities during the study period out of which 34.6% were males and 65.4% females. The majority (58%) were under the age of 40 years. Malignancy was the most common identified risk factor (30.9% of the cases) followed by prolonged immobilization 19.8%, pregnancy related problems 6.2% and severe trauma 6.2% of the patients. No apparent risk factor was found in 12.3%. Swelling was noted in 93.8% of the participants in combination with other manifestations or alone; whereas pain was noted in 70.4% of the patients. The study showed 59.3% had involvement of the left lower limb only; 11.1% had involvement of both lower limbs. The upper extremities were affected in only one patient having bilateral involvement of brachiocephalic veins. According to the study 84% of the patients had combined involvement of the deep veins of the lower extremities extending from the common iliac veins to the poplitial veins. The study revealed that 28.4% of participants were found to havecombined involvement of the common femoral vein (CFV), superficial femoral vein (SFV) & poplitial vein; 22.2% had combined involvement of the CFV & SFV. Conclusion: From the study we concluded that Malignancy, prolonged immobilization, pregnancy related problems and major trauma were the most common risk factors noted for DVT and Swelling was the most common presenting manifestation. Majority of the patients had multiple site deep vein involvement extending from the common iliac to the poplitial veins.Key words: Risk, Factors, Deep, Vein, Thrombosis, Duplex,Doppler

The role of microstructure and processing on the proton conducting properties of gadolinium-doped barium cerate

The influence of grain boundary conductivity and microstructure on the electrical properties of BaCe0.85Gd0.15O3-d have been examined. Grain sizes were varied by sintering at various temperatures. Impedance data were analyzed using the brick layer model, and some new consequences of this model are presented. The specific grain boundary conductivity exhibits an activation energy of ~0.7eV, and for similar processing routes, is independent of grain size. An isotope effect was observed, indicating that protons (or deuterons) are the mobile species. TEM investigations showed the intergranular regions to be free of any glassy phase that could account for the differences in bulk and grain boundary properties. Single crystal fibers, grown by a modified float zone process, were notably barium deficient, and exhibited a low conductivity, comparable to that of polycrystalline Ba0.96Ce0.85Gd0.15O3-δ