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1

Nuclear dependencies of azimuthal asymmetries in the Drell-Yan process  

NASA Astrophysics Data System (ADS)

We study nuclear dependencies of azimuthal asymmetries in the Drell-Yan lepton pair production in nucleon-nucleus collisions with polarized nucleons. We use the "maximal two-gluon correlation approximation," so that we can relate the transverse-momentum-dependent quark distribution in a nucleus to that in a nucleon by a convolution with a Gaussian broadening. We use the Gaussian ansatz for the transverse momentum dependence of such quark distribution functions and obtain the numerical results for the nuclear dependencies. These results show that the qT-integrated azimuthal asymmetries are suppressed.

Chen, Long; Gao, Jian-hua; Liang, Zuo-tang

2014-03-01

2

Nuclear dependence of azimuthal asymmetry in semi-inclusive deep inelastic scattering  

SciTech Connect

Within the framework of a generalized factorization, semi-inclusive deeply inelastic scattering (SIDIS) cross sections can be expressed as a series of products of collinear hard parts and transverse-momentum-dependent (TMD) parton distributions and correlations. The azimuthal asymmetry of unpolarized SIDIS in the small transverse-momentum region will depend on both twist-2 and -3 TMD quark distributions in target nucleons or nuclei. Nuclear broadening of these twist-2 and -3 quark distributions due to final-state multiple scattering in nuclei is investigated and the nuclear dependence of the azimuthal asymmetry is studied. It is shown that the azimuthal asymmetry is suppressed by multiple parton scattering and the transverse-momentum dependence of the suppression depends on the relative shape of the twist-2 and -3 quark distributions in the nucleon. A Gaussian ansatz for TMD twist-2 and -3 quark distributions in nucleon is used to demonstrate the nuclear dependence of the azimuthal asymmetry and to estimate the smearing effect due to fragmentation.

Gao Jianhua [School of Physics, Shandong University, Jinan, Shandong 250100 (China); Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Nuclear Science Division, MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Liang Zuotang [School of Physics, Shandong University, Jinan, Shandong 250100 (China); Wang Xinnian [Nuclear Science Division, MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2010-06-15

3

Nuclear dependence of azimuthal asymmetry in semi-inclusive deep inelastic scattering  

NASA Astrophysics Data System (ADS)

Within the framework of a generalized factorization, semi-inclusive deeply inelastic scattering (SIDIS) cross sections can be expressed as a series of products of collinear hard parts and transverse-momentum-dependent (TMD) parton distributions and correlations. The azimuthal asymmetry of unpolarized SIDIS in the small transverse-momentum region will depend on both twist-2 and -3 TMD quark distributions in target nucleons or nuclei. Nuclear broadening of these twist-2 and -3 quark distributions due to final-state multiple scattering in nuclei is investigated and the nuclear dependence of the azimuthal asymmetry is studied. It is shown that the azimuthal asymmetry is suppressed by multiple parton scattering and the transverse-momentum dependence of the suppression depends on the relative shape of the twist-2 and -3 quark distributions in the nucleon. A Gaussian ansatz for TMD twist-2 and -3 quark distributions in nucleon is used to demonstrate the nuclear dependence of the azimuthal asymmetry and to estimate the smearing effect due to fragmentation.

Gao, Jian-Hua; Liang, Zuo-Tang; Wang, Xin-Nian

2010-06-01

4

Flavor dependent azimuthal asymmetries in unpolarized semi-inclusive DIS at HERMES  

NASA Astrophysics Data System (ADS)

The azimuthal cos? h and cos2? h modulations of the distribution of hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of electrons and positrons off hydrogen and deuterium targets have been measured in the hermes experiment. For the first time these modulations were determined in a 4-Dimensional kinematic space for positively and negatively charged pions and kaons separately, as well as for unidentified hadrons. These azimuthal dependences are sensitive to the transverse motion and polarization of the quarks within the nucleon via, e.g., the Cahn, Boer-Mulders and Collins effects.

Giordano, F.

2014-01-01

5

Azimuthal dependence of forward-jet production in DIS in the high-energy limit  

Microsoft Academic Search

As a signal for the BFKL Pomeron in small-x deep inelastic $ep$ scattering, we calculate the azimuthal dependence of the inclusive cross section of forward jets relative to the outgoing electron. For not very large differences in rapidity between the current jet and the forward jet the cross section peaks at $\\\\pi\\/2$. For increasing rapidity BFKL dynamics predicts a decorrelation

Jochen Bartels; Vittorio Del Duca; Mark Wüsthoff

1997-01-01

6

Nuclear dependence of azimuthal asymmetry in semi-inclusive deep inelastic scattering  

Microsoft Academic Search

Within the framework of a generalized factorization, semi-inclusive deeply inelastic scattering (SIDIS) cross sections can be expressed as a series of products of collinear hard parts and transverse-momentum-dependent (TMD) parton distributions and correlations. The azimuthal asymmetry of unpolarized SIDIS in the small transverse-momentum region will depend on both twist-2 and -3 TMD quark distributions in target nucleons or nuclei. Nuclear

Jian-Hua Gao; Zuo-Tang Liang; Xin-Nian Wang

2010-01-01

7

Nuclear dependence of azimuthal asymmetry in semi-inclusive deep inelastic scattering  

Microsoft Academic Search

Within the framework of a generalized factorization, semi-inclusive deeply inelastic scattering (SIDIS) cross sections can be expressed as a series of products of collinear hard parts and transverse-momentum-dependent (TMD) parton distributions and correlations. The azimuthal asymmetry of unpolarized SIDIS in the small transverse-momentum region will depend on both twist-2 and -3 TMD quark distributions in target nucleons or nuclei.

Gao Jianhua; Liang Zuotang; Wang Xinnian

2010-01-01

8

Hadron Azimuthal Correlations and Mach-like Structures in a Partonic\\/Hadronic Transport Model  

Microsoft Academic Search

With a multi-phase transport model (AMPT) with both partonic and hadronic interactions, two- and three-particle azimuthal correlations in Au + Au collisions at sNN=200 GeV have been studied by the mixing-event technique. A Mach-like structure has been observed in two- and three-particle correlations in central collisions. It has been found that both partonic and hadronic dynamical mechanisms contribute to the Mach-like

G. L. Ma; S. Zhang; Y. G. Ma; X. Z. Cai; J. H. Chen; Z. J. He; H. Z. Huang; J. L. Long; W. Q. Shen; X. H. Shi; C. Zhong; J. X. Zuo

2007-01-01

9

Azimuthal angular dependence study of the atmospheric muon charge ratio at sea level using Geant4  

NASA Astrophysics Data System (ADS)

The azimuth dependence of the cosmic muon charge ratio at sea level was estimated using the Geant4 simulation package. Simulations were separately run at 12 azimuth angles ranging from 0° to 330° with 30° increment. Two hundred thousand proton and alpha particles were randomly distributed over the zenith angle range 30° < ? < 40° at each azimuth angle. The kinetic energy spectra of proton and helium nuclei were taken from the balloon-flight measurements. The atmospheric muon charge ratio was calculated at each azimuthal angle for low energy muons with a mean momentum around 0.5 GeV/c. The Geant4 simulation results have been compared with those of the CORSIKA simulation program and with the WILLI measurements. The simulation results reproduce well the measured east-west effect with a non-zero asymmetry AEW = 0.24. This asymmetry in the charge ratio decreases from 0.37 to 0.19 as the momentum increases from 0.22 to 0.70 GeV/c.

Arslan, Halil; Bektasoglu, Mehmet

2012-05-01

10

TRACING OUTFLOWS AND ACCRETION: A BIMODAL AZIMUTHAL DEPENDENCE OF Mg II ABSORPTION  

SciTech Connect

We report a bimodality in the azimuthal angle distribution of gas around galaxies as traced by Mg II absorption: halo gas prefers to exist near the projected galaxy major and minor axes. The bimodality is demonstrated by computing the mean azimuthal angle probability distribution function using 88 spectroscopically confirmed Mg II-absorption-selected galaxies [W{sub r} (2796) {>=} 0.1 A] and 35 spectroscopically confirmed non-absorbing galaxies [W{sub r} (2796) < 0.1 A] imaged with Hubble Space Telescope and Sloan Digital Sky Survey. The azimuthal angle distribution for non-absorbers is flat, indicating no azimuthal preference for gas characterized by W{sub r} (2796) < 0.1 A. We find that blue star-forming galaxies clearly drive the bimodality while red passive galaxies may exhibit an excess along their major axis. These results are consistent with galaxy evolution scenarios where star-forming galaxies accrete new gas, forming new stars and producing winds, while red galaxies exist passively due to reduced gas reservoirs. We further compute an azimuthal angle dependent Mg II absorption covering fraction, which is enhanced by as much as 20%-30% along the major and minor axes. The W{sub r} (2796) distribution for gas along the major axis is likely skewed toward weaker Mg II absorption than for gas along the projected minor axis. These combined results are highly suggestive that the bimodality is driven by gas accreted along the galaxy major axis and outflowing along the galaxy minor axis. Adopting these assumptions, we find that the opening angle of outflows and inflows to be 100 Degree-Sign and 40 Degree-Sign , respectively. We find that the probability of detecting outflows is {approx}60%, implying that winds are more commonly observed.

Kacprzak, Glenn G. [Swinburne University of Technology, Victoria 3122 (Australia); Churchill, Christopher W.; Nielsen, Nikole M., E-mail: gkacprzak@astro.swin.edu.au [New Mexico State University, Las Cruces, NM 88003 (United States)

2012-11-20

11

Constraining Poiseuille flow in the asthenosphere using depth-dependence of azimuthal seismic anisotropy  

NASA Astrophysics Data System (ADS)

Asthenospheric flow accommodates differential shear between plate and mantle motions (Couette flow) and hosts additional flow driven by horizontal pressure gradients (Poiseuille flow) that may be associated with mantle upwelling and subduction. Determining the relative importance and spatial distribution of Poiseuille flow in the asthenosphere could help discriminate among competing theories of asthenospheric origin and shed light on thermal history of the Earth. Large uncertainties in the flow field and rheological structure of the upper mantle have thus far hindered our ability to constrain the relative importance of Couette and Poiseuille flows in the asthenosphere. We propose a new method to quantify Poiseuille flow in the asthenosphere using observations of the depth-dependence of azimuthal seismic anisotropy. In particular, we employ a simple one-dimensional Couette-Poiseuille flow model and analytically solve for the depth-profiles of the strain axis orientation in the asthenosphere, which approximates the orientation of azimuthal seismic anisotropy. We find that Couette-Poiseuille flow induces rotation of azimuthal seismic anisotropy with depth provided that the horizontal pressure gradient has a component transverse to plate motion. We then construct an algorithm that utilizes observed rotations of azimuthal seismic anisotropy with depth and analytical depth-profiles of the strain axis to invert for the horizontal pressure gradients everywhere in the asthenosphere. We test our method on the output of a global numerical mantle flow model. A comparison of our predicted pressure gradients with those computed directly from the numerical model shows a high degree of agreement, indicating that our method is robust. We show that our algorithm is stable, except for the case in which the component of the pressure gradient transverse to plate motion is close to zero. We establish that Poiseuille flow drives about 40% of the total flow velocity amplitude in the asthenosphere of the numerical model, which indicates that pressure gradients from mantle convection may be an important component of asthenospheric dynamics.

Natarov, Svetlana I.

12

Azimuth-dependent Mapping Functions From Numerical Weather Models in VLBI Analysis for CONT02  

NASA Astrophysics Data System (ADS)

In the past few years a significant improvement of VLBI analysis has been obtained by the use of numerical weather models (NWM) for the determination of elevation-dependent mapping functions for the troposphere delays. For the VLBI campaign CONT02, which covers 15 consecutive 24 hour sessions with eight stations in the second half of October 2002, the operational analysis pressure level data from the European Centre for Medium-Range Weather Forecasts (ECMWF) is used to provide the hydrostatic and wet mapping functions not only once per station and epoch but also every 30 degrees in azimuth. The determination is based on a 3D ray-trace program which uses the following properties of the NWM: 20 deg x 20 deg grids with 50 km increments around each of the eight stations, 21 levels (from 1000 hPa to 1 hPa) vertical resolution of the profiles and six hours time intervals. The application of these azimuth-dependent mapping functions in the VLBI analysis of CONT02 shows that the hydrostatic gradients are well determined with this approach, whereas the accuracy of the wet gradients from a NWM as described above still contains some deficiencies. The azimuth-dependent hydrostatic mapping functions are compared to the tilting of the 200 hPa pressure levels, and the residual wet gradients estimated in the VLBI analysis are compared to those derived from the NWM. It is also discussed whether standard gradient models with north and east gradients can properly account for asymmetries of the troposphere. Thus, the presentation describes what presently available numerical weather models can do in terms of asymmetric modeling of the troposphere delays. The results of the VLBI analysis provide a reliable estimation how big the effect will be for GPS.

Boehm, J.; Schuh, H.

2004-12-01

13

The azimuthal path of myosin V and its dependence on lever-arm length  

PubMed Central

Myosin V (myoV) is a two-headed myosin capable of taking many successive steps along actin per diffusional encounter, enabling it to transport vesicular and ribonucleoprotein cargos in the dense and complex environment within cells. To better understand how myoV navigates along actin, we used polarized total internal reflection fluorescence microscopy to examine angular changes of bifunctional rhodamine probes on the lever arms of single myoV molecules in vitro. With a newly developed analysis technique, the rotational motions of the lever arm and the local orientation of each probe relative to the lever arm were estimated from the probe’s measured orientation. This type of analysis could be applied to similar studies on other motor proteins, as well as other proteins with domains that undergo significant rotational motions. The experiments were performed on recombinant constructs of myoV that had either the native-length (six IQ motifs and calmodulins [CaMs]) or truncated (four IQ motifs and CaMs) lever arms. Native-length myoV-6IQ mainly took straight steps along actin, with occasional small azimuthal tilts around the actin filament. Truncated myoV-4IQ showed an increased frequency of azimuthal steps, but the magnitudes of these steps were nearly identical to those of myoV-6IQ. The results show that the azimuthal deflections of myoV on actin are more common for the truncated lever arm, but the range of these deflections is relatively independent of its lever-arm length.

Lewis, John H.; Beausang, John F.; Sweeney, H. Lee

2012-01-01

14

Polar-azimuthal angle dependent efficiency of different infrared superconducting nanowire single-photon detector designs  

NASA Astrophysics Data System (ADS)

The illumination-angle-dependent absorptance was determined for three types of superconducting-nanowire singlephoton detector (SNSPD) designs: 1. periodic bare niobium-nitride (NbN) stripes with dimensions of conventional SNSPDs, 2. the same NbN patterns integrated with ~quarter-wavelength hydrogensilsesquioxane-filled nano- cavity, 3. similar cavity-integrated structures covered by a thin gold reflector. A three-dimensional finite-element method was applied to determine the optical response and near-field distribution as a function of p-polarized light illumination orientations specified by polar-angle, ?, and azimuthal-angle, ?. The numerical results proved that the NbN absorptance might be maximized via simultaneous optimization of the polar and azimuthal illumination angles. Complementary transfer-matrix-method calculations were performed on analogous film-stacks to uncover the phenomena contributing to the appearance of extrema on the optical response of NbN-patterns in P-structure-configuration. This comparative study showed that the absorptance of bare NbN patterns is zero at the angle corresponding to total internal reflection (TIR). In cavity-integrated structures the NbN absorptance curve indicates a maximum at the same orientation due to the phase shift introduced by the quarter-wavelength HSQ layer. The reflector promotes the NbN absorptance at small polar angles, but the available absorptance is limited by attenuated TIR in polar angle-intervals, where surface modes are excited on the gold film.

Csete, Mária; Sipos, Áron; Najafi, Faraz; Berggren, Karl K.

2011-09-01

15

Radial modal dependence of the azimuthal spectrum after parametric down-conversion  

NASA Astrophysics Data System (ADS)

The radial degrees of freedom of the biphoton states that are produced in spontaneous parametric down-conversion (SPDC) in the Laguerre-Gaussian (LG) basis are investigated, theoretically and experimentally. We calculated the theoretical azimuthal Schmidt numbers for different combinations of radial indices and found that a larger azimuthal Schmidt number is obtained for higher radial indices of the signal and idler beams. Moreover, larger azimuthal Schmidt numbers are also obtained when the difference between the two radial indices increases. Comparing these theoretical predictions with the azimuthal Schmidt numbers obtained from experimentally measurements, we found good agreement. Experimentally we demonstrated that it is possible to obtain a threefold increase in the azimuthal Schmidt number while maintaining a reasonable coincidence count rate by using LG modes with slightly larger radial indices.

Zhang, Yingwen; Roux, Filippus S.; McLaren, Melanie; Forbes, Andrew

2014-04-01

16

Cancellation of polarized impulsive noise using an azimuth-dependent conditional mean estimator  

Microsoft Academic Search

The separation of signals from noisy vector measurements is obtained by taking advantage of the Middleton Class A model of noise amplitude and the correlation of the components of the noise process due to their polarization. The signal is assumed to be white Gaussian. Noise is a superposition of M non-Gaussian processes, each with a fixed azimuth of polarization. Neither

Umberto Spagnolini

1998-01-01

17

Dependence of nuclear diffraction on the azimuthal angle: (002)- and (0010)-reflections of YIG  

Microsoft Academic Search

Nuclear diffraction of synchrotron radiation has been investigated using YIG single crystals in different scattering geometries.\\u000a Time resolved quantum beat spectra of pure nuclear (002) and (0010) Bragg reflections were observed in a set-up where the\\u000a hyperfine interaction was kept constant, while the azimuthal angle in the (001) surface between the [100] axis and the scattering\\u000a plane (k\\u000a in,k\\u000a out)

H. D. Rüter; R. Rüffer; R. Hollatz; W. Sturhahn; E. Gerdau

1990-01-01

18

Nuclear-mass dependence of azimuthal beam-helicity and beam-charge asymmetries in deeply virtual Compton scattering  

SciTech Connect

The nuclear-mass dependence of azimuthal cross-section asymmetries with respect to charge and longitudinal polarization of the lepton beam is studied for hard exclusive electroproduction of real photons. The observed beam-charge and beam-helicity asymmetries are attributed to the interference between the Bethe-Heitler and the deeply virtual Compton scattering processes. For various nuclei, the asymmetries are extracted for both coherent and incoherent-enriched regions, which involve different (combinations of) generalized parton distributions. For both regions, the asymmetries are compared to those for a free proton, and no nuclear-mass dependence is found.

Airapetian, A. [Physikalisches Institut, Universitaet Giessen, D-35392 Giessen (Germany); Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States); Akopov, N.; Avakian, R.; Avetissian, A.; Elbakian, G.; Gharibyan, V.; Karyan, G.; Marukyan, H.; Movsisyan, A.; Taroian, S. [Yerevan Physics Institute, 375036 Yerevan (Armenia); Akopov, Z.; Avetisyan, E.; Borissov, A.; Hartig, M.; Holler, Y.; Rostomyan, A.; Schueler, K. P.; Varanda, M.; Ye, Z.; Zihlmann, B. [DESY, D-22603 Hamburg (Germany)

2010-03-15

19

Azimuthal Electric Fields and Tandem Ambipolarity.  

National Technical Information Service (NTIS)

The importance of retaining the azimuthal variation of the electrostatic potential in transport and ambipolarity studies is demonstrated. Because the azimuthal electric field must satisfy quasi-neutrality, equilibrium ambipolar operation permitting differ...

P. J. Catto J. R. Myra X. S. Lee G. L. Francis

1984-01-01

20

Dynamical instability of a Keplerian disk - Dependence on azimuthal wave number, Mach number, and the size of the disk  

NASA Astrophysics Data System (ADS)

Unstable perturbations in a rotating fluid are investigated for a rotation law of ? ? r-1.5 where ? and r are the angular velocity and the radial distance, respectively. The growth rate of the unstable perturbation tends to be largest for the mode whose azimuthal wave number is roughly equal to the Mach number. This implies that large scale waves will be excited in a hot disk and small scale waves in a cold disk. The growth rate depends sensitively on the outer radius of the disk when the outer radius is not too large. However, the growth rate becomes insensitive to the outer radius and tends to a finite value as the outer radius tends to infinity. This means that the wave is reflected not at the outer boundary but within the flow when the outer boundary is sufficiently large. The result is applied to evaluate the turbulent viscosity. The viscous parameter ? is found to be inversely proportional to the Mach number. This is consistent with the theory of dwarf novae.

Hanawa, T.

1988-05-01

21

The cost of transportation`s oil dependence  

SciTech Connect

Transportation is critical to the world`s oil dependence problem because of the large share of world oil it consumes and because of its intense dependence on oil. This paper will focus on the economic costs of transportation`s oil dependence.

Greene, D.L.

1995-05-01

22

Azimuthal anisotropy of direct photons  

SciTech Connect

The electromagnetic bremsstrahlung produced by a quark interacting with nucleons or nuclei is azimuthally asymmetric. In the light-cone dipole approach this effect is related to the orientation dependent dipole cross section. Such a radiation anisotropy is expected to contribute to the azimuthal asymmetry of direct photons in pA and AA collisions, as well as in deep-inelastic scattering and in the production of dileptons.

Kopeliovich, B. Z. [Departamento de Fisica y Centro de Estudios Subatomicos, Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile); Joint Institute for Nuclear Research, Dubna (Russian Federation); Pirner, H. J. [Institute for Theoretical Physics, University of Heidelberg, Philosophenweg 19, D-69120 Heidelberg (Germany); Rezaeian, A. H.; Schmidt, Ivan [Departamento de Fisica y Centro de Estudios Subatomicos, Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile)

2008-02-01

23

Nuclear suppression of azimuthal asymmetries in semi-inclusive deep inelastic scattering off polarized targets  

NASA Astrophysics Data System (ADS)

We extend the study of nuclear dependence of the transverse momentum dependent parton distribution functions and azimuthal asymmetries to semi-inclusive deep inelastic scattering (SIDIS) off polarized nuclear targets. We show that azimuthal asymmetries are suppressed for SIDIS off a polarized nuclear target relative to that off a polarized nucleon due to multiple scattering inside the nucleus. Using the value of transport parameter inside large nuclei extracted from jet quenching analyses in SIDIS off nuclear targets, we also present a numerical estimate of the nuclear suppression of the azimuthal asymmetry that might be useful to guide the future experimental studies of SIDIS off polarized nuclear targets.

Song, Yu-kun; Liang, Zuo-tang; Wang, Xin-Nian

2014-06-01

24

Observation of charge-dependent azimuthal correlations and possible local strong parity violation in heavy-ion collisions  

SciTech Connect

Parity-odd domains, corresponding to non-trivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in non-central collisions. To study this effect, we investigate a three particle mixed harmonics azimuthal correlator which is a {Rho}-even observable, but directly sensitive to the charge separation effect. We report measurements of this observable using the STAR detector in Au+Au and Cu+Cu collisions at {radical}s{sub NN} = 200 and 62 GeV. The results are presented as a function of collision centrality, particle separation in rapidity, and particle transverse momentum. A signal consistent with several of the theoretical expectations is detected in all four data sets. We compare our results to the predictions of existing event generators, and discuss in detail possible contributions from other effects that are not related to parity violation.

STAR Collaboration; Abelev, Betty

2010-07-05

25

14 CFR 171.315 - Azimuth monitor system requirements.  

...Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES Microwave Landing System (MLS) § 171.315 Azimuth monitor system requirements. (a) The...

2014-01-01

26

Serotonin transporter gene polymorphisms in alcohol dependence  

Microsoft Academic Search

The serotonin transporter (5-HTT) gene is a candidate gene in alcohol dependence because serotonin reuptake inhibitors (SRIs) can alleviate alcohol withdrawal. Studies of the 5-HTT gene in alcohol dependence have not resulted in a consensus. Recent studies have examined the transcriptionally active promoter polymorphism, a 44-bp deletion resulting in short (S) or long (L) alleles. In this study, 131 alcohol-dependent

Miles D. Thompson; Nancy Gonzalez; Tuan Nguyen; David E. Comings; Susan R. George; Brian F. O'Dowd

2000-01-01

27

Azimuthal anisotropy of the Pacific region  

NASA Astrophysics Data System (ADS)

Azimuthal anisotropy is the dependence of local seismic properties on the azimuth of propagation. We present the azimuthally anisotropic component of a 3D SV velocity model for the Pacific Ocean, derived from the waveform modeling of over 56,000 multi-mode Rayleigh waves followed by a simultaneous inversion for isotropic and azimuthally anisotropic vsv structure. The isotropic vsv model is discussed in a previous paper (A. Maggi, E. Debayle, K. Priestley, G. Barruol, Multi-mode surface waveform tomography of the Pacific Ocean: a close look at the lithospheric cooling signature, Geophys. J. Int. 166 (3) (2006). doi:10.1111/j.1365-246x.2006.03037.x). The azimuthal anisotropy we find is consistent with the lattice preferred orientation model (LPO): the hypothesis of anisotropy generation in the Earth's mantle by preferential alignment of anisotropic crystals in response to the shear strains induced by mantle flow. At lithospheric depths we find good agreement between fast azimuthal anisotropy orientations and ridge spreading directions recorded by sea-floor magnetic anomalies. At asthenospheric depths we find a strong correlation between fast azimuthal anisotropy orientations and the directions of current plate motions. We observe perturbations in the pattern of seismic anisotropy close to Pacific hot-spots that are consistent with the predictions of numerical models of LPO generation in plume-disturbed plate motion-driven mantle flow. These observations suggest that perturbations in the patterns of azimuthal anisotropy may provide indirect evidence for plume-like upwelling in the mantle.

Maggi, Alessia; Debayle, Eric; Priestley, Keith; Barruol, Guilhem

2006-10-01

28

Flavor Dependence of the Boer-Mulders Function and its Influence on Azimuthal and Single-Spin Asymmetries in Semi-Inclusive Dis  

NASA Astrophysics Data System (ADS)

The chiral-odd and time reversal-odd transverse momentum dependent (TMD) parton distribution h?1, the so-called Boer-Mulders function, is calculated in the diquark spectator model for both an active up- and down-quark. In particular the signs of h?(u)1 and h?(d)1 are of interest as they were predicted in other works, and the result of this analysis is consistent with these predictions. Both flavors of the Boer-Mulders function contribute to observables such as the azimuthal cos(2?) asymmetry in semi-inclusive DIS. Using the results of this analysis for h?(u)1 and h?(d)1 and recent calculations of the Collins fragmentation function in a similar spectator model, phenomenological predictions for the cos(2?) asymmetry are presented. In addition, the chiral-odd but time-reversal even TMD h?1L is computed in the diquark spectator model, and is used to present predictions for the sin(2?) single-spin asymmetry for a longitudinally polarized target in SIDIS.

Gamberg, Leonard P.; Goldstein, Gary R.; Schlegel, Marc

2008-03-01

29

Time-dependent modelling of mass-loading, transport, chemistry and magnetic fields in Jupiter's magnetosphere  

NASA Astrophysics Data System (ADS)

Radial profiles of plasma flux tube content are often modelled using diffusive plasma transport using an assumed source rate and diffusion coefficient. Such diffusive transport modelling can be combined with neutral-cloud theory to provide time-dependent chemistry in the plasma torus. Independently, and not necessarily self-consistently, the radial profile of the plasma azimuthal velocity can be calculated using the Hill-Pontius equation, for the mathematically separable case where the source and transport regions are spatially distinct. These steady state profiles can be imposed into a magnetospheric model to understand the resulting fields and currents. In a non-steady state where the plasma source rate is varying, and/or the outflowing plasma is not in equilibrium, these solutions do not apply. Hence, important questions concerning time-dependent variability in the jovian and saturnian magnetospheres cannot be adequately addressed using such models. In this paper we present a new approach where we solve the time-dependent equations for diffusive radial transport of both mass and angular momentum coupled with a neutral-plasma chemistry model, thus allowing for time-dependent plasma sources and the motion of radial structures produced by such time-dependence. These time-dependent solutions are coupled to an Euler potential magnetospheric model to calculate time-dependent magnetospheric configurations. We present our modelling methodology and the first results from this coupled model.

Arridge, C. S.

2013-12-01

30

Charged particles time-dependent transverse transport  

NASA Astrophysics Data System (ADS)

We discuss an analytical derivation for the temporal dependence of the transverse transport coefficient for times smaller than the correlation time of the magnetic turbulence, as seen by the particle, where the quasi-linear theory is not valid. The transverse transport is assumed to be dominated by the guiding center motion. Contributions of wavelengths shorter and longer than the coherence length to particle drift from the local magnetic field lines and to the magnetic field lines random walk are assessed for slab and 3D isotropic turbulence. Extensions of this model will allow for a study of solar wind physically motivated anisotropy.

Fraschetti, F.; Jokipii, J. R.

2010-12-01

31

Gravity-Dependent Transport in Industrial Processes  

NASA Technical Reports Server (NTRS)

Gravity dependent transport phenomena in various industrial processes are investigated in order to indicate new directions for micro-gravity research that enhance the commercial success of the space program. The present article describes the commercialization possibilities of such topics associated with physicochemical transport phenomena. The topics are: coating flow, rotating electrochemical system, and convection in low Plandtl number fluids. The present study is directed to understand these phenomena, and to develop a knowledge base for their applications with emphasis to a micro-gravity environment.

Ostrach, Simon; Kamotani, Yasuhiro

1996-01-01

32

Azimuth and Altitude  

NSDL National Science Digital Library

When finding our way through the landscape, we use points of reference to orient ourselves. At sea, navigators use azimuth or bearing to describe the direction and altitude to describe the height of the sun or a star, lighthouse, or buoy used as a point of reference. In this activity students use a compass and their hands to find positions of stars and planets in the night sky or of the sun during the day. Terms introduced include 360 degree circle, azimuth, altitude, and bearing.

33

Azimuth Monitoring System.  

National Technical Information Service (NTIS)

A system is explained for monitoring changes in azimuth due to shifts in geological features of the earth's surface. This is done by a collimated laser beam which is split and reflected from a plane mirror and a prismatic mirror to target area showing tra...

T. E. Wirtanem

1978-01-01

34

Azimuthal decomposition with digital holograms.  

PubMed

We demonstrate a simple approach, using digital holograms, to perform a complete azimuthal decomposition of an optical field. Importantly, we use a set of basis functions that are not scale dependent so that unlike other methods, no knowledge of the initial field is required for the decomposition. We illustrate the power of the method by decomposing two examples: superpositions of Bessel beams and Hermite-Gaussian beams (off-axis vortex). From the measured decomposition we show reconstruction of the amplitude, phase and orbital angular momentum density of the field with a high degree of accuracy. PMID:22565722

Litvin, Igor A; Dudley, Angela; Roux, Filippus S; Forbes, Andrew

2012-05-01

35

Magnetic field dependence of asymmetry-induced transport: A new approach  

SciTech Connect

A new technique is used to experimentally study the dependence of asymmetry-induced radial particle flux {gamma} on an axial magnetic field B in a modified Malmberg-Penning trap. This dependence is complicated by the fact that B enters the physics in at least two places: in the asymmetry-induced first order radial drift velocity v{sub r}=E{sub {theta}}/B and in the zeroth order azimuthal drift velocity v{sub {theta}}=E{sub r}/B. To separate these, it is assumed that the latter always enters the physics in the combination {omega}-l{omega}{sub R}, where {omega}{sub R}(r)=v{sub {theta}}/r is the column rotation frequency and {omega} and l are the asymmetry frequency and azimuthal mode number, respectively. Points where {omega}-l{omega}{sub R}=0 are then selected from a {gamma} versus r versus {omega} data set, thus insuring that any function of this combination is constant. When the selected flux is plotted versus the density gradient {nabla}n, a roughly linear dependence is observed, showing that the assumption is valid and that the diffusive contribution to the transport has been isolated. The slope of a least-squares fitted line then gives the diffusion coefficient D{sub 0} for the selected flux. Varying the magnetic field, it is found that D{sub 0}{proportional_to}B{sup -1.33{+-}}{sup 0.05}. This does not match the scaling predicted by resonant particle transport theory.

Eggleston, D. L.; Williams, J. M. [Physics Department, Occidental College, Los Angeles, California 90041 (United States)

2008-03-15

36

Modeling sensitivity of temporal and azimuthal variability in the Io plasma torus  

NASA Astrophysics Data System (ADS)

During Cassini's inbound approach to Jupiter, the Cassini UVIS data revealed that the Io Plasma torus exhibits azimuthal (e.g. composition) and temporal (e.g. brightness) variations. The azimuthal variations were found to be modulated by the System III and System IV periods via hot (i.e. 10s to 100s eV) electron chemistry. While the System III hot electrons are understood to be governed, in part, by the longitude-dependent magnetic mirror ratio, the mechanism for modulating the hot electron abundance at the System IV period is undetermined and therefore motivates this study. Using an improved azimuthal physical chemistry model for the Io plasma torus, we will present sensitivity studies of torus properties to variations in neutral source rate, System III and System IV hot electron abundance, and the radial transport and azimuthal subcorotation timescales. We will investigate the range of parameters that yield quasi-stable azimuthal variation in composition that is imposed by a variable neutral source (i.e. similar to the inferred volcanic eruption preceding the Cassini flyby in 2000). These studies are relevant to the on-going analysis of the outbound Cassini UVIS data acquired between January and March 2001 and future observations of torus variability such as the EXCEED mission.

Copper, M.; Delamere, P. A.; Steffl, A. J.

2013-12-01

37

Dependence of enhanced asymmetry-induced transport on collision frequency  

NASA Astrophysics Data System (ADS)

Our previous studiesfootnotetextD. L. Eggleston, Phys. Plasmas 19, 042307 (2012). of asymmetry-induced radial transport using a single-particle code with collisional effects have identified, for asymmetries of the form ?1(r)(kz)(?t - l?), two sources for the transport: resonant particles (RPs) and axially trapped particles (ATPs). We observe that this latter type, which occurs near the radius where ? matches the azimuthal rotation frequency ?R, is often dominant at low collision frequency ? but becomes negligible at higher ?. This can be understood by noting that ATPs have a lower trapping frequency ?T^2= (l^2?1/rB)|d?R/dr| than RPs. In the low ? (banana) regime, the radial oscillations have amplitude ?r= vr/?T, so ATPs dominate, and the transport may even exceed the RP plateau regime level. As ? increases, collisions start to interrupt the slower ATP oscillations while the RPs are still in the banana regime, so the ATP contribution to the transport decreases. At the largest ? values, ATP transport is negligible and the observed diffusion coefficient matches that given by plateau regime RP theory.footnotetextD. L. Eggleston and T. M. O'Neil, Phys. Plasmas 6, 2699 (1999).

Eggleston, D. L.

2012-10-01

38

On the dependence of the efficiency of a 240 GHz high-power gyrotron on the displacement of the electron beam and on the azimuthal index  

NASA Astrophysics Data System (ADS)

Two issues in the cavity design for a Megawatt-class, 240 GHz gyrotron are addressed. Those are first, the effect of a misaligned electron beam on the gyrotron efficiency and second, a possible azimuthal instability of the gyrotron. The aforementioned effects are important for any gyrotron operation, but could be more critical in the operation of Megawatt-class gyrotrons at frequencies above 200 GHz, which will be the anticipated requirement of DEMO. The target is to provide some basic trends to be considered during the refinement and optimization of the design. Self-consistent calculations are the base for simulations wherever possible. However, in cases for which self-consistent models were not available, fixed-field results are presented. In those cases, the conservative nature of the results should be kept in mind.

Dumbrajs, O.; Avramidis, K. A.; Franck, J.; Jelonnek, J.

2014-01-01

39

Technology of optical azimuth transmission  

NASA Astrophysics Data System (ADS)

It often needs transfer a reference from one place to another place in aerospace and guided missile launching. At first, principles of several typical optical azimuth transmission methods are presented. Several typical methods are introduced, such as Theodolite (including gyro-theodolite) collimation method, Camera series method, Optical apparatus for azimuth method and polarization modulated light transmission method. For these typical azimuth transmission methods, their essential theories are elaborated. Then the devices, the application fields and limitations of these typical methods' are presented. Theodolite (including gyro-theodolite) collimation method is used in the ground assembly of spacecraft. Camera series method and optical apparatus for azimuth method are used in azimuth transmission between different decks of ship. Polarization modulated light transmission method is used in azimuth transmission of rocket and guided missile. At the last, the further developments of these methods are discussed.

Lu, Honggang; Hu, Chunsheng; Wang, Xingshu; Gao, Yang

2012-11-01

40

Azimuthal-Angle Dependence of Charged-Pion-Interferometry Measurements with Respect to Second- and Third-Order Event Planes in Au+Au Collisions at sqrt[s_{NN}]=200??GeV.  

PubMed

Charged-pion-interferometry measurements were made with respect to the second- and third-order event plane for Au+Au collisions at sqrt[s_{NN}]=200??GeV. A strong azimuthal-angle dependence of the extracted Gaussian-source radii was observed with respect to both the second- and third-order event planes. The results for the second-order dependence indicate that the initial eccentricity is reduced during the medium evolution, which is consistent with previous results. In contrast, the results for the third-order dependence indicate that the initial triangular shape is significantly reduced and potentially reversed by the end of the medium evolution, and that the third-order oscillations are largely dominated by the dynamical effects from triangular flow. PMID:24949761

Adare, A; Afanasiev, S; Aidala, C; Ajitanand, N N; Akiba, Y; Al-Bataineh, H; Alexander, J; Aoki, K; Aramaki, Y; Atomssa, E T; Averbeck, R; Awes, T C; Azmoun, B; Babintsev, V; Bai, M; Baksay, G; Baksay, L; Barish, K N; Bassalleck, B; Basye, A T; Bathe, S; Baublis, V; Baumann, C; Bazilevsky, A; Belikov, S; Belmont, R; Bennett, R; Berdnikov, A; Berdnikov, Y; Bickley, A A; Bok, J S; Boyle, K; Brooks, M L; Buesching, H; Bumazhnov, V; Bunce, G; Butsyk, S; Camacho, C M; Campbell, S; Chen, C-H; Chi, C Y; Chiu, M; Choi, I J; Choudhury, R K; Christiansen, P; Chujo, T; Chung, P; Chvala, O; Cianciolo, V; Citron, Z; Cole, B A; Connors, M; Constantin, P; Csanád, M; Csörg?, T; Dahms, T; Dairaku, S; Danchev, I; Das, K; Datta, A; David, G; Denisov, A; Deshpande, A; Desmond, E J; Dietzsch, O; Dion, A; Donadelli, M; Drapier, O; Drees, A; Drees, K A; Durham, J M; Durum, A; Dutta, D; Edwards, S; Efremenko, Y V; Ellinghaus, F; Engelmore, T; Enokizono, A; En'yo, H; Esumi, S; Fadem, B; Fields, D E; Finger, M; Finger, M; Fleuret, F; Fokin, S L; Fraenkel, Z; Frantz, J E; Franz, A; Frawley, A D; Fujiwara, K; Fukao, Y; Fusayasu, T; Garishvili, I; Glenn, A; Gong, H; Gonin, M; Goto, Y; Granier de Cassagnac, R; Grau, N; Greene, S V; Grosse Perdekamp, M; Gunji, T; Gustafsson, H-Ĺ; Haggerty, J S; Hahn, K I; Hamagaki, H; Hamblen, J; Han, R; Hanks, J; Hartouni, E P; Haslum, E; Hayano, R; He, X; Heffner, M; Hemmick, T K; Hester, T; Hill, J C; Hohlmann, M; Holzmann, W; Homma, K; Hong, B; Horaguchi, T; Hornback, D; Huang, S; Ichihara, T; Ichimiya, R; Ide, J; Ikeda, Y; Imai, K; Inaba, M; Isenhower, D; Ishihara, M; Isobe, T; Issah, M; Isupov, A; Ivanischev, D; Jacak, B V; Jia, J; Jin, J; Johnson, B M; Joo, K S; Jouan, D; Jumper, D S; Kajihara, F; Kametani, S; Kamihara, N; Kamin, J; Kang, J H; Kapustinsky, J; Karatsu, K; Kawall, D; Kawashima, M; Kazantsev, A V; Kempel, T; Khanzadeev, A; Kijima, K M; Kim, B I; Kim, D H; Kim, D J; Kim, E; Kim, E-J; Kim, S H; Kim, Y-J; Kinney, E; Kiriluk, K; Kiss, A; Kistenev, E; Kochenda, L; Komkov, B; Konno, M; Koster, J; Kotchetkov, D; Kozlov, A; Král, A; Kravitz, A; Kunde, G J; Kurita, K; Kurosawa, M; Kwon, Y; Kyle, G S; Lacey, R; Lai, Y S; Lajoie, J G; Lebedev, A; Lee, D M; Lee, J; Lee, K; Lee, K B; Lee, K S; Leitch, M J; Leite, M A L; Leitner, E; Lenzi, B; Li, X; Liebing, P; Linden Levy, L A; Liška, T; Litvinenko, A; Liu, H; Liu, M X; Love, B; Luechtenborg, R; Lynch, D; Maguire, C F; Makdisi, Y I; Malakhov, A; Malik, M D; Manko, V I; Mannel, E; Mao, Y; Masui, H; Matathias, F; McCumber, M; McGaughey, P L; Means, N; Meredith, B; Miake, Y; Mignerey, A C; Mikeš, P; Miki, K; Milov, A; Mishra, M; Mitchell, J T; Mohanty, A K; Morino, Y; Morreale, A; Morrison, D P; Moukhanova, T V; Murata, J; Nagamiya, S; Nagle, J L; Naglis, M; Nagy, M I; Nakagawa, I; Nakamiya, Y; Nakamura, T; Nakano, K; Newby, J; Nguyen, M; Niida, T; Nouicer, R; Nyanin, A S; O'Brien, E; Oda, S X; Ogilvie, C A; Oka, M; Okada, K; Onuki, Y; Oskarsson, A; Ouchida, M; Ozawa, K; Pak, R; Pantuev, V; Papavassiliou, V; Park, I H; Park, J; Park, S K; Park, W J; Pate, S F; Pei, H; Peng, J-C; Pereira, H; Peresedov, V; Peressounko, D Yu; Pinkenburg, C; Pisani, R P; Proissl, M; Purschke, M L; Purwar, A K; Qu, H; Rak, J; Rakotozafindrabe, A; Ravinovich, I; Read, K F; Reygers, K; Riabov, V; Riabov, Y; Richardson, E; Roach, D; Roche, G; Rolnick, S D; Rosati, M; Rosen, C A; Rosendahl, S S E; Rosnet, P; Rukoyatkin, P; Ruži?ka, P; Sahlmueller, B; Saito, N; Sakaguchi, T; Sakashita, K; Samsonov, V; Sano, S; Sato, T; Sawada, S; Sedgwick, K; Seele, J; Seidl, R; Semenov, A Yu; Seto, R; Sharma, D; Shein, I; Shibata, T-A; Shigaki, K; Shimomura, M; Shoji, K; Shukla, P; Sickles, A; Silva, C L; Silvermyr, D; Silvestre, C; Sim, K S; Singh, B K; Singh, C P; Singh, V; Slune?ka, M; Soltz, R A; Sondheim, W E; Sorensen, S P; Sourikova, I V; Sparks, N A; Stankus, P W; Stenlund, E; Stoll, S P; Sugitate, T; Sukhanov, A; Sziklai, J; Takagui, E M; Taketani, A; Tanabe, R; Tanaka, Y; Tanida, K; Tannenbaum, M J; Tarafdar, S; Taranenko, A; Tarján, P; Themann, H; Thomas, T L; Todoroki, T; Togawa, M; Toia, A; Tomášek, L; Torii, H; Towell, R S; Tserruya, I; Tsuchimoto, Y; Vale, C; Valle, H; van Hecke, H W; Vazquez-Zambrano, E; Veicht, A; Velkovska, J; Vértesi, R; Vinogradov, A A; Virius, M; Vrba, V; Vznuzdaev, E; Wang, X R; Watanabe, D; Watanabe, K; Watanabe, Y; Wei, F; Wei, R; Wessels, J; White, S N; Winter, D; Wood, J P; Woody, C L; Wright, R M; Wysocki, M; Xie, W; Yamaguchi, Y L; Yamaura, K; Yang, R; Yanovich, A; Ying, J; Yokkaichi, S; You, Z; Young, G R; Younus, I; Yushmanov, I E; Zajc, W A; Zhang, C; Zhou, S; Zolin, L

2014-06-01

41

Azimuthal-Angle Dependence of Charged-Pion-Interferometry Measurements with Respect to Second- and Third-Order Event Planes in Au +Au Collisions at ?sNN =200 GeV  

NASA Astrophysics Data System (ADS)

Charged-pion-interferometry measurements were made with respect to the second- and third-order event plane for Au +Au collisions at ?sNN =200 GeV. A strong azimuthal-angle dependence of the extracted Gaussian-source radii was observed with respect to both the second- and third-order event planes. The results for the second-order dependence indicate that the initial eccentricity is reduced during the medium evolution, which is consistent with previous results. In contrast, the results for the third-order dependence indicate that the initial triangular shape is significantly reduced and potentially reversed by the end of the medium evolution, and that the third-order oscillations are largely dominated by the dynamical effects from triangular flow.

Adare, A.; Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Al-Bataineh, H.; Alexander, J.; Aoki, K.; Aramaki, Y.; Atomssa, E. T.; Averbeck, R.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Baksay, G.; Baksay, L.; Barish, K. N.; Bassalleck, B.; Basye, A. T.; Bathe, S.; Baublis, V.; Baumann, C.; Bazilevsky, A.; Belikov, S.; Belmont, R.; Bennett, R.; Berdnikov, A.; Berdnikov, Y.; Bickley, A. A.; Bok, J. S.; Boyle, K.; Brooks, M. L.; Buesching, H.; Bumazhnov, V.; Bunce, G.; Butsyk, S.; Camacho, C. M.; Campbell, S.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choudhury, R. K.; Christiansen, P.; Chujo, T.; Chung, P.; Chvala, O.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Connors, M.; Constantin, P.; Csanád, M.; Csörg?, T.; Dahms, T.; Dairaku, S.; Danchev, I.; Das, K.; Datta, A.; David, G.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Dietzsch, O.; Dion, A.; Donadelli, M.; Drapier, O.; Drees, A.; Drees, K. A.; Durham, J. M.; Durum, A.; Dutta, D.; Edwards, S.; Efremenko, Y. V.; Ellinghaus, F.; Engelmore, T.; Enokizono, A.; En'yo, H.; Esumi, S.; Fadem, B.; Fields, D. E.; Finger, M.; Finger, M.; Fleuret, F.; Fokin, S. L.; Fraenkel, Z.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fujiwara, K.; Fukao, Y.; Fusayasu, T.; Garishvili, I.; Glenn, A.; Gong, H.; Gonin, M.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gunji, T.; Gustafsson, H.-Ĺ.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamblen, J.; Han, R.; Hanks, J.; Hartouni, E. P.; Haslum, E.; Hayano, R.; He, X.; Heffner, M.; Hemmick, T. K.; Hester, T.; Hill, J. C.; Hohlmann, M.; Holzmann, W.; Homma, K.; Hong, B.; Horaguchi, T.; Hornback, D.; Huang, S.; Ichihara, T.; Ichimiya, R.; Ide, J.; Ikeda, Y.; Imai, K.; Inaba, M.; Isenhower, D.; Ishihara, M.; Isobe, T.; Issah, M.; Isupov, A.; Ivanischev, D.; Jacak, B. V.; Jia, J.; Jin, J.; Johnson, B. M.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kajihara, F.; Kametani, S.; Kamihara, N.; Kamin, J.; Kang, J. H.; Kapustinsky, J.; Karatsu, K.; Kawall, D.; Kawashima, M.; Kazantsev, A. V.; Kempel, T.; Khanzadeev, A.; Kijima, K. M.; Kim, B. I.; Kim, D. H.; Kim, D. J.; Kim, E.; Kim, E.-J.; Kim, S. H.; Kim, Y.-J.; Kinney, E.; Kiriluk, K.; Kiss, Á.; Kistenev, E.; Kochenda, L.; Komkov, B.; Konno, M.; Koster, J.; Kotchetkov, D.; Kozlov, A.; Král, A.; Kravitz, A.; Kunde, G. J.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Kyle, G. S.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lebedev, A.; Lee, D. M.; Lee, J.; Lee, K.; Lee, K. B.; Lee, K. S.; Leitch, M. J.; Leite, M. A. L.; Leitner, E.; Lenzi, B.; Li, X.; Liebing, P.; Linden Levy, L. A.; Liška, T.; Litvinenko, A.; Liu, H.; Liu, M. X.; Love, B.; Luechtenborg, R.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Malakhov, A.; Malik, M. D.; Manko, V. I.; Mannel, E.; Mao, Y.; Masui, H.; Matathias, F.; McCumber, M.; McGaughey, P. L.; Means, N.; Meredith, B.; Miake, Y.; Mignerey, A. C.; Mikeš, P.; Miki, K.; Milov, A.; Mishra, M.; Mitchell, J. T.; Mohanty, A. K.; Morino, Y.; Morreale, A.; Morrison, D. P.; Moukhanova, T. V.; Murata, J.; Nagamiya, S.; Nagle, J. L.; Naglis, M.; Nagy, M. I.; Nakagawa, I.; Nakamiya, Y.; Nakamura, T.; Nakano, K.; Newby, J.; Nguyen, M.; Niida, T.; Nouicer, R.; Nyanin, A. S.; O'Brien, E.; Oda, S. X.; Ogilvie, C. A.; Oka, M.; Okada, K.; Onuki, Y.; Oskarsson, A.; Ouchida, M.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, I. H.; Park, J.; Park, S. K.; Park, W. J.; Pate, S. F.; Pei, H.; Peng, J.-C.; Pereira, H.; Peresedov, V.; Peressounko, D. Yu.; Pinkenburg, C.; Pisani, R. P.; Proissl, M.; Purschke, M. L.; Purwar, A. K.; Qu, H.; Rak, J.; Rakotozafindrabe, A.; Ravinovich, I.; Read, K. F.; Reygers, K.; Riabov, V.; Riabov, Y.; Richardson, E.; Roach, D.; Roche, G.; Rolnick, S. D.; Rosati, M.; Rosen, C. A.; Rosendahl, S. S. E.; Rosnet, P.; Rukoyatkin, P.; Ruži?ka, P.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sakashita, K.; Samsonov, V.; Sano, S.; Sato, T.; Sawada, S.; Sedgwick, K.; Seele, J.; Seidl, R.; Semenov, A. Yu.; Seto, R.; Sharma, D.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Silvestre, C.; Sim, K. S.; Singh, B. K.; Singh, C. P.; Singh, V.; Slune?ka, M.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Sparks, N. A.; Stankus, P. W.; Stenlund, E.; Stoll, S. P.; Sugitate, T.; Sukhanov, A.; Sziklai, J.; Takagui, E. M.; Taketani, A.; Tanabe, R.; Tanaka, Y.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarján, P.; Themann, H.; Thomas, T. L.; Todoroki, T.; Togawa, M.; Toia, A.; Tomášek, L.; Torii, H.; Towell, R. S.; Tserruya, I.; Tsuchimoto, Y.; Vale, C.; Valle, H.; van Hecke, H. W.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Vinogradov, A. A.; Virius, M.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, K.

2014-06-01

42

Particle-type dependence of azimuthal anisotropy and nuclear modification of particle production in Au+Au collisions at square root of sNN=200 GeV.  

PubMed

We present STAR measurements of the azimuthal anisotropy parameter v(2) and the binary-collision scaled centrality ratio R(CP) for kaons and lambdas (Lambda+Lambda) at midrapidity in Au+Au collisions at square root of s(NN)=200 GeV. In combination, the v(2) and R(CP) particle-type dependencies contradict expectations from partonic energy loss followed by standard fragmentation in vacuum. We establish p(T) approximately 5 GeV/c as the value where the centrality dependent baryon enhancement ends. The K(0)(S) and Lambda+Lambda v(2) values are consistent with expectations of constituent-quark-number scaling from models of hadron formation by parton coalescence or recombination. PMID:14995300

Adams, J; Adler, C; Aggarwal, M M; Ahammed, Z; Amonett, J; Anderson, B D; Anderson, M; Arkhipkin, D; Averichev, G S; Badyal, S K; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellwied, R; Berger, J; Bezverkhny, B I; Bhardwaj, S; Bhaskar, P; Bhati, A K; Bichsel, H; Billmeier, A; Bland, L C; Blyth, C O; Bonner, B E; Botje, M; Boucham, A; Brandin, A; Bravar, A; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca Sánchez, M; Carroll, J; Castillo, J; Castro, M; Cebra, D; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, Y; Chernenko, S P; Cherney, M; Chikanian, A; Choi, B; Christie, W; Coffin, J P; Cormier, T M; Cramer, J G; Crawford, H J; Das, D; Das, S; Derevschikov, A A; Didenko, L; Dietel, T; Dong, W J; Dong, X; Draper, J E; Du, F; Dubey, A K; Dunin, V B; Dunlop, J C; Dutta Majumdar, M R; Eckardt, V; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Estienne, M; Fachini, P; Faine, V; Faivre, J; Fatemi, R; Filimonov, K; Filip, P; Finch, E; Fisyak, Y; Flierl, D; Foley, K J; Fu, J; Gagliardi, C A; Gagunashvili, N; Gans, J; Ganti, M S; Gaudichet, L; Germain, M; Geurts, F; Ghazikhanian, V; Ghosh, P; Gonzalez, J E; Grachov, O; Grigoriev, V; Gronstal, S; Grosnick, D; Guedon, M; Guertin, S M; Gupta, A; Gushin, E; Gutierrez, T D; Hallman, T J; Hardtke, D; Harris, J W; Heinz, M; Henry, T W; Heppelmann, S; Herston, T; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horsley, M; Huang, H Z; Huang, S L; Humanic, T J; Igo, G; Ishihara, A; Jacobs, P; Jacobs, W W; Janik, M; Jiang, H; Johnson, I; Jones, P G; Judd, E G; Kabana, S; Kaneta, M; Kaplan, M; Keane, D; Khodyrev, V Yu; Kiryluk, J; Kisiel, A; Klay, J; Klein, S R; Klyachko, A; Koetke, D D; Kollegger, T; Kopytine, M; Kotchenda, L; Kovalenko, A D; Kramer, M; Kravtsov, P; Kravtsov, V I; Krueger, K; Kuhn, C; Kulikov, A I; Kumar, A; Kunde, G J; Kunz, C L; Kutuev, R Kh; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; Lansdell, C P; Lasiuk, B; Laue, F; Lauret, J; Lebedev, A; Lednický, R; LeVine, M J; Li, C; Li, Q; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Z; Liu, Q J; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Ludlam, T; Lynn, D; Ma, J; Ma, Y G; Magestro, D; Mahajan, S; Mangotra, L K; Mahapatra, D P; Majka, R; Manweiler, R; Margetis, S; Markert, C; Martin, L; Marx, J; Matis, H S; Matulenko, Yu A; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Messer, M; Miller, M L; Milosevich, Z; Minaev, N G; Mironov, C; Mishra, D; Mitchell, J; Mohanty, B; Molnar, L; Moore, C F; Mora-Corral, M J; Morozov, D A; Morozov, V; de Moura, M M; Munhoz, M G; Nandi, B K; Nayak, S K; Nayak, T K; Nelson, J M; Nevski, P; Nikitin, V A; Nogach, L V; Norman, B; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Paic, G; Pandey, S U; Pal, S K; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Perevoztchikov, V; Perkins, C; Peryt, W; Petrov, V A; Phatak, S C; Picha, R; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potekhin, M; Potrebenikova, E; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Rai, G; Rakness, G; Raniwala, R; Raniwala, S; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Ruan, L J; Sahoo, R; Sakrejda, I; Salur, S; Sandweiss, J; Savin, I; Schambach, J; Scharenberg, R P; Schmitz, N; Schroeder, L S; Schweda, K; Seger, J; Seliverstov, D; Seyboth, P; Shahaliev, E; Shao, M; Sharma, M; Shestermanov, K E; Shimanskii, S S; Singaraju, R N; Simon, F; Skoro, G; Smirnov, N; Snellings, R; Sood, G; Sorensen, P; Sowinski, J; Spinka, H M; Srivastava, B; Stanislaus, S; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Struck, C; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; de Toledo, A Szanto; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Thein, D; Thomas, J H; Tikhomirov, V; Tokarev, M; Tonjes, M B; Trainor, T A; Trentalange, S; Tribble, R E; Trivedi, M D; Trofimov, V; Tsai, O; Ullrich, T; Underwood, D G; Van Buren, G; VanderMolen, A M; Vasiliev, A N; Vasiliev, M; Vigdor, S E; Viyogi, Y P; Voloshin, S A; Waggoner, W; Wang, F; Wang, G; Wang, X L; Wang, Z M; Ward, H; Watson, J W; Wells, R; Westfall, G D; Whitten, C; Wieman, H; Willson, R; Wissink, S W; Witt, R; Wood, J; Wu, J; Xu, N; Xu, Z; Xu, Z Z; Yamamoto, E; Yepes, P; Yurevich, V I; Zanevski, Y V; Zborovský, I; Zhang, H; Zhang, W M; Zhang, Z P; Zo?nierczuk, P A; Zoulkarneev, R; Zoulkarneeva, J; Zubarev, A N

2004-02-01

43

XPORT Dependent Transport of TRP and Rhodopsin  

PubMed Central

SUMMARY TRP channels have emerged as key biological sensors in vision, taste, olfaction, hearing and touch. Despite their importance, virtually nothing is known about the folding and transport of TRP channels during biosynthesis. Here, we identify XPORT (exit protein of rhodopsin and TRP) as a critical chaperone for TRP and its G-protein coupled receptor (GPCR), rhodopsin (Rh1). XPORT is a resident ER and secretory pathway protein that interacts with TRP and Rh1, as well as with Hsp27 and Hsp90. XPORT promotes the targeting of TRP to the membrane in Drosophila S2 cells, a finding that provides a critical first step towards solving a longstanding problem in the successful heterologous expression of TRP. Mutations in xport result in defective transport of TRP and Rh1, leading to retinal degeneration. Our results identify XPORT as a novel molecular chaperone and provide a mechanistic link between TRP channels and their GPCRs during biosynthesis and transport.

Rosenbaum, Erica E.; Brehm, Kimberley S.; Vasiljevic, Eva; Liu, Che-Hsiung; Hardie, Roger C.; Colley, Nansi Jo

2011-01-01

44

Azimuthal Anisotropy of ?0 Production in Au+Au Collisions at sNN=200GeV: Path-Length Dependence of Jet Quenching and the Role of Initial Geometry  

NASA Astrophysics Data System (ADS)

We have measured the azimuthal anisotropy of ?0 production for 1dependence steeper than what is implied by current PQCD energy-loss models show reasonable agreement with the data.

Adare, A.; Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Al-Bataineh, H.; Alexander, J.; Aoki, K.; Aramaki, Y.; Atomssa, E. T.; Averbeck, R.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Baksay, G.; Baksay, L.; Barish, K. N.; Bassalleck, B.; Basye, A. T.; Bathe, S.; Baublis, V.; Baumann, C.; Bazilevsky, A.; Belikov, S.; Belmont, R.; Bennett, R.; Berdnikov, A.; Berdnikov, Y.; Bickley, A. A.; Bok, J. S.; Boyle, K.; Brooks, M. L.; Buesching, H.; Bumazhnov, V.; Bunce, G.; Butsyk, S.; Camacho, C. M.; Campbell, S.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choudhury, R. K.; Christiansen, P.; Chujo, T.; Chung, P.; Chvala, O.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Connors, M.; Constantin, P.; Csanád, M.; Csörg?, T.; Dahms, T.; Dairaku, S.; Danchev, I.; Das, K.; Datta, A.; David, G.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Dietzsch, O.; Dion, A.; Donadelli, M.; Drapier, O.; Drees, A.; Drees, K. A.; Durham, J. M.; Durum, A.; Dutta, D.; Edwards, S.; Efremenko, Y. V.; Ellinghaus, F.; Engelmore, T.; Enokizono, A.; En'Yo, H.; Esumi, S.; Fadem, B.; Fields, D. E.; Finger, M., Jr.; Finger, M.; Fleuret, F.; Fokin, S. L.; Fraenkel, Z.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fujiwara, K.; Fukao, Y.; Fusayasu, T.; Garishvili, I.; Glenn, A.; Gong, H.; Gonin, M.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gunji, T.; Gustafsson, H.-Ĺ.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamblen, J.; Hanks, J.; Han, R.; Hartouni, E. P.; Haslum, E.; Hayano, R.; Heffner, M.; Hegyi, S.; Hemmick, T. K.; Hester, T.; He, X.; Hill, J. C.; Hohlmann, M.; Holzmann, W.; Homma, K.; Hong, B.; Horaguchi, T.; Hornback, D.; Huang, S.; Ichihara, T.; Ichimiya, R.; Ide, J.; Ikeda, Y.; Imai, K.; Inaba, M.; Isenhower, D.; Ishihara, M.; Isobe, T.; Issah, M.; Isupov, A.; Ivanischev, D.; Jacak, B. V.; Jia, J.; Jin, J.; Johnson, B. M.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kajihara, F.; Kametani, S.; Kamihara, N.; Kamin, J.; Kang, J. H.; Kapustinsky, J.; Karatsu, K.; Kawall, D.; Kawashima, M.; Kazantsev, A. V.; Kempel, T.; Khanzadeev, A.; Kijima, K. M.; Kim, B. I.; Kim, D. H.; Kim, D. J.; Kim, E. J.; Kim, E.; Kim, S. H.; Kim, Y. J.; Kinney, E.; Kiriluk, K.; Kiss, Á.; Kistenev, E.; Kochenda, L.; Komkov, B.; Konno, M.; Koster, J.; Kotchetkov, D.; Kozlov, A.; Král, A.; Kravitz, A.; Kunde, G. J.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Kyle, G. S.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lebedev, A.; Lee, D. M.; Lee, J.; Lee, K. B.; Lee, K.; Lee, K. S.; Leitch, M. J.; Leite, M. A. L.; Leitner, E.; Lenzi, B.; Liebing, P.; Linden Levy, L. A.; Liška, T.; Litvinenko, A.; Liu, H.; Liu, M. X.; Li, X.; Love, B.; Luechtenborg, R.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Malakhov, A.; Malik, M. D.; Manko, V. I.; Mannel, E.; Mao, Y.; Masui, H.; Matathias, F.; McCumber, M.; McGaughey, P. L.; Means, N.; Meredith, B.; Miake, Y.; Mignerey, A. C.; Mikeš, P.; Miki, K.; Milov, A.; Mishra, M.; Mitchell, J. T.; Mohanty, A. K.; Morino, Y.; Morreale, A.; Morrison, D. P.; Moukhanova, T. V.; Murata, J.; Nagamiya, S.; Nagle, J. L.; Naglis, M.; Nagy, M. I.; Nakagawa, I.; Nakamiya, Y.; Nakamura, T.; Nakano, K.; Newby, J.; Nguyen, M.; Nouicer, R.; Nyanin, A. S.; O'Brien, E.; Oda, S. X.; Ogilvie, C. A.; Okada, K.; Oka, M.; Onuki, Y.; Oskarsson, A.; Ouchida, M.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, I. H.; Park, J.; Park, S. K.; Park, W. J.; Pate, S. F.; Pei, H.; Peng, J.-C.; Pereira, H.; Peresedov, V.; Peressounko, D. Yu.; Pinkenburg, C.; Pisani, R. P.; Proissl, M.; Purschke, M. L.; Purwar, A. K.; Qu, H.; Rak, J.; Rakotozafindrabe, A.; Ravinovich, I.; Read, K. F.; Reygers, K.; Riabov, V.; Riabov, Y.; Richardson, E.; Roach, D.; Roche, G.; Rolnick, S. D.; Rosati, M.; Rosen, C. A.; Rosendahl, S. S. E.; Rosnet, P.; Rukoyatkin, P.; Ruži?ka, P.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sakashita, K.; Samsonov, V.; Sano, S.; Sato, T.; Sawada, S.; Sedgwick, K.; Seele, J.; Seidl, R.; Semenov, A. Yu.; Seto, R.; Sharma, D.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Silvestre, C.; Sim, K. S.; Singh, B. K.; Singh, C. P.; Singh, V.; Slune?ka, M.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Sparks, N. A.; Stankus, P. W.; Stenlund, E.; Stoll, S. P.; Sugitate, T.; Sukhanov, A.; Sziklai, J.; Takagui, E. M.; Taketani, A.; Tanabe, R.; Tanaka, Y.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarján, P.; Themann, H.; Thomas, T. L.; Togawa, M.; Toia, A.; Tomášek, L.; Torii, H.; Towell, R. S.; Tserruya, I.; Tsuchimoto, Y.; Vale, C.; Valle, H.; van Hecke, H. W.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Vinogradov, A. A.; Virius, M.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, K.

2010-10-01

45

Aspects of Tmd Evolution of Azimuthal Asymmetries  

NASA Astrophysics Data System (ADS)

In this contribution TMD evolution of azimuthal asymmetries, in particular of the Sivers and double Collins asymmetries, is addressed. A comparison of the scale dependence is made between asymmetries described with TMD factorization at low transverse momentum and those described with collinear factorization at high transverse momentum. Finally, the advantages of Bessel weighting are discussed: convergence of transverse momentum integrals, suppression of large transverse momentum contributions, and well-defined lattice QCD evaluations of Bessel-weighted TMDs including proper gauge links.

Boer, Daniël

2014-01-01

46

Unpolarized azimuthal asymmetries in SIDIS at COMPASS  

NASA Astrophysics Data System (ADS)

The study of the spin structure of the nucleon and of the effects due to the quarks transverse momentum are part of the scientific program of COMPASS, a fixed target experiment at the CERN SPS. The azimuthal modulations which appear in the cross-section of SIDIS off unpolarised targets give insight on the intrinsic momentum structure of the nucleon and on the possible correlation between transverse spin and transverse momentum of the quarks. We present the results for the amplitudes of the cos(?), cos(2?), and sin(?) modulatuions (where ? is the azimuthal hadron angle in the gamma-nucleon system) obtained from the COMPASS data collected with a 160 GeV/c positive muon beam impinging on a deuteron target. The amplitudes are measured for both positive and negative hadrons, and the results on the dependence of the relevant kinematical variables obtained after a multi dimensional analysis are also presented.

Sbrizzai, G.

2014-01-01

47

Time-dependent density functional theory for quantum transport  

NASA Astrophysics Data System (ADS)

The rapid miniaturization of electronic devices motivates research interests in quantum transport. Recently time-dependent quantum transport has become an important research topic. Here we review recent progresses in the development of time-dependent density-functional theory for quantum transport including the theoretical foundation and numerical algorithms. In particular, the reduced-single electron density matrix based hierarchical equation of motion, which can be derived from Liouville-von Neumann equation, is reviewed in details. The numerical implementation is discussed and simulation results of realistic devices will be given.

Kwok, Yanho; Zhang, Yu; Chen, GuanHua

2013-07-01

48

Azimuthal Frustration and Bundling in Columnar DNA Aggregates  

PubMed Central

The interaction between two stiff parallel DNA molecules is discussed using linear Debye-Hückel screening theory with and without inclusion of the dielectric discontinuity at the DNA surface, taking into account the helical symmetry of DNA. The pair potential furthermore includes the amount and distribution of counterions adsorbed on the DNA surface. The interaction does not only depend on the interaxial separation of two DNA molecules, but also on their azimuthal orientation. The optimal mutual azimuthal angle is a function of the DNA-DNA interaxial separation, which leads to azimuthal frustrations in an aggregate. On the basis of the pair potential, the positional and orientational order in columnar B-DNA assemblies in solution is investigated. Phase diagrams are calculated using lattice sums supplemented with the entropic contributions of the counterions in solution. A variety of positionally and azimuthally ordered phases and bundling transitions is predicted, which strongly depend on the counterion adsorption patterns.

Harreis, H. M.; Likos, C. N.; Lowen, H.

2003-01-01

49

Flavor Dependence of the Boer-Mulders Function and its Influence on Azimuthal and Single-Spin Asymmetries in Semi-Inclusive Dis  

Microsoft Academic Search

The chiral-odd and time reversal-odd transverse momentum dependent (TMD) parton distribution h?1, the so-called Boer-Mulders function, is calculated in the diquark spectator model for both an active up- and down-quark. In particular the signs of h?(u)1 and h?(d)1 are of interest as they were predicted in other works, and the result of this analysis is consistent with these predictions. Both

Leonard P. Gamberg; Gary R. Goldstein; Marc Schlegel

2008-01-01

50

Experimental Investigation of the Magnetic Configuration Dependence of Turbulent Transport  

NASA Astrophysics Data System (ADS)

The dependence of turbulent transport on magnetic field properties is measured in detail on a plasma in a stellarator configuration. Pronounced poloidal asymmetries of fluctuation amplitudes and turbulent transport are observed. The transport maximum is located in regions where normal curvature of the magnetic field is negative and simultaneously the geodesic curvature has positive values. A major role of the local magnetic shear cannot be confirmed. The results can have important implications for the optimization of stellarators and the power influx into the scrape-off layer.

Birkenmeier, G.; Ramisch, M.; Manz, P.; Nold, B.; Stroth, U.

2011-07-01

51

Controllable spin-dependent transport in armchair graphene nanoribbon structures  

Microsoft Academic Search

Using the non-equilibrium Green's functions formalism in a tight binding\\u000amodel, the spin-dependent transport in armchair graphene nanoribbon (GNR)\\u000astructures controlled by a ferromagnetic gate is investigated. Beyond the\\u000aoscillatory behavior of conductance and spin polarization with respect to the\\u000abarrier height, which can be tuned by the gate voltage, we especially analyze\\u000athe effect of width-dependent band gap and

V. Hung Nguyen; V. Nam Do; A. Bournel; V. Lien Nguyen; P. Dollfus

2009-01-01

52

Heavy-flavor azimuthal correlations of D mesons  

NASA Astrophysics Data System (ADS)

Observables of heavy-quark azimuthal correlations in heavy-ion collisions are new and promising probes for the investigation of the in-medium energy loss. We explore the potential of these observables to discriminate the collisional and radiative contributions within a hybrid EPOS+MC@sHQ transport approach.

Nahrgang, Marlene; Aichelin, Jörg; Gossiaux, Pol Bernard; Werner, Klaus

2014-05-01

53

Differentiating anisotropy and lateral effects using azimuthal resistivity offset Wenner soundings  

Microsoft Academic Search

The flow regimes and chemical processes associated with fracture networks are complex and, hence, have considerable implications as regards waste disposal, groundwater protection, and contaminant transport. Azimuthal resistivity surveys increasingly are being used by hydrogeologists in the identification and characterization of fractured rocks. In these investigations, electrical resistivity is measured as a function of azimuth about a fixed central point.

Kathryn A. Watson; Ron D. Barker

1999-01-01

54

Electrogenic sodium-dependent glycine transport in sheep reticulocytes.  

PubMed

Na+-dependent glycine transport has been studied in reticulocyte-enriched fractions of blood obtained after massive bleeding of sheep. The activity is dependent on the sodium electrochemical potential and the membrane potential. The sodium chemical gradient was varied by changing either external or internal Na+ and the membrane potential, by addition of valinomycin. Similar results were obtained with resealed reticulocyte ghosts. Under conditions optimal for sodium pumping (intracellular Na+ greater than 50mM), ouabain inhibited glycine uptake prior to any measurable change in the cellular Na+ suggesting that in these cells an electrogenic sodium pump is sufficiently active to contribute to the membrane potential. Na+-dependent glycine transport undergoes a marked decrease during long-term incubation at 37 degrees C. During this time, the cells maintain their integrity and ATP content but undergo maturation as evidenced in the decrease in cells with reticulocyte morphology. PMID:667699

Benderoff, S; Johnstone, R M; Blostein, R

1978-06-01

55

Microfluidic-enabled liposomes elucidate size-dependent transdermal transport.  

PubMed

Microfluidic synthesis of small and nearly-monodisperse liposomes is used to investigate the size-dependent passive transdermal transport of nanoscale lipid vesicles. While large liposomes with diameters above 105 nm are found to be excluded from deeper skin layers past the stratum corneum, the primary barrier to nanoparticle transport, liposomes with mean diameters between 31-41 nm exhibit significantly enhanced penetration. Furthermore, multicolor fluorescence imaging reveals that the smaller liposomes pass rapidly through the stratum corneum without vesicle rupture. These findings reveal that nanoscale liposomes with well-controlled size and minimal size variance are excellent vehicles for transdermal delivery of functional nanoparticle drugs. PMID:24658111

Hood, Renee R; Kendall, Eric L; Junqueira, Mariana; Vreeland, Wyatt N; Quezado, Zenaide; Finkel, Julia C; DeVoe, Don L

2014-01-01

56

Microfluidic-Enabled Liposomes Elucidate Size-Dependent Transdermal Transport  

PubMed Central

Microfluidic synthesis of small and nearly-monodisperse liposomes is used to investigate the size-dependent passive transdermal transport of nanoscale lipid vesicles. While large liposomes with diameters above 105 nm are found to be excluded from deeper skin layers past the stratum corneum, the primary barrier to nanoparticle transport, liposomes with mean diameters between 31–41 nm exhibit significantly enhanced penetration. Furthermore, multicolor fluorescence imaging reveals that the smaller liposomes pass rapidly through the stratum corneum without vesicle rupture. These findings reveal that nanoscale liposomes with well-controlled size and minimal size variance are excellent vehicles for transdermal delivery of functional nanoparticle drugs.

Junqueira, Mariana; Vreeland, Wyatt N.; Quezado, Zenaide; Finkel, Julia C.; DeVoe, Don L.

2014-01-01

57

[Sodium-dependent inorganic phosphate transporters and biomineralization].  

PubMed

Phosphate (Pi), one of most abundant anions in living organisms, plays a crucial role in biomineralization. An adequate plasma Pi concentration is required to maintain the calcium × phosphate ion product within a range sufficient for physiological bone mineralization, but an increase in the calcium × phosphate product in extracellular fluids above a certain threshold can predispose to extraskeletal calcification. Membrane transport systems for Pi transport are key elements in maintaining homeostasis of Pi in organisms. Members of two families of solute carrier (SLC) proteins (SLC20 and SLC34) act as Na? -dependent, secondary-active cotransporters to transport Pi across cell membranes in mammals. This review summarizes the role of SLC20 and SCL34 proteins on biomineralization. PMID:24473358

Tatsumi, Sawako; Fujii, Osamu; Miyagawa, Atsumi; Miyamoto, Kenichi

2014-02-01

58

Engineering interband transport by time-dependent disorder  

SciTech Connect

We show how the evolution of atoms in a tilted lattice can be changed and controlled by phase noise on the lattice. Dependent on the characteristic parameters of the noise, the interband transport can be either suppressed or enhanced, which is of interest for very precise control in experiments with Bose-Einstein condensates. The effect of the noise on the survival probability in the ground band is summarized in a scaling plot, stressing the universality of our results.

Tayebirad, Ghazal [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 19, D-69120 Heidelberg (Germany); Mannella, Riccardo [Dipartimento di Fisica ''E. Fermi,'' Universita di Pisa, Largo Pontecorvo 3, I-56127 Pisa (Italy); Wimberger, Sandro [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 19, D-69120 Heidelberg (Germany); Heidelberg Center for Quantum Dynamics, Philosophenweg 12, D-69120 Heidelberg (Germany)

2011-09-15

59

CFTR-Dependent Anion Transport in Airway Epithelia  

Microsoft Academic Search

\\u000a Vertebrates use a variety of anion transport systems to drive transepithelial fluid secretion, each regulated by distinct\\u000a second messenger systems. Tissues such as the pancreatic duct and colon respond to peptide hormones and transmitters that\\u000a elevate intracellular levels of cAMP or cGMP (see Chap. 9 by J. F. White, this volume), whereas most exocrine glands have\\u000a a dominant calcium-dependent system,

J. W. Hanrahan

60

Iontophoretic transport pathways: dependence on penetrant physicochemical properties.  

PubMed

The objective of this work was to investigate how the preferred iontophoretic transport pathways of a molecule depend on its physicochemical properties. Laser scanning confocal microscopy (LSCM) was used to visualize in hairless mouse skin the distribution of two fluorescent penetrants: calcein, a multiply charged (-4), hydrophilic molecule; and nile red, a lipophilic, neutral compound. Iontophoresis and passive delivery of nile red showed that the percutaneous transport of this compound occurred via (inter- and intracellular) pathways that were clearly distinct from those followed by calcein. Although the distribution of nile red was influenced somewhat by the passage of current relative to the passive control, there was relatively little enhancement of the penetration of this compound into the skin. Calcein, on the other hand, did not passively enter the skin. However, with iontophoresis, greatly enhanced transport, with an important contribution from follicular structures, was observed. Sequential (dual) transport of the two fluorophores illustrated clearly the different pathways followed and reflected the transport and visualization studies of the individual species. It may be concluded, therefore, that the iontophoretic pathways followed across the skin are dictated by the physicochemical properties of the penetrant and by its affinity for the different environments available. PMID:9423151

Turner, N G; Guy, R H

1997-12-01

61

Scatterometer azimuthal response and wind wave directionality  

NASA Technical Reports Server (NTRS)

Azimuthal response of a scatterometer to radiation scattered by the sea surface was studied in a wind-wave tank. The variation of the normalized radar cross section with the azimuth angle is fitted by a three-term series. Results show that the upwind-downwind asymmetry decreases as the wind speed increases. The crosswind modulation depends on the wind velocity. The results show that the evolution of the long-wind-crosswind ratio evolves with wind speed in a manner similar to the evolution of the isotropy of short capillary-gravity waves. The maximum of the isotropy of the short wind waves is obtained for wind velocities close to 4 m/s. For the same value of the velocity, the variations of radar response between long-wind and crosswind directions is minimum. For lower or higher values of wind velocities the directional accuracy of the radar increases, since the wind-wave field tends to align in the wind direction.

Giovanangeli, J. P.; Le Calve, O.; Bliven, L.

1989-01-01

62

Direct Observation of Azimuthal Correlations between DNA in Hydrated Aggregates  

SciTech Connect

This study revisits the classical x-ray diffraction patterns from hydrated, noncrystalline fibers originally used to establish the helical structure of DNA. We argue that changes in these diffraction patterns with DNA packing density reveal strong azimuthally dependent interactions between adjacent molecules up to {approx}40 A interaxial or {approx}20 A surface-to-surface separations. These interactions appear to force significant torsional 'straightening' of DNA and strong azimuthal alignment of nearest neighbor molecules. The results are in good agreement with the predictions of recent theoretical models relating DNA-DNA interactions to the helical symmetry of their surface charge patterns.

Kornyshev, Alexei A.; Lee, Dominic J.; Wynveen, Aaron [Department of Chemistry, Imperial College London, SW7 2AZ London (United Kingdom); Leikin, Sergey [Section on Physical Biochemistry, NICHD, NIH, DHHS, Bethesda, Maryland 20892 (United States); Zimmerman, Steven B. [Laboratory of Molecular Biology, NIDDK, NIH, DHHS, Bethesda, Maryland 20892 (United States)

2005-09-30

63

Mode switching in a gyrotron with azimuthally corrugated resonator.  

PubMed

The operation of a gyrotron having a cylindrical resonator with an azimuthally corrugated wall is analyzed. In such a device, wall corrugation cancels the degeneracy of the modes with azimuthally standing patterns. The coupling between these modes depends on the radius of electron beam. It is shown that such a gyrotron can be easily switched from one mode to another. When the switching is done with the repetition frequency equal to the rotational frequency of magnetic islands, this sort of operation can be used for suppression of neoclassical tearing modes in large-scale tokamaks and stellarators. PMID:17677705

Nusinovich, G S; Sinitsyn, O V; Antonsen, T M

2007-05-18

64

AzimuthElevation Estimation Performance of a Spatially Dispersive Channel  

Microsoft Academic Search

A model is presented for the estimation of azimuth and elevation in a dispersive media where the signals come from a continuum of directions. These bounds depend upon the array ambiguity patterns and the channel spread function. Specific cases are discussed showing how the result reduces to an easily tractable analytical tool in many cases of interest. The model discussed

Terrence McGarty

1974-01-01

65

Activity-Dependent Regulation of Surface Glucose Transporter-3  

PubMed Central

Glucose transporter 3 (GLUT3) is the main facilitative glucose transporter in neurons. Glucose provides neurons with a critical energy source for neuronal activity. However, the mechanism by which neuronal activity controls glucose influx via GLUT3 is unknown. We investigated the influence of synaptic stimulation on GLUT3 surface expression and glucose import in primary cultured cortical and hippocampal neurons. Synaptic activity increased surface expression of GLUT3 leading to an elevation of intracellular glucose. The effect was blocked by N-Methyl-D-Aspartate receptor (NMDAR) and neuronal nitric oxide synthase (nNOS) inhibition. The Akt Inhibitor, Akt-I blocked NMDAR-induced GLUT3 surface expression while a nNOS-phosphomimetic mutant (S1412D) enhanced GLUT3 expression at cell surface. These results suggest that NMDAR/Akt-dependent nNOS phosphorylation is coupled to GLUT3 trafficking. We demonstrated that activation of cGMP-dependent protein kinase (cGK) increased the surface expression of GLUT3, which was repressed by Rp-8-pCPT-cGMPS, a potent cell permeable inhibitor of cGKs. These studies characterize the molecular basis for activity dependent increases in surface GLUT3 after stimulation of the NMDARs. NMDAR-induced increase in surface GLUT3 represents a novel pathway for control of energy supply during neuronal activity that is critical for maintaining glucose homeostasis during neuronal transmission.

Ferreira, Jainne M.; Burnett, Arthur L.; Rameau, Gerald A.

2011-01-01

66

Influences of electron spin ordering on spin dependent transport  

NASA Astrophysics Data System (ADS)

Spintronics is an emerging field in research and technology. The additional spin degree of freedom allows one to design devices with novel and superior performances. A good understanding of the spin transport process is necessary for achieving such goals. In this thesis we investigate the effects of electron spin ordering on spin dependent transport processes in micron-sized devices. In a disordered metallic system, the spontaneous spin ordering leads to an extraordinary Hall voltage transverse to the initial electron transport direction, and the voltage is proportional to the degree of ordering in the spin orientations. We use large amount of doping with heavy impurity atom (Pt) in ferromagnetic metals (Fe, Co, Ni, etc.), as well as reduce the film thickness down to the nanometer range in order to increase spin-orbit scatterings. We have observed record-high Hall slope (22.6muOˇcm/T at room temperature). In a well ordered epitaxial rutile system (CrO2/SnO 2), there still exist disorders on the order of ppm levels. The completely polarized spin current forming in the half-metal CrO2 are losing part of their spin polarizations after passing the SnO2 barrier, and limited TMR values (?14%) were observed in CrO2/SnO 2/Co MTJs at l0K. Interestingly, we have observed that the sign of Co spin polarization can be reversed by shifting the surface chemical bonding or applying sufficient bias voltage. The latter is an effect due to the disordered states inside SnO2 barrier. In the case of spin transport that maintains complete spin coherence (CoFeB/MgO/CoFeB), both the spin orientations and the momentum states of electrons are conserved across the MgO barrier, and a significant signal boost is immediately achieved with the realization of coherent spin tunneling. We explain the coexistence of low RA and nearly flat temperature/bias dependence of junction resistance with Butler's model. Detailed analysis on these junctions reveals existence of inelastic tunneling processes despite the nearly perfect band matches. In summary, we have studied spin transport in disordered, ordered, and completely coherent systems, and the manipulation of spin dependent scatterings enables us to achieve effective conversion from spin information into voltage information, which is key to spintronics.

Miao, Guo-Xing

67

PKC?-dependent phosphorylation of the glycine transporter 1  

PubMed Central

The extracellular levels of the neurotransmitter glycine in the brain are tightly regulated by the glycine transporter 1 (GlyT1) and the clearance rate for glycine depends on its rate of transport and the levels of cell surface GlyT1. Over the years, it has been shown that PKC tightly regulates the activity of several neurotransmitter transporters. In the present work, by stably expressing three N-terminus GlyT1 isoforms in porcine aortic endothelial cells and assaying for [32P]-orthophosphate metabolic labeling, we demonstrated that the isoforms GlyT1a, GlyT1b, and GlyT1c were constitutively phosphorylated, and that phosphorylation was dramatically enhanced, in a time dependent fashion, after PKC activation by phorbol ester. The phosphorylation was PKC-dependent, since pre-incubation of the cells with bisindolylmaleimide I, a selective PKC inhibitor, abolished the phorbol ester-induced phosphorylation. Blotting with specific anti-phospho-tyrosine antibodies did not yield any signal that could correspond to GlyT1 tyrosine phosphorylation, suggesting that the phosphorylation occurs at serine and/or threonine residues. In addition, a 23-40% -inhibition on Vmax was obtained by incubation with phorbol ester without a significant change on the apparent Km value. Furthermore, pre-incubation of the cells with the selective PKC?/? inhibitor Gö6976 abolished the downregulation effect of phorbol ester on uptake and phosphorylation, whereas the selective PKC? inhibitors (PKC? inhibitor or LY333531) prevented the phosphorylation without affecting glycine uptake, defining a specific role of classical PKC on GlyT1 uptake and phosphorylation. Taken together, these data suggest that phosphorylation that conventional PKC?/? regulates the uptake of glycine, whereas PKC? is responsible for GlyT1 phosphorylation.

Vargas-Medrano, Javier; Castrejon-Tellez, Vicente; Fernando, Plenge; Ramirez, Ivan; Miranda, Manuel

2011-01-01

68

Topographic Maps III: Back Azimuths and Triangulation  

NSDL National Science Digital Library

In this activity, students will learn the more advanced mapping skills of calculating back azimuths and triangulation. Using a local 7.5-minute series map, the teacher will select a starting point and an obstacle, have students follow an azimuth that leads them to the obstacle, let them construct a back azimuth and navigate around the obstacle while recording directions and distances. A number of viable solutions usually exist and can form the basis of a class discussion. For the triangulation portion of the exercise, the teacher will select and give grid coordinates for three points on the map and list the azimuths to be followed in the construction of a line through each point. Students will construct an azimuth-back azimuth line through each point until each end of the line hits a map margin. They will then record the coordinates and identify the object located at the intersection point of the three lines.

69

Time-dependent transport of electrons through a photon cavity  

NASA Astrophysics Data System (ADS)

We use a non-Markovian master equation to describe the transport of Coulomb-interacting electrons through an electromagnetic cavity with one quantized photon mode. The central system is a finite-parabolic quantum wire that is coupled weakly to external parabolic quasi-one-dimensional leads at t=0. With a stepwise introduction of complexity to the description of the system and a corresponding stepwise truncation of the ensuing many-body spaces, we are able to describe the time-dependent transport of Coulomb-interacting electrons through a geometrically complex central system. We take the full electromagnetic interaction of electrons and cavity photons without resorting to the rotating-wave approximation or reduction of the electron states to two levels into account. We observe that the number of initial cavity photons and their polarizations can have important effects on the transport properties of the system. The quasiparticles formed in the central system have lifetimes limited by the coupling to the leads and radiation processes active on a much longer time scale.

Gudmundsson, Vidar; Jonasson, Olafur; Tang, Chi-Shung; Goan, Hsi-Sheng; Manolescu, Andrei

2012-02-01

70

Dependence of zonal chondrocyte water transport properties on osmotic environment.  

PubMed

OBJECTIVE: The increasing concentration of proteoglycans from the surface to the deep zone of articular cartilage produces a depth-dependent gradient in fixed charge density, and therefore extracellular osmolarity, which may vary with loading conditions, growth and development, or disease. In this study we examine the relationship between in situ variations in osmolarity on chondrocyte water transport properties. Chondrocytes from the depth-dependent zones of cartilage, effectively preconditioned in varying osmolarities, were used to probe this relationship. DESIGN: First, depth variation in osmolarity of juvenile bovine cartilage under resting and loaded conditions was characterized using a combined experimental/theoretical approach. Zonal chondrocytes were isolated into two representative "baseline" osmolarities chosen from this analysis to reflect in situ conditions. Osmotic challenge was then used as a tool for determination of water transport properties at each of these baselines. Cell calcium signaling was monitored simultaneously as a preliminary examination of osmotic baseline effects on cell signaling pathways. RESULTS: Osmotic baseline exhibits a significant effect on the cell membrane hydraulic permeability of certain zonal subpopulations but not on cell water content or incidence of calcium signaling. CONCLUSIONS: Chondrocyte properties can be sensitive to changes in baseline osmolarity, such as those occurring during OA progression (decrease) and de novo tissue synthesis (increase). Care should be taken in comparing chondrocyte properties across zones when cells are tested in vitro in non-physiologic culture media. PMID:20011231

Oswald, Elizabeth S; Chao, Pen-Hsiu Grace; Bulinski, J Chloe; Ateshian, Gerard A; Hung, Clark T

2008-12-01

71

Strong wavevector dependence of hole transport in heterostructures  

NASA Astrophysics Data System (ADS)

Heterostructures such as resonant tunneling diodes, quantum well photodetectors and lasers, and cascade lasers break the symmetry of the crystalline lattice. Such break in lattice symmetry causes a strong interaction of heavy-, light- and split-off hole bands. A resonant tunneling diode is used as a vehicle to study hole transport in heterostructures including the subband dispersion transverse to the main transport direction. Four key findings are demonstrated: (1) the heavy and light hole interaction is shown to be strong enough to result in dominant current flow off the ? zone center (more holes flow through the structure at an angle than straight through), (2) explicit inclusion of the transverse momentum in the current integration is needed, (3) most of the current flow is due to injection from heavy holes in the emitter, and (4) the dependence on the angle ? of the transverse momentum k is weak. Two bandstructure models are utilized to demonstrate the underlying physics: (1) independent/uncoupled heavy-, light- and split-off bands, and (2) second-nearest neighbor sp3s* tight-binding model. Current-voltage ( I- V) simulations including explicit integration of the total energy E, transverse momentum | k | and transverse momentum angle ? are analyzed. An analytic formula for the current density J ( k) as a function of transverse momentum k is derived and utilized to explain the three independent mechanisms that generate off-zone-center current flow: (1) nonmonotonic (electron-like) hole dispersion, (2) different quantum well and emitter effective masses, and (3) momentum-dependent quantum well coupling strength. The analytic expression is also used to generate a complete I- V characteristic that compares well to the full numerical solution. The Fermi level and temperature dependence on the I- V is examined. Finally a simulation is compared to experimental data.

Klimeck, Gerhard; Bowen, R. Chris; Boykin, Timothy B.

2001-03-01

72

“Magnifying-Glass” Azimuthal Map Projections  

USGS Publications Warehouse

For maps focusing on a region of interest, but including surrounding areas to provide a setting, new azimuthal projections have been developed with a 'magnifying-glass' effect. On two such projections, inside a circle bounding the region of interest is a standard Azimuthal Equidistant or Lambert Azimuthal Equal-Area projection. Between this circle and an outer bounding circle azimuths remain true and the radial or area scale, respectively, remains constant, but at a reduced value. On four other projections, the inner portion is a standard azimuthal projection, which may be Stereographic, Gnomonic, or the above, but beyond this portion, the radial scale is gradually reduced to zero. Equivalents with rectangular boundaries are also available.

Snyder, John, P.

1987-01-01

73

Phase-dependent heat transport through magnetic Josephson tunnel junctions  

NASA Astrophysics Data System (ADS)

We present an exhaustive study of the coherent heat transport through superconductor-ferromagnet (SF) Josephson junctions including a spin-filter (Isf) tunneling barrier. By using the quasiclassical Keldysh Green's function technique we derive a general expression for the heat current flowing through a SF-Isf-FS junction and analyze the dependence of the thermal conductance on the spin-filter efficiency, the phase difference between the superconductors and the magnetization direction of the ferromagnetic layers. In the case of noncollinear magnetizations we show explicitly the contributions to the heat current stemming from the singlet and triplet components of the superconducting condensate. We also demonstrate that the magnetothermal resistance ratio of a SF-Isf-FS heat valve can be increased by the spin-filter effect under suitable conditions.

Bergeret, F. S.; Giazotto, F.

2013-07-01

74

Pyrene-sensitized electron transport across vesicle bilayers: Dependence of transport efficiency on pyrene substituents.  

PubMed

Endoergic electron transport across vesicle bilayers from ascorbate (Asc-) in the inner waterpool to methylviologen (MV2+) in the outer aqueous solution was driven by the irradiation of pyrene derivatives embedded in the vesicle bilayers. The initial rate of MV2+ reduction is dependent on the substituent group of the pyrenyl ring; a hydrophilic functional group linked with the pyrenyl ring by a short methylene chain acts as a sensitizer for the electron transport. Mechanistic studies using (1-pyrenyl)alkanoic acids (1a-c) as sensitizers suggest that the electron transport is mainly initiated by the reductive quenching of the singlet excited state of the pyrene by Asc- and proceeds by a mechanism involving electron exchange between the pyrenes located at the inner and outer interface across the vesicle bilayer. We designed and synthesized novel unsymmetrically substituted pyrenes having both a hydrophilic group linked by a short methylene chain and a hydrophobic long alkyl group (5a-c), which acted as excellent sensitizers for the electron transport across vesicle bilayers. PMID:17102879

Mizushima, Tadashi; Yoshida, Asako; Harada, Akitomo; Yoneda, Yu; Minatani, Tomiaki; Murata, Shigeru

2006-12-01

75

Evaluation of Fracture Azimuth by EM Wave and Elastic Wave  

NASA Astrophysics Data System (ADS)

Fracture system plays an important role in the development of underground energy, for example enhanced geothermal system (EGS), oil shale and shale gas, etc. Therefore, it becomes more and more important to detect and evaluate the fracture system. Geophysical prospecting is an useful method to evaluate the characteristics of the subsurface fractures. Currently, micro-seismology, multi-wave seismic exploration, and electromagnetic (EM) survey are reported to be used for the purpose. We are studying a method using both elastic wave and EM wave to detect and evaluate the fracture azimuth in laboratory. First, we build a 3D horizontal transverse isotropy (HTI) model, shown in the figure 1, by dry parallel fractures system, which was constructed by plexiglass plates and papers. Then, we used the ultrasonic system to obtain reflected S-wave data. Depending on the shear wave splitting, we evaluated the fracture azimuth by the algorithm of Pearson correlation coefficient. In addition, we used the full Polarimetric ultra wide band electromagnetic (FP-UWB-EM) wave System, shown in the figure 2, to obtain full polarimetric reflected EM-wave data. Depending on the rotation of the EM wave polarimetry, we evaluated the fracture azimuth by the the ration between maximum amplitude of co-polarimetric EM wave and maximum amplitude of cross-polarimetric EM wave. Finally, we used both EM-wave data and S-wave data to evaluate the fracture azimuth by the method of cross plot and statistical mathematics. To sum up, we found that FP-UWB-EM wave can be used to evaluated the fracture azimuth and is more accurate than ultrasound wave. Also joint evaluation using both data could improve the precision.

Feng, X.; Wang, Q.; Liu, C.; Lu, Q.; Zeng, Z.; Liang, W.; Yu, Y.; Ren, Q.

2013-12-01

76

Enhanced optical CD metrology by hybridization and azimuthal scatterometry  

NASA Astrophysics Data System (ADS)

Reducing parameter correlations to enhance scatterometry measurement accuracy, precision and tool matching is a crucial component of every modeling effort. Parameter sensitivity can largely depend on the orientation of the plane of incidence relative to the grating orientation. Conventional scatterometry is done with the plane if incidence normal to the grating orientation, whereas azimuthal scatterometry allows measurements at an arbitrary angle or set of angles. A second technique examined in this paper is hybrid metrology where inputs from source tools such as CD-SEM and CD-AFM are used to determine values of critical parameters. The first examples shows LER sensitivity gains by measuring narrow resist lines in an orientation parallel with the long axis of the grating. Hybridization of LER results in a CD and SWA FMP improvement of about 60%. We also showcase the benefits of azimuthal scatterometry measuring resist lines with CD larger than the wavelengths of the incident light. A CD and SWA FMP reduction of about 60% and 30% is obtained using azimuthal scatterometry at 0, 45 and 90 degrees azimuth angles. Hybridization of the ARC SWA after RIE results in CD and resist SWA FMP improvements by over 60% and 30%, respectively.

Zangooie, Shahin; Li, Jie; Boinapally, Karthik; Wilkens, Peter; Ver, Avraham; Khamsepour, Babak; Schroder, Holger; Piggot, John; Yedur, Sanjay; Liu, Zhuan; Hu, Jiangtao

2014-04-01

77

Relative azimuth inversion by way of damped maximum correlation estimates  

USGS Publications Warehouse

Horizontal seismic data are utilized in a large number of Earth studies. Such work depends on the published orientations of the sensitive axes of seismic sensors relative to true North. These orientations can be estimated using a number of different techniques: SensOrLoc (Sensitivity, Orientation and Location), comparison to synthetics (Ekstrom and Busby, 2008), or by way of magnetic compass. Current methods for finding relative station azimuths are unable to do so with arbitrary precision quickly because of limitations in the algorithms (e.g. grid search methods). Furthermore, in order to determine instrument orientations during station visits, it is critical that any analysis software be easily run on a large number of different computer platforms and the results be obtained quickly while on site. We developed a new technique for estimating relative sensor azimuths by inverting for the orientation with the maximum correlation to a reference instrument, using a non-linear parameter estimation routine. By making use of overlapping windows, we are able to make multiple azimuth estimates, which helps to identify the confidence of our azimuth estimate, even when the signal-to-noise ratio (SNR) is low. Finally, our algorithm has been written as a stand-alone, platform independent, Java software package with a graphical user interface for reading and selecting data segments to be analyzed.

Ringler, A.T.; Edwards, J.D.; Hutt, C.R.; Shelly, F.

2012-01-01

78

From Bacteria to Man: Archaic Proton-Dependent Peptide Transporters at Work  

NSDL National Science Digital Library

The present review focuses on the electrogenic peptide transporters as the best studied examples of proton-dependent nutrient transporters in mammals and summarizes the most recent findings on their physiological importance. Taking peptide transport as a general phenomenon found in nature, we also include peptide transport mechanisms in bacteria, yeast, invertebrates, and lower vertebrates, which are not that often addressed in physiology journals.

PhD Hannelore Daniel (Technical University of Munich Dept of Nut'l Scis-Ernaehrungs-Physiol); Britta Spanier (Technical University of Munich Department of Food and Nutrition); Gabor Kottra (Technical University of Munich Department of Food and Nutrition); Dietmar Weitz (Technical University of Munich Department of Food and Nutrition)

2006-04-01

79

Gymnemic acids inhibit sodium-dependent glucose transporter 1.  

PubMed

To evaluate the activity of botanicals used in Chinese Traditional Medicine as hypoglycemic agents for diabetes type II prevention and/or treatment, extracts prepared from 26 medicinal herbs were screened for their inhibitory activity on sodium-dependent glucose transporter 1 (SGLT1) by using two-electrode voltage-clamp recording of glucose uptake in Xenopus laevis oocytes microinjected with cRNA for SGLT1. Showing by far the strongest SGLT1 inhibitory effect, the phytochemicals extracted from Gymnema sylvestre (Retz.) Schult were located by means of activity-guided fractionation and identified as 3-O-?-d-glucuronopyranosyl-21-O-2-tigloyl-22-O-2-tigloyl gymnemagenin (1) and 3-O-?-d-glucuronopyranosyl-21-O-2-methylbutyryl-22-O-2-tigloyl gymnemagenin (2) by means of LC-MS/MS, UPLC-TOF/MS, and 1D/2D-NMR experiments. Both saponins exhibited low IC50 values of 5.97 (1) and 0.17 ?M (2), the latter of which was in the same range as found for the high-affinity inhibitor phlorizin (0.21 ?M). As SGLT1 is found in high levels in brush-border membranes of intestinal epithelial cells, these findings demonstrate for the first time the potential of these saponins for inhibiting electrogenic glucose uptake in the gastrointestinal tract. PMID:24856809

Wang, Yu; Dawid, Corinna; Kottra, Gabor; Daniel, Hannelore; Hofmann, Thomas

2014-06-25

80

Spin-dependent heat transport and thermal boundary resistance  

NASA Astrophysics Data System (ADS)

In this thesis, thermal conductivity change depending on the magnetic configurations has been studied. In order to make different magnetic configurations, we developed a spin valve structure, which has high MR ratio and low saturation field. The high MR ratio was achieved using Co/Cu multilayer and 21A or 34A thick Cu layer. The low saturation field was obtained by implementing different coercivities of the successive ferromagnetic layers. For this purpose, Co/Cu/Cu tri-layered structure was used with the thicknesses of the Co layers; 15 A and 30 A. For the thermal conductivity measurement, a three-omega method was employed with a thermally isolated microscale rod. We fabricated the microscale rod using optical lithography and MEMS process. Then the rod was wire-bonded to a chip-carver for further electrical measurement. For the thermal conductivity measurement, we built the three-omega measurement system using two lock-in amplifiers and two differential amplifiers. A custom-made electromagnet was added to the system to investigate the impact of magnetic field. We observed titanic thermal conductivity change depending on the magnetic configurations of the Co/Cu/Co multilayer. The thermal conductivity change was closely correlated with that of the electric conductivity in terms of the spin orientation, but the thermal conductivity was much more sensitive than that of the electric conductivity. The relative thermal conductivity change was 50% meanwhile that of electric resistivity change was 8.0%. The difference between the two ratios suggests that the scattering mechanism for charge and heat transport in the Co/Cu/Co multilayer is different. The Lorentz number in Weidemann-Franz law is also spin-dependent. Thermal boundary resistance between metal and dielectrics was also studied in this thesis. The thermal boundary resistance becomes critical for heat transport in a nanoscale because the thermal boundary resistance can potentially determine overall heat transport in thin film structures. A transient theraroreflectance (TTR) technique can be used for measuring the thermal conductivity of thin films in cross-sectional direction. In this study, a pump-probe scheme was employed for the TTR technique. We built an optical pump-probe system by using a nanosecond pulse laser for pumping and a continuous-wave laser for probing. A short-time heating event occured at the surface of a sample by shining a laser pulse on the surface. Then the time-resolved thermoreflectance signals were detected using a photodetector and an oscilloscope. The increased temperature decreases slowly and its thermal decay depends on the thermal properties of a sample. Since the reflectivity is linearly proportional to the temperature, the time-resolved thermoreflectance signals have the information of the thermal properties of a sample. In order to extract the thermal properties of a sample, a thermal analysis was performed by fitting the experimental data with thermal models. We developed 2-layered and 3-layered thermal models using the analogies between thermal conduction and electric conduction and a transmission-line concept. We used two sets of sample structures: Au/SiNx/Si substrate and Au/CoFe/SiNx/Si substrate with various thickness of SiN x layer. Using the pump-probe system, we measured the time-resolved thermoreflectance signals for each sample. Then, the thermal conductivity and thermal boundary resistance were obtained by fitting the experimental data with the thermal models. The thermal conductivity of SiNx films was measured to be 2.0 W/mK for both structures. In the case of the thermal boundary resistance, it was 0.81x10-5 m 2K/W at the Au/SiNx interface and 0.54x10 -5 m2K/W at the CoFe/SiNx interface, respectively. The difference of the thermal boundary resistance between Au/SiNx and CoFe/SiNx might be came from the different phonon dispersion of Au and CoFe. The thermal conductivity did not depend on the thickness of SiNx films in the thickness range of 50-200nm. However, the thermal boundary resistance at metal/SiNx interfaces will impa

Jeong, Taehee

81

Temperature-dependent thermal transport properties of Archean rocks  

NASA Astrophysics Data System (ADS)

Heat transfer controls the rates and styles of fundamental planetary processes including the formation and differentiation of planetary crust, the rheological behavior of the lithosphere and asthenosphere, and the secular cooling of the Earth following its accretion. The Earth's first few hundred million years were characterized by much higher radiogenic heat production and heat flow out of the mantle than seen today, and early continental crust was comprised of rock associations such as granite-greenstone belts and intrusions of tonalite-trondhjemite-granodiorite (TTG). The composition of Archean crustal rocks, and likely variations in radiogenic heat production, have been well documented in past studies. However, the thermal transport properties of these rocks, thermal diffusivity D and thermal conductivity (k=D?CP, where ? is density and CP is isobaric heat capacity), are less well constrained, especially at high temperatures. High temperature measurements of D and k are few, and contact methods may suffer from a combination of imperfect physical contacts and unwanted direct radiative transfer. Using the laser flash analysis (LFA) technique, we determined D of a suite of 14 granite-greenstone and TTG rocks including samples from the Abitibi and Barberton greenstone belts, over a range of crustal temperatures at atmospheric pressure. Dehydration and devolatilization of amphiboles and biotite prevented direct measurement of D for most samples above ~750K, however previous studies of T-dependent D have shown that values of bulk rock diffusivity asymptotically approach a constant value above the ?-? quartz transition (846K). Our measurements yielded a range of D at room temperature from ~3.8 mm2 s-1 for banded iron to ~1 mm2 s-1 for granodiorite. D for all samples decreases with increasing T, and the range of D for the suite narrows to ~0.45 and 0.70 mm2 s-1 for granodiorite and tholeiite basalt respectively by ~1000K. Density of each sample was measured using the Archimedean method and was assumed ~constant over crustal P and T. The T-dependence of CP was calculated from modal mineralogy and published CP data for mineral end-members. Calculated values of k ranged from ~5.7 Wm-1k-1 for a quartz-rich (~38%) tonalite to ~1.7 Wm-1k-1 for a quartz-free syenite at 280K. The range of k at higher temperatures is less restricted than D, as a result of the general increase in CP at higher temperatures and varied between ~2.5 Wm-1k-1 for amphibolite and ~1.5 Wm-1k-1 for syenite. These results show that the T-dependence of D and k cannot be ignored, and variations in thermal transport properties between different rock types, and for a single rock type at different temperatures, may be more important than differences in their radiogenic heat production. This has important implications for the geothermal gradient of Archean crust, its rheological behavior and potential for partial melting.

Merriman, J. D.; Hofmeister, A.; Nabelek, P. I.; Whittington, A. G.; Benn, K.

2010-12-01

82

Regions of azimuthal instability in gyrotrons  

SciTech Connect

This paper is devoted to the analysis of the instability of operating modes in high-power gyrotrons with cylindrically symmetric resonators. This instability manifests itself in destruction of the azimuthally uniform wave envelope rotating in a gyrotron resonator having a transverse size greatly exceeding the wavelength. The appearance of azimuthally nonuniform solutions can be interpreted as simultaneous excitation of modes with different azimuthal indices. This problem is studied self-consistently, i.e., taking into account the temporal evolution of both the azimuthal and axial structures of the wave envelope. The region of gyrotron operation free from this instability is identified. The efficiency achievable in this region can be only 1%-2% lower than the maximum efficiency. It is also possible to address the difference between the theory of mode interaction developed under assumption that all modes have fixed axial structure and the self-consistent theory presented here. As known, for fixed axial mode profiles, single-mode high-efficiency oscillations remain stable no matter how dense is the spectrum of competing modes, while the self-consistent theory predicts stable high-efficiency operation only when the azimuthal index does not exceed a certain critical value. It is shown that the azimuthal instability found in the self-consistent theory is caused by excitation of modes having axial structures different from that of the desired central mode.

Dumbrajs, O. [Institute of Solid State Physics, University of Latvia, Kengaraga Street 8, LV-1063 Riga (Latvia); Nusinovich, G. S.; Antonsen, T. M. Jr. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-3511 (United States)

2012-06-15

83

Heliostat tilt and azimuth angle charts and the heliostat orientation protractor  

SciTech Connect

This paper reports that using cartesian heliostat field coordinates analytical expressions were derived for the heliostat tilt angle s, and heliostat azimuth angle {gamma} (clockwise from south). These expressions are dependent on the field cartesian coordinates of the center of the heliostat and the solar zenith and azimuth angles (clockwise from south), {theta}{sub z} and {Psi}, respectively. Here, cylindrical coordinates are conveniently used to derive the expressions for the heliostat angles s and {gamma}. The expression of {gamma}is used to construct the so-called heliostat orientation protractor. The protractor is a useful tool to determine the instantaneous heliostat azimuth angle as will be illustrated.

Elsayed, M.M.; Al-Rabghi, O.M. (Thermal Energy Dept., King Abdulaziz Univ., Jeddah 21413 (SA))

1992-02-01

84

Interactions That Drive Sec-Dependent Bacterial Protein Transport†  

PubMed Central

Understanding the transport of hydrophilic proteins across biological membranes continues to be an important undertaking. The general secretory (Sec) pathway in Escherichia coli transports the majority of E. coli proteins from their point of synthesis in the cytoplasm to their sites of final localization, associating sequentially with a number of protein components of the transport machinery. The targeting signals for these substrates must be discriminated from those of proteins transported via other pathways. While targeting signals for each route have common overall characteristics, individual signal peptides vary greatly in their amino acid sequences. How do these diverse signals interact specifically with the proteins that comprise the appropriate transport machinery and, at the same time, avoid targeting to an alternate route? The recent publication of the crystal structures of components of the Sec transport machinery now allows a more thorough consideration of the interactions of signal sequences with these components.

Rusch, Sharyn L.; Kendall, Debra A.

2009-01-01

85

Probing TMDs through azimuthal distributions of pions inside a jet in hadronic collisions  

NASA Astrophysics Data System (ADS)

The azimuthal distributions around the jet axis of leading pions produced in the jet fragmentation process in pp collisions are studied within the framework of the so-called generalized parton model. The observable leading-twist azimuthal asymmetries are estimated in kinematic configurations presently investigated at RHIC. It is shown how the main contributions coming from the Collins and Sivers effects can be disentangled. In addition, a test of the process dependence of the Sivers function is provided.

D'Alesio, U.; Murgia, F.; Pisano, C.

2014-01-01

86

Type 1 Sodium-dependent Phosphate Transporter (SLC17A1 Protein) Is a Cl?-dependent Urate Exporter*  

PubMed Central

SLC17A1 protein (NPT1) is the first identified member of the SLC17 phosphate transporter family and mediates the transmembrane cotransport of Na+/Pi in oocytes. Although this protein is believed to be a renal polyspecific anion exporter, its transport properties are not well characterized. Here, we show that proteoliposomes containing purified SLC17A1 transport various organic anions such as p-aminohippuric acid and acetylsalicylic acid (aspirin) in an inside positive membrane potential (??)-dependent manner. We found that NPT1 also transported urate. The uptake characteristics were similar to that of SLC17 members in its Cl? dependence and inhibitor sensitivity. When arginine 138, an essential amino acid residue for members of the SLC17 family such as the vesicular glutamate transporter, was specifically mutated to alanine, the resulting mutant protein was inactive in ??-dependent anion transport. Heterologously expressed and purified human NPT1 carrying the single nucleotide polymorphism mutation that is associated with increased risk of gout in humans exhibited 32% lower urate transport activity compared with the wild type protein. These results strongly suggested that NPT1 is a Cl?-dependent polyspecific anion exporter involved in urate excretion under physiological conditions.

Iharada, Masafumi; Miyaji, Takaaki; Fujimoto, Takahiro; Hiasa, Miki; Anzai, Naohiko; Omote, Hiroshi; Moriyama, Yoshinori

2010-01-01

87

Glutamine transport in isolated epithelial intestinal cells. Identification of a Na + -dependent transport mechanism, highly specific for glutamine  

Microsoft Academic Search

L-Glutamine transport was evaluated in isolated cells from the guinea-pig small intestine by measuring [3H]-L-glutamine uptake. Villous and crypt cells expressed Na+-dependent and Na+-independent transport mechanisms. Glutamine transport systems were identified using various amino acids and analogues as inhibitors. In both villous and crypt cells, 2-(methylamino)-isobutyrate (MeAIB), a system A inhibitor, did not inhibit Na+-dependent glutamine influx. 2-Aminobicyclo(2,2,1)heptane-2-carboxylate (BCH), a

Jesffls R. del Castillo; María C. Súlbaran-Carrasco; Luis Burguillos

2002-01-01

88

Structural domains of chimeric dopamine-noradrenaline human transporters involved in the Na(+)- and Cl(-)-dependence of dopamine transport.  

PubMed

Catecholamine transporters constitute the biological targets for several important drugs, including antidepressants, cocaine, and related compounds. Some information exists about discrete domains of these transporters that are involved in substrate translocation and uptake blockade, but delineation of domains mediating the ionic dependence of the transport remains to be defined. In the present study, human neuronal transporters for dopamine and noradrenaline (hDAT and hNET) and a series of six functional chimeras were transiently expressed in LLC-PK1 cells. Substitution of Cl(-) by isethionate reveals that cassette IV (i.e., the region of the transporter encompassing transmembrane domain 9 through the COOH terminal) plays an important role in the Cl(-)- dependence of the uptake. Substitutions of Na(+) and NaCl by Tris(+) and sucrose, respectively, demonstrate that three different segments scattered across the transporter are involved in the Na(+)- dependence of the transport activity: cassette I (i.e., the region from the amino terminus through the first two transmembrane domains), cassette IV, and junction between transmembrane domains 3 to 5 and 6 to 8. Results of the present work also suggest that the use of Tris(+) as a substitute for Na(+) results in a biased estimate of the Hill number value for hDAT. This study provides useful clues for identifying specific residues involved in the uptake function of the catecholamine transporters. PMID:11093780

Syringas, M; Janin, F; Mezghanni, S; Giros, B; Costentin, J; Bonnet, J J

2000-12-01

89

A numerical study of the generation of an azimuthal current in a plasma cylinder using a transverse rotating magnetic field  

Microsoft Academic Search

The generation of a steady azimuthal current in a cylindrical plasma column using a rotating magnetic field is numerically investigated. The mixed initial-boundary-value problem is solved using a finite difference method. It is shown that substantial azimuthal current can be driven provided that the amplitude of the rotating magnetic field is greater than a certain threshold value which depends on

W. N. Hugrass; R. C. Grimm

1981-01-01

90

Numerical study of the generation of an azimuthal current in a plasma cylinder using a transverse rotating magnetic field  

Microsoft Academic Search

The generation of a steady azimuthal current in a cylindrical plasma column using a rotating magnetic field is numerically investigated. The mixed initial-boundary-value problem is solved using a finite difference method. It is shown that substantial azimuthal current can be driven provided that the amplitude of the rotating magnetic field is greater than a certain threshold value which depends on

W. N. Hugrass; R. C. Grimm

1980-01-01

91

Axonal transport of adeno-associated viral vectors is serotype-dependent  

PubMed Central

We have previously shown that AAV2 undergoes anterograde axonal transport in rat and non-human primate brain. We screened other AAV serotypes for axonal transport and found that AAV6 is transported almost exclusively in a retrograde direction and, like AAV2, it is also neuron-specific in rat brain. Our findings show that axonal transport of AAV is serotype-dependent and this has implications for gene therapy of neurological diseases such as Huntington’s disease.

Salegio, Ernesto A.; Samaranch, Lluis; Kells, Adrian P.; Mittermeyer, Gabriele; San Sebastian, Waldy; Zhou, Shangzhen; Beyer, Janine; Forsayeth, John; Bankiewicz, Krystof S.

2012-01-01

92

Azimuthal anisotropy measurements by STAR  

NASA Astrophysics Data System (ADS)

The recent study of centrality and transverse momentum (pT) dependence of inclusive charged hardron elliptic anisotropy (v2) at midrapidity (|?|<1.0) in Au+Au collision at ?{sNN}=7.7,11.5,19.6,27, and 39 GeV in STAR Beam Energy Scan program is presented. We show that the observed increase of inclusive v2 is mainly due to the average pT increase with energy. In Au+Au 200 GeV collisions, the triangular anisotropy (v3) measurements highly depend on measurement methods; v3 is strongly dependent on ??. The difference between two- and four-particle cumulants v2{2} and v2{4} for Au+Au and Cu+Cu collision at ?{sNN}=62.4 and 200 GeV is used to explore flow fluctuations. Furthermore, by exploiting the symmetry of average flow in pseudorapidity ? about midrapidity, the ??-dependent and independent components are separated using v2{2} and v2{4}.

Yi, Li

2014-06-01

93

Relationship between the IMF azimuthal angle and solar wind velocity  

NASA Astrophysics Data System (ADS)

The relationship between the IMF azimuthal angle and plasma velocity has been studied independently for three types of solar wind streams (recurrent and transient high-speed streams and low-speed background wind) based on the interplanetary medium parameters measured in the near-Earth orbits in 1964-1996. The relationships between the IMF azimuthal angle cotangent and plasma velocity are close to linear but strongly differ from one another and from the theoretical relationship for all types of streams. These differences area caused by the magnetic field disturbance on the time scales smaller than a day, and the effect of this disturbance has been studied quantitatively. The effective periods of rotation of the IMF sources on the Sun, depending on the solar cycle phase, have been obtained from the relations between the IMF azimuthal angle cotangent and plasma velocity. During the most part of the solar cycle, the periods of rotation of the IMF sources are close to the period of rotation of the solar equator but abruptly increase to the values typical of the solar circumpolar zones in the years of solar minimums.

Erofeev, D. V.

2008-04-01

94

Global azimuthal anisotropy in the transition zone.  

PubMed

Surface wave dispersion measurements for Love wave overtones carry evidence of azimuthal anisotropy in the transition zone of Earth's mantle (400 to 660 kilometers deep). A Backus-Gilbert inversion of anisotropic phase velocity maps, with resolution kernels mainly sensitive to the transition zone, shows a robust long-wavelength azimuthally anisotropic velocity structure. This observation puts new constraints on the mineralogy and dynamics of the transition zone because this anisotropy may result from aligned minerals, tilted laminated structures, or even organized pockets of fluid inclusions. PMID:12016310

Trampert, Jeannot; van Heijst, Hendrik Jan

2002-05-17

95

Mechanisms underlying azimuth selectivity in the auditory cortex of the pallid bat  

PubMed Central

This study focused on mechanisms underlying azimuth selectivity in the primary auditory cortex (A1) of pallid bats. The pallid bat listens to prey-generated noise (5–35 kHz) to localize and hunt terrestrial prey. The region of A1 tuned between 5–35 kHz consists of two clusters of neurons distinguished by interaural intensity difference (IID) selectivity: binaurally inhibited (EI) and peaked. The first aim of this study was to use sequential dichotic/free-field stimulation to test the hypothesis that IID is the primary cue underlying azimuth selectivity in neurons tuned in the prey-generated noise frequency band. IID selectivity and ear directionality at the neuron’s characteristic frequency (CF) were used to predict azimuth selectivity functions. The predicted azimuth selectivity was compared with the actual azimuth selectivity from the same neurons. Prediction accuracy was similarly high for EI neurons and peaked neurons with low CF, whereas predictions were increasingly inaccurate with increasing CF among the peaked neurons. The second aim of this study was to compare azimuth selectivity obtained with noise and CF tones to determine the extent to which stimulus bandwidth influences azimuth selectivity in neurons with different binaural properties. The azimuth selectivity functions were similar for the two stimuli in the majority of EI neurons. A greater percentage of peaked neurons showed differences in their azimuth selectivity for noise and tones. This included neurons with multiple peaks when tested with tones and a single peak when tested with noise. Taken together, data from the two aims suggest that azimuth tuning of EI neurons is primarily dictated by IID sensitivity at CF. Peaked neurons, particularly those with high CF, may integrate IID sensitivity across frequency to generate azimuth selectivity for broadband sound. The data are consistent with those found in cat and ferret A1 in that binaurally facilitated neurons depend to a greater extent (compared to EI neurons) on spectral integration of binaural properties to generate azimuth selectivity for broadband stimuli.

Razak, K.A.

2012-01-01

96

The SLC34 family of sodium-dependent phosphate transporters.  

PubMed

The SLC34 family of sodium-driven phosphate cotransporters comprises three members: NaPi-IIa (SLC34A1), NaPi-IIb (SLC34A2), and NaPi-IIc (SLC34A3). These transporters mediate the translocation of divalent inorganic phosphate (HPO4 (2-)) together with two (NaPi-IIc) or three sodium ions (NaPi-IIa and NaPi-IIb), respectively. Consequently, phosphate transport by NaPi-IIa and NaPi-IIb is electrogenic. NaPi-IIa and NaPi-IIc are predominantly expressed in the brush border membrane of the proximal tubule, whereas NaPi-IIb is found in many more organs including the small intestine, lung, liver, and testis. The abundance and activity of these transporters are mostly regulated by changes in their expression at the cell surface and are determined by interactions with proteins involved in scaffolding, trafficking, or intracellular signaling. All three transporters are highly regulated by factors including dietary phosphate status, hormones like parathyroid hormone, 1,25-OH2 vitamin D3 or FGF23, electrolyte, and acid-base status. The physiological relevance of the three members of the SLC34 family is underlined by rare Mendelian disorders causing phosphaturia, hypophosphatemia, or ectopic organ calcifications. PMID:24352629

Wagner, Carsten A; Hernando, Nati; Forster, Ian C; Biber, Jürg

2014-01-01

97

Proton-Dependent Coniferin Transport, a Common Major Transport Event in Differentiating Xylem Tissue of Woody Plants1[W  

PubMed Central

Lignin biosynthesis is an essential physiological activity of vascular plants if they are to survive under various environmental stresses on land. The biosynthesis of lignin proceeds in the cell wall by polymerization of precursors; the initial step of lignin polymerization is the transportation of lignin monomers from the cytosol to the cell wall, which is critical for lignin formation. There has been much debate on the transported form of the lignin precursor, either as free monolignols or their glucosides. In this study, we performed biochemical analyses to characterize the membrane transport mechanism of lignin precursors using angiosperms, hybrid poplar (Populus sieboldii × Populus grandidentata) and poplar (Populus sieboldii), as well gymnosperms, Japanese cypress (Chamaecyparis obtusa) and pine (Pinus densiflora). Membrane vesicles prepared from differentiating xylem tissues showed clear ATP-dependent transport activity of coniferin, whereas less than 4% of the coniferin transport activity was seen for coniferyl alcohol. Bafilomycin A1 and proton gradient erasers markedly inhibited coniferin transport in hybrid poplar membrane vesicles; in contrast, vanadate had no effect. Cis-inhibition experiments suggested that this transport activity was specific for coniferin. Membrane fractionation of hybrid poplar microsomes demonstrated that transport activity was localized to the tonoplast- and endomembrane-rich fraction. Differentiating xylem of Japanese cypress exhibited almost identical transport properties, suggesting the involvement of a common endomembrane-associated proton/coniferin antiport mechanism in the lignifying tissues of woody plants, both angiosperms and gymnosperms.

Tsuyama, Taku; Kawai, Ryo; Shitan, Nobukazu; Matoh, Toru; Sugiyama, Junji; Yoshinaga, Arata; Takabe, Keiji; Fujita, Minoru; Yazaki, Kazufumi

2013-01-01

98

The AMOS (azimuthal mode simulator) code  

Microsoft Academic Search

AMOS, a newly developed computer code that is finding application in the design of accelerator cavities, is described. The program simulates the temporal evolution of electromagnetic fields in rotationally symmetric structures. An explicit Fourier series expansion is assumed in the azimuthal coordinate, which allows different multiple modes to be simulated independently. Nonuniform electrical properties (ε, ?, ?) are permitted, and

J. F. DeFord; G. D. Craig; R. McLeod

1989-01-01

99

Sugar transport in Sulfolobus solfataricus is mediated by two families of binding protein-dependent ABC transporters  

Microsoft Academic Search

The extreme thermoacidophilic archaeon Sulfolobus solfataricus grows optimally at 80°C and pH 3 and uses a variety of sugars as sole carbon and energy source. Glucose transport in this organism is mediated by a high-affinity binding protein-dependent ATP-binding cassette (ABC) transporter. Sugar-binding studies revealed the presence of four additional membrane-bound binding proteins for arabinose, cellobiose, maltose and trehalose. These glycosylated

Marieke G. L. Elferink; Sonja-V. Albers; Wil N. Konings; Arnold J. M. Driessen

2001-01-01

100

Time-dependent nuclide transport through backfill into a fracture  

Microsoft Academic Search

This paper presents a transient analysis of radionuclide transport through backfill into a fissure. This report considers a waste canister surrounded by backfill in a borehole intersected by a fracture, in water-saturated rock. Radionuclides are released at a constant concentration C\\/sub s\\/ at the waste surface into the backfill. Ground water flows in the fissure. We assume no ground-water flow

C. H. Kang; P. L. Chambre; W. W. L. Lee; T. H. Pigford

1987-01-01

101

Expression of a rat renal sodium-dependent dicarboxylate transporter in Xenopus oocytes.  

PubMed Central

Microinjection of mRNA isolated from rat kidney cortex into Xenopus laevis oocytes resulted in the expression of a Na(+)-dependent dicarboxylate transporter, as detected by uptake measurements with [14C]succinate as substrate. The expressed transporter showed an S-shaped Na(+)-dependence with half-maximal activation at 19-21 mM Na+ and a Hill coefficient between 2 and 3. Endogenous succinate uptake was not Na(+)-dependent. Na(+)-stimulated succinate uptake in mRNA-injected oocytes exhibited a maximum at pH 7.5, whereas endogenous Na(+)-independent transporter was fastest at pH 8.5. The expressed dicarboxylate transporter also differed from the endogenous transporter in its sensitivity to citrate as well as dicarboxylates in trans and cis configurations. The expressed transporter resembled the renal basolateral transporter, especially with respect to affinity for succinate (Km 28 microM), activation by Na+, pH-dependence and substrate specificity. After injection of size-fractionated mRNA, succinate uptake was expressed by mRNA of 2-3 kb. Our results suggest expression of the basolateral Na(+)-dependent dicarboxylate transporter after injection of mRNA from rat kidney into Xenopus oocytes.

Steffgen, J; Kienle, S; Scheyerl, F; Franz, H E

1994-01-01

102

Twist4 contributions to the azimuthal asymmetry in SIDIS  

Microsoft Academic Search

We calculate the differential cross section for the unpolarized\\u000asemi-inclusive deeply inelastic scattering (SIDIS) process $e^-+N \\\\to e^-+q+X$\\u000ain leading order (LO) of perturbative QCD and up to twist-4 in power\\u000acorrections and study in particular the azimuthal asymmetry $$. The\\u000afinal results are expressed in terms of transverse momentum dependent (TMD)\\u000aparton matrix elements of the target nucleon up

Yu-kun Song; Jian-hua Gao; Zuo-tang Liang; Xin-Nian Wang

2010-01-01

103

A Thyroid Hormone Analog with Reduced Dependence on the Monocarboxylate Transporter 8 for Tissue Transport  

PubMed Central

Mutations of the thyroid hormone (TH) cell membrane transporter MCT8, on chromosome-X, produce severe mental and neurological impairment in men. We generated a Mct8-deficient mouse (Mct8KO) manifesting the human thyroid phenotype. Although these mice have no neurological manifestations, they have decreased brain T3 content and high deiodinase 2 (D2) activity, reflecting TH deprivation. In contrast and as in serum, liver T3 content is high, resulting in increased deiodinase 1 (D1), suggesting that in this tissue TH entry is Mct8 independent. We tested the effect of 3,5-diiodothyropropionic acid (DITPA), a TH receptor agonist, for its dependence on Mct8 in Mct8KO and wild-type (Wt) mice tissues. After depletion of endogenous TH, mice were given three different doses of DITPA. Effects were compared with treatment with two doses of l-T4. As expected, physiological doses of l-T4 normalized serum TSH, brain D2, and liver D1 in Wt mice but not the Mct8KO mice. The higher dose of T4 suppressed TSH in the Wt mice, normalized TSH and brain D2 in Mct8KO mice, but produced a thyrotoxic effect on liver D1 in both genotypes. In contrast DITPA produced similar effects on TSH, D2, and D1 in both Wt and Mct8KO mice. The higher dose fully normalized all measurements and other parameters of TH action. Thus, DITPA is relatively MCT8 independent for entry into the brain and corrects the TH deficit in Mct8KO mice without causing thyrotoxic effect in liver. The potential clinical utility of this analog to patients with MCT8 mutations requires further studies.

Di Cosmo, Caterina; Liao, Xiao-Hui; Dumitrescu, Alexandra M.; Weiss, Roy E.; Refetoff, Samuel

2009-01-01

104

Composition dependence of ion-transport coefficients in gas mixtures  

NASA Technical Reports Server (NTRS)

Simple momentum-transfer theory for the composition dependence of ion mobilities and diffusion coefficients in gas mixtures at arbitrary field strengths is corrected and extended, and compared with a similar theory based on momentum and energy transfer, and with results based on direct solution of the Boltzmann equation by Kihara's method. Final equations are recommended for predicting composition dependences, given only results on ion mobilities and diffusion coefficients in the pure component gases.

Whealton, J. H.; Mason, E. A.; Robson, R. E.

1974-01-01

105

Composition dependence of ion transport coefficients in gas mixtures  

NASA Technical Reports Server (NTRS)

A simple momentum-transfer theory for the composition dependence of ion mobilities and diffusion coefficients in gas mixtures at arbitrary field strengths is corrected, extended, and compared with a similar theory based on momentum and energy transfer, and with results based on direct solution of the Boltzmann equation by Kihara's method. Final equations are recommended for predicting composition dependences, given only results on ion mobilities and diffusion coefficients in the pure component gases.

Whealton, J. H.; Mason, E. A.; Robson, R. E.

1973-01-01

106

Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles  

NASA Technical Reports Server (NTRS)

The link between azimuthal modes in jet turbulence and in the acoustic sound field has been examined in cold, round jets. Chevron nozzles, however, impart an azimuthal structure on the jet with a shape dependent on the number, length and penetration angle of the chevrons. Two particular chevron nozzles, with 3 and 4 primary chevrons respectively, and a round baseline nozzle are compared at both cold and hot jet conditions to determine how chevrons impact the modal structure of the flow and how that change relates to the sound field. The results show that, although the chevrons have a large impact on the azimuthal shape of the mean axial velocity, the impact of chevrons on the azimuthal structure of the fluctuating axial velocity is small at the cold jet condition and smaller still at the hot jet condition. This is supported by results in the azimuthal structure of the sound field, which also shows little difference in between the two chevron nozzles and the baseline nozzle in the distribution of energy across the azimuthal modes measured.

Brown, Clifford A.; Bridges, James

2006-01-01

107

Azimuthal temperature modulations of Saturn's A ring caused by self-gravity wakes  

NASA Astrophysics Data System (ADS)

The physical temperatures of the Saturn's A ring measured by the Cassini Composite Infrared Spectrometer (CIRS) show quadrupole azimuthal modulations besides temperature drops in Saturn's shadow. These azimuthal modulations are likely to be caused by self-gravity wakes. In this paper, we develop a new thermal model in which wakes are modeled as elliptical cylinders ignoring inter-wake particles. All the heat fluxes are calculated explicitly taking into account inter-wake shadowing and heating. We apply our model to azimuthal scans of the A ring obtained by CIRS. It is found that the azimuthal modulation of the ring temperature is primarily caused by the azimuthal variation of the geometric filling factor of the ring seen from the Sun. The thermal inertia estimated from the eclipse data (data only inside and near Saturn's shadow) of the low phase scans is ˜10 J m-2 K-1 s-1/2. With this value of the thermal inertia, the amplitude of the azimuthal temperature modulation is overestimated in our model as compared with those observed. This is likely to be because our model ignores inter-wake particles. The bolometric reflectance of wakes is estimated to be 0.35-0.40 although lower values are required to reproduce temperatures at low solar phase angles. This apparent phase dependence of the reflectance indicates that roughness on the wake surfaces is necessary.

Morishima, Ryuji; Spilker, Linda; Turner, Neal

2014-01-01

108

Higher Twist Contributions to the Azimuthal Asymmetries in SIDIS  

NASA Astrophysics Data System (ADS)

This is intended to be a summary of a series of publications [1, 2, 3] carried out by our group. We showed that collinear expansion can be extended to the semi-inclusive deep inelastic scattering process e + p ? e + q + X as a systematic way of studying higher twist effects. We calculated the cross section up to twist-3 level for different polarized and unpolarized cases, and obtained the azimuthal asymmetry langlecos phirangle in terms of gauge invariant twist-3 TMD parton correlation functions [1]. We further calculated the complete cross section up to twist-4 level for the unpolarized case, and obtained the azimuthal asymmetry langlecos 2phirangle expressed in terms of gauge invariant twist-4 TMD parton correlation functions [3]. We also showed that the nuclear dependence of the TMD distributions can be obtained from the gauge link and studied the nuclear dependence of both langlecos phirangle and langlecos 2phirangle asymmetries with a Gaussian ansatz for transverse momentum dependence of parton correlation functions [2, 3].

Song, Yu-kun

2011-05-01

109

Models of long-distance transport: how is carrier-dependent auxin transport regulated in the stem?  

PubMed

• This paper presents two models of carrier-dependent long-distance auxin transport in stems that represent the process at different scales. • A simple compartment model using a single constant auxin transfer rate produced similar data to those observed in biological experiments. The effects of different underlying biological assumptions were tested in a more detailed model representing cellular and intracellular processes that enabled discussion of different patterns of carrier-dependent auxin transport and signalling. • The output that best fits the biological data is produced by a model where polar auxin transport is not limited by the number of transporters/carriers and hence supports biological data showing that stems have considerable excess capacity to transport auxin. • All results support the conclusion that auxin depletion following apical decapitation in pea (Pisum sativum) occurs too slowly to be the initial cause of bud outgrowth. Consequently, changes in auxin content in the main stem and changes in polar auxin transport/carrier abundance in the main stem are not correlated with axillary bud outgrowth. PMID:22443265

Renton, Michael; Hanan, Jim; Ferguson, Brett J; Beveridge, Christine A

2012-05-01

110

Shape-dependent charge and spin transport through an electron waveguide  

NASA Astrophysics Data System (ADS)

We study electron transport in nanosized semiconductor waveguides of different shapes. The spin-dependent transport through these nonuniform nanostructures is investigated in the presence of spin-orbit coupling of the Rashba and Dresselhaus types. The resulting spin rotation strongly depends on the shape of the waveguide. The crossover from the classical motion to the tunneling regime can be controlled in the waveguide with narrowing by modulating the strength of the Rashba spin-orbit coupling.

Ban, Yue; Sherman, E. Ya.

2013-01-01

111

The Contribution of Transporter-Dependent Uptake to Fetal Catecholamine Clearance  

Microsoft Academic Search

These studies were designed to determine the contribution of cocaine-sensitive, transporter-dependent, reuptake mechanisms to the intrauterine norepinephrine clearance rate in chronically catheterized fetal sheep. Baseline norepinephrine clearance and appearance rates were 125 ą 20 ml\\/kg\\/min and 85 ą 11 ng\\/kg\\/min, respectively. Transporter-dependent clearance represented 40% of the intrauterine clearance rate. The effects of chronic cocaine administration on fetal catecholamine clearance

Lisanne Bzoskie; Leslie Blount; Kent Kashiwai; James Humme; James F. Padbury

1997-01-01

112

Linear Approximation SAR Azimuth Processing Study  

NASA Technical Reports Server (NTRS)

A segmented linear approximation of the quadratic phase function that is used to focus the synthetic antenna of a SAR was studied. Ideal focusing, using a quadratic varying phase focusing function during the time radar target histories are gathered, requires a large number of complex multiplications. These can be largely eliminated by using linear approximation techniques. The result is a reduced processor size and chip count relative to ideally focussed processing and a correspondingly increased feasibility for spaceworthy implementation. A preliminary design and sizing for a spaceworthy linear approximation SAR azimuth processor meeting requirements similar to those of the SEASAT-A SAR was developed. The study resulted in a design with approximately 1500 IC's, 1.2 cubic feet of volume, and 350 watts of power for a single look, 4000 range cell azimuth processor with 25 meters resolution.

Lindquist, R. B.; Masnaghetti, R. K.; Belland, E.; Hance, H. V.; Weis, W. G.

1979-01-01

113

Linear approximation SAR azimuth processing study  

NASA Technical Reports Server (NTRS)

A segmented linear approximation of the quadratic phase function that is used to focus the synthetic antenna of a SAR was studied. Ideal focusing, using a quadratic varying phase focusing function during the time radar target histories are gathered, requires a large number of complex multiplications. These can be largely eliminated by using linear approximation techniques. The result is a reduced processor size and chip count relative to ideally focussed processing and a correspondingly increased feasibility for spaceworthy implementation. A preliminary design and sizing for a spaceworthy linear approximation SAR azimuth processor meeting requirements similar to those of the SEASAT-A SAR was developed. The study resulted in a design with approximately 1500 IC's, 1.2 cubic feet of volume, and 350 watts of power for a single look, 4000 range cell azimuth processor with 25 meters resolution.

Lindquist, R. B.; Masnaghetti, R. K.; Belland, E.; Hance, H. V.; Weis, W. G.

1979-01-01

114

Functional characterization of a Na+-dependent dicarboxylate transporter from Vibrio cholerae.  

PubMed

The SLC13 transporter family, whose members play key physiological roles in the regulation of fatty acid synthesis, adiposity, insulin resistance, and other processes, catalyzes the transport of Krebs cycle intermediates and sulfate across the plasma membrane of mammalian cells. SLC13 transporters are part of the divalent anion:Na(+) symporter (DASS) family that includes several well-characterized bacterial members. Despite sharing significant sequence similarity, the functional characteristics of DASS family members differ with regard to their substrate and coupling ion dependence. The publication of a high resolution structure of dimer VcINDY, a bacterial DASS family member, provides crucial structural insight into this transporter family. However, marrying this structural insight to the current functional understanding of this family also demands a comprehensive analysis of the transporter's functional properties. To this end, we purified VcINDY, reconstituted it into liposomes, and determined its basic functional characteristics. Our data demonstrate that VcINDY is a high affinity, Na(+)-dependent transporter with a preference for C4- and C5-dicarboxylates. Transport of the model substrate, succinate, is highly pH dependent, consistent with VcINDY strongly preferring the substrate's dianionic form. VcINDY transport is electrogenic with succinate coupled to the transport of three or more Na(+) ions. In contrast to succinate, citrate, bound in the VcINDY crystal structure (in an inward-facing conformation), seems to interact only weakly with the transporter in vitro. These transport properties together provide a functional framework for future experimental and computational examinations of the VcINDY transport mechanism. PMID:24821967

Mulligan, Christopher; Fitzgerald, Gabriel A; Wang, Da-Neng; Mindell, Joseph A

2014-06-01

115

Spin dependent transport and recombination in organic lightemitting diodes  

NASA Astrophysics Data System (ADS)

Electrically Detected Magnetic Resonance (EDMR) was used to study a series of multilayer organic devices based on aluminum (III) 8-hydroxyquinoline (Alq3). These devices were designed to identify the microscopic origin of different spin dependent process, i.e. hopping and exciton formation. For electroluminescent diode the EDMR signal can be decomposed in at least two gaussian components with peak-to-peak linewidth (HPP ) of 1.6 mT and another with 2.0 mT to 3.4 mT. These components are dependent on the applied bias or current used during EDMR measurements. The narrower line was attributed to the exciton precursor cations, while the broad one to the anions. These attributions are supported by the investigation of unipolar diodes, where hopping process related to dication and dianion formation were observed. In this work it is found that the probability of singlet exciton formation during electroluminescency is smaller than 25%.

Silva, George B.; Nüesch, Frank; Zuppiroli, Libero; Graeff, Carlos F. O.

2005-08-01

116

Spin dependent transport and recombination in organic lightemitting diodes  

Microsoft Academic Search

Electrically Detected Magnetic Resonance (EDMR) was used to study a series of multilayer organic devices based on aluminum (III) 8-hydroxyquinoline (Alq3). These devices were designed to identify the microscopic origin of different spin dependent process, i.e. hopping and exciton formation. For electroluminescent diode the EDMR signal can be decomposed in at least two gaussian components with peak-to-peak linewidth (HPP )

George B. Silva; Frank Nüesch; Libero Zuppiroli; Carlos F. O. Graeff

2005-01-01

117

Dopamine transporter as target for drug development of cocaine dependence medications.  

PubMed

Because much evidence implicates the dopamine transporter in the reinforcing effects of cocaine, development of potential medications for cocaine dependence has included the dopamine transporter as a target. The present overview covers progress in the drug development area regarding several classes of dopamine uptake inhibitors, with an emphasis on structure-activity relationships that enhance potency and selectivity at transporters for dopamine compared with those for serotonin or norepinephrine. The following categories of compounds are covered: tropane, benztropine, 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (GBR), methylphenidate, mazindol, and phencyclidine analogs. Activity at transporters as well as on behavior is highlighted. PMID:14612141

Dutta, Aloke K; Zhang, Shijun; Kolhatkar, Rohit; Reith, Maarten E A

2003-10-31

118

Diameter-dependent ion transport through the interior of isolated single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Nanopores that approach molecular dimensions demonstrate exotic transport behaviour and are theoretically predicted to display discontinuities in the diameter dependence of interior ion transport because of structuring of the internal fluid. No experimental study has been able to probe this diameter dependence in the 0.5-2?nm diameter regime. Here we observe a surprising fivefold enhancement of stochastic ion transport rates for single-walled carbon nanotube centered at a diameter of approximately 1.6?nm. An electrochemical transport model informed from literature simulations is used to understand the phenomenon. We also observe rates that scale with cation type as Li+>K+>Cs+>Na+ and pore blocking extent as K+>Cs+>Na+>Li+ potentially reflecting changes in hydration shell size. Across several ion types, the pore-blocking current and inverse dwell time are shown to scale linearly at low electric field. This work opens up new avenues in the study of transport effects at the nanoscale.

Choi, Wonjoon; Ulissi, Zachary W.; Shimizu, Steven F. E.; Bellisario, Darin O.; Ellison, Mark D.; Strano, Michael S.

2013-09-01

119

Size-dependent predilections of cardiogenic embolic transport.  

PubMed

While it is intuitively clear that aortic anatomy and embolus size could be important determinants for cardiogenic embolic stroke risk and stroke location, few data exist confirming or characterizing this hypothesis. The objective of this study is to use medical imaging and computational modeling to better understand if aortic anatomy and embolus size influence predilections for cardiogenic embolic transport and right vs. left hemisphere propensity. Anatomically accurate models of the human aorta and branch arteries to the head were reconstructed from computed tomography (CT) angiography of 10 patients. Blood flow was modeled by the Navier-Stokes equations using a well-validated flow solver with physiologic inflow and boundary conditions. Embolic particulate was released from the aortic root and tracked through the common carotid and vertebral arteries for a range of particle sizes. Cardiogenic emboli reaching the carotid and vertebral arteries appeared to have a strong size-destination relationship that varied markedly from expectations based on blood distribution. Observed trends were robust to modeling parameters. A patient's aortic anatomy appeared to significantly influence the probability a cardiogenic particle becomes embolic to the head. Right hemisphere propensity appeared dominant for cardiogenic emboli, which has been confirmed clinically. The predilections discovered through this modeling could represent an important mechanism underlying cardiogenic embolic stroke etiology. PMID:23792681

Carr, Ian A; Nemoto, Naohiko; Schwartz, Robert S; Shadden, Shawn C

2013-09-01

120

Deterministic methods for time-dependent stochastic neutron transport  

SciTech Connect

A numerical method is presented for solving the time-dependent survival probability equation in general (lD/2D/3D) geometries using the multi group SNmethod. Although this equation was first formulated by Bell in the early 1960's, it has only been applied to stationary systems (for other than idealized point models) until recently, and detailed descriptions of numerical solution techniques are lacking in the literature. This paper presents such a description and applies it to a dynamic system representative of a figurative criticality accident scenario.

Baker, Randal S [Los Alamos National Laboratory

2009-01-01

121

Feedback Control Of An Azimuthal Oscillation In The ExB Discharge of Hall Thrusters  

SciTech Connect

Feedback control of a low-frequency azimuthal wave known as a "rotating spoke" in the ExB discharge of a cylindrical Hall thruster was demonstrated. The rotating spoke is an m=1 azimuthal variation in density, electron temperature, and potential that rotates at about 10% of the local E x B electron rotation speed. It causes increased electron transport across the magnetic field and is suspected to be an ionization wave. Feedback control of this wave required special consideration because, although it causes a rotating azimuthal variation in the current density to the anode, it does not show up as a signal in the total thruster discharge current. Therefore, an extra source of information was needed to track the oscillation, which was addressed by using a special anode that was split azimuthally into four segments. The current to each segment oscillates as the rotating spoke passes over it, and feedback is accomplished by resistors connected in series with each anode segment which cause the voltage on a segment to decrease in proportion to the current through that segment. The feedback resulted in the disappearance of a coherent azimuthal wave and a decrease in the time-averaged total discharge current by up to 13.2%.

Martin E. Griswold, C.L. Ellison, Y. Raitses and N.J. Fisch

2012-04-06

122

Poplar potassium transporters capable of controlling K+ homeostasis and K+-dependent xylogenesis  

Microsoft Academic Search

Summary The cambial Kţ content of poplar increases during the growth period in a Kţ supply dependent manner. Upon Kţ starvation or application of tetraethylammoniumchloride (TEAţ), a Kţ channel blocker, the aver- age vessel lumen and expansion zone area were significantly reduced. In search for the molecular basis of potassium-dependent xylogenesis in poplar, Kţ transporters homologous to those of known

Katharina Langer; Peter Ache; Dietmar Geiger; Andrea Stinzing; Matthias Arend; Christa Wind; Sharon Regan; Jorg Fromm; Rainer Hedrich

2002-01-01

123

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

SciTech Connect

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)

Boyarinov, V. F.; Kondrushin, A. E.; Fomichenko, P. A. [National Research Center, Kurchatov Inst., Kurchatov Sq. 1, Moscow (Russian Federation)

2012-07-01

124

Asymptotic analysis of the several competitive equations to solve the time-dependent neutron transport equation  

SciTech Connect

Using conventional diffusion limit analysis, we asymptotically compare three competitive time-dependent equations (the telegrapher`s equation, the time-dependent Simplified P{sub 2} (SP{sub 2}) equation, and the time-dependent Simplified Evcn-Parity (SEP) equation). The time-dependent SP{sub 2} equation contains higher order asymptotic approximations of the time-dependent transport equation than the other equations in a physical regime in which the time-dependent diffusion equation is the leading order approximation. In addition, we derive the multigroup modified time-dependent SP{sub 2} equation from the multigroup time-dependent transport equation by means of an asymptotic expansion in which the multigroup time-dependent diffusion equation is the leading, order approximation. Numerical comparisons of the timedependent diffusion, the telegrapher`s, the time-dependent SP{sub 2}, and S{sub 8} solutions in 2-D X-Y geometry show that, in most cases, the SP{sub 2} solutions contain most of the transport corrections for the diffusion approximation.

Shin, U.; Miller, W.F. Jr. [California Univ., Berkeley, CA (United States)]|[Los Alamos National Lab., NM (United States); Morel, J.E. [Los Alamos National Lab., NM (United States)

1994-10-01

125

Evaluation of Different Strategies for Mitigating Azimuthally Asymmetric Tropospheric Delays  

NASA Astrophysics Data System (ADS)

Observations occurring at low elevation angles are beneficial for space geodetic techniques as they improve the observational geometry and redundancy of the estimated solutions. Due to horizontal variations in the Earth's neutral atmosphere, most tropospheric delay mapping functions are not capable of accurately modeling the delay at low elevation angles as they assume the Earth's atmosphere to be azimuthally symmetric. It is possible to estimate tropospheric gradient parameters to account for the bulk of the asymmetric delay, but these gradients account for only a single main direction of asymmetry, and their estimation reduces the redundancy of the solution especially for applications requiring short observation sessions. To help overcome these challenges, ray-tracing through numerical weather models (NWM) is a promising technique to model both the elevation angle- and azimuth-dependence of the tropospheric delay. We evaluate three strategies for mitigating the asymmetric tropospheric delay: (a) unaided GPS estimation; (b) NWM-aided GPS estimation; and (c) NWM-prediction (no GPS estimation). Strategy (a) consists of employing solely the GPS observations themselves to determine the tropospheric gradient parameters following the standard strategy, recommended in the updated IERS Conventions. In strategy (b) we employ a priori information provided by the NWM to constrain the direction of the delay gradient, needing to estimate only its magnitude from the GPS observations. Finally, in (c)we rely solely on the slant factors (the ratio between slant delays and zenith delay), obtained by ray-tracing in a 3D NWM. Notice that in (a) and (b) we assume the delay exhibits a single dominant direction of azimuthal asymmetry, while in (c) we make no assumptions about the nature of the asymmetries. While this work focuses on azimuthally asymmetric portion of the delay, we evaluate, en passant, the strategy of (d) constraining slant delays (or slant factors) at the observation level, thereby dismissing even the estimation of zenith delays. Unlike previous studies that have used three dimensional ray-traced slant delays (Hobiger, 2008), we have chosen to parameterize the delay in terms of slant factors. The use of slant factors will prove to be beneficial by allowing for the direct estimation of residual tropospheric delay and could allow the direct use of external troposphere zenith delay measurements in combination with the ray-traced slant factors. The four strategies for mitigating the asymmetric tropospheric delay are applied to a GPS precise point positioning (PPP) campaign. The tropospheric gradients derived from methods (a) - (c) are compared to determine to what degree they are capable of representing real neutral atmosphere variation. The impact of the four processing strategies are compared based on the estimated parameters and convergence time.

Urquhart, Landon; Nievinski, Felipe G.; Santos, Marcelo C.

2010-05-01

126

The temperature dependence of maltose transport in ale and lager strains of brewer's yeast  

PubMed Central

Lager beers are traditionally made at lower temperatures (6–14 °C) than ales (15–25 °C). At low temperatures, lager strains (Saccharomyces pastorianus) ferment faster than ale strains (Saccharomyces cerevisiae). Two lager and two ale strains had similar maltose transport activities at 20 °C, but at 0 °C the lager strains had fivefold greater activity. AGT1, MTT1 and MALx1 are major maltose transporter genes. In nine tested lager strains, the AGT1 genes contained premature stop codons. None of five tested ale strains had this defect. All tested lager strains, but no ale strain, contained MTT1 genes. When functional AGT1 from an ale strain was expressed in a lager strain, the resultant maltose transport activity had the high temperature dependence characteristic of ale yeasts. Lager yeast MTT1 and MALx1 genes were expressed in a maltose-negative laboratory strain of S. cerevisiae. The resultant Mtt1 transport activity had low temperature dependence and the Malx1 activity had high temperature dependence. Faster fermentation at low temperature by lager strains than ale strains may result from their different maltose transporters. The loss of Agt1 transporters during the evolution of lager strains may have provided plasma membrane space for the Mtt1 transporters that perform better at a low temperature.

Vidgren, Virve; Multanen, Jyri-Pekka; Ruohonen, Laura; Londesborough, John

2010-01-01

127

ATP-dependent transport of vinblastine in vesicles from human multidrug-resistant cells  

SciTech Connect

Resistance of human cancer cells to multiple cytotoxic hydrophobic agents (multidrug resistance) is due to overexpression of the MDR1 gene, whose product is the plasma membrane P-glycoprotein. Plasma membrane vesicles partially purified from multidrug-resistant human KB carcinoma cells, but not from drug-sensitive cells, accumulate ({sup 3}H)vinblastine in an ATP-dependent manner. This transport is osmotically sensitive, with an apparent K{sub m} of 38 {mu}M for ATP and of {approx} 2 {mu}M for vinblastine. The nonhydrolyzable analog adenosine 5{prime}-({beta},{gamma}-imido)triphosphate does not substitute for ATP but is a competitive inhibitor of ATP for the transport process. Vanadate, and ATPase inhibitor, is a potent noncompetitive inhibitor of transport. These results indicate that hydrolysis of ATP is probably required for active transport vinblastine. Several other drugs to which multidrug-resistant cell lines are resistant inhibit transport, with relative potencies as follows: vincristine > actinomycin D > daunomycin > colchicine = puromycin. Verapamil and quinidine, which reverse the multidrug-resistance phenotype, are good inhibitors of the transport process. These results confirm that multidrug-resistant cells express an energy-dependent plasma membrane transporter for hydrophobic drugs, and establish a system for the detailed biochemical analysis of this transport process.

Horio, M.; Gottesman, M.M.; Pastan, I. (National Institutes of Health, Bethesda, MD (USA))

1988-05-01

128

Transcellular Transport of Benzole Acid Across Caco-2 Cells by a pH-Dependent and Carrier-Mediated Transport Mechanism  

Microsoft Academic Search

The pH-dependent transcellular transport of [14 C]benzoic acid across a Caco-2 cell monolayer is shown to be mediated by a monocarboxylic acid-specific carrier-mediated transport system, localized on the apical membrane. Evidence for the carrier-mediated transport of benzoic acid includes (a) the significant temperature and concentration dependence, (b) the metabolic energy dependence, (c) the inhibition by unlabeled benzoic acid and other

Akira Tsuji; Hitomi Takanaga; Ikumi Tamai; Tetsuya Terasaki

1994-01-01

129

Influence of the symmetry energy on the cone-azimuthal emission  

NASA Astrophysics Data System (ADS)

In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, effects of the symmetry energy on the evolutions of the free n/p ratio and the charged pion ratio in the semicentral collision of 197Au+197Au at an incident beam energy of 400 MeV/nucleon are studied. At the beginning of the reaction (before 11 fm/c) they are both affected by the low-density behavior of the symmetry energy but soon after are affected by the high-density behavior of the symmetry energy after nuclei are compressed (after 11 fm/c), and the effects of the symmetry energy are generally smaller compared with the central collision case. Interestingly, their dependences on the symmetry energy are shown to rise with an increase of the cone-azimuthal angle of the emitted particles. In the direction perpendicular to the reaction plane, the ?-/?+ ratio or the free n/p ratio, especially at high kinetic energies, exhibits significant sensitivity to the symmetry energy.

Gao, Yuan; Yong, G. C.; Wang, Yongjia; Li, Qingfeng; Zuo, Wei

2013-11-01

130

Azimuth orientation of the dragonfly (Sympetrum)  

NASA Technical Reports Server (NTRS)

Evidence is presented of directional orientation by an alighting dragonfly relative to the azimuth of the sun. The effects of wind direction on this orientation are analyzed. It was concluded that wind does not play a major role in orientation but may have some secondary function in helping greater numbers of dragonflies face windward more often than leeward. A search was made to find the principle sensory receptor for orientation. Two possibilities, the large compound eye and the frontal ocelli, were noted; however, no conclusive evidence could be found.

Hisada, M.

1972-01-01

131

Frequency Dependent Phonon Transport in Two-Dimensional Silicon and Diamond Thin Films  

NASA Astrophysics Data System (ADS)

Phonon transport in two-dimensional silicon and aluminum films is investigated. The frequency dependent solution of Boltzmann transport equation is obtained numerically to account for the acoustic and optical phonon branches. The influence of film size on equivalent equilibrium temperature distribution in silicon and aluminum films is presented. It is found that increasing film width influences phonon transport in the film; in which case, the difference between the equivalent equilibrium temperature due to silicon and diamond films becomes smaller for wider films than that of the thinner films.

Yilbas, B. S.; Bin Mansoor, S.

132

Evidence of geomagnetic effect on the azimuthal distribution of EAS in the ARGO-YBJ experiment  

NASA Astrophysics Data System (ADS)

The geomagnetic field affects the trajectories of the secondary charged particles of extensive air showers, causing their lateral distribution to be stretched. Thus both the density of the secondaries near the shower axis and the trigger efficiency of detector arrays decrease. The effect depends on the direction of the showers, thus involving the measured azimuthal distribution. This work concerns the non-uniformity of the azimuthal distribution studied by means of ARGO-YBJ data. The modulation is deeply investigated for different zenith angles. The influence of the geomagnetic field and detector effects are studied by means of a Monte Carlo simulation.

Sbano, S. N.

2013-06-01

133

A Deterministic-Monte Carlo Hybrid Method for Time-Dependent Neutron Transport Problems  

SciTech Connect

A new deterministic-Monte Carlo hybrid solution technique is derived for the time-dependent transport equation. This new approach is based on dividing the time domain into a number of coarse intervals and expanding the transport solution in a series of polynomials within each interval. The solutions within each interval can be represented in terms of arbitrary source terms by using precomputed response functions. In the current work, the time-dependent response function computations are performed using the Monte Carlo method, while the global time-step march is performed deterministically. This work extends previous work by coupling the time-dependent expansions to space- and angle-dependent expansions to fully characterize the 1D transport response/solution. More generally, this approach represents and incremental extension of the steady-state coarse-mesh transport method that is based on global-local decompositions of large neutron transport problems. An example of a homogeneous slab is discussed as an example of the new developments.

Justin Pounders; Farzad Rahnema

2001-10-01

134

Forecasting Fractures in Coal Seams by Using Azimuthal Anisotropy from P-Wave Seismic Data  

Microsoft Academic Search

If the thickness of coal seams and the lithology of both roofs and floors of coal seams have not changed at all or only a little, then it is thought that the elastic anisotropy of coal seams depends mainly on fractures and obeys the horizontally symmetric model of an azimuth anisotropy. For a fixed offset, the amplitude A of the

Shou-hua DONG; Jian-hua YUE; Fen-xuan ZHANG

2007-01-01

135

Azimuthal Anisotropy of Light Extraction from Photonic Crystal Light-emitting Diodes  

Microsoft Academic Search

Photonic crystal light-emitting diodes exhibiting anisotropic light extraction efficiency have been investigated experimentally and theoretically. Images of the anisotropy in the azimuthal direction are obtained using annular structures with triangular lattice. Depending on the lattice constants, 6-fold symmetric patterns with varying number of petals are obtained.

H. T. Hsueh; J.-F. T. Wang; C. H. Chao; W. Y. YehandJ; J. Y. Chi; C. F. Lai; H. C. Kuo; T. C. Lu; S. C. Wang

2007-01-01

136

Using an electronic compass to determine telemetry azimuths  

USGS Publications Warehouse

Researchers typically collect azimuths from known locations to estimate locations of radiomarked animals. Mobile, vehicle-mounted telemetry receiving systems frequently are used to gather azimuth data. Use of mobile systems typically involves estimating the vehicle's orientation to grid north (vehicle azimuth), recording an azimuth to the transmitter relative to the vehicle azimuth from a fixed rosette around the antenna mast (relative azimuth), and subsequently calculating an azimuth to the transmitter (animal azimuth). We incorporated electronic compasses into standard null-peak antenna systems by mounting the compass sensors atop the antenna masts and evaluated the precision of this configuration. This system increased efficiency by eliminating vehicle orientation and calculations to determine animal azimuths and produced estimates of precision (azimuth SD=2.6 deg., SE=0.16 deg.) similar to systems that required orienting the mobile system to grid north. Using an electronic compass increased efficiency without sacrificing precision and should produce more accurate estimates of locations when marked animals are moving or when vehicle orientation is problematic.

Cox, R. R., Jr.; Scalf, J. D.; Jamison, B. E.; Lutz, R. S.

2002-01-01

137

Diameter-dependent electronic transport properties of Au-catalyst/Ge-nanowire Schottky diodes  

SciTech Connect

We present electronic transport measurements in individual Au-catalyst/Ge-nanowire interfaces demonstrating the presence of a Schottky barrier. Surprisingly, the small-bias conductance density increases with decreasing diameter. Theoretical calculations suggest that this effect arises because electron-hole recombination in the depletion region is the dominant charge transport mechanism, with a diameter dependence of both the depletion width and the electron-hole recombination time. The recombination time is dominated by surface contributions and depends linearly on the nanowire diameter.

Picraux, S Thomas [Los Alamos National Laboratory; Leonard, Francois [SNL; Swartzentruber, Brian S [SNL; Talin, A Alee [SNL

2008-01-01

138

A transition in mechanisms of size dependent electrical transport at nanoscale metal-oxide interfaces  

NASA Astrophysics Data System (ADS)

As device miniaturization approaches nanoscale dimensions, interfaces begin to dominate electrical properties. Here the system archetype Au/SrTiO3 is used to examine the origin of size dependent transport properties along metal-oxide interfaces. We demonstrate that a transition between two classes of size dependent electronic transport mechanisms exists, defined by a critical size ?. At sizes larger than ? an edge-related tunneling effect proportional to 1/D (the height of the supported Au nanoparticle) is observed; interfaces with sizes smaller than ? exhibit random fluctuations in current. The ability to distinguish between these mechanisms is important to future developments in nanoscale device design.

Hou, Jiechang; Nonnenmann, Stephen S.; Qin, Wei; Bonnell, Dawn A.

2013-12-01

139

Temperature dependent electrical transport behavior of InN/GaN heterostructure based Schottky diodes  

SciTech Connect

InN/GaN heterostructure based Schottky diodes were fabricated by plasma-assisted molecular beam epitaxy. The temperature dependent electrical transport properties were carried out for InN/GaN heterostructure. The barrier height and the ideality factor of the Schottky diodes were found to be temperature dependent. The temperature dependence of the barrier height indicates that the Schottky barrier height is inhomogeneous in nature at the heterostructure interface. The higher value of the ideality factor and its temperature dependence suggest that the current transport is primarily dominated by thermionic field emission (TFE) other than thermionic emission (TE). The room temperature barrier height obtained by using TE and TFE models were 1.08 and 1.43 eV, respectively.

Roul, Basanta; Kumar, Mahesh [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India); Rajpalke, Mohana K.; Bhat, Thirumaleshwara N.; Krupanidhi, S. B. [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Sinha, Neeraj [Office of Principal Scientific Advisor, Government of India, New Delhi 110011 (India); Kalghatgi, A. T. [Central Research Laboratory, Bharat Electronics, Bangalore 560013 (India)

2011-02-15

140

Identification of a high affinity taurine transporter which is not dependent on chloride.  

PubMed

Taurine transport by lactating gerbil mammary tissue has been examined. Taurine uptake is mediated by a high-affinity system which is specific for beta-amino acids. The uptake of taurine is Na(+)-dependent but appears not to be obligatory dependent upon Cl-. Thus, replacing Na+ with choline almost abolished taurine uptake. Substituting Cl- with NO3- had no effect whereas SCN- induced a small but significant increase in taurine influx. Taurine uptake was Na(+)-dependent under conditions where Cl- had been replaced with NO3-. However, it is apparent that the Na(+)-dependent taurine transport system requires the presence of a permeable anion because replacing Cl- with gluconate markedly reduced taurine uptake. Cell-swelling, induced by a hyposmotic challenge, increased the efflux of taurine from gerbil mammary tissue via a pathway sensitive to niflumic acid. PMID:8562874

Shennan, D B

1995-08-01

141

Drell-Yan Lepton Pair Azimuthal Asymmetry in Hadronic Processes  

SciTech Connect

We study the azimuthal asymmetry in the Drell-Yan lepton pair production in hadronic scattering processes at moderate transverse momentum region, taking into account the contributions from the twist-three quark-gluon correlations from the unpolarized hadrons. The contributions are found to dominate the asymmetry, and are not power suppressed by qt/Q at small qt where qt and Q are the transverse momentum and invariant mass of the lepton pair. Accordingly, the Lam-Tung relation will be violated at this momentum region, and its violation depends on the twist-three functions. However, at large transverse momentum qt~;;Q, the Lam-Tung relation still holds because all corrections are power suppressed by Lambda2/qt2 ~;; Lambda2/Q2 where Lambda is the typical nonperturbative scale.

Zhou, Jian; Yuan, Feng; Liang, Zuo-Tang

2009-01-22

142

Field Dependent Transport Properties in InAs Nanowire Field Effect Transistors  

Microsoft Academic Search

We present detailed studies of the field dependent transport properties of InAs nanowire field-effect transistors. Transconductance dependence on both vertical and lateral fields is discussed. Velocity-field plots are constructed from a large set of output and transfer curves that show negative differential conductance behavior and marked mobility degradation at high injection fields. Two dimensional electrothermal simulations at current densities similar

Shadi A. Dayeh; Darija Susac; Karen L. Kavanagh; Edward T. Yu; Deli Wang

2008-01-01

143

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

PubMed Central

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.

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

1993-01-01

144

pH-Dependent transport of pemetrexed by breast cancer resistance protein.  

PubMed

Breast cancer resistance protein (BCRP), an ATP-dependent efflux transporter, confers drug resistance to many chemotherapy agents. BCRP is overexpressed in tumors exposed to an acidic environment; therefore, it is important to establish the effect of low pH on BCRP transport activity. It has recently been reported that BCRP transports substrates more efficiently in an acidic microenvironment. In the study presented here, we examine the pH dependence of BCRP using methothrexate (MTX), pemetrexed (PMX), and estrone sulfate (ES) as model substrates. Our study revealed an increase of approximately 40-fold in the BCRP-mediated transport of PMX and MTX when the pH was decreased from 7.4 to 5.5. In contrast, only a 2-fold increase was observed for ES. These results indicate a mechanism of transport that is directly dependent on the effective ionization state of the substrates and BCRP. For ES, which retains a constant ionization state throughout the applied pH, the observed mild increase in activity is attributable to the overall changes in the effective ionization state and conformation of BCRP. For MTX and PMX, the marked increase in BCRP transport activity was likely due to the change in ionization state of MTX and PMX at lowered pH and their intermolecular interactions with BCRP. To further rationalize the molecular basis of the pH dependence, molecular modeling and docking studies were carried out using a homology model of BCRP, which has previously been closely examined in structural and site-directed mutagenesis studies (Am J Physiol Cell Physiol 299:C1100-C1109, 2010). On the basis of docking studies, all model compounds were found to associate with arginine 482 (Arg482) by direct salt-bridge interactions via their negatively charged carboxylate or sulfate groups. However, at lower pH, protonated MTX and PMX formed an additional salt-bridge interaction between their positively charged moieties and the nearby negatively charged aspartic acid 477 (Asp477) carboxylate side chain. The formation of this "salt-bridge triad" is expected to increase the overall electrostatic interactions between MTX and PMX with BCRP, which can form a rational basis for the pH dependence of the observed enhanced binding selectivity and transport activity. Removal of Arg482 in site-directed mutagenesis studies eliminated this pH dependence, which lends further support to our binding model. These results shed light on the importance of electrostatic interactions in transport activity and may have important implications in the design of ionizable chemotherapeutics intended for tumors in the acidic microenvironment. PMID:21628496

Li, Li; Sham, Yuk Yin; Bikadi, Zsolt; Elmquist, William F

2011-09-01

145

A general time-dependent stochastic method for solving Parker's transport equation in spherical coordinates  

Microsoft Academic Search

We present a detailed description of our newly developed stochastic approach for solving Parker's transport equation, which we believe is the first attempt to solve it with time dependence in 3-D, evolving from our 3-D steady state stochastic approach. Our formulation of this method is general and is valid for any type of heliospheric magnetic field, although we choose the

C. Pei; J. W. Bieber; R. A. Burger; J. Clem

2010-01-01

146

Molecular and functional analysis of SDCT2, a novel rat sodium-dependent dicarboxylate transporter.  

PubMed

Kidney proximal tubule cells take up Krebs cycle intermediates for metabolic purposes and for secretion of organic anions through dicarboxylate/organic anion exchange. Alteration in reabsorption of citrate is closely related to renal stone formation. The presence of distinct types of sodium-coupled dicarboxylate transporters has been postulated on either side of the polarized epithelial membrane in the kidney proximal tubule. Using a PCR-based approach, we isolated a novel member of the sodium-dependent dicarboxylate/sulfate transporter called SDCT2. SDCT2 is a 600-amino acid residue protein that has 47-48% amino acid identity to SDCT1 and NaDC-1, previously identified in kidney and intestine. Northern analysis gave a single band of 3.3 kb for SDCT2 in kidney, liver, and brain. In situ hybridization revealed that SDCT2 is prominently expressed in kidney proximal tubule S3 segments and in perivenous hepatocytes, consistent with the sites of high-affinity dicarboxylate transport identified based on vesicle studies. A signal was also detected in the meningeal layers of the brain. SDCT2 expressed in Xenopus oocytes mediated sodium-dependent transport of di- and tricarboxylates with substrate preference for succinate rather than citrate, but excluding monocarboxylates. SDCT2, unlike SDCT1, displayed a unique pH dependence for succinate transport (optimal pH 7.5-8.5) and showed a high affinity for dimethylsuccinate, two features characteristic of basolateral transport. These data help to interpret the mechanisms of renal citrate transport, their alteration in pathophysiological conditions, and their role in the elimination of organic anions and therapeutic drugs. PMID:10207168

Chen, X; Tsukaguchi, H; Chen, X Z; Berger, U V; Hediger, M A

1999-04-01

147

Molecular and functional analysis of SDCT2, a novel rat sodium-dependent dicarboxylate transporter  

PubMed Central

Kidney proximal tubule cells take up Krebs cycle intermediates for metabolic purposes and for secretion of organic anions through dicarboxylate/organic anion exchange. Alteration in reabsorption of citrate is closely related to renal stone formation. The presence of distinct types of sodium-coupled dicarboxylate transporters has been postulated on either side of the polarized epithelial membrane in the kidney proximal tubule. Using a PCR-based approach, we isolated a novel member of the sodium-dependent dicarboxylate/sulfate transporter called SDCT2. SDCT2 is a 600–amino acid residue protein that has 47–48% amino acid identity to SDCT1 and NaDC-1, previously identified in kidney and intestine. Northern analysis gave a single band of 3.3 kb for SDCT2 in kidney, liver, and brain. In situ hybridization revealed that SDCT2 is prominently expressed in kidney proximal tubule S3 segments and in perivenous hepatocytes, consistent with the sites of high-affinity dicarboxylate transport identified based on vesicle studies. A signal was also detected in the meningeal layers of the brain. SDCT2 expressed in Xenopus oocytes mediated sodium-dependent transport of di- and tricarboxylates with substrate preference for succinate rather than citrate, but excluding monocarboxylates. SDCT2, unlike SDCT1, displayed a unique pH dependence for succinate transport (optimal pH 7.5–8.5) and showed a high affinity for dimethylsuccinate, two features characteristic of basolateral transport. These data help to interpret the mechanisms of renal citrate transport, their alteration in pathophysiological conditions, and their role in the elimination of organic anions and therapeutic drugs.

Chen, Xiangmei; Tsukaguchi, Hiroyasu; Chen, Xing-Zhen; Berger, Urs V.; Hediger, Matthias A.

1999-01-01

148

An asymptotic-preserving Lagrangian algorithm for the time-dependent anisotropic heat transport equation  

SciTech Connect

We propose a Lagrangian numerical algorithm for a time-dependent, anisotropic tem- perature transport equation in magnetized plasmas in the large guide field regime. The approach is based on an analytical integral formal solution of the parallel (i.e., along the magnetic field) transport equation with sources, and it is able to accommodate both lo- cal and nonlocal parallel heat flux closures. The numerical implementation is based on an operator-split formulation, with two straightforward steps: a perpendicular transport step (including sources), and a Lagrangian (field-line integral) parallel transport step. Al- gorithmically, the first step is amenable to the use of modern iterative methods, while the second step has a fixed cost per degree of freedom (and is therefore scalable). Accuracy- wise, the approach is free from the numerical pollution introduced by the discrete par- allel transport term when the perpendicular to parallel transport coefficient ratio / becomes arbitrarily small, and is shown to capture the correct limiting solution when / 0. Therefore, the approach is asymptotic-preserving. We demonstrate the ca- pabilities of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of transport across a magnetic island.

Chacon, Luis [ORNL] [ORNL; Del-Castillo-Negrete, Diego B [ORNL] [ORNL; Hauck, C. [Oak Ridge National Laboratory (ORNL)] [Oak Ridge National Laboratory (ORNL)

2014-01-01

149

Childhood Adversity, Serotonin Transporter (5-HTTLPR) Genotype, and Risk for Cigarette Smoking and Nicotine Dependence in Alcohol Dependent Adults  

PubMed Central

Background This study examined the extent to which cigarette smoking and nicotine dependence in adults with alcohol dependence (AD) are associated with adverse childhood experiences. Gender, social support, and an allelic variant in the gene encoding the serotonin transporter (5-HTTLPR) were examined as moderators of this relationship. Methods The Semi-Structured Assessment for the Genetics of Alcoholism- Version II (SSAGA-II) was used to assess DSM-IV diagnoses and cigarette smoking characteristics as well as traumatic life events and social support during childhood in 256 AD men (n=149) and women (n=107). Results An increase in number of adverse childhood events was associated with heightened risk of cigarette use and nicotine dependence. 5-HTTLPR genotype, gender, and social support did not significantly moderate the relationships among childhood adversity and ever-smoking or nicotine dependence. Conclusions Results extend previous findings to suggest that childhood adversity is strongly related to risk for ever-smoking and nicotine dependence in AD individuals. Additional research is needed to examine other potential genetic and environmental moderators and mediators of the relationships among smoking, alcohol use, and childhood trauma.

Mingione, Carolyn J.; Heffner, Jaimee L.; Blom, Thomas J.; Anthenelli, Robert M.

2011-01-01

150

The AMOS (Azimuthal Mode Simulator) code  

SciTech Connect

AMOS is a newly developed computer code that is finding application in the design of accelerator cavities. The program simulates the temporal evolution of electromagnetic fields in rotationally symmetric structures. An explicit Fourier series expansion is assumed in the azimuthal coordinate, which allows different multipole modes to be simulated independently. Nonuniform electrical properties (epsilon, ..mu.., sigma) are permitted, and both impedance and radiation boundary conditions are available. A geometric editor (DRAGON) allows for simple and rapid development/modification of models, and a direct CAD system-DRAGON data link is being used to facilitate the study of existing and developmental linac accelerator cells. A wakefield postprocessor (ANDY) allows the calculation of wake potentials, cavity impedances, etc., from AMOS simulation data. Code verification has consisted of comparisons with exact and approximate analytic results for simple geometries. 6 refs., 3 figs.

DeFord, J.F.; Craig, G.D.; McLeod, R.

1989-03-10

151

VACUUM calculation in azimuthally symmetric geometry  

SciTech Connect

A robustly accurate and effective method is presented to solve Laplace`s equation in general azimuthally symmetric geometry for the magnetic scalar potential in the region surrounding a plasma discharge which may or may not contain external conducting shells. These shells can be topologically toroidal or spherical, and may have toroidal gaps in them. The solution is incorporated into the various MHD stability codes either through the volume integrated perturbed magnetic energy in the vacuum region or through the continuity requirements for the normal component of the perturbed magnetic field and the total perturbed pressure across the unperturbed plasma-vacuum boundary. The method is based upon using Green`s second identity and the method of collocation. As useful byproducts, the eddy currents and the simulation of Mirnov loop measurements are calculated.

Chance, M.S.

1996-11-01

152

Beam energy dependence of azimuthal anisotropy at RHIC-PHENIX  

SciTech Connect

Recent PHENIX measurements of the elliptic ({upsilon}{sub 2}) and hexadecapole ({upsilon}{sub 4}) Fourier flow coefficients for charged hadrons as a function of transverse momentum (p{sub T}), collision centrality and particle species are presented and compared with results from the PHOBOS and STAR Collaborations respectively. The status of extensions to future PHENIX measurements at lower beam energies is also discussed.

Taranenko, A., E-mail: arkadij@rcf.rhic.bnl.gov [Stony Brook University, Department of Chemistry (United States)

2012-05-15

153

Spin-dependent tunneling transport into CrO2 nanorod devices with nonmagnetic contacts.  

PubMed

Single-crystal nanorods of half-metallic chromium dioxide (CrO2) were synthesized and structurally characterized. Spin-dependent electrical transport was investigated in individual CrO2 nanorod devices contacted with nonmagnetic metallic electrodes. Negative magnetoresistance (MR) was observed at low temperatures due to the spin-dependent direct tunneling through the contact barrier and the high spin polarization in the half-metallic nanorods. The magnitude of this negative magnetoresistance decreases with increasing bias voltage and temperature due to spin-independent inelastic hopping through the barrier, and a small positive magnetoresistance was found at room temperature. It is believed that the contact barrier and the surface state of the nanorods have great influence on the spin-dependent transport limiting the magnitude of MR effect in this first attempt at spin filter devices of CrO2 nanorods with nonmagnetic contacts. PMID:18616325

Song, Yipu; Schmitt, Andrew L; Jin, Song

2008-08-01

154

Oesophageal transport of solid dosage forms depends on body position, swallowing volume and pharyngeal propulsion velocity.  

PubMed

Knowledge about transit of solid dosage forms (SDF) in the gastrointestinal tract is incomplete. Detection of magnetically marked capsules (MMC) via superconducting quantum interference device (SQUID) allows monitoring of oesophageal transport of SDF with high tempospatial resolution. The aim of the study was to investigate the influence of body position, volume at swallowing, and oesophageal motility on orogastric transport of SDF. In 360 measurements we determined tempospatial characteristics of orogastric transit of SDFs by a SQUID device in six volunteers. They swallowed MMCs with various amounts of water in upright and supine position with and without simultaneous oesophageal manometry. Orogastric transit time, oesophageal transport velocity and rate of oesophageal retention of SDF depend on swallowing volume and body position at all experimental conditions. At 50 mL water bolus and in upright position, the retention rate depends on the pharyngeal propulsion velocity, and the transport velocity of MMCs in the oesophageal body are faster than the propulsive oesophageal contractions. Body position, swallowing volume and pharyngeal propulsion velocity markedly influence the oesophageal transport of SDF. They should be taken in upright body position with at least 50 mL of water to minimize entrapment in the oesophagus. PMID:15500511

Osmanoglou, E; Van Der Voort, I R; Fach, K; Kosch, O; Bach, D; Hartmann, V; Strenzke, A; Weitschies, W; Wiedenmann, B; Trahms, L; Mönnikes, H

2004-10-01

155

Dispersive transport in the temperature dependent transient photoresponse of organic photodiodes and solar cells  

NASA Astrophysics Data System (ADS)

The nanosecond transient photoresponse of organic solar cells and photodiodes based on a conjugated polymer (poly(3-hexylthiophene-2,5-diyl)) blended with a fullerene derivative ([6,6]-phenyl C61-butyric acid methyl ester) exhibits a strong temperature dependence, whose origin can be traced back to charge carrier transport phenomena. In the framework of a drift-diffusion model including multiple-trapping, the temperature dependence of effective mobilities arises naturally without the need of using a temperature dependent parameterization of the mobilities. Furthermore, the extended drift-diffusion simulation reproduces the measured change of slope of the transient current density from j(t)~t(-1+?) to j(t)~t(-1-?), indicating dispersive charge carrier transport influenced by an exponential trap distribution characterized by the dimensionless parameter ?. A second kink is identified to be the point in time of the crossover from electron to hole dominated charge carrier transport, enabling for the determination of the donor and acceptor transport properties independent of each other.

Christ, Nico; Kettlitz, Siegfried; Mescher, Jan; Valouch, Sebastian; Lemmer, Uli

2013-06-01

156

ATP-dependent bile-salt transport in canalicular rat liver plasma-membrane vesicles.  

PubMed Central

The present study identifies and characterizes a novel ATP-dependent bile-salt transport system in isolated canalicular rat liver plasma-membrane (cLPM) vesicles. ATP (1-5 mM) stimulated taurocholate uptake into cLPM vesicles between 6- and 8-fold above equilibrium uptake values (overshoot) and above values for incubations in the absence of ATP. The ATP-dependent portion of taurocholate uptake was 2-fold higher in the presence of equilibrated KNO3 as compared with potassium gluconate, indicating that the stimulatory effect of ATP was not due to the generation of an intravesicular positive membrane potential. Saturation kinetics revealed a very high affinity (Km approximately 2.1 microM) of the system for taurocholate. The system could only minimally be stimulated by nucleotides other than ATP. Furthermore, it was preferentially inhibited by conjugated univalent bile salts. Further strong inhibitory effects were observed with valinomycin, oligomycin, 4,4'-di-isothiocyano-2,2'-stilbene disulphonate, sulphobromophthalein, leukotriene C4 and N-ethylmaleimide, whereas nigericin, vanadate, GSH, GSSG and daunomycin exerted only weak inhibitory effects or none at all. These results indicate the presence of a high-affinity primary ATP-dependent bile-salt transport system in cLPM vesicles. This transport system might be regulated in vivo by the number of carriers present at the perspective transport site(s), which, in addition to the canalicular membrane, might also include pericanalicular membrane vesicles.

Stieger, B; O'Neill, B; Meier, P J

1992-01-01

157

Mass transport equations unifying descriptions of isothermal diffusion, thermomigration, segregation, and position-dependent diffusivity  

NASA Astrophysics Data System (ADS)

Via the combined use of the jump frequency and chemical force formulation methods, a set of generalized mass transport equations has been derived. This set of equations unifies the descriptions of isothermal diffusion, thermomigration induced by a thermal gradient, and segregation and the position-dependent diffusivity arising from the crystal inhomogeneity. The equations reproduce Fick's laws for the isothermal homogeneous crystal case, and the diffusion-segregation equations for the isothermal inhomogeneous crystal case. Also, a new expression for the heat of transport of thermomigration is obtained.

Tan, T. Y.

1998-11-01

158

Magnetic Resonance Measurement of Scale Dependent Dynamics in Porous Media: Interplay of Structure and Transport  

NASA Astrophysics Data System (ADS)

Experimental measurements of anomalous transport are needed to further test and complement understanding of models and numerical simulations of transport in reactive porous media. Magnetic resonance microscopy (MRM) represents a powerful tool for acquiring useful data due to the noninvasive nature of the technique, which can measure time and length scale dependent displacement dynamics inside opaque porous media. Experimental results for a model site percolation system indicate a dynamical scaling of the super-diffusive hydrodynamic dispersion, in contrast to classic percolation scaling arguments which predict only geometric scaling, and serve as a template for the comparison of theory and MRM experiments. MRM measurements in bio-reactive porous media containing biofilms have previously been shown to be well described as a transition from normal transport in a homogeneous medium to anomalous transport in a heterogeneous medium [1]. Recent results indicate that the underlying porous media structure before biofilm growth can impact or control the transition of the dynamics during bioactivity. General ideas related to measurement of anomalous transport by MRM will be considered. 1. J.D. Seymour et al., Anomalous fluid transport in porous media induced by biofilm growth, Phys. Rev. Lett. 93 (2004) 198103.

Seymour, J. D.; Codd, S. L.

2008-12-01

159

Polarization-Dependent Selective Transport to the Apical Membrane by KIF5B in MDCK Cells  

PubMed Central

SUMMARY Microtubule-based vesicular transport is well documented in epithelial cells, but the specific motors involved and their regulation during polarization are largely unknown. We demonstrate that KIF5B mediates post-Golgi transport of an apical protein in epithelial cells, but only after polarity has developed. Time-lapse imaging of EB1-GFP in polarized MDCK cells showed microtubule plus ends growing toward the apical membrane, implying that plus end-directed N-kinesins might be used to transport apical proteins. Indeed, time-lapse microscopy revealed that expression of a KIF5B dominant negative or microinjection of function-blocking KIF5 antibodies inhibited selectively post-Golgi transport of the apical marker, p75-GFP, after polarization of MDCK cells. Expression of other KIF dominant negatives did not alter p75-GFP trafficking. Immunoprecipitation experiments demonstrated an interaction between KIF5B and p75-GFP in polarized, but not in subconfluent, MDCK cells. Our results demonstrate that apical protein transport depends on selective microtubule motors and that epithelial cells switch kinesins for post-Golgi transport during acquisition of polarity.

Jaulin, Fanny; Xue, Xiaoxiao; Rodriguez-Boulan, Enrique; Kreitzer, Geri

2007-01-01

160

Sodium dependent multivitamin transporter (SMVT): a potential target for drug delivery.  

PubMed

Sodium dependent multivitamin transporter (SMVT; product of the SLC5A6 gene) is an important transmembrane protein responsible for translocation of vitamins and other essential cofactors such as biotin, pantothenic acid and lipoic acid. Hydropathy plot (Kyte-Dolittle algorithm) revealed that human SMVT protein consists of 635 amino acids and 12 transmembrane domains with both amino and carboxyl termini oriented towards the cytoplasm. SMVT is expressed in various tissues such as placenta, intestine, brain, liver, lung, kidney, cornea, retina and heart. This transporter displays broad substrate specificity and excellent capacity for utilization in drug delivery. Drug absorption is often limited by the presence of physiological (epithelial tight junctions), biochemical (efflux transporters and enzymatic degradation) and chemical (size, lipophilicity, molecular weight, charge etc.) barriers. These barriers may cause many potential therapeutics to be dropped from the preliminary screening portfolio and subsequent entry into the market. Transporter targeted delivery has become a powerful approach to deliver drugs to target tissues because of the ability of the transporter to translocate the drug to intracellular organelles at a higher rate. This review highlights studies employing SMVT transporter as a target for drug delivery to improve bioavailability and investigate the feasibility of developing SMVT targeted drug delivery systems. PMID:22420308

Vadlapudi, Aswani Dutt; Vadlapatla, Ramya Krishna; Mitra, Ashim K

2012-06-01

161

Measurement of plasma current dependent changes in impurity transport and comparison with nonlinear gyrokinetic simulation  

SciTech Connect

Measured impurity transport coefficients are found to demonstrate a strong dependence on plasma current in the core of Alcator C-Mod. These measurements are compared directly with linear and nonlinear gyrokinetic simulation in an attempt to both qualitatively and quantitatively reproduce the measured impurity transport. Discharges constituting a scan of plasma current from 0.6 to 1.2 MA were performed during the 2010 run campaign. The impurity transport from these discharges was determined using a novel set of spectroscopic diagnostics available on Alcator C-Mod. This diagnostic suite allowed for the effective constraint of impurity transport coefficient profiles inside of r/a = 0.6. A decrease in the measured impurity diffusivity and inward convection is found with increased plasma current. Global, nonlinear gyrokinetic simulations were performed using the GYRO code [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] for all discharges in the experimental scan and are found to reproduce the experimental trends, while demonstrating good quantitative agreement with measurement. A more comprehensive quantitative comparison was performed on the 0.8 MA discharge of the current scan which demonstrates that simultaneous agreement between experiment and simulation in both the impurity particle transport and ion heat transport channels is attainable within experimental uncertainties.

Howard, N. T.; Greenwald, M.; White, A. E.; Reinke, M. L.; Ernst, D.; Podpaly, Y. [MIT-Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Mikkelsen, D. R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Candy, J. [General Atomics, San Diego, California 92186 (United States)

2012-05-15

162

Time-dependent 2-D modeling of edge plasma transport with high intermittency due to blobs  

SciTech Connect

The results on time-dependent 2-D fluid modeling of edge plasmas with non-diffusive intermittent transport across the magnetic field (termed cross-field) based on the novel macro-blob approach are presented. The capability of this approach to simulate the long temporal evolution ({approx}0.1 s) of the background plasma and simultaneously the fast spatiotemporal dynamics of blobs ({approx}10{sup -4} s) is demonstrated. An analysis of a periodic sequence of many macro-blobs (PSMB) is given showing that the resulting plasma attains a dynamic equilibrium. Plasma properties in the dynamic equilibrium are discussed. In PSMB modeling, the effect of macro-blob generation frequency on edge plasma parameters is studied. Comparison between PSMB modeling and experimental profile data is given. The calculations are performed for the same plasma discharge using two different models for anomalous cross-field transport: time-average convection and PSMB. Parametric analysis of edge plasma variation with transport coefficients in these models is presented. The capability of the models to accurately simulate enhanced transport due to blobs is compared. Impurity dynamics in edge plasma with macro-blobs is also studied showing strong impact of macro-blob on profiles of impurity charge states caused by enhanced outward transport of high-charge states and simultaneous inward transport of low-charge states towards the core. Macro-blobs cause enhancement of sputtering rates, increase radiation and impurity concentration in plasma, and change erosion/deposition patterns.

Pigarov, A. Yu.; Krasheninnikov, S. I. [University of California at San Diego, La Jolla, California 92093 (United States); Rognlien, T. D. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2012-07-15

163

Type 1 sodium-dependent phosphate transporter acts as a membrane potential-driven urate exporter.  

PubMed

SLC17A1 protein (NPT1) was the first identified member of the SLC17 phosphate transporter family, and is known to mediate Na(+)/inorganic phosphate (Pi) co-transport when expressed in Xenopus oocytes. Although this protein was suggested to be a renal polyspecific anion exporter, its transport properties were not well characterized. The clean biochemical approach revealed that proteoliposomes comprising purified NPT1 as the only protein source transport various organic anions such as urate, p-aminohippuric acid (PAH), and acetylsalicylic acid (aspirin) in a membrane potential (??)-driven and Cl(-) -dependent manner. Human NPT1 carrying an SNP mutation, Thr269Ile, known to increase the risk of gout, exhibited 32% lower urate transport activity compared to the wild type protein, leading to the conclusion that NPT1 is the long searched for transporter responsible for renal urate excretion. In the present article, we summarized the history of identification of the urate exporter and its possible involvement in the dynamism of urate under physiological and pathological conditions. PMID:23876149

Miyaji, Takaaki; Kawasaki, Tatsuya; Togawa, Natsuko; Omote, Hiroshi; Moriyama, Yoshinori

2013-07-01

164

Screening-induced temperature-dependent transport in two-dimensional graphene  

NASA Astrophysics Data System (ADS)

We calculate the temperature-dependent conductivity of graphene in the presence of randomly distributed Coulomb impurity charges arising from the temperature-dependent screening of the Coulomb disorder without any phonons. The purely electronic temperature dependence of our theory arises from two independent mechanisms: the explicit temperature dependence of the finite-temperature dielectric function ?(q,T) and the finite-temperature energy averaging of the transport scattering time. We find that the calculated temperature-dependent conductivity is nonmonotonic, decreasing with temperature at low temperatures, and increasing at high temperatures. We provide a critical comparison with the corresponding physics in semiconductor-based parabolic band 2D electron-gas systems.

Hwang, E. H.; Das Sarma, S.

2009-04-01

165

Frequency dependent enhancement of heat transport in a nanofluid with ZnO nanoparticles.  

PubMed

In this paper we report an observation of an unusual frequency dependent enhancement of the heat transport parameter (C(p)kappa, C(p) = heat capacity and kappa = thermal conductivity) of a nanofluid containing ZnO nanoparticles of an average size of 10 nm (volume fractiondependence on the measuring frequency where it decreases as the frequency is increased. The enhancement also depends on the temperature and also scales with the concentration of ZnO. This frequency dependent thermal conductivity of nanofluids cannot be explained by the classical effective medium theory. A new model has to be developed to explain the above phenomenon. We have suggested local aggregation as the likely cause that may give rise to the observed frequency dependence. PMID:19584421

Neogy, R K; Raychaudhuri, A K

2009-07-29

166

Cyclic GMP-dependent Stimulation of Serotonin Transport Does Not Involve Direct Transporter Phosphorylation by cGMP-dependent Protein Kinase*  

PubMed Central

The serotonin transporter (SERT) is responsible for reuptake of serotonin (5-hydroxytryptamine) after its exocytotic release from neurons. It is the primary target for antidepressants and stimulants, including “ecstasy” (3,4-methylenedioxymethamphetamine). SERT is regulated by several processes, including a cyclic GMP signaling pathway involving nitric oxide synthase, guanylyl cyclase, and cGMP-dependent protein kinase (PKG). Here, we show that SERT was phosphorylated in a PKG I?-dependent manner in vitro, but that SERT was not a direct substrate of PKG. We generated an analog-sensitive gatekeeper residue mutant of PKG I? (M438G) that efficiently used the ATP analog N6-benzyl-ATP. This mutant, but not the wild type (WT) kinase, used the ATP analog to phosphorylate both a model peptide substrate as well as an established protein substrate of PKG (vasodilator-stimulated phosphoprotein). PKG I? M438G effectively substituted for the WT kinase in stimulating SERT-mediated 5-hydroxytryptamine transport in cultured cells. Addition of either WT or mutant PKG I? M438G to membranes containing SERT in vitro led to radiolabel incorporation from [?-33P]ATP but not from similarly labeled N6-benzyl-ATP, indicating that SERT was phosphorylated by another kinase that could not utilize the ATP analog. These results are consistent with the proposed SERT phosphorylation site, Thr-276, being highly divergent from the consensus PKG phosphorylation site sequence, which we verified through peptide library screening. Another proposed SERT kinase, the p38 mitogen-activated protein kinase, could not substitute for PKG in this assay, and p38 inhibitors did not block PKG-dependent phosphorylation of SERT. The results suggest that PKG initiates a kinase cascade that leads to phosphorylation of SERT by an as yet unidentified protein kinase.

Wong, Albert; Zhang, Yuan-Wei; Jeschke, Grace R.; Turk, Benjamin E.; Rudnick, Gary

2012-01-01

167

Cyclic GMP-dependent stimulation of serotonin transport does not involve direct transporter phosphorylation by cGMP-dependent protein kinase.  

PubMed

The serotonin transporter (SERT) is responsible for reuptake of serotonin (5-hydroxytryptamine) after its exocytotic release from neurons. It is the primary target for antidepressants and stimulants, including "ecstasy" (3,4-methylenedioxymethamphetamine). SERT is regulated by several processes, including a cyclic GMP signaling pathway involving nitric oxide synthase, guanylyl cyclase, and cGMP-dependent protein kinase (PKG). Here, we show that SERT was phosphorylated in a PKG I?-dependent manner in vitro, but that SERT was not a direct substrate of PKG. We generated an analog-sensitive gatekeeper residue mutant of PKG I? (M438G) that efficiently used the ATP analog N(6)-benzyl-ATP. This mutant, but not the wild type (WT) kinase, used the ATP analog to phosphorylate both a model peptide substrate as well as an established protein substrate of PKG (vasodilator-stimulated phosphoprotein). PKG I? M438G effectively substituted for the WT kinase in stimulating SERT-mediated 5-hydroxytryptamine transport in cultured cells. Addition of either WT or mutant PKG I? M438G to membranes containing SERT in vitro led to radiolabel incorporation from [?-(33)P]ATP but not from similarly labeled N(6)-benzyl-ATP, indicating that SERT was phosphorylated by another kinase that could not utilize the ATP analog. These results are consistent with the proposed SERT phosphorylation site, Thr-276, being highly divergent from the consensus PKG phosphorylation site sequence, which we verified through peptide library screening. Another proposed SERT kinase, the p38 mitogen-activated protein kinase, could not substitute for PKG in this assay, and p38 inhibitors did not block PKG-dependent phosphorylation of SERT. The results suggest that PKG initiates a kinase cascade that leads to phosphorylation of SERT by an as yet unidentified protein kinase. PMID:22942288

Wong, Albert; Zhang, Yuan-Wei; Jeschke, Grace R; Turk, Benjamin E; Rudnick, Gary

2012-10-19

168

Substorms associated with azimuthal turnings of the interplanetary magnetic field  

Microsoft Academic Search

Whether the magnetospheric substorms can be triggered by the interplanetary magnetic field (IMF) variations is an important issue in the substorm research. In this work we investigate observationally the relationship between substorm activities and IMF By variations, i.e., azimuthal turnings. We have searched for the IMF's azimuthal turning events for a period of one year using the data from multispacecraft

S. H Bae; D.-Y Lee; E Lee; K. W Min; K. H Choi

2001-01-01

169

Azimuthal distributions of pions inside a jet in hadronic collisions  

Microsoft Academic Search

Using a generalized parton model approach including spin and intrinsic parton motion effects, and assuming the validity of factorization for large pT jet production in hadronic collisions, we study the azimuthal distribution around the jet axis of leading pions, produced in the jet fragmentation process. We identify the observable leading-twist azimuthal asymmetries, which are generated by all the physically allowed

Umberto D'Alesio; Francesco Murgia; Cristian Pisano

2011-01-01

170

Some aspects of general azimuth spectrum algorithm using series reversion  

Microsoft Academic Search

A generalized formulation of azimuth spectrum for high precision processing on complicated trajectory of both ECSA and EFSA is derived. Based on the method of series reversion (MSR), the azimuth spectrum on complicated trajectory incorporates a new curvature factor for an identical formulation comparing to the one of ideal trajectory. A pretreatment of Range Walk Correction (RWC) is proposed to

Liu. Gao-gao; Zhang. Lin-rang; Wang Chun; Liu Nan; Liu Xin; Zhang Bo

2011-01-01

171

Estimation of azimuthally varying attenuation from surface seismic data  

Microsoft Academic Search

Observing the azimuthally varying seismic attenuation in data that show az- imuthal velocity anisotropy could contribute not only to the interpretation of the subsurface symmetry systems, but also to the characterization of its phys- ical parameters. In this paper, we estimate azimuthal variations of the P-wave eectiv e quality factor (Q) from eld surface seismic data. We also provide an

Ivan Vasconcelos; Edward Jennery

172

Site Dependent Transport Properties of N-Doped Graphene Nanoribbons with Zigzag Edges  

NASA Astrophysics Data System (ADS)

The electronic structures and the electronic transport properties for nitrogen doped (zigzag grapheme nanoribbons) z-GNRs were investigated by first-principles calculations. For the perfect Z-5-8 GNR, the band structure, DOS and transimission spectrum is almost symmetry around the Fermi level, and the I-V curve is almost linear. For the N-doped Z-5-8 GNRs, there exist gaps in the band structures and DOS plots, and conductance is lower than that of the perfect one. As the doping site moves from inner to edge, electrical conductance is decreased. Nitrogen doping at the edge has the greatest impact on the transport properties of Z-5-8 GNR. Therefore, it can be concluded that influences of nitrogen doping on the transport properties for z-GNRs is sites dependent.

Hu, Yang; Gu, Yousong; Sun, Xu; Wang, Xueqiang

2012-08-01

173

Gas Pressure Dependence of the Heat Transport in Porous Solids with Pores Smaller than 10 ?m  

NASA Astrophysics Data System (ADS)

To elucidate the gaseous heat transfer in open porous materials with pore sizes below 10 ?m, an experimental setup for hot-wire measurements at high gas pressures was designed and tested. The samples investigated were organic, resorcinol-formaldehyde-based aerogels with average pore sizes of about 600 nm and 7?m. The range in gas pressure covered was 10 Pa to 10 MPa. To avoid effects due to mass transport along the inner surface of the porous backbone of the samples, He and Ar, i.e., gases with very low interaction with the sample surface at ambient temperature, were chosen. The study reveals a significant contribution of coupling effects to the thermal transport in nanoporous media. A model has been developed that qualitatively describes the observed gas pressure dependence of the heat transport.

Swimm, K.; Reichenauer, G.; Vidi, S.; Ebert, H.-P.

2009-07-01

174

Use of azimuthal resistivity survey in mapping subsurface fractures and assessing their hydraulic properties in crystalline rocks in Ghana  

Microsoft Academic Search

Azimuthal resistivity surveys (ARS) using the square array configuration were conducted at selected farmland sites in Nsawam District, Ghana with the objective of predicting the orientation of subsurface fractures which may serve as conduits for fluid flow and contaminant transport. Information about the orientations, apertures and lengths of fractures in the study area were obtained from geological mapping of few

J. Gyamfi; F. Boadu

2003-01-01

175

Angular Dependence of Transport AC Losses in Superconducting Wire with Position-Dependent Critical Current Density in a DC Magnetic Field  

NASA Astrophysics Data System (ADS)

Transport AC losses play a very important role in high temperature superconductors (HTSs), which usually carry AC transport current under applied magnetic field in typical application-like conditions. In this paper, we propose the analytical formula for transport AC losses in HTS wire by considering critical current density of both inhomogeneous and anisotropic field dependent. The angular dependence of critical current density is described by effective mass theory, and the HTS wire has inhomogeneous distribution cross-section of critical current density. We calculate the angular dependence of normalized AC losses under different DC applied magnetic fields. The numerical results of this formula agree well with the experiment data and are better than the results of Norris formula. This analytical formula can explain the deviation of experimental transport current losses from the Norris formula and apply to calculate transport AC losses in realistic practical condition.

Su, Xing-liang; Xiong, Li-ting; Gao, Yuan-wen; Zhou, You-he

2013-07-01

176

Symmetry-dependent transport properties and bipolar spin filtering in zigzag ?-graphyne nanoribbons  

NASA Astrophysics Data System (ADS)

First-principles calculations are performed to investigate the transport properties of zigzag ?-graphyne nanoribbons (Z?GNRs). It is found that asymmetric Z?GNRs behave as conductors with linear current-voltage relationships, whereas symmetric Z?GNRs have very small currents under finite bias voltages, similar to those of zigzag graphene nanoribbons. The symmetry-dependent transport properties arise from different coupling rules between the ? and ?* subbands around the Fermi level, which are dependent on the wave-function symmetry of the two subbands. Based on the coupling rules, we further demonstrate the bipolar spin-filtering effect in the symmetric Z?GNRs. It is shown that nearly 100% spin-polarized current can be produced and modulated by the direction of bias voltage and/or magnetization configuration of the electrodes. Moreover, the magnetoresistance effect with the order larger than 500000% is also predicted. Our calculations suggest Z?GNRs as a promising candidate material for spintronics.

Yue, Qu; Chang, Shengli; Tan, Jichun; Qin, Shiqiao; Kang, Jun; Li, Jingbo

2012-12-01

177

Asymptotic Analysis of Time-Dependent Neutron Transport Coupled with Isotopic Depletion and Radioactive Decay  

SciTech Connect

We describe an asymptotic analysis of the coupled nonlinear system of equations describing time-dependent three-dimensional monoenergetic neutron transport and isotopic depletion and radioactive decay. The classic asymptotic diffusion scaling of Larsen and Keller [1], along with a consistent small scaling of the terms describing the radioactive decay of isotopes, is applied to this coupled nonlinear system of equations in a medium of specified initial isotopic composition. The analysis demonstrates that to leading order the neutron transport equation limits to the standard time-dependent neutron diffusion equation with macroscopic cross sections whose number densities are determined by the standard system of ordinary differential equations, the so-called Bateman equations, describing the temporal evolution of the nuclide number densities.

Brantley, P S

2006-09-27

178

Martian global dust storms - Zonally symmetric numerical simulations including size-dependent particle transport  

NASA Technical Reports Server (NTRS)

A zonally symmetric primitive-equation grid-point model of the Martian atmosphere is coupled with an aerosol transport/microphysical model in order to numerically investigate the size-dependent transport of dust particles in the Martian atmosphere. The coupled model accounts for diabatic heating due to a radiatively active evolving dust field, but neglects feedbacks between atmosphere-surface interactions and surface dust lifting. The differing suspension lifetimes of dust particles of various sizes (radius = 1-80 microns), in conjunction with spatially varying atmospheric dynamics, result in latitudinal differences in several measurements of the column integrated particle concentration. This work indicates the importance of considering the full range of particle sizes (and shapes) of the suspended dust during Martian global dust storms and their impact upon the spatial extent and wavelength-dependent radiative influence of such storms.

Murphy, James R.; Haberle, Robert M.; Toon, Owen B.; Pollack, James B.

1993-01-01

179

Modelling charge sign dependent modulation of cosmic rays with stochastic transport models  

NASA Astrophysics Data System (ADS)

It is well established that cosmic rays (CRs), as charged particles, undergo gradient, curvature and neutral sheet drifts in the large scale heliospheric magnetic field (HMF). With the HMF polarity switching every ~22 years, the CR drift field also switches direction, leading to so-called charge-sign dependent modulation; drifts depend on both the polarity of the HMF and the charge of the CR particles. With this effect included in modulation models, the complexity of the resulting transport equation necessitates a numerical solution. A numerical scheme that has become fashionable in recent times is the implementation of stochastic differential equations (SDEs). We review this numerical scheme as well as some of the various applications of SDEs to the heliospheric transport of CRs. We also discuss the effectiveness of a SDE based modulation mode in reproducing drift effects, as well as the additional insights gained from using such a numerical technique.

Toit Strauss, Du; Potgieter, Marius

2012-07-01

180

Parametric dependence of particle pinch coefficients for electron particle transport in linear gyrokinetic theory  

SciTech Connect

Peaked density profiles are observed in the core of Tokamak plasmas in regimes where the core particle sources and neoclassical transport are negligible. Gyrokinetic theory predicts that microinstabilities can produce a net inward particle convection balancing outward diffusion and thus explaining the experimental observations. In this work we present a general methodology that allows to calculate the particle pinch coefficients, i.e. the off-diagonal elements of the transport matrix. We adopt this procedure to perform a systematic study of the parametric dependence of these coefficients for electron particle transport in different plasma conditions. Once the coefficients are computed, one can reconstruct the predicted gradient and compare with the experimental observations in regimes with parameters similar to the ones employed in these calculations. The procedure can predict the density logarithmic gradient at zero particle flux in a self-consistent way, based on first principles. The results can be helpful in understanding the possible range of variation of the predicted gradients as a function of the main plasma parameters and in clarifying the relevant dependencies for electrons. Finally, as instructive example, we discuss how this procedure can effectively help to interpret measurements of peaked density profiles in TCV electron Internal Transport Barriers and the significant thermodiffusive inward convection that is observed.

Fable, E.; Sauter, O. [Centre de Recherches en Physique des Plasmas Association EURATOM-Confederation Suisse Ecole Polytechnique Federate de Lausanne (EPFL) CH-1015 Lausanne (Switzerland); Angioni, C. [Max-Planck-Institut fuer Plasmaphysick, Garching (Germany)

2008-11-01

181

Modeling bacterial detachment during transport through porous media as a residence-time-dependent process  

SciTech Connect

Bacterial transport through porous media was modeled using detachment functions that incorporate the dependence of detachment rate on bacterial residence time on the collector. Model parameters and the relative merit of alternative forms for the detachment function were evaluated on the basis of comparisons between model simulations and experimentally derived bacterial breakthrough and elution curves. Only detachment functions that provided an initial period in which bacteria were rapidly released, followed by slow bacterial detachment, were able to reproduce the elution portion of the breakthrough curves. In optimal simulations, 90% of the bacteria that were captured by the porous medium detached within 1 min of attachment. Experiments involving saturated flow through columns packed with sand indicated that the time to achieve complete breakthrough was inversely related to the influent bacterial concentration. On this basis and because of the relatively slow approach to breakthrough that was typically observed in transport experiments, it was hypothesized that the experimental medium contained a number of preferred attachment sites that must be essentially filled before breakthrough is achieved. Only when such (irreversible) sorption sites were included in the model formulations was it possible to produce transport simulations that matched both the breakthrough and elution portions of the empirically derived curves. It is concluded that both a time-dependent detachment function and a degree of sorption site heterogeneity are required to describe bacterial attachment and detachment during transport as observed in our laboratory. 37 refs., 9 figs., 2 tabs.

Johnson, W.P.; Blue, K.A.; Logan, B.E. [Univ. of Arizona, Tucson, AZ (United States)] [and others] [Univ. of Arizona, Tucson, AZ (United States); and others

1995-11-01

182

Anion- and Proton-Dependent Gating of ClC-4 Anion/Proton Transporter under Uncoupling Conditions  

PubMed Central

ClC-4 is a secondary active transporter that exchanges Cl? ions and H+ with a 2:1 stoichiometry. In external SCN?, ClC-4 becomes uncoupled and transports anions with high unitary transport rate. Upon voltage steps, the number of active transporters varies in a time-dependent manner, resembling voltage-dependent gating of ion channels. We here investigated modification of the voltage dependence of uncoupled ClC-4 by protons and anions to quantify association of substrates with the transporter. External acidification shifts voltage dependence of ClC-4 transport to more positive potentials and leads to reduced transport currents. Internal pH changes had less pronounced effects. Uncoupled ClC-4 transport is facilitated by elevated external [SCN?] but impaired by internal Cl? and I?. Block by internal anions indicates the existence of an internal anion-binding site with high affinity that is not present in ClC channels. The voltage dependence of ClC-4 coupled transport is modulated by external protons and internal Cl? in a manner similar to what is observed under uncoupling conditions. Our data illustrate functional differences but also similarities between ClC channels and transporters.

Orhan, Gokce; Fahlke, Christoph; Alekov, Alexi K.

2011-01-01

183

Transverse-momentum-dependent parton distribution function and jet transport in a nuclear medium  

Microsoft Academic Search

We show that the gauge-invariant transverse-momentum-dependent (TMD) quark distribution function can be expressed as a sum of all higher-twist collinear parton matrix elements in terms of a transport operator. From such a general expression, we derive the nuclear broadening of the transverse-momentum distribution. Under the maximal two-gluon correlation approximation, in which all higher-twist nuclear multiple parton correlations with the leading

Liang Zuotang; Wang Xinnian; Zhou Jian

2008-01-01

184

Transport–dependent cell injury in the S3 segment of the proximal tubule  

Microsoft Academic Search

Transport–dependent cell injury in the S3 segment of the proximal tubule. Two distinct types of injury, cytoplasmic edema and cell fragmentation occur in the S3 segment of the proximal tubule in isolated hypoxic perfused rat kidneys (Krebs–albumin medium gassed without O2). The proportion of S3 tubules with fragmentation strongly correlated with the GFR and urine output during the perfusion, and

Paul F Shanley; Mayer Brezis; Katherine Spokes; Patricio Silva; Franklin H Epstein; Seymour Rosen

1986-01-01

185

A new mobile-immobile model for reactive solute transport with scale-dependent dispersion  

Microsoft Academic Search

This study proposed a new mobile-immobile model (MIM) to describe reactive solute transport with scale-dependent dispersion in heterogeneous porous media. The model was derived from the conventional MIM but assumed the dispersivity to be a linear or exponential function of travel distance. The linear adsorption and the first-order degradation of solute were also considered in the model. The Laplace transform

Guangyao Gao; Hongbin Zhan; Shaoyuan Feng; Bojie Fu; Ying Ma; Guanhua Huang

2010-01-01

186

Spin-dependent transport in armchair graphene nanoribbon structures with edge roughness effects  

Microsoft Academic Search

We analyze the spin-dependent transport in single ferromagnetic gate structures based on armchair graphene nanoribbon (GNR) using the non-equilibrium Green's function method in a tight binding model. It is shown that the spin polarized current oscillates as a function of the gate-induced barrier height. For perfect GNRs, the larger the energy band gap, the stronger the oscillation of the spin

V. Hung Nguyen; V. Nam Do; A. Bournel; V. Lien Nguyen; P. Dollfus

2009-01-01

187

Multisystemic Treatment of Substance-Abusing and Dependent Delinquents: Outcomes, Treatment Fidelity, and Transportability  

Microsoft Academic Search

The effectiveness and transportability of multisystemic therapy (MST) were examined in a study that included 118 juvenile offenders meeting DSM-III-R criteria for substance abuse or dependence and their families. Participants were randomly assigned to receive MST versus usual community services. Outcome measures assessed drug use, criminal activity, and days in out-of-home placement at posttreatment (T2) and at a 6-month posttreatment

Scott W. Henggeler; Susan G. Pickrel; Michael J. Brondino

1999-01-01

188

New Aspect of Renal Phosphate Reabsorption: The Type IIc Sodium-Dependent Phosphate Transporter  

Microsoft Academic Search

Abnormalities of the inorganic phosphate (Pi) reabsorption in the kidney result in various metabolic disorders. Na+-dependent Pi (Na\\/Pi) transporters in the brush border membrane of proximal tubular cells mediate the rate-limiting step in the overall Pi-reabsorptive process. Type IIa and type IIc Na\\/Pi cotransporters are expressed in the apical membrane of proximal tubular cells and mediate Na\\/Pi cotransport; the extent

Ken-ichi Miyamoto; Mikiko Ito; Sawako Tatsumi; Masashi Kuwahata; Hiroko Segawa

2007-01-01

189

Temperature dependent spin transport properties of platinum inferred from spin Hall magnetoresistance measurements  

NASA Astrophysics Data System (ADS)

We study the temperature dependence of the spin Hall magnetoresistance (SMR) in yttrium iron garnet/platinum hybrid structures via magnetization orientation dependent magnetoresistance measurements. Our experiments show a decrease of the SMR magnitude with decreasing temperature. Using the sensitivity of the SMR to the spin transport properties of the normal metal, we interpret our data in terms of a decrease of the spin Hall angle in platinum from 0.11 at room temperature to 0.075 at 10 K, while the spin diffusion length and the spin mixing conductance of the ferrimagnetic insulator/normal metal interface remain almost constant.

Meyer, Sibylle; Althammer, Matthias; Geprägs, Stephan; Opel, Matthias; Gross, Rudolf; Goennenwein, Sebastian T. B.

2014-06-01

190

Analytical temperature dependent model for nanoscale double-gate MOSFETs reproducing advanced transport models  

NASA Astrophysics Data System (ADS)

In this paper we extend our compact model for nanoscale double-gate (DG) MOSFETs which considers a hydrodynamic transport model to include the effect of the temperature dependence. Temperature dependence equations are incorporated to the expressions of the mobility and saturation velocity. For model validation we have considered a symmetric 22 nm double-gate MOSFET template device optimized for low-stand-by-power applications. Comparison between the numerical 2D Monte Carlo (MC) simulations and the compact model shows a good degree of agreement.

Cheralathan, Muthupandian; Sampedro, Carlos; Gámiz, Francisco; Ińiguez, Benjamin

2014-08-01

191

Cathode Work Function Dependence of Electron Transport Efficiency through Buffer Layer in Organic Solar Cells  

NASA Astrophysics Data System (ADS)

An electron transport mechanism through a cathode buffer layer of organic solar cells is experimentally investigated. Inverted organic solar cells with the structure of indium--tin oxide (ITO)/thin cathode metal/bathocuproine (BCP)/fullerene (C60)/copper phthalocyanine (CuPc)/pentacene/Ag (anode) are examined. A new model, in that electrons are transported across the BCP buffer layer not through defect states but over the lowest unoccupied molecular orbital (LUMO), is proposed. That is, the defect state density in the BCP layer is not important for electron transport, though the hopping transport model via the defect states is widely accepted. The transport efficiency is sensitive to the cathode work function (\\mathit{WF}C). As \\mathit{WF}C decreases, the energy difference between the BCP LUMO and the cathode Fermi level decreases. This introduces a low electronic potential barrier height from the cathode to the acceptor. The low \\mathit{WF}C is thus important to achieve a low series resistance. Furthermore, the dependence of \\mathit{WF}C on barrier height is also confirmed for tris(8-hydroxyquinolinato)aluminum buffer.

Oida, Tatsuya; Harafuji, Kenji

2012-09-01

192

Genome-wide Analysis of AP-3-dependent Protein Transport in Yeast  

PubMed Central

The evolutionarily conserved adaptor protein-3 (AP-3) complex mediates cargo-selective transport to lysosomes and lysosome-related organelles. To identify proteins that function in AP-3–mediated transport, we performed a genome-wide screen in Saccharomyces cerevisiae for defects in the vacuolar maturation of alkaline phosphatase (ALP), a cargo of the AP-3 pathway. Forty-nine gene deletion strains were identified that accumulated precursor ALP, many with established defects in vacuolar protein transport. Maturation of a vacuolar membrane protein delivered via a separate, clathrin-dependent pathway, was affected in all strains except those with deletions of YCK3, encoding a vacuolar type I casein kinase; SVP26, encoding an endoplasmic reticulum (ER) export receptor for ALP; and AP-3 subunit genes. Subcellular fractionation and fluorescence microscopy revealed ALP transport defects in yck3? cells. Characterization of svp26? cells revealed a role for Svp26p in ER export of only a subset of type II membrane proteins. Finally, ALP maturation kinetics in vac8? and vac17? cells suggests that vacuole inheritance is important for rapid generation of proteolytically active vacuolar compartments in daughter cells. We propose that the cargo-selective nature of the AP-3 pathway in yeast is achieved by AP-3 and Yck3p functioning in concert with machinery shared by other vacuolar transport pathways.

Anand, Vikram C.; Daboussi, Lydia; Lorenz, Todd C.

2009-01-01

193

N-Glycosylation is required for Na{sup +}-dependent vitamin C transporter functionality  

SciTech Connect

The human sodium-dependent vitamin C transporters (hSVCT1 and hSVCT2) mediate cellular uptake of ascorbic acid. Both these transporters contain potential sites for N-glycosylation in their extracellular domains (Asn-138, Asn-144 [hSVCT1]; Asn-188, Asn-196 [hSVCT2]), however the role of N-glycosylation in transporter function is unexplored. On the basis of the result that tunicamycin decreased {sup 14}C-ascorbic acid uptake in HepG2 cells, we systematically ablated all consensus N-glycosylation sites in hSVCT1 and hSVCT2 to resolve any effects on ascorbic acid uptake, transporter expression and targeting. We show that removal of individual N-glycosylation sites significantly impairs protein expression and consequently ascorbic acid uptake for hSVCT1 mutants (N138Q is retained intracellularly) and for hSVCT2 mutants (all of which reach the cell surface). N-Glycosylation is therefore essential for vitamin C transporter functionality.

Subramanian, Veedamali S. [Departments of Medicine, Physiology and Biophysics, University of California, Irvine, CA 92697 (United States)], E-mail: vsubrama@uci.edu; Marchant, Jonathan S. [Department of Pharmacology, University of Minnesota Medical School, MN 55455 (United States); Reidling, Jack C. [Departments of Medicine, Physiology and Biophysics, University of California, Irvine, CA 92697 (United States); Said, Hamid M. [Departments of Medicine, Physiology and Biophysics, University of California, Irvine, CA 92697 (United States); Department of Veterans Affairs Medical Center, Long Beach, CA 90822 (United States)

2008-09-12

194

Ultraweak azimuthal anchoring of a nematic liquid crystal on a planar orienting photopolymer  

SciTech Connect

The search of weak anchoring is an important issue for a whole class of liquid crystal displays. In this paper we present an orienting layer showing unreached weak planar azimuthal anchoring for 4-n-pentyl-4{sup '}-cyanobiphenyl nematic liquid crystal (5CB). Azimuthal extrapolation lengths as large as 80 {mu}m are easily obtained. Our layers are made with the commercial photocurable polymer Norland optical adhesive 60. The anisotropy of the film is induced by the adsorption of oriented liquid crystal molecules under a 2 T magnetic field applied parallel to the surfaces. We use the width of surface {pi}-walls and a high-field electro-optical method to measure, respectively, the azimuthal and the zenithal anchorings. The azimuthal anchoring is extremely sensitive to the ultraviolet (UV) dose and it also depends on the magnetic field application duration. On the opposite, the zenithal anchoring is only slightly sensitive to the preparation parameters. All these results are discussed in terms of the adsorption/desorption mechanisms of the liquid crystal molecules on the polymer layer and of the flexibility of the polymer network.

Nespoulous, Mathieu; Blanc, Christophe; Nobili, Maurizio [Laboratoire des Colloiedes, Verres et Nanomateriaux, Universite Montpellier II, Place Eugene Bataillon, 34090 Montpellier (France)

2007-10-01

195

Forward-rapidity azimuthal and radial flow of identified particles for s=200 GeV Au+Au collisions  

NASA Astrophysics Data System (ADS)

A strong azimuthal flow signature at RHIC suggests rapid system equilibration leading to an almost perfect fluid state. The longitudinal extent of the flow behavior depends on how this state is formed and can be studied by measuring the pseudorapidity and transverse momentum dependence of the second Fourier component (?(p)) of the azimuthal angular distribution. We report on a measurement of identified-particle ? as a function of p(0.5-2.0 GeV/c), centrality (0-25%, 25-50%), and pseudorapidity (0??<3.2) for s=200 GeV Au+Au collisions. The BRAHMS spectrometers are used for particle identification (?, K, p) and momentum determination and the BRAHMS global detectors are used to determine the corresponding reaction-plane angles. The results are discussed in terms of the pseudorapidity dependence of constituent quark scaling and in terms of models that develop the complete (azimuthal and radial) hydrodynamic aspects of the forward dynamics at RHIC.

Brahms Collaboration; Sanders, S. J.; BRAHMS Collaboration

2009-11-01

196

pH-dependent regulation of electron transport and ATP synthesis in chloroplasts.  

PubMed

This review is focused on pH-dependent mechanisms of regulation of photosynthetic electron transport and ATP synthesis in chloroplasts. The light-induced acidification of the thylakoid lumen is known to decelerate the plastoquinol oxidation by the cytochrome b 6 f complex, thus impeding the electron flow between photosystem II and photosystem I. Acidification of the lumen also triggers the dissipation of excess energy in the light-harvesting antenna of photosystem II, thereby protecting the photosynthetic apparatus against a solar stress. After brief description of structural and functional organization of the chloroplast electron transport chain, our attention is focused on the nature of the rate-limiting step of electron transfer between photosystem II and photosystem I. In the context of pH-dependent mechanism of photosynthetic control in chloroplasts, the mechanisms of plastoquinol oxidation by the cytochrome b 6 f complex have been considered. The light-induced alkalization of stroma is another factor of pH-dependent regulation of electron transport in chloroplasts. Alkalization of stroma induces activation of the Bassham-Benson-Calvin cycle reactions, thereby promoting efflux of electrons from photosystem I to NADP(+). The mechanisms of the light-induced activation of ATP synthase are briefly considered. PMID:23695653

Tikhonov, Alexander N

2013-10-01

197

5-hydroxytryptamine stimulates glucose transport in cardiomyocytes via a monoamine oxidase-dependent reaction.  

PubMed Central

This study deals with the effect of 5-hydroxytryptamine (5-HT; serotonin) on glucose transport in isolated rat cardiac myocytes. In these cells, 5-HT (10-300 microns), as well as tryptamine, 5-methoxytryptamine and dopamine, elicited a 3-5 fold increase in glucose transport, as compared with control. This effect was maximal after 90 min, and was concomitant with a 1.8- and 1.5-fold increase in the amounts of glucose transporters GLUT1 and GLUT4 at the cell surface of the cardiomyocytes, as determined by using the photoaffinity label 3H-2-N-[4-(1-azi-2,2,2-trifluoroethyl)benzoyl]-1,3-bis-(D-manno s-4-yl) propyl-2-amine (3H-ATB-BMPA). In contrast, 3-3000 microM of the selective 5-HT receptor agonists 5-carboxyamido-tryptamine, alpha-methyl-serotonin, 2-methyl-serotonin or renzapride failed to stimulate glucose transport. The effect of 5-HT was not affected by (i) the 5-HT receptor antagonists methysergide (1 microM), ketanserin (1 microM), cyproheptadine (1 microM), MDL 72222 (1 microM) or ICS 205-930 (3 microM), nor by (ii) the adrenergic receptor antagonists prazosin (1 microM), yohimbine (1 microM) or propranolol (5 microM), nor by (iii) the dopaminergic antagonists SCH 23390 (1 microM) or haloperidol (1 microM). The monoamine oxidase inhibitors clorgyline (1 microM) and tranylcypromine (1 microM) completely suppressed the effect of 5-HT, whereas the control and insulin-stimulated rates of glucose transport were unaffected. Addition of catalase or glutathione diminished the 5-HT-dependent stimulation of glucose transport by 50%; these two factors are known to favour the degradation of H2O2 (which can be formed during the deamination of amines by monoamine oxidases). Glutathione also depressed the stimulatory action of exogenously added H2O2 (20 microM) by 30%. Furthermore, in cells treated with 5_HT, a time-dependent accumulation of 5-hydroxy-1H-indol-3-ylacetic acid (a product of 5-HT metabolism via monoamine oxidases) was observed, which paralleled the changes in glucose transport. In conclusion, the stimulation of glucose transport by 5-HT in cardiomyocytes is not mediated by a 5-HT1, 5-HT2, 5-HT3 or 5-HT4 receptor, nor by an adrenergic or dopaminergic receptor, but is likely to occur through the degradation of by a monoamine oxidase and concomitant formation of H2O2.

Fischer, Y; Thomas, J; Kamp, J; Jungling, E; Rose, H; Carpene; Kammermeier, H

1995-01-01

198

Structure, function, and genomic organization of human Na(+)-dependent high-affinity dicarboxylate transporter.  

PubMed

We have cloned and functionally characterized the human Na(+)-dependent high-affinity dicarboxylate transporter (hNaDC3) from placenta. The hNaDC3 cDNA codes for a protein of 602 amino acids with 12 transmembrane domains. When expressed in mammalian cells, the cloned transporter mediates the transport of succinate in the presence of Na(+) [concentration of substrate necessary for half-maximal transport (K(t)) for succinate = 20+/-1 microM]. Dimethylsuccinate also interacts with hNaDC3. The Na(+)-to-succinate stoichiometry is 3:1 and concentration of Na(+) necessary for half-maximal transport (K(Na(+))(0.5)) is 49+/-1 mM as determined by uptake studies with radiolabeled succinate. When expressed in Xenopus laevis oocytes, hNaDC3 induces Na(+)-dependent inward currents in the presence of succinate and dimethylsuccinate. At a membrane potential of -50 mV, K(Suc)(0.5) is 102+/-20 microM and K(Na(+))(0.5) is 22+/-4 mM as determined by the electrophysiological approach. Simultaneous measurements of succinate-evoked charge transfer and radiolabeled succinate uptake in hNaDC3-expressing oocytes indicate a charge-to-succinate ratio of 1:1 for the transport process, suggesting a Na(+)-to-succinate stoichiometry of 3:1. pH titration of citrate-induced currents shows that hNaDC3 accepts preferentially the divalent anionic form of citrate as a substrate. Li(+) inhibits succinate-induced currents in the presence of Na(+). Functional analysis of rat-human and human-rat NaDC3 chimeric transporters indicates that the catalytic domain of the transporter lies in the carboxy-terminal half of the protein. The human NaDC3 gene is located on chromosome 20q12-13.1, as evidenced by fluorescent in situ hybridization. The gene is >80 kbp long and consists of 13 exons and 12 introns. PMID:10794676

Wang, H; Fei, Y J; Kekuda, R; Yang-Feng, T L; Devoe, L D; Leibach, F H; Prasad, P D; Ganapathy, V

2000-05-01

199

Time-dependent electron transport and optical emissions in the aurora  

NASA Astrophysics Data System (ADS)

This thesis presents the first time-dependent transport model of auroral electrons. The evolution of the spherical electron intensity in phase space is studied for a variety of incident electron intensities. It is shown that the secondary electrons with energies <10 eV and at altitudes >150 km can take over 300 ms to reach steady state in phase space. Since there are bright optical emissions in this region, such a time dependence in the auroral electrons is important. The emissions of N2(2PG) 3371 Ĺ and N+2 (1NG) 4278 Ĺ are studied for time-varying electron pulses to show for the first time that this ratio will change until the secondary electrons reach steady state in the ionosphere. The way in which the 3371Ĺ/4278Ĺ ratio changes with time-varying precipitation depends on the precipitating electron spectra. The changes in the emission ratio can be used to learn more about the auroral acceleration region and the role of the ionosphere in auroral emissions. Field-aligned bursts (FABs), often observed in electron spectra of instruments flying over flickering aurora, are modeled with the time-dependent transport model. How the ionosphere modifies these electrons is shown. The 3371 and 4278 Ĺ emissions of flickering FABs are modeled to study the optical effects of modulated electron intensities in time. A study of 4278 Ĺ emissions for electron source regions from 630 to 4,000 km are studied along with frequency variations from 5 to 100 Hz. This study shows that the percent variation of the maximum to the minimum column brightness is less for higher frequencies and more distant source regions. It is shown that with an accurate time-dependent transport calculation and 4278 Ĺ emission observations of flickering aurora it should be possible to deduce the source altitude of the modulated electrons creating the optical flickering.

Peticolas, Laura Marie

200

Gestational Age-Dependent Changes in Gene Expression of Metabolic Enzymes and Transporters in Pregnant Mice  

PubMed Central

Pregnancy-induced changes in drug pharmacokinetics can be explained by changes in expression of drug-metabolizing enzymes and transporters and/or normal physiology. In this study, we determined gestational age-dependent expression profiles for all metabolic enzyme and transporter genes in the maternal liver, kidney, small intestine, and placenta of pregnant mice by microarray analysis. We specifically examined the expression of genes important for xenobiotic, bile acid, and steroid hormone metabolism and disposition, namely, cytochrome P450s (Cyp), UDP-glucuronosyltranserases (Ugt), sulfotransferases (Sult), and ATP-binding cassette (Abc), solute carrier (Slc), and solute carrier organic anion (Slco) transporters. Few Ugt and Sult genes were affected by pregnancy. Cyp17a1 expression in the maternal liver increased 3- to 10-fold during pregnancy, which was the largest observed change in the maternal tissues. Cyp1a2, most Cyp2 isoforms, Cyp3a11, and Cyp3a13 expression in the liver decreased on gestation days (gd) 15 and 19 compared with nonpregnant controls (gd 0). In contrast, Cyp2d40, Cyp3a16, Cyp3a41a, Cyp3a41b, and Cyp3a44 in the liver were induced throughout pregnancy. In the placenta, Cyp expression on gd 10 and 15 was upregulated compared with gd 19. Notable changes were also observed in Abc and Slc transporters. Abcc3 expression in the liver and Abcb1a, Abcc4, and Slco4c1 expression in the kidney were downregulated on gd 15 and 19. In the placenta, Slc22a3 (Oct3) expression on gd 10 was 90% lower than that on gd 15 and 19. This study demonstrates important gestational age-dependent expression of metabolic enzyme and transporter genes, which may have mechanistic relevance to drug disposition in human pregnancy.

Shuster, Diana L.; Bammler, Theo K.; Beyer, Richard P.; MacDonald, James W.; Tsai, Jesse M.; Farin, Frederico M.; Hebert, Mary F.; Thummel, Kenneth E.

2013-01-01

201

Sodium ion-dependent amino acid transport in membrane vesicles of Bacillus stearothermophilus.  

PubMed Central

Amino acid transport in membrane vesicles of Bacillus stearothermophilus was studied. A relatively high concentration of sodium ions is needed for uptake of L-alanine (Kt = 1.0 mM) and L-leucine (Kt = 0.4 mM). In contrast, the Na(+)-H(+)-L-glutamate transport system has a high affinity for sodium ions (Kt less than 5.5 microM). Lithium ions, but no other cations tested, can replace sodium ions in neutral amino acid transport. The stimulatory effect of monensin on the steady-state accumulation level of these amino acids and the absence of transport in the presence of nonactin indicate that these amino acids are translocated by a Na+ symport mechanism. This is confirmed by the observation that an artificial delta psi and delta mu Na+/F but not a delta pH can act as a driving force for uptake. The transport system for L-alanine is rather specific. L-Serine, but not L-glycine or other amino acids tested, was found to be a competitive inhibitor of L-alanine uptake. On the other hand, the transport carrier for L-leucine also translocates the amino acids L-isoleucine and L-valine. The initial rates of L-glutamate and L-alanine uptake are strongly dependent on the medium pH. The uptake rates of both amino acids are highest at low external pH (5.5 to 6.0) and decline with increasing pH. The pH allosterically affects the L-glutamate and L-alanine transport systems. The maximal rate of L-glutamate uptake (Vmax) is independent of the external pH between pH 5.5 and 8.5, whereas the affinity constant (Kt) increases with increasing pH. A specific transport system for the basic amino acids L-lysine and L-arginine in the membrane vesicles has also been observed. Transport of these amino acids occurs most likely by a uniport mechanism.

Heyne, R I; de Vrij, W; Crielaard, W; Konings, W N

1991-01-01

202

Double spin azimuthal asymmetries ALT and ALL in semi-inclusive DIS  

SciTech Connect

Within the LO QCD parton model of SIDIS, lN {yields} lhX, with unintegrated quark distribution and fragmentation functions, we study the transverse momentum and azimuthal dependencies of the double spin asymmetries ALT and ALL. For later we include O(k perpendicular)/Q) kinematic corrections, which induce an azimuthal modulation of the asymmetry, analogous to the Cahn effect in unpolarized SIDIS. We show that a study of these asymmetries allows to extract the transverse momentum dependence of the unintegrated helicity distribution function g{sub 1L}{sup q}(x,k{sub perpendicular}) and g{sub 1T}{sup q}(x,k{sub perpendicular}).This report is based on research published in [1, 2], where predictions are given for ongoing COMPASS, HERMES and JLab experiments.

Kotzinian, Aram [Yerevan Physics Institute, 375036 Yerevan (Armenia); Dipartimento di Fisica Generale, Universita di Torino, Via P. Giuria 1, I-10125 Torino (Italy); INFN, Sezione di Torino, Via P. Giuria 1, I-10125 Torino (Italy); JINR, 141980 Dubna (Russian Federation)

2007-06-13

203

Wave-packet representation of leads for efficient simulations of time-dependent electronic transport  

NASA Astrophysics Data System (ADS)

We present theoretical foundations and numerical demonstration of an efficient method for performing time-dependent many-electron simulations for electronic transport. The method employs the concept of stroboscopic wave-packet basis for the description of electrons' dynamics in the semi-infinite leads. The rest of the system can be treated using common propagation schemes for finite electronic systems. We use the implementation of our method to study the time-dependent current response in armchair graphene nanoribbons (AGNRs) with sizes up to 800 atoms described within tight-binding approximation. The character of the time-dependent current is studied for different magnitudes of the bias voltage, variable width and length of AGNRs, different positions of the current measurement, and for full and reduced coupling of the AGNRs to the electrodes.

Konôpka, Martin; Bokes, Peter

2014-03-01

204

Composition-dependent layered structure and transport properties in BiTe thin films  

NASA Astrophysics Data System (ADS)

We have studied the compositional dependence of the layered structure of Bi1+xTe1-x thin films and its relation with the transport properties. We have observed that the Bi1+xTe1-x films have a stable structure near the Bi1Te1 composition and that their crystallinity depends strongly upon the compositional deviation from stoichiometric Bi1Te1. We have determined possible layered structures, configured with two sequences of Bi-Bi and Te-Bi-Te-Bi-Te, corresponding to Bi and Te binary compositions using x-ray diffraction analysis. Their c-axis lattice constants were in the range of 36 Ĺ and 136 Ĺ. Temperature-dependent thermopowers of the films reveal that as the composition changes from Te rich to Bi rich, the polarity varies from n type to p type.

Kim, Yunki; Cho, Sunglae; Divenere, Antonio; Wong, George K.; Ketterson, J. B.

2001-04-01

205

Potential-Dependent Anion Transport in Tonoplast Vesicles from Oat Roots 1  

PubMed Central

Potential-dependent anion movement into tonoplast vesicles from oat roots (Avena sativa L. var Lang) was monitored as dissipation of membrane potentials (??) using the fluorescence probe Oxonol V. The potentials (positive inside) were generated with the H+-pumping pyrophosphatase, which is K+ stimulated and anion insensitive. The relative rate of ?? dissipation by anions was used to estimate the relative permeabilities of the anions. In decreasing order they were: SCN? (100) > NO3? (72) = Cl? (70) > Br? (62) > SO42? (5) = H2PO4? (5) > malate (3) = acetate (3) > iminodiacetate (2). Kinetic studies showed that the rate of ?? dissipation by Cl? and NO3?, but not by SCN?, was saturable. The Km values for Cl? and NO3? uptake were about 2.3 and 5 millimolar, respectively, suggesting these anions move into the vacuole through proteinaceous porters. In contrast to a H+-coupled Cl? transporter on the same vesicles, the potential-dependent Cl? transport was insensitive to 4,4?-diisothiocyano-2,2?-stilbene disulfonate. These results suggest the existence of at least two different mechanisms for Cl? transport in these vesicles. The potentials generated by the H+-translocating ATPase and H+-pyrophosphatase were nonadditive, giving support to the model that both pumps are on tonoplast vesicles. No evidence for a putative Cl? conductance on the anion-sensitive H+-ATPase was found.

Kaestner, Klaus H.; Sze, Heven

1987-01-01

206

Transverse-momentum-dependent parton distribution function and jet transport in a nuclear medium  

SciTech Connect

We show that the gauge-invariant transverse-momentum-dependent (TMD) quark distribution function can be expressed as a sum of all higher-twist collinear parton matrix elements in terms of a transport operator. From such a general expression, we derive the nuclear broadening of the transverse-momentum distribution. Under the maximal two-gluon correlation approximation, in which all higher-twist nuclear multiple parton correlations with the leading nuclear enhancement are given by products of twist-two nucleon parton distributions, we find the nuclear transverse-momentum distribution as a convolution of a Gaussian distribution and the nucleon TMD quark distribution. The width of the Gaussian, or the mean total transverse-momentum broadening squared, is given by the path integral of the quark transport parameter q-circumflex{sub F} which can also be expressed in a gauge-invariant form and is given by the gluon distribution density in the nuclear medium. We further show that contributions from higher-twist nucleon gluon distributions can be resummed under the extended adjoint two-gluon correlation approximation and the nuclear transverse-momentum distribution can be expressed in terms of a transverse-scale-dependent quark transport parameter or gluon distribution density. We extend the study to hot medium and compare to dipole model approximation and N=4 supersymmetric Yang-Mills (SYM) theory in the strong coupling limit. We find that multiple gluon correlations become important in the strongly coupled system such as N=4 SYM plasma.

Liang Zuotang [Department of Physics, Shandong University, Jinan, Shandong 250100 (China); Wang Xinnian [Nuclear Science Division, MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Zhou Jian [Department of Physics, Shandong University, Jinan Shandong 250100 (China); Nuclear Science Division, MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2008-06-15

207

Transverse-momentum-dependent parton distribution function and jet transport in a nuclear medium  

NASA Astrophysics Data System (ADS)

We show that the gauge-invariant transverse-momentum-dependent (TMD) quark distribution function can be expressed as a sum of all higher-twist collinear parton matrix elements in terms of a transport operator. From such a general expression, we derive the nuclear broadening of the transverse-momentum distribution. Under the maximal two-gluon correlation approximation, in which all higher-twist nuclear multiple parton correlations with the leading nuclear enhancement are given by products of twist-two nucleon parton distributions, we find the nuclear transverse-momentum distribution as a convolution of a Gaussian distribution and the nucleon TMD quark distribution. The width of the Gaussian, or the mean total transverse-momentum broadening squared, is given by the path integral of the quark transport parameter q^F which can also be expressed in a gauge-invariant form and is given by the gluon distribution density in the nuclear medium. We further show that contributions from higher-twist nucleon gluon distributions can be resummed under the extended adjoint two-gluon correlation approximation and the nuclear transverse-momentum distribution can be expressed in terms of a transverse-scale-dependent quark transport parameter or gluon distribution density. We extend the study to hot medium and compare to dipole model approximation and N=4 supersymmetric Yang-Mills (SYM) theory in the strong coupling limit. We find that multiple gluon correlations become important in the strongly coupled system such as N=4 SYM plasma.

Liang, Zuo-Tang; Wang, Xin-Nian; Zhou, Jian

2008-06-01

208

Fully energy-dependent HZETRN (a galactic cosmic-ray transport code)  

NASA Astrophysics Data System (ADS)

For extended manned space missions, the radiation shielding design requires efficient and accurate cosmic-ray transport codes that can handle the physics processes in detail. The Langley Research Center galactic cosmic-ray transport code (HZETRN) is currently under development for such design use. The cross sections for the production of secondary nucleons in the existing HZETRN code are energy dependent only for nucleon collisions. The approximation of energy-independent, heavy-ion fragmentation cross section is now removed by implementing a mathematically simplified energy-dependent stepping formalism for heavy ions. The cross section at each computational grid is obtained by linear interpolation from a few tabulated data to minimize computing time. Test runs were made for galactic cosmic-ray transport through a liquid hydrogen shield and a water shield at solar minimum. The results show no appreciable change in total fluxes or computing time compared with energy-independent calculations. Differences in high LET (linear energy transfer) spectra are noted, however, because of the large variation in cross sections at the low-energy region. The high LET components are significantly higher in the new code and have important implications on biological risk estimates for heavy-ion exposure.

Shinn, Judy L.; John, Sarah; Tripathi, Ram K.; Norbury, John W.; Wilson, John W.; Townsend, Lawrence W.

1992-11-01

209

The COT2 gene is required for glucose-dependent divalent cation transport in Saccharomyces cerevisiae.  

PubMed Central

Eleven cobalt-tolerant mutants were found to belong to a single complementation group, cot2. In addition to cobalt, the cot2 mutants were found to tolerate increased levels of the divalent cations Zn2+, Mn2+, and Ni2+ as well. All of the cot2 mutants exhibited a wiener-shaped cellular morphology that was exacerbated by the carbon and nitrogen source but was unaffected by metals. The rate of glucose-dependent transport of cobalt into cells was reduced in strains that carry mutations in the COT2 gene. COT2 is not essential for growth. Strains that carry a COT2 allele conferring complete loss of function are viable and exhibit phenotypes similar to those of spontaneous cot2 mutations. The sequence of the COT2 gene shows that it is identical to GRR1, which encodes a protein required for glucose repression. The glucose dependence of the transport defect implies that cot2 mutations affect the link between glucose metabolism and divalent cation active transport. Images

Conklin, D S; Kung, C; Culbertson, M R

1993-01-01

210

Reconstitution and characterization of ATP-dependent bile acid transport in human and rat placenta.  

PubMed Central

Bile acid (BA) transport across the human microvillus maternal-facing trophoblast plasma membrane (mTPM) has been recently reported to be stimulated by the presence of ATP [Marin, Bravo, El-Mir and Serrano (1993) J. Hepatol. 18, S41]. Reconstitution of BA transport activity in proteoliposomes from human mTPM is reported in this paper. Typical characteristics of BA transport in native mTPM vesicles, including a requirement for ATP hydrolysis and inhibition by other BA species, were preserved in proteoliposome preparations. BA transport into 20- and 14-day-gestation rat mTPM vesicles was also stimulated by the presence of ATP as noted in human mTPM and in the rat liver canalicular membrane. Besides this functional similarity, these ATP-dependent carriers may share structural characteristics, as demonstrated by studies using an antibody (100 Ab) raised against the 100 kDa BA carrier of the canalicular membrane from rat liver which recognized proteins in both human and rat brush-border trophoblast membranes. Images Figure 2

Bravo, P; Marin, J J; Beveridge, M J; Novak, D A

1995-01-01

211

SURFACE CHARGE- AND SPACE-DEPENDENT TRANSPORT OF PROTEINS IN CROWDED ENVIRONMENTS OF NANOTAILORED POSTS  

PubMed Central

The reaction and diffusion of molecules across barriers and through crowded environments is integral to biological system function and to separation technologies. Ordered, microfabricated post arrays are a promising route to creating synthetic barriers with controlled chemical and physical characteristics. They can be used to create crowded environments, to mimic aspects of cellular membranes and to serve as engineered replacements of polymer-based separation media. Here, the translational diffusion of fluorescein isothiocyante and various forms of green fluorescent protein (GFP), including “supercharged” variants, are examined in a silicon-based post array environment. The technique of fluorescence recovery after photo-bleaching (FRAP) is combined with analytical approximations and numerical simulations to assess the relative effects of reaction and diffusion on molecular transport, respectively. FRAP experiments were conducted for 64 different cases where the molecular species, the spacing and density of the posts, and the chemical surface charge of the posts were varied. In all cases, the dense packing of the posts hindered the diffusive transport of the fluorescent species. The supercharged GFPs strongly interacted with oppositely charged surfaces. With similar molecular and surface charges, transport is primarily limited by hindered diffusion. For conventional, enhanced GFP in a positively charged surface environment, transport was limited by the coupled action of hindered diffusion and surface interaction with the posts. Quantification of the size-, space-, time-, and charge-dependent translational diffusion in the post array environments can provide insight into natural processes and guide the design and development of selective membrane systems.

Choi, Chang Kyoung; Fowlkes, Jason D.; Retterer, Scott T.; Siuti, Piro; Iyer, Sukanya; Doktycz, Mitchel J.

2010-01-01

212

Thermal and Wind Effects on the Azimuth Axis Tilt of the ASTE 10-m Antenna  

NASA Astrophysics Data System (ADS)

The azimuth axis tilt of the ASTE 10-m antenna induced by thermal and wind loadings was investigated with a dual-axis inclinometer on the azimuth axis, along with thermometers on the pedestal and yoke structures and an ultrasonic anemometer on a nearby weather station. The dependences of the inclinometer zero-point offsets against temperature of the device, temperature gradients in the pedestal and yoke structure were obtained for the measurements over 11 months during the antenna being parked at its home position (azimuth angles = ?180 degrees, an elevation angle = 60 degrees) under wind velocities < 8 m s-1. The temperature dependences of the zero-point offsets were found to be 1.24 and -0.46 arcseconds/degree, and were close to those obtained with an independent method. The azimuth axis tilts due to the temperature difference between the two opposite sides of pedestal walls were found to be about 1.1 and 1.7 arcseconds/degree, and consistent with 1.5 arcseconds/degree estimated with a simple model. The residual axis tilt of the whole samples after removal of the temperature dependences shows dependence against overturning moment estimated from the wind data. The stiffness of the antenna structures between the yoke base section and the ground was estimated to be 5.3 and 3.4 GNm/rad using the observed tilts in two directions; and were smaller than 6.0 GNm/rad from a mechanical model prediction. Based on these field experiments, we discuss the improvements and limitations of pointing performance with the inclinometer metrology system.

Ukita, Nobuharu; Ezawa, Hajime; Ikenoue, Bungo; Saito, Masao

2007-10-01

213

Fast and accurate frequency-dependent radiation transport for hydrodynamics simulations in massive star formation  

NASA Astrophysics Data System (ADS)

Context. Radiative feedback plays a crucial role in the formation of massive stars. The implementation of a fast and accurate description of the proceeding thermodynamics in pre-stellar cores and evolving accretion disks is therefore a main effort in current hydrodynamics simulations. Aims: We introduce our newly implemented three-dimensional frequency dependent radiation transport algorithm for hydrodynamics simulations of spatial configurations with a dominant central source. Methods: The module combines the advantage of the speed of an approximate flux limited diffusion (FLD) solver in the one-temperature approach, which is valid in the static diffusion limit, with the high accuracy of a frequency dependent first order ray-tracing routine. The ray-tracing routine especially compensates the introduced inaccuracies by standard approximate FLD solvers in transition regions from optically thin to thick and yields the correct optical depths for the frequency dependent stellar irradiation. Both components of our module make use of realistic tabulated dust opacities. The module is parallelized for distributed memory machines based on the message passing interface standard. We implemented the module in the three-dimensional high-order magneto-hydrodynamics code Pluto. Results: We prove the viability of the scheme in a standard radiation benchmark test compared to a full frequency dependent Monte-Carlo based radiative transfer code. The setup includes a central star, a circumstellar flared disk, as well as an envelope. The test is performed for different optical depths. Considering the frequency dependence of the stellar irradiation, the temperature distributions can be described precisely in the optically thin, thick, and irradiated transition regions. Resulting radiative forces onto dust grains are reproduced with high accuracy. The achievable parallel speedup of the method imposes no restriction on further radiative (magneto-) hydrodynamics simulations. Conclusions: The proposed approximate radiation transport method enables frequency dependent radiation hydrodynamics studies of the evolution of pre-stellar cores and circumstellar accretion disks around an evolving massive star in a highly efficient and accurate manner.

Kuiper, R.; Klahr, H.; Dullemond, C.; Kley, W.; Henning, T.

2010-02-01

214

Using variable-frequency asymmetries to probe the magnetic field dependence of radial transport in a Malmberg-Penning trap  

SciTech Connect

A new experimental technique is used to study the dependence of asymmetry-induced radial particle flux {gamma} on axial magnetic field B in a modified Malmberg-Penning trap. This dependence is complicated by the fact that B enters the physics in at least two places: in the asymmetry-induced first order radial drift velocity v{sub r} = E{sub {theta}}/B and in the zeroth order azimuthal drift velocity v{sub {theta}} = E{sub r}/B. To separate these, we employ the hypothesis that the latter always enters the physics in the combination {omega}-l{omega}{sub R}, where {omega}{sub R} = v{sub {theta}}/r is the column rotation frequency and {omega} and l are the asymmetry frequency and azimuthal mode number, respectively. Points where {omega}-l{omega}{sub R} = 0 are then selected from a {gamma} vs r vs {omega} data set, thus insuring that any function of this combination is constant. When the selected flux {gamma}{sub sel} is plotted versus the density gradient, a roughly linear dependence is observed, showing that this selected flux is diffusive. This linear dependence is roughly independent of the bias of the center wire in our trap {phi}{sub cw}. Since in our experiment {omega}{sub R} is proportional to {phi}{sub cw}, this latter point shows that our technique has successfully removed any dependence on {omega}{sub R} and its derivatives, thus confirming our hypothesis. The slope of a least-squares fitted line through the {gamma}{sub sel} vs density gradient data then gives the diffusion coefficient D{sub 0} under the condition {omega}-l{omega}{sub R} = 0. Varying the magnetic field, we find D{sub 0} is proportional to B{sup -1.33{+-}}{sup 0.05}, a scaling that does not match any theory we know. These findings are then used to constrain the form of the empirical flux equation. It may be possible to extend this technique to give the functional dependence of the flux on {omega}-l{omega}{sub R}.

Eggleston, D. L. [Occidental College, Los Angeles, California (United States)

2009-03-30

215

Auxin transport-dependent, stage-specific dynamics of leaf vein formation.  

PubMed

For centuries, the formation of vein patterns in the leaf has intrigued biologists, mathematicians and philosophers. In leaf development, files of vein-forming procambial cells emerge from seemingly homogeneous subepidermal tissue through the selection of anatomically inconspicuous preprocambial cells. Although the molecular details underlying the orderly differentiation of veins in the leaf remain elusive, gradually restricted transport paths of the plant hormone auxin have long been implicated in defining sites of vein formation. Several recent advances now appear to converge on a more precise definition of the role of auxin flow at different stages of vascular development. The picture that emerges is that of vein formation as a self-organizing, reiterative, auxin transport-dependent process. PMID:19513220

Sawchuk, Megan G; Donner, Tyler J; Scarpella, Enrico

2008-05-01

216

IFT25 Links the Signal-Dependent Movement of Hedgehog Components to Intraflagellar Transport  

PubMed Central

The intraflagellar transport (IFT) system is required for building primary cilia, sensory organelles that cells use to respond to their environment. IFT particles are composed of about 20 proteins and these proteins are highly conserved across ciliated species. IFT25, however, is absent from some ciliated organisms suggesting it may have a unique role distinct from ciliogenesis. Here, we generate an Ift25 null mouse and show that IFT25 is not required for ciliary assembly but is required for proper Hedgehog signaling, which in mammals occurs within cilia. Mutant mice die at birth with multiple phenotypes indicative of Hedgehog signaling dysfunction. Cilia lacking IFT25 have defects in the signal-dependent transport of multiple Hedgehog components including Patched-1, Smoothened, and Gli2 and fail to activate the pathway upon stimulation. Thus, IFT function is not restricted to building cilia where signaling occurs, but also plays a separable role in signal transduction events.

Keady, Brian T.; Samtani, Rajeev; Tobita, Kimimasa; Tsuchya, Maiko; San Agustin, Jovenal T.; Follit, John A.; Jonassen, Julie A.; Subramanian, Ramiah; Lo, Cecilia W.; Pazour, Gregory J.

2012-01-01

217

Anomalous polarization-dependent transport in nanoscale double-barrier superconductor/ferromagnet/superconductor junctions  

NASA Astrophysics Data System (ADS)

We study the transport properties of nanoscale superconducting (S) devices in which two superconducting electrodes are bridged by two parallel ferromagnetic (F) wires, forming an SFFS junction with a separation between the two wires less than the superconducting coherence length. This allows crossed Andreev reflection to take place. We find that the resistance as a function of temperature exhibits behavior reminiscent of the reentrant effect and, at low temperatures and excitation energies below the superconducting gap, the resistance corresponding to antiparallel alignment of the magnetization of the ferromagnetic wires is higher than that of parallel alignment, in contrast to the behavior expected from crossed Andreev reflection. We present a model based on spin-dependent interface scattering that explains this surprising result and demonstrates the sensitivity of the junction transport properties to interfacial parameters.

Colci, Madalina; Sun, Kuei; Shah, Nayana; Vishveshwara, Smitha; Van Harlingen, Dale J.

2012-05-01

218

Ehrenfest-time dependence of quantum transport corrections and spectral statistics.  

PubMed

The Ehrenfest-time scale in quantum transport separates essentially classical propagation from wave interference and here we consider its effect on the transmission and reflection through quantum dots. In particular, we calculate the Ehrenfest-time dependence of the next-to-leading-order quantum corrections to the transmission and reflection for dc and ac transport and check that our results are consistent with current conservation relations. Looking as well at spectral statistics in closed systems, we finally demonstrate how the contributions analyzed here imply changes in the calculation, given by Brouwer [Phys. Rev. E 74, 066208 (2006)], of the next-to-leading order of the spectral form factor. Our semiclassical result coincides with the result obtained by Tian and Larkin [Phys. Rev. B 70, 035305 (2004)] by field-theoretical methods. PMID:21230721

Waltner, Daniel; Kuipers, Jack

2010-12-01

219

Frequency-dependent critical current and transport ac loss of superconductor strip and Roebel cable  

NASA Astrophysics Data System (ADS)

The frequency-dependent critical current of a superconductor strip and Roebel cable has been studied using a 2D finite element simulation. It is shown that the critical current of the superconductor increases with frequency as f1/n, where n is the exponent of the power law flux creep model. Transport ac loss in a superconductor strip decreases with frequency as f - 2/n when the amplitude of the applied ac current is far less than its critical current. However, when the applied current is large and becomes comparable to the critical current, the transport ac loss decreases with frequency as 1/f. The analytical results are substantiated with available experimental data and the results of a 2D finite element simulation.

Prasad Thakur, Kailash; Raj, Ashish; Brandt, Ernst Helmut; Kvitkovic, Jozef; Pamidi, Sastry V.

2011-06-01

220

Temperature Dependent Transport Study of a Single-Wall Carbon Nanotube Network  

NASA Astrophysics Data System (ADS)

We report the temperature dependence of transport properties of SWCNT network FET devices. The nonlinear ISD-VSD characteristics become linear as increasing temperature because of more diffusive carriers at higher temperature. Zero-bias conductance data is calculated and fitted with simple power-law formula, G~Ta. We obtained two different exponent values of 0.064 and 0.70 from the temperature range from 4.6 K to 40 K, and from 40 K to 295 K respectively. The power-law exponent at high temperature range is consistent with previous studies. However, unusual small power-law exponent at low temperature is attributed to the network junctions, which are disturbing 1D transport in the network structure.

Hwang, Jongseung; Oh, Jung Hyun; Son, Maeng Ho; Ahn, Doyeol; Kim, Hee Tae; Hwang, Sung Woo

2010-01-01

221

A novel biological role of dehydroascorbic acid: Inhibition of Na(+)-dependent transport of ascorbic acid.  

PubMed

A U937 cell clone, in which low micromolar concentrations of ascorbic acid (AA) and dehydroascorbic acid (DHA) are taken up at identical rates, was used to investigate possible interactions between transport systems mediating cellular uptake of the two forms of the vitamin. Results obtained with different experimental approaches showed that DHA potently and reversibly inhibits AA uptake through Na(+)-AA cotransporters. Hence, a progressive increase in extracellular DHA concentrations in the presence of a fixed amount of AA caused an initial decrease in the net amount of vitamin C accumulated, and eventually, at higher levels, it caused an accumulation of the vitamin solely based on DHA uptake through hexose transporters. DHA-dependent inhibition of AA uptake was also detected in various other cell types. Taken together, our results provide evidence of a novel biological effect mediated by concentrations of DHA compatible with those produced at inflammatory sites. PMID:24769194

Fiorani, Mara; Azzolini, Catia; Guidarelli, Andrea; Cerioni, Liana; Cantoni, Orazio

2014-06-01

222

Bureau of Mines Direct-Reading Azimuth Protractor.  

National Technical Information Service (NTIS)

The report describes the construction and use of a direct reading azimuth protractor (DRAP) for measuring fracture orientations in mines, tunnels, or other excavations having a magnetic environment. DRAP allows a rapid and simultaneous measurement of dip ...

D. D. Bolstad M. A. Mahtab

1974-01-01

223

Overexpression of the Auxin Binding PROTEIN1 Modulates PIN-Dependent Auxin Transport in Tobacco Cells  

PubMed Central

Background Auxin binding protein 1 (ABP1) is a putative auxin receptor and its function is indispensable for plant growth and development. ABP1 has been shown to be involved in auxin-dependent regulation of cell division and expansion, in plasma-membrane-related processes such as changes in transmembrane potential, and in the regulation of clathrin-dependent endocytosis. However, the ABP1-regulated downstream pathway remains elusive. Methodology/Principal Findings Using auxin transport assays and quantitative analysis of cellular morphology we show that ABP1 regulates auxin efflux from tobacco BY-2 cells. The overexpression of ABP1can counterbalance increased auxin efflux and auxin starvation phenotypes caused by the overexpression of PIN auxin efflux carrier. Relevant mechanism involves the ABP1-controlled vesicle trafficking processes, including positive regulation of endocytosis of PIN auxin efflux carriers, as indicated by fluorescence recovery after photobleaching (FRAP) and pharmacological manipulations. Conclusions/Significance The findings indicate the involvement of ABP1 in control of rate of auxin transport across plasma membrane emphasizing the role of ABP1 in regulation of PIN activity at the plasma membrane, and highlighting the relevance of ABP1 for the formation of developmentally important, PIN-dependent auxin gradients.

Covanova, Milada; Sauer, Michael; Rychtar, Jan; Friml, Jiri; Petrasek, Jan; Zazimalova, Eva

2013-01-01

224

Application of the multigrid amplitude function method for time-dependent transport equation using MOC  

SciTech Connect

An efficient numerical method for time-dependent transport equation, the mutigrid amplitude function (MAF) method, is proposed. The method of characteristics (MOC) is being widely used for reactor analysis thanks to the advances of numerical algorithms and computer hardware. However, efficient kinetic calculation method for MOC is still desirable since it requires significant computation time. Various efficient numerical methods for solving the space-dependent kinetic equation, e.g., the improved quasi-static (IQS) and the frequency transform methods, have been developed so far mainly for diffusion calculation. These calculation methods are known as effective numerical methods and they offer a way for faster computation. However, they have not been applied to the kinetic calculation method using MOC as the authors' knowledge. Thus, the MAF method is applied to the kinetic calculation using MOC aiming to reduce computation time. The MAF method is a unified numerical framework of conventional kinetic calculation methods, e.g., the IQS, the frequency transform, and the theta methods. Although the MAF method is originally developed for the space-dependent kinetic calculation based on the diffusion theory, it is extended to transport theory in the present study. The accuracy and computational time are evaluated though the TWIGL benchmark problem. The calculation results show the effectiveness of the MAF method. (authors)

Tsujita, K.; Endo, T.; Yamamoto, A. [Nagoya University, Department of Material, Physics and Energy Engineering, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)] [Nagoya University, Department of Material, Physics and Energy Engineering, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)

2013-07-01

225

Mapping the zinc transporting system in mammary cells: Molecular analysis reveals a phenotype-dependent zinc transporting network during lactation  

PubMed Central

The mammary epithelial cell transitions from a, non-secreting to a terminally differentiated, secreting cell during lactation. Zinc (Zn) is a key modulator of phenotypic transition as it regulates over 300 biological functions including transcription, translation, energy transformation, intracellular signaling and apoptosis. In addition, Zn must be redirected from normal cellular functions into the secretory compartment, as many components of the secretory system are Zn-dependant and an extraordinary amount of Zn is secreted (1–3 mg Zn/d) into milk. Herein, we utilized a “systems biology” approach of genomic and proteomic profiling to explore mechanisms through which Zn is reallocated during phenotype transition in the lactating mammary gland from mice and cultured mammary cells. Nine Zn transporters play key roles in Zn redistribution within the network during lactation. Protein abundance of six Zip (Zip3, Zip5, Zip7, Zip8, Zip10, Zip11) and three ZnT (ZnT2, ZnT4, ZnT9) proteins was expanded > 2-fold during lactation, which was not necessarily reflected by changes in mRNA expression. Our data suggest that Zip5, Zip8 and Zip10 may be key to Zn acquisition from maternal circulation, while multiple Zip proteins reuptake Zn from milk. Confocal microscopy of cultured mammary cells identified the Golgi apparatus (modulated in part by ZnT5, Zip7 and Zip11) and the late endosomal compartment (modulated in part by ZnT2 and Zip3) as key intracellular compartments through which Zn is reallocated during lactation. These results provide an important framework for understanding the Zn transporting network through which mammary gland Zn pools are redistributed and secreted into milk.

Kelleher, Shannon L; Velasquez, Vanessa; Croxford, Thomas P; McCormick, Nicholas H; Lopez, Veronica; MacDavid, Joshua

2011-01-01

226

Azimuth axis design for huge telescopes: an update  

Microsoft Academic Search

Alt-azimuth mounted radio telescopes use since their beginning -- more than 50 years ago -- the wheel-on-track principle for the realization of the azimuth axis. For the very huge telescopes (as the Lovell telescope in Jodrell Bank, UK, 1956; the Effelsberg Telescope, Germany, 1969; and the Green Bank Telescope, USA 1996), the wheel-on-track system was and is always one of

Hans J. Kaercher

2004-01-01

227

Azimuthal asymmetries for hadron distributions inside jets in hadronic collisions  

Microsoft Academic Search

Using a generalized parton model approach including spin and intrinsic parton motion effects, and assuming the validity of factorization for large p_T jet production in hadronic collisions, we study the azimuthal distribution around the jet axis of leading pions, produced in the jet fragmentation process. We identify the observable leading-twist azimuthal asymmetries for the unpolarized and single-polarized case related to

Umberto D'Alesio; Francesco Murgia; Cristian Pisano

2010-01-01

228

Crack azimuths on Europa: Sequencing of the northern leading hemisphere  

NASA Astrophysics Data System (ADS)

Nonsynchronous rotation of Europa should result in a periodic change in stress azimuths at any given location, which may result in a corresponding change in crack azimuths. An early study seemed to provide evidence for such variation within a crack sequence in the northern trailing hemisphere. However, more recent work with higher-resolution imagery resulted in a more complete sequence of cracks in the region and showed that the azimuth variation with time was not systematic. Similar results were found in the southern leading region. Here we investigate whether the northern leading region contains a crack record, on the basis of crosscutting relationships, that is adequate to indicate nonsynchronous rotation. As in the previous studies of other regions, we find no clear evidence of nonsynchronous rotation within crack azimuth patterns. However, there are other lines of evidence in support of nonsynchronous rotation. Therefore the lack of a continuous pattern of azimuth change with time is likely due to only a few cracks forming per cycle, thus hiding any discernable signal from nonsynchronous rotation in those regions. In that case, the cracks would have formed over numerous cycles of nonsynchronous rotation. The study also reveals a distinctive distribution of crack azimuths, with gaps at certain values. This distribution may reflect a combination of observation selection due to illumination and less-favorable cracking orientations.

Sarid, Alyssa Rose; Greenberg, Richard; Hurford, T. A.

2006-08-01

229

Humidity Dependence of Charge Transport through DNA Revealed by Silicon-Based Nanotweezers Manipulation  

PubMed Central

The study of the electrical properties of DNA has aroused increasing interest since the last decade. So far, controversial arguments have been put forward to explain the electrical charge transport through DNA. Our experiments on DNA bundles manipulated with silicon-based actuated tweezers demonstrate undoubtedly that humidity is the main factor affecting the electrical conduction in DNA. We explain the quasi-Ohmic behavior of DNA and the exponential dependence of its conductivity with relative humidity from the adsorption of water on the DNA backbone. We propose a quantitative model that is consistent with previous studies on DNA and other materials, like porous silicon, subjected to different humidity conditions.

Yamahata, Christophe; Collard, Dominique; Takekawa, Tetsuya; Kumemura, Momoko; Hashiguchi, Gen; Fujita, Hiroyuki

2008-01-01

230

Twist-3 Single-Spin Asymmetry for SIDIS and its Azimuthal Structure  

NASA Astrophysics Data System (ADS)

We derive the complete twist-3 single-spin-dependent cross section for semi-inclusive DIS, ep?-->e?X, associated with the complete set of the twist-3 quark-gluon correlation functions in the transversely polarized nucleon, extending our previous study. The cross section consists of five independent structure functions with different azimuthal dependences, consistently with the transverse-momentum-dependent (TMD) factorization approach in the low qT region. Correspondence with the inclusive DIS limit and comparison with the TMD approach are briefly discussed.

Koike, Yuji; Tanaka, Kazuhiro

2009-08-01

231

Variable-range hopping transport: crossovers from temperature dependence to electric field dependence in disordered carbon materials  

NASA Astrophysics Data System (ADS)

Variable-range hopping (VRH) is an important conduction mechanism in disordered conductors. One example of such a disordered conductor is reduced graphene oxide in which VRH dominates the temperature dependence of electronic conduction. Electronic transport is generally by electric field-assisted, thermally-driven VRH, following the theory of Mott, and Pollak and Riess. However, with the increase of electric field and decrease of temperature, we identify a surprisingly smooth crossover to solely field-driven VRH described by the theory of Shklovskii. We give the analytic expression for the crossover field E_C as a function of temperature and coefficients from thermally-driven and field-driven VRH. Besides reduced graphene oxide, we show in this work that our crossover scenario can also account for the experimentally measured conductivity data of three-dimensional (3D) carbon networks as well as that of quasi-1D highly-doped conducting polymers, illustrating the wide validity of our proposed physical scenario. Our crossover scenario has the advantage of combining two distinct regimes of VRH conduction yet remaining within the currently established theoretical framework.

Cheah, Chun Y.; Kaiser, Alan B.

2014-04-01

232

Transport of bile acids in multidrug-resistance-protein 3-overexpressing cells co-transfected with the ileal Na+-dependent bile-acid transporter.  

PubMed Central

Many of the transporters involved in the transport of bile acids in the enterohepatic circulation have been characterized. The basolateral bile-acid transporter of ileocytes and cholangiocytes remains an exception. It has been suggested that rat multidrug resistance protein 3 (Mrp3) fulfills this function. Here we analyse bile-salt transport by human MRP3. Membrane vesicles from insect ( Spodoptera frugiperda ) cells expressing MRP3 show time-dependent uptake of glycocholate and taurocholate. Furthermore, sulphated bile salts were high-affinity competitive inhibitors of etoposide glucuronide transport by MRP3 (IC50 approximately 10 microM). Taurochenodeoxycholate, taurocholate and glycocholate inhibited transport at higher concentrations (IC50 approximately 100, 250 and 500 microM respectively). We used mouse fibroblast-like cell lines derived from mice with disrupted Mdr1a, Mdr1b and Mrp1 genes to generate transfectants that express the murine apical Na+-dependent bile-salt transporter (Asbt) and MRP3. Uptake of glycocholate by these cells is Na+-dependent, with a K(m) and V(max) of 29+/-7 microM and 660 +/- 63 pmol/min per mg of protein respectively and is inhibited by several organic-aniontransport inhibitors. Expression of MRP3 in these cells limits the accumulation of glycocholate and increases the efflux from cells preloaded with taurocholate or glycocholate. In conclusion, we find that MRP3 transports both taurocholate and glycocholate, albeit with low affinity, in contrast with the high-affinity transport by rat Mrp3. Our results suggest that MRP3 is unlikely to be the principal basolateral bile-acid transporter of ileocytes and cholangiocytes, but that it may have a role in the removal of bile acids from the liver in cholestasis.

Zelcer, Noam; Saeki, Tohru; Bot, Ilse; Kuil, Annemieke; Borst, Piet

2003-01-01

233

The hFbpABC Transporter from Haemophilus influenzae Functions as a Binding-Protein-Dependent ABC Transporter with High Specificity and Affinity for Ferric Iron  

PubMed Central

Pathogenic Haemophilus influenzae, Neisseria spp. (Neisseria gonorrhoeae and N. meningitidis), Serratia marcescens, and other gram-negative bacteria utilize a periplasm-to-cytosol FbpABC iron transporter. In this study, we investigated the H. influenzae FbpABC transporter in a siderophore-deficient Escherichia coli background to assess biochemical aspects of FbpABC transporter function. Using a radiolabeled Fe3+ transport assay, we established an apparent Km = 0.9 ?M and Vmax = 1.8 pmol/107cells/min for FbpABC-mediated transport. Complementation experiments showed that hFbpABC is dependent on the FbpA binding protein for transport. The ATPase inhibitor sodium orthovanadate demonstrated dose-dependent inhibition of FbpABC transport, while the protonmotive-force-inhibitor carbonyl cyanide m-chlorophenyl hydrazone had no effect. Metal competition experiments demonstrated that the transporter has high specificity for Fe3+ and selectivity for trivalent metals, including Ga3+ and Al3+, over divalent metals. Metal sensitivity experiments showed that several divalent metals, including copper, nickel, and zinc, exhibited general toxicity towards E. coli. Significantly, gallium-induced toxicity was specific only to E. coli expressing FbpABC. A single-amino-acid mutation in the gene encoding the periplasmic binding protein, FbpA(Y196I), resulted in a greatly diminished iron binding affinity Kd = 5.2 × 10?4 M?1, ?14 orders of magnitude weaker than that of the wild-type protein. Surprisingly, the mutant transporter [FbpA(Y196I)BC] exhibited substantial transport activity, ?35% of wild-type transport, with Km = 1.2 ?M and Vmax = 0.5 pmol/107cells/min. We conclude that the FbpABC complexes possess basic characteristics representative of the family of bacterial binding protein-dependent ABC transporters. However, the specificity and high-affinity binding characteristics suggest that the FbpABC transporters function as specialized transporters satisfying the strict chemical requirements of ferric iron (Fe3+) binding and membrane transport.

Anderson, Damon S.; Adhikari, Pratima; Nowalk, Andrew J.; Chen, Cheng Y.; Mietzner, Timothy A.

2004-01-01

234

Spin-Dependent Electron Transport in an Armchair Graphene Nanoribbon Subject to Charge and Spin Biases  

NASA Astrophysics Data System (ADS)

We study the spin-dependent electron transport in an armchair graphene nanoribbon sample driven by both the charge and the spin biases within the tight-binding framework. By numerical calculations we give the spin-dependent currents for a fixed spin bias as a function of the charge bias. It is found that we can let only one type of spin current pass through the graphene nanoribbon for a wide range of charge bias, which is due to the difference of the bias voltage windows for different spin electrons when the charge and the spin biases coexist. Moreover, the pure spin current can be controlled via the charge bias. Our results are suggestive for developing new kinds of spin filters.

Zhang, Xiao-Wei; Zhao, Hua; Sang, Tian; Liu, Xiao-Chun; Cai, Tuo

2013-01-01

235

Molecular origin of fast water transport in carbon nanotube membranes: superlubricity versus curvature dependent friction.  

PubMed

In this paper, we study the interfacial friction of water at graphitic interfaces with various topologies, water between planar graphene sheets, inside and outside carbon nanotubes, with the goal to disentangle confinement and curvature effects on friction. We show that the friction coefficient exhibits a strong curvature dependence; while friction is independent of confinement for the graphene slab, it decreases with carbon nanotube radius for water inside, but increases for water outside. As a paradigm the friction coefficient is found to vanish below a threshold diameter for armchair nanotubes. Using a statistical description of the interfacial friction, we highlight here a structural origin of this curvature dependence, mainly associated with a curvature-induced incommensurability between the water and carbon structures. These results support the recent experiments reporting fast transport of water in nanometric carbon nanotube membranes. PMID:20845964

Falk, Kerstin; Sedlmeier, Felix; Joly, Laurent; Netz, Roland R; Bocquet, Lydéric

2010-10-13

236

Nonlinear transport through quantum dot studied by the time-dependent DMRG  

NASA Astrophysics Data System (ADS)

Nonequilibrium transport properties of quantum dot under a finite bias voltage is investigated using the adaptive time-dependent density matrix renormalization group (TdDMRG) method. The validity of the authors’ previous study was limited for relatively weak coupling parameters because the small scale Kondo energy in the strong coupling regime caused a difficulty. By taking sufficiently long system size, keeping large number of states during the TdDMRG process and utilizing the fourth order Suzuki-Trotter decomposition, we can extend calculations of current-voltage characteristics in the strongly correlated region up to the Wilson ratio RW<1.97, close to the strong coupling limit. The wide domain of applicability suggests future applications of the method to various nonequilibrium and time-dependent problems.

Kirino, S.; Fujii, T.; Ueda, K.

2010-02-01

237

Modulation of ileal apical Na+-dependent bile acid transporter ASBT by protein kinase C.  

PubMed

Ileal apical Na(+)-dependent bile acid transporter (ASBT) is responsible for reabsorbing the majority of bile acids from the intestinal lumen. Rapid adaptation of ASBT function in response to physiological and pathophysiological stimuli is essential for the maintenance of bile acid homeostasis. However, not much is known about molecular mechanisms responsible for acute posttranscriptional regulation of ileal ASBT. The protein kinase C (PKC)-dependent pathway represents a major cell signaling mechanism influencing intestinal epithelial functions. The present studies were, therefore, undertaken to investigate ASBT regulation in intestinal Caco-2 monolayers by the well-known PKC activator phorbol 12-myristate 13-acetate (PMA). Our results showed that Na(+)-dependent [(3)H]taurocholic acid uptake in Caco-2 cells was significantly inhibited in response to 2 h incubation with 100 nM PMA compared with incubation with 4alpha-PMA (inactive form). The inhibitory effect of PMA was blocked in the presence of 5 microM bisindolylmaleimide I (PKC inhibitor) but not 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM (Ca(2+) chelator) or LY-294002 (phosphatidylinositol 3-kinase inhibitor). PMA inhibition of ASBT function was also abrogated in the presence of myristoylated PKCzeta pseudosubstrate peptide, indicating involvement of the atypical PKCzeta isoform. The inhibition by PMA was associated with a significant decrease in the maximal velocity of the transporter and a reduction in ASBT plasma membrane content, suggesting a modulation by vesicular recycling. Our novel findings demonstrate a posttranscriptional modulation of ileal ASBT function and membrane expression by phorbol ester via a PKCzeta-dependent pathway. PMID:19571234

Sarwar, Zaheer; Annaba, Fadi; Dwivedi, Alka; Saksena, Seema; Gill, Ravinder K; Alrefai, Waddah A

2009-09-01

238

Transport material dependence and structure effects on high-charge proton beams  

NASA Astrophysics Data System (ADS)

The ultimate focal size of a proton beam produced by laser-irradiation of a curved foil can be affected by surrounding structures and self-fields [1,2]. The focusing can further be affected as the beam transports into plasma. We present experimental measurements taken with the high intensity TRIDENT laser (75 J, 0.6 ps) at LANL in which protons were focused into a secondary foil of either Mylar, Al, Cu, or Au. XUV emission from a Au layer on the rear of the transport foil indicated a clear dependence of proton beam focused size on transport foil material with the Au layer producing the tightest spot (40 ?m) in spite of having the highest Z and areal density. A target consisting of a flat foil was also tested to compare with the curved foils. XUV emission in this case was undetectable. Coupling of hot electron energy to the structure supporting the target will also be discussed.[4pt] [1] Bartal, et al., Nature Physics 8, 139 (2012).[0pt] [2] M. E. Foord, et al., Phys. Plasmas, 19, 5 (2012).

McGuffey, C.; Link, A.; Gautier, D. C.; Kim, J.; Kerr, S.; Kemp, G. E.; Madden, R.; Giraldez, E. M.; Wei, M. S.; Stevens, R. B.; Foord, M. E.; McLean, H. S.; Patel, P. K.; Beg, F. N.

2012-10-01

239

Molecular expression of SLC4-derived Na+-dependent anion transporters in selected human tissues.  

PubMed

NaHCO(3) transporters are involved in maintenance of intracellular pH and transepithelial HCO(3)(-) movement in many rodent tissues. To establish the human relevance of the many investigations on rodents, this study aimed to map these transporters and a related polypeptide, NaBC1 [solute carrier 4 (SLC4)A11], to several human tissues by using PCR on reverse transcribed human mRNA and immunoperoxidase histochemistry. The mRNA encoding the electroneutral Na(+):HCO(3)(-) cotransporter (NBCe1; SLC4A4), was expressed in renal cortex, renal medulla, stomach, duodenum, jejunum, ileum, colon, pancreas, choroid plexus, cerebellum, cerebrum, and hippocampus. NBCe2 (SLC4A5) and NBCn1 (SLC4A7) mRNAs were mainly found in kidney and brain tissues, as was mRNA encoding the Na(+)-dependent anion exchangers NCBE (SLC4A10) and NDCBE1 (SLC4A8). In addition to previous findings, NBCn1 protein was localized to human renal medullary thick ascending limbs and duodenal epithelial villus cells and NBCe2 protein to renal collecting ducts. Finally, the message encoding NaBC1 was found in kidney, stomach, duodenum, pancreas, and brain, and the corresponding protein in the anterior and posterior corneal epithelia, renal corpuscules, proximal tubules, collecting ducts, pancreatic ducts, and the choroid plexus epithelium. In conclusion, the selected human tissues display distinct expression patterns of HCO(3)(-) transporters, which closely resemble that of rodent tissues. PMID:17715183

Damkier, Helle Hasager; Nielsen, Sřren; Praetorius, Jeppe

2007-11-01

240

Experimental Study of Local Anomalous Ion Thermal Transport with A Novel Time Dependent Energy Analyzer  

NASA Astrophysics Data System (ADS)

In the past we have reported measurements of global ion thermal transport due to ion temperature gradient (ITG) modes [1]. It is clearly more desirable to obtain local measurements of the same, which we now report for basic experiments in the Columbia Linear Machine. For local measurement of radial ion thermal transport we used a novel time dependent ion energy analyzer. For compensation of plasma potential fluctuations in energy analyzer measurements, we use floating potential fluctuation of Langmuir probe as a feedback signal with gain +1 and apply this voltage on energy selector grid. The simultaneous measurement of the ion current fluctuations of analyzer IIEA(t) and the fluctuation of ion saturation current of Langmuir probe ISAT(t) allow us to determine local fluctuations of ion temperature Ti(t). The local thermal flux is obtained from cross-correlation of ion temperature fluctuations and potential fluctuations. The radial profiles of the plasma density, ion temperature, and total thermal flux were obtained at different levels of ITG mode. The results indicate that the ion thermal transport is ?( TI/ r )^?, ?>1. [4pt] [1] B. Song, J. Chen, and A.K. Sen, Phys. Rev. Lett. 70, 2407 (1993).

Sokolov, Vladimir; Sen, Amiya K.

2009-11-01

241

Molecular size of a Na sup + -dependent amino acid transporter in Ehrlich ascites cell plasma membranes estimated by radiation inactivation  

Microsoft Academic Search

Radiation inactivation was used to estimate the molecular size of a Na{sup +}-dependent amino acid transport system in Ehrlich ascites cell plasma membrane vesicles. Na{sup +}-dependent Îą-aminoisobutyric acid uptake was measured after membranes were irradiated at -78.5C in a cryoprotective medium. Twenty-five percent of the transport activity was lost at low radiation doses (<0.5 Mrad), suggesting the presence of a

John I. McCormick; R. M. Johnstone; M. Jette; Richard Beliveau; M. Potier

1991-01-01

242

Azimuthal asymmetries for hadron distributions inside a jet in hadronic collisions  

NASA Astrophysics Data System (ADS)

Using a generalized parton model approach including spin and intrinsic parton motion effects, and assuming the validity of factorization for large pT jet production in hadronic collisions, we study the azimuthal distribution around the jet axis of leading pions, produced in the jet fragmentation process. We identify the observable leading-twist azimuthal asymmetries for the unpolarized and single-polarized case related to both quark and gluon-originated jets. We account for all physically allowed combinations of the transverse momentum dependent (TMD) parton distribution and fragmentation functions, with special attention to the Sivers, Boer-Mulders, and transversity quark distributions, and to the Collins fragmentation function for quarks (and to the analogous functions for gluon partons).

D'Alesio, Umberto; Murgia, Francesco; Pisano, Cristian

2011-05-01

243

Spin-dependent transport for armchair-edge graphene nanoribbons between ferromagnetic leads.  

PubMed

We theoretically investigate the spin-dependent transport for the system of an armchair-edge graphene nanoribbon (AGNR) between two ferromagnetic (FM) leads with arbitrary polarization directions at low temperatures, where a magnetic insulator is deposited on the AGNR to induce an exchange splitting between spin-up and -down carriers. By using the standard nonequilibrium Green's function (NGF) technique, it is demonstrated that the spin-resolved transport property for the system depends sensitively on both the width of AGNR and the polarization strength of FM leads. The tunneling magnetoresistance (TMR) around zero bias voltage possesses a pronounced plateau structure for a system with semiconducting 7-AGNR or metallic 8-AGNR in the absence of exchange splitting, but this plateau structure for the 8-AGNR system is remarkably broader than that for the 7-AGNR one. Interestingly, an increase of the exchange splitting ? suppresses the amplitude of the structure for the 7-AGNR system. However, the TMR is much enhanced for the 8-AGNR system under a bias amplitude comparable to the splitting strength. Further, the current-induced spin-transfer torque (STT) for the 7-AGNR system is systematically larger than that for the 8-AGNR one. The findings here suggest the design of GNR-based spintronic devices by using a metallic AGNR, but it is more favorable to fabricate a current-controlled magnetic memory element by using a semiconducting AGNR. PMID:21415476

Zhou, Benhu; Chen, Xiongwen; Zhou, Benliang; Ding, Kai-He; Zhou, Guanghui

2011-04-01

244

Ion channel activity of transmembrane segment 6 of Escherichia coli proton-dependent manganese transporter.  

PubMed

Synthetic peptides corresponding to the sixth transmembrane segment (TMS6) of secondary-active transporter MntH (Proton-dependent Manganese Transporter) from Escherichia coli and its two mutations in the functionally important conserved histidine residue were used as a model for structure-function study of MntH. The secondary structure of the peptides was estimated in different environments using circular dichroism spectroscopy. These peptides interacted with and adopted helical conformations in lipid membranes. Electrophysiological experiments demonstrated that TMS6 was able to form multi-state ion channels in model biological membranes. Electrophysiological properties of these weakly cation-selective ion channels were strongly dependent on the surrounding pH. Manganese ion, as a physiological substrate of MntH, enhanced the conductivity of TMS6 channels, influenced the transition between closed and open states, and affected the peptide conformations. Moreover, functional properties of peptides carrying two different mutations of His(211) were analogous to in vivo functional characteristics of Nramp/MntH proteins mutated at homologous residues. Hence, a single functionally important TMS can retain some of the functional properties of the full-length protein. These findings could contribute to understanding the structure-function relationship at the molecular level. However it remains unclear to what extent the peptide-specific channel activity represents a functional aspect of the full-length membrane carrier protein. PMID:20517953

Nunuková, Vera; Urbánková, Eva; Jelokhani-Niaraki, Masoud; Chaloupka, Roman

2010-08-01

245

Yeast Mn2+ transporter, Smf1p, is regulated by ubiquitin-dependent vacuolar protein sorting.  

PubMed

Conditional cdc1(Ts) mutants of S. cerevisiae arrest with a phenotype similar to that exhibited by Mn(2+)-depleted cells. Sequence similarity between Cdc1p and a class of Mn(2+)-dependent phosphoesterases, as well as the observation that conditional cdc1(Ts) growth can be ameliorated by Mn(2+) supplement, suggests that Cdc1p activity is sensitive to intracellular Mn(2+) levels. This article identifies several previously uncharacterized cdc1(Ts) suppressors as class E vps (vacuolar protein sorting) mutants and shows that these, as well as other vps mutants, accumulate high levels of intracellular Mn(2+). Yeast VPS genes play a role in delivery of membrane transporters to the vacuole for degradation, and we show that the vps mutants accumulate elevated levels of the high-affinity Mn(2+) transporter Smf1p. cdc1(Ts) conditional growth is also alleviated by mutations, including doa4 and ubc4, that compromise protein ubiquitination, and these ubiquitination defects are associated with Smf1p accumulation. Epistasis studies show that these suppressors require functional Smf1p to alleviate the cdc1(Ts) growth defect, whereas Smf1p is dispensable for cdc1(Ts) suppression by a mutation (cos16/per1) that does not influence intracellular Mn(2+) levels. Because Smf1p is ubiquitinated in vivo, we propose that Smf1p is targeted to the vacuole for degradation by ubiquitination-dependent protein sorting. PMID:15166140

Eguez, Lorena; Chung, Young-Sook; Kuchibhatla, Ajay; Paidhungat, Madan; Garrett, Stephen

2004-05-01

246

Yeast Mn2+ transporter, Smf1p, is regulated by ubiquitin-dependent vacuolar protein sorting.  

PubMed Central

Conditional cdc1(Ts) mutants of S. cerevisiae arrest with a phenotype similar to that exhibited by Mn(2+)-depleted cells. Sequence similarity between Cdc1p and a class of Mn(2+)-dependent phosphoesterases, as well as the observation that conditional cdc1(Ts) growth can be ameliorated by Mn(2+) supplement, suggests that Cdc1p activity is sensitive to intracellular Mn(2+) levels. This article identifies several previously uncharacterized cdc1(Ts) suppressors as class E vps (vacuolar protein sorting) mutants and shows that these, as well as other vps mutants, accumulate high levels of intracellular Mn(2+). Yeast VPS genes play a role in delivery of membrane transporters to the vacuole for degradation, and we show that the vps mutants accumulate elevated levels of the high-affinity Mn(2+) transporter Smf1p. cdc1(Ts) conditional growth is also alleviated by mutations, including doa4 and ubc4, that compromise protein ubiquitination, and these ubiquitination defects are associated with Smf1p accumulation. Epistasis studies show that these suppressors require functional Smf1p to alleviate the cdc1(Ts) growth defect, whereas Smf1p is dispensable for cdc1(Ts) suppression by a mutation (cos16/per1) that does not influence intracellular Mn(2+) levels. Because Smf1p is ubiquitinated in vivo, we propose that Smf1p is targeted to the vacuole for degradation by ubiquitination-dependent protein sorting.

Eguez, Lorena; Chung, Young-Sook; Kuchibhatla, Ajay; Paidhungat, Madan; Garrett, Stephen

2004-01-01

247

PET imaging of the serotonin transporter and 5HT1A receptor in alcohol dependence  

PubMed Central

Background Rodent models as well as studies in humans have suggested alterations in serotonin (5HT) innervation and transmission in early onset genetically determined or type II alcoholism. This study examines two indices of serotonergic transmission, 5HT transporter levels and 5-HT1A availability, in vivo, in type II alcoholism. This is the first report of combined tracers for pre and post-synaptic serotonergic transmission in the same alcoholic subjects and the first study of 5HT1A receptors in alcoholism. Method Fourteen alcohol dependent subjects were scanned (11 with both tracers, 1 with [11C]DASB only and two with [11C]WAY100635 only). Twelve healthy controls (HC) subjects were scanned with [11C]DASB and another 13 were scanned with [11C]WAY100635. Binding Potential (BPp, mL/cm3) and the specific to nonspecific partition coefficient (BPND, unitless) were derived for both tracers using 2 tissue compartment model and compared to HC across different brain regions. Relationships to severity of alcoholism were assessed. Results No significant differences were observed in regional BPp or BPND between patients and controls in any of the regions examined. No significant relationships were observed between regional 5HT transporter availability, 5-HT1A availability, and disease severity with the exception of a significant negative correlation between SERT and years of dependence in amygdala and insula. Conclusion This study did not find alterations in measures of 5-HT1A or 5HT transporter levels in patients with type II alcoholism.

Martinez, Diana; Slifstein, Mark; Gil, Roberto; Hwang, Dah-Ren; Huang, Yiyun; Perez, Audrey; Frankle, W. Gordon; Laruelle, Marc; Krystal, John; Abi-Dargham, Anissa

2009-01-01

248

Induction of Mrp3 and Mrp4 transporters during acetaminophen hepatotoxicity is dependent on Nrf2  

SciTech Connect

The transcription factor NFE2-related factor 2 (Nrf2) mediates detoxification and antioxidant gene transcription following electrophile exposure and oxidative stress. Mice deficient in Nrf2 (Nrf2-null) are highly susceptible to acetaminophen (APAP) hepatotoxicity and exhibit lower basal and inducible expression of cytoprotective genes, including NADPH quinone oxidoreductase 1 (Nqo1) and glutamate cysteine ligase (catalytic subunit, or Gclc). Administration of toxic APAP doses to C57BL/6J mice generates electrophilic stress and subsequently increases levels of hepatic Nqo1, Gclc and the efflux multidrug resistance-associated protein transporters 1-4 (Mrp1-4). It was hypothesized that induction of hepatic Mrp1-4 expression following APAP is Nrf2 dependent. Plasma and livers from wild-type (WT) and Nrf2-null mice were collected 4, 24 and 48 h after APAP. As expected, hepatotoxicity was greater in Nrf2-null compared to WT mice. Gene and protein expression of Mrp1-4 and the Nrf2 targets, Nqo1 and Gclc, was measured. Induction of Nqo1 and Gclc mRNA and protein after APAP was dependent on Nrf2 expression. Similarly, APAP treatment increased hepatic Mrp3 and Mrp4 mRNA and protein in WT, but not Nrf2-null mice. Mrp1 was induced in both genotypes after APAP, suggesting that elevated expression of this transporter was independent of Nrf2. Mrp2 was not induced in either genotype at the mRNA or protein levels. These results show that Nrf2 mediates induction of Mrp3 and Mrp4 after APAP but does not affect Mrp1 or Mrp2. Thus coordinated regulation of detoxification enzymes and transporters by Nrf2 during APAP hepatotoxicity is a mechanism by which hepatocytes may limit intracellular accumulation of potentially toxic chemicals.

Aleksunes, Lauren M. [Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, 69 North Eagleville Road, Unit 3092, Storrs, CT 06269-3092 (United States); Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS (United States)], E-mail: laleksunes@kumc.edu; Slitt, Angela L. [Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS (United States)], E-mail: aslitt@etal.uri.edu; Maher, Jonathan M. [Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS (United States)], E-mail: jmaher@tara.tsukuba.ac.jp; Augustine, Lisa M. [Department of Pharmacology and Toxicology, University of Arizona, Tucson, AZ (United States)], E-mail: bird@pharmacy.arizona.edu; Goedken, Michael J. [Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, 69 North Eagleville Road, Unit 3092, Storrs, CT 06269-3092 (United States)], E-mail: michael.goedken@gmail.com; Chan, Jefferson Y. [Department of Pathology, University of California, Irvine, CA (United States)], E-mail: jchan@uci.edu; Cherrington, Nathan J. [Department of Pharmacology and Toxicology, University of Arizona, Tucson, AZ (United States)], E-mail: cherrington@pharmacy.arizona.edu; Klaassen, Curtis D. [Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS (United States)], E-mail: cklaasse@kumc.edu; Manautou, Jose E. [Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, 69 North Eagleville Road, Unit 3092, Storrs, CT 06269-3092 (United States)], E-mail: jose.manautou@uconn.edu

2008-01-01

249

Potential-dependent passive calcium transport in vesicles of myocardial sarcolemma  

SciTech Connect

The influence of the membrane potential on passive Ca/sup 2 +/ transport in vesiculated preparations of the myocardial sarcolemma was investigated. It was shown with the aid of the potential-dependent fluorescent probe diS-C/sub 3/-(5) that the potential produced by establishing a K/sup +/ gradient across the membrane in the presence of valinomycin is close in value to the potassium equilibrium potential calculated using the Nernst equation. The initial rate of Ca/sup 2 +/ efflux from inside-out vesicles was considerably higher at a zero potential than at +55 or -80 mV. Preliminary polarization of the vesicles to +90 mV (a plus sign on the inside) did not increase the Ca/sup 2 +/ efflux upon subsequent depolarization. The potential-dependent Ca/sup 2 +/ efflux increased with increasing (Ca/sub i//sup 2 +/), demonstrating a saturation effect. The dependence of the rate of Ca/sup 2 +/ efflux on the membrane potential had a profile similar to the volt-ampere characteristics of the Ca/sup 2 +/ current obtained on isolated cardiomyocytes. It was assumed that the potential-dependent Ca/sup 2 +/ efflux from the vesicles occurs via the Ca/sup 2 +/ channels.

Vorobets, Z.D.; Puzyrev, S.Yu.; Kurskii, M.D.

1987-02-10

250

Azimuthal distributions of charged hadrons, pions, and kaons produced in deep-inelastic scattering off unpolarized protons and deuterons  

NASA Astrophysics Data System (ADS)

The azimuthal cos?? and cos?2? modulations of the distribution of hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of electrons and positrons off hydrogen and deuterium targets have been measured in the HERMES experiment. For the first time these modulations were determined in a four-dimensional kinematic space for positively and negatively charged pions and kaons separately, as well as for unidentified hadrons. These azimuthal dependences are sensitive to the transverse motion and polarization of the quarks within the nucleon via, e.g., the Cahn, Boer-Mulders and Collins effects.

Airapetian, A.; Akopov, N.; Akopov, Z.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetisyan, E.; Belostotski, S.; Blok, H. P.; Borissov, A.; Bowles, J.; Bryzgalov, V.; Burns, J.; Capiluppi, M.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; De Leo, R.; De Nardo, L.; De Sanctis, E.; Diefenthaler, M.; Di Nezza, P.; Düren, M.; Elbakian, G.; Ellinghaus, F.; Fantoni, A.; Felawka, L.; Frullani, S.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Giordano, F.; Gliske, S.; Golembiovskaya, M.; Hadjidakis, C.; Hartig, M.; Hasch, D.; Hillenbrand, A.; Hoek, M.; Holler, Y.; Hristova, I.; Imazu, Y.; Ivanilov, A.; Jackson, H. E.; Jo, H. S.; Joosten, S.; Kaiser, R.; Karyan, G.; Keri, T.; Kinney, E.; Kisselev, A.; Korotkov, V.; Kozlov, V.; Kravchenko, P.; Krivokhijine, V. G.; Lagamba, L.; Lapikás, L.; Lehmann, I.; Lenisa, P.; López Ruiz, A.; Lorenzon, W.; Ma, B.-Q.; Mahon, D.; Makins, N. C. R.; Manaenkov, S. I.; Manfré, L.; Mao, Y.; Marianski, B.; Martinez de la Ossa, A.; Marukyan, H.; Miller, C. A.; Miyachi, Y.; Movsisyan, A.; Murray, M.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaev, M.; Nowak, W.-D.; Pappalardo, L. L.; Perez-Benito, R.; Petrosyan, A.; Raithel, M.; Reimer, P. E.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Rubin, J.; Ryckbosch, D.; Salomatin, Y.; Sanftl, F.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Seitz, B.; Shibata, T.-A.; Stancari, M.; Statera, M.; Steijger, J. J. M.; Stewart, J.; Stinzing, F.; Terkulov, A.; Truty, R. M.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; Van Haarlem, Y.; Van Hulse, C.; Veretennikov, D.; Vikhrov, V.; Vilardi, I.; Wang, S.; Yaschenko, S.; Ye, Z.; Yen, S.; Yu, W.; Zagrebelnyy, V.; Zeiler, D.; Zihlmann, B.; Zupranski, P.

2013-01-01

251

Deep Source Anisotropy Revealed From Back-Azimuthal Variation of Shear-Wave Splitting in Southwest Ireland  

Microsoft Academic Search

Observation of large splitting in core shear wave phases such as SKS\\/SKKS are usually attributed to upper mantle anisotropy due to either a fossilized deformation imprint in the lithosphere or the influence of asthenospheric flow, or to a combination of both. Here we report splitting results from southwest Ireland that show a strong back-azimuthal dependence of fast direction which suggests

P. W. Readman; B. M. O'Reilly

2005-01-01

252

Unusual Temperature and Field Dependence of Transport Properties Ba(Fe1-xCox)2As2  

NASA Astrophysics Data System (ADS)

The in-plane transport properties of Ba(Fe1-xCox)2As2 single crystals with x = 0.02 ˜ 0.28 was measured as a function of temperature (2 ˜ 300 K) and magnetic field (up to 14 Tesla). A Cobalt doping composition-temperature (x-T) phase diagram was plotted and shows a non-Fermi liquid (NFL) transport behavior around the optimal doing level. The Hall effect and magneto-resistance results also show an anomaly and a change of field dependence around the optimal doing. The underlying physics of such unusual temperature and field dependence of transport properties ab plane will be discussed.

Xiong, Yimin; Li, Jianneng; Jin, Rongying

2010-10-01

253

Horizontal Contraction of Oceanic Lithosphere Tested Using Azimuths of Transform Faults  

NASA Astrophysics Data System (ADS)

A central hypothesis or approximation of plate tectonics is that the plates are rigid, which implies that oceanic lithosphere does not contract horizontally as it cools (hereinafter "no contraction"). An alternative hypothesis is that vertically averaged tensional thermal stress in the competent lithosphere is fully relieved by horizontal thermal contraction (hereinafter "full contraction"). These two hypotheses predict different azimuths for transform faults. We build on prior predictions of horizontal thermal contraction of oceanic lithosphere as a function of age to predict the bias induced in transform-fault azimuths by full contraction for 140 azimuths of transform faults that are globally distributed between 15 plate pairs. Predicted bias increases with the length of adjacent segments of mid-ocean ridges and depends on whether the adjacent ridges are stepped, crenellated, or a combination of the two. All else being equal, the bias decreases with the length of a transform fault and modestly decreases with increasing spreading rate. The value of the bias varies along a transform fault. To correct the observed transform-fault azimuths for the biases, we average the predicted values over the insonified portions of each transform fault. We find the bias to be as large as 2.5°, but more typically is ? 1.0°. We test whether correcting for the predicted biases improves the fit to plate motion data. To do so, we determine the sum-squared normalized misfit for various values of ?, which we define to be the fractional multiple of bias predicted for full contraction. ? = 1 corresponds to the full contraction, while ? = 0 corresponds to no contraction. We find that the minimum in sum-squared normalized misfit is obtained for ? = 0.9 ą0.4 (95% confidence limits), which excludes the hypothesis of no contraction, but is consistent with the hypothesis of full contraction. Application of the correction reduces but does not eliminate the longstanding misfit between the azimuth of the Kane transform fault with respect to those of the other North America-Nubia transform faults. We conclude that significant ridge-parallel horizontal thermal contraction occurs in young oceanic lithosphere and that it is accommodated by widening of transform-fault valleys, which causes biases in transform-fault azimuths up to 2.5°.

Gordon, R. G.; Mishra, J. K.

2012-12-01

254

Unsteady Annular Viscous Flows Between Oscillating Cylinders. Part II: A Hybrid Time-Integration Solution Based on Azimuthal Fourier Expansions for Configurations with Annular Backsteps  

Microsoft Academic Search

A hybrid time-integration method based on azimuthal Fourier expansions for solving the time-dependent incompressible Navier-Stokes equations has been developed in order to obtain superior computational efficiency; this will permit simultaneous time-integration of the coupled systems of equations of fluid and structural unsteady motions. The hybrid method uses highly convergent Fourier expansions in the azimuthal angular coordinate for the unsteady pressure

D. Mateescu; M. P. Paďdoussis; F. Belanger

1994-01-01

255

The Dependence of H-mode Energy Confinement and Transport on Collisionality in NSTX  

SciTech Connect

Understanding the dependence of confi nement on collisionality in tokamaks is important for the design of next-step devices, which will operate at collisionalities at least one order of magnitude lower than in present generation. A wide range of collisionality has been obtained in the National Spherical Torus Experiment (NSTX) by employing two different wall conditioning techniques, one with boronization and between-shot helium glow discharge conditioning (HeGDC+B), and one using lithium evaporation (Li EVAP). Previous studies of HeGDC+B plasmas indicated a strong and favorable dependence of normalized con nement on collisionality. Discharges with lithium conditioning discussed in the present study gen- erally achieved lower collisionality, extending the accessible range of collisionality by almost an order of unity. While the confinement dependences on dimensional, engineering variables of the HeGDC+B and Li EVAP datasets differed, collisionality was found to unify the trends, with the lower collisionality lithium conditioned discharges extending the trend of increasing normalized confi nement time with decreasing collisionality when other dimension less variables were held as fi xed as possible. This increase of confi nement with decreasing collisionality was driven by a large reduction in electron transport in the outer region of the plasma. This result is consistent with gyrokinetic calculations that show microtearing and Electron Temperature Gradient modes to be more stable for the lower collisionality discharges. Ion transport, near neoclassical at high collisionality, became more anomalous at lower collisionality, possibly due to the growth of hybrid TEM/KBM modes in the outer regions of the plasma

S.M.. Kaye, S. Gerhardt, W. Guttenfelder, R. Maingi, R.E. Bell, A. Diallo, B.P. LeBlanc and M. Podesta

2012-11-28

256

The Dependence of H-mode Energy Confinement and Transport on Collisionality in NSTX  

SciTech Connect

Understanding the dependence of confi nement on collisionality in tokamaks is important for the design of next-step devices, which will operate at collisionalities at least one order of magnitude lower than in present generation. A wide range of collisionality has been obtained in the National Spherical Torus Experiment (NSTX) by employing two different wall conditioning techniques, one with boronization and between-shot helium glow discharge conditioning (HeGDC+B), and one using lithium evaporation (Li EVAP). Previous studies of HeGDC+B plasmas indicated a strong and favorable dependence of normalized con nement on collisionality. Discharges with lithium conditioning discussed in the present study gen- erally achieved lower collisionality, extending the accessible range of collisionality by almost an order of unity. While the confinement dependences on dimensional, engineering variables of the HeGDC+B and Li EVAP datasets differed, collisionality was found to unify the trends, with the lower collisionality lithium conditioned discharges extending the trend of increasing normalized confi nement time with decreasing collisionality when other dimension less variables were held as fi xed as possible. This increase of confi nement with decreasing collisionality was driven by a large reduction in electron transport in the outer region of the plasma. This result is consistent with gyrokinetic calculations that show microtearing and Electron Temperature Gradient modes to be more stable for the lower collisionality discharges. Ion transport, near neoclassical at high collisionality, became more anomalous at lower collisionality, possibly due to the growth of hybrid TEM/KBM modes in the outer regions of the plasma.

S.M.. Kaye, S. Gerhardt, W. Guttenfelder, R. Maingi, R.E. Bell, A. Diallo, B.P. LeBlanc and M. Podesta

2012-11-27

257

Cloning and functional characterization of a system ASC-like Na+-dependent neutral amino acid transporter.  

PubMed

A cDNA was isolated from mouse testis which encodes a Na+-dependent neutral amino acid transporter. The encoded protein, designated ASCT2, showed amino acid sequence similarity to the mammalian glutamate transporters (40-44% identity), Na+-dependent neutral amino acid transporter ASCT1 (57% identity; Arriza, J. L., Kavanaugh, M. P., Fairman, W. A., Wu, Y.-N., Murdoch, G. H., North, R. A., and Amara, S. G.(1993) J. Biol. Chem. 268, 15329-15332; Shafqat, S., Tamarappoo, B. K., Kilberg, M. S., Puranam, R. S., McNamara, J. O., Guadano-Ferraz, A., and Fremeau, T., Jr. (1993) J. Biol. Chem. 268, 15351-15355) and a mouse adipocyte differentiation-associated gene product AAAT (94% identity; Liao, K., and Lane, D.(1995) Biochem. Biophys. Res. Commun. 208, 1008-1015). When expressed in Xenopus laevis oocytes, ASCT2 exhibited Na+-dependent uptakes of neutral amino acids such as L-alanine, L-serine, L-threonine, L-cysteine, and L-glutamine at high affinity with Km values around 20 microM. L-Methionine, L-leucine, L-glycine, and L-valine were also transported by ASCT2 but with lower affinity. The substrate selectivity of ASCT2 was typical of amino acid transport system ASC, which prefers neutral amino acids without bulky or branched side chains. ASCT2 also transported L-glutamate at low affinity (Km = 1.6 mM). L-Glutamate transport was enhanced by lowering extracellular pH, suggesting that L-glutamate was transported as protonated form. In contrast to electrogenic transport of glutamate transporters and the other ASC isoform ASCT1, ASCT2-mediated amino acid transport was electroneutral. Na+ dependence of L-alanine uptake fits to the Michaelis-Menten equation, suggesting a single Na+ cotransported with one amino acid, which was distinct from glutamate transporters coupled to two Na+. Northern blot hybridization revealed that ASCT2 was mainly expressed in kidney, large intestine, lung, skeletal muscle, testis, and adipose tissue. Functional characterization of ASCT2 provided fruitful information on the properties of substrate binding sites and the mechanisms of transport of Na+-dependent neutral and acidic amino acid transporter family, which would facilitate the structure-function analyses based on the comparison of the primary structures of ASCT2 and the other members of the family. PMID:8662767

Utsunomiya-Tate, N; Endou, H; Kanai, Y

1996-06-21

258

Azimuthal anisotropy in the D? layer beneath the Caribbean  

NASA Astrophysics Data System (ADS)

The lowermost mantle beneath Central America has anisotropic seismic velocity structure manifested in shear wave splitting of signals from South American earthquakes recorded at North American broadband recording stations. Prior studies of deep mantle anisotropy in this region have characterized the structure as having vertical transverse isotropy (VTI), which is sufficient to explain a general trend of early tangential (SH) component arrivals. However, VTI models cannot quantitatively match systematic waveform complexities in the onset of many of the shear waves that graze this region. After accounting for splitting effects of upper mantle anisotropy beneath the recording stations, we model the corrected waveform data using full wave theory for mantle velocity models with an anisotropic D? layer. This is the first attempt to quantitatively model a large data set including azimuthal anisotropy in D?. The models include transverse isotropy with either a vertical or tilted symmetry axis, the latter resulting in azimuthal anisotropy. For some initial shear wave polarizations, tilted transverse isotropy (TTI) produces small, reversed polarity arrivals on the SV components at the arrival time of SH, consistent with the data. Geographical variations in the azimuth of the TTI symmetry axis are indicated by the data. The lack of azimuthal coverage prevents unique resolution of the TTI orientation and also precludes distinguishing between TTI and other azimuthal anisotropy structures such as that predicted for lattice preferred orientation of minerals. Nonetheless, our modeling demonstrates the need for laterally varying anisotropic structure of more complex form than VTI for this region.

Maupin, ValéRie; Garnero, Edward J.; Lay, Thorne; Fouch, Matthew J.

2005-08-01

259

Transmembrane glucose transport in skeletal muscle of patients with non-insulin-dependent diabetes.  

PubMed Central

Insulin resistance for glucose metabolism in skeletal muscle is a key feature in non-insulin-dependent diabetes mellitus (NIDDM). Which cellular effectors of glucose metabolism are involved is still unknown. We investigated whether transmembrane glucose transport in vivo is impaired in skeletal muscle in nonobese NIDDM patients. We performed euglycemic insulin clamp studies in combination with the forearm balance technique (brachial artery and deep forearm vein catheterization) in six nonobese NIDDM patients and five age- and weight-matched controls. Unlabeled D-mannitol (a nontransportable molecule) and radioactive 3-O-methyl-D-glucose (the reference molecular probe to assess glucose transport activity) were simultaneously injected into the brachial artery, and the washout curves were measured in the deep venous effluent blood. In vivo transmembrane transport of 3-O-methyl-D-glucose in forearm muscle was determined by computerized analysis of the washout curves. At similar steady-state plasma concentrations of insulin (approximately 500 pmol/liter) and glucose (approximately 5.15 mmol/liter), transmembrane inward transport of 3-O-methyl-D-glucose in skeletal muscle was markedly reduced in the NIDDM patients (6.5 x 10(-2) +/- 0.56 x 10(-2).min-1) compared with controls (12.5 x 10(-2) +/- 1.5 x 10(-2).min-1, P < 0.005). Mean glucose uptake was also reduced in the diabetics both at the whole body level (9.25 +/- 1.84 vs. 28.3 +/- 2.44 mumol/min per kg, P < 0.02) and in the forearm tissues (5.84 +/- 1.51 vs. 37.5 +/- 7.95 mumol/min per kg, P < 0.02). When the latter rates were extrapolated to the whole body level, skeletal muscle accounted for approximately 80% of the defect in insulin action seen in NIDDM patients. We conclude that transmembrane glucose transport, when assessed in vivo in skeletal muscle, is insensitive to insulin in nonobese NIDDM patients, and plays a major role in determining whole body insulin resistance. Images

Bonadonna, R C; Del Prato, S; Saccomani, M P; Bonora, E; Gulli, G; Ferrannini, E; Bier, D; Cobelli, C; DeFronzo, R A

1993-01-01

260

Direction dependent prices in public transport: A good idea? The back haul pricing problem for a monopolistic public transport firm  

Microsoft Academic Search

Markets for transport are often characterised by unequal demand in both directions: every morning during peak hours the trains are crowded while moving towards the direction of large cities, whereas they may be almost empty in the other direction. In this paper we discuss the implications of these imbalances for price setting of transport firms. From the viewpoint of economic

Piet Rietveld; Roberto Roson

2002-01-01

261

Mitochondrial Electron Transport Inhibitors Cause Lipid Peroxidation-Dependent and Independent Cell Death: Protective Role of Antioxidants  

Microsoft Academic Search

Mitochondrial electron transport inhibitors induced two distinct pathways for acute cell death: lipid peroxidation-dependent and -independent in isolated rat hepatocytes. The toxic effects of mitochondrial complex I and II inhibitors, rotenone (ROT) and thenoyltrifluoroacetone (TTFA), respectively, were dependent on oxidative stress and lipid peroxidation, while cell death induced by inhibitors of complexes III and IV, antimycin A (AA) and cyanide

Jin-Gang Zhang; Mark A. Tirmenstein; Felicity A. Nicholls-Grzemski; Marc W. Fariss

2001-01-01

262

The Amino Terminus of Tau Inhibits Kinesin-Dependent Axonal Transport: Implications for Filament Toxicity  

PubMed Central

The neuropathology of Alzheimer's disease (AD) and other tauopathies is characterized by filamentous deposits of the microtubule-associated protein tau, but the relationship between tau polymerization and neurotoxicity is unknown. Here, we examined effects of filamentous tau on fast axonal transport (FAT) using isolated squid axoplasm. Monomeric and filamentous forms of recombinant human tau were perfused in axoplasm, and their effects on kinesin- and dynein-dependent FAT rates were evaluated by video microscopy. Although perfusion of monomeric tau at physiological concentrations showed no effect, tau filaments at the same concentrations selectively inhibited antero-grade (kinesin-dependent) FAT, triggering the release of conventional kinesin from axoplasmic vesicles. Pharmacological experiments indicated that the effect of tau filaments on FAT is mediated by protein phosphatase 1 (PP1) and glycogen synthase kinase-3 (GSK-3) activities. Moreover, deletion analysis suggested that these effects depend on a conserved 18-amino-acid sequence at the amino terminus of tau. Interestingly, monomeric tau isoforms lacking the C-terminal half of the molecule (including the microtubule binding region) recapitulated the effects of full-length filamentous tau. Our results suggest that pathological tau aggregation contributes to neurodegeneration by altering a regulatory pathway for FAT.

LaPointe, Nichole E.; Morfini, Gerardo; Pigino, Gustavo; Gaisina, Irina N.; Kozikowski, Alan P.; Binder, Lester I.; Brady, Scott T.

2009-01-01

263

Structural phase-dependent hole localization and transport in bismuth vanadate  

NASA Astrophysics Data System (ADS)

We present theoretical evidence for the phase dependence of hole localization and transport in bismuth vanadate (BiVO4). Our hybrid density-functional theory calculations predict that, in the tetragonal phase [tetragonal scheelite BiVO4 (ts-BiVO4)], an excess hole tends to localize around a BiO8 polyhedron with strong lattice distortion, whereas, in the monoclinic phase [monoclinic scheelite BiVO4 (ms-BiVO4)], it spreads over many lattice sites. The phase-dependent behavior is likely related to the higher structural stability of ms-BiVO4 than ts-BiVO4, which may suppress hole-induced lattice distortions. Our study also demonstrates that the relatively weakly localized hole in ms-BiVO4 undergoes faster diffusion compared to the case of ts-BiVO4, irrespective of the fact that the degrees of localization and mobility vary depending on the choice of exchange-correlation functional. The mobility difference may provide an explanation for the enhanced photocatalytic activity of ms-BiVO4 over ts-BiVO4 for water oxidation, considering that the increased mobility would lead to an increase in the hole current to the catalyst surface.

Kweon, Kyoung E.; Hwang, Gyeong S.

2013-05-01

264

Spin-dependent transport in elemental and compound semiconductors and nanostructures  

NASA Astrophysics Data System (ADS)

The results obtained on spin-dependent processes via electrically detected magnetic resonance (EDMR), capacitance-detected magnetic resonance (CDMR) and noise-detected magnetic resonance (NDMR) in a variety of different semiconductor materials, devices and nanostructures are reviewed. Similar to optically detected magnetic resonance (ODMR), these detection methods are significantly more sensitive for the detection of paramagnetic states and defects than conventional electron spin resonance (ESR) and can be applied also to semiconductors with an indirect band gap. Using GaAs/AlGaAs-heterostructures and thin films of amorphous hydrogenated silicon (a-Si:H) as examples, the physics of spin-dependent recombination and its detection via spin-dependent photoconductivity is briefly recapitulated. EDMR on pn-diodes from GaP, GaAsP and group-III nitrides, resonant spin-spin scattering in strained Si/SiGe heterostructures, new hysteresis effects in the longitudinal magneto-transport through two-dimensional electron gases and edge-magneto plasmons in different III-V heterostructures are discussed. Various aspects of ferromagnetic III-V semiconductors are investigated, including doping of GaN with Mn, inhomogeneous magnetization of GaMnAs and control of ferromagnetism in semiconductors via hydrogen. Finally, preliminary EDMR experiments on the detection of single paramagnetic defects in MOSFETs via random telegraph noise are presented.

Brandt, M. S.; Goennenwein, S. T. B.; Graf, T.; Huebl, H.; Lauterbach, S.; Stutzmann, M.

2004-07-01

265

Equations of the surface harmonics method for solving time-dependent neutron transport problems and their verification  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

266

Cell-cycle-dependent regulation of CNT1, a concentrative nucleoside transporter involved in the uptake of cell-cycle-dependent nucleoside-derived anticancer drugs  

Microsoft Academic Search

Most nucleoside-derived anticancer drugs are taken up by the high-affinity Na-dependent nucleoside transporter CNT1. Since such drugs are to some extent cell-cycle-dependent in their cytotoxic action, we examined the relationship between CNT1 expression and cell-cycle progression in the rat hepatoma cell line FAO. Cell cultures were synchronized either at late G1 or early S stages by combining mimosin treatment with

Raquel Valdés; F Javier Casado; Marçal Pastor-Anglada

2002-01-01

267

Studies of azimuthal modulations in two hadron fragmentation of a transversely polarised quark  

NASA Astrophysics Data System (ADS)

We study the azimuthal modulations of dihadron fragmentation functions (DiFFs) of a transversely polarised quark using an NJL-jet based model that incorporates the Collins effect for single hadron emission. The DiFFs are extracted as Monte Carlo (MC) averages of corresponding multiplicities using their probabilistic interpretation. To simplify the model and highlight the possible mechanisms that create this modulation, we choose the elementary Collins function to be proportional to the elementary unpolarised fragmentation and a constant probability (PSF) for the quark to flip its spin after a single hadron emission. Moreover, as a leading order calculation, only one of the produced hadrons in the decay chain of the quark is produced with elementary Collins modulation. We calculate the dependence of the polarised DiFFs on various angles such as the azimuthal angle of the single hadron and the angle of the two-hadron production plane ?R for several values of PSF. We observe that the polarised DiFFs for oppositely charged pion pairs exhibit a sin(?R) modulation. This effect is induced purely via the elementary Collins effect and persists even when the quark completely depolarises after a single hadron emission (PSF=0.5). Moreover, similar sine modulations are present in the distribution of pion pairs with respect to the azimuthal angle of their total transverse momentum, ?T.

Matevosyan, Hrayr H.; Kotzinian, Aram; Thomas, Anthony W.

2014-04-01

268

Canonical Azimuthal Rotations and Flanking Residues Constrain the Orientation of Transmembrane Helices  

PubMed Central

In biological membranes the alignment of embedded proteins provides crucial structural information. The transmembrane (TM) parts have well-defined secondary structures, in most cases ?-helices and their orientation is given by a tilt angle and an azimuthal rotation angle around the main axis. The tilt angle is readily visualized and has been found to be functionally relevant. However, there exist no general concepts on the corresponding azimuthal rotation. Here, we show that TM helices prefer discrete rotation angles. They arise from a combination of intrinsic properties of the helix geometry plus the influence of the position and type of flanking residues at both ends of the hydrophobic core. The helical geometry gives rise to canonical azimuthal angles for which the side chains of residues from the two ends of the TM helix tend to have maximum or minimum immersion within the membrane. This affects the preferential position of residues that fall near hydrophobic/polar interfaces of the membrane, depending on their hydrophobicity and capacity to form specific anchoring interactions. On this basis, we can explain the orientation and dynamics of TM helices and make accurate predictions, which correspond well to the experimental values of several model peptides (including dimers), and TM segments of polytopic membrane proteins.

Sanchez-Munoz, Orlando L.; Strandberg, Erik; Esteban-Martin, E.; Grage, Stephan L.; Ulrich, Anne S.; Salgado, Jesus

2013-01-01

269

Membrane topology structure of human high-affinity, sodium-dependent dicarboxylate transporter.  

PubMed

High-affinity, sodium-dependent dicarboxylate transporter (NaDC3) is responsible for transport of Krebs cycle intermediates and may involve in regulation of aging and life span. Hydropathy analysis predicts that NaDC3 contains 11 or 12 hydrophobic transmembrane (TM) domains. However, the actual membrane topological structure of NaDC3 remains unknown. In this study, confocal immunofluorescence microscopy and membrane biotinylation of epitope-tagged N and C termini of NaDC3 provide evidence of an extracellular C terminus and an intracellular N terminus, indicating an odd number of transmembrane regions. The position of hydrophilic loops within NaDC3 was identified with antibodies against the loops domains combined with cysteine accessibility methods. A confocal image of membrane localization and transport activity assay of the cysteine insertion mutants show behavior similar to that of wild-type NaDC3 in transfected HEK293 cells, suggesting that these mutants retain a native protein configuration. We find that NaDC3 contains 11 transmembrane helices. The loops 1, 3, 5, 7, and 9 face the extracellular side, and loops 2, 4, 6, and 10 face the cytoplasmic side. A re-entrant loop-like structure between TM8 and TM9 may protrude into the membrane. Our results support the topography of 11 transmembrane domains with an extracellular C terminus and an intracellular N terminus of NaDC3, and for the first time provide experimental evidence for a novel topological model for NaDC3. PMID:17426067

Bai, Xue-Yuan; Chen, Xiangmei; Sun, An-Qiang; Feng, Zhe; Hou, Kai; Fu, Bo

2007-08-01

270

Azimuthal Directivity of Fan Tones Containing Multiple Modes  

NASA Technical Reports Server (NTRS)

The directivity of fan tone noise is generally measured and plotted in the sideline or flyover plane and it is assumed that this curve is the same for all azimuthal angles. When two or more circumferential (m-order) modes of the same tone are present in the fan duct, an interference pattern develops in the azimuthal direction both in the duct and in the farfield. In this investigation two m-order modes of similar power were generated in a large low speed fan. Farfield measurements and a finite element propagation code both show substantial variations in the azimuthal direction. Induct mode measurement were made and used as input to the code. Although these tests may represent a worst case scenario, the validity of the current practice of assuming axisymmetry should be questioned.

Heidelberg, Laurence J.; Sutliff, Daniel L.; Nallasamy, M.

1997-01-01

271

Spin-dependent negative differential conductance in transport through single-molecule magnets  

NASA Astrophysics Data System (ADS)

Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads' magnetizations, the total current still greatly depends on the spin polarization of leads at certain particular bias region, and thus for large polarization a prominent negative differential conductance (NDC) emerges. This originates from the joint effect of single-direction transitions and spin polarization, which removes the symmetry between spin-up and spin-down transitions. The present mechanism of NDC is remarkably different from the previously reported mechanisms. To clarify the physics of the NDC, we further monitored the shot noise spectroscopy and found that the appearance of the NDC is accompanied by the rapid decrease of Fano factor.

Luo, Wei; Wang, Rui-Qiang; Hu, Liang-Bin; Yang, Mou

2013-04-01

272

Concentration Dependent Electrical Transport Properties of Ni-Cr Binary Alloys  

NASA Astrophysics Data System (ADS)

The concentration dependent electrical transport properties viz. electrical resistivity and thermal conductivity of liquid Ni-Cr alloys are computed at 1400 K temperature. The electrical resistivity has been studied according to Faber-Ziman model in wide range of Cr concentration. In the present work, the electron-ion interaction is incorporated through our well tested local model potential with screening function due to Sarkar et al.. [S] along with the Hartree [H] dielectric function. Good agreement is achieved between the presently calculated results of resistivity as well as thermal conductivity with the experimental data found in the literature, confirming the applicability of model potential and Faber-Ziman model for such a study.

Suthar, P. H.; Khambholja, S. G.; Thakore, B. Y.; Gajjar, P. N.; Jani, A. R.

2011-07-01

273

Structure-dependent optical and electrical transport properties of nanostructured Al-doped ZnO  

NASA Astrophysics Data System (ADS)

The structure-property relation of nanostructured Al-doped ZnO thin films has been investigated in detail through a systematic variation of structure and morphology, with particular emphasis on how they affect optical and electrical properties. A variety of structures, ranging from compact polycrystalline films to mesoporous, hierarchically organized cluster assemblies, are grown by pulsed laser deposition at room temperature at different oxygen pressures. We investigate the dependence of functional properties on structure and morphology and show how the correlation between electrical and optical properties can be studied to evaluate energy gap, conduction band effective mass and transport mechanisms. Understanding these properties opens up opportunities for specific applications in photovoltaic devices, where optimized combinations of conductivity, transparency and light scattering are required.

Gondoni, P.; Ghidelli, M.; Di Fonzo, F.; Carminati, M.; Russo, V.; Li Bassi, A.; Casari, C. S.

2012-09-01

274

Myristoylation of cGMP-dependent protein kinase dictates isoform specificity for serotonin transporter regulation.  

PubMed

By transporting serotonin (5-HT) into neurons and other cells, serotonin transporter (SERT) modulates the action of 5-HT at cell surface receptors. SERT itself is modulated by several processes, including the cGMP signaling pathway. Activation of SERT by cGMP requires the cGMP-dependent protein kinase (PKG). Here we show that in HeLa cells lacking endogenous PKG, expression of PKGI? or PKGI? was required for 8-bromoguanosine-3',5'-cyclic monophosphate (8-Br-cGMP) to stimulate SERT phosphorylation and 5-HT influx. Catalytically inactive PKG mutants and wild-type PKGII did not support this stimulation. However, a mutant PKGII (G2A) that was not myristoylated substituted for functional PKGI, suggesting that myristoylation and subsequent membrane association blocked productive interaction with SERT. PKG also influenced SERT expression and localization. PKGI isoforms increased total and cell surface SERT levels, and PKGII decreased cell surface SERT without altering total expression. Remarkably, these changes did not require 8-Br-cGMP or functional kinase activity and were also observed with a SERT mutant resistant to activation by PKG. Both PKGI? and PKGI? formed detergent-stable complexes with SERT, and this association did not require catalytic activity. The nonmyristoylated PKGII G2A mutant stimulated SERT expression similar to PKGI isoforms. These results suggest multiple mechanisms by which PKG can modulate SERT and demonstrate that the functional difference between PKG isoforms results from myristoylation of PKGII. PMID:21097501

Zhang, Yuan-Wei; Rudnick, Gary

2011-01-28

275

Isolation and characterization of a sodium-dependent phosphate transporter gene in Dunaliella viridis.  

PubMed

A sodium-dependent phosphate transporter gene, DvSPT1, was isolated from a cDNA library using a probe derived from a subtracted cDNA library of Dunaliella viridis. Sequencing analyses revealed a cDNA sequence of 2649 bp long and encoded an open-reading frame consisting of 672 amino acids. The deduced amino acid sequence of DvSPT1 exhibited 31.2% identity to that of TcPHO from Tetraselmis chui. Hydrophobicity and secondary structure prediction revealed 11 conserved transmembrane domains similar to those found in PHO89 from Saccharomyces cerevisiae and PHO4 from Neurospora crassa. Northern blot analysis indicated that the DvSPT1 expression was induced upon NaCl hyperosmotic stress or phosphate depletion. Functional characterization in yeast Na+ export pump mutant G19 suggested that DvSPT1 encoded a Na+ transporter protein. The gene sequence of GDvSPT1 (7922 bp) was isolated from a genomic library of D. viridis. Southern blot analysis indicated that there exist at least two homologous genes in D. viridis. PMID:16359638

Li, Qiyun; Gao, Xiaoshu; Sun, Yu; Zhang, Qingqi; Song, Rentao; Xu, Zhengkai

2006-02-01

276

Ammonium triggers lateral root branching in Arabidopsis in an AMMONIUM TRANSPORTER1;3-dependent manner.  

PubMed

Root development is strongly affected by the plant's nutritional status and the external availability of nutrients. Employing split-root systems, we show here that local ammonium supply to Arabidopsis thaliana plants increases lateral root initiation and higher-order lateral root branching, whereas the elongation of lateral roots is stimulated mainly by nitrate. Ammonium-stimulated lateral root number or density decreased after ammonium or Gln supply to a separate root fraction and did not correlate with cumulative uptake of (15)N-labeled ammonium, suggesting that lateral root branching was not purely due to a nutritional effect but most likely is a response to a sensing event. Ammonium-induced lateral root branching was almost absent in a quadruple AMMONIUM TRANSPORTER (qko, the amt1;1 amt1;2 amt1;3 amt2;1 mutant) insertion line and significantly lower in the amt1;3-1 mutant than in the wild type. Reconstitution of AMT1;3 expression in the amt1;3-1 or in the qko background restored higher-order lateral root development. By contrast, AMT1;1, which shares similar transport properties with AMT1;3, did not confer significant higher-order lateral root proliferation. These results show that ammonium is complementary to nitrate in shaping lateral root development and that stimulation of lateral root branching by ammonium occurs in an AMT1;3-dependent manner. PMID:21119058

Lima, Joni E; Kojima, Soichi; Takahashi, Hideki; von Wirén, Nicolaus

2010-11-01

277

Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys  

SciTech Connect

The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni{sub 10}Cr{sub 90} and Co{sub 20}Cr{sub 80} alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

Thakore, B. Y.; Khambholja, S. G.; Bhatt, N. K.; Jani, A. R. [Department of Physics, S P University, Vallabh Vidhyanagar, 388 120, Gujarat (India); Suthar, P. H. [Department of Physics, C U Shah Science College, Ahmedabad, 380 014, Gujarat (India); Gajjar, P. N. [Department of Physics, University Schools of Sciences, Gujarat University, Ahmedabad, 380 009, Gujarat (India)

2011-12-12

278

Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys  

NASA Astrophysics Data System (ADS)

The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni10Cr90 and Co20Cr80 alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Gajjar, P. N.; Bhatt, N. K.; Jani, A. R.

2011-12-01

279

The dependence of H-mode energy confinement and transport on collisionality in NSTX  

NASA Astrophysics Data System (ADS)

Understanding the dependence of confinement on collisionality in tokamaks is important for the design of next-step devices, which will operate at collisionalities at least one order of magnitude lower than in the present generation. A wide range of collisionality has been obtained in the National Spherical Torus Experiment (NSTX) by employing two different wall conditioning techniques, one with boronization and between-shot helium glow discharge conditioning (HeGDC+B), and one using lithium evaporation (Li EVAP). Previous studies of HeGDC+B plasmas indicated a strong increase of normalized confinement with decreasing collisionality. Discharges with lithium conditioning discussed in the present study generally achieved lower collisionality, extending the accessible range of collisionality by a factor of two. While the confinement dependences on dimensional, engineering variables of the HeGDC+B and Li EVAP datasets differed, collisionality was found to unify the trends, with the lower collisionality lithium conditioned discharges extending the trend of increasing normalized confinement time, BT?E, with decreasing collisionality when other dimensionless variables were held as fixed as possible. This increase of confinement with decreasing collisionality was driven by a large reduction in electron transport in the outer region of the plasma. This result is consistent with gyrokinetic calculations that show microtearing and electron temperature gradient (ETG) modes to be more stable for the lower collisionality discharges. Ion transport, near neoclassical at high collisionality, became more anomalous at lower collisionality, possibly due to the growth of hybrid TEM/KBM modes in the outer regions of the plasma.

Kaye, S. M.; Gerhardt, S.; Guttenfelder, W.; Maingi, R.; Bell, R. E.; Diallo, A.; LeBlanc, B. P.; Podesta, M.

2013-06-01

280

Experimental studies of Reynolds number dependence of turbulent mixing and transport  

NASA Astrophysics Data System (ADS)

Predicting turbulent mixing and transport remains a critical problem in industrial flows (combustion chambers, mixers, ventilation systems, etc.) and in the environment (smoke plumes, etc.). The mixing and transport processes are often a strong function of Reynolds number (Re) and yet there is a paucity of information on their Re dependence. We propose experiments of passive scalar mixing in isotropic grid turbulence whereby the Taylor Reynolds number (R(sub lambda)) will be varied from 30 to over 400 (60 less than R(sub l) less than 10,000). We will achieve the high R(sub lambda) by means of an active grid, which consists of grid bars with small wings that rotate and flap in a random way. We propose to study basic statistics (pdf, spectra, etc). of a homogeneous passive scalar (linear mean profile), as well as of an inhomogeneous scalar (passive line source) as a function of Re. There are many problems concerning the nature of the fine scale structure of a scalar (e.g., the existence of derivative skewness, the relation of the scalar spectrum to the velocity spectrum, and the rate of spreading of a contaminant plume), placing the similarity theory developed over the past 40 years in doubt, yet there is no information concerning its Reynolds number dependence in isotropic turbulence. The passive scalar will be temperature, although some experiments will be done using helium (which has a Schmidt number of 0.23). Particular emphasis will be placed on higher order statistics of both the signal and its derivative. Our experiments will be related to theory and modeling and to recent advances in direct numerical simulations. We will also do further work on mixing in a jet (also as a function of Re) and will relate this work to the (shearless) grid turbulence.

Warhaft, Z.

281

Nitrogen-dependent posttranscriptional regulation of the ammonium transporter AtAMT1;1.  

PubMed

Ammonium transporter (AMT) proteins of the AMT family mediate the transport of ammonium across plasma membranes. To investigate whether AMTs are regulated at the posttranscriptional level, a gene construct consisting of the cauliflower mosaic virus 35S promoter driving the Arabidopsis (Arabidopsis thaliana) AMT1;1 gene was introduced into tobacco (Nicotiana tabacum). Ectopic expression of AtAMT1;1 in transgenic tobacco lines led to high transcript levels and protein levels at the plasma membrane and translated into an approximately 30% increase in root uptake capacity for 15N-labeled ammonium in hydroponically grown transgenic plants. When ammonium was supplied as the major nitrogen (N) form but at limiting amounts to soil-grown plants, transgenic lines overexpressing AtAMT1;1 did not show enhanced growth or N acquisition relative to wild-type plants. Surprisingly, steady-state transcript levels of AtAMT1;1 accumulated to higher levels in N-deficient roots and shoots of transgenic tobacco plants in spite of expression being controlled by the constitutive 35S promoter. Moreover, steady-state transcript levels were decreased after addition of ammonium or nitrate in N-deficient roots, suggesting a role for N availability in regulating AtAMT1;1 transcript abundance. Nitrogen deficiency-dependent accumulation of AtAMT1;1 mRNA was also observed in 35S:AtAMT1;1-transformed Arabidopsis shoots but not in roots. Evidence for a regulatory role of the 3'-untranslated region of AtAMT1;1 alone in N-dependent transcript accumulation was not found. However, transcript levels of AtAMT1;3 did not accumulate in a N-dependent manner, even though the same T-DNA insertion line atamt1;1-1 was used for 35S:AtAMT1;3 expression. These results show that the accumulation of AtAMT1;1 transcripts is regulated in a N- and organ-dependent manner and suggest mRNA turnover as an additional mechanism for the regulation of AtAMT1;1 in response to the N nutritional status of plants. PMID:17172286

Yuan, Lixing; Loqué, Dominique; Ye, Fanghua; Frommer, Wolf B; von Wirén, Nicolaus

2007-02-01

282

Redistributing energy flow and polarization of a focused azimuthally polarized beam with rotationally symmetric sector-shaped obstacles.  

PubMed

The redistribution of transversal energy flow and polarization in the focal field are represented by obstructing an azimuthally polarized beam with rotationally symmetric sector-shaped obstacles. Several energy flow rings that can finally transport the absorptive particles into fixed locations are formed in the focal plane. Furthermore, the local polarization state of the focal field is also modified by use of the rotationally symmetric obstacles. This kind of energy flow may have wide applications in optical trapping and manipulation. PMID:22446217

Jiao, Xiangyang; Liu, Sheng; Wang, Qian; Gan, Xuetao; Li, Peng; Zhao, Jianlin

2012-03-15

283

Relative contributions of Na+-dependent phosphate co-transporters to phosphate transport in mouse kidney: RNase H-mediated hybrid depletion analysis.  

PubMed Central

Reabsorption of Pi in the proximal tubule of the kidney is an important determinant of Pi homoeostasis. At least three types (types I-III) of high-affinity Na+-dependent Pi co-transporters have been identified in mammalian kidneys. The relative roles of these three types of Na+/Pi co-transporters in Pi transport in mouse kidney cortex have now been investigated by RNase H-mediated hybrid depletion. Whereas isolated brush-border membrane vesicles showed the presence of two kinetically distinct Na+/Pi co-transport systems (high Km-low Vmax and low Km-high Vmax), Xenopus oocytes, microinjected with polyadenylated [poly(A)+] RNA from mouse kidney cortex, showed only the high-affinity Pi uptake system. Kidney poly(A)+ RNA was incubated in vitro with antisense oligonucleotides corresponding to Npt-1 (type I), NaPi -7 (type II) or Glvr-1 (type III) Na+/Pi co-transporter mRNAs, and then with RNase H. Injection of such treated RNA preparations into Xenopus oocytes revealed that an NaPi-7 antisense oligonucleotide that resulted in complete degradation of NaPi-7 mRNA (as revealed by Northern blot analysis), also induced complete inhibition of Pi uptake. Degradation of Npt-1 or Glvr-1 mRNAs induced by corresponding antisense oligonucleotides had no effect on Pi transport, which was subsequently measured in oocytes. These results indicate that the type II Na+/Pi co-transporter NaPi-7 mediated most Na+-dependent Pi transport in mouse kidney cortex.

Miyamoto, K; Segawa, H; Morita, K; Nii, T; Tatsumi, S; Taketani, Y; Takeda, E

1997-01-01

284

Magnetic Resonance Microscopy of Scale Dependent Transport Phenomena and Bioactivity in Porous Media  

NASA Astrophysics Data System (ADS)

Magnetic resonance microscopy (MRM) provides the ability to obtain data on the pore scale via imaging and the sample scale by bulk measurement, allowing for connection between microscale dynamics and macroscale transport phenomena. This has led to MRM techniques becoming a preeminent method for characterization of dynamics in porous media. A significant question in modeling transport in porous media is definition of the porous media structure as homogeneous (ordered) or heterogeneous (disordered)[1]. One means of defining the 'complexity' of a porous media is based on the dynamics of the system[2]. The ability of MRM to measure the time dependent statistics of the dynamics [3,4,5] provides quantification of the pre-asymptotic dynamics. The transition from preasymptotic to Gaussian transport consistent with models of homogeneous porous media is clearly visualized. Biological activity in porous media, such as microbial growth, typically manifests itself as biofilms or colonies of microbes that adhere to surfaces and are surrounded by a hydrogel of extracellular polymeric substance (EPS). The biofilm growth introduces complexity into the system structure in generation of physical pore blocking, trapping within the EPS gel, elastic interfaces due to the EPS and generation of channels in which faster flow occur. The hierarchy of length and time scales and multiple physical processes which are introduced by the biofilm growth impacts the porous media transport as reflected in the change in dynamics [6]. The transition can be modeled using statistical mechanical approaches based on continuous time random walk (CTRW) processes that generate fractional differential equations[7]. The bioactivity alters the structure of the porous media from homogeneous to heterogeneous resulting in the transition from a Gaussian to a non Gaussian subdiffusive dispersion process. References 1. M. Quintard and S. Whitaker, Transport in ordered and disordered porous media: Volume averaged equations, closure problems and comparison with experiment. Chemical Engineering Science, 48(14): 2537-2564 (1993). 2. N. Goldenfeld and L.P. Kadanoff, Simple lessons from complexity. Science, 284: 87-89 (1999). 3. J.D. Seymour and P.T. Callaghan, Generalized approach to NMR analysis of flow and dispersion in porous medium. AIChE Journal, 43: 2096-2111 (1997). 4. S.L. Codd, B. Manz, J.D. Seymour, and P.T. Callaghan, Taylor dispersion and molecular displacements in poiseuille flow. Physical Review E, 60(4): R3491-R3494 (1999). 5. P.T. Callaghan, Principles of Nuclear Magnetic Resonance Microscopy. New York: Oxford University Press (1991). 6. G.K. Batchelor, Developments in microhydrodynamics, in Theoretical and Applied Mechanics, W.T. Koiter, Editor. North-Holland: Amsterdam. p. 33-55 (1976). 7. J.D. Seymour, J.P. Gage, S.L. Codd, and R. Gerlach, Anomalous fluid transport in porous media induced by biofilm growth. Physical Review Letters, 93: 198103 (2004).

Seymour, J. D.; Codd, S. L.; Romanenko, K. V.; Hornemann, J. A.; Brosten, T. R.

2008-05-01

285

Phorbol myristate acetate stimulates ATP-dependent calcium transport by the plasma membrane of neutrophils.  

PubMed Central

We studied the effect of phorbol myristate acetate (PMA) on the plasma membrane ATP-dependent calcium pump in neutrophils. Plasma membrane-enriched fractions ("podosomes") from PMA-stimulated guinea pig neutrophils exhibited a twofold stimulation of ATP-dependent calcium transport when compared with control podosomes. The stimulatory effect was rapid (beginning less than 2 min after exposure to PMA) and reached maximal values within 5 min. PMA increased the maximum velocity but not the affinity of the calcium pump for Ca++. Pump activation was not preceded by a rise in cytosolic free calcium concentration [Ca++]i, as assessed by the intracellularly trapped fluorescent calcium indicator Quin 2, but instead slightly lowered [Ca++]i and prevented the rise in [Ca++]i normally induced by the chemotactic peptide formyl-methionyl-leucyl-phenylalanine. These results suggest that the calcium pump in the plasma membrane of neutrophils may be stimulated by calcium-independent pathways, and that this activation could be one of the earliest events mediating some of the effects of phorbol esters.

Lagast, H; Pozzan, T; Waldvogel, F A; Lew, P D

1984-01-01

286

Effect of temperature-dependent electrical conductivity on transport processes in magnetosolidmechanics  

NASA Technical Reports Server (NTRS)

The effect of temperature-dependent electrical conductivity on transport processes for a solid block is analyzed on the basis of a one-dimensional steady-state model under specified thermal boundary conditions. Assumptions are that the solid has an infinitely segmented electrode configuration, the magnetic field (By) may be resolved into a constant applied field and an induced field, the gradient of the electrochemical potential is equal to the electrostatic potential, a constant potential difference is applied externally across each pair of opposite electrodes, and all material properties except electrical conductivity are constant. Conductivity is expressed in normalized form in terms of a baseline conductivity and a constant for the material. The application of the assumptions of the model to the general phenomenological relations yields the governing equations. Solution of these equations gives the distribution of temperature, electric current density, and magnetic field strength along the length of the solid. It is shown that significant differences exist between the case for constant electrical conductivity and the case where electrical conductivity is temperature dependent.

Craig, G. T.; Arnas, O. A.

1975-01-01

287

Structural, electronic, magnetic and spin dependent transport properties of Fe/CaS/Fe (001) heterostructures  

NASA Astrophysics Data System (ADS)

Structural, electronic, and magnetic properties of Fe/CaS (001) interfaces and Fe/CaS/Fe (001) heterostructures have been studied by means of a self-consistent Green's function technique for surface and interfaces implemented within the tight-binding linear muffin-tin orbital formalism. Spin dependent transport properties of the Fe/CaS/Fe (001) tunnel junctions with thin and intermediate barriers, in the current-perpendicular-to-plane geometry, have been determined by means of Kubo-Landauer approach implemented within the tight-binding linear muffin-tin orbital formalism. A small charge rearrangement is evidenced at the Fe/CaS (001) interfaces. The iron interfacial magnetic moments are enhanced over the bulk value. A small exchange coupling with the sign depending on the Fe/CaS (001) interface geometric structure and the strength decaying exponentially with the barrier is evidenced. Interfacial charge transfer, interface iron magnetic moments, and tunneling currents are sensitive to the interfacial structure. Interface resonant states have a decisive role in the tunneling process and the main contribution to the current in the ferromagnetic state of the junction is given by the minority-spin electrons.

Vlaic, P.; Burzo, E.; Carva, K.

2013-02-01

288

Transport in multiterminal superconductor/ferromagnet junctions having spin-dependent interfaces  

NASA Astrophysics Data System (ADS)

We study electronic transport in junctions consisting of a superconductor electrode and two ferromagnet (F) leads in which crossed Andreev reflections (CAR) and elastic cotunnelings are accommodated. We model the system using an extended Blonder-Tinkham-Klapwijk treatment with a key modification that accounts for spin-dependent interfacial barriers (SDIB). We compute current-voltage relations as a function of parameters characterizing the SDIB, magnetization in the F leads, geometry of the junction, and temperature. Our results reveal a rich range of significantly altered physics due to a combination of interfering spin-dependent scattering processes and population imbalance in the ferromagnets, such as a significant enhancement in CAR current and a sign change in the relative difference between resistance of two cases having a antiparallel or parallel alignment of the magnetization in the F leads, respectively. Our model accounts for the surprising experimental findings of positive relative resistance by M. Colci [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.85.180512 85, 180512(R) (2012)] as well as previously measured negative relative resistance results, both within sufficiently large parameter regions.

Sun, Kuei; Shah, Nayana; Vishveshwara, Smitha

2013-02-01

289

Underexpression of the Na+-dependent neutral amino acid transporter ASCT2 in the spontaneously hypertensive rat kidney.  

PubMed

This study examined the inward transport of l-[(14)C]alanine, an ASCT2 preferential substrate, in monolayers of immortalized renal proximal tubular epithelial (PTE) cells from Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. The expression of ASCT2 in WKY and SHR PTE cells and kidney cortices from WKY and SHR was also evaluated. l-[(14)C]alanine uptake was highly dependent on extracellular Na(+). Replacement of NaCl by LiCl or choline chloride abolished transport activity in SHR and WKY PTE cells. In the presence of the system L inhibitor BCH, Na(+)-dependent l-alanine uptake in WKY and SHR PTE cells was inhibited by alanine, serine, and cysteine, which is consistent with amino acid transport through ASCT2. The saturable component of Na(+)-dependent l-alanine transport under V(max) conditions in SHR PTE cells was one-half of that in WKY PTE cells, with similar K(m) values. Differences in magnitude of Na(+)-dependent l-alanine uptake through ASCT2 between WKY and SHR PTE cells correlated positively with differences in ASCT2 protein expression, this being more abundant in WKY PTE cells. Abundance of ASCT2 transcript and protein in kidney cortices of SHR rats was also lower than that in normotensive WKY rats. In conclusion, immortalized SHR and WKY PTE cells take up l-alanine mainly through a high-affinity Na(+)-dependent amino acid transporter, with functional features of ASCT2 transport. The activity and expression of the ASCT2 transporter were considerably lower in the SHR cells. PMID:17475673

Pinho, Maria Joăo; Pinto, Vanda; Serrăo, Maria Paula; Jose, Pedro A; Soares-da-Silva, Patrício

2007-07-01

290

Glucose transport in human red cell membranes. Dependence of age, ATP, and insulin.  

PubMed

Glucose self-exchange flux (Jex) and net efflux (Jnet) in human red cells and ghosts were studied at 25 degrees C and pH 7.2 by means of the combined use of the Millipore-Swinnex filtering method and the continuous flow tube method to show the dependence of time of storage after aspiration, ATP and insulin. In fresh cells (RBC), ghosts (G), ghosts with 2 mM ATP (G +), and cells stored at 4 degrees C greater than 60 days (OC) both Jex and Jnet follow simple Michaelis-Menten kinetics where J = Jmax X Ci X (K1/2 + Ci)-1. Jmaxex and Jmaxnet (nmol X cm-2 X s-1), respectively, was: (RBC) 0.27 and 0.19, (G) 0.24 and 0.27, (G +) 0.23 and 0.24, (OC) 0.23 and 0.20. K1/2,ex and K1/2,net (mM), respectively, was: (RBC) 7.5 and 1.3, (G) 4.8 and 14.2, (G +) 11.6 and 6.8, (OC) 3.8 and 9.0. In ghosts, the ATP-dependent fraction of the permeability shows a hyperbolic dependence on glucose concentrations lower than 80 mM. Insulin up to 1 microM had effect on neither Jex nor Jnet in RBC. Based on reported values of cytochalasin B binding sites the turnover rate per site in RBC appears to be as high as in maximally insulin-stimulated fat cells. Our results suggest that the number of transport sites remains constant, independent of age, ATP and insulin. PMID:3297147

Jensen, M R; Brahm, J

1987-06-30

291

Dopamine Transporter Endocytic Trafficking in Striatal Dopaminergic Neurons: Differential Dependence on Dynamin and the Actin Cytoskeleton  

PubMed Central

Dopaminergic signaling profoundly impacts rewarding behaviors, movement, and executive function. The presynaptic dopamine (DA) transporter (DAT) recaptures released DA, thereby limiting synaptic DA availability and maintaining dopaminergic tone. DAT constitutively internalizes and PKC activation rapidly accelerates DAT endocytosis, resulting in DAT surface loss. Longstanding evidence supports PKC-stimulated DAT trafficking in heterologous expression studies. However, PKC-stimulated DAT internalization is not readily observed in cultured dopaminergic neurons. Moreover, conflicting reports implicate both classic and nonclassic endocytic mechanisms mediating DAT trafficking. Prior DAT trafficking studies relied primarily upon chronic gene disruption and dominant-negative protein expression, or were performed in cell lines and cultured neurons, yielding results difficult to translate to adult dopaminergic neurons. Here, we use newly described dynamin inhibitors to test whether constitutive and PKC-stimulated DAT internalization are dynamin-dependent in adult dopaminergic neurons. Ex vivo biotinylation studies in mouse striatal slices demonstrate that acute PKC activation drives native DAT surface loss, and that surface DAT surprisingly partitions between endocytic-willing and endocytic-resistant populations. Acute dynamin inhibition reveals that constitutive DAT internalization is dynamin-independent, whereas PKC-stimulated DAT internalization is dynamin-dependent. Moreover, total internal reflection fluorescence microscopy experiments demonstrate that constitutive DAT internalization occurs equivalently from lipid raft and nonraft microdomains, whereas PKC-stimulated DAT internalization arises exclusively from lipid rafts. Finally, DAT endocytic recycling relies on a dynamin-dependent mechanism that acts in concert with the actin cytoskeleton. These studies are the first comprehensive investigation of native DAT trafficking in ex vivo adult neurons, and reveal that DAT surface dynamics are governed by complex multimodal mechanisms.

Gabriel, Luke R.; Wu, Sijia; Kearney, Patrick; Bellve, Karl D.; Standley, Clive; Fogarty, Kevin E.

2013-01-01

292

Molecular size of a Na sup + -dependent amino acid transporter in Ehrlich ascites cell plasma membranes estimated by radiation inactivation  

SciTech Connect

Radiation inactivation was used to estimate the molecular size of a Na{sup +}-dependent amino acid transport system in Ehrlich ascites cell plasma membrane vesicles. Na{sup +}-dependent {alpha}-aminoisobutyric acid uptake was measured after membranes were irradiated at {minus}78.5C in a cryoprotective medium. Twenty-five percent of the transport activity was lost at low radiation doses (<0.5 Mrad), suggesting the presence of a high molecular weight transport complex. The remaining activity ({approximately}75% of total) decreased exponentially with increasing radiation dose, and a molecular size of 347 kDa was calculated for the latter carrier system. Radiation doses 2-3 fold higher than those required to inactivate amino acid transport were needed to cause significant volume changes. The relationship between the fragmentation of a 120-130-kDapeptide, a putative component of the Na{sup +}-dependent amino acid carrier and loss of transport activity in irradiated membranes was also examined. Peptide loss was quantitated by Western blot analysis. The data support the conclusion that fragmentation of the 120-130-kDa peptide is related to loss of amino acid transport in irradiation Ehrlich cell plasma membranes.

McCormick, J.I.; Johnstone, R.M. (McGill Univ., Montreal, Quebec (Canada)); Jette, M.; Beliveau, R. (Universite du Quebec a Montreal (Canada)); Potier, M. (Univ. de Montreal, Quebec (Canada))

1991-04-16

293

Improved Sihil image from 4C full azimuth node data  

Microsoft Academic Search

Summary A large 4C OBS seismic program was acquired for Pemex over the Cantarell field offshore Mexico to improve the structural definition of the deeper Sihil field underlying the giant Akal field. The acquisition was made using autonomous receivers planted with accurate positioning on a regular grid in the seabed. The data is acquired with a regular and full azimuth\\/offset

Marco Va?zquez Garcia; Gorgonio Garcia Molina; Francisco Maya; Carlos Federico Ruiz Torres; Eivind W. Berg; Claude Vuillermoz; Atle Fyhn

2005-01-01

294

Investigation of azimuthal staging concepts in annular gas turbines  

Microsoft Academic Search

In this work, the influence of azimuthal staging concepts on the thermoacoustic behavior of annular combustion chambers is assessed theoretically and numerically. Staging is a well-known and effective method to abate thermoacoustic pulsations in combustion chambers. However, in the case of, for example, fuel staging the associated inhomogeneity of equivalence ratio may result in increased levels of NOx emissions. In

Nicolas Noiray; Mirko Bothien; Bruno Schuermans

2011-01-01

295

QCD coherence studies using two particle azimuthal correlations  

Microsoft Academic Search

From a sample of 146900 hadronicZ0 decays recorded by the OPAL detector at LEP, we have studied the azimuthal correlations of particles in hadronic events. It is expected that these correlations are sensitive to interference effects in QCD. We have compared the data to QCD Monte Carlo models which include and which do not include interference effects. We find that

P. D. Acton; G. Alexander; J. Allison; P. P. Allport; K. J. Anderson; S. Arcelli; A. Astbury; D. Axen; G. Azuelos; G. A. Bahan; J. T. M. Baines; A. H. Ball; J. Banks; R. J. Barlow; S. Barnett; J. R. Batley; G. Beaudoin; A. Beck; J. Becker; T. Behnke; K. W. Bell; G. Bella; P. Berlich; S. Bethke; O. Biebel; U. Binder; I. J. Bloodworth; P. Bock; B. Boden; H. M. Bosch; S. Bougerolle; H. Breuker; R. M. Brown; A. Buijs; H. J. Burckardt; C. Burgard; P. Capiluppi; R. K. Carnegie; A. A. Carter; J. R. Carter; C. Y. Chang; D. G. Charlton; P. E. L. Clarke; I. Cohen; J. C. Clayton; W. J. Collins; J. E. Conboy; M. Cooper; M. Coupland; M. Cuffiani; S. Dado; G. M. Dallavalle; S. De Jong; L. A. del Pozo; H. Deng; A. Dieckmann; M. Dittmar; M. S. Dixit; E. do Couto e Silva; J. E. Duboscq; E. Duchovni; G. Duckeck; I. P. Duerdoth; D. J. P. Dumas; P. A. Elcombe; P. G. Estabrooks; E. Etzion; H. G. Evans; F. Fabbri; M. Fincke-Keeler; H. M. Fischer; D. G. Fong; M. Foucher; A. Gaidot; O. Ganel; J. W. Gary; J. Gascon; R. F. McGowan; N. I. Geddes; C. Geich-Gimbel; S. W. Gensler; F. X. Gentit; G. Giacomelli; V. Gibson; W. R. Gibson; J. D. Gillies; J. Goldberg; M. J. Goodrick; W. Gorn; C. Grandi; F. C. Grant; J. Hagemann; G. G. Hanson; M. Hansroul; C. K. Hargrove; P. F. Harrison; J. Hart; P. M. Hattersley; M. Hauschild; C. M. Hawkes; E. Heflin; R. J. Hemingway; R. D. Heuer; J. C. Hill; S. J. Hillier; T. Hilse; D. A. Hinshaw; J. D. Hobbs; P. R. Hobson; D. Hochman; R. J. Homer; A. K. Honma; C. P. Howarth; R. E. Hughes-Jones; R. Humbert; P. Igo-Kemenes; H. Ihssen; D. C. Imrie; A. C. Janissen; A. Jawahery; P. W. Jeffreys; H. Jeremie; M. Jimack; M. Jobes; R. W. L. Jones; P. Jovanovic; C. Jui; D. Karlen; K. Kawagoe; T. Kawamoto; R. K. Keeler; R. G. Kellogg; B. W. Kennedy; S. Kluth; T. Kobayashi; T. P. Kokott; S. Komamiya; L. Köpke; J. F. Kral; R. Kowalewski; J. von Krogh; J. Kroll; M. Kuwano; P. Kyberd; G. D. Lafferty; F. Lamarche; J. G. Layter; P. Le Du; P. Leblanc; A. M. Lee; M. H. Lehto; D. Lellouch; P. Lennert; C. Leroy; J. Letts; S. Levergrün; L. Levinson; S. L. Lloyd; F. K. Loebinger; J. M. Lorah; B. Lorazo; M. J. Losty; X. C. Lou; J. Ludwig; M. Mannelli; S. Marcellini; G. Maringer; C. Markus; A. J. Martin; J. P. Martin; T. Mashimo; P. Mättig; U. Maur; J. McKenna; T. J. McMahon; J. R. McNutt; F. Meijers; D. Menszner; F. S. Merritt; H. Mes; A. Michelini; R. P. Middleton; G. Mikenberg; J. Mildenberger; D. J. Miller; R. Mir; W. Mohr; C. Moisan; A. Montanari; T. Mori; M. Morii; T. Mouthuy; B. Nellen; H. H. Nguyen; M. Nozaki; S. W. O'Neale; F. G. Oakham; F. Odorici; H. O. Ogren; C. J. Oram; M. J. Oreglia; S. Orito; J. P. Pansart; B. Panzer-Steindel; P. Paschievici; G. N. Patrick; N. Paz-Jaoshvili; P. Pfister; J. E. Pilcher; D. Pitman; D. E. Plane; P. Poffenberger; B. Poli; A. Pouladdej; E. Prebys; T. W. Pritchard; H. Przysiezniak; G. Quast; M. W. Redmond; D. L. Rees; G. E. Richards; D. Robinson; A. Rollnik; J. M. Roney; E. Ros; S. Rossberg; A. M. Rossi; M. Rosvick; P. Routenburg; K. Runge; O. Runolfsson; D. R. Rust; M. Sasaki; C. Sbarra; A. D. Schaile; O. Schaile; W. Schappert; P. Scharff-Hansen; P. Schenk; H. von der Schmitt; S. Schreiber; C. Schwick; J. Schwiening; W. G. Scott; M. Settles; T. G. Shears; B. C. Shen; C. H. Shepherd-Themistocleous; P. Sherwood; R. Shypit; A. Simon; P. Singh; G. P. Siroli; A. Skuja; A. M. Smith; T. J. Smith; G. A. Snow; R. Sobie; R. W. Springer; M. Sproston; K. Stephens; J. Steuerer; R. Ströhmer; D. Strom; T. Takeshita; P. Taras; S. Tarem; M. Tecchio; P. Teixeira-Dias; N. Tesch; N. J. Thackray; G. Transtromer; N. J. Tresilian; T. Tsukamoto; M. F. Turner; G. Tysarczyk-Niemeyer; D. Van den Plas; R. van Kooten; G. J. VanDalen; G. Vasseur; C. J. Virtue; A. Wagner; D. L. Wagner; C. Wahl; J. P. Walker; C. P. Ward; D. R. Ward; P. M. Watklins; A. T. Watson; N. K. Watson; M. Weber; P. Weber; S. Weisz; P. S. Wells; N. Wermes; M. A. Whalley; G. W. Wilson; J. A. Wilson; V. H. Winterer; T. Wlodek; S. Wotton; T. R. Wyatt; R. Yaari; A. Yeaman; G. Yekutieli; M. Yurko; W. Zeuner; G. T. Zorn

1993-01-01

296

Monopulse Azimuth Measurement in the ATC Radar Beacon System.  

National Technical Information Service (NTIS)

A review is made of the application of sum-difference beam techniques to the ATC Radar Beacon System. A detailed error analysis is presented for the case of a monopulse azimuth measurement based on the existing beacon antenna with a modified feed network....

B. Kulke B. Rubinger G. G. Haroules

1971-01-01

297

Azimuthal correlations and alignment of particles in gamma families  

SciTech Connect

Azimuthal angular correlations and the alignment of photons are studied in gamma families recorded by the Pamir Collaboration in a carbon x-ray emulsion chamber. The present interpretation of these experimental data is based on a model of semihard parton scattering in nucleon-nucleus collisions and on arguments favoring the production of exotic beam strings and heavy leading resonances undergoing quasicoplanar decays.

Yuldashbaev, T. S., E-mail: tsju@uzsci.net; Chudakov, V. M.; Nuritdinov, Kh. [Uzbek Academy of Sciences, Institute for Physics and Technology, Fizika-Solntse Research and Production Association (Uzbekistan)

2008-11-15

298

Enteropathogenic Escherichia coli inhibits ileal sodium-dependent bile acid transporter ASBT  

PubMed Central

Apical sodium-dependent bile acid transporter (ASBT) is responsible for the absorption of bile acids from the intestine. A decrease in ASBT function and expression has been implicated in diarrhea associated with intestinal inflammation. Whether infection with pathogenic microorganisms such as the enteropathogenic Escherichia coli (EPEC) affect ASBT activity is not known. EPEC is a food-borne enteric pathogen that translocates bacterial effector molecules via type three secretion system (TTSS) into host cells and is a major cause of infantile diarrhea. We investigated the effects of EPEC infection on ileal ASBT function utilizing human intestinal Caco2 cells and HEK-293 cells stably transfected with ASBT-V5 fusion protein (2BT cells). ASBT activity was significantly inhibited following 60 min infection with EPEC but not with nonpathogenic E. coli. Mutations in bacterial escN, espA, espB, and espD, the genes encoding for the elements of bacterial TTSS, ablated EPEC inhibitory effect on ASBT function. Furthermore, mutation in the bacterial BFP gene encoding for bundle-forming pili abrogated the inhibition of ASBT by EPEC, indicating the essential role for bacterial aggregation and the early attachment. The inhibition by EPEC was associated with a significant decrease in the Vmax of the transporter and a reduction in the level of ASBT on the plasma membrane. The inhibition of ASBT by EPEC was blocked in the presence of protein tyrosine phosphatase inhibitors. Our studies provide novel evidence for the alterations in the activity of ASBT by EPEC infection and suggest a possible effect for EPEC in influencing intestinal bile acid homeostasis.

Annaba, Fadi; Sarwar, Zaheer; Gill, Ravinder K.; Ghosh, Amit; Saksena, Seema; Borthakur, Alip; Hecht, Gail A.; Dudeja, Pradeep K.

2012-01-01

299

Cation-Dependent Binding of Substrate to the Folate Transport Protein of Lactobacillus casei  

PubMed Central

Lactobacillus casei cells grown in the presence of limiting folate contained large amounts of a membrane-associated binding protein which mediates folate transport. Binding to this protein at 4°C was time and concentration dependent and at low levels (1 to 10 nM) of folate required 60 min to reach a steady state. The apparent dissociation constant (Kd) for folate was 1.2 nM at pH 7.5 in 100 mM K-phosphate buffer, and it varied by less than twofold when measured over a range of pH values (5.5 to 7.5) or in buffered salt solutions of differing ionic compositions. Conversely, removal of ions and their replacement with isotonic sucrose (pH 7.5) led to a 200-fold reduction in binding affinity for folate. Restoration of the high-affinity state of the binding protein could be achieved by the readdition of various cations to the sucrose medium. Kd measurements over a range of cation concentrations revealed that a half-maximal restoration of binding affinity was obtained with relatively low levels (10 to 50 ?M) of divalent cations (e.g., Ca2+, Mg2+, and ethylenediammonium2+ ions). Monovalent cations (e.g., Na+, K+, and Tris+) were also effective, but only at concentrations in the millimolar range. The Kd for folate reached a minimum of 0.6 nM at pH 7.5 in the presence of excess CaCl2. In cells suspended in sucrose, the affinity of the binding protein for folate increased 20-fold by decreasing the pH from 7.5 to 4.5, indicating that protons can partially fulfill the cation requirement. These results suggest that the folate transport protein of L. casei may contain both a substrate- and cation-binding site and that folate binds with a high affinity only after the cation-binding site has been occupied. The presence of these binding sites would support the hypothesis that folate is transported across the cell membrane via a cation-folate symport mechanism.

Henderson, Gary B.; Potuznik, Suzana

1982-01-01

300

South Carolina's Rural Labor Market and its Dependence on Public Transportation.  

National Technical Information Service (NTIS)

Rural South Carolina is undergoing significant demographic and economic changes, which, in concert with new transportation technologies, give potential rise to new opportunities for rural transportation systems. The authors' research project identifies th...

S. McDonald V. Gupta J. Albrecht

2004-01-01

301

A new approach to time-dependent transport through an interacting quantum dot within the Keldysh formalism  

NASA Astrophysics Data System (ADS)

The time-dependent transport through a nanoscale device consisting of a single spin-degenerate orbital with on-site Coulomb interaction, coupled to two leads, is investigated. Various gate and bias voltage time dependences are considered. The key and new point lies in the proposed way to avoid the difficulties of the usual heavy computation when dealing with two-time Green’s functions within the Keldysh formalism. The time-dependent retarded dot Green’s functions are evaluated, in an efficient manner within a non-canonical Hubbard I approximation. Calculations of the time-dependent current are then presented in the wide-band limit for different parameter sets. A comparison between the method and the Hartree-Fock approximation is performed as well. It is shown that the latter cannot account reliably for dynamical aspects of transport phenomena.

Vovchenko, V.; Anchishkin, D.; Azema, J.; Lombardo, P.; Hayn, R.; Daré, A.-M.

2014-01-01

302

Sweepless time-dependent transport calculations using the staggered block Jacobi method  

SciTech Connect

The Staggered-Block Jacobi (SBJ) method is a new numerical SN transport method for solving time-dependent problems without sweeps or low-order acceleration. Because it is a Jacobian method, it is trivial to parallelize and will scale linearly with the number of processors, It is highly accurate in thick-diffusive problems and unconditionally stable when combined with the lumped linear discontinuous finite element spatial discretization. In this way, the SBJ method is complementary to sweep-based methods, which are accurate and efficient in thin, streaming regions but inefficient in thick, diffusive problems without acceleration. We have extended previous work by demonstrating how sweep-based methods and the SBJ method may be combined to produce a method which is accurate and efficient without acceleration in all optical thicknesses while still retaining good parallel efficiency. Furthermore, iterations may also be added to the SBJ method. This is particularly useful for improving the accuracy of the SBJ method in intermediate-thickness problems.

Davidson, G [Los Alamos National Laboratory; Larsen, E W [Los Alamos National Laboratory

2009-01-01

303

Spindle orientation in Saccharomyces cerevisiae depends on the transport of microtubule ends along polarized actin cables.  

PubMed

Microtubules and actin filaments interact and cooperate in many processes in eukaryotic cells, but the functional implications of such interactions are not well understood. In the yeast Saccharomyces cerevisiae, both cytoplasmic microtubules and actin filaments are needed for spindle orientation. In addition, this process requires the type V myosin protein Myo2, the microtubule end-binding protein Bim1, and Kar9. Here, we show that fusing Bim1 to the tail of the Myo2 is sufficient to orient spindles in the absence of Kar9, suggesting that the role of Kar9 is to link Myo2 to Bim1. In addition, we show that Myo2 localizes to the plus ends of cytoplasmic microtubules, and that the rate of movement of these cytoplasmic microtubules to the bud neck depends on the intrinsic velocity of Myo2 along actin filaments. These results support a model for spindle orientation in which a Myo2-Kar9-Bim1 complex transports microtubule ends along polarized actin cables. We also present data suggesting that a similar process plays a role in orienting cytoplasmic microtubules in mating yeast cells. PMID:12743102

Hwang, Eric; Kusch, Justine; Barral, Yves; Huffaker, Tim C

2003-05-12

304

Solvent-type-dependent polymorphism and charge transport in a long fused-ring organic semiconductor.  

PubMed

Crystalline polymorphism of organic semiconductors is among the critical factors in determining the structure and properties of the resultant organic electronic devices. Herein we report for the first time a solvent-type-dependent polymorphism of a long fused-ring organic semiconductor and its crucial effects on charge transport. A new polymorph of 5,11-bis(triethylsilylethynyl)anthradithiophene (TES ADT) is obtained using solvent-assisted crystallization, and the crystalline polymorphism of TES ADT thin films is correlated with their measured hole mobilities. The best-performing organic thin film transistors of the two TES ADT polymorphs show subthreshold slopes close to 1 V dec(-1), and threshold voltages close to zero, indicating that the density of traps at the semiconductor-dielectric interface is negligible in these devices and the observed up to 10-fold differences in hole mobilities of devices fabricated with different solvents are largely resultant from the presence of two TES ADT polymorphs. Moreover, our results suggest that the best-performing TES ADT devices reported in the literature correspond to the new polymorph identified in this study, which involves crystallization from a weakly polar solvent (such as toluene and chloroform). PMID:24217182

Chen, Jihua; Shao, Ming; Xiao, Kai; Rondinone, Adam J; Loo, Yueh-Lin; Kent, Paul R C; Sumpter, Bobby G; Li, Dawen; Keum, Jong K; Diemer, Peter J; Anthony, John E; Jurchescu, Oana D; Huang, Jingsong

2014-01-01

305

Altered dynein-dependent transport in piRNA pathway mutants  

PubMed Central

Maintenance of genome integrity in germ cells is crucial for the success of future generations. In Drosophila, and mammals, transposable element activity in the germline can cause DNA breakage and sterility. Recent studies have shown that proteins involved in piRNA (PIWI-interacting RNA) biogenesis are necessary for retrotransposon silencing in the Drosophila germline. Females mutant for genes in the piRNA biogenesis pathway produce eggs with patterning defects that result from Chk-2 (checkpoint kinase-2) DNA damage checkpoint activation. Here we show that large ribonucleoprotein aggregates form in response to DNA damage checkpoint activation in egg chambers of females defective in piRNA biogenesis. Aggregate formation is specific to piRNA biogenesis mutants, as other mutations that activate the same Chk-2-dependent checkpoint do not cause aggregate formation. These aggregates contain components of the dynein motor machinery, retrotransposon RNA, and protein and axial patterning RNAs. Disruption of the aggregates by colcemid treatment leads to increased retrotransposon RNA levels, indicating that these structures may be the destination of retrotransposon RNA transport and may be degradation or sequestration sites. We propose that aggregate formation is a cellular response to protect germ cells from DNA damage caused by elevated retrotransposon expression.

Navarro, Caryn; Bullock, Simon; Lehmann, Ruth

2009-01-01

306

Modulation of Bacterial Type III Secretion System by a Spermidine Transporter Dependent Signaling Pathway  

PubMed Central

Background Many gram-negative bacterial pathogens employ Type III secretion systems (T3SS) to inject effector proteins into host cells in infectious processes. Methodology/Principal Findings By screening a transposon mutant library of P. aeruginosa, we found that mutation of spuDEFGH, which encode a major spermidine uptake system, abolished the expression of the exsCEBA operon that codes for key T3SS regulators under inducing conditions (low calcium). Whole genome microarray analysis revealed that inactivation of the spermidine uptake system significantly decreased the transcriptional expression of most, if not all, T3SS genes. Consistently, the spermidine uptake mutants showed decreased expression of the T3SS genes in responding to host cell extract and attenuated cytotoxicity. Furthermore, exogenous addition of spermidine to the wild type strain PAO1 enhanced the expression of exsCEBA and also the effector protein genes. Conclusion/Significance Cumulatively, these data have depicted a novel spermidine transporter-dependent signaling pathway, which appears to play an essential role in modulation of T3SS expression in P. aeruginosa.

Zhou, Lian; Wang, Jing; Zhang, Lian-Hui

2007-01-01

307

Transforming Growth Factor ?1 Inhibits Cystic Fibrosis Transmembrane Conductance Regulator-dependent cAMP-stimulated Alveolar Epithelial Fluid Transport via a Phosphatidylinositol 3-Kinase-dependent Mechanism*  

PubMed Central

Exogenous or endogenous ?2-adrenergic receptor agonists enhance alveolar epithelial fluid transport via a cAMP-dependent mechanism that protects the lungs from alveolar flooding in acute lung injury. However, impaired alveolar fluid clearance is present in most of the patients with acute lung injury and is associated with increased mortality, although the mechanisms responsible for this inhibition of the alveolar epithelial fluid transport are not completely understood. Here, we found that transforming growth factor ?1 (TGF-?1), a critical mediator of acute lung injury, inhibits ?2-adrenergic receptor agonist-stimulated vectorial fluid and Cl? transport across primary rat and human alveolar epithelial type II cell monolayers. This inhibition is due to a reduction in the cystic fibrosis transmembrane conductance regulator activity and biosynthesis mediated by a phosphatidylinositol 3-kinase (PI3K)-dependent heterologous desensitization and down-regulation of the ?2-adrenergic receptors. Consistent with these in vitro results, inhibition of the PI3K pathway or pretreatment with soluble chimeric TGF-? type II receptor restored ?2-adrenergic receptor agonist-stimulated alveolar epithelial fluid transport in an in vivo model of acute lung injury induced by hemorrhagic shock in rats. The results demonstrate a novel role for TGF-?1 in impairing the ?- adrenergic agonist-stimulated alveolar fluid clearance in acute lung injury, an effect that could be corrected by using PI3K inhibitors that are safe to use in humans.

Roux, Jeremie; Carles, Michel; Koh, Hidefumi; Goolaerts, Arnaud; Ganter, Michael T.; Chesebro, Brian B.; Howard, Marybeth; Houseman, Benjamin T.; Finkbeiner, Walter; Shokat, Kevan M.; Paquet, Agnes C.; Matthay, Michael A.; Pittet, Jean-Francois

2010-01-01

308

Polarized localization and borate-dependent degradation of the Arabidopsis borate transporter BOR1 in tobacco BY-2 cells  

PubMed Central

In Arabidopsis the borate transporter BOR1, which is located in the plasma membrane, is degraded in the presence of excess boron by an endocytosis-mediated mechanism. A similar mechanism was suggested in rice as excess boron decreased rice borate transporter levels, although in this case whether the decrease was dependent on an increase in degradation or a decrease in protein synthesis was not elucidated. To address whether the borate-dependent degradation mechanism is conserved among plant cells, we analyzed the fate of GFP-tagged BOR1 (BOR1-GFP) in transformed tobacco BY-2 cells. Cells expressing BOR1-GFP displayed GFP fluorescence at the plasma membrane, especially at the membrane between two attached cells. The plasma membrane signal was abolished when cells were incubated in medium with a high concentration of borate (3 to 5 mM). This decrease in BOR1-GFP signal was mediated by a specific degradation of the protein after internalization by endocytosis from the plasma membrane. Pharmacological analysis indicated that the decrease in BOR1-GFP largely depends on the increase in degradation rate and that the degradation was mediated by a tyrosine-motif and the actin cytoskeleton. Tyr mutants of BOR1-GFP, which has been shown to inhibit borate-dependent degradation in Arabidopsis root cells, did not show borate-dependent endocytosis in tobacco BY-2 cells. These findings indicate that the borate-dependent degradation machinery of the borate transporter is conserved among plant species.

Matsuoka, Ken

2013-01-01

309

Polarized localization and borate-dependent degradation of the Arabidopsis borate transporter BOR1 in tobacco BY-2 cells.  

PubMed

In Arabidopsis the borate transporter BOR1, which is located in the plasma membrane, is degraded in the presence of excess boron by an endocytosis-mediated mechanism. A similar mechanism was suggested in rice as excess boron decreased rice borate transporter levels, although in this case whether the decrease was dependent on an increase in degradation or a decrease in protein synthesis was not elucidated. To address whether the borate-dependent degradation mechanism is conserved among plant cells, we analyzed the fate of GFP-tagged BOR1 (BOR1-GFP) in transformed tobacco BY-2 cells. Cells expressing BOR1-GFP displayed GFP fluorescence at the plasma membrane, especially at the membrane between two attached cells. The plasma membrane signal was abolished when cells were incubated in medium with a high concentration of borate (3 to 5 mM). This decrease in BOR1-GFP signal was mediated by a specific degradation of the protein after internalization by endocytosis from the plasma membrane. Pharmacological analysis indicated that the decrease in BOR1-GFP largely depends on the increase in degradation rate and that the degradation was mediated by a tyrosine-motif and the actin cytoskeleton. Tyr mutants of BOR1-GFP, which has been shown to inhibit borate-dependent degradation in Arabidopsis root cells, did not show borate-dependent endocytosis in tobacco BY-2 cells. These findings indicate that the borate-dependent degradation machinery of the borate transporter is conserved among plant species. PMID:24715955

Yamauchi, Noboru; Gosho, Tadashi; Asatuma, Satoru; Toyooka, Kiminori; Fujiwara, Toru; Matsuoka, Ken

2013-01-01

310

Incongruent, time-dependent chemical vapour transport in multi-component systems: A case study in Cr-Ge-Si  

NASA Astrophysics Data System (ADS)

Single crystals of various compounds in the ternary system Cr-Ge-Si were grown by chemical vapour transport (CVT) with iodine in a temperature gradient from 800 to 1000 °C. The transport of the solid solution phases Cr(Ge,Si) 3 and Cr 5(Ge,Si) 3 was found to be strongly incongruent and time-dependent. While individual sink crystals are homogeneous and do not show any composition gradient (core-shell structure), the sink a whole is strongly inhomogeneous showing a uniform distribution crystal compositions over a wide composition range. Possible explanations for the observed transport mechanism and implications for synthetic use of incongruent transport systems are discussed. An isothermal section of the ternary phase diagram at 800 °C is given.

Jandl, Isabella; Richter, Klaus W.; Ipser, Herbert

2011-05-01

311

Expressed human hippocampal ASCT1 amino acid transporter exhibits a pH-dependent change in substrate specificity.  

PubMed

In mammalian cells, the basal Na+-dependent uptake for many of the neutral amino acids is mediated by a transport activity designated System ASC. A cloned human brain cDNA sequence, ASCT1, encodes a Na+-dependent neutral amino acid transport activity that exhibits a substrate specificity similar to that commonly associated with System ASC. However, the characteristics of ASC activity varies significantly between cell types and not all tissues contain detectable levels of ASCT1 mRNA. A unique property of System ASC activity is an altered substrate selectivity such that at pH values below 7.4 anionic amino acids function as inhibitors and substrates. The experiments in this report were designed to determine if the cloned ASCT1 transporter exhibited this pH-dependent anionic transport. Following transfection of HeLa cells with the ASCT1 cDNA, transport strongly favored neutral zwitterionic) amino acids when uptake was measured at a physiologic pH value of 7.5. However, lowering the assay pH to 5.5 significantly enhanced the interaction of the ASCT1 carrier with anionic amino acids such as cysteate, in a pH-dependent manner. The apparent pK for the titratable group was in the range of 6.5-7.0. These results provide evidence that the human brain ASCT1 transporter exhibits the most distinguishing characteristic known for System ASC and provides a model system to investigate the molecular basis for this shift in substrate acceptance. PMID:8603078

Tamarappoo, B K; McDonald, K K; Kilberg, M S

1996-03-13

312

Temperature dependence of transport properties of spiro-MeOTAD as a hole transport material in solid-state dye-sensitized solar cells.  

PubMed

The internal transport and recombination parameters of solid-state dye-sensitized solar cells (ssDSCs) using the amorphous organic semiconductor 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-MeOTAD) as a hole transport material (HTM) are investigated using electrical impedance spectroscopy. Devices were fabricated using flat and nanostructured TiO2 and compared to systems using nanostructured ZrO2 to differentiate between the transport processes within the different components of the ssDSC. The effect of chemically p-doping the HTM on its transport was investigated, and its temperature dependence was examined and analyzed using the Arrhenius equation. Using this approach the activation energy of the hole hopping transport within the undoped spiro-MeOTAD film was determined to be 0.34 ą 0.02 and 0.40 ą 0.02 eV for the mesoporous TiO2 and ZrO2 systems, respectively. PMID:23444960

Dualeh, Amalie; Moehl, Thomas; Nazeeruddin, Mohammad Khaja; Grätzel, Michael

2013-03-26

313

Azimuth axis design for huge telescopes: an update  

NASA Astrophysics Data System (ADS)

Alt-azimuth mounted radio telescopes use since their beginning -- more than 50 years ago -- the wheel-on-track principle for the realization of the azimuth axis. For the very huge telescopes (as the Lovell telescope in Jodrell Bank, UK, 1956; the Effelsberg Telescope, Germany, 1969; and the Green Bank Telescope, USA 1996), the wheel-on-track system was and is always one of the most sensitive and maintenance consuming subsystems. On the other hand, the huge optical telescopes use since Mount Palomar (and earlier) hydrostatic axes mechanisms, which need also some maintenance efforts, but are very robust and reliable. The paper gives an update of the design approaches for the new built radio telescopes LMT Mexico, and SRT Sardinia, and compares them with hydrostatic solutions for optical telescopes.

Kaercher, Hans J.

2004-09-01

314

Diffraction theory for azimuthally structured Fresnel zone plate.  

PubMed

A conventional Fresnel zone plate (FZP) consists of concentric rings with an alternating binary transmission of zero and one. In an azimuthally structured Fresnel zone plate (aFZP), the light transmission of the transparent zones is modulated in the azimuthal direction, too. The resulting structure is of interest for extreme ultraviolet and x-ray imaging, in particular, because of its improved mechanical stability as compared to the simple ring structure of an FZP. Here, we present an analysis of the optical performance of the aFZP based on scalar diffraction theory and show numerical results for the light distribution in the focal plane. These will be complemented by calculations of the optical transfer function. PMID:24562035

Vierke, Thordis; Jahns, Jürgen

2014-02-01

315

Azimuthal anisotropy at Valhall: The Helmholtz equation approach  

NASA Astrophysics Data System (ADS)

We used 6 h of continuous vertical records from 2320 sensors of the Valhall Life of Fields Seismic network to compute 2,690,040 cross-correlation functions between the full set of sensor pair combinations. We applied the "Helmholtz tomography" approach combined with the ambient noise correlation method to track the wave front across the network with every station considered as a virtual source. The gradient of the interpolated phase travel time gives us an estimate of the local phase speed and of the direction of wave propagation. By combining the individual measurements for every station, we estimated the distribution of Scholte's wave phase speeds with respect to azimuth. The observed cosine pattern indicates the presence of azimuthal anisotropy. The elliptic shape of the fast anisotropy direction is consistent with results of previous shear wave splitting studies and reflects the strong seafloor subsidence due to the hydrocarbon reservoir depletion at depth and is in good agreement with geomechanical modeling.

Mordret, AuréLien; Shapiro, Nikolai M.; Singh, Satish; Roux, Philippe; Montagner, Jean-Paul; Barkved, Olav. I.

2013-06-01

316

Replacement of the Green Bank Telescope azimuth track  

NASA Astrophysics Data System (ADS)

The azimuth track of the Green Bank Telescope did not perform as designed. Relative movement of components was noted during construction; in addition, fretting of the base plate and wear plate faying surfaces, fatigue cracking of the wear plates, fatigue failure of wear plate fasteners, and deterioration of the cementitous grout layer occurred at a rapid pace during the first few years of operation. After extensive failure analysis, a new system of components was designed and fabricated, and installation of the components was performed during 2007 (Symmes, Anderson, and Egan, "Improving the service life of the 100m Green Bank Telescope azimuth track", SPIE 7012-121). The highlights and lessons learned during the fabrication and installation phases are described herein. This information will benefit any organization performing a similar replacement, and may be helpful in new installations as well.

Anderson, Robert; Symmes, Arthur; Egan, Dennis

2008-07-01

317

Synthetic aperture radar range - Azimuth ambiguity design and constraints  

NASA Technical Reports Server (NTRS)

Problems concerning the design of a system for mapping a planetary surface with a synthetic aperture radar (SAR) are considered. Given an ambiguity level, resolution, and swath width, the problems are related to the determination of optimum antenna apertures and the most suitable pulse repetition frequency (PRF). From the set of normalized azimuth ambiguity ratio curves, the designer can arrive at the azimuth antenna length, and from the sets of normalized range ambiguity ratio curves, he can arrive at the range aperture length or pulse repetition frequency. A procedure based on this design method is shown in an example. The normalized curves provide results for a SAR using a uniformly or cosine weighted rectangular antenna aperture.

Mehlis, J. G.

1980-01-01

318

Velocity of axonal transport of labeled protein is not dependent on local concentration  

SciTech Connect

The velocity of axonal transport of protein labeled with (/sup 3/H)leucine was determined in rat sciatic nerve sensory axons after reversible cooling of the nerve, which provoked a local accumulation of transported material. The velocity of the wavefront of the labeled protein, as well as the slope of the wavefront, was not affected by the duration of cold-block prior to rewarming. In addition, the velocity and slope did not change as the wavefront moved distally from the site of block. In these axons, therefore, velocity of axonal transport is independent of the local concentration of rapidly transported protein.

Bisby, M.A.

1983-01-01

319

Surface harmonics method for two-dimensional time-dependent neutron transport problems of square-lattice nuclear reactors  

SciTech Connect

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)

Boyarinov, V. F.; Kondrushin, A. E.; Fomichenko, P. A. [National Research Centre Kurchatov Institute, Kurchatov Sq. 1, Moscow (Russian Federation)] [National Research Centre Kurchatov Institute, Kurchatov Sq. 1, Moscow (Russian Federation)

2013-07-01

320

Leptin Affects System A Amino Acid Transport Activity in the Human Placenta: Evidence for STAT3 Dependent Mechanisms  

PubMed Central

Background: Amino acids are important nutrients during fetal development, and the activity of placental amino acid transporters is crucial in the regulation of fetal growth. Leptin, an adipocyte- and placenta-derived hormone, has been proposed to act as a peripheral signal in reproduction in humans. Leptin is elevated during pregnancy and elevated further in pathologic pregnancies such as preeclampsia. However, the role of leptin in placental function has not been fully elucidated. We hypothesize that leptin plays a role in the regulation of placental amino acid transport by activation of the JAK-STAT pathway. Methods: Placental amino acid transport, specifically system A transport was studied in placental villous fragments using the amino acid analog, methylaminoisobutyric acid (MeAIB). Specific inhibitors of the JAK-STAT signal transduction pathway were used to further elucidate their role in leptin-mediated effects on amino acid transport activity. Western blotting was performed to identify STAT3 phosphorylation as a measure of leptin receptor activation. Results: Leptin significantly increased system A amino acid transporter activity by 22-42% after 1 h of incubation. Leptin activated JAK-STAT signaling pathway as evidenced by STAT3 phosphorylation, and inhibition of STAT3 or JAK2 resulted in 36-45% reduction in system A amino acid transporter activity. Furthermore, blocking endogenously produced leptin also decreased system A transport by 45% comparable to STAT3 inhibition. Conclusions: These data demonstrate that leptin stimulates system A by JAK-STAT dependent pathway in placental villous fragments. Our findings support the autocrine/paracrine role of leptin in regulating amino acid transport in the human placenta.

von Versen-Hoynck, F.; Rajakumar, A.; Parrott, M.S.; Powers, R.W.

2009-01-01

321

Modal Testing and FE-model Validation of Azimuthing Thruster  

Microsoft Academic Search

\\u000a Vibratory behavior of an azimuthing thruster was studied with FE-models and the results were verified by full-scale experiments.\\u000a Studied thruster systems are used both for main propulsion and for steering of vessels. Modeling techniques were developed\\u000a to take into account the most significant factors and phenomena affecting on the vibration behavior of the structure in real\\u000a operation conditions. Modeling of

Vesa Nieminen; Matti Tervonen

322

An Azimuthal Asymmetry in the LkH? 330 Disk  

NASA Astrophysics Data System (ADS)

Theory predicts that giant planets and low mass stellar companions shape circumstellar disks by opening annular gaps in the gas and dust spatial distribution. For more than a decade it has been debated whether this is the dominant process that leads to the formation of transitional disks. In this paper, we present millimeter-wave interferometric observations of the transitional disk around the young intermediate mass star LkH? 330. These observations reveal a lopsided ring in the 1.3 mm dust thermal emission characterized by a radius of about 100 AU and an azimuthal intensity variation of a factor of two. By comparing the observations with a Gaussian parametric model, we find that the observed asymmetry is consistent with a circular arc, that extends azimuthally by about 90° and emits about 1/3 of the total continuum flux at 1.3 mm. Hydrodynamic simulations show that this structure is similar to the azimuthal asymmetries in the disk surface density that might be produced by the dynamical interaction with unseen low mass companions orbiting within 70 AU from the central star. We argue that such asymmetries might lead to azimuthal variations in the millimeter-wave dust opacity and in the dust temperature, which will also affect the millimeter-wave continuum emission. Alternative explanations for the observed asymmetry that do not require the presence of companions cannot be ruled out with the existing data. Further observations of both the dust and molecular gas emission are required to derive firm conclusions on the origin of the asymmetry observed in the LkH? 330 disk.

Isella, Andrea; Pérez, Laura M.; Carpenter, John M.; Ricci, Luca; Andrews, Sean; Rosenfeld, Katherine

2013-09-01

323

Mirror and Azimuthal Drift Frequencies for Geomagnetically Trapped Particles  

Microsoft Academic Search

For charged particles trapped in the geomagnetic field, the frequencies of the mirror oscillationsoand the azimuthal driftoa are defined as appropriate averages over the helieM motion around the field lines and the mirror motion between reflection points in the two mag- netic hemispheres. These integrals foro, and oa are evaluated numerically. Results are tabulated, illustrated, and represented by approximate anMytieM

D. A. Hamlin; R. Karplus; R. C. Vik; K. M. Watson

1961-01-01

324

Azimuthal structures of produced particles in heavy-ion interactions  

SciTech Connect

The angular structures of particles produced in {sup 208}Pb at 158 A GeV/c and {sup 197}Au at 11.6 A GeV/c induced interactions with Ag(Br) nuclei in emulsion detector have been investigated. Nonstatistical well-ordered ring-like structures of produced particles in azimuthal plane of a collision have been found, and their parameters have been determined.

Vokal, S., E-mail: vokal@sunhe.jinr.ru; Orlova, G. I. [VBLHEP, JINR (Russian Federation); Lehocka, S. [University of P. J. Safarik (Slovakia)

2009-02-15

325

Propagation along azimuthally magnetized ferrite-loaded circular waveguides  

NASA Technical Reports Server (NTRS)

The paper describes the modal dispersion characteristics of electromagnetic waves traveling along the azimuthally magnetized ferrite-loaded coaxial transmission line and the ferrite-loaded wire. The modal dispersion curves are used to determine the pass and stop bands of normal propagation. Boundary-value problems were solved with Bolle-Heller functions. The dispersion characteristics of transverse electric modes are presented as plots of the normalized propagation constant vs the normalized frequency.

Mueller, R. S.; Rosenbaum, F. J.

1977-01-01

326

Azimuthal Asymmetry and Transverse Momentum of Hadrons in Deep Inelastic Muon Scattering at 490 GEV.  

NASA Astrophysics Data System (ADS)

The forward charged hadrons produced in deep inelastic scattering of 490 GeV muons from deuterium were studied. The data were taken by the E665 collaboration during the 1987 -1988 Fermilab fixed target run. 3 times 10^4 events (6 times 10^4 hadrons) were collected over a large range of kinematic variables: 100 GeV < nu < 500 GeV, 2 GeV^2 < Q^2 < 100 GeV ^2, 0.003 < x_{Bj } < 0.2, and 0.2 < y_ {Bj} < 0.9. Using the virtual photon axis as the z-axis, the distributions of the produced hadrons in azimuthal angle and in transverse momentum are examined. The primordial k_{|} of the struck patron and {cal O}(alpha _{S}) QCD effects are expected to contribute to an azimuthal asymmetry and to an increase in the average transverse momentum. Some theoretical work in the literature concerning these effects is described and some original results are derived concerning the effects of primordial k_{|} on the azimuthal distribution. A Monte Carlo program is described which includes these theoretical effects and models fragmentation, the detector response, and the event reconstruction. The data exhibit several surprising effects. First, the phi asymmetry in the data is independent of Q ^2, while theoretically it should be more pronounced at low Q^2 and vanish at high Q^2. Second, the phi asymmetry is carried by the most energetic particle in each event, which we call the Rank 1 particle, and there is very little phi asymmetry of the other charged hadrons. Third, this phi asymmetry in the Rank 1 particle is independent of the hadron energy fraction z_{h} . The Monte Carlo predicts a strong z_ {h} dependence and little rank dependence. Finally, the seagull plot shows an unexpected increase in transverse momentum p_{T} for high energy hadrons (z_{h} > 0.4) as a function of Q^2. It is clear from these results that more theoretical work is needed in order to understand primordial k_ {|} and the azimuthal asymmetry in deep inelastic scattering. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

Baker, Mark David

327

Sec24D-Dependent Transport of Extracellular Matrix Proteins Is Required for Zebrafish Skeletal Morphogenesis  

PubMed Central

Protein transport from endoplasmic reticulum (ER) to Golgi is primarily conducted by coated vesicular carriers such as COPII. Here, we describe zebrafish bulldog mutations that disrupt the function of the cargo adaptor Sec24D, an integral component of the COPII complex. We show that Sec24D is essential for secretion of cartilage matrix proteins, whereas the preceding development of craniofacial primordia and pre-chondrogenic condensations does not depend on this isoform. Bulldog chondrocytes fail to secrete type II collagen and matrilin to extracellular matrix (ECM), but membrane bound receptor ?1-Integrin and Cadherins appear to leave ER in Sec24D-independent fashion. Consequently, Sec24D-deficient cells accumulate proteins in the distended ER, although a subset of ER compartments and Golgi complexes as visualized by electron microscopy and NBD C6-ceramide staining appear functional. Consistent with the backlog of proteins in the ER, chondrocytes activate the ER stress response machinery and significantly upregulate BiP transcription. Failure of ECM secretion hinders chondroblast intercalations thus resulting in small and malformed cartilages and severe craniofacial dysmorphology. This defect is specific to Sec24D mutants since knockdown of Sec24C, a close paralog of Sec24D, does not result in craniofacial cartilage dysmorphology. However, craniofacial development in double Sec24C/Sec24D-deficient animals is arrested earlier than in bulldog/sec24d, suggesting that Sec24C can compensate for loss of Sec24D at initial stages of chondrogenesis, but Sec24D is indispensable for chondrocyte maturation. Our study presents the first developmental perspective on Sec24D function and establishes Sec24D as a strong candidate for cartilage maintenance diseases and craniofacial birth defects.

Sarmah, Swapnalee; Barrallo-Gimeno, Alejandro; Melville, David B.; Topczewski, Jacek; Solnica-Krezel, Lilianna; Knapik, Ela W.

2010-01-01

328

Gabapentin increases extracellular glutamatergic level in the locus coeruleus via astroglial glutamate transporter-dependent mechanisms.  

PubMed

Gabapentin has shown to be effective in animals and humans with acute postoperative and chronic pain. Yet the mechanisms by which gabapentin reduces pain have not been fully addressed. The current study performed in vivo microdialysis in the locus coeruleus (LC) in normal and spinal nerve ligated (SNL) rats to examine the effect of gabapentin on extracellular glutamate concentration and its mechanisms of action with focus on presynaptic GABA-B receptors, astroglial glutamate transporter-1 (GLT-1), and interactions with ?2? subunits of voltage-gated Ca(2+) channels and endogenous noradrenaline. Basal extracellular concentration and tissue content of glutamate in the LC were greater in SNL rats than normal ones. Intravenously administered and LC-perfused gabapentin increased extracellular glutamate concentration in the LC. The net amount of glutamate increased by gabapentin is larger in SNL rats compared with normal ones, although the percentage increases from the baseline did not differ. The gabapentin-related ?2? ligand pregabalin increased extracellular glutamate concentration in the LC, whereas another ?2? ligand, 3-exo-aminobicyclo [2.2.1] heptane-2-exo-carboxylic acid (ABHCA), did not. Selective blockade by the dihydrokainic acid or knock-down of GLT-1 by the small interfering RNA abolished the gabapentin-induced glutamate increase in the LC, whereas blockade of GABA-B receptors by the CGP-35348 and depletion of noradrenalin by the dopamine-?-hydroxylase antibody conjugated to saporin did not. These results suggest that gabapentin induces glutamate release from astrocytes in the LC via GLT-1-dependent mechanisms to stimulate descending inhibition. The present study also demonstrates that this target of gabapentin in astrocytes does not require interaction with ?2? subunits in neurons. PMID:24495399

Suto, Takashi; Severino, Amie L; Eisenach, James C; Hayashida, Ken-ichiro

2014-06-01

329

Transverse Dynamics of the Azimuthally Inhomogeneous Electron Bunch in a Multilayer Dielectric Cylindrical Waveguide  

NASA Astrophysics Data System (ADS)

In reference [1], a complete analytical solution for Cherenkov wakefields generated by an azimuthally asymmetric annular beam propagating in a coaxial two-channel dielectric structure was presented. A drive bunch generates Cherenkov radiation (wakefield) inside the dielectric loaded waveguide and a second (witness) bunch passing through the structure at an appropriate delay with respect to the drive bunch is accelerated by the wakefield. Use of a ring beam in a multi-layer waveguide can significantly increase the transformer ratio by providing different paths for the ring driver and the accelerated bunch to pass through the structure. The main challenge of this scheme originates in the transverse dynamics of the drive bunch because of its high charge and relatively low energy. To hold the inner dielectric tube inside the waveguide metal (titanium) threads are used. The threads are located inside the drive beam section of the waveguide that leads to the segmentation of the drive beam. In this paper, we study the transverse dynamics of the annular beam with various types of azimuthally asymmetries that depend on the specifics of the beam generation and multilayer waveguide parameters. The different types of beam asymmetry and hybrid mode dependencies are presented using the original BBU-3000 [7] beam dynamics code.

Altmark, A. M.; Kanareykin, A. D.

2014-05-01

330

An Azimuthal Dynamo Wave in Spherical Shell Convection  

NASA Astrophysics Data System (ADS)

We report the discovery of an azimuthal dynamo wave of a low-order (m = 1) mode in direct numerical simulations (DNS) of turbulent convection in spherical shells. Such waves are predicted by mean-field dynamo theory and have been obtained previously in mean-field models. An azimuthal dynamo wave has been proposed as a possible explanation for the persistent drifts of spots observed on several rapidly rotating stars, as revealed through photometry and Doppler imaging. However, this has been judged unlikely because evidence for such waves from DNS has been lacking. Here we present DNS of large-scale magnetic fields showing a retrograde m = 1 mode. Its pattern speed is nearly independent of latitude and does not reflect the speed of the differential rotation at any depth. The extrema of magnetic m = 1 structures coincide reasonably well with the maxima of m = 2 structures of the temperature. These results provide direct support for the observed drifts being due to an azimuthal dynamo wave.

Cole, Elizabeth; Käpylä, Petri J.; Mantere, Maarit J.; Brandenburg, Axel

2014-01-01

331

Refining cortical representation of sound azimuths by auditory discrimination training.  

PubMed

Although training-based auditory cortical plasticity in the adult brain has been previously demonstrated in multiparametric sound domains, neurochemical mechanisms responsible for this form of plasticity are not well understood. In this study, we trained adult rats to identify a target sound stimulus at a specific azimuth angle by using a reward-contingent auditory discrimination task. We found that auditory spatial discrimination training significantly enhanced representation of sound azimuths in the primary auditory cortex, as shown by sharper azimuth-selective curves and more evenly distributed best angles of cortical neurons. Training also facilitated long-term potentiation of field potentials in the primary auditory cortex induced by theta burst stimulation of the white matter. In parallel, there were significant alterations in expression levels of certain cortical GABA(A) and NMDA receptor subunits, resulting in a marked decrease in the level of GABA(A) relative to NMDA receptors. These changes in the expression profile of inhibitory and excitatory neurotransmitter receptor subunits might enhance synaptic transmission, thereby facilitating training-induced cortical plasticity in the spatial domain. PMID:23739966

Zhang, Ying; Zhao, Yan; Zhu, Xiaoqing; Sun, Xinde; Zhou, Xiaoming

2013-06-01

332

Sequence relationships between integral inner membrane proteins of binding protein-dependent transport systems: evolution by recurrent gene duplications.  

PubMed Central

Periplasmic binding protein-dependent transport systems are composed of a periplasmic substrate-binding protein, a set of 2 (sometimes 1) very hydrophobic integral membrane proteins, and 1 (sometimes 2) hydrophilic peripheral membrane protein that binds and hydrolyzes ATP. These systems are members of the superfamily of ABC transporters. We performed a molecular phylogenetic analysis of the sequences of 70 hydrophobic membrane proteins of these transport systems in order to investigate their evolutionary history. Proteins were grouped into 8 clusters. Within each cluster, protein sequences displayed significant similarities, suggesting that they derive from a common ancestor. Most clusters contained proteins from systems transporting analogous substrates such as monosaccharides, oligopeptides, or hydrophobic amino acids, but this was not a general rule. Proteins from diverse bacteria are found within each cluster, suggesting that the ancestors of current clusters were present before the divergence of bacterial groups. The phylogenetic trees computed for hydrophobic membrane proteins of these permeases are similar to those described for the periplasmic substrate-binding proteins. This result suggests that the genetic regions encoding binding protein-dependent permeases evolved as whole units. Based on the results of the classification of the proteins and on the reconstructed phylogenetic trees, we propose an evolutionary scheme for periplasmic permeases. According to this model, it is probable that these transport systems derive from an ancestral system having only 1 hydrophobic membrane protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Saurin, W.; Dassa, E.

1994-01-01

333

pH-dependent oxidant production following inhibition of the mitochondrial electron transport chain in pulmonary endothelial cells.  

PubMed

We investigated the effect of changes in intracellular pH (pHi) and Na/H antiport activity on intracellular oxidant production in human pulmonary artery endothelial cells (HPAEC) following disruption of cellular metabolism. Oxidant production was measured with oxidant-sensitive probes (2',7'-dichlorofluorescein diacetate [H2DCF], dihydroethidium [DHE]) following treatment with inhibitors of mitochondrial electron transport and glycolysis (antimycin/2-deoxyglucose, A/D). A/D treatment increased oxidant production in a dose-dependent fashion over 2 hours. Omission of 2-deoxyglucose did not alter the magnitude of oxidant production. Inhibition at more proximal sites in the mitochondrial electron transport chain inhibited oxidant production. These data suggested that the mitochondrial electron transport chain was the source of oxidant production. Fluorescent imaging experiments confirmed the mitochondrial origin of the increased oxidant production under these conditions. Maneuvers that reduced pHi and inhibited Na/H exchange (acidosis, specific Na/H exchange inhibitors) attenuated oxidant production, whereas maneuvers that raised pHi (monensin) potentiated oxidant production. The results with the pH-insensitive probe (DHE) confirmed that oxidant production was pH-dependent. Oxidant production preceded significant loss of cell viability at 6 h following A/D treatment. These results demonstrate that oxidant production following inhibition of mitochondrial electron transport in HPAEC is pH-dependent and may contribute to endothelial cell injury by increasing endogenous oxidative stress. PMID:12200958

Cutaia, M; Kroczynski, J; Tollefson, K

2002-01-01

334

The Insertion and Transport of Anandamide in Synthetic Lipid Membranes Are Both Cholesterol-Dependent  

Microsoft Academic Search

BackgroundAnandamide is a lipid neurotransmitter which belongs to a class of molecules termed the endocannabinoids involved in multiple physiological functions. Anandamide is readily taken up into cells, but there is considerable controversy as to the nature of this transport process (passive diffusion through the lipid bilayer vs. involvement of putative proteic transporters). This issue is of major importance since anandamide

Eric di Pasquale; Henri Chahinian; Patrick Sanchez; Jacques Fantini; Dimitris Fatouros

2009-01-01

335

A two-dimensional, time-dependent model of suspended sediment transport and bed reworking for continental shelves  

USGS Publications Warehouse

A two-dimensional, time-dependent solution to the transport equation is formulated to account for advection and diffusion of sediment suspended in the bottom boundary layer of continental shelves. This model utilizes a semi-implicit, upwind-differencing scheme to solve the advection-diffusion equation across a two-dimensional transect that is configured so that one dimension is the vertical, and the other is a horizontal dimension usually aligned perpendicular to shelf bathymetry. The model calculates suspended sediment concentration and flux; and requires as input wave properties, current velocities, sediment size distributions, and hydrodynamic sediment properties. From the calculated two-dimensional suspended sediment fluxes, we quantify the redistribution of shelf sediment, bed erosion, and deposition for several sediment sizes during resuspension events. The two-dimensional, time-dependent approach directly accounts for cross-shelf gradients in bed shear stress and sediment properties, as well as transport that occurs before steady-state suspended sediment concentrations have been attained. By including the vertical dimension in the calculations, we avoid depth-averaging suspended sediment concentrations and fluxes, and directly account for differences in transport rates and directions for fine and coarse sediment in the bottom boundary layer. A flux condition is used as the bottom boundary condition for the transport equation in order to capture time-dependence of the suspended sediment field. Model calculations demonstrate the significance of both time-dependent and spatial terms on transport and depositional patterns on continental shelves. ?? 2001 Elsevier Science Ltd. All rights reserved.

Harris, C. K.; Wiberg, P. L.

2001-01-01

336

Coherent quantum transport in disordered systems: II. Temperature dependence of carrier diffusion coefficients from the time-dependent wavepacket diffusion method  

NASA Astrophysics Data System (ADS)

The time-dependent wavepacket diffusion method for carrier quantum dynamics (Zhong and Zhao 2013 J. Chem. Phys. 138 014111), a truncated version of the stochastic Schrödinger equation/wavefunction approach that approximately satisfies the detailed balance principle and scales well with the size of the system, is applied to investigate the carrier transport in one-dimensional systems including both the static and dynamic disorders on site energies. The predicted diffusion coefficients with respect to temperature successfully bridge from band-like to hopping-type transport. As demonstrated in paper I (Moix et al 2013 New J. Phys. 15 085010), the static disorder tends to localize the carrier, whereas the dynamic disorder induces carrier dynamics. For the weak dynamic disorder, the diffusion coefficients are temperature-independent (band-like property) at low temperatures, which is consistent with the prediction from the Redfield equation, and a linear dependence of the coefficient on temperature (hopping-type property) only appears at high temperatures. In the intermediate regime of dynamic disorder, the transition from band-like to hopping-type transport can be easily observed at relatively low temperatures as the static disorder increases. When the dynamic disorder becomes strong, the carrier motion can follow the hopping-type mechanism even without static disorder. Furthermore, it is found that the memory time of dynamic disorder is an important factor in controlling the transition from the band-like to hopping-type motions.

Zhong, Xinxin; Zhao, Yi; Cao, Jianshu

2014-04-01

337

Efficiency improvement of organic light-emitting diodes depending on the thickness variation of BCP layer used for electron transport  

Microsoft Academic Search

In the devices structure of ITO\\/N, N'-diphenyl-N, N'bis(3-methylphenyl)-1, 1'-biphenyl-4, 4'-diamine (TPD)\\/tris(8-hydroxyquinoline)aluminum (Alq3) electron-transport-layer (ETL) (2, 9-Dimethyl-4), 7-diphenyl-1, 10-phenanthroline (BCP))\\/Al, we have studied the efficiency improvement of organic light-emitting diodes depending on the thickness variation of BCP using electron transport layer. The thickness of TPD and Alq3 was manufactured 40 nm, 60 nm under a base pressure of 5 times 10-6

Won-Jong Kim; Hyun-Min Choi; Joung-Sik Kim; Tae-Wan Kim; Jin-Woong Hong

2009-01-01

338

Thin and thick YBCO films grown by MOCVD processes. Study of the angular magnetic field dependence of current transport properties  

SciTech Connect

Thin and thick YBCO Films have been grown by Aerosol Assisted as well as by thermal MOCVD. The Aerosol Assisted MOCVD technique allows the growth of YBCO films from a single liquid source at deposition rates of up to 10 {mu}m/h. Transport measurements (I-V) on etched microbridges using a single pulse technique have been performed. The angular magnetic field dependence J{sub c}({Theta}) of the critical current density from T{sub c} down to 50 K has been measured. Transport properties are reported and discussed with respect to the microstructural features as determined by X-ray diffraction and electron microscopy.

Schmatz, U.; Dubourdieu, C.; Lebedev, O. [LMGP-ENSPG-INPG, St Martin d`Heres (France)] [and others

1996-12-01

339

Auxiliary Quantization Constraints on the Von Roos Ordering-Ambiguity at Zero Binding Energies; Azimuthally Symmetrized Cylindrical Coordinates  

NASA Astrophysics Data System (ADS)

Using azimuthally symmetrized cylindrical coordinates, we report the consequences of zero-energy quantal states on the von Roos Hamiltonian. A position-dependent mass (PDM) M(?, ?, z) = bzj?2?+1/2 is used. We show that the zero-energy setting not only offers an additional degree of freedom toward feasible separability for the von Roos Hamiltonian, but also manifestly yields auxiliary quantized ambiguity parametric constraints (i.e. the ambiguity parameters are given in terms of quantum numbers).

Mustafa, Omar

2013-06-01

340

Azimuthal anisotropy layering and plate motion in the Pacific Ocean  

NASA Astrophysics Data System (ADS)

We recently developed a three dimensional radially and azimuthally anisotropic model of the upper mantle in north America, using a combination of long-period 3-component surface and overtone waveforms, and SKS splitting measurements (Yuan and Romanowicz, 2010, Yuan et al., 2011). We showed that azimuthal anisotropy is a powerful tool to detect layering in the upper mantle, revealing two domains in the cratonic lithosphere, separated by a sharp laterally varying boundary in the depth range 100-150 km, which seems to coincide with the mid-lithospheric boundary (MLD) found in receiver function studies. Contrary to receiver functions, azimuthal anisotropy also detects the lithosphere-asthenosphere boundary (LAB) as manifested by a change in the fast axis direction, which becomes quasi-parallel to the absolute plate motion below ~250 km depth. A zone of stronger azimuthal anisotropy is found below the LAB both in the western US (peaking at depths of 100-150km) and in the craton (peaking at a depth of about 300 km). Here we show preliminary attempts at expanding our approach to the global scale, with a specific goal of determining whether such an anisotropic LAB can also be observed in the Pacific ocean. We started with our most recent global upper mantle radially anisotropic shear velocity model, determined using the Spectral Element Method (SEMum2; French et al., this meeting). We augment the corresponding global surface wave and overtone dataset (period range 60 to 400 s) with deep events and shorter period body waves, in order to ensure optimal deeper depth (>250km) anisotropy recovery due to the paucity of shear wave splitting measurements in the oceans. Our preliminary results, which do not yet incorporate SKS splitting measurements, look promising as they confirm the layering found previously in North America, using a different, global dataset and starting model. In the Pacific, our study confirms earlier azimuthal anisotropy results in the region (e.g. Smith et al. 2004; Maggi et al. 2006) that the shallow upper mantle beneath the ocean basin is strongly stratified. Our results further illustrate that 1) a shallow anisotropy domain (~100 km) is present, which is high in velocity and has in general a northward anisotropy direction where the plate is old (>80 Ma); and 2) there is a deeper domain (100-200 km) with stronger anisotropy, which correlates spatially with the low velocity zone and has a fast axis direction in good agreement with the absolute plate motion direction (HS3 NUVEL-1A). The boundary between the anisotropy domains clearly follows the age progressive deepening of the fast velocity in the shallow domain, suggesting an oceanic LAB that separates the Pacific lithosphere and the underlying asthenosphere.

Yuan, H.; Romanowicz, B. A.

2012-12-01

341

Contact metal-dependent electrical transport in carbon nanotubes and fabrication of graphene nanoribbons  

NASA Astrophysics Data System (ADS)

In this thesis, we fabricate and characterize carbon nanotube (CNT) and graphene-based field effect transistor devices. The CNT-based work centers around the physics of metal contacts to CNT, particularly relating the work function of contact metals to carrier transport across the junction. The graphene work is motivated by the desire to utilize the high carrier mobility of graphene in field effect transistors. CNT have excellent electrical properties including high carrier mobility, large field effect switching capabilities, and a long mean free path. Absent, however is an experimentally-backed model explaining contact-metal work function, device layout, and environment effects. To fill this void, we introduce a surface-inversion channel (SIC) model based on low temperature and electrical measurements of a distinct single-walled semiconducting CNT contacted by Hf, Cr, Ti and Pd electrodes. Anomalous barrier heights and metal-contact dependent band-to-band tunneling phenomena are utilized to show that dependent upon contact work function and gate field, transport occurs either directly between the metal and CNT channel or indirectly via injection of carriers from the metal-covered CNT region to the CNT channel. The model is consistent with previously contradictory experimental results, and the methodology is simple enough to apply in other contact-dominant systems. In agreement with the initial contact theory above, we further develop a model explain Isd-Vsd tendencies in CNT FETs. Using experimental and analytical analysis, we demonstrate a relationship between the contact metal work function and electrical transport properties saturation current (Isat) and differential conductance ssd=6Isd 6Vsd in ambient exposed CNT. A single chemical vapor deposition (CVD)-grown 6 millimeter long semiconducting single-walled CNT is electrically contacted with a statistically significant number of Hf, Cr, Ti, Pd, and Ti, Au electrodes, respectively. The observed exponentially increasing relationship of I sat and sigmasd with metal-contact work function that is explained by a theoretical model derived from thermionic field emission. Statistical analysis and spread of the data suggest that the conduction variability in same-CNT devices results from differences in local surface potential of the metal contact. Based on the theoretical model and methodology, an improved CNT-based gas sensing device layout is suggested; a method to experimentally determine gas-induced work function changes in metals is also proposed. Third, a performance analysis on CNT Schottky diodes using source-drain current anisotropy is explored. An analytical model is derived based on thermionic field emission and used to correlate experimental data from Pd-Hf, Ti-Hf, Cr-Hf, Ti-Cr, and Pd-Au mixed metal devices fabricated on one single 6 mm-long CNT. Results suggest that the difference in work functions of the two contact-metals, and not a dominant Schottky contact, determines diode performance. Results are further applied and demonstrated in a reversible polarity diode. Next, we develop experimental processes to grow high quality monolayer graphene on Cu foil. Cu foil is pre-annealed and hand polished to increase Cu crystalline domain size and reduce surface roughness. This is done to reduce nucleation sites for graphene during CVD growth. After growth on Cu foil, the graphene is transferred to SiO2 using a floating PMMA method described in section 3.2.2. Finally, the quality of the graphene is analyzed via Raman spectroscopy, optical imagery, and sheet resistance measurements. After demonstrating the quality of the graphene film, we investigate the effect of UV irradiation of graphene, CNT, and graphene/CNT hybrids in an oxygen environment. Samples were irradiated by 254/185 nm UV light in an oxygen environment for up to two hours. Results suggest a unique method to generate graphene nanoribbons using aligned carbon nanotubes (CNT) as a graphene etch mask. Ambient and cryogenic Gsd-Vg measurements of resulting ultrathin graphene nanoribbons show p-type character an

Perello, David

342

ATP-dependent transport of statins by human and rat MRP2/Mrp2.  

PubMed

Multidrug resistance associated protein-2, MRP2 (human), Mrp2 (rat) are an efflux transporter, responsible for the transport of numerous endogenous and xenobiotic compounds including taurocholate, methotrexate and carboxydichlorofluorescein (CDF). The present study aims to characterise transport of statins by human and rat MRP2/Mrp2 using membrane and vesicle preparations. All statins tested (simvastatin, pravastatin, pitavastatin, fluvastatin, atorvastatin, lovastatin and rosuvastatin) stimulated vanadate-sensitive ATPase activity in membranes expressing human or rat MRP2/Mrp2, suggesting that all statins are substrates of human and rat MRP2/Mrp2. The substrate affinity (Km) of all statins for MRP2/Mrp2 was comparable and no correlation between lipophilicity (logD7.0) and Km was seen. All statins also inhibited uptake of the fluorescent Mrp2 substrate, CDF (1?M) into vesicles expressing human or rat MRP2/Mrp2 with similar IC50 values. Fitting of the inhibitory data to the hill slope equation, gave hill coefficients (h) of greater than one, suggesting that transport involved more than one binding site for inhibitors of MPR2 and Mrp2. We conclude that statins were transported by both human and rat MRP2/Mrp2 with similar affinity. Statins were also shown to compete with other substrates for transport by MRP2/Mrp2 and that this transport involved more than one binding site on the Mrp2/MRP2 protein. PMID:23562342

Ellis, Lucy C J; Hawksworth, Gabrielle M; Weaver, Richard J

2013-06-01

343

Dependence of transport rate on area of lithography and pretreatment of tip in dip-pen nanolithography.  

PubMed

This study examines the lithographic capacity of tips in dip-pen nanolithography (DPN). The dependence of the transport rate (R) decay on the area of lithography (A(lith)), the dependence of A(lith) on the lithographic time (t), and the effect of piranha cleaning on the lithographic capacity are considered herein. The dependencies in the line-drawing lithography process are studied using 16-mercaptohexadecanoic acid (MHA) ink. On the basis of the linear decay dependence discovered in the R-A(lith) dependence, piranha treatment can increase the lithographic capacity by up to 35.5-fold, an improvement that may originate from a change in the tip's surface chemistry. Moreover, a theoretical model is derived to describe the A(lith)-t dependence accurately and to predict the tips' lifetime. Furthermore, an experiment involving DPN-based nanostructure fabrication demonstrates the importance of monitoring the tips' transport rate and lifetime. In addition to shedding light on the physical and chemical principles behind DPN, this study provides a comprehensive model for a quantitative analysis of the tips' behavior. PMID:23020585

Wu, Tzu-Heng; Lu, Hui-Hsin; Lin, Chii-Wann

2012-10-16

344

CLIP-170-dependent capture of membrane organelles by microtubules initiates minus-end directed transport  

PubMed Central

Summary Cytoplasmic microtubules (MTs) continuously grow and shorten at free plus ends. During mitosis, this dynamic behavior allows MTs to capture chromosomes to initiate their movement to the spindle poles, however, the role of MT dynamics in capturing organelles for transport in interphase cells has not been demonstrated. Here we used Xenopus melanophores to test the hypothesis that MT dynamics significantly contribute to the efficiency of MT minus-end directed transport of membrane organelles. We demonstrated that initiation of transport of membrane-bounded melanosomes (pigment granules) to the cell center involves their capture by MT plus ends, and that inhibition of MT dynamics or loss of the MT plus-end tracking protein CLIP-170 from MT tips dramatically inhibits pigment aggregation. We conclude that MT dynamics are required for the initiation of MT transport of membrane organelles in interphase cells, and that +TIPs such as CLIP-170 play an important role in this process.

Lomakin, Alexis J.; Semenova, Irina; Zaliapin, Ilya; Kraikivski, Pavel; Nadezhdina, Elena; Slepchenko, Boris M.; Akhmanova, Anna; Rodionov, Vladimir

2009-01-01

345

PH-domain-dependent selective transport of p75 by kinesin-3 family motors in non-polarized MDCK cells.  

PubMed

A key process during epithelial polarization involves establishment of polarized transport routes from the Golgi to distinct apical and basolateral membrane domains. To do this, the machinery involved in selective trafficking must be regulated during differentiation. Our previous studies showed that KIF5B selectively transports vesicles containing p75-neurotrophin receptors to the apical membrane of polarized, but not non-polarized MDCK cells. To identify the kinesin(s) responsible for p75 trafficking in non-polarized MDCK cells we expressed KIF-specific dominant-negative constructs and assayed for changes in post-Golgi transport of p75 by time-lapse fluorescence microscopy. Overexpression of the tail domains of kinesin-3 family members that contain a C-terminal pleckstrin homology (PH) domain, KIF1A or KIF1Bbeta, attenuated the rate of p75 exit from the Golgi in non-polarized MDCK cells but not in polarized cells. Analysis of p75 post-Golgi transport in cells expressing KIF1A or KIF1Bbeta with their PH domains deleted revealed that vesicle transport by these motors depends on the PH domains. Furthermore, purified KIF1A and KIF1Bbeta tails interact with p75 vesicles and these interactions require the PH domain. Knockdown of canine KIF1A also inhibited exit of p75 from the Golgi, and this was rescued by expression of human KIF1A. Together these data demonstrate that post-Golgi transport of p75 in non-polarized epithelial cells is mediated by kinesin-3 family motors in a PH-domain-dependent process. PMID:20427314

Xue, Xiaoxiao; Jaulin, Fanny; Espenel, Cedric; Kreitzer, Geri

2010-05-15

346

PH-domain-dependent selective transport of p75 by kinesin-3 family motors in non-polarized MDCK cells  

PubMed Central

A key process during epithelial polarization involves establishment of polarized transport routes from the Golgi to distinct apical and basolateral membrane domains. To do this, the machinery involved in selective trafficking must be regulated during differentiation. Our previous studies showed that KIF5B selectively transports vesicles containing p75-neurotrophin receptors to the apical membrane of polarized, but not non-polarized MDCK cells. To identify the kinesin(s) responsible for p75 trafficking in non-polarized MDCK cells we expressed KIF-specific dominant-negative constructs and assayed for changes in post-Golgi transport of p75 by time-lapse fluorescence microscopy. Overexpression of the tail domains of kinesin-3 family members that contain a C-terminal pleckstrin homology (PH) domain, KIF1A or KIF1B?, attenuated the rate of p75 exit from the Golgi in non-polarized MDCK cells but not in polarized cells. Analysis of p75 post-Golgi transport in cells expressing KIF1A or KIF1B? with their PH domains deleted revealed that vesicle transport by these motors depends on the PH domains. Furthermore, purified KIF1A and KIF1B? tails interact with p75 vesicles and these interactions require the PH domain. Knockdown of canine KIF1A also inhibited exit of p75 from the Golgi, and this was rescued by expression of human KIF1A. Together these data demonstrate that post-Golgi transport of p75 in non-polarized epithelial cells is mediated by kinesin-3 family motors in a PH-domain-dependent process.

Xue, Xiaoxiao; Jaulin, Fanny; Espenel, Cedric; Kreitzer, Geri

2010-01-01

347

Transcription-Dependent and Transcription-Independent Nuclear Transport of hnRNP Proteins  

Microsoft Academic Search

Heterogeneous nuclear RNAs and specific nuclear proteins form heterogeneous nuclear ribonucleoprotein complexes (hnRNPs), one of the most abundant components of the nucleus. In mitosis, as the nuclear envelope breaks down, hnRNPs disperse throughout the cell. At the end of mitosis, hnRNPs dissociate and their proteins are transported into the daughter cell nuclei separately. Some are transported immediately (early group), while

Serafin Pinol-Roma; Gideon Dreyfuss

1991-01-01

348

ExbBD-Dependent Transport of Maltodextrins through the Novel MalA Protein across the Outer Membrane of Caulobacter crescentus  

Microsoft Academic Search

Analysis of the genome sequence of Caulobacter crescentus predicts 67 TonB-dependent outer membrane proteins. To demonstrate that among them are proteins that transport nutrients other than chelated Fe3 and vitamin B12—the substrates hitherto known to be transported by TonB-dependent transporters—the outer membrane protein profile of cells grown on different substrates was determined by two-dimensional electro- phoresis. Maltose induced the synthesis

Heidi Neugebauer; Christina Herrmann; Winfried Kammer; Gerold Schwarz; Alfred Nordheim; Volkmar Braun

2005-01-01

349

Measurement of the cos(?) and cos(2?) Azimuthal Moments of the Deep Inelastic Scattering Cross-section  

NASA Astrophysics Data System (ADS)

The cross section for hadron production in deep-inelastic lepton scattering contains azimuthal modulations which can be related to transverse momentum dependent (TMD) distribution and fragmentation functions. The former provide a picture of how the quarks are moving within nucleons. Specifically, the cos? and cos2? modulations of the unpolarized cross section relate quark spin and quark transverse momentum. These moments have been carefully measured at the HERMES experiment in a fully differential way, as a function of x, y, z, and P for positive and negative hadrons produced from hydrogen and deuterium targets. These measurements give new access to the flavor dependent TMDs via their charge and target dependence.

HERMES Collaboration; Lamb, Rebecca; Giordano, Francesca; HERMES Collaboration

2009-08-01

350

Effects of the magnetic anchoring groups on spin-dependent transport properties of Ni(dmit)2 device  

NASA Astrophysics Data System (ADS)

By using non-equilibrium Green's functions in combination with the density functional theory, we investigated the spin-dependent electronic transport properties through a single-molecule-magnet (SMM) Ni(dmit)2 between two nanoscale Au(1 1 1) electrodes with different anchoring groups. The nonmagnetic (S) and magnetic (Ni, Mn) anchoring groups have been chosen. Our results show that the spin-dependent electronic transport properties can be modulated significantly by the anchoring groups, and many interesting phenomena such as high spin-filtering ratio, rectifying and negative differential resistance can be observed. These characteristics could be used in the study of spin physics and the realization of nano-spintronic devices based on SMMs.

Yan, Shenlang; Long, Mengqiu; Zhang, Xiaojiao; He, Jun; Xu, Hui; Chen, Keqiu

2014-07-01

351

Partitioning of Noncyclic Photosynthetic Electron Transport to O2-Dependent Dissipative Processes as Probed by Fluorescence and CO2 Exchange  

PubMed Central

The partitioning of noncyclic photosynthetic electron transport between net fixation of CO2 and collective O2-dependent, dissipative processes such as photorespiration has been examined in intact leaf tissue from Nicotiana tabacum. The method involves simultaneous application of CO2 exchange and pulse modulated fluorescence measurements. As either irradiance or CO2 concentration is varied at 1% O2 (i.e. absence of significant O2-dependent electron flow), the quantum efficiency of PSII electron transport (?se) with CO2 as the terminal acceptor is a linear function of the ratio of photochemical:nonphotochemical fluorescence quenching coefficients (i.e. qQ:qNP). When the ambient O2 concentration is raised to 20.5% or 42% the qQ:qNP is assumed to predict the quantum efficiency of total noncyclic electron transport (??se). A factor which represents the proportion of electron flow diverted to the aforementioned dissipative processes is calculated as (??se ? ?se)/??se where ?se is now the observed quantum efficiency of electron transport in support of net fixation of CO2. Examination of changes in electron allocation with CO2 and O2 concentration and irradiance at 25°C provides a test of the applicability of the Rubisco model to photosynthesis in vivo. Images Figure 3

Peterson, Richard B.

1989-01-01

352

Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field  

NASA Astrophysics Data System (ADS)

We present an exact analytical approach for arbitrary field-dependent critical state of high-Tc superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the Ia-Ba plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe

2013-12-01

353

Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field  

SciTech Connect

We present an exact analytical approach for arbitrary field-dependent critical state of high-T{sub c} superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the I{sub a}-B{sub a} plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe, E-mail: zhouyh@lzu.edu.cn [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, and Department of Mechanics and Engineering Sciences, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)] [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, and Department of Mechanics and Engineering Sciences, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

2013-12-15

354

Sodium-Dependent Neutral Amino Acid Transporter Type 1 Is an Auxiliary Receptor for Baboon Endogenous Retrovirus  

Microsoft Academic Search

The baboon endogenous retrovirus (BaEV) belongs to a large, widely dispersed interference group that includes the RD114 feline endogenous virus and primate type D retroviruses. Recently, we and another laboratory independently cloned a human receptor for these viruses and identified it as the human sodium- dependent neutral amino acid transporter type 2 (hASCT2). Interestingly, mouse and rat cells are efficiently

MARIANA MARIN; CHETANKUMAR S. TAILOR; ALI NOURI; DAVID KABAT

2000-01-01

355

Serotonin transporter polymorphism as a predictor for escitalopram treatment of major depressive disorder comorbid with alcohol dependence  

Microsoft Academic Search

The aim of this study was to determine whether the serotonin transporter gene polymorphism (5-HTTLPR) is associated with the treatment outcomes of escitalopram for patients with comorbid major depression and alcohol dependence. Eighty treatment-seeking patients were randomly assigned to either receive 20mg of escitalopram or a control of 20mg of the non-serotonergically acting memantine. Depression was measured by the Montgomery–Asberg

Leea H. Muhonen; Jari Lahti; Hannu Alho; Jouko Lönnqvist; Jari Haukka; Sirkku T. Saarikoski

2011-01-01

356

Lead inhibition of Mg\\/sup 2 +\\/-ATP-dependent calcium transport in rat liver plasma membranes  

Microsoft Academic Search

In every tissue in which lead\\/calcium interactions have been examined, lead interferes with cellular calcium homeostasis resulting in an apparent increase in cellular calcium and alterations in calcium-mediated processes. The mechanism(s) by which lead increases cellular calcium are unknown. This study examines the effect of lead (5 nM to 50 ..mu..M) on Mg\\/sup 2 +\\/-ATP-dependent calcium transport activity in rat

Schanne; F. A. X

1986-01-01

357

Carrier Concentration Dependencies of Magnetization & Transport in Ga1-xMnxAs1-yTey  

NASA Astrophysics Data System (ADS)

We have investigated the transport and magnetization characteristics of Ga1-xMnxAs intentionally compensated with shallow Te donors. Using ion implantation followed by pulsed-laser melting, we vary the Te compensation and drive the system through a metal-insulator transition (MIT). This MIT is associated with enhanced low-temperature magnetization and an evolution from concave to convex temperature-dependent magnetization.

Scarpulla, M. A.; Yu, K. M.; Walukiewicz, W.; Dubon, O. D.

2005-06-01

358

Azimuthal asymmetries for hadron distributions inside a jet in hadronic collisions  

NASA Astrophysics Data System (ADS)

Using a generalized parton model approach including spin and intrinsic parton motion effects, and assuming the validity of factorization for large-pT jet production in hadronic collisions, we study the azimuthal distribution around the jet axis of leading unpolarized or (pseudo)scalar hadrons, namely pions, produced in the jet fragmentation process. We identify the observable leading-twist azimuthal asymmetries for the unpolarized and single-polarized case related to quark and gluon-originated jets. We account for all physically allowed combinations of the transverse momentum-dependent (TMD) parton distribution and fragmentation functions, with special attention to the Sivers, Boer-Mulders, and transversity quark distributions, and to the Collins fragmentation function for quarks (and to the analogous functions for gluons). For each of these effects we evaluate, at central and forward rapidities and for kinematical configurations accessible at BNL-RHIC, the corresponding potentially maximized asymmetry (for ?+ production), obtained by saturating natural positivity bounds (and the Soffer bound for transversity) for the distribution and fragmentation functions involved and summing additively all partonic contributions. We then estimate, for both neutral and charged pions, the asymmetries involving TMD functions for which parametrizations are available. We also study the role of the different mechanisms, and the corresponding transverse single-spin asymmetries, for large-pT inclusive-jet production.

D'Alesio, Umberto; Murgia, Francesco; Pisano, Cristian

2011-02-01

359

Surface wave tomography and azimuthal anisotropy of the Philippine Sea Plate  

NASA Astrophysics Data System (ADS)

Long period and broadband waveform data from 1984 to 2007 extracted mainly from the IRIS Data Center with additional data from 1997 to 2007 extracted from the Ocean Hemisphere Project is used to perform a detailed mapping of Rayleigh wave group velocity and anisotropic structures of the Philippine Sea Plate (PSP). Our results show prominent high Rayleigh wave group velocity anomalies and heterogeneity in three marginal basins of the PSP at period up to 30 s. The convergent boundaries around the PSP are associated with low-velocity anomalies. Heterogeneity of velocity distribution at deep depths along the Ryukyu trench is also observed. Our results indicate that the azimuthal anisotropy in the PSP is depth dependent. The fast direction in the West Philippine Basin and the Shikoku Basin is in NE-SW at shorter periods, which is correlated with fossilized fabric produced by final phase of deformation, whereas the fast direction in the Parece Vela Basin is complex at shorter periods and becomes uniformly NE-SW-oriented at longer periods. At the depths near the lithosphere-asthenosphere boundary, the fast directions become parallel to the absolute plate motion for various parts of the PSP. The fast directions along subduction zones around the PSP are predominately trench-normal. The relatively simple patterns of azimuthal anisotropy may imply that the observed anisotropy originates from the A-type LPO of olivine fabric at shallow depths in the back-arc region and with slab-entrained mantle flow at deep depths.

Yeh, Yu-Lien; Kao, Honn; Wen, Strong; Chang, Wen-Yen; Chen, Chau-Huei

2013-04-01

360

New inhibitors for the neutral amino acid transporter ASCT2 reveal its Na+-dependent anion leak  

PubMed Central

The neutral amino acid transporter ASCT2 catalyses uncoupled anion flux across the cell membrane in the presence of transported substrates, such as alanine. Here, we report that ASCT2 conducts anions already in the absence of transported substrates through a leak anion-conducting pathway. The properties of this leak anion conductance were studied by electrophysiological recording from ASCT2-expressing HEK293 cells. We found that the leak anion conductance was inhibited by the binding of the newly characterized inhibitors benzylserine and benzylcysteine to ASCT2. These inhibitors competitively prevent binding of transported substrates to ASCT2, suggesting that they bind to the ASCT2 binding site for neutral amino acid substrates. The leak anion conductance exhibits permeation properties that are similar to the substrate-activated anion conductance of ASCT2, preferring hydrophobic anions such as thiocyanate. Inhibition of the leak anion conductance by benzylserine requires the presence of extracellular, but not intracellular Na+. The apparent affinity of ASCT2 for extracellular Na+ was determined as 0.3 mm. Interestingly, a Na+-dependent leak anion conductance with similar properties was previously reported for the related excitatory amino acid transporters (EAATs), suggesting that this leak anion conductance is highly conserved within the EAAT protein family.

Grewer, Christof; Grabsch, Eva

2004-01-01

361

The Nramp orthologue of Cryptococcus neoformans is a pH-dependent transporter of manganese, iron, cobalt and nickel  

PubMed Central

Cryptococcus neoformans is an important human opportunistic pathogen and a facultative intracellular parasite, particularly in HIV-infected individuals. Little is known about metal ion transport in this organism. C. neoformans encodes a single member of the Nramp (natural resistance-associated macrophage protein) family of bivalent cation transporters, known as Cramp, which we have cloned and expressed in Xenopus laevis oocytes and Spodoptera frugiperda Sf 21 insect cells. Cramp induces saturable transport of a broad range of bivalent transition series cations, including Mn2+, Fe2+, Co2+ and Ni2+. Maximal cation transport occurs at pH 5.5–6.0, consistent with the proton gradient-based energetics of other Nramp orthologues. Mn2+ transport is diminished in the presence of 140 mM Na+, compatible with a Na+ slippage mechanism proposed for the Saccharomyces cerevisiae Nramp orthologue Smf1p. Cramp resembles Smf1p with respect to predicted membrane topology, substrate specificity and pH dependence, but differs in terms of its apparent affinity for Mn2+ and negligible inhibition by Zn2+. Cramp is the first Nramp orthologue from a fungal pathogen to be functionally characterized. Insights afforded by these findings will allow the formulation of new hypotheses regarding the role of metal ions in the pathophysiology of cryptococcosis.

2004-01-01

362

P2Y1 receptor inhibits GABA transport through a calcium signalling-dependent mechanism in rat cortical astrocytes.  

PubMed

Astrocytes express a variety of purinergic (P2) receptors, involved in astrocytic communication through fast increases in [Ca(2+) ]i . Of these, the metabotropic ATP receptors (P2Y) regulate cytoplasmic Ca(2+) levels through the PLC-PKC pathway. GABA transporters are a substrate for a number of Ca(2+) -related kinases, raising the possibility that calcium signalling in astrocytes impact the control of extracellular levels of the major inhibitory transmitter in the brain. To access this possibility we tested the influence of P2Y receptors upon GABA transport into astrocytes. Mature primary cortical astroglial-enriched cultures expressed functional P2Y receptors, as evaluated through Ca(2+) imaging, being P2Y1 the predominant P2Y receptor subtype. ATP (100 ?M, for 1 min) caused an inhibition of GABA transport through either GAT-1 or GAT-3 transporters, decreasing the Vmax kinetic constant. ATP-induced inhibition of GATs activity was still evident in the presence of adenosine deaminase, precluding an adenosine-mediated effect. This, was mimicked by a specific agonist for the P2Y1,12,13 receptor (2-MeSADP). The effect of 2-MeSADP on GABA transport was blocked by the P2 (PPADS) and P2Y1 selective (MRS2179) receptor antagonists, as well as by the PLC inhibitor (U73122). 2-MeSADP failed to inhibit GABA transport in astrocytes where intracellular calcium had been chelated (BAPTA-AM) or where calcium stores were depleted (?-cyclopiazonic acid, CPA). In conclusion, P2Y1 receptors in astrocytes inhibit GABA transport through a mechanism dependent of P2Y1 -mediated calcium signalling, suggesting that astrocytic calcium signalling, which occurs as a consequence of neuronal firing, may operate a negative feedback loop to enhance extracellular levels of GABA. GLIA 2014;62:1211-1226. PMID:24733747

Jacob, Pedro F; Vaz, Sandra H; Ribeiro, Joaquim A; Sebastiăo, Ana M

2014-08-01

363

Single-Chip FPGA Azimuth Pre-Filter for SAR  

NASA Technical Reports Server (NTRS)

A field-programmable gate array (FPGA) on a single lightweight, low-power integrated-circuit chip has been developed to implement an azimuth pre-filter (AzPF) for a synthetic-aperture radar (SAR) system. The AzPF is needed to enable more efficient use of data-transmission and data-processing resources: In broad terms, the AzPF reduces the volume of SAR data by effectively reducing the azimuth resolution, without loss of range resolution, during times when end users are willing to accept lower azimuth resolution as the price of rapid access to SAR imagery. The data-reduction factor is selectable at a decimation factor, M, of 2, 4, 8, 16, or 32 so that users can trade resolution against processing and transmission delays. In principle, azimuth filtering could be performed in the frequency domain by use of fast-Fourier-transform processors. However, in the AzPF, azimuth filtering is performed in the time domain by use of finite-impulse-response filters. The reason for choosing the time-domain approach over the frequency-domain approach is that the time-domain approach demands less memory and a lower memory-access rate. The AzPF operates on the raw digitized SAR data. The AzPF includes a digital in-phase/quadrature (I/Q) demodulator. In general, an I/Q demodulator effects a complex down-conversion of its input signal followed by low-pass filtering, which eliminates undesired sidebands. In the AzPF case, the I/Q demodulator takes offset video range echo data to the complex baseband domain, ensuring preservation of signal phase through the azimuth pre-filtering process. In general, in an SAR I/Q demodulator, the intermediate frequency (fI) is chosen to be a quarter of the range-sampling frequency and the pulse-repetition frequency (fPR) is chosen to be a multiple of fI. The AzPF also includes a polyphase spatial-domain pre-filter comprising four weighted integrate-and-dump filters with programmable decimation factors and overlapping phases. To prevent aliasing of signals, the bandwidth of the AzPF is made 80 percent of fPR/M. The choice of four as the number of overlapping phases is justified by prior research in which it was shown that a filter of length 4M can effect an acceptable transfer function. The figure depicts prototype hardware comprising the AzPF and ancillary electronic circuits. The hardware was found to satisfy performance requirements in real-time tests at a sampling rate of 100 MHz.

Gudim, Mimi; Cheng, Tsan-Huei; Madsen, Soren; Johnson, Robert; Le, Charles T-C; Moghaddam, Mahta; Marina, Miguel

2005-01-01

364

Automobile dependence in cities: An international comparison of urban transport and land use patterns with implications for sustainability  

SciTech Connect

Cities around the world are subject to increasing levels of environmental impact from dependence on the automobile. In the highly auto-dependent cities of the US and Australia, this is manifested in problems such as urban sprawl and its destruction of prime farming land and natural landscapes, photochemical smog that can be primarily attributed to auto emissions. On top of the more local impacts of the automobile, the global dimension should not be forgotten. Perhaps the two most pressing issues in this regard are the oil problem and the greenhouse problem. A comparison of global cities over the period 1980 to 1990 reveals large differences in automobile dependence with implications for the future sustainability of cities in different countries. This study explores some of the underlying land use, transport, and economic reasons for these different transport patterns. It briefly reviews what the sustainability agenda means for transport and land use patterns in cities and suggests a suite of targets or goals for sustainability by which cities might measure their current directions and plans.

Kenworthy, J.R.; Laube, F.B. [Murdoch Univ., Perth (Australia). Inst. for Science and Technology Policy] [Murdoch Univ., Perth (Australia). Inst. for Science and Technology Policy

1996-07-01

365

[Nitric oxide as a possible regulator of energy-dependent Ca2+ transport in mitochondria of uterine smooth muscle].  

PubMed

The influence of the donor and the precursor of NO, namely 100 mM sodium nitroprusside and sodium nitrite on the energo-dependent Ca(2+)-transport in isolated mitochondria from rat myometrium was investigated. Changes in the mitochondrial matrix Ca(2+)-concentration was evaluated by spectrofluorimetry using Ca2+ sensitive probe Fluo-4 AM. Mg(2+)-ATP-dependent Ca(2+)-accumulation on mitochondria in the presence of succinate significantly stimulated by nitric oxide, in particular, 100 microM sodium nitroprusside amplified the transport by 1.6 times relative to its control values. NO effect becomes significant only when the incubation of mitochondria with the compounds was performed. Ca(2+)-accumulation in the presence of sodium nitroprusside effectively suppressed by protonophore (CCCP) and ruthenium red (10 microM). It was concluded that inner mitochondrial membrane Ca(2+)-uniporter stimulated by nitrogen oxide. Ca(2+)-accumulation in mitochondria in the presence of sodium nitroprusside was not sensitive to the action of a specific permeability transition pore inhibitor cyclosporine (5 microM). This data indicates that the role of permeability transition pore is less significant than Ca(2+)-uniporter in the processes of Ca(2+)-transport in mitochondria under the nitric oxide action. Thus, nitric oxide stimulates the energo-dependent Ca(2+)-accumulation by myometrium mitochondria mediated their inner membrane Ca(2+)-uniporter functioning. PMID:25007515

Danylovych, Iu V; Kolomiiets', O V; Danylovych, H V; Kosterin, S O

2014-01-01

366

Azimuthal anisotropy layering in the Pacific upper mantle  

NASA Astrophysics Data System (ADS)

As the mechanically strong outer layer of the Earth, the lithosphere is a fundamental component in plate tectonics. Resolving the internal structure of the lithosphere and underlying asthenosphere, as well as the coupling between the two, is critical for our understanding of the formation, stabilization and subsequent deformation of continents and oceans. One key aspect of the problem, identified as one of the Grand Challenges of modern seismology, is the thickness of lithosphere, or the depth of the lithosphere-asthenosphere-boundary (LAB). Seismic detection of the LAB, however, remains 'elusive', possibly due to the smooth character of the seismic velocity gradient across the boundary. In continents recent surface wave studies have proven azimuthal anisotropy a powerful tool in revealing the internal structure of the continental lithosphere and its boundary with the asthenosphere (e.g. Yuan and Romanowicz, 2010). Here we expand our regional waveform inversion to the much greater size Pacific region, focusing on the 3D anisotropic structure of the oceanic upper mantle. Specifically, we look for the anisotropy stratification signal beneath the ocean basins, and correlate it with simultaneously inverted isotropic shear velocities to infer the structure of the Pacific oceanic lithosphere and asthenosphere, and the LAB topography throughout the region. Our results show a strong age progressive pattern in isotropic shear velocity, radial anisotropy and azimuthal anisotropy. Two domains of azimuthal anisotropy are observed in the upper 250 km, each possessing a distinct fast axis direction of anisotropy. An anisotropic LAB is drawn in the Pacific, which maps the rapid depth variation of fast axis directions toward the current absolute plate direction. At slightly shallower depth, an isotropic shear velocity horizon is robustly defined throughout the ocean basin, based on maximum negative velocity gradients with respect to depth. We argue that the offset between the two horizons reflects differences in the thermal and chemical properties of the Pacific oceanic lithosphere.

Yuan, H.; French, S. W.; Romanowicz, B. A.

2013-12-01

367

Phosphorylation-regulated axonal dependent transport of syntaxin 1 is mediated by a Kinesin-1 adapter  

PubMed Central

Presynaptic nerve terminals are formed from preassembled vesicles that are delivered to the prospective synapse by kinesin-mediated axonal transport. However, precisely how the various cargoes are linked to the motor proteins remains unclear. Here, we report a transport complex linking syntaxin 1a (Stx) and Munc18, two proteins functioning in synaptic vesicle exocytosis at the presynaptic plasma membrane, to the motor protein Kinesin-1 via the kinesin adaptor FEZ1. Mutation of the FEZ1 ortholog UNC-76 in Caenorhabditis elegans causes defects in the axonal transport of Stx. We also show that binding of FEZ1 to Kinesin-1 and Munc18 is regulated by phosphorylation, with a conserved site (serine 58) being essential for binding. When expressed in C. elegans, wild-type but not phosphorylation-deficient FEZ1 (S58A) restored axonal transport of Stx. We conclude that FEZ1 operates as a kinesin adaptor for the transport of Stx, with cargo loading and unloading being regulated by protein kinases.

Chua, John Jia En; Butkevich, Eugenia; Worseck, Josephine M.; Kittelmann, Maike; Gr?nborg, Mads; Behrmann, Elmar; Stelzl, Ulrich; Pavlos, Nathan J.; Lalowski, Maciej M.; Eimer, Stefan; Wanker, Erich E.; Klopfenstein, Dieter Robert; Jahn, Reinhard

2012-01-01

368

Phosphorylation-regulated axonal dependent transport of syntaxin 1 is mediated by a Kinesin-1 adapter.  

PubMed

Presynaptic nerve terminals are formed from preassembled vesicles that are delivered to the prospective synapse by kinesin-mediated axonal transport. However, precisely how the various cargoes are linked to the motor proteins remains unclear. Here, we report a transport complex linking syntaxin 1a (Stx) and Munc18, two proteins functioning in synaptic vesicle exocytosis at the presynaptic plasma membrane, to the motor protein Kinesin-1 via the kinesin adaptor FEZ1. Mutation of the FEZ1 ortholog UNC-76 in Caenorhabditis elegans causes defects in the axonal transport of Stx. We also show that binding of FEZ1 to Kinesin-1 and Munc18 is regulated by phosphorylation, with a conserved site (serine 58) being essential for binding. When expressed in C. elegans, wild-type but not phosphorylation-deficient FEZ1 (S58A) restored axonal transport of Stx. We conclude that FEZ1 operates as a kinesin adaptor for the transport of Stx, with cargo loading and unloading being regulated by protein kinases. PMID:22451907

Chua, John Jia En; Butkevich, Eugenia; Worseck, Josephine M; Kittelmann, Maike; Grřnborg, Mads; Behrmann, Elmar; Stelzl, Ulrich; Pavlos, Nathan J; Lalowski, Maciej M; Eimer, Stefan; Wanker, Erich E; Klopfenstein, Dieter Robert; Jahn, Reinhard

2012-04-10

369

Fluoride-dependent interruption of the transport cycle of a CLC Cl?/H+ antiporter  

PubMed Central

Cl?/H+ antiporters of the CLC superfamily transport anions across biological membranes in varied physiological contexts. These proteins are weakly selective among anions commonly studied, including Cl?, Br?, I?,NO3?, and SCN?, but appear to be very selective against F?. The recent discovery of a new CLC clade of F?/H+ antiporters, which are highly selective for F? over Cl?, led us to investigate the mechanism of Cl?-over-F? selectivity by a CLC Cl?/H+ antiporter, CLC-ec1. By subjecting purified CLC-ec1 to anion transport measurements, electrophysiological recording, equilibrium ligand-binding studies, and x-ray crystallography, we show that F? binds in the Cl? transport pathway with affinity similar to Cl?, but stalls the transport cycle. Examination of various mutant antiporters implies a “lock-down” mechanism of F? inhibition, in which F?, by virtue of its unique H-bonding chemistry, greatly retards a proton-linked conformational change essential for the transport cycle of CLC-ec1.

Lim, Hyun-Ho; Stockbridge, Randy B.; Miller, Christopher

2013-01-01

370

Azimuthal and Radial Seismic Anisotropy Beneath the Baltic Shield  

NASA Astrophysics Data System (ADS)

The SVEKALAPKO passive seismic array in Finland provides us with an exceptional opportunity to study seismic anisotropy in and below the lithosphere in a shield. The array was composed of almost 150 sensors - out of which 46 were broadband - in a regular 2D grid which facilitated high-quality array analysis. We analyse phase velocities of both Love and Rayleigh waves to constrain radial and azimuthal anisotropy. We invert for the anisotropic parameters ? and Gc on the one hand, and for the percentage of aligned olivine on the other. This latter parametrization of the inverse problem makes it straightforward to quantitatively compare the radial and the azimuthal anisotropies, under the assumption that aligned olivine dominates the anisotropy. The radial anisotropy, for which we have resolution in the lithosphere only, is strong, and can be explained by 40%-60% of the rock being olivine with the a-axis in the horizontal plane, equivalent to values of ? between 1.09 and 1.14. This radial anisotropy is stronger than observed in shield areas in global models (e.g. Beghein and Trampert, 2004). The azimuthal anisotropy is on the contrary very small in the lithosphere. This indicates that the orientation of the olivine minerals is random within the horizontal plane or that the overall effect across the area is negligible due to different orientations in different domains. Results from body-waves (Plomerová et al., 2005, Vecsey et al., in prep.) would support the latter interpretation. The azimuthal anisotropy as estimated by Rayleigh wave analysis is on the contrary significant below 200-250km depth, and corresponds to approximately 15%-20% of the rock being olivine with the a-axis aligned in direction N20. Xenolith analysis in the area shows that the rheologic lithosphere is at most 250km thick, so we suggest that this observed anisotropy is sub-lithospheric. Interestingly, the fast direction is significantly different from the absolute plate motion of the Baltic Shield, indicating that the lithosphere is not simply coupled to the underlying convecting mantle.

Pedersen, H. A.; Bruneton, M.; Maupin, V.

2005-12-01

371

D0 Measurement of the Dijet Azimuthal Decorrelations  

NASA Astrophysics Data System (ADS)

We present the D0 measurement of correlations in the azimuthal angle between the two largest transverse momentum jets produced in pp collisions at a center-of-mass energy s = 1.96 TeV in the central rapidity region. The results are based on an inclusive dijet event sample corresponding to an integrated luminosity of 150 pb-1. Data is in good agreement with next-to-leading order (NLO) pQCD calculations, and with tuned PYTHIA, HERWIG, ALPGEN and SHERPA event generators.

Zieli?ski, Marek

2006-07-01

372

The azimuth axes mechanisms for the ATST telescope mount assembly  

NASA Astrophysics Data System (ADS)

The ATST Telescope Mount Assembly uses for the Azimuth axes mechanisms bearing and drive technologies as developed for the machine tool industry. An overview on the ATST mount project and design and its verification by analysis, simulation and tests are given in two separate papers of this conference. This paper describes the main design and accuracy features of the bearing and drive subsystems, their adaption to the ATST mount and their influence on the telescope structural design, and gives a hint to the challenges in the upcoming manufacturing, installation and commissioning phases.

Kärcher, Hans J.; Weis, Ulrich; Dreyer, Oliver; Jeffers, Paul F.; Bonomi, Giovanni

2012-09-01

373

THE DISTRIBUTION OF THE ELEMENTS IN THE GALACTIC DISK. II. AZIMUTHAL AND RADIAL VARIATION IN ABUNDANCES FROM CEPHEIDS  

SciTech Connect

This paper reports on the spectroscopic investigation of 101 Cepheids in the Carina region. These Cepheids extend previous samples by about 35% in number and increase the amount of the Galactic disk coverage especially in the direction of l {approx} 270{sup 0}. The new Cepheids do not add much information to the radial gradient, but provide a substantial increase in azimuthal coverage. We find no azimuthal dependence in abundance over an 80 deg. angle from the Galactic center in an annulus of 1 kpc depth centered on the Sun. A simple linear fit to the Cepheid data yields a gradient d[Fe/H]/dR{sub G} = -0.055 {+-} 0.003 dex kpc{sup -1} which is somewhat shallower than found from our previous, smaller Cepheid sample.

Luck, R. E. [Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215 (United States); Andrievsky, S. M.; Kovtyukh, V. V. [Department of Astronomy and Astronomical Observatory, Odessa National University, Isaac Newton Institute of Chile, Odessa Branch, Shevchenko Park, 65014 Odessa (Ukraine); Gieren, W.; Graczyk, D., E-mail: luck@fafnir.astr.cwru.edu, E-mail: scan@deneb1.odessa.ua, E-mail: val@deneb1.odessa.ua, E-mail: wgieren@astro-udec.cl, E-mail: darek@astro-udec.cl [Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

2011-08-15

374

The response of SAR imagery to azimuth travelling ocean surface waves as determined from shuttle SAR imagery  

NASA Technical Reports Server (NTRS)

Comparisons between two-dimensional ocean wave spectra, derived from synthetic aperture radar (SAR) imagery, and two-dimensional wave spectra from independent instruments have shown good agreement. The procedure by which raw SAR image intensity-variance spectra are converted to estimates of wave spectra is dependent upon models of how a SAR is able to image ocean waves. The greatest uncertainty exists about the mechanism by which azimuth (along track) traveling waves are imaged. In this paper, independent wave spectra from an airborne, radar ocean wave spectrometer (ROWS) are systematically compared with spatially and temporally coincident shuttle SAR image intensity-variance spectra to determine an optimum description of the relationship between the two. The result of these comparisons is to demonstrate that a SAR image intensity-variance spectrum is nearly proportional to the ocean wave slope-variance spectrum for azimuth traveling waves.

Monaldo, Frank M.; Jackson, Frederick C.

1987-01-01

375

The Distribution of the Elements in the Galactic Disk. II. Azimuthal and Radial Variation in Abundances from Cepheids  

NASA Astrophysics Data System (ADS)

This paper reports on the spectroscopic investigation of 101 Cepheids in the Carina region. These Cepheids extend previous samples by about 35% in number and increase the amount of the Galactic disk coverage especially in the direction of l ? 270°. The new Cepheids do not add much information to the radial gradient, but provide a substantial increase in azimuthal coverage. We find no azimuthal dependence in abundance over an 80° angle from the Galactic center in an annulus of 1 kpc depth centered on the Sun. A simple linear fit to the Cepheid data yields a gradient d[Fe/H]/dRG = -0.055 ą 0.003 dex kpc-1 which is somewhat shallower than found from our previous, smaller Cepheid sample.

Luck, R. E.; Andrievsky, S. M.; Kovtyukh, V. V.; Gieren, W.; Graczyk, D.

2011-08-01

376

Temperature Dependent Transport Properties of a Few-wall Carbon Nanotubes Network  

NASA Astrophysics Data System (ADS)

Transport properties of CVD grown few-wall carbon nanotubes random network were investigated over a wide temperature range from 6 to 500 K. In the low temperature regime 6-300 K, the transport property was analyzed with the two parallel conduction mechanisms viz. variable range hopping (VRH) and fluctuation assisted tunneling (FIT). Among these two mechanisms, the VRH dominates over the FIT. In the high temperature regime 300-500 K, the resistance measurement was repeated for 3 heating cycles. The resistance of the FWCNT network showed semiconducting behavior throughout the temperature range studied.

Kamalakannan, R.; Ganesan, K.; Kamruddin, M.; Tyagi, A. K.

2010-12-01

377

Experimental and theoretical study of nickel transport dependence on gradients in Tore Supra  

NASA Astrophysics Data System (ADS)

This paper reports on a Tore Supra experiment consisting in modifying locally the normalized electron temperature gradient R?Te/Te by playing with the electron cyclotron heating wave power deposition radius. Trace nickel was injected by the laser blow-off technique and its behaviour in the plasma has been analysed using a radial impurity transport code. The diffusion coefficient has been found to decrease steeply when |R?Te/Te| is decreased in conditions where linear gyrokinetic calculations find that turbulence is dominated by modes propagating in the electron drift direction. An experimental turbulence threshold for nickel transport has been deduced.

Villegas, D.; Guirlet, R.; Bourdelle, C.; Garbet, X.; Hoang, G. T.; Sabot, R.; Imbeaux, F.; Ségui, J. L.

2014-07-01

378

Cloning and functional characterization of the mouse sodium-dependent organic anion transporter Soat (Slc10a6).  

PubMed

The sodium-dependent organic anion transporter SOAT is a member of the Solute Carrier Family SLC10. In man, this carrier is predominantly expressed in the testis and has transport activity for sulfoconjugated steroid hormones. Here, we report on cloning, expression analysis and functional characterization of the mouse Soat (mSoat) and compare its characteristics with the human SOAT carrier. Quantitative mRNA expression analysis for mSoat in male mice revealed very high expression in lung and further high expression in testis and skin. Immunohistochemical studies showed expression of the mSoat protein in bronchial epithelial cells of the lung, in primary and secondary spermatocytes as well as round spermatids within the seminiferous tubules of the testis, in the epidermis of the skin, and in the urinary epithelium of the bladder. Stably transfected mSoat-HEK293 cells revealed sodium-dependent transport for dehydroepiandrosterone sulfate (DHEAS), estrone-3-sulfate, and pregnenolone sulfate (PREGS) with apparent Km values of 60.3?M, 2.1?M, and 2.5?M, respectively. In contrast to human SOAT, which has a preference for DHEAS as a substrate, mSoat exhibits the highest transport rate for PREGS, likely reflecting differences in the steroid pattern between both species. In conclusion, although certain differences between human SOAT and mSoat exist regarding quantitative gene expression in endocrine and non-endocrine tissues, as well as in the transport kinetics for steroid sulfates, in general, both can be regarded as homologous carriers. PMID:23562556

Grosser, Gary; Fietz, Daniela; Günther, Sabine; Bakhaus, Katharina; Schweigmann, Helene; Ugele, Bernhard; Brehm, Ralph; Petzinger, Ernst; Bergmann, Martin; Geyer, Joachim

2013-11-01

379

Expression of Madin-Darby canine kidney cell Na(+)-and Cl(-)-dependent taurine transporter in Xenopus laevis oocytes.  

PubMed

Expression of a Madin-Darby canine kidney (MDCK) cell taurine transporter was examined in Xenopus oocytes that had been injected with poly(A)+ RNA extracted from MDCK cells. Compared with water-injected oocytes, injection of total poly(A)+ RNA resulted in an increase in Na(+)-dependent taurine uptake which was directly related to the amount of RNA injected. The magnitude of expression in poly(A)+ RNA-injected oocytes was 5-10-fold higher than that of water-injected oocytes. Since the Vmax of taurine uptake in MDCK cells is increased by culture in hypertonic medium, we compared oocyte taurine uptake after injection with poly(A)+ RNA from MDCK cells cultured in hypertonic medium with uptake in oocytes injected with poly(A)+ RNA from hypertonic cells elicited twice the taurine uptake elicited by poly(A)+ RNA from isotonic cells. The transporter expressed in oocytes was like that in MDCK cells: it was completely dependent on external sodium and was also anion dependent (Cl- greater than or equal to Br- greater than SCN- much greater than gluconate-). Other beta-amino acids, beta-alanine and hypotaurine, inhibited taurine uptake, but L-alanine and 2-(methylamino) isobutyric acid did not. The apparent Km of the transporter was 7.0 microM. After size fractionation on a sucrose density gradient, poly(A)+ RNA encoding for the MDCK taurine transporter was found in the fraction whose average size was 4.4 kilobases. PMID:1709638

Uchida, S; Kwon, H M; Preston, A S; Handler, J S

1991-05-25

380

Dependence of Total Longshore Sediment Transport Rates on Incident Wave Parameters and Breaker Type.  

National Technical Information Service (NTIS)

Experiments were conducted in the Large-scale Sediment Transport Facility (LSTF) at the U.S. Army Engineer Research and Development Center to investigate the importance of wave height, period, and breaker type (spilling and plunging breakers) on total rat...

B. A. Ebersole, E. R. Smith, J. Zhang, P. Wang

2009-01-01

381

Transport activity-dependent intracellular sorting of the yeast general amino acid permease  

PubMed Central

Intracellular trafficking of the general amino acid permease, Gap1p, of Saccharomyces cerevisiae is regulated by amino acid abundance. When amino acids are scarce Gap1p is sorted to the plasma membrane, whereas when amino acids are abundant Gap1p is sorted from the trans-Golgi through the multivesicular endosome (MVE) and to the vacuole. Here we test the hypothesis that Gap1p itself is the sensor of amino acid abundance by examining the trafficking of Gap1p mutants with altered substrate specificity and transport activity. We show that trafficking of mutant Gap1pA297V, which does not transport basic amino acids, is also not regulated by these amino acids. Furthermore, we have identified a catalytically inactive mutant that does not respond to complex amino acid mixtures and constitutively sorts Gap1p to the plasma membrane. Previously we showed that amino acids govern the propensity of Gap1p to recycle from the MVE to the plasma membrane. Here we propose that in the presence of substrate the steady-state conformation of Gap1p shifts to a state that is unable to be recycled from the MVE. These results indicate a parsimonious regulatory mechanism by which Gap1p senses its transport substrates to set an appropriate level of transporter activity at the cell surface.

Cain, Natalie E.; Kaiser, Chris A.

2011-01-01

382

Dependence of heat transport on toroidal rotation in conventional H-modes in JT-60U  

NASA Astrophysics Data System (ADS)

The relation between heat transport in the plasma core and the toroidal rotation profile was examined in conventional ELMy H-mode plasmas in JT-60U. Heat transport in the plasma core is not strongly influenced locally by toroidal rotation. The large increase in heat conduction imposes a resilient profile of ion temperature, under which the local effect of the toroidal rotation profile on scale length of the ion temperature gradient is very weak. Energy confinement improvement is observed with toroidal rotation which increases in the co-direction with respect to the plasma current. In this case, the increase in the ion temperature in both the plasma core and the pedestal region is observed. However, heat transport in the plasma core varies while maintaining self-similar temperature profiles as the toroidal rotation profile is varied. Pressure at the H-mode pedestal becomes slightly larger with the toroidal rotation in the co-direction. Thus, energy confinement enhanced with co-toroidal rotation is determined by increased pedestal height and reduced transport brought on by profile resilience. When pedestal temperature was fixed between the cases of co- and counter-NBI by adjusting the plasma density, identical temperature profiles were obtained in spite of totally different toroidal rotation profiles.

Urano, H.; Takenaga, H.; Fujita, T.; Kamada, Y.; Koide, Y.; Oyama, N.; Yoshida, M.; JT-60 Team

2008-08-01

383

Proliferation-dependent changes in amino acid transport and glucose metabolism in glioma cell lines  

Microsoft Academic Search

Amino acid imaging is increasingly being used for assessment of brain tumor malignancy, extent of disease, and prognosis. This study explores the relationship between proliferative activity, amino acid transport, and glucose metabolism in three glioma cell lines (U87, Hs683, C6) at different phases of growth in culture. Growth phase was characterized by direct cell counting, proliferation index determined by flow

Toshio Sasajima; Tadashi Miyagawa; Takamitsu Oku; Juri G. Gelovani; Ronald Finn; Ronald Blasberg

2004-01-01

384

Transition from in-plane to out-of-plane azimuthal enhancement inAu+Au collisions  

SciTech Connect

The incident energy at which the azimuthal distributions in semi-central heavy ion collisions change from in-plane to out-of-plane enhancement--E{sub tran} is studied as a function of mass of emitted particles, their transverse momentum and centrality for Au+Au collisions. The analysis is performed in a reference frame rotated with the sidewards flow angle ({Theta}{sub flow}) relative to the beam axis. A systematic decrease of E{sub tran} as function of mass of the reaction products, their transverse momentum and collision centrality is evidenced. The predictions of a microscopic transport model (IQMD) are compared with the experimental results.

Andronic, A.; Stoicea, G.; Petrovici, M.; Simion, V.; Crochet,P.; Alard, J.P.; Averbeck, R.; Barret, V.; Basrak, Z.; Bastid, N.; Bendarag, A.; Berek, G.; Caplar, R.; Devismes, A.; Dupieux, Dzelalija M.; Eskef, M.; Finck, Ch.; Fodor, Z.; Gobbi, A.; Grishkin, Y.; Hartmann,O.N.; Herrmann, N.; Hildenbrand, K.D.; Hong, B.; Kecskemeti, J.; Kim,Y.J.; Kirejczyk, M.; Korolija, M.; Kotte, R.; Kress, T.; Kutsche, R.; Lebedev, A.; Lee, K.S.; Leifels, Y.; Manko, V.; Merlitz, H.; Neubert, W.; Pelte, D.; Plettner, C.; Rami, F.; Resdorf, W.; de Schauenberg, B.; Schull, D.; Seres, Z.; Sikora, B.; Sim, K.S.; Siwek-Wilczynska, K.; Smolyankin, V.; Stockmeier, M.R.; Vasiliev, M.; Wagner, P.; Wisniewski,K.; Wohlfarth, D.; Yushmanov, I.; Zhilin, A.

2000-08-09

385

A Novel Member of the Trehalose Transporter Family Functions as an H+-Dependent Trehalose Transporter in the Reabsorption of Trehalose in Malpighian Tubules  

PubMed Central

In insects, Malpighian tubules are functionally analogous to mammalian kidneys in that they not only are essential to excrete waste molecules into the lumen but also are responsible for the reabsorption of indispensable molecules, such as sugars, from the lumen to the principal cells. Among sugars, the disaccharide trehalose is highly important to insects because it is the main hemolymph sugar to serve as a source of energy and carbon. The trehalose transporter TRET1 participates in the transfer of newly synthesized trehalose from the fat body across the cellular membrane into the hemolymph. Although transport proteins must play a pivotal role in the reabsorption of trehalose in Malpighian tubules, the molecular context underlying this process remains obscure. Previously, we identified a Tret1 homolog (Nlst8) that is expressed principally in the Malpighian tubules of the brown planthopper (BPH). Here, we used the Xenopus oocyte expression system to show that NlST8 exerts trehalose transport activity that is elevated under low pH conditions. These functional assays indicate that Nlst8 encodes a proton-dependent trehalose transporter (H-TRET1). To examine the involvement of Nlst8 in trehalose reabsorption, we analyzed the sugar composition of honeydew by using BPH with RNAi gene silencing. Trehalose was detected in the honeydew as waste excreted from Nlst8-dsRNA-injected BPH under hyperglycemic conditions. However, trehalose was not expelled from GFP-dsRNA-injected BPH even under hyperglycemic conditions. We conclude that NlST8 could participate in trehalose reabsorption driven by a H+ gradient from the lumen to the principal cells of the Malpighian tubules.

Kikuta, Shingo; Hagiwara-Komoda, Yuka; Noda, Hiroaki; Kikawada, Takahiro

2012-01-01

386

Naturally occurring and forced azimuthal modes in a turbulent jet  

NASA Technical Reports Server (NTRS)

Naturally occurring instability modes in an axisymmetric jet were studied using the modal frequency technique. The evolution of the modal spectrum was obtained for a jet with a Reynolds number based on a diameter of 400,000 for both laminar and turbulent nozzle boundary layers. In the early evolution of the jet the axisymmetric mode was predominant, with the azimuthal modes growing rapidly but dominating only the end of the potential core. The growth of the azimuthal was observed closer to the nozzle exit for the jet in the laminar boundary layer case than for the turbulent. Target modes for efficient excitation of the jet were determined and two cases of excitation were studied. First, a jet was excited simultaneously by two helical modes, m equals plus 1 and m equals minus 1 at a Strouhal number based on jet diameter of 0.15 and the axisymmetric mode, m equals 0 at a jet diameter of 0.6. Second, m equals plus one and m equals minus 1 at jet diameter equals 0.3 and m equals 0 at jet diameter equals 0.6 were excited simultaneously. The downstream evolution of the hydrodynamic modes and the spreading rate of the jet were documented for each case. Higher jet spreading rates, accompanied by distorted jet cross sections were observed for the cases where combinations of axisymmetric and helical forcings were applied.

Raman, Ganesh; Rice, Edward J.; Reshotko, Eli

1991-01-01

387

Recent progress in structure-function analyses of Nramp proton-dependent metal-ion transporters.  

PubMed

The natural resistance-associated macrophage protein (Nramp) homologs form a family of proton-coupled transporters that facilitate the cellular absorption of divalent metal ions (Me2+, including Mn2+, Fe2+, Co2+, and Cd2+). The Nramp, or solute carrier 11 (SLC11), family is conserved in eukaryotes and bacteria. Humans and rodents express 2 parologous genes that are associated with iron disorders and immune diseases. The NRAMP1 (SLC11A1) protein is specific to professional phagocytes and extrudes Me2+ from the phagosome to defend against ingested microbes; polymorphisms in the NRAMP1 gene are associated with various immune diseases. Several isoforms of NRAMP2 (SLC11A2, DMT1, DCT1) are expressed ubiquitously in recycling endosomes or specifically at the apical membrane of epithelial cells in intestine and kidneys, and can contribute to iron overload, whereas mutations impairing NRAMP2 function cause a form of congenital microcytic hypochromic anemia. Structure-function studies, using various experimental models, and mutagenesis approaches have begun to reveal the overall transmembrane organization of Nramp, some of the transmembrane segments (TMS) that are functionally important, and an unusual mechanism coupling Me2+ and proton H+ transport. The approaches used include functional complementation of yeast knockout strains, electrophysiology analyses in Xenopus oocytes, and transport assays that use mammalian and bacterial cells and direct and indirect measurements of SLC11 transporter properties. These complementary studies enabled the identification of TMS1 and 6 as crucial structural segments for Me2+ and H+ symport, and will help develop a deeper understanding of the Nramp transport mechanism and its contribution to Me2+ homeostasis in human health and diseases. PMID:17215883

Courville, P; Chaloupka, R; Cellier, M F M

2006-12-01

388

Danofloxacin-mesylate is a substrate for ATP-dependent efflux transporters  

PubMed Central

Background and purpose: Next to its broad antimicrobial spectrum, the therapeutic advantages of the fluoroquinolone antimicrobial drug Danofloxacin-Mesylate (DM) are attributed to its rapid distribution to the major target tissues such as lungs, intestines and the mammary gland in animals. Previous analyses revealed that effective drug concentrations are achieved also in luminal compartments of these organs, suggesting that active transport proteins facilitate excretion into the luminal space. Members of the ATP-Binding Cassette (ABC) superfamily, including P-gp, BCRP and MRP2 are known to be expressed in many tissue barriers and in cell-membranes facing luminal compartments. Hence we hypothesized that DM is a substrate for one of these efflux-transporters. Experimental approach: Confluent monolayers of Caco-2 cells, grown on microporous membranes in two-chamber devices were used. DM concentrations were measured by fluorimetric assay after HPLC of the culture media. Key results: DM transport across Caco-2 cells was asymmetric, with a rate of secretion exceeding that of absorption. The P-gp inhibitors PSC833 and GF120918 and the MRP-inhibitor MK571 partially decreased the secretion of DM and increased its absorption rate. The BCRP inhibitor, Ko143, decreased secretion only at a concentration of 1??M. When DM was applied together with ciprofloxacin, secretion as well as absorption of DM decreased. Conclusions and Implications: DM is a substrate for the efflux transporters P-gp and MRP2, whereas the specific role of BCRP in DM transport needs further evaluation. These findings provide a mechanistic basis for the understanding of the pharmacokinetics of DM in healthy and diseased individuals.

Schrickx, J A; Fink-Gremmels, J

2007-01-01

389

Magnesium and ATP dependence of K-Cl co-transport in low K+ sheep red blood cells.  

PubMed Central

1. In low K+ (LK) sheep red blood cells, depletion of adenosine triphosphate (ATP) by glycolysis inhibition induced specific effects on ouabain-resistant Cl(-)-dependent K+ transport (K-Cl co-transport), depending on the osmolarity: stimulation in isosmotic while inhibition in hyposmotic solutions. However, these effects depended upon the presence of internal Mg2+. 2. In LK sheep red blood cells, ATP constituted nearly 90% of the Mg2+ buffering capacity. As no significant reduction of total Mg2+ was observed after ATP depletion, the overall internal Mg2+ in ATP-depleted cells exists in the free form. 3. The dependence of K+ efflux on internal Mg2+ was also directly related to the presence of ATP. In control cells, Mg2+ constituted an endogenous inhibitor, inducing a 70% inhibition of K-Cl fluxes but only 30% in ATP-depleted cells. The Cl(-)-insensitive component of K+ efflux was unaffected by the divalent cation. 4. After Mg2+ removal, the rate of K+ efflux was significantly increased at all osmolarities, between 240 mosM (swollen cells) and 440 mosM (shrunken cells