A frictional Cosserat model for the flow of granular materials through a vertical channel

A rigid-plastic Cosserat model has been used to study dense, fully developed flow of granular materials through a vertical channel. Frictional models based on the classical continuum do not predict the occurrence of shear layers, at variance with experimental observations. This feature has been attributed to the absence of a material length scale in their constitutive equations. The present model incorporates such a material length scale by treating the granular material as a Cosserat continuum. Thus localised couple stresses exist and the stress tensor is asymmetric. The velocity profiles predicted by the model are in close agreement with available experimental data. The predicted dependence of the shear layer thickness on the width of the channel is in reasonable agreement with data. In the limit of the ratio of the particle diameter to the half-width of the channel being small, the model predicts that the shear layer thickness scaled by the particle diameter grows.Comment: 17 pages, 12 PostScript figures, uses AmsLaTeX, psfrag and natbib. Accepted for publication in Acta Mechanic

A frictional Cosserat model for the slow shearing of granular materials

A rigid-plastic Cosserat model for slow frictional flow of granular materials, proposed by us in an earlier paper, has been used to analyse plane and cylindrical Couette flow. In this model, the hydrodynamic fields of a classical continuum are supplemented by the couple stress and the intrinsic angular velocity fields. The balance of angular momentum, which is satisfied implicitly in a classical continuum, must be enforced in a Cosserat continuum. As a result, the stress tensor could be asymmetric, and the angular velocity of a material point may differ from half the local vorticity. An important consequence of treating the granular medium as a Cosserat continuum is that it incorporates a material length scale in the model, which is absent in frictional models based on a classical continuum. Further, the Cosserat model allows determination of the velocity fields uniquely in viscometric flows, in contrast to classical frictional models. Experiments on viscometric flows of dense, slowly deforming granular materials indicate that shear is confined to a narrow region, usually a few grain diameters thick, while the remaining material is largely undeformed. This feature is captured by the present model, and the velocity profile predicted for cylindrical Couette flow is in good agreement with reported data. When the walls of the Couette cell are smoother than the granular material, the model predicts that the shear layer thickness is independent of the Couette gap H when the latter is large compared to the grain diameter dp. When the walls are of the same roughness as the granular material, the model predicts that the shear layer thickness varies as (H/dp)1/3 (in the limit H/dp [dbl greater-than sign] 1) for plane shear under gravity and cylindrical Couette flow

Silo Music and Silo Quake: Granular Flow Induced Vibration

Acceleration and sound measurements during granular discharge from silos are used to show that silo music is a sound resonance produced by silo quake. The latter is produced by stick-slip friction between the wall and the granular material in tall narrow silos. For the discharge rates studied, the occurrence and frequency of flow pulsations are determined primarily by the surface properties of the granular material and the silo wall. The measurements show that the pulsating motion of the granular material drives the oscillatory motion of the silo and the occurrence of silo quake does not require a resonant interaction between the silo and the granular material.Comment: 16 pages, submitted to Powder Technolog

Climate change adaptation and mitigation strategies for sustainable crop production

Climate change is the main environmental problem facing humanity. Evidences over the past few decades show that significant changes in climate are taking place all over the world as a result of enhanced human activities through deforestation emission of various greenhouse gases and indiscriminate use of fossil fuels. Carbon dioxide (CO2) Methane and Nitrous Oxide are the major greenhouse gases. CO2 enters the atmosphere mostly through burning fossil fuels. Methane emissions also result from livestock and other agricultural practices and Nitrous Oxide is emitted during agricultural and industrial activities. Global atmospheric concentration of CO2 has increased from pre-industrial level of 280 parts per million (ppm) to 408 ppm in Feb 2018. Global projections indicate higher temperature of 1.5 to 4.5°C by the year 2050 as a result of enhanced greenhouse gases. There is medium confidence in that the Indian summer monsoon circulation weakens but this is compensated by increased atmospheric moisture content leading to more rainfall. There is medium confidence in an increase of Indian summer monsoon rainfall and its extremes throughout the 21st century under all RCP (Representative Concentration Pathways) scenarios

Genotype dependent response to Azospirillum treatment in yield and nitrogenase activity in Brassica juncea L.

Twelve advanced lines of mustard (Brassica juncea L.) were evaluated for response to treatment with Azospirillum brasilense in yield and a few components. Two lines gave yield increases with concomitant increases in nitrogenase activity and Azospirillum population. In general, there were desirable and significant correlations between plot yield, nitrogenase activity and log, (Azospirillum population). The results point to the possibility of utilizing genotype-dependent response to Azospirillum in breeding programmes and also for exploring new avenues of Azospirillum-based cultural practices in sustaining improved productivity

The Inhibition of Arginase by Proline in Cell-free Extracts of Mouse Mammary Tumour

Arginase activity was found to be increased in precancerous nodules and mammary tumour when compared with the mammary gland. Proline inhibited the mammary tumour arginase and up to 30 mmo1 concentration the inhibition follows first order kinetics. Hill analysis of the inhibition of arginase by proline showed that proline inhibits the arginase activity by competing directly at the active site without conformational change. The inhibition may be of regulatory importanec, involving a feedback mechenism in mammary tumours

Ideotype and relationship between morpho-physiological characters and yield in Indian mustard (Brassica juncea)

Twelve genotypes of Indian mustard [Brassica juncea (L.) Czemj. & Cosson] were evaluated for various yield and morpho- physiological characters during 1990 and 1991. The genotypes were classified basal or non-basal branching type on the basis of the presence or absence of at least 1 productive primary branch within 30 cm height of the plant. A correlation analysis revealed that the traits related to basal branching were positively associated among themselves as well as with the seed yield. There were desirable and negative associations of basal branching characters with flowering time and plant height. Thus breeding for early maturing basal branching plant types with medium height and high yield is possible

A prospective open-label randomized comparative study in Alzheimer’s disease between two commonly used drugs in coastal Indian population

Background: Currently, therapy for Alzheimer’s disease (AD) is only symptomatic. Only two classes of drugs are approved by the United States Food and Drug Administration. Our study aimed at comparing efficacy and safety of memantine and donepezil in moderate to severe AD patients.Methods: Totally, 22 patients with moderate to severe AD were randomized into the 2 arms of the study. The study was divided into an initial 4 weeks for determination of onset of efficacy and subsequent 28 weeks of the treatment phase. Onset of efficacy and response was defined as >20% and >50% reduction in the mean total score of functional dementia scale (FDS) and clinical global impression scale (CGIS) from baseline to the study end, respectively.Results: Onset of efficacy on FDS and CGIS was 16.7% (mean-time 61.25 days) and 80% (mean-time 36 days) with memantine and donepezil, respectively. Response was 89.3% and 40% with memantine and Donepezil, respectively. Total reduction in FDS and CGIS score of from baseline to the study end was 39.50, 40.00, and 25.60, 27.20 with memantine and donepezil, respectively. Tolerability was 86.33% and 20% with memantine and donepezil, respectively. Anorexia, muscle cramps, constipation, headache, and insomnia, were the common side-effects and self-limiting. Safety was 100% in both groups.Conclusions: Onset of efficacy was faster with donepezil seen at 2 weeks. Response, improvement in CGIS, FDS, and tolerability were better seen with memantine at 40 weeks. Thus, in similar clinical settings, memantine can be preferred