Effect of Constituent Core-sizes on Microstructure and Dielectric Properties of BaTiO<Subscript>3</Subscript>@(0.6Ba-TiO<Subscript>3</Subscript>-0.4BiAlO<Subscript>3</Subscript>) Core-Shell Material

The fundamental characteristics of varied initial core-sizes of BaTiO₃(BT) and its influential role on the morphology and dielectric properties of BaTiO₃@0.6BaTiO₃-0.4BiAlO₃(BT@0.6BT-0.4BA) ceramic samples were studied. Alkoxide sol-precipitation method was adopted as revised chemical route to synthesize the constituent “core” BT powders in a dispersed phase, whereas the distinctive initial nano-sized particles were affected by the pre-calcination temperatures (600-900 °C).The microstructure of the uncoated BT ceramics revealed an exaggerated grain growth with an optimized dielectric constant (ε_max >9 000) whilst the coated ceramics behaved otherwise (grain growth inhibited) when sintered at an elevated temperature. Regardless of the previously studied solubility limit (about 0.1%) of BT-BA samples, BT@0.6BT-0.4BA maintained a maximum dielectric constant (ε_max) ranging from 1 592 to 1 708 and tan δ less than 2% under a unit mole ratio at room temperature. In view of all these analyses, the initial nanometer sizes of the as-prepared BT-core powders combined with the increase effect of cation substitutions of Bi³⁺ and Al³⁺ in the shell content, induced the diffuse transition phase of BT@0.6BT-0.4BA composition.     

Patterning a π-conjugated polyelectrolyte through sequential polymerization of a bifunctional ionic liquid monomer

An electronically conductive polyelectrolyte is prepared by the sequential polymerization of a bifunctional imidazolium-based ionic liquid (IL) monomer, composed of a thienyl and vinyl containing cation paired with a tetrafluoroborate anion. In the first step, potentiodynamic electropolymerization of the thienyl moiety forms a cationic polyalkylthiophene that is soluble in select organic solvents. Cyclic voltammetry (CV) was used to determine the polymer p-doping potential (0.31 V) and the bipolaronic state (1.49 V). The polymer exhibits electrochromism, converting from red in the neutral state (λ_max = 443 nm) to dark blue in the polaronic state (λ_max = 819 nm). The solution-processable polymer can be cast into a film, masked and patterned by UV-initiated free radical polymerization of the vinyl moiety. Small-angle X-ray scattering (SAXS) revealed that the insoluble crosslinked polyalkylthiophene–polyvinylimidazolium adopts a lamellar structure with a lattice spacing of 3.3 nm. Four-probe d.c. conductivity measurements determined the de-doped electrical conductivity was 1.0 × 10⁻² S/cm. The results underscore the importance of the anion in controlling the polymerization of IL monomers.     

HIV risk reduction for incarcerated women: A comparison of brief interventions based on two theoretical models.

Although female inmates are seropositive at rates that exceed those of male inmates, few studies have evaluated HIV risk reduction interventions for incarcerated women. This demonstration project compared an intervention based on social cognitive theory against a comparison condition based on the theory of gender and power. Incarcerated women (N?=?90) were assessed at baseline, postintervention, and again 6 months later. Both interventions produced increased self efficacy, self-esteem, Attitudes Toward Prevention Scale scores, AIDS knowledge, communication skill, and condom application skills that maintained through the 6-month follow-up period. Participants in the intervention based on social cognitive theory showed greater improvement in condom application skills, and women in the program based on the theory of gender and power evidenced greater commitment to change. The results suggests brief interventions in prison settings are feasible and beneficial. However, it is not yet known whether the changes will generalize into the natural environment after the women' s release into the community. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of processing methods on the dielectric properties of BaTi1-xGdxO3-x/2 - Based materials

In this study, the intermediate rare-earth oxide Gd₂O₃ (Gd) was substituted in different amounts (x = 0.2–2 mol%) for the formulation of BaTi_1-xGd_xO_3-x/2 (BTG_x) dielectric materials. The effect of B-site substitution was confirmed by the additional Raman active A_1g octahedral peak at ~835cm^-1 strengthened at x ≥ 0.4 mol%. Additionally, properties of 0.9BTG_0.007-0.1BA dielectric ceramics were analysed based on the influence of various processing methods as a function of sintering temperature. The focal samples were labelled Method-A (direct-mix) and Method-B (indirect-mix). As the sintering temperature (1075–1200 °C) increased, the 1 kHz response of the ε–T curves of Method-A samples transformed from a single peak to broad-narrow double peaks of high dielectric loss tangent (tan δ). Nonetheless, samples of Method-B possessed a clearly defined transmission electron microscopy (TEM) core-shell structure, flattened double-peak ε-T curves, optimised dielectric properties (ε = ~1563–1851 and tan δ < 1.5% at room temperature), and a wide-ranging temperature behaviour that meets the X8R dielectric standards (ΔC/C_25°C < ±15%). The maximum dielectric breakdown strength of Method-B samples reached ~131 kVcm, while the energy storage density was ~0.726 J/cm³ at a maximum efficiency of ~80% at 1100 °C. Thus, exhibiting good potentials for balancing temperature stability with energy storage applications.     

The role of the Yala swamp lakes in the conservation of Lake Victoria region haplochromine cichlids: Evidence from genetic and trophic ecology studies

Lake Kanyaboli, an isolated satellite lake of Lake Victoria, has been suggested as a potential refugium for haplochromine cichlids that have gone extinct in the main basin of Lake Victoria. Mitochondrial DNA (mtDNA) molecular markers, as well as feeding ecology studies, were employed in this study to re‐evaluate the evolutionary and ecological significance of six common Lake Kanyaboli haplochromines. The mtDNA marker revealed high genetic variability within four of the six haplochromine cichlids. Five haplotypes were discerned in Astatoreochromis alluaudi (n = 27), seven in Lipochromis maxillaris (n = 29), five in Astatotilapia nubila (n = 12) and 11 in the endangered Xystichromis phytophagus (n = 205). A haplotype genealogy suggests that Lake Kanyaboli harbours mtDNA haplotypes that could have been lost or not sampled in Lake Victoria, or could have arisen in situ. Lipochromis maxillaris appears to have undergone a recent demographic expansion. The pairwise F_STs indicated that only the comparison between X. phytophagus and A. nubila led to a non‐significant F_ST value. All other comparisons were significant at the 0.01 level, indicating the genetic distinctiveness of the haplochromines in the satellite lake. This could suggest that the lake harbours ‘pure’ relict populations of the haplochromines and therefore that Lake Kanyaboli can be considered a ‘genetic reservoir’. Gut content analysis of the six haplochromine species revealed that eight different food items were consumed. No single species fed exclusively on a single food item, but certain food items contributed higher proportions of the fish diet for each fish species. Resource partitioning therefore could be discerned within this haplochromine community. Thus, Lake Kanyaboli and similar satellite lakes provide an opportunity for conservation of both genetic and trophic diversity threatened by introduction of exotics in the Lake Victoria basin. Lake Kanyaboli should be recognized and conserved as important evolutionary significant units for Lake Victoria region haplochromine species.     

Electropolymerization of a Bifunctional Ionic Liquid Monomer Yields an Electroactive Liquid‐Crystalline Polymer

The preparation and polymerization of a bifunctional imidazolium‐based ionic liquid (IL) monomer that incorporates both a vinyl group and a thiophene moiety is reported. Potentiodynamic electropolymerization of the monomer produces an optically birefringent polymer film that strongly adheres to the electrode surface. Fourier transform IR spectroscopy shows that polymerization occurs through both the vinyl and thienyl groups. Cylic voltammetry (CV) is used to determine the polymer oxidation potential (1.66 V) and electrochemical bandgap, E_g, of 2.45 eV. The polymer exhibits electrochromism, converting from yellow in the neutral form (λ_max = 380 nm) to blue in the polaronic state at 0.6 V (λ_max = 672 nm) and to blue‐grey in the bipolaronic state at 1.2 V (λ_max > 800 nm). Topographic atomic force microscopy (AFM) images reveal isolated (separated) fibrils. Grazing‐incidence small‐angle X‐ray scattering (GISAXS) studies indicate a lamellar structure with a lattice spacing of 3.2 nm. Wide‐angle X‐ray diffraction (WAXD) studies further suggest that the polymerized thiophene sheets are oriented perpendicular to the polymerized vinylimidazolium. The electrical conductivity, as determined by four‐probe dc conductivity measurements was found to be 0.53 S cm^?1 in the neutral form and 2.36 S cm^?1 in the iodine‐doped state, values higher than typically observed for polyalkylthiophenes. The structural ordering is believed to contribute to the observed enhancement of the electrical conductivity.     

A cross-sectional observational study of helmet use among motorcyclists in Wa,Ghana

Motorcyclists’ injuries and fatalities are a major public health concern in many developing countries including Ghana. This study therefore aimed to investigate the prevalence of helmet use among motorcyclists in Wa, Ghana. The method used involved a cross-sectional roadside observation at 12 randomly selected sites within and outside the CBD of Wa. A total of 14,467 motorcyclists made up of 11,360 riders and 3107 pillion riders were observed during the study period. Most observed riders (86.5%) and pillion riders (61.7%) were males. The overall prevalence of helmet use among the observed motorcyclists was 36.9% (95% CI: 36.1–37.7). Helmet use for riders was 45.8% (95% CI: 44.8–46.7) whilst that for pillion riders was 3.7% (95 CI: 3.0–4.4). Based on logistic regression analysis, higher helmet wearing rates were found to be significantly associated with female gender, weekdays, morning periods and at locations within the CBD. Riders at locations outside the CBD were about 7 times less likely to wear a helmet than riders within the CBD (48.9% compared to 42.3%; χ²₍₁₎ = 49.526; p < 0.001). The study concluded that despite the existence of a national helmet legislation that mandates the use of helmets by both riders and pillion riders on all roads in Ghana, helmet use is generally low in Wa. This suggests that all stakeholders in road safety should jointly intensify education on helmet use and pursue rigorous enforcement on all road types especially at locations outside the CBD to improve helmet use in Wa.