Science.gov

Sample records for agency surface transportation

  1. 41 CFR 102-118.40 - How does my agency order transportation and transportation services?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false How does my agency order... Services § 102-118.40 How does my agency order transportation and transportation services? Your agency...., packaging, storage) with a Government contractor-issued charge card, purchase order (or...

  2. 43 CFR 3410.2-3 - Surface management agency.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Surface management agency. 3410.2-3... § 3410.2-3 Surface management agency. The authorized officer may issue an exploration license covering lands the surface of which is under the jurisdiction of any Federal agency other than the Bureau of...

  3. 41 CFR 102-118.40 - How does my agency order transportation and transportation services?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false How does my agency order transportation and transportation services? 102-118.40 Section 102-118.40 Public Contracts and Property... TRANSPORTATION 118-TRANSPORTATION PAYMENT AND AUDIT Ordering and Paying for Transportation and...

  4. 41 CFR 102-118.40 - How does my agency order transportation and transportation services?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false How does my agency order transportation and transportation services? 102-118.40 Section 102-118.40 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT REGULATION TRANSPORTATION 118-TRANSPORTATION PAYMENT...

  5. 41 CFR 102-118.40 - How does my agency order transportation and transportation services?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 41 Public Contracts and Property Management 3 2013-07-01 2013-07-01 false How does my agency order transportation and transportation services? 102-118.40 Section 102-118.40 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT REGULATION TRANSPORTATION 118-TRANSPORTATION PAYMENT...

  6. Transportation of the Handicapped: A Survey of State Education Agency Transportation Directors.

    ERIC Educational Resources Information Center

    Bluth, Linda, Ed.; Sweeney, Mary Kathleen, Ed.

    A survey of 45 State Education Agency Transportation Directors is reported concerning state transportation services for handicapped students. Summary data are given in both tabular and narrative form for the following areas: procedures used for transporting handicapped individuals, handicapped population transported by public and/or private…

  7. Supersonic transport. [using canard surfaces

    NASA Technical Reports Server (NTRS)

    Coe, P. L., Jr. (Inventor)

    1978-01-01

    An aircraft of supersonic transport configuration is described, featuring thrust vectoring in conjunction with wing apex segments used as canard surfaces during takeoff, landing, and low-speed flight. The angle of incidence of the wing apex segments, when the segments were functioning as canard surfaces, was variable with respect to the aircraft angle of attack. The wing apex segments furthermore formed a portion of the main wing panel swept leading edge when not functioning as canard surfaces. The combination of thrust vectoring and deployable wing apex segments resulted in increased aircraft range and improved low speed longitudinal stability while providing acceptable takeoff length capabilities.

  8. Polymer Transport Near Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Bloom, Moses; Whitmer, Jonathan; Luijten, Erik

    2011-03-01

    The rheology of dilute polymer solutions under confinement is important in biology, medicine, microfluidic device design, synthetic polymer processing, and even geologic porous media. However, the solution's specific interactions with the confining surface are poorly understood. This situation is exacerbated for composite nanoparticles, such as polymer/metallic hybrids. Using multi-particle collision dynamics, we find a rich array of transport regimes depending on small-scale surface roughness and the specific surface/solute interactions. These factors couple to hydrodynamic conditions, including flow strength and confinement geometry in unexpected ways. Our findings may be relevant to transport phenomena in certain rough-walled capillaries, such as the distribution of various nanoconjugates in vivo.

  9. Manned Mars mission surface transportation elements

    NASA Technical Reports Server (NTRS)

    Mcdaniel, S. Gregg; Mulqueen, Jack

    1986-01-01

    The necessity and advantage of surface transportation was well demonstrated by the Apollo 15, 16, and 17 missions. Baseline surface transportation elements for further studies are Lunar Rover, Elastic Loop Mobility System, Mobile Laboratory, Airplane, and Rocket Powered Flying Vehicles. These types of surface transportation are discussed. Starting points for further in-depth studies are identified.

  10. Surface transport in plasma-balls

    NASA Astrophysics Data System (ADS)

    Armas, Jay; Bhattacharya, Jyotirmoy; Kundu, Nilay

    2016-06-01

    We study the surface transport properties of stationary localized configurations of relativistic fluids to the first two non-trivial orders in a derivative expansion. By demanding that these finite lumps of relativistic fluid are described by a thermal partition function with arbitrary stationary background metric and gauge fields, we are able to find several constraints among surface transport coefficients. At leading order, besides recovering the surface thermodynamics, we obtain a generalization of the Young-Laplace equation for relativistic fluid surfaces, by considering a temperature dependence in the surface tension, which is further generalized in the context of superfluids. At the next order, for uncharged fluids in 3+1 dimensions, we show that besides the 3 independent bulk transport coefficients previously known, a generic localized configuration is characterized by 3 additional surface transport coefficients, one of which may be identified with the surface modulus of rigidity. Finally, as an application, we study the effect of temperature dependence of surface tension on some explicit examples of localized fluid configurations, which are dual to certain non-trivial black hole solutions via the AdS/CFT correspondence.

  11. Surface transport vehicles and supporting technology requirements

    NASA Technical Reports Server (NTRS)

    Matijevic, J. R.; Dias, W. C.; Levin, R. R.; Lindemann, R. A.; Smith, J. H.; Venkataraman, S. T.

    1992-01-01

    Requirements have been identified for surface transport vehicles which allow remote scientific exploration on the moon, as well as lunar resource recovery and emplacement of a permanent base on the lunar surface. Attention is given to the results of a design study which developed configurational concepts for lunar surface transport vehicles and inferred technology-development requirements, with a view to a phased program of implementation. Distinct benefits are noted for the design of simple vehicle platforms with high commonality, in order to reduce logistical-support requirements and maximize functional flexibility. Two generic vehicle classed are defined.

  12. 41 CFR 102-118.50 - How does my agency pay for transportation services?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... the Treasury regulations (31 CFR part 208). ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false How does my agency pay... Services § 102-118.50 How does my agency pay for transportation services? Your agency may pay...

  13. 41 CFR 102-118.45 - How does a transportation service provider (TSP) bill my agency for transportation and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false How does a transportation service provider (TSP) bill my agency for transportation and transportation services? 102-118.45 Section 102-118.45 Public Contracts and Property Management Federal Property Management Regulations...

  14. Exciton transport by surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Rudolph, J.; Hey, R.; Santos, P. V.

    2007-05-01

    Long-range acoustic transport of excitons in GaAs quantum wells (QWs) is demonstrated. The mobile strain field of a surface acoustic wave creates a dynamic lateral type I modulation of the conduction and valence bands in a double-quantum-well (DQW) structure. This mobile potential modulation transports long-living indirect excitons in the DQW over several hundreds of μm.

  15. Dust Charging and Transport on Surfaces

    NASA Astrophysics Data System (ADS)

    Wang, X.; Robertson, S.; Horányi, M.

    2011-11-01

    In this paper, we review laboratory studies of dust transport on surfaces in plasmas, performed for a number of different mechanisms: 1) Dust particles were levitated in plasma sheaths by electrostatic forces balancing the gravitational force. 2) Dust was observed to spread over and lift off a surface that repels electrons in a plasma. 3) Dust was transported on surfaces having different secondary electron yields in plasma with an electron beam as a consequence of differential charging. 4) We also report a mechanism of dust transport by electric fields occurring at electron beam impact/shadow boundaries. These processes are candidates to explain the formation of dust ponds that were recently observed in craters on the asteroid Eros by the NEAR Shoemaker spacecraft.

  16. 41 CFR 102-118.80 - Who is responsible for keeping my agency's electronic commerce transportation billing records?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... keeping my agency's electronic commerce transportation billing records? 102-118.80 Section 102-118.80... Transportation and Transportation Services § 102-118.80 Who is responsible for keeping my agency's electronic commerce transportation billing records? Your agency's internal financial regulations will...

  17. 41 CFR 102-118.80 - Who is responsible for keeping my agency's electronic commerce transportation billing records?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... keeping my agency's electronic commerce transportation billing records? 102-118.80 Section 102-118.80... Transportation and Transportation Services § 102-118.80 Who is responsible for keeping my agency's electronic commerce transportation billing records? Your agency's internal financial regulations will...

  18. 41 CFR 102-118.80 - Who is responsible for keeping my agency's electronic commerce transportation billing records?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... keeping my agency's electronic commerce transportation billing records? 102-118.80 Section 102-118.80... Transportation and Transportation Services § 102-118.80 Who is responsible for keeping my agency's electronic commerce transportation billing records? Your agency's internal financial regulations will...

  19. 49 CFR 1570.13 - False statements regarding security background checks by public transportation agency or railroad...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... checks by public transportation agency or railroad carrier. 1570.13 Section 1570.13 Transportation Other... regarding security background checks by public transportation agency or railroad carrier. (a) Scope. This... employee of a public transportation agency or a contractor or subcontractor of a public...

  20. 49 CFR 1570.13 - False statements regarding security background checks by public transportation agency or railroad...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... checks by public transportation agency or railroad carrier. 1570.13 Section 1570.13 Transportation Other... regarding security background checks by public transportation agency or railroad carrier. (a) Scope. This... employee of a public transportation agency or a contractor or subcontractor of a public...

  1. Proton transport via the membrane surface.

    PubMed Central

    Georgievskii, Yuri; Medvedev, Emile S; Stuchebrukhov, Alexei A

    2002-01-01

    Some proton pumps, such as cytochrome c oxidase (C(c)O), translocate protons across biological membranes at a rate that considerably exceeds the rate of proton transport to the entrance of the proton-conducting channel via bulk diffusion. This effect is usually ascribed to a proton-collecting antenna surrounding the channel entrance. In this paper, we consider a realistic phenomenological model of such an antenna. In our model, a homogeneous membrane surface, which can mediate proton diffusion toward the channel entrance, is populated with protolytic groups that are in dynamic equilibrium with the solution. Equations that describe coupled surface-bulk proton diffusion are derived and analyzed. A general expression for the rate constant of proton transport via such a coupled surface-bulk diffusion mechanism is obtained. A rigorous criterion is formulated of when proton diffusion along the surface enhances the transport. The enhancement factor is found to depend on the ratio of the surface and bulk diffusional constants, pK(a) values of surface protolytic groups, and their concentration. A capture radius for a proton on the surface and an effective size of the antenna are found. The theory also predicts the effective distance that a proton can migrate on the membrane surface between a source (such as CcO) and a sink (such as ATP synthase) without fully equilibrating with the bulk. In pure aqueous solutions, protons can travel over long distances (microns). In buffered solutions, the travel distance is much shorter (nanometers); still the enhancement effect of the surface diffusion on the proton flow to a target on the surface can be tens to hundreds at physiological buffer concentrations. These results are discussed in a general context of chemiosmotic theory. PMID:12023208

  2. Dust Levitation and Transport Near Surfaces

    NASA Astrophysics Data System (ADS)

    Sickafoose, A. A.; Colwell, J. E.; Horanyi, M.; Robertson, S.

    2002-12-01

    There are many examples of active dust transport near surfaces in the solar system: dust grains suspended above the lunar surface, spokes observed in Saturn's rings, and recent images of infilled craters from the NEAR spacecraft at Eros. Electrostatic dust levitation and transport have also been theorized to occur on Mercury, asteroids, and comets. Dusty regoliths are produced by the interplanetary micrometeoroid flux on nearly all airless bodies in the solar system. Therefore, understanding dust charging, levitation, and dynamics above surfaces is important for interpreting remote sensing data and analyzing the evolution of most planetary surfaces. Objects in a plasma, such as planetary bodies in the solar wind, charge to a floating potential determined by the balance between charging currents in the local plasma environment. The primary charging currents are due to collection of electrons and ions from the plasma, photoemission, and secondary electron emission. When photoemission is the dominant charging process, a photoelectron sheath forms near the surface of the object. Positively charged particles released from the surface can levitate above the surface at a height where the gravitational force is balanced by the electric force. In cases where secondary electron emission and photoemission are weak, objects will become negatively charged due to electron collection and will be surrounded by a plasma sheath. Negatively charged dust grains from these surfaces can levitate in the electric field created by the plasma sheath. Dust levitation and transport near surfaces in the solar system is thought to be primarily due to the interaction between charged dust particles and a photoelectron or plasma sheath on the surface. We report the results of experiments on the levitation and transport of dust particles in an argon plasma sheath above a flat, conducting surface. Levitation experiments are performed using monodisperse polystyrene DVB microbeads. Transport

  3. 41 CFR 102-118.90 - If my agency orders transportation and/or transportation services with a Government contractor...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false If my agency orders transportation and/or transportation services with a Government contractor issued charge card or charge account citation, is this subject to prepayment audit? 102-118.90 Section 102-118.90 Public Contracts and Property Management Federal...

  4. 41 CFR 102-118.50 - How does my agency pay for transportation services?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... the Treasury regulations (31 CFR part 208). ... transportation services in three ways: (a) Electronic funds transfer (EFT) (31 U.S.C. 3332, et seq.). Your agency is required by statute to make all payments by EFT unless your agency receives a waiver from...

  5. 75 FR 60772 - Agency Information Collection Activities: Transportation Entry and Manifest of Goods Subject to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-01

    ... published in the Federal Register (75 FR 43997) on July 27, 2010, allowing for a 60-day comment period. This... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Transportation Entry and Manifest of Goods Subject to CBP Inspection and Permit AGENCY: U.S. Customs and Border...

  6. USING SUBSURFACE TRANSPORT RESEARCH TO ACHIEVE AGENCY OUTCOMES

    EPA Science Inventory

    Gasoline leaks from underground storage tanks can cause ground water contamination because there are a number of organic chemicals in gasoline. These chemicals have varying properties that influence how far contamination extends from the release. Research on transport of these ...

  7. Surface charge transport in Silicon (111) nanomembranes

    NASA Astrophysics Data System (ADS)

    Hu, Weiwei; Scott, Shelley; Jacobson, Rb; Savage, Donald; Lagally, Max; The Lagally Group Team

    Using thin sheets (``nanomembranes'') of atomically flat crystalline semiconductors, we are able to investigate surface electronic properties, using back-gated van der Pauw measurement in UHV. The thinness of the sheet diminishes the bulk contribution, and the back gate tunes the conductivity until the surface dominates, enabling experimental determination of surface conductance. We have previously shown that Si(001) surface states interact with the body of the membrane altering the conductivity of the system. Here, we extended our prior measurements to Si(111) in order to probe the electronic transport properties of the Si(111) 7 ×7 reconstruction. Sharp (7 ×7) LEED images attest to the cleanliness of the Si(111) surface. Preliminary results reveal a highly conductive Si(111) 7 ×7 surface with a sheet conductance Rs of order of μS/ □, for 110nm thick membrane, and Rs is a very slowly varying function of the back gate voltage. This is in strong contrast to Si(001) nanomembranes which have a minimum conductance several orders of magnitude lower, and hints to the metallic nature of the Si(111) surface. Research supported by DOE.

  8. 41 CFR 302-9.10 - For what transportation expenses will my agency pay?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 41 Public Contracts and Property Management 4 2012-07-01 2012-07-01 false For what transportation expenses will my agency pay? 302-9.10 Section 302-9.10 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 9-ALLOWANCES...

  9. Risk Assessment of Carbon Fiber Composite in Surface Transportation

    NASA Technical Reports Server (NTRS)

    Hathaway, W. T.; Hergenrother, K. M.

    1980-01-01

    The vulnerability of surface transportation to airborne carbon fibers and the national risk associated with the potential use of carbon fibers in the surface transportation system were evaluated. Results show airborne carbon fibers may cause failure rates in surface transportation of less than one per year by 1995. The national risk resulting from the use of carbon fibers in the surface transportation system is discussed.

  10. 41 CFR 102-118.80 - Who is responsible for keeping my agency's electronic commerce transportation billing records?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... keeping my agency's electronic commerce transportation billing records? 102-118.80 Section 102-118.80... Transportation and Transportation Services § 102-118.80 Who is responsible for keeping my agency's electronic... responsibility for recordkeeping. In addition, the GSA Audit Division keeps a central repository of...

  11. 41 CFR 102-117.270 - What are agency performance measures for transportation?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false What are agency performance measures for transportation? 102-117.270 Section 102-117.270 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT...

  12. General theory of Taylor dispersion phenomena. Part 3. Surface transport

    SciTech Connect

    Dill, L.H.; Brenner, H.

    1982-01-01

    An asymptotic theory of Brownian tracer particle transport phenomena within a bulk fluid, as augmented by surface transport, is presented in the context of generalized Taylor dispersion theory. The analysis expands upon prior work, which was limited to transport wholly within a continuous phase, so as to now include surface adsorption, diffusion, and convection of the tracer along a continuous surface bounding the continuous fluid phase.

  13. 41 CFR 102-118.65 - Can my agency receive electronic billing for payment of transportation services?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... electronic billing for payment of transportation services? 102-118.65 Section 102-118.65 Public Contracts and... Transportation Services § 102-118.65 Can my agency receive electronic billing for payment of transportation... to use electronic billing for the procurement and billing of transportation services....

  14. 41 CFR 102-117.325 - May my agency appear on its own behalf before a transportation regulatory body proceeding?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... its own behalf before a transportation regulatory body proceeding? 102-117.325 Section 102-117.325... Regulatory Body Proceedings § 102-117.325 May my agency appear on its own behalf before a transportation regulatory body proceeding? Generally, no executive agency may appear on its own behalf in any...

  15. 41 CFR 102-117.325 - May my agency appear on its own behalf before a transportation regulatory body proceeding?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... its own behalf before a transportation regulatory body proceeding? 102-117.325 Section 102-117.325... Regulatory Body Proceedings § 102-117.325 May my agency appear on its own behalf before a transportation regulatory body proceeding? Generally, no executive agency may appear on its own behalf in any...

  16. 41 CFR 102-117.325 - May my agency appear on its own behalf before a transportation regulatory body proceeding?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... its own behalf before a transportation regulatory body proceeding? 102-117.325 Section 102-117.325... Regulatory Body Proceedings § 102-117.325 May my agency appear on its own behalf before a transportation regulatory body proceeding? Generally, no executive agency may appear on its own behalf in any...

  17. 41 CFR 102-117.325 - May my agency appear on its own behalf before a transportation regulatory body proceeding?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... its own behalf before a transportation regulatory body proceeding? 102-117.325 Section 102-117.325... Regulatory Body Proceedings § 102-117.325 May my agency appear on its own behalf before a transportation regulatory body proceeding? Generally, no executive agency may appear on its own behalf in any...

  18. 41 CFR 102-117.325 - May my agency appear on its own behalf before a transportation regulatory body proceeding?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... its own behalf before a transportation regulatory body proceeding? 102-117.325 Section 102-117.325... Regulatory Body Proceedings § 102-117.325 May my agency appear on its own behalf before a transportation regulatory body proceeding? Generally, no executive agency may appear on its own behalf in any...

  19. 41 CFR 102-118.190 - When buying passenger transportation must my agency reference the applicable contract?

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 41 Public Contracts and Property Management 3 2014-01-01 2014-01-01 false When buying passenger... Request (gtr) (until Form Retirement) § 102-118.190 When buying passenger transportation must my agency reference the applicable contract? Yes, when buying passenger transportation, your agency must reference...

  20. 41 CFR 102-118.190 - When buying passenger transportation must my agency reference the applicable contract?

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false When buying passenger... Request (gtr) (until Form Retirement) § 102-118.190 When buying passenger transportation must my agency reference the applicable contract? Yes, when buying passenger transportation, your agency must reference...

  1. 41 CFR 102-118.190 - When buying passenger transportation must my agency reference the applicable contract?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false When buying passenger... Request (gtr) (until Form Retirement) § 102-118.190 When buying passenger transportation must my agency reference the applicable contract? Yes, when buying passenger transportation, your agency must reference...

  2. 41 CFR 102-118.190 - When buying passenger transportation must my agency reference the applicable contract?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false When buying passenger... Request (gtr) (until Form Retirement) § 102-118.190 When buying passenger transportation must my agency reference the applicable contract? Yes, when buying passenger transportation, your agency must reference...

  3. 41 CFR 102-118.190 - When buying passenger transportation must my agency reference the applicable contract?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 41 Public Contracts and Property Management 3 2013-07-01 2013-07-01 false When buying passenger... Request (gtr) (until Form Retirement) § 102-118.190 When buying passenger transportation must my agency reference the applicable contract? Yes, when buying passenger transportation, your agency must reference...

  4. 78 FR 61251 - The National Public Transportation Safety Plan, the Public Transportation Agency Safety Plan, and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-03

    ...The Federal Transit Administration (FTA) is issuing this consolidated advance notice of proposed rulemaking (ANPRM) to request public comments on a wide range of topics pertaining to the new Public Transportation Safety Program (National Safety Program) and the requirements of the new transit asset management provisions (National TAM System) authorized by the Moving Ahead for Progress in the......

  5. Surface Transportation Board Reauthorization Act of 2014

    THOMAS, 113th Congress

    Sen. Rockefeller, John D., IV [D-WV

    2014-09-08

    12/12/2014 By Senator Rockefeller from Committee on Commerce, Science, and Transportation filed written report. Report No. 113-321. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  6. Nonlinear Transport In Gases, Traps And Surfaces

    NASA Astrophysics Data System (ADS)

    Šuvakov, M.; Marjanovic, S.

    2010-07-01

    We will present our numerical study of three different charge transport processes and we will compare properties, specially the nonlinearity, of these processes. First process is electron transport in gases in swarm regime. We used well tested Monte Carlo techique to investigate kinetic phenomena such as negative diferencial conductivity (NDC) or negative apsolute mobility (NAM). We explain these phenomena analysing the spatial profiles of the swarm and collision events. In the second part we will apply the same technique on positron transport to obtain the same level of understanding of positron transport as has been achieved for electrons. The influence of positronium formation, non-conservative process, is much larger than any comparable effects in electron transport due to attachment and/or ionisation. As a result several new phenomena have been observed, such as NDC for the bulk drift velocity. Additionaly, the same Monte Carlo technique is used for modeling and optimisation of Surko like positron traps in different geometries and field configurations. Third process we studied is the charge transport under voltage bias via single-electron tunnelings through the junctions between metallic particles on nanoparticle films. We show how the regular nanoparticle array and topologically inhomogeneous nanonetworks affect the charge transport. We find long-range correlations in the time series of charge fluctuation at individual nanoparticles and of flow along the junctions within the network. These correlations explain the occurrence of a large non-linearity in the simulated and experimentally measured current-voltage characteristics and non-Gaussian fluctuations of the current at the electrode.

  7. Oil droplet self-transportation on oleophobic surfaces.

    PubMed

    Li, Juan; Qin, Qi Hang; Shah, Ali; Ras, Robin H A; Tian, Xuelin; Jokinen, Ville

    2016-06-01

    Directional liquid transportation is important for a variety of biological processes and technical applications. Although surface engineering through asymmetric chemical modification or geometrical patterning facilitates effective liquid manipulation and enables water droplet self-transportation on synthetic surfaces, self-transportation of oil droplets poses a major challenge because of their low surface tension. We report oil droplet self-transportation on oleophobic surfaces that are microtextured with radial arrays of undercut stripes. More significantly, we observe three modes of oil motion on various sample surfaces, namely, inward transportation, pinned, and outward spreading, which can be switched by the structure parameters, including stripe intersection angle and width. Accompanying theoretical modeling provides an in-depth mechanistic understanding of the structure-droplet motion relationship. Finally, we reveal how to optimize the texture parameters to maximize oil droplet self-transportation capability and demonstrate spontaneous droplet movement for liquids down to a surface tension of 22.4 mN/m. The surfaces presented here open up new avenues for power-free liquid transportation and oil contamination self-removal applications in various analytical and fluidic devices. PMID:27386574

  8. Oil droplet self-transportation on oleophobic surfaces

    PubMed Central

    Li, Juan; Qin, Qi Hang; Shah, Ali; Ras, Robin H. A.; Tian, Xuelin; Jokinen, Ville

    2016-01-01

    Directional liquid transportation is important for a variety of biological processes and technical applications. Although surface engineering through asymmetric chemical modification or geometrical patterning facilitates effective liquid manipulation and enables water droplet self-transportation on synthetic surfaces, self-transportation of oil droplets poses a major challenge because of their low surface tension. We report oil droplet self-transportation on oleophobic surfaces that are microtextured with radial arrays of undercut stripes. More significantly, we observe three modes of oil motion on various sample surfaces, namely, inward transportation, pinned, and outward spreading, which can be switched by the structure parameters, including stripe intersection angle and width. Accompanying theoretical modeling provides an in-depth mechanistic understanding of the structure–droplet motion relationship. Finally, we reveal how to optimize the texture parameters to maximize oil droplet self-transportation capability and demonstrate spontaneous droplet movement for liquids down to a surface tension of 22.4 mN/m. The surfaces presented here open up new avenues for power-free liquid transportation and oil contamination self-removal applications in various analytical and fluidic devices. PMID:27386574

  9. Surface atmospheric extremes (Launch and transportation areas)

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The effects of extreme values of surface and low altitude atmospheric parameters on space vehicle design, tests, and operations are discussed. Atmospheric extremes from the surface to 150 meters for geographic locations of interest to NASA are given. Thermal parameters (temperature and solar radiation), humidity, pressure, and atmospheric electricity (lighting and static) are presented. Weather charts and tables are included.

  10. Transport Powder and Liquid Samples by Surface Acoustic Waves

    NASA Technical Reports Server (NTRS)

    Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Louyeh, Sahar

    2009-01-01

    Sample transport is an important requirement for In-situ analysis of samples in NASA planetary exploration missions. Tests have shown that powders or liquid drops on a surface can be transported by surface acoustic waves (SAW) that are generated on the surface using interdigital transducers. The phenomena were investigated experimentally and to generate SAWs interdigital electrodes were deposited on wafers of 128 deg rotated Y-cut LiNbO?. Transporting capability of the SAW device was tested using particles of various sizes and drops of various viscosities liquids. Because of different interaction mechanisms with the SAWs, the powders and the liquid drops were observed to move in opposite directions. In the preliminary tests, a speed of 180 mm/s was achieved for powder transportation. The detailed experimental setup and results are presented in this paper. The transporting mechanism can potentially be applied to miniaturize sample analysis system or " lab-on-chip" devices.

  11. Surface modification of tribological components in transportation

    SciTech Connect

    Fenske, G.R.

    1992-11-01

    This paper reviews a number of programs funded through the Engineered Tribological Interfaces (ETI) Task area of the Tribology Program that utilize energetic beams of atoms to enhance the mechanical and microstructural properties of near-surface regions to improve the tribological performance of critical components. The processes used in these programs include techniques based on chemical vapor deposition, physical vapor deposition, and ion implantation. A common feature of these techniques is their ability to produce dense and adherent modified surfaces without need for subsequent grinding/polishing treatments. Another feature of these techniques is their ability to introduce a wide range of elements into near-surface regions.

  12. Quantification of chemical transport processes from soil to surface runoff

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although there is a conceptual understanding on processes governing chemical transport from soil to surface runoff, there are little literature and research results actually quantifying these individual processes. We developed a laboratory flow cell and experimental procedures to quantify chemical ...

  13. 29 CFR 1926.902 - Surface transportation of explosives.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... provisions of Department of Transportation regulations contained in 46 CFR parts 146-149, Water Carriers; 49 CFR parts 171-179, Highways and Railways; 49 CFR part 195, Pipelines; and 49 CFR parts 390-397, Motor... 29 Labor 8 2010-07-01 2010-07-01 false Surface transportation of explosives. 1926.902 Section...

  14. 29 CFR 1926.902 - Surface transportation of explosives.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... provisions of Department of Transportation regulations contained in 46 CFR parts 146-149, Water Carriers; 49 CFR parts 171-179, Highways and Railways; 49 CFR part 195, Pipelines; and 49 CFR parts 390-397, Motor... 29 Labor 8 2012-07-01 2012-07-01 false Surface transportation of explosives. 1926.902 Section...

  15. 29 CFR 1926.902 - Surface transportation of explosives.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... provisions of Department of Transportation regulations contained in 46 CFR parts 146-149, Water Carriers; 49 CFR parts 171-179, Highways and Railways; 49 CFR part 195, Pipelines; and 49 CFR parts 390-397, Motor... 29 Labor 8 2014-07-01 2014-07-01 false Surface transportation of explosives. 1926.902 Section...

  16. 29 CFR 1926.902 - Surface transportation of explosives.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... provisions of Department of Transportation regulations contained in 46 CFR parts 146-149, Water Carriers; 49 CFR parts 171-179, Highways and Railways; 49 CFR part 195, Pipelines; and 49 CFR parts 390-397, Motor... 29 Labor 8 2013-07-01 2013-07-01 false Surface transportation of explosives. 1926.902 Section...

  17. 29 CFR 1926.902 - Surface transportation of explosives.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... provisions of Department of Transportation regulations contained in 46 CFR parts 146-149, Water Carriers; 49 CFR parts 171-179, Highways and Railways; 49 CFR part 195, Pipelines; and 49 CFR parts 390-397, Motor... 29 Labor 8 2011-07-01 2011-07-01 false Surface transportation of explosives. 1926.902 Section...

  18. Surface atmospheric extremes (launch and transportation areas)

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Criteria are provided on atmospheric extremes from the surface to 150 meters for geographical locations of interest to NASA. Thermal parameters (temperature and solar radiation), humidity, precipitation, pressure, and atmospheric electricity (lightning and static) are presented. Available data are also provided for the entire continental United States for use in future space programs.

  19. Controlled droplet transport on a gradient adhesion surface.

    PubMed

    Feng, Shile; Wang, Sijie; Liu, Chengcheng; Zheng, Yongmei; Hou, Yongping

    2015-04-01

    A surface with continuously changed adhesion from ultrahigh to ultralow is fabricated by an integrated method of anodic oxidation combined with octafluorocyclobutane (C4F8) plasma. The control of droplet transport along the direction of the adhesion gradient in length is achieved, as the surface is submitted to either tilted angle or vibration frequency. PMID:25740352

  20. Models of Fate and Transport of Pollutants in Surface Waters

    ERIC Educational Resources Information Center

    Okome, Gloria Eloho

    2013-01-01

    There is the need to answer very crucial questions of "what happens to pollutants in surface waters?" This question must be answered to determine the factors controlling fate and transport of chemicals and their evolutionary state in surface waters. Monitoring and experimental methods are used in establishing the environmental states.…

  1. An Atomistic View on Fundamental Transport Processes on Metal Surfaces

    SciTech Connect

    Giesen, Margret

    2007-06-14

    In this lecture I present an introduction to the time-resolved observation of atomic transport processes on metal surfaces using scanning tunneling microscopy video sequences. The experimental data is analyzed using scaling law concepts known from statistical thermodynamics. I will present studies from metal surfaces in vacuum as well as in electrolyte.

  2. 41 CFR 302-10.3 - What is the maximum amount my agency may authorize me to receive for transporting a mobile home?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... amount my agency may authorize me to receive for transporting a mobile home? 302-10.3 Section 302-10.3... TRANSPORTATION AND STORAGE OF PROPERTY 10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS USED AS A... authorize me to receive for transporting a mobile home? The maximum amount your agency may authorize you...

  3. 41 CFR 102-118.185 - When buying freight transportation, must my agency reference the applicable contract or tender on...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false When buying freight....185 When buying freight transportation, must my agency reference the applicable contract or tender on... tender when buying transportation on a bill of lading (including GBLs). However, the...

  4. 41 CFR 102-118.185 - When buying freight transportation, must my agency reference the applicable contract or tender on...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 41 Public Contracts and Property Management 3 2014-01-01 2014-01-01 false When buying freight....185 When buying freight transportation, must my agency reference the applicable contract or tender on... tender when buying transportation on a bill of lading (including GBLs). However, the...

  5. 41 CFR 102-118.185 - When buying freight transportation, must my agency reference the applicable contract or tender on...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 41 Public Contracts and Property Management 3 2013-07-01 2013-07-01 false When buying freight....185 When buying freight transportation, must my agency reference the applicable contract or tender on... tender when buying transportation on a bill of lading (including GBLs). However, the...

  6. 41 CFR 102-118.185 - When buying freight transportation, must my agency reference the applicable contract or tender on...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false When buying freight....185 When buying freight transportation, must my agency reference the applicable contract or tender on... tender when buying transportation on a bill of lading (including GBLs). However, the...

  7. 41 CFR 102-118.185 - When buying freight transportation, must my agency reference the applicable contract or tender on...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false When buying freight....185 When buying freight transportation, must my agency reference the applicable contract or tender on... tender when buying transportation on a bill of lading (including GBLs). However, the...

  8. 41 CFR 302-9.8 - Must my agency authorize transportation or emergency or temporary storage of my POV?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Management Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 9-ALLOWANCES FOR TRANSPORTATION AND EMERGENCY OR TEMPORARY STORAGE OF A PRIVATELY OWNED VEHICLE General Rules... 41 Public Contracts and Property Management 4 2012-07-01 2012-07-01 false Must my agency...

  9. Effects of vegetation on contaminant transport in surface flows

    SciTech Connect

    Green, R.; Govindaraju, R.S.; Erickson, L.E.; Roig, L.

    1996-12-31

    It is well known that vegetation reduces off-site contamination that would result from surface flows. A significant portion of heavy metal contamination occurs at abandoned mine sites due to sediment movement. The effects of vegetation on sediment transport and surface runoff are reviewed, with an emphasis on factors that can reduce or prevent the movement of such metals in mine tailings. Several mathematical models for sediment transport in surface flows are briefly discussed, including advantages and limitations of the Universal Soil-Loss Equation and CREAMS model. Reported experimental and field data on contaminant transport in surface flows are reviewed and evaluated, as well as studies in treating the bioavailability of heavy metals in attempts to reduce metal phytotoxicity or decreasing the potential for entrance of the metals into the food chain via vegetation. Pollutants of concern include lead, zinc, and cadmium. 55 refs.

  10. Conceptual Design of a Mars Surface Transportation System (MSTS)

    NASA Astrophysics Data System (ADS)

    Collins, Chad; Gomez, Alex; Muniz, Rick; Musson, Dave

    1999-01-01

    We have proposed a design for a Mars Surface Transportation System. The design will support multi-range and multi-purpose scientific/exploratory activities for extended periods. Several assumptions were made before developing a desiun: 1. This system is to be deployed early in a series of piloted landings on the planet surface. 2. A Mars surface base has already been established. 3. A transport system to and from Mars already exists. 4. The capacity to transport this proposed system exists within the current transport design. 5. Facilities exist at this base for the supply of fuel and other consumables. 6. Medical facilities are a component of the main base. 7. The surface conditions of Mars are known and are.accurate. It was decided that the transportation system design should support a crew of two for up to four weeks away from the primary base. In order to support multiple mission requirements, the system is modular and m multi-configurable, The main structural aspects of the design are: 1. An inflatable habitat module. 2. Independently powered and remotely controllable wheel trucks to allow multiple configurations and ease of system assembly. 3. Parabolic space trusses for hi-h structural stability with low overall system mass. In addition to these design aspects, new and existing concepts for control systems, power, radiation protection, and crew safety have been incorporated into the transportation system design.

  11. Mathematical Simulation of Sediment and Radionuclide Transport in Surface Waters

    SciTech Connect

    ,

    1981-04-01

    The study objective of "The Mathematical Simulation of Sediment and Radionuclide Transport in Surface Waters" is to synthesize and test radionuclide transport models capable of realistically assessing radionuclide transport in various types of surface water bodies by including the sediment-radionuclide interactions. These interactions include radionuclide adsorption by sediment; desorption from sediment into water; and transport, deposition, and resuspension of sorbed radionuclides controlled by the sediment movements. During FY-1979, the modification of sediment and contaminant (radionuclide) transport model, FETRA, was completed to make it applicable to coastal waters. The model is an unsteady, two-dimensional (longitudinal and lateral) model that consists of three submodels (for sediment, dissolved-contaminant, and particulate-contaminant transport), coupled to include the sediment-contaminant interactions. In estuaries, flow phenomena and consequent sediment and radionuclide migration are often three-dimensional in nature mainly because of nonuniform channel cross-sections, salinity intrusion, and lateral-flow circulation. Thus, an unsteady, three-dimensional radionuclide transport model for estuaries is also being synthesized by combining and modifying a PNL unsteady hydrothermal model and FETRA. These two radionuclide transport models for coastal waters and estuaries will be applied to actual sites to examine the validity of the codes.

  12. Thermoelectric transport of edge/surface states of topological insulators

    NASA Astrophysics Data System (ADS)

    Murakami, Shuichi; Takahashi, Ryuji

    2011-03-01

    In my talk we theoretically study thermoelectric properties of topological insulators (TI), where novel properties of edge/surface states are expected to appear. As compared to the number of bulk states, the edge/surface states are very few; we therefore consider a narrow ribbon for 2D and a thin slab for 3D TI to make the edge/surface-state transport larger. By considering edge/surface and bulk transport together, we calculate the charge and heat conductivity, and Seebeck coefficient. We find that in 2D TI the bulk and edge transport compete each other in the thermoelectric transport. By lowering temperature, the thermoelectric figure of merit ZT has a minimum, corresponding to the bulk-to-edge crossover, and then increases again at low temperature where the edge state dominates. The crossover is estimated to be at around 5K-10K for 10nm-width ribbon. We also discuss surface state transport for 3D TI as well.

  13. 76 FR 59186 - Renewal of Rail Energy Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-23

    ... Surface Transportation Board Renewal of Rail Energy Transportation Advisory Committee AGENCY: Surface... Board (Board) intends to renew the charter of the Rail Energy Transportation Advisory Committee (RETAC... discussion of emerging issues and concerns regarding the transportation by rail of energy...

  14. 77 FR 8947 - Notice of Rail Energy Transportation Advisory Committee Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-15

    ... regarding the transportation by rail of energy resources, particularly, but not necessarily limited to, coal... Surface Transportation Board Notice of Rail Energy Transportation Advisory Committee Meeting AGENCY: Surface Transportation Board, DOT. ACTION: Notice of Rail Energy Transportation Advisory Committee...

  15. 76 FR 16036 - Notice of Rail Energy Transportation Advisory Committee Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-22

    ... Surface Transportation Board Notice of Rail Energy Transportation Advisory Committee Meeting AGENCY: Surface Transportation Board, Department of Transportation. ACTION: Notice of Rail Energy Transportation Advisory Committee meeting. SUMMARY: Notice is hereby given of a meeting of the Rail Energy...

  16. Evaluation of hydraulic coal transport system concepts for surface mines

    SciTech Connect

    Roberge, J.; Stoukidis, M.; Rubin, L.; Burnett, M.

    1981-11-01

    Coal haulage from the pit of United States surface mines is most often accomplished with truck haul transportation schemes. The demand for domestic production of coal is expected to increase greatly over the next decade. Efforts to restrain and curtail increasing power production costs will require optimum productivity within the coal producing industry. The objective of this program was to develop concepts for in-pit hydraulic transport systems for surface coal mines that will permit significant increases in coal extraction and pit haulage productivity as compared to truck haulage. Large particle coal transport was demonstrated to be the most desirable for central and western United States surface mines. Three conceptual hydrotransport systems, including a centrifugal pump, jet pump and ventilated inducer system, were developed for each of two currently active mining operations. General and site-specific design parameters were developed for each of the conceptual hydrotransport systems. A detailed economic comparison of capital and operating and maintenance costs for each of the hydrotransport systems was made with the existing truck haul operations. An increase in haulage productivity of approximately 19% was demonstrated for the central surface mine, while that of the western surface mine increased by more than 180%. Included in this report is a bibliography containing over 600 citations pertinent to hydraulic transport of coal.

  17. Surface Hall Effect and Nonlocal Transport in SmB6: Evidence for Surface Conduction

    PubMed Central

    Kim, D. J.; Thomas, S.; Grant, T.; Botimer, J.; Fisk, Z.; Xia, Jing

    2013-01-01

    A topological insulator (TI) is an unusual quantum state in which the insulating bulk is topologically distinct from vacuum, resulting in a unique metallic surface that is robust against time-reversal invariant perturbations. The surface transport, however, remains difficult to isolate from the bulk conduction in most existing TI crystals (particularly Bi2Se3, Bi2Te3 and Sb2Te3) due to impurity caused bulk conduction. We report in large crystals of topological Kondo insulator (TKI) candidate material SmB6 the thickness-independent surface Hall effects and non-local transport, which persist after various surface perturbations. These results serve as proof that at low temperatures SmB6 has a metallic surface that surrounds an insulating bulk, paving the way for transport studies of the surface state in this proposed TKI material. PMID:24193196

  18. Water transport mechanism through open capillaries analyzed by direct surface modifications on biological surfaces.

    PubMed

    Ishii, Daisuke; Horiguchi, Hiroko; Hirai, Yuji; Yabu, Hiroshi; Matsuo, Yasutaka; Ijiro, Kuniharu; Tsujii, Kaoru; Shimozawa, Tateo; Hariyama, Takahiko; Shimomura, Masatsugu

    2013-01-01

    Some small animals only use water transport mechanisms passively driven by surface energies. However, little is known about passive water transport mechanisms because it is difficult to measure the wettability of microstructures in small areas and determine the chemistry of biological surfaces. Herein, we developed to directly analyse the structural effects of wettability of chemically modified biological surfaces by using a nanoliter volume water droplet and a hi-speed video system. The wharf roach Ligia exotica transports water only by using open capillaries in its legs containing hair- and paddle-like microstructures. The structural effects of legs chemically modified with a self-assembled monolayer were analysed, so that the wharf roach has a smart water transport system passively driven by differences of wettability between the microstructures. We anticipate that this passive water transport mechanism may inspire novel biomimetic fluid manipulations with or without a gravitational field. PMID:24149467

  19. Levitation and Transport of Charged Dust Over Surfaces in Space

    NASA Astrophysics Data System (ADS)

    Colwell, Joshua E.; Horányi, Mihály; Robertson, Scott; Sickafoose, Amanda A.

    2002-12-01

    Dust in planetary regoliths may become charged and levitated in plasma sheaths and photoelectron sheaths near the surface [1,2]. This provides an explanation for the observations of the lunar horizon glow [3]. Horizontal electric fields or inhomogeneities in the sheath may lead to net transport of dust on the surface. Electrostatic levitation of dust may also explain observations of regolith deposits in craters on the asteroid 433 Eros by the NEAR spacecraft [4]. We present the results of a simple model of dust transport in a photoelectron sheath across a surface with simple topographical forms. We find a net deposition of particles launched in random directions at photoelectron sheath boundaries such as might occur in the terminator region. Topographic boundaries such as blocks and craters provide an additional sink for particles moving horizontally across the surface in a sheath.

  20. Surface flux evolution constraints for flux transport dynamos

    NASA Astrophysics Data System (ADS)

    Cameron, R. H.; Schmitt, D.; Jiang, J.; Işık, E.

    2012-06-01

    The surface flux transport (SFT) model of solar magnetic fields involves empirically well-constrained velocity and magnetic fields. The basic evolution of the Sun's large-scale surface magnetic field is well described by this model. The azimuthally averaged evolution of the SFT model can be compared to the surface evolution of the flux transport dynamo (FTD), and the evolution of the SFT model can be used to constrain several near-surface properties of the FTD model. We compared the results of the FTD model with different upper boundary conditions and diffusivity profiles against the results of the SFT model. Among the ingredients of the FTD model, downward pumping of magnetic flux, related to a positive diffusivity gradient, has a significant effect in slowing down the diffusive radial transport of magnetic flux through the solar surface. Provided the pumping was strong enough to give rise to a downflow of a magnetic Reynolds number of 5 in the near-surface boundary layer, the FTD using a vertical boundary condition matches the SFT model based on the average velocities above the boundary layer. The FTD model with a potential field was unable to match the SFT results.

  1. Directional transport of impinging capillary jet on wettability engineered surfaces

    NASA Astrophysics Data System (ADS)

    Ghosh, Aritra; Chatterjee, Souvick; Sinha Mahapatra, Pallab; Ganguly, Ranjan; Megaridis, Constantine

    2015-11-01

    Impingement of capillary jet on a surface is important for applications like heat transfer, or for liquid manipulation in bio-microfluidic devices. Using wettability engineered surfaces, we demonstrate pump-less and directional transport of capillary jet on a flat surface. Spatial contrast of surface energy and a wedge-shape geometry of the wettability confined track on the substrate facilitate formation of instantaneous spherical bulges upon jet impingement; these bulges are further transported along the superhydrophilic tracks due to Laplace pressure gradient. Critical condition warranted for formation of liquid bulge along the varying width of the superhydrophilic track is calculated analytically and verified experimentally. The work throws light on novel fluid phenomena of unidirectional jet impingement on wettability confined surfaces and provides a platform for innovative liquid manipulation technique for further application. By varying the geometry and wettability contrast on the surface, one can achieve volume flow rates of ~ O(100 μL/sec) and directionally guided transport of the jet liquid, pumplessly at speeds of ~ O(10cm/sec).

  2. Strong Surface Orientation Dependent Thermal Transport in Si Nanowires

    PubMed Central

    Zhou, Yanguang; Chen, Yuli; Hu, Ming

    2016-01-01

    Thermoelectrics, which convert waste heat to electricity, offer an attractive pathway for addressing an important niche in the globally growing landscape of energy demand. Research to date has focused on reducing the thermal conductivity relative to the bulk. Si nanowires (NWs) have received exceptional attention due to their low-dimensionality, abundance of availability, and high carrier mobility. From thermal transport point of view, the thermal conductivity of Si NWs strongly depends on the detailed surface structure, such as roughness and surface orientation. Here, direct molecular dynamics simulations and theoretical models are used to investigate the thermal transport in Si NWs with diverse surface orientations. Our results show that the thermal conductivity of Si NWs with different surface orientation can differ by as large as 2.7~4.2 times, which suggests a new route to boost the thermoelectric performance. Using the full spectrum theory, we find that the surface orientation, which alters the distribution of atoms on the surface and determines the degree of phonon coupling between the core and the surface, is the dominant mechanism. Furthermore, using spectral thermal conductivity, the remarkable difference in the thermal conductivity for different surface orientation is found to only stem from the phonons in the medium frequency range, with minor contribution from low and high frequency phonons. PMID:27113556

  3. Strong Surface Orientation Dependent Thermal Transport in Si Nanowires.

    PubMed

    Zhou, Yanguang; Chen, Yuli; Hu, Ming

    2016-01-01

    Thermoelectrics, which convert waste heat to electricity, offer an attractive pathway for addressing an important niche in the globally growing landscape of energy demand. Research to date has focused on reducing the thermal conductivity relative to the bulk. Si nanowires (NWs) have received exceptional attention due to their low-dimensionality, abundance of availability, and high carrier mobility. From thermal transport point of view, the thermal conductivity of Si NWs strongly depends on the detailed surface structure, such as roughness and surface orientation. Here, direct molecular dynamics simulations and theoretical models are used to investigate the thermal transport in Si NWs with diverse surface orientations. Our results show that the thermal conductivity of Si NWs with different surface orientation can differ by as large as 2.7~4.2 times, which suggests a new route to boost the thermoelectric performance. Using the full spectrum theory, we find that the surface orientation, which alters the distribution of atoms on the surface and determines the degree of phonon coupling between the core and the surface, is the dominant mechanism. Furthermore, using spectral thermal conductivity, the remarkable difference in the thermal conductivity for different surface orientation is found to only stem from the phonons in the medium frequency range, with minor contribution from low and high frequency phonons. PMID:27113556

  4. Heat transport along domain walls and surfaces of superconductors

    NASA Astrophysics Data System (ADS)

    Vorontsov, Anton; Richard, Caroline

    2015-03-01

    We calculate thermal transport in non-uniform states of unconventional superconductors, that appear near pairbreaking surfaces, or due to formation of domain walls in the order parameter. The spectrum of the quasiparticles states in these regions is dominated by the Andreev bound states, including topologically protected modes. We investigate how these states contribute to the heat transport, using non-equilibrium quasiclassical theory in linear response. We report self-consistent calculation of the order parameter, impurity self-energies, density of states and vertex corrections. Particular attention is paid to the non-local nature of the response. We show differences and similarities between domain walls in d-wave materials, and surfaces of multi-component chiral superconducting states. We describe results for Born and unitary impurity scattering limits, and effects of the Zeeman magnetic field on thermal transport. Supported by NSF Grants DMR-0954342.

  5. Excess surface area in bioelectrochemical systems causes ion transport limitations

    PubMed Central

    Harrington, Timothy D.; Babauta, Jerome T.; Davenport, Emily K.; Renslow, Ryan S.; Beyenal, Haluk

    2014-01-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: 1) showing that serially increasing NaCl concentration up to 200 mM increased current linearly up to a total of +273% vs. 0 mM NaCl under advective conditions, 2) growing the biofilm with a starting concentration of 200 mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and 3) showing that un-colonized surface area remained even after steady-state current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential at the electrode surface. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant. PMID:25421463

  6. Excess Surface Area in Bioelectrochemical Systems Causes ion Transport Limitations

    SciTech Connect

    Harrington, Timothy D.; Babauta, Jerome T.; Davenport, Emily K.; Renslow, Ryan S.; Beyenal, Haluk

    2015-05-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: (i) showing that serially increasing NaCl concentration up to 200mM increased current linearly up to a total of þ273% vs. 0mM NaCl under advective conditions; (ii) growing the biofilm with a starting concentration of 200mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and (iii) showing that un-colonized surface area remained even after steadystate current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant.

  7. Excess surface area in bioelectrochemical systems causes ion transport limitations.

    PubMed

    Harrington, Timothy D; Babauta, Jerome T; Davenport, Emily K; Renslow, Ryan S; Beyenal, Haluk

    2015-05-01

    We investigated ion transport limitations on 3D graphite felt electrodes by growing Geobacter sulfurreducens biofilms with advection to eliminate external mass transfer limitations. We characterized ion transport limitations by: (i) showing that serially increasing NaCl concentration up to 200 mM increased current linearly up to a total of +273% vs. 0 mM NaCl under advective conditions; (ii) growing the biofilm with a starting concentration of 200 mM NaCl, which led to a maximum current increase of 400% vs. current generation without NaCl, and (iii) showing that un-colonized surface area remained even after steady-state current was reached. After accounting for iR effects, we confirmed that the excess surface area existed despite a non-zero overpotential. The fact that the biofilm was constrained from colonizing and producing further current under these conditions confirmed the biofilms under study here were ion transport-limited. Our work demonstrates that the use of high surface area electrodes may not increase current density when the system design allows ion transport limitations to become dominant. PMID:25421463

  8. Robust surface state transport in thin bismuth nanoribbons

    NASA Astrophysics Data System (ADS)

    Ning, Wei; Kong, Fengyu; Han, Yuyan; Du, Haifeng; Yang, Jiyong; Tian, Mingliang; Zhang, Yuheng

    2014-11-01

    While a two-dimensional (2D) metallic surface state in bismuth has been proposed, experimental 2D evidence of quantum transport, e.g., angular dependent Shubnikov-de Haas (SdH) oscillations is still lacking. Here, we report the angular-dependent magnetoresistance measurements in single-crystal Bi nanoribbons, and found that both the low-field weak antilocalization behavior and the high-field angle-dependent SdH oscillations follow exactly the 2D character, indicative of the 2D metallic surface states which dominate the transport properties of thin Bi nanoribbons. Moreover, by controllable exposing the ribbons to ambient environment (1 atm and room temperature), the metallic surface states were found to be robust to the oxidation although the carrier density in the surface states are modified after the exposures. These results suggest that the metallic surface states in Bi nanoribbons should be topologically protected which can provide key information in understanding the surface properties of Bi in nanometer scale.

  9. Robust surface state transport in thin bismuth nanoribbons

    PubMed Central

    Ning, Wei; Kong, Fengyu; Han, Yuyan; Du, Haifeng; Yang, Jiyong; Tian, Mingliang; Zhang, Yuheng

    2014-01-01

    While a two-dimensional (2D) metallic surface state in bismuth has been proposed, experimental 2D evidence of quantum transport, e.g., angular dependent Shubnikov-de Haas (SdH) oscillations is still lacking. Here, we report the angular-dependent magnetoresistance measurements in single-crystal Bi nanoribbons, and found that both the low-field weak antilocalization behavior and the high-field angle-dependent SdH oscillations follow exactly the 2D character, indicative of the 2D metallic surface states which dominate the transport properties of thin Bi nanoribbons. Moreover, by controllable exposing the ribbons to ambient environment (1 atm and room temperature), the metallic surface states were found to be robust to the oxidation although the carrier density in the surface states are modified after the exposures. These results suggest that the metallic surface states in Bi nanoribbons should be topologically protected which can provide key information in understanding the surface properties of Bi in nanometer scale. PMID:25404036

  10. 41 CFR 102-5.25 - What additional guidance concerning home-to-work transportation should Federal agencies issue?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false What additional guidance concerning home-to-work transportation should Federal agencies issue? 102-5.25 Section 102-5.25 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT REGULATION GENERAL...

  11. Neoclassical transport in toroidal plasmas with nonaxisymmetric flux surfaces

    NASA Astrophysics Data System (ADS)

    Belli, E. A.; Candy, J.

    2015-05-01

    The capability to treat nonaxisymmetric flux surface geometry has been added to the drift-kinetic code NEO (Belli and Candy 2008 Plasma Phys. Control. Fusion 50 095010). Geometric quantities (i.e. metric elements) are supplied by a recently-developed local 3D equilibrium solver, allowing neoclassical transport coefficients to be systematically computed while varying the 3D plasma shape in a simple and intuitive manner. Code verification is accomplished via detailed comparison with 3D Pfirsch-Schlüter theory. A discussion of the various collisionality regimes associated with 3D transport is given, with an emphasis on non-ambipolar particle flux, neoclassical toroidal viscosity, energy flux and bootstrap current. Finally, we compute the transport in the presence of ripple-type perturbations in a DIII-D-like H-mode edge plasma.

  12. Manipulation of spin transport in graphene by surface chemical doping.

    PubMed

    Pi, K; Han, Wei; McCreary, K M; Swartz, A G; Li, Yan; Kawakami, R K

    2010-05-01

    The effects of surface chemical doping on spin transport in graphene are investigated by performing nonlocal measurements in ultrahigh vacuum while depositing gold adsorbates. We demonstrate manipulation of the gate-dependent nonlocal spin signal as a function of gold coverage. We discover that charged impurity scattering is not the dominant mechanism for spin relaxation in graphene, despite its importance for momentum scattering. Finally, unexpected enhancements of the spin lifetime illustrate the complex nature of spin relaxation in graphene. PMID:20482203

  13. 41 CFR 302-10.206 - May my agency assume direct responsibility for the costs of preparing and transporting my mobile...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... direct responsibility for the costs of preparing and transporting my mobile home? 302-10.206 Section 302... ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS... responsibility for the costs of preparing and transporting my mobile home? Yes, your agency may assume...

  14. 41 CFR 302-10.206 - May my agency assume direct responsibility for the costs of preparing and transporting my mobile...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... direct responsibility for the costs of preparing and transporting my mobile home? 302-10.206 Section 302... ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 10-ALLOWANCES FOR TRANSPORTATION OF MOBILE HOMES AND BOATS... responsibility for the costs of preparing and transporting my mobile home? Yes, your agency may assume...

  15. Transport equations for linear surface waves with random underlying flows

    NASA Astrophysics Data System (ADS)

    Bal, Guillaume; Chou, Tom

    1999-11-01

    We define the Wigner distribution and use it to develop equations for linear surface capillary-gravity wave propagation in the transport regime. The energy density a(r, k) contained in waves propagating with wavevector k at field point r is given by dota(r,k) + nabla_k[U_⊥(r,z=0) \\cdotk + Ω(k)]\\cdotnabla_ra [13pt] \\: hspace1in - (nabla_r\\cdotU_⊥)a - nabla_r(k\\cdotU_⊥)\\cdotnabla_ka = Σ(δU^2) where U_⊥(r, z=0) is a slowly varying surface current, and Ω(k) = √(k^3+k)tanh kh is the free capillary-gravity dispersion relation. Note that nabla_r\\cdotU_⊥(r,z=0) neq 0, and that the surface currents exchange energy density with the propagating waves. When an additional weak random current √\\varepsilon δU(r/\\varepsilon) varying on the scale of k-1 is included, we find an additional scattering term Σ(δU^2) as a function of correlations in δU. Our results can be applied to the study of surface wave energy transport over a turbulent ocean.

  16. 41 CFR 302-7.15 - Must I use the method selected by my agency for transporting my HHG, PBP&E and temporary storage?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... selected by my agency for transporting my HHG, PBP&E and temporary storage? 302-7.15 Section 302-7.15... BOOKS, PAPERS, AND EQUIPMENT (PBP&E) General Rules § 302-7.15 Must I use the method selected by my agency for transporting my HHG, PBP&E and temporary storage? No, you do not have to use the...

  17. 41 CFR 302-9.170 - Under what specific conditions may my agency authorize transportation of a POV to my post of duty...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... conditions may my agency authorize transportation of a POV to my post of duty subsequent to the time of my assignment to that post? 302-9.170 Section 302-9.170 Public Contracts and Property Management Federal Travel... transportation of a POV to my post of duty subsequent to the time of my assignment to that post? Your agency...

  18. 41 CFR 302-9.140 - Under what specific conditions may my agency authorize transportation of a POV to my post of duty...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... conditions may my agency authorize transportation of a POV to my post of duty upon my assignment to that post... post of duty upon my assignment to that post of duty? Your agency may authorize transportation of a POV to your post of duty when: (a) It has determined in accordance with § 302-9.503 that it is in...

  19. TiN surface dynamics: role of surface and bulk mass transport processes

    SciTech Connect

    Bareno, J.; Swiech, W.; Petrova, V.; Petrov, I.; Greene, J. E.; Kodambaka, S.; Khare, S. V.

    2007-02-09

    Transition-metal nitrides, such as TiN, have a wide variety of applications as hard, wear-resistant coatings, as diffusion barriers, and as scratch-resistant and anti-reflective coatings in optics. Understanding the surface morphological and microstructural evolution of these materials is crucial for improving the performance of devices. Studies of surface step dynamics enable determination of the rate-limiting mechanisms, corresponding surface mass transport parameters, and step energies. However, most models describing these phenomena are limited in application to simple elemental metal and semiconductor surfaces. Here, we summarize recent progress toward elucidating the interplay of surface and bulk diffusion processes on morphological evolution of compound surfaces. Specifically, we analyze the coarsening/decay kinetics of two- and three-dimensional TiN(111) islands and the effect of surface-terminated dislocations on TiN(111) steps.

  20. 43 CFR 3900.61 - Federal minerals where the surface is owned or administered by other Federal agencies, by state...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Federal minerals where the surface is owned or administered by other Federal agencies, by state agencies or charitable organizations, or by private entities. 3900.61 Section 3900.61 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT,...

  1. 75 FR 70080 - Notice of Railroad-Shipper Transportation Advisory Council Vacancies

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-16

    ... Surface Transportation Board Notice of Railroad-Shipper Transportation Advisory Council Vacancies AGENCY: Surface Transportation Board (Board), DOT. ACTION: Notice of vacancies on the Railroad-Shipper Transportation Advisory Council (RSTAC) and solicitation of nominations. SUMMARY: The Board hereby gives...

  2. A global assessment of accelerations in surface mass transport

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoping; Heflin, Michael B.

    2015-08-01

    Water mass transport in the Earth's dynamic surface layer of atmosphere, cryosphere, and hydrosphere driven by various global change processes has complex spatiotemporal patterns. Here we determine global patterns and regional mean values of accelerations in surface mass variations during the Gravity Recovery and Climate Experiment (GRACE) mission's data span from 2002.2 to 2015.0. GRACE gravity data are supplemented by surface deformation from 607 Global Navigation Satellite System stations, an ocean bottom pressure model, satellite laser ranging, and loose a priori knowledge on mass variation regimes incorporating high-resolution geographic boundaries. While Greenland and West Antarctica have strong negative accelerations, Alaska and the Arctic Ocean show significant positive accelerations. In addition, the accelerations are not constant in time with some regions showing considerable variability due to irregular interannual changes. No evidence of significant nonsteric mean sea level acceleration has been found, but the uncertainty is quite large.

  3. Formation and transport of deethylatrazine and deisopropylatrazine in surface water

    USGS Publications Warehouse

    Thurman, E.M.; Meyer, M.T.; Mills, M.S.; Zimmerman, L.R.; Perry, C.A.; Goolsby, D.A.

    1994-01-01

    Field disappearance studies and a regional study of nine rivers in the Midwest Corn Belt show that deethylatrazine (DEA; 2-amino-4-chloro-6-isopropylamino-s-triazine) and deisopropylatrazine (DIA; 2-amino-4-chloro-6-ethylaminos-triazine) occur frequently in surface water that has received runoff from two parent triazine herbicides, atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and cyanazine (2-chloro-4-ethylamino-6-methylpropionitrileamino-s-triazine). The concentration of DEA and DIA in surface water varies with the hydrologic conditions of the basin and the timing of runoff, with maximum concentrations reaching 5 ??g/L (DEA + DIA). Early rainfall followed by a dry summer will result in an early peak concentration of metabolites in surface water. A wet summer will delay the maximum concentrations of metabolites and increase their runoff into surface water, occasionally resulting in a slight separation of the parent atrazine maximum concentrations from the metabolite maximum concentrations, giving a "second flush?? of triazine metabolites to surface water. Replicated field dissipation studies of atrazine and cyanazine indicate that DIA/DEA ratios will vary from 0.4 ?? 0.1 when atrazine is the major triazine present to 0.6 ?? 0.1 when significant amounts of cyanazine are present. A comparison of transport time of DEA and DIA from field plots to their appearance in surface water indicates that storage and dilution are occurring in the alluvial aquifers of the basin.

  4. Sediment transport in a surface-advected estuarine plume

    NASA Astrophysics Data System (ADS)

    Yao, H. Y.; Leonardi, N.; Li, J. F.; Fagherazzi, S.

    2016-03-01

    The interplay between suspended-sediment transport and plume hydrodynamics in a surface-advected estuarine plume is studied using a three-dimensional numerical model. Our analysis focuses on the formation of a sediment-rich alongshore current and on the effect of sediments on the structure of the recirculating freshwater bulge. We introduce the ratio Y between the traveling time of sediment along the bulge edge and the settling timescale. When Y <1, suspended sediments enter the alongshore coastal current. When Y >1 the sediments are deposited within the bulge. We find that a critical range of settling velocities exist above which no transport in the costal current is allowed. Critical settling-velocity values increase with river discharge. Therefore, low magnitude and long-lasting floods promote sediment sorting in the continental shelf. We further find that, for a given flood duration, intermediate flood magnitudes at the limit between subcritical and supercritical flow maximize the alongshore sediment transport. Similarly, for a fixed input of water and sediments, intermediate discharge durations maximize alongshore sediment transport.

  5. Role of Surface Chemistry in Nanoscale Electrokinetic Transport

    NASA Astrophysics Data System (ADS)

    Atalay, Selcuk

    This dissertation work presents the efforts to study the electrofluidics phenomena, with a focus on surface charge properties in nanoscale systems with the potential applications in imaging, energy conversion, ultrafiltration, DNA analysis/sequencing, DNA and protein transport, drug delivery, biological/chemical agent detection and micro/nano chip sensors. Since the ion or molecular or particle transport and also liquid confinement in nano-structures are strongly dominated by the surface charge properties, in regards of the fundamental understanding of electrofluidics at nanoscale, we have used surface charge chemistry properties based on 2-pK charging mechanism. Using this mechanism, we theoretically and analytically showed the surface charge properties of silica nanoparticles as a function of their size, pH level and salt ionic strength of aqueous solution. For a fixed particle size, the magnitude of the surface charge typically increases with an increase in pH or background salt concentration. Furthermore, we investigated the surface charge properties of a charged dielectric nanoparticle and flat wall in electrostatic interactions. According to the theoretical results strong interactions cause a non-uniform surface charge density on the nanoparticle and the plate as a result of the enhancement of proton concentration in the gap between the particle and the plate. This effect increases with decreased separation distance (Kh). We moreover investigated the ion confinement inside the nanospaces and using a continuum model, we showed the proton enhancement in extended nanochannels. The proton enrichment at the center of the nanochannel is significant when the bulk pH is medium high and the salt concentration is relatively low. The results gathered are informative for the development of biomimetic nanofluidic apparatuses and the interpretation of relevant experimental data. Later, we have developed an analytical model for electroosmotic ion transport inside p

  6. Overland and near-surface transport of Cryptosporidium parvum from vegetated and nonvegetated surfaces.

    PubMed

    Trask, Jennifer R; Kalita, Prasanta K; Kuhlenschmidt, Mark S; Smith, Ronald D; Funk, Ted L

    2004-01-01

    Understanding microbial pathogen transport patterns in overland flow is important for developing best management practices for limiting microbial transport to water resources. Knowledge about the effectiveness of vegetative filter strips (VFS) to reduce pathogen transport from livestock confinement areas is limited. In this study, overland and near-surface transport of Cryptosporidium parvum has been investigated. Effects of land slopes, vegetation, and rainfall intensities on oocyst transport were examined using a tilting soil chamber with two compartments, one with bare ground and the other with brome (Bromus inermis Leyss.) vegetation. Three slope conditions (1.5, 3.0, and 4.5%) were used in conjunction with two rainfall intensities (25.4 and 63.5 mm/h) for 44 min using a rainfall simulator. The vegetative surface was very effective in reducing C. parvum in surface runoff. For the 25.4 mm/h rainfall, the total percent recovery of oocysts in overland flow from the VFS varied from 0.6 to 1.7%, while those from the bare ground condition varied from 4.4 to 14.5%. For the 63.5 mm/h rainfall, the recovery percentages of oocysts varied from 0.8 to 27.2% from the VFS, and 5.3 to 59% from bare-ground conditions. For all slopes and rainfall intensities, the total (combining both surface and near-surface) recovery of C. parvum oocysts was considerably less from the vegetated surface than those from the bare-ground conditions. These results indicate that the VFS can be a best management practice for controlling C. parvum in runoff from animal production facilities. PMID:15224935

  7. Nanoscale electron transport at the surface of a topological insulator

    PubMed Central

    Bauer, Sebastian; Bobisch, Christian A.

    2016-01-01

    The use of three-dimensional topological insulators for disruptive technologies critically depends on the dissipationless transport of electrons at the surface, because of the suppression of backscattering at defects. However, in real devices, defects are unavoidable and scattering at angles other than 180° is allowed for such materials. Until now, this has been studied indirectly by bulk measurements and by the analysis of the local density of states in close vicinity to defect sites. Here, we directly measure the nanoscale voltage drop caused by the scattering at step edges, which occurs if a lateral current flows along a three-dimensional topological insulator. The experiments were performed using scanning tunnelling potentiometry for thin Bi2Se3 films. So far, the observed voltage drops are small because of large contributions of the bulk to the electronic transport. However, for the use of ideal topological insulating thin films in devices, these contributions would play a significant role. PMID:27098939

  8. Nanoscale electron transport at the surface of a topological insulator

    NASA Astrophysics Data System (ADS)

    Bauer, Sebastian; Bobisch, Christian A.

    2016-04-01

    The use of three-dimensional topological insulators for disruptive technologies critically depends on the dissipationless transport of electrons at the surface, because of the suppression of backscattering at defects. However, in real devices, defects are unavoidable and scattering at angles other than 180° is allowed for such materials. Until now, this has been studied indirectly by bulk measurements and by the analysis of the local density of states in close vicinity to defect sites. Here, we directly measure the nanoscale voltage drop caused by the scattering at step edges, which occurs if a lateral current flows along a three-dimensional topological insulator. The experiments were performed using scanning tunnelling potentiometry for thin Bi2Se3 films. So far, the observed voltage drops are small because of large contributions of the bulk to the electronic transport. However, for the use of ideal topological insulating thin films in devices, these contributions would play a significant role.

  9. Nanoscale electron transport at the surface of a topological insulator.

    PubMed

    Bauer, Sebastian; Bobisch, Christian A

    2016-01-01

    The use of three-dimensional topological insulators for disruptive technologies critically depends on the dissipationless transport of electrons at the surface, because of the suppression of backscattering at defects. However, in real devices, defects are unavoidable and scattering at angles other than 180° is allowed for such materials. Until now, this has been studied indirectly by bulk measurements and by the analysis of the local density of states in close vicinity to defect sites. Here, we directly measure the nanoscale voltage drop caused by the scattering at step edges, which occurs if a lateral current flows along a three-dimensional topological insulator. The experiments were performed using scanning tunnelling potentiometry for thin Bi2Se3 films. So far, the observed voltage drops are small because of large contributions of the bulk to the electronic transport. However, for the use of ideal topological insulating thin films in devices, these contributions would play a significant role. PMID:27098939

  10. Simulation of Martian surface conditions and dust transport

    NASA Astrophysics Data System (ADS)

    Nørnberg, P.; Merrison, J. P.; Finster, K.; Folkmann, F.; Gunnlaugsson, H. P.; Hansen, A.; Jensen, J.; Kinch, K.; Lomstein, B. Aa.; Mugford, R.

    2002-11-01

    The suspended atmospheric dust which is also found deposited over most of the Martian globe plays an important (possibly vital) role in shaping the surface environment. It affects the weather (solar flux), water transport and possibly also the electrical properties at the surface. The simulation facilities at Aarhus provide excellent tools for studying the properties of this Martian environment. Much can be learned from such simulations, supporting and often inspiring new investigations of the planet. Electrical charging of a Mars analogue dust is being studied within a wind tunnel simulation aerosol. Here electric fields are used to extract dust from suspension. Although preliminary the results indicate that a large fraction of the dust is charged to a high degree, sufficient to dominate adhesion/cohesion processes. A Mars analogue dust layer has been shown to be an excellent trap for moisture, causing increased humidity in the soil below. This allows the possibility for liquid water to be stable close to the surface (less than 10 cm). This is being investigated in an environment simulator where heat and moisture transport can be studied through layers of Mars analogue dust.

  11. Pesticide transport via sub-surface drains in Europe.

    PubMed

    Brown, Colin D; van Beinum, Wendy

    2009-12-01

    Transport of pesticides from point of application via sub-surface drains can contribute significantly to contamination of surface waters. Results of 23 field drainage experiments undertaken at sites across Europe were collated and analysed by residual maximum likelihood. Both maximum concentration of pesticide in drainflow (n = 167) and seasonal loss of pesticide to drains (n = 97) were significantly related to strength of pesticide sorption to soil, half-life of the pesticide in soil, the interval between application and first drainflow and the clay content of the soil. The statistical models accounted for 71% of the variability in both maximum concentration and seasonal load. Next, the dataset was used to evaluate the current methodology for assessment of aquatic exposure used in pesticide registration in Europe. Simulations for seven compounds with contrasting properties showed a good correspondence with field measurements. Finally, the review examines management approaches to reduce pesticide transport via sub-surface drains. Despite a large amount of work in this area, there are few dependable mitigation options other than to change application rate or timing or to restrict use of a compound in the most vulnerable situations. PMID:19608317

  12. 77 FR 38709 - Surface Transportation Environment and Planning Cooperative Research Program (STEP)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-28

    ... project delivery while improving environmental outcomes; (2) Conducting research to develop climate change... Federal Highway Administration Surface Transportation Environment and Planning Cooperative Research...-LU) established the Surface Transportation Environment and Planning Cooperative Research...

  13. 76 FR 50312 - Surface Transportation Environment and Planning Cooperative Research Program (STEP)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-12

    ... research to develop climate change mitigation, adaptation and livability strategies; (2) Developing and/or... Federal Highway Administration Surface Transportation Environment and Planning Cooperative Research...-LU) established the Surface Transportation Environment and Planning Cooperative Research...

  14. 75 FR 38605 - Surface Transportation Environment and Planning Cooperative Research Program (STEP)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-02

    ... implementation of a national research agenda that includes: (1) Conducting research to develop climate change... Federal Highway Administration Surface Transportation Environment and Planning Cooperative Research...-LU) established the Surface Transportation Environment and Planning Cooperative Research...

  15. Degree-1 Surface Mass Transport and Geocenter Motion

    NASA Astrophysics Data System (ADS)

    Wu, X.

    2015-12-01

    The longest-wavelength and hemisphere asymmetric surface mass transport is characterized by three degree-one spherical harmonic components. Such mass transport modes cause geocenter motion between the center-of-mass of the total Earth system (CM) and the center-of-figure of the solid Earth surface (CF), and deforms the solid Earth. GRACE's K-band ranging data system is not sensitive to these three variation modes. For a complete spherical harmonic spectral coverage of mass transport, degree-1 surface mass changes estimated through geocenter motion or degree-1 mass/deformation signatures from other space geodetic techniques should be combined with GRACE's time-variable gravity data. The degree-1 coefficients are critically important for mass variation assessments over large regions. For example, 1 mm error in geocenter motion can result in an error of 190 gigatons of global oceanic water mass change or, equivalently, an error of 0.5 mm of global mean sea level change when the geocenter motion is converted to degree-1 mass and combined with GRACE data. Yet, several different methods of geocenter motion estimation differ in results by more than 1 mm in annual amplitude. These differences have to be resolved after 13 years of successful GRACE operation. Recently, the difference between results from direct satellite laser ranging (SLR) determination and from a global inversion of Global Navigation Satellite System (GNSS) deformation measurements, GRACE, and an ocean bottom pressure (OBP) model has been largely reconciled as due to SLR's sparse station distribution. This result and our current efforts to examine possible systematic errors in GNSS data and the OBP model will be discussed along with a future perspective.

  16. Effect of the surface charge on ion transport through nanoslits

    NASA Astrophysics Data System (ADS)

    Schoch, Reto B.; van Lintel, Harald; Renaud, Philippe

    2005-10-01

    A description of ion transport through geometrically defined nanoslits is presented. It is characterized by the effective surface charge density and was obtained by impedance spectroscopy measurements of electrolytes with different physicochemical properties. The fluid channels were fabricated in a Pyrex-Pyrex field assisted bonding process with an intermediate layer of amorphous silicon. The height of the nanoslits was defined by the 50nm thickness of the amorphous silicon layer. Two microfluidic channels, containing electrodes for the characterization of the nanoslits, maintained fresh liquid on both sides of the nanoapertures. By changing the KCl concentration of the electrolyte, a conductance plateau (in log-log scale) was observed due to the dominance of the effective surface charge density, resulting in an excess of mobile counterions in the nanoslits at low salt concentrations. The effective surface charge density of the Pyrex nanoslits could be modified by changing the pH of the solution. It was verified that at higher pH values the nanoslit conductance increased. Field-effect experiments allowed changing the effective surface charge density as well. The polarity of the external voltage could be chosen such that the effective surface charge density was increased or decreased, resulting in a higher or lower nanoslit conductance. This regulation of ionic flow can be exploited for the fabrication of nanofluidic devices.

  17. Solar energy conversion using surface plasmons for broadband energy transport

    NASA Technical Reports Server (NTRS)

    Anderson, L. M.

    1982-01-01

    A new strategy for efficient solar energy conversion based on parallel processing with surface plasmons is introduced. The approach is unique in identifying: (1) a broadband carrier with suitable range for energy transport, and (2) a technique to extract more energy from the more energetic photons, without sequential losses or unique materials for each frequency band. The aim is to overcome the fundamental losses associated with the broad solar spectrum and to achieve a higher level of spectrum splitting than has been possible in semiconductor systems.

  18. Models of Fate and Transport of Pollutants in Surface Waters

    NASA Astrophysics Data System (ADS)

    Okome, Gloria Eloho

    There is the need to answer very crucial questions of "what happens to pollutants in surface waters?" This question must be answered to determine the factors controlling fate and transport of chemicals and their evolutionary state in surface waters. Monitoring and experimental methods are used in establishing the environmental states. These measurements are used with the known scientific principles to identify processes and to estimate the future environmental conditions. Conceptual and computational models are needed to analyze environmental processes by applying the knowledge gained from experimentation and theory. Usually, a computational framework includes the mathematics and the physics of the phenomenon, and the measured characteristics to model pollutants interactions and transport in surface water. However, under certain conditions, the complexity of the situation in the actual environment precludes the utilization of these techniques. Pollutants in several forms: Nitrogen (Nitrate, Nitrite, Kjeldhal Nitrogen and Ammonia), Phosphorus (orthophosphate and total phosphorus), bacteria (E-coli and Fecal coliform), Salts (Chloride and Sulfate) are chosen to follow for this research. The objective of this research is to model the fate and transport of these pollutants in non-ideal conditions of surface water measurements and to develop computational methods to forecast their fate and transport. In an environment of extreme drought such as in the Brazos River basin, where small streams flow intermittently, there is added complexity due to the absence of regularly sampled data. The usual modeling techniques are no longer applicable because of sparse measurements in space and time. Still, there is a need to estimate the conditions of the environment from the information that is present. Alternative methods for this estimation must be devised and applied to this situation, which is the task of this dissertation. This research devices a forecasting technique that is

  19. Electrostatic dust transport on the surfaces of airless bodies

    NASA Astrophysics Data System (ADS)

    Wang, X.; Schwan, J.; Hsu, H. W.; Horanyi, M.

    2015-12-01

    The surfaces of airless bodies are charged due to the exposure to solar wind plasma and UV radiation. Dust particles on the regolith of these surfaces can become charged, and may move and even get lofted due to electrostatic force. Electrostatic dust transport has been a long-standing problem that may be related to many observed phenomena on the surfaces of airless planetary bodies, including the lunar horizon glow, the dust ponds on asteroid Eros, the spokes in Saturn's rings, and more recently, the collection of dust particles ejected off Comet 67P, observed by Rosetta. In order to resolve these puzzles, a handful of laboratory experiments have been performed in the past and demonstrated that dust indeed moves and lifts from surfaces exposed to plasma. However, the exact mechanisms for the mobilization of dust particles still remain a mystery. Current charging models, including the so-called "shared charge model" and the charge fluctuation theory, will be discussed. It is found that neither of these models can explain the results from either laboratory experiments or in-situ observations. Recently, single dust trajectories were captured with our new dust experiments, enabling novel micro-scale investigations. The particles' initial launch speeds and size distributions are analyzed, and a new so-called "patched charge model" is proposed to explain our findings. We identify the role of plasma micro-cavities that are formed in-between neighboring dust particles. The emitted secondary or photo- electrons are proposed to be absorbed inside the micro-cavities, resulting in significant charge accumulation on the exposed patches of the surfaces of neighboring particles. The resulting enhanced Coulomb force (repulsion) between particles is likely the dominant force to mobilize and lift them off the surface. The role of other properties, including surface morphology, cohesion and photoelectron charging, will also be discussed.

  20. Pumpless Transport of Low Surface Tension Liquids in Surface Tension Confined (STC) Tracks

    NASA Astrophysics Data System (ADS)

    Megaridis, Constantine; Schutzius, Thomas; Elsharkawy, Mohamed; Tiwari, Manish

    2012-11-01

    Surfaces with patterned wettability have potential applications in microfluidics, fog capture, pool boiling, etc. With recent fabrication advancements, surfaces with adjacent superhydrophobic and superhydrophilic regions are feasible at a reasonable cost; with properly designed patterns, one can produce microfluidic paths (a.k.a. surface tension confined or STC tracks) where a liquid is confined and transported by surface tension alone. The surface tension of water is relatively high (72 mN/m), as compared with oils (~25 mN/m) and organic solvents (~20 mN/m). This makes the design of STC channels for oils and organic solvents far more difficult. In this study, open STC tracks for pumpless transport of low-surface tension liquids (acetone, ethanol, and hexadecane) on microfluidic chips are fabricated using a large-area, wet-processing technique. Wettable, wax-based, submillimeter-wide tracks are applied by a fountain-pen procedure on superoleophobic, fluoroacrylic carbon nanofiber (CNF) composite coatings. The fabricated anisotropic wetting patterns confine the low-surface tension liquids onto the flow tracks, driving them with meniscus velocities exceeding 3 cm/s. Scaling arguments and Washburn's equation provide estimates of the liquid velocities measured in these tracks, which also act as rails for directional sliding control of mm-sized water droplets. The present facile patterned wettability approach can be extended to deposit micrometer-wide tracks.

  1. Thermal energy transport in a surface phonon-polariton crystal

    NASA Astrophysics Data System (ADS)

    Ordonez-Miranda, Jose; Tranchant, Laurent; Joulain, Karl; Ezzahri, Younes; Drevillon, Jérémie; Volz, Sebastian

    2016-01-01

    We demonstrate that the energy transport of surface phonon polaritons can efficiently be observed in a crystal made up of a three-dimensional assembly of spheroidal nanoparticles of silicon carbide. The ultralow phonon thermal conductivity of this nanostructure, along with its high surface area-to-volume ratio, allows the predominance of the polariton energy over that generated by phonons. The polariton dispersion relation, propagation length, and thermal conductance are numerically determined as functions of the size, shape, and temperature of the nanoparticles. It is shown that the thermal conductance of a crystal with prolate nanoparticles at 500 K and a minor (major) axis of 50 nm (5 μ m ) is 0.5 nW K-1 , which is comparable to the quantum of thermal conductance of polar nanowires. We also show that a nanoparticle size dispersion of up to 200 nm does not change significantly the polariton energy, which supports the technological feasibility of the proposed crystal.

  2. Coherent transport of nanowire surface plasmons coupled to quantum dots.

    PubMed

    Chen, Wei; Chen, Guang-Yin; Chen, Yueh-Nan

    2010-05-10

    The coherent transport of surface plasmons with nonlinear dispersion relations on a metal nanowire coupled to two-level emitters is investigated theoretically. Real-space Hamiltonians are used to obtain the transmission and reflection spectra of the surface plasmons. For the single-dot case, we find that the scattering spectra can show completely different features due to the non-linear quadratic dispersion relation. For the double-dot case, we obtain the interference behavior in transmission and reflection spectra, similar to that in resonant tunneling through a double-barrier potential. Moreover, Fano-like line shape of the transmission spectrum is obtained due to the quadratic dispersion relation. All these peculiar behaviors indicate that the dot-nanowire system provides a onedimensional platform to demonstrate the bandgap feature widely observed in photonic crystals. PMID:20588891

  3. 76 FR 7560 - Agency Information Collection Activities; Proposed Collection; Comment Request; Transportation...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-10

    ...: Ozone, particulate matter (PM2.5 and PM10), carbon monoxide (CO), and nitrogen dioxide (NO2). The EPA... Conformity Determinations for Federally Funded and Approved Transportation Plans, Programs and Projects...: Transportation Conformity Determinations for Federally Funded and Approved Transportation Plans, Programs...

  4. Modeling marine surface microplastic transport to assess optimal removal locations

    NASA Astrophysics Data System (ADS)

    Sherman, Peter; van Sebille, Erik

    2016-01-01

    Marine plastic pollution is an ever-increasing problem that demands immediate mitigation and reduction plans. Here, a model based on satellite-tracked buoy observations and scaled to a large data set of observations on microplastic from surface trawls was used to simulate the transport of plastics floating on the ocean surface from 2015 to 2025, with the goal to assess the optimal marine microplastic removal locations for two scenarios: removing the most surface microplastic and reducing the impact on ecosystems, using plankton growth as a proxy. The simulations show that the optimal removal locations are primarily located off the coast of China and in the Indonesian Archipelago for both scenarios. Our estimates show that 31% of the modeled microplastic mass can be removed by 2025 using 29 plastic collectors operating at a 45% capture efficiency from these locations, compared to only 17% when the 29 plastic collectors are moored in the North Pacific garbage patch, between Hawaii and California. The overlap of ocean surface microplastics and phytoplankton growth can be reduced by 46% at our proposed locations, while sinks in the North Pacific can only reduce the overlap by 14%. These results are an indication that oceanic plastic removal might be more effective in removing a greater microplastic mass and in reducing potential harm to marine life when closer to shore than inside the plastic accumulation zones in the centers of the gyres.

  5. Aluminum in acidic surface waters: chemistry, transport, and effects.

    PubMed Central

    Driscoll, C T

    1985-01-01

    Ecologically significant concentrations of Al have been reported in surface waters draining "acid-sensitive" watersheds that are receiving elevated inputs of acidic deposition. It has been hypothesized that mineral acids from atmospheric deposition have remobilized Al previously precipitated within the soil during soil development. This Al is then thought to be transported to adjacent surface waters. Dissolved mononuclear Al occurs as aquo Al, as well as OH-, F-, SO4(2-), and organic complexes. Although past investigations have often ignored non-hydroxide complexes of Al, it appears that organic and F complexes are the predominant forms of Al in dilute (low ionic strength) acidic surface waters. The concentration of inorganic forms of Al increases exponentially with decreases in solution pH. This response is similar to the theoretical pH dependent solubility of Al mineral phases. The concentration of organic forms of Al, however, is strongly correlated with variations in organic carbon concentration of surface waters rather than pH. Elevated concentrations of Al in dilute acidic waters are of interest because: Al is an important pH buffer; Al may influence the cycling of important elements like P, organic carbon, and trace metals; and Al is potentially toxic to aquatic organisms. An understanding of the aqueous speciation of Al is essential for an evaluation of these processes. PMID:3935428

  6. Surface-charge-governed electrolyte transport in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Xue, Jian-Ming; Guo, Peng; Sheng, Qian

    2015-08-01

    The transport behavior of pressure-driven aqueous electrolyte solution through charged carbon nanotubes (CNTs) is studied by using molecular dynamics simulations. The results reveal that the presence of charges around the nanotube can remarkably reduce the flow velocity as well as the slip length of the aqueous solution, and the decreasing of magnitude depends on the number of surface charges and distribution. With 1-M KCl solution inside the carbon nanotube, the slip length decreases from 110 nm to only 14 nm when the number of surface charges increases from 0 to 12 e. This phenomenon is attributed to the increase of the solid-liquid friction force due to the electrostatic interaction between the charges and the electrolyte particles, which can impede the transports of water molecules and electrolyte ions. With the simulation results, we estimate the energy conversion efficiency of nanofluidic battery based on CNTs, and find that the highest efficiency is only around 30% but not 60% as expected in previous work. Project supported by the National Natural Science Foundation of China (Grant Nos. 11375031 and 11335003).

  7. 41 CFR 301-31.4 - Must my agency pay transportation and subsistence expenses?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... subsistence expenses? No. Your agency decides when it is appropriate to pay these expenses based on the nature of the threat against your life and/or the life of a member(s) of your immediate family....

  8. 41 CFR 301-31.4 - Must my agency pay transportation and subsistence expenses?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... subsistence expenses? No. Your agency decides when it is appropriate to pay these expenses based on the nature of the threat against your life and/or the life of a member(s) of your immediate family....

  9. 41 CFR 301-31.4 - Must my agency pay transportation and subsistence expenses?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... subsistence expenses? No. Your agency decides when it is appropriate to pay these expenses based on the nature of the threat against your life and/or the life of a member(s) of your immediate family....

  10. Transport of dissolved organic carbon from soil to surface water: Identifying the transport pathways

    NASA Astrophysics Data System (ADS)

    Van Gaelen, Nele

    2013-04-01

    Over the last decades, increasing concentrations of dissolved organic carbon (DOC) have been found in surface waters. It has also become clear that land use is an important driver for DOC export. However, causal factors controlling this temporal and spatial variation are not clear. Efforts to model DOC export on a catchment scale are rare. In this research, we aim to determine the factors controlling variations in DOC concentration and quality in surface waters. Secondly, the importance of the different pathways (surface runoff, subsurface flow and groundwater flow) for the transport of dissolved organic matter from the soil to the surface water is investigated. Six headwater catchments (100 - 400 ha) were selected in Belgium, representing three different types of land use, namely forest, grassland and arable land. At the outlet of each catchment, a flow-proportional sampler has been collecting samples of base flow and peak discharge since January 2010. In addition, samples of groundwater, subsurface water and precipitation water were collected on a regular base in three of the catchments. Samples were analyzed for DOC, specific UV absorbance (SUVA) and dissolved silica (DSi). Elemental analysis was carried out using ICP-OES. Since 2012, precipitation water and a selection of river water samples was also analyzed for O and H isotopes. Overall, DOC concentrations were highest in forest catchments and lowest in grassland catchments. For all land use types, measured DOC concentrations were highest during peak discharge. The rise in DOC concentrations was associated with a change in DOC quality. During periods of greater discharge, higher SUVA values were measured, indicating DOC with higher aromaticity (humic and fulvic fractions) reaches the outlet. ICP and DSi results also showed a significant difference in geochemical composition of the river water if peak events are compared to base flow samples. During an event, Ca, Mg, Na, S and DSi concentrations were lowered

  11. 43 CFR 3900.61 - Federal minerals where the surface is owned or administered by other Federal agencies, by state...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... remedies to challenge that decision offered by that particular surface management agency, if any. If the... (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR RANGE MANAGEMENT (4000) OIL SHALE MANAGEMENT-GENERAL Oil Shale Management-Introduction § 3900.61 Federal minerals where the surface is owned...

  12. 43 CFR 3900.61 - Federal minerals where the surface is owned or administered by other Federal agencies, by state...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... remedies to challenge that decision offered by that particular surface management agency, if any. If the... (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) OIL SHALE MANAGEMENT-GENERAL Oil Shale Management-Introduction § 3900.61 Federal minerals where the surface is owned...

  13. 43 CFR 3900.61 - Federal minerals where the surface is owned or administered by other Federal agencies, by state...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... remedies to challenge that decision offered by that particular surface management agency, if any. If the... (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) OIL SHALE MANAGEMENT-GENERAL Oil Shale Management-Introduction § 3900.61 Federal minerals where the surface is owned...

  14. Summary of ground water and surface water flow and contaminant transport computer codes used at the Idaho National Engineering Laboratory (INEL). [Contaminant transport computer codes

    SciTech Connect

    Bandy, P.J.; Hall, L.F.

    1993-03-01

    This report presents information on computer codes for numerical and analytical models that have been used at the Idaho National Engineering Laboratory (INEL) to model ground water and surface water flow and contaminant transport. Organizations conducting modeling at the INEL include: EG G Idaho, Inc., US Geological Survey, and Westinghouse Idaho Nuclear Company. Information concerning computer codes included in this report are: agency responsible for the modeling effort, name of the computer code, proprietor of the code (copyright holder or original author), validation and verification studies, applications of the model at INEL, the prime user of the model, computer code description, computing environment requirements, and documentation and references for the computer code.

  15. 77 FR 19680 - Extension of Agency Information Collection Activity Under OMB Review: Rail Transportation Security

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-02

    ... period soliciting comments, of the following collection of information on January 13, 2012, 77 FR 2077... Johnson, TSA PRA Officer, Office of Information Technology (OIT), TSA-11, Transportation...

  16. Transport properties of overheated electrons trapped on a helium surface

    NASA Astrophysics Data System (ADS)

    Closa, Fabien; Raphäel, Elie; Chepelianskii, Alexei D.

    2014-08-01

    An ultra-strong photovoltaic effect has recently been reported for electrons trapped on a liquid helium surface under a microwave excitation tuned at intersubband resonance [D. Konstantinov, A.D. Chepelianskii, K. Kono, J. Phys. Soc. Jpn 81, 093601 (2012)]. In this article, we analyze theoretically the redistribution of the electron density induced by an overheating of the surface electrons under irradiation, and obtain quantitative predictions for the photocurrent dependence on the effective electron temperature and confinement voltages. We show that the photo-current can change sign as a function of the parameters of the electrostatic confinement potential on the surface, while the photocurrent measurements reported so far have been performed only at a fixed confinement potential. The experimental observation of this sign reversal could provide a reliable estimation of the electron effective temperature in this new out of equilibrium state. Finally, we have also considered the effect of the temperature on the outcome of capacitive transport measurement techniques. These investigations led us to develop, numerical and analytical methods for solving the Poisson-Boltzmann equation in the limit of very low temperatures which could be useful for other systems.

  17. Transport through quantum wells and superlattices on topological insulator surfaces.

    PubMed

    Song, J-T; Li, Y-X; Sun, Q-F

    2014-05-01

    We investigate electron transmission coefficients through quantum wells and quantum superlattices on topological insulator surfaces. The quantum well or superlattice is not constituted by general electronic potential barriers but by Fermi velocity barriers which originate in the different topological insulator surfaces. It is found that electron resonant modes can be renormalized by quantum wells and more clearly by quantum superlattices. The depth and width of a quantum well and superlattice, the incident angle of an electron, and the Fermi energy can be used to effectively tune the electron resonant modes. In particular, the number N of periodic structures that constitute a superlattice can further strengthen these regulating effects. These results suggest that a device could be developed to select and regulate electron propagation modes on topological insulator surfaces. Finally, we also study the conductance and the Fano factor through quantum wells and quantum superlattices. In contrast to what has been reported before, the suppression factors of 0.4 in the conductance and 0.85 in the Fano factor are observed in a quantum well, while the transport for a quantum superlattice shows strong oscillating behavior at low energy and reaches the same saturated values as in the case of a quantum well at sufficiently large energies. PMID:24759077

  18. Mass transport of deposited particles by surface-to-surface contact.

    PubMed

    McDonagh, A; Sextro, R G; Byrne, M A

    2012-08-15

    The spread of particle-borne contamination by surface-to-surface contact and its implications for exposures within the indoor environment have been observed - largely qualitatively. The present study was conducted with the aim of quantifying the mass transfer efficiency (TE) of deposited aerosol particles when selected soft and hard surfaces come in contact. The surfaces used were 100% cotton, synthetic fleece, plastic laminate and brass. Contact transfer efficiencies ranging from 2 to 45% were observed; these are very significant numbers in terms of hazardous aerosol transport in the environment. Other observations include an increase in the mass transferred with increased surface roughness. An increase in the applied pressure between the two surfaces in contact leads to a step change in transfer efficiency, so that two pressure regimes can be identified, with a transition pressure between them that depends on surface type. Time of contact appears to have little to no effect on the mass transfer efficiency for the surfaces studied, while contaminant loading has some effect that is not systematic. PMID:22683108

  19. SURFACE COMPLEXATION OF ACTINIDES WITH IRON OXIDES: IMPLICATIONS FOR RADIONUCLIDE TRANSPORT IN NEAR-SURFACE AQUIFERS

    SciTech Connect

    J.L. Jerden Jr.; A.J. Kropf; Y. Tsai

    2005-08-25

    The surface complexation of actinides with iron oxides plays a key role in actinide transport and retardation in geosphere-biosphere systems. The development of accurate actinide transport models therefore requires a mechanistic understanding of surface complexation reactions (i.e. knowledge of chemical speciation at mineral/fluid interfaces). Iron oxides are particularly important actinide sorbents due to their pH dependent surface charges, relatively high surface areas and ubiquity in oxic and suboxic near-surface systems. In this paper we present results from field and laboratory investigations that elucidate the mechanisms involved in binding uranium and neptunium to iron oxide mineral substrates in near neutral groundwaters. The field study involved sampling and characterizing uranium-bearing groundwaters and solids from a saprolite aquifer overlying an unmined uranium deposit in the Virginia Piedmont. The groundwaters were analyzed by inductively coupled mass spectrometry and ion chromatography and the aquifer solids were analyzed by electron microprobe. The laboratory study involved a series of batch sorption tests in which U(VI) and Np(V) were reacted with goethite, hematite and magnetite in simulated groundwaters. The pH, ionic strength, aging time, and sorbent/sorbate ratios were varied in these experiments. The oxidation state and coordination environment of neptunium in solutions and sorbents from the batch tests were characterized by X-ray absorption spectroscopy (XAS) at the Advanced Photon Source, Argonne National Laboratory. Results from this work indicate that, in oxidizing near-surface aquifers, the dissolved concentration of uranium may be limited to less than 30 parts per billion due to uptake by iron oxide mineral coatings and the precipitation of sparingly soluble U(VI) phosphate minerals. Results from the batch adsorption tests showed that, in near neutral groundwaters, a significant fraction of the uranium and neptunium adsorbed as strongly

  20. 78 FR 76187 - Transportation Infrastructure Financing and Innovation Act (TIFIA) Program; Agency Information...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-16

    ...-day Federal Register notice was published on September 27, 2013, 2013 (78 FR 59751). Since the... Office of the Secretary Transportation Infrastructure Financing and Innovation Act (TIFIA) Program... Transportation Infrastructure Financing and Innovation Act (TIFIA) program to pay the subsidy cost of...

  1. 75 FR 75532 - Surface Transportation Project Delivery Pilot Program; Caltrans Audit Report

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-03

    ... Federal Highway Administration Surface Transportation Project Delivery Pilot Program; Caltrans Audit... (SAFETEA-LU) established the Surface Transportation Project Delivery Pilot Program, codified at 23 U.S.C... Delivery Pilot Program Federal Highway Administration Audit of California Department of Transportation...

  2. Effects of Communication and Transportation on Utilization of Agency Services by Rural Poor People in South Carolina. South Carolina State College Research Bulletin No. 5, January 1976.

    ERIC Educational Resources Information Center

    Howie, Marguerite Rogers; Hanna, Kathleen

    Use of five agencies offering adult education, vocational rehabilitation, food stamps, employment, and health services in Orangeburg County by rural poor people in Bowman, Elloree, and North was studied over a two-year period. The study examined whether communication, transportation, or both increased agency use. In Bowman, information about the…

  3. RESEARCH ACTIVITIES AT U.S. GOVERNMENT AGENCIES IN SUBSURFACE REACTIVE TRANSPORT MODELING

    EPA Science Inventory

    The fate of contaminants in the environment is controlled by both chemical reactions and transport phenomena in the subsurface. Our ability to understand the significance of these processes over time requires an accurate conceptual model that incorporates the various mechanisms ...

  4. 78 FR 59751 - Transportation Infrastructure Financing and Innovation Act (TIFIA) Program; Agency Information...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-27

    ... Office of the Secretary Transportation Infrastructure Financing and Innovation Act (TIFIA) Program... Infrastructure Financing and Innovation Act (TIFIA) program to pay the subsidy cost of supporting Federal credit..., including the use of appropriate automated, electronic, mechanical, or other technological...

  5. Surface trap mediated electronic transport in biofunctionalized silicon nanowires

    NASA Astrophysics Data System (ADS)

    Puppo, F.; Traversa, F. L.; Di Ventra, M.; De Micheli, G.; Carrara, S.

    2016-08-01

    Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface electronic transport in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I–V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I–V characteristics in other nanostructured devices, for different than antibody-based sensing as well as electronic applications.

  6. Surface trap mediated electronic transport in biofunctionalized silicon nanowires.

    PubMed

    Puppo, F; Traversa, F L; Ventra, M Di; Micheli, G De; Carrara, S

    2016-08-26

    Silicon nanowires (SiNWs), fabricated via a top-down approach and then functionalized with biological probes, are used for electrically-based sensing of breast tumor markers. The SiNWs, featuring memristive-like behavior in bare conditions, show, in the presence of biomarkers, modified hysteresis and, more importantly, a voltage memory component, namely a voltage gap. The voltage gap is demonstrated to be a novel and powerful parameter of detection thanks to its high-resolution dependence on charges in proximity of the wire. This unique approach of sensing has never been studied and adopted before. Here, we propose a physical model of the surface electronic transport in Schottky barrier SiNW biosensors, aiming at reproducing and understanding the voltage gap based behavior. The implemented model describes well the experimental I-V characteristics of the device. It also links the modification of the voltage gap to the changing concentration of antigens by showing the decrease of this parameter in response to increasing concentrations of the molecules that are detected with femtomolar resolution in real human samples. Both experiments and simulations highlight the predominant role of the dynamic recombination of the nanowire surface states, with the incoming external charges from bio-species, in the appearance and modification of the voltage gap. Finally, thanks to its compactness, and strict correlation with the physics of the nanodevice, this model can be used to describe and predict the I-V characteristics in other nanostructured devices, for different than antibody-based sensing as well as electronic applications. PMID:27418560

  7. 41 CFR 302-9.101 - In what situations may my agency authorize transportation of a POV to my post of duty?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION AND... 41 Public Contracts and Property Management 4 2012-07-01 2012-07-01 false In what situations may... OWNED VEHICLE Transportation General § 302-9.101 In what situations may my agency...

  8. 41 CFR 102-118.210 - May my agency use bills of lading other than the GBL for a transportation shipment?

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false May my agency use bills of lading other than the GBL for a transportation shipment? 102-118.210 Section 102-118.210 Public... the GBL for a transportation shipment? Yes, as long as the mandatory terms and conditions contained...

  9. 77 FR 71430 - New Agency Information Collection Activity Under OMB Review: Public Transportation Baseline...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-30

    ...This notice announces that the Transportation Security Administration (TSA) has forwarded the new Information Collection Request (ICR) abstracted below to the Office of Management and Budget (OMB) for review and approval under the Paperwork Reduction Act (PRA). The ICR describes the nature of the information collection and its expected burden. TSA published a Federal Register notice, with a......

  10. 36 CFR 13.460 - Use of snowmobiles, motorboats, dog teams, and other means of surface transportation...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... transportation in accordance with 43 CFR 36.11(c), (d), (e), and (g). ..., motorboats, dog teams, and other means of surface transportation traditionally employed by local rural... of snowmobiles, motorboats, dog teams, and other means of surface transportation...

  11. 36 CFR 13.460 - Use of snowmobiles, motorboats, dog teams, and other means of surface transportation...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... transportation in accordance with 43 CFR 36.11(c), (d), (e), and (g). ..., motorboats, dog teams, and other means of surface transportation traditionally employed by local rural... of snowmobiles, motorboats, dog teams, and other means of surface transportation...

  12. 36 CFR 13.460 - Use of snowmobiles, motorboats, dog teams, and other means of surface transportation...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... transportation in accordance with 43 CFR 36.11(c), (d), (e), and (g). ..., motorboats, dog teams, and other means of surface transportation traditionally employed by local rural... of snowmobiles, motorboats, dog teams, and other means of surface transportation...

  13. 36 CFR 13.460 - Use of snowmobiles, motorboats, dog teams, and other means of surface transportation...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... transportation in accordance with 43 CFR 36.11(c), (d), (e), and (g). ..., motorboats, dog teams, and other means of surface transportation traditionally employed by local rural... of snowmobiles, motorboats, dog teams, and other means of surface transportation...

  14. 36 CFR 13.460 - Use of snowmobiles, motorboats, dog teams, and other means of surface transportation...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... transportation in accordance with 43 CFR 36.11(c), (d), (e), and (g). ..., motorboats, dog teams, and other means of surface transportation traditionally employed by local rural... of snowmobiles, motorboats, dog teams, and other means of surface transportation...

  15. Neoclassical transport coefficients for tokamaks with bean-shaped flux surfaces

    SciTech Connect

    Chang, C.S. . Courant Inst. of Mathematical Sciences Korea Advanced Inst. of Science and Technology, Seoul ); Kaye, S.M. . Plasma Physics Lab.)

    1990-11-01

    Simple analytic representations of the neoclassical transport coefficients for indented flux surfaces are presented. It is shown that a transport coefficient for an indented flux surface can be expressed in terms of a linear combination of the previously known transport coefficients for two nonindented flux surfaces. Numerical calculations based on actual equilibria from the PBX-M tokamak indicate that, even for modestly indented flux surfaces, the ion neoclassical thermal transport can be over a factor of two smaller than in a circular plasma with the same midplane radius or with the equivalent areas. 6 refs., 5 figs., 1 tab.

  16. Transport on the surface of a topological insulator

    SciTech Connect

    Vargiamidis, V.; Vasilopoulos, P.

    2014-08-14

    We study theoretically dc and ac transport on the surface of a three-dimensional topological insulator when its time-reversal symmetry is broken. Starting with a Kubo formula, we derive an explicit expression for the dc Hall conductivity, valid for finite temperatures. At zero temperature this expression gives the dc half-quantum Hall conductivity, provided the Fermi level lies in the gap. Corrections when the Fermi level is outside the gap and scattering by impurities are quantified. The longitudinal conductivity is also examined. At finite frequencies, we find a modified Drude term in σ{sub xx}(ω) and logarithmic, frequency-dependent corrections in σ{sub yx}(ω). The ac Hall conductivity exhibits a robust logarithmic singularity for excitation energies equal to the gapwidth. For these energies, we also find that the power spectrum, which is pertinent to optical experiments, exhibits drastic increase. The Hall conductivity remains almost unaffected for temperatures up to approximately 300 K.

  17. Parameterizing Ocean Eddy Transports From Surface to Bottom

    NASA Astrophysics Data System (ADS)

    Aiki, H.; Jacobson, T.; Yamagata, T.

    2004-12-01

    To improve subgrid-scale physics of climate ocean models, in particular near the top and bottom boundaries, we consider new parameterization schemes for the extra transport velocity by waves and eddies in baroclinic instability. These come in the form of elliptic equations, previously unmentioned, which we derive for the eddy-induced overturning stream function. They guarantee decrease of the mean field potential energy. Our principal example gives a relationship between the vertical shear of the overturning velocity and the buoyancy torque of the main geostrophic current. Interestingly the parameterized velocity is nonsingular at the bottom and the sea surface, contrasting with the constant-coefficient Gent and McWilliams (1990)scheme. Idealized two-dimensional numerical experiments uccessfully reproduce meridional overturning circulation even when the background density gradient is uniform everywhere (the Eady problem) or when the bottom is steeply sloped. We further demonstrate that adding an eddy form drag (wave tress) term in the TRM momentum equations yields overturning of the velocity field.

  18. 78 FR 43261 - Transportation Infrastructure Financing and Innovation Act (TIFIA) Program; Agency Information...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-19

    ...The Department of Transportation (DOT) invites public comments on a request to the Office of Management and Budget (OMB) to approve an Emergency Information Collection Request in accordance with the requirements of the Paperwork Reduction Act of 1995 (Pub. L. 104-13, 44 USC 3501 et seq). This request is being submitted to OMB via an Emergency Information Collection Request. On July 6, 2012,......

  19. 49 CFR 1016.109 - Awards against other agencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 8 2010-10-01 2010-10-01 false Awards against other agencies. 1016.109 Section 1016.109 Transportation Other Regulations Relating to Transportation (Continued) SURFACE TRANSPORTATION... RECOVERY OF EXPENSES BY PARTIES TO BOARD ADJUDICATORY PROCEEDINGS General Provisions § 1016.109...

  20. Laboratory studies of aeolian sediment transport processes on planetary surfaces

    NASA Astrophysics Data System (ADS)

    Rasmussen, Keld R.; Valance, Alexandre; Merrison, Jonathan

    2015-09-01

    , but not all, older or recent wind tunnel observations. Similarly some measurements performed with uniform sand samples having grain diameters of the order of 0.25-0.40 mm indicate that ripple spacing depends on friction velocity in a similar way as particle jump length. The observations are thus in agreement with a recent ripple model that link the typical jump length to ripple spacing. A possible explanation for contradictory observations in some experiments may be that long observation sequences are required in order to assure that equilibrium exists between ripple geometry and wind flow. Quantitative understanding of saltation characteristics on Mars still lacks important elements. Based upon image analysis and numerical predictions, aeolian ripples have been thought to consist of relatively large grains (diameter > 0.6 mm) and that saltation occurs at high wind speeds (> 26 m/s) involving trajectories that are significantly longer than those on Earth (by a factor of 10-100). However, this is not supported by recent observations from the surface of Mars, which shows that active ripples in their geometry and composition have characteristics compatible with those of terrestrial ripples (Sullivan et al., 2008). Also the highest average wind speeds on Mars have been measured to be < 20 m/s, with even turbulent gusts not exceeding 25 m/s. Electrification is seen as a dominant factor in the transport dynamics of dust on Mars, affecting the structure, adhesive properties and detachment/entrainment mechanisms specifically through the formation of aggregates (Merrison et al., 2012). Conversely for terrestrial conditions electric fields typically observed are not intense enough to significantly affect sand transport rates while little is known in the case of extra-terrestrial environments.

  1. Air support facilities. [interface between air and surface transportation systems

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Airports are discussed in terms of the interface between the ground and air for transportation systems. The classification systems, design, facilities, administration, and operations of airports are described.

  2. Organic nature of colloidal actinides transported in surface water environments.

    PubMed

    Santschi, Peter H; Roberts, Kimberly A; Guo, Laodong

    2002-09-01

    Elevated levels of (239,240)Pu and 241Am have been present in surficial soils of the Rocky Flats Environmental Technology Site (RFETS), CO, since the 1960s, when soils were locally contaminated in the 1960s by leaking drums stored on the 903 Pad. Further dispersion of contaminated soil particles was by wind and water. From 1998 until 2001, we examined actinide ((239,240)Pu and 241Am) concentrations and phase speciation in the surface environment at RFETS through field studies and laboratory experiments. Measurements of total (239,240)Pu and 241Am concentrations in storm runoff and pond discharge samples, collected during spring and summer times in 1998-2000, demonstrate that most of the (239,240)Pu and 241Am transported from contaminated soils to streams occurred in the particulate (> or = 0.45 microm; 40-90%) and colloidal (approximately 2 nm or 3 kDa to 0.45 microm; 10-60%) phases. Controlled laboratory investigations of soil resuspension, which simulated storm and erosion events, confirmed that most of the Pu in the 0.45 microm filter-passing phase was in the colloidal phase (> or = 80%) and that remobilization of colloid-bound Pu during soil erosion events can be greatly enhanced by humic and fulvic acids present in these soils. Most importantly, isoelectric focusing experiments of radiolabeled colloidal matter extracted from RFETS soils revealed that colloidal Pu is in the four-valent state and is mostly associated with a negatively charged organic macromolecule with a pH(IEP) of 3.1 and a molecular weight of 10-15 kDa, rather than with the more abundant inorganic (iron oxide and clay) colloids. This finding has important ramifications for possible remediation, erosion controls, and land-management strategies. PMID:12322742

  3. Lunar surface transportation systems conceptual design lunar base systems study Task 5.2

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Conceptual designs for three categories of lunar surface transportation were described. The level of understanding for the capabilities and design approach varies between the vehicles representing these categories. A summary of the vehicle categories and current state of conceptual design is provided. Finally, a brief evaluation and discussion is provided for a systematic comparison of transportation categories and effectiveness in supporting transportation objectives.

  4. 77 FR 27273 - Surface Transportation Project Delivery Pilot Program; Caltrans Audit Report

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-09

    ... 77 FR 10599. The FHWA received one comment from Caltrans. This notice provides the final draft of the... Federal Highway Administration Surface Transportation Project Delivery Pilot Program; Caltrans Audit...) established the Surface Transportation Project Delivery Pilot Program, codified at 23 U.S.C. 327. To...

  5. 76 FR 5237 - Surface Transportation Project Delivery Pilot Program; Caltrans Audit Report

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-28

    ... fifth audit report in a Federal Register Notice published on December 3, 2010, at 75 FR 75532. The FHWA... Federal Highway Administration Surface Transportation Project Delivery Pilot Program; Caltrans Audit...) established the Surface Transportation Project Delivery Pilot Program, codified at 23 U.S.C. 327. To...

  6. Spatial variations in nutrient and microbial transport from feedlot surfaces

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nutrient and microbial transport by runoff may vary at different locations within a beef cattle feedlot. If the areas making the greatest contributions to nutrient and microbial transport can be identified, it may be possible to institute precision management practices to reduce nutrient and microbi...

  7. Bioinspired Directional Surfaces for Adhesion, Wetting and Transport

    PubMed Central

    Hancock, Matthew J.; Sekeroglu, Koray

    2013-01-01

    In Nature, directional surfaces on insect cuticle, animal fur, bird feathers, and plant leaves are comprised of dual micro-nanoscale features that tune roughness and surface energy. This feature article summarizes experimental and theoretical approaches for the design, synthesis and characterization of new bioinspired surfaces demonstrating unidirectional surface properties. The experimental approaches focus on bottom-up and top-down synthesis methods of unidirectional micro- and nanoscale films to explore and characterize their anomalous features. The theoretical component of the review focuses on computational tools to predict the physicochemical properties of unidirectional surfaces. PMID:23526120

  8. 78 FR 58383 - Renewal of Rail Energy Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-23

    ... TRANSPORTATION Surface Transportation Board Renewal of Rail Energy Transportation Advisory Committee AGENCY... the Surface Transportation Board (Board) intends to renew the charter of the Rail Energy... transportation by rail of energy resources, including, but not necessarily limited to, coal and biofuels (such...

  9. Modeling of turbulent transport in the surface layer

    NASA Technical Reports Server (NTRS)

    Smith, G. L.

    1973-01-01

    The turbulence equations as written by Donaldson using the method of invariant modeling have been applied to the following limiting cases of the surface or constant flux layer of the planetary boundary layer: (1) Neutrally stable; (2) stable (above influence of surface roughness); (3) nearly neutrally stable; and (4) very unstable (free convection). For the neutrally stable case, the equations are shown to admit as a solution the familiar logarithmic profile. By use of this result, boundary conditions suitable for the surface layer are defined and are simple to apply to rough surfaces.

  10. 78 FR 9940 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Surface...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-12

    ...; Surface Coal Mine--Daily Inspection, Certified Person, Inspection Report ACTION: Notice. SUMMARY: The Department of Labor (DOL) is submitting the Mine Safety and Health Administration (MSHA) sponsored information collection request (ICR) titled, ``Surface Coal Mine--Daily Inspection, Certified...

  11. Pathogen transport in surface runoff from manured agricultural fields

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research objective: Manure application to cultivated land is a sustainable approach for enhancing soil fertility and tilth. However, enteric pathogens are often common in manure and can be transported from the application site via runoff and potentially transmitted to livestock and humans. Our objec...

  12. 41 CFR 102-117.40 - When is it advantageous for me to use another agency's contract or rate tender for transportation...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false When is it advantageous for me to use another agency's contract or rate tender for transportation services? 102-117.40 Section 102-117.40 Public Contracts and Property Management Federal Property Management Regulations...

  13. 41 CFR 102-117.40 - When is it advantageous for me to use another agency's contract or rate tender for transportation...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false When is it advantageous for me to use another agency's contract or rate tender for transportation services? 102-117.40 Section 102-117.40 Public Contracts and Property Management Federal Property Management Regulations...

  14. 41 CFR 102-117.40 - When is it advantageous for me to use another agency's contract or rate tender for transportation...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false When is it advantageous for me to use another agency's contract or rate tender for transportation services? 102-117.40 Section 102-117.40 Public Contracts and Property Management Federal Property Management Regulations...

  15. 41 CFR 102-117.40 - When is it advantageous for me to use another agency's contract or rate tender for transportation...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 41 Public Contracts and Property Management 3 2014-01-01 2014-01-01 false When is it advantageous for me to use another agency's contract or rate tender for transportation services? 102-117.40 Section 102-117.40 Public Contracts and Property Management Federal Property Management Regulations...

  16. 41 CFR 102-117.40 - When is it advantageous for me to use another agency's contract or rate tender for transportation...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 41 Public Contracts and Property Management 3 2013-07-01 2013-07-01 false When is it advantageous for me to use another agency's contract or rate tender for transportation services? 102-117.40 Section 102-117.40 Public Contracts and Property Management Federal Property Management Regulations...

  17. 41 CFR 302-9.201 - In what situations will my agency pay to transport a POV from my post of duty?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...: (a) You are transferred back to the official station (including post of duty) from which you transferred to your current post of duty; (b) You are transferred to a new official station within CONUS; (c... my agency pay to transport a POV from my post of duty? 302-9.201 Section 302-9.201 Public...

  18. Intrinsic momentum transport in tokamaks with tilted elliptical flux surfaces

    NASA Astrophysics Data System (ADS)

    Ball, Justin; Parra, Felix; Barnes, Michael; Dorland, William; Hammett, Gregory; Rodrigues, Paulo; Loureiro, Nuno

    2014-10-01

    Recent work demonstrated that breaking the up-down symmetry of tokamaks removes a constraint limiting intrinsic momentum transport, and hence toroidal rotation, to be small. We show, through MHD analysis, that ellipticity is most effective at introducing up-down asymmetry throughout the plasma. Using GS2, a local δf gyrokinetic code that self-consistently calculates momentum transport, we simulate tokamaks with tilted elliptical poloidal cross-sections and a Shafranov shift. These simulations show both the magnitude and poloidal dependence of nonlinear momentum transport. The results are consistent with TCV experimental measurements and suggest that this mechanism can generate rotation with an Alfven Mach number of several percent in a tilted elliptical ITER-like machine. It appears that rotation generated with up-down asymmetry may be sufficient to stabilize the resistive wall mode in reactor-sized devices. J.R.B. and F.I.P. were partially supported by the RCUK Energy Programme (grant number EP/I501045) and the European Unions Horizon 2020 research and innovation programme.

  19. SURFACE CHEMICAL EFFECTS ON COLLOID STABILITY AND TRANSPORT THROUGH NATURAL POROUS MEDIA

    EPA Science Inventory

    Surface chemical effects on colloidal stability and transport through porous media were investigated using laboratory column techniques. Approximately 100 nm diameter, spherical, iron oxide particles were synthesized as the mobile colloidal phase. The column packing material was ...

  20. Phosphorus transport by surface and subsurface flow pathways in an upland agricultural watershed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Improved understanding of phosphorus transport by surface and subsurface flow pathways is critical to protecting water quality in agricultural watersheds. While considerable attention has been devoted to understanding phosphorus losses in overland flow, comparatively limited research has examined ph...

  1. E. coli transport through surface-connected biopores identified from smoke injection tests

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Macropores are the primary mechanism by which fecal bacteria from surface-applied manure can be transported into subsurface drains or shallow groundwater bypassing the soil matrix. Limited research has been performed investigating fecal bacteria transport through specific macropores identified in th...

  2. Fate and transport of glyphosate and aminomethylphosphonic acid in surface waters of agricultural basins

    USGS Publications Warehouse

    Gregoire, Caroline; Capel, Paul D.; Coupe, Richard H.; Kalkhoff, Stephen J.

    2011-01-01

    CONCLUSIONS: Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil.

  3. An exploration of coupled surface-subsurface solute transport in a fully integrated catchment model

    NASA Astrophysics Data System (ADS)

    Liggett, Jessica E.; Partington, Daniel; Frei, Sven; Werner, Adrian D.; Simmons, Craig T.; Fleckenstein, Jan H.

    2015-10-01

    Coupling surface and subsurface water flow in fully integrated hydrological codes is becoming common in hydrological research; however, the coupling of surface-subsurface solute transport has received much less attention. Previous studies on fully integrated solute transport focus on small scales, simple geometric domains, and have not utilised many different field data sources. The objective of this study is to demonstrate the inclusion of both flow and solute transport in a 3D, fully integrated catchment model, utilising high resolution observations of dissolved organic carbon (DOC) export from a wetland complex during a rainfall event. A sensitivity analysis is performed to span a range of transport conditions for the surface-subsurface boundary (e.g. advective exchange only, advection plus diffusion, advection plus full mechanical dispersion) and subsurface dispersivities. The catchment model captures some aspects of observed catchment behaviour (e.g. solute discharge at the catchment outlet, increasing discharge from wetlands with increased stream discharge, and counter-clockwise concentration-discharge relationships), although other known behaviours are not well represented in the model (e.g. slope of concentration-discharge plots). Including surface-subsurface solute transport aids in evaluating internal model processes, however there are challenges related to the influence of dispersion across the surface-subsurface interface, and non-uniqueness of the solute transport solution. This highlights that obtaining solute field data is especially important for constraining integrated models of solute transport.

  4. 19 CFR 18.9 - Examination by inspectors of trunk line associations or agents of the Surface Transportation Board.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... associations or agents of the Surface Transportation Board. 18.9 Section 18.9 Customs Duties U.S. CUSTOMS AND... agents of the Surface Transportation Board. (a) Upon presentation of proper credentials showing the applicant to be a representative of the Trunk Line Association, the Surface Transportation Board, the...

  5. Surface transport in the Ria de Vigo - Transport barriers in a tidal estuary with a complex geometry

    NASA Astrophysics Data System (ADS)

    Huhn, F.; von Kameke, A.; Montero, P.; Allen-Perkins, S.; Venancio, A.; Pérez-Muñuzuri, V.

    2012-04-01

    We study the submesoscale surface transport in the Ria de Vigo, NW Spain, an estuary with tidal and wind-driven circulation, analyzing the output of the coastal model MOHID with state-of-the-art Lagrangian methods, and comparing the results to drifter experiments. We extract Lagrangian Coherent Structures (LCS) as ridges in fields of the Finite-Time Lyapunov Exponent (FTLE) that can be identified with transport barriers. The LCS reveal the fundamental structure of the modelled circulation in the estaury that is a superposition of the tidal inflow and outflow, the wind-driven currents and the long-term drift on the shelf. In the Ria de Vigo, LCS are attached to prominent coastal boundaries, as islands or capes, indicating that the geometry of the flow patterns is dominated by bathymetry. Although the vertical flow which is not represented in the horizontal surface flow can be important at the coast, the found transport patterns can be seen as the surface footprint of the 3D circulation in the estaury. Comparing the trajectories of real surface drifters from four deployments to the computed transport barriers in different typical meteorological sitiations, we find that the drifter trajectories are in agreement with the different coherent water masses predicted by the model. The knowledge of the global transport patterns of water masses in this highly populated coastal region is indispensable for the assessment of the fate of contaminations, like possible oil spills or released waste water, but also for biological studies that deal with the drift of eggs and larvae of fish and other marine species, or investigate plankton blooms.

  6. Simulating the fate and transport of nanomaterials in surface waters

    EPA Science Inventory

    The unique properties of nanomaterials have resulted in their increased production. However, it is unclear how nanomaterials will move and react once released to the environment One approach for addressing possible exposure of nanomaterials in surface waters is by using numerical...

  7. Spatial Transport of Magnetic Flux Surfaces in Strongly Anisotropic Turbulence

    NASA Astrophysics Data System (ADS)

    Matthaeus, W. H.; Servidio, S.; Wan, M.; Ruffolo, D. J.; Rappazzo, A. F.; Oughton, S.

    2013-12-01

    Magnetic flux surfaces afford familiar descriptions of spatial structure, dynamics, and connectivity of magnetic fields, with particular relevance in contexts such as solar coronal flux tubes, magnetic field connectivity in the interplanetary and interstellar medium, as well as in laboratory plasmas and dynamo problems [1-4]. Typical models assume that field-lines are orderly, and flux tubes remain identifiable over macroscopic distances; however, a previous study has shown that flux tubes shred in the presence of fluctuations, typically losing identity after several correlation scales [5]. Here, the structure of magnetic flux surfaces is numerically investigated in a reduced magnetohydrodynamic (RMHD) model of homogeneous turbulence. Short and long-wavelength behavior is studied statistically by propagating magnetic surfaces along the mean field. At small scales magnetic surfaces become complex, experiencing an exponential thinning. At large scales, instead, the magnetic flux undergoes a diffusive behavior. The link between the diffusion of the coarse-grained flux and field-line random walk is established by means of a multiple scale analysis. Both large and small scales limits are controlled by the Kubo number. These results have consequences for understanding and interpreting processes such as magnetic reconnection and field-line diffusion in plasmas [6]. [1] E. N. Parker, Cosmical Magnetic Fields (Oxford Univ. Press, New York, 1979). [2] J. R. Jokipii and E. N. Parker, Phys. Rev. Lett. 21, 44 (1968). [3] R. Bruno et al., Planet. Space Sci. 49, 1201 (2001). [4] M. N. Rosenbluth et al., Nuclear Fusion 6, 297 (1966). [5] W. H. Matthaeus et al., Phys. Rev. Lett. 75, 2136 (1995). [6] S. Servidio et al., submitted (2013).

  8. Comparison of subsurface and surface runoff phosphorus transport rates in alluvial floodplains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phosphorus (P) loading to streams can occur by both surface runoff and subsurface transport. Although surface runoff is often considered the dominant pathway, groundwater P concentrations in alluvial aquifers can be significant, especially in preferential flow paths (PFPs). The objectives of this re...

  9. Transport of Ice on the Surface of Iapetus

    NASA Astrophysics Data System (ADS)

    Galuba, Götz G.

    2014-11-01

    The global black-and-white dichotomy as well as the dark floors and rims of equatorial craters on the Saturnian moon Iapetus can be explained by ice migration driven by a thermal feedback [1]. All icy moons in the Jovian and Saturnian systems are - with the exception of Titan - airless bodies. Yet it is unique, how these two types of surface features on Iapetus look. A physical model of the processes of absorption, sublimation and deposition was developed and a computational model that simulates ice migration of volatiles under these circumstances derived. The model tessellates the surfaces of an airless body into triangles of equal size that can each have different surface properties. These properties evolve while the model simulates a long-term development. A rate network of net migration is calculated from sublimation and redeposition under the assumptions ofa. a slowly rotating bodyb. undisturbed ballistic molecular trajectoriesc. isotropic emissiond. Maxwellian speed distributione. high sticking coefficients of the surfaces.The assumptions (b.) to (e.) are equally valid for all bigger outer solar system icy moons (except Titan). The very first assumption however is not equally valid throughout the moons of the outer solar system. Callisto being in many regards similar to Iapetus still has a five times higher rotation rate. So global effects depending on slow rotation are more profound on Iapetus. The computer model is complemented by a model for local ice migration from craters.First results show, that the global timescale of albedo change in our model is of the same order of magnitude as in the supporting material to [1] with a tendency towards slightly faster 2 Gyr instead of ~2.4 Gyr) darkening compared to the "Model B". The time rate of local crater darkening rates lies between the global darkening rate and rate of the opposing brightening effect as estimated in [2] to (τ between 10 and 100 MYr).[1] Formation of Iapetus’ Extreme Albedo Dichotomy by

  10. Influence of surface potential on aggregation and transport of titania nanoparticles.

    PubMed

    Guzman, Katherine A Dunphy; Finnegan, Michael P; Banfield, Jillian F

    2006-12-15

    To investigate the effect of pH on nanoparticle aggregation and transport in porous media, we quantified nanoparticle transport in two-dimensional structures. Titania was used as a model compound to explore the effects of surface potential on particle mobility in the subsurface. Results show that pH, and therefore, surface potential and aggregate size, dominate nanoparticle interactions with each other and surfaces. In each solution, nanoparticle aggregate size distributions were bimodal or trimodal, and aggregate sizes increased as the pH approached the pH of the point of zero charge (pHzpc). Over 80% of suspended particles and aggregates were mobile over the pH range of 1-12, except close to the pHzpc of the surfaces, where the particles are highly aggregated. The effect of pH on transport is not symmetric around the pHzpc of the particles due to charging of the channel surfaces. However, transport speed of nanoparticle aggregates did not vary with pH. The surface element integration technique, which takes into account the effect of curvature of particles on interaction energy, was used to evaluate the ability of theory to predict nanoparticle transport. PMID:17256514

  11. Modeling Fate and Transport of Rotavirus in Surface Flow by Integrating WEPP and a Pathogen Transport Model

    NASA Astrophysics Data System (ADS)

    Bhattarai, R.; Kalita, P. K.; Davidson, P. C.; Kuhlenschmidt, M. S.

    2012-12-01

    More than 3.5 million people die each year from a water related diseases in this world. Every 20 seconds, a child dies from a water-related illness. Even in a developed country like the United States, there have been at least 1870 outbreaks associated with drinking water during the period of 1920 to 2002, causing 883,806 illnesses. Most of these outbreaks are resulted due to the presence of microbial pathogens in drinking water. Rotavirus infection has been recognized as the most common cause of diarrhea in young children throughout the world. Laboratory experiments conducted at the University of Illinois have demonstrated that recovery of rotavirus has been significantly affected by climatic and soil-surface conditions like slope, soil types, and ground cover. The objective of this study is to simulate the fate and transport of Rotavirus in overland and near-surface flow using a process-based model. In order to capture the dynamics of sediment-bound pathogens, the Water Erosion Prediction Project (WEPP) is coupled with the pathogen transport model. Transport of pathogens in overland flow can be simulated mathematically by including terms for the concentration of the pathogens in the liquid phase (in suspension or free-floating) and the solid phase (adsorbed to the fine solid particles like clay and silt). Advection, adsorption, and decay processes are considered. The mass balance equations are solved using numerical technique to predict spatial and temporal changes in pathogen concentrations in two phases. Outputs from WEPP simulations (flow velocity, depth, saturated conductivity and the soil particle fraction exiting in flow) are transferred as input for the pathogen transport model. Three soil types and three different surface cover conditions have been used in the experimental investigations. Results from these conditions have been used in calibrating and validating the simulation results. Bare surface conditions have produced very good agreement between

  12. Surface harmonics method equations for solving the time-dependent neutron transport problems and their verification

    SciTech Connect

    Boyarinov, V. F.; Kondrushin, A. E.; Fomichenko, P. A.

    2012-07-01

    Finite-difference time-dependent equations of Surface Harmonics method have been obtained for plane geometry. Verification of these equations has been carried out by calculations of tasks from 'Benchmark Problem Book ANL-7416'. The capacity and efficiency of the Surface Harmonics method have been demonstrated by solution of the time-dependent neutron transport equation in diffusion approximation. The results of studies showed that implementation of Surface Harmonics method for full-scale calculations will lead to a significant progress in the efficient solution of the time-dependent neutron transport problems in nuclear reactors. (authors)

  13. Transport of radon and thoron at the earth's surface

    SciTech Connect

    Schery, S.D.

    1991-06-15

    This report covers progress under the current funding period Jan. 1, 1991 to Jan. 1, 1992 and presents the continuation proposal for Jan. 1, 1992 to Jan. 1, 1993. The previous progress report was submitted in May 1990, so activities during the last half of 1990 will also be included. Major activities over the last year have centered on the study of disequilibrium of radon progeny near the earth's surface and the sources of thoron in indoor air. In addition, we have carried out supplemental measurements of radon sorption coefficients in porous materials focusing on the physical mechanism of sorption.

  14. Effect of surface functionalization on the electronic transport properties of Ti3C2 MXene

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.

    2015-09-01

    The effects of surface functionalization on the electronic transport properties of the MXene compound Ti3C2 are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Fluorinated, oxidized and hydroxylated surfaces are considered and the obtained results are compared with the ones for the pristine MXene. It is found that the surface termination has a considerable impact on the electronic transport in MXene. For example, the fluorinated sample shows the largest transmission, whereas surface oxidation results in a considerable reduction of the electronic transmission. The current in the former sample can be up to 4 times larger for a given bias voltage as compared to the case of bare MXene. The increased transmission originates from the extended electronic states and smaller variations of the electrostatic potential profile. Our findings can be useful in designing MXene-based anode materials for energy storage applications, where enhanced electronic transport will be an asset.

  15. A laboratory study of colloid and solute transport in surface runoff on saturated soil

    NASA Astrophysics Data System (ADS)

    Yu, Congrong; Gao, Bin; Muñoz-Carpena, Rafael; Tian, Yuan; Wu, Lei; Perez-Ovilla, Oscar

    2011-05-01

    SummaryColloids in surface runoff may pose risks to the ecosystems not only because some of them (e.g., pathogens) are toxic, but also because they may facilitate the transport of other contaminants. Although many studies have been conducted to explore colloid fate and transport in the environment, current understanding of colloids in surface runoff is still limited. In this study, we conducted a range of laboratory experiments to examine the transport behavior of colloids in a surface runoff system, made of a soil box packed with quartz sand with four soil drainage outlets and one surface flow outlet. A natural clay colloid (kaolinite) and a conservative chemical tracer (bromide) were applied to the system under a simulated rainfall event (64 mm/h). Effluent soil drainage and surface flow samples were collected to determine the breakthrough concentrations of bromide and kaolinite. Under the experimental conditions tested, our results showed that surface runoff dominated the transport processes. As a result, kaolinite and bromide were found more in surface flow than in soil drainage. Comparisons between the breakthrough concentrations of bromide and kaolinite showed that kaolinite had lower mobility than bromide in the subsurface flow (i.e., soil drainage), but behaved almost identical to bromide in the surface runoff. Student's t-test confirmed the difference between kaolinite and bromide in subsurface flow ( p = 0.02). Spearman's test and linear regression analysis, however, showed a strong 1:1 correlation between kaolinite and bromide in surface runoff ( p < 0.0001). Our result indicate that colloids and chemical solutes may behave similarly in overland flow on bare soils with limited drainage when surface runoff dominates the transport processes.

  16. Is Agency Skin Deep? Surface Attributes Influence Infants' Sensitivity to Goal-Directed Action

    ERIC Educational Resources Information Center

    Guajardo, Jose J.; Woodward, Amanda L.

    2004-01-01

    Three studies investigated the role of surface attributes in infants' identification of agents, using a habituation paradigm designed to tap infants' interpretation of grasping as goal directed (Woodward, 1998). When they viewed a bare human hand grasping objects, 7- and 12-month-old infants focused on the relation between the hand and its goal.…

  17. The transport characteristics of passing fast ions produced by nonlocal overlapping of drift island surfaces and magnetic island surfaces

    NASA Astrophysics Data System (ADS)

    Cao, Jinjia; Gong, Xueyu; Xiang, Dong; Huang, Qianhong; Yu, Jun

    2016-08-01

    The structure of the drift-island surface of passing fast ions (PFIs) is investigated in the presence of the resonant interaction with a magnetic island. Two overlapping regions of the drift-island surface and the magnetic island surface are found, one corresponding to local overlapping region and the other to non-local one. Here, the word "nonlocal" denotes that the resonances in the core plasma can have effects on the PFIs near the plasma boundary, while the "local" represents that the PFIs just near the resonant location are influenced. The nonlocal overlapping constructs a transport path along which the PFIs can become losses. There are three kinds of drift-island surfaces to join in forming the transport paths. A pitch angle region, which is called pitch angle gap, is found near the plasma boundary, where the drift-island surface cannot be formed and few PFIs are lost. The pitch-angle selective features of PFI losses are obtained by analyzing the three kinds of drift-island surfaces. The coupling between the crowd drift island surfaces and the collision can induce the prompt losses of PFIs and rapidly slowing down of PFI energy. The time of the prompt losses and the slowing down rate are calculated. Qualitatively, the theoretical results are in well agreement with the experimental observations in ASDEX Upgrade [M. García-Muñoz et al., Nucl. Fusion 47, L10 (2007)].

  18. Pool boiling thermal transport through micro-patterned metal superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Searle, Matthew; Maynes, Daniel; Crockett, Julie

    2015-11-01

    Pool boiling thermal transport through horizontal superhydrophobic surfaces decorated with rib and post micro-patterns was explored experimentally. The pool consisted of a water reservoir heated from below by electric heaters embedded in an aluminum block. A test surface was located at the bottom of the pool and fixed to the block. Instrumentation allowed simultaneous measurement of heat flux through the test surface, test surface temperature, and pool water temperature. From these measurements, heat flux as a function of excess temperature (the difference between the test surface temperature and the water saturation temperature) was determined for each surface. Surface geometry was characterized by the cavity fraction (the ratio of projected cavity area to surface area on the test surface), distance between features, and microscale pattern geometry. The transition from nucleate to pool boiling was observed to occur at much lower excess temperatures for superhydrophobic surfaces than for hydrophobic surfaces, with greater deviation for larger cavity fraction. Heat flux versus excess temperature relationships are presented while exploring the influence of superhydrophobic surface microstructure on the thermal transport. NSF CBET-1235881.

  19. Stability and Transport of Graphene Oxide Nanoparticles in Groundwater and Surface Water

    PubMed Central

    Lanphere, Jacob D.; Rogers, Brandon; Luth, Corey; Bolster, Carl H.; Walker, Sharon L.

    2014-01-01

    Abstract The effects of groundwater and surface water constituents (i.e., natural organic matter [NOM] and the presence of a complex assortment of ions) on graphene oxide nanoparticles (GONPs) were investigated to provide additional insight into the factors contributing to fate and the mechanisms involved in their transport in soil, groundwater, and surface water environments. The stability and transport of GONPs was investigated using dynamic light scattering, electrokinetic characterization, and packed bed column experiments. Stability results showed that the hydrodynamic diameter of the GONPs at a similar ionic strength (2.1±1.1 mM) was 10 times greater in groundwater environments compared with surface water and NaCl and MgCl2 suspensions. Transport results confirmed that in groundwater, GONPs are less stable and are more likely to be removed during transport in porous media. In surface water and MgCl2 and NaCl suspensions, the relative recovery was 94%±3% indicating that GONPs will be very mobile in surface waters. Additional experiments were carried out in monovalent (KCl) and divalent (CaCl2) salts across an environmentally relevant concentration range (0.1–10 mg/L) of NOM using Suwannee River humic acid. Overall, the transport and stability of GONPs was increased in the presence of NOM. This study confirms that planar “carbonaceous-oxide” materials follow traditional theory for stability and transport, both due to their response to ionic strength, valence, and NOM presence and is the first to look at GONP transport across a wide range of representative conditions found in surface and groundwater environments. PMID:25053876

  20. Applications of asymmetric nanotextured parylene surface using its wetting and transport properties

    NASA Astrophysics Data System (ADS)

    Sekeroglu, Koray

    In this thesis, basic digital fluidics devices were introduced using polymeric nanorods (nano-PPX) inspired from nature. Natural inspiration ignited this research by observing butterfly wings, water strider legs, rye grass leaves, and their asymmetric functions. Nano-PPX rods, manufactured by an oblique angle polymerization (OAP) method, are asymmetrically aligned structures that have unidirectional wetting properties. Nano-PPX demonstrates similar functions to the directional textured surfaces of animals and plants in terms of wetting, adhesion, and transport. The water pin-release mechanism on the asymmetric nano-PPX surface with adhesion function provides a great transport property. How the asymmetry causes transport is discussed in terms of hysteresis and interface contact of water droplets. In this study, the transport property of nano-PPX rods is used to guide droplets as well as transporting cargo such as microgels. With the addition of tracks on the nano-PPX rods, the surfaces were transformed into basic digital fluidics devices. The track-assisted nano-PPX has been employed to applications (i.e. sorting, mixing, and carrying cargo particles). Thus, digital fluidics devices fabricated on nano-PPX surface is a promising pathway to assemble microgels in the field of bioengineering. The characterization of the nano textured surface was completed using methods such as Scanning Electron Microscopy, Atomic Force Microscopy, Contact Angle Goniometry, and Fourier Transform Infra-Red Spectroscopy. These methods helped to understand the physical and chemical properties of nano-PPX. Parameters such as advancing and receding contact angles, nanorod tilt angle, and critical drop volumes were utilized to investigate the anisotropic wetting properties of nano-PPX surface. This investigation explained the directional wetting behavior of the surface as well as approaching new design parameters for adjusting surface properties. The nanorod tilt angle was a key parameter

  1. DIRECT COMPARISON OF KINETIC AND LOCAL EQUILIBRIUM FORMULATIONS FOR SOLUTE TRANSPORT AFFECTED BY SURFACE REACTIONS.

    USGS Publications Warehouse

    Bahr, Jean M.; Rubin, Jacob

    1987-01-01

    Modeling transport of reacting solutes in porous media often requires a choice between models based on the local equilibrium assumption (LEA) and models involving reaction kinetics. Direct comparison of the mathematical formulations for these two types of transport models can aid in this choice. For cases of transport affected by surface reaction, such a comparison is made possible by a new derivation procedure. This procedure yields a kinetics-based formulation that is the sum of the LEA formulation and one or more kinetically influenced terms. The dimensionless form of the new kinetics-based formulation facilitates identification of critical parameter groupings which control the approach to transport behavior consistent with LEA model predictions. Results of numerical experiments demonstrate that criteria for LEA applicability can be expressed conveniently in terms of these parameter groupings. The derivation procedure is demonstrated for examples of surface reactions including first-order reversible sorption, Langmuir-type kinetics and binary, homovalent ion exchange.

  2. Identifying key surface parameters for optical photon transport in GEANT4/GATE simulations.

    PubMed

    Nilsson, Jenny; Cuplov, Vesna; Isaksson, Mats

    2015-09-01

    For a scintillator used for spectrometry, the generation, transport and detection of optical photons have a great impact on the energy spectrum resolution. A complete Monte Carlo model of a scintillator includes a coupled ionizing particle and optical photon transport, which can be simulated with the GEANT4 code. The GEANT4 surface parameters control the physics processes an optical photon undergoes when reaching the surface of a volume. In this work the impact of each surface parameter on the optical transport was studied by looking at the optical spectrum: the number of detected optical photons per ionizing source particle from a large plastic scintillator, i.e. the output signal. All simulations were performed using GATE v6.2 (GEANT4 Application for Tomographic Emission). The surface parameter finish (polished, ground, front-painted or back-painted) showed the greatest impact on the optical spectrum whereas the surface parameter σ(α), which controls the surface roughness, had a relatively small impact. It was also shown how the surface parameters reflectivity and reflectivity types (specular spike, specular lobe, Lambertian and backscatter) changed the optical spectrum depending on the probability for reflection and the combination of reflectivity types. A change in the optical spectrum will ultimately have an impact on a simulated energy spectrum. By studying the optical spectra presented in this work, a GEANT4 user can predict the shift in an optical spectrum caused be the alteration of a specific surface parameter. PMID:26046519

  3. Transport Barrier inside the Reversal Surface in the Chaotic Regime of the Reversed-Field Pinch

    SciTech Connect

    Spizzo, G.; Cappello, S.; Cravotta, A.; Predebon, I.; Marrelli, L.; Martin, P.; Escande, D.F.; White, R.B.

    2006-01-20

    Magnetic field lines and the corresponding particle orbits are computed for a typical chaotic magnetic field provided by a magnetohydrodynamics numerical simulation of the reversed-field pinch. The m=1 modes are phase locked and produce a toroidally localized bulging of the plasma which increases particle transport. The m=0 and m=1 modes produce magnetic chaos implying poor confinement. However, they also allow for the formation of magnetic islands which induce transport barriers inside the reversal surface.

  4. Effects of trans-Eurasian transport of air pollutants on surface ozone concentrations over Western China

    NASA Astrophysics Data System (ADS)

    Li, Xiaoyuan; Liu, Junfeng; Mauzerall, Denise L.; Emmons, Louisa K.; Walters, Stacy; Horowitz, Larry W.; Tao, Shu

    2014-11-01

    Due to a lack of industrialization in Western China, surface air there was, until recently, believed to be relatively unpolluted. However, recent measurements and modeling studies have found high levels of ozone (O3) there. Based on the state-of-the-science global chemical transport model MOZART-4, we identify the origin, pathway, and mechanism of trans-Eurasian transport of air pollutants to Western China in 2000. MOZART-4 generally simulates well the observed surface O3 over inland areas of China. Simulations find surface ozone concentrations over Western China on average to be about 10 ppbv higher than Eastern China. Using sensitivity studies, we find that anthropogenic emissions from all Eurasian regions except China contribute 10-15 ppbv surface O3 over Western China, superimposed upon a 35-40 ppbv natural background. Transport from European anthropogenic sources to Northwestern China results in 2-6 ppbv O3 enhancements in spring and summer. Indian anthropogenic sources strongly influence O3 over the Tibetan Plateau during the summer monsoon. Transport of O3 originating from emissions in the Middle East occasionally reach Western China and increase surface ozone there by about 1-4 ppbv. These influences are of similar magnitude as trans-Pacific and transatlantic transport of O3 and its precursors, indicating the significance of trans-Eurasian ozone transport in hemispheric transport of air pollution. Our study further indicates that mitigation of anthropogenic emissions from Europe, the Indian subcontinent, and the Middle East could benefit public health and agricultural productivity in Western China.

  5. Effects of trans-Eurasian transport of anthropogenic pollutants on surface ozone concentrations over China

    NASA Astrophysics Data System (ADS)

    Liu, J.; Li, X.; Mauzerall, D. L.; Emmons, L. K.; Horowitz, L. W.; Guo, Y.; Tao, S.

    2015-12-01

    Due to a lack of industrialization in Western China, surface air there was, until recently, believed to be relatively unpolluted. However, recent measurements and modeling studies have found high levels of ozone (O3) there. Based on the state-of-the-science global chemical transport model MOZART-4, we identify the origin, pathway, and mechanism of trans-Eurasian transport of air pollutants to Western China in 2000. MOZART-4 generally simulates well the observed surface O3 over inland areas of China. Simulations find surface ozone concentrations over Western China on average to be about 10 ppbv higher than Eastern China. Using sensitivity studies as well as a fully-tagged approach, we find that anthropogenic emissions from all Eurasian regions except China contribute 10-15 ppbv surface O3 over Western China, superimposed upon a 35-40 ppbv natural background. Transport from European anthropogenic sources to Northwestern China results in 2-6 ppbv O3 enhancements in spring and summer. Indian anthropogenic sources strongly influence O3 over the Tibetan Plateau during the summer monsoon. Transport of O3 originating from emissions in the Middle East occasionally reach Western China and increase surface ozone there by about 1-4 ppbv. These influences are of similar magnitude as trans-Pacific and transatlantic transport of O3 and its precursors, indicating the significance of trans-Eurasian ozone transport in hemispheric transport of air pollution. Our study further indicates that mitigation of anthropogenic emissions from Europe, the Indian subcontinent, and the Middle East could benefit public health and agricultural productivity in Western China.

  6. Measurements of mean flow and eddy transport over a film cooling surface

    SciTech Connect

    Wang, L.; Tsang, H.; Simon, T.; Eckert, E.

    1996-05-01

    Results of an experimental study of the effects of blowing Velocity Ratio (VR = 0.5 and 1.0) and Free-Stream Turbulence Intensity (FSTI = 0.5% and 12%) on turbulent transport over a film-cooling test surface are presented. The surface has a single lateral row of streamwise-oriented holes angled 35{degree} from the surface and separated from one another by three hole diameters. The film cooling flow and mainstream flow are at the same temperature and the film cooling is supplied through long delivery tubes. Velocity, turbulence intensity and eddy transport profiles are presented. The ratios of lateral eddy diffusivity to wall-normal eddy diffusivity values measured in this program (4-15) provide documentation of strong anisotropy of eddy transport in the flow.

  7. Light-Driven Transport of a Liquid Marble with and against Surface Flows.

    PubMed

    Kavokine, Nikita; Anyfantakis, Manos; Morel, Mathieu; Rudiuk, Sergii; Bickel, Thomas; Baigl, Damien

    2016-09-01

    Liquid marbles, that is, liquid drops coated by a hydrophobic powder, do not wet any solid or liquid substrate, making their transport and manipulation both highly desirable and challenging. Herein, we describe the light-driven transport of floating liquid marbles and emphasize a surprising motion behavior. Liquid marbles are deposited on a water solution containing photosensitive surfactants. Irradiation of the solution generates photoreversible Marangoni flows that transport the liquid marbles toward UV light and away from blue light when the thickness of the liquid substrate is large enough (Marangoni regime). Below a critical thickness, the liquid marbles move in the opposite direction to that of the surface flow at a speed increasing with decreasing liquid thickness (anti-Marangoni). We demonstrate that the anti-Marangoni motion is driven by the free surface deformation, which propels the non-wetting marble against the surface flow. We call this behavior "slide effect". PMID:27381297

  8. Tunable Surface Hydrophobicity and Fluid Transport through Nanoporous Membranes

    NASA Astrophysics Data System (ADS)

    Ostrowski, Joseph H. J.

    There are more than three billion people across the globe that struggle to obtain clean drinkable water. One of the most promising avenues for generating potable water is through reverse osmosis and nanofiltration. Both solutions require a semipermeable membrane that prohibits passage of unwanted solute particles but allows passage of the solvent. Atomically thin two-dimensional membranes based on porous graphene show great promise as semipermeable materials, but modeling fluid flow on length scales between the microscopic (nanometer and smaller) and macroscopic (micron and larger) regimes presents formidable challenges. This thesis explores both equilibrium and nonequilibrium aspects of this problem and develops new methodology for simulating systems away from thermal equilibrium. First, we hypothesize that there is a wetting penalty for water as it tries to breach a sheet of graphene that should be naturally hydrophobic. By using equilibrium molecular dynamics simulations, we show that the hydrophobicity depends sensitively on the degree of electrical doping, offering an opportunity to tune the hydrophobic effect of graphene using small amounts of doping. The wetting contact angle, a measure of hydrophobicity, changes dramatically with the voltage applied to single layer graphene. We find that the sensitivity of the hydrophobic effect to voltage depends not on hydrogen bonding motifs at the interface between graphene and water, but instead on a phenomenon known as electrowetting. The theory of electrowetting predicts that the difference in surface tensions that defines the contact angle is quartic in the voltage, rather than quadratic, as it would be in bilayer graphene or in a two-dimensional metal. To explore the nonequilibrium aspects of fluid passage through atomically thin membranes, we developed a molecular dynamics methodology for simulating fluid flow at constant flux based on Gauss's principle of least constraint. This method develops microscopic

  9. Continuous directional water transport on the peristome surface of Nepenthes alata.

    PubMed

    Chen, Huawei; Zhang, Pengfei; Zhang, Liwen; Liu, Hongliang; Jiang, Ying; Zhang, Deyuan; Han, Zhiwu; Jiang, Lei

    2016-04-01

    Numerous natural systems contain surfaces or threads that enable directional water transport. This behaviour is usually ascribed to hierarchical structural features at the microscale and nanoscale, with gradients in surface energy and gradients in Laplace pressure thought to be the main driving forces. Here we study the prey-trapping pitcher organs of the carnivorous plant Nepenthes alata. We find that continuous, directional water transport occurs on the surface of the 'peristome'--the rim of the pitcher--because of its multiscale structure, which optimizes and enhances capillary rise in the transport direction, and prevents backflow by pinning in place any water front that is moving in the reverse direction. This results not only in unidirectional flow despite the absence of any surface-energy gradient, but also in a transport speed that is much higher than previously thought. We anticipate that the basic 'design' principles underlying this behaviour could be used to develop artificial fluid-transport systems with practical applications. PMID:27078568

  10. Continuous directional water transport on the peristome surface of Nepenthes alata

    NASA Astrophysics Data System (ADS)

    Chen, Huawei; Zhang, Pengfei; Zhang, Liwen; Liu, Hongliang; Jiang, Ying; Zhang, Deyuan; Han, Zhiwu; Jiang, Lei

    2016-04-01

    Numerous natural systems contain surfaces or threads that enable directional water transport. This behaviour is usually ascribed to hierarchical structural features at the microscale and nanoscale, with gradients in surface energy and gradients in Laplace pressure thought to be the main driving forces. Here we study the prey-trapping pitcher organs of the carnivorous plant Nepenthes alata. We find that continuous, directional water transport occurs on the surface of the ‘peristome’—the rim of the pitcher—because of its multiscale structure, which optimizes and enhances capillary rise in the transport direction, and prevents backflow by pinning in place any water front that is moving in the reverse direction. This results not only in unidirectional flow despite the absence of any surface-energy gradient, but also in a transport speed that is much higher than previously thought. We anticipate that the basic ‘design’ principles underlying this behaviour could be used to develop artificial fluid-transport systems with practical applications.

  11. Automatic droplet transportation on a plastic microfluidic device having wettability gradient surface

    NASA Astrophysics Data System (ADS)

    Nakashima, Y.; Nakanishi, Y.; Yasuda, T.

    2015-01-01

    This paper presents a microfluidic device that can automatically transport a droplet on a plastic plate. This device consists of a Cyclo Olefin Polymer (COP) plate and a SiO2 membrane and has wettability gradient surface. Lithographic patterns of hydrophilic SiO2 permitted wettability modification of a hydrophobic COP surface. A series of alternate hydrophobic and hydrophilic wedge-shaped patterns generated a required gradient in wettability. When we dropped a droplet on the wettability gradient surface, it moved along the wettability gradient due to an imbalance between surface tension forces acting on the opposite sides of the droplet edge. The droplet transportation test was carried out using water of 5 μl. As a result, we succeeded in automatically transporting the droplet on the SiO2/COP wettability gradient pattern. We also carried out droplet transportation in an enclosed microchannel for preventing droplet evaporation using DI (Deionized) water of 5 μl. In this case, the droplet was automatically transported by forming the wettability gradient pattern at the top and bottom in an enclosed microchannel without evaporation.

  12. 75 FR 48409 - Establishment of the Toxic by Inhalation Hazard Common Carrier Transportation Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-10

    ... Surface Transportation Board Establishment of the Toxic by Inhalation Hazard Common Carrier Transportation Advisory Committee AGENCY: Surface Transportation Board. ACTION: Notice of establishment of the Toxic by... the Federal Advisory Committee Act (FACA), 5 U.S.C. app., the Surface Transportation Board...

  13. 76 FR 77888 - Student Transportation of America, Inc.-Control-Dairyland Buses, Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-14

    ... Surface Transportation Board Student Transportation of America, Inc.--Control--Dairyland Buses, Inc. AGENCY: Surface Transportation Board. ACTION: Notice Tentatively Approving and Authorizing Finance...: Surface Transportation Board, 395 E Street SW., Washington, DC 20423-0001. In addition, send one copy...

  14. Surface transport of nutrients from surface broadcast and subsurface-banded broiler litter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Broiler chicken litter is commonly used as a fertilizer on pastures and cropland in major broiler-producing states. However, phosphorus (P) loss from fields fertilized with broiler litter contributes to eutrophication and growth of toxic algae in surface waters. Recently, to reduce surface transpo...

  15. Quantum Electronic Transport of Topological Surface States in β-Ag2Se Nanowire.

    PubMed

    Kim, Jihwan; Hwang, Ahreum; Lee, Sang-Hoon; Jhi, Seung-Hoon; Lee, Sunghun; Park, Yun Chang; Kim, Si-In; Kim, Hong-Seok; Doh, Yong-Joo; Kim, Jinhee; Kim, Bongsoo

    2016-04-26

    Single-crystalline β-Ag2Se nanostructures, a new class of 3D topological insulators (TIs), were synthesized using the chemical vapor transport method. The topological surface states were verified by measuring electronic transport properties including the weak antilocalization effect, Aharonov-Bohm oscillations, and Shubnikov-de Haas oscillations. First-principles band calculations revealed that the band inversion in β-Ag2Se is caused by strong spin-orbit coupling and Ag-Se bonding hybridization. These investigations provide evidence of nontrivial surface state about β-Ag2Se TIs that have anisotropic Dirac cones. PMID:27018892

  16. 29 CFR 1978.108 - Role of Federal agencies.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 9 2011-07-01 2011-07-01 false Role of Federal agencies. 1978.108 Section 1978.108 Labor... THE SURFACE TRANSPORTATION ASSISTANCE ACT OF 1982 Litigation § 1978.108 Role of Federal agencies. (a... respondent. (2) If the Assistant Secretary assumes the role of prosecuting party in accordance with...

  17. BACTERIA TRANSPORT AND DEPOSITION UNDER UNSATURATED CONDITIONS: THE ROLE OF THE MATRIX GRAIN SIZE AND THE BACTERIA SURFACE PROTEIN

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Unsaturated (80% water saturated) packed column experiments were conducted to investigate the influence of grain size distribution and bacteria surface macromolecules on bacteria (Rhodococcus rhodochrous) transport and deposition mechanisms. Three sizes of silica sands were used in these transport ...

  18. Chondroitin Sulfate Accelerates Trans-Golgi-to-Surface Transport of Proteoglycan Amyloid Precursor Protein.

    PubMed

    Mihov, Deyan; Raja, Eva; Spiess, Martin

    2015-08-01

    The amyloid precursor protein (APP) is a membrane protein implicated in the pathogenesis of Alzheimer's disease. APP is a part-time proteoglycan, as splice variants lacking exon 15 are modified by a chondroitin sulfate glycosaminoglycan (GAG) chain. Investigating the effect of the GAG chain on the trafficking of APP in non-polarized cells, we found it to increase the steady-state surface-to-intracellular distribution, to reduce the rate of endocytosis and to accelerate transport kinetics from the trans-Golgi network (TGN) to the plasma membrane. Deletion of the cytosolic domain resulted in delayed surface arrival of GAG-free APP, but did not affect the rapid export kinetics of the proteoglycan form. Protein-free GAG chains showed the same TGN-to-cell surface transport kinetics as proteoglycan APP. Endosome ablation experiments were performed to distinguish between indirect endosomal and direct pathways to the cell surface. Surprisingly, TGN-to-cell surface transport of both GAG-free and proteoglycan APP was found to be indirect via transferrin-positive endosomes. Our results show that GAGs act as alternative sorting determinants in cellular APP transport that are dominant over cytoplasmic signals and involve distinct sorting mechanisms. PMID:25951880

  19. Atomic interactions at the (100) diamond surface and the impact of surface and interface changes on the electronic transport properties

    NASA Astrophysics Data System (ADS)

    Deferme, Wim

    Centuries and centuries already, diamond is a material that speaks to ones imagination. Till the 18th century it was only mined in India, after it was also found in Brazil and South-Africa. But along the fascinating properties of diamond, it is also a very interesting material for industry. After the discovery at the end of the 18th century that diamond consists of carbon, it took until the 50's of the previous century before research groups from Russia, Japan and the USA were able to reproduce the growth process of diamond. In 1989 it was discovered that the surface of intrinsic, insulation diamond can be made conductive by hydrogenating the surface. It was clear that not only hydrogen at the surface but also the so called "adsorbates" were responsible for this conductivity. It was still not completely clear what was the influence of other species (like oxygen) on the mechanism of surface conductivity and therefore in this thesis the influence of oxygen on the electronic transport properties of atomically flat diamond are researched. Besides the growth of atomically flat diamond with the use of CVD (chemical vapour deposition) en the study of the grown surfaces with characterising techniques such as AFM (atomic force microscopy) and STM (scanning tunnelling microscopy), the study of the surface treatment with plasma techniques is the main topic of this thesis. The influence of oxygen on the surface conductivity is studied and with the ToF (Time-of-Flight) technique the transport properties of the freestanding diamond are examined. With a short laserflash, electrons and holes are created at the diamond/aluminium interface and due to an electric field (up to 500V) the charge carriers are translated to the back contact. In this way the influence of the surface and the changes at the aluminum contacts is studied leading to very interesting results.

  20. Correlating Humidity-Dependent Ionically Conductive Surface Area with Transport Phenomena in Proton-Exchange Membranes

    SciTech Connect

    He, Qinggang; Kusoglu, Ahmet; Lucas, Ivan T.; Clark, Kyle; Weber, Adam Z.; Kostecki, Robert

    2011-08-01

    The objective of this effort was to correlate the local surface ionic conductance of a Nafion? 212 proton-exchange membrane with its bulk and interfacial transport properties as a function of water content. Both macroscopic and microscopic proton conductivities were investigated at different relative humidity levels, using electrochemical impedance spectroscopy and current-sensing atomic force microscopy (CSAFM). We were able to identify small ion-conducting domains that grew with humidity at the surface of the membrane. Numerical analysis of the surface ionic conductance images recorded at various relative humidity levels helped determine the fractional area of ion-conducting active sites. A simple square-root relationship between the fractional conducting area and observed interfacial mass-transport resistance was established. Furthermore, the relationship between the bulk ionic conductivity and surface ionic conductance pattern of the Nafion? membrane was examined.

  1. PTV measurements of Lagrangian particle transport by surface gravity wave groups

    NASA Astrophysics Data System (ADS)

    van den Bremer, Ton; Whittaker, Colin; Raby, Alison; Taylor, Paul

    2015-11-01

    We present detailed PTV (particle tracking velocimetry) measurements of the Lagrangian transport and trajectories of neutrally buoyant particles underneath two-dimensional surface gravity wave groups in a laboratory flume. By focussing our attention on wave groups of moderate steepness, we confirm the predictions of standard second-order multi-chromatic wave theory, in which the body of fluid satisfies the potential flow equations. Particles near the surface are transported forwards and their motion is dominated by Stokes drift. Particles at sufficient depth are transported backwards by the Eulerian return current that was first described by Longuet-Higgins & Stewart (1962) and forms an inseparable counterpart of Stokes drift for surface wave groups ensuring the (irrotational) mass balance holds. Finally, we provide experimental validation of a simple scaling relationship, derived based under the assumption of separation of scales, for the transition depth: the depth above which Lagrangian particles are transported forwards by the Stokes drift and below which such particles are transported backwards by the return current. We present results for a range of effective water depths.

  2. Solute Transport and Surface-Subsurface Exchange in the Everglades Characterized by a Tracer Release in Surface Water

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; Saiers, J. E.; Newlin, J. T.

    2003-12-01

    Solute tracer injections into flowing surface water are useful to characterize water velocity, dispersive mixing, and biogeochemical reactions that result from processes such as solute exchange between surface water and sediment porewater. Presently, there are few data or guidelines to understand transport processes in the Everglades. Our tracer study was conducted in central Shark Slough, Everglades National Park (25° 38' 31.2'' N, 80° 43' 20.4'' W) at an experimental flume facility. The flume consists of 4 side-by-side channels enclosing wetland vegetation in open-ended flow-ways (3-m by 100-m) that are subject to ambient flow conditions. The injection was conducted in one channel that, at the time of the experiment, had 60-cm of surface water and a typical assemblage of Everglades' slough vegetation, including rooted macrophytes (mainly Eleocharis sp.), and a well-developed layer (15-cm) of periphyton-coated vegetation (mainly Utricularia sp.) below the water surface. A constant-rate injection of sodium bromide (NaBr) was conducted for 22 hours by dividing the flow between four horizontally oriented soaker hoses that were evenly spaced in the water column. At a distance of 6.8 m downstream of the injection, small-volume (10 to 20-ml) water samples were collected on regular intervals for 48 hrs by withdrawing them by suction from 1/8-inch tubes deployed throughout the water column and in the peat sediment to a depth of 30-cm. Transport was characterized by adjusting the parameters of the USGS model OTIS (One-dimensional Transport with Inflow and Storage). Mean velocity of surface water during the experiment was 0.63 cm/s, longitudinal dispersion was 5 x 10-5 m2/s, and fluid residence times in two storage zones, where local mixing but no appreciable downstream transport occurred, were 1 hr (in periphyton-dominated floating vegetation)and 24 hrs in peat porewater), respectively. We conclude that storage-exchange affects solute transport in the Everglades by

  3. Relationship between cell surface properties and transport of bacteria through soil

    SciTech Connect

    Gannon, J.T.; Manilal, V.B.; Alexander, M. )

    1991-01-01

    One means of bringing about the remediation of underground sites containing polluting chemicals is to inoculate the sites with bacteria able to metabolize those compounds. However, successful bioremediation of such sites requires the movement of the biodegradative bacteria through soil, aquifer solids, or groundwater. A study was conducted to relate the properties of Enterobacter, Pseudomonas, Bacillus, Achromobacter, Flavobacterium, and Arthrobacter strains to their transport with water moving through soil. The bacteria differed markedly in their extent of transport; their hydrophobicity, as measured by adherence to n-octane and by hydrophobic-interaction chromatography; and their net surface electrostatic charge, as determined by electrostatic interaction chromatography and by measurements of the zeta potential. Transport of the 19 strains through Kendaia loam or their retention by this soil was not correlated with hydrophobicities or net surface charges of the cells or the presence of capsules. Among 10 strains tested, the presence of flagella was also not correlated with transport. Retention was statistically related to cell size, with bacteria shorter than 1.0 {mu}m usually showing higher percentages of cells being transported through the soil. We suggest that more than one characteristic of bacterial cells determines whether the organisms are transported through soil with moving water.

  4. Morphing Surfaces Enable Acoustophoretic Contactless Transport of Ultrahigh-Density Matter in Air

    NASA Astrophysics Data System (ADS)

    Foresti, Daniele; Sambatakakis, Giorgio; Bottan, Simone; Poulikakos, Dimos

    2013-11-01

    The controlled contactless transport of heavy drops and particles in air is of fundamental interest and has significant application potential. Acoustic forces do not rely on special material properties, but their utility in transporting heavy matter in air has been restricted by low power and poor controllability. Here we present a new concept of acoustophoresis, based on the morphing of a deformable reflector, which exploits the low reaction forces and low relaxation time of a liquid with enhanced surface tension through the use of thin overlaid membrane. An acoustically induced, mobile deformation (dimple) on the reflector surface enhances the acoustic field emitted by a line of discretized emitters and enables the countinuos motion of heavy levitated samples. With such interplay of emitters and reflecting soft-structure, a 5 mm steel sphere (0.5 grams) was contactlessly transported in air solely by acoustophoresis.

  5. Morphing Surfaces Enable Acoustophoretic Contactless Transport of Ultrahigh-Density Matter in Air

    PubMed Central

    Foresti, Daniele; Sambatakakis, Giorgio; Bottan, Simone; Poulikakos, Dimos

    2013-01-01

    The controlled contactless transport of heavy drops and particles in air is of fundamental interest and has significant application potential. Acoustic forces do not rely on special material properties, but their utility in transporting heavy matter in air has been restricted by low power and poor controllability. Here we present a new concept of acoustophoresis, based on the morphing of a deformable reflector, which exploits the low reaction forces and low relaxation time of a liquid with enhanced surface tension through the use of thin overlaid membrane. An acoustically induced, mobile deformation (dimple) on the reflector surface enhances the acoustic field emitted by a line of discretized emitters and enables the countinuos motion of heavy levitated samples. With such interplay of emitters and reflecting soft-structure, a 5 mm steel sphere (0.5 grams) was contactlessly transported in air solely by acoustophoresis. PMID:24212104

  6. 75 FR 9638 - Surface Transportation Project Delivery Pilot Program; Caltrans Audit Report

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-03

    ... the fourth audit report in a Federal Register Notice published on December 23, 2009, at 74 FR 68308... the fourth audit report in a Federal Register Notice published December 22, 2009, at 74 FR 68308. The... Federal Highway Administration Surface Transportation Project Delivery Pilot Program; Caltrans...

  7. Variability of Surface Characteristics and Transport Behavior of Escherichia coli Isolates from Different Host

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Escherichia coli is a commonly used indicator organism for detecting the presence of fecal-borne pathogenic microorganisms in water supplies. The importance of E. coli as an indicator organism has led to numerous studies looking at surface characteristics and transport behavior of this important mic...

  8. Investigation of the pathway of contaminated soil transported to plant surfaces by raindrop splash

    SciTech Connect

    Dreicer, M.; Hakonson, T.E.; Whicker, F.W.; White, G.C.

    1983-10-21

    The environmental transport pathway of soil-borne radioisotopes to vegetation surfaces via raindrop splash was studied. The data show that soil can significantly contribute to the contamination found on plants. Further detailed study is needed to calculate the rate constant for the raindrop splash and retention pathways. 8 references, 1 figure. (ACR)

  9. Fate and surface transport of urea in a coastal plain soil: a rainfall simulation study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface transport of urea has rarely been studied since it is assumed to undergo rapid hydrolysis to ammonia. However, studies have shown urea to exist in estuarine and coastal waters. Urea in small amounts can trigger the diatom Pseudo-nitzschia spp. to produce the toxin domoic acid, which is o...

  10. Escherichia coli Transport from Surface-Applied Manure to Subsurface Drains through Artificial Biopores

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport of pathogenic bacteria in soils primarily occurs through soil mesopores and macropores (e.g., biopores and cracks). Field research has demonstrated that biopores and subsurface drains can be hydraulically connected. This research was conducted to investigate the importance of surface conne...

  11. Aircraft surface coatings study: Energy efficient transport program. [sprayed and adhesive bonded coatings for drag reduction

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Surface coating materials for application on transport type aircraft to reduce drag, were investigated. The investigation included two basic types of materials: spray on coatings and adhesively bonded films. A cost/benefits analysis was performed, and recommendations were made for future work toward the application of this technology.

  12. Alternatives to motor fuel taxes for financing surface transportation improvements. Final report

    SciTech Connect

    Reno, A.T.; Stowers, J.R.

    1995-12-31

    The report contains recommendations, which are applicable to all levels of government, for evaluating alternatives to the motor fuel tax. An evaluation framework is presented and demonstrated. General assessments and recommendations on future expectations and trends are given. An approach that recommends a contract between transportation agencies and their customers is also suggested as an aid in generating adequate revenues. The research as documented in this report will be of interest to individuals who must deal with the identification of future revenue sources for transportation purposes, principally, highway related. All readers are directed first to the `Summary` for a general description of results; the full report, especially the applications in Chapter 3, is recommended to practitioners.

  13. Summary of ground water and surface water flow and contaminant transport computer codes used at the Idaho National Engineering Laboratory (INEL). Version 1.0

    SciTech Connect

    Bandy, P.J.; Hall, L.F.

    1993-03-01

    This report presents information on computer codes for numerical and analytical models that have been used at the Idaho National Engineering Laboratory (INEL) to model ground water and surface water flow and contaminant transport. Organizations conducting modeling at the INEL include: EG&G Idaho, Inc., US Geological Survey, and Westinghouse Idaho Nuclear Company. Information concerning computer codes included in this report are: agency responsible for the modeling effort, name of the computer code, proprietor of the code (copyright holder or original author), validation and verification studies, applications of the model at INEL, the prime user of the model, computer code description, computing environment requirements, and documentation and references for the computer code.

  14. The mammalian transferrin-independent iron transport system may involve a surface ferrireductase activity.

    PubMed Central

    Jordan, I; Kaplan, J

    1994-01-01

    Mammalian cells accumulate iron from ferric citrate or ferric nitrilotriacetate through the activity of a transferrin-independent iron transport system [Sturrock, Alexander, Lamb, Craven and Kaplan (1990) J. Biol. Chem. 265, 3139-3145]. The uptake system might recognize and transport ferric-anion complexes, or cells may reduce ferric iron at the surface and then transport ferrous iron. To distinguish between these possibilities we exposed cells to either [59Fe]ferric citrate or ferric [14C]citrate and determined whether accumulation of iron was accompanied by the obligatory accumulation of citrate. In HeLa cells and human skin fibroblasts the rate of accumulation of iron was three to five times greater than that of citrate. Incubation of fibroblasts with ferric citrate or ferric ammonium citrate resulted in an enhanced accumulation of iron and citrate; the molar ratio of accumulation approaching unity. A similar rate of citrate accumulation, however, was observed when ferric citrate-incubated cells were exposed to [14C]citrate alone. Further studies demonstrated the independence of iron and citrate accumulation: addition of unlabelled citrate to cells decreased the uptake of labelled citrate without affecting the accumulation of 59Fe; iron uptake was decreased by the addition of ferrous chelators whereas the uptake of citrate was unaffected; reduction of ferric iron by ascorbate increased the uptake of iron but had no effect on the uptake of citrate. When HeLa cells were depleted of calcium, iron uptake decreased, but there was little effect on citrate uptake. These results indicate that transport of iron does not require the obligatory transport of citrate and vice versa. The mammalian transferrin-independent iron transport system appears functionally similar to iron transport systems in both the bacterial and plant kingdoms which require the activities of both a surface reductase and a ferrous metal transporter. PMID:7945215

  15. Creating tomorrow`s surface transportation systems. Hearing before the Subcommittee on Technology, Environment and Aviation of the Committee on Science, Space, and Technology, House of Representatives, One Hundred Third Congress, Second Session, May 12, 1994

    SciTech Connect

    1994-12-31

    The hearing addresses the role of the Federal government in creating tomorrow`s surface transportation systems. Information is presented on the development of new systems including the fully automated highway for automobiles which is expected to improve computer flow and reduce accidents. The structure and role of the Department of Transportation in research and development of new systems is presented. Partnerships with other agencies and industry is examined, such as the Partnership of New Generation Vehicles. The threat of earthquakes to transportation systems is presented based on recent events around the world. Statements of government and industry officials are included along with documents submitted for the record.

  16. 41 CFR 302-9.7 - What POV transportation and emergency or temporary storage may my agency authorize at Government...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-9.7 Public Contracts and Property Management Federal Travel Regulation System RELOCATION ALLOWANCES... 41 Public Contracts and Property Management 4 2012-07-01 2012-07-01 false What POV transportation... PRIVATELY OWNED VEHICLE General Rules § 302-9.7 What POV transportation and emergency or temporary...

  17. 41 CFR 102-118.25 - Does GSA still require my agency to submit its overall transportation policies for approval?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT REGULATION TRANSPORTATION 118-TRANSPORTATION PAYMENT AND AUDIT General Introduction... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Does GSA still...

  18. The dissipated energy of electrode surfaces: Temperature jumps from coupled transport processes

    SciTech Connect

    Bedeaux, D.; Ratkje, S.K.

    1996-03-01

    Nonequilibrium thermodynamics for surfaces has been applied to the electrode surfaces of an electrochemical cell. It is shown that the temperature of the surface differs from that of the adjacent electrolyte and electrode, and that a temperature jump exists across the surface. mathematical expressions are derived for the temperature profiles of two cells at steady-state conditions. Methods for estimating transport coefficients for the coupled transport processes at the electrode surface are discussed. Possible numerical results for the temperature profile, the overpotential, and the dissipated energy are reported. The results reflect the relative importance of heat conductivities, electric conductivities, and the Peltier coefficients for the electrode surface phenomena in combination with bulk properties. Significant temperature jumps may occur at normal electrolysis conditions 10{sup 3} to 10{sup 4} A/m, and for temperature jump coefficients which are smaller than 10{sup 3} J/s K{sup 2} m{sup 2}. The overpotential may have contributions from the Peltier coefficients for the surface larger than the ohmic contribution. The method of analysis gives new information useful for heat control of electrochemical cells, electrode kinetic studies, and interpretation of overpotentials.

  19. Surface transport kinetics in low-temperature silicon deposition determined from topography evolution

    NASA Astrophysics Data System (ADS)

    Bray, K. R.; Parsons, G. N.

    2002-01-01

    In this article, surface transport kinetics during low-temperature silicon thin film deposition are characterized using time dependent surface topography and dynamic scaling models. Analysis of surface morphology indicates that diffusion of adsorbed species dominates surface transport, with a characteristic diffusion length that increases with surface temperature. A diffusion activation barrier of ~0.2 eV is obtained, consistent with hydrogen-mediated adspecies diffusion on the growth silicon surface. Samples are compared over a range of deposition temperatures (25 to 350 °C) and film thickness (20 to 5000 Å) deposited using silane with helium or argon dilution, on glass and silicon substrates. Self-similar surface structure is found to depend on detailed film growth conditions, but is independent of film thickness after nuclei coalescence. For films deposited using helium dilution, static and dynamic scaling parameters are consistent with self-similar fractal geometry scaling, and the lateral correlation length increases from 45 to 150 nm as temperature increases from 25 to 150 °C. These results are discussed in relation to current silicon deposition models and with topography evolution observed during low temperature growth of other amorphous material systems.

  20. Surface modification of PTMSP membranes by plasma treatment: Asymmetry of transport in organic solvent nanofiltration.

    PubMed

    Volkov, A V; Tsarkov, S E; Gilman, A B; Khotimsky, V S; Roldughin, V I; Volkov, V V

    2015-08-01

    For the first time, the effect of asymmetry of the membrane transport was studied for organic solvents and solutes upon their nanofiltration through the plasma-modified membranes based on poly(1-trimethylsilyl-1-propyne) (PTMSP). Plasma treatment is shown to provide a marked hydrophilization of the hydrophobic PTMSP surface (the contact angle of water decreases from 88 down to 20°) and leads to the development of a negative charge of -5.2 nC/cm(2). The XPS measurements prove the formation of the oxygen-containing groups (Si-O and C-O) due to the surface modification. The AFM images show that the small-scale surface roughness of the plasma-treated PTMSP sample is reduced but the large-scale surface heterogeneities become more pronounced. The modified membranes retain their hydrophilic surface properties even after the nanofiltration tests and 30-day storage under ambient conditions. The results of the filtration tests show that when the membrane is oriented so that its modified layer contacts the feed solution, the membrane permeability for linear alcohols (methanol-propanol) and acetone decreases nearly two times. When the modified membrane surface faces the permeate, the membrane is seen to regain its transport characteristics: the flux becomes equal to that of the unmodified PTMSP. The well-pronounced effect of the transport asymmetry is observed for the solution of the neutral dye Solvent Blue 35 in methanol, ethanol, and acetone. For example, the initial membrane shows the negative retention for the Solvent Blue 35 dye (-16%) upon its filtration from the ethanol solution whereas, for the modified PTMSP membrane, the retention increases up to 17%. Various effects contributing to the asymmetry of the membrane transport characteristics are discussed. PMID:25482845

  1. 41 CFR 302-3.218 - Are there any special circumstances when my agency may authorize me travel and transportation...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 41 Public Contracts and Property Management 4 2012-07-01 2012-07-01 false Are there any special... Alaska or Hawaii? 302-3.218 Section 302-3.218 Public Contracts and Property Management Federal Travel...; or (b) Your agency is in need to recruit employees with special skills and knowledge and/or to...

  2. GPS based surface displacements - a proxy for discharge and sediment transport from the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Hasholt, B.; Khan, S. A.; Mikkelsen, A. B.

    2014-07-01

    The elastic respond of the Earth's surface to mass changes has been measured with Global Positioning System (GPS). Mass loss as accumulated runoff and sediment transport from a 10 000 km2 segment of the Greenland Ice Sheet (GrIS) correlated very well (R2 = 0.83) with GPS measured uplift. Accumulated winter precipitation correlated fairly well with surface depression (R2 = 0.69). The relationships are based on seven years of runoff and sediment transport observations from the Watson River (2007-2013), winter precipitation from Kangerlussuaq Airport and GPS observations at Kellyville. GPS recordings of surface subsidence and uplift from 1996-2013 are used to calculate 18 years time series of annual runoff, sediment and solute transport and winter precipitation. Runoff and related transport of sediment and solutes increase over the period, while winter precipitation (land depression) tends to decrease. Based on the entire GPS record (1996-2013), it is shown that until 2005-2006 the mass balance of this segment of the GrIS was rather stable - since then there has been an increasing loss of mass, culminating in 2012.

  3. Cell shape-dependent rectification of surface receptor transport in a sinusoidal electric field.

    PubMed Central

    Lee, R C; Gowrishankar, T R; Basch, R M; Patel, P K; Golan, D E

    1993-01-01

    In the presence of an extracellular electric field, transport dynamics of cell surface receptors represent a balance between electromigration and mutual diffusion. Because mutual diffusion is highly dependent on surface geometry, certain asymmetrical cell shapes effectively create an anisotropic resistance to receptor electromigration. If the resistance to receptor transport along a single axis is anisotropic, then an applied sinusoidal electric field will drive a net time-average receptor displacement, effectively rectifying receptor transport. To quantify the importance of this effect, a finite difference mathematical model was formulated and used to describe charged receptor transport in the plane of a plasma membrane. Representative values for receptor electromigration mobility and diffusivity were used. Model responses were examined for low frequency (10(-4)-10 Hz) 10-V/cm fields and compared with experimental measurements of receptor back-diffusion in human fibroblasts. It was found that receptor transport rectification behaved as a low-pass filter; at the tapered ends of cells, sinusoidal electric fields in the 10(-3) Hz frequency range caused a time-averaged accumulation of receptors as great as 2.5 times the initial uniform concentration. The extent of effective rectification of receptor transport was dependent on the rate of geometrical taper. Model studies also demonstrated that receptor crowding could alter transmembrane potential by an order of magnitude more than the transmembrane potential directly induced by the field. These studies suggest that cell shape is important in governing interactions between alternating current (ac) electric fields and cell surface receptors. PMID:8381681

  4. Inhibition of Nucleotide Sugar Transport in Trypanosoma brucei Alters Surface Glycosylation*

    PubMed Central

    Liu, Li; Xu, Yu-Xin; Caradonna, Kacey L.; Kruzel, Emilia K.; Burleigh, Barbara A.; Bangs, James D.; Hirschberg, Carlos B.

    2013-01-01

    Nucleotide sugar transporters (NSTs) are indispensible for the biosynthesis of glycoproteins by providing the nucleotide sugars needed for glycosylation in the lumen of the Golgi apparatus. Mutations in NST genes cause human and cattle diseases and impaired cell walls of yeast and fungi. Information regarding their function in the protozoan parasite, Trypanosoma brucei, a causative agent of African trypanosomiasis, is unknown. Here, we characterized the substrate specificities of four NSTs, TbNST1–4, which are expressed in both the insect procyclic form (PCF) and mammalian bloodstream form (BSF) stages. TbNST1/2 transports UDP-Gal/UDP-GlcNAc, TbNST3 transports GDP-Man, and TbNST4 transports UDP-GlcNAc, UDP-GalNAc, and GDP-Man. TbNST4 is the first NST shown to transport both pyrimidine and purine nucleotide sugars and is demonstrated here to be localized at the Golgi apparatus. RNAi-mediated silencing of TbNST4 in the procyclic form caused underglycosylated surface glycoprotein EP-procyclin. Similarly, defective glycosylation of the variant surface glycoprotein (VSG221) as well as the lysosomal membrane protein p67 was observed in Δtbnst4 BSF T. brucei. Relative infectivity analysis showed that defects in glycosylation of the surface coat resulting from tbnst4 deletion were insufficient to impact the ability of this parasite to infect mice. Notably, the fact that inactivation of a single NST gene results in measurable defects in surface glycoproteins in different life cycle stages of the parasite highlights the essential role of NST(s) in glycosylation of T. brucei. Thus, results presented in this study provide a framework for conducting functional analyses of other NSTs identified in T. brucei. PMID:23443657

  5. Inhibition of nucleotide sugar transport in Trypanosoma brucei alters surface glycosylation.

    PubMed

    Liu, Li; Xu, Yu-Xin; Caradonna, Kacey L; Kruzel, Emilia K; Burleigh, Barbara A; Bangs, James D; Hirschberg, Carlos B

    2013-04-12

    Nucleotide sugar transporters (NSTs) are indispensible for the biosynthesis of glycoproteins by providing the nucleotide sugars needed for glycosylation in the lumen of the Golgi apparatus. Mutations in NST genes cause human and cattle diseases and impaired cell walls of yeast and fungi. Information regarding their function in the protozoan parasite, Trypanosoma brucei, a causative agent of African trypanosomiasis, is unknown. Here, we characterized the substrate specificities of four NSTs, TbNST1-4, which are expressed in both the insect procyclic form (PCF) and mammalian bloodstream form (BSF) stages. TbNST1/2 transports UDP-Gal/UDP-GlcNAc, TbNST3 transports GDP-Man, and TbNST4 transports UDP-GlcNAc, UDP-GalNAc, and GDP-Man. TbNST4 is the first NST shown to transport both pyrimidine and purine nucleotide sugars and is demonstrated here to be localized at the Golgi apparatus. RNAi-mediated silencing of TbNST4 in the procyclic form caused underglycosylated surface glycoprotein EP-procyclin. Similarly, defective glycosylation of the variant surface glycoprotein (VSG221) as well as the lysosomal membrane protein p67 was observed in Δtbnst4 BSF T. brucei. Relative infectivity analysis showed that defects in glycosylation of the surface coat resulting from tbnst4 deletion were insufficient to impact the ability of this parasite to infect mice. Notably, the fact that inactivation of a single NST gene results in measurable defects in surface glycoproteins in different life cycle stages of the parasite highlights the essential role of NST(s) in glycosylation of T. brucei. Thus, results presented in this study provide a framework for conducting functional analyses of other NSTs identified in T. brucei. PMID:23443657

  6. Technology and human purpose: the problem of solids transport on the Earth's surface

    NASA Astrophysics Data System (ADS)

    Haff, P. K.

    2012-11-01

    Displacement of mass of limited deformability ("solids") on the Earth's surface is opposed by friction and (the analog of) form resistance - impediments relaxed by rotational motion, self-powering of mass units, and transport infrastructure. These features of solids transport first evolved in the biosphere prior to the emergence of technology, allowing slope-independent, diffusion-like motion of discrete objects as massive as several tons, as illustrated by animal foraging and movement along game trails. However, high-energy-consumption technology powered by fossil fuels required a mechanism that could support fast advective transport of solids, i.e., long-distance, high-volume, high-speed, unidirectional, slope-independent transport across the land surface of materials like coal, containerized fluids, minerals, and economic goods. Pre-technology nature was able to sustain regional- and global-scale advection only in the limited form of piggybacking on geophysical flows of water (river sediment) and air (dust). The appearance of a mechanism for sustained advection of solids independent of fluid flows and gravity appeared only upon the emergence of human purpose. Purpose enables solids advection by, in effect, simulating a continuous potential gradient, otherwise lacking, between discrete and widely separated fossil-fuel energy sources and sinks. Invoking purpose as a mechanism in solids advection is an example of the need to import anthropic principles and concepts into the language and methodology of modern Earth system dynamics. As part of the emergence of a generalized solids advection mechanism, several additional transport requirements necessary to the function of modern large-scale technological systems were also satisfied. These include spatially accurate delivery of advected payload, targetability to essentially arbitrarily located destinations (such as cities), and independence of structure of advected payload from transport mechanism. The latter property

  7. Technology and human purpose: the problem of solids transport on the earth's surface

    NASA Astrophysics Data System (ADS)

    Haff, P. K.

    2012-05-01

    Displacement of mass of limited deformability ("solids") on the Earth's surface is opposed by friction and (the analog of) form resistance - impediments relaxed by rotational motion, self-powering of mass units, and transport infrastructure. These features of solids transport first evolved in the biosphere prior to the emergence of technology, allowing slope-independent, diffusion-like motion of discrete objects as massive as several tons, as illustrated by animal foraging and movement along game trails. However, high-energy-consumption technology powered by fossil fuels required a mechanism that could support advective transport of solids, i.e., long-distance, high-volume, high-speed, unidirectional, slope independent transport across the land surface of materials like coal, containerized fluids, and minerals. Pre-technology nature was able to sustain large-scale, long-distance solids advection only in the limited form of piggybacking on geophysical flows of water (river sediment) and air (dust). The appearance of a generalized mechanism for advection of solids independent of fluid flows and gravity appeared only upon the emergence of human purpose. Purpose enables solids advection by, in effect, enabling a simulated continuous potential gradient, otherwise lacking, between discrete and widely separated fossil-fuel energy sources and sinks. Invoking purpose as a mechanism in solids advection is an example of the need to import anthropic principles and concepts into the language and methodology of modern Earth system dynamics. As part of the emergence of a generalized solids advection mechanism, several additional transport requirements necessary to the function of modern large-scale technological systems were also satisfied. These include spatially accurate delivery of advected payload, targetability to essentially arbitrarily located destinations (such as cities), and independence of structure of advected payload from transport mechanism. The latter property

  8. A controlled field pilot for testing near surface CO2 detection techniques and transport models

    USGS Publications Warehouse

    Spangler, L.H.; Dobeck, L.M.; Repasky, K.; Nehrir, A.; Humphries, S.; Keith, C.; Shaw, J.; Rouse, J.; Cunningham, A.; Benson, S.; Oldenburg, C.M.; Lewicki, J.L.; Wells, A.; Diehl, R.; Strazisar, B.; Fessenden, J.; Rahn, Thomas; Amonette, J.; Barr, J.; Pickles, W.; Jacobson, J.; Silver, E.; Male, E.; Rauch, H.; Gullickson, K.; Trautz, R.; Kharaka, Y.; Birkholzer, J.; Wielopolski, L.

    2009-01-01

    A field facility has been developed to allow controlled studies of near surface CO2 transport and detection technologies. The key component of the facility is a shallow, slotted horizontal well divided into six zones. The scale and fluxes were designed to address large scale CO2 storage projects and desired retention rates for those projects. A wide variety of detection techniques were deployed by collaborators from 6 national labs, 2 universities, EPRI, and the USGS. Additionally, modeling of CO2 transport and concentrations in the saturated soil and in the vadose zone was conducted. An overview of these results will be presented. ?? 2009 Elsevier Ltd. All rights reserved.

  9. Magnetically Controlled Electronic Transport Properties of a Ferromagnetic Junction on the Surface of a Topological Insulator

    NASA Astrophysics Data System (ADS)

    Liu, Zheng-Qin; Wang, Rui-Qiang; Deng, Ming-Xun; Hu, Liang-Bin

    2015-06-01

    We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topological insulator. The current-voltage characteristic curve and the tunneling conductance are calculated theoretically. Two interesting transport features are predicted: observable negative differential conductances and linear conductances tunable from unit to nearly zero. These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization. Our results may contribute to the development of high-speed switching and functional applications or electrically controlled magnetization switching. Supported by National Natural Science Foundation of China under Grant Nos. 11174088, 11175067, 11274124

  10. Understanding extraction and beam transport in the ISIS H{sup -} Penning surface plasma ion source

    SciTech Connect

    Faircloth, D. C.; Letchford, A. P.; Gabor, C.; Whitehead, M. O.; Wood, T.; Jolly, S.; Pozimski, J.; Savage, P.; Woods, M.

    2008-02-15

    The ISIS H{sup -} Penning surface plasma source has been developed to produce beam currents up to 70 mA and pulse lengths up to 1.5 ms at 50 Hz. This paper details the investigation into beam extraction and beam transport in an attempt to understand the beam emittance and to try to improve the emittance. A scintillator profile measurement technique has been developed to assess the performance of different plasma electrode apertures, extraction electrode geometries, and postextraction acceleration configurations. This work shows that the present extraction, beam transport, and postacceleration system are suboptimal and further work is required to improve it.

  11. The role of roughness in predicting transport thresholds on desert surfaces: temporal and spatial variability

    NASA Astrophysics Data System (ADS)

    King, James; Haustein, Karsten; Wiggs, Giles F. S.; Eckardt, Frank; Thomas, David S. G.; Washington, Richard

    2013-04-01

    Dust emission schemes in climate models are relatively simple and tuned to represent observed background aerosol concentrations. A key component of the dust emission scheme is the sediment transport threshold, which is a function of soil size distribution, soil moisture, air and soil particle density, and surface roughness. For a particular region or landform that is not vegetated the variable that controls the transport threshold is soil moisture. This is because it is assumed that the other components vary little (air and soil particle densities) or are kept constant (soil size distribution and surface roughness). This in turn puts the emphasis very heavily on soil moisture and wind stress as the key drivers of dust emission for specific landforms and dust emission schemes. This highlights the necessity for current models to tune their model parameters to observations. Observations of dust emission were undertaken in 2011 and 2012 on Sua Pan in Botswana, a large, flat, unvegetated salt pan, as part of the Dust Observation for Models (DO4 Models) campaign. The observations consisted of eleven meteorological stations placed within a 144 km2 region recording wind velocity, soil moisture, soil and air temperature, horizontal transport, vertical transport, and radiative properties. Out of the measured and calculated erodibility parameters responsible for predicting transport threshold within current schemes, surface soil moisture and aerodynamic roughness length varied the most over the duration of the project and spatially across the pan. In some cases, the aerodynamic roughness length of the bare soil increased by three orders of magnitude within a three month period. This increase in roughness would almost double the modelled threshold shear velocity required for this surface to be emissive. The temporal and spatial variability of the calculated transport threshold is explored with observed data and compared with the modelled transport threshold for this region for

  12. Effects of magnetic drift tangential to magnetic surfaces on neoclassical transport in non-axisymmetric plasmas

    SciTech Connect

    Matsuoka, Seikichi; Satake, Shinsuke; Kanno, Ryutaro; Sugama, Hideo

    2015-07-15

    In evaluating neoclassical transport by radially local simulations, the magnetic drift tangential to a flux surface is usually ignored in order to keep the phase-space volume conservation. In this paper, effect of the tangential magnetic drift on the local neoclassical transport is investigated. To retain the effect of the tangential magnetic drift in the local treatment of neoclassical transport, a new local formulation for the drift kinetic simulation is developed. The compressibility of the phase-space volume caused by the tangential magnetic drift is regarded as a source term for the drift kinetic equation, which is solved by using a two-weight δf Monte Carlo method for non-Hamiltonian system [G. Hu and J. A. Krommes, Phys. Plasmas 1, 863 (1994)]. It is demonstrated that the effect of the drift is negligible for the neoclassical transport in tokamaks. In non-axisymmetric systems, however, the tangential magnetic drift substantially changes the dependence of the neoclassical transport on the radial electric field E{sub r}. The peaked behavior of the neoclassical radial fluxes around E{sub r }={sub  }0 observed in conventional local neoclassical transport simulations is removed by taking the tangential magnetic drift into account.

  13. Quantum Transport of Spin-helical Dirac Fermion Topological Surface States in Topological Insulators

    NASA Astrophysics Data System (ADS)

    Chen, Yong P.

    Three-dimensional (3D) topological insulators (TI) are a novel class of electronic materials with topologically-nontrivial band structure such that the bulk is gapped and insulating yet the surface has topologically protected gapless conducting states. Such ``topological surface states'' (TSS) give helically spin polarized Dirac fermions, and offer a promising platform to realize various other novel physics such as topological magnetoelectric effects and Majorana fermions. However, it is often challenging to unambiguously access and study the transport properties of TSS in many practical TI materials due to non-negligible bulk conducting states. I will discuss our recent experiments on high-quality ``intrinsic'' TIs with insulating bulk and surface-dominated conduction that allow us to reveal a number of characteristic transport properties of spin-helical Dirac fermion topological surface states. We have observed, for example, a thickness-independent and surface-dominated conductance (even at room temperature) in exfoliated TI thin films and well-developed ``half-integer'' Dirac fermion quantum Hall effect (QHE) arising from TSS (observed up to 40K); fully-tunable ``two-species'' Dirac fermion QHE and other intriguing states in dual gated devices where both top and bottom surfaces can be independently controlled; current-induced helical spin-polarization detected by spin sensitive transport measurements using magnetic electrodes; and in TI nanoribbons, Shubnikov-de Hass (SdH) oscillations showing gate-tunable Berry phase and ultra-relativistic Dirac mass; and a ``half-integer'' Aharonov-Bohm effect (ABE) unique to the circumferentially quantized spin helical Dirac fermion surface state modes (sub-bands), with a gate-tunable conductance oscillation and alternation between the ``half-integer'' ABE and regular ABE periodic in fermi momentum. Such TIs and related devices may enable promising future applications in spintronics, thermoelectrics and various topological

  14. Predicting uncertainty in sediment transport and landscape evolution - the influence of initial surface conditions

    NASA Astrophysics Data System (ADS)

    Hancock, G. R.; Coulthard, T. J.; Lowry, J. B. C.

    2016-05-01

    Numerical landscape evolution models were initially developed to examine natural catchment hydrology and geomorphology and have become a common tool to examine geomorphic behaviour over a range of time and space scales. These models all use a digital elevation model (DEM) as a representation of the landscape surface and a significant issue is the quality and resolution of this surface. Here we focus on how subtle perturbations or roughness on the DEM surface can produce alternative model results. This study is carried out by randomly varying the elevations of the DEM surface and examining the effect on sediment transport rates and geomorphology for a proposed rehabilitation design for a post-mining landscape using multiple landscape realisations with increasing magnitudes of random changes. We show that an increasing magnitude of random surface variability does not appear to have any significant effect on sediment transport over millennial time scales. However, the random surface variability greatly changes the temporal pattern or delivery of sediment output. A significant finding is that all simulations at the end of the 10,000 year modelled period are geomorphologically similar and present a geomorphological equifinality. However, the individual patterns of erosion and deposition were different for repeat simulations with a different sequence of random perturbations. The alternative positions of random perturbations strongly influence local patterns of hillslope erosion and evolution together with the pattern and behaviour of deposition. The findings demonstrate the complex feedbacks that occur even within a simple modelled system.

  15. Effective reaction rates for transport of particles to heterogeneous reactive (or porous) surfaces under shear

    NASA Astrophysics Data System (ADS)

    Shah, Preyas; Shaqfeh, Eric S. G.

    2015-11-01

    Mass transfer to heterogeneous reactive (or porous) surfaces is common in applications like heterogeneous catalysis, and biological porous media transport like drug delivery. This is modeled as advection-diffusion in a shear flow to an inert surface with first order reactive patches. We study transport of point particles using boundary element simulations. We show that the heterogeneous surface can be replaced with a uniform-flux boundary condition related to the Sherwood number (S), aka, the dimensionless flux to the reactive region. In the dilute limit of reactive regions, large-scale interaction between the reactive patches is important. In the dilute limit of inert regions, [S] grows as the reciprocal of the inert area fraction. Based on the method of resistances and numerical results, we provide correlations for [S] for general reactive surfaces and flow conditions. We model finite sized particles as general spheroids, specifically for biological applications. We do Brownian Dynamics simulations to account for hydrodynamic and steric interactions with the flow field and the domain geometry, and compare to the point particle results. We observe that anisotropic particles gave a higher pore transport flux compared to spherical particles at all flow conditions.

  16. The Influence of Surface Roughness on Volatile Transport on the Moon

    NASA Astrophysics Data System (ADS)

    Prem, Parvathy; Artemieva, Natalia A.; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.

    2015-11-01

    The Moon and other virtually airless bodies provide distinctive environments for the transport and sequestration of water and other volatiles delivered to their surfaces by various sources. Here, we conduct numerical simulations to investigate the delivery of water to the Moon through comet impacts, focusing on the role of small-scale topography (i.e. surface roughness unresolved by orbital measurements) in the migration and cold-trapping of impact-delivered water. The simulated comet impact generates a transient, collisonally thick water vapor atmosphere that surrounds the Moon for at least several lunar days. During this time, some water is captured by permanently shadowed craters (cold traps) near the lunar poles, where temperatures are sufficiently low that volatiles can remain sequestered over geological time scales. Surface temperature is a critical parameter that determines the residence time of a migrating water molecule on the lunar surface, thereby affecting the rapidity of volatile transport though pressure-driven winds, the susceptibility of migrating molecules to photo-destruction, and the large-scale structure of the impact-generated atmosphere - all of which ultimately affect the rate and magnitude of cold-trapping. The roughness of the lunar surface at small scales, the insulating nature of the lunar regolith and the absence of strong convective heat transport lead to sharp surface temperature gradients: surfaces separated by only a few millimeters can have dramatically different temperatures. Significantly, small-scale roughness gives rise to cold temporary and permanent shadows that may affect the rate at which water migrates to permanent cold traps near the lunar poles and to the temporary shelter of the cold lunar night side. Here, we develop a surface roughness/temperature model, consistent with observed bolometric brightness temperature at larger scales, suitable for simulations of volatile transport on a global scale. We will present a

  17. Atmosphere-surface exchange and long-range transport of persistent organic pollutants

    SciTech Connect

    Pul, W.A.J. van; Jaarsveld, J.A. van; Jacobs, C.M.J.

    1996-12-31

    Persistent Organic Pollutants (POPs) are compounds that are resistant to photolytic, biological and chemical degradation. Many POPs are semi-volatile at atmospheric conditions. Because of these characteristics POPs have a atmospheric lifetime of weeks or more and are subject to long-range atmospheric transport. During this transport POPs can be deposited as well as be re-emitted from soil and water bodies. In this study a model for the exchange of POP at the soil and sea surface is presented as well as its application in a long-range atmospheric transport model. The main goal of this study is to simulate the spatial distribution of POP deposition (accumulation) over Europe.

  18. Plutonium-238 observations as a test of modeled transport and surface deposition of meteoric smoke particles

    NASA Astrophysics Data System (ADS)

    Dhomse, S. S.; Saunders, R. W.; Tian, W.; Chipperfield, M. P.; Plane, J. M. C.

    2013-08-01

    are large uncertainties in the transport and surface deposition of upper atmospheric particles used to construct climate proxies. Here we use a 3-D chemistry-climate model (CCM) to simulate the transport and deposition of plutonium-238 oxide nanoparticles formed after the ablation of a power unit in the upper stratosphere (~11°S) in 1964. The model reproduces both the observed hemispheric asymmetry and time scale of Pu-238 deposition. We then use the CCM to investigate the transport of meteoric smoke particles (MSPs) from the upper mesosphere. The strongest MSP deposition is predicted to occur at middle latitudes, providing a significant source of Fe fertilization to the Southern Ocean. The model also predicts substantially more deposition in Greenland than in Antarctica (by a factor of ~15, in agreement with ice core measurements), showing that climate proxy measurements from a limited number of sites must be interpreted with care.

  19. Thermally driven transverse transports and magnetic dynamics on a topological surface capped with a ferromagnet strip

    NASA Astrophysics Data System (ADS)

    Deng, Ming-Xun; Zhong, Ming; Zheng, Shi-Han; Qiu, Jian-Ming; Yang, Mou; Wang, Rui-Qiang

    2016-02-01

    We theoretically study thermally driven transport of the Dirac fermions on the surface of a topological insulator capped with a ferromagnet strip. The generation and manipulation of anomalous Hall and Nernst effects are analyzed, in which the in-plane magnetization of the ferromagnet film is found to take a decisive role. This scenario is distinct from that modulated by Berry phase where the in-plane magnetization is independent. We further discuss the thermal spin-transfer torque as a backaction of the thermoelectric transports on the magnetization and calculate the dynamics of the anomalous Hall and Nernst effects self-consistently. It is found that the magnitude of the long-time steady Hall and Nernst conductance is determined by competition between the magnetic anisotropy and current-induced effective anisotropy. These results open up a possibility of magnetically controlling the transverse thermoelectric transports or thermally manipulating the magnet switching.

  20. Application of surface complexation modeling to the understanding of transportation cask weeping

    SciTech Connect

    Granstaff, V.E.; Chambers, W.B.

    1993-11-01

    A new application for surface complexation modeling is described. These models, which describe chemical equilibria among aqueous and adsorbed species, have typically been used for predicting groundwater transport of contaminants by modeling the natural adsorbents as various metal oxides. We have shown that this type of modeling can also be used to explain stainless steel surface contamination and decontamination mechanisms. Stainless steel transportation casks that are submerged in a spent fuel storage pool at nuclear power stations, can become contaminated with radionuclides such as {sup 137}CS, {sup 134}Cs, and {sup 60}Co. Subsequent release or desorption of these contaminants under varying environmental conditions occasionally results in the phenomenon known as ``cask weeping.`` We have postulated that contaminants in the storage pool adsorb onto the hydrous metal oxide surface of the passivated stainless steel and are subsequently released during transportation, due to varying environmental factors, such as humidity, road salt, dirt, and acid rain. It is well known that 304 stainless steel has a chromium enriched passive surface layer; thus its adsorption behavior should be similar to that of chromium oxide. Presented here are adsorption data for Co{sup +2} on Cr{sup 2}O{sup 3} which simulate the stainless steel surface contamination. These data are interpreted using electrostatic surface complexation models. The FITEQL computer program was used to obtain the electrostatic model constants from the experimental data. Because the concentrations of contaminants in the storage pool are too low to be measured accurately by conventional chemical analysis techniques, MINTEQA2 can be used, with the fitted constants, to extrapolate the equilibria to the low concentrations representative of storage pool water.

  1. Taking advantage of reduced droplet-surface interaction to optimize transport of bioanalytes in digital microfluidics.

    PubMed

    Freire, Sergio L S; Thorne, Nathaniel; Wutkowski, Michael; Dao, Selina

    2014-01-01

    Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of "lab-on-a-chip" platforms. Often, droplet motion relies on the wetting of a surface, directly associated with the application of an electric field; surface interactions, however, make motion dependent on droplet contents, limiting the breadth of applications of the technique. Some alternatives have been presented to minimize this dependence. However, they rely on the addition of extra chemical species to the droplet or its surroundings, which could potentially interact with droplet moieties. Addressing this challenge, our group recently developed Field-DW devices to allow the transport of cells and proteins in DMF, without extra additives. Here, the protocol for device fabrication and operation is provided, including the electronic interface for motion control. We also continue the studies with the devices, showing that multicellular, relatively large, model organisms can also be transported, arguably unaffected by the electric fields required for device operation. PMID:25407533

  2. Ozone Transport Aloft Drives Surface Ozone Maxima Across the Mojave Desert

    NASA Astrophysics Data System (ADS)

    VanCuren, R. A.

    2014-12-01

    A persistent layer of polluted air in the lower free troposphere over the Mojave Desert (California and Nevada) drives spring and summer surface ozone maxima as deep afternoon mixing delivers ozone and ozone precursors to surface measurement sites 200 km or more downwind of the mountains that separate the deserts from the heavily populated coastal areas of California. Pollutants in this elevated layer derive from California source regions (the Los Angeles megacity region and the intensive agricultural region of the San Joaquin Valley), and from long-range transport from Asia. Recognition of this poorly studied persistent layer explains and expands the significance of previously published reports of ozone and other pollutants observed in and over the Mojave Desert, resolves an apparent paradox in the timing of ozone peaks due to transport from the upwind basins, and provides a new perspective on the long-range downwind impacts of megacity pollution plumes.

  3. Surface trajectories of oil transport along the Northern Coastline of the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Dietrich, J. C.; Trahan, C. J.; Howard, M. T.; Fleming, J. G.; Weaver, R. J.; Tanaka, S.; Yu, L.; Luettich, R. A.; Dawson, C. N.; Westerink, J. J.; Wells, G.; Lu, A.; Vega, K.; Kubach, A.; Dresback, K. M.; Kolar, R. L.; Kaiser, C.; Twilley, R. R.

    2012-06-01

    After the destruction of the Deepwater Horizon drilling platform during the spring of 2010, the northern Gulf of Mexico was threatened by an oil spill from the Macondo well. Emergency responders were concerned about oil transport in the nearshore, where it threatened immediately the fishing waters and coastline from Louisiana to Florida. In this region, oil movement was influenced by a continental shelf with varying width, the protruding Mississippi River delta, the marshes and bayou of southern Louisiana, and the shallow sounds and barrier islands that protect the coastline. Transport forecasts require physics-based computational models and high-resolution meshes that represent the circulation in deep water, on the continental shelf, and within the complex nearshore environment. This work applies the coupled SWAN+ADCIRC model on a high-resolution computational mesh to simulate the current velocity field on the continental shelf, nearshore and marsh areas during the time that oil was visible on the surface of the Gulf. The SWAN+ADCIRC simulations account for the influence of tides, riverine discharge, winds and wind-driven waves. A highly efficient Lagrangian particle transport model is employed to simulate the surface trajectories of the oil. The transport model accounts for dispersion and advection by wind and currents. Transport is evaluated using 2-week long sequences of satellite images. During both periods, the SWAN+ADCIRC current fields alone appeared to be more successful moving the oil than when direct wind forcing was included. In addition, hypothetical oil transport is considered during two hurricane scenarios. Had a hurricane significantly impacted the northern Gulf while the spill was active, depending on the track of the storm relative to the spill location, oil would have moved farther into the marshes of southern Louisiana or farther along the shelf toward Texas than actually occurred during the spill.

  4. Investigation of dust transport on the lunar surface in laboratory plasmas

    NASA Astrophysics Data System (ADS)

    Wang, X.; Horanyi, M.; Robertson, S. H.

    2009-12-01

    There has been much evidence indicating dust levitation and transport on or near the lunar surface. Dust mobilization is likely to be caused by electrostatic forces acting on small lunar dust particles that are charged by UV radiation and solar wind plasma. To learn about the basic physical process, we investigated the dynamics of dust grains on a conducting surface in laboratory plasmas. The first experiment was conducted with a dust pile (JSC-Mars-1) sitting on a negatively biased surface in plasma. The dust pile spread and formed a diffusing dust ring. Dust hopping was confirmed by noticing grains on protruding surfaces. The electrostatic potential distributions measured above the dust pile show an outward pointing electrostatic force and a non-monotonic sheath above the dust pile, indicating a localized upward electrostatic force responsible for lifting dust off the surface. The second experiment was conducted with a dust pile sitting on an electrically floating conducting surface in plasma with an electron beam. Potential measurements show a horizontal electric field at the dust/surface boundary and an enhanced vertical electric field in the sheath above the dust pile when the electron beam current is set to be comparable to the Bohm ion current. Secondary electrons emitted from the surfaces play an important role in this case.

  5. Surface plasmon enhanced quantum transport in a hybrid metal nanoparticle array

    NASA Astrophysics Data System (ADS)

    Sun, Lin; Nan, Yali; Xu, Shang; Zhang, Sishi; Han, Min

    2014-07-01

    Hybrid Pd-Ag nanoparticle arrays composed of randomly distributed Pd nanoparticles in dense packing and a small number of dispersed Ag nanoparticles were fabricated with controlled coverage. Photo-enhanced conductance was observed in the nanoparticle arrays. Largest enhancement, which can be higher than 20 folds, was obtained with 450 nm light illumination. This wavelength was found to correlate with the surface plasmon resonance of the Ag nanoparticles. Electron transport measurements showed there were significant Coulomb blockade in the nanoparticle arrays and the blockade could be overcome with the surface plasmon enhanced local field of Ag nanoparticles induced by light illumination.

  6. Transport and Attenuation of Particles of Different Density and Surface Charge: A Karst Aquifer Field Study.

    PubMed

    Schiperski, Ferry; Zirlewagen, Johannes; Scheytt, Traugott

    2016-08-01

    Although karst aquifers are far more susceptible to contamination than porous aquifers, with the transport of particulate matter being an important factor, little is known about the attenuation of solutes within karst aquifers and even less about the attenuation of particulate matter. These in situ investigations have therefore aimed to systematically identify the processes that influence the transport and attenuation of particles within a karst aquifer through multitracer testing, using four different types of 1 μm fluorescent particles and the fluorescent dye uranine. Each of the types of particles used were detected at the observed spring, which drains the investigated aquifer. However, the transport behavior varied significantly between the various particles and the uranine dye, with the breakthrough of particles occurring slightly earlier than that of uranine. Attenuation was determined from the tracer recovery and attributed to filtration processes. These processes were affected by the hydrophobicity and surface charge of the particles. Carboxylated polystyrene particles with a density and surface charge comparable to pathogenic microorganisms were found to be mobile in groundwater over a distance of about 3 km. No attenuation was observed for plain silica particles. Particles with these characteristics thus pose a major threat to karst spring water as they might occur as contaminants themselves or facilitate the transport of other contaminants. PMID:27348254

  7. Transportation-Driven Mars Surface Operations Supporting an Evolvable Mars Campaign

    NASA Technical Reports Server (NTRS)

    Toups, Larry; Brown, Kendall; Hoffman, Stephen J.

    2015-01-01

    This paper describes the results of a study evaluating options for supporting a series of human missions to a single Mars surface destination. In this scenario the infrastructure emplaced during previous visits to this site is leveraged in following missions. The goal of this single site approach to Mars surface infrastructure is to enable "Steady State" operations by at least 4 crew for up to 500 sols at this site. These characteristics, along with the transportation system used to deliver crew and equipment to and from Mars, are collectively known as the Evolvable Mars Campaign (EMC). Information in this paper is presented in the sequence in which it was accomplished. First, a logical buildup sequence of surface infrastructure was developed to achieve the desired "Steady State" operations on the Mars surface. This was based on a concept of operations that met objectives of the EMC. Second, infrastructure capabilities were identified to carry out this concept of operations. Third, systems (in the form of conceptual elements) were identified to provide these capabilities. This included top-level mass, power and volume estimates for these elements. Fourth, the results were then used in analyses to evaluate three options (18t, 27t, and 40t landed mass) of Mars Lander delivery capability to the surface. Finally, Mars arrival mass estimates were generated based upon the entry, descent, and landing requirements for inclusion in separate assessments of in-space transportation capabilities for the EMC.

  8. Occurrence and Distribution of Agricultural Pesticides and Transport Modeling in Surface and Subsurface Environments

    NASA Astrophysics Data System (ADS)

    Chu, X.; Marino, M. A.

    2007-12-01

    The use of a variety of pesticides has increased dramatically during the past decades to improve agricultural efficiency and productivity. However, these agricultural chemicals are often washed to surface waters by runoff and leached through the vadose zone to ground water, thereby polluting waters and threatening human health as well as aquatic and terrestrial ecosystems. It is of particular importance to develop effective modeling tools to assess the induced nonpoint source pollution, to regulate the use of agricultural pesticides, and to circumvent further deterioration in water quality. Different physically-based pesticide transport models, ranging from simple analytical models to semidiscrete and more rigorous numerical models, are discussed. In particular, the effects of use of pesticides on their occurrence and distribution in surface and subsurface environments are examined in this study. A windows-based integrated pesticide transport model (IPTM) is used to simulate three-phase pesticide transport and transformation and quantify spatial and temporal distributions in a coupled canopy-soil system as well as pesticide loading potential to the adjacent surface water through surface runoff and erosion. Five different pesticides (diazinon, 2,4-D acid, DBCP, simazine, and lindane) are examined. It is found that occurrence and distribution of pesticides in the environment are closely related to their use and determined by a series of pesticide transport and transformation processes. The occurrence and use of pesticides follow extremely complex and dynamic patterns that are affected by numerous factors related to their use and properties, hydrology, and agricultural activities. It is also found that changes in pesticide use (application quantity, frequency, timing, and method) may result in distinct environmental fate of pesticides in terms of their occurrence extent as well as spatial and temporal distributions.

  9. Zeeman effect on surface electron transport in topological insulator Bi2Se3 nanoribbons

    NASA Astrophysics Data System (ADS)

    Wang, Li-Xian; Yan, Yuan; Zhang, Liang; Liao, Zhi-Min; Wu, Han-Chun; Yu, Da-Peng

    2015-10-01

    Topological insulators have exotic surface states that are massless Dirac fermions, manifesting special magnetotransport properties, such as the Aharonov-Bohm effect, Shubnikov-de Haas oscillations, and weak antilocalization effects. In the surface Dirac cone, the band structures are typically closely related to the p-orbitals and possess helical orbital texture. Here we report on the tunability of the transport properties via the interaction between the magnetic field and the spin-orbital angular momentum of the surface states in individual Bi2Se3 nanoribbons. Because the surface states have a large Landé factor and helical spin-orbital texture, the in-plane magnetic field induced Zeeman energy will result in the deformation of the Dirac cone, which gives rise to spin polarization of the surface states. The spin-dependent scattering of the conducting electrons on the existing local magnetic moments produces a giant negative magnetoresistance. The negative magnetoresistance is robust with a ratio of -20% at 2 K and -0.5% at 300 K under 14 T. The results are valuable for possible orbital-electronics based on topological insulators.Topological insulators have exotic surface states that are massless Dirac fermions, manifesting special magnetotransport properties, such as the Aharonov-Bohm effect, Shubnikov-de Haas oscillations, and weak antilocalization effects. In the surface Dirac cone, the band structures are typically closely related to the p-orbitals and possess helical orbital texture. Here we report on the tunability of the transport properties via the interaction between the magnetic field and the spin-orbital angular momentum of the surface states in individual Bi2Se3 nanoribbons. Because the surface states have a large Landé factor and helical spin-orbital texture, the in-plane magnetic field induced Zeeman energy will result in the deformation of the Dirac cone, which gives rise to spin polarization of the surface states. The spin-dependent scattering of

  10. Lunar Surface Charging and Dust Transport during the Passage of a Coronal Mass Ejection

    NASA Astrophysics Data System (ADS)

    Stubbs, T. J.; Farrell, W. M.; Zimmerman, M. I.; Collier, M. R.; Glenar, D. A.; Halekas, J. S.

    2012-12-01

    The surface of the Moon is directly exposed to the surrounding space plasma and energetic particle (> 10 keV) populations, as well as solar ultraviolet and soft X-ray radiation on the dayside, which result in it becoming electrically charged. Under certain conditions it is possible that the resulting near-surface electric fields could have a significant influence on the transport of charged lunar dust (< ~10 microns in radius). These processes are anticipated to be most extreme at various periods during the passage of a coronal mass ejection (CME). Such an event is studied here using solar wind observations from April/May 1998 as part of the Solar Storm-Lunar Atmosphere Modeling (SSLAM) Lunar Extreme Workshop (LEW) to investigate the entire lunar surface-exosphere-space plasma system during a space weather event at the Moon. This workshop was organized by the NASA Lunar Science Institute (NLSI) Dynamic Response of the Environment At the Moon (DREAM) team. In this study, surface charging models are used to predict surface potentials and electric fields during the April/May 1998 CME event, as well as assess the importance of the different current sources and the implications for electrostatic dust transport. As expected, at the subsolar point it is found that surface charging is dominated by photoemission currents, although secondary electron emission due to plasma electrons can often have a noticeable influence. Meanwhile at the terminator, surface charging is dominated by plasma electrons and the associated secondary electron emission. At certain times the secondary electron emission is predicted to be sufficiently intense to be able to charge the shadowed surface positive. In addition, it is found that intervals with high fluxes of particles with energies > 10 keV could be very important when their current contribution exceeds that of the plasma ions. The location of the transition from positive to negative surface charging on the lunar dayside, also referred to

  11. Modeling Fate and Transport of Cryptosporidium Parvum Oocysts in Overland and Near- surface Flow

    NASA Astrophysics Data System (ADS)

    Bhattarai, R.; Kalita, P.; Kuhlenschmidt, M. S.

    2008-12-01

    Cryptosporidium parvum is a manure-borne protozoan parasite which is common in the environment. It has been recognized as an important microbial contaminant of water and can cause infection and diarrhea in many mammalian hosts, including humans. The laboratory experiments carried out have demonstrated that recovery of C. parvum oocysts was significantly affected by climatic and surface conditions like slope, rainfall and surface cover. The objective of this study is to develop a model for simulating transport of C. parvum oocysts in overland and near-surface flow. Modeling can help understanding oocysts transport pathways. Accordingly, best management practices (BMP) can be developed. Transport of oocysts in overland flow can be simulated mathematically by including terms for the concentration of the oocysts in the liquid phase (in suspension or free-floating) and the solid phase (adsorbed to the fine solid particles like clay). Oocysts adsorption, advection and decay processes are considered. These processes are solved using numerical technique to predict spatial and temporal changes in oocyst concentrations in solid and liquid phases. The model results are compared with experimental data to validate the model outcome. The model output reproduced observed recovery kinetics for 1.5% slope but not for higher slopes (3.0% and 4.5%).

  12. Specific spacecraft evaluation: Special report. [charged particle transport from a mercury ion thruster to spacecraft surfaces

    NASA Technical Reports Server (NTRS)

    Sellen, J. M., Jr.

    1978-01-01

    Charged and neutral particle transport from an 8 cm mercury ion thruster to the surfaces of the P 80-1 spacecraft and to the Teal Ruby sensor and the ECOM-501 sensor of that spacecraft were investigated. Laboratory measurements and analyses were used to examine line-of-sight and nonline-of sight particle transport modes. The recirculation of Hg(+) ions in the magnetic field of the earth was analyzed for spacecraft velocity and Earth magnetic field vector configurations which are expected to occur in near Earth, circular, high inclination orbits. For these magnetic field and orbit conditions and for expected ion release distribution functions, in both angles and energies, the recirculation/re-interception of ions on spacecraft surfaces was evaluated. The refraction of weakly energetic ions in the electric fields of the thruster plasma plume and in the electric fields between this plasma plume and the material boundaries of the thruster, the thruster sputter shield, and the various spacecraft surfaces were examined. The neutral particle transport modes of interest were identified as sputtered metal atoms from the thruster beam shield. Results, conclusions, and future considerations are presented.

  13. 76 FR 64426 - Notice of Railroad-Shipper Transportation Advisory Council Vacancy

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-18

    ... TRANSPORTATION Surface Transportation Board Notice of Railroad-Shipper Transportation Advisory Council Vacancy AGENCY: Surface Transportation Board (Board). ACTION: Notice of vacancies on the Railroad-Shipper... of 7 vacancies on RSTAC for: (1) Representatives of 3 small shippers; (2) representatives of 2...

  14. Preferential targeting of human erythrocytes infected with the malaria parasite Plasmodium falciparumvia hexose transporter surface proteins.

    PubMed

    Heikham, Kajal Devi; Gupta, Ankit; Kumar, Ambrish; Singh, Chandan; Saxena, Juhi; Srivastava, Kumkum; Puri, Sunil K; Dwivedi, Anil K; Habib, Saman; Misra, Amit

    2015-04-10

    Glucose uptake by Plasmodium-infected erythrocytes (RBC) is higher compared to uninfected RBC. Glucose is transported across the cell membrane by transporter proteins. Particles of median size 146.3±18.7 nm, containing anti-malarial agents in corn starch were prepared for investigating: (a) whether the glucose moiety in starch targets RBC via hexose transporter(s), (b) whether there are differences in the extent of targeting to uninfected RBC versus infected RBC (iRBC) in view of higher cell surface density of these proteins on iRBC and (c) whether targeting provides enhanced efficacy against P. falciparum in comparison to drugs in solution. Binding of these particles to RBC was target-specific, since it could be blocked by phloretin, an inhibitor of glucose transporters (GLUT), or competed out in a dose-dependent manner with d-glucose in a flow cytometry assay. Significant (P=0.048, t-test) differences in extent of targeting to iRBC versus RBC were observed in flow cytometry. CDRI 97/63 incorporated in particles was 63% more efficacious than its solution at 250 ng/ml, while quinine was 20% more efficacious at 6.25 ng/ml in a SYBR Green incorporation assay. Preferential targeting of iRBC using an inexpensive excipient promises advantages in terms of dose reduction and toxicity alleviation. PMID:25666024

  15. The Australian methane budget: Interpreting surface and train-borne measurements using a chemistry transport model

    NASA Astrophysics Data System (ADS)

    Fraser, Annemarie; Chan Miller, Christopher; Palmer, Paul I.; Deutscher, Nicholas M.; Jones, Nicholas B.; Griffith, David W. T.

    2011-10-01

    We investigate the Australian methane budget from 2005-2008 using the GEOS-Chem 3D chemistry transport model, focusing on the relative contribution of emissions from different sectors and the influence of long-range transport. To evaluate the model, we use in situ surface measurements of methane, methane dry air column average (XCH4) from ground-based Fourier transform spectrometers (FTSs), and train-borne surface concentration measurements from an in situ FTS along the north-south continental transect. We use gravity anomaly data from Gravity Recovery and Climate Experiment to describe the spatial and temporal distribution of wetland emissions and scale it to a prior emission estimate, which better describes observed atmospheric methane variability at tropical latitudes. The clean air sites of Cape Ferguson and Cape Grim are the least affected by local emissions, while Wollongong, located in the populated southeast with regional coal mining, samples the most locally polluted air masses (2.5% of the total air mass versus <1% at other sites). Averaged annually, the largest single source above background of methane at Darwin is long-range transport, mainly from Southeast Asia, accounting for ˜25% of the change in surface concentration above background. At Cape Ferguson and Cape Grim, emissions from ruminant animals are the largest source of methane above background, at approximately 20% and 30%, respectively, of the surface concentration. At Wollongong, emissions from coal mining are the largest source above background representing 60% of the surface concentration. The train data provide an effective way of observing transitions between urban, desert, and tropical landscapes.

  16. New York state high-speed surface transportation study: Final report

    SciTech Connect

    Not Available

    1994-08-01

    In 1990, New York State Governor Mario M. Cuomo created an interagency task force under the leadership of Lt. Governor Stan Lundine to investigate the potential of high speed ground transportation (HSGT) systems. Building on information from previous agency activities, including consultant efforts contracted by the New York State Energy Research and Development Authority (NYSERDA), the New York State Thruway Authority (NYSTA), and in-house analyses performed by New York State Department of Transportation (NYSDOT), the task force focused on the corridor between New York City and the Niagara Frontier. In December 1991, NYSERDA issued a contract for a study of high speed ground transportation options for New York State. The study`s objective was to assess potential rights-of-way, ridership, energy and environmental impacts, economic benefits, capital, operating, and maintenance costs, and financial viability of HSGT systems. This study builds upon and supplements previous and on-going HSGT activities conducted by the members of the interagency task force. These activities include: Maglev Technical and Economic Feasibility Study (NYSERDA); Maglev Demonstration Site Investigation (NYSTA); and New York/Massachusetts High Speed Ground Transportation Study (NYSDOT). This study is intended to verify and refine previous information and analyses and provide supplemental information and insights to be used in determining if additional investigation and activities involving HSGT are desirable for New York State. This study evaluates HSGT technologies capable of speeds significantly higher than those achieved with the present rail system. Three HSGT categories are used in this study: incremental rail improvement, very high-speed rail, and Maglev.

  17. Arsenic transport between surface and groundwater in a moderately reducing zone: Geochemical approach

    NASA Astrophysics Data System (ADS)

    Khaska, Mahmoud; Le Gal La Salle, Corinne; Verdoux, Patrick

    2015-04-01

    Arsenic contamination represents a major risk to human health as one of the most prominent environmental causes of cancer mortality. Mining activities, particularly those involving arsenic rich ores have an impact on the environment and on human health that may persist for many decades after mine closure. The relationships between As released from alluvial aquifer in the vicinity of the sulfide-rich mine dumps was demonstrated with geochemical and isotopic tracers (major and traces elements, 87Sr/86Sr, 18O, 2H). Strontium isotopes were used to trace the transport of As downstream from a As rich tailing dam. Increasing As and Fe concentrations in surface water are explained by As release associated with alluvial groundwater discharge to the stream. This process occurs in a moderately reduced section of the stream downgradient from the sulfide-rich tailing dam. High As, total Fe and low Eh in groundwater confirm the discharge of alluvial groundwater and explain its impact on surface water. Transport of As between surface and groundwater can be described as follows: 1- Subsurface moderately reducing conditions prevail in groundwater downgradient from the tailing dams. This suggests a flux of reduced water from sulfide-rich tailing dams which is characterized by its high As and Fe content resulting from the reduction of Fe-sulfides. 2- Upon mixing with surface water, oxidizing conditions prevails and precipitate as Fe hydroxide on the stream bed. As and Sr subsequently adsorbed on the Fe -oxyhydroxide surface. This process contributes to the immobilization of As in surface water. Remaining dissolved As in surface water can be re-introduced in alluvial groundwater downstream of the reducing zone.

  18. A large-scale methane model by incorporating the surface water transport

    NASA Astrophysics Data System (ADS)

    Lu, Xiaoliang; Zhuang, Qianlai; Liu, Yaling; Zhou, Yuyu; Aghakouchak, Amir

    2016-06-01

    The effect of surface water movement on methane emissions is not explicitly considered in most of the current methane models. In this study, a surface water routing was coupled into our previously developed large-scale methane model. The revised methane model was then used to simulate global methane emissions during 2006-2010. From our simulations, the global mean annual maximum inundation extent is 10.6 ± 1.9 km2 and the methane emission is 297 ± 11 Tg C/yr in the study period. In comparison to the currently used TOPMODEL-based approach, we found that the incorporation of surface water routing leads to 24.7% increase in the annual maximum inundation extent and 30.8% increase in the methane emissions at the global scale for the study period, respectively. The effect of surface water transport on methane emissions varies in different regions: (1) the largest difference occurs in flat and moist regions, such as Eastern China; (2) high-latitude regions, hot spots in methane emissions, show a small increase in both inundation extent and methane emissions with the consideration of surface water movement; and (3) in arid regions, the new model yields significantly larger maximum flooded areas and a relatively small increase in the methane emissions. Although surface water is a small component in the terrestrial water balance, it plays an important role in determining inundation extent and methane emissions, especially in flat regions. This study indicates that future quantification of methane emissions shall consider the effects of surface water transport.

  19. Serotonin-induced down-regulation of cell surface serotonin transporter

    PubMed Central

    Jørgensen, Trine Nygaard; Christensen, Peter Møller; Gether, Ulrik

    2014-01-01

    The serotonin transporter (SERT) terminates serotonergic signaling and enables refilling of synaptic vesicles by mediating reuptake of serotonin (5-HT) released into the synaptic cleft. The molecular and cellular mechanisms controlling SERT activity and surface expression are not fully understood. Here we demonstrate that the substrate 5-HT itself causes acute down-regulation of SERT cell surface expression. To assess surface SERT expression by ELISA, we used a SERT variant (TacSERT) where the N-terminus of SERT was fused to the intracellular tail of the extracellularly FLAG-tagged single-membrane spanning protein Tac. In stably transfected HEK293 cells, 5-HT caused a dose-dependent reduction in TacSERT surface signal with an EC50 value equivalent to the Km value observed for 5-HT uptake. The 5-HT-induced reduction in surface signal reached maximum within 40-60 min and was blocked by the selective SERT inhibitor S-citalopram. 5-HT-induced reduction in SERT expression was further supported by surface biotinylation experiments showing 5-HT-induced reduction in wild type SERT plasma membrane levels. Moreover, preincubation with 5-HT lowered the Vmax for 5-HT uptake in cultured raphe serotonergic neurons, indicting that endogenous cell-surface resident SERT likewise is down-regulated in the presence of substrate. PMID:24462583

  20. Effects of different surfaces on the transport and deposition of ruthenium oxides in high temperature air

    NASA Astrophysics Data System (ADS)

    Vér, N.; Matus, L.; Pintér, A.; Osán, J.; Hózer, Z.

    2012-01-01

    In order to understand the behaviour of ruthenium oxides in the reactor coolant system during an air ingress accident, new tests were performed in the frame of the RUSET (RUthenium Separate Effect Test) experimental program. These aimed to ascertain the effects of different surfaces (quartz, stainless steel (SS), zirconium alloy, alumina, oxidised metal, and surfaces with Mo or Cs deposits) on the transport and decomposition of ruthenium oxides in air stream along the temperature gradient zone (1100-100 °C). The results demonstrated that the heterogeneous phase decomposition of RuO 3 and RuO 4 to RuO 2 is catalysed more efficiently by the quartz surface than by the SS or alumina surfaces. The presence of MoO 3 layers decreased the RuO x precipitation extent on all investigated surfaces. The trapping effect of Cs deposit on Ru in the temperature gradient zone was proved in the case of the SS surface. On the contrary, presence of Cs precipitate on alumina and especially on quartz surfaces was found to decrease their catalytic effect on the decomposition of ruthenium oxides, and thus increased the RuO 4 concentration in the outlet air. Similarly to the effect observed for Cs deposition, the presence of other fission products in the evaporation area (at 1100 °C) decreased the partial pressure of RuO 4 in the outlet air at the SS surface and increased it at quartz and alumina surfaces. When zirconium (E110) cladding material was placed in the temperature gradient zone, no Ru transmittance occurred until the high temperature end of the zirconium tube was completely oxidised. After the intense oxidation of E110, Ru release occurred only in the presence of other fission product species. Pre-oxidation of SS surfaces in steam had no significant effect on the Ru passage.

  1. Radioxenon Production and Transport from an Underground Nuclear Detonation to Ground Surface

    NASA Astrophysics Data System (ADS)

    Sun, Yunwei; Carrigan, Charles R.; Hao, Yue

    2015-02-01

    Radioxenon isotopes are considered as possible indicators for detecting and discriminating underground nuclear explosions. To monitor and sample the release of radioxenon isotopes, both independent and chain-reaction yields need to be considered together with multiphase transport in geological systems from the detonation point to the ground surface. For the sake of simplicity, modeling of radioxenon isotopic radioactivities has typically been focused either on chain reactions in a batch reactor without considering multiphase transport or on radionuclide transport with simplified reactions. Although numerical methods are available for integrating coupled differential equations of complex decay networks, the stiffness of ordinary differential equations due to greatly differing decay rates may require substantial additional effort to obtain solutions for the fully coupled system. For this reason, closed-form solutions for sequential reactions and numerical solutions for multiparent converging and multidaughter branching reactions were previously developed and used to simulate xenon isotopic radioactivities in the batch reactor mode. In this paper, we develop a fully coupled numerical model, which involves tracking 24 components (i.e., 22 radionuclide components plus air and water) in two phases to enhance model predictability of simultaneously simulating xenon isotopic transport and fully coupled chain reactions. To validate the numerical model and verify the corresponding computer code, we derived closed-form solutions for first-order xenon reactions in a batch reactor mode and for single-gas phase transport coupled with the xenon reactions in a one-dimensional column. Finally, cylindrical 3-D simulations of two-phase flow within a dual permeability fracture-matrix medium, simulating the geohydrologic regime of an underground nuclear explosion, indicate the existence of both a strong temporal and spatial dependence of xenon isotopic ratios sampled at the surface. In

  2. Atmospheric and Surface Contributions to Planetary Albedo and their Relationship to the Total Meridional Energy Transport

    NASA Astrophysics Data System (ADS)

    Donohoe, A.; Battisti, D. S.

    2010-12-01

    The meridional distribution of incident solar radiation and planetary albedo both contribute to the equator-to-pole gradient in absorbed solar radiation (ASR) in the observed climate system. While the former component is determined by the Earth-Sun geometry and composes 60% of the equator-to-pole gradient in ASR, the latter component makes a significant (40%) contribution to the ASR gradient and is potentially a function of climate state due to its dependence on both atmospheric and surface albedo. In turn, the equator-to-pole gradient in planetary albedo is found to be primarily (86% -89%) dictated by atmospheric albedo with meridional gradients in surface albedo playing a much smaller role in forcing the climate system on the equator-to-pole scale. Simulations of the pre-industrial climate system using the CMIP3 coupled models show large differences in the equator-to-pole gradient in planetary albedo which are mainly due to differences in the simulated cloud distribution, with surface processes playing a much smaller role. The inter-model spread in total meridional heat transport is also primarily (85% of the inter-model spread) due to differences in the simulated cloud distribution. Further model simulations demonstrate that the surface albedo changes associated with moving from the present climate to an ice free climate have a small effect on the equator-to-pole gradient of ASR as compared to the uncertainty in simulated cloud distributions, and hence a small effect on the meridional heat transport.

  3. Application of pneumatic lift and control surface technology to advanced transport aircraft

    NASA Technical Reports Server (NTRS)

    Englar, Robert J.

    1996-01-01

    The application of pneumatic (blown) aerodynamic technology to both the lifting and the control surfaces of advanced transport aircraft can provide revolutionary changes in the performance and operation of these vehicles, ranging in speed regime from Advanced Subsonic Transports to the High Speed Civil Transport, and beyond. This technology, much of it based on the Circulation Control Wing blown concepts, can provide aerodynamic force augmentations of 80 to 100 (i.e., return of 80-100 pounds of force per pound of input momentum from the blowing jet). This can be achieved without use of external mechanical surfaces. Clever application of this technology can provide no-moving-part lifting surfaces (wings/tails) integrated into the control system to greatly simplify aircraft designs while improving their aerodynamic performance. Lift/drag ratio may be pneumatically tailored to fit the current phase of the flight, and takeoff/landing performance can be greatly improved by reducing ground roll distances and liftoff/touchdown speeds. Alternatively, great increases in liftoff weights and payloads are possible, as are great reductions in wing and tail planform size, resulting in optimized cruise wing designs. Furthermore, lift generation independent of angle of attack provides much promise for increased safety of flight in the severe updrafts/downdrafts of microbursts and windshears, which is further augmented by the ability to sustain flight at greatly reduced airspeeds. Load-tailored blown wings can also reduce tip vorticity during highlift operations and the resulting vortex wake hazards near terminal areas. Reduced noise may also be possible as these jets can be made to operate at low pressures. The planned presentation will support the above statements through discussions of recent experimental and numerical (CFD) research and development of these advanced blown aerodynamic surfaces, portions of which have been conducted for NASA. Also to be presented will be

  4. Surface reconstructions and transport of epitaxial PtLuSb (001) thin films grown by MBE

    NASA Astrophysics Data System (ADS)

    Patel, Sahil J.; Logan, John A.; Harrington, Sean D.; Schultz, Brian D.; Palmstrøm, Chris J.

    2016-02-01

    This work presents the surface reconstructions and transport properties of the topological insulator PtLuSb grown on Al0.1In0.9Sb/GaAs (001). Two stable surface reconstructions, (1×3) and c(2×2), were observed on PtLuSb (001) surfaces. Antimony-dimerization was determined to be the nature of the (1×3) surface reconstruction as evidenced by chemical binding energy shifts in the antimony 4d core-level for surface bonding components. The two surface reconstructions were studied as a function of Sb4 overpressure and substrate temperature to create a reconstruction phase diagram. From this reconstruction phase diagram, a growth window from 320 °C to 380 °C using an antimony overpressure was identified. Within this window, the highest quality films were grown at a growth temperature of 380 °C. These films exhibited lower p-type carrier concentrations as well as relatively high hole mobilities.

  5. Transport and dispersion of pollutants in surface impoundments: a finite element model

    SciTech Connect

    Yeh, G.T.

    1980-07-01

    A surface impoundment model in finite element (SIMFE) is presented to enable the simulation of flow circulations and pollutant transport and dispersion in natural or artificial lakes, reservoirs or ponds with any number of islands. This surface impoundment model consists of two sub-models: hydrodynamic and pollutant transport models. Both submodels are simulated by the finite element method. While the hydrodynamic model is solved by the standard Galerkin finite element scheme, the pollutant transport model can be solved by any of the twelve optional finite element schemes built in the program. Theoretical approximations and the numerical algorithm of SIMFE are described. Detail instruction of the application are given and listing of FORTRAN IV source program are provided. Two sample problems are given. One is for an idealized system with a known solution to show the accuracy and partial validation of the models. The other is applied to Prairie Island for a set of hypothetical input data, typifying a class of problems to which SIMFE may be applied.

  6. Gate-tuned normal and superconducting transport at the surface of a topological insulator

    PubMed Central

    Sacépé, Benjamin; Oostinga, Jeroen B.; Li, Jian; Ubaldini, Alberto; Couto, Nuno J.G.; Giannini, Enrico; Morpurgo, Alberto F.

    2011-01-01

    Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi2Se3 single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulators. PMID:22146394

  7. Gate-tuned normal and superconducting transport at the surface of a topological insulator.

    PubMed

    Sacépé, Benjamin; Oostinga, Jeroen B; Li, Jian; Ubaldini, Alberto; Couto, Nuno J G; Giannini, Enrico; Morpurgo, Alberto F

    2011-01-01

    Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi(2)Se(3) single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulators. PMID:22146394

  8. Fate and transport of glyphosate and aminomethylphosphonic acid in surface waters of agricultural basins

    USGS Publications Warehouse

    Coupe, R.H.; Kalkhoff, S.J.; Capel, P.D.; Gregoire, C.

    2012-01-01

    Background: Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops and is heavily used on soybeans, corn and cotton. Glyphosate is used in almost all agricultural areas of the United States, and the agricultural use of glyphosate has increased from less than 10 000 Mg in 1992 to more than 80 000 Mg in 2007. The greatest intensity of glyphosate use is in the midwestern United States, where applications are predominantly to genetically modified corn and soybeans. In spite of the increase in usage across the United States, the characterization of the transport of glyphosate and its degradate aminomethylphosphonic acid (AMPA) on a watershed scale is lacking. Results: Glyphosate and AMPA were frequently detected in the surface waters of four agricultural basins. The frequency and magnitude of detections varied across basins, and the load, as a percentage of use, ranged from 0.009 to 0.86% and could be related to three general characteristics: source strength, rainfall runoff and flow route. Conclusions: Glyphosate use in a watershed results in some occurrence in surface water; however, the watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff and a flow route that does not include transport through the soil. ?? 2011 Society of Chemical Industry.

  9. The Fate and Transport of Glyphosate and AMPA into Surface Waters of Agricultural Watersheds

    NASA Astrophysics Data System (ADS)

    Coupe, R.; Kalkhoff, S.; Capel, P.; Gregoire, C.

    2010-12-01

    Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops, but is particularly heavily used on crops which are genetically modified to be glyphosate tolerant: predominately soybeans, corn, potatoes, and cotton. Glyphosate is used extensively in almost all agricultural areas of the United States, and annual application has increased from less than 10,000 Mg in 1992 to more than 80,000 Mg in 2007. The greatest areal use is in the Midwest where glyphosate is applied on genetically modified corn and soybeans. Although use is increasing, the characterization of glyphosate transport on the watershed scale is lacking. Glyphosate, and its degradate AMPA [aminomethylphosphoric acid], was frequently detected in the surface waters of four agricultural watersheds. The load as a percent of use of glyphosate ranged from 0.009 to 0.86 percent and can be related to three factors: source strength, hydrology, and flowpath. Glyphosate use within a watershed results in some occurrence in surface water at the part per billion level; however watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff, and a flowpath that does not include transport through the soil.

  10. Reading charge transport from the spin dynamics on the surface of a topological insulator.

    PubMed

    Liu, Xin; Sinova, Jairo

    2013-10-18

    Resolving the conductance of the topological surface states (TSSs) from the bulk contribution has been a great challenge for studying the transport properties of topological insulators. By developing a nonperturbative diffusion equation that describes fully the spin-charge dynamics in the strong spin-orbit coupling regime, we present a proposal to read the charge transport information of TSSs from its spin dynamics which can be isolated from the bulk contribution by the time-resolved second harmonic generation pump-probe measurement. We demonstrate the qualitatively different Dyaknov-Perel spin relaxation behavior between the TSSs and the two-dimensional spin-orbit coupling electron gas. The decay time of both in-plane and out-of-plane spin polarization is naturally proved to be identical to the charge transport time. The out-of-plane spin dynamics is shown to be in the experimentally reachable regime of the femtosecond pump-probe spectroscopy and thereby we suggest experiments to detect the charge transport properties of the TSSs from their unique spin dynamics. PMID:24182290

  11. The effects of surface aging on nanoparticle fate and transport in natural and engineered porous media

    NASA Astrophysics Data System (ADS)

    Mittelman, Anjuliee M.

    Nanomaterials will be subjected to various surface transformations in the environment and within water and wastewater treatment systems. A comprehensive understanding of the fate and transport behavior of "aged" nanomaterials in both natural and engineered porous media is required in order to accurately quantify ecological and human health risks. This research sought to (1) evaluate the impact of ultraviolet (UV) light aging on nanoparticle transport in water-saturated porous media; and (2) assess the effects of influent water quality on silver nanoparticle retention and dissolution in ceramic water filters. Additionally, the value of quartz crystal microbalance (QCM-D) data in nanoparticle fate and transport studies was evaluated by comparing deposition behavior in complementary QCM-D and sand columns experiments. Silver (nAg) and iron oxide nanoparticles exposed to UV light were up to 50% more strongly retained in porous media compared with freshly prepared suspensions due to less negative surface charge and larger aggregate sizes. UV-aged nAg were more prone to dissolution in sand columns, resulting in effluent Ag+ concentrations as high as 1.2 mg/L. In ceramic water filters, dissolution and cation exchange processes controlled silver release into treated water. The use of acidic, high salinity, or high hardness water accelerated oxidative dissolution of the silver coating and resulted in effluent silver concentrations 5-10 times above international drinking water guidelines. Results support the recommendation for a regular filter replacement or silver re-application schedule to ensure ongoing efficacy. Taken in concert, these research findings suggest that oxidative aging of nanomaterial surfaces (either through exposure to UV light or aggressive water chemistries) will alter the fate of nanomaterials in the environment and may decrease the effective lifetime of devices which utilize nanotechnology. Corresponding QCM-D and column experiments revealed that

  12. Simulation of light transport in scintillators based on 3D characterization of crystal surfaces

    PubMed Central

    Cherry, Simon R.

    2013-01-01

    In the development of positron emission tomography (PET) detectors, understanding and optimizing scintillator light collection is critical for achieving high performance, particularly when the design incorporates depth-of-interaction (DOI) encoding or time-of-flight information. Monte-Carlo simulations play an important role in guiding research in detector designs and popular software such as GATE now include models of light transport in scintillators. Although current simulation toolkits are able to provide accurate models of perfectly polished surfaces, they do not successfully predict light output for other surface finishes, for example those often used in DOI-encoding detectors. The lack of accuracy of those models mainly originates from a simplified description of rough surfaces as an ensemble of micro-facets determined by the distribution of their normal, typically a Gaussian distribution. The user can specify the standard deviation of this distribution, but this parameter does not provide a full description of the surface reflectance properties. We propose a different approach based on 3D measurements of the surface using atomic force microscopy (AFM). Polished and rough (unpolished) crystals were scanned to compute the surface reflectance properties. The angular distributions of reflectance and reflected rays were computed and stored in look-up tables (LUTs). The LUTs account for the effect of incidence angle and were integrated in a light transport model. Crystals of different sizes were simulated with and without reflector. The simulated maximum light output and the light output as a function of DOI showed very good agreement with experimental characterization of the crystals, indicating that our approach provides an accurate model of polished and rough surfaces and could be used to predict light collection in scintillators. This model is based on a true 3D representation of the surface, makes no assumption about the surface and provides insight on the

  13. Systematic study of transport via surface and bulk states in Bi2Te3 topological insulator

    NASA Astrophysics Data System (ADS)

    de Castro, S.; Peres, M. L.; Chitta, V. A.; Gratens, X.; Soares, D. A. W.; Fornari, C. I.; Rappl, P. H. O.; Abramof, E.; Oliveira, N. F., Jr.

    2016-07-01

    We performed magnetoresistance measurements on Bi2Te3 thin film in the temperature range of T = 1.2–4.0 K and for magnetic fields up to 2 T. The curves exhibited anomalous behavior for temperatures below 4.0 K. Different temperature intervals revealed electrical transport through different conductive channels with clear signatures of weak antilocalization. The magnetoresistance curves were explained using the Hikami–Larkin–Nagaoka model and the 2D Dirac modified model. The comparison between the parameters obtained from the two models revealed the transport via topological surface states and bulk states. In addition, a superconductive like transition is observed for the lowest temperatures and we suggest that this effect can be originated from the misfit dislocations caused by strain, giving rise to a superconductive channel between the interface of the film and the substrate.

  14. Predicting the sun's polar magnetic fields with a surface flux transport model

    SciTech Connect

    Upton, Lisa; Hathaway, David H. E-mail: lar0009@uah.edu

    2014-01-01

    The Sun's polar magnetic fields are directly related to solar cycle variability. The strength of the polar fields at the start (minimum) of a cycle determine the subsequent amplitude of that cycle. In addition, the polar field reversals at cycle maximum alter the propagation of galactic cosmic rays throughout the heliosphere in fundamental ways. We describe a surface magnetic flux transport model that advects the magnetic flux emerging in active regions (sunspots) using detailed observations of the near-surface flows that transport the magnetic elements. These flows include the axisymmetric differential rotation and meridional flow and the non-axisymmetric cellular convective flows (supergranules), all of which vary in time in the model as indicated by direct observations. We use this model with data assimilated from full-disk magnetograms to produce full surface maps of the Sun's magnetic field at 15 minute intervals from 1996 May to 2013 July (all of sunspot cycle 23 and the rise to maximum of cycle 24). We tested the predictability of this model using these maps as initial conditions, but with daily sunspot area data used to give the sources of new magnetic flux. We find that the strength of the polar fields at cycle minimum and the polar field reversals at cycle maximum can be reliably predicted up to 3 yr in advance. We include a prediction for the cycle 24 polar field reversal.

  15. Rayleigh surface waves, phonon mode conversion, and thermal transport in nanostructures

    NASA Astrophysics Data System (ADS)

    Maurer, Leon; Knezevic, Irena

    We study the effects of phonon mode conversion and Rayleigh (surface) waves on thermal transport in nanostructures. We present a technique to calculate thermal conductivity in the elastic-solid approximation: a finite-difference time-domain (FDTD) solution of the elastic or scalar wave equations combined with the Green-Kubo formula. The technique is similar to an equilibrium molecular dynamics simulation, captures phonon wave behavior, and scales well to nanostructures that are too large to simulate with many other techniques. By imposing fixed or free boundary conditions, we can selectively turn off mode conversion and Rayleigh waves to study their effects. In the example case of graphenelike nanoribbons with rough edges, we find that mode conversion among bulk modes has little effect on thermal transport, but that conversion between bulk and Rayleigh waves can significantly reduce thermal conductivity. With increasing surface disorder, Rayleigh waves readily become trapped by the disorder and draw energy away from the propagating bulk modes, which lowers thermal conductivity. We discuss the implications on the accuracy of popular phonon-surface scattering models that stem from scalar wave equations and cannot capture mode conversion to Rayleigh waves.

  16. A propagating ATPase gradient drives transport of surface-confined cellular cargo

    PubMed Central

    Vecchiarelli, Anthony G.; Neuman, Keir C.; Mizuuchi, Kiyoshi

    2014-01-01

    The faithful segregation of duplicated genetic material into daughter cells is critical to all organisms. In many bacteria, the segregation of chromosomes involves transport of “centromere-like” loci over the main body of the chromosome, the nucleoid, mediated by a two-protein partition system: a nonspecific DNA-binding ATPase, ParA, and an ATPase stimulator, ParB, which binds to the centromere-like loci. These systems have previously been proposed to function through a filament-based mechanism, analogous to actin- or microtubule-based movement. Here, we reconstituted the F-plasmid partition system using a DNA-carpeted flow cell as an artificial nucleoid surface and magnetic beads coated with plasmid partition complexes as surface-confined cargo. This minimal system recapitulated directed cargo motion driven by a surface ATPase gradient that propagated with the cargo. The dynamics are consistent with a diffusion-ratchet model, whereby the cargo dynamically establishes, and interacts with, a concentration gradient of the ATPase. A chemophoresis force ensues as the cargo perpetually chases the ATPase gradient, allowing the cargo to essentially “surf” the nucleoid on a continuously traveling wave of the ATPase. Demonstration of this non–filament-based motility mechanism in a biological context establishes a distinct class of motor system used for the transport and positioning of large cellular cargo. PMID:24567408

  17. Impact of microforms on nitrate transport at the groundwater-surface water interface in gaining streams

    NASA Astrophysics Data System (ADS)

    Hu, Haizhu; Binley, Andrew; Heppell, Catherine M.; Lansdown, Katrina; Mao, Xiaomin

    2014-11-01

    Small streambed structures (or microforms, 0.01-1 m in length) exist ubiquitously in riverbed systems. Small-scale topography is potentially important in controlling hyporheic exchange flow and transport of conservative and reactive solutes at the groundwater-surface water interface. The role of microforms on NO3- transfer in a riffle-scale (macroforms of >1 m length) hyporheic zone within a gaining river setting is investigated using a 2-D flow and transport model which accounts for both nitrification and denitrification. Results show that the short pathlines caused by microforms lead to more NO3- discharge to the river compared with a macroform-only condition due to shortened residence times of both surface water and groundwater in mixing zones. Short hyporheic exchange flow pathways caused by microforms could remain oxic along their entire length or switch from nitrate producing to nitrate consuming as oxygen concentrations decline. Microforms affect net NO3- flux by the combined effect of introducing more stream mass flux and reducing their residence time in mixing zones under different hydrological and biogeochemical conditions. Our findings underscore that ignoring microforms in river beds may underestimate NO3- load to the river and have practical implications for pore water sampling strategies in groundwater-surface water studies.

  18. Molecular views of surface driven transport : electro-osmosis, diffusio-osmosis, and beyond

    NASA Astrophysics Data System (ADS)

    Bocquet, Lyderic; Ybert, Christophe; Ajdari, Armand

    2006-11-01

    We investigate the molecular mechanisms associated with surface driven transport, such as electro-, diffusio- or thermo-osmosis, which generate flows by application of a macroscopic gradient (of electric potential, solute concentration or temperature). The driving force (e.g., electric or osmotic) is located typically within a nanometric distance to the surface and the resulting effects are thus expected to be strongly affected by modifications of surface properties. We show in this context that moderate departures from the no-slip hydrodynamic boundary condition can result in very large enhancement of most interfacially driven transport, - up to two orders of magnitude for hydrodynamic slip lengths in the nanometer range ! -. The amplification of the effect due to slippage scales as the ratio between the slip length and the interfacial characterisic length (debye length, or solute attraction or depletion range). These predictions are confirmed qualitatively and quantitatively by molecular dynamics simulation of electro- and diffusio -osmosis. We will discuss the pertinence of these effects for flow enhancement in nano- or micro- fluidic geometries, but also fortransport of macromolecules in externally applied or self- generated gradient, in line with recent experiments.

  19. What Supergranule Flow Models Tell Us About the Sun's Surface Shear Layer and Magnetic Flux Transport

    NASA Technical Reports Server (NTRS)

    Hathaway, David

    2011-01-01

    Models of the photospheric flows due to supergranulation are generated using an evolving spectrum of vector spherical harmonics up to spherical harmonic wavenumber l1500. Doppler velocity data generated from these models are compared to direct Doppler observations from SOHO/MDI and SDO/HMI. The models are adjusted to match the observed spatial power spectrum as well as the wavenumber dependence of the cell lifetimes, differential rotation velocities, meridional flow velocities, and relative strength of radial vs. horizontal flows. The equatorial rotation rate as a function of wavelength matches the rotation rate as a function of depth as determined by global helioseismology. This leads to the conclusions that the cellular structures are anchored at depths equal to their widths, that the surface shear layer extends to at least 70 degrees latitude, and that the poleward meridional flow decreases in amplitude and reverses direction at the base of the surface shear layer (approx.35 Mm below the surface). Using the modeled flows to passively transport magnetic flux indicates that the observed differential rotation and meridional flow of the magnetic elements are directly related to the differential rotation and meridional flow of the convective pattern itself. The magnetic elements are transported by the evolving boundaries of the supergranule pattern (where the convective flows converge) and are unaffected by the weaker flows associated with the differential rotation or meridional flow of the photospheric plasma.

  20. Importance of 3D Processes Near the Ocean's Surface for Material Transport

    NASA Astrophysics Data System (ADS)

    Ozgokmen, T. M.

    2014-12-01

    There are a number of practical problems that demand an accurate knowledge of ocean currents near the surface of the ocean. It is known that oceanic coherent features transport heat and carry out vertical exchange of biogeochemical tracers. Ocean currents can affect biological primary production, air-sea gas exchanges and global tracer budgets. Ocean currents are also important for the dispersion of substances that pose a danger to society, economy and human health. Examples of such events include algal blooms, the Fukushima nuclear plant incident in the Pacific Ocean in 2011, and repeated large oil spills in the Gulf of Mexico, namely the IXTOC in 1978 and the Deepwater Horizon event in 2010. Such incidents demand accurate answers to questions such as ``where will the pollutant go?", ``how fast will it get there?" and ``how much pollutant will arrive there?", and in some instances ``where did the pollutant come from?". The answers to these questions are critical to the allocation of limited response resources, and in determining the overall impact of the events. We will summarize the efforts by the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE). One of the primary objectives of CARTHE is to improve predictive modeling capability for flows near the air-sea interface. In particular, two large experiments, Grand Lagrangian Deployment (GLAD) and Surf-zone and Coastal Oil Pathways Experiment (SCOPE), coordinated with real-time modeling were instructive on processes influencing near-surface material transport. Findings on submesoscale flows as well as model deficiencies to capture processes relevant to transport will be discussed. Insight into future modeling and observational plans will be provided.

  1. High-Speed Transport of Fluid Drops and Solid Particles via Surface Acoustic Waves

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Bao, Xiaoqi; Sherrit, Stewart; Badescu, Mircea; Lih, Shyh-shiuh

    2012-01-01

    A compact sampling tool mechanism that can operate at various temperatures, and transport and sieve particle sizes of powdered cuttings and soil grains with no moving parts, has been created using traveling surface acoustic waves (SAWs) that are emitted by an inter-digital transducer (IDT). The generated waves are driven at about 10 MHz, and it causes powder to move towards the IDT at high speed with different speeds for different sizes of particles, which enables these particles to be sieved. This design is based on the use of SAWs and their propelling effect on powder particles and fluids along the path of the waves. Generally, SAWs are elastic waves propagating in a shallow layer of about one wavelength beneath the surface of a solid substrate. To generate SAWs, a piezoelectric plate is used that is made of LiNbO3 crystal cut along the x-axis with rotation of 127.8 along the y-axis. On this plate are printed pairs of fingerlike electrodes in the form of a grating that are activated by subjecting the gap between the electrodes to electric field. This configuration of a surface wave transmitter is called IDT. The IDT that was used consists of 20 pairs of fingers with 0.4-mm spacing, a total length of 12.5 mm. The surface wave is produced by the nature of piezoelectric material to contract or expand when subjected to an electric field. Driving the IDT to generate wave at high amplitudes provides an actuation mechanism where the surface particles move elliptically, pulling powder particles on the surface toward the wavesource and pushing liquids in the opposite direction. This behavior allows the innovation to separate large particles and fluids that are mixed. Fluids are removed at speed (7.5 to 15 cm/s), enabling this innovation of acting as a bladeless wiper for raindrops. For the windshield design, the electrodes could be made transparent so that they do not disturb the driver or pilot. Multiple IDTs can be synchronized to transport water or powder over larger

  2. A Modular, Reusable Latch and Decking System for Securing Payloads During Launch and Planetary Surface Transport

    NASA Technical Reports Server (NTRS)

    Doggett, William R.; Dorsey, John T.; Jones, Thomas C.; King, Bruce D.; Mikulas, Martin M.

    2011-01-01

    Efficient handling of payloads destined for a planetary surface, such as the moon or mars, requires robust systems to secure the payloads during transport on the ground, in space and on the planetary surface. In addition, mechanisms to release the payloads need to be reliable to ensure successful transfer from one vehicle to another. An efficient payload handling strategy must also consider the devices available to support payload handling. Cranes used for overhead lifting are common to all phases of payload handling on Earth. Similarly, both recent and past studies have demonstrated that devices with comparable functionality will be needed to support lunar outpost operations. A first generation test-bed of a new high performance device that provides the capabilities of both a crane and a robotic manipulator, the Lunar Surface Manipulation System (LSMS), has been designed, built and field tested and is available for use in evaluating a system to secure payloads to transportation vehicles. A payload handling approach must address all phases of payload management including: ground transportation, launch, planetary transfer and installation in the final system. In addition, storage may be required during any phase of operations. Each of these phases requires the payload to be lifted and secured to a vehicle, transported, released and lifted in preparation for the next transportation or storage phase. A critical component of a successful payload handling approach is a latch and associated carrier system. The latch and carrier system should minimize requirements on the: payload, carrier support structure and payload handling devices as well as be able to accommodate a wide range of payload sizes. In addition, the latch should; be small and lightweight, support a method to apply preload, be reusable, integrate into a minimal set of hard-points and have manual interfaces to actuate the latch should a problem occur. A latching system which meets these requirements has been

  3. A Modular, Reusable Latch and Decking System for Securing Payloads During Launch and Planetary Surface Transport

    NASA Technical Reports Server (NTRS)

    Doggett, William R.; Dorsey, John T.; Jones, Thomas C.; King, Bruce D.; Mikulas, Martin M.

    2010-01-01

    Efficient handling of payloads destined for a planetary surface, such as the moon or Mars, requires robust systems to secure the payloads during transport on the ground, in-space and on the planetary surface. In addition, mechanisms to release the payloads need to be reliable to ensure successful transfer from one vehicle to another. An efficient payload handling strategy must also consider the devices available to support payload handling. Cranes used for overhead lifting are common to all phases of payload handling on Earth. Similarly, both recent and past studies have demonstrated that devices with comparable functionality will be needed to support lunar outpost operations. A first generation test-bed of a new high performance device that provides the capabilities of both a crane and a robotic manipulator, the Lunar Surface Manipulation System (LSMS), has been designed, built and field tested and is available for use in evaluating a system to secure payloads to transportation vehicles. National Institute of Aerospace, Hampton Va 23662 A payload handling approach must address all phases of payload management including: ground transportation, launch, planetary transfer and installation in the final system. In addition, storage may be required during any phase of operations. Each of these phases requires the payload to be lifted and secured to a vehicle, transported, released and lifted in preparation for the next transportation or storage phase. A critical component of a successful payload handling approach is a latch and associated carrier system. The latch and carrier system should minimize requirements on the: payload, carrier support structure and payload handling devices as well as be able to accommodate a wide range of payload sizes. In addition, the latch should; be small and lightweight, support a method to apply preload, be reusable, integrate into a minimal set of hard-points and have manual interfaces to actuate the latch should a problem occur. A

  4. Zeeman effect on surface electron transport in topological insulator Bi2Se3 nanoribbons.

    PubMed

    Wang, Li-Xian; Yan, Yuan; Zhang, Liang; Liao, Zhi-Min; Wu, Han-Chun; Yu, Da-Peng

    2015-10-28

    Topological insulators have exotic surface states that are massless Dirac fermions, manifesting special magnetotransport properties, such as the Aharonov-Bohm effect, Shubnikov-de Haas oscillations, and weak antilocalization effects. In the surface Dirac cone, the band structures are typically closely related to the p-orbitals and possess helical orbital texture. Here we report on the tunability of the transport properties via the interaction between the magnetic field and the spin-orbital angular momentum of the surface states in individual Bi2Se3 nanoribbons. Because the surface states have a large Landé factor and helical spin-orbital texture, the in-plane magnetic field induced Zeeman energy will result in the deformation of the Dirac cone, which gives rise to spin polarization of the surface states. The spin-dependent scattering of the conducting electrons on the existing local magnetic moments produces a giant negative magnetoresistance. The negative magnetoresistance is robust with a ratio of -20% at 2 K and -0.5% at 300 K under 14 T. The results are valuable for possible orbital-electronics based on topological insulators. PMID:26400635

  5. Atmospheric transport and deposition, an additional input pathway for triazine herbicides to surface waters

    SciTech Connect

    Muir, D.C.G.; Rawn, D.F.

    1996-10-01

    Although surface runoff from treated fields is regarded as the major route of entry of triazine herbicides to surface waters, other pathways such as deposition via precipitation, gas absorption and dryfall may also be important. Triazine herbicides have been detected in precipitation but there has been only a very limited amount of work on gas phase and aerosols. To examine the importance of atmospheric inputs concentrations of atrazine, cyanazine and terbuthylazine in gas phase/aerosols, precipitation, and surface waters were determined (along with other herbicides) using selected ion GC-MS. Atrazine was detected at low ng/L concentrations in surface waters (<0.04-5.3 ng/L) and precipitation (0.1-53 ng/L), and at 0.02-0.1 ng/m{sup 3} in air. Cyanazine and terbuthylazine were detected in air and infrequently in water. Highest atrazine concentrations in air were found during June each year on both gas phase and particles. Concentrations of atrazine in surface waters at both locations increased during June, even in the absence of precipitation or overland flow, presumably due to inputs from dryfall and to gas areas and boreal forest lakes due to transport and deposition. Ecological risk assessment of triazines, especially for pristine aquatic environments should include consideration of this atmospheric pathway.

  6. Transport processes induced by metastable boiling water under Martian surface conditions

    NASA Astrophysics Data System (ADS)

    Massé, M.; Conway, S. J.; Gargani, J.; Patel, M. R.; Pasquon, K.; McEwen, A.; Carpy, S.; Chevrier, V.; Balme, M. R.; Ojha, L.; Vincendon, M.; Poulet, F.; Costard, F.; Jouannic, G.

    2016-06-01

    Liquid water may exist on the Martian surface today, albeit transiently and in a metastable state under the low atmospheric surface pressure. However, the identification of liquid water on Mars from observed morphological changes is hampered by our limited understanding of how metastable liquids interact with sediments. Here, we present lab experiments in which a block of ice melts and seeps into underlying sediment, and the resulting downslope fluid propagation and sediment transport are tracked. In experiments at Martian surface pressure, we find that pure water boils as it percolates into the sediment, inducing grain saltation and leading to wholesale slope destabilization: a hybrid flow mechanism involving both wet and dry processes. For metastable brines, which are more stable under Martian conditions than pure water, saltation intensity and geomorphological impact are reduced; however, we observed channel formation in some briny flow experiments that may be analogous to morphologies observed on Mars. In contrast, under terrestrial-like experimental conditions, there is little morphological impact of seeping water or brine, which are both stable. We propose that the hybrid flow mechanism operating in our experiments under Martian surface pressure could explain observed Martian surface changes that were originally interpreted as the products of either dry or wet processes.

  7. Effects of upper-surface nacelles on longitudinal aerodynamic characteristics of high-wing transport configuration

    NASA Technical Reports Server (NTRS)

    Putnam, L. E.

    1986-01-01

    An investigation has been conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of installing and streamline contouring upper-surface nacelles on the longitudinal aerodynamic characteristics of a high-wing transport configuration. Also investigated were the effects of adding a fairing under the nacelle. The investigation was conducted at free-stream Mach numbers from 0.60 to 0.83 at angles fo attack from -2 deg to 4 deg. Flow-through nacelles were used. Streamline contouring the nacelles substantially reduced the interference drag due to installing the nacelles.

  8. Quasi-optical electron transport across a magnetically induced junction on a topological insulator surface

    SciTech Connect

    Duan, Xiaopeng; Li, Xiaodong; Semenov, Yuriy G.; Kim, Ki Wook

    2014-12-14

    Quasi-optical Dirac electron transport is theoretically analyzed at the magnetic boundaries on a topological insulator (TI) surface. The electronic band mismatch induced by the spatially varying magnetization profile can form an effective junction akin to the electrostatic potential step. The transmission/reflection characteristics show a direct dependence on electron energy and incident angle with highly asymmetric patterns. The investigation also illustrates a nontrivial anomalous Hall current along the boundary which is further shown by a numerical simulation based on the finite-difference time-domain method. The results provide key design guidelines for prospective quasi-optical devices based on the TI-magnet heterostructures.

  9. Preliminary economic evaluation of the use of graphite composite materials in surface transportation, phase 1 results

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Composite materials are discussed with emphasis on the identification of the characteristics of those materials that make them attractive for use in surface transportation. Potential uses of graphite composites are given including automotive applications and the effects of materials substitution on vehicle characteristics and performance. Preliminary estimates of the economic effects of the use of graphite composite materials on vehicle manufacturers and consumers are included. The combined impact on the national economy of vehicle design changes to meet mandated fuel efficiency requirements and the extensive use of graphite composite materials in the automotive industry is considered.

  10. Accumulation and transport of Cd, Cu, and Pb in an estuarine salt marsh surface microlayer

    SciTech Connect

    Lion, L.W.; Leckie, J.O.

    1982-01-01

    Dissolved and particulate Cd, Cu, and Pb were measured in bulk solution and surface microlayer samples from an intertidal salt marsh in south San Francisco Bay. The phase distribution (dissolved vs. particulate) of metals was consistent with their calculated speciation in computer-simulated sea-salt matrices. Trace metal enrichment at the microlayer corresponded with physical events at the sample site. Advective exchange of Cd, Cu, and Pb between the estuary and marsh systems was dominated by transport of bulk suspended particulate metals, with an apparent net export from the marsh to the bay.

  11. 19 CFR 18.9 - Examination by inspectors of trunk line associations or agents of the Surface Transportation Board.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Examination by inspectors of trunk line associations or agents of the Surface Transportation Board. 18.9 Section 18.9 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY TRANSPORTATION IN BOND AND MERCHANDISE IN TRANSIT General Provisions...

  12. Localized Turbulence Suppression and Increased Flow Shear near the q=2 Surface during Internal-Transport-Barrier Formation

    SciTech Connect

    Shafer, M. W.; McKee, G. R.; Fonck, R. J.; Schlossberg, D. J.; Austin, M. E.; Burrell, K. H.

    2009-08-14

    Broadband turbulent fluctuations in the plasma density are transiently suppressed when low-order rational q surfaces first appear in negative central magnetic shear plasmas on the DIII-D tokamak, which can lead to the formation of internal transport barriers. Increased localized flow shear is simultaneously observed. It transiently exceeds the measured turbulence decorrelation rate, providing a mechanism to trigger the formation of the transport barrier. This increased flow shear and turbulence suppression propagates radially outward, following the q=2 surface.

  13. Transport and distribution of bacteria and diatoms in the aqueous surface micro-layer of a salt marsh

    USGS Publications Warehouse

    Harvey, Ronald W.; Lion, Leonard W.; Young, Lily Y.

    1983-01-01

    The effects of tide and wind upon the distribution and transport of bacteria and diatoms in the aqueous surface microlayers of a Massachusetts and San Francisco Bay salt marsh were examined. The compression of the surface films by both tide and wind resulted in significant enrichments of bacterioneuston. At the San Francisco Bay site, significant numbers of diatoms were transported within the microlayer over a tidal cycle.

  14. Virtual laboratory for the study of transport processes in surface waterflows

    NASA Astrophysics Data System (ADS)

    Aguilar, C.; Egüen, M.; Contreras, E.; Polo, M. J.

    2012-04-01

    The equations involved in the study of transport processes depend on the spatial and temporal scale of the study and according to the required level of detail can become very difficult to solve analytically. Besides, experimentation of processes with any transport phenomena involved is complex due to their natural or forced occurrence in the environment (eg. Rainfall-runoff, sediment yield, controlled and uncontrolled pollutant loadings, etc.) and the great diversity of substances and components with an specific chemical behavior. However, due to the numerous fields of application of transport phenomena (basic and applied research, hydrology and associated fluxes, sediment transport, pollutant loadings to water flows, industrial processes, soil and water quality, atmospheric emissions, legislation, etc.), realistic studies of transport processes are required. In this context, case study application, an active methodology according to the structural implications of the European Higher Education Area (EHEA), with the aid of computer tools constitute an interactive, instantaneous and flexible method with a new interplay between students and lecturers. Case studies allow the lecturer to design significant activities that generate knowledge in the students and motivates them to look for information, discuss, and be autonomous. This work presents the development of a graphical interface for the solution of different case studies for the acquisition of capacities and abilities in the autonomous apprenticeship of courses related to transport processes in Environmental Hydraulics. The interactive tool helps to develop and improve abilities in mixing and transport in surface water related courses. Thus, students clarify theoretical concepts and visualize processes with negative effects for the environment and that therefore, can only be reproduced in the laboratory or in the field under very controlled conditions and commonly with tracers instead of the real substances. The

  15. Wall surface temperature calculation in the SolEdge2D-EIRENE transport code

    NASA Astrophysics Data System (ADS)

    Denis, J.; Pégourié, B.; Bucalossi, J.; Bufferand, H.; Ciraolo, G.; Gardarein, J.-L.; Gaspar, J.; Grisolia, C.; Hodille, E.; Missirlian, M.; Serre, E.; Tamain, P.

    2016-02-01

    A thermal wall model is developed for the SolEdge2D-EIRENE edge transport code for calculating the surface temperature of the actively-cooled vessel components in interaction with the plasma. This is a first step towards a self-consistent evaluation of the recycling of particles, which depends on the wall surface temperature. The proposed thermal model is built to match both steady-state temperature and time constant of actively-cooled plasma facing components. A benchmark between this model and the Finite Element Modelling code CAST3M is performed in the case of an ITER-like monoblock. An example of application is presented for a SolEdge2D-EIRENE simulation of a medium-power discharge in the WEST tokamak, showing the steady-state wall temperature distribution and the temperature cycling due to an imposed Edge Localised Mode-like event.

  16. A charge transport study in diamond, surface passivated by high-k dielectric oxides

    SciTech Connect

    Kovi, Kiran Kumar Majdi, Saman; Gabrysch, Markus; Isberg, Jan

    2014-11-17

    The recent progress in the growth of high-quality single-crystalline diamond films has sparked interest in the realization of efficient diamond power electronic devices. However, finding a suitable passivation is essential to improve the reliability and electrical performance of devices. In the current work, high-k dielectric materials such as aluminum oxide and hafnium oxide were deposited by atomic layer deposition on intrinsic diamond as a surface passivation layer. The hole transport properties in the diamond films were evaluated and compared to unpassivated films using the lateral time-of-flight technique. An enhancement of the near surface hole mobility in diamond films of up to 27% is observed when using aluminum oxide passivation.

  17. Coupled heat and vapor transport: The thermostat effect of a freely evaporating land surface

    NASA Astrophysics Data System (ADS)

    Szilagyi, Jozsef; Schepers, Aaron

    2014-01-01

    Analytical solutions of the 2-D heat and vapor transport equations for a surface moisture jump are often based on a constant streamwise temperature (Tws) assumption over the wet vegetated surface. By analyzing 90 thermal infrared images taken over center-pivot irrigated areas in Nebraska, it has been demonstrated for the first time that such an assumption is realistic. Average temperature difference between the perimeter and core of the irrigated full or half circles stayed between -0.11 and 0.09°C (standard deviation of 0.25-0.41°C). It was further demonstrated that wet-bulb temperatures (a proxy of Tws) remain near constant during drying of the environment when net radiation and wind conditions stay largely unchanged, enabling estimation of Tws at any stage of drying, thus improving evaporation estimates of the Priestley-Taylor equation in arid and semiarid environments.

  18. Surface flux transport simulations. Inflows towards active regions and the modulation of the solar cycle.

    NASA Astrophysics Data System (ADS)

    Martin-Belda, David; Cameron, Robert

    2016-07-01

    Aims. We investigate the way near-surface converging flows towards active regions affect the build-up of magnetic field at the Sun's polar caps. In the Babcock-Leighton dynamo framework, this modulation of the polar fields could explain the variability of the solar cycle. Methods. We develop a surface flux transport code incorporating a parametrized model of the inflows and run simulations spanning several cycles. We carry out a parameter study to test how the strength and extension of the inflows affect the amplitude of the polar fields. Results. Inflows are seen to play an important role in the build-up of the polar fields, and can act as the non-linearity feedback mechanism required to limit the strength of the solar cycles in the Babcock-Leighton dynamo framework.

  19. A polyphenylene dendrimer drug transporter with precisely positioned amphiphilic surface patches.

    PubMed

    Stangenberg, René; Wu, Yuzhou; Hedrich, Jana; Kurzbach, Dennis; Wehner, Daniel; Weidinger, Gilbert; Kuan, Seah Ling; Jansen, Malin Insa; Jelezko, Fedor; Luhmann, Heiko J; Hinderberger, Dariush; Weil, Tanja; Müllen, Klaus

    2015-02-18

    The design and synthesis of a polyphenylene dendrimer (PPD 3) with discrete binding sites for lipophilic guest molecules and characteristic surface patterns is presented. Its semi-rigidity in combination with a precise positioning of hydrophilic and hydrophobic groups at the periphery yields a refined architecture with lipophilic binding pockets that accommodate defined numbers of biologically relevant guest molecules such as fatty acids or the drug doxorubicin. The size, architecture, and surface textures allow to even penetrate brain endothelial cells that are a major component of the extremely tight blood-brain barrier. In addition, low to no toxicity is observed in in vivo studies using zebrafish embryos. The unique PPD scaffold allows the precise placement of functional groups in a given environment and offers a universal platform for designing drug transporters that closely mimic many features of proteins. PMID:25182694

  20. Turbulence avoidance and the wind-driven transport of plankton in the surface Ekman layer

    NASA Astrophysics Data System (ADS)

    Pringle, James M.

    2007-03-01

    Observations of turbulence avoidance in zooplankton are compared to estimates of the wind-driven turbulence in the upper ocean. Plankton that avoid wind-driven turbulence by moving deeper are no longer transported by the wind-driven Ekman currents near the surface because they are no longer near the surface. Here, a threshold level of turbulence that triggers an avoidance response is estimated, and is used to infer the wind speed and water column stratification conditions that would lead to zooplankton leaving the Ekman layer. Turbulence avoidance is argued to lead to near-shore retention in wind-driven upwelling systems, and to a reduction of the delivery of zooplankton to Georges Bank from the deeper waters of the Gulf of Maine.

  1. Rectification of nanopores in aprotic solvents - transport properties of nanopores with surface dipoles

    NASA Astrophysics Data System (ADS)

    Plett, Timothy; Shi, Wenqing; Zeng, Yuhan; Mann, William; Vlassiouk, Ivan; Baker, Lane A.; Siwy, Zuzanna S.

    2015-11-01

    Nanopores have become a model system to understand transport properties at the nanoscale. We report experiments and modeling of ionic current in aprotic solvents with different dipole moments through conically shaped nanopores in a polycarbonate film and through glass nanopipettes. We focus on solutions of the salt LiClO4, which is of great importance in modeling lithium based batteries. Results presented suggest ion current rectification observed results from two effects: (i) adsorption of Li+ ions to the pore walls, and (ii) a finite dipole moment rendered by adsorbed solvent molecules. Properties of surfaces in various solvents were probed by means of scanning ion conductance microscopy, which confirmed existence of an effectively positive surface potential in aprotic solvents with high dipole moments.Nanopores have become a model system to understand transport properties at the nanoscale. We report experiments and modeling of ionic current in aprotic solvents with different dipole moments through conically shaped nanopores in a polycarbonate film and through glass nanopipettes. We focus on solutions of the salt LiClO4, which is of great importance in modeling lithium based batteries. Results presented suggest ion current rectification observed results from two effects: (i) adsorption of Li+ ions to the pore walls, and (ii) a finite dipole moment rendered by adsorbed solvent molecules. Properties of surfaces in various solvents were probed by means of scanning ion conductance microscopy, which confirmed existence of an effectively positive surface potential in aprotic solvents with high dipole moments. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06340j

  2. Energy transport of surface phonon polaritons propagating along a chain of spheroidal nanoparticles

    NASA Astrophysics Data System (ADS)

    Ordonez-Miranda, Jose; Tranchant, Laurent; Gluchko, Sergei; Volz, Sebastian

    2015-09-01

    We analyze in detail the energy transport of surface phonon polaritons propagating in a chain of spheroidal polar nanoparticles with both longitudinal and transversal polarizations. Explicit and closed-form expressions for the dispersion relation and propagation length are derived and used to determine the values of the nanoparticle polarizability and the interparticle distance that maximize the polariton propagation length. The thermal conductance in the ballistic regime and the thermal conductivity in the diffusive one are also determined and examined as a function of the geometry of the nanoparticles and their temperature. For a chain of cigar-shaped SiC nanoparticles in contact, an aspect ratio of 5, and surrounded by air; it is shown that: (i) The surface phonon polaritons propagate a distance of 10 μ m along a chain of 100 nanoparticles. This propagation length is one order of magnitude longer than that for spherical nanoparticles. (ii) The polariton thermal conductivity is comparable with the one of air in a wide range of temperatures and is 41 mW m-1K-1 at 500 K. (iii) The polariton thermal conductance increases with the temperature and at 500 K is 44 pW K-1 , which represents 9 % of the quantum of thermal conductance. In view of the ultralow phonon thermal conductivity of a chain of polar nanoparticles in contact and their high surface area-to-volume ratios, the proposed theoretical model and obtained results are expected to be useful to experimentally quantify the energy transport of surface phonon polaritons propagating along these nanostructures.

  3. Mechanism of Nitrate-N Transport in Surface Water and Groundwater in a Missourian Claypan Watershed

    NASA Astrophysics Data System (ADS)

    Liu, F.; Lerch, R. N.; Yang, J.; Baffaut, C.

    2014-12-01

    Nitrogen (N) fertilizer applications have resulted in widespread surface water and groundwater nitrate-N (NO3-N) contamination in the U.S. Corn Belt. However, the processes that control NO3-N concentrations in both surface water and groundwater were not well understood, particularly for claypan-dominated watersheds. The objective of this study was to understand the processes that control the transport of NO3-N in/from surface water and/to groundwater in Goodwater Creek Experimental Watershed (GCEW), a claypan-dominated watershed in north-central Missouri. The mean nitrate-N concentration in groundwater determined from more than 2000 samples collected during 1991 - 2004 was approximately three times that in stream water at GCEW. Despite the low hydraulic conductivity of the claypan soils, considerable NO3-N contamination of the glacial till aquifer occurred, with 38% of the wells exceeding 10 mg l-1. Groundwater recharge by preferential pathways through the claypan appeared to be the primary mechanism for NO3-N movement to the aquifer. In comparison, only 19-23% of sampled wells in non-claypan agricultural watersheds over the continental U.S. exceeded 10 mg l-1, suggesting that groundwater in GCEW appears to be more susceptible to NO3-N contamination than non-claypan watersheds. Using endmember mixing analysis based on conservative tracers, stream flow during the relatively low flow periods was primarily from surface runoff, shallow subsurface water and groundwater, with an average contribution of 25%, 44% and 31% from 2011 to 2014, respectively. Stable isotopic values of nitrate (d15N, d18O and D17O) also demonstrated that groundwater exerted a major control on nitrate concentrations in stream water. This information greatly improves our understanding of the processes that control NO3-N transport to the groundwater system of claypan-dominated watersheds.

  4. Alluvial Fans on Titan Reveal Atmosphere and Surface Interactions and Material Transport

    NASA Astrophysics Data System (ADS)

    Radebaugh, J.; Ventra, D.; Lorenz, R. D.; Farr, T. G.; Kirk, R. L.; Hayes, A.; Malaska, M. J.; Birch, S.; Liu, Z. Y. C.; Lunine, J. I.; Barnes, J. W.; Le Gall, A. A.; Lopes, R. M. C.; Stofan, E. R.; Wall, S. D.; Paillou, P.

    2015-12-01

    Alluvial fans, important depositional systems that record how sediment is stored and moved on planetary surfaces, are found on the surface of Titan, a body of significantly different materials and process rates than Earth. As seen by Cassini's Synthetic Aperture Radar (SAR) images at 350 m resolution, fans on Titan are found globally and are variable in size, shape and relationship to adjacent landforms. Their morphologies and SAR characteristics, which reveal roughness, textural patterns and other material properties, show similarities with fans in Death Valley seen by SAR and indicate there are regions of high relative relief locally, in the Ganesa, Xanadu and equatorial mountain belt regions. The Leilah Fluctus fans near Ganesa are ~30 km x 15 km, similar to the largest Death Valley fans, and revealing mountainous topography adjacent to plains. Others have gentle slopes over hundreds of kilometers, as in the high southern latitude lakes regions or the Mezzoramia southern midlatitudes, where a fan system is 200 km x 150 km, similar to the Qarn Alam fan emerging into the Rub al Khali in Oman. Additionally, there is evidence for a range of particle sizes, from relatively coarse (~2 cm or more) to fine, revealing long-term duration and variability in erosion by methane rainfall and transport. Some features have morphologies consistent with proximality to high-relief source areas and highly ephemeral runoff, while others appear to draw larger catchment areas and are perhaps characterized by more prolonged episodes of flow. The presence of many fans indicates the longevity of rainfall and erosion in Titan's surface processes and reveals that sediment transport and the precipitation that drives it are strongly episodic. Alluvial fans join rivers, lakes, eroded mountains, sand dunes and dissolution features in the list of surface morphologies derived from atmospheric and fluvial processes similar to those on Earth, strengthening comparisons between the two planetary

  5. Evaluation of Meteorological Analyses, Simulations, and Long-Range Transport Calculations Using ANATEX Surface Tracer Data.

    NASA Astrophysics Data System (ADS)

    Haagenson, Philip L.; Gao, Kun; Kuo, Ying-Hwa

    1990-12-01

    Perfluorocarbon tracer data collected during the Across North America Tracer Experiment (ANATEX) are used to evaluate different meteorological analysis, simulations, and long-range transport calculations. Three basic types of meteorological analysis and simulation are evaluated: objective analysis of observed data, prognostic simulation with observed lateral boundary conditions, and four-dimensional data assimilation (FDDA). The evaluation is based on 1) the root-mean-square separation between two-dimensional meteorological trajectories (constructed from different analyses or simulations) and surface tracer trajectories and 2) the relationship between the upward displacement of three-dimensional trajectories and the maximum value of the surface tracer concentration. The root-mean-square data indicate that the optimum value of the Newtonian nudging coefficient for the FDDA wind field in the lower troposphere is 6 × 104 s1, and the quality of the prognostic simulation is lower than that for FDDA or the objective analysis, particularly when surface fronts are present. These data also show that trajectory errors, with respect to transport distance, are larger in low-speed wind regimes than in medium- to high-speed regimes, and suggest that the rate of increase of trajectory error decreases with time, but the uncertainty of the rate of increase is quite large during the first 18 h of transit. The three-dimensional trajectories indicate that large-scale upward motion is a mechanism for removal of tracer from the boundary layer, and the strongest correlation between the upward displacement of the trajectory air parcels and the surface tracer concentration is obtained using the FDDA dataset. The overall results suggest that when both the vertical and horizontal components of the wind fields are considered, FDDA (using an appropriate value for the nudging coefficient) is better than the other methodologies.

  6. Observed and modeled surface Lagrangian transport between coastal regions in the Adriatic Sea with implications for marine protected areas

    NASA Astrophysics Data System (ADS)

    Carlson, Daniel F.; Griffa, Annalisa; Zambianchi, Enrico; Suaria, Giuseppe; Corgnati, Lorenzo; Magaldi, Marcello G.; Poulain, Pierre-Marie; Russo, Aniello; Bellomo, Lucio; Mantovani, Carlo; Celentano, Paolo; Molcard, Anne; Borghini, Mireno

    2016-04-01

    Surface drifters and virtual particles are used to investigate transport between seven coastal regions in the central and southern Adriatic Sea to estimate the degree to which these regions function as a network. Alongshore coastal currents and cyclonic gyres are the primary circulation features that connected regions in the Adriatic Sea. The historical drifter observations span 25 years and, thus, provide estimates of transport between regions realized by the mean surface circulation. The virtual particle trajectories and a dedicated drifter experiment show that southeasterly Sirocco winds can drive eastward cross-Adriatic transport from the Italian coast near the Gargano Promontory to the Dalmatian Islands in Croatia. Southeasterly winds disrupt alongshore transport on the west coast. Northwesterly Mistral winds enhanced east-to-west transport and resulted in stronger southeastward coastal currents in the western Adriatic current (WAC) and export to the northern Ionian Sea. The central Italian regions showed strong connections from north to south, likely realized by alongshore transport in the WAC. Alongshore, downstream transport was weaker on the east coast, likely due to the more complex topography introduced by the Dalmatian Islands of Croatia. Cross-Adriatic connection percentages were higher for east-to-west transport. Cross-Adriatic transport, in general, occurred via the cyclonic sub-gyres, with westward (eastward) transport observed in the northern (southern) arms of the central and southern gyres.

  7. 77 FR 42831 - Professional Transportation, Inc.-Asset Acquisition-CUSA ES, LLC and CUSA CSS, LLC

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-20

    ... published in the Federal Register (77 FR 38884-85). The notice contained an omission in the address... CSS, LLC AGENCY: Surface Transportation Board, Department of Transportation. ACTION: Correction...

  8. Surface transport and stable trapping of particles and cells by an optical waveguide loop.

    PubMed

    Hellesø, Olav Gaute; Løvhaugen, Pål; Subramanian, Ananth Z; Wilkinson, James S; Ahluwalia, Balpreet Singh

    2012-09-21

    Waveguide trapping has emerged as a useful technique for parallel and planar transport of particles and biological cells and can be integrated with lab-on-a-chip applications. However, particles trapped on waveguides are continuously propelled forward along the surface of the waveguide. This limits the practical usability of the waveguide trapping technique with other functions (e.g. analysis, imaging) that require particles to be stationary during diagnosis. In this paper, an optical waveguide loop with an intentional gap at the centre is proposed to hold propelled particles and cells. The waveguide acts as a conveyor belt to transport and deliver the particles/cells towards the gap. At the gap, the diverging light fields hold the particles at a fixed position. The proposed waveguide design is numerically studied and experimentally implemented. The optical forces on the particle at the gap are calculated using the finite element method. Experimentally, the method is used to transport and trap micro-particles and red blood cells at the gap with varying separations. The waveguides are only 180 nm thick and thus could be integrated with other functions on the chip, e.g. microfluidics or optical detection, to make an on-chip system for single cell analysis and to study the interaction between cells. PMID:22814473

  9. Methodologies for Removing/Desorbing and Transporting Particles from Surfaces to Instrumentation

    NASA Astrophysics Data System (ADS)

    Miller, Carla J.; Cespedes, Ernesto R.

    2012-12-01

    Explosive trace detection (ETD) continues to be a key technology supporting the fight against terrorist bombing threats. Very selective and sensitive ETD instruments have been developed to detect explosive threats concealed on personnel, in vehicles, in luggage, and in cargo containers, as well as for forensic analysis (e.g. post blast inspection, bomb-maker identification, etc.) in a broad range of homeland security, law enforcement, and military applications. A number of recent studies have highlighted the fact that significant improvements in ETD systems' capabilities will be achieved, not by increasing the selectivity/sensitivity of the sensors, but by improved techniques for particle/vapor sampling, pre-concentration, and transport to the sensors. This review article represents a compilation of studies focused on characterizing the adhesive properties of explosive particles, the methodologies for removing/desorbing these particles from a range of surfaces, and approaches for transporting them to the instrument. The objectives of this review are to summarize fundamental work in explosive particle characterization, to describe experimental work performed in harvesting and transport of these particles, and to highlight those approaches that indicate high potential for improving ETD capabilities.

  10. Quantitative Analysis of Axonal Transport by Using Compartmentalized and Surface Micropatterned Culture of Neurons

    PubMed Central

    2012-01-01

    Mitochondria, synaptic vesicles, and other cytoplasmic constituents have to travel long distance along the axons from cell bodies to nerve terminals. Interruption of this axonal transport may contribute to many neurodegenerative diseases including Alzheimer’s disease (AD). It has been recently shown that exposure of cultured neurons to β-amyloid (Aβ) resulted in severe impairment of mitochondrial transport. This Letter describes an integrated microfluidic platform that establishes surface patterned and compartmentalized culture of neurons for studying the effect of Aβ on mitochondria trafficking in full length of axons. We have successfully quantified the trafficking of fluorescently labeled mitochondria in distal and proximal axons using image processing. Selective treatment of Aβ in the somal or axonal compartments resulted in considerable decrease in mitochondria movement in a location dependent manner such that mitochondria trafficking slowed down more significantly proximal to the location of Aβ exposure. Furthermore, this result suggests a promising application of microfluidic technology for investigating the dysfunction of axonal transport related to neurodegenerative diseases. PMID:24358503

  11. A Global Assessment of Accelerations in Mass Transport of Surface Geophysical Fluid

    NASA Astrophysics Data System (ADS)

    Wu, X.; Heflin, M. B.

    2015-12-01

    Mass transport in the Earth's surface geophysical fluid layer has complex spatiotemporal patterns. The GRACE gravity mission provides an unprecedented global capability to monitor this important process with high accuracy and resolution. Accurate assessments of global mass transport patterns and budget also depend critically on changes in degree-1 coefficients (geocenter motion) and in Earth's dynamic oblateness coefficient J2. We combine GRACE measurements, time series of GNSS data, JPL's ECCO ocean bottom pressure model, and high-resolution loose a priori models of mass variation regimes to derive complete spherical harmonic spectra of detrended mass variations up to degree and order 180. Mass accelerations are estimated along with linear, annual, semiannual, and the 161-day tidal aliasing components from coefficient time series. The appropriateness of a priori information and estimate uncertainties are further evaluated by variance component estimation and residual statistics of fitting the time series. During the GRACE data period of 2002.2-2015.0, accelerations in mass transport are geographically uneven with significant positive or negative accelerations in various parts of the world. While Greenland and West Antarctica show strong accelerated mass losses, Alaska and the Arctic Ocean have significant positive accelerations with reversals of earlier mass loss trends. No evidence of non-Arctic global mean sea level acceleration due to mass has been found. Depending on region, some estimated accelerations are also not steady over time due to large irregular and interannual variations.

  12. Volatile transport on Venus and implications for surface geochemistry and geology

    NASA Technical Reports Server (NTRS)

    Brackett, Robert A.; Fegley, Bruce; Arvidson, Raymond E.

    1995-01-01

    The high vapor pressure of volatile metal halides and chalcogenides (e.g., of Cu, Zn, Sn, Pb, As, Sb, Bi) at typical Venus surface temperatures, coupled with the altitude-dependent temperature gradient of approximately 8.5 K/km, is calculated to transport volatile metal vapors to the highlands of Venus, where condensation and accumulation will occur. The predicted geochemistry of volatile metals on Venus is supported by observations of CuCl in volcanic gases at Kilauea and Nyiragongo, and large enrichments of these and other volatile elements in terrestrial volcanic aerosols. A one-dimensional finite difference vapor transport model shows the diffusive migration of a thickness of 0.01 to greater than 10 microns/yr of moderately to highly volatile phases (e.g., metal halides and chalcogenides) from the hot lowlands (740 K) to the cold highlands (660 K) on Venus. The diffusive transport of volatile phases on Venus may explain the observed low emissivity of the Venusian highlands, hazes at 6-km altitude observed by two Pioneer Venus entry probes, and the Pioneer Venus entry probe anomalies at 12.5 km.

  13. Atomic Scale Transport in Graphene on Stepped SiC(0001) Surfaces

    NASA Astrophysics Data System (ADS)

    Ji, Shuaihua; Hannon, James B.; Tromp, Ruud M.; Ellis, Arthur W.; Reuter, Mark C.; Ross, Frances M.

    2011-03-01

    Thermal decomposition of SiC is a promising route to wafer-scale epitaxial graphene. However, the initial SiC surface contains steps, and graphene formation induces additional steps. Here we consider how these steps affect current transport in graphene. 1-2ML graphene was grown by annealing SiC above 1300circ; C in disilane. Low energy electron microscopy was used to determine graphene thickness, and transport through 1ML thick regions was measured by scanning tunneling potentiometry. In this technique a bias is applied between two fixed probes while a third, scanning probe measures the local electrochemical potential as well as topography. This allows us to determine the resistivity of the graphene sheet on terraces and across substrate steps. Single steps with 0.5nm height show very weak scattering. However, multiple steps of height 1.0 and 1.5nm scatter strongly, exhibiting a potential drop equivalent to ~ 80 nm and 120nm respectively of terrace graphene. Thus, step bunching is important, and steps separated by less than a few hundred nm can dominate transport through a graphene sheet.

  14. Effects of dietary K on cell-surface expression of renal ion channels and transporters.

    PubMed

    Frindt, Gustavo; Palmer, Lawrence G

    2010-10-01

    Changes in apical surface expression of ion channels and transporters in the superficial rat renal cortex were assessed using biotinylation and immunoblotting during alterations in dietary K intake. A high-K diet increased, and a low-K diet decreased, both the overall and surface abundance of the β- and γ-subunits of the epithelial Na channel (ENaC). In the case of γ-ENaC, the effect was specific for the 65-kDa cleaved form of the protein. The overall amount of α-ENAC was also increased with increasing K intake. The total expression of the secretory K(+) channels (ROMK) increased with a high-K diet and decreased with a low-K diet. The surface expression of ROMK increased with high K intake but was not significantly altered by a low-K diet. In contrast, the amounts of total and surface protein representing the thiazide-sensitive NaCl cotransporter (NCC) decreased with increasing K intake. We conclude that modulation of K(+) secretion in response to changes in dietary K intake involves changes in apical K(+) permeability through regulation of K(+) channels and in driving force subsequent to alterations in both Na delivery to the distal nephron and Na(+) uptake across the apical membrane of the K(+) secretory cells. PMID:20702602

  15. Factors Contributing to the Off-Target Transport of Pyrethroid Insecticides From Urban Surfaces

    PubMed Central

    Jorgenson, Brant C.; Wissel-Tyson, Christopher; Young, Thomas M.

    2013-01-01

    Pyrethroid insecticides used in an urban and suburban context have been found in urban creek sediments and associated with toxicity in aquatic bioassays. The objectives of this study were to evaluate the main factors contributing to the off-target transport of pyrethroid insecticides from surfaces typical of residential landscapes. Controlled rainfall simulations over concrete, bare soil, and turf plots treated individually with pyrethroid insecticides in a suspension concentrate, an emulsifiable concentrate, or a granule formulation were conducted at different rainfall intensities and different product set-time intervals. Pyrethroid mass washoff varied by several orders of magnitude between experimental treatments. Suspension concentrate product application to concrete yielded significantly greater washoff than any other treatment; granule product application to turf yielded the least washoff. Fractional losses at 10 L of runoff ranged from 25.9% to 0.011% of pyrethroid mass applied and 10 L nominal mass losses ranged from 3,970 to 0.18 μg. Mass washoff depended principally on formulation and surface type combination and to a lesser degree set-time interval and rainfall intensity. Treatment effects were analyzed by ANOVA on main factors of formulation, surface type, and set time. Factor effects were not purely additive; a significant interaction between formulation and surface type was noted. PMID:22784034

  16. Controllable Molecule Transport and Release by a Restorable Surface-tethered DNA nanodevice.

    PubMed

    Wang, Zhaoyin; Xu, Yuanyuan; Wang, Haiyan; Liu, Fengzhen; Ren, Zhenning; Wang, Zhaoxia

    2016-01-01

    In this paper, we report a novel surface-tethered DNA nanodevice that may present three states and undergo conformational changes under the operation of pH. Besides, convenient regulation on the electrode surface renders the construction and operation of this DNA nanodevice restorable. To make full use of this DNA nanodevice, ferrocene (Fc) has been further employed for the fabrication of the molecular device. On one hand, the state switches of the DNA nanodevice can be characterized conveniently and reliably by the obtained electrochemical signals from Fc. On the other hand, β-cyclodextrin-ferrocene (β-CD-Fc) host-guest system can be introduced by Fc, which functionalizes this molecular device. Based on different electrochemical behaviors of β-CD under different states, this DNA nanodevice can actualize directional loading, transporting and unloading of β-CD in nanoscale. Therefore, this DNA nanodevice bares promising applications in controllable molecular transport and release, which are of great value to molecular device design. PMID:27384943

  17. Colloid Transport and Surface-Subsurface Exchange in an Acid Mine Drainage-Impacted Stream

    NASA Astrophysics Data System (ADS)

    Norvell, A. S.; Ryan, J. N.; Ren, J.; McKnight, D. M.

    2010-12-01

    Colloidal particles may provide an important control on the mobility of contaminants of concern; e.g., metals introduced into a stream from an acid mine drainage. In order to examine colloidal transport and surface-subsurface exchange, we injected synthesized ferrihydrite colloids along with a conservative tracer, bromide, into Lefthand Creek, a stream contaminated by acid mine drainage in northwestern Boulder County, Colorado. The ferrihydrite colloids were co-precipitated with yttrium to form yttrium-labelled colloids so that we could differentiate them from environmental colloids. Yttrium was measured in samples collected from the surface water and the hyporheic zone. The hyporheic zone samples were collected from a series of mini-piezometers embedded up to 1 m in depth and over a 61 m reach of the stream. A one-dimensional transient storage model (OTIS-P) was used to quantify parameters describing the transport of the conservative tracer and the colloids. Approximately 20% of the colloidal mass was lost over the 61 m reach. The loss of colloids is attributed to deposition in the shallow hyporheic zone. Laboratory column experiments demonstrated that the stream bed sediments effectively remove colloids from suspension at the pH, ionic strength, and dissolved organic matter concentration conditions occurring in Lefthand Creek.

  18. Oceanic Transport of Surface Meltwater from the Southern Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Luo, Hao; Castelao, Renato M.; Rennermalm, Asa K.; Tedesco, Marco; Bracco, Annalisa; Yager, Patricia L.; Mote, Thomas L.

    2016-01-01

    The Greenland ice sheet has undergone accelerating mass losses during recent decades. Freshwater runoff from ice melt can influence fjord circulation and dynamic1 and the delivery of bioavailable micronutrients to the ocean. It can also have climate implications, because stratification in the adjacent Labrador Sea may influence deep convection and the strength of the Atlantic meridional overturning circulation. Yet, the fate of the meltwater in the ocean remains unclear. Here, we use a high-resolution ocean model to show that only 1-15% of the surface meltwater runoff originating from southwest Greenland is transported westwards. In contrast, up to 50-60% of the meltwater runoff originating from southeast Greenland is transported westwards into the northern Labrador Sea, leading to significant salinity and stratification anomalies far from the coast. Doubling meltwater runoff, as predicted in future climate scenarios, results in a more-than-double increase in anomalies offshore that persists further into the winter. Interannual variability in offshore export of meltwater is tightly related to variability in wind forcing. The new insight that meltwaters originating from the west and east coasts have different fates indicates that future changes in mass loss rates and surface runoff will probably impact the ocean differently, depending on their Greenland origins.

  19. ATP-binding cassette transporter controls leaf surface secretion of anticancer drug components in Catharanthus roseus

    PubMed Central

    Yu, Fang; De Luca, Vincenzo

    2013-01-01

    The Madagascar periwinkle (Catharanthus roseus) is highly specialized for the biosynthesis of many different monoterpenoid indole alkaloids (MIAs), many of which have powerful biological activities. Such MIAs include the commercially important chemotherapy drugs vinblastine, vincristine, and other synthetic derivatives that are derived from the coupling of catharanthine and vindoline. However, previous studies have shown that biosynthesis of these MIAs involves extensive movement of metabolites between specialized internal leaf cells and the leaf epidermis that require the involvement of unknown secretory processes for mobilizing catharanthine to the leaf surface and vindoline to internal leaf cells. Spatial separation of vindoline and catharanthine provides a clear explanation for the low levels of dimers that accumulate in intact plants. The present work describes the molecular cloning and functional identification of a unique catharanthine transporter (CrTPT2) that is expressed predominantly in the epidermis of young leaves. CrTPT2 gene expression is activated by treatment with catharanthine, and its in planta silencing redistributes catharanthine to increase the levels of catharanthine–vindoline drug dimers in the leaves. Phylogenetic analysis shows that CrTPT2 is closely related to a key transporter involved in cuticle assembly in plants and that may be unique to MIA-producing plant species, where it mediates secretion of alkaloids to the plant surface. PMID:24019465

  20. ATP-binding cassette transporter controls leaf surface secretion of anticancer drug components in Catharanthus roseus.

    PubMed

    Yu, Fang; De Luca, Vincenzo

    2013-09-24

    The Madagascar periwinkle (Catharanthus roseus) is highly specialized for the biosynthesis of many different monoterpenoid indole alkaloids (MIAs), many of which have powerful biological activities. Such MIAs include the commercially important chemotherapy drugs vinblastine, vincristine, and other synthetic derivatives that are derived from the coupling of catharanthine and vindoline. However, previous studies have shown that biosynthesis of these MIAs involves extensive movement of metabolites between specialized internal leaf cells and the leaf epidermis that require the involvement of unknown secretory processes for mobilizing catharanthine to the leaf surface and vindoline to internal leaf cells. Spatial separation of vindoline and catharanthine provides a clear explanation for the low levels of dimers that accumulate in intact plants. The present work describes the molecular cloning and functional identification of a unique catharanthine transporter (CrTPT2) that is expressed predominantly in the epidermis of young leaves. CrTPT2 gene expression is activated by treatment with catharanthine, and its in planta silencing redistributes catharanthine to increase the levels of catharanthine-vindoline drug dimers in the leaves. Phylogenetic analysis shows that CrTPT2 is closely related to a key transporter involved in cuticle assembly in plants and that may be unique to MIA-producing plant species, where it mediates secretion of alkaloids to the plant surface. PMID:24019465

  1. Oceanic transport of surface meltwater from the southern Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Luo, Hao; Castelao, Renato M.; Rennermalm, Asa K.; Tedesco, Marco; Bracco, Annalisa; Yager, Patricia L.; Mote, Thomas L.

    2016-07-01

    The Greenland ice sheet has undergone accelerating mass losses during recent decades. Freshwater runoff from ice melt can influence fjord circulation and dynamics and the delivery of bioavailable micronutrients to the ocean. It can also have climate implications, because stratification in the adjacent Labrador Sea may influence deep convection and the strength of the Atlantic meridional overturning circulation. Yet, the fate of the meltwater in the ocean remains unclear. Here, we use a high-resolution ocean model to show that only 1-15% of the surface meltwater runoff originating from southwest Greenland is transported westwards. In contrast, up to 50-60% of the meltwater runoff originating from southeast Greenland is transported westwards into the northern Labrador Sea, leading to significant salinity and stratification anomalies far from the coast. Doubling meltwater runoff, as predicted in future climate scenarios, results in a more-than-double increase in anomalies offshore that persists further into the winter. Interannual variability in offshore export of meltwater is tightly related to variability in wind forcing. The new insight that meltwaters originating from the west and east coasts have different fates indicates that future changes in mass loss rates and surface runoff will probably impact the ocean differently, depending on their Greenland origins.

  2. Controllable Molecule Transport and Release by a Restorable Surface-tethered DNA nanodevice

    PubMed Central

    Wang, Zhaoyin; Xu, Yuanyuan; Wang, Haiyan; Liu, Fengzhen; Ren, Zhenning; Wang, Zhaoxia

    2016-01-01

    In this paper, we report a novel surface-tethered DNA nanodevice that may present three states and undergo conformational changes under the operation of pH. Besides, convenient regulation on the electrode surface renders the construction and operation of this DNA nanodevice restorable. To make full use of this DNA nanodevice, ferrocene (Fc) has been further employed for the fabrication of the molecular device. On one hand, the state switches of the DNA nanodevice can be characterized conveniently and reliably by the obtained electrochemical signals from Fc. On the other hand, β-cyclodextrin-ferrocene (β-CD-Fc) host-guest system can be introduced by Fc, which functionalizes this molecular device. Based on different electrochemical behaviors of β-CD under different states, this DNA nanodevice can actualize directional loading, transporting and unloading of β-CD in nanoscale. Therefore, this DNA nanodevice bares promising applications in controllable molecular transport and release, which are of great value to molecular device design. PMID:27384943

  3. Transportation.

    ERIC Educational Resources Information Center

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with transportation and energy use. Its objective is for the student to be able to discuss the implication of energy usage as it applies to the area of transportation. Some topics covered are efficiencies of various transportation…

  4. Applying GIS characterizing and modeling contaminant transport in surface water at Los Alamos National Laboratory

    SciTech Connect

    Becker, N.M.; Van Eeckhout, E.; David, N.A.; Irvine, J.M.

    1995-10-01

    During World War II, Los Alamos, New Mexico was chosen as the site for the secret development of the first atomic bomb. The remote location in the southwestern United States was ideal for such a project. After the war, research activities continued at the Los Alamos installation, focusing on new nuclear weapons models as well as greater effectiveness and reliability of existing weapons. Due to the emphasis on nuclear and non-nuclear weapons development as well as associated nuclear research, a large inventory of radionuclides and heavy metals have been tested, expended, and disposed of in the local environment, a high plateau of tuffaceous volcanic rocks incised by deep canyons in a semi-arid climate. In recent years an intensive evaluation of the environmental, impact of weapons testing at Los Alamos and elsewhere has been undertaken. GIS system utilization and image processing of past and current data has been an important part of this evaluation. Important problems can be more easily displayed and understood using this methodology. The main objective in this paper is to illustrate how transport of depleted uranium and associated heavy metals (copper in this case) used in dynamic testing of weapons components at open air firing sites can be evaluated and visualized. In our studies, surface water has been found to be the predominant transport mechanism. We have sampled soils, sediments, fallout, runoff water and snowmelt over a number of years in order to understand contaminant transport on- and offsite. Statistical analyses of these data have assisted in our characterization of issues such as contaminant variability, spatially and temporally, as well as in development of transport rates.

  5. Impact of the Topological Surface State on the Thermoelectric Transport in Sb2Te3 Thin Films.

    PubMed

    Hinsche, Nicki F; Zastrow, Sebastian; Gooth, Johannes; Pudewill, Laurens; Zierold, Robert; Rittweger, Florian; Rauch, Tomáš; Henk, Jürgen; Nielsch, Kornelius; Mertig, Ingrid

    2015-04-28

    Ab initio electronic structure calculations based on density functional theory and tight-binding methods for the thermoelectric properties of p-type Sb2Te3 films are presented. The thickness-dependent electrical conductivity and the thermopower are computed in the diffusive limit of transport based on the Boltzmann equation. Contributions of the bulk and the surface to the transport coefficients are separated, which enables to identify a clear impact of the topological surface state on the thermoelectric properties. When the charge carrier concentration is tuned, a crossover between a surface-state-dominant and a Fuchs-Sondheimer transport regime is achieved. The calculations are corroborated by thermoelectric transport measurements on Sb2Te3 films grown by atomic layer deposition. PMID:25826737

  6. No-Loss Transportation of Water Droplets by Patterning a Desired Hydrophobic Path on a Superhydrophobic Surface.

    PubMed

    Hu, Haibao; Yu, Sixiao; Song, Dong

    2016-07-26

    The directional transportation of droplets on solid surfaces is essential in a wide range of engineering applications. It is convenient to guide liquid droplets in a given direction by utilizing the gradient of wettability, by which the binding forces can be produced. In contrast to the mass-loss transportation of a droplet moving along hydrophilic paths on a horizontal superhydrophobic surface, we present no-loss transportation by fabricating a hydrophobic path on the same surface under tangential wind. In experimental exploration and theoretical analysis, the conditions of no-loss transportation of a droplet are mainly considered. We demonstrate that the lower (or upper) critical wind velocity, under which the droplet starts on the path (or is derailed from the path), is determined by the width of the path, the length of the contact area in the direction parallel to the path, the drift angle between the path and the wind direction, and the surface wettability of the pattern. Meanwhile, the no-loss transportation of water droplets along the desired path zigzagging on a superhydrophobic surface can be achieved steadily under appropriate conditions. We anticipate that such robust no-loss transportation will find an extensive range of applications. PMID:27359261

  7. Surface runoff from manured cropping systems assessed by the paired-watershed method, part 1: P, N, and sediment transport

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport of P, N, and sediment via runoff from crop fields can contribute to degradation of surface waters. We established a paired-watershed study in central Wisconsin to evaluate surface runoff losses of nutrients, sediment, and pathogens from different manure/crop/tillage management systems for ...

  8. Surface-modified silica colloidal crystals: nanoporous films and membranes with controlled ionic and molecular transport.

    PubMed

    Zharov, Ilya; Khabibullin, Amir

    2014-02-18

    Nanoporous membranes are important for the study of the transport of small molecules and macromolecules through confined spaces and in applications ranging from separation of biomacromolecules and pharmaceuticals to sensing and controlled release of drugs. For many of these applications, chemists need to gate the ionic and molecular flux through the nanopores, which in turn depends on the ability to control the nanopore geometry and surface chemistry. Most commonly used nanoporous membrane materials are based on polymers. However, the nanostructure of polymeric membranes is not well-defined, and their surface is hard to modify. Inorganic nanoporous materials are attractive alternatives for polymers in the preparation of nanoporous membranes. In this Account, we describe the preparation and surface modification of inorganic nanoporous films and membranes self-assembled from silica colloidal spheres. These spheres form colloidal crystals with close-packed face centered cubic lattices upon vertical deposition from colloidal solutions. Silica colloidal crystals contain ordered arrays of interconnected three dimensional voids, which function as nanopores. We can prepare silica colloidal crystals as supported thin films on various flat solid surfaces or obtain free-standing silica colloidal membranes by sintering the colloidal crystals above 1000 °C. Unmodified silica colloidal membranes are capable of size-selective separation of macromolecules, and we can surface-modify them in a well-defined and controlled manner with small molecules and polymers. For the surface modification with small molecules, we use silanol chemistry. We grow polymer brushes with narrow molecular weight distribution and controlled length on the colloidal nanopore surface using atom transfer radical polymerization or ring-opening polymerization. We can control the flux in the resulting surface-modified nanoporous films and membranes by pH and ionic strength, temperature, light, and small molecule

  9. Onsager heat of transport of carbon dioxide at the surface of aqueous ammonia: The remarkable effect of carbamate formation

    NASA Astrophysics Data System (ADS)

    Packwood, Daniel M.; Phillips, Leon F.

    2010-11-01

    The Onsager heat of transport Q∗ has been measured for CO 2 at the surface of aqueous ammonia. The heat of transport incorporates the enthalpy of reaction of gaseous CO 2 with ammonia, adsorbed on the liquid surface, to form adsorbed ammonium carbamate, with the result that -Q∗ has the unusually large value of 180 kJ mol -1. Measurement of Q∗ for transfer of a reactive species through a surfactant monolayer is proposed as a new method of studying reactions at liquid and quasi-liquid surfaces.

  10. Effect of nonionic surfactant on transport of surface-active and non-surface-active model drugs and emulsion stability in triphasic systems.

    PubMed

    Chidambaram, N; Burgess, D J

    2000-01-01

    The effect of surfactant concentration on transport kinetics in emulsions using surface-active (phenobarbital, barbital) and non- surface-active (phenylazoaniline, benzocaine) model drugs is determined. Mineral oil was chosen as the oil phase and the nonionic surfactant polyoxyethylene-10-oleyl-ether (Brij 97) was chosen as the emulsifier. Model drug transport in the triphasic systems was investigated using side-by-side diffusion cells mounted with hydrophilic dialysis membranes (molecular weight cutoffs 1 kd and 50 kd) and a novel bulk equilibrium reverse dialysis bag technique. Emulsion stability was determined by droplet size analysis as a function of time, temperature, and the presence of model drugs, using photon correlation spectroscopy. Mineral oil/water (O/W) partition coefficients and aqueous solubilities were determined in the presence of surfactant. The transport rates of model drugs in emulsions increased with an increase in Brij 97 micellar concentrations up to 1.0% wt/vol and then decreased at higher surfactant concentrations. The transport profiles of the model drugs appeared to be governed by model drug O/W partition coefficient values and by micellar shape changes at higher surfactant concentrations. Total transport rates of phenobarbital and barbital were faster than those of phenylazoaniline and benzocaine. Excess surfactant affected the transport rates of the model drugs in the emulsions depending on drug surface activity and lipophilicity. PMID:11741246

  11. Formulation Effects and the Off-target Transport of Pyrethroid Insecticides from Urban Hard Surfaces

    PubMed Central

    Jorgenson, Brant C.; Young, Thomas M.

    2010-01-01

    Controlled rainfall experiments utilizing drop forming rainfall simulators were conducted to study various factors contributing to off-target transport of off-the-shelf formulated pyrethroid insecticides from concrete surfaces. Factors evaluated included active ingredient, product formulation, time between application and rainfall (set time), and rainfall intensity. As much as 60% and as little as 0.8% of pyrethroid applied could be recovered in surface runoff depending primarily on product formulation, and to a lesser extent on product set time. Resulting wash-off profiles during one-hour storm simulations could be categorized based on formulation, with formulations utilizing emulsifying surfactants rather than organic solvents resulting in unique wash-off profiles with overall higher wash-off efficiency. These higher wash-off efficiency profiles were qualitatively replicated by applying formulation-free neat pyrethroid in the presence of independently applied linear alkyl benzene sulfonate (LAS) surfactant, suggesting that the surfactant component of some formulated products may be influential in pyrethroid wash-off from urban hard surfaces. PMID:20524665

  12. Electronic transport properties of transition metal dichalcogenide field-effect devices: surface and interface effects.

    PubMed

    Schmidt, Hennrik; Giustiniano, Francesco; Eda, Goki

    2015-11-01

    Recent explosion of interest in two-dimensional (2D) materials research has led to extensive exploration of physical and chemical phenomena unique to this new class of materials and their technological potential. Atomically thin layers of group 6 transition metal dichalcogenides (TMDs) such as MoS2 and WSe2 are remarkably stable semiconductors that allow highly efficient electrostatic control due to their 2D nature. Field effect transistors (FETs) based on 2D TMDs are basic building blocks for novel electronic and chemical sensing applications. Here, we review the state-of-the-art of TMD-based FETs and summarize the current understanding of interface and surface effects that play a major role in these systems. We discuss how controlled doping is key to tailoring the electrical response of these materials and realizing high performance devices. The first part of this review focuses on some fundamental features of gate-modulated charge transport in 2D TMDs. We critically evaluate the role of surfaces and interfaces based on the data reported in the literature and explain the observed discrepancies between the experimental and theoretical values of carrier mobility. The second part introduces various non-covalent strategies for achieving desired doping in these systems. Gas sensors based on charge transfer doping and electrostatic stabilization are introduced to highlight progress in this direction. We conclude the review with an outlook on the realization of tailored TMD-based field-effect devices through surface and interface chemistry. PMID:26088725

  13. A flexible numerical component to simulate surface runoff transport and biogeochemical processes through dense vegetation

    NASA Astrophysics Data System (ADS)

    Munoz-Carpena, R.; Perez-Ovilla, O.

    2012-12-01

    Methods to estimate surface runoff pollutant removal using dense vegetation buffers (i.e. vegetative filter strips) usually consider a limited number of factors (i.e. filter length, slope) and are in general based on empirical relationships. When an empirical approach is used, the application of the model is limited to those conditions of the data used for the regression equations. The objective of this work is to provide a flexible numerical mechanistic tool to simulate dynamics of a wide range of surface runoff pollutants through dense vegetation and their physical, chemical and biological interactions based on equations defined by the user as part of the model inputs. A flexible water quality model based on the Reaction Simulation Engine (RSE) modeling component is coupled to a transport module based on the traditional Bubnov -Galerkin finite element method to solve the advection-dispersion-reaction equation using the alternating split-operator technique. This coupled transport-reaction model is linked to the VFSMOD-W (http://abe.ufl.edu/carpena/vfsmod) program to mechanistically simulate mobile and stabile pollutants through dense vegetation based on user-defined conceptual models (differential equations written in XML language as input files). The key factors to consider in the creation of a conceptual model are the components in the buffer (i.e. vegetation, soil, sediments) and how the pollutant interacts with them. The biogeochemical reaction component was tested successfully with laboratory and field scale experiments. One of the major advantages when using this tool is that the pollutant transport and removal thought dense vegetation is related to physical and biogeochemical process occurring within the filter. This mechanistic approach increases the range of use of the model to a wide range of pollutants and conditions without modification of the core model. The strength of the model relies on the mechanistic approach used for simulating the removal of

  14. Determination of parameters of Cu surface mass transport on sapphire from morphological changes of beaded films caused by evaporation

    NASA Astrophysics Data System (ADS)

    Beszeda, I.; Beke, D. L.

    Basic parameters of surface mass transport - the surface diffusion length of adatoms, λs, the surface diffusion coefficient, Ds', and the surface reaction rate coefficient, βs', of Cu on alumina are determined in the temperature range 1048-1198 K. Measuring simultaneously the time dependence of the effective thickness, Heff(t), the lateral shift of the boundary, y(t) of beaded films (BF) and using vapour pressure data we concluded that the process is controlled by surface reaction at the perimeters of beads. Supposing Arrhenius-type temperature dependence for Ds', βs' and λs the activation energies and preexponential factors have been calculated.

  15. In situ investigation of titanium nitride surface dynamics: The role of surface and bulk mass transport processes

    NASA Astrophysics Data System (ADS)

    Bareno, Javier

    NaCl-structure TiN and related transition-metal (TM) nitrides are widely used as hard wear-resistant coatings on cutting tools, diffusion-barriers in microelectronic devices, corrosion-resistant layers on mechanical components, and abrasion-resistant thin films on optics and architectural glass. Since the elastic and physical properties of TiN are highly anisotropic, controlling the microstructural and surface morphological evolution of polycrystalline TM nitride films is important for all of the above applications. In this thesis, I used in-situ high-temperature low-energy electron microscopy (LEEM) to gain insight into film growth and microstructure development dynamics by studying mass-transport processes occurring during annealing of three dimensional (3D) structures on TiN surfaces. Additionally, in order to extend the current understanding of nanostructure development in binary nitride films to more complex ternary TM-nitride-based nanocomposites, I employed in-situ scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED), as well as ab-initio modeling, to investigate the atomic structure of the SiNx/TiN heterointerfaces which control the properties of SiNx-TiN nanocomposites. The LEEM studies of mass transport on TiN(111) focus on two specific surface morphologies which are observed to be present during growth of TiN single-crystals. (1) I investigated the temperature-dependent coarsening/decay kinetics of three-dimensional TiN island mounds on large (>1000 A) atomically-flat terraces; showing that TiN(111) steps are highly permeable and exhibit strong repulsive temperature-dependent step-step interactions that vary from 0.03 eV-A at 1559 K to 0.76 eV-A at 1651 K. (2) I studied the nucleation and growth of spiral steps originating at surface-terminated screw dislocations; I developed a model of spiral growth relating the emission rate of point defects from the bulk to the temperature-dependent spiral rotation frequency o(T); and I

  16. Using Contaminant Transport Modeling to Determine Historical Discharges at the Surface

    NASA Astrophysics Data System (ADS)

    Fogwell, T. W.

    2013-12-01

    When it is determined that a contaminated site needs to be remediated, the issue of who is going to pay for that remediation is an immediate concern. This means that there needs to be a determination of who the responsible parties are for the existing contamination. Seldom is it the case that records have been made and kept of the surface contaminant discharges. In many cases it is possible to determine the relative amount of contaminant discharge at the surface of the various responsible parties by employing a careful analysis of the history of contaminant transport through the surface, through the vadose zone, and within the saturated zone. The process begins with the development of a dynamic conceptual site model that takes into account the important features of the transport of the contaminants through the vadose zone and in the groundwater. The parameters for this model can be derived from flow data available for the site. The resulting contaminant transport model is a composite of the vadose zone transport model, together with the saturated zone (groundwater) flow model. Any calibration of the model should be carefully employed in order to avoid using information about the conclusions of the relative discharge amounts of the responsible parties in determining the calibrated parameters. Determination of the leading edge of the plume is an important first step. It is associated with the first discharges from the surface of the site. If there were several discharging parties at the same time, then it is important to establish a chemical or isotopic signature of the chemicals that were discharged. The time duration of the first discharger needs to be determined as accurately as possible in order to establish the appropriate characterization of the leading portion of the resulting plume in the groundwater. The information about the first discharger and the resulting part of the plume associated with this discharger serves as a basis for the determination of the

  17. Long range inhabited surface transportation system power source for the exploration of Mars (manned Mars mission)

    NASA Technical Reports Server (NTRS)

    Kohout, Lisa; Banyai, Mark; Amick, Robert

    1986-01-01

    A hydrogen-oxygen fuel cell system is identified as a viable power source for a long range inhabited surface transportation system for the exploration of Mars. Power system weights and power requirements are determined as a function of vehicle weight. For vehicles weighing from 2700 to 7300 kg in LEO, the total power system weight ranges from 1140 to 1860 kg, with the reactants and energy conversion hardware (fuel cells, reactant storage, and radiator) weighing 430 to 555 kg and 610 to 1110 kg, respectively. Vehicle power requirements range from 45 kW for a 2700 kg vehicle to 110 kW for a 7300 kg vehicle. Power system specific weights and power profiles for housekeeping and the operation of scientific equipment such as coring drills and power tools are also specified.

  18. Solution, surface, and single molecule platforms for the study of DNA-mediated charge transport

    PubMed Central

    Muren, Natalie B.; Olmon, Eric D.; Barton, Jacqueline K.

    2012-01-01

    The structural core of DNA, a continuous stack of aromatic heterocycles, the base pairs, which extends down the helical axis, gives rise to the fascinating electronic properties of this molecule that is so critical for life. Our laboratory and others have developed diverse experimental platforms to investigate the capacity of DNA to conduct charge, termed DNA-mediated charge transport (DNA CT). Here, we present an overview of DNA CT experiments in solution, on surfaces, and with single molecules that collectively provide a broad and consistent perspective on the essential characteristics of this chemistry. DNA CT can proceed over long molecular distances but is remarkably sensitive to perturbations in base pair stacking. We discuss how this foundation, built with data from diverse platforms, can be used both to inform a mechanistic description of DNA CT and to inspire the next platforms for its study: living organisms and molecular electronics. PMID:22850865

  19. Decay Characteristics of Surface Mounds with Contrasting Interlayer Mass Transport Channels

    SciTech Connect

    Li, Maozhi; Wendelken, J. F.; Liu, Bang-Gui; Wang, E. G.; Zhang, Zhenyu

    2001-03-12

    The decay characteristics of three-dimensional (3D) islands formed on surfaces are investigated theoretically considering two types of interlayer mass transport mechanisms. If an adatom on a given layer can easily descend from any site along the periphery of the layer, an optimal island slope and a constant terrace width will be selected during the decay. In contrast, if the adatom can descend primarily through selective (such as kinked) sites, the decay will be accompanied by a gradual increase in the island slope. These generic conclusions provide the basis for a microscopic understanding of the decay of nanostructures in fcc(111) and fcc(100) metal homoepitaxy and are applicable to other systems as well.

  20. River stage influences on uranium transport in a hydrologically dynamic groundwater-surface water transition zone

    NASA Astrophysics Data System (ADS)

    Zachara, John M.; Chen, Xingyuan; Murray, Chris; Hammond, Glenn

    2016-03-01

    A well-field within a uranium (U) plume in the groundwater-surface water transition zone was monitored for a 3 year period for water table elevation and dissolved solutes. The plume discharges to the Columbia River, which displays a dramatic spring stage surge resulting from snowmelt. Groundwater exhibits a low hydrologic gradient and chemical differences with river water. River water intrudes the site in spring. Specific aims were to assess the impacts of river intrusion on dissolved uranium (Uaq), specific conductance (SpC), and other solutes, and to discriminate between transport, geochemical, and source term heterogeneity effects. Time series trends for Uaq and SpC were complex and displayed large temporal and well-to-well variability as a result of water table elevation fluctuations, river water intrusion, and changes in groundwater flow directions. The wells were clustered into subsets exhibiting common behaviors resulting from the intrusion dynamics of river water and the location of source terms. Hot-spots in Uaq varied in location with increasing water table elevation through the combined effects of advection and source term location. Heuristic reactive transport modeling with PFLOTRAN demonstrated that mobilized Uaq was transported between wells and source terms in complex trajectories, and was diluted as river water entered and exited the groundwater system. While Uaq time-series concentration trends varied significantly from year-to-year as a result of climate-caused differences in the spring hydrograph, common and partly predictable response patterns were observed that were driven by water table elevation, and the extent and duration of river water intrusion.

  1. River stage influences on uranium transport in a hydrologically dynamic groundwater-surface water transition zone

    DOE PAGESBeta

    Zachara, John M.; Chen, Xingyuan; Murray, Chris; Hammond, Glenn

    2016-03-04

    In this study, a well-field within a uranium (U) plume in the groundwater-surface water transition zone was monitored for a 3 year period for water table elevation and dissolved solutes. The plume discharges to the Columbia River, which displays a dramatic spring stage surge resulting from snowmelt. Groundwater exhibits a low hydrologic gradient and chemical differences with river water. River water intrudes the site in spring. Specific aims were to assess the impacts of river intrusion on dissolved uranium (Uaq), specific conductance (SpC), and other solutes, and to discriminate between transport, geochemical, and source term heterogeneity effects. Time series trendsmore » for Uaq and SpC were complex and displayed large temporal and well-to-well variability as a result of water table elevation fluctuations, river water intrusion, and changes in groundwater flow directions. The wells were clustered into subsets exhibiting common behaviors resulting from the intrusion dynamics of river water and the location of source terms. Hot-spots in Uaq varied in location with increasing water table elevation through the combined effects of advection and source term location. Heuristic reactive transport modeling with PFLOTRAN demonstrated that mobilized Uaq was transported between wells and source terms in complex trajectories, and was diluted as river water entered and exited the groundwater system. While Uaq time-series concentration trends varied significantly from year-to-year as a result of climate-caused differences in the spring hydrograph, common and partly predictable response patterns were observed that were driven by water table elevation, and the extent and duration of river water intrusion.« less

  2. River stage influences on uranium transport in a hydrologically dynamic groundwater-surface water transition zone

    DOE PAGESBeta

    Zachara, John M.; Chen, Xingyuan; Murray, Chris; Hammond, Glenn

    2016-03-04

    A well-field within a uranium (U) plume in the groundwater-surface water transition zone was monitored for a 3 year period for water table elevation and dissolved solutes. The plume discharges to the Columbia River, which displays a dramatic spring stage surge resulting from snowmelt. Groundwater exhibits a low hydrologic gradient and chemical differences with river water. River water intrudes the site in spring. Specific aims were to assess the impacts of river intrusion on dissolved uranium (Uaq), specific conductance (SpC), and other solutes, and to discriminate between transport, geochemical, and source term heterogeneity effects. As a result of water tablemore » elevation fluctuations, river water intrusion, and changes in groundwater flow directions, time series trends for Uaq and SpC were found to be complex and displayed large temporal and well-to-well variability. The wells were clustered into subsets exhibiting common behaviors resulting from the intrusion dynamics of river water and the location of source terms. Hot-spots in Uaq varied in location with increasing water table elevation through the combined effects of advection and source term location. Heuristic reactive transport modeling with PFLOTRAN demonstrated that mobilized Uaq was transported between wells and source terms in complex trajectories, and was diluted as river water entered and exited the groundwater system. Moreover, while Uaq time-series concentration trends varied significantly from year-to-year as a result of climate-caused differences in the spring hydrograph, common and partly predictable response patterns were observed that were driven by water table elevation, and the extent and duration of river water intrusion.« less

  3. Inverse modeling of atmospheric mercury emissions using a global chemical transport model and surface observations

    NASA Astrophysics Data System (ADS)

    Song, S.; Selin, N. E.

    2012-12-01

    We use inverse modeling in combination with worldwide observational data to constrain atmospheric mercury fluxes and associated uncertainties from anthropogenic and natural sources. Though atmospheric transport is a critical pathway of global mercury transport, large uncertainties exist in estimating the magnitudes and temporal variabilities of mercury emissions to the atmosphere from both natural and anthropogenic processes. Previous estimations have primarily used a so-called "bottom-up" approach, which extrapolates the few direct measurements to larger regions or uses simplified process models to estimate fluxes. Here, we apply a "top-down" or inverse modeling approach. Worldwide surface observations of total gaseous mercury (TGM) and simulations from a global chemical transport model (GEOS-Chem version 9-01-02 with a 2 by 2.5 degree horizontal resolution) are combined to estimate mercury fluxes. Time-invariant anthropogenic emission and seasonally varying fluxes (e.g., ocean evasion, biomass burning, and soil volatilization) are optimally estimated by Kalman filter between 2005 and 2009 at a monthly time resolution. The reference source spatial distributions are shown in Figure 1. We collected data from 16 measurement sites with high precision and frequency, covering most active stations during our period of study. The observations and reference model outputs at 4 representative sites are compared in Figure 2. We test the inverse model by comparing model-measurement fits between the reference model and optimized emissions.igure 1. Mercury reference source spatial distributions. Annually averaged patterns are shown in log scale. igure 2. Comparison of TGM monthly mean observations between observations (black, shown with standard deviations) and reference model results (red) at 4 representative sites.

  4. Vitamin A Transport Mechanism of the Multitransmembrane Cell-Surface Receptor STRA6

    PubMed Central

    Kawaguchi, Riki; Zhong, Ming; Kassai, Miki; Ter-Stepanian, Mariam; Sun, Hui

    2015-01-01

    Vitamin A has biological functions as diverse as sensing light for vision, regulating stem cell differentiation, maintaining epithelial integrity, promoting immune competency, regulating learning and memory, and acting as a key developmental morphogen. Vitamin A derivatives have also been used in treating human diseases. If vitamin A is considered a drug that everyone needs to take to survive, evolution has come up with a natural drug delivery system that combines sustained release with precise and controlled delivery to the cells or tissues that depend on it. This “drug delivery system” is mediated by plasma retinol binding protein (RBP), the principle and specific vitamin A carrier protein in the blood, and STRA6, the cell-surface receptor for RBP that mediates cellular vitamin A uptake. The mechanism by which the RBP receptor absorbs vitamin A from the blood is distinct from other known cellular uptake mechanisms. This review summarizes recent progress in elucidating the fundamental molecular mechanism mediated by the RBP receptor and multiple newly discovered catalytic activities of this receptor, and compares this transport system with retinoid transport independent of RBP/STRA6. How to target this new type of transmembrane receptor using small molecules in treating diseases is also discussed. PMID:26343735

  5. Surface Flux Transport and the Evolution of the Sun's Polar Fields

    NASA Astrophysics Data System (ADS)

    Wang, Y.-M.

    2016-04-01

    The evolution of the polar fields occupies a central place in flux transport (Babcock-Leighton) models of the solar cycle. We discuss the relationship between surface flux transport and polar field evolution, focusing on two main issues: the latitudinal profile of the meridional flow and the axial tilts of active regions. Recent helioseismic observations indicate that the poleward flow speed peaks at much lower latitudes than inferred from magnetic feature tracking, which includes the effect of supergranular diffusion and thus does not represent the actual bulk flow. Employing idealized simulations, we demonstrate that flow profiles that peak at mid latitudes give rise to overly strong and concentrated polar fields. We discuss the differences between magnetic and white-light measurements of tilt angles, noting the large uncertainties inherent in the sunspot group measurements and their tendency to underestimate the actual tilts. We find no clear evidence for systematic cycle-to-cycle variations in Joy's law during cycles 21-23. Finally, based on the observed evolution of the Sun's axial dipole component and polar fields up to the end of 2015, we predict that cycle 25 will be similar in amplitude to cycle 24.

  6. The reactivity of chlorite surfaces: Microscopic alteration processes and the transport behaviour of uranium(VI)

    NASA Astrophysics Data System (ADS)

    Bosbach, D.; Brandt, F.; Arnold, T.; Krawczyk-Baersch, E.; Bernhard, G.

    2003-04-01

    The transport of U(VI) in phyllite rocks or on granitic fractures is significantly affected by the dissolution of chlorite and the re-precipitation of various secondary phases. However, in order to be able to predict the behaviour of radionuclides in these systems a sound understanding of the reaction kinetics of chlorite alteration/dissolution processes as well as the precipitation of secondary phases is required. We have studied the dissolution of chlorite with mixed-flow reactor experiments and in-situ AFM observations far from equilibrium over a broad pH range. Key parameters such as the reactive surface area as well as the stoichiometry and pH dependency of the dissolution reaction were determined. Speciation calculations indicate that no secondary phases have formed (except under neutral pH conditions). Under acidic conditions the brucite-like layer of the chlorite structure dissolves faster than the 2:1 TOT layer whereas above pH 8 a reverse dissolution behaviour was observed. Under acidic conditions (pH < 5) chlorite transforms to a vermiculite-like clay mineral, which has also been identified in field studies. In addition, static batch dissolution experiments with chlorite were performed in order to mimic more closely natural systems. In these experiments various secondary phases including hydrous ferrous oxides (HFO) were formed as coatings on chlorite surfaces and as colloids in solution. Batch adsorption experiments indicate that U(VI) has a strong affinity to HFO and that retardation of U(VI) occurs via adsorption to immobile HFO coatings on chlorite surfaces. Heterogeneous HFO formation seems to be favoured on {hk0} edge surfaces in the near neutral pH range. The formation mechanism of HFO coatings was studied systematically with titration experiments, in order to be able to quantify the homogeneous and heterogeneous formation of these secondary phases as a function of the geochemical conditions.

  7. Multiple Surface Regions on the Niemann-Pick C2 Protein Facilitate Intracellular Cholesterol Transport.

    PubMed

    McCauliff, Leslie A; Xu, Zhi; Li, Ran; Kodukula, Sarala; Ko, Dennis C; Scott, Matthew P; Kahn, Peter C; Storch, Judith

    2015-11-01

    The cholesterol storage disorder Niemann-Pick type C (NPC) disease is caused by defects in either of two late endosomal/lysosomal proteins, NPC1 and NPC2. NPC2 is a 16-kDa soluble protein that binds cholesterol in a 1:1 stoichiometry and can transfer cholesterol between membranes by a mechanism that involves protein-membrane interactions. To examine the structural basis of NPC2 function in cholesterol trafficking, a series of point mutations were generated across the surface of the protein. Several NPC2 mutants exhibited deficient sterol transport properties in a set of fluorescence-based assays. Notably, these mutants were also unable to promote egress of accumulated intracellular cholesterol from npc2(-/-) fibroblasts. The mutations mapped to several regions on the protein surface, suggesting that NPC2 can bind to more than one membrane simultaneously. Indeed, we have previously demonstrated that WT NPC2 promotes vesicle-vesicle interactions. These interactions were abrogated, however, by mutations causing defective sterol transfer properties. Molecular modeling shows that NPC2 is highly plastic, with several intense positively charged regions across the surface that could interact favorably with negatively charged membrane phospholipids. The point mutations generated in this study caused changes in NPC2 surface charge distribution with minimal conformational changes. The plasticity, coupled with membrane flexibility, probably allows for multiple cholesterol transfer routes. Thus, we hypothesize that, in part, NPC2 rapidly traffics cholesterol between closely appositioned membranes within the multilamellar interior of late endosomal/lysosomal proteins, ultimately effecting cholesterol egress from this compartment. PMID:26296895

  8. Nitrogen Transport from Atmospheric Deposition and Contaminated Groundwater to Surface Waters on a Watershed Scale.

    NASA Astrophysics Data System (ADS)

    Showers, W. J.; Demaster, D.

    2005-12-01

    Increasing nitrate contamination of surface water and groundwater is a problem in regions of intensive agriculture and near urban wastewater treatment facilities that land-apply biosolids. The 15N composition of groundwater nitrate has been used to assess potential sources of nitrogen contamination. But because of transformations of nitrogen within the hydrological system, contaminant source tracing with nitrogen isotopes has been complicated. We have used multiple isotope tracers of nitrate (15N, 17O, 18O) to distinguish between different N contamination sources, areas of extensive denitrification, and areas of atmospheric N deposition on the NC coastal plain and piedmont. Areas of extensive denitrification are often associated with hydric soils. The distribution of hydric soils on field and watershed scales correlates with surface and ground water quality degradation. The distribution of hydric soils may thus be an important element in prediction of environmental impacts of agriculture. Transport of atmospheric nitrogen into surface waters as indicated by the 17O of nitrate is event driven. Most surface waters in our study area have low concentrations of nitrate 17O, indicating that the importance of atmospheric N has been overestimated in riverine N flux from watersheds. However, when the atmospheric N flux is integrated over a discharge event, atmospheric N can approach 25 % of the total N riverine flux in urban areas. More work needs to be completed with multiple isotopic tracers and GIS analysis on watershed scales. Using a GIS / isotope approach, areas where the isotopic signature has been affected by denitrification can be predicted, and remediation efforts can be focused on potential areas of N contamination where extensive denitrification is unlikely to occur.

  9. Transport toward earth of ions sputtered from the moon's surface by the solar wind

    NASA Astrophysics Data System (ADS)

    Cladis, J. B.; Francis, W. E.; Vondrak, R. R.

    1994-01-01

    The transport of typical ions from the surface of the Moon to the vicinity of Earth was calculated using a test particle approach. It was assumed that the ions were sputtered from the surface by the solar wind, with fluxes in the range determined experimentally by Elphic et al. (1991), and were accelerated initially to 10 eV by the potential of the Moon on its sunlit side. Si(+) and Ca(+) ions were selected for this transport analysis because their masses are within two prominent ion mass groups that have high sputtering yields. In the solar wind the ion trajectories were traced in the following superimposed fields: (1) a steady magnetic field B0 at an angle of 45 deg to the solar wind velocity VSW, (2) the motional electric field Ezero = -V(sub SW x B0, and (3) turbulent magnetic and electric fields generated by hydromagnetic waves with a k-space power spectrum of absolute value of k-5/3 propagating along both directions of the magnetic field B0. Interactions with Earth's bow shock and magnetosphere were included. Case histories of the ions were recorded in the XGSM, YGSM plane and in various planes perpendicular to the E0 x B0 drift direction of the ions between the Moon and Earth. The number density, energy and angular distributions, and directional and omnidirectional fluxes of the ions were constructed from the case histories. It was found that the diffusion of the ions increases rapidly as the amplitude of the turbulence delta Brms increases beyond the value 0.04 B0. Recent measurements of lunar ions upstream of the bow shock by Hilchenbach et al. (1992) generally confirm the predicted behavior of the ions.

  10. Transport and retention of phosphorus in surface water in an urban slum area

    NASA Astrophysics Data System (ADS)

    Nyenje, P. M.; Meijer, L. M. G.; Foppen, J. W.; Kulabako, R.; Uhlenbrook, S.

    2013-08-01

    The transport of excessive phosphorus (P) discharged from unsewered informal settlements (slums) due to poor on-site sanitation is largely unknown. Hence, we investigated the processes governing P transport in a 28 km2 slum-dominated catchment in Kampala, Uganda. During high runoff events and a period of base flow, we collected hourly water samples (over 24 h) from a primary channel draining the catchment and from a small size tertiary channel draining one of the contributing slum areas (0.5 km2). Samples were analyzed for orthophosphate (PO4-P), particulate P (PP), total P (TP) and selected hydro-chemical parameters. Channel bed and suspended sediments were collected to determine their sorption potential, geo-available metals and dominant P forms. We found that P inputs in the catchment originated mainly from domestic wastewater as evidenced by high concentrations of Cl (36-144 mg L-1), HCO3 and other cations in the channels. Most P discharged during low flow conditions was particulate implying that much of it was retained in bed sediments. Retained P was mostly bound to Ca and Fe/Al oxides. Hence, we inferred that mineral precipitation and adsorption to Ca-minerals were the dominant P retention processes. Bed sediments were P-saturated and showed a tendency to release P to discharging waters. P released was likely due to Ca-bound P because of the strong correlation between Ca and total P in sediments (r2 = 0.9). High flows exhibited a strong flush of PP and SS implying that part of P retained was frequently flushed out of the catchment by surface erosion and resuspension of bed sediment. Our findings suggest that P accumulated in the channel bed during low flows and then was slowly released into surface water. Hence, it will likely take some time, even with improved wastewater management practices, before P loads to downstream areas can be significantly reduced.

  11. Effect of cationic surfactant on transport of surface-active and non-surface-active model drugs and emulsion stability in triphasic systems.

    PubMed

    Chidambaram, N; Burgess, D J

    2000-01-01

    A study was carried out to determine the effect of excess surfactant on transport kinetics in emulsions, using surface-active (phenobarbital, barbital) and non-surface-active (phenylazoaniline, benzocaine) model drugs (pH 7.0). Mineral oil was chosen as the oil phase, and the ionic surfactant cetyltrimethylammonium bromide (CTAB) was chosen as the emulsifier. The effect of nonionic surfactant Brij 97 on transport kinetics of these model drugs were determined by authors elsewhere. Model drug transport in the triphasic systems was investigated using side-by-side diffusion cells mounted with hydrophilic dialysis membranes (molecular weight cutoffs 1 kD and 50 kD) and a novel bulk equilibrium reverse dialysis bag technique. Emulsion stability was determined by droplet size analysis as a function of time, temperature, and the presence of model drugs using photon correlation spectroscopy. Mineral oil/water partition coefficients and aqueous solubilities were determined in the presence of surfactant. The droplet size of the CTAB-stabilized emulsion system is bigger than that of the Brij 97-stabilized system because of the relatively less dense interfacial packing of the cationic surfactant. CTAB forms a complex with the model drugs because of ionic interaction between CTAB and the aromatic and azo groups of the model drugs. This complexation is expected to increase emulsion stability and affect model drug transport kinetics. The transport rates of model drugs in emulsions increased with increases in CTAB micellar concentrations up to 0.5% w/v and then decreased at higher surfactant concentrations. Total transport rates of phenobarbital and barbital were faster than those of phenylazoaniline and benzocaine. Excess surfactant affected the transport rates of the model drugs in the emulsions depending on drug surface activity and lipophilicity. The transport profiles of the model drugs appeared to be governed by model drug oil/water partition coefficient values and by

  12. Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality

    SciTech Connect

    Morrison, Glenn C.

    1999-12-01

    In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, and separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10

  13. Spatio-Temporal Modelling of Dust Transport over Surface Mining Areas and Neighbouring Residential Zones

    PubMed Central

    Matejicek, Lubos; Janour, Zbynek; Benes, Ludek; Bodnar, Tomas; Gulikova, Eva

    2008-01-01

    Projects focusing on spatio-temporal modelling of the living environment need to manage a wide range of terrain measurements, existing spatial data, time series, results of spatial analysis and inputs/outputs from numerical simulations. Thus, GISs are often used to manage data from remote sensors, to provide advanced spatial analysis and to integrate numerical models. In order to demonstrate the integration of spatial data, time series and methods in the framework of the GIS, we present a case study focused on the modelling of dust transport over a surface coal mining area, exploring spatial data from 3D laser scanners, GPS measurements, aerial images, time series of meteorological observations, inputs/outputs form numerical models and existing geographic resources. To achieve this, digital terrain models, layers including GPS thematic mapping, and scenes with simulation of wind flows are created to visualize and interpret coal dust transport over the mine area and a neighbouring residential zone. A temporary coal storage and sorting site, located near the residential zone, is one of the dominant sources of emissions. Using numerical simulations, the possible effects of wind flows are observed over the surface, modified by natural objects and man-made obstacles. The coal dust drifts with the wind in the direction of the residential zone and is partially deposited in this area. The simultaneous display of the digital map layers together with the location of the dominant emission source, wind flows and protected areas enables a risk assessment of the dust deposition in the area of interest to be performed. In order to obtain a more accurate simulation of wind flows over the temporary storage and sorting site, 3D laser scanning and GPS thematic mapping are used to create a more detailed digital terrain model. Thus, visualization of wind flows over the area of interest combined with 3D map layers enables the exploration of the processes of coal dust deposition at a

  14. Neuronal activity mediated regulation of glutamate transporter GLT-1 surface diffusion in rat astrocytes in dissociated and slice cultures.

    PubMed

    Al Awabdh, Sana; Gupta-Agarwal, Swati; Sheehan, David F; Muir, James; Norkett, Rosalind; Twelvetrees, Alison E; Griffin, Lewis D; Kittler, Josef T

    2016-07-01

    The astrocytic GLT-1 (or EAAT2) is the major glutamate transporter for clearing synaptic glutamate. While the diffusion dynamics of neurotransmitter receptors at the neuronal surface are well understood, far less is known regarding the surface trafficking of transporters in subcellular domains of the astrocyte membrane. Here, we have used live-cell imaging to study the mechanisms regulating GLT-1 surface diffusion in astrocytes in dissociated and brain slice cultures. Using GFP-time lapse imaging, we show that GLT-1 forms stable clusters that are dispersed rapidly and reversibly upon glutamate treatment in a transporter activity-dependent manner. Fluorescence recovery after photobleaching and single particle tracking using quantum dots revealed that clustered GLT-1 is more stable than diffuse GLT-1 and that glutamate increases GLT-1 surface diffusion in the astrocyte membrane. Interestingly, the two main GLT-1 isoforms expressed in the brain, GLT-1a and GLT-1b, are both found to be stabilized opposed to synapses under basal conditions, with GLT-1b more so. GLT-1 surface mobility is increased in proximity to activated synapses and alterations of neuronal activity can bidirectionally modulate the dynamics of both GLT-1 isoforms. Altogether, these data reveal that astrocytic GLT-1 surface mobility, via its transport activity, is modulated during neuronal firing, which may be a key process for shaping glutamate clearance and glutamatergic synaptic transmission. GLIA 2016;64:1252-1264. PMID:27189737

  15. Neuronal activity mediated regulation of glutamate transporter GLT‐1 surface diffusion in rat astrocytes in dissociated and slice cultures

    PubMed Central

    Al Awabdh, Sana; Gupta‐Agarwal, Swati; Sheehan, David F.; Muir, James; Norkett, Rosalind; Twelvetrees, Alison E.; Griffin, Lewis D.

    2016-01-01

    The astrocytic GLT‐1 (or EAAT2) is the major glutamate transporter for clearing synaptic glutamate. While the diffusion dynamics of neurotransmitter receptors at the neuronal surface are well understood, far less is known regarding the surface trafficking of transporters in subcellular domains of the astrocyte membrane. Here, we have used live‐cell imaging to study the mechanisms regulating GLT‐1 surface diffusion in astrocytes in dissociated and brain slice cultures. Using GFP‐time lapse imaging, we show that GLT‐1 forms stable clusters that are dispersed rapidly and reversibly upon glutamate treatment in a transporter activity‐dependent manner. Fluorescence recovery after photobleaching and single particle tracking using quantum dots revealed that clustered GLT‐1 is more stable than diffuse GLT‐1 and that glutamate increases GLT‐1 surface diffusion in the astrocyte membrane. Interestingly, the two main GLT‐1 isoforms expressed in the brain, GLT‐1a and GLT‐1b, are both found to be stabilized opposed to synapses under basal conditions, with GLT‐1b more so. GLT‐1 surface mobility is increased in proximity to activated synapses and alterations of neuronal activity can bidirectionally modulate the dynamics of both GLT‐1 isoforms. Altogether, these data reveal that astrocytic GLT‐1 surface mobility, via its transport activity, is modulated during neuronal firing, which may be a key process for shaping glutamate clearance and glutamatergic synaptic transmission. GLIA 2016;64:1252–1264 PMID:27189737

  16. Surface Transportation Research and Development Act of 1997. House of Representatives, One Hundred Fifth Congress, Second Session

    SciTech Connect

    1998-12-31

    Mr. Sensenbrenner, from the Committee on Science, submitted this report together with additional views. The Committee on Science, to whom was referred the bill (H.R. 860) to authorize appropriations to the Department of Transportation for surface transportation research and development, and for other purposes, having considered the same, report favorably thereon with an amendment and recommend that the bill as amended do pass.

  17. Convergence at the surface; divergence beneath: cross-agency working within a small-scale, schools-based project.

    PubMed

    O'Brien, Mark

    2011-12-01

    In the UK school system social remits - requiring schools to work towards improved social as well as educational outcomes for children - have become significant over the last decade. This study focuses upon the inter-professional issues in the running of one small-scale intervention involving parents and their babies based in schools in an urban setting in the UK. The programme, run over the school year 2007/08, provided a professional framework in which parents from the local community surrounding a school brought their babies into classroom settings to talk about aspects of baby care and development. This professional framework included classroom teachers, one senior cross-school education manager, family health visitors and one senior children's health nurse. Despite agreement about the benefits of the programme there were also clear differences of priority. This paper describes the different perceptions that each of these two sets of professionals - from health and from education - had of the programme, and highlights some critical perspectives that tended to come more from health professionals. It also maps out potential solutions which draw upon recent literature that is similarly focused upon inter-professional and inter-agency service delivery. In so doing it offers valuable insights to professionals working in inter-agency collaborations in schools. PMID:21828171

  18. Particle transport over rough hillslope surfaces by dry ravel: Experiments and simulations with implications for nonlocal sediment flux

    NASA Astrophysics Data System (ADS)

    Gabet, Emmanuel J.; Mendoza, Morgan K.

    2012-02-01

    Past studies of hillslope evolution have typically assumed that soil creep processes are governed by a linear relationship between local hillslope angle and transport distance. The assumption of “linear diffusion” has fallen out of favor because, when coupled with an expression of mass continuity, it yields unrealistic hillslope profiles. As a consequence, a better understanding of the mechanics of sediment transport is needed. Here we report results from a series of flume experiments performed to investigate sediment transport by dry ravel, a common soil creep process in arid and semiarid environments. We find that, at gentle slopes, transport distances follow distributions characteristic of local transport. As gradients steepen, a fraction of the particles begins to exhibit nonlocal transport, and that fraction increases rapidly with slope. A stochastic discrete element model that couples an effective friction term with a shock term reproduces the results from the flume experiments, suggesting that it can be used to explore the nature of particle transport on rough surfaces. The model predicts that exponential distributions of transport distances on gentle slopes evolve into quasi-uniform distributions on steep slopes, and the transition occurs as slopes approach the angle of repose. Our results support previous findings that the angle of repose represents a threshold between friction and inertial regimes. In addition, we propose that the angle of repose represents a fuzzy boundary between local and nonlocal transport.

  19. Bulk, surface, and gas-phase limited water transport in aerosol.

    PubMed

    Davies, James F; Haddrell, Allen E; Miles, Rachael E H; Bull, Craig R; Reid, Jonathan P

    2012-11-15

    The influence of solute species on mass transfer to and from aqueous aerosol droplets is investigated using an electrodynamic balance coupled with light scattering techniques. In particular, we explore the limitations imposed on water evaporation by slow bulk phase diffusion and by the formation of surface organic films. Measurements of evaporation from ionic salt solutions, specifically sodium chloride and ammonium sulfate, are compared with predictions from an analytical model framework, highlighting the uncertainties associated with quantifying gas diffusional transport. The influence of low solubility organic acids on mass transfer is reported and compared to both model predictions and previous work. The limiting value of the evaporation coefficient that can be resolved by this approach, when uncertainties in key thermophysical quantities are accounted for, is estimated. The limitation of slow bulk phase diffusion on the evaporation rate is investigated for gel and glass states formed during the evaporation of magnesium sulfate and sucrose droplets, respectively. Finally, the effect of surfactants on evaporation has been probed, with soluble surfactants (such as sodium dodecyl sulfate) leading to little or no retardation of evaporation through slowing of surface layer kinetics. PMID:23095147

  20. ON POLAR MAGNETIC FIELD REVERSAL AND SURFACE FLUX TRANSPORT DURING SOLAR CYCLE 24

    SciTech Connect

    Sun, Xudong; Todd Hoeksema, J.; Liu, Yang; Zhao, Junwei

    2015-01-10

    As each solar cycle progresses, remnant magnetic flux from active regions (ARs) migrates poleward to cancel the old-cycle polar field. We describe this polarity reversal process during Cycle 24 using four years (2010.33-2014.33) of line-of-sight magnetic field measurements from the Helioseismic and Magnetic Imager. The total flux associated with ARs reached maximum in the north in 2011, more than two years earlier than the south; the maximum is significantly weaker than Cycle 23. The process of polar field reversal is relatively slow, north-south asymmetric, and episodic. We estimate that the global axial dipole changed sign in 2013 October; the northern and southern polar fields (mean above 60° latitude) reversed in 2012 November and 2014 March, respectively, about 16 months apart. Notably, the poleward surges of flux in each hemisphere alternated in polarity, giving rise to multiple reversals in the north. We show that the surges of the trailing sunspot polarity tend to correspond to normal mean AR tilt, higher total AR flux, or slower mid-latitude near-surface meridional flow, while exceptions occur during low magnetic activity. In particular, the AR flux and the mid-latitude poleward flow speed exhibit a clear anti-correlation. We discuss how these features can be explained in a surface flux transport process that includes a field-dependent converging flow toward the ARs, a characteristic that may contribute to solar cycle variability.

  1. Influence of surface charge on the transport characteristics of nanowire-field effect transistors in liquid environments

    SciTech Connect

    Nozaki, Daijiro E-mail: research@nano.tu-dresden.de; Kunstmann, Jens; Zörgiebel, Felix; Cuniberti, Gianaurelio

    2015-05-18

    One dimensional nanowire field effect transistors (NW-FETs) are a promising platform for sensor applications. The transport characteristics of NW-FETs are strongly modified in liquid environment due to the charging of surface functional groups accompanied with protonation or deprotonation. In order to investigate the influence of surface charges and ionic concentrations on the transport characteristics of Schottky-barrier NW-FETs, we have combined the modified Poisson-Boltzmann theory with the Landauer-Büttiker transport formalism. For a typical device, the model is able to capture the reduction of the sensitivity of NW-FETs in ionic solutions due to the screening from counter ions as well as a local gating from surface functional groups. Our approach allows to model, to investigate, and to optimize realistic Schottky-barrier NW-FET devices in liquid environment.

  2. Effects of surface and groundwater interactions on phosphorus transport within streambank sediments.

    PubMed

    Thompson, Carol A; McFarland, Anne M S

    2010-01-01

    Understanding internal stream P transfers is important in controlling eutrophication. To determine the direction of groundwater and surface water interactions and evaluate P retention within streambank sediments, groundwater well pairs, about 5-m deep, were installed at three locations along a second-order, eutrophic stream in north-central Texas. Well cores were analyzed for P, and groundwater levels were monitored for about 2 yr. Water levels in wells furthest upstream always indicated a losing stream, while wells further downstream showed a gaining stream except during flow reversals with storm events and periods with reservoir backwater. Total-P from well cores ranged from 54 to 254 mg kg(-1) and was typically high near surface, decreased downward until redoximorphic features were encountered and then increased notably with depth to near or above surface concentrations. Very little extractable P occurred in sediments from the two upstream well sets; however, the set furthest downstream showed extractable P throughout with a high of 21 mg kg(-1) near the bottom. Repeated wetting-drying at sites A and B as noted by redoximorphic features may have shifted P into more stable sediment-bound forms. The decrease in extractable P at sites A and B compared to site C may be explained by conditions at C that were wetter and potentially anaerobic. Because the overall stream reach was more often losing than gaining, there appears to be a mass flow of P into streambank sediments. Streambank erosion may then transport this P downstream if not controlled. PMID:20176828

  3. Glucose transporter 3 is a rab11-dependent trafficking cargo and its transport to the cell surface is reduced in neurons of CAG140 Huntington's disease mice.

    PubMed

    McClory, Hollis; Williams, Dana; Sapp, Ellen; Gatune, Leah W; Wang, Ping; DiFiglia, Marian; Li, Xueyi

    2014-01-01

    Huntington's disease (HD) disturbs glucose metabolism in the brain by poorly understood mechanisms. HD neurons have defective glucose uptake, which is attenuated upon enhancing rab11 activity. Rab11 regulates numerous receptors and transporters trafficking onto cell surfaces; its diminished activity in HD cells affects the recycling of transferrin receptor and neuronal glutamate/cysteine transporter EAAC1. Glucose transporter 3 (Glut3) handles most glucose uptake in neurons. Here we investigated rab11 involvement in Glut3 trafficking. Glut3 was localized to rab11 positive puncta in primary neurons and immortalized striatal cells by immunofluorescence labeling and detected in rab11-enriched endosomes immuno-isolated from mouse brain by Western blot. Expression of dominant active and negative rab11 mutants in clonal striatal cells altered the levels of cell surface Glut3 suggesting a regulation by rab11. About 4% of total Glut3 occurred at the cell surface of primary WT neurons. HD(140Q/140Q) neurons had significantly less cell surface Glut3 than did WT neurons. Western blot analysis revealed comparable levels of Glut3 in the striatum and cortex of WT and HD(140Q/140Q) mice. However, brain slices immunolabeled with an antibody recognizing an extracellular epitope to Glut3 showed reduced surface expression of Glut3 in the striatum and cortex of HD(140Q/140Q) mice compared to that of WT mice. Surface labeling of GABAα1 receptor, which is not dependent on rab11, was not different between WT and HD(140Q/140Q) mouse brain slices. These data define Glut3 to be a rab11-dependent trafficking cargo and suggest that impaired Glut3 trafficking arising from rab11 dysfunction underlies the glucose hypometabolism observed in HD. PMID:25526803

  4. Surface-Water to Groundwater Transport of Pharmaceuticals in a Wastewater-Impacted Stream in the U.S.

    NASA Astrophysics Data System (ADS)

    Bradley, P. M.; Barber, L. B.; Duris, J. W.; Foreman, W. T.; Furlong, E. T.; Hubbard, L. E.; Hutchinson, K. J.; Keefe, S. H.; Kolpin, D. W.

    2014-12-01

    Wastewater pharmaceutical contamination of shallow groundwater is a substantial concern in effluent-dominated streams, due to aqueous mobility and designed bioactivity of pharmaceuticals and due to effluent-driven hydraulic gradients. Improved understanding of the environmental fate and transport of wastewater-derived pharmaceuticals is essential for effective protection of vital aquatic ecosystem services, environmental health, and drinking-water supplies. Substantial longitudinal (downstream) transport of pharmaceutical contaminants has been documented in effluent-impacted streams. The comparative lack of information on vertical and lateral transport (infiltration) of wastewater contaminants from surface-water to hyporheic and shallow groundwater compartments is a critical scientific data gap, given the potential for contamination of groundwater supplies in effluent-impacted systems. Growing dependencies on bank filtration and artificial recharge applications for release of wastewater to the environment and for pretreatment of poor-quality surface-water for drinking water emphasize the critical need to better understand the exchange of wastewater contaminants, like pharmaceuticals, between surface-water and groundwater compartments. The potential transport of effluent-derived pharmaceutical contaminants from surface-water to hyporheic-water and shallow groundwater compartments was examined in a wastewater-treatment-facility (WWTF) impacted stream in Ankeny, Iowa under effluent-dominated (71-99% of downstream flow) conditions. Strong hydraulic gradients and hydrologic connectivity were evident between surface-water and shallow-groundwater compartments in the vicinity of the WWTF outfall. Carbamazepine, sulfamethoxazole, and immunologically-related compounds were detected in groundwater 10-20 meters from the stream bank. Direct aqueous-injection HPLC-MS/MS revealed high percentage detections of pharmaceuticals (110 total analytes) in surface-water and groundwater

  5. Magnetic transport apparatus for the production of ultracold atomic gases in the vicinity of a dielectric surface

    SciTech Connect

    Haendel, S.; Marchant, A. L.; Wiles, T. P.; Hopkins, S. A.; Cornish, S. L.

    2012-01-15

    We present an apparatus designed for studies of atom-surface interactions using quantum degenerate gases of {sup 85}Rb and {sup 87}Rb in the vicinity of a room temperature dielectric surface. The surface to be investigated is a super-polished face of a glass Dove prism mounted in a glass cell under ultra-high vacuum. To maintain excellent optical access to the region surrounding the surface, magnetic transport is used to deliver ultracold atoms from a separate vacuum chamber housing the magneto-optical trap (MOT). We present a detailed description of the vacuum apparatus highlighting the novel design features; a low profile MOT chamber and the inclusion of an obstacle in the transport path. We report the characterization and optimization of the magnetic transport around the obstacle, achieving transport efficiencies of 70% with negligible heating. Finally, we demonstrate the loading of a hybrid optical-magnetic trap with {sup 87}Rb and the creation of Bose-Einstein condensates via forced evaporative cooling close to the dielectric surface.

  6. Influence of surface wettability on transport mechanisms governing water droplet evaporation.

    PubMed

    Pan, Zhenhai; Weibel, Justin A; Garimella, Suresh V

    2014-08-19

    Prediction and manipulation of the evaporation of small droplets is a fundamental problem with importance in a variety of microfluidic, microfabrication, and biomedical applications. A vapor-diffusion-based model has been widely employed to predict the interfacial evaporation rate; however, its scope of applicability is limited due to incorporation of a number of simplifying assumptions of the physical behavior. Two key transport mechanisms besides vapor diffusion-evaporative cooling and natural convection in the surrounding gas-are investigated here as a function of the substrate wettability using an augmented droplet evaporation model. Three regimes are distinguished by the instantaneous contact angle (CA). In Regime I (CA ≲ 60°), the flat droplet shape results in a small thermal resistance between the liquid-vapor interface and substrate, which mitigates the effect of evaporative cooling; upward gas-phase natural convection enhances evaporation. In Regime II (60 ≲ CA ≲ 90°), evaporative cooling at the interface suppresses evaporation with increasing contact angle and counterbalances the gas-phase convection enhancement. Because effects of the evaporative cooling and gas-phase convection mechanisms largely neutralize each other, the vapor-diffusion-based model can predict the overall evaporation rates in this regime. In Regime III (CA ≳ 90°), evaporative cooling suppresses the evaporation rate significantly and reverses entirely the direction of natural convection induced by vapor concentration gradients in the gas phase. Delineation of these counteracting mechanisms reconciles previous debate (founded on single-surface experiments or models that consider only a subset of the governing transport mechanisms) regarding the applicability of the classic vapor-diffusion model. The vapor diffusion-based model cannot predict the local evaporation flux along the interface for high contact angle (CA ≥ 90°) when evaporative cooling is strong and the

  7. Predicting the Amplitude and Hemispheric Asymmetry of Solar Cycle 25 with Surface Flux Transport

    NASA Astrophysics Data System (ADS)

    Hathaway, David H.; Upton, Lisa

    2016-05-01

    Evidence from 40 years of magnetic field measurements, 110 years of polar faculae counts, and 150 years of geomagnetic field measurements, strongly indicates that the strength of the magnetic field at the Sun's poles near the time of a sunspot cycle minimum determines the strength of the following solar activity cycle. The processes that produce these polar fields are well observed and accurately modeled as the transport of magnetic flux (which emerges in active regions) by the horizontal flows in the Sun's near-surface shear layer, i.e. differential rotation, poleward meridional flow, and cellular convective motions. We use our Advective Flux Transport (AFT) code, with flows fully constrained by observations, to simulate the evolution of the Sun's polar magnetic fields from early 2016 to the end of 2019 – near the expected time of Cycle 24/25 minimum. We assimilate active regions from Cycle 14 (107 years earlier) to represent the continued development of Cycle 24. Cycle 14 was similar to Cycle 24 in size, shape, and hemispheric asymmetry. We run a series of simulations in which the uncertain conditions (convective motion details, active region tilt, and meridional flow profile) are varied within expected ranges. We find that the ensemble average of the strength of the polar fields near the end of Cycle 24 is about the same as that measured near the end of Cycle 23, indicating that Cycle 25 will be similar in strength to the current cycle with an expected maximum sunspot number (Version 2.0) of 100±15. In all cases within our ensemble the polar fields are asymmetric with fields in the south stronger than those in the north. After just four years of simulation the variability across our ensemble indicates an uncertainty of about 15%. This stochastic variability, intrinsic to the Sun itself, suggests that we may never be able to reliably predict solar cycles more than one cycle into the future.

  8. Evaluation of wastewater contaminant transport in surface waters using verified Lagrangian sampling.

    PubMed

    Antweiler, Ronald C; Writer, Jeffrey H; Murphy, Sheila F

    2014-02-01

    Contaminants released from wastewater treatment plants can persist in surface waters for substantial distances. Much research has gone into evaluating the fate and transport of these contaminants, but this work has often assumed constant flow from wastewater treatment plants. However, effluent discharge commonly varies widely over a 24-hour period, and this variation controls contaminant loading and can profoundly influence interpretations of environmental data. We show that methodologies relying on the normalization of downstream data to conservative elements can give spurious results, and should not be used unless it can be verified that the same parcel of water was sampled. Lagrangian sampling, which in theory samples the same water parcel as it moves downstream (the Lagrangian parcel), links hydrologic and chemical transformation processes so that the in-stream fate of wastewater contaminants can be quantitatively evaluated. However, precise Lagrangian sampling is difficult, and small deviations - such as missing the Lagrangian parcel by less than 1h - can cause large differences in measured concentrations of all dissolved compounds at downstream sites, leading to erroneous conclusions regarding in-stream processes controlling the fate and transport of wastewater contaminants. Therefore, we have developed a method termed "verified Lagrangian" sampling, which can be used to determine if the Lagrangian parcel was actually sampled, and if it was not, a means for correcting the data to reflect the concentrations which would have been obtained had the Lagrangian parcel been sampled. To apply the method, it is necessary to have concentration data for a number of conservative constituents from the upstream, effluent, and downstream sites, along with upstream and effluent concentrations that are constant over the short-term (typically 2-4h). These corrections can subsequently be applied to all data, including non-conservative constituents. Finally, we show how data

  9. Contributions of regional and intercontinental transport to surface ozone in Tokyo

    NASA Astrophysics Data System (ADS)

    Yoshitomi, M.; Wild, O.; Akimoto, H.

    2011-04-01

    Japan lies downwind of the Asian continent and for much of the year air quality is directly influenced by emissions of ozone precursors over these heavily-populated and rapidly-industrializing regions. This study examines the extent to which oxidant transport from regional and distant anthropogenic sources influences air quality in Japan in springtime, when these contributions are largest. We find that European and North American contributions to surface ozone over Japan in spring are persistent, averaging 3.5±1.1 ppb and 2.8±0.5 ppb respectively, and are greatest in cold continental outflow conditions following the passage of cold fronts. Contributions from China are larger, 4.0±2.8 ppb, and more variable, as expected for a closer source region, and are generally highest near cold fronts preceding the influence of more distant sources. The stratosphere provides a varying but ever-present background of ozone of about 11.2±2.5 ppb during spring. Local sources over Japan and Korea have a relatively small impact on mean ozone, 2.4±7.6 ppb, but this masks a strong diurnal signal, and local sources clearly dominate during episodes of high daytime ozone. By examining the meteorological mechanisms that favour transport from different source regions, we demonstrate that while maximum foreign influence generally does not occur at the same time as the greatest buildup of oxidants from local sources, it retains a significant influence under these conditions. It is thus clear that while meteorological boundaries provide some protection from foreign influence during oxidant outbreaks in Tokyo, these distant sources still make a substantial contribution to exceedance of the Japanese ozone air quality standard in springtime.

  10. Contributions of regional and intercontinental transport to surface ozone in the Tokyo area

    NASA Astrophysics Data System (ADS)

    Yoshitomi, M.; Wild, O.; Akimoto, H.

    2011-08-01

    Japan lies downwind of the Asian continent and for much of the year air quality is directly influenced by emissions of ozone precursors over these heavily-populated and rapidly-industrializing regions. This study examines the extent to which oxidant transport from regional and distant anthropogenic sources influences air quality in Japan in springtime, when these contributions are largest. We find that European and North American contributions to surface ozone over Japan in spring are persistent, averaging 3.5±1.1 ppb and 2.8±0.5 ppb respectively, and are greatest in cold continental outflow conditions following the passage of cold fronts. Contributions from China are larger, 4.0±2.8 ppb, and more variable, as expected for a closer source region, and are generally highest near cold fronts preceding the influence of more distant sources. The stratosphere provides a varying but ever-present background of ozone of about 11.2±2.5 ppb during spring. Local sources over Japan and Korea have a relatively small impact on mean ozone, 2.4±7.6 ppb, but this masks a strong diurnal signal, and local sources clearly dominate during episodes of high daytime ozone. By examining the meteorological mechanisms that favour transport from different source regions, we demonstrate that while maximum foreign influence generally does not occur at the same time as the greatest buildup of oxidants from local sources, it retains a significant influence under these conditions. It is thus clear that while meteorological boundaries provide some protection from foreign influence during oxidant outbreaks in Tokyo, these distant sources still make a substantial contribution to exceedance of the Japanese ozone air quality standard in springtime.

  11. Techniques for Increasing the Reliability of Estimates of Surface Water Transport Models

    NASA Astrophysics Data System (ADS)

    Boufadel, M. C.; Toran, L.; Gabriel, M.

    2002-05-01

    The Transient Storage Model (TSM) is widely used to simulate solute transport in stream settings. Within the TSM framework, solute transport is simulated using the advection dispersion equation in the main channel with additional mass transfer terms that represent the transverse exchange with surface water storage zones (dead zones) and the hyporheic zone (subsurface surrounding the stream). The TSM parameters are commonly treated as reach-averages, and they are estimated by fitting a theoretical to an experimental breakthrough curve. The parameters? values suffer from the problem of non-uniqueness whereby many combinations of parameters? values provide essentially the same fit. We explore various techniques for alleviating the problem of non-uniqueness. We use for this purpose stream-tracer studies that we conducted in a 190-m reach of Indian Creek, Philadelphia, Pennsylvania USA, where two stream-tracer studies were conducted and the concentration is monitored at two transects. We also conducted measurements of the cross section area at various transects and incorporated them into the objective function in a Bayesian parameter estimation framework. We found that using multiple stream tracer studies under various hydraulic conditions and/or the Bayesian framework alleviate the problem of non-uniqueness. We fitted the model to the data when the cross section area was treated as a distributed parameter while the other parameters were treated as reach-averages. While the fit was good, many reach-averaged parameters (exchange coefficient, dispersion coefficient) had to take to extreme values. This indicates that additional but incomplete geomorphic information does not necessarily improve the understanding of a particular stream system. The variation of the parameters with scale was also explored.

  12. Heterologous expression of rab4 reduces glucose transport and GLUT4 abundance at the cell surface in oocytes.

    PubMed Central

    Mora, S; Monden, I; Zorzano, A; Keller, K

    1997-01-01

    To evaluate the role of the small rab GTP-binding proteins in glucose transporter trafficking, we have heterologously co-expressed rab4 or rab5 and GLUT4 or GLUT1 glucose transporters in Xenopus oocytes. Co-injection of rab4 and GLUT4 cRNAs resulted in a dose-dependent decrease in glucose transport; this effect was specific for rab4, since co-injection of an inactive rab4 mutant or rab5 cRNA did not have any effect on glucose transport. The effect of rab4 was selective for GLUT4, since no effect was detected in GLUT1-expressing oocytes. The inhibitory effect of rab4 on GLUT4-induced glucose transport was not the result of a change in overall cellular levels of GLUT4 glucose transporters. However, rab4 expression caused a marked decrease in the abundance of GLUT4 transporters present at the cell surface. Finally, rab4 and inhibitors of PtdIns 3-kinase showed additive effects in decreasing glucose transport in GLUT4-expressing oocytes. We conclude that rab4 plays an important role in the regulation of the intracellular GLUT4 trafficking pathway, by contributing to the intracellular retention of GLUT4 through a PtdIns 3-kinase-independent mechanism. PMID:9182703

  13. Application of divided convective-dispersive transport model to simulate conservative transport processes in planted horizontal sub-surface flow constructed wetlands.

    PubMed

    Dittrich, Ernő; Klincsik, Mihály

    2015-11-01

    We have created a divided convective-dispersive transport (D-CDT) model that can be used to provide an accurate simulation of conservative transport processes in planted horizontal sub-surface flow constructed wetlands filled with coarse gravel (HSFCW-C). This model makes a fitted response curve from the sum of two independent CDT curves, which show the contributions of the main and side streams. The analytical solutions of both CDT curves are inverse Gaussian distribution functions. We used Fréchet distribution to provide a fast optimization mathematical procedure. As a result of our detailed analysis, we concluded that the most important role in the fast upward part of the tracer response curve is played by the main stream, with high porous velocity and dispersion. This gives the first inverse Gaussian distribution function. The side stream shows slower transport processes in the micro-porous system, and this shows the impact of back-mixing and dead zones, too. The significance of this new model is that it can simulate transport processes in this kind of systems more accurately than the conventionally used convective-dispersive transport (CDT) model. The calculated velocity and dispersion coefficients with the D-CDT model gave differences of 24-54% (of velocity) and 22-308% (of dispersion coeff.) from the conventional CDT model, and were closer to actual hydraulic behaviour. PMID:26178828

  14. RELATIONSHIP BETWEEN CELL SURFACE PROPERTIES AND TRANSPORT OF BACTERIA THROUGH SOIL

    EPA Science Inventory

    A study was conducted to relate the properties of Enterobacter, Pseudomonas, Bacillus, Achromobacter, Flavobacterium, and Arthrobacter strains to their transport with water moving through soil. the bacteria differed markedly in their extent of transport; their hydrophobicity, as...

  15. Material transport in a convective surface mixed layer under weak wind forcing

    NASA Astrophysics Data System (ADS)

    Mensa, Jean A.; Özgökmen, Tamay M.; Poje, Andrew C.; Imberger, Jörg

    2015-12-01

    Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (| u10 | = 5m s-1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind- and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the cross-wind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, kD(ℓ), than those reported by Okubo (1970), while the wind- and buoyancy-forced case shows a good agreement with Okubo's diffusivity amplitude, and the scaling is consistent with Richardson's 4/3rd law, kD ∼ ℓ4/3. These modeling results provide a framework for measuring material dispersion by mixed layer flows in future observational programs.

  16. Delineating the extracellular water-accessible surface of the proton-coupled folate transporter.

    PubMed

    Duddempudi, Phaneendra Kumar; Goyal, Raman; Date, Swapneeta Sanjay; Jansen, Michaela

    2013-01-01

    The proton-coupled folate transporter (PCFT) was recently identified as the major uptake route for dietary folates in humans. The three-dimensional structure of PCFT and its detailed interplay with function remain to be determined. We screened the water-accessible extracellular surface of HsPCFT using the substituted-cysteine accessibility method, to investigate the boundaries between the water-accessible surface and inaccessible buried protein segments. Single-cysteines, engineered individually at 40 positions in a functional cysteine-less HsPCFT background construct, were probed for plasma-membrane expression in Xenopus oocytes with a bilayer-impermeant primary-amine-reactive biotinylating agent (sulfosuccinimidyl 6-(biotinamido) hexanoate), and additionally for water-accessibility of the respective engineered cysteine with the sulfhydryl-selective biotinylating agent 2-((biotinoyl)amino)ethyl methanethiosulfonate. The ratio between Cys-selective over amine-selective labeling was further used to evaluate three-dimensional models of HsPCFT generated by homology / threading modeling. The closest homologues of HsPCFT with a known experimentally-determined three-dimensional structure are all members of one of the largest membrane protein super-families, the major facilitator superfamily (MFS). The low sequence identity--14% or less--between HsPCFT and these templates necessitates experiment-based evaluation and model refinement of homology/threading models. With the present set of single-cysteine accessibilities, the models based on GlpT and PepTSt are most promising for further refinement. PMID:24205192

  17. A parallel computational framework for integrated surface-subsurface flow and transport simulations

    NASA Astrophysics Data System (ADS)

    Park, Y.; Hwang, H.; Sudicky, E. A.

    2010-12-01

    HydroGeoSphere is a 3D control-volume finite element hydrologic model describing fully-integrated surface and subsurface water flow and solute and thermal energy transport. Because the model solves tighly-coupled highly-nonlinear partial differential equations, often applied at regional and continental scales (for example, to analyze the impact of climate change on water resources), high performance computing (HPC) is essential. The target parallelization includes the composition of the Jacobian matrix for the iterative linearization method and the sparse-matrix solver, a preconditioned Bi-CGSTAB. The matrix assembly is parallelized by using a coarse-grained scheme in that the local matrix compositions can be performed independently. The preconditioned Bi-CGSTAB algorithm performs a number of LU substitutions, matrix-vector multiplications, and inner products, where the parallelization of the LU substitution is not trivial. The parallelization of the solver is achieved by partitioning the domain into equal-size subdomains, with an efficient reordering scheme. The computational flow of the Bi-CGSTAB solver is also modified to reduce the parallelization overhead and to be suitable for parallel architectures. The parallelized model is tested on several benchmark simulations which include linear and nonlinear flow problems involving various domain sizes and degrees of hydrologic complexities. The performance is evaluated in terms of computational robustness and efficiency, using standard scaling performance measures. The results of simulation profiling indicate that the efficiency becomes higher with an increasing number of nodes/elements in the mesh, for increasingly nonlinear transient simulations, and with domains of irregular geometry. These characteristics are promising for the large-scale analysis water resources problems involved integrated surface/subsurface flow regimes.

  18. Forward Modeling of Atmospheric Carbon Dioxide in GEOS-5: Uncertainties Related to Surface Fluxes and Sub-Grid Transport

    NASA Technical Reports Server (NTRS)

    Pawson, Steven; Ott, Lesley E.; Zhu, Zhengxin; Bowman, Kevin; Brix, Holger; Collatz, G. James; Dutkiewicz, Stephanie; Fisher, Joshua B.; Gregg, Watson W.; Hill, Chris; Menemenlis, DImiris; Potter, Christopher S.; Gunson, Michael R.; Jucks, Kenneth W.

    2011-01-01

    Forward GEOS-5 AGCM simulations of CO2, with transport constrained by analyzed meteorology for 2009-2010, are examined. The CO2 distributions are evaluated using AIRS upper tropospheric CO2 and ACOS-GOSAT total column CO2 observations. Different combinations of surface C02 fluxes are used to generate ensembles of runs that span some uncertainty in surface emissions and uptake. The fluxes are specified in GEOS-5 from different inventories (fossil and biofuel), different data-constrained estimates of land biological emissions, and different data-constrained ocean-biology estimates. One set of fluxes is based on the established "Transcom" database and others are constructed using contemporary satellite observations to constrain land and ocean process models. Likewise, different approximations to sub-grid transport are employed, to construct an ensemble of CO2 distributions related to transport variability. This work is part of NASA's "Carbon Monitoring System Flux Pilot Project,"

  19. 49 CFR 173.427 - Transport requirements for low specific activity (LSA) Class 7 (radioactive) material and surface...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... this section must be packaged in accordance with 10 CFR part 71. (e) Tables 5 and 6 are as follows... (LSA) Class 7 (radioactive) material and surface contaminated objects (SCO). 173.427 Section 173.427... SHIPMENTS AND PACKAGINGS Class 7 (Radioactive) Materials § 173.427 Transport requirements for low...

  20. Transport of nutrients and sediment in surface runoff in a corn silage system: paired watershed methodology and calibration period results

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport of P, N, and sediment via runoff from crop fields, especially where manure has been applied, can contribute to degradation of surface waters, leading to eutrophication and potential health effects on humans and livestock. We used a paired-watershed design to evaluate field runoff losses of...

  1. Significance of wall structure, macromolecular composition, and surface polymers to the survival and transport of Cryptosporidium parvum Oocysts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The structure and composition of the oocyst wall are primary factors determining the survival of Cryptosporidium parvum oocysts outside the host. An external polymer matrix (glycocalyx) may mediate interactions with environmental surfaces and, thus, affect the transport of oocysts in water, soil, an...

  2. Understanding electric field-enhanced transport for the measurement of nanoparticles and their assembly on surfaces

    NASA Astrophysics Data System (ADS)

    Tsai, De-Hao

    The goal of this dissertation is to understand the synthesis, characterization, and integration of nanoparticles and nanoparticle-based devices by electric field-enhanced transport of nanoparticles. Chapter I describes the factors used for determining particle trajectories and found that electric fields provide the directional electrostatic force to overcome other non-directional influences on particle trajectories. This idea is widely applied in the nanoparticle classification, characterization, and assembly onto substrate surfaces as investigated in the following chapters. Chapter 2 presents a new assembly method to position metal nanoparticles delivered from the gas phase onto surfaces using the electrostatic force generated by biased p-n junction patterned substrates. Aligned deposition patterns of metal nanoparticles were observed, and the patterning selectivity quantified. A simple model accounting for the generated electric field, and the electrostatic, van der Waals, and image forces was used to explain the observed results. Chapter 2.2 describes a data set for particle size resolved deposition, from which a Brownian dynamics model for the process can be evaluated. Brownian motion and fluid convection of nanoparticles, as well as the interactions between the charged nanoparticles and the patterned substrate, including electrostatic force, image force and van der Waals force, are accounted for in the simulation. Using both experiment and simulation the effects of the particle size, electric field intensity, and the convective flow on coverage selectivity have been investigated. Coverage selectivity is most sensitive to electric field, which is controlled by the applied reverse bias voltage across the p-n junction. A non-dimensional analysis of the competition between the electrostatic and diffusion force is found to provide a means to collapse a wide range of process operating conditions and an effective indicator or process performance. Directed assembly of

  3. Surface plasmon resonance assay of inhibition by pharmaceuticals for thyroxine hormone binging to transport proteins.

    PubMed

    Kinouchi, Hiroki; Matsuyama, Keigo; Kitagawa, Hiroshi; Kamimori, Hiroshi

    2016-01-01

    We developed a surface plasmon resonance (SPR) assay to estimate the competitive inhibition by pharmaceuticals for thyroxine (T4) binding to thyroid hormone transport proteins, transthyretin (TTR) and thyroxine binding globulin (TBG). In this SPR assay, the competitive inhibition of pharmaceuticals for introducing T4 into immobilized TTR or TBG on the sensor chip can be estimated using a running buffer containing pharmaceuticals. The SPR assay showed reproducible immobilization of TTR and TBG, and the kinetic binding parameters of T4 to TTR or TBG were estimated. The equilibrium dissociation constants of TTR or TBG measured by SPR did not clearly differ from data reported for other binding assays. To estimate the competitive inhibition of tetraiodothyroacetic acid, diclofenac, genistein, ibuprofen, carbamazepine, and furosemide, reported to be competitive or noncompetitive pharmaceuticals for T4 binding to TTR or TBG, their 50% inhibition concentrations (IC50) (or 80% inhibition concentration, IC80) were calculated from the change of T4 responses in sensorgrams obtained with various concentrations of the pharmaceuticals. Our SPR method should be a useful tool for predicting the potential of thyroid toxicity of pharmaceuticals by evaluating the competitive inhibition of T4 binding to thyroid hormone binding proteins, TTR and TBG. PMID:26384643

  4. Effect of surface charge of immortalized mouse cerebral endothelial cell monolayer on transport of charged solutes.

    PubMed

    Yuan, Wei; Li, Guanglei; Gil, Eun Seok; Lowe, Tao Lu; Fu, Bingmei M

    2010-04-01

    Charge carried by the surface glycocalyx layer (SGL) of the cerebral endothelium has been shown to significantly modulate the permeability of the blood-brain barrier (BBB) to charged solutes in vivo. The cultured monolayer of bEnd3, an immortalized mouse cerebral endothelial cell line, is becoming a popular in vitro BBB model due to its easy growth and maintenance of many BBB characteristics over repeated passages. To test whether the SGL of bEnd3 monolayer carries similar charge as that in the intact BBB and quantify this charge, which can be characterized by the SGL thickness (L(f)) and charge density (C(mf)), we measured the solute permeability of bEnd3 monolayer to neutral solutes and to solutes with similar size but opposite charges: negatively charged alpha-lactalbumin (-11) and positively charged ribonuclease (+3). Combining the measured permeability data with a transport model across the cell monolayer, we predicted the L(f) and the C(mf) of bEnd3 monolayer, which is approximately 160 nm and approximately 25 mEq/L, respectively. We also investigated whether orosomucoid, a plasma glycoprotein modulating the charge of the intact BBB, alters the charge of bEnd3 monolayer. We found that 1 mg/mL orosomucoid would increase SGL charge density of bEnd3 monolayer to approximately 2-fold of its control value. PMID:20087768

  5. A non-equilibrium model for soil heating and moisture transport during extreme surface heating

    NASA Astrophysics Data System (ADS)

    Massman, William

    2016-04-01

    The increasing use of prescribed fire by land managers and increasing likelihood of wildfires due to climate change requires an improved modeling capability of extreme heating of soils during fires. This study describes a new model of soil evaporation and transport of heat, soil moisture, and water vapor, for use during fires. The model is based on conservation equations of energy and mass and its performance is evaluated against dynamic soil temperature and moisture observations obtained during laboratory experiments on soil samples exposed to surface heat fluxes ranging between 10,000 and 50,000 Wm2. In general, the model simulates the observed temperature dynamics quite well, but is less precise (but still good) at capturing the moisture dynamics. The model emulates the observed increase in soil moisture ahead of the drying front and the hiatus in the soil temperature rise during the strongly evaporative stage of drying. It also captures the observed rapid evaporation of soil moisture that occurs at relatively low temperatures (50-90 C), and can provide quite accurate predictions of the total amount of soil moisture evaporated during the laboratory experiments. Overall, this new model provides a much more physically realistic simulation over all previous models developed for the same purpose.

  6. Regulation of the cell surface expression of chloride transporters during epileptogenesis.

    PubMed

    González, Marco I

    2016-08-15

    The process is commonly known as epileptogenesis refers to the cascade of molecular and cellular changes that transform the brain to make it hyperexcitable and capable of generate recurrent spontaneous seizures. Unfortunately, our understanding of the molecular changes that affect the brain during epileptogenesis remains incomplete. Recent evidence suggests that dysfunction of cation-chloride transporters (CCCs) might be one of the factors that contribute to the deficits in inhibitory neurotransmission observed during epileptogenesis. This study analyzed the cell surface expression of CCCs during epileptogenesis and during chronic epilepsy to evaluate if a loss of CCCs from the plasma membrane might contribute to hyperexcitability. Alterations in the plasma membrane expression of CCCs were mostly detected during the early phase of the epileptogenic period, suggesting that dysfunction of CCCs might contribute to the alterations in the chloride gradient previously detected. Together, the findings presented here suggest that aberrant regulation of the plasma membrane levels of CCCs might contribute to the impartment of GABAergic neurotransmission and that CCCs dysfunction might be relevant for the initial appearance of spontaneous seizures. PMID:27345384

  7. A Review of Removable Surface Contamination on Radioactive Materials Transportation Containers

    SciTech Connect

    Kennedy, Jr, W. E.; Watson, E. C.; Murphy, D. W.; Harrer, B. J.; Harty, R.; Aldrich, J. M.

    1981-05-01

    This report contains the results of a study sponsored by the U.S. Nuclear Regulatory Commission (NRC) of removable surface contamination on radioactive materials transportation containers. The purpose of the study is to provide information to the NRC during their review of existing regulations. Data was obtained from both industry and literature on three major topics: 1) radiation doses, 2) economic costs, and 3) contamination frequencies. Containers for four categories of radioactive materials are considered including radiopharmaceuticals, industrial sources, nuclear fuel cycle materials, and low-level radioactive waste. Assumptions made in this study use current information to obtain realistic yet conservative estimates of radiation dose and economic costs. Collective and individual radiation doses are presented for each container category on a per container basis. Total doses, to workers and the public, are also presented for spent fuel cask and low-level waste drum decontamination. Estimates of the additional economic costs incurred by lowering current limits by factors of 10 and 100 are presented. Current contamination levels for each category of container are estimated from the data collected. The information contained in this report is designed to be useful to the NRC in preparing their recommendations for new regulations.

  8. Effects of surface ligands on the uptake and transport of gold nanoparticles in rice and tomato.

    PubMed

    Li, Hongying; Ye, Xinxin; Guo, Xisheng; Geng, Zhigang; Wang, Guozhong

    2016-08-15

    Nanotechnology is advancing rapidly and substantial amounts of nanomaterials are released into the environment. Plants are an essential base component of the ecological environment and play a critical role in the fate and transport of nanomaterials in the environment through plant uptake and bioaccumulation. In this study, plant uptake of gold nanoparticles (GNPs) functionalized with three types of short ligands [cysteamine (CA), cysteine (CYS) and thioglycolic acid (TGA)] and of nearly identical hydrodynamic size (8-12nm) was investigated in the major crops rice (Oryza sativa L.) and tomato (Solanum lycopersicum). Uptake and translocation of GNPs not only depended on particle surface charge, but were also related to the species of ligand on the GNPs. The negatively charged GNPs capped with the CYS ligand (GNP-CYS) were more efficiently absorbed in roots and transferred to shoots (including stems and leaves) than that of GNPs capped with CA and TGA. The absorption process of GNPs involved a combination of both clathrin-dependent and -independent mechanisms. The endocytosis of GNPs was strongly inhibited by wortmannin, suggesting that clathrin-independent endocytosis was an important pathway of nanoparticle internalization in plants. Competition experiments with a free ligand (CYS) showed that the CYS ligand probably facilitated the endocytosis process of GNPs and increased the internalization of GNP-CYS in plants. The results will aid understanding of the mechanisms of nanoparticle uptake and translocation in plants. PMID:27131459

  9. A Versatile Lifting Device for Lunar Surface Payload Handling, Inspection & Regolith Transport Operations

    NASA Astrophysics Data System (ADS)

    Doggett, William; Dorsey, John; Collins, Tim; King, Bruce; Mikulas, Martin

    2008-01-01

    Devices for lifting and transporting payloads and material are critical for efficient Earth-based construction operations. Devices with similar functionality will be needed to support lunar-outpost construction, servicing, inspection, regolith excavation, grading and payload placement. Past studies have proposed that only a few carefully selected devices are required for a lunar outpost. One particular set of operations involves lifting and manipulating payloads in the 100 kg to 3,000 kg range, which are too large or massive to be handled by unassisted astronauts. This paper will review historical devices used for payload handling in space and on earth to derive a set of desirable features for a device that can be used on planetary surfaces. Next, an innovative concept for a lifting device is introduced, which includes many of the desirable features. The versatility of the device is discussed, including its application to lander unloading, servicing, inspection, regolith excavation and site preparation. Approximate rules, which can be used to size the device for specific payload mass and reach requirements, are provided. Finally, details of a test-bed implementation of the innovative concept, which will be used to validate the structural design and develop operational procedures, is provided.

  10. A Versatile Lifting Device for Lunar Surface Payload Handling, Inspection and Regolith Transport Operations

    NASA Technical Reports Server (NTRS)

    Doggett, William R.; Dorsey, John T.; Collins, Timothy J.; King, Bruce D.; Mikulas, Martin M., Jr.

    2008-01-01

    Devices for lifting and transporting payloads and material are critical for efficient Earth-based construction operations. Devices with similar functionality will be needed to support lunar-outpost construction, servicing, inspection, regolith excavation, grading and payload placement. Past studies have proposed that only a few carefully selected devices are required for a lunar outpost. One particular set of operations involves lifting and manipulating payloads in the 100 kg to 3,000 kg range, which are too large or massive to be handled by unassisted astronauts. This paper will review historical devices used for payload handling in space and on earth to derive a set of desirable features for a device that can be used on planetary surfaces. Next, an innovative concept for a lifting device is introduced, which includes many of the desirable features. The versatility of the device is discussed, including its application to lander unloading, servicing, inspection, regolith excavation and site preparation. Approximate rules, which can be used to size the device for specific payload mass and reach requirements, are provided. Finally, details of a test-bed implementation of the innovative concept, which will be used to validate the structural design and develop operational procedures, is provided.

  11. Sound propagation over soft ground without and with crops and potential for surface transport noise attenuation.

    PubMed

    Bashir, Imran; Taherzadeh, Shahram; Shin, Ho-Chul; Attenborough, Keith

    2015-01-01

    Growing demand on transportation, road, and railway networks has resulted in increased levels of annoyance from road traffic. Optimized use of green surfaces in combination with vegetation may be desirable as a method for reducing the noise impact of road traffic in urban and rural environments. Sound propagation over soft ground and through crops has been studied through outdoor measurements at short and medium ranges and through predictions. At lower frequencies, ground effect is dominant, and there is little or no attenuation due to crops. At higher frequencies above 3-4 kHz, the attenuation in crops is dominant. It was also found that the ground effects and the influence of crops can be treated independently and can be added to obtain the total effect. Sound attenuation by crops is the result of multiple scattering between the stems and leaves, loss of coherence, and viscous and thermal losses due to foliage. The major contribution is associated with viscous and thermal losses. A model for sound attenuation by vegetation is proposed. Insertion losses for a typical road traffic noise source have been calculated that result either by replacing hard ground with different types of acoustically soft ground or by growing crops along the road sides. PMID:25618047

  12. 77 FR 69542 - V and S Railway, LLC-Acquisition and Operation Exemption-Colorado Department of Transportation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-19

    ... Surface Transportation Board V and S Railway, LLC--Acquisition and Operation Exemption-- Colorado Department of Transportation AGENCY: Surface Transportation Board. ACTION: Notice of exemption. SUMMARY: The... approximately 121.9 miles of rail line between milepost 747.5, near Towner, and milepost 869.4, near NA...

  13. Trend of surface solar radiation over Asia simulated by aerosol transport-climate model

    NASA Astrophysics Data System (ADS)

    Takemura, T.; Ohmura, A.

    2009-12-01

    Long-term records of surface radiation measurements indicate a decrease in the solar radiation between the 1950s and 1980s (“global dimming”), then its recovery afterward (“global brightening”) at many locations all over the globe [Wild, 2009]. On the other hand, the global brightening is delayed over the Asian region [Ohmura, 2009]. It is suggested that these trends of the global dimming and brightening are strongly related with a change in aerosol loading in the atmosphere which affect the climate change through the direct, semi-direct, and indirect effects. In this study, causes of the trend of the surface solar radiation over Asia during last several decades are analyzed with an aerosol transport-climate model, SPRINTARS. SPRINTARS is coupled with MIROC which is a general circulation model (GCM) developed by Center for Climate System Research (CCSR)/University of Tokyo, National Institute for Environmental Studies (NIES), and Frontier Research Center for Global Change (FRCGC) [Takemura et al., 2000, 2002, 2005, 2009]. The horizontal and vertical resolutions are T106 (approximately 1.1° by 1.1°) and 56 layers, respectively. SPRINTARS includes the transport, radiation, cloud, and precipitation processes of all main tropospheric aerosols (black and organic carbons, sulfate, soil dust, and sea salt). The model treats not only the aerosol mass mixing ratios but also the cloud droplet and ice crystal number concentrations as prognostic variables, and the nucleation processes of cloud droplets and ice crystals depend on the number concentrations of each aerosol species. Changes in the cloud droplet and ice crystal number concentrations affect the cloud radiation and precipitation processes in the model. Historical emissions, that is consumption of fossil fuel and biofuel, biomass burning, aircraft emissions, and volcanic eruptions are prescribed from database provided by the Aerosol Model Intercomparison Project (AeroCom) and the latest IPCC inventories

  14. 49 CFR 6.35 - Agency review.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 1 2013-10-01 2013-10-01 false Agency review. 6.35 Section 6.35 Transportation... PROCEEDINGS Procedures for Considering Applications § 6.35 Agency review. Where Department review of the underlying decision is permitted, either the applicant or agency counsel, may seek review of the...

  15. 5 CFR 6001.102 - Agency designees.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ....102 Administrative Personnel DEPARTMENT OF TRANSPORTATION SUPPLEMENTAL STANDARDS OF ETHICAL CONDUCT FOR EMPLOYEES OF THE DEPARTMENT OF TRANSPORTATION § 6001.102 Agency designees. For purposes of 5 CFR... of 5 CFR 2635.102(b): (a) The Designated Agency Ethics Official; (b) The Alternate Agency...

  16. Spin and charge transport induced by a twisted light beam on the surface of a topological insulator

    NASA Astrophysics Data System (ADS)

    Shintani, Kunitaka; Taguchi, Katsuhisa; Tanaka, Yukio; Kawaguchi, Yuki

    2016-05-01

    We theoretically study spin and charge transport induced by a twisted light beam irradiated on a disordered surface of a doped three-dimensional topological insulator (TI). We find that various types of spin vortices are imprinted on the surface of the TI depending on the spin and orbital angular momentum of the incident light. The key mechanism for the appearance of the unconventional spin structure is the spin-momentum locking in the surface state of the TI. Besides, the diffusive transport of electrons under an inhomogeneous electric field causes a gradient of the charge density, which then induces nonlocal charge current and spin density as well as the spin current. We discuss the relation between these quantities within the linear response to the applied electric field using the Keldysh-Green's function method.

  17. Mass transfer in fuel cells. [electron microscopy of components, thermal decomposition of Teflon, water transport, and surface tension of KOH solutions

    NASA Technical Reports Server (NTRS)

    Walker, R. D., Jr.

    1973-01-01

    Results of experiments on electron microscopy of fuel cell components, thermal decomposition of Teflon by thermogravimetry, surface area and pore size distribution measurements, water transport in fuel cells, and surface tension of KOH solutions are described.

  18. Modeling Np and Pu transport with a surface complexation model and spatially variant sorption capacities: implications for reactive transport modeling and performance assessments of nuclear waste disposal sites

    NASA Astrophysics Data System (ADS)

    Glynn, Pierre D.

    2003-04-01

    One-dimensional (1D) geochemical transport modeling is used to demonstrate the effects of speciation and sorption reactions on the ground-water transport of Np and Pu, two redox-sensitive elements. Earlier 1D simulations (Reardon, 1981) considered the kinetically limited dissolution of calcite and its effect on ion-exchange reactions (involving 90Sr, Ca, Na, Mg and K), and documented the spatial variation of a 90Sr partition coefficient under both transient and steady-state chemical conditions. In contrast, the simulations presented here assume local equilibrium for all reactions, and consider sorption on constant potential, rather than constant charge, surfaces. Reardon's (1981) seminal findings on the spatial and temporal variability of partitioning (of 90Sr) are reexamined and found partially caused by his assumption of a kinetically limited reaction. In the present work, sorption is assumed the predominant retardation process controlling Pu and Np transport, and is simulated using a diffuse-double-layer-surface-complexation (DDLSC) model. Transport simulations consider the infiltration of Np- and Pu-contaminated waters into an initially uncontaminated environment, followed by the cleanup of the resultant contamination with uncontaminated water. Simulations are conducted using different spatial distributions of sorption capacities (with the same total potential sorption capacity, but with different variances and spatial correlation structures). Results obtained differ markedly from those that would be obtained in transport simulations using constant Kd, Langmuir or Freundlich sorption models. When possible, simulation results (breakthrough curves) are fitted to a constant Kd advection-dispersion transport model and compared. Functional differences often are great enough that they prevent a meaningful fit of the simulation results with a constant Kd (or even a Langmuir or Freundlich) model, even in the case of Np, a weakly sorbed radionuclide under the simulation

  19. Modeling Np and Pu Transport with a Surface Complexation Model and Spatially Variant Sorption Capacities: Implications for Reactive Transport Modeling and Performance Assessments of Nuclear Waste Disposal Sites

    NASA Astrophysics Data System (ADS)

    Glynn, P. D.

    2002-12-01

    One-dimensional (1D) geochemical transport modeling is used to demonstrate the effects of speciation and sorption reactions on the ground-water transport of Np and Pu, two redox-sensitive elements. Earlier 1D simulations (Reardon, 1981) considered the kinetically-limited dissolution of calcite and its effect on ion-exchange reactions (involving 90Sr, Ca, Na, Mg and K), and documented the spatial variation of a 90Sr partition coefficient under both transient and steady-state chemical conditions. In contrast, the simulations presented here assume local equilibrium for all reactions, and consider sorption on constant potential, rather than constant charge, surfaces. Reardon's (1981) findings documenting the spatial and temporal variability of 90Sr partitioning are reexamined and found partially caused by his assumption of a kinetically-limited reaction. In the present simulations, sorption is assumed the only retardation process controlling Pu and Np transport, and is modeled using a diffuse-double-layer-surface-complexation model. Transport simulations consider the inflow of Np- and Pu-contaminated waters into an initially uncontaminated environment, followed by the cleanup of the resultant contamination with uncontaminated water. Simulations are conducted using different spatial distributions of sorption capacities (with the same total potential sorption capacity, i.e. the same total number of sorption sites, but with different variances and spatial correlation structures). A case with a spatially uniform distribution of sorption capacities was also simulated. Results obtained differ markedly from those that would be obtained in transport simulations using constant Kd, Langmuir, or Freundlich sorption models. When possible, simulation results (breakthrough curves) are fitted to a constant Kd advection-dispersion transport model and compared to each other. Functional differences are often great enough that they prevent a meaningful fit of the simulation results with

  20. Modeling Np and Pu transport with a surface complexation model and spatially variant sorption capacities: Implications for reactive transport modeling and performance assessments of nuclear waste disposal sites

    USGS Publications Warehouse

    Glynn, P.D.

    2003-01-01

    One-dimensional (1D) geochemical transport modeling is used to demonstrate the effects of speciation and sorption reactions on the ground-water transport of Np and Pu, two redox-sensitive elements. Earlier 1D simulations (Reardon, 1981) considered the kinetically limited dissolution of calcite and its effect on ion-exchange reactions (involving 90Sr, Ca, Na, Mg and K), and documented the spatial variation of a 90Sr partition coefficient under both transient and steady-state chemical conditions. In contrast, the simulations presented here assume local equilibrium for all reactions, and consider sorption on constant potential, rather than constant charge, surfaces. Reardon's (1981) seminal findings on the spatial and temporal variability of partitioning (of 90Sr) are reexamined and found partially caused by his assumption of a kinetically limited reaction. In the present work, sorption is assumed the predominant retardation process controlling Pu and Np transport, and is simulated using a diffuse-double-layer-surface-complexation (DDLSC) model. Transport simulations consider the infiltration of Np- and Pu-contaminated waters into an initially uncontaminated environment, followed by the cleanup of the resultant contamination with uncontaminated water. Simulations are conducted using different spatial distributions of sorption capacities (with the same total potential sorption capacity, but with different variances and spatial correlation structures). Results obtained differ markedly from those that would be obtained in transport simulations using constant Kd, Langmuir or Freundlich sorption models. When possible, simulation results (breakthrough curves) are fitted to a constant K d advection-dispersion transport model and compared. Functional differences often are great enough that they prevent a meaningful fit of the simulation results with a constant K d (or even a Langmuir or Freundlich) model, even in the case of Np, a weakly sorbed radionuclide under the

  1. Impacts of bridging complexation on the transport of surface-modified nanoparticles in saturated sand

    NASA Astrophysics Data System (ADS)

    Torkzaban, Saeed; Wan, Jiamin; Tokunaga, Tetsu K.; Bradford, Scott A.

    2012-08-01

    The transport of polyacrylic acid capped cadmium telluride (CdTe) quantum dots (QDs), carboxylate-modified latex (CML), and bare silica nanoparticles (NPs) was studied in packed columns at various electrolyte concentrations and cation types. The breakthrough curves (BTCs) of QDs and CML particles in acid-treated Accusand showed significant amounts of increasing deposition with 0.5, 1, and 2 mM Ca2+, but only minute deposition at 50 and 100 mM Na+. Negligible QD and CML deposition occurred at 2 mM Ca2+ in columns packed with ultrapure quartz sand that was similar in size to the Accusand. These observations are not consistent with interpretations based on Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations of interaction energies. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis demonstrated that there were regions on the acid-treated Accusand covered with small amounts of clay that were absent on the ultrapure quartz sand. A salt cleaning method was therefore used to remove the clay from the acid-treated Accusand. The BTCs of QDs and CML in this acid + salt treated Accusand exhibited much less deposition at any given Ca2+ concentration compared to those obtained from the acid-treated sand. SEM images showed that most of the QD deposited in acid-treated Accusand occurred on clay surfaces. Unlike our results with QDs and CML, negligible deposition of bare silica NPs occurred at 5 and 10 mM Ca2+ in acid-treated Accusand. The high deposition of QDs and CML particles was therefore attributed to bridging complexation in which Ca2+ serves as a bridge between the cation exchange locations on the clay and carboxyl functional groups on the QD and CML particles, which were absent on the bare silica NPs. Our results suggest that the transport of carboxylic ligand-modified NPs may be limited in subsurface environments because of the ubiquitous presence of clay and divalent cations.

  2. Particle transport and adjustments of the boundary layer over rough surfaces with an unrestricted, upwind supply of sediment

    NASA Astrophysics Data System (ADS)

    McKenna Neuman, Cheryl

    1998-10-01

    Most natural surfaces containing non-erodible roughness elements are considerably more complex than those studied in modelling exercises and wind tunnel simulations. Unlike idealized roughness elements, which are uniform in size, shape (i.e., spheres or cylinders) and spacing, natural elements are challenging to measure in 3-dimensional space. Similarly, most deflation lag surfaces, such those as found on sandar and beaches, are spatially heterogeneous open systems in which sediment transport from an external supply is very likely. The development of irregular deflation lag surfaces, and the transport of sediment over these surfaces from an upwind source of sediment, was studied in a series of wind tunnel simulations. Surfaces prepared with crushed gravel and natural beach shingle respond conservatively in terms of the adjustment to the deflation and deposition of sediment. Deflation lag surfaces, prepared with no spacing between the roughness elements (i.e., close packed), demonstrate little to no change in coverage with the introduction of particles from an upwind source. Neither the element type nor the friction velocity affect this outcome. As the center-to-center element spacing increases to 60 mm, infilling of the lag surface eventually is observed, with the element coverage reduced by a factor between 2 and 4. For a given threshold ratio ( Rt), the roughness density ( λ) is smaller than observed in previous simulation studies based on idealized roughness elements.

  3. Effect of Cyclic Precipitation and Radiation on the Fate and Transport of TNT and DNT Near Soil-Atmospheric Surfaces

    NASA Astrophysics Data System (ADS)

    Anaya, A.; Padilla, I. Y.; Hwang, S.

    2007-12-01

    Many explosive-related compounds (ERCs) are found near the soil-atmospheric surface in sites containing buried explosive devices, such as landmines and unexploded ordnance, detonation-residual solid explosives, and munitions residues from explosive manufacturing facilities. Accurate assessment of the fate and transport processes is essential for predicting their movement to the surface, groundwater, or any other important environmental compartment. The dynamics of ERCs movement is complex, involving multiple, interrelated processes. The transport processes controlling the direction and magnitude of the movement, and chemical, physical, and biological processes controlling the fate of the chemicals vary with environmental conditions. This research addresses the effect of variable rainfall, evaporation, temperature, and solar radiation on fate and transport of 2,4,6-Trinitrotoluene (TNT), 2,4-Dinitrotoluene (DNT), and other related chemicals in partially saturated soil. Fate and transport experiments were conducted in a laboratory-scale geo-environmental system containing a 3D SoilBed packed with a sandy soil, and equipped with rainfall and solar radiation simulators, and temperature control settings. Experiments were conducted by burying a TNT/DNT source under the soil surface and applying cyclic rainfall and radiation over the surface of the soil. Aqueous and gaseous concentrations of tracers, TNT, DNT and other related ERCs were monitored through time at several distances from the source. Measured hydraulic conditions and tracer concentrations during the experiments indicate the existence of preferential flow paths during infiltration events and solute accumulation during evaporation periods. TNT, DNT and an undetermined chemical believed to be a degradation by-product of TNT were detected non-continuously in space and time. Concentrations of TNT and DNT were much lower than their solubility limits, indicating rate- limited mass-transfer, dissolution limitations

  4. TRANSPORT AND DEFENSIVE ROLE OF ELATOL AT THE SURFACE OF THE RED SEAWEED LAURENCIA OBTUSA (CERAMIALES, RHODOPHYTA)(1).

    PubMed

    Sudatti, Daniela B; Rodrigues, Silvana V; Coutinho, Ricardo; Da Gama, Bernardo A P; Salgado, Leonardo T; Amado Filho, Gilberto M; Pereira, Renato C

    2008-06-01

    Natural within-thallus concentrations of elatol produced by Laurencia obtusa (Huds.) J. V. Lamour. inhibit herbivory and prevent fouling. However, elatol occurs in larger amounts within the thallus compared with the quantities from the surface of this alga. We evaluated whether the surface elatol concentrations inhibit both herbivory and fouling and whether the content of corps en cerise can be transferred to the external cell walls. Surface elatol concentrations did not inhibit herbivory by sea urchins, settlement of barnacle larvae, or mussel attachment. Evidence of a connection between the corps en cerise, where elatol is probably stored, and the cell wall of L. obtusa was based on channel-like membranous connections that transport vesicles from the corps to the cell wall region. Therefore, L. obtusa presents a specific process of chemical transport between the cell storage structures and the plant surface. We hypothesized that if high amounts of elatol are capable of inhibiting herbivory and fouling, if the tested organisms are ecologically relevant, and if elatol really occurs on the surface of L. obtusa and this seaweed can transport this compound to its surface, the low natural concentration of defensive chemicals on the surface of L. obtusa is probably not absolute but may be variable according to environmental conditions. We also hypothesized that herbivory and fouling would not exert the same selective force for the production of defensive chemicals on L. obtusa's surface since the low concentrations of elatol were inefficient to inhibit either processes or distinguish selective pressures. PMID:27041418

  5. Transport: Introduction

    NASA Technical Reports Server (NTRS)

    Lewis, William; Rosenberg, Sanders D.

    1992-01-01

    Space transportation requirements for the NASA baseline scenario for future space missions are discussed. Spacecraft/propulsion technologies required for surface-to-orbit, orbit-to-orbit, and surface (lunar) transportation are addressed.

  6. Estimation of Atmospheric Methane Surface Fluxes Using a Global 3-D Chemical Transport Model

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Prinn, R.

    2003-12-01

    Accurate determination of atmospheric methane surface fluxes is an important and challenging problem in global biogeochemical cycles. We use inverse modeling to estimate annual, seasonal, and interannual CH4 fluxes between 1996 and 2001. The fluxes include 7 time-varying seasonal (3 wetland, rice, and 3 biomass burning) and 3 steady aseasonal (animals/waste, coal, and gas) global processes. To simulate atmospheric methane, we use the 3-D chemical transport model MATCH driven by NCEP reanalyzed observed winds at a resolution of T42 ( ˜2.8° x 2.8° ) in the horizontal and 28 levels (1000 - 3 mb) in the vertical. By combining existing datasets of individual processes, we construct a reference emissions field that represents our prior guess of the total CH4 surface flux. For the methane sink, we use a prescribed, annually-repeating OH field scaled to fit methyl chloroform observations. MATCH is used to produce both the reference run from the reference emissions, and the time-dependent sensitivities that relate individual emission processes to observations. The observational data include CH4 time-series from ˜15 high-frequency (in-situ) and ˜50 low-frequency (flask) observing sites. Most of the high-frequency data, at a time resolution of 40-60 minutes, have not previously been used in global scale inversions. In the inversion, the high-frequency data generally have greater weight than the weekly flask data because they better define the observational monthly means. The Kalman Filter is used as the optimal inversion technique to solve for emissions between 1996-2001. At each step in the inversion, new monthly observations are utilized and new emissions estimates are produced. The optimized emissions represent deviations from the reference emissions that lead to a better fit to the observations. The seasonal processes are optimized for each month, and contain the methane seasonality and interannual variability. The aseasonal processes, which are less variable, are

  7. A non-equilibrium model for soil heating and moisture transport during extreme surface heating

    NASA Astrophysics Data System (ADS)

    Massman, W. J.

    2015-03-01

    With increasing use of prescribed fire by land managers and increasing likelihood of wildfires due to climate change comes the need to improve modeling capability of extreme heating of soils during fires. This issue is addressed here by developing a one-dimensional non-equilibrium model of soil evaporation and transport of heat, soil moisture, and water vapor, for use with surface forcing ranging from daily solar cycles to extreme conditions encountered during fires. The model employs a linearized Crank-Nicolson scheme for the conservation equations of energy and mass and its performance is evaluated against dynamic soil temperature and moisture observations obtained during laboratory experiments on soil samples exposed to surface heat fluxes ranging between 10 000 and 50 000 W m-2. The Hertz-Knudsen equation is the basis for constructing the model's non-equilibrium evaporative source term. The model includes a dynamic residual soil moisture as a function of temperature and soil water potential, which allows the model to capture some of the dynamic aspects of the strongly bound soil moisture that seems to require temperatures well beyond 150 °C to fully evaporate. Furthermore, the model emulates the observed increase in soil moisture ahead of the drying front and the hiatus in the soil temperature rise during the strongly evaporative stage of drying. It also captures the observed rapid evaporation of soil moisture that occurs at relatively low temperatures (50-90 °C). Sensitivity analyses indicate that the model's success results primarily from the use of a temperature and moisture potential dependent condensation coefficient in the evaporative source term. The model's solution for water vapor density (and vapor pressure), which can exceed one standard atmosphere, cannot be experimentally verified, but they are supported by results from (earlier and very different) models developed for somewhat different purposes and for different porous media. Overall, this non

  8. Equations of the surface harmonics method for solving time-dependent neutron transport problems and their verification

    NASA Astrophysics Data System (ADS)

    Boyarinov, V. F.; Kondrushin, A. E.; Fomichenko, P. A.

    2013-12-01

    Time-dependent equations of the surface harmonics method (SHM) are obtained for planar one-dimensional geometry. The equations are verified by calculations of test problems from Benchmark Problem Book ANL-7416, and the capabilities and efficiency of applying the SHM for solving the time-dependent neutron transport equation in the diffusion approximation are demonstrated. The results of the work show that the implementation of the SHG for full-scale computations will make possible substantial progress in the efficient solution of time-dependent problems of neutron transport in nuclear reactors.

  9. Non-Genomic Estrogen Regulation of Ion Transport and Airway Surface Liquid Dynamics in Cystic Fibrosis Bronchial Epithelium

    PubMed Central

    Saint-Criq, Vinciane; Kim, Sung Hoon; Katzenellenbogen, John A.; Harvey, Brian J.

    2013-01-01

    Male cystic fibrosis (CF) patients survive longer than females and lung exacerbations in CF females vary during the estrous cycle. Estrogen has been reported to reduce the height of the airway surface liquid (ASL) in female CF bronchial epithelium. Here we investigated the effect of 17β-estradiol on the airway surface liquid height and ion transport in normal (NuLi-1) and CF (CuFi-1) bronchial epithelial monolayers. Live cell imaging using confocal microscopy revealed that airway surface liquid height was significantly higher in the non-CF cells compared to the CF cells. 17β-estradiol (0.1–10 nM) reduced the airway surface liquid height in non-CF and CF cells after 30 min treatment. Treatment with the nuclear-impeded Estrogen Dendrimer Conjugate mimicked the effect of free estrogen by reducing significantly the airway surface liquid height in CF and non-CF cells. Inhibition of chloride transport or basolateral potassium recycling decreased the airway surface liquid height and 17β-estradiol had no additive effect in the presence of these ion transporter inhibitors. 17β-estradiol decreased bumetanide-sensitive transepithelial short-circuit current in non-CF cells and prevented the forskolin-induced increase in ASL height. 17β-estradiol stimulated an amiloride-sensitive transepithelial current and increased ouabain-sensitive basolateral short-circuit current in CF cells. 17β-estradiol increased PKCδ activity in CF and non-CF cells. These results demonstrate that estrogen dehydrates CF and non-CF ASL, and these responses to 17β-estradiol are non-genomic rather than involving the classical nuclear estrogen receptor pathway. 17β-estradiol acts on the airway surface liquid by inhibiting cAMP-mediated chloride secretion in non-CF cells and increasing sodium absorption via the stimulation of PKCδ, ENaC and the Na+/K+ATPase in CF cells. PMID:24223826

  10. Dust transport over the eastern Mediterranean derived from Total Ozone Mapping Spectrometer, Aerosol Robotic Network, and surface measurements

    NASA Astrophysics Data System (ADS)

    Kalivitis, N.; Gerasopoulos, E.; Vrekoussis, M.; Kouvarakis, G.; Kubilay, N.; Hatzianastassiou, N.; Vardavas, I.; Mihalopoulos, N.

    2007-02-01

    Multiyear surface PM10 measurements performed on Crete Island, Greece, have been used in conjunction with satellite (Total Ozone Mapping Spectrometer (TOMS)) and ground-based remote sensing measurements (Aerosol Robotic Network (AERONET)) to enhance our understanding of the evolution of mineral dust events over the eastern Mediterranean. An analysis of southerly air masses at altitudes of 1000 and 3000 m over a 5 year period (2000-2005), showed that dust can potentially arrive over Crete, either simultaneously in the lower free troposphere and inside the boundary layer (vertical extended transport (VET)) or initially into the free troposphere with the heavier particles gradually being scavenged inside the boundary layer (free troposphere transport (FTT)). Both pathways present significant seasonal variations but on an annual basis contribute almost equally to the dust transport in the area. During VET the aerosol index (AI) derived from TOMS was significantly correlated with surface PM10, and in general AI was found to be adequate for the characterization of dust loadings over the eastern Mediterranean on a climatological basis. A significant covariance between PM10 and AOT was observed during VET as well, indicating that AOT levels from AERONET may be estimated by PM10 levels at the surface. Surface measurements are thus crucial for the validation of remote sensing measurements and hence are a powerful tool for the investigation of the impact of aerosols on climate.

  11. Kinesin-5/Eg5 is important for transport of CARTS from the trans-Golgi network to the cell surface

    PubMed Central

    Villeneuve, Julien; van Galen, Josse; Cruz-Garcia, David; Tagaya, Mitsuo

    2013-01-01

    Here we report that the kinesin-5 motor Klp61F, which is known for its role in bipolar spindle formation in mitosis, is required for protein transport from the Golgi complex to the cell surface in Drosophila S2 cells. Disrupting the function of its mammalian orthologue, Eg5, in HeLa cells inhibited secretion of a protein called pancreatic adenocarcinoma up-regulated factor (PAUF) but, surprisingly, not the trafficking of vesicular stomatitis virus G protein (VSV-G) to the cell surface. We have previously reported that PAUF is transported from the trans-Golgi network (TGN) to the cell surface in specific carriers called CARTS that exclude VSV-G. Inhibition of Eg5 function did not affect the biogenesis of CARTS; however, their migration was delayed and they accumulated near the Golgi complex. Altogether, our findings reveal a surprising new role of Eg5 in nonmitotic cells in the facilitation of the transport of specific carriers, CARTS, from the TGN to the cell surface. PMID:23857769

  12. Wind-induced contaminant transport in near-surface soils with application to radon entry into buildings

    SciTech Connect

    Riley, W J

    1996-05-01

    Indoor air exposures to gaseous contaminants originating in soil can cause large human health risks. To predict and control these exposures, the mechanisms that affect vapor transport in near-surface soils need to be understood. In particular, radon exposure is a concern since average indoor radon concentrations lead to much higher risks than are generally accepted for exposure to other environmental contaminants. This dissertation examines an important component of the indoor radon problem: the impacts of wind on soil-gas and radon transport and entry into buildings. The research includes experimental and modeling studies of wind`s interactions with a building`s superstructure and the resulting soil-gas and radon flows in the surrounding soil. In addition to exploring the effects of steady winds, a novel modeling technique is developed to examine the impacts of fluctuating winds on soil-gas and radon transport.

  13. Long-range transport of Siberian biomass burning emissions and impact on surface ozone in western North America

    NASA Astrophysics Data System (ADS)

    Jaffe, Dan; Bertschi, Isaac; Jaeglé, Lyatt; Novelli, Paul; Reid, Jeffrey S.; Tanimoto, Hiroshi; Vingarzan, Roxanne; Westphal, Douglas L.

    2004-08-01

    During the summer of 2003, biomass fires burned a large area of Siberia, the largest in at least 10 years. We used the NRL Aerosol Analysis and Prediction System (NAAPS) model to forecast the transport of the smoke from these fires. Transport of these airmasses to North America was confirmed by aircraft and surface observations. The fires resulted in enhancements in summer background CO and O3 of 23-37 and 5-9 ppbv, respectively, at 10 sites in Alaska, Canada and the Pacific Northwest. From the area burned, we estimate that the Siberian fires generated 68 Tg of CO and 0.82 Tg of NOx (as N). In addition, we show that the background O3 enhancement contributed to an exceedance of the ozone air quality standard in the Pacific Northwest. These results show that regional air quality and health are linked to global processes, including climate, forest fires and long-range transport of pollutants.

  14. A preliminary investigation of the applicability of surface complexation modeling to the understanding of transportation cask weeping

    SciTech Connect

    Granstaff, V.E.; Chambers, W.B.; Doughty, D.H.

    1994-12-31

    A new application for surface complexation modeling is described. These models, which describe chemical equilibria among aqueous and adsorbed species, have typically been used for predicting groundwater transport of contaminants by modeling the natural adsorbents as various metal oxides. Our experiments suggest that this type of modeling can also explain stainless steel surface contamination and decontamination mechanisms. Stainless steel transportation casks, when submerged in a spent fuel storage pool at nuclear power stations, can become contaminated with radionuclides such as {sup 137}Cs, {sup 134}Cs, and {sup 60}Co. Subsequent release or desorption of these contaminants under varying environmental conditions occasionally results in the phenomenon known as {open_quotes}cask weeping.{close_quotes} We have postulated that contaminants in the storage pool adsorb onto the hydrous metal oxide surface of the passivated stainless steel and are subsequently released (by conversion from a fixed to a removable form) during transportation, due to varying environmental factors, such as humidity, road salt, dirt, and acid rain. It is well known that 304 stainless steel has a chromium enriched passive surface layer; thus its adsorption behavior should be similar to that of a mixed chromium/iron oxide. To help us interpret our studies of reversible binding of dissolved metals on stainless steel surfaces, we have studied the adsorption of Co{sup +2} on Cr{sub 2}O{sub 3}. The data are interpreted using electrostatic surface complexation models. The FITEQL computer program was used to obtain the model binding constants and site densities from the experimental data. The MINTEQA2 computer speciation model was used, with the fitted constants, in an attempt to validate this approach.

  15. An experimental investigation on the surface water transport process over an airfoil by using a digital image projection technique

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Wei, Tian; Hu, Hui

    2015-09-01

    In the present study, an experimental investigation was conducted to characterize the transient behavior of the surface water film and rivulet flows driven by boundary layer airflows over a NACA0012 airfoil in order to elucidate underlying physics of the important micro-physical processes pertinent to aircraft icing phenomena. A digital image projection (DIP) technique was developed to quantitatively measure the film thickness distribution of the surface water film/rivulet flows over the airfoil at different test conditions. The time-resolved DIP measurements reveal that micro-sized water droplets carried by the oncoming airflow impinged onto the airfoil surface, mainly in the region near the airfoil leading edge. After impingement, the water droplets formed thin water film that runs back over the airfoil surface, driven by the boundary layer airflow. As the water film advanced downstream, the contact line was found to bugle locally and developed into isolated water rivulets further downstream. The front lobes of the rivulets quickly advanced along the airfoil and then shed from the airfoil trailing edge, resulting in isolated water transport channels over the airfoil surface. The water channels were responsible for transporting the water mass impinging at the airfoil leading edge. Additionally, the transition location of the surface water transport process from film flows to rivulet flows was found to occur further upstream with increasing velocity of the oncoming airflow. The thickness of the water film/rivulet flows was found to increase monotonically with the increasing distance away from the airfoil leading edge. The runback velocity of the water rivulets was found to increase rapidly with the increasing airflow velocity, while the rivulet width and the gap between the neighboring rivulets decreased as the airflow velocity increased.

  16. On the Sensitivity of Atmospheric Model Implied Ocean Heat Transport to the Dominant Terms of the Surface Energy Balance

    SciTech Connect

    Gleckler, P J

    2004-11-03

    The oceanic meridional heat transport (T{sub o}) implied by an atmospheric General Circulation Model (GCM) can help evaluate a model's readiness for coupling with an ocean GCM. In this study we examine the T{sub o} from benchmark experiments of the Atmospheric Model Intercomparison Project, and evaluate the sensitivity of T{sub o} to the dominant terms of the surface energy balance. The implied global ocean TO in the Southern Hemisphere of many models is equatorward, contrary to most observationally-based estimates. By constructing a hybrid (model corrected by observations) T{sub o}, an earlier study demonstrated that the implied heat transport is critically sensitive to the simulated shortwave cloud radiative effects, which have been argued to be principally responsible for the Southern Hemisphere problem. Systematic evaluation of one model in a later study suggested that the implied T{sub o} could be equally as sensitive to a model's ocean surface latent heat flux. In this study we revisit the problem with more recent simulations, making use of estimates of ocean surface fluxes to construct two additional hybrid calculations. The results of the present study demonstrate that indeed the implied T{sub o} of an atmospheric model is very sensitive to problems in not only the surface net shortwave, but the latent heat flux as well. Many models underestimate the shortwave radiation reaching the surface in the low latitudes, and overestimate the latent heat flux in the same region. The additional hybrid transport calculations introduced here could become useful model diagnostic tests as estimates of implied ocean surface fluxes are improved.

  17. Heavy surface state in a possible topological Kondo insulator: Magnetothermoelectric transport on the (011) plane of SmB6

    DOE PAGESBeta

    Luo, Yongkang; Chen, Hua; Dai, Jianhui; Xu, Zhu -an; Thompson, J. D.

    2015-02-25

    Motivated by the high sensitivity to Fermi surface topology and scattering mechanisms in magnetothermoelectric transport, we have measured the thermopower and Nernst effect on the (011) plane of the proposed topological Kondo insulator SmB6. These experiments, together with electrical resistivity and Hall effect measurements, suggest that the (011) plane also harbors a metallic surface with an effective mass on the order of 10–102 m0. The surface and bulk conductances are well distinguished in these measurements and are categorized into metallic and nondegenerate semiconducting regimes, respectively. As a result, electronic correlations play an important role in enhancing scattering and also contributemore » to the heavy surface state.« less

  18. In-situ surface debris inspection and removal system for upward-facing transport mirrors of the National Ignition Facility

    SciTech Connect

    Gourdin, W H; Dzenitis, E; Martin, D; Listiyo, K; Sherman, G; Kent, W; Butlin, R; Stolz, C J; Pryatel, J

    2004-11-10

    We describe a system to inspect and remove surface debris in-situ from the surfaces of upward-facing mirrors that transport 1053 nm laser light to the target chamber of the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory. Grazing angle (2-5{sup o}) illumination with a bar light highlights debris {approx}10 {micro}m in size and larger, which is then viewed through windows in the enclosures of selected mirrors. Debris is removed with 1-second bursts of high velocity (76 m/s) clean air delivered across the optic surfaces by a commercially available linear nozzle (''gas knife''). Experiments with aluminum, stainless steel, glass and polystyrene particles of various sizes >30 {micro}m show that particle removal efficiency is near 100% over most of the mirror surfaces for all sizes tested.

  19. The influence of subgrid surface-layer variability on vertical transport of a chemical species in a convective environment

    NASA Astrophysics Data System (ADS)

    Devine, G. M.; Carslaw, K. S.; Parker, D. J.; Petch, J. C.

    2006-08-01

    We use a 2-D cloud-resolving model over a 256 km domain to examine the influence of subgrid-scale processes on the concentration and vertical transport of a chemical species (dimethyl sulphide, or DMS) in a deep convective marine environment. Two issues are highlighted. Firstly, deriving fluxes using a spatially averaged surface wind representative of a global model reduces the domain-mean DMS concentration by approximately 50%. Emission of DMS from the surface is greater in the CRM because it resolves the localized intense winds embedded in the dynamical structure of convective systems. Secondly, we find that the spatial pattern of DMS concentration in the boundary layer is positively correlated with the pattern of convective updraughts. Using a mean concentration field reduces transport to the upper troposphere by more than 50%. The explanation is that secondary convection occurs preferentially on the edges of cold pools, where DMS concentrations are higher than the domain mean.

  20. Feasibility of determining surface emissions of trace gases using an inverse method in a three-dimensional chemical transport model

    NASA Technical Reports Server (NTRS)

    Hartley, Dana; Prinn, Ronald

    1993-01-01

    The paper investigates the feasibility of using an inverse method based on a linear Kalman filter in a three-dimensional atmospheric transport model, for the determination of regional surface fluxes with rapid convergence, using data from a finite number of observation sites. It was found that the inverse method used was capable to accurately determine regional surface fluxes using the present ALE/GALE sites, and to converge to the correct solution within a year or two, using initial conditions very different from the final solution.

  1. Coupled Soil Water and Heat Transport Near the Land Surface in Arid and Semiarid Regions - Multi-Domain Modeling

    NASA Astrophysics Data System (ADS)

    Mohanty, Binayak; Yang, Zhenlei

    2016-04-01

    Understanding and simulating coupled water and heat transfer appropriately in the shallow subsurface is of vital significance for accurate prediction of soil evaporation that would improve the coupling between land surface and atmosphere, which consequently could enhance the reliability of weather as well as climate forecast. The theory of Philip and de Vries (1957), accounting for water vapor diffusion only, was considered physically incomplete and consequently extended and improved by several researchers by explicitly taking water vapor convection, dispersion or air flow into account. It is generally believed that the soil moisture is usually low in the near surface layer under highly transient field conditions, particularly in arid and semiarid regions, and that accurate characterization of water vapor transport is critical when modeling simultaneous water and heat transport in the shallow field soils. The first objective of this study is thus mainly to test existing coupled water and heat transport theories and to develop reasonable and simplified numerical models using field experimental data collected under semi-arid and arid hydro-climatic conditions. In addition, more complex multi-domain models are developed for ubiquitous heterogeneous terrestrial surfaces such as horizontal textural contrasts or structured heterogeneity including macropores (fractures, cracks, root channels, etc.). This would make coupled water and heat transfer models applicable in such non-homogeneous soils more meaningful and enhance the skill of land-atmosphere interaction models at a larger context.

  2. 77 FR 26355 - Surface Transportation Project Delivery Pilot Program; Caltrans Audit Report

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-03

    ... February 22, 2012, at 77 FR 10599. The FHWA received one comment from Caltrans. This notice provides the... the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users...

  3. Spin transport properties of n-polyacene molecules (n = 1–15) connected to Ni surface electrodes: Theoretical analysis

    PubMed Central

    Caliskan, S.; Laref, A.

    2014-01-01

    Using non-equilibrium Green function formalism in conjunction with density functional theory, we explore the spin-polarized transport characteristics of several planar n-acene molecules suspended between two semi-infinite Ni electrodes via the thiol group. We examine the spin-dependence transport on Ni-n-acenes-Ni junctions, while the number of fused benzene rings varies between 1 and 15. Intriguingly, the induced magnetic moments of small acene molecules are higher than that of longer acene rings. The augmentation of fused benzene rings affects both the magnetic and transport features, such as the transmission function and conductance owing to their coupling to the Ni surface contacts via the anchoring group. The interplay between the spin-polarized transport properties, structural configuration and molecular electronic is a fortiori essential in these attractive molecular devices. Thus, this can conduct to the engineering of the electron spin transport in atomistic and molecular junctions. These prominent molecules convincingly infer that the molecular spin valves can conduct to thriving molecular devices. PMID:25482076

  4. Continuum theory of swelling material surfaces with applications to thermo-responsive gel membranes and surface mass transport

    NASA Astrophysics Data System (ADS)

    Lucantonio, Alessandro; Teresi, Luciano; DeSimone, Antonio

    2016-04-01

    Soft membranes are commonly employed in shape-morphing applications, where the material is programmed to achieve a target shape upon activation by an external trigger, and as coating layers that alter the surface characteristics of bulk materials, such as the properties of spreading and absorption of liquids. In particular, polymer gel membranes experience swelling or shrinking when their solvent content change, and the non-homogeneous swelling field may be exploited to control their shape. Here, we develop a theory of swelling material surfaces to model polymer gel membranes and demonstrate its features by numerically studying applications in the contexts of biomedicine, micro-motility, and coating technology. We also specialize the theory to thermo-responsive gels, which are made of polymers that change their affinity with a solvent when temperature varies.

  5. 78 FR 19069 - Southfield Coinvest Holdings, LLC; Southfield Hallcon Investment Corp. and Hallcon Crew Transport...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-28

    ... Surface Transportation Board Southfield Coinvest Holdings, LLC; Southfield Hallcon Investment Corp. and Hallcon Crew Transport Inc., et al.--Acquisition of Control-- Renzenberger, Inc. AGENCY: Surface...: Send an original and 10 copies of any comments referring to Docket No. MCF 21052 to:...

  6. Effects of bulk charged impurities on the bulk and surface transport in three-dimensional topological insulators

    SciTech Connect

    Skinner, B.; Chen, T.; Shklovskii, B. I.

    2013-09-15

    In the three-dimensional topological insulator (TI), the physics of doped semiconductors exists literally side-by-side with the physics of ultrarelativistic Dirac fermions. This unusual pairing creates a novel playground for studying the interplay between disorder and electronic transport. In this mini-review, we focus on the disorder caused by the three-dimensionally distributed charged impurities that are ubiquitous in TIs, and we outline the effects it has on both the bulk and surface transport in TIs. We present self-consistent theories for Coulomb screening both in the bulk and at the surface, discuss the magnitude of the disorder potential in each case, and present results for the conductivity. In the bulk, where the band gap leads to thermally activated transport, we show how disorder leads to a smaller-than-expected activation energy that gives way to variable-range hopping at low temperatures. We confirm this enhanced conductivity with numerical simulations that also allow us to explore different degrees of impurity compensation. For the surface, where the TI has gapless Dirac modes, we present a theory of disorder and screening of deep impurities, and we calculate the corresponding zero-temperature conductivity. We also comment on the growth of the disorder potential in passing from the surface of the TI into the bulk. Finally, we discuss how the presence of a gap at the Dirac point, introduced by some source of time-reversal symmetry breaking, affects the disorder potential at the surface and the mid-gap density of states.

  7. Cell-surface targeting of α2-adrenergic receptors — Inhibition by a transport deficient mutant through dimerization

    PubMed Central

    Zhou, Fuguo; Filipeanu, Catalin M.; Duvernay, Matthew T.; Wu, Guangyu

    2009-01-01

    We previously demonstrated that the α2B-adrenergic receptor mutant, in which the F(x)6IL motif in the membrane-proximal carboxyl terminus were mutated to alanines (α2B-ARm), is deficient in export from the endoplasmic reticulum (ER). In this report, we determined if α2B-ARm could modulate transport from the ER to the cell surface and signaling of its wild-type counterpart. Transient expression of α2B-ARm in HEK293T cells markedly inhibited cell-surface expression of wild-type α2B-AR, as measured by radioligand binding. Subcellular localization demonstrated that α2B-ARm trapped α2B-AR in the ER. The α2B-AR was shown to form homodimers and heterodimers with α2B-ARm as measured by co-immunoprecipitation of the receptors tagged with green fluorescent protein and hemagglutinin epitopes. In addition to α2B-AR, the transport of α2A-AR and α2C-AR to the cell surface was also inhibited by α2B-ARm. Furthermore, transient expression of α2B-ARm significantly reduced cell-surface expression of endogenous α2-AR in NG108-15 and HT29 cells. Consistent with its effect on α2-AR cell-surface expression, α2B-ARm attenuated α2A-AR- and α2B-AR-mediated ERK1/2 activation. These data demonstrated that the ER-retained mutant α2B-ARm conferred a dominant negative effect on the cell-surface expression of wild-type α2-AR, which is likely mediated through heterodimerization. These data indicate a crucial role of ER export in the regulation of cell-surface targeting and signaling of G protein-coupled receptors. PMID:15961277

  8. Transport signatures of surface potentials on three-dimensional topological insulators

    NASA Astrophysics Data System (ADS)

    Roy, Sthitadhi; Das, Sourin

    2016-02-01

    The spin-momentum-locked nature of the robust surface states of three-dimensional topological insulators (3D TIs) makes them promising candidates for spintronics applications. Surface potentials which respect time-reversal symmetry can exist at the surface between a 3D TI and the trivial vacuum. These potentials can distort the spin texture of the surface states while retaining their gapless nature. In this work, the effect of all such surface potentials on the spin textures is studied. Since a tunnel magnetoresistance signal carries the information of the spin texture, it is proposed that spin-polarized tunneling of electrons to a 3D TI surface can be used to uniquely identify the surface potentials and quantitatively characterize them.

  9. From Soil to Surface Water: a Meta-Analysis of Catchment-Scale Organic Matter Production and Transport

    NASA Astrophysics Data System (ADS)

    Gabor, R. S.; Brooks, P. D.; Perdrial, J. N.

    2015-12-01

    Organic matter plays a fundamental role in the ecology and biogeochemistry of many ecosystems, from soils to headwater streams to oceans. In most catchments, the terrestrial environment is the dominant source of organic matter for the aquatic system, and thus DOM represents a fundamental linkage between soil and surface water. With trends of increasing DOC concentrations observed in many areas of the world, there is growing interest in identifying which factors drive DOM concentration and chemistry. Studies of systems ranging from tropical rainforests to boreal landscapes have identified many catchment characteristics that co-vary with DOM concentration and chemistry. These include climate elements such as solar radiation and precipitation patterns, chemical measurements such as sulfate or chloride concentration, and land use impacts such as percent agriculture. The question of which catchment characteristics actually control DOM can be broken down into two parts: which factors control the production of mobile DOM and what drives DOM transport from the terrestrial to the aquatic system. Here we review studies covering a range of ecosystems, scales, and measurement techniques, to categorize the major state factors that drive catchment controls of aquatic organic matter. Specifically, we identify three major transport vectors that vary both in their timing of DOM transport to surface water and the propensity for DOM originating from terrestrial source areas to be modified during transport. We use this three vector conceptual model of transport to group catchments and identify reproducible signatures of DOM export with varying levels of disturbance. By developing a generalized conceptual model of catchment-scale controls on aquatic organic matter, we can predict how dissolved organic matter will respond to environmental change. This knowledge can then help guide best management practices.

  10. Correlating structural, mechanical, and charge transport properties of molecular monolayers and surfaces

    NASA Astrophysics Data System (ADS)

    Qi, Yabing

    In this dissertation I present experimental studies of the correlation between the structural, mechanical, and electrical properties of organic monolayers, graphite, and GaAs using conductance-atomic force microscopy (C-AFM). I studied three kinds of molecular monolayers. The first kind is alkanethiol self-assembled monolayers (SAMs), a saturated molecular film representing the "resistor" type element in electronics; the second kind is trans-stilbene based SAMs, a molecular system which has been proposed for molecular switches; the third kind is oligothiophene Langmuir-Blodgett (LB) monolayers, a prototype molecular system with conjugated groups which has shown potential for low cost optoelectronic devices. In alkanethiol SAMs on Au(111), a correlation between charge transport and molecular tilt changes caused by pressure has been found. The junction I-V characteristics are sensitive to the load applied by the tip, which causes film thickness and current to change in a step-wise manner. We found that the tunneling decay constant beta through molecules of fixed chain length is significantly smaller than that for the case where the distance between electrodes is changed by using alkanethiol molecules of different lengths. We propose that changes in S-Au binding structure occur due to the steric forces acting between close packed molecules under pressure, which displace the S from hollow sites to bridge sites and possibly others. Such changes can produce much larger changes in the tunneling characteristics. The second kind of monolayer I studied is o-(trans-4-stilbene)alkylthiol SSAMs on Au(111). Heating in a nitrogen gas atmosphere at 120° C for 1 h caused the morphology of the sample surface to change from a uniform molecular film consisting of small grains 10 ~ 20 nm in size to a heterogeneous surface consisting of well-packed and flat islands 100 ~ 200 nm in size and disordered structures. The flat islands exhibit substantial reduction (50%) in friction

  11. Pseudospin-valve effect on transport in junctions of three-dimensional topological insulator surfaces

    NASA Astrophysics Data System (ADS)

    Roy, Sthitadhi; Roychowdhury, Krishanu; Das, Sourin

    2016-07-01

    We show that the surface states of pristine 3D topological insulators (TIs) are analogs of ferromagnetic half metals due to complete polarization of an emergent momentum independent pseudospin (SU(2)) degree of freedom on the surface. To put this claim on firm footing, we present results for TI surfaces perpendicular to the crystal growth axis, which clearly show that the tunneling conductance between two such TI surfaces of the same TI material is dominated by this half metallic behavior leading to physics reminiscent of a spin-valve. Further using the generalized tunnel magnetoresistance derived in this work we also study the tunneling current between arbitrary TI surfaces. We also perform a comprehensive study of the effect of all possible surface potentials allowed by time reversal symmetry on this spin-valve effect and show that it is robust against most of such potentials.

  12. Reversible modulation of electric transport properties by oxygen absorption and releasing on Nb:SrTiO{sub 3} surface

    SciTech Connect

    Lu, H. X.; Liu, Y. B.; Chen, Y. S. Wang, J.; Shen, B. G.; Sun, J. R.

    2014-11-07

    Pt Schottky contacts on (001)-orientated Nb-doped SrTiO{sub 3} (NSTO) in both ambient air and vacuum were investigated by the conductive atomic force microscope. The co-existed TiO{sub 2} and SrO termination layers were identified on the terrace-structured NSTO surface, where the former possessed a higher forward current than the latter. In ambient air, the barrier height of Pt/NSTO Schottky junction exhibited periodical variation with cyclic terrace plane and step sites, whereas it became homogeneous in ambient vacuum. We suggested that the oxygen absorption and releasing of surface dangling bonds were the origin for reversible changes in transport properties, which indicates a feasible approach for the surface modulation and band structure tailoring of NSTO based heterojunctions.

  13. Reversible modulation of electric transport properties by oxygen absorption and releasing on Nb:SrTiO3 surface

    NASA Astrophysics Data System (ADS)

    Lu, H. X.; Liu, Y. B.; Chen, Y. S.; Wang, J.; Shen, B. G.; Sun, J. R.

    2014-11-01

    Pt Schottky contacts on (001)-orientated Nb-doped SrTiO3 (NSTO) in both ambient air and vacuum were investigated by the conductive atomic force microscope. The co-existed TiO2 and SrO termination layers were identified on the terrace-structured NSTO surface, where the former possessed a higher forward current than the latter. In ambient air, the barrier height of Pt/NSTO Schottky junction exhibited periodical variation with cyclic terrace plane and step sites, whereas it became homogeneous in ambient vacuum. We suggested that the oxygen absorption and releasing of surface dangling bonds were the origin for reversible changes in transport properties, which indicates a feasible approach for the surface modulation and band structure tailoring of NSTO based heterojunctions.

  14. Ab-initio calculations of the hydrogen-uranium system. Part I: Surface phenomena, absorption, transport and trapping

    SciTech Connect

    Taylor, Christopher D; Lillard, R Scott

    2009-01-01

    Density functional theory was applied to the initial steps of uranium hydriding: surface phenomena, absorption, bulk transport and trapping. H adsorbs exothermically to the (0 0 1) surface, yet H absorption into the bulk is endothermic, with off-center octahedral absorption having the lowest absorption energy of 0.39 eV, relative to molecular H{sub 2}. H absorption in interstitial sites causes a local softening of the bulk modulus. Diffusion of H in unstrained {alpha}-U has a barrier of 0.6 eV. The energy of H absorption adjacent to the chemical impurities C, S, Si was lowered by an amount proportional to the size of the impurity atom, and the resulting lattice strain Si > S > C. Thus, impurities may promote hydriding by providing surfaces or prestrained zones for H uptake.

  15. Transonic unsteady airloads on an energy efficient transport wing with oscillating control surfaces

    NASA Technical Reports Server (NTRS)

    Sandford, M. C.; Ricketts, R. H.; Cazier, F. W., Jr.; Cunningham, H. J.

    1980-01-01

    An aspect ratio 10.8 supercritical wing with oscillating control surfaces is described. The wing is instrumental with 252 static orifices and 164 in situ dynamic pressure transducers for studying the effects of control surface deflection on steady and unsteady pressures at transonic speeds. Results from initial wind tunnel tests conducted in the Langley Transonic Dynamics Tunnel are discussed. Unsteady pressure results are presented for two trailing edge control surfaces oscillating separately at the design Mach number of 0.78. Some experimental results are compared with analytical results obtained by using linear lifting surface theory.

  16. Mass transport of contaminated soil released into surface water by landslides (Göta River, SW Sweden)

    NASA Astrophysics Data System (ADS)

    Göransson, G.; Larson, M.; Bendz, D.; Åkesson, M.

    2012-07-01

    Landslides of contaminated soil into surface water represent an overlooked exposure pathway that has not been addressed properly in existing risk analysis for landslide hazard, contaminated land, or river basin management. A landslide of contaminated soil into surface water implies an instantaneous exposure of the water to the soil, dramatically changing the prerequisites for the mobilisation and transport of pollutants. In this study, an analytical approach is taken to simulate the transport of suspended matter released in connection with landslides into rivers. Different analytical solutions to the advection-dispersion equation (ADE) were tested against the measured data from the shallow rotational, retrogressive landslide in clayey sediments that took place in 1993 on the Göta River, SW Sweden. The landslide encompassed three distinct events, namely an initial submerged slide, followed by a main slide, and a retrogressive slide. These slides generated three distinct and non-Gaussian peaks in the online turbidity recordings at the freshwater intake downstream the slide area. To our knowledge, this registration of the impact on a river of the sediment release from a landslide is one of few of its kind in the world and unique for Sweden. Considering the low frequency of such events, the data from this landslide are highly useful for evaluating how appropriate the ADE is to describe the effects of landslides into surface water. The results yielded realistic predictions of the measured variation in suspended particle matter (SPM) concentration, after proper calibration. For the three individual slides it was estimated that a total of about 0.6% of the total landslide mass went into suspension and was transported downstream. This release corresponds to about 1 to 2% of the annual suspended sediment transport for that river stretch. The studied landslide partly involved an industrial area, and by applying the analytical solution to estimate the transport of metals in

  17. Bacteria transport and deposition under unsaturated conditions: the role of the matrix grain size and the bacteria surface protein.

    PubMed

    Gargiulo, G; Bradford, S; Simůnek, J; Ustohal, P; Vereecken, H; Klumpp, E

    2007-07-17

    Unsaturated (80% water saturated) packed column experiments were conducted to investigate the influence of grain size distribution and bacteria surface macromolecules on bacteria (Rhodococcus rhodochrous) transport and deposition mechanisms. Three sizes of silica sands were used in these transport experiments, and their median grain sizes were 607, 567, and 330 microm. The amount of retained bacteria increased with decreasing sand size, and most of the deposited bacteria were found adjacent to the column inlet. The deposition profiles were not consistent with predictions based on classical filtration theory. The experimental data could be accurately characterized using a mathematical model that accounted for first-order attachment, detachment, and time and depth-dependent straining processes. Visual observations of the bacteria deposition as well as mathematical modelling indicated that straining was the dominant mechanism of deposition in these sands (78-99.6% of the deposited bacteria), which may have been enhanced due to the tendency of this bacterium to form aggregates. An additional unsaturated experiment was conducted to better deduce the role of bacteria surface macromolecules on attachment and straining processes. In this case, the bacteria surface was treated using a proteolitic enzyme. This technique was assessed by examining the Fourier-transform infrared spectrum and hydrophobicity of untreated and enzyme treated cells. Both of these analytical procedures demonstrated that this enzymatic treatment removed the surface proteins and/or associated macromolecules. Transport and modelling studies conducted with the enzyme treated bacteria, revealed a decrease in attachment, but that straining was not significantly affected by this treatment. PMID:17337313

  18. Field evaluation of two risk indicators for predicting likelihood of pesticide transport to surface water from two orchards.

    PubMed

    Oliver, Danielle P; Kookana, Rai S; Anderson, Jenny S; Umali, Beng

    2016-11-15

    Two pesticide risk indicators, Pesticide Impact Rating Index (PIRI) and Environmental Potential Risk Indicator for Pesticides (EPRIP), were used to determine the likelihood of off-site transport to surface water of pesticides used in a cherry (Prunus avium cultivars) and an apple (Malus domestica cultivars) orchard. The predictions of off-site transport of some of the pesticides were verified against actual pesticide concentrations in surface water continuously monitored over two years. To our knowledge, only one other study in the published literature has attempted this. Of the chemicals monitored there was good agreement between the predictions and the field measurements from the apple orchard, but less so for the cherry orchard. In both risk indicators the attenuation factor based on the width of the buffer strip over-estimated the effectiveness of the buffer strip. There was good agreement between the EPRIP and PIRI risk assessment except for ethephon which EPRIP rated a higher risk than PIRI and dithianon which EPRIP rated a lower risk than PIRI. A strong correlation was found between the field observations and the EPRIP predicted environmental concentrations for the majority of cases. This study showed that even simple risk indicators (e.g. PIRI and EPRIP) can be good predictors for a first tier risk assessment of pesticide transport to neighbouring water bodies. PMID:27424118

  19. Liquid freshwater transport and Polar Surface Water characteristics in the East Greenland Current during the AO-02 Oden expedition

    NASA Astrophysics Data System (ADS)

    Nilsson, Johan; Björk, Göran; Rudels, Bert; Winsor, Peter; Torres, Daniel

    2008-07-01

    Dynamical features of the East Greenland Current (EGC) are synthesized from a survey conducted by the Swedish icebreaker Oden during the International Arctic Ocean - 02 expedition (AO-02) in May 2002 with emphasis on the liquid freshwater transport and Polar Surface Water. The data include hydrography and lowered acoustic doppler current profiler (LADCP) velocities in eight transects along the EGC, from the Fram Strait in the north to the Denmark Strait in the south. The survey reveals a strong confinement of the low-salinity polar water in the EGC to the continental slope/shelf-a feature of relevance for the stability of the thermohaline circulation in the Arctic Mediterranean. The southward transport of liquid freshwater in the EGC was found to vary considerably between the sections, ranging between 0.01 and 0.1 Sverdrup. Computations based on geostrophic as well as LADCP velocities give a section-averaged southward freshwater transport of 0.06 Sverdrup in the EGC during May 2002. Furthermore, Oden data suggest that the liquid freshwater transport was as large north of the Fram Strait as it was south of the Denmark Strait.

  20. Models of muco-ciliary transport and tracer dispersion in airway surface liquid

    NASA Astrophysics Data System (ADS)

    Smith, David; Blake, John; Gaffney, Eamonn

    2003-11-01

    The airways of the lungs are protected by a thin layer of mucus ( 5-15 microns) which traps dust and other pathogens. The mucus plaque is secreted by specialised epithelial cells, then transported axially towards the pharynx by the action of a dense mat of beating cilia. The cilia beat in a watery `periciliary liquid' (PCL). According to previous theoretical analysis, axial transport of PCL is relatively small, consistent with an impermeable epithelium. However, tracer dispersion experiments by Matsui et al. (1998) appear to show large axial transport, consistent with a highly permeable epithelium. The resolution of the question of the amount of absorption of PCL is related to the issue of the pathogensis of cystic fibrosis lung disease. We present the results of a new model of mucociliary transport which combines the best features of several very different previous models. We also present a model of tracer dispersion and show how this can be used to interpret the findings of Matsui et al. and relate them to our theoretical results.

  1. Meteorite Infall and Transport in Antarctica: An Analysis of Icefields as Accumulation Surfaces

    NASA Technical Reports Server (NTRS)

    Benoit, P. H.; Sears, D. W. G.

    1997-01-01

    Over 10,000 meteorite fragments have been collected on only a dozen or so small icefields in Antarctica. The terrestrial history of these meteorites is important, both from the perspective of the effects of their ambient environment on the meteorites themselves, and on the information that can be derived in relation to ice flow and ice stability over periods of time up to 1 million years. We discuss the relative importance of meteorite infall, and ice and aeolian transport in creating meteorite accumulations and the importance of ice and aeolian transport and weathering in removing meteorites at various icefields in Antarctica. The present analysis is confined to equibrated ordinary chondrites. We use the natural thermoluminescence (TL) to to examine the effects of weathering. Natural TL is used in combination with size analysis to gauge the effects of aeolian transport. Some icefields, especially the Lewis Cliff Ice Tongue, are dominated by wind-transported fragments, while others, including the Far Western field at Allan Hills, have lost fragments. It appears that most Antarctic icefields preserve meteorite collections on time scales of a few tens of thousands of years.

  2. Stability and transport of graphene oxide nanoparticles in groundwater and surface water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A transport study investigating the effects of natural organic matter (NOM) in the presence of monovalent (KCl) and divalent (CaCl2) salts was performed in a packed bed column. The electrophoretic mobility (EPM) and effective diameter of the graphene oxide nanoparticles (GONPs) were measured as a fu...

  3. Impacts of bridging complexation on the transport of surface-modified nanoparticles in saturated sand

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The transport of polyacrylic acid capped cadmium telluride (CdTe) quantum dots (QDs) and carboxylate-modified latex (CML) nanoparticles (NPs) was studied in packed columns at various electrolyte concentrations and cation types. The breakthrough curves (BTCs) of QDs and CML NPs in acid-treated Accus...

  4. TWO-DIMENSIONAL MODELING OF CURRENT CIRCULATION AND CONTAMINANT TRANSPORT IN SURFACE WATERS

    EPA Science Inventory

    The main objectives of this paper are to briefly describe and evaluate three different applications of two-dimensional, depth-averaged, finite-element models for hydrodynamics (RMA2) and transport (RMA4) ([1] and [2], respectively), which were run using the FastTABS user interfac...

  5. Modeling of nanoparticle transport and deposition in a porous medium: Effects of pore surface heterogeneity

    NASA Astrophysics Data System (ADS)

    Pham, Ngoc; Papavassiliou, Dimitrios

    2014-11-01

    Pore surface charge heterogeneity has been found to affect particle retention in flow through porous media. In this study, retention of nanoparticles under different surface blocking conditions is numerically investigated. Micro-CT scanning is used to reconstruct the 3D geometry of sandstone and image-based analysis is used to characterize the pore space and the mineral composition of the rock. Flow of water through the sample is simulated with the lattice Boltzmann method. The motion of nanoparticles is modeled by injection of particles moving under convection and molecular diffusion and recording their trajectories in time. When interacting with the pore surface, particles can be retained onto the surface with a particular deposition rate. As deposited particles hinder the retention of other particles by blocking occupied sites, the deposition is considered to be a second order process. Particle breakthrough under different modeled and real distributions of surface heterogeneity as a function of various surface blocking conditions is investigated. The effect is stronger when parts of the surface are much more favorable for deposition than others. Acknowledgements: Advanced Energy Consortium (AEC BEG08-022) & XSEDE (CTS090017).

  6. Alpha2B-adrenergic receptor interaction with tubulin controls its transport from the endoplasmic reticulum to the cell surface.

    PubMed

    Duvernay, Matthew T; Wang, Hong; Dong, Chunmin; Guidry, Jesse J; Sackett, Dan L; Wu, Guangyu

    2011-04-22

    It is well recognized that the C terminus (CT) plays a crucial role in modulating G protein-coupled receptor (GPCR) transport from the endoplasmic reticulum (ER) to the cell surface. However the molecular mechanisms that govern CT-dependent ER export remain elusive. To address this issue, we used α(2B)-adrenergic receptor (α(2B)-AR) as a model GPCR to search for proteins interacting with the CT. By using peptide-conjugated affinity matrix combined with proteomics and glutathione S-transferase fusion protein pull-down assays, we identified tubulin directly interacting with the α(2B)-AR CT. The interaction domains were mapped to the acidic CT of tubulin and the basic Arg residues in the α(2B)-AR CT, particularly Arg-437, Arg-441, and Arg-446. More importantly, mutation of these Arg residues to disrupt tubulin interaction markedly inhibited α(2B)-AR transport to the cell surface and strongly arrested the receptor in the ER. These data provide the first evidence indicating that the α(2B)-AR C-terminal Arg cluster mediates its association with tubulin to coordinate its ER-to-cell surface traffic and suggest a novel mechanism of GPCR export through physical contact with microtubules. PMID:21357695

  7. Section 1. Simulation of surface-water integrated flow and transport in two-dimensions: SWIFT2D user's manual

    USGS Publications Warehouse

    Schaffranek, Raymond W.

    2004-01-01

    A numerical model for simulation of surface-water integrated flow and transport in two (horizontal-space) dimensions is documented. The model solves vertically integrated forms of the equations of mass and momentum conservation and solute transport equations for heat, salt, and constituent fluxes. An equation of state for salt balance directly couples solution of the hydrodynamic and transport equations to account for the horizontal density gradient effects of salt concentrations on flow. The model can be used to simulate the hydrodynamics, transport, and water quality of well-mixed bodies of water, such as estuaries, coastal seas, harbors, lakes, rivers, and inland waterways. The finite-difference model can be applied to geographical areas bounded by any combination of closed land or open water boundaries. The simulation program accounts for sources of internal discharges (such as tributary rivers or hydraulic outfalls), tidal flats, islands, dams, and movable flow barriers or sluices. Water-quality computations can treat reactive and (or) conservative constituents simultaneously. Input requirements include bathymetric and topographic data defining land-surface elevations, time-varying water level or flow conditions at open boundaries, and hydraulic coefficients. Optional input includes the geometry of hydraulic barriers and constituent concentrations at open boundaries. Time-dependent water level, flow, and constituent-concentration data are required for model calibration and verification. Model output consists of printed reports and digital files of numerical results in forms suitable for postprocessing by graphical software programs and (or) scientific visualization packages. The model is compatible with most mainframe, workstation, mini- and micro-computer operating systems and FORTRAN compilers. This report defines the mathematical formulation and computational features of the model, explains the solution technique and related model constraints, describes the

  8. Hydrogen transport through oxide metal surface under atom and ion irradiation

    NASA Astrophysics Data System (ADS)

    Begrambekov, L.; Dvoychenkova, O.; Evsin, A.; Kaplevsky, A.; Sadovskiy, Ya; Schitov, N.; Vergasov, S.; Yurkov, D.

    2014-11-01

    Both the latest and earlier achieved results on gas exchange processes on metal surfaces (including stainless steel, titanium, zirconium, tungsten with deposited aluminum oxide coating) under hydrogen atom or plasma irradiation with occasional oxygen impurity are presented in the paper. Mechanisms and regularities of these processes are discussed. It is demonstrated that surface oxide layer properties as a diffusion barrier strongly depend on external influence on the surface. In particular, it is revealed that low energy hydrogen ion irradiation could slow down hydrogen desorption from metals. Hydrogen atom or ion irradiation combined with simultaneous oxygen admixture accelerates hydrogen desorption from metals.

  9. Impacts of long-range transport and local emissions on California near-surface ozone and sulfur oxides during the ARCTAS period--A multi-scale modeling study

    NASA Astrophysics Data System (ADS)

    Huang, M.; Carmichael, G. R.; Spak, S.; Adhikary, B.; Kulkarni, S.; Cheng, Y.; Wei, C.; Tang, Y.; Parrish, D. D.; Oltmans, S. J.; D'Allura, A.; Wennberg, P. O.; Huey, L. G.; Dibb, J. E.; Jimenez, J. L.; Weinheimer, A. J.; Kaduwela, A.; Cai, C.; Wong, M.; Pierce, R.; Al-Saadi, J. A.; Streets, D. G.; Zhang, Q.

    2010-12-01

    Chronic ozone (O3) problems over California (CA) and other states at the U. S. west coast are affected by both long-range transport and local emissions. Multi-scale tracer and full-chemistry simulations with the STEM atmospheric chemistry model are used to analyze the effects of the long-range transported background from the eastern Pacific as well as the contribution of local emission sources on CA near-surface O3 levels during the ARCTAS experiment conducted in 2008. The coastal O3 vertical structures and coastal-inland transport patterns and are compared during spring (April) and summer (June-July) times by using correlation and trajectory studies. The sensitivity of model-predicted O3 to lateral boundary conditions (LBC) during summertime transport events is shown high and model predictions can be improved by using real-time global LBC that assimilated satellite observations and the NASA DC-8 flight observations. To discuss climate impacts on the long-range and coastal-inland transport patterns, we discuss sensitivity simulations by only replacing the meteorological fields and average LBCs respectively with situations in a 2002 case when the sea surface temperature (SST) anomaly differed from the ARCTAS periods. Biogenic, wildfire and maritime emissions to CA near-surface O3 levels are quantified by sensitivity simulations. Results vary in different model configurations but generally CA biogenic and fire emissions contribute 3-4 ppb to near-surface O3 over the South Coast (SC), with larger contribution to the Central Valley (up to ~12-15 ppb). Maritime emissions modify the NOx-VOC limitations and increase the mean flight-time (up to 3 ppb) and daily maximum O3 (up to 7-9 ppb) over the SC where one third of the cargo containers to the U. S. arrive. The contributions of transport and local emissions on California’s increasing sulfur oxides (SOx=SO2+SO4) ambient concentrations are also discussed. During the ARCTAS-CARB period the enhanced near-surface SOx levels

  10. Mass transport of contaminated soil released into surface water by landslides (Göta River, SW Sweden)

    NASA Astrophysics Data System (ADS)

    Göransson, G.; Larson, M.; Bendz, D.; Åkesson, M.

    2011-12-01

    Landslides of contaminated soil into surface water represent an overlooked exposure pathway that has not been addressed properly in existing risk analysis for landslide hazard, contaminated land, or river basin management. A landslide of contaminated soil into surface water implies an instantaneous exposure of the water to the contaminated soil, dramatically changing the prerequisites for the mobilisation and transport of pollutants. In this study, an analytical approach is taken to simulate the transport of suspended matter released in connection with landslides into rivers. Different analytical solutions to the advection-dispersion equation (ADE) were tested against the measured data from the shallow rotational, retrogressive landslide in clayey sediments that took place in 1993 on the Göta River, SW Sweden. The landslide encompassed three distinct events, namely an initial submerged slide, followed by a main slide, and a retrogressive slide. These slides generated three distinct and non-Gaussian peaks in the online turbidity recordings at the freshwater intake downstream the slide area. To our knowledge, this registration of the impact in a river of the sediment release from a landslide is one of the few of its kind in the world, and unique for Sweden considering the low frequency of landslide events, making it highly useful for evaluating how appropriate the ADE is to describe a landslide into surface water. The results yielded realistic predictions of the measured concentration variation, after proper calibration. For the three individual slides it was estimated that a total of about 0.6% (515 000 kg) of the total landslide mass went into suspension/was suspended and was transported downstream. This release corresponds to about 1 to 2% of the annual suspended sediment delivery for that river stretch. The studied landslide partly involved an industrial area and by applying the analytical solution for the transport of metals in the sediments it was found that

  11. Inefficient assembly limits transport and cell surface expression of HLA-Cw4 molecules in C1R.

    PubMed

    Zemmour, J

    1996-12-01

    HLA-C antigens are expressed to the cell surface at roughly 10% the level of HLA-B or -A, and their serological definition remains persistently difficult. To characterize the factors limiting surface expression, the processes of assembly and intracellular transport of HLA-Cw4 molecules were investigated in the C1R cell line. When appropriate peptides were added to cultured cells or in cell lysates significant amounts of conformed HLA-C molecules that associate with beta 2-microglobulin (beta 2 m) are detected, but are indeed not sufficient to restore expression to the level observed for HLA-A or -B molecules. Furthermore, a precursor/product relationship exists between the free class I heavy chain and the mature conformation of HLA-Cw4 molecules. Thus, HLA-C assembly promotes the conversion of HC-10-reactive molecules (weakly-beta 2m-associated non-ligand associated free HC form) into the beta 2m-associated class I molecules recognized by W6/32. To further investigate the factors that regulate cell surface expression, intracellular transport of HLA-Cw4 was studied in pulse chase analysis. In contrast to some HLA-A and B, maturation of HLA-Cw4 heavy chains and their export to the medial and trans-Golgi compartments are quite inefficient. After 4 h of chase period, roughly half of the pulse-labeled HLA-Cw4 molecules have transited to the medial-Golgi and acquired complex oligosaccharides characteristic of mature form. In addition, treatment with gamma-interferon does not appear to improve maturation of HLA-Cw4 heavy chains, suggesting that increased supply of peptides does not influence intracellular transport. Moreover, only a small fraction in the pool of HLA-Cw4 molecules was subsequently transported through the trans-Golgi network, as indicated by their acquisition of sialic acids. Taken together these studies show that HLA-Cw4 molecules are inefficiently transported through the Golgi apparatus and presumably retained in the endoplasmic reticulum or cis

  12. Direct observation of ultrafast surface transport of laser-driven fast electrons in a solid target

    NASA Astrophysics Data System (ADS)

    Singh, Prashant Kumar; Cui, Y. Q.; Chatterjee, Gourab; Adak, Amitava; Wang, W. M.; Ahmed, Saima; Lad, Amit D.; Sheng, Z. M.; Ravindra Kumar, G.

    2013-11-01

    We demonstrate rapid spread of surface ionization on a glass target excited by an intense, ultrashort laser pulse at an intensity of 3 × 1017 W cm-2. Time- and space-resolved reflectivity of the target surface indicates that the initial plasma region created by the pump pulse expands at c/7. The measured quasi-static megagauss magnetic field is found to expand in a manner very similar to that of surface ionization. Two-dimensional particle-in-cell simulations reproduce measurements of surface ionization and magnetic fields. Both the experiment and simulation convincingly demonstrate the role of self-induced electric and magnetic fields in confining fast electrons along the target-vacuum interface.

  13. Direct observation of ultrafast surface transport of laser-driven fast electrons in a solid target

    SciTech Connect

    Singh, Prashant Kumar; Chatterjee, Gourab; Adak, Amitava; Ahmed, Saima; Lad, Amit D.; Ravindra Kumar, G.; Cui, Y. Q.; Wang, W. M.; Sheng, Z. M.

    2013-11-15

    We demonstrate rapid spread of surface ionization on a glass target excited by an intense, ultrashort laser pulse at an intensity of 3 × 10{sup 17} W cm{sup −2}. Time- and space-resolved reflectivity of the target surface indicates that the initial plasma region created by the pump pulse expands at c/7. The measured quasi-static megagauss magnetic field is found to expand in a manner very similar to that of surface ionization. Two-dimensional particle-in-cell simulations reproduce measurements of surface ionization and magnetic fields. Both the experiment and simulation convincingly demonstrate the role of self-induced electric and magnetic fields in confining fast electrons along the target-vacuum interface.

  14. New York State high-speed surface transportation study. Executive summary

    SciTech Connect

    1994-08-01

    In 1990, New York State Governor Mario M. Cuomo created an interagency task force under the leadership of Lt. Governor Stan Lundine to investigate the potential of high speed ground transportation (HSGT) systems. the study`s objective was to assess potential rights-of-way, ridership, energy and environmental impacts, economic benefits, capital, operating, and maintenance costs, and financial viability of HSFT systems. The study builds upon and supplements previous and on-going HSGT activities conducted by the members of the interagency task force. These activities include: Maglev Technical and Economic Feasibility Study (NYSERDA); Maglev Demonstration Site Investigation (NYSTA); and New York/Massachusetts High Speed Ground Transportation Study (NYSDOT). The study is intended to verify and refine previous information and analyses and provide supplemental information and insights to be used in determining if additional investigation and activities involving HSGT are desirable for New York State.

  15. A propagating ATPase gradient drives transport of surface-confined cellular cargo

    NASA Astrophysics Data System (ADS)

    Vecchiarelli, Anthony; Neuman, Keir; Mizuuchi, Kiyoshi

    2014-03-01

    The process of DNA segregation is of central importance for all organisms. Although eukaryotic mitosis is relatively well established, the most common mechanism employed for bacterial DNA segregation has been unclear. ParA ATPases form dynamic patterns on the bacterial nucleoid, to spatially organize plasmids, chromosomes and other large cellular cargo, but the force generating mechanism has been a source of controversy and debate. A dominant view proposes that ParA-mediated transport and cargo positioning occurs via a filament-based mechanism that resembles eukaryotic mitosis. Here we present direct evidence against such models. Our cell-free reconstitution supports a non-filament-based mode of transport that may be as widely found in nature as actin filaments and microtubules.

  16. Transport and dispersion of pollutants in surface impoundments: a finite difference model

    SciTech Connect

    Yeh, G.T.

    1980-07-01

    A surface impoundment model by finite-difference (SIMFD) has been developed. SIMFD computes the flow rate, velocity field, and the concentration distribution of pollutants in surface impoundments with any number of islands located within the region of interest. Theoretical derivations and numerical algorithm are described in detail. Instructions for the application of SIMFD and listings of the FORTRAN IV source program are provided. Two sample problems are given to illustrate the application and validity of the model.

  17. Surface Roughness Effects on Fluid Transport Through a Natural Rock Fracture

    SciTech Connect

    Crandall, D.M.; Ahmadi, Goodarz; Smith, D.H.

    2008-04-01

    Fluid flow through rock fractures can be orders of magnitude faster than through the adjacent low-permeability rock. Understanding how fluid moves through these pathways is important for the prediction of sequestered CO2 transport in geologic reservoirs. Reservoir-scale, discrete-fracture simulators use simplified models of flow through fractures to determine transport properties in complex fracture networks. A high level of approximation is required in these reservoir-scale simulations due to the number of fractures within the domain of interest and because of the limited amount of information that can be obtained from geophysical well-logs (Long et al. (1996)). For this study, flow simulations through a CT-scanned fracture were performed to evaluate different fluid transport parameters that are important in geological flow analysis. The ‘roughness’ of the fracture was varied to determine the effect of the bumpy fracture walls on the fluid flow. The permeability and effective aperture were determined for flow under a constant pressure head. The fracture roughness is shown to dramatically reduce the flow through the fracture, and various relations are described.

  18. Transport and transformation of pharmaceuticals and other contaminants of emerging concern from wastewater discharge through surface water to drinking water intake and treatment

    EPA Science Inventory

    The ubiquitous presence of pharmaceuticals, hormones, and other contaminants of emerging concern (CECs) in surface-water resources have necessitated research that better elucidates pathways of transport and transformation for these compounds from their discharged wastewater, thro...

  19. Preparation of a hole transport layer tethered to ITO surface via a self-assembled monolayer with reactive terminal group

    NASA Astrophysics Data System (ADS)

    Hagihara, Yuya; Kim, Seong-Ho; Tanaka, Kuniaki; Advincula, Rigoberto C.; Usui, Hiroaki

    2014-01-01

    Characteristics of a junction between a polymer thin film and an indium-tin oxide (ITO) substrate was controlled by forming covalent chemical bonds at the interface through self-assembled monolayers (SAMs) with reactive terminal groups. For this purpose, SAMs with vinyl, epoxide, and benzophenone terminal groups were formed on ITO substrates, on which a vinyl derivative of a hole transport molecule was vapor-deposited, and then annealed in vacuum. This procedure produced a polymer layer strongly attached to the substrate surface. It was also found that the charge injection from the ITO electrode to the polymer layer can be improved by chemically tethering the interface via the SAMs.

  20. Surface harmonics method for two-dimensional time-dependent neutron transport problems of square-lattice nuclear reactors

    SciTech Connect

    Boyarinov, V. F.; Kondrushin, A. E.; Fomichenko, P. A.

    2013-07-01

    Time-dependent equations of the Surface Harmonics Method (SHM) have been derived from the time-dependent neutron transport equation with explicit representation of delayed neutrons for solving the two-dimensional time-dependent problems. These equations have been realized in the SUHAM-TD code. The TWIGL benchmark problem has been used for verification of the SUHAM-TD code. The results of the study showed that computational costs required to achieve necessary accuracy of the solution can be an order of magnitude less than with the use of the conventional finite difference method (FDM). (authors)

  1. Free-flight wind-tunnel investigation of a four-engine sweptwing upper-surface blown transport configuration

    NASA Technical Reports Server (NTRS)

    Parlett, L. P.

    1977-01-01

    The dynamic stability and control characteristics of a four-engine turbofan transport model having an upper-surface blown jet flap were investigated by means of the free-flight technique in the Langley full-scale tunnel. The flight characteristics of the model were investigated through a range of lift coefficients from 3 to 8 with all four engines operating and with one outboard engine not operating. Static characteristics were investigated by conventional power-on force tests over the flight-test angle-of-attack range and through the stall.

  2. Free-flight wind tunnel investigation of a four-engine sweptwing upper-surface blown transport configuration

    NASA Technical Reports Server (NTRS)

    Parlett, L. P.

    1974-01-01

    The dynamic stability characteristics of a four-engine turbofan transport model having an upper-surface blown-jet flap have been investigated by means of the free-flight technique in the Langley full-scale tunnel. The flight characteristics of the model were investigated through a range of lift coefficients from 3 to 8 with all four engines operating and with one outboard engine not operating. Static characteristics were investigated by conventional power-on force tests over the flight-test angle-of-attack range and through the stall.

  3. Impact of air pollutants from surface transport sources on human health: A modeling and epidemiological approach.

    PubMed

    Aggarwal, Preeti; Jain, Suresh

    2015-10-01

    This study adopted an integrated 'source-to-receptor' assessment paradigm in order to determine the effects of emissions from passenger transport on urban air quality and human health in the megacity, Delhi. The emission modeling was carried out for the base year 2007 and three alternate (ALT) policy scenarios along with a business as usual (BAU) scenario for the year 2021. An Activity-Structure-Emission Factor (ASF) framework was adapted for emission modeling, followed by a grid-wise air quality assessment using AERMOD and a health impact assessment using an epidemiological approach. It was observed that a 2021-ALT-III scenario resulted in a maximum concentration reduction of ~24%, ~42% and ~58% for carbon monoxide (CO), nitrogen dioxide (NO2) and particulate matter (PM), respectively, compared to a 2021-BAU scenario. Further, it results in significant reductions in respiratory and cardiovascular mortality, morbidity and Disability Adjusted Life Years (DALY) by 41% and 58% on exposure to PM2.5 and NO2 concentrations when compared to the 2021-BAU scenario, respectively. In other words, a mix of proposed policy interventions namely the full-phased introduction of the Integrated Mass Transit System, fixed bus speed, stringent vehicle emission norms and a hike in parking fees for private vehicles would help in strengthening the capability of passenger transport to cater to a growing transport demand with a minimum health burden in the Delhi region. Further, the study estimated that the transport of goods would be responsible for ~5.5% additional VKT in the 2021-BAU scenario; however, it will contribute ~49% and ~55% additional NO2 and PM2.5 concentrations, respectively, in the Delhi region. Implementation of diesel particulate filters for goods vehicles in the 2021-ALT-IV-O scenario would help in the reduction of ~87% of PM2.5 concentration, compared to the 2021-BAU scenario; translating into a gain of 1267 and 505 DALY per million people from exposure to PM2.5 and NO

  4. Quantum transport equation for systems with rough surfaces and its application to ultracold neutrons in a quantizing gravity field

    SciTech Connect

    Escobar, M.; Meyerovich, A. E.

    2014-12-15

    We discuss transport of particles along random rough surfaces in quantum size effect conditions. As an intriguing application, we analyze gravitationally quantized ultracold neutrons in rough waveguides in conjunction with GRANIT experiments (ILL, Grenoble). We present a theoretical description of these experiments in the biased diffusion approximation for neutron mirrors with both one- and two-dimensional (1D and 2D) roughness. All system parameters collapse into a single constant which determines the depletion times for the gravitational quantum states and the exit neutron count. This constant is determined by a complicated integral of the correlation function (CF) of surface roughness. The reliable identification of this CF is always hindered by the presence of long fluctuation-driven correlation tails in finite-size samples. We report numerical experiments relevant for the identification of roughness of a new GRANIT waveguide and make predictions for ongoing experiments. We also propose a radically new design for the rough waveguide.

  5. Reappraisal of the mucosal epithelial space associated with the surface of Hymenolepis diminuta and its effect on transport parameters.

    PubMed

    Murphy, W A; Lumsden, R D

    1984-08-01

    Using nonpermeating, radiolabeled solutes to estimate the magnitude of the "unstirred water layer" (="mucosal epithelial space") of the surface of Hymenolepis diminuta, a value approximating 1% of the worm's fluid volume (0.011-0.022 ml/g wet tissue) was obtained. This value was compared with those previously reported by other workers which were greater by an order of magnitude. The difference between these results appears to be related to the use in previous studies of a permeating marker (mannitol), and a failure to divest the surface of nonspecifically adherent bathing fluid in excess of the actual "unstirred layer". These parameters must be considered in future studies on this useful model for the study of transport. PMID:6438294

  6. COMSOL Modeling of Transport of Neutral Radicals to Substrate Surfaces Located Downstream from an Atmospheric Pressure Weakly Ionized Plasma Reactor

    NASA Astrophysics Data System (ADS)

    Islam, Rokibul; Lekobou, William; Wemlinger, Erik; Pedrow, Patrick

    2012-10-01

    An Atmospheric Pressure Weakly Ionized Plasma (APWIP) Reactor generates a significant number of charged particles and neutral radicals. In our work the carrier gas is argon and the precursor molecule is acetylene. The APWIP is generated by corona discharges associated with an array of high voltage metal needles facing a grounded metal screen. Neutral radical transport downstream from the grounded screen to the substrate via diffusion and convection will be modeled with COMSOL, a finite element software package. Substrates will include objects with various shapes and characteristic dimensions that range from nanometers to centimeters. After the model is validated against canonical problems with known solutions, thin film deposition rates will be compared with experimentally measured results. Substrate geometries will include discs, spheres, fibers and highly porous surfaces such as those found on asphalt road surfaces. A single generic neutral radical will be used to represent the entire family of neutral radicals resulting from acetylene bond scission by free electron impact.

  7. Quantum transport equation for systems with rough surfaces and its application to ultracold neutrons in a quantizing gravity field

    NASA Astrophysics Data System (ADS)

    Escobar, M.; Meyerovich, A. E.

    2014-12-01

    We discuss transport of particles along random rough surfaces in quantum size effect conditions. As an intriguing application, we analyze gravitationally quantized ultracold neutrons in rough waveguides in conjunction with GRANIT experiments (ILL, Grenoble). We present a theoretical description of these experiments in the biased diffusion approximation for neutron mirrors with both one- and two-dimensional (1D and 2D) roughness. All system parameters collapse into a single constant which determines the depletion times for the gravitational quantum states and the exit neutron count. This constant is determined by a complicated integral of the correlation function (CF) of surface roughness. The reliable identification of this CF is always hindered by the presence of long fluctuation-driven correlation tails in finite-size samples. We report numerical experiments relevant for the identification of roughness of a new GRANIT waveguide and make predictions for ongoing experiments. We also propose a radically new design for the rough waveguide.

  8. The Helium Field Effect Transistor (II): Gated Transport of Surface-State Electrons Through Micro-constrictions

    NASA Astrophysics Data System (ADS)

    Shaban, F.; Ashari, M.; Lorenz, T.; Rau, R.; Scheer, E.; Kono, K.; Rees, D. G.; Leiderer, P.

    2016-06-01

    We present transport measurements of surface-state electrons on liquid helium films in confined geometry. The measurements are taken using split-gate devices similar to a field effect transistor. The number of electrons passing between the source and drain areas of the device can be precisely controlled by changing the length of the voltage pulse applied to the gate electrode. We find evidence that the effective driving potential depends on electron-electron interactions, as well as the electric field applied to the substrate. Our measurements indicate that the mobility of electrons on helium films can be high and that microfabricated transistor devices allow electron manipulation on length scales close to the interelectron separation. Our experiment is an important step toward investigations of surface-state electron properties at much higher densities, for which the quantum melting of the system to a degenerate Fermi gas should be observed.

  9. Effect of low-concentration rhamnolipid on transport of Pseudomonas aeruginosa ATCC 9027 in an ideal porous medium with hydrophilic or hydrophobic surfaces.

    PubMed

    Zhong, Hua; Liu, Guansheng; Jiang, Yongbing; Brusseau, Mark L; Liu, Zhifeng; Liu, Yang; Zeng, Guangming

    2016-03-01

    The success of effective bioaugmentation processes for remediation of soil and groundwater contamination requires effective transport of the injected microorganisms in the subsurface environment. In this study, the effect of low concentrations of monorhamnolipid biosurfactant solutions on transport of Pseudomonas aeruginosa in an ideal porous medium (glass beads) with hydrophilic or hydrophobic surfaces was investigated by conducting miscible-displacement experiments. Transport behavior was examined for both glucose-grown and hexadecane-grown cells, with low and high surface hydrophobicity, respectively. A clean-bed colloid deposition model was used for determination of deposition rate coefficients. Results show that cells with high surface hydrophobicity exhibit greater retention than cells with low surface hydrophobicity. Rhamnolipid affects cell transport primarily by changing cell surface hydrophobicity, with an additional minor effect by increasing solution ionic strength. There is a good linear relation between k and rhamnolipid-regulated cell surface hydrophobicity presented as bacterial-adhesion-to-hydrocarbon (BATH) rate of cells (R(2)=0.71). The results of this study show the importance of hydrophobic interaction for transport of bacterial cells in silica-based porous media, and the potential of using low-concentration rhamnolipid solutions for facilitating bacterial transport in bioaugmentation efforts. PMID:26722821

  10. Long-range Transport of Asian Dust Storms: A Satellite/Surface Perspective on Societal and Scientific Influence

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Among the many components contributing to air pollution, airborne mineral dust plays an important role due to its biogeochemical impact on the ecosystem and its radiative forcing effect on the weather/climate system. As much as one-third to half of the global dust emissions, estimated about 800 Tg, are introduced annually into Earth's atmosphere from various deserts in China. Asian dust storm outbreaks are believed to have persisted for hundreds and thousands years over the vast territory of north and northwest China, but not until recent decades that many studies reveal the compelling evidence in recognizing the importance of these eolian dust particles for forming Chinese Loess Plateau and for biogeochemical cycling in the North Pacific Ocean to as far as in the Greenland ice-sheets through long-range transport. The Asian dust and air pollution aerosols can be detected by its colored appearance on current Earth observing satellites and its evolution monitored by satellite and surface network. In this paper, we will demonstrate the capability of a new satellite algorithm, called Deep Blue, to retrieve aerosol properties, particularly but not limited to, over bright-reflecting surfaces such as urban areas and deserts. Recently, many field campaigns were designed and executed to study the compelling variability in spatial and temporal scale of both pollution-derived and naturally occurring aerosols, which often exist in high concentrations over eastern Asia and along the rim of the western Pacific. We will provide an overview of the outbreak of Asian dust storms, near source/sink and their evolution along transport pathway, from space and surface observations. The climatic effects and societal impacts of the Asian dusts will be addressed in depth. (to be presented in the International Workshop on Semi-Arid Land Surface-

  11. 49 CFR 1016.309 - Agency review.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 8 2011-10-01 2011-10-01 false Agency review. 1016.309 Section 1016.309... Agency review. In the event the adjudicative officer is not the entire Board, the applicant or agency counsel may seek review of the initial decision on the fee application, or the Board may review...

  12. 49 CFR 1016.309 - Agency review.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 8 2010-10-01 2010-10-01 false Agency review. 1016.309 Section 1016.309... Agency review. In the event the adjudicative officer is not the entire Board, the applicant or agency counsel may seek review of the initial decision on the fee application, or the Board may review...

  13. 49 CFR 1016.309 - Agency review.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 8 2014-10-01 2014-10-01 false Agency review. 1016.309 Section 1016.309... Agency review. In the event the adjudicative officer is not the entire Board, the applicant or agency counsel may seek review of the initial decision on the fee application, or the Board may review...

  14. 48 CFR 19.1004 - Participating agencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    .... The Department of Transportation. The Department of Veterans Affairs. The Environmental Protection... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Participating agencies. 19... Participating agencies. The following agencies have been identified as participants in the demonstration...

  15. Soil surface searching and transport of Euphorbia characias seeds by ants

    NASA Astrophysics Data System (ADS)

    Espadaler, Xavier; Gómez, Crisanto

    The intensity of exploring the soil surface by ants was studied for the four species involved in the dispersal and predation of seeds of the West-Mediterranean myrmecochorous plant Euphorbia characias. During the dehiscence period (June) the whole soil surface is sccanned in 43 minutes. Not all ants that find a seed take it to the nest. For the four ant species studied ( Pheidole pallidula, Aphaenogaster senilis, Tapinoma nigerrimum, Messor barbarus) the proportion of ants that finally take the seed is 67.6%. In spite of this, the high level of soil surface searching explains the rather short time that seeds remain on the soil before being removed. The presence of an elaiosome is a key element in the outcome of the ant-seed interaction: a seed with elaiosome has a seven-fold increase in probability of being taken to the nest if found by a non-granivorous ant. The predator-avoidance hypothesis for myrmecochory is supported.

  16. 14 CFR 296.5 - Agency relationships.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Agency relationships. 296.5 Section 296.5 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS INDIRECT AIR TRANSPORTATION OF PROPERTY General § 296.5 Agency relationships. An indirect...

  17. 14 CFR 296.5 - Agency relationships.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Agency relationships. 296.5 Section 296.5 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS INDIRECT AIR TRANSPORTATION OF PROPERTY General § 296.5 Agency relationships. An indirect...

  18. The Effect of Diffusional Transport and Surface Catalysis on the Aerothermodynamic Heating for Martian Atmospheric Entry

    NASA Technical Reports Server (NTRS)

    Henline, William D.; Papadopoulos, Periklis; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    For the reentry heating of 70-degree blunt sphere-cones entering Mars at velocities in excess of 6 km/sec, a study was performed to determine the magnitude of both convective and catalytic heating on the cone forebody. Case studies of the peak heating conditions for the current NASA Mars Pathfinder entry probe, as well as the peak heating conditions of the proposed NASA Mars 2001 aerobraking orbiter mission were performed. Since the actual behavior of the chemical recombination of Mars atmosphere hypersonic shock layer species on heat shield materials is not known, and no experimental studies of any consequence have been done to determine surface reaction rates for the CO2 system, a parametric analysis of various reaction schemes and surface catalytic mechanistic models was performed. In many cases the actual Mars entry probe will have a heat shield composed of an ablative material which can either partially or completely preclude the existence of catalytic surface recombination phenomena. The extent of this blockage effect has not been examined at this time and is not considered in this effort. Instead only non-ablative computations are performed to separately evaluate the full extent of the surface catalysis and related diffusional phenomena. Parametric studies include peak heating point comparisons of non-catalytic, partially catalytic and fully catalytic total surface heat transfer for three difference surface recombination catalytic mechanisms (with and without simultaneous CO + O and O + O recombination) as well as with different species diffusion models. Diffusion model studies include constant Schmidt number (equal diffusivities) and the bifurcation, approximate multi-component diffusion model. Since the gas phase reaction kinetics for the Mars CO2 based atmosphere have also not been validated, the effect of two different (fast and slow) sets of gas kinetics on heat transfer is presented.

  19. Efficient coupling and transport of a surface plasmon at 780 nm in a gold nanostructure

    NASA Astrophysics Data System (ADS)

    Gong, Yu; Joly, Alan G.; El-Khoury, Patrick Z.; Hess, Wayne P.

    2015-08-01

    We study plasmonic nanostructures in single-crystal gold with scanning electron and femtosecond photoemission electron microscopies. We design an integrated laser coupling and nanowire waveguide structure by focused ion beam lithography in single-crystal gold flakes. The photoemission results show that the laser field is efficiently coupled into a propagating surface plasmon by a simple hole structure and propagates efficiently in an adjacent nano-bar waveguide. A strong local field is created by the propagating surface plasmon at the nano-bar tip. A similar structure, with a decreased waveguide width and thickness, displayed significantly more intense photoemission indicating enhanced local electric field at the sharper tip.

  20. Efficient Coupling and Transport of a Surface Plasmon at 780 nm in a Gold Nanostructure

    SciTech Connect

    Gong, Yu; Joly, Alan G.; El-Khoury, Patrick Z.; Hess, Wayne P.

    2015-08-28

    We studied plasmonic nanostructures in single-crystal gold with scanning electron and femtosecond photoemission electron microscopies. We designed an integrated laser coupling and nanowire waveguide structure by focused ion beam lithography in single-crystal gold flakes. The photoemission results show that the laser field is efficiently coupled into a propagating surface plasmon by a simple hole structure and propagates efficiently in an adjacent nano-bar waveguide. A strong local field is created by the propagating surface plasmon at the nano-bar tip. A similar structure, with a decreased waveguide width and thickness, displayed significantly more intense photoemission indicating enhanced local electric field at the sharper tip.