Enhanced Mechanical and Electromechanical Properties of Compositionally Complex Zirconia Zr1-x(Gd1/5Pr1/5Nd1/5Sm1/5Y1/5)xO2-δ Ceramics.

Compositionally complex oxides (CCOs) or high-entropy oxides (HEOs) are new multielement oxides with unexplored physical and functional properties. In this work, we report fluorite structure-derived compositionally complex zirconia with composition Zr1-x(Gd1/5Pr1/5Nd1/5Sm1/5Y1/5)xO2-δ (x = 0.1 and 0.2) synthesized in solid-state reaction route and sintered via hot pressing at 1350 °C. We explore the evolution of these oxides' structural, microstructural, mechanical, electrical, and electromechanical properties regarding phase separation and sintering mechanisms. Highly dense ceramics are achieved by bimodal mass diffusion, composing nanometric tetragonal and micrometric cubic grains microstructure. The material exhibits an anomalously large electrostriction response exceeding the M33 value of 10-17 m2/V2 at room temperature and viscoelastic properties of primary creep in nanoindentation measurement under fast loading. These findings are strikingly similar to those reported for doped ceria and bismuth oxide derivates, highlighting the presence of a large concentration of point defects linked to structural distortion and anelastic behavior, which are characteristics of nonclassical ionic electrostrictors.

Changing institutional landscape and transportation development in Dhaka, Bangladesh.

Cities in the global south, constrained by limited resources, face challenges in delivering efficient transportation infrastructure and services to support their rapidly growing urban populations. Dhaka, serves as an example, as it grapples with the increasing demand driven by population growth, exacerbated by factors like land and resource scarcity, as well as intricate geopolitical dynamics. Despite the construction of a metro rail and other similar mass transit options, Dhaka continues to face difficulties in meeting the increasing transportation demand, posing a persistent challenge. Multiple institutions, including a coordination authority, are working to provide improved transportation services by implementing diverse strategic approaches focusing on infrastructure development, and formulating policies aimed at facilitating better mobility and accessibility. Over the past fifty years, the institutional arrangement and roles within the transportation system have changed. This study examines the institutional arrangements and how they have evolved, along with reviewing transportation development policies during this period. The findings indicate the involvement of multiple organizations in the city's transportation system performing distinct activities-- administrative, coordinating, legislative, regulatory, construction and management, and law enforcement. These authorities often encounter challenges fulfilling their responsibilities stemming from differences in vision, organizational structure, jurisdiction and most notably, lack of coordinatoon, resulting in ineffective infrastructure development and duplicated activities. To improve the transportation system, this study recommends better equipping the existing coordinating authority and expanding its jurisdiction to include other institutions. This approach aims to enhance coordination and address the challenges faced by Dhaka's transportation system, ultimately facilitating improved mobility and accessibility for the city's growing population.

Electromechanically active pair dynamics in a Gd-doped ceria single crystal.

Oxygen-defective ceria, e.g. Gd-doped ceria, shows giant electromechanical properties related to a complex local rearrangement of its lattice. Although they are not entirely identified, the electroactive mechanisms arise from cation and oxygen vacancy (VO) pairs (i.e. Ce-VO), and the local structural elastic distortion in their surroundings. Here, we study the geometry and behaviour of Ce-VO pairs in a grain boundary-free bulk Ce0.9Gd0.1O1.95 single crystal under an AC electric field of ca. 11 kV cm-1. The analysis was carried out through X-ray absorption spectroscopy (XAS) techniques at the Ce L-III edge. Using Density Functional Theory (DFT) calculations, we investigated the effects of the strain on density of states and orbitals at the valence band edge. Our research indicates that electrostriction increases at low temperatures. The electromechanical strain has a structural nature and can rise by one order of magnitude, i.e., from 5 × 10-4 at room temperature to 5 × 10-3 at -193 °C, due to an increase in the population of the electrically active pairs. At a constant VO concentration, the material can thus configure heterogeneous pairs and elastic nanodomains that are either mechanically responsive or not.

Gigantic electro-chemo-mechanical properties of nanostructured praseodymium doped ceria.

Some oxygen defective fluorites are non-Newnham electrostrictors, i.e., the electromechanical response does not depend on their dielectric properties. Here, we show gigantic electrostriction in nanocrystalline 25 mol% praseodymium doped ceria (PCO) bulk ceramics. The material was fabricated with a field-assisted spark plasma sintering (SPS) process from high-purity nanoscale PCO powders (<20 nm). The SPS process consolidates the powders into a single-phase, highly dense material with a homogeneous microstructure and large grain boundary extension. Various thermally and chemically stable ionic defects are incorporated into the nanostructure, leading to superior electrical conductivity. The material shows an electrostriction strain coefficient (M33) of ∼10-16 m2 V-2 at frequencies below 100 Hz at room temperature. Such performance is comparable and even superior to Newnham's electrostrictors, such as ferroelectric ceramics and polymeric actuators. Comparative analysis with polycrystals suggests that nanostructured PCO possesses electromechanically active nanodomains of Pr3+-VO pairs. Such results are unexpected and open novel insights on non-Newnham electrostrictors.

Early Life UV and Risk of Basal and Squamous Cell Carcinoma in New South Wales, Australia.

Sun exposure is the main cause of squamous (SCC) and basal cell carcinoma (BCC) although pattern and amount differ by cancer type, and sun sensitivity is the major host risk factor. Our study investigated risk factors and residential ambient UV in a population-based sample of Australian 45 and Up Study participants: 916 BCC cases, 433 SCC cases, 1224 controls. Unconditional logistic regression models adjusting for key covariates demonstrated 60% increased BCC risk and two-fold increased SCC risk with sun sensitivity, and three- and four-fold increased risk, respectively, with solar keratoses. BCC but not SCC risk increased with higher early-life residential UV in all participants (odds ratio (OR) = 1.54; 95% CI 1.22-1.96 for intermediate; OR = 1.31; 95% CI 1.03-1.68 for high UV at birthplace) and similarly in Australian-born participants (P-values < 0.05). Risk of SCC but not BCC increased with long-term cumulative sun exposure assessed by self-reported outdoor work (OR 1.74, 95% CI 1.21-2.49). In conclusion, sun sensitivity is important for both cancers, early-life UV but not cumulative UV appears to increase BCC risk, the former an apparently novel finding, and SCC risk appears only to be related to long-term cumulative sun exposure.