RESUMO
The mechanical behavior of granular materials results from interparticle interactions, which are predominantly frictional. With the presence of even very small amounts of cohesion this frictional interparticle behavior significantly changes. In this study, we introduce trace amounts of cohesive binder between the intergranular contacts in a sample of quartz particles and apply one-dimensional (1D) compression loading. X-ray computed tomography is performed in situ during 1D compression. We make observations at three different length scales. At the macroscopic or ensemble scale, we track the evolution of the porosity, particle size and the stress-strain response during this compression. At the microstructure or interparticle scale, we compute the directional distribution of contacts and the particles. We also track the evolution of the fabric chains with continued compression. We also evaluate particle rotations, displacements, contact twist, rotation, and sliding. We show through our experiments that even a small amount of cohesion (as low as 1% by weight) significantly changes the response at multiple length scales. This interparticle cohesion suppresses the fragmentation of grains, alters force transmission and changes the structure of the ensemble.
RESUMO
Coix lacryma-jobi, commonly known as job's tear, is a tall grain-bearing tropical plant of the family Poaceae. The ethanolic root extract (ERE) of the plant was investigated for the first time for anti-venom activity against Indian cobra Naja naja venom. In-vitro studies were conducted to determine neutralization of phospholipase A2 (PLA2) activity of the Naja naja venom by the ERE. ERE showed significant inhibition of PLA2 activity, which was further confirmed from effective neutralization of human red blood cells (HRBC) lysis induced by the venom. In addition, venom-induced proteolysis, fibrinogenolysis, DNase activity were also neutralized by the ERE, which contained carbohydrates, glycolides, resins and tannins. Oral administration of ERE at doses levels 100, 200 and 400 mg/kg effectively inhibited Naja naja venom-induced lethality in mice. Myotoxicity induced by Naja naja venom, measured by creatine kinase activity in rats was significantly neutralized by the ERE at a dose of 200 mg/kg. Stigmasterol, as one of the component isolated from the ERE, was found to have venom phospholipase A2 inhibition potential, which was confirmed by molecular docking studies with PLA2. In summary, these studies indicate the ability of ERE of Coix lacryma-jobi to effectively neutralize the toxic effects of the venom is, in part, contributed by the inhibition of PLA2 activity among other venom-derived factors.
RESUMO
Manganese(III) acetate was prepared by the oxidation of manganese(II) acetate in aqueous acetic acid by electrolytic method. The anodically generated Mn(III) species was characterised by spectroscopic and redox potential studies. Conditions for the study of kinetics of Oxidation ofα-amino acids by Mn(III) in aqueous acetic acid was investigated. Plots of log[Mn(III)] versus time for the first order process, or Mn(III) versus time for zero order process were nonlinear. The rate constants computed from [Mn(III)](1/2) versus time plots were independent of [Mn(III)]0 indicating that the reaction goes through competitive zero and first order path-ways in [Mn(III)]0. The kinetic order in [amino acid], [H(+)] and [Mn(II)] were found out. Effect of added anions like CH3COO(-), F(-), Cl(-) and ClO 4 (-) were investigated. Evidence for the transient existence of the free radical reaction intermediate is given. Dependence of reaction rate on temperature is explained and activation parameters computed from Arrhenius and Eyring plots. A mechanism consistent with the observed results is proposed and discussed.
