CFD analysis of water gas shift membrane reactor

Fuel cell based modular power generation can be achieved by miniaturization and process intensification of equipments in the process. Fuel cells require hydrogen rich gas which can be generated through reforming and water gas shift reaction. The water gas shift reactor being kinetically limited occupies more volume to achieve the required CO conversion. A membrane reactor integrates the reaction and hydrogen separation stages and hence reduces the volume requirement. Computational Fluid Dynamics offers virtual prototyping of the reactor and thus helps in design, optimization and scale up of reactors. In this study customized User Defined Functions (UDFs) were developed to analyze the performance of low temperature water gas shift membrane reactor. The models were validated using literature data for the parameters – synthesis gas compositions, time factor, sweep flow rate and steam to CO ratio. The effect of all these parameters on the reactor was analyzed for CO conversion, H₂ recovery, DaPe, concentration polarization, concentration profiles and conversion index. The simulations have showed that the UDFs developed were capable of simulating the membrane reactor and this can be used for the design and optimization of the membrane reactor for any process conditions.     

The thiazide-sensitive Na-Cl cotransporter is an aldosterone-induced protein

Although the collecting duct is regarded as the primary site at which mineralocorticoids regulate renal sodium transport in the kidney, recent evidence points to the distal convoluted tubule as a possible site of mineralocorticoid action. To investigate whether mineralocorticoids regulate the expression of the thiazide-sensitive Na-Cl cotransporter (TSC), the chief apical sodium entry pathway of distal convoluted tubule cells, we prepared an affinity-purified, peptide-directed antibody to TSC. On immunoblots, the antibody recognized a prominent 165-kDa band in membrane fractions from the renal cortex but not from the renal medulla. Immunofluorescence immunocytochemistry showed TSC labeling only in distal convoluted tubule cells. Semiquantitative immunoblotting studies demonstrated a large increase in TSC expression in the renal cortex of rats on a low-NaCl diet (207 +/- 21% of control diet). Immunofluorescence localization in tissue sections confirmed the strong increase in TSC expression. Treatment of rats for 10 days with a continuous subcutaneous infusion of aldosterone also increased TSC expression (380 +/- 58% of controls). Furthermore, 7-day treatment of rats with an orally administered mineralocorticoid, fludrocortisone, increased TSC expression (656 +/- 114% of controls). We conclude that the distal convoluted tubule is an important site of action of the mineralocorticoid aldosterone, which strongly up-regulates the expression of TSC.     

Development of immortalized human cerebromicrovascular endothelial cell line as an in vitro model of the human blood-brain barrier

The objective of this study was to generate an immortal cell line representative of specialized human brain microvascular endothelia forming the blood-brain barrier (BBB) in vivo. Human capillary and microvascular endothelial cells (HCEC) were transfected with the plasmid pSV3-neo coding for the SV40 large T antigen and the neomycin gene. The neomycin-resistant transfected cells overcame proliferative senescence, and after a 6-8 wk period of crisis produced immortalization-competent cell colonies. Single-cell clones of near-diploid genotype were isolated from these colonies, propagated, and characterized. Immortalized HCEC (SV-HCEC) exhibited accelerated proliferation rates, but remained serum and anchorage dependent and retained the characteristic cobblestone morphology at confluence. SV-HCEC displayed a stable nuclear expression of SV40 large T antigen, lacked the invasiveness of transformed cells, and maintained major phenotypic properties of early passage control cells including expression of factor VIII-related antigen, uptake of acetylated low-density lipoprotein, binding of fluorescently labeled lectins, expression of transferrin receptor and transferrin receptor-mediated endocytosis, and high activities of the BBB-specific enzymes alkaline phosphatase and gamma-glutamyl transpeptidase. The diffusion of radiolabeled sucrose across SV-HCEC monolayers was fivefold lower than that observed with human lung microvascular endothelial cells. Furthermore, media conditioned by fetal human astrocytes increased the transendothelial electrical resistance of SV-HCEC monolayers by 2.5-fold. Therefore, this newly established human cell line expressing the specialized phenotype of BBB endothelium may serve as a readily available in vitro model for studying the properties of the human BBB.     

Acetals as nucleating agents for polypropylene

Nucleating agents increase the impact strength, tensile strength, and tensile elasticity modulus of semicrystalline polymers. Nucleating agents also decrease product cycle times, resulting in a cost savings per product unit. We have synthesized and tested 15 compounds as nucleactors for polypropylene. Of these, trinapthylidene sorbitol, tri-(4-methyl-1-naphthylidene)sorbitol, tri-(4-methoxy-1-naphthylidene) sorbitol, and dibenzylidene xylitol are efficient nucleators of polypropylene. Trinaphthylidene sorbitol (tns) has two major diastereomers: The “S” diastereomer yields a faster crystallization rate for polypropylene than does the commercial nucleator dibenzylidene sorbitol (Millad 3905). Crystallization rates are 208 and 88, respectively (t min^?1 × 1000). The “R” diastereomer, however, is a poor nucleator and interferes with the nucleating activity of the “S” diastereomer. A 52/48 mixture of diastereomers does not nucleate polypropylene, even at twice the concentration. This is first time that the importance of stereochemistry has been demonstrated in the nucleating action. © 1994 John Wiley & Sons, Inc.     

Adsorption of 2,4-dichlorophenol on metal-nitrate modified activated carbon

To remove 2,4-dichlorophenol (2,4-DCP) from aqueous solution, the surface of the activated carbon was first treated with HCl and then the surface was modified by using various metal ions (Cu, Co, Fe, Ni, Zn, and Mg). Metal doping significantly enhanced the adsorption efficiency of activated carbon, an effect that was further increased by HCl treatment of the modified activated carbons. Of all the preparations, the zinc(II)-modified activated carbon with HCl treatment showed the highest adsorption capacity for 2,4-DCP. Analysis of the zinc(II)-modified activated carbon by SEM and BET showed a surface area and micropore volume of around 1,154.69 m²/g and 0.291 cm³/g, respectively, values about 20% higher than in the starting material. In the pH range of 2.0–11.0, the maximum uptake of 2,4-DCP from an initial concentration of 1,000 mg/L was 508 mg/g at pH 4.0.     

Selection of optimal machining parameters for hexapod machine tool

Parallel kinematic machine tools (PKM) have the advantages of higher stiffness, higher payload capacity and lower inertia. Still their penetration into the machine tool industry is very less. One of the difficulties in using PKMs such as hexapod machine tools is that the stiffness continuously varies with configuration change at every instant. This makes location of work piece and selection of machining parameters difficult and complicated. A methodology is presented in this article to select optimal machining parameters for hexapod machine tools. Particle swarm optimization is used as a tool in the optimization process. A profile-milling example is also presented to demonstrate the selection of machining parameters.     

Rind of the rambutan, Nephelium lappaceum, a potential source of natural antioxidants

The rind of rambutan, which is normally discarded was found to contain extremely high antioxidant activity when assessed using several methods. Although having a yield of only 18%, the ethanolic rambutan rind extract had a total phenolic content of 762 ± 10 mg GAE/g extract, which is comparable to that of a commercial preparation of grape seed extract. Comparing the extract’s pro-oxidant capabilities with vitamin C, α-tocopherol, grape seed and green tea, the rind had the lowest pro-oxidant capacity. In addition, the extract at 100 μg/ml was seen to limit oxidant-induced cell death (DPPH at 50 μM) by apoptosis to an extent similar to that of grape seed. The extracts were not cytotoxic to normal mouse fibroblast cells or splenocytes while the powderised rind was seen to have heavy metals contents far below the permissible levels for nutraceuticals. Our study for the first time reveals the high phenolic content, low pro-oxidant capacity and strong antioxidant activity of the extract from rind of Nephelium lappaceum. This extract, either alone or in combination with other active principles, can be used in cosmetic, nutraceutical and pharmaceutical applications.     

Laser from the dimer state of a conjugated polymer (PFO) in solution

The spectral and laser properties of the conjugated polymer poly (9,9-dioctylfluorenyl-2, 7-diyl) (PFO) in benzene have been studied and presented in this paper. The absorption spectra of PFO in benzene under low concentration showed that there was only one peak at 390 nm. When the concentration was increased, a new peak at 437 nm appeared additionally, indicating dimer formation at higher concentration of PFO in benzene. The fluorescence spectra for low concentration showed two peaks at 422 nm and 444 nm, which could be attributed to the monomer and the excimer. At the longer wavelength side of these spectra, there was a hump at 465 nm. This hump became dominant for higher concentrations and in low temperatures, while the other peaks became weaker. So, this new peak at 465 nm may be due to the dimer. For still higher concentrations, the peaks at 422 nm and 444 nm vanished and there was a dominant peak only at 465 nm. Under suitable concentration and pump power excitation of Nd: YAG laser (355 nm) the amplified spontaneous emission (ASE) spectra were obtained. It could be seen that there were three ASE peaks at 422, 444 and 470 nm. These peaks could be attributed to the monomer, excimer and dimer respectively. This is perhaps the first report on ASE from dimers of the conjugated polymer, PFO in liquid solution.