Biodiesel production from mixture of mahua and simarouba oils with high free fatty acids

A suitable process comprising acid pretreatment followed by main base transesterification reaction was developed to produce biodiesel from mixture of Mahua (M) and Simarouba (S) oils with high free fatty acids (FFA). The acid pretreatment reduced the high FFAs of the mixture of oils to around 1% which were then transesterified with methanol and KOH as catalyst at a reaction temperature of 60 °C. A genetic algorithm coupled with artificial neural network (ANN-GA) model to obtain the best pretreatment process parameters for bringing down the FFA level of individual vegetable oils to around 1% was modified to include the wide range of oils and validated for mixtures of M and S oils. The quality of biodiesel produced was analyzed by gas chromatography (GC), which indicated above 90% ester conversion. The fuel properties of biodiesel were found to be comparable to diesel and were conforming to the latest biodiesel standards.     

MnPcS4: a new MRI contrast enhancing agent for tumor localisation in mice

Manganese-tetrasulfonated phthalocyanine (MnPcS4) has been evaluated as a potential contrast agent in Magnetic resonance imaging (MRI) for tumor localisation in mice. MnPcS4 showed favourable molar relaxivity, much better than Gd-DTPA and comparable to tetrasulfonated manganese complex of porphyrin (TPPS4). Tumors showed selective retention of the metal complex (dye) with the peak value reached at 24 hours following intravenous administration. Dye concentration in tumors remained consistently higher than either kidney or muscle tissue both at 1 and 24 hours and a 10-fold increase in tumor-to-muscle ratio over the control was seen at 24 hr. Normal liver tissue, however, showed higher concentration than tumor at all times during the study. A linear correlation was found between longitudinal relaxation rate (1/T1) and the corresponding concentration of MnPcS4 in various tissues. MR imaging done in animals using 1.5 T superconducting clinical imager showed a mean percent increase in signal intensity of 131.8% (SD +/- 32.86) in the tumor and a 70% increase in tumor-to-muscle ratio over the pretreatment value, at 24 hr. The results suggest that MnPcS4 is a potential tumor-selective contrast agent in MRI.     

Studies on kinetics of low-temperature chlorination of ZrO2 by gaseous carbon tetrachloride

Studies on the kinetics of chlorination of ZrO₂. powder by carbon tetrachloride vapor in mixture with nitrogen in a low-temperature range of 650 to 825 K at different periods and partial pressures of carbon tetrachloride were carried out. The chlorination results at 650 and 675 K seem to follow a diffusion-controlled reaction model of Jander’s type: [1−(1−R)^1/3]² =k ₁t whereR is the fraction of ZrO₂ chlorinated in timet andk ₁ is the rate constant. The approximate activation energy of the process was calculated fromk ₁ values at the previously mentioned two temperatures and found to be 278 kJ/mole. For the chlorination in the temperature range of 700 to 750 K, the topochemical reaction model 1−(1−R) ^1/3 =k ₂t was followed. The rate constant,k ₂, was found to be proportional to the partial pressure of carbon tetrachloride. The activation energy of this reaction was calculated to be 154 kJ/mole. In the temperature range of 775 to 825 K, the rate of chlorination was found to be directly proportional to the time of chlorination following Langmuir’s Adsorption Isotherm. Because of the very high rate of chlorination and thermodynamic possibility of decomposition of CCl₄ above 773 K, the rate-controlling step has been suggested to be the decomposition of the adsorbed complex formed by ZrO₂ with carbon and chlorine atoms, obtained from the decomposition of CCl₄ vapor. The activation energy of the process was 54 kJ/mole. In view of nearly complete chlorination of ZrO₂ by CCl₄ in a very short period of about 15 minutes, at a temperature around 800 K and lesser possibility of formation of toxic product gases, the process is recommended for commercial application.     

Thermosolutal convection in a fluid‐porous composite medium

In the present study analysis has been performed for thermosolutal convection in a fluid‐porous composite medium, consisting of a fluid‐saturated porous medium followed by an overlaying clean medium. The fluid‐porous composite medium is subjected to both a horizontal solutal and a thermal gradient. Top and bottom walls of the fluid‐porous composite medium are assumed to be impermeable and adiabatic. The Darcy‐Brinkman‐Forchheimer model is used to study the flow through the fluid‐porous composite medium. A single domain approach is taken into consideration for numerical simulation. The solution is done by control volume integration. A comprehensive analysis has been performed for various pertinent parameters to delineate their behavior. Results of the transport phenomenon have been provided in graphical and tabular form, for the complete understanding of the complex phenomenon. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21048     

On the thermodynamic properties of the phases zeta and AuSn in the system Au-Sn

Metal solution calorimetry has been used to measure the low temperature heats of formation and heat contents of two phases in the systemAu-Sn. The heats of formation of zeta containing 11.1, 14.0 and 16.0 at. pct Sn and AuSn at 78 K and of zeta containing 16.0 at. pct Sn and AuSn at 195 and 273 K have been measured. The heat contents (H _273K-H _78K) and (H _195K-H _78K) of zeta (16· at · pct Sn)and AuSn have also been measured. Heat contents at several temperatures and the standard heat and free energy of formation of AuSn at 298 K have been calculated. The stability of zeta and the unusual composition dependence of its heat of formation have been discussed in terms of its electronic structure.     

Estimation of parameters in exponential autoregressive models

The paper discusses the estimation of parameters in second order exponential autoregressive models.