Palladium-indium catalyzed reduction of N-nitrosodimethylamine: indium as a promoter metal

An emerging technology for the removal of N-nitrosodimethylamine (NDMA) from drinking and groundwater is reductive destruction using noble metal catalysts and hydrogen gas as a reducing agent. Bimetallic palladium-indium (Pd-In) supported on alumina combines the ability of Into activate NDMA with the hydrogen activating properties of Pd. This study examined the effect of In addition to a commercial 5% Pd by weight on gamma-Al2O3 catalyst on the efficacy of NDMA reduction. The pseudo-first-order rate constant increased proportionately to In loading from 0.057 h(-1) for 0% In to a maximum of 0.25 h(-1) for 1% In and then decreased with additional in loading. Data suggest that hydrogen activation occurred only on Pd surfaces and In activated NDMA 20 times more effectively than Pd on a mass basis. The rate-limiting factor was NDMA activation for In loadings below 1%. The decrease at higher loadings is interpreted as In blocking pore spaces and limiting access to Pd sites, suggesting monatomic hydrogen limitation. The only products detected were dimethylamine and ammonium with carbon and nitrogen balances in excess of 92%, consistent with a mechanism involving reductive N-N bond cleavage. Results from this study serve as a basis for optimizing bimetallic catalysts for treating NDMA contaminated waters.     

Trichloroethene dechlorination and H2 evolution are alternative biological pathways of electric charge utilization by a dechlorinating culture in a bioelectrochemical system

Recently,the proof-of-principle of an innovative bioelectrochemical process fortrichloroethene (TCE) bioremediation was presented. In this newly developed process, a solid-state electrode polarized to -450 mV (vs SHE), in the presence of a low-potential redox mediator (methyl viologen), is employed as an electron donor for the microbial reductive dechlorination of TCE to lower or nonchlorinated end products. In the present study, we investigated the influence of methyl viologen and TCE concentrations on process performance. Using a highly enriched hydrogenotrophic dechlorinating culture, as a source culture in batch experiments, we found that TCE dechlorination and H2 evolution were the two main biological reactions which were stimulated. The relative contribution of the two reactions appeared to be strongly dependent on the mediator concentration. At the lowest methyl viologen (MV) concentrations (25-750 microM), only TCE dechlorination was stimulated, and no H2 was produced; at higher MV concentrations, both reactions occurred simultaneously, although they showed distinct kinetic features. In batch experiments in which TCE was omitted from the system, the rate of H2 production was remarkably increased (up to 80 times), suggesting that protons represented an alternative electron sink in the absence of the more energetically favorable TCE. Clearly, optimization of the process for TCE dechlorination requires H2 evolution to be minimized by, for instance, operating the system at low mediator concentrations, and this can be possibly achieved through proper physical immobilization of the mediator at the electrode surface. On the other hand, the observed bioelectrocatalytic H2 production occurred at virtually no overpotentials with respect to the thermodynamic 2H+/H2 potential. This finding revealed that the dechlorinating culture employed represented quite an exceptional and previously unrecognized biocatalytic system for H2 production.     

Yttria-stabilized zirconia thin film electrolyte produced by RF sputtering for solid oxide fuel cell applications

Thin film (40-600 nm) yttria-stabilized zirconia (YSZ) electrolytes for solid oxide fuel cells (SOFC) were deposited on NiO-YSZ anodes and fused silica substrates by RF sputtering, using low applied power without the use of post deposition annealing heat treatment. YSZ film showed a nanocrystalline structure and consisted of the Zr_.85Y_.15O_1.93 (fcc) phase. The film was dense and the YSZ/anode interface was continuous and crack free. According to preliminary in-plane conductivity measurements (temperature range 550-750 °C) on the YSZ film, the activation energy for ionic conduction was found to be 1.18 ± 0.01 eV.     

A BEM analysis of a penny-shaped interface crack using the open and the frictionless contact models: Range of validity of various asymptotic solutions

The global elastic solution for the problem of a pressurized penny-shaped crack at the interface of two dissimilar half spaces has been numerically obtained employing the boundary element method (BEM). Using the Williams’ open model (for the whole range of feasible bi-material combinations), the comparison of the global BEM solution with an existing analytical asymptotic solution has shown: (i) that the extent of the zone in which the first term is dominant is always larger than the extent of the zone in which the interpenetrations take place and (ii) that, in the former zone, a recently proposed relation between the components of the complex stress intensity factor (SIF) and the components of the energy release rate (ERR) always yields accurate results. Consequently, the appearance of negative values of the normal contribution to the ERR in certain cases has been confirmed by the BEM solution, thus questioning the significance of the asymptotic results obtained from the open model in those cases. If the Comninou's frictionless contact model is employed, the ability of the BEM formulation employed to obtain accurate elastic solutions is shown by comparisons with an existing semi-analytical solution (for a particular bi-material combination).     

Molecular modulation of conductivity on H-terminated silicon-on-insulator substrates

The adsorption of a range of molecular species (water, pyridine, and ammonia) is found to reversibly modulate the conductivity of hydrogen-terminated silicon-on-insulator (H-SOI) substrates. Simultaneous sheet-resistance and Hall-effect measurements on moderately doped (10(15) cm(-3)) n- and p-type H-SOI samples mounted in a vacuum system are used to monitor the effect of gas exposure in the Torr range on the electrical-transport properties of these substrates. Reversible physisorption of "hole-trapping" species, such as pyridine (C(5)H(5)N) and ammonia (NH(3)) produces highly conductive minority-carrier channels (inversion) on p-type substrates, mimicking the action of a metallic gate in a field-effect transistor. The adsorption of these same molecules on n-type SOI induces strong electron-accumulation layers. Minority/majority channels are also formed upon controlled exposure to water vapor. These observations can be explained by a classical band-bending model, which considers the adsorbates as the source of a uniform surface charge ranging from +10(11) to +10(12)q cm(-2). These results demonstrate the utility of DC transport measurements of SOI platforms for studies of molecular adsorption and charge-transfer effects at semiconductor surfaces.     

Numerical computation of macroscopic turbulence quantities in representative elementary volumes of the porous medium

In this study, fully developed macroscopic turbulence quantities—based on their definitions in some existing turbulence models for porous media as well as those based on definitions introduced in a recently developed model [F.E. Teruel, Rizwan-uddin, A new turbulence model for porous media flows. Part I: Constitutive equations and model closure, Int. J. Heat Mass Transfer (2009)]—are computed and analyzed for different Reynolds numbers as well as for different porosity levels. When computed based on the definition introduced in the new model, these numerically computed, pore-level turbulent quantities provide closure to the formulation. A large set of microscopic turbulent flow simulations of the REV of a porous medium, formed by staggered square cylinders, is carried out to achieve these tasks. For each Reynolds number selected, ten different porosities are simulated in the 5–95% range. The Reynolds number is varied from Re = 10³ to Re = 10⁵, covering four different cases of the turbulence flow regime. Numerical results obtained for the macroscopic turbulent kinetic energy based on the new definition show that the spatial dispersion of the mean flow is the main contributor to this quantity at low porosities. Additionally, it is found that for high porosities, the spatial average of the turbulent kinetic energy is the main contributor but the spatial dispersion of the mean flow cannot be neglected. The new definition of the macroscopic dissipation rate is found to asymptotically approach the volume average of this quantity at high Reynolds numbers. It is confirmed that microscopic numerical simulations are consistent with the macroscopic law that states that the macroscopic dissipation rate is determined by the pressure-drop through the REV.     

Specific Cerebrospinal Fluid SerpinA1 Isoform Pattern in Alzheimer’s Disease

SerpinA1 (α1-antitrypsin) is a soluble glycoprotein, the cerebrospinal fluid (CSF) isoforms of which showed disease-specific changes in neurodegenerative disorders that are still unexplored in Alz-heimer’s disease (AD). By means of capillary isoelectric focusing immunoassay, we investigated six serpinA1 isoforms in CSF samples of controls (n = 29), AD-MCI (n = 29), AD-dem (n = 26) and Lewy body disease (LBD, n = 59) patients and correlated the findings with CSF AD core biomarkers (Aβ42/40 ratio, p-tau, t-tau). Four CSF serpinA1 isoforms were differently expressed in AD patients compared to controls and LBD patients, especially isoforms 2 and 4. AD-specific changes were found since the MCI stage and significantly correlated with decreased Aβ42/40 (p < 0.05) and in-creased p-tau and t-tau levels in CSF (p < 0.001). Analysis of serpinA1 isoform provided good di-agnostic accuracy in discriminating AD patients versus controls (AUC = 0.80) and versus LBD patients (AUC = 0.92), with best results in patients in the dementia stage (AUC = 0.97). SerpinA1 isoform expression is altered in AD patients, suggesting a common, albeit disease-specific, in-volvement of serpinA1 in most neurodegenerative disorders.     

Glycaemic Control in Patients Undergoing Percutaneous Coronary Intervention: What Is the Role for the Novel Antidiabetic Agents? A Comprehensive Review of Basic Science and Clinical Data

Coronary artery disease (CAD) remains one of the most important causes of morbidity and mortality worldwide, and revascularization through percutaneous coronary interventions (PCI) significantly improves survival. In this setting, poor glycaemic control, regardless of diabetes, has been associated with increased incidence of peri-procedural and long-term complications and worse prognosis. Novel antidiabetic agents have represented a paradigm shift in managing patients with diabetes and cardiovascular diseases. However, limited data are reported so far in patients undergoing coronary stenting. This review intends to provide an overview of the biological mechanisms underlying hyperglycaemia-induced vascular damage and the contrasting actions of new antidiabetic drugs. We summarize existing evidence on the effects of these drugs in the setting of PCI, addressing pre-clinical and clinical studies and drug-drug interactions with antiplatelet agents, thus highlighting new opportunities for optimal long-term management of these patients.