Comparison of microwave and conventionally heated reactor performances in catalytic dehydrogenation of ethane

In the present study, non-oxidative dehydrogenation of ethane was carried out by using conventional heated (CHRS) and microwave heated (MWHRS) reactor systems. Reactions were conducted in the presence of SBA-15 supported Cr or Mo catalysts, and the activity of the catalysts were evaluated in terms of ethane conversion and C₂H₄/H₂ ratio. The physicochemical properties of synthesized catalysts were determined by XRD, N₂ adsorption/desorption, ICP-OES, TPR, SEM, and EDS analysis. XRD pattern of reduced catalysts revealed the formation of metallic Mo and Eskolaite Cr₂O₃ over the catalysts. The mesoporous structure of SBA-15 was confirmed using N₂ adsorption/desorption analysis. Activity test results showed higher ethane conversion in the presence of Mo than Cr in both reactor systems. However, more side reaction took place over Mo than Cr based catalysts. Cr based catalyst showed better activity in terms of ethylene formation and C₂H₄/H₂ ratio. Results proved the superior performance of microwave heated reactor over the conventionally heated reactor. Significantly higher conversion was obtained over Cr based catalysts in MWHRS than CHRS due to the occurrence of micro-plasmas (hot spots) in the catalyst bed. The performance of 5Cr@SBA-15 in CHRS was poor due to negligible ethane conversion below 650 °C, while almost complete conversion could be achieved in MWHRS with this catalyst at identical conditions. The ethane conversion values obtained at 650 °C in CHRS were achieved at 450 °C, in MWHRS.     

Comparative costs of family planning services and hospital-based maternity care in Turkey

The effect of dietary fats on the chemical composition and enzyme activities has been studied in intestinal brush border membranes (BBM) or rats. Animals were given commercial rat pellet diet (RP) or semisynthetic diet rich in either saturated [coconut oil (CCO))] or polyunsaturated [n-6, corn oil (CO) or n-3, fish oil (FO)] fat at the 10% level for 5 weeks. The membrane cholesterol/phospholipid ratio was augmented in CO- or RP-fed rats. There was an increase in level of saturated fatty acids in BBM from CCO- or FO-fed animals. n-3 polyunsaturated fatty acid content was raised in FO-fed rats, while the proportion of linoleic acid and arachidonic acid was enhanced in animals given a CO diet. Membrane fluidity was in the order of CCO < RP = CO < FO. The membrane hexose content was high (p < 0.05) in the CCO group. Hexosamines were elevated (p < 0.05) in CCO- or FO-fed rat brush borders. Membrane fucose was unaltered, while sialic acid content was elevated in CO- (p < 0.05) and FO- (p < 0.01) fed vs. CCO-fed rats. Lectin binding to brush borders corroborated these findings. The activities of alkaline phosphatase, sucrase and lactase were augmented (p < 0.001) in CCO-fed animals. Leucine-aminopeptidase and sucrase activities were depressed by FO feeding. The activities of PNP-beta-glycosidases were the highest in FO-fed rats. These results indicate that dietary fat quality markedly affects microvillus membrane lipid composition, glycosylation and enzyme functions in rat intestine.     

Activated carbon supported silicotungstic acid catalysts for ethyl‐tert‐butyl ether synthesis

Vapor phase ethyl‐tert‐butyl ether (ETBE) production was conducted in the presence of Cesium salts of silicotungstic acid (Cs‐STA), activated carbon supported silicotungstic acid (AC‐STA), and activated carbon supported Cesium salts of silicotungstic acid (AC‐Cs‐STA) catalysts. Isobutene (IB) conversion to ETBE at 373 K were determined as 0.16 and 0.2 for STA and AC‐STA catalysts on constant space time basis. This increase of activity is one of the highlights of this study considering that STA loading in AC‐STA catalysts had been adjusted to 40%. IB conversion to ETBE obtained at 373 K in the presence of AC‐STA catalyst was found to be close to equilibrium. Stability of the synthesized catalysts were tested by applying a washing procedure with ethanol. Repeated ETBE synthesis with thoroughly washed samples indicated quite stable and active catalyts. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

Differentiation of Corynebacterium amycolatum, C. minutissimum, and C. striatum by carbon substrate assimilation tests

We tested the carbon substrate assimilation patterns of 40 Corynebacterium amycolatum strains, 19 C. minutissimum strains, 50 C. striatum strains, and 1 C. xerosis strain with the Biotype 100 system (bioMérieux, Marcy-l'Etoile, France). Twelve carbon substrates of 99 allowed discrimination among the species tested. Additionally, assimilation of 3 of these 12 carbon substrates (maltose, N-acetyl-D-glucosamine, and phenylacetate) was tested with the API 20 NE identification system (bioMérieux). Since concordant results were observed with the two systems for these three carbon substrates, either identification system can be used as a supplementary tool to achieve phenotypic differential identification of C. amycolatum, C. minutissimum, and C. striatum in the clinical microbiology laboratory.     

Enhancement of fibrinolysis with 40-kHz ultrasound

BACKGROUND: Ultrasound at frequencies of 0.5 to 1 MHz and intensities of > or =0.5 W/cm2 accelerates enzymatic fibrinolysis in vitro and in some animal models, but unacceptable tissue heating can occur, and limited penetration would restrict application to superficial vessels. Tissue heating is less and penetration better at lower frequencies, but little information is available regarding the effect of lower-frequency ultrasound on enzymatic fibrinolysis. We therefore examined the effect of 40-kHz ultrasound on fibrinolysis, tissue penetration, and heating. METHODS AND RESULTS: 125I-fibrin-radiolabeled plasma clots in thin-walled tubes were overlaid with plasma containing tissue plasminogen activator (tPA) and exposed to ultrasound. Enzymatic fibrinolysis was measured as solubilization of radiolabel. Tissue attenuation and heating were examined in samples of porcine rib cage. Fibrinolysis was increased significantly in the presence of 40-kHz ultrasound at 0.25 W/cm2, reaching 39+/-7% and 93+/-11% at 60 minutes and 120 minutes, compared with 13+/-8% and 37+/-4% in the absence of ultrasound (P<0.0001). The acceleration of fibrinolysis increased at higher intensities. Attenuation of the ultrasound field was only 1.7+/-0.5 dB/cm through the intercostal space and 3.4+/-0.9 dB/cm through rib. Temperature increments in rib were <1 C/(W/cm2). CONCLUSIONS: These findings indicate that 40-kHz ultrasound significantly accelerates enzymatic fibrinolysis at intensities of > or =0.25 W/cm2 with excellent tissue penetration and minimal heating. Externally applied 40-kHz ultrasound at low intensities is a potentially useful therapeutic adjunct to enzymatic fibrinolysis with sufficient tissue penetration for both peripheral vascular and coronary applications.     

Role of zinc in the structure and toxic activity of botulinum neurotoxin

Zn2+-protease activity of botulinum neurotoxin causes the blockage of neurotransmitter release resulting in botulism disease. We have investigated the role of Zn2+ in the biological activity of type A botulinum neurotoxin by removing the bound Zn2+ by EDTA treatment, followed by monitoring its structure in terms of secondary and tertiary folding (second derivative UV, FT-IR, and circular dichroism spectroscopy) and function in terms of its effect on the release of norepinephrine from PC12 cells. The single Zn2+ bound to each neurotoxin molecule was reversibly removed by EDTA treatment, whereas the biological activity of the neurotoxin was irreversibly lost. Based on the Amide III IR spectral analysis, the alpha-helical content of neurotoxin increased from 29% to 42% upon removal of Zn2+, which reverted to 31% upon treatment with 1:5 molar excess of exogenous Zn2+. Second derivative UV spectroscopy revealed no change in surface topography of Tyr residues with removal of Zn2+. However, near-UV circular dichroism signals suggested significant alterations in the topography of Phe and Tyr residues that could be buried in the protein matrix. Thermal unfolding experiments suggested that removal of Zn2+ results in the formation of the molten globule-like structure of type A botulinum neurotoxin. Tertiary structural changes introduced by Zn2+ removal were irreversible, which correlated well with the irreversibility of the biological activity of the neurotoxin. On the basis of these results, we suggest that Zn2+ plays a significant structural role in addition to its catalytic role in Zn2+-protease activity of type A botulinum neurotoxin.