Compensation Effect of Benzene Hydrogenation on Pt(111) and Pt(100) Analyzed by the Selective Energy Transfer Model

Kinetic measurements at low temperatures (310–360 K) using gas chromatography (GC) for benzene hydrogenation on Pt(100) and Pt(111) single crystal surfaces have been carried out at Torr pressures. These kinetic measurements demonstrated a linear compensation effect for the production of cyclohexane. A detailed application of the model of selective energy transfer to the experimentally obtained results yields the vibrational frequency of the adsorbate leading to reaction. This frequency is attributed to ring distortion modes. The vibrational frequency of the heat bath, or catalyst, is ascribed to a Pt-H mode. An approximate heat of adsorption of the reacting molecule is also calculated from the model.     

Structure and properties of amine‐hardened epoxy/benzoxazine hybrids: Effect of epoxy resin functionality

Bifunctional, trifunctional, and tetrafunctional epoxy resins (EP) were hardened with stoichiometric amount of 4,4′‐diaminodiphenyl methane in presence and absence of benzoxazine (BOX). The EP/BOX ratio of the hybrid systems was 100/0, 75/25, 50/50, and 25/75 wt %, respectively. Information on the structure of the hybrid systems was received from differential scanning calorimetry, dynamic‐mechanical thermal analysis, atomic force microscopy, and fractographic studies. The flexural and fracture mechanical properties of the EP/BOX hybrids were determined and compared to those of the reference EPs. The thermal degradation and fire resistance of the hybrids were also studied. It was found that the polymerized BOX was built in the network in from of nanoscale inclusions and acted as antiplasticizer. Incorporation of BOX enhanced the flexural modulus and strength and reduced the glass transition temperature of the parent EP. The fracture toughness and energy were practically not improved by hybridization with BOX. The charring and flame resistance were improved with increasing amount of BOX in the EP/BOX hybrids. The relative improvement in the latter was most prominent for the bifunctional EP/BOX systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of augmented reality training on percutaneous needle placement in spinal facet joint injections

The purpose of this study was to determine if augmented reality image overlay and laser guidance systems can assist medical trainees in learning the correct placement of a needle for percutaneous facet joint injection. The Perk Station training suite was used to conduct and record the needle insertion procedures. A total of 40 volunteers were randomized into two groups of 20. 1) The Overlay group received a training session that consisted of four insertions with image and laser guidance, followed by two insertions with laser overlay only. 2) The Control group received a training session of six classical freehand insertions. Both groups then conducted two freehand insertions. The movement of the needle was tracked during the series of insertions. The final insertion procedure was assessed to determine if there was a benefit to the overlay method compared to the freehand insertions. The Overlay group had a better success rate (83.3% versus 68.4%, p=0.002), and potential for less tissue damage as measured by the amount of needle movement inside the phantom (3077.6 mm(2) versus 5607.9 mm(2) , p =0.01). These results suggest that an augmented reality overlay guidance system can assist medical trainees in acquiring technical competence in a percutaneous needle insertion procedure.     

Swelling,compression and tribological behaviors of bentonite‐modified polyacrylate‐type hydrogels

Hydrogel was synthesized from acrylamide and 2‐acryloylamido‐2‐methylpropanesulfonic acid monomers (ratio: 50/50 wt %) and crosslinked with 0.25 wt % of methylene‐bisacrylamide. This hydrogel was also modified by adding 4 wt % of sodium bentonite (NB). Selected properties of the hydrogels with and without NB were investigated and compared. Their water uptake was measured gravimetrically; the compression and compression creep were assessed by dynamic‐mechanical and thermo‐mechanical analysis (DMA and TMA, respectively) techniques. The friction and wear of the hydrogels were determined in a shaft(metal)‐on‐plate(hydrogel) type testing configuration under water lubrication. The hydrogel was transparent and exhibited very high equilibrium water content (>99 wt %). The latter was less affected; however, the hydrogel became slightly more hazy after NB incorporation. The crosslink density of the hydrogels was deduced from swelling and compression tests and compared with the theoretical values. Modification by NB enhanced the ultimate compression strength and reduced the related compression strain. The compression creep response under both loading and deloading strongly depended on the level of the initial load. A very low friction coefficient (～ 0.003) and a relatively high specific wear rate (～ 0.05 mm³/N m) were registered under water lubricated sliding wear using a metallic counterpart with high surface roughness. Scanning electron microscopy combined with energy dispersive spectroscopy delivered additional information on the NB dispersion and surface structure of the hydrogels. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Essential work of fracture of poly(ϵ‐caprolactone)/boehmite alumina nanocomposites: Effect of surface coating

The essential work of fracture (EWF) approach was adopted to reveal the effect of nanofillers on the toughness of poly (?‐caprolactone) (PCL)/boehmite alumina (BA) nanocomposites. Synthetic BA particles with different surface treatments were dispersed into the PCL matrix by extrusion melt compounding. The morphology of the composites was studied by scanning electron microscopy. Differential scanning calorimetry and wide‐angle X‐ray scattering were used to detect changes in the crystalline structure of PCL. Also, mode I type EWF tests, dynamic mechanical analysis, and quasi‐static tensile tests were applied to study the effect of the BA nanofillers on the mechanical properties of the nanocomposites. BA was homogeneously dispersed and acted as heterogeneous crystallization nucleant and a nonreinforcing filler in PCL. The tensile modulus and yield strength slightly increased and the yield strain decreased with increasing BA content (up to 10 wt %). The effect of the BA surface treatment with octylsilane was negligible by contrast to that with alkylbenzene sulfonic acid (OS2). Like the tensile mechanical data, the essential and nonessential work of fracture parameters did not change significantly either. The improved PCL/BA adhesion in case of OS2 treatment excluded the usual EWF treatise. This was circumvented by energy partitioning between yielding and necking. The yielding‐related EWF decreased, whereas the nonessential EWF increased with BA content and with better interfacial adhesion. This was attributed to the effect of matrix/filler debonding. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure,thermal, and mechanical properties of DDM‐hardened epoxy/benzoxazine hybrids: Effects of epoxy resin functionality and ETBN toughening

Bifunctional, trifunctional, and tetrafunctional epoxy (EP) resins were hardened with stoichiometric amount of 4,4′‐diaminodiphenyl methane in presence and absence of benzoxazine (BOX). The EP/BOX ratio of the hybrid systems was constant, viz. 50/50 wt %. For the bifunctional EP, the EP/BOX range covered the ratios 75/25 and 25/75 wt %, as well. Epoxy‐terminated liquid nitrile rubber (ETBN) was incorporated in 10 wt % in the systems with trifunctional and tetrafunctional EP, and in 10, 15, and 20 wt % in the EP/BOX with bifunctional EP to improve their toughness. Information on the structure and morphology of the hybrid systems was received from differential scanning calorimetric, dynamic‐mechanical thermal analysis, atomic force microscopic, and scanning electron microscopic studies. The flexural, fracture mechanical properties, thermal degradation, and fire resistance of the EP/BOX and EP/BOX/ETBN hybrids were determined. It was found that some homopolymerized BOX was built in the EP/BOX conetwork in form of nanoscale inclusions, whereas ETBN formed micron scaled droplets of sea‐island structure. Incorporation of BOX improved the charring and fire resistance, enhanced the flexural modulus and strength, reduced the glass transition (T_g), the fracture toughness, and energy. Additional modification with ETBN decreased the charring, fire resistance, flexural modulus and strength, as well as T_g, however, improved the fracture toughness and especially the fracture energy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Catalysis in Energy Generation and Conversion: How Insight Into Nanostructure, Composition, and Electronic Structure Leads to Better Catalysts (Perspective)

Catalysts are essential for the generation of energy carriers like hydrocarbon fuels, hydrogen, and electrical current. The performance of catalysts can be related to their nanostructure (i.e., size and shape) and composition. To rationally design catalysts by tuning these properties, they should be measured in a meaningful way using surface-sensitive spectroscopic tools under reaction conditions. In this perspective, we provide case histories of recently published research aimed at understanding these properties using a spectroscopic strategy under reaction conditions. We limit this perspective to studies whose main focus was to understand how the nanostructure and composition impact the active phase and/or efficiency of catalysts for the generation and conversion of energy carriers. We discuss studies of a Pd/Ga₂O₃ catalyst for the generation of hydrogen fuel from methanol and water, a PtMo catalyst for the generation of hydrogen fuel from biomass and water, Pt/Rh catalysts for the conversion of hydrogen into electrical current, a CeO _x catalyst for the conversion of hydrogen into electrical current, and Fe and Co/CoPt catalysts for the generation of hydrocarbon fuel from carbon monoxide and hydrogen. Each study emphasizes how the use of spectroscopic tools under reactive conditions is beneficial for making rational decisions for improving catalysts. The studies demonstrate how different synthesis methods dictate the nanostructure and distribution of alloy components in the catalyst, certain pretreatment conditions create the active surface phase, while reactions and post-treatments can destroy it, and the nanostructure and composition change the electronic structure and alter the selectivity and activity.     

Chemical natures and distributions of metal impurities in multicrystalline silicon materials

We present a comprehensive summary of our observations of metal‐rich particles in multicrystalline silicon (mc‐Si) solar cell materials from multiple vendors, including directionally‐solidified ingot‐grown, sheet, and ribbon, as well as multicrystalline float zone materials contaminated during growth. In each material, the elemental nature, chemical states, and distributions of metal‐rich particles are assessed by synchrotron‐based analytical x‐ray microprobe techniques. Certain universal physical principles appear to govern the behavior of metals in nearly all materials: (a) Two types of metal‐rich particles can be observed (metal silicide nanoprecipitates and metal‐rich inclusions up to tens of microns in size, frequently oxidized), (b) spatial distributions of individual elements strongly depend on their solubility and diffusivity, and (c) strong interactions exist between metals and certain types of structural defects. Differences in the distribution and elemental nature of metal contamination between different mc‐Si materials can largely be explained by variations in crystal growth parameters, structural defect types, and contamination sources. Copyright © 2006 John Wiley & Sons, Ltd.     

Sulbactam/ampicillin in comparison with cefuroxime for infections of the lower respiratory tract. Results of a prospective, randomized comparative study

Gallbladder removal using laparoscopic techniques has rapidly been adopted by surgeons around the world. Questions have been raised concerning laparoscopic cholecystectomy, including the safety of the operation, its implications for management of common bile duct stones, and the means by which surgeons should be trained. In the present series, 424 patients were referred to a single surgeon for cholecystectomy during a 22-month period. A traditional open cholecystectomy was performed in 9 patients (2.1%) because of presumed contraindications to laparoscopic cholecystectomy. Laparoscopic cholecystectomy was attempted in the remaining 415 patients (97.9%). On the basis of preoperative investigations, 19 patients (4.6%) underwent endoscopic retrograde cholangiopancreatography. Endoscopic sphincterotomy and stone extraction were performed in the 13 patients (3.1%) demonstrating choledocholithiasis. Laparoscopic cholecystectomy was converted to an open operation in 8 patients (1.9%) owing to dense adhesions, obscure anatomy, or cholangiographic abnormalities. Laparoscopic cholecystectomy was successfully performed in 407 patients (96%) in 95 +/- 2 minutes (mean +/- SEM). Surgical trainees were involved in all operations and performed 68% of the procedures under supervision. Cystic duct cholangiograms were obtained selectively in 129 patients (30.4%). Intraoperative complications occurred in 3 patients, including 1 patient with a minor injury to the common bile duct (0.2%). There was no perioperative mortality, and major complications occurred in 6 patients (1.4%). Minor complications were seen in 12 others (2.8%), and one patient required reoperation for a trocar injury to the jejunum. Prolonged follow-up has revealed one case of asymptomatic retained common bile duct stones (0.2%). Laparoscopic cholecystectomy can therefore be performed in more than 95% of patients with no mortality and minimal morbidity.(ABSTRACT TRUNCATED AT 250 WORDS)