Two-dimensional modeling of water and heat fluxes in green roof substrates

NASA Astrophysics Data System (ADS)

Suarez, F. I.; Sandoval, V. P.

2016-12-01

Due to public concern towards sustainable development, greenhouse gas emissions and energy efficiency, green roofs have become popular in the last years. Green roofs integrate vegetation into infrastructures to reach additional benefits that minimize negative impacts of the urbanization. A properly designed green roof can reduce environmental pollution, noise levels, energetic requirements or surface runoff. The correct performance of green roofs depends on site-specific conditions and on each component of the roof. The substrate and the vegetation layers strongly influence water and heat fluxes on a green roof. The substrate is an artificial media that has an improved performance compared to natural soils as it provides critical resources for vegetation survival: water, nutrients, and a growing media. Hence, it is important to study the effects of substrate properties on green roof performance. The objective of this work is to investigate how the thermal and hydraulic properties affect the behavior of a green roof through numerical modeling. The substrates that were investigated are composed by: crushed bricks and organic soil (S1); peat with perlite (S2); crushed bricks (S3); mineral soil with tree leaves (S4); and a mixture of topsoil and mineral soil (S5). The numerical model utilizes summer-arid meteorological information to evaluate the performance of each substrate. Results show that the area below the water retention curve helps to define the substrate that retains more water. In addition, the non-linearity of the water retention curve can increment the water needed to irrigate the roof. The heat propagation through the roof depends strongly on the hydraulic behavior, meaning that a combination of a substrate with low thermal conductivity and more porosity can reduce the heat fluxes across the roof. Therefore, it can minimize the energy consumed of an air-conditioner system.

Monte Carlo study of the hetero-polytypical growth of cubic on hexagonal silicon carbide polytypes

NASA Astrophysics Data System (ADS)

Camarda, Massimo

2012-08-01

In this article we use three dimensional kinetic Monte Carlo simulations on super-lattices to study the hetero-polytypical growth of cubic silicon carbide polytype (3C-SiC) on misoriented hexagonal (4H and 6H) substrates. We analyze the quality of the 3C-SiC film varying the polytype, the miscut angle and the initial surface morphology of the substrate. We find that the use of 6H misoriented (4°-10° off) substrates, with step bunched surfaces, can strongly improve the quality of the cubic epitaxial film whereas the 3C/4H growth is affected by the generation of dislocations, due to the incommensurable periodicity of the 3C (3) and the 4H (4) polytypes. For these reasons, a proper pre-growth treatment of 6H misoriented substrates can be the key for the growth of high quality, twin free, 3C-SiC films.

Influence of metal substrates on the detection of explosive residues with laser-induced breakdown spectroscopy.

PubMed

Gottfried, Jennifer L

2013-02-01

Laser-induced breakdown spectroscopy is a promising approach for explosive residue detection, but several limitations to its widespread use remain. One issue is that the emission spectra of the residues are dependent on the substrate composition because some of the substrate is usually entrained in the laser-induced plasma and the laser-material interaction can be significantly affected by the substrate type. Here, we have demonstrated that despite the strong spectral variation in cyclotrimethylenetrinitramine (RDX) residues applied to various metal substrates, classification of the RDX residue independent of substrate type is feasible. Several approaches to improving the chemometric models based on partial least squares discriminant analysis (PLS-DA) have been described: classifying the RDX residue spectra together in one class independent of substrate, using selected emission intensities and ratios to increase the true positive rate (TPR) and decrease the false positive rate (FPR), and fusing the results from two PLS-DA models generated using the full broadband spectra and selected intensities and ratios. The combination of these approaches resulted in a TPR of 97.5% and a FPR of 1.0% for RDX classification on metal substrates.

Minimizing mixing intensity to improve the performance of rice straw anaerobic digestion via enhanced development of microbe-substrate aggregates.

PubMed

Kim, Moonkyung; Kim, Byung-Chul; Choi, Yongju; Nam, Kyoungphile

2017-12-01

The aim of this work was to study the effect of the differential development of microbe-substrate aggregates at different mixing intensities on the performance of anaerobic digestion of rice straw. Batch and semi-continuous reactors were operated for up to 50 and 300days, respectively, under different mixing intensities. In both batch and semi-continuous reactors, minimal mixing conditions exhibited maximum methane production and lignocellulose biodegradability, which both had strong correlations with the development of microbe-substrate aggregates. The results implied that the aggregated microorganisms on the particulate substrate played a key role in rice straw hydrolysis, determining the performance of anaerobic digestion. Increasing the mixing speed from 50 to 150rpm significantly reduced the methane production rate by disintegrating the microbe-substrate aggregates in the semi-continuous reactor. A temporary stress of high-speed mixing fundamentally affected the microbial communities, increasing the possibility of chronic reactor failure. Copyright © 2017 Elsevier Ltd. All rights reserved.

Elasticity modulated Electrowetting of a sessile liquid droplet

NASA Astrophysics Data System (ADS)

Kumar, Sumit; Subramanian, Sri Ganesh; Dasgupta, Sunando; Chakraborty, Suman

2017-11-01

The sessile liquid droplets on the elastic and soft deformable surface produce strong deformation near the three-phase contact line (TPCL). The capillary and elastic forces play an important role during this deformation, and deteriorate the wetting behaviour of a sessile drop. The present work combines the effects of liquid viscosity and substrate elasticity on the dynamics of EWOD. The influence of decreasing film elasticity and viscosity on the electrowetting response of a sessile drop is experimentally investigated by delineating the changes in equilibrium apparent contact angles on substrates with varying Young's modulus of elasticity. The increase in viscosity of the liquid leads to greater electrowetting for non-deformable substrates whereas; the dynamics are not greatly affected in case of soft substrates. Although the viscosity appears to be an influential factor, the dynamics are more skewed towards the substrate rigidity. The vertical component of Young's force creates a wetting ridge at the three-phase contact line, the height of which is a direct function of the substrate rigidity. The produced ridges reduce the overall wettability of the droplet.

Theoretical investigation of the electronic structure and quantum transport in the graphene-C(111) diamond surface system.

PubMed

Selli, Daniele; Baburin, Igor; Leoni, Stefano; Zhu, Zhen; Tománek, David; Seifert, Gotthard

2013-10-30

We investigate the interaction of a graphene monolayer with the C(111) diamond surface using ab initio density functional theory. To accommodate the lattice mismatch between graphene and diamond, the overlayer deforms into a wavy structure that binds strongly to the diamond substrate. The detached ridges of the wavy graphene overlayer behave electronically as free-standing polyacetylene chains with delocalized π electrons, separated by regions containing only sp(3) carbon atoms covalently bonded to the (111) diamond surface. We performed quantum transport calculations for different geometries of the system to study how the buckling of the graphene layer and the associated bonding to the diamond substrate affect the transport properties. The system displays high carrier mobility along the ridges and a wide transport gap in the direction normal to the ridges. These intriguing, strongly anisotropic transport properties qualify the hybrid graphene-diamond system as a viable candidate for electronic nanodevices.

Molecular Dynamics Simulations of the Oil-Detachment from the Hydroxylated Silica Surface: Effects of Surfactants, Electrostatic Interactions, and Water Flows on the Water Molecular Channel Formation.

PubMed

Tang, Jian; Qu, Zhou; Luo, Jianhui; He, Lanyan; Wang, Pingmei; Zhang, Ping; Tang, Xianqiong; Pei, Yong; Ding, Bin; Peng, Baoliang; Huang, Yunqing

2018-02-15

The detachment process of an oil molecular layer situated above a horizontal substrate was often described by a three-stage process. In this mechanism, the penetration and diffusion of water molecules between the oil phase and the substrate was proposed to be a crucial step to aid in removal of oil layer/drops from substrate. In this work, the detachment process of a two-dimensional alkane molecule layer from a silica surface in aqueous surfactant solutions is studied by means of molecular dynamics (MD) simulations. By tuning the polarity of model silica surfaces, as well as considering the different types of surfactant molecules and the water flow effects, more details about the formation of water molecular channel and the expansion processes are elucidated. It is found that for both ionic and nonionic type surfactant solutions, the perturbation of surfactant molecules on the two-dimensional oil molecule layer facilitates the injection and diffusion of water molecules between the oil layer and silica substrate. However, the water channel formation and expansion speed is strongly affected by the substrate polarity and properties of surfactant molecules. First, only for the silica surface with relative stronger polarity, the formation of water molecular channel is observed. Second, the expansion speed of the water molecular channel upon the ionic surfactant (dodecyl trimethylammonium bromide, DTAB and sodium dodecyl benzenesulfonate, SDBS) flooding is more rapidly than the nonionic surfactant system (octylphenol polyoxyethylene(10) ether, OP-10). Third, the water flow speed may also affect the injection and diffusion of water molecules. These simulation results indicate that the water molecular channel formation process is affected by multiple factors. The synergistic effects of perturbation of surfactant molecules and the electrostatic interactions between silica substrate and water molecules are two key factors aiding in the injection and diffusion of water molecules and helpful for the oil detachment from silica substrate.

Myxococcus xanthus Gliding Motors Are Elastically Coupled to the Substrate as Predicted by the Focal Adhesion Model of Gliding Motility

PubMed Central

Balagam, Rajesh; Litwin, Douglas B.; Czerwinski, Fabian; Sun, Mingzhai; Kaplan, Heidi B.; Shaevitz, Joshua W.; Igoshin, Oleg A.

2014-01-01

Myxococcus xanthus is a model organism for studying bacterial social behaviors due to its ability to form complex multi-cellular structures. Knowledge of M. xanthus surface gliding motility and the mechanisms that coordinated it are critically important to our understanding of collective cell behaviors. Although the mechanism of gliding motility is still under investigation, recent experiments suggest that there are two possible mechanisms underlying force production for cell motility: the focal adhesion mechanism and the helical rotor mechanism, which differ in the biophysics of the cell–substrate interactions. Whereas the focal adhesion model predicts an elastic coupling, the helical rotor model predicts a viscous coupling. Using a combination of computational modeling, imaging, and force microscopy, we find evidence for elastic coupling in support of the focal adhesion model. Using a biophysical model of the M. xanthus cell, we investigated how the mechanical interactions between cells are affected by interactions with the substrate. Comparison of modeling results with experimental data for cell-cell collision events pointed to a strong, elastic attachment between the cell and substrate. These results are robust to variations in the mechanical and geometrical parameters of the model. We then directly measured the motor-substrate coupling by monitoring the motion of optically trapped beads and find that motor velocity decreases exponentially with opposing load. At high loads, motor velocity approaches zero velocity asymptotically and motors remain bound to beads indicating a strong, elastic attachment. PMID:24810164

Effects of substrate conductivity on cell morphogenesis and proliferation using tailored, atomic layer deposition-grown ZnO thin films

PubMed Central

Choi, Won Jin; Jung, Jongjin; Lee, Sujin; Chung, Yoon Jang; Yang, Cheol-Soo; Lee, Young Kuk; Lee, You-Seop; Park, Joung Kyu; Ko, Hyuk Wan; Lee, Jeong-O

2015-01-01

We demonstrate that ZnO films grown by atomic layer deposition (ALD) can be employed as a substrate to explore the effects of electrical conductivity on cell adhesion, proliferation, and morphogenesis. ZnO substrates with precisely tunable electrical conductivity were fabricated on glass substrates using ALD deposition. The electrical conductivity of the film increased linearly with increasing duration of the ZnO deposition cycle (thickness), whereas other physical characteristics, such as surface energy and roughness, tended to saturate at a certain value. Differences in conductivity dramatically affected the behavior of SF295 glioblastoma cells grown on ZnO films, with high conductivity (thick) ZnO films causing growth arrest and producing SF295 cell morphologies distinct from those cultured on insulating substrates. Based on simple electrostatic calculations, we propose that cells grown on highly conductive substrates may strongly adhere to the substrate without focal-adhesion complex formation, owing to the enhanced electrostatic interaction between cells and the substrate. Thus, the inactivation of focal adhesions leads to cell proliferation arrest. Taken together, the work presented here confirms that substrates with high conductivity disturb the cell-substrate interaction, producing cascading effects on cellular morphogenesis and disrupting proliferation, and suggests that ALD-grown ZnO offers a single-variable method for uniquely tailoring conductivity. PMID:25897486

Flow variation and substrate type affect dislodgement of the freshwater polychaete, Manayunkia speciosa

USGS Publications Warehouse

Malakauskas, David M.; Wilson, Sarah J.; Wilzbach, Margaret A.; Som, Nicholas A.

2013-01-01

We quantified microscale flow forces and their ability to entrain the freshwater polychaete, Manayunkia speciosa, the intermediate host for 2 myxozoan parasites (Ceratomyxa shasta and Parvicapsula minibicornis) that cause substantial mortalities in salmonid fishes in the Pacific Northwest. In a laboratory flume, we measured the shear stress associated with 2 mean flow velocities and 3 substrates and quantified associated dislodgement of polychaetes, evaluated survivorship of dislodged polychaetes, and observed behavioral responses of the polychaetes in response to increased flow. We used a generalized linear mixed model to estimate the probability of polychaete dislodgement for treatment combinations of velocity (mean flow velocity  =  55 cm/s with a shear velocity  =  3 cm/s, mean flow velocity  =  140 cm/s with a shear velocity  =  5 cm/s) and substrate type (depositional sediments and analogs of rock faces and the filamentous alga, Cladophora). Few polychaetes were dislodged at shear velocities <3 cm/s on any substrate. Above this level of shear, probability of dislodgement was strongly affected by both substrate type and velocity. After accounting for substrate, odds of dislodgement were 8× greater at the higher flow. After accounting for velocity, probability of dislodgement was greatest from fine sediments, intermediate from rock faces, and negligible from Cladophora. Survivorship of dislodged polychaetes was high. Polychaetes exhibited a variety of behaviors for avoiding increases in flow, including extrusion of mucus, burrowing into sediments, and movement to lower-flow microhabitats. Our findings suggest that polychaete populations probably exhibit high resilience to flow-mediated disturbances.

Roughness of Ti Substrates for Control of the Preferred Orientation of TiO 2 Nanotube Arrays as a New Orientation Factor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seong, Won Mo; Kim, Dong Hoe; Park, Ik Jae

2015-06-11

We report the surface roughness of a Ti substrate as a critical factor for controlling the degree of the preferred orientation of anatase TiO2 nanotube arrays (NTAs) which are synthesized by anodization and a subsequent annealing process. The degree of the preferred orientation to the (004) plane of the anatase crystal structure has a strong dependency on the root-mean-square roughness (Sq) of the initial Ti substrate when the roughness-controlled substrates are anodized in an ethylene glycol-based electrolyte containing ~2 wt % of water. Highly preferred oriented NTAs were obtained from low-Sq (<10 nm) substrates, which were accompanied by uniform poremore » distribution and low concentration of hydroxyl ions in as-anodized amorphous NTAs. The mechanism of the preferred oriented crystallization of nanometer-scaled tube walls is explained considering the microscopic geometrical uniformity of the oxide barrier and nanopores at the early stage of anodization, which affected the local electric field and thus the insertion of the hydroxyl group into the amorphous TiO2 tube walls.« less

Ratchet Effects, Negative Mobility, and Phase Locking for Skyrmions on Periodic Substrates

NASA Astrophysics Data System (ADS)

Reichhardt, Charles; Ray, Dipanjan; Olson Reichhardt, Cynthia

We examine the dynamics of skyrmions interacting with 1D and 2D periodic substrates in the presence of dc and ac drives. We find that the Magnus term strongly affects the skyrmion dynamics and that new kinds of phenomena can occur which are absent for overdamped ac and dc driven particles interacting with similar substrates. We show that it is possible to realize a Magnus induced ratchet for skyrmions interacting with an asymmetric potential, where the application of an ac drive can produce quantized dc motion of the skyrmions even when the ac force is perpendicular to the substrate asymmetry direction. For symmetric substrates it is also possible to achieve a negative mobility effect where the net skyrmion motion runs counter to an applied dc drive. Here, as a function of increasing dc drive, the velocity-force curves show a series of locking phases that have different features from the classic Shapiro steps found in overdamped systems. In the phase locking and ratcheting states, the skyrmions undergo intricate 2D orbits induced by the Magnus term.

Substrate milling pretreatment as a key parameter for Solid-State Anaerobic Digestion optimization.

PubMed

Motte, J-C; Escudié, R; Hamelin, J; Steyer, J-P; Bernet, N; Delgenes, J-P; Dumas, C

2014-12-01

The effect of milling pretreatment on performances of Solid-State Anaerobic Digestion (SS-AD) of raw lignocellulosic residue is still controverted. Three batch reactors treating different straw particle sizes (milled 0.25 mm, 1 mm and 10 mm) were followed during 62 days (6 sampling dates). Although a fine milling improves substrate accessibility and conversion rate (up to 30% compared to coarse milling), it also increases the risk of media acidification because of rapid and high acids production during fermentation of the substrate soluble fraction. Meanwhile, a gradual adaptation of microbial communities, were observed according to both reaction progress and methanogenic performances. The study concluded that particle size reduction affected strongly the performances of the reaction due to an increase of substrate bioaccessibility. An optimization of SS-AD processes thanks to particle size reduction could therefore be applied at farm or industrial scale only if a specific management of the soluble compounds is established. Copyright © 2014 Elsevier Ltd. All rights reserved.

Thermally enhanced in situ bioremediation of groundwater contaminated with chlorinated solvents - A field test.

PubMed

Němeček, Jan; Steinová, Jana; Špánek, Roman; Pluhař, Tomáš; Pokorný, Petr; Najmanová, Petra; Knytl, Vladislav; Černík, Miroslav

2018-05-01

In situ bioremediation (ISB) using reductive dechlorination is a widely accepted but relatively slow approach compared to other technologies for the treatment of groundwater contaminated by chlorinated ethenes (CVOCs). Due to the known positive kinetic effect on microbial metabolism, thermal enhancement may be a viable means of accelerating ISB. We tested thermally enhanced ISB in aquifers situated in sandy saprolite and underlying fractured granite. The system comprised pumping, heating and subsequent injection of contaminated groundwater aiming at an aquifer temperature of 20-30°C. A fermentable substrate (whey) was injected in separate batches. The test was monitored using hydrochemical and molecular tools (qPCR and NGS). The addition of the substrate and increase in temperature resulted in a rapid increase in the abundance of reductive dechlorinators (e.g., Dehalococcoides mccartyi, Dehalobacter sp. and functional genes vcrA and bvcA) and a strong increase in CVOC degradation. On day 34, the CVOC concentrations decreased by 87% to 96% in groundwater from the wells most affected by the heating and substrate. On day 103, the CVOC concentrations were below the LOQ resulting in degradation half-lives of 5 to 6days. Neither an increase in biomarkers nor a distinct decrease in the CVOC concentrations was observed in a deep well affected by the heating but not by the substrate. NGS analysis detected Chloroflexi dechlorinating genera (Dehalogenimonas and GIF9 and MSBL5 clades) and other genera capable of anaerobic metabolic degradation of CVOCs. Of these, bacteria of the genera Acetobacterium, Desulfomonile, Geobacter, Sulfurospirillum, Methanosarcina and Methanobacterium were stimulated by the substrate and heating. In contrast, groundwater from the deep well (affected by heating only) hosted representatives of aerobic metabolic and aerobic cometabolic CVOC degraders. The test results document that heating of the treated aquifer significantly accelerated the treatment process but only in the case of an abundant substrate. Copyright © 2017. Published by Elsevier B.V.

Influence of the substrate material on the optical properties of tungsten diselenide monolayers

NASA Astrophysics Data System (ADS)

Lippert, Sina; Schneider, Lorenz Maximilian; Renaud, Dylan; Kang, Kyung Nam; Ajayi, Obafunso; Kuhnert, Jan; Halbich, Marc-Uwe; Abdulmunem, Oday M.; Lin, Xing; Hassoon, Khaleel; Edalati-Boostan, Saeideh; Duck Kim, Young; Heimbrodt, Wolfram; Yang, Eui-Hyeok; Hone, James C.; Rahimi-Iman, Arash

2017-06-01

Monolayers of transition-metal dichalcogenides such as WSe2 have become increasingly attractive due to their potential in electrical and optical applications. Because the properties of these 2D systems are known to be affected by their surroundings, we report how the choice of the substrate material affects the optical properties of monolayer WSe2. To accomplish this study, pump-density-dependent micro-photoluminescence measurements are performed with time-integrating and time-resolving acquisition techniques. Spectral information and power-dependent mode intensities are compared at 290 K and 10 K for exfoliated WSe2 on SiO2/Si, sapphire (Al2O3), hBN/Si3N4/Si, and MgF2, indicating substrate-dependent appearance and strength of exciton, trion, and biexciton modes. Additionally, one CVD-grown WSe2 monolayer on sapphire is included in this study for direct comparison with its exfoliated counterpart. Time-resolved micro-photoluminescence shows how radiative decay times strongly differ for different substrate materials. Our data indicates exciton-exciton annihilation as a shortening mechanism at room temperature, and subtle trends in the decay rates in correlation to the dielectric environment at cryogenic temperatures. On the measureable time scales, trends are also related to the extent of the respective 2D-excitonic modes’ appearance. This result highlights the importance of further detailed characterization of exciton features in 2D materials, particularly with respect to the choice of substrate.

Experimental Investigation of Terminal Fans Prograding on a Salt Substrate: 3-d Physical Experiments

NASA Astrophysics Data System (ADS)

Chatmas, E.; Kim, W.

2015-12-01

Interactions between geologic features and a mobile substrate layer are present in several passive margin locations throughout the world. Deformation of a substrate layer is primarily due to differential loading of sediment and results in complexities within the morphology and subsequently the stratigraphic record. By using simplified scaled tank experiments, we investigated the relationship between substrate deformation and fan evolution in a fluvial-dump-wind-redistribution setting. In this system, sediment is being eroded from a mountain range and creating terminal fans; fluvial channels form off of the fan body and the deposited fluvial sediment is the source for an aeolian dune field. Several past experimental studies have focused on how deltas and dunes are affected on when deposited on a salt substrate, however terminal fans and channel formation off of fans have not been thoroughly investigated. The current experiments focused on which variables are the most significant in controlling fan growth, channel initiation and channel behavior on the salt substrate. Our experimental basin is 120 cm long, 60 cm wide and 30 cm tall. The materials used for a suite of five experiments involved a polymer polydimethylsiloxane (PDMS) as the deformable substrate analog and 100-μm quartz sand. By isolating certain variables such as substrate thickness, basin slope and sediment discharge we are able to see how terminal fans and channels are affected in different settings. The experimental results show that 1) increase in substrate thickness increased the amount of subsidence around the fan body, limiting sediment transport to channels off of the toe of the fan, 2) a higher basin slope increased the number of channels formed and increased sinuosity and width variations of channels over distance, and 3) a higher sediment discharge rate on a thin substrate allowed for the farthest downstream fan deposits. Preliminary results show that channel behavior and fan morphology is strongly dependent on substrate thickness and basin slope directly influences channel geometry. These findings will also be compared to the Mojave River Wash located in southern California off the San Bernardino Mountains near Zzyzx, CA to further understand the dynamics of terminal fans on a mobile substrate.

On the uniqueness of the receding contact angle: effects of substrate roughness and humidity on evaporation of water drops.

PubMed

Pittoni, Paola G; Lin, Chia-Hui; Yu, Teng-Shiang; Lin, Shi-Yow

2014-08-12

Could a unique receding contact angle be indicated for describing the wetting properties of a real gas-liquid-solid system? Could a receding contact angle be defined if the triple line of a sessile drop is not moving at all during the whole measurement process? To what extent is the receding contact angle influenced by the intrinsic properties of the system or the measurement procedures? In order to answer these questions, a systematic investigation was conducted in this study on the effects of substrate roughness and relative humidity on the behavior of pure water drops spreading and evaporating on polycarbonate (PC) surfaces characterized by different morphologies. Dynamic, advancing, and receding contact angles were found to be strongly affected by substrate roughness. Specifically, a receding contact angle could not be measured at all for drops evaporating on the more rugged PC surfaces, since the drops were observed strongly pinning to the substrate almost until their complete disappearance. Substrate roughness and system relative humidity were also found responsible for drastic changes in the depinning time (from ∼10 to ∼60 min). Thus, for measurement observations not sufficiently long, no movement of the triple line could be noted, with, again, the failure to find a receding contact angle. Therefore, to keep using concepts such as the receding contact angle as meaningful specifications of a given gas-liquid-solid system, the imperative to carefully investigate and report the inner characteristics of the system (substrate roughness, topography, impurities, defects, chemical properties, etc.) is pointed out in this study. The necessity of establishing methodological standards (drop size, measurement method, system history, observation interval, relative humidity, etc.) is also suggested.

Dipeptidyl peptidase IV (DPPIV) enzyme activity on immature T-cell line R1.1 is down-regulated by dynorphin-A(1-17) as a non-substrate inhibitor.

PubMed

Gabrilovac, Jelka; Abramić, Marija; Uzarević, Branka; Andreis, Ana; Poljak, Ljiljana

2003-05-30

In this study we examined surface expression of CD26 and the corresponding enzyme activity of dipeptidyl peptidase IV (DPPIV) on the cells of immature murine T-cell line, R1.1. The data obtained have shown that R1.1 cells express high density of surface CD26 as compared to normal thymus cells. This was associated with strong enzyme activity, which, based on substrates and inhibitor specificity, corresponded to DPPIV. The DPPIV enzyme activity of R1.1 cells was 10 times stronger than that found on normal murine thymus cells (V(max) = 39 micromol/min/10(6) cells, vs 3.7 micromol/min/10(6) cells, respectively). Upon activation with anti-CD3, up-regulation of both membrane CD26, as well as of DPPIV enzyme activity on R1.1 cells were observed. The finding of strong DPPIV on R1.1 cells makes them suitable model for testing putative substrates/inhibitors of the enzyme in its natural microenvironment. Since in addition to strong DPPIV, R1.1 cells also express kappa opioid receptors (KOR) [European Journal of Pharmacology 227 (1992) 257], we tested the effect of dynorphin-A(1-17), an endogenous opioid peptide with KOR selectivity, on DPPIV of R1.1 cells. Dynorphin-A(1-17) down-regulated DPPIV in a dose-dependent manner, with the potency similar to that of substance P, a known natural DPPIV substrate [Journal of Pharmacology and Experimental Therapeutics 260 (1992) 1257]. DPPIV down-regulation was resistant to bestatin and thiorphan, the inhibitors of two cell surface peptidases (APN and NEP, respectively) with potential of dynorphin-A(1-17) degradation, suggesting that the mechanism underlying the observed effect does not involve degradative products of dynorphin-A(1-17). DPPIV down-regulation was also resistent to KOR antagonist, NBI, suggesting that the mechanism underlying the observed phenomenon involves neither cointernalization of KOR and DPPIV. Collectively, cells of immature T cell line, R1.1 exert strong DPPIV enzyme activity, which could be down-regulated in the presence of dynorphin-A(1-17) by mechanism that presumably includes non-substrate inhibition. By down-regulating DPPIV, dynorphin-A(1-17) may indirectly affect activity and/or specificity of natural substrates of DPPIV, such as substance P, RANTES, and endomorphins.

Pressurized Martian-Like Pure CO2 Atmosphere Supports Strong Growth of Cyanobacteria, and Causes Significant Changes in their Metabolism

NASA Astrophysics Data System (ADS)

Murukesan, Gayathri; Leino, Hannu; Mäenpää, Pirkko; Ståhle, Kurt; Raksajit, Wuttinun; Lehto, Harry J.; Allahverdiyeva-Rinne, Yagut; Lehto, Kirsi

2016-03-01

Surviving of crews during future missions to Mars will depend on reliable and adequate supplies of essential life support materials, i.e. oxygen, food, clean water, and fuel. The most economical and sustainable (and in long term, the only viable) way to provide these supplies on Martian bases is via bio-regenerative systems, by using local resources to drive oxygenic photosynthesis. Selected cyanobacteria, grown in adequately protective containment could serve as pioneer species to produce life sustaining substrates for higher organisms. The very high (95.3 %) CO2 content in Martian atmosphere would provide an abundant carbon source for photo-assimilation, but nitrogen would be a strongly limiting substrate for bio-assimilation in this environment, and would need to be supplemented by nitrogen fertilizing. The very high supply of carbon, with rate-limiting supply of nitrogen strongly affects the growth and the metabolic pathways of the photosynthetic organisms. Here we show that modified, Martian-like atmospheric composition (nearly 100 % CO2) under various low pressure conditions (starting from 50 mbar to maintain liquid water, up to 200 mbars) supports strong cellular growth. Under high CO2 / low N2 ratio the filamentous cyanobacteria produce significant amount of H2 during light due to differentiation of high amount of heterocysts.

Forest composition modifies litter dynamics and decomposition in regenerating tropical dry forest.

PubMed

Schilling, Erik M; Waring, Bonnie G; Schilling, Jonathan S; Powers, Jennifer S

2016-09-01

We investigated how forest composition, litter quality, and rainfall interact to affect leaf litter decomposition across three successional tropical dry forests in Costa Rica. We monitored litter stocks and bulk litter turnover in 18 plots that exhibit substantial variation in soil characteristics, tree community structure, fungal communities (including forests dominated by ecto- or arbuscular mycorrhizal host trees), and forest age. Simultaneously, we decomposed three standard litter substrates over a 6-month period spanning an unusually intense drought. Decay rates of standard substrates depended on the interaction between litter identity and forest type. Decomposition rates were correlated with tree and soil fungal community composition as well as soil fertility, but these relationships differed among litter types. In low fertility soils dominated by ectomycorrhizal oak trees, bulk litter turnover rates were low, regardless of soil moisture. By contrast, in higher fertility soils that supported mostly arbuscular mycorrhizal trees, bulk litter decay rates were strongly dependent on seasonal water availability. Both measures of decomposition increased with forest age, as did the frequency of termite-mediated wood decay. Taken together, our results demonstrate that soils and forest age exert strong control over decomposition dynamics in these tropical dry forests, either directly through effects on microclimate and nutrients, or indirectly by affecting tree and microbial community composition and traits, such as litter quality.

Silicon/HfO{sub 2} interface: Effects of gamma irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maurya, Savita

2016-05-23

Quality of MOS devices is a strong function of substrate and oxide interface. In this work we have studied how gamma photon irradiation affects the interface of a 13 nm thick, atomic layer deposited hafnium dioxide deposited on silicon wafer. CV and GV measurements have been done for pristine and irradiated samples to quantify the effect of gamma photon irradiation. Gamma photon irradiation not only introduces positive charge in the oxide and at the interface of Si/HfO{sub 2} interface but also induce phase change of oxide layer. Maximum oxide capacitances are affected by gamma photon irradiation.

Effects of experimental conditions on the morphologies, structures and growth modes of pulsed laser-deposited CdS nanoneedles

PubMed Central

2014-01-01

CdS nanoneedles with different morphologies, structures, and growth modes have been grown on Ni-coated Si(100) surface under different experimental conditions by pulsed laser deposition method. The effects of catalyst layer, substrate temperature, and laser pulse energy on the growth of the CdS nanoneedles were studied in detail. It was confirmed that the formation of the molten catalyst spheres is the key to the nucleation of the CdS nanoneedles by observing the morphologies of the Ni catalyst thin films annealed at different substrate temperatures. Both the substrate temperature and laser pulse energy strongly affected the growth modes of the CdS nanoneedles. The secondary growth of the smaller nanoneedles on the top of the main nanoneedles was found at appropriate conditions. A group of more completed pictures of the growth modes of the CdS nanoneedles were presented. PMID:24559455

Density functional theory for hard uniaxial particles: Complex ordering of pear-shaped and spheroidal particles near a substrate

NASA Astrophysics Data System (ADS)

Schönhöfer, Philipp W. A.; Schröder-Turk, Gerd E.; Marechal, Matthieu

2018-03-01

We develop a density functional for hard particles with a smooth uniaxial shape (including non-inversion-symmetric particles) within the framework of fundamental measure theory. By applying it to a system of tapered, aspherical liquid-crystal formers, reminiscent of pears, we analyse their behaviour near a hard substrate. The theory predicts a complex orientational ordering close to the substrate, which can be directly related to the particle shape, in good agreement with our simulation results. Furthermore, the lack of particle inversion-symmetry implies the possibility of alternating orientations in subsequent layers as found in a smectic/lamellar phase of such particles. Both theory and Monte Carlo simulations confirm that such ordering occurs in our system. Our results are relevant for adsorption processes of asymmetric colloidal particles and molecules at hard interfaces and show once again that tapering strongly affects the properties of orientationally ordered phases.

Measurements of weak interactions between truncated substrates and a hammerhead ribozyme by competitive kinetic analyses: implications for the design of new and efficient ribozymes with high sequence specificity

PubMed Central

Kasai, Yasuhiro; Shizuku, Hideki; Takagi, Yasuomi; Warashina, Masaki; Taira, Kazunari

2002-01-01

Exploitation of ribozymes in a practical setting requires high catalytic activity and strong specificity. The hammerhead ribozyme R32 has considerable potential in this regard since it has very high catalytic activity. In this study, we have examined how R32 recognizes and cleaves a specific substrate, focusing on the mechanism behind the specificity. Comparing rates of cleavage of a substrate in a mixture that included the correct substrate and various substrates with point mutations, we found that R32 cleaved the correct substrate specifically and at a high rate. To clarify the source of this strong specificity, we quantified the weak interactions between R32 and various truncated substrates, using truncated substrates as competitive inhibitors since they were not readily cleaved during kinetic measurements of cleavage of the correct substrate, S11. We found that the strong specificity of the cleavage reaction was due to a closed form of R32 with a hairpin structure. The self-complementary structure within R32 enabled the ribozyme to discriminate between the correct substrate and a mismatched substrate. Since this hairpin motif did not increase the Km (it did not inhibit the binding interaction) or decrease the kcat (it did not decrease the cleavage rate), this kind of hairpin structure might be useful for the design of new ribozymes with strong specificity and high activity. PMID:12034825

Effects of genetic polymorphisms on the OCT1 and OCT2-mediated uptake of ranitidine.

PubMed

Meyer, Marleen Julia; Seitz, Tina; Brockmöller, Jürgen; Tzvetkov, Mladen Vassilev

2017-01-01

Ranitidine (Zantac®) is a H2-receptor antagonist commonly used for the treatment of acid-related gastrointestinal diseases. Ranitidine was reported to be a substrate of the organic cation transporters OCT1 and OCT2. The hepatic transporter OCT1 is highly genetically variable. Twelve major alleles confer partial or complete loss of OCT1 activity. The effects of these polymorphisms are highly substrate-specific and therefore difficult to predict. The renal transporter OCT2 has a common polymorphism, Ala270Ser, which was reported to affect OCT2 activity. In this study we analyzed the effects of genetic polymorphisms in OCT1 and OCT2 on the uptake of ranitidine and on its potency to inhibit uptake of other drugs. We characterized ranitidine uptake using HEK293 and CHO cells stably transfected to overexpress wild type OCT1, OCT2, or their naturally occurring allelic variants. Ranitidine was transported by wild-type OCT1 with a Km of 62.9 μM and a vmax of 1125 pmol/min/mg protein. Alleles OCT1*5, *6, *12, and *13 completely lacked ranitidine uptake. Alleles OCT1*2, *3, *4, and *10 had vmax values decreased by more than 50%. In contrast, OCT1*8 showed an increase of vmax by 25%. The effects of OCT1 alleles on ranitidine uptake strongly correlated with the effects on morphine uptake suggesting common interaction mechanisms of both drugs with OCT1. Ranitidine inhibited the OCT1-mediated uptake of metformin and morphine at clinically relevant concentrations. The inhibitory potency for morphine uptake was affected by the OCT1*2 allele. OCT2 showed only a limited uptake of ranitidine that was not significantly affected by the Ala270Ser polymorphism. We confirmed ranitidine as an OCT1 substrate and demonstrated that common genetic polymorphisms in OCT1 strongly affect ranitidine uptake and modulate ranitidine's potential to cause drug-drug interactions. The effects of the frequent OCT1 polymorphisms on ranitidine pharmacokinetics in humans remain to be analyzed.

Effects of genetic polymorphisms on the OCT1 and OCT2-mediated uptake of ranitidine

PubMed Central

Meyer, Marleen Julia; Seitz, Tina; Brockmöller, Jürgen

2017-01-01

Background Ranitidine (Zantac®) is a H2-receptor antagonist commonly used for the treatment of acid-related gastrointestinal diseases. Ranitidine was reported to be a substrate of the organic cation transporters OCT1 and OCT2. The hepatic transporter OCT1 is highly genetically variable. Twelve major alleles confer partial or complete loss of OCT1 activity. The effects of these polymorphisms are highly substrate-specific and therefore difficult to predict. The renal transporter OCT2 has a common polymorphism, Ala270Ser, which was reported to affect OCT2 activity. Aim In this study we analyzed the effects of genetic polymorphisms in OCT1 and OCT2 on the uptake of ranitidine and on its potency to inhibit uptake of other drugs. Methods and results We characterized ranitidine uptake using HEK293 and CHO cells stably transfected to overexpress wild type OCT1, OCT2, or their naturally occurring allelic variants. Ranitidine was transported by wild-type OCT1 with a Km of 62.9 μM and a vmax of 1125 pmol/min/mg protein. Alleles OCT1*5, *6, *12, and *13 completely lacked ranitidine uptake. Alleles OCT1*2, *3, *4, and *10 had vmax values decreased by more than 50%. In contrast, OCT1*8 showed an increase of vmax by 25%. The effects of OCT1 alleles on ranitidine uptake strongly correlated with the effects on morphine uptake suggesting common interaction mechanisms of both drugs with OCT1. Ranitidine inhibited the OCT1-mediated uptake of metformin and morphine at clinically relevant concentrations. The inhibitory potency for morphine uptake was affected by the OCT1*2 allele. OCT2 showed only a limited uptake of ranitidine that was not significantly affected by the Ala270Ser polymorphism. Conclusions We confirmed ranitidine as an OCT1 substrate and demonstrated that common genetic polymorphisms in OCT1 strongly affect ranitidine uptake and modulate ranitidine’s potential to cause drug-drug interactions. The effects of the frequent OCT1 polymorphisms on ranitidine pharmacokinetics in humans remain to be analyzed. PMID:29236753

Low-pressure large-area magnetron sputter deposition of YBa2Cu3O7-δ films for industrial applications

NASA Astrophysics Data System (ADS)

Wördenweber, Roger; Hollmann, Eugen; Poltiasev, Michael; Neumüller, Heinz-Werner

2003-05-01

This paper addresses the development of a technically relevant sputter-deposition process for YBa2Cu3O7-delta films. First, the simulation of the particle transport from target to substrate indicates that only at a reduced pressure of p approx 1-10 Pa can a sufficiently large deposition rate and homogeneous stoichiometric distribution of the particles during large-area deposition be expected. The results of the simulations are generally confirmed by deposition experiments on CeO2 buffered sapphire and LaAlO3 substrates using a magnetron sputtering system suitable for large-area deposition. However, it is shown that in addition to the effect of scattering during particle transport, the conditions at the substrate lead to a selective growth of Y-Ba-Cu-O phases that, among others, strongly affect the growth rate. For example, the growth rate is more than three times larger for optimized parameters compared to the same set of parameters but at 100 K lower substrate temperature. Stoichiometrical and structural perfect films can be grown at low pressure (p < 10 Pa). However, the superconducting transition temperature of these films is reduced. The Tc reduction seems to be correlated with the c-axis length of YBa2Cu3O7-delta. Two possible explanations for the increased c-axis length and the correlated reduced transition temperature are discussed, i.e. reduced oxygen content and strong cation site disorder due to the heavy particle bombardment.

Refractive Index Imaging of Cells with Variable-Angle Near-Total Internal Reflection (TIR) Microscopy.

PubMed

Bohannon, Kevin P; Holz, Ronald W; Axelrod, Daniel

2017-10-01

The refractive index in the interior of single cells affects the evanescent field depth in quantitative studies using total internal reflection (TIR) fluorescence, but often that index is not well known. We here present method to measure and spatially map the absolute index of refraction in a microscopic sample, by imaging a collimated light beam reflected from the substrate/buffer/cell interference at variable angles of incidence. Above the TIR critical angle (which is a strong function of refractive index), the reflection is 100%, but in the immediate sub-critical angle zone, the reflection intensity is a very strong ascending function of incidence angle. By analyzing the angular position of that edge at each location in the field of view, the local refractive index can be estimated. In addition, by analyzing the steepness of the edge, the distance-to-substrate can be determined. We apply the technique to liquid calibration samples, silica beads, cultured Chinese hamster ovary cells, and primary culture chromaffin cells. The optical technique suffers from decremented lateral resolution, scattering, and interference artifacts. However, it still provides reasonable results for both refractive index (~1.38) and for distance-to-substrate (~150 nm) for the cells, as well as a lateral resolution to about 1 µm.

Entropy-driven crystal formation on highly strained substrates

PubMed Central

Savage, John R.; Hopp, Stefan F.; Ganapathy, Rajesh; Gerbode, Sharon J.; Heuer, Andreas; Cohen, Itai

2013-01-01

In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropy-driven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substrate-mediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate. PMID:23690613

Egg-laying substrate selection for optimal camouflage by quail.

PubMed

Lovell, P George; Ruxton, Graeme D; Langridge, Keri V; Spencer, Karen A

2013-02-04

Camouflage is conferred by background matching and disruption, which are both affected by microhabitat. However, microhabitat selection that enhances camouflage has only been demonstrated in species with discrete phenotypic morphs. For most animals, phenotypic variation is continuous; here we explore whether such individuals can select microhabitats to best exploit camouflage. We use substrate selection in a ground-nesting bird (Japanese quail, Coturnix japonica). For such species, threat from visual predators is high and egg appearance shows strong between-female variation. In quail, variation in appearance is particularly obvious in the amount of dark maculation on the light-colored shell. When given a choice, birds consistently selected laying substrates that made visual detection of their egg outline most challenging. However, the strategy for maximizing camouflage varied with the degree of egg maculation. Females laying heavily maculated eggs selected the substrate that more closely matched egg maculation color properties, leading to camouflage through disruptive coloration. For lightly maculated eggs, females chose a substrate that best matched their egg background coloration, suggesting background matching. Our results show that quail "know" their individual egg patterning and seek out a nest position that provides most effective camouflage for their individual phenotype. Copyright © 2013 Elsevier Ltd. All rights reserved.

Active substrates improving sensitivity in biomedical fluorescence microscopy

NASA Astrophysics Data System (ADS)

Le Moal, E.; Leveque-Fort, S.; Fort, E.; Lacharme, J.-P.; Fontaine-Aupart, M.-P.; Ricolleau, C.

2005-08-01

Fluorescence is widely used as a spectroscopic tool or for biomedical imaging, in particular for DNA chips. In some cases, detection of very low molecular concentrations and precise localization of biomarkers are limited by the weakness of the fluorescence signal. We present a new method based on sample substrates that improve fluorescence detection sensitivity. These active substrates consist in glass slides covered with metal (gold or silver) and dielectric (alumina) films and can directly be used with common microscope set-up. Fluorescence enhancement affects both excitation and decay rates and is strongly dependant on the distance to the metal surface. Furthermore, fluorescence collection is improved since fluorophore emission lobes are advantageously modified close to a reflective surface. Finally, additional improvements are achieved by structuring the metallic layer. Substrates morphology was mapped by Atomic Force Microscopy (AFM). Substrates optical properties were studied using mono- and bi-photonic fluorescence microscopy with time resolution. An original set-up was implemented for spatial radiation pattern's measurement. Detection improvement was then tested on commercial devices. Several biomedical applications are presented. Enhancement by two orders of magnitude are achieved for DNA chips and signal-to-noise ratio is greatly increased for cells imaging.

Evaluation of Environmental Risk of Metal Contaminated Soils and Sediments Near Mining Sites in Aguascalientes, Mexico.

PubMed

Mitchell, Kerry Nigel; Ramos Gómez, Magdalena Samanta; Guerrero Barrera, Alma Lilian; Yamamoto Flores, Laura; Flores de la Torre, Juan Armando; Avelar González, Francisco Javier

2016-08-01

A total of sixteen composite soil and sediment samples were collected during the rainy and dry season in Asientos, Aguascalientes, Mexico, an area recently affected by increased mining operations. Physicochemical characterization showed that substrates were moderately to strongly calcareous with predominantly neutral to slightly alkaline pH, moderate to high cation-exchange capacity and high organic matter content. Due to these conditions, Cd, Pb, Cu and Zn were not water leachable despite high concentrations; up to 105.3, 7052.8, 414.7 and 12,263.2 mg kg(-1) respectively. However, Cd and Pb were considered to be easily mobilizable as they were found predominantly associated with exchangeable and carbonate fractions, whereas Cu and Zn were found associated with Fe/Mn oxide and organic matter fractions. The results highlighted the influence of physicochemical substrate properties on the mobility of metals and its importance during the evaluation of the potential current and future risk metal contamination presents in affected areas.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishiyama, Takeshi, E-mail: ishiyama@ee.tut.ac.jp; Nakane, Takaya, E-mail: ishiyama@ee.tut.ac.jp; Fujii, Tsutomu, E-mail: ishiyama@ee.tut.ac.jp

Arrays of single-crystal zinc oxide (ZnO) nanowires have been synthesized on silicon substrates by vapor-liquid-solid growth techniques. The effect of growth conditions including substrate temperature and Ar gas flow rate on growth properties of ZnO nanowire arrays were studied. Structural and optical characterization was performed using scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. SEM images of the ZnO nanowire arrays grown at various Ar gas flow rates indicated that the alignment and structural features of ZnO nanowires were affected by the gas flow rate. The PL of the ZnO nanowire arrays exhibited strong ultraviolet (UV) emission at 380 nmmore » and green emission around 510 nm. Moreover, the green emission reduced in Ga-doped sample.« less

Characterization of Dislocations in Semiconductor Heterostructures Using X-ray Rocking Curve Pendellösung

NASA Astrophysics Data System (ADS)

Althowibi, Fahad A.; Ayers, John E.

2018-02-01

In this work we investigated the dislocation-dependent behavior of Pendellösung fringes from two types of semiconductor heterostructures: a uniform-composition InGaAs epitaxial layer grown on a GaAs (001) substrate with an intermediate step-graded InGaAs buffer, and an InGaAs/InAlAs high electron mobility transistor grown on an InP (001) substrate. Dynamical x-ray diffraction simulations were carried out in the 004, 115,135, and 117 geometry, assuming Cu kα1 incident radiation, for both structures. The dislocation density strongly affects the intensities and widths of Pendellösung fringes, and we have established quantitative relationships which will allow characterization of the dislocation density.

Effects of temperature and cadmium exposure on the mitochondria of oysters (Crassostrea virginica) exposed to hypoxia and subsequent reoxygenation.

PubMed

Ivanina, Anna V; Kurochkin, Ilya O; Leamy, Larry; Sokolova, Inna M

2012-09-15

Intertidal bivalves are commonly exposed to multiple stressors including periodic hypoxia, temperature fluctuations and pollution, which can strongly affect energy metabolism. We used top-down control and elasticity analyses to determine the interactive effects of intermittent hypoxia, cadmium (Cd) exposure and acute temperature stress on mitochondria of the eastern oyster Crassostrea virginica. Oysters were acclimated at 20°C for 30 days in the absence or presence of 50 μg l(-1) Cd and then subjected to a long-term hypoxia (6 days at <0.5% O(2) in seawater) followed by normoxic recovery. Mitochondrial function was assessed at the acclimation temperature (20°C), or at elevated temperature (30°C) mimicking acute temperature stress in the intertidal zone. In the absence of Cd or temperature stress, mitochondria of oysters showed high resilience to transient hypoxia. In control oysters at 20°C, hypoxia/reoxygenation induced elevated flux capacity of all three studied mitochondrial subsystems (substrate oxidation, phosphorylation and proton leak) and resulted in a mild depolarization of resting mitochondria. Elevated proton conductance and enhanced capacity of phosphorylation and substrate oxidation subsystems may confer resistance to hypoxia/reoxygenation stress in oyster mitochondria by alleviating production of reactive oxygen species and maintaining high aerobic capacity and ATP synthesis rates during recovery. Exposure to environmental stressors such as Cd and elevated temperatures abolished the putative adaptive responses of the substrate oxidation and phosphorylation subsystems, and strongly enhanced proton leak in mitochondria of oysters subjected to hypoxia/reoxygenation stress. Our findings suggest that Cd exposure and acute temperature stress may lead to the loss of mitochondrial resistance to hypoxia and reoxygenation and thus potentially affect the ability of oysters to survive periodic oxygen deprivation in coastal and estuarine habitats.

The Effect of Substrate Microstructure on the Heat-Affected Zone Size in Sn-Zn Alloys Due to Adjoining Ni-Al Reactive Multilayer Foil Reaction

DOE PAGES

Hooper, R. J.; Adams, D. P.; Hirschfeld, D.; ...

2015-08-05

The rapid release of energy from reactive multilayer foils can create extreme local temperature gradients near substrate materials. To fully exploit the potential of these materials, a better understanding of the interaction between the substrate or filler material and the foil is needed. In particular, this work investigates how variations in local properties within the substrate (i.e. differences between properties in constituent phases) can affect heat transport into the substrate. Furthermore, this can affect the microstructural evolution observed within the substrate, which may affect the final joint properties. The effect of the initial substrate microstructure on microstructural evolution within themore » heat-affected zone is evaluated experimentally in two Sn-Zn alloys and numerical techniques are utilized to inform the analysis.« less

Coarsening of protein clusters on subcellular drops exhibits strong and sudden size selectivity

NASA Astrophysics Data System (ADS)

Brown, Aidan; Rutenberg, Andrew

2015-03-01

Autophagy is an important process for the degradation of cellular components, with receptor proteins targeting substrates to downstream autophagy machinery. An important question is how receptor protein interactions lead to their selective accumulation on autophagy substrates. Receptor proteins have recently been observed in clusters, raising the possibility that clustering could affect autophagy selectivity. We investigate the clustering dynamics of the autophagy receptor protein NBR1. In addition to standard receptor protein domains, NBR1 has a ``J'' domain that anchors it to membranes, and a coiled-coil domain that enhances self-interaction. We model coarsening clusters of NBR1 on the surfaces of a polydisperse collection of drops, representing organelles. Despite the disconnected nature of the drop surfaces, we recover dynamical scaling of cluster sizes. Significantly, we find that at a well-defined time after coarsening begins, clusters evaporate from smaller drops and grow on larger drops. Thus, coarsening-driven size selection will localize protein clusters to larger substrates, leaving smaller substrates without clusters. This provides a possible physical mechanism for autophagy selectivity, and can explain reports of size selection during peroxisome degradation.

Measurement of cell adhesion force by vertical forcible detachment using an arrowhead nanoneedle and atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryu, Seunghwan; Hashizume, Yui; Mishima, Mari

Graphical abstract: - Highlights: • We developed a method to measure cell adhesion force by detaching cell using an arrowhead nanoneedle and AFM. • A nanofilm consisting of fibronectin and gelatin was formed on cell surface to reinforce the cell cortex. • By the nanofilm lamination, detachment efficiencies of strongly adherent cell lines were improved markedly. - Abstract: The properties of substrates and extracellular matrices (ECM) are important factors governing the functions and fates of mammalian adherent cells. For example, substrate stiffness often affects cell differentiation. At focal adhesions, clustered–integrin bindings link cells mechanically to the ECM. In order tomore » quantitate the affinity between cell and substrate, the cell adhesion force must be measured for single cells. In this study, forcible detachment of a single cell in the vertical direction using AFM was carried out, allowing breakage of the integrin–substrate bindings. An AFM tip was fabricated into an arrowhead shape to detach the cell from the substrate. Peak force observed in the recorded force curve during probe retraction was defined as the adhesion force, and was analyzed for various types of cells. Some of the cell types adhered so strongly that they could not be picked up because of plasma membrane breakage by the arrowhead probe. To address this problem, a technique to reinforce the cellular membrane with layer-by-layer nanofilms composed of fibronectin and gelatin helped to improve insertion efficiency and to prevent cell membrane rupture during the detachment process, allowing successful detachment of the cells. This method for detaching cells, involving cellular membrane reinforcement, may be beneficial for evaluating true cell adhesion forces in various cell types.« less

Atomic moments in Mn 2CoAl thin films analyzed by X-ray magnetic circular dichroism

DOE PAGES

Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; ...

2014-12-05

Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn 2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

Sorting it out: bedding particle size and nesting material processing method affect nest complexity.

PubMed

Robinson-Junker, Amy; Morin, Amelia; Pritchett-Corning, Kathleen; Gaskill, Brianna N

2017-04-01

As part of routine husbandry, an increasing number of laboratory mice receive nesting material in addition to standard bedding material in their cages. Nesting material improves health outcomes and physiological performance in mice that receive it. Providing usable nesting material uniformly and efficiently to various strains of mice remains a challenge. The aim of this study was to determine how bedding particle size, method of nesting material delivery, and processing of the nesting material before delivery affected nest building in mice of strong (BALB/cAnNCrl) and weak (C3H/HeNCrl) gathering abilities. Our data suggest that processing nesting material through a grinder in conjunction with bedding material, although convenient for provision of bedding with nesting material 'built-in', negatively affects the integrity of the nesting material and subsequent nest-building outcomes. We also found that C3H mice, previously thought to be poor nest builders, built similarly scored nests to those of BALB/c mice when provided with unprocessed nesting material. This was true even when nesting material was mixed into the bedding substrate. We also observed that when nesting material was mixed into the bedding substrate, mice of both strains would sort their bedding by particle size more often than if it were not mixed in. Our findings support the utility of the practice of distributing nesting material mixed in with bedding substrate, but not that of processing the nesting material with the bedding in order to mix them.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hooper, R. J.; Adams, D. P.; Hirschfeld, D.

The rapid release of energy from reactive multilayer foils can create extreme local temperature gradients near substrate materials. To fully exploit the potential of these materials, a better understanding of the interaction between the substrate or filler material and the foil is needed. In particular, this work investigates how variations in local properties within the substrate (i.e. differences between properties in constituent phases) can affect heat transport into the substrate. Furthermore, this can affect the microstructural evolution observed within the substrate, which may affect the final joint properties. The effect of the initial substrate microstructure on microstructural evolution within themore » heat-affected zone is evaluated experimentally in two Sn-Zn alloys and numerical techniques are utilized to inform the analysis.« less

Electronic screening in stacked graphene flakes revealed by scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Feng, Xiaofeng; Salmeron, Miquel

2013-02-01

Electronic doping and screening effects in stacked graphene flakes on Ru and Cu substrates have been observed using scanning tunneling microscopy (STM). The screening affects the apparent STM height of each flake in successive layers reflecting the density of states near the Fermi level and thus the doping level. It is revealed in this way that the strong doping of the first graphene layer on Ru(0001) is attenuated in the second one, and almost eliminated in the third and fourth layers. Similar effect is also observed in graphene flakes on Cu(111). In contrast, the strong doping effect is suppressed immediately by a water layer intercalated between the graphene and Ru.

Quantum mechanical hydrogen tunneling in bacterial copper amine oxidase reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murakawa, Takeshi; Okajima, Toshihide; Kuroda, Shun'ichi

A key step decisively affecting the catalytic efficiency of copper amine oxidase is stereospecific abstraction of substrate {alpha}-proton by a conserved Asp residue. We analyzed this step by pre-steady-state kinetics using a bacterial enzyme and stereospecifically deuterium-labeled substrates, 2-phenylethylamine and tyramine. A small and temperature-dependent kinetic isotope effect (KIE) was observed with 2-phenylethylamine, whereas a large and temperature-independent KIE was observed with tyramine in the {alpha}-proton abstraction step, showing that this step is driven by quantum mechanical hydrogen tunneling rather than the classical transition-state mechanism. Furthermore, an Arrhenius-type preexponential factor ratio approaching a transition-state value was obtained in the reactionmore » of a mutant enzyme lacking the critical Asp. These results provide strong evidence for enzyme-enhanced hydrogen tunneling. X-ray crystallographic structures of the reaction intermediates revealed a small difference in the binding mode of distal parts of substrates, which would modulate hydrogen tunneling proceeding through either active or passive dynamics.« less

Morphology of viscoplastic drop impact on viscoplastic surfaces.

PubMed

Chen, Simeng; Bertola, Volfango

2017-01-25

The impact of viscoplastic drops onto viscoplastic substrates characterized by different magnitudes of the yield stress is investigated experimentally. The interaction between viscoplastic drops and surfaces has an important application in additive manufacturing, where a fresh layer of material is deposited on a partially cured or dried layer of the same material. So far, no systematic studies on this subject have been reported in literature. The impact morphology of different drop/substrate combinations, with yield stresses ranging from 1.13 Pa to 11.7 Pa, was studied by high speed imaging for impact Weber numbers between 15 and 85. Experimental data were compared with one of the existing models for Newtonian drop impact onto liquid surfaces. Results show the magnitude of the yield stress of drop/substrate strongly affects the final shape of the impacting drop, permanently deformed at the end of impact. The comparison between experimental data and model predictions suggests the crater evolution model is only valid when predicting the evolution of the crater at sufficiently high Weber numbers.

Anisotropic MoS2 Nanosheets Grown on Self-Organized Nanopatterned Substrates.

PubMed

Martella, Christian; Mennucci, Carlo; Cinquanta, Eugenio; Lamperti, Alessio; Cappelluti, Emmanuele; Buatier de Mongeot, Francesco; Molle, Alessandro

2017-05-01

Manipulating the anisotropy in 2D nanosheets is a promising way to tune or trigger functional properties at the nanoscale. Here, a novel approach is presented to introduce a one-directional anisotropy in MoS 2 nanosheets via chemical vapor deposition (CVD) onto rippled patterns prepared on ion-sputtered SiO 2 /Si substrates. The optoelectronic properties of MoS 2 are dramatically affected by the rippled MoS 2 morphology both at the macro- and the nanoscale. In particular, strongly anisotropic phonon modes are observed depending on the polarization orientation with respect to the ripple axis. Moreover, the rippled morphology induces localization of strain and charge doping at the nanoscale, thus causing substantial redshifts of the phonon mode frequencies and a topography-dependent modulation of the MoS 2 workfunction, respectively. This study paves the way to a controllable tuning of the anisotropy via substrate pattern engineering in CVD-grown 2D nanosheets. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fatigue behavior of thermal sprayed WC-CoCr- steel systems: Role of process and deposition parameters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vackel, Andrew; Sampath, Sanjay

Thermal spray deposited WC-CoCr coatings are extensively used for surface protection of wear prone components in a variety of applications. Although the primary purpose of the coating is wear and corrosion protection, many of the coated components are structural systems (aero landing gear, hydraulic cylinders, drive shafts etc.) and as such experience cyclic loading during service and are potentially prone to fatigue failure. It is of interest to ensure that the coating and the application process does not deleteriously affect the fatigue strength of the parent structural metal. It has long been appreciated that the relative fatigue life of amore » thermal sprayed component can be affected by the residual stresses arising from coating deposition. The magnitude of these stresses can be managed by torch processing parameters and can also be influenced by deposition effects, particularly the deposition temperature. In this study, the effect of both torch operating parameters (particle states) and deposition conditions (notably substrate temperature) were investigated through rotating bending fatigue studies. The results indicate a strong influence of process parameters on relative fatigue life, including credit or debit to the substrate's fatigue life measured via rotating bend beam studies. Damage progression within the substrate was further explored by stripping the coating off part way through fatigue testing, revealing a delay in the onset of substrate damage with more fatigue resistant coatings but no benefit with coatings with inadequate properties. Finally, the results indicate that compressive residual stress and adequate load bearing capability of the coating (both controlled by torch and deposition parameters) delay onset of substrate damage, enabling fatigue credit of the coated component.« less

Fatigue behavior of thermal sprayed WC-CoCr- steel systems: Role of process and deposition parameters

DOE PAGES

Vackel, Andrew; Sampath, Sanjay

2017-02-27

Thermal spray deposited WC-CoCr coatings are extensively used for surface protection of wear prone components in a variety of applications. Although the primary purpose of the coating is wear and corrosion protection, many of the coated components are structural systems (aero landing gear, hydraulic cylinders, drive shafts etc.) and as such experience cyclic loading during service and are potentially prone to fatigue failure. It is of interest to ensure that the coating and the application process does not deleteriously affect the fatigue strength of the parent structural metal. It has long been appreciated that the relative fatigue life of amore » thermal sprayed component can be affected by the residual stresses arising from coating deposition. The magnitude of these stresses can be managed by torch processing parameters and can also be influenced by deposition effects, particularly the deposition temperature. In this study, the effect of both torch operating parameters (particle states) and deposition conditions (notably substrate temperature) were investigated through rotating bending fatigue studies. The results indicate a strong influence of process parameters on relative fatigue life, including credit or debit to the substrate's fatigue life measured via rotating bend beam studies. Damage progression within the substrate was further explored by stripping the coating off part way through fatigue testing, revealing a delay in the onset of substrate damage with more fatigue resistant coatings but no benefit with coatings with inadequate properties. Finally, the results indicate that compressive residual stress and adequate load bearing capability of the coating (both controlled by torch and deposition parameters) delay onset of substrate damage, enabling fatigue credit of the coated component.« less

A quantitative method for photovoltaic encapsulation system optimization

NASA Technical Reports Server (NTRS)

Garcia, A., III; Minning, C. P.; Cuddihy, E. F.

1981-01-01

It is pointed out that the design of encapsulation systems for flat plate photovoltaic modules requires the fulfillment of conflicting design requirements. An investigation was conducted with the objective to find an approach which will make it possible to determine a system with optimum characteristics. The results of the thermal, optical, structural, and electrical isolation analyses performed in the investigation indicate the major factors in the design of terrestrial photovoltaic modules. For defect-free materials, minimum encapsulation thicknesses are determined primarily by structural considerations. Cell temperature is not strongly affected by encapsulant thickness or thermal conductivity. The emissivity of module surfaces exerts a significant influence on cell temperature. Encapsulants should be elastomeric, and ribs are required on substrate modules. Aluminum is unsuitable as a substrate material. Antireflection coating is required on cell surfaces.

Inhibition of thiopurine S-methyltransferase activity by impurities in commercially available substrates: a factor for differing results of TPMT measurements.

PubMed

Kröplin, T; Fischer, C; Iven, H

1999-06-01

Thiopurine S-methyltransferase (TPMT) activity, when measured in red blood cells (RBC) with a recently published TPMT activity assay using 6-thioguanine (6-TG) as substrate, could not be reproduced in another laboratory. We investigated factors which could influence the results of the TPMT activity measurement. We tested twelve 6-TG and four 6-mercaptopurine (6-MP) compounds from different suppliers as substrates and determined the enzyme kinetic parameters Km and Vmax. Furthermore, we studied the influence of different 6-TG compounds on the affinity of the methyl donor S-adenosyl-L-methionine (SAM) to the TPMT enzyme. All 6-TG products were of equal purity (declared >98% by the supplier): this was ascertained by HPLC. However, the rate of methylation obtained following incubation with 6-TG from different suppliers ranged from 10% to 100% when incubated with the same RBC lysate. The lowest apparent Km value for a 6-TG was 22.3 micromol x l(-1), while the product with the highest methylation rate showed a Km of 156 micromol x l(-1). From these results we assume that there is a contaminant in some 6-TG products, which acts as a strong inhibitor of TPMT activity. Compounds possibly used for the synthesis of 6-TG (guanine, pyridine, 6-chloroguanine) did not affect the methylation rate. Thioxanthine, which is known to be a strong inhibitor of TPMT when added to the assay system to give a 2% contamination, reduced TPMT activity from 100% to 72%. Using 6-MP from different suppliers as substrate resulted in Km values ranging from 110 to 162 micromol x l(-1) and Vmox values ranging from 54 to 68 nmol 6-MMP x g(-1)Hb x h(-1). The Km value for the methyl donor SAM was similar to and independent from the thiopurine substrates tested (range 4.9-11 micromol-l(-1) SAM). In contrast to other investigators, we found non-enzymatic S-methylation, which was negligible under our assay conditions (3% with 128 micromol x l(-1) SAM), but could become relevant in experiments using higher SAM concentrations. TPMT enzyme activity determined with 6-TG as substrate may be strongly inhibited by a contaminant in some of the 6-TG lots distributed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simoes, A.Z.; Riccardi, C.S.; Cavalcante, L.S.

The film thickness dependence on the ferroelectric properties of lanthanum modified bismuth titanate Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} was investigated. Films with thicknesses ranging from 230 to 404 nm were grown on platinum-coated silicon substrates by the polymeric precursor method. The internal strain is strongly influenced by the film thickness. The morphology of the film changes as the number of layers increases indicating a thickness dependent grain size. The leakage current, remanent polarization and drive voltage were also affected by the film thickness.

A comparative study of performance parameters of n(+)-p InP solar cells made by closed-ampoule sulfur diffusion into Cd- and Zn-doped p-type InP substrates

NASA Technical Reports Server (NTRS)

Faur, Mircea; Faur, Maria; Goradia, Chandra; Goradia, Manju; Thomas, Ralph D.; Brinker, David J.; Fatemi, Navid S.; Honecy, Frank S.

1991-01-01

Preliminary results indicate that Cd-doped substrates are better candidates for achieving high efficiency solar cells fabricated by closed-ampoule sulfur (S) diffusion than Zn-doped substrates. The differences in performance parameters (i.e., 14.3 percent efficiency for Cd-doped vs. 11.83 percent in the case of Zn-doped substrates of comparable doping and etch pit densities) were explained in terms of a large increase in dislocation density as a result of S diffusion in the case of Zn-doped as compared to Cd-doped substrates. The In(x)S(y) and probably Zn(S) precipitates in the case of Zn-doped substrates, produce a dead layer which extends deep below the surface and strongly affects the performance parameters. It should be noted that the cells had an unoptimized single layer antireflective coating of SiO, a grid shadowing of 6.25 percent, and somewhat poor contacts, all contributing to a reduction in efficiency. It is believed that by reducing the external losses and further improvement in cell design, efficiencies approaching 17 percent at 1 AMO, 25 degrees should be possible for cells fabricated on these relatively high defect density Cd-doped substrates. Even higher efficiencies, 18 to 19 percent should be possible by using long-lifetime substrates and further improving front surface passivation. If solar cells fabricated on Cd-doped substrates turn out to have comparable radiation tolerance as those reported in the case of cells fabricated on Zn-doped substrates, then for certain space missions 18 to 19 percent efficient cells made by this method of fabrication would be viable.

On the measurement of relaxation times of acoustic vibrations in metal nanowires.

PubMed

Devkota, Tuphan; Chakraborty, Debadi; Yu, Kuai; Beane, Gary; Sader, John E; Hartland, Gregory V

2018-06-25

The mechanical resonances of metal nanostructures are strongly affected by their environment. In this paper the way the breathing modes of single metal nanowires are damped by liquids with different viscosities was studied by ultrafast pump-probe microscopy experiments. Both nanowires supported on a glass substrate and nanowires suspended over trenches were investigated. The measured quality factors for liquid damping for the suspended nanowires are in good agreement with continuum mechanics calculations for an inviscid fluid that assume continuity in stress and displacement at the nanowire-liquid interface. This shows that liquid damping is controlled by radiation of sound waves into the medium. For the nanowires on the glass surface the quality factors for liquid damping are approximately 60% higher than those for the suspended nanowires. This is attributed to a shadowing effect. The nanowires in our measurements have pentagonal cross-sections. This produces two different breathing modes and also means that one of the faces for the supported nanowires is blocked by the substrate, which reduces the amount of damping from the liquid. Comparing the supported and suspended nanowires also allows us to estimate the effect of the substrate on the acoustic mode damping. We find that the substrate has a weak effect, which is attributed to poor mechanical contact between the nanowires and the substrate.

Interfacial Activation of Candida antarctica Lipase B: Combined Evidence from Experiment and Simulation.

PubMed

Zisis, Themistoklis; Freddolino, Peter L; Turunen, Petri; van Teeseling, Muriel C F; Rowan, Alan E; Blank, Kerstin G

2015-09-29

Lipase immobilization is frequently used for altering the catalytic properties of these industrially used enzymes. Many lipases bind strongly to hydrophobic surfaces where they undergo interfacial activation. Candida antarctica lipase B (CalB), one of the most commonly used biocatalysts, is frequently discussed as an atypical lipase lacking interfacial activation. Here we show that CalB displays an enhanced catalytic rate for large, bulky substrates when adsorbed to a hydrophobic interface composed of densely packed alkyl chains. We attribute this increased activity of more than 7-fold to a conformational change that yields a more open active site. This hypothesis is supported by molecular dynamics simulations that show a high mobility for a small "lid" (helix α5) close to the active site. Molecular docking calculations confirm that a highly open conformation of this helix is required for binding large, bulky substrates and that this conformation is favored in a hydrophobic environment. Taken together, our combined approach provides clear evidence for the interfacial activation of CalB on highly hydrophobic surfaces. In contrast to other lipases, however, the conformational change only affects large, bulky substrates, leading to the conclusion that CalB acts like an esterase for small substrates and as a lipase for substrates with large alcohol substituents.

Influence of substrate and film thickness on polymer LIPSS formation

NASA Astrophysics Data System (ADS)

Cui, Jing; Nogales, Aurora; Ezquerra, Tiberio A.; Rebollar, Esther

2017-02-01

Here we focus on the influence of both, substrate and film thickness on polymer Laser Induced Periodic Surface Structures (LIPSS) formation in polymer films. For this aim a morphological description of ripples structures generated on spin-coated polystyrene (PS) films by a linearly polarized laser beam with a wavelength of 266 nm is presented. The influence of different parameters on the quality and characteristics of the formed laser-induced periodic surface structures (LIPSS) was investigated. We found that well-ordered LIPSS are formed either on PS films thinner than 200 nm or thicker than 400 nm supported on silicon substrates as well as on thicker free standing films. However less-ordered ripples are formed on silicon supported films with intermediate thicknesses in the range of 200-380 nm. The effect of the thermal and optical properties of the substrate on the quality of LIPSS was analyzed. Differences observed in the fluence and number of pulses needed for the onset of surface morphological modifications is explained considering two main effects which are: (1) The temperature increase on polymer surface induced by the action of cumulative laser irradiation and (2) The differences in thermal conductivity between the polymer and the substrate which strongly affect the heat dissipation generated by irradiation.

Molecular aspect ratio and anchoring strength effects in a confined Gay-Berne liquid crystal

NASA Astrophysics Data System (ADS)

Cañeda-Guzmán, E.; Moreno-Razo, J. A.; Díaz-Herrera, E.; Sambriski, E. J.

2014-04-01

Phase diagrams for Gay-Berne (GB) fluids were obtained from molecular dynamics simulations for GB(2, 5, 1, 2) (i.e. short mesogens) and GB(3, 5, 1, 2) (i.e. long mesogens), which yield isotropic, nematic, and smectic-B phases. The long-mesogen fluid also yields the smectic-A phase. Ordered phases of the long-mesogen fluid form at higher temperatures and lower densities when compared to those of the short-mesogen fluid. The effect of confinement under weak and strong substrate couplings in slab geometry was investigated. Compared to the bulk, the isotropic-nematic transition does not shift in temprature significantly for the weakly coupled substrate in either mesogen fluid. However, the strongly coupled substrate shifts the transition to lower temperature. Confinement induces marked stratification in the short-mesogen fluid. This effect diminishes with distance from the substrate, yielding bulk-like behaviour in the slab central region. Fluid stratification is very weak for the long-mesogen fluid, but the strongly coupled substrate induces 'smectisation', an ordering effect that decays with distance. Orientation of the fluid on the substrate depends on the mesogen. There is no preferred orientation in a plane parallel to the substrate for the weakly coupled case. In the strongly coupled case, the mesogen orientation mimics that of adjacent fluid layers. Planar anchoring is observed with a broad distribution of orientations in the weakly coupled case. In the strongly coupled case, the distribution leans toward planar orientations for the short-mesogen fluid, while a marginal preference for tilting persists in the long-mesogen fluid.

Hole doping, hybridization gaps, and electronic correlation in graphene on a platinum substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwang, Jinwoong; Hwang, Hwihyeon; Kim, Min-Jeong

The interaction between graphene and substrates provides a viable route to enhance the functionality of both materials. Depending on the nature of electronic interaction at the interface, the electron band structure of graphene is strongly influenced, allowing us to make use of the intrinsic properties of graphene or to design additional functionalities in graphene. In this paper, we present an angle-resolved photoemission study on the interaction between graphene and a platinum substrate. The formation of an interface between graphene and platinum leads to a strong deviation in the electronic structure of graphene not only from its freestanding form but alsomore » from the behavior observed on typical metals. Finally, the combined study on the experimental and theoretical electron band structure unveils the unique electronic properties of graphene on a platinum substrate, which singles out graphene/platinum as a model system investigating graphene on a metallic substrate with strong interaction.« less

Hole doping, hybridization gaps, and electronic correlation in graphene on a platinum substrate

DOE PAGES

Hwang, Jinwoong; Hwang, Hwihyeon; Kim, Min-Jeong; ...

2017-08-02

The interaction between graphene and substrates provides a viable route to enhance the functionality of both materials. Depending on the nature of electronic interaction at the interface, the electron band structure of graphene is strongly influenced, allowing us to make use of the intrinsic properties of graphene or to design additional functionalities in graphene. In this paper, we present an angle-resolved photoemission study on the interaction between graphene and a platinum substrate. The formation of an interface between graphene and platinum leads to a strong deviation in the electronic structure of graphene not only from its freestanding form but alsomore » from the behavior observed on typical metals. Finally, the combined study on the experimental and theoretical electron band structure unveils the unique electronic properties of graphene on a platinum substrate, which singles out graphene/platinum as a model system investigating graphene on a metallic substrate with strong interaction.« less

Controlling Growth Orientation of Phthalocyanine Films by Electrical Fields

NASA Technical Reports Server (NTRS)

Zhu, S.; Banks, C. E.; Frazier, D. O.; Ila, D.; Muntele, I.; Penn, B. G.; Sharma, A.; Rose, M. Franklin (Technical Monitor)

2001-01-01

Organic Phthalocyanine films have many applications ranging from data storage to various non-linear optical devices whose quality is affected by the growth orientation of Phthalocyanine films. Due to the structural and electrical properties of Phthalocyanine molecules, the film growth orientation depends strongly on the substrate surface states. In this presentation, an electrical field up to 4000 V/cm is introduced during film growth. The Phthalocyanine films are synthesized on quartz substrates using thermal evaporation. An intermediate layer is deposited on some substrates for introducing the electrical field. Scanning electron microscopy, x-ray diffraction, and Fourier transform infrared spectroscopy are used for measuring surface morphology, film structure, and optical properties, respectively. The comparison of Phthalocyanine films grown with and without the electrical field reveals different morphology, film density, and growth orientation, which eventually change optical properties of these films. These results suggest that the growth method in the electrical field can be used to synthesized Phthalocyanine films with a preferred crystal orientation as well as propose an interaction mechanism between the substrate surface and the depositing molecules. The details of growth conditions and of the growth model of how the Phthalocyanine molecules grow in the electrical field will be discussed.

Co-administration of rivaroxaban with drugs that share its elimination pathways: pharmacokinetic effects in healthy subjects

PubMed Central

Mueck, Wolfgang; Kubitza, Dagmar; Becka, Michael

2013-01-01

Aims The anticoagulant rivaroxaban is an oral, direct Factor Xa inhibitor for the management of thromboembolic disorders. Metabolism and excretion involve cytochrome P450 3A4 (CYP3A4) and 2J2 (CYP2J2), CYP-independent mechanisms, and P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) (ABCG2). Methods The pharmacokinetic effects of substrates or inhibitors of CYP3A4, P-gp and Bcrp (ABCG2) on rivaroxaban were studied in healthy volunteers. Results Rivaroxaban did not interact with midazolam (CYP3A4 probe substrate). Exposure to rivaroxaban when co-administered with midazolam was slightly decreased by 11% (95% confidence interval [CI] −28%, 7%) compared with rivaroxaban alone. The following drugs moderately affected rivaroxaban exposure, but not to a clinically relevant extent: erythromycin (moderate CYP3A4/P-gp inhibitor; 34% increase [95% CI 23%, 46%]), clarithromycin (strong CYP3A4/moderate P-gp inhibitor; 54% increase [95% CI 44%, 64%]) and fluconazole (moderate CYP3A4, possible Bcrp [ABCG2] inhibitor; 42% increase [95% CI 29%, 56%]). A significant increase in rivaroxaban exposure was demonstrated with the strong CYP3A4, P-gp/Bcrp (ABCG2) inhibitors (and potential CYP2J2 inhibitors) ketoconazole (158% increase [95% CI 136%, 182%] for a 400 mg once daily dose) and ritonavir (153% increase [95% CI 134%, 174%]). Conclusions Results suggest that rivaroxaban may be co-administered with CYP3A4 and/or P-gp substrates/moderate inhibitors, but not with strong combined CYP3A4, P-gp and Bcrp (ABCG2) inhibitors (mainly comprising azole-antimycotics, apart from fluconazole, and HIV protease inhibitors), which are multi-pathway inhibitors of rivaroxaban clearance and elimination. PMID:23305158

Structure-Function Relationship of a Plant NCS1 Member – Homology Modeling and Mutagenesis Identified Residues Critical for Substrate Specificity of PLUTO, a Nucleobase Transporter from Arabidopsis

PubMed Central

Witz, Sandra; Panwar, Pankaj; Schober, Markus; Deppe, Johannes; Pasha, Farhan Ahmad; Lemieux, M. Joanne; Möhlmann, Torsten

2014-01-01

Plastidic uracil salvage is essential for plant growth and development. So far, PLUTO, the plastidic nucleobase transporter from Arabidopsis thaliana is the only known uracil importer at the inner plastidic membrane which represents the permeability barrier of this organelle. We present the first homology model of PLUTO, the sole plant NCS1 member from Arabidopsis based on the crystal structure of the benzyl hydantoin transporter MHP1 from Microbacterium liquefaciens and validated by molecular dynamics simulations. Polar side chains of residues Glu-227 and backbones of Val-145, Gly-147 and Thr-425 are proposed to form the binding site for the three PLUTO substrates uracil, adenine and guanine. Mutational analysis and competition studies identified Glu-227 as an important residue for uracil and to a lesser extent for guanine transport. A differential response in substrate transport was apparent with PLUTO double mutants E227Q G147Q and E227Q T425A, both of which most strongly affected adenine transport, and in V145A G147Q, which markedly affected guanine transport. These differences could be explained by docking studies, showing that uracil and guanine exhibit a similar binding mode whereas adenine binds deep into the catalytic pocket of PLUTO. Furthermore, competition studies confirmed these results. The present study defines the molecular determinants for PLUTO substrate binding and demonstrates key differences in structure-function relations between PLUTO and other NCS1 family members. PMID:24621654

Structure-function relationship of a plant NCS1 member--homology modeling and mutagenesis identified residues critical for substrate specificity of PLUTO, a nucleobase transporter from Arabidopsis.

PubMed

Witz, Sandra; Panwar, Pankaj; Schober, Markus; Deppe, Johannes; Pasha, Farhan Ahmad; Lemieux, M Joanne; Möhlmann, Torsten

2014-01-01

Plastidic uracil salvage is essential for plant growth and development. So far, PLUTO, the plastidic nucleobase transporter from Arabidopsis thaliana is the only known uracil importer at the inner plastidic membrane which represents the permeability barrier of this organelle. We present the first homology model of PLUTO, the sole plant NCS1 member from Arabidopsis based on the crystal structure of the benzyl hydantoin transporter MHP1 from Microbacterium liquefaciens and validated by molecular dynamics simulations. Polar side chains of residues Glu-227 and backbones of Val-145, Gly-147 and Thr-425 are proposed to form the binding site for the three PLUTO substrates uracil, adenine and guanine. Mutational analysis and competition studies identified Glu-227 as an important residue for uracil and to a lesser extent for guanine transport. A differential response in substrate transport was apparent with PLUTO double mutants E227Q G147Q and E227Q T425A, both of which most strongly affected adenine transport, and in V145A G147Q, which markedly affected guanine transport. These differences could be explained by docking studies, showing that uracil and guanine exhibit a similar binding mode whereas adenine binds deep into the catalytic pocket of PLUTO. Furthermore, competition studies confirmed these results. The present study defines the molecular determinants for PLUTO substrate binding and demonstrates key differences in structure-function relations between PLUTO and other NCS1 family members.

Microbial respiration and kinetics of extracellular enzymes activities through rhizosphere and detritusphere at agricultural site

NASA Astrophysics Data System (ADS)

Löppmann, Sebastian; Blagodatskaya, Evgenia; Kuzyakov, Yakov

2014-05-01

Rhizosphere and detritusphere are soil microsites with very high resource availability for microorganisms affecting their biomass, composition and functions. In the rhizosphere low molecular compounds occur with root exudates and low available polymeric compounds, as belowground plant senescence. In detritusphere the substrate for decomposition is mainly a polymeric material of low availability. We hypothesized that microorganisms adapted to contrasting quality and availability of substrates in the rhizosphere and detritusphere are strongly different in affinity of hydrolytic enzymes responsible for decomposition of organic compounds. According to common ecological principles easily available substrates are quickly consumed by microorganisms with enzymes of low substrate affinity (i.e. r-strategists). The slow-growing K-strategists with enzymes of high substrate affinity are better adapted for growth on substrates of low availability. Estimation of affinity of enzyme systems to the substrate is based on Michaelis-Menten kinetics, reflecting the dependency of decomposition rates on substrate amount. As enzymes-mediated reactions are substrate-dependent, we further hypothesized that the largest differences in hydrolytic activity between the rhizosphere and detritusphere occur at substrate saturation and that these differences are smoothed with increasing limitation of substrate. Affected by substrate limitation, microbial species follow a certain adaptation strategy. To achieve different depth gradients of substrate availability 12 plots on an agricultural field were established in the north-west of Göttingen, Germany: 1) 4 plots planted with maize, reflecting lower substrate availability with depth; 2) 4 unplanted plots with maize litter input (0.8 kg m-2 dry maize residues), corresponding to detritusphere; 3) 4 bare fallow plots as control. Maize litter was grubbed homogenously into the soil at the first 5 cm to ensure comparable conditions for the herbivore and detritivore communities in the soil. The kinetics (Km and Vmax) of four extracellular hydrolytic enzymes responsible for C- and phosphorous-cycle (β-glucosidase, β-xylosidase, β-cellobiohydrolase and acid phosphatase), microbial biomass, basal respiration (BR) and substrate-induced respiration (SIR) were measured in rhizosphere, detritusphere and control from 0 - 10 and 10 - 20 cm. The metabolic quotient (qCO2) was calculated as specific indicator for efficiency of microbial substrate utilization. We observed clear differences in enzymes activities at low and high concentrations of substrate. At substrate saturation enzyme activity rates of were significantly higher in rooted plots compared to litter amended plots, whereas at lower concentration no treatment effect could be found. The BR, SIR and qCO2 values were significantly higher at 0 - 10 cm of the planted treatment compared to litter and control plots, revealing a significantly higher respiration at lower efficiency of microbial substrate utilization in the rhizosphere. The Michaelis-Menten constant (Km) decreased with depth, especially for β-glucosidase, acid phosphatase and β-xylosidase, indicating higher substrate affinity of microorganisms in deeper soil and therefore different enzyme systems functioning. The substrate affinity factor (Vmax/Km) increased 2-fold with depth for various enzymes, reflecting a switch of predominantly occurring microbial strategies. Vmax/Km ratio indicated relative domination of zymogenous microbial communities (r-strategists) in 0 - 10 cm depth as compared with 10 - 20 cm depth where the K-strategists dominated.

Uncovering the Affective Core of Conscientiousness: The Role of Self-Conscious Emotions

PubMed Central

Fayard, Jennifer V.; Roberts, Brent W.; Robins, Richard W.; Watson, David

2013-01-01

We conducted 3 studies to test the idea that guilt is a key affective component of Conscientiousness and that it can account for the relation between Conscientiousness and negative affect. Study 1 used meta-analysis to show that Conscientiousness was associated with specific emotions and overall negative affect but was most strongly associated with guilt. Conscientiousness was negatively related to guilt experience but positively related to guilt proneness. Also, guilt experience mediated the relation between Conscientiousness and negative affect. Study 2 (N = 142) examined the relation between facets of Conscientiousness and guilt. We replicated results from Study 1 and showed that the relation between Conscientiousness and guilt was not due to overlap with Extraversion and Neuroticism. Study 3 (n = 176) examined the interplay between Conscientiousness and guilt on grades in a short-term longitudinal study. These studies showed that Conscientiousness is primarily related to guilt and highlighted the importance of examining the emotional substrate of Conscientiousness. PMID:21241309

Uncovering the affective core of conscientiousness: the role of self-conscious emotions.

PubMed

Fayard, Jennifer V; Roberts, Brent W; Robins, Richard W; Watson, David

2012-02-01

We conducted 3 studies to test the idea that guilt is a key affective component of Conscientiousness and that it can account for the relation between Conscientiousness and negative affect. Study 1 used meta-analysis to show that Conscientiousness was associated with specific emotions and overall negative affect but was most strongly associated with guilt. Conscientiousness was negatively related to guilt experience but positively related to guilt proneness. Also, guilt experience mediated the relation between Conscientiousness and negative affect. Study 2 (N = 142) examined the relation between facets of Conscientiousness and guilt. We replicated results from Study 1 and showed that the relation between Conscientiousness and guilt was not due to overlap with Extraversion and Neuroticism. Study 3 (n = 176) examined the interplay between Conscientiousness and guilt on grades in a short-term longitudinal study. These studies showed that Conscientiousness is primarily related to guilt and highlighted the importance of examining the emotional substrate of Conscientiousness. © 2012 The Authors. Journal of Personality © 2012, Wiley Periodicals, Inc.

Rechargeable lithium/polymer cathode batteries

NASA Astrophysics Data System (ADS)

Osaka, Tetsuya; Nakajima, Toshiki; Shiota, Koh; Owens, Boone B.

1989-06-01

Polypyrrole (PPy) and polyaniline (PAn) were investigated for cathode materials of rechargeable lithium batteries. PPy films prepared with PF6(-) anion and/or platinum substrate precoated with nitrile butadiene rubber (NBR) were excellent cathode materials because of rough and/or highly oriented film structure. PAn films were successfully prepared from non-aqueous propylene carbonate solution containing aniline, CF3COOH and lithium perchlorate. Its acidity strongly affects the anion doping-undoping behavior. The PAn cathode prepared in high acidic solution (e.g., 4:1 ratio of acid:aniline) gives the excellent battery performance.

Wetting properties of molecularly rough surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Svoboda, Martin; Lísal, Martin, E-mail: lisal@icpf.cas.cz; Department of Physics, Institute of Science, J. E. Purkinje University, 400 96 Ústí n. Lab.

2015-09-14

We employ molecular dynamics simulations to study the wettability of nanoscale rough surfaces in systems governed by Lennard-Jones (LJ) interactions. We consider both smooth and molecularly rough planar surfaces. Solid substrates are modeled as a static collection of LJ particles arranged in a face-centered cubic lattice with the (100) surface exposed to the LJ fluid. Molecularly rough solid surfaces are prepared by removing several strips of LJ atoms from the external layers of the substrate, i.e., forming parallel nanogrooves on the surface. We vary the solid-fluid interactions to investigate strongly and weakly wettable surfaces. We determine the wetting properties bymore » measuring the equilibrium droplet profiles that are in turn used to evaluate the contact angles. Macroscopic arguments, such as those leading to Wenzel’s law, suggest that surface roughness always amplifies the wetting properties of a lyophilic surface. However, our results indicate the opposite effect from roughness for microscopically corrugated surfaces, i.e., surface roughness deteriorates the substrate wettability. Adding the roughness to a strongly wettable surface shrinks the surface area wet with the liquid, and it either increases or only marginally affects the contact angle, depending on the degree of liquid adsorption into the nanogrooves. For a weakly wettable surface, the roughness changes the surface character from lyophilic to lyophobic due to a weakening of the solid-fluid interactions by the presence of the nanogrooves and the weaker adsorption of the liquid into the nanogrooves.« less

Spinterface between tris(8-hydroxyquinoline)metal(III) molecules and magnetic surfaces: a first-principles study

NASA Astrophysics Data System (ADS)

Jiang, W.; Wang, Jingying; Dougherty, Daniel; Liu, Feng; Feng Liu Team; Daniel Dougherty Team

Using first-principles calculations, we have systematically investigated the hybridization between tris(8-hydroxyquinoline)metal(III) (Mq3, M = Fe, Cr, Al) molecules and magnetic substrates (Co and Cr). Mq3 with different central metal elements but the same organic framework has dramatically different interaction with different magnetic substrates, which affect the interface state significantly. AFM coupling was observed between magnetic Mq3 molecules and ferromagnetic (Co) as well as antiferromagnetic (Cr) substrate, manifested with a superexchange and direct exchange interaction, respectively. Such strong magnetic interfacial coupling may open a gap around the Fermi level and significantly change interface transport properties. Nonmagnetic Alq3 molecule was found to enhance the interface spin polarization due to hybridization between the lowest unoccupied molecular orbitals (LUMO) of Alq3 and metallic surface state. These findings will help better understand spinterface and shed new light on future application of Mq3 molecules in spintronics devices. This work was support by NSF-MRSEC (DMR-1121252) and DOE-BES (DE-FG02-04ER46148).

High-speed and on-chip graphene blackbody emitters for optical communications by remote heat transfer.

PubMed

Miyoshi, Yusuke; Fukazawa, Yusuke; Amasaka, Yuya; Reckmann, Robin; Yokoi, Tomoya; Ishida, Kazuki; Kawahara, Kenji; Ago, Hiroki; Maki, Hideyuki

2018-03-29

High-speed light emitters integrated on silicon chips can enable novel architectures for silicon-based optoelectronics, such as on-chip optical interconnects, and silicon photonics. However, conventional light sources based on compound semiconductors face major challenges for their integration with a silicon-based platform because of their difficulty of direct growth on a silicon substrate. Here we report ultra-high-speed (100-ps response time), highly integrated graphene-based on-silicon-chip blackbody emitters in the near-infrared region including telecommunication wavelength. Their emission responses are strongly affected by the graphene contact with the substrate depending on the number of graphene layers. The ultra-high-speed emission can be understood by remote quantum thermal transport via surface polar phonons of the substrates. We demonstrated real-time optical communications, integrated two-dimensional array emitters, capped emitters operable in air, and the direct coupling of optical fibers to the emitters. These emitters can open new routes to on-Si-chip, small footprint, and high-speed emitters for highly integrated optoelectronics and silicon photonics.

Efficient surface enhanced Raman scattering on confeito-like gold nanoparticle-adsorbed self-assembled monolayers.

PubMed

Chang, Chia-Chi; Imae, Toyoko; Chen, Liang-Yih; Ujihara, Masaki

2015-12-28

Confeito-like gold nanoparticles (AuNPs; average diameter = 80 nm) exhibiting a plasmon absorption band at 590 nm were adsorbed through immersion-adsorption on two self-assembled monolayers (SAMs) of 3-aminopropyltriethoxysilane (APTES-SAM) and polystyrene spheres coated with amine-terminated poly(amido amine) dendrimers (DEN/PS-SAM). The surface enhanced Raman scattering (SERS) effect on the SAM substrates was examined using the molecules of a probe dye, rhodamine 6G (R6G). The Raman scattering was strongly intensified on both substrates, but the enhancement factor (>10,000) of the AuNP/DEN/PS-SAM hierarchy substrate was 5-10 times higher than that of the AuNP/APTES-SAM substrate. This strong enhancement is attributed to the large surface area of the substrate and the presence of hot spots. Furthermore, analyzing the R6G concentration dependence of SERS suggested that the enhancement mechanism effectively excited the R6G molecules in the first layer on the hot spots and invoked the strong SERS effect. These results indicate that the SERS activity of confeito-like AuNPs on SAM substrates has high potential in molecular electronic devices and ultrasensitive analyses.

Rational design of Raman-labeled nanoparticles for a dual-modality, light scattering immunoassay on a polystyrene substrate.

PubMed

Israelsen, Nathan D; Wooley, Donald; Hanson, Cynthia; Vargis, Elizabeth

2016-01-01

Surface-enhanced Raman scattering (SERS) is a powerful light scattering technique that can be used for sensitive immunoassay development and cell labeling. A major obstacle to using SERS is the complexity of fabricating SERS probes since they require nanoscale characterization and optical uniformity. The light scattering response of SERS probes may also be modulated by the substrate used for SERS analysis. A typical SERS substrate such as quartz can be expensive. Polystyrene is a cheaper substrate option but can decrease the SERS response due to interfering Raman emission peaks and high background fluorescence. The goal of this research is to develop an optimized process for fabricating Raman-labeled nanoparticles for a SERS-based immunoassay on a polystyrene substrate. We have developed a method for fabricating SERS nanoparticle probes for use in a light scattering immunoassay on a polystyrene substrate. The light scattering profile of both spherical gold nanoparticle and gold nanorod SERS probes were characterized using Raman spectroscopy and optical absorbance spectroscopy. The effects of substrate interference and autofluorescence were reduced by selecting a Raman reporter with a strong light scattering response in a spectral region where interfering substrate emission peaks are minimized. Both spherical gold nanoparticles and gold nanorods SERS probes used in the immunoassay were detected at labeling concentrations in the low pM range. This analytical sensitivity falls within the typical dynamic range for direct labeling of cell-surface biomarkers using SERS probes. SERS nanoparticle probes were fabricated to produce a strong light scattering signal despite substrate interference. The optical extinction and inelastic light scattering of these probes was detected by optical absorbance spectroscopy and Raman spectroscopy, respectively. This immunoassay demonstrates the feasibility of analyzing strongly enhanced Raman signals on polystyrene, which is an inexpensive yet non-ideal Raman substrate. The assay sensitivity, which is in the low pM range, suggests that these SERS probe particles could be used for Raman labeling of cell or tissue samples in a polystyrene tissue culture plate. With continued development, this approach could be used for direct labeling of multiple cell surface biomarkers on strongly interfering substrate platforms.

Invasive plant architecture alters trophic interactions by changing predator abundance and behavior.

PubMed

Pearson, Dean E

2009-03-01

As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spotted knapweed (Centaurea maculosa), has fundamentally altered the architecture of native grassland vegetation. Here, I use long-term monitoring, observational studies, and field experiments to document how changes in vegetation architecture have affected native web spider populations and predation rates. Native spiders that use vegetation as web substrates were collectively 38 times more abundant in C. maculosa-invaded grasslands than in uninvaded grasslands. This increase in spider abundance was accompanied by a large shift in web spider community structure, driven primarily by the strong response of Dictyna spiders to C. maculosa invasion. Dictyna densities were 46-74 times higher in C. maculosa-invaded than native grasslands, a pattern that persisted over 6 years of monitoring. C. maculosa also altered Dictyna web building behavior and foraging success. Dictyna webs on C. maculosa were 2.9-4.0 times larger and generated 2.0-2.3 times higher total prey captures than webs on Achillea millefolium, their primary native substrate. Dictyna webs on C. maculosa also captured 4.2 times more large prey items, which are crucial for reproduction. As a result, Dictyna were nearly twice as likely to reproduce on C. maculosa substrates compared to native substrates. The overall outcome of C. maculosa invasion and its transformative effects on vegetation architecture on Dictyna density and web building behavior were to increase Dictyna predation on invertebrate prey >/=89 fold. These results indicate that invasive plants that change the architecture of native vegetation can substantially impact native food webs via nontraditional plant --> predator --> consumer linkages.

Oxygen precipitation and bulk microdefects induced by the pre- and postepitaxial annealing in N/N + (100) silicon wafers

NASA Astrophysics Data System (ADS)

Wijaranakula, W.; Matlock, J. H.; Mollenkopf, H.

1987-12-01

Substrate wafers used for fabrication of epitaxial silicon wafers heavily doped with antimony at the concentration of 1020 atoms/cm3 were preannealed at a temperature between 500 and 900 °C prior to epitaxial deposition. Device fabrication thermal simulation was performed by heat treating the preannealed epitaxial wafers at 1050 °C in dry oxygen ambient for 16 h. Postepitaxial nucleation heat treatment at 750 °C for 4 h prior to the 1050 °C heat treament cycle was also applied on some epitaxial wafers for the purpose of enhancing the oxygen precipitation in silicon. It was observed that morphology and density of the bulk defects induced by the thermal treatment are affected by the preannealing temperature. The results also indicate that nucleation and growth kinetics of oxygen precipitates in preannealed n+ degenerate silicon substrate is strongly governed by oxygen and point defect diffusion.

Growth and characterization of ZnO multipods on functional surfaces with different sizes and shapes of Ag particles

NASA Astrophysics Data System (ADS)

A, Kamalianfar; S, A. Halim; Mahmoud Godarz, Naseri; M, Navasery; Fasih, Ud Din; J, A. M. Zahedi; Kasra, Behzad; K, P. Lim; A Lavari, Monghadam; S, K. Chen

2013-08-01

Three-dimensional ZnO multipods are successfully synthesized on functional substrates using the vapor transport method in a quartz tube. The functional surfaces, which include two different distributions of Ag nanoparticles and a layer of commercial Ag nanowires, are coated onto silicon substrates before the growth of ZnO nanostructures. The structures and morphologies of the ZnO/Ag heterostructures are investigated using X-ray diffraction and field emission scanning electron microscopy. The sizes and shapes of the Ag particles affect the growth rates and initial nucleations of the ZnO structures, resulting in different numbers and shapes of multipods. They also influence the orientation and growth quality of the rods. The optical properties are studied by photoluminescence, UV-vis, and Raman spectroscopy. The results indicate that the surface plasmon resonance strongly depends on the sizes and shapes of the Ag particles.

Pulsed laser deposition of niobium nitride thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farha, Ashraf Hassan, E-mail: ahass006@odu.edu; Elsayed-Ali, Hani E., E-mail: helsayed@odu.edu; Applied Research Center, Jefferson National Accelerator Facility, Newport News, VA 23606

2015-12-04

Niobium nitride (NbN{sub x}) films were grown on Nb and Si(100) substrates using pulsed laser deposition. NbN{sub x} films were deposited on Nb substrates using PLD with a Q-switched Nd:YAG laser (λ = 1064 nm, ∼40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, nitrogen background pressures and deposition substrate temperatures. When all the fabrication parameters are fixed, except for the laser fluence, the surface roughness, nitrogen content, and grain size increase with increasing laser fluence. Increasing nitrogen background pressure leads to a change in the phase structure of the NbN{sub x} films from mixed β-Nb{sub 2}N and cubicmore » δ-NbN phases to single hexagonal β-Nb{sub 2}N. The substrate temperature affects the preferred orientation of the crystal structure. The structural and electronic, properties of NbN{sub x} deposited on Si(100) were also investigated. The NbN{sub x} films exhibited a cubic δ-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The observations establish guidelines for adjusting the deposition parameters to achieve the desired NbN{sub x} film morphology and phase.« less

Stokes flow inside an evaporating liquid line for any contact angle

NASA Astrophysics Data System (ADS)

Petsi, A. J.; Burganos, V. N.

2008-09-01

Evaporation of droplets or liquid films lying on a substrate induces internal viscous flow, which affects the transport of suspended particles and, thus, the final deposit profile in numerous applications. In this work, the problem of Stokes flow inside a two-dimensional droplet, representing the cross section of an evaporating liquid line lying on a flat surface, is considered. The stream function formulation is adopted, leading to the biharmonic equation in bipolar coordinates. A solution in closed form is obtained for any contact angle in (0,π) and is, thus, valid for both hydrophilic and hydrophobic substrates. The solution can be used with any type of evaporation mechanism, including diffusion, convection, or kinetically controlled modes. Both pinned and depinned contact lines are considered. For the boundary conditions to be compatible at the contact lines, the Navier slip boundary condition is applied on the substrate. Numerical results are presented for kinetically and diffusion controlled evaporation. For pinned contact lines, the flow inside the evaporating liquid line is directed towards the edges, thus, promoting the coffee stain phenomenon. In the case of depinned contact lines and contact angle less than π/2 , the flow is directed towards the center of the droplet, whereas, for strongly hydrophobic substrates it is directed outwards.

Cysteine Scanning Mutagenesis of Transmembrane Domain 10 in Organic Anion Transporting Polypeptide 1B1

PubMed Central

2015-01-01

Organic anion transporting polypeptide (OATP) 1B1 is an important drug transporter expressed in human hepatocytes. Previous studies have indicated that transmembrane (TM) domain 2, 6, 8, 9, and in particular 10 might be part of the substrate binding site/translocation pathway. To explore which amino acids in TM10 are important for substrate transport, we mutated 34 amino acids individually to cysteines, expressed them in HEK293 cells, and determined their surface expression. Transport activity of the two model substrates estrone-3-sulfate and estradiol-17β-glucuronide as well as of the drug substrate valsartan for selected mutants was measured. Except for F534C and F537C, all mutants were expressed at the plasma membrane of HEK293 cells. Mutants Q541C and A549C did not transport estradiol-17β-glucuronide and showed negligible estrone-3-sulfate transport. However, A549C showed normal valsartan transport. Pretreatment with the anionic and cell impermeable sodium (2-sulfonatoethyl)methanethiosulfonate (MTSES) affected the transport of each substrate differently. Pretreatment of L545C abolished estrone-3-sulfate uptake almost completely, while it stimulated estradiol-17β-glucuronide uptake. Further analyses revealed that mutant L545C in the absence of MTSES showed biphasic kinetics for estrone-3-sulfate that was converted to monophasic kinetics with a decreased apparent affinity, explaining the previously seen inhibition. In contrast, the apparent affinity for estradiol-17β-glucuronide was not changed by MTSES treatment, but the Vmax value was increased about 4-fold, explaining the previously seen stimulation. Maleimide labeling of L545C was affected by preincubation with estrone-3-sulfate but not with estradiol-17β-glucuronide. These results strongly suggest that L545C is part of the estrone-3-sulfate binding site/translocation pathway but is not directly involved in binding/translocation of estradiol-17β-glucuronide. PMID:24673529

DICER-ARGONAUTE2 Complex in Continuous Fluorogenic Assays of RNA Interference Enzymes

PubMed Central

Bernard, Mark A.; Wang, Leyu; Tachado, Souvenir D.

2015-01-01

Mechanistic studies of RNA processing in the RNA-Induced Silencing Complex (RISC) have been hindered by lack of methods for continuous monitoring of enzymatic activity. “Quencherless” fluorogenic substrates of RNAi enzymes enable continuous monitoring of enzymatic reactions for detailed kinetics studies. Recombinant RISC enzymes cleave the fluorogenic substrates targeting human thymidylate synthase (TYMS) and hypoxia-inducible factor 1-α subunit (HIF1A). Using fluorogenic dsRNA DICER substrates and fluorogenic siRNA, DICER+ARGONAUTE2 mixtures exhibit synergistic enzymatic activity relative to either enzyme alone, and addition of TRBP does not enhance the apparent activity. Titration of AGO2 and DICER in enzyme assays suggests that AGO2 and DICER form a functional high-affinity complex in equimolar ratio. DICER and DICER+AGO2 exhibit Michaelis-Menten kinetics with DICER substrates. However, AGO2 cannot process the fluorogenic siRNA without DICER enzyme, suggesting that AGO2 cannot self-load siRNA into its active site. The DICER+AGO2 combination processes the fluorogenic siRNA substrate (K m=74 nM) with substrate inhibition kinetics (K i=105 nM), demonstrating experimentally that siRNA binds two different sites that affect Dicing and AGO2-loading reactions in RISC. This result suggests that siRNA (product of DICER) bound in the active site of DICER may undergo direct transfer (as AGO2 substrate) to the active site of AGO2 in the DICER+AGO2 complex. Competitive substrate assays indicate that DICER+AGO2 cleavage of fluorogenic siRNA is specific, since unlabeled siRNA and DICER substrates serve as competing substrates that cause a concentration-dependent decrease in fluorescent rates. Competitive substrate assays of a series of DICER substrates in vitro were correlated with cell-based assays of HIF1A mRNA knockdown (log-log slope=0.29), suggesting that improved DICER substrate designs with 10-fold greater processing by the DICER+AGO2 complex can provide a strong (~2800-fold) improvement in potency for mRNA knockdown. This study lays the foundation of a systematic biochemical approach to optimize nucleic acid-based therapeutics for Dicing and ARGONAUTE2-loading for improving efficacy. PMID:25793518

Physical, chemical, and biological characteristics of the Boise River from Veterans Memorial Parkway, Boise to Star, Idaho, October 1987 to March 1988

USGS Publications Warehouse

Frenzel, S.A.

1988-01-01

Physical, chemical, and biological characteristics of the Boise River were examined from October 1987 to March 1988 to determine whether trace elements in effluents from two Boise wastewater treatment facilities were detrimental to aquatic communities. Cadmium, chromium, hexavalent chromium, cyanide, lead, nickel, and silver concentrations in the Boise River were less than or near analytical detection levels and were less than chronic toxicity criteria when detectable. Arsenic, copper, and zinc were detected in concentrations less than chronic toxicity criteria. Concentrations of trace elements in bottom material generally were small and could not be attributed to effluents from wastewater treatment facilities. From October to December 1987, mean density of benthic invertebrates colonizing artificial substrates was from 6,100 individuals/substrate downstream from the West Boise wastewater treatment facility to 14,000 individuals per substrate downstream from the Lander Street wastewater treatment facility. From January to March 1988 , mean density of benthic invertebrates colonizing artificial substrates was from 7,100 individuals per substrate downstream from the West Boise facility to 10,000 individuals per substrate near Star. Insect communities upstream and downstream from the wastewater treatment facilities were strongly associated, and coeffients of community loss indicated that effluents had benign enriching effects. Distribution of mayflies indicates that trace-element concentrations in effluents did not adversely affect intolerant organisms in the Boise River. Condition factor of whitefish was significantly increased downstream from the Lander Street wastewater treatment facility and was significantly decreased downstream from the West Boise wastewater treatment facility.

Acetoacetate is a more efficient energy-yielding substrate for human mesenchymal stem cells than glucose and generates fewer reactive oxygen species.

PubMed

Board, Mary; Lopez, Colleen; van den Bos, Christian; Callaghan, Richard; Clarke, Kieran; Carr, Carolyn

2017-07-01

Stem cells have been assumed to demonstrate a reliance on anaerobic energy generation, suited to their hypoxic in vivo environment. However, we found that human mesenchymal stem cells (hMSCs) have an active oxidative metabolism with a range of substrates. More ATP was consistently produced from substrate oxidation than glycolysis by cultured hMSCs. Strong substrate preferences were shown with the ketone body, acetoacetate, being oxidised at up to 35 times the rate of glucose. ROS-generation was 45-fold lower during acetoacetate oxidation compared with glucose and substrate preference may be an adaptation to reduce oxidative stress. The UCP2 inhibitor, genipin, increased ROS production with either acetoacetate or glucose by 2-fold, indicating a role for UCP2 in suppressing ROS production. Addition of pyruvate stimulated acetoacetate oxidation and this combination increased ATP production 27-fold, compared with glucose alone, which has implications for growth medium composition. Oxygen tension during culture affected metabolism by hMSCs. Between passages 2 and 5, rates of both glycolysis and substrate-oxidation increased at least 2-fold for normoxic (20% O 2 )- but not hypoxic (5% O 2 )-cultured hMSCs, despite declining growth rates and no detectable signs of differentiation. Culture of the cells with 3-hydroxybutyrate abolished the increased rates of these pathways. These findings have implications for stem cell therapy, which necessarily involves in vitro culture of cells, since low passage number normoxic cultured stem cells show metabolic adaptations without detectable changes in stem-like status. Copyright © 2017. Published by Elsevier Ltd.

Accelerating bioelectric functional development of neural stem cells by graphene coupling: Implications for neural interfacing with conductive materials.

PubMed

Guo, Rongrong; Zhang, Shasha; Xiao, Miao; Qian, Fuping; He, Zuhong; Li, Dan; Zhang, Xiaoli; Li, Huawei; Yang, Xiaowei; Wang, Ming; Chai, Renjie; Tang, Mingliang

2016-11-01

In order to govern cell-specific behaviors in tissue engineering for neural repair and regeneration, a better understanding of material-cell interactions, especially the bioelectric functions, is extremely important. Graphene has been reported to be a potential candidate for use as a scaffold and neural interfacing material. However, the bioelectric evolvement of cell membranes on these conductive graphene substrates remains largely uninvestigated. In this study, we used a neural stem cell (NSC) model to explore the possible changes in membrane bioelectric properties - including resting membrane potentials and action potentials - and cell behaviors on graphene films under both proliferation and differentiation conditions. We used a combination of single-cell electrophysiological recordings and traditional cell biology techniques. Graphene did not affect the basic membrane electrical parameters (capacitance and input resistance), but resting membrane potentials of cells on graphene substrates were more strongly negative under both proliferation and differentiation conditions. Also, NSCs and their progeny on graphene substrates exhibited increased firing of action potentials during development compared to controls. However, graphene only slightly affected the electric characterizations of mature NSC progeny. The modulation of passive and active bioelectric properties on the graphene substrate was accompanied by enhanced NSC differentiation. Furthermore, spine density, synapse proteins expressions and synaptic activity were all increased in graphene group. Modeling of the electric field on conductive graphene substrates suggests that the electric field produced by the electronegative cell membrane is much higher on graphene substrates than that on control, and this might explain the observed changes of bioelectric development by graphene coupling. Our results indicate that graphene is able to accelerate NSC maturation during development, especially with regard to bioelectric evolvement. Our findings provide a fundamental understanding of the role of conductive materials in tuning the membrane bioelectric properties in a graphene model and pave the way for future studies on the development of methods and materials for manipulating membrane properties in a controllable way for NSC-based therapies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesis of Hexagonal Boron Nitride Mono layer: Control of Nucleation and Crystal Morphology

DOE PAGES

Stehle, Yijing Y.; Meyer, III, Harry M.; Unocic, Raymond R.; ...

2015-11-10

Mono layer hexagonal boron nitride (hBN) attracts significant attention due to the potential to be used as a complementary two-dimensional dielectric in fabrication of functional 2D heterostructures. Here we investigate the growth stages of the hBN single crystals and show that hBN crystals change their shape from triangular to truncated triangular and further to hexagonal depending on copper substrate distance from the precursor. We suggest that the observed hBN crystal shape variation is affected by the ratio of boron to nitrogen active species concentrations on the copper surface inside the CVD reactor. Strong temperature dependence reveals the activation energies formore » the hBN nucleation process of similar to 5 eV and crystal growth of similar to 3.5 eV. We also show that the resulting h-BN film morphology is strongly affected by the heating method of borazane precursor and the buffer gas. Elucidation of these details facilitated synthesis of high quality large area monolayer hexagonal boron nitride by atmospheric pressure chemical vapor deposition on copper using borazane as a precursor.« less

Direct Observation of Asphaltene Nanoparticles on Model Mineral Substrates.

PubMed

Raj, Gijo; Lesimple, Alain; Whelan, Jamie; Naumov, Panče

2017-06-27

The propensity for adherence to solid surfaces of asphaltenes, a complex solubility class of heteropolycyclic aromatic compounds from the heavy fraction of crude oil, has long been the root cause of scale deposition and remains an intractable problem in the petroleum industry. Although the adhesion is essential to understanding the process of asphaltene deposition, the relationship between the conformation of asphaltene molecules on mineral substrates and its impact on adhesion and mechanical properties of the deposits is not completely understood. To rationalize the primary processes in the process of organic scale deposition, here we use atomic force microscopy (AFM) to visualize the morphology of petroleum asphaltenes deposited on model mineral substrates. High imaging contrast was achieved by the differential adhesion of the tip between asphaltenes and the mineral substrate. While asphaltenes form smooth continuous films on all substrates at higher concentrations, they deposit as individual nanoparticles at lower concentrations. The size, shape, and spatial distribution of the nanoaggregates are strongly affected by the nature of the substrate; while uniformly distributed spherical particles are formed on highly polar and hydrophilic substrates (mica), irregular islands and thicker patches are observed with substrates of lower polarity (silica and calcite). Asphaltene nanoparticles flatten when adsorbed on highly oriented pyrolytic graphite due to π-π interactions with the polycyclic core. Force-distance profiles provide direct evidence of the conformational changes of asphaltene molecules on hydrophilic/hydrophobic substrates that result in dramatic changes in adhesion and mechanical properties of asphaltene deposits. Such an understanding of the nature of adhesion and mechanical properties tuned by surface properties, on the level of asphaltene nanoaggregates, would contribute to the design of efficient asphaltene inhibitors for preventing asphaltene fouling on targeted surfaces. Unlike flat surfaces, the AFM phase contrast images of defected calcite surfaces show that asphaltenes form continuous deposits to fill the recesses, and this process could trigger the onset for asphaltene deposition.

New insights gained on mechanisms of low-energy proton-induced SEUs by minimizing energy straggle

DOE PAGES

Dodds, Nathaniel Anson; Dodd, Paul E.; Shaneyfelt, Marty R.; ...

2015-12-01

In this study, we present low-energy proton single-event upset (SEU) data on a 65 nm SOI SRAM whose substrate has been completely removed. Since the protons only had to penetrate a very thin buried oxide layer, these measurements were affected by far less energy loss, energy straggle, flux attrition, and angular scattering than previous datasets. The minimization of these common sources of experimental interference allows more direct interpretation of the data and deeper insight into SEU mechanisms. The results show a strong angular dependence, demonstrate that energy straggle, flux attrition, and angular scattering affect the measured SEU cross sections, andmore » prove that proton direct ionization is the dominant mechanism for low-energy proton-induced SEUs in these circuits.« less

Pinus sylvestris switches respiration substrates under shading but not during drought

NASA Astrophysics Data System (ADS)

Hartmann, Henrik; Fischer, Sarah; Hanf, Stefan; Frosch, Torsten; Poppp, Jürgen; Trumbore, Susan

2015-04-01

Reduced carbon assimilation during prolonged drought forces trees to rely on stored carbon to maintain vital processes like respiration. It has been shown, however, that the use of carbohydrates, a major carbon storage pool and main respiratory substrate in plants, strongly declines with deceasing plant hydration. Yet, no empirical evidence has been produced to what degree other carbon storage compounds like lipids and proteins may fuel respiration during drought. We exposed young scots pine trees to carbon limitation using either drought or shading and assessed respiratory substrate use by monitoring the respiratory quotient, δ13C of respired CO2and concentrations of the major storage compounds, i.e. carbohydrates (COH), lipids and amino acids. Generally, respiration was dominated by the most abundant substrate. Only shaded trees shifted from carbohydrate-dominated to lipid-dominated respiration and showed progressive carbohydrate depletion. In drought trees respiration was strongly reduced and fueled with carbohydrates from also strongly reduced carbon assimilation. Initial COH content was maintained during drought probably due to reduced COH mobilization and use and the maintained COH content may have prevented lipid catabolism via sugar signaling. Our results suggest that respiratory substrates other than carbohydrates are used under carbohydrate limitation but not during drought. Thus, respiratory substrate change cannot provide an efficient means to counterbalance carbon limitation under natural drought.

Effects of substrate misorientation and growth rate on ordering in GaInP

NASA Astrophysics Data System (ADS)

Su, L. C.; Ho, I. H.; Stringfellow, G. B.

1994-05-01

Epitaxial layers of GaxIn1-xP with x≊0.52 have been grown by organometallic vapor-phase epitaxy on GaAs substrates misoriented from the (001) plane in the [1¯10] direction by angles ϑm, of 0°, 3°, 6°, and 9°. For each substrate orientation growth rates rg of 1, 2, and 4 μm/h have been used. The ordering was characterized using transmission electron diffraction (TED), dark-field imaging, and photoluminescence. The (110) cross-sectional images show domains of the Cu-Pt structure separated by antiphase boundaries (APBs). The domain size and shape and the degree of order are found to be strongly affected by both the substrate misorientation and the growth rate. For example, lateral domain dimensions range from 50 Å for layers grown with rg=4 μm/h and ϑm=0° to 2500 Å for rg=1 μm/h and ϑm=9°. The APBs generally propagate from the substrate/epilayer interface to the top surface at an angle to the (001) plane that increases dramatically as the angle of misorientation increases. The angle is nearly independent of growth rate. From the superspot intensities in the TED patterns, the degree of order appears to be a maximum for ϑm≊5°. Judging from the reduction in photoluminescence peak energy caused by ordering, the maximum degree of order appears to occur at ϑm≊4°.

Arbuscular Mycorrhiza Alleviates Restrictions to Substrate Water Flow and Delays Transpiration Limitation to Stronger Drought in Tomato.

PubMed

Bitterlich, Michael; Sandmann, Martin; Graefe, Jan

2018-01-01

Arbuscular mycorrhizal fungi (AMF) proliferate in soil pores, on the surface of soil particles and affect soil structure. Although modifications in substrate moisture retention depend on structure and could influence plant water extraction, mycorrhizal impacts on water retention and hydraulic conductivity were rarely quantified. Hence, we asked whether inoculation with AMF affects substrate water retention, water transport properties and at which drought intensity those factors become limiting for plant transpiration. Solanum lycopersicum plants were set up in the glasshouse, inoculated or not with Funneliformis mosseae , and grown for 35 days under ample water supply. After mycorrhizal establishment, we harvested three sets of plants, one before (36 days after inoculation) and the second (day 42) and third (day 47) within a sequential drying episode. Sampling cores were introduced into pots before planting. After harvest, moisture retention and substrate conductivity properties were assessed and water retention and hydraulic conductivity models were fitted. A root water uptake model was adopted in order to identify the critical substrate moisture that induces soil derived transpiration limitation. Neither substrate porosity nor saturated water contents were affected by inoculation, but both declined after substrates dried. Drying also caused a decline in pot water capacity and hydraulic conductivity. Plant available water contents under wet (pF 1.8-4.2) and dry (pF 2.5-4.2) conditions increased in mycorrhizal substrates and were conserved after drying. Substrate hydraulic conductivity was higher in mycorrhizal pots before and during drought exposure. After withholding water from pots, higher substrate drying rates and lower substrate water potentials were found in mycorrhizal substrates. Mycorrhiza neither affected leaf area nor root weight or length. Consistently with higher substrate drying rates, AMF restored the plant hydraulic status, and increased plant transpiration when soil moisture declined. The water potential at the root surface and the resistance to water flow in the rhizosphere were restored in mycorrhizal pots although the bulk substrate dried more. Finally, substrates colonized by AMF can be more desiccated before substrate water flux quantitatively limits transpiration. This is most pronounced under high transpiration demands and complies with a difference of over 1,000 hPa in substrate water potential.

Structural paradox in submonolayer chlorine coverage on Au(111)

NASA Astrophysics Data System (ADS)

Zheltov, V. V.; Cherkez, V. V.; Andryushechkin, B. V.; Zhidomirov, G. M.; Kierren, B.; Fagot-Revurat, Y.; Malterre, D.; Eltsov, K. N.

2014-05-01

In this work, we present a combined low-temperature scanning tunneling microscopy (STM) and density functional theory (DFT) study of chlorine adsorption on Au(111) at low coverages. Our STM study of Cl/Au(111) system has shown that at submonolayer coverages (θ < 0.1 ML) chlorine atoms form chainlike structures with abnormally short distances of 3.8 Å between them. Our DFT calculations have shown that chlorine atoms can interact with each other through distortion of the substrate and this indirect elastic interaction is strong enough to affect their arrangement in the chainlike structures.

Decreases in activation energy and substrate affinity in cold-adapted A4-lactate dehydrogenase: evidence from the Antarctic notothenioid fish Chaenocephalus aceratus.

PubMed

Fields, Peter A; Houseman, Daniel E

2004-12-01

Enzyme function is strongly affected by temperature, and orthologs from species adapted to different thermal environments often show temperature compensation in kinetic properties. Antarctic notothenioid fishes live in a habitat of constant, extreme cold (-1.86 +/- 2 degrees C), and orthologs of the enzyme A4-lactate dehydrogenase (A4-LDH) in these species have adapted to this environment through higher catalytic rates, lower Arrhenius activation energies (Ea), and increases in the apparent Michaelis constant for the substrate pyruvate (Km(PYR)). Here, site-directed mutagenesis was used to determine which amino acid substitutions found in A4-LDH of the notothenioid Chaenocephalus aceratus, with respect to orthologs from warm-adapted teleosts, are responsible for these adaptive changes in enzyme function. Km(PYR) was measured in eight single and two double mutants, and Ea was tested in five single and two double mutants in the temperature range 0 degrees C-20 degrees C. Of the four mutants that had an effect on these parameters, two increased Ea but did not affect Km(PYR) (Gly224Ser, Ala310Pro), and two increased both Ea and Km(PYR) (Glu233Met, Gln317Val). The double mutants Glu233Met/Ala310Pro and Glu233Met/Gln317Val increased Km(PYR) and Ea to levels not significantly different from the A4-LDH of a warm temperate fish (Gillichthys mirabilis, habitat temperature 10 degrees C-35 degrees C). The four single mutants are associated with two alpha-helices that move during the catalytic cycle; those that affect Ea but not Km(PYR) are further from the active site than those that affect both parameters. These results provide evidence that (1) cold adaptation in A4-LDH involves changes in mobility of catalytically important molecular structures; (2) these changes may alter activation energy alone or activation energy and substrate affinity together; and (3) the extent to which these parameters are affected may depend on the location of the substitutions within the mobile alpha-helices, perhaps due to differences in proximity to the active site.

Abiotic Factors Affecting Benthic Invertebrate Biomass and Community Structure in a Fourth-Order Rocky Mountain Watershed

NASA Astrophysics Data System (ADS)

Chanat, J. G.; Clements, W. H.; MacDonald, L. H.

2005-05-01

The potential ecological impact of excess streambed sediment resulting from forest management activities is a persistent concern for land managers. This study examined the relationship between streambed sediment, along with other site- and reach-scale abiotic factors, and benthic macroinvertebrate community structure in a 272 km2 basin in the Colorado Front Range. Physical habitat parameters and invertebrates were sampled in late summer at 68 sites located in sixteen stream reaches. Invertebrate data were used to formulate twenty indices of community structure. Multiple regression identified site-level substrate particle size as the most important predictor of six indices, including total density (R2 = 0.22), biomass (R2 = 0.17), and taxa richness (R2 = 0.32). All of the remaining fourteen indices were most strongly predicted by reach-level variables, including discharge (percent shredders, R2 = 0.24; Plecoptera density, R2 = 0.29), and elevation (percent collector-filterers, R2 = 0.28; Trichoptera density, R2 = 0.37). Although the sites represented a wide range of substrate composition and embeddedness, no physical variable associated with fine sediment appeared as a strong predictor of any of the twenty indices. Thus, sediment is not among the most important factors associated with site-to-site variability of benthic community structure in this relatively pristine watershed.

Highly sensitive optically controlled tunable capacitor and photodetector based on a metal-insulator-semiconductor on silicon-on-insulator substrates

NASA Astrophysics Data System (ADS)

Mikhelashvili, V.; Cristea, D.; Meyler, B.; Yofis, S.; Shneider, Y.; Atiya, G.; Cohen-Hyams, T.; Kauffmann, Y.; Kaplan, W. D.; Eisenstein, G.

2015-01-01

We describe a new type of optically sensitive tunable capacitor with a wide band response ranging from the ultraviolet (245 nm) to the near infrared (880 nm). It is based on a planar Metal-Oxide-Semiconductor (MOS) structure fabricated on an insulator on silicon substrate where the insulator layer comprises a double layer dielectric stack of SiO2-HfO2. Two operating configurations have been examined, a single diode and a pair of back-to-back connected devices, where either one or both diodes are illuminated. The varactors exhibit, in all cases, very large sensitivities to illumination. Near zero bias, the capacitance dependence on illumination intensity is sub linear and otherwise it is nearly linear. In the back-to-back connected configuration, the reverse biased diode acts as a light tunable resistor whose value affects strongly the capacitance of the second, forward biased, diode and vice versa. The proposed device is superior to other optical varactors in its large sensitivity to illumination in a very broad wavelength range (245 nm-880 nm), the strong capacitance dependence on voltage and the superior current photo responsivity. Above and beyond that structure requires a very simple fabrication process which is CMOS compatible.

Initial substrate moisture content and storage temperature affects chemical properties of bagged substrates containing controlled release fertilizer at two different temperatures

USDA-ARS?s Scientific Manuscript database

Bagged potting mixes can be stored for weeks or months before being used by consumers. Some bagged potting mixes are amended with controlled release fertilizers (CRF). The objective of this research was to observe how initial substrate moisture content and storage temperature affect the chemical p...

Affective agnosia: Expansion of the alexithymia construct and a new opportunity to integrate and extend Freud's legacy.

PubMed

Lane, Richard D; Weihs, Karen L; Herring, Anne; Hishaw, Alex; Smith, Ryan

2015-08-01

We describe a new type of agnosia consisting of an impairment in the ability to mentally represent or know what one is feeling. Freud the neurologist coined the term "agnosia" in 1891 before creating psychoanalysis in 1895 but the term has not been previously applied to the domain of affective processing. We propose that the concept of "affective agnosia" advances the theory, measurement and treatment of what is now called "alexithymia," meaning "lack of words for emotion." We trace the origin of the alexithymia construct and discuss the strengths and limitations of extant research. We review evidence that the ability to represent and put emotions into words is a developmental achievement that strongly influences one's ability to experience, recognize, understand and use one's own emotional responses. We describe the neural substrates of emotional awareness and affective agnosia and compare and contrast these with related conditions. We then describe how this expansion of the conceptualization and measurement of affective processing deficits has important implications for basic emotion research and clinical practice. Copyright © 2015 Elsevier Ltd. All rights reserved.

A novel assay of DGAT activity based on high temperature GC/MS of triacylglycerol.

PubMed

Greer, Michael S; Zhou, Ting; Weselake, Randall J

2014-08-01

Diacylglycerol acyltransferase (DGAT) catalyzes the final step in the acyl-CoA-dependent biosynthesis of triacylglycerol (TAG), a high-energy compound composed of three fatty acids esterified to a glycerol backbone. In vitro DGAT assays, which are usually conducted with radiolabeled substrate using microsomal fractions, have been useful in identifying compounds and genetic modifications that affect DGAT activity. Here, we describe a high-temperature gas chromatography (GC)/mass spectrometry (MS)-based method for monitoring molecular species of TAG produced by the catalytic action of microsomal DGAT. This method circumvents the need for radiolabeled or modified substrates, and only requires a simple lipid extraction prior to GC. The utility of the method is demonstrated using a recombinant type-1 Brassica napus DGAT produced in a strain of Saccharomyces cerevisae that is deficient in TAG synthesis. The GC/MS-based assay of DGAT activity was strongly correlated with the typical in vitro assay of the enzyme using [1-(14)C] acyl-CoA as an acyl donor. In addition to determining DGAT activity, the method is also useful for determining substrate specificity and selectivity properties of the enzyme.

A multidisciplinary approach to study the functional properties of neuron-like cell models constituting a living bio-hybrid system: SH-SY5Y cells adhering to PANI substrate

NASA Astrophysics Data System (ADS)

Caponi, S.; Mattana, S.; Ricci, M.; Sagini, K.; Juarez-Hernandez, L. J.; Jimenez-Garduño, A. M.; Cornella, N.; Pasquardini, L.; Urbanelli, L.; Sassi, P.; Morresi, A.; Emiliani, C.; Fioretto, D.; Dalla Serra, M.; Pederzolli, C.; Iannotta, S.; Macchi, P.; Musio, C.

2016-11-01

A living bio-hybrid system has been successfully implemented. It is constituted by neuroblastic cells, the SH-SY5Y human neuroblastoma cells, adhering to a poly-anyline (PANI) a semiconductor polymer with memristive properties. By a multidisciplinary approach, the biocompatibility of the substrate has been analyzed and the functionality of the adhering cells has been investigated. We found that the PANI films can support the cell adhesion. Moreover, the SH-SY5Y cells were successfully differentiated into neuron-like cells for in vitro applications demonstrating that PANI can also promote cell differentiation. In order to deeply characterize the modifications of the bio-functionality induced by the cell-substrate interaction, the functional properties of the cells have been characterized by electrophysiology and Raman spectroscopy. Our results confirm that the PANI films do not strongly affect the general properties of the cells, ensuring their viability without toxic effects on their physiology. Ascribed to the adhesion process, however, a slight increase of the markers of the cell suffering has been evidenced by Raman spectroscopy and accordingly the electrophysiology shows a reduction at positive stimulations in the cells excitability.

Analysis of five rice 4-coumarate:coenzyme A ligase enzyme activity and stress response for potential roles in lignin and flavonoid biosynthesis in rice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Haiyan; Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan 430070; College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070

Highlights: ► 4CLs play important roles in both lignin and flavonoids biosynthesis. ► PA and FA are the two main substrates of 4CL (Os4CL1/3/4/5) for lignin biosynthesis. ► Os4CL2 is suggested for flavonoid formation in defense against UV radiation. -- Abstract: 4-Coumarate:coenzyme A ligase (4CL) catalyzes the conversion of hydroxycinnamates into corresponding CoA esters for biosynthesis of flavonoids and lignin. In this study, five members of the 4CL gene family from rice were cloned and analyzed. Recombinant 4CL data revealed that 4-coumaric acid and ferulic acid were the two main substrates of 4CL (Os4CL1/3/4/5) for monolignol biosynthesis in rice. Os4CL2more » was specifically expressed in the anther and was strongly activated by UV irradiation, suggesting its potential involvement in flavonoid formation. Moreover, bioinformatics analysis showed that the existence of valine residue at the substrate-binding pocket may mainly affect rice 4CL activities toward sinapic acid.« less

Co-biodegradation of anthracene and naphthalene by the bacterium Acinetobacter johnsonii.

PubMed

Jiang, Yan; Qi, Hui; Zhang, Xian M

2018-04-16

NAP (Naphthalene) and ANT (anthracene) usually co-exist in environment and possessed interactional effects on their biodegradation in environment. Presently, a strain of Acinetobacter johnsonii was employed to degrade NAP and ANT in single- and dual-substrate systems. NAP was utilized as prefer substrate by cells to accelerate ANT biodegradation. As much as 200 mg L -1 ANT could be entirely degraded with 1,500 mg L -1 NAP, which was beyond bacterial potential in single substrate system. Especially, the shortest biodegradation period (103 h) for ANT was observed with the presence of 50 mg L -1 NAP. By contrast, ANT showed strong inhibition on NAP degradation, while the peak biodegradation of 1,950 mg L -1 NAP with 50 mg L -1 ANT could still proceed. By introducing an inhibition constant parameter to fit the inhibition on cells, modeling indicated the substrate inhibition for NAP and ANT over the concentrations of 174 and 49 mg L -1 , respectively. Furthermore, enzyme assay revealed the pathway of meta fission in NAP biodegradation due to the appearance of catechol 2,3-dioxygenase activity, and low-level lipase excretion was also found in both NAP and ANT biodegradation, but hardly affect NAP and ANT biodegradation in the present study. To research the interplay of NAP and ANT is conducive to targeted decontamination.

Strong Surface Diffusion Mediated Glancing-Angle Deposition: Growth, Recrystallization and Reorientation of Tin Nanorods

NASA Astrophysics Data System (ADS)

Wang, Huan-Hua; Shi, Yi-Jian; William, Chu; Yigal, Blum

2008-01-01

Different from usual glancing-angle deposition where low surface diffusion is necessary to form nanorods, strong surface diffusion mediated glancing-angle deposition is exemplified by growing tin nanorod films on both silicon and glass substrates simultaneously via thermal evaporation. During growth, the nanorods were simultaneously baked by the high-temperature evaporator, and therefore re-crystallized into single crystals in consequence of strong surface diffusion. The monocrystalline tin nanorods have a preferred orientation perpendicular to the substrate surface, which is quite different from the usual uniformly oblique nanorods without recrystallization.

Surface Effects and Challenges for Application of Piezoelectric Langasite Substrates in Surface Acoustic Wave Devices Caused by High Temperature Annealing under High Vacuum.

PubMed

Seifert, Marietta; Rane, Gayatri K; Kirbus, Benjamin; Menzel, Siegfried B; Gemming, Thomas

2015-12-19

Substrate materials that are high-temperature stable are essential for sensor devices which are applied at high temperatures. Although langasite is suggested as such a material, severe O and Ga diffusion into an O-affine deposited film was observed during annealing at high temperatures under vacuum conditions, leading to a damage of the metallization as well as a change of the properties of the substrate and finally to a failure of the device. Therefore, annealing of bare LGS (La 3 Ga 5 SiO 14 ) substrates at 800 ∘ C under high vacuum conditions is performed to analyze whether this pretreatment improves the suitability and stability of this material for high temperature applications in vacuum. To reveal the influence of the pretreatment on the subsequently deposited metallization, RuAl thin films are used as they are known to oxidize on LGS at high temperatures. A local study of the pretreated and metallized substrates using transmission electron microscopy reveals strong modification of the substrate surface. Micro cracks are visible. The composition of the substrate is strongly altered at those regions. Severe challenges for the application of LGS substrates under high-temperature vacuum conditions arise from these substrate damages, revealing that the pretreatment does not improve the applicability.

The Role of Interfacial Electronic Properties on Phonon Transport in Two-Dimensional MoS 2 on Metal Substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Zhequan; Chen, Liang; Yoon, Mina

2016-11-08

In this paper, we investigate the role of interfacial electronic properties on the phonon transport in two-dimensional MoS 2 adsorbed on metal substrates (Au and Sc) using first-principles density functional theory and the atomistic Green’s function method. Our study reveals that the different degree of orbital hybridization and electronic charge distribution between MoS 2 and metal substrates play a significant role in determining the overall phonon–phonon coupling and phonon transmission. The charge transfer caused by the adsorption of MoS 2 on Sc substrate can significantly weaken the Mo–S bond strength and change the phonon properties of MoS 2, which resultmore » in a significant change in thermal boundary conductance (TBC) from one lattice-stacking configuration to another for same metallic substrate. In a lattice-stacking configuration of MoS 2/Sc, weakening of the Mo–S bond strength due to charge redistribution results in decrease in the force constant between Mo and S atoms and substantial redistribution of phonon density of states to low-frequency region which affects overall phonon transmission leading to 60% decrease in TBC compared to another configuration of MoS 2/Sc. Strong chemical coupling between MoS 2 and the Sc substrate leads to a significantly (~19 times) higher TBC than that of the weakly bound MoS 2/Au system. Our findings demonstrate the inherent connection among the interfacial electronic structure, the phonon distribution, and TBC, which helps us understand the mechanism of phonon transport at the MoS 2/metal interfaces. Finally, the results provide insights for the future design of MoS 2-based electronics and a way of enhancing heat dissipation at the interfaces of MoS 2-based nanoelectronic devices.« less

Application of High-Throughput Seebeck Microprobe Measurements on Thermoelectric Half-Heusler Thin Film Combinatorial Material Libraries.

PubMed

Ziolkowski, Pawel; Wambach, Matthias; Ludwig, Alfred; Mueller, Eckhard

2018-01-08

In view of the variety and complexity of thermoelectric (TE) material systems, combinatorial approaches to materials development come to the fore for identifying new promising compounds. The success of this approach is related to the availability and reliability of high-throughput characterization methods for identifying interrelations between materials structures and properties within the composition spread libraries. A meaningful characterization starts with determination of the Seebeck coefficient as a major feature of TE materials. Its measurement, and hence the accuracy and detectability of promising material compositions, may be strongly affected by thermal and electrical measurement conditions. This work illustrates the interrelated effects of the substrate material, the layer thickness, and spatial property distributions of thin film composition spread libraries, which are studied experimentally by local thermopower scans by means of the Potential and Seebeck Microprobe (PSM). The study is complemented by numerical evaluation. Material libraries of the half-Heusler compound system Ti-Ni-Sn were deposited on selected substrates (Si, AlN, Al 2 O 3 ) by magnetron sputtering. Assuming homogeneous properties of a film, significant decrease of the detected thermopower S m can be expected on substrates with higher thermal conductivity, yielding an underestimation of materials thermopower between 15% and 50%, according to FEM (finite element methods) simulations. Thermally poor conducting substrates provide a better accuracy with thermopower underestimates lower than 8%, but suffer from a lower spatial resolution. According to FEM simulations, local scanning of sharp thermopower peaks on lowly conductive substrates is linked to an additional deviation of the measured thermopower of up to 70% compared to homogeneous films, which is 66% higher than for corresponding cases on substrates with higher thermal conductivity of this study.

Magnetic poly(ε-caprolactone)/iron-doped hydroxyapatite nanocomposite substrates for advanced bone tissue engineering

PubMed Central

Gloria, A.; Russo, T.; D'Amora, U.; Zeppetelli, S.; D'Alessandro, T.; Sandri, M.; Bañobre-López, M.; Piñeiro-Redondo, Y.; Uhlarz, M.; Tampieri, A.; Rivas, J.; Herrmannsdörfer, T.; Dediu, V. A.; Ambrosio, L.; De Santis, R.

2013-01-01

In biomedicine, magnetic nanoparticles provide some attractive possibilities because they possess peculiar physical properties that permit their use in a wide range of applications. The concept of magnetic guidance basically spans from drug delivery and hyperthermia treatment of tumours, to tissue engineering, such as magneto-mechanical stimulation/activation of cell constructs and mechanosensitive ion channels, magnetic cell-seeding procedures, and controlled cell proliferation and differentiation. Accordingly, the aim of this study was to develop fully biodegradable and magnetic nanocomposite substrates for bone tissue engineering by embedding iron-doped hydroxyapatite (FeHA) nanoparticles in a poly(ε-caprolactone) (PCL) matrix. X-ray diffraction analyses enabled the demonstration that the phase composition and crystallinity of the magnetic FeHA were not affected by the process used to develop the nanocomposite substrates. The mechanical characterization performed through small punch tests has evidenced that inclusion of 10 per cent by weight of FeHA would represent an effective reinforcement. The inclusion of nanoparticles also improves the hydrophilicity of the substrates as evidenced by the lower values of water contact angle in comparison with those of neat PCL. The results from magnetic measurements confirmed the superparamagnetic character of the nanocomposite substrates, indicated by a very low coercive field, a saturation magnetization strictly proportional to the FeHA content and a strong history dependence in temperature sweeps. Regarding the biological performances, confocal laser scanning microscopy and AlamarBlue assay have provided qualitative and quantitative information on human mesenchymal stem cell adhesion and viability/proliferation, respectively, whereas the obtained ALP/DNA values have shown the ability of the nanocomposite substrates to support osteogenic differentiation. PMID:23303218

The Roles of Sea-Ice, Light and Sedimentation in Structuring Shallow Antarctic Benthic Communities

PubMed Central

Clark, Graeme F.; Stark, Jonathan S.; Palmer, Anne S.; Riddle, Martin J.; Johnston, Emma L.

2017-01-01

On polar coasts, seasonal sea-ice duration strongly influences shallow marine environments by affecting environmental conditions, such as light, sedimentation, and physical disturbance. Sea-ice dynamics are changing in response to climate, but there is limited understanding of how this might affect shallow marine environments and benthos. Here we present a unique set of physical and biological data from a single region of Antarctic coast, and use it to gain insights into factors shaping polar benthic communities. At sites encompassing a gradient of sea-ice duration, we measured temporal and spatial variation in light and sedimentation and hard-substrate communities at different depths and substrate orientations. Biological trends were highly correlated with sea-ice duration, and appear to be driven by opposing gradients in light and sedimentation. As sea-ice duration decreased, there was increased light and reduced sedimentation, and concurrent shifts in community structure from invertebrate to algal dominance. Trends were strongest on shallower, horizontal surfaces, which are most exposed to light and sedimentation. Depth and substrate orientation appear to mediate exposure of benthos to these factors, thereby tempering effects of sea-ice and increasing biological heterogeneity. However, while light and sedimentation both varied spatially with sea-ice, their dynamics differed temporally. Light was sensitive to the site-specific date of sea-ice breakout, whereas sedimentation fluctuated at a regional scale coincident with the summer phytoplankton bloom. Sea-ice duration is clearly the overarching force structuring these shallow Antarctic benthic communities, but direct effects are imposed via light and sedimentation, and mediated by habitat characteristics. PMID:28076438

The Roles of Sea-Ice, Light and Sedimentation in Structuring Shallow Antarctic Benthic Communities.

PubMed

Clark, Graeme F; Stark, Jonathan S; Palmer, Anne S; Riddle, Martin J; Johnston, Emma L

2017-01-01

On polar coasts, seasonal sea-ice duration strongly influences shallow marine environments by affecting environmental conditions, such as light, sedimentation, and physical disturbance. Sea-ice dynamics are changing in response to climate, but there is limited understanding of how this might affect shallow marine environments and benthos. Here we present a unique set of physical and biological data from a single region of Antarctic coast, and use it to gain insights into factors shaping polar benthic communities. At sites encompassing a gradient of sea-ice duration, we measured temporal and spatial variation in light and sedimentation and hard-substrate communities at different depths and substrate orientations. Biological trends were highly correlated with sea-ice duration, and appear to be driven by opposing gradients in light and sedimentation. As sea-ice duration decreased, there was increased light and reduced sedimentation, and concurrent shifts in community structure from invertebrate to algal dominance. Trends were strongest on shallower, horizontal surfaces, which are most exposed to light and sedimentation. Depth and substrate orientation appear to mediate exposure of benthos to these factors, thereby tempering effects of sea-ice and increasing biological heterogeneity. However, while light and sedimentation both varied spatially with sea-ice, their dynamics differed temporally. Light was sensitive to the site-specific date of sea-ice breakout, whereas sedimentation fluctuated at a regional scale coincident with the summer phytoplankton bloom. Sea-ice duration is clearly the overarching force structuring these shallow Antarctic benthic communities, but direct effects are imposed via light and sedimentation, and mediated by habitat characteristics.

Arbuscular Mycorrhiza Alleviates Restrictions to Substrate Water Flow and Delays Transpiration Limitation to Stronger Drought in Tomato

PubMed Central

Bitterlich, Michael; Sandmann, Martin; Graefe, Jan

2018-01-01

Arbuscular mycorrhizal fungi (AMF) proliferate in soil pores, on the surface of soil particles and affect soil structure. Although modifications in substrate moisture retention depend on structure and could influence plant water extraction, mycorrhizal impacts on water retention and hydraulic conductivity were rarely quantified. Hence, we asked whether inoculation with AMF affects substrate water retention, water transport properties and at which drought intensity those factors become limiting for plant transpiration. Solanum lycopersicum plants were set up in the glasshouse, inoculated or not with Funneliformis mosseae, and grown for 35 days under ample water supply. After mycorrhizal establishment, we harvested three sets of plants, one before (36 days after inoculation) and the second (day 42) and third (day 47) within a sequential drying episode. Sampling cores were introduced into pots before planting. After harvest, moisture retention and substrate conductivity properties were assessed and water retention and hydraulic conductivity models were fitted. A root water uptake model was adopted in order to identify the critical substrate moisture that induces soil derived transpiration limitation. Neither substrate porosity nor saturated water contents were affected by inoculation, but both declined after substrates dried. Drying also caused a decline in pot water capacity and hydraulic conductivity. Plant available water contents under wet (pF 1.8–4.2) and dry (pF 2.5–4.2) conditions increased in mycorrhizal substrates and were conserved after drying. Substrate hydraulic conductivity was higher in mycorrhizal pots before and during drought exposure. After withholding water from pots, higher substrate drying rates and lower substrate water potentials were found in mycorrhizal substrates. Mycorrhiza neither affected leaf area nor root weight or length. Consistently with higher substrate drying rates, AMF restored the plant hydraulic status, and increased plant transpiration when soil moisture declined. The water potential at the root surface and the resistance to water flow in the rhizosphere were restored in mycorrhizal pots although the bulk substrate dried more. Finally, substrates colonized by AMF can be more desiccated before substrate water flux quantitatively limits transpiration. This is most pronounced under high transpiration demands and complies with a difference of over 1,000 hPa in substrate water potential. PMID:29503655

Mixing of water masses caused by a drifting iceberg affects bacterial activity, community composition and substrate utilization capability in the Southern Ocean.

PubMed

Dinasquet, Julie; Richert, Inga; Logares, Ramiro; Yager, Patricia; Bertilsson, Stefan; Riemann, Lasse

2017-06-01

The number of icebergs produced from ice-shelf disintegration has increased over the past decade in Antarctica. These drifting icebergs mix the water column, influence stratification and nutrient condition, and can affect local productivity and food web composition. Data on whether icebergs affect bacterioplankton function and composition are scarce, however. We assessed the influence of iceberg drift on bacterial community composition and on their ability to exploit carbon substrates during summer in the coastal Southern Ocean. An elevated bacterial production and a different community composition were observed in iceberg-influenced waters relative to the undisturbed water column nearby. These major differences were confirmed in short-term incubations with bromodeoxyuridine followed by CARD-FISH. Furthermore, one-week bottle incubations amended with inorganic nutrients and carbon substrates (a mix of substrates, glutamine, N-acetylglucosamine, or pyruvate) revealed contrasting capacity of bacterioplankton to utilize specific carbon substrates in the iceberg-influenced waters compared with the undisturbed site. Our study demonstrates that the hydrographical perturbations introduced by a drifting iceberg can affect activity, composition, and substrate utilization capability of marine bacterioplankton. Consequently, in a context of global warming, increased frequency of drifting icebergs in polar regions holds the potential to affect carbon and nutrient biogeochemistry at local and possibly regional scales. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Removing bonded skin from a substrate

NASA Technical Reports Server (NTRS)

Chartier, E. N.

1980-01-01

Metal skin is peeled off like sardine-can cover with key. Method is useful in removing bonded skins from any substrate where substrate is strong enough not to buckle or tear when bonded skin is rolled free. Also, it is useful for removing sections of damaged skin where bladders of other equipment below substrate might be damaged if saw or router were used to cut completely through skin.

Substrate-Related Factors Affecting Enzymatic Saccharification of Lignocelluloses: Our Recent Understanding

Treesearch

Shao-Yuan Leu; J.Y. Zhu

2013-01-01

Enzymatic saccharification of cellulose is a key step in conversion of plant biomass to advanced biofuel and chemicals. Many substrate-related factors affect saccharification. Rather than examining the role of each individual factor on overall saccharification efficiency, this study examined how each factor affects the three basic processes of a heterogeneous...

Decreased carbon limitation of litter respiration in a mortality-affected pinon-juniper woodland

Treesearch

Erin Berryman; John D. Marshall; Thom Rahn; Marcie Litvak; John Butnor

2013-01-01

Microbial respiration depends on microclimatic variables and carbon (C) substrate availability, all of which are altered when ecosystems experience major disturbance. Widespread tree mortality, currently affecting pinon-juniper ecosystems in southwestern North America, may affect C substrate availability in several ways, for example, via litterfall pulses and loss of...

Influence of basal-plane dislocation structures on expansion of single Shockley-type stacking faults in forward-current degradation of 4H-SiC p-i-n diodes

NASA Astrophysics Data System (ADS)

Hayashi, Shohei; Yamashita, Tamotsu; Senzaki, Junji; Miyazato, Masaki; Ryo, Mina; Miyajima, Masaaki; Kato, Tomohisa; Yonezawa, Yoshiyuki; Kojima, Kazutoshi; Okumura, Hajime

2018-04-01

The origin of expanded single Shockley-type stacking faults in forward-current degradation of 4H-SiC p-i-n diodes was investigated by the stress-current test. At a stress-current density lower than 25 A cm-2, triangular stacking faults were formed from basal-plane dislocations in the epitaxial layer. At a stress-current density higher than 350 A cm-2, both triangular and long-zone-shaped stacking faults were formed from basal-plane dislocations that converted into threading edge dislocations near the interface between the epitaxial layer and the substrate. In addition, the conversion depth of basal-plane dislocations that expanded into the stacking fault was inside the substrate deeper than the interface. These results indicate that the conversion depth of basal-plane dislocations strongly affects the threshold stress-current density at which the expansion of stacking faults occurs.

Bioconversion of sugar cane crop residues with white-rot fungiPleurotus sp.

PubMed

Ortega, G M; Martínez, E O; Betancourt, D; González, A E; Otero, M A

1992-07-01

Four mushroom strains ofPleurotus spp. were cultivated on sugar cane crop residues for 30 days at 26°C. Biochemical changes affected the substrate as a result of fungal growth, in terms of nitrogen, lignin, cellulose and hemicellulose contents. All strains showed a strong ligninolytic activity together with variable cellulolytic and xylanolytic action.Pleurotus sajor-caju attacked lignin and cellulose at the same rate, showing a degradation of 47% and 55%, respectively. A better balance was shown by theP. ostreatus-P. pulmonarius hybrid, which exhibited the poorest cellulolytic action (39%) and the highest ligninolytic activity (67%). The average composition of mushroom fruit bodies, in terms of nitrogen, carbohydrates, fats and amino acid profiles, was determined. Crude protein and total carbohydrate varied from 23% to 33% and 36% to 68% of dry matter, respectively. Fat ranged from 3.3% to 4.7% and amino acid content from 12.2% to 22.2%. Slight evidence for a nitrogen fixing capability was encountered in the substrate to fruit body balance.

Effect of pH and nitrite concentration on nitrite oxidation rate.

PubMed

Jiménez, E; Giménez, J B; Ruano, M V; Ferrer, J; Serralta, J

2011-10-01

The effect of pH and nitrite concentration on the activity of the nitrite oxidizing bacteria (NOB) in an activated sludge reactor has been determined by means of laboratory batch experiments based on respirometric techniques. The bacterial activity was measured at different pH and at different total nitrite concentrations (TNO₂). The experimental results showed that the nitrite oxidation rate (NOR) depends on the TNO₂ concentration independently of the free nitrous acid (FNA) concentration, so FNA cannot be considered as the real substrate for NOB. NOB were strongly affected by low pH values (no activity was detected at pH 6.5) but no inhibition was observed at high pH values (activity was nearly the same for the pH range 7.5-9.95). A kinetic expression for nitrite oxidation process including switch functions to model the effect of TNO₂ concentration and pH inhibition is proposed. Substrate half saturation constant and pH inhibition constants have been obtained. Copyright © 2011 Elsevier Ltd. All rights reserved.

Stereoselectivity of the demethylation of nicotine piperidine homologues by Nicotiana plumbaginifolia cell suspension cultures.

PubMed

Bartholomeusz, Trixie Ann; Molinié, Roland; Roscher, Albrecht; Felpin, François-Xavier; Gillet, Françoise; Lebreton, Jacques; Mesnard, François; Robins, Richard J

2005-08-01

The metabolism of (R,S)-N-methylanabasine and (R,S)-N-methylanatabine has been studied in a cell suspension culture of Nicotiana plumbaginifolia. Both substrates are effectively demethylated, anabasine or anatabine, respectively, accumulating in the medium. Similarly, there is strong stereoselectivity for the (R)-isomers of both substrates. The kinetics of metabolism of (R,S)-N-methylanabasine differ significantly from those of nicotine in that no further degradation of the initial demethylation product occurs. (R,S)-N-Methylanatabine, however, shows kinetics closer to those of nicotine, with loss of alkaloid from the system. Further more, (R,S)-N-methylanabasine does not diminish (S)-nicotine demethylation, indicating a lack of competition. However, the metabolism of (S)-nicotine is affected by the presence of (R,S)-N-methylanabasine. Hence, the demethylation of the piperidine homologues of nicotine is seen to be similar but not identical to that of the pyridine analogues. The implications of these different metabolic profiles in relation to the demethylation activity are discussed.

Interaction of overlayers of Al and Rb with single-crystalline surfaces of Bi2Sr2CaCu2O8

NASA Astrophysics Data System (ADS)

Lindberg, P. A. P.; Wells, B. O.; Shen, Z.-X.; Dessau, D. S.; Lindau, I.; Spicer, W. E.; Mitzi, D. B.; Kapitulnik, A.

1990-03-01

Photoemission results from Al and Rb interfaces with single crystals of Bi2Sr2CaCu2O8 high-temperature superconductors are reported. The Al and Rb adsorbates are found to react quite differently with the Bi2Sr2CaCu2O8 substrate. While adatoms of Rb significantly affect only the Bi and O atoms in the top atomic layer, the Al adsorbate profoundly disrupts the bonding character of the whole Bi2Sr2CaCu2O8 material. For Al, the Bi and Cu states are strongly reduced, and the Sr and O states show evidence of oxidized components. In addition, Al causes a strong out-diffusion of oxygen from the bulk. The differences in the reactivity of Al and Rb are discussed in terms of the different mobility of the two atoms.

Total Dose Effects on Bipolar Integrated Circuits at Low Temperature

NASA Technical Reports Server (NTRS)

Johnston, A. H.; Swimm, R. T.; Thorbourn, D. O.

2012-01-01

Total dose damage in bipolar integrated circuits is investigated at low temperature, along with the temperature dependence of the electrical parameters of internal transistors. Bandgap narrowing causes the gain of npn transistors to decrease far more at low temperature compared to pnp transistors, due to the large difference in emitter doping concentration. When irradiations are done at temperatures of -140 deg C, no damage occurs until devices are warmed to temperatures above -50 deg C. After warm-up, subsequent cooling shows that damage is then present at low temperature. This can be explained by the very strong temperature dependence of dispersive transport in the continuous-time-random-walk model for hole transport. For linear integrated circuits, low temperature operation is affected by the strong temperature dependence of npn transistors along with the higher sensitivity of lateral and substrate pnp transistors to radiation damage.

Photoluminescence enhancement of silicon quantum dot monolayer by plasmonic substrate fabricated by nano-imprint lithography

NASA Astrophysics Data System (ADS)

Yanagawa, Hiroto; Inoue, Asuka; Sugimoto, Hiroshi; Shioi, Masahiko; Fujii, Minoru

2017-12-01

Near-field coupling between a silicon quantum dot (Si-QD) monolayer and a plasmonic substrate fabricated by nano-imprint lithography and having broad multiple resonances in the near-infrared (NIR) window of biological substances was studied by precisely controlling the QDs-substrate distance. A strong enhancement of the NIR photoluminescence (PL) of Si-QDs was observed. Detailed analyses of the PL and PL excitation spectra, the PL decay dynamics, and the reflectance spectra revealed that both the excitation cross-sections and the emission rates are enhanced by the surface plasmon resonances, thanks to the broad multiple resonances of the plasmonic substrate, and that the relative contribution of the two enhancement processes depends strongly on the excitation wavelength. Under excitation by short wavelength photons (405 nm), where enhancement of the excitation cross-section is not expected, the maximum enhancement was obtained when the QDs-substrate distance was around 30 nm. On the other hand, under long wavelength excitation (641 nm), where strong excitation cross-section enhancement is expected, the largest enhancement was obtained when the distance was minimum (around 1 nm). The achievement of efficient excitation of NIR luminescence of Si-QDs by long wavelength photons paves the way for the development of Si-QD-based fluorescence bio-sensing devices with a high bound-to-free ratio.

Interactions of acylated methylglucoside derivatives with CO2: simulation and calculations.

PubMed

Chang, H H; Cao, R X; Yang, C C; Wei, W L; Pang, X Y; Qiao, Y

2016-01-01

Carbohydrates have drawn considerable interest from researchers recently due to their affinity for CO2. However, most of the research in this field has focused on peracetylated derivatives. Compared with acetylated carbohydrates, which have already been studied in depth, methyl D-glucopyranoside derivatives are more stable and could have additional applications. Thus, in the present work, ab initio calculations were performed to elucidate the characteristics of the interactions of methylglucoside derivatives with CO2, and to investigate how the binding energy (ΔE) is affected by isomerization or the introduction of various acyl groups. Four methyl D-glucopyranosides (each with two anomers) bearing acetyl, propionyl, butyryl, and isobutyryl moieties, respectively, were designed as substrates, and the 1:1 complexes of a CO2 molecule with each of these sugar substrates were modeled. The results indicate that ΔE is mainly influenced by interaction distance and the number of negatively charged donors or interacting pairs in the complex; the structure of the acyl group present in the substrate is a secondary influence. Except in the case of methyl 2-O-acetyl-D-glucopyranose, the ΔE values of the α- and β-anomers of each methylglucoside were found to be almost the same. Therefore, we would expect the CO2 affinities of the four derivatives studied here to be as strong as or even stronger than that of peracetylated D-glucopyranose. Graphical Abstract The binding energy between methyl D-glucopyranoside derivatives with various substituted acyl groups and CO2 are evaluated by ab initio calculations. The strong interaction between these methyl dglucopyranoside derivatives and CO2 showed the potential of their application for CO2 capture.

Inorganic resist materials based on zirconium phosphonate for atomic force microscope lithography

NASA Astrophysics Data System (ADS)

Kang, Mankyu; Kim, Seonae; Jung, JinHyuck; Kim, Heebom; Shin, Inkyun; Jeon, Chanuk; Lee, Haiwon

2014-03-01

New inorganic resist materials based on metal complexes were investigated for atomic force microscope (AFM) lithography. Phosphoric acids are good for self-assembly because of their strong binding energy. In this work, zirconium phosphonate system are newly synthesized for spin-coatable materials in aqueous solutions and leads to negative tone pattern for improving line edge roughness. Low electron exposure by AFM lithography could generate a pattern by electrochemical reaction and cross-linking of metal-oxo complexes. It has been reported that the minimum pattern results are affected by lithographic speed, and the applied voltage between a tip and a substrate.

Disposable gold coated pyramidal SERS sensor on the plastic platform.

PubMed

Oo, S Z; Siitonen, S; Kontturi, V; Eustace, D A; Charlton, M D B

2016-01-11

In this paper we investigate suitability of arrays of gold coated pyramids for surface-enhanced Raman scattering (SERS) sensing applications. Pyramidarrays composed of 1000 nm pit size with 1250 nm pitch lengthwerereplicated on a plastic substrate by roll-to-roll (R2R) ultraviolet (UV) embossing. The level of SERS enhancement, and qualitative performance provided by the new substrate is investigated by comparing Raman spectrum of benzenethiol (BTh) test molecules to the benchmark Klarite SERS substrate which comprises inverted pyramid arrays(1500 nm pit size with 2000 nm pitch length) fabricated on a silicon substrate. The new substrate is found to provide upto 11 times increase in signal in comparison to the inverted pyramid (IV-pyramid) arrays fabricated on an identical plastic substrate. Numerical simulation and experimental evidence suggest that strongly confined electromagnetic fields close to the base of the pyramids, are mainly responsible for the Raman enhancement factor, instead of the fields localized around the tip. Unusually strong plasmon fields are projected upto 200nm from the sidewalls at the base of the pyramid increasing the cross sectional sensing volume.

Structure and corrosion properties of PVD Cr-N coatings

NASA Astrophysics Data System (ADS)

Liu, C.; Bi, Q.; Ziegele, H.; Leyland, A.; Matthews, A.

2002-05-01

PVD Cr-N coatings produced by physical vapor deposition (PVD) are increasingly used for mechanical and tribological applications in various industrial sectors. These coatings are particularly attractive for their excellent corrosion resistance, which further enhances the lifetime and service quality of coated components. PVD Cr-N coated steels in an aqueous solution are usually corroded by galvanic attack via through-coating ``permeable'' defects (e.g., pores). Therefore, the corrosion performance of Cr-N coated steel is determined by a number of variables of the coating properties and corrosive environment. These variables include: (i) surface continuity and uniformity; (ii) through-coating porosity; (iii) film density and chemical stability; (iv) growth stresses; (v) interfacial and intermediate layers; (vi) coating thickness; (vii) coating composition; and (viii) substrate properties. In this article, PVD Cr-N coatings were prepared, by electron-beam PVD and sputter deposition, with different compositions, thicknesses, and surface roughnesses, by changing the N2 flow rate, applying multilayering techniques and changing the substrate finish prior to coating. The microstructure of such coatings is investigated by various analytical techniques such as glancing angle x-ray diffraction and scanning electron microscopy, which are also correlated with the corrosion performance of the coated steel. Both dc polarization and ac impedance spectroscopy were employed to investigate the corrosion resistance of Cr-N coated steel in a 0.5N NaCl solution. It has been found that the N2 flow rate during reactive deposition strongly determines the microstructure of Cr-N coatings (due to the changing nitrogen content in the film) and can thus affect the corrosion resistance of coated systems. The surface finish of the steel substrate also affects the uniformity and coverage of PVD coatings; grooves and inclusions on the original substrate can raise the susceptibility of coated systems to crevice corrosion. Increased coating thickness can also greatly reduce the incidence of through-coating porosity such that the improvement in corrosion performance of thicker Cr-N coatings is significant.

Nitrogen form affects pH and EC of whole pine tree substrate and growth of petunia

USDA-ARS?s Scientific Manuscript database

Wood-based substrates are potential alternatives or amendments to traditional peat-based and pine bark substrates. Undesirable changes in substrate pH may result from the application of supplemental fertilizer required by some crops grown in wood-based substrates. Experiments were conducted to evalu...

Biological bases of human musicality.

PubMed

Perrone-Capano, Carla; Volpicelli, Floriana; di Porzio, Umberto

2017-04-01

Music is a universal language, present in all human societies. It pervades the lives of most human beings and can recall memories and feelings of the past, can exert positive effects on our mood, can be strongly evocative and ignite intense emotions, and can establish or strengthen social bonds. In this review, we summarize the research and recent progress on the origins and neural substrates of human musicality as well as the changes in brain plasticity elicited by listening or performing music. Indeed, music improves performance in a number of cognitive tasks and may have beneficial effects on diseased brains. The emerging picture begins to unravel how and why particular brain circuits are affected by music. Numerous studies show that music affects emotions and mood, as it is strongly associated with the brain's reward system. We can therefore assume that an in-depth study of the relationship between music and the brain may help to shed light on how the mind works and how the emotions arise and may improve the methods of music-based rehabilitation for people with neurological disorders. However, many facets of the mind-music connection still remain to be explored and enlightened.

Droplets move over viscoelastic substrates by surfing a ridge

PubMed Central

Karpitschka, S.; Das, S.; van Gorcum, M.; Perrin, H.; Andreotti, B.; Snoeijer, J. H.

2015-01-01

Liquid drops on soft solids generate strong deformations below the contact line, resulting from a balance of capillary and elastic forces. The movement of these drops may cause strong, potentially singular dissipation in the soft solid. Here we show that a drop on a soft substrate moves by surfing a ridge: the initially flat solid surface is deformed into a sharp ridge whose orientation angle depends on the contact line velocity. We measure this angle for water on a silicone gel and develop a theory based on the substrate rheology. We quantitatively recover the dynamic contact angle and provide a mechanism for stick–slip motion when a drop is forced strongly: the contact line depins and slides down the wetting ridge, forming a new one after a transient. We anticipate that our theory will have implications in problems such as self-organization of cell tissues or the design of capillarity-based microrheometers. PMID:26238436

Effect of tacticity on the structure and glass transition temperature of polystyrene adsorbed onto solid surfaces

NASA Astrophysics Data System (ADS)

Negash, Solomon; Tatek, Yergou B.; Tsige, Mesfin

2018-04-01

We have carried out atomistic (all-atom) molecular dynamics simulations to investigate the effect of tacticity on the structure and glass transition temperature (Tg) of polystyrene (PS) thin films adsorbed on two distinct types of solid substrates. The systems consist of thin films made of atactic, isotactic, and syndiotactic PS chains supported by graphite or hydroxylated α-quartz substrates, which are known to be atomically flat but chemically and structurally different. We have observed a marked dependence of the film structure on substrate type as well as on tacticity. For instance, rings' orientation near substrate surfaces depends on substrate type for atactic PS and isotactic PS films, while no such dependence is observed for syndiotactic PS films whose interfacial structure seems to result from their propensity to adopt the trans conformation rather than their specific interaction with the substrates. Moreover, our results indicate that glass transition temperatures of substrate supported polystyrene films are higher compared to those of the corresponding free-standing films. More specifically, PS films on graphite exhibit larger Tg values than those on α-quartz, and we have noticed that syndiotactic PS has the largest Tg irrespective of the substrate type. Furthermore, the local Tg in the region of the film in contact with the substrates shows a strong tacticity and substrate dependence, whereas no dependencies were found for the local Tg in the middle of the film. Substrate-film interaction energy and chains' dynamics near substrate-film interfaces were subsequently investigated in order to substantiate the obtained Tgs, and it was found that films with higher Tgs are strongly adsorbed on the substrates and/or exhibit smaller interfacial chains' dynamics essentially due to steric hindrance.

Biochar affects macronutrient leaching from a soilless substrate

USDA-ARS?s Scientific Manuscript database

Byproducts of pyrolysis, known collectively as biochar, are becoming more common and readily available as ventures into alternative energy generation are explored. Little is known about how these materials affect greenhouse substrates. The objective of this research was to determine the effect of ...

Ambiguous Role of Growth-Induced Defects on the Semiconductor-to-Metal Characteristics in Epitaxial VO2/TiO2 Thin Films.

PubMed

Mihailescu, Cristian N; Symeou, Elli; Svoukis, Efthymios; Negrea, Raluca F; Ghica, Corneliu; Teodorescu, Valentin; Tanase, Liviu C; Negrila, Catalin; Giapintzakis, John

2018-04-25

Controlling the semiconductor-to-metal transition temperature in epitaxial VO 2 thin films remains an unresolved question both at the fundamental as well as the application level. Within the scope of this work, the effects of growth temperature on the structure, chemical composition, interface coherency and electrical characteristics of rutile VO 2 epitaxial thin films grown on TiO 2 substrates are investigated. It is hereby deduced that the transition temperature is lower than the bulk value of 340 K. However, it is found to approach this value as a function of increased growth temperature even though it is accompanied by a contraction along the V 4+ -V 4+ bond direction, the crystallographic c-axis lattice parameter. Additionally, it is demonstrated that films grown at low substrate temperatures exhibit a relaxed state and a strongly reduced transition temperature. It is suggested that, besides thermal and epitaxial strain, growth-induced defects may strongly affect the electronic phase transition. The results of this work reveal the difficulty in extracting the intrinsic material response to strain, when the exact contribution of all strain sources cannot be effectively determined. The findings also bear implications on the limitations in obtaining the recently predicted novel semi-Dirac point phase in VO 2 /TiO 2 multilayer structures.

An experimental investigation of the effect of hydrophobicity on the rate of frost growth in laminar channel flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyer, J.M.; Storey, B.D.; Hoke, J.L.

2000-07-01

An experimental investigation of the effect of the substrate on frost growth rate is presented. Measurements of frost height as a function of time are presented for a flat, bare, horizontally oriented aluminum substrate and four coated substrates, two hydrophilic and two hydrophobic. The average frost growth rate on the hydrophilic coated aluminum substrate is 13% higher than the control substrate, while the frost growth rate on the hydrophilic kapton substrate is 4% higher. Frost grows on the hydrophobic substrates at a rate 19% and 3% lower than the reference substrate for the polytetrafluoroethylene (PTFE) coated steel and PTFE tape,more » respectively. Differences in the receding and advancing contact angles for these substrates do not fully explain the difference in growth rates. Differences in initial water deposition, freezing, and frost growth on hydrophilic and hydrophobic substrates are examined using confocal microscopy. On the basis of the microscopic observations, the authors hypothesize that the water coverage on the substrate before and after freezing can affect the thermal resistance of the mature frost layer. Differences in thermal resistance, in turn, affect the growth rate.« less

When Field Experiments Yield Unexpected Results: Lessons Learned from Measuring Selection in White Sands Lizards

PubMed Central

Hardwick, Kayla M.; Harmon, Luke J.; Hardwick, Scott D.; Rosenblum, Erica Bree

2015-01-01

Determining the adaptive significance of phenotypic traits is key for understanding evolution and diversification in natural populations. However, evolutionary biologists have an incomplete understanding of how specific traits affect fitness in most populations. The White Sands system provides an opportunity to study the adaptive significance of traits in an experimental context. Blanched color evolved recently in three species of lizards inhabiting the gypsum dunes of White Sands and is likely an adaptation to avoid predation. To determine whether there is a relationship between color and susceptibility to predation in White Sands lizards, we conducted enclosure experiments, quantifying survivorship of Holbrookia maculate exhibiting substrate-matched and substrate-mismatched phenotypes. Lizards in our study experienced strong predation. Color did not have a significant effect on survival, but we found several unexpected relationships including variation in predation over small spatial and temporal scales. In addition, we detected a marginally significant interaction between sex and color, suggesting selection for substrate matching may be stronger for males than females. We use our results as a case study to examine six major challenges frequently encountered in field-based studies of natural selection, and suggest that insight into the complexities of selection often results when experiments turn out differently than expected. PMID:25714838

Effect of CoSi2 buffer layer on structure and magnetic properties of Co films grown on Si (001) substrate

NASA Astrophysics Data System (ADS)

Hu, Bo; He, Wei; Ye, Jun; Tang, Jin; Syed Sheraz, Ahmad; Zhang, Xiang-Qun; Cheng, Zhao-Hua

2015-01-01

Buffer layer provides an opportunity to enhance the quality of ultrathin magnetic films. In this paper, Co films with different thickness of CoSi2 buffer layers were grown on Si (001) substrates. In order to investigate morphology, structure, and magnetic properties of films, scanning tunneling microscope (STM), low energy electron diffraction (LEED), high resolution transmission electron microscopy (HRTEM), and surface magneto-optical Kerr effect (SMOKE) were used. The results show that the crystal quality and magnetic anisotropies of the Co films are strongly affected by the thickness of CoSi2 buffer layers. Few CoSi2 monolayers can prevent the interdiffusion of Si substrate and Co film and enhance the Co film quality. Furthermore, the in-plane magnetic anisotropy of Co film with optimal buffer layer shows four-fold symmetry and exhibits the two-jumps of magnetization reversal process, which is the typical phenomenon in cubic (001) films. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB921801 and 2012CB933102), the National Natural Science Foundation of China (Grant Nos. 11374350, 11034004, 11274361, and 11274033), and the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20131102130005).

Mechanosensitivity in axon growth and guidance

NASA Astrophysics Data System (ADS)

Urbach, Jeff

2013-03-01

In the developing nervous system, axons respond to a diverse array of cues to generate the intricate connection network required for proper function. The growth cone, a highly motile structure at the tip of a growing axon, integrates information about the local environment and modulates outgrowth and guidance, but little is known about effects of external mechanical cues and internal mechanical forces on growth cone behavior. We have investigated axon outgrowth and force generation on soft elastic substrates for dorsal root ganglion (DRG) neurons (from the peripheral nervous system) and hippocampal neurons (from the central) to see how the mechanics of the microenvironment affect different populations. We find that force generation and stiffness-dependent outgrowth are strongly dependent on cell type. We also observe very different internal dynamics and substrate coupling in the two populations, suggesting that the difference in force generation is due to stronger adhesions and therefore stronger substrate engagement in the peripheral nervous system neurons. We will discuss the biological origins of these differences, and recent analyses of the dynamic aspects of growth cone force generation and the implications for the role of mechanosensitivity in axon guidance. In collaboration with D. Koch, W. Rosoff, and H. M. Geller. Supported by NINDS grant 1R01NS064250-01 (J.S.U.) and the NHLBI Intramural Research Program (H.M.G.).

Production of methoxylated flavonoids in yeast using ring A hydroxylases and flavonoid O-methyltransferases from sweet basil.

PubMed

Berim, Anna; Gang, David R

2018-07-01

Numerous methoxylated flavonoids exhibit pronounced bioactivities. Their biotechnological production and diversification are therefore of interest to pharmaceutical and nutraceutical industries. We used a set of enzymes from sweet basil (Ocimum basilicum) to construct five strains of Saccharomyces cerevisiae producing 8- and/or 6-substituted, methoxylated flavones from their natural precursor apigenin. After identifying several growth parameters affecting the overall yields and flux, we applied optimized conditions and explored the ability of the generated strains to utilize alternative substrates. The yeast cells produced substantial amounts of 6-hydroxylated, methylated derivatives of naringenin and luteolin while the corresponding derivatives of flavonol kaempferol were only detected in trace amounts. Analysis of the intermediates and by-products of the different bioconversions suggested that the substrate specificity of both the hydroxylases and the flavonoid O-methyltransferases is imposing barriers on yields obtained with alternative substrates and highlighted steps that appear to represent bottlenecks en route to increasing the strains' efficiencies. Additionally, analysis of flavonoid localization during fermentation revealed unequal distribution with strong intracellular accumulation of a number of methylated flavonoids and extracellular enrichment of several pathway intermediates. This work establishes a platform for the production of complex methoxylated flavonoids and discusses strategies for its improvement.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jana, Dipankar, E-mail: dip2602@gmail.com; Porwal, S.; Sharma, T. K., E-mail: tarun@rrcat.gov.in

Pump-probe Surface Photovoltage Spectroscopy (SPS) measurements are performed on semiconductor epitaxial layers. Here, an additional sub-bandgap cw pump laser beam is used in a conventional chopped light geometry SPS setup under the pump-probe configuration. The main role of pump laser beam is to saturate the sub-bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. It also affects the magnitude of Dember voltage in case of semi-insulating (SI) semiconductor substrates. Pump-probe SPS technique enables an accurate determination of the bandgap of semiconductor epitaxial layers even under the strong influence of localized sub-bandgap states. The pumpmore » beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states. The overall magnitude of SPV signal is decided by the dependence of charge separation mechanisms on the intensity of the pump beam. On the contrary, an above bandgap cw pump laser can be used to distinguish the signatures of sub-bandgap states by suppressing the band edge related feature. Usefulness of the pump-probe SPS technique is established by unambiguously determining the bandgap of p-GaAs epitaxial layers grown on SI-GaAs substrates, SI-InP wafers, and p-GaN epilayers grown on Sapphire substrates.« less

Pump-probe surface photovoltage spectroscopy measurements on semiconductor epitaxial layers.

PubMed

Jana, Dipankar; Porwal, S; Sharma, T K; Kumar, Shailendra; Oak, S M

2014-04-01

Pump-probe Surface Photovoltage Spectroscopy (SPS) measurements are performed on semiconductor epitaxial layers. Here, an additional sub-bandgap cw pump laser beam is used in a conventional chopped light geometry SPS setup under the pump-probe configuration. The main role of pump laser beam is to saturate the sub-bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. It also affects the magnitude of Dember voltage in case of semi-insulating (SI) semiconductor substrates. Pump-probe SPS technique enables an accurate determination of the bandgap of semiconductor epitaxial layers even under the strong influence of localized sub-bandgap states. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states. The overall magnitude of SPV signal is decided by the dependence of charge separation mechanisms on the intensity of the pump beam. On the contrary, an above bandgap cw pump laser can be used to distinguish the signatures of sub-bandgap states by suppressing the band edge related feature. Usefulness of the pump-probe SPS technique is established by unambiguously determining the bandgap of p-GaAs epitaxial layers grown on SI-GaAs substrates, SI-InP wafers, and p-GaN epilayers grown on Sapphire substrates.

Rare earth elements concentration in mushroom cultivation substrates affects the production process and fruit-bodies content of Pleurotus ostreatus and Cyclocybe cylindracea.

PubMed

Koutrotsios, Georgios; Danezis, Georgios P; Georgiou, Constantinos A; Zervakis, Georgios I

2018-04-20

Concentrations of 16 rare earth elements (REEs) and two actinides were determined for the first time both in cultivated mushrooms and in their production substrates by inductively coupled plasma mass spectroscopy. Moreover, the effect of REEs on cultivation parameters and composition of the final product was assessed, together with their potential use for authentication purposes. The concentrations of REEs varied greatly among seven cultivation substrates and correlated with measurements in Cyclocybe cylindracea mushrooms; no such correlation was established in Pleurotus ostreatus. Reduction of hemicellulose, cellulose, and lignin in substrates during P. ostreatus cultivation was positively correlated with REE concentrations, which also affected the production performance depending on the species examined. In all cases, a negative correlation was established between bioconcentration factors (BCF) in mushrooms and REE content in substrates, while the effect of substrate composition on BCF values varied according to the element studied. The estimated daily intake values of REEs through mushroom consumption was at much lower levels than those reported as potentially harmful for human health. The content of REEs in cultivation substrates and in mushrooms revealed that the bioaccumulation of elements differed in each fungus. The nature/origin of substrates seemed to affect the concentration of REEs in mushrooms to a considerable extent. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Quantification of Valleys of Randomly Textured Substrates as a Function of Opening Angle: Correlation to the Defect Density in Intrinsic nc-Si:H.

PubMed

Kim, Do Yun; Hänni, Simon; Schüttauf, Jan-Willem; van Swaaij, René A C M M; Zeman, Miro

2016-08-17

Optical and electrical properties of hydrogenated nanocrystalline silicon (nc-Si:H) solar cells are strongly influenced by the morphology of underlying substrates. By texturing the substrates, the photogenerated current of nc-Si:H solar cells can increase due to enhanced light scattering. These textured substrates are, however, often incompatible with defect-less nc-Si:H growth resulting in lower Voc and FF. In this study we investigate the correlation between the substrate morphology, the nc-Si:H solar-cell performance, and the defect density in the intrinsic layer of the solar cells (i-nc-Si:H). Statistical surface parameters representing the substrate morphology do not show a strong correlation with the solar-cell parameters. Thus, we first quantify the line density of potentially defective valleys of randomly textured ZnO substrates where the opening angle is smaller than 130° (ρ<130). This ρ<130 is subsequently compared with the solar-cell performance and the defect density of i-nc-Si:H (ρdefect), which is obtained by fitting external photovoltaic parameters from experimental results and simulations. We confirm that when ρ<130 increases the Voc and FF significantly drops. It is also observed that ρdefect increases following a power law dependence of ρ<130. This result is attributed to more frequently formed defective regions for substrates having higher ρ<130.

Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices.

PubMed

Li, Zhe; Ho Chiu, Kar; Shahid Ashraf, Raja; Fearn, Sarah; Dattani, Rajeev; Cheng Wong, Him; Tan, Ching-Hong; Wu, Jiaying; Cabral, João T; Durrant, James R

2015-10-15

Morphological stability is a key requirement for outdoor operation of organic solar cells. We demonstrate that morphological stability and lifetime of polymer/fullerene based solar cells under thermal stress depend strongly on the substrate interface on which the active layer is deposited. In particular, we find that the stability of benchmark PCDTBT/PCBM solar cells under modest thermal stress is substantially increased in inverted solar cells employing a ZnO substrate compared to conventional devices employing a PSS substrate. This improved stability is observed to correlate with PCBM nucleation at the 50 nm scale, which is shown to be strongly influenced by different substrate interfaces. Employing this approach, we demonstrate remarkable thermal stability for inverted PCDTBT:PC70BM devices on ZnO substrates, with negligible (<2%) loss of power conversion efficiency over 160 h under 85 °C thermal stress and minimal thermally induced "burn-in" effect. We thus conclude that inverted organic solar cells, in addition to showing improved environmental stability against ambient humidity exposure as widely reported previously, can also demonstrate enhanced morphological stability. As such we show that the choice of suitable substrate interfaces may be a key factor in achieving prolonged lifetimes for organic solar cells under thermal stress conditions.

Preparation of high-strength nanometer scale twinned coating and foil

DOEpatents

Zhang, Xinghang [Los Alamos, NM; Misra, Amit [Los Alamos, NM; Nastasi, Michael A [Santa Fe, NM; Hoagland, Richard G [Santa Fe, NM

2006-07-18

Very high strength single phase stainless steel coating has been prepared by magnetron sputtering onto a substrate. The coating has a unique microstructure of nanometer spaced twins that are parallel to each other and to the substrate surface. For cases where the coating and substrate do not bind strongly, the coating can be peeled off to provide foil.

Prey versus substrate as determinants of habitat choice in a feeding shorebird

NASA Astrophysics Data System (ADS)

Finn, Paul G.; Catterall, Carla P.; Driscoll, Peter V.

2008-11-01

Many shorebirds on their non-breeding grounds feed on macrobenthic fauna which become available at low tide in coastal intertidal flats. The Eastern Curlew Numenius madagascariensis in Moreton Bay Australia, varies greatly in density among different tidal flats. This study asks: how important is the abundance of intertidal prey as a predictor of this variation? We quantified feeding curlews' diet across 12 sites (different tidal flats, each re-visited at least eight times), through 970 focal observations. We also estimated the abundance of total macrobenthic fauna, potential prey taxa and crustacean prey on each tidal flat; measured as the number of individuals and a relative biomass index per unit substrate surface area obtained from substrate core samples. We estimated curlew density at each site using low-tide surveys from every site visit. Curlew density showed a strong positive association with both the density and biomass of fauna and of potential prey ( r values all around 0.70) across the 12 flats. Associations with crustacean density and biomass were also statistically significant (r values both 0.60). However, these variables also showed a strong negative correlation with a measure of substrate resistance (based on the amount of hard material in the substrate core), which was the best predictor of curlew density ( r = -0.82). Curlews were most abundant at sites with the least resistant substrate, and these sites also generally had the highest faunal density and biomass. When the effect of substrate resistance was statistically removed, curlew density was no longer significantly correlated with fauna density and biomass. This suggests that macro-scale habitat choice by Eastern Curlew on their non-breeding grounds is more strongly influenced by prey availability (which is higher when substrate resistance is lower) than by prey density or biomass, although in Moreton Bay a positive correlation across sites meant that these factors were synergistic.

Quality-enhanced In{sub 0.3}Ga{sub 0.7}As film grown on GaAs substrate with an ultrathin amorphous In{sub 0.6}Ga{sub 0.4}As buffer layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Fangliang; Li, Guoqiang, E-mail: msgli@scut.edu.cn

2014-01-27

Using low-temperature molecular beam epitaxy, amorphous In{sub 0.6}Ga{sub 0.4}As layers have been grown on GaAs substrates to act as buffer layers for the subsequent epitaxial growth of In{sub 0.3}Ga{sub 0.7}As films. It is revealed that the crystallinity of as-grown In{sub 0.3}Ga{sub 0.7}As films is strongly affected by the thickness of the large-mismatched amorphous In{sub 0.6}Ga{sub 0.4}As buffer layer. Given an optimized thickness of 2 nm, this amorphous In{sub 0.6}Ga{sub 0.4}As buffer layer can efficiently release the misfit strain between the In{sub 0.3}Ga{sub 0.7}As epi-layer and the GaAs substrate, trap the threading and misfit dislocations from propagating to the following In{sub 0.3}Ga{submore » 0.7}As epi-layer, and reduce the surface fluctuation of the as-grown In{sub 0.3}Ga{sub 0.7}As, leading to a high-quality In{sub 0.3}Ga{sub 0.7}As film with competitive crystallinity to that grown on GaAs substrate using compositionally graded In{sub x}Ga{sub 1-x}As metamorphic buffer layers. Considering the complexity of the application of the conventional In{sub x}Ga{sub 1-x}As graded buffer layers, this work demonstrates a much simpler approach to achieve high-quality In{sub 0.3}Ga{sub 0.7}As film on GaAs substrate and, therefore, is of huge potential for the InGaAs-based high-efficiency photovoltaic industry.« less

Effect of Pd Surface Roughness on the Bonding Process and High Temperature Reliability of Au Ball Bonds

NASA Astrophysics Data System (ADS)

Huang, Y.; Kim, H. J.; McCracken, M.; Viswanathan, G.; Pon, F.; Mayer, M.; Zhou, Y. N.

2011-06-01

A 0.3- μm-thick electrolytic Pd layer was plated on 1 μm of electroless Ni on 1 mm-thick polished and roughened Cu substrates with roughness values ( R a) of 0.08 μm and 0.5 μm, respectively. The rough substrates were produced with sand-blasting. Au wire bonding on the Ni/Pd surface was optimized, and the electrical reliability was investigated under a high temperature storage test (HTST) during 800 h at 250°C by measuring the ball bond contact resistance, R c. The average value of R c of optimized ball bonds on the rough substrate was 1.96 mΩ which was about 40.0% higher than that on the smooth substrate. The initial bondability increased for the rougher surface, so that only half of the original ultrasonic level was required, but the reliability was not affected by surface roughness. For both substrate types, HTST caused bond healing, reducing the average R c by about 21% and 27%, respectively. Au diffusion into the Pd layer was observed in scanning transmission electron microscopy/ energy dispersive spectroscopy (STEM-EDS) line-scan analysis after HTST. It is considered that diffusion of Au or interdiffusion between Au and Pd can provide chemically strong bonding during HTST. This is supported by the R c decrease measured as the aging time increased. Cu migration was indicated in the STEM-EDS analysis, but its effect on reliability can be ignored. Au and Pd tend to form a complete solid solution at the interface and can provide reliable interconnection for high temperature (250°C) applications.

Lipid Microarray Biosensor for Biotoxin Detection.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Anup K.; Throckmorton, Daniel J.; Moran-Mirabal, Jose C.

2006-05-01

We present the use of micron-sized lipid domains, patterned onto planar substrates and within microfluidic channels, to assay the binding of bacterial toxins via total internal reflection fluorescence microscopy (TIRFM). The lipid domains were patterned using a polymer lift-off technique and consisted of ganglioside-populated DSPC:cholesterol supported lipid bilayers (SLBs). Lipid patterns were formed on the substrates by vesicle fusion followed by polymer lift-off, which revealed micron-sized SLBs containing either ganglioside GT1b or GM1. The ganglioside-populated SLB arrays were then exposed to either Cholera toxin subunit B (CTB) or Tetanus toxin fragment C (TTC). Binding was assayed on planar substrates bymore » TIRFM down to 1 nM concentration for CTB and 100 nM for TTC. Apparent binding constants extracted from three different models applied to the binding curves suggest that binding of a protein to a lipid-based receptor is strongly affected by the lipid composition of the SLB and by the substrate on which the bilayer is formed. Patterning of SLBs inside microfluidic channels also allowed the preparation of lipid domains with different compositions on a single device. Arrays within microfluidic channels were used to achieve segregation and selective binding from a binary mixture of the toxin fragments in one device. The binding and segregation within the microfluidic channels was assayed with epifluorescence as proof of concept. We propose that the method used for patterning the lipid microarrays on planar substrates and within microfluidic channels can be easily adapted to proteins or nucleic acids and can be used for biosensor applications and cell stimulation assays under different flow conditions. KEYWORDS. Microarray, ganglioside, polymer lift-off, cholera toxin, tetanus toxin, TIRFM, binding constant.4« less

Strong, non-magnetic, cube textured alloy substrates

DOEpatents

Goyal, Amit [Knoxville, TN

2011-02-01

A warm-rolled, annealed, polycrystalline, cube-textured, {100}<100>, FCC-based alloy substrate is characterized by a yield strength greater than 200 MPa and a biaxial texture characterized by a FWHM of less than 15.degree. in all directions.

The effect of copper pre-cleaning on graphene synthesis.

PubMed

Kim, Soo Min; Hsu, Allen; Lee, Yi-Hsien; Dresselhaus, Mildred; Palacios, Tomás; Kim, Ki Kang; Kong, Jing

2013-09-13

Copper foil is the most common substrate to synthesize monolayer graphene by chemical vapor deposition (CVD). The surface morphology and conditions of the copper foil can be very different depending on the various suppliers or different batches. These surface properties of copper strongly affect the growth behavior of graphene, thus rendering the growth conditions irreproducible when different batches of Cu foil are used. Furthermore, the quality of the graphene is severely affected as well. In this work, we report a facile method of copper pre-cleaning to improve the graphene quality and the reproducibility of the growth process. We found that the commercial Ni etchant (based on nitric acid) or nitric acid is the most effective cleaning agent among various acidic or basic solutions. The graphene grown on thus-treated copper surfaces is very clean and mostly monolayer when observed under scanning electron microscopy (SEM) and optical imaging, as compared to the graphene grown on untreated copper foil. Different batches (but with the same catalog number) of copper foil from Alfa Aesar Company were examined to explore the effect of copper pre-cleaning; consistent growth results were obtained when pre-cleaning was used. This method overcomes a commonly encountered problem in graphene growth and could become one of the standard protocols for preparing the copper foil substrate for growing graphene or other 2D materials.

Steel slag affects pH and Si content of container substrates

USDA-ARS?s Scientific Manuscript database

A substrate representing a typical greenhouse potting mix was prepared using 85% sphagnum peat and 15% perlite. The substrate was filled into 10 cm wide containers. A pulverized steel slag (SS) from a basic oxygen furnace, and dolomitic limestone (DL) were amended to the base substrate at a rate o...

Na+ Interactions with the Neutral Amino Acid Transporter ASCT1*

PubMed Central

Scopelliti, Amanda J.; Heinzelmann, Germano; Kuyucak, Serdar; Ryan, Renae M.; Vandenberg, Robert J.

2014-01-01

The alanine, serine, cysteine transporters (ASCTs) belong to the solute carrier family 1A (SLC1A), which also includes the excitatory amino acid transporters (EAATs) and the prokaryotic aspartate transporter GltPh. Acidic amino acid transport by the EAATs is coupled to the co-transport of three Na+ ions and one proton, and the counter-transport of one K+ ion. In contrast, neutral amino acid exchange by the ASCTs does not require protons or the counter-transport of K+ ions and the number of Na+ ions required is not well established. One property common to SLC1A family members is a substrate-activated anion conductance. We have investigated the number and location of Na+ ions required by ASCT1 by mutating residues in ASCT1 that correspond to residues in the EAATs and GltPh that are involved in Na+ binding. Mutations to all three proposed Na+ sites influence the binding of substrate and/or Na+, or the rate of substrate exchange. A G422S mutation near the Na2 site reduced Na+ affinity, without affecting the rate of exchange. D467T and D467A mutations in the Na1 site reduce Na+ and substrate affinity and also the rate of substrate exchange. T124A and D380A mutations in the Na3 site selectively reduce the affinity for Na+ and the rate of substrate exchange without affecting substrate affinity. In many of the mutants that reduce the rate of substrate transport the amplitudes of the substrate-activated anion conductances are not substantially affected indicating altered ion dependence for channel activation compared with substrate exchange. PMID:24808181

Arbuscular Mycorrhiza Improves Substrate Hydraulic Conductivity in the Plant Available Moisture Range Under Root Growth Exclusion.

PubMed

Bitterlich, Michael; Franken, Philipp; Graefe, Jan

2018-01-01

Arbuscular mycorrhizal fungi (AMF) proliferate in soils and are known to affect soil structure. Although their contribution to structure is extensively investigated, the consequences of those processes for soil water extractability and transport has, so far, gained surprisingly little attention. Therefore we asked, whether AMF can affect water retention and unsaturated hydraulic conductivity under exclusion of root ingrowth, in order to minimize plant driven effects. We carried out experiments with tomato inoculated with Rhizoglomus irregulare in a soil substrate with sand and vermiculite that created variation in colonization by mixed pots with wild type (WT) plants and mycorrhiza resistant (RMC) mutants. Sampling cores were introduced and used to assess substrate moisture retention dynamics and modeling of substrate water retention and hydraulic conductivity. AMF reduced the saturated water content and total porosity, but maintained air filled porosity in soil spheres that excluded root ingrowth. The water content between field capacity and the permanent wilting point (6-1500 kPa) was only reduced in mycorrhizal substrates that contained at least one RMC mutant. Plant available water contents correlated positively with soil protein contents. Soil protein contents were highest in pots that possessed the strongest hyphal colonization, but not significantly affected. Substrate conductivity increased up to 50% in colonized substrates in the physiologically important water potential range between 6 and 10 kPa. The improvements in hydraulic conductivity are restricted to substrates where at least one WT plant was available for the fungus, indicating a necessity of a functional symbiosis for this effect. We conclude that functional mycorrhiza alleviates the resistance to water movement through the substrate in substrate areas outside of the root zone.

Touching moments: desire modulates the neural anticipation of active romantic caress

PubMed Central

Ebisch, Sjoerd J.; Ferri, Francesca; Gallese, Vittorio

2014-01-01

A romantic caress is a basic expression of affiliative behavior and a primary reinforcer. Given its inherent affective valence, its performance also would imply the prediction of reward values. For example, touching a person for whom one has strong passionate feelings likely is motivated by a strong desire for physical contact and associated with the anticipation of hedonic experiences. The present study aims at investigating how the anticipatory neural processes of active romantic caress are modulated by the intensity of the desire for affective contact as reflected by passionate feelings for the other. Functional magnetic resonance imaging scanning was performed in romantically involved partners using a paradigm that allowed to isolate the specific anticipatory representations of active romantic caress, compared with control caress, while testing for the relationship between neural activity and measures of feelings of passionate love for the other. The results demonstrated that right posterior insula activity in anticipation of romantic caress significantly co-varied with the intensity of desire for union with the other. This effect was independent of the sensory-affective properties of the performed touch, like its pleasantness. Furthermore, functional connectivity analysis showed that the same posterior insula cluster interacted with brain regions related to sensory-motor functions as well as to the processing and anticipation of reward. The findings provide insight on the neural substrate mediating between the desire for and the performance of romantic caress. In particular, we propose that anticipatory activity patterns in posterior insula may modulate subsequent sensory-affective processing of skin-to-skin contact. PMID:24616676

Global genetic analyses reveal strong inter-ethnic variability in the loss of activity of the organic cation transporter OCT1.

PubMed

Seitz, Tina; Stalmann, Robert; Dalila, Nawar; Chen, Jiayin; Pojar, Sherin; Dos Santos Pereira, Joao N; Krätzner, Ralph; Brockmöller, Jürgen; Tzvetkov, Mladen V

2015-01-01

The organic cation transporter OCT1 (SLC22A1) mediates the uptake of vitamin B1, cationic drugs, and xenobiotics into hepatocytes. Nine percent of Caucasians lack or have very low OCT1 activity due to loss-of-function polymorphisms in OCT1 gene. Here we analyzed the global genetic variability in OCT1 to estimate the therapeutic relevance of OCT1 polymorphisms in populations beyond Caucasians and to identify evolutionary patterns of the common loss of OCT1 activity in humans. We applied massively parallel sequencing to screen for coding polymorphisms in 1,079 unrelated individuals from 53 populations worldwide. The obtained data was combined with the existing 1000 Genomes data comprising an additional 1,092 individuals from 14 populations. The identified OCT1 variants were characterized in vitro regarding their cellular localization and their ability to transport 10 known OCT1 substrates. Both the population genetics data and transport data were used in tandem to generate a world map of loss of OCT1 activity. We identified 16 amino acid substitutions potentially causing loss of OCT1 function and analyzed them together with five amino acid substitutions that were not expected to affect OCT1 function. The variants constituted 16 major alleles and 14 sub-alleles. Six major alleles showed improper subcellular localization leading to substrate-wide loss in activity. Five major alleles showed correct subcellular localization, but substrate-specific loss of activity. Striking differences were observed in the frequency of loss of OCT1 activity worldwide. While most East Asian and Oceanian individuals had completely functional OCT1, 80 % of native South American Indians lacked functional OCT1 alleles. In East Asia and Oceania the average nucleotide diversity of the loss-of-function variants was much lower than that of the variants that do not affect OCT1 function (ratio of 0.03) and was significantly lower than the theoretically expected heterozygosity (Tajima's D = -1.64, P < 0.01). Comprehensive genetic analyses showed strong global variations in the frequency of loss of OCT1 activity with selection pressure for maintaining OCT1 activity in East Asia and Oceania. These results not only enable pharmacogenetically-based optimization of drug treatment worldwide, but may help elucidate the functional role of human OCT1.

Simulation of thermal management in AlGaN/GaN HEMTs with integrated diamond heat spreaders

NASA Astrophysics Data System (ADS)

Wang, A.; Tadjer, M. J.; Calle, F.

2013-05-01

We investigated the impact of diamond heat spreading layers on the performance of AlGaN/GaN high-electron-mobility-transistors (HEMTs). A finite element method was used to simulate the thermal and electrical characteristics of the devices under dc and pulsed operation conditions. The results show that the device performance can be improved significantly by optimized heat spreading, an effect strongly dependent on the lateral thermal conductivity of the initial several micrometers of diamond deposition. Of crucial importance is the proximity of the diamond layer to the heat source, which makes this method advantageous over other thermal management procedures, especially for the device in pulsed operation. In this case, the self-heating effect can be suppressed, and it is not affected by either the substrate or its thermal boundary resistance at the GaN/substrate at wider pulses. The device with a 5 µm diamond layer can present 10.5% improvement of drain current, and the self-heating effect can be neglected for a 100 ns pulse width at 1 V gate and 20 V drain voltage.

Optical properties of ordered ZnO/Ag thin films on polystyrene spheres

NASA Astrophysics Data System (ADS)

Li, Xiu; Chen, Xiuyan; Xin, Zhiqing; Li, Luhai; Xu, Yanfang

2017-08-01

A thorough research of the optical properties of ZnO/Ag structures sputtered by RF on PS colloidal crystal molds with different diameters is reported. The influences of the period of the substrates on the performance of ZnO thin films were studied. The results of scanning electron microscopic, X-ray diffraction patterns and UV-vis absorption spectroscopy indicated that the ZnO/Ag thin films were well-covering on PS colloidal crystal molds. The diameter of the polystyrene particles significantly influenced the PL spectrum intensity of ZnO/Ag by affecting the interferences of light. After adding PS colloidal crystal molds with different diameters, all the samples show two luminescent regions, namely a strong, narrow UV emission peak and a wide, weak visible emission band. However, the signal of UV emission increases more significantly. In particular, the maximum enhancement occurs when the diameter is 300 nm. This work proposes an effective way to improve ZnO light emission based on a simple, rapid and cost effective method to fabricate ordered periodic substrates by preparing single layer polystyrene microspheres masks.

Epitaxial Fe{sub 3}Pt/FePt nanocomposites on MgO and SrTiO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casoli, F., E-mail: casoli@imem.cnr.it; Nasi, L.; Cabassi, R.

We have exploited the pseudomorphic growth of the magnetically soft Fe{sub 3}Pt phase on top of L1{sub 0}-FePt to obtain fully epitaxial soft/hard nanocomposites on both MgO(100) and SrTiO{sub 3}(100). The magnetic properties of this new nanocomposite system, driven by the soft/hard exchange-coupling, can be tailored by varying soft phase thickness, soft phase magnetic anisotropy and substrate. Coercivity is strongly reduced by the addition of the soft phase, a reduction which is definitely affected by the nominal composition of the soft phase and by the substrate choice; similarly is the magnetic phase diagram of the composite system. Coercive field decreasesmore » down to 21% of the hard layer value for Fe{sub 3}Pt(5 nm)/FePt(3.55 nm) nanocomposites on SrTiO{sub 3}; this maximum coercivity reduction was obtained with a nominal atomic content of Fe in the soft phase of 80%.« less

Bacteria Associated with Copestylum (Diptera, Syrphidae) Larvae and Their Cactus Host Isolatocereus dumortieri

PubMed Central

Martínez-Falcón, Ana Paola; Durbán, Ana; Latorre, Amparo; Antón, Josefa; Marcos-García, María de los Ángeles

2011-01-01

We describe the gut bacterial diversity inhabiting two saprophagous syrphids and their breeding substrate (decayed tissues of the columnar cactus Isolatocereus dumortieri). We analyzed the gut microbiota of Copestylum latum (scooping larvae that feed on decayed cactus tissues) and Copestylum limbipenne (whose larvae can also feed on semiliquid tissues) using molecular techniques. DNA was extracted from larval guts and cactus tissues. The V1-V3 region of the 16S rRNA genes was amplified and sequenced. A total of 31079 sequences were obtained. The main findings are: C. limbipenne is dominated by several Enterobacteriaceae, including putative nitrogen-fixing genera and pectinolitic species and some denitrifying species, whereas in C. latum unclassified Gammaproteobacteria predominate. Decayed tissues have a dominant lactic acid bacterial community. The bacterial communities were more similar between larval species than between each larva and its breeding substrate. The results suggest that the gut bacterial community in these insects is not strongly affected by diet and must be dependent on other factors, such as vertical transmission, evolutionary history and host innate immunity. PMID:22132101

3D printing of an interpenetrating network hydrogel material with tunable viscoelastic properties.

PubMed

Bootsma, Katherine; Fitzgerald, Martha M; Free, Brandon; Dimbath, Elizabeth; Conjerti, Joe; Reese, Greg; Konkolewicz, Dominik; Berberich, Jason A; Sparks, Jessica L

2017-06-01

Interpenetrating network (IPN) hydrogel materials are recognized for their unique mechanical properties. While IPN elasticity and toughness properties have been explored in previous studies, the factors that impact the time-dependent stress relaxation behavior of IPN materials are not well understood. Time-dependent (i.e. viscoelastic) mechanical behavior is a critical design parameter in the development of materials for a variety of applications, such as medical simulation devices, flexible substrate materials, cellular mechanobiology substrates, or regenerative medicine applications. This study reports a novel technique for 3D printing alginate-polyacrylamide IPN gels with tunable elastic and viscoelastic properties. The viscoelastic stress relaxation behavior of the 3D printed alginate-polyacrylamide IPN hydrogels was influenced most strongly by varying the concentration of the acrylamide cross-linker (MBAA), while the elastic modulus was affected most by varying the concentration of total monomer material. The material properties of our 3D printed IPN constructs were consistent with those reported in the biomechanics literature for soft tissues such as skeletal muscle, cardiac muscle, skin and subcutaneous tissue. Copyright © 2017 Elsevier Ltd. All rights reserved.

LAND USE AND NATURAL HYDRAULIC CONTROLS ON STREAM SUBSTRATE AND MACROINVERTEBRATE ASSEMBLAGES IN REGIONAL SURVEYS

EPA Science Inventory

In large regions, human land uses typically overlay wide ranges of natural geomorphic factors that control stream habitat characteristics and benthic macroinvertebrate assemblages. Many macroinvertebrate measures of stream "health" show strong association with substrate size, a ...

Spontaneous and strong multi-layer graphene n-doping on soda-lime glass and its application in graphene-semiconductor junctions

DOE PAGES

Dissanayake, D. M. N. M.; Ashraf, A.; Dwyer, D.; ...

2016-02-12

Scalable and low-cost doping of graphene could improve technologies in a wide range of fields such as microelectronics, optoelectronics, and energy storage. While achieving strong p-doping is relatively straightforward, non-electrostatic approaches to n-dope graphene, such as chemical doping, have yielded electron densities of 9.5 × 10 12 e/cm 2 or below. Furthermore, chemical doping is susceptible to degradation and can adversely affect intrinsic graphene’s properties. Here we demonstrate strong (1.33 × 10 13 e/cm 2), robust, and spontaneous graphene n-doping on a soda-lime-glass substrate via surface-transfer doping from Na without any external chemical, high-temperature, or vacuum processes. Remarkably, the n-dopingmore » reaches 2.11 × 10 13 e/cm 2 when graphene is transferred onto a p-type copper indium gallium diselenide (CIGS) semiconductor that itself has been deposited onto soda-lime-glass, via surface-transfer doping from Na atoms that diffuse to the CIGS surface. Using this effect, we demonstrate an n-graphene/p-semiconductor Schottky junction with ideality factor of 1.21 and strong photo-response. As a result, the ability to achieve strong and persistent graphene n-doping on low-cost, industry-standard materials paves the way toward an entirely new class of graphene-based devices such as photodetectors, photovoltaics, sensors, batteries, and supercapacitors.« less

Tuning the Hydration and Lubrication of the Embedded Load-Bearing Hydrogel Fibers.

PubMed

Zhang, Ran; Feng, Yange; Ma, Shuanhong; Cai, Meirong; Yang, Jun; Yu, Bo; Zhou, Feng

2017-03-07

One of the most prominent properties of hydrogels is their excellent hydrolubrication that derives from the strong hydration of the gel network. However, excessive hydration makes hydrogels exhibit a very poor mechanical property, which limits their practical applications. Here, we prepared a novel composite surface of hydrogel nanofibers embedded in an anodic aluminum oxide substrate which exhibited both excellent lubrication and a high load-bearing capacity. Through the copolymerization of acrylic acid and 3-sulfopropyl methacrylate potassium salt, the gel network swelled sufficiently in aqueous solution and caused high osmotic pressure repulsion to bear heavy loads and hence exhibited excellent aqueous lubrication (μ ≈ 0.01). Notably, the friction coefficient of gels showed no dependence on the load in the experiment, whereas it was strongly influenced by the sliding velocity. Additionally, both electrolyte solution and ionic surfactants affect the conformation of the polymer chains, which results in a significant impact on the friction properties of hydrogel fibers.

Coated substrates and process

DOEpatents

Chu, Wei-kan; Childs, Charles B.

1991-01-01

Disclosed herein is a coated substrate and a process for forming films on substrates and for providing a particularly smooth film on a substrate. The method of this invention involves subjecting a surface of a substrate to contact with a stream of ions of an inert gas having sufficient force and energy to substantially change the surface characteristics of said substrate, and then exposing a film-forming material to a stream of ions of an inert gas having sufficient energy to vaporize the atoms of said film-forming material and to transmit the vaporized atoms to the substrate surface with sufficient force to form a film bonded to the substrate. This process is particularly useful commercially because it forms strong bonds at room temperature. This invention is particularly useful for adhering a gold film to diamond and forming ohmic electrodes on diamond, but also can be used to bond other films to substrates.

Modeling diffusion control on organic matter decomposition in unsaturated soil pore space

NASA Astrophysics Data System (ADS)

Vogel, Laure; Pot, Valérie; Garnier, Patricia; Vieublé-Gonod, Laure; Nunan, Naoise; Raynaud, Xavier; Chenu, Claire

2014-05-01

Soil Organic Matter decomposition is affected by soil structure and water content, but field and laboratory studies about this issue conclude to highly variable outcomes. Variability could be explained by the discrepancy between the scale at which key processes occur and the measurements scale. We think that physical and biological interactions driving carbon transformation dynamics can be best understood at the pore scale. Because of the spatial disconnection between carbon sources and decomposers, the latter rely on nutrient transport unless they can actively move. In hydrostatic case, diffusion in soil pore space is thus thought to regulate biological activity. In unsaturated conditions, the heterogeneous distribution of water modifies diffusion pathways and rates, thus affects diffusion control on decomposition. Innovative imaging and modeling tools offer new means to address these effects. We have developed a new model based on the association between a 3D Lattice-Boltzmann Model and an adimensional decomposition module. We designed scenarios to study the impact of physical (geometry, saturation, decomposers position) and biological properties on decomposition. The model was applied on porous media with various morphologies. We selected three cubic images of 100 voxels side from µCT-scanned images of an undisturbed soil sample at 68µm resolution. We used LBM to perform phase separation and obtained water phase distributions at equilibrium for different saturation indices. We then simulated the diffusion of a simple soluble substrate (glucose) and its consumption by bacteria. The same mass of glucose was added as a pulse at the beginning of all simulations. Bacteria were placed in few voxels either regularly spaced or concentrated close to or far from the glucose source. We modulated physiological features of decomposers in order to weight them against abiotic conditions. We could evidence several effects creating unequal substrate access conditions for decomposers, hence inducing contrasted decomposition kinetics: position of bacteria relative to the substrate diffusion pathways, diffusion rate and hydraulic connectivity between bacteria and substrate source, local substrate enrichment due to restricted mass transfer. Physiological characteristics had a strong impact on decomposition only when glucose diffused easily but not when diffusion limitation prevailed. This suggests that carbon dynamics should not be considered to derive from decomposers' physiology alone but rather from the interactions of biological and physical processes at the microscale.

Strong thin membrane structure. [solar sails

NASA Technical Reports Server (NTRS)

Frazer, R. E. (Inventor)

1979-01-01

A continuous process is described for producing strong lightweight structures for use as solar sails for spacecraft propulsion by radiation pressure. A thin reflective coating, such as aluminum, is applied to a rotating cylinder. A nylon mesh, applied over the aluminum coating, is then coated with a polymerizing material such as a para-xylylene monomer gas to polymerize as a film bound to the mesh and the aluminum. An emissivity increasing material such as chromium or silicon monoxide is applied to the polymer film to disperse such material colloidally into the growing polymer film, or to the final polymer film. The resulting membrane structure is then removed from the cylinder. Alternately, the membrane structure can be formed by etching a substrate in the form of an organic film such as a polymide, or a metal foil, to remove material from the substrate and reduce its thickness. A thin reflective coating (aluminum) is applied on one side of the substrate, and an emissivity increasing coating is applied on the reverse side of the substrate.

Nanofabricated Collagen-Inspired Synthetic Elastomers for Primary Rat Hepatocyte Culture

PubMed Central

Bettinger, Christopher J.; Kulig, Katherine M.; Vacanti, Joseph P.

2009-01-01

Synthetic substrates that mimic the properties of extracellular matrix proteins hold significant promise for use in systems designed for tissue engineering applications. In this report, we designed a synthetic polymeric substrate that is intended to mimic chemical, mechanical, and topological characteristics of collagen. We found that elastomeric poly(ester amide) substrates modified with replica-molded nanotopographic features enhanced initial attachment, spreading, and adhesion of primary rat hepatocytes. Further, hepatocytes cultured on nanotopographic substrates also demonstrated reduced albumin secretion and urea synthesis, which is indicative of strongly adherent hepatocytes. These results suggest that these engineered substrates can function as synthetic collagen analogs for in vitro cell culture. PMID:18847357

High performance and reusable SERS substrates using Ag/ZnO heterostructure on periodic silicon nanotube substrate

NASA Astrophysics Data System (ADS)

Lai, Yi-Chen; Ho, Hsin-Chia; Shih, Bo-Wei; Tsai, Feng-Yu; Hsueh, Chun-Hway

2018-05-01

Surface-enhanced Raman scattering (SERS) substrate with a higher surface area, enhanced light harvesting, multiple hot spots and strong electromagnetic field enhancements would exhibit enhanced Raman signals. Herein, the Ag nanoparticle/ZnO nanowire heterostructure decorated periodic silicon nanotube (Ag@ZnO@SiNT) substrate was proposed and fabricated. The proposed structure employed as SERS-active substrate was examined, and the results showed both the high performance in terms of high sensitivity and good reproducibility. Furthermore, the Ag@ZnO@SiNT substrate demonstrated the self-cleaning performance through the photocatalytic degradation of probed molecules upon UV-irradiation. The results showed that the proposed nanostructure had high performance, good reproducibility and reusability, and it is a promising SERS-active substrate for molecular sensing and cleaning.

Strong metal support interaction of Pt on TiO2 grown by atomic layer deposition and physical vapor deposition for fuel cell applications

NASA Astrophysics Data System (ADS)

Hansen, Robin Paul

Several roadblocks prevent the large-scale commercialization of hydrogen fuel cells, including the stability of the Pt catalysts and their substrates, as well as the high cost of Pt. This is particularly true for the cathode, which requires a higher Pt loading because of the slow kinetics of the oxygen reduction reaction (ORR). The problem with the stability of the substrate can be solved by replacing the traditional carbon support with a conductive metal oxide such as reduced TiO2, which will not easily corrode and should result in longer lasting fuel cells. In this study, Pt was deposited either by atomic layer deposition (ALD) or physical vapor deposition (PVD). The typical size of the Pt islands that were grown using these deposition techniques was 3-8 nm. One factor that can inhibit the catalytic activity of a metal catalyst on a metal oxide is the strong metal support interaction (SMSI). This is where a metal on a reducible metal oxide can be encapsulated by a layer of the metal oxide support material at elevated temperatures. The processing of materials through atomic layer deposition can exceed this temperature. The TiO2 substrates used in this study were either grown by ALD, which results in a polycrystalline anatase film, or were single-crystal rutile TiO2(110) samples prepared in ultra-high vacuum (UHV). The Pt/TiO2 samples were tested electrochemically using cyclic voltammetry (CV) to determine the level of catalytic activity. To determine the effect of the SMSI interaction on the catalytic activity of the PVD grown samples, CV was performed on samples that were annealed in high vacuum after Pt deposition. Additional characterization was performed with scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), and four point probe analysis. Platinum that was deposited by PVD was used as a standard since it is not affected by the SMSI at the low temperature of the substrate during deposition. These samples were analyzed after deposition and then annealed to higher temperatures to induce the SMSI effect. The AR-XPS results for the single crystal TiO2 substrate show that there is an increase in the Ti emission at glancing exit angle after an anneal at 150 °C, which indicates the onset of the SMSI. For the ALD TiO2 substrate, the onset of SMSI was at 380 °C. This work is believed to be the first time in which the SMSI was observed in this fashion. The CV data for the samples with PVD Pt the single crystal TiO2 substrate showed a large reduction of the hydrogen adsortion at 380 °C. For the ORR, there was a reduction in the ORR signal at 380 °C. By 750 °C, the ORR was almost completely suppressed. For the PVD Pt grown on the ALD TiO2 substrates, there was a large increase in the resistivity of the samples after exposure to the acidic electrolyte used during the CV measurements. This resulted in no CV signal for those samples. Another aspect that was significantly different for the two different substrates was the Pt growth morphology. Both the AR-XPS and SEM measurements indicate that the Pt on the single crystal TiO2 substrates grows as distinct islands. For the ALD TiO2 substrates, the Pt islands had a lower profile than the islands grown on the single crystal substrates. This morphology difference is believed to be due to the large defect density of the ALD generated TiO2 or possibly from the different chemical properties of the anatase surface. These results indicate that the ALD generated substrates are more resistant to the effects of the SMSI, but that the ALD substrates are more sensitive to surface contamination.

Effect of Root-Zone Moisture Variations on Growth of Lettuce and Pea Plants

NASA Astrophysics Data System (ADS)

Ilieva, Iliana; Ivanova, Tania

2008-06-01

Variations in substrate moisture lead to changes in water and oxygen availability to plant roots. Ground experiments were carried out in the laboratory prototype of SVET-2 Space Greenhouse to study the effect of variation of root-zone moisture conditions on growth of lettuce and pea plants. The effect of transient increase (for 1 day) and drastic increase (waterlogging for 10 days) of substrate moisture was studied with 16-day old pea and 21-day old lettuce plants respectively. Pea height and fresh biomass accumulation were not affected by transient substrate moisture increase. Net photosynthetic rate (Pn) of pea plants showed fast response to substrate moisture variation, while chlorophyll content did not change. Drastic change of substrate moisture suppressed lettuce Pn, chlorophyll biosynthesis and plant growth. These parameters slowly recovered after termination of waterlogging treatment but lettuce yield was greatly affected. The results showed that the most sensitive physiological parameter to substrate moisture variations is photosynthesis.

Role of Vision and Mechanoreception in Bed Bug, Cimex lectularius L. Behavior

PubMed Central

Singh, Narinderpal; Wang, Changlu; Cooper, Richard

2015-01-01

The role of olfactory cues such as carbon dioxide, pheromones, and kairomones in bed bug, Cimex lectularius L. behavior has been demonstrated. However, the role of vision and mechanoreception in bed bug behavior is poorly understood. We investigated bed bug vision by determining their responses to different colors, vertical objects, and their ability to detect colors and vertical objects under low and complete dark conditions. Results show black and red paper harborages are preferred compared to yellow, green, blue, and white harborages. A bed bug trapping device with a black or red exterior surface was significantly more attractive to bed bugs than that with a white exterior surface. Bed bugs exhibited strong orientation behavior toward vertical objects. The height (15 vs. 30 cm tall) and color (brown vs. black) of the vertical object had no significant effect on orientation behavior of bed bugs. Bed bugs could differentiate color and detect vertical objects at very low background light conditions, but not in complete darkness. Bed bug preference to different substrate textures (mechanoreception) was also explored. Bed bugs preferred dyed tape compared to painted tape, textured painted plastic, and felt. These results revealed that substrate color, presence of vertical objects, and substrate texture affect host-seeking and harborage-searching behavior of bed bugs. Bed bugs may use a combination of vision, mechanoreception, and chemoreception to locate hosts and seek harborages. PMID:25748041

Unusual dewetting of thin polymer films in liquid media containing a poor solvent and a nonsolvent.

PubMed

Xu, Lin; Sharma, Ashutosh; Joo, Sang Woo; Liu, Hui; Shi, Tongfei

2014-12-16

We investigate the control of pattern size and kinetics in spontaneous dewetting of thin polymer films (polystyrene) that are stable to thermal annealing by annealing in a poor solvent (acetone)/nonsolvent (ethanol or n-hexane) liquid mixture. Dewetting occurs by the formation and growth of circular holes that coalesce to form droplets. The influence of the nature and the volume fraction of the nonsolvents on the contact angle of polymer droplets, number density of holes, and the kinetics of holes formation and growth is studied. Addition of ethanol greatly increases the hole density and slows down the kinetics substantially, while affecting only a small change in wettability. n-Hexane addition shows an interesting nonmonotonic response in decreasing the hole density and contact angle in the volume fraction range of 0-0.3 but an opposite effect beyond that. Although the two nonsolvents chosen cannot by themselves induce dewetting, their relative affinity for the solid substrate vis-à-vis acetone can strongly influence the observed dewetting scenarios that are not understood by the existing theoretical considerations. n-Hexane, for example, has great affinity for silicon substrate. In addition to the changes in wettability, viscosity, and film interfacial tension engendered by the nonsolvents, the possibility of the formation of adsorbed liquid layers at the substrate-polymer interface, which can modify the interfacial friction and slippage, needs to be considered.

Vermiculite's strong buffer capacity renders it unsuitable for studies of acidity on soybean (Glycine max L.) nodulation and growth.

PubMed

Indrasumunar, Arief; Gresshoff, Peter M

2013-11-14

Vermiculite is the most common soil-free growing substrate used for plants in horticultural and scientific studies due to its high water holding capacity. However, some studies are not suitable to be conducted in it. The described experiments aimed to test the suitability of vermiculite to study the effect of acidity on nodulation and growth of soybean (Glycine max L.). Two different nutrient solutions (Broughton & Dilworth, and modified Herridge nutrient solutions) with or without MES buffer addition were used to irrigate soybean grown on vermiculite growth substrates. The pH of nutrient solutions was adjusted to either pH 4.0 or 7.0 prior its use. The nodulation and vegetative growth of soybean plants were assessed at 3 and 4 weeks after inoculation. The unsuitability of presumably inert vermiculite as a physical plant growth substrate for studying the effects of acidity on soybean nodulation and plant growth was illustrated. Nodulation and growth of soybean grown in vermiculite were not affected by irrigation with pH-adjusted nutrient solution either at pH 4.0 or 7.0. This was reasonably caused by the ability of vermiculite to neutralise (buffer) the pH of the supplied nutrient solution (pH 2.0-7.0). Due to its buffering capacity, vermiculite cannot be used as growth support to study the effect of acidity on nodulation and plant growth.

Substrate dependent stability of conducting polymer coatings on medical electrodes.

PubMed

Green, Rylie A; Hassarati, Rachelle T; Bouchinet, Lucie; Lee, Chaekyung S; Cheong, Gin L M; Yu, Jin F; Dodds, Christopher W; Suaning, Gregg J; Poole-Warren, Laura A; Lovell, Nigel H

2012-09-01

Conducting polymer (CP) coatings on medical electrodes have the potential to provide superior performance when compared to conventional metallic electrodes, but their stability is strongly dependant on the substrate properties. The aim of this study was to examine the effect of laser roughening of underlying platinum (Pt) electrode surfaces on the mechanical, electrical and biological performance of CP coatings. In addition, the impact of dopant type on electrical performance and stability was assessed. The CP poly(ethylene dioxythiophene) (PEDOT) was coated on Pt microelectrode arrays, with three conventional dopant ions. The in vitro electrical characteristics were assessed by cyclic voltammetry and biphasic stimulation. Results showed that laser roughening of the underlying substrate did not affect the charge injection limit of the coated material, but significantly improved the passive stability and chronic stimulation lifetime without failure of the coating. Accelerated material ageing and long-term biphasic stimulus studies determined that some PEDOT variants experienced delamination within as little as 10 days when the underlying Pt was smooth, but laser roughening to produce a surface index of 2.5 improved stability, such that more than 1.3 billion stimulation cycles could be applied without evidence of failure. PEDOT doped with paratoluene sulfonate (PEDOT/pTS) was found to be the most stable CP on roughened Pt, and presented a surface topography which encouraged neural cell attachment. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

Assessment of benthic macroinvertebrates at Nile tilapia production using artificial substrate samplers.

PubMed

Moura E Silva, M S G; Graciano, T S; Losekann, M E; Luiz, A J B

2016-05-17

Biomonitoring is a cheap and effective tool for evaluation of water quality, and infer on the balance of aquatic ecosystems. The benthic macroinvertebrates are bioindicators sensitive to environmental changes, and can assist in detecting and preventing impacts such as organic enrichment and imbalance in the food chain. We compared the structure of benthic communities on artificial substrate samplers located in places near and far from net cages for production of Nile tilapia (Oreochromis niloticus). Samplers were manufactured with nylon net, using substrates such as crushed stone, gravel, loofah and cattail leaves. Samples were collected after 30 days of colonization, rinsed and then the specimens were identified and quantified. The following metrics were calculated: richness of Operational Taxonomic Units, Margalef richness, abundance of individuals, Shannon index and evenness index. The macrobenthic community structure was strongly modified according to the proximity of the net cages. Metrics showed significant differences (p < 0.05) between near and distant sites, for both periods (dry and rainy seasons). The position of the samplers significantly affected the structure of macroinvertebrate community, as near sites showed higher values for the community metrics, such as richness and diversity. Near sites presented a larger number of individuals, observed both in the dry and rainy seasons, with a predominance of Chironomidae (Diptera) in the dry season and Tubificidae (Oligochaeta) in the rainy season.

Role of vision and mechanoreception in bed bug, Cimex lectularius L. behavior.

PubMed

Singh, Narinderpal; Wang, Changlu; Cooper, Richard

2015-01-01

The role of olfactory cues such as carbon dioxide, pheromones, and kairomones in bed bug, Cimex lectularius L. behavior has been demonstrated. However, the role of vision and mechanoreception in bed bug behavior is poorly understood. We investigated bed bug vision by determining their responses to different colors, vertical objects, and their ability to detect colors and vertical objects under low and complete dark conditions. Results show black and red paper harborages are preferred compared to yellow, green, blue, and white harborages. A bed bug trapping device with a black or red exterior surface was significantly more attractive to bed bugs than that with a white exterior surface. Bed bugs exhibited strong orientation behavior toward vertical objects. The height (15 vs. 30 cm tall) and color (brown vs. black) of the vertical object had no significant effect on orientation behavior of bed bugs. Bed bugs could differentiate color and detect vertical objects at very low background light conditions, but not in complete darkness. Bed bug preference to different substrate textures (mechanoreception) was also explored. Bed bugs preferred dyed tape compared to painted tape, textured painted plastic, and felt. These results revealed that substrate color, presence of vertical objects, and substrate texture affect host-seeking and harborage-searching behavior of bed bugs. Bed bugs may use a combination of vision, mechanoreception, and chemoreception to locate hosts and seek harborages.

Molecular tailoring of interfaces for thin film on substrate systems

NASA Astrophysics Data System (ADS)

Grady, Martha Elizabeth

Thin film on substrate systems appear most prevalently within the microelectronics industry, which demands that devices operate in smaller and smaller packages with greater reliability. The reliability of these multilayer film systems is strongly influenced by the adhesion of each of the bimaterial interfaces. During use, microelectronic components undergo thermo-mechanical cycling, which induces interfacial delaminations leading to failure of the overall device. The ability to tailor interfacial properties at the molecular level provides a mechanism to improve thin film adhesion, reliability and performance. This dissertation presents the investigation of molecular level control of interface properties in three thin film-substrate systems: photodefinable polyimide films on passivated silicon substrates, self-assembled monolayers at the interface of Au films and dielectric substrates, and mechanochemically active materials on rigid substrates. For all three materials systems, the effect of interfacial modifications on adhesion is assessed using a laser-spallation technique. Laser-induced stress waves are chosen because they dynamically load the thin film interface in a precise, noncontacting manner at high strain rates and are suitable for both weak and strong interfaces. Photodefinable polyimide films are used as dielectrics in flip chip integrated circuit packages to reduce the stress between silicon passivation layers and mold compound. The influence of processing parameters on adhesion is examined for photodefinable polyimide films on silicon (Si) substrates with three different passivation layers: silicon nitride (SiNx), silicon oxynitride (SiOxNy), and the native silicon oxide (SiO2). Interfacial strength increases when films are processed with an exposure step as well as a longer cure cycle. Additionally, the interfacial fracture energy is assessed using a dynamic delamination protocol. The high toughness of this interface (ca. 100 J/m2) makes it difficult to use more conventional interfacial fracture testing techniques. Self-assembled monolayers (SAMs) provide an enabling platform for molecular tailoring of the chemical and physical properties of an interface in an on-demand fashion. The SAM end-group functionality is systematically varied and the corresponding effect on interfacial adhesion between a transfer printed gold (Au) film and a fused silica substrate is measured. SAMs with four different end groups are investigated: methyl, amine, bromine and thiol. In addition to these four end groups, mixed monolayers of increasing molar ratio of thiol to methyl SAMs in solution are investigated. There is a strong dependence of interfacial chemistry on the adhesion strength of Au films. In addition to the chemical functionality of the SAM, surface roughness of the underlying substrate also has a significant impact on the interfacial strength. Thin films of mechanochemically active polymer are subjected to laser-generated, high amplitude acoustic pulses. Stress wave propagation through the film produces large amplitude stresses (>100 MPa) in short time frames (10-20 ns), leading to very high strain-rates (ca. 107-108 s -1). The polymer system, spiropyran (SP)- linked polystyrene (PS), undergoes a force-induced chemical reaction causing fluorescence and color change. Activation of SP is evident via a fluorescence signal in thin films subject to high strain-rates. In contrast, quasi-static loading of bulk SP-linked PS samples failed to result in SP activation. Mechanoresponsive coatings have potential to indicate deformation under shockwave loading conditions. In addition to SP-linked polymer films, the activation of spiropyran interfacial molecules with different side groups is characterized as they adsorb onto a SAM platform with preferential amine terminating chemistry. The reactivity of SP monolayers due to UV irradiation is evaluated by water contact angle goniometry and fluorescence spectroscopy. Side groups on the interfacial spiropyran molecule affect the reactivity and the proximity of neighboring spiropyrans can prevent efficient mobility.

Substrate specificity effects of lipoxygenase products and inhibitors on soybean lipoxygenase-1.

PubMed

Wecksler, Aaron T; Garcia, Natalie K; Holman, Theodore R

2009-09-15

Recently, it has been shown that lipoxygenase (LO) products affect the substrate specificity of human 15-LO. In the current paper, we demonstrate that soybean LO-1 (sLO-1) is not affected by its own products, however, inhibitors which bind the allosteric site, oleyl sulfate (OS) and palmitoleyl sulfate (PS), not only lower catalytic activity, but also change the substrate specificity, by increasing the arachidonic acid (AA)/linoleic acid (LA) ratio to 4.8 and 4.0, respectively. The fact that LO inhibitors can lower activity and also change the LO product ratio is a new concept in lipoxygenase inhibition, where the goal is to not only reduce the catalytic activity but also alter substrate selectivity towards a physiologically beneficial product.

Strong thin membrane structure for use as solar sail comprising substrate with reflective coating on one surface and an infra red emissivity increasing coating on the other surface

NASA Technical Reports Server (NTRS)

Frazer, Robert E. (Inventor)

1982-01-01

Production of strong lightweight membrane structure by applying a thin reflective coating such as aluminum to a rotating cylinder, applying a mesh material such as nylon over the aluminum coating, coating the mesh overlying the aluminum with a polymerizing material such as a para-xylylene monomer gas to polymerize as a film bound to the mesh and the aluminum, and applying an emissivity increasing material such as chromium and silicon monoxide to the polymer film to disperse such material colloidally into the growing polymer film, or applying such material to the final polymer film, and removing the resulting membrane structure from the cylinder. Alternatively, such membrane structure can be formed by etching a substrate in the form of an organic film such as a polyimide, or a metal foil, to remove material from the substrate and reduce its thickness, applying a thin reflective coating such as aluminum on one side of the substrate and applying an emissivity increasing coating such as chromium and silicon monoxide on the reverse side of the substrate.

Falling films on flexible inclines

NASA Astrophysics Data System (ADS)

Matar, O. K.; Craster, R. V.; Kumar, S.

2007-11-01

The nonlinear stability and dynamic behavior of falling fluid films is studied for flow over a flexible substrate. We use asymptotic methods to deduce governing equations valid in various limits. Long-wave theory is used to derive Benney-like coupled equations for the film thickness and substrate deflection. Weakly nonlinear equations are then derived from these equations that, in the limit of large wall damping and/or large wall tension, reduce to the Kuramoto-Sivashinsky equation. These models break down when inertia becomes more significant, so we also use a long-wave approximation in conjunction with integral theory to derive three strongly coupled nonlinear evolution equations for the film thickness, substrate deflection, and film volumetric flow rate valid at higher Reynolds numbers. These equations, accounting for inertia, capillary, viscous, wall tension, and damping effects, are solved over a wide range of parameters. Our results suggest that decreasing wall damping and/or wall tension can promote the development of chaos in the weakly nonlinear regime and lead to severe substrate deformations in the strongly nonlinear regime; these can give rise to situations in which the free surface and underlying substrate come into contact in finite time.

Sexual dimorphism in the attachment ability of the ladybird beetle Coccinella septempunctata on soft substrates

NASA Astrophysics Data System (ADS)

Heepe, Lars; Petersen, Dennis S.; Tölle, Lisa; Wolff, Jonas O.; Gorb, Stanislav N.

2017-01-01

Many insects possess adhesive foot pads, which enable reliable attachment to diverse and unpredictable substrates. The function of these adhesive organs was shown to be affected by environmental conditions such as substrate roughness, chemistry, and ambient humidity. So far, the attachment ability of insects and also that of spiders and geckos has been tested on rigid substrates only. However, the natural habitats of climbing animals may provide a variety of substrate stiffness ranging from rigid rock surfaces to soft, biofilm covered substrates. In order to test the effect of different substrate stiffness on the attachment ability of insects, we have performed friction experiments with female and male ladybird beetles Coccinella septempunctata on smooth silicone elastomer substrates of different stiffness, using a centrifugal force tester. Whereas in females, the attachment ability was not affected by the substrate stiffness within the range of tested stiffness, males showed decreasing attachment ability with decreasing substrate stiffness. This sexual dimorphism in attachment ability is explained by the presence of a specialized, discoidal seta type in males, which is not present in females. It is argued that discoidal setae, when softer if compared to the substrate, may show an advantageous peak-free interfacial stress distribution when being pulled off the substrate. For such setae being stiffer if compared the substrate, they potentially show increased edge stress concentration. In this case, lower pull-off forces are expected, in agreement with the experimentally obtained results. With the present study, we demonstrate for the first time that the substrate stiffness may have an effect on the attachment ability of climbing animals, which may also be of relevance for technical and medical applications involving adhesion to soft substrates.

Investigating the Impact of Asp181 Point Mutations on Interactions between PTP1B and Phosphotyrosine Substrate

NASA Astrophysics Data System (ADS)

Liu, Mengyuan; Wang, Lushan; Sun, Xun; Zhao, Xian

2014-05-01

Protein tyrosine phosphatase 1B (PTP1B) is a key negative regulator of insulin and leptin signaling, which suggests that it is an attractive therapeutic target in type II diabetes and obesity. The aim of this research is to explore residues which interact with phosphotyrosine substrate can be affected by D181 point mutations and lead to increased substrate binding. To achieve this goal, molecular dynamics simulations were performed on wild type (WT) and two mutated PTP1B/substrate complexes. The cross-correlation and principal component analyses show that point mutations can affect the motions of some residues in the active site of PTP1B. Moreover, the hydrogen bond and energy decomposition analyses indicate that apart from residue 181, point mutations have influence on the interactions of substrate with several residues in the active site of PTP1B.

pKa Modulation of the Acid/Base Catalyst within GH32 and GH68: A Role in Substrate/Inhibitor Specificity?

PubMed Central

Yuan, Shuguang; Le Roy, Katrien; Venken, Tom; Lammens, Willem; Van den Ende, Wim; De Maeyer, Marc

2012-01-01

Glycoside hydrolases of families 32 (GH32) and 68 (GH68) belong to clan GH-J, containing hydrolytic enzymes (sucrose/fructans as donor substrates) and fructosyltransferases (sucrose/fructans as donor and acceptor substrates). In GH32 members, some of the sugar substrates can also function as inhibitors, this regulatory aspect further adding to the complexity in enzyme functionalities within this family. Although 3D structural information becomes increasingly available within this clan and huge progress has been made on structure-function relationships, it is not clear why some sugars bind as inhibitors without being catalyzed. Conserved aspartate and glutamate residues are well known to act as nucleophile and acid/bases within this clan. Based on the available 3D structures of enzymes and enzyme-ligand complexes as well as docking simulations, we calculated the pKa of the acid-base before and after substrate binding. The obtained results strongly suggest that most GH-J members show an acid-base catalyst that is not sufficiently protonated before ligand entrance, while the acid-base can be fully protonated when a substrate, but not an inhibitor, enters the catalytic pocket. This provides a new mechanistic insight aiming at understanding the complex substrate and inhibitor specificities observed within the GH-J clan. Moreover, besides the effect of substrate entrance on its own, we strongly suggest that a highly conserved arginine residue (in the RDP motif) rather than the previously proposed Tyr motif (not conserved) provides the proton to increase the pKa of the acid-base catalyst. PMID:22662155

Nemesia Root Hair Response to Paper Pulp Substrate for Micropropagation

PubMed Central

Labrousse, Pascal; Delmail, David; Decou, Raphaël; Carlué, Michel; Lhernould, Sabine; Krausz, Pierre

2012-01-01

Agar substrates for in vitro culture are well adapted to plant micropropagation, but not to plant rooting and acclimatization. Conversely, paper-pulp-based substrates appear as potentially well adapted for in vitro culture and functional root production. To reinforce this hypothesis, this study compares in vitro development of nemesia on several substrates. Strong differences between nemesia roots growing in agar or in paper-pulp substrates were evidenced through scanning electron microscopy. Roots developed in agar have shorter hairs, larger rhizodermal cells, and less organized root caps than those growing on paper pulp. In conclusion, it should be noted that in this study, in vitro microporous substrates such as paper pulp lead to the production of similar root hairs to those found in greenhouse peat substrates. Consequently, if agar could be used for micropropagation, rooting, and plant acclimatization, enhancement could be achieved if rooting stage was performed on micro-porous substrates such as paper pulp. PMID:22312323

Nemesia root hair response to paper pulp substrate for micropropagation.

PubMed

Labrousse, Pascal; Delmail, David; Decou, Raphaël; Carlué, Michel; Lhernould, Sabine; Krausz, Pierre

2012-01-01

Agar substrates for in vitro culture are well adapted to plant micropropagation, but not to plant rooting and acclimatization. Conversely, paper-pulp-based substrates appear as potentially well adapted for in vitro culture and functional root production. To reinforce this hypothesis, this study compares in vitro development of nemesia on several substrates. Strong differences between nemesia roots growing in agar or in paper-pulp substrates were evidenced through scanning electron microscopy. Roots developed in agar have shorter hairs, larger rhizodermal cells, and less organized root caps than those growing on paper pulp. In conclusion, it should be noted that in this study, in vitro microporous substrates such as paper pulp lead to the production of similar root hairs to those found in greenhouse peat substrates. Consequently, if agar could be used for micropropagation, rooting, and plant acclimatization, enhancement could be achieved if rooting stage was performed on micro-porous substrates such as paper pulp.

Assessing Posidonia oceanica seedling substrate preference: an experimental determination of seedling anchorage success in rocky vs. sandy substrates.

PubMed

Alagna, Adriana; Fernández, Tomás Vega; Anna, Giovanni D; Magliola, Carlo; Mazzola, Salvatore; Badalamenti, Fabio

2015-01-01

In the last decades the growing awareness of the ecological importance of seagrass meadows has prompted increasing efforts to protect existing beds and restore degraded habitats. An in-depth knowledge of factors acting as major drivers of propagule settlement and recruitment is required in order to understand patterns of seagrass colonization and recovery and to inform appropriate management and conservation strategies. In this work Posidonia oceanica seedlings were reared for five months in a land-based culture facility under simulated natural hydrodynamic conditions to identify suitable substrates for seedling anchorage. Two main substrate features were investigated: firmness (i.e., sand vs. rock) and complexity (i.e., size of interstitial spaces between rocks). Seedlings were successfully grown in culture tanks, obtaining overall seedling survival of 93%. Anchorage was strongly influenced by substrate firmness and took place only on rocks, where it was as high as 89%. Anchorage occurred through adhesion by sticky root hairs. The minimum force required to dislodge plantlets attached to rocky substrates reached 23.830 N (equivalent to 2.43 kg), which would potentially allow many plantlets to overcome winter storms in the field. The ability of rocky substrates to retain seedlings increased with their complexity. The interstitial spaces between rocks provided appropriate microsites for seedling settlement, as seeds were successfully retained, and a suitable substrate for anchorage was available. In conclusion P. oceanica juveniles showed a clear-cut preference for hard substrates over the sandy one, due to the root system adhesive properties. In particular, firm and complex substrates allowed for propagule early and strong anchorage, enhancing persistence and establishment probabilities. Seedling substrate preference documented here leads to expect a more successful sexual recruitment on hard bottoms compared with soft ones. This feature could have influenced P. oceanica patterns of colonization in past and present time.

Variable substrate preference among phospholipase D toxins from sicariid spiders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lajoie, Daniel M.; Roberts, Sue A.; Zobel-Thropp, Pamela A.

Venoms of the sicariid spiders contain phospholipase D enzyme toxins that can cause severe dermonecrosis and even death in humans. These enzymes convert sphingolipid and lysolipid substrates to cyclic phosphates by activating a hydroxyl nucleophile present in both classes of lipid. The most medically relevant substrates are thought to be sphingomyelin and/or lysophosphatidylcholine. To better understand the substrate preference of these toxins, we used 31P NMR to compare the activity of three related but phylogenetically diverse sicariid toxins against a diverse panel of sphingolipid and lysolipid substrates. Two of the three showed significantly faster turnover of sphingolipids over lysolipids, andmore » all three showed a strong preference for positively charged (choline and/or ethanolamine) over neutral (glycerol and serine) headgroups. Strikingly, however, the enzymes vary widely in their preference for choline, the headgroup of both sphingomyelin and lysophosphatidylcholine, versus ethanolamine. An enzyme from Sicarius terrosus showed a strong preference for ethanolamine over choline, whereas two paralogous enzymes from Loxosceles arizonica either preferred choline or showed no significant preference. Intrigued by the novel substrate preference of the Sicarius enzyme, we solved its crystal structure at 2.1 Å resolution. Lastly, the evolution of variable substrate specificity may help explain the reduced dermonecrotic potential of some natural toxin variants, because mammalian sphingolipids use primarily choline as a positively charged headgroup; it may also be relevant for sicariid predatory behavior, because ethanolamine-containing sphingolipids are common in insect prey.« less

Variable substrate preference among phospholipase D toxins from sicariid spiders

DOE PAGES

Lajoie, Daniel M.; Roberts, Sue A.; Zobel-Thropp, Pamela A.; ...

2015-03-09

Venoms of the sicariid spiders contain phospholipase D enzyme toxins that can cause severe dermonecrosis and even death in humans. These enzymes convert sphingolipid and lysolipid substrates to cyclic phosphates by activating a hydroxyl nucleophile present in both classes of lipid. The most medically relevant substrates are thought to be sphingomyelin and/or lysophosphatidylcholine. To better understand the substrate preference of these toxins, we used 31P NMR to compare the activity of three related but phylogenetically diverse sicariid toxins against a diverse panel of sphingolipid and lysolipid substrates. Two of the three showed significantly faster turnover of sphingolipids over lysolipids, andmore » all three showed a strong preference for positively charged (choline and/or ethanolamine) over neutral (glycerol and serine) headgroups. Strikingly, however, the enzymes vary widely in their preference for choline, the headgroup of both sphingomyelin and lysophosphatidylcholine, versus ethanolamine. An enzyme from Sicarius terrosus showed a strong preference for ethanolamine over choline, whereas two paralogous enzymes from Loxosceles arizonica either preferred choline or showed no significant preference. Intrigued by the novel substrate preference of the Sicarius enzyme, we solved its crystal structure at 2.1 Å resolution. Lastly, the evolution of variable substrate specificity may help explain the reduced dermonecrotic potential of some natural toxin variants, because mammalian sphingolipids use primarily choline as a positively charged headgroup; it may also be relevant for sicariid predatory behavior, because ethanolamine-containing sphingolipids are common in insect prey.« less

Variable Substrate Preference among Phospholipase D Toxins from Sicariid Spiders*

PubMed Central

Lajoie, Daniel M.; Roberts, Sue A.; Zobel-Thropp, Pamela A.; Delahaye, Jared L.; Bandarian, Vahe; Binford, Greta J.; Cordes, Matthew H. J.

2015-01-01

Venoms of the sicariid spiders contain phospholipase D enzyme toxins that can cause severe dermonecrosis and even death in humans. These enzymes convert sphingolipid and lysolipid substrates to cyclic phosphates by activating a hydroxyl nucleophile present in both classes of lipid. The most medically relevant substrates are thought to be sphingomyelin and/or lysophosphatidylcholine. To better understand the substrate preference of these toxins, we used 31P NMR to compare the activity of three related but phylogenetically diverse sicariid toxins against a diverse panel of sphingolipid and lysolipid substrates. Two of the three showed significantly faster turnover of sphingolipids over lysolipids, and all three showed a strong preference for positively charged (choline and/or ethanolamine) over neutral (glycerol and serine) headgroups. Strikingly, however, the enzymes vary widely in their preference for choline, the headgroup of both sphingomyelin and lysophosphatidylcholine, versus ethanolamine. An enzyme from Sicarius terrosus showed a strong preference for ethanolamine over choline, whereas two paralogous enzymes from Loxosceles arizonica either preferred choline or showed no significant preference. Intrigued by the novel substrate preference of the Sicarius enzyme, we solved its crystal structure at 2.1 Å resolution. The evolution of variable substrate specificity may help explain the reduced dermonecrotic potential of some natural toxin variants, because mammalian sphingolipids use primarily choline as a positively charged headgroup; it may also be relevant for sicariid predatory behavior, because ethanolamine-containing sphingolipids are common in insect prey. PMID:25752604

Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof.

PubMed

Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy

2016-05-15

Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%-26% volumetric moisture content) and temperature (21°C-36°C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat heterogeneity. Copyright © 2016 Elsevier B.V. All rights reserved.

Optimization of the optical and electrical properties of electron beam evaporated aluminum-doped zinc oxide films for opto-electronic applications

NASA Astrophysics Data System (ADS)

Ali, H. M.; Abd El-Raheem, M. M.; Megahed, N. M.; Mohamed, H. A.

2006-08-01

Aluminum-doped zinc oxide (AZO) thin films have been deposited by electron beam evaporation technique on glass substrates. The structural, electrical and optical properties of AZO films have been investigated as a function of annealing temperature. It was observed that the optical properties such as transmittance, reflectance, optical band gap and refractive index of AZO films were strongly affected by annealing temperature. The transmittance values of 84% in the visible region and 97% in the NIR region were obtained for AZO film annealed at 475 °C. The room temperature electrical resistivity of 4.6×10-3 Ω cm has been obtained at the same temperature of annealing. It was found that the calculated refractive index has been affected by the packing density of the thin films, whereas, the high annealing temperature gave rise to improve the homogeneity of the films. The single-oscillator model was used to analyze the optical parameters such as the oscillator and dispersion energies.

Microbial BOD sensors based on Zr (IV)-loaded collagen fiber.

PubMed

Zhao, Lei; He, Li; Chen, Shujuan; Zou, Likou; Zhou, Kang; Ao, Xiaolin; Liu, Shuliang; Hu, Xinjie; Han, Guoquan

2017-03-01

Biochemical oxygen demand (BOD) sensors based on Zr (IV)-loaded collagen fiber (ZrCF), a novel material with great porous structure, were developed. This novel material shows adsorbability by microorganisms. Saccharomyces cerevisiae and Escherichia coli were used for the construction of BOD sensors. Factors affecting BOD sensor performance were examined. The ZrCF-based BOD sensor showed different sensitivities and linear response ranges with different biofilm densities. The amount of microorganisms strongly affected the performance of the BOD sensor. Poor permeability of previously reported immobilization carriers were greatly circumvented by ZrCF. The service life of the ZrCF-based BOD sensor was more than 42 days. The immobilized microorganisms can be stored for more than 6 months under 4°C in PB solution. There was good correlation between the results of the sensor method and the standard 5-day BOD method in the determination of pure organic substrates and real water samples. Copyright © 2016 Elsevier Inc. All rights reserved.

Substrate-Influenced Thermo-Mechanical Fatigue of Copper Metallizations: Limits of Stoney’s Equation

PubMed Central

Bigl, Stephan; Wurster, Stefan; Cordill, Megan J.

2017-01-01

Rapid progress in the reduction of substrate thickness for silicon-based microelectronics leads to a significant reduction of the device bending stiffness and the need to address its implication for the thermo-mechanical fatigue behavior of metallization layers. Results on 5 µm thick Cu films reveal a strong substrate thickness-dependent microstructural evolution. Substrates with hs = 323 and 220 µm showed that the Cu microstructure exhibits accelerated grain growth and surface roughening. Moreover, curvature-strain data indicates that Stoney’s simplified curvature-stress relation is not valid for thin substrates with regard to the expected strains, but can be addressed using more sophisticated plate bending theories. PMID:29120407

Characterization of cortactin as an in vivo protein kinase D substrate: interdependence of sites and potentiation by Src.

PubMed

De Kimpe, Line; Janssens, Katrien; Derua, Rita; Armacki, Milena; Goicoechea, Silvia; Otey, Carol; Waelkens, Etienne; Vandoninck, Sandy; Vandenheede, Jackie R; Seufferlein, Thomas; Van Lint, Johan

2009-02-01

Protein Kinase D (PKD) has been implicated in the regulation of actin turnover at the leading edge, invasion and migration. In particular, a complex between cortactin, paxillin and PKD in the invadopodia of invasive breast cancer cells has been described earlier, but so far this complex remained ill defined. Here we have investigated the possible role of PKD as a cortactin kinase. Using a mass spectrometric approach, we found that PKD phosphorylates cortactin on Ser 298 in the 6th cortactin repeat region and on Ser 348, right before the helical-proline rich domain of cortactin. We developed phosphospecific antibodies against these phosphorylated sequences, and used them as tools to follow the in vivo phosphorylation of cortactin by PKD. Examination of cortactin phosphorylation kinetics revealed that Ser 298 serves as a priming site for subsequent phosphorylation of Ser 348. Src, a well-known cortactin kinase, strongly potentiated the in vivo PKD mediated cortactin phosphorylation. This Src effect is neither mediated by pre-phosphorylation of cortactin nor by activation of PKD by Src. Phosphorylation of cortactin by PKD does not affect its subcellular localization, nor does it affect its translocation to podosomes or membrane ruffles. Moreover, there was no effect of PKD mediated cortactin phosphorylation on EGF receptor degradation and LPA induced migration. Taken together, these data establish cortactin as a novel PKD substrate and reveal a novel connection between Src and PKD.

Mutations in the C-terminal fragment of DnaK affecting peptide binding.

PubMed Central

Burkholder, W F; Zhao, X; Zhu, X; Hendrickson, W A; Gragerov, A; Gottesman, M E

1996-01-01

Escherichia coli DnaK acts as a molecular chaperone through its ATP-regulated binding and release of polypeptide substrates. Overexpressing a C-terminal fragment (CTF) of DnaK (Gly-384 to Lys-638) containing the polypeptide substrate binding domain is lethal in wild-type E. coli. This dominant-negative phenotype may result from the nonproductive binding of CTF to cellular polypeptide targets of DnaK. Mutations affecting DnaK substrate binding were identified by selecting noncytotoxic CTF mutants followed by in vitro screening. The clustering of such mutations in the three-dimensional structure of CTF suggests the model that loops L1,2 and L4,5 form a rigid core structure critical for interactions with substrate. Images Fig. 1 Fig. 2 Fig. 3 PMID:8855230

Nonlinear optical parameters of nanocrystalline AZO thin film measured at different substrate temperatures

NASA Astrophysics Data System (ADS)

Jilani, Asim; Abdel-wahab, M. Sh; Al-ghamdi, Attieh A.; Dahlan, Ammar sadik; Yahia, I. S.

2016-01-01

The 2.2 wt% of aluminum (Al)-doped zinc oxide (AZO) transparent and preferential c-axis oriented thin films were prepared by using radio frequency (DC/RF) magnetron sputtering at different substrate temperature ranging from room temperature to 200 °C. For structural analysis, X-ray Diffraction (XRD) and Atomic Force Electron Microscope (AFM) was used for morphological studies. The optical parameters such as, optical energy gap, refractive index, extinction coefficient, dielectric loss, tangent loss, first and third order nonlinear optical properties of transparent films were investigated. High transmittance above 90% and highly homogeneous surface were observed in all samples. The substrate temperature plays an important role to get the best transparent conductive oxide thin films. The substrate temperature at 150 °C showed the growth of highly transparent AZO thin film. Energy gap increased with the increased in substrate temperature of Al doped thin films. Dielectric constant and loss were found to be photon energy dependent with substrate temperature. The change in substrate temperature of Al doped thin films also affect the non-liner optical properties of thin films. The value of χ(3) was found to be changed with the grain size of the thin films that directly affected by the substrate temperature of the pure and Al doped ZnO thin films.

V(D)J recombination on minichromosomes is not affected by transcription.

PubMed

Hsieh, C L; McCloskey, R P; Lieber, M R

1992-08-05

It has been shown previously by others that transcription is temporally correlated with the onset of V(D)J recombination at the endogenous antigen receptor loci. We have been interested in determining whether this temporal correlation indicates a causal connection between these two processes. We have compared V(D)J recombination minichromosome substrates that have transcripts running through the recombination zone with substrates that do not in a transient transfection assay. In this system, the substrates acquire a minichromosome conformation within the first several hours after transfection. We find that the substrates recombine equally well over a 100-fold range in transcriptional variation. In additional studies, we have taken substrates that have low levels of transcription and inhibited transcription further by methylating the substrate DNA or by treating the cells with a general transcription inhibitor (alpha-amanitin). Although these treatments decrease the level of expression an additional 10-100-fold, there is still no observable effect on V(D)J recombination. Based on these results, we conclude that transcription is not necessary for the V(D)J reaction mechanism and does not alter substrate structure at the DNA level or at the simplest levels of chromatin structure in a way that affects the reaction.

Process for making dense thin films

DOEpatents

Jacobson, Craig P.; Visco, Steven J.; DeJonghe, Lutgard C.

2005-07-26

Provided are low-cost, mechanically strong, highly electronically conductive porous substrates and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures. The invention provides solid state electrochemical device substrates of novel composition and techniques for forming thin electrode/membrane/electrolyte coatings on the novel or more conventional substrates. In particular, in one embodiment the invention provides techniques for firing of device substrate to form densified electrolyte/membrane films 5 to 20 microns thick. In another embodiment, densified electrolyte/membrane films 5 to 20 microns thick may be formed on a pre-sintered substrate by a constrained sintering process. In some cases, the substrate may be a porous metal, alloy, or non-nickel cermet incorporating one or more of the transition metals Cr, Fe, Cu and Ag, or alloys thereof.

Structure–Function Studies of Hydrophobic Residues That Clamp a Basic Glutamate Side Chain during Catalysis by Triosephosphate Isomerase

PubMed Central

2016-01-01

Kinetic parameters are reported for the reactions of whole substrates (kcat/Km, M–1 s–1) (R)-glyceraldehyde 3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP) and for the substrate pieces [(kcat/Km)E·HPi/Kd, M–2 s–1] glycolaldehyde (GA) and phosphite dianion (HPi) catalyzed by the I172A/L232A mutant of triosephosphate isomerase from Trypanosoma brucei brucei (TbbTIM). A comparison with the corresponding parameters for wild-type, I172A, and L232A TbbTIM-catalyzed reactions shows that the effect of I172A and L232A mutations on ΔG⧧ for the wild-type TbbTIM-catalyzed reactions of the substrate pieces is nearly the same as the effect of the same mutations on TbbTIM previously mutated at the second side chain. This provides strong evidence that mutation of the first hydrophobic side chain does not affect the functioning of the second side chain in catalysis of the reactions of the substrate pieces. By contrast, the effects of I172A and L232A mutations on ΔG⧧ for wild-type TbbTIM-catalyzed reactions of the whole substrate are different from the effect of the same mutations on TbbTIM previously mutated at the second side chain. This is due to the change in the rate-determining step that determines the barrier to the isomerization reaction. X-ray crystal structures are reported for I172A, L232A, and I172A/L232A TIMs and for the complexes of these mutants to the intermediate analogue phosphoglycolate (PGA). The structures of the PGA complexes with wild-type and mutant enzymes are nearly superimposable, except that the space opened by replacement of the hydrophobic side chain is occupied by a water molecule that lies ∼3.5 Å from the basic side chain of Glu167. The new water at I172A mutant TbbTIM provides a simple rationalization for the increase in the activation barrier ΔG⧧ observed for mutant enzyme-catalyzed reactions of the whole substrate and substrate pieces. By contrast, the new water at the L232A mutant does not predict the decrease in ΔG⧧ observed for the mutant enzyme-catalyzed reactions of the substrate piece GA. PMID:27149328

Influence of pine bark particle size and pH on cation exchange capacity

USDA-ARS?s Scientific Manuscript database

Cation exchange capacity (CEC) describes the maximum quantity of cations a soil or substrate can hold while being exchangeable with the soil solution. While CEC has been studied for peat-based substrates, relatively little work has documented factors that affect CEC of pine bark substrates. The ob...

Analysis of factors affecting the accuracy, reproducibility, and interpretation of microbial community carbon source utilization patterns

USGS Publications Warehouse

Haack, S.K.; Garchow, H.; Klug, M.J.; Forney, L.J.

1995-01-01

We determined factors that affect responses of bacterial isolates and model bacterial communities to the 95 carbon substrates in Biolog microliter plates. For isolates and communities of three to six bacterial strains, substrate oxidation rates were typically nonlinear and were delayed by dilution of the inoculum. When inoculum density was controlled, patterns of positive and negative responses exhibited by microbial communities to each of the carbon sources were reproducible. Rates and extents of substrate oxidation by the communities were also reproducible but were not simply the sum of those exhibited by community members when tested separately. Replicates of the same model community clustered when analyzed by principal- components analysis (PCA), and model communities with different compositions were clearly separated un the first PCA axis, which accounted for >60% of the dataset variation. PCA discrimination among different model communities depended on the extent to which specific substrates were oxidized. However, the substrates interpreted by PCA to be most significant in distinguishing the communities changed with reading time, reflecting the nonlinearity of substrate oxidation rates. Although whole-community substrate utilization profiles were reproducible signatures for a given community, the extent of oxidation of specific substrates and the numbers or activities of microorganisms using those substrates in a given community were not correlated. Replicate soil samples varied significantly in the rate and extent of oxidation of seven tested substrates, suggesting microscale heterogeneity in composition of the soil microbial community.

Room temperature rubbing for few-layer two-dimensional thin flakes directly on flexible polymer substrates

PubMed Central

Yu, Yan; Jiang, Shenglin; Zhou, Wenli; Miao, Xiangshui; Zeng, Yike; Zhang, Guangzu; Liu, Sisi

2013-01-01

The functional layers of few-layer two-dimensional (2-D) thin flakes on flexible polymers for stretchable applications have attracted much interest. However, most fabrication methods are “indirect” processes that require transfer steps. Moreover, previously reported “transfer-free” methods are only suitable for graphene and not for other few-layer 2-D thin flakes. Here, a friction based room temperature rubbing method is proposed for fabricating different types of few-layer 2-D thin flakes (graphene, hexagonal boron nitride (h-BN), molybdenum disulphide (MoS2), and tungsten disulphide (WS2)) on flexible polymer substrates. Commercial 2-D raw materials (graphite, h-BN, MoS2, and WS2) that contain thousands of atom layers were used. After several minutes, different types of few-layer 2-D thin flakes were fabricated directly on the flexible polymer substrates by rubbing procedures at room temperature and without any transfer step. These few-layer 2-D thin flakes strongly adhere to the flexible polymer substrates. This strong adhesion is beneficial for future applications. PMID:24045289

Response of nematode-trapping fungi to organic substrates in a coastal grassland soil.

PubMed

Nguyen, Vi L; Bastow, Justin L; Jaffee, Bruce A; Strong, Don R

2007-07-01

To understand why Arthrobotrys oligospora and other nematode-trapping fungi are common and sometimes abundant in the coastal grassland soils of the Bodega Marine Reserve (BMR, Sonoma County, CA), we examined how resident trapping fungi responded to the addition of eight organic substrates (lupine leaves, grass leaves, dead isopods, dead moth larvae, isopod faeces, deer faeces, shrimp shells, and powdered chitin). We were especially interested in the effects of dead isopods because isopods are abundant at BMR and because previous studies had documented strong responses of A. oligospora to other arthropods (dead moth larvae). Soil from BMR was packed into vials (40 g dry mass equivalent per vial with water potential at -230 kPa and bulk density at 0.9 gcm(-3)), and one substrate or no substrate was added to the soil surface. After 30 d at 20 degrees C, trapping fungi were quantified by dilution plating and most probable number procedures. The response of A. oligospora was inversely related to substrate carbon:nitrogen (C:N) ratio: substrates with low C:N ratios (dead isopods, lupine leaves, dead moth larvae) usually caused large increases in A. oligospora whereas those with higher C:N ratios (isopod faeces, deer faeces, grass leaves) did not. An exception was chitin powder, which had a low C:N ratio, but which did not cause A. oligospora to proliferate. Responses of A. oligospora were directly related to the quantity of nitrogen added with each substrate, and those substrates that caused large increases in resident nematodes usually caused large increases in A. oligospora. Other trapping fungi did not respond as strongly as A. oligospora.

Self-Assembled Carbon-Polyoxometalate Composites for Electrochemical Capacitors

NASA Astrophysics Data System (ADS)

Genovese, Matthew

The development of high performance yet cost effective energy storage devices is critical for enabling the growth of important emerging sectors from the internet of things to grid integration of renewable energy. Material costs are by far the largest contributor to the overall cost of energy storage devices and thus research into cost effective energy storage materials will play an important role in developing technology to meet real world storage demands. In this thesis, low cost high performance composite electrode materials for supercapacitors (SCs) have been developed through the surface modification of electrochemically double layer capacitive (EDLC) carbon substrates with pseudocapacitive Polyoxometalates (POMs). Significant fundamental contributions have been made to the understanding of all components of the composite electrode including the POM active layer, cation linker, and carbon substrate. The interaction of different POM chemistries in solution has been studied to elucidate the novel ways in which these molecules combine and the mechanism underlying this combination. A more thorough understanding regarding the cation linker's role in electrode fabrication has been developed through examining the linker properties which most strongly affect electrode performance. The development of porosity in biomass derived carbon materials has also been examined leading to important insights regarding the effect of substrate porosity on POM modification and electrochemical properties. These fundamental contributions enabled the design and performance optimization of POM-carbon composite SC electrodes. Understanding how POMs combine in solution, allowed for the development of mixed POM molecular coatings with tunable electrochemical properties. These molecular coatings were used to modify low cost biomass derived carbon substrates that had been structurally optimized to accommodate POM molecules. The resulting electrode composites utilizing low cost materials fabricated through simple scalable techniques demonstrated (i) high capacitance (361 F g-1), (ii) close to ideal pseudocapacitive behavior, (iii) stable cycling, and (iv) good rate performance.

Fabricating nanowire devices on diverse substrates by simple transfer-printing methods.

PubMed

Lee, Chi Hwan; Kim, Dong Rip; Zheng, Xiaolin

2010-06-01

The fabrication of nanowire (NW) devices on diverse substrates is necessary for applications such as flexible electronics, conformable sensors, and transparent solar cells. Although NWs have been fabricated on plastic and glass by lithographic methods, the choice of device substrates is severely limited by the lithographic process temperature and substrate properties. Here we report three new transfer-printing methods for fabricating NW devices on diverse substrates including polydimethylsiloxane, Petri dishes, Kapton tapes, thermal release tapes, and many types of adhesive tapes. These transfer-printing methods rely on the differences in adhesion to transfer NWs, metal films, and devices from weakly adhesive donor substrates to more strongly adhesive receiver substrates. Electrical characterization of fabricated NW devices shows that reliable ohmic contacts are formed between NWs and electrodes. Moreover, we demonstrated that Si NW devices fabricated by the transfer-printing methods are robust piezoresistive stress sensors and temperature sensors with reliable performance.

Controlling the Electronic Structure of Graphene Using Surface-adsorbate Interactions

DTIC Science & Technology

2015-07-21

substrate via n doping, with or without intercalation, suggests that the graphene-to-substrate interaction could be controlled dynamically. DOI : 10.1103...which form a Dirac cone and are degenerate at the Fermi level [1]. These states change in response to atoms adsorbed on top of graphene (doping) or when...coupling to the substrate is strong. In the case of graphene on metals, the energy of the Dirac cone can change as a result of interfacial doping, or

Slow Off-rates and Strong Product Binding Are Required for Processivity and Efficient Degradation of Recalcitrant Chitin by Family 18 Chitinases*

PubMed Central

Kurašin, Mihhail; Kuusk, Silja; Kuusk, Piret; Sørlie, Morten; Väljamäe, Priit

2015-01-01

Processive glycoside hydrolases are the key components of enzymatic machineries that decompose recalcitrant polysaccharides, such as chitin and cellulose. The intrinsic processivity (PIntr) of cellulases has been shown to be governed by the rate constant of dissociation from polymer chain (koff). However, the reported koff values of cellulases are strongly dependent on the method used for their measurement. Here, we developed a new method for determining koff, based on measuring the exchange rate of the enzyme between a non-labeled and a 14C-labeled polymeric substrate. The method was applied to the study of the processive chitinase ChiA from Serratia marcescens. In parallel, ChiA variants with weaker binding of the N-acetylglucosamine unit either in substrate-binding site −3 (ChiA-W167A) or the product-binding site +1 (ChiA-W275A) were studied. Both ChiA variants showed increased off-rates and lower apparent processivity on α-chitin. The rate of the production of insoluble reducing groups on the reduced α-chitin was an order of magnitude higher than koff, suggesting that the enzyme can initiate several processive runs without leaving the substrate. On crystalline chitin, the general activity of the wild type enzyme was higher, and the difference was magnifying with hydrolysis time. On amorphous chitin, the variants clearly outperformed the wild type. A model is proposed whereby strong interactions with polymer in the substrate-binding sites (low off-rates) and strong binding of the product in the product-binding sites (high pushing potential) are required for the removal of obstacles, like disintegration of chitin microfibrils. PMID:26468285

Slow Off-rates and Strong Product Binding Are Required for Processivity and Efficient Degradation of Recalcitrant Chitin by Family 18 Chitinases.

PubMed

Kurašin, Mihhail; Kuusk, Silja; Kuusk, Piret; Sørlie, Morten; Väljamäe, Priit

2015-11-27

Processive glycoside hydrolases are the key components of enzymatic machineries that decompose recalcitrant polysaccharides, such as chitin and cellulose. The intrinsic processivity (P(Intr)) of cellulases has been shown to be governed by the rate constant of dissociation from polymer chain (koff). However, the reported koff values of cellulases are strongly dependent on the method used for their measurement. Here, we developed a new method for determining koff, based on measuring the exchange rate of the enzyme between a non-labeled and a (14)C-labeled polymeric substrate. The method was applied to the study of the processive chitinase ChiA from Serratia marcescens. In parallel, ChiA variants with weaker binding of the N-acetylglucosamine unit either in substrate-binding site -3 (ChiA-W167A) or the product-binding site +1 (ChiA-W275A) were studied. Both ChiA variants showed increased off-rates and lower apparent processivity on α-chitin. The rate of the production of insoluble reducing groups on the reduced α-chitin was an order of magnitude higher than koff, suggesting that the enzyme can initiate several processive runs without leaving the substrate. On crystalline chitin, the general activity of the wild type enzyme was higher, and the difference was magnifying with hydrolysis time. On amorphous chitin, the variants clearly outperformed the wild type. A model is proposed whereby strong interactions with polymer in the substrate-binding sites (low off-rates) and strong binding of the product in the product-binding sites (high pushing potential) are required for the removal of obstacles, like disintegration of chitin microfibrils. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Graphene revisited: From orbital mapping to its impact as a substrate

NASA Astrophysics Data System (ADS)

Draxl, Claudia

Graphene, the material of the 21st century, is without doubt one of the best characterized solids. Despite the enormous amount of investigations and related publications, it still it offers a variety of exciting aspects to explore, in particular in view of its excitations. Combining density-functional theory with many-body perturbation theory, as implemented in the all-electron full-potential package exciting, provides a powerful framework for this purpose. (i) The first example concerns the question, whether we can ``see'' orbitals in an electron microscope. Indeed, transmission electron microscopy can be used for mapping atomic orbitals, as demonstrated recently by a first-principles approach. For defected graphene, exhibiting either an isolated vacancy or a substitutional nitrogen atom different kinds of images are to be expected, depending on the orbital character. (ii) Graphene/BN heterostructures absorb light over a broad frequency range, from the near-infrared to the ultraviolet region, exhibiting novel features induced by the stacking. Peculiar features of their excitations are inter-layer excitons that can be modulated upon layer patterning. By choosing the stacking arrangement, the electronic coupling between the individual components can be tuned to enhance light-matter interaction. (iii) As demonstrated for azobenzene monolayers, graphene as a substrate strongly impacts the photo-switching behavior of molecules. Despite the weak hybridization, the photo-absorption of the molecules is remarkably modulated. While substrate polarization reduces the band-gap of the adsorbate, enhanced dielectric screening weakens the attractive interaction between electrons and holes. Furthermore, excitations corresponding to intermolecular electron-hole pairs, which are dark in the isolated monolayers, are activated by the presence of the substrate. (iv) Finally, we ask how first- and second-order Raman spectra of graphene are affected by strain that may be induced by an underlying substrate. Support from the DFG and the FWF is appreciated.

Controls on bacterial and archaeal community structure and greenhouse gas production in natural, mined, and restored Canadian peatlands

PubMed Central

Basiliko, Nathan; Henry, Kevin; Gupta, Varun; Moore, Tim R.; Driscoll, Brian T.; Dunfield, Peter F.

2013-01-01

Northern peatlands are important global C reservoirs, largely because of their slow rates of microbial C mineralization. Particularly in sites that are heavily influenced by anthropogenic disturbances, there is scant information about microbial ecology and whether or not microbial community structure influences greenhouse gas production. This work characterized communities of bacteria and archaea using terminal restriction fragment length polymorphism (T-RFLP) and sequence analysis of 16S rRNA and functional genes across eight natural, mined, or restored peatlands in two locations in eastern Canada. Correlations were explored among chemical properties of peat, bacterial and archaeal community structure, and carbon dioxide (CO2) and methane (CH4) production rates under oxic and anoxic conditions. Bacteria and archaea similar to those found in other peat soil environments were detected. In contrast to other reports, methanogen diversity was low in our study, with only 2 groups of known or suspected methanogens. Although mining and restoration affected substrate availability and microbial activity, these land-uses did not consistently affect bacterial or archaeal community composition. In fact, larger differences were observed between the two locations and between oxic and anoxic peat samples than between natural, mined, and restored sites, with anoxic samples characterized by less detectable bacterial diversity and stronger dominance by members of the phylum Acidobacteria. There were also no apparent strong linkages between prokaryote community structure and CH4 or CO2 production, suggesting that different organisms exhibit functional redundancy and/or that the same taxa function at very different rates when exposed to different peat substrates. In contrast to other earlier work focusing on fungal communities across similar mined and restored peatlands, bacterial and archaeal communities appeared to be more resistant or resilient to peat substrate changes brought about by these land uses. PMID:23914185

Wetting and spreading behavior of molten brazing filler metallic alloys on metallic substrate

NASA Astrophysics Data System (ADS)

Kogi, Satoshi; Kajiura, Tetsurou; Hanada, Yukiakira; Miyazawa, Yasuyuki

2014-08-01

Wetting and spreading of molten brazing filler material are important factors that influence the brazing ability of a joint to be brazed. Several investigations into the wetting ability of a brazing filler alloy and its surface tension in molten state, in addition to effects of brazing time and temperature on the contact angle, have been carried out. In general, dissimilar-metals brazing technology and high-performance brazed joint are necessities for the manufacturing field in the near future. Therefore, to address this requirement, more such studies on wetting and spreading of filler material are required for a deeper understanding. Generally, surface roughness and surface conditions affect spreading of molten brazing filler material during brazing. Wetting by and interfacial reactions of the molten brazing filler material with the metallic substrate, especially, affect strongly the spreading of the filler material. In this study, the effects of surface roughness and surface conditions on the spreading of molten brazing filler metallic alloys were investigated. Ag-(40-x)Cu-xIn and Ag- (40-x)Cu-xSn (x=5, 10, 15, 20, 25) alloys were used as brazing filler materials. A mild-steel square plate (S45C (JIS); side: 30 mm; thickness: 3mm) was employed as the substrate. A few surfaces with varying roughness were prepared using emery paper. Brazing filler material and metallic base plate were first washed with acetone, and then a flux was applied to them. The filler, 50 mg, was placed on the center of the metallic base with the flux. A spreading test was performed under Ar gas using an electrically heated furnace, after which, the original spreading area, defined as the sessile drop area, and the apparent spreading area, produced by the capillary grooves, were both evaluated. It was observed that the spreading area decreased with increasing In and Sn content.

Growth and micro structural studies on Yittria Stabilized Zirconia (YSZ) and Strontium Titanate (STO) buffer layers

NASA Technical Reports Server (NTRS)

Srinivas, S.; Pinto, R.; Pai, S. P.; Dsousa, D. P.; Apte, P. R.; Kumar, D.; Purandare, S. C.; Bhatnagar, A. K.

1995-01-01

Microstructure of Yittria Stabilized Zirconia (YSZ) and Strontium Titanate (STO) of radio frequency magnetron sputtered buffer layers was studied at various sputtering conditions on Si (100), Sapphire and LaAlO3 (100) substrates. The effect of substrate temperatures up to 800 C and sputtering gas pressures in the range of 50 mTorr. of growth conditions was studied. The buffer layers of YSZ and STO showed a strong tendency for columnar growth was observed above 15 mTorr sputtering gas pressure and at high substrate temperatures. Post annealing of these films in oxygen atmosphere reduced the oxygen deficiency and strain generated during growth of the films. Strong c-axis oriented superconducting YBa2Cu3O7-x (YBCO) thin films were obtained on these buffer layers using pulsed laser ablation technique. YBCO films deposited on multilayers of YSZ and STO were shown to have better superconducting properties.

Substrate misorientation induced strong increase in the hole concentration in Mg doped GaN grown by metalorganic vapor phase epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suski, T.; Litwin-Staszewska, E.; Piotrzkowski, R.

We demonstrate that relatively small GaN substrate misorientation can strongly change hole carrier concentration in Mg doped GaN layers grown by metalorganic vapor phase epitaxy. In this work intentionally misoriented GaN substrates (up to 2 deg. with respect to ideal <0001> plane) were employed. An increase in the hole carrier concentration to the level above 10{sup 18} cm{sup -3} and a decrease in GaN:Mg resistivity below 1 {omega} cm were achieved. Using secondary ion mass spectroscopy we found that Mg incorporation does not change with varying misorientation angle. This finding suggests that the compensation rate, i.e., a decrease in unintentionalmore » donor density, is responsible for the observed increase in the hole concentration. Analysis of the temperature dependence of electrical transport confirms this interpretation.« less

Broadband omnidirectional antireflection coating based on subwavelength surface Mie resonators

PubMed Central

Spinelli, P.; Verschuuren, M.A.; Polman, A.

2012-01-01

Reflection is a natural phenomenon that occurs when light passes the interface between materials with different refractive index. In many applications, such as solar cells or photodetectors, reflection is an unwanted loss process. Many ways to reduce reflection from a substrate have been investigated so far, including dielectric interference coatings, surface texturing, adiabatic index matching and scattering from plasmonic nanoparticles. Here we present an entirely new concept that suppresses the reflection of light from a silicon surface over a broad spectral range. A two-dimensional periodic array of subwavelength silicon nanocylinders designed to possess strongly substrate-coupled Mie resonances yields almost zero total reflectance over the entire spectral range from the ultraviolet to the near-infrared. This new antireflection concept relies on the strong forward scattering that occurs when a scattering structure is placed in close proximity to a high-index substrate with a high optical density of states. PMID:22353722

Palladium Nanoparticle-Loaded Cellulose Paper: A Highly Efficient, Robust, and Recyclable Self-Assembled Composite Catalytic System.

PubMed

Zheng, Guangchao; Kaefer, Katharina; Mourdikoudis, Stefanos; Polavarapu, Lakshminarayana; Vaz, Belén; Cartmell, Samantha E; Bouleghlimat, Azzedine; Buurma, Niklaas J; Yate, Luis; de Lera, Ángel R; Liz-Marzán, Luis M; Pastoriza-Santos, Isabel; Pérez-Juste, Jorge

2015-01-15

We present a novel strategy based on the immobilization of palladium nanoparticles (Pd NPs) on filter paper for development of a catalytic system with high efficiency and recyclability. Oleylamine-capped Pd nanoparticles, dispersed in an organic solvent, strongly adsorb on cellulose filter paper, which shows a great ability to wick fluids due to its microfiber structure. Strong van der Waals forces and hydrophobic interactions between the particles and the substrate lead to nanoparticle immobilization, with no desorption upon further immersion in any solvent. The prepared Pd NP-loaded paper substrates were tested for several model reactions such as the oxidative homocoupling of arylboronic acids, the Suzuki cross-coupling reaction, and nitro-to-amine reduction, and they display efficient catalytic activity and excellent recyclability and reusability. This approach of using NP-loaded paper substrates as reusable catalysts is expected to open doors for new types of catalytic support for practical applications.

Moiré superlattice-level stick-slip instability originated from geometrically corrugated graphene on a strongly interacting substrate

NASA Astrophysics Data System (ADS)

Shi, Ruoyu; Gao, Lei; Lu, Hongliang; Li, Qunyang; Ma, Tian-Bao; Guo, Hui; Du, Shixuan; Feng, Xi-Qiao; Zhang, Shuai; Liu, Yanmin; Cheng, Peng; Hu, Yuan-Zhong; Gao, Hong-Jun; Luo, Jianbin

2017-06-01

Two dimensional (2D) materials often exhibit novel properties due to various coupling effects with their supporting substrates. Here, using friction force microscopy (FFM), we report an unusual moiré superlattice-level stick-slip instability on monolayer graphene epitaxially grown on Ru(0 0 0 1) substrate. Instead of smooth friction modulation, a significant long-range stick-slip sawtooth modulation emerges with a period coinciding with the moiré superlattice structure, which is robust against high external loads and leads to an additional channel of energy dissipation. In contrast, the long-range stick-slip instability reduces to smooth friction modulation on graphene/Ir(1 1 1) substrate. The moiré superlattice-level slip instability could be attributed to the large sliding energy barrier, which arises from the morphological corrugation of graphene on Ru(0 0 0 1) surface as indicated by density functional theory (DFT) calculations. The locally steep humps acting as obstacles opposing the tip sliding, originates from the strong interfacial electronic interaction between graphene and Ru(0 0 0 1). This study opens an avenue for modulating friction by tuning the interfacial atomic interaction between 2D materials and their substrates.

Pinus sylvestris switches respiration substrates under shading but not during drought.

PubMed

Fischer, Sarah; Hanf, Stefan; Frosch, Torsten; Gleixner, Gerd; Popp, Jürgen; Trumbore, Susan; Hartmann, Henrik

2015-08-01

Reduced carbon (C) assimilation during prolonged drought forces trees to rely on stored C to maintain vital processes like respiration. It has been shown, however, that the use of carbohydrates, a major C storage pool and apparently the main respiratory substrate in plants, strongly declines with decreasing plant hydration. Yet no empirical evidence has been produced to what degree other C storage compounds like lipids and proteins may fuel respiration during drought. We exposed young scots pine trees to C limitation using either drought or shading and assessed respiratory substrate use by monitoring the respiratory quotient, δ(13) C of respired CO2 and concentrations of the major storage compounds, that is, carbohydrates, lipids and amino acids. Only shaded trees shifted from carbohydrate-dominated to lipid-dominated respiration and showed progressive carbohydrate depletion. In drought trees, the fraction of carbohydrates used in respiration did not decline but respiration rates were strongly reduced. The lower consumption and potentially allocation from other organs may have caused initial carbohydrate content to remain constant during the experiment. Our results suggest that respiratory substrates other than carbohydrates are used under carbohydrate limitation but not during drought. Thus, respiratory substrate shift cannot provide an efficient means to counterbalance C limitation under natural drought. © 2015 The Authors New Phytologist © 2015 New Phytologist Trust.

Substrate stiffness regulates cadherin-dependent collective migration through myosin-II contractility

PubMed Central

Ng, Mei Rosa; Besser, Achim

2012-01-01

The mechanical microenvironment is known to influence single-cell migration; however, the extent to which mechanical cues affect collective migration of adherent cells is not well understood. We measured the effects of varying substrate compliance on individual cell migratory properties in an epithelial wound-healing assay. Increasing substrate stiffness increased collective cell migration speed, persistence, and directionality as well as the coordination of cell movements. Dynamic analysis revealed that wounding initiated a wave of motion coordination from the wound edge into the sheet. This was accompanied by a front-to-back gradient of myosin-II activation and establishment of cell polarity. The propagation was faster and farther reaching on stiff substrates, indicating that substrate stiffness affects the transmission of directional cues. Manipulation of myosin-II activity and cadherin–catenin complexes revealed that this transmission is mediated by coupling of contractile forces between neighboring cells. Thus, our findings suggest that the mechanical environment integrates in a feedback with cell contractility and cell–cell adhesion to regulate collective migration. PMID:23091067

Oviposition Substrate of the Mountain Fly Drosophila nigrosparsa (Diptera: Drosophilidae)

PubMed Central

Tratter, Magdalena; Bächli, Gerhard; Kirchmair, Martin; Kaufmann, Rüdiger; Arthofer, Wolfgang; Schlick-Steiner, Birgit C.; Steiner, Florian M.

2016-01-01

The survival of insect larvae often depends on the mother’s choice of oviposition substrate, and thus, this choice is an essential part of an insect species’ ecology. Especially species with narrow substrate preferences may suffer from changes in substrate availability triggered by, for example, climate change. Recent climate warming is affecting species directly (e.g., physiology) but also indirectly (e.g., biological interactions) leading to mismatching phenologies and distributions. However, the preferred oviposition substrate is still unknown for many drosophilid species, especially for those at higher elevations. In this study, we investigated the oviposition-substrate preference of the montane-alpine fly Drosophila nigrosparsa in rearing and multiple-choice experiments using natural substrates in the laboratory. Insect emergence from field-collected substrates was tested. More than 650 insects were reared from natural substrates, among them 152 drosophilids but no individual of D. nigrosparsa. In the multiple-choice experiments, D. nigrosparsa preferred ovipositing on mushrooms (> 93% of eggs); additionally, a few eggs were laid on berries but none on other substrates such as cow faeces, rotten plant material, and soil. The flies laid 24 times more eggs per day when mushrooms were included in the substrates than when they were excluded. We infer that D. nigrosparsa is a mushroom breeder with some variation in oviposition choice. The flies favoured some mushrooms over others, but they were not specialised on a single fungal taxon. Although it is unclear if and how climate change will affect D. nigrosparsa, our results indicate that this species will not be threatened by oviposition-substrate limitations in the near future because of the broad altitudinal distribution of the mushrooms considered here, even if the flies will have to shift upwards to withstand increasing temperatures. PMID:27788257

Effects of simulated solar radiation on the transmission of magnesium fluoride and cryolite thin films

NASA Technical Reports Server (NTRS)

Heslin, T.

1974-01-01

Thin films of cryolite magnesium fluoride on fused silica substrates were exposed to 1126 equivalent sun-hours of radiation. The optical transmissions of the samples were measured before and after irradiation. The results indicate that, after the degradation of the silica substrate is accounted for, the cryolite is severely affected by the simulated solar radiation, but the magnesium fluoride is only slightly affected.

Method and apparatus for coating substrates using a laser

NASA Technical Reports Server (NTRS)

Zaplatynsky, I. (Inventor)

1984-01-01

Metal substrates, preferably of titanium and titanium alloys, are coated by alloying or forming TiN on a substrate surface. A laser beam strikes the surface of a moving substrate in the presence of purified nitrogen gas. A small area of the substrate surface is quickly heated without melting. This heated area reacts with the nitrogen to form a solid solution. The alloying or formation of TiN occurs by diffusion of nitrogen into the titanium. Only the surface layer of the substrate is heated because of the high power density of the laser beam and short exposure time. The bulk of the substrate is not affected, and melting of the substrate is avoided because it would be detrimental.

Effect of thermal annealing on the redistribution of alkali metals in Cu(In,Ga)Se2 solar cells on glass substrate

NASA Astrophysics Data System (ADS)

Kamikawa, Yukiko; Nishinaga, Jiro; Ishizuka, Shogo; Tayagaki, Takeshi; Guthrey, Harvey; Shibata, Hajime; Matsubara, Koji; Niki, Shigeru

2018-03-01

The precise control of alkali-metal concentrations in Cu(In,Ga)Se2 (CIGS) solar cells via post deposition treatment (PDT) has recently attracted attention. When PDT is performed at an elevated temperature, an accompanying annealing effect is expected. Here, we investigate how thermal annealing affects the redistribution of alkali metals in CIGS solar cells on glass substrates and the properties of the solar cells. In addition, we investigate the origin of non-homogeneous alkali-metal depth profiles that are typical of CIGS grown using a three-stage process. In particular, we use secondary-ion mass spectrometry measurements of the ion concentration as a function of distance from the CIGS surface to investigate the impact of thermal annealing on the distribution of alkali metals (Na, Ka, and Rb) and constituent elements (Ga and In) in the CIGS absorbers. We find that the depth profiles of the alkali metals strongly reflect the density of sites that tend to accommodate alkali metals, i.e., vacancies. Annealing at elevated temperature caused a redistribution of the alkali metals. The thermal-diffusion kinetics of alkali metals depends strongly on the species involved. We introduced low flux potassium fluoride (KF) to study a side effect of KF-PDT, i.e., Na removal from CIGS, separately from its predominant effects such as surface modification. When sufficient amounts of Na are supplied from the soda lime glass via annealing at an elevated temperature, the negative effect was not apparent. Conversely, when the Na supply was not sufficient, it caused a deterioration of the photovoltaic properties.

Formation and characterization of preferred oriented perovskite thin films on single-crystalline substrates

NASA Astrophysics Data System (ADS)

Chen, Lung-Chien; Chen, Cheng-Chiang; Hsiung Chang, Sheng; Lee, Kuan-Lin; Tseng, Zong-Liang; Chen, Sheng-Hui; Kuo, Hao-Chung

2018-06-01

Three single-crystalline (Al2O3, GaN/Al2O3 and InAs) substrates are used to assist the formation of crystallographically preferred oriented CH3NH3PbI3 (MAPbI3) thin films. The estimation of the lattice mismatch at the MAPbI3/substrate interface and water-droplet contact angle experiments indicate that the formation of a preferred oriented MAPbI3 thin film is induced by the single-crystalline substrate and is insensitive to the surface wettibility of the substrate. Moreover, the experimental results suggest that the lattice mismatch at the MAPbI3/single-crystalline semiconductor interface can strongly influence the photovoltaic performance of tandem solar cells.

Starch synthase 4 is essential for coordination of starch granule formation with chloroplast division during Arabidopsis leaf expansion

PubMed Central

Crumpton-Taylor, Matilda; Pike, Marilyn; Lu, Kuan-Jen; Hylton, Christopher M; Feil, Regina; Eicke, Simona; Lunn, John E; Zeeman, Samuel C; Smith, Alison M

2013-01-01

Arabidopsis thaliana mutants lacking the SS4 isoform of starch synthase have strongly reduced numbers of starch granules per chloroplast, suggesting that SS4 is necessary for the normal generation of starch granules. To establish whether it plays a direct role in this process, we investigated the circumstances in which granules are formed in ss4 mutants. Starch granule numbers and distribution and the accumulation of starch synthase substrates and products were investigated during ss4 leaf development, and in ss4 mutants carrying mutations or transgenes that affect starch turnover or chloroplast volume. We found that immature ss4 leaves have no starch granules, but accumulate high concentrations of the starch synthase substrate ADPglucose. Granule numbers are partially restored by elevating the capacity for glucan synthesis (via expression of bacterial glycogen synthase) or by increasing the volumes of individual chloroplasts (via introduction of arc mutations). However, these granules are abnormal in distribution, size and shape. SS4 is an essential component of a mechanism that coordinates granule formation with chloroplast division during leaf expansion and determines the abundance and the flattened, discoid shape of leaf starch granules. PMID:23952675

Regulation of selective autophagy: the p62/SQSTM1 paradigm.

PubMed

Lamark, Trond; Svenning, Steingrim; Johansen, Terje

2017-12-12

In selective autophagy, cytoplasmic components are selected and tagged before being sequestered into an autophagosome by means of selective autophagy receptors such as p62/SQSTM1. In this review, we discuss how selective autophagy is regulated. An important level of regulation is the selection of proteins or organelles for degradation. Components selected for degradation are tagged, often with ubiquitin, to facilitate recognition by autophagy receptors. Another level of regulation is represented by the autophagy receptors themselves. For p62, its ability to co-aggregate with ubiquitinated substrates is strongly induced by post-translational modifications (PTMs). The transcription of p62 is also markedly increased during conditions in which selective autophagy substrates accumulate. For other autophagy receptors, the LC3-interacting region (LIR) motif is regulated by PTMs, inhibiting or stimulating the interaction with ATG8 family proteins. ATG8 proteins are also regulated by PTMs. Regulation of the capacity of the core autophagy machinery also affects selective autophagy. Importantly, autophagy receptors can induce local recruitment and activation of ULK1/2 and PI3KC3 complexes at the site of cargo sequestration. © 2017 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

Parameter Extraction Method for the Electrical Model of a Silicon Photomultiplier

NASA Astrophysics Data System (ADS)

Licciulli, Francesco; Marzocca, Cristoforo

2016-10-01

The availability of an effective electrical model, able to accurately reproduce the signals generated by a Silicon Photo-Multiplier coupled to the front-end electronics, is mandatory when the performance of a detection system based on this kind of detector has to be evaluated by means of reliable simulations. We propose a complete extraction procedure able to provide the whole set of the parameters involved in a well-known model of the detector, which includes the substrate ohmic resistance. The technique allows achieving very good quality of the fit between simulation results provided by the model and experimental data, thanks to accurate discrimination between the quenching and substrate resistances, which results in a realistic set of extracted parameters. The extraction procedure has been applied to a commercial device considering a wide range of different conditions in terms of input resistance of the front-end electronics and interconnection parasitics. In all the considered situations, very good correspondence has been found between simulations and measurements, especially for what concerns the leading edge of the current pulses generated by the detector, which strongly affects the timing performance of the detection system, thus confirming the effectiveness of the model and the associated parameter extraction technique.

The effect of copper substrate’s roughness on graphene growth process via PECVD

NASA Astrophysics Data System (ADS)

Fan, Tengfei; Yan, Cuixia; Lu, Jianchen; Zhang, Lianchang; Cai, Jinming

2018-04-01

Despite many excellent properties, the synthesis of high quality graphene with low-cost way is still a challenge, thus many different factors have been researched. In this work, the effect of surface roughness to the graphene quality was studied. Graphene was synthesized by plasma enhanced chemical vapor deposition (PECVD) method on copper substrates with different roughness from 0.074 μm to 0.339 μm, which were prepared via annealing, corrosion or polishing, respectively. Ar+ plasma cleaning was applied before graphene growth in order to accommodate similar surface chemical reactivity to each other. Scanning electron microscope and Raman spectroscope were employed to investigate the effect of surface roughness, which reveals that the graphene quality decrease first and then increase again according to the ratio of ID/IG in Raman spectroscopy. When the ratio of ID/IG reaches the largest number, the substrate roughness is 0.127 μm, where is the graphene quality changing point. First principle calculation was applied to explain the phenomenon and revealed that it is strongly affected by the graphene grain size and quantity which can induce defects. This strategy is expected to guide the industrial production of graphene.

Constrained Sintering in Fabrication of Solid Oxide Fuel Cells

PubMed Central

Lee, Hae-Weon; Park, Mansoo; Hong, Jongsup; Kim, Hyoungchul; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook

2016-01-01

Solid oxide fuel cells (SOFCs) are inevitably affected by the tensile stress field imposed by the rigid substrate during constrained sintering, which strongly affects microstructural evolution and flaw generation in the fabrication process and subsequent operation. In the case of sintering a composite cathode, one component acts as a continuous matrix phase while the other acts as a dispersed phase depending upon the initial composition and packing structure. The clustering of dispersed particles in the matrix has significant effects on the final microstructure, and strong rigidity of the clusters covering the entire cathode volume is desirable to obtain stable pore structure. The local constraints developed around the dispersed particles and their clusters effectively suppress generation of major process flaws, and microstructural features such as triple phase boundary and porosity could be readily controlled by adjusting the content and size of the dispersed particles. However, in the fabrication of the dense electrolyte layer via the chemical solution deposition route using slow-sintering nanoparticles dispersed in a sol matrix, the rigidity of the cluster should be minimized for the fine matrix to continuously densify, and special care should be taken in selecting the size of the dispersed particles to optimize the thermodynamic stability criteria of the grain size and film thickness. The principles of constrained sintering presented in this paper could be used as basic guidelines for realizing the ideal microstructure of SOFCs. PMID:28773795

Structures and fabrication techniques for solid state electrochemical devices

DOEpatents

Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

2006-10-10

Low-cost, mechanically strong, highly electronically conductive porous substrates and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures provide solid state electrochemical device substrates of novel composition and techniques for forming thin electrode/membrane/electrolyte coatings on the novel or more conventional substrates. In particular, in one aspect the invention provides techniques for co-firing of device substrate (often an electrode) with an electrolyte or membrane layer to form densified electrolyte/membrane films 5 to 20 microns thick. In another aspect, densified electrolyte/membrane films 5 to 20 microns thick may be formed on a pre-sintered substrate by a constrained sintering process. In some cases, the substrate may be a porous metal, alloy, or non-nickel cermet incorporating one or more of the transition metals Cr, Fe and Cu, or alloys thereof.

Redox-dependent substrate-cofactor interactions in the Michaelis-complex of a flavin-dependent oxidoreductase

NASA Astrophysics Data System (ADS)

Werther, Tobias; Wahlefeld, Stefan; Salewski, Johannes; Kuhlmann, Uwe; Zebger, Ingo; Hildebrandt, Peter; Dobbek, Holger

2017-07-01

How an enzyme activates its substrate for turnover is fundamental for catalysis but incompletely understood on a structural level. With redox enzymes one typically analyses structures of enzyme-substrate complexes in the unreactive oxidation state of the cofactor, assuming that the interaction between enzyme and substrate is independent of the cofactors oxidation state. Here, we investigate the Michaelis complex of the flavoenzyme xenobiotic reductase A with the reactive reduced cofactor bound to its substrates by X-ray crystallography and resonance Raman spectroscopy and compare it to the non-reactive oxidized Michaelis complex mimics. We find that substrates bind in different orientations to the oxidized and reduced flavin, in both cases flattening its structure. But only authentic Michaelis complexes display an unexpected rich vibrational band pattern uncovering a strong donor-acceptor complex between reduced flavin and substrate. This interaction likely activates the catalytic ground state of the reduced flavin, accelerating the reaction within a compressed cofactor-substrate complex.

Selective photocatalytic transformations on microporous titanosilicate ETS-10 driven by size and polarity of molecules.

PubMed

Shiraishi, Yasuhiro; Tsukamoto, Daijiro; Hirai, Takayuki

2008-11-04

Photocatalytic activity of microporous titanosilicate ETS-10 has been studied in water. The photoactivated ETS-10 shows catalytic activity driven by size and polarity of substrates. ETS-10 efficiently catalyzes a conversion of substrates with a size larger than the pore diameter of ETS-10. In contrast, the reactivity of small substrates depends strongly on substrate polarity; less polar substrates show higher reactivity on ETS-10. Electron spin resonance analysis reveals that large substrates or less polar substrates scarcely diffuse inside the highly polarized micropores of ETS-10 and, hence, react efficiently with hydroxyl radicals (*OH) formed on titanol (Ti-OH) groups exposed on the external surface of ETS-10. In contrast, small polar substrates diffuse easily inside the micropores of ETS-10 and scarcely react with *OH, resulting in low reactivity. The photocatalytic activity of ETS-10 is successfully applicable to selective transformations of large reactants or less polar reactants to small polar products, enabling highly selective dehalogenation and hydroxylation of aromatics.

Redox-dependent substrate-cofactor interactions in the Michaelis-complex of a flavin-dependent oxidoreductase

PubMed Central

Werther, Tobias; Wahlefeld, Stefan; Salewski, Johannes; Kuhlmann, Uwe; Zebger, Ingo; Hildebrandt, Peter; Dobbek, Holger

2017-01-01

How an enzyme activates its substrate for turnover is fundamental for catalysis but incompletely understood on a structural level. With redox enzymes one typically analyses structures of enzyme–substrate complexes in the unreactive oxidation state of the cofactor, assuming that the interaction between enzyme and substrate is independent of the cofactors oxidation state. Here, we investigate the Michaelis complex of the flavoenzyme xenobiotic reductase A with the reactive reduced cofactor bound to its substrates by X-ray crystallography and resonance Raman spectroscopy and compare it to the non-reactive oxidized Michaelis complex mimics. We find that substrates bind in different orientations to the oxidized and reduced flavin, in both cases flattening its structure. But only authentic Michaelis complexes display an unexpected rich vibrational band pattern uncovering a strong donor–acceptor complex between reduced flavin and substrate. This interaction likely activates the catalytic ground state of the reduced flavin, accelerating the reaction within a compressed cofactor–substrate complex.

Critical assessment of enhancement factor measurements in surface-enhanced Raman scattering on different substrates.

PubMed

Rodrigues, Daniel C; de Souza, Michele L; Souza, Klester S; dos Santos, Diego P; Andrade, Gustavo F S; Temperini, Marcia L A

2015-09-07

The SERS enhancement factor (SERS-EF) is one of the most important parameters that characterizes the ability of a given substrate to enhance the Raman signal for SERS applications. The comparison of SERS intensities and SERS-EF values across different substrates is a common practice to unravel the performance of a given substrate. In this study, it is shown that such a comparison may lack significance if we compare substrates of very distinct nature and optical properties. It is specifically shown that the SERS-EF values for static substrates (e.g. immobilized metallic nanostructures) cannot be compared to those of dynamic ones (e.g. colloidal metal nanoparticle solutions), and that the optical properties for the latter show strong dependence on the metal-molecule interaction dynamics. The most representative experimental results concerning the dynamic substrates have been supported by generalized Mie theory simulations, which are tools used to describe the substrate complexity and the microscopic information not usually taken into account.

Patterned forests of vertically-aligned multiwalled carbon nanotubes using metal salt catalyst solutions.

PubMed

Garrett, David J; Flavel, Benjamin S; Baronian, Keith H R; Downard, Alison J

2013-01-01

A simple method for producing patterned forests of multiwalled carbon nanotubes (MWCNTs) is described. An aqueous metal salt solution is spin-coated onto a substrate patterned with photoresist by standard methods. The photoresist is removed by acetone washing leaving the acetone-insoluble catalyst pattern on the substrate. Dense forests of vertically aligned (VA) MWCNTs are grown on the patterned catalyst layers by chemical vapour deposition. The procedures have been demonstrated by growing MWCNT forests on two substrates: silicon and conducting graphitic carbon films. The forests adhere strongly to the substrates and when grown directly on carbon film, offer a simple method of preparing MWCNT electrodes.

Probing cytoskeletal pre-stress and nuclear mechanics in endothelial cells with spatiotemporally controlled (de-)adhesion kinetics on micropatterned substrates

PubMed Central

Versaevel, Marie; Riaz, Maryam; Corne, Tobias; Grevesse, Thomas; Lantoine, Joséphine; Mohammed, Danahe; Bruyère, Céline; Alaimo, Laura; De Vos, Winnok H.; Gabriele, Sylvain

2017-01-01

ABSTRACT The mechanical properties of living cells reflect their propensity to migrate and respond to external forces. Both cellular and nuclear stiffnesses are strongly influenced by the rigidity of the extracellular matrix (ECM) through reorganization of the cyto- and nucleoskeletal protein connections. Changes in this architectural continuum affect cell mechanics and underlie many pathological conditions. In this context, an accurate and combined quantification of the mechanical properties of both cells and nuclei can contribute to a better understanding of cellular (dys-)function. To address this challenge, we have established a robust method for probing cellular and nuclear deformation during spreading and detachment from micropatterned substrates. We show that (de-)adhesion kinetics of endothelial cells are modulated by substrate stiffness and rely on the actomyosin network. We combined this approach with measurements of cell stiffness by magnetic tweezers to show that relaxation dynamics can be considered as a reliable parameter of cellular pre-stress in adherent cells. During the adhesion stage, large cellular and nuclear deformations occur over a long time span (>60 min). Conversely, nuclear deformation and condensed chromatin are relaxed in a few seconds after detachment. Finally, our results show that accumulation of farnesylated prelamin leads to modifications of the nuclear viscoelastic properties, as reflected by increased nuclear relaxation times. Our method offers an original and non-intrusive way of simultaneously gauging cellular and nuclear mechanics, which can be extended to high-throughput screens of pathological conditions and potential countermeasures. PMID:27111836

Probing cytoskeletal pre-stress and nuclear mechanics in endothelial cells with spatiotemporally controlled (de-)adhesion kinetics on micropatterned substrates.

PubMed

Versaevel, Marie; Riaz, Maryam; Corne, Tobias; Grevesse, Thomas; Lantoine, Joséphine; Mohammed, Danahe; Bruyère, Céline; Alaimo, Laura; De Vos, Winnok H; Gabriele, Sylvain

2017-01-02

The mechanical properties of living cells reflect their propensity to migrate and respond to external forces. Both cellular and nuclear stiffnesses are strongly influenced by the rigidity of the extracellular matrix (ECM) through reorganization of the cyto- and nucleoskeletal protein connections. Changes in this architectural continuum affect cell mechanics and underlie many pathological conditions. In this context, an accurate and combined quantification of the mechanical properties of both cells and nuclei can contribute to a better understanding of cellular (dys-)function. To address this challenge, we have established a robust method for probing cellular and nuclear deformation during spreading and detachment from micropatterned substrates. We show that (de-)adhesion kinetics of endothelial cells are modulated by substrate stiffness and rely on the actomyosin network. We combined this approach with measurements of cell stiffness by magnetic tweezers to show that relaxation dynamics can be considered as a reliable parameter of cellular pre-stress in adherent cells. During the adhesion stage, large cellular and nuclear deformations occur over a long time span (>60 min). Conversely, nuclear deformation and condensed chromatin are relaxed in a few seconds after detachment. Finally, our results show that accumulation of farnesylated prelamin leads to modifications of the nuclear viscoelastic properties, as reflected by increased nuclear relaxation times. Our method offers an original and non-intrusive way of simultaneously gauging cellular and nuclear mechanics, which can be extended to high-throughput screens of pathological conditions and potential countermeasures.

Effects of pH and Oxygen on Photosynthetic Reactions of Intact Chloroplasts 1

PubMed Central

Heber, Ulrich; Andrews, T. John; Boardman, N. Keith

1976-01-01

Oxygen inhibition of photosynthesis was studied with intact spinach (Spinacia oleracea L.) chloroplasts which exhibited very high rates of photosynthetic CO2 reduction and were insensitive to additions of photosynthetic intermediates when CO2 was available at saturating concentrations. Photosynthetic rates were measured polarographically as O2 evolution, and the extent of the reduction of substrate was estimated from the amount of O2 evolved. With CO2 as substrate, inhibition of photosynthesis by O2 was dependent on pH. At pH values above 8, rates of O2 evolution were strongly inhibited by O2 and only a fraction of the added bicarbonate was reduced before O2 evolution ceased. The extent of O2 evolution declined with increasing O2 concentration and decreasing initial bicarbonate concentration. At pH 7.2, the initial photosynthetic rate was inhibited about 30% at high O2 levels, but the extent of O2 evolution was unaffected and most of the added bicarbonate was reduced. Photosynthetic O2 evolution with 3-phosphoglycerate as substrate was similarly dependent on pH and O2 concentration. In contrast, there was little effect of O2 and pH on oxaloacetate-dependent oxygen evolution. Acid-base shift experiments with osmotically shocked chloroplasts showed that ATP formation was not affected by O2. The results are discussed in terms of a balance between photosynthetic O2 evolution and O2 consumption by the ribulose diphosphate oxygenase reaction. PMID:16659466

A novel serine protease from strawberry (Fragaria ananassa): Purification and biochemical characterization.

PubMed

Alici, Esma Hande; Arabaci, Gulnur

2018-03-27

In this study, a protease enzyme was purified from strawberry by using Sepharose-4B-l-tyrosine-p-amino benzoic acid affinity chromatography. The molecular weight of pure protease was determined 65.8 kDa by SDS-PAGE. The single band observed on the gel showed that the enzyme had a single polypeptide chain and was successfully purified. Purification of the protease by the chromatographic method resulted in a 395.6-fold increase in specific activity (3600 U/mg). Optimum pH and temperature for the enzyme were 6 and 40 °C, respectively. The protease was stable at a wide temperature range of 40 to 70 °C and a pH range of 3.0 to 9.0. Co 2+ ions stimulated protease activity very strongly. Cu 2+ , Hg 2+ , Cd 2+ and Mn 2+ ions significantly inhibited protease activity. While 2-propanol completely inhibited the enzyme, the enzyme maintained its activity better in the presence of ethanol and methanol. The strawberry protease showed the highest specificity towards hemoglobin among all the natural substrates tested. The specificity of the enzyme towards synthetic substrates was also investigated and it was concluded that it has broad substrate specificity. The obtained results indicated that this purified protease was highly-likely a serine protease and its activity was significantly affected by the presence of metal ions. Copyright © 2018. Published by Elsevier B.V.

Sorafenib metabolism, transport, and enterohepatic recycling: physiologically based modeling and simulation in mice.

PubMed

Edginton, Andrea N; Zimmerman, Eric I; Vasilyeva, Aksana; Baker, Sharyn D; Panetta, John C

2016-05-01

This study used uncertainty and sensitivity analysis to evaluate a physiologically based pharmacokinetic (PBPK) model of the complex mechanisms of sorafenib and its two main metabolites, sorafenib glucuronide and sorafenib N-oxide in mice. A PBPK model for sorafenib and its two main metabolites was developed to explain disposition in mice. It included relevant influx (Oatp) and efflux (Abcc2 and Abcc3) transporters, hepatic metabolic enzymes (CYP3A4 and UGT1A9), and intestinal β-glucuronidase. Parameterization of drug-specific processes was based on in vitro, ex vivo, and in silico data along with plasma and liver pharmacokinetic data from single and multiple transporter knockout mice. Uncertainty analysis demonstrated that the model structure and parameter values could explain the observed variability in the pharmacokinetic data. Global sensitivity analysis demonstrated the global effects of metabolizing enzymes on sorafenib and metabolite disposition and the local effects of transporters on their respective substrate exposures. In addition, through hypothesis testing, the model supported that the influx transporter Oatp is a weak substrate for sorafenib and a strong substrate for sorafenib glucuronide and that the efflux transporter Abcc2 is not the only transporter affected in the Abcc2 knockout mouse. Translation of the mouse model to humans for the purpose of explaining exceptionally high human pharmacokinetic variability and its relationship with exposure-dependent dose-limiting toxicities will require delineation of the importance of these processes on disposition.

Neural mechanisms underlying the integration of situational information into attribution outcomes.

PubMed

Brosch, Tobias; Schiller, Daniela; Mojdehbakhsh, Rachel; Uleman, James S; Phelps, Elizabeth A

2013-08-01

When forming impressions and trying to figure out why other people behave the way they do, we should take into account not only dispositional factors (i.e., personality traits) but also situational constraints as potential causes for a behavior. However, in their attributions, people often ignore the importance of situational factors. To investigate the neural mechanisms underlying the integration of situational information into attributions, we decomposed the attribution process by separately presenting information about behaviors and about the situational circumstances in which they occur. After reading the information, participants judged whether dispositional or situational causes explained the behavior (attribution), and how much they liked the person described in the scenario (affective evaluation). The dorsolateral prefrontal cortex showed increased blood oxygenation-level-dependent activation during the encoding of situational information when the resulting attribution was situational, relative to when the attribution was dispositional, potentially reflecting a controlled process that integrates situational information into attributions. Interestingly, attributions were strongly linked to subsequent affective evaluations, with the dorsomedial prefrontal cortex emerging as potential substrate of the integration of attributions and affective evaluations. Our findings demonstrate how top-down control processes regulate impression formation when situational information is taken into account to understand others.

Neural mechanisms underlying the integration of situational information into attribution outcomes

PubMed Central

Brosch, Tobias; Schiller, Daniela; Mojdehbakhsh, Rachel; Uleman, James S.; Phelps, Elizabeth A.

2013-01-01

When forming impressions and trying to figure out why other people behave the way they do, we should take into account not only dispositional factors (i.e. personality traits) but also situational constraints as potential causes for a behavior. However, in their attributions, people often ignore the importance of situational factors. To investigate the neural mechanisms underlying the integration of situational information into attributions, we decomposed the attribution process by separately presenting information about behaviors and about the situational circumstances in which they occur. After reading the information, participants judged whether dispositional or situational causes explained the behavior (attribution), and how much they liked the person described in the scenario (affective evaluation). The dorsolateral prefrontal cortex showed increased blood oxygenation-level-dependent activation during the encoding of situational information when the resulting attribution was situational, relative to when the attribution was dispositional, potentially reflecting a controlled process that integrates situational information into attributions. Interestingly, attributions were strongly linked to subsequent affective evaluations, with the dorsomedial prefrontal cortex emerging as potential substrate of the integration of attributions and affective evaluations. Our findings demonstrate how top-down control processes regulate impression formation when situational information is taken into account to understand others. PMID:23446840

Convergent Loss of ABC Transporter Genes From Clostridioides difficile Genomes Is Associated With Impaired Tyrosine Uptake and p-Cresol Production.

PubMed

Steglich, Matthias; Hofmann, Julia D; Helmecke, Julia; Sikorski, Johannes; Spröer, Cathrin; Riedel, Thomas; Bunk, Boyke; Overmann, Jörg; Neumann-Schaal, Meina; Nübel, Ulrich

2018-01-01

We report the frequent, convergent loss of two genes encoding the substrate-binding protein and the ATP-binding protein of an ATP-binding cassette (ABC) transporter from the genomes of unrelated Clostridioides difficile strains. This specific genomic deletion was strongly associated with the reduced uptake of tyrosine and phenylalanine and production of derived Stickland fermentation products, including p -cresol, suggesting that the affected ABC transporter had been responsible for the import of aromatic amino acids. In contrast, the transporter gene loss did not measurably affect bacterial growth or production of enterotoxins. Phylogenomic analysis of publically available genome sequences indicated that this transporter gene deletion had occurred multiple times in diverse clonal lineages of C. difficile , with a particularly high prevalence in ribotype 027 isolates, where 48 of 195 genomes (25%) were affected. The transporter gene deletion likely was facilitated by the repetitive structure of its genomic location. While at least some of the observed transporter gene deletions are likely to have occurred during the natural life cycle of C. difficile , we also provide evidence for the emergence of this mutation during long-term laboratory cultivation of reference strain R20291.

Convergent Loss of ABC Transporter Genes From Clostridioides difficile Genomes Is Associated With Impaired Tyrosine Uptake and p-Cresol Production

PubMed Central

Steglich, Matthias; Hofmann, Julia D.; Helmecke, Julia; Sikorski, Johannes; Spröer, Cathrin; Riedel, Thomas; Bunk, Boyke; Overmann, Jörg; Neumann-Schaal, Meina; Nübel, Ulrich

2018-01-01

We report the frequent, convergent loss of two genes encoding the substrate-binding protein and the ATP-binding protein of an ATP-binding cassette (ABC) transporter from the genomes of unrelated Clostridioides difficile strains. This specific genomic deletion was strongly associated with the reduced uptake of tyrosine and phenylalanine and production of derived Stickland fermentation products, including p-cresol, suggesting that the affected ABC transporter had been responsible for the import of aromatic amino acids. In contrast, the transporter gene loss did not measurably affect bacterial growth or production of enterotoxins. Phylogenomic analysis of publically available genome sequences indicated that this transporter gene deletion had occurred multiple times in diverse clonal lineages of C. difficile, with a particularly high prevalence in ribotype 027 isolates, where 48 of 195 genomes (25%) were affected. The transporter gene deletion likely was facilitated by the repetitive structure of its genomic location. While at least some of the observed transporter gene deletions are likely to have occurred during the natural life cycle of C. difficile, we also provide evidence for the emergence of this mutation during long-term laboratory cultivation of reference strain R20291. PMID:29867812

Pharmacoproteomics of a metalloproteinase hydroxamate inhibitor in breast cancer cells: dynamics of membrane type 1 matrix metalloproteinase-mediated membrane protein shedding.

PubMed

Butler, Georgina S; Dean, Richard A; Tam, Eric M; Overall, Christopher M

2008-08-01

Broad-spectrum matrix metalloproteinase (MMP) inhibitors (MMPI) were unsuccessful in cancer clinical trials, partly due to side effects resulting from limited knowledge of the full repertoire of MMP substrates, termed the substrate degradome, and hence the in vivo functions of MMPs. To gain further insight into the degradome of MMP-14 (membrane type 1 MMP) an MMPI, prinomastat (drug code AG3340), was used to reduce proteolytic processing and ectodomain shedding in human MDA-MB-231 breast cancer cells transfected with MMP-14. We report a quantitative proteomic evaluation of the targets and effects of the inhibitor in this cell-based system. Proteins in cell-conditioned medium (the secretome) and membrane fractions with levels that were modulated by the MMPI were identified by isotope-coded affinity tag (ICAT) labeling and tandem mass spectrometry. Comparisons of the expression of MMP-14 with that of a vector control resulted in increased MMP-14/vector ICAT ratios for many proteins in conditioned medium, indicating MMP-14-mediated ectodomain shedding. Following MMPI treatment, the MMPI/vehicle ICAT ratio was reversed, suggesting that MMP-14-mediated shedding of these proteins was blocked by the inhibitor. The reduction in shedding or the release of substrates from pericellular sites in the presence of the MMPI was frequently accompanied by the accumulation of the protein in the plasma membrane, as indicated by high MMPI/vehicle ICAT ratios. Considered together, this is a strong predictor of biologically relevant substrates cleaved in the cellular context that led to the identification of many undescribed MMP-14 substrates, 20 of which we validated biochemically, including DJ-1, galectin-1, Hsp90alpha, pentraxin 3, progranulin, Cyr61, peptidyl-prolyl cis-trans isomerase A, and dickkopf-1. Other proteins with altered levels, such as Kunitz-type protease inhibitor 1 and beta-2-microglobulin, were not substrates in biochemical assays, suggesting an indirect affect of the MMPI, which might be important in drug development as biomarkers or, in preclinical phases, to predict systemic drug actions and adverse side effects. Hence, this approach describes the dynamic pattern of cell membrane ectodomain shedding and its perturbation upon metalloproteinase drug treatment.

Effect of diet composition and feeding pattern on the prececal digestibility of starches from diverse botanical origins measured with the mobile nylon bag technique in horses.

PubMed

de Fombelle, A; Veiga, L; Drogoul, C; Julliand, V

2004-12-01

This trial was conducted to determine the extent of prececal starch digestibility depending on the botanical origin of starch and on diet characteristics (i.e., composition and feeding pattern). The prececal disappearance of six substrates (oats, barley, corn, horse bean, potato, and wheat) was measured in four cannulated horses fed (as-fed basis) 11.8 g/kg BW of a high-fiber (HF) or high-starch (HS) pelleted feed and 10.0 g/kg BW of meadow hay using the mobile bag technique (MBT). The daily feeding pattern was either three meals (two meals of pellets and one meal of hay) or five meals (three meals of pellets and two meals of hay). The experimental procedure was a 2 x 2 factorial arrangement tested in a Latin square design. After 2 wk of adaptation to the diet, collections were made on 5 d. Thirty nylon bags, composed of five bags of each substrate, were intubated to each horse during the ingestion of the morning meal. Bags were collected in the cecum, using a magnet, at 9 h postintubation. In spite of strong interindividual differences, approximately 80% of the intubated bags were collected. On average, the mean retention time of the bags was 6.2 h (+/-0.17). Regardless of the feeding pattern, the transit of the bags was faster when the fiber content of the diet was higher (P = 0.003). Likewise, regardless of the meal composition, transit was also faster when the ration was split into five daily meals (P = 0.001). The DM disappearance, corrected with particulate losses (DMD(c)), differed depending on the substrate tested (33.5, 57.1, 63.8, 67.7, 78.6, and 86.2% for potato, horse bean, oats, barley, corn, and wheat, respectively; P = 0.001). The DMD(c) of corn, barley, and potato was higher when HS was fed (P = 0.020); regardless of the substrate, DMD(c) was higher with five daily meals (P = 0.001). The starch disappearance (StarchD(c)) was different depending on the substrate (P = 0.001; 36.1, 71.2, 86.6, 89.2, 99.0, and 99.7% for potato, horse bean, barley, corn, wheat, and oats, respectively). Whatever the substrate, StarchD(c) was higher when HS was fed (P = 0.007), but it was not affected by the feeding pattern of the diet. Although passage rate was modified and feed intake was different, the botanical origin of starch was the main factor that affected prececal starch disappearance in horses.

Enzyme localization, crowding, and buffers collectively modulate diffusion-influenced signal transduction: Insights from continuum diffusion modeling

PubMed Central

Kekenes-Huskey, Peter M.; Eun, Changsun; McCammon, J. A.

2015-01-01

Biochemical reaction networks consisting of coupled enzymes connect substrate signaling events with biological function. Substrates involved in these reactions can be strongly influenced by diffusion “barriers” arising from impenetrable cellular structures and macromolecules, as well as interactions with biomolecules, especially within crowded environments. For diffusion-influenced reactions, the spatial organization of diffusion barriers arising from intracellular structures, non-specific crowders, and specific-binders (buffers) strongly controls the temporal and spatial reaction kinetics. In this study, we use two prototypical biochemical reactions, a Goodwin oscillator, and a reaction with a periodic source/sink term to examine how a diffusion barrier that partitions substrates controls reaction behavior. Namely, we examine how conditions representative of a densely packed cytosol, including reduced accessible volume fraction, non-specific interactions, and buffers, impede diffusion over nanometer length-scales. We find that diffusion barriers can modulate the frequencies and amplitudes of coupled diffusion-influenced reaction networks, as well as give rise to “compartments” of decoupled reactant populations. These effects appear to be intensified in the presence of buffers localized to the diffusion barrier. These findings have strong implications for the role of the cellular environment in tuning the dynamics of signaling pathways. PMID:26342355

Laser-generated ultrasound for high-precision cutting of tissue-mimicking gels (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lee, Taehwa; Luo, Wei; Li, Qiaochu; Guo, L. Jay

2017-03-01

Laser-generated focused ultrasound has shown great promise in precisely treating cells and tissues by producing controlled micro-cavitation within the acoustic focal volume (<100 um). However, the previous demonstration used cells and tissues cultured on glass substrates. The glass substrates were found to be critical to cavitation, because ultrasound amplitude doubles due to the reflection from the substrate, thus allowing for reaching pressure amplitude to cavitation threshold. In other words, without the sound reflecting substrate, pressure amplitude may not be strong enough to create cavitation, thus limiting its application to only cultured biomaterials on the rigid substrates. By using laser-generated focused ultrasound without relying on sound-reflecting substrates, we demonstrate free-field cavitation in water and its application to high-precision cutting of tissue-mimicking gels. In the absence of a rigid boundary, strong pressure for cavitation was enabled by recently optimized photoacoustic lens with increased focal gain (>30 MPa, negative pressure amplitude). By moving cavitation spots along pre-defined paths through a motorized stage, tissue-mimicking gels of different elastic moduli were cut into different shapes (rectangle, triangle, and circle), leaving behind the same shape of holes, whose sizes are less than 1 mm. The cut line width is estimated to be less than 50 um (corresponding to localized cavitation region), allowing for accurate cutting. This novel approach could open new possibility for in-vivo treatment of diseased tissues in a high-precision manner (i.e., high-precision invisible sonic scalpel).

Enormous Hydrogen Bond Strength Enhancement through π-Conjugation Gain: Implications for Enzyme Catalysis.

PubMed

Wu, Chia-Hua; Ito, Keigo; Buytendyk, Allyson M; Bowen, K H; Wu, Judy I

2017-08-22

Surprisingly large resonance-assistance effects may explain how some enzymes form extremely short, strong hydrogen bonds to stabilize reactive oxyanion intermediates and facilitate catalysis. Computational models for several enzymic residue-substrate interactions reveal that when a π-conjugated, hydrogen bond donor (XH) forms a hydrogen bond to a charged substrate (Y - ), XH can become significantly more π-electron delocalized, and this "extra" stabilization may boost the [XH···Y - ] hydrogen bond strength by ≥15 kcal/mol. This reciprocal relationship departs from the widespread pK a concept (i.e., the idea that short, strong hydrogen bonds form when the interacting moieties have matching pK a values), which has been the rationale for enzymic acid-base reactions. The findings presented here provide new insight into how short, strong hydrogen bonds could form in enzymes.

Strong polarization-dependent terahertz modulation of aligned Ag nanowires on Si substrate.

PubMed

Lee, Gyuseok; Maeng, Inhee; Kang, Chul; Oh, Myoung-Kyu; Kee, Chul-Sik

2018-05-14

Optically tunable, strong polarization-dependent transmission of terahertz pulses through aligned Ag nanowires on a Si substrate is demonstrated. Terahertz pulses primarily pass through the Ag nanowires and the transmittance is weakly dependent on the angle between the direction of polarization of the terahertz pulse and the direction of nanowire alignment. However, the transmission of a terahertz pulse through optically excited materials strongly depends on the polarization direction. The extinction ratio increases as the power of the pumping laser increases. The enhanced polarization dependency is explained by the redistribution of photocarriers, which accelerates the sintering effect along the direction of alignment of the Ag nanowires. The photocarrier redistribution effect is examined by the enhancement of terahertz emission from the sample. Oblique metal nanowires on Si could be utilized for designing optically tunable terahertz polarization modulators.

The effects of electrospun substrate-mediated cell colony morphology on the self-renewal of human induced pluripotent stem cells.

PubMed

Maldonado, Maricela; Wong, Lauren Y; Echeverria, Cristina; Ico, Gerardo; Low, Karen; Fujimoto, Taylor; Johnson, Jed K; Nam, Jin

2015-05-01

The development of xeno-free, chemically defined stem cell culture systems has been a primary focus in the field of regenerative medicine to enhance the clinical application of pluripotent stem cells (PSCs). In this regard, various electrospun substrates with diverse physiochemical properties were synthesized utilizing various polymer precursors and surface treatments. Human induced pluripotent stem cells (IPSCs) cultured on these substrates were characterized by their gene and protein expression to determine the effects of the substrate physiochemical properties on the cells' self-renewal, i.e., proliferation and the maintenance of pluripotency. The results showed that surface chemistry significantly affected cell colony formation via governing the colony edge propagation. More importantly, when surface chemistry of the substrates was uniformly controlled by collagen conjugation, the stiffness of substrate was inversely related to the sphericity, a degree of three dimensionality in colony morphology. The differences in sphericity subsequently affected spontaneous differentiation of IPSCs during a long-term culture, implicating that the colony morphology is a deciding factor in the lineage commitment of PSCs. Overall, we show that the capability of controlling IPSC colony morphology by electrospun substrates provides a means to modulate IPSC self-renewal. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of a blend of essential oil compounds on the colonization of starch-rich substrates by bacteria in the rumen.

PubMed

Duval, S M; McEwan, N R; Graham, R C; Wallace, R J; Newbold, C J

2007-12-01

To investigate the mode of action of a blend of essential oil compounds on the colonization of starch-rich substrates by rumen bacteria. Starch-rich substrates were incubated, in nylon bags, in the rumen of sheep organized in a 4 x 4 latin square design and receiving a 60:40 silage : concentrate diet. The concentrate was either high or low in crude protein, and the diet was supplemented or not with a commercial blend of essential oil compounds (110 mg per day). The total genomic DNA was extracted from the residues in the bags. The total eubacterial DNA was quantified by real-time PCR and the proportion of Ruminobacter amylophilus, Streptococcus bovis and Prevotella bryantii was determined. Neither the supplementation with essential oil compounds nor the amount of crude protein affected the colonization of the substrates by the bacteria quantified. However, colonization was significantly affected by the substrate colonized. The effect of essential oils on the colonization of starch-rich substrates is not mediated through the selective inhibition of R. amylophilus. This study enhances our understanding of the colonization of starch-rich substrates, as well as of the mode of action of the essential oils as rumen manipulating agents.

Capacitance-voltage characterization of Al/Al2O3/PVA-PbSe MIS diode

NASA Astrophysics Data System (ADS)

Gawri, Isha; Sharma, Mamta; Jindal, Silky; Singh, Harpreet; Tripathi, S. K.

2018-05-01

The present paper reports the capacitance-voltage characterization of Al/Al2O3/PVA-PbSe MIS diode using chemical bath deposition method. Here anodic alumina layer prepared using electrolytic deposition method on Al substrate is used as insulating material. Using the capacitance-voltage variation at a fixed frequency, the different parameters such as Depletion layer width, Barrier height, Built-in voltage and Carrier concentration has been calculated at room temperature as well as at temperature range from 123 K to 323 K. With the increase in temperature the barrier height and depletion layer width follow a decreasing trend. Therefore, the capacitance-voltage characterization at different temperatures characterization provides strong evidence that the properties of MIS diode are primarily affected by diode parameters.

Flow Visualization in Evaporating Liquid Drops and Measurement of Dynamic Contact Angles and Spreading Rate

NASA Technical Reports Server (NTRS)

Zhang, Neng-Li; Chao, David F.

2001-01-01

A new hybrid optical system, consisting of reflection-refracted shadowgraphy and top-view photography, is used to visualize flow phenomena and simultaneously measure the spreading and instant dynamic contact angle in a volatile-liquid drop on a nontransparent substrate. Thermocapillary convection in the drop, induced by evaporation, and the drop real-time profile data are synchronously recorded by video recording systems. Experimental results obtained from this unique technique clearly reveal that thermocapillary convection strongly affects the spreading process and the characteristics of dynamic contact angle of the drop. Comprehensive information of a sessile drop, including the local contact angle along the periphery, the instability of the three-phase contact line, and the deformation of the drop shape is obtained and analyzed.

Silylative Reductive Amination of α,β-Unsaturated Aldehydes: A Convenient Synthetic Route to β-Silylated Secondary Amines.

PubMed

Kim, Eunae; Park, Sehoon; Chang, Sukbok

2018-04-17

Described here is a reductive amination/hydrosilylation cascade of α,β-unsaturated aldehydes mediated by a Lewis acidic borane catalyst. The present reaction system provides an one-pot synthetic route towards β-silylated secondary amines that have not been accessible by other previous catalysis. Comparative 1 H NMR studies on the silylative reduction of enimines revealed that steric bulkiness of primary amine reactants strongly affects both catalytic efficiency and regioselectivity. This strategy was applicable to a broad range of substrates and amenable to one-pot gram-scale synthesis. Moreover, a diastereoselective introduction of the β-silyl group was also found to be feasible (d.r. up to 71:29). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cuttlefish dynamic camouflage: responses to substrate choice and integration of multiple visual cues.

PubMed

Allen, Justine J; Mäthger, Lydia M; Barbosa, Alexandra; Buresch, Kendra C; Sogin, Emilia; Schwartz, Jillian; Chubb, Charles; Hanlon, Roger T

2010-04-07

Prey camouflage is an evolutionary response to predation pressure. Cephalopods have extensive camouflage capabilities and studying them can offer insight into effective camouflage design. Here, we examine whether cuttlefish, Sepia officinalis, show substrate or camouflage pattern preferences. In the first two experiments, cuttlefish were presented with a choice between different artificial substrates or between different natural substrates. First, the ability of cuttlefish to show substrate preference on artificial and natural substrates was established. Next, cuttlefish were offered substrates known to evoke three main camouflage body pattern types these animals show: Uniform or Mottle (function by background matching); or Disruptive. In a third experiment, cuttlefish were presented with conflicting visual cues on their left and right sides to assess their camouflage response. Given a choice between substrates they might encounter in nature, we found no strong substrate preference except when cuttlefish could bury themselves. Additionally, cuttlefish responded to conflicting visual cues with mixed body patterns in both the substrate preference and split substrate experiments. These results suggest that differences in energy costs for different camouflage body patterns may be minor and that pattern mixing and symmetry may play important roles in camouflage.

Aqueous phase hydrogenation of phenol catalyzed by Pd and PdAg on ZrO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Resende, Karen A.; Hori, Carla E.; Noronha, Fabio B.

The impact of particle size of ZrO 2-supported Pd and of alloying with Ag was explored for hydrogenation of phenol in aqueous phase. Kinetic assessments were performed in a batch reactor, on monometallic Pd/ZrO 2 samples with different Pd loadings (0.5%, 1% and 2%), as well as on a 1% PdAg/ZrO 2 sample. The catalytic activity normalized to accessible Pd (turnover frequency, TOF) increased with the particle size of Pd. Reaction orders in phenol and H 2 and lower activation energies suggest that smaller particles bind the reacting substrates more strongly, leading to higher surface coverages by phenol. But, surprisingly,more » smaller Pd particles exhibited lower TOFs. The lower activity of the small Pd particles is attributed to lower activation entropies for the strongly bound species. Furthermore, the presence of Ag increased the catalyst activity by decreasing the apparent energy of activation and increasing the coverages of phenol and H 2, without negatively affecting the activation entropy.« less

Aqueous phase hydrogenation of phenol catalyzed by Pd and PdAg on ZrO 2

DOE PAGES

Resende, Karen A.; Hori, Carla E.; Noronha, Fabio B.; ...

2017-08-05

The impact of particle size of ZrO 2-supported Pd and of alloying with Ag was explored for hydrogenation of phenol in aqueous phase. Kinetic assessments were performed in a batch reactor, on monometallic Pd/ZrO 2 samples with different Pd loadings (0.5%, 1% and 2%), as well as on a 1% PdAg/ZrO 2 sample. The catalytic activity normalized to accessible Pd (turnover frequency, TOF) increased with the particle size of Pd. Reaction orders in phenol and H 2 and lower activation energies suggest that smaller particles bind the reacting substrates more strongly, leading to higher surface coverages by phenol. But, surprisingly,more » smaller Pd particles exhibited lower TOFs. The lower activity of the small Pd particles is attributed to lower activation entropies for the strongly bound species. Furthermore, the presence of Ag increased the catalyst activity by decreasing the apparent energy of activation and increasing the coverages of phenol and H 2, without negatively affecting the activation entropy.« less

Lightweight Electrode For Nickel/Hydrogen Cell

NASA Technical Reports Server (NTRS)

Britton, Doris L.

1994-01-01

Improved substrate for nickel electrode increases specific energy of nickel/hydrogen cell. Consists of 50 percent by weight nickel fiber, 35 percent nickel powder, and 15 percent cobalt powder. Porosity and thickness of nickel electrodes affect specific energy, initial performance, and cycle life of cell. Substrate easily manufactured with much larger porosities than those of heavy-sintered state-of-art nickel substrate.

Shape and color naming are inherently asymmetrical: Evidence from practice-based interference.

PubMed

Protopapas, Athanassios; Markatou, Artemis; Samaras, Evangelos; Piokos, Andreas

2017-01-01

Stroop interference is characterized by strong asymmetry between word and color naming such that the former is faster and interferes with the latter but not vice versa. This asymmetry is attributed to differential experience with naming in the two dimensions, i.e., words and colors. Here we show that training on visual-verbal paired associate tasks equivalent to color and shape naming, not involving word reading, leads to strongly asymmetric interference patterns. In two experiments adults practiced naming colors and shapes, one dimension more extensively (10days) than the other (2days), depending on group assignment. One experiment used novel shapes (ideograms) and the other familiar geometric shapes, associated with nonsense syllables. In a third experiment participants practiced naming either colors or shapes using cross-category shape and color names, respectively, for 12days. Across experiments, despite equal training of the two groups in naming the two different dimensions, color naming was strongly affected by shape even after extensive practice, whereas shape naming was resistant to interference. To reconcile these findings with theoretical accounts of interference, reading may be conceptualized as involving visual-verbal associations akin to shape naming. An inherent or early-developing advantage for naming shapes may provide an evolutionary substrate for the invention and development of reading. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of deposition rate on melting point of copper film catalyst substrate at atomic scale

NASA Astrophysics Data System (ADS)

Marimpul, Rinaldo; Syuhada, Ibnu; Rosikhin, Ahmad; Winata, Toto

2018-03-01

Annealing process of copper film catalyst substrate was studied by molcular dynamics simulation. This copper film catalyst substrate was produced using thermal evaporation method. The annealing process was limited in nanosecond order to observe the mechanism at atomic scale. We found that deposition rate parameter affected the melting point of catalyst substrate. The change of crystalline structure of copper atoms was observed before it had been already at melting point. The optimum annealing temperature was obtained to get the highest percentage of fcc structure on copper film catalyst substrate.

Substrate Effects for Atomic Chain Electronics

NASA Technical Reports Server (NTRS)

Yamada, Toshishige; Saini, Subhash (Technical Monitor)

1998-01-01

A substrate for future atomic chain electronics, where adatoms are placed at designated positions and form atomically precise device components, is studied theoretically. The substrate has to serve as a two-dimensional template for adatom mounting with a reasonable confinement barrier and also provide electronic isolation, preventing unwanted coupling between independent adatom structures. For excellent structural stability, we demand chemical bonding between the adatoms and substrate atoms, but then good electronic isolation may not be guaranteed. Conditions are clarified for good isolation. Because of the chemical bonding, fundamental adatom properties are strongly influenced: a chain with group IV adatoms having two chemical bonds, or a chain with group III adatoms having one chemical bond is semiconducting. Charge transfer from or to the substrate atoms brings about unintentional doping, and the electronic properties have to be considered for the entire combination of the adatom and substrate systems even if the adatom modes are well localized at the surface.

Structure and magnetic properties of spinel-perovskite nanocomposite thin films on SrTiO3 (111) substrates

NASA Astrophysics Data System (ADS)

Kim, Dong Hun; Yang, Junho; Kim, Min Seok; Kim, Tae Cheol

2016-09-01

Epitaxial CoFe2O4-BiFeO3 nanocomposite thin films were synthesized on perovskite structured SrTiO3 (001) and (111) substrates by combinatorial pulsed laser deposition and characterized using scanning electron microscopy, x-ray diffraction, and vibrating sample magnetometer. Triangular BiFeO3 nanopillars were formed in a CoFe2O4 matrix on (111) oriented SrTiO3 substrates, while CoFe2O4 nanopillars with rectangular or square top surfaces grew in a BiFeO3 matrix on (001) substrates. The magnetic hysteresis loops of nanocomposites on (111) oriented SrTiO3 substrates showed isotropic properties due to the strain relaxation while those of films on SrTiO3 (001) substrates exhibited a strong out-of-plane anisotropy originated from shape and strain effects.

Preparation of CuIn{sub x}Ga{sub 1{minus}x}Se{sub 2} thin films on Si substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamamoto, Yukio; Yamaguchi, Toshiyuki; Suzuki, Masayoshi

For fabricating efficient tandem solar cells, CuIn{sub x}Ga{sub 1{minus}x}Se{sub 2} thin films have been prepared on Si(100), Si(110) and Si(111) substrates in the temperature range (R.T.{approximately}400 C) by rf sputtering. From EPMA analysis, these sputtered thin films are found to be nearly stoichiometric over the whole substrate temperature range, irrespective of the azimuth plane of the Si substrate. XPS studies showed that the compositional depth profile in these thin films is uniform. X-ray diffraction analysis indicated that all the thin films had a chalcopyrite structure. CuIn{sub x}Ga{sub 1{minus}x}Se{sub 2} thin films were strongly oriented along the (112) plane with increasingmore » the substrate temperature, independent of the azimuth plane of the Si substrate, suggesting the larger grain growth.« less

Structures And Fabrication Techniques For Solid State Electrochemical Devices

DOEpatents

Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

2005-12-27

Provided are low-cost, mechanically strong, highly electronically conductive porous substrates and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures. The invention provides solid state electrochemical device substrates of novel composition and techniques for forming thin electrode/membrane/electrolyte coatings on the novel or more conventional substrates. In particular, in one embodiment the invention provides techniques for co-firing of device substrate (often an electrode) with an electrolyte or membrane layer to form densified electrolyte/membrane films 5 to 20 microns thick. In another embodiment, densified electrolyte/membrane films 5 to 20 microns thick may be formed on a pre-sintered substrate by a constrained sintering process. In some cases, the substrate may be a porous metal, alloy, or non-nickel cermet incorporating one or more of the transition metals Cr, Fe, Cu and Ag, or alloys thereof.

Structures and fabrication techniques for solid state electrochemical devices

DOEpatents

Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

2003-08-12

Provided are low-cost, mechanically strong, highly electronically conductive porous substrates and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures. The invention provides solid state electrochemical device substrates of novel composition and techniques for forming thin electrode/membrane/electrolyte coatings on the novel or more conventional substrates. In particular, in one embodiment the invention provides techniques for co-firing of device substrate (often an electrode) with an electrolyte or membrane layer to form densified electrolyte/membrane films 5 to 20 microns thick. In another embodiment, densified electrolyte/membrane films 5 to 20 microns thick may be formed on a pre-sintered substrate by a constrained sintering process. In some cases, the substrate may be a porous metal, alloy, or non-nickel cermet incorporating one or more of the transition metals Cr, Fe, Cu and Ag, or alloys thereof.

2-(Benzothiazol-2-yl)-phenyl-β-d-galactopyranoside derivatives as fluorescent pigment dyeing substrates and their application for the assay of β-d-galactosidase activities.

PubMed

Otsubo, Tadamune; Minami, Akira; Fujii, Haruna; Taguchi, Risa; Takahashi, Tadanobu; Suzuki, Takashi; Teraoka, Fumiteru; Ikeda, Kiyoshi

2013-04-01

2-(Benzothiazol-2-yl)-phenyl-β-d-galactopyranoside derivatives were synthesized as novel artificial fluorescent pigment dyeing substrates for β-d-galactosidase. The substrates, which exhibited non-fluorescence or weak fluorescence in solution phase, were smoothly hydrolyzed by β-d-galactosidase from Aspergillus oryzae and yielded a water-insoluble strong fluorescent pigment. The difference of fluorescent intensity exhibited a linear relationship with the amount of enzyme. Copyright © 2013 Elsevier Ltd. All rights reserved.

Carbon Conversion Efficiency and Limits of Productive Bacterial Degradation of Methyl tert-Butyl Ether and Related Compounds▿

PubMed Central

Müller, Roland H.; Rohwerder, Thore; Harms, Hauke

2007-01-01

The utilization of the fuel oxygenate methyl tert-butyl ether (MTBE) and related compounds by microorganisms was investigated in a mainly theoretical study based on the YATP concept. Experiments were conducted to derive realistic maintenance coefficients and Ks values needed to calculate substrate fluxes available for biomass production. Aerobic substrate conversion and biomass synthesis were calculated for different putative pathways. The results suggest that MTBE is an effective heterotrophic substrate that can sustain growth yields of up to 0.87 g g−1, which contradicts previous calculation results (N. Fortin et al., Environ. Microbiol. 3:407-416, 2001). Sufficient energy equivalents were generated in several of the potential assimilatory routes to incorporate carbon into biomass without the necessity to dissimilate additional substrate, efficient energy transduction provided. However, when a growth-related kinetic model was included, the limits of productive degradation became obvious. Depending on the maintenance coefficient ms and its associated biomass decay term b, growth-associated carbon conversion became strongly dependent on substrate fluxes. Due to slow degradation kinetics, the calculations predicted relatively high threshold concentrations, Smin, below which growth would not further be supported. Smin strongly depended on the maximum growth rate μmax, and b and was directly correlated with the half maximum rate-associated substrate concentration Ks, meaning that any effect impacting this parameter would also change Smin. The primary metabolic step, catalyzing the cleavage of the ether bond in MTBE, is likely to control the substrate flux in various strains. In addition, deficits in oxygen as an external factor and in reduction equivalents as a cellular variable in this reaction should further increase Ks and Smin for MTBE. PMID:17220260

Evaporation-induced flow in an inviscid liquid line at any contact angle

NASA Astrophysics Data System (ADS)

Petsi, A. J.; Burganos, V. N.

2006-04-01

The problem of potential flow inside an evaporating liquid line, shaped as an infinitely long cylindrical segment lying on a flat surface, is considered and an analytical solution is obtained for any contact angle in (0,π) . In this way, microflow details inside linear liquid bodies evaporating on hydrophilic, hydrophobic, and strongly hydrophobic substrates can now be obtained. The mathematical formulation employs the velocity potential and stream function formulations in bipolar coordinates and the solution is obtained using the technique of Fourier transform. Both pinned and depinned contact lines are considered. The solution is applicable to any evaporation mechanism but for illustration purposes numerical results are presented here for the particular case of kinetically controlled evaporation. For hydrophilic substrates, the flow inside the evaporating liquid line is directed towards the edges for pinned contact lines, thus, promoting a coffee stain effect. The opposite flow direction is observed for depinned contact lines. However, for strongly hydrophobic substrates, flow is directed outwards for both pinned and depinned contact lines, but owing to its low magnitude compared to that on hydrophilic substrates, a craterlike colloidal deposit should be expected rather than a ringlike deposit, in agreement with experimental observations.

Optical properties of silicene, Si/Ag(111), and Si/Ag(110)

NASA Astrophysics Data System (ADS)

Hogan, C.; Pulci, O.; Gori, P.; Bechstedt, F.; Martin, D. S.; Barritt, E. E.; Curcella, A.; Prevot, G.; Borensztein, Y.

2018-05-01

We present a state-of-the-art study of the optical properties of free-standing silicene and of single-layer Si one- and two-dimensional (1D and 2D) nanostructures supported on Ag(110) and Ag(111) substrates. Ab initio simulations of reflectance anisotropy spectroscopy (RAS) and surface differential reflectivity spectroscopy (SDRS) applied to the clean Ag surface and Si/Ag interfaces are compared with new measurements. For Si/Ag(110), we confirm a pentagonal nanoribbon geometry, strongly bonded to the substrate, and rule out competing zigzag chain and silicenelike models. For Si/Ag(111), we reproduce the main experimental features and isolate the optical signal of the epitaxial silicene overlayer. The absorption spectrum of a silicene sheet computed including excitonic and local field effects is found to be quite similar to that calculated within an independent particle approximation and shows strong modifications when adsorbed on a Ag substrate. Important details of the computational approach are examined and the origins of the RAS and SDRS signals are explained in terms of the interface and substrate response functions. Our study does not find any evidence for Si adlayers that retain the properties of freestanding silicene.

Light scattering properties of self-organized nanostructured substrates for thin-film solar cells.

PubMed

Mennucci, C; Del Sorbo, S; Pirotta, S; Galli, M; Andreani, L C; Martella, C; Giordano, M C; Buatier de Mongeot, F

2018-06-01

We investigate the scattering properties of novel kinds of nano-textured substrates, fabricated in a self-organized fashion by defocused ion beam sputtering. These substrates provide strong and broadband scattering of light and can be useful for applications in thin-film solar cells. In particular, we characterize the transmitted light in terms of haze and angle-resolved scattering, and we compare our results with those obtained for the commonly employed Asahi-U texture. The results indicate that the novel substrate has better scattering properties compared to reference Asahi-U substrates. We observe super-Lambertian light scattering behavior in selected spectral and angular regions due to the peculiar morphology of the nano-textured interface, which combines high aspect ratio pseudo random structures with a one-dimensional periodic pattern. The enhancement of light absorption observed in a prototype thin film semiconductor absorber grown on nano-textured glass with respect to an Asahi-U substrate further confirms the superior light trapping properties of the novel substrate.

Hierarchical macroscopic fibrillar adhesives: in situ study of buckling and adhesion mechanisms on wavy substrates.

PubMed

Bauer, Christina T; Kroner, Elmar; Fleck, Norman A; Arzt, Eduard

2015-10-23

Nature uses hierarchical fibrillar structures to mediate temporary adhesion to arbitrary substrates. Such structures provide high compliance such that the flat fibril tips can be better positioned with respect to asperities of a wavy rough substrate. We investigated the buckling and adhesion of hierarchically structured adhesives in contact with flat smooth, flat rough and wavy rough substrates. A macroscopic model for the structural adhesive was fabricated by molding polydimethylsiloxane into pillars of diameter in the range of 0.3-4.8 mm, with up to three different hierarchy levels. Both flat-ended and mushroom-shaped hierarchical samples buckled at preloads one quarter that of the single level structures. We explain this behavior by a change in the buckling mode; buckling leads to a loss of contact and diminishes adhesion. Our results indicate that hierarchical structures can have a strong influence on the degree of adhesion on both flat and wavy substrates. Strategies are discussed that achieve highly compliant substrates which adhere to rough substrates.

Scalable cell alignment on optical media substrates.

PubMed

Anene-Nzelu, Chukwuemeka G; Choudhury, Deepak; Li, Huipeng; Fraiszudeen, Azmall; Peh, Kah-Yim; Toh, Yi-Chin; Ng, Sum Huan; Leo, Hwa Liang; Yu, Hanry

2013-07-01

Cell alignment by underlying topographical cues has been shown to affect important biological processes such as differentiation and functional maturation in vitro. However, the routine use of cell culture substrates with micro- or nano-topographies, such as grooves, is currently hampered by the high cost and specialized facilities required to produce these substrates. Here we present cost-effective commercially available optical media as substrates for aligning cells in culture. These optical media, including CD-R, DVD-R and optical grating, allow different cell types to attach and grow well on them. The physical dimension of the grooves in these optical media allowed cells to be aligned in confluent cell culture with maximal cell-cell interaction and these cell alignment affect the morphology and differentiation of cardiac (H9C2), skeletal muscle (C2C12) and neuronal (PC12) cell lines. The optical media is amenable to various chemical modifications with fibronectin, laminin and gelatin for culturing different cell types. These low-cost commercially available optical media can serve as scalable substrates for research or drug safety screening applications in industry scales. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mapping coral and sponge habitats on a shelf-depth environment using multibeam sonar and ROV video observations: Learmonth Bank, northern British Columbia, Canada

NASA Astrophysics Data System (ADS)

Neves, Bárbara M.; Du Preez, Cherisse; Edinger, Evan

2014-01-01

Efforts to locate and map deep-water coral and sponge habitats are essential for the effective management and conservation of these vulnerable marine ecosystems. Here we test the applicability of a simple multibeam sonar classification method developed for fjord environments to map the distribution of shelf-depth substrates and gorgonian coral- and sponge-dominated biotopes. The studied area is a shelf-depth feature Learmonth Bank, northern British Columbia, Canada and the method was applied aiming to map primarily non-reef forming coral and sponge biotopes. Aside from producing high-resolution maps (5 m2 raster grid), biotope-substrate associations were also investigated. A multibeam sonar survey yielded bathymetry, acoustic backscatter strength and slope. From benthic video transects recorded by remotely operated vehicles (ROVs) six primary substrate types and twelve biotope categories were identified, defined by the primary sediment and dominant biological structure, respectively. Substrate and biotope maps were produced using a supervised classification mostly based on the inter-quartile range of the acoustic variables for each substrate type and biotope. Twenty-five percent of the video observations were randomly reserved for testing the classification accuracy. The dominant biotope-defining corals were red tree coral Primnoa pacifica and small styasterids, of which Stylaster parageus was common. Demosponges and hexactinellid sponges were frequently observed but no sponge reefs were observed. The substrate classification readily distinguished fine sediment, Sand and Bedrock from the other substrate types, but had greater difficulty distinguishing Bedrock from Boulders and Cobble. The biotope classification accurately identified Gardens (dense aggregations of sponges and corals) and Primnoa-dominated biotopes (67% accuracy), but most other biotopes had lower accuracies. There was a significant correspondence between Learmonth's biotopes and substrate types, with many biotopes strongly associated with only a single substrate type. This strong correspondence allowed substrate types to function as a surrogate for helping to map biotope distributions. Our results add new information on the distribution of corals and sponges at Learmonth Bank, which can be used to guide management at this location.

Spatially resolved, substrate-induced rectification in C 60 bilayers on copper

DOE PAGES

Smerdon, J. A.; Darancet, P.; Guest, J. R.

2017-02-22

Here, we demonstrate rectification ratios ( RR) of ≳1000 at biases of 1.3 V in bilayers of C 60 deposited on copper. Using scanning tunneling spectroscopy and first-principles calculations, we show that the strong coupling between C 60 and the Cu(111) surface leads to the metallization of the bottom C 60 layer, while the molecular orbitals of the top C60 are essentially unaffected. Due to this substrate-induced symmetry breaking and to a tunneling transport mechanism, the system behaves as a hole-blocking layer, with a spatial dependence of the onset voltage on intra-layer coordination. Together with previous observations of strong electron-blockingmore » character of pentacene/C 60 bilayers on Cu(111), this work further demonstrates the potential of strongly hybridized, C 60-coated electrodes to harness the electrical functionality of molecular components.« less

Dolomitic lime amendment affects pine bark substrate pH, nutrient availability, and plant growth: A review

USDA-ARS?s Scientific Manuscript database

Dolomitic lime (DL) is one of the most commonly used fertilizer amendments in nursery container substrates. It is used to adjust pH of pine bark substrates from their native pH, 4.1 to 5.1, up to about pH 6. Additions of DL have been shown to be beneficial, inconsequential, or detrimental dependin...

Substrate Chemistry and Rainfall Regime Regulate Elemental Composition of Tree Leaves in Karst Forests

Treesearch

Ernesto Medina; Elvira Cuevas; Ariel Lugo

2017-01-01

Forests on calcareous substrates constitute a large fraction of the vegetation in Puerto Rico. Plant growth on these substrates may be affected by nutrient deficiencies, mainly P and Fe, resulting from high pH and formation of insoluble compounds of these elements. The occurrence of these forests in humid and dry areas provides an opportunity to compare nutrient...

Substrate Dependence in the Growth of Three-Dimensional Gold Nanoparticle Superlattices

DTIC Science & Technology

2001-11-01

the Hamaker constants between gold nanoparticle assemblies and substrates through the suspension. Van der Waals interactions estimated from this...finally dialyzed to remove inorganic (Na, Cl, and B) and organic impurities. The surfactant affects the dispersion of Au nanoparticles in aqueous...be taken into account for complete understanding of the observed substrate dependency. To consider volume interactions, we calculate the Hamaker

A novel fibrinolytic enzyme (nattokinase) in the vegetable cheese Natto; a typical and popular soybean food in the Japanese diet.

PubMed

Sumi, H; Hamada, H; Tsushima, H; Mihara, H; Muraki, H

1987-10-15

A strong fibrinolytic activity was demonstrated in the vegetable cheese Natto, which is a typical soybean food eaten in Japan. The average activity was calculated at about 40 CU (plasmin units)/g wet weight. This novel fibrinolytic enzyme, named nattokinase, was easily extracted with saline. The mol. wt and pI were about 20,000 and 8.6, respectively. Nattokinase not only digested fibrin but also the plasmin substrate H-D-Val-Leu-Lys-pNA (S-2251), which was more sensitive to the enzyme than other substrates tried. Diisopropyl fluorophosphate and 2,2,2-trichloro-1-hydroxyethyl-o,o-dimethylphosphate strongly inhibited this fibrinolytic enzyme.

Macroinvertebrates communities associated with the decomposition of Phragmites australis and Fucus vesiculosus in transitional systems

NASA Astrophysics Data System (ADS)

Lopes, Marta Lobão; Martins, Patrícia; Rodrigues, Ana Maria; Quintino, Victor

2013-10-01

The decomposition rates of a macrophyte (Phragmites australis) and an alga (Fucus vesiculosus) and the associated macrofauna communities were studied along a full salinity gradient, using the leaf-bag technique and four sampling times (days 3, 7, 15 and 30). A control was set up using an artificial substrate. A subsequent study conducted in the mesohaline part of the salinity gradient also included empty bags as procedure control. The decay rates of the alga and the macrophyte were significantly different, the alga decaying faster, and presented an opposite trend along the salinity gradient, with the faster decay rate for reed in the less saline areas and for the alga in the euhaline part of the gradient. The fauna associated with the decaying and the artificial substrate showed equally well the benthic succession from the marine to the freshwater areas, in all sampling times. Arthropods were dominant in all substrates along the estuarine gradient and replaced by annelids in freshwater. No significant differences were found between the benthic communities associated with P. australis and F. vesiculosus, despite the strong differences in the decay rates, suggesting that these do not seem to be primarily related to the benthic colonizers. Although the organic substrates sustained a more abundant fauna, the benthic communities did not show significant differences between the organic and the artificial substrates, especially at the level of the species composition, suggesting that the macroinvertebrates may colonize both substrates to feed on the biofilm and/or to seek shelter. The strongly impoverished benthic community sampled by the empty bags reinforced this idea.

The Catalytic Function of Enzymes.

ERIC Educational Resources Information Center

Splittgerber, Allan G.

1985-01-01

Discusses: structure of the enzyme molecule; active site; reaction mechanism; transition state; factors affecting enzyme reaction rates, concentration of enzyme; concentration of substrate; product concentration; temperature effects and pH effects; factors causing a lowering of activation energy; proximity and orientation effects; substrate strain…

Improved process for epitaxial deposition of silicon on prediffused substrates

NASA Technical Reports Server (NTRS)

Clarke, M. G.; Halsor, J. L.; Word, J. C.

1968-01-01

Process for fabricating integrated circuits uniformly deposits silicon epitaxially on prediffused substrates without affecting the sublayer diffusion pattern. Two silicon deposits from different sources, and deposited at different temperatures, protect the sublayer pattern from the silicon tetrachloride reaction.

Nonlinear Magnus-induced dynamics and Shapiro spikes for ac and dc driven skyrmions on periodic quasi-one-dimensional substrates

NASA Astrophysics Data System (ADS)

Reichhardt, Charles; Reichhardt, Cynthia J. Olson

We numerically examine skyrmions interacting with a periodic quasi-one-dimensional substrate. When we drive the skyrmions perpendicular to the substrate periodicity direction, a rich variety of nonlinear Magnus-induced effects arise, in contrast to an overdamped system that shows only a linear velocity-force curve for this geometry. The skyrmion velocity-force curve is strongly nonlinear and we observe a Magnus-induced speed-up effect when the pinning causes the Magnus velocity response to align with the dissipative response. At higher applied drives these components decouple, resulting in strong negative differential conductivity. For skyrmions under combined ac and dc driving, we find a new class of phase locking phenomena in which the velocity-force curves contain a series of what we call Shapiro spikes, distinct from the Shapiro steps observed in overdamped systems. There are also regimes in which the skyrmion moves in the direction opposite to the applied dc drive to give negative mobility.

Conformational heterogeneity within the Michaelis complex of lactate dehydrogenase†

PubMed Central

Deng, Hua; Vu, Dung V.; Clinch, Keith; Desamero, Ruel; Dyer, R. Brian; Callender, Robert

2011-01-01

A series of isotope edited IR measurements, both static as well as temperature jump relaxation spectroscopy, are performed on lactate dehydrogenase (LDH) to determine the ensemble of structures available to its Michaelis complex. There clearly has been a substantial reduction in the number of states available to the pyruvate substrate (as modeled by the substrate mimic, oxamate) and NADH when bound to protein compared to dissolved in solution, as determined by the bandwidths and positions of the critical C2=O band of bound substrate mimic and the C4-H stretch of NADH reduced nicotinamide group. Moreover, it is found that a strong ionic bond (characterized by a signature IR band discovered in this study) is formed between the carboxyl group of bound pyruvate with (presumably) Arg171, forming a strong ‘anchor’ within the protein matrix. However, conformational heterogeneity within the Michaelis complex is found that has an impact on both catalytic efficiency and thermodynamics of the enzyme. PMID:21568287

Flexoelectro-optic effect and two-beam energy exchange in a hybrid photorefractive cholesteric cell with a short-pitch horizontal helix

NASA Astrophysics Data System (ADS)

Reshetnyak, V. Yu.; Pinkevych, I. P.; Evans, D. R.

2018-06-01

We develop a theoretical model to describe two-beam energy exchange in a hybrid photorefractive cholesteric cell with a short-pitch helix oriented parallel to the cell substrates (so-called uniformly lying helix configuration). Weak and strong light beams incident on the hybrid cell interfere and induce a periodic space-charge field in the photorefractive substrate of the cell, which penetrates into the cholesteric liquid crystal (LC). Due to the flexoelectro-optic effect an interaction of the photorefractive field with the LC flexopolarization causes the spatially periodic modulation of the helix axis in the plane parallel to the cell substrates. Coupling of a weak signal beam with a strong pump beam at the LC permittivity grating, induced by the periodically tilted helix axis, leads to the energy gain of the weak signal beam. Dependence of the signal beam gain coefficient on the parameters of the short-pitch cholesteric LC is studied.

Magnetic anisotropies and magnetic switching in Co films

NASA Astrophysics Data System (ADS)

Bland, J. A. C.; Baird, M. J.; Leung, H. T.; Ives, A. J. R.; Mackay, K. D.; Hughes, H. P.

1992-07-01

We have used the magneto-optical Kerr effect to investigate the role of the substrate and growth conditions in determining the magnetic switching behaviour of Co films in the thickness range 100-200 Å supported by GaAs(001) and Si(111) substrates. We discuss the anisotropic magnetic hysteresis behaviour observed for Co/GaAs and Co/Si films in terms of coherent rotation of the magnetisation vector during magnetic switching. Equivalent films supported by glass substrates are found to be almost isotropic in-plane. The in-plane coercive and saturation fields are observed to lie in the range 20-80 Oe but perpendicular saturation fields of 25 and 19 kOe are found for the Co/Si and Co/GaAs systems respectively which substantially exceed the demagnetising field in each case. The measured perpendicular anisotropy fields differ strongly from the values for hcp and bcc Co and are attributed to the details of the interface and film structure. We also report strongly frequency dependent magnetic switching behaviour in these Co films.

Purification and characterization of a strong fibrinolytic enzyme (nattokinase) in the vegetable cheese natto, a popular soybean fermented food in Japan.

PubMed

Fujita, M; Nomura, K; Hong, K; Ito, Y; Asada, A; Nishimuro, S

1993-12-30

A strong fibrinolytic enzyme (nattokinase) was purified from the vegetable cheese natto. Nattokinase was extracted from natto with saline and isolated by sequential use of hydrophobic chromatography on Butyl-Toyopearl, ion-exchange chromatography on CM-Toyopearl, and gel-filtration on Sephadex G-50. The isolated protein gave a single sharp band on SDS-PAGE either before or after reduction. The sequence, as determined by automated Edman degradation of the uncleaved molecule and its enzymatically derived peptide, consisted of a total 275 amino acid residues (M.W = 27,728) and exhibited a high homology with the subtilisins. The purified nattokinase digested not only fibrin but also several synthetic substrates. Among the synthetic substrates, the most sensitive substrate was Suc-Ala-Ala-Pro-Phe-pNA for subtilisin. PMSF inhibited both the fibrinolytic activity and the amidolytic activity. The results indicate that nattokinase is a subtilisin-like serine protease.

Alloyed surfaces: New substrates for graphene growth

NASA Astrophysics Data System (ADS)

Tresca, C.; Verbitskiy, N. I.; Fedorov, A.; Grüneis, A.; Profeta, G.

2017-11-01

We report a systematic ab-initio density functional theory investigation of Ni(111) surface alloyed with elements of group IV (Si, Ge and Sn), demonstrating the possibility to use it to grow high quality graphene. Ni(111) surface represents an ideal substrate for graphene, due to its catalytic properties and perfect matching with the graphene lattice constant. However, Dirac bands of graphene growth on Ni(111) are completely destroyed due to the strong hybridization between carbon pz and Ni d orbitals. Group IV atoms, namely Si, Ge and Sn, once deposited on Ni(111) surface, form an ordered alloyed surface with √{ 3} ×√{ 3} -R30° reconstruction. We demonstrate that, at variance with the pure Ni(111) surface, alloyed surfaces effectively decouple graphene from the substrate, resulting unstrained due to the nearly perfect lattice matching and preserves linear Dirac bands without the strong hybridization with Ni d states. The proposed surfaces can be prepared before graphene growth without resorting on post-growth processes which necessarily alter the electronic and structural properties of graphene.

Fungal Diversity Is Not Determined by Mineral and Chemical Differences in Serpentine Substrates

PubMed Central

Daghino, Stefania; Murat, Claude; Sizzano, Elisa; Girlanda, Mariangela; Perotto, Silvia

2012-01-01

The physico-chemical properties of serpentine soils lead to strong selection of plant species. Whereas many studies have described the serpentine flora, little information is available on the fungal communities dwelling in these sites. Asbestos minerals, often associated with serpentine rocks, can be weathered by serpentine-isolated fungi, suggesting an adaptation to this substrate. In this study, we have investigated whether serpentine substrates characterized by the presence of rocks with distinct mineral composition could select for different fungal communities. Both fungal isolation and 454 pyrosequencing of amplicons obtained from serpentine samples following direct DNA extraction revealed some fungal taxa shared by the four ophiolitic substrates, but also highlighted several substrate-specific taxa. Bootstrap analysis of 454 OTU abundances indicated weak clustering of fungal assemblages from the different substrates, which did not match substrate classification based on exchangeable macronutrients and metals. Intra-substrate variability, as assessed by DGGE profiles, was similar across the four serpentine substrates, and comparable to inter-substrate variability. These findings indicate the absence of a correlation between the substrate (mineral composition and available cations) and the diversity of the fungal community. Comparison of culture-based and culture-independent methods supports the higher taxonomic precision of the former, as complementation of the better performance of the latter. PMID:23028507

Superstrong encapsulated monolayer graphene by the modified anodic bonding

NASA Astrophysics Data System (ADS)

Jung, Wonsuk; Yoon, Taeshik; Choi, Jongho; Kim, Soohyun; Kim, Yong Hyup; Kim, Taek-Soo; Han, Chang-Soo

2013-12-01

We report a superstrong adhesive of monolayer graphene by modified anodic bonding. In this bonding, graphene plays the role of a superstrong and ultra-thin adhesive between SiO2 and glass substrates. As a result, monolayer graphene presented a strong adhesion energy of 1.4 J m-2 about 310% that of van der Waals bonding (0.45 J m-2) to SiO2 and glass substrates. This flexible solid state graphene adhesive can tremendously decrease the adhesive thickness from about several tens of μm to 0.34 nm for epoxy or glue at the desired bonding area. As plausible causes of this superstrong adhesion, we suggest conformal contact with the rough surface of substrates and generation of C-O chemical bonding between graphene and the substrate due to the bonding process, and characterized these properties using optical microscopy, atomic force microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy.We report a superstrong adhesive of monolayer graphene by modified anodic bonding. In this bonding, graphene plays the role of a superstrong and ultra-thin adhesive between SiO2 and glass substrates. As a result, monolayer graphene presented a strong adhesion energy of 1.4 J m-2 about 310% that of van der Waals bonding (0.45 J m-2) to SiO2 and glass substrates. This flexible solid state graphene adhesive can tremendously decrease the adhesive thickness from about several tens of μm to 0.34 nm for epoxy or glue at the desired bonding area. As plausible causes of this superstrong adhesion, we suggest conformal contact with the rough surface of substrates and generation of C-O chemical bonding between graphene and the substrate due to the bonding process, and characterized these properties using optical microscopy, atomic force microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03822j

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohammad, Sabah M., E-mail: Sabahaskari14@gmail.com; Ahmed, Naser M.; Abd-Alghafour, Nabeel M.

Vertically, well-aligned and high density ZnO nanorods were successfully hydrothermally grown on glass and silicon substrates using a simple and low cost system. The mechanism of synthesis of ZnO nanorods, generated with our system under hydrothermal conditions, is investigated in this report. Field-emission scanning electron microscopy indicated that the fabricated ZnO nanorods on both substrates have hexagonal shape with diameters ranging from 20 nm to 70 nm which grew vertically from the substrate. XRD analysis confirms the formation of wurtzite ZnO phase with a preferred orientation along (002) direction perpendicular on the substrate and enhanced crystallinity. The low value ofmore » the tensile strain (0.126 %) revealed that ZnO nanorods preferred to grow along the c-axis for both substrates. Photoluminescence spectra exhibited a strong, sharp UV near band edge emission peak with narrow FWHM values for both samples.« less

Characteristics of Ge-Sb-Te films prepared by cyclic pulsed plasma-enhanced chemical vapor deposition.

PubMed

Suk, Kyung-Suk; Jung, Ha-Na; Woo, Hee-Gweon; Park, Don-Hee; Kim, Do-Heyoung

2010-05-01

Ge-Sb-Te (GST) thin films were deposited on TiN, SiO2, and Si substrates by cyclic-pulsed plasma-enhanced chemical vapor deposition (PECVD) using Ge{N(CH3)(C2H5)}, Sb(C3H7)3, Te(C3H7)3 as precursors in a vertical flow reactor. Plasma activated H2 was used as the reducing agent. The growth behavior was strongly dependent on the type of substrate. GST grew as a continuous film on TiN regardless of the substrate temperature. However, GST formed only small crystalline aggregates on Si and SiO2 substrates, not a continuous film, at substrate temperatures > or = 200 degrees C. The effects of the deposition temperature on the surface morphology, roughness, resistivity, crystallinity, and composition of the GST films were examined.

Detection of volatile organic compounds by surface enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Chang, Allan S. P.; Maiti, Amitesh; Ileri, Nazar; Bora, Mihail; Larson, Cindy C.; Britten, Jerald A.; Bond, Tiziana C.

2012-06-01

We present the detection of volatile organic compounds directly in their vapor phase by surface-enhanced Raman scattering (SERS) substrates based on lithographically-defined two-dimensional rectangular array of nanopillars. The type of nanopillars is known as the tapered pillars. For the tapered pillars, SERS enhancement arises from the nanofocusing effect due to the sharp tip on top. SERS experiments were carried out on these substrates using various concentrations of toluene vapor. The results show that SERS signal from a toluene vapor is strongly influenced by the substrate temperature, and the toluene vapor can be detected within minutes of exposing the SERS substrate to the vapor. A simple adsorption model is developed which gives results matching the experimental data. The results also show promising potential for the use of these substrates in environmental monitoring of gases and vapors.

Regulation of tomato fruit ascorbate content is more highly dependent on fruit irradiance than leaf irradiance.

PubMed

Gautier, Hélène; Massot, Capucine; Stevens, Rebecca; Sérino, Sylvie; Génard, Michel

2009-02-01

The mechanisms involving light control of vitamin C content in fruits are not yet fully understood. The present study aimed to evaluate the impact of fruit and leaf shading on ascorbate (AsA) accumulation in tomato fruit and to determine how fruit sugar content (as an AsA precursor) affected AsA content. Cherry tomato plants were grown in a glasshouse. The control treatment (normally irradiated fruits and irradiated leaves) was compared with the whole-plant shading treatment and with leaf or fruit shading treatments in fruits harvested at breaker stage. In a second experiment, the correlation between sugars and AsA was studied during ripening. Fruit shading was the most effective treatment in reducing fruit AsA content. Under normal conditions, AsA and sugar content were correlated and increased with the ripening stage. Reducing fruit irradiance strongly decreased the reduced AsA content (-74 %), without affecting sugars, so that sugar and reduced AsA were no longer correlated. Leaf shading delayed fruit ripening: it increased the accumulation of oxidized AsA in green fruits (+98 %), whereas it decreased the reduced AsA content in orange fruits (-19 %), suggesting that fruit AsA metabolism also depends on leaf irradiance. Under fruit shading only, the absence of a correlation between sugars and reduced AsA content indicated that fruit AsA content was not limited by leaf photosynthesis or sugar substrate, but strongly depended on fruit irradiance. Leaf shading most probably affected fruit AsA content by delaying fruit ripening, and suggested a complex regulation of AsA metabolism which depends on both fruit and leaf irradiance and fruit ripening stage.

Regulation of tomato fruit ascorbate content is more highly dependent on fruit irradiance than leaf irradiance

PubMed Central

Gautier, Hélène; Massot, Capucine; Stevens, Rebecca; Sérino, Sylvie; Génard, Michel

2009-01-01

Background and Aims The mechanisms involving light control of vitamin C content in fruits are not yet fully understood. The present study aimed to evaluate the impact of fruit and leaf shading on ascorbate (AsA) accumulation in tomato fruit and to determine how fruit sugar content (as an AsA precursor) affected AsA content. Methods Cherry tomato plants were grown in a glasshouse. The control treatment (normally irradiated fruits and irradiated leaves) was compared with the whole-plant shading treatment and with leaf or fruit shading treatments in fruits harvested at breaker stage. In a second experiment, the correlation between sugars and AsA was studied during ripening. Key Results Fruit shading was the most effective treatment in reducing fruit AsA content. Under normal conditions, AsA and sugar content were correlated and increased with the ripening stage. Reducing fruit irradiance strongly decreased the reduced AsA content (−74 %), without affecting sugars, so that sugar and reduced AsA were no longer correlated. Leaf shading delayed fruit ripening: it increased the accumulation of oxidized AsA in green fruits (+98 %), whereas it decreased the reduced AsA content in orange fruits (−19 %), suggesting that fruit AsA metabolism also depends on leaf irradiance. Conclusions Under fruit shading only, the absence of a correlation between sugars and reduced AsA content indicated that fruit AsA content was not limited by leaf photosynthesis or sugar substrate, but strongly depended on fruit irradiance. Leaf shading most probably affected fruit AsA content by delaying fruit ripening, and suggested a complex regulation of AsA metabolism which depends on both fruit and leaf irradiance and fruit ripening stage. PMID:19033285

Pressure-Sensitive Paint: Effect of Substrate

PubMed Central

Quinn, Mark Kenneth; Yang, Leichao; Kontis, Konstantinos

2011-01-01

There are numerous ways in which pressure-sensitive paint can be applied to a surface. The choice of substrate and application method can greatly affect the results obtained. The current study examines the different methods of applying pressure-sensitive paint to a surface. One polymer-based and two porous substrates (anodized aluminum and thin-layer chromatography plates) are investigated and compared for luminescent output, pressure sensitivity, temperature sensitivity and photodegradation. Two luminophores [tris-Bathophenanthroline Ruthenium(II) Perchlorate and Platinum-tetrakis (pentafluorophenyl) Porphyrin] will also be compared in all three of the substrates. The results show the applicability of the different substrates and luminophores to different testing environments. PMID:22247685

Water and glucose gradients in the substrate measured with NMR imaging during solid-state fermentation with Aspergillus oryzae.

PubMed

Nagel, Frank-Jan; Van As, Henk; Tramper, Johannes; Rinzema, Arjen

2002-09-20

Gradients inside substrate particles cannot be prevented in solid-state fermentation. These gradients can have a strong effect on the physiology of the microorganisms but have hitherto received little attention in experimental studies. We report gradients in moisture and glucose content during cultivation of Aspergillus oryzae on membrane-covered wheat-dough slices that were calculated from (1)H-NMR images. We found that moisture gradients in the solid substrate remain small when evaporation is minimized. This is corroborated by predictions of a diffusion model. In contrast, strong glucose gradients developed. Glucose concentrations just below the fungal mat remained low due to high glucose uptake rates, but deeper in the matrix glucose accumulated to very high levels. Integration of the glucose profile gave an average concentration close to the measured average content. On the basis of published data, we expect that the glucose levels in the matrix cause a strong decrease in water activity. The results demonstrate that NMR can play an important role in quantitative analysis of water and glucose gradients at the particle level during solid-state fermentation, which is needed to improve our understanding of the response of fungi to this nonconventional fermentation environment. Copyright 2002 Wiley Periodicals, Inc.

Heme Structural Perturbation of PEG-Modified Horseradish Peroxidase C in Aromatic Organic Solvents Probed by Optical Absorption and Resonance Raman Dispersion Spectroscopy

PubMed Central

Huang, Qing; Al-Azzam, Wasfi; Griebenow, Kai; Schweitzer-Stenner, Reinhard

2003-01-01

The heme structure perturbation of poly(ethylene glycol)-modified horseradish peroxidase (HRP-PEG) dissolved in benzene and toluene has been probed by resonance Raman dispersion spectroscopy. Analysis of the depolarization ratio dispersion of several Raman bands revealed an increase of rhombic B1g distortion with respect to native HRP in water. This finding strongly supports the notion that a solvent molecule has moved into the heme pocket where it stays in close proximity to one of the heme's pyrrole rings. The interactions between the solvent molecule, the heme, and the heme cavity slightly stabilize the hexacoordinate high spin state without eliminating the pentacoordinate quantum mixed spin state that is dominant in the resting enzyme. On the contrary, the model substrate benzohydroxamic acid strongly favors the hexacoordinate quantum mixed spin state and induces a B2g-type distortion owing to its position close to one of the heme methine bridges. These results strongly suggest that substrate binding must have an influence on the heme geometry of HRP and that the heme structure of the enzyme-substrate complex (as opposed to the resting state) must be the key to understanding the chemical reactivity of HRP. PMID:12719258

The determination of substrate conditions from the orientations of solitary rugose corals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolton, J.C.; Driese, S.G.

1990-10-01

The substrate conditions of mudstone strata formed in ancient epicontinental settings may be determined from taphonomic assemblages of solitary rugose corals. Equal-area plots on the orientations of preserved corals can be used to infer whether subsequent hydrodynamic conditions affected any post-mortem reworking of the corals. Mechanically stable positions for curved corals can be determined. Curved corals preserved in mechanically stable positions are interpreted to have been deposited on firm or hard substrates. Curved corals preserved in mechanically unstable positions were probably embedded in soft or soupy substrates.

Effect of thermal annealing on the redistribution of alkali metals in Cu(In,Ga)Se 2 solar cells on glass substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamikawa, Yukiko; Nishinaga, Jiro; Ishizuka, Shogo

The precise control of alkali-metal concentrations in Cu(In,Ga)Se 2 (CIGS) solar cells via post deposition treatment (PDT) has recently attracted attention. When PDT is performed at an elevated temperature, an accompanying annealing effect is expected. Here, we investigate how thermal annealing affects the redistribution of alkali metals in CIGS solar cells on glass substrates and the properties of the solar cells. In addition, we investigate the origin of non-homogeneous alkali-metal depth profiles that are typical of CIGS grown using a three-stage process. In particular, we use secondary-ion mass spectrometry measurements of the ion concentration as a function of distance frommore » the CIGS surface to investigate the impact of thermal annealing on the distribution of alkali metals (Na, Ka, and Rb) and constituent elements (Ga and In) in the CIGS absorbers. We find that the depth profiles of the alkali metals strongly reflect the density of sites that tend to accommodate alkali metals, i.e., vacancies. Annealing at elevated temperature caused a redistribution of the alkali metals. The thermal-diffusion kinetics of alkali metals depends strongly on the species involved. We introduced low flux potassium fluoride (KF) to study a side effect of KF-PDT, i.e., Na removal from CIGS, separately from its predominant effects such as surface modification. When sufficient amounts of Na are supplied from the soda lime glass via annealing at an elevated temperature, the negative effect was not apparent. Conversely, when the Na supply was not sufficient, it caused a deterioration of the photovoltaic properties.« less

Effect of thermal annealing on the redistribution of alkali metals in Cu(In,Ga)Se 2 solar cells on glass substrate

DOE PAGES

Kamikawa, Yukiko; Nishinaga, Jiro; Ishizuka, Shogo; ...

2018-03-07

The precise control of alkali-metal concentrations in Cu(In,Ga)Se 2 (CIGS) solar cells via post deposition treatment (PDT) has recently attracted attention. When PDT is performed at an elevated temperature, an accompanying annealing effect is expected. Here, we investigate how thermal annealing affects the redistribution of alkali metals in CIGS solar cells on glass substrates and the properties of the solar cells. In addition, we investigate the origin of non-homogeneous alkali-metal depth profiles that are typical of CIGS grown using a three-stage process. In particular, we use secondary-ion mass spectrometry measurements of the ion concentration as a function of distance frommore » the CIGS surface to investigate the impact of thermal annealing on the distribution of alkali metals (Na, Ka, and Rb) and constituent elements (Ga and In) in the CIGS absorbers. We find that the depth profiles of the alkali metals strongly reflect the density of sites that tend to accommodate alkali metals, i.e., vacancies. Annealing at elevated temperature caused a redistribution of the alkali metals. The thermal-diffusion kinetics of alkali metals depends strongly on the species involved. We introduced low flux potassium fluoride (KF) to study a side effect of KF-PDT, i.e., Na removal from CIGS, separately from its predominant effects such as surface modification. When sufficient amounts of Na are supplied from the soda lime glass via annealing at an elevated temperature, the negative effect was not apparent. Conversely, when the Na supply was not sufficient, it caused a deterioration of the photovoltaic properties.« less

Seasonal Regulation of Repair Evaluation, Maintenance, and Rehabilitation (REMR) Activities. Repair, Evaluation, Maintenance, and Rehabilitation Research Program

DTIC Science & Technology

1988-08-01

availability and bioaccumulation of heavy metals, petroleum hydrocarbons , synthetic organic compounds, and radionuclides in sediments. Specific...toxins, petroleum pollution, noise, removal of colonized hard substrate, and ~~addition of new hard substrate. Using this information, in addition to...the disturbance. 16. Sedimentation and/or removal of substrate in areas adjacent to structures may affect benthic resources such as mollusc beds

Patterning N-type and S-type neuroblastoma cells with Pluronic F108 and ECM proteins.

PubMed

Corey, Joseph M; Gertz, Caitlyn C; Sutton, Thomas J; Chen, Qiaoran; Mycek, Katherine B; Wang, Bor-Shuen; Martin, Abbey A; Johnson, Sara L; Feldman, Eva L

2010-05-01

Influencing cell shape using micropatterned substrates affects cell behaviors, such as proliferation and apoptosis. Cell shape may also affect these behaviors in human neuroblastoma (NBL) cancer, but to date, no substrate design has effectively patterned multiple clinically important human NBL lines. In this study, we investigated whether Pluronic F108 was an effective antiadhesive coating for human NBL cells and whether it would localize three NBL lines to adhesive regions of tissue culture plastic or collagen I on substrate patterns. The adhesion and patterning of an S-type line, SH-EP, and two N-type lines, SH-SY5Y and IMR-32, were tested. In adhesion assays, F108 deterred NBL adhesion equally as well as two antiadhesive organofunctional silanes and far better than bovine serum albumin. Patterned stripes of F108 restricted all three human NBL lines to adhesive stripes of tissue culture plastic. We then investigated four schemes of applying collagen and F108 to different regions of a substrate. Contact with collagen obliterates the ability of F108 to deter NBL adhesion, limiting how both materials can be applied to substrates to produce high fidelity NBL patterning. This patterned substrate design should facilitate investigations of the role of cell shape in NBL cell behavior. Copyright 2009 Wiley Periodicals, Inc.

Patterning N-type and S-type Neuroblastoma Cells with Pluronic F108 and ECM Proteins

PubMed Central

Corey, Joseph M.; Gertz, Caitlyn C.; Sutton, Thomas J.; Chen, Qiaoran; Mycek, Katherine B.; Wang, Bor-Shuen; Martin, Abbey A.; Johnson, Sara L.; Feldman, Eva L.

2009-01-01

Influencing cell shape using micropatterned substrates affects cell behaviors, such as proliferation and apoptosis. Cell shape may also affect these behaviors in human neuroblastoma (NBL) cancer, but to date, no substrate design has effectively patterned multiple clinically important human NBL lines. In this study, we investigated whether Pluronic F108 was an effective anti-adhesive coating for human NBL cells and whether it would localize three NBL lines to adhesive regions of tissue culture plastic or collagen I on substrate patterns. The adhesion and patterning of an S-type line, SH-EP, and two N-type lines, SH-SY5Y and IMR-32, were tested. In adhesion assays, F108 deterred NBL adhesion equally as well as two anti-adhesive organofunctional silanes and far better than bovine serum albumin. Patterned stripes of F108 restricted all three human NBL lines to adhesive stripes of tissue culture plastic. We then investigated four schemes of applying collagen and F108 to different regions of a substrate. Contact with collagen obliterates the ability of F108 to deter NBL adhesion, limiting how both materials can be applied to substrates to produce high fidelity NBL patterning. This patterned substrate design should facilitate investigations of the role of cell shape in NBL cell behavior. PMID:19609877

Swelling and Contraction of Corn Mitochondria 1

PubMed Central

Stoner, C. D.; Hanson, J. B.

1966-01-01

A survey has been made of the properties of corn mitochondria in swelling and contraction. The mitochondria swell spontaneously in KCl but not in sucrose. Aged mitochondria will swell rapidly in sucrose if treated with citrate or EDTA. Swelling does not impair oxidative phosphorylation if bovine serum albumin is present. Contraction can be maintained or initiated with ATP + Mg or an oxidizable substrate, contraction being more rapid with the substrate. Magnesium is not required for substrate powered contraction. Contraction powered by ATP is accompanied by the release of phosphate. Oligomycin inhibits both ATP-powered contraction and the release of phosphate. However, it does not affect substrate-powered contraction. Substrate powered contraction is inhibited by electron-transport inhibitors. The uncoupler, carbonyl cyanide m-chlorophenyl hydrazone, accelerates swelling and inhibits both ATP-and substrate-powered contraction. However, the concentrations required are well in excess of those required to produce uncoupling and to accelerate adenosine triphosphatase; the concentrations required inhibit respiration in a phosphorylating medium. Phosphate is a very effective inhibitor of succinate-powered contraction. Neither oligomycin nor Mg affects the phosphate inhibition. Phosphate is less inhibitory with the ATP-powered contraction. The results are discussed in terms of a hypothesis that contraction is associated with a nonphosphorylated high energy intermediate of oxidative phosphorylation. Images PMID:16656248

Substrate degradation by the proteasome: a single-molecule kinetic analysis

PubMed Central

Lu, Ying; Lee, Byung-hoon; King, Randall W; Finley, Daniel; Kirschner, Marc W

2015-01-01

To address how the configuration of conjugated ubiquitins determines the recognition of substrates by the proteasome, we analyzed the degradation kinetics of substrates with chemically defined ubiquitin configurations. Contrary to the view that a tetraubiquitin chain is the minimal signal for efficient degradation, we find that distributing the ubiquitins as diubiquitin chains provides a more efficient signal. To understand how the proteasome actually discriminates among ubiquitin configurations, we developed single-molecule assays that distinguished intermediate steps of degradation kinetically. The level of ubiquitin on a substrate drives proteasome-substrate interaction, whereas the chain structure of ubiquitin affects translocation into the axial channel on the proteasome. Together these two features largely determine the susceptibility of substrates for proteasomal degradation. PMID:25859050

Vibrational Studies of Adsorbate-Induced Reconstruction on Molybdenum Surfaces.

NASA Astrophysics Data System (ADS)

Lopinski, Gregory Peter

Adsorbate-induced rearrangement of the substrate structure strongly modifies the adsorbate-substrate and adsorbate-adsorbate interactions, leading to the complex behavior observed in many chemisorption systems. In this thesis the H/Mo(211), O/Mo(211) and Na/Mo(100) systems have been studied using high resolution electron energy loss spectroscopy (HREELS) to observe vibrations of the adsorbed atoms. The vibrational data is correlated with observations of the long-range order probed by LEED as well as the work function changes induced by adsorption. Adsorbate -induced substrate reconstruction plays an important role in all three of these systems. Studies of the coadsorption systems O+H/Mo(211) and Na+O/Mo(100) indicate how these effects can influence interactions between adsorbates. For H/Mo(211), above 1ML a (1 x 1) to (1 x 2) transition is observed and attributed to modification of the substrate periodicity. Below 1ML, H atoms are bridge bonded and induce local distortions of the substrate. The transition to the (1 x 2) phase involves the ordering of these displacements and occupation of three-fold sites partially populated by conversion of the bridge bonded species. This conversion accounts for the sawtooth-like coverage dependence of the work function. The structural model proposed for this system is also supported by the desorption parameters and partial molar entropy extracted from adsorption isobars. Oxygen adsorption on Mo(211) involves the occupation of multiple binding sites, with both the long-range order and the local geometry of the adsorbate phases strongly temperature dependent. Coadsorption of low coverages of oxygen and hydrogen leads to segregation of the two adsorbates which can be understood in terms of a substrate-mediated repulsive interaction between O and H. For Na/Mo(100), the frequency of the Na-Mo symmetric stretch mode does not shift with coverage although the mode intensity is strongly coverage dependent. The absence of a frequency shift as well as the form of the observed coverage dependence differ from the predictions of the traditional charge transfer model of alkali adsorption. The relevance of the vibrational results to the Na-induced structural changes observed on this surface are also discussed. Na adsorption has been found to dramatically alter the interaction of oxygen with this surface, due to the presence of a strong attractive interaction between Na and O that forces O atoms to occupy a different binding site than on a clean surface.

Atomically precise cluster catalysis towards quantum controlled catalysts

PubMed Central

Watanabe, Yoshihide

2014-01-01

Catalysis of atomically precise clusters supported on a substrate is reviewed in relation to the type of reactions. The catalytic activity of supported clusters has generally been discussed in terms of electronic structure. Several lines of evidence have indicated that the electronic structure of clusters and the geometry of clusters on a support, including the accompanying cluster-support interaction, are strongly correlated with catalytic activity. The electronic states of small clusters would be easily affected by cluster–support interactions. Several studies have suggested that it is possible to tune the electronic structure through atomic control of the cluster size. It is promising to tune not only the number of cluster atoms, but also the hybridization between the electronic states of the adsorbed reactant molecules and clusters in order to realize a quantum-controlled catalyst. PMID:27877723

Cell-substrate impedance fluctuations of single amoeboid cells encode cell-shape and adhesion dynamics

NASA Astrophysics Data System (ADS)

Leonhardt, Helmar; Gerhardt, Matthias; Höppner, Nadine; Krüger, Kirsten; Tarantola, Marco; Beta, Carsten

2016-01-01

We show systematic electrical impedance measurements of single motile cells on microelectrodes. Wild-type cells and mutant strains were studied that differ in their cell-substrate adhesion strength. We recorded the projected cell area by time-lapse microscopy and observed irregular oscillations of the cell shape. These oscillations were correlated with long-term variations in the impedance signal. Superposed to these long-term trends, we observed fluctuations in the impedance signal. Their magnitude clearly correlated with the adhesion strength, suggesting that strongly adherent cells display more dynamic cell-substrate interactions.

Glassy dynamics of dense particle assemblies on a spherical substrate.

PubMed

Vest, Julien-Piera; Tarjus, Gilles; Viot, Pascal

2018-04-28

We study by molecular dynamics simulation a dense one-component system of particles confined on a spherical substrate. We more specifically investigate the evolution of the structural and dynamical properties of the system when changing the control parameters, the temperature and the curvature of the substrate. We find that the dynamics become glassy at low temperature, with a strong slowdown of the relaxation and the emergence of dynamical heterogeneity. The prevalent local 6-fold order is frustrated by curvature and we analyze in detail the role of the topological defects in the statics and the dynamics of the particle assembly.

Modeling the competition between PHA-producing and non-PHA-producing bacteria in feast-famine SBR and staged CSTR systems.

PubMed

Marang, Leonie; van Loosdrecht, Mark C M; Kleerebezem, Robbert

2015-12-01

Although the enrichment of specialized microbial cultures for the production of polyhydroxyalkanoates (PHA) is generally performed in sequencing batch reactors (SBRs), the required feast-famine conditions can also be established using two or more continuous stirred-tank reactors (CSTRs) in series with partial biomass recirculation. The use of CSTRs offers several advantages, but will result in distributed residence times and a less strict separation between feast and famine conditions. The aim of this study was to investigate the impact of the reactor configuration, and various process and biomass-specific parameters, on the enrichment of PHA-producing bacteria. A set of mathematical models was developed to predict the growth of Plasticicumulans acidivorans-as a model PHA producer-in competition with a non-storing heterotroph. A macroscopic model considering lumped biomass and an agent-based model considering individual cells were created to study the effect of residence time distribution and the resulting distributed bacterial states. The simulations showed that in the 2-stage CSTR system the selective pressure for PHA-producing bacteria is significantly lower than in the SBR, and strongly affected by the chosen feast-famine ratio. This is the result of substrate competition based on both the maximum specific substrate uptake rate and substrate affinity. Although the macroscopic model overestimates the selective pressure in the 2-stage CSTR system, it provides a quick and fairly good impression of the reactor performance and the impact of process and biomass-specific parameters. © 2015 Wiley Periodicals, Inc.

Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition

PubMed Central

Jaramillo, Rafael; Steinmann, Vera; Yang, Chuanxi; Hartman, Katy; Chakraborty, Rupak; Poindexter, Jeremy R.; Castillo, Mariela Lizet; Gordon, Roy; Buonassisi, Tonio

2015-01-01

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent thermal evaporation, and it absorbs visible light strongly. However, for a long time the record power conversion efficiency of SnS solar cells remained below 2%. Recently we demonstrated new certified record efficiencies of 4.36% using SnS deposited by atomic layer deposition, and 3.88% using thermal evaporation. Here the fabrication procedure for these record solar cells is described, and the statistical distribution of the fabrication process is reported. The standard deviation of efficiency measured on a single substrate is typically over 0.5%. All steps including substrate selection and cleaning, Mo sputtering for the rear contact (cathode), SnS deposition, annealing, surface passivation, Zn(O,S) buffer layer selection and deposition, transparent conductor (anode) deposition, and metallization are described. On each substrate we fabricate 11 individual devices, each with active area 0.25 cm2. Further, a system for high throughput measurements of current-voltage curves under simulated solar light, and external quantum efficiency measurement with variable light bias is described. With this system we are able to measure full data sets on all 11 devices in an automated manner and in minimal time. These results illustrate the value of studying large sample sets, rather than focusing narrowly on the highest performing devices. Large data sets help us to distinguish and remedy individual loss mechanisms affecting our devices. PMID:26067454

Time Evolution of the Wettability of Supported Graphene under Ambient Air Exposure

PubMed Central

2016-01-01

The wettability of graphene is both fundamental and crucial for interfacing in most applications, but a detailed understanding of its time evolution remains elusive. Here we systematically investigate the wettability of metal-supported, chemical vapor deposited graphene films as a function of ambient air exposure time using water and various other test liquids with widely different surface tensions. The wettability of graphene is not constant, but varies with substrate interactions and air exposure time. The substrate interactions affect the initial graphene wettability, where, for instance, water contact angles of ∼85 and ∼61° were measured for Ni and Cu supported graphene, respectively, after just minutes of air exposure. Analysis of the surface free energy components indicates that the substrate interactions strongly influence the Lewis acid–base component of supported graphene, which is considerably weaker for Ni supported graphene than for Cu supported graphene, suggesting that the classical van der Waals interaction theory alone is insufficient to describe the wettability of graphene. For prolonged air exposure, the effect of physisorption of airborne contaminants becomes increasingly dominant, resulting in an increase of water contact angle that follows a universal linear-logarithmic relationship with exposure time, until saturating at a maximum value of 92–98°. The adsorbed contaminants render all supported graphene samples increasingly nonpolar, although their total surface free energy decreases only by 10–16% to about 37–41 mJ/m2. Our finding shows that failure to account for the air exposure time may lead to widely different wettability values and contradicting arguments about the wetting transparency of graphene. PMID:26900413

Rethinking chemisorption: New insights into the factors controlling the binding energy

NASA Astrophysics Data System (ADS)

Alcantara Ortigoza, Marisol; Stolbov, Sergey

2015-03-01

Chemisorption of atomic and molecular species on a substrate induces electronic charge redistribution upon which substrate nuclei respond by adjusting their positions. This lattice distortion has been linked to the binding energy EB of the adsorbed species and attached to the so-called surface relaxation energy, Erx. We have found, however, that for transition metals the energy associated with the mere charge redistribution Eelec is much larger than Erx and thus both contributions must be considered [1]. In this work, we quantify the electronic and structural perturbation energy EP brought by various adsorbates on surfaces to understand anomalous adsorbate binding energies, i.e., those in which EP strongly influences the magnitude of EB. For example, for O adsorption on Au(111), while Erx is only 0.25 eV, the overall perturbation energy EP affecting EB(O) is ~ 1 eV [1]. This indicates that EP cannot be ignored but also that local bonds may not be as weak as portrayed by EB, even though EB is significantly reduced. We expose cases in which EP is really dominated by the lattice distortion energy, as well as a rationale for its trends as a function of the substrate and adsorbate. We discuss the implications of the fact that EB is not always predominately controlled by the bond-strength on heterogeneous catalysis, as well as the applications of the same fact. M. Alcántara Ortigoza and S. Stolbov; ``The Perturbation Energy: The missing key to understand gold `nobleness.' '' Submitted in October 2014 This work was supported the NSF under Grant CBET-1249134.

Anomalous x-ray diffraction on InAs/GaAs quantum dot systems

NASA Astrophysics Data System (ADS)

Schulli, T. U.; Sztucki, M.; Chamard, V.; Metzger, T. H.; Schuh, D.

2002-07-01

Free-standing InAs quantum dots on a GaAs (001) substrate have been investigated using grazing incidence x-ray diffraction. To suppress the strong scattering contribution from the GaAs substrate, we performed anomalous diffraction experiments at the superstructure (200) reflection, showing that the relative intensities from the dots and the substrate undergo a significant change with the x-ray energy below and above the As K edge. Since the signal from the substrate material can essentially be suppressed, this method is ideally suited for the investigation of strain, shape, and interdiffusion of buried quantum dots and quantum dots embedded in heteroepitaxial multilayers. In addition, we show that it can be used as a tool for studying wetting layers.

Molecular beam epitaxy of graphene on ultra-smooth nickel: growth mode and substrate interactions

NASA Astrophysics Data System (ADS)

Wofford, J. M.; Oliveira, M. H., Jr.; Schumann, T.; Jenichen, B.; Ramsteiner, M.; Jahn, U.; Fölsch, S.; Lopes, J. M. J.; Riechert, H.

2014-09-01

Graphene is grown by molecular beam epitaxy using epitaxial Ni films on MgO(111) as substrates. Raman spectroscopy and scanning tunneling microscopy reveal the graphene films to have few crystalline defects. While the layers are ultra-smooth over large areas, we find that Ni surface features lead to local non-uniformly thick graphene inclusions. The influence of the Ni surface structure on the position and morphology of these inclusions strongly suggests that multilayer graphene on Ni forms at the interface of the first complete layer and metal substrate in a growth-from-below mechanism. The interplay between Ni surface features and graphene growth behavior may facilitate the production of films with spatially resolved multilayer inclusions through engineered substrate surface morphology.

Interfacial and thermal energy driven growth and evolution of Langmuir-Schaefer monolayers of Au-nanoparticles.

PubMed

Mukhopadhyay, Mala; Hazra, S

2018-01-03

Structures of Langmuir-Schaefer (LS) monolayers of thiol-coated Au-nanoparticles (DT-AuNPs) deposited on H-terminated and OTS self-assembled Si substrates (of different hydrophobic strength and stability) and their evolution with time under ambient conditions, which plays an important role for their practical use as 2D-nanostructures over large areas, were investigated using the X-ray reflectivity technique. The strong effect of substrate surface energy (γ) on the initial structures and the competitive role of room temperature thermal energy (kT) and the change in interfacial energy (Δγ) at ambient conditions on the evolution and final structures of the DT-AuNP LS monolayers are evident. The strong-hydrophobic OTS-Si substrate, during transfer, seems to induce strong attraction towards hydrophobic DT-AuNPs on hydrophilic (repulsive) water to form vertically compact partially covered (with voids) monolayer structures (of perfect monolayer thickness) at low pressure and nearly covered buckled monolayer structures (of enhanced monolayer thickness) at high pressure. After transfer, the small kT-energy (in absence of repulsive water) probably fluctuates the DT-AuNPs to form vertically expanded monolayer structures, through systematic exponential growth with time. The effect is prominent for the film deposited at low pressure, where the initial film-coverage and film-thickness are low. On the other hand, the weak-hydrophobic H-Si substrate, during transfer, appears to induce optimum attraction towards DT-AuNPs to better mimic the Langmuir monolayer structures on it. After transfer, the change in the substrate surface nature, from weak-hydrophobic to weak-hydrophilic with time (i.e. Δγ-energy, apart from the kT-energy), enhances the size of the voids and weakens the monolayer/bilayer structure to form a similar expanded monolayer structure, the thickness of which is probably optimized by the available thermal energy.

Effect of Moisture Exchange on Interface Formation in the Repair System Studied by X-ray Absorption

PubMed Central

Lukovic, Mladena; Ye, Guang

2015-01-01

In concrete repair systems, material properties of the repair material and the interface are greatly influenced by the moisture exchange between the repair material and the substrate. If the substrate is dry, it can absorb water from the repair material and reduce its effective water-to-cement ratio (w/c). This further affects the hydration rate of cement based material. In addition to the change in hydration rate, void content at the interface between the two materials is also affected. In this research, the influence of moisture exchange on the void content in the repair system as a function of initial saturation level of the substrate is investigated. Repair systems with varying level of substrate saturation are made. Moisture exchange in these repair systems as a function of time is monitored by the X-ray absorption technique. After a specified curing age (3 d), the internal microstructure of the repair systems was captured by micro-computed X-ray tomography (CT-scanning). From reconstructed images, different phases in the repair system (repair material, substrate, voids) can be distinguished. In order to quantify the void content, voids were thresholded and their percentage was calculated. It was found that significantly more voids form when the substrate is dry prior to application of the repair material. Air, initially filling voids and pores of the dry substrate, is being released due to the moisture exchange. As a result, air voids remain entrapped in the repair material close to the interface. These voids are found to form as a continuation of pre-existing surface voids in the substrate. Knowledge about moisture exchange and its effects provides engineers with the basis for recommendations about substrate preconditioning in practice. PMID:28787801

High-level accumulation of oleyl oleate in plant seed oil by abundant supply of oleic acid substrates to efficient wax ester synthesis enzymes.

PubMed

Yu, Dan; Hornung, Ellen; Iven, Tim; Feussner, Ivo

2018-01-01

Biotechnology enables the production of high-valued industrial feedstocks from plant seed oil. The plant-derived wax esters with long-chain monounsaturated acyl moieties, like oleyl oleate, have favorite properties for lubrication. For biosynthesis of wax esters using acyl-CoA substrates, expressions of a fatty acyl reductase (FAR) and a wax synthase (WS) in seeds are sufficient. For optimization of the enzymatic activity and subcellular localization of wax ester synthesis enzymes, two fusion proteins were created, which showed wax ester-forming activities in Saccharomyces cerevisiae . To promote the formation of oleyl oleate in seed oil, WSs from Acinetobactor baylyi ( Ab WSD1) and Marinobacter aquaeolei ( Ma WS2), as well as the two created fusion proteins were tested in Arabidopsis to evaluate their abilities and substrate preference for wax ester production. The tested seven enzyme combinations resulted in different yields and compositions of wax esters. Expression of a FAR of Marinobacter aquaeolei ( Ma FAR) with Ab WSD1 or Ma WS2 led to a high incorporation of C 18 substrates in wax esters. The Ma FAR/TM Mm AWAT2- Ab WSD1 combination resulted in the incorporation of more C 18:1 alcohol and C 18:0 acyl moieties into wax esters compared with Ma FAR/ Ab WSD1. The fusion protein of a WS from Simmondsia chinensis ( Sc WS) with MaFAR exhibited higher specificity toward C 20:1 substrates in preference to C 18:1 substrates. Expression of Ma FAR/ Ab WSD1 in the Arabidopsis fad2 fae1 double mutant resulted in the accumulation of oleyl oleate (18:1/18:1) in up to 62 mol% of total wax esters in seed oil, which was much higher than the 15 mol% reached by Ma FAR/ Ab WSD1 in Arabidopsis Col-0 background. In order to increase the level of oleyl oleate in seed oil of Camelina , lines expressing Ma FAR/ Sc WS were crossed with a transgenic high oleate line. The resulting plants accumulated up to >40 mg g seed -1 of wax esters, containing 27-34 mol% oleyl oleate. The overall yields and the compositions of wax esters can be strongly affected by the availability of acyl-CoA substrates and to a lesser extent, by the characteristics of wax ester synthesis enzymes. For synthesis of oleyl oleate in plant seed oil, appropriate wax ester synthesis enzymes with high catalytic efficiency and desired substrate specificity should be expressed in plant cells; meanwhile, high levels of oleic acid-derived substrates need to be supplied to these enzymes by modifying the fatty acid profile of developing seeds.

Alcohol-to-acid ratio and substrate concentration affect product structure in chain elongation reactions initiated by unacclimatized inoculum.

PubMed

Liu, Yuhao; Lü, Fan; Shao, Liming; He, Pinjing

2016-10-01

The objective of the study was to investigate whether the ratio of ethanol to acetate affects yield and product structure in chain elongation initiated by unacclimatized mixed cultures. The effect of varying the substrate concentration, while maintaining the same ratio of alcohol to acid, was also investigated. With a high substrate concentration, an alcohol to acid ratio >2:1 provided sufficient electron donor capacity for the chain elongation reaction. With an ethanol to acetate ratio of 3:1 (300mM total carbon), the highest n-caproate concentration (3033±98mg/L) was achieved during the stable phase of the reaction. A lower substrate concentration (150mM total carbon) gave a lower yield of products and led to reduced carbon transformation efficiency compared with other reaction conditions. The use of unacclimatized inoculum in chain elongation can produce significant amounts of odd-carbon-number carboxylates as a result of protein hydrolysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of stripping and cooling atmospheres on surface properties and corrosion of zinc galvanizing coatings

NASA Astrophysics Data System (ADS)

Yasakau, K. A.; Giner, I.; Vree, C.; Ozcan, O.; Grothe, R.; Oliveira, A.; Grundmeier, G.; Ferreira, M. G. S.; Zheludkevich, M. L.

2016-12-01

In this work the influence of stripping/cooling atmospheres used after withdrawal of steel sheet from Zn or Zn-alloy melt on surface properties of Zn (Z) and Zn-Al-Mg (ZM) hot-dip galvanizing coatings has been studied. The aim was to understand how the atmosphere (composed by nitrogen (N2) or air) affects adhesion strength to model adhesive and corrosive behaviour of the galvanized substrates. It was shown that the surface chemical composition and Volta potential of the galvanizing coatings prepared under the air or nitrogen atmosphere are strongly influenced by the atmosphere. The surface chemistry Z and ZM surfaces prepared under N2 contained a higher content of metal atoms and a richer hydroxide density than the specimens prepared under air atmosphere as assessed by X-ray photoelectron spectroscopy (XPS). The induced differences on the microstructure of the galvanized coatings played a key role on the local corrosion induced defects as observed by means of in situ Atomic force microscopy (AFM). Peel force tests performed on the substrates coated by model adhesive films indicate a higher adhesive strength to the surfaces prepared under nitrogen atmosphere. The obtained results have been discussed in terms of the microstructure and surface chemical composition of the galvanizing coatings.

Oxidation and reduction under cover: Chemistry at the confined space between ultra-thin nanoporous silicates and Ru(0001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. Anibal Boscoboinik; Zhong, Jian -Qiang; Kestell, John

2016-03-23

The oxidation and reduction of Ru(0001) surfaces at the confined space between two-dimensional nanoporous silica frameworks and Ru(0001) have been investigated using synchrotron-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS). The porous nature of the frameworks and the weak interaction between the silica and the ruthenium substrate allow oxygen and hydrogen molecules to go through the nanopores and react with the metal at the interface between the silica framework and the metal surface. In this work, three types of two-dimensional silica frameworks have been used to study their influence in the oxidation and reduction of the ruthenium surface at elevated pressuresmore » and temperatures. These frameworks are bilayer silica (0.5 nm thick), bilayer aluminosilicate (0.5 nm thick), and zeolite MFI nanosheets (3 nm thick). It is found that the silica frameworks stay essentially intact under these conditions, but they strongly affect the oxidation of ruthenium, with the 0.5 nm thick aluminosilicate bilayer completely inhibiting the oxidation. Furthermore, the latter is believed to be related to the lower chemisorbed oxygen content arising from electrostatic interactions between the negatively charged aluminosilicate framework and the Ru(0001) substrate.« less

Inhibition effect of flavonoids on monocarboxylate transporter 1 (MCT1) in Caco-2 cells.

PubMed

Shim, Chang-Koo; Cheon, Eun-Pa; Kang, Keon Wook; Seo, Ki-Soo; Han, Hyo-Kyung

2007-11-01

This study aimed to investigate the inhibition effect of flavonoids on monocarboxylate transporter 1 (MCT1) in Caco-2 cells. The cellular uptake of benzoic acid was examined in the presence and the absence of naringin, naringenin, morin, silybin and quercetin in Caco-2 cells. All the tested flavonoids except naringin significantly inhibited (P<0.05) the cellular uptake of [(14)C]-benzoic acid. Particularly, naringenin and silybin exhibited strong inhibition effects with IC50 values of 23.4 and 30.2 microM, respectively. Kinetic analysis indicated that the inhibition mode of naringenin and silybin on MCT1 activity was competitive with a Ki of 15-20 microM. The effect of flavonoids on the gene expression of MCT1 was also examined by using RT-PCR and western blot analysis. Results indicated that the expression level of MCT1 was not affected by the treatment with naringenin or silybin. The cellular accumulation of naringenin in Caco-2 cells was not changed in the presence of benzoic acid or L-lactic acid, implying that naringenin might not be a substrate of MCT1. In conclusion, some flavonoids appeared to be competitive inhibitors of MCT1, suggesting the potential for diet-drug interactions between flavonoids and MCT1 substrates.

Conductive scanning probe microscopy of the semicontinuous gold film and its SERS enhancement toward two-step photo-induced charge transfer and effect of the supportive layer

NASA Astrophysics Data System (ADS)

Sinthiptharakoon, K.; Sapcharoenkun, C.; Nuntawong, N.; Duong, B.; Wutikhun, T.; Treetong, A.; Meemuk, B.; Kasamechonchung, P.; Klamchuen, A.

2018-05-01

The semicontinuous gold film, enabling various electronic applications including development of surface-enhanced Raman scattering (SERS) substrate, is investigated using conductive atomic force microscopy (CAFM) and Kelvin probe force microscopy (KPFM) to reveal and investigate local electronic characteristics potentially associated with SERS generation of the film material. Although the gold film fully covers the underlying silicon surface, CAFM results reveal that local conductivity of the film is not continuous with insulating nanoislands appearing throughout the surface due to incomplete film percolation. Our analysis also suggests the two-step photo-induced charge transfer (CT) play the dominant role in the enhancement of SERS intensity with strong contribution from free electrons of the silicon support. Silicon-to-gold charge transport is illustrated by KPFM results showing that Fermi level of the gold film is slightly inhomogeneous and far below the silicon conduction band. We propose that inhomogeneity of the film workfunction affecting chemical charge transfer between gold and Raman probe molecule is associated with the SERS intensity varying across the surface. These findings provide deeper understanding of charge transfer mechanism for SERS which can help in design and development of the semicontinuous gold film-based SERS substrate and other electronic applications.

Phytostabilisation with Mediterranean shrubs and liming improved soil quality in a pot experiment with a pyrite mine soil.

PubMed

Moreno-Jiménez, Eduardo; Esteban, Elvira; Carpena-Ruiz, Ramón O; Lobo, María Carmen; Peñalosa, Jesús M

2012-01-30

Phytoremediation can be a suitable option to manage derelict mine soils. A pot experiment was carried out under semi-controlled conditions with a mine-impacted soil. A further contamination event was mimicked by applying 5% of pyritic sludge. Four species were planted in pots (Myrtus communis, Retama sphaerocarpa, Rosmarinus officinalis and Tamarix gallica), and some pots remained unplanted as a control. The substrates were moderately to highly contaminated, mainly with arsenic and zinc. The strong acidification induced by the pyritic sludge was buffered with lime and plants survived in all the pots. Liming provoked an effective immobilisation of metals and arsenic. Plant establishment decreased labile As in the substrate by 50%, mainly M. communis, although the levels of extractable metals were not affected by the plants. R. sphaerocarpa and M. communis increased the levels of C and N in the soil by 23% and 34% respectively, and also enhanced enzymatic activities and microbial respiration to the double in some cases. The low transfer of trace elements to shoots limited the phytoextraction rate. Our results support the use of phytostabilisation in Mediterranean mine soils and show how plants of R. sphaerocarpa and M. communis may increase soil health and quality during revegetation. Copyright © 2011 Elsevier B.V. All rights reserved.

Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature.

PubMed

Hang, Da-Ren; Islam, Sk Emdadul; Sharma, Krishna Hari; Kuo, Shiao-Wei; Zhang, Cheng-Zu; Wang, Jun-Jie

2014-01-01

Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications.

The peptide transporter PepT2 mediates the uptake of the glutathione precursor CysGly in astroglia-rich primary cultures.

PubMed

Dringen, R; Hamprecht, B; Bröer, S

1998-07-01

The intracellular content of glutathione in astroglia-rich primary cultures derived from the brains of newborn rats was used as an indicator for the ability of these cultures to utilize cysteinylglycine (CysGly) for glutathione synthesis. After a 24-h starvation period in the absence of glucose and amino acids, CysGly was able to substitute for cysteine plus glycine in the restoration of glutathione. Glutathione restoration from CysGly plus glutamate was only slightly affected by the dipeptides carnosine or serylglycine in a 200-fold excess. Captopril, a substrate of the peptide transporter PepT1, had almost no effect on glutathione restoration. In contrast, with increasing concentrations of alanylalanine or cefadroxil, known substrates of the peptide transporter PepT2, the amount of glutathione restored in the presence of CysGly and glutamate was strongly reduced. Cefadroxil in a 200-fold excess totally prevented the utilization of CysGly for glutathione restoration. The presence of mRNA for PepT2 in astroglia-rich primary cultures was demonstrated by application of RT-PCR. These results demonstrate that PepT2 is expressed in astroglia-rich primary cultures and that this transporter is highly likely to be responsible for the uptake of CysGly in these cultures.

Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature

PubMed Central

2014-01-01

Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications. PMID:25520589

Selective hydrogenation of citral over supported Pt catalysts: insight into support effects

NASA Astrophysics Data System (ADS)

Wang, Xiaofeng; Hu, Weiming; Deng, Baolin; Liang, Xinhua

2017-04-01

Highly dispersed platinum (Pt) nanoparticles (NPs) were deposited on various substrates by atomic layer deposition (ALD) in a fluidized bed reactor at 300 °C. The substrates included multi-walled carbon nanotubes (MWCNTs), silica gel (SiO2), commercial γ-Al2O3, and ALD-prepared porous Al2O3 particles (ALD-Al2O3). The results of TEM analysis showed that 1.3 nm Pt NPs were highly dispersed on all different supports. All catalysts were used for the reaction of selective hydrogenation of citral to unsaturated alcohols (UA), geraniol, and nerol. Both the structure and acidity of supports affected the activity and selectivity of Pt catalysts. Pt/SiO2 showed the highest activity due to the strong acidity of SiO2 and the conversion of citral reached 82% after 12 h with a selectivity of 58% of UA. Pt/MWCNTs showed the highest selectivity of UA, which reached 65% with a conversion of 38% due to its unique structure and electronic effect. The cycling experiments indicated that Pt/MWCNTs and Pt/ALD-Al2O3 catalysts were more stable than Pt/SiO2, as a result of the different interactions between the Pt NPs and the supports.

The effect of poly(vinyl alcohol) type and radiation treatment on the properties of starch-poly(vinyl alcohol) films

NASA Astrophysics Data System (ADS)

Cieśla, Krystyna; Abramowska, Anna; Boguski, Jacek; Drewnik, Joanna

2017-12-01

Our present study concerns the effect of application of various PVA substrates and the influence of ionising radiation on the properties of films based on starch and PVA. Four PVAs revealing various molecular masses (in the range of 11-145 kDa) were selected for this purpose. The films characterized by starch: PVA ratios of 40:60 were prepared by solution casting and irradiated with 60Co gamma rays (under nitrogen) and with fast electrons (under air) applying the absorbed dose of 25 kGy. Mechanical properties of the films (tensile strength, elongation at break and Young Modulus) were examined, as well as the contact angle to water and swelling in water, in regard for evaluation of the hydrophilic/hydrophobic properties. Gel content in the samples was also determined. Physicochemical properties of the films and their sensitivity to irradiation strongly depend on the applied PVA substrate. This can be related to differences in the capability of particular PVAs for forming the crosslinked starch-PVA network during the films' synthesis and future treatment. In particular, the usage of the PVA characterized by the high molecular mass has appeared more rewarding as compared to those based on the low molecular mass PVAs. Additionally, properties of these films were not affected or improved after irradiation.

Effects of the PPy layer thickness on Co-PPy composite films

NASA Astrophysics Data System (ADS)

Haciismailoglu, Murside

2015-11-01

Co-PPy composite films were electrodeposited on ITO substrate from two different solutions potentiostatically. Firstly, the PPy layers with the thicknesses changing from 20 to 5000 nm were produced on ITO. Then Co was electrodeposited on these PPy/ITO substrates with a charge density of 1000 mC cm-2. The electrochemical properties were investigated by the current density-time transients and the variation of the elapsed time for the Co deposition depending on the PPy layer thickness. X-ray photoelectron (XPS) spectra indicated the presence of both Co metal and its oxides on the surface. The weak reflections of the Co3O4, CoO and hcp Co were detected by the X-ray diffraction (XRD) technique. According to scanning electron microscopy (SEM) images, the thickness of the PPy layer strongly affects the Co nucleation. The composite films with the PPy layer thinner than 200 nm and thicker than 2000 nm have an isotropic magnetic behavior due to the symmetrical crystal field. The composite films with the PPy layer thicknesses between 200 and 2000 nm have an anisotropic magnetic behavior attributable to the deterioration of this symmetrical crystal field by the PPy bubbles on the surface. All films are hard magnetic material, since the coercivities are larger than 125 Oe.

Anisotropic Strain Relaxation of Graphene by Corrugation on Copper Crystal Surfaces.

PubMed

Deng, Bing; Wu, Juanxia; Zhang, Shishu; Qi, Yue; Zheng, Liming; Yang, Hao; Tang, Jilin; Tong, Lianming; Zhang, Jin; Liu, Zhongfan; Peng, Hailin

2018-05-01

Corrugation is a ubiquitous phenomenon for graphene grown on metal substrates by chemical vapor deposition, which greatly affects the electrical, mechanical, and chemical properties. Recent years have witnessed great progress in controlled growth of large graphene single crystals; however, the issue of surface roughness is far from being addressed. Here, the corrugation at the interface of copper (Cu) and graphene, including Cu step bunches (CuSB) and graphene wrinkles, are investigated and ascribed to the anisotropic strain relaxation. It is found that the corrugation is strongly dependent on Cu crystallographic orientations, specifically, the packed density and anisotropic atomic configuration. Dense Cu step bunches are prone to form on loose packed faces due to the instability of surface dynamics. On an anisotropic Cu crystal surface, Cu step bunches and graphene wrinkles are formed in two perpendicular directions to release the anisotropic interfacial stress, as revealed by morphology imaging and vibrational analysis. Cu(111) is a suitable crystal face for growth of ultraflat graphene with roughness as low as 0.20 nm. It is believed the findings will contribute to clarifying the interplay between graphene and Cu crystal faces, and reducing surface roughness of graphene by engineering the crystallographic orientation of Cu substrates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of surface pre-conditioning treatments on the local composition of Zr-based conversion coatings formed on aluminium alloys

NASA Astrophysics Data System (ADS)

Cerezo, J.; Vandendael, I.; Posner, R.; de Wit, J. H. W.; Mol, J. M. C.; Terryn, H.

2016-03-01

This study investigates the effect of different alkaline, acidic and thermal pre-conditioning treatments applied to different Al alloy surfaces. The obtained results are compared to the characteristics of Zr-based conversion coatings that were subsequently generated on top of these substrates. Focus is laid on typical elemental distributions on the sample surfaces, in particular on the amount of precipitated functional additives such as Cu species that are present in the substrate matrix as well as in the conversion bath solutions. To this aim, Field Emission Auger Electron spectra, depth profiles and surface maps with superior local resolution were acquired and compared to scanning electron microscopy images of the sample. The results show how de-alloying processes, which occur at and around intermetallic particles in the Al matrix during typical industrial alkaline or acidic cleaning procedures, provide a significant source of crystallization cores for any following coating processes. This is in particular due for Cu-species, as the resulting local Cu structures on the surface strongly affect the film formation and compositions of state-of-the-art Zr-based films. The findings are highly relevant for industrial treatments of aluminium surfaces, especially for those that undergo corrosion protection and painting process steps prior to usage.

Trapping of intermediates with substrate analog HBOCoA in the polymerizations catalyzed by class III polyhydroxybutyrate (PHB) synthase from Allochromatium vinosum.

PubMed

Chen, Chao; Cao, Ruikai; Shrestha, Ruben; Ward, Christina; Katz, Benjamin B; Fischer, Christopher J; Tomich, John M; Li, Ping

2015-05-15

Polyhydroxybutyrate (PHB) synthases (PhaCs) catalyze the formation of biodegradable PHB polymers that are considered as an ideal alternative to petroleum-based plastics. To provide strong evidence for the preferred mechanistic model involving covalent and noncovalent intermediates, a substrate analog HBOCoA was synthesized chemoenzymatically. Substitution of sulfur in the native substrate HBCoA with an oxygen in HBOCoA enabled detection of (HB)nOCoA (n = 2-6) intermediates when the polymerization was catalyzed by wild-type (wt-)PhaECAv at 5.84 h(-1). This extremely slow rate is due to thermodynamically unfavorable steps that involve the formation of enzyme-bound PHB species (thioesters) from corresponding CoA oxoesters. Synthesized standards (HB)nOCoA (n = 2-3) were found to undergo both reacylation and hydrolysis catalyzed by the synthase. Distribution of the hydrolysis products highlights the importance of the penultimate ester group as previously suggested. Importantly, the reaction between primed synthase [(3)H]-sT-PhaECAv and HBOCoA yielded [(3)H]-sTet-O-CoA at a rate constant faster than 17.4 s(-1), which represents the first example that a substrate analog undergoes PHB chain elongation at a rate close to that of the native substrate (65.0 s(-1)). Therefore, for the first time with a wt-synthase, strong evidence was obtained to support our favored PHB chain elongation model.

Au coated PS nanopillars as a highly ordered and reproducible SERS substrate

NASA Astrophysics Data System (ADS)

Kim, Yong-Tae; Schilling, Joerg; Schweizer, Stefan L.; Sauer, Guido; Wehrspohn, Ralf B.

2017-07-01

Noble metal nanostructures with nanometer gap size provide strong surface-enhanced Raman scattering (SERS) which can be used to detect trace amounts of chemical and biological molecules. Although several approaches were reported to obtain active SERS substrates, it still remains a challenge to fabricate SERS substrates with high sensitivity and reproducibility using low-cost techniques. In this article, we report on the fabrication of Au sputtered PS nanopillars based on a template synthetic method as highly ordered and reproducible SERS substrates. The SERS substrates are fabricated by anodic aluminum oxide (AAO) template-assisted infiltration of polystyrene (PS) resulting in hemispherical structures, and a following Au sputtering process. The optimum gap size between adjacent PS nanopillars and thickness of the Au layers for high SERS sensitivity are investigated. Using the Au sputtered PS nanopillars as an active SERS substrate, the Raman signal of 4-methylbenzenethiol (4-MBT) with a concentration down to 10-9 M is identified with good signal reproducibility, showing great potential as promising tool for SERS-based detection.

A differential scanning calorimetric study of the effects of metal ions, substrate/product, substrate analogues and chaotropic anions on the thermal denaturation of yeast enolase 1.

PubMed

Brewer, J M; Wampler, J E

2001-03-14

The thermal denaturation of yeast enolase 1 was studied by differential scanning calorimetry (DSC) under conditions of subunit association/dissociation, enzymatic activity or substrate binding without turnover and substrate analogue binding. Subunit association stabilizes the enzyme, that is, the enzyme dissociates before denaturing. The conformational change produced by conformational metal ion binding increases thermal stability by reducing subunit dissociation. 'Substrate' or analogue binding additionally stabilizes the enzyme, irrespective of whether turnover is occurring, perhaps in part by the same mechanism. More strongly bound metal ions also stabilize the enzyme more, which we interpret as consistent with metal ion loss before denaturation, though possibly the denaturation pathway is different in the absence of metal ion. We suggest that some of the stabilization by 'substrate' and analogue binding is owing to the closure of moveable polypeptide loops about the active site, producing a more 'closed' and hence thermostable conformation.

IR Reflectance Properties Of Weakly And Strongly Absorbing Surface Films

NASA Astrophysics Data System (ADS)

Yen, Yu-Sze; Wong, James S.

1989-12-01

In an external reflection measurement, the optical properties of a surface film can give rise to a variety of spectral behavior on metallic and nonmetallic substrates. The diversity of behavior can be explained by the presence of transverse optical (TO) and longitudinal optical (LO) bands of the film in the infrared region. The excitation modes associated with these bands are directional with respect to the plane of the surface. Spectral interpretation is facilitated by understanding the roles of the TO and LO bands in reflectance spectra, the substrate selection rules for the appearance of these bands, and the relationship between the TO and LO frequencies. We will show that weakly absorbing films have a simpler optical behavior than strongly absorbing films.

Competitive binding effects on surface-enhanced Raman scattering of peptide molecules

NASA Astrophysics Data System (ADS)

Seballos, Leo; Richards, Nicole; Stevens, Daniel J.; Patel, Mira; Kapitzky, Laura; Lokey, Scott; Millhauser, Glenn; Zhang, Jin Z.

2007-10-01

Surface enhanced Raman scattering (SERS) has been conducted on tryptophan (W), proline (P) and tyrosine (Y) containing peptides that include W-P-Y, Y-P-W, W-P-P-P-Y, Y-P-P-P-W, W-P-P-P-P-P-Y, and Y-P-P-P-P-P-W to gain insight into molecular binding behavior on a metal substrate to eventually apply in protein SERS detection. The peptides are shown to bind through the molecule's carboxylic end, but the strong affinity of the tryptophan residue to the substrate surface, in conjunction with its large polarizability, dominates each molecule's SERS signal with the strong presence of its ring modes in all samples. These results are important for understanding SERS of protein molecules.

Effects of garlic oil, nitrate, saponin and their combinations supplemented to different substrates on in vitro fermentation, ruminal methanogenesis, and abundance and diversity of microbial populations.

PubMed

Patra, A K; Yu, Z

2015-07-01

To investigate the effect of garlic oil (G), nitrate (N), saponin (S) and their combinations supplemented to different forage to concentrate substrates on methanogenesis, fermentation, diversity and abundances of bacteria and Archaea in vitro. The study was conducted in an 8 × 2 factorial design with eight treatments and two substrates using mixed ruminal batch cultures obtained. Quillaja S (0·6 g l(-1) ), N (5 mmol l(-1) ) and G (0·27 g l(-1) ) were used separately or in binary and tertiary combinations. The two substrates contained grass hay and a dairy concentrate mixture at a 70 : 30 (high-forage substrate) ratio or a 30 : 70 (high-concentrate substrate) ratio. Ruminal fermentation and cellulolytic bacterial populations were affected by interaction between substrate and anti-methanogenic compounds. The inhibitor combinations decreased the methane production additively regardless of substrate. For the high-concentrate substrate, S decreased methane production to a greater extent, so did G and N individually for the high-forage substrate. Feed degradability and total volatile fatty acid (VFA) concentrations were not decreased by any of the treatments. Fibre degradability was actually improved by N+S for the high-forage substrate. VFA concentrations and profiles were affected differently by different anti-methanogenic inhibitors and their combinations. All treatments inhibited the growth of Archaea, but the effect on Fibrobacter succinogenes, Ruminococcus albus and Ruminococcus flavefaciens varied. The results suggest that substrate influences the efficacy of these inhibitors when they are used separately, but in combinations, they can lower methanogenesis additively without much influence from the substrate. The presented research provided evidence that binary and tertiary combination of garlic oil, nitrate and saponin can lower the methane production additively without adversely impacting rumen fermentation and degradability, and forage to concentrate ratio does not change the above effects. These anti-methanogenic inhibitors in combination may have practical application to mitigate methane emission from ruminants. © 2015 The Society for Applied Microbiology.

Change in enzyme production by gradually drying culture substrate during solid-state fermentation.

PubMed

Ito, Kazunari; Gomi, Katsuya; Kariyama, Masahiro; Miyake, Tsuyoshi

2015-06-01

The influence of drying the culture substrate during solid-state fermentation on enzyme production was investigated using a non-airflow box. The drying caused a significant increase in enzyme production, while the mycelium content decreased slightly. This suggests that changes in the water content in the substrate during culture affect enzyme production in fungi. Copyright © 2014 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Deficient plasticity in the hippocampus and the spiral of addiction: focus on adult neurogenesis.

PubMed

Canales, Juan J

2013-01-01

Addiction is a complex neuropsychiatric disorder which causes disruption at multiple levels, including cognitive, emotional, and behavioral domains. Traditional biological theories of addiction have focused on the mesolimbic dopamine pathway and the nucleus accumbens as anatomical substrates mediating addictive-like behaviors. More recently, we have begun to recognize the engagement and dynamic influence of a much broader circuitry which encompasses the frontal cortex, the amygdala, and the hippocampus. In particular, neurogenesis in the adult hippocampus has become a major focus of attention due to its ability to influence memory, motivation, and affect, all of which are disrupted in addiction. First, I summarize toxicological data that reveal strongly suppressive effects of drug exposure on adult hippocampal neurogenesis. Then, I discuss the impact of deficient neurogenesis on learning and memory function, stress responsiveness and affective behavior, as they relate to addiction. Finally, I examine recent behavioral observations that implicate neurogenesis in the adult hippocampus in the emergence and maintenance of addictive behavior. The evidence reviewed here suggests that deficient neurogenesis is associated with several components of the downward spiraling loop that characterizes addiction, including elevated sensitivity to drug-induced reward and reinforcement, enhanced neurohormonal responsiveness, emergence of a negative affective state, memory impairment, and inflexible behavior.

Measurement of strong Marangoni flow near a contact line of a water droplet on hydrophobic surfaces

NASA Astrophysics Data System (ADS)

Park, Joonsik; Breuer, Kenneth S.

2015-11-01

Strong Marangoni flow from a water droplet on unheated substrate has been theoretically predicted but not been quantitatively measured. Using two different experimental techniques, multi-layer flood illumination and Total Internal Reflection Fluorescence Microscopy (TIRFM), we report Marangoni flows with large (O(100 μm/s)) velocity near a contact line of a water droplet on hydrophobic substrates. The flow is measured by tracking the motion of nanoparticles with respect to the contact line, using statistical particle tracking velocimetry combined with sub-pixel edge detection algorithm. Under multi-layer flood illumination, the recirculating convective flow is identified within 5 μm vertically from the substrate. From the TIRFM measurement, the changes in the bulk-averaged velocity (O(100 μm/s)) and the shear rate (O(100 s-1)) as the distance from the contact line are identified within 550 nm vertically from the substrate, and compared to the characteristic shear rate and speed from Marangoni effect, respectively. Surprisingly, both Flood and TIRFM measurements indicate high slip velocities extending as far as 33 μm from the contact line. One possible explanation is that the high slip velocity is due to the accumulation of nanobubbles near the contact line which were formed at the deposition of a droplet.

Highly (001) oriented L1{sub 0}-CoPt/TiN multilayer films on glass substrates with perpendicular magnetic anisotropy

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Hongyu; Sannomiya, Takumi; Muraishi, Shinji

2015-03-15

To obtain strong perpendicular magnetic anisotropy (PMA) based on L1{sub 0} structure for magnetic storage devices, costly single crystalline substrates are generally required to achieve (001) texture. Recently, various studies also have focused on depositing different kinds of seed layers on glass or other amorphous substrates to promote (001) preferred orientation of L1{sub 0} CoPt and FePt. TiN is a very promising seed layer material because of its cubic crystalline structure (similar to MgO) and excellent diffusion barring property even at high temperatures. In the present work, highly (001) oriented L1{sub 0}-CoPt/TiN multilayer films have been successfully deposited on glassmore » substrates. After annealing at 700 °C, the film exhibits PMA, and a strong (001) peak is detected from the x-ray diffraction profiles, indicating the ordering transformation of CoPt layers from fcc (A1) to L1{sub 0} structure. It also is found that alternate deposition of cubic TiN and CoPt effectively improves the crystallinity and (001) preferred orientation of CoPt layers. This effect is verified by the substantial enhancement of (001) reflection and PMA with increasing the period number of the multilayer films.« less

An AAA Motor-Driven Mechanical Switch in Rpn11 Controls Deubiquitination at the 26S Proteasome.

PubMed

Worden, Evan J; Dong, Ken C; Martin, Andreas

2017-09-07

Poly-ubiquitin chains direct protein substrates to the 26S proteasome, where they are removed by the deubiquitinase Rpn11 during ATP-dependent substrate degradation. Rapid deubiquitination is required for efficient degradation but must be restricted to committed substrates that are engaged with the ATPase motor to prevent premature ubiquitin chain removal and substrate escape. Here we reveal the ubiquitin-bound structure of Rpn11 from S. cerevisiae and the mechanisms for mechanochemical coupling of substrate degradation and deubiquitination. Ubiquitin binding induces a conformational switch of Rpn11's Insert-1 loop from an inactive closed state to an active β hairpin. This switch is rate-limiting for deubiquitination and strongly accelerated by mechanical substrate translocation into the AAA+ motor. Deubiquitination by Rpn11 and ubiquitin unfolding by the ATPases are in direct competition. The AAA+ motor-driven acceleration of Rpn11 is therefore important to ensure that poly-ubiquitin chains are removed only from committed substrates and fast enough to prevent their co-degradation. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of the Cold-Sprayed Aluminum Coating-Substrate Interface Morphology on Bond Strength for Aircraft Repair Application

NASA Astrophysics Data System (ADS)

Blochet, Quentin; Delloro, Francesco; N'Guyen, Franck; Jeulin, Dominique; Borit, François; Jeandin, Michel

2017-04-01

This article is dealing with the effects of surface preparation of the substrate on aluminum cold-sprayed coating bond strength. Different sets of AA2024-T3 specimens have been coated with pure Al 1050 feedstock powder, using a conventional cold spray coating technique. The sets were grit-blasted (GB) before coating. The study focuses on substrate surface topography evolution before coating and coating-substrate interface morphology after coating. To study coating adhesion by LASAT® technique for each set, specimens with and without preceding GB treatment were tested in load-controlled conditions. Then, several techniques were used to evaluate the effects of substrate surface treatment on the final coating mechanical properties. Irregularities induced by the GB treatment modify significantly the interface morphology. Results showed that particle anchoring was improved dramatically by the presence of craters. The substrate surface was characterized by numerous anchors. Numerical simulation results exhibited the increasing deformation of particle onto the grit-blasted surface. In addition, results showed a strong relationship between the coating-substrate bond strength on the deposited material and surface preparation.

Basic Residues R260 and K357 Affect the Conformational Dynamics of the Major Facilitator Superfamily Multidrug Transporter LmrP

PubMed Central

Wang, Wei; van Veen, Hendrik W.

2012-01-01

Secondary-active multidrug transporters can confer resistance on cells to pharmaceuticals by mediating their extrusion away from intracellular targets via substrate/H+(Na+) antiport. While the interactions of catalytic carboxylates in these transporters with coupling ions and substrates (drugs) have been studied in some detail, the functional importance of basic residues has received much less attention. The only two basic residues R260 and K357 in transmembrane helices in the Major Facilitator Superfamily transporter LmrP from Lactococcus lactis are present on the outer surface of the protein, where they are exposed to the phospholipid head group region of the outer leaflet (R260) and inner leaflet (K357) of the cytoplasmic membrane. Although our observations on the proton-motive force dependence and kinetics of substrate transport, and substrate-dependent proton transport demonstrate that K357A and R260A mutants are affected in ethidium-proton and benzalkonium-proton antiport compared to wildtype LmrP, our findings suggest that R260 and K357 are not directly involved in the binding of substrates or the translocation of protons. Secondary-active multidrug transporters are thought to operate by a mechanism in which binding sites for substrates are alternately exposed to each face of the membrane. Disulfide crosslinking experiments were performed with a double cysteine mutant of LmrP that reports the substrate-stimulated transition from the outward-facing state to the inward-facing state with high substrate-binding affinity. In the experiments, the R260A and K357A mutations were found to influence the dynamics of these major protein conformations in the transport cycle, potentially by removing the interactions of R260 and K357 with phospholipids and/or other residues in LmrP. The R260A and K357A mutations therefore modify the maximum rate at which the transport cycle can operate and, as the transitions between conformational states are differently affected by components of the proton-motive force, the mutations also influence the energetics of transport. PMID:22761697

Ultrafast time-resolved photoemission of a metallic tip/substrate junction

NASA Astrophysics Data System (ADS)

Meng, Xiang; Jin, Wencan; Yang, Hao; Dadap, Jerry; Osgood, Richard; Camillone, Nicholas, III

The strong near-field enhancement of metallic-tip nanostructures has attracted great interest in scanning microscopy techniques, such as surface-enhanced Raman scattering, near-field scanning optical microscopy and tip-enhanced nonlinear imaging. In this talk, we use a full vectorial 3D-FDTD method to investigate the spatial characteristics of the optical field confinement and localization between a tungsten nanoprobe and an infinite planar silver substrate, with two-color ultrafast laser excitation scheme. The degree of two-color excited field enhancement, geometry dependence, the exact mechanism of optical tip-substrate coupling and tip-substrate plasmon resonances are significant in understanding the electrodynamical responses at tip-substrate junction. The demonstrated measurements with subpicosecond time and subnanometer spatial resolution suggest a new approach to ultrafast time-resolved measurements of surface electron dynamics. DE-FG 02-90-ER-14104; DE-FG 02-04-ER-46157.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Rabindar K., E-mail: rkrksharma6@gmail.com; Reddy, G. B., E-mail: rkrksharma6@gmail.com

In this report, we synthesize vertically aligned molybdenum trioxide (α−MoO{sub 3}) nanoflakes (NFs) with high aspect ratio (height/thickness >15) on the cobalt coated glass substrates by the plasma assisted sublimation process, employing Mo metal strip as a sublimation source. The effect of substrate temperature, nature of substrate as well as the geometry of the sublimation source (Mo-strip) have been investigated on the morphological, structural and optical properties of the grown NFs, keeping plasma parameters as fixed. The surface morphology, crystalline structure and optical properties of MoO{sub 3} NFs have been studied systematically by using scanning electron microscope (SEM), transmission electronmore » microscope (TEM) with selected area electron diffraction (SAED), X-ray diffractometer, and IR- spectroscopy. The experimental observations endorse that the characteristics of MoO{sub 3} NFs are strongly depend on substrate temperature, substrate nature as well as geometry of Mo-strip. All the observed results are well in consonance with each other.« less

Metallization of electronic insulators

DOEpatents

Gottesfeld, Shimshon; Uribe, Francisco A.

1994-01-01

An electroplated element is formed to include an insulating substrate, a conducting polymer polymerized in situ on the substrate, and a metal layer deposited on the conducting polymer. In one application a circuit board is formed by polymerizing pyrrole on an epoxy-fiberglass substrate in a single step process and then electrodepositing a metal over the resulting polypyrrole polymer. No chemical deposition of the metal is required prior to electroplating and the resulting layer of substrate-polymer-metal has excellent adhesion characteristics. The metal deposition is surprisingly smooth and uniform over the relatively high resistance film of polypyrrole. A continuous manufacturing process is obtained by filtering the solution between successive substrates to remove polymer formed in the solution, by maintaining the solution oxidizing potential within selected limits, and by adding a strong oxidant, such as KMnO.sub.4 at periodic intervals to maintain a low sheet resistivity in the resulting conducting polymer film.

A field study to evaluate the impact of different factors on the nutrient pollutant concentrations in green roof runoff.

PubMed

Wang, Xiaochen; Zhao, Xinhua; Peng, Chenrui; Zhang, Xinbo; Wang, Jianghai

2013-01-01

The objectives of this study are to investigate the impact of different factors on the nutrient pollutant concentrations in green roof runoff and to provide reference data for the engineering design of dual substrate layer green roofs. The data were collected from eight different trays under three kinds of artificial rains. The results showed that except for total phosphorus, dual substrate layer green roofs behaved as a sink for most of the nutrient pollutants (significant at p < 0.05), and the first-flush effect did not occur during the 27 simulated rain events. The results also revealed that the concentration of these nutrient pollutants in the runoff strongly depended on the features of the nutrient substrates used in the green roof and the depth of the adsorption substrates. Compared with the influence of the substrates, the influence of the plant density and drainage systems was small.

Initial nitrogen enrichment conditions determines variations in nitrogen substrate utilization by heterotrophic bacterial isolates.

PubMed

Ghosh, Suchismita; Ayayee, Paul A; Valverde-Barrantes, Oscar J; Blackwood, Christopher B; Royer, Todd V; Leff, Laura G

2017-04-04

The nitrogen (N) cycle consists of complex microbe-mediated transformations driven by a variety of factors, including diversity and concentrations of N compounds. In this study, we examined taxonomic diversity and N substrate utilization by heterotrophic bacteria isolated from streams under complex and simple N-enrichment conditions. Diversity estimates differed among isolates from the enrichments, but no significant composition were detected. Substrate utilization and substrate range of bacterial assemblages differed within and among enrichments types, and not simply between simple and complex N-enrichments. N substrate use patterns differed between isolates from some complex and simple N-enrichments while others were unexpectedly similar. Taxonomic composition of isolates did not differ among enrichments and was unrelated to N use suggesting strong functional redundancy. Ultimately, our results imply that the available N pool influences physiology and selects for bacteria with various abilities that are unrelated to their taxonomic affiliation.

Toward nanomolar detection by NMR through SABRE hyperpolarization.

PubMed

Eshuis, Nan; Hermkens, Niels; van Weerdenburg, Bram J A; Feiters, Martin C; Rutjes, Floris P J T; Wijmenga, Sybren S; Tessari, Marco

2014-02-19

SABRE is a nuclear spin hyperpolarization technique based on the reversible association of a substrate molecule and para-hydrogen (p-H2) to a metal complex. During the lifetime of such a complex, generally fractions of a second, the spin order of p-H2 is transferred to the nuclear spins of the substrate molecule via a transient scalar coupling network, resulting in strongly enhanced NMR signals. This technique is generally applied at relatively high concentrations (mM), in large excess of substrate with respect to metal complex. Dilution of substrate ligands below stoichiometry results in progressive decrease of signal enhancement, which precludes the direct application of SABRE to the NMR analysis of low concentration (μM) solutions. Here, we show that the efficiency of SABRE at low substrate concentrations can be restored by addition of a suitable coordinating ligand to the solution. The proposed method allowed NMR detection below 1 μM in a single scan.

Implication of substrate-assisted catalysis on improving lipase activity or enantioselectivity in organic solvents.

PubMed

Tsai, Shau-Wei; Chen, Chun-Chi; Yang, Hung-Shien; Ng, I-Son; Chen, Teh-Liang

2006-08-01

In comparison with the biocatalyst engineering and medium engineering approaches, very few examples have been reported on using the substrate engineering approach such as substrate-assisted catalysis (SAC) for naturally occurring or engineered lipases and serine proteases to improve the enzyme activity and enantioselectivity. By employing lipase-catalyzed hydrolysis of (R,S)-naproxen esters in water-saturated isooctane as the model system, we demonstrate the proton shuttle device to the leaving alcohol of the substrate as a new means of SAC to effectively improve the lipase activity or enantioselectivity. The result cannot only provide a strong evidence for the rate-limiting proton transfer for the bond-breaking of tetrahedron intermediate of the acylation step, but also sheds light for performing the hydrolysis, transesterification or aminolysis in organic solvents for the ester substrate that originally lipases cannot catalyze, but now can after introducing the device.

Hysteresis in the Cell Response to Time-Dependent Substrate Stiffness

PubMed Central

Besser, Achim; Schwarz, Ulrich S.

2010-01-01

Abstract Mechanical cues like the rigidity of the substrate are main determinants for the decision-making of adherent cells. Here we use a mechano-chemical model to predict the cellular response to varying substrate stiffnesses. The model equations combine the mechanics of contractile actin filament bundles with a model for the Rho-signaling pathway triggered by forces at cell-matrix contacts. A bifurcation analysis of cellular contractility as a function of substrate stiffness reveals a bistable response, thus defining a lower threshold of stiffness, below which cells are not able to build up contractile forces, and an upper threshold of stiffness, above which cells are always in a strongly contracted state. Using the full dynamical model, we predict that rate-dependent hysteresis will occur in the cellular traction forces when cells are exposed to substrates of time-dependent stiffness. PMID:20655823

Substrate utilization profiles of bacterial strains in plankton from the River Warnow, a humic and eutrophic river in north Germany.

PubMed

Freese, Heike M; Eggert, Anja; Garland, Jay L; Schumann, Rhena

2010-01-01

Bacteria are very important degraders of organic substances in aquatic environments. Despite their influential role in the carbon (and many other element) cycle(s), the specific genetic identity of active bacteria is mostly unknown, although contributing phylogenetic groups had been investigated. Moreover, the degree to which phenotypic potential (i. e., utilization of environmentally relevant carbon substrates) is related to the genomic identity of bacteria or bacterial groups is unclear. The present study compared the genomic fingerprints of 27 bacterial isolates from the humic River Warnow with their ability to utilize 14 environmentally relevant substrates. Acetate was the only substrate utilized by all bacterial strains. Only 60% of the strains respired glucose, but this substrate always stimulated the highest bacterial activity (respiration and growth). Two isolates, both closely related to the same Pseudomonas sp., also had very similar substrate utilization patterns. However, similar substrate utilization profiles commonly belonged to genetically different strains (e.g., the substrate profile of Janthinobacterium lividum OW6/RT-3 and Flavobacterium sp. OW3/15-5 differed by only three substrates). Substrate consumption was sometimes totally different for genetically related isolates. Thus, the genomic profiles of bacterial strains were not congruent with their different substrate utilization profiles. Additionally, changes in pre-incubation conditions strongly influenced substrate utilization. Therefore, it is problematic to infer substrate utilization and especially microbial dissolved organic matter transformation in aquatic systems from bacterial molecular taxonomy.

Hydrophobic fluorescent probes introduce artifacts into single molecule tracking experiments due to non-specific binding.

PubMed

Zanetti-Domingues, Laura C; Tynan, Christopher J; Rolfe, Daniel J; Clarke, David T; Martin-Fernandez, Marisa

2013-01-01

Single-molecule techniques are powerful tools to investigate the structure and dynamics of macromolecular complexes; however, data quality can suffer because of weak specific signal, background noise and dye bleaching and blinking. It is less well-known, but equally important, that non-specific binding of probe to substrates results in a large number of immobile fluorescent molecules, introducing significant artifacts in live cell experiments. Following from our previous work in which we investigated glass coating substrates and demonstrated that the main contribution to this non-specific probe adhesion comes from the dye, we carried out a systematic investigation of how different dye chemistries influence the behaviour of spectrally similar fluorescent probes. Single-molecule brightness, bleaching and probe mobility on the surface of live breast cancer cells cultured on a non-adhesive substrate were assessed for anti-EGFR affibody conjugates with 14 different dyes from 5 different manufacturers, belonging to 3 spectrally homogeneous bands (491 nm, 561 nm and 638 nm laser lines excitation). Our results indicate that, as well as influencing their photophysical properties, dye chemistry has a strong influence on the propensity of dye-protein conjugates to adhere non-specifically to the substrate. In particular, hydrophobicity has a strong influence on interactions with the substrate, with hydrophobic dyes showing much greater levels of binding. Crucially, high levels of non-specific substrate binding result in calculated diffusion coefficients significantly lower than the true values. We conclude that the physic-chemical properties of the dyes should be considered carefully when planning single-molecule experiments. Favourable dye characteristics such as photostability and brightness can be offset by the propensity of a conjugate for non-specific adhesion.

Hydrophobic Fluorescent Probes Introduce Artifacts into Single Molecule Tracking Experiments Due to Non-Specific Binding

PubMed Central

Rolfe, Daniel J.; Clarke, David T.; Martin-Fernandez, Marisa

2013-01-01

Single-molecule techniques are powerful tools to investigate the structure and dynamics of macromolecular complexes; however, data quality can suffer because of weak specific signal, background noise and dye bleaching and blinking. It is less well-known, but equally important, that non-specific binding of probe to substrates results in a large number of immobile fluorescent molecules, introducing significant artifacts in live cell experiments. Following from our previous work in which we investigated glass coating substrates and demonstrated that the main contribution to this non-specific probe adhesion comes from the dye, we carried out a systematic investigation of how different dye chemistries influence the behaviour of spectrally similar fluorescent probes. Single-molecule brightness, bleaching and probe mobility on the surface of live breast cancer cells cultured on a non-adhesive substrate were assessed for anti-EGFR affibody conjugates with 14 different dyes from 5 different manufacturers, belonging to 3 spectrally homogeneous bands (491 nm, 561 nm and 638 nm laser lines excitation). Our results indicate that, as well as influencing their photophysical properties, dye chemistry has a strong influence on the propensity of dye-protein conjugates to adhere non-specifically to the substrate. In particular, hydrophobicity has a strong influence on interactions with the substrate, with hydrophobic dyes showing much greater levels of binding. Crucially, high levels of non-specific substrate binding result in calculated diffusion coefficients significantly lower than the true values. We conclude that the physic-chemical properties of the dyes should be considered carefully when planning single-molecule experiments. Favourable dye characteristics such as photostability and brightness can be offset by the propensity of a conjugate for non-specific adhesion. PMID:24066121

The Local Dinucleotide Preference of APOBEC3G Can Be Altered from 5′-CC to 5′-TC by a Single Amino Acid Substitution

PubMed Central

Rathore, Anurag; Carpenter, Michael A; Demir, Özlem; Ikeda, Terumasa; Li, Ming; Shaban, Nadine; Law, Emily K.; Anokhin, Dmitry; Brown, William L.; Amaro, Rommie E.; Harris, Reuben S.

2013-01-01

APOBEC3A and APOBEC3G are DNA cytosine deaminases with biological functions in foreign DNA and retrovirus restriction, respectively. APOBEC3A has an intrinsic preference for cytosine preceded by thymine (5′-TC) in single-stranded DNA substrates, whereas APOBEC3G prefers the target cytosine to be preceded by another cytosine (5′-CC). To determine the amino acids responsible for these strong dinucleotide preferences, we analyzed a series of chimeras in which putative DNA binding loop regions of APOBEC3G were replaced with the corresponding regions from APOBEC3A. Loop 3 replacement enhanced APOBEC3G catalytic activity but did not alter its intrinsic 5′-CC dinucleotide substrate preference. Loop 7 replacement caused APOBEC3G to become APOBEC3A-like and strongly prefer 5′-TC substrates. Simultaneous loop 3/7 replacement resulted in a hyperactive APOBEC3G variant that also preferred 5′-TC dinucleotides. Single amino acid exchanges revealed D317 as a critical determinant of dinucleotide substrate specificity. Multi-copy explicitly solvated all-atom molecular dynamics simulations suggested a model in which D317 acts as a helix-capping residue by constraining the mobility of loop 7, forming a novel binding pocket that favorably accommodates cytosine. All catalytically active APOBEC3G variants, regardless of dinucleotide preference, retained HIV-1 restriction activity. These data support a model in which the loop 7 region governs the selection of local dinucleotide substrates for deamination but is unlikely to be part of the higher level targeting mechanisms that direct these enzymes to biological substrates such as HIV-1 cDNA. PMID:23938202

Discovery and characterization of a highly efficient enantioselective mandelonitrile hydrolase from Burkholderia cenocepacia J2315 by phylogeny-based enzymatic substrate specificity prediction.

PubMed

Wang, Hualei; Sun, Huihui; Wei, Dongzhi

2013-02-18

A nitrilase-mediated pathway has significant advantages in the production of optically pure (R)-(-)-mandelic acid. However, unwanted byproduct, low enantioselectivity, and specific activity reduce its value in practical applications. An ideal nitrilase that can efficiently hydrolyze mandelonitrile to optically pure (R)-(-)-mandelic acid without the unwanted byproduct is needed. A novel nitrilase (BCJ2315) was discovered from Burkholderia cenocepacia J2315 through phylogeny-based enzymatic substrate specificity prediction (PESSP). This nitrilase is a mandelonitrile hydrolase that could efficiently hydrolyze mandelonitrile to (R)-(-)-mandelic acid, with a high enantiomeric excess of 98.4%. No byproduct was observed in this hydrolysis process. BCJ2315 showed the highest identity of 71% compared with other nitrilases in the amino acid sequence. BCJ2315 possessed the highest activity toward mandelonitrile and took mandelonitrile as the optimal substrate based on the analysis of substrate specificity. The kinetic parameters Vmax, Km, Kcat, and Kcat/Km toward mandelonitrile were 45.4 μmol/min/mg, 0.14 mM, 15.4 s(-1), and 1.1×10(5) M(-1)s(-1), respectively. The recombinant Escherichia coli M15/BCJ2315 had a strong substrate tolerance and could completely hydrolyze mandelonitrile (100 mM) with fewer amounts of wet cells (10 mg/ml) within 1 h. PESSP is an efficient method for discovering an ideal mandelonitrile hydrolase. BCJ2315 has high affinity and catalytic efficiency toward mandelonitrile. This nitrilase has great advantages in the production of optically pure (R)-(-)-mandelic acid because of its high activity and enantioselectivity, strong substrate tolerance, and having no unwanted byproduct. Thus, BCJ2315 has great potential in the practical production of optically pure (R)-(-)-mandelic acid in the industry.

Enantioselective Hydroformylation of Aniline Derivatives

PubMed Central

Joe, Candice L.; Tan, Kian L.

2011-01-01

We have developed a ligand that reversibly binds to aniline substrates allowing for the control of regioselectivity and enantioselectivity in hydroformylation. In this paper we address how the electronics of the aniline ring affect both binding of the substrate to the ligand and the enantioselectivity in this reaction. PMID:21842847

A Camelid-derived Antibody Fragment Targeting the Active Site of a Serine Protease Balances between Inhibitor and Substrate Behavior*

PubMed Central

Kromann-Hansen, Tobias; Oldenburg, Emil; Yung, Kristen Wing Yu; Ghassabeh, Gholamreza H.; Muyldermans, Serge; Declerck, Paul J.; Huang, Mingdong; Andreasen, Peter A.; Ngo, Jacky Chi Ki

2016-01-01

A peptide segment that binds the active site of a serine protease in a substrate-like manner may behave like an inhibitor or a substrate. However, there is sparse information on which factors determine the behavior a particular peptide segment will exhibit. Here, we describe the first x-ray crystal structure of a nanobody in complex with a serine protease. The nanobody displays a new type of interaction between an antibody and a serine protease as it inserts its complementary determining region-H3 loop into the active site of the protease in a substrate-like manner. The unique binding mechanism causes the nanobody to behave as a strong inhibitor as well as a poor substrate. Intriguingly, its substrate behavior is incomplete, as 30–40% of the nanobody remained intact and inhibitory after prolonged incubation with the protease. Biochemical analysis reveals that an intra-loop interaction network within the complementary determining region-H3 of the nanobody balances its inhibitor versus substrate behavior. Collectively, our results unveil molecular factors, which may be a general mechanism to determine the substrate versus inhibitor behavior of other protease inhibitors. PMID:27226628

Pharmacoproteomics of a Metalloproteinase Hydroxamate Inhibitor in Breast Cancer Cells: Dynamics of Membrane Type 1 Matrix Metalloproteinase-Mediated Membrane Protein Shedding ▿ ‡

PubMed Central

Butler, Georgina S.; Dean, Richard A.; Tam, Eric M.; Overall, Christopher M.

2008-01-01

Broad-spectrum matrix metalloproteinase (MMP) inhibitors (MMPI) were unsuccessful in cancer clinical trials, partly due to side effects resulting from limited knowledge of the full repertoire of MMP substrates, termed the substrate degradome, and hence the in vivo functions of MMPs. To gain further insight into the degradome of MMP-14 (membrane type 1 MMP) an MMPI, prinomastat (drug code AG3340), was used to reduce proteolytic processing and ectodomain shedding in human MDA-MB-231 breast cancer cells transfected with MMP-14. We report a quantitative proteomic evaluation of the targets and effects of the inhibitor in this cell-based system. Proteins in cell-conditioned medium (the secretome) and membrane fractions with levels that were modulated by the MMPI were identified by isotope-coded affinity tag (ICAT) labeling and tandem mass spectrometry. Comparisons of the expression of MMP-14 with that of a vector control resulted in increased MMP-14/vector ICAT ratios for many proteins in conditioned medium, indicating MMP-14-mediated ectodomain shedding. Following MMPI treatment, the MMPI/vehicle ICAT ratio was reversed, suggesting that MMP-14-mediated shedding of these proteins was blocked by the inhibitor. The reduction in shedding or the release of substrates from pericellular sites in the presence of the MMPI was frequently accompanied by the accumulation of the protein in the plasma membrane, as indicated by high MMPI/vehicle ICAT ratios. Considered together, this is a strong predictor of biologically relevant substrates cleaved in the cellular context that led to the identification of many undescribed MMP-14 substrates, 20 of which we validated biochemically, including DJ-1, galectin-1, Hsp90α, pentraxin 3, progranulin, Cyr61, peptidyl-prolyl cis-trans isomerase A, and dickkopf-1. Other proteins with altered levels, such as Kunitz-type protease inhibitor 1 and beta-2-microglobulin, were not substrates in biochemical assays, suggesting an indirect affect of the MMPI, which might be important in drug development as biomarkers or, in preclinical phases, to predict systemic drug actions and adverse side effects. Hence, this approach describes the dynamic pattern of cell membrane ectodomain shedding and its perturbation upon metalloproteinase drug treatment. PMID:18505826

The Important Role of Halogen Bond in Substrate Selectivity of Enzymatic Catalysis

NASA Astrophysics Data System (ADS)

Jiang, Shuiqin; Zhang, Lujia; Cui, Dongbin; Yao, Zhiqiang; Gao, Bei; Lin, Jinping; Wei, Dongzhi

2016-10-01

The use of halogen bond is widespread in drug discovery, design, and clinical trials, but is overlooked in drug biosynthesis. Here, the role of halogen bond in the nitrilase-catalyzed synthesis of ortho-, meta-, and para-chlorophenylacetic acid was investigated. Different distributions of halogen bond induced changes of substrate binding conformation and affected substrate selectivity. By engineering the halogen interaction, the substrate selectivity of the enzyme changed, with the implication that halogen bond plays an important role in biosynthesis and should be used as an efficient and reliable tool in enzymatic drug synthesis.

Differential contribution of key metabolic substrates and cellular oxygen in HIF signalling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhdanov, Alexander V., E-mail: a.zhdanov@ucc.ie; Waters, Alicia H.C.; Golubeva, Anna V.

2015-01-01

Changes in availability and utilisation of O{sub 2} and metabolic substrates are common in ischemia and cancer. We examined effects of substrate deprivation on HIF signalling in PC12 cells exposed to different atmospheric O{sub 2}. Upon 2–4 h moderate hypoxia, HIF-α protein levels were dictated by the availability of glutamine and glucose, essential for deep cell deoxygenation and glycolytic ATP flux. Nuclear accumulation of HIF-1α dramatically decreased upon inhibition of glutaminolysis or glutamine deprivation. Elevation of HIF-2α levels was transcription-independent and associated with the activation of Akt and Erk1/2. Upon 2 h anoxia, HIF-2α levels strongly correlated with cellular ATP,more » produced exclusively via glycolysis. Without glucose, HIF signalling was suppressed, giving way to other regulators of cell adaptation to energy crisis, e.g. AMPK. Consequently, viability of cells deprived of O{sub 2} and glucose decreased upon inhibition of AMPK with dorsomorphin. The capacity of cells to accumulate HIF-2α decreased after 24 h glucose deprivation. This effect, associated with increased AMPKα phosphorylation, was sensitive to dorsomorphin. In chronically hypoxic cells, glutamine played no major role in HIF-2α accumulation, which became mainly glucose-dependent. Overall, the availability of O{sub 2} and metabolic substrates intricately regulates HIF signalling by affecting cell oxygenation, ATP levels and pathways involved in production of HIF-α. - Highlights: • Gln and Glc regulate HIF levels in hypoxic cells by maintaining low O{sub 2} and high ATP. • HIF-α levels under anoxia correlate with cellular ATP and critically depend on Glc. • Gln and Glc modulate activity of Akt, Erk and AMPK, regulating HIF production. • HIF signalling is differentially inhibited by prolonged Glc and Gln deprivation. • Unlike Glc, Gln plays no major role in HIF signalling in chronically hypoxic cells.« less

Purification and Characterization of Allophanate Hydrolase (AtzF) from Pseudomonas sp. Strain ADP

PubMed Central

Shapir, Nir; Sadowsky, Michael J.; Wackett, Lawrence P.

2005-01-01

AtzF, allophanate hydrolase, is a recently discovered member of the amidase signature family that catalyzes the terminal reaction during metabolism of s-triazine ring compounds by bacteria. In the present study, the atzF gene from Pseudomonas sp. strain ADP was cloned and expressed as a His-tagged protein, and the protein was purified and characterized. AtzF had a deduced subunit molecular mass of 66,223, based on the gene sequence, and an estimated holoenzyme molecular mass of 260,000. The active protein did not contain detectable metals or organic cofactors. Purified AtzF hydrolyzed allophanate with a kcat/Km of 1.1 × 104 s−1 M−1, and 2 mol of ammonia was released per mol allophanate. The substrate range of AtzF was very narrow. Urea, biuret, hydroxyurea, methylcarbamate, and other structurally analogous compounds were not substrates for AtzF. Only malonamate, which strongly inhibited allophanate hydrolysis, was an alternative substrate, with a greatly reduced kcat/Km of 21 s−1 M−1. Data suggested that the AtzF catalytic cycle proceeds through a covalent substrate-enzyme intermediate. AtzF reacts with malonamate and hydroxylamine to generate malonohydroxamate, potentially derived from hydroxylamine capture of an enzyme-tethered acyl group. Three putative catalytically important residues, one lysine and two serines, were altered by site-directed mutagenesis, each with complete loss of enzyme activity. The identity of a putative serine nucleophile was probed using phenyl phosphorodiamidate that was shown to be a time-dependent inhibitor of AtzF. Inhibition was due to phosphoroamidation of Ser189 as shown by liquid chromatography/matrix-assisted laser desorption ionization mass spectrometry. The modified residue corresponds in sequence alignments to the nucleophilic serine previously identified in other members of the amidase signature family. Thus, AtzF affects the cleavage of three carbon-to-nitrogen bonds via a mechanism similar to that of enzymes catalyzing single-amide-bond cleavage reactions. AtzF orthologs appear to be widespread among bacteria. PMID:15901697

Composition and functional group characterization of extracellular polymeric substances (EPS) in activated sludge: the impacts of polymerization degree of proteinaceous substrates.

PubMed

Wang, Bin-Bin; Liu, Xue-Ting; Chen, Jian-Meng; Peng, Dang-Cong; He, Feng

2018-02-01

Characteristics of extracellular polymeric substances (EPS) in activated sludge strongly depend on wastewater substrates. Proteinaceous substrates (ProS) present in heterogeneous polymeric form are intrinsic and important parts of wastewater substrates for microorganisms in activated sludge systems. However, correlations between ProS and characteristics of EPS are scarce. This study systematically explored the impacts of monomeric (Mono-), low polymeric (LoP-) and high polymeric (HiP-) ProS on compositions and functional groups of EPS in activated sludge. The results showed that the change of polymerization degree of ProS significantly altered the composition of EPS. Compared to EPS Mono-ProS , the proportion of proteins in EPS LoP-ProS and EPS HiP-ProS increased by 12.8% and 27.7%, respectively, while that of polysaccharides decreased by 22.9% and 63.6%, respectively. Moreover, the proportion of humic compounds in EPS LoP-ProS and EPS HiP-ProS were ∼6 and ∼16-fold higher than that in EPS Mono-ProS , respectively. The accumulation of humic compounds in EPS increased the unsaturation degree of EPS molecules, and thereby reduced the energy requirement for electrons transition of amide bonds and aromatic groups. Size exclusion chromatography (SEC) analyses detected more molecular clusters in EPS HiP-ProS , indicating more complex composition of EPS in HiP-ProS fed activated sludge. Spectroscopic characterization revealed the dominance of hydrocarbon, protein, polysaccharide and aromatic associated bonds in all three EPS. Nevertheless, with the increase of polymerization degree of ProS, the protein associated bonds (such as CONH, CO, NC, NH) increased, while the polysaccharide associated bonds (such as COC, COH, OCOH) decreased. This paper paves a path to understand the role of ProS in affecting the production and characteristics of EPS in biological wastewater treatment systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Time-Dependent Migratory Behaviors in the Long-Term Studies of Fibroblast Durotaxis on a Hydrogel Substrate Fabricated with a Soft Band

PubMed Central

2015-01-01

Durotaxis, biased cell movement up a stiffness gradient on culture substrates, is one of the useful taxis behaviors for manipulating cell migration on engineered biomaterial surfaces. In this study, long-term durotaxis was investigated on gelatinous substrates containing a soft band of 20, 50, and 150 μm in width fabricated using photolithographic elasticity patterning; sharp elasticity boundaries with a gradient strength of 300 kPa/50 μm were achieved. Time-dependent migratory behaviors of 3T3 fibroblast cells were observed during a time period of 3 days. During the first day, most of the cells were strongly repelled by the soft band independent of bandwidth, exhibiting the typical durotaxis behavior. However, the repellency by the soft band diminished, and more cells crossed the soft band or exhibited other mixed migratory behaviors during the course of the observation. It was found that durotaxis strength is weakened on the substrate with the narrowest soft band and that adherent affinity-induced entrapment becomes apparent on the widest soft band with time. Factors, such as changes in surface topography, elasticity, and/or chemistry, likely contributing to the apparent diminishing durotaxis during the extended culture were examined. Immunofluorescence analysis indicated preferential collagen deposition onto the soft band, which is derived from secretion by fibroblast cells, resulting in the increasing contribution of haptotaxis toward the soft band over time. The deposited collagen did not affect surface topography or surface elasticity but did change surface chemistry, especially on the soft band. The observed time-dependent durotaxis behaviors are the result of the mixed mechanical and chemical cues. In the studies and applications of cell migratory behavior under a controlled stimulus, it is important to thoroughly examine other (hidden) compounding stimuli in order to be able to accurately interpret data and to design suitable biomaterials to manipulate cell migration. PMID:24851722

Effect of External Electric Field on Substrate Transport of a Secondary Active Transporter.

PubMed

Zhang, Ji-Long; Zheng, Qing-Chuan; Yu, Li-Ying; Li, Zheng-Qiang; Zhang, Hong-Xing

2016-08-22

Substrate transport across a membrane accomplished by a secondary active transporter (SAT) is essential to the normal physiological function of living cells. In the present research, a series of all-atom molecular dynamics (MD) simulations under different electric field (EF) strengths was performed to investigate the effect of an external EF on the substrate transport of an SAT. The results show that EF both affects the interaction between substrate and related protein's residues by changing their conformations and tunes the timeline of the transport event, which collectively reduces the height of energy barrier for substrate transport and results in the appearance of two intermediate conformations under the existence of an external EF. Our work spotlights the crucial influence of external EFs on the substrate transport of SATs and could provide a more penetrating understanding of the substrate transport mechanism of SATs.

Cognitive impairment and associated loss in brain white microstructure in aircrew members exposed to engine oil fumes.

PubMed

Reneman, Liesbeth; Schagen, Sanne B; Mulder, Michel; Mutsaerts, Henri J; Hageman, Gerard; de Ruiter, Michiel B

2016-06-01

Cabin air in airplanes can be contaminated with engine oil contaminants. These contaminations may contain organophosphates (OPs) which are known neurotoxins to brain white matter. However, it is currently unknown if brain white matter in aircrew is affected. We investigated whether we could objectify cognitive complaints in aircrew and whether we could find a neurobiological substrate for their complaints. After medical ethical approval from the local institutional review board, informed consent was obtained from 12 aircrew (2 females, on average aged 44.4 years, 8,130 flying hours) with cognitive complaints and 11 well matched control subjects (2 females, 43.4 years, 233 flying hours). Depressive symptoms and self-reported cognitive symptoms were assessed, in addition to a neuropsychological test battery. State of the art Magnetic Resonance Imaging (MRI) techniques were administered that assess structural and functional changes, with a focus on white matter integrity. In aircrew we found significantly more self-reported cognitive complaints and depressive symptoms, and a higher number of tests scored in the impaired range compared to the control group. We observed small clusters in the brain in which white matter microstructure was affected. Also, we observed higher cerebral perfusion values in the left occipital cortex, and reduced brain activation on a functional MRI executive function task. The extent of cognitive impairment was strongly associated with white matter integrity, but extent of estimated number of flight hours was not associated with cognitive impairment nor with reductions in white matter microstructure. Defects in brain white matter microstructure and cerebral perfusion are potential neurobiological substrates for cognitive impairments and mood deficits reported in aircrew.

Surface chemistry in photodissociation regions

NASA Astrophysics Data System (ADS)

Esplugues, G. B.; Cazaux, S.; Meijerink, R.; Spaans, M.; Caselli, P.

2016-06-01

Context. The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Aims: Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. Methods: We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmic-ray processes on dust grains. Results: We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO2 and H2O ices in different environments. In addition, we study how chemistry is affected by the presence/absence of ice mantles (bare dust or icy dust) and the impact of considering different desorption probabilities. Conclusions: The type of substrate (bare dust or icy dust) and the probability of desorption can significantly alter the chemistry occurring on grain surfaces, leading to differences of several orders of magnitude in the abundances of gas-phase species, such as CO, H2CO, and CH3OH. The type of substrate, together with the density and intensity of the radiation field, also determine the threshold extinction to form ices of CO2 and H2O. We also conclude that H2CO and CH3OH are mainly released into the gas phase of low, far-ultraviolet illuminated PDRs through chemical desorption upon two-body surface reactions, rather than through photodesorption.

The neural substrates of impaired finger tapping regularity after stroke.

PubMed

Calautti, Cinzia; Jones, P Simon; Guincestre, Jean-Yves; Naccarato, Marcello; Sharma, Nikhil; Day, Diana J; Carpenter, T Adrian; Warburton, Elizabeth A; Baron, Jean-Claude

2010-03-01

Not only finger tapping speed, but also tapping regularity can be impaired after stroke, contributing to reduced dexterity. The neural substrates of impaired tapping regularity after stroke are unknown. Previous work suggests damage to the dorsal premotor cortex (PMd) and prefrontal cortex (PFCx) affects externally-cued hand movement. We tested the hypothesis that these two areas are involved in impaired post-stroke tapping regularity. In 19 right-handed patients (15 men/4 women; age 45-80 years; purely subcortical in 16) partially to fully recovered from hemiparetic stroke, tri-axial accelerometric quantitative assessment of tapping regularity and BOLD fMRI were obtained during fixed-rate auditory-cued index-thumb tapping, in a single session 10-230 days after stroke. A strong random-effect correlation between tapping regularity index and fMRI signal was found in contralesional PMd such that the worse the regularity the stronger the activation. A significant correlation in the opposite direction was also present within contralesional PFCx. Both correlations were maintained if maximal index tapping speed, degree of paresis and time since stroke were added as potential confounds. Thus, the contralesional PMd and PFCx appear to be involved in the impaired ability of stroke patients to fingertap in pace with external cues. The findings for PMd are consistent with repetitive TMS investigations in stroke suggesting a role for this area in affected-hand movement timing. The inverse relationship with tapping regularity observed for the PFCx and the PMd suggests these two anatomically-connected areas negatively co-operate. These findings have implications for understanding the disruption and reorganization of the motor systems after stroke. Copyright (c) 2009 Elsevier Inc. All rights reserved.

Adhesion Strength Study of EVA Encapsulants on Glass Substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F. J.; Glick, S. H.

2003-05-01

An extensive peel-test study was conducted to investigate the various factors that may affect the adhesion strength of photovoltaic module encapsulants, primarily ethylene-vinyl acetate (EVA), on glass substrates of various laminates based on a common configuration of glass/encapsulant/backfoil. The results show that"pure" or"absolute" adhesion strength of EVA-to-glass was very difficult to obtain because of tensile deformation of the soft, semi-elastic EVA layer upon pulling. A mechanically"strong enough" backing foil on the EVA was critical to achieving the"apparent" adhesion strength. Peel test method with a 90-degree-pull yielded similar results to a 180-degree-pull. The 90-degree-pull method better revealed the four stages ofmore » delamination failure of the EVA/backfoil layers. The adhesion strength is affected by a number of factors, which include EVA type, formulation, backfoil type and manufacturing source, glass type, and surface priming treatment on the glass surface or on the backfoil. Effects of the glass-cleaning method and surface texture are not obvious. Direct priming treatments used in the work did not improve, or even worsened, the adhesion. Aging of EVA by storage over~5 years reduced notably the adhesion strength. Lower adhesion strengths were observed for the blank (unformulated) EVA and non-EVA copolymers, such as poly(ethylene-co-methacrylate) (PEMA) or poly(ethylene-co-butylacrylate) (PEBA). Their adhesion strengths increased if the copolymers were cross-linked. Transparent fluoropolymer superstrates such as TefzelTM and DureflexTM films used for thin-film PV modules showed low adhesion strengths to the EVA at a level of~2 N/mm.« less

High-intensity pulse light sintering of silver nanowire transparent films on polymer substrates: the effect of the thermal properties of substrates on the performance of silver films.

PubMed

Jiu, Jinting; Sugahara, Tohru; Nogi, Masaya; Araki, Teppei; Suganuma, Katsuaki; Uchida, Hiroshi; Shinozaki, Kenji

2013-12-07

Silver nanowire (AgNW) films with a random mesh structure have attracted considerable attention as high-performance flexible transparent electrodes that can replace the expensive and brittle ITO-sputtered films widely used in displays, touch screens, and solar cells. Methods such as heating, pressure treatment, and light treatment are usually used to obtain an optically transparent and electrically conductive film comparable to those of commercial ITO. However, the adhesion between the AgNW film and the substrate is so weak that other overcoatings or extra treatments are necessary. Here, a high-intensity pulsed light (HIPL) sintering technique was developed to rapidly and simply sinter the AgNW film and thus achieve strong adhesion and even high conductivity on these flexible polymer substrates which will be widely applied to the printing of electronic devices. The conductivity of the AgNW film closely depended on the thermal performance of substrates, and the adhesion was determined by the soft state of the substrate surface originating from the glass transition or melting of substrates with light intensity. The rapid sintering technique can be popularized to fabricate new devices on these polymer substrates by considering the thermal properties of the substrate to improve the performance of devices.

Epitaxial Growth and Cracking Mechanisms of Thermally Sprayed Ceramic Splats

NASA Astrophysics Data System (ADS)

Chen, Lin; Yang, Guan-jun

2018-02-01

In the present study, the epitaxial growth and cracking mechanisms of thermally sprayed ceramic splats were explored. We report, for the first time, the epitaxial growth of various splat/substrate combinations at low substrate temperatures (100 °C) and large lattice mismatch (- 11.26%). Our results suggest that thermal spray deposition was essentially a liquid-phase epitaxy, readily forming chemical bonding. The interface temperature was also estimated. The results convincingly demonstrated that atoms only need to diffuse and rearrange over a sufficiently short range during extremely rapid solidification. Concurrently, severe cracking occurred in the epitaxial splat/substrate systems, which indicated high tensile stress was produced during splat deposition. The origin of the tensile stress was attributed to the strong constraint of the locally heated substrate by its cold surroundings.

Heterogeneous reactions of chlorine nitrate and hydrogen chloride on type I polar stratospheric clouds

NASA Technical Reports Server (NTRS)

Leu, Ming-Taun; Moore, Steven B.; Keyser, Leon F.

1991-01-01

A fast-flow reactor coupled with a quadrupole mass spectrometer was used to study the heterogeneous reactions ClONO2 + HCl yields Cl2 + HNO3 (1) and ClONO2 + H2O yields HOCl + HNO3 (2) on vapor-deposited HNO3-H2O ice substrates. It was found that the sticking coefficient of HCl on these substrates was a strong function of the substrate composition, ranging from about 2 x 10 exp -5 at nitric acid trihydrate composition to 6 x 10 exp -3 at 45 wt pct HNO3. The HNO3-H2O ice substrates were found to have large internal surface areas, and corrections for gas-phase diffusion within the porous ices were applied to observed loss rates.

Anaerobic wastewater treatment and membrane filtration: a one night stand or a sustainable relationship?

PubMed

Jeison, D; van Lier, J B

2008-01-01

Several anaerobic membrane bioreactors (AnMBR) were operated, under various conditions, applying different reactor configurations. Applicable fluxes were strongly determined by the physical properties of the sludge present in the reactors. Results show that particle size is a key determining factor for the attainable fluxes. Under thermophilic conditions, small sludge particle size was observed, resulting in low critical fluxes reaching 6-7 L/m2h for the submerged configuration and acidified substrate. In contrast, under mesophilic conditions critical fluxes of 20 L/m2h were obtained. The acidification level also showed a strong effect. Under thermophilic conditions, the presence of a significant fraction of non-acidified organic matter induced the growth of suspended acidogenic biomass that seriously affected the applicable fluxes, both in submerged and side-stream configurations. Under all conditions tested cake formation showed to be the limiting factor determining the applicable fluxes. Only low levels of irreversible fouling were observed. Due to technical and economical considerations, most interesting perspectives for the application of AnMBR are expected with the treatment of high-strength particulate wastewaters, and with extreme wastewaters characterised by high temperature, salinity, etc.

Morphological evolution of thin polymer film on chemically patterned substrates

NASA Astrophysics Data System (ADS)

Singh, Satya Pal

2018-05-01

In this paper work, pattern formation in ultra thin polymer film, adsorbed on chemically patterned substrates, is reported under strong confinement. The observations indicate for the strong influence of the surface attraction over evolution of spindoal waves, leading to the flattening of the film. But, the film appears to be torn apart in strip or nano fiber like structures, because of coalescences of the monomers at the free ends of the chains. The beads at the free ends of the chain are relatively more mobile. The chain diffusion towards attractive part of the chemically patterned surfaces is clearly seen. Prewetting or crystallization like phenomena seems to appear resulting into formation of strips with coexistence of molten phase drops at the top of the ruptured film. The investigation mimics spindoal dewetting because of the fact that the rupturing occurs in case of strong attractive surface. The investigation is of technical importance as it highlights the formation of nano scale strips and fibers though in a quasi equilibrium case.

The effectiveness of strong afterglow phosphor powder in the detection of fingermarks.

PubMed

Liu, Li; Zhang, Zhongliang; Zhang, Limei; Zhai, Yuchun

2009-01-10

There are numerous types of fluorescent fingermark powders or reagents used with the visualization of latent fingermarks deposited on multicolored substrate surfaces that can present a contrast problem if developed with regular fingermark powders. The developed fingermarks can show bright fluorescence upon exposure to laser, ultraviolet light and other light sources. These kinds of methods share a common concern, where surfaces and other substrates may fluoresce also. To overcome this concern, we have developed a phosphor powder which offers a strong afterglow effect which aid in the establishment of better fingermark detection. With the advent of a phosphor powder no special devices are required and the results obtained from fresh or a few days aged latent fingermarks left on: non-porous; semi-porous and also on some porous surfaces have been good. The strong afterglow effect offered by phosphor powder is also applicable for cyanoacrylate fumed fingermarks. Lift off and photography procedures of the developed fingermarks are incorporated in this paper.

Multifunctional epitaxial systems on silicon substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singamaneni, Srinivasa Rao, E-mail: ssingam@ncsu.edu; Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709; Department of Physics, The University of Texas at El Paso, El Paso, Texas 79968

2016-09-15

Multifunctional heterostructures can exhibit a wide range of functional properties, including colossal magneto-resistance, magnetocaloric, and multiferroic behavior, and can display interesting physical phenomena including spin and charge ordering and strong spin-orbit coupling. However, putting this functionality to work remains a challenge. To date, most of the work reported in the literature has dealt with heterostructures deposited onto closely lattice matched insulating substrates such as DyScO{sub 3}, SrTiO{sub 3} (STO), or STO buffered Si(100) using concepts of lattice matching epitaxy (LME). However, strain in heterostructures grown by LME is typically not fully relaxed and the layers contain detrimental defects such asmore » threading dislocations that can significantly degrade the physical properties of the films and adversely affect the device characteristics. In addition, most of the substrates are incompatible with existing CMOS-based technology, where Si (100) substrates dominate. This review discusses recent advances in the integration of multifunctional oxide and non-oxide materials onto silicon substrates. An alternative thin film growth approach, called “domain matching epitaxy,” is presented which identifies approaches for minimizing lattice strain and unwanted defects in large misfit systems (7%–25% and higher). This approach broadly allows for the integration of multifunctional materials onto silicon substrates, such that sensing, computation, and response functions can be combined to produce next generation “smart” devices. In general, pulsed laser deposition has been used to epitaxially grow these materials, although the concepts developed here can be extended to other deposition techniques, as well. It will be shown that TiN and yttria-stabilized zirconia template layers provide promising platforms for the integration of new functionality into silicon-based computer chips. This review paper reports on a number of thin-film heterostructure systems that span a variety of ferroelectric, multiferroic, magnetic, photocatalytic, and smart materials. Their properties have been extensively investigated and their functionality found to be comparable to films grown on single-crystal oxide substrates previously reported by researchers in this field. In addition, this review explores the utility of using laser processing to introduce stable defects in a controlled way and induce magnetism and engineer the optical and electrical properties of nonmagnetic oxides such as BaTiO{sub 3}, VO{sub 2}, NiO, and TiO{sub 2} as an alternative for incorporating additional magnetic and conducting layers into the structure. These significant materials advancements herald a flurry of exciting new advances in CMOS-compatible multifunctional devices.« less

Enzyme architecture: optimization of transition state stabilization from a cation-phosphodianion pair.

PubMed

Reyes, Archie C; Koudelka, Astrid P; Amyes, Tina L; Richard, John P

2015-04-29

The side chain cation of R269 lies at the surface of l-glycerol 3-phosphate dehydrogenase (GPDH) and forms an ion pair to the phosphodianion of substrate dihydroxyacetone phosphate (DHAP), which is buried at the nonpolar protein interior. The R269A mutation of GPDH results in a 110-fold increase in K(m) (2.8 kcal/mol effect) and a 41,000-fold decrease in k(cat) (6.3 kcal/mol effect), which corresponds to a 9.1 kcal/mol destabilization of the transition state for GPDH-catalyzed reduction of DHAP by NADH. There is a 6.7 kcal/mol stabilization of the transition state for the R269A mutant GPDH-catalyzed reaction by 1.0 M guanidinium ion, and the transition state for the reaction of the substrate pieces is stabilized by an additional 2.4 kcal/mol by their covalent attachment at wildtype GPDH. These results provide strong support for the proposal that GPDH invests the 11 kcal/mol intrinsic phosphodianion binding energy of DHAP in trapping the substrate at a nonpolar active site, where strong electrostatic interactions are favored, and obtains a 9 kcal/mol return from stabilizing interactions between the side chain cation and transition state trianion. We propose a wide propagation for the catalytic motif examined in this work, which enables strong transition state stabilization from enzyme-phosphodianion pairs.

Using ALD To Bond CNTs to Substrates and Matrices

NASA Technical Reports Server (NTRS)

Wong, Eric W.; Bronikowski, Michael J.; Kowalczyk, Robert S.

2008-01-01

Atomic-layer deposition (ALD) has been shown to be effective as a means of coating carbon nanotubes (CNTs) with layers of Al2O3 that form strong bonds between the CNTs and the substrates on which the CNTs are grown. ALD is a previously developed vaporphase thin-film-growth technique. ALD differs from conventional chemical vapor deposition, in which material is deposited continually by thermal decomposition of a precursor gas. In ALD, material is deposited one layer of atoms at a time because the deposition process is self-limiting and driven by chemical reactions between the precursor gas and the surface of the substrate or the previously deposited layer.

Dynamics of reflection high-energy electron diffraction intensity oscillations during molecular beam epitaxial growth of GaAs on (111)B GaAs substrates

NASA Astrophysics Data System (ADS)

Yen, M. Y.; Haas, T. W.

1990-06-01

We have observed intensity oscillations in reflection high-energy electron diffraction during molecular beam epitaxial growth of GaAs on (111)B GaAs substrates. These oscillations only exist over a narrow range of growth conditions and their behavior is strongly dependent on the migration kinetics of group III and the molecular dissociative reaction of group V elements.

Improved dot size uniformity and luminescense of InAs quantum dots on InP substrate

NASA Technical Reports Server (NTRS)

Qiu, Y.; Uhl, D.

2002-01-01

InAs self-organized quantum dots have been grown in InGaAs quantum well on InP substrates by metalorganic vapor phase epitaxy. Atomic Force Microscopy confirmed of quantum dot formation with dot density of 3X10(sup 10) cm(sup -2). Improved dot size uniformity and strong room temperature photoluminescence up to 2 micron were observed after modifying the InGaAs well.

Effects of land use, stream habitat, and water quality on biological communities of wadeable streams in the Illinois River Basin of Arkansas, 2011 and 2012

USGS Publications Warehouse

Petersen, James C.; Justus, B.G.; Meredith, Bradley J.

2014-01-01

The Illinois River Basin includes an area of diverse land use in northwestern Arkansas. Land-use data collected in 2006 indicate that most of the land in the basin is agricultural. The agricultural land is used primarily for production of poultry and cattle. Eighteen sites were selected from the list of candidate sites based on drainage area, land use, presence or absence of an upstream wastewater-treatment plant, water quality, and other information gathered during the reconnaissance. An important consideration in the process was to select sites along gradients of forest to urban land use and forest to agricultural land use. Water-quality samples were collected for analysis of nutrients, and a multiparameter field meter was used to measure water temperature, specific conductance, pH, and dissolved oxygen. Streamflow was measured immediately following the water-quality sampling. Macroalgae coverage was estimated and periphyton, macroinvertebrate, and fish communities were sampled at each site. Stream habitat also was assessed. Many types of land-use, water-quality, and habitat factors affected one or more aspects of the biological communities. Several macroinvertebrate and fish metrics changed in response to changes in percent forest; sites that would be considered most disturbed, based on these metrics, are sites with the highest percentages of urban land use in their associated basins. The presence of large mats of macroalgae was one of the most noticeable biological characteristics in several streams within the Illinois River Basin. The highest macroalgae percent cover values were recorded at four sites downstream from wastewater-treatment plants. Macroalgae percent cover was strongly correlated only with bed substrate size, canopy closure, and specific conductance. Periphyton metrics were most often and most strongly correlated with riparian shading, specific conductance, substrate turbidity, percent agriculture, poultry house density, and unpaved road density; some of these factors were strongly correlated with percent forest, percent urban, or percent agriculture. Total biovolume of periphyton was not strongly correlated with any of the land use, habitat, or water-quality factors assessed in the present study. Although algal growth typically increases with higher nutrient concentrations and less shading, the standing crop of periphyton on rocks can be reduced by herbivorous macroinvertebrates and fish, which may explain why total biovolume in Ozark streams was not strongly affected by water-quality (or other habitat) factors. A macroinvertebrate index and several macroinvertebrate metrics were adversely affected by increasing urban and agricultural land use and associated environmental factors. Factors most commonly affecting the index and metrics included factors associated with water quality, stream geometry, sediment, land-use percentages, and road density. In general, the macroinvertebrate index was higher (indicative of least disturbance) at sites with greater percentages of forest in their basins, lower percentages of urban land in their basins, and lower paved road density. Upstream wastewater-treatment plants affected several metrics. For example, three of the five lowest macroinvertebrate index scores, two of the five lowest percent predator values, and two of the five highest percent gatherer-collector values were at sites downstream from wastewater-treatment plants. The Ozark Highlands fish index of biotic integrity and several fish metrics were adversely affected by increasing urban and agricultural land use and associated factors. Factors affecting these metrics included factors associated with nutrients, sediment, and shading. In general, the fish index of biotic integrity was higher at sites with higher percentages of forest in their basins, lower percentages of urban land in their basins, higher unpaved road density, and lower paved and total road density. Upstream wastewater-treatment plants seemed to affect some fish community metrics substantially but had little effect on other metrics. For example, three of the five lowest relative abundances of lithophilic spawner minus stonerollers and four of the five highest stoneroller abundances were at sites downstream from wastewater-treatment plants. Interpretations of the results of the study described in this report are limited by a number of factors. These factors individually and collectively add to uncertainty and variability in the responses to various environmental stresses. Notwithstanding the limiting factors, the biological responses of macroalgae cover and periphyton, macroinvertebrate, and fish metrics to environmental variables provide multiple lines of evidence that biological communities of these streams are affected by recent and ongoing land-use practices. For several biological metrics there appears to be a threshold of about 40 to 50 percent forest where values of these metrics change in magnitude. However, the four sites with more than 50 percent forest in their basins were the four sites sampled in late May–early June of 2012 (rather than July–August of 2011). The relative influence of season and forest percentage on the biological communities at these sites is unknown.

Depth and type of substrate influence the ability of Nasonia vitripennis to locate a host

PubMed Central

Frederickx, Christine; Dekeirsschieter, Jessica; Verheggen, François J.; Haubruge, Eric

2014-01-01

Abstract The foraging behaviour of a parasitoid insect species includes the host’s habitat and subsequent location of the host. Habitats substrate, substrate moisture, and light levels can affect the host searching of different species of parasitoids. However, the depth at which parasitoids concentrate their search effort is another important ecological characteristic and plays an important role in locating a host. Here, we investigated the ability of a pupal parasitoid, Nasonia vitripennis Walker (Hymenoptera: Pteromalidae), to penetrate and kill fly pupae located at different depths of the substrate. Three different types of substrate were tested: loam soil, compost, and vermiculite substrate. In both loam soil and compost, all of the parasitism activity was restricted to pupae placed directly on the surface. Parasitism activity in vermiculite showed that the average number of pupae parasitized decreased with depth of substrate. These results suggest that fly pupae situated deeper in the substrate are less subjected to parasitism by N. vitripennis . PMID:25373205

Photo-Attachment of Biomolecules for Miniaturization on Wicking Si-Nanowire Platform

PubMed Central

Cheng, He; Zheng, Han; Wu, Jia Xin; Xu, Wei; Zhou, Lihan; Leong, Kam Chew; Fitzgerald, Eugene; Rajagopalan, Raj; Too, Heng Phon; Choi, Wee Kiong

2015-01-01

We demonstrated the surface functionalization of a highly three-dimensional, superhydrophilic wicking substrate using light to immobilize functional biomolecules for sensor or microarray applications. We showed here that the three-dimensional substrate was compatible with photo-attachment and the performance of functionalization was greatly improved due to both increased surface capacity and reduced substrate reflectivity. In addition, photo-attachment circumvents the problems induced by wicking effect that was typically encountered on superhydrophilic three-dimensional substrates, thus reducing the difficulty of producing miniaturized sites on such substrate. We have investigated various aspects of photo-attachment process on the nanowire substrate, including the role of different buffers, the effect of wavelength as well as how changing probe structure may affect the functionalization process. We demonstrated that substrate fabrication and functionalization can be achieved with processes compatible with microelectronics processes, hence reducing the cost of array fabrication. Such functionalization method coupled with the high capacity surface makes the substrate an ideal candidate for sensor or microarray for sensitive detection of target analytes. PMID:25689680

Improved field emission properties of carbon nanotubes grown on stainless steel substrate and its application in ionization gauge

NASA Astrophysics Data System (ADS)

Li, Detian; Cheng, Yongjun; Wang, Yongjun; Zhang, Huzhong; Dong, Changkun; Li, Da

2016-03-01

Vertically aligned carbon nanotube (CNT) arrays were fabricated by chemical vapor deposition (CVD) technique on different substrates. Microstructures and field emission characteristics of the as-grown CNT arrays were investigated systematically, and its application in ionization gauge was also evaluated preliminarily. The results indicate that the as-grown CNT arrays are vertically well-aligned relating to the substrate surfaces, but the CNTs grown on stainless steel substrate are longer and more crystalline than the ones grown on silicon wafer substrate. The field emission behaviors of the as-grown CNT arrays are strongly dependent upon substrate properties. Namely, the CNT array grown on stainless steel substrate has better field emission properties, including lower turn on and threshold fields, better emission stability and repeatability, compared with the one grown on silicon wafer substrate. The superior field emission properties of the CNT array grown on stainless steel substrate are mainly attributed to low contact resistance, high thermal conductivity, good adhesion strength, etc. In addition, the metrological behaviors of ionization gauge with the CNT array grown on stainless steel substrate as an electron source were investigated, and this novel cathode ionization gauge extends the lower limit of linear pressure measurement to 10-8 Pa, which is one order of magnitude lower than the result reported for the same of gauge with CNT cathode.

Carbon catabolite repression and cell dispersal affect degradation of the xenobiotic compound 3,4-dichloroaniline in Comamonas testosteroni WDL7 biofilms.

PubMed

Horemans, Benjamin; Breugelmans, Philip; Hofkens, Johan; Springael, Dirk

2017-03-01

Organic pollutant degrading biofilms in natural ecosystems and water treatment systems are often exposed to other carbon sources in addition to the pollutant. The availability of auxiliary carbon sources can lead to surplus biomass growth, changes in biofilm structure and carbon catabolite repression (CCR) which together will affect pollutant degradation rate and efficiency of the system. To understand the interplay between these processes, continuous biofilms of the 3,4-dichloroaniline (3,4-DCA) degrading Comamonas testosteroni WDL7-RFP were grown in single- and dual-substrate conditions with 3,4-DCA and/or citrate and reciprocal effects on 3,4-DCA/citrate degradation, biofilm biomass and biofilm structure were examined. The main mechanism affecting 3,4-DCA degradation in biofilms in dual-substrate conditions was citrate-mediated CCR as reflected by a decrease in specific 3,4-DCA degrading activity. Growth on citrate partially compensated for the lowered specific 3,4-DCA degradation activity under dual substrate conditions but not to the extent expected from growth observed under single-substrate conditions with citrate. This was explained by higher residual 3,4-DCA concentrations in the presence of citrate that increased cell dispersal in the biofilms. Our results show hampered pollutant removal in biofilms due to a complex interplay of auxiliary organic C source utilization for growth affecting the specific pollutant degradation rate and changes in cell physiology due to increased exposure to the pollutant as a result of lowered pollutant degradation rates. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

An Acrobatic Substrate Metamorphosis Reveals a Requirement for Substrate Conformational Dynamics in Trypsin Proteolysis*

PubMed Central

Kayode, Olumide; Wang, Ruiying; Pendlebury, Devon F.; Cohen, Itay; Henin, Rachel D.; Hockla, Alexandra; Soares, Alexei S.; Papo, Niv; Caulfield, Thomas R.; Radisky, Evette S.

2016-01-01

The molecular basis of enzyme catalytic power and specificity derives from dynamic interactions between enzyme and substrate during catalysis. Although considerable effort has been devoted to understanding how conformational dynamics within enzymes affect catalysis, the role of conformational dynamics within protein substrates has not been addressed. Here, we examine the importance of substrate dynamics in the cleavage of Kunitz-bovine pancreatic trypsin inhibitor protease inhibitors by mesotrypsin, finding that the varied conformational dynamics of structurally similar substrates can profoundly impact the rate of catalysis. A 1.4-Å crystal structure of a mesotrypsin-product complex formed with a rapidly cleaved substrate reveals a dramatic conformational change in the substrate upon proteolysis. By using long all-atom molecular dynamics simulations of acyl-enzyme intermediates with proteolysis rates spanning 3 orders of magnitude, we identify global and local dynamic features of substrates on the nanosecond-microsecond time scale that correlate with enzymatic rates and explain differential susceptibility to proteolysis. By integrating multiple enhanced sampling methods for molecular dynamics, we model a viable conformational pathway between substrate-like and product-like states, linking substrate dynamics on the nanosecond-microsecond time scale with large collective substrate motions on the much slower time scale of catalysis. Our findings implicate substrate flexibility as a critical determinant of catalysis. PMID:27810896

Wettability of eutectic NaLiCO3 salt on magnesium oxide substrates at 778 K

NASA Astrophysics Data System (ADS)

Li, Chuan; Li, Qi; Cao, Hui; Leng, Guanghui; Li, Yongliang; Wang, Li; Zheng, Lifang; Ding, Yulong

2018-06-01

We investigated the wetting behavior of a eutectic carbonate salt of NaLiCO3 on MgO substrates at an elevated temperature of 778 K by measuring contact angle with a sessile drop method. Both sintered and non-sintered MgO were prepared and used as the substrates. The sintered substrates were obtained by sintering compacted MgO powders at 500-1300 °C. For comparison purposes, a single crystal MgO substrate was also used in the work. The different sintering temperatures provided MgO substrates with different structures, allowing their effects on salt penetration and hence wettability and surface energy to be investigated. A scanning electron microscope equipped with energy dispersive spectrometry and an atomic force microscope were used to observe the morphology and structures of the MgO substrates as well as the salt penetration. The results showed a good wettability of the carbonate salt on both the sintered and non-sintered MgO substrates and the wettability depended strongly on the structure of the substrates. The non-sintered MgO substrate has a loose surface particle packing with large pores and crevices, leading to significant salt infiltration, and the corresponding contact angle was measured to be ∼25°. The contact angle of the salt on the sintered MgO substrates increased with an increase in the sintering temperature of the MgO substrate, and the contact angle of the salt on the single crystal substrate was the highest at ∼40°. The effect of the sintering temperature for making the MgO substrate could be linked to the surface energy, and the linkage is validated by the AFM measurements of the adhesion forces of the MgO substrates.

STN1 OB Fold Mutation Alters DNA Binding and Affects Selective Aspects of CST Function

PubMed Central

Bhattacharjee, Anukana; Stewart, Jason; Chaiken, Mary; Price, Carolyn M.

2016-01-01

Mammalian CST (CTC1-STN1-TEN1) participates in multiple aspects of telomere replication and genome-wide recovery from replication stress. CST resembles Replication Protein A (RPA) in that it binds ssDNA and STN1 and TEN1 are structurally similar to RPA2 and RPA3. Conservation between CTC1 and RPA1 is less apparent. Currently the mechanism underlying CST action is largely unknown. Here we address CST mechanism by using a DNA-binding mutant, (STN1 OB-fold mutant, STN1-OBM) to examine the relationship between DNA binding and CST function. In vivo, STN1-OBM affects resolution of endogenous replication stress and telomere duplex replication but telomeric C-strand fill-in and new origin firing after exogenous replication stress are unaffected. These selective effects indicate mechanistic differences in CST action during resolution of different replication problems. In vitro binding studies show that STN1 directly engages both short and long ssDNA oligonucleotides, however STN1-OBM preferentially destabilizes binding to short substrates. The finding that STN1-OBM affects binding to only certain substrates starts to explain the in vivo separation of function observed in STN1-OBM expressing cells. CST is expected to engage DNA substrates of varied length and structure as it acts to resolve different replication problems. Since STN1-OBM will alter CST binding to only some of these substrates, the mutant should affect resolution of only a subset of replication problems, as was observed in the STN1-OBM cells. The in vitro studies also provide insight into CST binding mechanism. Like RPA, CST likely contacts DNA via multiple OB folds. However, the importance of STN1 for binding short substrates indicates differences in the architecture of CST and RPA DNA-protein complexes. Based on our results, we propose a dynamic DNA binding model that provides a general mechanism for CST action at diverse forms of replication stress. PMID:27690379

Controlling phase separation in vanadium dioxide thin films via substrate engineering

NASA Astrophysics Data System (ADS)

Gilbert Corder, Stephanie N.; Jiang, Jianjuan; Chen, Xinzhong; Kittiwatanakul, Salinporn; Tung, I.-Cheng; Zhu, Yi; Zhang, Jiawei; Bechtel, Hans A.; Martin, Michael C.; Carr, G. Lawrence; Lu, Jiwei; Wolf, Stuart A.; Wen, Haidan; Tao, Tiger H.; Liu, Mengkun

2017-10-01

The strong electron-lattice interactions in correlated electron systems provide unique opportunities for altering the material properties with relative ease and flexibility. In this Rapid Communication, we use localized strain control via a focused-ion-beam patterning of Ti O2 substrates to demonstrate that one can selectively engineer the insulator-to-metal transition temperature, the fractional component of the insulating and metallic phases, and the degree of optical anisotropy down to the length scales of the intrinsic phase separation in V O2 thin films without altering the quality of the films. The effects of localized strain control on the strongly correlated electron system are directly visualized by state-of-the-art IR near-field imaging and spectroscopy techniques and x-ray microdiffraction measurements.

Controlling phase separation in vanadium dioxide thin films via substrate engineering

DOE PAGES

Gilbert Corder, Stephanie N.; Jiang, Jianjuan; Chen, Xinzhong; ...

2017-10-23

The strong electron-lattice interactions in correlated electron systems provide unique opportunities for altering the material properties with relative ease and flexibility. Here in this Rapid Communication, we use localized strain control via a focused-ion-beam patterning of TiO 2 substrates to demonstrate that one can selectively engineer the insulator-to-metal transition temperature, the fractional component of the insulating and metallic phases, and the degree of optical anisotropy down to the length scales of the intrinsic phase separation in VO 2 thin films without altering the quality of the films. The effects of localized strain control on the strongly correlated electron system aremore » directly visualized by state-of-the-art IR near-field imaging and spectroscopy techniques and x-ray microdiffraction measurements.« less

Tomography of a Probe Potential Using Atomic Sensors on Graphene.

PubMed

Wyrick, Jonathan; Natterer, Fabian D; Zhao, Yue; Watanabe, Kenji; Taniguchi, Takashi; Cullen, William G; Zhitenev, Nikolai B; Stroscio, Joseph A

2016-12-27

Our ability to access and explore the quantum world has been greatly advanced by the power of atomic manipulation and local spectroscopy with scanning tunneling and atomic force microscopes, where the key technique is the use of atomically sharp probe tips to interact with an underlying substrate. Here we employ atomic manipulation to modify and quantify the interaction between the probe and the system under study that can strongly affect any measurement in low charge density systems, such as graphene. We transfer Co atoms from a graphene surface onto a probe tip to change and control the probe's physical structure, enabling us to modify the induced potential at a graphene surface. We utilize single Co atoms on a graphene field-effect device as atomic scale sensors to quantitatively map the modified potential exerted by the scanning probe over the whole relevant spatial and energy range.

Structure, function and folding of phosphoglycerate kinase are strongly perturbed by macromolecular crowding.

NASA Astrophysics Data System (ADS)

Samiotakis, Antonios; Dhar, Apratim; Ebbinghaus, Simon; Nienhaus, Lea; Homouz, Dirar; Gruebele, Martin; Cheung, Margaret

2010-10-01

We combine experiment and computer simulation to show how macromolecular crowding dramatically affects the structure, function and folding landscape of phosphoglycerate kinase (PGK). Fluorescence labeling shows that compact states of yeast PGK are populated as the amount of crowding agents (Ficoll 70) increases. Coarse-grained molecular simulations reveal three compact ensembles: C (crystal structure), CC (collapsed crystal) and Sph (spherical compact). With an adjustment for viscosity, crowded wild type PGK and fluorescent PGK are about 15 times or more active in 200 mg/ml Ficoll than in aqueous solution. Our results suggest a new solution to the classic problem of how the ADP and diphosphoglycerate binding sites of PGK come together to make ATP: rather than undergoing a hinge motion, the ADP and substrate sites are already located in proximity under crowded conditions that mimic the in vivo conditions under which the enzyme actually operates.

In female rat heart mitochondria, oophorectomy results in loss of oxidative phosphorylation.

PubMed

Pavón, Natalia; Cabrera-Orefice, Alfredo; Gallardo-Pérez, Juan Carlos; Uribe-Alvarez, Cristina; Rivero-Segura, Nadia A; Vazquez-Martínez, Edgar Ricardo; Cerbón, Marco; Martínez-Abundis, Eduardo; Torres-Narvaez, Juan Carlos; Martínez-Memije, Raúl; Roldán-Gómez, Francisco-Javier; Uribe-Carvajal, Salvador

2017-02-01

Oophorectomy in adult rats affected cardiac mitochondrial function. Progression of mitochondrial alterations was assessed at one, two and three months after surgery: at one month, very slight changes were observed, which increased at two and three months. Gradual effects included decrease in the rates of oxygen consumption and in respiratory uncoupling in the presence of complex I substrates, as well as compromised Ca 2+ buffering ability. Malondialdehyde concentration increased, whereas the ROS-detoxifying enzyme Mn 2+ superoxide dismutase (MnSOD) and aconitase lost activity. In the mitochondrial respiratory chain, the concentration and activity of complex I and complex IV decreased. Among other mitochondrial enzymes and transporters, adenine nucleotide carrier and glutaminase decreased. 2-Oxoglutarate dehydrogenase and pyruvate dehydrogenase also decreased. Data strongly suggest that in the female rat heart, estrogen depletion leads to progressive, severe mitochondrial dysfunction. © 2017 Society for Endocrinology.

Effect of Palagonite Dust Deposition on the Automated Detection of Carbonate Vis/NIR Spectra

NASA Technical Reports Server (NTRS)

Gilmore, Martha S.; Merrill, Matthew D.; Castano, Rebecca; Bornstein, Benjamin; Greenwood, James

2004-01-01

Currently Mars missions can collect more data than can be returned. Future rovers of increased mission lifetime will benefit from onboard autonomous data processing systems to guide the selection, measurement and return of scientifically important data. One approach is to train a neural net to recognize spectral reflectance characteristics of minerals of interest. We have developed a carbonate detector using a neural net algorithm trained on 10,000 synthetic Vis/NIR (350-2500 nm) spectra. The detector was able to correctly identify carbonates in the spectra of 30 carbonate and noncarbonate field samples with 100% success. However, Martian dust coatings strongly affect the spectral characteristics of surface rocks potentially masking the underlying substrate rock. In this experiment, we measure Vis/NIR spectra of calcite coated with different thicknesses of palagonite dust and evaluate the performance of the carbonate detector.

Advanced Q-switched DPSS lasers for ID-card marking

NASA Astrophysics Data System (ADS)

Hertwig, Michael; Paster, Martin; Terbrueggen, Ralf

2008-02-01

Increased homeland security concerns across the world have generated a strong demand for forgery-proof ID documents. Manufacturers currently employ a variety of high technology techniques to produce documents that are difficult to copy. However, production costs and lead times are still a concern when considering any possible manufacturing technology. Laser marking has already emerged as an important tool in the manufacturer's arsenal, and is currently being utilized to produce a variety of documents, such as plastic ID cards, drivers' licenses, health insurance cards and passports. The marks utilized can range from simple barcodes and text to high resolution, true grayscale images. The technical challenges posed by these marking tasks include delivering adequate mark legibility, minimizing substrate burning or charring, accurately reproducing grayscale data, and supporting the required process throughput. This article covers the advantages and basic requirements on laser marking of cards and reviews how laser output parameters affect marking quality, speed and overall process economics.

The effect of K and Na excess on the ferroelectric and piezoelectric properties of K0.5Na0.5NbO3 thin films

NASA Astrophysics Data System (ADS)

Ahn, C. W.; Y Lee, S.; Lee, H. J.; Ullah, A.; Bae, J. S.; Jeong, E. D.; Choi, J. S.; Park, B. H.; Kim, I. W.

2009-11-01

We have fabricated K0.5Na0.5NbO3 (KNN) thin films on Pt substrates by a chemical solution deposition method and investigated the effect of K and Na excess (0-30 mol%) on ferroelectric and piezoelectric properties of KNN thin film. It was found that with increasing K and Na excess in a precursor solution from 0 to 30 mol%, the leakage current and ferroelectric properties were strongly affected. KNN thin film synthesized by using 20 mol% K and Na excess precursor solution exhibited a low leakage current density and well saturated ferroelectric P-E hysteresis loops. Moreover, the optimized KNN thin film had good fatigue resistance and a piezoelectric constant of 40 pm V-1, which is comparable to that of polycrystalline PZT thin films.

Multiple running speed signals in medial entorhinal cortex

PubMed Central

Hinman, James R.; Brandon, Mark P.; Climer, Jason R.; Chapman, G. William; Hasselmo, Michael E.

2016-01-01

Grid cells in medial entorhinal cortex (MEC) can be modeled using oscillatory interference or attractor dynamic mechanisms that perform path integration, a computation requiring information about running direction and speed. The two classes of computational models often use either an oscillatory frequency or a firing rate that increases as a function of running speed. Yet it is currently not known whether these are two manifestations of the same speed signal or dissociable signals with potentially different anatomical substrates. We examined coding of running speed in MEC and identified these two speed signals to be independent of each other within individual neurons. The medial septum (MS) is strongly linked to locomotor behavior and removal of MS input resulted in strengthening of the firing rate speed signal, while decreasing the strength of the oscillatory speed signal. Thus two speed signals are present in MEC that are differentially affected by disrupted MS input. PMID:27427460

Role of mitochondrial processing peptidase and AAA proteases in processing of the yeast acetohydroxyacid synthase precursor.

PubMed

Dasari, Suvarna; Kölling, Ralf

2016-07-01

We studied presequence processing of the mitochondrial-matrix targeted acetohydroxyacid synthase (Ilv2). C-terminal 3HA-tagging altered the cleavage pattern from a single step to sequential two-step cleavage, giving rise to two Ilv2-3HA forms (A and B). Both cleavage events were dependent on the mitochondrial processing peptidase (MPP). We present evidence for the involvement of three AAA ATPases, m- and i-AAA proteases, and Mcx1, in Ilv2-3HA processing. Both, precursor to A-form and A-form to B-form cleavage were strongly affected in a ∆yme1 mutant. These defects could be suppressed by overexpression of MPP, suggesting that MPP activity is limiting in the ∆yme1 mutant. Our data suggest that for some substrates AAA ATPases could play an active role in the translocation of matrix-targeted proteins.

Mechanism of supercooled droplet freezing on surfaces.

PubMed

Jung, Stefan; Tiwari, Manish K; Doan, N Vuong; Poulikakos, Dimos

2012-01-10

Understanding ice formation from supercooled water on surfaces is a problem of fundamental importance and general utility. Superhydrophobic surfaces promise to have remarkable 'icephobicity' and low ice adhesion. Here we show that their icephobicity can be rendered ineffective by simple changes in environmental conditions. Through experiments, nucleation theory and heat transfer physics, we establish that humidity and/or the flow of a surrounding gas can fundamentally switch the ice crystallization mechanism, drastically affecting surface icephobicity. Evaporative cooling of the supercooled liquid can engender ice crystallization by homogeneous nucleation at the droplet-free surface as opposed to the expected heterogeneous nucleation at the substrate. The related interplay between droplet roll-off and rapid crystallization is also studied. Overall, we bring a novel perspective to icing and icephobicity, unveiling the strong influence of environmental conditions in addition to the accepted effects of the surface conditions and hydrophobicity.

The analysis of ion-selective field-effect transistor operation in chemical sensors

NASA Astrophysics Data System (ADS)

Hotra, Zenon; Holyaka, Roman; Hladun, Michael; Humenuk, Iryna

2003-09-01

In this paper we present the research results of influence of substrate potential in ion-selective field-effect transistors (ISFET) on output signal of chemical sensors, e.g. PH-meters. It is shown that the instability of substrate-source p-n junction bias in well-known chemical sensors, which use grounded reference electrode - ISFET gate, affect on sensor characteristics in negative way. The analytical description and research results of 'substrate effect' on ISFET characteristics are considered.

D-malate production by permeabilized Pseudomonas pseudoalcaligenes; optimization of conversion and biocatalyst productivity.

PubMed

Michielsen, M J; Frielink, C; Wijffels, R H; Tramper, J; Beeftink, H H

2000-04-14

For the development of a continuous process for the production of solid D-malate from a Ca-maleate suspension by permeabilized Pseudomonas pseudoalcaligenes, it is important to understand the effect of appropriate process parameters on the stability and activity of the biocatalyst. Previously, we quantified the effect of product (D-malate2 -) concentration on both the first-order biocatalyst inactivation rate and on the biocatalytic conversion rate. The effects of the remaining process parameters (ionic strength, and substrate and Ca2 + concentration) on biocatalyst activity are reported here. At (common) ionic strengths below 2 M, biocatalyst activity was unaffected. At high substrate concentrations, inhibition occurred. Ca2+ concentration did not affect biocatalyst activity. The kinetic parameters (both for conversion and inactivation) were determined as a function of temperature by fitting the complete kinetic model, featuring substrate inhibition, competitive product inhibition and first-order irreversible biocatalyst inactivation, at different temperatures simultaneously through three extended data sets of substrate concentration versus time. Temperature affected both the conversion and inactivation parameters. The final model was used to calculate the substrate and biocatalyst costs per mmol of product in a continuous system with biocatalyst replenishment and biocatalyst recycling. Despite the effect of temperature on each kinetic parameter separately, the overall effect of temperature on the costs was found to be negligible (between 293 and 308 K). Within pertinent ranges, the sum of the substrate and biocatalyst costs per mmol of product was calculated to decrease with the influent substrate concentration and the residence time. The sum of the costs showed a minimum as a function of the influent biocatalyst concentration.

Spin crossover in Fe(phen)2(NCS)2 complexes on metallic surfaces

NASA Astrophysics Data System (ADS)

Gruber, Manuel; Miyamachi, Toshio; Davesne, Vincent; Bowen, Martin; Boukari, Samy; Wulfhekel, Wulf; Alouani, Mebarek; Beaurepaire, Eric

2017-03-01

In this review, we give an overview on the spin crossover of Fe(phen)2(NCS)2 complexes adsorbed on Cu(100), Cu2N/Cu(100), Cu(111), Co/Cu(111), Co(100), Au(100), and Au(111) surfaces. Depending on the strength of the interaction of the molecules with the substrates, the spin crossover behavior can be drastically changed. Molecules in direct contact with non-magnetic metallic surfaces coexist in both the high- and low-spin states but cannot be switched between the two. Our analysis shows that this is due to a strong interaction with the substrate in the form of a chemisorption that dictates the spin state of the molecules through its adsorption geometry. Upon reducing the interaction to the surface either by adding a second molecular layer or inserting an insulating thin film of Cu2N, the spin crossover behavior is restored and molecules can be switched between the two states with the help of scanning tunneling microscopy. Especially on Cu2N, the two states of single molecules are stable at low temperature and thus allow the realization of a molecular memory. Similarly, the molecules decoupled from metallic substrates in the second or higher layers display thermally driven spin crossover as has been revealed by X-ray absorption spectroscopy. Finally, we discuss the situation when the complex is brought into contact with a ferromagnetic substrate. This leads to a strong exchange coupling between the Fe spin in the high-spin state and the magnetization of the substrate as deduced from spin-polarized scanning tunneling spectroscopy and ab initio calculation.

Effect of ferromagnetic exchange field on band gap and spin polarisation of graphene on a TMD substrate

NASA Astrophysics Data System (ADS)

Goswami, Partha

2018-03-01

We calculate the electronic band dispersion of graphene monolayer on a two-dimensional transition metal dichalcogenide substrate (GrTMD) around K and K^' } points by taking into account the interplay of the ferromagnetic impurities and the substrate-induced interactions. The latter are (strongly enhanced) intrinsic spin-orbit interaction (SOI), the extrinsic Rashba spin-orbit interaction (RSOI) and the one related to the transfer of the electronic charge from graphene to substrate. We introduce exchange field ( M) in the Hamiltonian to take into account the deposition of magnetic impurities on the graphene surface. The cavalcade of the perturbations yield particle-hole symmetric band dispersion with an effective Zeeman field due to the interplay of the substrate-induced interactions with RSOI as the prime player. Our graphical analysis with extremely low-lying states strongly suggests the following: The GrTMDs, such as graphene on WY2, exhibit (direct) band-gap narrowing / widening (Moss-Burstein (MB) gap shift) including the increase in spin polarisation ( P) at low temperature due to the increase in the exchange field ( M) at the Dirac points. The polarisation is found to be electric field tunable as well. Finally, there is anticrossing of non-parabolic bands with opposite spins, the gap closing with same spins, etc. around the Dirac points. A direct electric field control of magnetism at the nanoscale is needed here. The magnetic multiferroics, like BiFeO3 (BFO), are useful for this purpose due to the coupling between the magnetic and electric order parameters.

Development of nanostructured biocompatible materials for chemical and biological sensors

NASA Astrophysics Data System (ADS)

Curley, Michael; Chilvery, Ashwith K.; Kukhatreva, Tatiana; Sharma, Anup; Corda, John; Farley, Carlton

2012-10-01

This research is focused on the fabrication of thin films followed by Surface Enhanced Raman Spectroscopy (SERS) testing of these films for various applications. One technique involves the mixture of nanoparticles with twophoton material to be used as an indicator dye. Another method involved embedding silver nanoparticles in a ceramic nano-membrane. The substrates were characterized by both Atom Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). We applied the nanostructured substrate to measure the SERS spectra of 10-6 Mol/L Rhodomine 6G(Rh6G), e-coli bacteria and RDX explosive. Our results showed that silver coated ceramic membranes can serve as appropriate substrates to enhance Raman signals. In addition, we demonstrated that the in-house-made colloidal silver can work for enhancement of the Raman spectra for bacteria. We measured the Raman spectra of Rh6G molecules on a substrate absorbed by a nanofluid of silver. We observed several strong Raman bands - 613cm-1,768 cm-1,1308cm-1 1356 cm-1,1510cm-1, which correspond to Rh6G vibrational modes υ53,υ65,υ115,υ117,υ146 respectively, using a ceramic membrane coated by silver. The Raman spectra of Rh6G absorbed by silver nanofluid showed strong enhancement of Raman bands 1175cm-1 and 1529cm-1, 1590 cm-1. Those correspond to vibrational frequency modes - υ103,υ151,152. We also measured the Raman spectra of e-coli bacteria, both absorbed by silver nanofluid, and on nanostructured substrate. In addition, the Fourier Transfer Infrared Spectra (FTIR) of the bacteria was measured.

Effect of Preferential Orientation of Lamellae in the Interfacial Region between a Block Copolymer-based Pressure-Sensitive Adhesive and a Solid Substrate on the Peel Strength.

PubMed

Shimokita, Keisuke; Saito, Itsuki; Yamamoto, Katsuhiro; Takenaka, Mikihito; Yamada, Norifumi L; Miyazaki, Tsukasa

2018-02-27

We have investigated the relationship between the peel strength of a block copolymer-based pressure-sensitive adhesive comprising of poly(methyl methacrylate) (PMMA) and poly(n-butyl acrylate) (PnBA) components from the substrate and the microdomain orientations in the interfacial region between the adhesive and the substrate. For the PMMA substrate, the PMMA component in the adhesive with a strong affinity for the substrate is attached to the surface of the substrate during an aging process of the sample at 140 °C. Next, the PMMA layer adjacent to the substrate surface is overlaid with a PnBA layer, which gets covalently connected, resulting in the horizontal alignment of the lamellae in the interfacial region. The peel strength of the adhesive substantially increases during aging at 140 °C, which takes the same time as the completion of the horizontally oriented lamellar structure. However, in the case of the polystyrene (PS) substrate, both the components in the adhesive repel the substrate, leading to the formation of the vertically oriented lamellar structure. As a result, the peel strength of the adhesive with respect to its PS substrate does not entirely increase on aging. It is suggested that the peel strength of the adhesive is highly correlated with the interfacial energy between the adhesive and substrate, which can be estimated from the microdomain orientation in the interfacial region.

Sulfhydryl modification of V449C in the glutamate transporter EAAT1 abolishes substrate transport but not the substrate-gated anion conductance

PubMed Central

Seal, Rebecca P.; Shigeri, Yasushi; Eliasof, Scott; Leighton, Barbara H.; Amara, Susan G.

2001-01-01

Excitatory amino acid transporters (EAATs) buffer and remove synaptically released l-glutamate and maintain its concentrations below neurotoxic levels. EAATs also mediate a thermodynamically uncoupled substrate-gated anion conductance that may modulate cell excitability. Here, we demonstrate that modification of a cysteine substituted within a C-terminal domain of EAAT1 abolishes transport in both the forward and reverse directions without affecting activation of the anion conductance. EC50s for l-glutamate and sodium are significantly lower after modification, consistent with kinetic models of the transport cycle that link anion channel gating to an early step in substrate translocation. Also, decreasing the pH from 7.5 to 6.5 decreases the EC50 for l-glutamate to activate the anion conductance, without affecting the EC50 for the entire transport cycle. These findings demonstrate for the first time a structural separation of transport and the uncoupled anion flux. Moreover, they shed light on some controversial aspects of the EAAT transport cycle, including the kinetics of proton binding and anion conductance activation. PMID:11752470

Substrate stiffness affects skeletal myoblast differentiation in vitro

NASA Astrophysics Data System (ADS)

Romanazzo, Sara; Forte, Giancarlo; Ebara, Mitsuhiro; Uto, Koichiro; Pagliari, Stefania; Aoyagi, Takao; Traversa, Enrico; Taniguchi, Akiyoshi

2012-12-01

To maximize the therapeutic efficacy of cardiac muscle constructs produced by stem cells and tissue engineering protocols, suitable scaffolds should be designed to recapitulate all the characteristics of native muscle and mimic the microenvironment encountered by cells in vivo. Moreover, so not to interfere with cardiac contractility, the scaffold should be deformable enough to withstand muscle contraction. Recently, it was suggested that the mechanical properties of scaffolds can interfere with stem/progenitor cell functions, and thus careful consideration is required when choosing polymers for targeted applications. In this study, cross-linked poly-ɛ-caprolactone membranes having similar chemical composition and controlled stiffness in a supra-physiological range were challenged with two sources of myoblasts to evaluate the suitability of substrates with different stiffness for cell adhesion, proliferation and differentiation. Furthermore, muscle-specific and non-related feeder layers were prepared on stiff surfaces to reveal the contribution of biological and mechanical cues to skeletal muscle progenitor differentiation. We demonstrated that substrate stiffness does affect myogenic differentiation, meaning that softer substrates can promote differentiation and that a muscle-specific feeder layer can improve the degree of maturation in skeletal muscle stem cells.

CONTRASTING BEHAVIOR OF CONFORMATIONALLY LOCKED CARBOCYCLIC NUCLEOSIDES OF ADENOSINE AND CYTIDINE AS SUBSTRATES FOR DEAMINASES

PubMed Central

Schroeder, Gottfried K.; Ludek, Olaf R.; Siddiqui, Maqbool A.; Ezzitouni, Abdallah; Wolfenden, Richard

2010-01-01

In addition to the already known differences between adenosine deaminase (ADA) and cytidine deaminase (CDA) in terms of their tertiary structure, the sphere of Zn+2 coordination, and their reverse stereochemical preference, we present evidence that the enzymes also differ significantly in terms of the North/South conformational preferences for their substrates and the extent to which the lack of the O(4’) oxygen affects the kinetics of the enzymatic deamination of carbocyclic substrates. The carbocyclic nucleoside substrates used in this study have either a flexible cyclopentane ring or a rigid bicyclo[3.1.0]hexane scaffold. PMID:20183605

Modeling linear and cyclic PKS intermediates through atom replacement.

PubMed

Shakya, Gaurav; Rivera, Heriberto; Lee, D John; Jaremko, Matt J; La Clair, James J; Fox, Daniel T; Haushalter, Robert W; Schaub, Andrew J; Bruegger, Joel; Barajas, Jesus F; White, Alexander R; Kaur, Parminder; Gwozdziowski, Emily R; Wong, Fiona; Tsai, Shiou-Chuan; Burkart, Michael D

2014-12-03

The mechanistic details of many polyketide synthases (PKSs) remain elusive due to the instability of transient intermediates that are not accessible via conventional methods. Here we report an atom replacement strategy that enables the rapid preparation of polyketone surrogates by selective atom replacement, thereby providing key substrate mimetics for detailed mechanistic evaluations. Polyketone mimetics are positioned on the actinorhodin acyl carrier protein (actACP) to probe the underpinnings of substrate association upon nascent chain elongation and processivity. Protein NMR is used to visualize substrate interaction with the actACP, where a tetraketide substrate is shown not to bind within the protein, while heptaketide and octaketide substrates show strong association between helix II and IV. To examine the later cyclization stages, we extended this strategy to prepare stabilized cyclic intermediates and evaluate their binding by the actACP. Elongated monocyclic mimics show much longer residence time within actACP than shortened analogs. Taken together, these observations suggest ACP-substrate association occurs both before and after ketoreductase action upon the fully elongated polyketone, indicating a key role played by the ACP within PKS timing and processivity. These atom replacement mimetics offer new tools to study protein and substrate interactions and are applicable to a wide variety of PKSs.

Non-competitive inhibition by active site binders.

PubMed

Blat, Yuval

2010-06-01

Classical enzymology has been used for generations to understand the interactions of inhibitors with their enzyme targets. Enzymology tools enabled prediction of the biological impact of inhibitors as well as the development of novel, more potent, ones. Experiments designed to examine the competition between the tested inhibitor and the enzyme substrate(s) are the tool of choice to identify inhibitors that bind in the active site. Competition between an inhibitor and a substrate is considered a strong evidence for binding of the inhibitor in the active site, while the lack of competition suggests binding to an alternative site. Nevertheless, exceptions to this notion do exist. Active site-binding inhibitors can display non-competitive inhibition patterns. This unusual behavior has been observed with enzymes utilizing an exosite for substrate binding, isomechanism enzymes, enzymes with multiple substrates and/or products and two-step binding inhibitors. In many of these cases, the mechanisms underlying the lack of competition between the substrate and the inhibitor are well understood. Tools like alternative substrates, testing the enzyme reaction in the reverse direction and monitoring inhibition time dependence can be applied to enable distinction between 'badly behaving' active site binders and true exosite inhibitors.

P(VDF/TrFE) morphologies and crystalline lamellae orientations dependence on substrates characterized by scanning probe microscopy

NASA Astrophysics Data System (ADS)

Lakbita, Imane; El-Hami, Khalil

2018-02-01

Ultra-thin films of the polyvinylidene fluoride and trifluoroethylene (P(VDF/TrFE)) copolymer were elaborated on various different substrates by the spin coating method. The purpose of this paper is to study the P(VDF/TrFE) morphologies and crystalline lamellae orientation dependence on substrates. We chose the potassium chloride (KCl), Sodium Chloride (NaCl) and Potassium Bromide (KBr) with the [110] direction and the highly ordered pyrolytic graphite (HOPG) substrates because they present different crystallographic structures. The atomic force microscopy is used for imaging P(VDF/TrFE) morphologies with nanometer resolution and determining the surface roughness. The analysis of the AFM topography images revealed that the P(VDF/TrFE) film has, almost, the same texture on KCl, NaCl or on KBr substrates and their crystalline lamellae had grown in two preferred orientations. Unlike the HOPG substrate, their crystalline lamellae were entangled, randomly oriented and positioned adjacent to each other. The growth texture of the P(VDF/TrFE) copolymer showed experimentally a strong dependence on substrate types. Since the P(VDF/TrFE) is ferroelectric, piezoelectric and pyroelectric, this finding may lead to potential applications.

Cold Gas-Sprayed Deposition of Metallic Coatings onto Ceramic Substrates Using Laser Surface Texturing Pre-treatment

NASA Astrophysics Data System (ADS)

Kromer, R.; Danlos, Y.; Costil, S.

2018-04-01

Cold spraying enables a variety of metals dense coatings onto metal surfaces. Supersonic gas jet accelerates particles which undergo with the substrate plastic deformation. Different bonding mechanisms can be created depending on the materials. The particle-substrate contact time, contact temperature and contact area upon impact are the parameters influencing physicochemical and mechanical bonds. The resultant bonding arose from plastic deformation of the particle and substrate and temperature increasing at the interface. The objective was to create specific topography to enable metallic particle adhesion onto ceramic substrates. Ceramic did not demonstrate deformation during the impact which minimized the intimate bonds. Laser surface texturing was hence used as prior surface treatment to create specific topography and to enable mechanical anchoring. Particle compressive states were necessary to build up coating. The coating deposition efficiency and adhesion strength were evaluated. Textured surface is required to obtain strong adhesion of metallic coatings onto ceramic substrates. Consequently, cold spray coating parameters depend on the target material and a methodology was established with particle parameters (diameters, velocities, temperatures) and particle/substrate properties to adapt the surface topography. Laser surface texturing is a promising tool to increase the cold spraying applications.

Role of substrate in the surface diffusion and kinetic roughening of nanocrystallised nickel electrodeposits

NASA Astrophysics Data System (ADS)

Nzoghe-Mendome, L.; Aloufy, A.; Ebothé, J.; El Messiry, M.; Hui, D.

2009-02-01

The surface growth and roughening of nano-crystallised Ni electrodeposits prepared at the same conditions have been studied on Cu, Au and ITO substrates. The Ni films obtained are characterised by the same face-centred cubic structure with a texture affected by the substrate chemical nature. Practically, the same small-sized grains of 83 nm mean height depicting a statistical mono-mode feature grow on Cu. A three-modal feature corresponding to the biggest and compact crystallites of 335, 368 and 400 nm mean height is obtained with Au. Two typical modes, respectively, linked to isolated big crystallites of 343 nm mean height and large zones of small grains of 170 nm height, result from the ITO effect. The surface transport properties of Ni ad-atoms on each substrate have been studied from the theoretical approach including the film global roughness measured by AFM. It is shown that the ad-atom diffusion coefficients ( D s) ranged in the interval 10 -10-10 -9 cm 2 s -1 are greatly affected by the non-equilibrium conditions of the film formation. Cu and ITO, respectively, lead to Λ s=11.92 and 14.30 nm, while the higher D s value and diffusion length Λ s=37.32 nm are obtained with Au substrate.

Infrared photothermal imaging of trace explosives on relevant substrates

NASA Astrophysics Data System (ADS)

Kendziora, Christopher A.; Furstenberg, Robert; Papantonakis, Michael; Nguyen, Viet; Borchert, James; Byers, Jeff; McGill, R. Andrew

2013-06-01

We are developing a technique for the stand-off detection of trace explosives on relevant substrate surfaces using photo-thermal infrared (IR) imaging spectroscopy (PT-IRIS). This approach leverages one or more compact IR quantum cascade lasers, tuned to strong absorption bands in the analytes and directed to illuminate an area on a surface of interest. An IR focal plane array is used to image the surface and detect small increases in thermal emission upon laser illumination. The PT-IRIS signal is processed as a hyperspectral image cube comprised of spatial, spectral and temporal dimensions as vectors within a detection algorithm. The ability to detect trace analytes on relevant substrates is critical for stand-off applications, but is complicated by the optical and thermal analyte/substrate interactions. This manuscript describes recent PT-IRIS experimental results and analysis for traces of RDX, TNT, ammonium nitrate (AN) and sucrose on relevant substrates (steel, polyethylene, glass and painted steel panels). We demonstrate that these analytes can be detected on these substrates at relevant surface mass loadings (10 μg/cm2 to 100 μg/cm2) even at the single pixel level.

Vapor bridges between solid substrates in the presence of the contact line pinning effect: Stability and capillary force

NASA Astrophysics Data System (ADS)

Liu, Yawei; Zhang, Xianren

2016-12-01

In this work, we focus on investigating how nanobubbles mediate long-range interaction between neighboring solid substrates in the presence of the contact line pinning effect caused by surface heterogeneities. Using the constrained lattice density functional theory (LDFT), we prove that the nanobubbles, which take the form of vapor bridges here, are stabilized by the pinning effect if the separation between two substrates is less than a critical distance. The critical distance strongly depends on the chemical potential (i.e., the degree of saturation) and could become extremely long at a special chemical potential. Moreover, under the pinning effect, the substrate chemistry only determines the stability of the vapor bridges and the range of the capillary force, but has less influences on the magnitude of the capillary force, indicating that the substrate chemistry or the apparent contact angle for droplets or bubbles on the substrates is no longer a direct parameter to determine the magnitude of capillary force. A qualitative analysis for the two dimensional vapor bridges by considering the feedback mechanism can explain the results from the LDFT calculations.

Self-assembled nanospheres with multiple endohedral binding sites pre-organize catalysts and substrates for highly efficient reactions

NASA Astrophysics Data System (ADS)

Wang, Qi-Qiang; Gonell, Sergio; Leenders, Stefan H. A. M.; Dürr, Maximilian; Ivanović-Burmazović, Ivana; Reek, Joost N. H.

2016-03-01

Tuning reagent and catalyst concentrations is crucial in the development of efficient catalytic transformations. In enzyme-catalysed reactions the substrate is bound—often by multiple non-covalent interactions—in a well-defined pocket close to the active site of the enzyme; this pre-organization facilitates highly efficient transformations. Here we report an artificial system that co-encapsulates multiple catalysts and substrates within the confined space defined by an M12L24 nanosphere that contains 24 endohedral guanidinium-binding sites. Cooperative binding means that sulfonate guests are bound much more strongly than carboxylates. This difference has been used to fix gold-based catalysts firmly, with the remaining binding sites left to pre-organize substrates. This strategy was applied to a Au(I)-catalysed cyclization of acetylenic acid to enol lactone in which the pre-organization resulted in much higher reaction rates. We also found that the encapsulated sulfonate-containing Au(I) catalysts did not convert neutral (acid) substrates, and so could have potential in the development of substrate-selective catalysis and base-triggered on/off switching of catalysis.

Unique structural modulation of a non-native substrate by cochaperone DnaJ.

PubMed

Tiwari, Satyam; Kumar, Vignesh; Jayaraj, Gopal Gunanathan; Maiti, Souvik; Mapa, Koyeli

2013-02-12

The role of bacterial DnaJ protein as a cochaperone of DnaK is strongly appreciated. Although DnaJ unaccompanied by DnaK can bind unfolded as well as native substrate proteins, its role as an individual chaperone remains elusive. In this study, we demonstrate that DnaJ binds a model non-native substrate with a low nanomolar dissociation constant and, more importantly, modulates the structure of its non-native state. The structural modulation achieved by DnaJ is different compared to that achieved by the DnaK-DnaJ complex. The nature of structural modulation exerted by DnaJ is suggestive of a unique unfolding activity on the non-native substrate by the chaperone. Furthermore, we demonstrate that the zinc binding motif along with the C-terminal substrate binding domain of DnaJ is necessary and sufficient for binding and the subsequent binding-induced structural alterations of the non-native substrate. We hypothesize that this hitherto unknown structural alteration of non-native states by DnaJ might be important for its chaperoning activity by removing kinetic traps of the folding intermediates.

Loss of an actin crosslinker uncouples cell spreading from cell stiffening on gels with a gradient of stiffness

NASA Astrophysics Data System (ADS)

Wen, Qi; Byfield, Fitzroy J.; Nordstrom, Kerstin; Arratia, Paulo E.; Miller, R. Tyler; Janmey, Paul A.

2009-03-01

We use microfluidics techniques to produce gels with a gradient of stiffness to show the essential function of the actin crosslinker filamin A in cell responses to mechanical stimuli. M2 melanoma cells null for filamin A do not alter their adherent area in response to increased substrate stiffness when they link to the substrate only through collagen receptors, but change adherent area normally when bound through fibronectin receptors. In contrast, filamin A-replete A7 cells change adherent area on both substrates and respond more strongly to collagen 1-coated gels than to fibronectin-coated gels. A7 cells alter their stiffness, as measured by atomic force microscopy, to match the elastic modulus of the substrate immediately adjacent to them on the gradient. M2 cells, in contrast, maintain a constant stiffness on all substrates that is as low as that of A7 cells on the softest gels achievable (1000 Pa). By contrasting the responses of these cell types to different adhesive substrates, cell spreading can be dissociated from stiffening.

Development and characterization of a 3D multicell microtissue culture model of airway smooth muscle.

PubMed

West, Adrian R; Zaman, Nishat; Cole, Darren J; Walker, Matthew J; Legant, Wesley R; Boudou, Thomas; Chen, Christopher S; Favreau, John T; Gaudette, Glenn R; Cowley, Elizabeth A; Maksym, Geoffrey N

2013-01-01

Airway smooth muscle (ASM) cellular and molecular biology is typically studied with single-cell cultures grown on flat 2D substrates. However, cells in vivo exist as part of complex 3D structures, and it is well established in other cell types that altering substrate geometry exerts potent effects on phenotype and function. These factors may be especially relevant to asthma, a disease characterized by structural remodeling of the airway wall, and highlights a need for more physiologically relevant models of ASM function. We utilized a tissue engineering platform known as microfabricated tissue gauges to develop a 3D culture model of ASM featuring arrays of ∼0.4 mm long, ∼350 cell "microtissues" capable of simultaneous contractile force measurement and cell-level microscopy. ASM-only microtissues generated baseline tension, exhibited strong cellular organization, and developed actin stress fibers, but lost structural integrity and dissociated from the cantilevers within 3 days. Addition of 3T3-fibroblasts dramatically improved survival times without affecting tension development or morphology. ASM-3T3 microtissues contracted similarly to ex vivo ASM, exhibiting reproducible responses to a range of contractile and relaxant agents. Compared with 2D cultures, microtissues demonstrated identical responses to acetylcholine and KCl, but not histamine, forskolin, or cytochalasin D, suggesting that contractility is regulated by substrate geometry. Microtissues represent a novel model for studying ASM, incorporating a physiological 3D structure, realistic mechanical environment, coculture of multiple cells types, and comparable contractile properties to existing models. This new model allows for rapid screening of biochemical and mechanical factors to provide insight into ASM dysfunction in asthma.

Detailed characterisation of focused ion beam induced lateral damage on silicon carbide samples by electrical scanning probe microscopy and transmission electron microscopy

NASA Astrophysics Data System (ADS)

Stumpf, F.; Abu Quba, A. A.; Singer, P.; Rumler, M.; Cherkashin, N.; Schamm-Chardon, S.; Cours, R.; Rommel, M.

2018-03-01

The lateral damage induced by focused ion beam on silicon carbide was characterized using electrical scanning probe microscopy (SPM), namely, scanning spreading resistance microscopy and conductive atomic force microscopy (c-AFM). It is shown that the damage exceeds the purposely irradiated circles with a radius of 0.5 μm by several micrometres, up to 8 μm for the maximum applied ion dose of 1018 cm-2. Obtained SPM results are critically compared with earlier findings on silicon. For doses above the amorphization threshold, in both cases, three different areas can be distinguished. The purposely irradiated area exhibits resistances smaller than the non-affected substrate. A second region with strongly increasing resistance and a maximum saturation value surrounds it. The third region shows the transition from maximum resistance to the base resistance of the unaffected substrate. It correlates to the transition from amorphized to defect-rich to pristine crystalline substrate. Additionally, conventional transmission electron microscopy (TEM) and annular dark-field STEM were used to complement and explain the SPM results and get a further understanding of the defect spreading underneath the surface. Those measurements also show three different regions that correlate well with the regions observed from electrical SPM. TEM results further allow to explain observed differences in the electrical results for silicon and silicon carbide which are most prominent for ion doses above 3 × 1016 cm-2. Furthermore, the conventional approach to perform current-voltage measurements by c-AFM was critically reviewed and several improvements for measurement and analysis process were suggested that result in more reliable and impactful c-AFM data.

Transforming a Fructan:Fructan 6G-Fructosyltransferase from Perennial Ryegrass into a Sucrose:Sucrose 1-Fructosyltransferase1[C

PubMed Central

Lasseur, Bertrand; Schroeven, Lindsey; Lammens, Willem; Le Roy, Katrien; Spangenberg, German; Manduzio, Hélène; Vergauwen, Rudy; Lothier, Jérémy; Prud'homme, Marie-Pascale; Van den Ende, Wim

2009-01-01

Fructosyltransferases (FTs) synthesize fructans, fructose polymers accumulating in economically important cool-season grasses and cereals. FTs might be crucial for plant survival under stress conditions in species in which fructans represent the major form of reserve carbohydrate, such as perennial ryegrass (Lolium perenne). Two FT types can be distinguished: those using sucrose (S-type enzymes: sucrose:sucrose 1-fructosyltransferase [1-SST], sucrose:fructan 6-fructosyltransferase) and those using fructans (F-type enzymes: fructan:fructan 1-fructosyltransferase [1-FFT], fructan:fructan 6G-fructosyltransferase [6G-FFT]) as preferential donor substrate. Here, we report, to our knowledge for the first time, the transformation of an F-type enzyme (6G-FFT/1-FFT) into an S-type enzyme (1-SST) using perennial ryegrass 6G-FFT/1-FFT (Lp6G-FFT/1-FFT) and 1-SST (Lp1-SST) as model enzymes. This transformation was accomplished by mutating three amino acids (N340D, W343R, and S415N) in the vicinity of the active site of Lp6G-FFT/1-FFT. In addition, effects of each amino acid mutation alone or in combination have been studied. Our results strongly suggest that the amino acid at position 343 (tryptophan or arginine) can greatly determine the donor substrate characteristics by influencing the position of the amino acid at position 340. Moreover, the presence of arginine-343 negatively affects the formation of neofructan-type linkages. The results are compared with recent findings on donor substrate selectivity within the group of plant cell wall invertases and fructan exohydrolases. Taken together, these insights contribute to our knowledge of structure/function relationships within plant family 32 glycosyl hydrolases and open the way to the production of tailor-made fructans on a larger scale. PMID:18952861

The Use of Bryophytes as Indicators of Hydric Soils and Wetland Hydrology during Wetland Delineations in the United States

DTIC Science & Technology

2010-09-01

wetland delineations generally involves separating plants into layers or strata based on life form: tree, vine , shrub , and herb (USACE 1987). ERDC/CRREL...trunks, roots, and coarse woody debris in many wetland types, including floodplain forests (Muhle and LeBlanc 1975), cypress domes (Carr et al. 2006...depositing woody debris, rock, and sediments. Because many bryophytes exhibit strong preferences for a particular substrate, substrate diversity

An Acrobatic Substrate Metamorphosis Reveals a Requirement for Substrate Conformational Dynamics in Trypsin Proteolysis

DOE PAGES

Kayode, Olumide; Wang, Ruiying; Pendlebury, Devon F.; ...

2016-11-03

The molecular basis of enzyme catalytic power and specificity derives from dynamic interactions between enzyme and substrate during catalysis. While considerable effort has been devoted to understanding how conformational dynamics within enzymes affect catalysis, the role of conformational dynamics within protein substrates has not been addressed. Here in this paper, we examine the importance of substrate dynamics in the cleavage of Kunitz-BPTI protease inhibitors by mesotrypsin, finding that the varied conformational dynamics of structurally similar substrates can profoundly impact the rate of catalysis. A 1.4 Å crystal structure of a mesotrypsin-product complex formed with a rapidly cleaved substrate reveals amore » dramatic conformational change in the substrate upon proteolysis. Using long all-atom molecular dynamics simulations of acyl-enzyme intermediates with proteolysis rates spanning three orders of magnitude, we identify global and local dynamic features of substrates on the ns-μs timescale that correlate with enzymatic rates and explain differential susceptibility to proteolysis. By integrating multiple enhanced sampling methods for molecular dynamics, we model a viable conformational pathway between substratelike and product-like states, linking substrate dynamics on the ns-μs timescale with large collective substrate motions on the much slower timescale of catalysis. Our findings implicate substrate flexibility as a critical determinant of catalysis.« less

A Camelid-derived Antibody Fragment Targeting the Active Site of a Serine Protease Balances between Inhibitor and Substrate Behavior.

PubMed

Kromann-Hansen, Tobias; Oldenburg, Emil; Yung, Kristen Wing Yu; Ghassabeh, Gholamreza H; Muyldermans, Serge; Declerck, Paul J; Huang, Mingdong; Andreasen, Peter A; Ngo, Jacky Chi Ki

2016-07-15

A peptide segment that binds the active site of a serine protease in a substrate-like manner may behave like an inhibitor or a substrate. However, there is sparse information on which factors determine the behavior a particular peptide segment will exhibit. Here, we describe the first x-ray crystal structure of a nanobody in complex with a serine protease. The nanobody displays a new type of interaction between an antibody and a serine protease as it inserts its complementary determining region-H3 loop into the active site of the protease in a substrate-like manner. The unique binding mechanism causes the nanobody to behave as a strong inhibitor as well as a poor substrate. Intriguingly, its substrate behavior is incomplete, as 30-40% of the nanobody remained intact and inhibitory after prolonged incubation with the protease. Biochemical analysis reveals that an intra-loop interaction network within the complementary determining region-H3 of the nanobody balances its inhibitor versus substrate behavior. Collectively, our results unveil molecular factors, which may be a general mechanism to determine the substrate versus inhibitor behavior of other protease inhibitors. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Strain-Dependence of the Structure and Ferroic Properties of Epitaxial NiTiO 3 Thin Films Grown on Different Substrates

DOE PAGES

Varga, Tamas; Droubay, Timothy C.; Bowden, Mark E.; ...

2015-01-01

Polarization-induced weak ferromagnetism has been predicted a few years back in perovskite MTiO 3 (M = Fe, Mn, and Ni). We set out to stabilize this metastable perovskite structure by growing NiTiO 3 epitaxially on different substrates and to investigate the dependence of polar and magnetic properties on strain. Epitaxial NiTiO 3 films were deposited on Al 2 O 3 , Fe 2 O 3 , and LiNbO 3 substrates by pulsed laser deposition and characterized using several techniques. The effect of substrate choice on lattice strain, film structure, and physical properties was investigated. Our structural data from X-ray diffractionmore » and electron microscopy shows that substrate-induced strain has a marked effect on the structure and crystalline quality of the films. Physical property measurements reveal a dependence of the weak ferromagnetism and lattice polarization on strain and highlight our ability to control the ferroic properties in NiTiO 3 thin films by the choice of substrate. Our results are also consistent with the theoretical prediction that the ferromagnetism in acentric NiTiO 3 is polarization induced. From the substrates studied here, the perovskite substrate LiNbO 3 proved to be the most promising one for strong multiferroism.« less

Ovipositional site selection by Anopheles gambiae: influences of substrate moisture and texture.

PubMed

Huang, J; Walker, E D; Giroux, P Y; Vulule, J; Miller, J R

2005-12-01

The influence of substrate moisture (hydration) and grain size (texture) on oviposition was quantified in choice tests using Anopheles gambiae sensu stricto Giles (Diptera: Culicidae) laboratory strains and gravid An. gambiae sensu lato from a natural population in Western Kenya. A strong, positive correlation was found between moisture content and the degree of egg-laying, which peaked at saturation with standing water. Soil moisture quantified as surface conductivity, was measured with an electronic leaf-wetness sensor slightly modified from a unit available commercially. Although An. gambiae females were sensitive to measurable differences in substrate moisture, they distributed eggs on both fully hydrated and less hydrated substrates. In contrast, An. gambiae females showed little response to substrate texture: they oviposited with equal frequency on all silica substrates of eight particle size classes, ranging from small pebbles (850 microm diameter) to very fine grains (< 38 microm diameter), when all were moist. Female An. gambiae laid more eggs on dark than white substrates against a light background, but did not discriminate between moist, pulverized black soapstone and moist black Kenyan soil taken from typical An. gambiae larval habitats. We conclude that hydration and visual contrast are critical ovipositional site qualities for An. gambiae, but substrate texture is not.

Supersonic Love waves in strong piezoelectrics of symmetry mm2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darinskii, A. N.; Weihnacht, M.

A study has been made of the Love wave propagation on piezoelectric substrates of symmetry mm2. It has been shown that under certain conditions the velocity of the Love wave exceeds that of shear horizontal (SH) bulk waves in the substrate. This occurs when the slowness curve of SH bulk waves in the substrate either has a concavity or is convex with nearly zero curvature. For such {open_quotes}supersonic{close_quotes} Love waves to appear, it is also required that the substrate as well as the layer be specially oriented and that their material constants fulfill a number of inequalities. Numerical computations havemore » been carried out for a number of structures. The results of numerical computations have been compared with approximate analytical estimations. {copyright} 2001 American Institute of Physics.« less

Preparation and Raman enhancement properties of gold nanostars

NASA Astrophysics Data System (ADS)

Shan, Feng; Zhang, Tong

2018-03-01

Gold nanostars (GNSs) have a series of sharp tips structures, which will produce strong hot spots and have great application potential in Raman enhancement. In this paper, muti-tip GNSs have been prepared experimentally, and the control techniques of their tip and size have been mastered. For the first time, a fast and efficient self-assembly technique without additives has been developed, and a series of Surface Enhanced Raman Scattering (SERS) substrates have been successfully prepared by using this technique. The effect of different GNSs density of substrates on SERS signal is further studied experimentally. The results show that the SERS signal is closely related to the density of particles in the substrate. The higher density of GNSs in the substrate, the more hot spots covered by the incident light plate, and the greater contribution to the SERS signal.

Specificity of a protein-protein interface: local dynamics direct substrate recognition of effector caspases.

PubMed

Fuchs, Julian E; von Grafenstein, Susanne; Huber, Roland G; Wallnoefer, Hannes G; Liedl, Klaus R

2014-04-01

Proteases are prototypes of multispecific protein-protein interfaces. Proteases recognize and cleave protein and peptide substrates at a well-defined position in a substrate binding groove and a plethora of experimental techniques provide insights into their substrate recognition. We investigate the caspase family of cysteine proteases playing a key role in programmed cell death and inflammation, turning caspases into interesting drug targets. Specific ligand binding to one particular caspase is difficult to achieve, as substrate specificities of caspase isoforms are highly similar. In an effort to rationalize substrate specificity of two closely related caspases, we investigate the substrate promiscuity of the effector Caspases 3 and 7 by data mining (cleavage entropy) and by molecular dynamics simulations. We find a strong correlation between binding site rigidity and substrate readout for individual caspase subpockets explaining more stringent substrate readout of Caspase 7 via its narrower conformational space. Caspase 3 subpockets S3 and S4 show elevated local flexibility explaining the more unspecific substrate readout of that isoform in comparison to Caspase 7. We show by in silico exchange mutations in the S3 pocket of the proteases that a proline residue in Caspase 7 contributes to the narrowed conformational space of the binding site. These findings explain the substrate specificities of caspases via a mechanism of conformational selection and highlight the crucial importance of binding site local dynamics in substrate recognition of proteases. Proteins 2014; 82:546-555. © 2013 Wiley Periodicals, Inc. Copyright © 2013 The Authors Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc.

CRISPR-Cas9 induced mutations along de novo purine synthesis in HeLa cells result in accumulation of individual enzyme substrates and affect purinosome formation.

PubMed

Baresova, Veronika; Krijt, Matyas; Skopova, Vaclava; Souckova, Olga; Kmoch, Stanislav; Zikanova, Marie

2016-11-01

Purines are essential molecules for nucleic acid synthesis and are the most common carriers of chemical energy in all living organisms. The cellular pool of purines is maintained by the balance between their de novo synthesis (DNPS), recycling and degradation. DNPS includes ten reactions catalysed by six enzymes. To date, two genetically determined disorders of DNPS enzymes have been described, and the existence of other defects manifested by neurological symptoms and the accumulation of DNPS intermediates in bodily fluids is highly presumable. In the current study, we prepared specific recombinant DNPS enzymes and used them for the biochemical preparation of their commercially unavailable substrates. These compounds were used as standards for the development and validation of quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS). To simulate manifestations of known and putative defects of DNPS we prepared CRISPR-Cas9 genome-edited HeLa cells deficient for the individual steps of DNPS (CR-cells), assessed the substrates accumulation in cell lysates and growth media and tested how the mutations affect assembly of the purinosome, the multi-enzyme complex of DNPS enzymes. In all model cell lines with the exception of one, an accumulation of the substrate(s) for the knocked out enzyme was identified. The ability to form the purinosome was reduced. We conclude that LC-MS/MS analysis of the dephosphorylated substrates of DNPS enzymes in bodily fluids is applicable in the selective screening of the known and putative DNPS disorders. This approach should be considered in affected individuals with neurological and neuromuscular manifestations of unknown aetiology. Prepared in vitro human model systems can serve in various studies that aim to provide a better characterization and understanding of physiology and pathology of DNPS, to study the role of each DNPS protein in the purinosome formation and represent an interesting way for the screening of potential therapeutic agents. Copyright © 2016 Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kayode, Olumide; Wang, Ruiying; Pendlebury, Devon F.

The molecular basis of enzyme catalytic power and specificity derives from dynamic interactions between enzyme and substrate during catalysis. While considerable effort has been devoted to understanding how conformational dynamics within enzymes affect catalysis, the role of conformational dynamics within protein substrates has not been addressed. Here in this paper, we examine the importance of substrate dynamics in the cleavage of Kunitz-BPTI protease inhibitors by mesotrypsin, finding that the varied conformational dynamics of structurally similar substrates can profoundly impact the rate of catalysis. A 1.4 Å crystal structure of a mesotrypsin-product complex formed with a rapidly cleaved substrate reveals amore » dramatic conformational change in the substrate upon proteolysis. Using long all-atom molecular dynamics simulations of acyl-enzyme intermediates with proteolysis rates spanning three orders of magnitude, we identify global and local dynamic features of substrates on the ns-μs timescale that correlate with enzymatic rates and explain differential susceptibility to proteolysis. By integrating multiple enhanced sampling methods for molecular dynamics, we model a viable conformational pathway between substratelike and product-like states, linking substrate dynamics on the ns-μs timescale with large collective substrate motions on the much slower timescale of catalysis. Our findings implicate substrate flexibility as a critical determinant of catalysis.« less

Superhydrophobic Ag nanostructures on polyaniline membranes with strong SERS enhancement.

PubMed

Liu, Weiyu; Miao, Peng; Xiong, Lu; Du, Yunchen; Han, Xijiang; Xu, Ping

2014-11-07

We demonstrate here a facile fabrication of n-dodecyl mercaptan-modified superhydrophobic Ag nanostructures on polyaniline membranes for molecular detection based on SERS technique, which combines the superhydrophobic condensation effect and the high enhancement factor. It is calculated that the as-fabricated superhydrophobic substrate can exhibit a 21-fold stronger molecular condensation, and thus further amplifies the SERS signal to achieve more sensitive detection. The detection limit of the target molecule, methylene blue (MB), on this superhydrophobic substrate can be 1 order of magnitude higher than that on the hydrophilic substrate. With high reproducibility, the feasibility of using this SERS-active superhydrophobic substrate for quantitative molecular detection is explored. A partial least squares (PLS) model was established for the quantification of MB by SERS, with correlation coefficient R(2) = 95.1% and root-mean-squared error of prediction (RMSEP) = 0.226. We believe this superhydrophobic SERS substrate can be widely used in trace analysis due to its facile fabrication, high signal reproducibility and promising SERS performance.

Determination of long-range scalar (1)H-(1)H coupling constants responsible for polarization transfer in SABRE.

PubMed

Eshuis, Nan; Aspers, Ruud L E G; van Weerdenburg, Bram J A; Feiters, Martin C; Rutjes, Floris P J T; Wijmenga, Sybren S; Tessari, Marco

2016-04-01

SABRE (Signal Amplification By Reversible Exchange) nuclear spin hyperpolarization method can provide strongly enhanced NMR signals as a result of the reversible association of small molecules with para-hydrogen (p-H2) at an iridium metal complex. The conversion of p-H2 singlet order to enhanced substrate proton magnetization within such complex is driven by the scalar coupling interactions between the p-H2 derived hydrides and substrate nuclear spins. In the present study these long-range homonuclear couplings are experimentally determined for several SABRE substrates using an NMR pulse sequence for coherent hyperpolarization transfer at high magnetic field. Pyridine and pyrazine derivatives appear to have a similar ∼1.2 Hz (4)J coupling to p-H2 derived hydrides for their ortho protons, and a much lower (5)J coupling for their meta protons. Interestingly, the (4)J hydride-substrate coupling for five-membered N-heterocyclic substrates is well below 1 Hz. Copyright © 2016 Elsevier Inc. All rights reserved.

Determination of long-range scalar 1H-1H coupling constants responsible for polarization transfer in SABRE

NASA Astrophysics Data System (ADS)

Eshuis, Nan; Aspers, Ruud L. E. G.; van Weerdenburg, Bram J. A.; Feiters, Martin C.; Rutjes, Floris P. J. T.; Wijmenga, Sybren S.; Tessari, Marco

2016-04-01

SABRE (Signal Amplification By Reversible Exchange) nuclear spin hyperpolarization method can provide strongly enhanced NMR signals as a result of the reversible association of small molecules with para-hydrogen (p-H2) at an iridium metal complex. The conversion of p-H2 singlet order to enhanced substrate proton magnetization within such complex is driven by the scalar coupling interactions between the p-H2 derived hydrides and substrate nuclear spins. In the present study these long-range homonuclear couplings are experimentally determined for several SABRE substrates using an NMR pulse sequence for coherent hyperpolarization transfer at high magnetic field. Pyridine and pyrazine derivatives appear to have a similar ∼1.2 Hz 4J coupling to p-H2 derived hydrides for their ortho protons, and a much lower 5J coupling for their meta protons. Interestingly, the 4J hydride-substrate coupling for five-membered N-heterocyclic substrates is well below 1 Hz.

Modifying Surface Fluctuations of Polymer Melt Films with Substrate Modification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yang; He, Qiming; Zhang, Fan

Deposition of a plasma polymerized film on a silicon substrate substantially changes the fluctuations on the surface of a sufficiently thin, melt polystyrene (PS) film atop the substrate. Surface fluctuation relaxation times measured with X-ray photon correlation spectroscopy (XPCS) for ca. 4R g thick melt films of 131 kg/mol linear PS on silicon and on a plasma polymer modified silicon wafer can both be described using a hydrodynamic continuum theory (HCT) that assumes the film is characterized throughout its depth by the bulk viscosity. However, when the film thickness is reduced to ~3R g, confinement effects are evident. The surfacemore » fluctuations are slower than predicted using the HCT, and the confinement effect for the PS on silicon is larger than that for the PS on the plasma polymerized film. This deviation is thus due to a difference in the thicknesses of the strongly adsorbed layers at the substrate which are impacted by the substrate surface energy.« less

Electronic structure of BaO/W cathode surfaces

NASA Technical Reports Server (NTRS)

Muller, Wolfgang

1989-01-01

The local electronic structure of the emissive layer of barium dispenser thermionic cathodes is investigated theoretically using the relativistic scattered-wave approach. The interaction of Ba and O with W, Os, and W-Os alloy surfaces is studied with atomic clusters modeling different absorption environments representative of B- and M-type cathodes. Ba is found to be strongly oxidized, while O and the metal substrate are in a reduced chemical state. The presence of O enhances the surface dipole and Ba binding energy relative to Ba on W. Model results for W-Os alloy substrates show only relatively small changes in Ba and O for identical geometries, but very large charge redistributions inside the substrate, which are attributed to the electronegativity difference between Os and W. If Os is present in the surface layer, the charge transfer from Ba to the substrate and the Ba binding energy increase relative to W. Explanations are offered for the improved electron emission from alloy surfaces and the different emission enhancement for different alloy substrates.

Rational composition control of mixed-lanthanide metal-organic frameworks by an interfacial reaction with metal ion-doped polymer substrates

NASA Astrophysics Data System (ADS)

Tsuruoka, Takaaki; Miyanaga, Ayumi; Ohhashi, Takashi; Hata, Manami; Takashima, Yohei; Akamatsu, Kensuke

2017-09-01

A simple composition control route to mixed-lanthanide metal-organic frameworks (MOFs) was developed based on an interfacial reaction with mixed-lanthanide metal ion-doped polymer substrates. By controlling the composition of lanthanide ion (Eu3+ and Tb3+) dopants in polymer substrates to be used as metal ion precursors and scaffolding for the formation of MOFs, [EuxTb2-x(bdc)3(H2O)4]n crystals with a tunable metal composition could be routinely prepared on polymer substrates. Inductively coupled plasma (ICP) measurements revealed that the composition of the obtained frameworks was almost the same as that of the initial polymer substrates. In addition, the resulting [EuxTb2-x(bdc)3(H2O)4]n crystals showed strong phosphorescence because of Eu3+ transitions, indicating that the energy transfer from Tb3+ to Eu3+ ions in the frameworks could be achieved with high efficiency.

Hydrogen isotope fractionation during lipid biosynthesis by Haloarcula marismortui

NASA Astrophysics Data System (ADS)

Dirghangi, Sitindra S.; Pagani, Mark

2013-10-01

We studied the controls on the fractionation of hydrogen isotopes during lipid biosynthesis by Haloarcula marismortui, a halophilic archaea, in pure culture experiments by varying organic substrate, the hydrogen isotope composition (D/H) of water, temperature, and salinity. Cultures were grown on three substrates: succinate, pyruvate and glycerol with known hydrogen isotope compositions, and in water with different hydrogen isotopic compositions. All culture series grown on a particular substrate show strong correlations between δDarchaeol and δDwater. However, correlations are distinctly different for cultures grown on different substrates. Our results indicate that the metabolic pathway of substrate exerts a fundamental influence on the δD value of lipids, likely by influencing the D/H composition of NADPH (nicotinamide adenine dinucleotide phosphate), the reducing agent that contributes hydrogen to carbon atoms during lipid biosynthesis. Temperature and salinity have smaller, but similar effects on δDlipid, primarily due to the way temperature and salinity influence growth rate, as well as temperature effects on the activity of enzymes.

Modifying Surface Fluctuations of Polymer Melt Films with Substrate Modification

DOE PAGES

Zhou, Yang; He, Qiming; Zhang, Fan; ...

2017-08-14

Deposition of a plasma polymerized film on a silicon substrate substantially changes the fluctuations on the surface of a sufficiently thin, melt polystyrene (PS) film atop the substrate. Surface fluctuation relaxation times measured with X-ray photon correlation spectroscopy (XPCS) for ca. 4R g thick melt films of 131 kg/mol linear PS on silicon and on a plasma polymer modified silicon wafer can both be described using a hydrodynamic continuum theory (HCT) that assumes the film is characterized throughout its depth by the bulk viscosity. However, when the film thickness is reduced to ~3R g, confinement effects are evident. The surfacemore » fluctuations are slower than predicted using the HCT, and the confinement effect for the PS on silicon is larger than that for the PS on the plasma polymerized film. This deviation is thus due to a difference in the thicknesses of the strongly adsorbed layers at the substrate which are impacted by the substrate surface energy.« less

Compositions of Mg and Se, surface morphology, roughness and Raman property of Zn1-xMgxSeyTe1-y layers grown at various substrate temperatures or dopant transport rates by MOVPE

NASA Astrophysics Data System (ADS)

Nishio, Mitsuhiro; Saito, Katsuhiko; Urata, Kensuke; Okamoto, Yasuhiro; Tanaka, Daichi; Araki, Yasuhiro; Abiru, Masakatsu; Mori, Eiichiro; Tanaka, Tooru; Guo, Qixin

2015-03-01

The growth of undoped and phosphorus (P)-doped Zn1-xMgxSeyTe1-y layers on (100) ZnTe substrates by metalorganic vapor phase epitaxy was carried out. The compositions of Mg and Se, surface morphology, roughness and Raman property were characterized as a function of substrate temperature. Not only the compositions of Mg and Se but also the crystal quality of undoped Zn1-xMgxSeyTe1-y layer strongly depended upon the substrate temperature. Furthermore, the growth of Zn1-xMgxSeyTe1-y layer nearly-lattice-matched to ZnTe substrate was achieved independent of the transport rate of trisdimethylaminophosphorus. Undoped Zn1-xMgxSeyTe1-y layer nearly-lattice-matched to ZnTe led to improvement of surface roughness. On the other hand, P doping brought about deterioration of crystalline quality.

Understanding and controlling the substrate effect on graphene electron-transfer chemistry via reactivity imprint lithography

NASA Astrophysics Data System (ADS)

Wang, Qing Hua; Jin, Zhong; Kim, Ki Kang; Hilmer, Andrew J.; Paulus, Geraldine L. C.; Shih, Chih-Jen; Ham, Moon-Ho; Sanchez-Yamagishi, Javier D.; Watanabe, Kenji; Taniguchi, Takashi; Kong, Jing; Jarillo-Herrero, Pablo; Strano, Michael S.

2012-09-01

Graphene has exceptional electronic, optical, mechanical and thermal properties, which provide it with great potential for use in electronic, optoelectronic and sensing applications. The chemical functionalization of graphene has been investigated with a view to controlling its electronic properties and interactions with other materials. Covalent modification of graphene by organic diazonium salts has been used to achieve these goals, but because graphene comprises only a single atomic layer, it is strongly influenced by the underlying substrate. Here, we show a stark difference in the rate of electron-transfer reactions with organic diazonium salts for monolayer graphene supported on a variety of substrates. Reactions proceed rapidly for graphene supported on SiO2 and Al2O3 (sapphire), but negligibly on alkyl-terminated and hexagonal boron nitride (hBN) surfaces, as shown by Raman spectroscopy. We also develop a model of reactivity based on substrate-induced electron-hole puddles in graphene, and achieve spatial patterning of chemical reactions in graphene by patterning the substrate.

Fast assembling microarrays of superparamagnetic Fe3O4@Au nanoparticle clusters as reproducible substrates for surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Ye, Min; Wei, Zewen; Hu, Fei; Wang, Jianxin; Ge, Guanglu; Hu, Zhiyuan; Shao, Mingwang; Lee, Shuit-Tong; Liu, Jian

2015-08-01

It is currently a very active research area to develop new types of substrates which integrate various nanomaterials for surface-enhanced Raman scattering (SERS) techniques. Here we report a unique approach to prepare SERS substrates with reproducible performance. It features silicon mold-assisted magnetic assembling of superparamagnetic Fe3O4@Au nanoparticle clusters (NCs) into arrayed microstructures on a wafer scale. This approach enables the fabrication of both silicon-based and hydrogel-based substrates in a sequential manner. We have demonstrated that strong SERS signals can be harvested from these substrates due to an efficient coupling effect between Fe3O4@Au NCs, with enhancement factors >106. These substrates have been confirmed to provide reproducible SERS signals, with low variations in different locations or batches of samples. We investigate the spatial distributions of electromagnetic field enhancement around Fe3O4@Au NCs assemblies using finite-difference-time-domain (FDTD) simulations. The procedure to prepare the substrates is straightforward and fast. The silicon mold can be easily cleaned out and refilled with Fe3O4@Au NCs assisted by a magnet, therefore being re-useable for many cycles. Our approach has integrated microarray technologies and provided a platform for thousands of independently addressable SERS detection, in order to meet the requirements of a rapid, robust, and high throughput performance.It is currently a very active research area to develop new types of substrates which integrate various nanomaterials for surface-enhanced Raman scattering (SERS) techniques. Here we report a unique approach to prepare SERS substrates with reproducible performance. It features silicon mold-assisted magnetic assembling of superparamagnetic Fe3O4@Au nanoparticle clusters (NCs) into arrayed microstructures on a wafer scale. This approach enables the fabrication of both silicon-based and hydrogel-based substrates in a sequential manner. We have demonstrated that strong SERS signals can be harvested from these substrates due to an efficient coupling effect between Fe3O4@Au NCs, with enhancement factors >106. These substrates have been confirmed to provide reproducible SERS signals, with low variations in different locations or batches of samples. We investigate the spatial distributions of electromagnetic field enhancement around Fe3O4@Au NCs assemblies using finite-difference-time-domain (FDTD) simulations. The procedure to prepare the substrates is straightforward and fast. The silicon mold can be easily cleaned out and refilled with Fe3O4@Au NCs assisted by a magnet, therefore being re-useable for many cycles. Our approach has integrated microarray technologies and provided a platform for thousands of independently addressable SERS detection, in order to meet the requirements of a rapid, robust, and high throughput performance. Electronic supplementary information (ESI) available: XRD, reflection spectra, zeta potential, TEM images, evaluations of reproducibility, EDS, tables of EF and RSD values of different substrates. See DOI: 10.1039/c5nr02491a

Processing Conditions Affecting Grain Size and Mechanical Properties in Nanocomposites Produced via Cold Spray

NASA Astrophysics Data System (ADS)

Cavaliere, P.; Perrone, A.; Silvello, A.

2014-10-01

Cold spray is a coating technology based on aerodynamics and high-speed impact dynamics. In this process, spray particles (usually 1-50 μm in diameter) are accelerated to a high velocity (typically 300-1200 m/s) by a high-speed gas (pre-heated air, nitrogen, or helium) flow that is generated through a convergent-divergent de Laval-type nozzle. A coating is formed through the intensive plastic deformation of particles impacting on a substrate at a temperature below the melting point of the spray material. In the present paper the main processing parameters affecting the microstructural and mechanical behavior of metal-metal cold spray deposits are described. The effect of process parameters on grain refinement and mechanical properties were analyzed for composite particles of Al-Al2O3, Ni-BN, Cu-Al2O3, and Co-SiC. The properties of the formed nanocomposites were compared with those of the parent materials sprayed under the same conditions. The process conditions, leading to a strong grain refinement with an acceptable level of the deposit mechanical properties such as porosity and adhesion strength, are discussed.

In vitro effects of household products on Calliphoridae larvae development: implication for forensic entomology.

PubMed

Aubernon, Cindy; Devigne, Cedric; Hedouin, Valery; Gosset, Didier; Charabidze, Damien

2015-01-01

Several parameters can delay the first arrival of flies on a corpse and the subsequent development of the larvae. This study focuses on the development of Lucilia sericata (Diptera: Calliphoridae) (Meigen, 1826) on household chemical-contaminated substrates. bleach, perfume, hydrochloric acid, caustic soda, insecticide, mosquito repellent, and gasoline in quantities consistent with an amount that could possibly be spilled on a corpse were mixed with beef liver to simulate contaminated fleshes. Larvae were bred at 25 °C on these media until emergence. Four developmental parameters were followed: survival rates, development times, sex ratios, and adult sizes. Hydrochloric acid, insecticide, and gasoline killed all larvae. In low quantities, caustic soda and mosquito repellent increased the development time and decreased the adult size. However, high quantities of these chemicals killed all larvae. Lastly, bleach and perfume did not affect the survival rate and barely impacted the development time or adult size. These results demonstrate common household products spilled on a corpse can strongly affect the development of Calliphoridae larvae. The effects of such products should be considered in forensic entomology cases. © 2014 American Academy of Forensic Sciences.

Synthesis of Graphene Based Membranes: Effect of Substrate Surface Properties on Monolayer Graphene Transfer.

PubMed

Kafiah, Feras; Khan, Zafarullah; Ibrahim, Ahmed; Atieh, Muataz; Laoui, Tahar

2017-01-21

In this work, we report the transfer of graphene onto eight commercial microfiltration substrates having different pore sizes and surface characteristics. Monolayer graphene grown on copper by the chemical vapor deposition (CVD) process was transferred by the pressing method over the target substrates, followed by wet etching of copper to obtain monolayer graphene/polymer membranes. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) measurements were carried out to explore the graphene layer transferability. Three factors, namely, the substrate roughness, its pore size, and its surface wetting (degree of hydrophobicity) are found to affect the conformality and coverage of the transferred graphene monolayer on the substrate surface. A good quality graphene transfer is achieved on the substrate with the following characteristics; being hydrophobic (CA > 90°), having small pore size, and low surface roughness, with a CA to RMS (root mean square) ratio higher than 2.7°/nm.

c-Myc Alters Substrate Utilization and O-GlcNAc Protein Posttranslational Modifications without Altering Cardiac Function during Early Aortic Constriction

PubMed Central

Ledee, Dolena; Smith, Lincoln; Bruce, Margaret; Kajimoto, Masaki; Isern, Nancy; Portman, Michael A.; Olson, Aaron K.

2015-01-01

Hypertrophic stimuli cause transcription of the proto-oncogene c-Myc (Myc). Prior work showed that myocardial knockout of c-Myc (Myc) attenuated hypertrophy and decreased expression of metabolic genes after aortic constriction. Accordingly, we assessed the interplay between Myc, substrate oxidation and cardiac function during early pressure overload hypertrophy. Mice with cardiac specific, inducible Myc knockout (MycKO-TAC) and non-transgenic littermates (Cont-TAC) were subjected to transverse aortic constriction (TAC; n = 7/group). Additional groups underwent sham surgery (Cont-Sham and MycKO-Sham, n = 5 per group). After two weeks, function was measured in isolated working hearts along with substrate fractional contributions to the citric acid cycle by using perfusate with 13C labeled mixed fatty acids, lactate, ketone bodies and unlabeled glucose and insulin. Cardiac function was similar between groups after TAC although +dP/dT and -dP/dT trended towards improvement in MycKO-TAC versus Cont-TAC. In sham hearts, Myc knockout did not affect cardiac function or substrate preferences for the citric acid cycle. However, Myc knockout altered fractional contributions during TAC. The unlabeled fractional contribution increased in MycKO-TAC versus Cont-TAC, whereas ketone and free fatty acid fractional contributions decreased. Additionally, protein posttranslational modifications by O-GlcNAc were significantly greater in Cont-TAC versus both Cont-Sham and MycKO-TAC. In conclusion, Myc alters substrate preferences for the citric acid cycle during early pressure overload hypertrophy without negatively affecting cardiac function. Myc also affects protein posttranslational modifications by O-GlcNAc during hypertrophy, which may regulate Myc-induced metabolic changes. PMID:26266538

Broadly tunable terahertz difference-frequency generation in quantum cascade lasers on silicon

NASA Astrophysics Data System (ADS)

Jung, Seungyong; Kim, Jae Hyun; Jiang, Yifan; Vijayraghavan, Karun; Belkin, Mikhail A.

2018-01-01

We report broadly tunable terahertz (THz) sources based on intracavity Cherenkov difference-frequency generation in quantum cascade lasers transfer-printed on high-resistivity silicon substrates. Spectral tuning from 1.3 to 4.3 THz was obtained from a 2-mm long laser chip using a modified Littrow external cavity setup. The THz power output and the midinfrared-to-THz conversion efficiency of the devices transferred on silicon are dramatically enhanced, compared with the devices on a native semi-insulating InP substrate. Enhancement is particularly significant at higher THz frequencies, where the tail of the Reststrahlen band results in a strong absorption of THz light in the InP substrate.

Enhanced transparency, mechanical durability, and antibacterial activity of zinc nanoparticles on glass substrate

PubMed Central

Choi, Hyung-Jin; Choi, Jin-Seok; Park, Byeong-Ju; Eom, Ji-Ho; Heo, So-Young; Jung, Min-Wook; An, Ki-Seok; Yoon, Soon-Gil

2014-01-01

Homogeneously distributed zinc nanoparticles (NPs) on the glass substrate were investigated for the transmittance, mechanical durability, and antibacterial effect. The buffered Ti NPs between Zn NPs and glass substrate were studied for an enhancement of the transmittance and mechanical endurance. The Ti NPs buffered Zn NPs showed a high transmittance of approximately 91.5% (at a wavelength of 550 nm) and a strong antibacterial activity for Staphylococcus aureus and Escherichia coli bacteria. The buffered Ti NPs are attractive for an excellent mechanical endurance of the Zn NPs. The Zn NPs did not require the protection layer to prevent the degradation of the performance for both the antibacterial effect and the transmittance. PMID:25183360

A nanoforest structure for practical surface-enhanced Raman scattering substrates

NASA Astrophysics Data System (ADS)

Seol, Myeong-Lok; Choi, Sung-Jin; Baek, David J.; Park, Tae Jung; Ahn, Jae-Hyuk; Lee, Sang Yup; Choi, Yang-Kyu

2012-03-01

A nanoforest structure for surface-enhanced Raman scattering (SERS) active substrates is fabricated and analyzed. The detailed morphology of the resulting structure can be easily controlled by modifying the process parameters such as initial gold layer thickness and etching time. The applicability of the nanoforest substrate as a label-free SERS immunosensor is demonstrated using influenza A virus subtype H1N1. Selective binding of the H1N1 surface antigen and the anti-H1 antibody is directly detected by the SERS signal differences. Simple fabrication and high throughput with strong in-plane hot-spots imply that the nanoforest structure can be a practical sensing component of a chip-based SERS sensing system.

The effect of grooves in amorphous substrates on the orientation of metal deposits. I - Carbon substrates

NASA Technical Reports Server (NTRS)

Anton, R.; Poppa, H.; Flanders, D. C.

1982-01-01

The graphoepitaxial alignment of vapor-deposited discrete metal crystallites is investigated in the nucleation and growth stages and during annealing by in situ UHV/TEM techniques. Various stages of nucleation, growth and coalescence of vapor deposits of Au, Ag, Pb, Sn, and Bi on amorphous, topographically structured C substrates are analyzed by advanced dark-field techniques to detect preferred local orientations. It is found that the topography-induced orientation of metal crystallites depends strongly on their mobility and their respective tendency to develop pronounced crystallographic shapes. Lowering of the average surface free energies and increasing the crystallographic surface energy anisotropies cause generally improved graphoepitaxial alignments.

water-soluble fluorocarbon coating

NASA Technical Reports Server (NTRS)

Nanelli, P.

1979-01-01

Water-soluble fluorocarbon proves durable nonpolluting coating for variety of substrates. Coatings can be used on metals, masonry, textiles, paper, and glass, and have superior hardness and flexibility, strong resistance to chemicals fire, and weather.

Conducting LaAlO3/SrTiO3 heterointerfaces on atomically-flat substrates prepared by deionized-water

PubMed Central

Connell, J. G.; Nichols, J.; Gruenewald, J. H.; Kim, D.-W.; Seo, S. S. A.

2016-01-01

We have investigated how the recently-developed water-leaching method for atomically-flat SrTiO3 (STO) substrates affects the transport properties of LaAlO3 (LAO) and STO heterointerfaces. Using pulsed laser deposition at identical growth conditions, we have synthesized epitaxial LAO thin-films on two different STO substrates, which are prepared by water-leaching and buffered hydrofluoric acid (BHF) etching methods. The structural, transport, and optical properties of LAO/STO heterostructures grown on water-leached substrates show the same high-quality as the samples grown on BHF-etched substrates. These results indicate that the water-leaching method can be used to grow complex oxide heterostructures with atomically well-defined heterointerfaces without safety concerns. PMID:27033248

Iron films deposited on porous alumina substrates

NASA Astrophysics Data System (ADS)

Yamada, Yasuhiro; Tanabe, Kenichi; Nishida, Naoki; Kobayashi, Yoshio

2016-12-01

Iron films were deposited on porous alumina substrates using an arc plasma gun. The pore sizes (120 - 250 nm) of the substrates were controlled by changing the temperature during the anodic oxidation of aluminum plates. Iron atoms penetrated into pores with diameters of less than 160 nm, and were stabilized by forming γ-Fe, whereas α-Fe was produced as a flat plane covering the pores. For porous alumina substrates with pore sizes larger than 200 nm, the deposited iron films contained many defects and the resulting α-Fe had smaller hyperfine magnetic fields. In addition, only a very small amount of γ-Fe was obtained. It was demonstrated that the composition and structure of an iron film can be affected by the surface morphology of the porous alumina substrate on which the film is grown.

Affective neural response to restricted interests in Autism Spectrum Disorders

PubMed Central

Cascio, Carissa J.; Foss-Feig, Jennifer H.; Heacock, Jessica; Schauder, Kimberly B.; Loring, Whitney A.; Rogers, Baxter P.; Pryweller, Jennifer R.; Newsom, Cassandra R.; Cockhren, Jurnell; Cao, Aize; Bolton, Scott

2013-01-01

Background Restricted interests are a class of repetitive behavior in autism spectrum disorders (ASD) whose intensity and narrow focus often contribute to significant interference with daily functioning. While numerous neuroimaging studies have investigated executive circuits as putative neural substrates of repetitive behavior, recent work implicates affective neural circuits in restricted interests. We sought to explore the role of affective neural circuits and determine how restricted interests are distinguished from hobbies or interests in typical development. Methods We compared a group of children with ASD to a typically developing (TD) group of children with strong interests or hobbies, employing parent report, an operant behavioral task, and functional imaging with personalized stimuli based on individual interests. Results While performance on the operant task was similar between the two groups, parent report of intensity and interference of interests was significantly higher in the ASD group. Both the ASD and TD groups showed increased BOLD response in widespread affective neural regions to pictures of their own interest. When viewing pictures of other children's interests, the TD group showed a similar pattern, whereas BOLD response in the ASD group was much more limited. Increased BOLD response in the insula and anterior cingulate cortex distinguished the ASD from the TD group, and parent report of the intensity and interference with daily life of the child's restricted interest predicted insula response. Conclusions While affective neural network response and operant behavior are comparable in typical and restricted interests, the narrowness of focus that clinically distinguishes restricted interests in ASD is reflected in more interference in daily life and aberrantly enhanced insula and anterior cingulate response to individuals’ own interests in the ASD group. These results further support the involvement of affective neural networks in repetitive behaviors in ASD. PMID:24117668

Effect of Substrate Roughness on Adhesion and Structural Properties of Ti-Ni Shape Memory Alloy Thin Film.

PubMed

Kim, Donghwan; Lee, Hyunsuk; Bae, Joohyeon; Jeong, Hyomin; Choi, Byeongkeun; Nam, Taehyun; Noh, Jungpil

2018-09-01

Ti-Ni shape memory alloy (SMA) thin films are very attractive material for industrial and medical applications such as micro-actuator, micro-sensors, and stents for blood vessels. An important property besides shape memory effect in the application of SMA thin films is the adhesion between the film and the substrate. When using thin films as micro-actuators or micro-sensors in MEMS, the film must be strongly adhered to the substrate. On the other hand, when using SMA thin films in medical devices such as stents, the deposited alloy thin film must be easily separable from the substrate for efficient processing. In this study, we investigated the effect of substrate roughness on the adhesion of Ti-Ni SMA thin films, as well as the structural properties and phase-transformation behavior of the fabricated films. Ti-Ni SMA thin films were deposited onto etched glass substrates with magnetron sputtering. Radio frequency plasma was used for etching the substrate. The adhesion properties were investigated through progressive scratch test. Structural properties of the films were determined via Feld emission scanning electron microscopy, X-ray diffraction measurements (XRD) and Energy-dispersive X-ray spectroscopy analysis. Phase transformation behaviors were observed with differential scanning calorimetry and low temperature-XRD. Ti-Ni SMA thin film deposited onto rough substrate provides higher adhesive strength than smooth substrate. However the roughness of the substrate has no influence on the growth and crystallization of the Ti-Ni SMA thin films.

An Acrobatic Substrate Metamorphosis Reveals a Requirement for Substrate Conformational Dynamics in Trypsin Proteolysis.

PubMed

Kayode, Olumide; Wang, Ruiying; Pendlebury, Devon F; Cohen, Itay; Henin, Rachel D; Hockla, Alexandra; Soares, Alexei S; Papo, Niv; Caulfield, Thomas R; Radisky, Evette S

2016-12-16

The molecular basis of enzyme catalytic power and specificity derives from dynamic interactions between enzyme and substrate during catalysis. Although considerable effort has been devoted to understanding how conformational dynamics within enzymes affect catalysis, the role of conformational dynamics within protein substrates has not been addressed. Here, we examine the importance of substrate dynamics in the cleavage of Kunitz-bovine pancreatic trypsin inhibitor protease inhibitors by mesotrypsin, finding that the varied conformational dynamics of structurally similar substrates can profoundly impact the rate of catalysis. A 1.4-Å crystal structure of a mesotrypsin-product complex formed with a rapidly cleaved substrate reveals a dramatic conformational change in the substrate upon proteolysis. By using long all-atom molecular dynamics simulations of acyl-enzyme intermediates with proteolysis rates spanning 3 orders of magnitude, we identify global and local dynamic features of substrates on the nanosecond-microsecond time scale that correlate with enzymatic rates and explain differential susceptibility to proteolysis. By integrating multiple enhanced sampling methods for molecular dynamics, we model a viable conformational pathway between substrate-like and product-like states, linking substrate dynamics on the nanosecond-microsecond time scale with large collective substrate motions on the much slower time scale of catalysis. Our findings implicate substrate flexibility as a critical determinant of catalysis. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Japan Report, Science and Technology.

DTIC Science & Technology

1987-05-06

Figure 17. Microcapsule Type Enzyme Immobilized Membrane Such metabolites as creatinine, uric acid , and vitamin B12 are relatively easily adsorbed by...WEST EUROPE ivory AFRICA (SUB-SAHARA) tan SCIENCE $ TECHNOLOGY gray WORLDWIDES pewter The changes that are of interest to readers of this report...condition and that they are unstable in strong acids , strong bases, organic solvents, and heat. Ordinarily, an enzyme docks with a substrate in an

[Is there a "biology of violence"?].

PubMed

Karli, Pierre

2004-01-01

Human violence does not stem from any specific biological substrate. As affective processes play a pre-eminent role in the elaboration and evolution of social interactions, a "biology of violence" draws essentially upon the concepts, methods and techniques of "affective neuroscience".

Magnetic Dirac Fermions and Chern Insulator Supported on Pristine Silicon Surface

NASA Astrophysics Data System (ADS)

Fu, Huixia; Liu, Zheng; Sun, Jia-Tao; Meng, Sheng

Emergence of ferromagnetism in non-magnetic semiconductors is strongly desirable, especially in topological materials thanks to the possibility to achieve quantum anomalous Hall effect. Based on first principles calculations, we propose that for Si thin film grown on metal substrate, the pristine Si(111)-r3xr3 surface with a spontaneous weak reconstruction has a strong tendency of ferromagnetism and nontrivial topological properties, characterized by spin polarized Dirac-fermion surface states. In contrast to conventional routes relying on introduction of alien charge carriers or specially patterned substrates, the spontaneous magnetic order and spin-orbit coupling on the pristine silicon surface together gives rise to quantized anomalous Hall effect with a finite Chern number C = -1. This work suggests exciting opportunities in silicon-based spintronics and quantum computing free from alien dopants or proximity effects.

Compensation of strong thermal lensing in high-optical-power cavities.

PubMed

Zhao, C; Degallaix, J; Ju, L; Fan, Y; Blair, D G; Slagmolen, B J J; Gray, M B; Lowry, C M Mow; McClelland, D E; Hosken, D J; Mudge, D; Brooks, A; Munch, J; Veitch, P J; Barton, M A; Billingsley, G

2006-06-16

In an experiment to simulate the conditions in high optical power advanced gravitational wave detectors, we show for the first time that the time evolution of strong thermal lenses follows the predicted infinite sum of exponentials (approximated by a double exponential), and that such lenses can be compensated using an intracavity compensation plate heated on its cylindrical surface. We show that high finesse approximately 1400 can be achieved in cavities with internal compensation plates, and that mode matching can be maintained. The experiment achieves a wave front distortion similar to that expected for the input test mass substrate in the Advanced Laser Interferometer Gravitational Wave Observatory, and shows that thermal compensation schemes are viable. It is also shown that the measurements allow a direct measurement of substrate optical absorption in the test mass and the compensation plate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usanov, D. A., E-mail: UsanovDA@info.sgu.ru; Nikitov, S. A.; Skripal, A. V.

A method is proposed for the measurement of the electrophysical characteristics of semiconductor structures: the electrical conductivity of the n layer, which plays the role of substrate for a semiconductor structure, and the thickness and electrical conductivity of the strongly doped epitaxial n{sup +} layer. The method is based on the use of a one-dimensional microwave photonic crystal with a violation of periodicity containing the semiconductor structure under investigation. The characteristics of epitaxial gallium-arsenide structures consisting of an epitaxial layer and the semi-insulating substrate measured by this method are presented.

From immobilized cells to motile cells on a bed-of-nails: effects of vertical nanowire array density on cell behaviour

PubMed Central

Persson, Henrik; Li, Zhen; Tegenfeldt, Jonas O.; Oredsson, Stina; Prinz, Christelle N.

2015-01-01

The field of vertical nanowire array-based applications in cell biology is growing rapidly and an increasing number of applications are being explored. These applications almost invariably rely on the physical properties of the nanowire arrays, creating a need for a better understanding of how their physical properties affect cell behaviour. Here, we investigate the effects of nanowire density on cell migration, division and morphology for murine fibroblasts. Our results show that few nanowires are sufficient to immobilize cells, while a high nanowire spatial density enables a ”bed-of-nails” regime, where cells reside on top of the nanowires and are fully motile. The presence of nanowires decreases the cell proliferation rate, even in the “bed-of-nails” regime. We show that the cell morphology strongly depends on the nanowire density. Cells cultured on low (0.1 μm−2) and medium (1 μm−2) density substrates exhibit an increased number of multi-nucleated cells and micronuclei. These were not observed in cells cultured on high nanowire density substrates (4 μm−2). The results offer important guidelines to minimize cell-function perturbations on nanowire arrays. Moreover, these findings offer the possibility to tune cell proliferation and migration independently by adjusting the nanowire density, which may have applications in drug testing. PMID:26691936

Time to stop mucking around? Impacts of underwater photography on cryptobenthic fauna found in soft sediment habitats.

PubMed

De Brauwer, Maarten; Saunders, Benjamin J; Ambo-Rappe, Rohani; Jompa, Jamaluddin; McIlwain, Jennifer L; Harvey, Euan S

2018-07-15

Scuba diving tourism is a sustainable source of income for many coastal communities, but can have negative environmental impacts if not managed effectively. Diving on soft sediment habitats, typically referred to as 'muck diving', is a growing multi-million dollar industry with a strong focus on photographing cryptobenthic fauna. We assessed how the environmental impacts of scuba divers are affected by the activity they are engaged in while diving and the habitat they dive in. To do this, we observed 66 divers on coral reefs and soft sediment habitats in Indonesia and the Philippines. We found diver activity, specifically interacting with and photographing fauna, causes greater environmental disturbances than effects caused by certification level, gender, dive experience or age. Divers touched the substrate more often while diving on soft sediment habitats than on coral reefs, but this did not result in greater environmental damage on soft sediment sites. Divers had a higher impact on the substrate and touch animals more frequently when observing or photographing cryptobenthic fauna. When using dSLR-cameras, divers spent up to five times longer interacting with fauna. With the unknown, long-term impacts on cryptobenthic fauna or soft sediment habitats, and the increasing popularity of underwater photography, we argue for the introduction of a muck diving code of conduct. Copyright © 2018 Elsevier Ltd. All rights reserved.

Tributyltin (TBT) and dibutyltin (DBT) differently inhibit the mitochondrial Mg-ATPase activity in mussel digestive gland.

PubMed

Nesci, Salvatore; Ventrella, Vittoria; Trombetti, Fabiana; Pirini, Maurizio; Borgatti, Anna Rosa; Pagliarani, Alessandra

2011-02-01

Tri-n-butyltin (TBT) has long been considered as the most toxic among organotins, especially to membrane systems. The partially dealkylated derivative di-n-butyltin (DBT) has up to now received poor attention and, whenever considered, shown to be less toxic than TBT except on the immune system. The present kinetic approach evidences that both TBT and DBT in vitro inhibit the Mg-ATPase in mussel digestive gland mitochondria by a different mechanism. DBT even displays a higher efficiency than TBT (IC(50)=0.32 μM for TBT vs. 0.19 μM for DBT) in inhibiting the enzyme hydrolytic activity. Differently from TBT which at high concentrations (>1 μM) apparently decreases the oligomycin-sensitivity of the Mg-ATPase, DBT at any concentration tested does not affect the oligomycin sensitivity. TBT probably binds to F(0), either in the form of free enzyme or of enzyme-substrate complex (Ki=K'i), acting as non-competitive inhibitor with respect to the ATP substrate. Conversely DBT, which acts as uncompetitive inhibitor of ATP and as competitive inhibitor of Mg(2+) cofactor, may bind strongly to F(1) subunit, thus preventing ATP hydrolysis. The Mg-ATPase inhibition by both organotins warns against a potential threat to crucial cell energy metabolism processes even after years from contamination and partial TBT debutylation. Copyright © 2010 Elsevier Ltd. All rights reserved.

Exopolysaccharides from yeast: insight into optimal conditions for biosynthesis, chemical composition and functional properties - review.

PubMed

Gientka, Iwona; Błażejak, Stanisław; Stasiak-Różańska, Lidia; Chlebowska-Śmigiel, Anna

2015-01-01

xopolysaccharides (EPS) are not a well-established group of metabolites. An industrial scale    of this EPS production is limited mainly by low yield biosynthesis. Until now, enzymes and biosynthesis pathways, as well as the role of regulatory genes, have not been described. Some of yeast EPS show antitumor, immunostimulatory and antioxidant activity. Others, absorb heavy metals and can function as bioactive components of food. Also, the potential of yeast EPS as thickeners or stabilizers can be found. Optimal conditions for the biosynthesis of yeast exopolysaccharides require strong oxygenation and low temperature of the culture, due to the physiology of the producer strains. The medium should contain sucrose as a carbon source and ammonium sulfate as inorganic nitrogen source, wherein the C:N ratio in the substrate should be 15:1. The cultures are long and the largest accumulation of polymers is observed after 4 or 5 days of culturing. The structure of yeast EPS is complex which affects the strain and culture condition. The EPS from yeast are linear mannans, pullulan, glucooligosaccharides, galactooligosaccharides and other heteropolysaccharides containing α-1,2; α-1,3; α-1,6; β-1,3; β-1,4 bonds. Mannose and glucose have the largest participation of carbohydrates for. t exopolysaccharides (EPS) are not a well-established group of metabolites. An industrial scale    of this EPS production is limited mainly by low yield biosynthesis. Until now, enzymes and biosynthesis pathways, as well as the role of regulatory genes, have not been described. Some of yeast EPS show antitumor, immunostimulatory and antioxidant activity. Others, absorb heavy metals and can function as bioactive components of food. Also, the potential of yeast EPS as thickeners or stabilizers can be found. Optimal conditions for the biosynthesis of yeast exopolysaccharides require strong oxygenation and low temperature of the culture, due to the physiology of the producer strains. The medium should contain sucrose as a carbon source and ammonium sulfate as inorganic nitrogen source, wherein the C:N ratio in the substrate should be 15:1. The cultures are long and the largest accumulation of polymers is observed after 4 or 5 days of culturing. The structure of yeast EPS is complex which affects the strain and culture condition. The EPS from yeast are linear mannans, pullulan, glucooligosaccharides, galactooligosaccharides and other heteropolysaccharides containing α-1,2; α-1,3; α-1,6; β-1,3; β-1,4 bonds. Mannose and glucose have the largest participation of carbohydrates formin. t exopolysaccharides (EPS) are not a well-established group of metabolites. An industrial scale    of this EPS production is limited mainly by low yield biosynthesis. Until now, enzymes and biosynthesis pathways, as well as the role of regulatory genes, have not been described. Some of yeast EPS show antitumor, immunostimulatory and antioxidant activity. Others, absorb heavy metals and can function as bioactive components of food. Also, the potential of yeast EPS as thickeners or stabilizers can be found. Optimal conditions for the biosynthesis of yeast exopolysaccharides require strong oxygenation and low temperature of the culture, due to the physiology of the producer strains. The medium should contain sucrose as a carbon source and ammonium sulfate as inorganic nitrogen source, wherein the C:N ratio in the substrate should be 15:1. The cultures are long and the largest accumulation of polymers is observed after 4 or 5 days of culturing. The structure of yeast EPS is complex which affects the strain and culture condition. The EPS from yeast are linear mannans, pullulan, glucooligosaccharides, galactooligosaccharides and other heteropolysaccharides containing α-1,2; α-1,3; α-1,6; β-1,3; β-1,4 bonds. Mannose and glucose have the largest participation of carbohydrates forming EPS.

Influence of substrate mineralogy on bacterial mineralization of calcium carbonate: implications for stone conservation.

PubMed

Rodriguez-Navarro, Carlos; Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnación; González-Muñoz, María Teresa

2012-06-01

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed.

Influence of Substrate Mineralogy on Bacterial Mineralization of Calcium Carbonate: Implications for Stone Conservation

PubMed Central

Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnación; González-Muñoz, María Teresa

2012-01-01

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed. PMID:22447589

The inhibition of 45A ncRNA expression reduces tumor formation, affecting tumor nodules compactness and metastatic potential in neuroblastoma cells

PubMed Central

Russo, Debora; Poggi, Alessandro; Villa, Federico; Brizzolara, Antonella; Canale, Claudio; Mescola, Andrea; Daga, Antonio; Russo, Claudio; Nizzari, Mario; Florio, Tullio; Menichini, Paola; Pagano, Aldo

2017-01-01

We recently reported the in vitro over-expression of 45A, a RNA polymerase III-transcribed non-coding (nc)RNA, that perturbs the intracellular content of FE65L1 affecting cell proliferation rate, short-term response to genotoxic stress, substrate adhesion capacity and, ultimately, increasing the tumorigenic potential of human neuroblastoma cells. In this work, to deeply explore the mechanism by which 45A ncRNA contributes to cancer development, we targeted in vitro and in vivo 45A levels by the stable overexpression of antisense 45A RNA. 45A downregulation leads to deep modifications of cytoskeleton organization, adhesion and migration of neuroblastoma cells. These effects are correlated with alterations in the expression of several genes including GTSE1 (G2 and S phase-expressed-1), a crucial regulator of tumor cell migration and metastatic potential. Interestingly, the downregulation of 45A ncRNA strongly affects the in vivo tumorigenic potential of SKNBE2 neuroblastoma cells, increasing tumor nodule compactness and reducing GTSE1 protein expression in a subcutaneous neuroblastoma mouse model. Moreover, intracardiac injection of neuroblastoma cells showed that downregulation of 45A ncRNA also influences tumor metastatic ability. In conclusion, our data highlight a key role of 45A ncRNA in cancer development and suggest that its modulation might represent a possible novel anticancer therapeutic approach. PMID:28029658

The inhibition of 45A ncRNA expression reduces tumor formation, affecting tumor nodules compactness and metastatic potential in neuroblastoma cells.

PubMed

Penna, Ilaria; Gigoni, Arianna; Costa, Delfina; Vella, Serena; Russo, Debora; Poggi, Alessandro; Villa, Federico; Brizzolara, Antonella; Canale, Claudio; Mescola, Andrea; Daga, Antonio; Russo, Claudio; Nizzari, Mario; Florio, Tullio; Menichini, Paola; Pagano, Aldo

2017-01-31

We recently reported the in vitro over-expression of 45A, a RNA polymerase III-transcribed non-coding (nc)RNA, that perturbs the intracellular content of FE65L1 affecting cell proliferation rate, short-term response to genotoxic stress, substrate adhesion capacity and, ultimately, increasing the tumorigenic potential of human neuroblastoma cells. In this work, to deeply explore the mechanism by which 45A ncRNA contributes to cancer development, we targeted in vitro and in vivo 45A levels by the stable overexpression of antisense 45A RNA.45A downregulation leads to deep modifications of cytoskeleton organization, adhesion and migration of neuroblastoma cells. These effects are correlated with alterations in the expression of several genes including GTSE1 (G2 and S phase-expressed-1), a crucial regulator of tumor cell migration and metastatic potential. Interestingly, the downregulation of 45A ncRNA strongly affects the in vivo tumorigenic potential of SKNBE2 neuroblastoma cells, increasing tumor nodule compactness and reducing GTSE1 protein expression in a subcutaneous neuroblastoma mouse model. Moreover, intracardiac injection of neuroblastoma cells showed that downregulation of 45A ncRNA also influences tumor metastatic ability. In conclusion, our data highlight a key role of 45A ncRNA in cancer development and suggest that its modulation might represent a possible novel anticancer therapeutic approach.

Role of geometric parameters in electrical measurements of insulating thin films deposited on a conductive substrate

NASA Astrophysics Data System (ADS)

Kumar, S.; Gerhardt, R. A.

2012-03-01

The effects of film thickness, electrode size and substrate thickness on the impedance parameters of alternating frequency dielectric measurements of insulating thin films deposited on conductive substrates were studied through parametric finite-element simulations. The quasi-static forms of Maxwell's electromagnetic equations in a time harmonic mode were solved using COMSOL Multiphysics® for several types of 2D models (linear and axisymmetric). The full 2D model deals with a configuration in which the impedance is measured between two surface electrodes on top of a film deposited on a conductive substrate. For the simplified 2D models, the conductive substrate is ignored and the two electrodes are placed on the top and bottom of the film. By comparing the full model and the simplified models, approximations and generalizations are deduced. For highly insulating films, such as the case of insulating SiO2 films on a conducting Si substrate, even the simplified models predict accurate capacitance values at all frequencies. However, the edge effects on the capacitance are found to be significant when the film thickness increases and/or the top electrode contact size decreases. The thickness of the substrate affects predominantly the resistive components of the dielectric response while having no significant effect on the capacitive components. Changing the electrode contact size or the film thickness determines the specific values of the measured resistance or capacitance while the material time constant remains the same, and thus this affects the frequency dependence that is able to be detected. This work highlights the importance of keeping in mind the film thickness and electrode contact size for the correct interpretation of the measured dielectric properties of micro/nanoscale structures that are often investigated using nanoscale capacitance measurements.

In vitro proliferation and osteogenic differentiation of mesenchymal stem cells on nanoporous alumina

PubMed Central

Song, Yuanhui; Ju, Yang; Song, Guanbin; Morita, Yasuyuki

2013-01-01

Cell adhesion, migration, and proliferation are significantly affected by the surface topography of the substrates on which the cells are cultured. Alumina is one of the most popular implant materials used in orthopedics, but few data are available concerning the cellular responses of mesenchymal stem cells (MSCs) grown on nanoporous structures. MSCs were cultured on smooth alumina substrates and nanoporous alumina substrates to investigate the interaction between surface topographies of nanoporous alumina and cellular behavior. Nanoporous alumina substrates with pore sizes of 20 nm and 100 nm were used to evaluate the effect of pore size on MSCs as measured by proliferation, morphology, expression of integrin β1, and osteogenic differentiation. An MTT assay was used to measure cell viability of MSCs on different substrates, and determined that cell viability decreased with increasing pore size. Scanning electron microscopy was used to investigate the effect of pore size on cell morphology. Extremely elongated cells and prominent cell membrane protrusions were observed in cells cultured on alumina with the larger pore size. The expression of integrin β1 was enhanced in MSCs cultured on porous alumina, revealing that porous alumina substrates were more favorable for cell growth than smooth alumina substrates. Higher levels of osteoblastic differentiation markers such as alkaline phosphatase, osteocalcin, and mineralization were detected in cells cultured on alumina with 100 nm pores compared with cells cultured on alumina with either 20 nm pores or smooth alumina. This work demonstrates that cellular behavior is affected by variation in pore size, providing new insight into the potential application of this novel biocompatible material for the developing field of tissue engineering. PMID:23935364

Evaluation of the endothelin receptor antagonists ambrisentan, darusentan, bosentan, and sitaxsentan as substrates and inhibitors of hepatobiliary transporters in sandwich-cultured human hepatocytes.

PubMed

Hartman, J Craig; Brouwer, Kenneth; Mandagere, Arun; Melvin, Lawrence; Gorczynski, Richard

2010-06-01

To evaluate potential mechanisms of clinical hepatotoxicity, 4 endothelin receptor antagonists (ERAs) were examined for substrate activity and inhibition of hepatic uptake and efflux transporters in sandwich-cultured human hepatocytes. The 4 transporters studied were sodium-dependent taurocholate cotransporter (NTCP), organic anion transporter (OATP), bile salt export pump (BSEP), and multidrug resistance-associated protein 2 (MRP2). ERA transporter inhibition was examined using the substrates taurocholate (for NTCP and BSEP), [(3)H]estradiol-17beta-D-glucuronide (for OATP), and [2-D-penicillamine, 5-D-penicillamine]enkephalin (for MRP2). ERA substrate activity was evaluated using probe inhibitors ritonavir (OATP and BSEP), bromosulfalein (OATP), erythromycin (P-glycoprotein), probenecid (MRP2 and OATP), and cyclosporin (NTCP). ERAs were tested at 2, 20, and 100 micromol*L-1 for inhibition and at 2 micromol*L-1 as substrates. OATP, NTCP, or BSEP transport activity was not reduced by ambrisentan or darusentan. Bosentan and sitaxsentan attenuated NTCP transport at higher concentrations. Only sitaxsentan decreased OATP transport (52%), and only bosentan reduced BSEP transport (78%). MRP2 transport activity was unaltered. OATP inhibitors decreased influx of all ERAs. Darusentan influx was least affected (84%-100% of control), whereas bosentan was most affected (32%-58% of control). NTCP did not contribute to influx of ERAs. Only bosentan and darusentan were shown as substrates for both BSEP and P-glycoprotein efflux. All ERAs tested were substrates for at least one hepatic transporter. Bosentan and sitaxsentan, but not ambrisentan and darusentan, inhibited human hepatic transporters, which provides a potential mechanism for the increased hepatotoxicity observed for these agents in the clinical setting.

Sapphire substrate-induced effects in VO2 thin films grown by oxygen plasma-assisted pulsed laser deposition

NASA Astrophysics Data System (ADS)

Skuza, J. R.; Scott, D. W.; Pradhan, A. K.

2015-11-01

We investigate the structural and electronic properties of VO2 thin films on c-plane sapphire substrates with three different surface morphologies to control the strain at the substrate-film interface. Only non-annealed substrates with no discernible surface features (terraces) provided a suitable template for VO2 film growth with a semiconductor-metal transition (SMT), which was much lower than the bulk transition temperature. In addition to strain, oxygen vacancy concentration also affects the properties of VO2, which can be controlled through deposition conditions. Oxygen plasma-assisted pulsed laser deposition allows favorable conditions for VO2 film growth with SMTs that can be easily tailored for device applications.

Self-organization of gold nanoparticles on silanated surfaces.

PubMed

Kyaw, Htet H; Al-Harthi, Salim H; Sellai, Azzouz; Dutta, Joydeep

2015-01-01

The self-organization of monolayer gold nanoparticles (AuNPs) on 3-aminopropyltriethoxysilane (APTES)-functionalized glass substrate is reported. The orientation of APTES molecules on glass substrates plays an important role in the interaction between AuNPs and APTES molecules on the glass substrates. Different orientations of APTES affect the self-organization of AuNps on APTES-functionalized glass substrates. The as grown monolayers and films annealed in ultrahigh vacuum and air (600 °C) were studied by water contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, UV-visible spectroscopy and ultraviolet photoelectron spectroscopy. Results of this study are fundamentally important and also can be applied for designing and modelling of surface plasmon resonance based sensor applications.

Surface plasmon resonances of protein-conjugated gold nanoparticles on graphitic substrates

NASA Astrophysics Data System (ADS)

Phan, Anh D.; Hoang, Trinh X.; Nghiem, Thi H. L.; Woods, Lilia M.

2013-10-01

We present theoretical calculations for the absorption properties of protein-coated gold nanoparticles on graphene and graphite substrates. As the substrate is far away from nanoparticles, numerical results show that the number of protein bovine serum molecules aggregating on gold surfaces can be quantitatively determined for gold nanoparticles with arbitrary size by means of the Mie theory and the absorption spectra. The presence of a graphene substrate near the protein-conjugated gold nanoparticles results in a red shift of the surface plasmon resonances of the nanoparticles. This effect can be modulated upon changing the graphene chemical potential. Our findings show that the graphene and graphite affect the absorption spectra in a similar way.

An enzyme-mediated protein-fragment complementation assay for substrate screening of sortase A.

PubMed

Li, Ning; Yu, Zheng; Ji, Qun; Sun, Jingying; Liu, Xiao; Du, Mingjuan; Zhang, Wei

2017-04-29

Enzyme-mediated protein conjugation has gained great attention recently due to the remarkable site-selectivity and mild reaction condition affected by the nature of enzyme. Among all sorts of enzymes reported, sortase A from Staphylococcus aureus (SaSrtA) is the most popular enzyme due to its selectivity and well-demonstrated applications. Position scanning has been widely applied to understand enzyme substrate specificity, but the low throughput of chemical synthesis of peptide substrates and analytical methods (HPLC, LC-ESI-MS) have been the major hurdle to fully decode enzyme substrate profile. We have developed a simple high-throughput substrate profiling method to reveal novel substrates of SaSrtA 7M, a widely used hyperactive peptide ligase, by modified protein-fragment complementation assay (PCA). A small library targeting the LPATG motif recognized by SaSrtA 7M was generated and screened against proteins carrying N-terminal glycine. Using this method, we have confirmed all currently known substrates of the enzyme, and moreover identified some previously unknown substrates with varying activities. The method provides an easy, fast and highly-sensitive way to determine substrate profile of a peptide ligase in a high-throughput manner. Copyright © 2017 Elsevier Inc. All rights reserved.

Dynamic wetting on a thin film of soluble polymer: effects of nonlinearities in the sorption isotherm.

PubMed

Dupas, Julien; Verneuil, Emilie; Ramaioli, Marco; Forny, Laurent; Talini, Laurence; Lequeux, Francois

2013-10-08

The wetting dynamics of a solvent on a soluble substrate interestingly results from the rates of the solvent transfers into the substrate. When a supported film of a hydrosoluble polymer with thickness e is wet by a spreading droplet of water with instantaneous velocity U, the contact angle is measured to be inversely proportionate to the product of thickness and velocity, eU, over two decades. As for many hydrosoluble polymers, the polymer we used (a polysaccharide) has a strongly nonlinear sorption isotherm φ(a(w)), where φ is the volume fraction of water in the polymer and aw is the activity of water. For the first time, this nonlinearity is accounted for in the dynamics of water uptake by the substrate. Indeed, by measuring the water content in the polymer around the droplet φ at distances as small as 5 μm, we find that the hydration profile exhibits (i) a strongly distorted shape that results directly from the nonlinearities of the sorption isotherm and (ii) a cutoff length ξ below which the water content in the substrate varies very slowly. The nonlinearities in the sorption isotherm and the hydration at small distances from the line were not accounted for by Tay et al., Soft Matter 2011, 7, 6953. Here, we develop a comprehensive description of the hydration of the substrate ahead of the contact line that encompasses the two water transfers at stake: (i) the evaporation-condensation process by which water transfers into the substrate through the atmosphere by the condensation of the vapor phase, which is fed by the evaporation from the droplet itself, and (ii) the diffusion of liquid water along the polymer film. We find that the eU rescaling of the contact angle arises from the evaporation-condensation process at small distances. We demonstrate why it is not modified by the second process.

Bursting at the Seams: Rippled Monolayer Bismuth on NbSe 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Alan; Adamo, Carolina; Jia, Shuang

Bismuth, one of the heaviest semimetals in nature, ignited the interest of the materials-physics community for its potential impact on topological quantum-material systems that utilize its strong spin-orbit coupling (SOC) and unique orbital hybridization. In particular, recent theoretical predictions of unique topological and superconducting properties of thin bismuth films and interfaces prompted intense research on the growth of sub- to a few monolayers of bismuth on different substrates. Similar to bulk rhombohedral bismuth, the initial growth of bismuth films on most substrates results in buckled bilayers that either grow in the (111) or (110) directions, with a lattice constant closemore » to that of bulk Bi. By contrast, in this paper we show a new growth pattern for bismuth monolayers on NbSe 2. We find that the initial growth of Bi can form a strongly bonded commensurate layer, resulting in a compressively strained two-dimensional triangular lattice. A unique pattern of 1D ripples and domain walls is observed. The single layer of bismuth also introduces strong marks on the electronic properties at the surface.« less

Suppression of the ATP-binding cassette transporter ABCC4 impairs neuroblastoma tumour growth and sensitises to irinotecan in vivo.

PubMed

Murray, Jayne; Valli, Emanuele; Yu, Denise M T; Truong, Alan M; Gifford, Andrew J; Eden, Georgina L; Gamble, Laura D; Hanssen, Kimberley M; Flemming, Claudia L; Tan, Alvin; Tivnan, Amanda; Allan, Sophie; Saletta, Federica; Cheung, Leanna; Ruhle, Michelle; Schuetz, John D; Henderson, Michelle J; Byrne, Jennifer A; Norris, Murray D; Haber, Michelle; Fletcher, Jamie I

2017-09-01

The ATP-binding cassette transporter ABCC4 (multidrug resistance protein 4, MRP4) mRNA level is a strong predictor of poor clinical outcome in neuroblastoma which may relate to its export of endogenous signalling molecules and chemotherapeutic agents. We sought to determine whether ABCC4 contributes to development, growth and drug response in neuroblastoma in vivo. In neuroblastoma patients, high ABCC4 protein levels were associated with reduced overall survival. Inducible knockdown of ABCC4 strongly inhibited the growth of human neuroblastoma cells in vitro and impaired the growth of neuroblastoma xenografts. Loss of Abcc4 in the Th-MYCN transgenic neuroblastoma mouse model did not impact tumour formation; however, Abcc4-null neuroblastomas were strongly sensitised to the ABCC4 substrate drug irinotecan. Our findings demonstrate a role for ABCC4 in neuroblastoma cell proliferation and chemoresistance and provide rationale for a strategy where inhibition of ABCC4 should both attenuate the growth of neuroblastoma and sensitise tumours to ABCC4 chemotherapeutic substrates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Bursting at the Seams: Rippled Monolayer Bismuth on NbSe 2

DOE PAGES

Fang, Alan; Adamo, Carolina; Jia, Shuang; ...

2018-04-13

Bismuth, one of the heaviest semimetals in nature, ignited the interest of the materials-physics community for its potential impact on topological quantum-material systems that utilize its strong spin-orbit coupling (SOC) and unique orbital hybridization. In particular, recent theoretical predictions of unique topological and superconducting properties of thin bismuth films and interfaces prompted intense research on the growth of sub- to a few monolayers of bismuth on different substrates. Similar to bulk rhombohedral bismuth, the initial growth of bismuth films on most substrates results in buckled bilayers that either grow in the (111) or (110) directions, with a lattice constant closemore » to that of bulk Bi. By contrast, in this paper we show a new growth pattern for bismuth monolayers on NbSe 2. We find that the initial growth of Bi can form a strongly bonded commensurate layer, resulting in a compressively strained two-dimensional triangular lattice. A unique pattern of 1D ripples and domain walls is observed. The single layer of bismuth also introduces strong marks on the electronic properties at the surface.« less

Super-stretchable metallic interconnects on polymer with a linear strain of up to 100%

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arafat, Yeasir; Dutta, Indranath; Panat, Rahul, E-mail: Rahul.panat@wsu.edu

Metal interconnects in flexible and wearable devices are heterogeneous metal-polymer systems that are expected to sustain large deformation without failure. The principal strategy to make strain tolerant interconnect lines on flexible substrates has comprised of creating serpentine structures of metal films with either in-plane or out-of-plane waves, using porous substrates, or using highly ductile materials such as gold. The wavy and helical serpentine patterns preclude high-density packing of interconnect lines on devices, while ductile materials such as Au are cost prohibitive for real world applications. Ductile copper films can be stretched if bonded to the substrate, but show high levelmore » of cracking beyond few tens of % strain. In this paper, we demonstrate a material system consisting of Indium metal film over an elastomer (PDMS) with a discontinuous Cr layer such that the metal interconnect can be stretched to extremely high linear strain (up to 100%) without any visible cracks. Such linear strain in metal interconnects exceeds that reported in literature and is obtained without the use of any geometrical manipulations or porous substrates. Systematic experimentation is carried out to explain the mechanisms that allow the Indium film to sustain the high strain level without failure. The islands forming the discontinuous Cr layer are shown to move apart from each other during stretching without delamination, providing strong adhesion to the Indium film while accommodating the large strain in the system. The Indium film is shown to form surface wrinkles upon release from the large strain, confirming its strong adhesion to PDMS. A model is proposed based upon the observations that can explain the high level of stretch-ability of the Indium metal film over the PDMS substrate.« less

Diel variations in carbon isotopic composition and concentration of organic acids and their impact on plant dark respiration in different species.

PubMed

Lehmann, M M; Wegener, F; Werner, R A; Werner, C

2016-09-01

Leaf respiration in the dark and its C isotopic composition (δ(13) CR ) contain information about internal metabolic processes and respiratory substrates. δ(13) CR is known to be less negative compared to potential respiratory substrates, in particular shortly after darkening during light enhanced dark respiration (LEDR). This phenomenon might be driven by respiration of accumulated (13) C-enriched organic acids, however, studies simultaneously measuring δ(13) CR during LEDR and potential respiratory substrates are rare. We determined δ(13) CR and respiration rates (R) during LEDR, as well as δ(13) C and concentrations of potential respiratory substrates using compound-specific isotope analyses. The measurements were conducted throughout the diel cycle in several plant species under different environmental conditions. δ(13) CR and R patterns during LEDR were strongly species-specific and showed an initial peak, which was followed by a progressive decrease in both values. The species-specific differences in δ(13) CR and R during LEDR may be partially explained by the isotopic composition of organic acids (e.g., oxalate, isocitrate, quinate, shikimate, malate), which were (13) C-enriched compared to other respiratory substrates (e.g., sugars and amino acids). However, the diel variations in both δ(13) C and concentrations of the organic acids were generally low. Thus, additional factors such as the heterogeneous isotope distribution in organic acids and the relative contribution of the organic acids to respiration are required to explain the strong (13) C enrichment in leaf dark-respired CO2 . © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

On Substrate for Atomic Chain Electronics

NASA Technical Reports Server (NTRS)

Yamada, Toshishige; Bauschlicher, Charles W., Jr.; Partridge, Harry; Saini, Subhash (Technical Monitor)

1998-01-01

A substrate for future atomic chain electronics, where adatoms are placed at designated positions and form atomically precise device components, is studied theoretically. The substrate has to serve as a two-dimensional template for adatom mounting with a reasonable confinement barrier and also provide electronic isolation, preventing unwanted coupling between independent adatom structures. However, the two requirements conflict. For excellent electronic isolation, we may seek adatom confinement via van der Waals interaction without chemical bonding to the substrate atoms, but the confinement turns out to be very weak and hence unsatisfactory. An alternative chemical bonding scheme with excellent structural strength is examined, but even fundamental adatom chain properties such as whether chains are semiconducting or metallic are strongly influenced by the nature of the chemical bonding, and electronic isolation is not always achieved. Conditions for obtaining semiconducting chains with well-localized surface-modes, leading to good isolation, are clarified and discussed.

Subdigital setae of chameleon feet: friction-enhancing microstructures for a wide range of substrate roughness.

PubMed

Spinner, Marlene; Westhoff, Guido; Gorb, Stanislav N

2014-06-27

Hairy adhesive systems of microscopic setae with triangular flattened tips have evolved convergently in spiders, insects and arboreal lizards. The ventral sides of the feet and tails in chameleons are also covered with setae. However, chameleon setae feature strongly elongated narrow spatulae or fibrous tips. The friction enhancing function of these microstructures has so far only been demonstrated in contact with glass spheres. In the present study, the frictional properties of subdigital setae of Chamaeleo calyptratus were measured under normal forces in the physical range on plane substrates having different roughness. We showed that chameleon setae maximize friction on a wide range of substrate roughness. The highest friction was measured on asperities of 1 μm. However, our observations of the climbing ability of Ch. calyptratus on rods of different diameters revealed that also claws and grasping feet are additionally responsible for the force generation on various substrates during locomotion.

RF performances of inductors integrated on localized p+-type porous silicon regions

PubMed Central

2012-01-01

To study the influence of localized porous silicon regions on radiofrequency performances of passive devices, inductors were integrated on localized porous silicon regions, full porous silicon sheet, bulk silicon and glass substrates. In this work, a novel strong, resistant fluoropolymer mask is introduced to localize the porous silicon on the silicon wafer. Then, the quality factors and resonant frequencies obtained with the different substrates are presented. A first comparison is done between the performances of inductors integrated on same-thickness localized and full porous silicon sheet layers. The effect of the silicon regions in the decrease of performances of localized porous silicon is discussed. Then, the study shows that the localized porous silicon substrate significantly reduces losses in comparison with high-resistivity silicon or highly doped silicon bulks. These results are promising for the integration of both passive and active devices on the same silicon/porous silicon hybrid substrate. PMID:23009746

Superstrong encapsulated monolayer graphene by the modified anodic bonding.

PubMed

Jung, Wonsuk; Yoon, Taeshik; Choi, Jongho; Kim, Soohyun; Kim, Yong Hyup; Kim, Taek-Soo; Han, Chang-Soo

2014-01-07

We report a superstrong adhesive of monolayer graphene by modified anodic bonding. In this bonding, graphene plays the role of a superstrong and ultra-thin adhesive between SiO2 and glass substrates. As a result, monolayer graphene presented a strong adhesion energy of 1.4 J m(-2) about 310% that of van der Waals bonding (0.45 J m(-2)) to SiO2 and glass substrates. This flexible solid state graphene adhesive can tremendously decrease the adhesive thickness from about several tens of μm to 0.34 nm for epoxy or glue at the desired bonding area. As plausible causes of this superstrong adhesion, we suggest conformal contact with the rough surface of substrates and generation of C-O chemical bonding between graphene and the substrate due to the bonding process, and characterized these properties using optical microscopy, atomic force microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy.