Experiences in the development of magnesium cell technology at Central Electrochemical Research Institute, Karaikudi

Research activities on the preparation of magnesium metal by molten salt electrolytic process were initiated in CECRI as early as in 1958. CECRI started its experiments on a bench scale level and further developed into pilot plant scale and finally to the scale of semicommercial unit. Various types of electrolytic cells were developed at CECRI which include externally heated cells with different design modifications, modular cells, bipolar/multipolar cells and new modified monopolar ceUs. The primary aim of each development was aimed at high current efficiencies energy efficiencies and space time yields. Various types of raw materials like magnesite, sea bitterns, and byproduct MgCl2 from ZrrTi plants etc. were utilised during the investigations. These studies were carried out with financial grants from Govt. of Tamil Nadu, CSIR, DRDO and Nuclear Fuel Complex. The paper illustrates the design and operational features of different electrolytic cells with consequent gradual decrease in specific energy consumption for magnesium production and increased space time yields with improvement in cell design and operational parameters

Genetic regulation of adult hippocampal neurogenesis: A Systems genetics approach using BXD recombinant inbred mouse strains

Adult hippocampal neurogenesis is regulated at various levels and by various factors. Genetic influence is an important key determinant of adult neurogenesis and exerts its effects at all levels. In vivo studies have suggested that adult hippocampal neurogenesis is highly variable and heritable among different laboratory strains of mice. To dissect the genetic effect from other contributing factors, it is necessary to study adult neurogenesis under highly controlled environment conditions. We extracted adult hippocampal precursor cells (AHPCs) from 20 strains of the BXD set of recombinant inbred mice, cultured them and studied the effect of genetic background on neurogenesis. The BXD panel consists of mouse lines derived from an intercross between inbred parentals C57BL/6J and DBA/2J. Both of the parentals are fully sequenced and all the strains are well characterized in terms of genotypic and phenotypic characteristics. This allows us to use advanced genetic techniques to identify novel genomic loci and gene-gene interactions important in adult neurogenesis. Comparison of the AHPCs from 20 BXD strains, with respect to cell proliferation and neuronal and astrocytic differentiation in vitro, revealed a large variation for these traits across the strains. Proliferation, as measured by BrdU incorporation, showed over two- fold differences between the extremes. Similar differences were observed for neurogenic (4-fold) and astrogenic differentiation (2-fold). These three traits all showed strong heritability values indicating that the differences were mainly attributed to the genetic component. QTL mapping, with these phenotypic data, revealed that there was no major contribution from single loci controlling these traits. Instead, we found many loci with smaller effects associated with these traits. Gene expression profiling using RNA samples from proliferating cultures of the 20 BXD mice strains yielded two cis eQTL candidates that directly regulated proliferation, LRP6 and Chchd8. LRP6 is well known as a co-receptor of Wnt signaling, but the function of Chchd8 is not known. Further experimentation, using over expression and gene silencing demonstrated that LRP6 negatively regulates AHPCs proliferation. Thus, from this study using a system genetics approach, we were able to identify, LRP6 as a novel regulator of adult hippocampal neurogenesis

ANTIMICROBIAL ACTIVITY AND PHYTOCHEMICAL SCREENING OF THE LEAF EXTRACTS OF EUCALYPTUS GLOBULUS

Objective: To investigate the antimicrobial activity and phytochemical analysis of Eucalyptus globulus leaves.Methods: The antimicrobial activity of the leaves of E. globulus extracted with acetone, ethanol and petroleum ether was studied using well diffusion method against the selected bacterial and fungal isolates. The antimicrobial susceptibility of the bacteria and fungi to various concentrations of the extract was evaluated by the micro broth dilution method. The preliminary phytochemical screening was performed in the acetone extract of E. globulus. The presence of functional groups in the acetone extract of the leaves of E. globulus was determined by Fourier to transform infrared (FT-IR) spectroscopy.Results: Results suggested that the acetone extract exhibited maximum antimicrobial activity against the tested bacteria and fungi when compared with ciprofloxacin and fluconazole respectively (standard antibiotics). Minimum inhibitory concentration (MIC) showed that the wells containing a concentration of 12.5 mg/ml and 6.25 mg/ml of acetone extract inhibited the bacteria and fungi effectively. Phytochemical screening of acetone extract of E. globulus showed the presence of alkaloids, flavonoids, phenols, tannins, quinones, glycosides, steroids, terpenoids and leucoanthocyanides. FT-IR spectral analysis of the leaf extract of E. globulus showed the presence of functional groups such as–OH,-NH, C=O and–COOH.Conclusion: Thus to conclude, different plants and their formulations have been used in ayurveda to cure diseases for several decades. The findings of the study indicate the potential to exploit the leaves of Eucalyptus globulus in the treatment of microbial diseases

Numerical control of laser processing and simulation of microstructures and temperature profiles - a fuzzy approach

The use of high power density laser beam for surface modification of many important alloys often leads to appreciable changes in the composition & tribological properties. These changes are dependent on process variables such as beam size, energy, scan rate, laser mode and the Chemistry and metallurgy of steel. Appro-ximate solutions to heat flow equations are combined with kinetic models to predict the microstructures and temperature distributions. A transient fuzzy logic based heat flow model is developed to predict temperature zones instead of discrete temperature calculations. A set of separate membership functions are formulated for dete-rmining temperature zones by means of continuous iteration process the same method is adopted to evaluate micro-structures for a specific temperature zone by incorporat-ing the kinetic and thermal datas available. Alloy steel of CK45 grade and stainless steel of 316 grade are used for this investigations and the results obtained are compared with the temperature profiles obtained from conventional methods and hence their microstructures. An attempt is also made to compute the dendrite cell width distribution during laser melt solidification of 316 LN steel by means of the above mentioned method

LARVICIDAL ACTIVITY OF BACILLUS THURINGIENSIS ISOLATED FROM Bt COTTON RHIZOSPHERE SOIL AGAINST ANOPHELES MOSQUITO LARVAE (CULICIDAE)

Objective: The objective of the study was to isolate and identify Bacillus thuringiensis (Bt) from Bt cotton rhizosphere soil and analyze its larvicidal activity against Anopheles mosquito larvae.Methods: Soil samples were collected from Bt cotton field, and B. thuringiensis was isolated and characterized by biochemical and microscopical characterization. Crystal (Cry) proteins were extracted and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and its larvicidal activity was checked by mortality analysis. Effective Bt isolates were identified by 16S rRNA sequencing.Results: A total of 24 isolates were characterized as Bacillus sp. by biochemical characterization. Further, parasporal inclusion and Cry proteins were extracted, and it was quantified by Bradford assay. The precipitated Cry proteins were analyzed by SDS-PAGE and the results have indicates Cry I protein at 100kDa, Cry3 protein at 44kDa, and cytolytic protein (Cyt) at 29kDa in most of the isolates. Larvicidal activity was checked by the 4th instar Anopheles mosquito larvae. Among the tested isolates, RBL10 and RBL20 have shown the highest percentage of larvicidal activity at 96 and 83%, respectively. Further, the two isolates RBL10 and RBL20 were identified as Bt by 16S rRNA sequencing.Conclusion: B. thuringiensis producing Cry and Cyt proteins posses potential larvicidal activity against Anopheles mosquito larvae which has biological and economic importance in mosquito control

Modelin combustion of multicomponent fuel droplets: formulation and application to transportation fuels

The quasi-steady, spherically symmetric combustion of multicomponent isolated fuel droplets has been modeled using modified Shvab-Zeldovich variable mechanism. Newly developed modified Shvab-Zeldovich equations have been used to describe the gas phase reactions. Vapor-liquid equilibrium model has been applied to describe the phase change at the droplet surface. Constant gas phase specific heats are assumed. The liquid phase is assumed to be of uniform composition and temperature. Radiative heat transfer between the droplet and surroundings is neglected. The results of evaporation of gasoline with discrete composition of hydrocarbons have been presented. The evaporation rates seem to follow the pattern of volatility differentials. The evaporation rate constant was obtained as 0.344mm2/sec which compared well with the unsteady results of Reitz et al. The total evaporation time of the droplet at an ambience of 1000K was estimated to be around 0.63 seconds. Next, the results of evaporation of representative diesel fuels have been compared with previously reported experimental data. The previous experiments showed sufficient liquid phase diffusional resistance in the droplet. Numerical results are consistent with the qualitative behavior of the experiments. The quantitative deviation during the vaporization process can be attributed to the diffusion time inside the droplet which is unaccounted for in the model. Transient evaporation results have also been presented for the representative diesel droplets. The droplet temperature profile indicates that the droplet temperature does not reach an instantaneous steady state as in the case of single-component evaporation. To perform similar combustion calculations for multicomponent fuel droplets, no simple model existed prior to this work. Accordingly, a new simplified approximate mechanism for multicomponent combustion of fuel droplets has been developed and validated against several independent data sets. The new mechanism is simple enough to be used for computational studies of multicomponent droplets. The new modified Shvab-Zeldovich mechanism for multicomponent droplet combustion has been used to model the combustion characteristics of a binary alcohol-alkane droplet and validated against experimental data. Burn rate for the binary droplet of octanol-undecane was estimated to be 1.17mm2/sec in good concurrence with the experimental value of 0.952mm2/sec obtained by Law and Law. The model has then been used to evaluate the combustion characteristics of diesel fuels assuming only gas phase reactions. Flame sheet approximation has been invoked in the formulation of the model

Spectroscopic, thermal, second order and third order NLO studies of N, N’ -dimethyl urea crystal

Nonlinear optical (NLO) crystals are classified into organic, inorganic and semi organic crystals and these crystals are used in the fields of optical communication, optical computing, frequency doubling, optical data processing and opto electronics. In this work an organic NLO crystal namely DMU crystal was prepared. Slow evaporation technique was adopted to grow the single crystals of DMU after the growth period of 35 days. The harvested crystals have been subjected to various characterization techniques like XRD, FTIR, FT-Raman, TG/DTA, SHG, EDAX, impedance, optical and Z-scan studies. From the studies, is observed that DMU crystal has orthorhombic structure and it has the melting point at 105 oC and has the decomposition point at 275 oC. The relative SHG efficiency of DMU crystal was found to be more than one and third order NLO parameters were evaluated. The optical band gap of DMU crystal was found to be 5.008 eV.The results from various studies were analyzed.

MICROSTRUCTURAL MODELING DURING MULTI-PASS ROLLING OF A NICKEL-BASE SUPERALLOY

Microstructure present at the end of rolling and cooling operations controls the product properties. Therefore, control of grain size is an important characteristic in any hot-working. The narrow temperature range for hot working of Alloy 718 makes the grain size control more difficult. In the current work, a systematic nu- merical approach to predict the microstructure of Alloy 718 during multi-pass rolling is developed. This approach takes into account the severe deformation that takes place during each pass and also the possible reheating between passes. In order to predict the grain size at the end of rolling process, microstructural processes such as dynamic recrystallization (DRX), metadynamic recrystallization (MDRX), and static grain growth need to be captured at every deformation step for superalloys. Empirical relationships between the average grain size from various microstructural processes and the macroscopic variables such as temperature (T ), effective strain (e ¯) and strain rate (e ¯ ?) form the basis for the current work. The empirical relationships considered in this work are based on Avrami equations and utilize data taken from various forging analyses. The macroscopic variables are calculated using the Finite Element Method (FEM) by modeling the rolling process as a creeping flow problem. FEM incorporates a mesh re-zoning algorithm that enables the analysis to continue for several passes. A two-dimensional transient thermal analysis is carried out between passes that can capture the MDRX and/or static grain growth during the microstructural evolution. The microstructure prediction algorithm continuously updates two families of grains, namely, the recrystallized family and strained family at the start of deformation in any given pass. In addition, the algorithm calculates various subgroups within these two families at every deformation step within a pass. As the material undergoes deformation between the rolls, recrystallization equations are invoked depending on critical strain and strain rate conditions that are characteristics of Alloy 718. This approach predicts the microstructural evolution based on recrystallization kinetics and static grain growth only. Precipitation of phases such as ?', ?'' and d are not considered. Modeling this complex precipitation is difficult and requires a more detailed understanding than is presently available. Nevetheless, comparisons of the grain sizes from the proposed numerical models with experimental results for 16-stand rolling process show very good agreement