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Sample records for barrier oxidation dependence

  1. Alveolar macrophage inducible nitric oxide synthase-dependent pulmonary microvascular endothelial cell septic barrier dysfunction.

    PubMed

    Farley, K S; Wang, L F; Law, C; Mehta, S

    2008-11-01

    Inducible nitric oxide (NO) synthase (iNOS) from neutrophils and alveolar macrophages (AM) contributes to the pathophysiology of murine septic acute lung injury (ALI). It is not known if AM iNOS has a direct effect on septic pulmonary microvascular endothelial cell (PMVEC) permeability. We hypothesized that AM iNOS mediates PMVEC permeability in vitro under septic conditions through NO and peroxynitrite. 100,000 confluent PMVEC on cell-culture inserts were co-incubated with iNOS+/+ vs. iNOS-/- AM, in various ratios of AM to PMVEC. PMVEC injury was assessed by trans-PMVEC Evans Blue-labelled albumin flux in the presence or absence of cytomix (equimolar TNF-alpha, IL-1beta and IFN-gamma). Cytomix stimulation dose-dependently increased trans-PMVEC EB-albumin flux, which was exaggerated (1.4+/-0.1% vs. 0.4+/-0.1% in unstimulated PMVEC, p<0.05) in the presence of iNOS+/+, but not iNOS-/-, AM in the upper compartment. Similarly, iNOS+/+, but not iNOS-/-, AM in the lower compartment also enhanced septic trans-PMVEC albumin leak. The mechanism of iNOS-dependent septic PMVEC permeability was pursued through pharmacologic studies with inhibitors of NOS, and scavengers of NO, superoxide, and peroxynitrite, and treatment of PMVEC with the NO donor, DETA-NONOate. Septic iNOS+/+ AM-dependent trans-PMVEC albumin leak was significantly attenuated by pharmacologic iNOS inhibition (L-NAME and 1400W), and scavenging of either NO (oxyhemoglobin), superoxide (PEG-SOD), or peroxynitrite (FeTPPS). Exogenous NO (DETA-NONOate) had no effect on PMVEC permeability. These data are consistent with a direct role of AM iNOS in septic PMVEC barrier dysfunction, which is likely mediated, in part, through peroxynitrite.

  2. Evidence of a barrier oxidation dependence on the interfacialmagnetism in co/alumina based magnetic tunnel junctions

    SciTech Connect

    Telling, N.D.; van der Laan, G.; Ladak, S.; Hicken, R.J.; Arenholz, E.

    2005-09-29

    Soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co L{sub 2,3} edge have been applied to explore the near-interfacial magnetism of Co electrodes in Co/alumina based magnetic tunnel junctions. By taking into account the formation of CoO at the FM/barrier interface, the change in the total magnetic moment on metallic Co atoms as a function of barrier oxidation has been determined. The results demonstrate a strong correlation between the Co moments and measured TMR values, and an enhancement in the Co moments for moderate oxidation times.

  3. Effect of oxide barrier height in spin dependent tunneling in MTJ of FeO-MgO multilayer structure

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, M.; Nemade, H.; Bandyopadhyay, D.

    2016-10-01

    We study the spin dependent tunneling current properties through oxide multilayers in a magnetic tunnel junction (MTJ). For this purpose, nonequilibrium Green's function approach along-with the density-functional theory have been applied. We employed three structural models of FeO-MgO-FeO multi-layer with three different width of FeO and MgO layer. An atomistic model is considered to describe the effect of oxide multilayers of different heights. Spin dependent study for tunneling reveals that the parallel spin shows higher tunneling current whereas anti-parallel spin conducts very less. Further, the lowest tunneling current is obtained for the case where the FeO and MgO each has 3 atomic layers of height whereas the tunneling current is highest in 4 atomic layers of FeO/1 atomic layers of MgO/4 atomic layers of MgO multilayer structure. Importantly, when the MgO or FeO layers are increased or decreased from this level, the tunneling current decreases significantly. The study reveals that the layer height in the tunneling domain can be important factor for tuning and adjusting tunneling current in the nanoscale regime of oxide layer thickness.

  4. Epitaxial complex oxide tunnel barriers

    NASA Astrophysics Data System (ADS)

    Son, Junwoo; Moetakef, Pouya; Cagnon, Joël; Stemmer, Susanne

    2009-03-01

    Tunnel junctions with complex oxide thin film barriers are of interest for studies of the critical thickness of ferroelectricity, of phonon modes in ultrathin films and of traps by inelastic tunneling spectroscopy. We show that high-quality epitaxial SrTiO3 and BaTiO3 tunnel barriers can be grown on Pt bottom electrodes. Coherent, epitaxial Pt films with roughness of less than a unit cell were grown on (001) SrTiO3 to serve as bottom electrodes for epitaxial SrTiO3 and BaTiO3 tunnel barriers. All interfaces were atomically abrupt as confirmed by atomic resolution Z-contrast imaging. The IV characteristics were non-linear, demonstrating good insulating properties. For the SrTiO3 barriers and voltage sweeps up to ± 0.5 V, the measured tunnel current was independent of the sweep direction. At low biases, dynamic conductance curves showed a symmetrical parabolic shape around the origin in both resistance states. At high bias, deviation from the ideal tunnel behavior was observed. A large increase of the tunnel conductance occurred above a minimum positive bias. A dramatic decrease of tunnel conductance occurred for a large negative bias, indicating bipolar switching. We show the contributions to the resistive switching. Phonon modes and traps are determined using inelastic tunneling spectroscopy with both paraelectric and ferroelectric tunnel barriers.

  5. Lung endothelial barrier protection by resveratrol involves inhibition of HMGB1 release and HMGB1-induced mitochondrial oxidative damage via an Nrf2-dependent mechanism.

    PubMed

    Dong, Wen-Wen; Liu, Yu-Jian; Lv, Zhou; Mao, Yan-Fei; Wang, Ying-Wei; Zhu, Xiao-Yan; Jiang, Lai

    2015-11-01

    High-mobility group box 1 (HMGB1) contributes to lung vascular hyperpermeability during ventilator-induced lung injury. We aimed to determine whether the natural antioxidant resveratrol protected against HMGB1-induced endothelial hyperpermeability both in vitro and in vivo. We found that HMGB1 decreased vascular endothelial (VE)-cadherin expression and increased endothelial permeability, leading to mitochondrial oxidative damage in primary cultured mouse lung vascular endothelial cells (MLVECs). Both the mitochondrial superoxide dismutase 2 mimetic MnTBAP and resveratrol blocked HMGB1-induced mitochondrial oxidative damage, VE-cadherin downregulation, and endothelial hyperpermeability. In in vivo studies, anesthetized male ICR mice were ventilated for 4h using low tidal volume (6 ml/kg) or high tidal volume (HVT; 30 ml/kg) ventilation. The mice were injected intraperitoneally with resveratrol immediately before the onset of ventilation. We found that resveratrol attenuated HVT-associated lung vascular hyperpermeability and HMGB1 production. HVT caused a significant increase in nuclear factor-erythroid 2-related factor 2 (Nrf2) nuclear translocation and Nrf2 target gene expression in lung tissues, which was further enhanced by resveratrol treatment. HMGB1 had no effect on Nrf2 activation, whereas resveratrol treatment activated the Nrf2 signaling pathway in HMGB1-treated MLVECs. Moreover, Nrf2 knockdown reversed the inhibitory effects of resveratrol on HMGB1-induced mitochondrial oxidative damage and endothelial hyperpermeability. The inhibitory effect of resveratrol on cyclic stretch-induced HMGB1 mRNA expression in primary cultured MLVECs was also abolished by Nrf2 knockdown. In summary, this study demonstrates that resveratrol protects against lung endothelial barrier dysfunction initiated by HVT. Lung endothelial barrier protection by resveratrol involves inhibition of mechanical stretch-induced HMGB1 release and HMGB1-induced mitochondrial oxidative damage

  6. Alloy-grain-size dependence of the effectiveness of silica coatings as oxidation barriers on stainless steel

    SciTech Connect

    McDowell, C.S.; Basu, S.N.

    1995-04-01

    In order to determine the effect of alloy grain size on the oxidation properties of silica-coated austenitic Fe-18Cr-20Ni stainless steel, both coarse-grain (100-{mu}m grain size) forms of the alloy were produced. A 1-{mu}m-thick vitreous silica coating was deposited by chemical-vapor deposition on the alloys, which were subjected to isothermal and cyclic oxidation in air at 900{degrees}C. The coarse-grain alloys underwent widespread oxidation below the silica coating, leading to extensive coating spallation. This was attributed to the inability of the alloy to supply a sufficient outward flux of chromium to prevent oxygen penetration through microcracks in the silica coating. Due to an abundance of chromium available at the surface of the fine-grain alloy, chromia formed in the microcracks within the silica layer. As a result, the silica-coated, fine-grain alloy demonstrated superior oxidation resistance and excellent adhesion of the coating.

  7. Controlling barrier penetration via exothermic iron oxidation.

    PubMed

    Wood, Daniel G; Brown, Marc B; Jones, Stuart A

    2011-02-14

    Exothermic iron oxidation is an elegant means to generate heat, with the potential to modulate barrier penetration if reaction kinetics can be controlled. This aim of this study was to gain a fundamental understanding of how these temperature change kinetics influenced barrier diffusion rate. Lidocaine transport through a hydrophilic carboxymethyl cellulose (CMC) gel was compared using two rapid iron oxidation reactions initiated by water (ExoRap(50), T(max)-47.7 ± 0.6 °C, t(max)-3.3 ± 0.6 min, ExoRap(60), T(max)-60.4 ± 0.3 °C, t(max)-9.3 ± 0.6 min) and a slower reaction initiated by oxygen (ExoSl(45)T(max)-ca. 44 °C, t(max) ca. 240 min). Temperature change induced by the oxygen initiated reaction (ExoSl(45)) was almost double those initiated by water (over 4h), but lidocaine diffusion was approximately 4 times higher for the latter (ExoRap(50), 555.61 ± 22.04 μg/cm(2)/h; ExoRap(60), 663.1 ± 50.95 μg/cm(2)/h; compared to ExoSl(45), 159.36 ± 29.44 μg/cm(2)/h). The large influence of temperature change kinetics on lidocaine diffusion suggested that transport was heavily dependent on temperature induced structural changes of the barrier. CMC, like many polymers adsorbs more water when exposed to moderate increases in temperature and this appeared to be a critical determinant of lidocaine barrier diffusion rate. Copyright © 2010 Elsevier B.V. All rights reserved.

  8. The formation mechanism of aluminum oxide tunnel barriers.

    SciTech Connect

    Cerezo, A.; Petford-Long, A. K.; Larson, D. J.; Pinitsoontorn, S.; Singleton, E. W.; Materials Science Division; Univ. Oxford; Seagate Tech.

    2006-01-01

    The functional properties of magnetic tunnel junctions are critically dependant on the nanoscale morphology of the insulating barrier (usually only a few atomic layers thick) that separates the two ferromagnetic layers. Three-dimensional atom probe analysis has been used to study the chemistry of a magnetic tunnel junction structure comprising an aluminium oxide barrier formed by in situ oxidation, both in the under-oxidized and fully oxidized states and before and after annealing. Low oxidation times result in discrete oxide islands. Further oxidation leads to a more continuous, but still non-stoichiometric, barrier with evidence that oxidation proceeds along the top of grain boundaries in the underlying CoFe layer. Post-deposition annealing leads to an increase in the barrier area, but only in the case of the fully oxidized and annealed structure is a continuous planar layer formed, which is close to the stoichiometric Al:O ratio of 2:3. These results are surprising, in that the planar layers are usually considered unstable with respect to breaking up into separate islands. Analysis of the various driving forces suggests that the formation of a continuous layer requires a combination of factors, including the strain energy resulting from the expansion of the oxide during internal oxidation on annealing.

  9. Spin-dependent tunnel junctions with ZrOx barriers

    NASA Astrophysics Data System (ADS)

    Wang, Jianguo; Freitas, P. P.; Snoeck, E.; Wei, P.; Soares, J. C.

    2001-12-01

    Spin-dependent tunnel junctions with crystalline ZrOx barriers were fabricated, with tunnel magnetoresistance (TMR) reaching 20% and a resistance×area product of 24 k Ω μm2, after annealing at 260 °C. Effective barrier height and thickness are 1.6 eV and 10.6 Å, respectively. The ZrOx barriers were fabricated by rf plasma oxidation of a 5 Å thick Zr layer. High-resolution transmission electron microscopy and Rutherford backscattering spectrometry were used to characterize the as-deposited barrier. Both ZrO and ZrO2 phases are present, together with (CoFe)Ox. Upon annealing, the interfacial oxygen moves into the barrier, resulting in an increase of TMR from 2% to 19.2%, an increase of barrier height from 0.3 to 1.6 eV, and a reduction of barrier thickness from 18.5 to 10.5 Å.

  10. Graphene tunnel junctions with aluminum oxide barrier

    NASA Astrophysics Data System (ADS)

    Feng, Ying; Trainer, Daniel J.; Chen, Ke

    2016-10-01

    We report a development of graphene tunnel junctions made by chemical vapor deposition grown graphene and sputtered aluminum insulating by an in-situ grown aluminum oxide. The thin oxide layer formed in between the metal layer and the two-dimensional material is a crucial part of a tunnel junction. We characterized surface morphology of oxide layers and studied tunneling spectra of lead and silver tunnel junctions to estimate the quality of the aluminum oxide. The Brinkman-Rowell-Dynes model was applied to fit the conductance-voltage plots to calculate the thickness of oxide layers. Junctions with graphene both on bottom and on top were fabricated and their tunneling properties were characterized after exposure to air for weeks to test time stability. Furthermore, the resistances of graphene tunnel junctions with aluminum oxide formed naturally and in an oxygen atmosphere were studied. Our results demonstrate that in-situ aluminum oxide is an effective barrier for graphene tunnel junctions. The methods of barrier formation enable the realization of more tunnel devices and circuits based on graphene.

  11. Moderate Hypoxia Followed by Reoxygenation Results in Blood-Brain Barrier Breakdown via Oxidative Stress-Dependent Tight-Junction Protein Disruption

    PubMed Central

    Zehendner, Christoph M.; Librizzi, Laura; Hedrich, Jana; Bauer, Nina M.; Angamo, Eskedar A.; de Curtis, Marco; Luhmann, Heiko J.

    2013-01-01

    Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using 2′,7′-dichlorodihydrofluorescein diacetate (DCF), MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ) integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI) was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1) and claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in

  12. Moderate hypoxia followed by reoxygenation results in blood-brain barrier breakdown via oxidative stress-dependent tight-junction protein disruption.

    PubMed

    Zehendner, Christoph M; Librizzi, Laura; Hedrich, Jana; Bauer, Nina M; Angamo, Eskedar A; de Curtis, Marco; Luhmann, Heiko J

    2013-01-01

    Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using 2',7'-dichlorodihydrofluorescein diacetate (DCF), MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ) integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI) was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1) and claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in this

  13. Polyelectrolyte/Graphene Oxide Barrier Film for Flexible OLED.

    PubMed

    Yang, Seung-Yeol; Park, Jongwhan; Kim, Yong-Seog

    2015-10-01

    Ultra-thin flexible nano-composite barrier layer consists of graphene oxide and polyelectrolyte was prepared using the layer-by-layer processing method. Microstructures of the barrier layer was optimized via modifying coating conditions and inducing chemical reactions. Although the barrier layer consists of hydrophilic polyelectrolyte was not effective in blocking the water vapor permeation, the chemical reduction of graphene oxide as well as conversion of polyelectrolyte to hydrophobic nature were very effective in reducing the permeation.

  14. Signalling of DNA damage and cytokines across cell barriers exposed to nanoparticles depends on barrier thickness

    NASA Astrophysics Data System (ADS)

    Sood, A.; Salih, S.; Roh, D.; Lacharme-Lora, L.; Parry, M.; Hardiman, B.; Keehan, R.; Grummer, R.; Winterhager, E.; Gokhale, P. J.; Andrews, P. W.; Abbott, C.; Forbes, K.; Westwood, M.; Aplin, J. D.; Ingham, E.; Papageorgiou, I.; Berry, M.; Liu, J.; Dick, A. D.; Garland, R. J.; Williams, N.; Singh, R.; Simon, A. K.; Lewis, M.; Ham, J.; Roger, L.; Baird, D. M.; Crompton, L. A.; Caldwell, M. A.; Swalwell, H.; Birch-Machin, M.; Lopez-Castejon, G.; Randall, A.; Lin, H.; Suleiman, M.-S.; Evans, W. H.; Newson, R.; Case, C. P.

    2011-12-01

    The use of nanoparticles in medicine is ever increasing, and it is important to understand their targeted and non-targeted effects. We have previously shown that nanoparticles can cause DNA damage to cells cultured below a cellular barrier without crossing this barrier. Here, we show that this indirect DNA damage depends on the thickness of the cellular barrier, and it is mediated by signalling through gap junction proteins following the generation of mitochondrial free radicals. Indirect damage was seen across both trophoblast and corneal barriers. Signalling, including cytokine release, occurred only across bilayer and multilayer barriers, but not across monolayer barriers. Indirect toxicity was also observed in mice and using ex vivo explants of the human placenta. If the importance of barrier thickness in signalling is a general feature for all types of barriers, our results may offer a principle with which to limit the adverse effects of nanoparticle exposure and offer new therapeutic approaches.

  15. Oxidation behavior of a thermal barrier coating

    NASA Technical Reports Server (NTRS)

    Miller, R. A.

    1984-01-01

    Thermal barrier coatings, consisting of a plasma sprayed calcium silicate ceramic layer and a CoCrAlY or NiCrAlY bond coat, were applied on B-1900 coupons and cycled hourly in air in a rapid-response furnace to maximum temperatures of 1030, 1100, or 1160 C. Eight specimens were tested for each of the six conditions of bond-coat composition and temperature. Specimens were removed from test at the onset of failure, which was taken to be the formation of a fine surface crack visible at 10X magnification. Specimens were weighed periodically, and plots of weight gain vs time indicate that weight is gained at a parabolic rate after an initial period where weight was gained at a much greater rate. The high initial oxidation rate is thought to arise from the initially high surface area in the porous bond coat. Specimen life (time to first crack) was found to be a strong function of temperature. However, while test lives varied greatly with time, the weight gain at the time of specimen failure was quite insensitive to temperature. This indicates that there is a critical weight gain at which the coating fails when subjected to this test.

  16. Fragmented oxidation products define barrier disruptive endothelial cell response to OxPAPC

    PubMed Central

    Birukova, Anna A.; Starosta, Vitaliy; Tian, Xinyong; Higginbotham, Katherine; Koroniak, Lukas; Berliner, Judith A.; Birukov, Konstantin G.

    2013-01-01

    Excessive concentrations of oxidized phospholipids (OxPL), the products of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphatidylcholine (PAPC) oxidation have been detected in atherosclerosis, septic inflammation, and ALI; and have been shown to induce vascular barrier dysfunction. In contrast, oxidized PAPC (OxPAPC) at low concentrations exhibit potent barrier protective effects. The nature of such biphasic effects remains unclear. We tested the hypothesis that barrier-disruptive effects of high OxPAPC doses on endothelial cell (EC) monolayer are defined by fragmented products of PAPC oxidation (lyso-PC, POVPC, PGPC), while barrier enhancing effects are mediated by full length oxidated PAPC products and may be reproduced by single compounds contained in the OxPAPC such as PEIPC. All three fragmented OxPAPC products increased EC permeability in a dose-dependent manner, while PEIPC decreased it and reversed barrier disruptive effects of lyso-PC, POVPC and PGPC monitored by measurements of transendothelial electrical resistance. Immunofluorescence staining and western blot analysis showed that PGPC mimicked the cytoskeletal remodeling and tyrosine phosphorylation of adherens junction (AJ) protein VE-cadherin leading to EC barrier dysfunction induced by high OxPAPC concentrations. Barrier-disruptive effects of PGPC were abrogated by ROS inhibitor, N-acetyl cysteine, or Src kinase inhibitor, PP-2. The results of this study show that barrier disruptive effects of fragmented OxPAPC constituents (lyso-PC, POVPC, PGPC) are balanced by barrier enhancing effects of full length oxygenated products (PEIPC). These data strongly suggest that barrier disruptive effects of OxPAPC at higher concentrations are dictated by predominant effects of fragmented phospholipids such as PGPC, which promote ROS-dependent activation of Src kinase and VE-cadherin phosphorylation at Tyr658 and Tyr731 leading to disruption of endothelial cell AJs. PMID:23305708

  17. Diffusion Barriers to Increase the Oxidative Life of Overlay Coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Lei, Jih-Fen

    1999-01-01

    Currently, most blades and vanes in the hottest section of aero gas turbine engines require some type of coating for oxidation protection. Newly developed single crystal superalloys have the mechanical potential to operate at increasingly higher component temperatures. However, at these elevated temperatures, coating/substrate interdiffusion can shorten the protective life of the coating. Diffusion barriers between overlay coatings and substrates are being examined to extend the protective life of the coating. A previously- developed finite-difference diffusion model has been modified to predict the oxidative life enhancement due to use of a diffusion barrier. The original diffusion model, designated COSIM, simulates Al diffusion in the coating to the growing oxide scale as well as Al diffusion into the substrate. The COSIM model incorporates an oxide growth and spalling model to provide the rate of Al consumption during cyclic oxidation. Coating failure is predicted when the Al concentration at the coating surface drops to a defined critical level. The modified COSIM model predicts the oxidative life of an overlay coating when a diffusion barrier is present eliminating diffusion of Al from the coating into the substrate. Both the original and the modified diffusion models have been used to predict the effectiveness of a diffusion barrier in extending the protective life of a NiCrAl overlay coating undergoing cyclic oxidation at 1100 C.

  18. Oxidation of tunnel barrier metals in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Yang, J. Joshua; Ladwig, Peter F.; Yang, Ying; Ji, Chengxiang; Chang, Y. Austin; Liu, Feng X.; Pant, Bharat B.; Schultz, Allan E.

    2005-05-01

    The oxidation of an ultrathin metal layer (<1nm) to form an oxide tunnel barrier is of critical importance for the fabrication of magnetic tunnel junctions (MTJs) with low product of resistance and area (R×A). Nonuniform and excessive or insufficient oxidation will occur by using conventional plasma, air, or O2 and noble gas mixtures as oxidation methods. An oxidation method was investigated to oxidize only an ultrathin layer of metal (such as Y) without oxidizing adjacent ferromagnetic thin film layers. We have now demonstrated that a gas mixture of H2O/H2 with a fixed chemical potential of oxygen determined by the relative amounts of the two gases can oxidize Y and Ta thin layers while simultaneously keeping a Co ferromagnetic layer completely unoxidized. This universal method can be used to preferentially oxidize a host of other metals with high tendency to form oxides, such as Zr, Hf, Nb, rare earth metals, etc. and may allow us to access the feasible lower limit of barrier thickness in MTJs.

  19. Oxidation and degradation of thermal barrier coating systems

    NASA Astrophysics Data System (ADS)

    Haynes, James Allen

    Thermal barrier coatings (TBCs), which consist of an oxidation-resistant metallic bond coating overlaid with a thermally-insulating Ysb2Osb3-stabilized ZrOsb2 (YSZ) top coating, are used to protect superalloy hardware in gas turbine engines. Spallation of the YSZ is accelerated by growth of an interfacial Alsb2Osb3 scale at high temperatures. The mechanisms of oxidation-related degradation are not well understood for air plasma-sprayed (APS) TBCs, whereas Alsb2Osb3 thermomechanical failure is the dominant degradation mode in electron beam-physical vapor deposition (EB-PVD) TBCs. This work investigated the isothermal oxidation and thermocyclic degradation of various TBC systems; with particular emphasis on the growth kinetics, microstructures, flaw content, fracture behavior and micro-mechanical properties of the Alsb2Osb3 interfacial scales. The isothermal oxidation kinetics of plasma-sprayed NiCrAlY were not influenced by the presence of an APS YSZ top coating (at 1150sp°C). However, the isothermal oxidation rate constants of NiCoCrAlY bond coatings were accelerated by a factor of 2 (at 950, 1050 and 1150sp°C) when overlaid with a commercial EB-PVD TBC. Thermocyclic failure of APS TBCs occurred by progressive YSZ fracture and crack link-up. Severe fracture and buckling of the interfacial Alsb2Osb3 during thermal cycling did not induce rapid failure of APS TBCs. Evaluation of the interfacial Alsb2Osb3 scale microstructures (on APS TBCs) after thermal cycling revealed the following: thermocyclic damage occurred by both oxide-metal delamination and by internal fracture; Alsb2Osb3 scale crack healing by sintering occurred at 1150sp°C; surfaces with a sharp radius of curvature induced less Alsb2Osb3 damage than gradually convex surfaces; scale grain boundary void growth was accelerated by thermal cycling; and higher void contents were observed in scales which formed on convex surfaces. There were no significant changes in the hardness or Young's modulus of the Alsb2

  20. Magnetic Field Dependence of Spin Glass Free Energy Barriers.

    PubMed

    Guchhait, Samaresh; Orbach, Raymond L

    2017-04-14

    We measure the field dependence of spin glass free energy barriers in a thin amorphous Ge:Mn film through the time dependence of the magnetization. After the correlation length ξ(t,T) has reached the film thickness L=155  Å so that the dynamics are activated, we change the initial magnetic field by δH. In agreement with the scaling behavior exhibited in a companion Letter [M. Baity-Jesi et al., Phys. Rev. Lett. 118, 157202 (2017)PRLTAO0031-900710.1103/PhysRevLett.118.157202], we find that the activation energy is increased when δH<0. The change is proportional to (δH)^{2} with the addition of a small (δH)^{4} term. The magnitude of the change of the spin glass free energy barriers is in near quantitative agreement with the prediction of a barrier model.

  1. Barriers to employment for drug dependent postpartum women.

    PubMed

    Bowden, Kelley; Goodman, Daisy

    2015-01-01

    Employment represents the key to independence for women, and equal opportunity has been an elusive goal. For women with substance dependence, employment is strongly linked to the ability to sustain recovery. Unfortunately, for postpartum mothers with substance use disorders, gender-based barriers are magnified. A case analysis is provided to illustrate the interaction of multiple barriers to employment success in one postpartum woman's experience. To elucidate the complex factors involved in return to employment for postpartum women being treated for substance use disorders. A review of the current literature on employment, substance use, and the postpartum period was performed. Themes identified in the literature were applied to analyze a representative case. Postpartum women with substance use disorders face a variety of challenges to employment success. Lack of education and job skills are common barriers to successful employment of women in addiction recovery. These barriers may be complicated by emotional or logistical challenges, or related to external factors such as stigma and/or previous criminal history. Assessment of employment history, marketable skills, and barriers should be an essential component of substance abuse treatment programs. Professionals working to increase employment opportunities for postpartum women with substance use disorders should be particularly aware of the multiple barriers they face and integrate employment assessment and skills training into the early stages of treatment programs.

  2. Thermal expansion mismatch and oxidation in thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Chang, G. C.; Phucharoen, W.; Miller, R. A.

    1985-01-01

    Thermal barrier coatings (TBC) for advanced gas turbine blades have been under intensive development during the last several years. This investigation is intended to achieve a clearer understanding of the mechanical behavior of plasma sprayed zirconia-yttria TBCs, involving a nickle-chromium-aluminum bond coat. The near term objectives are to study the stress states in a relatively simple model TBC subjected to steady state thermal loading. The resulting thermal expansion mismatch and oxidation have been primary targets for the study. The finite element approach and the effects of thermal mismatch and oxidation are described. A proposed mechanism for oxidation induced coating failure is also presented.

  3. Mercury Oxidation via Catalytic Barrier Filters Phase II

    SciTech Connect

    Wayne Seames; Michael Mann; Darrin Muggli; Jason Hrdlicka; Carol Horabik

    2007-09-30

    In 2004, the Department of Energy National Energy Technology Laboratory awarded the University of North Dakota a Phase II University Coal Research grant to explore the feasibility of using barrier filters coated with a catalyst to oxidize elemental mercury in coal combustion flue gas streams. Oxidized mercury is substantially easier to remove than elemental mercury. If successful, this technique has the potential to substantially reduce mercury control costs for those installations that already utilize baghouse barrier filters for particulate removal. Completed in 2004, Phase I of this project successfully met its objectives of screening and assessing the possible feasibility of using catalyst coated barrier filters for the oxidation of vapor phase elemental mercury in coal combustion generated flue gas streams. Completed in September 2007, Phase II of this project successfully met its three objectives. First, an effective coating method for a catalytic barrier filter was found. Second, the effects of a simulated flue gas on the catalysts in a bench-scale reactor were determined. Finally, the performance of the best catalyst was assessed using real flue gas generated by a 19 kW research combustor firing each of three separate coal types.

  4. Silicon oxide permeation barrier coating of PET bottles and foils

    NASA Astrophysics Data System (ADS)

    Steves, Simon; Deilmann, Michael; Awakowicz, Peter

    2009-10-01

    Modern packaging materials such as polyethylene terephthalate (PET) have displaced established materials in many areas of food and beverage packaging. Plastic packing materials offer are various advantages concerning production and handling. PET bottles for instance are non-breakable and lightweight compared to glass and metal containers. However, PET offers poor barrier properties against gas permeation. Therefore, the shelf live of packaged food is reduced. Permeation of gases can be reduced by depositing transparent plasma polymerized silicon oxide (SiOx) barrier coatings. A microwave (2.45 GHz) driven low pressure plasma reactor is developed based on a modified Plasmaline antenna to treat PET foils or bottles. To increase the barrier properties of the coatings furthermore a RF substrate bias (13.56 MHz) is applied. The composition of the coatings is analyzed by means of Fourier transform infrared (FTIR) spectroscopy regarding carbon and hydrogen content. Influence of gas phase composition and substrate bias on chemical composition of the coatings is discussed. A strong relation between barrier properties and film composition is found: good oxygen barriers are observed as carbon content is reduced and films become quartz-like. Regarding oxygen permeation a barrier improvement factor (BIF) of 70 is achieved.

  5. Breathable Vapor Toxicant Barriers Based on Multilayer Graphene Oxide.

    PubMed

    Spitz Steinberg, Ruben; Cruz, Michelle; Mahfouz, Naser G A; Qiu, Yang; Hurt, Robert H

    2017-06-27

    There is tremendous interest in graphene-based membranes as protective molecular barriers or molecular sieves for separation technologies. Graphene oxide (GO) films in the dry state are known to be effective barriers for molecular transport and to expand in the presence of moisture to create enlarged intersheet gallery spaces that allow rapid water permeation. Here we explore an application for GO membranes as water-breathable barrier layers for personal protective equipment, which are designed to allow outward perspiration while protecting the wearer from chemical toxicants or biochemical agents in the local environment. A device was developed to measure permeation rates of small-molecular toxicants in the presence of counter-current water flow simulating active perspiration. The technique was applied to trichloroethylene (TCE) and benzene, which are important environmental toxicants, and ethanol as a limiting case to model very small, highly water-soluble organic molecules. Submicron GO membranes are shown to be effective TCE barriers, both in the presence and absence of simulated perspiration flux, and to outperform current barrier technologies. A molecular transport model is developed, which suggests the limited toxicant back-permeation observed occurs not by diffusion against the convective perspiration flow in hydrophobic channels, but rather through oxidized domains where hydrogen-bonding produces a near-stagnant water phase. Benzene and ethanol permeation fluxes are higher than those for TCE, likely reflecting the effects of higher water solubility and smaller minimum molecular dimension. Overall, GO films have high water breathability relative to competing technologies and are known to exclude most classes of target toxicants, including particles, bacteria, viruses, and macromolecules. The present results show good barrier performance for some very small-molecule species, but not others, with permeation being favored by high water solubility and small

  6. Evaluation of Oxidation Damage in Thermal Barrier Coating Systems

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1996-01-01

    A method based on the technique of dilatometry has been established to quantitatively evaluate the interfacial damage due to the oxidation in a thermal barrier coating system. Strain isolation and adhesion coefficients have been proposed to characterize the thermal barrier coating (TBC) performance based on its thermal expansion behavior. It has been found that, for a thermal barrier coating system consisting of ZrO2-8%Y2O3/FeCrAlY/4140 steel substrate, the oxidation of the bond coat and substrate significantly reduced the ceramic coating adherence, as inferred from the dilatometry measurements. The in-situ thermal expansion measurements under 30 deg C to 700 deg C thermal cycling in air showed that the adhesion coefficient, A(sub i) decreased by 25% during the first 35 oxidation cycles. Metallography showed that delamination occurred at both the ceramic/bond coat and bond coat/substrate interfaces. In addition, the strain isolation effect has been improved by increasing the FeCrAlY bond coat thickness. The strain isolation coefficient, Si, increased from about 0.04 to 0.25, as the bond coat thickness changed from 0.1 mm to 1.0 mm. It may be possible to design optimum values of strain isolation and interface adhesion coefficients to achieve the best TBC performance.

  7. In situ determination of the pore opening point during wet-chemical etching of the barrier layer of porous anodic aluminum oxide: nonuniform impurity distribution in anodic oxide.

    PubMed

    Han, Hee; Park, Sang-Joon; Jang, Jong Shik; Ryu, Hyun; Kim, Kyung Joong; Baik, Sunggi; Lee, Woo

    2013-04-24

    Wet-chemical etching of the barrier oxide layer of anodic aluminum oxide (AAO) was systematically investigated by using scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and a newly devised experimental setup that allows accurate in situ determination of the pore opening point during chemical etching of the barrier oxide layer. We found that opening of the barrier oxide layer by wet-chemical etching can be significantly influenced by anodization time (tanodi). According to secondary ion mass spectrometry (SIMS) analysis, porous anodic aluminum oxide (AAO) samples formed by long-term anodization contained a lower level of anionic impurity in the barrier oxide layer compared to the short-term anodized one and consequently exhibited retarded opening of the barrier oxide layer during the wet-chemical etching. The observed compositional dependence on the anodization time (tanodi) in the barrier oxide layer is attributed to the progressive decrease of the electrolyte concentration upon anodization. The etching rate of the outer pore wall at the bottom part is lower than that of the one at the top part due to the lower level of impurity content in that region. This indicates that a concentration gradient of anionic impurity in the outer pore wall oxide may be established along both the vertical and radial directions of cylindrical pores. Apart from the effect of electrolyte concentration on the chemical composition of the barrier oxide layer, significantly decreased current density arising from the lowered concentration of electrolyte during the long-term anodization (~120 h) was found to cause disordering of pores. The results of the present work are expected to provide viable information not only for practical applications of nanoporous AAO in nanotechnology but also for thorough understanding of the self-organized formation of oxide nanopores during anodization.

  8. Modeling Oxidation Induced Stresses in Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Ferguson, B. L.; Freborg, A. M.; Petrus, G. J.; Brindley, William J.

    1998-01-01

    The use of thermal barrier coatings (TBC's) in gas turbines has increased dramatically in recent years, due mainly to the need for component protection from ever increasing service temperatures. Oxidation of the bond coat has been identified as an important contributing factor to spallation of the ceramic top coat during service. Additional variables found to influence TBC thermal cycle life include bond coat coefficient of thermal expansion, creep behavior of both the ceramic and bond coat layers, and modulus of elasticity. The purpose of this work was to characterize the effects of oxidation on the stress states within the TBC system, as well as to examine the interaction of oxidation with other factors affecting TBC life.

  9. Electrical properties of graphene tunnel junctions with high-κ metal-oxide barriers

    NASA Astrophysics Data System (ADS)

    Feng, Ying; Trainer, Daniel J.; Chen, Ke

    2017-04-01

    An insulating barrier is one of the key components in electronic devices that makes use of quantum tunneling principles. Many metal-oxides have been used as a good barrier material in a tunnel junction for their large band gap, stable chemical properties and superb properties for forming a thin and pin-hole-free insulating layer. The reduced dimensions of transistors have led to the need for alternative, high dielectric constant (high-κ) oxides to replace conventional silicon-based dielectrics to reduce the leaking current induced by electron tunneling. On the other hand, a tunnel junction with one or both electrodes made of graphene may lead to novel applications due to the massless Dirac fermions from the graphene. Here we have fabricated sandwich-type graphene tunnel junctions with high-κ metal-oxides as barriers, including Al2O3, HfO2, ZrO2, and TiO2. Tunneling properties are investigated by observing the temperature and time dependences of the tunneling spectra. Our results show the potential for applications of high-κ oxides in graphene tunnel junctions and bringing new opportunities for memory and logic electronic devices.

  10. All magnesium diboride Josephson junctions with MgO and native oxide barriers

    NASA Astrophysics Data System (ADS)

    Costache, M. V.; Moodera, J. S.

    2010-02-01

    We present results on all-MgB2 tunnel junctions, where the tunnel barrier is deposited MgO or native-oxide of base electrode. For the junctions with MgO, the hysteretic I-V curve resembles a conventional underdamped Josephson junction characteristic with critical current-resistance product nearly independent of the junction area. The dependence of the critical current with temperature up to 20 K agrees with the [Ambegaokar and Baratoff, Phys. Rev. Lett. 10, 486 (1963)] expression. For the junctions with native-oxide, conductance at low bias exhibits subgap features while at high bias reveals thick barriers. As a result no supercurrent was observed in the latter, despite the presence of superconducting-gaps to over 30 K.

  11. Graphene Oxide Bionanocomposite Coatings with High Oxygen Barrier Properties

    PubMed Central

    Uysal Unalan, Ilke; Boyacı, Derya; Ghaani, Masoud; Trabattoni, Silvia; Farris, Stefano

    2016-01-01

    In this work, we present the development of bionanocomposite coatings on poly(ethylene terephthalate) (PET) with outstanding oxygen barrier properties. Pullulan and graphene oxide (GO) were used as main polymer phase and nanobuilding block (NBB), respectively. The oxygen barrier performance was investigated at different filler volume fractions (ϕ) and as a function of different relative humidity (RH) values. Noticeably, the impermeable nature of GO was reflected under dry conditions, in which an oxygen transmission rate (OTR, mL·m−2·24 h−1) value below the detection limit of the instrument (0.01 mL·m−2·24 h−1) was recorded, even for ϕ as low as 0.0004. A dramatic increase of the OTR values occurred in humid conditions, such that the barrier performance was totally lost at 90% RH (the OTR of coated PET films was equal to the OTR of bare PET films). Modelling of the experimental OTR data by Cussler’s model suggested that the spatial ordering of GO sheets within the main pullulan phase was perturbed because of RH fluctuations. In spite of the presence of the filler, all the formulations allowed the obtainment of final materials with haze values below 3%, the only exception being the formulation with the highest loading of GO (ϕ ≈ 0.03). The mechanisms underlying the experimental observations are discussed. PMID:28335372

  12. Correlation between Barrier Width, Barrier Height, and DC Bias Voltage Dependences on the Magnetoresistance Ratio in Ir-Mn Exchange Biased Single and Double Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Saito, Yoshiaki; Amano, Minoru; Nakajima, Kentaro; Takahashi, Shigeki; Sagoi, Masayuki; Inomata, Koichiro

    2000-10-01

    Dual spin-valve-type double tunnel junctions (DTJs) of Ir-Mn/CoFe/AlOx/Co90Fe10/AlOx/CoFe/Ir-Mn and spin-valve-type single tunnel junctions (STJs) of Ir-Mn/CoFe/AlOx/CoFe/Ni-Fe were fabricated using an ultrahigh vacuum sputtering system, conventional photolithography and ion-beam milling. The STJs could be fabricated with various barrier heights by changing the oxidization conditions during deposition and changing the annealing temperature after deposition, while the AlOx layer thickness remained unchanged. There was a correlation between barrier width, height estimated using Simmons’ expressions, and dc bias voltage dependence on the MR ratio. The VB dependence on the tunneling magnetoresistance (TMR) ratio was mainly related to the barrier width, and the decrease in the TMR ratio with increasing bias voltage is well explained, taking into account the spin-independent two-step tunneling via defect states in the barrier, as a main mechanism, at room temperature. Under optimized oxidization and annealing conditions, the maximum TMR ratio at a low bias voltage, and the dc bias voltage value at which the TMR ratio decreases in value by half (V1/2) were 42.4% and 952 mV in DTJs, and 49.0% and 425 mV in STJs, respectively.

  13. Methane oxidation in a landfill cover with capillary barrier.

    PubMed

    Berger, J; Fornés, L V; Ott, C; Jager, J; Wawra, B; Zanke, U

    2005-01-01

    The methane oxidation potential of a landfill cover with capillary barrier was investigated in an experimental plant (4.8 m x 0.8 m x 2.1m). The cover soil consisted of two layers, a mixture of compost plus sand (0.3 m) over a layer of loamy sand (0.9 m). Four different climatic conditions (summer, winter, spring and fall) were simulated. In and outgoing fluxes were measured. Gas composition, temperature, humidity, matrix potential and gas pressure were monitored in two profiles. CH4 oxidation rate within the investigated top cover ranged from 98% to 57%. The minimum was observed for a short time after irrigation. Temperature distribution, gas concentration profiles and lab-scaled batch experiments indicate that before irrigation the highest oxidising activity took place in a depth of about 30 cm. After irrigation the oxidising horizon seemed to migrate upwards since methanotrophic bacteria develop better there due to an adequate supply with oxygen. It can be assumed that the absence of oxygen is one of the most important limiting factors for the CH4 oxidation process. Abrupt cross-overs between horizons of different soil material may lead to zones of increased water saturation and decreased soil respiration.

  14. MgB2 tunnel junctions with native or thermal oxide barriers

    NASA Astrophysics Data System (ADS)

    Singh, R. K.; Gandikota, R.; Kim, J.; Newman, N.; Rowell, J. M.

    2006-07-01

    MgB2 tunnel junctions (MgB2/barrier/MgB2) were fabricated using a native oxide grown on the bottom MgB2 film as the tunnel barrier. Such barriers therefore survive the deposition of the second electrode at 300°C, even over junction areas of ˜1mm2. Studies of such junctions and those of the type MgB2/native or thermal oxide/metal (Pb, Au, or Ag) show that tunnel barriers grown on MgB2 exhibit a wide range of barrier heights and widths.

  15. MERCURY OXIDIZATION IN NON-THERMAL PLASMA BARRIER DISCHARGE SYSTEM

    SciTech Connect

    V.K. Mathur

    2003-02-01

    In the past decade, the emission of toxic elements from human activities has become a matter of great public concern. Hg, As, Se and Cd typically volatilize during a combustion process and are not easily caught with conventional air pollution control techniques. In addition, there is no pollution prevention technique available now or likely be available in the foreseeable future that can prevent the emission of these trace elements. These trace elements pose additional scientific challenge as they are present at only ppb levels in large gas streams. Mercury, in particular, has attracted significant attention due to its high volatility, toxicity and potential threat to human health. In the present research work, a non-thermal plasma dielectric barrier discharge technique has been used to oxidize Hg{sup 0}(g) to HgO. The basic premise of this approach is that Hg{sup 0} in vapor form cannot be easily removed in an absorption tower whereas HgO as a particulate is amiable to water scrubbing. The work presented in this report consists of three steps: (1) setting-up of an experimental apparatus to generate mercury vapors at a constant rate and modifying the existing non-thermal plasma reactor system, (2) solving the analytical challenge for measuring mercury vapor concentration at ppb level, and (3) conducting experiments on mercury oxidation under plasma conditions to establish proof of concept.

  16. High performance metal-supported solid oxide fuel cells with Gd-doped ceria barrier layers

    NASA Astrophysics Data System (ADS)

    Klemensø, Trine; Nielsen, Jimmi; Blennow, Peter; Persson, Åsa H.; Stegk, Tobias; Christensen, Bjarke Holl; Sønderby, Steffen

    Metal-supported solid oxide fuel cells are believed to have commercial advantages compared to conventional anode (Ni-YSZ) supported cells, with the metal-supported cells having lower material costs, increased tolerance to mechanical and thermal stresses, and lower operational temperatures. The implementation of a metallic support has been challenged by the need to revise the cell fabrication route, as well as electrode microstructures and material choices, to compete with the energy output and stability of full ceramic cells. The metal-supported SOFC design developed at Risø DTU has been improved, and an electrochemical performance beyond the state-of-the-art anode-supported SOFC is demonstrated possible, by introducing a CGO barrier layer in combination with Sr-doped lanthanum cobalt oxide (LSC) cathode. Area specific resistances (ASR) down to 0.27 Ω cm 2, corresponding to a maximum power density of 1.14 W cm -2 at 650 °C and 0.6 V, were obtained on cells with barrier layers fabricated by magnetron sputtering. The performance is dependent on the density of the barrier layer, indicating Sr 2+ diffusion is occurring at the intermediate SOFC temperatures. The optimized design further demonstrate improved durability with steady degradation rates of 0.9% kh -1 in cell voltage for up to 3000 h galvanostatic testing at 650 °C and 0.25 A cm -2.

  17. Role of atomic layer deposited aluminum oxide as oxidation barrier for silicon based materials

    SciTech Connect

    Fiorentino, Giuseppe Morana, Bruno; Forte, Salvatore; Sarro, Pasqualina Maria

    2015-01-15

    In this paper, the authors study the protective effect against oxidation of a thin layer of atomic layer deposited (ALD) aluminum oxide (Al{sub 2}O{sub 3}). Nitrogen doped silicon carbide (poly-SiC:N) based microheaters coated with ALD Al{sub 2}O{sub 3} are used as test structure to investigate the barrier effect of the alumina layers to oxygen and water vapor at very high temperature (up to 1000 °C). Different device sets have been fabricated changing the doping levels, to evaluate possible interaction between the dopants and the alumina layer. The as-deposited alumina layer morphology has been evaluated by means of AFM analysis and compared to an annealed sample (8 h at 1000 °C) to estimate the change in the grain structure and the film density. The coated microheaters are subjected to very long oxidation time in dry and wet environment (up to 8 h at 900 and 1000 °C). By evaluating the electrical resistance variation between uncoated reference devices and the ALD coated devices, the oxide growth on the SiC is estimated. The results show that the ALD alumina coating completely prevents the oxidation of the SiC up to 900 °C in wet environment, while an oxide thickness reduction of 50% is observed at 1000 °C compared to uncoated devices.

  18. Investigation of special features of parameters of Schottky barrier contacts caused by a nonlinear bias dependence of the barrier height

    NASA Astrophysics Data System (ADS)

    Bozhkov, V. G.; Shmargunov, A. V.

    2012-03-01

    The results of studying the IV-characteristics (IVCs) of the contact Au-n-GaAs obtained by electrochemical deposition are presented. The observed characteristics - the bias dependence of the ideality factor (n), the measured (ϕbm) and effective (ϕbI) barrier heights, an inverse relationship between the measured barrier height and ideality factor, and the edge effects (the dependence of n, ϕbm, and ϕbI on the contact diameter) are explained by the nonlinear bias dependence on the effective barrier height. The explanation is given on the basis of the contact model with an intermediate layer and interface states (Bardeen model), and the intimate contact model with the subsurface states. The nonlinearity of the bias dependence on the barrier height is due to the inhomogeneous energy distribution of the interface states (a decrease in density from the edges to the middle of the bandgap) and the inhomogeneous energy and coordinate (from the surface to the depth) distribution of the subsurface states. An essential feature for every model is also the condition that the barrier height and ideality factor are measured at a constant current (or in a constant range of currents) while studying contacts with different diameters or when measuring the IVCs at different temperatures. This condition is not difficult to achieve, but gives the necessary certainty to different barrier height values used in examining experimental results. Some limitations and shortcomings of the widely used model of inhomogeneous Schottky barrier contact with the "saddle points" are also discussed.

  19. Metallic oxide nanoparticle translocation across the human bronchial epithelial barrier

    NASA Astrophysics Data System (ADS)

    George, Isabelle; Naudin, Grégoire; Boland, Sonja; Mornet, Stéphane; Contremoulins, Vincent; Beugnon, Karine; Martinon, Laurent; Lambert, Olivier; Baeza-Squiban, Armelle

    2015-02-01

    Inhalation is the most frequent route of unintentional exposure to nanoparticles (NPs). Our aim was to quantify the translocation of different metallic NPs across human bronchial epithelial cells and to determine the factors influencing this translocation. Calu-3 cells forming a tight epithelial barrier when grown on a porous membrane in a two compartment chamber were exposed to fluorescently labelled NPs to quantify the NP translocation. NP translocation and uptake by cells were also studied by confocal and transmission electron microscopy. Translocation was characterized according to NP size (16, 50, or 100 nm), surface charge (negative or positive SiO2), composition (SiO2 or TiO2), presence of proteins or phospholipids and in an inflammatory context. Our results showed that NPs can translocate through the Calu-3 monolayer whatever their composition (SiO2 or TiO2), but this translocation was increased for the smallest and negatively charged NPs. Translocation was not associated with an alteration of the integrity of the epithelial monolayer, suggesting a transcytosis of the internalized NPs. By modifying the NP corona, the ability of NPs to cross the epithelial barrier differed depending on their intrinsic properties, making positively charged NPs more prone to translocate. NP translocation can be amplified by using agents known to open tight junctions and to allow paracellular passage. NP translocation was also modulated when mimicking an inflammatory context frequently found in the lungs, altering the epithelial integrity and inducing transient tight junction opening. This in vitro evaluation of NP translocation could be extended to other inhaled NPs to predict their biodistribution.Inhalation is the most frequent route of unintentional exposure to nanoparticles (NPs). Our aim was to quantify the translocation of different metallic NPs across human bronchial epithelial cells and to determine the factors influencing this translocation. Calu-3 cells forming a

  20. Li-substituted MgAl2O4 barriers for spin-dependent coherent tunneling

    NASA Astrophysics Data System (ADS)

    Scheike, Thomas; Sukegawa, Hiroaki; Mitani, Seiji

    2016-11-01

    Epitaxial magnetic tunnel junctions (MTJs) with a Li-substituted spinel MgAl2O4 barrier were prepared by sputtering and plasma oxidation of an Mg/LiAl bilayer. The formed MTJ with Fe(001) electrodes showed a relatively large tunnel magnetoresistance (TMR) ratio of 120% (174%) at room temperature (3 K) and two local minima in the tunneling conductance spectra (parallel magnetization), revealing the occurrence of the coherent tunneling effect through the Li-substituted spinel barrier. The results are likely to pave the way for a variety of quaternary spinel oxide barriers in which structural and transport properties of MTJs can be engineered in the coherent tunneling regime.

  1. Life Prediction of Atmospheric Plasma-Sprayed Thermal Barrier Coatings Using Temperature-Dependent Model Parameters

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Chen, Kuiying; Baddour, N.; Patnaik, P. C.

    2017-06-01

    The failure analysis and life prediction of atmospheric plasma-sprayed thermal barrier coatings (APS-TBCs) were carried out for a thermal cyclic process. A residual stress model for the top coat of APS-TBC was proposed and then applied to life prediction. This residual stress model shows an inversion characteristic versus thickness of thermally grown oxide. The capability of the life model was demonstrated using temperature-dependent model parameters. Using existing life data, a comparison of fitting approaches of life model parameters was performed. A larger discrepancy was found for the life predicted using linearized fitting parameters versus temperature compared to those using non-linear fitting parameters. A method for integrating the residual stress was proposed by using the critical time of stress inversion. The role of the residual stresses distributed at each individual coating layer was explored and their interplay on the coating's delamination was analyzed.

  2. Inside out: Speed-dependent barriers to reactive mixing

    NASA Astrophysics Data System (ADS)

    Kelley, Douglas; Nevins, Thomas

    2015-11-01

    Reactive mixing occurs wherever fluid flow and chemical or biological growth interact over time and space. Those interactions often lead to steep gradients in reactant and product concentration, arranged in complex spatial structures that can cause wide variation in the global reaction rate and concentrations. By simultaneously measuring fluid velocity and reaction front locations in laboratory experiments with the Belousov-Zhabotinsky reaction, we find that the barriers defining those structures vary dramatically with speed. In particular, we find that increasing flow speed causes reacted regions to move from vortex edges to vortex cores, thus turning the barriers ``inside out''. This observation has implications for reactive mixing of phytoplankton in global oceans.

  3. Criegee intermediate reaction with CO: mechanism, barriers, conformer-dependence, and implications for ozonolysis chemistry.

    PubMed

    Kumar, Manoj; Busch, Daryle H; Subramaniam, Bala; Thompson, Ward H

    2014-03-13

    Density functional theory and transition state theory rate constant calculations have been performed to gain insight into the bimolecular reaction of the Criegee intermediate (CI) with carbon monoxide (CO) that is proposed to be important in both atmospheric and industrial chemistry. A new mechanism is suggested in which the CI acts as an oxidant by transferring an oxygen atom to the CO, resulting in the formation of a carbonyl compound (aldehyde or ketone depending upon the CI) and carbon dioxide. Fourteen different CIs, including ones resulting from biogenic ozonolysis, are considered. Consistent with previous reports for other CI bimolecular reactions, the anti conformers are found to react faster than the syn conformers. However, this can be attributed to steric effects and not hyperconjugation as generally invoked. The oxidation reaction is slow, with barrier heights between 6.3 and 14.7 kcal/mol and estimated reaction rate constants 6-12 orders-of-magnitude smaller than previously reported literature estimates. The reaction is thus expected to be unimportant in the context of tropospheric oxidation chemistry. However, the reaction mechanism suggests that CO could be exploited in ozonolysis to selectively obtain industrially important carbonyl compounds.

  4. Non-thermal dielectric-barrier discharge plasma damages human keratinocytes by inducing oxidative stress

    PubMed Central

    KIM, KI CHEON; PIAO, MEI JING; HEWAGE, SUSARA RUWAN KUMARA MADDUMA; HAN, XIA; KANG, KYOUNG AH; JO, JIN OH; MOK, YOUNG SUN; SHIN, JENNIFER H.; PARK, YEUNSOO; YOO, SUK JAE; HYUN, JIN WON

    2016-01-01

    The aim of this study was to identify the mechanisms through which dielectric-barrier discharge plasma damages human keratinocytes (HaCaT cells) through the induction of oxidative stress. For this purpose, the cells were exposed to surface dielectric-barrier discharge plasma in 70% oxygen and 30% argon. We noted that cell viability was decreased following exposure of the cells to plasma in a time-dependent manner, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The levels of intracellular reactive oxygen species (ROS) were determined using 2′,7′-dichlorodihydro-fluorescein diacetate and dihydroethidium was used to monitor superoxide anion production. Plasma induced the generation of ROS, including superoxide anions, hydrogen peroxide and hydroxyl radicals. N-acetyl cysteine, which is an antioxidant, prevented the decrease in cell viability caused by exposure to plasma. ROS generated by exposure to plasma resulted in damage to various cellular components, including lipid membrane peroxidation, DNA breaks and protein carbonylation, which was detected by measuring the levels of 8-isoprostane and diphenyl-1-pyrenylphosphine assay, comet assay and protein carbonyl formation. These results suggest that plasma exerts cytotoxic effects by causing oxidative stress-induced damage to cellular components. PMID:26573561

  5. Non-thermal dielectric-barrier discharge plasma damages human keratinocytes by inducing oxidative stress.

    PubMed

    Kim, Ki Cheon; Piao, Mei Jing; Madduma Hewage, Susara Ruwan Kumara; Han, Xia; Kang, Kyoung Ah; Jo, Jin Oh; Mok, Young Sun; Shin, Jennifer H; Park, Yeunsoo; Yoo, Suk Jae; Hyun, Jin Won

    2016-01-01

    The aim of this study was to identify the mechanisms through which dielectric-barrier discharge plasma damages human keratinocytes (HaCaT cells) through the induction of oxidative stress. For this purpose, the cells were exposed to surface dielectric-barrier discharge plasma in 70% oxygen and 30% argon. We noted that cell viability was decreased following exposure of the cells to plasma in a time-dependent manner, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The levels of intracellular reactive oxygen species (ROS) were determined using 2',7'-dichlorodihydrofluorescein diacetate and dihydroethidium was used to monitor superoxide anion production. Plasma induced the generation of ROS, including superoxide anions, hydrogen peroxide and hydroxyl radicals. N-acetyl cysteine, which is an antioxidant, prevented the decrease in cell viability caused by exposure to plasma. ROS generated by exposure to plasma resulted in damage to various cellular components, including lipid membrane peroxidation, DNA breaks and protein carbonylation, which was detected by measuring the levels of 8-isoprostane and diphenyl-1-pyrenylphosphine assay, comet assay and protein carbonyl formation. These results suggest that plasma exerts cytotoxic effects by causing oxidative stress-induced damage to cellular components.

  6. Regular dependence of the Peierls barriers on perturbations

    NASA Astrophysics Data System (ADS)

    Chen, Qinbo; Cheng, Chong-Qing

    2017-05-01

    Let f be an exact area-preserving monotone twist diffeomorphism of the infinite cylinder and Pω,f (ξ) be the associated Peierls barrier. In this paper, we give the Hölder regularity of Pω,f (ξ) with respect to the parameter f. In fact, we prove that if the rotation symbol ω ∈ (R ∖ Q) ⋃ (Q +) ⋃ (Q -), then Pω,f (ξ) is 1/3-Hölder continuous in f, i.e.

  7. Online program for treating chemical dependency breaks down barriers.

    PubMed

    2002-01-01

    Providers caring for patients with substance abuse difficulties know how hard it is to get those patients the kind of help they need. Beyond insurance difficulties and a significant shortage of treatment programs, many patients lack the time needed to enter into traditional programs or they have privacy concerns that keep them from accessing this type of care. A new online approach to treatment seeks to address all these barriers while providing a traditional 12-step approach to care.

  8. Intracellular mediators of JAM-A-dependent epithelial barrier function.

    PubMed

    Monteiro, Ana C; Parkos, Charles A

    2012-06-01

    Junctional adhesion molecule-A (JAM-A) is a critical signaling component of the apical junctional complex, a structure composed of several transmembrane and scaffold molecules that controls the passage of nutrients and solutes across epithelial surfaces. Observations from JAM-A-deficient epithelial cells and JAM-A knockout animals indicate that JAM-A is an important regulator of epithelial paracellular permeability; however, the mechanism(s) linking JAM-A to barrier function are not understood. This review highlights recent findings relevant to JAM-A-mediated regulation of epithelial permeability, focusing on the role of upstream and downstream signaling candidates. We draw on what is known about proteins reported to associate with JAM-A in other pathways and on known modulators of barrier function to propose candidate effectors that may mediate JAM-A regulation of epithelial paracellular permeability. Further investigation of pathways highlighted in this review may provide ideas for novel therapeutics that target debilitating conditions associated with barrier dysfunction, such as inflammatory bowel disease.

  9. Comparison between two models of absorption of matter waves by a thin time-dependent barrier

    NASA Astrophysics Data System (ADS)

    Barbier, Maximilien; Beau, Mathieu; Goussev, Arseni

    2015-11-01

    We report a quantitative, analytical, and numerical comparison between two models of the interaction of a nonrelativistic quantum particle with a thin time-dependent absorbing barrier. The first model represents the barrier by a set of time-dependent discontinuous matching conditions, which are closely related to Kottler boundary conditions used in stationary-wave optics as a mathematical basis for Kirchhoff diffraction theory. The second model mimics the absorbing barrier with an off-diagonal δ potential with a time-dependent amplitude. We show that the two models of absorption agree in their predictions in a semiclassical regime, the regime readily accessible in modern experiments with ultracold atoms.

  10. Tantalum oxide-based plasma-sprayed environmental barrier coatings

    NASA Astrophysics Data System (ADS)

    Weyant, Christopher M.

    Energy efficiency in gas turbine engines is linked to the high temperature capabilities of materials used in the hot section of the engine. To facilitate a significant increase in engine efficiency, tough structural ceramics have been developed that can handle the thermo-mechanical stresses that gas turbine components experience. Unfortunately, the high-temperature, high-pressure, and high-velocity combustion gases in a gas turbine contain water vapor and/or hydrogen which have been shown to volatilize the protective silica layer on silicon-based ceramics. This degradation leads to significant surface recession in ceramic gas turbine components. In order to maintain their structural integrity, an environmental barrier coating (EBC) could be used to protect ceramics from the harsh gas turbine environment. Due to its coefficient of thermal expansion and phase stability at elevated temperatures, tantalum oxide (Ta2O5) was examined as the base material for an air plasma-sprayed EBC on Si3N 4 ceramics. As-sprayed pure Ta2O5 was comprised of both low-temperature beta-Ta2O5 and high-temperature alpha-Ta 2O5 that was quenched into the structure. Residual stress measurements via X-ray diffraction determined the as-sprayed coating to be in tension and extensive vertical macrocracks were observed in the coating. Heat treatments of the pure coating led to conversion of alpha-Ta2 O5 to beta-Ta2O5, conversion of tensile stresses to compressive, localized buckling of the coating, and significant grain growth which caused microcracking in the coating. The pure coating was found to be an inadequate EBC. Al2O3 was investigated as a solid solution alloying addition designed to enhance the stability of beta-Ta2O 5, and reduce grain growth by slowing grain boundary diffusion. La 2O3 was investigated as an alloying addition designed to form second phase particles which would reduce grain growth through pinning. Al2O3 was successful at both stabilizing beta-Ta 2O5 and reducing grain

  11. Dependence of Andreev reflection and Schottky barriers on GaMnAs/Nb interface treatment

    SciTech Connect

    Eid, K. F. Dahliah, D. F.; Abujeib, H. A.; Liu, X.; Furdyna, J. K.

    2015-05-07

    We studied the interfacial contact between GaMnAs and superconducting Nb micro-structures both with and without removing the native GaMnAs surface oxide. Our results show that a strong Schottky barrier forms at the interface when the oxide layer is left between Nb and GaMnAs. This barrier can be confused for Andreev Reflection and erroneously used to extract spin polarization. A simple acid etch is shown to remove the oxide film, thus decreasing the interface resistance, removing the Schottky barrier, and causing a clear Andreev reflection effect. One key recommendation for point contact Andreev reflection studies is to push the tip hard enough into contact and verify that the total resistance is not too high.

  12. Temperature dependent barrier height and ideality factor of electrodeposited n-CdSe/Cu Schottky barrier diode

    NASA Astrophysics Data System (ADS)

    Mahato, S.; Shiwakoti, N.; Kar, A. K.

    2015-06-01

    This article reports the measurement of temperature-dependent barrier height and ideality factor of n-CdSe/Cu Schottky barrier diode. The Cadmium Selenide (CdSe) thin films have been deposited by simple electrodeposition technique. The XRD measurements ravels the deposited single phase CdSe films are highly oriented on (002) plane and the average particle size has been calculated to be ~18 nm. From SEM characterization, it is clear that the surface of CdSe thin films are continuous, homogeneous and the film is well adhered to the substrate and consists of fine grains which are irregular in shape and size. Current-Voltage characteristics have been measured at different temperatures in the range (298 K - 353 K). The barrier height and ideality factor are found to be strongly temperature dependent. The inhomogenious barrier height increases and ideality factor decreases with increase in temperature. The expectation value has been calculated and its value is 0.30 eV.

  13. Temperature dependent barrier height and ideality factor of electrodeposited n-CdSe/Cu Schottky barrier diode

    SciTech Connect

    Mahato, S. Shiwakoti, N.; Kar, A. K.

    2015-06-24

    This article reports the measurement of temperature-dependent barrier height and ideality factor of n-CdSe/Cu Schottky barrier diode. The Cadmium Selenide (CdSe) thin films have been deposited by simple electrodeposition technique. The XRD measurements ravels the deposited single phase CdSe films are highly oriented on (002) plane and the average particle size has been calculated to be ~18 nm. From SEM characterization, it is clear that the surface of CdSe thin films are continuous, homogeneous and the film is well adhered to the substrate and consists of fine grains which are irregular in shape and size. Current-Voltage characteristics have been measured at different temperatures in the range (298 K – 353 K). The barrier height and ideality factor are found to be strongly temperature dependent. The inhomogenious barrier height increases and ideality factor decreases with increase in temperature. The expectation value has been calculated and its value is 0.30 eV.

  14. Influence of the nonlinear bias dependence of the barrier height on measured Schottky-barrier contact parameters

    NASA Astrophysics Data System (ADS)

    Bozhkov, V. G.; Shmargunov, A. V.

    2011-06-01

    A numerical investigation of current-voltage characteristics (IVCs) of the ideal metal-semiconductor Schottky-barrier contact (SBC) metal-n-GaAs in the wide range of temperatures, contact diameters and doping levels considering the influence of image force and tunneling effects is presented. The analysis is carried out on the basis of model, taking into account the nonlinear bias dependence of the barrier height (generally, effective one) and assuming that the SBC parameters are determined at constant (specified) current value in the temperature or contact diameter ranges, which corresponds practically to experimental conditions of measurement of SBC parameters. It is shown that such SBCs have behavior peculiarities typical for most real contacts: the "low temperature anomaly" (the ideality factor n increase and the barrier height ϕbm (measured by the saturation current) decrease with temperature decrease), edge effects (increase of n and decrease of ϕbm with contact diameter decrease), the inverse connection between ϕbm and n, when the growth of one of them is followed by the decrease of the other. A simple and very precise analytic representation of the IVC is given for the SBC in wide temperature and doping level ranges. This representation agrees closely with known experimental results. The high-accuracy method of the barrier height determining is proposed on this basis.

  15. Phase stability of thermal barrier oxides based on t'-zirconia with trivalent oxide additions

    NASA Astrophysics Data System (ADS)

    Rebollo Franco, Noemi Rosa

    Zirconia stabilized with 7+/-1 wt.% addition of yttria (7YSZ) is widely used for thermal barrier coatings (TBC's) on actively cooled gas turbine components, selected partly because of its superior durability under thermal cyclic conditions. As deposited, 7YSZ occurs as a metastable single-phase tetragonal solid solution (t') that is thermodynamically stable against the deleterious transformation to monoclinic upon cooling. However, at high temperatures t' is driven to decompose diffusionally into an equilibrium mixture of high-Y cubic and low-Y tetragonal; the latter becomes transformable to monoclinic compromising the mechanical integrity of the system. This dissertation explores the effects of trivalent stabilizers, including Y, Sc and selected rare-earth oxides (REO's), on the phase stability of the resulting solid solutions in zirconia. The REO additions are of interest because they can potentially enhance the insulation efficiency on the coating allowing higher operating temperatures. However, understanding of their effects on phase stability and potentially on cyclic durability at the projected use temperature in next generation engines (1200-1400°C) is insufficient to guide the design of coatings with the desirable combination of lower thermal conductivity and acceptable durability. Sc was also investigated because of previous reports on the higher phase stability of materials doped with Sc, and Y served as the baseline. The experimental approach is based on powders synthesized by reverse co-precipitation of precursor solutions, usually compacted and then subjected to a variety of heat treatments, following their evolution by means of X-ray diffractometry, dilatometry, transmission electron microscopy and Raman spectroscopy. The use of powders facilitated the synthesis of a wider range of compositions that would not have been possible by coating deposition approaches, and because the synthesis occurs at low temperature, it also enabled the starting

  16. Methamphetamine disrupts blood-brain barrier function by induction of oxidative stress in brain endothelial cells.

    PubMed

    Ramirez, Servio H; Potula, Raghava; Fan, Shongshan; Eidem, Tess; Papugani, Anil; Reichenbach, Nancy; Dykstra, Holly; Weksler, Babette B; Romero, Ignacio A; Couraud, Pierre O; Persidsky, Yuri

    2009-12-01

    Methamphetamine (METH), a potent stimulant with strong euphoric properties, has a high abuse liability and long-lasting neurotoxic effects. Recent studies in animal models have indicated that METH can induce impairment of the blood-brain barrier (BBB), thus suggesting that some of the neurotoxic effects resulting from METH abuse could be the outcome of barrier disruption. In this study, we provide evidence that METH alters BBB function through direct effects on endothelial cells and explore possible underlying mechanisms leading to endothelial injury. We report that METH increases BBB permeability in vivo, and exposure of primary human brain microvascular endothelial cells (BMVEC) to METH diminishes the tightness of BMVEC monolayers in a dose- and time-dependent manner by decreasing the expression of cell membrane-associated tight junction (TJ) proteins. These changes were accompanied by the enhanced production of reactive oxygen species, increased monocyte migration across METH-treated endothelial monolayers, and activation of myosin light chain kinase (MLCK) in BMVEC. Antioxidant treatment attenuated or completely reversed all tested aspects of METH-induced BBB dysfunction. Our data suggest that BBB injury is caused by METH-mediated oxidative stress, which activates MLCK and negatively affects the TJ complex. These observations provide a basis for antioxidant protection against brain endothelial injury caused by METH exposure.

  17. Bi-functional anodic TiO2 oxide: Nanotubes for wettability control and barrier oxide for uniform coloring

    NASA Astrophysics Data System (ADS)

    Kim, Sunkyu; Jung, Minkyeong; Kim, Moonsu; Choi, Jinsub

    2017-06-01

    A uniformly colored TiO2, on which the surface is functionalized with nanotubes to control wettability, was prepared by a two-step anodization; the first anodization was carried out to prepare nanotubes for a super-hydrophilic or -hydrophobic surface and the second anodization was performed to fabricate a thin film barrier oxide to ensure uniform coloring. The effect of the nanotubes on barrier oxide coloring was examined by spectrophotometry and UV-vis-IR spectroscopy. We found four different regimes governing the color changes in terms of anodization voltage, indicating that the color of the duplex TiO2 was primarily determined by the thickness of the barrier oxide layer formed during the second anodization step. The surface wettability, as confirmed by the water contact angle, revealed that the single barrier TiO2 yielded 74.6° ± 2.1, whereas the nanotubes on the barrier oxide imparted super-hydrophilic properties as a result of increasing surface roughness as well as imparting a higher hydrophobicity after organic acid treatment.

  18. Advanced Multi-Component Defect Cluster Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1990-01-01

    The advantages of using ceramic thermal barrier coatings in gas turbine engine hot sections include increased fuel efficiency and improved engine reliability. However, current thermal barrier coatings will not have the low thermal conductivity and necessary sintering resistance under higher operating temperatures and thermal gradients required by future advanced ultra-efficient and low-emission aircraft engines. In this paper, a novel oxide defect cluster design approach is described for achieving low thermal conductivity and excellent thermal stability of the thermal barrier coating systems. This approach utilizes multi-component rare earth and other metal cluster oxide dopants that are incorporated in the zirconia-yttria based systems, thus significantly reducing coating thermal conductivity and sintering resistance by effectively promoting the formation of thermodynamically stable, essentially immobile defect clusters and/or nanoscale phases. The performance of selected plasma-sprayed cluster oxide thermal barrier coating systems has been evaluated. The advanced multi-component thermal barrier coating systems were found to have significantly lower initial and long-term thermal conductivities, and better high temperature stability. The effect of oxide cluster dopants on coating thermal conductivity, sintering resistance, oxide grain growth behavior and durability will be discussed.

  19. Advanced Multi-Component Defect Cluster Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    2003-01-01

    The advantages of using ceramic thermal barrier coatings in gas turbine engine hot sections include increased fuel efficiency and improved engine reliability. However, current thermal barrier coatings will not have the low thermal conductivity and necessary sintering resistance under higher operating temperatures and thermal gradients required by future advanced ultra efficient and low emission aircraft engines. In this paper, a novel oxide defect cluster design approach is described for achieving low thermal conductivity and excellent thermal stability of the thermal barrier coating systems. This approach utilizes multi-component rare earth and other metal cluster oxide dopants that are incorporated in the zirconia-yttna based systems, thus significantly reducing coating thermal conductivity and sintering resistance by effectively promoting the formation of thermodynamically stable, essentially immobile defect clusters and/or nanoscale phases. The performance of selected plasma-sprayed cluster oxide thermal barrier coating systems has been evaluated. The advanced multi-component thermal barrier coating systems were found to have significantly lower initial and long-term thermal conductivities, and better high temperature stability. The effect of oxide cluster dopants on coating thermal conductivity, sintering resistance, oxide grain growth behavior and durability will be discussed.

  20. Barriers to Quitting Smoking Among Substance Dependent Patients Predict Smoking Cessation Treatment Outcome.

    PubMed

    Martin, Rosemarie A; Cassidy, Rachel N; Murphy, Cara M; Rohsenow, Damaris J

    2016-05-01

    For smokers with substance use disorders (SUD), perceived barriers to quitting smoking include concerns unique to effects on sobriety as well as usual concerns. We expanded our Barriers to Quitting Smoking in Substance Abuse Treatment (BQS-SAT) scale, added importance ratings, validated it, and then used the importance scores to predict smoking treatment response in smokers with substance use disorders (SUD) undergoing smoking treatment in residential treatment programs in two studies (n=184 and 340). Both components (general barriers, weight concerns) were replicated with excellent internal consistency reliability. Construct validity was supported by significant correlations with pretreatment nicotine dependence, smoking variables, smoking self-efficacy, and expected effects of smoking. General barriers significantly predicted 1-month smoking abstinence, frequency and heaviness, and 3-month smoking frequency; weight concerns predicted 1-month smoking frequency. Implications involve addressing barriers with corrective information in smoking treatment for smokers with SUD.

  1. A sphingolipid-dependent diffusion barrier confines ER stress to the yeast mother cell

    PubMed Central

    Clay, Lori; Caudron, Fabrice; Denoth-Lippuner, Annina; Boettcher, Barbara; Buvelot Frei, Stéphanie; Snapp, Erik Lee; Barral, Yves

    2014-01-01

    In many cell types, lateral diffusion barriers compartmentalize the plasma membrane and, at least in budding yeast, the endoplasmic reticulum (ER). However, the molecular nature of these barriers, their mode of action and their cellular functions are unclear. Here, we show that misfolded proteins of the ER remain confined into the mother compartment of budding yeast cells. Confinement required the formation of a lateral diffusion barrier in the form of a distinct domain of the ER-membrane at the bud neck, in a septin-, Bud1 GTPase- and sphingolipid-dependent manner. The sphingolipids, but not Bud1, also contributed to barrier formation in the outer membrane of the dividing nucleus. Barrier-dependent confinement of ER stress into the mother cell promoted aging. Together, our data clarify the physical nature of lateral diffusion barriers in the ER and establish the role of such barriers in the asymmetric segregation of proteotoxic misfolded proteins during cell division and aging. DOI: http://dx.doi.org/10.7554/eLife.01883.001 PMID:24843009

  2. Coherent magnetotunneling based on (001) magnesium oxide barrier

    NASA Astrophysics Data System (ADS)

    Mazumdar, Dipanjan

    2007-12-01

    Spintronics (spin-based electronics) is an emerging field which relies on the electronic spin degree of freedom to create superior devices. In 2001, first-principles calculations predicted extremely large magnetoresistance (MR) of well over 1000% in magnetic tunnel junctions (MTJs) that used (001) MgO as the insulating barrier. This large effect is achieved when conduction electrons conserve their symmetry inside the barrier, leading to spin-coherent tunneling. Since then, a few experimental groups, which include our group at Brown, have successfully realized high MR values on such systems. I shall present our recent work on MTJs with (001) MgO tunnel barrier. After a brief introduction of the MR effect, I shall focus on the fabrication and room temperature transport properties of MgO-based MTJs with MR values of over 200%. Also, these MTJs are highly suitable for low magnetic field sensing. In the later half, I shall describe our investigations of the low frequency noise in these devices. Noise spectra are 1/f, and scales with the field sensitivity of the MTJ, indicating that the noise arises predominantly from intrinsic magnetization fluctuations. Special attention was paid to reduce the magnetic field noise level. We show that the application of an external hard-axis bias field significantly reduces this noise by suppressing the magnetic fluctuations.

  3. Spin-dependent tunneling junctions with AlN and AlON barriers

    NASA Astrophysics Data System (ADS)

    Sharma, Manish; Nickel, Janice H.; Anthony, Thomas C.; Wang, Shan X.

    2000-10-01

    We report on ferromagnetic spin-dependent tunneling (SDT) junctions with NiFe/AlN/NiFe and NiFe/AlON/NiFe structures. Good barriers were formed by plasma nitridation and oxy-nitridation of Al films. Tunneling magnetoresistance ratios (TMR) up to 18% were observed at room temperature. The devices exhibit lower resistance-area products than those seen in reference junctions with Al2O3 barriers. The degradation in TMR at higher bias voltages is found to be less than that found in standard alumina junctions. AlN and AlON could thus be alternate materials for the tunnel barrier in SDT junctions.

  4. Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

    SciTech Connect

    Baggetto, Loic; Charvillat, Cedric; Thebault, Yannick; Esvan, Jerome; Lafont, Marie-Christine; Scheid, Emmanuel; Veith, Gabriel M.; Vahlas, Constantin

    2015-12-02

    Ti/Al2O3 bilayer stacks are used as model systems to investigate the role of atomic layer deposition (ALD) and chemical vapor deposition (CVD) to prepare 30-180 nm thick amorphous alumina films as protective barriers for the medium temperature oxidation (500-600⁰C) of titanium, which is employed in aeronautic applications. X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) results show that the films produced from the direct liquid injection (DLI) CVD of aluminum tri-isopropoxide (ATI) are poor oxygen barriers. The films processed using the ALD of trimethylaluminum (TMA) show good barrier properties but an extensive intermixing with Ti which subsequently oxidizes. In contrast, the films prepared from dimethyl aluminum isopropoxide (DMAI) by CVD are excellent oxygen barriers and show little intermixing with Ti. Overall, these measurements correlate the effect of the alumina coating thickness, morphology, and stoichiometry resulting from the preparation method to the oxidation barrier properties, and show that compact and stoichiometric amorphous alumina films offer superior barrier properties.

  5. Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

    DOE PAGES

    Baggetto, Loic; Charvillat, Cedric; Thebault, Yannick; ...

    2015-12-02

    Ti/Al2O3 bilayer stacks are used as model systems to investigate the role of atomic layer deposition (ALD) and chemical vapor deposition (CVD) to prepare 30-180 nm thick amorphous alumina films as protective barriers for the medium temperature oxidation (500-600⁰C) of titanium, which is employed in aeronautic applications. X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) results show that the films produced from the direct liquid injection (DLI) CVD of aluminum tri-isopropoxide (ATI) are poor oxygen barriers. The films processed using the ALD of trimethylaluminum (TMA) show good barrier properties butmore » an extensive intermixing with Ti which subsequently oxidizes. In contrast, the films prepared from dimethyl aluminum isopropoxide (DMAI) by CVD are excellent oxygen barriers and show little intermixing with Ti. Overall, these measurements correlate the effect of the alumina coating thickness, morphology, and stoichiometry resulting from the preparation method to the oxidation barrier properties, and show that compact and stoichiometric amorphous alumina films offer superior barrier properties.« less

  6. Thin Oxides as a Cu Diffusion Barrier for NIF Be Ablator Capsules

    SciTech Connect

    Youngblood, Kelly P.; Huang, H.; Xu, H. W.; Hayes, J.; Moreno, K. A.; Wu, J. J.; Nikroo, A.; Alford, C. A.; Hamza, A. V.; Kucheyev, S. O.; Wang, Y. M.; Wu, K. J.

    2013-03-01

    The NIF point design uses a five-layer capsule to modify the X-ray absorption in order to achieve optimized shock timing. A stepped copper dopant design defines the layer structure. The production of the capsule involves pyrolysis to remove the inner plastic mandrel. Copper atoms diffuse radially and azimuthally throughout the capsule during pyrolysis. This diffusion significantly diminishes the capsule performance during implosion. Thermal and coated oxide barrier layers employed between layers mitigate the diffusion of copper during the mandrel removal process. The copper atoms do not diffuse through this barrier during pyrolysis. A capsule fabrication method that produces a capsule with a thin oxide layer will be discussed.

  7. Highly defective oxides as sinter resistant thermal barrier coating

    DOEpatents

    Subramanian, Ramesh

    2005-08-16

    A thermal barrier coating material formed of a highly defective cubic matrix structure having a concentration of a stabilizer sufficiently high that the oxygen vacancies created by the stabilizer interact within the matrix to form multi-vacancies, thereby improving the sintering resistance of the material. The concentration of stabilizer within the cubic matrix structure is greater than that concentration of stabilizer necessary to give the matrix a peak ionic conductivity value. The concentration of stabilizer may be at least 30 wt. %. Embodiments include a cubic matrix of zirconia stabilized by at least 30-50 wt. % yttria, and a cubic matrix of hafnia stabilized by at least 30-50 wt. % gadolinia.

  8. Healthcare Preferences among Nursing Home Residents: Perceived Barriers and Situational Dependencies

    PubMed Central

    Bangerter, Lauren R.; Abbott, Katherine; Heid, Allison R.; Klumpp, Rachel E.; Van Haitsma, Kimberly

    2016-01-01

    While much research has examined end of life care preferences of nursing home (NH) residents, little work has examined resident preferences for everyday healthcare. The present study conducted interviews with 255 residents recruited from 35 NHs. Content analysis identified barriers (hindrances to the fulfillment of resident preferences) and situational dependencies (what would make residents change their mind about the importance of these preferences) associated with preferences for utilizing mental health services, choosing a medical care provider, and choosing individuals involved in care discussions. Barriers and situational dependencies were embedded within the person, facility environment, and social environment. Nearly half of residents identified barriers to their preferences of choosing others involved in care and choosing a medical care provider. In contrast, the importance of mental health services was situationally dependent on needs of residents. Results highlight opportunities for improvement in practice and facility policies that promote person-centered care. PMID:26716460

  9. Oxidation Resistance: One Barrier to Moving Beyond Ni-Base Superalloys

    SciTech Connect

    Pint, Bruce A; Distefano, James R; Wright, Ian G

    2006-01-01

    The implementation of new high-temperature materials is often hampered by their lack of oxidation or environmental resistance. This failing is one of the strongest barriers to moving beyond Ni-base superalloys for many commercial applications. In practice, usable high-temperature alloys have at least reasonable oxidation resistance, but the current generation of single-crystal Ni-base superalloys has sufficient oxidation resistance that optimized versions can be used without a metallic bond coating and only an oxygen-transparent ceramic coating for thermal protection. The material development process often centers around mechanical properties, while oxidation resistance, along with other realities, is given minor attention. For many applications, the assumption that an oxidation-resistant coating can be used to protect a substrate is seriously flawed, as coatings often do not provide sufficient reliability for critical components. Examples of oxidation problems are given for currently used materials and materials classes with critical oxidation resistance problems.

  10. Nox2-dependent glutathionylation of endothelial NOS leads to uncoupled superoxide production and endothelial barrier dysfunction in acute lung injury.

    PubMed

    Wu, Feng; Szczepaniak, William S; Shiva, Sruti; Liu, Huanbo; Wang, Yinna; Wang, Ling; Wang, Ying; Kelley, Eric E; Chen, Alex F; Gladwin, Mark T; McVerry, Bryan J

    2014-12-15

    Microvascular barrier integrity is dependent on bioavailable nitric oxide (NO) produced locally by endothelial NO synthase (eNOS). Under conditions of limited substrate or cofactor availability or by enzymatic modification, eNOS may become uncoupled, producing superoxide in lieu of NO. This study was designed to investigate how eNOS-dependent superoxide production contributes to endothelial barrier dysfunction in inflammatory lung injury and its regulation. C57BL/6J mice were challenged with intratracheal LPS. Bronchoalveolar lavage fluid was analyzed for protein accumulation, and lung tissue homogenate was assayed for endothelial NOS content and function. Human lung microvascular endothelial cell (HLMVEC) monolayers were exposed to LPS in vitro, and barrier integrity and superoxide production were measured. Biopterin species were quantified, and coimmunoprecipitation (Co-IP) assays were performed to identify protein interactions with eNOS that putatively drive uncoupling. Mice exposed to LPS demonstrated eNOS-dependent increased alveolar permeability without evidence for altered canonical NO signaling. LPS-induced superoxide production and permeability in HLMVEC were inhibited by the NOS inhibitor nitro-l-arginine methyl ester, eNOS-targeted siRNA, the eNOS cofactor tetrahydrobiopterin, and superoxide dismutase. Co-IP indicated that LPS stimulated the association of eNOS with NADPH oxidase 2 (Nox2), which correlated with augmented eNOS S-glutathionylation both in vitro and in vivo. In vitro, Nox2-specific inhibition prevented LPS-induced eNOS modification and increases in both superoxide production and permeability. These data indicate that eNOS uncoupling contributes to superoxide production and barrier dysfunction in the lung microvasculature after exposure to LPS. Furthermore, the results implicate Nox2-mediated eNOS-S-glutathionylation as a mechanism underlying LPS-induced eNOS uncoupling in the lung microvasculature.

  11. Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide

    NASA Technical Reports Server (NTRS)

    Douglas, F. C.; Paradis, E. L.; Veltri, R. D.

    1973-01-01

    A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed.

  12. Use of aluminum as an oxidation barrier for titanium

    NASA Technical Reports Server (NTRS)

    Unnam, J.; Shenoy, R. N.; Wiedemann, K. E.; Clark, R. K.

    1985-01-01

    A study is conducted of the use of aluminum coatings as oxidation retardants for Ti alloys, using room temperature normal emittance and spectral emittance as bases for the characterization of oxidation properties with and without the coatings. Thermal exposures were conducted in a thermogravimetric analysis apparatus in which specimen weight was continuously monitored. The results obtained indicate that the weight gains are proportional to the square root of the time for uncoated alloys and for 649 C-exposed aluminum-coated alloys. For the 704 C-exposed aluminum-coated alloys, weight gain exhibits a low rate for short and a high rate for long exposure times, implying that the 0.5-micron coating's protection decreases for long exposures at this temperature.

  13. Asymmetric spin absorption across a low-resistance oxide barrier

    SciTech Connect

    Chen, Shuhan; Qin, Chuan; Ji, Yi

    2015-07-21

    An unconventional method of nonlocal spin detection is demonstrated in mesoscopic lateral spin valves at room temperature. Clear nonlocal spin signals are detected between the two ends of an extended ferromagnetic spin detector. This is different from the conventional method in which the nonlocal voltage is measured between the spin detector and the nonmagnetic channel. The results can be understood as spatially non-uniform absorption of a pure spin current into the spin detector across a low-resistance oxide interface.

  14. Comparison study of ferrofluid and powder iron oxide nanoparticle permeability across the blood–brain barrier

    PubMed Central

    Hoff, Dan; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

    2013-01-01

    In the present study, the permeability of 11 different iron oxide nanoparticle (IONP) samples (eight fluids and three powders) was determined using an in vitro blood–brain barrier model. Importantly, the results showed that the ferrofluid formulations were statistically more permeable than the IONP powder formulations at the blood–brain barrier, suggesting a role for the presently studied in situ synthesized ferrofluid formulations using poly(vinyl) alcohol, bovine serum albumin, collagen, glutamic acid, graphene, and their combinations as materials which can cross the blood–brain barrier to deliver drugs or have other neurological therapeutic efficacy. Conversely, the results showed the least permeability across the blood–brain barrier for the IONP with collagen formulation, suggesting a role as a magnetic resonance imaging contrast agent but limiting IONP passage across the blood–brain barrier. Further analysis of the data yielded several trends of note, with little correlation between permeability and fluid zeta potential, but a larger correlation between permeability and fluid particle size (with the smaller particle sizes having larger permeability). Such results lay the foundation for simple modification of iron oxide nanoparticle formulations to either promote or inhibit passage across the blood–brain barrier, and deserve further investigation for a wide range of applications. PMID:23426527

  15. Comparison study of ferrofluid and powder iron oxide nanoparticle permeability across the blood-brain barrier.

    PubMed

    Hoff, Dan; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

    2013-01-01

    In the present study, the permeability of 11 different iron oxide nanoparticle (IONP) samples (eight fluids and three powders) was determined using an in vitro blood-brain barrier model. Importantly, the results showed that the ferrofluid formulations were statistically more permeable than the IONP powder formulations at the blood-brain barrier, suggesting a role for the presently studied in situ synthesized ferrofluid formulations using poly(vinyl) alcohol, bovine serum albumin, collagen, glutamic acid, graphene, and their combinations as materials which can cross the blood-brain barrier to deliver drugs or have other neurological therapeutic efficacy. Conversely, the results showed the least permeability across the blood-brain barrier for the IONP with collagen formulation, suggesting a role as a magnetic resonance imaging contrast agent but limiting IONP passage across the blood-brain barrier. Further analysis of the data yielded several trends of note, with little correlation between permeability and fluid zeta potential, but a larger correlation between permeability and fluid particle size (with the smaller particle sizes having larger permeability). Such results lay the foundation for simple modification of iron oxide nanoparticle formulations to either promote or inhibit passage across the blood-brain barrier, and deserve further investigation for a wide range of applications.

  16. Temperature-dependent electrical transport properties of (Au/Ni)/n-GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Dogan, Hulya; Elagoz, Sezai

    2014-09-01

    The temperature-dependent electrical properties of (Au/Ni)/n-GaN Schottky barrier diodes (SBDs)have been investigated in the wide temperature range of 40-400 K. The analysis of the main electrical characteristics such as zero-bias barrier height (ΦB0), ideality factor (n) and series resistance (Rs) were found strongly temperature dependent. Such behavior is attributed to barrier inhomogeneities by assuming a Gaussian distribution (GD) of barrier heights (BHs) at the interface. It is evident that the diode parameters such as zero-bias barrier height increases and the ideality factor decreases with increasing temperature. The values of series resistance that are obtained from Cheung's method are decreasing with increasing temperature. The temperature dependence of Schottky barrier height (SBD) and ideality factor (n) are explained by invoking three sets of Gaussian distribution of (SBH) in the temperature ranges of 280-400 K, 120-260 K and 40-100 K, respectively. (Au/Ni)/n-GaN Schottky barrier diode have been shown a Gaussian distribution giving mean BHs (ΦbarB0) of 1.167, 0.652 and 0.356 eV and standard deviation σs of 0.178, 0.087 and 0.133 V for the three temperature regions. A modified ln(I0/T2)-q2σ2/2k2T2 vs. 1/kT plot have given ΦbarB0 and A* as 1.173 eV and 34.750 A/cm2 K2, 0.671 eV and 26.293 A/cm2 K2, 0.354 eV and 10.199 A/cm2 K2, respectively.

  17. Radiation dose dependent change in physiochemical, mechanical and barrier properties of guar gum based films.

    PubMed

    Saurabh, Chaturbhuj K; Gupta, Sumit; Bahadur, Jitendra; Mazumder, S; Variyar, Prasad S; Sharma, Arun

    2013-11-06

    Mechanical and water vapor barrier properties of biodegradable films prepared from radiation processed guar gum were investigated. Films prepared from GG irradiated up to 500 Gy demonstrated significantly higher tensile strength as compared to non-irradiated control films. This improvement in tensile strength observed was demonstrated to be due to the ordering of polymer structures as confirmed by small angle X-ray scattering analysis. Exposure to doses higher than 500 Gy, however, resulted in a dose dependent decrease in tensile strength. A dose dependent decrease in puncture strength with no significant differences in the percent elongation was also observed at all the doses studied. Water vapor barrier properties of films improved up to 15% due to radiation processing. Radiation processing at lower doses for improving mechanical and barrier properties of guar based packaging films is demonstrated here for the first time.

  18. Manganese Dependent Anaerobic Oxidation of Methane

    NASA Astrophysics Data System (ADS)

    Beal, E.; House, C.

    2007-12-01

    Understanding the anaerobic oxidation is not only important for understanding hydrocarbon degradation but it also important for understanding the global carbon cycle. The anaerobic oxidation of methane (AOM) is a large sink for methane consuming 5-20% of today's methane flux (Valentine and Reeburgh, 2000), yet the requirements for this process are not well understood. It has been suggested that no other electron acceptors other than sulfate can be used in the AOM (Nauhaus, 2005). However, our new data suggests that manganese, in the form of birnessite, can be used as an electron acceptor instead of sulfate (Beal et al., in prep). Methane seep sediment from the Eel River Basin, CA was incubated with methane, 13C-labeled methane, and carbon dioxide. Because the net result of the AOM is the production of carbon dioxide from methane, the rate of the AOM in each of the incubations can be determined by measuring the incorporation of 13C in the carbon dioxide. Using this method, it was found that cultures incubated with nitrate showed inhibition of the AOM, while cultures incubated with iron gave inconclusive results. The only positive results that were found for alternate electron acceptors are the incubations that were given manganese and no sulfate, which showed methane oxidation. Further, when more manganese was injected into these incubations, the rate of AOM increased. Preliminary analysis of the microbial population using terminal restriction fragment length polymorphism (TRFLP) targeting the mcr gene showed an unidentified organism in these cultures. Future work with TRFLP, as well as clone libraries, will help to identify the organisms responsible for this process. Nauhaus, K., 2005, Environmental regulation of the anaerobic oxidation of methane: a comparison of ANME-I and ANME-II communities: Environmental microbiology, v. 7, p. 98. Valentine, D.L., and Reeburgh, W.S., 2000, New perspectives on anaerobic methane oxidation: Environmental Microbiology, v. 2, p

  19. Vasoinhibins regulate the inner and outer blood-retinal barrier and limit retinal oxidative stress

    PubMed Central

    Arredondo Zamarripa, David; Díaz-Lezama, Nundehui; Meléndez García, Rodrigo; Chávez Balderas, Jesús; Adán, Norma; Ledesma-Colunga, Maria G.; Arnold, Edith; Clapp, Carmen; Thebault, Stéphanie

    2014-01-01

    Vasoinhibins are prolactin fragments present in the retina, where they have been shown to prevent the hypervasopermeability associated with diabetes. Enhanced bradykinin (BK) production contributes to the increased transport through the blood-retina barrier (BRB) in diabetes. Here, we studied if vasoinhibins regulate BRB permeability by targeting the vascular endothelium and retinal pigment epithelium (RPE) components of this barrier. Intravitreal injection of BK in male rats increased BRB permeability. Vasoinhibins prevented this effect, as did the B2 receptor antagonist Hoe-140. BK induced a transient decrease in mouse retinal and brain capillary endothelial monolayer resistance that was blocked by vasoinhibins. Both vasoinhibins and the nitric oxide (NO) synthase inhibitor L-NAME, but not the antioxidant N-acetyl cysteine (NAC), blocked the transient decrease in bovine umbilical vein endothelial cell (BUVEC) monolayer resistance induced by BK; this block was reversed by the NO donor DETANONOate. Vasoinhibins also prevented the BK-induced actin cytoskeleton redistribution, as did L-NAME. BK transiently decreased human RPE (ARPE-19) cell monolayer resistance, and this effect was blocked by vasoinhibins, L-NAME, and NAC. DETANONOate reverted the blocking effect of vasoinhibins. Similar to BK, the radical initiator Luperox induced a reduction in ARPE-19 cell monolayer resistance, which was prevented by vasoinhibins. These effects on RPE resistance coincided with actin cytoskeleton redistribution. Intravitreal injection of vasoinhibins reduced the levels of reactive oxygen species (ROS) in retinas of streptozotocin-induced diabetic rats, particularly in the RPE and capillary-containing layers. Thus, vasoinhibins reduce BRB permeability by targeting both its main inner and outer components through NO- and ROS-dependent pathways, offering potential treatment strategies against diabetic retinopathies. PMID:25368550

  20. Isothermal and cyclic oxidation of an air plasma-sprayed thermal barrier coating system

    SciTech Connect

    Haynes, J.A.; Ferber, M.K.; Porter, W.D.; Rigney, E.D.

    1996-08-01

    Thermogravimetric methods for evaluating bond coat oxidation in plasma-sprayed thermal barrier coating (TBC) systems were assessed by high-temperature testing of TBC systems with air plasma-sprayed (APS) Ni-22Cr-10Al-1Y bond coatings and yttria-stabilized zirconia top coatings. High-mass thermogravimetric analysis (at 1150{sup degrees}C) was used to measure bond coat oxidation kinetics. Furnace cycling was used to evaluate APS TBC durability. This paper describes the experimental methods and relative oxidation kinetics of the various specimen types. Characterization of the APS TBCs and their reaction products is discussed.

  1. Oxidative challenge enhances REGγ-proteasome-dependent protein degradation.

    PubMed

    Zhang, Yuanyuan; Liu, Shuang; Zuo, Qiuhong; Wu, Lin; Ji, Lei; Zhai, Wanli; Xiao, Jianru; Chen, Jiwu; Li, Xiaotao

    2015-05-01

    Elimination of oxidized proteins is important to cells as accumulation of damaged proteins causes cellular dysfunction, disease, and aging. Abundant evidence shows that the 20S proteasome is largely responsible for degradation of oxidative proteins in both ubiquitin-dependent and ubiquitin-independent pathways. However, the role of the REGγ-proteasome in degrading oxidative proteins remains unclear. Here, we focus on two of the well-known REGγ-proteasome substrates, p21(Waf1/Cip1) and hepatitis C virus (HCV) core protein, to analyze the impact of oxidative stress on REGγ-proteasome functions. We demonstrate that REGγ-proteasome is essential for oxidative stress-induced rapid degradation of p21 and HCV proteins. Silencing REGγ abrogated this response in multiple cell lines. Furthermore, pretreatment with proteasome inhibitor MG132 completely blunted oxidant-induced p21 degradation, indicating a proteasome-dependent action. Cellular oxidation promoted REGγ-proteasome-dependent trypsin-like activity by enhancing the interaction between REGγ and 20S proteasome. Antioxidant could counteract oxidation-induced protein degradation, indicating that REGγ-proteasome activity may be regulated by redox state. This study provides further insights into the actions of a unique proteasome pathway in response to an oxidative stress environment, implying a novel molecular basis for REGγ-proteasome functions in antioxidation. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Anaerobic Nitrate-Dependent Metal Bio-Oxidation

    NASA Astrophysics Data System (ADS)

    Weber, K.; Knox, T.; Achenbach, L. A.; Coates, J. D.

    2007-12-01

    Direct biological oxidation of reduced metals (Fe(II) and U(IV)) coupled to nitrate reduction at circumneutral pH under anaerobic conditions has been recognized in several environments as well as pure culture. Several phylogentically diverse mesophilic bacteria have been described as capable of anaerobic, nitrate-dependent Fe(II) oxidation (NFOx). Our recent identification of a freshwater mesophilic, lithoautotroph, Ferrutens nitratireducens strain 2002, capable of growth through NFOx presents an opportunity to further study metal bio- oxidation. Continuing physiological studies revealed that in addition to Fe(II) oxidation, strain 2002 is capable of oxidizing U(IV) (4 μM) in washed cell suspensions with nitrate serving as the electron acceptor. Pasteurized cultures exhibited abiotic oxidation of 2 μM U(IV). Under growth conditions, strain 2002 catalyzed the oxidation of 12 μM U(IV) within a two week period. Cultures amended with sodium azide, an electron transport inhibitor, demonstrated limited oxidation (7 μM) similar to pasteurized cultures, supporting the direct role of electron transport in U(IV) bio-oxidation. The oxidation of U(IV) coupled denitrification at circumneutral pH would yield enough energy to support anaerobic microbial growth (ΔG°'= -460.36 kJ/mole). It is currently unknown whether or not strain 2002 can couple this metabolism to growth. The growth of F. nitratireducens strain 2002 utilizing Fe(II) as the sole electron donor was previously demonstrated. The amount of U(IV) (~12 μM) that strain 2002 oxidized under similar autotrophic growth conditions yields 0.0019 kJ, enough energy for the generation of ATP (5.3 x 10-20 kJ ATP-1), but not enough energy for cell replication as calculated for nitrate-dependent Fe(II) oxidizing conditions (0.096 kJ) assuming a similar metabolism. In addition to F. nitratireducens strain 2002, a nitrate-dependent Fe(II) oxidizing bacterium isolated from U contaminated groundwater, Diaphorobacter sp. strain

  3. Mechanism of the development of a weakly alkaline barrier slurry without BTA and oxidizer

    NASA Astrophysics Data System (ADS)

    Xiaodong, Luan; Yuling, Liu; Xinhuan, Niu; Juan, Wang

    2015-07-01

    Controllable removal rate selectivity with various films (Cu, Ta, SiO2) is a challenging job in barrier CMP. H2O2 as an oxidizer and benzotriazole (BTA) as an inhibitor is considered to be an effective method in barrier CMP. Slurries that contain hydrogen peroxide have a very short shelf life because H2O2 is unstable and easily decomposed. BTA can cause post-CMP challenges, such as organic residue, toxicity and particle adhesion. We have been engaged in studying a weakly alkaline barrier slurry without oxidizer and benzotriazole. Based on these works, the objective of this paper is to discuss the mechanism of the development of the barrier slurry without oxidizer and benzotriazole by studying the effects of the different components (containing colloidal silica, FA/O complexing agent, pH of polishing solution and guanidine nitrate) on removal rate selectivity. The possible related polishing mechanism has also been proposed. Project supported by the Major National Science and Technology Special Projects (No. 2009ZX02308), the National Natural Science Foundation of Hebei Province, China (No. E2013202247), and the Department of Education-Funded Research Projects of Hebei Province, China (No. QN2014208).

  4. Methamphetamine-induced nitric oxide promotes vesicular transport in blood–brain barrier endothelial cells

    PubMed Central

    Martins, Tânia; Burgoyne, Thomas; Kenny, Bridget-Ann; Hudson, Natalie; Futter, Clare E.; Ambrósio, António F.; Silva, Ana P.; Greenwood, John; Turowski, Patric

    2013-01-01

    Methamphetamine's (METH) neurotoxicity is thought to be in part due to its ability to induce blood–brain barrier (BBB) dysfunction. Here, we investigated the effect of METH on barrier properties of cultured rat primary brain microvascular endothelial cells (BMVECs). Transendothelial flux doubled in response to METH, irrespective of the size of tracer used. At the same time, transendothelial electrical resistance was unchanged as was the ultrastructural appearance of inter-endothelial junctions and the distribution of key junction proteins, suggesting that METH promoted vesicular but not junctional transport. Indeed, METH significantly increased uptake of horseradish peroxidase into vesicular structures. METH also enhanced transendothelial migration of lymphocytes indicating that the endothelial barrier against both molecules and cells was compromised. Barrier breakdown was only observed in response to METH at low micromolar concentrations, with enhanced vesicular uptake peaking at 1 μM METH. The BMVEC response to METH also involved rapid activation of endothelial nitric oxide synthase and its inhibition abrogated METH-induced permeability and lymphocyte migration, indicating that nitric oxide was a key mediator of BBB disruption in response to METH. This study underlines the key role of nitric oxide in BBB function and describes a novel mechanism of drug-induced fluid-phase transcytosis at the BBB. PMID:22960442

  5. Methamphetamine-induced nitric oxide promotes vesicular transport in blood-brain barrier endothelial cells.

    PubMed

    Martins, Tânia; Burgoyne, Thomas; Kenny, Bridget-Ann; Hudson, Natalie; Futter, Clare E; Ambrósio, António F; Silva, Ana P; Greenwood, John; Turowski, Patric

    2013-02-01

    Methamphetamine's (METH) neurotoxicity is thought to be in part due to its ability to induce blood-brain barrier (BBB) dysfunction. Here, we investigated the effect of METH on barrier properties of cultured rat primary brain microvascular endothelial cells (BMVECs). Transendothelial flux doubled in response to METH, irrespective of the size of tracer used. At the same time, transendothelial electrical resistance was unchanged as was the ultrastructural appearance of inter-endothelial junctions and the distribution of key junction proteins, suggesting that METH promoted vesicular but not junctional transport. Indeed, METH significantly increased uptake of horseradish peroxidase into vesicular structures. METH also enhanced transendothelial migration of lymphocytes indicating that the endothelial barrier against both molecules and cells was compromised. Barrier breakdown was only observed in response to METH at low micromolar concentrations, with enhanced vesicular uptake peaking at 1 μM METH. The BMVEC response to METH also involved rapid activation of endothelial nitric oxide synthase and its inhibition abrogated METH-induced permeability and lymphocyte migration, indicating that nitric oxide was a key mediator of BBB disruption in response to METH. This study underlines the key role of nitric oxide in BBB function and describes a novel mechanism of drug-induced fluid-phase transcytosis at the BBB.

  6. Shape-dependence of the barrier for skyrmions on a two-lane racetrack

    NASA Astrophysics Data System (ADS)

    Müller, Jan

    2016-10-01

    Single magnetic skyrmions are localized whirls in the magnetization with an integer winding number. They have been observed on nano-meter scales up to room temperature in multilayer structures. Due to their small size, topological winding number, and their ability to be manipulated by extremely tiny forces, they are often called interesting candidates for future memory devices. The two-lane racetrack has to exhibit two lanes that are separated by an energy barrier. The information is then encoded in the position of a skyrmion which is located in one of these close-by lanes. The artificial barrier between the lanes can be created by an additional nanostrip on top of the track. Here we study the dependence of the potential barrier on the shape of the additional nanostrip, calculating the potentials for a rectangular, triangular, and parabolic cross section, as well as interpolations between the first two. We find that a narrow barrier is always repulsive and that the height of the potential strongly depends on the shape of the nanostrip, whereas the shape of the potential is more universal. We finally show that the shape-dependence is redundant for possible applications.

  7. The effect of bond coat oxidation on the failure of thermal barrier coatings

    SciTech Connect

    Lee, E.Y.; Sisson, R.D. Jr.

    1994-12-31

    The formation of the oxides such as the spinel (Ni(Al,Cr){sub 2}O{sub 4}), Cr{sub 2}O{sub 3}, NiO and CoO in the bond coat oxidation products would accelerate the failure of the EB-PVD thermal barrier coatings during cyclic oxidation. It was found that Al{sub 2}O{sub 3} developed first, followed by the Cr/Ni rich oxides (such as Ni(Al,Cr){sub 2}O{sub 4}, Cr{sub 2}O{sub 3} and NiO) at the interface between the PSZ ceramic coatings and NiCoCrAlY bond coats in a cyclic high temperature environment. For the EB-PVD TBCs, the smooth interface between the PSZ ceramic coating and the bond coat would be also responsible for the failure during cyclic oxidation.

  8. Impedance Analysis of 7YSZ Thermal Barrier Coatings During High-Temperature Oxidation

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Long; Liu, Min; Zhang, Ji-Fu

    2016-12-01

    ZrO2-7 wt.%Y2O3 (7YSZ) thermal barrier coatings (TBCs) were prepared by atmospheric plasma spraying. High-temperature oxidation of 7YSZ TBCs was accomplished at 950 °C and characterized by impedance spectroscopy and scanning electron microscopy with energy-dispersive spectrometry. The results indicated that the thermally grown oxide (TGO) mainly contained alumina. The increase of the thickness of the TGO layer appeared to follow a parabolic law. Impedance analysis demonstrated that the resistance of the TGO increased with increasing oxidation time, also following a parabolic law, and that characterization of the TGO thickness based on fitting an equivalent circuit to its measured resistance is feasible. The YSZ grain-boundary resistance increased due to increasing cracks within the coating for oxidation time less than 50 h. However, beyond 150 h, the YSZ grain-boundary resistance slightly decreased, mainly due to sintering of the coating during the oxidation process.

  9. Tuning of barrier crossing time of a particle by time dependent magnetic field.

    PubMed

    Baura, Alendu; Ray, Somrita; Bag, Bidhan Chandra

    2013-06-28

    We have studied the effect of time dependent magnetic field on the barrier crossing dynamics of a charged particle. An interplay of the magnetic field induced electric field and the applied field reveals several interesting features. For slowly oscillating field the barrier crossing rate increases remarkably particularly at large amplitude of the field. For appreciably large frequency a generically distinct phenomenon appears by virtue of parametric resonance manifested in multiple peaks appearing in the variation of the mean first passage time as a function of the amplitude. The parametric resonance is more robust against the variation of amplitude of the oscillating field compared to the case of variation of frequency. The barrier crossing time of a particle can be tuned para-metrically by appropriate choice of amplitude and frequency of the oscillating magnetic field.

  10. Atomic structure and oxygen deficiency of the ultrathin aluminium oxide barrier in Al/AlOx/Al Josephson junctions

    NASA Astrophysics Data System (ADS)

    Zeng, Lunjie; Tran, Dung Trung; Tai, Cheuk-Wai; Svensson, Gunnar; Olsson, Eva

    2016-07-01

    Al/AlOx/Al Josephson junctions are the building blocks of a wide range of superconducting quantum devices that are key elements for quantum computers, extremely sensitive magnetometers and radiation detectors. The properties of the junctions and the superconducting quantum devices are determined by the atomic structure of the tunnel barrier. The nanoscale dimension and disordered nature of the barrier oxide have been challenges for the direct experimental investigation of the atomic structure of the tunnel barrier. Here we show that the miniaturized dimension of the barrier and the interfacial interaction between crystalline Al and amorphous AlOx give rise to oxygen deficiency at the metal/oxide interfaces. In the interior of the barrier, the oxide resembles the atomic structure of bulk aluminium oxide. Atomic defects such as oxygen vacancies at the interfaces can be the origin of the two-level systems and contribute to decoherence and noise in superconducting quantum circuits.

  11. Atomic structure and oxygen deficiency of the ultrathin aluminium oxide barrier in Al/AlOx/Al Josephson junctions.

    PubMed

    Zeng, Lunjie; Tran, Dung Trung; Tai, Cheuk-Wai; Svensson, Gunnar; Olsson, Eva

    2016-07-12

    Al/AlOx/Al Josephson junctions are the building blocks of a wide range of superconducting quantum devices that are key elements for quantum computers, extremely sensitive magnetometers and radiation detectors. The properties of the junctions and the superconducting quantum devices are determined by the atomic structure of the tunnel barrier. The nanoscale dimension and disordered nature of the barrier oxide have been challenges for the direct experimental investigation of the atomic structure of the tunnel barrier. Here we show that the miniaturized dimension of the barrier and the interfacial interaction between crystalline Al and amorphous AlOx give rise to oxygen deficiency at the metal/oxide interfaces. In the interior of the barrier, the oxide resembles the atomic structure of bulk aluminium oxide. Atomic defects such as oxygen vacancies at the interfaces can be the origin of the two-level systems and contribute to decoherence and noise in superconducting quantum circuits.

  12. Atomic structure and oxygen deficiency of the ultrathin aluminium oxide barrier in Al/AlOx/Al Josephson junctions

    PubMed Central

    Zeng, Lunjie; Tran, Dung Trung; Tai, Cheuk-Wai; Svensson, Gunnar; Olsson, Eva

    2016-01-01

    Al/AlOx/Al Josephson junctions are the building blocks of a wide range of superconducting quantum devices that are key elements for quantum computers, extremely sensitive magnetometers and radiation detectors. The properties of the junctions and the superconducting quantum devices are determined by the atomic structure of the tunnel barrier. The nanoscale dimension and disordered nature of the barrier oxide have been challenges for the direct experimental investigation of the atomic structure of the tunnel barrier. Here we show that the miniaturized dimension of the barrier and the interfacial interaction between crystalline Al and amorphous AlOx give rise to oxygen deficiency at the metal/oxide interfaces. In the interior of the barrier, the oxide resembles the atomic structure of bulk aluminium oxide. Atomic defects such as oxygen vacancies at the interfaces can be the origin of the two-level systems and contribute to decoherence and noise in superconducting quantum circuits. PMID:27403611

  13. Field-dependent energy barriers in Co/CoO core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Nieves, P.; Kechrakos, D.; Chubykalo-Fesenko, O.

    2016-02-01

    We perform atomistic modeling of Co/CoO nanoparticles with a diameter of a few nanometers and realistic values of the exchange and anisotropy parameters in order to study the field-dependent energy barriers under forward and backward reversal of the magnetization. The barriers are extracted from the constrained energy minimization using the integration of the Landau-Lifshitz-Gilbert equations and the Lagrange multiplier method. We show that the applied field and the interface exchange strength have opposite effects on the values of the energy barriers. In particular, while the backward (forward) energy barrier increases (decreases) linearly with the strength of the interface exchange coupling, it decreases (increases) almost quadratically with the applied magnetic field. Our results are in good agreement with the well-known Meiklejohn-Bean model of exchange bias, and allow us to analyze the limits of applicability of the macrospin approach to the study of energy barriers in core-shell Co/CoO nanoparticles.

  14. A p53/ARF-dependent anticancer barrier activates senescence and blocks tumorigenesis without impacting apoptosis.

    PubMed

    Sinha, Vidya C; Qin, Lan; Li, Yi

    2015-02-01

    In response to oncogene activation and oncogene-induced aberrant proliferation, mammalian cells activate apoptosis and senescence, usually via the p53-ARF tumor-suppressor pathway. Apoptosis is a known barrier to cancer and is usually downregulated before full malignancy, but senescence as an anticancer barrier is controversial due to its presence in the tumor environment. In addition, senescence may aid cancer progression via releasing senescence-associated factors that instigate neighboring tumor cells. Here, it is demonstrated that apoptosis unexpectedly remains robust in ErbB2 (ERBB2/HER2)-initiated mammary early lesions arising in adult mice null for either p53 or ARF. These early lesions, however, downregulate senescence significantly. This diminished senescence response is associated with accelerated progression to cancer in ARF-null mice compared with ARF-wild-type mice. Thus, the ARF-p53 pathway is dispensable for the apoptosis anticancer barrier in the initiation of ErbB2 breast cancer, the apoptosis barrier alone cannot halt mammary tumorigenesis, and senescence is a key barrier against carcinogenesis. Findings in this relevant mouse model of HER2-driven breast cancer suggest that effective prevention relies upon preserving both ARF/p53-independent apoptosis and ARF/p53-dependent senescence. ©2014 American Association for Cancer Research.

  15. Effect of oxidation and annealing on tunnel barrier structure and composition in IrMn/CoFe/TiOx/CoFe magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Kirk, Daniel J.; Cockayne, David J. H.; Petford-Long, Amanda K.; Yi, Ge

    2009-12-01

    The effects of oxidation time and annealing conditions on sputter-deposited magnetic tunnel junctions with a TiOx barrier have been investigated. High resolution electron microscopy showed that longer oxidation times led to a significant increase in barrier layer width and to the formation of large volumes of oxides of Co and Fe. Annealing promoted extensive diffusion of Mn to the barrier region and the oxidation of Mn to MnOx concurrent with the reduction in oxides of Co and Fe. Annealing also increased the peak oxygen content of the barrier region and resulted in a distinct asymmetry in the barrier oxide structure.

  16. Oxidation of trichloroethylene, toluene, and ethanol vapors by a partially saturated permeable reactive barrier

    NASA Astrophysics Data System (ADS)

    Mahmoodlu, Mojtaba G.; Hassanizadeh, S. Majid; Hartog, Niels; Raoof, Amir

    2014-08-01

    The mitigation of volatile organic compound (VOC) vapors in the unsaturated zone largely relies on the active removal of vapor by ventilation. In this study we considered an alternative method involving the use of solid potassium permanganate to create a horizontal permeable reactive barrier for oxidizing VOC vapors. Column experiments were carried out to investigate the oxidation of trichloroethylene (TCE), toluene, and ethanol vapors using a partially saturated mixture of potassium permanganate and sand grains. Results showed a significant removal of VOC vapors due to the oxidation. We found that water saturation has a major effect on the removal capacity of the permeable reactive layer. We observed a high removal efficiency and reactivity of potassium permanganate for all target compounds at the highest water saturation (Sw = 0.6). A change in pH within the reactive layer reduced oxidation rate of VOCs. The use of carbonate minerals increased the reactivity of potassium permanganate during the oxidation of TCE vapor by buffering the pH. Reactive transport of VOC vapors diffusing through the permeable reactive layer was modeled, including the pH effect on the oxidation rates. The model accurately described the observed breakthrough curve of TCE and toluene vapors in the headspace of the column. However, miscibility of ethanol in water in combination with produced water during oxidation made the modeling results less accurate for ethanol. A linear relationship was found between total oxidized mass of VOC vapors per unit volume of permeable reactive layer and initial water saturation. This behavior indicates that pH changes control the overall reactivity and longevity of the permeable reactive layer during oxidation of VOCs. The results suggest that field application of a horizontal permeable reactive barrier can be a viable technology against upward migration of VOC vapors through the unsaturated zone.

  17. Glucose oxidation and PQQ-dependent dehydrogenases in Gluconobacter oxydans.

    PubMed

    Hölscher, Tina; Schleyer, Ute; Merfort, Marcel; Bringer-Meyer, Stephanie; Görisch, Helmut; Sahm, Hermann

    2009-01-01

    Gluconobacter oxydans is famous for its rapid and incomplete oxidation of a wide range of sugars and sugar alcohols. The organism is known for its efficient oxidation of D-glucose to D-gluconate, which can be further oxidized to two different keto-D-gluconates, 2-keto-D-gluconate and 5-keto-D-gluconate, as well as 2,5-di-keto-D-gluconate. For this oxidation chain and for further oxidation reactions, G. oxydans possesses a high number of membrane-bound dehydrogenases. In this review, we focus on the dehydrogenases involved in D-glucose oxidation and the products formed during this process. As some of the involved dehydrogenases contain pyrroloquinoline quinone (PQQ) as a cofactor, also PQQ synthesis is reviewed. Finally, we will give an overview of further PQQ-dependent dehydrogenases and discuss their functions in G. oxydans ATCC 621H (DSM 2343). Copyright (c) 2008 S. Karger AG, Basel.

  18. Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

    SciTech Connect

    Fergus, Jeffrey W.

    2014-04-12

    One of the important applications of yttria stabilized zirconia is as a thermal barrier coating for gas turbine engines. While yttria stabilized zirconia performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatings are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.

  19. Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

    DOE PAGES

    Fergus, Jeffrey W.

    2014-04-12

    One of the important applications of yttria stabilized zirconia is as a thermal barrier coating for gas turbine engines. While yttria stabilized zirconia performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatingsmore » are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.« less

  20. Reducing ac losses of Bi(2223) multifilamentary tapes by oxide barriers

    NASA Astrophysics Data System (ADS)

    Huang, Y. B.; Flükiger, R.

    1998-01-01

    A new type of sheath material, consisting of a thin layer BaZrO 3 around each filament, has been used to fabricate Bi(2223) multifilamentary tapes. The transverse resistivity is enhanced by a factor of 10, thus leading to a significant reduction of ac coupling losses in Bi(2223) multifilamentary tapes. The electric decoupling effect of these barriers is clearly demonstrated by “magnetic length scale” and Hall sensor magnetisation experiments. Moreover, it is possible to twist these tapes with a pitch length of 2 cm, thus yielding an even higher decoupling effect without deterioration of the transport properties. The uniformity of filament size and barrier layer thickness have been improved by a modified PIT method using four-roll deformation. The critical current density of these Bi(2223) tapes with BaZrO 3 oxide barriers so far reaches 15 kA/cm 2 (77 K, 0 T).

  1. Novel RpoS-Dependent Mechanisms Strengthen the Envelope Permeability Barrier during Stationary Phase.

    PubMed

    Mitchell, Angela M; Wang, Wei; Silhavy, Thomas J

    2017-01-15

    Gram-negative bacteria have effective methods of excluding toxic compounds, including a largely impermeable outer membrane (OM) and a range of efflux pumps. Furthermore, when cells become nutrient limited, RpoS enacts a global expression change providing cross-protection against many stresses. Here, we utilized sensitivity to an anionic detergent (sodium dodecyl sulfate [SDS]) to probe changes occurring to the cell's permeability barrier during nutrient limitation. Escherichia coli is resistant to SDS whether cells are actively growing, carbon limited, or nitrogen limited. In actively growing cells, this resistance depends on the AcrAB-TolC efflux pump; however, this pump is not necessary for protection under either carbon-limiting or nitrogen-limiting conditions, suggesting an alternative mechanism(s) of SDS resistance. In carbon-limited cells, RpoS-dependent pathways lessen the permeability of the OM, preventing the necessity for efflux. In nitrogen-limited but not carbon-limited cells, the loss of rpoS can be completely compensated for by the AcrAB-TolC efflux pump. We suggest that this difference simply reflects the fact that nitrogen-limited cells have access to a metabolizable energy (carbon) source that can efficiently power the efflux pump. Using a transposon mutant pool sequencing (Tn-Seq) approach, we identified three genes, sanA, dacA, and yhdP, that are necessary for RpoS-dependent SDS resistance in carbon-limited stationary phase. Using genetic analysis, we determined that these genes are involved in two different envelope-strengthening pathways. These genes have not previously been implicated in stationary-phase stress responses. A third novel RpoS-dependent pathway appears to strengthen the cell's permeability barrier in nitrogen-limited cells. Thus, though cells remain phenotypically SDS resistant, SDS resistance mechanisms differ significantly between growth states. Gram-negative bacteria are intrinsically resistant to detergents and many

  2. Novel RpoS-Dependent Mechanisms Strengthen the Envelope Permeability Barrier during Stationary Phase

    PubMed Central

    Wang, Wei

    2016-01-01

    ABSTRACT Gram-negative bacteria have effective methods of excluding toxic compounds, including a largely impermeable outer membrane (OM) and a range of efflux pumps. Furthermore, when cells become nutrient limited, RpoS enacts a global expression change providing cross-protection against many stresses. Here, we utilized sensitivity to an anionic detergent (sodium dodecyl sulfate [SDS]) to probe changes occurring to the cell's permeability barrier during nutrient limitation. Escherichia coli is resistant to SDS whether cells are actively growing, carbon limited, or nitrogen limited. In actively growing cells, this resistance depends on the AcrAB-TolC efflux pump; however, this pump is not necessary for protection under either carbon-limiting or nitrogen-limiting conditions, suggesting an alternative mechanism(s) of SDS resistance. In carbon-limited cells, RpoS-dependent pathways lessen the permeability of the OM, preventing the necessity for efflux. In nitrogen-limited but not carbon-limited cells, the loss of rpoS can be completely compensated for by the AcrAB-TolC efflux pump. We suggest that this difference simply reflects the fact that nitrogen-limited cells have access to a metabolizable energy (carbon) source that can efficiently power the efflux pump. Using a transposon mutant pool sequencing (Tn-Seq) approach, we identified three genes, sanA, dacA, and yhdP, that are necessary for RpoS-dependent SDS resistance in carbon-limited stationary phase. Using genetic analysis, we determined that these genes are involved in two different envelope-strengthening pathways. These genes have not previously been implicated in stationary-phase stress responses. A third novel RpoS-dependent pathway appears to strengthen the cell's permeability barrier in nitrogen-limited cells. Thus, though cells remain phenotypically SDS resistant, SDS resistance mechanisms differ significantly between growth states. IMPORTANCE Gram-negative bacteria are intrinsically resistant to

  3. Thin Oxides as a Cu Diffusion Barrier for NIF Be Ablator Capsules

    DOE PAGES

    Youngblood, Kelly P.; Huang, H.; Xu, H. W.; ...

    2013-03-01

    The NIF point design uses a five-layer capsule to modify the X-ray absorption in order to achieve optimized shock timing. A stepped copper dopant design defines the layer structure. The production of the capsule involves pyrolysis to remove the inner plastic mandrel. Copper atoms diffuse radially and azimuthally throughout the capsule during pyrolysis. This diffusion significantly diminishes the capsule performance during implosion. Thermal and coated oxide barrier layers employed between layers mitigate the diffusion of copper during the mandrel removal process. The copper atoms do not diffuse through this barrier during pyrolysis. A capsule fabrication method that produces a capsulemore » with a thin oxide layer will be discussed.« less

  4. Real-time oxide evolution of copper protected by graphene and boron nitride barriers.

    PubMed

    Galbiati, M; Stoot, A C; Mackenzie, D M A; Bøggild, P; Camilli, L

    2017-01-09

    Applying protective or barrier layers to isolate a target item from the environment is a common approach to prevent or delay its degradation. The impermeability of two-dimensional materials such as graphene and hexagonal boron nitride (hBN) has generated a great deal of interest in corrosion and material science. Owing to their different electronic properties (graphene is a semimetal, whereas hBN is a wide-bandgap insulator), their protection behaviour is distinctly different. Here we investigate the performance of graphene and hBN as barrier coatings applied on copper substrates through a real-time study in two different oxidative conditions. Our findings show that the evolution of the copper oxidation is remarkably different for the two coating materials.

  5. Real-time oxide evolution of copper protected by graphene and boron nitride barriers

    PubMed Central

    Galbiati, M.; Stoot, A. C.; Mackenzie, D. M. A.; Bøggild, P.; Camilli, L.

    2017-01-01

    Applying protective or barrier layers to isolate a target item from the environment is a common approach to prevent or delay its degradation. The impermeability of two-dimensional materials such as graphene and hexagonal boron nitride (hBN) has generated a great deal of interest in corrosion and material science. Owing to their different electronic properties (graphene is a semimetal, whereas hBN is a wide-bandgap insulator), their protection behaviour is distinctly different. Here we investigate the performance of graphene and hBN as barrier coatings applied on copper substrates through a real-time study in two different oxidative conditions. Our findings show that the evolution of the copper oxidation is remarkably different for the two coating materials. PMID:28067249

  6. Real-time oxide evolution of copper protected by graphene and boron nitride barriers

    NASA Astrophysics Data System (ADS)

    Galbiati, M.; Stoot, A. C.; MacKenzie, D. M. A.; Bøggild, P.; Camilli, L.

    2017-01-01

    Applying protective or barrier layers to isolate a target item from the environment is a common approach to prevent or delay its degradation. The impermeability of two-dimensional materials such as graphene and hexagonal boron nitride (hBN) has generated a great deal of interest in corrosion and material science. Owing to their different electronic properties (graphene is a semimetal, whereas hBN is a wide-bandgap insulator), their protection behaviour is distinctly different. Here we investigate the performance of graphene and hBN as barrier coatings applied on copper substrates through a real-time study in two different oxidative conditions. Our findings show that the evolution of the copper oxidation is remarkably different for the two coating materials.

  7. Ultrathin epitaxial barrier layer to avoid thermally induced phase transformation in oxide heterostructures

    SciTech Connect

    Baek, David J.; Lu, Di; Hikita, Yasuyuki; Hwang, Harold Y.; Kourkoutis, Lena F.

    2016-12-22

    Incorporating oxides with radically different physical and chemical properties into heterostructures offers tantalizing possibilities to derive new functions and structures. Recently, we have fabricated freestanding 2D oxide membranes using the water-soluble perovskite Sr3Al2O6 as a sacrificial buffer layer. Here, with atomic-resolution spectroscopic imaging, we observe that direct growth of oxide thin films on Sr3Al2O6 can cause complete phase transformation of the buffer layer, rendering it water-insoluble. More importantly, we demonstrate that an ultrathin SrTiO3 layer can be employed as an effective barrier to preserve Sr3Al2O6 during subsequent growth, thus allowing its integration in a wider range of oxide heterostructures.

  8. Ultrathin epitaxial barrier layer to avoid thermally induced phase transformation in oxide heterostructures

    DOE PAGES

    Baek, David J.; Lu, Di; Hikita, Yasuyuki; ...

    2016-12-22

    Incorporating oxides with radically different physical and chemical properties into heterostructures offers tantalizing possibilities to derive new functions and structures. Recently, we have fabricated freestanding 2D oxide membranes using the water-soluble perovskite Sr3Al2O6 as a sacrificial buffer layer. Here, with atomic-resolution spectroscopic imaging, we observe that direct growth of oxide thin films on Sr3Al2O6 can cause complete phase transformation of the buffer layer, rendering it water-insoluble. More importantly, we demonstrate that an ultrathin SrTiO3 layer can be employed as an effective barrier to preserve Sr3Al2O6 during subsequent growth, thus allowing its integration in a wider range of oxide heterostructures.

  9. Optimizing thermally grown oxide for thermal barrier coatings on TiAl components via fluorine treatment

    NASA Astrophysics Data System (ADS)

    Donchev, A.; Braun, R.; Schütze, M.

    2010-01-01

    Titanium aluminides suffer from non-protective mixed-oxide scale formation during high-temperature exposure in oxidizing environments, so that they cannot be used at temperatures above approximately 800° C for longer times without additional treatment. A fluorine treatment on γ-TiAl alloys leads to the formation of a pure protective alumina scale and allows their use at service temperatures above 800°C. This thermally grown aluminum oxide layer can be used for bonding ceramic thermal barrier coatings to the TiAl substrate. Zirconia topcoats deposited by electron-beam physical vapor deposition were very adherent to F-treated TiA samples during cyclic oxidation tests at 900 to 1,000°C. A separate bond coat is not needed in this case.

  10. Ultrasonic characterization of thermally grown oxide in thermal barrier coating by reflection coefficient amplitude spectrum.

    PubMed

    Ma, Zhiyuan; Zhao, Yang; Luo, Zhongbing; Lin, Li

    2014-04-01

    The thermally grown oxide (TGO) growth at the interface of ceramic coating/bond coating in thermal barrier coatings (TBCs) was evaluated by ultrasonic reflection coefficient amplitude spectrum (URCAS). A theoretical analysis was performed about the influence of acoustic impedance match relationship between the ceramic coating and its adjacent media on URCAS. The immersion ultrasonic narrow pulse echo method was carried out on the TBC specimen before and after oxidation under 1050°C×1h for 15cycles. The resonant peaks of URCAS obtained before and after oxidation showed that TGO which generated between the ceramic coating and bond coating due to the oxidation, changed the acoustic impedance match between the ceramic coating and its adjacent media. This method is able to nondestructively characterize the generation of TGO in TBCs, and is important to practical engineering application.

  11. GRP78 is a novel receptor initiating a vascular barrier protective response to oxidized phospholipids.

    PubMed

    Birukova, Anna A; Singleton, Patrick A; Gawlak, Grzegorz; Tian, Xinyong; Mirzapoiazova, Tamara; Mambetsariev, Bolot; Dubrovskyi, Oleksii; Oskolkova, Olga V; Bochkov, Valery N; Birukov, Konstantin G

    2014-07-01

    Vascular integrity and the maintenance of blood vessel continuity are fundamental features of the circulatory system maintained through endothelial cell-cell junctions. Defects in the endothelial barrier become an initiating factor in several pathologies, including ischemia/reperfusion, tumor angiogenesis, pulmonary edema, sepsis, and acute lung injury. Better understanding of mechanisms stimulating endothelial barrier enhancement may provide novel therapeutic strategies. We previously reported that oxidized phospholipids (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine [OxPAPC]) promote endothelial cell (EC) barrier enhancement both in vitro and in vivo. This study examines the initiating mechanistic events triggered by OxPAPC to increase vascular integrity. Our data demonstrate that OxPAPC directly binds the cell membrane-localized chaperone protein, GRP78, associated with its cofactor, HTJ-1. OxPAPC binding to plasma membrane-localized GRP78 leads to GRP78 trafficking to caveolin-enriched microdomains (CEMs) on the cell surface and consequent activation of sphingosine 1-phosphate receptor 1, Src and Fyn tyrosine kinases, and Rac1 GTPase, processes essential for cytoskeletal reorganization and EC barrier enhancement. Using animal models of acute lung injury with vascular hyperpermeability, we observed that HTJ-1 knockdown blocked OxPAPC protection from interleukin-6 and ventilator-induced lung injury. Our data indicate for the first time an essential role of GRP78 and HTJ-1 in OxPAPC-mediated CEM dynamics and enhancement of vascular integrity.

  12. Physicochemical Factors that Affect Metal and Metal Oxide Nanoparticle Passage Across Epithelial Barriers

    PubMed Central

    Elder, Alison; Vidyasagar, Sadasivan; DeLouise, Lisa

    2014-01-01

    The diversity of nanomaterials in terms of size, shape, and surface chemistry poses a challenge to those who are trying to characterize the human health and environmental risks associated with incidental and unintentional exposures. There are numerous products that are already commercially available that contain solid metal and metal oxide nanoparticles, either embedded in a matrix or in solution. Exposure assessments for these products are often incomplete or difficult due to technological challenges associated with detection and quantitation of nanoparticles in gaseous or liquid carriers. The main focus of recent research has been on hazard identification. However, risk is a product of hazard and exposure, and one significant knowledge gap is that of the target organ dose following in vivo exposures. In order to reach target organs, nanoparticles must first breech the protective barriers of the respiratory tract, gastrointestinal tract, or skin. The fate of those nanoparticles that reach physiological barriers is in large part determined by the properties of the particles and the barriers themselves. This article reviews the physiological properties of the lung, gut, and skin epithelia, the physicochemical properties of metal and metal oxide nanoparticles that are likely to affect their ability to breech epithelial barriers, and what is known about their fate following in vivo exposures. PMID:20049809

  13. Enhancing the barrier height in oxide Schottky junctions using interface dipoles

    NASA Astrophysics Data System (ADS)

    Tachikawa, Takashi; Hwang, Harold Y.; Hikita, Yasuyuki

    2017-08-01

    We demonstrate a 0.37 eV increase in the n-type Schottky barrier height at the Pt/TiO2-terminated SrTiO3 (001) interface by insertion of an ultrathin insulator AgTaO3. While a conventional metal-insulator-semiconductor model predicts a reduction in the barrier height with insulator thickness, the observed increase originates from the two polar surface layers, (AgO)- and (TaO2)+ in AgTaO3 (001), forming an electrostatic dipole directed towards the metal, increasing the barrier height. Based on directly measured optical and dielectric properties of high quality AgTaO3 thin films, we determine the interface energy band diagram including the interface dipole. The capability to exploit the strong ionic charges of oxide surfaces to manipulate interface band alignments beyond bulk values greatly expands the design strategies for tailoring functional oxide interfaces. Up to now, the use of an ultrathin LaAlO3 layer could only decrease the barrier height, but now bidirectional control is possible.

  14. Modeling of Schottky Barrier Modulation due to Oxidation at Metallic Electrode and Semiconducting Carbon Nanotube Junction

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2003-01-01

    A model is proposed for the previously reported lower Schottky barrier for holes PHI (sub bH) in air than in vacuum at a metallic electrode - semiconducting carbon nanotube (CNT) junction. We assume that there is a transition region between the electrode and the CNT, and an appreciable potential can drop there. The role of the oxidation is to increase this potential drop with negatively charged oxygen molecules on the CNT, leading to lower PHI(sub Bh) after oxidation. The mechanism prevails in both p- and n-CNTs, and the model consistently explains the key experimental findings.

  15. Irsogladine maleate regulates gap junctional intercellular communication-dependent epithelial barrier in human nasal epithelial cells.

    PubMed

    Miyata, Ryo; Nomura, Kazuaki; Kakuki, Takuya; Takano, Ken-Ichi; Kohno, Takayuki; Konno, Takumi; Sawada, Norimasa; Himi, Tetsuo; Kojima, Takashi

    2015-04-01

    The airway epithelium of the human nasal mucosa acts as the first physical barrier that protects against inhaled substances and pathogens. Irsogladine maleate (IM) is an enhancer of gastric mucosal protective factors via upregulation of gap junctional intercellular communication (GJIC). GJIC is thought to participate in the formation of functional tight junctions. However, the effects of IM on GJIC and the epithelial barrier in human nasal epithelial cells (HNECs) remain unknown. To investigate the effects of IM on GJIC and the tight junctional barrier in HNECs, primary cultures of HNECs transfected with human telomerase reverse transcriptase (hTERT-HNECs) were treated with IM and the GJIC inhibitors oleamide and 18β-GA. Some cells were pretreated with IM before treatment with TLR3 ligand poly(I:C) to examine whether IM prevented the changes via TLR3-mediated signal pathways. In hTERT-HNECs, GJIC blockers reduced the expression of tight junction molecules claudin-1, -4, -7, occludin, tricellulin, and JAM-A. IM induced GJIC activity and enhanced the expression of claudin-1, -4, and JAM-A at the protein and mRNA levels with an increase of barrier function. GJIC blockers prevented the increase of the tight junction proteins induced by IM. Furthermore, IM prevented the reduction of JAM-A but not induction of IL-8 and TNF-α induced by poly(I:C). In conclusion, IM can maintain the GJIC-dependent tight junctional barrier via regulation of GJIC in upper airway nasal epithelium. Therefore, it is possible that IM may be useful as a nasal spray to prevent the disruption of the epithelial barrier by viral infections and exposure to allergens in human nasal mucosa.

  16. Reliability enhancement due to in-situ post-oxidation of sputtered MgO barrier in double MgO barrier magnetic tunnel junction

    NASA Astrophysics Data System (ADS)

    Yoshida, Chikako; Noshiro, Hideyuki; Yamazaki, Yuichi; Sugii, Toshihiro

    2017-06-01

    We have investigated the effects of in-situ post-oxidation (PO) of a sputtered MgO barrier in a double-MgO-barrier magnetic tunnel junction (MTJ) and found that the short error rate was significantly reduced, the magnetoresistance (MR) ratio was increased approximately 18%, and the endurance lifetime was extend. In addition, we found that the distribution of breakdown number (a measure of endurance) exhibits trimodal characteristics, which indicates competition between extrinsic and intrinsic failures. This improvement in reliability might be related to the suppression of Fe and Co diffusion to the MgO barrier, as revealed by electron energy-loss spectroscopy (EELS) analysis.

  17. Furnace Cyclic Oxidation Behavior of Multi-Component Low Conductivity Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Nesbitt, James A.; Barrett, Charles A.; McCue, Terry R.; Miller, Robert A.

    2004-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to further increase engine operating temperatures and reduce cooling, thus helping achieve future engine low emission, high efficiency and improved reliability goals. Advanced multi-component zirconia-based thermal barrier coatings are being developed using an oxide defect clustering design approach to achieve the required coating low thermal conductivity and high temperature stability. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of the candidate coating materials was conducted using conventional furnace cyclic oxidation tests. In this paper, furnace cyclic oxidation behavior of plasma-sprayed zirconia-based defect cluster thermal barrier coatings was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied using scanning electron microscopy (SEM) combined with X-ray diffraction (XRD) phase analysis after the furnace tests. The coating cyclic lifetime is also discussed in relation to coating processing, phase structures, dopant concentration, and other thermo-physical properties.

  18. Vitamin C crosses the blood-brain barrier in the oxidized form through the glucose transporters.

    PubMed Central

    Agus, D B; Gambhir, S S; Pardridge, W M; Spielholz, C; Baselga, J; Vera, J C; Golde, D W

    1997-01-01

    Vitamin C concentrations in the brain exceed those in blood by 10-fold. In both tissues, the vitamin is present primarily in the reduced form, ascorbic acid. We identified the chemical form of vitamin C that readily crosses the blood-brain barrier, and the mechanism of this process. Ascorbic acid was not able to cross the blood-brain barrier in our studies. In contrast, the oxidized form of vitamin C, dehydroascorbic acid (oxidized ascorbic acid), readily entered the brain and was retained in the brain tissue in the form of ascorbic acid. Transport of dehydroascorbic acid into the brain was inhibited by d-glucose, but not by l-glucose. The facilitative glucose transporter, GLUT1, is expressed on endothelial cells at the blood-brain barrier, and is responsible for glucose entry into the brain. This study provides evidence showing that GLUT1 also transports dehydroascorbic acid into the brain. The findings define the transport of dehydroascorbic acid by GLUT1 as a mechanism by which the brain acquires vitamin C, and point to the oxidation of ascorbic acid as a potentially important regulatory step in accumulation of the vitamin by the brain. These results have implications for increasing antioxidant potential in the central nervous system. PMID:9389750

  19. Control of the anodic aluminum oxide barrier layer opening process by wet chemical etching.

    PubMed

    Han, Catherine Y; Willing, Gerold A; Xiao, Zhili; Wang, H Hau

    2007-01-30

    In this work, it has been shown that, through a highly controlled process, the chemical etching of the anodic aluminum oxide membrane barrier layer can be performed in such a way as to achieve nanometer-scale control of the pore opening. As the barrier layer is etched away, subtle differences revealed through AFM phase imaging in the alumina composition in the barrier layer give rise to a unique pattern of hexagonal walls surrounding each of the barrier layer domes. These nanostructures observed in both topography and phase images can be understood as differences in the oxalate anion contaminated alumina versus pure alumina. This information bears significant implication for catalysis, template synthesis, and chemical sensing applications. From the pore opening etching studies, the etching rate of the barrier layer (1.3 nm/min) is higher than that of the inner cell wall (0.93 nm/min), both of which are higher than the etching rate of pure alumina layer (0.5-0.17 nm/min). The established etching rates together with the etching temperature allow one to control the pore diameter systematically from 10 to 95 nm.

  20. The burnup dependence of light water reactor spent fuel oxidation

    SciTech Connect

    Hanson, B.D.

    1998-07-01

    Over the temperature range of interest for dry storage or for placement of spent fuel in a permanent repository under the conditions now being considered, UO{sub 2} is thermodynamically unstable with respect to oxidation to higher oxides. The multiple valence states of uranium allow for the accommodation of interstitial oxygen atoms in the fuel matrix. A variety of stoichiometric and nonstoichiometric phases is therefore possible as the fuel oxidizers from UO{sub 2} to higher oxides. The oxidation of UO{sub 2} has been studied extensively for over 40 years. It has been shown that spent fuel and unirradiated UO{sub 2} oxidize via different mechanisms and at different rates. The oxidation of LWR spent fuel from UO{sub 2} to UO{sub 2.4} was studied previously and is reasonably well understood. The study presented here was initiated to determine the mechanism and rate of oxidation from UO{sub 2.4} to higher oxides. During the early stages of this work, a large variability in the oxidation behavior of samples oxidized under nearly identical conditions was found. Based on previous work on the effect of dopants on UO{sub 2} oxidation and this initial variability, it was hypothesized that the substitution of fission product and actinide impurities for uranium atoms in the spent fuel matrix was the cause of the variable oxidation behavior. Since the impurity concentration is roughly proportional to the burnup of a specimen, the oxidation behavior of spent fuel was expected to be a function of both temperature and burnup. This report (1) summarizes the previous oxidation work for both unirradiated UO{sub 2} and spent fuel (Section 2.2) and presents the theoretical basis for the burnup (i.e., impurity concentration) dependence of the rate of oxidation (Sections 2.3, 2.4, and 2.5), (2) describes the experimental approach (Section 3) and results (Section 4) for the current oxidation tests on spent fuel, and (3) establishes a simple model to determine the activation energies

  1. Environmental degradation of oxidation resistant and thermal barrier coatings for fuel-flexible gas turbine applications

    NASA Astrophysics Data System (ADS)

    Mohan, Prabhakar

    The development of thermal barrier coatings (TBCs) has been undoubtedly the most critical advancement in materials technology for modern gas turbine engines. TBCs are widely used in gas turbine engines for both power-generation and propulsion applications. Metallic oxidation-resistant coatings (ORCs) are also widely employed as a stand-alone protective coating or bond coat for TBCs in many high-temperature applications. Among the widely studied durability issues in these high-temperature protective coatings, one critical challenge that received greater attention in recent years is their resistance to high-temperature degradation due to corrosive deposits arising from fuel impurities and CMAS (calcium-magnesium-alumino-silicate) sand deposits from air ingestion. The presence of vanadium, sulfur, phosphorus, sodium and calcium impurities in alternative fuels warrants a clear understanding of high-temperature materials degradation for the development of fuel-flexible gas turbine engines. Degradation due to CMAS is a critical problem for gas turbine components operating in a dust-laden environment. In this study, high-temperature degradation due to aggressive deposits such as V2O5, P2O 5, Na2SO4, NaVO3, CaSO4 and a laboratory-synthesized CMAS sand for free-standing air plasma sprayed (APS) yttria stabilized zirconia (YSZ), the topcoat of the TBC system, and APS CoNiCrAlY, the bond coat of the TBC system or a stand-alone ORC, is examined. Phase transformations and microstructural development were examined by using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. This study demonstrated that the V2O5 melt degrades the APS YSZ through the formation of ZrV2O7 and YVO 4 at temperatures below 747°C and above 747°C, respectively. Formation of YVO4 leads to the depletion of the Y2O 3 stabilizer and the deleterious transformation of the YSZ to the monoclinic ZrO2 phase. The investigation on the YSZ degradation by Na 2SO4 and a Na2SO4 + V2

  2. "It's important, but…": Perceived Barriers and Situational Dependencies to Social Contact Preferences of Nursing Home Residents.

    PubMed

    Abbott, Katherine M; Bangerter, Lauren R; Humes, Sarah; Klumpp, Rachel; Van Haitsma, Kimberly

    2017-06-22

    U.S. Nursing homes (NH) are shifting toward a person-centered philosophy of care, where staff understand each residents preferences, goals and values, and seek to honor them throughout the care delivery process. Social interactions are a major component of life and while low rates of social interactions are typically found among NH residents, little research has examined resident preferences for specific types of social interactions. The purpose of this study is to explore, from the perspective of the NH resident, barriers to social contact preferences and situations when social preferences change. Two interviews were conducted with 255 NH residents 3 months apart, recruited from 32 NHs using 13 social-contact items from the Preferences for Everyday Living Inventory-NH. Content analysis of 1,461 spontaneous comments identified perceived barriers to preference fulfillment along with reasons why residents would change their mind about the importance of a preference (situational dependencies). Nearly 50% of social preferences for choosing a roommate, having regular contact with friends, giving gifts, and volunteering were associated with barriers. Social preferences were likely to change based upon the quality of the social interaction and the resident's level of interest. Knowledge of barriers regarding social preferences can inform care efforts vital to advancing the delivery of person-centered care. In addition, understanding the reasons why NH resident preferences change based upon context can help providers with staff training leading to individualized care and develop meaningful social programs that are in line with resident preferences.

  3. Regulation of taurine transport at the blood-placental barrier by calcium ion, PKC activator and oxidative stress conditions

    PubMed Central

    2010-01-01

    Background In the present study, we investigated the changes of uptake and efflux transport of taurine under various stress conditions using rat conditionally immortalized syncytiotrophoblast cell line (TR-TBT cells), as in vitro blood-placental barrier (BPB) model. Methods The transport of taurine in TR-TBT cells were characterized by cellular uptake study using radiolabeled taurine. The efflux of taurine was measured from the amount of radiolabeled taurine remaining in the cells after the uptake of radiolabeled taurine for 60 min. Results Taurine uptake was significantly decreased by phosphorylation of protein kinase C (PKC) activator in TR-TBT cells. Also, calcium ion (Ca2+) was involved in taurine transport in TR-TBT cells. Taurine uptake was inhibited and efflux was enhanced under calcium free conditions in the cells. In addition, oxidative stress induced the change of taurine transport in TR-TBT cells, but the changes were different depending on the types of oxidative stress inducing agents. Tumor necrosis factor-α (TNF-α), lipopolysaccharide (LPS) and diethyl maleate (DEM) significantly increased taurine uptake, but H2O2 and nitric oxide (NO) donor decreased taurine uptake in the cells. Taurine efflux was down-regulated by TNF-α in TR-TBT cells. Conclusion Taurine transport in TR-TBT cells were regulated diversely at extracellular Ca2+ level, PKC activator and oxidative stress conditions. It suggested that variable stresses affected the taurine supplies from maternal blood to fetus and taurine level of fetus. PMID:20804613

  4. Nonthermal dielectric-barrier discharge plasma-induced inactivation involves oxidative DNA damage and membrane lipid peroxidation in Escherichia coli.

    PubMed

    Joshi, Suresh G; Cooper, Moogega; Yost, Adam; Paff, Michelle; Ercan, Utku K; Fridman, Gregory; Friedman, Gary; Fridman, Alexander; Brooks, Ari D

    2011-03-01

    Oxidative stress leads to membrane lipid peroxidation, which yields products causing variable degrees of detrimental oxidative modifications in cells. Reactive oxygen species (ROS) are the key regulators in this process and induce lipid peroxidation in Escherichia coli. Application of nonthermal (cold) plasma is increasingly used for inactivation of surface contaminants. Recently, we reported a successful application of nonthermal plasma, using a floating-electrode dielectric-barrier discharge (FE-DBD) technique for rapid inactivation of bacterial contaminants in normal atmospheric air (S. G. Joshi et al., Am. J. Infect. Control 38:293-301, 2010). In the present report, we demonstrate that FE-DBD plasma-mediated inactivation involves membrane lipid peroxidation in E. coli. Dose-dependent ROS, such as singlet oxygen and hydrogen peroxide-like species generated during plasma-induced oxidative stress, were responsible for membrane lipid peroxidation, and ROS scavengers, such as α-tocopherol (vitamin E), were able to significantly inhibit the extent of lipid peroxidation and oxidative DNA damage. These findings indicate that this is a major mechanism involved in FE-DBD plasma-mediated inactivation of bacteria.

  5. Pathological neoangiogenesis depends on oxidative stress regulation by ATM.

    PubMed

    Okuno, Yuji; Nakamura-Ishizu, Ayako; Otsu, Kinya; Suda, Toshio; Kubota, Yoshiaki

    2012-08-01

    The ataxia telangiectasia mutated (ATM) kinase, a master regulator of the DNA damage response (DDR), acts as a barrier to cellular senescence and tumorigenesis. Aside from DDR signaling, ATM also functions in oxidative defense. Here we show that Atm in mice is activated specifically in immature vessels in response to the accumulation of reactive oxygen species (ROS). Global or endothelial-specific Atm deficiency in mice blocked pathological neoangiogenesis in the retina. This block resulted from increased amounts of ROS and excessive activation of the mitogen activated kinase p38α rather than from defects in the canonical DDR pathway. Atm deficiency also lowered tumor angiogenesis and enhanced the antiangiogenic action of vascular endothelial growth factor (Vegf) blockade. These data suggest that pathological neoangiogenesis requires ATM-mediated oxidative defense and that agents that promote excessive ROS generation may have beneficial effects in the treatment of neovascular disease.

  6. Sub-barrier fusion excitation function data and energy dependent Woods-Saxon potential

    NASA Astrophysics Data System (ADS)

    Gautam, Manjeet Singh

    2016-07-01

    This paper analyzed the role of intrinsic degrees of freedom of colliding nuclei in the enhancement of sub-barrier fusion cross-section data of various heavy ion fusion reactions. The influences of inelastic surface vibrations of colliding pairs are found to be dominant and their couplings result in the significantly larger fusion enhancement over the predictions of the one dimensional barrier penetration model at sub-barrier energies. The theoretical calculations are performed by using energy dependent Woods-Saxon potential model (EDWSP model) in conjunction with the one dimensional Wong formula. The effects of dominant intrinsic channels are entertained within framework of the coupled channel calculations obtained by using the code CCFULL. It is quite interesting to note that the energy dependence in Woods-Saxon potential simulates the effects of inelastic surface vibrational states of reactants wherein significantly larger value of diffuseness parameter ranging from a = 0.85 fm to a = 0.95 fm is required to address the observed fusion excitation function data of the various heavy ion fusion reactions.

  7. Akt-mediated transactivation of the S1P1 receptor in caveolin-enriched microdomains regulates endothelial barrier enhancement by oxidized phospholipids.

    PubMed

    Singleton, Patrick A; Chatchavalvanich, Santipongse; Fu, Panfeng; Xing, Junjie; Birukova, Anna A; Fortune, Jennifer A; Klibanov, Alexander M; Garcia, Joe G N; Birukov, Konstantin G

    2009-04-24

    Endothelial cell (EC) barrier dysfunction results in increased vascular permeability, leading to increased mass transport across the vessel wall and leukocyte extravasation, the key mechanisms in pathogenesis of tissue inflammation and edema. We have previously demonstrated that OxPAPC (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine) significantly enhances vascular endothelial barrier properties in vitro and in vivo and attenuates endothelial hyperpermeability induced by inflammatory and edemagenic agents via Rac and Cdc42 GTPase dependent mechanisms. These findings suggested potential important therapeutic value of barrier-protective oxidized phospholipids. In this study, we examined involvement of signaling complexes associated with caveolin-enriched microdomains (CEMs) in barrier-protective responses of human pulmonary ECs to OxPAPC. Immunoblotting from OxPAPC-treated ECs revealed OxPAPC-mediated rapid recruitment (5 minutes) to CEMs of the sphingosine 1-phosphate receptor (S1P(1)), the serine/threonine kinase Akt, and the Rac1 guanine nucleotide exchange factor Tiam1 and phosphorylation of caveolin-1, indicative of signaling activation in CEMs. Abolishing CEM formation (methyl-beta-cyclodextrin) blocked OxPAPC-mediated Rac1 activation, cytoskeletal reorganization, and EC barrier enhancement. Silencing (small interfering RNA) Akt expression blocked OxPAPC-mediated S1P(1) activation (threonine phosphorylation), whereas silencing S1P(1) receptor expression blocked OxPAPC-mediated Tiam1 recruitment to CEMs, Rac1 activation, and EC barrier enhancement. To confirm our in vitro results in an in vivo murine model of acute lung injury with pulmonary vascular hyperpermeability, we observed that selective lung silencing of caveolin-1 or S1P(1) receptor expression blocked OxPAPC-mediated protection from ventilator-induced lung injury. Taken together, these results suggest Akt-dependent transactivation of S1P(1) within CEMs is important for Ox

  8. Effects of intrinsic degrees of freedom in enhancement of sub-barrier fusion excitation function data and energy-dependent one-dimensional barrier penetration model

    NASA Astrophysics Data System (ADS)

    Gautam, M. S.

    2016-03-01

    We have analyzed the role of barrier modification effects (barrier height, barrier position, barrier curvature) introduced due to the energy-dependent Woods-Saxon potential model (EDWSP model) and the coupled channel model on the sub-barrier fusion dynamics of {}_{16}^{32,36} {{S}} + {}_{40}^{90,96} {{Zr}} reactions. The influence of inelastic surface excitations of colliding pairs and multi-neutron transfer channels is found to be a dominant mode of couplings. The coupling of relative motion of colliding nuclei to these dominant intrinsic degrees of freedom leads to a substantially large fusion enhancement at below-barrier energies over the expectations of one-dimensional barrier penetration model. The coupled channel calculations based upon static Woods-Saxon potential must include the internal nuclear structure degrees of freedom of colliding nuclei for complete description of experimental data. On the other hand, theoretical calculations based upon the EDWSP model along with Wong formula provide a complete description of sub-barrier fusion enhancement of various heavy-ion fusion reactions. In EDWSP model calculations, significantly larger values of diffuseness parameter ranging from a = 0.98 fm to a = 0.85 fm are required to address the observed sub-barrier fusion enhancement of {}_{16}^{32,36} {{S}} + {}_{40}^{90,96} {{Zr}} reactions. Furthermore, within the context of EDWSP model, it is possible to achieve an agreement with the experimental fusion cross-sectional data within 10 %. For four heavy-ion fusion reactions, only at 4 fusion data points out of 90 fusion data points deviates exceeding 5 %, while 86 fusion data points lie within 5 % and hence the EDWSP model is able to account the above-barrier portion of the fusion cross-sectional data within 5 % with a probability greater than 90 %.

  9. Understanding the Barriers to Use of Free, Proactive Telephone Counseling for Tobacco Dependence

    PubMed Central

    Sheffer, Christine E.; Brackman, Sharon L.; Cottoms, Naomi; Olsen, Mary

    2012-01-01

    We sought to gain an empirical and practical understanding of the barriers experienced by Arkansas Mississippi Delta residents to using the free telephone counseling (quitline) for tobacco dependence. Barriers included lack of knowledge about the quitline, lack of trust in the providers, as well as multiple root causes to seeking and achieving abstinence from tobacco including issues related to the poor socio-economic context and concerns about negative health effects of quitting. A strong belief in the role of faith in the process of quitting was expressed. Participants suggested strategies for increasing knowledge and trust levels, but were not hopeful about addressing root causes. Given the considerable resources being allocated to quitlines and the burden of tobacco use and disease in lower socioeconomic and minority groups, understanding utilization of quitlines by these groups has implications for policy development, the promotion of quitlines, and the provision of alternate tobacco treatment services. PMID:21464470

  10. Master equation approach to time-dependent escape rate over a periodically oscillating barrier.

    PubMed

    Wang, Xin-Xin; Bao, Jing-Dong

    2011-01-01

    We propose a master equation approach to investigate the transition function and the escape dynamics of a general damping particle in a metastable potential. The transition function in the master equation is obtained analytically from the Langevin dynamics. We apply it to the oscillating barrier problem, in which the potential is structured by a harmonic potential smoothly linking with an inverse harmonic one, and thus both the barrier height and the curvature of potential change periodically with time. We use a Monte Carlo method to simulate the master equation and then calculate a time-dependent escape rate. This can decrease the coarse grain and save more computing time in comparison with the Langevin simulation. Our result has shown that there is a resonant activation phenomenon for the escape rate in the underdamped case.

  11. Novel synthesis and shape-dependent catalytic performance of Cu-Mn oxides for CO oxidation

    NASA Astrophysics Data System (ADS)

    Li, Zhixun; Wang, Honglei; Wu, Xingxing; Ye, Qinglan; Xu, Xuetang; Li, Bin; Wang, Fan

    2017-05-01

    Transition metal oxides with large specific surface area are attractive for high-activity catalysts, and hierarchical structures of transition metal oxides with porous feature possess the structural advantage in the transfer of gaseous reactant and product. In this work, porous Cu-Mn oxides with high surface area were successfully obtained through low-temperature coprecipitation method in alcohol/water solvent and then post-annealing. The addition of alcohol showed great influences on the shape and catalytic performances for CO oxidation. Dumbbell-like Cu-Mn oxide particles with splitting ends displayed high catalytic activity and a complete conversion of CO was achieved at 45 °C, suggesting a shape-dependent catalytic activity. The oxidative activity was attributed to a combination of factors including specific surface area, active surface oxygen species and Mn(IV) cations. The results may supply a new thought to design high-performance Cu-Mn oxide catalysts.

  12. Gas Barrier and Separation Behavior of Graphene Oxide Nanobrick Wall Thin Films

    NASA Astrophysics Data System (ADS)

    Grunlan, Jaime

    2015-03-01

    In many cases, electronics packaging requires electrical conductivity and barrier to oxygen, even under humid conditions. These two properties have simultaneously been realized through the use of surfactant-free aqueous layer-by-layer (LbL) processing, in the form of a polymer composite nanocoating. By layering graphene oxide (GO) with polyethyleneimine (PEI), a ``nano brick wall'' structure has been created, imparting gas barrier properties to the film. Reducing the graphene oxide with a thermal treatment further produces high oxygen barrier in humid conditions and imparts high electrical conductivity (σ ~ 1750 S/m). These thin films (<400 nm) are flexible relative traditional conductive thin films (e.g. ITO), and processing occurs under ambient conditions with water as the only solvent. Additionally, these PEI/GO thin films exhibit H2/CO2 selectivity (>300), making them interesting for gas purification membranes. The flexible nature of the aforementioned thin films, along with their excellent combination of transport properties, make them ideal candidates for use in a broad range of electronics and other packaging applications.

  13. Effect of shot peening on the oxidation behavior of thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Karaoglanli, Abdullah Cahit; Doleker, Kadir Mert; Demirel, Bilal; Turk, Ahmet; Varol, Remzi

    2015-11-01

    A conventional thermal barrier coating (TBC) system is made up of a multilayered coating system that comprises a metallic bond coat including oxidation-resistant MCrAlY and a thermally insulating ceramic top coat including yttria stabilized zirconia (YSZ). In this study, in order to improve the oxidation behavior in conventionally produced TBC systems, shot peening process is applied for modification of surface layer structure of atmospheric plasma spray (APS) bond coats. The oxidation behavior of TBCs, produced by the APS process and subjected to shot peening, was investigated. Oxidation tests were performed under isothermal conditions at 1000 °C for different time periods. The coatings produced by the APS process include high porosity and oxide content due to atmospheric production conditions as well as exposure to very high temperature. In this study, the coatings, produced by the APS process, subsequently subjected to shot-peening, were compared with the ones which were not shot peened. Following the application of the shot peening process, a dense structure is obtained due to the plastic deformation effect in the metallic bond coating structure at a certain distance from the surface. To this end, the effects of the shot-peening on the high temperature oxidation behavior of the coatings are investigated and evaluated.

  14. Nitric Oxide and Airway Epithelial Barrier Function: Regulation of Tight Junction Proteins and Epithelial Permeability

    PubMed Central

    Olson, Nels; Greul, Anne-Katrin; Hristova, Milena; Bove, Peter F.; Kasahara, David I.; van der Vliet, Albert

    2008-01-01

    Acute airway inflammation is associated with enhanced production of nitric oxide (NO•) and altered airway epithelial barrier function, suggesting a role of NO• or its metabolites in epithelial permeability. While high concentrations of S-nitrosothiols disrupted transepithelial resistance (TER) and increased permeability in 16HBE14o- cells, no significant barrier disruption was observed by NONOates, in spite of altered distribution and expression of some TJ proteins. Barrier disruption of mouse tracheal epithelial (MTE) cell monolayers in response to inflammatory cytokines was independent of NOS2, based on similar effects in MTE cells from NOS2-/- mice and a lack of effect of the NOS2-inhibitor 1400W. Cell pre-incubation with LPS protected MTE cells from TER loss and increased permeability by H2O2, which was independent of NOS2. However, NOS2 was found to contribute to epithelial wound repair and TER recovery after mechanical injury. Overall, our results demonstrate that epithelial NOS2 is not responsible for epithelial barrier dysfunction during inflammation, but may contribute to restoration of epithelial integrity. PMID:19100237

  15. Adhesion Issues with Polymer/Oxide Barrier Coatings on Organic Displays

    SciTech Connect

    Matson, Dean W.; Martin, Peter M.; Graff, Gordon L.; Gross, Mark E.; Burrows, Paul E.; Bennett, Wendy D.; Hall, Michael G.; Mast, Eric S.; Bonham, Charles C.; Zumhoff, Mac R.; Rutherford, Nicole M.; Moro, Lorenza; Rosenblum, Martin; Praino, Robert F.; Visser, Robert J.

    2005-01-01

    Multilayer polymer/oxide coatings are being developed to protect sensitive organic display devices, such as OLEDs, from oxygen and water vapor permeation. The coatings have permeation levels ~ 10-6 g/m2/d for water vapor and ~10-6 cc/m2/d for oxygen, and are deposited by vacuum polymer technology. The coatings consist of either a base Al2O3 or acrylate polymer adhesion layer followed by alternating Al2O3/polymer layers. The polymer is used to decouple the 30 nm-thick Al2O3 barrier layers. Adhesion of the barrier coating to the substrate and display device is critical for the operating lifetime of the device. The substrate material could be any transparent flexible plastic. The coating technology can also be used to encapsulate organic-based electronic devices to protect them from atmospheric degradation. Plasma pretreatment is also needed for good adhesion to the substrate, but if it is too aggressive, it will damage the organic display device. We report on the effects of plasma treatment on the adhesion of barrier coatings to plastic substrates and the performance of OLED devices after plasma treatment and barrier coating deposition. We find that initial OLED performance is not significantly affected by the deposition process and plasma treatment, as demonstrated by luminosity and I-V curves.

  16. Manganese- and iron-dependent marine methane oxidation.

    PubMed

    Beal, Emily J; House, Christopher H; Orphan, Victoria J

    2009-07-10

    Anaerobic methanotrophs help regulate Earth's climate and may have been an important part of the microbial ecosystem on the early Earth. The anaerobic oxidation of methane (AOM) is often thought of as a sulfate-dependent process, despite the fact that other electron acceptors are more energetically favorable. Here, we show that microorganisms from marine methane-seep sediment in the Eel River Basin in California are capable of using manganese (birnessite) and iron (ferrihydrite) to oxidize methane, revealing that marine AOM is coupled, either directly or indirectly, to a larger variety of oxidants than previously thought. Large amounts of manganese and iron are provided to oceans from rivers, indicating that manganese- and iron-dependent AOM have the potential to be globally important.

  17. Nitrate- and nitrite-dependent anaerobic oxidation of methane.

    PubMed

    Welte, Cornelia U; Rasigraf, Olivia; Vaksmaa, Annika; Versantvoort, Wouter; Arshad, Arslan; Op den Camp, Huub J M; Jetten, Mike S M; Lüke, Claudia; Reimann, Joachim

    2016-12-01

    Microbial methane oxidation is an important process to reduce the emission of the greenhouse gas methane. Anaerobic microorganisms couple the oxidation of methane to the reduction of sulfate, nitrate and nitrite, and possibly oxidized iron and manganese minerals. In this article, we review the recent finding of the intriguing nitrate- and nitrite-dependent anaerobic oxidation of methane (AOM). Nitrate-dependent AOM is catalyzed by anaerobic archaea belonging to the ANME-2d clade closely related to Methanosarcina methanogens. They were named 'Candidatus Methanoperedens nitroreducens' and use reverse methanogenesis with the key enzyme methyl-coenzyme M (methyl-CoM) reductase for methane activation. Their major end product is nitrite which can be taken up by nitrite-dependent methanotrophs. Nitrite-dependent AOM is performed by the NC10 bacterium 'Candidatus Methylomirabilis oxyfera' that probably utilizes an intra-aerobic pathway through the dismutation of NO to N2 and O2 for aerobic methane activation by methane monooxygenase, yet being a strictly anaerobic microbe. Environmental distribution, physiological and biochemical aspects are discussed in this article as well as the cooperation of the microorganisms involved. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  18. Superoxide-dependent oxidation of melatonin by myeloperoxidase.

    PubMed

    Ximenes, Valdecir F; Silva, Sueli de O; Rodrigues, Maria R; Catalani, Luiz H; Maghzal, Ghassan J; Kettle, Anthony J; Campa, Ana

    2005-11-18

    Myeloperoxidase uses hydrogen peroxide to oxidize numerous substrates to hypohalous acids or reactive free radicals. Here we show that neutrophils oxidize melatonin to N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK) in a reaction that is catalyzed by myeloperoxidase. Production of AFMK was highly dependent on superoxide but not hydrogen peroxide. It did not require hypochlorous acid, singlet oxygen, or hydroxyl radical. Purified myeloperoxidase and a superoxide-generating system oxidized melatonin to AFMK and a dimer. The dimer would result from coupling of melatonin radicals. Oxidation of melatonin was partially inhibited by catalase or superoxide dismutase. Formation of AFMK was almost completely eliminated by superoxide dismutase but weakly inhibited by catalase. In contrast, production of melatonin dimer was enhanced by superoxide dismutase and blocked by catalase. We propose that myeloperoxidase uses superoxide to oxidize melatonin by two distinct pathways. One pathway involves the classical peroxidation mechanism in which hydrogen peroxide is used to oxidize melatonin to radicals. Superoxide adds to these radicals to form an unstable peroxide that decays to AFMK. In the other pathway, myeloperoxidase uses superoxide to insert dioxygen into melatonin to form AFMK. This novel activity expands the types of oxidative reactions myeloperoxidase can catalyze. It should be relevant to the way neutrophils use superoxide to kill bacteria and how they metabolize xenobiotics.

  19. High thermal stability of magnetic tunnel junctions with oxide diffusion barrier layers

    NASA Astrophysics Data System (ADS)

    Fukumoto, Yoshiyuki; Shimura, Ken-ichi; Kamijo, Atsushi; Tahara, Shuichi; Yoda, Hiroaki

    2004-01-01

    We developed two types of magnetic tunnel junctions (MTJs) that showed high thermal stability. One is a PtMn exchange-biased spin-valve MTJ with a CoFe/Al-oxide (AlOx)/NiFe free layer and a CoFeTaOx/CoFe pinned layer, and the other is a pseudo-spin-valve (PSV) MTJ with a CoFe/AlOx/NiFe soft layer, where AlOx and CoFeTaOx act as barriers for Ni and Mn diffusion toward the tunnel barrier, respectively. After 390 °C-1H annealing, the PSV MTJs maintained 28% and the SV MTJs 39% of tunnel magnetoresistance. Transmission electron microscopy observation of the SV MTJs after 380 °C-1H annealing revealed that the migrated Mn atoms were trapped at the CoFeTaOx layer.

  20. Targeting Transporters: Promoting Blood-Brain Barrier Repair in Response to Oxidative Stress Injury

    PubMed Central

    Ronaldson, Patrick T.; Davis, Thomas P.

    2015-01-01

    The blood-brain barrier (BBB) is a physical and biochemical barrier that precisely regulates the ability of endogenous and exogenous substances to accumulate within brain tissue. It possesses structural and biochemical features (i.e., tight junction and adherens junction protein complexes, influx and efflux transporters) that work in concert to control solute permeation. Oxidative stress, a critical component of several diseases including cerebral hypoxia/ischemia and peripheral inflammatory pain, can cause considerable injury to the BBB and lead to significant CNS pathology. This suggests a critical need for novel therapeutic approaches that can protect the BBB in diseases with an oxidative stress component. Recent studies have identified molecular targets (i.e., endogenous transporters, intracellular signaling systems) that can be exploited for optimization of endothelial drug delivery or for control of transport of endogenous substrates such as the antioxidant glutathione (GSH). In particular, targeting transporters offers a unique approach to protect BBB integrity by promoting repair of cell-cell interactions at the level of the brain microvascular endothelium. This review summarizes current knowledge in this area and emphasizes those targets that present considerable opportunity for providing BBB protection and/or promoting BBB repair in the setting of oxidative stress. PMID:25796436

  1. Protein kinase C-mediated endothelial barrier regulation is caveolin-1-dependent.

    PubMed

    Waschke, Jens; Golenhofen, Nikola; Kurzchalia, Teymuras V; Drenckhahn, Detlev

    2006-07-01

    Protein kinase C (PKC) is activated in response to various inflammatory mediators and contributes significantly to the endothelial barrier breakdown. However, the mechanisms underlying PKC-mediated permeability regulation are not well understood. We prepared microvascular myocardial endothelial cells from both wild-type (WT) and caveolin-1-deficient mice. Activation of PKC by phorbol myristate acetate (PMA) (100 nM) for 30 min induced intercellular gap formation and fragmentation of VE-cadherin immunoreactivity in WT but not in caveolin-1-deficient monolayers. To test the effect of PKC activation on VE-cadherin-mediated adhesion, we allowed VE-cadherin-coated microbeads to bind to the endothelial cell surface and probed their adhesion by laser tweezers. PMA significantly reduced bead binding to 78+/-6% of controls in WT endothelial cells without any effect in caveolin-1-deficient cells. In WT cells, PMA caused an 86+/-18% increase in FITC-dextran permeability whereas no increase in permeability was observed in caveolin-1-deficient monolayers. Inhibition of PKC by staurosporine (50 nM, 30 min) did not affect barrier functions in both WT and caveolin-1-deficient MyEnd cells. Theses data indicate that PKC activation reduces endothelial barrier functions at least in part by the reduction of VE-cadherin-mediated adhesion and demonstrate that PKC-mediated permeability regulation depends on caveolin-1.

  2. Borate cross-linked graphene oxide-chitosan as robust and high gas barrier films

    NASA Astrophysics Data System (ADS)

    Yan, Ning; Capezzuto, Filomena; Lavorgna, Marino; Buonocore, Giovanna G.; Tescione, Fabiana; Xia, Hesheng; Ambrosio, Luigi

    2016-05-01

    Chitosan (CS) is one of the most promising polymers due to its biocompatibility, biodegradability, and natural abundance. However, its poor mechanical and barrier properties make it difficult to satisfy a wide range of applications. Herein, borate ions, originating from the hydrolysis of sodium tetraborate decahydrate (borax), have been used to crosslink chitosan and graphene oxide (GO) nanocomposites. Chitosan films consisting of 1.0 wt% boron and 1.0 wt% GO exhibit a significant improvement in both the toughness and oxygen barrier properties compared to pristine chitosan. In particular the tensile strength of the samples after thermal treatment increases by ~160% compared to pristine chitosan, whereas their oxygen permeability reduces by ~90%. This is ascribed to the chemical crosslinking between chitosan and GO nanoplatelets through borate ions, as well as the formation of a layered morphology with graphene nanoplatelets oriented parallel to the sample surface. The exceptional robust and high gas barrier film has promising application in the packaging industry. The borate-crosslinking chemistry represents the potential strategy for improving properties of other polymer nanocomposites.Chitosan (CS) is one of the most promising polymers due to its biocompatibility, biodegradability, and natural abundance. However, its poor mechanical and barrier properties make it difficult to satisfy a wide range of applications. Herein, borate ions, originating from the hydrolysis of sodium tetraborate decahydrate (borax), have been used to crosslink chitosan and graphene oxide (GO) nanocomposites. Chitosan films consisting of 1.0 wt% boron and 1.0 wt% GO exhibit a significant improvement in both the toughness and oxygen barrier properties compared to pristine chitosan. In particular the tensile strength of the samples after thermal treatment increases by ~160% compared to pristine chitosan, whereas their oxygen permeability reduces by ~90%. This is ascribed to the chemical

  3. Drugs of abuse and blood-brain barrier endothelial dysfunction: A focus on the role of oxidative stress

    PubMed Central

    Sajja, Ravi K; Rahman, Shafiqur

    2015-01-01

    Psychostimulants and nicotine are the most widely abused drugs with a detrimental impact on public health globally. While the long-term neurobehavioral deficits and synaptic perturbations are well documented with chronic use of methamphetamine, cocaine, and nicotine, emerging human and experimental studies also suggest an increasing incidence of neurovascular complications associated with drug abuse. Short- or long-term administration of psychostimulants or nicotine is known to disrupt blood-brain barrier (BBB) integrity/function, thus leading to an increased risk of brain edema and neuroinflammation. Various pathophysiological mechanisms have been proposed to underlie drug abuse-induced BBB dysfunction suggesting a central and unifying role for oxidative stress in BBB endothelium and perivascular cells. This review discusses drug-specific effects of methamphetamine, cocaine, and tobacco smoking on brain microvascular crisis and provides critical assessment of oxidative stress-dependent molecular pathways focal to the global compromise of BBB. Additionally, given the increased risk of human immunodeficiency virus (HIV) encephalitis in drug abusers, we have summarized the synergistic pathological impact of psychostimulants and HIV infection on BBB integrity with an emphasis on unifying role of endothelial oxidative stress. This mechanistic framework would guide further investigations on specific molecular pathways to accelerate therapeutic approaches for the prevention of neurovascular deficits by drugs of abuse. PMID:26661236

  4. Drugs of abuse and blood-brain barrier endothelial dysfunction: A focus on the role of oxidative stress.

    PubMed

    Sajja, Ravi K; Rahman, Shafiqur; Cucullo, Luca

    2016-03-01

    Psychostimulants and nicotine are the most widely abused drugs with a detrimental impact on public health globally. While the long-term neurobehavioral deficits and synaptic perturbations are well documented with chronic use of methamphetamine, cocaine, and nicotine, emerging human and experimental studies also suggest an increasing incidence of neurovascular complications associated with drug abuse. Short- or long-term administration of psychostimulants or nicotine is known to disrupt blood-brain barrier (BBB) integrity/function, thus leading to an increased risk of brain edema and neuroinflammation. Various pathophysiological mechanisms have been proposed to underlie drug abuse-induced BBB dysfunction suggesting a central and unifying role for oxidative stress in BBB endothelium and perivascular cells. This review discusses drug-specific effects of methamphetamine, cocaine, and tobacco smoking on brain microvascular crisis and provides critical assessment of oxidative stress-dependent molecular pathways focal to the global compromise of BBB. Additionally, given the increased risk of human immunodeficiency virus (HIV) encephalitis in drug abusers, we have summarized the synergistic pathological impact of psychostimulants and HIV infection on BBB integrity with an emphasis on unifying role of endothelial oxidative stress. This mechanistic framework would guide further investigations on specific molecular pathways to accelerate therapeutic approaches for the prevention of neurovascular deficits by drugs of abuse. © The Author(s) 2015.

  5. Atomic and electronic structure of ultrathin fluoride barrier layers at the oxide/Si interface

    NASA Astrophysics Data System (ADS)

    Pasquali, L.; Montecchi, M.; Nannarone, S.; Boscherini, F.

    2011-09-01

    A SrF2 ultrathin barrier layer on Si(001) is used to form a sharp interface and block reactivity and intermixing between the semiconductor and a Yb2O3 overlayer. Yb2O3/Si(001) and Yb2O3/SrF2/Si(001) interfaces grown in ultra high vacuum by molecular beam epitaxy are studied by photoemission and x-ray absorption fine structure. Without the fluoride interlayer, Yb2O3/Si(001) presents an interface reacted region formed by SiOx and/or silicate compounds, which is about 9 Å thick and increases up to 14-15 Å after annealing at 500-700 °C. A uniform single layer of SrF2 molecules blocks intermixing and reduces the oxidized Si region to 2.4 Å after deposition and to 3.5 Å after annealing at 500 °C. In both cases we estimate a conduction band offset and a valence band offset of ~ 1.7 eV and 2.4 eV between the oxide and Si, respectively. X-ray absorption fine structure measurements at the Yb LIII edge suggest that the Yb oxide films exhibit a significant degree of static disorder with and without the fluoride barrier. Sr K edge measurements indicate that the ultrathin fluoride films are reacted, with the formation of bonds between Si and Sr; the Sr-Sr and Sr-F interatomic distances in the ultrathin fluoride barrier film are relaxed to the bulk value.

  6. Morphology-dependent nanocatalysts: rod-shaped oxides.

    PubMed

    Li, Yong; Shen, Wenjie

    2014-03-07

    Nanocatalysts are characterised by the unique nanoscale properties that originate from their highly reduced dimensions. Extensive studies over the past few decades have demonstrated that the size and shape of a catalyst particle on the nanometre scale profoundly affect its reaction performance. In particular, controlling the catalyst particle morphology allows a selective exposure of a larger fraction of the reactive facets on which the active sites can be enriched and tuned. This desirable surface coordination of catalytically active atoms or domains substantially improves catalytic activity, selectivity, and stability. This phenomenon is called morphology-dependent nanocatalysts: catalyst particles with anisotropic morphologies on the nanometre scale greatly affect the reaction performance by selectively exposing the desired facets. In this review, we highlight important progress in morphology-dependent nanocatalysts based on the use of rod-shaped metal oxides with characteristic redox and acid-base features. The correlation between the catalytic properties and the exposed facets verifies the chemical nature of the morphology effect. Moreover, we provide an overview of the interactions between the rod-shaped oxides and the metal nanoparticles in metal-oxide catalyst systems, involving crystal-facet-selective deposition of metal particles onto different crystal facets in the oxide supports. A fundamental understanding of active sites in morphologically tuneable oxides enclosed by the desired reactive facets is expected to direct the development of highly efficient nanocatalysts.

  7. Characterization of Aluminum Oxide Tunnel Barrier for use in a Non-Local Spin Detection Device

    NASA Astrophysics Data System (ADS)

    Abel, Joseph; Garramone, John; Sitnitsky, Ilona; Labella, Vincent

    2010-03-01

    Aluminum oxide can be utilized as an interface layer between ferromagnetic metals and silicon to achieve spin injection into silicon. The goal of our research is to inject and readout spins using a non-local measurement device that utilizes 1-2 nm aluminum oxide interface layers as tunnel barriers. An important step of fabricating a non-local measurement device out of silicon is the growth of an aluminum oxide tunnel barrierfootnotetextO. van't Erve, A. Hanbicki, M. Holub, C. Li, C. Awo-Affouda, P. Thompson and B. Jonker, Appl. Phys. Lett. 91, 212109 (2007).. Aluminum Oxide thin films where grown using a Knudsen cell to deposit 1 nm, 2 nm, and 3 nm of aluminum. The films were then oxidized in O2. X-ray photoelectron spectroscopy (XPS) was performed to characterize the film stoichiometry, and the band gap. We will also report on current voltage measurements of these films after they have been capped with metal and compare the resistance area product to those calculated for spin injection into siliconfootnotetextB.-C. Min, K. Motohashi, C. Lodder, and R. Jansen, Nat. Mater. 5, 817 (2006). .

  8. Oxidation and degradation of a plasma-sprayed thermal barrier coating system

    SciTech Connect

    Haynes, J.A.; Ferber, M.K.; Porter, W.D.

    1996-04-01

    The isothermal oxidation behavior of thermal barrier coating (TBC) specimens consisting of single-crystal superalloy substrates, vacuum plasma-sprayed Ni-22Cr-10Al-1Y bond coatings and air plasma-sprayed 7.5 wt.% yttria stabilized zirconia top coatings was evaluated by thermogravimetric analysis at 1150{degrees}C for up to 200 hours. Coating durability was assessed by furnace cycling at 1150{degrees}C. Coatings and reaction products were identified by x-ray diffraction, field-emission scanning electron microscopy and energy dispersive spectroscopy.

  9. Investigation of NOx Reduction by Low Temperature Oxidation Using Ozone Produced by Dielectric Barrier Discharge

    NASA Astrophysics Data System (ADS)

    Stamate, Eugen; Irimiea, Cornelia; Salewski, Mirko

    2013-05-01

    NOx reduction by low temperature oxidation using ozone produced by a dielectric barrier discharge generator is investigated for different process parameters in a 6 m long reactor in serpentine arrangement using synthetic dry flue gas with NOx levels below 500 ppm, flows up to 50 slm and temperatures up to 80 °C. The role of different mixing schemes and the impact of a steep temperature gradient are also taken into consideration. The process chemistry is monitored by Fourier transform infrared spectroscopy, chemiluminescence and absorption spectroscopy. The kinetic mechanism during the mixing in a cross flow configuration is investigated using three-dimensional simulations.

  10. Time dependent semiclassical tunneling through one dimensional barriers using only real valued trajectories

    SciTech Connect

    Herman, Michael F.

    2015-10-28

    The time independent semiclassical treatment of barrier tunneling has been understood for a very long time. Several semiclassical approaches to time dependent tunneling through barriers have also been presented. These typically involve trajectories for which the position variable is a complex function of time. In this paper, a method is presented that uses only real valued trajectories, thus avoiding the complications that can arise when complex trajectories are employed. This is accomplished by expressing the time dependent wave packet as an integration over momentum. The action function in the exponent in this expression is expanded to second order in the momentum. The expansion is around the momentum, p{sub 0{sup *}}, at which the derivative of the real part of the action is zero. The resulting Gaussian integral is then taken. The stationary phase approximation requires that the derivative of the full action is zero at the expansion point, and this leads to a complex initial momentum and complex tunneling trajectories. The “pseudo-stationary phase” approximation employed in this work results in real values for the initial momentum and real valued trajectories. The transmission probabilities obtained are found to be in good agreement with exact quantum results.

  11. Fe nanoparticles on ZnSe: Reversible temperature dependence of the surface barrier potential

    NASA Astrophysics Data System (ADS)

    Cantoni, M.; Bertacco, R.; Brambilla, A.; Finazzi, M.; Duò, L.; Ciccacci, F.; Verdini, A.; Floreano, L.; Morgante, A.; Passoni, M.; Casari, C. S.; Li Bassi, A.

    2012-04-01

    The Fe growth on ZnSe(001) takes place via the initial formation of superparamagnetic nano-islands that subsequently coalesce, giving rise to a continuous film for a nominal thickness of 8 Fe monolayers. For a very low Fe coverage (2 Fe monolayers), we show that the surface barrier potential (i.e. the barrier potential seen by electrons incident on the surface), measured by absorbed current spectroscopy, attains very large values (6.9 eV at room temperature) and dramatically changes as a function of temperature, with an increase of ˜1.5 eV from room temperature down to 130 K, largely exceeding similar changes observed in both thin films and nanoparticles. This phenomenon disappears as the thickness increases and is fully reversible with temperature. Nonequilibrium phenomena due to the experimental conditions are present, but are not able to explain the observed data. Inverse photoemission, core level photoemission, x-ray photoemission diffraction, and scanning tunneling microscopy are employed in order to find temperature-dependent properties of the Fe islands: while only minor changes as a function of temperature are present in the electronic band structure, the Fe crystal structure, and the morphology of the islands, a noticeable temperature dependence of the Se segregation through the Fe islands is found.

  12. Baicalin Attenuates Subarachnoid Hemorrhagic Brain Injury by Modulating Blood-Brain Barrier Disruption, Inflammation, and Oxidative Damage in Mice.

    PubMed

    Shi, Xianqing; Fu, Yongjian; Zhang, SongSong; Ding, Hao; Chen, Jin

    2017-01-01

    In subarachnoid hemorrhagic brain injury, the early crucial events are edema formation due to inflammatory responses and blood-brain barrier disruption. Baicalin, a flavone glycoside, has antineuroinflammatory and antioxidant properties. We examined the effect of baicalin in subarachnoid hemorrhagic brain injury. Subarachnoid hemorrhage was induced through filament perforation and either baicalin or vehicle was administered 30 min prior to surgery. Brain tissues were collected 24 hours after surgery after evaluation of neurological scores. Brain tissues were processed for water content, real-time PCR, and immunoblot analyses. Baicalin improved neurological score and brain water content. Decreased levels of tight junction proteins (occludin, claudin-5, ZO-1, and collagen IV) required for blood-brain barrier function were restored to normal level by baicalin. Real-time PCR data demonstrated that baicalin attenuated increased proinflammatory cytokine (IL-1β, IL-6, and CXCL-3) production in subarachnoid hemorrhage mice. In addition to that, baicalin attenuated microglial cell secretion of IL-1β and IL-6 induced by lipopolysaccharide (100 ng/ml) dose dependently. Finally, baicalin attenuated induction of NOS-2 and NOX-2 in SAH mice at the mRNA and protein level. Thus, we demonstrated that baicalin inhibited microglial cell activation and reduced inflammation, oxidative damage, and brain edema.

  13. Processing Methods Established To Fabricate Porous Oxide Ceramic Spheres for Thermal Barrier Coating Applications

    NASA Technical Reports Server (NTRS)

    Dynys, Frederick W.

    2003-01-01

    As gas turbine technology advances, the demand for efficient engines and emission reduction requires a further increase in operating temperatures, but combustion temperatures are currently limited by the temperature capability of the engine components. The existing thermal barrier coating (TBC) technology does not provide sufficient thermal load reduction at a 3000 F (1649 C) operating condition. Advancement in thermal barrier coating technology is needed to meet this aggressive goal. One concept for improving thermal barrier coating effectiveness is to design coating systems that incorporate a layer that reflects or scatters photon radiation. This can be achieved by using porous structures. The refractive index mismatch between the solid and pore, the pore size, and the pore density can be engineered to efficiently scatter photon radiation. Under NASA s Ultra-Efficient Engine Technology (UEET) Program, processing methods to fabricate porous ceramic spheres suitable for scattering photon radiation at elevated temperatures have been established. A straightforward templating process was developed at the NASA Glenn Research Center that requires no special processing equipment. The template was used to define particle shape, particle size, and pore size. Spherical organic cation exchange resins were used as a structure-directing template. The cation exchange resins have dual template capabilities that can produce different pore architectures. This process can be used to fabricate both metal oxide and metal carbide spheres.

  14. Ecofriendly Fabrication of Modified Graphene Oxide Latex Nanocomposites with High Oxygen Barrier Performance.

    PubMed

    Guan, Yidan; Meyers, Kevin P; Mendon, Sharathkumar K; Hao, Guangjie; Douglas, Jessica R; Trigwell, Steve; Nazarenko, Sergei I; Patton, Derek L; Rawlins, James W

    2016-12-07

    Large-scale industrial applications of barrier films and coatings that prevent permeation of degradative gases and moisture call for the development of cost-efficient and ecofriendly polymer nanocomposites. Herein, we report the facile fabrication of latex nanocomposites (LNCs) by incorporating surface-modified graphene oxide (mGO) at various loadings (0.025-1.2 wt %) into a styrene-acrylic latex using water as the processing solvent. LNCs fabricated with mGO exhibited significant reductions (up to 67%) in water vapor sorption, resulting in greater environmental stability when compared to LNCs fabricated with equivalent loading of hydrophilic, unmodified GO. The assembly and coalescence of the exfoliated latex/mGO dispersions during the film formation process produced highly dispersed and well-ordered mGO domains with high aspect ratios, where alignment and overlap of the mGO domains improved with increasing mGO content. The addition of only 0.7 vol % (1.2 wt %) mGO led to an 84% decrease (relative to the neat polymer latex film) in oxygen permeability of the LNC films, an excellent barrier performance attributed to the observed LNC film morphologies. This work enables ecofriendly development of mechanically flexible mGO/LNC films with superior barrier properties for many industrial applications including protective coatings, food packaging, and biomedical products.

  15. Isothermal Oxidation Behavior of Supersonic Atmospheric Plasma-Sprayed Thermal Barrier Coating System

    NASA Astrophysics Data System (ADS)

    Bai, Yu; Ding, Chunhua; Li, Hongqiang; Han, Zhihai; Ding, Bingjun; Wang, Tiejun; Yu, Lie

    2013-10-01

    In this work, Y2O3 stabilized zirconia-based thermal barrier coatings (TBCs) were deposited by conventional atmospheric plasma spraying (APS) and high efficiency supersonic atmospheric plasma spraying (SAPS), respectively. The effect of Al2O3 layer stability on the isothermal growth behavior of thermally grown oxides (TGOs) was studied. The results revealed that the Al2O3 layer experienced a three-stage change process, i.e., (1) instantaneous growth stage, (2) steady-state growth stage, and (3) depletion stage. The thickness of Al2O3 scale was proved to be an important factor for the growth rate of TGOs. The SAPS-TBCs exhibited a higher Al2O3 stability and better oxidation resistance as compared with the APS-TBCs. Additionally, it was found that inner oxides, especially nucleated on the top of the crest, continually grew and swallowed the previously formed Al2O3 layer, leading to the granulation and disappearance of continuous Al2O3 scale, which was finally replaced by the mixed oxides and spinel.

  16. Effects of Doping on Thermal Conductivity of Pyrochlore Oxides for Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dongming; Eslamloo-Grami, Maryam

    2006-01-01

    Pyrochlore oxides of general composition, A2B2O7, where A is a 3(+) cation (La to Lu) and B is a 4(+) cation (Zr, Hf, Ti, etc.) have high melting point, relatively high coefficient of thermal expansion, and low thermal conductivity which make them suitable for applications as high-temperature thermal barrier coatings. The effect of doping at the A site on the thermal conductivity of a pyrochlore oxide La2Zr2O7, has been investigated. Oxide powders of various compositions La2Zr2O7, La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 were synthesized by the citric acid sol-gel method. These powders were hot pressed into discs and used for thermal conductivity measurements using a steady-state laser heat flux test technique. The rare earth oxide doped pyrochlores La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 had lower thermal conductivity than the un-doped La2Zr2O7. The Gd2O3 and Yb2O3 co-doped composition showed the lowest thermal conductivity.

  17. PH Dependent Interactions between Aqueous Iodide Ion and Selected Oxidizers.

    DTIC Science & Technology

    1985-12-06

    between the oxidizers oeroxydisultte, peroxide. percarbonate, and perborate ions and aqueous iodide have been measured at pH 1. 4. 7, 9. Reactions were... Perborate and percarbonate are salts with "hydrogen peroxide of crystallization" (see formulae listed in Table i). These salts appear to release this...between hydrogen peroxide and iodide are highly pH dependent. These materials react very slowly, or not at all, at pH 49. 2). Perborate and percarbonate are

  18. Thermal Properties of Oxides With Magnetoplumbite Structure for Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dongming; Eslamloo-Grami, Maryam

    2007-01-01

    Oxides having magnetoplumbite structure are promising candidate materials for applications as high temperature thermal barrier coatings because of their high thermal stability, high thermal expansion, and low thermal conductivity. In this study, powders of LaMgAl11O19, GdMgAl11O19, SmMgAl11O19, and Gd0.7Yb0.3MgAl11O19 magnetoplumbite oxides were synthesized by citric acid sol-gel method and hot pressed into disk specimens. The thermal expansion coefficients (CTE) of these oxide materials were measured from room temperature to 1500 C. The average CTE value was found to be approx.9.6x10(exp -6)/C. Thermal conductivity of these magnetoplumbite-based oxide materials was also evaluated using steady-state laser heat flux test method. The effects of doping on thermal properties were also examined. Thermal conductivity of the doped Gd0.7Yb0.3MgAl11O19 composition was found to be lower than that of the undoped GdMgAl11O19. In contrast, thermal expansion coefficient was found to be independent of the oxide composition and appears to be controlled by the magnetoplumbite crystal structure. Thermal conductivity testing of LaMgAl11O19 and LaMnAl11O19 magnetoplumbite oxide coatings plasma sprayed on NiCrAlY/Rene N5 superalloy substrates indicated resistance of these coatings to sintering even at temperatures as high as 1600 C.

  19. Pressure dependence of prototype structures of metastable niobium oxides

    NASA Astrophysics Data System (ADS)

    Obara, Kozo

    1993-03-01

    Faculty of Engineering, Kagoshima University, Korimoto, 1-21-40, Kagoshima 890, Japan Pressure dependences of prototypes of nonstoichiometric metastable niobium oxides formed by a magnetron sputtering system were investigated. The morphology of derived crystals depended strongly on the argon pressure. At argon pressure PAr< 0.2 Torr, thin microcrystals with five types of superlattice structures were derived. Observed lattice constants were transformed into one another by simple lattice deformations within 1% error. All types of superlattice structures were related to the cubic lattice a0 = 3.22 Å. At PAr > 0.3 Torr, metastable niobium oxide super-fine particles with a cubic lattice constant a = 3.44 Å were obtained. Unique relationships between lattice constants were found on the oxidized niobium super-fine particles, NbO and NbO2 formed above 0.3 Torr within 0.5% error. In this case, the lattice structure with a = 3.44 ,Å (BCC) is related to all structures. These lattices a0 = 3.22 ,Å and a = 3.44 Å seem to be the prototypes at PAr ≤ 0.2 Torr and PAr ≥ 0.3 Tort, respectively. These structural changes due to pressure difference depend on the density and the enthalpy of vacancies in as-grown crystals. The density of vacancies is related to the condensation rate of the crystals.

  20. Hedgehog Signaling Overcomes an EZH2-Dependent Epigenetic Barrier to Promote Cholangiocyte Expansion

    PubMed Central

    Lu, Jie; Almada, Luciana L.; Lomberk, Gwen; Fernandez-Zapico, Martin E.; Urrutia, Raul; Huebert, Robert C.

    2016-01-01

    Background & Aims Developmental morphogens play an important role in coordinating the ductular reaction and portal fibrosis occurring in the setting of cholangiopathies. However, little is known about how membrane signaling events in ductular reactive cells (DRCs) are transduced into nuclear transcriptional changes to drive cholangiocyte maturation and matrix deposition. Therefore, the aim of this study was to investigate potential mechanistic links between cell signaling events and epigenetic regulators in DRCs. Methods Using directed differentiation of induced pluripotent stem cells (iPSC), isolated DRCs, and in vivo models, we examine the mechanisms whereby sonic hedgehog (Shh) overcomes an epigenetic barrier in biliary precursors and promotes both cholangiocyte maturation and deposition of fibronectin (FN). Results We demonstrate, for the first time, that Gli1 influences the differentiation state and fibrogenic capacity of iPSC-derived hepatic progenitors and isolated DRCs. We outline a novel pathway wherein Shh-mediated Gli1 binding in key cholangiocyte gene promoters overcomes an epigenetic barrier conferred by the polycomb protein, enhancer of zeste homolog 2 (EZH2) and initiates the transcriptional program of cholangiocyte maturation. We also define previously unknown functional Gli1 binding sites in the promoters of cytokeratin (CK)7, CK19, and FN. Our in vivo results show that EZH2 KO mice fed the choline-deficient, ethanolamine supplemented (CDE) diet have an exaggerated cholangiocyte expansion associated with more robust ductular reaction and increased peri-portal fibrosis. Conclusion We conclude that Shh/Gli1 signaling plays an integral role in cholangiocyte maturation in vitro by overcoming an EZH2-dependent epigenetic barrier and this mechanism also promotes biliary expansion in vivo. PMID:27936185

  1. The advantages and barriers in the implementation of a substance dependence treatment information system (SDTIS).

    PubMed

    Ajami, Sima; Mellat-Karkevandi, Zahra

    2015-11-01

    Addiction is a phenomenon that causes structural changes in different systems of society. Studies show for planning of addiction prevention and treatment, it is necessary to create an information management system. Substance dependence information systems refer to systems which collect, analyse and report data related to substance dependence information. The aim of this study was to identify advantages and barriers to implement Substance Dependence Treatment Information System (SDTIS). This study was a narrative review. Our review divided into three phases: literature collection, assessing, and selection. We employed the following keywords and their combinations in different areas of articles. In this study, 22 of collected articles and reports were selected based on their relevancy. We found many advantages for a substance dependence treatment information system such as recording sufficient, complete and accurate information and easy and timely access to them and monitoring and enhancing the quality of care received by patients. But we may face some concerns for implementing this information system like taking time and funds from client services, being expensive or even problems regarding the quality of data contained in these information systems. There are some important problems in the way of implementing. In order to overcome these issues, we need to raise community awareness.

  2. The advantages and barriers in the implementation of a substance dependence treatment information system (SDTIS)

    PubMed Central

    Ajami, Sima; Mellat-Karkevandi, Zahra

    2015-01-01

    Addiction is a phenomenon that causes structural changes in different systems of society. Studies show for planning of addiction prevention and treatment, it is necessary to create an information management system. Substance dependence information systems refer to systems which collect, analyse and report data related to substance dependence information. The aim of this study was to identify advantages and barriers to implement Substance Dependence Treatment Information System (SDTIS). This study was a narrative review. Our review divided into three phases: literature collection, assessing, and selection. We employed the following keywords and their combinations in different areas of articles. In this study, 22 of collected articles and reports were selected based on their relevancy. We found many advantages for a substance dependence treatment information system such as recording sufficient, complete and accurate information and easy and timely access to them and monitoring and enhancing the quality of care received by patients. But we may face some concerns for implementing this information system like taking time and funds from client services, being expensive or even problems regarding the quality of data contained in these information systems. There are some important problems in the way of implementing. In order to overcome these issues, we need to raise community awareness. PMID:26941816

  3. In Situ XPS Chemical Analysis of MnSiO3 Copper Diffusion Barrier Layer Formation and Simultaneous Fabrication of Metal Oxide Semiconductor Electrical Test MOS Structures.

    PubMed

    Byrne, Conor; Brennan, Barry; McCoy, Anthony P; Bogan, Justin; Brady, Anita; Hughes, Greg

    2016-02-03

    Copper/SiO2/Si metal-oxide-semiconductor (MOS) devices both with and without a MnSiO3 barrier layer at the Cu/SiO2 interface have been fabricated in an ultrahigh vacuum X-ray photoelectron spectroscopy (XPS) system, which allows interface chemical characterization of the barrier formation process to be directly correlated with electrical testing of barrier layer effectiveness. Capacitance voltage (CV) analysis, before and after tube furnace anneals of the fabricated MOS structures showed that the presence of the MnSiO3 barrier layer significantly improved electric stability of the device structures. Evidence of improved adhesion of the deposited copper layer to the MnSiO3 surface compared to the clean SiO2 surface was apparent both from tape tests and while probing the samples during electrical testing. Secondary ion mass spectroscopy (SIMS) depth profiling measurements of the MOS test structures reveal distinct differences of copper diffusion into the SiO2 dielectric layers following the thermal anneal depending on the presence of the MnSiO3 barrier layer.

  4. Role of energy dependent interaction potential in sub-barrier fusion of S2814i +Z9040r system

    NASA Astrophysics Data System (ADS)

    Gautam, Manjeet Singh; Sharma, Manoj K.

    2015-08-01

    We have analyzed the importance of the inelastic surface vibrations of colliding nuclei in the sub-barrier fusion enhancement of S2814i +Z9040r system by using the energy dependent Woods-Saxon potential model (EDWSP model) in conjunction with one dimensional Wong formula and the coupled channel formulation using the code CCFULL. The multi-phonon vibrational states of colliding nuclei seem to impart significant contribution. The coupling between relative motion of reactants and these relevant channels in turn produce anomalously large sub-barrier fusion enhancement over the expectations of one dimensional barrier penetration model. Furthermore, the effects of coupling to inelastic surface excitations are imitated due to energy dependence in the Woods-Saxon potential. In EDWSP model calculations, a wide range of diffuseness parameter much larger than the elastic scattering predictions is needed to account the observed fusion enhancement in the close vicinity of Coulomb barrier.

  5. Spin-dependent tunneling time in periodic diluted-magnetic-semiconductor/nonmagnetic-barrier superlattices

    SciTech Connect

    Yang, Ping-Fan; Guo, Yong

    2016-02-01

    We investigate the tunneling time (dwell time) in periodic diluted-magnetic-semiconductor/nonmagnetic-barrier (DMS/NB) superlattices subjected to an external magnetic field. It is found that spin-dependent resonant bands form in the spectra of dwell time, which can be effectively manipulated by not only the external magnetic field but also the geometric parameters of the system. Moreover, an intuitive semiclassical delay is defined to illustrate the behavior of the dwell time, and the former one is shown to be the result of “smoothing out” the latter one. We also find that the dwell time in diluted-magnetic-semiconductor/semiconductor superlattices behaves surprisingly different from the DMS/NB case, especially for spin-down electrons.

  6. Scale dependent behavior the foredune: Implications for barrier island response to storms and sea level rise

    NASA Astrophysics Data System (ADS)

    Houser, Chris; Wernette, Phil; Weymer, Bradley

    2017-04-01

    The impact of storm surge on a barrier island tends to be considered from a single cross-shore dimension, dependent only on the relative elevations of the storm surge and dune. However, the foredune line is rarely uniform, and can exhibit considerable variation in height and width at a range of length scales ranging from tens of meters to several kilometers. LiDAR data from barrier islands in Texas and Florida are used to explore how shoreline position and dune morphology vary alongshore, and to determine how this variability is altered or reinforced by storms and post-storm recovery. Wavelet analysis reveals that a power law can approximate long-term shoreline change across all scales, but that storm-scale shoreline change ( 10 years) and dune height exhibit similar scale-dependent variations at swash (0-50 m) and surf zone scales (<50-1000 m). The in-phase nature of this relationship between dune height and storm-scale shoreline change indicates that areas of greater storm-scale shoreline retreat are associated with areas of smaller dunes. Decoupling of storm-scale and long-term shoreline change at swash and surf zone scales suggests an alongshore redistribution of sediment towards a more dissipative shoreline over time. Post-storm recovery for Gulf Islands in Florida is dissipative at the smallest scales, which suggests that given sufficient time between storms it is possible that small-scale variations in dune height can be repaired through alongshore recovery and expansion of vegetation, but the timescales of recovery exceed the time between storms capable of eroding and overwashing the dune. Since historical shoreline retreat is correlated with dune height variance at swash and surf zone scales, the persistence of the variations in dune height are argued to be an important control on island transgression in response to sea level rise.

  7. Tirandamycin biosynthesis is mediated by co-dependent oxidative enzymes

    NASA Astrophysics Data System (ADS)

    Carlson, Jacob C.; Li, Shengying; Gunatilleke, Shamila S.; Anzai, Yojiro; Burr, Douglas A.; Podust, Larissa M.; Sherman, David H.

    2011-08-01

    Elucidation of natural product biosynthetic pathways provides important insights into the assembly of potent bioactive molecules, and expands access to unique enzymes able to selectively modify complex substrates. Here, we show full reconstitution, in vitro, of an unusual multi-step oxidative cascade for post-assembly-line tailoring of tirandamycin antibiotics. This pathway involves a remarkably versatile and iterative cytochrome P450 monooxygenase (TamI) and a flavin adenine dinucleotide-dependent oxidase (TamL), which act co-dependently through the repeated exchange of substrates. TamI hydroxylates tirandamycin C (TirC) to generate tirandamycin E (TirE), a previously unidentified tirandamycin intermediate. TirE is subsequently oxidized by TamL, giving rise to the ketone of tirandamycin D (TirD), after which a unique exchange back to TamI enables successive epoxidation and hydroxylation to afford, respectively, the final products tirandamycin A (TirA) and tirandamycin B (TirB). Ligand-free, substrate- and product-bound crystal structures of bicovalently flavinylated TamL oxidase reveal a likely mechanism for the C10 oxidation of TirE.

  8. Tirandamycin biosynthesis is mediated by co-dependent oxidative enzymes.

    PubMed

    Carlson, Jacob C; Li, Shengying; Gunatilleke, Shamila S; Anzai, Yojiro; Burr, Douglas A; Podust, Larissa M; Sherman, David H

    2011-07-17

    Elucidation of natural product biosynthetic pathways provides important insights into the assembly of potent bioactive molecules, and expands access to unique enzymes able to selectively modify complex substrates. Here, we show full reconstitution, in vitro, of an unusual multi-step oxidative cascade for post-assembly-line tailoring of tirandamycin antibiotics. This pathway involves a remarkably versatile and iterative cytochrome P450 monooxygenase (TamI) and a flavin adenine dinucleotide-dependent oxidase (TamL), which act co-dependently through the repeated exchange of substrates. TamI hydroxylates tirandamycin C (TirC) to generate tirandamycin E (TirE), a previously unidentified tirandamycin intermediate. TirE is subsequently oxidized by TamL, giving rise to the ketone of tirandamycin D (TirD), after which a unique exchange back to TamI enables successive epoxidation and hydroxylation to afford, respectively, the final products tirandamycin A (TirA) and tirandamycin B (TirB). Ligand-free, substrate- and product-bound crystal structures of bicovalently flavinylated TamL oxidase reveal a likely mechanism for the C10 oxidation of TirE.

  9. Graphene Oxide as an Effective Barrier on a Porous Nanofibrous Membrane for Water Treatment.

    PubMed

    Wang, Jianqiang; Zhang, Pan; Liang, Bin; Liu, Yuxuan; Xu, Tao; Wang, Lifang; Cao, Bing; Pan, Kai

    2016-03-09

    A novel graphene oxide (GO)-based nanofiltration membrane on a highly porous polyacrylonitrile nanofibrous mat (GO@PAN) is prepared for water treatment applications. GO with large lateral size (more than 200 μm) is first synthesized through an improved Hummers method and then assembled on a highly porous nanofibrous mat by vacuum suction method. The prepared GO@PAN membrane is characterized by scanning electron microscopy, transmission electron microscopy, Raman spectrum, X-ray diffraction, and so forth. The results show that graphene oxide can form a barrier on the top of a PAN nanofibrous mat with controllable thickness. The obtained graphene oxide layer exhibits "ideal" pathways (hydrophobic nanochannel) for water molecules between the well-stacked GO nanosheets. Water flux under an extremely low external pressure (1.0 bar) significantly increased due to the unique structure of the GO layer and nanofibrous support. Furthermore, the GO@PAN membrane shows high rejection performance (nearly 100% rejection of Congo red and 56.7% for Na2SO4). A hydrophilic-hydrophobic "gate"-nanochannel model is presented for explaining the water diffusion mechanism through the GO layer. This method for fabrication of the GO membrane on a highly porous support may provide many new opportunities for high performance nanofiltration applications.

  10. Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

    1996-01-01

    A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

  11. Cofactor-dependent pathways of formaldehyde oxidation in methylotrophic bacteria.

    PubMed

    Vorholt, Julia A

    2002-10-01

    Methylotrophic bacteria can grow on a number of substrates as energy source with only one carbon atom, such as methanol, methane, methylamine, and dichloromethane. These compounds are metabolized via the cytotoxin formaldehyde. The formaldehyde consumption pathways, especially the pathways for the oxidation of formaldehyde to CO(2) for energy metabolism, are a central and critical part of the metabolism of these aerobic bacteria. Principally, two main types of pathways for the conversion of formaldehyde to CO(2) have been described: (1) a cyclic pathway initiated by the condensation of formaldehyde with ribulose monophosphate, and (2) distinct linear pathways that involve a dye-linked formaldehyde dehydrogenase or C(1) unit conversion bound to the cofactors tetrahydrofolate (H(4)F), tetrahydromethanopterin (H(4)MPT), glutathione (GSH), or mycothiol (MySH). The pathways involving the four cofactors have in common the following sequence of events: the spontaneous or enzyme-catalyzed condensation of formaldehyde and the respective C(1) carrier, the oxidation of the cofactor-bound C(1) unit and its conversion to formate, and the oxidation of formate to CO(2). However, the H(4)MPT pathway is more complex and involves intermediates that were previously known solely from the energy metabolism of methanogenic archaea. The occurrence of the different formaldehyde oxidation pathways is not uniform among different methylotrophic bacteria. The pathways are in part also used by other organisms to provide C(1) units for biosynthetic reactions (e.g., H(4)F-dependent enzymes) or detoxification of formaldehyde (e.g., GSH-dependent enzymes).

  12. Nitric oxide-dependent hypotensive effects of wax gourd juice.

    PubMed

    Nakashima, Miki; Shigekuni, Yukiko; Obi, Takeshi; Shiraishi, Mitsuya; Miyamoto, Atsushi; Yamasaki, Hideo; Etoh, Takeomi; Iwai, Sumio

    2011-11-18

    The wax gourd (Benincasa hispida (Thunb) Cong.) is a long-season vegetable that has been used in traditional Chinese medicine to treat high blood pressure. However, precise details of its effect and the mechanism of action involved are still lacking. Ten-fold-condensed wax gourd juice was used for the experiments. We measured (1) blood pressure of anesthetized normal Wistar rats in vivo, (2) isolated rat aortic contraction and relaxation, and (3) nitric oxide production from cultured porcine endothelial cells. The rats mentioned had not been treated with the investigational medicine. Intravenous injection of the juice produced a dose-dependent decrease in blood pressure. Treatment with the juice induced concentration-dependent relaxation of isolated rat aortic rings that had been precontracted with noradrenaline. The relaxation induced by the juice was strongly inhibited by treatment with the nitric oxide (NO) synthase inhibitor N(G)-nitro-l-arginine methyl ester hydrochloride (l-NAME) or endothelial denudation. Treatment with the juice produced NO from cultured porcine aortic endothelial cells. This NO production was significantly inhibited by l-NAME. The present findings suggest that wax gourd juice exerts a hypotensive effect via endothelium-dependent vasodilation. The main endothelium-derived relaxing factor involved might be NO. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  13. Exceptional oxygen barrier performance of pullulan nanocomposites with ultra-low loading of graphene oxide

    NASA Astrophysics Data System (ADS)

    Uysal Unalan, Ilke; Wan, Chaoying; Figiel, Łukasz; Olsson, Richard T.; Trabattoni, Silvia; Farris, Stefano

    2015-07-01

    Polymer nanocomposites are increasingly important in food packaging sectors. Biopolymer pullulan is promising in manufacturing packaging films or coatings due to its excellent optical clarity, mechanical strength, and high water-solubility as compared to other biopolymers. This work aims to enhance its oxygen barrier properties and overcome its intrinsic brittleness by utilizing two-dimensional planar graphene oxide (GO) nanoplatelets. It has been found that the addition of only 0.2 wt% of GO enhanced the tensile strength, Young’s modulus, and elongation at break of pullulan films by about 40, 44 and 52%, respectively. The light transmittance at 550 nm of the pullulan/GO films was 92.3% and haze values were within 3.0% threshold, which meets the general requirement for food packaging materials. In particular, the oxygen permeability coefficient of pullulan was reduced from 6337 to 2614 mL μm m-2 (24 h-1) atm-1 with as low as 0.05 wt% of GO loading and further to 1357 mL μm m-2 (24 h-1) atm-1 when GO concentration reached 0.3 wt%. The simultaneous improvement of the mechanical and oxygen barrier properties of pullulan was ascribed to the homogeneous distribution and prevalent unidirectional alignment of GO nanosheets, as determined from the characterization and theoretical modelling results. The exceptional oxygen barrier properties of pullulan/GO nanocomposites with enhanced mechanical flexibility and good optical clarity will add new values to high performance food packaging materials.

  14. Advanced Oxide Material Systems for 1650 C Thermal/Environmental Barrier Coating Applications

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    Advanced thermal and environmental barrier coatings (TEBCs) are being developed for low-emission SiC/SiC ceramic matrix composite (CMC) combustor and vane applications to extend the CMC liner and vane temperature capability to 1650 C (3000 F) in oxidizing and water-vapor-containing combustion environments. The advanced 1650 C TEBC system is required to have a better high-temperature stability, lower thermal conductivity, and more resistance to sintering and thermal stress than current coating systems under engine high-heat-flux and severe thermal cycling conditions. In this report, the thermal conductivity and water vapor stability of selected candidate hafnia-, pyrochlore- and magnetoplumbite-based TEBC materials are evaluated. The effects of dopants on the materials properties are also discussed. The test results have been used to downselect the TEBC materials and help demonstrate the feasibility of advanced 1650 C coatings with long-term thermal cycling durability.

  15. Electromechanical Breakdown of Barrier-Type Anodized Aluminum Oxide Thin Films Under High Electric Field Conditions

    NASA Astrophysics Data System (ADS)

    Chen, Jianwen; Yao, Manwen; Yao, Xi

    2016-02-01

    Barrier-type anodized aluminum oxide (AAO) thin films were formed on a polished aluminum substrate via electrochemical anodization in 0.1 mol/L aqueous solution of ammonium pentaborate. Electromechanical breakdown occurred under high electric field conditions as a result of the accumulation of mechanical stress in the film-substrate system by subjecting it to rapid thermal treatment. Before the breakdown event, the electricity of the films was transported in a highly nonlinear way. Immediately after the breakdown event, dramatic cracking of the films occurred, and the cracks expanded quickly to form a mesh-like dendrite network. The breakdown strength was significantly reduced because of the electromechanical coupling effect, and was only 34% of the self-healing breakdown strength of the AAO film.

  16. Advanced Oxide Material Systems For 1650 C Thermal/Environmental Barrier Coating Applications

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    Advanced thermal/environmental barrier coatings (T/EBCs) are being developed for low emission SiC/SiC ceramic matrix composite (CMC) combustor and vane applications to extend the CMC liner and vane temperature capability to 1650 C (3000 F) in oxidizing and water-vapor containing combustion environments. The 1650 C T/EBC system is required to have better thermal stability, lower thermal conductivity, and improved sintering and thermal stress resistance than current coating systems. In this paper, the thermal conductivity, water vapor stability and cyclic durability of selected candidate zirconia-/hafnia-, pyrochlore- and magnetoplumbite-based T/EBC materials are evaluated. The test results have been used to downselect the T/EBC coating materials, and help demonstrate advanced 1650OC coatings feasibility with long-term cyclic durability.

  17. Metallic oxide p-I-n junctions with ferroelectric as the barrier

    NASA Astrophysics Data System (ADS)

    Yuan, J.; Wu, H.; Cao, L. X.; Zhao, L.; Jin, K.; Zhu, B. Y.; Zhu, S. J.; Zhong, J. P.; Miao, J.; Xu, B.; Qi, X. Y.; Qiu, X. G.; Duan, X. F.; Zhao, B. R.

    2007-03-01

    The authors report the formation of the metallic oxide p-I-n junctions with the ferroelectric (Ba ,Sr)TiO3 (BST) as the barrier. The junctions with different thicknesses of BST are investigated. With appropriate thickness, the junctions possess definite parameters, such as the negligible reversed current density (⩽10-7A/cm2), large breakdown voltage (>7V), and ultrahigh rectification (>2×104) in the bias voltage ⩽2.0V and temperature range from 5to300K. It is under consideration that the built-in field V0, the ferroelectric reversed polarized field Vrp, and the resistivity of the BST layer together decide the transport properties of the junctions.

  18. Schottky barrier at graphene/metal oxide interfaces: insight from first-principles calculations

    PubMed Central

    Cheng, Kai; Han, Nannan; Su, Yan; Zhang, Junfeng; Zhao, Jijun

    2017-01-01

    Anode materials play an important role in determining the performance of lithium ion batteries. In experiment, graphene (GR)/metal oxide (MO) composites possess excellent electrochemical properties and are promising anode materials. Here we perform density functional theory calculations to explore the interfacial interaction between GR and MO. Our result reveals generally weak physical interactions between GR and several MOs (including Cu2O, NiO). The Schottky barrier height (SBH) in these metal/semiconductor heterostructures are computed using the macroscopically averaged electrostatic potential method, and the role of interfacial dipole is discussed. The calculated SBHs below 1 eV suggest low contact resistance; thus these GR/MO composites are favorable anode materials for better lithium ion batteries. PMID:28165485

  19. Schottky barrier at graphene/metal oxide interfaces: insight from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Cheng, Kai; Han, Nannan; Su, Yan; Zhang, Junfeng; Zhao, Jijun

    2017-02-01

    Anode materials play an important role in determining the performance of lithium ion batteries. In experiment, graphene (GR)/metal oxide (MO) composites possess excellent electrochemical properties and are promising anode materials. Here we perform density functional theory calculations to explore the interfacial interaction between GR and MO. Our result reveals generally weak physical interactions between GR and several MOs (including Cu2O, NiO). The Schottky barrier height (SBH) in these metal/semiconductor heterostructures are computed using the macroscopically averaged electrostatic potential method, and the role of interfacial dipole is discussed. The calculated SBHs below 1 eV suggest low contact resistance; thus these GR/MO composites are favorable anode materials for better lithium ion batteries.

  20. Spinel oxides: 1 spin-filter barrier for a class of magnetic tunnel junctions

    SciTech Connect

    Zhang, J.; Zhang, Xiaoguang; Han, Prof. X. F.

    2012-01-01

    The orbital composition of the electrode wave functions and the complex bands within the barrier band gap are two important factors in deciding the spin-filter effect. This is illustrated in a class of spinel oxides, including MgAl2O4, ZnAl2O4, SiMg2O4, and SiZn2O4. Through first-principles calculations of the complex bands and electron transmission along the [001] direction, they are shown to have the same D1 spin-filter effect as MgO due to the combination of both factors. Due to better lattice match with typical bcc magnetic electrodes than MgO, these materials provide a broad spectrum of candidate materials for magnetic tunnel junctions.

  1. The oxidative burst reaction in mammalian cells depends on gravity

    PubMed Central

    2013-01-01

    Gravity has been a constant force throughout the Earth’s evolutionary history. Thus, one of the fundamental biological questions is if and how complex cellular and molecular functions of life on Earth require gravity. In this study, we investigated the influence of gravity on the oxidative burst reaction in macrophages, one of the key elements in innate immune response and cellular signaling. An important step is the production of superoxide by the NADPH oxidase, which is rapidly converted to H2O2 by spontaneous and enzymatic dismutation. The phagozytosis-mediated oxidative burst under altered gravity conditions was studied in NR8383 rat alveolar macrophages by means of a luminol assay. Ground-based experiments in “functional weightlessness” were performed using a 2 D clinostat combined with a photomultiplier (PMT clinostat). The same technical set-up was used during the 13th DLR and 51st ESA parabolic flight campaign. Furthermore, hypergravity conditions were provided by using the Multi-Sample Incubation Centrifuge (MuSIC) and the Short Arm Human Centrifuge (SAHC). The results demonstrate that release of reactive oxygen species (ROS) during the oxidative burst reaction depends greatly on gravity conditions. ROS release is 1.) reduced in microgravity, 2.) enhanced in hypergravity and 3.) responds rapidly and reversible to altered gravity within seconds. We substantiated the effect of altered gravity on oxidative burst reaction in two independent experimental systems, parabolic flights and 2D clinostat / centrifuge experiments. Furthermore, the results obtained in simulated microgravity (2D clinorotation experiments) were proven by experiments in real microgravity as in both cases a pronounced reduction in ROS was observed. Our experiments indicate that gravity-sensitive steps are located both in the initial activation pathways and in the final oxidative burst reaction itself, which could be explained by the role of cytoskeletal dynamics in the assembly and

  2. The oxidative burst reaction in mammalian cells depends on gravity.

    PubMed

    Adrian, Astrid; Schoppmann, Kathrin; Sromicki, Juri; Brungs, Sonja; von der Wiesche, Melanie; Hock, Bertold; Kolanus, Waldemar; Hemmersbach, Ruth; Ullrich, Oliver

    2013-12-20

    Gravity has been a constant force throughout the Earth's evolutionary history. Thus, one of the fundamental biological questions is if and how complex cellular and molecular functions of life on Earth require gravity. In this study, we investigated the influence of gravity on the oxidative burst reaction in macrophages, one of the key elements in innate immune response and cellular signaling. An important step is the production of superoxide by the NADPH oxidase, which is rapidly converted to H2O2 by spontaneous and enzymatic dismutation. The phagozytosis-mediated oxidative burst under altered gravity conditions was studied in NR8383 rat alveolar macrophages by means of a luminol assay. Ground-based experiments in "functional weightlessness" were performed using a 2 D clinostat combined with a photomultiplier (PMT clinostat). The same technical set-up was used during the 13th DLR and 51st ESA parabolic flight campaign. Furthermore, hypergravity conditions were provided by using the Multi-Sample Incubation Centrifuge (MuSIC) and the Short Arm Human Centrifuge (SAHC). The results demonstrate that release of reactive oxygen species (ROS) during the oxidative burst reaction depends greatly on gravity conditions. ROS release is 1.) reduced in microgravity, 2.) enhanced in hypergravity and 3.) responds rapidly and reversible to altered gravity within seconds. We substantiated the effect of altered gravity on oxidative burst reaction in two independent experimental systems, parabolic flights and 2D clinostat / centrifuge experiments. Furthermore, the results obtained in simulated microgravity (2D clinorotation experiments) were proven by experiments in real microgravity as in both cases a pronounced reduction in ROS was observed. Our experiments indicate that gravity-sensitive steps are located both in the initial activation pathways and in the final oxidative burst reaction itself, which could be explained by the role of cytoskeletal dynamics in the assembly and function

  3. A study on thermal barrier coatings including thermal expansion mismatch and bond coat oxidation

    NASA Technical Reports Server (NTRS)

    Chang, George C.; Phucharoen, Woraphat; Miller, Robert A.

    1986-01-01

    The present investigation deals with a plasma-sprayed thermal barrier coating (TBC) intended for high temperature applications to advanced gas turbine blades. Typically, this type of coating system consists of a zirconia-yttria ceramic layer with a nickel-chromium-aluminum bond coat on a superalloy substrate. The problem on hand is a complex one due to the fact that bond coat oxidation and thermal mismatch occur in the TBC. Cracking in the TBC has also been experimentally illustrated. A clearer understanding of the mechanical behavior of the TBC is investigated. The stress states in a model thermal barrier coating as it cools down in air is studied. The powerful finite element method was utilized to model a coating cylindrical specimen. Four successively refined finite element models were developed. Some results obtained using the first two models have been reported previously. The major accomplishment is the successful development of an elastic TBC finite element model known as TBCG with interface geometry between the ceramic layer and the bond coat. An equally important milestone is the near-completion of the new elastic-plastic TBC finite element model called TBCGEP which yielded initial results. Representative results are presented.

  4. Scale dependent behavior the foredune: Implications for barrier island response to storms and sea level rise

    NASA Astrophysics Data System (ADS)

    Houser, C.; Wernette, P. A.; Weymer, B. A.

    2015-12-01

    The impact of elevated storm surge on a barrier island tends to be considered from a single cross-shore dimension and dependent only on the relative elevations of the storm surge and dune. However, the foredune line is rarely uniform and can exhibit considerable variation in height and width alongshore at a range of length scales ranging from tens of meters to several kilometers. LiDAR data from Santa Rosa Island in northwest Florida, Padre Island, Texas and Assateague Island, Maryland are used to explore how the dune morphology varies alongshore and how this variability is altered by storms and post-storm recovery. While the alongshore variation in dune height can be approximated by a power law, there are scale-dependent variations in the dune that exhibit different responses to storm erosion and post-storm recovery. This suggests that the alongshore variation in dune morphology reflects the history of storm impact and recovery, and that changes in the variance magnitude through time may provide insight into whether the island will be resilient as it transgresses with rising sea level. The difference in variance magnitude at large spatial scales is associated with the framework geology unique to each island and a dominant control on island response to sea level rise.

  5. Temperature dependence of the current in Schottky-barrier source-gated transistors

    NASA Astrophysics Data System (ADS)

    Sporea, R. A.; Overy, M.; Shannon, J. M.; Silva, S. R. P.

    2015-05-01

    The temperature dependence of the drain current is an important parameter in thin-film transistors. In this paper, we propose that in source-gated transistors (SGTs), this temperature dependence can be controlled and tuned by varying the length of the source electrode. SGTs comprise a reverse biased potential barrier at the source which controls the current. As a result, a large activation energy for the drain current may be present which, although useful in specific temperature sensing applications, is in general deleterious in many circuit functions. With support from numerical simulations with Silvaco Atlas, we describe how increasing the length of the source electrode can be used to reduce the activation energy of SGT drain current, while maintaining the defining characteristics of SGTs: low saturation voltage, high output impedance in saturation, and tolerance to geometry variations. In this study, we apply the dual current injection modes to obtain drain currents with high and low activation energies and propose mechanisms for their exploitation in future large-area integrated circuit designs.

  6. Temperature dependent electrical transport of disordered reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Muchharla, Baleeswaraiah; Narayanan, T. N.; Balakrishnan, Kaushik; Ajayan, Pulickel M.; Talapatra, Saikat

    2014-06-01

    We report on the simple route for the synthesis of chemically reduced graphene oxide (rGO) using ascorbic acid (a green chemical) as a reducing agent. Temperature-dependent electrical transport properties of rGO thin films have been studied in a wide range (50 K T 400 K) of temperature. Electrical conduction in rGO thin films was displayed in two different temperature regimes. At higher temperatures, Arrhenius-like temperature dependence of resistance was observed indicating a band gap dominating transport behavior. At lower temperatures, the rGO sample showed a conduction mechanism consistent with Mott's two-dimensional variable range hopping (2D-VRH). An unsaturated negative magnetoresistance (MR) was observed up to 3 T field. A decrease in negative MR at high temperatures is attributed to the phonon scattering of charge carriers.

  7. Nitric oxide attenuates hydrogen peroxide-induced barrier disruption and protein tyrosine phosphorylation in monolayers of intestinal epithelial cell.

    PubMed

    Katsube, Takanori; Tsuji, Hideo; Onoda, Makoto

    2007-06-01

    The intestinal epithelium provides a barrier to the transport of harmful luminal molecules into the systemic circulation. A dysfunctional epithelial barrier is closely associated with the pathogenesis of a variety of intestinal and systemic disorders. We investigated here the effects of nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) on the barrier function of a human intestinal epithelial cell line, Caco-2. When treated with H(2)O(2), Caco-2 cell monolayers grown on permeable supports exhibited several remarkable features of barrier dysfunction as follows: a decrease in transepithelial electrical resistance, an increase in paracellular permeability to dextran, and a disruption of the intercellular junctional localization of the scaffolding protein ZO-1. In addition, an induction of tyrosine phosphorylation of numerous cellular proteins including ZO-1, E-cadherin, and beta-catenin, components of tight and adherens junctions, was observed. On the other hand, combined treatment of Caco-2 monolayers with H(2)O(2) and an NO donor (NOC5 or NOC12) relieved the damage to the barrier function and suppressed the protein tyrosine phosphorylation induced by H(2)O(2) alone. These results suggest that NO protects the barrier function of intestinal epithelia from oxidative stress by modulating some intracellular signaling pathways of protein tyrosine phosphorylation in epithelial cells.

  8. Size-dependent magnetic properties of branchlike nickel oxide nanocrystals

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Li, Dongsheng; Yang, Deren

    2017-01-01

    Branchlike nickel oxide nanocrystals with narrow size distribution are obtained by a solution growth method. The size-dependent of magnetic properties of the nickel oxides were investigated. The results of magnetic characterization indicate that the NiO nanocrystals with size below 12.8 nm show very weak ferromagnetic state at room temperature due to the uncompensated spins. Both of the average blocking temperature (Tb) and the irreversible temperature (Tirr) increase with the increase of nanoparticle sizes, while both the remnant magnetization and the coercivity at 300 K increase with the decrease of the particle sizes. Moreover, the disappearance of two-magnon (2M) band and redshift of one-phonon longitudinal (1LO) and two-phonon LO in vibrational properties due to size reduction are observed. Compared to the one with the spherical morphological, it is also found that nano-structured nickel oxides with the branchlike morphology have larger remnant magnetization and the coercivity at 5 K due to their larger surface-to-volume ratio and greater degree of broken symmetry at the surface or the higher proportion of broken bonds.

  9. Excitation wavelength dependent fluorescence of graphene oxide controlled by strain.

    PubMed

    Cushing, Scott K; Ding, Weiqiang; Chen, Gang; Wang, Chao; Yang, Feng; Huang, Fuqiang; Wu, Nianqiang

    2017-02-09

    Unlike conventional fluorophores, the fluorescence emission of graphene oxide (GO) sheets can shift hundreds of nanometers as the excitation wavelength increases. The excitation wavelength dependent fluorescence is referred to as a giant red-edge effect and originates in a local reorganization potential slowing down the solvation dynamics of the excited state to the same time scale as the fluorescence lifetime. The present work has discovered that out-of-plane strain in the graphene oxide sheet leads to the intra-layer interaction necessary to slow down the solvation time scale. The oxygen percentage, dopant percentage, disorder, and strain are correlated with the presence and extent of the red-edge effect in oxygen, boron, nitrogen, and fluorine doped graphene oxide. Of these commonly cited possibilities, only out-of-plane strain is directly correlated to the red-edge effect. Furthermore, it is shown that the extent of the red-edge effect, or how far the emission wavelength can shift with increasing excitation wavelength, can be tuned by the electronegativity of the dopant. The present work interprets why the giant red-edge effect is present in some GO sheets but not in other GO sheets.

  10. Use of aluminum oxide as a permeation barrier for producing thin films on aluminum substrates

    SciTech Connect

    Provo, James L.

    2016-07-15

    Aluminum has desirable characteristics of good thermal properties, good electrical characteristics, good optical properties, and the characteristic of being nonmagnetic and having a low atomic weight (26.98 g atoms), but because of its low melting point (660 °C) and ability as a reactive metal to alloy with most common metals in use, it has been ignored as a substrate material for use in processing thin films. The author developed a simple solution to this problem, by putting a permeation barrier of alumina (Al{sub 2}O{sub 3}) onto the surface of pure Al substrates by using a standard chemical oxidation process of the surface (i.e., anodization), before additional film deposition of reactive metals at temperatures up to 500 °C for 1-h, without the formation of alloys or intermetallic compounds to affect the good properties of Al substrates. The chromic acid anodization process used (MIL-A-8625) produced a film barrier of ∼(500–1000) nm of alumina. The fact that refractory Al{sub 2}O{sub 3} can inhibit the reaction of metals with Al at temperatures below 500 °C suggests that Al is a satisfactory substrate if properly oxidized prior to film deposition. To prove this concept, thin film samples of Cr, Mo, Er, Sc, Ti, and Zr were prepared on anodized Al substrates and studied by x-ray diffraction, Rutherford ion back scattering, and Auger/argon sputter surface profile analysis to determine any film substrate interactions. In addition, a major purpose of our study was to determine if ErD{sub 2} thin films could be produced on Al substrates with fully hydrided Er films. Thus, a thin film of ErD{sub 2} on an anodized Al substrate was prepared and studied, with and without the alumina permeation barrier. Films for study were prepared on 1.27 cm diameter Al substrates with ∼500 nm of the metals studied after anodization. Substrates were weighed, cleaned, and vacuum fired at 500 °C prior to use. The Al substrates were deposited using standard electron

  11. Investigation on edge fringing effect and oxide thickness dependence of inversion current in metal-oxide-semiconductor tunneling diodes with comb-shaped electrodes

    SciTech Connect

    Lin, Chien-Chih; Hsu, Pei-Lun; Lin, Li; Hwu, Jenn-Gwo

    2014-03-28

    A particular edge-dependent inversion current behavior of metal-oxide-semiconductor (MOS) tunneling diodes was investigated utilizing square and comb-shaped electrodes. The inversion tunneling current exhibits the strong dependence on the tooth size of comb-shaped electrodes and oxide thickness. Detailed illustrations of current conduction mechanism are developed by simulation and experimental measurement results. It is found that the electron diffusion current and Schottky barrier height lowering for hole tunneling current both contribute on inversion current conduction. In MOS tunneling photodiode applications, the photoresponse can be improved by decreasing SiO{sub 2} thickness and using comb-shaped electrodes with smaller tooth spacing. Meantime, the high and steady photosensitivity can also be approached by introducing HfO{sub 2} into dielectric stacks.

  12. Investigation on edge fringing effect and oxide thickness dependence of inversion current in metal-oxide-semiconductor tunneling diodes with comb-shaped electrodes

    NASA Astrophysics Data System (ADS)

    Lin, Chien-Chih; Hsu, Pei-Lun; Lin, Li; Hwu, Jenn-Gwo

    2014-03-01

    A particular edge-dependent inversion current behavior of metal-oxide-semiconductor (MOS) tunneling diodes was investigated utilizing square and comb-shaped electrodes. The inversion tunneling current exhibits the strong dependence on the tooth size of comb-shaped electrodes and oxide thickness. Detailed illustrations of current conduction mechanism are developed by simulation and experimental measurement results. It is found that the electron diffusion current and Schottky barrier height lowering for hole tunneling current both contribute on inversion current conduction. In MOS tunneling photodiode applications, the photoresponse can be improved by decreasing SiO2 thickness and using comb-shaped electrodes with smaller tooth spacing. Meantime, the high and steady photosensitivity can also be approached by introducing HfO2 into dielectric stacks.

  13. Low-index nanopatterned barrier for hybrid oxide-free III-V silicon conductive bonding.

    PubMed

    Bougot-Robin, Kristelle; Talneau, Anne; Benisty, Henri

    2014-09-22

    Oxide-free bonding of a III-V active stack emitting at 1300-1600 nm to a silicon-on-insulator wafer offers the capability to electrically inject lasers from the silicon side. However, a typical 500-nm-thick silicon layer notably attracts the fundamental guided mode of the silicon + III-V stack, a detrimental feature compared to established III-V Separate-Confinement Heterostructure (SCH) stacks. We experimentally probe with photoluminescence as an internal light source the guiding behavior for oxide-free bonding to a nanopatterned silicon wafer that acts as a low-index barrier. We use a sub-wavelength square array of small holes as an effective "low-index silicon" medium. It is weakly modulated along one dimension (superperiodic array) to outcouple the resulting guided modes to free space, where we use an angle-resolved spectroscopy study. Analysis of experimental branches confirms the capability to operate with a fundamental mode well localized in the III-V heterostructures.

  14. Influence of the microstructure and topography on the barrier properties of oxide scales generated on blasted Ti6Al4V surfaces.

    PubMed

    Barranco, V; Escudero, M L; García-Alonso, M C

    2011-06-01

    The long-term interfacial bond between an implant and bone may be improved by creating a rough surface on the implant in order to increase the surface area available for bone/implant apposition. A natural consequence of surface roughening is an increase in metal ion release, which is itself a surface dominated process. Based on this fact, the aim of this work is to study the influence of the microstructure and topography on the barrier properties of oxide scales thermally generated at 700 °C for 1h on Ti6Al4V surfaces after blasting with Al(2)O(3) particles (coarse) or SiO(2) and ZrO(2) particles (fine). The microstructural and topographical characterization of the thermally treated blasted surfaces has been studied by means of scanning electron microscopy coupled with energy dispersive X-ray analysis, contact profilometry and X-ray diffraction. The barrier properties and corrosion behaviour of the oxide layers have been studied by means of electrochemical impedance spectroscopy (EIS) in Hank's solution. Thermal treatment at 700 °C for 1h promotes the formation of oxide scales with different morphologies and crystalline structures depending on the degree of deformation of the blasted surface. The oxide scale grown on the finely blasted sample has a pine needle-like morphology which is mainly formed of anatase TiO(2). In contrast, the oxide scale grown on the coarsely blasted sample has a globular morphology formed mainly of rutile TiO(2). The differences in morphology, i.e. fine or coarse, of the oxide scales influence the corrosion response of the blasted thermally treated samples in Hank's solution. The EIS results permit evaluation of the different oxide scales from the capacitance and resistance values obtained in the high-frequency region and show a good correlation between the morphology and barrier properties. Oxidation treatment at 700 °C for 1h of Ti6Al4V samples coarsely blasted with Al(2)O(3) improves the corrosion behaviour due to an increase in the

  15. Approximate Dependence of Diffusion Barriers on Nearest-Neighbor Configurations on fcc(100) Metals, and Some Consequences

    NASA Astrophysics Data System (ADS)

    Einstein, T. L.; Jacobsen, J.; Schiff, C.

    1997-03-01

    To simulate epitaxial growth, one needs an a priori understanding of how atomic diffusion barriers depend on the occupation of near-neighbor sites of the initial and final positions. From a histogram of such barriers computed for Cu/Cu(100) using the embedded atom method (EAM), Karimi et al.(M. Karimi, T. Tomkowski, G. Vidali, and O. Biham, Phys. Rev. B 52), 5364 (1995); O. Biham et al., preprint found that these energies fell into four groups. They proposed a simple approximation for the local-configuration dependence of the energy barriers. From a reexamination of these energies, using effective medium theory, we propose an approximation which also depends solely on near-neighbor occupations but accounts better for the energy barriers. The scheme is comparably accurate for Ag/Ag(100), but requires some modification for Ni/Ni(100). We also describe some noteworthy effects of fcc geometry in this approximation, particularly a mechanism which, like the Ehrlich-Schwoebel barrier, enhances roughness with increasing temperature. In the next talk we describe and compare simulations using both approximations.

  16. Carbonylation and disassembly of the F-actin cytoskeleton in oxidant induced barrier dysfunction and its prevention by epidermal growth factor and transforming growth factor α in a human colonic cell line

    PubMed Central

    Banan, A; Zhang, Y; Losurdo, J; Keshavarzian, A

    2000-01-01

    BACKGROUND—Intestinal barrier dysfunction concomitant with high levels of reactive oxygen metabolites (ROM) in the inflamed mucosa have been observed in inflammatory bowel disease (IBD). The cytoskeletal network has been suggested to be involved in the regulation of barrier function. Growth factors (epidermal growth factor (EGF) and transforming growth factor α (TGF-α)) protect gastrointestinal barrier integrity against a variety of noxious agents. However, the underlying mechanisms of oxidant induced disruption and growth factor mediated protection remain elusive.
AIMS—To determine: (1) if oxidation and disassembly of actin (a key cytoskeletal component) plays a major role in ROM induced epithelial monolayer barrier dysfunction; and (2) if growth factor mediated protection involves prevention of theses alterations.
METHODS—Caco-2 monolayers were preincubated with EGF, TGF-α, or vehicle before incubation with ROM (H2O2 or HOCl). Effects on cell integrity, barrier function, and G- and F-actin (oxidation, disassembly, and assembly) were determined.
RESULTS—ROM dose dependently and significantly increased F- and G-actin oxidation (carbonylation), decreased the stable F-actin fraction (index of stability), and increased the monomeric G-actin fraction (index of disassembly). Concomitant with these changes were disruption of the actin cytoskeleton and loss of the monolayer barrier function. In contrast, growth factor pretreatment decreased actin oxidation and enhanced the stable F-actin, while in concert prevented actin disruption and restored normal barrier function of monolayers exposed to ROM. Cytochalasin-D, an inhibitor of actin assembly, not only caused actin disassembly and barrier dysfunction but also abolished the protective action of growth factors. Moreover, an actin stabilising agent, phalloidin, mimicked the protective actions of the growth factors.
CONCLUSIONS—Oxidation, disassembly, and instability of the actin cytoskeleton appears to

  17. Temperature-dependent Schottky barrier in high-performance organic solar cells

    PubMed Central

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-01

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions. PMID:28071700

  18. Temperature-dependent Schottky barrier in high-performance organic solar cells.

    PubMed

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-10

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions.

  19. Temperature-dependent Schottky barrier in high-performance organic solar cells

    NASA Astrophysics Data System (ADS)

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-01

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions.

  20. Educational-Cognitive Barriers in the Preparation of Future Social Pedagogues for the Prevention of Social Dependencies

    ERIC Educational Resources Information Center

    Neskoromnykh, Nataliya I.; Chernenko, Nataliya V.; Mamadaliev, Anvar M.; Vorozhbitova, Aleksandra A.

    2017-01-01

    This paper brings to light the essence, characteristics, and role of educational-cognitive barriers in the preparation of college-attending future social pedagogues that may arise in the process of their mastering social-pedagogical skills related to the prevention of social dependencies. The authors share the findings of their study of a typology…

  1. Barriers to employability among substance dependent and nonsubstance-affected women on federal welfare: implications for program design.

    PubMed

    Morgenstern, Jon; McCrady, Barbara S; Blanchard, Kimberly A; McVeigh, Katharine H; Riordan, Annette; Irwin, Thomas W

    2003-03-01

    This study examined barriers to employability among women meeting criteria for a substance dependence disorder who were identified by routine screening conducted in welfare offices. The characteristics of these women were compared to other women on welfare who did not have a substance use disorder. A sample of 214 substance dependent women on federal welfare were recruited to participate in a substance use disorders welfare demonstration project. An additional 69 nonsubstance-affected women on welfare served as a comparison sample. All participants were assessed in welfare settings through a standardized battery of measures. Substance dependent women reported moderate to severe substance use problems. They also reported significantly higher rates than the women with no substance use disorder of other barriers such as domestic violence, mental health problems, legal problems, child welfare investigations and fewer job skills. Findings raise questions about the likely effectiveness of existing welfare reform services in addressing the needs of substance dependent women.

  2. Time-dependent behavior and thermal fracture in functionally graded thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Rangaraj, Sudarshan V.

    The objective of this research was to characterize the thermo-mechanical response and fracture behavior of zirconia-bond coat (BC) alloy functionally graded thermal barrier coatings (TBCs) under high heat flux thermal loads. Under the resulting high surface temperatures and gradients, the coatings develop surface cracks as well as TBC-BC interface cracks. Time-dependent (viscoplastic) deformations in the TBC layers were the major cause for surface and interface fracture. Micromechanics models were developed to estimate the effective thermo-elastic properties and time-dependent response of YSZ-BC alloy particulate composites that constitute the layers of a graded TBC. These effective properties were then utilized in numerical fracture mechanics analyses to study the influence of coating architecture on its fracture response. The driving force for surface crack initiation and for the formation of multiple surface cracks was found to increase with compositional gradation. It was also found that replacing a single-layer (non-graded) TBC by a functionally graded TBC of comparable thermal resistance resulted in a reduced driving force for interface crack growth. The formation of multiple surface cracks and its higher flexural stiffness were found to impart a graded TBC with a higher resistance to interface fracture. Methodologies were developed to estimate the fracture resistance and toughness of graded TBCs. It was found that both the single-layer zirconia TBC as well as functionally graded TBCs showed an increase in fracture resistance with crack advance. The addition of BC alloy was found to enhance the fracture toughness of the layers in a graded TBC. However, the magnitude of toughness enhancement seen was not very significant. Laser thermal shock experiments were conducted on plasma sprayed single-layer zirconia-BC alloy composite coatings. Coatings with three different compositions, of similar thermal resistance were considered. It was found that coatings with a

  3. Chromium oxide as a metal diffusion barrier layer: An x-ray absorption fine structure spectroscopy study

    NASA Astrophysics Data System (ADS)

    Ahamad Mohiddon, Md.; Lakshun Naidu, K.; Ghanashyam Krishna, M.; Dalba, G.; Ahmed, S. I.; Rocca, F.

    2014-01-01

    The interaction at the interface between chromium and amorphous Silicon (a-Si) films in the presence of a sandwich layer of chromium oxide is investigated using X-ray absorption fine structure (XAFS) spectroscopy. The oxidized interface was created, in situ, prior to the deposition of a 400 nm tick a-Si layer over a 50 nm tick Cr layer. The entire stack of substrate/metallic Cr/Cr2O3/a-Si was then annealed at temperatures from 300 up to 700 °C. Analysis of the near edge and extended regions of each XAFS spectrum shows that only a small fraction of Cr is able to diffuse through the oxide layer up to 500 °C, while the remaining fraction is buried under the oxide layer in the form of metallic Cr. At higher temperatures, diffusion through the oxide layer is enhanced and the diffused metallic Cr reacts with a-Si to form CrSi2. At 700 °C, the film contains Cr2O3 and CrSi2 without evidence of unreacted metallic Cr. The activation energy and diffusion coefficient of Cr are quantitatively determined in the two temperature regions, one where the oxide acts as diffusion barrier and another where it is transparent to Cr diffusion. It is thus demonstrated that chromium oxide can be used as a diffusion barrier to prevent metal diffusion into a-Si.

  4. Correlation between nicotine dependence and barriers to cessation between exclusive cigarette smokers and dual (water pipe) smokers among Arab Americans.

    PubMed

    El-Shahawy, Omar; Haddad, Linda

    2015-01-01

    Evidence suggests that dual cigarette and water pipe use is growing among minority groups, particularly among Arab Americans. Differences in nicotine dependence and barriers to smoking cessation among such dual smokers have not been previously examined in this population. We examined potential differences that might exist between exclusive cigarette smokers and dual smokers (cigarette and water pipe) pertaining to nicotine dependence and barriers to cessation among Arab Americans. We conducted a cross-sectional study using a convenience sample of self-identified Arab immigrant smokers (n=131) living in the Richmond, VA metropolitan area. Data were collected using four questionnaires: Demographic and Cultural Information questionnaire, Tobacco Use questionnaire, Fagerström Test for Nicotine Dependence (FTND) questionnaire, and Barriers to Cessation questionnaire. We examined differences in nicotine dependence and barriers to cessation between exclusive cigarette smokers and dual smokers of cigarettes and water pipe. Furthermore, we explored the correlations of these measures with select variables. There was a significant difference in the FTND scores between the exclusive cigarette smokers (mean M=2.55, standard deviation [SD] =2.10) and dual smokers (M=3.71, SD =2.42); t(129) = (2.51), P=0.0066. There was also a significant difference in the Barriers to Cessation scores between exclusive cigarette smokers (M=38.47, SD =13.07) and dual smokers (M=45.21, SD =9.27); t(129) = (2.56), P=0.0058. Furthermore, there was a highly significant correlation among FTND scores, Barriers to Cessation scores, and past quit attempts among dual smokers. Water pipe tobacco smoking seems to be both adding to the dependence potential of cigarette smoking and enhancing barriers to cessation in our study sample. However, the high correlation between quit attempts, FTND, and barriers to cessation needs further investigation to ascertain the possible reasons behind it. This preliminary

  5. Reduced temperature and bias-voltage dependence of the magnetoresistance in magnetic tunnel junctions with Hf-inserted Al2O3 barrier

    NASA Astrophysics Data System (ADS)

    Park, Byong Guk; Lee, Taek Dong

    2002-09-01

    A modified tunnel barrier structure for the magnetic tunnel junction (MTJ) was fabricated by inserting a Hf layer in the middle of the Al2O3 tunnel barrier. MTJs with the Hf-inserted barrier show a higher tunnel mangnetoresistance (TMR) ratio and weaker temperature and bias-voltage dependence of TMR compared to the MTJs with a conventional Al2O3 barrier. The enhancement of the TMR ratio and the reduction of the temperature and bias-voltage dependence were attributed to the reduction of defects in the barrier.

  6. Size-dependent antimicrobial response of zinc oxide nanoparticles.

    PubMed

    Palanikumar, Loganathan; Ramasamy, Sinna Nadar; Balachandran, Chandrasekaran

    2014-06-01

    Antibacterial and antifungal activities of zinc oxide nanoparticles (ZnO NPs) were investigated against infectious microorganisms. ZnO NPs were prepared by wet chemical precipitation method varying the pH values. Particle size and morphology of the as-prepared ZnO powders were characterised by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscope. The zone of inhibition by NPs ranged from 0 to 17 mm. The lowest minimum inhibitory concentration value of NPs is 25 µg.ml(-1) against Staphylococcus epidermidis. These studies demonstrate that ZnO NPs have wide range of antimicrobial activities towards various microorganisms. The results obtained in the authors' study indicate that the inhibitory efficacy of ZnO NPs is significantly dependent on its chosen concentration and size. Significant inhibition in antibacterial response was observed for S. epidermidis when compared with control antibiotic.

  7. Concentration-dependent toxicity of iron oxide nanoparticles mediated by increased oxidative stress

    PubMed Central

    Naqvi, Saba; Samim, Mohammad; Abdin, MZ; Ahmed, Farhan Jalees; Maitra, AN; Prashant, CK; Dinda, Amit K

    2010-01-01

    Iron oxide nanoparticles with unique magnetic properties have a high potential for use in several biomedical, bioengineering and in vivo applications, including tissue repair, magnetic resonance imaging, immunoassay, drug delivery, detoxification of biologic fluids, cell sorting, and hyperthermia. Although various surface modifications are being done for making these nonbiodegradable nanoparticles more biocompatible, their toxic potential is still a major concern. The current in vitro study of the interaction of superparamagnetic iron oxide nanoparticles of mean diameter 30 nm coated with Tween 80 and murine macrophage (J774) cells was undertaken to evaluate the dose- and time-dependent toxic potential, as well as investigate the role of oxidative stress in the toxicity. A 15–30 nm size range of spherical nanoparticles were characterized by transmission electron microscopy and zeta sizer. MTT assay showed >95% viability of cells in lower concentrations (25–200 μg/mL) and up to three hours of exposure, whereas at higher concentrations (300–500 μg/mL) and prolonged (six hours) exposure viability reduced to 55%–65%. Necrosis-apoptosis assay by propidium iodide and Hoechst-33342 staining revealed loss of the majority of the cells by apoptosis. H2DCFDDA assay to quantify generation of intracellular reactive oxygen species (ROS) indicated that exposure to a higher concentration of nanoparticles resulted in enhanced ROS generation, leading to cell injury and death. The cell membrane injury induced by nanoparticles studied using the lactate dehydrogenase assay, showed both concentration- and time-dependent damage. Thus, this study concluded that use of a low optimum concentration of superparamagnetic iron oxide nanoparticles is important for avoidance of oxidative stress-induced cell injury and death. PMID:21187917

  8. Hydroxyalkenals and oxidized phospholipids modulation of endothelial cytoskeleton, focal adhesion and adherens junction proteins in regulating endothelial barrier function.

    PubMed

    Usatyuk, Peter V; Natarajan, Viswanathan

    2012-01-01

    Lipid peroxidation of polyunsaturated fatty acids generates bioactive aldehydes, which exhibit pro- and anti-inflammatory effects in cells and tissues. Accumulating evidence indicates that 4-hydroxynonenal (4-HNE), a major aldehyde derived from lipid peroxidation of n-6 polyunsaturated fatty acids trigger signals that modulates focal adhesion and adherens junction proteins thereby inducing endothelial barrier dysfunction. Similarly, oxidized phospholipids (Ox-PLs) generated by lipid peroxidation of phospholipids with polyunsaturated fatty acids have been implicated in atherogenesis, inflammation and gene expression. Interestingly, physiological concentration of Ox-PLs is anti-inflammatory and protect against endotoxin- and ventilator-associated acute lung injury. Thus, excess generation of bioactive hydroxyalkenals and Ox-PLs during oxidative stress contributes to pathophysiology of various diseases by modulating signaling pathways that regulate pro- and anti-inflammatory responses and barrier regulation. This review summarizes the role of 4-HNE and Ox-PLs affecting cell signaling pathways and endothelial barrier dysfunction through modulation of the activities of proteins/enzymes by Michael adducts formation, enhancing the level of protein tyrosine phosphorylation of the target proteins, and by reorganization of cytoskeletal, focal adhesion, and adherens junction proteins. A better understanding of molecular mechanisms of hydroxyalkenals- and Ox-PLs-mediated pro-and anti-inflammatory responses and barrier function may lead to development of novel therapies to ameliorate oxidative stress related cardio-pulmonary disorders. Copyright © 2011 Elsevier Inc. All rights reserved.

  9. Anaerobic, Nitrate-Dependent Oxidation of U(IV) Oxide Minerals by the Chemolithoautotrophic Bacterium Thiobacillus denitrificans

    PubMed Central

    Beller, Harry R.

    2005-01-01

    Under anaerobic conditions and at circumneutral pH, cells of the widely distributed, obligate chemolithoautotrophic bacterium Thiobacillus denitrificans oxidatively dissolved synthetic and biogenic U(IV) oxides (uraninite) in nitrate-dependent fashion: U(IV) oxidation required the presence of nitrate and was strongly correlated with nitrate consumption. This is the first report of anaerobic U(IV) oxidation by an autotrophic bacterium. PMID:15812053

  10. Anaerobic, Nitrate-Dependent Oxidation of U(IV) Oxide Minerals by the Chemolithoautotrophic Bacterium Thiobacillus denitrificans

    SciTech Connect

    Beller, H R

    2004-06-25

    Under anaerobic conditions and at circumneutral pH, cells of the widely-distributed, obligate chemolithoautotrophic bacterium Thiobacillus denitrificans oxidatively dissolved synthetic and biogenic U(IV) oxides (uraninite) in nitrate-dependent fashion: U(IV) oxidation required the presence of nitrate and was strongly correlated to nitrate consumption. This is the first report of anaerobic U(IV) oxidation by an autotrophic bacterium.

  11. Exhaled nitric oxide is age-dependent in asthma.

    PubMed

    Avital, Avraham; Uwyyed, Kamal; Berkman, Neville; Bar-Yishay, Ephraim; Godfrey, Simon; Springer, Chaim

    2003-11-01

    We determined whether the exhaled nitric oxide (eNO) level in asthmatics is age-dependent. Eighty-seven asthmatic patients aged 2-41 years were studied. Hyperreactivity to adenosine 5'-monophosphate (AMP) was used to confirm asthma (dependent, with lower values in young children.

  12. Surface oxidation of polycrystalline cadmium telluride thin films for Schottky barrier junction solar cells

    NASA Astrophysics Data System (ADS)

    Yi, X.; Liou, J. J.

    1995-06-01

    Polycrystalline CdTe thin films grown on graphite or tungsten-coated graphite substrates by chemical vapor deposition (CVD) were exposed to the air at room temperature in a natural atmosphere of about 60% air humidity for 6 months. X-ray photoemission spectroscopy (XPS) and Auger electron spectroscopy (AES) of the films indicate that a tellurium dioxide (TeO 2) overlayer has formed from this process. The effects of such an overlayer on the electrical property of polycrystalline CdTe-based Schottky barrier junction solar cells have also been discussed for the first time. It is shown that a solar cell formed on a CdTe film with TeO 2 overlayer has considerably higher open-circuit voltage and fill factor than that formed on a CdTe film without TeO 2 overlayer. Our study further indicates that using a polycrystalline CdTe film which is thermally oxidized at above room temperature (100-400°C) does not provide any improvement on the solar cell efficiency.

  13. Protective effects of isothiocyanates on blood-CSF barrier disruption induced by oxidative stress

    PubMed Central

    Alesi, Gina N.; Zhou, Ningna; Keep, Richard F

    2012-01-01

    The choroid plexuses (CPs) form the blood-cerebrospinal fluid (CSF) barrier (BCSFB) and play an important role in maintaining brain normal function and the brain response to injury. Many neurological disorders are associated with oxidative stress that can impact CP function. This study examined the effects of isothiocyanates, an abundant component in cruciferous vegetables, on H2O2-induced BCSFB disruption and CP cell death in vitro. It further examined the potential role of a transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2), in isothiocyanate-induced protection. Sulforaphane (SF) significantly reduced H2O2-induced BCSFB disruption as assessed by transepithelial electrical resistance (29 ± 7% reduction vs. 92 ± 2% decrease in controls) and [3H]mannitol permeability. Allyl-isothiocyanate (AITC) had a similar protective effect. H2O2-induced epithelial cell death was also reduced by these isothiocyanates. In primary CP cells, SF and AITC reduced cell death by 42 ± 3% and 53 ± 10%, respectively. Similar protection was found in a CP cell line Z310. Protection was only found with pretreatment for 12–48 h and not with acute exposure (1 h). The protective effects of SF and AITC were associated with Nrf2 nuclear translocation and upregulated expression of antioxidative systems regulated by Nrf2, including heme oxygenase-1, NAD(P)H quinine oxidoreductase, and cysteine/glutamate exchange transporter. Thus isothiocyanates, as diet or medicine, may be a method for protecting BCSFB in neurological disorders. PMID:22573102

  14. Sputter Deposition of Yttrium-Barium Superconductor and Strontium Titanium Oxide Barrier Layer Thin Films

    NASA Astrophysics Data System (ADS)

    Truman, James Kelly

    1992-01-01

    The commercial application of superconducting rm YBa_2Cu_3O_{7 -x} thin films requires the development of deposition methods which can be used to reproducibly deposit films with good superconducting properties on insulating and semiconducting substrates. Sputter deposition is the most popular method to fabricate Y-Ba-Cu-O superconductor thin films, but when used in the standard configuration suffers from a deviation between the compositions of the Y-Ba-Cu-O sputter target and deposited films, which is thought to be primarily due to resputtering of the film by negative ions sputtered from the target. In this study, the negative ions were explicitly identified and were found to consist predominantly O^-. The sputter yield of O^- was found to depend on the Ba compound used in the fabrication of Y -Ba-Cu-O targets and was related to the electronegativity difference between the components. An unreacted mixture of rm Y_2O_3, CuO, and BaF_2 was found to have the lowest O^- yield among targets with Y:Ba:Cu = 1:2:3. The high yield of O^- from rm YBa_2Cu_3O _{7-x} was found to depend on the target temperature and be due to the excess oxygen present. The SIMS negative ion data supported the composition data for sputter-deposited Y-Ba-Cu-O films. Targets using BaF _2 were found to improve the Ba deficiency, the run-to-run irreproducibility and the nonuniformity of the film composition typically found in sputtered Y -Ba-Cu-O films. Superconducting Y-Ba-Cu-O films were formed on SrTiO_3 substrates by post-deposition heat treatment of Y-Ba-Cu-O-F films in humid oxygen. The growth of superconducting rm YBa_2Cu_3O_{7-x}, thin films on common substrates such as sapphire or silicon requires the use of a barrier layer to prevent the deleterious interaction which occurs between Y-Ba-Cu-O films and these substrates. Barrier layers of SrTiO_3 were studied and found to exhibit textured growth with a preferred (111) orientation on (100) Si substrates. However, SrTiO_3 was found to be

  15. Barriers to community-based drug dependence treatment: implications for police roles, collaborations and performance indicators

    PubMed Central

    Ma, Yi; Du, Chunhua; Cai, Thomas; Han, Qingfeng; Yuan, Huanhuan; Luo, Tingyan; Ren, Guoliang; Mburu, Gitau; Wang, Bangyuan; Golichenko, Olga; Zhang, Chaoxiong

    2016-01-01

    Introduction Worldwide, people who use drugs (PWUD) are among the populations at highest risk for HIV infection. In China, PWUD are primarily sentenced to compulsory detainment centres, in which access to healthcare, including HIV treatment and prevention services, is limited or non-existent. In 2008, China's 2008 Anti-Drug Law encouraged the development and use of community-based drug dependence rehabilitation, yet there is limited evidence evaluating the efficacy and challenges of this model in China. In this study, we explore these challenges and describe how cooperation between law enforcement and health departments can meet the needs of PWUD. Methods In 2015, we conducted semi-structured, in-depth interviews with all four staff members and 16 clients of the Ping An Centre No. 1 for community-based drug treatment, three local police officers and three officials from the local Centre for Disease Control. Interviews explored obstacles in implementing community-based drug dependence treatment and efforts to resolve these difficulties. Transcripts were coded and analyzed with qualitative data analysis software (MAXQDA 11). Results We identified three challenges to community-based drug treatment at the Ping An Centre No. 1: (1) suboptimal coordination among parties involved, (2) a divergence in attitudes towards PWUD and harm reduction between law enforcement and health officials and (3) conflicting performance targets for police and health officials that undermine the shared goal of treatment. We also identified the take-home methadone maintenance treatment model at the Ping An Centre No. 1 as an example of an early successful collaboration between the police, the health department and PWUD. Conclusions To overcome barriers to effective community-based drug treatment, we recommend aligning the goals of law enforcement and public health agencies towards health-based performance indicators. Furthermore, tensions between PWUD and police need to be addressed and trust

  16. Type-dependent oxidative damage in frontotemporal lobar degeneration: cortical astrocytes are targets of oxidative damage.

    PubMed

    Martínez, Anna; Carmona, Margarita; Portero-Otin, Manuel; Naudí, Alba; Pamplona, Reinald; Ferrer, Isidre

    2008-12-01

    Oxidative injury and stress responses are common features of many neurodegenerative diseases. To assess oxidative stress responses in frontotemporal lobar degeneration (FTLD), we identified increased 4-hydroxynonenal (HNE) adducts using gel electrophoresis and Western blotting in frontal cortex samples in 6 of 6 cases of FTLD with the P301L mutation in the tau gene (FTLD-tau), in 3 of 10 cases with tau-negative ubiquitin-immunoreactive inclusions, and in 2 of 3 cases associated with motor neuron disease. Selectively increased lipoxidation-derived protein damage associated with altered membrane unsaturation and fatty acid profiles was verified by mass spectrometry in FTLD-tau and FTLD associated with motor neuron disease. All FTLD-tau and most cases with increased HNE-positive bands had marked astrocytosis as determined by glial fibrillary acidic protein (GFAP) immunohistochemistry and increased GFAP expression on Western blotting; 2 FTLD cases with tau-negative ubiquitin-immunoreactive inclusions and with increased GFAP expression did not have increased HNE adducts. Bidimensional gel electrophoresis, Western blotting, in-gel digestion, and mass spectrometry identified GFAP as a major target of lipoxidation in all positive cases; confocal microscopy revealed colocalization of HNE and GFAP in cortical astrocytes, superoxide dismutase 1 in astrocytes, and superoxide dismutase 2 in astrocytes and neurons in all FTLD types. Thus, in FTLD, there is variable disease-dependent oxidative damage that is prominent in FTLD-tau, astrocytes are targets of oxidative damage, and GFAP is a target of lipoxidation. Astrocytes are, therefore, crucial elements of oxidative stress responses in FTLD.

  17. Size-dependent selectivity and activity of silver nanoclusters in the partial oxidation of propylene to propylene oxide and acrolein : A joint experimental and theoretical study.

    SciTech Connect

    Molina, L M.; Lee, S.; Sell, K.; Barcaro, G.; Fortunelli, A.; Lee, B.; Seifert, S.; Winans, R. E.; Elam, J. W.; Pellin, M. J.; Barke, I.; von Oeynhausen, V.; Lei, Y.; Meyer, R. J.; Alonso, J. A.; Fraile-Rodriguez, A.; Kleibert, A.; Giorgio, S.; Henry, C. R.; Heinz Meiwes-Broer, K.; Vadja, S.; Univ. de Valladolid; Univ. Rostock; IPCF-CNR; Univ. of Illinois at Chicago; Swiss Light Source; CINaM-CNRS and Aix-Marseille Univ.; Yale Univ.

    2011-02-02

    Model silver nanocatalysts between 9 and 23 nm in size were prepared by size-selected cluster deposition from a free cluster beam on amorphous alumina films and their size-dependent catalytic performance studied in the partial oxidation of propylene under realistic reaction conditions. Smaller clusters preferentially produced acrolein, while the 23 nm particles were considerably more selective towards the formation of propylene oxide, at reaction rates far exceeding those previously reported for larger silver particles. The activity of clusters dropped significantly with increasing particle size. First-principle calculations, of the activation energies for oxygen adsorption and its dissociation, at variable surface coverage yielded surface energies which resulted in particle shapes resembling the experimentally observed shapes of partially oxidized silver clusters. The calculated activation barriers for propylene oxide and acrolein formation on various facets and on the edges of the nanoparticles provided detailed information about the energetics of the competing reaction pathways. The size- and corresponding morphology dependent theoretical activity and selectivity are in good accord with experimental observations.

  18. Temperature dependence of graphene oxide reduced by hydrazine hydrate

    NASA Astrophysics Data System (ADS)

    Ren, Peng-Gang; Yan, Ding-Xiang; Ji, Xu; Chen, Tao; Li, Zhong-Ming

    2011-02-01

    Graphene oxide (GO) was successfully prepared by a modified Hummer's method. The reduction effect and mechanism of the as-prepared GO reduced with hydrazine hydrate at different temperatures and time were characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), x-ray diffractions (XRD), Raman spectroscopy and thermo-gravimetric analysis (TGA). The results showed that the reduction effect of GO mainly depended on treatment temperature instead of treatment time. Desirable reduction of GO can only be obtained at high treatment temperature. Reduced at 95 °C for 3 h, the C/O atomic ratio of GO increased from 3.1 to 15.1, which was impossible to obtain at low temperatures, such as 80, 60 or 15 °C, even for longer reduction time. XPS, 13C NMR and FTIR results show that most of the epoxide groups bonded to graphite during the oxidation were removed from GO and form the sp2 structure after being reduced by hydrazine hydrate at high temperature (>60 °C), leading to the electric conductivity of GO increasing from 1.5 × 10 - 6 to 5 S cm - 1, while the hydroxyls on the surface of GO were not removed by hydrazine hydrate even at high temperature. Additionally, the FTIR, XRD and Raman spectrum indicate that the GO reduced by hydrazine hydrate can not be entirely restored to the pristine graphite structures. XPS and FTIR data also suggest that carbonyl and carboxyl groups can be reduced by hydrazine hydrate and possibly form hydrazone, but not a C = C structure.

  19. Temperature dependence of graphene oxide reduced by hydrazine hydrate.

    PubMed

    Ren, Peng-Gang; Yan, Ding-Xiang; Ji, Xu; Chen, Tao; Li, Zhong-Ming

    2011-02-04

    Graphene oxide (GO) was successfully prepared by a modified Hummer's method. The reduction effect and mechanism of the as-prepared GO reduced with hydrazine hydrate at different temperatures and time were characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), x-ray diffractions (XRD), Raman spectroscopy and thermo-gravimetric analysis (TGA). The results showed that the reduction effect of GO mainly depended on treatment temperature instead of treatment time. Desirable reduction of GO can only be obtained at high treatment temperature. Reduced at 95 °C for 3 h, the C/O atomic ratio of GO increased from 3.1 to 15.1, which was impossible to obtain at low temperatures, such as 80, 60 or 15 °C, even for longer reduction time. XPS, 13C NMR and FTIR results show that most of the epoxide groups bonded to graphite during the oxidation were removed from GO and form the sp(2) structure after being reduced by hydrazine hydrate at high temperature (>60 °C), leading to the electric conductivity of GO increasing from 1.5 × 10(-6) to 5 S cm(-1), while the hydroxyls on the surface of GO were not removed by hydrazine hydrate even at high temperature. Additionally, the FTIR, XRD and Raman spectrum indicate that the GO reduced by hydrazine hydrate can not be entirely restored to the pristine graphite structures. XPS and FTIR data also suggest that carbonyl and carboxyl groups can be reduced by hydrazine hydrate and possibly form hydrazone, but not a C = C structure.

  20. Chemical dynamics between wells across a time-dependent barrier: Self-similarity in the Lagrangian descriptor and reactive basins

    NASA Astrophysics Data System (ADS)

    Junginger, Andrej; Duvenbeck, Lennart; Feldmaier, Matthias; Main, Jörg; Wunner, Günter; Hernandez, Rigoberto

    2017-08-01

    In chemical or physical reaction dynamics, it is essential to distinguish precisely between reactants and products for all times. This task is especially demanding in time-dependent or driven systems because therein the dividing surface (DS) between these states often exhibits a nontrivial time-dependence. The so-called transition state (TS) trajectory has been seen to define a DS which is free of recrossings in a large number of one-dimensional reactions across time-dependent barriers and thus, allows one to determine exact reaction rates. A fundamental challenge to applying this method is the construction of the TS trajectory itself. The minimization of Lagrangian descriptors (LDs) provides a general and powerful scheme to obtain that trajectory even when perturbation theory fails. Both approaches encounter possible breakdowns when the overall potential is bounded, admitting the possibility of returns to the barrier long after the trajectories have reached the product or reactant wells. Such global dynamics cannot be captured by perturbation theory. Meanwhile, in the LD-DS approach, it leads to the emergence of additional local minima which make it difficult to extract the optimal branch associated with the desired TS trajectory. In this work, we illustrate this behavior for a time-dependent double-well potential revealing a self-similar structure of the LD, and we demonstrate how the reflections and side-minima can be addressed by an appropriate modification of the LD associated with the direct rate across the barrier.

  1. Suppression of spin transport in ferromagnet/oxide/semiconductor junctions by magnetic impurities in the tunnel barrier

    NASA Astrophysics Data System (ADS)

    Spiesser, Aurélie; Saito, Hidekazu; Yuasa, Shinji; Jansen, Ron

    2016-10-01

    We have studied how the insertion of sub-monolayer amounts of Mn impurities in the middle of the oxide tunnel barrier of Fe/GeO2 on p-type Ge affects the spin transport, using three-terminal Hanle measurements. Strikingly, the magnitude of the Hanle spin voltage is strongly reduced by increasing the amount of Mn dopants and is even completely absent for devices having an amount of Mn impurities equivalent to a 0.2-nm-thick layer. This demonstrates that magnetic impurities in the tunnel barrier are detrimental to the spin transport in ferromagnet/oxide/semiconductor junctions, and that the localized states associated with such magnetic impurities do not produce three-terminal Hanle spin signals.

  2. Tyrosine-dependent oxidative DNA damage induced by carcinogenic tetranitromethane.

    PubMed

    Murata, Mariko; Kurimoto, Saori; Kawanishi, Shosuke

    2006-10-01

    Tetranitromethane (TNM) is used as an oxidizer in rocket propellants and explosives and as an additive to increase the cetane number of diesel fuel. TNM was reported to induce pulmonary adenocarcinomas and squamous cell carcinomas in mice and rats. However, the mechanisms underlying carcinogenesis induced by TNM has not yet been clarified. We previously revealed that nitroTyr and nitroTyr-containing peptides caused Cu(II)-dependent DNA damage in the presence of P450 reductase, which is considered to yield nitroreduction. Since TNM is a reagent for nitration of Tyr in proteins and peptides, we have hypothesized that TNM-treated Tyr and Tyr-containing peptides induce DNA damage by the modification of Tyr. We examined DNA damage induced by TNM-treated amino acids or peptides using (32)P-5'-end-labeled DNA fragments obtained from the human p53 tumor suppressor gene and the c-Ha-ras-1 protooncogene. TNM-treated Tyr and Lys-Tyr-Lys induced DNA damage including the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine in the presence of Cu(II) and NADH. DNA damage was inhibited by catalase and bathocuproine, indicating the involvement of H(2)O(2) and Cu(I). The cytosine residue of the ACG sequence complementary to codon 273, well-known hotspots of the p53 gene, was cleaved with piperidine and Fpg treatments. On the other hand, nitroTyr and Lys-nitroTyr-Lys did not induce DNA damage in the presence of Cu(II) and NADH. Time-of-flight mass spectrometry confirmed that reactions between Lys-Tyr-Lys and TNM yielded not only Lys-nitroTyr-Lys but also Lys-nitrosoTyr-Lys. Therefore, it is speculated that the nitrosotyrosine residue can induce oxidative DNA damage in the presence of Cu(II) and NADH. It is concluded that Tyr-dependent DNA damage may play an important role in the carcinogenicity of TNM. TNM is a new type of carcinogen that induces DNA damage not by itself but via Tyr modification.

  3. The Development of HfO2-Rare Earth Based Oxide Materials and Barrier Coatings for Thermal Protection Systems

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Harder, Bryan James

    2014-01-01

    Advanced hafnia-rare earth oxides, rare earth aluminates and silicates have been developed for thermal environmental barrier systems for aerospace propulsion engine and thermal protection applications. The high temperature stability, low thermal conductivity, excellent oxidation resistance and mechanical properties of these oxide material systems make them attractive and potentially viable for thermal protection systems. This paper will focus on the development of the high performance and high temperature capable ZrO2HfO2-rare earth based alloy and compound oxide materials, processed as protective coating systems using state-or-the-art processing techniques. The emphasis has been in particular placed on assessing their temperature capability, stability and suitability for advanced space vehicle entry thermal protection systems. Fundamental thermophysical and thermomechanical properties of the material systems have been investigated at high temperatures. Laser high-heat-flux testing has also been developed to validate the material systems, and demonstrating durability under space entry high heat flux conditions.

  4. Orientation dependent behavior of the Coulomb barrier parameters for deformed-deformed nuclei

    NASA Astrophysics Data System (ADS)

    Ismail, M.; Adel, A.

    2011-06-01

    The Coulomb barrier parameters (radius, R, and height, V) for the interaction between two deformed nuclei are calculated in phenomenological way in the framework of the double folding model with the realistic M3Y nucleon-nucleon ( NN) interaction. The variations of R and V for the reactions Ar48+Pu238, Mg26+Cm248, Mg26+U238, and Ne22+U238 in the orientation degrees of freedom are investigated. It is found that the distribution of the Coulomb barrier parameters in the orientation degrees of freedom shows almost the same patterns as the sum of the nuclear radii of the interacting nuclei along the direction of the separation vector joining their two centers of mass. The orientation Coulomb barrier radius distribution follows the same variations as the sum of radii while the barrier height distribution follows it inversely. This correlation (anticorrelation) between R ( V) and the nuclear radii of the deformed nuclei dose not give the values of R and V. This suggests a simple and straightforward way to predict the behavior of the barrier parameters with different orders of deformations without performing the heavy numerical calculations necessary when the two nuclei are being deformed. It also allows us to estimate, with reasonable accuracy, the compact and elongated configurations of the interacting nuclei which lead to hot and cold fusion reactions, respectively.

  5. Simultaneous Nitrite-Dependent Anaerobic Methane and Ammonium Oxidation Processes▿

    PubMed Central

    Luesken, Francisca A.; Sánchez, Jaime; van Alen, Theo A.; Sanabria, Janeth; Op den Camp, Huub J. M.; Jetten, Mike S. M.; Kartal, Boran

    2011-01-01

    Nitrite-dependent anaerobic oxidation of methane (n-damo) and ammonium (anammox) are two recently discovered processes in the nitrogen cycle that are catalyzed by n-damo bacteria, including “Candidatus Methylomirabilis oxyfera,” and anammox bacteria, respectively. The feasibility of coculturing anammox and n-damo bacteria is important for implementation in wastewater treatment systems that contain substantial amounts of both methane and ammonium. Here we tested this possible coexistence experimentally. To obtain such a coculture, ammonium was fed to a stable enrichment culture of n-damo bacteria that still contained some residual anammox bacteria. The ammonium supplied to the reactor was consumed rapidly and could be gradually increased from 1 to 20 mM/day. The enriched coculture was monitored by fluorescence in situ hybridization and 16S rRNA and pmoA gene clone libraries and activity measurements. After 161 days, a coculture with about equal amounts of n-damo and anammox bacteria was established that converted nitrite at a rate of 0.1 kg-N/m3/day (17.2 mmol day−1). This indicated that the application of such a coculture for nitrogen removal may be feasible in the near future. PMID:21841030

  6. Microbubble type and distribution dependence of focused ultrasound-induced blood-brain barrier opening.

    PubMed

    Wang, Shutao; Samiotaki, Gesthimani; Olumolade, Oluyemi; Feshitan, Jameel A; Konofagou, Elisa E

    2014-01-01

    Focused ultrasound, in the presence of microbubbles, has been used non-invasively to induce reversible blood-brain barrier (BBB) opening in both rodents and non-human primates. This study was aimed at identifying the dependence of BBB opening properties on polydisperse microbubble (all clinically approved microbubbles are polydisperse) type and distribution by using a clinically approved ultrasound contrast agent (Definity microbubbles) and in-house prepared polydisperse (IHP) microbubbles in mice. A total of 18 C57 BL/6 mice (n = 3) were used in this study, and each mouse was injected with either Definity or IHP microbubbles via the tail vein. The concentration and size distribution of activated Definity and IHP microbubbles were measured, and the microbubbles were diluted to 6 × 10(8)/mL before injection. Immediately after microbubble administration, mice were subjected to focused ultrasound with the following parameters: frequency = 1.5 MHz, pulse repetition frequency = 10 Hz, 1000 cycles, in situ peak rarefactional acoustic pressures = 0.3, 0.45 and 0.6 MPa for a sonication duration of 60 s. Contrast-enhanced magnetic resonance imaging was used to confirm BBB opening and allowed for image-based analysis. Permeability of the treated region and volume of BBB opening did not significantly differ between the two types of microbubbles (p > 0.05) at peak rarefractional acoustic pressures of 0.45 and 0.6 MPa, whereas IHP microbubbles had significantly higher permeability and opening volume (p < 0.05) at the relatively lower pressure of 0.3 MPa. The results from this study indicate that microbubble type and distribution could have significant effects on focused ultrasound-induced BBB opening at lower pressures, but less important effects at higher pressures, possibly because of the stable cavitation that governs the former. This difference may have become less significant at higher pressures, where inertial cavitation typically occurs.

  7. Gold-thickness-dependent Schottky barrier height for charge transfer in metal-assisted chemical etching of silicon

    PubMed Central

    2013-01-01

    Large-area, vertically aligned silicon nanowires with a uniform diameter along the height direction were fabricated by combining in situ-formed anodic aluminum oxide template and metal-assisted chemical etching. The etching rate of the Si catalyzed using a thick Au mesh is much faster than that catalyzed using a thin one, which is suggested to be induced by the charge transport process. The thick Au mesh in contact with the Si produces a low Au/Si Schottky barrier height, facilitating the injection of electronic holes from the Au to the Si, thus resulting in a high etching rate. PMID:23618313

  8. Gold-thickness-dependent Schottky barrier height for charge transfer in metal-assisted chemical etching of silicon.

    PubMed

    Zuo, Zewen; Cui, Guanglei; Shi, Yi; Liu, Yousong; Ji, Guangbin

    2013-04-26

    Large-area, vertically aligned silicon nanowires with a uniform diameter along the height direction were fabricated by combining in situ-formed anodic aluminum oxide template and metal-assisted chemical etching. The etching rate of the Si catalyzed using a thick Au mesh is much faster than that catalyzed using a thin one, which is suggested to be induced by the charge transport process. The thick Au mesh in contact with the Si produces a low Au/Si Schottky barrier height, facilitating the injection of electronic holes from the Au to the Si, thus resulting in a high etching rate.

  9. pH dependent protein stability: A quantitative approach based on Kramer's barrier escape

    NASA Astrophysics Data System (ADS)

    Chatterjee, Debarati

    2015-01-01

    The folding-unfolding mechanism of a protein in a living cell is the result of its molecular response to various perturbations due to changes in the chemical environment such as pH, ion concentration, ligand binding and many other complex chemical reactions. In this letter, a theoretical scheme based on single molecule force spectroscopy experiments and related theories, has been followed to capture the effect of the change of pH for a slow protonation-coupled folding-unfolding process, and the free energy landscape has been quantified in terms of protonation numbers, barrier height and pH, following Kramer's barrier crossing formalism.

  10. Health Care Preferences Among Nursing Home Residents: Perceived Barriers and Situational Dependencies to Person-Centered Care.

    PubMed

    Bangerter, Lauren R; Abbott, Katherine; Heid, Allison R; Klumpp, Rachel E; Van Haitsma, Kimberly

    2016-02-01

    Although much research has examined end-of-life care preferences of nursing home (NH) residents, little work has examined resident preferences for everyday health care. The current study conducted interviews with 255 residents recruited from 35 NHs. Content analysis identified barriers (i.e., hindrances to the fulfillment of resident preferences) and situational dependencies (i.e., what would make residents change their mind about the importance of these preferences) associated with preferences for using mental health services, choosing a medical care provider, and choosing individuals involved in care discussions. Barriers and situational dependencies were embedded within the individual, facility environment, and social environment. Approximately one half of residents identified barriers to their preferences of choosing others involved in care and choosing a medical care provider. In contrast, the importance of mental health services was situationally dependent on needs of residents. Results highlight opportunities for improvement in practice and facility policies that promote person-centered care. [Journal of Gerontological Nursing, 42(2), 11-16.]. Copyright 2016, SLACK Incorporated.

  11. The Ehrlich-Schwoebel barrier on an oxide surface: a combined Monte-Carlo and in situ scanning tunneling microscopy approach.

    PubMed

    Gianfrancesco, Anthony G; Tselev, Alexander; Baddorf, Arthur P; Kalinin, Sergei V; Vasudevan, Rama K

    2015-11-13

    The controlled growth of epitaxial films of complex oxides requires an atomistic understanding of key parameters determining final film morphology, such as termination dependence on adatom diffusion, and height of the Ehrlich-Schwoebel (ES) barrier. Here, through an in situ scanning tunneling microscopy study of mixed-terminated La5/8Ca3/8MnO3 (LCMO) films, we image adatoms and observe pile-up at island edges. Image analysis allows determination of the population of adatoms at the edge of islands and fractions on A-site and B-site terminations. A simple Monte-Carlo model, simulating the random walk of adatoms on a sinusoidal potential landscape using Boltzmann statistics is used to reproduce the experimental data, and provides an estimate of the ES barrier as ∼0.18 ± 0.04 eV at T = 1023 K, similar to those of metal adatoms on metallic surfaces. These studies highlight the utility of in situ imaging, in combination with basic Monte-Carlo methods, in elucidating the factors which control the final film growth in complex oxides.

  12. The Ehrlich-Schwoebel barrier on an oxide surface: a combined Monte-Carlo and in situ scanning tunneling microscopy approach

    NASA Astrophysics Data System (ADS)

    Gianfrancesco, Anthony G.; Tselev, Alexander; Baddorf, Arthur P.; Kalinin, Sergei V.; Vasudevan, Rama K.

    2015-11-01

    The controlled growth of epitaxial films of complex oxides requires an atomistic understanding of key parameters determining final film morphology, such as termination dependence on adatom diffusion, and height of the Ehrlich-Schwoebel (ES) barrier. Here, through an in situ scanning tunneling microscopy study of mixed-terminated La5/8Ca3/8MnO3 (LCMO) films, we image adatoms and observe pile-up at island edges. Image analysis allows determination of the population of adatoms at the edge of islands and fractions on A-site and B-site terminations. A simple Monte-Carlo model, simulating the random walk of adatoms on a sinusoidal potential landscape using Boltzmann statistics is used to reproduce the experimental data, and provides an estimate of the ES barrier as ˜0.18 ± 0.04 eV at T = 1023 K, similar to those of metal adatoms on metallic surfaces. These studies highlight the utility of in situ imaging, in combination with basic Monte-Carlo methods, in elucidating the factors which control the final film growth in complex oxides.

  13. Pressure dependence in the methyl vinyl ketone + OH and methacrolein + OH oxidation reactions: an electronic structure study.

    PubMed

    Ochando-Pardo, Montserrat; Nebot-Gil, Ignacio; González-Lafont, Angels; Lluch, José M

    2005-08-12

    High-level electronic structure calculations were carried out for the study of the reaction pathways in the OH-initiated oxidations of methyl vinyl ketone (MVK) and methacrolein (MACR). For the two conformers of MVK (called synperiplanar and antiperiplanar), the addition channels of OH to the terminal and central carbon atom of the double bond dominate the overall rate constant, whereas the abstraction of the methyl hydrogen atoms has no significant kinetic role. In the case of MACR, only the antiperiplanar conformer is important in its reactivity. In addition, the lower Gibbs free energy barrier for MACR corresponds to the aldehydic hydrogen abstraction reaction, which will be somewhat more favorable than the addition processes. The subtle balance between the different pathways (additions versus abstractions) serves to give an understanding of the pressure dependence of the rate constants of these tropospheric oxidation processes.

  14. Epidermal ADAM17 maintains the skin barrier by regulating EGFR ligand–dependent terminal keratinocyte differentiation

    PubMed Central

    Cobzaru, Cristina; Triantafyllopoulou, Antigoni; Löffek, Stefanie; Horiuchi, Keisuke; Threadgill, David W.; Kurz, Thomas; van Rooijen, Nico; Bruckner-Tuderman, Leena

    2012-01-01

    ADAM17 (a disintegrin and metalloproteinase 17) is ubiquitously expressed and cleaves membrane proteins, such as epidermal growth factor receptor (EGFR) ligands, l-selectin, and TNF, from the cell surface, thus regulating responses to tissue injury and inflammation. However, little is currently known about its role in skin homeostasis. We show that mice lacking ADAM17 in keratinocytes (A17ΔKC) have a normal epidermal barrier and skin architecture at birth but develop pronounced defects in epidermal barrier integrity soon after birth and develop chronic dermatitis as adults. The dysregulated expression of epidermal differentiation proteins becomes evident 2 d after birth, followed by reduced transglutaminase (TGM) activity, transepidermal water loss, up-regulation of the proinflammatory cytokine IL-36α, and inflammatory immune cell infiltration. Activation of the EGFR was strongly reduced in A17ΔKC skin, and topical treatment of A17ΔKC mice with recombinant TGF-α significantly improved TGM activity and decreased skin inflammation. Finally, we show that mice lacking the EGFR in keratinocytes (EgfrΔKC) closely resembled A17ΔKC mice. Collectively, these results identify a previously unappreciated critical role of the ADAM17–EGFR signaling axis in maintaining the homeostasis of the postnatal epidermal barrier and suggest that this pathway could represent a good target for treatment of epidermal barrier defects. PMID:22565824

  15. Comparing cost per use of 3M Cavilon No Sting Barrier Film with zinc oxide oil in incontinent patients.

    PubMed

    Baatenburg de Jong, H; Admiraal, H

    2004-10-01

    This study compares the total cost of treatment, skin-condition management and prevention of skin breakdown of perianal/buttock skin in incontinent patients receiving 3M Cavilon No Sting Barrier Film (Cavilon NSBF) and zinc oxide oil. This single-centre open-label prospective randomised study involved 40 patients with at least moderate skin damage resulting from incontinence. Patients were randomised to receive either zinc oxide oil or Cavilon NSBF and were treated for 14 days. The study products and other treatment-related products used were recorded, as was the time needed to cleanse the application site and apply the product. Use of both products resulted in an improvement in skin condition after 14 days, but this was significantly better with Cavilon NSBF than zinc oxide oil. Cavilon NSBF was more cost-effective as fewer applications were required, less time was spent applying the skin barrier product and faster healing rates were achieved. The cost-effectiveness ratio per treatment group showed an improvement of one point in the total score of the skin-assessment scale costs: 28.36 Euro for Cavilon NSBF versus 98.06 Euro for zinc oxide oil. Both products resulted in an improvement in skin condition after 14 days, but Cavilon NSBF was found to be more cost-effective. This study was supported by an educational grant from 3M.

  16. Effect of Layer-Graded Bond Coats on Edge Stress Concentration and Oxidation Behavior of Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Ghosn, Louis J.; Miller, Robert A.

    1998-01-01

    Thermal barrier coating (TBC) durability is closely related to design, processing and microstructure of the coating Z, tn systems. Two important issues that must be considered during the design of a thermal barrier coating are thermal expansion and modulus mismatch between the substrate and the ceramic layer, and substrate oxidation. In many cases, both of these issues may be best addressed through the selection of an appropriate bond coat system. In this study, a low thermal expansion and layer-graded bond coat system, that consists of plasma-sprayed FeCoNiCrAl and FeCrAlY coatings, and a high velocity oxyfuel (HVOF) sprayed FeCrAlY coating, is developed to minimize the thermal stresses and provide oxidation resistance. The thermal expansion and oxidation behavior of the coating system are also characterized, and the strain isolation effect of the bond coat system is analyzed using the finite element method (FEM). Experiments and finite element results show that the layer-graded bond coat system possesses lower interfacial stresses. better strain isolation and excellent oxidation resistance. thus significantly improving the coating performance and durability.

  17. Oral administration of Bifidobacterium breve attenuates UV-induced barrier perturbation and oxidative stress in hairless mice skin.

    PubMed

    Ishii, Yuki; Sugimoto, Saho; Izawa, Naoki; Sone, Toshiro; Chiba, Katsuyoshi; Miyazaki, Kouji

    2014-07-01

    Recent studies have shown that some probiotics affect not only the gut but also the skin. However, the effects of probiotics on ultraviolet (UV)-induced skin damage are poorly understood. In this study, we aim to examine whether oral administration of live Bifidobacterium breve strain Yakult (BBY), a typical probiotic, can attenuate skin barrier perturbation caused by UV and reactive oxygen species (ROS) in hairless mice. The mice were orally supplemented with a vehicle only or BBY once a day for nine successive days. Mouse dorsal skin was irradiated with UV from days 6 to 9. The day after the final irradiation, the transepidermal water loss (TEWL), stratum corneum hydration, and oxidation-related factors of the skin were evaluated. We elucidated that BBY prevented the UV-induced increase in TEWL and decrease in stratum corneum hydration. In addition, BBY significantly suppressed the UV-induced increase in hydrogen peroxide levels, oxidation of proteins and lipids, and xanthine oxidase activity in the skin. Conversely, antioxidant capacity did not change regardless of whether BBY was administered or not. In parameters we evaluated, there was a positive correlation between the increase in TEWL and the oxidation levels of proteins and lipids. Our results suggest that oral administration of BBY attenuates UV-induced barrier perturbation and oxidative stress of the skin, and this antioxidative effect is not attributed to enhancement of antioxidant capacity but to the prevention of ROS generation.

  18. Fabrication of high resistive barrier through metal oxidation method for the reduction of AC loss in Bi-2223 tapes

    NASA Astrophysics Data System (ADS)

    Nakamura, Yuichi; Kohashi, Takahito; Inada, Ryoji; Oota, Akio

    2006-10-01

    Ag sheathed Bi-2223 tapes have the performances of Ic values over 100 A and length of 1000 m which are enough for prototype configuration. However, their AC loss is still too high for the practical applications. To reduce the AC coupling loss, the introduction of high resistive barrier between the filaments and the twisting of the filaments are effective. In this study, we try to introduce CuO barrier between the filaments through the in situ metal oxidation method. A silver tube packing Bi-2223 precursor powder was inserted into a copper metal tube. The Ag-Cu clad tubes were stacked into Ag pipe to form a 7-filamentary wire, and the stacked wire was drawn and rolled into tape shape. The Cu inter-filamentary layers were uniformly arranged between filaments of the tape. To oxidize this Cu to form CuO, the pre-oxidation of Cu before heating up to sintering temperature is found to be required to avoid the eutectic melting of the Ag-Cu system. The CuO layer was successfully formed after sintering using the pre-oxidation process, and the Jc value of the tape with the CuO layer reached 1.5 × 104 A/cm2. The continuity of CuO layer, however, became worse after final sintering, and this must be improved, for example, by increasing the thickness of Cu layer before sintering.

  19. Effect of Coating Process Condition on High-Temperature Oxidation and Mechanical Failure Behavior for Plasma Sprayed Thermal Barrier Coating Systems

    NASA Astrophysics Data System (ADS)

    Takahashi, Satoru; Yoshiba, Masayuki; Harada, Yoshio

    In order to clarify the thermal and/or mechanical failure behavior of the plasma sprayed thermal barrier coating (TBC) system in connection with their coating characteristics depending on the coating process condition, two kinds of the failure analytical tests were conducted for TBC systems processed under different conditions. One was the high-temperature oxidation test, which was conducted at 1100°C under both the isothermal and thermal cycle conditions. The other was the in-situ observation of mechanical failure behavior, which was conducted under the static loadings at ambient temperature; as the most fundamental aspect, by means of an optical microscopy. It was found that the thermal and mechanical failure behavior of TBC system depends strongly on the top-coat (TC)/bond-coat (BC) interfacial condition, the reheat-treatment (RHT) after spraying and so on. For the TBC system with vacuum plasma sprayed (VPS) BC as well as for that with atmospheric plasma sprayed (APS) BC, in particular, the RHT at an appropriate temperature in Ar atmosphere was found to be effective for improving the oxidation property. For the TBC system with APS-BC, however, it was impossible to prevent the crack growth into the BC interior under the tensile loading in spite of conducting the RHT, since the microdefects such as oxides within the APS-BC tend to provide an easy crack propagation path. Furthermore, it was clarified that the smoothening process on the BC surface is able to prevent perfectly the occurrence of the wart-like oxide during oxidation, but at the same time increases also the risk of the TC spalling under the mechanical loading.

  20. Geochemical controls on microbial nitrate-dependent U(IV) oxidation

    USGS Publications Warehouse

    Senko, John M.; Suflita, Joseph M.; Krumholz, Lee R.

    2005-01-01

    After reductive immobilization of uranium, the element may be oxidized and remobilized in the presence of nitrate by the activity of dissimilatory nitrate-reducing bacteria. We examined controls on microbially mediated nitrate-dependent U(IV) oxidation in landfill leachate-impacted subsurface sediments. Nitrate-dependent U(IV)-oxidizing bacteria were at least two orders of magnitude less numerous in these sediments than glucose- or Fe(II)-oxidizing nitrate-reducing bacteria and grew more slowly than the latter organisms, suggesting that U(IV) is ultimately oxidized by Fe(III) produced by nitrate-dependent Fe(II)-oxidizing bacteria or by oxidation of Fe(II) by nitrite that accumulates during organotrophic dissimilatory nitrate reduction. We examined the effect of nitrate and reductant concentration on nitrate-dependent U(IV) oxidation in sediment incubations and used the initial reductive capacity (RDC = [reducing equivalents] - [oxidizing equivalents]) of the incubations as a unified measurement of the nitrate or reductant concentration. When we lowered the RDC with progressively higher nitrate concentrations, we observed a corresponding increase in the extent of U(IV) oxidation, but did not observe this relationship between RDC and U(IV) oxidation rate, especially when RDC > 0, suggesting that nitrate concentration strongly controls the extent, but not the rate of nitrate-dependent U(IV) oxidation. On the other hand, when we raised the RDC in sediment incubations with progressively higher reductant (acetate, sulfide, soluble Fe(II), or FeS) concentrations, we observed progressively lower extents and rates of nitrate-dependent U(IV) oxidation. Acetate was a relatively poor inhibitor of nitrate-dependent U(IV) oxidation, while Fe(II) was the most effective inhibitor. Based on these results, we propose that it may be possible to predict the stability of U(IV) in a bioremediated aquifer based on the geochemical characteristics of that aquifer.

  1. Dependence of riverine nitrous oxide emissions on dissolved oxygen levels

    NASA Astrophysics Data System (ADS)

    Rosamond, Madeline S.; Thuss, Simon J.; Schiff, Sherry L.

    2012-10-01

    Nitrous oxide is a potent greenhouse gas, and it destroys stratospheric ozone. Seventeen per cent of agricultural nitrous oxide emissions come from the production of nitrous oxide in streams, rivers and estuaries, in turn a result of inorganic nitrogen input through leaching, runoff and sewage. The Intergovernmental Panel on Climate Change and global nitrous oxide budgets assume that riverine nitrous oxide emissions increase linearly with dissolved inorganic nitrogen loads, but data are sparse and conflicting. Here we report measurements over two years of nitrous oxide emissions in the Grand River, Canada, a seventh-order temperate river that is affected by agricultural runoff and outflow from a waste-water treatment plant. Emissions were disproportionately high in urban areas and during nocturnal summer periods. Moreover, annual emission estimates that are based on dissolved inorganic nitrogen loads overestimated the measured emissions in a wet year and underestimated them in a dry year. We found no correlations of nitrous oxide emissions with nitrate or dissolved inorganic nitrogen, but detected negative correlations with dissolved oxygen, suggesting that nitrate concentrations did not limit emissions. We conclude that future increases in nitrate export to rivers will not necessarily lead to higher nitrous oxide emissions, but more widespread hypoxia most likely will.

  2. Stress dependent oxidation of sputtered niobium and effects on superconductivity

    NASA Astrophysics Data System (ADS)

    David Henry, M.; Wolfley, Steve; Monson, Todd; Clark, Blythe G.; Shaner, Eric; Jarecki, Robert

    2014-02-01

    We report on the suppression of room temperature oxidation of DC sputtered niobium films and the effects upon the superconductive transition temperature, Tc. Niobium was sputter-deposited on silicon dioxide coated 150 mm wafers and permitted to oxidize at room temperature and pressure for up to two years. Resistivity and stress measurements indicate that tensile films greater than 400 MPa resist bulk oxidation with measurements using transmission electron microscope, electron dispersive X-ray spectroscopy, x-ray photoelectric spectroscopy, and secondary ion mass spectrometry confirming this result. Although a surface oxide, Nb2O5, consumed the top 6-10 nm, we measure less than 1 at. % oxygen and nitrogen in the bulk of the films after the oxidation period. Tc measurements using a SQUID magnetometer indicate that the tensile films maintained a Tc approaching the dirty superconductive limit of 8.4 K after two years of oxidation while maintaining room temperature sheet resistance. This work demonstrates that control over niobium film stress during deposition can prevent bulk oxidation by limiting the vertical grain boundaries ability to oxidize, prolonging the superconductive properties of sputtered niobium when exposed to atmosphere.

  3. Stress dependent oxidation of sputtered niobium and effects on superconductivity

    SciTech Connect

    David Henry, M. Wolfley, Steve; Monson, Todd; Clark, Blythe G.; Shaner, Eric; Jarecki, Robert

    2014-02-28

    We report on the suppression of room temperature oxidation of DC sputtered niobium films and the effects upon the superconductive transition temperature, T{sub c}. Niobium was sputter-deposited on silicon dioxide coated 150 mm wafers and permitted to oxidize at room temperature and pressure for up to two years. Resistivity and stress measurements indicate that tensile films greater than 400 MPa resist bulk oxidation with measurements using transmission electron microscope, electron dispersive X-ray spectroscopy, x-ray photoelectric spectroscopy, and secondary ion mass spectrometry confirming this result. Although a surface oxide, Nb{sub 2}O{sub 5}, consumed the top 6–10 nm, we measure less than 1 at. % oxygen and nitrogen in the bulk of the films after the oxidation period. T{sub c} measurements using a SQUID magnetometer indicate that the tensile films maintained a T{sub c} approaching the dirty superconductive limit of 8.4 K after two years of oxidation while maintaining room temperature sheet resistance. This work demonstrates that control over niobium film stress during deposition can prevent bulk oxidation by limiting the vertical grain boundaries ability to oxidize, prolonging the superconductive properties of sputtered niobium when exposed to atmosphere.

  4. Schottky barrier height switching in thin metal oxide films studied in diode and solar cell device configurations

    NASA Astrophysics Data System (ADS)

    Wing, Dahvyd; Rothschild, Avner; Tessler, Nir

    2015-08-01

    We investigate changes in the properties of 8 nm thin metal oxide (Nb-doped SrTiO3) films in response to relatively high voltage or light soaking under three Sun excitation. We measure the current-voltage behavior of metal|insulator|metal type diodes and use a device model to relate changes in device behavior to the metal oxide film properties. We find that the device's resistive switching is mainly associated with shifts (switching) of the metal oxide work function between high and low injection barrier states. The method presented here can be used for in situ monitoring of the contact work function and for quantifying the uniformity of this value across the device. We also discuss the effect of non-uniform work function on the apparent diode's ideality factor.

  5. Isothermal Oxidation Behavior of VC and Columnar Structured Thermal Barrier Coatings Deposited by Suspension Plasma Spray Technology

    NASA Astrophysics Data System (ADS)

    Li, Xiaolong; Yang, Qi; Huang, Xiao; Tang, Zhaolin

    2015-08-01

    The effects of different thermal barrier coating (TBC) top coat structures and substrate alloys on the isothermal oxidation behaviors of TBC systems were investigated at 1080 °C in lab air. The tested TBC systems consisted of two nickel-based superalloy substrates (CMSX-4 and IN738LC), a platinum aluminide bond coat and two 8YSZ top coats (vertical cracked and columnar structured). Samples with IN738LC substrate demonstrated longer isothermal oxidation lives than the counterparts with CMSX-4 substrate. Outward refractory elemental diffusion in coating systems with CMSX-4 substrate and void formation at the interface between thermally grown oxide and bond coat was found to be responsible for the early failure of TBCs. Columnar structured YSZ top coat seemed to provide better protection of the bond coating and substrate, marginally delaying the failure of the both coating systems with IN738LC and CMSX-4.

  6. DNA damage signalling barrier, oxidative stress and treatment-relevant DNA repair factor alterations during progression of human prostate cancer.

    PubMed

    Kurfurstova, Daniela; Bartkova, Jirina; Vrtel, Radek; Mickova, Alena; Burdova, Alena; Majera, Dusana; Mistrik, Martin; Kral, Milan; Santer, Frederic R; Bouchal, Jan; Bartek, Jiri

    2016-06-01

    The DNA damage checkpoints provide an anti-cancer barrier in diverse tumour types, however this concept has remained unexplored in prostate cancer (CaP). Furthermore, targeting DNA repair defects by PARP1 inhibitors (PARPi) as a cancer treatment strategy is emerging yet requires suitable predictive biomarkers. To address these issues, we performed immunohistochemical analysis of multiple markers of DNA damage signalling, oxidative stress, DNA repair and cell cycle control pathways during progression of human prostate disease from benign hyperplasia, through intraepithelial neoplasia to CaP, complemented by genetic analyses of TMPRSS2-ERG rearrangement and NQO1, an anti-oxidant factor and p53 protector. The DNA damage checkpoint barrier (γH2AX, pATM, p53) mechanism was activated during CaP tumorigenesis, albeit less and with delayed culmination compared to other cancers, possibly reflecting lower replication stress (slow proliferation despite cases of Rb loss and cyclin D1 overexpression) and progressive loss of ATM activator NKX3.1. Oxidative stress (8-oxoguanine lesions) and NQO1 increased during disease progression. NQO1 genotypes of 390 men did not indicate predisposition to CaP, yet loss of NQO1 in CaP suggested potential progression-opposing tumour suppressor role. TMPRSS2-ERG rearrangement and PTEN loss, events sensitizing to PARPi, occurred frequently along with heterogeneous loss of DNA repair factors 53BP1, JMJD1C and Rev7 (all studied here for the first time in CaP) whose defects may cause resistance to PARPi. Overall, our results reveal an unorthodox DNA damage checkpoint barrier scenario in CaP tumorigenesis, and provide novel insights into oxidative stress and DNA repair, with implications for biomarker guidance of future targeted therapy of CaP.

  7. Nitric oxide-dependent penile erection in mice lacking neuronal nitric oxide synthase.

    PubMed Central

    Burnett, A. L.; Nelson, R. J.; Calvin, D. C.; Liu, J. X.; Demas, G. E.; Klein, S. L.; Kriegsfeld, L. J.; Dawson, V. L.; Dawson, T. M.; Snyder, S. H.

    1996-01-01

    BACKGROUND: Nitric oxide (NO) has been implicated as a mediator of penile erection, because the neuronal isoform of NO synthase (NOS) is localized to the penile innervation and NOS inhibitors selectively block erections. NO can also be formed by two other NOS isoforms derived from distinct genes, inducible NOS (iNOS) and endothelial NOS (eNOS). To clarify the source of NO in penile function, we have examined mice with targeted deletion of the nNOS gene (nNOS- mice). MATERIALS AND METHODS: Mating behavior, electrophysiologically induced penile erection, isolated erectile tissue isometric tension, and eNOS localization by immunohistochemistry and Western blot were performed on nNOS- mice and wild-type controls. RESULTS: Both intact animal penile erections and isolated erectile tissue function are maintained in nNOS mice, in agreement with demonstrated normal sexual behaviors, but is stereospecifically blocked by the NOS inhibitor, L-nitroarginine methyl ester (L-NAME). eNOS is abundantly present in endothelium of penile vasculature and sinusoidal endothelium within the corpora cavemosa, with levels that are significantly higher in nNOS- mice than in wild-type controls. CONCLUSIONS: eNOS mediates NO-dependent penile erection in nNOS- animals and normal penile erection. These data clarify the role of nitric oxide in penile erection and may have implications for therapeutic agents with selective effects on NOS isoforms. Images FIG. 2 FIG. 3 FIG. 5 PMID:8784782

  8. Nitric oxide-dependent penile erection in mice lacking neuronal nitric oxide synthase.

    PubMed

    Burnett, A L; Nelson, R J; Calvin, D C; Liu, J X; Demas, G E; Klein, S L; Kriegsfeld, L J; Dawson, V L; Dawson, T M; Snyder, S H

    1996-05-01

    Nitric oxide (NO) has been implicated as a mediator of penile erection, because the neuronal isoform of NO synthase (NOS) is localized to the penile innervation and NOS inhibitors selectively block erections. NO can also be formed by two other NOS isoforms derived from distinct genes, inducible NOS (iNOS) and endothelial NOS (eNOS). To clarify the source of NO in penile function, we have examined mice with targeted deletion of the nNOS gene (nNOS- mice). Mating behavior, electrophysiologically induced penile erection, isolated erectile tissue isometric tension, and eNOS localization by immunohistochemistry and Western blot were performed on nNOS- mice and wild-type controls. Both intact animal penile erections and isolated erectile tissue function are maintained in nNOS mice, in agreement with demonstrated normal sexual behaviors, but is stereospecifically blocked by the NOS inhibitor, L-nitroarginine methyl ester (L-NAME). eNOS is abundantly present in endothelium of penile vasculature and sinusoidal endothelium within the corpora cavemosa, with levels that are significantly higher in nNOS- mice than in wild-type controls. eNOS mediates NO-dependent penile erection in nNOS- animals and normal penile erection. These data clarify the role of nitric oxide in penile erection and may have implications for therapeutic agents with selective effects on NOS isoforms.

  9. Contributions of altered permeability of intestinal barrier and defecation behavior to toxicity formation from graphene oxide in nematode Caenorhabditis elegans.

    PubMed

    Wu, Qiuli; Yin, Li; Li, Xing; Tang, Meng; Zhang, Tao; Wang, Dayong

    2013-10-21

    Graphene oxide (GO) has been extensively studied for potential biomedical applications. Meanwhile, potential GO toxicity arises in both biomedical applications and non-biomedical products where environmental exposures may occur. In the present study, we examined the potential adverse effects of GO and the underlying mechanism using nematode Caenorhabditis elegans as the assay system. We compared the in vivo effects of GO between acute exposure and prolonged exposure, and found that prolonged exposure to 0.5-100 mg L(-1) of GO caused damage on functions of both primary (intestine) and secondary (neuron and reproductive organ) targeted organs. In the intestine, ROS production was significantly correlated with the formation of adverse effects on functions of both primary and secondary targeted organs. GO could be translocated into intestinal cells with loss of microvilli, and distributed to be adjacent to or surrounding mitochondria. Prolonged exposure to GO resulted in a hyper-permeable state of the intestinal barrier, an increase in mean defecation cycle length, and alteration of genes required for intestinal development and defecation behavior. Thus, our data suggest that prolonged exposure to GO may cause potential risk to environmental organisms after release into the environment. GO toxicity may be due to the combinational effects of oxidative stress in the intestinal barrier, enhanced permeability of the biological barrier, and suppressed defecation behavior in C. elegans.

  10. The Effect of Interface Roughness and Oxide Film Thickness on the Inelastic Response of Thermal Barrier Coatings to Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Pindera, Marek-Jerzy; Aboudi, Jacob; Arnold, Steven M.

    1999-01-01

    The effects of interfacial roughness and oxide film thickness on thermally-induced stresses in plasma-sprayed thermal barrier coatings subjected to thermal cycling are investigated using the recently developed higher-order theory for functionally graded materials. The higher-order theory is shown to be a viable alternative to the finite-element approach, capable of modeling different interfacial roughness architectures in the presence of an aluminum oxide layer and capturing the high stress gradients that occur at the top coat/bond coat interface. The oxide layer thickness is demonstrated to have a substantially greater effect on the evolution of residual stresses than local variations in interfacial roughness. Further, the location of delamination initiation in the top coat is predicted to change with increasing oxide layer thickness. This result can be used to optimize the thickness of a pre-oxidized layer introduced at the top coat/bond coat interface in order to enhance TBC durability as suggested by some researchers. The results of our investigation also support a recently proposed hypothesis regarding delamination initiation and propagation in the presence of an evolving bond coat oxidation, while pointing to the importance of interfacial roughness details and specimen geometry in modeling this phenomenon.

  11. Oxidation resistance of Al2O3-nanostructured/CSZ composite compared to conventional CSZ and YSZ thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Keyvani, A.; Bahamirian, M.

    2016-10-01

    Thermal barrier coatings are widely used in combustion sections of turbine engines, however, their main disadvantage is the spallation from the bond coat, occurring due to oxidation and formation of thermally grown oxide (TGO). In this paper, the oxidation resistance of yttria stabilized zirconia (YSZ), ceria stabilized zirconia (CSZ), and Al2O3-nanostructured/CSZ composite coatings have been studied and compared with each other. Samples were heated in air at 1100 °C using an electrical furnace. Three types of the top coats were applied by thermal spray technique on IN738LC base metal. Scanning electron microscopy was used to study the microstructure of the coatings before and after the oxidation. The experimental results showed that Al2O3-nanostructured/CSZ composite coating exhibits considerably better oxidation resistance compared to conventional YSZ and CSZ coatings. The microstructural analysis indicated a smaller growth of TGO in the Al2O3-nanostructured/CSZ composite coating, improving the oxidation resistance of the coating.

  12. Surface plasmon resonance measurement of AlOx insulating barriers in magnetic tunnel junctions formed by remote rf plasma oxidation process

    NASA Astrophysics Data System (ADS)

    Park, J. H.; Yoon, K. S.; Yang, J. Y.; Kim, E. K.; Lee, C. H.; Kim, C. O.; Hong, J. P.

    2002-09-01

    A surface plasmon resonance spectroscopy (SPRS) measurement was carried out to determine dielectric properties, oxidation states, and optimum thickness of AlOx insulating barrier in magnetic tunnel junctions. The insulating barriers were prepared as a function of oxidation time by using a remote rf plasma oxidation process. The experimental results revealed that the dielectric value and optimum thickness of the AlOx insulating barrier in our junctions were found to be 1.79+i1.77 and 11.26 A, respectively. For comparison, the magnetic tunneling junction was also fabricated using the same oxidation condition. The best magneto-resistance ratio of about 34% was observed at an optimum oxidation time of 70 s, as expected by the SPRS measurement.

  13. Coal tar induces AHR-dependent skin barrier repair in atopic dermatitis

    PubMed Central

    van den Bogaard, Ellen H.; Bergboer, Judith G.M.; Vonk-Bergers, Mieke; van Vlijmen-Willems, Ivonne M.J.J.; Hato, Stanleyson V.; van der Valk, Pieter G.M.; Schröder, Jens Michael; Joosten, Irma; Zeeuwen, Patrick L.J.M.; Schalkwijk, Joost

    2013-01-01

    Topical application of coal tar is one of the oldest therapies for atopic dermatitis (AD), a T helper 2 (Th2) lymphocyte–mediated skin disease associated with loss-of-function mutations in the skin barrier gene, filaggrin (FLG). Despite its longstanding clinical use and efficacy, the molecular mechanism of coal tar therapy is unknown. Using organotypic skin models with primary keratinocytes from AD patients and controls, we found that coal tar activated the aryl hydrocarbon receptor (AHR), resulting in induction of epidermal differentiation. AHR knockdown by siRNA completely abrogated this effect. Coal tar restored filaggrin expression in FLG-haploinsufficient keratinocytes to wild-type levels, and counteracted Th2 cytokine–mediated downregulation of skin barrier proteins. In AD patients, coal tar completely restored expression of major skin barrier proteins, including filaggrin. Using organotypic skin models stimulated with Th2 cytokines IL-4 and IL-13, we found coal tar to diminish spongiosis, apoptosis, and CCL26 expression, all AD hallmarks. Coal tar interfered with Th2 cytokine signaling via dephosphorylation of STAT6, most likely due to AHR-regulated activation of the NRF2 antioxidative stress pathway. The therapeutic effect of AHR activation herein described opens a new avenue to reconsider AHR as a pharmacological target and could lead to the development of mechanism-based drugs for AD. PMID:23348739

  14. Schottky barrier height reduction for holes by Fermi level depinning using metal/nickel oxide/silicon contacts

    SciTech Connect

    Islam, Raisul Shine, Gautam; Saraswat, Krishna C.

    2014-11-03

    We report the experimental demonstration of Fermi level depinning using nickel oxide (NiO) as the insulator material in metal-insulator-semiconductor (M-I-S) contacts. Using this contact, we show less than 0.1 eV barrier height for holes in platinum/NiO/silicon (Pt/NiO/p-Si) contact. Overall, the pinning factor was improved from 0.08 (metal/Si) to 0.26 (metal/NiO/Si). The experimental results show good agreement with that obtained from theoretical calculation. NiO offers high conduction band offset and low valence band offset with Si. By reducing Schottky barrier height, this contact can be used as a carrier selective contact allowing hole transport but blocking electron transport, which is important for high efficiency in photonic applications such as photovoltaics and optical detectors.

  15. Temperature-dependent bias-stress-induced electrical instability of amorphous indium-gallium-zinc-oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Qian, Hui-Min; Yu, Guang; Lu, Hai; Wu, Chen-Fei; Tang, Lan-Feng; Zhou, Dong; Ren, Fang-Fang; Zhang, Rong; Zheng, You-Liao; Huang, Xiao-Ming

    2015-07-01

    The time and temperature dependence of threshold voltage shift under positive-bias stress (PBS) and the following recovery process are investigated in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. It is found that the time dependence of threshold voltage shift can be well described by a stretched exponential equation in which the time constant τ is found to be temperature dependent. Based on Arrhenius plots, an average effective energy barrier Eτstress = 0.72 eV for the PBS process and an average effective energy barrier Eτrecovery = 0.58 eV for the recovery process are extracted respectively. A charge trapping/detrapping model is used to explain the threshold voltage shift in both the PBS and the recovery process. The influence of gate bias stress on transistor performance is one of the most critical issues for practical device development. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB301900 and 2011CB922100) and the Priority Academic Program Development of Jiangsu Higher Education Institutions, China

  16. Potential of Lactobacillus plantarum CCFM639 in Protecting against Aluminum Toxicity Mediated by Intestinal Barrier Function and Oxidative Stress.

    PubMed

    Yu, Leilei; Zhai, Qixiao; Tian, Fengwei; Liu, Xiaoming; Wang, Gang; Zhao, Jianxin; Zhang, Hao; Narbad, Arjan; Chen, Wei

    2016-12-02

    Aluminum (Al) is a ubiquitous metal that can seriously harm the health of animals and humans. In our previous study, we demonstrated that Lactobacillus plantarum CCFM639 can decrease Al burden in the tissues of mice by inhibiting intestinal Al absorption. The main aim of the present research was to investigate whether the protection by the strain is also associated with enhancement of the intestinal barrier, alleviation of oxidative stress and modulation of the inflammatory response. In an in vitro cell model, two protection modes (intervention and therapy) were examined and the results indicated that L. plantarum CCFM639 alleviated Al-induced cytotoxicity. In a mouse model, L. plantarum CCFM639 treatment was found to significantly alleviate oxidative stress in the intestinal tract, regulate the function of the intestinal mucosal immune system, restore the integrity of tight junction proteins and maintain intestinal permeability. These results suggest that in addition to Al sequestration, L. plantarum CCFM639 can also inhibit Al absorption by protecting the intestinal barrier, alleviating Al-induced oxidative stress and inflammatory response. Therefore, L. plantarum CCFM639 has the potential to be a dietary supplement ingredient that provides protection against Al-induced gut injury.

  17. Potential of Lactobacillus plantarum CCFM639 in Protecting against Aluminum Toxicity Mediated by Intestinal Barrier Function and Oxidative Stress

    PubMed Central

    Yu, Leilei; Zhai, Qixiao; Tian, Fengwei; Liu, Xiaoming; Wang, Gang; Zhao, Jianxin; Zhang, Hao; Narbad, Arjan; Chen, Wei

    2016-01-01

    Aluminum (Al) is a ubiquitous metal that can seriously harm the health of animals and humans. In our previous study, we demonstrated that Lactobacillus plantarum CCFM639 can decrease Al burden in the tissues of mice by inhibiting intestinal Al absorption. The main aim of the present research was to investigate whether the protection by the strain is also associated with enhancement of the intestinal barrier, alleviation of oxidative stress and modulation of the inflammatory response. In an in vitro cell model, two protection modes (intervention and therapy) were examined and the results indicated that L. plantarum CCFM639 alleviated Al-induced cytotoxicity. In a mouse model, L. plantarum CCFM639 treatment was found to significantly alleviate oxidative stress in the intestinal tract, regulate the function of the intestinal mucosal immune system, restore the integrity of tight junction proteins and maintain intestinal permeability. These results suggest that in addition to Al sequestration, L. plantarum CCFM639 can also inhibit Al absorption by protecting the intestinal barrier, alleviating Al-induced oxidative stress and inflammatory response. Therefore, L. plantarum CCFM639 has the potential to be a dietary supplement ingredient that provides protection against Al-induced gut injury. PMID:27918411

  18. Glucose influence on copper ion-dependent oxidation of low density lipoprotein.

    PubMed

    Ghaffari, Mohammad Ali; Mojab, Samad

    2009-01-01

    It is well established that oxidative modification of low density lipoprotein (LDL) plays a causal role in human atherogenesis and the risk of atherosclerosis is increased in patients with diabetes mellitus. We examined the in vitro effect of glucose on native and glycated LDL oxidation using copper ion dependent oxidation system. In this study, LDL was isolated from plasma by ultracentrifugation using a single step discontinuous gradient. Native LDL preparations were glycated by glucose and also were oxidized by copper ions. LDL glycation and oxidation levels were estimated by sodium periodate assay and thiobarbituric acid reactive substances (TBARS), respectively. Then, native LDL was incubated with glucose and copper and LDL oxidation was estimated by TBARS. Finally, oxidation of glycated LDL was studied in presence of copper ions by TBARS and relative electrophoretic mobility on polyacrylamide gel. This study showed that glucose considerably decreased the oxidation of native LDL by copper ions. But oxidation of glycated LDL elevated with presence of copper ions. The results of this investigation show that LDL glycated in vitro is prone to oxidation by copper ions. Thus, promotion of glycated LDL oxidation by glucose is specific for copper ion dependent oxidation and involves increased copper ion reduction. These results provide one mechanism that may enhanced LDL oxidation in diabetes and thus contribute to the pathogenesis of atherosclerosis in diabetic patients.

  19. Patient-centered Care to Address Barriers for Pregnant Women with Opioid Dependence.

    PubMed

    Sutter, Mary Beth; Gopman, Sarah; Leeman, Lawrence

    2017-03-01

    Pregnant women affected by substance use often encounter barriers to treatment, including housing insecurity, poverty, mental health issues, social stigma, and access to health care. Providers may lack the resources needed to provide quality care. Clinicians offering prenatal care to women with substance use disorder are encouraged to support family-centered, multidisciplinary care to women and their infants, focusing on harm reduction. Collaboration between providers of maternity care, substance abuse treatment, case management, family primary care, and pediatric developmental care can improve outcomes during pregnancy and through the early years of parenting.

  20. Propionate Ameliorates Dextran Sodium Sulfate-Induced Colitis by Improving Intestinal Barrier Function and Reducing Inflammation and Oxidative Stress

    PubMed Central

    Tong, Ling-chang; Wang, Yue; Wang, Zhi-bin; Liu, Wei-ye; Sun, Sheng; Li, Ling; Su, Ding-feng; Zhang, Li-chao

    2016-01-01

    Propionate is a short chain fatty acid that is abundant as butyrate in the gut and blood. However, propionate has not been studied as extensively as butyrate in the treatment of colitis. The present study was to investigate the effects of sodium propionate on intestinal barrier function, inflammation and oxidative stress in dextran sulfate sodium (DSS)-induced colitis mice. Animals in DSS group received drinking water from 1 to 6 days and DSS [3% (w/v) dissolved in double distilled water] instead of drinking water from 7 to 14 days. Animals in DSS+propionate (DSS+Prop) group were given 1% sodium propionate for 14 consecutive days and supplemented with 3% DSS solution on day 7–14. Intestinal barrier function, proinflammatory factors, oxidative stress, and signal transducer and activator of transcription 3 (STAT3) signaling pathway in the colon were determined. It was found that sodium propionate ameliorated body weight loss, colon-length shortening and colonic damage in colitis mice. Sodium propionate significantly inhibited the increase of FITC-dextran in serum and the decrease of zonula occludens-1 (ZO-1), occludin, and E-cadherin expression in the colonic tissue. It also inhibited the expression of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) mRNA and phosphorylation of STAT3 in colitis mice markedly, reduced the myeloperoxidase (MPO) level, and increased the superoxide dismutase and catalase level in colon and serum compared with DSS group. Sodium propionate inhibited macrophages with CD68 marker infiltration into the colonic mucosa of colitis mice. These results suggest that oral administration of sodium propionate could ameliorate DSS-induced colitis mainly by improving intestinal barrier function and reducing inflammation and oxidative stress via the STAT3 signaling pathway. PMID:27574508

  1. Thermal barrier coating life and isothermal oxidation of low-pressure plasma-sprayed bond coat alloys

    NASA Technical Reports Server (NTRS)

    Brindley, W. J.; Miller, R. A.

    1990-01-01

    The paper investigates the isothermal oxidation kinetics of Ni-35Cr-6Al-0.95Y, Ni-18Cr-12Al-0.3Y, and Ni-16Cr-6Al-0.3Y low-pressure plasma-sprayed bond coat alloys and examines the effect of these alloys on the thermal barrier coating (TBC) cyclic life. TBC life was examined by cycling substrates coated with the different bond coats and a ZrO2-7 wt pct Y2O3 TBC in an air-rich burner rig flame between 1150 C and room temperature. The oxidation kinetics of the three bond coat alloys was examined by isothermal oxidation of monolithic NJiCrAlY coupons at 1083 C. The Ni-35Cr-6Al-0.95Y alloy exhibits comparatively high isothermal oxidation weight gains and provides the longest TBC life, whereas the Ni-16Cr-6Al-0.3Y alloy had the lowest weight gains and provided the shortest TBC life. The results show that, although bond coat oxidation is known to have a strong detrimental effect on TBC life, it is not the only bond coat factor that determines TBC life.

  2. Thermal barrier coating life and isothermal oxidation of low-pressure plasma-sprayed bond coat alloys

    NASA Technical Reports Server (NTRS)

    Brindley, W. J.; Miller, R. A.

    1990-01-01

    The paper investigates the isothermal oxidation kinetics of Ni-35Cr-6Al-0.95Y, Ni-18Cr-12Al-0.3Y, and Ni-16Cr-6Al-0.3Y low-pressure plasma-sprayed bond coat alloys and examines the effect of these alloys on the thermal barrier coating (TBC) cyclic life. TBC life was examined by cycling substrates coated with the different bond coats and a ZrO2-7 wt pct Y2O3 TBC in an air-rich burner rig flame between 1150 C and room temperature. The oxidation kinetics of the three bond coat alloys was examined by isothermal oxidation of monolithic NJiCrAlY coupons at 1083 C. The Ni-35Cr-6Al-0.95Y alloy exhibits comparatively high isothermal oxidation weight gains and provides the longest TBC life, whereas the Ni-16Cr-6Al-0.3Y alloy had the lowest weight gains and provided the shortest TBC life. The results show that, although bond coat oxidation is known to have a strong detrimental effect on TBC life, it is not the only bond coat factor that determines TBC life.

  3. Size-dependent magnetic properties of iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Patsula, Vitalii; Moskvin, Maksym; Dutz, Silvio; Horák, Daniel

    2016-01-01

    Uniform iron oxide nanoparticles in the size range from 10 to 24 nm and polydisperse 14 nm iron oxide particles were prepared by thermal decomposition of Fe(III) carboxylates in the presence of oleic acid and co-precipitation of Fe(II) and Fe(III) chlorides by ammonium hydroxide followed by oxidation, respectively. While the first method produced hydrophobic oleic acid coated particles, the second one formed hydrophilic, but uncoated, nanoparticles. To make the iron oxide particles water dispersible and colloidally stable, their surface was modified with poly(ethylene glycol) and sucrose, respectively. Size and size distribution of the nanoparticles was determined by transmission electron microscopy, dynamic light scattering and X-ray diffraction. Surface of the PEG-functionalized and sucrose-modified iron oxide particles was characterized by Fourier transform infrared (FT-IR) and Raman spectroscopy and thermogravimetric analysis (TGA). Magnetic properties were measured by means of vibration sample magnetometry and specific absorption rate in alternating magnetic fields was determined calorimetrically. It was found, that larger ferrimagnetic particles showed higher heating performance than smaller superparamagnetic ones. In the transition range between superparamagnetism and ferrimagnetism, samples with a broader size distribution provided higher heating power than narrow size distributed particles of comparable mean size. Here presented particles showed promising properties for a possible application in magnetic hyperthermia.

  4. Effect of barrier properties of zein colloidal particles and oil-in-water emulsions on oxidative stability of encapsulated bioactive compounds

    USDA-ARS?s Scientific Manuscript database

    Oxidation of encapsulated bioactive compounds is a key challenge that limits shelf-life of bioactive containing products. The objectives of this study were to compare differences between the oxidative barrier properties of biopolymer particle based encapsulation system (zein colloidal particles) and...

  5. Nitric oxide synthase-dependent nitric oxide production is associated with salt tolerance in Arabidopsis.

    PubMed

    Zhao, Min-Gui; Tian, Qiu-Ying; Zhang, Wen-Hao

    2007-05-01

    Nitric oxide (NO) has emerged as a key molecule involved in many physiological processes in plants. To characterize roles of NO in tolerance of Arabidopsis (Arabidopsis thaliana) to salt stress, effect of NaCl on Arabidopsis wild-type and mutant (Atnoa1) plants with an impaired in vivo NO synthase (NOS) activity and a reduced endogenous NO level was investigated. Atnoa1 mutant plants displayed a greater Na+ to K+ ratio in shoots than wild-type plants due to enhanced accumulation of Na+ and reduced accumulation of K+ when exposed to NaCl. Germination of Atnoa1 seeds was more sensitive to NaCl than that of wild-type seeds, and wild-type plants exhibited higher survival rates than Atnoa1 plants when grown under salt stress. Atnoa1 plants had higher levels of hydrogen peroxide than wild-type plants under both control and salt stress, suggesting that Atnoa1 is more vulnerable to salt and oxidative stress than wild-type plants. Treatments of wild-type plants with NOS inhibitor and NO scavenger reduced endogenous NO levels and enhanced NaCl-induced increase in Na+ to K+ ratio. Exposure of wild-type plants to NaCl inhibited NOS activity and reduced quantity of NOA1 protein, leading to a decrease in endogenous NO levels measured by NO-specific fluorescent probe. Treatment of Atnoa1 plants with NO donor sodium nitroprusside attenuated the NaCl-induced increase in Na+ to K+ ratio. Therefore, these findings provide direct evidence to support that disruption of NOS-dependent NO production is associated with salt tolerance in Arabidopsis.

  6. Size dependence of inter- and intra-cluster interactions in core-shell iron-iron oxide nanoclusters

    SciTech Connect

    Kaur, Maninder; McCloy, John S.; Jiang, Weilin; Yao, Qi; Qiang, You

    2012-06-15

    The room temperature magnetic properties of core-shell iron-iron oxide nanoclusters (NCs) synthesized by a cluster deposition system have been investigated, and their dependence on mean cluster size has been discussed. In this study, the surface/boundary spins of clusters were not frozen and were thermally activated during the measurements. The inter-cluster interactions between clusters and intra-cluster interactions between the iron core (ferromagnetic) and iron oxide shell (ferrimagnetic) have been investigated by field dependent isothermal remanent magnetization and dc demagnetization measurements at room temperature. The Henkel plot and delta M plot support the existence of dipolar inter-cluster interactions which become stronger with the growth of cluster size. The derivative of the initial magnetization curve implies that smaller clusters require less field and time than the bigger ones to overcome various energy barriers before aligning along the field direction. Coercive field and magnetization are also correlated with the interaction parameters. To compare the room temperature magnetic results, one system was studied at low temperature, where exchange coupling at the interface between the oxide and metallic phases was observed through bias effect and anisotropy enhancement.

  7. Obesity in Aging Exacerbates Blood–Brain Barrier Disruption, Neuroinflammation, and Oxidative Stress in the Mouse Hippocampus: Effects on Expression of Genes Involved in Beta-Amyloid Generation and Alzheimer’s Disease

    PubMed Central

    Tucsek, Zsuzsanna; Toth, Peter; Sosnowska, Danuta; Gautam, Tripti; Mitschelen, Matthew; Koller, Akos; Szalai, Gabor; Sonntag, William E.; Csiszar, Anna

    2014-01-01

    There is growing evidence that obesity has deleterious effects on the brain and cognitive function in the elderly population. However, the specific mechanisms through which aging and obesity interact to promote cognitive decline remain unclear. To test the hypothesis that aging exacerbates obesity-induced cerebromicrovascular damage and neuroinflammation, we compared young (7 months) and aged (24 months) high fat diet–fed obese C57BL/6 mice. Aging exacerbated obesity-induced systemic inflammation and blood–brain barrier disruption, as indicated by the increased circulating levels of proinflammatory cytokines and increased presence of extravasated immunoglobulin G in the hippocampus, respectively. Obesity-induced blood–brain barrier damage was associated with microglia activation, upregulation of activating Fc-gamma receptors and proinflammatory cytokines, and increased oxidative stress. Treatment of cultured primary microglia with sera derived from aged obese mice resulted in significantly more pronounced microglia activation and oxidative stress, as compared with treatment with young sera. Serum-induced activation and oxidative stress were also exacerbated in primary microglia derived from aged animals. Hippocampal expression of genes involved in regulation of the cellular amyloid precursor protein–dependent signaling pathways, beta-amyloid generation, and the pathogenesis of tauopathy were largely unaffected by obesity in aged mice. Collectively, obesity in aging is associated with a heightened state of systemic inflammation, which exacerbates blood–brain barrier disruption. The resulting neuroinflammation and oxidative stress in the mouse hippocampus likely contribute to the significant cognitive decline observed in aged obese animals. PMID:24269929

  8. Commensal Bacteria-Dependent Indole Production Enhances Epithelial Barrier Function in the Colon

    PubMed Central

    Shimada, Yosuke; Kinoshita, Makoto; Harada, Kazuo; Mizutani, Masafumi; Masahata, Kazunori; Kayama, Hisako; Takeda, Kiyoshi

    2013-01-01

    Microbiota have been shown to have a great influence on functions of intestinal epithelial cells (ECs). The role of indole as a quorum-sensing (QS) molecule mediating intercellular signals in bacteria has been well appreciated. However, it remains unknown whether indole has beneficial effects on maintaining intestinal barriers in vivo. In this study, we analyzed the effect of indole on ECs using a germ free (GF) mouse model. GF mice showed decreased expression of junctional complex molecules in colonic ECs. The feces of specific pathogen-free (SPF) mice contained a high amount of indole; however the amount was significantly decreased in the feces of GF mice by 27-fold. Oral administration of indole-containing capsules resulted in increased expression of both tight junction (TJ)- and adherens junction (AJ)-associated molecules in colonic ECs in GF mice. In accordance with the increased expression of these junctional complex molecules, GF mice given indole-containing capsules showed higher resistance to dextran sodium sulfate (DSS)-induced colitis. A similar protective effect of indole on DSS-induced epithelial damage was also observed in mice bred in SPF conditions. These findings highlight the beneficial role of indole in establishing an epithelial barrier in vivo. PMID:24278294

  9. Skin Barrier Development Depends on CGI-58 Protein Expression during Late-Stage Keratinocyte Differentiation.

    PubMed

    Grond, Susanne; Radner, Franz P W; Eichmann, Thomas O; Kolb, Dagmar; Grabner, Gernot F; Wolinski, Heimo; Gruber, Robert; Hofer, Peter; Heier, Christoph; Schauer, Silvia; Rülicke, Thomas; Hoefler, Gerald; Schmuth, Matthias; Elias, Peter M; Lass, Achim; Zechner, Rudolf; Haemmerle, Guenter

    2017-02-01

    Adipose triglyceride lipase (ATGL) and its coactivator comparative gene identification-58 (CGI-58) are limiting in cellular triglyceride catabolism. Although ATGL deficiency is compatible with normal skin development, mice globally lacking CGI-58 die postnatally and exhibit a severe epidermal permeability barrier defect, which may originate from epidermal and/or peripheral changes in lipid and energy metabolism. Here, we show that epidermis-specific disruption of CGI-58 is sufficient to provoke a defect in the formation of a functional corneocyte lipid envelope linked to impaired ω-O-acylceramide synthesis. As a result, epidermis-specific CGI-58-deficient mice show severe skin dysfunction, arguing for a tissue autonomous cause of disease development. Defective skin permeability barrier formation in global CGI-58-deficient mice could be reversed via transgenic restoration of CGI-58 expression in differentiated but not basal keratinocytes suggesting that CGI-58 is essential for lipid metabolism in suprabasal epidermal layers. The compatibility of ATGL deficiency with normal epidermal function indicated that CGI-58 may stimulate an epidermal triglyceride lipase beyond ATGL required for the adequate provision of fatty acids as a substrate for ω-O-acylceramide synthesis. Pharmacological inhibition of ATGL enzyme activity similarly reduced triglyceride-hydrolytic activities in wild-type and CGI-58 overexpressing epidermis implicating that CGI-58 participates in ω-O-acylceramide biogenesis independent of its role as a coactivator of epidermal triglyceride catabolism. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  10. Muscle oxidative capacity during IL-6-dependent cancer cachexia

    PubMed Central

    White, James P.; Baltgalvis, Kristen A.; Puppa, Melissa J.; Sato, Shuichi; Baynes, John W.

    2011-01-01

    Many diseases are associated with catabolic conditions that induce skeletal muscle wasting. These various catabolic states may have similar and distinct mechanisms for inducing muscle protein loss. Mechanisms related to muscle wasting may also be related to muscle metabolism since glycolytic muscle fibers have greater wasting susceptibility with several diseases. The purpose of this study was to determine the relationship between muscle oxidative capacity and muscle mass loss in red and white hindlimb muscles during cancer cachexia development in the ApcMin/+ mouse. Gastrocnemius and soleus muscles were excised from ApcMin/+ mice at 20 wk of age. The gastrocnemius muscle was partitioned into red and white portions. Body mass (−20%), gastrocnemius muscle mass (−41%), soleus muscle mass (−34%), and epididymal fat pad (−100%) were significantly reduced in severely cachectic mice (n = 8) compared with mildly cachectic mice (n = 6). Circulating IL-6 was fivefold higher in severely cachectic mice. Cachexia significantly reduced the mitochondrial DNA-to-nuclear DNA ratio in both red and white portions of the gastrocnemius. Cytochrome c and cytochrome-c oxidase complex subunit IV (Cox IV) protein were reduced in all three muscles with severe cachexia. Changes in muscle oxidative capacity were not associated with altered myosin heavy chain expression. PGC-1α expression was suppressed by cachexia in the red and white gastrocnemius and soleus muscles. Cachexia reduced Mfn1 and Mfn2 mRNA expression and markers of oxidative stress, while Fis1 mRNA was increased by cachexia in all muscle types. Muscle oxidative capacity, mitochondria dynamics, and markers of oxidative stress are reduced in both oxidative and glycolytic muscle with severe wasting that is associated with increased circulating IL-6 levels. PMID:21148472

  11. Temperature dependent electrical characteristics of Pt Schottky barriers fabricated on lightly and highly doped n-type 4H-SiC

    NASA Astrophysics Data System (ADS)

    Huang, Lingqin; Wang, Dejun

    2015-11-01

    The temperature dependent electronic characteristics of Pt Schottky barriers fabricated on lightly and relatively highly doped n-type 4H-SiC (1 × 1016 and 1 × 1018 cm-3) are comparatively investigated. It is found that the abnormal temperature dependence of barrier height and ideality factor estimated from the thermionic emission (TE) model for both lightly and highly doped samples could be successfully explained in terms of Gaussian distribution of inhomogeneous barrier heights. However, the estimated mean barrier height according to Gaussian distribution for the highly doped sample is much lower than the actual mean value from the capacitance-voltage (C-V) measurements. Interestingly, the values of barrier height from the thermionic field emission (TFE) model are found to be close to those from the C-V measurements, indicating that the TFE model is more appropriate to explain the electrical transport for the highly doped sample.

  12. Role of humic substances in promoting autotrophic growth in nitrate-dependent iron-oxidizing bacteria.

    PubMed

    Kanaparthi, Dheeraj; Conrad, Ralf

    2015-05-01

    Nitrate-dependent iron oxidation was discovered in 1996 and has been reported from various environments ever since. To date, despite the widespread nature of this process, all attempts to cultivate chemolithoautotrophic nitrate-dependent iron oxidizers have been unsuccessful. The present study was focused on understanding the influence of natural chelating agents of iron, like humic substances, on the culturability, activity, and enumeration, of these microorganisms. Pure culture studies conducted with Thiobacillus denitrificans showed a constant increase in cell mass with a corresponding nitrate-dependent iron oxidation activity only when Fe(II) was provided together with humic substances, compared to no growth in control incubations without humic substances. The presence of a relatively strong chelating agent, such as EDTA, inhibited the growth of Thiobacillus denitrificans. It was concluded that complex formation between humic substances and iron was required for chemolithoautotrophic nitrate-dependent iron oxidation. Most probable number enumerations showed that numbers of chemolithoautotrophic nitrate-dependent iron-oxidizing bacteria were one to three orders of magnitude higher in the presence of humic substances compared to media without. Similar results were obtained when potential nitrate-dependent iron oxidation activity was determined in soil samples. In summary, this study showed that humic substances significantly enhanced the growth and activity of autotrophic nitrate-dependent iron-oxidizing microorganisms, probably by chelation of iron. Copyright © 2015 Elsevier GmbH. All rights reserved.

  13. ALD grown bilayer junction of ZnO:Al and tunnel oxide barrier for SIS solar cell☆

    PubMed Central

    Bethge, O.; Nobile, M.; Abermann, S.; Glaser, M.; Bertagnolli, E.

    2013-01-01

    Various metal oxides are probed as extrinsic thin tunnel barriers in Semiconductor Insulator Semiconductor solar cells. Namely Al2O3, ZrO2, Y2O3, and La2O3 thin films are in between n-type ZnO:Al (AZO) and p-type Si substrates by means of Atomic Layer Deposition. Low reverse dark current–density as low as 3×10−7 A/cm2, a fill factor up to 71.3%, and open-circuit voltage as high as 527 mV are obtained, achieving conversion efficiency of 8% for the rare earth oxide La2O3. ZrO2 and notably Al2O3 show drawbacks in performance suggesting an adverse reactivity with AZO as also indicated by X-ray Photoelectron Spectroscopy. PMID:26877596

  14. Characterization of aluminum oxide tunnel barriers by combining transport measurements and transmission electron microscopy imaging

    SciTech Connect

    Aref, T.; Averin, A.; Nguyend, H. Q.; Pekola, J. P.; Dijken, S. van; Yao, L. D.; Ferring, A.; Koberidze, M.; Nieminen, R. M.

    2014-08-21

    We present two approaches for studying the uniformity of a tunnel barrier. The first approach is based on measuring single-electron and two-electron tunneling in a hybrid single-electron transistor. Our measurements indicate that the effective area of a conduction channel is about one order of magnitude larger than predicted by theoretical calculations. With the second method, transmission electron microscopy, we demonstrate that variations in the barrier thickness are a plausible explanation for the larger effective area and an enhancement of higher order tunneling processes.

  15. Metabolically dependent blood-brain barrier breakdown in chronic relapsing experimental allergic encephalomyelitis.

    PubMed

    Hawkins, C P; Munro, P M; Landon, D N; McDonald, W I

    1992-01-01

    We have studied chronic relapsing experimental allergic encephalomyelitis (CREAE), a model of immune-mediated demyelination, using gadolinium (Gd)-enhanced magnetic resonance imaging in vivo and the blood-brain barrier (BBB) markers, lanthanum nitrate and Gd nitrate, histologically. In regions of the spinal cord showing Gd enhancement, there was evidence for vesicular transport as a mechanism of BBB breakdown in CREAE, shown by an increased number of endothelial vesicles containing lanthanide (lanthanum or Gd, whichever had been perfused) and deposition of tracer in the perivascular space; tight interendothelial junctions remained intact. Prior perfusion with 2,4-dinitrophenol, a metabolic inhibitor, suppressed the appearance of endothelial vesicles containing lanthanide and tracer in the perivascular space. We conclude that an important contribution to BBB breakdown in CREAE is mediated by a metabolic change in the endothelial cells associated with increased vesicular transport.

  16. Temperature-dependent hydration at micellar surface: activation energy barrier crossing model revisited.

    PubMed

    Mitra, Rajib Kumar; Sinha, Sudarson Sekhar; Pal, Samir Kumar

    2007-07-05

    In recent years, the validity of the activation energy barrier crossing model at the micellar surface brings notable controversy (Sen, P.; Mukherjee, S.; Halder, A.; Bhattacharyya, K. Chem. Phys. Lett. 2004, 385, 357-361. Kumbhakar, M.; Goel, T.; Mukherjee, T.; Pal, H. J. Phys. Chem. B 2004, 108, 19246-19254.) in the literature. In order to check the validity of the model by time-resolved solvation of a probe fluorophore, a wider range of temperature must be considered. At the same time, spatial heterogeneity (solubilization) of the probe and structural perturbation of the host micelle should carefully be avoided, which was not strictly maintained in the earlier studies. We report here the solvation dynamics of 4-(dicyanomethylene)-2-methyl-6(p-dimethylamino-styryl) 4H-pyran (DCM) in the SDS micelle at 298, 323, and 348 K. The probe DCM is completely insoluble in bulk water in this wide range of temperature. The size of the micelle at different temperatures using the dynamic light scattering (DLS) technique is found to have insignificant change. The hydration number of the micelle, determined by sound velocity measurements, decreases with increasing temperature. Time-resolved fluorescence anisotropy reveals the retention of the probe in the micellar interface within the temperature range. The average solvation time decreases with increasing temperature. The result of the solvation study has been analyzed in the light of energetics of bound to free water conversion at a constant size and decreasing hydration number at the micellar surface. The solvation process at the micellar surface has been found to be the activation energy barrier crossing type, in which interfacially bound type water molecules get converted into free type molecules. We have calculated Ea to be 3.5 kcal mol-1, which is in good agreement with that obtained by molecular dynamics simulation studies.

  17. Borate cross-linking chitosan/graphene oxide films: Toward the simultaneous enhancement of gases barrier and mechanical properties

    NASA Astrophysics Data System (ADS)

    Yan, Ning; Capezzuto, Filomena; Buonocore, Giovanna G.; Tescione, Fabiana; Lavorgna, Marino; Xia, Hesheng; Ambrosio, Luigi

    2015-12-01

    Borate adducts, originated from hydrolysis of sodium tetraborate decahydrate (borax), have been used to crosslink chitosan (CS) and graphene oxide (GO) nanosheets for the production of innovative composite sustainable materials. CS/GO film consisting of 10wt% borax and 1wt% GO exhibits a significant improvement of both toughness and oxygen barrier properties in comparison to pristine chitosan. In particular the tensile strength increases by about 100% and 150% after thermal annealing of samples at 90°C for 50min whereas the oxygen permeability reduces of about 90% compared to pristine chitosan. The enhancement of both mechanical and barrier properties is ascribed to the formation of a resistant network due to the chemical crosslinking, including borate orthoester bonds and hydroxyl moieties complexes, formed among borate ions, chitosan, and GO nanoplatelets. The crosslinked graphene-based chitosan material with its enhanced mechanical and barrier properties may significantly broad the range of applications of chitosan based-materials which presently are very limited and addressed only to packaging.

  18. Probiotics ameliorate the hydrogen peroxide-induced epithelial barrier disruption by a PKC- and MAP kinase-dependent mechanism.

    PubMed

    Seth, A; Yan, Fang; Polk, D Brent; Rao, R K

    2008-04-01

    Probiotics promote intestinal epithelial integrity and reduce infection and diarrhea. We evaluated the effect of Lactobacillus rhamnosus GG-produced soluble proteins (p40 and p75) on the hydrogen peroxide-induced disruption of tight junctions and barrier function in Caco-2 cell monolayers. Pretreatment of cell monolayers with p40 or p75 attenuated the hydrogen peroxide-induced decrease in transepithelial resistance and increase in inulin permeability in a time- and dose-dependent manner. p40 and p75 also prevented hydrogen peroxide-induced redistribution of occludin, ZO-1, E-cadherin, and beta-catenin from the intercellular junctions and their dissociation from the detergent-insoluble fractions. Both p40 and p75 induced a rapid increase in the membrane translocation of PKCbetaI and PKCepsilon. The attenuation of hydrogen peroxide-induced inulin permeability and redistribution of tight junction proteins by p40 and p75 was abrogated by Ro-32-0432, a PKC inhibitor. p40 and p75 also rapidly increased the levels of phospho-ERK1/2 in the detergent-insoluble fractions. U0126 (a MAP kinase inhibitor) attenuated the p40- and p75-mediated reduction of hydrogen peroxide-induced tight junction disruption and inulin permeability. These studies demonstrate that probiotic-secretory proteins protect the intestinal epithelial tight junctions and the barrier function from hydrogen peroxide-induced insult by a PKC- and MAP kinase-dependent mechanism.

  19. Probiotics ameliorate the hydrogen peroxide-induced epithelial barrier disruption by a PKC- and MAP kinase-dependent mechanism

    PubMed Central

    Seth, A.; Yan, Fang; Polk, D.Brent; Rao, R. K.

    2009-01-01

    Probiotics promote intestinal epithelial integrity and reduce infection and diarrhea. We evaluated the effect of Lactobacillus rhamnosus GG-produced soluble proteins (p40 and p75) on the hydrogen peroxide-induced disruption of tight junctions and barrier function in Caco-2 cell monolayers. Pretreatment of cell monolayers with p40 or p75 attenuated the hydrogen peroxide-induced decrease in transepithelial resistance and increase in inulin permeability in a time- and dose-dependent manner. p40 and p75 also prevented hydrogen peroxide-induced redistribution of occludin, ZO-1, E-cadherin, and β-catenin from the intercellular junctions and their dissociation from the detergent-insoluble fractions. Both p40 and p75 induced a rapid increase in the membrane translocation of PKCβI and PKCε. The attenuation of hydrogen peroxide-induced inulin permeability and redistribution of tight junction proteins by p40 and p75 was abrogated by Ro-32-0432, a PKC inhibitor. p40 and p75 also rapidly increased the levels of phospho-ERK1/2 in the detergent-insoluble fractions. U0126 (a MAP kinase inhibitor) attenuated the p40- and p75-mediated reduction of hydrogen peroxide-induced tight junction disruption and inulin permeability. These studies demonstrate that probiotic-secretory proteins protect the intestinal epithelial tight junctions and the barrier function from hydrogen peroxide-induced insult by a PKC- and MAP kinase-dependent mechanism. PMID:18292183

  20. Communication: Transition state trajectory stability determines barrier crossing rates in chemical reactions induced by time-dependent oscillating fields.

    PubMed

    Craven, Galen T; Bartsch, Thomas; Hernandez, Rigoberto

    2014-07-28

    When a chemical reaction is driven by an external field, the transition state that the system must pass through as it changes from reactant to product--for example, an energy barrier--becomes time-dependent. We show that for periodic forcing the rate of barrier crossing can be determined through stability analysis of the non-autonomous transition state. Specifically, strong agreement is observed between the difference in the Floquet exponents describing stability of the transition state trajectory, which defines a recrossing-free dividing surface [G. T. Craven, T. Bartsch, and R. Hernandez, "Persistence of transition state structure in chemical reactions driven by fields oscillating in time," Phys. Rev. E 89, 040801(R) (2014)], and the rates calculated by simulation of ensembles of trajectories. This result opens the possibility to extract rates directly from the intrinsic stability of the transition state, even when it is time-dependent, without requiring a numerically expensive simulation of the long-time dynamics of a large ensemble of trajectories.

  1. Cultured cells of the blood-brain barrier from apolipoprotein B-100 transgenic mice: effects of oxidized low-density lipoprotein treatment.

    PubMed

    Lénárt, Nikolett; Walter, Fruzsina R; Bocsik, Alexandra; Sántha, Petra; Tóth, Melinda E; Harazin, András; Tóth, Andrea E; Vizler, Csaba; Török, Zsolt; Pilbat, Ana-Maria; Vígh, László; Puskás, László G; Sántha, Miklós; Deli, Mária A

    2015-07-17

    The apolipoprotein B-100 (ApoB-100) transgenic mouse line is a model of human atherosclerosis. Latest findings suggest the importance of ApoB-100 in the development of neurodegenerative diseases and microvascular/perivascular localization of ApoB-100 protein was demonstrated in the cerebral cortex of ApoB-100 transgenic mice. The aim of the study was to characterize cultured brain endothelial cells, pericytes and glial cells from wild-type and ApoB-100 transgenic mice and to study the effect of oxidized low-density lipoprotein (oxLDL) on these cells. Morphology of cells isolated from brains of wild type and ApoB-100 transgenic mice was characterized by immunohistochemistry and the intensity of immunolabeling was quantified by image analysis. Toxicity of oxLDL treatment was monitored by real-time impedance measurement and lactate dehydrogenase release. Reactive oxygen species and nitric oxide production, barrier permeability in triple co-culture blood-brain barrier model and membrane fluidity were also determined after low-density lipoprotein (LDL) or oxLDL treatment. The presence of ApoB-100 was confirmed in brain endothelial cells, while no morphological change was observed between wild type and transgenic cells. Oxidized but not native LDL exerted dose-dependent toxicity in all three cell types, induced barrier dysfunction and increased reactive oxygen species (ROS) production in both genotypes. A partial protection from oxLDL toxicity was seen in brain endothelial and glial cells from ApoB-100 transgenic mice. Increased membrane rigidity was measured in brain endothelial cells from ApoB-100 transgenic mice and in LDL or oxLDL treated wild type cells. The morphological and functional properties of cultured brain endothelial cells, pericytes and glial cells from ApoB-100 transgenic mice were characterized and compared to wild type cells for the first time. The membrane fluidity changes in ApoB-100 transgenic cells related to brain microvasculature indicate

  2. Dimensionality dependent water splitting mechanisms on free manganese oxide clusters.

    PubMed

    Lang, Sandra M; Fleischer, Irene; Bernhardt, Thorsten M; Barnett, Robert N; Landman, Uzi

    2013-01-01

    The interaction of ligand-free manganese oxide nanoclusters with water is investigated, aiming at uncovering phenomena which could aid the design of artificial water-splitting molecular catalysts. Gas phase measurements in an ion trap in conjunction with first-principles calculations provide new mechanistic insight into the water splitting process mediated by bi- and tetra-nuclear singly charged manganese oxide clusters, Mn2O2(+) and Mn4O4(+). In particular, a water-induced dimensionality change of Mn4O4(+) is predicted, entailing transformation from a two-dimensional ring-like ground state structure of the bare cluster to a cuboidal octa-hydroxy-complex for the hydrated one. It is further predicted that the water splitting process is facilitated by the cluster dimensionality crossover. The vibrational spectra calculated for species occurring along the predicted pathways of the reaction of Mn4O4(+) with water provide the impetus for future explorations, including vibrational spectroscopic experiments.

  3. A dielectric barrier discharge terminally inactivates RNase A by oxidizing sulfur-containing amino acids and breaking structural disulfide bonds

    NASA Astrophysics Data System (ADS)

    Lackmann, J.-W.; Baldus, S.; Steinborn, E.; Edengeiser, E.; Kogelheide, F.; Langklotz, S.; Schneider, S.; Leichert, L. I. O.; Benedikt, J.; Awakowicz, P.; Bandow, J. E.

    2015-12-01

    RNases are among the most stable proteins in nature. They even refold spontaneously after heat inactivation, regaining full activity. Due to their stability and universal presence, they often pose a problem when experimenting with RNA. We investigated the capabilities of nonthermal atmospheric-pressure plasmas to inactivate RNase A and studied the inactivation mechanism on a molecular level. While prolonged heating above 90 °C is required for heat inactivating RNase A, direct plasma treatment with a dielectric barrier discharge (DBD) source caused permanent inactivation within minutes. Circular dichroism spectroscopy showed that DBD-treated RNase A unfolds rapidly. Raman spectroscopy indicated methionine modifications and formation of sulfonic acid. A mass spectrometry-based analysis of the protein modifications that occur during plasma treatment over time revealed that methionine sulfoxide formation coincides with protein inactivation. Chemical reduction of methionine sulfoxides partially restored RNase A activity confirming that sulfoxidation is causal and sufficient for RNase A inactivation. Continued plasma exposure led to over-oxidation of structural disulfide bonds. Using antibodies, disulfide bond over-oxidation was shown to be a general protein inactivation mechanism of the DBD. The antibody’s heavy and light chains linked by disulfide bonds dissociated after plasma exposure. Based on their ability to inactivate proteins by oxidation of sulfur-containing amino acids and over-oxidation of disulfide bonds, DBD devices present a viable option for inactivating undesired or hazardous proteins on heat or solvent-sensitive surfaces.

  4. Anisotropic spin-dependent electron tunneling in a triple-barrier resonant tunneling diode

    NASA Astrophysics Data System (ADS)

    Isić, Goran; Radovanović, Jelena; Milanović, Vitomir

    2007-12-01

    The one-band envelope function approximation is used to investigate the spin-dependent tunneling of conduction band electrons in semiconductor heterostructures when both the bulk inversion asymmetry (BIA) and structure inversion asymmetry (SIA) are present. It is shown that under certain conditions the interplay between BIA and SIA may be used to induce a strong dependence of transmission probabilities on the direction of electrons lateral momenta thus offering means to improve the existing designs of nonmagnetic semiconductor spin filters.

  5. Histidine oxidation photosensitized by pterin: pH dependent mechanism.

    PubMed

    Castaño, Carolina; Oliveros, Esther; Thomas, Andrés H; Lorente, Carolina

    2015-12-01

    Aromatic pterins accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder, due to the oxidation of tetrahydrobiopterin, the biologically active form of pterins. In this work, we have investigated the ability of pterin, the parent compound of aromatic pterins, to photosensitize the oxidation of histidine in aqueous solutions under UV-A irradiation. Histidine is an α-amino acid with an imidazole functional group, and is frequently present at the active sites of enzymes. The results highlight the role of the pH in controlling the competition between energy and electron transfer mechanisms. It has been previously demonstrated that pterins participate as sensitizers in photosensitized oxidations, both by type I (electron-transfer) and type II mechanisms (singlet oxygen ((1)O2)). By combining different analytical techniques, we could establish that a type I photooxidation was the prevailing mechanism at acidic pH, although a type II mechanism is also present, but it is more important in alkaline solutions.

  6. Texture-dependent anaerobic microsites constrain soil carbon oxidation rates

    NASA Astrophysics Data System (ADS)

    Keiluweit, Marco; Fendorf, Scott

    2016-04-01

    Soil texture, which is a product of parent material, climate and other soil forming factors, is a predictor for long-term storage of soil organic carbon (SOC) storage in many soil ecosystems. Positive correlation between texture (particularly clay content) and SOC storage have long been attributed to protective associations between clay minerals and organic compounds that prevent microbial and enzymatic access - a mechanism commonly referred to as 'mineral protection'. Texture therefore acts as the primary proxy for mineral protection in terrestrial ecosystem models used to assess SOC storage and its sensitivity to global change impacts. Here we show that this protective effect of texture is not only due to mineral protection, but also to the formation of anaerobic microsites. Combining micro-scale laboratory experiments with field-scale observations, we find that oxygen diffusion limitations within clay-rich domains create anaerobic microsites within seemingly well-aerated soils, shifting microbial metabolism to less efficient anaerobic SOC oxidation pathways. Kinetic and thermodynamic constraints reduce SOC oxidation rates within these anaerobic microsites by an order of magnitude relative to aerobic rates, and caused the preservation of bioavailable, polymeric and reduced organic compounds. Lifting these metabolic constraints through increased soil aeration (e.g., through changes in precipitation patterns or land use) may stimulate microbial oxidation of this inherently bioavailable SOC pool. Models that attribute the effects of texture merely to 'mineral protection' may therefore underestimate the vulnerability of soil C to global change impacts.

  7. Size- and composition-dependent radio frequency magnetic permeability of iron oxide nanocrystals.

    PubMed

    Yun, Hongseok; Liu, Xiyu; Paik, Taejong; Palanisamy, Duraivelan; Kim, Jungkwun; Vogel, William D; Viescas, Arthur J; Chen, Jun; Papaefthymiou, Georgia C; Kikkawa, James M; Allen, Mark G; Murray, Christopher B

    2014-12-23

    We investigate the size- and composition-dependent ac magnetic permeability of superparamagnetic iron oxide nanocrystals for radio frequency (RF) applications. The nanocrystals are obtained through high-temperature decomposition synthesis, and their stoichiometry is determined by Mössbauer spectroscopy. Two sets of oxides are studied: (a) as-synthesized magnetite-rich and (b) aged maghemite nanocrystals. All nanocrystalline samples are confirmed to be in the superparamagnetic state at room temperature by SQUID magnetometry. Through the one-turn inductor method, the ac magnetic properties of the nanocrystalline oxides are characterized. In magnetite-rich iron oxide nanocrystals, size-dependent magnetic permeability is not observed, while maghemite iron oxide nanocrystals show clear size dependence. The inductance, resistance, and quality factor of hand-wound inductors with a superparamagnetic composite core are measured. The superparamagnetic nanocrystals are successfully embedded into hand-wound inductors to function as inductor cores.

  8. Size- and Composition-Dependent Radio Frequency Magnetic Permeability of Iron Oxide Nanocrystals

    SciTech Connect

    Yun, H; Liu, XY; Paik, T; Palanisamy, D; Kim, J; Vogel, WD; Viescas, AJ; Chen, J; Papaefthymiou, GC; Kikkawa, JM; Allen, MG; Murray, CB

    2014-12-01

    We investigate the size- and composition-dependent ac magnetic permeability of superparamagnetic iron oxide nanocrystals for radio frequency (RF) applications. The nanocrystals are obtained through high-temperature decomposition synthesis, and their stoichiometry is determined by Mossbauer spectroscopy. Two sets of oxides are studied: (a) as-synthesized magnetite-rich and (b) aged maghemite nanocrystals. All nanocrystalline samples are confirmed to be in the superparamagnetic state at room temperature by SQUID magnetometry. Through the one-turn inductor method, the ac magnetic properties of the nanocrystalline oxides are characterized. In magnetite-rich iron oxide nanocrystals, size-dependent magnetic permeability is not observed, while maghemite iron oxide nanocrystals show clear size dependence. The inductance, resistance, and quality factor of hand-wound inductors with a superparamagnetic composite core are measured. The superparamagnetic nanocrystals are successfully embedded into hand-wound inductors to function as inductor cores.

  9. Inhibition of vitamin B12-dependent microbial growth by nitrous oxide

    SciTech Connect

    Alston, T.A. )

    1991-01-01

    In methionine-free media, nitrous oxide inhibits the growth of an auxotrophic strain of Escherichia coli lacking a cobalamin-independent pathway for the de novo synthesis of methionine. Prototrophic E. coli is similarly inhibited by nitrous oxide if the cobalamin-independent pathway is selectively depressed by sulfanilamide. Nitrous oxide thus effectively inactivates cobalamin-dependent 5-methyltetrahydrofolate-homocysteine methyltransferase in intact bacteria.

  10. 3-O-Laurylglyceryl ascorbate reinforces skin barrier function through not only the reduction of oxidative stress but also the activation of ceramide synthesis.

    PubMed

    Katsuyama, Y; Taira, N; Tsuboi, T; Yoshioka, M; Masaki, H; Muraoka, O

    2017-02-01

    A higher trans-epidermal water loss (TEWL) occurs in rough skin, in elder skin and also in atopic dermatitis. An impaired skin barrier function is considered to be caused by an incomplete construction of the intercellular lamellar structure due to the quantitative reduction of ceramides. Since these symptoms coexist with oxidative stress, we hypothesized that impairment of the skin barrier function is accelerated by oxidative stress. Thus, the purpose of this study was to clarify the effect of oxidative stress on ceramide synthesis and to characterize whether antioxidants can improve skin barrier function. 3-O-Laurylglyceryl ascorbate (VC-3LG), which is a newly amphipathic derivative of ascorbic acid, was evaluated as a candidate antioxidant. We characterized the mRNA expression levels of serine palmitoyltransferase (SPT) in normal human epidermal keratinocytes (NHEKs) treated with H2 O2 using real-time PCR analysis. In order to evaluate the effect of VC-3LG on skin barrier function, we used several assays with reconstructed human epidermis equivalents (RHEEs). Ceramide synthesis was down-regulated in NHEKs by oxidative stress. Treatment with VC-3LG abrogated the down-regulation of SPT mRNA in NHEKs caused by oxidative stress, and stimulated SPT mRNA expression levels. In experiments characterizing the antioxidative properties of VC-3LG, VC-3LG reduced oxidative stress in NHEKs by up-regulating catalase mRNA expression. In addition, VC-3LG stimulated the skin barrier function in RHEEs, which had lower TEWL values compared with untreated RHEEs. Furthermore, VC-3LG increased the quantity of ceramide in RHEEs. Taken together, we conclude that VC-3LG reinforces the skin barrier function due to its reduction of oxidative stress and its promotion of ceramide synthesis. © 2016 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  11. Annealing of CoFeB/MgO based single and double barrier magnetic tunnel junctions: Tunnel magnetoresistance, bias dependence, and output voltage

    NASA Astrophysics Data System (ADS)

    Feng, G.; van Dijken, Sebastiaan; Feng, J. F.; Coey, J. M. D.; Leo, T.; Smith, David J.

    2009-02-01

    Co40Fe40B20/MgO single and double barrier magnetic tunnel junctions (MTJs) were grown using target-facing-target sputtering for MgO barriers and conventional dc magnetron sputtering for Co40Fe40B20 ferromagnetic electrodes. Large tunnel magnetoresistance (TMR) ratios, 230% for single barrier MTJs and 120% for the double barrier MTJs, were obtained after postdeposition annealing in a field of 800 mT. The lower TMR ratio for double barrier MTJs can be attributed to the amorphous nature of the middle Co40Fe40B20 free layer, which could not be crystallized during postannealing. A highly asymmetric bias voltage dependence of the TMR can be observed for both single and double barrier MTJs in the as-deposited states and after field annealing at low temperature. The asymmetry decreases with increasing annealing temperature and the bias dependence becomes almost symmetric after annealing at 350 °C. Maximum output voltages of 0.65 and 0.85 V were obtained for both single and double barrier MTJs, respectively, after annealing at 300 °C, a temperature which is high enough for large TMR ratios but insufficient to completely remove asymmetry from the TMR bias dependence.

  12. Purinergic receptor P2RY12-dependent microglial closure of the injured blood–brain barrier

    PubMed Central

    Lou, Nanhong; Takano, Takahiro; Pei, Yong; Xavier, Anna L.; Goldman, Steven A.; Nedergaard, Maiken

    2016-01-01

    Microglia are integral functional elements of the central nervous system, but the contribution of these cells to the structural integrity of the neurovascular unit has not hitherto been assessed. We show here that following blood–brain barrier (BBB) breakdown, P2RY12 (purinergic receptor P2Y, G-protein coupled, 12)-mediated chemotaxis of microglia processes is required for the rapid closure of the BBB. Mice treated with the P2RY12 inhibitor clopidogrel, as well as those in which P2RY12 was genetically ablated, exhibited significantly diminished movement of juxtavascular microglial processes and failed to close laser-induced openings of the BBB. Thus, microglial cells play a previously unrecognized protective role in the maintenance of BBB integrity following cerebrovascular damage. Because clopidogrel antagonizes the platelet P2Y12 receptor, it is widely prescribed for patients with coronary artery and cerebrovascular disease. As such, these observations suggest the need for caution in the postincident continuation of P2RY12-targeted platelet inhibition. PMID:26755608

  13. Ruthenium tetraoxide oxidations of alkanes: DFT calculations of barrier heights and kinetic isotope effects.

    PubMed

    Drees, Markus; Strassner, Thomas

    2006-03-03

    The oxidation of C-H and C-C bonds by metal-oxo compounds is of general interest. We studied the RuO4-mediated catalytic oxidation of several cycloalkanes such as adamantane and cis- and trans-decalin as well as methane. B3LYP/6-31G(d) calculations on the experimentally proposed (3+2) mechanism are in good agreement with known experimental results. Comparison of experimental and theoretical kinetic isotope effects confirms the proposed mechanism. Besides RuO4, we also looked at RuO4(OH)- as a potential active species to account for ruthenium tetraoxide oxidations under strong basic conditions.

  14. Huntingtin inclusion bodies are iron-dependent centers of oxidative events.

    PubMed

    Firdaus, Wance J J; Wyttenbach, Andreas; Giuliano, Paola; Kretz-Remy, Carole; Currie, R William; Arrigo, André-Patrick

    2006-12-01

    Recently, we reported that the transient expression of huntingtin exon1 polypeptide containing polyglutamine tracts of various sizes (httEx1-polyQ) in cell models of Huntington disease generated an oxidative stress whose intensity was CAG repeat expansion-dependent. Here, we have analyzed the intracellular localization of the oxidative events generated by the httEx1-polyQ polypeptides. Analysis of live COS-7 cells as well as neuronal SK-N-SH and PC12 cells incubated with hydroethidine or dichlorofluorescein diacetate revealed oxidation of these probes at the level of the inclusion bodies formed by httEx1-polyQ polypeptides. The intensity and frequency of the oxidative events among the inclusions were CAG repeat expansion-dependent. Electron microscopic analysis of cell sections revealed the presence of oxidation-dependent morphologic alterations in the vicinity of httEx1-polyQ inclusion bodies. Moreover, a high level of oxidized proteins was recovered in partially purified inclusions. We also report that the iron chelator deferroxamine altered the structure, localization and oxidative potential of httEx1-polyQ inclusion bodies. Hence, despite the fact that the formation of inclusion bodies may represent a defense reaction of the cell to eliminate httEx1 mutant polypeptide, this phenomenon appears inherent to the generation of iron-dependent oxidative events that can be deleterious to the cell.

  15. Capturing local atomic environment dependence of activation barriers in metals using cluster expansion models

    NASA Astrophysics Data System (ADS)

    Kulkarni, Nimish; Chatterjee, Abhijit

    2016-10-01

    It is well known that surface diffusion in metals can proceed via multiple mechanisms, such as hop, exchange and other types of concerted moves. However, the manner in which kinetic rates associated with a mechanism can depend sensitively on local atomic environment is relatively less understood. We describe recent attempts in our research group to capture the atomic environment dependence using the cluster expansion model (CEM). In particular, we focus on hop and exchange moves at the (001) surface in homoepitaxy, and show that while CEM can work remarkably well in most cases, it can sometimes provide inaccurate predictions for concerted moves.

  16. Size Dependence of [n]Cycloparaphenylenes (n=5-12) in Electrochemical Oxidation.

    PubMed

    Kayahara, Eiichi; Fukayama, Kei; Nishinaga, Tohru; Yamago, Shigeru

    2016-06-21

    The oxidation processes of [n]cycloparaphenylenes ([n]CPPs) (n=5-12) were systematically investigated by cyclic and rotating disk electrode voltammetry. All CPPs underwent pseudo-reversible two-electron oxidation irrespective of ring size, forming the corresponding radical cations and then dications. The results were in sharp contrast to those observed for linear oligoparaphenylenes, which only undergo one-electron oxidation. The difference in the first and second oxidation potentials in the CPP oxidation was affected by the ring size and became more significant as the decrease of CPP size. In other words, while the first oxidation from neutral CPP to the radical cation occurred faster as the size of CPP becomes smaller, the second oxidation from the radical cation to dication exhibited opposite size dependence.

  17. LOXL2 Oxidizes Methylated TAF10 and Controls TFIID-Dependent Genes during Neural Progenitor Differentiation.

    PubMed

    Iturbide, Ane; Pascual-Reguant, Laura; Fargas, Laura; Cebrià, Joan Pau; Alsina, Berta; García de Herreros, Antonio; Peiró, Sandra

    2015-06-04

    Protein function is often regulated and controlled by posttranslational modifications, such as oxidation. Although oxidation has been mainly considered to be uncontrolled and nonenzymatic, many enzymatic oxidations occur on enzyme-selected lysine residues; for instance, LOXL2 oxidizes lysines by converting the ε-amino groups into aldehyde groups. Using an unbiased proteomic approach, we have identified methylated TAF10, a member of the TFIID complex, as a LOXL2 substrate. LOXL2 oxidation of TAF10 induces its release from its promoters, leading to a block in TFIID-dependent gene transcription. In embryonic stem cells, this results in the inactivation of the pluripotency genes and loss of the pluripotent capacity. During zebrafish development, the absence of LOXL2 resulted in the aberrant overexpression of the neural progenitor gene Sox2 and impaired neural differentiation. Thus, lysine oxidation of the transcription factor TAF10 is a controlled protein modification and demonstrates a role for protein oxidation in regulating pluripotency genes.

  18. Neuropsychiatric disease relevance of circulating anti-NMDA receptor autoantibodies depends on blood-brain barrier integrity.

    PubMed

    Hammer, C; Stepniak, B; Schneider, A; Papiol, S; Tantra, M; Begemann, M; Sirén, A-L; Pardo, L A; Sperling, S; Mohd Jofrry, S; Gurvich, A; Jensen, N; Ostmeier, K; Lühder, F; Probst, C; Martens, H; Gillis, M; Saher, G; Assogna, F; Spalletta, G; Stöcker, W; Schulz, T F; Nave, K-A; Ehrenreich, H

    2014-10-01

    In 2007, a multifaceted syndrome, associated with anti-NMDA receptor autoantibodies (NMDAR-AB) of immunoglobulin-G isotype, has been described, which variably consists of psychosis, epilepsy, cognitive decline and extrapyramidal symptoms. Prevalence and significance of NMDAR-AB in complex neuropsychiatric disease versus health, however, have remained unclear. We tested sera of 2817 subjects (1325 healthy, 1081 schizophrenic, 263 Parkinson and 148 affective-disorder subjects) for presence of NMDAR-AB, conducted a genome-wide genetic association study, comparing AB carriers versus non-carriers, and assessed their influenza AB status. For mechanistic insight and documentation of AB functionality, in vivo experiments involving mice with deficient blood-brain barrier (ApoE(-/-)) and in vitro endocytosis assays in primary cortical neurons were performed. In 10.5% of subjects, NMDAR-AB (NR1 subunit) of any immunoglobulin isotype were detected, with no difference in seroprevalence, titer or in vitro functionality between patients and healthy controls. Administration of extracted human serum to mice influenced basal and MK-801-induced activity in the open field only in ApoE(-/-) mice injected with NMDAR-AB-positive serum but not in respective controls. Seropositive schizophrenic patients with a history of neurotrauma or birth complications, indicating an at least temporarily compromised blood-brain barrier, had more neurological abnormalities than seronegative patients with comparable history. A common genetic variant (rs524991, P=6.15E-08) as well as past influenza A (P=0.024) or B (P=0.006) infection were identified as predisposing factors for NMDAR-AB seropositivity. The >10% overall seroprevalence of NMDAR-AB of both healthy individuals and patients is unexpectedly high. Clinical significance, however, apparently depends on association with past or present perturbations of blood-brain barrier function.

  19. O2 adsorption dependent photoluminescence emission from metal oxide nanoparticles.

    PubMed

    Gheisi, Amir R; Neygandhi, Chris; Sternig, Andreas K; Carrasco, Esther; Marbach, Hubertus; Thomele, Daniel; Diwald, Oliver

    2014-11-21

    Optical properties of metal oxide nanoparticles are subject to synthesis related defects and impurities. Using photoluminescence spectroscopy and UV diffuse reflectance in conjunction with Auger electron spectroscopic surface analysis we investigated the effect of surface composition and oxygen adsorption on the photoluminescence properties of vapor phase grown ZnO and MgO nanoparticles. On hydroxylated MgO nanoparticles as a reference system, intense photoluminescence features exclusively originate from surface excitons, the radiative deactivation of which results in collisional quenching in an O2 atmosphere. Conversely, on as-prepared ZnO nanoparticles a broad yellow emission feature centered at hνEm = 2.1 eV exhibits an O2 induced intensity increase. Attributed to oxygen interstitials as recombination centers this enhancement effect originates from adsorbate-induced band bending, which is pertinent to the photoluminescence active region of the nanoparticles. Annealing induced trends in the optical properties of the two prototypical metal oxide nanoparticle systems, ZnO and MgO, are explained by changes in the surface composition and underline that particle surface and interface changes that result from handling and processing of nanoparticles critically affect luminescence.

  20. Barriers to Effective Tobacco-Dependence Treatment for the Very Poor

    PubMed Central

    Christiansen, Bruce; Reeder, Kevin; Hill, Maureen; Baker, Timothy B.; Fiore, Michael C.

    2012-01-01

    Objective: People who live in poverty have a high prevalence of smoking, are less likely to engage in evidence-based treatment, and find it harder to quit. Their beliefs about smoking and quitting can serve as barriers to quitting. Little is known about the smoking and quitting beliefs of the very poor (about U.S. $15,000 or less annual family income) because they tend not to be included in research. This study sought to assess beliefs about smoking and quitting by the very poor in relation to past quitting behavior and intention to quit in the future. Method: A survey was administered in person to residents in randomly selected addresses in two very impoverished Milwaukee, WI, ZIP codes during the day to ensure the inclusion of the very poor. Results: Six hundred fifty-four people completed the survey, a response rate of 78.3%. Sixty-eight percent reported annual household incomes of less than $15,000 compared with 30.8% in the community as a whole and 13.0% of households nationally. Self-reported smoking prevalence was 42.1%. Specific beliefs about smoking and quitting were related to past quit attempts and intentions to quit in the future. Both race and income predicted beliefs and quitting-related variables independently and jointly. Conclusions: Continued tobacco-control progress requires addressing specific populations with known high tobacco use. One of these populations is those with low income. Efforts to engage them in treatment will have to address specific beliefs about smoking and quitting. PMID:23036204

  1. Improved free energy profile for reduction of NO in cytochrome c dependent nitric oxide reductase (cNOR).

    PubMed

    Blomberg, Margareta R A; Siegbahn, Per E M

    2016-07-15

    Quantum chemical calculations play an essential role in the elucidation of reaction mechanisms for redox-active metalloenzymes. For example, the cleavage and the formation of covalent bonds can usually not be described only on the basis of experimental information, but can be followed by the calculations. Conversely, there are properties, like reduction potentials, which cannot be accurately calculated. Therefore, computational and experimental data has to be carefully combined to obtain reliable descriptions of entire catalytic cycles involving electron and proton uptake from donors outside the enzyme. Such a procedure is illustrated here, for the reduction of nitric oxide (NO) to nitrous oxide and water in the membrane enzyme, cytochrome c dependent nitric oxide reductase (cNOR). A surprising experimental observation is that this reaction is nonelectrogenic, which means that no energy is conserved. On the basis of hybrid density functional calculations a free energy profile for the entire catalytic cycle is obtained, which agrees much better with experimental information on the active site reduction potentials than previous ones. Most importantly the energy profile shows that the reduction steps are endergonic and that the entire process is rate-limited by high proton uptake barriers during the reduction steps. This result implies that, if the reaction were electrogenic, it would become too slow when the gradient is present across the membrane. This explains why this enzyme does not conserve any of the free energy released. © 2016 Wiley Periodicals, Inc.

  2. Size-dependent passage of liposome nanocarriers with preserved posttransport integrity across the middle-inner ear barriers in rats.

    PubMed

    Zou, Jing; Sood, Rohit; Ranjan, Sanjeev; Poe, Dennis; Ramadan, Usama Abo; Pyykkö, Ilmari; Kinnunen, Paavo K J

    2012-06-01

    The goal of this study was to evaluate the impact of liposome nanocarrier size on the efficacy of its transport across the middle-inner ear barriers. The dynamic distribution of liposome nanocarriers encapsulating gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (LPS+Gd-DOTA) of sizes 95, 130, and 240 nm were observed with a 4.7 T magnetic resonance machine after transtympanic injection in Wistar rats. Histology was performed with confocal microscopy using TRITC conjugated LPS+Gd-DOTA. The integrity of the LPS+Gd-DOTA after transportation was evaluated using cryo-transmission electron microscopy (Cryo-TEM). Size-dependent transport of the LPS+Gd-DOTA across the middle-inner ear barriers was shown using magnetic resonance imaging, which indicated that the 95-nm nanocarrier showed the significantly highest transport percentage, that the 130-nm nanocarrier showed moderate transport, and that the 240 nm nanocarrier showed the lowest transport. Histologic examinations showed that the LPS+Gd-DOTA were distributed in the epithelial cells of the utricle, capillaries of the spiral ligament, and the spiral ganglion cells. LPS+Gd-DOTA remained intact in the perilymph after transportation. The nanocarrier delivery strategy used in this work could be effective in the development of novel inner ear treatments.

  3. Scattering of surface plasmon polaritons by impedance barriers: Dependence on angle of incidence

    NASA Astrophysics Data System (ADS)

    Nikitin, A. Yu.; Brucoli, G.; García-Vidal, F. J.; Martín-Moreno, L.

    2008-05-01

    This paper studies theoretically surface plasmon polariton scattering by one-dimensional defects of metal surface impedance at oblique incidence. Surface impedance boundary conditions are used to formulate an integral equation which can be solved both analytically and numerically to yield the transmission, reflection, and out-of-plane cross section as a function of angle of incidence and other parameters. Numerical calculations, as well as analytical expressions, obtained within the Born approximation are presented. Green’s tensor approach is also applied so as to expand such analysis to region in which the surface impedance boundary conditions are not appropriate. We show that the angular dependencies for surface plasmon polariton scattering by impedance defects and by surface relief defects are essentially different. The angular dependency of surface plasmon polariton scattering by an impedance defect features an analog to Brewster’s angle that is explained in terms of dipole polarization of the defect.

  4. Interfacing BiVO4 with Reduced Graphene Oxide for Enhanced Photoactivity: A Tale of Facet Dependence of Electron Shuttling.

    PubMed

    Tan, Hui Ling; Tahini, Hassan A; Wen, Xiaoming; Wong, Roong Jien; Tan, Xin; Iwase, Akihide; Kudo, Akihiko; Amal, Rose; Smith, Sean C; Ng, Yun Hau

    2016-10-01

    Efficient interfacial charge transfer is essential in graphene-based semiconductors to realize their superior photoactivity. However, little is known about the factors (for example, semiconductor morphology) governing the charge interaction. Here, it is demonstrated that the electron transfer efficacy in reduced graphene oxide-bismuth oxide (RGO/BiVO4 ) composite is improved as the relative exposure extent of {010}/{110} facets on BiVO4 increases, indicated by the greater extent of photocurrent enhancement. The dependence of charge transfer ability on the exposure degree of {010} relative to {110} is revealed to arise due to the difference in electronic structures of the graphene/BiVO4 {010} and graphene/BiVO4 {110} interfaces, as evidenced by the density functional theory calculations. The former interface is found to be metallic with higher binding energy and smaller Schottky barrier than that of the latter semiconducting interface. The facet-dependent charge interaction elucidated in this study provides new aspect for design of graphene-based semiconductor photocatalyst useful in manifold applications.

  5. Effects of the nitric oxide donor JS-K on the blood-tumor barrier and on orthotopic U87 rat gliomas assessed by MRI.

    PubMed

    Weidensteiner, Claudia; Reichardt, Wilfried; Shami, Paul J; Saavedra, Joseph E; Keefer, Larry K; Baumer, Brunhilde; Werres, Anna; Jasinski, Robert; Osterberg, Nadja; Weyerbrock, Astrid

    2013-04-01

    Nitric oxide (NO) released from NO donors can be cytotoxic in tumor cells and can enhance the transport of drugs into brain tumors by altering blood-tumor barrier permeability. The NO donor JS-K [O(2)-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl]diazen-1-ium-1,2-diolate] releases NO upon enzymatic activation selectively in cells overexpressing glutathione-S-transferases (GSTs) such as gliomas. Thus, JS-K-dependent NO effects - especially on cell viability and vascular permeability - were investigated in U87 glioma cells in vitro and in an orthotopic U87 xenograft model in vivo by magnetic resonance imaging (MRI). In vitro experiments showed dose-dependent antiproliferative and cytotoxic effects in U87 cells. In addition, treatment of U87 cells with JS-K resulted in a dose-dependent activation of soluble guanylate cyclase and intracellular accumulation of cyclic guanosine monophosphate (cGMP) which was irreversibly inhibited by the selective inhibitor of soluble guanylate cyclase ODQ (1H-[1,2,4]oxadiazolo(4,3a)quinoxaline-1-one). Using dynamic contrast enhanced MRI (DCE-MRI) as a minimally invasive technique, we demonstrated for the first time a significant increase in the DCE-MRI read-out initial area under the concentration curve (iAUC60) indicating an acute increase in blood-tumor barrier permeability after i.v. treatment with JS-K. Repeated MR imaging of animals with intracranial U87 gliomas under treatment with JS-K (3.5 μmol/kg JS-K 3×/week) and of untreated controls on day 12 and 19 after tumor inoculation revealed no significant changes in tumor growth, edema formation or tumor perfusion. Immunohistochemical workup of the brains showed a significant antiproliferative effect of JS-K in the gliomas. Taken together, in vitro and in vivo data suggest that JS-K has antiproliferative effects in U87 gliomas and opens the blood-tumor barrier by activation of the NO/cGMP signaling pathway. This might be a novel approach to facilitate entry of therapeutic

  6. Oxidation of limonene using activated carbon modified in dielectric barrier discharge plasma

    NASA Astrophysics Data System (ADS)

    Glonek, Karolina; Wróblewska, Agnieszka; Makuch, Edyta; Ulejczyk, Bogdan; Krawczyk, Krzysztof; Wróbel, Rafał. J.; Koren, Zvi C.; Michalkiewicz, Beata

    2017-10-01

    The waste from industrial fruits processing is utilized for the extraction of limonene, a renewable terpene biomass compound obtained from orange peels. This was followed by limonene oxidation, which produces highly useful oxygenated derivatives (carveol, and perillyl alcohol, 1,2-epoxylimonene and its diol). New catalysts were obtained by treating relatively inexpensive commercially available EuroPh and FPV activated carbons with plasma. These catalysts were characterized by the following instrumental methods XRD, sorption of N2 and CO2, SEM, EDS, TEM, XPS, and Raman spectroscopy. The activities of the plasma-treated catalysts were measured in the oxidation of limonene by means of either hydrogen peroxide or t-butyl hydroperoxide as the oxidizing agents. During the oxidation with hydrogen peroxide the new plasma-treated catalysts were more active than their untreated counterparts. This effect was noticeable in the considerable increase in the conversion of limonene. The mechanism explaining this property is proposed, and it takes into account the role of the appropriate functional groups on the surface of the catalysts. This work has shown for the first time that the commercial EuroPh and FPV activated carbons, after having been treated by plasma, are active catalysts for the selective limonene oxidation for the production of value-added industrial products.

  7. Boswellia serrata Preserves Intestinal Epithelial Barrier from Oxidative and Inflammatory Damage.

    PubMed

    Catanzaro, Daniela; Rancan, Serena; Orso, Genny; Dall'Acqua, Stefano; Brun, Paola; Giron, Maria Cecilia; Carrara, Maria; Castagliuolo, Ignazio; Ragazzi, Eugenio; Caparrotta, Laura; Montopoli, Monica

    2015-01-01

    Aminosalicylates, corticosteroids and immunosuppressants are currently the therapeutic choices in inflammatory bowel diseases (IBD), however, with limited remission and often serious side effects. Meanwhile complementary and alternative medicine (CAM) use is increasing, particularly herbal medicine. Boswellia serrata is a traditional Ayurvedic remedy with anti-inflammatory properties, of interest for its usefulness in IBDs. The mechanism of this pharmacological potential of Boswellia serrata was investigated in colonic epithelial cell monolayers exposed to H2O2 or INF-γ+TNF-α, chosen as in vitro experimental model of intestinal inflammation. The barrier function was evaluated by the transepithelial electrical resistance (TEER) and paracellular permeability assay, and by the tight junction proteins (zonula occludens-1, ZO-1 and occludin) immunofluorescence. The expression of phosphorylated NF-κB and reactive oxygen species (ROS) generation were determined by immunoblot and cytofluorimetric assay, respectively. Boswellia serrata oleo-gum extract (BSE) and its pure derivative acetyl-11-keto-β-boswellic acid (AKBA), were tested at 0.1-10 μg/ml and 0.027 μg/ml, respectively. BSE and AKBA safety was demonstrated by no alteration of intestinal cell viability and barrier function and integrity biomarkers. H2O2 or INF-γ+TNF-α treatment of Caco-2 cell monolayers significantly reduced TEER, increased paracellular permeability and caused the disassembly of tight junction proteins occludin and ZO-1. BSE and AKBA pretreatment significantly prevented functional and morphological alterations and also the NF-κB phosphorylation induced by the inflammatory stimuli. At the same concentrations BSE and AKBA counteracted the increase of ROS caused by H2O2 exposure. Data showed the positive correlation of the antioxidant activity with the mechanism involved in the physiologic maintenance of the integrity and function of the intestinal epithelium. This study elucidates the

  8. Boswellia serrata Preserves Intestinal Epithelial Barrier from Oxidative and Inflammatory Damage

    PubMed Central

    Catanzaro, Daniela; Rancan, Serena; Orso, Genny; Dall’Acqua, Stefano; Brun, Paola; Giron, Maria Cecilia; Carrara, Maria; Castagliuolo, Ignazio; Ragazzi, Eugenio; Caparrotta, Laura; Montopoli, Monica

    2015-01-01

    Aminosalicylates, corticosteroids and immunosuppressants are currently the therapeutic choices in inflammatory bowel diseases (IBD), however, with limited remission and often serious side effects. Meanwhile complementary and alternative medicine (CAM) use is increasing, particularly herbal medicine. Boswellia serrata is a traditional Ayurvedic remedy with anti-inflammatory properties, of interest for its usefulness in IBDs. The mechanism of this pharmacological potential of Boswellia serrata was investigated in colonic epithelial cell monolayers exposed to H2O2 or INF-γ+TNF-α, chosen as in vitro experimental model of intestinal inflammation. The barrier function was evaluated by the transepithelial electrical resistance (TEER) and paracellular permeability assay, and by the tight junction proteins (zonula occludens-1, ZO-1 and occludin) immunofluorescence. The expression of phosphorylated NF-κB and reactive oxygen species (ROS) generation were determined by immunoblot and cytofluorimetric assay, respectively. Boswellia serrata oleo-gum extract (BSE) and its pure derivative acetyl-11-keto-β-boswellic acid (AKBA), were tested at 0.1-10 μg/ml and 0.027μg/ml, respectively. BSE and AKBA safety was demonstrated by no alteration of intestinal cell viability and barrier function and integrity biomarkers. H2O2 or INF-γ+TNF-α treatment of Caco-2 cell monolayers significantly reduced TEER, increased paracellular permeability and caused the disassembly of tight junction proteins occludin and ZO-1. BSE and AKBA pretreatment significantly prevented functional and morphological alterations and also the NF-κB phosphorylation induced by the inflammatory stimuli. At the same concentrations BSE and AKBA counteracted the increase of ROS caused by H2O2 exposure. Data showed the positive correlation of the antioxidant activity with the mechanism involved in the physiologic maintenance of the integrity and function of the intestinal epithelium. This study elucidates the

  9. High performance trench MOS barrier Schottky diode with high-k gate oxide

    NASA Astrophysics Data System (ADS)

    Zhai, Dong-Yuan; Zhu, Jun; Zhao, Yi; Cai, Yin-Fei; Shi, Yi; Zheng, You-Liao

    2015-07-01

    A novel trench MOS barrier Schottky diode (TMBS) device with a high-k material introduced into the gate insulator is reported, which is named high-k TMBS. By simulation with Medici, it is found that the high-k TMBS can have 19.8% lower leakage current while maintaining the same breakdown voltage and forward turn-on voltage compared with the conventional regular trench TMBS. Project supported by the National Basic Research Program of China (Grant No. 2011CBA00607), the National Natural Science Foundation of China (Grant Nos. 61106089 and 61376097), and the Zhejiang Provincial Natural Science Foundation of China (Grant No. LR14F040001).

  10. Entrance Channel Mass Asymmetry Effects in Sub-Barrier Fusion Dynamics by Using Energy Dependent Woods-Saxon Potential

    NASA Astrophysics Data System (ADS)

    Manjeet Singh, Gautam

    2015-12-01

    The present article highlights the inconsistency of static Woods-Saxon potential and the applicability of energy dependent Woods-Saxon potential to explore the fusion dynamics of {}4822Ti+58,60,6428Ni, {}4622Ti+{}6428Ni,{}5022Ti+{}6028Ni, and {}199F+9341Nb reactions leading to formation of different Sn-isotopes via different entrance channels. Theoretical calculations based upon one-dimensional Wong formula obtained by using static Woods-Saxon potential unable to provide proper explanation for sub-barrier fusion enhancement of these projectile-target combinations. However, the predictions of one-dimensional Wong formula based upon energy dependent Woods-Saxon potential model (EDWSP model) accurately describe the observed fusion dynamics of these systems wherein the significantly larger value of diffuseness parameter ranging from a = 0.85 fm to a = 0.97 fm is required to address the experimental data in whole range of energy. Therefore, the energy dependence in nucleus-nucleus potential simulates the influence of the nuclear structure degrees of freedom of the colliding pairs. Supported by Dr. D.S. Kothari Post-Doctoral Fellowship Scheme sponsored by University Grants Commission (UGC), New Delhi, India

  11. Blood-Brain Barrier Disruption Caused by Ultrasound Bursts Combined with Microbubbles Depends on Anesthesia

    NASA Astrophysics Data System (ADS)

    McDannold, Nathan; Zhang, Yongzhi; Vykhodtseva, Natalia

    2011-09-01

    Prior works on BBB disruption via inter-arterial infusions of osmotic agents have shown a strong dependence on anesthesia. Here, we investigated whether different anesthesia agents can affect ultrasound-induced BBB disruption. A piston transducer fired through a rubber aperture (frequency: 532 kHz, diameter: 4 cm, aperture diameter: 16 mm) was used to generate the ultrasound fields, and sonications combined with an ultrasound contrast agent were performed at 5 power levels. BBB disruption was quantified by measuring the MRI contrast enhancement in T1-weighted MRI, and erythrocyte extravasation characterized in light microscopy. For each exposure level tested, experiments performed with ketamine/xylazine resulted in significantly greater (P<0.05) enhancement than with isoflurane/oxygen. The onset of severe red blood cell extravasation occurred at lower power levels with ketamine/xylazine. These results suggest ultrasound-induced BBB disruption can depend on anesthesia agent, possibly due effects on the vasculature. These results suggest that care is needed in comparing experiments with different anesthesia agents and physiological factors need to be considered with ultrasound-induced BBB disruption.

  12. Nitric oxide-dependent posttranslational modification in plants: an update.

    PubMed

    Astier, Jeremy; Lindermayr, Christian

    2012-11-16

    Nitric oxide (NO) has been demonstrated as an essential regulator of several physiological processes in plants. The understanding of the molecular mechanism underlying its critical role constitutes a major field of research. NO can exert its biological function through different ways, such as the modulation of gene expression, the mobilization of second messengers, or interplays with protein kinases. Besides this signaling events, NO can be responsible of the posttranslational modifications (PTM) of target proteins. Several modifications have been identified so far, whereas metal nitrosylation, the tyrosine nitration and the S-nitrosylation can be considered as the main ones. Recent data demonstrate that these PTM are involved in the control of a wide range of physiological processes in plants, such as the plant immune system. However, a great deal of effort is still necessary to pinpoint the role of each PTM in plant physiology. Taken together, these new advances in proteomic research provide a better comprehension of the role of NO in plant signaling.

  13. Temperature dependent rheological property of copper oxide nanoparticles suspension (nanofluid).

    PubMed

    Kulkarni, Devdatta P; Das, Debendra K; Chukwu, Godwin A

    2006-04-01

    A nanofluid is the dispersion of metallic solid particles of nanometer size in a base fluid such as water or ethylene glycol. The presence of these nanoparticles affects the physical properties of a nanofluid via various factors including shear stress, particle loading, and temperature. In this paper the rheological behavior of copper oxide (CuO) nanoparticles of 29 nm average diameter dispersed in deionized (DI) water is investigated over a range of volumetric solids concentrations of 5 to 15% and various temperatures varying from 278-323 degrees K. These experiments showed that these nanofluids exhibited time-independent pseudoplastic and shear-thinning behavior. The suspension viscosities of nanofluids decrease exponentially with respect to the shear rate. Suspension viscosity follows the correlation in the form ln(mus) = A(1/T)-B, where constants A and B are the functions of volumetric concentrations. The calculated viscosities from the developed correlations and experimental values were found to be within +/- 10% of their values.

  14. Nitric Oxide-Dependent Posttranslational Modification in Plants: An Update

    PubMed Central

    Astier, Jeremy; Lindermayr, Christian

    2012-01-01

    Nitric oxide (NO) has been demonstrated as an essential regulator of several physiological processes in plants. The understanding of the molecular mechanism underlying its critical role constitutes a major field of research. NO can exert its biological function through different ways, such as the modulation of gene expression, the mobilization of second messengers, or interplays with protein kinases. Besides this signaling events, NO can be responsible of the posttranslational modifications (PTM) of target proteins. Several modifications have been identified so far, whereas metal nitrosylation, the tyrosine nitration and the S-nitrosylation can be considered as the main ones. Recent data demonstrate that these PTM are involved in the control of a wide range of physiological processes in plants, such as the plant immune system. However, a great deal of effort is still necessary to pinpoint the role of each PTM in plant physiology. Taken together, these new advances in proteomic research provide a better comprehension of the role of NO in plant signaling. PMID:23203119

  15. Kinetic-dependent Killing of Oral Pathogens with Nitric Oxide

    PubMed Central

    Backlund, C.J.; Worley, B.V.; Sergesketter, A.R.

    2015-01-01

    Nitric oxide (NO)–releasing silica nanoparticles were synthesized via the co-condensation of tetramethyl orthosilicate with aminosilanes and subsequent conversion of secondary amines to N-diazeniumdiolate NO donors. A series of ~150 nm NO-releasing particles with different NO totals and release kinetics (i.e., half-lives) were achieved by altering both the identity and mol% composition of the aminosilane precursors. Independent of identical 2 h NO-release totals, enhanced antibacterial action was observed against the periodontopathogens Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis with extended NO-release kinetics at pH 7.4. Negligible bactericidal effect was observed against cariogenic Streptococcus mutans at pH 7.4, even when using NO-releasing silica particles with greater NO-release totals. However, antibacterial activity was observed against S. mutans at lower pH (6.4). This result was attributed to more rapid proton-initiated decomposition of the N-diazeniumdiolate NO donors and greater NO-release payloads. The data suggest a differential sensitivity to NO between cariogenic and periodontopathogenic bacteria with implications for the future development of NO-releasing oral care therapeutics. PMID:26078424

  16. Development of oxide based diffusion barrier coatings for CFC components applied in modern furnaces

    NASA Astrophysics Data System (ADS)

    Bobzin, Kirsten; Zhao, Lidong; Schlaefer, Thomas; Warda, Thomas

    2011-12-01

    Carbon fibre reinforced carbon (CFC) materials show a high potential for usage in furnaces as sample carriers for example, which is due to their excellent thermal stability compared to steel carriers. Only their tendency to react with different metals at high temperatures by Cdiffusion is a disadvantage, which can be solved by application of diffusion barriers. In order to enable the utilization of CFC-carriers for e.g. brazing furnaces, within the frame of this study thermally sprayed diffusion barrier coatings were developed. Coatings of mullite and ZrO2-7% Y2O3 (YSZ) were prepared by air plasma spraying (APS). The coatings were investigated in terms of their microstructure and thermal shock behaviour. In order to prove the suitability of the coatings for the application in brazing furnaces, the wettability of the coating surfaces by a Ni-based brazing alloy was investigated. The results showed that both mullite and YSZ could be deposited on CFC substrates with a bond coat of W or SiC. Both coatings exhibited good thermal shock behaviour and an excellent non-wetting behaviour against the used Ni-based braze alloy.

  17. Pleiotrophin Induces Nitric Oxide Dependent Migration of Endothelial Progenitor Cells

    PubMed Central

    Heiss, Christian; Wong, Maelene L.; Block, Vanessa I.; Lao, David; Real, Wendy May; Yeghiazarians, Yerem; Lee, Randall J.; Springer, Matthew L.

    2009-01-01

    Pleiotrophin (PTN) is produced under ischemic conditions and has been shown to induce angiogenesis in vivo. We studied whether or not PTN exerts chemotaxis of pro-angiogenic early endothelial progenitor cells (EPCs), a population of circulating cells that have been reported to participate in and stimulate angiogenesis. Chemotaxis of EPCs, isolated from blood of healthy humans (n=5), was measured in transwell assays. PTN at 10–500 ng/mL elicited dose-dependent chemotaxis of both EPCs and human umbilical vein endothelial cells (HUVECs), but not of human coronary artery smooth muscle cells (CASMCs) and T98G glioblastoma cells that lack PTN receptors. The degree of chemotaxis was comparable to that induced by the angiogenic factors VEGF and SDF-1α. Chemotaxis to PTN was blocked by the NOS inhibitors L-NNA and L-NMMA, the NO scavenger PTIO, the phosphoinositide-3 kinase inhibitor wortmannin, and the guanylyl cyclase inhibitor ODQ, suggesting dependence of EPC chemotaxis on these pathways. PTN induced NOS-dependent production of NO to a similar degree as did VEGF, as indicated by the NO indicator DAF-2. PTN increased proliferation in EPCs and HUVECs to a similar extent as VEGF, but did not induce proliferation of CASMCs. While L-NNA abolished PTN-induced migration in EPCs and HUVECs, it did not inhibit PTN- and VEGF-enhanced proliferation and also caused proliferation by itself. These data suggest that PTN may mediate its pro-angiogenic effects by increasing the local number of not only endothelial cells but also early EPCs at angiogenic sites. PMID:17960557

  18. Magnetic resonance imaging of post-ischemic blood-brain barrier damage with PEGylated iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Dong-Fang; Qian, Cheng; An, Yan-Li; Chang, Di; Ju, Sheng-Hong; Teng, Gao-Jun

    2014-11-01

    Blood-brain barrier (BBB) damage during ischemia may induce devastating consequences like cerebral edema and hemorrhagic transformation. This study presents a novel strategy for dynamically imaging of BBB damage with PEGylated supermagnetic iron oxide nanoparticles (SPIONs) as contrast agents. The employment of SPIONs as contrast agents made it possible to dynamically image the BBB permeability alterations and ischemic lesions simultaneously with T2-weighted MRI, and the monitoring could last up to 24 h with a single administration of PEGylated SPIONs in vivo. The ability of the PEGylated SPIONs to highlight BBB damage by MRI was demonstrated by the colocalization of PEGylated SPIONs with Gd-DTPA after intravenous injection of SPION-PEG/Gd-DTPA into a mouse. The immunohistochemical staining also confirmed the leakage of SPION-PEG from cerebral vessels into parenchyma. This study provides a novel and convenient route for imaging BBB alteration in the experimental ischemic stroke model.

  19. DEPENDENCE OF NITRIC OXIDE EMISSIONS ON VEHICLE LOAD: RESULTS FROM THE GTRP INSTRUMENTED VEHICLE PROGRAM

    EPA Science Inventory

    The presentation discussed the dependence of nitric oxide (NO) emissions on vehicle load, bases on results from an instrumented-vehicle program. The accuracy and feasibility of modal emissions models depend on algorithms to allocate vehicle emissions based on a vehicle operation...

  20. Covalent dependence of octahedral rotations in orthorhombic perovskite oxides.

    PubMed

    Cammarata, Antonio; Rondinelli, James M

    2014-09-21

    The compositional dependence of metal-oxygen BO6 octahedral distortions, including bond elongations and rotations, is frequently discussed in the ABO3 perovskite literature; structural distortions alleviate internal stresses driven by under- or over-coordinated bond environments. Here we identify the dependence of octahedral rotations from changes in metal-oxygen bond covalency in orthorhombic perovskites. Using density functional theory we formulate a covalency metric, which captures both the real and k-space interactions between the magnitude and sense, i.e., in-phase or out-of-phase, octahedral rotations, to explore the link between the ionic-covalent Fe-O bond and the interoctahedral Fe-O-Fe bond angles in Pbnm ferrates. Our survey finds that the covalency of the metal-oxygen bond is correlated with the rotation amplitude: We find the more covalent the Fe-O bond, the less distorted is the structure and the more important the long-range inter-octahedral (Fe-O-Fe bond angle) interactions. Finally, we show how to indirectly tune the B-O bond covalency by A-cation induced BO6 rotations independent of ionic size, facilitating design of targeted bonding interactions in complex perovskites.

  1. Nitric oxide mediates local activity-dependent excitatory synapse development.

    PubMed

    Nikonenko, Irina; Nikonenko, Alexander; Mendez, Pablo; Michurina, Tatyana V; Enikolopov, Grigori; Muller, Dominique

    2013-10-29

    Learning related paradigms play an important role in shaping the development and specificity of synaptic networks, notably by regulating mechanisms of spine growth and pruning. The molecular events underlying these synaptic rearrangements remain poorly understood. Here we identify NO signaling as a key mediator of activity-dependent excitatory synapse development. We find that chronic blockade of NO production in vitro and in vivo interferes with the development of hippocampal and cortical excitatory spine synapses. The effect results from a selective loss of activity-mediated spine growth mechanisms and is associated with morphological and functional alterations of remaining synapses. These effects of NO are mediated by a cGMP cascade and can be reproduced or prevented by postsynaptic expression of vasodilator-stimulated phosphoprotein phospho-mimetic or phospho-resistant mutants. In vivo analyses show that absence of NO prevents the increase in excitatory synapse density induced by environmental enrichment and interferes with the formation of local clusters of excitatory synapses. We conclude that NO plays an important role in regulating the development of excitatory synapses by promoting local activity-dependent spine-growth mechanisms.

  2. pH-dependent growth of zinc oxide nanorods

    NASA Astrophysics Data System (ADS)

    Baruah, Sunandan; Dutta, Joydeep

    2009-04-01

    Here we study the effect of pH variation on the dimension and morphology of zinc oxide (ZnO) nanorods grown through hydrothermal process at temperatures less than 100 °C. ZnO nanorods were grown on pre-seeded glass substrates using zinc nitrate hexahydrate as the source of Zn ions and hexamethylenetetramine as the source of hydroxyl ions. The pH of the reaction bath was found to change gradually from 6.4 to 7.3 in 5 h during the growth process. The growth of the ZnO nanorods was observed to be faster, both laterally and longitudinally, when the growth solution was in basic conditions. However, flower petal like ZnO nanostructures were obtained when the growth process was initiated in basic condition (pH 8-12), indicating that initial acidic conditions were required to obtain nanorods with well-defined hexagonal facets. ZnO is known to erode in acidic condition and the final dimension of the nanorods is determined by a competition between crystal growth and etching. ZnO nanorods of different dimensions, both laterally (diameters ranging from 220 nm to 1 μm) and longitudinally (lengths ranging from 1 to 5.6 μm) were successfully synthesized using the same concentration of zinc nitrate and hexamine in the reaction bath and the same growth duration of 5 h simply through appropriate control of the pH of the reactant solution between 6 and 7.3.

  3. Application of Iron Oxide as a pH-dependent Indicator for Improving the Nutritional Quality

    PubMed Central

    2016-01-01

    Acid food indicators can be used as pH indicators for evaluating the quality and freshness of fermented products during the full course of distribution. Iron oxide particles are hardly suspended in water, but partially or completely agglomerated. The agglomeration degree of the iron oxide particles depends on the pH. The pH-dependent particle agglomeration or dispersion can be useful for monitoring the acidity of food. The zeta potential of iron oxide showed a decreasing trend as the pH increased from 2 to 8, while the point of zero charge (PZC) was observed around at pH 6.0-7.0. These results suggested that the size of the iron oxide particles was affected by the change in pH levels. As a result, the particle sizes of iron oxide were smaller at lower pH than at neutral pH. In addition, agglomeration of the iron oxide particles increased as the pH increased from 2 to 7. In the time-dependent aggregation test, the average particle size was 730.4 nm and 1,340.3 nm at pH 2 and 7, respectively. These properties of iron oxide particles can be used to develop an ideal acid indicator for food pH and to monitor food quality, besides a colorant or nutrient for nutrition enhancement and sensory promotion in food industry. PMID:27482521

  4. Ultraviolet-oxidized mercaptan-terminated organosilane nanolayers as diffusion barriers at Cu-silica interfaces

    NASA Astrophysics Data System (ADS)

    Gandhi, D. D.; Tisch, U.; Singh, B.; Eizenberg, M.; Ramanath, G.

    2007-10-01

    We demonstrate the use of UV-exposed molecular nanolayers (MNLs) of 3-mercaptan-propyl-trimethoxysilane to inhibit copper-transport across Cu -SiO2 interfaces more efficiently than the pristine MNLs. Bias-thermal-annealing tests of Cu /MNL/SiO2/Si(001)/Al capacitors, with MNLs exposed to 254nm UV radiation, exhibit enhanced barrier properties to Cu diffusion, when compared with capacitors with MNLs not exposed to UV light. X-ray photoelectron spectroscopy reveals that UV exposure converts the mercaptan termini to sulfonates, which are more effective in inhibiting Cu diffusion. Our findings are of importance for tailoring the chemical and mechanical integrity of interfaces for use in applications such as nanodevice wiring and molecular electronics.

  5. Two Distinct Coagulase-Dependent Barriers Protect Staphylococcus aureus from Neutrophils in a Three Dimensional in vitro Infection Model

    PubMed Central

    Guggenberger, Christoph; Wolz, Christiane; Morrissey, Julie A.; Heesemann, Jürgen

    2012-01-01

    Staphylococcus aureus is a pyogenic abscess-forming facultative pathogenic microorganism expressing a large set of virulence-associated factors. Among these, secreted proteins with binding capacity to plasma proteins (e.g. fibrinogen binding proteins Eap and Emp) and prothrombin activators such as Coagulase (Coa) and vWbp are involved in abscess formation. By using a three-dimensional collagen gel (3D-CoG) supplemented with fibrinogen (Fib) we studied the growth behavior of S. aureus strain Newman and a set of mutants as well as their interaction with mouse neutrophils by real-time confocal microscopy. In 3D-CoG/Fib, S. aureus forms microcolonies which are surrounded by an inner pseudocapsule and an extended outer dense microcolony-associated meshwork (MAM) containing fibrin. Coa is involved in formation of the pseudocapsule whereas MAM formation depends on vWbp. Moreover, agr-dependent dispersal of late stage microcolonies could be observed. Furthermore, we demonstrate that the pseudocapsule and the MAM act as mechanical barriers against neutrophils attracted to the microcolony. The thrombin inhibitor argatroban is able to prevent formation of both pseudocapsule and MAM and supports access of neutrophils to staphylococci. Taken together, this model can simulate specific stages of S. aureus abscess formation by temporal dissection of bacterial growth and recruitment of immune cells. It can complement established animal infection models in the development of new treatment options. PMID:22253592

  6. Calcium-dependent potassium channels as a target protein for modulation of the blood-brain tumor barrier.

    PubMed

    Ningaraj, Nagendra S; Rao, Mamatha; Black, Keith L

    2003-06-01

    Even though the blood-brain tumor barrier (BTB) is more permeable than the blood-brain barrier (BBB), the BTB still significantly restricts the delivery of anticancer drugs to brain tumors. Brain tumor capillaries that form the BTB, however, express certain unique protein markers that are absent or barely detectable in normal brain capillaries. We were able to biochemically modulate one such protein marker, the calcium-dependent potassium (K(Ca)) channel, by using a specific K(Ca) channel agonist, NS-1619, to obtain sustained enhancement of selective drug delivery, including molecules of varying sizes, to tumors in rat syngeneic and xenograft brain tumor models. Immunolocalization and potentiometric studies showed increased K(Ca) channel distribution on tumor cells compared with normal cells, suggesting that tumor cell-specific signals might induce overexpression of K(Ca) channels in capillary endothelial cells, leading to increased BTB permeability. We also demonstrated that the cellular mechanism for K(Ca) channel-mediated BTB permeability increase is due to accelerated formation of pinocytotic vesicles, which can transport therapeutic molecules across the BTB. This concept was investigated by using NS-1619 to facilitate increased delivery of carboplatin to brain tumor leading to enhanced survival in rats with brain tumors. Additionally, we showed that K(Ca) channel modulation resulted in enhanced permeability to macromolecules, including Her-2 monoclonal antibody and green fluorescent protein-adenoviral vectors, in a human, primary brain-tumor xenograft model. Therefore, K(Ca) channels are a potential, promising target for biochemical modulation of BTB permeability to increase antineoplastic drug delivery selectively to brain tumors.

  7. A graphene-oxide-based thin coating on the separator: an efficient barrier towards high-stable lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Yunbo; Miao, Lixiao; Ning, Jing; Xiao, Zhichang; Hao, Long; Wang, Bin; Zhi, Linjie

    2015-06-01

    The electrochemical performance of lithium-sulfur (Li-S) batteries can be significantly improved by simply coating a thin barrier layer on the separator. The spray-coating of a mixture of graphene oxides (GO) and oxidized carbon nanotubes (o-CNT) can achieve a barrier coating of only 0.3 mg cm-2, which is much less than conventional interlayers and has no negative impact on the energy density but significantly enhances the electrochemical performances of the whole battery device. Due to the binding forces induced by functional groups on GO and the interconnected nanoscale channels provided by o-CNT, the thus fabricated Li-S batteries show dramatically improved specific discharge capacities of up to 750 mAh g-1 at 1 C even after 100 cycles, more than twice those of batteries without barrier coatings.

  8. Influence of capillary barrier effect on biogas distribution at the base of passive methane oxidation biosystems: Parametric study.

    PubMed

    Ahoughalandari, Bahar; Cabral, Alexandre R

    2017-05-01

    The efficiency of methane oxidation in passive methane oxidation biosystems (PMOBs) is influenced by, among other things, the intensity and distribution of the CH4 loading at the base of the methane oxidation layer (MOL). Both the intensity and distribution are affected by the capillary barrier that results from the superposition of the two materials constituting the PMOB, namely the MOL and the gas distribution layer (GDL). The effect of capillary barriers on the unsaturated flow of water has been well documented in the literature. However, its effect on gas flow through PMOBs is still poorly documented. In this study, sets of numerical simulations were performed to evaluate the effect of unsaturated hydraulic characteristics of the MOL material on the value and distribution of moisture and hence, the ease and uniformity in the distribution of the upward flow of biogas along the GDL-MOL interface. The unsaturated hydraulic parameters of the materials used to construct the experimental field plot at the St-Nicephore landfill (Quebec, Canada) were adopted to build the reference simulation of the parametric study. The behavior of the upward flow of biogas for this particular material was analyzed based on its gas intrinsic permeability function, which was obtained in the laboratory. The parameters that most influenced the distribution and the ease of biogas flow at the base of the MOL were the saturated hydraulic conductivity and pore size distribution of the MOL material, whose effects were intensified as the slope of the interface increased. The effect of initial dry density was also assessed herein. Selection of the MOL material must be made bearing in mind that these three parameters are key in the effort to prevent unwanted restriction in the upward flow of biogas, which may result in the redirection of biogas towards the top of the slope, leading to high CH4 fluxes (hotspots). In a well-designed PMOB, upward flow of biogas across the GDL-MOL interface is

  9. Anaerobic, Nitrate-Dependent Fe(II) Oxidation Under Advective Flow

    NASA Astrophysics Data System (ADS)

    Weber, K. A.; Coates, J. D.

    2005-12-01

    Microbially-catalyzed nitrate-dependent Fe(II) oxidation has been identified as a ubiquitous biogeochemical process contributing to anaerobic iron redox cycling in sedimentary environments. Most probable number enumeration revealed nitrate-dependent Fe(II) oxidizing microbial communities in groundwater and subsurface sediments in the order of 0 - 2.04 x 103 cells mL-1 and 2.39 x 102 - 1.17 x 103 cells (g wet sediment)-1, respectively. The efficacy of nitrate-dependent Fe(II) oxidation under advective flow was evaluated in a meso-scale column reactor packed with sterile low iron sand amended with subsurface sediments collected from the NABIR FRC background field site (10% mass/mass). Continuous flow of minimal medium mimicked the natural groundwater. Periodic FeCl2 and nitrate injections over a period of 49 days resulted in the retention of 95% of the iron (290 mmol). Extraction of solid-phase Fe revealed a net increase in Fe(III) of 160 mmol above background Fe(III) content indicating that 55% of the injected Fe(II) was oxidized. Differential solubility analysis of 0.5M HCl-extractable Fe and 3M HCl-extractable Fe indicated that the oxidation product was crystalline in nature as only 20% was soluble in 0.5M HCl. This formation of crystalline biogenic Fe(III) oxides is consistent with previous studies. Periodic injections of nitrate and acetate did not result in significant changes in Fe(II) or Fe(III) throughout a control column. Together these results demonstrate that native subsurface sediments harbor microbial communities capable of nitrate-dependent Fe(II) oxidation under advective flow. The biogenic formation of reactive Fe(III) oxide minerals capable of immobilizing heavy metals and radionuclides presents a plausible bioremediative strategy for contaminated subsurface environments.

  10. H2O2-dependent substrate oxidation by an engineered diiron site in a bacterial hemerythrin.

    PubMed

    Okamoto, Yasunori; Onoda, Akira; Sugimoto, Hiroshi; Takano, Yu; Hirota, Shun; Kurtz, Donald M; Shiro, Yoshitsugu; Hayashi, Takashi

    2014-04-04

    The O2-binding carboxylate-bridged diiron site in DcrH-Hr was engineered in an effort to perform the H2O2-dependent oxidation of external substrates. A His residue was introduced near the diiron site in place of a conserved residue, Ile119. The I119H variant promotes the oxidation of guaiacol and 1,4-cyclohexadiene upon addition of H2O2.

  11. An unusual temperature dependence in the oxidation of oxycarbide layers on uranium

    NASA Astrophysics Data System (ADS)

    Ellis, Walton P.

    An anomalous temperature dependence has been observed for the oxidation kinetics of outermost oxycarbide layers on polycrystalline uranium metal. Normally, oxidation or corrosion reactions are expected to proceed more rapidly as the temperature is elevated. Thus, it came as a surprise when we observed that the removal of the outermost atomic layers of carbon from uranium oxycarbide by O 2 reproducibly proceeds at a much faster rate at 25°C than at 280°C.

  12. An unusual temperature dependence in the oxidation of oxycarbide layers on uranium

    NASA Astrophysics Data System (ADS)

    Ellis, Walton P.

    1981-09-01

    An anomalous temperature dependence has been observed for the oxidation kinetics of outermost oxycarbide layers on polycrystalline uranium metal. Normally, oxidation or corrosion reactions are expected to proceed more rapidly as the temperature is elevated. Thus, it came as a surprise when we observed that the removal of the outermost atomic layers of carbon from uranium oxycarbide by O 2 reproducibly proceeds at a much faster rate at 25°C than at 280°C.

  13. Oxidative and pro-inflammatory impact of regular and denicotinized cigarettes on blood brain barrier endothelial cells: is smoking reduced or nicotine-free products really safe?

    PubMed

    Naik, Pooja; Fofaria, Neel; Prasad, Shikha; Sajja, Ravi K; Weksler, Babette; Couraud, Pierre-Olivier; Romero, Ignacio A; Cucullo, Luca

    2014-04-23

    Both active and passive tobacco smoke (TS) potentially impair the vascular endothelial function in a causative and dose-dependent manner, largely related to the content of reactive oxygen species (ROS), nicotine, and pro-inflammatory activity. Together these factors can compromise the restrictive properties of the blood-brain barrier (BBB) and trigger the pathogenesis/progression of several neurological disorders including silent cerebral infarction, stroke, multiple sclerosis and Alzheimer's disease. Based on these premises, we analyzed and assessed the toxic impact of smoke extract from a range of tobacco products (with varying levels of nicotine) on brain microvascular endothelial cell line (hCMEC/D3), a well characterized human BBB model. Initial profiling of TS showed a significant release of reactive oxygen (ROS) and reactive nitrogen species (RNS) in full flavor, nicotine-free (NF, "reduced-exposure" brand) and ultralow nicotine products. This release correlated with increased oxidative cell damage. In parallel, membrane expression of endothelial tight junction proteins ZO-1 and occludin were significantly down-regulated suggesting the impairment of barrier function. Expression of VE-cadherin and claudin-5 were also increased by the ultralow or nicotine free tobacco smoke extract. TS extract from these cigarettes also induced an inflammatory response in BBB ECs as demonstrated by increased IL-6 and MMP-2 levels and up-regulation of vascular adhesion molecules, such as VCAM-1 and PECAM-1. In summary, our results indicate that NF and ultralow nicotine cigarettes are potentially more harmful to the BBB endothelium than regular tobacco products. In addition, this study demonstrates that the TS-induced toxicity at BBB ECs is strongly correlated to the TAR and NO levels in the cigarettes rather than the nicotine content.

  14. Temperature Dependent Residual Stress Models for Ultra-High-Temperature Ceramics on High Temperature Oxidation

    NASA Astrophysics Data System (ADS)

    Wang, Ruzhuan; Li, Weiguo

    2017-08-01

    The strength of SiC-depleted layer of ultra-high-temperature ceramics on high temperature oxidation degrades seriously. The research for residual stresses developed within the SiC-depleted layer is important and necessary. In this work, the residual stress evolutions in the SiC-depleted layer and the unoxidized substrate in various stages of oxidation are studied by using the characterization models. The temperature and oxidation time dependent mechanical/thermal properties of each phase in SiC-depleted layer are considered in the models. The study shows that the SiC-depleted layer would suffer from large tensile stresses due to the great temperature changes and the formation of pores on high temperature oxidation. The stresses may lead to the cracking and even the delamination of the oxidation layer.

  15. Temperature Dependent Residual Stress Models for Ultra-High-Temperature Ceramics on High Temperature Oxidation

    NASA Astrophysics Data System (ADS)

    Wang, Ruzhuan; Li, Weiguo

    2016-11-01

    The strength of SiC-depleted layer of ultra-high-temperature ceramics on high temperature oxidation degrades seriously. The research for residual stresses developed within the SiC-depleted layer is important and necessary. In this work, the residual stress evolutions in the SiC-depleted layer and the unoxidized substrate in various stages of oxidation are studied by using the characterization models. The temperature and oxidation time dependent mechanical/thermal properties of each phase in SiC-depleted layer are considered in the models. The study shows that the SiC-depleted layer would suffer from large tensile stresses due to the great temperature changes and the formation of pores on high temperature oxidation. The stresses may lead to the cracking and even the delamination of the oxidation layer.

  16. Role for Fe(III) minerals in nitrate-dependent microbial U(IV) oxidation

    USGS Publications Warehouse

    Senko, John M.; Mohamed, Yasser; Dewers , Thomas A.; Krumholz, Lee R.

    2005-01-01

    Microbiological reduction of soluble U(VI) to insoluble U(IV) is a means of preventing the migration of that element in groundwater, but the presence of nitrate in U(IV)-containing sediments leads to U(IV) oxidation and remobilizaton. Nitrite or iron(III) oxyhydroxides may oxidize U(IV) under nitrate-reducing conditions, and we determined the rate and extent of U(IV) oxidation by these compounds. Fe(III) oxidized U(IV) at a greater rate than nitrite (130 and 10 μM U(IV)/day, respectively). In aquifer sediments, Fe(III) may be produced during microbial nitrate reduction by oxidation of Fe(II) with nitrite, or by enzymatic Fe(II) oxidation coupled to nitrate reduction. To determine which of these mechanisms was dominant, we isolated a nitrate-dependent acetate- and Fe(II)-oxidizing bacterium from a U(VI)- and nitrate-contaminated aquifer. This organism oxidized U(IV) at a greater rate and to a greater extent under acetate-oxidizing (where nitrite accumulated to 50 mM) than under Fe(II)-oxidizing conditions. We show that the observed differences in rate and extent of U(IV) oxidation are due to mineralogical differences between Fe(III) produced by reaction of Fe(II) with nitrite (amorphous) and Fe(III) produced enzymatically (goethite or lepidocrocite). Our results suggest the mineralogy and surface area of Fe(III) minerals produced under nitrate-reducing conditions affect the rate and extent of U(IV) oxidation. These results may be useful for predicting the stability of U(IV) in aquifers.

  17. Oxidative Stress Impact on Barrier Function of Porcine Angular Aqueous Plexus Cell Monolayers

    PubMed Central

    Lei, Yuan; Stamer, William D.; Wu, Jihong; Sun, Xinghuai

    2013-01-01

    Purpose. Our goal was to investigate the effect of chronic oxidative stress on angular aqueous plexus (AAP, functional equivalent to human Schlemm's canal) endothelial cells from porcine eyes. Methods. AAP cells were differentially isolated from porcine outflow tissues using puromycin selection. Confluent cultures of porcine AAP cells were grown for 2 weeks in physiological (5% O2) or hyperoxic conditions (40% O2) to model elevated oxidative stress associated with ageing. Cell growth rate, size, transendothelial electrical resistance (TEER), and hydraulic conductivity (HC) were measured. The expression of senescence-associated β-galactosidase and DNA damage marker 8-hydroxy-2′-deoxyguanosine (8-OHdG) was monitored, and the levels of cytoskeletal and cell–cell adhesion proteins such as F-actin, phospho-myosin light chain (phosphor-MLC), occludin, claudin-5, ZO-1, β-catenin, and VE-cadherin were measured by immunofluorescence staining and Western blot analysis. Results. Data showed that chronic hyperoxia inhibited cell growth rate from day 3 onward, the cell size increased by 18.2% ± 5.1%, and cells stained positive for β-galactosidase and 8-OHdG. Hyperoxia resulted in a significant 30% increase in TEER compared with the control group (P < 0.05, n = 6). When perfused in the basal-to-apical direction at 4 mm Hg, HC of AAP cells was 1.97 ± 0.12 and 1.54 ± 0.13 μL/mm Hg/min/cm2 in control and hyperoxia groups, respectively (P < 0.05, n = 6). Stressed cells expressed a significantly greater abundance of F-actin, phospho-MLC, occludin, claudin-5, β-catenin, and VE-cadherin compared to the control group by both immunofluorescence and Western blot analyses. Conclusions. Chronic exposure of AAP cells to oxidative stress decreased cell monolayer permeability and up-regulated cytoskeletal and cell–cell adhesion protein expression; suggesting that, with age and increased oxidative stress, resistance at the level of Schlemm's canal increases. PMID:23761078

  18. Enalapril attenuates ischaemic brain oedema and protects the blood-brain barrier in rats via an anti-oxidant action.

    PubMed

    Panahpour, Hamdollah; Dehghani, Gholam Abbas; Bohlooli, Shahab

    2014-03-01

    1. In the present study, we investigated the effects of postischaemic angiotensin-converting enzyme (ACE) inhibition with enalapril on vasogenic oedema formation and blood-brain barrier (BBB) integrity following transient focal cerebral ischaemia in rats. 2. Cerebral ischaemia was induced by 60 min occlusion of the right middle cerebral artery, followed by 24 h reperfusion. Vehicle and a non-hypotensive dose of enalapril (0.03 mg/kg) were administered at the beginning of the reperfusion period. A neurological deficit score (NDS) was determined for all rats at the end of the reperfusion period. Then, brain oedema formation was investigated using the wet-dry weight method and BBB permeability was evaluated on the basis of extravasation of Evans blue (EB) dye. In addition, oxidative stress was assessed by measuring reduced glutathione (GSH) and malondialdehyde (MDA) in brain homogenates. 3. Inhibition of ACE by enalapril significantly reduced NDS and decreased brain oedema formation (P < 0.05 for both). Disruption of the BBB following ischaemia resulted in considerable leakage of EB dye into the brain parenchyma of the ipsilateral hemispheres of vehicle-treated rats. Enalapril significantly (P < 0.05) decreased EB extravasation into the lesioned hemisphere. Enalapril also augmented anti-oxidant activity in ischaemic brain tissue by increasing GSH concentrations and significantly (P < 0.05) attenuating the increased MDA levels in response to ischaemia. 4. In conclusion, inhibition of ACE with a non-hypotensive dose of enalapril may protect BBB function and attenuate oedema formation via anti-oxidant actions.

  19. Size-dependent cytotoxicity of yttrium oxide nanoparticles on primary osteoblasts in vitro

    NASA Astrophysics Data System (ADS)

    Zhou, Guoqiang; Li, Yunfei; Ma, Yanyan; Liu, Zhu; Cao, Lili; Wang, Da; Liu, Sudan; Xu, Wenshi; Wang, Wenying

    2016-05-01

    Yttrium oxide nanoparticles are an excellent host material for the rare earth metals and have high luminescence efficiency providing a potential application in photodynamic therapy and biological imaging. In this study, the effects of yttrium oxide nanoparticles with four different sizes were investigated using primary osteoblasts in vitro. The results demonstrated that the cytotoxicity generated by yttrium oxide nanoparticles depended on the particle size, and smaller particles possessed higher toxicological effects. For the purpose to elucidate the relationship between reactive oxygen species generation and cell damage, cytomembrane integrity, intracellular reactive oxygen species level, mitochondrial membrane potential, cell apoptosis rate, and activity of caspase-3 in cells were then measured. Increased reactive oxygen species level was also observed in a size-dependent way. Thus, our data demonstrated that exposure to yttrium oxide nanoparticles resulted in a size-dependent cytotoxicity in cultured primary osteoblasts, and reactive oxygen species generation should be one possible damage pathway for the toxicological effects produced by yttrium oxide particles. The results may provide useful information for more rational applications of yttrium oxide nanoparticles in the future.

  20. Review of temperature dependent effects on the oxidation protection of carbon/carbon

    SciTech Connect

    Courtright, E.L.

    1991-10-01

    There is continued interest in the use of carbon/carbon for a variety of structural applications because of the excellent strength retention exhibited by this composite at high temperatures. However, the principal performance limiting issue, which is oxidation protection, has yet to be solved. Coating development efforts have been extensively pursued and the factors that limit the effectiveness of oxidation protection systems are identified. This paper reviews the temperature dependency of several important criteria such as the limitations imposed by oxygen permeability, and the kinetics of oxidation for candidate coating materials. The influence of active/passive transition, mass loss by evaporation, and thermochemical stability are also included.

  1. Induction of nitric oxide-dependent apoptosis in motor neurons by zinc-deficient superoxide dismutase.

    PubMed

    Estévez, A G; Crow, J P; Sampson, J B; Reiter, C; Zhuang, Y; Richardson, G J; Tarpey, M M; Barbeito, L; Beckman, J S

    1999-12-24

    Mutations in copper, zinc superoxide dismutase (SOD) have been implicated in the selective death of motor neurons in 2 percent of amyotrophic lateral sclerosis (ALS) patients. The loss of zinc from either wild-type or ALS-mutant SODs was sufficient to induce apoptosis in cultured motor neurons. Toxicity required that copper be bound to SOD and depended on endogenous production of nitric oxide. When replete with zinc, neither ALS-mutant nor wild-type copper, zinc SODs were toxic, and both protected motor neurons from trophic factor withdrawal. Thus, zinc-deficient SOD may participate in both sporadic and familial ALS by an oxidative mechanism involving nitric oxide.

  2. Impaired endothelial barrier function in apolipoprotein M–deficient mice is dependent on sphingosine-1-phosphate receptor 1

    PubMed Central

    Christensen, Pernille M.; Liu, Catherine H.; Swendeman, Steven L.; Obinata, Hideru; Qvortrup, Klaus; Nielsen, Lars B.; Hla, Timothy; Christoffersen, Christina

    2016-01-01

    Apolipoprotein M (ApoM) transports sphingosine-1-phosphate (S1P) in plasma, and ApoM-deficient mice (Apom−/−) have ∼50% reduced plasma S1P levels. There are 5 known S1P receptors, and S1P induces adherens junction formation between endothelial cells through the S1P1 receptor, which in turn suppresses vascular leak. Increased vascular permeability is a hallmark of inflammation. The purpose of this study was to explore the relationships between vascular leakage in ApoM deficiency and S1P1 function in normal physiology and in inflammation. Vascular permeability in the lungs was assessed by accumulation of dextran molecules (70 kDa) and was increased ∼40% in Apom−/− mice compared to WT (C57Bl6/j) mice. Reconstitution of plasma ApoM/S1P or treatment with an S1P1 receptor agonist (SEW2871) rapidly reversed the vascular leakage to a level similar to that in WT mice, suggesting that it is caused by decreased plasma levels of S1P and reduced S1P1 stimulation. In a carrageenan-induced model of inflammation, Apom−/− mice had increased vascular leakage compared with that in WT mice. Adenoviral overexpression of ApoM in Apom−/− mice decreased the vascular leakage compared to adenoviral overexpression of green fluorescent protein. The study suggests that vascular leakage of albumin-sized particles in ApoM deficiency is S1P- and S1P1-dependent and this dependency exacerbates the response to inflammatory stimuli.—Christensen, P. M., Liu, C. H., Swendeman, S. L., Obinata, H., Qvortrup, K., Nielsen, L B., Hla, T., Di Lorenzo, A., Christoffersen, C. Impaired endothelial barrier function in apolipoprotein M-deficient mice is dependent on sphingosine-1-phosphate receptor 1. PMID:26956418

  3. Impaired endothelial barrier function in apolipoprotein M-deficient mice is dependent on sphingosine-1-phosphate receptor 1.

    PubMed

    Christensen, Pernille M; Liu, Catherine H; Swendeman, Steven L; Obinata, Hideru; Qvortrup, Klaus; Nielsen, Lars B; Hla, Timothy; Di Lorenzo, Annarita; Christoffersen, Christina

    2016-06-01

    Apolipoprotein M (ApoM) transports sphingosine-1-phosphate (S1P) in plasma, and ApoM-deficient mice (Apom(-/-)) have ∼50% reduced plasma S1P levels. There are 5 known S1P receptors, and S1P induces adherens junction formation between endothelial cells through the S1P1 receptor, which in turn suppresses vascular leak. Increased vascular permeability is a hallmark of inflammation. The purpose of this study was to explore the relationships between vascular leakage in ApoM deficiency and S1P1 function in normal physiology and in inflammation. Vascular permeability in the lungs was assessed by accumulation of dextran molecules (70 kDa) and was increased ∼40% in Apom(-/-) mice compared to WT (C57Bl6/j) mice. Reconstitution of plasma ApoM/S1P or treatment with an S1P1 receptor agonist (SEW2871) rapidly reversed the vascular leakage to a level similar to that in WT mice, suggesting that it is caused by decreased plasma levels of S1P and reduced S1P1 stimulation. In a carrageenan-induced model of inflammation, Apom(-/-) mice had increased vascular leakage compared with that in WT mice. Adenoviral overexpression of ApoM in Apom(-/-) mice decreased the vascular leakage compared to adenoviral overexpression of green fluorescent protein. The study suggests that vascular leakage of albumin-sized particles in ApoM deficiency is S1P- and S1P1-dependent and this dependency exacerbates the response to inflammatory stimuli.-Christensen, P. M., Liu, C. H., Swendeman, S. L., Obinata, H., Qvortrup, K., Nielsen, L B., Hla, T., Di Lorenzo, A., Christoffersen, C. Impaired endothelial barrier function in apolipoprotein M-deficient mice is dependent on sphingosine-1-phosphate receptor 1. © FASEB.

  4. Shape-dependent bactericidal activity of copper oxide nanoparticle mediated by DNA and membrane damage

    SciTech Connect

    Laha, Dipranjan; Pramanik, Arindam; Laskar, Aparna; Jana, Madhurya; Pramanik, Panchanan; Karmakar, Parimal

    2014-11-15

    Highlights: • Spherical and sheet shaped copper oxide nanoparticles were synthesized. • Physical characterizations of these nanoparticles were done by TEM, DLS, XRD, FTIR. • They showed shape dependent antibacterial activity on different bacterial strain. • They induced both membrane damage and ROS mediated DNA damage in bacteria. - Abstract: In this work, we synthesized spherical and sheet shaped copper oxide nanoparticles and their physical characterizations were done by the X-ray diffraction, fourier transform infrared spectroscopy, transmission electron microscopy and dynamic light scattering. The antibacterial activity of these nanoparticles was determined on both gram positive and gram negative bacterial. Spherical shaped copper oxide nanoparticles showed more antibacterial property on gram positive bacteria where as sheet shaped copper oxide nanoparticles are more active on gram negative bacteria. We also demonstrated that copper oxide nanoparticles produced reactive oxygen species in both gram negative and gram positive bacteria. Furthermore, they induced membrane damage as determined by atomic force microscopy and scanning electron microscopy. Thus production of and membrane damage are major mechanisms of the bactericidal activity of these copper oxide nanoparticles. Finally it was concluded that antibacterial activity of nanoparticles depend on physicochemical properties of copper oxide nanoparticles and bacterial strain.

  5. Low-Thermal-Conductivity Pyrochlore Oxide Materials Developed for Advanced Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Zhu, Dong-Ming

    2005-01-01

    When turbine engines operate at higher temperatures, they consume less fuel, have higher efficiencies, and have lower emissions. The upper-use temperatures of the base materials (superalloys, silicon-based ceramics, etc.) used for the hot-section components of turbine engines are limited by the physical, mechanical, and corrosion characteristics of these materials. Thermal barrier coatings (TBCs) are applied as thin layers on the surfaces of these materials to further increase the operating temperatures. The current state-of-the-art TBC material in commercial use is partially yttria-stabilized zirconia (YSZ), which is applied on engine components by plasma spraying or by electron-beam physical vapor deposition. At temperatures higher than 1000 C, YSZ layers are prone to sintering, which increases thermal conductivity and makes them less effective. The sintered and densified coatings can also reduce thermal stress and strain tolerance, which can reduce the coating s durability significantly. Alternate TBC materials with lower thermal conductivity and better sintering resistance are needed to further increase the operating temperature of turbine engines.

  6. Failure Morphologies of Cyclically Oxidized ZrO2-Based Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Zhu, Dongming; Miller, Robert A.; Barrett, Charles A.

    2002-01-01

    Advanced and baseline thermal barrier coatings (TBCs) were thermal cycle tested in air at 1163 C until delamination or spallation of the ceramic top coat. The top coat of the advanced TBC s consisted of ZrO2 with various amounts of Y2O3, Yb2O3, Gd2O3, or Nd2O3 dopants. The composition of the top coat of the baseline TBC was ZrO2-8wt.%Y2O3. All top coats were deposited by air plasma spraying. A NiCrAlY or NiCoCrAlY bond coat was deposited by low pressure plasma spraying onto a single-crystal, Ni-base superalloy. The TBC lifetime for the baseline coatings was approximately 190 cycles (45 minutes at 1163 C per cycle) while the lifetime for the advanced coatings was as high as 425 cycles. The fracture surfaces and sample cross sections were examined after TBC failure by SEM and optical microscopy, and the top coats were further examined by X-ray diffraction. These post-test studies revealed that the fracture path largely followed splat boundaries with some trans-splat fracture. However, there were no obvious distinguishing features which explained the difference in TBC lifetimes between some of the advanced and baseline coatings.

  7. Effect of oxygen barrier coatings on oxidation and embrittlement of Ti-6Al-2Sn-4Zr-2Mo foil in heat shield applications

    NASA Technical Reports Server (NTRS)

    Clark, R. K.; Unnam, J.; Wiedemann, K. E.

    1986-01-01

    Because of the loss of ductility with exposure to oxidizing conditions, long time applications of titanium alloys have been limited to temperatures below 700 K and short time applications have been limited to temperatures below 815 K. Oxygen barrier coatings for shielding Ti-6Al-2Sn-4Zr-2Mo alloy from oxidation during exposure to high temperatures were studied using foil gage specimens. The coatings included micrometer-thick sputtered SiO2 and chemical-vapor-deposited silicate layers both with and without an aluminum basecoat. The oxidation rates and resistance to embrittlement of the coated specimens were significantly better than those of the uncoated specimens.

  8. Obesity in aging exacerbates blood-brain barrier disruption, neuroinflammation, and oxidative stress in the mouse hippocampus: effects on expression of genes involved in beta-amyloid generation and Alzheimer's disease.

    PubMed

    Tucsek, Zsuzsanna; Toth, Peter; Sosnowska, Danuta; Gautam, Tripti; Mitschelen, Matthew; Koller, Akos; Szalai, Gabor; Sonntag, William E; Ungvari, Zoltan; Csiszar, Anna

    2014-10-01

    There is growing evidence that obesity has deleterious effects on the brain and cognitive function in the elderly population. However, the specific mechanisms through which aging and obesity interact to promote cognitive decline remain unclear. To test the hypothesis that aging exacerbates obesity-induced cerebromicrovascular damage and neuroinflammation, we compared young (7 months) and aged (24 months) high fat diet-fed obese C57BL/6 mice. Aging exacerbated obesity-induced systemic inflammation and blood-brain barrier disruption, as indicated by the increased circulating levels of proinflammatory cytokines and increased presence of extravasated immunoglobulin G in the hippocampus, respectively. Obesity-induced blood-brain barrier damage was associated with microglia activation, upregulation of activating Fc-gamma receptors and proinflammatory cytokines, and increased oxidative stress. Treatment of cultured primary microglia with sera derived from aged obese mice resulted in significantly more pronounced microglia activation and oxidative stress, as compared with treatment with young sera. Serum-induced activation and oxidative stress were also exacerbated in primary microglia derived from aged animals. Hippocampal expression of genes involved in regulation of the cellular amyloid precursor protein-dependent signaling pathways, beta-amyloid generation, and the pathogenesis of tauopathy were largely unaffected by obesity in aged mice. Collectively, obesity in aging is associated with a heightened state of systemic inflammation, which exacerbates blood-brain barrier disruption. The resulting neuroinflammation and oxidative stress in the mouse hippocampus likely contribute to the significant cognitive decline observed in aged obese animals. © The Author 2013. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  9. Oxidative removal of implanted photoresists and barrier metals in semiconductor processing

    NASA Astrophysics Data System (ADS)

    Govindarajan, Rajkumar

    Chemical systems containing oxidants are widely used at various stages in semiconductor processing, particularly for wet cleaning and polishing applications. This dissertation presents a series of studies related to oxidative removal of materials in the Front-End-Of-Line (FEOL) and Chemical Mechanical Planarization (CMP) processes during IC fabrication. In the first part of this study, stripping of photoresists exposed to high dose of ions (1E16 As/cm2) was investigated in activated hydrogen peroxide systems. Stripping of photoresists (PR) exposed to high dose (>1E15/cm2) ion beams is one of the most challenging steps in FEOL processing. This is due to unreactive crust layer that forms on the resist surface during ion implantation. The use of hydrogen peroxide systems activated by metal ion or UV light, for disrupting crust formed on deep UV resist to enable complete removal of crust as well as underlying photoresist was investigated. A systematic evaluation of variables such as hydrogen peroxide and metal ion concentration, UV intensity, temperature and time was conducted and an optimal formulation capable of attacking the crust was developed. A two step process involving pretreatment with activated hydrogen peroxide solution, followed by treatment with sulfuric acid-hydrogen peroxide mixture (SPM) was developed for complete removal of crusted resist films. In the second part of this study, electrochemically enhanced abrasive removal of Ta/TaN films was investigated in solutions containing 2,5 dihydroxy benzene sulfonic acid (DBSA) and potassium iodate (KIO3). This method known as Electrically-assisted Chemical Mechanical Planarization (ECMP) is generating a lot of interest in IC manufacturing. Ta/TaN films were abraded at low pressures (<0.5 psi) on a polyurethane pad under galvanostatic conditions. The effect of variables including pH, KIO3 concentration, and current density has been explored. In the optimized formulation, tantalum and tantalum nitride removal

  10. Light-Dependent Aerobic Methane Oxidation Reduces Methane Emissions from Seasonally Stratified Lakes

    PubMed Central

    Oswald, Kirsten; Milucka, Jana; Brand, Andreas; Littmann, Sten; Wehrli, Bernhard; Kuypers, Marcel M. M.; Schubert, Carsten J.

    2015-01-01

    Lakes are a natural source of methane to the atmosphere and contribute significantly to total emissions compared to the oceans. Controls on methane emissions from lake surfaces, particularly biotic processes within anoxic hypolimnia, are only partially understood. Here we investigated biological methane oxidation in the water column of the seasonally stratified Lake Rotsee. A zone of methane oxidation extending from the oxic/anoxic interface into anoxic waters was identified by chemical profiling of oxygen, methane and δ13C of methane. Incubation experiments with 13C-methane yielded highest oxidation rates within the oxycline, and comparable rates were measured in anoxic waters. Despite predominantly anoxic conditions within the zone of methane oxidation, known groups of anaerobic methanotrophic archaea were conspicuously absent. Instead, aerobic gammaproteobacterial methanotrophs were identified as the active methane oxidizers. In addition, continuous oxidation and maximum rates always occurred under light conditions. These findings, along with the detection of chlorophyll a, suggest that aerobic methane oxidation is tightly coupled to light-dependent photosynthetic oxygen production both at the oxycline and in the anoxic bottom layer. It is likely that this interaction between oxygenic phototrophs and aerobic methanotrophs represents a widespread mechanism by which methane is oxidized in lake water, thus diminishing its release into the atmosphere. PMID:26193458

  11. Mechanisms Underpinning Degradation of Protective Oxides and Thermal Barrier Coatings in High Hydrogen Content (HHC) - Fueled Turbines

    SciTech Connect

    Mumm, Daniel

    2013-08-31

    The overarching goal of this research program has been to evaluate the potential impacts of coal-derived syngas and high-hydrogen content fuels on the degradation of turbine hot-section components through attack of protective oxides and thermal barrier coatings. The primary focus of this research program has been to explore mechanisms underpinning the observed degradation processes, and connections to the combustion environments and characteristic non-combustible constituents. Based on the mechanistic understanding of how these emerging fuel streams affect materials degradation, the ultimate goal of the program is to advance the goals of the Advanced Turbine Program by developing materials design protocols leading to turbine hot-section components with improved resistance to service lifetime degradation under advanced fuels exposures. This research program has been focused on studying how: (1) differing combustion environments – relative to traditional natural gas fired systems – affect both the growth rate of thermally grown oxide (TGO) layers and the stability of these oxides and of protective thermal barrier coatings (TBCs); and (2) how low levels of fuel impurities and characteristic non-combustibles interact with surface oxides, for instance through the development of molten deposits that lead to hot corrosion of protective TBC coatings. The overall program has been comprised of six inter-related themes, each comprising a research thrust over the program period, including: (i) evaluating the role of syngas and high hydrogen content (HHC) combustion environments in modifying component surface temperatures, heat transfer to the TBC coatings, and thermal gradients within these coatings; (ii) understanding the instability of TBC coatings in the syngas and high hydrogen environment with regards to decomposition, phase changes and sintering; (iii) characterizing ash deposition, molten phase development and infiltration, and associated corrosive

  12. Exocyst Sec10 protects epithelial barrier integrity and enhances recovery following oxidative stress, by activation of the MAPK pathway.

    PubMed

    Park, Kwon Moo; Fogelgren, Ben; Zuo, Xiaofeng; Kim, Jinu; Chung, Daniel C; Lipschutz, Joshua H

    2010-03-01

    Cell-cell contacts are essential for epithelial cell function, and disruption is associated with pathological conditions including ischemic kidney injury. We hypothesize that the exocyst, a highly-conserved eight-protein complex that targets secretory vesicles carrying membrane proteins, is involved in maintaining renal epithelial barrier integrity. Accordingly, increasing exocyst expression in renal tubule cells may protect barrier function from oxidative stress resulting from ischemia and reperfusion (I/R) injury. When cultured on plastic, Madin-Darby canine kidney (MDCK) cells overexpressing Sec10, a central exocyst component, formed domes showing increased resistance to hydrogen peroxide (H2O2). Transepithelial electric resistance (TER) of Sec10-overexpressing MDCK cells grown on Transwell filters was higher than in control MDCK cells, and the rate of TER decrease following H2O2 treatment was less in Sec10-overexpressing MDCK cells compared with control MDCK cells. After removal of H2O2, TER returned to normal more rapidly in Sec10-overexpressing compared with control MDCK cells. In collagen culture MDCK cells form cysts, and H2O2 treatment damaged Sec10-overexpressing MDCK cell cysts less than control MDCK cell cysts. The MAPK pathway has been shown to protect animals from I/R injury. Levels of active ERK, the final MAPK pathway step, were higher in Sec10-overexpressing compared with control MDCK cells. U0126 inhibited ERK activation, exacerbated the H2O2-induced decrease in TER and cyst disruption, and delayed recovery of TER following H2O2 removal. Finally, in mice with renal I/R injury, exocyst expression decreased early and returned to normal concomitant with functional recovery, suggesting that the exocyst may be involved in the recovery following I/R injury.

  13. Exocyst Sec10 protects epithelial barrier integrity and enhances recovery following oxidative stress, by activation of the MAPK pathway

    PubMed Central

    Park, Kwon Moo; Fogelgren, Ben; Zuo, Xiaofeng; Kim, Jinu; Chung, Daniel C.

    2010-01-01

    Cell-cell contacts are essential for epithelial cell function, and disruption is associated with pathological conditions including ischemic kidney injury. We hypothesize that the exocyst, a highly-conserved eight-protein complex that targets secretory vesicles carrying membrane proteins, is involved in maintaining renal epithelial barrier integrity. Accordingly, increasing exocyst expression in renal tubule cells may protect barrier function from oxidative stress resulting from ischemia and reperfusion (I/R) injury. When cultured on plastic, Madin-Darby canine kidney (MDCK) cells overexpressing Sec10, a central exocyst component, formed domes showing increased resistance to hydrogen peroxide (H2O2). Transepithelial electric resistance (TER) of Sec10-overexpressing MDCK cells grown on Transwell filters was higher than in control MDCK cells, and the rate of TER decrease following H2O2 treatment was less in Sec10-overexpressing MDCK cells compared with control MDCK cells. After removal of H2O2, TER returned to normal more rapidly in Sec10-overexpressing compared with control MDCK cells. In collagen culture MDCK cells form cysts, and H2O2 treatment damaged Sec10-overexpressing MDCK cell cysts less than control MDCK cell cysts. The MAPK pathway has been shown to protect animals from I/R injury. Levels of active ERK, the final MAPK pathway step, were higher in Sec10-overexpressing compared with control MDCK cells. U0126 inhibited ERK activation, exacerbated the H2O2-induced decrease in TER and cyst disruption, and delayed recovery of TER following H2O2 removal. Finally, in mice with renal I/R injury, exocyst expression decreased early and returned to normal concomitant with functional recovery, suggesting that the exocyst may be involved in the recovery following I/R injury. PMID:20053792

  14. Oxidants Positively or Negatively Regulate Nuclear Factor κB in a Context-dependent Manner*

    PubMed Central

    Loukili, Noureddine; Rosenblatt-Velin, Nathalie; Rolli, Joëlle; Levrand, Sandra; Feihl, François; Waeber, Bernard; Pacher, Pal; Liaudet, Lucas

    2010-01-01

    Redox-based mechanisms play critical roles in the regulation of multiple cellular functions. NF-κB, a master regulator of inflammation, is an inducible transcription factor generally considered to be redox-sensitive, but the modes of interactions between oxidant stress and NF-κB are incompletely defined. Here, we show that oxidants can either amplify or suppress NF-κB activation in vitro by interfering both with positive and negative signals in the NF-κB pathway. NF-κB activation was evaluated in lung A549 epithelial cells stimulated with tumor necrosis factor α (TNFα), either alone or in combination with various oxidant species, including hydrogen peroxide or peroxynitrite. Exposure to oxidants after TNFα stimulation produced a robust and long lasting hyperactivation of NF-κB by preventing resynthesis of the NF-κB inhibitor IκB, thereby abrogating the major negative feedback loop of NF-κB. This effect was related to continuous activation of inhibitor of κB kinase (IKK), due to persistent IKK phosphorylation consecutive to oxidant-mediated inactivation of protein phosphatase 2A. In contrast, exposure to oxidants before TNFα stimulation impaired IKK phosphorylation and activation, leading to complete prevention of NF-κB activation. Comparable effects were obtained when interleukin-1β was used instead of TNFα as the NF-κB activator. This study demonstrates that the influence of oxidants on NF-κB is entirely context-dependent, and that the final outcome (activation versus inhibition) depends on a balanced inhibition of protein phosphatase 2A and IKK by oxidant species. Our findings provide a new conceptual framework to understand the role of oxidant stress during inflammatory processes. PMID:20299457

  15. Bacterial production of organic acids enhances H2O2-dependent iodide oxidation.

    PubMed

    Li, Hsiu-Ping; Yeager, Chris M; Brinkmeyer, Robin; Zhang, Saijin; Ho, Yi-Fang; Xu, Chen; Jones, Whitney L; Schwehr, Kathleen A; Otosaka, Shigeyoshi; Roberts, Kimberly A; Kaplan, Daniel I; Santschi, Peter H

    2012-05-01

    To develop an understanding of the role that microorganisms play in the transport of (129)I in soil-water systems, bacteria isolated from subsurface sediments were assessed for iodide oxidizing activity. Spent liquid medium from 27/84 bacterial cultures enhanced iodide oxidation 2-10 fold in the presence of H(2)O(2). Organic acids secreted by the bacteria were found to enhance iodide oxidation by (1) lowering the pH of the spent medium, and (2) reacting with H(2)O(2) to form peroxy carboxylic acids, which are extremely strong oxidizing agents. H(2)O(2)-dependent iodide oxidation increased exponentially from 8.4 to 825.9 μM with decreasing pH from 9 to 4. Organic acids with ≥2 carboxy groups enhanced H(2)O(2)-dependent iodide oxidation (1.5-15-fold) as a function of increasing pH above pH 6.0, but had no effect at pH ≤ 5.0. The results indicate that as pH decreases (≤5.0), increasing H(2)O(2) hydrolysis is the driving force behind iodide oxidation. However, at pH ≥ 6.0, spontaneous decomposition of peroxy carboxylic acids, generated from H(2)O(2) and organic acids, contributes significantly to iodide oxidation. The results reveal an indirect microbial mechanism, organic acid secretion coupled to H(2)O(2) production, that could enhance iodide oxidation and organo-iodine formation in soils and sediments. © 2012 American Chemical Society

  16. A consistent approach for the development of a comprehensive data base of time-dependent parameters for concrete engineered barriers

    SciTech Connect

    Seetharam, Suresh C; Perko, Janez; Jacques, Diederik; Mallants, Dirk

    2013-07-01

    This paper presents a consistent approach for the development of a comprehensive data base of time-dependent hydraulic and transport parameters for concrete engineered barriers of the future Dessel near surface repository for low level waste. The parameter derivation is based on integration of selected data obtained through an extensive literature review, data from experimental studies on cementitious materials specific for the Dessel repository and numerical modelling using physically-based models of water and mass transport. Best estimate parameter values for assessment calculations are derived, together with source and expert range and their probability density function wherever the data was sufficient. We further discuss a numerical method for up-scaling laboratory derived parameter values to the repository scale; the resulting large-scale effective parameters are commensurate with numerical grids used in models for radionuclide migration. To accommodate different levels of conservatism in the various assessment calculations defined by ONDRAF/NIRAS, several sets of parameter values have been derived based on assumptions that introduce different degrees of conservatism. For pertinent parameters, the time evolution of such properties due to the long-term concrete degradation is also addressed. The implementation of the consistent approach is demonstrated by considering the pore water diffusion coefficient as an example. (authors)

  17. Junction-Structure-Dependent Schottky Barrier Inhomogeneity and Device Ideality of Monolayer MoS2 Field-Effect Transistors.

    PubMed

    Moon, Byoung Hee; Han, Gang Hee; Kim, Hyun; Choi, Homin; Bae, Jung Jun; Kim, Jaesu; Jin, Youngjo; Jeong, Hye Yun; Joo, Min-Kyu; Lee, Young Hee; Lim, Seong Chu

    2017-03-29

    Although monolayer transition metal dichalcogenides (TMDs) exhibit superior optical and electrical characteristics, their use in digital switching devices is limited by incomplete understanding of the metal contact. Comparative studies of Au top and edge contacts with monolayer MoS2 reveal a temperature-dependent ideality factor and Schottky barrier height (SBH). The latter originates from inhomogeneities in MoS2 caused by defects, charge puddles, and grain boundaries, which cause local variation in the work function at Au-MoS2 junctions and thus different activation temperatures for thermionic emission. However, the effect of inhomogeneities due to impurities on the SBH varies with the junction structure. The weak Au-MoS2 interaction in the top contact, which yields a higher SBH and ideality factor, is more affected by inhomogeneities than the strong interaction in the edge contact. Observed differences in the SBH and ideality factor in different junction structures clarify how the SBH and inhomogeneities can be controlled in devices containing TMD materials.

  18. Defect Clustering and Nano-phase Structure Characterization of Multicomponent Rare Earth-Oxide-Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    2004-01-01

    Advanced thermal barrier coatings (TBCs) have been developed by incorporating multicomponent rare earth oxide dopants into zirconia-based thermal barrier coatings to promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nanophases within the coating systems. In this paper, the defect clusters, induced by Nd, Gd, and Yb rare earth dopants in the zirconia-yttria thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The TEM lattice imaging, selected area diffraction (SAD), and electron energy-loss spectroscopy (EELS) analyses demonstrated that the extensive nanoscale rare earth dopant segregation exists in the plasma-sprayed and electron-physical-vapor-deposited (EB PVD) thermal barrier coatings. The nanoscale concentration heterogeneity and the resulting large lattice distortion promoted the formation of parallel and rotational defective lattice clusters in the coating systems. The presence of the 5-to 100-nm-sized defect clusters and nanophases is believed to be responsible for the significant reduction of thermal conductivity, improved sintering resistance, and long-term high temperature stability of the advanced thermal barrier coating systems.

  19. Phosphorylation of Grainy head by ERK is essential for wound-dependent regeneration but not for development of an epidermal barrier.

    PubMed

    Kim, Myungjin; McGinnis, William

    2011-01-11

    Grainy head (GRH) is a key transcription factor responsible for epidermal barrier formation and repair, whose function is highly conserved across diverse animal species. However, it is not known how GRH function is reactivated to repair differentiated epidermal barriers after wounding. Here, we show that GRH is directly regulated by extracellular signal-regulated kinase (ERK) phosphorylation, which is required for wound-dependent expression of GRH target genes in epidermal cells. Serine 91 is the principal residue in GRH that is phosphorylated by ERK. Although mutations of the ERK phosphorylation sites in GRH do not impair its DNA binding function, the ERK sites in GRH are required to activate Dopa decarboxylase (Ddc) and misshapen (msn) epidermal wound enhancers as well as functional regeneration of an epidermal barrier upon wounding. This result indicates that the phosphorylation sites are essential for damaged epidermal barrier repair. However, GRH with mutant ERK phosphorylation sites can still promote barrier formation during embryonic epidermal development, suggesting that ERK sites are dispensable for the GRH function in establishing epidermal barrier integrity. These results provide mechanistic insight into how tissue repair can be initiated by posttranslational modification of a key transcription factor that normally mediates the developmental generation of that tissue.

  20. Microbubble-size dependence of focused ultrasound-induced blood-brain barrier opening in mice in vivo.

    PubMed

    Choi, James J; Feshitan, Jameel A; Baseri, Babak; Wang, Shougang; Tung, Yao-Sheng; Borden, Mark A; Konofagou, Elisa E

    2010-01-01

    The therapeutic efficacy of neurological agents is severely limited, because large compounds do not cross the blood-brain barrier (BBB). Focused ultrasound (FUS) sonication in the presence of microbubbles has been shown to temporarily open the BBB, allowing systemically administered agents into the brain. Until now, polydispersed microbubbles (1-10 microm in diameter) were used, and, therefore, the bubble sizes better suited for inducing the opening remain unknown. Here, the FUS-induced BBB opening dependence on microbubble size is investigated. Bubbles at 1-2 and 4-5 microm in diameter were separately size-isolated using differential centrifugation before being systemically administered in mice (n = 28). The BBB opening pressure threshold was identified by varying the peak-rarefactional pressure amplitude. BBB opening was determined by fluorescence enhancement due to systemically administered, fluorescent-tagged, 3-kDa dextran. The identified threshold fell between 0.30 and 0.46 MPa in the case of 1-2 microm bubbles and between 0.15 and 0.30 MPa in the 4-5 microm case. At every pressure studied, the fluorescence was greater with the 4-5 mum than with the 1-2 microm bubbles. At 0.61 MPa, in the 1-2 microm bubble case, the fluorescence amount and area were greater in the thalamus than in the hippocampus. In conclusion, it was determined that the FUS-induced BBB opening was dependent on both the size distribution in the injected microbubble volume and the brain region targeted.

  1. Microbubble-Size Dependence of Focused Ultrasound-Induced Blood–Brain Barrier Opening in Mice In Vivo

    PubMed Central

    Choi, James J.; Feshitan, Jameel A.; Baseri, Babak; Wang, Shougang; Tung, Yao-Sheng; Borden, Mark A.; Konofagou, Elisa E.

    2014-01-01

    The therapeutic efficacy of neurological agents is severely limited, because large compounds do not cross the blood–brain barrier (BBB). Focused ultrasound (FUS) sonication in the presence of microbubbles has been shown to temporarily open the BBB, allowing systemically administered agents into the brain. Until now, polydispersed microbubbles (1–10 μm in diameter) were used, and, therefore, the bubble sizes better suited for inducing the opening remain unknown. Here, the FUS-induced BBB opening dependence on microbubble size is investigated. Bubbles at 1–2 and 4–5 μm in diameter were separately size-isolated using differential centrifugation before being systemically administered in mice (n = 28). The BBB opening pressure threshold was identified by varying the peak-rarefactional pressure amplitude. BBB opening was determined by fluorescence enhancement due to systemically administered, fluorescent-tagged, 3-kDa dextran. The identified threshold fell between 0.30 and 0.46 MPa in the case of 1–2 μm bubbles and between 0.15 and 0.30 MPa in the 4–5 μm case. At every pressure studied, the fluorescence was greater with the 4–5 μm than with the 1–2 μm bubbles. At 0.61 MPa, in the 1–2 μm bubble case, the fluorescence amount and area were greater in the thalamus than in the hippocampus. In conclusion, it was determined that the FUS-induced BBB opening was dependent on both the size distribution in the injected microbubble volume and the brain region targeted. PMID:19846365

  2. The Dependence of the Ultrasound-Induced Blood-Brain Barrier Opening Characteristics on Microbubble Size In Vivo

    NASA Astrophysics Data System (ADS)

    Choi, James J.; Feshitan, Jameel A.; Wang, Shougang; Tung, Yao-Sheng; Baseri, Babak; Borden, Mark A.; Konofagou, Elisa E.

    2009-04-01

    Recent neuropharmaceutical developments have led to potent disease-modifying drugs. In spite of these advancements, most agents cannot traverse the blood-brain barrier (BBB) and deposit in the brain. Focused ultrasound (FUS) with microbubbles has been shown to induce noninvasive, localized, and transient BBB opening. Although promising, safety and efficacy concerns still remain. Previously reported experiments used conventional imaging contrast agents that have a wide size distribution. In this study, we hypothesize that BBB opening characteristics are dependent on bubble diameter. A 25 μl bolus of in-house manufactured, lipid-shelled bubbles with either 1-2 or 4-5 μm diameter ranges was injected intravenously. Pulsed FUS (frequency: 1.5 MHz, peak-negative pressure: 146-607 kPa, duty cycle: 20%, duration: 1-min) was then applied to the left hippocampus of mice (n = 16) in vivo through the intact skin and skull. MRI or fluorescence microscopy was used to determine BBB opening. Contrast-enhanced (Omniscan™; 0.75 mL; molecular weight: 574 Da) MRI (9.4-T) was acquired on multiple days after sonication to determine BBB opening and closing. Fluorescence microscopy was also used to determine the feasibility of delivering large, 3 kDa dextran compounds through the BBB. The BBB opening acoustic pressure threshold for the 4-5μm bubbles was in the 146-304 kPa range while the threshold for the 1-2μm bubbles was higher. In conclusion, FUS-induced BBB opening and closing was shown to be dependent on the bubble diameter indicating the possibility of specifically designing bubbles to enhance this therapeutic application.

  3. Study of polystyrene-poly(ethylene oxide) diblock copolymer monolayers as barriers to protein adsorption

    NASA Astrophysics Data System (ADS)

    Jogikalmath, Gangadhar

    Protein adsorption resistant surfaces find use in many biomedical applications, such as catheters, dialysis devices and biosensors that involve blood contacting surfaces. To ensure long-term functioning of a device in an environment containing protein, there is a need to produce homogeneous surfaces that are resistant to protein adsorption. A polymer brush covered surface, produced by either physical adsorption or chemical grafting of hydrophilic polymers to surfaces, is one of the approaches used in creating such surfaces. High grafting densities needed to make an effective barrier are usually not realized in chemical grafting/adsorption from solution, due to self-exclusion of surface grafted molecules. In this dissertation polymer brush surfaces formed by chemically grafted PEO molecules and transferred monolayers of PS-b-PEO diblock copolymers are investigated using atomic force microscopy (AFM), surface plasmon resonance (SPR) and surface pressure measurement techniques. An AFM adhesion mapping technique was used to evaluate the surface heterogeneity of chemically modified PEO and transferred diblock copolymer monolayer surfaces. The behavior of PS-b-PEO molecules at the air-water interface was studied using Langmuir trough. The stability of transferred diblock copolymer monolayers was investigated using AFM. Using SPR, protein adsorption to the diblock copolymer layers was investigated as a function of protein size (using HSA and ferritin) as a function of grafting density of PEO in the monolayer. It was seen that a lower density of the PS-b-PEO monolayer was sufficient to prevent ferritin adsorption (larger protein) while a higher density brush layer was required to achieve complete prevention of HSA adsorption to the surface. The effect of mobility of the polymer brush layer on protein adsorption prevention was analyzed using SPR and surface pressure measurements. It was seen that the copolymer monolayer (at the air-buffer interface) rearranged itself to

  4. Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

    PubMed Central

    Fenske, Daniela; Bardenhagen, Ingo; Westphal, Anne; Knipper, Martin; Plaggenborg, Thorsten; Kolny-Olesiak, Joanna; Parisi, Jürgen

    2015-01-01

    Summary Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx + oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous α-Mn2O3 particles were synthesized by calcination of Mn(II) glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD) measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II) glycolate precursor to α-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM) and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous α-Mn2O3 species. PMID:25671151

  5. Applied voltage dependence of nano-oxidation of ferromagnetic thin films using atomic force microscope

    NASA Astrophysics Data System (ADS)

    Takemura, Yasushi; Kidaka, Seiichi; Watanabe, Keizo; Nasu, Yasuaki; Yamada, Tsutomu; Shirakashi, Jun-ichi

    2003-05-01

    Nanodots of Ni, CoFe, and Cr oxide were fabricated by the nano-oxidation technique using atomic force microscope. The dot size was controlled from 40 to 200 nm by changing the pulse voltage applied to the cantilever from 2 to 10 V. In order to evaluate the size of the nanostructures quantitatively, the electric field emitted from the cantilever was calculated. The threshold electric field strength was defined as the minimum strength to promote the oxidation. The threshold field strength of the order of 107 V/m was derived by fitting the experimental results. The voltage dependence of the size of fabricated Cr-oxide dots was fitted well by the calculation. The dot size of the ferromagnet-based oxide was fluctuating and did not agree with the calculation. From the theoretical analysis, it was suggested that the size of the nanostructures did not depend on the distance between the cantilever and film surface, but significantly depended on the curvature radius of the cantilever.

  6. Polyinosinic:polycytidylic acid induces protein kinase D-dependent disassembly of apical junctions and barrier dysfunction in airway epithelial cells.

    PubMed

    Rezaee, Fariba; Meednu, Nida; Emo, Jason A; Saatian, Bahman; Chapman, Timothy J; Naydenov, Nayden G; De Benedetto, Anna; Beck, Lisa A; Ivanov, Andrei I; Georas, Steve N

    2011-12-01

    Disruption of the epithelial barrier might be a risk factor for allergen sensitization and asthma. Viral respiratory tract infections are strongly associated with asthma exacerbation, but the effects of respiratory viruses on airway epithelial barrier function are not well understood. Many viruses generate double-stranded RNA, which can lead to airway inflammation and initiate an antiviral immune response. We investigated the effects of the synthetic double-stranded RNA polyinosinic:polycytidylic acid (polyI:C) on the structure and function of the airway epithelial barrier in vitro. 16HBE14o- human bronchial epithelial cells and primary airway epithelial cells at an air-liquid interface were grown to confluence on Transwell inserts and exposed to polyI:C. We studied epithelial barrier function by measuring transepithelial electrical resistance and paracellular flux of fluorescent markers and structure of epithelial apical junctions by means of immunofluorescence microscopy. PolyI:C induced a profound decrease in transepithelial electrical resistance and increase in paracellular permeability. Immunofluorescence microscopy revealed markedly reduced junctional localization of zonula occludens-1, occludin, E-cadherin, β-catenin, and disorganization of junction-associated actin filaments. PolyI:C induced protein kinase D (PKD) phosphorylation, and a PKD antagonist attenuated polyI:C-induced disassembly of apical junctions and barrier dysfunction. PolyI:C has a powerful and previously unsuspected disruptive effect on the airway epithelial barrier. PolyI:C-dependent barrier disruption is mediated by disassembly of epithelial apical junctions, which is dependent on PKD signaling. These findings suggest a new mechanism potentially underlying the associations between viral respiratory tract infections, airway inflammation, and allergen sensitization. Copyright © 2011 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

  7. Polyinosinic:polycytidylic acid induces protein kinase D–dependent disassembly of apical junctions and barrier dysfunction in airway epithelial cells

    PubMed Central

    Rezaee, Fariba; Meednu, Nida; Emo, Jason A.; Saatian, Bahman; Chapman, Timothy J.; Naydenov, Nayden G.; De Benedetto, Anna; Beck, Lisa A.; Ivanov, Andrei I.; Georas, Steve N.

    2011-01-01

    Background Disruption of the epithelial barrier might be a risk factor for allergen sensitization and asthma. Viral respiratory tract infections are strongly associated with asthma exacerbation, but the effects of respiratory viruses on airway epithelial barrier function are not well understood. Many viruses generate double-stranded RNA, which can lead to airway inflammation and initiate an antiviral immune response. Objectives We investigated the effects of the synthetic double-stranded RNA polyinosinic:polycytidylic acid (polyI:C) on the structure and function of the airway epithelial barrier in vitro. Methods 16HBE14o- human bronchial epithelial cells and primary airway epithelial cells at an air-liquid interface were grown to confluence on Transwell inserts and exposed to polyI:C. We studied epithelial barrier function by measuring transepithelial electrical resistance and paracellular flux of fluorescent markers and structure of epithelial apical junctions by means of immunofluorescence microscopy. Results PolyI:C induced a profound decrease in transepithelial electrical resistance and increase in paracellular permeability. Immunofluorescence microscopy revealed markedly reduced junctional localization of zonula occludens-1, occludin, E-cadherin, β-catenin, and disorganization of junction-associated actin filaments. PolyI:C induced protein kinase D (PKD) phosphorylation, and a PKD antagonist attenuated polyI:C-induced disassembly of apical junctions and barrier dysfunction. Conclusions PolyI:C has a powerful and previously unsuspected disruptive effect on the airway epithelial barrier. PolyI:C-dependent barrier disruption is mediated by disassembly of epithelial apical junctions, which is dependent on PKD signaling. These findings suggest a new mechanism potentially underlying the associations between viral respiratory tract infections, airway inflammation, and allergen sensitization. PMID:21996340

  8. Sliding Speed-Dependent Tribochemical Wear of Oxide-Free Silicon

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Qi, Yaqiong; Yu, Bingjun; Qian, Linmao

    2017-06-01

    Fundamental understanding of tribochemical wear mechanism of oxide-free single crystalline silicon (without native oxide layer) is essential to optimize the process of ultra-precision surface manufacturing. Here, we report sliding speed-dependent nanowear of oxide-free silicon against SiO2 microspheres in air and in deionized water. When contact pressure is too low to induce Si yield, tribochemical wear occurs with the existence of water molecules and wear volume decreases logarithmically to constant as sliding speed increased. TEM and Raman observations indicate that the dynamics of rupture and reformation of interfacial bonding bridges result in the variation of tribochemical wear of the oxide-free Si with the increase of sliding speed.

  9. Spectrum-Dependent Spiro-OMeTAD Oxidization Mechanism in Perovskite Solar Cells.

    PubMed

    Wang, Shen; Yuan, Wen; Meng, Ying Shirley

    2015-11-11

    We propose a spectrum-dependent mechanism for the oxidation of 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) with bis(trifluoromethane)sulfonimide lithium salt (LiTFSI), which is commonly used in perovskite solar cells as the hole transport layer. The perovskite layer plays different roles in the Spiro-OMeTAD oxidization for various spectral ranges. The effect of oxidized Spiro-OMeTAD on the solar cell performance was observed and characterized. With the initial long-wavelength illumination (>450 nm), the charge recombination at the TiO2/Spiro-OMeTAD interface was increased due to the higher amount of the oxidized Spiro-OMeTAD. On the other hand, the increased conductivity of the Spiro-OMeTAD layer and enhanced charge transfer at the Au/Spiro-OMeTAD interface facilitated the solar cell performance.

  10. Transparent bionanocomposite films based on chitosan and TEMPO-oxidized cellulose nanofibers with enhanced mechanical and barrier properties.

    PubMed

    Soni, Bhawna; Hassan, El Barbary; Schilling, M Wes; Mahmoud, Barakat

    2016-10-20

    The development of biobased active films for use in food packaging is increasing due to low cost, environmental appeal, renewability and availability. The objective of this research was to develop an effective and complete green approach for the production of bionanocomposite films with enhanced mechanical and barrier properties. This was accomplished by incorporating TEMPO-oxidized cellulose nanofibers (2,2,6,6-tetramethylpiperidine-1-oxyl radical) into a chitosan matrix. An aqueous suspension of chitosan (100-75wt%), sorbitol (25wt%) and TEMPO-oxidized cellulose nanofibers (TEMPO-CNFs, 0-25wt%) were cast in an oven at 40°C for 2-4days. Films were preconditioned at 25°C and 50% RH for characterization. The surface morphology of the films was revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties and crystal structure of the films were evaluated by thermogravimetric analysis (TGA-DTG) and X-ray diffraction (XRD). Incorporation of TEMPO-CNFs enhanced the mechanical strength of the films due to the high aspect ratio (3-20nm width, and 10-100nm length) of TEMPO-CNFs and strong interactions with the chitosan matrix. Oxygen and water vapor transmission rates for films that are prepared with chitosan and TEMPO-CNFs (15-25wt%) were significantly reduced. Furthermore, these bionanocomposite films had good thermal stability. Use of TEMPO-CNFs in this method makes it possible to produce bionanocomposite films that are flexible, transparent, and thus have potential in food packaging applications.

  11. Lycium Barbarum Polysaccharides Reduce Neuronal Damage, Blood-Retinal Barrier Disruption and Oxidative Stress in Retinal Ischemia/Reperfusion Injury

    PubMed Central

    Li, Suk-Yee; Yang, Di; Yeung, Chung-Man; Yu, Wing-Yan; Chang, Raymond Chuen-Chung; So, Kwok-Fai; Wong, David; Lo, Amy C. Y.

    2011-01-01

    Neuronal cell death, glial cell activation, retinal swelling and oxidative injury are complications in retinal ischemia/reperfusion (I/R) injuries. Lycium barbarum polysaccharides (LBP), extracts from the wolfberries, are good for “eye health” according to Chinese medicine. The aim of our present study is to explore the use of LBP in retinal I/R injury. Retinal I/R injury was induced by surgical occlusion of the internal carotid artery. Prior to induction of ischemia, mice were treated orally with either vehicle (PBS) or LBP (1 mg/kg) once a day for 1 week. Paraffin-embedded retinal sections were prepared. Viable cells were counted; apoptosis was assessed using TUNEL assay. Expression levels of glial fibrillary acidic protein (GFAP), aquaporin-4 (AQP4), poly(ADP-ribose) (PAR) and nitrotyrosine (NT) were investigated by immunohistochemistry. The integrity of blood-retinal barrier (BRB) was examined by IgG extravasations. Apoptosis and decreased viable cell count were found in the ganglion cell layer (GCL) and the inner nuclear layer (INL) of the vehicle-treated I/R retina. Additionally, increased retinal thickness, GFAP activation, AQP4 up-regulation, IgG extravasations and PAR expression levels were observed in the vehicle-treated I/R retina. Many of these changes were diminished or abolished in the LBP-treated I/R retina. Pre-treatment with LBP for 1 week effectively protected the retina from neuronal death, apoptosis, glial cell activation, aquaporin water channel up-regulation, disruption of BRB and oxidative stress. The present study suggests that LBP may have a neuroprotective role to play in ocular diseases for which I/R is a feature. PMID:21298100

  12. Visualization of Oxidative Stress Induced by Experimental Periodontitis in Keap1-Dependent Oxidative Stress Detector-Luciferase Mice.

    PubMed

    Kataoka, Kota; Ekuni, Daisuke; Tomofuji, Takaaki; Irie, Koichiro; Kunitomo, Muneyoshi; Uchida, Yoko; Fukuhara, Daiki; Morita, Manabu

    2016-11-16

    The aim of this study was to investigate whether a Keap1-dependent oxidative stress detector-luciferase (OKD-LUC) mouse model would be useful for the visualization of oxidative stress induced by experimental periodontitis. A ligature was placed around the mandibular first molars for seven days to induce periodontitis. Luciferase activity was measured with an intraperitoneal injection of d-luciferin on days 0, 1, and 7. The luciferase activity in the periodontitis group was significantly greater than that in the control group at seven days. The expressions of heme oxygenase-1 (HO-1) and malondialdehyde in periodontal tissue were significantly higher in the periodontitis group than in the control group. Immunofluorescent analysis confirmed that the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) occurred more frequently in the periodontitis group than in the control group. This study found that under oxidative stress induced by experimental periodontitis, the Nrf2/antioxidant defense pathway was activated and could be visualized from the luciferase activity in the OKD-LUC model. Thus, the OKD-LUC mouse model may be useful for exploring the mechanism underlying the relationship between the Nrf2/antioxidant defense pathway and periodontitis by enabling the visualization of oxidative stress over time.

  13. Oxidative stress activates FUS1 and RLM1 transcription in the yeast Saccharomyces cerevisiae in an oxidant-dependent Manner.

    PubMed

    Staleva, Liliana; Hall, Andrea; Orlow, Seth J

    2004-12-01

    Mating in haploid Saccharomyces cerevisiae occurs after activation of the pheromone response pathway. Biochemical components of this pathway are involved in other yeast signal transduction networks. To understand more about the coordination between signaling pathways, we used a "chemical genetic" approach, searching for compounds that would activate the pheromone-responsive gene FUS1 and RLM1, a reporter for the cell integrity pathway. We found that catecholamines (l-3,4-hydroxyphenylalanine [l-dopa], dopamine, adrenaline, and noradrenaline) elevate FUS1 and RLM1 transcription. N-Acetyl-cysteine, a powerful antioxidant in yeast, completely reversed this effect, suggesting that FUS1 and RLM1 activation in response to catecholamines is a result of oxidative stress. The oxidant hydrogen peroxide also was found to activate transcription of an RLM1 reporter. Further genetic analysis combined with immunoblotting revealed that Kss1, one of the mating mitogen-activated protein kinases (MAPKs), and Mpk1, an MAPK of the cell integrity pathway, participated in l-dopa-induced stimulation of FUS1 and RLM1 transcription. We also report that Mpk1 and Hog1, the high osmolarity MAPK, were phosphorylated upon induction by hydrogen peroxide. Together, our results demonstrate that cells respond to oxidative stress via different signal transduction machinery dependent upon the nature of the oxidant.

  14. Visualization of Oxidative Stress Induced by Experimental Periodontitis in Keap1-Dependent Oxidative Stress Detector-Luciferase Mice

    PubMed Central

    Kataoka, Kota; Ekuni, Daisuke; Tomofuji, Takaaki; Irie, Koichiro; Kunitomo, Muneyoshi; Uchida, Yoko; Fukuhara, Daiki; Morita, Manabu

    2016-01-01

    The aim of this study was to investigate whether a Keap1-dependent oxidative stress detector-luciferase (OKD-LUC) mouse model would be useful for the visualization of oxidative stress induced by experimental periodontitis. A ligature was placed around the mandibular first molars for seven days to induce periodontitis. Luciferase activity was measured with an intraperitoneal injection of d-luciferin on days 0, 1, and 7. The luciferase activity in the periodontitis group was significantly greater than that in the control group at seven days. The expressions of heme oxygenase-1 (HO-1) and malondialdehyde in periodontal tissue were significantly higher in the periodontitis group than in the control group. Immunofluorescent analysis confirmed that the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) occurred more frequently in the periodontitis group than in the control group. This study found that under oxidative stress induced by experimental periodontitis, the Nrf2/antioxidant defense pathway was activated and could be visualized from the luciferase activity in the OKD-LUC model. Thus, the OKD-LUC mouse model may be useful for exploring the mechanism underlying the relationship between the Nrf2/antioxidant defense pathway and periodontitis by enabling the visualization of oxidative stress over time. PMID:27854327

  15. Silicon oxide barrier films deposited on PET foils in pulsed plasmas: influence of substrate bias on deposition process and film properties

    NASA Astrophysics Data System (ADS)

    Steves, S.; Ozkaya, B.; Liu, C.-N.; Ozcan, O.; Bibinov, N.; Grundmeier, G.; Awakowicz, P.

    2013-02-01

    A widely used plastic for packaging, polyethylene terephtalate (PET) offers limited barrier properties against gas permeation. For many applications of PET (from food packaging to micro electronics) improved barrier properties are essential. A silicon oxide barrier coating of PET foils is applied by means of a pulsed microwave driven low-pressure plasma. While the adjustment of the microwave power allows for a control of the ion production during the plasma pulse, a substrate bias controls the energy of ions impinging on the substrate. Detailed analysis of deposited films applying oxygen permeation measurements, x-ray photoelectron spectroscopy and atomic force microscopy are correlated with results from plasma diagnostics describing the deposition process. The influence of a change in process parameters such as gas mixture and substrate bias on the gas temperature, electron density, mean electron energy, ion energy and the atomic oxygen density is studied. An additional substrate bias results in an increase in atomic oxygen density up to a factor of 6, although plasma parameter such as electron density of ne = 3.8 ± 0.8 × 1017 m-3 and electron temperature of kBTe = 1.7 ± 0.1 eV are unmodified. It is shown that atomic oxygen densities measured during deposition process higher than nO = 1.8 × 1021 m-3 yield in barrier films with a barrier improvement factor up to 150. Good barrier films are highly cross-linked and show a smooth morphology.

  16. A photoemission study of the effectiveness of nickel, manganese, and cobalt based corrosion barriers for silicon photo-anodes during water oxidation

    SciTech Connect

    O'Connor, Robert; Bogan, Justin; McCoy, Anthony; Byrne, Conor; Hughes, Greg

    2016-05-21

    Silicon is an attractive material for solar water splitting applications due to its abundance and its capacity to absorb a large fraction of incident solar radiation. However, it has not received as much attention as other materials due to its tendency to oxidize very quickly in aqueous environments, particularly when it is employed as the anode where it drives the oxygen evolution reaction. In recent years, several works have appeared in the literature examining the suitability of thin transition metal oxide films grown on top of the silicon to act as a corrosion barrier. The film should be transparent to solar radiation, allow hole transport from the silicon surface to the electrolyte, and stop the diffusion of oxygen from the electrolyte back to the silicon. In this work, we compare Mn-oxide, Co-oxide, and Ni-oxide thin films grown using physical vapor deposition in order to evaluate which material offers the best combination of photocurrent and corrosion protection. In addition to the electrochemical data, we also present a detailed before-and-after study of the surface chemistry of the films using x-ray photoelectron spectroscopy. This approach allows for a comprehensive analysis of the mechanisms by which the corrosion barriers protect the underlying silicon, and how they degrade during the water oxidation reaction.

  17. A photoemission study of the effectiveness of nickel, manganese, and cobalt based corrosion barriers for silicon photo-anodes during water oxidation

    NASA Astrophysics Data System (ADS)

    O'Connor, Robert; Bogan, Justin; McCoy, Anthony; Byrne, Conor; Hughes, Greg

    2016-05-01

    Silicon is an attractive material for solar water splitting applications due to its abundance and its capacity to absorb a large fraction of incident solar radiation. However, it has not received as much attention as other materials due to its tendency to oxidize very quickly in aqueous environments, particularly when it is employed as the anode where it drives the oxygen evolution reaction. In recent years, several works have appeared in the literature examining the suitability of thin transition metal oxide films grown on top of the silicon to act as a corrosion barrier. The film should be transparent to solar radiation, allow hole transport from the silicon surface to the electrolyte, and stop the diffusion of oxygen from the electrolyte back to the silicon. In this work, we compare Mn-oxide, Co-oxide, and Ni-oxide thin films grown using physical vapor deposition in order to evaluate which material offers the best combination of photocurrent and corrosion protection. In addition to the electrochemical data, we also present a detailed before-and-after study of the surface chemistry of the films using x-ray photoelectron spectroscopy. This approach allows for a comprehensive analysis of the mechanisms by which the corrosion barriers protect the underlying silicon, and how they degrade during the water oxidation reaction.

  18. Graphite oxide incorporated crosslinked polyvinyl alcohol and sulfonated styrene nanocomposite membrane as separating barrier in single chambered microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Rudra, Ruchira; Kumar, Vikash; Pramanik, Nilkamal; Kundu, Patit Paban

    2017-02-01

    Different membranes with varied molar concentrations of graphite oxide (GO), 'in situ' polymerized sulfonated polystyrene (SS) and glutaraldehyde (GA) cross linked polyvinyl alcohol (PVA), have been analyzed as an effective and low cost nanocomposite barrier in single chambered microbial fuel cells (MFCs). The synthesized composite membranes, namely GO0.2, GO0.4 and GO0.6 exhibited comparatively better results with reduced water uptake (WU) and swelling ratios (SR) over the native PVA. The variation in properties is illustrated with membrane analyses, where GO0.4 showed an increased proton conductivity (PC) and ion exchange capacity (IEC) of 0.128 S cm-1 and 0.33 meq g-1 amongst all of the used membranes. In comparison, reduced oxygen diffusivity with lower water uptake showed a two-fold decrease in GO0.4 over pure PVA membrane (∼2.09 × 10-4 cm s-1). A maximum power density of 193.6 mW m-2 (773.33 mW m-3) with a current density of 803.33 mA m-2 were observed with GO0.4 fitted MFC, where ∼81.89% of chemical oxygen demand (COD) was removed using mixed firmicutes, as biocatalyst, in 25 days operation. In effect, the efficacy of GO incorporated crosslinked PVA and SS nanocomposite membrane has been evaluated as a polymer electrolyte membrane for harnessing bio-energy from single chambered MFCs.

  19. Voluntary exercise protects against methamphetamine-induced oxidative stress in brain microvasculature and disruption of the blood-brain barrier.

    PubMed

    Toborek, Michal; Seelbach, Melissa J; Rashid, Cetewayo S; András, Ibolya E; Chen, Lei; Park, Minseon; Esser, Karyn A

    2013-06-24

    There is no effective therapeutic intervention developed targeting cerebrovascular toxicity of drugs of abuse, including methamphetamine (METH). We hypothesize that exercise protects against METH-induced disruption of the blood-brain barrier (BBB) by enhancing the antioxidant capacity of cerebral microvessels and modulating caveolae-associated signaling. Mice were subjected to voluntary wheel running for 5 weeks resembling the voluntary pattern of human exercise, followed by injection with METH (10 mg/kg). The frequency, duration, and intensity of each running session were monitored for each mouse via a direct data link to a computer and the running data are analyzed by Clock lab™ Analysis software. Controls included mice sedentary that did not have access to running wheels and/or injections with saline. METH induced oxidative stress in brain microvessels, resulting in up regulation of caveolae-associated NAD(P)H oxidase subunits, and phosphorylation of mitochondrial protein 66Shc. Treatment with METH disrupted also the expression and colocalization of tight junction proteins. Importantly, exercise markedly attenuated these effects and protected against METH-induced disruption of the BBB integrity. The obtained results indicate that exercise is an important modifiable behavioral factor that can protect against METH-induced cerebrovascular toxicity. These findings may provide new strategies in preventing the toxicity of drug of abuse.

  20. Comparison of the rates of phenol advanced oxidation in deionized and tap water within a dielectric barrier discharge reactor.

    PubMed

    Marotta, Ester; Ceriani, Elisa; Schiorlin, Milko; Ceretta, Claudio; Paradisi, Cristina

    2012-12-01

    Electric non-thermalizing discharges provide promising novel means to induce oxidation of organic pollutants in water. The decomposition of phenol in solutions prepared with deionized (milliQ) and tap water was studied and compared in a Dielectric Barrier Discharge (DBD) reactor. Interestingly, a significant rate increase was found in tap with respect to milliQ water. Control experiments proved that this was not the effect of conductivity or of traces of iron or of residual active chlorine from the depuration process operated in the aqueducts of Italian cities. The same increase in efficiency as observed in tap water was instead obtained when phenol was treated in solutions containing bicarbonate anions in the same concentration as present in tap water, an effect attributed to buffering of the solution pH. The role of pH has been investigated thoroughly by measuring the process efficiency over a wide pH range, from 2 to 10, by using different buffer systems to probe reactivity at near neutral pH, the most relevant for drinking water applications, and by testing the effect of different buffer concentrations. These latter experiments failed to detect any significant kinetic effect attributable to the well known reactivity of bicarbonate as quencher of OH radicals. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. The effect of oxygen and water vapor on nitric oxide conversion with a dielectric barrier discharge reactor

    SciTech Connect

    Yin, S.E.; Sun, B.M.; Gao, X.D.; Xiao, H.P.

    2009-12-15

    The effect of O{sub 2} and H{sub 2}O vapor on the Nitric oxide (NO) removal rate, the NO{sub 2} generation rate and the discharge characteristics were investigated using the dielectric barrier discharge (DBD) reactor at 1 atm pressure and at room temperature (20{sup o}). The results showed that the O{sub 2} present in the flue gas always hampered the removal of NO and the generation of N{sub 2}O, but that the O{sub 2} could enhance the generation of NO{sub 2} in the NO/N{sub 2}/O{sub 2} mixtures. Furthermore, with the increase of oxygen, the average discharge current gradually decreases in the reactor. The H{sub 2}O present in N-2/NO hindered the removal of NO and the generation of NO{sub 2} but had no impact on the average discharge current in the reactor in the NO/N{sub 2}/H{sub 2}O mixtures in which the HNO{sub 2} and HNO{sub 3} was detected. The energy efficiency of the DBD used to remove the NO from the flue gas was also estimated.

  2. Optimizing superparamagnetic iron oxide nanoparticles as drug carriers using an in vitro blood–brain barrier model

    PubMed Central

    Shi, Di; Mi, Gujie; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

    2016-01-01

    In the current study, an optimized in vitro blood–brain barrier (BBB) model was established using mouse brain endothelial cells (b.End3) and astrocytes (C8-D1A). Before measuring the permeability of superparamagnetic iron oxide nanoparticle (SPION) samples, the BBB was first examined and confirmed by an immunofluorescent stain and evaluating the transendothelial electrical resistance. After such confirmation, the permeability of the following five previously synthesized SPIONs was determined using this optimized BBB model: 1) GGB (synthesized using glycine, glutamic acid, and bovine serum albumin [BSA]), 2) GGC (glycine, glutamic acid, and collagen), 3) GGP (glycine, glutamic acid, and polyvinyl alcohol), 4) BPC (BSA, polyethylene glycol, and collagen), and 5) CPB (collagen, polyvinyl alcohol, and BSA). More importantly, after the permeability test, transmission electron microscopy thin section technology was used to investigate the mechanism behind this process. Transmission electron microscopy thin section images supported the hypothesis that collagen-coated CPB SPIONs displayed better cellular uptake than glycine and glutamine acid-coated GGB SPIONs. Such experimental data demonstrated how one can modify SPIONs to better deliver drugs to the brain to treat a wide range of neurological disorders. PMID:27799764

  3. Optimizing superparamagnetic iron oxide nanoparticles as drug carriers using an in vitro blood-brain barrier model.

    PubMed

    Shi, Di; Mi, Gujie; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

    In the current study, an optimized in vitro blood-brain barrier (BBB) model was established using mouse brain endothelial cells (b.End3) and astrocytes (C8-D1A). Before measuring the permeability of superparamagnetic iron oxide nanoparticle (SPION) samples, the BBB was first examined and confirmed by an immunofluorescent stain and evaluating the transendothelial electrical resistance. After such confirmation, the permeability of the following five previously synthesized SPIONs was determined using this optimized BBB model: 1) GGB (synthesized using glycine, glutamic acid, and bovine serum albumin [BSA]), 2) GGC (glycine, glutamic acid, and collagen), 3) GGP (glycine, glutamic acid, and polyvinyl alcohol), 4) BPC (BSA, polyethylene glycol, and collagen), and 5) CPB (collagen, polyvinyl alcohol, and BSA). More importantly, after the permeability test, transmission electron microscopy thin section technology was used to investigate the mechanism behind this process. Transmission electron microscopy thin section images supported the hypothesis that collagen-coated CPB SPIONs displayed better cellular uptake than glycine and glutamine acid-coated GGB SPIONs. Such experimental data demonstrated how one can modify SPIONs to better deliver drugs to the brain to treat a wide range of neurological disorders.

  4. Voluntary exercise protects against methamphetamine-induced oxidative stress in brain microvasculature and disruption of the blood–brain barrier

    PubMed Central

    2013-01-01

    Background There is no effective therapeutic intervention developed targeting cerebrovascular toxicity of drugs of abuse, including methamphetamine (METH). We hypothesize that exercise protects against METH-induced disruption of the blood–brain barrier (BBB) by enhancing the antioxidant capacity of cerebral microvessels and modulating caveolae-associated signaling. Mice were subjected to voluntary wheel running for 5 weeks resembling the voluntary pattern of human exercise, followed by injection with METH (10 mg/kg). The frequency, duration, and intensity of each running session were monitored for each mouse via a direct data link to a computer and the running data are analyzed by Clock lab™ Analysis software. Controls included mice sedentary that did not have access to running wheels and/or injections with saline. Results METH induced oxidative stress in brain microvessels, resulting in up regulation of caveolae-associated NAD(P)H oxidase subunits, and phosphorylation of mitochondrial protein 66Shc. Treatment with METH disrupted also the expression and colocalization of tight junction proteins. Importantly, exercise markedly attenuated these effects and protected against METH-induced disruption of the BBB integrity. Conclusions The obtained results indicate that exercise is an important modifiable behavioral factor that can protect against METH-induced cerebrovascular toxicity. These findings may provide new strategies in preventing the toxicity of drug of abuse. PMID:23799892

  5. The topical use of non-thermal dielectric barrier discharge (DBD): nitric oxide related effects on human skin.

    PubMed

    Heuer, Kiara; Hoffmanns, Martin A; Demir, Erhan; Baldus, Sabrina; Volkmar, Christine M; Röhle, Mirco; Fuchs, Paul C; Awakowicz, Peter; Suschek, Christoph V; Opländer, Christian

    2015-01-30

    Dielectric barrier discharge (DBD) devices generate air plasma above the skin containing active and reactive species including nitric oxide (NO). Since NO plays an essential role in skin physiology, a topical application of NO by plasma may be useful in the treatment of skin infections, impaired microcirculation and wound healing. Thus, after safety assessments of plasma treatment using human skin specimen and substitutes, NO-penetration through the epidermis, the loading of skin tissue with NO-derivates in vitro and the effects on human skin in vivo were determined. After the plasma treatment (0-60 min) of skin specimen or reconstructed epidermis no damaging effects were found (TUNEL/MTT). By Franz diffusion cell experiments plasma-induced NO penetration through epidermis and dermal enrichment with NO related species (nitrite 6-fold, nitrate 7-fold, nitrosothiols 30-fold) were observed. Furthermore, skin surface was acidified (~pH 2.7) by plasma treatment (90 s). Plasma application on the forearms of volunteers increased microcirculation fourfold in 1-2 mm and twofold in 6-8 mm depth in the treated skin areas. Regarding the NO-loading effects, skin acidification and increase in dermal microcirculation, plasma devices represent promising tools against chronic/infected wounds. However, efficacy of plasma treatment needs to be quantified in further studies and clinical trials.

  6. Lipid oxidation inactivates the anticoagulant function of protein Z-dependent protease inhibitor (ZPI).

    PubMed

    Huang, Xin; Liu, Baoxin; Wei, Yidong; Beyea, Ryan; Yan, Han; Olson, Steven T

    2017-09-01

    Lipid oxidation due to oxidative stress plays an important role in the pathogenesis of inflammatory and thrombotic cardiovascular diseases. Several findings suggest that lipid peroxidation can alter the function of coagulation proteins and contribute to a hypercoagulable state, but the molecular mechanisms are unclear. Here, we report that oxidized phospholipids suppress the anticoagulant function of the serpin, protein Z-dependent protease inhibitor (ZPI), a specific inhibitor of membrane-associated factor Xa (FXa) that requires protein Z (PZ), phospholipid, and calcium as cofactors. We found that this suppression arises from a diminished ability of the oxidized membrane to function as a cofactor to promote ZPI inhibition of membrane-bound FXa, due fully or in part to the susceptibility of the bound ZPI-PZ complex to oxidative inactivation. Surprisingly, free ZPI was also susceptible to inactivation by oxidized membrane vesicles in the absence of calcium. Oxidized vesicles containing both phosphatidylserine and polyunsaturated fatty acids were required to promote inactivation of the ZPI-PZ complex or free ZPI, indicating that binding of the PZ-complexed or free ZPI to peroxide-modified phospholipid vesicles mediates the inactivation. Heparin protected the ZPI-PZ complex and free ZPI from inactivation, suggesting that blocking the heparin-binding site on ZPI interferes with ZPI binding to lipid or to PZ. This was confirmed by direct lipid-binding experiments. Native PAGE indicated that oxidization induced dissociation of the ZPI-PZ complex and increased the negative charge of ZPI. We conclude that compromised ZPI anticoagulant function could contribute to thrombus initiation and growth in oxidative stress-induced cardiovascular diseases. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  7. Sulfur globule oxidation in green sulfur bacteria is dependent on the dissimilatory sulfite reductase system.

    PubMed

    Holkenbrink, Carina; Barbas, Santiago Ocón; Mellerup, Anders; Otaki, Hiroyo; Frigaard, Niels-Ulrik

    2011-04-01

    Green sulfur bacteria (GSB) oxidize sulfide and thiosulfate to sulfate, with extracellular globules of elemental sulfur as an intermediate. Here we investigated which genes are involved in the formation and consumption of these sulfur globules in the green sulfur bacterium Chlorobaculum tepidum. We show that sulfur globule oxidation is strictly dependent on the dissimilatory sulfite reductase (DSR) system. Deletion of dsrM/CT2244 or dsrT/CT2245, or the two dsrCABL clusters (CT0851-CT0854, CT2247-2250), abolished sulfur globule oxidation and prevented formation of sulfate from sulfide, whereas deletion of dsrU/CT2246 had no effect. The DSR system also seems to be involved in the formation of thiosulfate, because thiosulfate was released from wild-type cells during sulfide oxidation, but not from the dsr mutants. The dsr mutants incapable of complete substrate oxidation oxidized sulfide and thiosulfate about twice as fast as the wild-type, while having only slightly lower growth rates (70-80 % of wild-type). The increased oxidation rates seem to compensate for the incomplete substrate oxidation to satisfy the requirement for reducing equivalents during growth. A mutant in which two sulfide : quinone oxidoreductases (sqrD/CT0117 and sqrF/CT1087) were deleted exhibited a decreased sulfide oxidation rate (~50 % of wild-type), yet formation and consumption of sulfur globules were not affected. The observation that mutants lacking the DSR system maintain efficient growth suggests that the DSR system is dispensable in environments with sufficiently high sulfide concentrations. Thus, the DSR system in GSB may have been acquired by horizontal gene transfer as a response to a need for enhanced substrate utilization in sulfide-limiting habitats.

  8. CYP2E1-dependent hepatotoxicity and oxidative damage after ethanol administration in human primary hepatocytes

    PubMed Central

    Liu, Lie-Gang; Yan, Hong; Yao, Ping; Zhang, Wen; Zou, Li-Jun; Song, Fang-Fang; Li, Ke; Sun, Xiu-Fa

    2005-01-01

    AIM: To observe the relationship between ethanol-induced oxidative damage in human primary cultured hepatocytes and cytochrome P450 2E1 (CYP2E1) activity, in order to address if inhibition of CYP2E1 could attenuate ethanol-induced cellular damage. METHODS: The dose-dependent (25-100 mmol/L) and time-dependent (0-24 h) exposures of primary human cultured hepatocytes to ethanol were carried out. CYP2E1 activity and protein expression were detected by spectrophotometer and Western blot analysis respectively. Hepatotoxicity was investigated by determination of lactate dehydrogenase (LDH) and aspartate transaminase (AST) level in hepatocyte culture supernatants, as well as the intracellular formation of malondialdehyde (MDA). RESULTS: A dose-and time-dependent response between ethanol exposure and CYP2E1 activity in human hepatocytes was demonstrated. Moreover, there was a time-dependent increase of CYP2E1 protein after 100 mmol/L ethanol exposure. Meanwhile, ethanol exposure of hepatocytes caused a time-dependent increase of cellular MDA level, LDH, and AST activities in supernatants. Furthermore, the inhibitor of CYP2E1, diallyl sulfide (DAS) could partly attenuate the increases of MDA, LDH, and AST in human hepatocytes. CONCLUSION: A positive relationship between ethanol-induced oxidative damage in human primary cultured hepatocytes and CYP2E1 activity was exhibited, and the inhibition of CYP2E1 could partly attenuate ethanol-induced oxidative damage. PMID:16052683

  9. On the temperature dependent current transport mechanisms and barrier inhomogeneity in Au/SnO2-PVA/n-Si Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Bilkan, Ç.; Badali, Y.; Fotouhi-Shablou, S.; Azizian-Kalandaragh, Y.; Altındal, Ş.

    2017-08-01

    In this paper, we report the preparation and characterization of SnO2-PVA nanocomposite film as interlayer for Schottky barrier diodes (SBDs). The possible current transport mechanisms (CTMs) of the prepared SBDs were investigated using the forward-bias current-voltage ( I- V) characteristics in the temperature range of 80-400 K. The structure of nanocomposite film was characterized by an X-ray diffractometer (XRD) and the surface morphology was investigated using a Scanning Electron Microscopy (SEM) at room temperature. The values of ideality factor ( n) and zero-bias barrier height (\\overline{\\varPhi }_{Bo}) showed variation with temperature, such that they changed from 19.10 to 3.77 and 0.190 to 0.844 eV, respectively. \\overline{\\varPhi }_{Bo}- n, \\overline{\\varPhi }_{Bo}- q/2 kT, and n -1- q/2 kT plots were drawn to get evidence to the Gaussian Distribution (GD) of the barrier height (BH). These plots revealed two distinct linear regions with different slopes for low temperatures (80-160 K) (LTs) and high temperatures (180-400 K) (HTs). This behavior is an evidence to the existence double GD of BHs which provides an average value for BH (\\overline{\\varPhi }_{Bo}) and a standard deviation (σs) for each region. The high value of n especially at low temperatures was attributed to the existence of interlayer: interface states ( N ss) and barrier inhomogeneity at Au/n-Si interface. The values of \\overline{\\varPhi }_{Bo} and σs were obtained from the intercept and slope of mentioned plots as 0.588 and 0.0768 V for LTs and 1.183 eV and 0.158 V for HTs, respectively. Moreover, the modified ln( I s/ T 2)- q 2σ s 2 /2 k 2 T 2 vs q/ kT plot also showed two linear regions. The values of \\overline{\\varPhi }_{Bo} and effective Richardson constant ( A *) were extracted from the slope and intercept of this plot as 0.610 eV and 93.13 A/cm2 K2 for LTs and 1.235 eV and 114.65 A/cm2 K2 for HTs, respectively. The value of A* for HTs is very close to the theoretical

  10. Thermal barrier coating life prediction model development

    NASA Technical Reports Server (NTRS)

    Cruse, T. A.; Stewart, S. E.; Ortiz, M.

    1988-01-01

    A life prediction model for correlating the spallation life of ceramic thermal barrier coatings is developed which includes both cyclic and time-dependent damage. The cyclic damage is related to the calculated cyclic inelastic strain range, while the time-dependent damage is related to the oxidation kinetics at the bond-ceramic interface. The cyclic inelastic strain range is calculated using a modified form of the Walker viscoplastic material model; calculation of the oxidation kinetics is based on traditional oxidation algorithms using experimentally determined parameters. The correlation between the actual and predicted spallation lives is within a factor of 3.

  11. Nano rare-earth oxides induced size-dependent vacuolization: an independent pathway from autophagy

    PubMed Central

    Zhang, Ying; Yu, Chenguang; Huang, Guanyi; Wang, Changli; Wen, Longping

    2010-01-01

    Four rare earth oxides have been shown to induce autophagy. Interestingly, we often noticed plentiful vacuolization, which was not always involved in this autophagic process. In this study, we investigated three other rare-earth elements, including Yttrium (Y), Ytterbium (Yb), and Lanthanum (La). Autophagic effect could be induced by all of them but only Y2O3 and Yb2O3 could cause massive vacuolization. Y2O3 and Yb2O3 treated by sonication or centrifugation to reduce particle size were used to test vacuolization level in HeLa cell lines. The results showed that rare earth oxides-induced vacuolization is size-dependent and differs from autophagic pathway. To further clarify the characteristics of this autophagic process, we used MEF Atg-5 (autophagy associated gene 5) knockout cell line, and the result showed that the autophagic process induced by rare earth oxides is Atg-5-dependent and the observed vacuolization was independent from autophagy. Similar results could also be observed in our tests on 3-methyladenine(3-MA), a well-known autophagy inhibitor. In conclusion, for the first time, we clarified the relationship between massive vacuolization and autophagic process induced by rare earth oxides and pointed out the size effect of rare earth oxides on the formation of vacuoles, which give clues to further investigation on the mechanisms underlying their biological effects. PMID:20856835

  12. Grain and burnup dependence of spent fuel oxidation: geological repository impact

    SciTech Connect

    Hanson, B. D.; Kansa, E. J.; Stoot, R.B.

    1998-10-15

    Further refinements to the oxidation model of Stout et al. have been made. The present model incorporates the burnup dependence of the oxidation rate in addition to an allowance for a distribution of grain sizes. The model was tested by comparing the model results with the oxidation histories of spent fuel samples oxidized in Thermogravimetric Analysis (TGA) or Oven Dry-Bath (ODB) experiments. The comparison between the experimental and model results are remarkably close and confirm the assumption that grain-size distributions and activation energies are the important parameters to predicting oxidation behavior. The burnup dependence of the activation energy was shown to have a greater effect than decreasing the effective grain size in suppressing the rate of the reaction U{sub 4}O{sub 9}(rightwards arrow)U{sub 3} O{sub 4}. Model results predict that U{sub 3}O{sub 8} formation of spent fuels exposed to oxygen will be suppressed even for high burnup fuels that have undergone restructuring in the rim region, provided the repository temperature is kept sufficient.

  13. Selenate-dependent anaerobic arsenite oxidation by a bacterium from Mono Lake, California.

    PubMed

    Fisher, Jenny C; Hollibaugh, James T

    2008-05-01

    Arsenate was produced when anoxic Mono Lake water samples were amended with arsenite and either selenate or nitrate. Arsenite oxidation did not occur in killed control samples or live samples with no added terminal electron acceptor. Potential rates of anaerobic arsenite oxidation with selenate were comparable to those with nitrate ( approximately 12 to 15 mumol.liter(-1) h(-1)). A pure culture capable of selenate-dependent anaerobic arsenite oxidation (strain ML-SRAO) was isolated from Mono Lake water into a defined salts medium with selenate, arsenite, and yeast extract. This strain does not grow chemoautotrophically, but it catalyzes the oxidation of arsenite during growth on an organic carbon source with selenate. No arsenate was produced in pure cultures amended with arsenite and nitrate or oxygen, indicating that the process is selenate dependent. Experiments with washed cells in mineral medium demonstrated that the oxidation of arsenite is tightly coupled to the reduction of selenate. Strain ML-SRAO grows optimally on lactate with selenate or arsenate as the electron acceptor. The amino acid sequences deduced from the respiratory arsenate reductase gene (arrA) from strain ML-SRAO are highly similar (89 to 94%) to those from two previously isolated Mono Lake arsenate reducers. The 16S rRNA gene sequence of strain ML-SRAO places it within the Bacillus RNA group 6 of gram-positive bacteria having low G+C content.

  14. Nano rare-earth oxides induced size-dependent vacuolization: an independent pathway from autophagy.

    PubMed

    Zhang, Ying; Yu, Chenguang; Huang, Guanyi; Wang, Changli; Wen, Longping

    2010-09-07

    Four rare earth oxides have been shown to induce autophagy. Interestingly, we often noticed plentiful vacuolization, which was not always involved in this autophagic process. In this study, we investigated three other rare-earth elements, including Yttrium (Y), Ytterbium (Yb), and Lanthanum (La). Autophagic effect could be induced by all of them but only Y(2)O(3) and Yb(2)O(3) could cause massive vacuolization. Y(2)O(3) and Yb(2)O(3) treated by sonication or centrifugation to reduce particle size were used to test vacuolization level in HeLa cell lines. The results showed that rare earth oxides-induced vacuolization is size-dependent and differs from autophagic pathway. To further clarify the characteristics of this autophagic process, we used MEF Atg-5 (autophagy associated gene 5) knockout cell line, and the result showed that the autophagic process induced by rare earth oxides is Atg-5-dependent and the observed vacuolization was independent from autophagy. Similar results could also be observed in our tests on 3-methyladenine(3-MA), a well-known autophagy inhibitor. In conclusion, for the first time, we clarified the relationship between massive vacuolization and autophagic process induced by rare earth oxides and pointed out the size effect of rare earth oxides on the formation of vacuoles, which give clues to further investigation on the mechanisms underlying their biological effects.

  15. Microbially catalyzed nitrate-dependent metal/radionuclide oxidation in shallow subsurface sediments

    NASA Astrophysics Data System (ADS)

    Weber, K.; Healy, O.; Spanbauer, T. L.; Snow, D. D.

    2011-12-01

    Anaerobic, microbially catalyzed nitrate-dependent metal/radionuclide oxidation has been demonstrated in a variety of sediments, soils, and groundwater. To date, studies evaluating U bio-oxidation and mobilization have primarily focused on anthropogenically U contaminated sites. In the Platte River Basin U originating from weathering of uranium-rich igneous rocks in the Rocky Mountains was deposited in shallow alluvial sediments as insoluble reduced uranium minerals. These reduced U minerals are subject to reoxidation by available oxidants, such nitrate, in situ. Soluble uranium (U) from natural sources is a recognized contaminant in public water supplies throughout the state of Nebraska and Colorado. Here we evaluate the potential of anaerobic, nitrate-dependent microbially catalyzed metal/radionuclide oxidation in subsurface sediments near Alda, NE. Subsurface sediments and groundwater (20-64ft.) were collected from a shallow aquifer containing nitrate (from fertilizer) and natural iron and uranium. The reduction potential revealed a reduced environment and was confirmed by the presence of Fe(II) and U(IV) in sediments. Although sediments were reduced, nitrate persisted in the groundwater. Nitrate concentrations decreased, 38 mg/L to 30 mg/L, with increasing concentrations of Fe(II) and U(IV). Dissolved U, primarily as U(VI), increased with depth, 30.3 μg/L to 302 μg/L. Analysis of sequentially extracted U(VI) and U(IV) revealed that virtually all U in sediments existed as U(IV). The presence of U(IV) is consistent with reduced Fe (Fe(II)) and low reduction potential. The increase in aqueous U concentrations with depth suggests active U cycling may occur at this site. Tetravalent U (U(IV)) phases are stable in reduced environments, however the input of an oxidant such as oxygen or nitrate into these systems would result in oxidation. Thus co-occurrence of nitrate suggests that nitrate could be used by bacteria as a U(IV) oxidant. Most probable number

  16. The oxidative costs of reproduction are group-size dependent in a wild cooperative breeder

    PubMed Central

    Cram, Dominic L.; Blount, Jonathan D.; Young, Andrew J.

    2015-01-01

    Life-history theory assumes that reproduction entails a cost, and research on cooperatively breeding societies suggests that the cooperative sharing of workloads can reduce this cost. However, the physiological mechanisms that underpin both the costs of reproduction and the benefits of cooperation remain poorly understood. It has been hypothesized that reproductive costs may arise in part from oxidative stress, as reproductive investment may elevate exposure to reactive oxygen species, compromising survival and future reproduction and accelerating senescence. However, experimental evidence of oxidative costs of reproduction in the wild remains scarce. Here, we use a clutch-removal experiment to investigate the oxidative costs of reproduction in a wild cooperatively breeding bird, the white-browed sparrow weaver, Plocepasser mahali. Our results reveal costs of reproduction that are dependent on group size: relative to individuals in groups whose eggs were experimentally removed, individuals in groups that raised offspring experienced an associated cost (elevated oxidative damage and reduced body mass), but only if they were in small groups containing fewer or no helpers. Furthermore, during nestling provisioning, individuals that provisioned at higher rates showed greater within-individual declines in body mass and antioxidant protection. Our results provide rare experimental evidence that reproduction can negatively impact both oxidative status and body mass in the wild, and suggest that these costs can be mitigated in cooperative societies by the presence of additional helpers. These findings have implications for our understanding of the energetic and oxidative costs of reproduction, and the benefits of cooperation in animal societies. PMID:26582023

  17. Opposing effects of oxidative challenge and carotenoids on antioxidant status and condition-dependent sexual signalling

    PubMed Central

    Tomášek, Oldřich; Gabrielová, Barbora; Kačer, Petr; Maršík, Petr; Svobodová, Jana; Syslová, Kamila; Vinkler, Michal; Albrecht, Tomáš

    2016-01-01

    Several recent hypotheses consider oxidative stress to be a primary constraint ensuring honesty of condition-dependent carotenoid-based signalling. The key testable difference between these hypotheses is the assumed importance of carotenoids for redox homeostasis, with carotenoids being either antioxidant, pro-oxidant or unimportant. We tested the role of carotenoids in redox balance and sexual signalling by exposing adult male zebra finches (Taeniopygia guttata) to oxidative challenge (diquat dibromide) and manipulating carotenoid intake. As the current controversy over the importance of carotenoids as antioxidants could stem from the hydrophilic basis of commonly-used antioxidant assays, we used the novel measure of in vivo lipophilic antioxidant capacity. Oxidative challenge reduced beak pigmentation but elicited an increase in antioxidant capacity suggesting resource reallocation from signalling to redox homeostasis. Carotenoids counteracted the effect of oxidative challenge on lipophilic (but not hydrophilic) antioxidant capacity, thereby supporting carotenoid antioxidant function in vivo. This is inconsistent with hypotheses proposing that signalling honesty is maintained through either ROS-induced carotenoid degradation or the pro-oxidant effect of high levels of carotenoid-cleavage products acting as a physiological handicap. Our data further suggest that assessment of lipophilic antioxidant capacity is necessary to fully understand the role of redox processes in ecology and evolution. PMID:27000655

  18. The oxidative costs of reproduction are group-size dependent in a wild cooperative breeder.

    PubMed

    Cram, Dominic L; Blount, Jonathan D; Young, Andrew J

    2015-11-22

    Life-history theory assumes that reproduction entails a cost, and research on cooperatively breeding societies suggests that the cooperative sharing of workloads can reduce this cost. However, the physiological mechanisms that underpin both the costs of reproduction and the benefits of cooperation remain poorly understood. It has been hypothesized that reproductive costs may arise in part from oxidative stress, as reproductive investment may elevate exposure to reactive oxygen species, compromising survival and future reproduction and accelerating senescence. However, experimental evidence of oxidative costs of reproduction in the wild remains scarce. Here, we use a clutch-removal experiment to investigate the oxidative costs of reproduction in a wild cooperatively breeding bird, the white-browed sparrow weaver, Plocepasser mahali. Our results reveal costs of reproduction that are dependent on group size: relative to individuals in groups whose eggs were experimentally removed, individuals in groups that raised offspring experienced an associated cost (elevated oxidative damage and reduced body mass), but only if they were in small groups containing fewer or no helpers. Furthermore, during nestling provisioning, individuals that provisioned at higher rates showed greater within-individual declines in body mass and antioxidant protection. Our results provide rare experimental evidence that reproduction can negatively impact both oxidative status and body mass in the wild, and suggest that these costs can be mitigated in cooperative societies by the presence of additional helpers. These findings have implications for our understanding of the energetic and oxidative costs of reproduction, and the benefits of cooperation in animal societies.

  19. Opposing effects of oxidative challenge and carotenoids on antioxidant status and condition-dependent sexual signalling.

    PubMed

    Tomášek, Oldřich; Gabrielová, Barbora; Kačer, Petr; Maršík, Petr; Svobodová, Jana; Syslová, Kamila; Vinkler, Michal; Albrecht, Tomáš

    2016-03-22

    Several recent hypotheses consider oxidative stress to be a primary constraint ensuring honesty of condition-dependent carotenoid-based signalling. The key testable difference between these hypotheses is the assumed importance of carotenoids for redox homeostasis, with carotenoids being either antioxidant, pro-oxidant or unimportant. We tested the role of carotenoids in redox balance and sexual signalling by exposing adult male zebra finches (Taeniopygia guttata) to oxidative challenge (diquat dibromide) and manipulating carotenoid intake. As the current controversy over the importance of carotenoids as antioxidants could stem from the hydrophilic basis of commonly-used antioxidant assays, we used the novel measure of in vivo lipophilic antioxidant capacity. Oxidative challenge reduced beak pigmentation but elicited an increase in antioxidant capacity suggesting resource reallocation from signalling to redox homeostasis. Carotenoids counteracted the effect of oxidative challenge on lipophilic (but not hydrophilic) antioxidant capacity, thereby supporting carotenoid antioxidant function in vivo. This is inconsistent with hypotheses proposing that signalling honesty is maintained through either ROS-induced carotenoid degradation or the pro-oxidant effect of high levels of carotenoid-cleavage products acting as a physiological handicap. Our data further suggest that assessment of lipophilic antioxidant capacity is necessary to fully understand the role of redox processes in ecology and evolution.

  20. Subunit dependent oxidative stress sensitivity of LRRC8 volume regulated anion channels.

    PubMed

    Gradogna, Antonella; Gavazzo, Paola; Boccaccio, Anna; Pusch, Michael

    2017-08-25

    The volume-regulated anion channel (VRAC) is formed by heteromers of LRRC8 proteins containing the essential LRRC8A subunit and at least one among the LRRC8B-E subunits. Reactive oxygen species (ROS) play physiological and pathophysiological roles and VRAC channels are highly ROS sensitive. However, it is unclear if ROS act directly on the channels or on molecules involved in the activation pathway. We used fluorescently tagged LRRC8 proteins that yield large constitutive currents to test direct effects of oxidation. We found that 8A/8E heteromers are dramatically potentiated (more than 10-fold) by oxidation of intracellular cysteine residues by chloramine-T or tert-butyl hydroperoxide. Oxidation was, however, not necessary for hypotonicity induced activation. In contrast, 8A/8C and 8A/8D heteromers were strongly inhibited by oxidation. Endogenous VRAC currents in Jurkat T lymphocytes were similarly inhibited by oxidation, in agreement with the finding that LRRC8C and LRRC8D subunits were more abundantly expressed than LRRC8E in Jurkat cells. Our results show that LRRC8 channels are directly modulated by oxidation in a subunit dependent manner. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  1. Temperature dependence of D removal from JET codeposits by thermo-oxidation

    NASA Astrophysics Data System (ADS)

    Tsui, C. K.; Haasz, A. A.; Davis, J. W.; Coad, J. P.; Widdowson, A. M.; Likonen, J.; Hakola, A.

    2009-12-01

    The present study presents new findings for the temperature dependence of D removal from JET Mark II Gas Box divertor codeposits via thermo-oxidation. D removal efficiencies are presented for oxidation with 21 kPa O 2 pressure at temperatures in the range 523-623 K (the 623 K results have been recently published [9,10]). The codeposits analysed in this study have Be concentrations of up to ˜40% Be/(Be + C) and thicknesses ranging from 5.5 to 54 μm. The hypothesis that codeposits are porous in nature is supported by post-oxidation surface analysis and codeposit erosion trends. Initial D removal rates from oxidized JET divertor codeposits vary linearly with inherent D content and codeposit thickness, and are independent of Be content and codeposit geometry. The percentage of recoverable D from the JET divertor codeposits was ˜65% at 523 K, ˜75% at 573 K and ˜90% at 623 K, all at 21 kPa. SIMS and NRA surface analyses confirm the fact that codeposit characteristics vary widely even among specimens cut adjacent to one another. This is true even after aggressive oxidation where in some cases the codeposit is totally depleted of the inherent deuterium without a significant reduction in thickness. However, the overall D removal effectiveness of thermo-oxidation appears to be unaffected by these large variations in codeposit structure and composition.

  2. Anomalous quantum efficiency for photoconduction and its power dependence in metal oxide semiconductor nanowires.

    PubMed

    Chen, R S; Wang, W C; Lu, M L; Chen, Y F; Lin, H C; Chen, K H; Chen, L C

    2013-08-07

    The quantum efficiency and carrier lifetime that decide the photoconduction (PC) efficiencies in the metal oxide semiconductor nanowires (NWs) have been investigated. The experimental result surprisingly shows that the SnO2, TiO2, WO3, and ZnO NWs reveal extraordinary quantum efficiencies in common, which are over one to three orders of magnitude lower than the theoretical expectation. The surface depletion region (SDR)-controlled photoconductivity is proposed to explain the anomalous quantum efficiency and its power dependence. The inherent difference between the metal oxide nanostructures such as carrier lifetime, carrier concentration, and dielectric constant leading to the distinct PC performance and behavior are also discussed.

  3. Permeability dependence study of the focused ultrasound-induced blood-brain barrier opening at distinct pressures and microbubble diameters using DCE-MRI.

    PubMed

    Vlachos, Fotios; Tung, Yao-Sheng; Konofagou, Elisa

    2011-09-01

    Blood-brain barrier opening using focused ultrasound and microbubbles has been experimentally established as a noninvasive and localized brain drug delivery technique. In this study, the permeability of the opening is assessed in the murine hippocampus after the application of focused ultrasound at three different acoustic pressures and microbubble sizes. Using dynamic contrast-enhanced MRI, the transfer rates were estimated, yielding permeability maps and quantitative K(trans) values for a predefined region of interest. The volume of blood-brain barrier opening according to the K(trans) maps was proportional to both the pressure and the microbubble diameter. A K(trans) plateau of ∼0.05 min(-1) was reached at higher pressures (0.45 and 0.60 MPa) for the larger sized bubbles (4-5 and 6-8 μm), which was on the same order as the K(trans) of the epicranial muscle (no barrier). Smaller bubbles (1-2 μm) yielded significantly lower permeability values. A small percentage (7.5%) of mice showed signs of damage under histological examination, but no correlation with permeability was established. The assessment of the blood-brain barrier permeability properties and their dependence on both the pressure and the microbubble diameter suggests that K(trans) maps may constitute an in vivo tool for the quantification of the efficacy of the focused ultrasound-induced blood-brain barrier opening.

  4. Thickness-Dependent Charge Carrier Dynamics in CdSe/ZnSe/CdS Core/Barrier/Shell Nanoheterostructures.

    PubMed

    Yadav, Sushma; Chowdhury, Apurba; Sapra, Sameer

    2016-03-03

    We report the synthesis of CdSe/ZnSe/CdS heterostructures composed of type I and type II band alignments, where ZnSe acts as a barrier for charge carriers between the CdSe core and the CdS shell as well as being an active component of the type I (CdSe/ZnSe) and type II (ZnSe/CdS) structure simultaneously. We investigated the effect of the thickness of the barrier and the shell on the charge carrier dynamics by using UV/Vis absorbance, photoluminescence (PL), and time-resolved fluorescence techniques. The experimental data are supported by simple theoretical calculations based on effective mass approximation (EMA). PL results indicate the emission from both type I and type II structures. Time-resolved fluorescence studies show that the lifetime of the core emission decreases with increasing barrier width, owing to a greater confinement of the exciton to the core, whereas it increases with shell width because of the tunneling of charge carriers, primarily electrons, delaying the recombination of the exciton. The lifetime of the shell emission decreases with shell width as well as barrier width and height, with a larger effect being observed for the barrier width and negligible for the associated changes in the barrier height. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Defect Clustering and Nano-Phase Structure Characterization of Multi-Component Rare Earth Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    2003-01-01

    Advanced oxide thermal barrier coatings have been developed by incorporating multi-component rare earth oxide dopants into zirconia-yttria to effectively promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nano-scale phases within the coating systems. The presence of these nano-sized defect clusters has found to significantly reduce the coating intrinsic thermal conductivity, improve sintering resistance, and maintain long-term high temperature stability. In this paper, the defect clusters and nano-structured phases, which were created by the addition of multi-component rare earth dopants to the plasma-sprayed and electron-beam physical vapor deposited thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The defect cluster size, distribution, crystallographic and compositional information were investigated using high-resolution TEM lattice imaging, selected area diffraction (SAD), electron energy-loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) analysis techniques. The results showed that substantial defect clusters were formed in the advanced multi-component rare earth oxide doped zirconia- yttria systems. The size of the oxide defect clusters and the cluster dopant segregation was typically ranging from 5 to 50 nm. These multi-component dopant induced defect clusters are an important factor for the coating long-term high temperature stability and excellent performance.

  6. Defect Clustering and Nano-Phase Structure Characterization of Multi-Component Rare Earth Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    2003-01-01

    Advanced oxide thermal barrier coatings have been developed by incorporating multi-component rare earth oxide dopants into zirconia-yttria to effectively promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nano-scale phases within the coating systems. The presence of these nano-sized defect clusters has found to significantly reduce the coating intrinsic thermal conductivity, improve sintering resistance, and maintain long-term high temperature stability. In this paper, the defect clusters and nano-structured phases, which were created by the addition of multi-component rare earth dopants to the plasma-sprayed and electron-beam physical vapor deposited thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The defect cluster size, distribution, crystallographic and compositional information were investigated using high-resolution TEM lattice imaging, selected area diffraction (SAD), electron energy-loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) analysis techniques. The results showed that substantial defect clusters were formed in the advanced multi-component rare earth oxide doped zirconia- yttria systems. The size of the oxide defect clusters and the cluster dopant segregation was typically ranging from 5 to 50 nm. These multi-component dopant induced defect clusters are an important factor for the coating long-term high temperature stability and excellent performance.

  7. Defect Clustering and Nano-Phase Structure Characterization of Multi-Component Rare Earth Oxide Doped Zirconia-Yttria Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Chen, Yuan L.; Miller, Robert A.

    1990-01-01

    Advanced oxide thermal barrier coatings have been developed by incorporating multi- component rare earth oxide dopants into zirconia-yttria to effectively promote the creation of the thermodynamically stable, immobile oxide defect clusters and/or nano-scale phases within the coating systems. The presence of these nano-sized defect clusters has found to significantly reduce the coating intrinsic thermal conductivity, improve sintering resistance, and maintain long-term high temperature stability. In this paper, the defect clusters and nano-structured phases, which were created by the addition of multi-component rare earth dopants to the plasma- sprayed and electron-beam physical vapor deposited thermal barrier coatings, were characterized by high-resolution transmission electron microscopy (TEM). The defect cluster size, distribution, crystallographic and compositional information were investigated using high-resolution TEM lattice imaging, selected area diffraction (SAD), and energy dispersive spectroscopy (EDS) analysis techniques. The results showed that substantial defect clusters were formed in the advanced multi-component rare earth oxide doped zirconia-yttria systems. The size of the oxide defect clusters and the cluster dopant segregation was typically ranging fiom 5 to 50 nm. These multi-component dopant induced defect clusters are an important factor for the coating long-term high temperature stability and excellent performance.

  8. DEGRADATION OF SM2ZR2O7 THERMAL BARRIER COATING CAUSED BY CALCIUM-MAGNESIUM-ALUMINUM-SILICON OXIDE (CMAS) DEPOSITION

    SciTech Connect

    Wang, Honglong; Sheng, Zhizhi; Tarwater, Emily; Zhang, Xingxing; Dasgupta, Sudip; Fergus, Jeffrey

    2015-03-16

    Rare earth zirconates are promising materials for use as thermal barrier coatings in gas turbine engines. Among the lanthanide zirconate materials, Sm2Zr2O7 with the pyrochlore structure has lower thermal conductivity and better corrosion resistance against calcium-magnesium-aluminum-silicon oxide (CMAS). In this work, after reaction with CMAS, the pyrochlore structure transforms to the cubic fluorite structure and Ca2Sm8(SiO4)6O2 forms in elongated grain.

  9. Wet oxidation of Al{sub x}GA{sub 1-x}As: arsenic barriers on the road to mis

    SciTech Connect

    Ashby, C.I.H.; Sullivan, J.P.; Newcomer, P.P.; Missert, N.A.; Hou, H.Q.; Hammons, B.E.; Baca, A.G.

    1997-02-01

    Three characteristic regimes were identified during wet thermal oxidation of AlxGa(1-x)As (x=1 to 0.90) on GaAs: oxidation of Al and Ga in the alloy to form to an amorphous oxide layer, formation and elimination of elemental As and of amorphous As2O3, and crystallization of the oxide film. Residual As can produce up to a 100fold increase in leakage current and a 30% increase in bulk dielectric constant. Very low As levels produce partial Fermi-level pinning at the oxidized AlxGa(1-x)As/GaAs interface. Local Schottky- barrier pinning of the Fermi level at As precipitates at the oxide/GaAs interface may be the source of the apparent high interface state density. The presence of thermodynamically favored interfacial As may impose a fundamental limit on the application of AlGaAs wet oxidation for achieving MIS devices without post-oxidation processing to remove the residual As from the interface.

  10. Neutron transfer versus inelastic surface vibrations in the enhancement of sub-barrier fusion excitation function data and the energy dependent Woods-Saxon potential

    NASA Astrophysics Data System (ADS)

    Singh Gautam, Manjeet

    2015-02-01

    This work deeply analyzed the relative importance of the neutron transfer channels and inelastic surface vibrations of colliding nuclei in the sub-barrier fusion enhancement of various heavy ion systems using an energy dependent Woods-Saxon potential (EDWSP) model in conjunction with a one-dimensional Wong formula and the coupled channel formulation using the code CCFULL. The multi-phonon vibrational states of colliding nuclei and the nucleon transfer channels are found to be dominant internal degrees of freedom. The coupling between the relative motion of reactants and these relevant channels produces anomalously large sub-barrier fusion enhancement over the expectations of the one-dimensional barrier penetration model. In some cases, the influence of neutron transfer dominates over the couplings to low lying surface vibrational states of collision partners. Furthermore, the effects of coupling to inelastic surface excitations and the impact of neutron transfer channels with positive ground state Q-values are imitated due to energy dependence in the Woods-Saxon potential. In the EDWSP model calculations, a wide range for the diffuseness parameter, which is much larger than the value extracted from the elastic scattering data, is needed to account for the observed fusion enhancement in the close vicinity of the Coulomb barrier.

  11. Na(+)-dependent glutamate transporters (EAAT1, EAAT2, and EAAT3) of the blood-brain barrier. A mechanism for glutamate removal.

    PubMed

    O'Kane, R L; Martínez-López, I; DeJoseph, M R; Viña, J R; Hawkins, R A

    1999-11-05

    Na(+)-dependent transporters for glutamate exist on astrocytes (EAAT1 and EAAT2) and neurons (EAAT3). These transporters presumably assist in keeping the glutamate concentration low in the extracellular fluid of brain. Recently, Na(+)-dependent glutamate transport was described on the abluminal membrane of the blood-brain barrier. To determine whether the above-mentioned transporters participate in glutamate transport of the blood-brain barrier, total RNA was extracted from bovine cerebral capillaries. cDNA for EAAT1, EAAT2, and EAAT3 was observed, indicating that mRNA was present. Western blot analysis demonstrated all three transporters were expressed on abluminal membranes, but none was detectable on luminal membranes of the blood-brain barrier. Measurement of transport kinetics demonstrated voltage dependence, K(+)-dependence, and an apparent K(m) of 14 microM (aggregate of the three transporters) at a transmembrane potential of -61 mV. Inhibition of glutamate transport was observed using inhibitors specific for EAAT2 (kainic acid and dihydrokainic acid) and EAAT3 (cysteine). The relative activity of the three transporters was found to be approximately 1:3:6 for EAAT1, EAAT2, and EAAT3, respectively. These transporters may assist in maintaining low glutamate concentrations in the extracellular fluid.

  12. Draft Genome Sequence of a Potential Nitrate-Dependent Fe(II)-Oxidizing Bacterium, Aquabacterium parvum B6

    PubMed Central

    Zhang, Xiaoxin

    2016-01-01

    Aquabacterium parvum B6 is a potential nitrate-dependent Fe(II)-oxidizing bacterium. The genes related to its denitrifying mechanism and iron metabolisms were unknown. We present the draft genome of Aquabacterium parvum B6, which could provide further insight into the nitrate-dependent Fe(II)-oxidizing mechanism of strain B6. PMID:26823591

  13. Draft Genome Sequence of a Potential Nitrate-Dependent Fe(II)-Oxidizing Bacterium, Aquabacterium parvum B6.

    PubMed

    Zhang, Xiaoxin; Ma, Fang; Szewzyk, Ulrich

    2016-01-28

    Aquabacterium parvum B6 is a potential nitrate-dependent Fe(II)-oxidizing bacterium. The genes related to its denitrifying mechanism and iron metabolisms were unknown. We present the draft genome of Aquabacterium parvum B6, which could provide further insight into the nitrate-dependent Fe(II)-oxidizing mechanism of strain B6. Copyright © 2016 Zhang et al.

  14. Link between cancer and Alzheimer disease via oxidative stress induced by nitric oxide-dependent mitochondrial DNA overproliferation and deletion.

    PubMed

    Aliev, Gjumrakch; Obrenovich, Mark E; Tabrez, Shams; Jabir, Nasimudeen R; Reddy, V Prakash; Li, Yi; Burnstock, Geoffrey; Cacabelos, Ramon; Kamal, Mohammad Amjad

    2013-01-01

    Nitric oxide- (NO-) dependent oxidative stress results in mitochondrial ultrastructural alterations and DNA damage in cases of Alzheimer disease (AD). However, little is known about these pathways in human cancers, especially during the development as well as the progression of primary brain tumors and metastatic colorectal cancer. One of the key features of tumors is the deficiency in tissue energy that accompanies mitochondrial lesions and formation of the hypoxic smaller sized mitochondria with ultrastructural abnormalities. We speculate that mitochondrial involvement may play a significant role in the etiopathogenesis of cancer. Recent studies also demonstrate a potential link between AD and cancer, and anticancer drugs are being explored for the inhibition of AD-like pathology in transgenic mice. Severity of the cancer growth, metastasis, and brain pathology in AD (in animal models that mimic human AD) correlate with the degree of mitochondrial ultrastructural abnormalities. Recent advances in the cell-cycle reentry of the terminally differentiated neuronal cells indicate that NO-dependent mitochondrial abnormal activities and mitotic cell division are not the only important pathogenic factors in pathogenesis of cancer and AD, but open a new window for the development of novel treatment strategies for these devastating diseases.

  15. Surface temperature dependence of oxidation of Cu3Au(111) by an energetic oxygen molecule

    NASA Astrophysics Data System (ADS)

    Tsuda, Yasutaka; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio

    2016-03-01

    We report a study on the surface-temperature (T s) dependence of oxidation process at Cu3Au(111) by using a hyperthermal oxygen molecular beam and synchrotron-radiation x-ray photoemission spectroscopy. The O-1s spectra and the corresponding O-uptake curves demonstrate that Cu2O domains grow effectively at high T s of 400 and 500 K. The simple analysis of the O distribution suggests that the temperature-induced atomic diffusion causes the Cu2O domains growing thicker at 500 K. The oxidation of Cu3Au(111) is less efficient at T s = 300-500 K than that of Cu(111), demonstrating that the protective nature of Cu3Au against oxidation, in comparison to Cu, remains even at high T s.

  16. Mechanistic analysis of temperature-dependent current conduction through thin tunnel oxide in n+-polySi/SiO2/n+-Si structures

    NASA Astrophysics Data System (ADS)

    Samanta, Piyas

    2017-09-01

    We present a detailed investigation on temperature-dependent current conduction through thin tunnel oxides grown on degenerately doped n-type silicon (n+-Si) under positive bias ( VG ) on heavily doped n-type polycrystalline silicon (n+-polySi) gate in metal-oxide-semiconductor devices. The leakage current measured between 298 and 573 K and at oxide fields ranging from 6 to 10 MV/cm is primarily attributed to Poole-Frenkel (PF) emission of trapped electrons from the neutral electron traps located in the silicon dioxide (SiO2) band gap in addition to Fowler-Nordheim (FN) tunneling of electrons from n+-Si acting as the drain node in FLOating gate Tunnel OXide Electrically Erasable Programmable Read-Only Memory devices. Process-induced neutral electron traps are located at 0.18 eV and 0.9 eV below the SiO2 conduction band. Throughout the temperature range studied here, PF emission current IPF dominates FN electron tunneling current IFN at oxide electric fields Eox between 6 and 10 MV/cm. A physics based new analytical formula has been developed for FN tunneling of electrons from the accumulation layer of degenerate semiconductors at a wide range of temperatures incorporating the image force barrier rounding effect. FN tunneling has been formulated in the framework of Wentzel-Kramers-Brilloiun taking into account the correction factor due to abrupt variation of the energy barrier at the cathode/oxide interface. The effect of interfacial and near-interfacial trapped-oxide charges on FN tunneling has also been investigated in detail at positive VG . The mechanism of leakage current conduction through SiO2 films plays a crucial role in simulation of time-dependent dielectric breakdown of the memory devices and to precisely predict the normal operating field or applied floating gate (FG) voltage for lifetime projection of the devices. In addition, we present theoretical results showing the effect of drain doping concentration on the FG leakage current.

  17. Role of nitric oxide synthases in early blood-brain barrier disruption following transient focal cerebral ischemia.

    PubMed

    Jiang, Zheng; Li, Chun; Arrick, Denise M; Yang, Shu; Baluna, Alexandra E; Sun, Hong

    2014-01-01

    The role of nitric oxide synthases (NOSs) in early blood-brain barrier (BBB) disruption was determined using a new mouse model of transient focal cerebral ischemia. Ischemia was induced by ligating the middle cerebral artery (MCA) at its M2 segment and reperfusion was induced by releasing the ligation. The diameter alteration of the MCA, arterial anastomoses and collateral arteries were imaged and measured in real time. BBB disruption was assessed by Evans Blue (EB) and sodium fluorescein (Na-F) extravasation at 3 hours of reperfusion. The reperfusion produced an extensive vasodilation and a sustained hyperemia. Although expression of NOSs was not altered at 3 hours of reperfusion, L-NAME (a non-specific NOS inhibitor) abolished reperfusion-induced vasodilation/hyperemia and significantly reduced EB and Na-F extravasation. L-NIO (an endothelial NOS (eNOS) inhibitor) significantly attenuated cerebral vasodilation but not BBB disruption, whereas L-NPA and 7-NI (neuronal NOS (nNOS) inhibitors) significantly reduced BBB disruption but not cerebral vasodilation. In contrast, aminoguanidine (AG) (an inducible NOS (iNOS) inhibitor) had less effect on either cerebral vasodilation or BBB disruption. On the other hand, papaverine (PV) not only increased the vasodilation/hyperemia but also significantly reduced BBB disruption. Combined treatment with L-NAME and PV preserved the vasodilation/hyperemia and significantly reduced BBB disruption. Our findings suggest that nNOS may play a major role in early BBB disruption following transient focal cerebral ischemia via a hyperemia-independent mechanism.

  18. Oral atorvastatin therapy increases nitric oxide-dependent cutaneous vasodilation in humans by decreasing ascorbate-sensitive oxidants.

    PubMed

    Holowatz, Lacy A; Kenney, W Larry

    2011-09-01

    Elevated low-density lipoproteins (LDL) are associated with cutaneous microvascular dysfunction partially mediated by increased arginase activity, which is decreased following a systemic atorvastatin therapy. We hypothesized that increased ascorbate-sensitive oxidant stress, partially mediated through uncoupled nitric oxide synthase (NOS) induced by upregulated arginase, contributes to cutaneous microvascular dysfunction in hypercholesterolemic (HC) humans. Four microdialysis fibers were placed in the skin of nine HC (LDL = 177 ± 6 mg/dl) men and women before and after 3 mo of a systemic atorvastatin intervention and at baseline in nine normocholesterolemic (NC) (LDL = 95 ± 4 mg/dl) subjects. Sites served as control, NOS inhibited, L-ascorbate, and arginase-inhibited+L-ascorbate. Skin blood flow was measured while local skin heating (42°C) induced NO-dependent vasodilation. After the established plateau in all sites, 20 mM ≪ngname≫ was infused to quantify NO-dependent vasodilation. Data were normalized to maximum cutaneous vascular conductance (CVC) (sodium nitroprusside + 43°C). The plateau in vasodilation during local heating (HC: 78 ± 4 vs. NC: 96 ± 2% CVC(max), P < 0.01) and NO-dependent vasodilation (HC: 40 ± 4 vs. NC: 54 ± 4% CVC(max), P < 0.01) was reduced in the HC group. Acute L-ascorbate alone (91 ± 5% CVC(max), P < 0.001) or combined with arginase inhibition (96 ± 3% CVC(max), P < 0.001) augmented the plateau in vasodilation in the HC group but not the NC group (ascorbate: 96 ± 2; combo: 93 ± 4% CVC(max), both P > 0.05). After the atorvastatin intervention NO-dependent vasodilation was augmented in the HC group (HC postatorvastatin: 64 ± 4% CVC(max), P < 0.01), and there was no further effect of ascorbate alone (58 ± 4% CVC(max,) P > 0.05) or combined with arginase inhibition (67 ± 4% CVC(max,) P > 0.05). Increased ascorbate-sensitive oxidants contribute to hypercholesteromic associated cutaneous microvascular dysfunction which is

  19. Anomalous quantum efficiency for photoconduction and its power dependence in metal oxide semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Chen, R. S.; Wang, W. C.; Lu, M. L.; Chen, Y. F.; Lin, H. C.; Chen, K. H.; Chen, L. C.

    2013-07-01

    The quantum efficiency and carrier lifetime that decide the photoconduction (PC) efficiencies in the metal oxide semiconductor nanowires (NWs) have been investigated. The experimental result surprisingly shows that the SnO2, TiO2, WO3, and ZnO NWs reveal extraordinary quantum efficiencies in common, which are over one to three orders of magnitude lower than the theoretical expectation. The surface depletion region (SDR)-controlled photoconductivity is proposed to explain the anomalous quantum efficiency and its power dependence. The inherent difference between the metal oxide nanostructures such as carrier lifetime, carrier concentration, and dielectric constant leading to the distinct PC performance and behavior are also discussed.The quantum efficiency and carrier lifetime that decide the photoconduction (PC) efficiencies in the metal oxide semiconductor nanowires (NWs) have been investigated. The experimental result surprisingly shows that the SnO2, TiO2, WO3, and ZnO NWs reveal extraordinary quantum efficiencies in common, which are over one to three orders of magnitude lower than the theoretical expectation. The surface depletion region (SDR)-controlled photoconductivity is proposed to explain the anomalous quantum efficiency and its power dependence. The inherent difference between the metal oxide nanostructures such as carrier lifetime, carrier concentration, and dielectric constant leading to the distinct PC performance and behavior are also discussed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01635h

  20. Effect of magnetic field on spin-dependent hole transport through a type-I Cd1-xMnxTe/CdTe double barrier heterostrucutre

    NASA Astrophysics Data System (ADS)

    Chandrasekar, L. Bruno; Gnanasekar, K.; Karunakaran, M.; Chandramohan, R.

    2017-06-01

    We study the effect of the magnetic field on the spin-dependent hole transport through a diluted magnetic semiconductor double barrier heterostrucutre such as Cd1- x Mn x Te/CdTe. Using the transfer matrix, the barrier transparency, polarization efficiency and tunneling lifetime of a light hole and a heavy hole are calculated. The spin separation is found out and is observed that it is the same for both the light and the heavy hole. The heavy hole takes more time to travel in the heterostrucutre than the light hole. The effect of the magnetic field influences the tunneling lifetime. The results give the basic idea about the spin-dependent transport of light and heavy holes.

  1. Zinc oxide nanoparticles as a substitute for zinc oxide or colistin sulfate: Effects on growth, serum enzymes, zinc deposition, intestinal morphology and epithelial barrier in weaned piglets.

    PubMed

    Wang, Chao; Zhang, Ligen; Su, Weipeng; Ying, Zhixiong; He, Jintian; Zhang, Lili; Zhong, Xiang; Wang, Tian

    2017-01-01

    The objective of this study was to evaluate effects of zinc oxide nanoparticles (nano-ZnOs) as a substitute for colistin sulfate (CS) and/or zinc oxide (ZnO) on growth performance, serum enzymes, zinc deposition, intestinal morphology and epithelial barrier in weaned piglets. A total of 216 crossbred Duroc×(Landrace×Yorkshire) piglets weaned at 23 days were randomly assigned into 3 groups, which were fed with basal diets supplemented with 20 mg/kg CS (CS group), 20mg/kg CS+3000 mg/kg ZnO (CS+ZnO group), and 1200 mg/kg nano-ZnOs (nano-ZnO group) for 14 days. Results indicated that compared to CS group, supplementation of 1200 mg/kg nano-ZnOs (about 30 nm) significantly increased final body weight and average daily gain, and 3000 mg/kg ZnO plus colistin sulfate significantly increased average daily gain and decreased diarrhea rate in weaned piglets. There was no significant difference in growth performance and diarrhea rate between nano-ZnO and CS+ZnO groups. Supplementation of nano-ZnOs did not affect serum enzymes (glutamic oxalacetic transaminase, glutamic-pyruvic transaminase, and lactate dehydrogenase), but significantly increased plasma and tissue zinc concentrations (liver, tibia), improved intestinal morphology (increased duodenal and ileal villus length, crypt depth, and villus surface), enhanced mRNA expression of ZO-1 in ileal mucosa, and significantly decreased diamine oxidase activity in plasma, total aerobic bacterial population in MLN as compared to CS group. Effects of nano-ZnOs on serum enzymes, intestinal morphology, and mRNA expressions of tight junction were similar to those of high dietary ZnO plus colistin sulfate, while nano-ZnOs significantly reduced zinc concentrations of liver, tibia, and feces, and decreased total aerobic bacterial population in MLN as compared to CS+ZnO group. These results suggested that nano-ZnOs (1200 mg/kg) might be used as a substitute for colistin sulfate and high dietary ZnO in weaned piglets.

  2. Energy dependence of the trapping of uranium atoms by aluminum oxide surfaces

    NASA Technical Reports Server (NTRS)

    Librecht, K. G.

    1979-01-01

    The energy dependence of the trapping probability for sputtered U-235 atoms striking an oxidized aluminum collector surface at energies between 1 eV and 184 eV was measured. At the lowest energies, approximately 10% of the uranium atoms are not trapped, while above 10 eV essentially all of them stick. Trapping probabilities averaged over the sputtered energy distribution for uranium incident on gold and mica are also presented.

  3. Salinity-dependent nickel accumulation and oxidative stress responses in the euryhaline killifish (Fundulus heteroclitus).

    PubMed

    Blewett, Tamzin A; Wood, Chris M

    2015-02-01

    The mechanisms of nickel (Ni) toxicity in marine fish remain unclear, although evidence from freshwater (FW) fish suggests that Ni can act as a pro-oxidant. This study investigated the oxidative stress effects of Ni on the euryhaline killifish (Fundulus heteroclitus) as a function of salinity. Killifish were exposed to sublethal levels (5, 10, and 20 mg L(-1)) of waterborne Ni for 96 h in FW (0 ppt) and 100 % saltwater (SW) (35 ppt). In general, SW was protective against both Ni accumulation and indicators of oxidative stress [protein carbonyl formation and catalase (CAT) activity]. This effect was most pronounced at the highest Ni exposure level. For example, FW intestine showed increased Ni accumulation relative to SW intestine at 20 mg Ni L(-1), and this was accompanied by significantly greater protein carbonylation and CAT activity in this tissue. There were exceptions, however, in that although liver of FW killifish at the highest exposure concentration showed greater Ni accumulation relative to SW liver, levels of CAT activity were greatly decreased. This may relate to tissue- and salinity-specific differences in oxidative stress responses. The results of the present study suggest (1) that there was Ni-induced oxidative stress in killifish, (2) that the effects of salinity depend on differences in the physiology of the fish in FW versus SW, and (3) that increased levels of cations (sodium, calcium, potassium, and magnesium) and anions (SO4 and Cl) in SW are likely protective against Ni accumulation in tissues exposed to the aquatic environment.

  4. Urolithins display both antioxidant and pro-oxidant activities depending on assay system and conditions.

    PubMed

    Kallio, Tuija; Kallio, Johanna; Jaakkola, Mari; Mäki, Marianne; Kilpeläinen, Pekka; Virtanen, Vesa

    2013-11-13

    The biological effects of polyphenolic ellagitannins are mediated by their intestinal metabolites, urolithins. This study investigated redox properties of urolithins A and B using ORAC assay, three cell-based assays, copper-initiated pro-oxidant activity (CIPA) assay, and cyclic voltammetry. Urolithins were strong antioxidants in the ORAC assay, but mostly pro-oxidants in cell-based assays, although urolithin A was an antioxidant in cell culture medium. Parent compound ellagic acid was a strong extracellular antioxidant, but showed no response in the intracellular assay. The CIPA assay confirmed the pro-oxidant activity of ellagitannin metabolites. In the cell proliferation assay, urolithins but not ellagic acid decreased growth and metabolism of HepG2 liver cells. In cyclic voltammetry, the oxidation of urolithin A was partly reversible, but that of urolithin B was irreversible. These results illustrate how strongly measured redox properties depend on the employed assay system and conditions and emphasize the importance of studying pro-oxidant and antioxidant activities in parallel.

  5. Spin dependent charge pumping in SiC metal-oxide-semiconductor field-effect-transistors

    NASA Astrophysics Data System (ADS)

    Bittel, B. C.; Lenahan, P. M.; Ryan, J. T.; Fronheiser, J.; Lelis, A. J.

    2011-08-01

    We demonstrate a very powerful electrically detected magnetic resonance (EDMR) technique, spin dependent charge pumping (SDCP) and apply it to 4H SiC metal-oxide-semiconductor field-effect-transistors. SDCP combines a widely used electrical characterization tool with the most powerful analytical technique for providing atomic scale structure of point defects in electronic materials. SDCP offers a large improvement in sensitivity over the previously established EDMR technique called spin dependent recombination, offering higher sensitivity and accessing a wider energy range within the bandgap.

  6. The red-vine-leaf extract AS195 increases nitric oxide synthase-dependent nitric oxide generation and decreases oxidative stress in endothelial and red blood cells.

    PubMed

    Grau, Marijke; Bölck, Birgit; Bizjak, Daniel Alexander; Stabenow, Christina Julia Annika; Bloch, Wilhelm

    2016-02-01

    The red-vine-leaf extract AS195 improves cutaneous oxygen supply and the microcirculation in patients suffering from chronic venous insufficiency. Regulation of blood flow was associated to nitric oxide synthase (NOS)-dependent NO (nitric oxide) production, and endothelial and red blood cells (RBC) have been shown to possess respective NOS isoforms. It was hypothesized that AS195 positively affects NOS activation in human umbilical vein endothelial cells (HUVECs) and RBC. Because patients with microvascular disorders show increased oxidative stress which limits NO bioavailability, it was further hypothesized that AS195 increases NO bioavailability by decreasing the content of reactive oxygen species (ROS) and increasing antioxidant capacity. Cultured HUVECs and RBCs from healthy volunteers were incubated with AS195 (100 μmol/L), tert-butylhydroperoxide (TBHP, 1 mmol/L) to induce oxidative stress and with both AS195 and TBHP. Endothelial and red blood cell-nitric oxide synthase (RBC-NOS) activation significantly increased after AS195 incubation. Nitrite concentration, a marker for NO production, increased in HUVEC but decreased in RBC after AS195 application possibly due to nitrite scavenging potential of flavonoids. S-nitrosylation of RBC cytoskeletal spectrins and RBC deformability were increased after AS195 incubation. TBHP-induced ROS were decreased by AS195, and antioxidative capacity was significantly increased in AS195-treated cells. TBHP also reduced RBC deformability, but reduction was attenuated by parallel incubation with AS195. Adhesion of HUVEC was also reduced after AS195 treatment. Red-vine-leaf extract AS195 increases NOS activation and decreases oxidative stress. Both mechanisms increase NO bioavailability, improve cell function, and may thus account for enhanced microcirculation in both health and disease.

  7. Overexpression of endothelial nitric oxide synthase improves endothelium-dependent vasodilation in arteries infused with helper-dependent adenovirus.

    PubMed

    Jiang, Bo; Du, Liang; Flynn, Rowan; Dronadula, Nagadhara; Zhang, Jingwan; Kim, Francis; Dichek, David

    2012-11-01

    Adenoviral vectors (Ad) are useful tools for in vivo gene transfer into endothelial cells. However, endothelium-dependent vasodilation is impaired after Ad infusion, and this impairment is not prevented by use of advanced-generation "helper-dependent" (HD) Ad that lack all viral genes. We hypothesized that endothelium-dependent vasodilation could be improved in Ad-infused arteries by overexpression of endothelial nitric oxide synthase (eNOS). We tested this hypothesis in hyperlipidemic, atherosclerosis-prone rabbits because HDAd will likely be used for treating and preventing atherosclerosis. Moreover, the consequences of eNOS overexpression might differ in normal and atherosclerosis-prone arteries and could include atherogenic effects, as reported in transgenic mice. We cloned rabbit eNOS and constructed an HDAd that expresses it. HDAdeNOS increased NO production by cultured endothelial cells and increased arterial eNOS mRNA in vivo by ∼10-fold. Compared to arteries infused with a control HDAd, HDAdeNOS-infused arteries of hyperlipidemic rabbits had significantly improved endothelium-dependent vasodilation, and similar responses to phenylephrine and nitroprusside. Moreover, infusion of HDAdeNOS had local atheroprotective effects including large, significant decreases in intimal lipid accumulation and arterial tumor necrosis factor (TNF)-α expression (p≤0.04 for both). HDAdeNOS infusion yields a durable (≥2 weeks) increase in arterial eNOS expression, improves vasomotor function, and reduces artery wall inflammation and lipid accumulation. Addition of an eNOS expression cassette improves the performance of HDAd, has no harmful effects, and may reduce atherosclerotic lesion growth.

  8. Gap Junction Proteins in the Blood-Brain Barrier Control Nutrient-Dependent Reactivation of Drosophila Neural Stem Cells

    PubMed Central

    Spéder, Pauline; Brand, Andrea H.

    2014-01-01

    Summary Neural stem cells in the adult brain exist primarily in a quiescent state but are reactivated in response to changing physiological conditions. How do stem cells sense and respond to metabolic changes? In the Drosophila CNS, quiescent neural stem cells are reactivated synchronously in response to a nutritional stimulus. Feeding triggers insulin production by blood-brain barrier glial cells, activating the insulin/insulin-like growth factor pathway in underlying neural stem cells and stimulating their growth and proliferation. Here we show that gap junctions in the blood-brain barrier glia mediate the influence of metabolic changes on stem cell behavior, enabling glia to respond to nutritional signals and reactivate quiescent stem cells. We propose that gap junctions in the blood-brain barrier are required to translate metabolic signals into synchronized calcium pulses and insulin secretion. PMID:25065772

  9. Annealing dependence of diamond-metal Schottky barrier heights probed by hard x-ray photoelectron spectroscopy

    SciTech Connect

    Gaowei, M.; Muller, E. M.; Rumaiz, A. K.; Weiland, C.; Cockayne, E.; Woicik, J. C.; Jordan-Sweet, J.; Smedley, J.

    2012-05-14

    Hard x-ray photoelectron spectroscopy was applied to investigate the diamond-metal Schottky barrier heights for several metals and diamond surface terminations. The position of the diamond valence-band maximum was determined by theoretically calculating the diamond density of states and applying cross section corrections. The diamond-platinum Schottky barrier height was lowered by 0.2 eV after thermal annealing, indicating annealing may increase carrier injection in diamond devices leading to photoconductive gain. The platinum contacts on oxygen-terminated diamond was found to provide a higher Schottky barrier and therefore a better blocking contact than that of the silver contact in diamond-based electronic devices.

  10. Gap junction proteins in the blood-brain barrier control nutrient-dependent reactivation of Drosophila neural stem cells.

    PubMed

    Spéder, Pauline; Brand, Andrea H

    2014-08-11

    Neural stem cells in the adult brain exist primarily in a quiescent state but are reactivated in response to changing physiological conditions. How do stem cells sense and respond to metabolic changes? In the Drosophila CNS, quiescent neural stem cells are reactivated synchronously in response to a nutritional stimulus. Feeding triggers insulin production by blood-brain barrier glial cells, activating the insulin/insulin-like growth factor pathway in underlying neural stem cells and stimulating their growth and proliferation. Here we show that gap junctions in the blood-brain barrier glia mediate the influence of metabolic changes on stem cell behavior, enabling glia to respond to nutritional signals and reactivate quiescent stem cells. We propose that gap junctions in the blood-brain barrier are required to translate metabolic signals into synchronized calcium pulses and insulin secretion. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  11. The spontaneous fission of 8Be and the fusion at sub-coloumb barrier energies in the time-dependent cluster theory

    NASA Astrophysics Data System (ADS)

    Drożdż, S.; Okolowicz, J.; Ploszajczak, M.

    1983-08-01

    The time-dependent cluster theory is applied for a description of the spontaneous fission of 8Be and for a calculation of the α-α fusion cross section at sub-Coulomb barrier energies. The calculated spontaneous fission decay width Γ(cal) ≅ 7.5 eV reproduces the experimental value Γ(ex) = 6.8 +/- 1.7 eV.

  12. Molecular orientation dependence of hole-injection barrier in pentacene thin film on the Au surface in organic thin film transistor

    NASA Astrophysics Data System (ADS)

    Ihm, Kyuwook; Kim, Bongsoo; Kang, Tai-Hee; Kim, Ki-Jeong; Joo, Min Ho; Kim, Tae Hyeong; Yoon, Sang Soo; Chung, Sukmin

    2006-07-01

    We have investigated the effects of a buffer layer insertion on the performance of the pentacene based thin film transistor with a bottom contact structure. When the pentacene molecules have a standing up coordination on the Au surface that is modified by the benzenethiol or methanethiol, the transition region in the pentacene thin film is removed along the boundary between the Au and silicon oxide region, and the hole-injection barrier decreases by 0.4eV. Pentacene on various surfaces showed that the highly occupied molecular level is 0.2-0.4eV lower in the standing up coordination than in the lying down coordination.

  13. Efficient spin injection through a crystalline AlOx tunnel barrier prepared by the oxidation of an ultra-thin Al epitaxial layer on GaAs

    NASA Astrophysics Data System (ADS)

    Nishizawa, N.; Munekata, H.

    2013-07-01

    We report that an ultra-thin, post-oxidized aluminum epilayer grown on the AlGaAs surface works as a high-quality tunnel barrier for spin injection from a ferromagnetic metal to a semiconductor. One of the key points of the present oxidation method is the formation of the crystalline AlOx template layer without oxidizing the AlGaAs region near the Al/AlGaAs interface. The oxidized Al layer is not amorphous but show well-defined single crystalline feature reminiscent of the spinel γ-AlOx phase. A spin-light emitting diode consisting of a Fe layer, a crystalline AlOx barrier layer, and an AlGaAs-InGaAs double hetero-structure has exhibited circularly polarized electroluminescence with circular polarization of PEL ˜ 0.145 at the remnant magnetization state of the Fe layer, indicating the relatively high spin injection efficiency (≡2PEL/PFe) of 0.63.

  14. Impact of eNOS-Dependent Oxidative Stress on Endothelial Function and Neointima Formation

    PubMed Central

    Suvorava, Tatsiana; Nagy, Nadine; Pick, Stephanie; Lieven, Oliver; Rüther, Ulrich; Dao, Vu Thao-Vi; Fischer, Jens W.; Weber, Martina

    2015-01-01

    Abstract Aims: Vascular oxidative stress generated by endothelial NO synthase (eNOS) was observed in experimental and clinical cardiovascular disease, but its relative importance for vascular pathologies is unclear. We investigated the impact of eNOS-dependent vascular oxidative stress on endothelial function and on neointimal hyperplasia. Results: A dimer-destabilized mutant of bovine eNOS where cysteine 101 was replaced by alanine was cloned and introduced into an eNOS-deficient mouse strain (eNOS-KO) in an endothelial-specific manner. Destabilization of mutant eNOS in cells and eNOS-KO was confirmed by the reduced dimer/monomer ratio. Purified mutant eNOS and transfected cells generated less citrulline and NO, respectively, while superoxide generation was enhanced. In eNOS-KO, introduction of mutant eNOS caused a 2.3–3.7-fold increase in superoxide and peroxynitrite formation in the aorta and myocardium. This was completely blunted by an NOS inhibitor. Nevertheless, expression of mutant eNOS in eNOS-KO completely restored maximal aortic endothelium-dependent relaxation to acetylcholine. Neointimal hyperplasia induced by carotid binding was much larger in eNOS-KO than in mutant eNOS-KO and C57BL/6, while the latter strains showed comparable hyperplasia. Likewise, vascular remodeling was blunted in eNOS-KO only. Innovation: Our results provide the first in vivo evidence that eNOS-dependent oxidative stress is unlikely to be an initial cause of impaired endothelium-dependent vasodilation and/or a pathologic factor promoting intimal hyperplasia. These findings highlight the importance of other sources of vascular oxidative stress in cardiovascular disease. Conclusion: eNOS-dependent oxidative stress is unlikely to induce functional vascular damage as long as concomitant generation of NO is preserved. This underlines the importance of current and new therapeutic strategies in improving endothelial NO generation. Antioxid. Redox Signal. 23, 711–723. PMID:25764009

  15. Eltrombopag, a thrombopoietin mimetic, crosses the blood-brain barrier and impairs iron-dependent hippocampal neuron dendrite development.

    PubMed

    Bastian, T W; Duck, K A; Michalopoulos, G C; Chen, M J; Liu, Z-J; Connor, J R; Lanier, L M; Sola-Visner, M C; Georgieff, M K

    2017-03-01

    Essentials Potential neurodevelopmental side effects of thrombopoietin mimetics need to be considered. The effects of eltrombopag (ELT) on neuronal iron status and dendrite development were assessed. ELT crosses the blood-brain barrier and causes iron deficiency in developing neurons. ELT blunts dendrite maturation, indicating a need for more safety studies before neonatal use.

  16. Oxidative Burst-Dependent NETosis Is Implicated in the Resolution of Necrosis-Associated Sterile Inflammation

    PubMed Central

    Biermann, Mona H. C.; Podolska, Malgorzata J.; Knopf, Jasmin; Reinwald, Christiane; Weidner, Daniela; Maueröder, Christian; Hahn, Jonas; Kienhöfer, Deborah; Barras, Alexandre; Boukherroub, Rabah; Szunerits, Sabine; Bilyy, Rostyslav; Hoffmann, Markus; Zhao, Yi; Schett, Georg; Herrmann, Martin; Munoz, Luis E.

    2016-01-01

    Necrosis is associated with a profound inflammatory response. The regulation of necrosis-associated inflammation, particularly the mechanisms responsible for resolution of inflammation is incompletely characterized. Nanoparticles are known to induce plasma membrane damage and necrosis followed by sterile inflammation. We observed that injection of metabolically inert nanodiamonds resulted in paw edema in WT and Ncf1** mice. However, while inflammation quickly resolved in WT mice, it persisted over several weeks in Ncf1** mice indicating failure of resolution of inflammation. Mechanistically, NOX2-dependent reactive oxygen species (ROS) production and formation of neutrophil extracellular traps were essential for the resolution of necrosis-induced inflammation: hence, by evaluating the fate of the particles at the site of inflammation, we observed that Ncf1** mice deficient in NADPH-dependent ROS failed to generate granulation tissue therefore being unable to trap the nanodiamonds. These data suggest that NOX2-dependent NETosis is crucial for preventing the chronification of the inflammatory response to tissue necrosis by forming NETosis-dependent barriers between the necrotic and healthy surrounding tissue. PMID:27990145

  17. Oxidative Burst-Dependent NETosis Is Implicated in the Resolution of Necrosis-Associated Sterile Inflammation.

    PubMed

    Biermann, Mona H C; Podolska, Malgorzata J; Knopf, Jasmin; Reinwald, Christiane; Weidner, Daniela; Maueröder, Christian; Hahn, Jonas; Kienhöfer, Deborah; Barras, Alexandre; Boukherroub, Rabah; Szunerits, Sabine; Bilyy, Rostyslav; Hoffmann, Markus; Zhao, Yi; Schett, Georg; Herrmann, Martin; Munoz, Luis E

    2016-01-01

    Necrosis is associated with a profound inflammatory response. The regulation of necrosis-associated inflammation, particularly the mechanisms responsible for resolution of inflammation is incompletely characterized. Nanoparticles are known to induce plasma membrane damage and necrosis followed by sterile inflammation. We observed that injection of metabolically inert nanodiamonds resulted in paw edema in WT and Ncf1** mice. However, while inflammation quickly resolved in WT mice, it persisted over several weeks in Ncf1** mice indicating failure of resolution of inflammation. Mechanistically, NOX2-dependent reactive oxygen species (ROS) production and formation of neutrophil extracellular traps were essential for the resolution of necrosis-induced inflammation: hence, by evaluating the fate of the particles at the site of inflammation, we observed that Ncf1** mice deficient in NADPH-dependent ROS failed to generate granulation tissue therefore being unable to trap the nanodiamonds. These data suggest that NOX2-dependent NETosis is crucial for preventing the chronification of the inflammatory response to tissue necrosis by forming NETosis-dependent barriers between the necrotic and healthy surrounding tissue.

  18. Genome-enabled studies of anaerobic, nitrate-dependent iron oxidation in the chemolithoautotrophic bacterium Thiobacillus denitrificans

    PubMed Central

    Beller, Harry R.; Zhou, Peng; Legler, Tina C.; Chakicherla, Anu; Kane, Staci; Letain, Tracy E.; A. O’Day, Peggy

    2013-01-01

    Thiobacillus denitrificans is a chemolithoautotrophic bacterium capable of anaerobic, nitrate-dependent U(IV) and Fe(II) oxidation, both of which can strongly influence the long-term efficacy of in situ reductive immobilization of uranium in contaminated aquifers. We previously identified two c-type cytochromes involved in nitrate-dependent U(IV) oxidation in T. denitrificans and hypothesized that c-type cytochromes would also catalyze Fe(II) oxidation, as they have been found to play this role in anaerobic phototrophic Fe(II)-oxidizing bacteria. Here we report on efforts to identify genes associated with nitrate-dependent Fe(II) oxidation, namely (a) whole-genome transcriptional studies [using FeCO3, Fe2+, and U(IV) oxides as electron donors under denitrifying conditions], (b) Fe(II) oxidation assays performed with knockout mutants targeting primarily highly expressed or upregulated c-type cytochromes, and (c) random transposon-mutagenesis studies with screening for Fe(II) oxidation. Assays of mutants for 26 target genes, most of which were c-type cytochromes, indicated that none of the mutants tested were significantly defective in nitrate-dependent Fe(II) oxidation. The non-defective mutants included the c1-cytochrome subunit of the cytochrome bc1 complex (complex III), which has relevance to a previously proposed role for this complex in nitrate-dependent Fe(II) oxidation and to current concepts of reverse electron transfer. A transposon mutant with a disrupted gene associated with NADH:ubiquinone oxidoreductase (complex I) was ~35% defective relative to the wild-type strain; this strain was similarly defective in nitrate reduction with thiosulfate as the electron donor. Overall, our results indicate that nitrate-dependent Fe(II) oxidation in T. denitrificans is not catalyzed by the same c-type cytochromes involved in U(IV) oxidation, nor have other c-type cytochromes yet been implicated in the process. PMID:24065960

  19. Cortactin deficiency causes increased RhoA/ROCK1-dependent actomyosin contractility, intestinal epithelial barrier dysfunction, and disproportionately severe DSS-induced colitis.

    PubMed

    Citalán-Madrid, A F; Vargas-Robles, H; García-Ponce, A; Shibayama, M; Betanzos, A; Nava, P; Salinas-Lara, C; Rottner, K; Mennigen, R; Schnoor, M

    2017-01-25

    The intestinal epithelium constitutes a first line of defense of the innate immune system. Epithelial dysfunction is a hallmark of intestinal disorders such as inflammatory bowel diseases (IBDs). The actin cytoskeleton controls epithelial barrier integrity but the function of actin regulators such as cortactin is poorly understood. Given that cortactin controls endothelial permeability, we hypothesized that cortactin is also important for epithelial barrier regulation. We found increased permeability in the colon of cortactin-KO mice that was accompanied by reduced levels of ZO-1, claudin-1, and E-cadherin. By contrast, claudin-2 was upregulated. Cortactin deficiency increased RhoA/ROCK1-dependent actomyosin contractility, and inhibition of ROCK1 rescued the barrier defect. Interestingly, cortactin deficiency caused increased epithelial proliferation without affecting apoptosis. KO mice did not develop spontaneous colitis, but were more susceptible to dextran sulfate sodium colitis and showed severe colon tissue damage and edema formation. KO mice with colitis displayed strong mucus deposition and goblet cell depletion. In healthy human colon tissues, cortactin co-localized with ZO-1 at epithelial cell contacts. In IBDs patients, we observed decreased cortactin levels and loss of co-localization with ZO-1. Thus, cortactin is a master regulator of intestinal epithelial barrier integrity in vivo and could serve as a suitable target for pharmacological intervention in IBDs.Mucosal Immunology advance online publication, 25 January 2017; doi:10.1038/mi.2016.136.

  20. Concentration dependent effect of calcium on brain mitochondrial bioenergetics and oxidative stress parameters

    PubMed Central

    Pandya, Jignesh D.; Nukala, Vidya N.; Sullivan, Patrick G.

    2013-01-01

    Mitochondrial dysfunction following traumatic brain and spinal cord injury (TBI and SCI) plays a pivotal role in the development of secondary pathophysiology and subsequent neuronal cell death. Previously, we demonstrated a loss of mitochondrial bioenergetics in the first 24 h following TBI and SCI initiates a rapid and extensive necrotic event at the primary site of injury. Within the mitochondrial derived mechanisms, the cross talk and imbalance amongst the processes of excitotoxicity, Ca2+ cycling/overload, ATP synthesis, free radical production and oxidative damage ultimately lead to mitochondrial damage followed by neuronal cell death. Mitochondria are one of the important organelles that regulate intracellular calcium (Ca2+) homeostasis and are equipped with a tightly regulated Ca2+ transport system. However, owing to the lack of consensus and the link between downstream effects of calcium in published literature, we undertook a systematic in vitro study for measuring concentration dependent effects of calcium (100–1000 nmols/mg mitochondrial protein) on mitochondrial respiration, enzyme activities, reactive oxygen/nitrogen species (ROS/RNS) generation, membrane potential (ΔΨ) and oxidative damage markers in isolated brain mitochondria. We observed a dose- and time-dependent inhibition of mitochondrial respiration by calcium without influencing mitochondrial pyruvate dehydrogenase complex (PDHC) and NADH dehydrogenase (Complex I) enzyme activities. We observed dose-dependent decreased production of hydrogen peroxide and total ROS/RNS species generation by calcium and no significant changes in protein and lipid oxidative damage markers. These results may shed new light on the prevailing dogma of the direct effects of calcium on mitochondrial bioenergetics, free radical production and oxidative stress parameters that are primary regulatory mitochondrial mechanisms following neuronal injury. PMID:24385963

  1. Anaerobic Oxidization of Methane in a Minerotrophic Peatland: Enrichment of Nitrite-Dependent Methane-Oxidizing Bacteria

    PubMed Central

    Zhu, Baoli; van Dijk, Gijs; Fritz, Christian; Smolders, Alfons J. P.; Pol, Arjan; Jetten, Mike S. M.

    2012-01-01

    The importance of anaerobic oxidation of methane (AOM) as a methane sink in freshwater systems is largely unexplored, particularly in peat ecosystems. Nitrite-dependent anaerobic methane oxidation (n-damo) was recently discovered and reported to be catalyzed by the bacterium “Candidatus Methylomirabilis oxyfera,” which is affiliated with the NC10 phylum. So far, several “Ca. Methylomirabilis oxyfera” enrichment cultures have been obtained using a limited number of freshwater sediments or wastewater treatment sludge as the inoculum. In this study, using stable isotope measurements and porewater profiles, we investigated the potential of n-damo in a minerotrophic peatland in the south of the Netherlands that is infiltrated by nitrate-rich ground water. Methane and nitrate profiles suggested that all methane produced was oxidized before reaching the oxic layer, and NC10 bacteria could be active in the transition zone where countergradients of methane and nitrate occur. Quantitative PCR showed high NC10 bacterial cell numbers at this methane-nitrate transition zone. This soil section was used to enrich the prevalent NC10 bacteria in a continuous culture supplied with methane and nitrite at an in situ pH of 6.2. An enrichment of nitrite-reducing methanotrophic NC10 bacteria was successfully obtained. Phylogenetic analysis of retrieved 16S rRNA and pmoA genes showed that the enriched bacteria were very similar to the ones found in situ and constituted a new branch of NC10 bacteria with an identity of less than 96 and 90% to the 16S rRNA and pmoA genes of “Ca. Methylomirabilis oxyfera,” respectively. The results of this study expand our knowledge of the diversity and distribution of NC10 bacteria in the environment and highlight their potential contribution to nitrogen and methane cycles. PMID:23042166

  2. Plasma oxidation for achieving supported TiO2 photocatalysts derived from adsorbed TiCl4 using dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Zhang, Xiu-Ling; Nie, Long-Hui; Xu, Yong; Shi, Chuan; Yang, Xue-Feng; Zhu, Ai-Min

    2007-03-01

    At atmospheric pressure and room temperature, dielectric barrier discharge induced plasma oxidation for achieving supported TiO2 photocatalysts derived from TiCl4 adsorbed onto γ-Al2O3 pellets was studied. The supported TiO2/γ-Al2O3photocatalysts prepared by a cyclic 'adsorption-discharge' approach, without requirement of heat treatment, exhibit high activity in the photocatalytic degradation reaction of formaldehyde. The mass spectra and optical emission spectra during O2/Ar discharge for oxidizing the adsorbed-state TiCl4 were measured. The mechanism for the TiO2 formation from adsorbed-state TiCl4 by plasma oxidation was discussed.

  3. Thermoelectric properties of nano-granular indium-tin-oxide within modified electron filtering model with chemisorption-type potential barriers

    NASA Astrophysics Data System (ADS)

    Brinzari, V.; Nika, D. L.; Damaskin, I.; Cho, B. K.; Korotcenkov, G.

    2016-07-01

    In this work, an approach to the numerical study of the thermoelectric parameters of nanoscale indium tin oxide (ITO, Sn content<10 at%) based on an electron filtering model (EFM) was developed. Potential barriers at grain boundaries were assumed to be responsible for a filtering effect. In the case of the dominant inelastic scattering of electrons, the maximal distance between potential barriers was limited in this modified model. The algorithm for such characteristic length calculation was proposed, and its value was evaluated for ITO. In addition, the contributions of different scattering mechanisms (SMs) in electron transport were examined. It was confirmed that in bulk ITO, the scattering on polar optical phonons (POPs) and ionized impurities dominates, limiting electron transport. In the framework of the filtering model, the basic thermoelectric parameters (i.e., electrical conductivity, mobility, Seebeck coefficient, and power factor (PF)) were calculated for ITO in the temperature range of 100-500 °C as a function of potential barrier height. The results demonstrated a sufficient rise of the Seebeck coefficient with an increase in barrier height and specific behavior of PF. It was found that PF is very sensitive to barrier height, and at its optimal value for granular ITO, it may exceed the PF for bulk ITO by 3-5 times. The PF maximum was achieved by band bending, slightly exceeding Fermi energy. The nature of surface potential barriers in nano-granular ITO with specific grains is due to the oxygen chemisorption effect, and this can be observed despite of the degeneracy of the conduction band (CB). This hypothesis and the corresponding calculations are in good agreement with recent experimental studies [Brinzari et al. Thin Solid Films 552 (2014) 225].

  4. Investigation of Thickness Dependence of Metal Layer in Al/Mo/4H-SiC Schottky Barrier Diodes.

    PubMed

    Lee, Seula; Lee, Jinseon; Kang, Tai-Young; Kyoung, Sinsu; Jung, Eun Sik; Kim, Kyung Hwan

    2015-11-01

    In this paper, we present the preparation and characterization of Schottky barrier diodes based on silicon carbide with various Schottky metal layer thickness values. In this structure, molybdenum and aluminum were employed as the Schottky barrier metal and top electrode, respectively. Schottky metal layers were deposited with thicknesses ranging from 1000 to 3000 Å, and top electrodes were deposited with thickness as much as 3000 Å. The deposition of both metal layers was performed using the facing target sputtering (FTS) method, and the fabricated samples were annealed with the tubular furnace at 300 degrees C under argon ambient for 10 min. The Schottky barrier height, series resistance, and ideality factor was calculated from the forward I-V characteristic curve using the methods proposed by Cheung and Cheung, and by Norde. For as-deposited Schottky diodes, we observed an increase of the threshold voltage (V(T)) as the thickness of the Schottky metal layer increased. After the annealing, the Schottky barrier heights (SBHs) of the diodes, including Schottky metal layers of over 2000 Å, increased. In the case of the Schottky metal layer deposited to 1000 Å, the barrier heights decreased due to the annealing process. This may have been caused by the interfacial penetration phenomenon through the Schottky metal layer. For variations of V(T), the SBH changed with a similar tendency. The ideality factor and series resistance showed no significant changes before or after annealing. This indicates that this annealing condition is appropriate for Mo SiC structures. Our results confirm that it is possible to control V(T) by adjusting the thickness of the Schottky metal layer.

  5. Overexpression of Endothelial Nitric Oxide Synthase Improves Endothelium-Dependent Vasodilation in Arteries Infused with Helper-Dependent Adenovirus

    PubMed Central

    Jiang, Bo; Du, Liang; Flynn, Rowan; Dronadula, Nagadhara; Zhang, Jingwan; Kim, Francis

    2012-01-01

    Abstract Adenoviral vectors (Ad) are useful tools for in vivo gene transfer into endothelial cells. However, endothelium-dependent vasodilation is impaired after Ad infusion, and this impairment is not prevented by use of advanced-generation “helper-dependent” (HD) Ad that lack all viral genes. We hypothesized that endothelium-dependent vasodilation could be improved in Ad-infused arteries by overexpression of endothelial nitric oxide synthase (eNOS). We tested this hypothesis in hyperlipidemic, atherosclerosis-prone rabbits because HDAd will likely be used for treating and preventing atherosclerosis. Moreover, the consequences of eNOS overexpression might differ in normal and atherosclerosis-prone arteries and could include atherogenic effects, as reported in transgenic mice. We cloned rabbit eNOS and constructed an HDAd that expresses it. HDAdeNOS increased NO production by cultured endothelial cells and increased arterial eNOS mRNA in vivo by ∼10-fold. Compared to arteries infused with a control HDAd, HDAdeNOS-infused arteries of hyperlipidemic rabbits had significantly improved endothelium-dependent vasodilation, and similar responses to phenylephrine and nitroprusside. Moreover, infusion of HDAdeNOS had local atheroprotective effects including large, significant decreases in intimal lipid accumulation and arterial tumor necrosis factor (TNF)-α expression (p≤0.04 for both). HDAdeNOS infusion yields a durable (≥2 weeks) increase in arterial eNOS expression, improves vasomotor function, and reduces artery wall inflammation and lipid accumulation. Addition of an eNOS expression cassette improves the performance of HDAd, has no harmful effects, and may reduce atherosclerotic lesion growth. PMID:22906141

  6. Size- and support-dependent evolution of the oxidation state and structure by oxidation of subnanometer cobalt clusters.

    PubMed

    Yin, Chunrong; Zheng, Fan; Lee, Sungsik; Guo, Jinghua; Wang, Wei-Cheng; Kwon, Gihan; Vajda, Viktor; Wang, Hsien-Hau; Lee, Byeongdu; DeBartolo, Janae; Seifert, Sönke; Winans, Randall E; Vajda, Stefan

    2014-09-18

    Size-selected subnanometer cobalt clusters with 4, 7, and 27 cobalt atoms supported on amorphous alumina and ultrananocrystalline diamond (UNCD) surfaces were oxidized after exposure to ambient air. Grazing incidence X-ray absorption near-edge spectroscopy (GIXANES) and near-edge X-ray absorption fine structure (NEXAFS) were used to characterize the clusters revealed a strong dependency of the oxidation state and structure of the clusters on the surface. A dominant Co(2+) phase was identified in all samples. However, XANES analysis of cobalt clusters on UNCD showed that ∼10% fraction of a Co(0) phase was identified for all three cluster sizes and about 30 and 12% fraction of a Co(3+) phase in 4, 7, and 27 atom clusters, respectively. In the alumina-supported clusters, the dominating Co(2+) component was attributed to a cobalt aluminate, indicative of a very strong binding to the support. NEXAFS showed that in addition to strong binding of the clusters to alumina, their structure to a great extent follows the tetrahedral morphology of the support. All supported clusters were found to be resistant to agglomeration when exposed to reactive gases at elevated temperatures and atmospheric pressure.

  7. Shape-Dependent Activity of Ceria for Hydrogen Electro-Oxidation in Reduced-Temperature Solid Oxide Fuel Cells.

    PubMed

    Tong, Xiaofeng; Luo, Ting; Meng, Xie; Wu, Hao; Li, Junliang; Liu, Xuejiao; Ji, Xiaona; Wang, Jianqiang; Chen, Chusheng; Zhan, Zhongliang

    2015-11-04

    Single crystalline ceria nanooctahedra, nanocubes, and nanorods are hydrothermally synthesized, colloidally impregnated into the porous La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) scaffolds, and electrochemically evaluated as the anode catalysts for reduced temperature solid oxide fuel cells (SOFCs). Well-defined surface terminations are confirmed by the high-resolution transmission electron microscopy--(111) for nanooctahedra, (100) for nanocubes, and both (110) and (100) for nanorods. Temperature-programmed reduction in H2 shows the highest reducibility for nanorods, followed sequentially by nanocubes and nanooctahedra. Measurements of the anode polarization resistances and the fuel cell power densities reveal different orders of activity of ceria nanocrystals at high and low temperatures for hydrogen electro-oxidation, i.e., nanorods > nanocubes > nanooctahedra at T ≤ 450 °C and nanooctahedra > nanorods > nanocubes at T ≥ 500 °C. Such shape-dependent activities of these ceria nanocrystals have been correlated to their difference in the local structure distortions and thus in the reducibility. These findings will open up a new strategy for design of advanced catalysts for reduced-temperature SOFCs by elaborately engineering the shape of nanocrystals and thus selectively exposing the crystal facets. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Size- and Support-Dependent Evolution of the Oxidation State and Structure by Oxidation of Subnanometer Cobalt Clusters

    SciTech Connect

    Yin, Chunrong; Zheng, Fan; Lee, Sungsik; Guo, Jinghua; Wang, Wei-Cheng; Kwon, Gihan; Vajda, Viktor; Wang, Hsien-Hau; Lee, Byeongdu; DeBartolo, Janae; Seifert, Sönke; Winans, Randall E.; Vajda, Stefan

    2014-09-18

    Size-selected subnanometer cobalt clusters with 4, 7 and 27 cobalt atoms supported on amorphous alumina and ultrananocrystalline diamond (UNCD) surfaces were oxidized after exposure to ambient air. Grazing incidence X-ray absorption near edge spectroscopy (GIXANES) and near edge X-ray absorption fine structure (NEXAFS) used to characterize the clusters revealed a strong dependency of the oxidation state and structure of the clusters on the surface. A dominant Co2+ phase was identified in all samples. However, form XANES analysis, on UNCD about 10% fraction of Co0 phase was identified for all three cluster sizes and about 30% and 12% fraction of Co3+ phase in 4, 7 and 27 atoms, respectively. In the alumina-supported clusters, the dominating Co2+ component was attributed to cobalt aluminate, indicative of a very strong binding to the support. NEXAFS showed that in addition to strong binding of the clusters to alumina, their structure in great extent follows the tetrahedral morphology of the support. The supported clusters of all three sizes were found resistant to agglomeration when exposed to reactive gases at elevated temperatures and atmospheric pressure.

  9. Atomic scale understanding of nanostructures in a double barrier tunneling junction: Scanning tunneling microscopy of alkali doped buckminsterfullerenes on partially oxidized nickel aluminide(110)

    NASA Astrophysics Data System (ADS)

    Liu, Ning

    The electronic and vibrational properties of single 4,7,12,15-tetrakis[2,2]paracyclophane molecules, single C60 and C70 molecules, C60 monolayer, and alkali-doped C60 adsorbed on the partially oxidized NiAl(110) surface have been studied by scanning tunneling microscopy and spectroscopy. All experiments were carried out with a homebuilt variable temperature STM housed in an ultrahigh vacuum chamber. The dI/dV and d2I/dV2 signals were acquired with a lock-in amplifier. Spatially resolved inelastic tunneling microscopy has revealed the spatial distribution of vibrational intensity in different functional groups of the DMAS-PCP molecule at various vibrational modes. The ab initio calculations indicate that the electron-phonon coupling matrix element is a good value to estimate the relative intensity of the vibrational signal in STM-IETS measurements. Due to the unique double barrier tunneling junction configuration consisting of the vacuum gap, the molecules or the nanostructures, and the thin oxide film, interesting phenomena such as vibronic progressions and the Coulomb charging effect have been observed in the conductance measurements. The observation of these phenomena highlights the interplay of the tunneling electron with the vibrational motions of the molecule during the resonant tunneling process and the influence of the electrostatic energy to the tunneling event when the size of the structure is reduced to the nano scale. A distance dependent interaction between alkali adatoms mediated by C60 monolayer was observed. This interaction is characterized by the energy splitting of a single unoccupied resonance of the alkali atoms into the bonding and antibonding states. Due to the indirect interaction through C60 molecules, the energy splitting decays much slower than that in the gas phase. These results offer valuable knowledge on the electron-phonon coupling within a molecule enhanced by surface phonons, molecular conductance, the role of impurities, and the

  10. 5-hydroxytryptamine actions in adipocytes: involvement of monoamine oxidase-dependent oxidation and subsequent PPARγ activation.

    PubMed

    Grès, Sandra; Gomez-Zorita, Saioa; Gomez-Ruiz, Ana; Carpéné, Christian

    2013-06-01

    Serotonin (5-HT) is a brain neurotransmitter instrumental for the antidepressant action of selective inhibitors of serotonin reuptake (SSRIs) while it also plays important roles in peripheral organs. Recently, the 5-HT oxidation products, 5-hydroxyindoleacetate and 5-methoxy-indoleacetate, have been shown to bind to peroxisome proliferator-activated receptor γ (PPARγ) and to enhance lipid accumulation in preadipocytes. Since we already reported that adipocytes exhibit elevated monoamine oxidase (MAO) and primary amine oxidase activities, we verified how adipocytes readily oxidize 5-HT, with the objective to determine whether such oxidation promotes PPARγ activation and lipid storage. To this aim, serotonin was tested on cultured 3T3 F442A preadipocytes and on human adipocytes. Results showed that 5-HT was oxidized by MAO in both models. Daily treatment of 3T3 F442A preadipocytes for 8 days with 100-500 μM 5-HT promoted triglyceride accumulation and emergence of adipogenesis markers. At 250 μM, 5-HT alone reproduced half of 50 nM insulin-induced adipogenesis, and exhibited an additive differentiating effect when combined with insulin. Moreover, the 5-HT-induced expression of PPARγ-responsive genes (PEPCK, aP2/FABP4) was blocked by GW 9662, a PPARγ-inhibitor, or by pargyline, a MAO-inhibitor. In human fat cells, 6-h exposure to 100 μM 5-HT increased PEPCK expression as did the PPARγ-agonist rosiglitazone. Since hydrogen peroxide, another amine oxidation product, did not reproduce such enhancement, we propose that serotonin can promote PPARγ activation in fat cells, via the indoleacetate produced during MAO-dependent oxidation. Such pathway could be involved in the adverse effects of several antidepressant SSRIs on body weight gain.

  11. Temperature-Dependent Deicing Properties of Electrostatically Anchored Branched Brush Layers of Poly(ethylene oxide).

    PubMed

    Heydari, Golrokh; Tyrode, Eric; Visnevskij, Ceslav; Makuska, Ricardas; Claesson, Per M

    2016-05-03

    The hydration water of hydrophilic polymers freezes at subzero temperatures. The adsorption of such polymers will result in a hydrophilic surface layer that strongly binds water. Provided this interfacial hydration water remains liquidlike at subzero temperatures, its presence could possibly reduce ice adhesion, in particular, if the liquidlike layer is thicker than or comparable to the surface roughness. To explore this idea, a diblock copolymer, having one branched bottle-brush block of poly(ethylene oxide) and one linear cationic block, was electrostatically anchored on flat silica surfaces. The shear ice adhesion strength on such polymer-coated surfaces was investigated down to -25 °C using a homebuilt device. In addition, the temperature dependence of the ice adhesion on surfaces coated with only the cationic block, only the branched bottle-brush block, and with linear poly(ethylene oxide) was investigated. Significant ice adhesion reduction, in particular, at temperatures above -15 °C, was observed on silica surfaces coated with the electrostatically anchored diblock copolymer. Differential scanning calorimetry measurements on bulk polymer solutions demonstrate different thermal transitions of water interacting with branched and linear poly(ethylene oxide) (with hydration water melting points of about -18 and -10 °C, respectively). This difference is consistent with the low shear ice adhesion strength measured on surfaces carrying branched bottle-brush structured poly(ethylene oxide) at -10 °C, whereas no significant adhesion reduction was obtained with linear poly(ethylene oxide) at this temperature. We propose a lubrication effect of the hydration water bound to the branched bottle-brush structured poly(ethylene oxide), which, in the bulk, does not freeze until -18 °C.

  12. Effect of Oxidation Rate and Fe(II) State on Microbial Nitrate-Dependent Fe(III) Mineral Formation

    PubMed Central

    Senko, John M.; Dewers, Thomas A.; Krumholz, Lee R.

    2005-01-01

    A nitrate-dependent Fe(II)-oxidizing bacterium was isolated and used to evaluate whether Fe(II) chemical form or oxidation rate had an effect on the mineralogy of biogenic Fe(III) (hydr)oxides resulting from nitrate-dependent Fe(II) oxidation. The isolate (designated FW33AN) had 99% 16S rRNA sequence similarity to Klebsiella oxytoca. FW33AN produced Fe(III) (hydr)oxides by oxidation of soluble Fe(II) [Fe(II)sol] or FeS under nitrate-reducing conditions. Based on X-ray diffraction (XRD) analysis, Fe(III) (hydr)oxide produced by oxidation of FeS was shown to be amorphous, while oxidation of Fe(II)sol yielded goethite. The rate of Fe(II) oxidation was then manipulated by incubating various cell concentrations of FW33AN with Fe(II)sol and nitrate. Characterization of products revealed that as Fe(II) oxidation rates slowed, a stronger goethite signal was observed by XRD and a larger proportion of Fe(III) was in the crystalline fraction. Since the mineralogy of Fe(III) (hydr)oxides may control the extent of subsequent Fe(III) reduction, the variables we identify here may have an effect on the biogeochemical cycling of Fe in anoxic ecosystems. PMID:16269756

  13. Effect of the oxidation rate and Fe(II) state on microbial nitrate-dependent Fe(III) mineral formation

    USGS Publications Warehouse

    Senko, John M.; Dewers , Thomas A.; Krumholz, Lee R.

    2005-01-01

    A nitrate-dependent Fe(II)-oxidizing bacterium was isolated and used to evaluate whether Fe(II) chemical form or oxidation rate had an effect on the mineralogy of biogenic Fe(III) (hydr)oxides resulting from nitrate-dependent Fe(II) oxidation. The isolate (designated FW33AN) had 99% 16S rRNA sequence similarity to Klebsiella oxytoca. FW33AN produced Fe(III) (hydr)oxides by oxidation of soluble Fe(II) [Fe(II)sol] or FeS under nitrate-reducing conditions. Based on X-ray diffraction (XRD) analysis, Fe(III) (hydr)oxide produced by oxidation of FeS was shown to be amorphous, while oxidation of Fe(II)sol yielded goethite. The rate of Fe(II) oxidation was then manipulated by incubating various cell concentrations of FW33AN with Fe(II)sol and nitrate. Characterization of products revealed that as Fe(II) oxidation rates slowed, a stronger goethite signal was observed by XRD and a larger proportion of Fe(III) was in the crystalline fraction. Since the mineralogy of Fe(III) (hydr)oxides may control the extent of subsequent Fe(III) reduction, the variables we identify here may have an effect on the biogeochemical cycling of Fe in anoxic ecosystems.

  14. Keap1 redox-dependent regulation of doxorubicin-induced oxidative stress response in cardiac myoblasts

    SciTech Connect

    Nordgren, Kendra K.S. Wallace, Kendall B.

    2014-01-01

    Doxorubicin (DOX) is a widely prescribed treatment for a broad scope of cancers, but clinical utility is limited by the cumulative, dose-dependent cardiomyopathy that occurs with repeated administration. DOX-induced cardiotoxicity is associated with the production of reactive oxygen species (ROS) and oxidation of lipids, DNA and proteins. A major cellular defense mechanism against such oxidative stress is activation of the Keap1/Nrf2-antioxidant response element (ARE) signaling pathway, which transcriptionally regulates expression of antioxidant genes such as Nqo1 and Gstp1. In the present study, we address the hypothesis that an initial event associated with DOX-induced oxidative stress is activation of the Keap1/Nrf2-dependent expression of antioxidant genes and that this is regulated through drug-induced changes in redox status of the Keap1 protein. Incubation of H9c2 rat cardiac myoblasts with DOX resulted in a time- and dose-dependent decrease in non-protein sulfhydryl groups. Associated with this was a near 2-fold increase in Nrf2 protein content and enhanced transcription of several of the Nrf2-regulated down-stream genes, including Gstp1, Ugt1a1, and Nqo1; the expression of Nfe2l2 (Nrf2) itself was unaltered. Furthermore, both the redox status and the total amount of Keap1 protein were significantly decreased by DOX, with the loss of Keap1 being due to both inhibited gene expression and increased autophagic, but not proteasomal, degradation. These findings identify the Keap1/Nrf2 pathway as a potentially important initial response to acute DOX-induced oxidative injury, with the primary regulatory events being the oxidation and autophagic degradation of the redox sensor Keap1 protein. - Highlights: • DOX caused a ∼2-fold increase in Nrf2 protein content. • DOX enhanced transcription of several Nrf2-regulated down-stream genes. • Redox status and total amount of Keap1 protein were significantly decreased by DOX. • Loss of Keap1 protein was due to

  15. Furnace Cyclic Behavior of Plasma-Sprayed Zirconia-Yttria and Multi-Component Rare Earth Oxide Doped Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Nesbitt, James A.; McCue, Terry R.; Barrett, Charles A.; Miller, Robert A.

    2002-01-01

    Ceramic thermal barrier coatings will play an increasingly important role in advanced gas turbine engines because of their ability to enable further increases in engine temperatures. However, the coating performance and durability become a major concern under the increasingly harsh thermal cycling conditions. Advanced zirconia- and hafnia-based cluster oxide thermal barrier coatings with lower thermal conductivity and improved thermal stability are being developed using a high-heat-flux laser-rig based test approach. Although the new composition coatings were not yet optimized for cyclic durability, an initial durability screening of numerous candidate coating materials was carried out using conventional furnace cyclic tests. In this paper, furnace thermal cyclic behavior of the advanced plasma-sprayed zirconia-yttria-based thermal barrier coatings that were co-doped with multi-component rare earth oxides was investigated at 1163 C using 45 min hot cycles. The ceramic coating failure mechanisms were studied by using scanning electron microscopy combined with X-ray diffraction phase analysis after the furnace tests. The coating cyclic lifetime will be discussed in relation to coating phase structures, total dopant concentrations, and other properties.

  16. Cigarette smoke causes lung vascular barrier dysfunction via oxidative stress-mediated inhibition of RhoA and focal adhesion kinase

    PubMed Central

    Sakhatskyy, Pavlo; Grinnell, Katie; Newton, Julie; Ortiz, Melanie; Wang, Yulian; Sanchez-Esteban, Juan; Harrington, Elizabeth O.; Rounds, Sharon

    2011-01-01

    Cigarette smoke (CS) is a major cause of chronic lung and cardiovascular diseases. Recent studies indicate that tobacco use is also a risk factor for acute lung injury (ALI) associated with blunt trauma. Increased endothelial cell (EC) permeability is a hallmark of ALI. CS increases EC permeability in vitro and in vivo; however, the underlying mechanism is not well understood. In this study, we found that only 6 h of exposure to CS impaired endothelial barrier function in vivo, an effect associated with increased oxidative stress in the lungs and attenuated by the antioxidant N-acetylcysteine (NAC). CS also exacerbated lipopolysaccharide (LPS)-induced increase in vascular permeability in vivo. Similar additive effects were also seen in cultured lung EC exposed to cigarette smoke extract (CSE) and LPS. We further demonstrated that CSE caused disruption of focal adhesion complexes (FAC), F-actin fibers, and adherens junctions (AJ) and decreased activities of RhoA and focal adhesion kinase (FAK) in cultured lung EC. CSE-induced inhibition of RhoA and FAK, endothelial barrier dysfunction, and disassembly of FAC, F-actin, and AJ were prevented by NAC. In addition, the deleterious effects of CSE on FAC, F-actin fibers, and AJ were blunted by overexpression of constitutively active RhoA and of FAK. Our data indicate that CS causes endothelial barrier dysfunction via oxidative stress-mediated inhibition of RhoA and FAK. PMID:21984567

  17. Isothermal oxidation behaviour of thermal barrier coatings with CoCrAlY bond coat irradiated by high-current pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Cai, Jie; Guan, Qingfeng; Hou, Xiuli; Wang, Zhiping; Su, Jingxin; Han, Zhiyong

    2014-10-01

    Thermal sprayed CoCrAlY bond coat irradiated by high-current pulsed electron beam (HCPEB) and thermal barrier coatings (TBCs) prepared with the irradiated bond coat and the ceramic top coat were investigated. The high temperature oxidation resistance of these specimens was tested at 1050 °C in air. Microstructure observations revealed that the original coarse surface of the as-sprayed bond coat was significantly changed as the interconnected bulged nodules with a compact appearance after HCPEB irradiation. Abundant Y-rich alumina particulates and very fine grains were dispersed on the irradiated surface. After high temperature oxidation test, the thermally grown oxide (TGO) in the initial TBCs grew rapidly and was comprised of two distinct layers: a large percentage of mixed oxides in the outer layer and a relatively small portion of Al2O3 in the inner layer. Severe local internal oxidation and extensive cracks in the TGO layer were discovered as well. Comparatively, the irradiated TBCs exhibited thinner TGO layer, slower TGO growth rate, and homogeneous TGO composition (primarily consisting of Al2O3). The results indicate that TBCs with the irradiated bond coat have a much higher oxidation resistance.

  18. Oxidative stress and redox regulation on hippocampal-dependent cognitive functions.

    PubMed

    Huang, Ting-Ting; Leu, David; Zou, Yani

    2015-06-15

    Hippocampal-dependent cognitive functions rely on production of new neurons and maintenance of dendritic structures to provide the synaptic plasticity needed for learning and formation of new memories. Hippocampal formation is exquisitely sensitive to patho-physiological changes, and reduced antioxidant capacity and exposure to low dose irradiation can significantly impede hippocampal-dependent functions of learning and memory by reducing the production of new neurons and alter dendritic structures in the hippocampus. Although the mechanism leading to impaired cognitive functions is complex, persistent oxidative stress likely plays an important role in the SOD-deficient and radiation-exposed hippocampal environment. Aging is associated with increased production of pro-oxidants and accumulation of oxidative end products. Similar to the hippocampal defects observed in SOD-deficient mice and mice exposed to low dose irradiation, reduced capacity in learning and memory, diminishing hippocampal neurogenesis, and altered dendritic network are universal in the aging brains. Given the similarities in cellular and structural changes in the aged, SOD-deficient, and radiation-exposed hippocampal environment and the corresponding changes in cognitive decline, understanding the shared underlying mechanism will provide more flexible and efficient use of SOD deficiency or irradiation to model age-related changes in cognitive functions and identify potential therapeutic or intervention methods. Published by Elsevier Inc.

  19. Microbial nitrate-dependent cyclohexane degradation coupled with anaerobic ammonium oxidation.

    PubMed

    Musat, Florin; Wilkes, Heinz; Behrends, Astrid; Woebken, Dagmar; Widdel, Friedrich

    2010-10-01

    An anaerobic nitrate-reducing enrichment culture was established with a cyclic saturated petroleum hydrocarbon, cyclohexane, the fate of which in anoxic environments has been scarcely investigated. GC-MS showed cyclohexylsuccinate as a metabolite, in accordance with an anaerobic enzymatic activation of cyclohexane by carbon-carbon addition to fumarate. Furthermore, long-chain cyclohexyl-substituted cell fatty acids apparently derived from cyclohexane were detected. Nitrate reduction was not only associated with cyclohexane utilization but also with striking depletion of added ammonium ions. Significantly more ammonium was consumed than could be accounted for by assimilation. This indicated the occurrence of anaerobic ammonium oxidation (anammox) with nitrite from cyclohexane-dependent nitrate reduction. Indeed, nitrite depletion was stimulated upon further addition of ammonium. Analysis of 16S rRNA genes and subsequent cell hybridization with specific probes showed that approximately 75% of the bacterial cells affiliated with the Geobacteraceae and approximately 18% with Candidatus 'Brocadia anammoxidans' (member of the Planctomycetales), an anaerobic ammonium oxidizer. These results and additional quantitative growth experiments indicated that the member of the Geobacteraceae reduced nitrate with cyclohexane to nitrite and some ammonium; the latter two and ammonium added to the medium were scavenged by anammox bacteria to yield dinitrogen. A model was established to quantify the partition of each microorganism in the overall process. Such hydrocarbon oxidation by an alleged 'denitrification' ('pseudo-denitrification'), which in reality is a dissimilatory loop through anammox, can in principle also occur in other microbial systems with nitrate-dependent hydrocarbon attenuation.

  20. Energy-dependent relaxation time in quaternary amorphous oxide semiconductors probed by gated Hall effect measurements

    NASA Astrophysics Data System (ADS)

    Socratous, Josephine; Watanabe, Shun; Banger, Kulbinder K.; Warwick, Christopher N.; Branquinho, Rita; Barquinha, Pedro; Martins, Rodrigo; Fortunato, Elvira; Sirringhaus, Henning

    2017-01-01

    Despite the success of exploiting the properties of amorphous oxide semiconductors for device applications, the charge transport in these materials is still not clearly understood. The observation of a definite Hall voltage suggests that electron transport in the conduction band is free-electron-like. However, the temperature dependence of the Hall and field-effect mobilities cannot be explained using a simple bandlike model. Here, we perform gated Hall effect measurements in field-effect transistors, which allow us to make two independent estimates of the charge carrier concentration and determine the Hall factor providing information on the energy dependence of the relaxation time. We demonstrate that the Hall factor in a range of sputtered and solution-processed quaternary amorphous oxides, such as a-InGaZnO, is close to two, while in ternary oxides, such as InZnO, it is near unity. This suggests that quaternary elements like Ga act as strong ionized impurity scattering centers in these materials.

  1. Infertility and recurrent miscarriage with complex II deficiency-dependent mitochondrial oxidative stress in animal models.

    PubMed

    Ishii, Takamasa; Yasuda, Kayo; Miyazawa, Masaki; Mitsushita, Junji; Johnson, Thomas E; Hartman, Phil S; Ishii, Naoaki

    2016-04-01

    Oxidative stress is associated with some forms of both male and female infertility. However, there is insufficient knowledge of the influence of oxidative stress on the maintenance of a viable pregnancy, including pregnancy complications and fetal development. There are a number of animal models for understanding age-dependent decrease of reproductive ability and diabetic embryopathy, especially abnormal spermatogenesis, oogenesis and embryogenesis with mitochondrial dysfunctions. Several important processes occur in mitochondria, including ATP synthesis, calcium ion storage, induction of apoptosis and production of reactive oxygen species (ROS). These events have different effects on the several aspects of reproductive function. Tet-mev-1 conditional transgenic mice, developed after studies with the mev-1 mutant of the nematode C. elegans, offer the ability to carefully regulate expression of doxycycline-induced mutated SDHC(V69E) levels and hence modulate endogenous oxidative stress. The mev-1 models have served to illuminate the effects of complex II deficiency-dependent mitochondrial ROS production, although interestingly they maintain normal mitochondrial and intracellular ATP levels. In this review, the reproductive dysfunctions are presented focusing on fertility potentials in each gamete, early embryogenesis, maternal conditions with placental function and neonatal development.

  2. Improved tolerance of acute severe hypoxic stress in chronic hypoxic diaphragm is nitric oxide-dependent.

    PubMed

    Lewis, Philip; McMorrow, Clodagh; Bradford, Aidan; O'Halloran, Ken D

    2015-09-01

    The effects of chronic hypoxia (CH) on respiratory muscle performance have hardly been investigated, despite clinical relevance. Results from recent studies are indicative of unique adaptive strategies in hypoxic diaphragm. Respiratory muscle tolerance of acute severe hypoxic stress was examined in normoxic and CH diaphragm in the presence and absence of a nitric oxide (NO) synthase inhibitor. We tested the hypothesis that improved tolerance of severe hypoxic stress in CH diaphragm is NO-dependent. Wistar rats were exposed to normoxia (sea-level, n = 6) or CH (ambient pressure = 380 mmHg, n = 6) for 6 weeks. Diaphragm muscle functional properties were determined ex vivo under severe hypoxic conditions (gassed with 95%N2/5% CO2) with and without 1 mM L-N(G)-nitroarginine (L-NNA, nNOS inhibitor). Fatigue tolerance, but not force, was significantly improved in CH diaphragm (p = 0.008). CH exposure did not affect diaphragm muscle fibre oxidative capacity determined from cluster analysis of area-density plots of muscle fibre succinate dehydrogenase activity. Acute NOS inhibition reduced diaphragm peak tetanic force (p = 0.018), irrespective of gas treatment, and completely reversed improved fatigue tolerance of the CH diaphragm. We conclude that CH exposure improves fatigue tolerance during acute severe hypoxic stress in an NO-dependent manner, independent of muscle fibre oxidative capacity.

  3. Endoplasmic Reticulum Oxidative Stress Triggers Tgf-Beta-Dependent Muscle Dysfunction by Accelerating Ascorbic Acid Turnover

    PubMed Central

    Pozzer, Diego; Favellato, Mariagrazia; Bolis, Marco; Invernizzi, Roberto William; Solagna, Francesca; Blaauw, Bert; Zito, Ester

    2017-01-01

    Endoplasmic reticulum (ER) and oxidative stress are two related phenomena that have important metabolic consequences. As many skeletal muscle diseases are triggered by oxidative stress, we explored the chain of events linking a hyperoxidized ER (which causes ER and oxidative stress) with skeletal muscle dysfunction. An unbiased exon expression array showed that the combined genetic modulation of the two master ER redox proteins, selenoprotein N (SEPN1) and endoplasmic oxidoreductin 1 (ERO1), led to an SEPN1-related myopathic phenotype due to excessive signalling of transforming growth factor (TGF)-beta. The increased TGF-beta activity in the genetic mutants was caused by accelerated turnover of the ER localized (anti-oxidant) ascorbic acid that affected collagen deposition in the extracellular matrix. In a mouse mutant of SEPN1, which is dependent on exogenous ascorbic acid, a limited intake of ascorbic acid revealed a myopathic phenotype as a consequence of an altered TGF-beta signalling. Indeed, systemic antagonism of TGF-beta re-established skeletal muscle function in SEPN1 mutant mice. In conclusion, this study sheds new light on the molecular mechanism of SEPN1-related myopathies and indicates that the TGF-beta/ERO1/ascorbic acid axis offers potential for their treatment. PMID:28106121

  4. Coating-dependent induction of cytotoxicity and genotoxicity of iron oxide nanoparticles.

    PubMed

    Magdolenova, Zuzana; Drlickova, Martina; Henjum, Kristi; Rundén-Pran, Elise; Tulinska, Jana; Bilanicova, Dagmar; Pojana, Giulio; Kazimirova, Alena; Barancokova, Magdalena; Kuricova, Miroslava; Liskova, Aurelia; Staruchova, Marta; Ciampor, Fedor; Vavra, Ivo; Lorenzo, Yolanda; Collins, Andrew; Rinna, Alessandra; Fjellsbø, Lise; Volkovova, Katarina; Marcomini, Antonio; Amiry-Moghaddam, Mahmood; Dusinska, Maria

    2015-05-01

    Surface coatings of nanoparticles (NPs) are known to influence advantageous features of NPs as well as potential toxicity. Iron oxide (Fe3O4) NPs are applied for both medical diagnostics and targeted drug delivery. We investigated the potential cytotoxicity and genotoxicity of uncoated iron oxide (U-Fe3O4) NPs in comparison with oleate-coated iron oxide (OC-Fe3O4) NPs. Testing was performed in vitro in human lymphoblastoid TK6 cells and in primary human blood cells. For cytotoxicity testing, relative growth activity, trypan blue exclusion, (3)H-thymidine incorporation and cytokinesis-block proliferation index were assessed. Genotoxicity was evaluated by the alkaline comet assay for detection of strand breaks and oxidized purines. Particle characterization was performed in the culture medium. Cellular uptake, morphology and pathology were evaluated by electron microscopy. U-Fe3O4 NPs were found not to be cytotoxic (considering interference of NPs with proliferation test) or genotoxic under our experimental conditions. In contrast, OC-Fe3O4 NPs were cytotoxic in a dose-dependent manner, and also induced DNA damage, indicating genotoxic potential. Intrinsic properties of sodium oleate were excluded as a cause of the toxic effect. Electron microscopy data were consistent with the cytotoxicity results. Coating clearly changed the behaviour and cellular uptake of the NPs, inducing pathological morphological changes in the cells.

  5. Mitophagy is triggered by mild oxidative stress in a mitochondrial fission dependent manner.

    PubMed

    Frank, Magdalena; Duvezin-Caubet, Stéphane; Koob, Sebastian; Occhipinti, Angelo; Jagasia, Ravi; Petcherski, Anton; Ruonala, Mika O; Priault, Muriel; Salin, Bénédicte; Reichert, Andreas S

    2012-12-01

    Mitochondrial dysfunction is linked to apoptosis, aging, cancer, and a number of neurodegenerative and muscular disorders. The interplay between mitophagy and mitochondrial dynamics has been linked to the removal of dysfunctional mitochondria ensuring mitochondrial quality control. An open question is what role mitochondrial fission plays in the removal of mitochondria after mild and transient oxidative stress; conditions reported to result in moderately elevated reactive oxygen species (ROS) levels comparable to physical activity. Here we show that applying such conditions led to fragmentation of mitochondria and induction of mitophagy in mouse and human cells. These conditions increased ROS levels only slightly and neither triggered cell death nor led to a detectable induction of non-selective autophagy. Starvation led to hyperfusion of mitochondria, to high ROS levels, and to the induction of both non-selective autophagy and to a lesser extent to mitophagy. We conclude that moderate levels of ROS specifically trigger mitophagy but are insufficient to trigger non-selective autophagy. Expression of a dominant-negative variant of the fission factor DRP1 blocked mitophagy induction by mild oxidative stress as well as by starvation. Taken together, we demonstrate that in mammalian cells under mild oxidative stress a DRP1-dependent type of mitophagy is triggered while a concomitant induction of non-selective autophagy was not observed. We propose that these mild oxidative conditions resembling well physiological situations are thus very helpful for studying the molecular pathways governing the selective removal of dysfunctional mitochondria.

  6. Kaempferol derivatives prevent oxidative stress-induced cell death in a DJ-1-dependent manner.

    PubMed

    Qu, Wei; Fan, Li; Kim, Yun-chul; Ishikawa, Shizuma; Iguchi-Ariga, Sanae M M; Pu, Xiao-Ping; Ariga, Hiroyoshi

    2009-06-01

    DJ-1, a causative gene product of a familial form of Parkinson's disease (PD), PARK7, plays a role in anti-oxidative stress, and loss of its function is thought to result in the onset of PD. Superfluous oxidation of cysteine at amino acid 106 (C106) of DJ-1 renders DJ-1 inactive, and such oxidized DJ-1 was observed in patients with the sporadic form of PD. In this study, we examined the relationship between DJ-1 and compounds extracted from traditional Chinese medicines possessing anti-oxidant activity. Of the 12 compounds tested, 5 were found to specifically bind to the C106 region by using a quartz crystal microbalance. Although 4 compounds prevented rat PC12 and primary neuronal cells from undergoing H2O2-induced cell death, the protective activity of 2 compounds, kaempferol 3-O-beta-rutinoside and 6-hydroxykaempferol 3,6-di-O-beta-D-glucoside, was diminished in cells transfected with siRNA targeting DJ-1, indicating DJ-1-dependent reaction of these compounds. Furthermore, these compounds reduced the level of reactive oxygen species and restored tyrosine hydroxylase activity that had been induced and compromised, respectively, by treatment of cells with H2O2. The results suggest that these compounds are useful lead compounds for PD therapy.

  7. Oxidation-induced calcium-dependent dehydration of normal human red blood cells.

    PubMed