Abstract: The tandem multimeric expression of various peptides has been explored by many researchers. However, expression levels have usually not been proportional to the degree of multimerization. To increase the expression level in Escherichia coli of tandem multimers of a cationic antimicrobial peptide, buforin II, fused to an anionic peptide, we studied the effect of the DEAD-box protein and the trxB mutant on the expression of tandem multimers. An expression vector with a tac promoter was more effective in directing multimeric expression than one with a T7 promoter. The expression level of large multimers was substantially increased with the tac promoter, possibly through stabilization of long transcripts by synchronization of transcription and translation. Coexpression of the DEAD-box protein, an RNA-binding protein, with the T7 expression system increased the expression level of multimers, especially large multimers, due to protection of the long RNA transcripts. In addition, the use of the trxB mutant also enhanced the expression level of tandem multimers, which contain two cysteine residues at both ends of the monomeric unit. It seems that disulfide bonds formed in the multimers in the trxB mutant might help efficient charge neutralization for inclusion body formation of the multimers, resulting in enhancement of expression. Our results show that the expression of multimers can be improved through the stabilization of the long transcripts by the DEAD-box protein or the expression, under an oxidizing environment, of the trxB mutant in which covalent cross-links through disulfide bonds facilitate inclusion body formation of the multimeric fusion peptide.

Abstract: The effects of gas velocity, inlet gas temperature and the solid feed rate on the drying efficiency, the outlet solid moisture content, bed temperature in each stage, the outlet gas humidity and temperature in a rectangular acryl multistage fluidized bed (0.172 m×0.192 m×1.5 m-high) with a downcomer (0.04 m-I.D.) were investigated. The experiments were performed by using 1.9 mm millet particles. The final moisture contents of the solids increased with increasing the solid feed rate. The drying efficiency increased with increasing the wetted solid feed rate but decreased with increasing the inlet gas temperature. The drying performance of the multistage fluidized bed was compared with the single-stage fluidized bed and found to be superior under identical operation conditions. The model predicted values were well matched with the experimental data in the multistage fluidized bed dryer.

Abstract: The displacement of carbon black to polypyrrole as a catalyst supporter in the fuel electrode of a direct methanol fuel cell was investigated. Polypyrrole was obtained as a black powder by the chemical polymerization of pyrrole with three different oxidants. The synthesized polypyrroles were pasted on carbon paper and transformed to the fuel electrodes with electrochemically deposited platinum. The prepared fuel electrode was assembled and mounted in a unit cell using a membrane and cathodic electrode film. In comparison with the carbon black fuel electrode, the performance of the unit cell was analyzed in relation to the state of the catalyst, the type of oxidant, and the morphology of the polypyrrole powder.

Abstract: Carbon Molecular Sieves (CMS) obtained by coke deposition through deep cracking of hydrocarbons on the wide pore mouths of coal and coconut char are important adsorbents for separation of, difficult to separate, gaseous as well as liquid mixtures. The adsorption studies on these CMS show a high selectivity towards the adsorption of one or the other component from its mixture. In this work, CMS is prepared from pre treated raw materials like bituminous coal and coconut shell. The product samples are characterized in terms of kinetic adsorption and equilibrium adsorption of various gas adsorbents. It is observed that, all these samples are very good for CO2 removal from mixtures containing CH4 or H2 in it. The CMS prepared from coconut shell showed an uptake ratio ∼4, for adsorption of O2 and N2, indicating that separation of nitrogen from air is viable by choosing suitable conditions in Pressure Swing Adsorption (PSA) Technique.

Abstract: The objective of this study was to verify experimentally the recovery of high-purity ethylene from LDPE off-gas by a vacuum swing adsorption process. Adsorbent for this purpose was prepared by the impregnation of AgNO3 on Montmorillonite clay. The prepared adsorbent with an original substrate-shaped form shows high adsorption selectivities of light olefins to the corresponding paraffins. A 4-bed vacuum swing adsorption process using the above adsorbent, in which steps comprise adsorption (feeding), cocurrent rinse with ethylene product, countercurrent desorption (production) of ethylene by vacuum pump, pressurization-1 with paraffin stream, pressurization-2 with the rinse off-gas from the other bed and pressurization-3 with paraffin stream, was experimentally applied to recover ethylene from LDPE off-gas. Ethylene product purity of 99.95% could be obtained with the recovery of over 93%. The ethylene productivity of prepared adsorbent was 1.98 mol/kg-hr.

Abstract: A dynamic game growth model with infrastructure capital is analyzed and it is shown that the pattern of growth can be either endogenous or exogenous depending on agents’ commitment behavior. If the agents commit their future actions, there is a unique Nash equilibrium with endogenous growth. However, if they cannot commit their future actions and they condition their actions on the state variable at each time, then for any level of infrastructure capital there exist infinitely many equilibria: some of them exhibit endogenous growth and others show no growth in the long run (or even in the short run).