Role of friction in pattern formation in oscillated granular layers

Particles in granular flows are often modeled as frictionless (smooth) inelastic spheres; however, there exist no frictionless grains, just as there are no elastic grains. Our molecular dynamics simulations reveal that friction is essential for realistic modeling of vertically oscillated granular layers: simulations of frictionless particles yield patterns with an onset at a container acceleration about 30% smaller than that observed in experiments and simulations with friction. More importantly, even though square and hexagonal patterns form for a wide range of the oscillation parameters in experiments and in our simulations of frictional inelastic particles, only stripe patterns form in the simulations without friction, even if the inelasticity is increased to obtain as much dissipation as in frictional particles. We also consider the effect of particle friction on the shock wave that forms each time the granular layer strikes the container. While a shock wave still forms for frictionless particles, the height and time dependence of the hydrodynamic fields differ for the cases with and without friction.Comment: final version appeared in Phys. Rev.

A nonlinear hydrodynamical approach to granular materials

We propose a nonlinear hydrodynamical model of granular materials. We show how this model describes the formation of a sand pile from a homogeneous distribution of material under gravity, and then discuss a simulation of a rotating sandpile which shows, in qualitative agreement with experiment, a static and dynamic angle of repose.Comment: 17 pages, 14 figures, RevTeX4; minor changes to wording and some additional discussion. Accepted by Phys. Rev.

Synthesis, anti-toxoplasma gondii and antimicrobial activities of 2-hydrazolyl-3-phenyl-5-(4-nitrobenzylidene)-4-thiazolidinone substituted derivatives

A novel series of 2-hydrazolyl-3-phenyl-5-(4-nitrobenzylidene)-4-thiazolidinone substituted (3a-p) has been synthesized. The intermediates 2-hydrazolyl-3-phenyl-4-thiazolidinone substituted (2a-p) were prepared by condensation of benzaldehyde 4-phenyl-3-thiosemicarbazone substituted (1a-p) with ethyl chloroacetate. Theses intermediates were submitted to reaction with ethyl 2-cyano-3-(4-nitrophenyl)-acetate to give the title compounds. The 4-thiazolidinones were screened for their anti-Toxoplasma gondii, and all derivatives promoted decrease of percentage of infection of Vero cells, with elimination of intracellular tachyzoites. The LD50 ranged around 0.5 mM for the intracellular parasites and were higher than 10 mM for Vero cells. According to results of antimicrobial activity, only two compounds showed significant inhibition against M. luteus, but demonstrated higher values of MIC and MBC when compared with standard drug.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Synthesis, anti-toxoplasma gondii and antimicrobial activities of 2-hydrazolyl-3-phenyl-5-(4-nitrobenzylidene)-4-thiazolidinone substituted derivatives

A novel series of 2-hydrazolyl-3-phenyl-5-(4-nitrobenzylidene)-4-thiazolidinone substituted (3a-p) has been synthesized. The intermediates 2-hydrazolyl-3-phenyl-4-thiazolidinone substituted (2a-p) were prepared by condensation of benzaldehyde 4-phenyl-3-thiosemicarbazone substituted (1a-p) with ethyl chloroacetate. Theses intermediates were submitted to reaction with ethyl 2-cyano-3-(4-nitrophenyl)-acetate to give the title compounds. The 4-thiazolidinones were screened for their anti-Toxoplasma gondii, and all derivatives promoted decrease of percentage of infection of Vero cells, with elimination of intracellular tachyzoites. The LD50 ranged around 0.5 mM for the intracellular parasites and were higher than 10 mM for Vero cells. According to results of antimicrobial activity, only two compounds showed significant inhibition against M. luteus, but demonstrated higher values of MIC and MBC when compared with standard drug.Colegio de Farmacéuticos de la Provincia de Buenos Aire