Thermodynamics of the Cr-Mn system using an isopiestic technique

Activities of manganese in solid chromium-manganese alloys have been determined at 1223, 1273, and 1323 K using an isopiestic technique. The activities of manganese show positive deviations from Raoult’s law over chromium-rich compositions. The positive deviation of the system is found to decrease progressively with increase in the manganese content of the alloys. The data have been interpreted based on calculation involving solid-liquid equilibria in the system.     

Dietary ether lipid incorporation into tissue plasmalogens of humans and rodents

Chronic feeding of 1-O-octadecyl-sn-glycerol (batyl alcohol) to patients suffering from congenital deficiency in tissue ether glycerolipids showed an increase in the plasmalogens content of their erythrocytes. However, nothing is known about the ether lipid content of other tissues in these patients. Feeding 1-O-heptadecyl-sn-glycerol to young rats showed that this uncommon ether lipid was incorporated to a high extent into the plasmalogens of all tissues except brain. Comparative studies with other precursors, such as 3-O-heptadecyl-sn-glycerol, heptadecanol and heptadecanoic acid, indicated a stereospecific incorporation of the dietary 1-O-alkyl-sn-glycerols into tissue plasmalogens without cleavage of the ether bond. Dietary ether lipids were also shown to be transferred from mothers to suckling rats, but not from pregnant rats to fetuses. The implication of these results to possible dietary ether lipid therapy for patients suffering from peroxisomal disorders is discussed.     

Recent advances and perspectives on starch nanocomposites for packaging applications

Starch nanocomposites are popular and abundant materials in packaging sectors. The aim of this work is to review some of the most popular starch nanocomposite systems that have been used nowadays. Due to a wide range of applicable reinforcements, nanocomposite systems are investigated based on nanofiller type such as nanoclays, polysaccharides and carbonaceous nanofillers. Furthermore, the structures of starch and material preparation methods for their nanocomposites are also mentioned in this review. It is clearly presented that mechanical, thermal and barrier properties of plasticised starch can be improved with well-dispersed nanofillers in starch nanocomposites.     

Thermodynamics of surfaces and adsorption in the Fe-O and Fe-O-N systems at 1823 K

The present investigation calculates the surface tension and adsorption functions of the Fe-O and Fe-O-N melts at 1823 K using the modified form of Butler’s equations and the derived values of the surface interaction parameters of the systems. The calculated values are found to be in good agreement with those of the experimental data of the systems. The present analysis indicates a characteristic saturation behavior of oxygen in the Fe-O system at 1823 K, whereas a linear adsorption behavior is observed in the Fe-N system. An inverse relationship in the adsorption behavior, which exists between oxygen and nitrogen in the Fe-O-N system, is similar to that observed in our earlier study of the Fe-S-N system.     

Fabrication of metallic Cd multifarious prismatic microcrystals (CMPMCs) under NH3 gas ambient

We report here highly dense and pure metallic cadmium (Cd) multifarious prismatic microcrystals (CMPMCs) fabricated by thermal decomposition of cadmium oxide (CdO) powder at 700 °C for 60 min under NH₃ gas ambient inside horizontal tube furnace. CMPMCs were observed to be 1-1.5 μm in size with interesting morphologies of various cross sections such as triangular, trapezoidal, pentagonal and hexagonal etc. having solid, hollow/semi-hollow appearances. The as-synthesized CMPMCS were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Room temperature photoluminescence (PL) spectrum for Cd metal microcrystals exhibited a prominent emission band at 365 along with a shoulder peak at 404 nm. The UV main emission band is ascribed to radiative recombination of the electrons in the s, p conduction band near the Fermi surface and holes in the d bands generated under xenon light excitation whereas shoulder peak may be owing to surface oxidation effects or induced defects. This study shows the potential of CMPMCs for applications in optical devices. Based on vapour-solid (VS) process, growth mechanism for the formation of CMPMCs is also proposed and discussed briefly.     

Effect of scale‐up on wall shear rates in circulating bubble columns

Effective wall shear rates were investigated experimentally in an external loop circulating bubble column made from transparent acrylic resin. The riser (D_R) and downcomer (D_D) diameters were 0.19 m and 0.14 m, respectively. The column working volume (V_R) was 170 dm³, with a scale‐up factor (A_D/A_R) of 0.54, and a dispersion height (H_D) of 2.25 m. Polymer solutions of xanthan gum and carboxymethyl cellulose were used to simulate non‐Newtonian behavior of biological systems. Effective wall shear rates for the non‐Newtonian solutions were found by analogy with Newtonian glycerol solutions, employing downcomer liquid velocity as the measurable and comparable parameter. The experimental shear rate results were found to fit between those of the literature data. A new single correlation taking into account all the relevant data in the literature and the results of this work is proposed. The new correlation is an improvement over the other correlations because it includes two important design constants: scale‐up factor and dispersion height. Copyright © 2005 Society of Chemical Industry     

Synthesis,micellization and cytotoxic studies of ester-functionalized imidazolium gemini surfactants

The fatty acid-based imidazolium gemini surfactants containing hydroxy-substituted spacers were synthesized and characterized by different spectral techniques. The micellization behavior of product compounds was studied by determining their critical micelle concentration (cmc) values from steady state fluorescence and conductivity measurements. The thermodynamic parameters of micellization of synthesized gemini surfactants confirmed that the micelle formation is a thermodynamically favorable, endothermic and an entropy driven phenomenon. The surfactants were further analyzed for their cytotoxic nature by treating them upon human embryonic kidney cell (HEK-293) line and were found to be significantly low cytotoxic. The interesting features like low cmc values, non-cytotoxic and eco-friendly nature of the gemini surfactants may offer new and more efficient substitutes to the conventional drug delivery systems. Thus the gemini surfactants may serve as promising candidates in the biomedical and pharmaceutical fields.     

Greener energy: Issues and challenges for Pakistan—Solar energy prospective

Energy plays a pivotal role in socio-economic development by raising standard of living. It is becoming gradually accepted that current energy systems, networks encompassing every thing from primary energy sources to final energy services, are becoming unsustainable. Development of conventional forms of energy for meeting the growing energy needs of society at a reasonable cost is the responsibility of the Governments. In recent years, public and political sensitivities to environmental issues and energy security have led to the promotion of renewable energy resources. Diversification of fuel sources is imperative to address these issues; and limited fossil resources and environmental problems associated with them have emphasized the need for new sustainable energy supply options that use renewable energies. Development and promotion of new non-conventional, alternate and renewable sources of energy such as solar, wind and bio-energy, etc. are now getting sustained attention. Solar power is one of the hottest areas in energy investment right now, but there is much debate about the future of solar technology and solar energy markets. This investigates the progress and challenges for solar power in Pakistan according to the overall concept of sustainable development, and identifies the region wise potential of solar power in Pakistan and its current status. Barriers are examined over the whole solar energy spectrum and policy issues and institutional roles and responsibilities are discussed.     

Thermodynamics of surfaces and adsorption in the Fe-C-S-O system

Surface tension experiments have been conducted on Fe-C-S-O alloys using the sessile drop technique at 1823, 1873, and 1923 K in a purified argon atmosphere. The experimental data indicate lowering of surface tension values for alloys with low carbon and oxygen contents relative to the corresponding tenary Fe-S-O system of comparable compositions. The data exhibit an increasing trend of the surface tension values as a function of carbon and oxygen contents and temperature of the melt. Modified Butler’s equations have been used in conjunction with the consistent thermodynamic relations for a dilute quaternary system to calculate the surface tensions and adsorption functions of the system. The calculated values are in excellent agreement with those of the experimental data for compositions having lower oxygen at 1823 K, however, the values for the alloys containing higher oxygen contents depart from those of the experimental data. The calculated surfact tension values agree within 150 mN/m with those of the experimental data at 1873 K. The agreement, in general, has been favorable despite the constraints involved in the calculations as discussed in the text.