Improved Determination of Surface and Atmospheric Temperatures Using Only Shortwave AIRS Channels

NASA Technical Reports Server (NTRS)

Susskind,Joel

2009-01-01

AIRS was launched on EOS Aqua on May 4, 2002, together with AMSU-A and HSB, to form a next generation polar orbiting infrared and microwave atmospheric sounding system. AIRS is a grating spectrometer with a number of linear arrays of detectors with each detector sensitive to outgoing radiation in a characteristic frequency v(sub i) with a spectral band pass delta v(sub i) of roughly v(sub i) /1200. AIRS contains 2378 spectral channels covering portions of the spectral region 650 cm(exp -1) (15.38 gm) - 2665 cm(exp -1)' (3.752 micrometers). These spectral regions contain significant absorption features from two CO2 absorption bands, the 15 micrometer (longwave) CO2 band, and the 4.3 micrometer (shortwave) CO, absorption band. There are also two atmospheric window regions, the 12 micrometerm - 8 micrometer (longwave) window, and the 4.17 micrometer - 3.75 micrometer (shortwave) window. Historically, determination of surface and atmospheric temperatures from satellite observations was performed using primarily observations in the longwave window and CO2 absorption regions. One reason for this was concerns about the effects, during the day, of reflected sunlight and non-Local Thermodynamic Equilibrium (non-LTE) on the observed radiances in the shortwave portion of the spectrum. According to cloud clearing theory, more accurate soundings of both surface skin and atmospheric temperatures can be obtained under partial cloud cover conditions if one uses the longwave channels to determine cloud cleared radiances R(sub i) for all channels, and uses R(sub i) only from shortwave channels in the determination of surface and atmospheric temperatures. This procedure is now being used by the AIRS Science Team in preparation for the AIRS Version 6 Retrieval Algorithm. This paper describes how the effects on the radiances of solar radiation reflected by clouds and the Earth's surface, and also of non-LTE, are accounted for in the analysis of the data. Results are presented for both daytime and nighttime conditions showing improved surface and atmospheric soundings under partial cloud cover resulted from not using R(sub i) in the retrieval process for any longwave channels sensitive to cloud effects. This improvement is made possible because AIRS NEDT in the shortwave portion of the spectrum is extremely low.

Conduction mechanism of nitronyl-nitroxide molecular magnetic compounds

NASA Astrophysics Data System (ADS)

Dotti, N.; Heintze, E.; Slota, M.; Hübner, R.; Wang, F.; Nuss, J.; Dressel, M.; Bogani, L.

2016-04-01

We investigate the conduction mechanisms of nitronyl-nitroxide (NIT) molecular radicals, as useful for the creation of nanoscopic molecular spintronic devices, finding that it does not correspond to standard Mott behavior, as previously postulated. We provide a complete investigation using transport measurements, low-energy, sub-THz spectroscopy and introducing differently substituted phenyl appendages. We show that a nontrivial surface-charge-limited regime is present in addition to the standard low-voltage Ohmic conductance. Scaling analysis allows one to determine all the main transport parameters for the compounds and highlights the presence of charge-trapping effects. Comparison among the different compounds shows the relevance of intermolecular stacking between the aromatic ring of the phenyl appendix and the NIT motif in the creation of useful electron transport channels. The importance of intermolecular pathways is further highlighted by electronic structure calculations, which clarify the nature of the electronic channels and their effect on the Mott character of the compounds.

Accuracy of sea ice temperature derived from the advanced very high resolution radiometer

NASA Technical Reports Server (NTRS)

Yu, Y.; Rothrock, D. A.; Lindsay, R. W.

1995-01-01

The accuracy of Arctic sea ice surface temperatures T(sub s) dericed from advanced very high resolution radiometer (AVHRR) thermal channels is evaluated in the cold seasons by comparing them with surface air temperatures T(sub air) from drifting buoys and ice stations. We use three different estimates of satellite surface temperatures, a direct estimate from AVHRR channel 4 with only correction for the snow surface emissivity but not for the atmosphere, a single-channel regression of T(sub s) with T(sub air), and Key and Haefliger's (1992) polar multichannel algorithm. We find no measurable bias in any of these estimates and few differences in their statistics. The similar performance of all three methods indicates that an atmospheric water vapor correction is not important for the dry winter atmosphere in the central Arctic, given the other sources of error that remain in both the satellite and the comparison data. A record of drifting station data shows winter air temperature to be 1.4 C warmer than the snow surface temperature. `Correcting' air temperatures to skin temperature by subtracting this amount implies that satellite T(sub s) estimates are biased warm with respect to skin temperature by about this amount. A case study with low-flying aircraft data suggests that ice crystal precipitation can cause satellite estimates of T(sub s) to be several degrees warmer than radiometric measurements taken close to the surface, presumably below the ice crystal precipitation layer. An analysis in which errors are assumed to exist in all measurements, not just the satellite measurements, gives a standard deviation in the satellite estimates of 0.9 C, about half the standard deviation of 1.7 C estimated by assigning all the variation between T(sub s) and T(sub air) to errors in T(sub s).

Split-Channel Ballistic Transport in an InSb Nanowire.

PubMed

Estrada Saldaña, Juan Carlos; Niquet, Yann-Michel; Cleuziou, Jean-Pierre; Lee, Eduardo J H; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; De Franceschi, Silvano

2018-04-11

We report an experimental study of one-dimensional (1D) electronic transport in an InSb semiconducting nanowire. A total of three bottom gates are used to locally deplete the nanowire, creating a ballistic quantum point contact with only a few conducting channels. In a magnetic field, the Zeeman splitting of the corresponding 1D sub-bands is revealed by the emergence of conductance plateaus at multiples of e 2 /h, yet we find a quantized conductance pattern largely dependent on the configuration of voltages applied to the bottom gates. In particular, we can make the first plateau disappear, leaving a first conductance step of 2 e 2 / h, which is indicative of a remarkable 2-fold sub-band degeneracy that can persist up to several tesla. For certain gate voltage settings, we also observe the presence of discrete resonant states producing conductance features that can resemble those expected from the opening of a helical gap in the sub-band structure. We explain our experimental findings through the formation of two spatially separated 1D conduction channels.

Temperature gradient scale length measurement: A high accuracy application of electron cyclotron emission without calibration

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

Houshmandyar, S., E-mail: houshmandyar@austin.utexas.edu; Phillips, P. E.; Rowan, W. L.

2016-11-15

Calibration is a crucial procedure in electron temperature (T{sub e}) inference from a typical electron cyclotron emission (ECE) diagnostic on tokamaks. Although the calibration provides an important multiplying factor for an individual ECE channel, the parameter ΔT{sub e}/T{sub e} is independent of any calibration. Since an ECE channel measures the cyclotron emission for a particular flux surface, a non-perturbing change in toroidal magnetic field changes the view of that channel. Hence the calibration-free parameter is a measure of T{sub e} gradient. B{sub T}-jog technique is presented here which employs the parameter and the raw ECE signals for direct measurement ofmore » electron temperature gradient scale length.« less

A microreactor array for spatially resolved measurement of catalytic activity for high-throughput catalysis science

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

Kondratyuk, Petro; Gumuslu, Gamze; Shukla, Shantanu

2013-04-01

We describe a 100 channel microreactor array capable of spatially resolved measurement of catalytic activity across the surface of a flat substrate. When used in conjunction with a composition spread alloy film (CSAF, e.g. Pd{sub x}Cu{sub y}Au{sub 1-x-y}) across which component concentrations vary smoothly, such measurements permit high-throughput analysis of catalytic activity and selectivity as a function of catalyst composition. In the reported implementation, the system achieves spatial resolution of 1 mm{sup 2} over a 10×10 mm{sup 2} area. During operation, the reactant gases are delivered at constant flow rate to 100 points of differing composition on the CSAF surfacemore » by means of a 100-channel microfluidic device. After coming into contact with the CSAF catalyst surface, the product gas mixture from each of the 100 points is withdrawn separately through a set of 100 isolated channels for analysis using a mass spectrometer. We demonstrate the operation of the device on a Pd{sub x}Cu{sub y}Au{sub 1-x-y} CSAF catalyzing the H{sub 2}-D{sub 2} exchange reaction at 333 K. In essentially a single experiment, we measured the catalytic activity over a broad swathe of concentrations from the ternary composition space of the Pd{sub x}Cu{sub y}Au{sub 1-x-y} alloy.« less

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

Liau, Leo Chau-Kuang, E-mail: lckliau@saturn.yzu.edu.tw; Hsu, Tzu-Hsien; Lo, Pei-Hsuan

We report the characteristics of p-channel thin film transistors (p-TFTs) with ZnO/hydrated polyvinyl alcohol (PVA) (ZnO/PVA) conducting channels. The metal-oxide-semiconductor structure of the p-TFTs was composed of indium tin oxide (ITO)/SiO{sub 2}/ZnO/PVA layers. The TFT was assembled using PVA gel, which was glued to ITO substrates patterned to form source and drain electrodes. The ZnO/PVA composite film acted as an effective conducting film because of the chemisorption reaction at the film interface where free electrons can be generated. The formation of the conducting channel was also affected by V{sub G} applied to the TFT. The ZnO/PVA-based TFTs demonstrated p-channel transistormore » performance, shown by current-voltage (I-V) data analysis. The electrical parameters of the device were evaluated, including the on/off ratio (∼10{sup 3}), threshold voltage (V{sub th}, −1 V), and subthreshold swing (−2.2 V/dec). The PVA/ZnO-based p-TFTs were fabricated using simple and cost-effective approaches instead of doping methods.« less

AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

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

Hodges, C., E-mail: chris.hodges@bristol.ac.uk; Anaya Calvo, J.; Kuball, M.

2013-11-11

AlGaN/GaN heterostructure field effect transistors with a 150 nm thick GaN channel within stacked Al{sub x}Ga{sub 1−x}N layers were investigated using Raman thermography. By fitting a thermal simulation to the measured temperatures, the thermal conductivity of the GaN channel was determined to be 60 W m{sup −1} K{sup −1}, over 50% less than typical GaN epilayers, causing an increased peak channel temperature. This agrees with a nanoscale model. A low thermal conductivity AlGaN buffer means the GaN spreads heat; its properties are important for device thermal characteristics. When designing power devices with thin GaN layers, as well as electrical considerations, the reducedmore » channel thermal conductivity must be considered.« less

Designer proton-channel transgenic algae for photobiological hydrogen production

DOEpatents

Lee, James Weifu [Knoxville, TN

2011-04-26

A designer proton-channel transgenic alga for photobiological hydrogen production that is specifically designed for production of molecular hydrogen (H.sub.2) through photosynthetic water splitting. The designer transgenic alga includes proton-conductive channels that are expressed to produce such uncoupler proteins in an amount sufficient to increase the algal H.sub.2 productivity. In one embodiment the designer proton-channel transgene is a nucleic acid construct (300) including a PCR forward primer (302), an externally inducible promoter (304), a transit targeting sequence (306), a designer proton-channel encoding sequence (308), a transcription and translation terminator (310), and a PCR reverse primer (312). In various embodiments, the designer proton-channel transgenic algae are used with a gas-separation system (500) and a gas-products-separation and utilization system (600) for photobiological H.sub.2 production.

C-H surface diamond field effect transistors for high temperature (400 °C) and high voltage (500 V) operation

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

Kawarada, H., E-mail: kawarada@waseda.jp; Institute of Nano-Science and Nano-Engineering, Waseda University, Shinjuku, Tokyo 169-8555; Kagami Memorial Laboratory for Material Science and Technology, Waseda University, Shinjuku, Tokyo 169-0051

2014-07-07

By forming a highly stable Al{sub 2}O{sub 3} gate oxide on a C-H bonded channel of diamond, high-temperature, and high-voltage metal-oxide-semiconductor field-effect transistor (MOSFET) has been realized. From room temperature to 400 °C (673 K), the variation of maximum drain-current is within 30% at a given gate bias. The maximum breakdown voltage (V{sub B}) of the MOSFET without a field plate is 600 V at a gate-drain distance (L{sub GD}) of 7 μm. We fabricated some MOSFETs for which V{sub B}/L{sub GD} > 100 V/μm. These values are comparable to those of lateral SiC or GaN FETs. The Al{sub 2}O{sub 3} was deposited on the C-Hmore » surface by atomic layer deposition (ALD) at 450 °C using H{sub 2}O as an oxidant. The ALD at relatively high temperature results in stable p-type conduction and FET operation at 400 °C in vacuum. The drain current density and transconductance normalized by the gate width are almost constant from room temperature to 400 °C in vacuum and are about 10 times higher than those of boron-doped diamond FETs.« less

Locating hidden channels for placer gold exploration in the Cariboo District, British Columbia, Canada: A case study

NASA Astrophysics Data System (ADS)

Eberle, Detlef; Bastian, Dennis; Ebel, Norbert; Schwarz, Rüdiger

2017-01-01

During the past 150 years, most of the modern day creeks were the target of miners roaming the Cariboo Mountains, British Columbia, in the search for placer gold. In these days, the probability to locate new placer gold occurrence in recent river beds is therefore substantially reduced. New, promising exploration targets appear to be channels mostly buried under alluvial cover sediments. It is airborne geophysical methods that can reveal hidden channels fast and cost-effectively as these penetrate the sub-surface contactless and reflect physical properties of the sub-surface, such as electric conductivity and magnetic susceptibility or magnetization, respectively. We applied the airborne geophysical exploration approach on four exploration areas in the Cariboo gold district. Helicopter-borne transient electromagnetic (TEM) and magnetic data were flown using the SkyTEM system. To our knowledge, it has been innovatory to apply high resolution, high density airborne geophysics in the search for placer gold deposited in pre-Holocene sedimentary channel fills of the Cariboo Mountains. A particular effort of our studies aimed at the Mary creek claims which straddle the boundary of the Quesnel and Kootenay terranes of the Canadian Cordillera and include the dormant Toop mine situated in the Mary creek area known for many finds of coarse nugget from the pre-glacial buried Toop channel. Our objective was to locate the southbound extension of the channel buried in Pleistocene sediments of the Toop plateau. Careful analysis of the airborne geophysical data sets provided indications from both the TEM and magnetic data sets favouring the existence of a hidden channel beneath the plateau. The evaluation of seven reverse circulation (RC) drill holes sunk into a promising elongated narrow conductor beneath the plateau was not conclusive as not clearly showing the sedimentary pattern of a channel with gravels typically at its bottom. Only electric conductivity-depth sections compiled from the airborne TEM and 2D direct current (DC) multi-electrode resistivity ground survey data enabled the interpretation of the airborne TEM and magnetic responses recorded over the Toop plateau. The sections suggest that the electric conductor is generated by an upwarp of a conductive layer extending at the bottom of the Pleistocene sediments. Another feature separated by ≤ 100 m from the conductor line is reflected by low electric conductivity, but is rarely prominent through its neat magnetic signature. Fine accumulations of black minerals, i.e. magnetite grains, in sediments of the area are frequently met when panning material from the creeks. We therefore interpret this low conductivity, magnetic feature as expression of a gravel lense hosting accumulations of magnetite grains and possibly indicating the southbound extension of the Toop channel beneath the plateau. Careful analysis of the airborne magnetic data set led to the result in that magnetite is not only wide-spread in present day rivers and creeks, but also in buried channels and palaeo precipitation run-off paths. Magnetic data proved to be very helpful in this project with regard of pursuing not only present day, but buried valleys and channels, in particular. Our experience made on the Mary creek claims is summarized in a straightforward exploration concept for hidden, possibly gold-bearing channels in the Cariboo gold district.

Quantum oscillations in strong magnetic fields, berry phase, and superconductivity in three-dimensional topological Bi{sub 2–x}Cu{sub x}Se{sub 3} insulators

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

Vedeneev, S. I., E-mail: vedeneev@sci.lebedev.ru; Knyazev, D. A.; Prudkoglyad, V. A.

2015-07-15

Two-dimensional (2D) Shubnikov–de Haas oscillations and 2D Hall oscillations are observed in 3D copper-doped Bi{sub 2}Se{sub 3} single crystals in magnetic fields up to 19.5 T at temperatures down to 0.3 K. Three samples with a high bulk carrier concentration (n ≈ 10{sup 19}–10{sup 20} cm{sup –3}) are studied. The rotation of the samples in a magnetic field shows that these oscillations are related to numerous parallel 2D conducting channels 1–5 nm thick. Their basic kinetic parameters are found. Quantized Hall resistance R{sub xy} is detected in 1-nm-thick 2D conducting channels at high fields. The distance Δ(1/R{sub xy}) between themore » steps in the field dependence of 1/R{sub xy} is found to be constant for different Landau levels, 1.3e{sup 2}/h per 1-nm-thick layer. The constructed fan diagrams of 2D Landau levels for various angles of sample inclination with respect to the magnetic field direction allowed us to conclude that the Berry phase in the 2D conducting channels is γ ≈ π and independent of the magnetic field direction. When studying the angular dependence of upper resistive critical magnetic field H{sub c2} in one of the superconducting samples, we showed that it can be considered as a bulk superconductor consisting of superconducting layers with an effective thickness of about 50 nm.« less

Contrasted structuring effects of mesoscale features on the seabird community in the Mozambique Channel

NASA Astrophysics Data System (ADS)

Jaquemet, S.; Ternon, J. F.; Kaehler, S.; Thiebot, J. B.; Dyer, B.; Bemanaja, E.; Marteau, C.; Le Corre, M.

2014-02-01

The Mozambique Channel (western Indian Ocean) is a dynamic environment characterised by strong mesoscale features, which influence all biological components of the pelagic ecosystem. We investigated the distribution, abundance and feeding behaviour of seabirds in the Mozambique Channel in relation to physical and biological environmental variables, with a specific interest in mesoscale features. Seabird censuses were conducted in summer and winter during 7 cruises in the southern and northern Mozambique Channel. Tropical species accounted for 49% of the 37 species identified and 97% of the individuals, and species from the sub-Antarctic region constituted 30% of the identifications. The typically tropical sooty tern (Onychoprion fuscata) was the dominant species during all cruises, and overall accounted for 74% of the species observations and 85% of counted birds. Outputs of Generalised Linear Models at the scale of the Mozambique Channel suggested that higher densities of flying and feeding birds occurred in areas with lower sea surface temperatures and lower surface chlorophyll a concentrations. Most of the flocks of feeding birds did not associate with surface schools of fish or marine mammals, but when they did, these flocks were larger, especially when associated with tuna. While tropical species seemed to favour cyclonic eddies, frontal and divergence zones, non-tropical species were more frequently recorded over shelf waters. Sooty terns foraged preferentially in cyclonic eddies where zooplankton, micronekton and tuna schools were abundant. Among other major tropical species, frigatebirds (Fregata spp.) predominated in frontal zones between eddies, where tuna schools also frequently occurred and where geostrophic currents were the strongest. Red-footed boobies (Sula sula) concentrated in divergence zones characterised by low sea level anomalies, low geostrophic currents, and high zooplankton biomass close to the surface. Our results highlight the importance of mescoscale features in structuring the tropical seabird community in the Mozambique Channel, in addition to segregating tropical and non-tropical species. The mechanisms underlying the segregation of tropical seabirds seem to partially differ from that of other tropical regions, and this may be a consequence of the strong local mesoscale activity, affecting prey size and availability schemes. Beyond characterising the foraging habitats of the seabird community of the Mozambique Channel, this study highlights the importance of this region as a hot spot for seabirds; especially the southern part, where several endangered sub-Antarctic species over-winter.

Origins of enhanced thermoelectric power factor in topologically insulating Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} thin films

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

Liu, Wei; State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070; Chi, Hang

2016-01-25

In this research, we report the enhanced thermoelectric power factor in topologically insulating thin films of Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} with a thickness of 6–200 nm. Measurements of scanning tunneling spectroscopy and electronic transport show that the Fermi level lies close to the valence band edge, and that the topological surface state (TSS) is electron dominated. We find that the Seebeck coefficient of the 6 nm and 15 nm thick films is dominated by the valence band, while the TSS chiefly contributes to the electrical conductivity. In contrast, the electronic transport of the reference 200 nm thick film behaves similar to bulk thermoelectric materialsmore » with low carrier concentration, implying the effect of the TSS on the electronic transport is merely prominent in the thin region. The conductivity of the 6 nm and 15 nm thick film is obviously higher than that in the 200 nm thick film owing to the highly mobile TSS conduction channel. As a consequence of the enhanced electrical conductivity and the suppressed bipolar effect in transport properties for the 6 nm thick film, an impressive power factor of about 2.0 mW m{sup −1} K{sup −2} is achieved at room temperature for this film. Further investigations of the electronic transport properties of TSS and interactions between TSS and the bulk band might result in a further improved thermoelectric power factor in topologically insulating Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} thin films.« less

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

DOEpatents

Spahn, O.B.; Lear, K.L.

1998-03-10

The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

DOEpatents

Spahn, Olga B.; Lear, Kevin L.

1998-01-01

A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.

Ge{sub 0.83}Sn{sub 0.17} p-channel metal-oxide-semiconductor field-effect transistors: Impact of sulfur passivation on gate stack quality

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

Lei, Dian; Wang, Wei; Gong, Xiao, E-mail: elegong@nus.edu.sg, E-mail: yeo@ieee.org

2016-01-14

The effect of room temperature sulfur passivation of the surface of Ge{sub 0.83}Sn{sub 0.17} prior to high-k dielectric (HfO{sub 2}) deposition is investigated. X-ray photoelectron spectroscopy (XPS) was used to examine the chemical bonding at the interface of HfO{sub 2} and Ge{sub 0.83}Sn{sub 0.17}. Sulfur passivation is found to be effective in suppressing the formation of both Ge oxides and Sn oxides. A comparison of XPS results for sulfur-passivated and non-passivated Ge{sub 0.83}Sn{sub 0.17} samples shows that sulfur passivation of the GeSn surface could also suppress the surface segregation of Sn atoms. In addition, sulfur passivation reduces the interface trapmore » density D{sub it} at the high-k dielectric/Ge{sub 0.83}Sn{sub 0.17} interface from the valence band edge to the midgap of Ge{sub 0.83}Sn{sub 0.17}, as compared with a non-passivated control. The impact of the improved D{sub it} is demonstrated in Ge{sub 0.83}Sn{sub 0.17} p-channel metal-oxide-semiconductor field-effect transistors (p-MOSFETs). Ge{sub 0.83}Sn{sub 0.17} p-MOSFETs with sulfur passivation show improved subthreshold swing S, intrinsic transconductance G{sub m,int}, and effective hole mobility μ{sub eff} as compared with the non-passivated control. At a high inversion carrier density N{sub inv} of 1 × 10{sup 13 }cm{sup −2}, sulfur passivation increases μ{sub eff} by 25% in Ge{sub 0.83}Sn{sub 0.17} p-MOSFETs.« less

An experimental investigation on liquid methane heat transfer enhancement through the use of longitudinal fins in cooling channels

NASA Astrophysics Data System (ADS)

Galvan, Manuel de Jesus

In the past years, hydrocarbon fuels have been the focus of attention as the interest in developing reusable, high-performing liquid rocket engines has grown. Liquid methane (LCH4) has been of particular interest because of the cost, handling, and storage advantages that it presents when compared to currently used propellants. Deep space exploration requires thrusters that can operate reliably during long-duration missions. One of the challenges in the development of a reliable engine has been providing adequate combustion chamber cooling to prevent engine failure. Regenerative (regen) cooling has presented itself as an appealing option because it provides improved cooling and engine efficiency over other types of cooling, such as film or dump cooling. Due to limited availability of experimental sub-critical liquid methane cooling data for pressure-fed regen engine design, there has been an interest in studying the heat transfer characteristics of the propellant. For this reason, recent experimental studies at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso (UTEP) have focused on investigating the heat transfer characteristics of sub-critical CH4 flowing through smooth sub-scale cooling channels. In addition to investigating smooth channels, the cSETR has conducted experiments to investigate the effects of internal longitudinal fins on the heat transfer of methane. To conduct the experiments, the cSETR developed a conduction-based thermal concentrator known as the High Heat Flux Test Facility (HHFTF) in which the channels are heated. In this study, a smooth channel and three channels with longitudinal fins all with cross sectional geometries of 3.2 mm x 3.2 mm were tested. The Nusselt numbers ranged from 70 and 510, and Reynolds numbers were between 50,000 and 128,000. Sub-cooled film-boiling phenomena were discovered in the data pertaining to the smooth and two finned channels. Sub-cooled film-boiling was not observed in the channel that had the fins with the highest height. Film-boiling onset at Critical Heat Flux (CHF) was correlated to a Boiling Number (Bo) of approximately 0.1 for the channels studies. Convective Nusselt number follows predicted trends for Reynolds number with a wall temperature correction factor for both the boiling and non-boiling regimes.

Influence of an anomalous dimension effect on thermal instability in amorphous-InGaZnO thin-film transistors

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

Liu, Kuan-Hsien; Chou, Wu-Ching, E-mail: tcchang3708@gmail.com, E-mail: wuchingchou@mail.nctu.edu.tw; Chang, Ting-Chang, E-mail: tcchang3708@gmail.com, E-mail: wuchingchou@mail.nctu.edu.tw

2014-10-21

This paper investigates abnormal dimension-dependent thermal instability in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. Device dimension should theoretically have no effects on threshold voltage, except for in short channel devices. Unlike short channel drain-induced source barrier lowering effect, threshold voltage increases with increasing drain voltage. Furthermore, for devices with either a relatively large channel width or a short channel length, the output drain current decreases instead of saturating with an increase in drain voltage. Moreover, the wider the channel and the shorter the channel length, the larger the threshold voltage and output on-state current degradation that is observed. Because of themore » surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer, the self-heating effect will be pronounced in wider/shorter channel length devices and those with a larger operating drain bias. To further clarify the physical mechanism, fast I{sub D}-V{sub G} and modulated peak/base pulse time I{sub D}-V{sub D} measurements are utilized to demonstrate the self-heating induced anomalous dimension-dependent threshold voltage variation and on-state current degradation.« less

Rietveld refinement and ionic conductivity of Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}

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

Tmar Trabelsi, I., E-mail: ilhem_tmar@yahoo.fr; Madani, A.; Mercier, A.M.

2013-01-15

The structure of Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}, isostructural with Fluoroapatite, was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed that the formula of this compound is [Ca{sub 4}]{sup 4f}[Ca{sub 4.4}Bi{sub 1.6}]{sup 6h}(PO{sub 4}){sub 6}[O{sub 1.8}]{sup 2a}, space group P63/m (a=9.468 (3) A, c=6.957 (3) A). A total substitution of Bi{sup 3+} ions in the (6h) sites was related particularly to the high polarizability of the Bi{sup 3+} ion compared to Ca{sup 2+}. The observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit-cell group analyses and inmore » comparison with Fluoroapatite and other oxyapatites. The ionic conductivity over a wide range of temperature was investigated according to the complex impedance method. The highest overall conductivity values were found at {sigma}{sub 700 Degree-Sign C} =5.03 Multiplication-Sign 10{sup -7} S cm{sup -1} and E{sub a}=0.50 eV. - Graphical abstract: The final Rietveld refinement plot of the Ca{sub 8.4}Bi{sub 1.6} (PO{sub 4}){sub 6}O{sub 1.8}. Highlights: Black-Right-Pointing-Pointer The Rietveld refinement revealed that the formula of this compound is Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}. Black-Right-Pointing-Pointer Vibrational spectroscopy supports the high symmetry P63/m space group for this apatite. Black-Right-Pointing-Pointer This apatite contained channels where oxygen ions were located in 2a sites. Black-Right-Pointing-Pointer The possibility of anionic conduction along these channels was considered.« less

Structural Studies of Inositol 1,4,5-Trisphosphate Receptor COUPLING LIGAND BINDING TO CHANNEL GATING

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

Chan, Jenny; Yamazaki, Haruka; Ishiyama, Noboru

2010-11-22

The three isoforms of the inositol 1,4,5-trisphosphate receptor (IP{sub 3}R) exhibit distinct IP{sub 3} sensitivities and cooperativities in calcium (Ca{sup 2+}) channel function. The determinants underlying this isoform-specific channel gating mechanism have been localized to the N-terminal suppressor region of IP3R. We determined the 1.9 {angstrom} crystal structure of the suppressor domain from type 3 IP{sub 3}R (IP{sub 3}R3{sub SUP}, amino acids 1-224) and revealed structural features contributing to isoform-specific functionality of IP{sub 3}R by comparing it with our previously determined structure of the type 1 suppressor domain (IP{sub 3}R1{sub SUP}). The molecular surface known to associate with the ligandmore » binding domain (amino acids 224-604) showed marked differences between IP{sub 3}R3{sub SUP} and IP{sub 3}R1{sub SUP}. Our NMR and biochemical studies showed that three spatially clustered residues (Glu-20, Tyr-167, and Ser-217 in IP{sub 3}R1 and Glu-19, Trp-168, and Ser-218 in IP{sub 3}R3) within the N-terminal suppressor domains of IP{sub 3}R1{sub SUP} and IP{sub 3}R3{sub SUP} interact directly with their respective C-terminal fragments. Together with the accompanying paper (Yamazaki, H., Chan, J., Ikura, M., Michikawa, T., and Mikoshiba, K. (2010) J. Biol. Chem. 285, 36081-36091), we demonstrate that the single aromatic residue in this region (Tyr-167 in IP{sub 3}R1 and Trp-168 in IP{sub 3}R3) plays a critical role in the coupling between ligand binding and channel gating.« less

Infrared study of CO{sub 2} sorption over 'molecular basket' sorbent consisting of polyethylenimine-modified mesoporous molecular sieve

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

Wang, X.X.; Schwartz, V.; Clark, J.C.

2009-04-15

An infrared study has been conducted on CO{sub 2} sorption into nanoporous CO{sub 2} 'molecular basket' sorbents prepared by loading polyethylenimine (PEI) into mesoporous molecular sieve SBA-15. IR results from DRIFTS showed that a part of loaded PEI is anchored on the surface of SBA-15 through the interaction between amine groups and isolated surface silanol groups. Raising the temperature from 25 to 75{sup o}C increased the molecular flexibility of PEI loaded in the mesopore channels, which may partly contribute to the increase of CO{sub 2} sorption capacity at higher temperatures. CO{sub 2} sorption/desorption behavior studied by in situ transmission FTIRmore » showed that CO{sub 2} is sorbed on amine sites through the formation of alkylammonium carbamates and absorbed into the multiple layers of PEI located in mesopores of SBA-15. A new observation by in situ IR is that two broad IR bands emerged at 2450 and 2160 cm{sup -1} with CO{sub 2} flowing over PEI(50)/SBA-15, which could be attributed to chemically sorbed CO{sub 2} species on PEI molecules inside the mesopores of SBA-15. The intensities of these two bands also increased with increasing CO{sub 2} exposure time and with raising CO{sub 2} sorption temperature. By comparison of the CO{sub 2} sorption rate at 25 and 75{sup o}C in terms of differential IR intensities, it was found that CO{sub 2} sorption over molecular basket sorbent includes two rate regimes which suggest two distinct steps: rapid sorption on exposed outer surface layers of PEI (controlled by sorption affinity or thermodynamics) and the diffusion and sorption inside the bulk of multiple layers of PEI (controlled by diffusion). The sorption of CO{sub 2} is reversible at 75{sup o}C.« less

Global Clear-Sky Surface Skin Temperature from Multiple Satellites Using a Single-Channel Algorithm with Angular Anisotropy Corrections

NASA Technical Reports Server (NTRS)

Scarino, Benjamin R.; Minnis, Patrick; Chee, Thad; Bedka, Kristopher M.; Yost, Christopher R.; Palikonda, Rabindra

2017-01-01

Surface skin temperature (T(sub s)) is an important parameter for characterizing the energy exchange at the ground/water-atmosphere interface. The Satellite ClOud and Radiation Property retrieval System (SatCORPS) employs a single-channel thermal-infrared (TIR) method to retrieve T(sub s) over clear-sky land and ocean surfaces from data taken by geostationary Earth orbit (GEO) and low Earth orbit (LEO) satellite imagers. GEO satellites can provide somewhat continuous estimates of T(sub s) over the diurnal cycle in non-polar regions, while polar T(sub s) retrievals from LEO imagers, such as the Advanced Very High Resolution Radiometer (AVHRR), can complement the GEO measurements. The combined global coverage of remotely sensed T(sub s), along with accompanying cloud and surface radiation parameters, produced in near-realtime and from historical satellite data, should be beneficial for both weather and climate applications. For example, near-realtime hourly T(sub s) observations can be assimilated in high-temporal-resolution numerical weather prediction models and historical observations can be used for validation or assimilation of climate models. Key drawbacks to the utility of TIR-derived T(sub s) data include the limitation to clear-sky conditions, the reliance on a particular set of analyses/reanalyses necessary for atmospheric corrections, and the dependence on viewing and illumination angles. Therefore, T(sub s) validation with established references is essential, as is proper evaluation of T(sub s) sensitivity to atmospheric correction source. This article presents improvements on the NASA Langley GEO satellite and AVHRR TIR-based T(sub s) product that is derived using a single-channel technique. The resulting clear-sky skin temperature values are validated with surface references and independent satellite products. Furthermore, an empirically adjusted theoretical model of satellite land surface temperature (LST) angular anisotropy is tested to improve satellite LST retrievals. Application of the anisotropic correction yields reduced mean bias and improved precision of GOES-13 LST relative to independent Moderate-resolution Imaging Spectroradiometer (MYD11_L2) LST and Atmospheric Radiation Measurement Program ground station measurements. It also significantly reduces inter-satellite differences between LSTs retrieved simultaneously from two different imagers. The implementation of these universal corrections into the SatCORPS product can yield significant improvement in near-global-scale, near-realtime, satellite-based LST measurements. The immediate availability and broad coverage of these skin temperature observations should prove valuable to modelers and climate researchers looking for improved forecasts and better understanding of the global climate model.

Defining the Post-Machined Sub-surface in Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Srinivasan, N.; Sunil Kumar, B.; Kain, V.; Birbilis, N.; Joshi, S. S.; Sivaprasad, P. V.; Chai, G.; Durgaprasad, A.; Bhattacharya, S.; Samajdar, I.

2018-04-01

Austenitic stainless steels grades, with differences in chemistry, stacking fault energy, and thermal conductivity, were subjected to vertical milling. Anodic potentiodynamic polarization was able to differentiate (with machining speed/strain rate) between different post-machined sub-surfaces in SS 316L and Alloy A (a Cu containing austenitic stainless steel: Sanicroe 28™), but not in SS 304L. However, such differences (in the post-machined sub-surfaces) were revealed in surface roughness, sub-surface residual stresses and misorientations, and in the relative presence of sub-surface Cr2O3 films. It was shown, quantitatively, that higher machining speed reduced surface roughness and also reduced the effective depths of the affected sub-surface layers. A qualitative explanation on the sub-surface microstructural developments was provided based on the temperature-dependent thermal conductivity values. The results herein represent a mechanistic understanding to rationalize the corrosion performance of widely adopted engineering alloys.

Defining the Post-Machined Sub-surface in Austenitic Stainless Steels

NASA Astrophysics Data System (ADS)

Srinivasan, N.; Sunil Kumar, B.; Kain, V.; Birbilis, N.; Joshi, S. S.; Sivaprasad, P. V.; Chai, G.; Durgaprasad, A.; Bhattacharya, S.; Samajdar, I.

2018-06-01

Austenitic stainless steels grades, with differences in chemistry, stacking fault energy, and thermal conductivity, were subjected to vertical milling. Anodic potentiodynamic polarization was able to differentiate (with machining speed/strain rate) between different post-machined sub-surfaces in SS 316L and Alloy A (a Cu containing austenitic stainless steel: Sanicroe 28™), but not in SS 304L. However, such differences (in the post-machined sub-surfaces) were revealed in surface roughness, sub-surface residual stresses and misorientations, and in the relative presence of sub-surface Cr2O3 films. It was shown, quantitatively, that higher machining speed reduced surface roughness and also reduced the effective depths of the affected sub-surface layers. A qualitative explanation on the sub-surface microstructural developments was provided based on the temperature-dependent thermal conductivity values. The results herein represent a mechanistic understanding to rationalize the corrosion performance of widely adopted engineering alloys.

Development of High-k Dielectric for Antimonides and a sub 350 degree Celsius III-V pMOSFET Outperforming Germanium

DTIC Science & Technology

2010-12-01

due to BTBT was observed in the surface channel device (Figure 23). Buried channel device moves the maximum E-field due to VGD in the WB cap (Figure...23(inset)) suppressing BTBT which might be the dominant component of IOFF in scaled devices [10]. Lastly, a 4.3% increase in ID was observed when...inset : SS with T). Fig. 21 : Temp Dependence of mobility. Fig. 23 :GIDL due to BTBT seen in surface channel device at 80K. Use of wide bandgap (WB

Measurement of dissolved Cs-137 in stream water, soil water and groundwater at Headwater Forested Catchment in Fukushima after Fukushima Dai-ichi Nuclear Power Plant Accident

NASA Astrophysics Data System (ADS)

Iwagami, Sho; Tsujimura, Maki; Onda, Yuichi; Sakakibara, Koichi; Konuma, Ryohei; Sato, Yutaro

2016-04-01

Radiocesium migration from headwater forested catchment is important perception as output from the forest which is also input to the subsequent various land use and downstream rivers after Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. In this study, dissolved Cs-137 concentration of stream water, soil water and groundwater were measured. Observations were conducted at headwater catchment in Yamakiya district, located 35 km northwest of FDNPP from April 2014 to November 2015. Stream water discharge was monitored and stream water samples were taken at main channel and sub channel. Stream water discharge was monitored by combination of parshallflume and v-notch weir. Stream water was sampled manually at steady state condition in 3-4 month interval and also intense few hours interval sampling were conducted during rainfall events using automated water sampler. Around the sub channel, it is found that there is a regularly saturated area at the bottom of the slope, temporary saturated area which saturate during the rainy season in summer and regularly dry area. 6 interval cameras were installed to monitor the changing situation of saturated area. Suction lysimeters were installed at three areas (regularly saturated area, temporary saturated area and dry area) for sampling soil water in depth of 0.1 m and 0.3 m. Boreholes were installed at three points along the sub channel. Three boreholes with depth of 3 m, 5 m and 10 m were installed at temporary saturated area, 20 m upstream of sub channel weir. Another three boreholes with depth of 3 m, 5 m and 10 m were installed at dry area, 40 m upstream of sub channel weir. And a borehole with depth of 20 m was installed at ridge of sub catchment, 52 m upstream of sub channel weir. Groundwater was sampled by electrically powered pump and groundwater level was monitored. Also suction-free lysimeter was installed at temporary saturated area for sampling the near surface subsurface water. Soil water samples were collected as much as collected in flask. Stream water and groundwater samples were collected for 40 L each. All the water samples were filtered through 0.45 μm pore-size membrane. Water samples with less than few L were concentrated by evaporative concentration. Water samples with more than 40 L were concentrated using the ammonium molybdophosphate (AMP)/Cs compound method. The Cs-137 concentration was determined using gamma-ray spectrometry with a germanium semiconductor detector. Spatial distribution of dissolved Cs-137 concentration in the slope was obtained and the source of Cs-137 concentration in stream water was examined. The Cs-137 concentration in groundwater showed low value of 0.0004-0.001 Bq/L. The Cs-137 concentration of soil water showed 0.01-0.1 Bq/L. And Cs-137 concentrations of stream water were 0.007-0.03 Bq/L at steady state condition. Also Cs-137 concentrations in stream water showed temporary increase during rainfall event. The source of dissolved Cs-137 was suggested to be shallow soil water under saturated condition or leaching from the litter might be affecting.

Improved Surface and Tropospheric Temperatures Determined Using Only Shortwave Channels: The AIRS Science Team Version-6 Retrieval Algorithm

NASA Technical Reports Server (NTRS)

Susskind, Joel; Blaisdell, John; Iredell, Lena

2011-01-01

The Goddard DISC has generated products derived from AIRS/AMSU-A observations, starting from September 2002 when the AIRS instrument became stable, using the AIRS Science Team Version-5 retrieval algorithm. The AIRS Science Team Version-6 retrieval algorithm will be finalized in September 2011. This paper describes some of the significant improvements contained in the Version-6 retrieval algorithm, compared to that used in Version-5, with an emphasis on the improvement of atmospheric temperature profiles, ocean and land surface skin temperatures, and ocean and land surface spectral emissivities. AIRS contains 2378 spectral channels covering portions of the spectral region 650 cm(sup -1) (15.38 micrometers) - 2665 cm(sup -1) (3.752 micrometers). These spectral regions contain significant absorption features from two CO2 absorption bands, the 15 micrometers (longwave) CO2 band, and the 4.3 micrometers (shortwave) CO2 absorption band. There are also two atmospheric window regions, the 12 micrometer - 8 micrometer (longwave) window, and the 4.17 micrometer - 3.75 micrometer (shortwave) window. Historically, determination of surface and atmospheric temperatures from satellite observations was performed using primarily observations in the longwave window and CO2 absorption regions. According to cloud clearing theory, more accurate soundings of both surface skin and atmospheric temperatures can be obtained under partial cloud cover conditions if one uses observations in longwave channels to determine coefficients which generate cloud cleared radiances R(sup ^)(sub i) for all channels, and uses R(sup ^)(sub i) only from shortwave channels in the determination of surface and atmospheric temperatures. This procedure is now being used in the AIRS Version-6 Retrieval Algorithm. Results are presented for both daytime and nighttime conditions showing improved Version-6 surface and atmospheric soundings under partial cloud cover.

Amphotericin B channels in phospholipid membrane-coated nanoporous silicon surfaces: implications for photovoltaic driving of ions across membranes.

PubMed

Yilma, Solomon; Liu, Nangou; Samoylov, Alexander; Lo, Ting; Brinker, C Jeffrey; Vodyanoy, Vitaly

2007-03-15

The antimycotic agent amphotericin B (AmB) functions by forming complexes with sterols to form ion channels that cause membrane leakage. When AmB and cholesterol mixed at 2:1 ratio were incorporated into phospholipid bilayer membranes formed on the tip of patch pipettes, ion channel current fluctuations with characteristic open and closed states were observed. These channels were also functional in phospholipid membranes formed on nanoporous silicon surfaces. Electrophysiological studies of AmB-cholesterol mixtures that were incorporated into phospholipid membranes formed on the surface of nanoporous (6.5 nm pore diameter) silicon plates revealed large conductance ion channels ( approximately 300 pS) with distinct open and closed states. Currents through the AmB-cholesterol channels on nanoporous silicon surfaces can be driven by voltage applied via conventional electrical circuits or by photovoltaic electrical potential entirely generated when the nanoporous silicon surface is illuminated with a narrow laser beam. Electrical recordings made during laser illumination of AmB-cholesterol containing membrane-coated nanoporous silicon surfaces revealed very large conductance ion channels with distinct open and closed states. Our findings indicate that nanoporous silicon surfaces can serve as mediums for ion-channel-based biosensors. The photovoltaic properties of nanoporous silicon surfaces show great promise for making such biosensors addressable via optical technologies.

N2O EMISSIONS FROM STREAMS IN THE NEUSE RIVER WATERSHED, NORTH CAROLINA

EPA Science Inventory

The paper presents N₂O emission data from 11 sites in the Neuse River watershed. Emissions were measured using a static surface enclosure technique deployed on eight sites on the main river channel and three tributary sites. Ancillary data collected included dissolved ...

Origin and enhancement of spin polarized current in diluted magnetic oxides by oxygen vacancies

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

Chou, Hsiung, E-mail: hchou@mail.nsysu.edu.tw; Yang, Kung-Shang; Tsao, Yao-Chung

Spin polarized current (SPC) is a crucial characteristic of diluted magnetic oxides due to the potential application of oxides in spintronic devices. However, most research has been focused on ferromagnetic properties rather than polarization of electric current, because direct measurements are difficult and the origin of SPC has yet to be fully understood. The method to increase the SPC percentage is beyond practical consideration at present. To address this problem, we focus on the role of oxygen vacancies (V{sub O}) on SPC, which are controlled by growing the Co-doped ZnO thin-films at room temperature in a reducing atmosphere [Ar + (1%–30%)H{sub 2}].more » We found that the conductivity increases with an increase of V{sub O} via two independent channels: the variable range hopping (VRH) within localized states and the itinerant transport in the conduction band. The point contact Andreev reflection measurements at 4.2 K, where the electric conduction is governed only by the VRH mechanism, prove that the current flowing in the VRH hopping channel is SPC. The percentage of SPC increases with the introduction of V{sub O} and increase in its concentration. The transport measurement shows that by manipulating V{sub O}, one can control the percentage of VRH hopping conduction such that it can even dominate room temperature conduction. The highest achieved SPC ratio at room temperature was 80%.« less

Infrared Study of CO2 Sorption over ?Molecular Basket? Sorbent Consisting of Polyethylenimine-Modified Mesoporous Molecular Sieve

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

Overbury, Steven; Wang, Xiaoxing; Clark, Jason

2009-01-01

An infrared study has been conducted on CO{sub 2} sorption into nanoporous CO{sub 2} 'molecular basket' sorbents prepared by loading polyethylenimine (PEI) into mesoporous molecular sieve SBA-15. IR results from DRIFTS showed that a part of loaded PEI is anchored on the surface of SBA-15 through the interaction between amine groups and isolated surface silanol groups. Raising the temperature from 25 to 75 C increased the molecular flexibility of PEI loaded in the mesopore channels, which may partly contribute to the increase of CO{sub 2} sorption capacity at higher temperatures. CO{sub 2} sorption/desorption behavior studied by in situ transmission FTIRmore » showed that CO{sub 2} is sorbed on amine sites through the formation of alkylammonium carbamates and absorbed into the multiple layers of PEI located in mesopores of SBA-15. A new observation by in situ IR is that two broad IR bands emerged at 2450 and 2160 cm{sup -1} with CO{sub 2} flowing over PEI(50)/SBA-15, which could be attributed to chemically sorbed CO{sub 2} species on PEI molecules inside the mesopores of SBA-15. The intensities of these two bands also increased with increasing CO{sub 2} exposure time and with raising CO{sub 2} sorption temperature. By comparison of the CO{sub 2} sorption rate at 25 and 75 C in terms of differential IR intensities, it was found that CO{sub 2} sorption over molecular basket sorbent includes two rate regimes which suggest two distinct steps: rapid sorption on exposed outer surface layers of PEI (controlled by sorption affinity or thermodynamics) and the diffusion and sorption inside the bulk of multiple layers of PEI (controlled by diffusion). The sorption of CO{sub 2} is reversible at 75 C. Comparative IR examination of the CO{sub 2} sorption/desorption spectra on dry and prewetted PEI/SBA-15 sorbent revealed that presorbed water does not significantly affect the CO{sub 2}-amine interaction patterns.« less

An experimental investigation of liquid methane convection and boiling in rocket engine cooling channels

NASA Astrophysics Data System (ADS)

Trujillo, Abraham Gerardo

In the past decades, interest in developing hydrocarbon-fueled rocket engines for deep spaceflight missions has continued to grow. In particular, liquid methane (LCH4) has been of interest due to the weight efficiency, storage, and handling advantages it offers over several currently used propellants. Deep space exploration requires reusable, long life rocket engines. Due to the high temperatures reached during combustion, the life of an engine is significantly impacted by the cooling system's efficiency. Regenerative (regen) cooling is presented as a viable alternative to common cooling methods such as film and dump cooling since it provides improved engine efficiency. Due to limited availability of experimental sub-critical liquid methane cooling data for regen engine design, there has been an interest in studying the heat transfer characteristics of the propellant. For this reason, recent experimental studies at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso (UTEP) have focused on investigating the heat transfer characteristics of sub-critical CH4 flowing through sub-scale cooling channels. To conduct the experiments, the csETR developed a High Heat Flux Test Facility (HHFTF) where all the channels are heated using a conduction-based thermal concentrator. In this study, two smooth channels with cross sectional geometries of 1.8 mm x 4.1 mm and 3.2 mm x 3.2 mm were tested. In addition, three roughened channels all with a 3.2 mm x 3.2 mm square cross section were also tested. For the rectangular smooth channel, Reynolds numbers ranged between 68,000 and 131,000, while the Nusselt numbers were between 40 and 325. For the rough channels, Reynolds numbers ranged from 82,000 to 131,000, and Nusselt numbers were between 65 and 810. Sub-cooled film-boiling phenomena were confirmed for all the channels presented in this work. Film-boiling onset at Critical Heat Flux (CHF) was correlated to a Boiling Number (Bo) of approximately 0.1 for all channels. Convective Nusselt number follows predicted trends for Reynolds number with a wall temperature correction for both the boiling and non-boiling regimes.

Top-gated field-effect LaAlO{sub 3}/SrTiO{sub 3} devices made by ion-irradiation

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

Hurand, S.; Jouan, A.; Feuillet-Palma, C.

2016-02-01

We present a method to fabricate top-gated field-effect devices in a LaAlO{sub 3}/SrTiO{sub 3} two-dimensional electron gas (2-DEG). Prior to the gate deposition, the realisation of micron size conducting channels in the 2-DEG is achieved by an ion-irradiation with high-energy oxygen ions. After identifying the ion fluence as the key parameter that determines the electrical transport properties of the channels, we demonstrate the field-effect operation. At low temperature, the normal state resistance and the superconducting T{sub c} can be tuned over a wide range by a top-gate voltage without any leakage. A superconductor-to-insulator quantum phase transition is observed for amore » strong depletion of the 2-DEG.« less

Development and characterization of a diamond-insulated graphitic multi electrode array realized with ion beam lithography.

PubMed

Picollo, Federico; Battiato, Alfio; Carbone, Emilio; Croin, Luca; Enrico, Emanuele; Forneris, Jacopo; Gosso, Sara; Olivero, Paolo; Pasquarelli, Alberto; Carabelli, Valentina

2014-12-30

The detection of quantal exocytic events from neurons and neuroendocrine cells is a challenging task in neuroscience. One of the most promising platforms for the development of a new generation of biosensors is diamond, due to its biocompatibility, transparency and chemical inertness. Moreover, the electrical properties of diamond can be turned from a perfect insulator into a conductive material (resistivity ~mΩ·cm) by exploiting the metastable nature of this allotropic form of carbon. A 16‑channels MEA (Multi Electrode Array) suitable for cell culture growing has been fabricated by means of ion implantation. A focused 1.2 MeV He+ beam was scanned on a IIa single-crystal diamond sample (4.5 × 4.5 × 0.5 mm3) to cause highly damaged sub-superficial structures that were defined with micrometric spatial resolution. After implantation, the sample was annealed. This process provides the conversion of the sub-superficial highly damaged regions to a graphitic phase embedded in a highly insulating diamond matrix. Thanks to a three-dimensional masking technique, the endpoints of the sub-superficial channels emerge in contact with the sample surface, therefore being available as sensing electrodes. Cyclic voltammetry and amperometry measurements of solutions with increasing concentrations of adrenaline were performed to characterize the biosensor sensitivity. The reported results demonstrate that this new type of biosensor is suitable for in vitro detection of catecholamine release.

Modeling and analysis of sub-surface leakage current in nano-MOSFET under cutoff regime

NASA Astrophysics Data System (ADS)

Swami, Yashu; Rai, Sanjeev

2017-02-01

The high leakage current in nano-meter regimes is becoming a significant portion of power dissipation in nano-MOSFET circuits as threshold voltage, channel length, and gate oxide thickness are scaled down to nano-meter range. Precise leakage current valuation and meticulous modeling of the same at nano-meter technology scale is an increasingly a critical work in designing the low power nano-MOSFET circuits. We present a specific compact model for sub-threshold regime leakage current in bulk driven nano-MOSFETs. The proposed logical model is instigated and executed into the latest updated PTM bulk nano-MOSFET model and is found to be in decent accord with technology-CAD simulation data. This paper also reviews various transistor intrinsic leakage mechanisms for nano-MOSFET exclusively in weak inversion, like drain-induced barricade lowering (DIBL), gate-induced drain leakage (GIDL), gate oxide tunneling (GOT) leakage etc. The root cause of the sub-surface leakage current is mainly due to the nano-scale short channel length causing source-drain coupling even in sub-threshold domain. Consequences leading to carriers triumphing the barricade between the source and drain. The enhanced model effectively considers the following parameter dependence in the account for better-quality value-added results like drain-to-source bias (VDS), gate-to-source bias (VGS), channel length (LG), source/drain junction depth (Xj), bulk doping concentration (NBULK), and operating temperature (Top).

Electrically conducting polyimide film containing tin complexes

NASA Technical Reports Server (NTRS)

St. Clair, Anne K. (Inventor); Ezzell, Stephen A. (Inventor); Taylor, Larry T. (Inventor); Boston, Harold G. (Inventor)

1996-01-01

Disclosed is a thermally-stable SnO.sub.2 -surfaced polyimide film wherein the electrical conductivity of the SnO.sub.2 surface is within the range of about 3.0.times.10.sup.-3 to about 1.times.10.sup.-2 ohms.sup.-1,. Also disclosed is a method of preparing this film from a solution containing a polyamic acid and SnCl.sub.4 (DMSO).sub.2.

Damage free Ar ion plasma surface treatment on In{sub 0.53}Ga{sub 0.47}As-on-silicon metal-oxide-semiconductor device

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

Koh, Donghyi; Shin, Seung Heon; Ahn, Jaehyun

2015-11-02

In this paper, we investigated the effect of in-situ Ar ion plasma surface pre-treatment in order to improve the interface properties of In{sub 0.53}Ga{sub 0.47}As for high-κ top-gate oxide deposition. X-ray photoelectron spectroscopy (XPS) and metal-oxide-semiconductor capacitors (MOSCAPs) demonstrate that Ar ion treatment removes the native oxide on In{sub 0.53}Ga{sub 0.47}As. The XPS spectra of Ar treated In{sub 0.53}Ga{sub 0.47}As show a decrease in the AsO{sub x} and GaO{sub x} signal intensities, and the MOSCAPs show higher accumulation capacitance (C{sub acc}), along with reduced frequency dispersion. In addition, Ar treatment is found to suppress the interface trap density (D{sub it}),more » which thereby led to a reduction in the threshold voltage (V{sub th}) degradation during constant voltage stress and relaxation. These results outline the potential of surface treatment for III-V channel metal-oxide-semiconductor devices and application to non-planar device process.« less

Electroosmotic flow and ionic conductance in a pH-regulated rectangular nanochannel

NASA Astrophysics Data System (ADS)

Sadeghi, Morteza; Saidi, Mohammad Hassan; Sadeghi, Arman

2017-06-01

Infinite series solutions are obtained for electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties of long pH-regulated rectangular nanochannels of low surface potential utilizing the double finite Fourier transform method. Closed form expressions are also obtained for channels of large height to width ratio for which the depthwise variations vanish. Neglecting the Stern layer impact, the effects of EDL (Electric Double Layer) overlap, multiple ionic species, and association/dissociation reactions on the surface are all taken into account. Moreover, finite-element-based numerical simulations are conducted to account for the end effects as well as to validate the analytical solutions. We show that, with the exception of the migratory ionic conductivity, all the physicochemical parameters are strong functions of the channel aspect ratio. Accordingly, a slit geometry is not a good representative of a rectangular channel when the width is comparable to the height. It is also observed that the distribution of the electrical potential is not uniform over the surface of a charge-regulated channel. In addition, unlike ordinary channels for which an increase in the background salt concentration is always accompanied by higher flow rates, quite the opposite may be true for a pH-regulated duct at higher salt concentrations.

A permutationally invariant full-dimensional ab initio potential energy surface for the abstraction and exchange channels of the H + CH{sub 4} system

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

Li, Jun, E-mail: jli15@cqu.edu.cn, E-mail: zhangdh@dicp.ac.cn; Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131; Chen, Jun

2015-05-28

We report a permutationally invariant global potential energy surface (PES) for the H + CH{sub 4} system based on ∼63 000 data points calculated at a high ab initio level (UCCSD(T)-F12a/AVTZ) using the recently proposed permutation invariant polynomial-neural network method. The small fitting error (5.1 meV) indicates a faithful representation of the ab initio points over a large configuration space. The rate coefficients calculated on the PES using tunneling corrected transition-state theory and quasi-classical trajectory are found to agree well with the available experimental and previous quantum dynamical results. The calculated total reaction probabilities (J{sub tot} = 0) including themore » abstraction and exchange channels using the new potential by a reduced dimensional quantum dynamic method are essentially the same as those on the Xu-Chen-Zhang PES [Chin. J. Chem. Phys. 27, 373 (2014)].« less

Delayed fission and multifragmentation in sub-keV C60 - Au(0 0 1) collisions via molecular dynamics simulations: Mass distributions and activated statistical decay

NASA Astrophysics Data System (ADS)

Bernstein, V.; Kolodney, E.

2017-10-01

We have recently observed, both experimentally and computationally, the phenomenon of postcollision multifragmentation in sub-keV surface collisions of a C60 projectile. Namely, delayed multiparticle breakup of a strongly impact deformed and vibrationally excited large cluster collider into several large fragments, after leaving the surface. Molecular dynamics simulations with extensive statistics revealed a nearly simultaneous event, within a sub-psec time window. Here we study, computationally, additional essential aspects of this new delayed collisional fragmentation which were not addressed before. Specifically, we study here the delayed (binary) fission channel for different impact energies both by calculating mass distributions over all fission events and by calculating and analyzing lifetime distributions of the scattered projectile. We observe an asymmetric fission resulting in a most probable fission channel and we find an activated exponential (statistical) decay. Finally, we also calculate and discuss the fragment mass distribution in (triple) multifragmentation over different time windows, in terms of most abundant fragments.

S-matrix decomposition, natural reaction channels, and the quantum transition state approach to reactive scattering

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

Manthe, Uwe, E-mail: uwe.manthe@uni-bielefeld.de; Ellerbrock, Roman, E-mail: roman.ellerbrock@uni-bielefeld.de

2016-05-28

A new approach for the quantum-state resolved analysis of polyatomic reactions is introduced. Based on the singular value decomposition of the S-matrix, energy-dependent natural reaction channels and natural reaction probabilities are defined. It is shown that the natural reaction probabilities are equal to the eigenvalues of the reaction probability operator [U. Manthe and W. H. Miller, J. Chem. Phys. 99, 3411 (1993)]. Consequently, the natural reaction channels can be interpreted as uniquely defined pathways through the transition state of the reaction. The analysis can efficiently be combined with reactive scattering calculations based on the propagation of thermal flux eigenstates. Inmore » contrast to a decomposition based straightforwardly on thermal flux eigenstates, it does not depend on the choice of the dividing surface separating reactants from products. The new approach is illustrated studying a prototypical example, the H + CH{sub 4} → H{sub 2} + CH{sub 3} reaction. The natural reaction probabilities and the contributions of the different vibrational states of the methyl product to the natural reaction channels are calculated and discussed. The relation between the thermal flux eigenstates and the natural reaction channels is studied in detail.« less

The study and development of the empirical correlations equation of natural convection heat transfer on vertical rectangular sub-channels

NASA Astrophysics Data System (ADS)

Kamajaya, Ketut; Umar, Efrizon; Sudjatmi, K. S.

2012-06-01

This study focused on natural convection heat transfer using a vertical rectangular sub-channel and water as the coolant fluid. To conduct this study has been made pipe heaters are equipped with thermocouples. Each heater is equipped with five thermocouples along the heating pipes. The diameter of each heater is 2.54 cm and 45 cm in length. The distance between the central heating and the pitch is 29.5 cm. Test equipment is equipped with a primary cooling system, a secondary cooling system and a heat exchanger. The purpose of this study is to obtain new empirical correlations equations of the vertical rectangular sub-channel, especially for the natural convection heat transfer within a bundle of vertical cylinders rectangular arrangement sub-channels. The empirical correlation equation can support the thermo-hydraulic analysis of research nuclear reactors that utilize cylindrical fuel rods, and also can be used in designing of baffle-free vertical shell and tube heat exchangers. The results of this study that the empirical correlation equations of natural convection heat transfer coefficients with rectangular arrangement is Nu = 6.3357 (Ra.Dh/x)0.0740.

Dysregulated Zn2+ homeostasis impairs cardiac type-2 ryanodine receptor and mitsugumin 23 functions, leading to sarcoplasmic reticulum Ca2+ leakage.

PubMed

Reilly-O'Donnell, Benedict; Robertson, Gavin B; Karumbi, Angela; McIntyre, Connor; Bal, Wojciech; Nishi, Miyuki; Takeshima, Hiroshi; Stewart, Alan J; Pitt, Samantha J

2017-08-11

Aberrant Zn 2+ homeostasis is associated with dysregulated intracellular Ca 2+ release, resulting in chronic heart failure. In the failing heart a small population of cardiac ryanodine receptors (RyR2) displays sub-conductance-state gating leading to Ca 2+ leakage from sarcoplasmic reticulum (SR) stores, which impairs cardiac contractility. Previous evidence suggests contribution of RyR2-independent Ca 2+ leakage through an uncharacterized mechanism. We sought to examine the role of Zn 2+ in shaping intracellular Ca 2+ release in cardiac muscle. Cardiac SR vesicles prepared from sheep or mouse ventricular tissue were incorporated into phospholipid bilayers under voltage-clamp conditions, and the direct action of Zn 2+ on RyR2 channel function was examined. Under diastolic conditions, the addition of pathophysiological concentrations of Zn 2+ (≥2 nm) caused dysregulated RyR2-channel openings. Our data also revealed that RyR2 channels are not the only SR Ca 2+ -permeable channels regulated by Zn 2+ Elevating the cytosolic Zn 2+ concentration to 1 nm increased the activity of the transmembrane protein mitsugumin 23 (MG23). The current amplitude of the MG23 full-open state was consistent with that previously reported for RyR2 sub-conductance gating, suggesting that in heart failure in which Zn 2+ levels are elevated, RyR2 channels do not gate in a sub-conductance state, but rather MG23-gating becomes more apparent. We also show that in H9C2 cells exposed to ischemic conditions, intracellular Zn 2+ levels are elevated, coinciding with increased MG23 expression. In conclusion, these data suggest that dysregulated Zn 2+ homeostasis alters the function of both RyR2 and MG23 and that both ion channels play a key role in diastolic SR Ca 2+ leakage. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

In situ monitoring of atomic layer controlled pore reduction in alumina tubular membranes using sequential surface reactions

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

Berland, B.S.; Gartland, I.P.; Ott, A.W.

1998-12-01

The pore diameter in alumina tubular membranes with an initial diameter of 50 {angstrom} was systematically reduced using the atomic layer controlled deposition of Al{sub 2}O{sub 3}. The Al{sub 2}O{sub 3} was deposited using sequential exposures of Al(CH{sub 3}){sub 3} (trimethylaluminum, TMA) and H{sub 2}O in an ABAB... binary reaction sequence. The pore diameter reduction was monitored using in situ N{sub 2} and Ar conductance measurements. The conductance, C = Q/{Delta}P, was measured using a mass flow controller to define a constant gas throughput, Q, and a pair of capacitance manometers to monitor the transmembrane pressure drop, {Delta}P. Conductance measurementsmore » were periodically obtained at 298 K as a function of AB binary reaction cycles. These conductance measurements were consistent with a pore diameter reduction from 50 {angstrom} to {approximately}5--10 {angstrom} at a rate of {approximately}2.5 {angstrom} for each AB cycle. Conductance measurements were also performed during the Al{sub 2}O{sub 3} deposition at 500 K after each half-reaction in the binary reaction sequence. These in situ conductance measurements demonstrate that the pore diameters in mesoporous membranes can be reduced to molecular dimensions with atomic layer control using sequential surface reactions. Poe diameters can be tailored for specific applications by varying the number of AB cycles and changing the nature of the terminating surface functional groups.« less

Solid oxide fuel cell with multi-unit construction and prismatic design

DOEpatents

McPheeters, Charles C.; Dees, Dennis W.; Myles, Kevin M.

1999-01-01

A single cell unit of a solid oxide fuel cell that is individually fabricated and sintered prior to being connected to adjacent cells to form a solid oxide fuel cell. The single cell unit is comprised of a shaped anode sheet positioned between a flat anode sheet and an anode-electrolyte-cathode (A/E/C) sheet, and a shaped cathode sheet positioned between the A/E/C sheet and a cathode-interconnect-anode (C/I/A) sheet. An alternate embodiment comprises a shaped cathode sheet positioned between an A/E/C sheet and a C/I/A sheet. The shaped sheets form channels for conducting reactant gases. Each single cell unit is individually sintered to form a finished sub-assembly. The finished sub-assemblies are connected in electrical series by interposing connective material between the end surfaces of adjacent cells, whereby individual cells may be inspected for defects and interchanged with non-defective single cell units.

Heteroepitaxial growth of In{sub 0.30}Ga{sub 0.70}As high-electron mobility transistor on 200 mm silicon substrate using metamorphic graded buffer

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

Kohen, David, E-mail: david.kohen@asm.com; Nguyen, Xuan Sang; Made, Riko I

We report on the growth of an In{sub 0.30}Ga{sub 0.70}As channel high-electron mobility transistor (HEMT) on a 200 mm silicon wafer by metal organic vapor phase epitaxy. By using a 3 μm thick buffer comprising a Ge layer, a GaAs layer and an InAlAs compositionally graded strain relaxing buffer, we achieve threading dislocation density of (1.0 ± 0.3) × 10{sup 7} cm{sup −2} with a surface roughness of 10 nm RMS. No phase separation was observed during the InAlAs compositionally graded buffer layer growth. 1.4 μm long channel length transistors are fabricated from the wafer with I{sub DS} of 70more » μA/μm and g{sub m} of above 60 μS/μm, demonstrating the high quality of the grown materials.« less

Nanostructuring of conduction channels in (In,Ga)As-InP heterostructures: Overcoming carrier generation caused by Ar ion milling

NASA Astrophysics Data System (ADS)

Hortelano, V.; Weidlich, H.; Semtsiv, M. P.; Masselink, W. T.; Ramsteiner, M.; Jahn, U.; Biermann, K.; Takagaki, Y.

2018-04-01

Nanometer-sized channels are fabricated in (In,Ga)As-InP heterostructures using Ar ion milling. The ion milling causes spontaneous creation of nanowires, and moreover, electrical conduction of the surface as carriers is generated by sputtering-induced defects. We demonstrate a method to restore electrical isolation in the etched area that is compatible with the presence of the nanochannels. We remove the heavily damaged surface layer using a diluted HCl solution and subsequently recover the crystalline order in the moderately damaged part by annealing. We optimize the HCl concentration to make the removal stop on its own before reaching the conduction channel part. The lateral depletion in the channels is shown to be almost absent.

Measuring stream discharge by non-contact methods: A proof-of-concept experiment

USGS Publications Warehouse

Costa, J.E.; Spicer, K.R.; Cheng, R.T.; Haeni, F.P.; Melcher, N.B.; Thurman, E.M.; Plant, W.J.; Keller, W.C.

2000-01-01

This report describes an experiment to make a completely non-contact open-channel discharge measurement. A van-mounted, pulsed doppler (10GHz) radar collected surface-velocity data across the 183-m wide Skagit River, Washington at a USGS streamgaging station using Bragg scattering from short waves produced by turbulent boils on the surface of the river. Surface velocities were converted to mean velocities for 25 sub-sections by assuming a normal open-channel velocity profile (surface velocity times 0.85). Channel cross-sectional area was measured using a 100 MHz ground-penetrating radar antenna suspended from a cableway car over the river. Seven acoustic doppler current profiler discharge measurements and a conventional current-meter discharge measurement were also made. Three non-contact discharge measurements completed in about a 1-hour period were within 1 % of the gaging station rating curve discharge values. With further refinements, it is thought that open-channel flow can be measured reliably by non-contact methods.

A microscale three-dimensional urban energy balance model for studying surface temperatures

NASA Astrophysics Data System (ADS)

Krayenhoff, E. Scott; Voogt, James A.

2007-06-01

A microscale three-dimensional (3-D) urban energy balance model, Temperatures of Urban Facets in 3-D (TUF-3D), is developed to predict urban surface temperatures for a variety of surface geometries and properties, weather conditions, and solar angles. The surface is composed of plane-parallel facets: roofs, walls, and streets, which are further sub-divided into identical square patches, resulting in a 3-D raster-type model geometry. The model code is structured into radiation, conduction and convection sub-models. The radiation sub-model uses the radiosity approach and accounts for multiple reflections and shading of direct solar radiation. Conduction is solved by finite differencing of the heat conduction equation, and convection is modelled by empirically relating patch heat transfer coefficients to the momentum forcing and the building morphology. The radiation and conduction sub-models are tested individually against measurements, and the complete model is tested against full-scale urban surface temperature and energy balance observations. Modelled surface temperatures perform well at both the facet-average and the sub-facet scales given the precision of the observations and the uncertainties in the model inputs. The model has several potential applications, such as the calculation of radiative loads, and the investigation of effective thermal anisotropy (when combined with a sensor-view model).

Study of the interaction mechanisms between absorbed NO{sub 2} and por-Si/SnO{sub x} nanocomposite layers

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

Bolotov, V. V.; Kan, V. E., E-mail: kan@obisp.oscsbras.ru; Makushenko, R. K.

2013-10-15

The interaction mechanisms between NO{sub 2} molecules and the surface of por-Si/SnO{sub x} nanocomposites obtained by magnetron deposition and chemical vapor deposition (CVD) are studied by infrared absorption spectroscopy and electron paramagnetic resonance methods. The observed increase in the free carrier concentration in the por-Si/SnO{sub x} nanocomposite layers is explained by a change in the charge state of P{sub b} centers due to the formation of neutral 'surface defect-adsorbed NO{sub 2} molecule' complexes with free carrier generation in the crystallite bulk. In the nanocomposite layers grown by the CVD method, the increase in the free hole concentration during NO{sub 2}more » adsorption is much less pronounced in comparison with the composite grown by magnetron deposition, which is caused by the competing interaction channel of NO{sub 2} molecules with electrically neutral P{sub b} centers.« less

Streamer discharges as advancing imperfect conductors: inhomogeneities in long ionized channels

NASA Astrophysics Data System (ADS)

Luque, A.; González, M.; Gordillo-Vázquez, F. J.

2017-12-01

A major obstacle for the understanding of long electrical discharges is the complex dynamics of streamer coronas, formed by many thin conducting filaments. Building macroscopic models for these filaments is one approach to attain a deeper knowledge of the discharge corona. Here, we present a one-dimensional, macroscopic model of a propagating streamer channel with a finite and evolving internal conductivity. We represent the streamer as an advancing finite-conductivity channel with a surface charge density at its boundary. This charge evolves self-consistently due to the electric current that flows through the streamer body and within a thin layer at its surface. We couple this electrodynamic evolution with a field-dependent set of chemical reactions that determine the internal channel conductivity. With this one-dimensional model, we investigate the formation of persisting structures in the wake of a streamer head. In accordance with experimental observations, our model shows that a within a streamer channel some regions are driven towards high fields that can be maintaned for tens of nanoseconds.

Sub-micron surface plasmon resonance sensor systems

NASA Technical Reports Server (NTRS)

Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

2012-01-01

A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single microchip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

Sub-micron surface plasmon resonance sensor systems

NASA Technical Reports Server (NTRS)

Glazier, James A. (Inventor); Dragnea, Bogdan (Inventor); Amarie, Dragos (Inventor)

2010-01-01

A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single microchip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

Sub-micron surface plasmon resonance sensor systems

NASA Technical Reports Server (NTRS)

Amarie, Dragos (Inventor); Glazier, James A. (Inventor); Dragnea, Bogdan (Inventor)

2010-01-01

A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single micro-chip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

Sub-micron surface plasmon resonance sensor systems

NASA Technical Reports Server (NTRS)

Glazier, James A. (Inventor); Amarie, Dragos (Inventor)

2011-01-01

A sensor for detecting the presence of a target analyte, ligand or molecule in a test fluid, comprising a light transmissive substrate on which an array of surface plasmon resonant (SPR) elements is mounted is described. A multi-channel sensor for detecting the presence of several targets with a single micro-chip sensor is described. A multi-channel sensor including collections of SPR elements which are commonly functionalized to one of several targets is also described. The detectors sense changes in the resonant response of the SPR elements indicative of binding with the targets.

Channel Temperature Determination for AlGaN/GaN HEMTs on SiC and Sapphire

NASA Technical Reports Server (NTRS)

Freeman, Jon C.; Mueller, Wolfgang

2008-01-01

Numerical simulation results (with emphasis on channel temperature) for a single gate AlGaN/GaN High Electron Mobility Transistor (HEMT) with either a sapphire or SiC substrate are presented. The static I-V characteristics, with concomitant channel temperatures (T(sub ch)) are calculated using the software package ATLAS, from Silvaco, Inc. An in-depth study of analytical (and previous numerical) methods for the determination of T(sub ch) in both single and multiple gate devices is also included. We develop a method for calculating T(sub ch) for the single gate device with the temperature dependence of the thermal conductivity of all material layers included. We also present a new method for determining the temperature on each gate in a multi-gate array. These models are compared with experimental results, and show good agreement. We demonstrate that one may obtain the channel temperature within an accuracy of +/-10 C in some cases. Comparisons between different approaches are given to show the limits, sensitivities, and needed approximations, for reasonable agreement with measurements.

Evaluation of JPL Version-5.9.12 Temperature Profiles, Ocean Skin Temperature, Surface Emissivity, and Cloud Cleared Radiances

NASA Technical Reports Server (NTRS)

Susskind, Joel; Blaisdell, John; Iredell, Lena

2011-01-01

Slide presentation discusses: (1) Modifications to JPL 5.9.12 compared to V5.9.1, (2) Some results showing that V5.9.12 O, with original water vapor sounding channels, is preferable to V5.9.12 N with Antonia Gambacorta s new water vapor channels. (3) Comparison of V5.9.12, V5.9.12 AO, V5.9.1, and V5.0, (4) Accuracy and yield of channel by channel Quality Controlled clear-column radiances R(sub i) and (5) Plans for Version-7.

Communication: Direct measurements of nascent O({sup 3}P{sub 0,1,2}) fine-structure distributions and branching ratios of correlated spin-orbit resolved product channels CO(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) in VUV photodissociation of CO{sub 2}

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

Lu, Zhou; Chang, Yih Chung; Gao, Hong

2014-06-21

We present a generally applicable experimental method for the direct measurement of nascent spin-orbit state distributions of atomic photofragments based on the detection of vacuum ultraviolet (VUV)-excited autoionizing-Rydberg (VUV-EAR) states. The incorporation of this VUV-EAR method in the application of the newly established VUV-VUV laser velocity-map-imaging-photoion (VMI-PI) apparatus has made possible the branching ratio measurement for correlated spin-orbit state resolved product channels, CO(ã{sup 3}Π; v) + O({sup 3}P{sub 0,1,2}) and CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}), formed by VUV photoexcitation of CO{sub 2} to the 4s(1{sub 0}{sup 1}) Rydberg state at 97,955.7 cm{sup −1}. The total kinetic energy releasemore » (TKER) spectra obtained from the O{sup +} VMI-PI images of O({sup 3}P{sub 0,1,2}) reveal the formation of correlated CO(ã{sup 3}Π; v = 0–2) with well-resolved v = 0–2 vibrational bands. This observation shows that the dissociation of CO{sub 2} to form the spin-allowed CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel has no potential energy barrier. The TKER spectra for the spin-forbidden CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel were found to exhibit broad profiles, indicative of the formation of a broad range of rovibrational states of CO(Χ{sup ~1}Σ{sup +})  with significant vibrational populations for v = 18–26. While the VMI-PI images for the CO(ã{sup 3}Π; v = 0–2) + O({sup 3}P{sub 0,1,2}) channel are anisotropic, indicating that the predissociation of CO{sub 2} 4s(1{sub 0}{sup 1}) occurs via a near linear configuration in a time scale shorter than the rotational period, the angular distributions for the CO(Χ{sup ~1}Σ{sup +}; v) + O({sup 3}P{sub 0,1,2}) channel are close to isotropic, revealing a slower predissociation process, which possibly occurs on a triplet surface via an intersystem crossing mechanism.« less

TRIC-B channels display labile gating: evidence from the TRIC-A knockout mouse model.

PubMed

Venturi, Elisa; Matyjaszkiewicz, Antoni; Pitt, Samantha J; Tsaneva-Atanasova, Krasimira; Nishi, Miyuki; Yamazaki, Daiju; Takeshima, Hiroshi; Sitsapesan, Rebecca

2013-08-01

Sarcoplasmic/endoplasmic reticulum (SR) and nuclear membranes contain two related cation channels named TRIC-A and TRIC-B. In many tissues, both subtypes are co-expressed, making it impossible to distinguish the distinct single-channel properties of each subtype. We therefore incorporated skeletal muscle SR vesicles derived from Tric-a-knockout mice into bilayers in order to characterise the biophysical properties of native TRIC-B without possible misclassification of the channels as TRIC-A, and without potential distortion of functional properties by detergent purification protocols. The native TRIC-B channels were ideally selective for cations. In symmetrical 210 mM K(+), the maximum (full) open channel level (199 pS) was equivalent to that observed when wild-type SR vesicles were incorporated into bilayers. Analysis of TRIC-B gating revealed complex and variable behaviour. Four main sub-conductance levels were observed at approximately 80 % (161 pS), 60 % (123 pS), 46 % (93 pS), and 30 % (60 pS) of the full open state. Seventy-five percent of the channels were voltage sensitive with Po being markedly reduced at negative holding potentials. The frequent, rapid transitions between TRIC-B sub-conductance states prevented development of reliable gating models using conventional single-channel analysis. Instead, we used mean-variance plots to highlight key features of TRIC-B gating in a more accurate and visually useful manner. Our study provides the first biophysical characterisation of native TRIC-B channels and indicates that this channel would be suited to provide counter current in response to Ca(2+) release from the SR. Further experiments are required to distinguish the distinct functional properties of TRIC-A and TRIC-B and understand their individual but complementary physiological roles.

Development and Characterization of a Diamond-Insulated Graphitic Multi Electrode Array Realized with Ion Beam Lithography

PubMed Central

Picollo, Federico; Battiato, Alfio; Carbone, Emilio; Croin, Luca; Enrico, Emanuele; Forneris, Jacopo; Gosso, Sara; Olivero, Paolo; Pasquarelli, Alberto; Carabelli, Valentina

2015-01-01

The detection of quantal exocytic events from neurons and neuroendocrine cells is a challenging task in neuroscience. One of the most promising platforms for the development of a new generation of biosensors is diamond, due to its biocompatibility, transparency and chemical inertness. Moreover, the electrical properties of diamond can be turned from a perfect insulator into a conductive material (resistivity ∼mΩ·cm) by exploiting the metastable nature of this allotropic form of carbon. A 16-channels MEA (Multi Electrode Array) suitable for cell culture growing has been fabricated by means of ion implantation. A focused 1.2 MeV He+ beam was scanned on a IIa single-crystal diamond sample (4.5 × 4.5 × 0.5 mm3) to cause highly damaged sub-superficial structures that were defined with micrometric spatial resolution. After implantation, the sample was annealed. This process provides the conversion of the sub-superficial highly damaged regions to a graphitic phase embedded in a highly insulating diamond matrix. Thanks to a three-dimensional masking technique, the endpoints of the sub-superficial channels emerge in contact with the sample surface, therefore being available as sensing electrodes. Cyclic voltammetry and amperometry measurements of solutions with increasing concentrations of adrenaline were performed to characterize the biosensor sensitivity. The reported results demonstrate that this new type of biosensor is suitable for in vitro detection of catecholamine release. PMID:25558992

Nanometer-scale water- and proton-diffusion heterogeneities across water channels in polymer electrolyte membranes.

PubMed

Song, Jinsuk; Han, Oc Hee; Han, Songi

2015-03-16

Nafion, the most widely used polymer for electrolyte membranes (PEMs) in fuel cells, consists of a fluorocarbon backbone and acidic groups that, upon hydration, swell to form percolated channels through which water and ions diffuse. Although the effects of the channel structures and the acidic groups on water/ion transport have been studied before, the surface chemistry or the spatially heterogeneous diffusivity across water channels has never been shown to directly influence water/ion transport. By the use of molecular spin probes that are selectively partitioned into heterogeneous regions of the PEM and Overhauser dynamic nuclear polarization relaxometry, this study reveals that both water and proton diffusivity are significantly faster near the fluorocarbon and the acidic groups lining the water channels than within the water channels. The concept that surface chemistry at the (sub)nanometer scale dictates water and proton diffusivity invokes a new design principle for PEMs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Developmentally-regulated sodium channel subunits are differentially sensitive to {alpha}-cyano containing pyrethroids

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

Meacham, Connie A.; Brodfuehrer, Peter D.; Watkins, Jennifer A.

2008-09-15

Juvenile rats have been reported to be more sensitive to the acute neurotoxic effects of the pyrethroid deltamethrin than adults. While toxicokinetic differences between juveniles and adults are documented, toxicodynamic differences have not been examined. Voltage-gated sodium channels, the primary targets of pyrethroids, are comprised of {alpha} and {beta} subunits, each of which have multiple isoforms that are expressed in a developmentally-regulated manner. To begin to test whether toxicodynamic differences could contribute to age-dependent deltamethrin toxicity, deltamethrin effects were examined on sodium currents in Xenopus laevis oocytes injected with different combinations of rat {alpha} (Na{sub v}1.2 or Na{sub v}1.3) andmore » {beta} ({beta}{sub 1} or {beta}{sub 3}) subunits. Deltamethrin induced tail currents in all isoform combinations and increased the percent of modified channels in a concentration-dependent manner. Effects of deltamethrin were dependent on subunit combination; Na{sub v}1.3-containing channels were modified to a greater extent than were Na{sub v}1.2-containing channels. In the presence of a {beta} subunit, deltamethrin effects were significantly greater, an effect most pronounced for Na{sub v}1.3 channels; Na{sub v}1.3/{beta}{sub 3} channels were more sensitive to deltamethrin than Na{sub v}1.2/{beta}{sub 1} channels. Na{sub v}1.3/{beta}{sub 3} channels are expressed embryonically, while the Na{sub v}1.2 and {beta}{sub 1} subunits predominate in adults, supporting the hypothesis for age-dependent toxicodynamic differences. Structure-activity relationships for sensitivity of these subunit combinations were examined for other pyrethroids. Permethrin and tetramethrin did not modify currents mediated by either subunit combination. Cypermethrin, {beta}-cyfluthrin, esfenvalerate and fenpropathrin all modified sodium channel function; effects were significantly greater on Na{sub v}1.3/{beta}{sub 3} than on Na{sub v}1.2/{beta}{sub 1} channels. These data demonstrate a greater sensitivity of Na{sub v}1.3 vs Na{sub v}1.2 channels to deltamethrin and other cyano-containing pyrethroids, particularly in the presence of a {beta} subunit.« less

Crystal Structure of the Ternary Complex of a NaV C-Terminal Domain, a Fibroblast Growth Factor Homologous Factor, and Calmodulin

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

Wang, Chaojian; Chung, Ben C.; Yan, Haidun

2012-11-13

Voltage-gated Na{sup +} (Na{sub V}) channels initiate neuronal action potentials. Na{sub V} channels are composed of a transmembrane domain responsible for voltage-dependent Na{sup +} conduction and a cytosolic C-terminal domain (CTD) that regulates channel function through interactions with many auxiliary proteins, including fibroblast growth factor homologous factors (FHFs) and calmodulin (CaM). Most ion channel structural studies have focused on mechanisms of permeation and voltage-dependent gating but less is known about how intracellular domains modulate channel function. Here we report the crystal structure of the ternary complex of a human NaV CTD, an FHF, and Ca{sup 2+}-free CaM at 2.2 {angstrom}.more » Combined with functional experiments based on structural insights, we present a platform for understanding the roles of these auxiliary proteins in NaV channel regulation and the molecular basis of mutations that lead to neuronal and cardiac diseases. Furthermore, we identify a critical interaction that contributes to the specificity of individual NaV CTD isoforms for distinctive FHFs.« less

Full-frame, high-speed 3D shape and deformation measurements using stereo-digital image correlation and a single color high-speed camera

NASA Astrophysics Data System (ADS)

Yu, Liping; Pan, Bing

2017-08-01

Full-frame, high-speed 3D shape and deformation measurement using stereo-digital image correlation (stereo-DIC) technique and a single high-speed color camera is proposed. With the aid of a skillfully designed pseudo stereo-imaging apparatus, color images of a test object surface, composed of blue and red channel images from two different optical paths, are recorded by a high-speed color CMOS camera. The recorded color images can be separated into red and blue channel sub-images using a simple but effective color crosstalk correction method. These separated blue and red channel sub-images are processed by regular stereo-DIC method to retrieve full-field 3D shape and deformation on the test object surface. Compared with existing two-camera high-speed stereo-DIC or four-mirror-adapter-assisted singe-camera high-speed stereo-DIC, the proposed single-camera high-speed stereo-DIC technique offers prominent advantages of full-frame measurements using a single high-speed camera but without sacrificing its spatial resolution. Two real experiments, including shape measurement of a curved surface and vibration measurement of a Chinese double-side drum, demonstrated the effectiveness and accuracy of the proposed technique.

Targeting sediment management strategies using sediment quantification and fingerprinting methods

NASA Astrophysics Data System (ADS)

Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; hUallacháin, Daire Ó.

2016-04-01

Cost-effective sediment management is required to reduce excessive delivery of fine sediment due to intensive land uses such as agriculture, resulting in the degradation of aquatic ecosystems. Prioritising measures to mitigate dominant sediment sources is, however, challenging, as sediment loss risk is spatially and temporally variable between and within catchments. Fluctuations in sediment supply from potential sources result from variations in land uses resulting in increased erodibility where ground cover is low (e.g., cultivated, poached and compacted soils), and physical catchment characteristics controlling hydrological connectivity and transport pathways (surface and/or sub-surface). Sediment fingerprinting is an evidence-based management tool to identify sources of in-stream sediments at the catchment scale. Potential sediment sources are related to a river sediment sample, comprising a mixture of source sediments, using natural physico-chemical characteristics (or 'tracers'), and contributions are statistically un-mixed. Suspended sediment data were collected over two years at the outlet of three intensive agricultural catchments (approximately 10 km2) in Ireland. Dominant catchment characteristics were grassland on poorly-drained soils, arable on well-drained soils and arable on moderately-drained soils. High-resolution (10-min) calibrated turbidity-based suspended sediment and discharge data were combined to quantify yield. In-stream sediment samples (for fingerprinting analysis) were collected at six to twelve week intervals, using time-integrated sediment samplers. Potential sources, including stream channel banks, ditches, arable and grassland field topsoils, damaged road verges and tracks were sampled, oven-dried (<40oC) and sieved (125 microns). Soil and sediment samples were analysed for mineral magnetics, geochemistry and radionuclide tracers, particle size distribution and soil organic carbon. Tracer data were corrected to account for particle size and organic matter selectivity processes. Contributions from potential sources type groups (channel - ditches and stream banks, roads - road verges and tracks, fields - grassland and arable topsoils) were statistically un-mixed using FR2000, an uncertainty-inclusive algorithm, and combined with sediment yield data. Results showed sediment contributions from channel, field and road groups were 70%, 25% and 5% in the poorly-drained catchment, 59%, 22% and 19% in the well-drained catchment, and 17%, 74% and 9% in the moderately-drained catchment. Higher channel contributions in the poorly-drained catchment were attributed to bank erosion accelerated by the rapid diversion of surface runoff into channels, facilitated by surface and sub-surface artificial drainage networks, and bank seepage from lateral pressure gradients due to confined groundwater. Despite the greatest proportion of arable soils in the well-drained catchment, this source was frequently hydrologically disconnected as well-drained soils largely infiltrated rainfall and prevented surface soil erosion. Periods of high and intense rainfall were associated with greater proportions of field losses in the well-drained catchment likely due to infiltration exceeding the saturated hydraulic conductivity of soils and establishment of surface hydrological connectivity. Losses from field topsoils dominated in the moderately-drained catchment as antecedent soil wetness maintained surface flow pathways and coincided with low groundcover on arable soils. For cost-effective management of sediment pressures to aquatic ecosystems, catchment specific variations in sediment sources must be considered.

Influence of non-adherent yeast cells on electrical characteristics of diamond-based field-effect transistors

NASA Astrophysics Data System (ADS)

Procházka, Václav; Cifra, Michal; Kulha, Pavel; Ižák, Tibor; Rezek, Bohuslav; Kromka, Alexander

2017-02-01

Diamond thin films provide unique features as substrates for cell cultures and as bio-electronic sensors. Here we employ solution-gated field effect transistors (SGFET) based on nanocrystalline diamond thin films with H-terminated surface which exhibits the sub-surface p-type conductive channel. We study an influence of yeast cells (Saccharomyces cerevisiae) on electrical characteristics of the diamond SGFETs. Two different cell culture solutions (sucrose and yeast peptone dextrose-YPD) are used, with and without the cells. We have found that transfer characteristics of the SGFETs exhibit a negative shift of the gate voltage by -26 mV and -42 mV for sucrose and YPD with cells in comparison to blank solutions without the cells. This effect is attributed to a local pH change in close vicinity of the H-terminated diamond surface due to metabolic processes of the yeast cells. The pH sensitivity of the diamond-based SGFETs, the role of cell and protein adhesion on the gate surface and the role of negative surface charge of yeast cells on the SGFETs electrical characteristics are discussed as well.

Improving performance of armchair graphene nanoribbon field effect transistors via boron nitride doping

NASA Astrophysics Data System (ADS)

Goharrizi, A. Yazdanpanah; Sanaeepur, M.; Sharifi, M. J.

2015-09-01

Device performance of 10 nm length armchair graphene nanoribbon field effect transistors with 1.5 nm and 4 nm width (13 and 33 atoms in width respectively) are compared in terms of Ion /Ioff , trans-conductance, and sub-threshold swing. While narrow devices suffer from edge roughness wider devices are subject to more substrate surface roughness and reduced bandgap. Boron Nitride doping is employed to compensate reduced bandgap in wider devices. Simultaneous effects of edge and substrate surface roughness are considered. Results show that in the presence of both the edge and substrate surface roughness the 4 nm wide device with boron nitride doping shows improved performance with respect to the 1.5 nm one (both of which incorporate the same bandgap AGNR as channel material). Electronic simulations are performed via NEGF method along with tight-binding Hamiltonian. Edge and surface roughness are created by means of one and two dimensional auto correlation functions respectively. Electronic characteristics are averaged over a large number of devices due to statistic nature of both the edge and surface roughness.

Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

DOEpatents

Singh, Prabhakar; Ruka, Roswell J.

1995-01-01

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO.sub.3 particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr.sub.2 O.sub.3 on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO.sub.3 layer coated with CaO and Cr.sub.2 O.sub.3 surface deposit at from about 1000.degree. C. to 1200.degree. C. to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO.sub.3 layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power.

Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

DOEpatents

Singh, P.; Ruka, R.J.

1995-02-14

A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO{sub 3} particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr{sub 2}O{sub 3} on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO{sub 3} layer coated with CaO and Cr{sub 2}O{sub 3} surface deposit at from about 1,000 C to 1,200 C to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO{sub 3} layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power. 5 figs.

Insulation of the conduction pathway of muscle transverse tubule calcium channels from the surface charge of bilayer phospholipid

PubMed Central

1986-01-01

Functional calcium channels present in purified skeletal muscle transverse tubules were inserted into planar phospholipid bilayers composed of the neutral lipid phosphatidylethanolamine (PE), the negatively charged lipid phosphatidylserine (PS), and mixtures of both. The lengthening of the mean open time and stabilization of single channel fluctuations under constant holding potentials was accomplished by the use of the agonist Bay K8644. It was found that the barium current carried through the channel saturates as a function of the BaCl2 concentration at a maximum current of 0.6 pA (at a holding potential of 0 mV) and a half-saturation value of 40 mM. Under saturation, the slope conductance of the channel is 20 pS at voltages more negative than -50 mV and 13 pS at a holding potential of 0 mV. At barium concentrations above and below the half-saturation point, the open channel currents were independent of the bilayer mole fraction of PS from XPS = 0 (pure PE) to XPS = 1.0 (pure PS). It is shown that in the absence of barium, the calcium channel transports sodium or potassium ions (P Na/PK = 1.4) at saturating rates higher than those for barium alone. The sodium conductance in pure PE bilayers saturates as a function of NaCl concentration, following a curve that can be described as a rectangular hyperbola with a half-saturation value of 200 mM and a maximum conductance of 68 pS (slope conductance at a holding potential of 0 mV). In pure PS bilayers, the sodium conductance is about twice that measured in PE at concentrations below 100 mM NaCl. The maximum channel conductance at high ionic strength is unaffected by the lipid charge. This effect at low ionic strength was analyzed according to J. Bell and C. Miller (1984. Biophysical Journal. 45:279- 287) and interpreted as if the conduction pathway of the calcium channel were separated from the bilayer lipid by approximately 20 A. This distance thereby effectively insulates the ion entry to the channel from the bulk of the bilayer lipid surface charge. Current vs. voltage curves measured in NaCl in pure PE and pure PS show that similarly small surface charge effects are present in both inward and outward currents. This suggests that the same conduction insulation is present at both ends of the calcium channel. PMID:2425043

Preliminary results of the optical calibration for the stereo camera STC onboard the Bepicolombo mission

NASA Astrophysics Data System (ADS)

Da Deppo, V.; Martellato, E.; Simioni, E.; Borrelli, D.; Dami, M.; Aroldi, G.; Naletto, G.; Veltroni, I. Ficai; Cremonese, G.

2017-11-01

BepiColombo is one of the cornerstone missions of the European Space Agency dedicated to the exploration of the planet Mercury and it is expected to be launched in July 2016. One of the BepiColombo instruments is the STereoscopic imaging Channel (STC), which is a channel of the Spectrometers and Imagers for MPO BepiColombo Integrated Observatory SYStem (SIMBIOSYS) suite: an integrated system for imaging and spectroscopic investigation of the Mercury surface. STC main aim is the 3D global mapping of the entire surface of the planet Mercury during the BepiColombo one year nominal mission. The STC instrument consists in a novel concept of stereocamera: two identical cameras (sub-channels) looking at +/-20° from nadir which share most of the optical components and the detector. Being the detector a 2D matrix, STC is able to adopt the push-frame acquisition technique instead of the much common push-broom one. The camera has the capability of imaging in five different spectral bands: one panchromatic and four intermediate bands, in the range between 410 and 930 nm. To avoid mechanisms, the technical solution chosen for the filters is the single substrate stripe-butted filter in which different glass pieces, with different transmission properties, are glued together and positioned just in front of the detector. The useful field of view (FoV) of each sub-channel, though divided in 3 strips, is about 5.3° x 3.2°. The optical design, a modified Schmidt layout, is able to guarantee that over all the FoV the diffraction Ensquared Energy inside one pixel of the detector is of the order of 70-80%. To effectively test and calibrate the overall STC channel, an ad hoc Optical Ground Support Equipment has been developed. Each of the sub-channels has to be separately calibrated, but also the data of one sub-channel have to be easily correlated with the other one. In this paper, the experimental results obtained by the analysis of the data acquired during the preliminary onground optical calibration campaign on the STC Flight Model will be presented. This analysis shows a good agreement between the theoretical expected performance and the experimental results.

Current conduction in junction gate field effect transistors. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Kim, C.

1970-01-01

The internal physical mechanism that governs the current conduction in junction-gate field effect transistors is studied. A numerical method of analyzing the devices with different length-to-width ratios and doping profiles is developed. This method takes into account the two dimensional character of the electric field and the field dependent mobility. Application of the method to various device models shows that the channel width and the carrier concentration in the conductive channel decrease with increasing drain-to-source voltage for conventional devices. It also shows larger differential drain conductances for shorter devices when the drift velocity is not saturated. The interaction of the source and the drain gives the carrier accumulation in the channel which leads to the space-charge-limited current flow. The important parameters for the space-charge-limited current flow are found to be the L/L sub DE ratio and the crossover voltage.

Crystalline polyoxometalate (POM)–polyethylene glycol (PEG) composites aimed as non-humidified intermediate-temperature proton conductors

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

Tsuboi, Masaki; Hibino, Mitsuhiro; Mizuno, Noritaka

2016-02-15

Crystalline polyoxometalate (POM)–polyethylene glycol (PEG) composites aimed as non-humidified intermediate-temperature proton conductors were synthesized and characterized by single crystal and powder XRD, solid state MASNMR, and TG-DTA measurements. Among the POM–PEG composites, Cs{sub 2.7}H{sub 0.3}[PW{sub 12}O{sub 40}]·1.2PEG1000 (CsHPW-PEG1000) possessed one-dimensional channels with diameters of ca. 6 and 8 Å, where PEG probably resided, and showed the best performance as a proton conductor (1.2×10{sup −5} S cm{sup −1} at 443 K). Proton conductivities of POM–PEG composites decreased by the increase in molecular weights of PEG (CsHPW-PEG12,000) or anion charges (CsHSiW-PEG1000). Variable contact time {sup 13}C-CP (cross polarization) MASNMR revealed that localmore » mobility (i.e., segmental motion) of PEG is related to the trends in proton conductivities. These results show that amount of acidic protons (H{sup +}) is not the primary factor in proton conduction and that segmental motion of PEG assists the proton hopping among POMs in the crystal lattice of POM–PEG composites. - Graphical abstract: Non-humidified intermediate-temperature proton conduction in crystalline polyoxometalate (POM)–polyethylene (PEG) composites are assisted by the segmental motion of PEG. - Highlights: • Crystalline polyoxometalate–polyethlene glycol (PEG) composites were synthesized. • CsHPW-PEG1000 possessed one-dimensional channels and showed the highest proton conductivity. • {sup 13}C CPMASNMR revealed that segmental motion of PEG is related to the proton conduction.« less

The channels of Mars

NASA Technical Reports Server (NTRS)

Baker, V. R.

1982-01-01

Early observations of Mars conducted by means of telescopes are considered. Secchi introduced the Italian word 'canale' ('channel') in 1869 to describe apparent lines on the planet's surface. Between 1877 and 1888 Schiaparelli mapped a profusion of 'canali'. Schiaparelli's work led to famous controversies about Mars. This book attempts to investigate the puzzle posed by the Martian channels, taking into account also the results of the studies conducted with the aid of the two orbiting Viking spacecraft which have produced a total number of nearly 60,000 pictures. The channel types are discussed along with questions regarding the distribution, the ages, and the proposed origins of the channels. Attention is given to the geomorphology of Mars, the patterns and networks of Martian valleys, ice and the Martian surface, the outflow channels, catastrophic flood processes, questions of analogy between terrestrial and Martian geographic features, and Martian phenomena associated with water liquid or water ice.

Phosphorylation of rat brain purified mitochondrial Voltage-Dependent Anion Channel by c-Jun N-terminal kinase-3 modifies open-channel noise.

PubMed

Gupta, Rajeev

2017-09-02

The drift kinetic energy of ionic flow through single ion channels cause vibrations of the pore walls which are observed as open-state current fluctuations (open-channel noise) during single-channel recordings. Vibration of the pore wall leads to transitions among different conformational sub-states of the channel protein in the open-state. Open-channel noise analysis can provide important information about the different conformational sub-state transitions and how biochemical modifications of ion channels would affect their transport properties. It has been shown that c-Jun N-terminal kinase-3 (JNK3) becomes activated by phosphorylation in various neurodegenerative diseases and phosphorylates outer mitochondrion associated proteins leading to neuronal apoptosis. In our earlier work, JNK3 has been reported to phosphorylate purified rat brain mitochondrial voltage-dependent anion channel (VDAC) in vitro and modify its conductance and opening probability. In this article we have compared the open-state noise profile of the native and the JNK3 phosphorylated VDAC using Power Spectral Density vs frequency plots. Power spectral density analysis of open-state noise indicated power law with average slope value α ≈1 for native VDAC at both positive and negative voltage whereas average α value < 0.5 for JNK3 phosphorylated VDAC at both positive and negative voltage. It is proposed that 1/f 1 power law in native VDAC open-state noise arises due to coupling of ionic transport and conformational sub-states transitions in open-state and this coupling is perturbed as a result of channel phosphorylation. Copyright © 2017 Elsevier Inc. All rights reserved.

Energies of the X- and L-valleys in In{sub 0.53}Ga{sub 0.47}As from electronic structure calculations

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

Greene-Diniz, Gabriel; Greer, J. C.; Fischetti, M. V.

2016-02-07

Several theoretical electronic structure methods are applied to study the relative energies of the minima of the X- and L-conduction-band satellite valleys of In{sub x}Ga{sub 1−x}As with x = 0.53. This III-V semiconductor is a contender as a replacement for silicon in high-performance n-type metal-oxide-semiconductor transistors. The energy of the low-lying valleys relative to the conduction-band edge governs the population of channel carriers as the transistor is brought into inversion, hence determining current drive and switching properties at gate voltages above threshold. The calculations indicate that the position of the L- and X-valley minima are ∼1 eV and ∼1.2 eV, respectively, higher in energymore » with respect to the conduction-band minimum at the Γ-point.« less

S-acylation dependent post-translational cross-talk regulates large conductance calcium- and voltage- activated potassium (BK) channels

PubMed Central

Shipston, Michael J.

2014-01-01

Mechanisms that control surface expression and/or activity of large conductance calcium-activated potassium (BK) channels are important determinants of their (patho)physiological function. Indeed, BK channel dysfunction is associated with major human disorders ranging from epilepsy to hypertension and obesity. S-acylation (S-palmitoylation) represents a major reversible, post-translational modification controlling the properties and function of many proteins including ion channels. Recent evidence reveals that both pore-forming and regulatory subunits of BK channels are S-acylated and control channel trafficking and regulation by AGC-family protein kinases. The pore-forming α-subunit is S-acylated at two distinct sites within the N- and C-terminus, each site being regulated by different palmitoyl acyl transferases (zDHHCs) and acyl thioesterases (APTs). S-acylation of the N-terminus controls channel trafficking and surface expression whereas S-acylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. S-acylation of the regulatory β4-subunit controls ER exit and surface expression of BK channels but does not affect ion channel kinetics at the plasma membrane. Furthermore, a significant number of previously identified BK-channel interacting proteins have been shown, or are predicted to be, S-acylated. Thus, the BK channel multi-molecular signaling complex may be dynamically regulated by this fundamental post-translational modification and thus S-acylation likely represents an important determinant of BK channel physiology in health and disease. PMID:25140154

Morphology, composition and electrical properties of SnO{sub 2}:Cl thin films grown by atomic layer deposition

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

Cheng, Hsyi-En, E-mail: sean@mail.stust.edu.tw; Wen, Chia-Hui; Hsu, Ching-Ming

2016-01-15

Chlorine doped SnO{sub 2} thin films were prepared using atomic layer deposition at temperatures between 300 and 450 °C using SnCl{sub 4} and H{sub 2}O as the reactants. Composition, structure, surface morphology, and electrical properties of the as-deposited films were examined. Results showed that the as-deposited SnO{sub 2} films all exhibited rutile structure with [O]/[Sn] ratios between 1.35 and 1.40. The electrical conductivity was found independent on [O]/[Sn] ratio but dependent on chlorine doping concentration, grain size, and surface morphology. The 300 °C-deposited film performed a higher electrical conductivity of 315 S/cm due to its higher chlorine doping level, larger grain size, andmore » smoother film surface. The existence of Sn{sup 2+} oxidation state was demonstrated to minimize the effects of chlorine on raising the electrical conductivity of films.« less

Nonlinear Hall effect and multichannel conduction in LaTiO3/SrTiO3 superlattices

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

Kim, Jun Sung; Seo, Sung Seok A; Chisholm, Matthew F

2010-01-01

We report magnetotransport properties of heterointerfaces between the Mott insulator LaTiO{sub 3} and the band insulator SrTiO{sub 3} in a delta-doping geometry. At low temperatures, we have found a strong nonlinearity in the magnetic field dependence of the Hall resistivity, which can be effectively controlled by varying the temperature and the electric field. We attribute this effect to multichannel conduction of interfacial charges generated by an electronic reconstruction. In particular, the formation of a highly mobile conduction channel revealed by our data is explained by the greatly increased dielectric permeability of SrTiO{sub 3} at low temperatures and its electric fieldmore » dependence reflects the spatial distribution of the quasi-two-dimensional electron gas.« less

Spacer engineered Trigate SOI TFET: An investigation towards harsh temperature environment applications

NASA Astrophysics Data System (ADS)

Mallikarjunarao; Ranjan, Rajeev; Pradhan, K. P.; Artola, L.; Sahu, P. K.

2016-09-01

In this paper, a novel N-channel Tunnel Field Effect Transistor (TFET) i.e., Trigate Silicon-ON-Insulator (SOI) N-TFET with high-k spacer is proposed for better Sub-threshold swing (SS) and OFF-state current (IOFF) by keeping in mind the sensitivity towards temperature. The proposed model can achieve a Sub-threshold swing less than 35 mV/decade at various temperatures, which is desirable for designing low power CTFET for digital circuit applications. In N-TFET source doping has a significant effect on the ON-state current (ION) level; therefore more electrons will tunnel from source to channel region. High-k Spacer i.e., HfO2 is used to enhance the device performance and also it avoids overlapping of transistors in an integrated circuits (IC's). We have designed a reliable device by performing the temperature analysis on Transfer characteristics, Drain characteristics and also on various performance metrics like ON-state current (ION), OFF-state current (IOFF), ION/IOFF, Trans-conductance (gm), Trans-conductance Generation Factor (TGF), Sub-threshold Swing (SS) to observe the applications towards harsh temperature environment.

Mechanism of HERG potassium channel inhibition by tetra-n-octylammonium bromide and benzethonium chloride

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

Long, Yan; Lin, Zuoxian; Xia, Menghang

Tetra-n-octylammonium bromide and benzethonium chloride are synthetic quaternary ammonium salts that are widely used in hospitals and industries for the disinfection and surface treatment and as the preservative agent. Recently, the activities of HERG channel inhibition by these compounds have been found to have potential risks to induce the long QT syndrome and cardiac arrhythmia, although the mechanism of action is still elusive. This study was conducted to investigate the mechanism of HERG channel inhibition by these compounds by using whole-cell patch clamp experiments in a CHO cell line stably expressing HERG channels. Tetra-n-octylammonium bromide and benzethonium chloride exhibited concentration-dependentmore » inhibitions of HERG channel currents with IC{sub 50} values of 4 nM and 17 nM, respectively, which were also voltage-dependent and use-dependent. Both compounds shifted the channel activation I–V curves in a hyperpolarized direction for 10–15 mV and accelerated channel activation and inactivation processes by 2-fold. In addition, tetra-n-octylammonium bromide shifted the inactivation I–V curve in a hyperpolarized direction for 24.4 mV and slowed the rate of channel deactivation by 2-fold, whereas benzethonium chloride did not. The results indicate that tetra-n-octylammonium bromide and benzethonium chloride are open-channel blockers that inhibit HERG channels in the voltage-dependent, use-dependent and state-dependent manners. - Highlights: ► Tetra-n-octylammonium and benzethonium are potent HERG channel inhibitors. ► Channel activation and inactivation processes are accelerated by the two compounds. ► Both compounds are the open-channel blockers to HERG channels. ► HERG channel inhibition by both compounds is use-, voltage- and state dependent. ► The in vivo risk of QT prolongation needs to be studied for the two compounds.« less

Few layered vanadyl phosphate nano sheets-MWCNT hybrid as an electrode material for supercapacitor application

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

Dutta, Shibsankar; De, Sukanta, E-mail: sukanta.physics@presiuniv.ac.in

It have been already seen that 2-dimensional nano materials are the suitable choice for the supercapacitor application due to their large specific surface area, electrochemical active sites, micromechanical flexibility, expedite ion migration channel properties. Free standing hybrid films of functionalized MWCNT (– COOH group) and α-Vanadyl phosphates (VOPO{sub 4}2H{sub 2}O) are prepared by vacuum filtering. The surface morphology and microstructure of the samples are studied by transmission electron microscope, field emission scanning electron microscope, XRD, Electrochemical properties of hybrid films have been investigated systematically in 1M Na{sub 2}SO{sub 4} aqueous electrolyte. The hybrid material exhibits a high specific capacitance 236more » F/g with high energy density of 65.6 Wh/Kg and a power density of 1476 W/Kg.« less

Suppression of surface charge accumulation on Al{sub 2}O{sub 3}-filled epoxy resin insulator under dc voltage by direct fluorination

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

Zhang, Boya; Zhang, Guixin, E-mail: guixin@mail.tsinghua.edu.cn; Li, Chuanyang

2015-12-15

Surface charge accumulation on insulators under high dc voltage is a major factor that may lead to the reduction of insulation levels in gas insulated devices. In this paper, disc insulators made of Al{sub 2}O{sub 3}-filled epoxy resin were surface fluorinated using a F{sub 2}/N{sub 2} mixture (12.5% F{sub 2}) at 50 °C and 0.1 MPa for different durations of 15 min, 30 min and 60 min. A dc voltage was applied to the insulator for 30 min and the charge density on its surface was measured by an electrostatic probe. The results revealed significant lower surface charge densities on themore » fluorinated insulators in comparison with the original one. Surface conductivity measurements indicated a higher surface conductivity by over three orders of magnitude after fluorination, which would allow the charges to transfer along the surface and thus may suppress their accumulation. Further, attenuated total reflection infrared analysis and surface morphology observations of the samples revealed that the introduction of fluoride groups altered the surface physicochemical properties. These structure changes, especially the physical defects reduced the depth of charge traps in the surface layer, which was verified by the measurement of energy distributions of the electron and hole traps based on the isothermal current theory. The results in this paper demonstrate that fluorination can be a promising and effective method to suppress surface charge accumulation on epoxy insulators in gas insulated devices.« less

Adsorption and movement of water by skin of the Australian thorny devil (Agamidae: Moloch horridus)

NASA Astrophysics Data System (ADS)

Comanns, Philipp; Esser, Falk J.; Kappel, Peter H.; Baumgartner, Werner; Shaw, Jeremy; Withers, Philip C.

2017-09-01

Moisture-harvesting lizards, such as the Australian thorny devil Moloch horridus, have remarkable adaptations for inhabiting arid regions. Their microstructured skin surface, with channels in between overlapping scales, enables them to collect water by capillarity and passively transport it to the mouth for ingestion. We characterized this capillary water transport for live thorny devils using high-speed video analyses. Comparison with preserved specimens showed that live lizards are required for detailed studies of skin water transport. For thorny devils, there was no directionality in cutaneous water transport (unlike Phrynosoma) as 7 µl water droplets applied to the skin were transported radially over more than 9.2 mm. We calculated the total capillary volume as 5.76 µl cm-2 (dorsal) and 4.45 µl cm-2 (ventral), which is reduced to 50% filling by the time transportation ceases. Using micro-computed tomography and scanning electron microscopy of shed skin to investigate capillary morphology, we found that the channels are hierarchically structured as a large channel between the scales that is sub-divided by protrusions into smaller sub-capillaries. The large channel quickly absorbs water whereas the sub-capillary structure extends the transport distance by about 39% and potentially reduces the water volume required for drinking. An adapted dynamics function, which closely reflects the channel morphology, includes that ecological role.

Adsorption and movement of water by skin of the Australian thorny devil (Agamidae: Moloch horridus).

PubMed

Comanns, Philipp; Esser, Falk J; Kappel, Peter H; Baumgartner, Werner; Shaw, Jeremy; Withers, Philip C

2017-09-01

Moisture-harvesting lizards, such as the Australian thorny devil Moloch horridus , have remarkable adaptations for inhabiting arid regions. Their microstructured skin surface, with channels in between overlapping scales, enables them to collect water by capillarity and passively transport it to the mouth for ingestion. We characterized this capillary water transport for live thorny devils using high-speed video analyses. Comparison with preserved specimens showed that live lizards are required for detailed studies of skin water transport. For thorny devils, there was no directionality in cutaneous water transport (unlike Phrynosoma ) as 7 µl water droplets applied to the skin were transported radially over more than 9.2 mm. We calculated the total capillary volume as 5.76 µl cm -2 (dorsal) and 4.45 µl cm -2 (ventral), which is reduced to 50% filling by the time transportation ceases. Using micro-computed tomography and scanning electron microscopy of shed skin to investigate capillary morphology, we found that the channels are hierarchically structured as a large channel between the scales that is sub-divided by protrusions into smaller sub-capillaries. The large channel quickly absorbs water whereas the sub-capillary structure extends the transport distance by about 39% and potentially reduces the water volume required for drinking. An adapted dynamics function, which closely reflects the channel morphology, includes that ecological role.

Solid oxide fuel cell with multi-unit construction and prismatic design

DOEpatents

McPheeters, C.C.; Dees, D.W.; Myles, K.M.

1999-03-16

A single cell unit of a solid oxide fuel cell is described that is individually fabricated and sintered prior to being connected to adjacent cells to form a solid oxide fuel cell. The single cell unit is comprised of a shaped anode sheet positioned between a flat anode sheet and an anode-electrolyte-cathode (A/E/C) sheet, and a shaped cathode sheet positioned between the A/E/C sheet and a cathode-interconnect-anode (C/I/A) sheet. An alternate embodiment comprises a shaped cathode sheet positioned between an A/E/C sheet and a C/I/A sheet. The shaped sheets form channels for conducting reactant gases. Each single cell unit is individually sintered to form a finished sub-assembly. The finished sub-assemblies are connected in electrical series by interposing connective material between the end surfaces of adjacent cells, whereby individual cells may be inspected for defects and interchanged with non-defective single cell units. 7 figs.

Embedded gage impact study

NASA Technical Reports Server (NTRS)

Schramm, S. W.; Daniel, I. M.

1984-01-01

Impact damage in graphite/epoxy laminates was characterized and transient strain history during impact was correlated. The material investigated was AS-4/3501-6 graphite/epoxy. Eight-ply and sixteen-ply quasi-isotropic laminates of 45/0/-45/90 sub s and 45/0/-45/90 sub 2s layups were fabricated with strain gages embedded between plies during the strain gages and leads from the highly conductive graphite fibers. The specimens were circular plates 12.7 cm (5 in.) in diameter and clamped along their circumference. The specimens were impacted with a 185 gm impactor, dropped from heights of 1.20 m and 1.65 m. An accelerometer was attached to the back surface of the specimen opposite the impact point and was used to trigger the recording instrumentation. The transient strain data were recorded with an eight channel waveform digitizer capable of sampling data at 0.5 microsec intervals. The data were stored, processed, and plotted by means of a microcomputer. Transient strain data were correlated with results from ultrasonic inspection of the specimens.

Studies of snowpack properties by passive microwave radiometry

NASA Technical Reports Server (NTRS)

Chang, A. T. C.; Hall, D. K.; Foster, J. L.; Rango, A.; Schmugge, T. J.

1979-01-01

Research involving the microwave characteristics of snow was undertaken in order to expand the information content currently available from remote sensing, namely the measurement of snowcovered area. Microwave radiation emitted from beneath the snow surface can be sensed and thus permits information on internal snowpack properties to be inferred. The intensity of radiation received is a function of the average temperature and emissivity of the snow layers and is commonly referred to as the brightness temperature (T sub B). The T sub B varies with snow grain and crystal sizes, liquid water content, and snowpack temperature. The T sub B of the 0.8 cm wavelength channel was found to decrease more so with increasing snow depth than the 1.4 cm channel. More scattering of the shorter wavelength radiation occurs thus resulting in a lower T sub B for shorter wavelengths in a dry snowpack. The longer 21.0 cm wavelength was used to assess the condition of the underlying ground.

Self-adaptive method for high frequency multi-channel analysis of surface wave method

USDA-ARS?s Scientific Manuscript database

When the high frequency multi-channel analysis of surface waves (MASW) method is conducted to explore soil properties in the vadose zone, existing rules for selecting the near offset and spread lengths cannot satisfy the requirements of planar dominant Rayleigh waves for all frequencies of interest ...

Fast events in single-channel currents activated by acetylcholine and its analogues at the frog muscle end-plate.

PubMed Central

Colquhoun, D; Sakmann, B

1985-01-01

The fine structure of ion-channel activations by junctional nicotinic receptors in adult frog muscle fibres has been investigated. The agonists used were acetylcholine (ACh), carbachol (CCh), suberyldicholine (SubCh) and decan-1,10-dicarboxylic acid dicholine ester (DecCh). Individual activations (bursts) were interrupted by short closed periods; the distribution of their durations showed a major fast component ('short gaps') and a minor slower component ('intermediate gaps'). The mean duration of both short and intermediate gaps was dependent on the nature of the agonist. For short gaps the mean durations (microseconds) were: ACh, 20; SubCh, 43; DecCh, 71; CCh, 13. The mean number of short gaps per burst were: ACh, 1.9; SubCh, 4.1; DecCh, 2.0. The mean number of short gaps per burst, and the mean number per unit open time, were dependent on the nature of the agonist, but showed little dependence on agonist concentration or membrane potential for ACh, SubCh and DecCh. The short gaps in CCh increased in frequency with agonist concentration and were mainly produced by channel blockages by CCh itself. Partially open channels (subconductance states) were clearly resolved rarely (0.4% of gaps within bursts) but regularly. Conductances of 18% (most commonly) and 71% of the main value were found. However, most short gaps were probably full closures. The distribution of burst lengths had two components. The faster component represented mainly isolated short openings that were much more common at low agonist concentrations. The slower component represented bursts of longer openings. Except at very low concentrations more than 85% of activations were of this type, which corresponds to the 'channel lifetime' found by noise analysis. The frequency of channel openings increased slightly with hyperpolarization. The short gaps during activations were little affected when (a) the [H+]o or [Ca2+]o were reduced to 1/10th of normal, (b) when extracellular Ca2+ was replaced by Mg2+, (c) when the [Cl-]i was raised or (d) when, in one experiment on an isolated inside-out patch, the normal intracellular constituents were replaced by KCl. Reduction of [Ca2+]O to 1/10 of normal increased the single-channel conductance by 50%, and considerably increased the number of intermediate gaps. No temporal asymmetry was detectable in the bursts of openings. Positive correlations were found between the lengths of successive apparent open times at low SubCh concentrations, but no correlations between burst lengths were detectable. The component of brief openings behaves, at low concentrations, as though it originates from openings of singly occupied channels.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 11 Fig. 14 Plate 1 PMID:2419552

Combining Methods to Describe Important Marine Habitats for Top Predators: Application to Identify Biological Hotspots in Tropical Waters.

PubMed

Thiers, Laurie; Louzao, Maite; Ridoux, Vincent; Le Corre, Matthieu; Jaquemet, Sébastien; Weimerskirch, Henri

2014-01-01

In tropical waters resources are usually scarce and patchy, and predatory species generally show specific adaptations for foraging. Tropical seabirds often forage in association with sub-surface predators that create feeding opportunities by bringing prey close to the surface, and the birds often aggregate in large multispecific flocks. Here we hypothesize that frigatebirds, a tropical seabird adapted to foraging with low energetic costs, could be a good predictor of the distribution of their associated predatory species, including other seabirds (e.g. boobies, terns) and subsurface predators (e.g., dolphins, tunas). To test this hypothesis, we compared distribution patterns of marine predators in the Mozambique Channel based on a long-term dataset of both vessel- and aerial surveys, as well as tracking data of frigatebirds. By developing species distribution models (SDMs), we identified key marine areas for tropical predators in relation to contemporaneous oceanographic features to investigate multi-species spatial overlap areas and identify predator hotspots in the Mozambique Channel. SDMs reasonably matched observed patterns and both static (e.g. bathymetry) and dynamic (e.g. Chlorophyll a concentration and sea surface temperature) factors were important explaining predator distribution patterns. We found that the distribution of frigatebirds included the distributions of the associated species. The central part of the channel appeared to be the best habitat for the four groups of species considered in this study (frigatebirds, brown terns, boobies and sub-surface predators).

Inversion of membrane surface charge by trivalent cations probed with a cation-selective channel

PubMed Central

Gurnev, Philip A.; Bezrukov, Sergey M.

2014-01-01

We demonstrate that the cation-selective channel formed by gramicidin A can be used as a reliable sensor for studying the multivalent ion accumulation at the surfaces of charged lipid membranes and the “charge inversion” phenomenon. In asymmetrically charged membranes with the individual leaflets formed from pure negative and positive lipids bathed by 0.1 M CsCl solutions the channel exhibits current rectification which is comparable to that of a typical n/p semiconductor diode. We show that even at these highly asymmetrical conditions the channel conductance can be satisfactorily described by the electrodiffusion equation in the constant field approximation but, due to predictable limitations, only when the applied voltages do not exceed 50 mV. Analysis of the changes in the voltage-dependent channel conductance upon addition of trivalent cations allows us to gauge their interactions with the membrane surface. The inversion of the sign of the effective surface charge takes place at the concentrations which correlate with the cation size. Specifically, these concentrations are close to 0.05 mM for lanthanum, 0.25 mM for hexaamminecobalt, and 4 mM for spermidine. PMID:23088396

Inversion of membrane surface charge by trivalent cations probed with a cation-selective channel.

PubMed

Gurnev, Philip A; Bezrukov, Sergey M

2012-11-13

We demonstrate that the cation-selective channel formed by gramicidin A can be used as a reliable sensor for studying the multivalent ion accumulation at the surfaces of charged lipid membranes and the "charge inversion" phenomenon. In asymmetrically charged membranes with the individual leaflets formed from pure negative and positive lipids bathed by 0.1 M CsCl solutions the channel exhibits current rectification, which is comparable to that of a typical n/p semiconductor diode. We show that even at these highly asymmetrical conditions the channel conductance can be satisfactorily described by the electrodiffusion equation in the constant field approximation but, due to predictable limitations, only when the applied voltages do not exceed 50 mV. Analysis of the changes in the voltage-dependent channel conductance upon addition of trivalent cations allows us to gauge their interactions with the membrane surface. The inversion of the sign of the effective surface charge takes place at the concentrations, which correlate with the cation size. Specifically, these concentrations are close to 0.05 mM for lanthanum, 0.25 mM for hexaamminecobalt, and 4 mM for spermidine.

H{sub 2}S does not regulate proliferation via T-type Ca{sup 2+} channels

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

Elies, Jacobo; Johnson, Emily; Boyle, John P.

T-type Ca{sup 2+} channels (Cav3.1, 3.2 and 3.3) strongly influence proliferation of various cell types, including vascular smooth muscle cells (VSMCs) and certain cancers. We have recently shown that the gasotransmitter carbon monoxide (CO) inhibits T-type Ca{sup 2+} channels and, in so doing, attenuates proliferation of VSMC. We have also shown that the T-type Ca{sup 2+} channel Cav3.2 is selectively inhibited by hydrogen sulfide (H{sub 2}S) whilst the other channel isoforms (Cav3.1 and Cav3.3) are unaffected. Here, we explored whether inhibition of Cav3.2 by H{sub 2}S could account for the anti-proliferative effects of this gasotransmitter. H{sub 2}S suppressed proliferation inmore » HEK293 cells expressing Cav3.2, as predicted by our previous observations. However, H{sub 2}S was similarly effective in suppressing proliferation in wild type (non-transfected) HEK293 cells and those expressing the H{sub 2}S insensitive channel, Cav3.1. Further studies demonstrated that T-type Ca{sup 2+} channels in the smooth muscle cell line A7r5 and in human coronary VSMCs strongly influenced proliferation. In both cell types, H{sub 2}S caused a concentration-dependent inhibition of proliferation, yet by far the dominant T-type Ca{sup 2+} channel isoform was the H{sub 2}S-insensitive channel, Cav3.1. Our data indicate that inhibition of T-type Ca{sup 2+} channel-mediated proliferation by H{sub 2}S is independent of the channels’ sensitivity to H{sub 2}S. - Highlights: • T-type Ca{sup 2+} channels regulate proliferation and are sensitive to the gasotransmitters CO and H{sub 2}S. • H{sub 2}S reduced proliferation in HEK293 cells expressing the H{sub 2}S sensitive Cav3.2 channel. • H{sub 2}S also inhibited proliferation in non-transfected cells and HEK293 cells expressing Cav3.1. • Native smooth muscle cells primarily express Cav3.1. Their proliferation was also inhibited by H{sub 2}S. • Unlike CO, H{sub 2}S does not regulate smooth muscle proliferation via T-type Ca{sup 2+} channel inhibition.« less

First stage of reaction of molten Al with MgO substrate

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

Morgiel, J., E-mail: j.morgiel@imim.pl; Sobczak, N.; Motor Transport Institute, 80 Jagiellońska St., 03-301 Warsaw

The Al/MgO couple was produced in vacuum (~ 5 × 10{sup −} {sup 4} Pa) by contact heating from RT up to 1000 °C and holding at that temperature for 1 h of a small 4 × 4 × 4 mm aluminium (5 N) sample placed on the [100] MgO single crystal substrate. TEM observations backed with electron diffraction analysis indicated that the interaction between liquid aluminium and MgO starts from a redox reaction producing a continuous layer of MgAl{sub 2}O{sub 4} spinel on the substrate surface. Its growth is controlled by solid state out-diffusion of magnesium and oxygen towardsmore » the surface being in contact with liquid metal. The thickening of spinel layer is accompanied by its cracking and infiltration with aluminium. The above process enables local dissolution of the MgO substrate and formation in it of a thin region of interpenetrating metallic channels walled with spinel. The removal of dissolved magnesium through open aluminium channels towards the drop and to vacuum locally produces areas of aluminium enriched with dissolved oxygen, which results in the nucleation of α-Al{sub 2}O{sub 3} at spinel clad walls. The growth of α-Al{sub 2}O{sub 3} is controlled only by the dissolution rate of MgO by aluminium, liquid state diffusion of Mg to drop/vacuum and oxygen to the front of the of α-Al{sub 2}O{sub 3} crystallites growing into MgO substrate. - Highlights: • New unique evidence of first stages of interaction of liquid Al with MgO substrates • Interaction of liquid Al with MgO starts with the formation of a layer MgAl{sub 2}O{sub 4}. • Growth of MgAl{sub 2}O{sub 4} is slow as controlled by solid state out-diffusion of Mg and O. • MgAl{sub 2}O{sub 4} serves as a nucleation site for Al{sub 2}O{sub 3} and consumed by it soon after. • Growth of Al{sub 2}O{sub 3} is fast as controlled by diffusion in liquid state.« less

Dynamics of Charge Carriers in Silicon Nanowire Photoconductors Revealed by Photo Hall Effect Measurements.

PubMed

Chen, Kaixiang; Zhao, Xiaolong; Mesli, Abdelmadjid; He, Yongning; Dan, Yaping

2018-04-24

Photoconductors have extraordinarily high gain in quantum efficiency, but the origin of the gain has remained in dispute for decades. In this work, we employ photo Hall effect to reveal the gain mechanisms by probing the dynamics of photogenerated charge carriers in silicon nanowire photoconductors. The results reveal that a large number of photogenerated minority electrons are localized in the surface depletion region and surface trap states. The same number of excess hole counterparts is left in the nanowire conduction channel, resulting in the fact that excess holes outnumber the excess electrons in the nanowire conduction channel by orders of magnitude. The accumulation of the excess holes broadens the conduction channel by narrowing down the depletion region, which leads to the experimentally observed high photo gain.

A comparison of surface biophysical properties and remotely sensed variables from FIFE

NASA Technical Reports Server (NTRS)

Sellers, Piers; Heiser, Mark; Walthall, C. W.; Huemmrich, F.; Strebel, D. E.; Hall, F. G.

1990-01-01

A method for calculating surface energy balances is investigated which incorporates the vegetation index and/or other indicators of surface conductance at visible and near-IR channels. Data from the Konza Prairie are employed to confirm the hypothesized relationship between maximum canopy conductance and the observed simple-ratio vegetation index. The relationship is established, but more data regarding soil-surface contributions are required to estimate the total surface conductance to evapotranspiration.

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

Pereyra, Pedro, E-mail: pereyrapedro@gmail.com; Mendoza-Figueroa, M. G.

Transport properties of electrons through biased double barrier semiconductor structures with finite transverse width w{sub y}, in the presence of a channel-mixing transverse electric field E{sub T} (along the y-axis), were studied. We solve the multichannel Schrödinger equation using the transfer matrix method and transport properties, like the conductance G and the transmission coefficients T{sub ij} have been evaluated as functions of the electrons' energy E and the transverse and longitudinal (bias) electric forces, f{sub T} and f{sub b}. We show that peak-suppression effects appear, due to the applied bias. Similarly, coherent interference of wave-guide states induced by the transversemore » field is obtained. We show also that the coherent interference of resonant wave-guide states gives rise to resonant conductance, which can be tuned to produce broad resonant peaks, implying operation frequencies of the order of 10 THz or larger.« less

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

Smith, Dayle; Danyal, Karamatullah; Raugei, Simone

Mo-dependent nitrogenase catalyzes the biological reduction of N 2 to 2NH 3 at the FeMo-cofactor buried deep inside the MoFe protein. Access of substrates, such as N 2, to the active site is likely restricted by the surrounding protein, requiring substrate channels that lead from the surface to the active site. Earlier studies on crystallographic structures of the MoFe protein have suggested three putative substrate channels. Here, we have utilized sub-microsecond atomistic molecular dynamics simulations to allow the nitrogenase MoFe protein to explore its conformational space in an aqueous solution at physiological ionic strength, revealing a putative substrate channel notmore » previously reported. The viability of the proposed channel was tested by examining the free energy of passage of N 2 from the surface through the channel to FeMo-cofactor, with discovery of a very low energy barrier. These studies point to a viable substrate channel in nitrogenase that appears during thermal motions of the protein in an aqueous environment that approaches a face of FeMo-cofactor earlier implicated in substrate binding.« less

Conductivity fuel cell collector plate and method of fabrication

DOEpatents

Braun, James C.

2002-01-01

An improved method of manufacturing a PEM fuel cell collector plate is disclosed. During molding a highly conductive polymer composite is formed having a relatively high polymer concentration along its external surfaces. After molding the polymer rich layer is removed from the land areas by machining, grinding or similar process. This layer removal results in increased overall conductivity of the molded collector plate. The polymer rich surface remains in the collector plate channels, providing increased mechanical strength and other benefits to the channels. The improved method also permits greater mold cavity thickness providing a number of advantages during the molding process.

Replication fidelity assessment of large area sub-μm structured polymer surfaces using scatterometry

NASA Astrophysics Data System (ADS)

Calaon, M.; Madsen, M. H.; Weirich, J.; Hansen, H. N.; Tosello, G.; Hansen, P. E.; Garnaes, J.; Tang, P. T.

2015-12-01

The present study addresses one of the key challenges in the product quality control of transparent structured polymer substrates, the replication fidelity of sub-μm structures over a large area. Additionally the work contributes to the development of new techniques focused on in-line characterization of large nanostructured surfaces using scatterometry. In particular an approach to quantify the replication fidelity of high volume manufacturing processes such as polymer injection moulding is presented. Both periodic channels and semi-spherical structures were fabricated on nickel shims used for later injection moulding of Cyclic-olefin-copolymer (COC) substrate were the sub-μm features where ultimately transferred. The scatterometry system was validated using calibrated atomic force microscopy measurements and a model based on scalar diffraction theory employed to calculate the expected angular distribution of the reflected and the transmitted intensity for the nickel surfaces and structured COC and, respectively.

Improvement of the overall performances of LiMn{sub 2}O{sub 4} via surface-modification by polypyrrole

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

Wang, Ting; Wang, Wan; Zhu, Ding

2015-11-15

Graphical abstract: Polypyrrole(PPy) film has improved the rate performance of LiMn{sub 2}O{sub 4} efficiently due to its excellent conductivity. PPy@LiMn{sub 2}O{sub 4} could provide more energy under the higher power than pristine LMO. - Highlights: • The PPy layer on the surface of LMO particles hasn’t been studied in LiMn{sub 2}O{sub 4} so far. • The solvent in the synthesis process of PPy@LMO is absolute ethyl alcohol. • The differences of surface-modification between the PPy and PI for LMO. • The analyses of rate performances are through specific power. - Abstract: Polypyrrole (PPy) is an excellent conductive polymer and themore » study on its utilization in the surface modification of the LiMn{sub 2}O{sub 4} (LMO) is few. In this work, the structure, morphology and electrochemical performance of surface-modified LiMn{sub 2}O{sub 4} composites with PPy and polyimides (PI) were discussed. The crystal structure, chemical bonds and morphology were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. Moreover, the specific power and cycling performance were tested at room and high (55 °C) temperature. The PPy@LMO (surface-modified LMO composites with PPy) shows better performances than the pristine LMO. The addition of PPy not only weakens the corrosion caused by electrolyte, but also improves the discharge capacity at higher rates. The charge transfer resistance of the PPy@LMO is much lower than that of the pristine LMO after cycling.« less

Wiring assembly and method of forming a channel in a wiring assembly for receiving conductor and providing separate regions of conductor contact with the channel

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

Stelzer, Gerald; Meinke, Rainer; Senti, Mark

A conductor assembly and method for constructing an assembly of the type which, when conducting current, generates a magnetic field or which, in the presence of a changing magnetic field, induces a voltage. In one embodiment the method provides a first insulative layer tubular in shape and including a surface along which a conductor segment may be positioned. A channel formed in the surface of the insulative layer defines a first conductor path and includes a surface of first contour in cross section along a first plane transverse to the conductor path. A segment of conductor having a surface ofmore » second contour in cross section is positioned at least partly in the channel and extends along the conductor path. Along the first plane, contact between the conductor surface of second contour and the channel surface of first contour includes at least two separate regions of contact.« less

Gating of high-mobility InAs metamorphic heterostructures

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

Shabani, J.; McFadden, A. P.; Shojaei, B.

We investigate the performance of gate-defined devices fabricated on high mobility InAs metamorphic heterostructures. We find that heterostructures capped with In{sub 0.75}Ga{sub 0.25}As often show signs of parallel conduction due to proximity of their surface Fermi level to the conduction band minimum. Here, we introduce a technique that can be used to estimate the density of this surface charge that involves cool-downs from room temperature under gate bias. We have been able to remove the parallel conduction under high positive bias, but achieving full depletion has proven difficult. We find that by using In{sub 0.75}Al{sub 0.25}As as the barrier withoutmore » an In{sub 0.75}Ga{sub 0.25}As capping, a drastic reduction in parallel conduction can be achieved. Our studies show that this does not change the transport properties of the quantum well significantly. We achieved full depletion in InAlAs capped heterostructures with non-hysteretic gating response suitable for fabrication of gate-defined mesoscopic devices.« less

Differentiation of surface and bulk conductivities in topological insulator via four-probe spectroscopy

DOE PAGES

Zhang, Xiaoguang; McGuire, Michael A.; Chen, Yong P.; ...

2016-03-08

Topological insulators, with characteristic topological surface states, have emerged as a new state of matter with rich potentials for both fundamental physics and device applications. However, the experimental detection of the surface transport has been hampered by the unavoidable extrinsic conductivity associated with the bulk crystals. Here we show that a four-probe transport spectroscopy in a multi-probe scanning tunneling microscopy system can be used to differentiate conductivities from the surface states and the coexisting bulk states in topological insulators. We derive a scaling relation of measured resistance with respect to varying inter-probe spacing for two interconnected conduction channels, which allowsmore » quantitative determination of conductivities from both channels. Using this method, we demonstrate the separation of 2D and 3D conduction in topological insulators by comparing the conductance scaling of Bi 2Se 3, Bi 2Te 2Se, and Sb-doped Bi 2Se 3 with that of a pure 2D conductance of graphene on SiC substrate. We also report the 2D conductance enhancement due to the surface doping effect in topological insulators. This technique can be applied to reveal 2D to 3D crossover of conductance in other complex systems.« less

BRNBOX v.1.0

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

Aldridge, David F.

Program BRNBOX conducts a systematic search through a pre-defined 3D volume of candidate sub-surface Born scattering points in order to identify the particular point that minimizes the misfit between predicted (i.e., calculated) and observed electromagnetic (EM) data. This global minimum misfit point is interpreted as the location where electrically conductive proppant is injected into a sub-surface petroleum reservoir in a hydraulic fracturing experiment.

Structural characterization of the voltage sensor domain and voltage-gated K+- channel proteins vectorially-oriented within a single bilayer membrane at the solid/vapor and solid/liquid interfaces via neutron interferometry

PubMed Central

Gupta, S.; Dura, J.A.; Freites, J.A.; Tobias, D.J.; Blasie, J. K.

2012-01-01

The voltage-sensor domain (VSD) is a modular 4-helix bundle component that confers voltage sensitivity to voltage-gated cation channels in biological membranes. Despite extensive biophysical studies and the recent availability of x-ray crystal structures for a few voltage-gated potassium (Kv-) channels and a voltage-gate sodium (Nav-) channel, a complete understanding of the cooperative mechanism of electromechanical coupling, interconverting the closed-to-open states (i.e. non-conducting to cation conducting) remains undetermined. Moreover, the function of these domains is highly dependent on the physical-chemical properties of the surrounding lipid membrane environment. The basis for this work was provided by a recent structural study of the VSD from a prokaryotic Kv-channel vectorially-oriented within a single phospholipid (POPC; 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) membrane investigated by x-ray interferometry at the solid/moist He (or solid/vapor) and solid/liquid interfaces thus achieving partial to full hydration, respectively (Gupta et. al. Phys. Rev E. 2011, 84). Here, we utilize neutron interferometry to characterize this system in substantially greater structural detail at the sub-molecular level, due to its inherent advantages arising from solvent contrast variation coupled with the deuteration of selected sub-molecular membrane components, especially important for the membrane at the solid/liquid interface. We demonstrate the unique vectorial orientation of the VSD and the retention of its molecular conformation manifest in the asymmetric profile structure of the protein within the profile structure of this single bilayer membrane system. We definitively characterize the asymmetric phospholipid bilayer solvating the lateral surfaces of the VSD protein within the membrane. The profile structures of both the VSD protein and phospholipid bilayer depend upon the hydration state of the membrane. We also determine the distribution of water and exchangeable hydrogen throughout the profile structure of both the VSD itself and the VSD:POPC membrane. These two experimentally-determined water and exchangeable hydrogen distribution profiles are in good agreement with molecular dynamics simulations of the VSD protein vectorially-oriented within a fully hydrated POPC bilayer membrane, supporting the existence of the VSD’s water pore. This approach was extended to the full-length Kv-channel (KvAP) at solid/liquid interface, providing the separate profile structures of the KvAP protein and the POPC bilayer within the reconstituted KvAP:POPC membrane. PMID:22686684

Nanoscale current imaging of the conducting channels in proton exchange membrane fuel cells.

PubMed

Bussian, David A; O'Dea, James R; Metiu, Horia; Buratto, Steven K

2007-02-01

The electrochemically active area of a proton exchange membrane fuel cell (PEMFC) is investigated using conductive probe atomic force microscopy (CP-AFM). A platinum-coated AFM tip is used as a nanoscale cathode in an operating PEMFC. We present results that show highly inhomogeneous distributions of conductive surface domains at several length scales. At length scales on the order of the aqueous domains of the membrane, approximately 50 nm, we observe single channel electrochemistry. I-V curves for single conducting channels are obtained, which yield insight into the nature of conductive regions across the PEM. In addition, we demonstrate a new characterization technique, phase current correlation microscopy, which gives a direct measure of the electrochemical activity for each aqueous domain. This shows that a large number ( approximately 60%) of the aqueous domains present at the surface of an operating Nafion membrane are inactive. We attribute this to a combination of limited aqueous domain connectivity and catalyst accessibility.

Morphological change on the River Towy, Wales assessed using aerial photogrammetry

NASA Astrophysics Data System (ADS)

Ahmed, Joshua; Hodge, Michael

2017-04-01

The dynamic nature of meandering channels has fascinated geomorphologists for decades; with the onset of remote sensing, and technological advances in field equipment, scientists are able to capture high-resolution data from the Earth's surface using cost-effective techniques that require minimal manual labour. Here we present a morphological assessment of three meander bends on the River Towy, Wales, using aerial photography captured by the Welsh Assembly Government and supplemented by data captured by a UAV. Migration rates and changes in channel length were measured between 1969 and 2016 and compared to a coupled discharge record to quantify the effects of discharge variability on the morphological evolution of the channel. A short-term (seasonal) assessment of channel change was conducted by comparing sub-metre resolution 3D point cloud and digital elevation models, generated using a UAV and Structure-from-Motion (SfM) photogrammetry. Our results suggest that discharge variability plays a crucial role in controlling the evolution of meandering planforms and can be an effective means of excavating floodplain material over relatively short timescales, although erosion rates can be suppressed by bankline roughness, which effectively disrupts outwardly directed flow momentum. These findings have implications for land managers and those modelling the effects of climate change on hydrological regimes which are ultimately used to forecast channel planform changes. Additionally, our results demonstrate the potential of low-cost field surveying techniques in producing high resolution models of landscape change.

Gravity dependency of the gramicidin A channel conductivity. A model for gravity perception on the cellular level.

PubMed

Schatz, A; Linke-Hommes, A; Neubert, J

1996-01-01

Theoretical investigations involving the membrane-solution interface have revealed that the density of the solution varies appreciably within interfacial layers adjacent to charged membrane surfaces. The hypothesis that gravity interacts with this configuration and modifies transport rates across horizontal and vertical membranes differently was supported by initial experiments with gramicidin A channels in phosphatidylserine (PS) membranes in 0.1 M KCl. Channel conductivity was found to be about 1.6 times higher in horizontal membranes than in vertical membranes. Here we present the results of further experiments with gramicidin A channels (incorporated into charged PS- and uncharged phosphatidylcholine (PC) membranes in KCl- and CsCl-solutions) to demonstrate that the hypothesis is more generally applicable. Again, channel conductivity was found to be higher in horizontal PS membranes by a factor of between 1.20 and 1.75 in 0.1 M CsCl. No difference in channel conductivity was found for uncharged PC membranes in 0.1 M KCl and in 0.1 M CsCl. However, for PC membranes in 0.05 M KCl the channel conductivity was significantly higher in horizontal membranes by a factor of between 1.07 and 1.14. These results are consistent with the results of our model calculations of layer density and extension, which showed that the layer formation is enhanced by increasing membrane surface charge and decreasing electrolyte ion concentration. The mechanism of gravity interaction with membrane transport processes via interface reactions might be utilized by biological systems for orientational behaviour in the gravity field, which has been observed even for cellular systems.

Evaluation of electrical conductivity of Cu and Al through sub microsecond underwater electrical wire explosion

NASA Astrophysics Data System (ADS)

Sheftman, D.; Shafer, D.; Efimov, S.; Krasik, Ya. E.

2012-03-01

Sub-microsecond timescale underwater electrical wire explosions using Cu and Al materials have been conducted. Current and voltage waveforms and time-resolved streak images of the discharge channel, coupled to 1D magneto-hydrodynamic simulations, have been used to determine the electrical conductivity of the metals for the range of conditions between hot liquid metal and strongly coupled non-ideal plasma, in the temperature range of 10-60 KK. The results of these studies showed that the conductivity values obtained are typically lower than those corresponding to modern theoretical electrical conductivity models and provide a transition between the conductivity values obtained in microsecond time scale explosions and those obtained in nanosecond time scale wire explosions. In addition, the measured wire expansion shows good agreement with equation of state tables.

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

Chen, Yan; Cai, Lu; An, Ke, E-mail: kean@ornl.gov

This letter reports the correlation of anisotropy and directional conduction in the fast Li{sup +} conductor β-Li{sub 3}PS{sub 4}, one of the low-symmetry crystalline electrolyte candidates. The material has both high conductivity and good stability that serves well for the large-scale energy storage applications of all-solid-state lithium ion batteries. The anisotropic physical properties, demonstrated here by the thermal expansion coefficients, are crucial for compatibility in the solid-state system and battery performance. Neutron and X-ray powder diffraction measurements were done to determine the crystal structure and thermal stability. The crystallographic b-axis was revealed as a fast expansion direction, while negligible thermalmore » expansion was observed along the a-axis around the battery operating temperatures. The anisotropic behavior has its structural origin from the Li{sup +} conduction channels with incomplete Li occupancy and a flexible connection of LiS{sub 4} and PS{sub 4} tetrahedra within the framework. This indicates a strong correlation in the direction of the ionic transport in the low-symmetry Li{sup +} conductor.« less

Interspecific variation in SO/sub 2/ flux: leaf surface versus internal flux, and components of leaf conductance. [Pisum sativum L. , Lycopersicon esculentum Mill. Flacca, Geranium carolinianum L. , Diplacus aurantiacus (Curtis) Jeps

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

Olszyk, D.M.; Tingey, D.T.

The objective of this study was to clarify the relationships among stomatal, residual, and epidermal conductances in determining the flux of SO/sub 2/ air pollution to leaves. Variations in leaf SO/sub 2/ and H/sub 2/O vapor fluxes were determined using four plant species: Pisum sativum L. (garden pea), Lycopersicon esculentum Mill. flacca (mutant of tomato), Geranium carolinianum L. (wild geranium), and Diplacus aurantiacus (Curtis) Jeps. (a native California shrub). Fluxes were measured using the mass-balance approach during exposure to 4.56 micromoles per cubic meter (0.11 microliters per liter) SO/sub 2/ for 2 hours in a controlled environmental chamber. Flux throughmore » adaxial and abaxial leaf surfaces with closed stomata ranged from 1.9 to 9.4 nanomoles per square meter per second for SO/sub 2/, and 0.3 to 1.3 millimoles per square meter per second for H/sub 2/O vapor. Flux of SO/sub 2/ into leaves through stomata ranged from approx.0 to 8.5 (dark) and 3.8 to 16.0 (light) millimoles per square meter per second. Flux of H/sub 2/O vapor from leaves through stomata ranged from approx.0 to 0.6 (dark) to 0.4 to 0.9 (light) millimole per square meter per second. Lycopersicon had internal flux rates for both SO/sub 2/ and H/sub 2/O vapor over twice as high as for the other species. Stomatal conductance based on H/sub 2/O vapor flux averaged from 0.07 to 0.13 mole per square meter per second among the four species. Internal conductance of SO/sub 2/ as calculated from SO/sub 2/ flux was from 0.04 mole per square meter per second lower to 0.06 mole per square meter per second higher than stomatal conductance. For Pisum, Geranium, and Diplacus stomatal conductance was the same or slightly higher than internal conductance, indicating that, in general, SO/sub 2/ flux could be predicted from stomatal conductance for H/sub 2/O vapor.« less

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

Zhang, Xiaoguang; McGuire, Michael A.; Chen, Yong P.

Topological insulators, with characteristic topological surface states, have emerged as a new state of matter with rich potentials for both fundamental physics and device applications. However, the experimental detection of the surface transport has been hampered by the unavoidable extrinsic conductivity associated with the bulk crystals. Here we show that a four-probe transport spectroscopy in a multi-probe scanning tunneling microscopy system can be used to differentiate conductivities from the surface states and the coexisting bulk states in topological insulators. We derive a scaling relation of measured resistance with respect to varying inter-probe spacing for two interconnected conduction channels, which allowsmore » quantitative determination of conductivities from both channels. Using this method, we demonstrate the separation of 2D and 3D conduction in topological insulators by comparing the conductance scaling of Bi 2Se 3, Bi 2Te 2Se, and Sb-doped Bi 2Se 3 with that of a pure 2D conductance of graphene on SiC substrate. We also report the 2D conductance enhancement due to the surface doping effect in topological insulators. This technique can be applied to reveal 2D to 3D crossover of conductance in other complex systems.« less

Design and synthesis of guest-host nanostructures to enhance ionic conductivity across nanocomposite membranes

DOEpatents

Hu, Michael Z [Knoxville, TN; Kosacki, Igor [Oak Ridge, TN

2010-01-05

An ion conducting membrane has a matrix including an ordered array of hollow channels and a nanocrystalline electrolyte contained within at least some or all of the channels. The channels have opposed open ends, and a channel width of 1000 nanometers or less, preferably 60 nanometers or less, and most preferably 10 nanometers or less. The channels may be aligned perpendicular to the matrix surface, and the length of the channels may be 10 nanometers to 1000 micrometers. The electrolyte has grain sizes of 100 nanometers or less, and preferably grain sizes of 1 to 50 nanometers. The electrolyte may include grains with a part of the grain boundaries aligned with inner walls of the channels to form a straight oriented grain-wall interface or the electrolyte may be a single crystal. In one form, the electrolyte conducts oxygen ions, the matrix is silica, and the electrolyte is yttrium doped zirconia.

Study of condensation of refrigerants in a micro-channel for development of future compact micro-channel condensers

NASA Astrophysics Data System (ADS)

Chowdhury, Sourav

2009-12-01

Mini- and micro-channel technology has gained considerable ground in the recent years in industry and is favored due to its several advantages stemming from its high surface to volume ratio and high values of proof pressure it can withstand. Micro-channel technology has paved the way to development of highly compact heat exchangers with low cost and mass penalties. In the present work, the issues related to the sizing of compact micro-channel condensers have been explored. The considered designs encompass both the conventional and MEMS fabrication techniques. In case of MEMS-fabricated micro-channel condenser, wet etching of the micro-channel structures, followed by bonding of two such wafers with silicon nitride layers at the interface was attempted. It was concluded that the silicon nitride bonding requires great care in terms of high degree of surface flatness and absence of roughness and also high degree of surface purity and thus cannot be recommended for mass fabrication. Following this investigation, a carefully prepared experimental setup and test micro-channel with hydraulic diameter 700 mum and aspect ratio 7:1 was fabricated and overall heat transfer and pressure drop aspects of two condensing refrigerants, R134a and R245fa were studied at a variety of test conditions. To the best of author's knowledge, so far no data has been reported in the literature on condensation in such high aspect ratio micro-channels. Most of the published experimental works on condensation of refrigerants are concerning conventional hydraulic diameter channels (> 3mm) and only recently some experimental data has been reported in the sub-millimeter scale channels for which the surface tension and viscosity effects play a dominant role and the effect of gravity is diminished. It is found that both experimental data and empirically-derived correlations tend to under-predict the present data by an average of 25%. The reason for this deviation could be because a high aspect ratio channel tends to collect the condensate in the corners of its cross-section leaving only a thin liquid film on the flat side surfaces for better heat transfer than in circular or low aspect ratio channels.

Can p-channel tunnel field-effect transistors perform as good as n-channel?

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

Verhulst, A. S., E-mail: anne.verhulst@imec.be; Pourghaderi, M. A.; Collaert, N.

2014-07-28

We show that bulk semiconductor materials do not allow perfectly complementary p- and n-channel tunnel field-effect transistors (TFETs), due to the presence of a heavy-hole band. When tunneling in p-TFETs is oriented towards the gate-dielectric, field-induced quantum confinement results in a highest-energy subband which is heavy-hole like. In direct-bandgap IIIV materials, the most promising TFET materials, phonon-assisted tunneling to this subband degrades the subthreshold swing and leads to at least 10× smaller on-current than the desired ballistic on-current. This is demonstrated with quantum-mechanical predictions for p-TFETs with tunneling orthogonal to the gate, made out of InP, In{sub 0.53}Ga{sub 0.47}As, InAs,more » and a modified version of In{sub 0.53}Ga{sub 0.47}As with an artificially increased conduction-band density-of-states. We further show that even if the phonon-assisted current would be negligible, the build-up of a heavy-hole-based inversion layer prevents efficient ballistic tunneling, especially at low supply voltages. For p-TFET, a strongly confined n-i-p or n-p-i-p configuration is therefore recommended, as well as a tensily strained line-tunneling configuration.« less

Structure and dynamics in low-dimensional guest host solids

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

Fischer, J.

1991-04-01

This progress report presents results from work during the period of June 1, 1990 through May 31st, 1991. Topics discussed include instrumentation, publications, and personnel. Work areas discussed include: pressure-induced transitions in Li- and Ag-TiS{sub 2}, hyper-dense superconducting GIC's, temperature-dependent x-ray structure of (CH){sub x} and (CH){sub 2{sup x}}:analogies to rotator phases in short-chain alkanes, trans-(CH){sub x} at high'' pressure, broken symmetries'' in polymer intercalation channel lattices, high-resolution study of conductivity and cell potential vs. concentration in K-doped (CH){sub x}, new'' doped (CH){sub x} phases: ternary compounds and amorphous'' intercalation compounds, and vibrational density states from inelastic neutron scattering. (JF).

Suppression of 1/f noise in near-ballistic h-BN-graphene-h-BN heterostructure field-effect transistors

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

Stolyarov, Maxim A.; Liu, Guanxiong; Balandin, Alexander A., E-mail: balandin@ee.ucr.edu

2015-07-13

We have investigated low-frequency 1/f noise in the boron nitride–graphene–boron nitride heterostructure field-effect transistors on Si/SiO{sub 2} substrates (f is a frequency). The device channel was implemented with a single layer graphene encased between two layers of hexagonal boron nitride. The transistors had the charge carrier mobility in the range from ∼30 000 to ∼36 000 cm{sup 2}/Vs at room temperature. It was established that the noise spectral density normalized to the channel area in such devices can be suppressed to ∼5 × 10{sup −9 }μm{sup 2 }Hz{sup −1}, which is a factor of ×5 – ×10 lower than that in non-encapsulated graphene devices on Si/SiO{sub 2}. The physicalmore » mechanism of noise suppression was attributed to screening of the charge carriers in the channel from traps in SiO{sub 2} gate dielectric and surface defects. The obtained results are important for the electronic and optoelectronic applications of graphene.« less

Simulations of the effects of water vapor, cloud liquid water, and ice on AMSU moisture channel brightness temperatures

NASA Technical Reports Server (NTRS)

Muller, Bradley M.; Fuelberg, Henry E.; Xiang, Xuwu

1994-01-01

Radiative transfer simulations are performed to determine how water vapor and nonprecipitating cloud liquid water and ice particles within typical midlatitude atmospheres affect brightness temperatures T(sub B)'s of moisture sounding channels used in the Advanced Microwave Sounding Unit (AMSU) and AMSU-like instruments. The purpose is to promote a general understanding of passive top-of-atmosphere T(sub B)'s for window frequencies at 23.8, 89.0, and 157.0 GHz, and water vapor frequencies at 176.31, 180.31, and 182.31 GHz by documenting specific examples. This is accomplished through detailed analyses of T(sub B)'s for idealized atmospheres, mostly representing temperate conditions over land. Cloud effects are considered in terms of five basic properties: droplet size distribution, phase, liquid or ice water content, altitude, and thickness. Effects on T(sub B) of changing surface emissivity also are addressed. The brightness temperature contribution functions are presented as an aid to physically interpreting AMSU T(sub B)'s. Both liquid and ice clouds impact the T(sub B)'s in a variety of ways. The T(sub B)'s at 23.8 and 89 GHz are more strongly affected by altostratus liquid clouds than by cirrus clouds for equivalent water paths. In contrast, channels near 157 and 183 GHz are more strongly affected by ice clouds. Higher clouds have a greater impact on 157- and 183-GHz T(sub B)'s than do lower clouds. Clouds depress T(sub B)'s of the higher-frequency channels by suppressing, but not necessarily obscuring, radiance contributions from below. Thus, T(sub B)'s are less closely associated with cloud-top temperatures than are IR radiometric temperatures. Water vapor alone accounts for up to 89% of the total attenuation by a midtropospheric liquid cloud for channels near 183 GHz. The Rayleigh approximation is found to be adequate for typical droplet size distributions; however, Mie scattering effects from liquid droplets become important for droplet size distribution functions with modal radii greater than 20 micrometers near 157 and 183 GHz, and greater than 30-40 micrometers at 89 GHz. This is due mainly to the relatively small concentrations of droplets much larger than the mode radius. Orographic clouds and tropical cumuli have been observed to contain droplet size distributions with mode radii in the 30-40 micrometers range. Thus, as new instruments bridge the gap between microwave and infrared to frequencies even higher than 183 GHz, radiative transfer modelers are cautioned to explicitly address scattering characteristics of such clouds.

Communication: Towards catalytic nitric oxide reduction via oligomerization on boron doped graphene

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

Cantatore, Valentina, E-mail: valcan@chalmers.se; Panas, Itai

We use density functional theory to describe a novel way for metal free catalytic reduction of nitric oxide NO utilizing boron doped graphene. The present study is based on the observation that boron doped graphene and O—N=N—O{sup −} act as Lewis acid-base pair allowing the graphene surface to act as a catalyst. The process implies electron assisted N=N bond formation prior to N—O dissociation. Two N{sub 2} + O{sub 2} product channels, one of which favoring N{sub 2}O formation, are envisaged as outcome of the catalytic process. Besides, we show also that the N{sub 2} + O{sub 2} formation pathwaysmore » are contrasted by a side reaction that brings to N{sub 3}O{sub 3}{sup −} formation and decomposition into N{sub 2}O + NO{sub 2}{sup −}.« less

Electrical dependence on the chemical composition of the gate dielectric in indium gallium zinc oxide thin-film transistors

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

Tari, Alireza, E-mail: atari@uwaterloo.ca; Lee, Czang-Ho; Wong, William S.

Bottom-gate thin-film transistors were fabricated by depositing a 50 nm InGaZnO (IGZO) channel layer at 150 °C on three separate gate dielectric films: (1) thermal SiO{sub 2}, (2) plasma-enhanced chemical-vapor deposition (PECVD) SiN{sub x}, and (3) a PECVD SiO{sub x}/SiN{sub x} dual-dielectric. X-ray photoelectron and photoluminescence spectroscopy showed the V{sub o} concentration was dependent on the hydrogen concentration of the underlying dielectric film. IGZO films on SiN{sub x} (high V{sub o}) and SiO{sub 2} (low V{sub o}) had the highest and lowest conductivity, respectively. A PECVD SiO{sub x}/SiN{sub x} dual-dielectric layer was effective in suppressing hydrogen diffusion from the nitride layer intomore » the IGZO and resulted in higher resistivity films.« less

Collisions of excited Na atoms with H/sub 2/ molecules. I. Ab initio potential energy surfaces and qualitative discussion of the quenching process

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

Botschwina, P.; Meyer, W.; Hertel, I.V.

Potential energy surfaces have been calculated for the four lowest electronic states of Na (3 /sup 2/S, 3 /sup 2/P)+H/sub 2/(/sup 1/..sigma../sup +//sub g/) by means of the RHF--SCF and PNO--CEPA methods. For the so-called quenching process of Na (3 /sup 2/P) by H/sub 2/ at low initial translational energies (E--VRT energy transfer) the energetically most favorable path occurs in C/sub 2v/ symmetry, since: at intermediate Na--H/sub 2/ separation: the A /sup 2/B/sub 2/ potential energy surface is attractive. From the CEPA calculations, the crossing point of minimal energy between the X /sup 2/A/sub 1/ and A /sup 2/B/sub 2/more » surfaces is obtained at R/sub c/ = 3.57 a.u. and r/sub c/ = 2.17 a.u. with an energy difference to the asymptotic limit (R = infinity, r = r/sub e/) of -0.06 eV. It is thus classically accessible without any initial translational energy, but at low initial translational energies (approx.0.1 eV) quenching will be efficient only for arrangements of collision partners close to C/sub 2v/ symmetry. There is little indication of an avoiding crossing with an ionic intermediate correlating asymptotically with Na/sup +/ and H/sub 2//sup -/ as was assumed in previous discussions of the quenching process. The dependence of the total quenching cross sections on the initial translational energy is discussed by means of the ''absorbing sphere'' model, taking the initial zero-point vibrational energy of the hydrogen molecule into account. New experimental data of the product channel distribution in H/sub 2/ for center-of-mass forward scattering are presented. The final vibrational states v' = 3, 2, 1, and 0 of H/sub 2/ are populated to about 26%, 61%, 13%, and 0%, respectively. The observed distributions in H/sub 2/ (and D/sub 2/) may be rationalized by simple dynamic considerations on the basis of the calculated surfaces.« less

Regulation of surface expression of TRPV2 channels in the retinal pigment epithelium.

PubMed

Reichhart, Nadine; Keckeis, Susanne; Fried, Frederik; Fels, Gabriele; Strauss, Olaf

2015-06-01

The retinal pigment epithelium (RPE) interacts closely with the photoreceptors in fulfilling tasks of visual function. Since an understanding of the RPE function is essential for understanding the patho-mechanisms involved in vision loss, we explored the regulation of the vanilloid receptor subtype transient receptor potential TRPV2 channels that trigger insulin-like growth factor-1 (IGF-1)-induced vascular endothelial growth factor A (VEGF-A) secretion. Immunohistochemistry was used to assess TRPV2 expression in retinal cross-sections or ARPE-19 cells, and surface expression of TRPV2 was quantified using confocal microscopy. Membrane currents of ARPE-19 cells were recorded using a whole-cell configuration of the patch-clamp technique. TRPV2 expression was detected in the RPE of the mouse retina as well as in ARPE-19 cells. Increasing the temperature to 45 °C activated membrane conductance sensitive to SKF-96365 and ruthenium red in 60 % of cells. Preincubation with either cannabidiol (CBD) or IGF-1 led to a three- or fourfold increase in current density, respectively, in all cells, which was blocked by SKF-96365. In contrast to IGF-1, CBD stimulation of membrane conductance was further increased by heat. TRPV2 surface expression was increased by both IGF-1 and CBD, with the increase by CBD twice as large as that by IGF-1. The phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 abolished the effects on membrane conductance and surface expression. Both CBD and IGF-1 enhance TRPV2 channel activity by specific proportions of both channel activation and PI 3-kinase-dependent surface expression: IGF-1 predominantly increases ion channel activity, whereas CBD is more active in increasing TRPV2 surface expression. Thus, differential regulation of TRPV2 surface expression is an important mechanism for modulating the responsiveness of the RPE to growth factors.

Studies of snowpack properties by passive microwave radiometry

NASA Technical Reports Server (NTRS)

Chang, A. T. C.; Hall, D. K.; Foster, J. L.; Rango, A.; Schmugge, T. J.

1978-01-01

Research involving the microwave characteristics of snow was undertaken in order to expand the information content currently available from remote sensing, namely the measurement of snowcovered area. Microwave radiation emitted from beneath the snow surface can be sensed and thus permits information on internal snowpack properties to be inferred. The intensity of radiation received is a function of the average temperature and emissivity of the snow layers and is commonly referred to as the brightness temperature (T sub b). The T sub b varies with snow grain and crystal sizes, liquid water content and snowpack temperature. The T sub b of the 0.8 cm wavelength channel was found to decrease moreso with increasing snow depth than the 1.4 cm channel. More scattering of the shorter wavelength radiation occurs thus resulting in a lower T sub b for shorter wavelengths in a dry snowpack. The longer 21.0 cm wavelength was used to assess the condition of the underlying ground. Ultimately it may be possible to estimate snow volume over large areas using calibrated brightness temperatures and consequently improve snowmelt runoff predictions.

Impedance spectroscopy study on graphene wrapped nanocrystalline V{sub 2}O{sub 5}

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

Bhaskaram, D. Surya, E-mail: dsurya.b@gmail.com; Govindaraj, G.; Cheruku, Rajesh

2016-05-23

Nanocrystalline V{sub 2}O{sub 5} was synthesized by solvothermal technique, which has potential application as electrode material in supercapacitors. The graphene oxide (GO) was prepared by modified Hummer’s method. The V{sub 2}O{sub 5}/ reduced graphene oxide (RGO) composite was synthesized using surfactant free hydrothermal technique to enhance the functionality in terms of conductivity and surface area of V{sub 2}O{sub 5}. The structural characterization was accomplished through X-ray diffraction and Raman spectroscopy. Morphology was identified by SEM and surface area of VRGO was enhanced by 8 times in comparison with V{sub 2}O{sub 5} nano particles, as confirmed through BET surface area analysis.more » Electrical characterization was done through impedance spectroscopy and the results showed decrease in sample resistance after wrapping V{sub 2}O{sub 5} with RGO.« less

Rate equation analysis of hydrogen uptake on Si (100) surfaces

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

Inanaga, S.; Rahman, F.; Khanom, F.

2005-09-15

We have studied the uptake process of H on Si (100) surfaces by means of rate equation analysis. Flowers' quasiequilibrium model for adsorption and desorption of H [M. C. Flowers, N. B. H. Jonathan, A. Morris, and S. Wright, Surf. Sci. 396, 227 (1998)] is extended so that in addition to the H abstraction (ABS) and {beta}{sub 2}-channel thermal desorption (TD) the proposed rate equation further includes the adsorption-induced desorption (AID) and {beta}{sub 1}-TD. The validity of the model is tested by the experiments of ABS and AID rates in the reaction system H+D/Si (100). Consequently, we find it canmore » well reproduce the experimental results, validating the proposed model. We find the AID rate curve as a function of surface temperature T{sub s} exhibits a clear anti-correlation with the bulk dangling bond density versus T{sub s} curve reported in the plasma-enhanced chemical vapor deposition (CVD) for amorphous Si films. The significance of the H chemistry in plasma-enhanced CVD is discussed.« less

Hydraulic and field water-chemistry characteristics of piedmont alluvial deposits in the Middle Tyger River near Lyman, Spartanburg County, South Carolina, 2005

USGS Publications Warehouse

Harrelson, Larry G.; Addison, Adrian D.

2006-01-01

This study explores the possibility of developing a bank-filtration process to improve water quality in which alluvial deposits serve as a natural sand filter to pretreat water to be used as a secondary drinking-water source in a small piedmont reservoir along the Middle Tyger River near Lyman in Spartanburg County, South Carolina. From January 2004 to September 2005, data from 10 auger borings, 2 sediment cores, 29 ground-penetrating radar transects, and 3 temporary observation wells, and field water-chemistry data were collected and analyzed. These data were collected and used to characterize the lithology, geometry, hydraulic properties, yield potential, and water-chemistry characteristics of the alluvial deposits in the channel and on the right bank of the reservoir. The assessment was undertaken to determine if an adequate amount of water could be withdrawn from the alluvial deposits to sustain a bank-filtration process and to characterize the water chemistry of the surface water and pore water. The heterogeneous alluvial and fill material at the study site--clay, silty clay, clayey sand, fine- to coarse-grained sand, and mica--on the right bank of the Middle Tyger River ranges in thickness from 0.6 to 7 meters, has a calculated horizontal hydraulic conductivity of 1 meter per day, and yields approximately 0.07 liter per second of water. The small calculated horizontal hydraulic conductivity and water yield for these deposits restrict the use of the right bank as a potential bank-filtration site. The coarse-grained alluvial sand deposit in the channel of the Middle Tyger River, however, may be used for a limited bank-filtration process. The discharge during pumping of the channel deposit yielded water at the rate of 1.9 liters per second. The coarse-grained channel deposit is approximately 49 meters wide and 3 meters thick near the dam. At approximately 183 meters upstream from the dam, the channel narrows to roughly 9 meters and the channel deposits thin to approximately 0.1 meter. Slug tests conducted in the channel deposits near the dam produced a calculated horizontal hydraulic conductivity of 60 meters per day. The limited thickness and aerial extent of the coarse-grained channel deposits coupled with large horizontal hydraulic conductivity likely would allow rapid transmission of water and may degrade the effectiveness of some water-chemistry improvements typical of a bank-filtration process. Field water-chemistry data were collected for approximately 1 hour and 45 minutes at 10 to 15 minute intervals to compare the surface-water and pore-water quality in and beneath the channel of the Middle Tyger River. The waterchemistry data indicate that (1) the mean water temperature was higher in surface water (22.5 degrees Celsius) than in pore water (18.5 degrees Celsius), (2) the mean specific conductance was less in surface water (56.9 microsiemens per centimeter at 25 degrees Celsius) than in pore water (125.7 microsiemens per centimeter at 25 degrees Celsius), (3) alkalinity was lower in surface water (22.5 milligrams per liter) than in pore water (44.6 milligrams per liter), and (4) recorded pH values ranged between 6.2 and 6.3 in the surface water and pore water during the sampling period. The flow velocity was orders of magnitude slower in the pore water than in the surface water; therefore, the pore water interacts with the alluvial sediment for a longer period of time producing the variation in water-chemistry data between the two waters.

Crustal and Uppermost Mantle Structure across the Tibet-Qinling Transition Zone in NE Tibet: Implications for Material Extrusion of the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Ye, Z.; Li, J.; Gao*, R.; Song, X.; Li, Q.; Li, Y.; Huang, X.; Xiong, X.; Li, W.; WANG, Y.

2017-12-01

Based on a dense linear seismic array traversing across the eastern margin of the Tibetan plateau to the Qinling belt, we conducted joint inversion of receiver functions and surface wave dispersions under constraints of P-wave velocity and derived a crustal and uppermost mantle Vs profile simultaneously with a Vp/Vs ratio profile. Our observations indicate that the Qinling belt, which shows ratio Vp/Vs<1.8 indicative of intermediate-to-felsic components in the lower crust, is currently not acting as a channel accommodating extrusion of the mid-lower crustal flow; and extrusion of Tibet's ductile mantle flow through the Qinling belt as a channel would only be feasible in the sub-lithosphere depth (asthenosphere). Our results suggest that ductile material extrusion of the mid-lower crustal flow accompanied with fault-related tectonics and gravitational buoyancy resulted from lithospheric detachment (triggered by the asthenospheric flow) may jointly work on the plateau uplift and expansion in this Tibet-Qinling transition zone. Corresponding Author: R.Gao, ruigao126@126.com

Energetic distributions of interface states Dit(phi sub s) of MOS transistors in extension of Kuhn's quasistatic C(V)-method

NASA Astrophysics Data System (ADS)

Krautschneider, W.; Wagemann, H. G.

1983-10-01

Kuhn's quasi-static C(V)-method has been extended to MOS transistors by considering the capacitances of the source and drain p-n junctions additionally to the MOS varactor circuit model. The width of the space charge layers w(phi sub s) is calculated as a function of the surface potential phi sub s and applied to the MOS capacitance as a function of the gate voltage. Capacitance behavior for different channel length is presented as a model and compared to measurement results and evaluations of energetic distributions of interface states Dit(phi sub s) for MOS transistor and MOS varactor on the same chip.

Superhydrophobic nanofluidic channels for enhanced electrokinetic conversion

NASA Astrophysics Data System (ADS)

Checco, Antonio; Al Hossain, Aktaruzzaman; Rahmani, Amir; Black, Charles; Doerk, Gregory; Colosqui, Carlos

2017-11-01

We present current efforts in the development of novel slit nanofluidic channels with superhydrophobic nanostructured surfaces designed to enhance hydrodynamic conductivity and improve selective transport and electrokinetic energy conversion efficiencies (mechanical-electrical energy conversion). The nanochannels are fabricated on silicon wafers using UV lithography, and their internal surface is patterned with conical nanostructures (feature size and spacing 30 nm) defined by block copolymer self-assembly and plasma etching. These nanostructures are rendered superhydrophobic by passivation with a hydrophobic silane monolayer. We experimentally characterize hydrodynamic conductivity, effective zeta potentials, and eletrokinetic flows for the patterned nanochannels, comparing against control channels with bare surfaces. Experimental observations are rationalized using both continuum-based modeling and molecular dynamics simulations. Scientific and technical knowledge produced by this work is particularly relevant for sustainable energy conversion and storage, separation processes and water treatment using nanoporous materials. The ONR Contract # N000141613178 and NSF-CBET award# 1605809.

A Channelization-Based DOA Estimation Method for Wideband Signals

PubMed Central

Guo, Rui; Zhang, Yue; Lin, Qianqiang; Chen, Zengping

2016-01-01

In this paper, we propose a novel direction of arrival (DOA) estimation method for wideband signals with sensor arrays. The proposed method splits the wideband array output into multiple frequency sub-channels and estimates the signal parameters using a digital channelization receiver. Based on the output sub-channels, a channelization-based incoherent signal subspace method (Channelization-ISM) and a channelization-based test of orthogonality of projected subspaces method (Channelization-TOPS) are proposed. Channelization-ISM applies narrowband signal subspace methods on each sub-channel independently. Then the arithmetic mean or geometric mean of the estimated DOAs from each sub-channel gives the final result. Channelization-TOPS measures the orthogonality between the signal and the noise subspaces of the output sub-channels to estimate DOAs. The proposed channelization-based method isolates signals in different bandwidths reasonably and improves the output SNR. It outperforms the conventional ISM and TOPS methods on estimation accuracy and dynamic range, especially in real environments. Besides, the parallel processing architecture makes it easy to implement on hardware. A wideband digital array radar (DAR) using direct wideband radio frequency (RF) digitization is presented. Experiments carried out in a microwave anechoic chamber with the wideband DAR are presented to demonstrate the performance. The results verify the effectiveness of the proposed method. PMID:27384566

Calcium-activated potassium channels in basolateral membranes of colon epithelial cells; reconstitution and functional properties.

PubMed

Wiener, H; Turnheim, K

1990-10-26

Using differential sedimentation, isopycnic and Ficoll-400 barrier centrifugation, basolateral membrane vesicles of surface and crypt cells of the rabbit distal colon were enriched 34- and 9-fold, respectively. 86Rb(+)-uptake into these vesicles, driven by an electrical potential difference, was stimulated by submicromolar Ca2+ activities and inhibited by Ba2+. These findings indicate the presence of Ca2(+)-activated K+ channels. The K+ channels in surface and crypt cell membranes differed with respect to inhibition by the bee venom apamin, the scorpion venom charybdotoxin and tetraethylammonium and exhibited a different pH dependence. Fusion of basolateral membrane vesicles with planar phospholipid bilayers revealed the presence of high-conductance Ba2(+)-sensitive K+ channels which were activated by micromolar Ca2+ and inhibited by crude scorpion venom and trifluoperazine. These K+ channels may be involved in the coupling of apical and basolateral membrane conductances during Na+ absorption and Cl- secretion, but they may also play a role in cell volume regulation.

Using surface curvature to map geomorphic process regimes in a bedrock landscape, Henry Mountains, Utah

NASA Astrophysics Data System (ADS)

Corbett, S.; Sklar, L. S.; Davis, J.

2009-12-01

Linkages between form and process are much better understood in soil-mantled landscapes than in bedrock landscapes, despite the wide occurrence of bedrock landscapes in arid and mountainous terrain. Soil-mantled hillslope topography can be characterized by hillslope gradient and its spatial derivative, which is commonly referred to as curvature and defined as the Laplacian of elevation. Surface curvature can also be quantified using techniques that are invariant to the orientation of the surface. These approaches are useful in many geoscience applications, including structural analysis of folded surfaces within deforming crustal blocks. Here we explore the use of surface curvature of bedrock topography as a metric to identify and map distinct geomorphic process regimes in a landscape devoid of soil cover. Our study site is Simpson Creek, a 2.5 km2 watershed on the east flank of Mt. Hillers in the Henry Mountains, Utah, which drains to the Colorado River in Glen Canyon. The land surface is entirely exposed Navajo Sandstone bedrock, with isolated patches of wind-blown sand deposits. The channel network is discontinuous, with alternating reaches of steep, deeply-incised, frequently-potholed slots, and lower-gradient, sand-bedded channels. Hillslope topography is characterized by dome-shaped and sub-linear ridges, and is influenced by prominent structural joints. We calculate two measures of the surface-normal curvature using an ALSM-derived digital elevation model. The mean and Gaussian surface curvatures are the average and product respectively of the magnitudes of the maximum and minimum curvature vectors, obtained by differentiating a polynomial fit at each point in a grid with 1 m spacing. Plots of mean versus Gaussian curvature reveal distinct clusters of landscape elements, which we associate with specific process regimes. In this parameter space, there are four quadrants, classified as dome, basin, synformal saddle and antiformal saddle. The channel and valley network corresponds to negative mean curvature, where concave and convex profile segments plot as basins and synformal saddles (positive and negative Gaussian curvature) respectively. We are able to use surface curvature to map what can be interpreted as bedrock channel width, as well as knickpoints, sand-bedrock bed transitions, and even individual large potholes. The tips of the channel network also have a distinct surface-curvature signature, and are associated with prominent polygonal bedrock fracturing at the sub-meter scale. In the hillslope portion of the landscape (positive mean curvature), the distribution of landscape elements has several modes, including a characteristic dome curvature that may be associated with sheet jointing and weathering-influenced exfoliation erosion, and an antiformal saddle curvature where solution pits occur, particularly on higher ridges most distant from the main-stem slot canyon channels. One key goal of this work is to quantify the effect of variable erosion rate on the distribution of process regime as expressed by these characteristic modes of bedrock surface curvature.

Anatomy of La Jolla submarine canyon system; offshore southern California

USGS Publications Warehouse

Paull, C.K.; Caress, D.W.; Lundsten, E.; Gwiazda, R.; Anderson, K.; McGann, M.; Conrad, J.; Edwards, B.; Sumner, E.J.

2013-01-01

An autonomous underwater vehicle (AUV) carrying a multibeam sonar and a chirp profiler was used to map sections of the seafloor within the La Jolla Canyon, offshore southern California, at sub-meter scales. Close-up observations and sampling were conducted during remotely operated vehicle (ROV) dives. Minisparker seismic-reflection profiles from a surface ship help to define the overall geometry of the La Jolla Canyon especially with respect to the pre-canyon host sediments. The floor of the axial channel is covered with unconsolidated sand similar to the sand on the shelf near the canyon head, lacks outcrops of the pre-canyon host strata, has an almost constant slope of 1.0° and is covered with trains of crescent shaped bedforms. The presence of modern plant material entombed within these sands confirms that the axial channel is presently active. The sand on the canyon floor liquefied during vibracore collection and flowed downslope, illustrating that the sediment filling the channel can easily fail even on this gentle slope. Data from the canyon walls help constrain the age of the canyon and extent of incision. Horizontal beds of moderately cohesive fine-grained sediments exposed on the steep canyon walls are consistently less than 1.232 million years old. The lateral continuity of seismic reflectors in minisparker profiles indicate that pre-canyon host strata extend uninterrupted from outside the canyon underneath some terraces within the canyon. Evidence of abandoned channels and point bar-like deposits are noticeably absent on the inside bend of channel meanders and in the subsurface of the terraces. While vibracores from the surface of terraces contain thin (< 10 cm) turbidites, they are inferred to be part of a veneer of recent sediment covering pre-canyon host sediments that underpin the terraces. The combined use of state of the art seafloor mapping and exploration tools provides a uniquely detailed view of the morphology within an active submarine canyon.

Simple and robust resistive dual-axis accelerometer using a liquid metal droplet

NASA Astrophysics Data System (ADS)

Huh, Myoung; Won, Dong-Joon; Kim, Joong Gil; Kim, Joonwon

2017-12-01

This paper presents a novel dual-axis accelerometer that consists of a liquid metal droplet in a cone-shaped channel and an electrode layer with four Nichrome electrodes. The sensor uses the advantages of the liquid metal droplet (i.e., high surface tension, electrical conductivity, high density, and deformability). The cone-shaped channel imposes a restoring force on the liquid metal droplet. We conducted simulation tests to determine the appropriate design specifications of the cone-shaped channel. Surface modifications to the channel enhanced the nonwetting performance of the liquid metal droplet. The performances of the sensor were analyzed by a tilting test. When the acceleration was applied along the axial direction, the device showed 6 kΩ/g of sensitivity and negligible crosstalk between the X- and Y-axes. In a diagonal direction test, the device showed 4 kΩ/g of sensitivity.

Permeation and gating properties of the L-type calcium channel in mouse pancreatic beta cells

PubMed Central

1993-01-01

Ba2+ currents through L-type Ca2+ channels were recorded from cell- attached patches on mouse pancreatic beta cells. In 10 mM Ba2+, single- channel currents were recorded at -70 mV, the beta cell resting membrane potential. This suggests that Ca2+ influx at negative membrane potentials may contribute to the resting intracellular Ca2+ concentration and thus to basal insulin release. Increasing external Ba2+ increased the single-channel current amplitude and shifted the current-voltage relation to more positive potentials. This voltage shift could be modeled by assuming that divalent cations both screen and bind to surface charges located at the channel mouth. The single- channel conductance was related to the bulk Ba2+ concentration by a Langmuir isotherm with a dissociation constant (Kd(gamma)) of 5.5 mM and a maximum single-channel conductance (gamma max) of 22 pS. A closer fit to the data was obtained when the barium concentration at the membrane surface was used (Kd(gamma) = 200 mM and gamma max = 47 pS), which suggests that saturation of the concentration-conductance curve may be due to saturation of the surface Ba2+ concentration. Increasing external Ba2+ also shifted the voltage dependence of ensemble currents to positive potentials, consistent with Ba2+ screening and binding to membrane surface charge associated with gating. Ensemble currents recorded with 10 mM Ca2+ activated at more positive potentials than in 10 mM Ba2+, suggesting that external Ca2+ binds more tightly to membrane surface charge associated with gating. The perforated-patch technique was used to record whole-cell currents flowing through L-type Ca2+ channels. Inward currents in 10 mM Ba2+ had a similar voltage dependence to those recorded at a physiological Ca2+ concentration (2.6 mM). BAY-K 8644 (1 microM) increased the amplitude of the ensemble and whole-cell currents but did not alter their voltage dependence. Our results suggest that the high divalent cation solutions usually used to record single L-type Ca2+ channel activity produce a positive shift in the voltage dependence of activation (approximately 32 mV in 100 mM Ba2+). PMID:7687645

Method of forming a plasma sprayed interconnection layer on an electrode of an electrochemical cell

DOEpatents

Spengler, Charles J.; Folser, George R.; Vora, Shailesh D.; Kuo, Lewis; Richards, Von L.

1995-01-01

A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by plasma spraying doped LaCrO.sub.3 powder, preferably compensated with chromium as Cr.sub.2 O.sub.3 and/or dopant element, preferably by plasma arc spraying; and, (C) heating the doped and compensated LaCrO.sub.3 layer to about 1100.degree. C. to 1300.degree. C. to provide a dense, substantially gas-tight, substantially hydration-free, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the unselected portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell.

Method of forming a plasma sprayed interconnection layer on an electrode of an electrochemical cell

DOEpatents

Spengler, C.J.; Folser, G.R.; Vora, S.D.; Kuo, L.; Richards, V.L.

1995-06-20

A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by plasma spraying doped LaCrO{sub 3} powder, preferably compensated with chromium as Cr{sub 2}O{sub 3} and/or dopant element, preferably by plasma arc spraying; and, (C) heating the doped and compensated LaCrO{sub 3} layer to about 1100 C to 1300 C to provide a dense, substantially gas-tight, substantially hydration-free, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the unselected portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell. 6 figs.

Near interface traps in SiO{sub 2}/4H-SiC metal-oxide-semiconductor field effect transistors monitored by temperature dependent gate current transient measurements

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

Fiorenza, Patrick; La Magna, Antonino; Vivona, Marilena

This letter reports on the impact of gate oxide trapping states on the conduction mechanisms in SiO{sub 2}/4H-SiC metal-oxide-semiconductor field effect transistors (MOSFETs). The phenomena were studied by gate current transient measurements, performed on n-channel MOSFETs operated in “gate-controlled-diode” configuration. The measurements revealed an anomalous non-steady conduction under negative bias (V{sub G} > |20 V|) through the SiO{sub 2}/4H-SiC interface. The phenomenon was explained by the coexistence of a electron variable range hopping and a hole Fowler-Nordheim (FN) tunnelling. A semi-empirical modified FN model with a time-depended electric field is used to estimate the near interface traps in the gate oxide (N{sub trap} ∼ 2 × 10{supmore » 11} cm{sup −2}).« less

H-tailored surface conductivity in narrow band gap In(AsN)

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

Velichko, A. V., E-mail: amalia.patane@nottingham.ac.uk, E-mail: anton.velychko@nottingham.ac.uk; Patanè, A., E-mail: amalia.patane@nottingham.ac.uk, E-mail: anton.velychko@nottingham.ac.uk; Makarovsky, O.

2015-01-12

We show that the n-type conductivity of the narrow band gap In(AsN) alloy can be increased within a thin (∼100 nm) channel below the surface by the controlled incorporation of H-atoms. This channel has a large electron sheet density of ∼10{sup 18 }m{sup −2} and a high electron mobility (μ > 0.1 m{sup 2}V{sup −1}s{sup −1} at low and room temperature). For a fixed dose of impinging H-atoms, its width decreases with the increase in concentration of N-atoms that act as H-traps thus forming N-H donor complexes near the surface.

Dynamic modulation of electronic properties of graphene by localized carbon doping using focused electron beam induced deposition

NASA Astrophysics Data System (ADS)

Kim, S.; Russell, M.; Henry, M.; Kim, S. S.; Naik, R. R.; Voevodin, A. A.; Jang, S. S.; Tsukruk, V. V.; Fedorov, A. G.

2015-09-01

We report on the first demonstration of controllable carbon doping of graphene to engineer local electronic properties of a graphene conduction channel using focused electron beam induced deposition (FEBID). Electrical measurements indicate that an ``n-p-n'' junction on graphene conduction channel is formed by partial carbon deposition near the source and drain metal contacts by low energy (<50 eV) secondary electrons due to inelastic collisions of long range backscattered primary electrons generated from a low dose of high energy (25 keV) electron beam (1 × 1018 e- per cm2). Detailed AFM imaging provides direct evidence of the new mechanism responsible for dynamic evolution of the locally varying graphene doping. The FEBID carbon atoms, which are physisorbed and weakly bound to graphene, diffuse towards the middle of graphene conduction channel due to their surface chemical potential gradient, resulting in negative shift of Dirac voltage. Increasing a primary electron dose to 1 × 1019 e- per cm2 results in a significant increase of carbon deposition, such that it covers the entire graphene conduction channel at high surface density, leading to n-doping of graphene channel. Collectively, these findings establish a unique capability of FEBID technique to dynamically modulate the doping state of graphene, thus enabling a new route to resist-free, ``direct-write'' functional patterning of graphene-based electronic devices with potential for on-demand re-configurability.We report on the first demonstration of controllable carbon doping of graphene to engineer local electronic properties of a graphene conduction channel using focused electron beam induced deposition (FEBID). Electrical measurements indicate that an ``n-p-n'' junction on graphene conduction channel is formed by partial carbon deposition near the source and drain metal contacts by low energy (<50 eV) secondary electrons due to inelastic collisions of long range backscattered primary electrons generated from a low dose of high energy (25 keV) electron beam (1 × 1018 e- per cm2). Detailed AFM imaging provides direct evidence of the new mechanism responsible for dynamic evolution of the locally varying graphene doping. The FEBID carbon atoms, which are physisorbed and weakly bound to graphene, diffuse towards the middle of graphene conduction channel due to their surface chemical potential gradient, resulting in negative shift of Dirac voltage. Increasing a primary electron dose to 1 × 1019 e- per cm2 results in a significant increase of carbon deposition, such that it covers the entire graphene conduction channel at high surface density, leading to n-doping of graphene channel. Collectively, these findings establish a unique capability of FEBID technique to dynamically modulate the doping state of graphene, thus enabling a new route to resist-free, ``direct-write'' functional patterning of graphene-based electronic devices with potential for on-demand re-configurability. Electronic supplementary information (ESI) available: Optimization of a PMMA-mediated wet transfer method of graphene, transfer characteristics of all the channels, raw data of drain-source current measured by sweeping a backgate voltage and an AFM topography image and cross-sectional profiles of Fig. 4 and the corresponding electrical measurement along with an estimation of carbon diffusion coefficient. See DOI: 10.1039/c5nr04063a

Luminescent microporous metal–organic framework with functional Lewis basic sites on the pore surface: Quantifiable evaluation of luminescent sensing mechanisms towards Fe{sup 3+}

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

Jin, Jun-Cheng; Technology Promotion Center of Nano Composite Material of Biomimetic Sensor and Detecting Technology, Preparation and Application, Anhui Provincial Laboratory West Anhui University, Anhui 237012; Guo, Rui-Li

2016-11-15

A systematic study has been conducted on a novel luminescent metal-organic framework, ([Zn(bpyp)(L-OH)]·DMF·2H{sub 2}O){sub n} (1), to explore its sensing mechanisms to Fe{sup 3+}. Structure analyses show that compound 1 exist pyridine N atoms and -OH groups on the pore surface for specific sensing of metal ions via Lewis acid-base interactions. On this consideration, the quenching mechanisms are studied and the processes are controlled by multiple mechanisms in which dynamic and static mechanisms are calculated, achieving the quantification evaluation of the quenching process. This work not only achieves the quantitative evaluation of the luminescence quenching but also provides certain insightsmore » into the quenching process, and the possible mechanisms explored in this work may inspire future research and design of target luminescent metal-organic frameworks (LMOFs) with specific functions. - Graphical abstract: A systematic study has been conducted on a novel luminescent metal-organic framework to explore its sensing mechanisms to Fe{sup 3+}. The quenching mechanisms are studied and the processes are controlled by multiple mechanisms in which dynamic and static mechanisms are calculated, achieving the quantification evaluation of the quenching process. - Highlights: • A novel porous luminescent MOF containing uncoordinated groups in interlayer channels was successfully synthesized. • The compound 1 can exhibit significant luminescent sensitivity to Fe{sup 3+}, which make its good candidate as luminescent sensor. • The corresponding dynamic and static quenching constants are calculated, achieving the quantification evaluation of the quenching process.« less

A single amino acid substitution within the transmembrane domain of the human immunodeficiency virus type 1 Vpu protein renders simian-human immunodeficiency virus (SHIV{sub KU-1bMC33}) susceptible to rimantadine

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

Hout, David R.; Gomez, Lisa M.; Pacyniak, Erik

2006-05-10

Previous studies from our laboratory have shown that the transmembrane domain (TM) of the Vpu protein of human immunodeficiency virus type 1 (HIV-1) contributes to the pathogenesis of SHIV{sub KU-1bMC33} in macaques and that the TM domain of Vpu could be replaced with the M2 protein viroporin from influenza A virus. Recently, we showed that the replacement of the TM domain of Vpu with that of the M2 protein of influenza A virus resulted in a virus (SHIV{sub M2}) that was sensitive to rimantadine [Hout, D.R., Gomez, M.L., Pacyniak, E., Gomez, L.M., Inbody, S.H., Mulcahy, E.R., Culley, N., Pinson, D.M.,more » Powers, M.F., Wong, S.W., Stephens, E.B., 2006. Substitution of the transmembrane domain of Vpu in simian human immunodeficiency virus (SHIV{sub KU-1bMC33}) with that of M2 of influenza A results in a virus that is sensitive to inhibitors of the M2 ion channel and is pathogenic for pig-tailed macaques. Virology 344, 541-558]. Based on previous studies of the M2 protein which have shown that the His-X-X-X-Trp motif within the M2 is essential to the function of the M2 proton channel, we have constructed a novel SHIV in which the alanine at position 19 of the TM domain was replaced with a histidine residue resulting in the motif His-Ile-Leu-Val-Trp. The SHIV{sub VpuA19H} replicated with similar kinetics as the parental SHIV{sub KU-1bMC33} and pulse-chase analysis revealed that the processing of viral proteins was similar to SHIV{sub KU-1bMC33}. This SHIV{sub VpuA19H} virus was found to be more sensitive to the M2 ion channel blocker rimantadine than SHIV{sub M2}. Electron microscopic examination of SHIV{sub VpuA19H}-infected cells treated with rimantadine revealed an accumulation of viral particles at the cell surface and within intracellular vesicles, which was similar to that previously observed to SHIV{sub M2}-infected cells treated with rimantadine. These data indicate that the Vpu protein of HIV-1 can be converted into a rimantadine-sensitive ion channel with the alteration of one amino acid and provide additional evidence that drugs targeting the Vpu TM/ion channel can be effective anti-HIV-1 drugs.« less

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

Ben Smida, Youssef; Marzouki, Riadh; Georges, Samuel

A new sodium cobalt (II) arsenate Na{sub 4}Co{sub 7}(AsO{sub 4}){sub 6} has been synthesized by a solid-state reaction and its crystal structure determined from single crystal X-ray diffraction data. It crystallizes in the monoclinic system, space group C2/m, with a=10.7098(9) Å, b=14.7837(9) Å, c=6.6845(7) Å, and β=105.545(9)°. The structure is described as a three-dimensional framework built up of corner-edge sharing CoO{sub 6}, CoO{sub 4} and AsO{sub 4} polyhedra, with interconnecting channels along [100] in which the Na{sup +} cations are located. The densest ceramics with relative density of 94% was obtained by ball milling and optimization of sintering temperature, andmore » its microstructure characterized by scanning electron microscopy. The electrical properties of the ceramics were studied over a temperature interval from 280 °C to 560 °C using the complex impedance spectroscopy over the range of 13 MHz–5 Hz. The ionic bulk conductivity value of the sample at 360 °C is 2.51 10{sup −5} S cm{sup −1} and the measured activation energy is Ea=1 eV. The sodium migration pathways in the crystal structure were investigated computationally using the bond valence site energy (BVSE) model and classical molecular dynamics (MD) simulations. - Graphical abstract: Correlation between crystal structure, microstructure and ionic conductivity . Display Omitted - Highlights: • A new arsenate Na{sub 4}Co{sub 7}(AsO{sub 4}){sub 6} was prepared by solid state reaction. • Its crystal structure was determined by powder X-ray diffraction. • Na{sup +} ionic conductivity was probed by complex impedance spectroscopy. • Na{sup +} conduction pathways were modeled by bond-valence method and molecular dynamics.« less

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

Choi, Hyun-Sik; Jeon, Sanghun, E-mail: jeonsh@korea.ac.kr

Upon light exposure, an indium-zinc-oxide (IZO) thin-film transistor (TFT) presents higher photoconductivity by several orders of magnitude at the negative gate bias region. Among various device geometrical factors, scaling down the channel length of the photo-transistor results in an anomalous increase in photoconductivity. To probe the origin of this high photoconductivity in short-channel device, we measured transient current, current–voltage, and capacitance–voltage characteristics of IZO–TFTs with various channel lengths and widths before and after illumination. Under the illumination, the equilibrium potential region which lies far from front interface exists only in short-channel devices, forming the un-depleted conducting back channel. This regionmore » plays an important role in carrier transport under the illumination, leading to high photoconductivity in short-channel devices. Photon exposure coupled with gate-modulated band bending for short-channel devices leads to the accumulation of V{sub o}{sup ++} at the front channel and screening negative gate bias, thereby generating high current flow in the un-depleted back-channel region.« less

Sediment transport simulation in an armoured stream

USGS Publications Warehouse

Milhous, Robert T.; Bradley, Jeffrey B.; Loeffler, Cindy L.

1986-01-01

Improved methods of calculating bed material stability and transport must be developed for a gravel bed stream having an armoured surface in order to use the HEC-6 model to examine channel change. Good possibilities exist for use of a two layer model based on the Schoklitsch and the Einstein-Brown transport equations. In Einstein-Brown the D35 of the armour is used for stabilities and the D50 of the bed (sub-surface) is used for transport. Data on the armour and sub-surface size distribution needs to be obtained as part of a bed material study in a gravel bed river; a "shovel" sample is not adequate. The Meyer-Peter, Muller equation should not be applied to a gravel bed stream with an armoured surface to estimate the initiation of transport or for calculation of transport at low effective bed shear stress.

Comparison of structural and electrical properties of Lu{sub 2}O{sub 3} and Lu{sub 2}TiO{sub 5} gate dielectrics for α-InGaZnO thin-film transistors

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

Pan, Tung-Ming, E-mail: tmpan@mail.cgu.edu.tw; Chen, Ching-Hung; Her, Jim-Long

We compared the structural properties and electrical characteristics of high-κ Lu{sub 2}O{sub 3} and Lu{sub 2}TiO{sub 5} gate dielectrics for amorphous indium-gallium-zinc oxide (α-InGaZnO) thin-film transistor (TFT) applications. The Lu{sub 2}O{sub 3} film has a strong Lu{sub 2}O{sub 3} (400) peak in the X-ray diffraction pattern, while the Lu{sub 2}TiO{sub 5} sample shows a relatively weak Lu{sub 2}TiO{sub 5} (102) peak. Atomic force microscopy reveals that the Lu{sub 2}O{sub 3} dielectric exhibits a rougher surface (about three times) than Lu{sub 2}TiO{sub 5} one. In X-ray photoelectron spectroscopy analysis, we found that the intensity of the O 1s peak corresponding tomore » Lu(OH){sub x} for Lu{sub 2}O{sub 3} film was higher than that of Lu{sub 2}TiO{sub 5} film. Furthermore, compared with the Lu{sub 2}O{sub 3} dielectric, the α-InGaZnO TFT using the Lu{sub 2}TiO{sub 5} gate dielectric exhibited a lower threshold voltage (from 0.43 to 0.25 V), a higher I{sub on}/I{sub off} current ratio (from 3.5 × 10{sup 6} to 1.3 × 10{sup 8}), a smaller subthreshold swing (from 276 to 130 mV/decade), and a larger field-effect mobility (from 14.5 to 24.4 cm{sup 2}/V s). These results are probably due to the incorporation of TiO{sub x} into the Lu{sub 2}O{sub 3} film to form a Lu{sub 2}TiO{sub 5} structure featuring a smooth surface, a low moisture absorption, a high dielectric constant, and a low interface state density at the oxide/channel interface. Furthermore, the stability of Lu{sub 2}O{sub 3} and Lu{sub 2}TiO{sub 5} α-InGaZnO TFTs was investigated under positive gate-bias stress (PGBS) and negative gate-bias stress (NGBS). The threshold voltage of the TFT performed under NGBS is more degradation than that under PGBS. This behavior may be attributed to the electron charge trapping at the dielectric–channel interface under PGBS, whereas the oxygen vacancies occurred in the InGaZnO under NGBS.« less

Functional Annotation of Ion Channel Structures by Molecular Simulation.

PubMed

Trick, Jemma L; Chelvaniththilan, Sivapalan; Klesse, Gianni; Aryal, Prafulla; Wallace, E Jayne; Tucker, Stephen J; Sansom, Mark S P

2016-12-06

Ion channels play key roles in cell membranes, and recent advances are yielding an increasing number of structures. However, their functional relevance is often unclear and better tools are required for their functional annotation. In sub-nanometer pores such as ion channels, hydrophobic gating has been shown to promote dewetting to produce a functionally closed (i.e., non-conductive) state. Using the serotonin receptor (5-HT 3 R) structure as an example, we demonstrate the use of molecular dynamics to aid the functional annotation of channel structures via simulation of the behavior of water within the pore. Three increasingly complex simulation analyses are described: water equilibrium densities; single-ion free-energy profiles; and computational electrophysiology. All three approaches correctly predict the 5-HT 3 R crystal structure to represent a functionally closed (i.e., non-conductive) state. We also illustrate the application of water equilibrium density simulations to annotate different conformational states of a glycine receptor. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Solar Powered CO.Sub.2 Conversion

NASA Technical Reports Server (NTRS)

Chen, Bin (Inventor)

2016-01-01

Methods and devices for reducing CO.sub.2 to produce hydrocarbons are disclosed. A device comprises a photoanode capable of splitting H.sub.2O into electrons, protons, and oxygen; an electrochemical cell cathode comprising an electro-catalyst capable of reducing CO.sub.2; H.sub.2O in contact with the surface of the photoanode; CO.sub.2 in contact with the surface of the cathode; and a proton-conducting medium positioned between the photoanode and the cathode. Electrical charges associated with the protons and the electrons move from the photoanode to the cathode, driven in part by a chemical potential difference sufficient to drive the electrochemical reduction of CO.sub.2 at the cathode. A light beam is the sole source of energy used to drive chemical reactions. The photoanode can comprise TiO.sub.2 nanowires or nanotubes, and can also include WO.sub.3 nanowires or nanotubes, quantum dots of CdS or PbS, and Ag or Au nanostructures. The cathode can comprise a conductive gas diffusion layer with nanostructures of an electro-catalyst such as Cu or Co.

Hydrological responses to channelization and the formation of valley plugs and shoals

USGS Publications Warehouse

Pierce, Aaron R.; King, Sammy L.

2017-01-01

Rehabilitation of floodplain systems focuses on restoring interactions between the fluvial system and floodplain, however, there is a paucity of information on the effects of valley plugs and shoals on floodplain hydrological processes. We investigated hydrologic regimes in floodplains at three valley plug sites, two shoal sites, and three unchannelized sites. Valley plug sites had altered surface and sub-surface hydrology relative to unchannelized sites, while only sub-surface hydrology was affected at shoal sites. Some of the changes were unexpected, such as reduced flood duration and flood depth in floodplains associated with valley plugs. Our results emphasize the variability associated with hydrologic processes around valley plugs and our rudimentary understanding of the effects associated with these geomorphic features. Water table levels were lower at valley plug sites compared to unchannelized sites, however, valley plug sites had a greater proportion of days when water table inundation was above mean root collar depth than both shoal and unchannelized sites as a result of lower root collar depths and higher deposition rates. This study has provided evidence that valley plugs can affect both surface and sub-surface hydrology in different ways than previously thought and illustrates the variability in hydrological responses to valley plug formation.

Non-adiabatic dynamics investigation of the radiationless decay mechanism of trans-urocanic acid in the S{sub 2} state

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

Zhao, Li; University of the Chinese Academy of Sciences, Beijing 100049; Zhou, Pan-Wang, E-mail: pwzhou@dicp.ac.cn, E-mail: gjzhao@dicp.ac.cn

2016-07-28

The trans-urocanic acid, a UV chromophore in the epidermis of human skin, was found to exhibit a wavelength dependent isomerization property. The isomerization quantum yield to cis-urocanic is greatest when being excited to the S{sub 1} state, whereas exciting the molecule to the S{sub 2} state causes almost no isomerization. The comparative photochemical behavior of the trans-urocanic on the S{sub 1} and S{sub 2} states continues to be the subject of intense research effort. This study is concerned with the unique photo-behavior of this interesting molecule on the S{sub 2} state. Combining the on-the-fly surface hopping dynamics simulations and staticmore » electronic structure calculations, three decay channels were observed following excitation to the S{sub 2} state. An overwhelming majority of the molecules decay to the S{sub 1} state through a planar or pucker characterized minimum energy conical intersection (MECI), and then decay to the ground state along a relaxation coordinate driven by a pucker deformation of the ring. A very small fraction of molecules decay to the S{sub 1} state by a MECI characterized by a twisting motion around the CC double bond, which continues to drive the molecule to deactivate to the ground state. The latter channel is related with the photoisomerization process, whereas the former one will only generate the original trans-form products. The present work provides a novel S{sub 2} state decay mechanism of this molecule, which offers useful information to explain the wavelength dependent isomerization behavior.« less

Semiconductor to metallic transition in bulk accumulated amorphous indium-gallium-zinc-oxide dual gate thin-film transistor

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

Chun, Minkyu; Chowdhury, Md Delwar Hossain; Jang, Jin, E-mail: jjang@khu.ac.kr

We investigated the effects of top gate voltage (V{sub TG}) and temperature (in the range of 25 to 70 {sup o}C) on dual-gate (DG) back-channel-etched (BCE) amorphous-indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) characteristics. The increment of V{sub TG} from -20V to +20V, decreases the threshold voltage (V{sub TH}) from 19.6V to 3.8V and increases the electron density to 8.8 x 10{sup 18}cm{sup −3}. Temperature dependent field-effect mobility in saturation regime, extracted from bottom gate sweep, show a critical dependency on V{sub TG}. At V{sub TG} of 20V, the mobility decreases from 19.1 to 15.4 cm{sup 2}/V ⋅ s with increasingmore » temperature, showing a metallic conduction. On the other hand, at V{sub TG} of - 20V, the mobility increases from 6.4 to 7.5cm{sup 2}/V ⋅ s with increasing temperature. Since the top gate bias controls the position of Fermi level, the temperature dependent mobility shows metallic conduction when the Fermi level is above the conduction band edge, by applying high positive bias to the top gate.« less

Suppression of vortex-induced vibrations in a flexible cylinder with elastic splitter plates

NASA Astrophysics Data System (ADS)

Huera-Huarte, Francisco

2013-11-01

Suppression of vortex-induced vibrations (VIV) is a topic that has received a lot of attention due to its practical implications in engineering design. Experiments have been conducted in a recirculating free surface water channel, with a working section of dimensions 1 × 1.1 × 2.5 m. A cylinder model made of a spring and a plastic cover was used for the experiments. It was placed horizontally and fully submerged in the water channel's free stream, hanging from two submersible load cells arranged to measure the total drag force on the cylinder. The model had several white points painted on its surface, so its VIV motion was obtained by imaging it with two cameras synchronised with a strobe light. Image processing allowed to obtain the displacements along the length of the cylinder with sub-pixel accuracy. Digital Particle Image Velocimetry (DPIV) was also used to quantify the wake downstream the cylinder. A full set of experiments was made for reference purposes with a plain cylinder without suppressors, and for the same conditions, several passive suppression devices such as elastic splitter plates of different sizes and shapes, were installed on the cylinder. Passive VIV suppression with drag reduction was achieved with some of the configurations tested. Funding provided by the Spanish Ministry of Science through grant DPI2012-37904 is acknowledged.

Combined heat and mass transfer device for improving separation process

DOEpatents

Tran, Thanh Nhon

1999-01-01

A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area.

Combined heat and mass transfer device for improving separation process

DOEpatents

Tran, T.N.

1999-08-24

A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area. 12 figs.

Experimental Study of Two Phase Flow Behavior Past BWR Spacer Grids

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

Ratnayake, Ruwan K.; Hochreiter, L.E.; Ivanov, K.N.

2002-07-01

Performance of best estimate codes used in the nuclear industry can be significantly improved by reducing the empiricism embedded in their constitutive models. Spacer grids have been found to have an important impact on the maximum allowable Critical Heat Flux within the fuel assembly of a nuclear reactor core. Therefore, incorporation of suitable spacer grids models can improve the critical heat flux prediction capability of best estimate codes. Realistic modeling of entrainment behavior of spacer grids requires understanding the different mechanisms that are involved. Since visual information pertaining to the entrainment behavior of spacer grids cannot possibly be obtained frommore » operating nuclear reactors, experiments have to be designed and conducted for this specific purpose. Most of the spacer grid experiments available in literature have been designed in view of obtaining quantitative data for the purpose of developing or modifying empirical formulations for heat transfer, critical heat flux or pressure drop. Very few experiments have been designed to provide fundamental information which can be used to understand spacer grid effects and phenomena involved in two phase flow. Air-water experiments were conducted to obtain visual information on the two-phase flow behavior both upstream and downstream of Boiling Water Reactor (BWR) spacer grids. The test section was designed and constructed using prototypic dimensions such as the channel cross-section, rod diameter and other spacer grid configurations of a typical BWR fuel assembly. The test section models the flow behavior in two adjacent sub channels in the BWR core. A portion of a prototypic BWR spacer grid accounting for two adjacent channels was used with industrial mild steel rods for the purpose of representing the channel internals. Symmetry was preserved in this practice, so that the channel walls could effectively be considered as the channel boundaries. Thin films were established on the rod surfaces by injecting water through a set of perforations at the bottom ends of the rods, ensuring that the flow upstream of the bottom-most spacer grid is predominantly annular. The flow conditions were regulated such that they represent typical BWR operating conditions. Photographs taken during experiments show that the film entrainment increases significantly at the spacer grids, since the points of contact between the rods and the grids result in a peeling off of large portions of the liquid film from the rod surfaces. Decreasing the water flow resulted in eventual drying out, beginning at positions immediately upstream of the spacer grids. (authors)« less

Methanol Formation via Oxygen Insertion Chemistry in Ices

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

Bergner, Jennifer B.; Öberg, Karin I.; Rajappan, Mahesh

We present experimental constraints on the insertion of oxygen atoms into methane to form methanol in astrophysical ice analogs. In gas-phase and theoretical studies this process has previously been demonstrated to have a very low or nonexistent energy barrier, but the energetics and mechanisms have not yet been characterized in the solid state. We use a deuterium UV lamp filtered by a sapphire window to selectively dissociate O{sub 2} within a mixture of O{sub 2}:CH{sub 4} and observe efficient production of CH{sub 3}OH via O({sup 1}D) insertion. CH{sub 3}OH growth curves are fit with a kinetic model, and we observemore » no temperature dependence of the reaction rate constant at temperatures below the oxygen desorption temperature of 25 K. Through an analysis of side products we determine the branching ratio of ice-phase oxygen insertion into CH{sub 4}: ∼65% of insertions lead to CH{sub 3}OH, with the remainder leading instead to H{sub 2}CO formation. There is no evidence for CH{sub 3} or OH radical formation, indicating that the fragmentation is not an important channel and that insertions typically lead to increased chemical complexity. CH{sub 3}OH formation from O{sub 2} and CH{sub 4} diluted in a CO-dominated ice similarly shows no temperature dependence, consistent with expectations that insertion proceeds with a small or nonexistent barrier. Oxygen insertion chemistry in ices should therefore be efficient under low-temperature ISM-like conditions and could provide an important channel to complex organic molecule formation on grain surfaces in cold interstellar regions such as cloud cores and protoplanetary disk midplanes.« less

Effects of Stern layer conductance on electrokinetic energy conversion in nanofluidic channels.

PubMed

Davidson, Christian; Xuan, Xiangchun

2008-03-01

A thermo-electro-hydro-dynamic model is developed to analytically account for the effects of Stern layer conductance on electrokinetic energy conversion in nanofluidic channels. The optimum electrokinetic devices performance is dependent on a figure of merit, in which the Stern layer conductance appears as a nondimensional Dukhin number. Such surface conductance is found to significantly reduce the figure of merit and thus the efficiency and power output. This finding may explain why the recently measured electrokinetic devices performances are far below the theoretical predictions where the effects of Stern layer conductance have been ignored.

Palmitoylation of the β4-Subunit Regulates Surface Expression of Large Conductance Calcium-activated Potassium Channel Splice Variants*

PubMed Central

Chen, Lie; Bi, Danlei; Tian, Lijun; McClafferty, Heather; Steeb, Franziska; Ruth, Peter; Knaus, Hans Guenther; Shipston, Michael J.

2013-01-01

Regulatory β-subunits of large conductance calcium- and voltage-activated potassium (BK) channels play an important role in generating functional diversity and control of cell surface expression of the pore forming α-subunits. However, in contrast to α-subunits, the role of reversible post-translational modification of intracellular residues on β-subunit function is largely unknown. Here we demonstrate that the human β4-subunit is S-acylated (palmitoylated) on a juxtamembrane cysteine residue (Cys-193) in the intracellular C terminus of the regulatory β-subunit. β4-Subunit palmitoylation is important for cell surface expression and endoplasmic reticulum (ER) exit of the β4-subunit alone. Importantly, palmitoylated β4-subunits promote the ER exit and surface expression of the pore-forming α-subunit, whereas β4-subunits that cannot be palmitoylated do not increase ER exit or surface expression of α-subunits. Strikingly, however, this palmitoylation- and β4-dependent enhancement of α-subunit surface expression was only observed in α-subunits that contain a putative trafficking motif (… REVEDEC) at the very C terminus of the α-subunit. Engineering this trafficking motif to other C-terminal α-subunit splice variants results in α-subunits with reduced surface expression that can be rescued by palmitoylated, but not depalmitoylated, β4-subunits. Our data reveal a novel mechanism by which palmitoylated β4-subunit controls surface expression of BK channels through masking of a trafficking motif in the C terminus of the α-subunit. As palmitoylation is dynamic, this mechanism would allow precise control of specific splice variants to the cell surface. Our data provide new insights into how complex interplay between the repertoire of post-transcriptional and post-translational mechanisms controls cell surface expression of BK channels. PMID:23504458

Control of Ambipolar Transport in SnO Thin-Film Transistors by Back-Channel Surface Passivation for High Performance Complementary-like Inverters.

PubMed

Luo, Hao; Liang, Lingyan; Cao, Hongtao; Dai, Mingzhi; Lu, Yicheng; Wang, Mei

2015-08-12

For ultrathin semiconductor channels, the surface and interface nature are vital and often dominate the bulk properties to govern the field-effect behaviors. High-performance thin-film transistors (TFTs) rely on the well-defined interface between the channel and gate dielectric, featuring negligible charge trap states and high-speed carrier transport with minimum carrier scattering characters. The passivation process on the back-channel surface of the bottom-gate TFTs is indispensable for suppressing the surface states and blocking the interactions between the semiconductor channel and the surrounding atmosphere. We report a dielectric layer for passivation of the back-channel surface of 20 nm thick tin monoxide (SnO) TFTs to achieve ambipolar operation and complementary metal oxide semiconductor (CMOS) like logic devices. This chemical passivation reduces the subgap states of the ultrathin channel, which offers an opportunity to facilitate the Fermi level shifting upward upon changing the polarity of the gate voltage. With the advent of n-type inversion along with the pristine p-type conduction, it is now possible to realize ambipolar operation using only one channel layer. The CMOS-like logic inverters based on ambipolar SnO TFTs were also demonstrated. Large inverter voltage gains (>100) in combination with wide noise margins are achieved due to high and balanced electron and hole mobilities. The passivation also improves the long-term stability of the devices. The ability to simultaneously achieve field-effect inversion, electrical stability, and logic function in those devices can open up possibilities for the conventional back-channel surface passivation in the CMOS-like electronics.

Interdigitated photovoltaic power conversion device

DOEpatents

Ward, James Scott; Wanlass, Mark Woodbury; Gessert, Timothy Arthur

1999-01-01

A photovoltaic power conversion device has a top surface adapted to receive impinging radiation. The device includes at least two adjacent, serially connected cells. Each cell includes a semi-insulating substrate and a lateral conductivity layer of a first doped electrical conductivity disposed on the substrate. A base layer is disposed on the lateral conductivity layer and has the same electrical charge conductivity thereof. An emitter layer of a second doped electrical conductivity of opposite electrical charge is disposed on the base layer and forms a p-n junction therebetween. A plurality of spaced channels are formed in the emitter and base layers to expose the lateral conductivity layer at the bottoms thereof. A front contact grid is positioned on the top surface of the emitter layer of each cell. A first current collector is positioned along one outside edge of at least one first cell. A back contact grid is positioned in the channels at the top surface of the device for engagement with the lateral conductivity layer. A second current collector is positioned along at least one outside edge of at least one oppositely disposed second cell. Finally, an interdigitation mechanism is provided for serially connecting the front contact grid of one cell to the back contact grid of an adjacent cell at the top surface of the device.

Interdigitated photovoltaic power conversion device

DOEpatents

Ward, J.S.; Wanlass, M.W.; Gessert, T.A.

1999-04-27

A photovoltaic power conversion device has a top surface adapted to receive impinging radiation. The device includes at least two adjacent, serially connected cells. Each cell includes a semi-insulating substrate and a lateral conductivity layer of a first doped electrical conductivity disposed on the substrate. A base layer is disposed on the lateral conductivity layer and has the same electrical charge conductivity thereof. An emitter layer of a second doped electrical conductivity of opposite electrical charge is disposed on the base layer and forms a p-n junction therebetween. A plurality of spaced channels are formed in the emitter and base layers to expose the lateral conductivity layer at the bottoms thereof. A front contact grid is positioned on the top surface of the emitter layer of each cell. A first current collector is positioned along one outside edge of at least one first cell. A back contact grid is positioned in the channels at the top surface of the device for engagement with the lateral conductivity layer. A second current collector is positioned along at least one outside edge of at least one oppositely disposed second cell. Finally, an interdigitation mechanism is provided for serially connecting the front contact grid of one cell to the back contact grid of an adjacent cell at the top surface of the device. 15 figs.

Analysis of conductive target influence in plasma jet experiments through helium metastable and electric field measurements

NASA Astrophysics Data System (ADS)

Darny, T.; Pouvesle, J.-M.; Puech, V.; Douat, C.; Dozias, S.; Robert, Eric

2017-04-01

The use of cold atmospheric pressure plasma jets for in vivo treatments implies most of the time plasma interaction with conductive targets. The effect of conductive target contact on the discharge behavior is studied here for a grounded metallic target and compared to the free jet configuration. In this work, realized with a plasma gun, we measured helium metastable HeM (23S1) concentration (by laser absorption spectroscopy) and electric field (EF) longitudinal and radial components (by electro-optic probe). Both diagnostics were temporally and spatially resolved. Mechanisms after ionization front impact on the target surface have been identified. The remnant conductive ionized channel behind the ionization front electrically transiently connects the inner high voltage electrode to the target. Due to impedance mismatching between the ionized channel and the target, a secondary ionization front is initiated and rapidly propagates from the target surface to the inner electrode through this ionized channel. This leads to a greatly enhanced HeM production inside the plasma plume and the capillary. Forward and reverse dynamics occur with further multi reflections of more or less damped ionization fronts between the inner electrode and the target as long as the ionized channel is persisting. This phenomenon is very sensitive to parameters such as target distance and ionized channel conductivity affecting electrical coupling between these two and evidenced using positive or negative voltage polarity and nitrogen admixture. In typical operating conditions for the plasma gun used in this work, it has been found that after the secondary ionization front propagation, when the ionized channel is conductive enough, a glow like discharge occurs with strong conduction current. HeM production and all species excitation, especially reactive ones, are then driven by high voltage pulse evolution. The control of forward and reverse dynamics, impacting on the production of the glow like discharge, will be useful for biomedical applications on living tissues.

An extensive investigation of work function modulated trapezoidal recessed channel MOSFET

NASA Astrophysics Data System (ADS)

Lenka, Annada Shankar; Mishra, Sikha; Mishra, Satyaranjan; Bhanja, Urmila; Mishra, Guru Prasad

2017-11-01

The concept of silicon on insulator (SOI) and grooved gate help to lessen the short channel effects (SCEs). Again the work function modulation along the metal gate gives a better drain current due to the uniform electric field along the channel. So all these concepts are combined and used in the proposed MOSFET structure for more improved performance. In this work, trapezoidal recessed channel silicon on insulator (TRC-SOI) MOSFET and work function modulated trapezoidal recessed channel silicon on insulator (WFM-TRC-SOI) MOSFET are compared with DC and RF parameters and later linearity of both the devices is tested. An analytical model is formulated by using a 2-D Poisson's equation and develops a compact equation for threshold voltage using minimum surface potential. In this work we analyze the effect of negative junction depth and the corner angle on various device parameters such as minimum surface potential, sub-threshold slope (SS), drain induced barrier lowering (DIBL) and threshold voltage. The analysis interprets that the switching performance of WFM-TRC-SOI MOSFET surpasses TRC-SOI MOSFET in terms of high Ion/Ioff ratio and also the proposed structure can minimize the short channel effects (SCEs) in RF application. The validity of proposed model has been verified with simulation result performed on Sentaurus TCAD device simulator.

Evaluation of nefazodone-induced cardiotoxicity in human induced pluripotent stem cell-derived cardiomyocytes

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

Lee, Sujeong, E-mail: crystalee@gmail.com; Lee, Hyang-Ae, E-mail: hyangaelee@gmail.com; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 110-799

2016-04-01

The recent establishment of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), which express the major cardiac ion channels and recapitulate spontaneous mechanical and electrical activities, may provide a possible solution for the lack of in vitro human-based cardiotoxicity testing models. Cardiotoxicity induced by the antidepressant nefazodone was previously revealed to cause an acquired QT prolongation by hERG channel blockade. To elucidate the cellular mechanisms underlying the cardiotoxicity of nefazodone beyond hERG, its effects on cardiac action potentials (APs) and ion channels were investigated using hiPSC-CMs with whole-cell patch clamp techniques. In a proof of principle study, we examined the effectsmore » of cardioactive channel blockers on the electrophysiological profile of hiPSC-CMs in advance of the evaluation of nefazodone. Nefazodone dose-dependently prolonged the AP duration at 90% (APD{sub 90}) and 50% (APD{sub 50}) repolarization, reduced the maximum upstroke velocity (dV/dt{sub max}) and induced early after depolarizations. Voltage-clamp studies of hiPSC-CMs revealed that nefazodone inhibited various voltage-gated ion channel currents including I{sub Kr}, I{sub Ks}, I{sub Na}, and I{sub Ca}. Among them, I{sub Kr} and I{sub Na} showed relatively higher sensitivity to nefazodone, consistent with the changes in the AP parameters. In summary, hiPSC-CMs enabled an integrated approach to evaluate the complex interactions of nefazodone with cardiac ion channels. These results suggest that hiPSC-CMs can be an effective model for detecting drug-induced arrhythmogenicity beyond the current standard assay of heterologously expressed hERG K{sup +} channels. - Highlights: • Nefazodone prolonged APD and decreased upstroke velocity of APs in hiPSC-CMs. • Nefazodone inhibited cardiac ion channels, especially I{sub Kr} and I{sub Na}, in hiPSC-CMs. • Nefazodone-induced AP changes are mainly the result of I{sub Kr} and I{sub Na} inhibition. • hiPSC-CMs are sensitive model to validate nefazodone-induced cardiotoxicity. • hiPSC-CMs provide an integrated approach for evaluating mechanism of drug actions.« less

Mechanistic study of atomic layer deposition of Al{sub x}Si{sub y}O thin film via in-situ FTIR spectroscopy

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

Cho, Jea; Kim, Taeseung; Seegmiller, Trevor

2015-09-15

A study of surface reaction mechanism on atomic layer deposition (ALD) of aluminum silicate (Al{sub x}Si{sub y}O) was conducted with trimethylaluminum (TMA) and tetraethoxysilane (TEOS) as precursors and H{sub 2}O as the oxidant. In-situ Fourier transform infrared spectroscopy (FTIR) was utilized to elucidate the underlying surface mechanism that enables the deposition of Al{sub x}Si{sub y}O by ALD. In-situ FTIR study revealed that ineffective hydroxylation of the surface ethoxy (–OCH{sub 2}CH{sub 3}) groups prohibits ALD of SiO{sub 2} by TEOS/H{sub 2}O. In contrast, effective desorption of the surface ethoxy group was observed in TEOS/H{sub 2}O/TMA/H{sub 2}O chemistry. The presence of Al-OH*more » group in vicinity of partially hydroxylated ethoxy (–OCH{sub 2}CH{sub 3}) group was found to propagate disproportionation reaction, which results in ALD of Al{sub x}Si{sub y}O. The maximum thickness from incorporation of SiO{sub x} from alternating exposures of TEOS/H{sub 2}O chemistry in Al{sub x}Si{sub y}O was found to be ∼2 Å, confirmed by high resolution transmission electron microscopy measurements.« less

Computational study of collisions between O({sup 3}P) and NO({sup 2}Π) at temperatures relevant to the hypersonic flight regime

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

Castro-Palacio, Juan Carlos; Nagy, Tibor; Meuwly, Markus, E-mail: m.meuwly@unibas.ch

2014-10-28

Reactions involving N and O atoms dominate the energetics of the reactive air flow around spacecraft when reentering the atmosphere in the hypersonic flight regime. For this reason, the thermal rate coefficients for reactive processes involving O({sup 3}P) and NO({sup 2}Π) are relevant over a wide range of temperatures. For this purpose, a potential energy surface (PES) for the ground state of the NO{sub 2} molecule is constructed based on high-level ab initio calculations. These ab initio energies are represented using the reproducible kernel Hilbert space method and Legendre polynomials. The global PES of NO{sub 2} in the ground statemore » is constructed by smoothly connecting the surfaces of the grids of various channels around the equilibrium NO{sub 2} geometry by a distance-dependent weighting function. The rate coefficients were calculated using Monte Carlo integration. The results indicate that at high temperatures only the lowest A-symmetry PES is relevant. At the highest temperatures investigated (20 000 K), the rate coefficient for the “O1O2+N” channel becomes comparable (to within a factor of around three) to the rate coefficient of the oxygen exchange reaction. A state resolved analysis shows that the smaller the vibrational quantum number of NO in the reactants, the higher the relative translational energy required to open it and conversely with higher vibrational quantum number, less translational energy is required. This is in accordance with Polanyi's rules. However, the oxygen exchange channel (NO2+O1) is accessible at any collision energy. Finally, this work introduces an efficient computational protocol for the investigation of three-atom collisions in general.« less

A novel passive micromixer based on unbalanced splits and collisions of fluid streams

NASA Astrophysics Data System (ADS)

Ansari, Mubashshir Ahmad; Kim, Kwang-Yong; Anwar, Khalid; Kim, Sun Min

2010-05-01

A new passive micromixer based on the concept of unbalanced splits and cross-collisions of fluid streams is designed and fabricated. Experimental and numerical studies have been carried out on the micromixer at Reynolds numbers ranging from 10 to 80. The three-dimensional Navier-Stokes equations have been used to analyze the mixing and flow behavior of the micromixer, which is composed of two sub-channels of unequal widths which repeatedly undergo splitting and recombination. The difference between the mass flow rates in the two sub-channels creates an unbalanced collision of the two fluid streams. Mixing is mainly due to the combined effect of unbalanced collisions of the fluid streams and Dean vortices. The micromixer shows interesting mixing behavior for different ratios of the widths of the two split sub-channels. The sub-channels wherein the major sub-channel is twice as wide as the minor sub-channel exhibit the highest mixing performance at Reynolds numbers larger than 40. The results show the lowest mixing performance for the case of uniform width, where balanced collisions occur.

Controlled calculation of the thermal conductivity for a spinon Fermi surface coupled to a U(1) gauge field

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

Freire, Hermann, E-mail: hfreire@mit.edu

2014-10-15

Motivated by recent transport measurements on the candidate spin-liquid phase of the organic triangular lattice insulator EtMe{sub 3}Sb[Pd(dmit){sub 2}]{sub 2}, we perform a controlled calculation of the thermal conductivity at intermediate temperatures in a spin liquid system where a spinon Fermi surface is coupled to a U(1) gauge field. The present computation builds upon the double expansion approach developed by Mross et al. (2010) for small ϵ=z{sub b}−2 (where z{sub b} is the dynamical critical exponent of the gauge field) and large number of fermionic species N. Using the so-called memory matrix formalism that most crucially does not assume the existencemore » of well-defined quasiparticles at low energies in the system, we calculate the temperature dependence of the thermal conductivity κ of this model due to non-critical Umklapp scattering of the spinons for a finite N and small ϵ. Then we discuss the physical implications of such theoretical result in connection with the experimental data available in the literature.« less

A spectral method determination of the first critical Rayleigh number for a low-Prandtl number crystal melt in a cylindrical container

NASA Technical Reports Server (NTRS)

Dietz, C. M., Jr.; Diplas, P.

1993-01-01

The onset of laminar axisymmetric Rayleigh-Benard convection is investigated for a low-Prandtl number liquid metal in a cylindrical container. All surfaces are considered to be solid and no-slip. Two separate cases are examined for the thermal boundary conditions at the side wall, one with conducting and the other with insulated surface. The governing Boussinesq system is first perturbed and then simplified by introducing a Stokes stream function. Subsequently, a Chebyshev Galerkin spectral model is employed to reduce the simplified system to a system of first-order nonlinear ordinary differential equations. A local stability analysis determines the two values of the first critical Rayleigh number, Ra(sub cl), for the insulated and conducting side walls. As expected, the conducting Ra(sub cl) value of 2882.5 obtained from the present approach exceeded the corresponding insulated Ra(sub cl) value of 2331.6. For the insulated case, an earlier study using a different numerical approach suggests that Ra(sub cl) = 2261.9, while an experimental study measured Ra(sub cl) = 2700.

Down-regulation of voltage-dependent sodium channels initiated by sodium influx in developing neurons

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

Dargent, B.; Couraud, F.

1990-08-01

To address the issue of whether regulatory feedback exists between the electrical activity of a neuron and ion-channel density, the authors investigated the effect of Na{sup +}-channel activators (scorpion {alpha} toxin, batrachotoxin, and veratridine) on the density of Na{sup +} channels in fetal rat brain neurons in vitro. A partial but rapid (t{sub 1/2}, 15 min) disappearance of surface Na{sup +} channels was observed as measured by a decrease in the specific binding of ({sup 3}H)saxitoxin and {sup 125}I-labeled scorpion {beta} toxin and a decrease in specific {sup 22}Na{sup +} uptake. Moreover, the increase in the number of Na{sup +}more » channels that normally occurs during neuronal maturation in vitro was inhibited by chronic channel activator treatment. The induced disappearance of Na{sup +} channels was abolished by tetrodotoxin, was found to be dependent on the external Na{sup +} concentration, and was prevented when either choline (a nonpermeant ion) or Li{sup +} (a permeant ion) was substituted for Na{sup +}. Amphotericin B, a Na{sup +} ionophore, and monensin were able to mimick the effect of Na{sup +}-channel activators, while a KCl depolarization failed to do this. This feedback regulation seems to be a neuronal property since Na{sup +}-channel density in cultured astrocytes was not affected by channel activator treatment or by amphotericin B. The present evidence suggests that an increase in intracellular Na{sup +} concentration, whether elicited by Na{sup +}-channel activators or mediated by a Na{sup +} ionophore, can induce a decrease in surface Na{sup +} channels and therefore is involved in down-regulation of Na{sup +}-channel density in fetal rat brain neurons in vitro.« less

High-efficient photo-electron transport channel in SiC constructed by depositing cocatalysts selectively on specific surface sites for visible-light H{sub 2} production

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

Wang, Da; Peng, Yuan; Wang, Qi

2016-04-18

Control cocatalyst location on a metal-free semiconductor to promote surface charge transfer for decreasing the electron-hole recombination is crucial for enhancing solar energy conversion. Based on the findings that some metals have an affinity for bonding with the specific atoms of polar semiconductors at a heterostructure interface, we herein control Pt deposition selectively on the Si sites of a micro-SiC photocatalyst surface via in-situ photo-depositing. The Pt-Si bond forming on the interface constructs an excellent channel, which is responsible for accelerating photo-electron transfer from SiC to Pt and then reducing water under visible-light. The hydrogen production is enhanced by twomore » orders of magnitude higher than that of bare SiC, and 2.5 times higher than that of random-depositing nano-Pt with the same loading amount.« less

Fabrication of Super-Hydrophobic Microchannels via Strain-Recovery Deformations of Polystyrene and Oxygen Reactive Ion Etch.

PubMed

Chakraborty, Anirban; Xiang, Mingming; Luo, Cheng

2013-08-19

In this article, we report a simple approach to generate micropillars (whose top portions are covered by sub-micron wrinkles) on the inner surfaces of polystyrene (PS) microchannels, as well as on the top surface of the PS substrate, based on strain-recovery deformations of the PS and oxygen reactive ion etch (ORIE). Using this approach, two types of micropillar-covered microchannels are fabricated. Their widths range from 118 μm to 132 μm, depths vary from 40 μm to 44 μm, and the inclined angles of their sidewalls are from 53° to 64°. The micropillars enable these microchannels to have super-hydrophobic properties. The contact angles observed on the channel-structured surfaces are above 162°, and the tilt angles to make water drops roll off from these channel-structured substrates can be as small as 1°.

Dicamptodon tenebrosus larvae within hyporheic zones of intermittent streams in California

Treesearch

David Feral; Michael A. Camann; Hartwell H. Welsh Jr.

2005-01-01

Lotic ecosystems are increasingly viewed as having three interactive spatial compartments, i.e., channel sediments, the hyporheic zone, and flood plains or riparian areas (Cummins et al. 1983; Ward 1989). The hyporheic zone is the sub-benthic habitat of interstitial spaces between substrate particles in the stream bed, and is the transition zone between surface flow...

Mass and Charge Transport in Electronically Conductive Polymers

DTIC Science & Technology

1990-08-02

This method is based on coating an electrode surface with an insulating nitrile butadiene rubber ( NBR ). The electrolyte for polymerization (LiCIO4...in acetonitrile) etches channels through the NBR ; pyrrole is then polymerized in these channels. After polymerization the NBR is extracted away with

Material from the Internal Surface of Squid Axon Exhibits Excess Noise

PubMed Central

Fishman, Harvey M.

1981-01-01

A fluid material from a squid (Loligo pealei) axon was isolated by mechanical application of two types of microcapillary (1-3-μm Diam) to the internal surface of intact and cut-axon preparations. Current noise in the isolated material exceeded thermal levels and power spectra were 1/f in form in the frequency range 1.25-500 Hz with voltage-dependent intensities that were unrelated to specific ion channels. Whether conduction in this material is a significant source of excess noise during axon conduction remains to be determined. Nevertheless, a source of excess noise external to or within an ion channel may not be properly represented solely as an additive term to the spectrum of ion channel noise; a deconvolution of these spectral components may be required for modeling purposes. PMID:6266542

Reconstruction of Cell Surface Densities of Ion Pumps, Exchangers, and Channels from mRNA Expression, Conductance Kinetics, Whole-Cell Calcium, and Current-Clamp Voltage Recordings, with an Application to Human Uterine Smooth Muscle Cells

PubMed Central

Atia, Jolene; McCloskey, Conor; Shmygol, Anatoly S.; Rand, David A.; van den Berg, Hugo A.; Blanks, Andrew M.

2016-01-01

Uterine smooth muscle cells remain quiescent throughout most of gestation, only generating spontaneous action potentials immediately prior to, and during, labor. This study presents a method that combines transcriptomics with biophysical recordings to characterise the conductance repertoire of these cells, the ‘conductance repertoire’ being the total complement of ion channels and transporters expressed by an electrically active cell. Transcriptomic analysis provides a set of potential electrogenic entities, of which the conductance repertoire is a subset. Each entity within the conductance repertoire was modeled independently and its gating parameter values were fixed using the available biophysical data. The only remaining free parameters were the surface densities for each entity. We characterise the space of combinations of surface densities (density vectors) consistent with experimentally observed membrane potential and calcium waveforms. This yields insights on the functional redundancy of the system as well as its behavioral versatility. Our approach couples high-throughput transcriptomic data with physiological behaviors in health and disease, and provides a formal method to link genotype to phenotype in excitable systems. We accurately predict current densities and chart functional redundancy. For example, we find that to evoke the observed voltage waveform, the BK channel is functionally redundant whereas hERG is essential. Furthermore, our analysis suggests that activation of calcium-activated chloride conductances by intracellular calcium release is the key factor underlying spontaneous depolarisations. PMID:27105427

Photofragment Coincidence Imaging of Small I- (H2O)n Clusters Excited to the Charge-transfer-to-solvent State

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

Neumark, D. E. Szpunar, K. E. Kautzman, A. E. Faulhaber, and D. M.; Kautzman, K.E.; Faulhaber, A.E.

2005-11-09

The photodissociation dynamics of small I{sup -}(H{sub 2}O){sub n} (n = 2-5) clusters excited to their charge-transfer-to-solvent (CTTS) states have been studied using photofragment coincidence imaging. Upon excitation to the CTTS state, two photodissociation channels were observed. The major channel ({approx}90%) is a 2-body process forming neutral I + (H{sub 2}O){sub n} photofragments, and the minor channel is a 3-body process forming I + (H{sub 2}O){sub n-1} + H{sub 2}O fragments. Both process display translational energy (P(E{sub T})) distributions peaking at E{sub T} = 0 with little available energy partitioned into translation. Clusters excited to the detachment continuum rather thanmore » to the CTTS state display the same two channels with similar P(E{sub T}) distributions. The observation of similar P(E{sub T}) distributions from the two sets of experiments suggests that in the CTTS experiments, I atom loss occurs after autodetachment of the excited (I(H{sub 2}O){sub n}{sup -})* cluster, or, less probably, that the presence of the excess electron has little effect on the departing I atom.« less

Dopant selection for control of charge carrier density and mobility in amorphous indium oxide thin-film transistors: Comparison between Si- and W-dopants

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

Mitoma, Nobuhiko, E-mail: MITOMA.Nobuhiko@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Kizu, Takio; Lin, Meng-Fang

The dependence of oxygen vacancy suppression on dopant species in amorphous indium oxide (a-InO{sub x}) thin film transistors (TFTs) is reported. In a-InO{sub x} TFTs incorporating equivalent atom densities of Si- and W-dopants, absorption of oxygen in the host a-InO{sub x} matrix was found to depend on difference of Gibbs free energy of the dopants for oxidation. For fully oxidized films, the extracted channel conductivity was higher in the a-InO{sub x} TFTs containing dopants of small ionic radius. This can be explained by a reduction in the ionic scattering cross sectional area caused by charge screening effects.

Low-frequency noise in AlN/AlGaN/GaN metal-insulator-semiconductor devices: A comparison with Schottky devices

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

Le, Son Phuong; Nguyen, Tuan Quy; Shih, Hong-An

2014-08-07

We have systematically investigated low-frequency noise (LFN) in AlN/AlGaN/GaN metal-insulator-semiconductor (MIS) devices, where the AlN gate insulator layer was sputtering-deposited on the AlGaN surface, in comparison with LFN in AlGaN/GaN Schottky devices. By measuring LFN in ungated two-terminal devices and heterojunction field-effect transistors (HFETs), we extracted LFN characteristics in the intrinsic gated region of the HFETs. Although there is a bias regime of the Schottky-HFETs in which LFN is dominated by the gate leakage current, LFN in the MIS-HFETs is always dominated by only the channel current. Analyzing the channel-current-dominated LFN, we obtained Hooge parameters α for the gated regionmore » as a function of the sheet electron concentration n{sub s} under the gate. In a regime of small n{sub s}, both the MIS- and Schottky-HFETs exhibit α∝n{sub s}{sup −1}. On the other hand, in a middle n{sub s} regime of the MIS-HFETs, α decreases rapidly like n{sub s}{sup −ξ} with ξ ∼ 2-3, which is not observed for the Schottky-HFETs. In addition, we observe strong increase in α∝n{sub s}{sup 3} in a large n{sub s} regime for both the MIS- and Schottky-HFETs.« less

Experimental study of electrostatic discharges of spacecraft solar array protective coatings under radiation

NASA Astrophysics Data System (ADS)

Khasanshin, Rashid; Novikov, Lev

Action of charged particles on low-conductive dielectrics causes formation of areas with a high charge density inside; their fields may give rise to development of electrostatic discharge between the charged area and the surface of the dielectric. Discharge channels are growing due to breakdown of dielectric and formation of a conducting phase. Generation of the channels is a complex stochastic process accompanied by such physical and chemical processes as ionization, gas formation, heating, and so on, which cause formation of conducting phase in a glass. That is why no quantitative theory describing formation of conductive channels has been formulated yet. The study of electrostatic discharges in dielectrics under radiation is essential both from a scientific point of view and for the solution of applied problems. In particular, interaction of a spacecraft with ambient plasma causes accumulation of electric charges on its surface producing, as a consequence, electric potential between the spacecraft surface and the plasma. For example, potentials on the surface of satellites operating on a geostationary orbit reach up to 20 kV. Elec-trostatic discharges caused by such potentials can produce not only the considerable electromag-netic interference, but also lead to the destruction of hardware components and structural ele-ments. Electrostatic charging due to electrons from the Earth’s radiation belts causes degradation of solar arrays as a result of surface and internal electrostatic discharges. In the work, surface of K-208 spacecraft solar array protective coatings irradiated by 20 and 40 keV electrons and protons has studied using by AFM methods. Traces of electrostatic dis-charges at different radiation flux densities were analyzed.

Bipolar plate/diffuser for a proton exchange membrane fuel cell

DOEpatents

Besmann, Theodore M.; Burchell, Timothy D.

2001-01-01

A combination bipolar plate/diffuser fuel cell component includes an electrically conducting solid material having: a porous region having a porous surface; and a hermetic region, the hermetic region defining at least a portion of at least one coolant channel, the porous region defining at least a portion of at least one reactant channel, the porous region defining a flow field medium for diffusing the reactant to the porous surface.

Bipolar plate/diffuser for a proton exchange membrane fuel cell

DOEpatents

Besmann, Theodore M.; Burchell, Timothy D.

2000-01-01

A combination bipolar plate/diffuser fuel cell component includes an electrically conducting solid material having: a porous region having a porous surface; and a hermetic region, the hermetic region defining at least a portion of at least one coolant channel, the porous region defining at least a portion of at least one reactant channel, the porous region defining a flow field medium for diffusing the reactant to the porous surface.

Atmospheric and soil-gas monitoring for surface leakage at the San Juan Basin CO{sub 2} pilot test site at Pump Canyon New Mexico, using perfluorocarbon tracers, CO{sub 2} soil-gas flux and soil-gas hydrocarbons

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

Wells, Arthur W; Diehl, J Rodney; Strazisar, Brian R

2012-05-01

Near-surface monitoring and subsurface characterization activities were undertaken in collaboration with the Southwest Regional Carbon Sequestration Partnership on their San Juan Basin coal-bed methane pilot test site near Navajo City, New Mexico. Nearly 18,407 short tons (1.670 × 107 kg) of CO{sub 2} were injected into 3 seams of the Fruitland coal between July 2008 and April 2009. Between September 18 and October 30, 2008, two additions of approximately 20 L each of perfluorocarbon (PFC) tracers were mixed with the CO{sub 2} at the injection wellhead. PFC tracers in soil-gas and in the atmosphere were monitored over a period ofmore » 2 years using a rectangular array of permanent installations. Additional monitors were placed near existing well bores and at other locations of potential leakage identified during the pre-injection site survey. Monitoring was conducted using sorbent containing tubes to collect any released PFC tracer from soil-gas or the atmosphere. Near-surface monitoring activities also included CO{sub 2} surface flux and carbon isotopes, soil-gas hydrocarbon levels, and electrical conductivity in the soil. The value of the PFC tracers was demonstrated when a significant leakage event was detected near an offset production well. Subsurface characterization activities, including 3D seismic interpretation and attribute analysis, were conducted to evaluate reservoir integrity and the potential that leakage of injected CO{sub 2} might occur. Leakage from the injection reservoir was not detected. PFC tracers made breakthroughs at 2 of 3 offset wells which were not otherwise directly observable in produced gases containing 20–30% CO{sub 2}. These results have aided reservoir geophysical and simulation investigations to track the underground movement of CO{sub 2}. 3D seismic analysis provided a possible interpretation for the order of appearance of tracers at production wells.« less

Regulation of Cl^- Channels in Normal and Cystic Fibrosis Airway Epithelial Cells by Extracellular ATP

NASA Astrophysics Data System (ADS)

Stutts, M. J.; Chinet, T. C.; Mason, S. J.; Fullton, J. M.; Clarke, L. L.; Boucher, R. C.

1992-03-01

The rate of Cl^- secretion by human airway epithelium is determined, in part, by apical cell membrane Cl^- conductance. In cystic fibrosis airway epithelia, defective regulation of Cl^- conductance decreases the capability to secrete Cl^-. Here we report that extracytosolic ATP in the luminal bath of cultured human airway epithelia increased transepithelial Cl^- secretion and apical membrane Cl^- permeability. Single-channel studies in excised membrane patches revealed that ATP increased the open probability of outward rectifying Cl^- channels. The latter effect occurs through a receptor mechanism that requires no identified soluble second messengers and is insensitive to probes of G protein function. These results demonstrate a mode of regulation of anion channels by binding ATP at the extracellular surface. Regulation of Cl^- conductance by external ATP is preserved in cystic fibrosis airway epithelia.

Vacuum field-effect transistor with a deep submicron channel fabricated by electro-forming

NASA Astrophysics Data System (ADS)

Wang, Xiao; Shen, Zhihua; Wu, Shengli; Zhang, Jintao

2017-06-01

Vacuum field-effect transistors (VFETs) with channel lengths down to 500 nm (i.e., the deep submicron scale) were fabricated with the mature technology of the surface conduction electron emitter fabrication process in our former experiments. The vacuum channel of this new VFET was generated by using the electro-forming process. During electro-forming, the joule heat cracks the conductive film and then generates the submicron scale gap that serves as the vacuum channel. The gap separates the conductive film into two plane-to-plane electrodes, which serve as a source (cathode) electrode and a drain (anode) electrode of the VFET, respectively. Experimental results reveal that the fabricated device demonstrates a clear triode behavior of the gate modulation. Fowler-Nordheim theory was used to analyze the electron emission mechanism and operating principle of the device.

Spatial variation of dissolved organic matter composition and characteristics in an urbanized watershed

NASA Astrophysics Data System (ADS)

Hsieh, C.; Li, M.

2013-12-01

Dissolved organic matter (DOM) is a chemically complex mixture of organic polymers that plays an important role in river ecosystems and originates from various sources. Some DOMs are autochthonous originating through phytoplankton and microbial activity in situ. On the other hand, some DOMs are allochthonous which are transported to river from the surrounding watershed by natural or anthropogenic activities. The studies of DOM in river are usually conducted at the watershed scale; however, factors of local spatial scale affecting DOM composition also need to take into consideration for the study of DOM in an urbanized watershed. Through increasing urbanization, changes in a watershed occur not only in land use patterns but also in river channel characteristics. The objective of this study is to investigate effects of different river channel characteristics and patterns on changes in DOM source and composition. In this study, we chose three tributaries of Tamsui river in Taiwan according to its land use pattern and river channel characteristics. At each sub-basin, river water samples were sampled from three study sites. River water DOM was measured by using optical measurements of UV absorption and fluorescence spectroscopy. Water samples were also collected for laboratory analysis of different water quality parameters. From our study sites, they are from three sub-basins which are in the similar physical environments but with different river channel types: the highly channelized Keelung river, the less channelized Xindian river, and less channelized Dahan river with five human-made wetlands. From the upstream to the urbanized downstream, composition of DOM showed variation among different sampled sites. In all three sub-basins, the trends of 5-day biochemical oxygen demand (BOD5) and suspended solids (SS) are also different. The changes in DOM source and composition as well as different water quality parmaters occur at the local spatial-scale depended on their river channel characters in urbanized watersheds. Based on our result, it indicates river channel characters which can have effects on biogeochemical processes of DOM. This knowledge can help us in understanding biogeochemical processes controlled or manipulated by anthropogenic activities at different spatial scales, and help us to make an integrative river health management in a watershed.

Electrochemical properties of polycrystalline TiO/sub 2/ electrodes prepared by anodic oxidation

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

Nogami, G.; Ogawa, V.; Nishiyama, Y.

1988-12-01

Polycrystalline TiO/sub 2/ electrodes were characterized by electroluminescence and capacitance-voltage measurements. The intensity of electroluminescence in a polycrystalline TiO/sub 2/ was about two orders of magnitude larger than that in a single crystalline TiO/sub 2/. Due to the intensive light emission which could be seen with the naked eye, a spectroscopic analysis by using a monochromator was possible. The emission spectrum showed a broad band peaked at 570 nm, which was assigned to a radiation recombination of a hole injected from the electrolyte with an electron on the surface state, the distribution of which was estimated from the C-V measurements.more » Mott-Schottky plots for a polycrystalline TiO/sub 2/ showed little frequency dispersion. Cole-Cole plots could be fitted by two semicircles. Through the analysis of relaxation times, charging and discharging process at the electrode surface could be clarified. The analysis of the impedance data have revealed that the surface state is distributed from the conduction bandage to the midgap in the forbidden gap. The surface-state density falls with energy from the conduction band. It has been concluded that the dynamic electron distribution of the surface states, which is determined by the competitive charge transfer process of electrons and holes injected from the electrolyte and from the semiconductor determines the luminescence characteristics of this material.« less

Carbon mediated reduction of silicon dioxide and growth of copper silicide particles in uniform width channels

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

Pizzocchero, Filippo; Bøggild, Peter; Booth, Timothy J.

We show that surface arc-discharge deposited carbon plays a critical intermediary role in the breakdown of thermally grown oxide diffusion barriers of 90 nm on a silicon wafer at 1035 °C in an Ar/H{sub 2} atmosphere, resulting in the formation of epitaxial copper silicide particles in ≈ 10 μm wide channels, which are aligned with the intersections of the (100) surface of the wafer and the (110) planes on an oxidized silicon wafer, as well as endotaxial copper silicide nanoparticles within the wafer bulk. We apply energy dispersive x-ray spectroscopy, in combination with scanning and transmission electron microscopy of focusedmore » ion beam fabricated lammelas and trenches in the structure to elucidate the process of their formation.« less

RBS-channeling study of radiation damage in Ar{sup +} implanted CuInSe{sub 2} crystals

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

Yakushev, Michael V., E-mail: michael.yakushev@strath.ac.uk; Ural Federal University, Ekaterinburg 620002; Institute of Solid State Chemistry of the Urals Branch of RAS, Ekaterinburg 620990

2016-09-15

Chalcopyrite solar cells are reported to have a high tolerance to irradiation by high energy electrons or ions, but the origin of this is not well understood. This work studies the evolution of damage in Ar{sup +}-bombarded CuInSe{sub 2} single crystal using Rutherford backscattering/channeling analysis. Ar{sup +} ions of 30 keV were implanted with doses in the range from 10{sup 12} to 3 × 10{sup 16} cm{sup −2} at room temperature. Implantation was found to create two layers of damage: (1) on the surface, caused by preferential sputtering of Se and Cu atoms; (2) at the layer of implanted Ar, possibly consisting of stackingmore » faults and dislocation loops. The damage in the second layer was estimated to be less than 2% of the theoretical prediction suggesting efficient healing of primary implantation defects.« less

An electrodynamic description of lightning return strokes and dart leaders: Guided wave propagation along conducting cylindrical channels

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

Borovsky, J.E.

1995-02-20

The return-stroke breakdown pulse and the dart leader are treated as electric waves guided by conducting lightning channels; such waves are launched when current is injected into a conducting channel (producing the dart leader) or when charge on a channel begins to drain to Earth (producing the return stroke). The guided waves are self-consistent solutions to the full set of Maxwell`s equations, obeying the physical boundary conditions for cylindrical channels. These waves are shown (1) to move with velocities substantially slower than c along the channel, (2) to push current inside the lightning channel, (3) to move charge and voltagemore » along the channel, and (4) to transport energy along and into the channel via Poynting flux. The velocity of a guided wave is a function of only three parameters: the channel radius r{sub ch}, the channel temperature T, and the risetime {triangle}t of the wave front. These velocities are found to fall in the range of velocities of return strokes and of dart leaders. The dart leader and the return stroke are caused by the same type of guided electromagnetic waves: the difference in velocity is owed mostly to the difference in channel temperature. In the case of the dart leader the waves deliver Poynting flux along the outside of the channel down from a thundercloud generator to the downward-propagating wave front. At the wave front of the dart leader the delivered energy goes into heating the channel and into storage in the form of E{sup 2}/8{pi} around the newly charged channel. In the case of the return stroke the Poynting flux is localized to the vicinity of the wave front where stored energy E{sup 2}/8{pi} is delivered radially inward onto the channel to heat the channel in the propagating front. The net result of a dart leader and return stroke is that charge is moved from the cloud to the ground and that energy is moved from the cloud onto the channel. 123 refs., 11 figs., 5 tabs.« less

Cycle time improvement for plastic injection moulding process by sub groove modification in conformal cooling channel

NASA Astrophysics Data System (ADS)

Kamarudin, K.; Wahab, M. S.; Batcha, M. F. M.; Shayfull, Z.; Raus, A. A.; Ahmed, Aqeel

2017-09-01

Mould designers have been struggling for the improvement of the cooling system performance, despite the fact that the cooling system complexity is physically limited by the fabrication capability of the conventional tooling methods. However, the growth of Solid Free Form Technology (SFF) allow the mould designer to develop more than just a regular conformal cooling channel. Numerous researchers demonstrate that conformal cooling channel was tremendously given significant result in the improvement of productivity and quality in the plastic injection moulding process. This paper presents the research work that applies the passive enhancement method in square shape cooling channel to enhance the efficiency of cooling performance by adding the sub groove to the cooling channel itself. Previous design that uses square shape cooling channel was improved by adding various numbers of sub groove to meet the best sub groove design that able reduced the cooling time. The effect of sub groove design on cooling time was investigated by Autodesk Modlflow Insight software. The simulation results showed that the various sub groove designs give different values to ejection time. The Design 7 showed the lowest value of ejection time with 24.3% increment. The addition of sub groove significantly increased a coolant velocity and a rate of heat transfer from molten plastic to coolant.

Hyper-resistivity and electron thermal conductivity due to destroyed magnetic surfaces in axisymmetric plasma equilibria

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

Weening, R. H.

2012-06-15

In order to model the effects of small-scale current-driven magnetic fluctuations in a mean-field theoretical description of a large-scale plasma magnetic field B(x,t), a space and time dependent hyper-resistivity {Lambda}(x,t) can be incorporated into the Ohm's law for the parallel electric field E Dot-Operator B. Using Boozer coordinates, a theoretical method is presented that allows for a determination of the hyper-resistivity {Lambda}({psi}) functional dependence on the toroidal magnetic flux {psi} for arbitrary experimental steady-state Grad-Shafranov axisymmetric plasma equilibria, if values are given for the parallel plasma resistivity {eta}({psi}) and the local distribution of any auxiliary plasma current. Heat transport inmore » regions of plasma magnetic surfaces destroyed by resistive tearing modes can then be modeled by an electron thermal conductivity k{sub e}({psi})=({epsilon}{sub 0}{sup 2}m{sub e}/e{sup 2}){Lambda}({psi}), where e and m{sub e} are the electron charge and mass, respectively, while {epsilon}{sub 0} is the permittivity of free space. An important result obtained for axisymmetric plasma equilibria is that the {psi}{psi}-component of the metric tensor of Boozer coordinates is given by the relation g{sup {psi}{psi}}({psi}){identical_to}{nabla}{psi} Dot-Operator {nabla}{psi}=[{mu}{sub 0}G({psi})][{mu}{sub 0}I({psi})]/{iota}({psi}), with {mu}{sub 0} the permeability of free space, G({psi}) the poloidal current outside a magnetic surface, I({psi}) the toroidal current inside a magnetic surface, and {iota}({psi}) the rotational transform.« less

Crystal structure of the true Nasicon: Na/sub 3/Zr/sub 2/Si/sub 2/PO/sub 12/

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

Boilot, J.P.; Collin, G.; Colomban, P.

For the first time, the results of single crystal determination of the true Nasicon are given. The structure refinement yielded the following composition: Na/sub 3.09(8)/Zr/sub 2.01(1)/P/sub 0.91/Si/sub 2.09/O/sub 12/. Evidence of the total occupancy of the Zr octahedron is found, displaying that only the Si/P non-stoichiometry mechanism is present in the Nasicon crystal. For the two temperatures which have been investigated (R.T. and 623K), the structures are very close to that of the Nasicon analog: Na/sub 3/Sc/sub 2/P/sub 3/O/sub 12/. However the Si/P substitution prevents the sodium long range ordering even in the monoclinic low temperature phase and therefore themore » cross over to the rhombohedral symmetry only involves very small atomic displacements. For both structures, a new sodium position (mid-Na) is displayed in the conduction channel, intermediate between the usual Na(1) and Na(2) sites.« less

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

Mineo, H.; Kuo, J. L.; Niu, Y. L.

The results of application of the quantum-mechanical adiabatic theory to vibrational predissociation (VPD) of water dimers, (H{sub 2}O){sub 2} and (D{sub 2}O){sub 2}, are presented. We consider the VPD processes including the totally symmetric OH mode of the dimer and the bending mode of the fragment. The VPD in the adiabatic representation is induced by breakdown of the vibrational adiabatic approximation, and two types of nonadiabatic coupling matrix elements are involved: one provides the VPD induced by the low-frequency dissociation mode and the other provides the VPD through channel interactions induced by the low-frequency modes. The VPD rate constants weremore » calculated using the Fermi golden rule expression. A closed form for the nonadiabatic transition matrix element between the discrete and continuum states was derived in the Morse potential model. All of the parameters used were obtained from the potential surfaces of the water dimers, which were calculated by the density functional theory procedures. The VPD rate constants for the two processes were calculated in the non-Condon scheme beyond the so-called Condon approximation. The channel interactions in and between the initial and final states were taken into account, and those are found to increase the VPD rates by 3(1) orders of magnitude for the VPD processes in (H{sub 2}O){sub 2} ((D{sub 2}O){sub 2}). The fraction of the bending-excited donor fragments is larger than that of the bending-excited acceptor fragments. The results obtained by quantum-mechanical approach are compared with both experimental and quasi-classical trajectory calculation results.« less

Differential state-dependent modification of rat Na{sub v}1.6 sodium channels expressed in human embryonic kidney (HEK293) cells by the pyrethroid insecticides tefluthrin and deltamethrin

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

He, Bingjun; Soderlund, David M., E-mail: dms6@cornell.edu

2011-12-15

We expressed rat Na{sub v}1.6 sodium channels in combination with the rat {beta}1 and {beta}2 auxiliary subunits in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on expressed sodium currents using the whole-cell patch clamp technique. Both pyrethroids produced concentration-dependent, resting modification of Na{sub v}1.6 channels, prolonging the kinetics of channel inactivation and deactivation to produce persistent 'late' currents during depolarization and tail currents following repolarization. Both pyrethroids also produced concentration dependent hyperpolarizing shifts in the voltage dependence of channel activation and steady-state inactivation. Maximal shifts in activation, determined from the voltagemore » dependence of the pyrethroid-induced late and tail currents, were {approx} 25 mV for tefluthrin and {approx} 20 mV for deltamethrin. The highest attainable concentrations of these compounds also caused shifts of {approx} 5-10 mV in the voltage dependence of steady-state inactivation. In addition to their effects on the voltage dependence of inactivation, both compounds caused concentration-dependent increases in the fraction of sodium current that was resistant to inactivation following strong depolarizing prepulses. We assessed the use-dependent effects of tefluthrin and deltamethrin on Na{sub v}1.6 channels by determining the effect of trains of 1 to 100 5-ms depolarizing prepulses at frequencies of 20 or 66.7 Hz on the extent of channel modification. Repetitive depolarization at either frequency increased modification by deltamethrin by {approx} 2.3-fold but had no effect on modification by tefluthrin. Tefluthrin and deltamethrin were equally potent as modifiers of Na{sub v}1.6 channels in HEK293 cells using the conditions producing maximal modification as the basis for comparison. These findings show that the actions of tefluthrin and deltamethrin of Na{sub v}1.6 channels in HEK293 cells differ from the effects of these compounds on Na{sub v}1.6 channels in Xenopus oocytes and more closely reflect the actions of pyrethroids on channels in their native neuronal environment. -- Highlights: Black-Right-Pointing-Pointer We expressed rat Na{sub v}1.6 voltage-gated sodium channels in HEK293 cells. Black-Right-Pointing-Pointer Tefluthrin and deltamethrin caused resting modification of Na{sub v}1.6 channels. Black-Right-Pointing-Pointer Only deltamethrin exhibited use-dependent enhancement of modification. Black-Right-Pointing-Pointer State-dependent effects of pyrethroids are influenced by the cellular context. Black-Right-Pointing-Pointer Channels in HEK293 cells exhibit properties similar to native neuronal channels.« less

Modeling of leachate generation from MSW landfills by a 2-dimensional 2-domain approach

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

Fellner, Johann, E-mail: j.fellner@tuwien.ac.a; Brunner, Paul H., E-mail: paul.h.brunner@tuwien.ac.a

2010-11-15

The flow of water through Municipal Solid Waste (MSW) landfills is highly non-uniform and dominated by preferential pathways. Thus, concepts to simulate landfill behavior require that a heterogeneous flow regime is considered. Recent models are based on a 2-domain approach, differentiating between channel domain with high hydraulic conductivity, and matrix domain of slow water movement with high water retention capacity. These models focus on the mathematical description of rapid water flow in channel domain. The present paper highlights the importance of water exchange between the two domains, and expands the 1-dimensional, 2-domain flow model by taking into account water flowsmore » in two dimensions. A flow field consisting of a vertical path (channel domain) surrounded by the waste mass (matrix domain) is defined using the software HYDRUS-2D. When the new model is calibrated using data sets from a MSW-landfill site the predicted leachate generation corresponds well with the observed leachate discharge. An overall model efficiency in terms of r{sup 2} of 0.76 was determined for a simulation period of almost 4 years. The results confirm that water in landfills follows a preferential path way characterized by high permeability (K{sub s} = 300 m/d) and zero retention capacity, while the bulk of the landfill (matrix domain) is characterized by low permeability (K{sub s} = 0.1 m/d) and high retention capacity. The most sensitive parameters of the model are the hydraulic conductivities of the channel domain and the matrix domain, and the anisotropy of the matrix domain.« less

Measurement of surface tension and viscosity by open capillary techniques

DOEpatents

Rye,Robert R. , Yost,Frederick G.

1998-01-01

An open-channel capillary is provided, having preferably a v-shaped groove in a flat wettable surface. The groove has timing marks and a source marker in which the specimen to be tested is deposited. The time of passage between the timing marks is recorded, and the ratio of surface tension .gamma. to viscosity .mu. is determined from the equation given below: ##EQU1## where h.sub.0 is the groove depth, .alpha. is the groove angle, .theta. is the liquid/solid contact angle, and t is the flow time. It has been shown by the

Isotopic dependence of fusion enhancement of various heavy ion systems using energy dependent Woods-Saxon potential

NASA Astrophysics Data System (ADS)

Gautam, Manjeet Singh

2015-01-01

In the present work, the fusion of symmetric and asymmetric projectile-target combinations are deeply analyzed within the framework of energy dependent Woods-Saxon potential model (EDWSP model) in conjunction with one dimensional Wong formula and the coupled channel code CCFULL. The neutron transfer channels and the inelastic surface excitations of collision partners are dominating mode of couplings and the coupling of relative motion of colliding nuclei to such relevant internal degrees of freedom produces a significant fusion enhancement at sub-barrier energies. It is quite interesting that the effects of dominant intrinsic degrees of freedom such as multi-phonon vibrational states, neutron transfer channels and proton transfer channels can be simulated by introducing the energy dependence in the nucleus-nucleus potential (EDWSP model). In the EDWSP model calculations, a wide range of diffuseness parameter ranging from a = 0.85 fm to a = 0.97 fm, which is much larger than a value (a = 0.65 fm) extracted from the elastic scattering data, is needed to reproduce sub-barrier fusion data. However, such diffuseness anomaly, which might be an artifact of some dynamical effects, has been resolved by trajectory fluctuation dissipation (TFD) model wherein the resulting nucleus-nucleus potential possesses normal diffuseness parameter.

One-step surface doping of organic nanofibers to achieve high dark conductivity and chemiresistor sensing of amines.

PubMed

Huang, Helin; Gross, Dustin E; Yang, Xiaomei; Moore, Jeffrey S; Zang, Ling

2013-08-28

High dark electrical conductivity was obtained for a p-type organic nanofibril material simply through a one-step surface doping. The nanofibril composite thus fabricated has been proven robust under ambient conditions. The high conductivity, combined with the intrinsic large surface area of the nanofibers, enables development of chemiresistor sensors for trace vapor detection of amines, with detection limit down to sub-parts per billion range.

Calcium sulfate crystallization along citrus root channels in a Florida soil exhibiting acid sulfate properties

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

Syslo, S.K.; Myhre, D.L.; Harris, W.G.

1988-02-01

The authors observed euhedral crystals in Manatee soil in a citrus grove in St. Lucie County, Florida. The material was identified as gypsum (CaSO/sub 4/ /times/ 2H/sub 2/O) using x-ray diffraction and infrared spectra. Photomicrography and scanning electron microscopy revealed that gypsum accumulated both in old root channels and within citrus root tissue of the Btg horizon. The subsurface horizons had elevated sulfate levels, a low initial pH, a drop (0.5 unit) in pH upon air-drying. Electrical conductivity paralleled the concentration of water-soluble sulfate. High levels of calcium and sulfate occurred for horizons above the water table. This accumulation ismore » attributed to groundwater bearing these ions and subsequently discharging them to the overlying soil. Dead citrus roots appear to act as wicks to aid water transfer from lower to higher horizons. The roots and their empty channels provide spaces in which the gypsum can precipitate if the concentrations of calcium and sulfate in the evaporating groundwater exceed the solubility product of gypsum.« less

Calculation of the conductance of two dimensional narrow wires

NASA Astrophysics Data System (ADS)

Kander, Ilan

1989-05-01

There is an interest in the quantum transport of electrons in systems where the sample dimensions are less than a phase coherence length L(sub phi) which is the distance across which the electrons lose phase memory (typically by inelastic scattering). The two-contact conductance is examined of 2-D systems (strips) as functions of Fermi energy system dimensions as is the amount of disorder at zero temperature. Under these conditions all scattering processes are elastic. The term channel is used in order to describe a quantum state with a given transverse quantum number and the appropriate longitudinal momentum. A channel is considered conducting if its longitudinal momentum is real, and decaying if its longitudinal momentum is imaginary. The calculation of the conductance is done in two ways. Transfer matrix for very long systems and Green's function for relatively short ones. The conductance curve in an ordered system is quantized and in a disordered system it is smeared. Interesting changes in the conductance near the thresholds for changes in the quantized value of the conductance are observed.

Photodissociation dynamics of CH{sub 3}C(O)SH in argon matrix: A QM/MM nonadiabatic dynamics simulation

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

Xia, Shu-Hua; Liu, Xiang-Yang; Fang, Qiu

2015-11-21

In this work, we have first employed the combined quantum mechanics/molecular mechanics (QM/MM) method to study the photodissociation mechanism of thioacetic acid CH{sub 3}C(O)SH in the S{sub 1}, T{sub 1}, and S{sub 0} states in argon matrix. CH{sub 3}C(O)SH is treated quantum mechanically using the complete active space self-consistent field and complete active space second-order perturbation theory methods; argon matrix is described classically using Lennard-Jones potentials. We find that the C-S bond fission is predominant due to its small barriers of ca. 3.0 and 1.0 kcal/mol in the S{sub 1} and T{sub 1} states. It completely suppresses the nearby C—Cmore » bond fission. After the bond fission, the S{sub 1} radical pair of CH{sub 3}CO and SH can decay to the S{sub 0} and T{sub 1} states via internal conversion and intersystem crossing, respectively. In the S{sub 0} state, the radical pair can either recombine to form CH{sub 3}C(O)SH or proceed to form molecular products of CH{sub 2}CO and H{sub 2}S. We have further employed our recently developed QM/MM generalized trajectory-based surface-hopping method to simulate the photodissociation dynamics of CH{sub 3}C(O)SH. In 1 ps dynamics simulation, 56% trajectories stay at the Franck-Condon region; the S{sub 1} C—S bond fission takes place in the remaining 44% trajectories. Among all nonadiabatic transitions, the S{sub 1} → S{sub 0} internal conversion is major (55%) but the S{sub 1} → T{sub 1} intersystem crossing is still comparable and cannot be ignored, which accounts for 28%. Finally, we have found a radical channel generating the molecular products of CH{sub 2}CO and H{sub 2}S, which is complementary to the concerted molecular channel. The present work sets the stage for simulating photodissociation dynamics of similar thio-carbonyl systems in matrix.« less

Structure of the CLC-1 chloride channel from Homo sapiens.

PubMed

Park, Eunyong; MacKinnon, Roderick

2018-05-29

CLC channels mediate passive Cl - conduction, while CLC transporters mediate active Cl - transport coupled to H + transport in the opposite direction. The distinction between CLC-0/1/2 channels and CLC transporters seems undetectable by amino acid sequence. To understand why they are different functionally we determined the structure of the human CLC-1 channel. Its 'glutamate gate' residue, known to mediate proton transfer in CLC transporters, adopts a location in the structure that appears to preclude it from its transport function. Furthermore, smaller side chains produce a wider pore near the intracellular surface, potentially reducing a kinetic barrier for Cl - conduction. When the corresponding residues are mutated in a transporter, it is converted to a channel. Finally, Cl - at key sites in the pore appear to interact with reduced affinity compared to transporters. Thus, subtle differences in glutamate gate conformation, internal pore diameter and Cl - affinity distinguish CLC channels and transporters. © 2018, Park & MacKinnon.

Use of upscaled elevation and surface roughness data in two-dimensional surface water models

USGS Publications Warehouse

Hughes, J.D.; Decker, J.D.; Langevin, C.D.

2011-01-01

In this paper, we present an approach that uses a combination of cell-block- and cell-face-averaging of high-resolution cell elevation and roughness data to upscale hydraulic parameters and accurately simulate surface water flow in relatively low-resolution numerical models. The method developed allows channelized features that preferentially connect large-scale grid cells at cell interfaces to be represented in models where these features are significantly smaller than the selected grid size. The developed upscaling approach has been implemented in a two-dimensional finite difference model that solves a diffusive wave approximation of the depth-integrated shallow surface water equations using preconditioned Newton–Krylov methods. Computational results are presented to show the effectiveness of the mixed cell-block and cell-face averaging upscaling approach in maintaining model accuracy, reducing model run-times, and how decreased grid resolution affects errors. Application examples demonstrate that sub-grid roughness coefficient variations have a larger effect on simulated error than sub-grid elevation variations.

Organic transistors making use of room temperature ionic liquids as gating medium

NASA Astrophysics Data System (ADS)

Hoyos, Jonathan Javier Sayago

The ability to couple ionic and electronic transport in organic transistors, based on pi conjugated organic materials for the transistor channel, can be particularly interesting to achieve low voltage transistor operation, i.e. below 1 V. The operation voltage in typical organic transistors based on conventional dielectrics (200 nm thick SiO2) is commonly higher than 10 V. Electrolyte-gated (EG) transistors, i.e. employing an electrolyte as the gating medium, permit current modulations of several orders of magnitude at relatively low gate voltages thanks to the exceptionally high capacitance at the electrolyte/transistor channel interface, in turn due to the low thickness (ca. 3 nm) of the electrical double layers forming at the electrolyte/semiconductor interface. Electrolytes based on room temperature ionic liquids (RTILs) are promising in EG transistor applications for their high electrochemical stability and good ionic conductivity. The main motivation behind this work is to achieve low voltage operation in organic transistors by making use of RTILs as gating medium. First we demonstrate the importance of the gate electrode material in the EG transistor performance. The use of high surface area carbon gate electrodes limits undesirable electrochemical processes and renders unnecessary the presence of a reference electrode to monitor the channel potential. This was demonstrated using activated carbon as gate electrode, the electronic conducting polymer MEH-PPV, poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] channel material, and the ionic liquid [EMIM][TFSI] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), as gating medium. Using high surface area gate electrodes resulted in sub-1 V operation and charge carrier mobilities of (1.0 +/- 0.5) x 10-2 cm2V -1s-1. A challenge in the field of EG transistors is to decrease their response time, a consequence of the slow ion redistribution in the transistor channel upon application of electric biases. We systematically investigated EG transistors employing RTILs belonging to the same family, i.e. based on a common anion and different cations. The transistor characteristics showed a limited cation influence in establishing the p-type doping of the conducting polymer. Interestingly, we observed that the transistor response time depends on at least two processes: the redistribution of ions from the electrolyte into the transistor channel, affecting the gate-source current (I gs); and the redistribution of charges in the transistor channel, affecting the drain-source current (Ids), as a function of time. The two processes have different rates, with the latter being the slowest. Incorporating propylene carbonate in the electrolyte proved to be an effective solution to increase the ionic conductivity, to lower the viscosity and, consequently, to reduce the transistor response time. Finally, we were able to demonstrate a multifunctional device integrating the transistor logic function with that of energy storage in a supercapacitor: the TransCap. The polymer/electrolyte/carbon vertical stacking of the EG transistor features the cell configuration of a hybrid supercapacitor. Supercapacitors are high specific power systems that, for their ability to store/deliver charge within short times may outperform batteries in applications having high power demand. When the TransCap is ON (open transistor channel), the polymer and the carbon gate electrodes store charge (Q) at a given Vgs, hence the stored energy equals Q˙V gs. When the TransCap is switched OFF, the channel and the gate are discharged and the energy can be delivered back to power other electronic components. EG transistors, making use of activated carbon as gate electrode and different RTILs as well as RTIL solvent mixtures as electrolyte gating medium, are interesting towards low voltage printable electronics. The high capacitance at the interface between the electrolyte and the transistor channel enables energy storage within the EG transistor architecture.

Process for introducing electrical conductivity into high-temperature polymeric materials

DOEpatents

Liepins, R.; Jorgensen, B.S.; Liepins, L.Z.

1993-12-21

High-temperature electrically conducting polymers are described. The in situ reactions: AgNO[sub 3] + RCHO [yields] Ag + RCOOH and R[sub 3]M [yields] M + 3R, where M=Au or Pt have been found to introduce either substantial bulk or surface conductivity in high-temperature polymers. The reactions involving the R[sub 3]M were caused to proceed thermally suggesting the possibility of using laser means for initiating such reactions in selected areas or volumes of the polymeric materials. The polymers successfully investigated to date are polyphenylquinoxaline, polytolylquinoxaline, polyquinoline, polythiazole, and pyrone.

Process for introducing electrical conductivity into high-temperature polymeric materials

DOEpatents

Liepins, Raimond; Jorgensen, Betty S.; Liepins, Leila Z.

1993-01-01

High-temperature electrically conducting polymers. The in situ reactions: AgNO.sub.3 +RCHO.fwdarw.Ag.degree.+RCOOH and R.sub.3 M.fwdarw.M.degree.+3R, where M=Au or Pt have been found to introduce either substantial bulk or surface conductivity in high-temperature polymers. The reactions involving the R.sub.3 M were caused to proceed thermally suggesting the possibility of using laser means for initiating such reactions in selected areas or volumes of the polymeric materials. The polymers successfully investigated to date are polyphenylquinoxaline, polytolylquinoxaline, polyquinoline, polythiazole, and pyrrone.

Process for introducing electrical conductivity into high-temperature polymeric materials

DOEpatents

Liepins, Raimond; Jorgensen, Betty S.; Liepins, Leila Z.

1989-01-01

High-temperature electrically conducting polymers. The in situ reactions: AgNO.sub.3 +RCHO.fwdarw.AG.sup.0 +RCOOH and R.sub.3 M.fwdarw.M.sup.0 3R, where M=Au or Pt have been found to introduce either substantial bulk or surface conductivity in high-temperature polymers. The reactions involving the R.sub.3 M were caused to proceed thermally suggesting the possibility of using laser means for initiating such reactions in selected areas or volumes of the polymeric materials. The polymers successfully investigated to date are polyphenylquinoxaline, polytolylquinoxaline, polyquinoline, polythiazole, and pyrrone.

Process for introducing electrical conductivity into high-temperature polymeric materials

DOEpatents

Liepins, R.; Jorgensen, B.S.; Liepins, L.Z.

1987-08-27

High-temperature electrically conducting polymers. The in situ reactions: AgNO/sub 3/ + RCHO ..-->.. Ag/sup 0/ + RCOOH and R/sub 3/M ..-->.. M/sup 0/ + 3R, where M = Au or Pt have been found to introduce either substantial bulk or surface conductivity in high- temperature polymers. The reactions involving the R/sub 3/M were caused to proceed thermally suggesting the possibility of using laser means for initiating such reactions in selected areas or volumes of the polymeric materials. The polymers successfully investigated to date are polyphenylquinoxaline, polytolylquinoxaline, polyquinoline, polythiazole, and pyrrone. 3 tabs.

Effect of chromium substitution on the dielectric properties of mixed Ni-Zn ferrite prepared by WOWS sol–gel technique

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

Ashtar, M.; Munir, A.; Anis-ur-Rehman, M.

2016-07-15

Graphical abstract: Variation of AC conductivity (σ{sub AC}) as a function of natural log of angular frequency (lnω) for Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2-x}Cr{sub x}O{sub 4} nanoferrites at room temperature. - Highlights: • Cr doped mixed Ni-Zn ferrites were successfully synthesized by a newly developed WOWS sol gel technique. • The specific surface area and specific surface area to volume ratio increased with decrease in particle size. • The resonance peaks appeared in dielectric loss graphs, shifting towards low frequency with the increase in Cr concentration. • The prepared samples have the lowest values of the dielectric constant. • The dielectricmore » constant were observed to be inversely proportional to square root of the AC resistivity. - Abstract: Cr{sup +3} doped Ni-Zn nanoferrite samples with composition Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2-x}Cr{sub x}O{sub 4}(x = 0.1, 0.2, 0.3, 0.4) were synthesized With Out Water and Surfactant (WOWS) sol-gel technique. The structural, morphological and dielectric properties of the samples were investigated. The lattice constant, crystallite size, theoretical density and porosity of each sample were obtained from X-ray diffraction (XRD) data. The specific surface area and specific surface area to volume ratio increased with the decrease in the size of Cr{sup +3} doped Ni-Zn ferrite nanoparticles, as the concentration of Cr{sup +3} increased. The SEM analysis revealed that the particles were of nano size and of spherical shape. The dielectric parameters such as dielectric constant (ε′) and dielectric loss (tanδ) of all the samples as a function of frequency at room temperature were measured. The AC conductivity (σ{sub AC}) was determined from the dielectric parameters, which showed increasing trend with the rise in frequency.« less

Modulation of KvAP Unitary Conductance and Gating by 1-Alkanols and Other Surface Active Agents

PubMed Central

Finol-Urdaneta, Rocio K.; McArthur, Jeffrey R.; Juranka, Peter F.; French, Robert J.; Morris, Catherine E.

2010-01-01

Abstract The actions of alcohols and anesthetics on ion channels are poorly understood. Controversy continues about whether bilayer restructuring is relevant to the modulatory effects of these surface active agents (SAAs). Some voltage-gated K channels (Kv), but not KvAP, have putative low affinity alcohol-binding sites, and because KvAP structures have been determined in bilayers, KvAP could offer insights into the contribution of bilayer mechanics to SAA actions. We monitored KvAP unitary conductance and macroscopic activation and inactivation kinetics in PE:PG/decane bilayers with and without exposure to classic SAAs (short-chain 1-alkanols, cholesterol, and selected anesthetics: halothane, isoflurane, chloroform). At levels that did not measurably alter membrane specific capacitance, alkanols caused functional changes in KvAP behavior including lowered unitary conductance, modified kinetics, and shifted voltage dependence for activation. A simple explanation is that the site of SAA action on KvAP is its entire lateral interface with the PE:PG/decane bilayer, with SAA-induced changes in surface tension and bilayer packing order combining to modulate the shape and stability of various conformations. The KvAP structural adjustment to diverse bilayer pressure profiles has implications for understanding desirable and undesirable actions of SAA-like drugs and, broadly, predicts that channel gating, conductance and pharmacology may differ when membrane packing order differs, as in raft versus nonraft domains. PMID:20197029

Unravelling recent environmental change in a lowland river valley, eastern Ireland: geoarchaeological applications

NASA Astrophysics Data System (ADS)

Foster, Gez; Turner, Jonathan

2010-05-01

This paper reports the preliminary findings of an Irish Heritage Council INSTAR funded research project on the geoarchaeology and fluvial geomorphology of the lower River Boyne valley, eastern Ireland. The nature and evolution of the contemporary Boyne floodplain at Dunmoe, Co. Meath (53° 40' 22.8" N, 6° 37' 54.7" W) has been investigated using a multi-technique approach combining field and terrestrial LiDAR-based geomorphological mapping, radiocarbon dating of channel migration activity, electrical resistivity tomography surveys of sub-surface topography and high-resolution X-ray and XRF geochemical characterisation of fine-grained sediment fill sequences. All of these lines of evidence support a tripartite sub-division of the floodplain. Valley marginal floodplain Zone 1 is characterised by a colluvial sediment fill which has buried an irregular ditch-basin-platform surface containing recent archaeological material. Subtle variations in mapped elevation suggest that the buried surface may represent the site of an abandoned river-side complex, possibly a small docking area or port. Geomorphological field relationships suggest that the possible archaeological site was connected to a former bank line position of the main River Boyne (floodplain Zone 2) via a small canal. Radiocarbon dating of Zone 2 channel gravels suggests that the channel associated with this bank position was abandoned some time before 1490-1610 AD. Subsequent vertical and lateral channel migration, the onset of which has been radiocarbon dated to the 17th or 18th century AD, led to the development of the lowest and most recent floodplain surface (Zone 3). The sedimentology and geochemistry of the Zone 2 and 3 fluvial sediment sequences suggests that recent centuries have involved an increase in fluvial flood risk, evidenced by the burial of alluvial soils by bedded, shell-rich sands. A more complete understanding of the timing and environmental drivers of increasing flood risk is anticipated from ongoing radionuclide (Pb-210 and Cs-137) and pollen analysis of the fluvial sediment sequences. However, based on the established chronology and geomorphic field relationships, it is plausible that the archaeological complex represents a late medieval site linked to Dunmoe Castle (14th to 17th century AD), which overlooks the floodplain.

Enthalpy restoration in geothermal energy processing system

DOEpatents

Matthews, Hugh B.

1983-01-01

A geothermal deep well energy extraction system is provided of the general type in which solute-bearing hot water is pumped to the earth's surface from a relatively low temperature geothermal source by transferring thermal energy from the hot water to a working fluid for driving a primary turbine-motor and a primary electrical generator at the earth's surface. The superheated expanded exhaust from the primary turbine motor is conducted to a bubble tank where it bubbles through a layer of sub-cooled working fluid that has been condensed. The superheat and latent heat from the expanded exhaust of the turbine transfers thermal energy to the sub-cooled condensate. The desuperheated exhaust is then conducted to the condenser where it is condensed and sub-cooled, whereupon it is conducted back to the bubble tank via a barometric storage tank. The novel condensing process of this invention makes it possible to exploit geothermal sources which might otherwise be non-exploitable.

Present Practice of Using Nautical Depth to Manage Navigation Channels in the Presence of Fluid Mud

DTIC Science & Technology

2017-05-01

material surfaces cannot be interpreted reliably unless other correlating information is developed. Surveying of fluid mud properties. At some locations...depth to manage navigation channels and ports requires a mud property that determines a navigability criteria, a practical method for surveying that...for managing navigation channels, (3) issues related to conducting hydrographic surveying in waterways with fluid mud bottoms, (4) the newest

The Shubnikov-de Haas effect and thermoelectric properties of Tl-doped Sb{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3}

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

Kulbachinskii, V. A., E-mail: kulb@mig.phys.msu.ru; Kudryashov, A. A.; Kytin, V. G.

2015-06-15

The influence of doping with Tl on the Shubnikov-de Haas effect at T = 4.2 K in magnetic fields up to 38 T in p-Sb{sub 2−x}Tl{sub x}Te{sub 3} (x = 0, 0.005, 0.015, and 0.05) and n-Bi{sub 2−x}Tl{sub x}Se{sub 3} (x = 0, 0.01, 0.02, 0.04, and 0.06) single crystals is investigated. Extreme cross-sections of the Fermi surface in both materials decrease upon doping with Tl: the hole concentration decreases in Sb{sub 2−x}Tl{sub x}Te{sub 3} due to the donor effect of Tl and the electron concentration in n-Bi{sub 2−x}Tl{sub x}Se{sub 3} decreases due to the acceptor effect of Tl. Themore » temperature dependences of the Seebeck coefficient, electrical conductivity, thermal conductivity, and dimensionless thermoelectric figure of merit in a temperature range of 77–300 K are measured. The thermal conductivity and electrical conductivity decrease upon doping with Tl both in p-Sb{sub 2−x}Tl{sub x}Te{sub 3} and in n-Bi{sub 2−x}Tl{sub x}Se{sub 3}. The Seebeck coefficient increases in all compositions upon an increase in doping over the entire measured temperature range. The thermoelectric figure of merit increases upon doping with Tl.« less

Interaction of the BKCa channel gating ring with dendrotoxins

PubMed Central

Takacs, Zoltan; Imredy, John P; Bingham, Jon-Paul; Zhorov, Boris S; Moczydlowski, Edward G

2014-01-01

Two classes of small homologous basic proteins, mamba snake dendrotoxins (DTX) and bovine pancreatic trypsin inhibitor (BPTI), block the large conductance Ca2+-activated K+ channel (BKCa, KCa1.1) by production of discrete subconductance events when added to the intracellular side of the membrane. This toxin-channel interaction is unlikely to be pharmacologically relevant to the action of mamba venom, but as a fortuitous ligand-protein interaction, it has certain biophysical implications for the mechanism of BKCa channel gating. In this work we examined the subconductance behavior of 9 natural dendrotoxin homologs and 6 charge neutralization mutants of δ-dendrotoxin in the context of current structural information on the intracellular gating ring domain of the BKCa channel. Calculation of an electrostatic surface map of the BKCa gating ring based on the Poisson-Boltzmann equation reveals a predominantly electronegative surface due to an abundance of solvent-accessible side chains of negatively charged amino acids. Available structure-activity information suggests that cationic DTX/BPTI molecules bind by electrostatic attraction to site(s) on the gating ring located in or near the cytoplasmic side portals where the inactivation ball peptide of the β2 subunit enters to block the channel. Such an interaction may decrease the apparent unitary conductance by altering the dynamic balance of open versus closed states of BKCa channel activation gating. PMID:25483585

Comparison of Summer and Winter California Central Valley Aerosol Distributions from Lidar and MODIS Measurements

NASA Technical Reports Server (NTRS)

Lewis, Jasper; DeYoung, Russell; Ferrare, Richard; Chu, D. Allen

2010-01-01

Aerosol distributions from two aircraft lidar campaigns conducted in the California Central Valley are compared in order to identify seasonal variations. Aircraft lidar flights were conducted in June 2003 and February 2007. While the ground PM(sub 2.5) concentration is highest in the winter, the aerosol optical depth measured from MODIS is highest in the summer. A seasonal comparison shows that PM(sub 2.5) in the winter can exceed summer PM(sub 2.5) by 55%, while summer AOD exceeds winter AOD by 43%. Higher temperatures and wildfires in the summer produce elevated aerosol layers that are detected by satellite measurements, but not surface particulate matter monitors. Temperature inversions, especially during the winter, contribute to higher PM(sub 2.5) measurements at the surface. Measurements of the boundary layer height from lidar instruments provide valuable information need to understand the relationship between satellite measurements of optical depth and in-situ measurements of PM(sub 2.5).

Spectra of surface plasmon polariton enhanced electroluminescence from electroformed Al-Al{sub 2}O{sub 3}-Ag diodes

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

Hickmott, T. W.

Narrow band-pass filters have been used to measure the spectral distribution of electroluminescent photons with energies between 1.8 eV and 3.0 eV from electroformed Al-Al{sub 2}O{sub 3}-Ag diodes with anodic Al{sub 2}O{sub 3} thicknesses between 12 nm and 18 nm. Electroforming of metal-insulator-metal (MIM) diodes is a non-destructive dielectric breakdown that results in a conducting channel in the insulator and changes the initial high resistance of the MIM diode to a low resistance state. It is a critical step in the development of resistive-switching memories that utilize MIM diodes as the active element. Electroforming of Al-Al{sub 2}O{sub 3}-Ag diodes in vacuum results in voltage-controlledmore » negative resistance (VCNR) in the current-voltage (I-V) characteristics. Electroluminescence (EL) and electron emission into vacuum (EM) develop simultaneously with the current increase that results in VCNR in the I-V characteristics. EL is due to recombination of electrons injected at the Al-Al{sub 2}O{sub 3} interface with radiative defect centers in Al{sub 2}O{sub 3}. Measurements of EL photons between 1.8 eV and 3.0 eV using a wide band-pass filter showed that EL intensity is exponentially dependent on Al{sub 2}O{sub 3} thickness for Al-Al{sub 2}O{sub 3}-Ag diodes between 12 nm and 20 nm thick. Enhanced El intensity in the thinnest diodes is attributed to an increase in the spontaneous emission rate of recombination centers due to high electromagnetic fields generated in Al{sub 2}O{sub 3} when EL photons interact with electrons in Ag or Al to form surface plasmon polaritons at the Al{sub 2}O{sub 3}-Ag or Al{sub 2}O{sub 3}-Al interface. El intensity is a maximum at 2.0–2.2 eV for Al-Al{sub 2}O{sub 3}-Ag diodes with Al{sub 2}O{sub 3} thicknesses between 12 nm and 18 nm. EL in diodes with 12 nm or 14 nm of Al{sub 2}O{sub 3} is enhanced by factors of 8–10 over EL from a diode with 18 nm of Al{sub 2}O{sub 3}. The extent of EL enhancement in the thinnest diodes can vary significantly between samples. A narrow band of recombination centers was found in one Al-Al{sub 2}O{sub 3}-Ag diode with 12 nm of Al{sub 2}O{sub 3}; it had EL intensity 100 times greater at 2.15 eV than the diode with 18 nm of Al{sub 2}O{sub 3}. EL intensity for photons with energies greater than 2.6 eV is nearly the same for all diodes.« less

A note on the R sub 0-parameter for discrete memoryless channels

NASA Technical Reports Server (NTRS)

Mceliece, R. J.

1980-01-01

An explicit class of discrete memoryless channels (q-ary erasure channels) is exhibited. Practical and explicit coded systems of rate R with R/R sub o as large as desired can be designed for this class.

The abnormal electrical and optical properties in Na and Ni codoped BiFeO{sub 3} nanoparticles

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

Xu, Xunling; Liu, Weifang, E-mail: wfliu@tju.edu.cn, E-mail: shouyu.wang@yahoo.com; Zhang, Hong

2015-05-07

Bi{sub 0.97}Na{sub 0.03}Fe{sub 1−x}Ni{sub x}O{sub 3} (x = 0, 0.005, 0.01, 0.015) nanoparticles are prepared via a sol-gel method. Weak ferromagnetism and exchange bias phenomenon without field cooling are observed in the samples. The oxygen vacancy concentration and leakage current density are increased with increasing the Ni content. However, with the increase of Ni content, the band gap of Bi{sub 0.97}Na{sub 0.03}Fe{sub 1−x}Ni{sub x}O{sub 3} nanoparticles first decreases and then increases. To explain the abnormal phenomenon, the interplay of oxygen vacancy donor and hole acceptor is analyzed and a phenomenological qualitative model based on the electronic energy band is proposed. Additionally, themore » threshold switching behavior appears in Bi{sub 0.97}Na{sub 0.03}Fe{sub 1−x}Ni{sub x}O{sub 3} samples with x = 0.01, 0.015 and the effect is qualitatively explained by introducing a conducting channel model based on the high-density mobile charges.« less

Self-regenerating and hybrid irreversible/reversible PDMS microfluidic devices.

PubMed

Shiroma, Letícia S; Piazzetta, Maria H O; Duarte-Junior, Gerson F; Coltro, Wendell K T; Carrilho, Emanuel; Gobbi, Angelo L; Lima, Renato S

2016-05-16

This paper outlines a straightforward, fast, and low-cost method to fabricate polydimethylsiloxane (PDMS) chips. Termed sandwich bonding (SWB), this method requires only a laboratory oven. Initially, SWB relies on the reversible bonding of a coverslip over PDMS channels. The coverslip is smaller than the substrate, leaving a border around the substrate exposed. Subsequently, a liquid composed of PDMS monomers and a curing agent is poured onto the structure. Finally, the cover is cured. We focused on PDMS/glass chips because of their key advantages in microfluidics. Despite its simplicity, this method created high-performance microfluidic channels. Such structures featured self-regeneration after leakages and hybrid irreversible/reversible behavior. The reversible nature was achieved by removing the cover of PDMS with acetone. Thus, the PDMS substrate and glass coverslip could be detached for reuse. These abilities are essential in the stages of research and development. Additionally, SWB avoids the use of surface oxidation, half-cured PDMS as an adhesive, and surface chemical modification. As a consequence, SWB allows surface modifications before the bonding, a long time for alignment, the enclosure of sub-micron channels, and the prototyping of hybrid devices. Here, the technique was successfully applied to bond PDMS to Au and Al.

Self-regenerating and hybrid irreversible/reversible PDMS microfluidic devices

PubMed Central

Shiroma, Letícia S.; Piazzetta, Maria H. O.; Duarte-Junior, Gerson F.; Coltro, Wendell K. T.; Carrilho, Emanuel; Gobbi, Angelo L.; Lima, Renato S.

2016-01-01

This paper outlines a straightforward, fast, and low-cost method to fabricate polydimethylsiloxane (PDMS) chips. Termed sandwich bonding (SWB), this method requires only a laboratory oven. Initially, SWB relies on the reversible bonding of a coverslip over PDMS channels. The coverslip is smaller than the substrate, leaving a border around the substrate exposed. Subsequently, a liquid composed of PDMS monomers and a curing agent is poured onto the structure. Finally, the cover is cured. We focused on PDMS/glass chips because of their key advantages in microfluidics. Despite its simplicity, this method created high-performance microfluidic channels. Such structures featured self-regeneration after leakages and hybrid irreversible/reversible behavior. The reversible nature was achieved by removing the cover of PDMS with acetone. Thus, the PDMS substrate and glass coverslip could be detached for reuse. These abilities are essential in the stages of research and development. Additionally, SWB avoids the use of surface oxidation, half-cured PDMS as an adhesive, and surface chemical modification. As a consequence, SWB allows surface modifications before the bonding, a long time for alignment, the enclosure of sub-micron channels, and the prototyping of hybrid devices. Here, the technique was successfully applied to bond PDMS to Au and Al. PMID:27181918

Extended horizon lifting for periodic gain adjustment in control systems, and for equalization of communication channels

NASA Technical Reports Server (NTRS)

Bayard, David S. (Inventor)

1994-01-01

Periodic gain adjustment in plants of irreducible order, n, or for equalization of communications channels is effected in such a way that the plant (system) appears to be minimum phase by choosing a horizon time N is greater than n of liftings in periodic input and output windows rho sub u and rho sub y, respectively, where N is an integer chosen to define the extent (length) of each of the windows rho sub u and rho sub y, and n is the order of an irreducible input/output plant. The plant may be an electrical, mechanical, or chemical system, in which case output tracking (OT) is carried out for feedback control or a communication channel, in which case input tracking (IT) is performed. Conditions for OT are distinct from IT in terms of zero annihilation, namely H(sub s)H(sub s)(sup +) = I for OT and H(sub s)H(sub s)(sup +) = I of IT, where the OT conditions are intended for gain adjustments in the control system, and IT conditions are intended for equalization for communication channels.

Oestrogen directly inhibits the cardiovascular L-type Ca{sup 2+} channel Ca{sub v}1.2

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

Ullrich, Nina D.; Koschak, Alexandra; MacLeod, Kenneth T.

2007-09-21

Oestrogen can modify the contractile function of vascular smooth muscle and cardiomyocytes. The negative inotropic actions of oestrogen on the heart and coronary vasculature appear to be mediated by L-type Ca{sup 2+} channel (Ca{sub v}1.2) inhibition, but the underlying mechanisms remain elusive. We tested the hypothesis that oestrogen directly inhibits the cardiovascular L-type Ca{sup 2+} current, I {sub CaL}. The effect of oestrogen on I {sub CaL} was measured in Ca{sub v}1.2-transfected HEK-293 cells using the whole-cell patch-clamp technique. The current revealed typical activation and inactivation profiles of nifedipine- and cadmium-sensitive I {sub CaL}. Oestrogen (50 {mu}M) rapidly reduced Imore » {sub CaL} by 50% and shifted voltage-dependent activation and availability to more negative potentials. Furthermore, oestrogen blocked the Ca{sup 2+} channel in a rate-dependent way, exhibiting higher efficiency of block at higher stimulation frequencies. Our data suggest that oestrogen inhibits I {sub CaL} through direct interaction of the steroid with the channel protein.« less

Porous framework of T{sub 2}[Fe(CN){sub 6}].xH{sub 2}O with T=Co, Ni, Cu, Zn, and H{sub 2} storage

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

Avila, M.; Reguera, L.; Rodriguez-Hernandez, J.

2008-11-15

The materials under study were prepared from aqueous solutions of ferrocyanic acid and salts of the involved transition metals and their crystal structure solved and refined from X-ray powder diffraction data. Complementary information from thermogravimetric, infrared and Moessbauer data was also used for the structural study. Three different crystal structures were found: hexagonal (P-3) for Zn with the zinc atom coordinated to three N ends of CN groups plus a water molecule, cubic (Pm-3m) for Ni and Cu, and monoclinic (P2{sub 1}/m) for Co. For Ni and Cu the obtained solids have an open channel framework related to 50% ofmore » vacancies for the building unit, [Fe(CN){sub 6}]. In the as-synthesized material the framework free volume is occupied by coordinated and hydrogen-bonded water molecules. These of hexacyanoferrates (II) have received certain attention as prototype of materials for the hydrogen storage. In the anhydrous phase of Ni and Cu, 50% of the metal (T) coordination sites, located at the cavities surface, will be available to interact with the hydrogen molecule. However, when the crystal waters are removed the porous frameworks collapse as it is suggested by H{sub 2} and CO{sub 2} adsorption data. For Co, a structure of stacked layers was found where the cobalt atoms have both tetrahedral and octahedral coordination. The layers remain together through a network of hydrogen-bonding interactions between coordinated and weakly bonded water molecules. No H{sub 2} adsorption was observed in the anhydrous phase of Co. For Zn, the porous framework remains stable on the water removal but with a system of narrow channels and a small available volume, also inaccessible to H{sub 2}. - Graphical abstract: Structure of stacked layers for CO{sub 2}[Fe(CN){sub 6}].xH{sub 2}O.« less

Study of a MHEMT heterostructure with an In{sub 0.4}Ga{sub 0.6}As channel MBE-grown on a GaAs substrate using reciprocal space mapping

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

Aleshin, A. N., E-mail: a.n.aleshin@mail.ru; Bugaev, A. S.; Ermakova, M. A.

2015-08-15

The crystallographic characteristics of the design elements of a metamorphic high-electron-mobility (MHEMT) heterostructure with an In{sub 0.4}Ga{sub 0.6}As channel are determined based on reciprocal space mapping. The heterostructure is grown by molecular beam epitaxy on the vicinal surface of a GaAs substrate with a deviation angle from the (001) plane of 2° and consists of a stepped metamorphic buffer containing six layers including an inverse step, a high-temperature buffer layer with constant composition, and active HEMT layers. The InAs content in the layers of the metamorphic buffer is varied from 0.1 to 0.48. Reciprocal space maps are constructed for themore » (004) symmetric reflection and (224)+ asymmetric reflection. It is found that the heterostructure layers are characterized both by a tilt angle relative to the plane of the (001) substrate and a rotation angle around the [001] axis. The tilt angle of the layer increases as the InAs concentration in the layer increases. It is shown that a high-temperature buffer layer of constant composition has the largest degree of relaxation compared with all other layers of the heterostructure.« less

Double-pulse 2-μm integrated path differential absorption lidar airborne validation for atmospheric carbon dioxide measurement.

PubMed

Refaat, Tamer F; Singh, Upendra N; Yu, Jirong; Petros, Mulugeta; Remus, Ruben; Ismail, Syed

2016-05-20

Field experiments were conducted to test and evaluate the initial atmospheric carbon dioxide (CO₂) measurement capability of airborne, high-energy, double-pulsed, 2-μm integrated path differential absorption (IPDA) lidar. This IPDA was designed, integrated, and operated at the NASA Langley Research Center on-board the NASA B-200 aircraft. The IPDA was tuned to the CO₂ strong absorption line at 2050.9670 nm, which is the optimum for lower tropospheric weighted column measurements. Flights were conducted over land and ocean under different conditions. The first validation experiments of the IPDA for atmospheric CO₂ remote sensing, focusing on low surface reflectivity oceanic surface returns during full day background conditions, are presented. In these experiments, the IPDA measurements were validated by comparison to airborne flask air-sampling measurements conducted by the NOAA Earth System Research Laboratory. IPDA performance modeling was conducted to evaluate measurement sensitivity and bias errors. The IPDA signals and their variation with altitude compare well with predicted model results. In addition, off-off-line testing was conducted, with fixed instrument settings, to evaluate the IPDA systematic and random errors. Analysis shows an altitude-independent differential optical depth offset of 0.0769. Optical depth measurement uncertainty of 0.0918 compares well with the predicted value of 0.0761. IPDA CO₂ column measurement compares well with model-driven, near-simultaneous air-sampling measurements from the NOAA aircraft at different altitudes. With a 10-s shot average, CO₂ differential optical depth measurement of 1.0054±0.0103 was retrieved from a 6-km altitude and a 4-GHz on-line operation. As compared to CO₂ weighted-average column dry-air volume mixing ratio of 404.08 ppm, derived from air sampling, IPDA measurement resulted in a value of 405.22±4.15  ppm with 1.02% uncertainty and 0.28% additional bias. Sensitivity analysis of environmental systematic errors correlates the additional bias to water vapor. IPDA ranging resulted in a measurement uncertainty of <3  m.

Selectively-etched nanochannel electrophoretic and electrochemical devices

DOEpatents

Surh, Michael P.; Wilson, William D.; Barbee, Jr., Troy W.; Lane, Stephen M.

2004-11-16

Nanochannel electrophoretic and electrochemical devices having selectively-etched nanolaminates located in the fluid transport channel. The normally flat surfaces of the nanolaminate having exposed conductive (metal) stripes are selectively-etched to form trenches and baffles. The modifications of the prior utilized flat exposed surfaces increase the amount of exposed metal to facilitate electrochemical redox reaction or control the exposure of the metal surfaces to analytes of large size. These etched areas variously increase the sensitivity of electrochemical detection devices to low concentrations of analyte, improve the plug flow characteristic of the channel, and allow additional discrimination of the colloidal particles during cyclic voltammetry.

Selectively-etched nanochannel electrophoretic and electrochemical devices

DOEpatents

Surh, Michael P [Livermore, CA; Wilson, William D [Pleasanton, CA; Barbee, Jr., Troy W.; Lane, Stephen M [Oakland, CA

2006-06-27

Nanochannel electrophoretic and electrochemical devices having selectively-etched nanolaminates located in the fluid transport channel. The normally flat surfaces of the nanolaminate having exposed conductive (metal) stripes are selectively-etched to form trenches and baffles. The modifications of the prior utilized flat exposed surfaces increase the amount of exposed metal to facilitate electrochemical redox reaction or control the exposure of the metal surfaces to analytes of large size. These etched areas variously increase the sensitivity of electrochemical detection devices to low concentrations of analyte, improve the plug flow characteristic of the channel, and allow additional discrimination of the colloidal particles during cyclic voltammetry.

Regional two-dimensional magnetotelluric profile in West Bohemia/Vogtland reveals deep conductive channel into the earthquake swarm region

NASA Astrophysics Data System (ADS)

Muñoz, Gerard; Weckmann, Ute; Pek, Josef; Kováčiková, Světlana; Klanica, Radek

2018-03-01

The West Bohemia/Vogtland region, characterized by the intersection of the Eger (Ohře) Rift and the Mariánské Lázně fault, is a geodynamically active area exhibiting repeated occurrence of earthquake swarms, massive CO2 emanations and mid Pleistocene volcanism. The Eger Rift is the only known intra-continental region in Europe where such deep seated, active lithospheric processes currently take place. We present an image of electrical resistivity obtained from two-dimensional inversion of magnetotelluric (MT) data acquired along a regional profile crossing the Eger Rift. At the near surface, the Cheb basin and the aquifer feeding the mofette fields of Bublák and Hartoušov have been imaged as part of a region of very low resistivity. The most striking resistivity feature, however, is a deep reaching conductive channel which extends from the surface into the lower crust spatially correlated with the hypocentres of the seismic events of the Nový Kostel Focal Zone. This channel has been interpreted as imaging a pathway from a possible mid-crustal fluid reservoir to the surface. The resistivity model reinforces the relation between the fluid circulation along deep-reaching faults and the generation of the earthquakes. Additionally, a further conductive channel has been revealed to the south of the profile. This other feature could be associated to fossil hydrothermal alteration related to Mýtina and/or Neualbenreuth Maar structures or alternatively could be the signature of a structure associated to the suture between the Saxo-Thuringian and Teplá-Barrandian zones, whose surface expression is located only a few kilometres away.

On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons

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

Karamitaheri, Hossein; Neophytou, Neophytos, E-mail: N.Neophytou@warwick.ac.uk

The thermal conductivity of low-dimensional materials and graphene nanoribbons, in particular, is limited by the strength of line-edge-roughness scattering. One way to characterize the roughness strength is the dependency of the thermal conductivity on the channel's width in the form W{sup β}. Although in the case of electronic transport, this dependency is very well studied, resulting in W{sup 6} for nanowires and quantum wells and W{sup 4} for nanoribbons, in the case of phonon transport it is not yet clear what this dependence is. In this work, using lattice dynamics and Non-Equilibrium Green's Function simulations, we examine the width dependencemore » of the thermal conductivity of ultra-narrow graphene nanoribbons under the influence of line edge-roughness. We show that the exponent β is in fact not a single well-defined number, but it is different for different parts of the phonon spectrum depending on whether phonon transport is ballistic, diffusive, or localized. The exponent β takes values β < 1 for semi-ballistic phonon transport, values β ≫ 1 for sub-diffusive or localized phonons, and β = 1 only in the case where the transport is diffusive. The overall W{sup β} dependence of the thermal conductivity is determined by the width-dependence of the dominant phonon modes (usually the acoustic ones). We show that due to the long phonon mean-free-paths, the width-dependence of thermal conductivity becomes a channel length dependent property, because the channel length determines whether transport is ballistic, diffusive, or localized.« less

Tidal currents and bedload transport at the mouth of a rock-bound estuary during low river discharge conditions (Guadiana Estuary, Portugal)

NASA Astrophysics Data System (ADS)

Garel, E.; Pacheco, A.; Ferreira, Ó.

2009-04-01

The present study documents the poorly-described hydro-sediment dynamics of narrow bedrock-controlled estuaries during periods of low-river discharge. The results also contribute to assess the geomorphological evolution of these systems, when affected by drastic flow regulation. The Guadiana Estuary is a narrow rock-bound mesotidal estuary, 80 km in length, located at the southern border between Spain and Portugal. Until recently, the river inputs to the estuary displayed high (annual and seasonal) variability, characterized by periods of droughts, and episodic flood events with (monthly-averaged) fluvial discharge as high as 5,000 m3s-1 (160 m3s-1 in average, for the period 1947/2001). This pattern has ceased in February 2002, with the impoundment of the main river by the large Alqueva dam, 60 km upstream from the estuary head. At present, the daily-averaged river discharge is generally kept low throughout the year (< 50 m3s-1). In the absence of significant flood events to expel massively sediment out of the estuary, concerns have been raised about sand infilling at the mouth and increased erosion at the adjacent coastline. For the assessment of the sediment balance of the estuary under present hydrodynamic conditions, this study examines the tidal currents and bedload transport at the entrance of the estuarine channel. Current measurement transects were performed across the 600 m-wide channel entrance using a ship borne Acoustic Doppler Profiler (ADP, operating at 1.5 MHz frequency) during 2 entire tidal cycles, at spring (17 September 2008, 3.0 m tidal range) and at neap tide (21 October 2008, 1.6 m tidal range). Surficial sediment samples were also collected across the channel during the spring tidal cycle. The bed sediment consists of well-sorted medium sand with mean grain size ranging from 0.5 to 0.3 mm (with coarser material at the deepest part of the channel cross-section). Tidal currents were analysed along 6 sub-sections to take into account these grain size variations. The friction velocity and bed shear stress were computed based on the mean depth-averaged velocities of each sub-sections and considering a power law vertical velocity profile. The transport rate of sand was then estimated using Nielsen (1992) formula for bedload transport. The transport of sand in suspension was not considered in the study, as the skin friction velocities were lesser than the estimated settling velocities of the grains. Maximum velocity values (about 1.2 and 0.8 m.s-1 at spring and neap, respectively) were observed near the surface of the deepest sub-section of the channel. The tidal prism was about 1.5 times larger at spring (39x106 m3) than at neap (25x106m3), whereas the fresh water inputs during both tidal cycles were comparatively negligible. Maximum depth-averaged, bed and surface current velocities were ebb-directed at both neap and spring tides, for each of the 6 channel sub-sections. No significant lateral variation of the tidal flow was observed, in relation with the narrowness of the channel. Vertical residual velocity profiles were also directed downstream at both neap and spring tide. At neap, however, the (ebb-directed) residual velocities were slower near the bed and faster near the surface, when compared to the spring tide. These differences were induced by the reinforcement of the estuarine circulation, in relation with enhanced stratified conditions during neap periods (weak currents and reduced mixing). The net bedload transport of sand was also directed downstream for all channel sub-sections. The transport rates of the entire channel were estimated to be of about 30 and 10 m3 for the spring and neap tidal cycles, respectively. Extrapolation of these extreme (i.e. neap and spring) rates yielded a potential seaward export of sand of approximately 15,000 m3yr-1. This study suggests that the Guadiana estuary departs from typical estuaries where landward net transport of sediment is generally described. The outputs of the study are important with respect to the long-term (decades) geomorphological evolution and sustainable management of the estuary mouth and adjacent coastline.

Adaptive Quadrature Detection for Multicarrier Continuous-Variable Quantum Key Distribution

NASA Astrophysics Data System (ADS)

Gyongyosi, Laszlo; Imre, Sandor

2015-03-01

We propose the adaptive quadrature detection for multicarrier continuous-variable quantum key distribution (CVQKD). A multicarrier CVQKD scheme uses Gaussian subcarrier continuous variables for the information conveying and Gaussian sub-channels for the transmission. The proposed multicarrier detection scheme dynamically adapts to the sub-channel conditions using a corresponding statistics which is provided by our sophisticated sub-channel estimation procedure. The sub-channel estimation phase determines the transmittance coefficients of the sub-channels, which information are used further in the adaptive quadrature decoding process. We define the technique called subcarrier spreading to estimate the transmittance conditions of the sub-channels with a theoretical error-minimum in the presence of a Gaussian noise. We introduce the terms of single and collective adaptive quadrature detection. We also extend the results for a multiuser multicarrier CVQKD scenario. We prove the achievable error probabilities, the signal-to-noise ratios, and quantify the attributes of the framework. The adaptive detection scheme allows to utilize the extra resources of multicarrier CVQKD and to maximize the amount of transmittable information. This work was partially supported by the GOP-1.1.1-11-2012-0092 (Secure quantum key distribution between two units on optical fiber network) project sponsored by the EU and European Structural Fund, and by the COST Action MP1006.

Experimental and Coupled-channels Investigation of the Radiative Properties of the N2 c4 (sup 1)Sigma+(sub u) - X (sup 1)Sigma+(sub g) Band System

NASA Technical Reports Server (NTRS)

Liu, Xianming; Shemansky, Donald E.; Malone, Charles P.; Johnson, Paul V.; Ajello, Joseph M.; Kanik, Isik; Heays, Alan N.; Lewis, Brenton R.; Gibson, Stephen T.; Stark, Glenn

2008-01-01

The emission properties of the N2 c(sup prime)(sub 4) (sup 1)Sigma+(sub u) - Chi (sup 1)Sigma+(sub g) band system have been investigated in a joint experimental and coupled-channels theoretical study. Relative intensities of the c(sup prime)(sub 4) (sup 1)Sigma+(sub u)(0) - Chi (sup 1)Sigma+(sub g)(v(sub i)) transitions, measured via electron-impact-induced emission spectroscopy, are combined with a coupled-channel Schroedinger equation (CSE) model of the N2 molecule, enabling determination of the diabatic electronic transition moment for the c(sup prime)(sub 4) (sup 1)Sigma+(sub u) - Chi (sup 1)Sigma+(sub g) system as a function of internuclear distance. The CSE probabilities are further verified by comparison with a high-resolution experimental spectrum. Spontaneous transition probabilities of the c(sup prime)(sub 4) (sup 1)Sigma+(sub u) - Chi (sup 1)Sigma+(sub g) modeling atmospheric emission, can now be calculated reliably.

Fuel cell assembly fluid flow plate having conductive fibers and rigidizing material therein

DOEpatents

Walsh, Michael M.

2000-01-01

A fluid flow plate is preferably formed with three initial sections, for instance, two layers of conductive (e.g., metal) fibers and a barrier material (e.g., metal foil) which is interposed between the two layers. For example, sintering of these three sections can provide electrical path(s) between outer faces of the two layers. Then, the sintered sections can be, for instance, placed in a mold for forming of flow channel(s) into one or more of the outer faces. Next, rigidizing material (e.g., resin) can be injected into the mold, for example, to fill and/or seal space(s) about a conductive matrix of the electrical path(s). Preferably, abrading of surface(s) of the outer face(s) serves to expose electrical contact(s) to the electrical path(s).

Verification of combined thermal-hydraulic and heat conduction analysis code FLOWNET/TRUMP

NASA Astrophysics Data System (ADS)

Maruyama, Soh; Fujimoto, Nozomu; Kiso, Yoshihiro; Murakami, Tomoyuki; Sudo, Yukio

1988-09-01

This report presents the verification results of the combined thermal-hydraulic and heat conduction analysis code, FLOWNET/TRUMP which has been utilized for the core thermal hydraulic design, especially for the analysis of flow distribution among fuel block coolant channels, the determination of thermal boundary conditions for fuel block stress analysis and the estimation of fuel temperature in the case of fuel block coolant channel blockage accident in the design of the High Temperature Engineering Test Reactor(HTTR), which the Japan Atomic Energy Research Institute has been planning to construct in order to establish basic technologies for future advanced very high temperature gas-cooled reactors and to be served as an irradiation test reactor for promotion of innovative high temperature new frontier technologies. The verification of the code was done through the comparison between the analytical results and experimental results of the Helium Engineering Demonstration Loop Multi-channel Test Section(HENDEL T(sub 1-M)) with simulated fuel rods and fuel blocks.

HEC-1 Flood Hydrograph Package. Users Manual

DTIC Science & Technology

1987-03-01

98 Perv Catchment 200 .02 .35 80 85 SUB7 Ip Catchment 100 .06 .24 15 .96 98 Perv Catchnmnt 190 .03 .35 85 85 TABLE 12.2b CWNEL DATA (Test 2)(RK RECORD...02 .55 TRAP 0 1 AIN CHANNEL 14000 .005 .09 - TRAP 2 2 no SUB7 COLLECTOR CHANNEL 2100 .024 .02 .74 TRAP 0 1 MAIN CHANNEL 7000 .011 .05 TRAP 50 3 yes...35 80 125 RK 2200 .011 .02 .55 TRAP 0 126 RK 14000 .005 .09 TRAP 2 2 127 9K SUB7 128 KM COMBINE RUNOFF FROM SUB4, SUDS, AND SUB6 129 HC 3 130 1IK

Characterizing supraglacial meltwater channel hydraulics on the Greenland Ice Sheet from in situ observations

USGS Publications Warehouse

Gleason, Colin J.; Smith, Laurence C.; Chu, Vena W.; Legleiter, Carl; Pitcher, Lincoln H.; Overstreet, Brandon T.; Rennermalm, Asa K.; Forster, Richard R.; Yang, Kang

2016-01-01

Supraglacial rivers on the Greenland ice sheet (GrIS) transport large volumes of surface meltwater toward the ocean, yet have received relatively little direct research. This study presents field observations of channel width, depth, velocity, and water surface slope for nine supraglacial channels on the southwestern GrIS collected between 23 July and 20 August, 2012. Field sites are located up to 74 km inland and span 494-1485 m elevation, and contain measured discharges larger than any previous in situ study: from 0.006 to 23.12 m3/s in channels 0.20 to 20.62 m wide. All channels were deeply incised with near vertical banks, and hydraulic geometry results indicate that supraglacial channels primarily accommodate greater discharges by increasing velocity. Smaller streams had steeper water surface slopes (0.74-8.83%) than typical in terrestrial settings, yielding correspondingly high velocities (0.40-2.60 m/s) and Froude numbers (0.45-3.11) with supercritical flow observed in 54% of measurements. Derived Manning's n values were larger and more variable than anticipated from channels of uniform substrate, ranging from 0.009 to 0.154 with a mean value of 0.035 +/- 0.027 despite the absence of sediment, debris, or other roughness elements. Ubiquitous micro-depressions in shallow sections of the channel bed may explain some of these roughness values. However, we find that other, unobserved sources of flow resistance likely contributed to these elevated n values: future work should explicitly consider additional sources of flow resistance beyond bed roughness in supraglacial channels. We conclude that hydraulic modelling for these channels must allow for both sub- and supercritical flow, and most importantly must refrain from assuming that all ice-substrate channels exhibit similar hydraulic behavior, especially for Froude numbers and Manning's n. Finally, this study highlights that further theoretical and empirical work on supraglacial channel hydraulics is necessary before broad scale understanding of ice sheet hydrology can be achieved. This article is protected by copyright. All rights reserved.

Multi-scale controls on spatial variability in river biogeochemical cycling

NASA Astrophysics Data System (ADS)

Blaen, Phillip; Kurz, Marie; Knapp, Julia; Mendoza-Lera, Clara; Lee-Cullin, Joe; Klaar, Megan; Drummond, Jennifer; Jaeger, Anna; Zarnetske, Jay; Lewandowski, Joerg; Marti, Eugenia; Ward, Adam; Fleckenstein, Jan; Datry, Thibault; Larned, Scott; Krause, Stefan

2016-04-01

Excessive nutrient concentrations are common in surface waters and groundwaters in agricultural catchments worldwide. Increasing geomorphological heterogeneity in river channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with the hyporheic zone; a site of intense microbial activity where biogeochemical cycling rates can be high. However, the controls on spatial variability in biogeochemical cycling, particularly at scales relevant for river managers, are largely unknown. Here, we aimed to assess: 1) how differences in river geomorphological heterogeneity control solute transport and rates of biogeochemical cycling at sub-reach scales (102 m); and 2) the relative magnitude of these differences versus those relating to reach scale substrate variability (103 m). We used the reactive tracer resazurin (Raz), a weakly fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland river in southern England. Solute tracer tests were conducted in two reaches with contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach was divided into sub-reaches that varied in geomorphic complexity (e.g. by the presence of pool-riffle sequences or the abundance of large woody debris). Slug injections of Raz and the conservative tracer fluorescein were conducted in each reach during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation rates in the gravel-dominated reach were more than 50% higher than those in the sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation rates and conservative solute transport parameters suggests small scale targeted management interventions to alter geomorphic heterogeneity may be effective in creating hotspots of river biogeochemical cycling and nutrient load attenuation.

Mitragynine and its potential blocking effects on specific cardiac potassium channels

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

Tay, Yea Lu; Teah, Yi Fan; Chong, Yoong Min

2016-08-15

Mitragyna speciosa Korth is known for its euphoric properties and is frequently used for recreational purposes. Several poisoning and fatal cases involving mitragynine have been reported but the underlying causes remain unclear. Human ether-a-go-go-related gene (hERG) encodes the cardiac I{sub Kr} current which is a determinant of the duration of ventricular action potentials and QT interval. On the other hand, I{sub K1}, a Kir current mediated by Kir2.1 channel and I{sub KACh}, a receptor-activated Kir current mediated by GIRK channel are also known to be important in maintaining the cardiac function. This study investigated the effects of mitragynine on themore » current, mRNA and protein expression of hERG channel in hERG-transfected HEK293 cells and Xenopus oocytes. The effects on Kir2.1 and GIRK channels currents were also determined in the oocytes. The hERG tail currents following depolarization pulses were inhibited by mitragynine with an IC{sub 50} value of 1.62 μM and 1.15 μM in the transfected cell line and Xenopus oocytes, respectively. The S6 point mutations of Y652A and F656A attenuated the inhibitor effects of mitragynine, indicating that mitragynine interacts with these high affinity drug-binding sites in the hERG channel pore cavity which was consistent with the molecular docking simulation. Interestingly, mitragynine does not affect the hERG expression at the transcriptional level but inhibits the protein expression. Mitragynine is also found to inhibit I{sub KACh} current with an IC{sub 50} value of 3.32 μM but has no significant effects on I{sub K1}. Blocking of both hERG and GIRK channels may cause additive cardiotoxicity risks. - Highlights: • The potential cardiac potassium channel blocking properties of mitragynine were investigated. • Mitragynine blocks hERG channel and I{sub Kr} in hERG-transfected HEK293 cells and hERG cRNA-injected Xenopus oocytes. • Mitragynine inhibits the hERG protein but not the mRNA expression. • Mitragynine inhibits GIRK channel. • Simultaneous hERG and GIRK channel blockade may cause additive cardiotoxicity risks.« less

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

Zhang, Yingjie, E-mail: yzx@ansto.gov.au; Bhadbhade, Mohan; Karatchevtseva, Inna

Three new coordination polymers of uranium(VI) with pyromellitic acid (H{sub 4}btca) have been synthesized and structurally characterized. (ED)[(UO{sub 2})(btca)]·(DMSO)·3H{sub 2}O (1) (ED=ethylenediammonium; DMSO=dimethylsulfoxide) has a lamellar structure with intercalation of ED and DMSO. (NH{sub 4}){sub 2}[(UO{sub 2}){sub 6}O{sub 2}(OH){sub 6}(btca)]·~6H{sub 2}O (2) has a 3D framework built from 7-fold coordinated uranyl trinuclear units and btca ligands with 1D diamond-shaped channels (~8.5 Å×~8.6 Å). [(UO{sub 2}){sub 2}(H{sub 2}O)(btca)]·4H{sub 2}O (3) has a 3D network constructed by two types of 7-fold coordinated uranium polyhedron. The unique μ{sub 5}-coordination mode of btca in 3 enables the formation of 1D olive-shaped large channels (~4.5more » Å×~19 Å). Vibrational modes, thermal stabilities and fluorescence properties have been investigated. - Graphical abstract: Table of content: three new uranium(VI) coordination polymers with pyromellitic acid (H{sub 4}btca) have been synthesized via room temperature and hydrothermal synthesis methods, and structurally characterized. Two to three dimensional (3D) frameworks are revealed. All 3D frameworks have unique 1D large channels. Their vibrational modes, thermal stabilities and photoluminescence properties have been investigated. - Highlights: • Three new coordination polymers of U(VI) with pyromellitic acid (H{sub 4}btca). • Structures from a 2D layer to 3D frameworks with unique 1D channels. • Unusual µ{sub 5}-(η{sub 1}:η{sub 2}:η{sub 1}:η{sub 2:}η{sub 1}) coordination mode of btca ligand. • Vibrational modes, thermal stabilities and luminescent properties reported.« less

Exploring mechanisms of a tropospheric archetype: CH{sub 3}O{sub 2} + NO

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

Launder, Andrew M.; Agarwal, Jay; Schaefer, Henry F., E-mail: ccq@uga.edu

Methylperoxy radical (CH{sub 3}O{sub 2}) and nitric oxide (NO) contribute to the propagation of photochemical smog in the troposphere via the production of methoxy radical (CH{sub 3}O) and nitrogen dioxide (NO{sub 2}). This reaction system also furnishes trace quantities of methyl nitrate (CH{sub 3}ONO{sub 2}), a sink for reactive NO{sub x} species. Here, the CH{sub 3}O{sub 2} + NO reaction is examined with highly reliable coupled-cluster methods. Specifically, equilibrium geometries for the reactants, products, intermediates, and transition states of the ground-state potential energy surface are characterized. Relative reaction enthalpies at 0 K (ΔH{sub 0K}) are reported; these values are comprisedmore » of electronic energies extrapolated to the complete basis set limit of CCSDT(Q) and zero-point vibrational energies computed at CCSD(T)/cc-pVTZ. A two-part mechanism involving CH{sub 3}O and NO{sub 2} production followed by radical recombination to CH{sub 3}ONO{sub 2} is determined to be the primary channel for formation of CH{sub 3}ONO{sub 2} under tropospheric conditions. Constrained optimizations of the reaction paths at CCSD(T)/cc-pVTZ suggest that the homolytic bond dissociations involved in this reaction path are barrierless.« less

Surface stoichiometry modification and improved DC/RF characteristics by plasma treated and annealed AlGaN/GaN HEMTs

NASA Astrophysics Data System (ADS)

Upadhyay, Bhanu B.; Takhar, Kuldeep; Jha, Jaya; Ganguly, Swaroop; Saha, Dipankar

2018-03-01

We demonstrate that N2 and O2 plasma treatment followed by rapid thermal annealing leads to surface stoichiometry modification in a AlGaN/GaN high electron mobility transistor. Both the source/drain access and gate regions respond positively improving the transistor characteristics albeit to different extents. Characterizations indicate that the surface show the characteristics of that of a higher band-gap material like AlxOy and GaxOy along with N-vacancy in the sub-surface region. The N-vacancy leads to an increased two-dimensional electron gas density. The formation of oxides lead to a reduced gate leakage current and surface passivation. The DC characteristics show increased transconductance, saturation drain current, ON/OFF current ratio, sub-threshold swing and lower ON resistance by a factor of 2.9, 2.0, 103.3 , 2.3, and 2.1, respectively. The RF characteristics show an increase in unity current gain frequency by a factor of 1.7 for a 500 nm channel length device.

External pH effects on the depolarization-activated K channels in guard cell protoplasts of Vicia faba

PubMed Central

1994-01-01

Previous studies reveal that the pH of the apoplastic solution in the guard cell walls may vary between 7.2 and 5.1 in closed and open stomata, respectively. During these aperture and pH changes, massive K+ fluxes cross the cellular plasma membrane driving the osmotic turgor and volume changes of guard cells. Therefore, we examined the effect of extracellular pH on the depolarization-activated K channels (KD channels), which constitute the K+ efflux pathway, in the plasma membrane of Vicia faba guard cell protoplasts. We used patch clamp, both in whole cells as well as in excised outside-out membrane patches. Approximately 500 KD channels, at least, could be activated by depolarization in one protoplast (density: approximately 0.6 micron-2). Acidification from ph 8.1 to 4.4 decreased markedly the whole-cell conductance, GK, of the KD channels, shifted its voltage dependence, GK- EM, to the right on the voltage axis, slowed the rate of activation and increased the rate of deactivation, whereas the single channel conductance was not affected significantly. Based on the GK-EM shifts, the estimated average negative surface charge spacing near the KD channel is 39 A. To quantify the effects of protons on the rates of transitions between the hypothesized conformational states of the channels, we fitted the experimental macroscopic steady state conductance-voltage relationship and the voltage dependence of time constants of activation and deactivation, simultaneously, with a sequential three-state model CCO. In terms of this model, protonation affects the voltage-dependent properties via a decrease in localized, rather than homogeneous, surface charge sensed by the gating moieties. In terms of either the CO or CCO model, the protonation of a site with a pKa of 4.8 decreases the voltage-independent number of channels, N, that are available for activation by depolarization. PMID:8035163

Regenerable adsorption system

NASA Technical Reports Server (NTRS)

Roychoudhury, Subir (Inventor); Perry, Jay (Inventor); Walsh, Dennis (Inventor)

2006-01-01

A method for regenerable adsorption includes providing a substrate that defines at least one layer of ultra short channel length mesh capable of conducting an electrical current therethrough, coating at least a portion of the substrate with a desired sorbent for trace contaminant control or CO.sub.2 sorption, resistively heating the substrate, and passing a flowstream through the substrate and in contact with the sorbent.

Solar cell collector and method for producing same

NASA Technical Reports Server (NTRS)

Evans, J. C., Jr. (Inventor)

1978-01-01

A transparent, conductive collector layer containing conductive metal channels is formed as a layer on a photovoltaic substrate by coating a photovoltaic substract with a conductive mixed metal layer. A heat sink having portions protruding from one of its surfaces is attached. These protruding portions define a continuous pattern in combination with recessed regions among them such that they are in contact with the conductive layer of the photovoltaic substrate. Heating the substrate while simultaneously oxidizing the portions of the conductive layer exposed to a gaseous oxidizing substance forced into the recessed regions of the heat sink, creates a transparent metal oxide layer on the substrate. A continous pattern of highly conductive metal channels is contained in the metal oxide layer.

Tailored fischer-tropsch synthesis product distribution

DOEpatents

Wang, Yong [Richland, WA; Cao, Chunshe [Kennewick, WA; Li, Xiaohong Shari [Richland, WA; Elliott, Douglas C [Richland, WA

2012-06-19

Novel methods of Fischer-Tropsch synthesis are described. It has been discovered that conducting the Fischer-Tropsch synthesis over a catalyst with a catalytically active surface layer of 35 microns or less results in a liquid hydrocarbon product with a high ratio of C.sub.5-C.sub.20:C.sub.20+. Descriptions of novel Fischer-Tropsch catalysts and reactors are also provided. Novel hydrocarbon compositions with a high ratio of C.sub.5-C.sub.20:C.sub.20+ are also described.

Charon's light curves, as observed by New Horizons' Ralph color camera (MVIC) on approach to the Pluto system

NASA Astrophysics Data System (ADS)

Howett, C. J. A.; Ennico, K.; Olkin, C. B.; Buie, M. W.; Verbiscer, A. J.; Zangari, A. M.; Parker, A. H.; Reuter, D. C.; Grundy, W. M.; Weaver, H. A.; Young, L. A.; Stern, S. A.

2017-05-01

Light curves produced from color observations taken during New Horizons' approach to the Pluto-system by its Multi-spectral Visible Imaging Camera (MVIC, part of the Ralph instrument) are analyzed. Fifty seven observations were analyzed, they were obtained between 9th April and 3rd July 2015, at a phase angle of 14.5° to 15.1°, sub-observer latitude of 51.2 °N to 51.5 °N, and a sub-solar latitude of 41.2°N. MVIC has four color channels; all are discussed for completeness but only two were found to produce reliable light curves: Blue (400-550 nm) and Red (540-700 nm). The other two channels, Near Infrared (780-975 nm) and Methane-Band (860-910 nm), were found to be potentially erroneous and too noisy respectively. The Blue and Red light curves show that Charon's surface is neutral in color, but slightly brighter on its Pluto-facing hemisphere. This is consistent with previous studies made with the Johnson B and V bands, which are at shorter wavelengths than that of the MVIC Blue and Red channel respectively.

Charon's Light Curves, as Observed by New Horizons' Ralph Color Camera (MVIC) on Approach to the Pluto System.

NASA Technical Reports Server (NTRS)

Howett, C. J. A.; Ennico, K.; Olkin, C. B.; Buie, M. W.; Verbiscer, A. J.; Zangari, A. M.; Parker, A. H.; Reuter, D. C.; Grundy, W. M.; Weaver, H. A.;

Prominent metallic surface conduction and the singular magnetic response of topological Dirac fermion in three-dimensional topological insulator Bi1.5Sb0.5Te1.7Se1.3.

PubMed

Dutta, Prithwish; Pariari, Arnab; Mandal, Prabhat

2017-07-07

We report semiconductor to metal-like crossover in the temperature dependence of resistivity (ρ) due to the switching of charge transport from bulk to surface channel in three-dimensional topological insulator Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 . Unlike earlier studies, a much sharper drop in ρ(T) is observed below the crossover temperature due to the dominant surface conduction. Remarkably, the resistivity of the conducting surface channel follows a rarely observable T 2 dependence at low temperature, as predicted theoretically for a two-dimensional Fermi liquid system. The field dependence of magnetization shows a cusp-like paramagnetic peak in the susceptibility (χ) at zero field over the diamagnetic background. The peak is found to be robust against temperature and χ decays linearly with the field from its zero-field value. This unique behavior of the χ is associated with the spin-momentum locked topological surface state in Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 . The reconstruction of the surface state with time is clearly reflected through the reduction of the peak height with the age of the sample.

GABA/sub B/ receptor activation inhibits Ca/sup 2 +/-activated potassium channels in synaptosomes: involvement of G-proteins

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

Ticku, M.K.; Delgado, A.

1989-01-01

/sup 86/Rb-efflux assay from preloaded synaptosomes of rat cerebral cortex was developed to study the effect of GABA/sub B/ receptor agonist baclofen on Ca/sup 2 +/-activated K/sup +/-channels. Depolarization of /sup 86/Rb-loaded synaptosomes in physiological buffer increased Ca/sup 2 +/-activated /sup 86/Rb-efflux by 400%. The /sup 86/Rb-efflux was blocked by quinine sulfate, tetraethylammonium, and La/sup 3 +/ indicating the involvement of Ca/sup 2 +/-activated K/sup +/-channels. (-)Baclofen inhibited Ca/sup 2 +/-activated /sup 86/Rb-efflux in a stereospecific manner. The inhibitory effect of (-)baclofen was mediated by GABA/sub B/ receptor activation, since it was blocked by GABA/sub B/ antagonist phaclofen, but notmore » by bicuculline. Further, pertussis toxin also blocked the ability of baclofen or depolarizing action to affect Ca/sup 2 +/-activated K/sup +/-channels. These results suggest that baclofen inhibits Ca/sup 2 +/-activated K/sup +/-channels in synaptosomes and these channels are regulated by G-proteins. This assay may provide an ideal in vitro model to study GABA/sub B/ receptor pharmacology.« less

3-D indium(III)-btc channel frameworks and their ion-exchange properties (btc=1,3,5-benzenetricarboxylate)

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

Lin Zhengzhong; Chen Lian; Yue Chengyang

2006-04-15

Assembly of InCl{sub 3} with 1,3,5-benzenetricarboxylic acid (H{sub 3}btc) and pyridine or pyridine derivatives under hydrothermal conditions produces a series of isostructural coordination polymers with the interesting frameworks: {l_brace}(HL)[In{sub 4}(OH){sub 4}(btc){sub 3}].L.3H{sub 2}O{r_brace} {sub n} {sub ,} L=pyridine (1); L=2-picoline (2); L=4-picoline (3) and {l_brace}(Hdpea)[In{sub 4}(OH){sub 4}(btc){sub 3}].3H{sub 2}O{r_brace} {sub n} (4) (dpea=1,2-di(4-pyridyl)ethane). In these four complexes, carboxyl and hydroxyl oxygen atoms bridge indium(III) centers to form octahedral chain-like sinusoidal curves, which are further interlinked by btc{sup 3-} moieties to generate 3-D frameworks with 1-D channels. The protonated guests HL in 1-3 located at the channels can be fully exchangedmore » by K{sup +} ion or partially exchanged by Sr{sup 2+}, and Ba{sup 2+} ions.« less

Strain effects in Hg/sub 1-//sub x/Cd/sub x/Te (xapprox. 0. 2) photovoltaic arrays

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

Weiss, E.; Mainzer, N.

1989-03-01

The effect of stress and strain on the performance of Hg/sub 1-//sub x/Cd/sub x/Te (xapprox.0.2) photovoltaic arrays was studied both in the dark and under illumination. Stress, external as well as internal, affects the current--voltage characteristic of the photodiode. The combined action of illumination and strain yields an anomalous response to light absorption in the device. A model is conceived wherein the photodiode and guard ring are treated as a metal-insulator semiconductor field effect transistor (MISFET). Stress developed in the vicinity of small contact windows causes n-type damage, which brings about a forward bias in the device. The effect ofmore » strain on the reverse current of the photodiode is explained by a change in the n-channel conductivity of the MISFET. This change is caused by charges which are due either to a piezoelectric effect or n-type damage. Using this model observed phenomena in Hg/sub 1-//sub x/Cd/sub x/Te photovoltaic arrays are explained, as due to internal stresses originating from wafer deformation.« less

Determination of heat transfer coefficient for an interaction of sub-cooled gas and metal

NASA Astrophysics Data System (ADS)

Zaidi Sidek, Mohd; Syahidan Kamarudin, Muhammad

2016-02-01

Heat transfer coefficient (HTC) for a hot metal surface and their surrounding is one of the need be defined parameter in hot forming process. This study has been conducted to determine the HTC for an interaction between sub-cooled gas sprayed on a hot metal surface. Both experiments and finite element have been adopted in this work. Initially, the designated experiment was conducted to obtain temperature history of spray cooling process. Then, an inverse method was adopted to calculate the HTC value before we validate in a finite element simulation model. The result shows that the heat transfer coefficient for interaction of subcooled gas and hot metal surface is 1000 W/m2K.

Dominant-Negative Regulation of Cell Surface Expression by a Pentapeptide Motif at the Extreme COOH Terminus of an Slo1 Calcium-Activated Potassium Channel Splice Variant

PubMed Central

Chiu, Yu-Hsin; Alvarez-Baron, Claudia; Kim, Eun Young

2010-01-01

Large-conductance Ca2+-activated K+ (BKCa) channels regulate the physiology of many cell types. A single vertebrate gene variously known as Slo1, KCa1.1, or KCNMA1 encodes the pore-forming subunits of BKCa channel but is expressed in a potentially very large number of alternative splice variants. Two splice variants of Slo1, Slo1VEDEC and Slo1QEERL, which differ at the extreme COOH terminus, show markedly different steady-state expression levels on the cell surface. Here we show that Slo1VEDEC and Slo1QEERL can reciprocally coimmunoprecipitate, indicating that they form heteromeric complexes. Moreover, coexpression of even small amounts of Slo1VEDEC markedly reduces surface expression of Slo1QEERL and total Slo1 as indicated by cell-surface biotinylation assays. The effects of Slo1VEDEC on steady-state surface expression can be attributed primarily to the last five residues of the protein based on surface expression of motif-swapped constructs of Slo1 in human embryonic kidney (HEK) 293T cells. In addition, the presence of the VEDEC motif at the COOH terminus of Slo1 channels is sufficient to confer a dominant-negative effect on cell surface expression of itself or other types of Slo1 subunits. Treating cells with short peptides containing the VEDEC motif increased surface expression of Slo1VEDEC channels transiently expressed in HEK293T cells and increased current through endogenous BKCa channels in mouse podocytes. Slo1VEDEC and Slo1QEERL channels are removed from the HEK293T cell surface with similar kinetics and to a similar extent, which suggests that the inhibitory effect of the VEDEC motif is exerted primarily on forward trafficking into the plasma membrane. PMID:20051533

Passivation of GaSb using molecular beam epitaxy Y{sub 2}O{sub 3} to achieve low interfacial trap density and high-performance self-aligned inversion-channel p-metal-oxide-semiconductor field-effect-transistors

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

Chu, R. L.; Chiang, T. H.; Hsueh, W. J.

2014-11-03

Molecular beam epitaxy deposited rare-earth oxide of Y{sub 2}O{sub 3} has effectively passivated GaSb, leading to low interfacial trap densities of (1–4) × 10{sup 12 }cm{sup −2} eV{sup −1} across the energy bandgap of GaSb. A high saturation drain current density of 130 μA/μm, a peak transconductance of 90 μS/μm, a low subthreshold slope of 147 mV/decade, and a peak field-effect hole mobility of 200 cm{sup 2}/V-s were obtained in 1 μm-gate-length self-aligned inversion-channel GaSb p-Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs). In this work, high-κ/GaSb interfacial properties were better in samples with a high substrate temperature of 200 °C than in those with high κ's deposited at room temperature, in terms of themore » interfacial electrical properties, particularly, the reduction of interfacial trap densities near the conduction band and the MOSFET device performance.« less

Atomic Structure of the Cystic Fibrosis Transmembrane Conductance Regulator.

PubMed

Zhang, Zhe; Chen, Jue

2016-12-01

The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel evolved from the ATP-binding cassette (ABC) transporter family. In this study, we determined the structure of zebrafish CFTR in the absence of ATP by electron cryo-microscopy to 3.7 Å resolution. Human and zebrafish CFTR share 55% sequence identity, and 42 of the 46 cystic-fibrosis-causing missense mutational sites are identical. In CFTR, we observe a large anion conduction pathway lined by numerous positively charged residues. A single gate near the extracellular surface closes the channel. The regulatory domain, dephosphorylated, is located in the intracellular opening between the two nucleotide-binding domains (NBDs), preventing NBD dimerization and channel opening. The structure also reveals why many cystic-fibrosis-causing mutations would lead to defects either in folding, ion conduction, or gating and suggests new avenues for therapeutic intervention. Copyright © 2016 Elsevier Inc. All rights reserved.

Apparatus and method for collection and concentration of respirable particles into a small fluid volume

DOEpatents

Simon, Jonathan N.; Brown, Steve B.

2002-01-01

An apparatus and method for the collection of respirable particles and concentration of such particles into a small fluid volume. The apparatus captures and concentrates small (1-10 .mu.m) respirable particles into a sub-millileter volume of fluid. The method involves a two step operation, collection and concentration: wherein collection of particles is by a wetted surface having small vertical slits that act as capillary channels; and concentration is carried out by transfer of the collected particles to a small volume (sub-milliliter) container by centrifugal force whereby the particles are forced through the vertical slits and contact a non-wetted wall surface, and are deflected to the bottom where they are contained for analysis, such as a portable flow cytometer or a portable PCR DNA analysis system.

Charge carrier transport and optical properties of SAM-induced conducting channel in organic semiconductors.

NASA Astrophysics Data System (ADS)

Podzorov, Vitaly

2009-03-01

Certain types of self-assembled monolayers (SAM) grown directly at the surface of organic semiconductors can induce a high surface conductivity in these materials [1]. For example, the conductivity induced by perfluorinated alkyl silanes in organic molecular crystals approaches 10 to -5 Siemens per square. The observed large electronic effect opens new opportunities for nanoscale surface functionalization of organic semiconductors and provides experimental access to the regime of high carrier density. Here, we will discuss temperature variable measurements of SAM-induced conductivity in several types of organic semiconductors. [1]. M. F. Calhoun, J. Sanchez, D. Olaya, M. E. Gershenson and V. Podzorov, ``Electronic functionalization of the surface of organic semiconductors with self-assembled monolayers'', Nature Mat. 7, 84 (2008).

Methods of fabricating a conductor assembly having a curvilinear arcuate shape

DOEpatents

Meinke, Rainer [Melbourne, FL

2011-08-23

A method for manufacture of a conductor assembly along a curvilinear axis. The assembly may be of the type which, when conducting current, generates a magnetic field or in which, in the presence of a changing magnetic field, a voltage is induced. In one example, the assembly includes a structure having a curved shape extending along the axis. A surface of the structure is positioned for formation of a channel along the curved shape. The structure is rotated about a second axis. While rotating the structure, a channel is formed in the surface that results in a helical shape in the structure. The channel extends both around and along the first axis.

Polished Downhole Transducer Having Improved Signal Coupling

DOEpatents

Hall, David R.; Fox, Joe

2006-03-28

Apparatus and methods to improve signal coupling in downhole inductive transmission elements to reduce the dispersion of magnetic energy at the tool joints and to provide consistent impedance and contact between transmission elements located along the drill string. A transmission element for transmitting information between downhole tools is disclosed in one embodiment of the invention as including an annular core constructed of a magnetically conductive material. The annular core forms an open channel around its circumference and is configured to form a closed channel by mating with a corresponding annular core along an annular mating surface. The mating surface is polished to provide improved magnetic coupling with the corresponding annular core. An annular conductor is disposed within the open channel.

Preparation of mesoporous titanium dioxide anode by a film- and pore-forming agent for the dye-sensitized solar cell

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

Hou, Wenjing; Xiao, Yaoming, E-mail: ymxiao@sxu.edu.cn; Han, Gaoyi, E-mail: han_gaoyis@sxu.edu.cn

2016-04-15

Highlights: • PVP is used as a film- and pore-forming agent to prepare the mesoporous TiO{sub 2} anode. • The TiO{sub 2} anode supplies high surface area for the dye adsorption. • The DSSC efficiency is strongly dependent on the pore properties of the TiO{sub 2} anode. • The DSSC efficiency with the TiO{sub 2} anode prepared by 20 wt% PVP reaches 8.39%. - Abstract: A novel mean of generating mesoporous titanium dioxide (TiO{sub 2}) anodes by employing polyvinylpyrrolidone (PVP) as the film- and pore-forming agent are proposed for dye-sensitized solar cells (DSSCs). The influences on the morphology and photovoltaicmore » performances of the TiO{sub 2} anodes are investigated by adjusting the PVP content in synthesizing the mesoporous TiO{sub 2} anodes. The photovoltaic conversion efficiency of the DSSC is found to be strongly dependent on the pore properties of the TiO{sub 2} anode. After the sintering process, the removal of the PVP leaves porously interconnected channel structures inside the TiO{sub 2} anode, supplying enhanced specific surface area for the dye adsorption as well as the efficient electron transmission. As a result, the TiO{sub 2} anode prepared by 20 wt% PVP presents the highest performances, based on which the DSSC achieves the highest conversion efficiency of 8.39%, approximately increased by 56.53% than that of the DSSC fabricated without PVP (5.36%).« less

Micromachined peristaltic pumps

NASA Technical Reports Server (NTRS)

Hartley, Frank T. (Inventor)

1999-01-01

Micromachined pumps including a channel formed between a first membrane and a substrate or between first and second flexible membranes. A series of electrically conductive strips is applied to a surface of the substrate or one of the membranes. Application of a sequential voltage to the series of strips causes a region of closure to progress down the channel to achieve a pumping action.

Effect of Levee and Channel Structures on Long Lava Flow Emplacement: Martian Examples from THEMIS and MOLA Data

NASA Technical Reports Server (NTRS)

Peitersen, M. N.; Zimbelman, J. R.; Christensen, P. R.; Bare, C.

2003-01-01

Long lava flows (discrete flow units with lengths exceeding 50 km) are easily identified features found on many planetary surfaces. An ongoing investigation is being conducted into the origin of these flows. Here, we limit our attention to long lava flows which show evidence of channel-like structures.

Ion Transport in Confined Geometries below the Nanoscale: Access Resistance Dominates Protein Channel Conductance in Diluted Solutions.

PubMed

Alcaraz, Antonio; López, M Lidón; Queralt-Martín, María; Aguilella, Vicente M

2017-10-24

Synthetic nanopores and mesoscopic protein channels have common traits like the importance of electrostatic interactions between the permeating ions and the nanochannel. Ion transport at the nanoscale occurs under confinement conditions so that the usual assumptions made in microfluidics are challenged, among others, by interfacial effects such as access resistance (AR). Here, we show that a sound interpretation of electrophysiological measurements in terms of channel ion selective properties requires the consideration of interfacial effects, up to the point that they dominate protein channel conductance in diluted solutions. We measure AR in a large ion channel, the bacterial porin OmpF, by means of single-channel conductance measurements in electrolyte solutions containing varying concentrations of high molecular weight PEG, sterically excluded from the pore. Comparison of experiments performed in charged and neutral planar membranes shows that lipid surface charges modify the ion distribution and determine the value of AR, indicating that lipid molecules are more than passive scaffolds even in the case of large transmembrane proteins. We also found that AR may reach up to 80% of the total channel conductance in diluted solutions, where electrophysiological recordings register essentially the AR of the system and depend marginally on the pore characteristics. These findings may have implications for several low aspect ratio biological channels that perform their physiological function in a low ionic strength and macromolecule crowded environment, just the two conditions enhancing the AR contribution.

Synthesis of hectorite-TiO2 and kaolinite-TiO2 nanocomposites with photocatalytic activity for the degradation of model air pollutants

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

Destaillats, Hugo; Kibanova, D.; Trejo, M.

2008-03-01

We studied the synthesis and photocatalytic activity of small-sized TiO{sub 2} supported on hectorite and kaolinite. Deposition of TiO{sub 2} on the clay mineral surface was conducted by using a sol-gel method with titanium isopropoxide as precursor. Anatase TiO{sub 2} particles formation was achieved by hydrothermal treatment at 180 C. Material characterization was conducted using XRD, SEM, XPS, ICP-OES, BET and porosimetry analysis. Efficiency in synthesizing clay-TiO{sub 2} composites depended strongly on the clay mineral structure. Incorporation of anatase in hectorite, an expandable clay mineral, was found to be very significant (> 36 wt.% Ti) and to be followed bymore » important structural changes at the clay mineral surface. Instead, no major structural modifications of the clay were observed for kaolinite-TiO{sub 2}, as compared with the untreated material. Photocatalytic performance of clay-TiO{sub 2} composites was evaluated with ATR-FTIR following the oxidation of adsorbed toluene and d-limonene, two model air pollutants. In either case, the photocatalytic removal efficiency of these hydrophobic substrates by the synthesized clay-TiO{sub 2} composites was comparable to that observed using pure commercial TiO{sub 2} (Degussa P25).« less

The Role of Basal Channels in Ice Shelf Calving.

NASA Astrophysics Data System (ADS)

Dow, C. F.; Lee, W. S.; Greenbaum, J. S.; Greene, C. A.; Blankenship, D. D.; Poinar, K.; Forrest, A.; Young, D. A.; Zappa, C. J.

2017-12-01

Increased rates of ice shelf break-up drives acceleration of grounded glacial ice into the ocean, resulting in sea-level rise. Ice shelves are vulnerable to thinning, which make them more susceptible to calving. Here, we examine basal channels under three ice shelves that locally thin the ice and drive formation of transverse ice shelf fractures. The basal channels also cause surface depressions due to hydrostatic buoyancy effects and can draw in surface water to form rivers. These rivers exacerbate thinning by surface melting and hydraulic loading, and can accelerate rifting when they flow into the transverse fractures. Our investigation focuses on Nansen Ice Shelf in the Ross Sea Embayment, East Antarctica. We use ice-sounding radar and single-beam laser altimeter data from two aerogeophysical campaigns conducted in 2011 and 2014, ice surface DEM reconstruction, and satellite imagery analysis, to examine the role of a substantial basal channel in the stability of this ice shelf. Nansen Ice Shelf calved two large icebergs totaling 214 km2 in area in April 2016. The transverse fracture that eventually rifted to form these icebergs initiated directly over the basal channel in 1987. In years when surface water formed on Nansen Ice Shelf, a river flowed into the transverse fracture. In November 2016, we identified a new fracture over the basal channel during in-situ data collection. We compare the Nansen Ice Shelf fractures with those at other vulnerable ice-shelf systems, including Petermann Glacier in Greenland and Totten Glacier in East Antarctica, to evaluate the role that basal channels may play in simultaneous basal and surface weakening and their consequent effect on ice-shelf rifting and stability.

Electron Transport and Ion Acceleration in a Low-power Cylindrical Hall Thruster

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

A. Smirnov; Y. Raitses; N.J. Fisch

2004-06-24

Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are therefore more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been studied through the analysis of experimental data and Monte Carlo simulations of electron dynamics in the thruster channel. The numerical model takes into account elastic and inelastic electron collisions with atoms, electron-wall collisions, including secondary electron emission, and Bohm diffusion. We show that in order to explainmore » the observed discharge current, the electron anomalous collision frequency {nu}{sub B} has to be on the order of the Bohm value, {nu}{sub B} {approx} {omega}{sub c}/16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant. The plasma density peak observed at the axis of the 2.6 cm cylindrical Hall thruster is likely to be due to the convergent flux of ions, which are born in the annular part of the channel and accelerated towards the thruster axis.« less

Linking high-resolution geomorphic mapping, sediment sources, and channel types in a formerly glaciated basin of northeastern Alto-Adige/Sudtirol, Italy

NASA Astrophysics Data System (ADS)

Brardinoni, F.; Perina, E.; Bonfanti, G.; Falsitta, G.; Agliardi, F.

2012-04-01

To characterize channel-network morphodynamics and response potential in the Gadria-Strimm basin (14.8 km^2) we conduct a concerted effort entailing: (i) high-resolution mapping of landforms, channel reaches, and sediment sources; and (ii) historical evolution of colluvial channel disturbance through sequential aerial photosets (1945-59-69-82-90-00-06-11). The mapping was carried out via stereographic inspection of aerial photographs, examination of 2.5-m gridded DTM and DSM, and extensive field work. The study area is a formerly glaciated basin characterized by peculiar landform assemblages imposed by a combination of tectonic and glacial first-order structures. The most striking feature in Strimm Creek is a structurally-controlled valley step separating an upper hanging valley, dominated by periglacial and fluvial processes, and a V-notched lower part in which lateral colluvial channels are directly connected to Strimm's main stem. In Gadria Creek, massive kame terraces located in proximity of the headwaters provide virtually unlimited sediment supply to frequent debris-flow activity, making this sub-catchment an ideal site for monitoring, hence studying the mechanics of these processes. Preliminary results point to a high spatial variability of the colluvial channel network, in which sub-sectors have remained consistently active during the study period while others have become progressively dormant with notable forest re-growth. In an attempt to link sediment flux to topography and substrate type, future work will involve photogrammetric analysis across the sequential aerial photosets as well as a morphometric/geomechanical characterization of the surficial materials.

Method of bonding a conductive layer on an electrode of an electrochemical cell

DOEpatents

Bowker, J.C.; Singh, P.

1989-08-29

A dense, electronically conductive interconnection layer is bonded onto a porous, tubular, electronically conductive air electrode structure, optionally supported by a ceramic support, by (A) providing an air electrode surface, (B) forming on a selected portion of the electrode surface, without the use of pressure, particles of LaCrO[sub 3] doped with an element selected from the group consisting of Sr, Mg, Ca, Ba, Co, and mixtures thereof, where the particles have a deposit on their surface comprising calcium oxide and chromium oxide; (C) heating the particles with the oxide surface deposit in an oxidizing atmosphere at from 1,300 C to 1,550 C, without the application of pressure, to provide a dense, sintered, interconnection material bonded to the air electrode, where calcium and chromium from the surface deposit are incorporated into the structure of the LaCrO[sub 3]. A solid electrolyte layer can be applied to the uncovered portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell. 4 figs.

Method of bonding a conductive layer on an electrode of an electrochemical cell

DOEpatents

Bowker, Jeffrey C.; Singh, Prabhakar

1989-01-01

A dense, electronically conductive interconnection layer 26 is bonded onto a porous, tubular, electronically conductive air electrode structure 16, optionally supported by a ceramic support 22, by (A) providing an air electrode surface, (B) forming on a selected portion of the electrode surface 24, without the use of pressure, particles of LaCrO.sub.3 doped with an element selected from the group consisting of Sr, Mg, Ca, Ba, Co, and mixtures thereof, where the particles have a deposit on their surface comprising calcium oxide and chromium oxide; (C) heating the particles with the oxide surface deposit in an oxidizing atmosphere at from 1,300.degree. C. to 1,550.degree. C., without the application of pressure, to provide a dense, sintered, interconnection material 26 bonded to the air electrode 16, where calcium and chromium from the surface deposit are incorporated into the structure of the LaCrO.sub.3. A solid electrolyte layer 18 can be applied to the uncovered portion of the air electrode, and a fuel electrode 20 can be applied to the solid electrolyte, to provide an electrochemical cell 10.

Profound blockage of CXCR4 signaling at multiple points using the synergy between plerixafor, mirtazapine, and clotrimazole as a new glioblastoma treatment adjunct.

PubMed

Kast, Richard E

2010-10-01

CXCL12 signaling at CXCR4 is important in glioblastoma growth promotion as a migration-directing chemokine and as a mitosis-stimulating cytokine system. Recent developments in other areas of medicine may have made it now possible to comprehensively block glioblastoma's use of CXCL12 signaling. CXCL12 signaling at CXCR4 requires an active intermediate conductance Ca2+-activated K+ channel to function. Plerixafor (AMD3100) is a new small molecular weight inhibitor of CXCR4, FDA approved to aid in stem cell mobilization. Inhibition of CXCR4 by plerixafor is expected to inhibit particularly the glioblastoma stem cell population by inhibiting that sub-population's homing to the protective hypoxic niche. Histamine signals through the H1 receptor in glioblastoma cells to activate the intermediate conductance Ca2+-activated K+ channel also, thereby forming a potential bypass for inhibition of CXCR4-initiated signaling. The antidepressant mirtazapine is perhaps the most potent H1 antagonist in common clinical use. By inhibiting H1 stimulation of intermediate conductance Ca2+-activated K+ channels, it could prevent circumvention of CXCR4 inhibition by that path. The anti-fungal clotrimazole directly inhibits the intermediate conductance Ca2+- activated K+ channel at clinically achievable and well-tolerated doses. These three drugs used simultaneously are potential low morbidity paths to deeply inhibit CXCR4/CXCL12 signaling during cytotoxic glioblastoma treatment.

Effects of the β1 auxiliary subunit on modification of Rat Na{sub v}1.6 sodium channels expressed in HEK293 cells by the pyrethroid insecticides tefluthrin and deltamethrin

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

He, Bingjun; Soderlund, David M., E-mail: dms6@cornell.edu

We expressed rat Na{sub v}1.6 sodium channels with or without the rat β1 subunit in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on whole-cell sodium currents. In assays with the Na{sub v}1.6 α subunit alone, both pyrethroids prolonged channel inactivation and deactivation and shifted the voltage dependence of channel activation and steady-state inactivation toward hyperpolarization. Maximal shifts in activation were ~ 18 mV for tefluthrin and ~ 24 mV for deltamethrin. These compounds also caused hyperpolarizing shifts of ~ 10–14 mV in the voltage dependence of steady-state inactivation and increased inmore » the fraction of sodium current that was resistant to inactivation. The effects of pyrethroids on the voltage-dependent gating greatly increased the size of sodium window currents compared to unmodified channels; modified channels exhibited increased probability of spontaneous opening at membrane potentials more negative than the normal threshold for channel activation and incomplete channel inactivation. Coexpression of Na{sub v}1.6 with the β1 subunit had no effect on the kinetic behavior of pyrethroid-modified channels but had divergent effects on the voltage-dependent gating of tefluthrin- or deltamethrin-modified channels, increasing the size of tefluthrin-induced window currents but decreasing the size of corresponding deltamethrin-induced currents. Unexpectedly, the β1 subunit did not confer sensitivity to use-dependent channel modification by either tefluthrin or deltamethrin. We conclude from these results that functional reconstitution of channels in vitro requires careful attention to the subunit composition of channel complexes to ensure that channels in vitro are faithful functional and pharmacological models of channels in neurons. - Highlights: • We expressed Na{sub v}1.6 sodium channels with or without β1 subunits in HEK293 cells. • Tefluthrin and deltamethrin shifted channel gating to hyperpolarized potentials. • The β1 subunit had opposite effects on the actions of tefluthrin and deltamethrin. • Auxiliary subunits are required for full reconstitution of channel function. • Channels in HEK293 cells exhibit properties similar to channels in neurons.« less

Effect of segmented electrode length on the performances of Hall thruster

NASA Astrophysics Data System (ADS)

Duan, Ping; Chen, Long; Liu, Guangrui; Bian, Xingyu; Yin, Yan

2016-09-01

The influences of the low-emissive graphite segmented electrode placed near the channel exit on the discharge characteristics of Hall thruster are studied using the particle-in-cell method. A two-dimensional physical model is established according to the Hall thruster discharge channel configuration. The effects of electrode length on potential, ion density, electron temperature, ionization rate and discharge current are investigated. It is found that, with the increasing of segmented electrode length, the equipotential lines bend towards the channel exit, and approximately parallel to the wall at the channel surface, radial velocity and radial flow of ions are increased, and the electron temperature is also enhanced. Due to the conductive characteristic of electrodes, the radial electric field and the axial electron conductivity near the wall are enhanced, and the probability of the electron-atom ionization is reduced, which leads to the degradation of ionization rate in discharge channel. However, the interaction between electrons and the wall enhances the near wall conductivity, therefore the discharge current grows along with the segmented electrode length, and the performance of the thruster is also affected.

Cross-flow electrochemical reactor cells, cross-flow reactors, and use of cross-flow reactors for oxidation reactions

DOEpatents

Balachandran, Uthamalingam; Poeppel, Roger B.; Kleefisch, Mark S.; Kobylinski, Thaddeus P.; Udovich, Carl A.

1994-01-01

This invention discloses cross-flow electrochemical reactor cells containing oxygen permeable materials which have both electron conductivity and oxygen ion conductivity, cross-flow reactors, and electrochemical processes using cross-flow reactor cells having oxygen permeable monolithic cores to control and facilitate transport of oxygen from an oxygen-containing gas stream to oxidation reactions of organic compounds in another gas stream. These cross-flow electrochemical reactors comprise a hollow ceramic blade positioned across a gas stream flow or a stack of crossed hollow ceramic blades containing a channel or channels for flow of gas streams. Each channel has at least one channel wall disposed between a channel and a portion of an outer surface of the ceramic blade, or a common wall with adjacent blades in a stack comprising a gas-impervious mixed metal oxide material of a perovskite structure having electron conductivity and oxygen ion conductivity. The invention includes reactors comprising first and second zones seprated by gas-impervious mixed metal oxide material material having electron conductivity and oxygen ion conductivity. Prefered gas-impervious materials comprise at least one mixed metal oxide having a perovskite structure or perovskite-like structure. The invention includes, also, oxidation processes controlled by using these electrochemical reactors, and these reactions do not require an external source of electrical potential or any external electric circuit for oxidation to proceed.

Effect of band filling on anomalous Hall conductivity and magneto-crystalline anisotropy in NiFe epitaxial thin films

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

Shi, Zhong; Jiang, Hang-Yu; Zhou, Shi-Ming, E-mail: shiming@tongji.edu.cn

2016-01-15

The anomalous Hall effect (AHE) and magneto-crystalline anisotropy (MCA) are investigated in epitaxial Ni{sub x}Fe{sub 1−x} thin films grown on MgO (001) substrates. The scattering independent term b of anomalous Hall conductivity shows obvious correlation with cubic magneto-crystalline anisotropy K{sub 1}. When nickel content x decreasing, both b and K{sub 1} vary continuously from negative to positive, changing sign at about x = 0.85. Ab initio calculations indicate Ni{sub x}Fe{sub 1−x} has more abundant band structures than pure Ni due to the tuning of valence electrons (band fillings), resulting in the increased b and K{sub 1}. This remarkable correlation betweenmore » b and K{sub 1} can be attributed to the effect of band filling near the Fermi surface.« less

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

Tong Dongge; Han Xue; Chu Wei

Co-B flowers with mesoporous structure were first prepared via reduction of cobalt acetate by potassium borohydride in the presence of complexing agent ethylenediamine. The as-prepared Co-B flowers were characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, N{sub 2} adsorption-desorption, and magnetic performance test. The Co-B flowers exhibited enhanced coercivity, and weakened saturation magnetization and remanet magnetization as compared with the regular Co-B. During the hydrolysis of KBH{sub 4}, the Co-B flowers exhibited higher catalytic activity than the regular Co-B. It is attributed to themore » larger specific surface area and mesoporous channels. During the successive reactions, the conversion of KBH{sub 4} over Co-B flowers was about 97%. The average H{sub 2} generation rate of Co-B flowers was 4620 mL/min/g-catalyst in 1.5 wt% NaOH + 15 wt% KBH{sub 4} solution, which may give a successive H{sub 2} supply for a 748 W polymer electrolyte membrane fuel cell (PEMFC) at 100% H{sub 2} utilization.« less

VizieR Online Data Catalog: Ultra-compact HII regions & methanol masers. I. (Hu+, 2016)

NASA Astrophysics Data System (ADS)

Hu, B.; Menten, K. M.; Wu, Y.; Bartkiewicz, A.; Rygl, K.; Reid, M. J.; Urquhart, J. S.; Zheng, X.

2017-03-01

372 unique targets were selected from the following methanol maser surveys: the Methanol Multi-Beam catalog (MMB; Caswell & Breen 2010MNRAS.407.2599C; Green+ 2010-2012, VIII/96), the Arecibo Methanol Maser Galactic Plane Survey (AMGPS; Pandian+ 2011ApJ...730...55P), the Torun catalog of 6.7GHz methanol masers (Szymczak+ 2012, J/AN/333/634), and other individual observations of known 6.7GHz methanol masers or MSFRs (Caswell+ 1995MNRAS.272...96C; Walsh+ 1997, J/MNRAS/291/261; 1998, J/MNRAS/301/640; Xu+ 2008A&A...485..729X; Caswell 2009, J/other/PASA/26.454). The observations were conducted with the VLA in C-configuration using five sessions from 2012 February 28 to April 16. Spectral line data used 2048 channels across 8MHz, yielding a channel spacing of 3.90625kHz at the central frequency of 6.6685192GHz and a velocity resolution of 0.176km/s. The continuum observations employed two 1GHz sub-bands from 4.9840 to 6.0080GHz (the low band) and from 6.6245 to 7.6485GHz (the high band) and each sub-band was divided into 16 channels. (4 data files).

An Adaptive OFDMA-Based MAC Protocol for Underwater Acoustic Wireless Sensor Networks

PubMed Central

Khalil, Issa M.; Gadallah, Yasser; Hayajneh, Mohammad; Khreishah, Abdallah

2012-01-01

Underwater acoustic wireless sensor networks (UAWSNs) have many applications across various civilian and military domains. However, they suffer from the limited available bandwidth of acoustic signals and harsh underwater conditions. In this work, we present an Orthogonal Frequency Division Multiple Access (OFDMA)-based Media Access Control (MAC) protocol that is configurable to suit the operating requirements of the underwater sensor network. The protocol has three modes of operation, namely random, equal opportunity and energy-conscious modes of operation. Our MAC design approach exploits the multi-path characteristics of a fading acoustic channel to convert it into parallel independent acoustic sub-channels that undergo flat fading. Communication between node pairs within the network is done using subsets of these sub-channels, depending on the configurations of the active mode of operation. Thus, the available limited bandwidth gets fully utilized while completely avoiding interference. We derive the mathematical model for optimal power loading and subcarrier selection, which is used as basis for all modes of operation of the protocol. We also conduct many simulation experiments to evaluate and compare our protocol with other Code Division Multiple Access (CDMA)-based MAC protocols. PMID:23012517

An adaptive OFDMA-based MAC protocol for underwater acoustic wireless sensor networks.

PubMed

Khalil, Issa M; Gadallah, Yasser; Hayajneh, Mohammad; Khreishah, Abdallah

2012-01-01

Underwater acoustic wireless sensor networks (UAWSNs) have many applications across various civilian and military domains. However, they suffer from the limited available bandwidth of acoustic signals and harsh underwater conditions. In this work, we present an Orthogonal Frequency Division Multiple Access (OFDMA)-based Media Access Control (MAC) protocol that is configurable to suit the operating requirements of the underwater sensor network. The protocol has three modes of operation, namely random, equal opportunity and energy-conscious modes of operation. Our MAC design approach exploits the multi-path characteristics of a fading acoustic channel to convert it into parallel independent acoustic sub-channels that undergo flat fading. Communication between node pairs within the network is done using subsets of these sub-channels, depending on the configurations of the active mode of operation. Thus, the available limited bandwidth gets fully utilized while completely avoiding interference. We derive the mathematical model for optimal power loading and subcarrier selection, which is used as basis for all modes of operation of the protocol. We also conduct many simulation experiments to evaluate and compare our protocol with other Code Division Multiple Access (CDMA)-based MAC protocols.

Plasma treatments of wool fiber surface for microfluidic applications

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

Jeon, So-Hyoun; Hwang, Ki-Hwan; Lee, Jin Su

Highlights: • We used atmospheric plasma for tuning the wettability of wool fibers. • The wicking rates of the wool fibers increased with increasing treatment time. • The increasing of wettability results in removement of fatty acid on the wool surface. - Abstract: Recent progress in health diagnostics has led to the development of simple and inexpensive systems. Thread-based microfluidic devices allow for portable and inexpensive field-based technologies enabling medical diagnostics, environmental monitoring, and food safety analysis. However, controlling the flow rate of wool thread, which is a very important part of thread-based microfluidic devices, is quite difficult. For thismore » reason, we focused on thread-based microfluidics in the study. We developed a method of changing the wettability of hydrophobic thread, including wool thread. Thus, using natural wool thread as a channel, we demonstrate herein that the manipulation of the liquid flow, such as micro selecting and micro mixing, can be achieved by applying plasma treatment to wool thread. In addition to enabling the flow control of the treated wool channels consisting of all natural substances, this procedure will also be beneficial for biological sensing devices. We found that wools treated with various gases have different flow rates. We used an atmospheric plasma with O{sub 2}, N{sub 2} and Ar gases.« less

Note: A dual-channel sensor for dew point measurement based on quartz crystal microbalance.

PubMed

Li, Ning; Meng, Xiaofeng; Nie, Jing

2017-05-01

A new sensor with dual-channel was designed for eliminating the temperature effect on the frequency measurement of the quartz crystal microbalance (QCM) in dew point detection. The sensor uses active temperature control, produces condensation on the surface of QCM, and then detects the dew point. Both the single-channel and the dual-channel methods were conducted based on the device. The measurement error of the single-channel method was less than 0.5 °C at the dew point range of -2 °C-10 °C while the dual-channel was 0.3 °C. The results showed that the dual-channel method was able to eliminate the temperature effect and yield better measurement accuracy.

Note: A dual-channel sensor for dew point measurement based on quartz crystal microbalance

NASA Astrophysics Data System (ADS)

Li, Ning; Meng, Xiaofeng; Nie, Jing

2017-05-01

A new sensor with dual-channel was designed for eliminating the temperature effect on the frequency measurement of the quartz crystal microbalance (QCM) in dew point detection. The sensor uses active temperature control, produces condensation on the surface of QCM, and then detects the dew point. Both the single-channel and the dual-channel methods were conducted based on the device. The measurement error of the single-channel method was less than 0.5 °C at the dew point range of -2 °C-10 °C while the dual-channel was 0.3 °C. The results showed that the dual-channel method was able to eliminate the temperature effect and yield better measurement accuracy.

{omega} meson production in pp collisions with a polarized beam

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

Balasubramanyam, J.; Venkataraya,; Ramachandran, G.

2008-07-15

Model independent formulas are derived for the beam analyzing power A{sub y} and beam to meson spin transfers in pp{yields}pp{omega}, taking into consideration all six threshold partial wave amplitudes f{sub 1},...,f{sub 6} covering the Ss, Sp, and Ps channels. It is shown that the lowest three partial wave amplitudes f{sub 1},f{sub 2},f{sub 3} can be determined empirically without any discrete ambiguities. Partial information with regard to the amplitudes f{sub 4},f{sub 5},f{sub 6} covering the Ps channel may be extracted, if the measurements are carried through at the double differential level.

α-Actinin Promotes Surface Localization and Current Density of the Ca2+ Channel CaV1.2 by Binding to the IQ Region of the α1 Subunit.

PubMed

Tseng, Pang-Yen; Henderson, Peter B; Hergarden, Anne C; Patriarchi, Tommaso; Coleman, Andrea M; Lillya, Mark W; Montagut-Bordas, Carlota; Lee, Boram; Hell, Johannes W; Horne, Mary C

2017-07-18

The voltage-gated L-type Ca 2+ channel Ca V 1.2 is crucial for initiating heartbeat and control of a number of neuronal functions such as neuronal excitability and long-term potentiation. Mutations of Ca V 1.2 subunits result in serious health problems, including arrhythmia, autism spectrum disorders, immunodeficiency, and hypoglycemia. Thus, precise control of Ca V 1.2 surface expression and localization is essential. We previously reported that α-actinin associates and colocalizes with neuronal Ca V 1.2 channels and that shRNA-mediated depletion of α-actinin significantly reduces localization of endogenous Ca V 1.2 in dendritic spines in hippocampal neurons. Here we investigated the hypothesis that direct binding of α-actinin to Ca V 1.2 supports its surface expression. Using two-hybrid screens and pull-down assays, we identified three point mutations (K1647A, Y1649A, and I1654A) in the central, pore-forming α 1 1.2 subunit of Ca V 1.2 that individually impaired α-actinin binding. Surface biotinylation and flow cytometry assays revealed that Ca V 1.2 channels composed of the corresponding α-actinin-binding-deficient mutants result in a 35-40% reduction in surface expression compared to that of wild-type channels. Moreover, the mutant Ca V 1.2 channels expressed in HEK293 cells exhibit a 60-75% decrease in current density. The larger decrease in current density as compared to surface expression imparted by these α 1 1.2 subunit mutations hints at the possibility that α-actinin not only stabilizes surface localization of Ca V 1.2 but also augments its ion conducting activity.

An Investigation Into the Ecohydrology of Riparian Wetlands Along the Gila River, NM, USA

NASA Astrophysics Data System (ADS)

Samson, J.; Stone, M. C.

2013-12-01

The dynamism of the Gila River, in southwestern New Mexico, USA, has resulted in the creation of a topographically diverse floodplain that supports an array of riparian wetlands. The purpose of this study is to investigate the ecohydrologic and ecohydraulic processes of two of these wetlands, in order to predict their potential response to anthropogenic or natural changes in hydrology. One represents a natural wetland and the other a wetland that exists only as a result of an anthropogenic modification to the river system. A network of 30 wells and 2 weather stations were installed in early 2013 to provide a high resolution of data on surface water and ground water hydrologic conditions. Phreatic surface contour maps were produced to aid in the visualization of sub-surface gradients. Based on these results, an electrical resistivity investigation was conducted to identify paleoflow channels as well as depth to bedrock and other potential areas of interest. These data formed the development of three dimensional ModFlow models that were used to investigate potential future stream flow scenarios on wetland hydrology. The model outputs are being used in tandem with the results of quarterly ecological surveys on vegetation, algae, benthic, and bird communities, to make predictions of potential changes in community structure and function.

Degradation of Adenine on the Martian Surface in the Presence of Perchlorates and Ionizing Radiation: A Reflectron Time-of-flight Mass Spectrometric Study

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

Góbi, Sándor; Bergantini, Alexandre; Kaiser, Ralf I., E-mail: ralfk@hawaii.edu

The aim of the present work is to unravel the radiolytic decomposition of adenine (C{sub 5}H{sub 5}N{sub 5}) under conditions relevant to the Martian surface. Being the fundamental building block of (deoxy)ribonucleic acids, the possibility of survival of this biomolecule on the Martian surface is of primary importance to the astrobiology community. Here, neat adenine and adenine–magnesium perchlorate mixtures were prepared and irradiated with energetic electrons that simulate the secondary electrons originating from the interaction of the galactic cosmic rays with the Martian surface. Perchlorates were added to the samples since they are abundant—and therefore relevant oxidizers on the surfacemore » of Mars—and they have been previously shown to facilitate the radiolysis of organics such as glycine. The degradation of the samples were monitored in situ via Fourier transformation infrared spectroscopy and the electron ionization quadruple mass spectrometric method; temperature-programmed desorption profiles were then collected by means of the state-of-the-art single photon photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS), allowing for the detection of the species subliming from the sample. The results showed that perchlorates do increase the destruction rate of adenine by opening alternative reaction channels, including the concurrent radiolysis/oxidation of the sample. This new pathway provides a plethora of different radiolysis products that were identified for the first time. These are carbon dioxide (CO{sub 2}), isocyanic acid (HNCO), isocyanate (OCN{sup −}), carbon monoxide (CO), and nitrogen monoxide (NO); an oxidation product containing carbonyl groups (R{sub 1}R{sub 2}–C=O) with a constrained five-membered cyclic structure could also be observed. Cyanamide (H{sub 2}N–C≡N) was detected in both irradiated samples as well.« less

Study on GaN buffer leakage current in AlGaN/GaN high electron mobility transistor structures grown by ammonia-molecular beam epitaxy on 100-mm Si(111)

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

Ravikiran, L.; Radhakrishnan, K., E-mail: ERADHA@e.ntu.edu.sg; Ng, G. I.

2015-06-28

The effect of carbon doping on the structural and electrical properties of GaN buffer layer of AlGaN/GaN high electron mobility transistor (HEMT) structures has been studied. In the undoped HEMT structures, oxygen was identified as the dominant impurity using secondary ion mass spectroscopy and photoluminescence (PL) measurements. In addition, a notable parallel conduction channel was identified in the GaN buffer at the interface. The AlGaN/GaN HEMT structures with carbon doped GaN buffer using a CBr{sub 4} beam equivalent pressure of 1.86 × 10{sup −7} mTorr showed a reduction in the buffer leakage current by two orders of magnitude. Carbon doped GaN buffersmore » also exhibited a slight increase in the crystalline tilt with some pits on the growth surface. PL and Raman measurements indicated only a partial compensation of donor states with carbon acceptors. However, AlGaN/GaN HEMT structures with carbon doped GaN buffer with 200 nm thick undoped GaN near the channel exhibited good 2DEG characteristics.« less

The structural properties of Zr-based bulk metallic glasses subjected to high pressure torsion at different temperatures

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

Boltynjuk, E. V., E-mail: boltynjuk@gmail.com; Ubyivovk, E. V.; Kshumanev, A. M.

2016-06-17

The structural properties of a Zr{sub 62}Cu{sub 22}Al{sub 10}Fe{sub 5}Dy{sub 1} bulk metallic glasses were investigated. Cylindrical rods of the Zr{sub 62}Cu{sub 22}Al{sub 10}Fe{sub 5}Dy{sub 1} BMG were subjected to high pressure torsion at temperatures of 20°C and 150°C. X-ray diffraction, transmission electron microscopy were used to determine peculiarities of the modified structure. Analysis of fracture surfaces, nanohardness measurements were conducted to investigate the influence of structural changes on mechanical behavior of processed samples.

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

Yin Yunpeng; Sawin, Herbert H.

The impact of etching kinetics and etching chemistries on surface roughening was investigated by etching thermal silicon dioxide and low-k dielectric coral materials in C{sub 4}F{sub 8}/Ar plasma beams in an inductive coupled plasma beam reactor. The etching kinetics, especially the angular etching yield curves, were measured by changing the plasma pressure and the feed gas composition which influence the effective neutral-to-ion flux ratio during etching. At low neutral-to-ion flux ratios, the angular etching yield curves are sputteringlike, with a peak around 60 deg. -70 deg. off-normal angles; the surface at grazing ion incidence angles becomes roughened due to ionmore » scattering related ion-channeling effects. At high neutral-to-ion flux ratios, ion enhanced etching dominates and surface roughening at grazing angles is mainly caused by the local fluorocarbon deposition induced micromasking mechanism. Interestingly, the etched surfaces at grazing angles remain smooth for both films at intermediate neutral-to-ion flux ratio regime. Furthermore, the oxygen addition broadens the region over which the etching without roughening can be performed.« less

Integration of sub-wavelength nanofluidics on suspended photonic crystal sensors

NASA Astrophysics Data System (ADS)

Huang, Min; Yanik, Ahmet Ali; Chang, Tsung-Yao; Altug, Hatice

2010-08-01

In this paper, we introduce a novel sensor scheme which merges nano-photonics and nano-fluidics on a single platform through the use of free-standing photonic crystals (PhCs). PhCs offer great freedom to manipulate the spatial extent and the spectral characteristics of the electromagnetic fields. Also, nanoholes in PhCs provide a natural platform to transport solutions. By harnessing these nano-scale openings, we theoretically and experimentally demonstrate that both fluidics and light can be manipulated at sub-wavelength scales. In this scheme, the free standing PhCs are sealed in a chamber such that only the nano-scale hole arrays enable the flow between the top and the bottom channels. The nanohole arrays are used as sensing structures as well as nanofluidic channels. Compared to the conventional fluidic channels, we can actively steer the convective flow through the nanohole openings for effective delivery of the analytes to the sensor surface. This scheme also helps to overcome the surface tension of highly viscous solution and guarantees that the sensor can be totally immersed in solution. We apply this method to detect refractive index changes in aqueous solutions. Bulk measurements indicate that active delivery of the convective flow results in better performance. The sensitivity of the sensor reaches 510 nm/RIU for resonance located around 850 nm with a line-width of {10 nm in solution. Experimental results are matched very well with numerical simulations. We also show that cross-polarization measurements can be employed to further improve the detection limit by increasing the signal-to-noise ratio.

Alternative splice isoforms of small conductance calcium-activated SK2 channels differ in molecular interactions and surface levels

PubMed Central

Scholl, Elizabeth Storer; Pirone, Antonella; Cox, Daniel H; Duncan, R Keith; Jacob, Michele H

2014-01-01

Small conductance Ca2+-sensitive potassium (SK2) channels are voltage-independent, Ca2+-activated ion channels that conduct potassium cations and thereby modulate the intrinsic excitability and synaptic transmission of neurons and sensory hair cells. In the cochlea, SK2 channels are functionally coupled to the highly Ca2+ permeant α9/10-nicotinic acetylcholine receptors (nAChRs) at olivocochlear postsynaptic sites. SK2 activation leads to outer hair cell hyperpolarization and frequency-selective suppression of afferent sound transmission. These inhibitory responses are essential for normal regulation of sound sensitivity, frequency selectivity, and suppression of background noise. However, little is known about the molecular interactions of these key functional channels. Here we show that SK2 channels co-precipitate with α9/10-nAChRs and with the actin-binding protein α-actinin-1. SK2 alternative splicing, resulting in a 3 amino acid insertion in the intracellular 3′ terminus, modulates these interactions. Further, relative abundance of the SK2 splice variants changes during developmental stages of synapse maturation in both the avian cochlea and the mammalian forebrain. Using heterologous cell expression to separately study the 2 distinct isoforms, we show that the variants differ in protein interactions and surface expression levels, and that Ca2+ and Ca2+-bound calmodulin differentially regulate their protein interactions. Our findings suggest that the SK2 isoforms may be distinctly modulated by activity-induced Ca2+ influx. Alternative splicing of SK2 may serve as a novel mechanism to differentially regulate the maturation and function of olivocochlear and neuronal synapses. PMID:24394769

Enhanced H{sub 2} sensing by substituting polyaniline nanoparticles with nanofibers

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

Sharma, Preetam K., E-mail: preetam.nano@gmail.com; Srivastava, Subodh, E-mail: preetam.nano@gmail.com; Singh, M.

2014-04-24

We have synthesized Polyaniline nanoparticles and nanofibers using chemical oxidation method and tested them for their Hydrogen sensing properties. PANI nanoparticles and nanofibers have demonstrated sensor response of 1.38 and 1.52, respectively. Reaction kinetics has also enhanced in case of PANI nanofibers with response and recovery times of 170 and 95 s, respectively. The increased conductivity, sensor response and reaction kinetics in case of the nanofibers as compared to nanoparticles is attributed to the 1-D conductive channel provided by the nanofibers for faster and better electron transfer.

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

He Liang; Xiu Faxian; Huang Guan

In this paper, we report the epitaxial growth of Bi{sub 2}Se{sub 3} thin films on Si (111) substrate, using molecular beam epitaxy (MBE). We show that the as-grown samples have good crystalline quality, and their surfaces exhibit terracelike quintuple layers. Angel-resolved photoemission experiments demonstrate single-Dirac-conelike surface states. These results combined with the temperature- and thickness-dependent magneto-transport measurements, suggest the presence of a shallow impurity band. Below a critical temperature of {approx}100K, the surface states of a 7 nm thick film contribute up to 50% of the total conduction.

Activation of calcium-sensing receptor increases TRPC3 expression in rat cardiomyocytes

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

Feng, Shan-Li; Sun, Ming-Rui; Li, Ting-Ting

Research highlights: {yields} Calcium-sensing receptor (CaR) activation stimulates TRP channels. {yields} CaR promoted transient receptor potential C3 (TRPC3) expression. {yields} Adult rat ventricular myocytes display capacitative calcium entry (CCE), which was operated by TRPCs. {yields} TRPC channels activation induced by CaR activator sustained the increased [Ca{sup 2+}]{sub i} to evoke cardiomyocytes apoptosis. -- Abstract: Transient receptor potential (TRP) channels are expressed in cardiomyocytes, which gate a type of influx of extracellular calcium, the capacitative calcium entry. TRP channels play a role in mediating Ca{sup 2+} overload in the heart. Calcium-sensing receptors (CaR) are also expressed in rat cardiac tissue andmore » promote the apoptosis of cardiomyocytes by Ca{sup 2+} overload. However, data about the link between CaR and TRP channels in rat heart are few. In this study, reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting were used to examine the expression of the TRP canonical proteins TRPC1 and TRPC3 in adult and neonatal rat cardiomyocytes. Laser scan confocal microscopy was used to detect intracellular [Ca{sup 2+}]{sub i} levels in isolated adult rat ventricular myocytes. The results showed that, in adult rat cardiomyocytes, the depletion of Ca{sup 2+} stores in the endoplasmic/sarcoplasmic reticulum (ER/SR) by thapsigargin induced a transient increase in [Ca{sup 2+}]{sub i} in the absence of [Ca{sup 2+}]{sub o} and the subsequent restoration of [Ca{sup 2+}]{sub o} sustained the increased [Ca{sup 2+}]{sub i} for a few minutes, whereas, the persisting elevation of [Ca{sup 2+}]{sub i} was reduced in the presence of the TRPC inhibitor SKF96365. The stimulation of CaR by its activator gadolinium chloride (GdCl{sub 3}) or spermine also resulted in the same effect and the duration of [Ca{sup 2+}]{sub i} increase was also shortened in the absence of [Ca{sup 2+}]{sub o}. In adult and neonatal rat cardiomyocytes, GdCl{sub 3} increased the expression of TRPC3 mRNA and protein, which were reversed by SKF96365 but not by inhibitors of the L-type channels and the Na{sup +}/Ca{sup 2+} exchangers. However, GdCl{sub 3} had no obvious effect on the expression of TRPC1 protein. These results suggested that CaR stimulation induced activation of TRP channels and promoted the expression of TRPC3, but not TRPC1, that sustained the increased [Ca{sup 2+}]{sub i}.« less

Validation of HF Radar ocean surface currents in the Ibiza Channel using lagrangian drifters, moored current meter and underwater gliders

NASA Astrophysics Data System (ADS)

Lana, Arancha; Fernández, Vicente; Orfila, Alejandro; Troupin, Charles; Tintoré, Joaquín

2015-04-01

SOCIB High Frequency (HF) radar is one component of a multi-platform system located in the Balearic Islands and made up of Lagrangian platforms (profilers and drifting buoys), fixed stations (sea-level, weather, mooring and coastal), beach monitoring (camera), gliders, a research vessel as well as an ocean forecast system (waves and hydrodynamics). The HF radar system overlooks the Ibiza Channel, known as a 'choke point" where Atlantic and Mediterranean water masses interact and where meridional exchanges of water mass properties between the Balearic and the Algerian sub-basins take place. In order to determine the reliability of surface velocity measurements in this area, a quality assessment of the HF Radar is essential. We present the results of several validation experiments performed in the Ibiza Channel in 2013 and 2014. Of particular interest is an experiment started in September 2014 when a set of 13 surface drifters with different shapes and drogue lengths were released in the area covered by the HF radar. The drifter trajectories can be examined following the SOCIB Deployment Application (DAPP): http://apps.socib.es/dapp. Additionally, a 1-year long time series of surface currents obtained from a moored surface current-meter located in the Ibiza Channel, inside the area covered by the HF radar, was also used as a useful complementary validation exercise. Direct comparison between both radial surface currents from each radar station and total derived velocities against drifters and moored current meter velocities provides an assessment of the HF radar data quality at different temporal periods and geographical areas. Statistics from these comparisons give good correlation and low root-mean-square deviation. The results will be discussed for different months, geographical areas and types of surface drifters and wind exposure. Moreover, autonomous underwater glider constitutes an additional source of information for the validation of the observed velocity structures and some statistics will be presented.

Size effects in the thermal conductivity of gallium oxide (β-Ga{sub 2}O{sub 3}) films grown via open-atmosphere annealing of gallium nitride

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

Szwejkowski, Chester J.; Giri, Ashutosh; Donovan, Brian F.

2015-02-28

Gallium nitride (GaN) is a widely used semiconductor for high frequency and high power devices due to of its unique electrical properties: a wide band gap, high breakdown field, and high electron mobility. However, thermal management has become a limiting factor regarding efficiency, lifetime, and advancement of GaN devices and GaN-based applications. In this work, we study the thermal conductivity of beta-phase gallium oxide (β-Ga{sub 2}O{sub 3}) thin films, a component of typical gate oxides used in such devices. We use time domain thermoreflectance to measure the thermal conductivity of a variety of polycrystalline β-Ga{sub 2}O{sub 3} films of differentmore » thicknesses grown via open atmosphere annealing of the surfaces of GaN films on sapphire substrates. We show that the measured effective thermal conductivity of these β-Ga{sub 2}O{sub 3} films can span 1.5 orders of magnitude, increasing with an increased film thickness, which is indicative of the relatively large intrinsic thermal conductivity of the β-Ga{sub 2}O{sub 3} grown via this technique (8.8 ± 3.4 W m{sup −1} K{sup −1}) and large mean free paths compared to typical gate dielectrics commonly used in GaN device contacts. By conducting time domain thermoreflectance (TDTR) measurements with different metal transducers (Al, Au, and Au with a Ti wetting layer), we attribute this variation in effective thermal conductivity to a combination of size effects in the β-Ga{sub 2}O{sub 3} film resulting from phonon scattering at the β-Ga{sub 2}O{sub 3}/GaN interface and thermal transport across the β-Ga{sub 2}O{sub 3}/GaN interface. The measured thermal properties of open atmosphere-grown β-Ga{sub 2}O{sub 3} and its interface with GaN set the stage for thermal engineering of gate contacts in high frequency GaN-based devices.« less

Controlled preparation of Ag–Cu{sub 2}O nanocorncobs and their enhanced photocatalytic activity under visible light

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

Yang, Siyuan; Zhang, Shengsen; College of Science, South China Agricultural University, Guangzhou 510642

Graphical abstract: The corncob-like Ag–Cu{sub 2}O nanostructure with suitably exposed Ag surface exhibited much higher photocatalytic activity than Ag@Cu{sub 2}O nanocables and Cu{sub 2}O nanowires. - Highlights: • Ag–Cu{sub 2}O nanocorncobs have been controllably prepared by a simple synthesis. • The possible formation mechanism of Ag–Cu{sub 2}O has been studied. • Ag–Cu{sub 2}O exhibits noticeable improved photocurrent compared with the pure Cu{sub 2}O NWs. • Ag–Cu{sub 2}O with suitably exposed Ag surface shows much higher photocatalytic activity. - Abstract: Novel corncob-like nano-heterostructured Ag–Cu{sub 2}O photocatalyst has been controllably prepared by adjusting the synthetic parameters, and the possible formation mechanism hasmore » been also studied. The photoelectrochemical and photocatalytic performances demonstrated that the as-prepared Ag–Cu{sub 2}O nanocorncobs exhibited higher photocatalytic activity than both pure Cu{sub 2}O nanowires and cable-like Ag@Cu{sub 2}O nano-composites. It was concluded that Ag–Cu{sub 2}O nanocorncobs with suitably exposed Ag surface not only effectively inhibit the recombination of electron–hole pairs but also suitably increase the active sites of electronic conduction, and thus increasing the photocatalytic activity under visible light irradiation.« less

Active tectonic deformation along rejuvenated faults in tropical Borneo: Inferences obtained from tectono-geomorphic evaluation

NASA Astrophysics Data System (ADS)

Mathew, Manoj Joseph; Menier, David; Siddiqui, Numair; Kumar, Shashi Gaurav; Authemayou, Christine

2016-08-01

The island of Borneo is enveloped by tropical rainforests and hostile terrain characterized by high denudation rates. Owing to such conditions, studies pertaining to neotectonics and consequent geomorphic expressions with regard to surface processes and landscape evolution are inadequately constrained. Here we demonstrate the first systematic tectono-geomorphic evaluation of north Borneo through quantitative and qualitative morphotectonic analysis at sub-catchment scale, for two large drainage basins located in Sarawak: the Rajang and Baram basins. The extraction of morphometric parameters utilizing digital elevation models arranged within a GIS environment focuses on hypsometric curve analysis, distribution of hypsometric integrals through spatial autocorrelation statistics, relative uplift values, the asymmetry factor and the normalized channel steepness index. Hypsometric analysis suggests a young topography adjusting to changes in tectonic boundary conditions. Autocorrelation statistics show clusters of high values of hypsometric integrals as prominent hotspots that are associated with less eroded, young topography situated in the fold and thrust belts of the Interior Highlands of Borneo. High channel steepness and gradients (> 200 m0.9) are observed in zones corresponding to the hotspots. Relative uplift values reveal the presence of tectonically uplifted blocks together with relatively subsided or lesser uplifted zones along known faults. Sub-catchments of both basins display asymmetry indicating tectonic tilting. Stream longitudinal profiles demonstrate the presence of anomalies in the form of knickzones without apparent lithological controls along their channel reaches. Surfaces represented by cold spots of low HI values and low channel gradients observed in the high elevation headwaters of both basins are linked to isolated erosional planation surfaces that could be remnants of piracy processes. The implication of our results is that Borneo experiences active folding of the Rajang Group fold-thrust belt to present and these events reactivated old major faults and minor related dislocations. From geomorphic analysis associated with sedimentary record, we posit that the terrain could have undergone high uplift rates since 5 Ma or multi-phased uplift with periodic intermittent pulses of high and low uplift rates.

Design considerations and emerging challenges for nanotube-, nanowire-, and negative capacitor-field effect transistors

NASA Astrophysics Data System (ADS)

Wahab, Md. Abdul

As the era of classical planar metal-oxide-semiconductor field-effect transistors (MOSFETs) comes to an end, the semiconductor industry is beginning to adopt 3D device architectures, such as FinFETs, starting at the 22 nm technology node. Since physical limits such as short channel effect (SCE) and self-heating may dominate, it may be difficult to scale Si FinFET below 10 nm. In this regard, transistors with different materials, geometries, or operating principles may help. For example, gate has excellent electrostatic control over 2D thin film channel with planar geometry, and 1D nanowire (NW) channel with gate-all-around (GAA) geometry to reduce SCE. High carrier mobility of single wall carbon nanotube (SWNT) or III-V channels may reduce VDD to reduce power consumption. Therefore, as channel of transistor, 2D thin film of array SWNTs and 1D III-V multi NWs are promising for sub 10 nm technology nodes. In this thesis, we analyze the potential of these transistors from process, performance, and reliability perspectives. For SWNT FETs, we discuss a set of challenges (such as how to (i) characterize diameter distribution, (ii) remove metallic (m)-SWNTs, and (iii) avoid electrostatic cross-talk among the neighboring SWNTs), and demonstrate solution strategies both theoretically and experimentally. Regarding self-heating in these new class of devices (SWNT FET and GAA NW FET including state-of-the-art FinFET), higher thermal resistance from poor thermal conducting oxides results significant temperature rise, and reduces the IC life-time. For GAA NW FETs, we discuss accurate self-heating evaluation with good spatial, temporal, and thermal resolutions. The introduction of negative capacitor (NC), as gate dielectric stack of transistor, allows sub 60 mV/dec operation to reduce power consumption significantly. Taken together, our work provides a comprehensive perspective regarding the challenges and opportunities of sub 10 nm technology nodes.

COMPONENTS OF SURFACE AND SUBSURFACE CONNECTIVITY IN A LARGE OREGON (USA) RIVER--WHAT CAN BE RESTORED?

EPA Science Inventory

We conducted research on the Willamette River in western Oregon (USA) to determine the ecological functions of off-channel habitats (OCH). OCHs have declined in our 70 km study reach of the active floodplain since European settlement. Surface and subsurface connectivity between...

76 FR 21857 - Endangered and Threatened Species; Take of Anadromous Fish

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-19

... permit to conduct research for scientific purposes from the United Water Conservation District (United... altered channel with a dynamic groundwater and surface water interchange, and (2) evaluate the effects of increased water temperature during surface flow loss and how this affects migration rates of smolts and the...

Water quality of a coastal Louisiana swamp and how dredging is undermining restoration efforts

NASA Astrophysics Data System (ADS)

Lane, Robert R.; Huang, Haosheng; Day, John W.; Justic, Dubravko; DeLaune, Ronald D.

2015-01-01

The Bayou Boeuf Basin (BBB), a sub-basin of the Barataria Basin estuary in coastal Louisiana, consists of forested and floating wetlands receiving drainage from surrounding agricultural fields and urban watersheds. We characterized surface water quality in the BBB, and determined through hydrologic modeling if a series of levee breaks along major drainage channels would significantly improve water quality by allowing flow into surrounding wetlands. Surface water monitoring found surrounding sugarcane farm fields to be major sources of nutrient and sediment loading. Hydrological modeling indicated that levee breaks would increase N reduction from the current 21.4% to only 29.2%, which is much lower than the anticipated 90-100% removal rate. This was due to several factors, one them being dredging of main drainage channels to such a degree that water levels do not rise much above the surrounding wetland elevation even during severe storms, so only a very small fraction of the stormwater carried in the channel is exposed to wetlands. These unexpected results provide insight into an undoubtedly pervasive problem in human dominated wetland systems; that of decreased flooding during storm events due to channel deepening by dredging activities. Additional water quality management practices should be implemented at the farm field level, prior to water entering major drainage canals.

Evaluation of HFIR LEU Fuel Using the COMSOL Multiphysics Platform

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

Primm, Trent; Ruggles, Arthur; Freels, James D

2009-03-01

A finite element computational approach to simulation of the High Flux Isotope Reactor (HFIR) Core Thermal-Fluid behavior is developed. These models were developed to facilitate design of a low enriched core for the HFIR, which will have different axial and radial flux profiles from the current HEU core and thus will require fuel and poison load optimization. This report outlines a stepwise implementation of this modeling approach using the commercial finite element code, COMSOL, with initial assessment of fuel, poison and clad conduction modeling capability, followed by assessment of mating of the fuel conduction models to a one dimensional fluidmore » model typical of legacy simulation techniques for the HFIR core. The model is then extended to fully couple 2-dimensional conduction in the fuel to a 2-dimensional thermo-fluid model of the coolant for a HFIR core cooling sub-channel with additional assessment of simulation outcomes. Finally, 3-dimensional simulations of a fuel plate and cooling channel are presented.« less

Substance P modulation of TRPC3/7 channels improves respiratory rhythm regularity and ICAN-dependent pacemaker activity

PubMed Central

Ben-Mabrouk, Faiza; Tryba, Andrew Kieran

2011-01-01

Neuromodulators, such as Substance P (SubP) play an important role in modulating many rhythmic activities driven by central pattern generators (e.g., locomotion, respiration). However, the mechanism by which SubP enhances breathing regularity has not been determined. Here, we used mouse brainstem slices containing the pre-Bötzinger Complex (Pre-BötC) to demonstrate, for the first time, that SubP activates transient receptor protein canonical (TRPC) channels to enhance respiratory rhythm regularity. Moreover, SubP enhancement of network regularity is accomplished via selective enhancement of ICAN-dependent intrinsic bursting properties. In contrast to INaP-dependant pacemakers, ICAN-dependant pacemaker bursting activity is TRPC dependent. Western Blots reveal TRPC3 and TRPC7 channels are expressed in rhythmically active ventral respiratory group (VRG) island preparations. Taken together, these data suggest that SubP-mediated activation of TRPC3/7 channels underlies rhythmic ICAN-dependent pacemaker activity and enhances the regularity of respiratory rhythm activity. PMID:20345918

Substance P modulation of TRPC3/7 channels improves respiratory rhythm regularity and ICAN-dependent pacemaker activity.

PubMed

Ben-Mabrouk, Faiza; Tryba, Andrew K

2010-04-01

Neuromodulators, such as substance P (SubP), play an important role in modulating many rhythmic activities driven by central pattern generators (e.g. locomotion, respiration). However, the mechanism by which SubP enhances breathing regularity has not been determined. Here, we used mouse brainstem slices containing the pre-Bötzinger complex to demonstrate, for the first time, that SubP activates transient receptor protein canonical (TRPC) channels to enhance respiratory rhythm regularity. Moreover, SubP enhancement of network regularity is accomplished via selective enhancement of ICAN (inward non-specific cation current)-dependent intrinsic bursting properties. In contrast to INaP (persistent sodium current)-dependent pacemakers, ICAN-dependent pacemaker bursting activity is TRPC-dependent. Western Blots reveal TRPC3 and TRPC7 channels are expressed in rhythmically active ventral respiratory group island preparations. Taken together, these data suggest that SubP-mediated activation of TRPC3/7 channels underlies rhythmic ICAN-dependent pacemaker activity and enhances the regularity of respiratory rhythm activity.

Evaluation of an Infiltration Model with Microchannels

NASA Astrophysics Data System (ADS)

Garcia-Serrana, M.; Gulliver, J. S.; Nieber, J. L.

2015-12-01

This research goal is to develop and demonstrate the means by which roadside drainage ditches and filter strips can be assigned the appropriate volume reduction credits by infiltration. These vegetated surfaces convey stormwater, infiltrate runoff, and filter and/or settle solids, and are often placed along roads and other impermeable surfaces. Infiltration rates are typically calculated by assuming that water flows as sheet flow over the slope. However, for most intensities water flow occurs in narrow and shallow micro-channels and concentrates in depressions. This channelization reduces the fraction of the soil surface covered with the water coming from the road. The non-uniform distribution of water along a hillslope directly affects infiltration. First, laboratory and field experiments have been conducted to characterize the spatial pattern of flow for stormwater runoff entering onto the surface of a sloped surface in a drainage ditch. In the laboratory experiments different micro-topographies were tested over bare sandy loam soil: a smooth surface, and three and five parallel rills. All the surfaces experienced erosion; the initially smooth surface developed a system of channels over time that increased runoff generation. On average, the initially smooth surfaces infiltrated 10% more volume than the initially rilled surfaces. The field experiments were performed in the side slope of established roadside drainage ditches. Three rates of runoff from a road surface into the swale slope were tested, representing runoff from 1, 2, and 10-year storm events. The average percentage of input runoff water infiltrated in the 32 experiments was 67%, with a 21% standard deviation. Multiple measurements of saturated hydraulic conductivity were conducted to account for its spatial variability. Second, a rate-based coupled infiltration and overland model has been designed that calculates stormwater infiltration efficiency of swales. The Green-Ampt-Mein-Larson assumptions were implemented to calculate infiltration along with a kinematic wave model for overland flow that accounts for short-circuiting of flow. Additionally, a sensitivity analysis on the parameters implemented in the model has been performed. Finally, the field experiments results have been used to quantify the validity of the coupled model.

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

Moritz, MichaL; Laniecki, Marek, E-mail: laniecki@amu.edu.pl

A series of modified SBA-15 materials were applied in drug delivery systems. The internal surface of siliceous hexagonal structure of SBA-15 was modified with different amount of (3-mercaptopropyl)trimethoxysilane (MPTMS) and oxidized in the presence of hydrogen peroxide. The sulfonated material was loaded with metoprolol tartrate or papaverine hydrochloride. Both drugs indicated strong chemical interaction with modified mesoporous surface. The characteristic of the obtained materials was performed with XRD and DRUV-vis spectrometry, themogravimetry and nitrogen adsorption (BET) measurements. The obtained results show that modification of the mesoporous materials leads towards significant decrease of the drug delivery rate. - Graphical abstract: XRDmore » and DSC of the -SO{sub 3}H modified SBA-15 loaded with metoprolol. Highlights: > Modification of SBA-15 internal channels with SO{sub 3}H groups. > Adsorption of metoprolol and papaverine on modified SBA-15. > Uniform and homogeneous distribution of the drugs inside the mesoporous structure of SBA-15. > Release of the supported drugs.« less

In-channel Restoration Structures and the Implications on Hyporheic Exchange: a Laboratory Experiment

NASA Astrophysics Data System (ADS)

Han, B.; Chu, H. H.; Endreny, T. A.

2014-12-01

In-channel structures, i.e. cross-vanes and J-hooks, are commonly installed in river restoration projects to modify the streambed morphology and stream water surface profile, and are known to change hyporhiec exchange flux and habitats for riverine animals. However, few studies have continuous and accurate pre- and post-treatment data to evaluate the impact of these structures on channel hydraulic gradients and morphology. To quantify the effects of in-channel structures, we developed a scaled physical model of a meandering stream with a cross-vane and 6 J-hooks on a mobile-bed river table. Close-range photogrammetry technique was applied to obtain 3-D water and ground surface profiles with sub-millimeter vertical accuracy and horizontal resolution. The experiment was compared with a control experiment without structures while maintaining the same initial conditions of river bed, floodplain and stream flow. Results indicated that the cross-vane caused an average local head loss that represented 16% of the total stream reach head loss, and a 74% increase in channel load in the entire stream reach. Most J-hooks can create stepwise patterns in stream longitudinal profile, and cross-vane can create even more significant ones. Hydraulic gradients across the intra-meander zone also increased with in-channel structures, i.e. from 2.5% to 3.5% at the meander neck. Scour pools developed downstream of the cross-vane, and mostly around the 4 meander apex J-hooks at their hooked tip. Backwater caused by the cross-vane steepened the local water table profile by an additional 4.2%, and was the primary driver of statistically significant hydraulic gradient increase. Reach scale water and streambed surface profiles from our study provided detailed data to improve the understanding of in-channel structure effects, and may serve as reliable data source in computational modeling of hyporheic exchange.

A Prospective Study of Ripple Mapping the Post-Infarct Ventricular Scar to Guide Substrate Ablation for Ventricular Tachycardia.

PubMed

Luther, Vishal; Linton, Nick W F; Jamil-Copley, Shahnaz; Koa-Wing, Michael; Lim, Phang Boon; Qureshi, Norman; Ng, Fu Siong; Hayat, Sajad; Whinnett, Zachary; Davies, D Wyn; Peters, Nicholas S; Kanagaratnam, Prapa

2016-06-01

Post-infarct ventricular tachycardia is associated with channels of surviving myocardium within scar characterized by fractionated and low-amplitude signals usually occurring late during sinus rhythm. Conventional automated algorithms for 3-dimensional electro-anatomic mapping cannot differentiate the delayed local signal of conduction within the scar from the initial far-field signal generated by surrounding healthy tissue. Ripple mapping displays every deflection of an electrogram, thereby providing fully informative activation sequences. We prospectively used CARTO-based ripple maps to identify conducting channels as a target for ablation. High-density bipolar left ventricular endocardial electrograms were collected using CARTO3v4 in sinus rhythm or ventricular pacing and reviewed for ripple mapping conducting channel identification. Fifteen consecutive patients (median age 68 years, left ventricular ejection fraction 30%) were studied (6 month preprocedural implantable cardioverter defibrillator therapies: median 19 ATP events [Q1-Q3=4-93] and 1 shock [Q1-Q3=0-3]). Scar (<1.5 mV) occupied a median 29% of the total surface area (median 540 points collected within scar). A median of 2 ripple mapping conducting channels were seen within each scar (length 60 mm; initial component 0.44 mV; delayed component 0.20 mV; conduction 55 cm/s). Ablation was performed along all identified ripple mapping conducting channels (median 18 lesions) and any presumed interconnected late-activating sites (median 6 lesions; Q1-Q3=2-12). The diastolic isthmus in ventricular tachycardia was mapped in 3 patients and colocated within the ripple mapping conducting channels identified. Ventricular tachycardia was noninducible in 85% of patients post ablation, and 71% remain free of ventricular tachycardia recurrence at 6-month median follow-up. Ripple mapping can be used to identify conduction channels within scar to guide functional substrate ablation. © 2016 American Heart Association, Inc.

Electron tunneling characteristics of a cubic quantum dot, (PbS){sub 32}

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

Gupta, Sanjeev K., E-mail: sanjeevg@mtu.edu, E-mail: haiying.he@valpo.edu; Banyai, Douglas; Pandey, Ravindra

The electron transport properties of the cubic quantum dot, (PbS){sub 32}, are investigated. The stability of the quantum dot has been established by recent scanning tunneling microscope experiments [B. Kiran, A. K. Kandalam, R. Rallabandi, P. Koirala, X. Li, X. Tang, Y. Wang, H. Fairbrother, G. Gantefoer, and K. Bowen, J. Chem. Phys. 136(2), 024317 (2012)]. In spite of the noticeable energy band gap (∼2 eV), a relatively high tunneling current for (PbS){sub 32} is predicted affirming the observed bright images for (PbS){sub 32}. The calculated I-V characteristics of (PbS){sub 32} are predicted to be substrate-dependent; (PbS){sub 32} on themore » Au (001) exhibits the molecular diode-like behavior and the unusual negative differential resistance effect, though this is not the case with (PbS){sub 32} on the Au (110). Appearance of the conduction channels associated with the hybridized states of quantum dot and substrate together with their asymmetric distribution at the Fermi level seem to determine the tunneling characteristics of the system.« less

The detection of intestinal spike activity on surface electroenterograms

NASA Astrophysics Data System (ADS)

Ye-Lin, Y.; Garcia-Casado, J.; Martinez-de-Juan, J. L.; Prats-Boluda, G.; Ponce, J. L.

2010-02-01

Myoelectrical recording could provide an alternative technique for assessing intestinal motility, which is a topic of great interest in gastroenterology since many gastrointestinal disorders are associated with intestinal dysmotility. The pacemaker activity (slow wave, SW) of the electroenterogram (EEnG) has been detected in abdominal surface recordings, although the activity related to bowel contractions (spike bursts, SB) has to date only been detected in experimental models with artificially favored electrical conductivity. The aim of the present work was to assess the possibility of detecting SB activity in abdominal surface recordings under physiological conditions. For this purpose, 11 recording sessions of simultaneous internal and external myolectrical signals were conducted on conscious dogs. Signal analysis was carried out in the spectral domain. The results show that in periods of intestinal contractile activity, high-frequency components of EEnG signals can be detected on the abdominal surface in addition to SW activity. The energy between 2 and 20 Hz of the surface myoelectrical recording presented good correlation with the internal intestinal motility index (0.64 ± 0.10 for channel 1 and 0.57 ± 0.11 for channel 2). This suggests that SB activity can also be detected in canine surface EEnG recording.

The Great Exoplanet Eclipse: Spitzer Observations of the Benchmark Sub-Saturn-Mass Planet KELT-11b

NASA Astrophysics Data System (ADS)

Colon, Knicole; Beatty, Thomas; Line, Michael; Kreidberg, Laura; Lopez, Eric; Stassun, Keivan; Rodriguez, Joseph; Pepper, Joshua; James, David

2017-10-01

KELT-11b is a unique sub-Saturn-mass planet with a super-Jupiter radius that is in orbit around a bright, metal-rich, sub-giant star. We propose to observe a single eclipse of KELT-11b with Spitzer in IRAC Channel 2, which will allow us to precisely constrain the orbital eccentricity of the planet, study atmospheric circulation in an as yet unexplored regime of planetary surface gravity and temperature, and perform comparative science with other exoplanets in order to explore the correlation between surface gravity and thermal structure. Spitzer is the only active facility capable of providing the high precision, continuous infrared eclipse photometry of KELT-11b that is required to reach these objectives. The Spitzer infrared eclipse combined with near-infrared transmission spectroscopy that we will obtain with WFC3 on the Hubble Space Telescope will ultimately enable a detailed investigation of the atmospheric properties of KELT-11b and will provide a benchmark for planning thermal observations of exoplanets with the James Webb Space Telescope.

Urban flood simulation and prioritization of critical urban sub-catchments using SWMM model and PROMETHEE II approach

NASA Astrophysics Data System (ADS)

Babaei, Sahar; Ghazavi, Reza; Erfanian, Mahdi

2018-06-01

Urban runoff increased due to augment of impervious surfaces. In order to flood mitigation during rainy season, determination of critical urban sub-catchments is very important for urban planners. Due to lack of information, adopting a simulation approach is one of the practical ways to identify the surcharged junctions and critical sub-catchments. Occurrence of destructive floods in the rainy seasons indicates the inappropriateness of the urban drainage system in Urmia. The main aims of this study were to estimate the surface runoff of urban sub-catchments using SWMM, to evaluate the accuracy of the drainage system of the study urban area and to prioritize sub-catchments using PROMETHEE II approach and SWMM. In the present study, the occurrence of rainfall event of the Urmia city (West Azerbaijan province, Iran) used for estimation of runoff depth. The study area was divided into 22 sub-catchments. For calibration and validation of model parameters, 3 rainfall events and their related runoff were measured. According to sensitivity analysis CN was the most sensitive parameter for model calibration. Amount of surcharged conduits and junctions indicates that the drainage system of the study area has not enough capacity for converting of the runoff and. For 10 year return period, depth of channels should increase by 20% for prevention of flooding in these sub-catchments. Sub-catchments were prioritized using PROMETHEE II approach and its results were compared with SWMM simulation outcomes. Based on SWMM simulation, S11, S7, S18, S16 and S1 sub-catchments are more critical sub-catchments respectively, while according to PROMETHEE method, S1, S11, S16, S14 and S18 are determined as the critical areas.

First results from different investigations on MHD flow in multichannel U-Bends

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

Reimann, J.; Barleon, L.; Molokov, S.

1995-04-01

In electrically coupled multichannel ducts with a U-bend geometry, MHD effects can result in strongly non-uniform distributions of flow rates Q{sub i} and pressure drops {Delta}p{sub i} in the individual channels. A multichannel U-bend geometry is part of the KfK self-cooled Pb-17Li blanket design for a fusion reactor (radial-toroidal-radial channels). However, inserts are proposed which decouple electrically the radial channels. The multi-channel effects (MCDs) were investigated by (i) Screening test with InGaSn at LAS, Riga, and (ii) more detailed experiments with NaK at KfK, Karlsruhe. Different flow channel geometries and channel numbers between 1 and 5 were used. Hartmann numbersmore » and interaction parameters were varied between O {le} M {le} 2300 and O {le} N {le} 40000. In parallel, a theoretical analysis was performed, based on the method of core flow approximation (CFA) which is valid for M {r_arrow} {infinity} and N {r_arrow} {infinity}. Significant MCEs occur in all ducts with totally electrically coupled channels. For the mode {Delta}p{sub i} = const, the flow rates in the outer channels can become significantly larger than those in the inner channels. For Q{sub i} = const, the highest pressure drop occurs in the middle channel and the lowest in the outer channels. The CFA predicts correctly the ratios of the pressure drops of the single channels but gives lower values than observed experimentally. No marked MCE was found for flow geometry which is similar to the KfK design, i.e., a fairly uniform flow rate and pressure drop distribution was observed for all values of M and N.« less

Charybdotoxin is a new member of the K sup + channel toxin family that includes dendrotoxin I and mast cell degranulating peptide

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

Schweitz, H.; Bidard, J.N.; Lazdunski, M.

1989-12-12

A polypeptide was identified in the venom of the scorpion Leiurus quinquestriatus hebraeus by its potency to inhibit the high affinity binding of the radiolabeled snake venom toxin dendrotoxin I ({sup 125}I-DTX{sub I}) to its receptor site. It has been purified, and its properties investigated by different techniques were found to be similar to those of MCD and DTX{sub I}, two polypeptide toxins active on a voltage-dependent K{sup +} channel. However, its amino acid sequence was determined, and it was shown that this toxin is in fact charybdotoxin (ChTX), a toxin classically used as a specific tool to block onemore » class of Ca{sup 2+}-activated K{sup +} channels. ChTX, DTX{sub I}, and MCD are potent convulsants and are highly toxic when injected intracerebroventricularly in mice. Their toxicities correlate well with their affinities for their receptors in rat brain. These three structurally different toxins release ({sup 3}H)GABA from preloaded synaptosomes, the efficiency order being DTX{sub I} > ChTX > MCD. Both binding and cross-linking experiments of ChTX to rat brain membranes and to the purified MCD/DTX{sub I} binding protein have shown that the {alpha}-subunit of the MCD/DTX{sub I}-sensitive K{sup +} channel protein also contains the ChTX binding sites. Binding sites for DTX{sub I}, MCD, and ChTX are in negative allosteric interaction. The results show that charybdotoxin belongs to the family of toxins which already includes the dendrotoxins and MCD, which are blockers of voltage-sensitive K{sup +} channels. ChTX is clearly not selective for Ca{sup 2+}-activated K{sup +} channel.« less

The effect of bed roughness on the free surface of an open channel flow and implications for remotely monitoring river discharge

NASA Astrophysics Data System (ADS)

Johnson, Erika; Cowen, Edwin

2013-11-01

The effect of increased bed roughness on the free surface turbulence signature of an open channel flow is investigated with the goal of incorporating the findings into a methodology to remotely monitor volumetric flow rates. Half of a wide (B = 2 m) open channel bed is covered with a 3 cm thick layer of loose gravel (D50 = 0.6 cm). Surface PIV (particle image velocimetry) experiments are conducted for a range of flow depths (B/H = 10-30) and Reynolds numbers (ReH = 10,000-60,000). It is well established that bed roughness in wall-bounded flows enhances the vertical velocity fluctuations (e.g. Krogstad et al. 1992). When the vertical velocity fluctuations approach the free surface they are redistributed (e.g. Cowen et al. 1995) to the surface parallel component directions. It is anticipated and confirmed that the interaction of these two phenomena result in enhanced turbulence at the free surface. The effect of the rough bed on the integral length scales and the second order velocity structure functions calculated at the free surface are investigated. These findings have important implications for developing new technologies in stream gaging.

Theoretical and experimental studies of electric field distribution in N-polar GaN/AlGaN/GaN heterostructures

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

Gladysiewicz, M., E-mail: marta.gladysiewicz@pwr.edu.pl; Janicki, L.; Kudrawiec, R.

2015-12-28

Electric field distribution in N-polar GaN(channel)/AlGaN/GaN(buffer) heterostructures was studied theoretically by solving Schrodinger and Poisson equations in a self-consistent manner for various boundary conditions and comparing results of these calculations with experimental data, i.e., measurements of electric field in GaN(channel) and AlGaN layers by electromodulation spectroscopy. A very good agreement between theoretical calculations and experimental data has been found for the Fermi-level located at ∼0.3 eV below the conduction band at N-polar GaN surface. With this surface boundary condition, the electric field distribution and two dimensional electron gas concentration are determined for GaN(channel)/AlGaN/GaN(buffer) heterostructures of various thicknesses of GaN(channel) and AlGaNmore » layers.« less

JOCG Aircraft/Stores Compatibility Symposium Proceedings (8th) Held in Fort Walton Beach, Florida on 23-25 October 1990

DTIC Science & Technology

1990-10-25

Compatibility Sub- Group Steering Committee Sub- Group Chairman Wiley I. Robinson Air Force Systems Command Study Group Chairmen Electrical Interface Joe...on the surface of the body organized into groups defining the corners of a series of four -sided surface panel elements which represent a faceted...Structures Technology. In the Aeroanalysis Group , Dr. Cunningham has conducted many studies leading to devel- opments in the area of analytically

Manufacturing process of nanofluidics using afm probe

NASA Astrophysics Data System (ADS)

Karingula, Varun Kumar

A new process for fabricating a nano fluidic device that can be used in medical application is developed and demonstrated. Nano channels are fabricated using a nano tip in indentation mode on AFM (Atomic Force Microscopy). The nano channels are integrated between the micro channels and act as a filter to separate biomolecules. Nano channels of 4 to7 m in length, 80nm in width, and at varying depths from 100nm to 850 nm allow the resulting device to separate selected groups of lysosomes and other viruses. Sharply developed vertical micro channels are produced from a deep reaction ion etching followed by deposition of different materials, such as gold and polymers, on the top surface, allowing the study of alternative ways of manufacturing a nanofluidic device. PDMS (Polydimethylsiloxane) bonding is performed to close the top surface of the device. An experimental setup is used to test and validate the device by pouring fluid through the channels. A detailed cost evaluation is conducted to compare the economical merits of the proposed process. It is shown that there is a 47:7% manufacturing time savings and a 60:6% manufacturing cost savings.

Riparian vegetation patterns in relation to fluvial landforms and channel evolution along selected rivers of Tuscany (Central Italy)

USGS Publications Warehouse

Hupp, C.R.; Rinaldi, M.

2007-01-01

Riparian vegetation distribution patterns and diversity relative to various fluvial geomorphic channel patterns, landforms, and processes are described and interpreted for selected rivers of Tuscany, Central Italy; with emphasis on channel evolution following human impacts. Field surveys were conducted along thirteen gauged reaches for species presence, fluvial landforms, and the type and amount of channel/riparian zone change. Inundation frequency of different geomorphic surfaces was determined, and vegetation data were analyzed using BDA (binary discriminate analysis) and DCA (detrended correspondence analysis) and related to hydrogeomorphology. Multivariate analyses revealed distinct quantitative vegetation patterns relative to six major fluvial geomorphic surfaces. DCA of the vegetation data also showed distinct associations of plants to processes of adjustment that are related to stage of channel evolution, and clearly separated plants along disturbance/landform/soil moisture gradients. Species richness increases from the channel bed to the terrace and on heterogeneous riparian areas, whereas species richness decreases from moderate to intense incision and from low to intense narrowing. ?? 2007 by Association of American Geographers.

Divergent actions of the pyrethroid insecticides S-bioallethrin, tefluthrin, and deltamethrin on rat Na{sub v}1.6 sodium channels

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

Tan Jianguo; Soderlund, David M., E-mail: dms6@cornell.ed

2010-09-15

We expressed rat Na{sub v}1.6 sodium channels in combination with the rat {beta}{sub 1} and {beta}{sub 2} auxiliary subunits in Xenopus laevis oocytes and evaluated the effects of the pyrethroid insecticides S-bioallethrin, deltamethrin, and tefluthrin on expressed sodium currents using the two-electrode voltage clamp technique. S-Bioallethrin, a type I structure, produced transient modification evident in the induction of rapidly decaying sodium tail currents, weak resting modification (5.7% modification at 100 {mu}M), and no further enhancement of modification upon repetitive activation by high-frequency trains of depolarizing pulses. By contrast deltamethrin, a type II structure, produced sodium tail currents that were {approx}more » 9-fold more persistent than those caused by S-bioallethrin, barely detectable resting modification (2.5% modification at 100 {mu}M), and 3.7-fold enhancement of modification upon repetitive activation. Tefluthrin, a type I structure with high mammalian toxicity, exhibited properties intermediate between S-bioallethrin and deltamethrin: intermediate tail current decay kinetics, much greater resting modification (14.1% at 100 {mu}M), and 2.8-fold enhancement of resting modification upon repetitive activation. Comparison of concentration-effect data showed that repetitive depolarization increased the potency of tefluthrin {approx} 15-fold and that tefluthrin was {approx} 10-fold more potent than deltamethrin as a use-dependent modifier of Na{sub v}1.6 sodium channels. Concentration-effect data from parallel experiments with the rat Na{sub v}1.2 sodium channel coexpressed with the rat {beta}{sub 1} and {beta}{sub 2} subunits in oocytes showed that the Na{sub v}1.6 isoform was at least 15-fold more sensitive to tefluthrin and deltamethrin than the Na{sub v}1.2 isoform. These results implicate sodium channels containing the Na{sub v}1.6 isoform as potential targets for the central neurotoxic effects of pyrethroids.« less

Iterative retrieval of surface emissivity and temperature for a hyperspectral sensor

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

Borel, C.C.

1997-11-01

The central problem of temperature-emissivity separation is that we obtain N spectral measurements of radiance and need to find N + 1 unknowns (N emissivities and one temperature). To solve this problem in the presence of the atmosphere we need to find even more unknowns: N spectral transmissions {tau}{sub atmo}({lambda}) up-welling path radiances L{sub path}{up_arrow}({lambda}) and N down-welling path radiances L{sub path}{down_arrow}({lambda}). Fortunately there are radiative transfer codes such as MODTRAN 3 and FASCODE available to get good estimates of {tau}{sub atmo}({lambda}), L{sub path}{up_arrow}({lambda}) and L{sub path}{down_arrow}({lambda}) in the order of a few percent. With the growing use of hyperspectralmore » imagers, e.g. AVIRIS in the visible and short-wave infrared there is hope of using such instruments in the mid-wave and thermal IR (TIR) some day. We believe that this will enable us to get around using the present temperature - emissivity separation (TES) algorithms using methods which take advantage of the many channels available in hyperspectral imagers. The first idea we had is to take advantage of the simple fact that a typical surface emissivity spectrum is rather smooth compared to spectral features introduced by the atmosphere. Thus iterative solution techniques can be devised which retrieve emissivity spectra {epsilon} based on spectral smoothness. To make the emissivities realistic, atmospheric parameters are varied using approximations, look-up tables derived from a radiative transfer code and spectral libraries. By varying the surface temperature over a small range a series of emissivity spectra are calculated. The one with the smoothest characteristic is chosen. The algorithm was tested on synthetic data using MODTRAN and the Salisbury emissivity database.« less

Effects of cadmium on intercellular junctions in a renal epithelial cell line grown on permeable membrane supports

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

Prozialeck, W.C.; Niewenhuis, R.J.

1991-03-11

Recent findings from the authors laboratories have shown that Cd{sup 2+} has relatively specific damaging effects on adhering and occluding junctions in the established porcine renal epithelial cell line, LLC-PK{sub 1}. The present studies were undertaken in order to further characterize the junction-perturbing effects of Cd{sup 2+} in polarized monolayers of LLC-PK{sub 1} cells, and to begin to identify the mechanisms underlying these effects. LLC-PK{sub 1} cells were grown to confluency on Millicell HA chambers and exposed to Cd{sup 2+} in polarized monolayers of LLC-PK{sub 1} cells, and to begin to identify the mechanisms underlying these effects. LLC-PK{sub 1} cellsmore » were grown to confluency on Millicell HA chambers an exposed to Cd{sup 2+} by adding CdCl{sub 2} to the solutions on either side of the cell monolayer. The integrity of cell-cell junctions was assessed by monitoring the transepithelial electrical resistance. The results showed that exposure to Cd{sup 2+} caused a pronounced decrease in transepithelial resistance without causing the cells to detach from the Millicell membrane. This decrease in resistance occurred more quickly and was much more pronounced when Cd{sup 2+} was added to the basolateral surface rather than the apical surface. Furthermore, the effects of Cd{sup 2+} were greatly reduced when excess Ca{sup 2+} was present in the medium. These results suggest that Cd{sup 2+} was present in the medium. These results suggest that Cd{sup 2+} may disrupt cell-cell junctions by interacting with Ca{sup 2+} binding sites or Ca{sup 2+} channels that are oriented toward the basolateral cell surface.« less

Acute ENaC Stimulation by cAMP in a Kidney Cell Line is Mediated by Exocytic Insertion from a Recycling Channel Pool

PubMed Central

Butterworth, Michael B.; Edinger, Robert S.; Johnson, John P.; Frizzell, Raymond A.

2005-01-01

Acute hormonal regulation of the epithelial sodium channel (ENaC) in tight epithelia increases transcellular Na+ transport via trafficking of intracellular channels to the apical surface. The fate of the channels removed from the apical surface following agonist washout is less clear. By repetitively stimulating polarized mouse cortical collecting duct (mCCD, MPKCCD14) epithelia, we evaluated the hypothesis that ENaC recycles through an intracellular pool to be available for reinsertion into the apical membrane. Short circuit current (ISC), membrane capacitance (CT), and conductance (GT) were recorded from mCCD epithelia mounted in modified Ussing chambers. Surface biotinylation of ENaC demonstrated an increase in channel number in the apical membrane following cAMP stimulation. This increase was accompanied by a 83 ± 6% (n = 31) increase in ISC and a 15.3 ± 1.5% (n = 15) increase in CT. Selective membrane permeabilization demonstrated that the CT increase was due to an increase in apical membrane capacitance. ISC and CT declined to basal levels on stimulus washout. Repetitive cAMP stimulation and washout (∼1 h each cycle) resulted in response fatigue; ΔISC decreased ∼10% per stimulation–recovery cycle. When channel production was blocked by cycloheximide, ΔISC decreased ∼15% per stimulation cycle, indicating that newly synthesized ENaC contributed a relatively small fraction of the channels mobilized to the apical membrane. Selective block of surface ENaC by benzamil demonstrated that channels inserted from a subapical pool made up >90% of the stimulated ISC, and that on restimulation a large proportion of channels retrieved from the apical surface were reinserted into the apical membrane. Channel recycling was disrupted by brefeldin A, which inhibited ENaC exocytosis, by chloroquine, which inhibited ENaC endocytosis and recycling, and by latrunculin A, which blocked ENaC exocytosis. A compartment model featuring channel populations in the apical membrane and intracellular recycling pool provided an adequate kinetic description of the ISC responses to repetitive stimulation. The model supports the concept of ENaC recycling in response to repetitive cAMP stimulation. PMID:15623897

Acute ENaC stimulation by cAMP in a kidney cell line is mediated by exocytic insertion from a recycling channel pool.

PubMed

Butterworth, Michael B; Edinger, Robert S; Johnson, John P; Frizzell, Raymond A

2005-01-01

Acute hormonal regulation of the epithelial sodium channel (ENaC) in tight epithelia increases transcellular Na(+) transport via trafficking of intracellular channels to the apical surface. The fate of the channels removed from the apical surface following agonist washout is less clear. By repetitively stimulating polarized mouse cortical collecting duct (mCCD, (MPK)CCD(14)) epithelia, we evaluated the hypothesis that ENaC recycles through an intracellular pool to be available for reinsertion into the apical membrane. Short circuit current (I(SC)), membrane capacitance (C(T)), and conductance (G(T)) were recorded from mCCD epithelia mounted in modified Ussing chambers. Surface biotinylation of ENaC demonstrated an increase in channel number in the apical membrane following cAMP stimulation. This increase was accompanied by a 83 +/- 6% (n = 31) increase in I(SC) and a 15.3 +/- 1.5% (n = 15) increase in C(T). Selective membrane permeabilization demonstrated that the C(T) increase was due to an increase in apical membrane capacitance. I(SC) and C(T) declined to basal levels on stimulus washout. Repetitive cAMP stimulation and washout (approximately 1 h each cycle) resulted in response fatigue; DeltaI(SC) decreased approximately 10% per stimulation-recovery cycle. When channel production was blocked by cycloheximide, DeltaI(SC) decreased approximately 15% per stimulation cycle, indicating that newly synthesized ENaC contributed a relatively small fraction of the channels mobilized to the apical membrane. Selective block of surface ENaC by benzamil demonstrated that channels inserted from a subapical pool made up >90% of the stimulated I(SC), and that on restimulation a large proportion of channels retrieved from the apical surface were reinserted into the apical membrane. Channel recycling was disrupted by brefeldin A, which inhibited ENaC exocytosis, by chloroquine, which inhibited ENaC endocytosis and recycling, and by latrunculin A, which blocked ENaC exocytosis. A compartment model featuring channel populations in the apical membrane and intracellular recycling pool provided an adequate kinetic description of the I(SC) responses to repetitive stimulation. The model supports the concept of ENaC recycling in response to repetitive cAMP stimulation.

Communication: Determining the structure of the N{sub 2}Ar van der Waals complex with laser-based channel-selected Coulomb explosion

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

Wu, Chengyin, E-mail: cywu@pku.edu.cn; Liu, Yunquan; Gong, Qihuang

2014-04-14

We experimentally reconstructed the structure of the N{sub 2}Ar van der Waals complex with the technique of laser-based channel-selected Coulomb explosion imaging. The internuclear distance between the N{sub 2} center of mass and the Ar atom, i.e., the length of the van der Waals bond, was determined to be 3.88 Å from the two-body explosion channels. The angle between the van der Waals bond and the N{sub 2} principal axis was determined to be 90° from the three-body explosion channels. The reconstructed structure was contrasted with our high level ab initio calculations. The agreement demonstrated the potential application of laser-basedmore » Coulomb explosion in imaging transient molecular structure, particularly for floppy van der Waals complexes, whose structures remain difficult to be determined by conventional spectroscopic methods.« less

GEONETCast Americas

Science.gov Websites

-channel CIIFEN Centro Internacional para la Investigación del Fenómeno de El Niño / International Conocimiento y Uso de la Biodiversidad / National Commission for Knowledge and Use of Biodiversity Sub-channel Center for the Investigation of the El Niño Phenomenon Sub-channel CMACast Regional GEOENTCast Component

Development of a high-performance boiling heat exchanger by improved liquid supply to narrow channels.

PubMed

Ohta, Haruhiko; Ohno, Toshiyuki; Hioki, Fumiaki; Shinmoto, Yasuhisa

2004-11-01

A two-phase flow loop is a promising method for application to thermal management systems for large-scale space platforms handling large amounts of energy. Boiling heat transfer reduces the size and weight of cold plates. The transportation of latent heat reduces the mass flow rate of working fluid and pump power. To develop compact heat exchangers for the removal of waste heat from electronic devices with high heat generation density, experiments on a method to increase the critical heat flux for a narrow heated channel between parallel heated and unheated plates were conducted. Fine grooves are machined on the heating surface in a transverse direction to the flow and liquid is supplied underneath flattened bubbles by the capillary pressure difference from auxiliary liquid channels separated by porous metal plates from the main heated channel. The critical heat flux values for the present heated channel structure are more than twice those for a flat surface at gap sizes 2 mm and 0.7 mm. The validity of the present structure with auxiliary liquid channels is confirmed by experiments in which the liquid supply to the grooves is interrupted. The increment in the critical heat flux compared to those for a flat surface takes a maximum value at a certain flow rate of liquid supply to the heated channel. The increment is expected to become larger when the length of the heated channel is increased and/or the gravity level is reduced.

The Development of III-V Semiconductor MOSFETs for Future CMOS Applications

NASA Astrophysics Data System (ADS)

Greene, Andrew M.

Alternative channel materials with superior transport properties over conventional strained silicon are required for supply voltage scaling in low power complementary metal-oxide-semiconductor (CMOS) integrated circuits. Group III-V compound semiconductor systems offer a potential solution due to their high carrier mobility, low carrier effective mass and large injection velocity. The enhancement in transistor drive current at a lower overdrive voltage allows for the scaling of supply voltage while maintaining high switching performance. This thesis focuses on overcoming several material and processing challenges associated with III-V semiconductor development including a low thermal processing budget, high interface trap state density (Dit), low resistance source/drain contacts and growth on lattice mismatched substrates. Non-planar In0.53Ga0.47As FinFETs were developed using both "gate-first" and "gate-last" fabrication methods for n-channel MOSFETs. Electron beam lithography and anisotropic plasma etching processes were optimized to create highly scaled fins with near vertical sidewalls. Plasma damage was removed using a wet etch process and improvements in gate efficiency were characterized on MOS capacitor structures. A two-step, selective removal of the pre-grown n+ contact layer was developed for "gate-last" recess etching. The final In0.53Ga 0.47As FinFET devices demonstrated an ION = 70 mA/mm, I ON/IOFF ratio = 15,700 and sub-threshold swing = 210 mV/dec. Bulk GaSb and strained In0.36Ga0.64Sb quantum well (QW) heterostructures were developed for p-channel MOSFETs. Dit was reduced to 2 - 3 x 1012 cm-2eV-1 using an InAs surface layer, (NH4)2S passivation and atomic layer deposition (ALD) of Al2O3. A self-aligned "gate-first" In0.36Ga0.64Sb MOSFET fabrication process was invented using a "T-shaped" electron beam resist patterning stack and intermetallic source/drain contacts. Ni contacts annealed at 300°C demonstrated an ION = 166 mA/mm, ION/IOFF ratio = 1,500 and sub-threshold swing = 340 mV/dec. Split C-V measurements were used to extract an effective channel mobility of muh* = 300 cm2/Vs at Ns = 2 x 1012 cm -2. "Gate-last" MOSFETs grown with an epitaxial p + contact layer were fabricated using selective gate-recess etching techniques. A parasitic "n-channel" limited ION/I OFF ratio and sub-threshold swing, most likely due to effects from the InAs surface layer.

May cause environmental damage the diversion of the Danube in the Szigetköz area, Hungary?

NASA Astrophysics Data System (ADS)

Novak, Brigitta

2009-04-01

Summary The floodplain area between the main channel of Danube and its branch river Mosoni-Duna is called the Szigetköz. This wetland area has special flora and fauna, and it is a natural protection area. Underneath of the Szigetköz, there are a thick (several hundreds meters) sedimentary sequence, the so called Kisalföld Quaternary Aquifer. This aquifer system is fed by the surface river system of Danube and supplies excellent quality drinking water for several hundred thousands of people in Hungary and Slovakia. The Szigetköz Monitoring Network was established in 1991 to describe the environmental effects of the Bős-Nagymaros Dam System, which was partly built in 1992 on the Slovakian part of the Danube. The dam diverts three-quarter of the Danube runoff to a 40 km long artificial concrete channel north of the original river bed. The effect of this diversion is spectacular on the wetland area. Water level in the meandering channels have decreased significantly, part of the wetland area frequently becomes dry. The natural flow pattern has disappeared. As a consequence, the channel characteristics of the river network, therefore the flow pattern, the quantity and quality of surface and subsurface water on the upper region of the Danube have significantly changed. The aim of our research is to describe the relationship between surface water and groundwater and considering the variable geology of the area, to describe trends in chemistry and to find the possible reasons for extreme values. Also to detect possible connection between the extreme values and the changes in flow pattern caused by the human intervention. Water sample pairs from surface water and shallow and deeper ground water were taken in every season at 18 locations. To sample shallow ground-water 1,5 m long, screened metal probes were derived into the sediment at the possible nearest point to the surface water. On the field pH, temperature, dissolved oxygen, specific conductivity, and in the wells redox potential were measured. Samples were taken for further laboratory analyses (major and trace components, nitrate. The chemical parameters of surface and subsurface water show seasonal changes, due to the changes of temperature, of precipitation, of biological and microbiological activity. At the monitoring points along the main channel the surface and subsurface water is closely related, and the velocity of groundwater can be calculated by the seasonal periodical dislocation. At the monitoring points on the north-western part of the study area (point 1), subsurface water replenished by the rivers, and water level in the probes follow the surface water level changes with short shift. Practically water quality is the same in the probe as in the surface. It is the same on the south-eastern part of the study area, where the diverted channel rejoins to the original river channel (point 10). The middle section (at points 4 and 5) of the study area, water level in the probes is higher than surface water level. Also concentrations of some chemical components are higher in the subsurface water here. These components are typically the results of water - sediment interaction. Based on these observations, the study area can be differentiated by the hydrochemical composition for losing and gaining sections. At the monitoring points along the meandering sub-branch system, water in the probes is reductive, the connection between surface and subsurface water is week, furthermore at some point is non-existent. At some points surface water has slow flow, or it is even stagnant. This means reductive environments, and high concentrations of some components, especially at the monitoring points of 31 and 41. For example, concentrations of ammonium, sulphate, phosphate, magnesium, iron, manganese are extremely high in the shallow groundwater. Originally the Danube supplied fresh, oxygen-rich water to the area, while nowadays at these locations surface water and subsurface water almost has no connection, and these sections of river bed already turned muddy, and organic material accumulated in the sediment, which further increase the rate of reduction and decrease the flow rate. The extreme values, and values not following the trend in the time series of chemical parameters can be explained only by further detailed examination. On the whole, it is unambiguously clear, since the diversion of Danube the water replenishment of the meandering sub-branch system is poorer, causing unfavourable changes in water chemistry both in surface and subsurface water. Other research teams of the monitoring system, studying ecology, have found that the water regulation has major adverse effects on the biology as well. The typical floodplain vegetation is changing toward species tolerating dryness. In the water flora and fauna alters gradually as well, due to the changing chemical characteristic of water and the decreasing flow. Considering that the abiotic environment react slower than the biotic to the anthropologic influence, we do not have a clear view how the water quality will deteriorate on the long run. Furthermore, the changes in flora and fauna have already caused changes in water chemistry, and these changes will persist causing a slow but continuous diversion from the original, natural values. In Szigetköz area, the decreased flow and the deteriorating quality of surface water will endanger the important subsurface drinking water aquifer on the long-term.

Disruption of ATP-sensitive potassium channel function in skeletal muscles promotes production and secretion of musclin

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

Sierra, Ana, E-mail: ana-sierra@uiowa.edu; Subbotina, Ekaterina, E-mail: ekaterina-subbotina@uiowa.edu; Zhu, Zhiyong, E-mail: zhiyong-zhu@uiowa.edu

Sarcolemmal ATP-sensitive potassium (K{sub ATP}) channels control skeletal muscle energy use through their ability to adjust membrane excitability and related cell functions in accordance with cellular metabolic status. Mice with disrupted skeletal muscle K{sub ATP} channels exhibit reduced adipocyte size and increased fatty acid release into the circulation. As yet, the molecular mechanisms underlying this link between skeletal muscle K{sub ATP} channel function and adipose mobilization have not been established. Here, we demonstrate that skeletal muscle-specific disruption of K{sub ATP} channel function in transgenic (TG) mice promotes production and secretion of musclin. Musclin is a myokine with high homology tomore » atrial natriuretic peptide (ANP) that enhances ANP signaling by competing for elimination. Augmented musclin production in TG mice is driven by a molecular cascade resulting in enhanced acetylation and nuclear exclusion of the transcription factor forkhead box O1 (FOXO1) – an inhibitor of transcription of the musclin encoding gene. Musclin production/secretion in TG is paired with increased mobilization of fatty acids and a clear trend toward increased circulating ANP, an activator of lipolysis. These data establish K{sub ATP} channel-dependent musclin production as a potential mechanistic link coupling “local” skeletal muscle energy consumption with mobilization of bodily resources from fat. Understanding such mechanisms is an important step toward designing interventions to manage metabolic disorders including those related to excess body fat and associated co-morbidities. - Highlights: • ATP-sensitive K{sup +} channels regulate musclin production by skeletal muscles. • Lipolytic ANP signaling is promoted by augmented skeletal muscle musclin production. • Skeletal muscle musclin transcription is promoted by a CaMKII/HDAC/FOXO1 pathway. • Musclin links adipose mobilization to energy use in K{sub ATP} channel deficient skeletal muscle.« less

Mapping the Coulomb Environment in Interference-Quenched Ballistic Nanowires.

PubMed

Gutstein, D; Lynall, D; Nair, S V; Savelyev, I; Blumin, M; Ercolani, D; Ruda, H E

2018-01-10

The conductance of semiconductor nanowires is strongly dependent on their electrostatic history because of the overwhelming influence of charged surface and interface states on electron confinement and scattering. We show that InAs nanowire field-effect transistor devices can be conditioned to suppress resonances that obscure quantized conduction thereby revealing as many as six sub-bands in the conductance spectra as the Fermi-level is swept across the sub-band energies. The energy level spectra extracted from conductance, coupled with detailed modeling shows the significance of the interface state charge distribution revealing the Coulomb landscape of the nanowire device. Inclusion of self-consistent Coulomb potentials, the measured geometrical shape of the nanowire, the gate geometry and nonparabolicity of the conduction band provide a quantitative and accurate description of the confinement potential and resulting energy level structure. Surfaces of the nanowire terminated by HfO 2 are shown to have their interface donor density reduced by a factor of 30 signifying the passivating role played by HfO 2 .

Adsorption of ammonia at GaN(0001) surface in the mixed ammonia/hydrogen ambient - a summary of ab initio data

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

Kempisty, Paweł; Krukowski, Stanisław; Interdisciplinary Centre for Materials Modelling, Warsaw University, Pawińskiego 5a, 02-106 Warsaw

Adsorption of ammonia at NH{sub 3}/NH{sub 2}/H-covered GaN(0001) surface was analyzed using results of ab initio calculations. The whole configuration space of partially NH{sub 3}/NH{sub 2}/H-covered GaN(0001) surface was divided into zones of differently pinned Fermi level: at the Ga broken bond state for dominantly bare surface (region I), at the valence band maximum (VBM) for NH{sub 2} and H-covered surface (region II), and at the conduction band minimum (CBM) for NH{sub 3}-covered surface (region III). The electron counting rule (ECR) extension was formulated for the case of adsorbed molecules. The extensive ab intio calculations show the validity of themore » ECR in case of all mixed H-NH{sub 2}-NH{sub 3} coverages for the determination of the borders between the three regions. The adsorption was analyzed using the recently identified dependence of the adsorption energy on the charge transfer at the surface. For region I ammonia adsorbs dissociatively, disintegrating into a H adatom and a HN{sub 2} radical for a large fraction of vacant sites, while for region II adsorption of ammonia is molecular. The dissociative adsorption energy strongly depends on the Fermi level at the surface (pinned) and in the bulk (unpinned) while the molecular adsorption energy is determined by bonding to surface only, in accordance to the recently published theory. Adsorption of Ammonia in region III (Fermi level pinned at CBM) leads to an unstable configuration both molecular and dissociative, which is explained by the fact that broken Ga-bonds are doubly occupied by electrons. The adsorbing ammonia brings 8 electrons to the surface, necessitating the transfer of these two electrons from the Ga broken bond state to the Fermi level. This is an energetically costly process. Adsorption of ammonia at H-covered site leads to the creation of a NH{sub 2} radical at the surface and escape of H{sub 2} molecule. The process energy is close to 0.12 eV, thus not large, but the direct inverse process is not possible due to the escape of the hydrogen molecule.« less

Synthesis of tetraaza bromide macrocyclic and studies of its effect on poly(methyl methacrylate) grafted natural rubber (MG49) - lithium tertrafluoroborate (LiBF{sub 4}) films

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

Mariam, Siti Nor; Yamin, Bohari M.; Ahmad, Azizan

2013-11-27

Good Poly(Methyl Methacrylate) Grafted natural Rubber (MG49) films with homogeneous and smooth surface were obtained in the presence of Lithium Tertrafluoroborate (LiBF{sub 4}) and 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-7,14-dienium bromide, (Me{sub 6}N{sub 4}H{sub 4})Br{sub 2} as dopants. The conductivity was found to be 3.63×10{sup −6} S/cm an increase by seven fold compare to the undoped MG49.

Surface and Flow Field Measurements on the FAITH Hill Model

NASA Technical Reports Server (NTRS)

Bell, James H.; Heineck, James T.; Zilliac, Gregory; Mehta, Rabindra D.; Long, Kurtis R.

2012-01-01

A series of experimental tests, using both qualitative and quantitative techniques, were conducted to characterize both surface and off-surface flow characteristics of an axisymmetric, modified-cosine-shaped, wall-mounted hill named "FAITH" (Fundamental Aero Investigates The Hill). Two separate models were employed: a 6" high, 18" base diameter machined aluminum model that was used for wind tunnel tests and a smaller scale (2" high, 6" base diameter) sintered nylon version that was used in the water channel facility. Wind tunnel and water channel tests were conducted at mean test section speeds of 165 fps (Reynolds Number based on height = 500,000) and 0.1 fps (Reynolds Number of 1000), respectively. The ratio of model height to boundary later height was approximately 3 for both tests. Qualitative techniques that were employed to characterize the complex flow included surface oil flow visualization for the wind tunnel tests, and dye injection for the water channel tests. Quantitative techniques that were employed to characterize the flow included Cobra Probe to determine point-wise steady and unsteady 3D velocities, Particle Image Velocimetry (PIV) to determine 3D velocities and turbulence statistics along specified planes, Pressure Sensitive Paint (PSP) to determine mean surface pressures, and Fringe Imaging Skin Friction (FISF) to determine surface skin friction (magnitude and direction). This initial report summarizes the experimental set-up, techniques used, data acquired and describes some details of the dataset that is being constructed for use by other researchers, especially the CFD community. Subsequent reports will discuss the data and their interpretation in more detail

Divergence Considerations, 1

NASA Technical Reports Server (NTRS)

Quirein, J. A.

1973-01-01

The case is considered of n distinct, normally distributed classes or populations of two dimensional response vectors x = (lambda sub 1, lambda sub 2), where lambda sub i is a measurement of the relative reponse of x along channel i. The problem dealt with is to determine the best channel in the sense of divergence and in the sense of minimizing the probability of misclassification.

Growth of ultrathin twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7} {sub –} {sub x} films

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

Stepantsov, E. A., E-mail: stepantsov@ns.crys.ras.ru; Arpaia, R.; Lombardi, F.

2017-01-15

Twin-free b-oriented YBa{sub 2}Cu{sub 3}O{sub 7–x} films with a thickness less than 40 nm have been epitaxially grown on (100)SrLaGaO{sub 4} crystals. Based on the temperature dependence of resistance, the onset temperature of the transition to the superconducting state is found to be 90 K; the transition width is 4 K. The film growth has been performed in two stages. A (100)PrBa{sub 2}Cu{sub 3}O{sub 7–x} buffer layer was previously grown on a (100)SrLaGaO{sub 4} substrate by rf magnetron sputtering in an Ar–O{sub 2} gas mixture at a continuous and monotonic increase in temperature from 660 to 830°C. The main YBa{submore » 2}Cu{sub 3}O{sub 7–x} film was grown on the buffer layer surface by pulsed laser deposition in an oxygen medium at a fixed temperature (800°C). The above processes were implemented in different chambers, which were connected by a vacuum channel for transporting samples. Both films were grown in situ, without contacting atmosphere in all growth stages. An X-ray diffraction study has shown that the YBa{sub 2}Cu{sub 3}O{sub 7–x} films are single-crystal and free of precipitates of other phases and domains of other orientations.« less

Fabrication of microwave guides using high-Tc superconductors. Final report, 15 July 1989-14 January 1990

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

Trivedi, S.B.

1990-01-14

The objective of this study was to produce bulk high Tc superconductor YBa{sub 2}Cu{sub 3}O{sub 7-x} with microwave conductivity at least as good or better than that of copper. The subsequent aim was to fabricate cylindrical wave guide using this material. The ultimate goal of this study is to produce YBa{sub 2}Cu{sub 3}O{sub 7-x} with microwave conductivity exceedingly higher (at least two orders of magnitude better) than that of copper. In principle, this is possible if the microstructure of the superconductor material is carefully controlled. The above-stated goal could be easily achieved if the large single crystals of YBa{sub 2}Cu{submore » 3}O{sub 7-x} are available or if the inside surface of a suitable substrate material in the form of hollow cylinder, could be coated with the superconductor material of high quality. The former approach, currently, seems to be far from practical realization.« less

Role of Penning ionization in the enhancement of streamer channel conductivity and Ar(1s{sub 5}) production in a He-Ar plasma jet

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

Sands, Brian L.; Huang, Shih K.; Speltz, Jared W.

2013-04-21

Plasma jet devices that use a helium gas flow mixed with a small percentage of argon have been shown to operate with a larger discharge current and enhanced production of the Ar(1s{sub 5}) metastable state, particularly in the discharge afterglow. In this experiment, time-resolved quantitative measurements of He(2{sup 3}S{sub 1}) and Ar(1s{sub 5}) metastable species were combined with current and spectrally resolved emission measurements to elucidate the role of Penning ionization in a helium plasma jet with a variable argon admixture. The plasma jet was enclosed in a glass chamber through which a flowing nitrogen background was maintained at 600more » Torr. At 3%-5% Ar admixture, we observed a {approx}50% increase in the peak circuit current and streamer velocity relative to a pure helium plasma jet for the same applied voltage. The streamer initiation delay also decreased by {approx}20%. Penning ionization of ground-state argon was found to be the dominant quenching pathway for He(2{sup 3}S{sub 1}) up to 2% Ar and was directly correlated with a sharp increase in both the circuit current and afterglow production of Ar(1s{sub 5}) for Ar admixtures up to 1%, but not necessarily with the streamer velocity, which increased more gradually with Ar concentration. Ar(1s{sub 5}) was produced in the afterglow through recombination of Ar{sup +} and dissociative recombination of Ar{sub 2}{sup +} as the local mean electron energy decreased in the plasma channel behind the streamer head. The discharge current and argon metastable enhancement are contingent on the rapid production of He(2{sup 3}S{sub 1}) near the streamer head, >5 Multiplication-Sign 10{sup 12} cm{sup -3} in 30 ns under the conditions of this experiment.« less

Role of protein kinase A and class II phosphatidylinositol 3-kinase C2β in the downregulation of KCa3.1 channel synthesis and membrane surface expression by lyso-globotriaosylceramide

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

Choi, Ju Yeon; Park, Seonghee, E-mail: sp@ewha.ac.kr

The intermediate conductance calcium-activated potassium channel (KCa3.1) mediates proliferation of many cell types including fibroblasts, and is a molecular target for intervention in various cell proliferative diseases. Our previous study showed that reduction of KCa3.1 channel expression by lyso-globotriaosylceramide (lyso-Gb3) inhibits differentiation into myofibroblasts and collagen synthesis, which might lead to development of ascending thoracic aortic aneurysm secondary to Fabry disease. However, how lyso-Gb3 downregulates KCa3.1 channel expression is unknown. Therefore, we aimed to investigate the underlying mechanisms of lyso-Gb3-mediated KCa3.1 channel downregulation, focusing on the cAMP signaling pathway. We found that lyso-Gb3 increased the intracellular cAMP concentration by upregulationmore » of adenylyl cyclase 6 and inhibited ERK 1/2 phosphorylation through the protein kinase A (PKA) pathway, leading to the inhibition of KCa3.1 channel synthesis, not the exchange protein directly activated by cAMP (Epac) pathway. Moreover, lyso-Gb3 suppressed expression of class II phosphatidylinositol 3-kinase C2β (PI3KC2β) by PKA activation, which reduces the production of phosphatidylinositol 3-phosphate [PI(3)P], and the reduced membrane surface expression of KCa3.1 channel was recovered by increasing the intracellular levels of PI(3)P. Consequently, our findings that lyso-Gb3 inhibited both KCa3.1 channel synthesis and surface expression by increasing intracellular cAMP, and controlled surface expression through changes in PI3KC2β-mediated PI(3)P production, suggest that modulation of PKA and PI3KC2β activity to control of KCa3.1 channel expression can be an alternative important target to attenuate ascending thoracic aortic aneurysms in Fabry disease. - Highlights: • Lyso-Gb3 causes elevation of intracellular cAMP. • Lyso-Gb3 inhibits the ERK 1/2 phosphorylation through PKA, thereby reducing KCa3.1 channel synthesis. • Lyso-Gb3 reduces PI3KC2β-mediated intracellular PI(3)P production. • Lyso-Gb3 reduces both surface and total expression of the KCa3.1 channel. • Increasing intracellular levels of PI(3)P only recovers the reduced surface expression.« less

Silver transfer in proustite Ag{sub 3}AsS{sub 3} at high temperatures: Conductivity and single-crystal X-ray studies

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

Gagor, Anna; Pawlowski, Antoni; Pietraszko, Adam

2009-03-15

Single crystals of proustite Ag{sub 3}AsS{sub 3} have been characterised by impedance spectroscopy and single-crystal X-ray diffraction in the temperature ranges of 295-543 and 295-695 K, respectively. An analysis of the one-particle potential of silver atoms shows that in the whole measuring temperature range defects in the silver substructure play a major role in the conduction mechanism. Furthermore, the silver transfer is equally probable within silver chains and spirals, as well as between chains and spirals. The trigonal R3c room temperature phase does not change until the decomposition of the crystal. The electric anomaly of the first-order character which appearsmore » near 502 K is related to an increase in the electronic component of the total conductivity resulting from Ag{sub 2}S deposition at the sample surface. - Joint probability density function map of silver atoms at T=695 K.« less

SiN sub x passivation of silicon surfaces

NASA Technical Reports Server (NTRS)

Olsen, L. C.

1986-01-01

The objectives were to perform surface characterization of high efficiency n+/p and p+/n silicon cells, to relate surface density to substrate dopant concentration, and to identify dominant current loss mechanisms in high efficiency cells. The approach was to measure density of states on homogeneously doped substrates with high frequency C-V and Al/SiN sub x/Si structures; to investigate density of states and photoresponse of high efficiency N+/P and P+/N cells; and to conduct I-V-T studies to identify current loss nechanisms in high efficiency cells. Results are given in tables and graphs.

Ultraviolet-enhanced photodetection in a graphene/SiO{sub 2}/Si capacitor structure with a vacuum channel

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

Kim, Myungji; Kim, Hong Koo, E-mail: hkk@pitt.edu

2015-09-14

We report photodetection properties of a graphene/oxide/silicon capacitor structure with a nanoscale vacuum channel. The photogenerated two-dimensional electron gas (2DEG) inversion charges at SiO{sub 2}/Si interface are extracted out to air and transported along the void channel at low bias voltage (<5 V). A monolayer graphene, placed on top of SiO{sub 2} and suspended on the void channel, is utilized as a photon-transparent counter-electrode to the 2DEG layer and a collector electrode for the out-of-plane transported electrons, respectively. The photocurrent extracted through a void channel reveals high responsivity (1.0 A/W at 633 nm) as measured in a broad spectral range (325–1064 nm), especially demonstratingmore » a UV-enhanced performance (0.43 A/W responsivity and 384% internal quantum efficiency at 325 nm). The mechanisms underlying photocarrier generation, emission, and transport in a suspended-graphene/SiO{sub 2}/Si structure are proposed.« less

Silicon micro-mold and method for fabrication

DOEpatents

Morales, Alfredo M.

2005-01-11

The present invention describes a method for rapidly fabricating a robust 3-dimensional silicon micro-mold for use in preparing complex metal micro-components. The process begins by depositing a conductive metal layer onto one surface of a silicon wafer. A thin photoresist and a standard lithographic mask are then used to transfer a trace image pattern onto the opposite surface of the wafer by exposing and developing the resist. The exposed portion of the silicon substrate is anisotropically etched through the wafer thickness down to conductive metal layer to provide an etched pattern consisting of a series of rectilinear channels and recesses in the silicon which serve as the silicon micro-mold. Microcomponents are prepared with this mold by first filling the mold channels and recesses with a metal deposit, typically by electroplating, and then removing the silicon micro-mold by chemical etching.

Silicon micro-mold

DOEpatents

Morales, Alfredo M [Livermore, CA

2006-10-24

The present invention describes a method for rapidly fabricating a robust 3-dimensional silicon-mold for use in preparing complex metal micro-components. The process begins by depositing a conductive metal layer onto one surface of a silicon wafer. A thin photoresist and a standard lithographic mask are then used to transfer a trace image pattern onto the opposite surface of the wafer by exposing and developing the resist. The exposed portion of the silicon substrate is anisotropically etched through the wafer thickness down to conductive metal layer to provide an etched pattern consisting of a series of rectilinear channels and recesses in the silicon which serve as the silicon micro-mold. Microcomponents are prepared with this mold by first filling the mold channels and recesses with a metal deposit, typically by electroplating, and then removing the silicon micro-mold by chemical etching.

Improving Forecast Skill by Assimilation of Quality Controlled AIRS Version 5 Temperature Soundings

NASA Technical Reports Server (NTRS)

Susskind, Joel; Reale, Oreste

2009-01-01

The AIRS Science Team Version 5 retrieval algorithm has been finalized and is now operational at the Goddard DAAC in the processing (and reprocessing) of all AIRS data. The AIRS Science Team Version 5 retrieval algorithm contains two significant improvements over Version 4: 1) Improved physics allows for use of AIRS observations in the entire 4.3 micron CO2 absorption band in the retrieval of temperature profile T(p) during both day and night. Tropospheric sounding 15 micron CO2 observations are now used primarily in the generation of cloud cleared radiances R(sub i). This approach allows for the generation of accurate values of R(sub i) and T(p) under most cloud conditions. 2) Another very significant improvement in Version 5 is the ability to generate accurate case-by-case, level-by-level error estimates for the atmospheric temperature profile, as well as for channel-by-channel error estimates for R(sub i). These error estimates are used for Quality Control of the retrieved products. We have conducted forecast impact experiments assimilating AIRS temperature profiles with different levels of Quality Control using the NASA GEOS-5 data assimilation system. Assimilation of Quality Controlled T(p) resulted in significantly improved forecast skill compared to that obtained from analyses obtained when all data used operationally by NCEP, except for AIRS data, is assimilated. We also conducted an experiment assimilating AIRS radiances uncontaminated by clouds, as done operationally by ECMWF and NCEP. Forecast resulting from assimilated AIRS radiances were of poorer quality than those obtained assimilating AIRS temperatures.

Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

1991-01-01

A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approximately 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approximately 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approximately 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition superconducting thin films at microwave frequencies.

Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Miranda, F. A.; Gordon, W. L.; Newman, H. S.

1990-01-01

A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approx. 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approx. 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approx. 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition temperature superconducting thin films at microwave frequencies.

A threshold-based cloud mask for the high-resolution visible channel of Meteosat Second Generation SEVIRI

NASA Astrophysics Data System (ADS)

Bley, S.; Deneke, H.

2013-10-01

A threshold-based cloud mask for the high-resolution visible (HRV) channel (1 × 1 km2) of the Meteosat SEVIRI (Spinning Enhanced Visible and Infrared Imager) instrument is introduced and evaluated. It is based on operational EUMETSAT cloud mask for the low-resolution channels of SEVIRI (3 × 3 km2), which is used for the selection of suitable thresholds to ensure consistency with its results. The aim of using the HRV channel is to resolve small-scale cloud structures that cannot be detected by the low-resolution channels. We find that it is of advantage to apply thresholds relative to clear-sky reflectance composites, and to adapt the threshold regionally. Furthermore, the accuracy of the different spectral channels for thresholding and the suitability of the HRV channel are investigated for cloud detection. The case studies show different situations to demonstrate the behavior for various surface and cloud conditions. Overall, between 4 and 24% of cloudy low-resolution SEVIRI pixels are found to contain broken clouds in our test data set depending on considered region. Most of these broken pixels are classified as cloudy by EUMETSAT's cloud mask, which will likely result in an overestimate if the mask is used as an estimate of cloud fraction. The HRV cloud mask aims for small-scale convective sub-pixel clouds that are missed by the EUMETSAT cloud mask. The major limit of the HRV cloud mask is the minimum cloud optical thickness (COT) that can be detected. This threshold COT was found to be about 0.8 over ocean and 2 over land and is highly related to the albedo of the underlying surface.

Evaluation of biofouling in stainless microfluidic channels for implantable multilayered dialysis device

NASA Astrophysics Data System (ADS)

Ota, Takashi; To, Naoya; Kanno, Yoshihiko; Miki, Norihisa

2017-06-01

An implantable artificial kidney can markedly improve the quality of life of renal disease patients. Our group has developed an implantable multilayered dialysis system consisting of microfluidic channels and dialysis membranes. Long-term evaluation is necessary for implant devices where biofouling is a critical factor, culminating in the deterioration of dialysis performance. Our previous work revealed that surface conditions, which depend on the manufacturing process, determine the amount of biofouling, and that electrolytic etching is the most suitable technique for forming a channel wall free of biofouling. In this study, we investigated the electrolytic etching conditions in detail. We conducted in vitro experiments for 7 d and evaluated the adhesion of biomaterials by scanning electron microscopy. The experiments revealed that a surface mirror-finished by electrolytic etching effectively prevents biofouling.

Vibrational Action Spectroscopy of Solids: New Surface-Sensitive Technique

NASA Astrophysics Data System (ADS)

Wu, Zongfang; Płucienik, Agata; Feiten, Felix E.; Naschitzki, Matthias; Wachsmann, Walter; Gewinner, Sandy; Schöllkopf, Wieland; Staemmler, Volker; Kuhlenbeck, Helmut; Freund, Hans-Joachim

2017-09-01

Vibrational action spectroscopy employing infrared radiation from a free-electron laser has been successfully used for many years to study the vibrational and structural properties of gas phase aggregates. Despite the high sensitivity of this method no relevant studies have yet been conducted for solid sample surfaces. We have set up an experiment for the application of this method to such targets, using infrared light from the free-electron laser of the Fritz Haber Institute. In this Letter, we present first results of this technique with adsorbed argon and neon atoms as messengers. We were able to detect surface-located vibrations of a thin V2O3(0 0 0 1 ) film on Au(111) as well as adsorbate vibrations, demonstrating that this method is highly surface sensitive. We consider that the dominant channel for desorption of the messenger atoms is direct inharmonic vibrational coupling, which is essentially insensitive to subsurface or bulk vibrations. Another channel is thermal desorption due to sample heating by absorption of infrared light. The high surface sensitivity of the nonthermal channel and its insensitivity to subsurface modes makes this technique an ideal tool for the study of surface-located vibrations.

Vibrational Action Spectroscopy of Solids: New Surface-Sensitive Technique.

PubMed

Wu, Zongfang; Płucienik, Agata; Feiten, Felix E; Naschitzki, Matthias; Wachsmann, Walter; Gewinner, Sandy; Schöllkopf, Wieland; Staemmler, Volker; Kuhlenbeck, Helmut; Freund, Hans-Joachim

2017-09-29

Vibrational action spectroscopy employing infrared radiation from a free-electron laser has been successfully used for many years to study the vibrational and structural properties of gas phase aggregates. Despite the high sensitivity of this method no relevant studies have yet been conducted for solid sample surfaces. We have set up an experiment for the application of this method to such targets, using infrared light from the free-electron laser of the Fritz Haber Institute. In this Letter, we present first results of this technique with adsorbed argon and neon atoms as messengers. We were able to detect surface-located vibrations of a thin V_{2}O_{3}(0001) film on Au(111) as well as adsorbate vibrations, demonstrating that this method is highly surface sensitive. We consider that the dominant channel for desorption of the messenger atoms is direct inharmonic vibrational coupling, which is essentially insensitive to subsurface or bulk vibrations. Another channel is thermal desorption due to sample heating by absorption of infrared light. The high surface sensitivity of the nonthermal channel and its insensitivity to subsurface modes makes this technique an ideal tool for the study of surface-located vibrations.

Effect of top gate bias on photocurrent and negative bias illumination stress instability in dual gate amorphous indium-gallium-zinc oxide thin-film transistor

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

Lee, Eunji; Chowdhury, Md Delwar Hossain; Park, Min Sang

We have studied the effect of top gate bias (V{sub TG}) on the generation of photocurrent and the decay of photocurrent for back channel etched inverted staggered dual gate structure amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Upon 5 min of exposure of 365 nm wavelength and 0.7 mW/cm{sup 2} intensity light with negative bottom gate bias, the maximum photocurrent increases from 3.29 to 322 pA with increasing the V{sub TG} from −15 to +15 V. By changing V{sub TG} from negative to positive, the Fermi level (E{sub F}) shifts toward conduction band edge (E{sub C}), which substantially controls the conversion of neutral vacancy to charged one (V{submore » O} → V{sub O}{sup +}/V{sub O}{sup 2+} + e{sup −}/2e{sup −}), peroxide (O{sub 2}{sup 2−}) formation or conversion of ionized interstitial (O{sub i}{sup 2−}) to neutral interstitial (O{sub i}), thus electron concentration at conduction band. With increasing the exposure time, more carriers are generated, and thus, maximum photocurrent increases until being saturated. After negative bias illumination stress, the transfer curve shows −2.7 V shift at V{sub TG} = −15 V, which gradually decreases to −0.42 V shift at V{sub TG} = +15 V. It clearly reveals that the position of electron quasi-Fermi level controls the formation of donor defects (V{sub O}{sup +}/V{sub O}{sup 2+}/O{sub 2}{sup 2−}/O{sub i}) and/or hole trapping in the a-IGZO /interfaces.« less

Synthesis and Structural Characterization of Magnesium Based Coordination Networks in Different Solvents

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

D Banerjee; J Finkelstein; A Smirnov

2011-12-31

Three magnesium based metal-organic frameworks, Mg{sub 3}(3,5-PDC){sub 3}(DMF){sub 3} {center_dot} DMF [1], Mg(3,5-PDC)(H{sub 2}O) {center_dot} (H{sub 2}O) [3], and Mg{sub 4}(3,5-PDC){sub 4}(DMF){sub 2}(H{sub 2}O){sub 2} {center_dot} 2DMF {center_dot} 4.5H{sub 2}O [4], and a 2-D coordination polymer, [Mg(3,5-PDC)(H{sub 2}O){sub 2}] [2] [PDC = pyridinedicarboxylate], were synthesized using a combination of DMF, methanol, ethanol, and water. Compound 1 [space group P2{sub 1}/n, a = 12.3475(5) {angstrom}, b = 11.1929(5) {angstrom}, c = 28.6734(12) {angstrom}, {beta} = 98.8160(10){sup o}, V = 3916.0(3) {angstrom}{sup 3}] consists of a combination of isolated and corner-sharing magnesium octahedra connected by the organic linkers to form a 3-Dmore » network with a 12.2 {angstrom} x 4.6 {angstrom} 1-D channel. The channel contains coordinated and free DMF molecules. In compound 2 [space group C2/c, a = 9.964(5) {angstrom}, b = 12.0694(6) {angstrom}, c = 7.2763(4) {angstrom}, {beta} = 106.4970(6){sup o}, V = 836.70(6) {angstrom}{sup 3}], PDC connects isolated seven coordinated magnesium polyhedra into a layered structure. Compound 3 [space group P6{sub 1}22, a = 11.479(1) {angstrom}, c = 14.735(3) {angstrom}, V = 1681.7(4) {angstrom}{sup 3}] (previously reported) contains isolated magnesium octahedra connected by the organic linker with each other forming a 3D network. Compound 4 [space group P2{sub 1}/c, a = 13.7442(14) {angstrom}, b = 14.2887(15) {angstrom}, c = 14.1178(14) {angstrom}, {beta} = 104.912(2){sup o}, V = 2679.2(5) {angstrom}{sup 3}] also exhibits a 3D network based on isolated magnesium octahedra with square cavities containing both disordered DMF and water molecules. The structural topologies originate due to the variable coordination ability of solvent molecules with the metal center. Water molecules coordinate with the magnesium metal centers preferably over other polar solvents (DMF, methanol, ethanol) used to synthesize the coordination networks. Despite testing multiple desolvation routes, we were unable to measure BET surface areas greater than 51.9 m{sup 2}/g for compound 1.« less

Leakage and field emission in side-gate graphene field effect transistors

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

Di Bartolomeo, A., E-mail: dibant@sa.infn.it; Iemmo, L.; Romeo, F.

We fabricate planar graphene field-effect transistors with self-aligned side-gate at 100 nm from the 500 nm wide graphene conductive channel, using a single lithographic step. We demonstrate side-gating below 1 V with conductance modulation of 35% and transconductance up to 0.5 mS/mm at 10 mV drain bias. We measure the planar leakage along the SiO{sub 2}/vacuum gate dielectric over a wide voltage range, reporting rapidly growing current above 15 V. We unveil the microscopic mechanisms driving the leakage, as Frenkel-Poole transport through SiO{sub 2} up to the activation of Fowler-Nordheim tunneling in vacuum, which becomes dominant at higher voltages. We report a field-emission current densitymore » as high as 1 μA/μm between graphene flakes. These findings are important for the miniaturization of atomically thin devices.« less

Evaluation of wavelength groups for discrimination of agricultural cover types. [remote sensing of environment in INDIANA

NASA Technical Reports Server (NTRS)

Kumar, R.

1978-01-01

Multispectral scanner data in twelve spectral channels, in the wavelength range 0.46 to 11.7 mm, acquired in July 1971 for three flightlines, were analyzed by applying automatic pattern recognition techniques. These twelve spectral channels were divided into four wavelength groups (W1, W2, W3 and W4), each consisting of three wavelength channels -- with respect to their estimated probability of correct classification (P sub c) in discriminating agricultural cover types. The same analysis was also done for the data acquired in August, to investigate the effect of time on these results. The effect of deletion of each of the wavelength groups on P sub C in the subsets of one to nine channels, is given. Values of P sub C for all possible combinations of wavelength groups, in the subsets of one to eleven channels are also given.

Recoil /sup 18/F chemistry. XI. High pressure investigation of 1,1-difluoroethane

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

Manning, R.G.; Root, J.W.

1980-06-15

Nuclear recoil /sup 18/F reactions in CH/sub 3/CHF/sub 2/ have been investigated throughout the effective pressure range 0.3--190 atm. The principal reaction channel is F-to-HF abstraction for which the combined yield from quasithermal and energetic processes in the presence of 5 mole% H/sub 2/S additive is 83.4% +- 0.2%. A reaction mechanism is proposed that involves the organic product forming channels F-for-F, F-for-..cap alpha..H, F-for-..beta..H, F-for-CH/sub 3/ and F-for-CHF/sub 2/. The results are compared with those reported for the /sup 18/F+CH/sub 3/CF/sub 3/ system.

Photodissociation of van der Waals clusters of isoprene with oxygen, C{sub 5}H{sub 8}-O{sub 2}, in the wavelength range 213-277 nm

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

Vidma, Konstantin V.; Frederix, Pim W. J. M.; Parker, David H.

2012-08-07

The speed and angular distribution of O atoms arising from the photofragmentation of C{sub 5}H{sub 8}-O{sub 2}, the isoprene-oxygen van der Waals complex, in the wavelength region of 213-277 nm has been studied with the use of a two-color dissociation-probe method and the velocity map imaging technique. Dramatic enhancement in the O atoms photo-generation cross section in comparison with the photodissociation of individual O{sub 2} molecules has been observed. Velocity map images of these 'enhanced' O atoms consisted of five channels, different in their kinetic energy, angular distribution, and wavelength dependence. Three channels are deduced to be due to themore » one-quantum excitation of the C{sub 5}H{sub 8}-O{sub 2} complex into the perturbed Herzberg III state ({sup 3}{Delta}{sub u}) of O{sub 2}. This excitation results in the prompt dissociation of the complex giving rise to products C{sub 5}H{sub 8}+O+O when the energy of exciting quantum is higher than the complex photodissociation threshold, which is found to be 41740 {+-} 200 cm{sup -1} (239.6{+-}1.2 nm). This last threshold corresponds to the photodissociation giving rise to an unexcited isoprene molecule. The second channel, with threshold shifted to the blue by 1480 {+-} 280 cm{sup -1}, corresponds to dissociation with formation of rovibrationally excited isoprene. A third channel was observed at wavelengths up to 243 nm with excitation below the upper photodissociation threshold. This channel is attributed to dissociation with the formation of a bound O atom C{sub 5}H{sub 8}-O{sub 2}+hv{yields} C{sub 5}H{sub 8}-O{sub 2}({sup 3}{Delta}{sub u}) {yields} C{sub 5}H{sub 8}O + O and/or to dissociation of O{sub 2} with borrowing of the lacking energy from incompletely cooled complex internal degrees of freedom C{sub 5}H{sub 8}{sup *}-O{sub 2}+hv{yields} C{sub 5}H{sub 8}{sup *}-O{sub 2}({sup 3}{Delta}{sub u}) {yields} C{sub 5}H{sub 8}+ O + O. The kinetic energy of the O atoms arising in two other observed channels corresponds to O atoms produced by photodissociation of molecular oxygen in the excited a {sup 1}{Delta}{sub g} and b {sup 1}{Sigma}{sub g}{sup +} singlet states as the precursors. This indicates the formation of singlet oxygen O{sub 2}(a {sup 1}{Delta}{sub g}) and O{sub 2}(b {sup 1}{Sigma}{sub g}{sup +}) after excitation of the C{sub 5}H{sub 8}-O{sub 2} complex. Cooperative excitation of the complex with a simultaneous change of the spin of both partners {sup 1}X-{sup 3}O{sub 2}+h{nu}{yields}{sup 3}X-{sup 1}O{sub 2}{yields}{sup 3}X +{sup 1}O{sub 2} is suggested as a source of singlet oxygen O{sub 2}(a {sup 1}{Delta}{sub g}) and O{sub 2}(b {sup 1}{Sigma}{sub g}{sup +}). This cooperative excitation is in agreement with little or no vibrational excitation of O{sub 2}(a {sup 1}{Delta}{sub g}), produced from the C{sub 5}H{sub 8}-O{sub 2} complex as studied in the current paper as well as from the C{sub 3}H{sub 6}-O{sub 2} and CH{sub 3}I-O{sub 2} complexes reported in our previous paper [Baklanov et al., J. Chem. Phys. 126, 124316 (2007)]. The formation of O{sub 2}(a {sup 1}{Delta}{sub g}) from C{sub 5}H{sub 8}-O{sub 2} was observed at {lambda}{sub pump}= 213-277 nm with the yield going down towards the long wavelength edge of this interval. This spectral profile is interpreted as the red-side wing of the band of a cooperative transition {sup 1}X-{sup 3}O{sub 2}+h{nu}{yields}{sup 3}X(T{sub 2})-{sup 1}O{sub 2}(a {sup 1}{Delta}{sub g}) in the C{sub 5}H{sub 8}-O{sub 2} complex.« less

Structure-activity relationships for the action of 11 pyrethroid insecticides on rat Na{sub v}1.8 sodium channels expressed in Xenopus oocytes

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

Choi, J.-S.; Soderlund, David M.

2006-03-15

Pyrethroid insecticides bind to voltage-sensitive sodium channels and modify their gating kinetics, thereby disrupting nerve function. This paper describes the action of 11 structurally diverse commercial pyrethroid insecticides on the rat Na{sub v}1.8 sodium channel isoform, the principal carrier of the tetrodotoxin-resistant, pyrethroid-sensitive sodium current of sensory neurons, expressed in Xenopus laevis oocytes. All 11 compounds produced characteristic sodium tail currents following a depolarizing pulse that ranged from rapidly-decaying monoexponential currents (allethrin, cismethrin and permethrin) to persistent biexponential currents (cyfluthrin, cyhalothrin, cypermethrin and deltamethrin). Tail currents for the remaining compounds (bifenthrin, fenpropathrin, fenvalerate and tefluthrin) were monoexponential and decayed withmore » kinetics intermediate between these extremes. Reconstruction of currents carried solely by the pyrethroid-modified subpopulation of channels revealed two types of pyrethroid-modified currents. The first type, found with cismethrin, allethrin, permethrin and tefluthrin, activated relatively rapidly and inactivated partially during a 40-ms depolarization. The second type, found with cypermethrin, cyfluthrin, cyhalothrin, deltamethrin, fenpropathrin and fenvalerate, activated more slowly and did not detectably inactivate during a 40-ms depolarization. Only bifenthrin did not produce modified currents that fit clearly into either of these categories. In all cases, the rate of activation of modified channels was strongly correlated with the rate of tail current decay following repolarization. Modification of Na{sub v}1.8 sodium channels by cyfluthrin, cyhalothrin, cypermethrin and deltamethrin was enhanced 2.3- to 3.4-fold by repetitive stimulation; this effect appeared to result from the accumulation of persistently open channels rather than preferential binding to open channel states. Fenpropathrin was the most effective compound against Na{sub v}1.8 sodium channels from the perspective of either resting or use-dependent modification. When use dependence is taken into account, cypermethrin, deltamethrin and tefluthrin approached the effectiveness of fenpropathrin. The selective expression of Na{sub v}1.8 sodium channels in nociceptive neurons suggests that these channels may be important targets for pyrethroids in the production of paresthesia following dermal expo0010su.« less

Characterization of electrical discharges on Teflon dielectrics used as spacecraft thermal control

NASA Technical Reports Server (NTRS)

Yadlowsky, E. J.; Hazelton, R. C.; Churchill, R. J.

1979-01-01

The dual effects of system degradation and reduced life of synchronous-orbit satellites as a result of differential spacecraft charging underscore the need for a clearer understanding of the prevailing electrical discharge phenomena. In a laboratory simulation, the electrical discharge current, surface voltage, emitted particle fluxes, and photo-emission associated with discharge events on electron beam irradiated silver-backed Teflon samples were measured. Sample surface damage was examined with optical and electron beam microscopes. The results are suggestive of a model in which the entire sample surface is discharged by lateral sub-surface currents flowing from a charge deposition layer through a localized discharge channel to the back surface of the sample. The associated return current pulse appears to have a duration which may be a signature by which different discharge processes may be characterized.

Dependence of Pentacene Crystal Growth on Dielectric Roughness for Fabrication of Flexible Field-Effect Transistors

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

Yang, H.; Yang, C; Kim, S

2010-01-01

The dependence of pentacene nanostructures on gate dielectric surfaces were investigated for flexible organic field-effect transistor (OFET) applications. Two bilayer types of polymer/aluminum oxide (Al{sub 2}O{sub 3}) gate dielectrics were fabricated on commercial Al foils laminated onto a polymer back plate. Some Al foils were directly used as gate electrodes, and others were smoothly polished by an electrolytic etching. These Al surfaces were then anodized and coated with poly({alpha}-methyl styrene) (PAMS). For PAMS/Al{sub 2}O{sub 3} dielectrics onto etched Al foils, surface roughness up to 1 nm could be reached, although isolated dimples with a lateral diameter of several micrometers weremore » still present. On PAMS/Al{sub 2}O{sub 3} dielectrics (surface roughness >40 nm) containing mechanical grooves of Al foil, average hole mobility ({mu}FET) of 50 nm thick pentacene-FETs under the low operating voltages (|V| < 6 V) was {approx}0.15 cm{sup 2} V{sup -1} s{sup -1}. In contrast, pentacene-FETs employing the etched Al gates exhibited {mu}FET of 0.39 cm{sup 2} V{sup -1} s{sup -1}, which was comparable to that of reference samples with PAMS/Al{sub 2}O{sub 3} dielectrics onto flat sputtered Al gates. Conducting-probe atomic force microscopy and two-dimensional X-ray diffraction of pentacene films with various thicknesses revealed different out-of-plane and in-plane crystal orderings of pentacene, depending on the surface roughness of the gate dielectrics.« less

Disorder Effects in Charge Transport and Spin Response of Topological Insulators

NASA Astrophysics Data System (ADS)

Zhao, Lukas Zhonghua

Topological insulators are a class of solids in which the non-trivial inverted bulk band structure gives rise to metallic surface states that are robust against impurity backscattering. First principle calculations predicted Bi2Te3, Sb2Te3 and Bi2Se3 to be three-dimensional (3D) topological insulators with a single Dirac cone on the surface. The topological surface states were subsequently observed by angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM). The investigations of charge transport through topological surfaces of 3D topological insulators, however, have faced a major challenge due to large charge carrier densities in the bulk donated by randomly distributed defects such as vacancies and antisites. This bulk disorder intermixes surface and bulk conduction channels, thereby complicating access to the low-energy (Dirac point) charge transport or magnetic response and resulting in the relatively low measured carrier mobilities. Moreover, charge inhomogeneity arising from bulk disorder can result in pronounced nanoscale spatial fluctuations of energy on the surface, leading to the formation of surface `puddles' of different carrier types. Great efforts have been made to combat the undesirable effects of disorder in 3D topological insulators and to reduce bulk carriers through chemical doping, nanostructure fabrication, and electric gating. In this work we have developed a new way to reduce bulk carrier densities using high-energy electron irradiation, thereby allowing us access to the topological surface quantum channels. We also found that disorder in 3D topological insulators can be beneficial. It can play an important part in enabling detection of unusual magnetic response from Dirac fermions and in uncovering new excitations, namely surface superconductivity in Dirac `puddles'. In Chapter 3 we show how by using differential magnetometry we could probe spin rotation in the 3D topological material family (Bi2Se 3, Bi2Te3 and Sb2Te3), and describe our detection of paramagnetic singularity in the magnetic susceptibility at low magnetic fields that persists up to room temperature, and which we have demonstrated to arise from the surfaces of the samples. The singularity is universal to the entire family, largely independent of the bulk carrier density, and consistent with the existence of electronic states near the spin-degenerate Dirac point of the 2D helical metal. The exceptional thermal stability of the signal points to an intrinsic surface cooling process, probably of thermoelectric organ, and establishes a sustainable platform for the singular field-tunable Dirac spin response. In Chapter 4 we describe our discovery of surface superconductivity in a hole-conducting topological insulator Sb2Te3 with transition to zero resistance induced through a minor tuning of growth chemistry that depletes bulk conduction channels. The depletion shifts Fermi energy towards the Dirac point as witnessed by over two orders of magnitude reduced bulk hole density and by the largest carrier mobility (~ 25,000 cm 2 V-1 s-1) found in any topological material. Direct evidence from transport, the unprecedentedly large diamagnetic screening, and the presence of up to ~ 25 meV gaps in differential conductance detected by scanning tunneling spectroscopy (STM) reveal the superconducting condensate to emerge first in surface puddles at unexpectedly high temperature, near 50 K. Percolative Josephson paths mediated by diffusing quasiparticles establish global phase coherence around 9 K. Rich structure of this state lends itself to manipulation and tuning via growth conditions and the topological material's parameters such as Fermi velocity and mean free path. In Chapter 5 we describe a new approach we have developed to reaching stable charge neutrality in 3D topological materials. The technique uses swift (~ 2.5 MeV energy) electron beams to compensate charged bulk defects and bring the Fermi level back into the bulk gap. By controlling the beam fluence we could tune bulk conductivity from p- (hole-like) to n-type (electron-like), crossing the Dirac point and back, while preserving the robust topological signatures of surface channels. We establish that at charge neutrality conductance has a two-dimensional (2D) character with a minimum value on the order of ten conductance quanta G=e 2 /h. From quantum interference contribution to 2D conductance we demonstrate in two systems, Bi2Te3 and Bi2Se 3, that at charge neutrality only two quantum channels corresponding to two topological surfaces are present. The charge neutrality point achieved using electron irradiation with long penetration range shows a route to intrinsic quantum transport of the topological states unconstrained by the bulk size.

Primary effects of metals on osmoregulatory processes

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

DiBona, D.R.; Kendall, L.K.; Ferreria, H.G.

1995-12-31

Isolated skins of the bullfrog, Rana catesbiana, were chamber-mounted as sheets, bathed on the inside (serosa) with a Ringer`s solution but on the outside with simulations of freshwater to mimic environmental conditions. An automatic voltage-clamping protocol measured short-circuit current (I{sub sc}), an index of transepithelial Na{sup +} transport, and total tissue conductance (G{sub t}). Aluminum, cadmium, chromium, copper, lead, mercury and zinc were studied separately as additives to the outer bath and yielded qualitatively similar results. Al has been most thoroughly examined. At 200 ppB (7.4 {micro}M) or more, and at pH 5.0 or below, Al inhibits both I{sub sc}more » and G{sub t}. Effects are precluded by the addition of amiloride, a diuretic that blocks Na{sup +} transport at the level of the Na{sup +} channel. Kinetic analysis reveals that Al and amiloride compete for a single binding site on the channel protein. At levels of 10 ppM, Al addition results in amiloride-insensitive increases in G{sub t} (10-fold or more) and I{sub sc} (20+ {micro}A/cm{sup 2}). Isotopic flux measurements suggest that these effects are due to an ``opening`` of epithelial tight junctions with passive, downhill diffusion of salt from inside to outside; the polarity of the resulting current reflects enhanced paracellular permeability with specificity for Cl{sup {minus}} over Na{sup +}. Varying medium pH indicates that Al{sup 3+} is the dominant species in each of the two effects. Al addition to the inner bathing medium was without effect despite access to the Na{sup +}-K{sup +}-ATPase. Contaminant metals may interfere with osmoregulation by impairing salt accumulation and by enlarging leak pathways through which solutes are lost to the environment.« less

Hierarchical macro-mesoporous structures in the system TiO{sub 2}-Al{sub 2}O{sub 3}, obtained by hydrothermal synthesis using Tween-20 as a directing agent

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

Garcia-Benjume, M.L.; Espitia-Cabrera, M.I.; Contreras-Garcia, M.E., E-mail: eucontre@zeus.umich.mx

2009-12-15

Macro-mesoporous powders of titania, alumina, and mixed titania-20%alumina systems were obtained by hydrothermal synthesis employing surfactant Tween-20 as structural directing agent in order to promote the textural properties of titania. The effect of the alumina in the titania phase and on textural properties was analyzed. The obtained powders presented a macroporous channel structure that was characterized by X-ray diffractometry, scanning and transmission electron microscopy, N{sub 2} adsorption-desorption analysis, pore size distribution, Fourier transform infrared spectrometry, and thermogravimetric analysis. It was found that alumina content retarded the anatase phase crystallization and increased the Brunauer-Emmet-Teller surface area from 136 to 210 m{supmore » 2}/g. The powders calcined at 400 deg. C are thermally stable and possess an interconnected macro-mesoporous hierarchical structure; the results indicate that this synthesis can be employed to prepare mixed titania-alumina with good textural properties.« less

Emergence of Metallic Properties at LiFePO4 Surfaces and LiFePO4/Li2S Interfaces: An Ab Initio Study.

PubMed

Timoshevskii, Vladimir; Feng, Zimin; Bevan, Kirk H; Zaghib, Karim

2015-08-26

The atomic and electronic structures of the LiFePO4 (LFP) surface, both bare and reconstructed upon possible oxygenation, are theoretically studied by ab initio methods. On the basis of total energy calculations, the atomic structure of the oxygenated surface is proposed, and the effect of surface reconstruction on the electronic properties of the surface is clarified. While bare LFP(010) surface is insulating, adsorption of oxygen leads to the emergence of semimetallic behavior by inducing the conducting states in the band gap of the system. The physical origin of these conducting states is investigated. We further demonstrate that deposition of Li2S layers on top of oxygenated LFP(010) surface leads to the formation of additional conducting hole states in the first layer of Li2S surface because of the charge transfer from sulfur p-states to the gap states of LFP surface. This demonstrates that oxygenated LFP surface not only provides conducting layers itself, but also induces conducting channels in the top layer of Li2S. These results help to achieve further understanding of potential role of LFP particles in improving the performance of Li-S batteries through emergent interface conductivity.

Determination of a transient heat transfer property of acrylic using thermochromic liquid crystals

NASA Technical Reports Server (NTRS)

Heidmann, James D.

1994-01-01

An experiment was performed to determine a transient heat transfer property of acrylic. The experiment took advantage of the known analytical solution for heat conduction in a homogeneous semi-infinite solid with a constant surface heat flux. Thermochromic liquid crystals were used to measure the temperature nonintrusively. The relevant property in this experiment was the transient thermal conduction coefficient h(sub t), which is the square root of the product of density p, specific heat c(sub p), and thermal conductivity k (i.e., square root of pc(sub p)k). A value of 595.6 W square root of s/sq m K was obtained for h(sub t), with a standard deviation of 5.1 W square root of s/sq m K. Although there is no generally accepted value for h(sub t), a commonly used one is 580 W square root of s/sq m K, which is almost 3 percent less than the h(sub t) value obtained in this experiment. Since these results were highly repeatable and since there is no definitive value for h(sub t), the new value is recommended for future use.

Scanning electrochemical microscopy of graphene/polymer hybrid thin films as supercapacitors: Physical-chemical interfacial processes

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

Gupta, Sanju, E-mail: sanju.gupta@wku.edu; Price, Carson

2015-10-15

Hybrid electrode comprising an electric double-layer capacitor of graphene nanosheets and a pseudocapacitor of the electrically conducting polymers namely, polyaniline; PAni and polypyrrole; PPy are constructed that exhibited synergistic effect with excellent electrochemical performance as thin film supercapacitors for alternative energy. The hybrid supercapacitors were prepared by layer-by-layer (LbL) assembly based on controlled electrochemical polymerization followed by reduction of graphene oxide electrochemically producing ErGO, for establishing intimate electronic contact through nanoscale architecture and chemical stability, producing a single bilayer of (PAni/ErGO){sub 1}, (PPy/ErGO){sub 1}, (PAni/GO){sub 1} and (PPy/GO){sub 1}. The rationale design is to create thin films that possess interconnectedmore » graphene nanosheets (GNS) with polymer nanostructures forming well-defined tailored interfaces allowing sufficient surface adsorption and faster ion transport due to short diffusion distances. We investigated their electrochemical properties and performance in terms of gravimetric specific capacitance, C{sub s}, from cyclic voltammograms. The LbL-assembled bilayer films exhibited an excellent C{sub s} of ≥350 F g{sup −1} as compared with constituents (∼70 F g{sup −1}) at discharge current density of 0.3 A g{sup −1} that outperformed many other hybrid supercapacitors. To gain deeper insights into the physical-chemical interfacial processes occurring at the electrode/electrolyte interface that govern their operation, we have used scanning electrochemical microscopy (SECM) technique in feedback and probe approach modes. We present our findings from viewpoint of reinforcing the role played by heterogeneous electrode surface composed of nanoscale graphene sheets (conducting) and conducting polymers (semiconducting) backbone with ordered polymer chains via higher/lower probe current distribution maps. Also targeted is SECM imaging that allowed to determine electrochemical (re)activity of surface ion adsorption sites density at solid/liquid interface.« less

Enhanced stability of steep channel beds to mass failure and debris flow initiation

NASA Astrophysics Data System (ADS)

Prancevic, J.; Lamb, M. P.; Ayoub, F.; Venditti, J. G.

2015-12-01

Debris flows dominate bedrock erosion and sediment transport in very steep mountain channels, and are often initiated from failure of channel-bed alluvium during storms. While several theoretical models exist to predict mass failures, few have been tested because observations of in-channel bed failures are extremely limited. To fill this gap in our understanding, we performed laboratory flume experiments to identify the conditions necessary to initiate bed failures in non-cohesive sediment of different sizes (D = 0.7 mm to 15 mm) on steep channel-bed slopes (S = 0.45 to 0.93) and in the presence of water flow. In beds composed of sand, failures occurred under sub-saturated conditions on steep bed slopes (S > 0.5) and under super-saturated conditions at lower slopes. In beds of gravel, however, failures occurred only under super-saturated conditions at all tested slopes, even those approaching the dry angle of repose. Consistent with theoretical models, mass failures under super-saturated conditions initiated along a failure plane approximately one grain-diameter below the bed surface, whereas the failure plane was located near the base of the bed under sub-saturated conditions. However, all experimental beds were more stable than predicted by 1-D infinite-slope stability models. In partially saturated sand, enhanced stability appears to result from suction stress. Enhanced stability in gravel may result from turbulent energy losses in pores or increased granular friction for failures that are shallow with respect to grain size. These grain-size dependent effects are not currently included in stability models for non-cohesive sediment, and they may help to explain better the timing and location of debris flow occurrence.

An optofluidic channel model for in vivo nanosensor networks in human blood

NASA Astrophysics Data System (ADS)

Johari, Pedram; Jornet, Josep M.

2017-05-01

In vivo Wireless Nanosensor Networks (iWNSNs) consist of nano-sized communicating devices with unprece- dented sensing and actuation capabilities, which are able to operate inside the human body. iWNSNs are a disruptive technology that enables the monitoring and control of biological processes at the cellular and sub- cellular levels. Compared to ex vivo measurements, which are conducted on samples extracted from the human body, iWNSNs can track (sub) cellular processes when and where they occur. Major progress in the field of na- noelectronics, nanophotonics and wireless communication is enabling the interconnection of nanosensors. Among others, plasmonic nanolasers with sub-micrometric footprint, plasmonic nano-antennas able to confine light in nanometric structures, and single-photon detectors with unrivaled sensitivity, enable the communication among implanted nanosensors in the near infrared and optical transmission windows. Motivated by these results, in this paper, an optofluidic channel model is developed to investigate the communication properties and temporal dynamics between a pair of in vivo nanosensors in the human blood. The developed model builds upon the authors' recent work on light propagation modeling through multi-layered single cells and cell assemblies and takes into account the geometric, electromagnetic and microfluidic properties of red blood cells in the human circulatory system. The proposed model guides the development of practical communication strategies among nanosensors, and paves the way through new nano-biosensing strategies able to identify diseases by detecting the slight changes in the channel impulse response, caused by either the change in shape of the blood cells or the presence of pathogens.

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

Gholipur, Reza, E-mail: gholipur.reza@gmail.com; Bahari, Ali, E-mail: a.bahari@umz.ac.ir

Highlights: • Glassy Ce{sub x}La{sub 1−x}O{sub y} nanostructure films were grown on Si(1 0 0) substrate using the sol–gel method. • G{sub p} = ωϵ{sub 0}ϵ′ tan(δ) was calculated at different temperatures. • Electrical and structural the Ce{sub x}La{sub 1−x}O{sub y} samples were studied. • The conductivity-temperature study shows that the compound obeys the Arrhenius law. - Abstract: The Ce{sub x}La{sub 1−x}O{sub y} samples are synthesized, characterized and their electrical properties are reported at different molar ratios in the frequency range of 10{sup −1}–10{sup +5} Hz. Ac conductivity and permittivity data are analyzed by using conductivity formalism. The values ofmore » capacitance and tan(δ) were recorded with respect to different frequencies and temperatures. X-ray diffraction (XRD) patterns of the films show that the films posses crystalline phases. Surface morphology of the films is analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analyses reveal that elemental composition is in right stoichiometry. Electrical characterizations of the Ce{sub x}La{sub 1−x}O{sub y} samples were done by capacitance–voltage (C–V) and current density–voltage (J–V) measurements of MOS structures. Investigation showed high value of k = 44.80 and low leakage current (∼1 × 10{sup −5} A/cm{sup 2}) of the Ce{sub 0.4}La{sub 0.6}O{sub y} film.« less

Combined wet and dry cleaning of SiGe(001)

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

Park, Sang Wook; Kaufman-Osborn, Tobin; Kim, Hyonwoong

Combined wet and dry cleaning via hydrofluoric acid (HF) and atomic hydrogen on Si{sub 0.6}Ge{sub 0.4}(001) surface was studied at the atomic level using ultrahigh vacuum scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and x-ray photoelectron spectroscopy to understand the chemical transformations of the surface. Aqueous HF removes native oxide, but residual carbon and oxygen are still observed on Si{sub 0.6}Ge{sub 0.4}(001) due to hydrocarbon contamination from post HF exposure to ambient. The oxygen contamination can be eliminated by shielding the sample from ambient via covering the sample in the HF cleaning solution until the sample is introduced tomore » the vacuum chamber or by transferring the sample in an inert environment; however, both processes still leave carbon contaminant. Dry in-situ atomic hydrogen cleaning above 330 °C removes the carbon contamination on the surface consistent with a thermally activated atomic hydrogen reaction with surface hydrocarbon. A postdeposition anneal at 550 °C induces formation of an atomically flat and ordered SiGe surface observed by STM. STS verifies that the wet and dry cleaned surface has an unpinned Fermi level with no states between the conduction and valence band edge comparable to sputter cleaned SiGe surfaces.« less

Roy-Steiner equations for πN scattering

NASA Astrophysics Data System (ADS)

Ruiz de Elvira, J.; Ditsche, C.; Hoferichter, M.; Kubis, B.; Meißner, U.-G.

2014-06-01

In this talk, we present a coupled system of integral equations for the πN → πN (s-channel) and ππ → N̅N (t-channel) lowest partial waves, derived from Roy-Steiner equations for pion-nucleon scattering. After giving a brief overview of this system of equations, we present the solution of the t-channel sub-problem by means of Muskhelishvili-Omnès techniques, and solve the s-channel sub-problem after finding a set of phase shifts and subthreshold parameters which satisfy the Roy-Steiner equations.

Sub-tidal Circulation in a deep-silled fjord: Douglas Channel, British Columbia (Canada)

NASA Astrophysics Data System (ADS)

Wan, Di; Hannah, Charles; Foreman, Mike

2016-04-01

Douglas Channel, a deep fjord on the west coast of British Columbia, Canada, is the main waterway in Kitimat fjord system that opens to Queen Charlotte Sound and Hecate Strait. The fjord is separated from the open shelf by a broad sill that is about 150 m deep, and there is another sill (200 m) that separates the fjord into an outer and an inner basin. This study examines the low-frequency (from seasonal to meteorological bands) circulation in Douglas Channel from data collected from three moorings deployed during 2013-2015, and the water property observations collected during six cruises (2014 and 2015). Estuarine flow dominates the circulation above the sill-depth. The deep flows are dominated by a yearly renewal that takes place from early June to September, and this dense water renews both basins in the form of gravity currents at 0.1 - 0.2 m/s with a thickness of 100 m. At other times of the year, the deep flow structures and water properties suggest horizontal and vertical processes and support the re-circulation idea in the inner and the outer basins. The near surface current velocity fluctuations are dominated by the along-channel wind. Overall, the circulation in the meteorological band is a mix of the estuarine flow, direct wind driven flow, and the baroclinic response to changes to the surface pressure gradient caused by the wind driven currents.

Simultaneous enhancement of photovoltage and charge transfer in Cu{sub 2}O-based photocathode using buffer and protective layers

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

Li, Changli; Delaunay, Jean-Jacques, E-mail: jean@mech.t.u-tokyo.ac.jp; Hisatomi, Takashi

2016-07-18

Coating n-type buffer and protective layers on Cu{sub 2}O may be an effective means to improve the photoelectrochemical (PEC) water-splitting performance of Cu{sub 2}O-based photocathodes. In this letter, the functions of the buffer layer and protective layer on Cu{sub 2}O are examined. It is found that a Ga{sub 2}O{sub 3} buffer layer can form a buried junction with Cu{sub 2}O, which inhibits Cu{sub 2}O self-reduction as well as increases the photovoltage through a small conduction band offset between the two semiconductors. The introduction of a TiO{sub 2} thin protective layer not only improves the stability of the photocathode but alsomore » enhances the electron transfer from the photocathode surface into the electrolyte, thus resulting in an increase in photocurrent at positive potentials. These results show that the selection of overlayers with appropriate conduction band positions provides an effective strategy for obtaining a high photovoltage and high photocurrent in PEC systems.« less

Ion channels in artificial bolaamphiphile membranes deposited on sensor chips: optical detection in an ion-channel-based biosensor

NASA Astrophysics Data System (ADS)

Schalkhammer, Thomas G. M.; Weiss-Wichert, Christof; Smetazko, Michaela M.; Valina-Saba, Miriam

1997-06-01

Signal amplification using labels should be replaced by a technique monitoring the biochemical binding event directly. The use of a ligand coupled to an artificial gated membrane ion channel is a new promising strategy. Binding of protein- or DNA/RNA-analytes at ligand modified peptide channels results in an on/off-response of the channel current due to channel closure or distortion. The sensor consists of stable transmembrane channels with a ligand bound covalently at the peptide channel entrance, a sensor chip with a photostructurized hydrophobic polymer frame, a hydrophilic ion conducting membrane support, a lipid membrane incorporating the engineered ion channels, and a current amplifier or a sensitive fluorescence monitor. Detection of channel opening or closure can ether be obtained by directly monitoring membrane conductivity or a transient change of pH or ion concentration within the membrane compartment. This change can be induced by electrochemical or optical means and its decay is directly correlated to the permeability of the membrane. The ion concentration in the sub membrane compartment was monitored by incorporation of fluorescent indicator dyes. To obtain the stable sensor membrane the lipid layer had to be attached on a support and the floating of the second lipid membrane on top of the first one had to be prevented. Both problems do not occur using our new circular C44-C76 bolaamphiphilic lipids consisting of a long hydrophobic core region and two hydrophilic heads. Use of maleic ester-head groups enabled us to easily modify the lipids with amines, thioles, alcohols, phosphates, boronic acid as well as fluorescent dyes. The properties of these membranes were studied using LB and fluorescence techniques. Based on this detection principle miniaturized sensor chips with significantly enhanced sensitivity and large multi analyte arrays are under construction.

Method and apparatus for enhancing microchannel plate data

DOEpatents

Thoe, R.S.

1983-10-24

A method and apparatus for determining centroid channel locations are disclosed for use in a system activated by one or more multichannel plates and including a linear diode array providing channels of information 1, 2, ...,n, ..., N containing signal amplitudes A/sub n/. A source of analog A/sub n/ signals, and a source of digital clock signals n, are provided. Non-zero A/sub n/ values are detected in a discriminator. A digital signal representing p, the value of n immediately preceding that whereat A/sub n/ takes its first non-zero value, is generated in a scaler. The analog A/sub n/ signals are converted to digital in an analog to digital converter. The digital A/sub n/ signals are added to produce a digital ..sigma..A/sub n/ signal in a full adder. Digital 1, 2, ..., m signals representing the number of non-zero A/sub n/ are produced by a discriminator pulse counter. Digital signals representing 1 A/sub p+1/, 2 A/sub p+2/, ..., m A/sub p+m/ are produced by pairwise multiplication in multiplier. These signal are added in multiplier summer to produce a digital ..sigma..nA/sub n/ - p..sigma..A/sub n/ signal. This signal is divided by the digital ..sigma..A/sub n/ signal in divider to provide a digital (..sigma..nA/sub n//..sigma..A/sub n/) -p signal. Finally, this last signal is added to the digital p signal in an offset summer to provide ..sigma..nA/sub n//..sigma..A/sub n/, the centroid channel locations.

High Mobility SiGe/Si Transistor Structures on Sapphire Substrates Using Ion Implantation

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Mueller, C. H.; Croke, E. T.

2003-01-01

High mobility n-type SiGe/Si transistor structures have been fabricated on sapphire substrates by ion implanting phosphorus ions into strained 100 Angstrom thick silicon channels for the first time. The strained Si channels were sandwiched between Si(sub 0.7)Ge(sub 0.3) layers, which, in turn, were deposited on Si(sub 0.7)Ge(sub 0.3) virtual substrates and graded SiGe buffer layers. After the molecular beam epitaxy (MBE) film growth process was completed, ion thick silicon channels implantation and post-annealing were used to introduce donors. The phosphorous ions were preferentially located in the Si channel at a peak concentration of approximately 1x10(exp 18)/cu cm. Room temperature electron mobilities exceeding 750 sq cm/V-sec at carrier densities of 1x10(exp 12)/sq cm were measured. Electron concentration appears to be the key factor that determines mobility, with the highest mobility observed for electron densities in the 1 - 2x10(exp 12)/sq cm range.

Transient Numerical Modeling of Catalytic Channels

NASA Technical Reports Server (NTRS)

Struk, Peter M.; Dietrich, Daniel L.; Miller, Fletcher J.; T'ien, James S.

2007-01-01

This paper presents a transient model of catalytic combustion suitable for isolated channels and monolith reactors. The model is a lumped two-phase (gas and solid) model where the gas phase is quasi-steady relative to the transient solid. Axial diffusion is neglected in the gas phase; lateral diffusion, however, is accounted for using transfer coefficients. The solid phase includes axial heat conduction and external heat loss due to convection and radiation. The combustion process utilizes detailed gas and surface reaction models. The gas-phase model becomes a system of stiff ordinary differential equations while the solid phase reduces, after discretization, into a system of stiff ordinary differential-algebraic equations. The time evolution of the system came from alternating integrations of the quasi-steady gas and transient solid. This work outlines the numerical model and presents some sensitivity studies on important parameters including internal transfer coefficients, catalytic surface site density, and external heat-loss (if applicable). The model is compared to two experiments using CO fuel: (1) steady-state conversion through an isothermal platinum (Pt) tube and (2) transient propagation of a catalytic reaction inside a small Pt tube. The model requires internal mass-transfer resistance to match the experiments at lower residence times. Under mass-transport limited conditions, the model reasonably predicted exit conversion using global mass-transfer coefficients. Near light-off, the model results did not match the experiment precisely even after adjustment of mass-transfer coefficients. Agreement improved for the first case after adjusting the surface kinetics such that the net rate of CO adsorption increased compared to O2. The CO / O2 surface mechanism came from a sub-set of reactions in a popular CH4 / O2 mechanism. For the second case, predictions improved for lean conditions with increased external heat loss or adjustment of the kinetics as in the first case. Finally, the results show that different initial surface-species distribution leads to different steady-states under certain conditions. These results demonstrate the utility of a lumped two-phase model of a transient catalytic combustor with detailed chemistry.

Innovative techniques for analyzing the three-dimensional behavioral results from acoustically tagged fish

NASA Astrophysics Data System (ADS)

Steig, Tracey W.; Timko, Mark A.

2005-04-01

Acoustic tags were used to monitor the swimming patterns of downstream migrating salmon smolts approaching various dams on the Columbia River, USA. Downstream migrating yearling chinook (Oncorhynchus tshawytscha), steelhead (Oncorhynchus mykiss), sockeye (Oncorhynchus nerka), and sub-yearling chinook smolts were surgically implanted with acoustic tags. Fish were tracked in three-dimensions as they approached and passed into the turbine intakes, spillways, and surface bypass channel entrances at the dams during the 2004 spring and summer outmigrations. A number of advances in the analysis techniques and software have been made over the past few years. Some of these improvements include the development of various fish density algorithms, stream trace modeling analysis, and advances of three-dimensional animation programs. Three-dimensional tracks of fish approaching the turbine intakes, spillways, and surface bypass channel entrances will be presented. Concentrations of fish passage will be presented as three-dimensional fish densities superimposed over dam structures. Stream trace modeling animation will be presented showing predicted fish passage routes.

Atomic-scale and pit-free flattening of GaN by combination of plasma pretreatment and time-controlled chemical mechanical polishing

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

Deng, Hui; Endo, Katsuyoshi; Yamamura, Kazuya, E-mail: yamamura@upst.eng.osaka-u.ac.jp

2015-08-03

Chemical mechanical polishing (CMP) combined with atmospheric-pressure plasma pretreatment was applied to a GaN (0001) substrate. The irradiation of a CF{sub 4}-containing plasma was proven to be very useful for modifying the surface of GaN. When CMP was conducted on a plasma-irradiated surface, a modified layer of GaF{sub 3} acted as a protective layer on GaN by preventing the formation of etch pits. Within a short duration (8 min) of CMP using a commercially available CeO{sub 2} slurry, an atomically flat surface with a root mean square (rms) roughness of 0.11 nm was obtained. Moreover, etch pits, which are inevitably introduced inmore » conventional CMP, could not be observed at the dislocation sites on the polished GaN surface. It was revealed that CMP combined with the plasma pretreatment was very effective for obtaining a pit-free and atomically flat GaN surface.« less

Donor defects and small polarons on the TiO{sub 2}(110) surface

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

Moses, P. G.; Janotti, A., E-mail: janotti@udel.edu; Van de Walle, C. G.

2016-05-14

The role of defects in the chemical activity of the rutile TiO{sub 2}(110) surface remains a rich topic of research, despite the rutile (110) being one of the most studied surfaces of transition-metal oxides. Here, we present results from hybrid functional calculations that reconcile apparently disparate views on the impact of donor defects, such as oxygen vacancies and hydrogen impurities, on the electronic structure of the (110) rutile surface. We find that the bridging oxygen vacancy and adsorbed or substitutional hydrogen are actually shallow donors, which do not induce gap states. The excess electrons from these donor centers tend tomore » localize in the form of small polarons, which are the factual cause of the deep states ∼1 eV below the conduction band, often observed in photoelectron spectroscopy measurements. Our results offer a new framework for understanding the surface electronic structure of TiO{sub 2} and related oxides.« less

Comparative investigation of surface transfer doping of hydrogen terminated diamond by high electron affinity insulators

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

Verona, C.; Marinelli, Marco; Verona-Rinati, G.

We report on a comparative study of transfer doping of hydrogenated single crystal diamond surface by insulators featured by high electron affinity, such as Nb{sub 2}O{sub 5}, WO{sub 3}, V{sub 2}O{sub 5}, and MoO{sub 3}. The low electron affinity Al{sub 2}O{sub 3} was also investigated for comparison. Hole transport properties were evaluated in the passivated hydrogenated diamond films by Hall effect measurements, and were compared to un-passivated diamond films (air-induced doping). A drastic improvement was observed in passivated samples in terms of conductivity, stability with time, and resistance to high temperatures. The efficiency of the investigated insulators, as electron acceptingmore » materials in hydrogenated diamond surface, is consistent with their electronic structure. These surface acceptor materials generate a higher hole sheet concentration, up to 6.5 × 10{sup 13} cm{sup −2}, and a lower sheet resistance, down to 2.6 kΩ/sq, in comparison to the atmosphere-induced values of about 1 × 10{sup 13} cm{sup −2} and 10 kΩ/sq, respectively. On the other hand, hole mobilities were reduced by using high electron affinity insulator dopants. Hole mobility as a function of hole concentration in a hydrogenated diamond layer was also investigated, showing a well-defined monotonically decreasing trend.« less

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

Ma, Changdong; Department of Radiation Oncology, Qilu Hospital, Shandong University, Jinan, Shandong 250012; Lu, Fei, E-mail: lufei@sdu.edu.cn

We investigated lattice modification and its physical mechanism in H and He co-implanted, z-cut potassium titanyl phosphate (KTiOPO{sub 4}). The samples were implanted with 110 keV H and 190 keV He, both to a fluence of 4 × 10{sup 16 }cm{sup −2}, at room temperature. Rutherford backscattering/channeling, high-resolution x-ray diffraction, and transmission electron microscopy were used to examine the implantation-induced structural changes and strain. Experimental and simulated x-ray diffraction results show that the strain in the implanted KTiOPO{sub 4} crystal is caused by interstitial atoms. The strain and stress are anisotropic and depend on the crystal's orientation. Transmission electron microscopy studies indicate that ion implantationmore » produces many dislocations in the as-implanted samples. Annealing can induce ion aggregation to form nanobubbles, but plastic deformation and ion out-diffusion prevent the KTiOPO{sub 4} surface from blistering.« less

NO ICE HYDROGENATION: A SOLID PATHWAY TO NH{sub 2}OH FORMATION IN SPACE

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

Congiu, Emanuele; Dulieu, Francois; Chaabouni, Henda

2012-05-01

Icy dust grains in space act as catalytic surfaces onto which complex molecules form. These molecules are synthesized through exothermic reactions from precursor radicals and, mostly, hydrogen atom additions. Among the resulting products are species of biological relevance, such as hydroxylamine-NH{sub 2}OH-a precursor molecule in the formation of amino acids. In this Letter, laboratory experiments are described that demonstrate NH{sub 2}OH formation in interstellar ice analogs for astronomically relevant temperatures via successive hydrogenation reactions of solid nitric oxide (NO). Inclusion of the experimental results in an astrochemical gas-grain model proves the importance of a solid-state NO+H reaction channel as amore » starting point for prebiotic species in dark interstellar clouds and adds a new perspective to the way molecules of biological importance may form in space.« less

Antagonistic Regulation of Cystic Fibrosis Transmembrane Conductance Regulator Cell Surface Expression by Protein Kinases WNK4 and Spleen Tyrosine Kinase ▿

PubMed Central

Mendes, Ana Isabel; Matos, Paulo; Moniz, Sónia; Luz, Simão; Amaral, Margarida D.; Farinha, Carlos M.; Jordan, Peter

2011-01-01

Members of the WNK (with-no-lysine [K]) subfamily of protein kinases regulate various ion channels involved in sodium, potassium, and chloride homeostasis by either inducing their phosphorylation or regulating the number of channel proteins expressed at the cell surface. Here, we describe findings demonstrating that the cell surface expression of the cystic fibrosis transmembrane conductance regulator (CFTR) is also regulated by WNK4 in mammalian cells. This effect of WNK4 is independent of the presence of kinase and involves interaction with and inhibition of spleen tyrosine kinase (Syk), which phosphorylates Tyr512 in the first nucleotide-binding domain 1 (NBD1) of CFTR. Transfection of catalytically active Syk into CFTR-expressing baby hamster kidney cells reduces the cell surface expression of CFTR, whereas that of WNK4 promotes it. This is shown by biotinylation of cell surface proteins, immunofluorescence microscopy, and functional efflux assays. Mutation of Tyr512 to either glutamic acid or phenylalanine is sufficient to alter CFTR surface levels. In human airway epithelial cells, downregulation of endogenous Syk and WNK4 confirms their roles as physiologic regulators of CFTR surface expression. Together, our results show that Tyr512 phosphorylation is a novel signal regulating the prevalence of CFTR at the cell surface and that WNK4 and Syk perform an antagonistic role in this process. PMID:21807898

Extrinsic and intrinsic properties in metal–insulator transition of hydrothermally prepared vanadium dioxide crystals

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

Lee, Myeongsoon; Kim, Don, E-mail: donkim@pknu.ac.kr

2014-03-01

The clear insulator (monoclinic-VO{sub 2}) to metal (rutile-VO{sub 2}) transition (IMT) was observed in electrical conductivity and differential scanning calorimeter (DSC) measurements at around 340 K, which is IMT temperature (T{sub H}), in the hydrothermally prepared VO{sub 2} crystals. The occurrence of metal to insulator transition (MIT) temperature (T{sub C}) was observed below 333 K during the first resistance measurement cycle in the most of cases. The sudden jump of the electrical resistance at IMT and MIT points was amplified several times than that of the first cycle during the repeated successive thermal cycles (heating and cooling across the IMTmore » and MIT temperatures). T{sub C} and T{sub H} shifted to higher temperature by the repeated successive thermal cycles. This shift and the amplified jump might be related to the mechanical stress between the VO{sub 2} crystals, i.e. extrinsic properties. However, the starting point of MIT, T{sub CS} = ∼ 336 K, and the starting point of IMT, T{sub HS} = ∼ 338 K, kept almost constant during the repeated thermal cycles (< 10 times). These two temperatures may be related to the intrinsic properties of the VO{sub 2}: the phase transitions initiated at these temperatures regardless of the number of the repeated thermal cycles. The neat surface of the VO{sub 2} crystals was severely damaged and the average size of particles reduced from 110 nm to 70–90 nm after extensively repeated thermal cycles (> 70 times). The damaged surface and the smaller particles, which would be originated from the mechanical stress caused by crystal volume change during the first order transition of the VO{sub 2}, would weaken the electrical conduction path (loosen grain boundaries) between the VO{sub 2} single crystals and would result in the amplified jump at the following MIT. This report may boost the study for the improved stability and lifetime of the VO{sub 2} based electronic devices. - Highlights: • The sharp phase transition in cluster of VO{sub 2} crystals depends on repeated thermal cycles. • Two intrinsic and two extrinsic temperatures are observed during the phase transition. • The mechanical stress change and surface damage may cause the extrinsic properties in transport measurement.« less

Synthesis and Structural Characterization of Magnesium Based Coordination Networks in Different Solvents

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

Banerjee, Debasis; Finkelstein, Jeffrey; Smirnov, A.

2015-10-15

Three magnesium based metal-organic frameworks, Mg{sub 3}(3,5-PDC){sub 3}(DMF){sub 3} {center_dot} DMF [1], Mg(3,5-PDC)(H{sub 2}O) {center_dot} (H{sub 2}O) [3], and Mg4(3,5-PDC)4(DMF){sub 2}(H{sub 2}O){sub 2} {center_dot} 2DMF {center_dot} 4.5H{sub 2}O [4], and a 2-D coordination polymer, [Mg(3,5-PDC)(H{sub 2}O){sub 2}] [2] [PDC = pyridinedicarboxylate], were synthesized using a combination of DMF, methanol, ethanol, and water. Compound 1 [space group P2{sub 1}/n, a = 12.3475(5) {angstrom}, b = 11.1929(5) {angstrom}, c = 28.6734(12) {angstrom}, {beta} = 98.8160(10){sup o}, V = 3916.0(3) {angstrom}{sup 3}] consists of a combination of isolated and corner-sharing magnesium octahedra connected by the organic linkers to form a 3-D network withmore » a 12.2 {angstrom} x 4.6 {angstrom} 1-D channel. The channel contains coordinated and free DMF molecules. In compound 2 [space group C2/c, a = 9.964(5) {angstrom}, b = 12.0694(6) {angstrom}, c = 7.2763(4) {angstrom}, {beta} = 106.4970(6){sup o}, V = 836.70(6) {angstrom}{sup 3}], PDC connects isolated seven coordinated magnesium polyhedra into a layered structure. Compound 3 [space group P6{sub 1}22, a = 11.479(1) {angstrom}, c = 14.735(3) {angstrom}, V = 1681.7(4) {angstrom}{sup 3}] (previously reported) contains isolated magnesium octahedra connected by the organic linker with each other forming a 3D network. Compound 4 [space group P2{sub 1}/c, a = 13.7442(14) {angstrom}, b = 14.2887(15) {angstrom}, c = 14.1178(14) {angstrom}, {beta} = 104.912(2){sup o}, V = 2679.2(5) {angstrom}{sup 3}] also exhibits a 3D network based on isolated magnesium octahedra with square cavities containing both disordered DMF and water molecules. The structural topologies originate due to the variable coordination ability of solvent molecules with the metal center. Water molecules coordinate with the magnesium metal centers preferably over other polar solvents (DMF, methanol, ethanol) used to synthesize the coordination networks. Despite testing multiple desolvation routes, we were unable to measure BET surface areas greater than 51.9 m{sup 2}/g for compound 1.« less

Geomorphic and substrate controls on spatial variability in river solute transport and biogeochemical cycling

NASA Astrophysics Data System (ADS)

Blaen, Phillip; Kurz, Marie; Knapp, Julia; Mendoza-Lera, Clara; Lee-Cullin, Joe; Klaar, Megan; Drummond, Jen; Jaeger, Anna; Zarnetske, Jay; Lewandowski, Joerg; Marti, Eugenia; Ward, Adam; Fleckenstein, Jan; Datry, Thibault; Larned, Scott; Krause, Stefan

2016-04-01

Nutrient concentrations in surface waters and groundwaters are increasing in many agricultural catchments worldwide as a result of anthropogenic activities. Increasing geomorphological heterogeneity in river channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with the hyporheic zone; a site of intense microbial activity where biogeochemical transformation rates (e.g. denitrification) can be high. However, the controls on spatial variability in biogeochemical cycling, particularly at scales relevant for river managers, are not well understood. Here, we aimed to assess: 1) how differences in geomorphological heterogeneity control river solute transport and rates of biogeochemical cycling at sub-reach scales (102 m); and 2) the relative magnitude of these differences versus those relating to reach scale substrate variability (103 m). We used the reactive 'smart' tracer resazurin (Raz), a weakly fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland river in southern England. Solute tracer tests were conducted in two reaches with contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach was divided into sub-reaches that varied in geomorphic complexity (e.g. by the presence of pool-riffle sequences or the abundance of large woody debris). Slug injections of Raz and the conservative tracer fluorescein were conducted in each reach during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation rates in the gravel-dominated reach were more than 50% higher than those in the sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation rates and conservative solute transport parameters suggests small-scale targeted management interventions to alter geomorphic heterogeneity may be effective in creating hotspots of river biogeochemical cycling and nutrient load attenuation.

Morphodynamics of Migration Surveyed at Large Spatial and Temporal Scales

NASA Astrophysics Data System (ADS)

Aalto, R.; Schwendel, A.; Nicholas, A. P.

2012-04-01

The controls on rivers migration are diverse and often complex. One way forwards is to select study rivers that meet certain simplifying conditions: near-pristine (no anthropogenic complications), large size and rapid mobility (resulting in significant change viewable in Landsat imagery), limited geological complexity (no bedrock), steady hydrology (relatively little variation in discharge and sediment load), and simplified base level control (no tides or other substantial perturbations). Such systems could then be measured at appropriate spatial and temporal scales to extract the reach-scale dynamics while averaging out the more stochastic behaviour of individual meander bends. Such an approach requires both special rivers and novel techniques, which we have investigated and present here. The two explored examples are the near-pristine Beni River basin in northern Bolivia (800 km channel length) and the similarly natural Fly-Strickland River basin in Papua New Guinea (400 km channel length) - large, tropical sand-bedded rivers that meet the above criteria. First, we conducted a GIS analysis of migration using image collections that include 1950s military aerial reconnaissance -- this allowed us to characterize mobility decades before the first Landsat satellite was launched. Following this approach, we characterized migration rate, sinuosity, and other parameters at the reach scale of 10km and the temporal scale of 50+ years, with clear patterns of rate and morphology emerging as a function of location within the systems. We conducted extensive fieldwork to explore potential controls on these patterns, with the focus of this talk being the results from DGPS surveys of river and valley slope. The length scale of these rivers, the density of the forested floodplains, and the hostility of the environments precluded the use of standard RTK-DGPS methods. Instead, we employed three novel techniques for long baseline (100s of km) DGPS surveys: OmniStar HP/XP GLONASS kinematic RT-DGPS (sub-decimetre), filtered static RT-DGPS using OmniStar VBS (sub-metre), and post-processed DGPS using newly available Precise Point Positioning methods (sub-metre). We compare these novel DGPS techniques simultaneously (recent 2011 and 2010 surveys) and over time (our 2004, 2001, and 1999 surveys), presenting an assessment of their utility for long baseline surveys of large rivers. Additionally, we present a comparison to water surface profiles developed from the raw version of the 2001 SRTM DEM, with the water elevations determined from MINIMUM 1-arc-second values (not the average 3-arc-second values previously released) - this is the first evaluation of such 'minimum' data of which we are aware. The field surveys ultimately produced quality elevation profiles that allow us to characterize and investigate the strong relationships of both reach-scale migration rate and sinuosity to water surface slope - empirical results realized over time and length scales that serve to average out stochastic noise at the bend scale.

A type of all-optical logic gate based on graphene surface plasmon polaritons

NASA Astrophysics Data System (ADS)

Wu, Xiaoting; Tian, Jinping; Yang, Rongcao

2017-11-01

In this paper, a novel type of all-optical logic device based on graphene surface plasmon polaritons (GSP) is proposed. By utilizing linear interference between the GSP waves propagating in the different channels, this new structure can realize six different basic logic gates including OR, XOR, NOT, AND, NOR, and NAND. The state of ;ON/OFF; of each input channel can be well controlled by tuning the optical conductivity of graphene sheets, which can be further controlled by changing the external gate voltage. This type of logic gate is compact in geometrical sizes and is a potential block in the integration of nanophotonic devices.

Synthesis, structural characterization and selectively catalytic properties of metal-organic frameworks with nano-sized channels: A modular design strategy

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

Qiu Lingguang; Gu Lina; Hu Gang

2009-03-15

Modular design method for designing and synthesizing microporous metal-organic frameworks (MOFs) with selective catalytical activity was described. MOFs with both nano-sized channels and potential catalytic activities could be obtained through self-assembly of a framework unit and a catalyst unit. By selecting hexaaquo metal complexes and the ligand BTC (BTC=1,3,5-benzenetricarboxylate) as framework-building blocks and using the metal complex [M(phen){sub 2}(H{sub 2}O){sub 2}]{sup 2+} (phen=1,10-phenanthroline) as a catalyst unit, a series of supramolecular MOFs 1-7 with three-dimensional nano-sized channels, i.e. [M{sup 1}(H{sub 2}O){sub 6}].[M{sup 2}(phen){sub 2}(H{sub 2}O){sub 2}]{sub 2}.2(BTC).xH{sub 2}O (M{sup 1}, M{sup 2}=Co(II), Ni(II), Cu(II), Zn(II), or Mn(II), phen=1,10-phenanthroline, BTC=1,3,5-benzenetricarboxylate, x=22-24),more » were synthesized through self-assembly, and their structures were characterized by IR, elemental analysis, and single-crystal X-ray diffraction. These supramolecular microporous MOFs showed significant size and shape selectivity in the catalyzed oxidation of phenols, which is due to catalytic reactions taking place in the channels of the framework. Design strategy, synthesis, and self-assembly mechanism for the construction of these porous MOFs were discussed. - Grapical abstract: A modular design strategy has been developed to synthesize microporous metal-organic frameworks with potential catalytic activity by self-assembly of the framework-building blocks and the catalyst unit.« less

Capillary Channel Flow (CCF) EU2-02 on the International Space Station (ISS): An Experimental Investigation of Passive Bubble Separations in an Open Capillary Channel

NASA Technical Reports Server (NTRS)

Weislogel, Mark M.; Wollman, Andrew P.; Jenson, Ryan M.; Geile, John T.; Tucker, John F.; Wiles, Brentley M.; Trattner, Andy L.; DeVoe, Claire; Sharp, Lauren M.; Canfield, Peter J.;

Strain effects in low-dimensional silicon MOS and AlGaN/GaN HEMT devices

NASA Astrophysics Data System (ADS)

Baykan, Mehmet Onur

Strained silicon technology is a well established method to enhance sub-100nm MOSFET performance. With the scalability of process-induced strain, strained silicon channels have been used in every advanced CMOS technology since the 90nm node. At the 22nm node, due to the detrimental short channel effects, non-planar silicon CMOS has emerged as a viable solution to sustain transistor scaling without compromising the device performance. Therefore, it is necessary to conduct a physics based investigation of the effects of mechanical strain in silicon MOS device performance enhancement, as the transverse and longitudinal device dimensions scale down for future technology nodes. While silicon is widely used as the material basis for logic transistors, AlGaN/GaN HEMTs promise a superior device platform over silicon based power MOSFETs for high-frequency and high-power applications. In contrast to the mature Si crystal growth technology, the abundance of defects in the GaN material system creates obstacles for the realization of a reliable AlGaN/GaN HEMT device technology. Due to the high levels of internal mechanical strain present in AlGaN/GaN HEMTs, it is of utmost importance to understand the impact of mechanical stress on AlGaN/GaN trap generation. First, we have investigated the underlying physics of the comparable electron mobility observed in (100) and (110) sidewall silicon double-gate FinFETs, which is different from the observed planar (100) and (110) electron mobility. By conducting a systematic experimental study, it is shown that the undoped body, metal gate induced stress, and volume-inversion effects do not explain the comparable electron mobility. Using a self-consistent double-gate FinFET simulator, we have showed that for (110) FinFETs, an increased population of electrons is obtained for the Delta2 valley due to the heavy nonparabolic confinement mass, leading to a comparable average electron transport effective mass for both orientations. The width dependent strain response of tri-gate p-type FinFETs are experimentally extracted using a 4-point bending jig. It is found that the low-field piezoresistance coefficient of p-type FinFETs can be modeled by using a weighted conductance average of the top and sidewall bulk piezoresistance coefficients. Next, the strain enhancement of p-type ballistic silicon nanowire MOSFETs is studied using sp3d 5s* basis nearest-neighbor tight-binding simulations coupled with a semiclassical top-of-the-barrier transport model. Size and orientation dependent strain enhancement of ballistic hole transport is explained by the strain-induced modification of the 1D nanowire valence band density-of-states. Further insights are provided for future p-type high-performance silicon nanowire logic devices. A physics based investigation is conducted to understand the strain effects on surface roughness limited electron mobility in silicon inversion layers. Based on the evidence from electrical and material characterization, a strain-induced surface morphology change is hypothesized. To model the observed electrical characteristics, we have employed a self-consistent MOSFET mobility simulator coupled with an ad hoc strain-induced roughness modification. The strain induced surface morphology change is found to be consistent among electrical and materials characterization, as well as transport simulations. In order to bridge the gap between the drift-diffusion based models for long-channel devices and the quasi-ballistic models for nanoscale channels, a unified carrier transport model is developed using an updated one-flux theory. Including the high-field and carrier confinement effects, a surface-potential based analytical transmission expression is obtained for the entire MOSFET operation range. With the new channel transmission equation and average carrier drift velocity, a new expression for channel ballisticity is defined. Impact of mechanical strain on carrier transport for both nMOSFETs and pMOSFETs in both linear and saturation regimes is explained using the new channel transmission definitions. To understand the impact of mechanical strain on AlGaN/GaN HEMT trap generation, we have devised an experimental method to obtain the photon flux-normalized relative areal trap density distribution using photoionization spectroscopy technique. The details of the trap extraction method and the experimental setup are given. Using this setup, the trap characteristics are extracted for both ungated transmission line module (TLM) and gated HEMT devices from both Si and SiC substrates. The changes in the device trap characteristics are emphasized before and after electrical stressing. It is found through the step-voltage stressing of the AlGaN/GaN HEMT gate stack that the device degradation is due to the near bandgap trap generation, which are shown to be related to the structural defects in GaN.

Low-frequency noise in MoSe{sub 2} field effect transistors

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

Das, Suprem R., E-mail: srdaspurdue@gmail.com, E-mail: janes@purdue.edu; Kwon, Jiseok; Prakash, Abhijith

One of the important performance metrics of emerging nanoelectronic devices, including low dimensional Field Effect Transistors (FETs), is the magnitude of the low-frequency noise. Atomically thin 2D semiconductor channel materials such as MoX{sub 2} (X ≡ S, Se) have shown promising transistor characteristics such as I{sub ON}/I{sub OFF} ratio exceeding 10{sup 6} and low I{sub OFF}, making them attractive as channel materials for next generation nanoelectronic devices. However, MoS{sub 2} FETs demonstrated to date exhibit high noise levels under ambient conditions. In this letter, we report at least two orders of magnitude smaller values of Hooge parameter in a back-gatedmore » MoSe{sub 2} FET (10 atomic layers) with nickel S/D contacts and measured at atmospheric pressure and temperature. The channel dominated regime of noise was extracted from the total noise spectrum and is shown to follow a mobility fluctuation model with 1/f dependence. The low noise in MoSe{sub 2} FETs is comparable to other 1D nanoelectronic devices such as carbon nanotube FETs (CNT-FETs) and paves the way for use in future applications in precision sensing and communications.« less

Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron-pnictide single crystals

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

Lu, Xin; Park, W.K.; Yuan, H.Q.

2010-04-23

Point-contact Andreev reflection spectroscopy is applied to investigate the gap structure in iron pnictide single-crystal superconductors of the AFe{sub 2}As{sub 2} (A = Ba, Sr) family ('Fe-122'). The observed point-contact junction conductance curves, G(V), can be divided into two categories: one where Andreev reflection is present for both (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} and Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, and the other with a V{sup 2/3} background conductance universally observed, extending even up to 100 meV for Sr{sub 0.6}Na{sub 0.4}Fe{sub 2}As{sub 2} and Sr(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}. The latter is also observed in point-contact junctions on the nonsuperconducting parentmore » compound BaFe{sub 2}As{sub 2} and superconducting (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} crystals. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors in the superconducting samples. For Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, double peaks due to Andreev reflection with a strongly sloping background are frequently observed for point contacts on freshly cleaved c-axis surfaces. If normalized using a background baseline and analyzed using the Blonder–Tinkham–Klapwijk model, the data show a gap size of ~ 3.0–4.0 meV with 2Δ{sub 0}/k{sub B}T{sub c} ~ 2.0–2.6, consistent with the smaller gap size reported for the LnFeAsO family ('Fe-1111'). For the Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, the G(V) curves typically display a zero-bias conductance peak.« less

Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals

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

Lu, Xin; Park, W. K.; Yuan, H. Q.

2010-01-01

Point-contact Andreev reflection spectroscopy is applied to investigate the gap structure in iron pnictide single-crystal superconductors of the AFe{sub 2}As{sub 2} (A = Ba, Sr) family (Fe-122). The observed point-contact junction conductance curves, G(V), can be divided into two categories: one where Andreev reflection is present for both (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} and Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, and the other with a V{sup 2/3} background conductance universally observed, extending even up to 100 meV for Sr{sub 0.6}Na{sub 0.4}Fe{sub 2}As{sub 2} and Sr(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}. The latter is also observed in point-contact junctions on the nonsuperconducting parentmore » compound BaFe{sub 2}As{sub 2} and superconducting (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} crystals. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors in the superconducting samples. For Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, double peaks due to Andreev reflection with a strongly sloping background are frequently observed for point contacts on freshly cleaved c-axis surfaces. If normalized using a background baseline and analyzed using the Blonder-Tinkham-Klapwijk model, the data show a gap size of {approx} 3.0-4.0 meV with 2{Delta}{sub 0}/k{sub B}T{sub c} {approx} 2.0-2.6, consistent with the smaller gap size reported for the LnFeAsO family (Fe-1111). For the Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, the G(V) curves typically display a zero-bias conductance peak.« less

The influence of atmosphere on performance of pure-phase WZ and ZB InAs nanowire transistors.

PubMed

Ullah, Abu Rifat; Joyce, Hannah J; Tan, Hoe; Jagadish, Chennupati; Micolich, Adam P

2017-09-21

We compare the characteristics of phase-pure MOCVD grown ZB and WZ InAs nanowire transistors in several atmospheres: air, dry pure N₂ and O₂, and N₂ bubbled through liquid H₂O and alcohols to identify whether phase-related structural/surface differences affect their response. Both WZ and ZB give poor gate characteristics in dry state. Adsorption of polar species reduces off-current by 2-3 orders of magnitude, increases on-off ratio and significantly reduces sub-threshold slope. The key difference is the greater sensitivity of WZ to low adsorbate level. We attribute this to facet structure and its influence on the separation between conduction electrons and surface adsorption sites. We highlight the important role adsorbed species play in nanowire device characterisation. WZ is commonly thought superior to ZB in InAs nanowire transistors. We show this is an artefact of the moderate humidity found in ambient laboratory conditions: WZ and ZB perform equally poorly in the dry gas limit yet equally well in the wet gas limit. We also highlight the vital role density-lowering disorder has in improving gate characteristics, be it stacking faults in mixed-phase WZ or surface adsorbates in pure-phase nanowires. © 2017 IOP Publishing Ltd.

Temperature independent quantum well FET with delta channel doping

NASA Technical Reports Server (NTRS)

Young, P. G.; Mena, R. A.; Alterovitz, S. A.; Schacham, S. E.; Haugland, E. J.

1992-01-01

A temperature independent device is presented which uses a quantum well structure and delta doping within the channel. The device requires a high delta doping concentration within the channel to achieve a constant Hall mobility and carrier concentration across the temperature range 300-1.4 K. Transistors were RF tested using on-wafer probing and a constant G sub max and F sub max were measured over the temperature range 300-70 K.

Bradykinin-activated transmembrane signals are coupled via N/sub o/ or N/sub i/ to production of inositol 1,4,5-trisphosphate, a second messenger in NG108-15 neuroblastoma-glioma hybrid cells

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

Higashida, H.; Streaty, R.A.; Klee, W.

1986-02-01

The addition of bradykinin to NG108-15 cells results in a transient hyperpolarization followed by prolonged cell depolarization. Injection of inositol 1,4,5-trisphosphate or CaS into the cytoplasm of NG108-15 cells also elicits cell hyperpolarization followed by depolarization. Tetraethylammonium ions inhibit the hyperpolarizing response of cells to bradykinin or inositol 1,4,5-trisphosphate. Thus, the hyperpolarizing phase of the cell response may be due to inositol 1,4,5-trisphosphate-dependent release of stored UVCa-labelled CaS into the cytoplasm, which activates CaS -dependent K channels. The depolarizing phase of the cell response to bradykinin is due largely to inhibition of M channels, thereby decreasing the rate of Kmore » efflux from cells and, to a lesser extent, to activation of CaS -dependent ion channels and CaS channels. In contrast, injection of inositol 1,4,5-trisphosphate or CaS into the cytosol did not alter M channel activity. Incubation of NG108-15 cells with pertussis toxin inhibits bradykinin-dependent cell hyperpolarization and depolarization. Bradykinin stimulates low K/sub m/ GTPase activity and inhibits adenylate cyclase in NG108-15 membrane preparations but not in membranes prepared from cells treated with pertussis toxin. These results show that (bradykinin-receptor) complexes interact with N/sub o/ or N/sub i/ and suggest that N/sub o/ and/or N/sub i/ mediate the transduction of signals from bradykinin receptors to phospholipase C and adenylate cyclase.« less

Assessment and intercomparison of numerical simulations in the Western Mediterranean Sea

NASA Astrophysics Data System (ADS)

Juza, Mélanie; Mourre, Baptiste; Renault, Lionel; Tintoré, Joaquin

2014-05-01

The Balearic Islands Coastal Observing and Forecasting System (SOCIB, www.socib.es) is developing high resolution numerical simulations (hindcasts and forecasts) in the Western Mediterranean Sea (WMOP). WMOP uses a regional configuration of the Regional Ocean Modelling System (ROMS, Shchepetkin and McWilliams, 2005) with a high spatial resolution of 1/50º (1.5-2km). Thus, theses simulations are able to reproduce mesoscale and in some cases sub-mesoscale features that are key in the Mediterranean Sea since they interact and modify the basin and sub-basin circulation. These simulations are initialized from and nested in either the Mediterranean Forecasting System (MFS, 1/16º) or Mercator-Océan simulations (MERCATOR, 1/12º). A repeated glider section in the Ibiza Channel, operated by SOCIB, has revealed significant differences between two WMOP simulations using either MFS or MERCATOR (hereafter WMOP-MFS and WMOP-MERC). In this study, MFS, MERCATOR, WMOP-MFS and WMOP-MERC are compared and evaluated using available multi-platform observations such as satellite products (Sea Level Anomaly, Sea Surface Temperature) and in situ measurements (temperature and salinity profiles from Argo floats, CTD, XBT, fixed moorings and gliders; velocity fields from HF radar and currentmeters). A quantitative comparison is necessary to evaluate the capacity of the simulations to reproduce observed ocean features, and to quantify the possible simulations biases. This will in turn allow to improve the simulations, so as to produce better ocean forecast systems, to study and better understand ocean processes and to address climate studies. Therefore, various statistical diagnostics have been developed to assess and intercompare the simulations at various spatial and temporal scales, in different sub-regions (Alboran Sea, Western and Eastern Algerian sub-basins, Balearic Sea, Gulf of Lion), in different dynamical zones (coastal areas, shelves and "open" sea), along key sections (Ibiza and Mallorca Channels, Corsica Channel, ...) and during specific events.

Validity of Binary Collision Theory in Ion-Surface Interactions at 50-500 eV

NASA Astrophysics Data System (ADS)

Gordon, Michael; Giapis, Kostas

2003-10-01

Ion-surface interactions in the 50-500 eV regime have become increasingly important in plasma processing. Concerns exist in literature about the validity of the binary collision approximation (BCA) at low impact energies because peculiarities are frequently seen in the scattered ion energy distribution. Sub-surface processes, multiple bouncing, and super-elastic phenomena have all been hypothesized. This talk will explore the usefulness of BCA theory in predicting energy transfer during ion-surface collisions in the 50-500 eV energy range. Well-defined beams of rare gas ions (Ne, Ar, Kr) were scattered off semiconductor (Si, Ge) and metal surfaces (Ag, Au, Ni, Nb) to measure energy loss upon impact. The ion beams were produced from a floating ICP reactor coupled to a small accelerator beamline for transport and mass filtering. Exit channel energies were measured using a 90 gegree electrostatic sector coupled to a quadrupole mass filter with single ion detection capability. Although the BCA presents an over-simplified picture of the collision process, our results demonstrate that it is remarkably accurate in the low energy range for a variety of projectile-target combinations. In addition, reactive ion scattering of O2+ and O+ on inert and reactive surfaces (Au vs. Ag, Pt) suggests there may be rather high energy threshold processes which determine exit channel selectivity.

Polyglycolic and Polylactic Acid Copolymers as Ureteral Replacements

DTIC Science & Technology

1978-08-25

lumen into many channels as early as 3 months (Figure 4). Many of these channels appeared to be patent and covered by urothelium at six months...Immediately following the connective tissue proliferation as seen in the 2 month samples the urothelium continued to proliferate over the surface of the...tissue cylinder lined by urothelium . Such a newly formed organ could function as a normal ureter. The peristaltic conduction of urine could return if no

LES Modeling with Experimental Validation of a Compound Channel having Converging Floodplain

NASA Astrophysics Data System (ADS)

Mohanta, Abinash; Patra, K. C.

2018-04-01

Computational fluid dynamics (CFD) is often used to predict flow structures in developing areas of a flow field for the determination of velocity field, pressure, shear stresses, effect of turbulence and others. A two phase three-dimensional CFD model along with the large eddy simulation (LES) model is used to solve the turbulence equation. This study aims to validate CFD simulations of free surface flow or open channel flow by using volume of fluid method by comparing the data observed in hydraulics laboratory of the National Institute of Technology, Rourkela. The finite volume method with a dynamic sub grid scale was carried out for a constant aspect ratio and convergence condition. The results show that the secondary flow and centrifugal force influence flow pattern and show good agreement with experimental data. Within this paper over-bank flows have been numerically simulated using LES in order to predict accurate open channel flow behavior. The LES results are shown to accurately predict the flow features, specifically the distribution of secondary circulations both for in-bank channels as well as over-bank channels at varying depth and width ratios in symmetrically converging flood plain compound sections.

Combining molecular dynamics and an electrodiffusion model to calculate ion channel conductance

NASA Astrophysics Data System (ADS)

Wilson, Michael A.; Nguyen, Thuy Hien; Pohorille, Andrew

2014-12-01

Establishing the relation between the structures and functions of protein ion channels, which are protein assemblies that facilitate transmembrane ion transport through water-filled pores, is at the forefront of biological and medical sciences. A reliable way to determine whether our understanding of this relation is satisfactory is to reproduce the measured ionic conductance over a broad range of applied voltages. This can be done in molecular dynamics simulations by way of applying an external electric field to the system and counting the number of ions that traverse the channel per unit time. Since this approach is computationally very expensive we develop a markedly more efficient alternative in which molecular dynamics is combined with an electrodiffusion equation. This alternative approach applies if steady-state ion transport through channels can be described with sufficient accuracy by the one-dimensional diffusion equation in the potential given by the free energy profile and applied voltage. The theory refers only to line densities of ions in the channel and, therefore, avoids ambiguities related to determining the surface area of the channel near its endpoints or other procedures connecting the line and bulk ion densities. We apply the theory to a simple, model system based on the trichotoxin channel. We test the assumptions of the electrodiffusion equation, and determine the precision and consistency of the calculated conductance. We demonstrate that it is possible to calculate current/voltage dependence and accurately reconstruct the underlying (equilibrium) free energy profile, all from molecular dynamics simulations at a single voltage. The approach developed here applies to other channels that satisfy the conditions of the electrodiffusion equation.

Development of a Distributed Source Containment Transport, Transformation, and Fate (CTT&F) Sub-Model for Military Installations

DTIC Science & Technology

2007-08-01

includes soil erodibility terms from the Universal Soil Lass Equation ( USLE ) for estimating the overland sediment transport capacity (for both the x and y...q = unit flow rate of water = va h [L2/T] vc = critical velocity for erosion overland [L/T] K = USLE soil erodibility factor C = USLE soil ...cover factor P = USLE soil management practice factor Be = width of eroding surface in flow direction [L]. In channels, sediment particles can be

Parametric Evaluation of Thin, Transonic Circulation-Control Airfoils

NASA Technical Reports Server (NTRS)

Schlecht, Robin; Anders, Scott

2007-01-01

Wind-tunnel tests were conducted in the NASA Langley Transonic Dynamics Tunnel on a 6 percent-thick, elliptical circulation-control airfoil with upper-surface and lower-surface blowing capability. Results for elliptical Coanda trailing-edge geometries, biconvex Coanda trailing-edge geometries, and leading-edge geometries are reported. Results are presented at subsonic and transonic Mach numbers of 0.3 and 0.8, respectively. When considering one fixed trailing-edge geometry, for both the subsonic and transonic conditions it was found that the [3.0:1] ratio elliptical Coanda surface with the most rounded leading-edge [03] performed favorably and was determined to be the best compromise between comparable configurations that took advantage of the Coanda effect. This configuration generated a maximum. (Delta)C(sub 1) = 0.625 at a C(sub mu) = 0.06 at M = 0.3, alpha = 6deg. This same configuration generated a maximum (Delta)C(sub 1) = 0.275 at a C(sub mu) = 0.0085 at M = 0.8, alpha = 3deg.

Irradiation-induced precipitation and mechanical properties of vanadium alloys at <430 C

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

Chung, H.M.; Gazda, J.; Smith, D.L.

Recent attention to V-base alloys has focused on the effect of low-temperature (<430 C) irradiation on tensile and impact properties of V-4Cr-4Ti. In previous studies, dislocation channeling, which causes flow localization and severe loss of work-hardening capability, has been attributed to dense, irradiation-induced precipitation of very fine particles. However, efforts to identify the precipitates were unsuccessful until now. In this study, analysis by transmission electron microscopy (TEM) was conducted on unalloyed V, V-5Ti, V-3Ti-1Si, and V-4Cr-4Ti specimens that were irradiated at <430 C in conventional and dynamic helium charging experiments. By means of dark-field imaging and selected-area-diffraction analysis, the characteristicmore » precipitates were identified to be (V,Ti{sub 1{minus}x})(C,O,N). In V-3Ti-1Si, precipitation of (V,Ti{sub 1{minus}x})(C,O,N) was negligible at <430 C, and as a result, dislocation channeling did not occur and work-hardening capability was high.« less

Growth behavior and properties of atomic layer deposited tin oxide on silicon from novel tin(II)acetylacetonate precursor and ozone

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

Kannan Selvaraj, Sathees; Feinerman, Alan; Takoudis, Christos G., E-mail: takoudis@uic.edu

In this work, a novel liquid tin(II) precursor, tin(II)acetylacetonate [Sn(acac){sub 2}], was used to deposit tin oxide films on Si(100) substrate, using a custom-built hot wall atomic layer deposition (ALD) reactor. Three different oxidizers, water, oxygen, and ozone, were tried. Resulting growth rates were studied as a function of precursor dosage, oxidizer dosage, reactor temperature, and number of ALD cycles. The film growth rate was found to be 0.1 ± 0.01 nm/cycle within the wide ALD temperature window of 175–300 °C using ozone; no film growth was observed with water or oxygen. Characterization methods were used to study the composition, interface quality, crystallinity, microstructure,more » refractive index, surface morphology, and resistivity of the resulting films. X-ray photoelectron spectra showed the formation of a clean SnO{sub x}–Si interface. The resistivity of the SnO{sub x} films was calculated to be 0.3 Ω cm. Results of this work demonstrate the possibility of introducing Sn(acac){sub 2} as tin precursor to deposit conducting ALD SnO{sub x} thin films on a silicon surface, with clean interface and no formation of undesired SiO{sub 2} or other interfacial reaction products, for transparent conducting oxide applications.« less

Direct wafer bonding of highly conductive GaSb/GaInAs and GaSb/GaInP heterojunctions prepared by argon-beam surface activation

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

Predan, Felix, E-mail: felix.predan@ise.fraunhofer.de; Reinwand, Dirk; Cariou, Romain

The authors present a low-temperature wafer bonding process for the formation of electrically conductive n-GaSb/n-Ga{sub 0.79}In{sub 0.21}As and n-GaSb/n-Ga{sub 0.32}In{sub 0.68}P heterojunctions. The surfaces are deoxidized by sputter-etching with an argon-beam and bonded in ultrahigh vacuum. The sputtering behavior was investigated for each material, revealing a distinct selective sputtering characteristic for Ga{sub 0.32}In{sub 0.68}P. According to these findings, the settings for the bonding process were chosen. The mechanical and electrical properties of the wafer bonds were studied. Fully bonded 2 in. wafer pairs were found for both material combinations exhibiting high bond energies, which are comparable to the binding energiesmore » in the semiconductors. Furthermore, bond resistances below 5 mΩ cm{sup 2} could be reached, which are in the range of the lowest resistances that have been reported for wafer bonded heterojunctions. This speaks, together with the high bond energies, for a high amount of covalent bonds at the interfaces. These promising bond characteristics make the integration of antimonides with arsenides or phosphides by wafer bonding attractive for various optoelectronic applications such as multijunction solar cells.« less

Planar MEMS bio-chip for recording ion-channel currents in biological cells

NASA Astrophysics Data System (ADS)

Pandey, Santosh; Ferdous, Zannatul; White, Marvin H.

2003-10-01

We describe a planar MEMS silicon structure to record ion-channel currents in biological cells. The conventional method of performing an electrophysiological experiment, 'patch-clamping,' employs a glass micropipette. Despite careful treatments of the micropipette tip, such as fire polishing and surface coating, the latter is a source of thermal noise because of its inherent, tapered, conical structure, which gives rise to a large pipette resistance. This pipette resistance, when coupled with the self-capacitance of the biological cell, limits the available bandwidth and processing of fast transient, ion channel current pulses. In this work, we reduce considerably the pipette resistance with a planar micropipette on a silicon chip to permit the resolution of sub-millisecond, ion-channel pulses. We discuss the design topology of the device, describe the fabrication sequence, and highlight important critical issues. The design of an integrated on-chip CMOS instrumentation amplifier is described, which has a low-noise front-end, input-offset cancellation, correlated double sampling (CDS), and an ultra-high gain in the order of 1012V/A.

Thermally-Conductive Metallic Coatings and Applications for Heat Removal on In-Space Cryogenic Vehicles

NASA Technical Reports Server (NTRS)

Ameen, Lauren; Hervol, David; Waters, Deborah

2017-01-01

For large in-space cryogenic upper stages, substantial axial heat removal from a forward skirt by vapor-based heat interception may not be achieved by simple attachment methods unless sufficient thermal conductance from the skirt to the cooling fluid can be achieved. Preferable methods would allow for the addition of the cooling system to existing structure with minimal impact on the structure. Otherwise, significant modification to the basic structural design andor novel and complex attachment mechanisms with high effective thermal conductance are likely to be required. The approach being pursued by evolvable Cryogenics (eCryo) is to increase the thermal performance of a relatively simple attachment system by applying metallic or other thermally conductive material coatings to the mating surface area of the fluid channel where it is attached the skirt wall. The expectation of candidate materials is that the dramatic increase in conductivity of pure metals at temperatures close to liquid hydrogen vapor temperature will compensate for the reduced actual contact area typical of mechanical joints. Basic contact conductance data at low temperatures for candidate interface materials is required to enable the test approach. A test rig was designed at NASA Glenn Research Center to provide thermal contact resistance testing between small sample coupons coated with conductive material via electron beam evaporation, a low-temperature option that will not affect physical properties of base materials. Average coating thicknesses were 10 k. The test fixture was designed to mount directly to a cryocooler cold head within a vacuum test chamber. The purpose of this test was to determine qualitative contact conductance between various test samples. Results from this effort will be implemented in a sub-scale vapor-based heat interception test, where the applicability for increased heat removal on large structural skirts will be considered.

Evaluation of spectral channels and wavelength regions for separability of agricultural cover types

NASA Technical Reports Server (NTRS)

Dejesusparada, N. (Principal Investigator); Kumar, R.

1977-01-01

The author has identified the following significant results. Multispectral scanner data in twelve spectral channels in the wavelength range of 0.4 to 11.7 microns acquired in the middle of July for three flightlines were analyzed by applying automatic pattern recognition techniques. The same analysis was performed for the data acquired in mid August, over the same three flightlines, to investigate the effect of time on the results. The effect of deletion of each spectral channel, as well as each wavelength region on P sub c, is given. Values of P sub c for all possible combinations of wavelength regions in the subsets of one to twelve spectral channels are also given. The overall values of P sub c were found to be greater for the data of mid August than the data from mid July.

Glass microfluidic devices with thin membrane voltage junctions for electrospray mass spectrometry.

PubMed

Yue, Guihua Eileen; Roper, Michael G; Jeffery, Erin D; Easley, Christopher J; Balchunas, Catherine; Landers, James P; Ferrance, Jerome P

2005-06-01

In this study a novel glass membrane was prepared for conducting high voltage (HV) to solution in the channel of a microfabricated device for generation of liquid electrospray. Taylor cone formation and mass spectra obtained from this microdevice confirmed the utility of the glass membrane, but voltage conduction through the membrane could not be successfully explained based solely on the conductivity of the glass itself. This novel method for developing a high-voltage interface for microdevices avoids direct metal/liquid contact eliminating bubble formation in the channel due to water hydrolysis on the surface of the metal. Further, this arrangement produces no dead volume as is often found with traditional liquid junctions. At the same time, preliminary investigations into the outlet design of glass microdevices for interfacing with electrospray mass spectrometry, was explored. Both the exit shape and the use of hydrophobic coatings at the channel exit of the microdevice electrospray interface were evaluated using standard proteins with results indicating the utility of this type of design after further optimization.

Channel Transmission Loss Studies During Ephemeral Flow Events: ER-5-3 Channel and Cambric Ditch, Nevada Test Site, Nye County, Nevada

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

J.J. Miller; S.A. Mizell; R.H. French

2005-10-01

Transmission losses along ephemeral channels are an important, yet poorly understood, aspect of rainfall-runoff prediction. Losses occur as flow infiltrates channel bed, banks, and floodplains. Estimating transmission losses in arid environments is difficult because of the variability of surficial geomorphic characteristics and infiltration capacities of soils and near-surface low-permeability geologic layers (e.g., calcrete). Transmission losses in ephemeral channels are nonlinear functions of discharge and time (Lane, 1972), and vary spatially along the channel reach and with soil antecedent moisture conditions (Sharma and Murthy, 1994). Rainfall-runoff models used to estimate peak discharge and runoff volume for flood hazard assessment are notmore » designed specifically for ephemeral channels, where transmission loss can be significant because of the available storage volume in channel soils. Accuracy of the flow routing and rainfall-runoff models is dependent on the transmission loss estimate. Transmission loss rate is the most uncertain parameter in flow routing through ephemeral channels. This research, sponsored by the U.S. Department of Energy, National Nuclear Security Administration (DOE/NNSA) and conducted at the Nevada Test Site (NTS), is designed to improve understanding of the impact of transmission loss on ephemeral flood modeling and compare various methodologies for predicting runoff from rainfall events. Various applications of this research to DOE projects include more site-specific accuracy in runoff prediction; possible reduction in size of flood mitigation structures at the NTS; and a better understanding of expected infiltration from runoff losses into landfill covers. Two channel transmission loss field experiments were performed on the NTS between 2001 and 2003: the first was conducted in the ER-5-3 channel (Miller et al., 2003), between March and June 2001, and the second was conducted in the Cambric Ditch (Mizell et al., 2005), between April and July 2003. Both studies used water discharged from unrelated drilling activities during well development and aquifer pump tests. Discharge measurements at several flumes located along the channels were used to directly measure transmission losses. Flume locations were chosen in relation to geomorphic surface types and ages, vegetative cover and types, subsurface indurated layers (calcrete), channel slopes, etc. Transmission losses were quantified using three different analysis methods. Method 1 uses Lane's Method (Lane, 1983) for estimating flood magnitude in ephemeral channels. Method 2 uses heat as a subsurface tracer for infiltration. Numerical modeling, using HYDRUS-2D (Simunek et al., 1999), a finite-element-based flow and transport code, was applied to estimate infiltration from soil temperature data. Method 3 uses hydraulic gradient and water content in a Darcy's Law approach (Freeze and Cherry, 1979) to calculate one-dimensional flow rates. Heat dissipation and water content data were collected for this analysis.« less

Synthesis, structure, and magnetic characterization of Cr{sub 4}US{sub 8}

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

Ward, Matthew D.; Chan, Ian Y.; Malliakas, Christos D.

The compound Cr{sub 4}US{sub 8} has been synthesized at 1073 K and its crystal structure has been determined at 100 K. The structure is modulated with a two-fold commensurate supercell. The subcell may be indexed in an orthorhombic cell but weak supercell reflections lead to the monoclinic superspace group P2{sub 1}/c(α0γ)0s with two Cr sites, one U site, and four S sites. The structure comprises a three-dimensional framework of CrS{sub 6} octahedra with channels that are partially occupied by U atoms. Each U atom in these channels is coordinated by eight S atoms in a bicapped trigonal-prismatic arrangement. The magneticmore » behavior of Cr{sub 4}US{sub 8} is complex. At temperatures above ~120 K at all measured fields, there is little difference between field-cooled and zero field-cooled data and χ(T) decreases monotonously with temperature, which is reminiscent of the Curie–Weiss law. At lower temperatures, the temperature dependence of χ(T) is complex and strongly dependent on the magnetic field strength. - Graphical abstract: Structure of Cr{sub 4}US{sub 8} viewed down the a axis. - Highlights: • At 1073 K Cr{sub 4}US{sub 8} was synthesized and at 100 K its crystal structure was determined. • The 3D structure comprises CrS{sub 6} octahedra with channels partially occupied by U. • The magnetic behavior of Cr{sub 4}US{sub 8} is complex.« less

Measuring flood discharge in unstable stream channels using ground-penetrating radar

USGS Publications Warehouse

Spicer, K.R.; Costa, J.E.; Placzek, G.

1997-01-01

Field experiments were conducted to test the ability of ground-penetrating radar (GPR) to measure stream-channel cross sections at high flows without the necessity of placing instruments in the water. Experiments were conducted at four U.S. Geological Survey gaging stations in southwest Washington State. With the GPR antenna suspended above the water surface from a bridge or cableway, traverses were made across stream channels to collect radar profile plots of the streambed. Subsequent measurements of water depth were made using conventional depth-measuring equipment (weight and tape) and were used to calculate radar signal velocities. Other streamflow-parameter data were collected to examine their relation to radar signal velocity and to claritv of streambed definition. These initial tests indicate that GPR is capable of producing a reasonably accurate (??20%) stream-channel profile and discharge far more quickly than conventional stream-gaging procedures, while avoiding the problems and hazards associated with placing instruments in the water.

Self-Optimized Biological Channels in Facilitating the Transmembrane Movement of Charged Molecules

PubMed Central

Huyen, V. T. N.; Lap, Vu Cong; Nguyen, V. Lien

2016-01-01

We consider an anisotropically two-dimensional diffusion of a charged molecule (particle) through a large biological channel under an external voltage. The channel is modeled as a cylinder of three structure parameters: radius, length, and surface density of negative charges located at the channel interior-lining. These charges induce inside the channel a potential that plays a key role in controlling the particle current through the channel. It was shown that to facilitate the transmembrane particle movement the channel should be reasonably self-optimized so that its potential coincides with the resonant one, resulting in a large particle current across the channel. Observed facilitation appears to be an intrinsic property of biological channels, regardless of the external voltage or the particle concentration gradient. This facilitation is very selective in the sense that a channel of definite structure parameters can facilitate the transmembrane movement of only particles of proper valence at corresponding temperatures. Calculations also show that the modeled channel is nonohmic with the ion conductance which exhibits a resonance at the same channel potential as that identified in the current. PMID:27022394

Method and apparatus for enhancing microchannel plate data

DOEpatents

Thoe, Robert S.

1987-01-01

A method and apparatus for determining centroid channel locations is disclosed for use in a system activated by one or more multichannel plates (16,18) and including a linear diode array (24) providing channels of information 1, 2, . . . , n, . . . , N containing signal amplitudes A.sub.n. A source of analog A.sub.n signals (40), and a source of digital clock signals n (48), are provided. Non-zero A.sub.n values are detected in a discriminator (42). A digital signal representing p, the value of n immediately preceding that whereat A.sub.n takes its first non-zero value, is generated in a scaler (50). The analog A.sub.n signals are converted to digital in an analog to digital converter (44). The digital A.sub.n signals are added to produce a digital .SIGMA.A.sub.n signal in a full adder (46). Digital 1, 2, . . . , m signals representing the number of non-zero A.sub.n are produced by a discriminator pulse counter (52). Digital signals representing 1 A.sub.p+ 1, 2 A.sub.p+2, . . . , m A.sub.p+m are produced by pairwise multiplication in multiplier (54). These signals are added in multiplier summer (56) to produce a digital .SIGMA.nA.sub.n -p.SIGMA.A.sub.n signal. This signal is divided by the digital .SIGMA.A.sub.n signal in divider (58) to provide a digital (.SIGMA.nA.sub.n /.SIGMA.A.sub.n) -p signal. Finally, this last signal is added to the digital p signal in an offset summer (60) to provide .SIGMA.nA.sub.n /.SIGMA.A.sub.n, the centroid channel locations.

Many light Higgs bosons in the next-to-minimal supersymmetric model

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

Dermisek, Radovan; Gunion, John F.

2009-03-01

The next-to-minimal supersymmetric model with a light doubletlike CP-odd Higgs boson and small tan{beta} can satisfy all experimental limits on Higgs bosons even with light superpartners. In these scenarios, the two lightest CP-even Higgs bosons, h{sub 1} and h{sub 2}, and the charged Higgs boson, h{sup +}, can all be light enough to be produced at CERN LEP and yet have decays that have not been looked for or are poorly constrained by existing collider experiments. The channel h{sub 1}{yields}a{sub 1}a{sub 1} with a{sub 1}{yields}{tau}{sup +}{tau}{sup -} or 2j is still awaiting LEP constraints for m{sub h{sub 1}}>86 or 82more » GeV, respectively. LEP data may also contain e{sup +}e{sup -}{yields}h{sub 2}a{sub 1} events where h{sub 2}{yields}Za{sub 1} is the dominant decay, a channel that was never examined. Decays of the charged Higgs bosons are often dominated by H{sup {+-}}{yields}W{sup {+-}}{sup (}*{sup )}a{sub 1} with a{sub 1}{yields}gg, cc, and {tau}{sup +}{tau}{sup -}. This is a channel that has so far been ignored in the search for t{yields}h{sup +}b decays at the Tevatron. A specialized analysis might reveal a signal. The light a{sub 1} might be within the reach of B factories via {upsilon}{yields}{gamma}a{sub 1} decays. We study typical mass ranges and branching ratios of Higgs bosons in this scenario and compare these scenarios where the a{sub 1} has a large doublet component to the more general scenarios with arbitrary singlet component for the a{sub 1}.« less

Carbonation and CO{sub 2} uptake of concrete

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

Yang, Keun-Hyeok, E-mail: yangkh@kgu.ac.kr; Seo, Eun-A, E-mail: ssooaa@naver.com; Tae, Sung-Ho, E-mail: jnb55@hanyang.ac.kr

This study developed a reliable procedure to assess the carbon dioxide (CO{sub 2}) uptake of concrete by carbonation during the service life of a structure and by the recycling of concrete after demolition. To generalize the amount of absorbable CO{sub 2} per unit volume of concrete, the molar concentration of carbonatable constituents in hardened cement paste was simplified as a function of the unit content of cement, and the degree of hydration of the cement paste was formulated as a function of the water-to-cement ratio. The contribution of the relative humidity, type of finishing material for the concrete surface, andmore » the substitution level of supplementary cementitious materials to the CO{sub 2} diffusion coefficient in concrete was reflected using various correction factors. The following parameters varying with the recycling scenario were also considered: the carbonatable surface area of concrete crusher-runs and underground phenomena of the decreased CO{sub 2} diffusion coefficient and increased CO{sub 2} concentration. Based on the developed procedure, a case study was conducted for an apartment building with a principal wall system and an office building with a Rahmen system, with the aim of examining the CO{sub 2} uptake of each structural element under different exposure environments during the service life and recycling of the building. As input data necessary for the case study, data collected from actual surveys conducted in 2012 in South Korea were used, which included data on the surrounding environments, lifecycle inventory database, life expectancy of structures, and recycling activity scenario. Ultimately, the CO{sub 2} uptake of concrete during a 100-year lifecycle (life expectancy of 40 years and recycling span of 60 years) was estimated to be 15.5%–17% of the CO{sub 2} emissions from concrete production, which roughly corresponds to 18%–21% of the CO{sub 2} emissions from the production of ordinary Portland cement. - Highlights: • CO{sub 2} uptake assessment approach owing to the concrete carbonation is developed. • An equation to directly determine the absorbable CO{sub 2} amount in concrete is proposed. • The carbonatable surface area of concrete crusher-runs for CO{sub 2} uptake is ascertained. • This study provides typical data for uptake and emission of CO{sub 2} in concrete building.« less

Long-term hypoxia increases calcium affinity of BK channels in ovine fetal and adult cerebral artery smooth muscle

PubMed Central

Tao, Xiaoxiao; Lin, Mike T.; Thorington, Glyne U.; Wilson, Sean M.; Longo, Lawrence D.

2015-01-01

Acclimatization to high-altitude, long-term hypoxia (LTH) reportedly alters cerebral artery contraction-relaxation responses associated with changes in K+ channel activity. We hypothesized that to maintain oxygenation during LTH, basilar arteries (BA) in the ovine adult and near-term fetus would show increased large-conductance Ca2+ activated potassium (BK) channel activity. We measured BK channel activity, expression, and cell surface distribution by use of patch-clamp electrophysiology, flow cytometry, and confocal microscopy, respectively, in myocytes from normoxic control and LTH adult and near-term fetus BA. Electrophysiological data showed that BK channels in LTH myocytes exhibited 1) lowered Ca2+ set points, 2) left-shifted activation voltages, and 3) longer dwell times. BK channels in LTH myocytes also appeared to be more dephosphorylated. These differences collectively make LTH BK channels more sensitive to activation. Studies using flow cytometry showed that the LTH fetus exhibited increased BK β1 subunit surface expression. In addition, in both fetal groups confocal microscopy revealed increased BK channel clustering and colocalization to myocyte lipid rafts. We conclude that increased BK channel activity in LTH BA occurred in association with increased channel affinity for Ca2+ and left-shifted voltage activation. Increased cerebrovascular BK channel activity may be a mechanism by which LTH adult and near-term fetal sheep can acclimatize to long-term high altitude hypoxia. Our findings suggest that increasing BK channel activity in cerebral myocytes may be a therapeutic target to ameliorate the adverse effects of high altitude in adults or of intrauterine hypoxia in the fetus. PMID:25599571

Multi-channel gas-delivery system

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

Rozenzon, Yan; Trujillo, Robert T.; Beese, Steven C.

One embodiment of the present invention provides a gas-delivery system for delivering reaction gas to a reactor chamber. The gas-delivery system includes a main gas-inlet port for receiving reaction gases and a gas-delivery plate that includes a plurality of gas channels. A gas channel includes a plurality of gas holes for allowing the reaction gases to enter the reactor chamber from the gas channel. The gas-delivery system further includes a plurality of sub-gas lines coupling together the main gas-inlet port and the gas-delivery plate, and a respective sub-gas line is configured to deliver a portion of the received reaction gasesmore » to a corresponding gas channel.« less

Surface potentials measure ion concentrations near lipid bilayers during rapid solution changes.

PubMed Central

Laver, D R; Curtis, B A

1996-01-01

We describe a puffing method for changing solutions near one surface of lipid bilayers that allows simultaneous measurement of channel activity and extent of solution change at the bilayer surface. Ion adsorption to the lipid headgroups and screening of the bilayer surface charge by mobile ions provided a convenient probe for the ionic composition of the solution at the bilayer surface. Rapid ionic changes induced a shift in bilayer surface potential that generated a capacitive transient current under voltage-clamp conditions. This depended on the ion species and bilayer composition and was accurately described by the Stern-Gouy-Chapman theory. The time course of solute concentrations during solution changes could also be modeled by an exponential exchange of bath and puffing solutions with time constants ranging from 20 to 110 ms depending on the flow pressure. During changes in [Cs+] and [Ca2+] (applied separately or together) both the mixing model and capacitive currents predicted [Cs+] and [Ca2+] transients consistent with those determined experimentally from: 1) the known Cs(+)-dependent conductance of open ryanodine receptor channels and 2) the Ca(2+)-dependent gating of ryanodine receptor Ca2+ channels from cardiac and skeletal muscle. Images FIGURE 1 FIGURE 4 FIGURE 5 FIGURE 8 PMID:8842210

Oceanic lithosphere and asthenosphere: The thermal and mechanical structure

NASA Technical Reports Server (NTRS)

Schubert, G.; Froidevaux, C.; Yuen, D. A.

1976-01-01

A coupled thermal and mechanical solid state model of the oceanic lithosphere and asthenosphere is presented. The model includes vertical conduction of heat with a temperature dependent thermal conductivity, horizontal and vertical advection of heat, viscous dissipation or shear heating, and linear or nonlinear deformation mechanisms with temperature and pressure dependent constitutive relations between shear stress and strain rate. A constant horizontal velocity u sub 0 and temperature t sub 0 at the surface and zero horizontal velocity and constant temperature t sub infinity at great depth are required. In addition to numerical values of the thermal and mechanical properties of the medium, only the values of u sub 0, t sub 0 and t sub infinity are specified. The model determines the depth and age dependent temperature horizontal and vertical velocity, and viscosity structures of the lithosphere and asthenosphere. In particular, ocean floor topography, oceanic heat flow, and lithosphere thickness are deduced as functions of the age of the ocean floor.

In-line optofluidic refractive index sensing in a side-channel photonic crystal fiber.

PubMed

Zhang, Nan; Humbert, Georges; Wu, Zhifang; Li, Kaiwei; Shum, Perry Ping; Zhang, Nancy Meng Ying; Cui, Ying; Auguste, Jean-Louis; Dinh, Xuan Quyen; Wei, Lei

2016-11-28

An in-line optofluidic refractive index (RI) sensing platform is constructed by splicing a side-channel photonic crystal fiber (SC-PCF) with side-polished single mode fibers. A long-period grating (LPG) combined with an intermodal interference between LP₀₁ and LP₁₁ core modes is used for sensing the RI of the liquid in the side channel. The resonant dip shows a nonlinear wavelength shift with increasing RI over the measured range from 1.3330 to 1.3961. The RI response of this sensing platform for a low RI range of 1.3330-1.3780 is approximately linear, and exhibits a sensitivity of 1145 nm/RIU. Besides, the detection limit of our sensing scheme is improved by around one order of magnitude by introducing the intermodal interference.

A Physically Based Distributed Hydrologic Model with a no-conventional terrain analysis

NASA Astrophysics Data System (ADS)

Rulli, M.; Menduni, G.; Rosso, R.

2003-12-01

A physically based distributed hydrological model is presented. Starting from a contour-based terrain analysis, the model makes a no-conventional discretization of the terrain. From the maximum slope lines, obtained using the principles of minimum distance and orthogonality, the models obtains a stream tubes structure. The implemented model automatically can find the terrain morphological characteristics, e.g. peaks and saddles, and deal with them respecting the stream flow. Using this type of discretization, the model divides the elements in which the water flows in two classes; the cells, that are mixtilinear polygons where the overland flow is modelled as a sheet flow and channels, obtained by the interception of two or more stream tubes and whenever surface runoff occurs, the surface runoff is channelised. The permanent drainage paths can are calculated using one of the most common methods: threshold area, variable threshold area or curvature. The subsurface flow is modelled using the Simplified Bucket Model. The model considers three type of overland flow, depending on how it is produced:infiltration excess;saturation of superficial layer of the soil and exfiltration of sub-surface flow from upstream. The surface flow and the subsurface flow across a element are routed according with the mono-dimensional equation of the kinematic wave. The also model considers the spatial variability of the channels geometry with the flow. The channels have a rectangular section with length of the base decreasing with the distance from the outlet and depending on a power of the flow. The model was tested on the Rio Gallina and Missiaga catchments and the results showed model good performances.

Formation of a physiological complex between TRPV2 and RGA protein promotes cell surface expression of TRPV2.

PubMed

Stokes, Alexander J; Wakano, Clay; Del Carmen, Kimberly A; Koblan-Huberson, Murielle; Turner, Helen

2005-03-01

The transient receptor potential, sub-family Vanilloid (TRPV)(2) cation channel is activated in response to extreme temperature elevations in sensory neurons. However, TRPV2 is widely expressed in tissues with no sensory function, including cells of the immune system. Regulation of GRC, the murine homolog of TRPV2 has been studied in insulinoma cells and myocytes. GRC is activated in response to certain growth factors and neuropeptides, via a mechanism that involves regulated access of the channel to the plasma membrane. This is likely to be an important primary control mechanism for TRPV2 outside the CNS. Here, we report that a regulated trafficking step controls the access of TRPV2 to the cell surface in mast cells. In mast cells, elevations in cytosolic cAMP are sufficient to drive plasma membrane localization of TRPV2. We have previously proposed that the recombinase gene activator protein (RGA), a four-transmembrane domain, intracellular protein, associates with TRPV2 during the biosynthesis and early trafficking of the channel. We use a polyclonal antibody to RGA to confirm the formation of a physiological complex between RGA and TRPV2. Finally, we show that over-expression of the RGA protein potentiates the basal surface localization of TRPV2. We propose that trafficking and activation mechanisms intersect for TRPV2, and that cAMP mobilizing stimuli may regulate TRPV2 localization in non-sensory cells. RGA participates in the control of TRPV2 surface levels, and co-expression of RGA may be a key component of experimental systems that seek to study TRPV2 physiology.

Ion Channel Modulators in Cystic Fibrosis.

PubMed

Gentzsch, Martina; Mall, Marcus A

2018-05-08

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and remains one of the most common life-shortening genetic diseases affecting the lung and other organs. CFTR functions as a cAMP-dependent anion channel that transports chloride and bicarbonate across epithelial surfaces and disruption of these ion transport processes plays a central role in the pathogenesis of CF. These findings provided the rationale for pharmacological modulation of ion transport, either by targeting mutant CFTR or alternative ion channels that can compensate for CFTR dysfunction, as a promising therapeutic approach. High throughput screening has supported the development of CFTR modulator compounds. CFTR correctors are designed to improve defective protein processing, trafficking and cell surface expression, whereas potentiators increase the activity of mutant CFTR at the cell surface. The approval of the first potentiator ivacaftor for the treatment of patients with specific CFTR mutations and, more recently the corrector lumacaftor in combination with ivacaftor for patients homozygous for the common F508del mutation, were major breakthroughs on the path to causal therapies for all patients with CF. In this review, we focus on recent developments and remaining challenges of CFTR-directed therapies, as well as modulators of other ion channels such as alternative chloride channels and the epithelial sodium channel (ENaC) as additional targets in CF lung disease. Further, we discuss how patient-derived precision medicine models may aid the translation of emerging next generation ion channel modulators from the laboratory to the clinic and tailor their use for optimal therapeutic benefits in individual patients with CF. Copyright © 2018. Published by Elsevier Inc.

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

Chen, Wen-Hua; Yan, Hao-Jie; Chen, Hui

Dipyridyl sulphide ligands 4-(pyridin-4-ylmethylthio)pyridine (abbreviated as L1) and 3-(pyridin-4-ylmethylthio)pyridine (abbreviated as L2) have been designed and used as μ-{sub N},{sub N}-bridging linkages to construct coordination polymers with free –S–CH{sub 2}– groups as secondary donor sites. By use solvent control method, coordination polymers ([Ag{sub 3}SO{sub 4}(L1){sub 3}](Cl)·4.5H{sub 2}O){sub ∞}(1), ([Ag{sub 2}SO{sub 4}(L1){sub 2}]·6H{sub 2}O·2CH{sub 3}OH){sub ∞}(2), ([Ag{sub 2}SO{sub 4}(L2){sub 2}]·H{sub 2}O){sub ∞}(3) and ([Ag{sub 4}(SO{sub 4}){sub 2}(L2){sub 4}]·5H{sub 2}O){sub ∞}(4) with different architectures were obtained. Complexes 1, 3 and 4 feature 1D channel with different sizes and structures. Complex 1 exhibits guest exchange by THF and 1,4-dioxane, and Hg{sup 2+} sorptionmore » ability from solution due to its relative larger channel and available bonding sites of –S– exposed to the channel region. All complexes have been characterized through single-crystal and powder X-ray diffraction (PXRD), FT-IR spectra, X-ray photoelectron spectroscopy (XPS), elemental and thermogravimetric analyses. The guest exchange and Hg{sup 2+} sorption were monitored and identified, and the structure-property relationship of coordination polymers 1–4 are discussed. - Graphical abstract: Coordination polymers of silver(I) sulfate with secondary donor sites are shown guest exchange property and Hg{sup 2+} absorb ability from solution. This work provides a new method to construct functional materials with potential application. - Highlights: • New example of constructing functional coordination polymer with secondary donor methylthio group. • Guest exchange and interesting Hg(II) absorb ability from solution are investigated. • New method to construct functional materials with potential application.« less

Enhanced heat transfer combustor technology, subtasks 1 and 2, tast C.1

NASA Technical Reports Server (NTRS)

Baily, R. D.

1986-01-01

Analytical and experimental studies are being conducted for NASA to evaluate means of increasing the heat extraction capability and service life of a liquid rocket combustor. This effort is being conducted in conjunction with other tasks to develop technologies for an advanced, expander cycle, oxygen/hydrogen engine planned for upper stage propulsion applications. Increased heat extraction, needed to raise available turbine drive energy for higher chamber pressure, is derived from combustion chamber hot gas wall ribs that increase the heat transfer surface area. Life improvement is obtained through channel designs that enhance cooling and maintain the wall temperature at an accepatable level. Laboratory test programs were conducted to evaluate the heat transfer characteristics of hot gas rib and coolant channel geometries selected through an analytical screening process. Detailed velocity profile maps, previously unavailable for rib and channel geometries, were obtained for the candidate designs using a cold flow laser velocimeter facility. Boundary layer behavior and heat transfer characteristics were determined from the velocity maps. Rib results were substantiated by hot air calorimeter testing. The flow data were analytically scaled to hot fire conditions and the results used to select two rib and three enhanced coolant channel configurations for further evaluation.

TM surface wave diffraction by a truncated dielectric slab recessed in a perfectly conducting surface. [considering flush mounted space shuttle antenna

NASA Technical Reports Server (NTRS)

Pathak, P. H.; Kouyoumjian, R. G.

1974-01-01

The diffraction of a TM sub o surface wave by a terminated dielectric slab which is flush mounted in a perfectly conducting surface is studied. The incident surface wave gives rise to waves reflected and diffracted by the termination; these reflected and diffracted fields may be expressed in terms of the geometrical theory of diffraction by introducing surface wave reflection and diffraction coefficients which are associated with the termination. In this investigation, the surface wave reflection and diffraction coefficients have been deduced from a formally exact solution to this canonical problem. The solution is obtained by a combination of the generalized scattering matrix technique and function theoretic methods.

Electrostatic attraction of weak monoacid anions increases probability for protonation and passage through aquaporins.

PubMed

Rothert, Monja; Rönfeldt, Deike; Beitz, Eric

2017-06-02

A positive electrostatic field emanating from the center of the aquaporin (AQP) water and solute channel is responsible for the repulsion of cations. At the same time, however, a positive field will attract anions. In this regard, l-lactate/lactic acid permeability has been shown for various isoforms of the otherwise highly water and neutral substrate selective AQP family. The structural requirements rendering certain AQPs permeable for weak monoacids and the mechanism of conduction have remained unclear. Here, we show by profiling pH-dependent substrate permeability, measurements of media alkalization, and proton decoupling that AQP9 acts as a channel for the protonated, neutral monocarboxylic acid species. Intriguingly, the obtained permeability rates indicate an up to 10 times higher probability of passage via AQP9 than given by the fraction of the protonated acid substrate at a certain pH. We generated AQP9 point mutants showing that this effect is independent from properties of the channel interior but caused by the protein surface electrostatics. Monocarboxylic acid-conducting AQPs thus employ a mechanism similar to the family of formate-nitrite transporters for weak monoacids. On a more general basis, our data illustrate semiquantitatively the contribution of surface electrostatics to the interaction of charged molecule substrates or ligands with target proteins, such as channels, transporters, enzymes, or receptors. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Rescue of CF airway epithelial cell function in vitro by a CFTR potentiator, VX-770

PubMed Central

Van Goor, Fredrick; Hadida, Sabine; Grootenhuis, Peter D. J.; Burton, Bill; Cao, Dong; Neuberger, Tim; Turnbull, Amanda; Singh, Ashvani; Joubran, John; Hazlewood, Anna; Zhou, Jinglan; McCartney, Jason; Arumugam, Vijayalaksmi; Decker, Caroline; Yang, Jennifer; Young, Chris; Olson, Eric R.; Wine, Jeffery J.; Frizzell, Raymond A.; Ashlock, Melissa; Negulescu, Paul

2009-01-01

Cystic fibrosis (CF) is a fatal genetic disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), a protein kinase A (PKA)-activated epithelial anion channel involved in salt and fluid transport in multiple organs, including the lung. Most CF mutations either reduce the number of CFTR channels at the cell surface (e.g., synthesis or processing mutations) or impair channel function (e.g., gating or conductance mutations) or both. There are currently no approved therapies that target CFTR. Here we describe the in vitro pharmacology of VX-770, an orally bioavailable CFTR potentiator in clinical development for the treatment of CF. In recombinant cells VX-770 increased CFTR channel open probability (Po) in both the F508del processing mutation and the G551D gating mutation. VX-770 also increased Cl− secretion in cultured human CF bronchial epithelia (HBE) carrying the G551D gating mutation on one allele and the F508del processing mutation on the other allele by ≈10-fold, to ≈50% of that observed in HBE isolated from individuals without CF. Furthermore, VX-770 reduced excessive Na+ and fluid absorption to prevent dehydration of the apical surface and increased cilia beating in these epithelial cultures. These results support the hypothesis that pharmacological agents that restore or increase CFTR function can rescue epithelial cell function in human CF airway. PMID:19846789

Water quality and quantity assessment of pervious pavements performance in experimental car park areas.

PubMed

Sañudo-Fontaneda, Luis A; Charlesworth, Susanne M; Castro-Fresno, Daniel; Andres-Valeri, Valerio C A; Rodriguez-Hernandez, Jorge

2014-01-01

Pervious pavements have become one of the most used sustainable urban drainage system (SUDS) techniques in car parks. This research paper presents the results of monitoring water quality from several experimental car park areas designed and constructed in Spain with bays made of interlocking concrete block pavement, porous asphalt, polymer-modified porous concrete and reinforced grass with plastic and concrete cells. Moreover, two different sub-base materials were used (limestone aggregates and basic oxygen furnace slag). This study therefore encompasses the majority of the materials used as permeable surfaces and sub-base layers all over the world. Effluent from the test bays was monitored for dissolved oxygen, pH, electric conductivity, total suspended solids, turbidity and total petroleum hydrocarbons in order to analyze the behaviour shown by each combination of surface and sub-base materials. In addition, permeability tests were undertaken in all car parks using the 'Laboratorio Caminos Santander' permeameter and the Cantabrian Portable Infiltrometer. All results are presented together with the influence of surface and sub-base materials on water quality indicators using bivariate correlation statistical analysis at a confidence level of 95%. The polymer-modified porous concrete surface course in combination with limestone aggregate sub-base presented the best performance.

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

Khader, S. Abdul, E-mail: khadersku@gmail.com; Sankarappa, T., E-mail: sankarappa@rediffmail.com; Muneeswaran, M.

The Particulate nano-composites of ferrite and ferroelectric phases having the general formula (x) Mg{sub 0.25}Cu{sub 0.25}Zn{sub 0.5}Fe{sub 2}O{sub 4} + (1-x) BaTiO{sub 3} (x=15%, 30% and 45%) were synthesized by sintering mixtures of highly ferroelectric BaTiO{sub 3} (BT) and highly magneto-strictive magnetic component Mg{sub 0.25}Cu{sub 0.25}Zn{sub 0.5}Fe{sub 2}O{sub 4}(MCZF). The presence of constituent phases of ferrite, ferroelectric and their composites were probed and confirmed by X-ray diffraction (XRD) studies. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The variation of dielectric constant and dissipation factor as a function of frequency from 100 Hzmore » to 1 MHz at room temperature were carried out using a Hioki LCR Hi-Tester. The dielectric constant and dielectric loss were found to decrease rapidly in the low frequency region and became almost constant in the high frequency region. The electrical conductivity deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in these composites is in conformity with small polaron hopping model. The ferroelectric properties of synthesized magneto-electric nano-composites were measured using P-E loop tracer.« less

Thermal performance of Al{sub 2}O{sub 3} in water - ethylene glycol nanofluid mixture as cooling medium in mini channel

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

Zakaria, Irnie Azlin; Mohamed, Wan Ahmad Najmi Wan; Mamat, Aman Mohd Ihsan

Continuous need for an optimum conversion efficiency of a Proton Exchange Membrane Fuel Cell (PEMFC) operation has triggered varieties of advancements namely on the thermal management engineering scope. Nanofluids as an innovative heat transfer fluid solution are expected to be a promising candidate for alternative coolant in mini channel cooling plate of PEMFC. In this work, heat transfer performance of low concentration of 0.1, 0.3 and 0.5 % Al{sub 2}O{sub 3} in water: Ethylene glycol (EG) mixtures of 100:0 and 50:50 nanofluids have been studied and compared against its base fluids at Re number ranging from 10 to 100. Amore » steady, laminar and incompressible flow with constant heat flux is assumed in the channel of 140mm × 200mm. It was found that nanofluids have performed better than the base fluid but the demerit is on the pumping power due to the higher pressure drop across mini channel geometry as expected.« less

Optical beat interference noise reduction in OFDMA optical access link using self-homodyne balanced detection

NASA Astrophysics Data System (ADS)

Jung, Sang-Min; Won, Yong-Yuk; Han, Sang-Kook

2013-12-01

A Novel technique for reducing the OBI noise in optical OFDMA-PON uplink is presented. OFDMA is a multipleaccess/ multiplexing scheme that can provide multiplexing operation of user data streams onto the downlink sub-channels and uplink multiple access by means of dividing OFDM subcarriers as sub-channels. The main issue of high-speed, single-wavelength upstream OFDMA-PON arises from optical beating interference noise. Because the sub-channels are allocated dynamically to multiple access users over same nominal wavelength, it generates the optical beating interference among upstream signals. In this paper, we proposed a novel scheme using self-homodyne balanced detection in the optical line terminal (OLT) to reduce OBI noise which is generated in the uplink transmission of OFDMA-PON system. When multiple OFDMA sub-channels over the same nominal wavelength are received at the same time in the proposed architecture, OBI noises can be removed using balanced detection. Using discrete multitone modulation (DMT) to generate real valued OFDM signals, the proposed technique is verified through experimental demonstration.

Microbial community assembly patterns under incipient conditions in a basaltic soil system

NASA Astrophysics Data System (ADS)

Sengupta, A.; Stegen, J.; Alves Meira Neto, A.; Wang, Y.; Chorover, J.; Troch, P. A. A.; Maier, R. M.

2017-12-01

In sub-surface environments, the biotic components are critically linked to the abiotic processes. However, there is limited understanding of community establishment, functional associations, and community assembly processes of such microbes in sub-surface environments. This study presents the first analysis of microbial signatures in an incipient terrestrial basalt soil system conducted under controlled conditions. A sub-meter scale sampling of a soil mesocosm revealed the contrasting distribution patterns of simple soil parameters such as bulk density and electrical conductivity. Phylogenetic analysis of 16S rRNA gene indicated the presence of a total 40 bacterial and archaeal phyla, with high relative abundance of Actinobacteria on the surface and highest abundance of Proteobacteria throughout the system. Community diversity patterns were inferred to be dependent on depth profile and average water content in the system. Predicted functional gene analysis suggested mixotrophy lifestyles with both autotrophic and heterotrophic metabolisms, likelihood of a unique salt tolerant methanogenic pathway with links to novel Euryarchea, signatures of an incomplete nitrogen cycle, and predicted enzymes of extracellular iron (II) to iron (III) conversion followed by intracellular uptake, transport and regulation. Null modeling revealed microbial community assembly was predominantly governed by variable selection, but the influence of the variable selection did not show systematic spatial structure. The presence of significant heterogeneity in predicted functions and ecologically deterministic shifts in community composition in a homogeneous incipient basalt highlights the complexity exhibited by microorganisms even in the simplest of environmental systems. This presents an opportunity to further develop our understanding of how microbial communities establish, evolve, impact, and respond in sub-surface environments.

Atomic layer deposition of Al{sub 2}O{sub 3} for single electron transistors utilizing Pt oxidation and reduction

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

McConnell, Michael S., E-mail: mmcconn5@nd.edu; Schneider, Louisa C.; Karbasian, Golnaz

This work describes the fabrication of single electron transistors using electron beam lithography and atomic layer deposition to form nanoscale tunnel transparent junctions of alumina (Al{sub 2}O{sub 3}) on platinum nanowires using either water or ozone as the oxygen precursor and trimethylaluminum as the aluminum precursor. Using room temperature, low frequency conductance measurements between the source and drain, it was found that devices fabricated using water had higher conductance than devices fabricated with ozone. Subsequent annealing caused both water- and ozone-based devices to increase in conductance by more than 2 orders of magnitude. Furthermore, comparison of devices at low temperaturesmore » (∼4 K) showed that annealed devices displayed much closer to the ideal behavior (i.e., constant differential conductance) outside of the Coulomb blockade region and that untreated devices showed nonlinear behavior outside of the Coulomb blockade region (i.e., an increase in differential conductance with source-drain voltage bias). Transmission electron microscopy cross-sectional images showed that annealing did not significantly change device geometry, but energy dispersive x-ray spectroscopy showed an unusually large amount of oxygen in the bottom platinum layer. This suggests that the atomic layer deposition process results in the formation of a thin platinum surface oxide, which either decomposes or is reduced during the anneal step, resulting in a tunnel barrier without the in-series native oxide contribution. Furthermore, the difference between ozone- and water-based devices suggests that ozone promotes atomic layer deposition nucleation by oxidizing the surface but that water relies on physisorption of the precursors. To test this theory, devices were exposed to forming gas at room temperature, which also reduces platinum oxide, and a decrease in resistance was observed, as expected.« less

Surface-plasmon polariton scattering from a finite array of nanogrooves/ridges: Efficient mirrors

NASA Astrophysics Data System (ADS)

Sánchez-Gil, José A.; Maradudin, Alexei A.

2005-06-01

The scattering of surface-plasmon polaritons (SPP) by finite arrays of one-dimensional nanodefects on metal surfaces is theoretically investigated on the basis of the reduced Rayleigh equation. Numerical calculations are carried out that rigorously account for all the scattering channels: SPP reflection and transmission, and radiative leakage. We analyze the range of parameters (defect size and number) for which high SPP reflection efficiency (low radiative losses) is achieved within a SPP band gap (negligible SPP transmission), neglecting ohmic losses (justified for array lengths significantly shorter than the SPP inelastic length): Smaller defects play better as SPP mirrors (e.g., efficiency >90% at λ ˜650nm for Gaussian ridges/grooves with sub-30nm height and half-width) than larger defects, since the latter yield significant radiative losses.

Defect assistant band alignment transition from staggered to broken gap in mixed As/Sb tunnel field effect transistor heterostructure

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

Zhu, Y.; Jain, N.; Vijayaraghavan, S.

2012-11-01

The compositional dependence of effective tunneling barrier height (E{sub beff}) and defect assisted band alignment transition from staggered gap to broken gap in GaAsSb/InGaAs n-channel tunnel field effect transistor (TFET) structures were demonstrated by x-ray photoelectron spectroscopy (XPS). High-resolution x-ray diffraction measurements revealed that the active layers are internally lattice matched. The evolution of defect properties was evaluated using cross-sectional transmission electron microscopy. The defect density at the source/channel heterointerface was controlled by changing the interface properties during growth. By increasing indium (In) and antimony (Sb) alloy compositions from 65% to 70% in In{sub x}Ga{sub 1-x}As and 60% to 65%more » in GaAs{sub 1-y}Sb{sub y} layers, the E{sub beff} was reduced from 0.30 eV to 0.21 eV, respectively, with the low defect density at the source/channel heterointerface. The transfer characteristics of the fabricated TFET device with an E{sub beff} of 0.21 eV show 2 Multiplication-Sign improvement in ON-state current compared to the device with E{sub beff} of 0.30 eV. On contrary, the value of E{sub beff} was decreased from 0.21 eV to -0.03 eV due to the presence of high defect density at the GaAs{sub 0.35}Sb{sub 0.65}/In{sub 0.7}Ga{sub 0.3}As heterointerface. As a result, the band alignment was converted from staggered gap to broken gap, which leads to 4 orders of magnitude increase in OFF-state leakage current. Therefore, a high quality source/channel interface with a properly selected E{sub beff} and well maintained low defect density is necessary to obtain both high ON-state current and low OFF-state leakage in a mixed As/Sb TFET structure for high-performance and lower-power logic applications.« less

Understanding carbon nanotube channel formation in the lipid membrane

NASA Astrophysics Data System (ADS)

Choi, Moon-ki; Kim, Hyunki; Lee, Byung Ho; Kim, Teayeop; Rho, Junsuk; Kim, Moon Ki; Kim, Kyunghoon

2018-03-01

Carbon nanotubes (CNTs) have been considered a prominent nano-channel in cell membranes because of their prominent ion-conductance and ion-selectivity, offering agents for a biomimetic channel platform. Using a coarse-grained molecular dynamics simulation, we clarify a construction mechanism of vertical CNT nano-channels in a lipid membrane for a long period, which has been difficult to observe in previous CNT-lipid interaction simulations. The result shows that both the lipid coating density and length of CNT affect the suitable fabrication condition for a vertical and stable CNT channel. Also, simulation elucidated that a lipid coating on the surface of the CNT prevents the CNT from burrowing into the lipid membrane and the vertical channel is stabilized by the repulsion force between the lipids in the coating and membrane. Our study provides an essential understanding of how CNTs can form stable and vertical channels in the membrane, which is important for designing new types of artificial channels as biosensors for bio-fluidic studies.

Effect of Pore Topology and Accessibility on Gas Adsorption Capacity in Zeolitic-Imidazolate Frameworks: Bringing Molecular Simulation Close to Experiment

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

Babarao, Ravichandar; Dai, Sheng; Jiang, Deen

2011-01-01

When all cages are assumed to be accessible, popular force fields such as universal force field (UFF) and DREIDING dramatically overpredicted gas adsorption capacity in two widely studied zeolitic-imidazolate frameworks (ZIFs), ZIF-68 and -69. Instead of adjusting the force-field parameters to match the experiments, herein we show that when the pore topology and accessibility are correctly taken into account, simulations with the standard force fields agree very well with the experiments. Careful inspection shows that ZIF-68 and -69 have two one-dimensional channels, which are not interaccessible to gases. The small channel consists of alternating small (HPR) and medium (GME) cages,more » while the large channel comprises the large (KNO) cages. Our analysis indicates that the small channel is not accessible to gases such as CO{sub 2}. So when the cages in the small channel are intentionally blocked in our simulation, the predicted adsorption capacities of CO{sub 2}, CH{sub 4} and N{sub 2} at room temperature from standard force-field parameters for the framework show excellent agreement with the experimental results. In the case of H{sub 2}, all cages are accessible, so simulation results without cage-blocking show excellent agreement with experiment. Due to the promising potential of ZIFs in gas storage and separation, our work here shows that pore topology and accessibility should be carefully examined to understand how gases adsorb in ZIFs.« less

Effect of methyl red dye on dielectric and conductivity properties of PEO/CdCl{sub 2} electrolytes

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

Kamath, Archana; Devendrappa, H., E-mail: dehu2010@gmail.com

2016-05-06

In this report the conductivity and dielectric properties of polyethylene oxide-cadmium chloride (PEO/CdCl{sub 2}) polymer electrolyte films doped with an azo dye methyl red (MR) are discussed. The films were prepared by solution casting technique at different concentrations of the dye in PEO/CdCl{sub 2} electrolyte. The thermal behavior, chemical interaction of the dye with the electrolyte and surface morphology were studied by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) respectively. The conductivity and dielectric properties were measured as a function of composition and temperature using complex impedance spectroscopy. The temperature dependent electrical conductivitymore » of the films exhibited Arrhenius type behavior. Conductivity and dielectric results also signify the enhancement in the amorphous phase of the polymer electrolyte dye systems. The value of highest conductivity observed is 1.21x10{sup −4} at 343K and the conductivity of the film was enhanced by a three orders of magnitude.« less

MapX: 2D XRF for Planetary Exploration - Image Formation and Optic Characterization

DOE PAGES

Sarrazin, P.; Blake, D.; Gailhanou, M.; ...

2018-04-01

Map-X is a planetary instrument concept for 2D X-Ray Fluorescence (XRF) spectroscopy. The instrument is placed directly on the surface of an object and held in a fixed position during the measurement. The formation of XRF images on the CCD detector relies on a multichannel optic configured for 1:1 imaging and can be analyzed through the point spread function (PSF) of the optic. The PSF can be directly measured using a micron-sized monochromatic X-ray source in place of the sample. Such PSF measurements were carried out at the Stanford Synchrotron and are compared with ray tracing simulations. It is shownmore » that artifacts are introduced by the periodicity of the PSF at the channel scale and the proximity of the CCD pixel size and the optic channel size. A strategy of sub-channel random moves was used to cancel out these artifacts and provide a clean experimental PSF directly usable for XRF image deconvolution.« less

MapX: 2D XRF for Planetary Exploration - Image Formation and Optic Characterization

NASA Astrophysics Data System (ADS)

Sarrazin, P.; Blake, D.; Gailhanou, M.; Marchis, F.; Chalumeau, C.; Webb, S.; Walter, P.; Schyns, E.; Thompson, K.; Bristow, T.

2018-04-01

Map-X is a planetary instrument concept for 2D X-Ray Fluorescence (XRF) spectroscopy. The instrument is placed directly on the surface of an object and held in a fixed position during the measurement. The formation of XRF images on the CCD detector relies on a multichannel optic configured for 1:1 imaging and can be analyzed through the point spread function (PSF) of the optic. The PSF can be directly measured using a micron-sized monochromatic X-ray source in place of the sample. Such PSF measurements were carried out at the Stanford Synchrotron and are compared with ray tracing simulations. It is shown that artifacts are introduced by the periodicity of the PSF at the channel scale and the proximity of the CCD pixel size and the optic channel size. A strategy of sub-channel random moves was used to cancel out these artifacts and provide a clean experimental PSF directly usable for XRF image deconvolution.

MapX: 2D XRF for Planetary Exploration - Image Formation and Optic Characterization

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

Sarrazin, P.; Blake, D.; Gailhanou, M.

Map-X is a planetary instrument concept for 2D X-Ray Fluorescence (XRF) spectroscopy. The instrument is placed directly on the surface of an object and held in a fixed position during the measurement. The formation of XRF images on the CCD detector relies on a multichannel optic configured for 1:1 imaging and can be analyzed through the point spread function (PSF) of the optic. The PSF can be directly measured using a micron-sized monochromatic X-ray source in place of the sample. Such PSF measurements were carried out at the Stanford Synchrotron and are compared with ray tracing simulations. It is shownmore » that artifacts are introduced by the periodicity of the PSF at the channel scale and the proximity of the CCD pixel size and the optic channel size. A strategy of sub-channel random moves was used to cancel out these artifacts and provide a clean experimental PSF directly usable for XRF image deconvolution.« less

{phi} meson production in pp annihilation at rest

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

Srisuphaphon, S.; Yan, Y.; Thailand Center of Excellence in Physics, Ministry of Education, Bangkok

2011-10-01

Apparent channel-dependent violations of the Okubo-Zwieg-Iizuka (OZI) rule in nucleon-antinucleon annihilation reactions in the presence of an intrinsic strangeness component in the nucleon are discussed. Admixture of ss quark pairs in the nucleon wave function enables the direct coupling to the {phi}-meson in the annihilation channel without violating the OZI rule. Three forms are considered in this work for the strangeness content of the proton wave function, namely, the uud cluster with a ss sea-quark component, kaon-hyperon clusters based on a simple chiral quark model, and the pentaquark picture uudss. Nonrelativistic quark model calculations reveal that the strangeness magnetic momentmore » {mu}{sub s} and the strangeness contribution to the proton spin {sigma}{sub s} from the first two models are consistent with recent experimental data, where {mu}{sub s} and {sigma}{sub s} are negative. For the third model, the uuds subsystem with the configurations [31]{sub FS}[211]{sub F}[22]{sub S} and [31]{sub FS}[31]{sub F}[22]{sub S} leads to negative values of {mu}{sub s} and {sigma}{sub s}. With effective quark line diagrams incorporating the {sup 3}P{sub 0} model, we give estimates for the branching ratios of the annihilation reactions at rest pp{yields}{phi}X (X={pi}{sup 0}, {eta}, {rho}{sup 0}, {omega}). Results for the branching ratios of {phi}X production from atomic pp s-wave states are for the first and third model found to be strongly channel dependent, in good agreement with measured rates.« less

A comparative study of the Au + H{sub 2}, Au{sup +} + H{sub 2}, and Au{sup −} + H{sub 2} systems: Potential energy surfaces and dynamics of reactive collisions

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

Dorta-Urra, Anaís; Zanchet, Alexandre; Roncero, Octavio

2015-04-21

In order to study the Au{sup −} + H{sub 2} collision, a new global potential energy surface (PES) describing the ground electronic state of AuH{sub 2}{sup −} system is developed and compared with the PESs of the neutral [Zanchet et al., J. Chem. Phys. 132, 034301 (2010)] and cationic systems [Anaís et al., J. Chem. Phys. 135, 091102 (2011)]. We found that Au{sup −} − H{sub 2} presents a H-Au-H insertion minimum attributed to the stabilization of the LUMO 3b{sub 2} orbital, which can be considered as the preamble of the chemisorption well appearing in larger gold clusters. While themore » LUMO orbital is stabilized, the HOMO 6a{sub 1} is destabilized, creating a barrier at the geometry where the energy orbitals’ curves are crossing. In the anion, this HOMO is doubly occupied, while in the neutral system is half-filled and completely empty in the cation, explaining the gradual disappearance of the well and the barrier as the number of electrons decreases. The cation presents a well in the entrance channel partially explained by electrostatic interactions. The three systems’ reactions are highly endothermic, by 1.66, 2.79, and 3.23 eV for AuH, AuH{sup +}, and AuH{sup −} products, respectively. The reaction dynamics is studied using quasi-classical trajectory method for the three systems. The one corresponding to the anionic system is new in this work. Collision energies between 1.00 and 8.00 eV, measured for the cation, are in good agreement with the simulated cross section for the AuH{sup +}. It was also found that the total fragmentation, in three atoms, competes becoming dominant at sufficiently high energy. Here, we study the competition between the two different reaction pathways for the anionic, cationic, and neutral species, explaining the differences using a simple model based on the topology of the potential energy surfaces.« less

Inversion layer on the Ge(001) surface from the four-probe conductance measurements

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

Wojtaszek, Mateusz; Lis, Jakub, E-mail: j.lis@uj.edu.pl; Zuzak, Rafal

2014-07-28

We report four-probe conductance measurements with sub-micron resolution on atomically clean Ge(001) surfaces. A qualitative difference between n-type and p-type crystals is observed. The scaling behavior of the resistance on n-type samples indicates two-dimensional current flow, while for the p-type crystal a three-dimensional description is appropriate. We interpret this in terms of the formation of an inversion layer at the surface. This result points to the surface states, i.e., dangling bonds, as the driving force behind band bending in germanium. It also explains the intrinsic character of band bending in germanium.

Compensated amorphous silicon solar cell

DOEpatents

Devaud, Genevieve

1983-01-01

An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon over said substrate and having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the electrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF.sub.3 doped intrinsic layer.

Visible light absorbance enhanced by nitrogen embedded in the surface layer of Mn-doped sodium niobate crystals, detected by ultra violet - visible spectroscopy, x-ray photoelectron spectroscopy, and electric conductivity tests

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

Molak, A., E-mail: andrzej.molak@us.edu.pl; Pilch, M.

2016-05-28

Sodium niobate crystals doped with manganese ions, Na(NbMn)O{sub 3}, were annealed in a nitrogen N{sub 2} flow at 600, 670, and 930 K. It was verified that simultaneous doping with Mn ions and annealing in nitrogen enhanced the photocatalytic features of sodium niobate. The transmission in the ultraviolet-visible range was measured at room temperature. The absorbance edge is in the range from 3.4 to 2.3 eV. The optical band gap E{sub gap} = 1.2–1.3 eV was evaluated using the Tauc relation. Crystals annealed at 670 K and 930 K exhibited an additional shift of the absorption edge of ∼20–40 nm toward longer wavelengths. The optical energy gap narrowedmore » as a result of the superimposed effect of Mn and N co-doping. The x-ray photoelectron spectroscopy test showed that N ions incorporated into the surface layer. The valence band consisted of O 2p states hybridized with Nb 4d, Mn 3d, and N 2s states. The disorder detected in the surroundings of Nb and O ions decreased due to annealing. The binding energy of oxygen ions situated within the surface layer was E{sub B} ≈ 531 eV. The other contributions were assigned to molecular contamination. The contribution centered at 535.5 eV vanished after annealing at 600 K and 670 K. The contribution centered at 534 eV vanished after annealing at 930 K. The N{sub 2} annealing partly removed carbonates from the surfaces of the samples. In the 480–950 K range, the electric conductivity activation energy, E{sub a} = 0.7–1.2 eV, was comparable with the optical E{sub gap}. The electric permittivity showed dispersion in the 0.1–800 kHz range that corresponds to the occurrence of defects.« less

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

Ren, Xueguang, E-mail: xue.g.ren@ptb.de; Pflüger, Thomas; Weyland, Marvin

The ionization and fragmentation of methane induced by low-energy (E{sub 0} = 66 eV) electron-impact is investigated using a reaction microscope. The momentum vectors of all three charged final state particles, two outgoing electrons, and one fragment ion, are detected in coincidence. Compared to the earlier study [Xu et al., J. Chem. Phys. 138, 134307 (2013)], considerable improvements to the instrumental mass and energy resolutions have been achieved. The fragment products CH{sub 4}{sup +}, CH{sub 3}{sup +}, CH{sub 2}{sup +}, CH{sup +}, and C{sup +} are clearly resolved. The binding energy resolution of ΔE = 2.0 eV is a factormore » of three better than in the earlier measurements. The fragmentation channels are investigated by measuring the ion kinetic energy distributions and the binding energy spectra. While being mostly in consistence with existing photoionization studies the results show differences including missing fragmentation channels and previously unseen channels.« less

Up-regulation of K{sub ir}2.1 by ER stress facilitates cell death of brain capillary endothelial cells

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

Kito, Hiroaki; Yamazaki, Daiju; Department of Biological Chemistry, Kyoto University, Graduate School of Pharmaceutical Sciences, Kyoto

Highlights: {yields} We found that application of endoplasmic reticulum (ER) stress with tunicamycin to brain capillary endothelial cells (BCECs) induced cell death. {yields} The ER stress facilitated the expression of inward rectifier K{sup +} channel (K{sub ir}2.1) and induced sustained membrane hyperpolarization. {yields} The membrane hyperpolarization induced sustained Ca{sup 2+} entry through voltage-independent nonspecific cation channels and consequently facilitated cell death. {yields} The K{sub ir}2.1 up-regulation by ER stress is, at least in part, responsible for cell death of BCECs under pathological conditions. -- Abstract: Brain capillary endothelial cells (BCECs) form blood brain barrier (BBB) to maintain brain homeostasis. Cellmore » turnover of BCECs by the balance of cell proliferation and cell death is critical for maintaining the integrity of BBB. Here we found that stimuli with tunicamycin, endoplasmic reticulum (ER) stress inducer, up-regulated inward rectifier K{sup +} channel (K{sub ir}2.1) and facilitated cell death in t-BBEC117, a cell line derived from bovine BCECs. The activation of K{sub ir} channels contributed to the establishment of deeply negative resting membrane potential in t-BBEC117. The deep resting membrane potential increased the resting intracellular Ca{sup 2+} concentration due to Ca{sup 2+} influx through non-selective cation channels and thereby partly but significantly regulated cell death in t-BBEC117. The present results suggest that the up-regulation of K{sub ir}2.1 is, at least in part, responsible for cell death/cell turnover of BCECs induced by a variety of cellular stresses, particularly ER stress, under pathological conditions.« less

A Three-Frequency Feed for Millimeter-Wave Radiometry

NASA Technical Reports Server (NTRS)

Hoppe, Daniel J.; Khayatian, Behrouz; Sosnowski, John B.; Johnson, Alan K.; Bruneau, Peter J.

2012-01-01

A three-frequency millimeter-wave feed horn was developed as part of an advanced component technology task that provides components necessary for higher-frequency radiometers to meet the needs of the Surface Water and Ocean Topography (SWOT) mission. The primary objectives of SWOT are to characterize ocean sub-mesoscale processes on 10-km and larger scales in the global oceans, and to measure the global water storage in inland surface water bodies, including rivers, lakes, reservoirs, and wetlands. In this innovation, the feed provides three separate output ports in the 87-to- 97-GHz, 125-to-135-GHz, and 161-to-183- GHz bands; WR10 for the 90-GHz channel, WR8 for the 130-GHz channel, and WR5 for the 170-GHz channel. These ports are in turn connected to individual radiometer channels that will also demonstrate component technology including new PIN-diode switches and noise diodes for internal calibration integrated into each radiometer front end. For this application, a prime focus feed is required with an edge taper of approximately 20 dB at an illumination angle of 40 deg. A single polarization is provided in each band. Preliminary requirements called for a return loss of better than 15 dB, which is achieved across all three bands. Good pattern symmetry is also obtained throughout all three-frequency bands. This three-frequency broadband millimeter-wave feed also minimizes mass and provides a common focal point for all three millimeter-wave bands.

In situ high temperature microwave microscope for nondestructive detection of surface and sub-surface defects.

PubMed

Wang, Peiyu; Li, Zhencheng; Pei, Yongmao

2018-04-16

An in situ high temperature microwave microscope was built for detecting surface and sub-subsurface structures and defects. This system was heated with a self-designed quartz lamp radiation module, which is capable of heating to 800°C. A line scanning of a metal grating showed a super resolution of 0.5 mm (λ/600) at 1 GHz. In situ scanning detections of surface hole defects on an aluminium plate and a glass fiber reinforced plastic (GFRP) plate were conducted at different high temperatures. A post processing algorithm was proposed to remove the background noises induced by high temperatures and the 3.0 mm-spaced hole defects were clearly resolved. Besides, hexagonal honeycomb lattices were in situ detected and clearly resolved under a 1.0 mm-thick face panel at 20°C and 50°C, respectively. The core wall positions and bonding width were accurately detected and evaluated. In summary, this in situ microwave microscope is feasible and effective in sub-surface detection and super resolution imaging at different high temperatures.

Correlating sea level rise still-stands to marine terraces and undiscovered submerged shoreline features in the Channel Islands (USA) using autonomous and remotely operated systems

NASA Astrophysics Data System (ADS)

Raineault, N.; Ballard, R. D.; Fahy, J.; Mayer, L. A.; Heffron, E.; Krasnosky, K.; Roman, C.; Schmidt, V. E.; McLeod, A.; Bursek, J.; Broad, K.

2017-12-01

In 2017, the Ocean Exploration Trust aggregated onboard and autonomous mapping technologies to identify and explore paleo shorelines and discover previously undocumented submerged shoreline features in and around the Channel Islands offshore of California. Broad area mapping was conducted with the hull mounted multibeam echosounder aboard the E/V Nautilus. This Kongsberg EM302 provided maps at 2-10 m resolution, at depths generally greater than 50 m. From this data marine terraces were identified for higher resolution mapping via an Autonomous Surface Vehicle (ASV). The precision data from the ASV's Kongsberg EM2040p echosounder allowed identification of the knickpoints associated with cliffs on the landward extent of each terrace. Sub-sea cave targets were identified using backscatter and slope maps from a combination of both the broad area and high resolution multibeam data. To ground-truth the targets identified through mapping, remotely operated vehicles (ROVs) and a highly specialized team of cave divers explored these targets. The results from the visual inspection were then fed back into the analysis fostering the rapid iteration of the onboard identification criteria and resulted in locating submerged shorelines containing numerous large caves, arches, and concretions. Caves were found at still-stands at 8, 33, 66, and 103 m depth at Santa Cruz Island, Santa Barbara Island platform, and Osborn Bank, along the vertical escarpment at the cliff-face and aligned with the strike of fractures in the volcanic rock. These terraces correspond to different sea level still-stands. ROV grab samples of fossiliferous marine terraces will provide ages and aid in reconstructions of sea level change and tectonic history for each location. Finally, caves were mapped in sub-cm resolution using a Kongsberg M3 sonar mounted vertically on the front of the ROV to test the capabilities of the system to provide accurate information about exterior dimensions and morphology.

Preferential flow and pesticide transport in a clay-rich till: Field, laboratory, and modeling analysis

NASA Astrophysics Data System (ADS)

JøRgensen, Peter R.; Hoffmann, Martin; Kistrup, Jens P.; Bryde, Claus; Bossi, Rossana; Villholth, Karen G.

2002-11-01

This study investigates vertical flow and pesticide transport along fractures in water saturated unoxidized clayey till. From two experimental fields, each 40 m2, 96% and 98%, respectively, of total vertical flow was conducted along fractures in the till, while the remaining 2-4% of flow occurred in the clay matrix at very slow flow rate. An applied dye tracer was observed only along 10-26% of the total fracture length measured on the horizontal surface of the experimental fields. In vertical sections the dyed fracture portions constituted root channels, which penetrated the till vertically along the fractures into the local aquifer at 5 m depth. No dye tracer was observed in the fractures without root channels or in the unfractured clay matrix, suggesting that root growth along the fracture surfaces was the principal agent of fracture aperture enhancement. Using hydraulic fracture aperture values determined from large undisturbed column (LUC) collected from one of the experimental fields, it was estimated that 94% of flow in the fractures was conducted along the fracture root channels, while only 6% of flow was conducted along the fracture sections without root channels. For natural vertical hydraulic gradients (0.8-2.3 at the site), flow rates of 0.8-2 km/d were determined for a fracture root channel, while fracture sections without root channels revealed flow rates of 9-22 m/d. Corresponding flow rates in the unfractured matrix were 7-19 mm/yr. For infiltrated bromide (nonreactive tracer) and mobile pesticides mecoprop (MCPP) and metsulfuron, very rapid migration (0.28-0.5 m/d) and high relative breakthrough concentrations (30-60%) into the aquifer were observed to occur along the fracture root channels using a constant hydraulic gradient of 1. Only traces were measured from infiltration of the strongly sorbed pesticide prochloraz. The concentrations of the bromide and pesticides in the monitoring wells were modeled with a discrete fracture matrix diffusion (DFDM) model coupled with a single porosity model (SP) for the till and aquifer, respectively. Using effective fracture spacings and mean fracture apertures for the fracture channel sections as modeling input parameters for the till, the concentrations observed in the wells of the aquifer could be reasonably approximated.

Determination of shelf heat transfer coefficients along the shelf flow path of a freeze dryer using the shelf fluid temperature perturbation approach.

PubMed

Kuu, Wei Y; Nail, Steven L; Hardwick, Lisa M

2007-01-01

The spatial distribution of local shelf heat transfer coefficients, Ks, was determined by mapping the transient temperature response of the shelf surface along the serpentine internal channels of the shelf while the temperature of the heat transfer fluid was ramped from -40 degrees to 40 degrees C. The solution of a first-order non-steady-state differential equation resulted in a predicted shelf surface temperature as a function of the shelf fluid temperature at any point along the flow path. During the study, the shelf surfaces were maintained under a thermally insulated condition so that the heat transfers by gas conduction and radiation were negligible. To minimize heat conduction by gas, the chamber was evacuated to a low pressure, such as 100 mTorr. To minimize heat transfers between shelves, shelves were moved close together, with a gap of approximately 3 mm between any two shelves, because the shelf surface temperatures at corresponding vertical locations of two shelves are virtually equal. In addition, this also provides a shielding from radiation heat transfer from shelf to walls. Local heat transfer coefficients at the probed locations h(x) ( approximately Ks) were calculated by fitting the experimental shelf temperature response to the theoretical value. While the resulting values of K(s) are in general agreement with previously reported values, the values of Ks close to the inlet are significantly higher than those of other locations of the shelf channel. This observation is most likely attributed to the variation of the flow pattern of heat transfer fluid within the channels.

Development of a general method for obtaining the geometry of microfluidic networks

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

Razavi, Mohammad Sayed, E-mail: m.sayedrazavi@gmail.com; Salimpour, M. R.; Shirani, Ebrahim

2014-01-15

In the present study, a general method for geometry of fluidic networks is developed with emphasis on pressure-driven flows in the microfluidic applications. The design method is based on general features of network's geometry such as cross-sectional area and length of channels. Also, the method is applicable to various cross-sectional shapes such as circular, rectangular, triangular, and trapezoidal cross sections. Using constructal theory, the flow resistance, energy loss and performance of the network are optimized. Also, by this method, practical design strategies for the fabrication of microfluidic networks can be improved. The design method enables rapid prediction of fluid flowmore » in the complex network of channels and is very useful for improving proper miniaturization and integration of microfluidic networks. Minimization of flow resistance of the network of channels leads to universal constants for consecutive cross-sectional areas and lengths. For a Y-shaped network, the optimal ratios of consecutive cross-section areas (A{sub i+1}/A{sub i}) and lengths (L{sub i+1}/L{sub i}) are obtained as A{sub i+1}/A{sub i} = 2{sup −2/3} and L{sub i+1}/L{sub i} = 2{sup −1/3}, respectively. It is shown that energy loss in the network is proportional to the volume of network. It is also seen when the number of channels is increased both the hydraulic resistance and the volume occupied by the network are increased in a similar manner. Furthermore, the method offers that fabrication of multi-depth and multi-width microchannels should be considered as an integral part of designing procedures. Finally, numerical simulations for the fluid flow in the network have been performed and results show very good agreement with analytic results.« less

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

Azizah, N., E-mail: norazizahparmin84@gmail.com; Gopinath, Subash C. B.; Nadzirah, Sh.

Titanium dioxide (TiO{sub 2}) nanoparticles based Interdigitated Device Electrodes (IDEs) Nanobiosensor device was developed for intracellular biochemical detection. Fabrication and characterization of pH sensors using IDE nanocoated with TiO{sub 2} was studied in this paper. In this paper, a preliminary assessment of this intracellular sensor with electrical measurement under different pH levels. 3-aminopropyltriethoxysilane (APTES) was used to enhance the sensitivity of titanium dioxide layer as well as able to provide surface modification by undergoing protonation and deprotonation process. Different types of pH solution provide different resistivity and conductivity towards the surface. Base solution has the higher current compared to anmore » acid solution. Amine and oxide functionalized TiO{sub 2} based IDE exhibit pH-dependent could be understood in terms of the change in surface charge during protonation and deprotonation. The simple fabrication process, high sensitivity, and fast response of the TiO{sub 2} based IDEs facilitate their applications in a wide range of areas. The small size of semiconductor TiO{sub 2} based IDE for sensitive, label-free, real time detection of a wide range of biological species could be explored in vivo diagnostics and array-based screening.« less

Dynamic modification of optical nonlinearities related to femtosecond laser filamentation in gases

NASA Astrophysics Data System (ADS)

Romanov (1, 3), Dmitri; Tarazkar (2, 3), Maryam; Levis (2, 3), Robert

2017-04-01

During and immediately after the passing of a filamenting laser pulse through a gas-phase medium, the nonlinear optical characteristics of the emerging filament-wake channel undergo substantial transient modification, which stems from ionization and electronic excitation of constituent atoms/molecules. We calculate the related hyperpolarizability coefficients of individual ions, and we develop a theoretical model of filament channel evolution applicable to atmospheric-pressure and high-pressure gases. The evolution is mediated by energetic free-electron gas that results from the strong-field ionization and gains considerable energy via inverse Bremsstrahlung process. The ensuing impact ionization and excitation of the residual neutral atoms/molecules proceeds inhomogeneously both inside the channel and on its surface, being strongly influenced by the thermal conduction of the electron gas. The model shows critical importance of channel-surface effects, especially as regards the effective electron temperature. The calculated spatial-temporal evolution patterns ultimately determine the transient modifications of linear and nonlinear optical properties of filament wake channels. Medium-specific estimates are made for atmospheric- and high-pressure argon, as well as for molecular nitrogen gas. Support of Defense Threat Reduction Agency (Grant No. HDTRA1-12-1-0014) is gratefully acknowledged.

Ammonia concentration distribution measurements in the exhaust of a heavy duty diesel engine based on limited data absorption tomography.

PubMed

Stritzke, Felix; van der Kley, Sani; Feiling, Alexander; Dreizler, Andreas; Wagner, Steven

2017-04-03

A multichannel tunable diode laser absorption spectrometer is used to measure absolute ammonia concentrations and their distributions in exhaust gas applications with intense CO₂ and H₂O background. Designed for in situ diagnostics in SCR after treatment systems with temperatures up to 800 K, the system employs a fiber coupled near-infrared distributed feedback diode laser. With the laser split into eight coplanar beams crossing the exhaust pipe, the sensor provides eight concentration measurements simultaneously. Three ammonia ro-vibrational transitions coinciding near 2200.5 nm with rather weak temperature dependency and negligible CO₂/H₂O interference were probed during the measurements. The line-of-sight averaged channel concentrations are transformed into 2-D ammonia distributions using limited data IR species tomography based on Tikhonov regularization. This spectrometer was successfully applied in the exhaust system of a 340 kW heavy duty diesel engine operated without oxidation catalyst or particulate filter. In this harsh environment the multi-channel sensor achieved single path ammonia detection limits of 25 to 80 ppm_V with a temporal resolution of 1 Hz whereas, while operated as a single-channel sensor, these characteristics improved to 10 ppm_V and 100 Hz. Spatial averaging of the reconstructed 2-D ammonia distributions shows good agreement to cross-sectional extractive measurements. In contrast to extractive methods more information about spatial inhomogeneities and transient operating conditions can be derived from the new spectrometer.

Rapid Water Permeation Through Carbon Nanomembranes with Sub-Nanometer Channels.

PubMed

Yang, Yang; Dementyev, Petr; Biere, Niklas; Emmrich, Daniel; Stohmann, Patrick; Korzetz, Riko; Zhang, Xianghui; Beyer, André; Koch, Sascha; Anselmetti, Dario; Gölzhäuser, Armin

2018-05-22

The provision of clean water is a global challenge, and membrane filtration is a key technology to address it. Conventional filtration membranes are constrained by a trade-off between permeance and selectivity. Recently, some nanostructured membranes demonstrated the ability to overcome this limitation by utilizing well-defined carbon nanoconduits that allow a coordinated passage of water molecules. The fabrication of these materials is still very challenging, but their performance inspires research toward nanofabricated membranes. This study reports on molecularly thin membranes with sub-nanometer channels that combine high water selectivity with an exceptionally high permeance. Carbon nanomembranes (CNMs) of ∼1.2 nm thickness are fabricated from terphenylthiol (TPT) monolayers. Scanning probe microscopy and transport measurements reveal that TPT CNMs consist of a dense network of sub-nanometer channels that efficiently block the passage of most gases and liquids. However, water passes through with an extremely high permeance of ∼1.1 × 10 -4 mol·m -2 ·s -1 ·Pa -1 , as does helium, but with a ∼ 2500 times lower flux. Assuming all channels in a TPT CNM are active in mass transport, we find a single-channel permeation of ∼66 water molecules·s -1 ·Pa -1 . This suggests that water molecules translocate fast and cooperatively through the sub-nanometer channels, similar to carbon nanotubes and membrane proteins (aquaporins). CNMs are thus scalable two-dimensional sieves that can be utilized toward energy-efficient water purification.

Measurement of host-to-activator transfer efficiency in nano-crystalline Y{sub 2}O{sub 3}:Eu{sup 3+} under VUV excitation

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

Waite, Christopher; Mann, Rusty; Diaz, Anthony L., E-mail: DiazA@cwu.edu

2013-02-15

We have conducted a systematic study of the excitation and reflectance spectra of nano-crystalline Y{sub 2}O{sub 3}:Eu prepared by combustion synthesis. Excitation through the host lattice becomes relatively more efficient as the firing temperature of the precursor is increased, while reflectance properties remain essentially unchanged. Using these data, host-to-activator transfer efficiencies were calculated for excitation at the band edge of Y{sub 2}O{sub 3}, and evaluated using a competition kinetics model. From this analysis we conclude that the relatively low luminous efficiency of these materials is due more to poor bulk crystallinity than to surface loss effects. - Graphical abstract: Themore » low luminous efficiency of nano-crystalline Y{sub 2}O{sub 3}:Eu{sup 3+} prepared by combustion synthesis is due to poor bulk crystallinity rather than surface loss effects. Highlights: Black-Right-Pointing-Pointer We report on the optical properties of Y{sub 2}O{sub 3}:Eu{sup 3+} prepared by combustion synthesis. Black-Right-Pointing-Pointer Host-to-activator transfer efficiencies under VUV excitation were calculated. Black-Right-Pointing-Pointer The low luminous efficiency of these materials is due to poor bulk crystallinity.« less

Mixed conductivity, structural and microstructural characterization of titania-doped yttria tetragonal zirconia polycrystalline/titania-doped yttria stabilized zirconia composite anode matrices

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

Colomer, M.T., E-mail: tcolomer@icv.csic.e; Maczka, M.

2011-02-15

Taking advantage of the fact that TiO{sub 2} additions to 8YSZ cause not only the formation of a titania-doped YSZ solid solution but also a titania-doped YTZP solid solution, composite materials based on both solutions were prepared by solid state reaction. In particular, additions of 15 mol% of TiO{sub 2} give rise to composite materials constituted by 0.51 mol fraction titania-doped yttria tetragonal zirconia polycrystalline and 0.49 mol fraction titania-doped yttria stabilized zirconia (0.51TiYTZP/0.49TiYSZ). Furthermore, Y{sub 2}(Ti{sub 1-y}Zr{sub y}){sub 2}O{sub 7} pyrochlore is present as an impurity phase with y close to 1, according to FT-Raman results. Lower and highermore » additions of titania than that of 15 mol%, i.e., x=0, 5, 10, 20, 25 and 30 mol% were considered to study the evolution of 8YSZ phase as a function of the TiO{sub 2} content. Furthermore, zirconium titanate phase (ZrTiO{sub 4}) is detected when the titania content is equal or higher than 20 mol% and this phase admits Y{sub 2}O{sub 3} in solid solution according to FE-SEM-EDX. The 0.51TiYTZP/0.49TiYSZ duplex material was selected in this study to establish the mechanism of its electronic conduction under low oxygen partial pressures. In the pO{sub 2} range from 0.21 to 10{sup -7.5} atm. the conductivity is predominantly ionic and constant over the range and its value is 0.01 S/cm. The ionic plus electronic conductivity is 0.02 S/cm at 1000 {sup o}C and 10{sup -12.3} atm. Furthermore, the onset of electronic conductivity under reducing conditions exhibits a -1/4 pO{sub 2} dependence. Therefore, it is concluded that the n-type electronic conduction in the duplex material can be due to a small polaron-hopping between Ti{sup 3+} and Ti{sup 4+}. -- Graphical abstract: FE-SEM micrograph of a polished and thermal etched surface of a Ti-doped YTZP/Ti-doped YSZ composite material. Display Omitted Research highlights: {yields} Ti-doped YTZP/Ti-doped YSZ composite materials are mixed conductors under low partial pressures. {yields} From 5 mol% of TiO{sub 2}, Y{sub 2}(Ti{sub 1-y},Zr{sub y}){sub 2}O{sub 7} pyrochlore is present as a minor phase, being y close to 1 according to FT-Raman studies. {yields} The onset of the electronic conductivity under reducing conditions exhibit a -1/4 pO{sub 2} dependence. The n-type electronic conduction is due to a small polaron-hopping between Ti{sup 3+} and Ti{sup 4+}.« less

Experimental study of the reactive processes in the gas phase K{sup +}+i-C{sub 3}H{sub 7}Cl collisions: A comparison with Li and Na ions

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

Aguilar, J.; Lucas, J. M.; Andres, J. de

2013-05-14

Reactive collisions between alkali ions (Li{sup +}, Na{sup +}, and K{sup +}) and halogenated hydrocarbon molecules have been studied recently in our research group. In this paper, we have reported on the K{sup +}+i-C{sub 3}H{sub 7}Cl system in the 0.20-14.00 eV center-of-mass energy range using a radio frequency guided-ion beam apparatus developed in our laboratory. Aiming at increasing our knowledge about this kind of reactions, we compare our latest results for K{sup +} with those obtained previously for Li{sup +} and Na{sup +}. While the reaction channels are the same in all three cases, their energy profiles, reactivity, measured reactivemore » cross-section energy dependences, and even their reaction mechanisms, differ widely. By comparing experimentally measured reactive cross-sections as a function of the collision energy with the ab initio calculations for the different potential energy surfaces, a qualitative interpretation of the dynamics of the three reactive systems is presented in the present work.« less

Influence of cross-sectional geometry on the sensitivity and hysteresis of liquid-phase electronic pressure sensors

NASA Astrophysics Data System (ADS)

Park, Yong-Lae; Tepayotl-Ramirez, Daniel; Wood, Robert J.; Majidi, Carmel

2012-11-01

Cross-sectional geometry influences the pressure-controlled conductivity of liquid-phase metal channels embedded in an elastomer film. These soft microfluidic films may function as hyperelastic electric wiring or sensors that register the intensity of surface pressure. As pressure is applied to the elastomer, the cross-section of the embedded channel deforms, and the electrical resistance of the channel increases. In an effort to improve sensitivity and reduce sensor nonlinearity and hysteresis, we compare the electrical response of 0.25 mm2 channels with different cross-sectional geometries. We demonstrate that channels with a triangular or concave cross-section exhibit the least nonlinearity and hysteresis over pressures ranging from 0 to 70 kPa. These experimental results are in reasonable agreement with predictions made by theoretical calculations that we derive from elasticity and Ohm's Law.

Sulfuric acid and hydrogen peroxide surface passivation effects on AlGaN/GaN high electron mobility transistors

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

Zaidi, Z. H., E-mail: zaffar.zaidi@sheffield.ac.uk; Lee, K. B.; Qian, H.

2014-12-28

In this work, we have compared SiN{sub x} passivation, hydrogen peroxide, and sulfuric acid treatment on AlGaN/GaN HEMTs surface after full device fabrication on Si substrate. Both the chemical treatments resulted in the suppression of device pinch-off gate leakage current below 1 μA/mm, which is much lower than that for SiN{sub x} passivation. The greatest suppression over the range of devices is observed with the sulfuric acid treatment. The device on/off current ratio is improved (from 10{sup 4}–10{sup 5} to 10{sup 7}) and a reduction in the device sub-threshold (S.S.) slope (from ∼215 to 90 mV/decade) is achieved. The sulfuric acid ismore » believed to work by oxidizing the surface which has a strong passivating effect on the gate leakage current. The interface trap charge density (D{sub it}) is reduced (from 4.86 to 0.90 × 10{sup 12 }cm{sup −2} eV{sup −1}), calculated from the change in the device S.S. The gate surface leakage current mechanism is explained by combined Mott hopping conduction and Poole Frenkel models for both untreated and sulfuric acid treated devices. Combining the sulfuric acid treatment underneath the gate with the SiN{sub x} passivation after full device fabrication results in the reduction of D{sub it} and improves the surface related current collapse.« less

Inhaled Carbon Nanotubes Reach the Sub-Pleural Tissue in Mice

PubMed Central

Ryman-Rasmussen, Jessica P.; Cesta, Mark F.; Brody, Arnold R.; Shipley-Phillips, Jeanette K.; Everitt, Jeffrey; Tewksbury, Earl W.; Moss, Owen R.; Wong, Brian A.; Dodd, Darol E.; Andersen, Melvin E.; Bonner, James C.

2009-01-01

Summary Carbon nanotubes have fibre-like shape1 and stimulate inflammation at the surface of the peritoneum when injected into the abdominal cavity of mice2, raising concerns that inhaled nanotubes3 may cause pleural fibrosis and/or mesothelioma4. Here we show that multi-walled carbon nanotubes reach the sub-pleura in mice after a single inhalation exposure of 30 mg/m3 for 6 hours. Nanotubes were embedded in the sub-pleural wall and within sub-pleural macrophages. Mononuclear cell aggregates on the pleural surface increased in number and size after 1 day and nanotube-containing macrophages were observed within these foci. Sub-pleural fibrosis increased after 2 and 6 weeks following inhalation. None of these effects were seen in mice that inhaled carbon black nanoparticles or a lower dose of nanotubes (1 mg/m3). This work advances a growing literature on pulmonary toxicology of nanotubes5 and suggests that minimizing inhalation of nanotubes during handling is prudent until further long term assessments are conducted. PMID:19893520

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

Rodenbücher, C.; Hildebrandt, E.; Sharath, S. U.

On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO{sub 2−x}) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfC{sub x}) at the surface during vacuum annealing at temperatures as low as 600 °C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfC{sub x} surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO{sub 2} thin films prepared and measured under identical conditions, the formation of HfC{sub x} was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films providesmore » a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating.« less

Zirconium doped TiO{sub 2} thin films: A promising dielectric layer

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

Kumar, Arvind; Mondal, Sandip, E-mail: sandipmondal@physics.iisc.ernet.in; Rao, K. S. R. Koteswara

2016-05-06

In the present work, we have fabricated the zirconium doped TiO{sub 2} thin (ZTO) films from a facile spin – coating method. The addition of Zirconium in TiO{sub 2} offers conduction band offset to Si and consequently decreased the leakage current density by approximately two orders as compared to pure TiO{sub 2} thin (TO) films. The ZTO thin film shows a high dielectric constant 27 with a very low leakage current density ∼10{sup −8} A/cm{sup 2}. The oxide capacitate, flat band voltage and change in flat band voltage are 172 pF, -1.19 V and 54 mV. The AFM analysis confirmed the compactmore » and pore free flat surface. The RMS surface roughness is found to be 1.5 Å. The ellipsometry analysis also verified the fact with a high refractive index 2.21.« less

Characteristics of inositol trisphosphate mediated Ca/sup 2 +/ release from permeabilized hepatocytes

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

Joseph, S.K.; Williamson, J.R.

1986-05-01

Ca/sup 2 +/ release triggered by inositol trisphosphate (IP/sub 3/) has been measured in saponin-permeabilized hepatocytes with /sup 45/Ca/sup 2 +/ or Quin 2. The initial rate of Ca/sup 2 +/ release was not markedly affected by the incubation temperature (175 +/- 40 pmol/s/mg at 30/sup 0/C versus 133 +/- 24 pmol/s/mg at 4/sup 0/C). This result is consistent with the membrane translocation of Ca/sup 2 +/ occurring through an ion-channel rather than an ion-carrier. The amount of Ca/sup 2 +/ released by IP/sub 3/ was not affected by pH (6.5-8.0) or by compounds that inhibit voltage-gated Ca/sup 2 +/more » channels. La/sup 3 +/ (100 ..mu..M) markedly inhibits the effect of 1 ..mu..M IP/sub 3/. The possibility that La/sup 3 +/ chelates IP/sub 3/ cannot be excluded since the effect of La/sup 3 +/ can be overcome by increasing the IP/sub 3/ concentration. IP/sub 3/-mediated Ca/sup 2 +/ release displays a requirement for a permeant cation in the incubation medium. Optimal release is observed with K/sup +/ gluconate. Other monovalent cations, with the exception of Li/sup +/, can substitute for K/sup +/. Permeant anions, at concentrations above 40 mM, inhibit Ca/sup 2 +/ release produced by IP/sub 3/. Cl/sup -/, Br/sup -/, I/sup -/, and SO/sub 4//sup 2 -/ were equally effective. Ca/sup 2 +/ release was not inhibited by DIDS or Furosemide. /sup 85/Sr/sup 2 +/ and /sup 54/Mn/sup 2 +/ fluxes were also stimulated by IP/sub 3/. These results suggest that IP/sub 3/ acts to gate a divalent cation channel. The translocation of positive charge through this channel is balanced by ancillary movements of monovalent cations and anions across the reticular membrane.« less

Rf-assisted current startup in the Fusion Engineering Device (FED)

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

Borowski, S.K.; Peng, Y.K.M.; Kammash, T.

1982-08-01

Auxiliary rf heating of electrons before and during the current rise phase in the Fusion Engineering Device is examined as a means of reducing both the initiation loop voltage and resistive flux expenditure during startup. Prior to current initiation 1 to 2 MW of electron cyclotron resonance heating (ECRH) power at approx. 90 GHz is used to create a small volume of high conductivity plasma (T/sub e/ approx. = 100 eV, n/sub e/ approx. = 10/sup 13/ cm/sup -3/) near the upper hybrid resonance (UHR) region. This plasma conditioning permits a small radius (a/sub o/ approx. = 0.2 to 0.4more » m) current channel to be established with a relatively low initial loop voltage (less than or equal to 25 V). During the subsequent plasma expansion and current ramp phase, additional rf power is introduced to reduce volt-second consumption due to plasma resistance. A near classical particle and energy transport model has been developed to estimate the efficiency of electron heating in a currentless toroidal plasma. The model assumes that preferential electron heating at the UHR leads to the formation of an ambipolar sheath potential between the neutral plasma and the conducting vacuum vessel and limiter. The ambipolar electric field (E/sub AMB/) enables the plasma to neutralize itself via poloidal E vector/sub AMB/ x B vector drift. This form of effective rotational transform short-circuits the vertical charge separation and improves particle confinement.« less

In-situ SiN{sub x}/InN structures for InN field-effect transistors

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

Zervos, Ch., E-mail: hzervos@physics.uoc.gr; Georgakilas, A.; Department of Physics, University of Crete, P.O. Box 2208, GR-71003 Heraklion, Crete

Critical aspects of InN channel field-effect transistors (FETs) have been investigated. SiN{sub x} dielectric layers were deposited in-situ, in the molecular beam epitaxy system, on the surface of 2 nm InN layers grown on GaN (0001) buffer layers. Metal-insulator-semiconductor Ni/SiN{sub x}/InN capacitors were analyzed by capacitance-voltage (C-V) and current-voltage measurements and were used as gates in InN FET transistors (MISFETs). Comparison of the experimental C-V results with self-consistent Schrödinger-Poisson calculations indicates the presence of a positive charge at the SiN{sub x}/InN interface of Q{sub if} ≈ 4.4 – 4.8 × 10{sup 13 }cm{sup −2}, assuming complete InN strain relaxation. Operation of InN MISFETs was demonstrated, but their performancemore » was limited by a catastrophic breakdown at drain-source voltages above 2.5–3.0 V, the low electron mobility, and high series resistances of the structures.« less

Effect of Segmented Electrode Length on the Performances of an Aton-Type Hall Thruster

NASA Astrophysics Data System (ADS)

Duan, Ping; Bian, Xingyu; Cao, Anning; Liu, Guangrui; Chen, Long; Yin, Yan

2016-05-01

The influences of the low-emissive graphite segmented electrode placed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle-in-cell method. A two-dimensional physical model is established according to the Hall thruster discharge channel configuration. The effects of electrode length on the potential, ion density, electron temperature, ionization rate and discharge current are investigated. It is found that, with the increasing of the segmented electrode length, the equipotential lines bend towards the channel exit, and approximately parallel to the wall at the channel surface, the radial velocity and radial flow of ions are increased, and the electron temperature is also enhanced. Due to the conductive characteristic of electrodes, the radial electric field and the axial electron conductivity near the wall are enhanced, and the probability of the electron-atom ionization is reduced, which leads to the degradation of the ionization rate in the discharge channel. However, the interaction between electrons and the wall enhances the near wall conductivity, therefore the discharge current grows along with the segmented electrode length, and the performance of the thruster is also affected. supported by National Natural Science Foundation of China (Nos. 11375039 and 11275034) and the Key Project of Science and Technology of Liaoning Province, China (No. 2011224007) and the Fundamental Research Funds for the Central Universities, China (No. 3132014328)