A gantry-based tri-modality system for bioluminescence tomography

A gantry-based tri-modality system that combines bioluminescence (BLT), diffuse optical (DOT), and x-ray computed tomography (XCT) into the same setting is presented here. The purpose of this system is to perform bioluminescence tomography using a multi-modality imaging approach. As parts of this hybrid system, XCT and DOT provide anatomical information and background optical property maps. This structural and functional a priori information is used to guide and restrain bioluminescence reconstruction algorithm and ultimately improve the BLT results. The performance of the combined system is evaluated using multi-modality phantoms. In particular, a cylindrical heterogeneous multi-modality phantom that contains regions with higher optical absorption and x-ray attenuation is constructed. We showed that a 1.5 mm diameter bioluminescence inclusion can be localized accurately with the functional a priori information while its source strength can be recovered more accurately using both structural and the functional a priori information.     

Online monitoring of diallyldimethylammonium chloride polymerization

Diallyldimethylammonium chloride, which is an acidic salt with numerous applications, was polymerized in water at three different monomer concentrations and at three different pHs which the monomer is in charged form. Reactions were investigated by the automatic continuous online monitoring of polymerization technique. Conversion, molecular weight, and reduced viscosity were monitored. The reaction is found to be second‐order with respect to monomer. Rate constants and molecular weights tend to increase with pH and concentration. POLYM. ENG. SCI., 54:1350–1356, 2014. © 2013 Society of Plastics Engineers     

Rheological and fusion behaviors of PVC micro‐ and nano‐composites evaluated from torque rheometer data

The effects of calcium carbonate (CaCO₃) particle size on the fusion and rheological behaviors of rigid poly(vinyl chloride) (PVC) composites prepared in a Haake torque rheometer were investigated by means of torque data recorded during processing. Increasing the number of particles in the same blend volume by decreasing the particle size resulted in increasing frictional forces. This increase led in turn to increased fusion torque and decreased fusion time and temperature. The power‐law‐index values of the composites increased with decreasing particle size except for 25‐nm CaCO₃. The viscosities of all composites were found to decrease with shear rate; therefore, high pseudoplasticity was observed. At a particular rotor speed, viscosity of the composites decreased with decreasing particle size except for 25‐nm CaCO₃. The overall results showed that the particle size of CaCO₃ altered the fusion characteristics and rheological behavior of PVC. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Petrochemicals from ethanol over a W-Si-based nanocomposite bidisperse solid acid catalyst

Very high ethylene selectivity values approaching 100% and very high ethanol conversion values approaching 85% were obtained in dehydration of ethanol over a new W-silicate-based nanocomposite catalyst having both meso and macropores and containing a W/Si atomic ratio of 0.85. Silicotungsticacid was successfully incorporated into the catalyst structure following a one-pot hydrothermal synthesis procedure. This catalyst is highly stable and does not loose activity in polar solvents and it has a sufficiently high surface area for catalytic applications. Calcination temperature of the catalyst was found to have a very significant effect on the catalyst structure and also on its catalytic performance in ethanol dehydration. Maximum selectivity of the second major reaction product diethylether was obtained as 0.7 at 200 °C, with the catalyst which was calcined at 400 °C. Very high ethylene and diethylether yield values obtained in this study at different reaction conditions are highly promising for the production of petrochemicals from ethanol.     

Antimicrobial effect of PEG–PLA on food-spoilage microorganisms

Food Science and Biotechnology - Polyethylene glycol (PEG) and polyethylene glycol–polylactic acid (PEG–PLA) have an organic structure and no negative effect on human health. The...     

Effects of the time dependence of a bioluminescent source on the tomographic reconstruction

There are two goals in this simulation study: (1) to show that the time variation of the bioluminescence source can cause artifacts in the tomographic images such that quantification and localization becomes impossible; and (2) to show that the a priori knowledge of the light kinetics can be used to eliminate these artifacts. These goals are motivated by the fact that the half-life of luciferase has been reported as 30 min to 2 h in vivo. We perform two-dimensional simulations. We consider a 40 mm diameter circular region with an inclusion of 6 mm diameter located 10 mm away from the center. The measurement data is simulated using a finite-element-based forward solver. We model the noncontact measurements such that four-wavelength data is collected from four 90 degrees apart views. The results show that the ratio of the total imaging time to the half-life of the exponentially decaying bioluminescent source is the deciding factor in the reconstruction of the source. It is also demonstrated that a priori knowledge of the source kinetics is required to perform tomographic bioluminescence imaging of short half-life bioluminescent sources and the use of spatial a priori information alone is not adequate.     

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.     

Polyethersulfone containing sulfonimide groups as proton exchange membrane fuel cells

In this publication a new synthesis approach of polyethersulfone containing sulfonimide groups (SI-PES), by chemical modification of sulfonated polyethersulfone (S-PES), was developed. The synthesis protocol was optimized in order to turn all the sulfonic function into sulfonimide. The effect of replacing arylsulfonic acid function with a more acidic one, i.e. aryl trifluoromethanesulfonimide, was evaluated through thermal, dynamic mechanical analysis, water uptake and conductivity. For similar ionic exchange capacity (IEC), i.e. 1.8 H⁺/dm³, at 60 °C and 95% relative humidity, the conductivity of SI-PSF is 9.5 mS/cm while that of S-PSF is only 3.5 mS/cm. However, at 60 °C the water uptake is 3 times higher for SI-PSF membranes as compare with S-PSF. An important change is observed in the slope of the conductivity and water uptake plots of SI-PES membranes, at different temperatures, depending of IEC. This could be explained by an important change in membrane morphology.     

Preparation and characterization of palladium-plated porous glass for hydrogen enrichment

In this study, cylindrical porous glass tablets were plated by palladium using electroless plating technique. Hypophosphite and Co(II) complexes were used as reducing agents in the prepared plating baths. Experiments were carried out in an especially designed glass vessel in which helium gas was continuously bubbled through the solution to create uniform concentration and to remove hydrogen gas from the surface for the case of hypophosphite-based procedure. XRF analysis of the upper layer of the composite membrane prepared by the hypophosphite-based bath showed a Pd/Si ratio of 4.6. SEM photographs indicated impregnation of Pd into the substrate upto 200 μm. However, the thickness of the dense Pd layer was only about 15 μm. SEM photographs and XRF results showed that hypophosphite-based bath was much more successful than the Co(II) complex-bath in Pd plating. Permeation experiments carried out at different temperatures showed that the contribution of surface diffusion to the permeation was significant at low temperatures and solution–diffusion mechanism was not important in the 40–200 °C temperature range for these membranes. The selectivity ratio for H₂/N₂ was found to be about 7 at 200 °C.     

Activity and stability enhancement of Ni-MCM-41 catalysts by Rh incorporation for hydrogen from dry reforming of methane

Ni incorporated and Ni–Rh incorporated bimetallic MCM-41 like mesoporous catalysts, which were synthesized following a one-pot hydrothermal procedure, showed very high activity in dry reforming of methane. Among the Ni incorporated catalysts, Ni-MCM-41-V, with a Ni/Si ratio of 0.19, showed the best catalytic performance. Rh incorporation into this catalyst by the one-pot procedure improved both activity and time on stream stability of the catalyst. However, Rh incorporation by impregnation caused instabilities due to coke formation, after about 11 h of reaction time. Occurrence of reverse water gas shift reaction caused higher CO selectivity than H₂ selectivity, with the Ni incorporated catalysts. Rh incorporation into these catalysts decreased the relative significance of reverse water gas shift reaction, with respect to dry reforming reaction.