Local structure and vibrational dynamics of proton conducting Ba2In2O5(H2O)x

We study the local structure and vibrational dynamics of the brownmillerite-based proton conductors Ba2In2O5(H2O)x, with x = 0.30, 0.76, and 0.92, using infrared spectroscopy, inelastic neutron scattering and ab initio molecular dynamics simulations. Ba2In2O5(H2O)x is found to exhibit two main types of proton sites, H(1) and H(2). The H(1) site is characterised by the coexistence of two intra-octahedral hydrogen-bond geometries, whereas the H(2) site is characterised by inter-octahedral hydrogen bonding. While the strength of the hydrogen bonding is similar for the majority of protons in the two proton sites, ≈10% of the H(2) protons forms unusually strong hydrogen bonds due to local proton environments characterised by an unusually short oxygen-oxygen separation distance of ≈2.6 \uc5. These local proton environments are manifested as two O-H stretch bands in the infrared absorbance spectra, at 255 and 290 meV, respectively. These O-H stretch bands are as well observed in the related class of In-doped perovskite-type oxides, BaInyZr1-yO3-y/2 (0.25 ≤ y ≤ 0.75), suggesting that these perovskites may display brownmillerite-like distortions on a local length scale. In effect, these results point towards a clustering of the In atoms in these perovskite materials. Further, the infrared spectra of Ba2In2O5(H2O)x show a minor evolution as a function of x, because the protons tend to segregate into oxygen-rich hydrogen-rich domains upon dehydration. This points towards a highly anisotropic proton conduction mechanism in partially hydrated phases. This insight motivates efforts to identify ways to avoid phase separation, perhaps by suitable cation substitutions, as a route to accommodate high proton conductivity

Electrochemical Performance of SrWO4 Electrolyte for SOFC

Scheelite structured SrWO4 material was synthesized by the solid-state sintering method and studied with respect to phase stability and ionic conductivity under condition of technological relevance for SOFC applications. The resulting compound was crystallized in the single phase of tetragonal scheelite structure with the space group of I41/a. Room temperature X-ray diffraction and subsequent Rietveld analysis confirms its symmetry, space group and structural parameters. Analysis by SEM illustrated a highly dense structure. SrWO4 sample shows lower conductivity compared to the traditional BCZY perovskite structured materials. SrWO4 sample exhibited an ionic conductivity of 1.93 × 10−6 S cm-¹ at 1000℃ in dry Ar condition. Since this scheelite type compound demonstrated significant conductivity and a dense microstructure, it could serve in SOFC as a mixed ion-conducting electrolyte

Dementia, Islamic indication and scientific evidence

Background: The increasing prevalence of dementia has dramatic effects on lives of millions of people across the regions and on public health costs. This is a commonly elderly health health problem as indicated in the Holy Qur’an. Although there is no cure yet but much can be done to improve the quality of life of people with dementia. Methods: An extensive review of the literature, including the Holy Qur’an, in several pertinent areas of inquiry that may deleniate the prevalence, potential risk factors related to dementia was under taken. Results: The overall prevalence of dementia for males and females doubled for every five years increase in age after the age of 65. It is largely a disease of older people. Results highlight a number risk factors associated with dementia. Inter alia, these include physical activities, education, occupation, stress, cholesterol and APOE gene. A number risk factors associated with dementia are modifiable. Conclusion: The prevalence of dementia rises as the people ages. The modifiable risk factors may have potential as strategies useful in preventing or delaying dementia among elderly subjects

A New Solid-State Proton Conductor: The Salt Hydrate Based on Imidazolium and 12-Tungstophosphate

We report the structure and charge transport properties of a novel solid-state proton conductor obtained by acid-base chemistry via proton transfer from 12-tungstophosphoric acid to imidazole. The resulting material (henceforth named Imid3WP) is a solid salt hydrate that, at room temperature, includes four water molecules per structural unit. To our knowledge, this is the first attempt to tune the properties of a heteropolyacid-based solid-state proton conductor by means of a mixture of water and imidazole, interpolating between water-based and ionic liquid-based proton conductors of high thermal and electrochemical stability. The proton conductivity of Imid3WP\ub74H2O measured at truly anhydrous conditions reads 0.8 7 10-6 S cm-1 at 322 K, which is higher than the conductivity reported for any other related salt hydrate, despite the lower hydration. In the pseudoanhydrous state, that is, for Imid3WP\ub72H2O, the proton conductivity is still remarkable and, judging from the low activation energy (Ea = 0.26 eV), attributed to structural diffusion of protons. From complementary X-ray diffraction data, vibrational spectroscopy, and solid-state NMR experiments, the local structure of this salt hydrate was resolved, with imidazolium cations preferably orienting flat on the surface of the tungstophosphate anions, thus achieving a densely packed solid material, and water molecules of hydration that establish extremely strong hydrogen bonds. Computational results confirm these structural details and also evidence that the path of lowest energy for the proton transfer involves primarily imidazole and water molecules, while the proximate Keggin anion contributes with reducing the energy barrier for this particular pathway

Insight into the dehydration behaviour of scandium-substituted barium titanate perovskites via simultaneous in situ neutron powder thermodiffractometry and thermogravimetric analysis

Hydration-dehydration cycles are critical to the mechanical performance of ceramic proton conductors. The development of in situ methods is desirable in order to study their structural response under conditions that mimic the operating ones. Neutron powder diffraction studies combined with simultaneous thermogravimetric analysis were performed on the hydrated forms of two members of the oxygen deficient perovskite BaTi1−xScxO3−δseries, with x = 0.5 and x = 0.7. Rietveld analyses agreed with in situ gravimetric data, allowing correlation of occupancy factors of the oxygen site to hydration levels and other structural data. Dehydration is an activated process that impacts on structural parameters and the level of Sc substitution was found to control the structural response during in situ dehydration, with higher Sc content leading to significantly greater volume contraction. This was rationalised by the chemical expansion due to hydration of oxygen vacancies within the x = 0.5 sample being anomalously small. Furthermore, the behaviour of the x = 0.5 system revealed an unexpected cell expansion during the early stages of dehydration, suggesting the hydration level may influence the thermal expansion coefficient (TEC)

In-situ activated hydrogen evolution by molybdate addition to neutral and alkaline electrolytes

Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron

Enhancement of proton conductivity through Yb and Zn doping in BaCe0.5Zr0.35Y0.15O3-δ electrolyte for IT-SOFCs

The new compositions of BaCe0.5Zr0.3Y0.15-xYbxZn0.05O3-δ perovskite electrolytes (x = 0.1 and 0.15) were prepared by solid state synthesis and final sintering at 1500 °C. The obtained ceramics were investigated using X-ray diffraction, scanning electron microscopy, thermo-gravimetric analysis and impedance spectroscopy. The refinement of XRD data confirmed cubic crystal structure with Pm3m space group for both samples. SEM morphology showed larger and compacted grains which enables obtaining of high density and high protonic conductivity. The relative densities of the samples were about 99% of the theoretical density after sintering at 1500 °C. The protonic conductivities at 650 °C were 2.8×10-4 S/cm and 4.2×10-3 S/cm for x = 0.1 and 0.15, respectively. The obtained results showed that higher Yb-content increases the ionic conductivity and both of these perovskites are promising electrolyte for intermediate temperature solid oxide fuel cells to get high efficiency, long-term stability and relatively low cost energy system

Dementia : prevalence and risk factors

The increasing prevalence of dementia already has dramatic effects on lives of millions of people across the regions and on public health costs. There is no cure yet but much can be done to improve the quality of life of people with dementia and the families who care for them. An extensive review of the literature in several pertinent areas of inquiry that may determine and delineate the prevalence, potential risk factors related to dementia was undertaken. The overall prevalence for males and females doubled for every five years increase in age after the age of 65. It is largely a disease of older people, but 2% of those affected were under 65 years of age. Results highlight a number of risk factors associated with dementia. Inter alia, these include physical activities, education, occupation, stress, cholesterol and APOE gene. Dementia is increased in certain population and the trend is on the rise. A number of risk factors associated with dementia are modifiable and may have potential as strategies useful in preventing or delaying dementia among elderly subjects. Further research is needed to determine the validity and strength of associations of risk factors of dementia including ascertainment of its causality

Antimicrobial use and factors influencing prescribing in medical wards of a tertiary care hospital in Malaysia

Abstract: To ascertain the pattern of antimicrobial use and to analyze the selected core drug use indicators – prescribing indicators – a prospective study was conducted in 2008 in medical wards of a tertiary care hospital in Malaysia. Every patient in the medical wards of the selected hospital who was being treated with antimicrobial(s) during the data collection period was considered a potential study subject for this study. The treatment charts of 209 admitted patients were reviewed. Pneumonia was the leading diseases among them (26.3%). The most commonly used antimicrobials were amoxicillin with clavulanate (augmentin), erythromycin, cefuroxime, ceftriaxone and ampicillin sodium with sulbactam sodium (unasyn). The level of generic prescribing of antimicrobials was just above the half of all prescribed courses (54.3%) and the intravenous route was the preferred method of administration (57.3%). The mean number antimicrobials received by the studied patients were 1.8 (± 0.9). The majority of them (53.6%) received two or more antimicrobials for their treatments. The evident of high percentages of patients received antimicrobial treatment in combinations reflected the potential of higher proportion of inappropriate treatment of different diseases and suggested the ample scope for intervention to improve antimicrobial use in the hospital