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     

Ru incorporated Ni-MCM-41 mesoporous catalysts for dry reforming of methane: Effects of Mg addition, feed composition and temperature

Nickel incorporated MCM-41-like mesoporous materials, which were synthesized following a one-pot hydrothermal route, were promoted by Ru and Mg in order to improve their catalytic performances for dry reforming of methane. In this study, Ni-MCM-41 based catalysts (with a Ni/Si molar ratio of 0.2), containing different amounts of Ru (0.5-3.0 wt%) and Mg (1 and 5 wt%) were prepared by using sequential impregnation of Ru and Mg into Ni-MCM-41. Dry reforming of methane was studied in a tubular flow reactor in the temperature range of 500-600 °C with different CH₄/CO₂ ratios in the feed stream. Quite high hydrogen yield values and improved stability of these catalysts indicated the promoting effects of Ru for the Ni-MCM-41 type catalysts. Ru incorporation (1.0% Ru) was shown to improve H₂ yields. Mg impregnation into 1.0Ru@Ni-MCM-41 improved catalytic performance by increasing CH₄ conversion and decreasing the contribution of reverse water gas shift reaction, especially at initial times (first 60 min). Coke formation by decomposition of CH₄ contributed to the hydrogen selectivity, but did not cause significant change in catalytic performance, especially at longer reaction times.     

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     

Hydrogen diffusivity enhancement in alumina pellets due to impregnated palladium

Single-pellet moment technique was used for the evaluation of effective diffusivities and adsorption equilibrium constants of hydrogen, carbon dioxide, and helium in pure alumina and palladium-impregnated alumina pellets. It was found that hydrogen was strongly adsorbed on palladium of Pd-alumina pellets, and significant enhancement of hydrogen diffusivity was observed due to impregnated palladium at 40°C. On the other hand, for carbon dioxide and helium, effective diffusivities obtained in Pd-alumina pellets were smaller than the corresponding values in pure alumina due to higher tortuosity factor values of Pd-alumina pellets.     

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.     

SMAQ: a measurement-based tool for traffic modeling and queuinganalysis. II. Network applications

For pt. I see ibid. p.56-65 (1998). SMAQ is a measurement-based tool for integration of traffic modeling and queuing analysis. It can be used in a variety of network design areas. For instance, it can be used as a traffic generator to generate various traces for network testing. It also provides numerical solutions of the queue length and loss rate performance for transport of multimedia traffic. Several application modules are built into the tool for the evaluation of statistical multiplexing, buffer dimensioning, and link bandwidth allocation. Other examples include the evaluation of traffic shaping, local-congestion control, and the modeling of wireless channel dynamics. As one will find, the SMAQ tool indeed provides a solution technique for network engineers to solve many of the current design issues     

Synthesis and characterization of V,Mo and Nb incorporated micro–mesoporous MCM-41 materials

Highly microporous metal-MCM-41 ordered mesoporous structure catalysts having different metal/Si (V, Mo, Nb) atomic ratios and combinations of metal sources were hydrothermally synthesized. The structural properties estimated using different techniques were found to be in agreement with each other. Metals were successfully incorporated into MCM-41 without deteriorating the ordered hexagonal structure. The metal ions in the synthesis solutions probably settled on the hydrophilic end of the template hence the metal incorporation resulted improvements in the micropore structure. Low loading of metals caused an increase in the surface area and pore volume values of the catalysts. The highest total (1310 m² g^?1) and micropore surface area values (1083 m² g^?1) were obtained by Nb incorporation. The micro- and mesopore dimensions of MCM-41 increased from 0.5 to 1.1 nm and from 2.5 to 2.8 nm, respectively, with metal incorporation. Low V/Si ratios and presence of Nb in the starting solution enhanced narrow mesopore size distribution. The pore dimension and wall thickness values estimated from nitrogen adsorption and X-ray diffraction methods were consistent with the corresponding values obtained using transmission electron microscopy.     

Collapse of acrylamide‐based polyampholyte hydrogels in water

The swelling behavior of balanced acrylamide (AAm)‐based polyampholyte hydrogels in water and in aqueous salt (NaCl) solutions was investigated. Equimolar ratio of the ionic comonomers 4‐vinylpyridine (cationic monomer) and acrylic acid (anionic monomer) were used together with the nonionic monomer AAm in the hydrogel preparation. The variations of the hydrogel volume in response to changes in pH were measured. It was found that the hydrogels are in a collapsed state not only at the pH of the isoelectric point pH_IEP but also over a wide range of pH including pH_IEP. The width of the collapsed plateau increased and the hydrogels assumed a more compact state as the ionic group content is increased. The antipolyelectrolyte behavior was observed along the collapsed plateau region, where the gel occupies a larger volume in salt solution. The experimental swelling data were compared with the predictions of the Flory‐Rehner theory of swelling equilibrium including the ideal Donnan equilibria. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

MCM-41 supported PdNi catalysts for dry reforming of methane

A series of bimetallic PdNi catalysts supported on mesoporous MCM-41 with different Ni content (Ni/Si ratio of 0.2–0.4) was synthesized. The effect of Pd addition to Ni-containing catalysts as well as the effect of the Ni content on the surface and catalytic properties of the catalysts was studied. The samples were characterized using various techniques, such as energy-dispersive X-ray spectroscopy, N₂ adsorption–desorption isotherms, X-ray diffraction, thermogravimetric and differential analyses, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and temperature-programmed reduction. Reforming of methane with carbon dioxide was used as a test reaction. The results indicated that the addition of a small amount of Pd (0.5%) to Ni-containing catalysts leads to formation of small nano-sized, easy reducible NiO particles. Agglomeration of NiO as well as of metallic nickel phase over PdNi samples increased with increasing the Ni content. Formation of filamentous carbon over surface of spent monometallic Ni and bimetallic PdNi catalyst was observed. In spite of filamentous carbon deposition, the catalytic activity and stability of bimetallic PdNi catalysts are higher than those of monometallic Ni one. Within bimetallic system, the PdNi catalyst with Ni/Si ratio of 0.3 revealed the best performance and stability caused by presence of small nickel particles well dispersed on the catalyst surface.