Some properties of linear strain triangles and optimal finite element models

A detailed study of the linear strain triangle (LST), which is very applicable in plane stress finite element analysis, is presented. Based on analytical stiffnesses, it is shown that the LST stiffnesses are easily obtainable from the stiffnesses of the corresponding simple constant strain triangle (CST). The optimization of finite element models is related to the configuration of the elements, and this analysis is also based upon the LST element. A procedure for changing to an improved finite element model is presented which does not require re-analysis. Several examples are discussed.     

Evidence for sex transformation of germline cells in ovarian tumor mutants of Drosophila

Mutations at a few genetic loci in Drosophila cause ovarian tumors with hundreds of poorly differentiated germ cells. We examined several of these mutants to test the hypothesis that such ovarian tumors contain sex-transformed cells. By testing for expression of male germline traits, we determined that partial germline sex transformation occurs in otu, snf, Sxlfs, and bam ovarian tumors. Thus these genes are likely to be required for proper establishment of germline sexual identity.     

Buckling load optimization for 2D continuum models,with alternative formulation for buckling load estimation

Buckling load estimation of continua modeled by finite element (FE) should be based on non-linear equilibrium. When such equilibrium is obtained by incremental solutions and when sensitivity analysis as well as iterative redesigns are included, the computational demands are large especially due to optimization. Therefore, examples presented in the literature relate to few design variables and/or few degrees of freedom. In the present paper a non-incremental analysis is suggested, and a simple sensitivity analysis as well as recursive redesign is proposed. The implicit geometrical non-linear analysis, based on Green-Lagrange strains, apply the secant stiffness matrix as well as the tangent stiffness matrix, both determined for the equilibrium corresponding to a given reference load, obtained by the Newton-Raphson method. For the formulated eigenvalue problem, which solution gives the estimated buckling load, the tangent stiffness matrix is of major importance. In contrast to formulations based on incremental solutions, the tangent stiffness matrix is here divided into two matrices, the stress stiffness matrix that is linear depending on stresses and the remaining part of the tangent stiffness matrix. Examples verify the effectiveness of the proposed procedure.     

Ellipsometric response of titanium electrodes in sulphate acid solutions under different potential perturbations

Optical characteristics and thickness of thin oxide films potentiodynamically formed on a titanium electrode in acidic sulphate solutions at pH 4.0 were investigated by dynamic and steady ellipsometric measurements. The dynamic ellipsometric response of an electrode polarized up to 1.0 V vs rhe depends on the charge involved in the massive oxide electroformation. Cycling the electrode at a constant potential sweep rate between −0.65 and 0 V produces a decrease on film thickness and the electrode reactivation. This electrode treatment becomes less effective as oxide electroformation is repeated several times. Experiments performed by holding the potential at the negative limit were not so effective in reducing film thickness and an appreciable change on optical constants was found. Results were interpreted as hydrogenated species formation within the oxide film.     

X-ray absorption near-edge structure analysis of the chemical environment of zinc in the tribological film formed by zinc dialkyl dithiophosphate decomposition on steel

Calculation of X-ray absorption near-edge structure (XANES) has been used to investigate the chemical nature of zinc in thermal films formed on the surfaces of steel coupons by the additive zinc dialkyl dithiophosphate (ZDDP) in oil solution. Carbon K, oxygen K, and zinc L edge XANES spectra were used to characterize the thermal films and a model film formed by addition of cumene hydroperoxide (CHP) to the ZDDP. Thermal films formed by heating at up to 100 °C for 5 h showed little change from unreacted ZDDP. At 160 °C for 5 h, the ZDDP underwent thermal solution decomposition with similarities to the oxidation induced by CHP. The Zn L edge XANES spectra were compared to calculated spectra of the model surface species ZnO and ZnS in the wurtzite structure and ZnS in the zinc blende structure. Agreement between experiment and simulation is found for the 160 °C thermal film with a roughly two monolayer film of ZnO and for oxidation by CHP with a three to four monolayer film of ZnS.     

Rue and Brazilian peppertree essential oils inhibit the germination and initial development of the invasive plant lovegrass

ABSTRACT

Lovegrass (Eragrostis plana) is the most important invasive plant in pastures of southern Brazil. The research evaluated the potential of Ruta graveolens (rue) and Schinus terebinthifolius (Brazilian peppertree) essential oils (EOs) to inhibit germination and initial development of lovegrass. The in vitro treatments tested were control (distilled water), alcohol control, 0.001, 0.005, 0.01, 0.05 and 0.1% (v/v) of both EOs. Higher concentrations of these EOs were applied to germinated plants under greenhouse conditions. The EOs of both species were effective in reducing lovegrass germination, with emphasis on rue. Height and shoot dry mass, at greenhouse conditions, were significantly reduced by both EOs, especially when applied at a concentration of 1%. The results point to the potential of rue and Brazilian peppertree EOs for the formulation of natural herbicides.     

Behavioral and neurophysiological evidence for altered processing of anxiety-related words in panic disorder.

Body-related and nonsomatic words were presented tachistoscopically to 15 panic patients and 15 healthy controls at each participant's threshold for correctly identifying 50% of neutral words. Behavioral (proportion of words correctly recognized) and electrocortical (event-related brain potentials [ERPs]) measures were registered. Panic patients recognized more body-related than nonsomatic words, and body-related as compared with nonsomatic words elicited, in these patients, significantly larger P300 amplitudes and enhanced positive slow waves (600 to 800 ms after stimulus presentation) . In healthy controls, the number of correct recognized words and the ERPs were not differentially affected by the 2 word types. These results are grossly consistent with cognitive models of panic disorders, assuming that certain bodily sensations are perceived and processed in an affective manner that differentiates panic patients from healthy controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)