Investigation on the changes effected by tool profile on mechanical and tribological properties of friction stir processed AZ31B magnesium alloy

The present study investigates the effect of tool shoulder profile on the mechanical and tribological properties of friction stir processed AZ31B magnesium alloy. The tool rotational speed and feed rate are the chosen process parameters. The experiments were conducted with 3 level 2 factors full factorial design. The recorded responses were tensile strength, wear losses and corrosion rate. The results were analyzed with the help microstructures of the processed samples. The study reveals that, for concave shoulder tool, the strain hardening effect was playing a major role in determining the properties of the processed materials and for the step shoulder tool, the grain size plays a major role in determining the properties of the processed materials.     

A Mechanistic Model Describing the Degradation of Polymers

This study examined the cooperative effects of diffusion and reaction on the degradation of a polymer. The work was intended to describe bulk degradation processes, where the polymer volume remains nearly constant. Test coupons made from poly (2-ethyl 2-oxazoline) were immersed in water for controlled durations. The coupons were weighed before and after immersion in the wet and dried condition. The coupons were observed to gain weight for short immersion durations. At longer durations the weight change became negative as the solvent reacted with and dissolved the polymer. An average solvent concentration was found from the weight measurements. Fick’s law was used to express the increase in concentration while a first order reaction law was used to represent the decrease in concentration of the solvent. The competing changes in concentration were combined from which the net solvent concentration at any given time was obtained. The model was compared with the experimental measurements using coupons of various thicknesses. The model was found to describe the observed polymer degradation in water including thickness effects.     

Phytoplankton as index of water quality with reference to industrial pollution

In this paper Shannon-Weaver (SI-3.58-4.07, SII-3.1-3.72, SIII-1.64-2.25, SIV-2.54-2.95 and SV-3.09-3.23) diversity index was applied to surface phytoplankton to study the water quality status of river Bhadra receiving Mysore paper mill and Iron and steel mill effluent. A total of 45 species of phytoplankton belonging to 5 classes were recorded and study indicated that the phytoplankton diversity (Chlorophyceae-19 species, Bacillanophyceae-16 species, Cyanophyceae-07 species, Euglenophyceae-2 species and Chrysophyceae-1 species) did not reveal the same type of water quality (water temperature 24.62-27.32 degrees C, pH-7.08-7.25, electrical conductivity-67.49-201.94 micromhos/cm, dissolved oxygen-4.13-5.98 mgl(-1), chloride-12.30-40.85 mgl(-1), calcium-6.49-23.74 mgl(-1), total hardness 28.98-76.65 mgl(1), magnesium-4.69-15.92 mgl(-1), total alkalinity-77.26-86.53 mgl(-1), BOD-1.88-4.01 mgl(-1), COD - 16.53-45 mgl(-1), phosphate-0.001-0.53 mgl(-1), sodium-2.70-7.46 mgl(-1) and potassium-2.37-7.88 mgl(-1)). The investigation emphasized the need of phytoplankton community as index of water quality polluted by industrial effluents at the downstream stretch of the Bhadra river.     

Effects of methylisocyanate on soil microflora and the biochemical activity of soils

Methylisocyanate at 500, 1000 and 2500 microg ml(-1) h(-1) markedly affected the fungal propagules in treated soils. Immediately after exposure to gas, both bacteria and actinomycetes were appreciably reduced, although by the seventh day, their populations had gradually increased. Increased soil respiration was evident at 500 microg ml(-1) of methylisocyanate, whereas, inhibition of respiration occurred at 1000 and 2500 microg ml(-1) h(-1). Methylisocyanate adversely affected soil nitrification; inhibition increased with increasing concentration. Up to 2500 microg ml(-1) h(-1), it stimulated ammonification, but the NH(4)-N level gradually declined with increased incubation.     

Electro-Deposited Lead Dioxide Plates: A New Technique for Sulfation Rate Studies

Sulfation rates have long been used to estimate roughly atmospheric SO2 content on a monthly basis. Either lead dioxide coated candles or petri dishes (Huey plates) have so far been used.^1-6 Although in many advanced countries there are now commercially available duly coated petri dishes which are relatively rugged and can stand moderately rough handling during routine operations, small working groups, particularly in developing countries have to be content with “homemade” plates. In tropical climate we find the Huey plates prone to peeling and damage under adverse climatic conditions or routine operations. Besides, the Pb02 slurry deposition technique demands uniformity and submicron size of deposited PbC>2 which is hard to obtain particularly in “homemade” plates.     

Beryllium Concentrations in Ambient Air and Its Source Identification

Beryllium concentrations in atmospheric particulate and soil samples in and around a Beryllium Processing Facility (BPF) have been measured. The mean air concentration level of beryllium in and around the fence line of the BPF is 0.48 ± 0.43 ng m^-3 (n = 397) and is mostly influenced by diurnaland seasonal changes. The observed air concentration levelswere well below the prescribed ambient air quality (AAQ)standard of 10 ng m^-3. The soil concentration levels ofberyllium in the study area were found to be in the range of 1.42–2.75 g g^-1. The mass median aerodynamic diameter (MMAD)of beryllium aerosols in ambient air was found to be 6.9 m.Source identification using the Enrichment Factor (EF) approachindicates soil as the predominant contributory source for air concentrations at the site.     

Direct coupling of a genome-scale microbial in silico model and a groundwater reactive transport model

The activity of microorganisms often plays an important role in dynamic natural attenuation or engineered bioremediation of subsurface contaminants, such as chlorinated solvents, metals, and radionuclides. To evaluate and/or design bioremediated systems, quantitative reactive transport models are needed. State-of-the-art reactive transport models often ignore the microbial effects or simulate the microbial effects with static growth yield and constant reaction rate parameters over simulated conditions, while in reality microorganisms can dynamically modify their functionality (such as utilization of alternative respiratory pathways) in response to spatial and temporal variations in environmental conditions. Constraint-based genome-scale microbial in silico models, using genomic data and multiple-pathway reaction networks, have been shown to be able to simulate transient metabolism of some well studied microorganisms and identify growth rate, substrate uptake rates, and byproduct rates under different growth conditions. These rates can be identified and used to replace specific microbially-mediated reaction rates in a reactive transport model using local geochemical conditions as constraints. We previously demonstrated the potential utility of integrating a constraint-based microbial metabolism model with a reactive transport simulator as applied to bioremediation of uranium in groundwater. However, that work relied on an indirect coupling approach that was effective for initial demonstration but may not be extensible to more complex problems that are of significant interest (e.g., communities of microbial species and multiple constraining variables). Here, we extend that work by presenting and demonstrating a method of directly integrating a reactive transport model (FORTRAN code) with constraint-based in silico models solved with IBM ILOG CPLEX linear optimizer base system (C library). The models were integrated with BABEL, a language interoperability tool. The modeling system is designed in such a way that constraint-based models targeting different microorganisms or competing organism communities can be easily plugged into the system. Constraint-based modeling is very costly given the size of a genome-scale reaction network. To save computation time, a binary tree is traversed to examine the concentration and solution pool generated during the simulation in order to decide whether the constraint-based model should be called. We also show preliminary results from the integrated model including a comparison of the direct and indirect coupling approaches and evaluated the ability of the approach to simulate field experiment.