Microstructure and wear behavior of spark plasma sintering sintered Al2O3/WC-based composite

Various alumina/tungsten carbide based nanocomposites have been fabricated by spark plasma sintering and their wear properties have been investigated by performing ball-on-disk type wear test at room temperature under ambient environment. Our results reveal that the main facture behavior of the Al2O3/tungsten carbide composites sliding against Al2O3 balls is the plastic deformation. Crack formation and grain pull-out in the wear processes are responsible for lowering the wear rate. The Vickers hardness and toughness values are directly related to wear behavior of the composites that grounds Al2O3/WC to show lower wear rate on smoothly worn surface. (C) 2015 Elsevier Ltd. All rights reserve

Análise dos determinantes do endividamento das empresas de capital aberto do agronegócio brasileiro

Estudos sobre a estrutura de capital e a identificação de seus determinantes são temas relevantes nas pesquisas envolvendo a gestão financeira das empresas. Neste aspecto, o presente estudo teve como objetivo avaliar os determinantes da alavancagem das empresas do agronegócio brasileiro conforme o modelo de Rajan e Zingales (1995). Na definição da amostra, foram selecionadas 26 empresas que estavam enquadradas em alguma das três subdivisões do agronegócio brasileiro: a) o setor de produção agropecuária; b) setor fornecedor de insumos e fatores de produção e c) setor de processamento e distribuição, com base em classificação da CNA (Confederação da Agricultura e Pecuária do Brasil). O estudo foi feito com base no banco de dados da Economática®, tendo sido utilizado o modelo de regressão com dados em painel. Os resultados indicaram que as variáveis tangibilidade dos ativos, oportunidadede crescimento, tamanho e lucratividade foram estatisticamente significantes e podem ser interpretadas como fatores determinantes do endividamento das empresas do agronegócio brasileiro. Conclui-se, ainda, que o modelo estimado por meio da regressão com dados em painel gerou resultado compatível com aqueles preconizados pela pecking order theory.<br>Studies involving capital structure and the identification of its determinants are relevant issues in the field of corporate finance management research. In this regard, the present study intends to evaluate the determinants of corporate leverage in the Brazilian agribusiness sector using the model of Rajan and Zingales (1995). In the definition of the sample there were selected 26 companies that are classified in one of three subdivisions of the Brazilian agribusiness sector: a) the agriculture or cattle raising; b) inputs or production factors and c) processing and distribution sector, using as reference the CNA classification. The study used data from the Economatica® database, with the adoption of panel data methods. The results indicated that the variables tangibility of assets, growth opportunities, size and profitability were statiscally significant as determinant factors of the debt structure of Brazilian agribusiness companies. It is also possible to conclude that the model estimated by panel data generated results that are compatible with those suggested by the pecking order theory

Variable salinity responses of 12 alfalfa genotypes and comparative expression analyses of salt-response genes

Twelve alfalfa genotypes that were selected for biomass under salinity, differences in Na and Cl concentrations in shoots and K/Na ratio were evaluated in this long-term salinity experiment. The selected plants were cloned to reduce genetic variability within each genotype. Salt tolerance (ST) index of the genotypes ranged from 0.39 to 1. The most salt-tolerant genotypes SISA14-1 (G03) and AZ-90ST (G10), the top performers for biomass, exhibited the least effect on shoot number and height. SISA14-1 (G03) accumulated low Na and Cl under salinity. Most genotypes exhibited a net reduction in shoot Ca, Mg, P, Fe, and Cu, while Mn and Zn increased under salinity. Salinity reduced foliar area and stomatal conductance; while net photosynthetic rate and transpiration were not affected. Interestingly, salinity increased chlorophyll and antioxidant capacity in most genotypes; however neither parameter correlated well to ST index. Salt-tolerant genotypes showed upregulation of the SOS1, SOS2, SOS3, HKT1, AKT1, NHX1, P5CS1, HSP90.7, HSP81.2, HSP71.1, HSPC025, OTS1, SGF29 and SAL1 genes. Gene expression analyses allowed us to classify genotypes based on their ability to regulate different components of the salt tolerance mechanism. Pyramiding different components of the salt tolerance mechanism may lead to superior salt-tolerant alfalfa genotypes