In situ stress analysis of multilayer environmental barrier coatings

The biaxial stress and thermal expansion of multilayer doped-aluminosilicate environmental barrier coatings were measured in situ during cooling using microfocused high-energy X-rays in transmission. Coating stresses during cooling from 1000 °C were measured for as-sprayed and thermally cycled samples. In the as-sprayed state, tensile stresses as high as 75 MPa were measured in the doped-aluminosilicate topcoat at 375 °C, after which a drop in the stress occurred accompanied by through-thickness cracking of the two outermost layers. After thermally cycling the samples, the stress in the topcoat was reduced to approximately 50 MPa, and there was no drop in stress upon cooling. This stress reduction was attributed to a crystallographic phase transformation of the topcoat and the accompanying change in thermal expansion coefficient. The addition of a doped aluminosilicate to the mullite layer did not lower the stress in the topcoat, but may offer increased durability due to an increased compressive stress

Lifetime mental disorders and suicidal behaviour in South Africa

Background: There is relatively little data on the relationship between lifetime mental disorders and suicidal behaviour in low and middle income countries. This study examines the relationship between lifetime mental disorders, and subsequent suicide ideation, plans, and suicide attempts in South Africa. Method: A national survey of 4185 South African adults was conducted using the World Health Organization Composite International Diagnostic Interview (CIDI) to generate psychiatric diagnoses and suicidal behaviour. Bivariate, multivariate and discrete-time survival analyses were employed to investigate the associations between mental disorders and subsequent suicide ideation, plans, and attempts. Results: Sixty-one percent of people who seriously considered killing themselves at some point in their lifetime reported having a prior DSM-IV disorder. Mental disorders predict the onset of suicidal ideation, but have weaker effects in predicting suicide plans or attempts. After controlling for comorbid mental disorders, PTSD was the strongest predictor of suicidal ideation and attempts. There is a relationship between number of mental disorders and suicidal behaviour, with comorbidity having significantly sub-additive effects. Conclusion: Consistent with data from the developed world, mental disorders are strong predictors of suicidal behaviour, and these associations are more often explained by the prediction of ideation, rather than the prediction of attempts amongst ideators. This suggests some universality of the relevant mechanisms underlying the genesis of suicidal thoughts, and the progression to suicide attempts

Communication Behaviors of County Extension Directors Post-Hurricane

In disaster crises, communication among stakeholders and response organizations are important. In Florida, the role of the County Extension Director (CED) is threefold – educational programming, leadership of a county extension program, and county office administrative responsibilities. However, their primary role in disaster emergencies is to facilitate collaborations with state and federal partners. During Hurricane Irma in 2017, UF/IFAS CEDs assisted in response efforts. However, communication efforts can become challenging in such chaotic and stressful situations. This research explored communication challenges among CEDs, clients, and statewide partners in hurricane events. Insights into the communication role of CEDs could enhance UF/IFAS Extension’s communication plan for effective information dissemination post-disaster. The Uses and Gratifications Theory guided this qualitative study. Interviews occurred with nine CEDs from various counties across Florida. Results showed CEDs used numerous communication channels to connect with clients, staff, and statewide partners, mainly for the purposes of information dissemination. The main reasons for selecting these communication channels depended on its accessibility, reliability, and whether it was a usual form of communication. Some participants were unaware of available resources which resulted in duplicate efforts. Thus, they required additional information from statewide partners. Some participants also had difficulty connecting clients with people who could assist them with insurance information and aid. As such, this study recommended a central communication system to avoid redundant efforts, strengthening relationships with disaster agencies to promote information-sharing and avoid miscommunication, and developing a list of resources and contacts for CEDs’ first engagement in disaster response

Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.

Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction) and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years

Moduli Stacks of Vector Bundles and Frobenius Morphisms

We describe the action of the different Frobenius morphisms on the cohomology ring of the moduli stack of algebraic vector bundles of fixed rank and determinant on an algebraic curve over a finite field in characteristic p and analyse special situations like vector bundles on the projective line and relations with infinite Grassmannians.Comment: 19 page

Analysis of strain and stacking faults in single nanowires using Bragg coherent diffraction imaging

Coherent diffraction imaging (CDI) on Bragg reflections is a promising technique for the study of three-dimensional (3D) composition and strain fields in nanostructures, which can be recovered directly from the coherent diffraction data recorded on single objects. In this article we report results obtained for single homogeneous and heterogeneous nanowires with a diameter smaller than 100 nm, for which we used CDI to retrieve information about deformation and faults existing in these wires. The article also discusses the influence of stacking faults, which can create artefacts during the reconstruction of the nanowire shape and deformation.Comment: 18 pages, 6 figures Submitted to New Journal of Physic

Tilt Texture Domains on a Membrane and Chirality induced Budding

We study the equilibrium conformations of a lipid domain on a planar fluid membrane where the domain is decorated by a vector field representing the tilt of the stiff fatty acid chains of the lipid molecules, while the surrounding membrane is fluid and structureless. The inclusion of chirality in the bulk of the domain induces a novel budding of the membrane, which preempts the budding induced by a decrease in interfacial tension.Comment: 5 pages, 3 figure

Projected shell model study of odd-odd f-p-g shell proton-rich nuclei

A systematic study of 2-quasiparticle bands of the proton-rich odd-odd nuclei in the mass A ~ 70-80 region is performed using the projected shell model approach. The study includes Br-, Rb-, and Y-isotopes with N = Z+2, and Z+4. We describe the energy spectra and electromagnetic transition strengths in terms of the configuration mixing of the angular-momentum projected multi-quasiparticle states. Signature splitting and signature inversion in the rotational bands are discussed and are shown to be well described. A preliminary study of the odd-odd N = Z nucleus, 74Rb using the concept of spontaneous symmetry breaking is also presented.Comment: 14 pages, 7 figures, final version accepted by Phys. Rev.