Morphology, structure, optical, and electrical properties of AgSbO₃

The morphology of defect pyrochlore-type, AgSbO₃ microparticle/nanoparticles obtained via solid state reaction evolve from irregular to Fullerene-like polyhedra before finally decomposing into metal-organic framework-5 like particles with increase in sintering temperature. The defect pyrochlore-type AgSbO₃ particles are slightly Ag deficient while the valence of the antimony ion is shown to be +5 giving rise to a probable stoichiometry of Ag₁ˍₓ SbVO₃ˍₓ/₂, with x∼0.01–0.04. A highly structured diffuse intensity distribution observed via electron diffraction is interpreted in terms of correlated displacements of one-dimensional (1D) silver ion chains along ⟨110⟩ directions. A redshifting in the absorption edges in UV-visible absorption spectra is observed for samples prepared at sintering temperatures higher than 1000 °C and attributed to the surface plasma resonance effect associated with small amounts of excess metallic Ag on the Ag₁ˍₓ SbVO₃ˍₓ/₂ particles. An electrical properties investigation of the silver antimonate samples via dielectric, conductivity, and electric modulus spectroscopy shows a prominent dielectric relaxation associated with grain boundaries. The silver ion conductivity is associated with correlated displacements of 1D silver ion chains along ⟨110⟩ directions.Z.G.Y., Y.L., and R.L.W. acknowledge financial support from the Australian Research Council ARC in the form of ARC Discovery Grants

A review of residual stress analysis using thermoelastic techniques

Thermoelastic Stress Analysis (TSA) is a full-field technique for experimental stress analysis that is based on infra-red thermography. The technique has proved to be extremely effective for studying elastic stress fields and is now well established. It is based on the measurement of the temperature change that occurs as a result of a stress change. As residual stress is essentially a mean stress it is accepted that the linear form of the TSA relationship cannot be used to evaluate residual stresses. However, there are situations where this linear relationship is not valid or departures in material properties due to manufacturing procedures have enabled evaluations of residual stresses. The purpose of this paper is to review the current status of using a TSA based approach for the evaluation of residual stresses and to provide some examples of where promising results have been obtained

Zirconia toughened SiC whisker reinforced alumina composites small business innovation research

The objective of this phase 1 project was to develop a ceramic composite with superior fracture toughness and high strength, based on combining two toughness inducing materials: zirconia for transformation toughening and SiC whiskers for reinforcement, in a controlled microstructure alumina matrix. The controlled matrix microstructure is obtained by controlling the nucleation frequency of the alumina gel with seeds (submicron alpha-alumina). The results demonstrate the technical feasibility of producing superior binary composites (Al2O3-ZrO2) and tertiary composites (Al2O3-ZrO2-SiC). Thirty-two composites were prepared, consolidated, and fracture toughness tested. Statistical analysis of the results showed that: (1) the SiC type is the key statistically significant factor for increased toughness; (2) sol-gel processing with a-alumina seed had a statistically significant effect on increasing toughness of the binary and tertiary composites compared to the corresponding mixed powder processing; and (3) ZrO2 content within the range investigated had a minor effect. Binary composites with an average critical fracture toughness of 6.6MPam sup 1/2, were obtained. Tertiary composites with critical fracture toughness in the range of 9.3 to 10.1 MPam sup 1/2 were obtained. Results indicate that these composites are superior to zirconia toughened alumina and SiC whisker reinforced alumina ceramic composites produced by conventional techniques with similar composition from published data

Mammalian models of extended healthy lifespan

Over the last two centuries, there has been a significant increase in average lifespan expectancy in the developed world. One unambiguous clinical implication of getting older is the risk of experiencing age-related diseases including various cancers, dementia, type-2 diabetes, cataracts and osteoporosis. Historically, the ageing process and its consequences were thought to be intractable. However, over the last two decades or so, a wealth of empirical data has been generated which demonstrates that longevity in model organisms can be extended through the manipulation of individual genes. In particular, many pathological conditions associated with the ageing process in model organisms, and importantly conserved from nematodes to humans, are attenuated in long-lived genetic mutants. For example, several long-lived genetic mouse models show attenuation in age-related cognitive decline, adiposity, cancer and glucose intolerance. Therefore, these long-lived mice enjoy a longer period without suffering the various sequelae of ageing. The greatest challenge in the biology of ageing is to now identify the mechanisms underlying increased healthy lifespan in these model organisms. Given that the elderly are making up an increasingly greater proportion of society, this focused approach in model organisms should help identify tractable interventions that can ultimately be translated to humans

Structurally frustrated polar nanoregions in BaTiO₃-based relaxor ferroelectric systems

This letter presents direct electron diffraction evidence that structurally frustrated one-dimensional polar nanoregions arising from anticorrelated displacements of Ti and nearest neighboring O ions are responsible for the relaxation behavior observed in dopedBaTiO₃relaxor ferroelectrics, rather than chemical short range ordering. The role of the dopant ions is not to directly induce polar nanoregions but rather to set up random local strain fields preventing homogeneous strain distortion, thereby suppressing transverse correlation from one chain dipole to the next and hence the development of long range ferroelectric order.Y.L., R.L.W., and B.N. acknowledge financial support from the Australian Research Council ARC in the form of an ARC Discovery Grant

Structurally frustrated polar nanoregions in BaTaO₂N and the relationship between its high dielectric permittivity and that of BaTiO₃

This letter presents direct evidence for the existence of the same inherently polar one-dimensional (1D), displacive disorder in BaTaO₂N as occurs in paraelectric BaTiO₃ as well as in doped BaTiO₃relaxor ferroelectric systems. The inherently polar, off-center and oppositely directed displacements of Ta and neighboring O∕N ions along give rise to 1D polar nanoregions (PNRs) and are responsible for the dielectric properties of BaTaO₂N. A bond valence sum analysis of the underlying crystal chemistry of BaTaO₂N shows clearly that O∕N ordering is not directly responsible for inducing the observed 1D PNRs.R.L.W. and Y.L. acknowledge the financial support from the Australian Research Council ARC in the form of an ARC Discovery Grant. P.M.W. and Y.I.K. acknowledge funding from the National Science Foundation through their support of the Centre for the Design of Materials CHE- 043567

Martian M2 peak behaviour in the dayside near-terminator ionosphere during ICMEs

The interplanetary coronal mass ejections (ICMEs) can pose significant impacts on the Martian ionosphere, resulting in plasma depletion, variability, and escape to space. However, the connections between the ICMEs and the associated responses of the dayside near-terminator Martian ionospheric M2 peak are not well understood. The present study primarily investigates the behaviour of the ionospheric peak density (Nm) and height (hm) during the passage of ICMEs using observations from the Radio Occultation Science Experiment (ROSE) aboard MAVEN spacecraft. We have selected 8 such ICMEs (during 2017-2022) at Mars from the existing catalogs and studied the ROSE electron density profiles during quiet and disturbed time (ICMEs) for identical solar zenith angle range. We observed the elevation of the M2 peak (hm ~4-16 km) during disturbed time (ICMEs) with a decrease in Nm (0.41-2.8 * 10^10 m-3) in comparison to the quiet time. The present study, for the first time, addressed the influence of ICMEs on the M2 peak parameters (Nm and hm). We have proposed that the development of large vertical pressure gradient and electron temperature enhancement are plausible causes for ionospheric variability. Therefore, the present study provides new insights to understand the peak plasma behaviour in the dayside near-terminator ionosphere during ICMEs

Educação ambiental e a experiência da Embrapa Florestas.

A educação ambiental tornou-se uma prática indispensável em todas as empresas e instituições públicas e privadas nas esferas municipal, estadual e federal. Este trabalho objetivou apresentar a experiência do Programa de Educação Ambiental da Embrapa Florestas (PREA), no período de 2001 a 2006. Durante seis anos de atividades, o PREA ministrou inúmeros cursos e palestras, conduziu grupos em trilhas ecológicas, participou de eventos, organizou encontros referentes a meio ambiente, realizou diagnósticos ambientais, estabeleceu parcerias de cooperação técnica com vários órgãos e empresas e publicou material didático sobre educação ambiental. Os resultados indicaram que a Embrapa Florestas, juntamente com seus parceiros, desenvolveu e aplicou métodos eficientes de educação ambiental e os transmitiu para um número significativo de pessoas.bitstream/CNPF-2009-09/41611/1/BPD29_CD.pd