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1

Randall-Sundrum graviton spin determination using azimuthal angular dependence  

E-print Network

Quantum interference of helicity amplitudes provides a powerful tool for measuring the spins of new particles. By looking at the azimuthal angular dependence of the differential cross-section in the production followed by decay of a new particle species one can determine its spin by looking at the various cosine modes. The heavy spin-2 Kaluza-Klein (KK) graviton provides a unique signature with a $\\cos{(4 \\phi)}$ mode. We study the feasibility of this approach to measuring the spin of the KK graviton in the Randall-Sundrum Model at the LHC.

Hitoshi Murayama; Vikram Rentala

2009-04-29

2

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

3

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. PMID:22291144

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

2012-01-01

4

Anisotropic parton escape is the dominant source of azimuthal anisotropy from A Multi-Phase Transport  

E-print Network

We trace the development of azimuthal anisotropy ($v_n$) in A Multi-Phase Transport (AMPT) model using parton-parton collision history. The parton $v_n$ is studied as a function of the number of collisions of each parton in Au+Au and d+Au collisions at $\\sqrt{S_{NN}}$=200~GeV. It is found that the majority of $v_n$ comes from the anisotropic escape probability of partons, with no fundamental difference at low and high transverse momenta. The contribution to $v_n$ from the parton collective flow appears small; however, it is this small anisotropy from the collective flow, not that from the anisotropic escape probability, that is most relevant for medium properties in heavy ion collisions.

Liang He; Terrence Edmonds; Zi-Wei Lin; Feng Liu; Denes Molnar; Fuqiang Wang

2015-02-19

5

System size dependence of nuclear modification and azimuthal anisotropy of jet quenching  

E-print Network

We investigate the system size dependence of jet-quenching by analyzing transverse momentum spectra of neutral pions in Au+Au and Cu+Cu collisions at $\\sqrt{s_{\\textrm{NN}}}$ =200 GeV for different centralities. The fast partons are assumed to lose energy by radiating gluons as they traverse the plasma and undergo multiple collisions. The energy loss per collision, $\\epsilon$, is taken as proportional to $E$(where $E$ is the energy of the parton), proportional to $\\sqrt{E}$, or a constant depending on whether the formation time of the gluon is less than the mean path, greater than the mean free path but less than the path length, or greater than the path length of the partons, respectively. NLO pQCD is used to evaluate pion production by modifying the fragmentation function to account for the energy loss. We reproduce the nuclear modification factor $R_\\textrm{AA}$ by treating $\\epsilon$ as the only free parameter, depending on the centrality and the mechanism of energy loss. These values are seen to explain the nuclear modification of prompt photons, caused by the energy lost by final state quarks before they fragment into photons. These also reproduce the azimuthal asymmetry of transverse momentum distribution for pions within a factor of two and for prompt photons in a fair agreement with experimental data.

Somnath De; Dinesh K. Srivastava

2011-09-26

6

System size dependence of nuclear modification and azimuthal anisotropy of jet quenching  

NASA Astrophysics Data System (ADS)

We investigate the system size dependence of jet quenching by analysing transverse momentum spectra of neutral pions in Au+Au and Cu+Cu collisions at \\sqrt{s_{\\textrm {NN}}} =200 GeV for different centralities. The fast partons are assumed to lose energy by radiating gluons as they traverse the plasma and undergo multiple collisions. The energy loss per collision, ?, is taken as proportional to E (where E is the energy of the parton), proportional to \\sqrt{E}, or a constant depending on whether the formation time of the gluon is less than the mean path, greater than the mean-free path but less than the path length, or greater than the path length of the partons, respectively. NLO pQCD is used to evaluate pion production by modifying the fragmentation function to account for the energy loss. We reproduce the nuclear modification factor RAA by treating ? as the only free parameter, depending on the centrality and the mechanism of energy loss. These values are seen to explain the nuclear modification of prompt photons caused by the energy lost by final state quarks before they fragment into photons. These also reproduce the azimuthal asymmetry of transverse momentum distribution for pions within a factor of 2 and for prompt photons in fair agreement with experimental data.

De, Somnath; Srivastava, Dinesh K.

2012-01-01

7

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

8

Rapidity and centrality dependence of azimuthal correlations in Deuteron-Gold collisions at RHIC  

E-print Network

We calculate azimuthal correlations in dAu collisions at different rapidities and centralities and argue that experimentally observed depletion of the back-to-back pick can be quantitatively explained by gluon saturation in the Color Glass Condensate of the Gold nucleus.

Kirill Tuchin

2010-06-01

9

On the azimuthally dependent contribution of crustal magnetization to the magnetic field  

Microsoft Academic Search

The way in which induced or remanent magnetization contributes to the crustal magnetic field at a point r on or above the Earth's surface is investigated. It is shown that only smoothly varying components of magnetization along an azimuth phi about r contribute to the crustal magnetic field. Stated mathematically, if the distribution of magnetization is expanded in a discrete

Vincent Lesur

2000-01-01

10

Magnetic-azimuth dependence of D-layer radio reflectivity, using lightning sferics as radio transmitters  

NASA Astrophysics Data System (ADS)

The Very Low Frequency (3-30 kHz) and Low-Frequency (30-300 kHz) radiation from lightning strokes provides a convenient intense source for studying radio propagation in the ionospheric D-region [Cheng and Cummer, 2005; Cheng et al., 2006; Cheng et al., 2007; Cummer et al., 1998; Jacobson et al., 2010; Shao and Jacobson, 2009]. In this poster we present a new study of the magnetic-azimuth dependence of D-layer radio reflectivity at relatively short ranges (r < 1000 km). This range regime is poorly adapted to a waveguide approach but is well treated by our discrete-reflection approach [Jacobson et al., 2009]. We use cloud-to-ground strokes, which are ~100X more numerous than the Narrow Bipolar Pulse sferics to which our method had previously been confined. Cheng, Z., and S. A. Cummer (2005), Broadband VLF measurements of lightning-induced ionospheric perturbations, Geophys. Res. Lett., 32, L08804, doi:08810.01029/02004GL022187. Cheng, Z., S. A. Cummer, D. N. Baker, and S. G. Kanekal (2006), Nighttime D region electron density profiles and variabilities inferred from broadband measurements using VLF radio emissions from lightning, J. Geophys. Res., 111, A05302, doi:05310.01029/02005JA011308. Cheng, Z., S. A. Cummer, H.-T. Su, and R.-R. Hsu (2007), Broadband very low frequency measurement of D region ionospheric perturbations caused by lightning electromagnetic pulses, J. Geophys. Res., 112, A06318. Cummer, S. A., U. S. Inan, and T. F. Bell (1998), Ionospheric D region remote sensing using VLF radio atmospherics, Radio Sci., 33, 1781-1792. Jacobson, A. R., X. Shao, and R. H. Holzworth (2009), Full-wave reflection of lightning long-wave radio pulses from the ionospheric D-region: Numerical model, J. Geophys. Res.- Space, 114, A03303, doi:03310.01029/02008JA013642. Jacobson, A. R., R. Holzworth, and X.-M. Shao (2010), Full-wave reflection of lightning long-wave radio pulses from the ionospheric D-region: Comparison with midday observations of broadband lightning signals, J. Geophys. Res. -Space, 115, A00E27, doi:10.1029/2009JA014540. Shao, X.-M., and A. R. Jacobson (2009), Model simulation of Very-Low-Frequency and Low-Frequency lightning signal propagation over intermediate ranges, IEEE Trans. Electromag. Compat., 51(3), 519-525.

Jacobson, A. R.; Shao, X.; Holzworth, R. H.; Lay, E. H.

2011-12-01

11

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

NASA Astrophysics Data System (ADS)

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.; Akopov, N.; Akopov, Z.; Amarian, M.; Aschenauer, E. C.; Augustyniak, W.; Avakian, R.; Avetissian, A.; Avetisyan, E.; Ball, B.; Belostotski, S.; Bianchi, N.; Blok, H. P.; Böttcher, H.; Borissov, A.; Bowles, J.; Bryzgalov, V.; Burns, J.; Capiluppi, M.; Capitani, G. P.; Cisbani, E.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Deconinck, W.; Leo, R. De; Nardo, L. De; Sanctis, E. De; Diefenthaler, M.; Nezza, P. Di; Düren, M.; Ehrenfried, M.; Elbakian, G.; Ellinghaus, F.; Fabbri, R.; Fantoni, A.; Felawka, L.; Frullani, S.; Gabbert, D.; Gapienko, G.; Gapienko, V.; Garibaldi, F.; Gavrilov, G.; Gharibyan, V.; Giordano, F.; Gliske, S.; Guler, H.; Guzey, V.; Haan, S.; Hadjidakis, C.; Hartig, M.; Hasch, D.; Hill, G.; 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.; Lagamba, L.; Lamb, R.; Lapikás, L.; Lehmann, I.; Lenisa, P.; López Ruiz, A.; Lorenzon, W.; Lu, X.-G.; Lu, X.-R.; Ma, B.-Q.; Mahon, D.; Makins, N. C. R.; Manaenkov, S. I.; Manfré, L.; Mao, Y.; Marianski, B.; de La Ossa, A. Martinez; Marukyan, H.; Miller, C. A.; Miyachi, Y.; Movsisyan, A.; Muccifora, V.; Murray, M.; Mussgiller, A.; Nappi, E.; Naryshkin, Y.; Nass, A.; Negodaev, M.; Nowak, W.-D.; Pappalardo, L. L.; Perez-Benito, R.; Raithel, M.; Reimer, P. E.; Reolon, A. R.; Riedl, C.; Rith, K.; Rosner, G.; Rostomyan, A.; Rubin, J.; Ryckbosch, D.; Salomatin, Y.; Schäfer, A.; Schnell, G.; Schüler, K. P.; Shanidze, R.; Shibata, T.-A.; Shutov, V.; Stancari, M.; Statera, M.; Steffens, E.; Steijger, J. J. M.; Stewart, J.; Stinzing, F.; Taroian, S.; Terkulov, A.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; Haarlem, Y. Van; Hulse, C. Van; Varanda, M.; Veretennikov, D.; Vikhrov, V.; Vilardi, I.; Wang, S.; Yaschenko, S.; Ye, H.; Ye, Z.; Yu, W.; Zeiler, D.; Zihlmann, B.; Zupranski, P.; sHERMES Collaboration

2010-03-01

12

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

E-print Network

The nuclear-mass dependence of azimuthal cross section asymmetries with respect to charge and longitudinal polarization of the lepton beam is studiedfor hard exclusive electroproduction of real photons. The observed beam-charge and beam-helicity asymmetries are attributed to the interference between the Bethe-Heitler and 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.

The HERMES collaboration; A. Airapetian

2010-01-22

13

Dependence of planar alignment layer upon enhancement of azimuthal anchoring energy by reactive mesogens  

NASA Astrophysics Data System (ADS)

Reactive mesogens (RMs) can enhance the azimuthal anchoring energy of planar alignment layers used in liquid crystal (LC) devices; herein, we studied the interactions between the RMs and the planar alignment material that determine whether this enhancement can occur. Two alignment-layer materials were studied: polyamic acid (PA) and polyimide (PI). The addition of RMs to the PI-type alignment layer was effective in enhancing the azimuthal anchoring energy, whereas the addition of RMs to the PA-type alignment layer had little effect. Surface analysis revealed that the RMs adhered well to the PI-type alignment surface only; in the resulting cell, the presence of the RMs enhanced both the rise and decay times in fringe field switching (FFS)-mode operation.

Kim, Youngsik; Lee, You-Jin; Baek, Ji-Ho; Yu, Chang-Jae; Kim, Jae-Hoon

2015-01-01

14

Multiplicity dependence of two-particle azimuthal correlations in pp collisions at the LHC  

NASA Astrophysics Data System (ADS)

We present the measurements of particle pair yields per trigger particle obtained from di-hadron azimuthal correlations in pp collisions at = 0 .9, 2.76, and 7 TeV recorded with the ALICE detector. The yields are studied as a function of the charged particle multiplicity. Taken together with the single particle yields the pair yields provide information about parton fragmentation at low transverse momenta, as well as on the contribution of multiple parton interactions to particle production. Data are compared to calculations using the PYTHIA6, PYTHIA8, and PHOJET event generators. [Figure not available: see fulltext.

Abelev, B.; Adam, J.; Adamová, D.; Adare, A. M.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agocs, A. G.; Agostinelli, A.; Ahammed, Z.; Ahmad Masoodi, A.; Ahmad, N.; Ahmed, I.; Ahn, S. U.; Ahn, S. A.; Aimo, I.; Ajaz, M.; Akindinov, A.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altini, V.; Altinpinar, S.; Altsybeev, I.; Andrei, C.; Andronic, A.; Anguelov, V.; Anielski, J.; Anson, C.; Anti?i?, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arbor, N.; Arcelli, S.; Arend, A.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I. C.; Arslandok, M.; Asryan, A.; Augustinus, A.; Averbeck, R.; Awes, T. C.; Äystö, J.; Azmi, M. D.; Bach, M.; Badalà, A.; Baek, Y. W.; Bailhache, R.; Bala, R.; Baldisseri, A.; Baltasar Dos Santos Pedrosa, F.; Bán, J.; Baral, R. C.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartke, J.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batyunya, B.; Batzing, P. C.; Baumann, C.; Bearden, I. G.; Beck, H.; Behera, N. K.; Belikov, I.; Bellini, F.; Bellwied, R.; Belmont-Moreno, E.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdanikov, Y.; Berenyi, D.; Bergognon, A. A. E.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhati, A. K.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Biel?ík, J.; Biel?íková, J.; Bilandzic, A.; Bjelogrlic, S.; Blanco, F.; Blanco, F.; Blau, D.; Blume, C.; Boccioli, M.; Bock, F.; Böttger, S.; Bogdanov, A.; Bøggild, H.; Bogolyubsky, M.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Bornschein, J.; Bossú, F.; Botje, M.; Botta, E.; Braidot, E.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brun, R.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Caffarri, D.; Cai, X.; Caines, H.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Canoa Roman, V.; Cara Romeo, G.; Carena, F.; Carena, W.; Carlin Filho, N.; Carminati, F.; Casanova Díaz, A.; Castillo Castellanos, J.; Castillo Hernandez, J. F.; Casula, E. A. R.; Catanescu, V.; Cavicchioli, C.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Chang, B.; Chapeland, S.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Chochula, P.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Conesa Balbastre, G.; Conesa del Valle, Z.; Connors, M. E.; Contin, G.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortese, P.; Cortés Maldonado, I.; Cosentino, M. R.; Costa, F.; Cotallo, M. E.; Crescio, E.; Crochet, P.; Cruz Alaniz, E.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Czopowicz, T. R.; Dainese, A.; Dang, R.; Danu, A.; Das, I.; Das, S.; Das, D.; Das, K.; Dash, S.; Dash, A.; De, S.; de Barros, G. O. V.; De Caro, A.; de Cataldo, G.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; Delagrange, H.; Deloff, A.; De Marco, N.; Dénes, E.; De Pasquale, S.; Deppman, A.; Erasmo, G. D.; de Rooij, R.; Diaz Corchero, M. A.; Di Bari, D.; Dietel, T.; Di Giglio, C.; Di Liberto, S.; Di Mauro, A.; Di Nezza, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Dobrowolski, T.; Dönigus, B.; Dordic, O.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Dutta Majumdar, A. K.; Elia, D.; Elwood, B. G.; Emschermann, D.; Engel, H.; Erazmus, B.; Erdal, H. A.; Eschweiler, D.; Espagnon, B.; Estienne, M.; Esumi, S.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabris, D.; Faivre, J.; Falchieri, D.; Fantoni, A.; Fasel, M.; Fehlker, D.; Feldkamp, L.; Felea, D.; Feliciello, A.; Fenton-Olsen, B.; Feofilov, G.; Fernández Téllez, A.; Ferretti, A.; Festanti, A.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Floratos, E.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Garishvili, I.; Gerhard, J.; Germain, M.; Gheata, M.; Gheata, A.; Ghidini, B.; Ghosh, P.; Gianotti, P.; Giubellino, P.; Gladysz-Dziadus, E.; Glässel, P.; Goerlich, L.; Gomez, R.; Ferreiro, E. G.; González-Zamora, P.; Gorbunov, S.; Goswami, A.; Gotovac, S.; Graczykowski, L. K.; Grajcarek, R.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Gros, P.; Grosse-Oetringhaus, J. F.; Grossiord, J.-Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Guilbaud, M.

2013-09-01

15

Dependence of enhanced asymmetry-induced transport on collision frequency  

SciTech Connect

A single-particle code with collisional effects is used to study how asymmetry-induced radial transport in a non-neutral plasma depends on collision frequency. For asymmetries of the form ?{sub 1}(r)?cos(kz)?cos(?t?l?), two sources for the transport have been identified: resonant particles and axially trapped particles. The simulation shows that this latter type, which occurs near the radius where ? matches the azimuthal rotation frequency ?{sub R}, is usually dominant at low collision frequency ? but becomes negligible at higher ?. This behavior can be understood by noting that axially trapped particles have a lower trapping frequency than resonant particles. In the low ? (banana) regime, the radial oscillations have amplitude ?r???v{sub r}/?{sub T}, so axially trapped particles dominate, and the transport may even exceed the resonant particle plateau regime level. As ? increases, collisions start to interrupt the slower axially trapped particle oscillations, while the resonant particles are still in the banana regime, so the axially trapped particle contribution to the transport decreases. At the largest ? values, axially trapped particle transport is negligible and the observed diffusion coefficient matches that given by plateau regime resonant particle theory. Heuristic models based on these considerations give reasonable agreement with the observed scaling laws for the value of the collision frequency where axially trapped particle transport starts to decrease and for the enhancement of the diffusion coefficient produced by axially trapped particles.

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

2014-07-15

16

Dependence of enhanced asymmetry-induced transport on collision frequency  

NASA Astrophysics Data System (ADS)

A single-particle code with collisional effects is used to study how asymmetry-induced radial transport in a non-neutral plasma depends on collision frequency. For asymmetries of the form ?1(r) cos(kz) cos(?t-l?), two sources for the transport have been identified: resonant particles and axially trapped particles. The simulation shows that this latter type, which occurs near the radius where ? matches the azimuthal rotation frequency ?R, is usually dominant at low collision frequency ? but becomes negligible at higher ?. This behavior can be understood by noting that axially trapped particles have a lower trapping frequency than resonant particles. In the low ? (banana) regime, the radial oscillations have amplitude ?r ? vr/?T, so axially trapped particles dominate, and the transport may even exceed the resonant particle plateau regime level. As ? increases, collisions start to interrupt the slower axially trapped particle oscillations, while the resonant particles are still in the banana regime, so the axially trapped particle contribution to the transport decreases. At the largest ? values, axially trapped particle transport is negligible and the observed diffusion coefficient matches that given by plateau regime resonant particle theory. Heuristic models based on these considerations give reasonable agreement with the observed scaling laws for the value of the collision frequency where axially trapped particle transport starts to decrease and for the enhancement of the diffusion coefficient produced by axially trapped particles.

Eggleston, D. L.

2014-07-01

17

System Size Dependence of Azimuthal Correlations in Relativistic Heavy Ion Collisions  

E-print Network

Systematic comparisons of jet pair correlations obtained in Cu+Cu and Au+Au collisions at $\\sqrt{s_{NN}}=$200 GeV are presented. The measured jet-pair distributions for both systems, show strong modification of the away-side jet. For the same number of participating nucleons, the modification does not show a strong dependence on the collision system. It is suggested that such comparisons can provide important constraints for models which predict specific path length dependent jet modification effects.

Wolf G. Holzmann; for the PHENIX Collaboration

2006-08-17

18

Observation of Transverse Spin-Dependent Azimuthal Correlations of Charged Pion Pairs in $p^\\uparrow+p$ at $\\sqrt{s}=200$ GeV  

E-print Network

We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in $p^\\uparrow+p$ collisions at RHIC. These correlations directly probe quark transversity distributions. We measure signals in excess of five standard deviations at high transverse momenta, at high pseudorapidities eta>0.5, and for pair masses around the mass of the rho-meson. This is the first direct transversity measurement in p+p collisions. Comparing the results to data from lepton-nucleon scattering will test the universality of these spin-dependent quantities.

STAR Collaboration; L. Adamczyk; J. K. Adkins; G. Agakishiev; M. M. Aggarwal; Z. Ahammed; I. Alekseev; J. Alford; A. Aparin; D. Arkhipkin; E. C. Aschenauer; G. S. Averichev; A. Banerjee; R. Bellwied; A. Bhasin; A. K. Bhati; P. Bhattarai; J. Bielcik; J. Bielcikova; L. C. Bland; I. G. Bordyuzhin; J. Bouchet; A. V. Brandin; I. Bunzarov; T. P. Burton; J. Butterworth; H. Caines; M. Calder'on de la Barca S'anchez; J. M. Campbell; D. Cebra; M. C. Cervantes; I. Chakaberia; P. Chaloupka; Z. Chang; S. Chattopadhyay; J. H. Chen; X. Chen; J. Cheng; M. Cherney; W. Christie; G. Contin; H. J. Crawford; S. Das; L. C. De Silva; R. R. Debbe; T. G. Dedovich; J. Deng; A. A. Derevschikov; B. di Ruzza; L. Didenko; C. Dilks; X. Dong; J. L. Drachenberg; J. E. Draper; C. M. Du; L. E. Dunkelberger; J. C. Dunlop; L. G. Efimov; J. Engelage; G. Eppley; R. Esha; O. Evdokimov; O. Eyser; R. Fatemi; S. Fazio; P. Federic; J. Fedorisin; Z. Feng; P. Filip; Y. Fisyak; C. E. Flores; L. Fulek; C. A. Gagliardi; D. Garand; F. Geurts; A. Gibson; M. Girard; L. Greiner; D. Grosnick; D. S. Gunarathne; Y. Guo; S. Gupta; A. Gupta; W. Guryn; A. Hamad; A. Hamed; R. Haque; J. W. Harris; L. He; S. Heppelmann; S. Heppelmann; A. Hirsch; G. W. Hoffmann; D. J. Hofman; S. Horvat; B. Huang; X. Huang; H. Z. Huang; P. Huck; T. J. Humanic; G. Igo; W. W. Jacobs; H. Jang; K. Jiang; E. G. Judd; S. Kabana; D. Kalinkin; K. Kang; K. Kauder; H. W. Ke; D. Keane; A. Kechechyan; Z. H. Khan; D. P. Kikola; I. Kisel; A. Kisiel; L. Kochenda; D. D. Koetke; T. Kollegger; L. K. Kosarzewski; A. F. Kraishan; P. Kravtsov; K. Krueger; I. Kulakov; L. Kumar; R. A. Kycia; M. A. C. Lamont; J. M. Landgraf; K. D. Landry; J. Lauret; A. Lebedev; R. Lednicky; J. H. Lee; X. Li; C. Li; W. Li; Z. M. Li; Y. Li; X. Li; M. A. Lisa; F. Liu; T. Ljubicic; W. J. Llope; M. Lomnitz; R. S. Longacre; X. Luo; Y. G. Ma; G. L. Ma; L. Ma; R. Ma; N. Magdy; R. Majka; A. Manion; S. Margetis; C. Markert; H. Masui; H. S. Matis; D. McDonald; K. Meehan; N. G. Minaev; S. Mioduszewski; B. Mohanty; M. M. Mondal; D. Morozov; M. K. Mustafa; B. K. Nandi; Md. Nasim; T. K. Nayak; G. Nigmatkulov; L. V. Nogach; S. Y. Noh; J. Novak; S. B. Nurushev; G. Odyniec; A. Ogawa; K. Oh; V. Okorokov; D. Olvitt Jr.; B. S. Page; R. Pak; Y. X. Pan; Y. Pandit; Y. Panebratsev; B. Pawlik; H. Pei; C. Perkins; A. Peterson; P. Pile; M. Planinic; J. Pluta; N. Poljak; K. Poniatowska; J. Porter; M. Posik; A. M. Poskanzer; N. K. Pruthi; J. Putschke; H. Qiu; A. Quintero; S. Ramachandran; R. Raniwala; S. Raniwala; R. L. Ray; H. G. Ritter; J. B. Roberts; O. V. Rogachevskiy; J. L. Romero; A. Roy; L. Ruan; J. Rusnak; O. Rusnakova; N. R. Sahoo; P. K. Sahu; I. Sakrejda; S. Salur; J. Sandweiss; A. Sarkar; J. Schambach; R. P. Scharenberg; A. M. Schmah; W. B. Schmidke; N. Schmitz; J. Seger; P. Seyboth; N. Shah; E. Shahaliev; P. V. Shanmuganathan; M. Shao; M. K. Sharma; B. Sharma; W. Q. Shen; S. S. Shi; Q. Y. Shou; E. P. Sichtermann; R. Sikora; M. Simko; M. J. Skoby; D. Smirnov; N. Smirnov; L. Song; P. Sorensen; H. M. Spinka; B. Srivastava; T. D. S. Stanislaus; M. Stepanov; R. Stock; M. Strikhanov; B. Stringfellow; M. Sumbera; B. Summa; X. Sun; Z. Sun; X. M. Sun; Y. Sun; B. Surrow; N. Svirida; M. A. Szelezniak; A. H. Tang; Z. Tang; T. Tarnowsky; A. N. Tawfik; J. H. Thomas; A. R. Timmins; D. Tlusty; M. Tokarev; S. Trentalange; R. E. Tribble; P. Tribedy; S. K. Tripathy; B. A. Trzeciak; O. D. Tsai; T. Ullrich; D. G. Underwood; I. Upsal; G. Van Buren; G. van Nieuwenhuizen; M. Vandenbroucke; R. Varma; A. N. Vasiliev; R. Vertesi; F. Videbæk; Y. P. Viyogi; S. Vokal; S. A. Voloshin; A. Vossen; G. Wang; Y. Wang; F. Wang; Y. Wang; H. Wang; J. S. Wang; J. C. Webb; G. Webb; L. Wen; G. D. Westfall; H. Wieman; S. W. Wissink; R. Witt; Y. F. Wu; Z. G. Xiao; W. Xie; K. Xin; Q. H. Xu; Z. Xu; H. Xu; N. Xu; Y. F. Xu; Q. Yang; Y. Yang; S. Yang; Y. Yang; C. Yang; Z. Ye; P. Yepes; L. Yi; K. Yip; I. -K. Yoo; N. Yu; H. Zbroszczyk; W. Zha; X. P. Zhang; J. Zhang; Y. Zhang; J. Zhang; J. B. Zhang; S. Zhang; Z. Zhang; J. Zhao; C. Zhong; L. Zhou; X. Zhu; Y. Zoulkarneeva; M. Zyzak

2015-04-01

19

Observation of Transverse Spin-Dependent Azimuthal Correlations of Charged Pion Pairs in $p^\\uparrow+p$ at $\\sqrt{s}=200$ GeV  

E-print Network

We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in $p^\\uparrow+p$ collisions at RHIC. These correlations directly probe quark transversity distributions. We measure signals in excess of five standard deviations at high transverse momenta, at high pseudorapidities eta>0.5, and for pair masses around the mass of the rho-meson. This is the first direct transversity measurement in p+p collisions. Comparing the results to data from lepton-nucleon scattering will test the universality of these spin-dependent quantities.

Adamczyk, L; Agakishiev, G; Aggarwal, M M; Ahammed, Z; Alekseev, I; Alford, J; Aparin, A; Arkhipkin, D; Aschenauer, E C; Averichev, G S; Banerjee, A; Bellwied, R; Bhasin, A; Bhati, A K; Bhattarai, P; Bielcik, J; Bielcikova, J; Bland, L C; Bordyuzhin, I G; Bouchet, J; Brandin, A V; Bunzarov, I; Burton, T P; Butterworth, J; Caines, H; S'anchez, M Calder'on de la Barca; Campbell, J M; Cebra, D; Cervantes, M C; Chakaberia, I; Chaloupka, P; Chang, Z; Chattopadhyay, S; Chen, J H; Chen, X; Cheng, J; Cherney, M; Christie, W; Contin, G; Crawford, H J; Das, S; De Silva, L C; Debbe, R R; Dedovich, T G; Deng, J; Derevschikov, A A; di Ruzza, B; Didenko, L; Dilks, C; Dong, X; Drachenberg, J L; Draper, J E; Du, C M; Dunkelberger, L E; Dunlop, J C; Efimov, L G; Engelage, J; Eppley, G; Esha, R; Evdokimov, O; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Fedorisin, J; Feng, Z; Filip, P; Fisyak, Y; Flores, C E; Fulek, L; Gagliardi, C A; Garand, D; Geurts, F; Gibson, A; Girard, M; Greiner, L; Grosnick, D; Gunarathne, D S; Guo, Y; Gupta, S; Gupta, A; Guryn, W; Hamad, A; Hamed, A; Haque, R; Harris, J W; He, L; Heppelmann, S; Hirsch, A; Hoffmann, G W; Hofman, D J; Horvat, S; Huang, B; Huang, X; Huang, H Z; Huck, P; Humanic, T J; Igo, G; Jacobs, W W; Jang, H; Jiang, K; Judd, E G; Kabana, S; Kalinkin, D; Kang, K; Kauder, K; Ke, H W; Keane, D; Kechechyan, A; Khan, Z H; Kikola, D P; Kisel, I; Kisiel, A; Kochenda, L; Koetke, D D; Kollegger, T; Kosarzewski, L K; Kraishan, A F; Kravtsov, P; Krueger, K; Kulakov, I; Kumar, L; Kycia, R A; Lamont, M A C; Landgraf, J M; Landry, K D; Lauret, J; Lebedev, A; Lednicky, R; Lee, J H; Li, X; Li, C; Li, W; Li, Z M; Li, Y; Lisa, M A; Liu, F; Ljubicic, T; Llope, W J; Lomnitz, M; Longacre, R S; Luo, X; Ma, Y G; Ma, G L; Ma, L; Ma, R; Magdy, N; Majka, R; Manion, A; Margetis, S; Markert, C; Masui, H; Matis, H S; McDonald, D; Meehan, K; Minaev, N G; Mioduszewski, S; Mohanty, B; Mondal, M M; Morozov, D; Mustafa, M K; Nandi, B K; Nasim, Md; Nayak, T K; Nigmatkulov, G; Nogach, L V; Noh, S Y; Novak, J; Nurushev, S B; Odyniec, G; Ogawa, A; Oh, K; Okorokov, V; Olvitt, D; Page, B S; Pak, R; Pan, Y X; Pandit, Y; Panebratsev, Y; Pawlik, B; Pei, H; Perkins, C; Peterson, A; Pile, P; Planinic, M; Pluta, J; Poljak, N; Poniatowska, K; Porter, J; Posik, M; Poskanzer, A M; Pruthi, N K; Putschke, J; Qiu, H; Quintero, A; Ramachandran, S; Raniwala, R; Raniwala, S; Ray, R L; Ritter, H G; Roberts, J B; Rogachevskiy, O V; Romero, J L; Roy, A; Ruan, L; Rusnak, J; Rusnakova, O; Sahoo, N R; Sahu, P K; Sakrejda, I; Salur, S; Sandweiss, J; Sarkar, A; Schambach, J; Scharenberg, R P; Schmah, A M; Schmidke, W B; Schmitz, N; Seger, J; Seyboth, P; Shah, N; Shahaliev, E; Shanmuganathan, P V; Shao, M; Sharma, M K; Sharma, B; Shen, W Q; Shi, S S; Shou, Q Y; Sichtermann, E P; Sikora, R; Simko, M; Skoby, M J; Smirnov, D; Smirnov, N; Song, L; Sorensen, P; Spinka, H M; Srivastava, B; Stanislaus, T D S; Stepanov, M; Stock, R; Strikhanov, M; Stringfellow, B; Sumbera, M; Summa, B; Sun, X; Sun, Z; Sun, X M; Sun, Y; Surrow, B; Svirida, N; Szelezniak, M A; Tang, A H; Tang, Z; Tarnowsky, T; Tawfik, A N; Thomas, J H; Timmins, A R; Tlusty, D; Tokarev, M; Trentalange, S; Tribble, R E; Tribedy, P; Tripathy, S K; Trzeciak, B A; Tsai, O D; Ullrich, T; Underwood, D G; Upsal, I; Van Buren, G; van Nieuwenhuizen, G; Vandenbroucke, M; Varma, R; Vasiliev, A N; Vertesi, R; Videbæk, F; Viyogi, Y P; Vokal, S; Voloshin, S A; Vossen, A; Wang, G; Wang, Y; Wang, F; Wang, H; Wang, J S; Webb, J C; Webb, G; Wen, L; Westfall, G D; Wieman, H; Wissink, S W; Witt, R; Wu, Y F; Xiao, Z G; Xie, W; Xin, K; Xu, Q H; Xu, Z; Xu, H; Xu, N; Xu, Y F; Yang, Q; Yang, Y; Yang, S; Yang, C; Ye, Z; Yepes, P; Yi, L; Yip, K; Yoo, I -K; Yu, N; Zbroszczyk, H; Zha, W; Zhang, X P; Zhang, J; Zhang, Y; Zhang, J B; Zhang, S; Zhang, Z; Zhao, J; Zhong, C; Zhou, L; Zhu, X; Zoulkarneeva, Y; Zyzak, M

2015-01-01

20

Measurement of the Azimuthal Angle Dependence of Inclusive Jet Yields in Pb + Pb Collisions at ?s[subscript NN] = 2.76??TeV with the ATLAS Detector  

E-print Network

Measurements of the variation of inclusive jet suppression as a function of relative azimuthal angle, ??, with respect to the elliptic event plane provide insight into the path-length dependence of jet quenching. ATLAS has ...

Taylor, Frank E.

21

Electron transfer and energy loss processes in fluorine scattering on oxygen covered Ag(1 1 0) - Crystal azimuthal dependence  

NASA Astrophysics Data System (ADS)

Measurements of energy-losses and electron transfer processes in 1-4 keV fluorine ions and atoms scattering on clean and oxygen covered Ag(1 1 0) were studied. We report data for surface channeling conditions for different surface azimuths for the clean and oxygen covered O(2 × 1)-Ag(1 1 0) (2 × 1) reconstructed surface. Adsorption of oxygen results in strong changes in energy losses and a decrease in the negative ion fraction. Energy loss results are discussed in the light of calculations using non-linear models for stopping power, ab initio crystal structure calculations of the electronic density and semi-classical deterministic simulations.

Canario, A. R.; Guillemot, L.; Diaz-Valdés, J.; Valdés, J. E.; Vargas, P.; Esaulov, V. A.

2013-11-01

22

Gravity-dependent transport in industrial processes  

NASA Technical Reports Server (NTRS)

Gravity-dependent transport phenomena in various industrial processes are investigated in order to address a broader range of microgravity phenomena and to develop new applications of microgravity. A number of important topics are identified and analyzed in detail. The present article describes results on coating flow, zeolite growth, and rotating electrochemical system.

Ostrach, Simon; Kamotani, Yasuhiro

1994-01-01

23

Intrinsic spin-dependent thermal transport.  

PubMed

Most studies of spin caloritronic effects to date, including spin-Seebeck effect, utilize thin films on substrates. We use patterned ferromagnetic thin film to demonstrate the profound effect of a substrate on the spin-dependent thermal transport. With different sample patterns and on varying the direction of temperature gradient, both longitudinal and transverse thermal voltages exhibit asymmetric instead of symmetric spin dependence. This unexpected behavior is due to an out-of-plane temperature gradient imposed by the thermal conduction through the substrate and the mixture of anomalous Nernst effects. Only with substrate-free samples have we determined the intrinsic spin-dependent thermal transport with characteristics and field sensitivity similar to those of the anisotropic magnetoresistance effect. PMID:22181905

Huang, S Y; Wang, W G; Lee, S F; Kwo, J; Chien, C L

2011-11-18

24

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

25

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

26

Time-dependent angularly averaged inverse transport  

E-print Network

This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain.

Guillaume Bal; Alexandre Jollivet

2009-05-07

27

Spin Dependent Transport in Novel Magnetic Heterostructures  

NASA Astrophysics Data System (ADS)

Magnetic oxides have become of interest source for spin transport devices due to their high spin polarization. But the real applications of these oxides remains unsatisfactory up to date, mostly due to the change of properties as a result of nano structuring. Magnetite (Fe3O4) is one such a material. High Curie temperature and the half metallicity of Fe 3O4 make it a good potential candidate for spin transport devices. Studies have shown that the nano structuring Fe3O 4 changes most of it's important properties. This includes high saturation magnetization and drop of conductivity by a few orders of magnitude in Fe 3O4 thin films. In this study, we have successfully grown Fe3O4 by reactive sputtering and studied the effect of transition metal buffer layers on structural, transport, and magnetic properties of Fe3O 4. It is shown that the lattice strain created by different buffer layers has major impacts on the properties of Fe3O4 thin films. Also for the first time, the magnetic force microscopic measurements were carried out in Fe3O4 thin films through Verway transition. MFM data with the magnetization data have confirmed that the magnetization of Fe3O4 thin films rotate slightly out of the plane below the Verway transition. Fe3O4 thin films were also successfully used in fabricating spin valve structures with Chromium and Permalloy. Here, the Fe 3O4 was used to generated the spin polarized electrons through reflection instead of direct spin injection. This is a novel method that can be used to inject spins into materials with different conductivities, where the traditional direct spin injection fails. Also the effect of growth field on Fe3O4 and Fe3O4/Cr/Py spin valves were investigated. In Fe3O4 the growth field induced an uni-axial anisotropy while it creates a well define parallel and anti-parallel states in spin valves. Magneto thermal phenomenon including spin dependent Seebeck effectt, Planar Nernst effectt and Anomalous Nernst effectt were measured in ferromagnetic thin films and spin valves. Spin dependent Seebeck effectt and planar Nernst effectt were directly compared with the charge counterpart anisotropic magneto resistance. All the effects exhibited similar behavior indicating the same origin, namely spin dependent scattering.

Jayathilaka, Priyanga Buddhika

28

Sequence Dependence of Electronic Transport in DNA  

E-print Network

We study electronic transport in long DNA chains using the tight-binding approach for a ladder-like model of DNA. We find insulating behavior with localizaton lengths xi ~ 25 in units of average base-pair seperation. Furthermore, we observe small, but significant differences between lambda-DNA, centromeric DNA, promoter sequences as well as random-ATGC DNA.

Antonio Rodriguez; Rudolf A. Roemer; Matthew S. Turner

2005-08-30

29

TonB-Dependent Transporters Expressed by Neisseria gonorrhoeae  

PubMed Central

Neisseria gonorrhoeae causes the common sexually transmitted infection, gonorrhea. This microorganism is an obligate human pathogen, existing nowhere in nature except in association with humans. For growth and proliferation, N. gonorrhoeae requires iron and must acquire this nutrient from within its host. The gonococcus is well-adapted for growth in diverse niches within the human body because it expresses efficient transport systems enabling use of a diverse array of iron sources. Iron transport systems facilitating the use of transferrin, lactoferrin, and hemoglobin have two components: one TonB-dependent transporter and one lipoprotein. A single component TonB-dependent transporter also allows N. gonorrhoeae to avail itself of iron bound to heterologous siderophores produced by bacteria within the same ecological niche. Other TonB-dependent transporters are encoded by the gonococcus but have not been ascribed specific functions. The best characterized iron transport system expressed by N. gonorrhoeae enables the use of human transferrin as a sole iron source. This review summarizes the molecular mechanisms involved in gonococcal iron acquisition from human transferrin and also reviews what is currently known about the other TonB-dependent transport systems. No vaccine is available to prevent gonococcal infections and our options for treating this disease are compromised by the emergence of antibiotic resistance. Because iron transport systems are critical for the survival of the gonococcus in vivo, the surface-exposed components of these systems are attractive candidates for vaccine development or therapeutic intervention. PMID:21747812

Cornelissen, Cynthia Nau; Hollander, Aimee

2011-01-01

30

Centrality dependence of dihadron correlations and azimuthal anisotropy harmonics in PbPb collisions at $\\sqrt{s_{NN}}= 2.76\\ \\mbox{TeV}$  

SciTech Connect

Measurements from the CMS experiment at the LHC of dihadron correlations for charged particles produced in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2.76 TeV are presented. The results are reported as a function of the particle transverse momenta (pt) and collision centrality over a broad range in relative pseudorapidity [Delta(eta)] and the full range of relative azimuthal angle [Delta(phi)]. The observed two-dimensional correlation structure in Delta(eta) and Delta(phi) is characterised by a narrow peak at (Delta(eta), Delta(phi)) approximately (0, 0) from jet-like correlations and a long-range structure that persists up to at least |Delta(eta)| = 4. An enhancement of the magnitude of the short-range jet peak is observed with increasing centrality, especially for particles of pt around 1-2 GeV/c. The long-range azimuthal dihadron correlations are extensively studied using a Fourier decomposition analysis. The extracted Fourier coefficients are found to factorise into a product of single-particle azimuthal anisotropies up to pt approximately 3-3.5 GeV/c for at least one particle from each pair, except for the second-order harmonics in the most central PbPb events. Various orders of the single-particle azimuthal anisotropy harmonics are extracted for associated particle pt of 1-3 GeV/c, as a function of the trigger particle pt up to 20 GeV/c and over the full centrality range.

Chatrchyan, Serguei; et al.

2012-05-01

31

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.

32

Chloride dependent amino acid transport in the human small intestine  

Microsoft Academic Search

Carriers of beta amino acids and imino acids in the small intestine of rabbits and guinea pigs are chloride dependent, and a cotransport of chloride, sodium, and 2-methyl-aminoisobutyric acid has been shown. This study examines the chloride dependence of amino acid transport in the human small intestine. The steady state tissue uptake of amino acids, given as the ratio between

L K Munck

1995-01-01

33

ATP-DEPENDENT SUGAR TRANSPORT COMPLEXITY IN HUMAN ERYTHROCYTES  

PubMed Central

Human erythrocyte glucose sugar transport was examined in resealed red cell ghosts under equilibrium exchange conditions ([sugar]intracellular = [sugar]extracellular). Exchange 3-O-methylglucose (3MG) import and export are monophasic in the absence of cytoplasmic ATP but are biphasic when ATP is present. Biphasic exchange is observed as the rapid filling of a large compartment (66% cell volume) followed by the slow filling of the remaining cytoplasmic space. Biphasic exchange at 20 mM 3MG eliminates the possibility that the rapid exchange phase represents ATP-dependent 3MG binding to the glucose transport protein (GLUT1; cellular [GLUT1] ? 20 ?M). Immunofluorescence activated cell sorting analysis shows that biphasic exchange does not result from heterogeneity in cell size or GLUT1 content. Nucleoside transporter mediated uridine exchange proceeds as rapidly as 3MG exchange but is monoexponential regardless of cytoplasmic [ATP]. This eliminates cellular heterogeneity or an ATP-dependent, nonspecific intracellular diffusion barrier as causes of biphasic exchange. Red cell ghost 3MG and uridine equilibrium volumes (130 fL) are unaffected by ATP. GLUT1 intrinsic activity is unchanged during rapid and slow phases of 3MG exchange. Two models for biphasic sugar transport are presented in which 3MG must overcome a sugar-specific, physical (diffusional) or chemical (isomerization) barrier to equilibrate with cell water. Partial transport inhibition using cytochalasin B or maltose depresses both rapid and slow phases of transport thereby eliminating the physical barrier hypothesis. We propose that biphasic 3MG transport results from ATP-dependent, differential transport of 3MG anomers in which Vmax/Km(app) for ?-3MG exchange transport is 19-fold greater than Vmax/Km(app) for ?-3MG transport. PMID:16928769

Leitch, Jeffry; Carruthers, Anthony

2014-01-01

34

TonB-dependent transporters and their occurrence in cyanobacteria  

PubMed Central

Background Different iron transport systems evolved in Gram-negative bacteria during evolution. Most of the transport systems depend on outer membrane localized TonB-dependent transporters (TBDTs), a periplasma-facing TonB protein and a plasma membrane localized machinery (ExbBD). So far, iron chelators (siderophores), oligosaccharides and polypeptides have been identified as substrates of TBDTs. For iron transport, three uptake systems are defined: the lactoferrin/transferrin binding proteins, the porphyrin-dependent transporters and the siderophore-dependent transporters. However, for cyanobacteria almost nothing is known about possible TonB-dependent uptake systems for iron or other substrates. Results We have screened all publicly available eubacterial genomes for sequences representing (putative) TBDTs. Based on sequence similarity, we identified 195 clusters, where elements of one cluster may possibly recognize similar substrates. For Anabaena sp. PCC 7120 we identified 22 genes as putative TBDTs covering almost all known TBDT subclasses. This is a high number of TBDTs compared to other cyanobacteria. The expression of the 22 putative TBDTs individually depends on the presence of iron, copper or nitrogen. Conclusion We exemplified on TBDTs the power of CLANS-based classification, which demonstrates its importance for future application in systems biology. In addition, the tentative substrate assignment based on characterized proteins will stimulate the research of TBDTs in different species. For cyanobacteria, the atypical dependence of TBDT gene expression on different nutrition points to a yet unknown regulatory mechanism. In addition, we were able to clarify a hypothesis of the absence of TonB in cyanobacteria by the identification of according sequences. PMID:19821963

Mirus, Oliver; Strauss, Sascha; Nicolaisen, Kerstin; von Haeseler, Arndt; Schleiff, Enrico

2009-01-01

35

Azimuthal-angle dependence of charged-pion-interferometry measurements with respect to 2$^{\\rm nd}$- and $3^{\\rm rd}$-order event planes in Au$+$Au collisions at $\\sqrt{s_{_{NN}}}=200$ GeV  

E-print Network

Charged-pion-interferometry measurements were made with respect to the 2$^{\\rm nd}$- and 3$^{\\rm rd}$-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 2$^{\\rm nd}$- and 3$^{\\rm rd}$-order event planes. The results for the 2$^{\\rm nd}$-order dependence indicate that the initial eccentricity is reduced during the medium evolution, but not reversed in the final state, which is consistent with previous results. In contrast, the results for the 3$^{\\rm rd}$-order dependence indicate that the initial triangular shape is significantly reduced and potentially reversed by the end of the medium evolution, and that the 3$^{\\rm rd}$-order oscillations are largely dominated by the dynamical effects from triangular flow.

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

2014-01-29

36

Azimuthal-angle dependence of charged-pion-interferometry measurements with respect to second- and third-order event planes in Au+Au collisions at ?[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-Å; 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

37

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  

SciTech Connect

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. [Institute of Solid State Physics (ISSP), Association EUROATOM-University of Latvia, Kengaraga iela 8, LV-1063 Riga (Latvia)] [Institute of Solid State Physics (ISSP), Association EUROATOM-University of Latvia, Kengaraga iela 8, LV-1063 Riga (Latvia); Avramidis, K. A.; Franck, J.; Jelonnek, J. [Karlsruhe Institute of Technology (KIT), Institute for Pulsed Power and Microwave Technology (IHM), Association EURATOM-KIT, Kaiserstrasse 12, 76131 Karlsruhe (Germany)] [Karlsruhe Institute of Technology (KIT), Institute for Pulsed Power and Microwave Technology (IHM), Association EURATOM-KIT, Kaiserstrasse 12, 76131 Karlsruhe (Germany)

2014-01-15

38

Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires  

E-print Network

Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires Yuri M. Zuev, Jin properties of individual single crystal antimony telluride (Sb2Te3) nanowires with diameters in the range figure of merit in single crystal chalcogenide Sb2Te3 NWs. Antimony telluride (Sb2Te3) is a small bandgap

Heller, Eric

39

The CU 2-dimensional MAX-DOAS instrument - Part 1: Retrieval of NO2 in 3 dimensions and azimuth dependent OVOC ratios  

NASA Astrophysics Data System (ADS)

We present an innovative instrument telescope, and describe a retrieval method to probe 3-D distributions of atmospheric trace gases that are relevant to air pollution and tropospheric chemistry. The University of Colorado (CU) two dimensional (2-D) Multi-AXis-Differential Optical Absorption Spectroscopy (CU 2D-MAX-DOAS) instrument measures nitrogen dioxide (NO2), formaldehyde (HCHO), glyoxal (CHOCHO), oxygen dimer (O2-O2, or O4) and water vapor (H2O); also nitrous acid (HONO), bromine monoxide (BrO), iodine monoxide (IO) among other gases can in principle be measured. Information about aerosols is derived through coupling with a radiative transfer model (RTM). The 2-D telescope has 3 modes of operation: (mode 1) measures solar scattered photons from any pair of elevation angle (-20° < EA < +90° or zenith; zero is to the horizon) and azimuth angle (-180° < AA < +180°; zero being North), (mode 2) measures any set of AA at constant EA (almucantar scans); and (mode 3) tracks the direct solar beam via a separate view port. Vertical profiles of trace gases are measured, and used to estimate planetary boundary layer height (PBL). Horizontal distributions are then derived using PBL and parameterization of RTM (Sinreich et al., 2013). NO2 is evaluated at different wavelengths (350, 450, and 560 nm), exploiting the fact that the effective path length varies systematically with wavelength. The area probed is constrained by O4 observations at nearby wavelengths, and has an effective radius of 7.5 to 20 km around the instrument location; i.e., up to 1250 km2 can be sampled near-instantaneously, and with high time resolution. The instrument was deployed as part of the Multi Axis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) in Mainz, Germany from 7 June to 6 July 2013. We present first measurements (modes 1 and 2 only) and describe a four-step retrieval to derive (a) boundary layer vertical profiles of NO2 and PBL; (b) near-surface horizontal distributions of NO2; (c) range resolved NO2 horizontal distribution measurements using an "onion peeling" approach; and (d) the ratios HCHO-to-NO2 (RFN), CHOCHO-to-NO2 (RGN), and CHOCHO-to-HCHO (RGF) at 14 pre-set azimuth angles distributed over a 360° view. 2D-MAX-DOAS provides an innovative, regional perspective about trace gases, their spatial and temporal concentration gradients, and maximizes information to compare near-surface observations with atmospheric models and satellites.

Ortega, I.; Koenig, T.; Sinreich, R.; Thomson, D.; Volkamer, R.

2014-11-01

40

Temperature dependence of electronic transport property in ferroelectric polymer films  

NASA Astrophysics Data System (ADS)

The leakage current mechanism of ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene prepared by Langmuir-Blodgett was investigated in the temperature range from 100 K to 350 K. The electron as the dominant injected carrier was observed in the ferroelectric copolymer films. The transport mechanisms in copolymer strongly depend on the temperature and applied voltage. From 100 K to 200 K, Schottky emission dominates the conduction. With temperature increasing, the Frenkel-Poole emission instead of the Schottky emission to conduct the carrier transport. When the temperature gets to 260 K, the leakage current becomes independent of temperature, and the space charge limited current conduction was observed.

Zhao, X. L.; Wang, J. L.; Tian, B. B.; Liu, B. L.; Zou, Y. H.; Wang, X. D.; Sun, S.; Sun, J. L.; Meng, X. J.; Chu, J. H.

2014-10-01

41

Three-Particle Azimuthal Correlations  

E-print Network

Two-particle azimuthal correlations in central Au+Au collisional at RHIC have revealed a broadened away-side structure, with respect to perpherial Au+Au, pp, and d+Au. This could be explained by different physics mechanisms such as: large angle gluon radiation, deflected jets, Cerenkov gluon radiation, and conical flow generated by hydrodynamic shock-waves. We can discriminate the scenarios with conical emission, Cerenkov radiation and conical flow, from the other mechanisms though three-particle correlations. In addition, the associated particle pT dependence can be used to distinguish conical flow from simple Cerenkov gluon radiation. We will discuss three-particle correlation analyses that have been performed at RHIC and what can be done at the LHC.

Jason Glyndwr Ulery

2007-09-11

42

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

43

Strain-modulation of spin-dependent transport in graphene  

SciTech Connect

We investigate strain modulation of the spin-dependent electron transport in a graphene junction using the transfer matrix method. As an analogy to optics, we define the modulation depth in the electron optics domain. Additionally, we discuss the transport properties and show that the modulation depth and the conductance depend on the spin-orbit coupling strength, the strain magnitude, the width of the strained area, and the energy of the incident electron. The conductances of the spin-down and spin-up electrons have opposite and symmetrical variations, which results in the analogous features of their modulation depths. The maximum conditions for both the modulation depth and the electron spin upset rate are also analyzed.

Cao, Zhen-Zhou, E-mail: zhenzhoucao@hotmail.com; Hou, Jin; Cheng, Yan-Fu, E-mail: chengyf@mail.scuec.edu.cn [College of Electronics and Information, South-Central University for Nationalities, Wuhan 430074 (China); Li, Guan-Qiang [Faculty of Science, Shaanxi University of Science and Technology, Xian 710021 (China); MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and Department of Applied Physics, Xi'an Jiaotong University, Xi'an 710049 (China)

2014-10-27

44

Temperature dependent electrical transport of disordered reduced graphene oxide  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

45

Fully spin-dependent transport of triangular graphene flakes  

Microsoft Academic Search

The magnetic moment and spin-polarized electron transport properties of triangular graphene flakes surrounded by boron nitride sheets (BNC structures) are studied by using first-principles calculations based on density functional theory. Their dependence on the BNC structure is discussed, revealing that small isolated graphene flakes have large magnetic moment. When the BNC structure is suspended between graphene electrodes, the spin-polarized charge

Tomoya Ono; Tadashi Ota; Yoshiyuki Egami

2011-01-01

46

MINARET: Towards a time-dependent neutron transport parallel solver  

NASA Astrophysics Data System (ADS)

We present the newly developed time-dependent 3D multigroup discrete ordinates neutron transport solver that has recently been implemented in the MINARET code. The solver is the support for a study about computing acceleration techniques that involve parallel architectures. In this work, we will focus on the parallelization of two of the variables involved in our equation: the angular directions and the time. This last variable has been parallelized by a (time) domain decomposition method called the parareal in time algorithm.

Baudron, A.-M.; Lautard, J. J.; Maday, Y.; Mula, O.

2014-06-01

47

Time-dependent deterministic transport on parallel architectures using PARTISN  

SciTech Connect

In addition to the ability to solve the static transport equation, the authors have also incorporated time dependence into the parallel S{sub N} code PARTISN. Using a semi-implicit scheme, PARTISN is capable of performing time-dependent calculations for both fissioning and pure source driven problems. They have applied this to various types of problems such as shielding and prompt fission experiments. This paper describes the form of the time-dependent equations implemented, their solution strategies in PARTISN including iteration acceleration, and the strategies used for time-step control. Results are presented for a iron-water shielding calculation and a criticality excursion in a uranium solution configuration.

Alcouffe, R.E.; Baker, R.S.

1998-07-01

48

Transport of hydrogen in metals with occupancy dependent trap energies  

SciTech Connect

Common diffusion trapping models for modeling hydrogen transport in metals are limited to traps with single de-trapping energies and a saturation occupancy of one. While they are successful in predicting typical mono isotopic ion implantation and thermal degassing experiments, they fail at describing recent experiments on isotope exchange at low temperatures. This paper presents a new modified diffusion trapping model with fill level dependent de-trapping energies that can also explain these new isotope exchange experiments. Density function theory (DFT) calculations predict that even mono vacancies can store between 6 and 12?H atoms with de-trapping energies that depend on the fill level of the mono vacancy. The new fill level dependent diffusion trapping model allows to test these DFT results by bridging the gap in length and time scale between DFT calculations and experiment.

Schmid, K., E-mail: klaus.schmid@ipp.mpg.de; Toussaint, U. von; Schwarz-Selinger, T. [Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching b. München (Germany)

2014-10-07

49

Transport of hydrogen in metals with occupancy dependent trap energies  

NASA Astrophysics Data System (ADS)

Common diffusion trapping models for modeling hydrogen transport in metals are limited to traps with single de-trapping energies and a saturation occupancy of one. While they are successful in predicting typical mono isotopic ion implantation and thermal degassing experiments, they fail at describing recent experiments on isotope exchange at low temperatures. This paper presents a new modified diffusion trapping model with fill level dependent de-trapping energies that can also explain these new isotope exchange experiments. Density function theory (DFT) calculations predict that even mono vacancies can store between 6 and 12 H atoms with de-trapping energies that depend on the fill level of the mono vacancy. The new fill level dependent diffusion trapping model allows to test these DFT results by bridging the gap in length and time scale between DFT calculations and experiment.

Schmid, K.; von Toussaint, U.; Schwarz-Selinger, T.

2014-10-01

50

Two-dimensional time dependent Riemann solvers for neutron transport  

SciTech Connect

A two-dimensional Riemann solver is developed for the spherical harmonics approximation to the time dependent neutron transport equation. The eigenstructure of the resulting equations is explored, giving insight into both the spherical harmonics approximation and the Riemann solver. The classic Roe-type Riemann solver used here was developed for one-dimensional problems, but can be used in multidimensional problems by treating each face of a two-dimensional computation cell in a locally one-dimensional way. Several test problems are used to explore the capabilities of both the Riemann solver and the spherical harmonics approximation. The numerical solution for a simple line source problem is compared to the analytic solution to both the P{sub 1} equation and the full transport solution. A lattice problem is used to test the method on a more challenging problem.

Brunner, Thomas A. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185-1186 (United States)]. E-mail: tabrunn@sandia.gov; Holloway, James Paul [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109-2014 (United States)

2005-11-20

51

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 (22.6muO·cm/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

52

Vesicular glutamate transporter-dependent glutamate release from astrocytes.  

PubMed

Astrocytes exhibit excitability based on variations of their intracellular Ca2+ concentrations, which leads to glutamate release, that in turn can signal to adjacent neurons. This glutamate-mediated astrocyte-neuron signaling occurs at physiological intracellular Ca2+ levels in astrocytes and includes modulation of synaptic transmission. The mechanism underlying Ca2+-dependent glutamate release from astrocytes is most likely exocytosis, because astrocytes express the protein components of the soluble N-ethyl maleimide-sensitive fusion protein attachment protein receptors complex, including synaptobrevin 2, syntaxin, and synaptosome-associated protein of 23 kDa. Although these proteins mediate Ca2+-dependent glutamate release from astrocytes, it is not well understood whether astrocytes express functional vesicular glutamate transporters (VGLUTs) that are critical for vesicle refilling. Here, we find in cultured and freshly isolated astrocytes the presence of brain-specific Na+-dependent inorganic phosphate cotransporter and differentiation-associated Na+-dependent inorganic phosphate cotransporter that have recently been identified as VGLUTs 1 and 2. Indirect immunocytochemistry showed a punctate pattern of VGLUT immunoreactivity throughout the entire cell body and processes, whereas pharmacological inhibition of VGLUTs abolished mechanically and agonist-evoked Ca2+-dependent glutamate release from astrocytes. Taken together, these data indicate that VGLUTs play a functional role in exocytotic glutamate release from astrocytes. PMID:15028755

Montana, Vedrana; Ni, Yingchun; Sunjara, Vice; Hua, Xue; Parpura, Vladimir

2004-03-17

53

Sodium-dependent bile salt transporters of the SCL10A Transporter Family: More than solute transporters  

PubMed Central

Summary The SLC10A transporter gene family consists of seven members and substrates transported by three members (SLC10A1, SLC10A2 and SLC10A6) are Na+-dependent. SLC10A1 (sodium taurocholate cotransporting polypeptide or NTCP) and SLC10A2 (apical sodium-dependent bile salt transporter or ASBT) transport bile salts and play an important role in maintaining enterohepatic circulation of bile salts. Solutes other than bile salts are also transported by NTCP. However, ASBT has not been shown to be a transporter for non-bile salt substrates. While the transport function of NTCP can potentially be used as liver function test, interpretation of such a test may be complicated by altered expression of NTCP in diseases and presence of drugs that may inhibit NTCP function. Transport of bile salts by NTCP and ASBT is inhibited by a number of drugs and it appears that ASBT is more permissive to drug inhibition than NTCP. The clinical significance of this inhibition in drug disposition and drug-drug interaction remains to be determined. Both NCTP and ASBT undergo post-translational regulations that involve phosphorylation/dephosphorylation, translocation to and retrieval from the plasma membrane and degradation by the ubiquitin-proteasome system. These posttranslational regulations are mediated via signaling pathways involving cAMP, calcium, nitric oxide, phosphoinositide-3-kinase (PI3K), protein kinase C (PKC) and protein phosphatases. There appears to be species difference in the substrate specificity and the regulation of plasma membrane localization of human and rodent NTCP. These differences should be taken into account when extrapolating rodent data for human clinical relevance and developing novel therapies. NTCP has recently been shown to play an important role in HBV and HDV infection by serving as a receptor for entry of these viruses into hepatocytes. PMID:24196564

Anwer, M. Sawkat; Stieger, Bruno

2013-01-01

54

Temperature dependent transport characteristics of graphene/n-Si diodes  

NASA Astrophysics Data System (ADS)

Realizing an optimal Schottky interface of graphene on Si is challenging, as the electrical transport strongly depends on the graphene quality and the fabrication processes. Such interfaces are of increasing research interest for integration in diverse electronic devices as they are thermally and chemically stable in all environments, unlike standard metal/semiconductor interfaces. We fabricate such interfaces with n-type Si at ambient conditions and find their electrical characteristics to be highly rectifying, with minimal reverse leakage current (<10-10 A) and rectification of more than 106. We extract Schottky barrier height of 0.69 eV for the exfoliated graphene and 0.83 eV for the CVD graphene devices at room temperature. The temperature dependent electrical characteristics suggest the influence of inhomogeneities at the graphene/n-Si interface. A quantitative analysis of the inhomogeneity in Schottky barrier heights is presented using the potential fluctuation model proposed by Werner and Güttler.

Parui, S.; Ruiter, R.; Zomer, P. J.; Wojtaszek, M.; van Wees, B. J.; Banerjee, T.

2014-12-01

55

Development of a cyclin-dependent kinase inhibitor devoid of ABC transporter-dependent drug resistance  

PubMed Central

Background: Cyclin-dependent kinases (CDKs) control cell cycle progression, RNA transcription and apoptosis, making them attractive targets for anticancer drug development. Unfortunately, CDK inhibitors developed to date have demonstrated variable efficacy. Methods: We generated drug-resistant cells by continuous low-dose exposure to a model pyrazolo[1,5-a]pyrimidine CDK inhibitor and investigated potential structural alterations for optimal efficacy. Results: We identified induction of the ATP-binding cassette (ABC) transporters, ABCB1 and ABCG2, in resistant cells. Assessment of features involved in the ABC transporter substrate specificity from a compound library revealed high polar surface area (>100?Å2) as a key determinant of transporter interaction. We developed ICEC-0782 that preferentially inhibited CDK2, CDK7 and CDK9 in the nanomolar range. The compound inhibited phosphorylation of CDK substrates and downregulated the short-lived proteins, Mcl-1 and cyclin D1. ICEC-0782 induced G2/M arrest and apoptosis. The permeability and cytotoxicity of ICEC-0782 were unaffected by ABC transporter expression. Following daily oral dosing, the compound inhibited growth of human colon HCT-116 and human breast MCF7 tumour xenografts in vivo by 84% and 94%, respectively. Conclusion: We identified a promising pyrazolo[1,5-a]pyrimidine compound devoid of ABC transporter interaction, highly suitable for further preclinical and clinical evaluation for the treatment of cancer. PMID:24071597

Kaliszczak, M; Patel, H; Kroll, S H B; Carroll, L; Smith, G; Delaney, S; Heathcote, D A; Bondke, A; Fuchter, M J; Coombes, R C; Barrett, A G M; Ali, S; Aboagye, E O

2013-01-01

56

Measurement of the azimuthal angle dependence of inclusive jet yields in Pb+Pb collisions at ?(sNN)=2.76 TeV with the ATLAS detector.  

PubMed

Measurements of the variation of inclusive jet suppression as a function of relative azimuthal angle, ??, with respect to the elliptic event plane provide insight into the path-length dependence of jet quenching. ATLAS has measured the ?? dependence of jet yields in 0.14 nb(-1) of ?(s(NN))=2.76 TeV Pb+Pb collisions at the LHC for jet transverse momenta p(T)>45 GeV in different collision centrality bins using an underlying event subtraction procedure that accounts for elliptic flow. The variation of the jet yield with ?? was characterized by the parameter, v(2)(jet), and the ratio of out-of-plane (??~?/2) to in-plane (??~0) yields. Nonzero v(2)(jet) values were measured in all centrality bins for p(T)<160 GeV. The jet yields are observed to vary by as much as 20% between in-plane and out-of-plane directions. PMID:24160592

Aad, G; Abajyan, T; Abbott, B; Abdallah, J; Abdel Khalek, S; Abdinov, O; Aben, R; Abi, B; Abolins, M; AbouZeid, O S; Abramowicz, H; Abreu, H; Abulaiti, Y; Acharya, B S; Adamczyk, L; Adams, D L; Addy, T N; Adelman, J; Adomeit, S; Adye, T; Aefsky, S; Agatonovic-Jovin, T; Aguilar-Saavedra, J A; Agustoni, M; Ahlen, S P; Ahmad, A; Ahsan, M; Aielli, G; Akesson, T P A; Akimoto, G; Akimov, A V; Alam, M A; Albert, J; Albrand, S; Alconada Verzini, M J; Aleksa, M; Aleksandrov, I N; Alessandria, F; Alexa, C; Alexander, G; Alexandre, G; Alexopoulos, T; Alhroob, M; Aliev, M; Alimonti, G; Alio, L; Alison, J; Allbrooke, B M M; Allison, L J; Allport, P P; Allwood-Spiers, S E; Almond, J; Aloisio, A; Alon, R; Alonso, A; Alonso, F; Altheimer, A; Alvarez Gonzalez, B; Alviggi, M G; Amako, K; Amaral Coutinho, Y; Amelung, C; Ammosov, V V; Amor Dos Santos, S P; Amorim, A; Amoroso, S; Amram, N; Anastopoulos, C; Ancu, L S; Andari, N; Andeen, T; Anders, C F; Anders, G; Anderson, K J; Andreazza, A; Andrei, V; Anduaga, X S; Angelidakis, S; Anger, P; Angerami, A; Anghinolfi, F; Anisenkov, A V; Anjos, N; Annovi, A; Antonaki, A; Antonelli, M; Antonov, A; Antos, J; Anulli, F; Aoki, M; Aperio Bella, L; Apolle, R; Arabidze, G; Aracena, I; Arai, Y; Arce, A T H; Arfaoui, S; Arguin, J-F; Argyropoulos, S; Arik, E; Arik, M; Armbruster, A J; Arnaez, O; Arnal, V; Artamonov, A; Artoni, G; Arutinov, D; Asai, S; Asbah, N; Ask, S; Åsman, B; Asquith, L; Assamagan, K; Astalos, R; Astbury, A; Atkinson, M; Atlay, N B; Auerbach, B; Auge, E; Augsten, K; Aurousseau, M; Avolio, G; Axen, D; Azuelos, G; Azuma, Y; Baak, M A; Bacci, C; Bach, A M; Bachacou, H; Bachas, K; Backes, M; Backhaus, M; Backus Mayes, J; Badescu, E; Bagiacchi, P; Bagnaia, P; Bai, Y; Bailey, D C; Bain, T; Baines, J T; Baker, O K; Baker, S; Balek, P; Balli, F; Banas, E; Banerjee, Sw; Banfi, D; Bangert, A; Bansal, V; Bansil, H S; Barak, L; Baranov, S P; Barber, T; Barberio, E L; Barberis, D; Barbero, M; Bardin, D Y; Barillari, T; Barisonzi, M; Barklow, T; Barlow, N; Barnett, B M; Barnett, R M; Baroncelli, A; Barone, G; Barr, A J; Barreiro, F; Barreiro Guimarães da Costa, J; Bartoldus, R; Barton, A E; Bartsch, V; Basye, A; Bates, R L; Batkova, L; Batley, J R; Battistin, M; Bauer, F; Bawa, H S; Beale, S; Beau, T; Beauchemin, P H; Beccherle, R; Bechtle, P; Beck, H P; Becker, K; Becker, S; Beckingham, M; Becks, K H; Beddall, A J; Beddall, A; Bedikian, S; Bednyakov, V A; Bee, C P; Beemster, L J; Beermann, T A; Begel, M; Belanger-Champagne, C; Bell, P J; Bell, W H; Bella, G; Bellagamba, L; Bellerive, A; Bellomo, M; Belloni, A; Beloborodova, O L; Belotskiy, K; Beltramello, O; Benary, O; Benchekroun, D; Bendtz, K; Benekos, N; Benhammou, Y; Benhar Noccioli, E; Benitez Garcia, J A; Benjamin, D P; Bensinger, J R; Benslama, K; Bentvelsen, S; Berge, D; Bergeaas Kuutmann, E; Berger, N; Berghaus, F; Berglund, E; Beringer, J; Bernard, C; Bernat, P; Bernhard, R; Bernius, C; Bernlochner, F U; Berry, T; Bertella, C; Bertolucci, F; Besana, M I; Besjes, G J; Bessidskaia, O; Besson, N; Bethke, S; Bhimji, W; Bianchi, R M; Bianchini, L; Bianco, M; Biebel, O; Bieniek, S P; Bierwagen, K; Biesiada, J; Biglietti, M; Bilbao De Mendizabal, J; Bilokon, H; Bindi, M; Binet, S; Bingul, A; Bini, C; Bittner, B; Black, C W; Black, J E; Black, K M; Blackburn, D; Blair, R E; Blanchard, J-B; Blazek, T; Bloch, I; Blocker, C; Blocki, J; Blum, W; Blumenschein, U; Bobbink, G J; Bobrovnikov, V S; Bocchetta, S S; Bocci, A; Boddy, C R; Boehler, M; Boek, J; Boek, T T; Boelaert, N; Bogaerts, J A; Bogdanchikov, A G; Bogouch, A; Bohm, C; Bohm, J; Boisvert, V; Bold, T; Boldea, V; Bolnet, N M; Bomben, M; Bona, M; Boonekamp, M; Bordoni, S; Borer, C; Borisov, A; Borissov, G; Borri, M; Borroni, S; Bortfeldt, J; Bortolotto, V; Bos, K; Boscherini, D; Bosman, M; Boterenbrood, H; Bouchami, J; Boudreau, J; Bouhova-Thacker, E V; Boumediene, D; Bourdarios, C; Bousson, N; Boutouil, S; Boveia, A; Boyd, J; Boyko, I R; Bozovic-Jelisavcic, I; Bracinik, J; Branchini, P; Brandt, A; Brandt, G; Brandt, O; Bratzler, U; Brau, B; Brau, J E; Braun, H M; Brazzale, S F; Brelier, B; Bremer, J; Brendlinger, K; Brenner, R; Bressler, S; Bristow, T M; Britton, D; Brochu, F M; Brock, I; Brock, R; Broggi, F; Bromberg, C; Bronner, J; Brooijmans, G; Brooks, T; Brooks, W K; Brost, E; Brown, G; Brown, J; Bruckman de Renstrom, P A; Bruncko, D; Bruneliere, R; Brunet, S; Bruni, A; Bruni, G; Bruschi, M; Bryngemark, L; Buanes, T; Buat, Q; Bucci, F; Buchanan, J; Buchholz, P; Buckingham, R M; Buckley, A G; Buda, S I; Budagov, I A; Budick, B; Bugge, L; Bulekov, O; Bundock, A C; Bunse, M; Buran, T; Burckhart, H; Burdin, S; Burgess, T; Burke, S; Busato, E; Büscher, V; Bussey, P; Buszello, C P; Butler, B; Butler, J M; Buttar, C M; Butterworth, J M; Buttinger, W; Byszewski, M; Cabrera Urbán, S; Caforio, D; Cakir, O; Calafiura, P; Calderini, G

2013-10-11

57

Path dependence in urban transport: An institutional analysis of urban passenger transport in Melbourne, Australia, 1956–2006  

Microsoft Academic Search

In order to deepen understanding of path dependence in urban transport, this article presents a case study of urban passenger transport institutions in Melbourne, Australia over 50 years. The institutional capacity of the roads and public transport sectors are explored separately and the trends are then compared and contrasted. The main components of the analysis are: structural changes to the

Nicholas Low; Rachel Astle

2009-01-01

58

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

59

Control parameter dependence of transport coefficients near the glass transition  

NASA Astrophysics Data System (ADS)

The master curves for transport coefficients, such as self-diffusion coefficient D, shear viscosity ?, and electrical conductivity ?, near the glass transition are studied based on the fact recently proposed by the present author that the long-time self-diffusion coefficients in both fragile and strong liquids are well described by the following two types of master curves, depending on whether the control parameter is an intensive one (X) or an extensive one (Y); f(x) = (1-x)2+?exp[62x3+?(1-x)2+?] and g(y) = (1-y)2/y, where x = X/Xf and y = Y/Yf, Xf and Yf being fictive singular points to be determined. Here ? = 4/3 for fragile liquids and 5/3 for strong liquids. The thermodynamic function Y = h(X) is then used to relate f(x) with g(y) and vice versa. The experimental data and the simulation results for the shear viscosity and the electrical conductivity are also analyzed by using the master curves f(x) and g(y). Thus, it is shown that any transport coefficients are well described by those master curves up to the deviation point, above which all the data start to deviate from the master curves and the system becomes out of equilibrium.

Tokuyama, Michio

2013-02-01

60

High temperature dependence of thermal transport in graphene foam  

NASA Astrophysics Data System (ADS)

In contrast to the decreased thermal property of carbon materials with temperature according to the Umklapp phonon scattering theory, highly porous free-standing graphene foam (GF) exhibits an abnormal characteristic that its thermal property increases with temperature above room temperature. In this work, the temperature dependence of thermal properties of free-standing GF is investigated by using the transient electro-thermal technique. Significant increase for thermal conductivity and thermal diffusivity from ?0.3 to 1.5 W m?1 K?1 and ?4 × 10?5 to ?2 × 10?4 m2 s?1 respectively is observed with temperature from 310 K to 440 K for three GF samples. The quantitative analysis based on a physical model for porous media of Schuetz confirms that the thermal conductance across graphene contacts rather than the heat conductance inside graphene dominates thermal transport of our GFs. The thermal expansion effect at an elevated temperature makes the highly porous structure much tighter is responsible for the reduction in thermal contact resistance. Besides, the radiation heat exchange inside the pores of GFs improves the thermal transport at high temperatures. Since free-standing GF has great potential for being used as supercapacitor and battery electrode where the working temperature is always above room temperature, this finding is beneficial for thermal design of GF-based energy applications.

Li, Man; Sun, Yi; Xiao, Huying; Hu, Xuejiao; Yue, Yanan

2015-03-01

61

High temperature dependence of thermal transport in graphene foam.  

PubMed

In contrast to the decreased thermal property of carbon materials with temperature according to the Umklapp phonon scattering theory, highly porous free-standing graphene foam (GF) exhibits an abnormal characteristic that its thermal property increases with temperature above room temperature. In this work, the temperature dependence of thermal properties of free-standing GF is investigated by using the transient electro-thermal technique. Significant increase for thermal conductivity and thermal diffusivity from ?0.3 to 1.5 W m(-1) K(-1) and ?4 × 10(-5) to ?2 × 10(-4) m(2) s(-1) respectively is observed with temperature from 310 K to 440 K for three GF samples. The quantitative analysis based on a physical model for porous media of Schuetz confirms that the thermal conductance across graphene contacts rather than the heat conductance inside graphene dominates thermal transport of our GFs. The thermal expansion effect at an elevated temperature makes the highly porous structure much tighter is responsible for the reduction in thermal contact resistance. Besides, the radiation heat exchange inside the pores of GFs improves the thermal transport at high temperatures. Since free-standing GF has great potential for being used as supercapacitor and battery electrode where the working temperature is always above room temperature, this finding is beneficial for thermal design of GF-based energy applications. PMID:25683178

Li, Man; Sun, Yi; Xiao, Huying; Hu, Xuejiao; Yue, Yanan

2015-03-13

62

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)

2006-04-01

63

Spin-dependent transport phenomena in organic semiconductors  

NASA Astrophysics Data System (ADS)

Thin-film organic semiconductors transport can have an anomalously high sensitivity to low magnetic fields. Such a response is unexpected considering that thermal fluctuation energies are greater than the energy associated with the intrinsic spin of charge carriers at a modest magnetic field of 100 Oe by a factor of more than 104 at room temperature and is still greater by 102 even at liquid helium temperatures. Nevertheless, we report experimental characterization of (1) spin-dependent injection, detection and transport of spin-polarized current through organic semiconductors and (2) the influence of a magnetic field on the spin dynamics of recombination-limited transport. The first focus of this work was accomplished by fabricating basic spin-valve devices consisting of two magnetic layers spatially separated by a nonmagnetic organic semiconductor. The spin-valve effect is a change in electrical resistance due to the magnetizations of the magnetic layers changing from parallel to antiparallel alignment, or vice versa. The conductivities of the metallic contacts and that of the semiconductor differed by many orders of magnitude, which inhibited the injection of a spin-polarized current from the magnet into the nonmagnet. We successfully overcame the problem of conductivity mismatch by inserting ultra-thin tunnel barriers at the metal/semiconductor interfaces which aided in yielding a ˜20% spin-valve effect at liquid helium temperatures and the effect persisted up to 150 K. We built on this achievement by constructing spin valves where one of the metallic contacts was replaced by the organic-based magnetic semiconductor vanadium tetracyanoethylene (V[TCNE]2). At 10 K these devices produced the switching behavior of the spin-valve effect. The second focus of this work was the bulk magnetoresistance (MR) of small molecule, oligomer and polymer organic semiconductors in thin-film structures. At room temperature the resistance can change up to 8% at 100 Oe and 15% at 1000 Oe. Depending on parameters such as temperature, layer thickness, or applied voltage, the resistance of these materials may increase or decrease as a function of field. A model for this phenomenon, termed magnetoresistance by the interconversion of singlets and triplets (MIST), is developed to account for this anomalous behavior. This model predicts that increasing the spin-orbit coupling in the organic semiconductor should decrease the magnitude of the MR. In an experiment where the small molecule Alq3 was doped with phosphorescent sensitizers, to increase the spin-orbit coupling, the MR was observed to decrease by an order of magnitude or more, depending on the doping. In addition to low-magnetic-field effects, we show the experimental observation of high-field MR in devices with and without magnetic contacts. To the best of our knowledge, we are the first to report (1) a tunnel-barrier-assisted spin-valve effect into an organic semiconductor using partially polarized metallic magnetic electrodes and (2) an experimental characterization of the central impact of the hyperfine interaction and spin-orbit coupling on MR in organic semiconductors.

Bergeson, Jeremy D.

64

pH-Dependent passive and active transport of acidic drugs across Caco-2 cell monolayers.  

PubMed

The aim of this study was to investigate pH-dependent passive and active transport of acidic drugs across Caco-2 cells. Therefore, the bidirectional pH-dependent transport of two acidic drugs, indomethacin and salicylic acid, across Caco-2 cells was studied in the physiological pH range of the gastrointestinal tract. The transport of both drugs decreased with increased pH, as expected from the pH-partition hypothesis. Net absorption occurred when the basolateral pH exceeded the apical pH. Concentration dependence and transporter inhibition studies indicated passive transport for indomethacin and a mixture of pH-dependent passive and active influx for salicylic acid. Unexpectedly, active and passive drug transport results were indistinguishable in temperature dependency studies. The transport of salicylic acid (apical pH 5.0; basolateral pH 7.4) was partly blocked by inhibitors of the proton-dependent transporters MCT1 (SLC16A1) and OATP-B (SLC21A9, SLCO2B1). This study shows that the asymmetry in bidirectional transport of acidic drugs is affected by both passive and active components in the presence of pH gradients across Caco-2 cells. Thus, combined studies of concentration-dependency and transport-inhibition are preferred when acidic drug transport is studied in a pH gradient. The findings of this in vitro study can be extrapolated to in vivo situations involving an acidic microclimate. PMID:15911216

Neuhoff, Sibylle; Ungell, Anna-Lena; Zamora, Ismael; Artursson, Per

2005-06-01

65

Microtubule-dependent transport in neurons: steps towards an understanding of regulation, function and dysfunction  

Microsoft Academic Search

Intracellular transport by microtubule-dependent motors is crucial for neuronal survival and function. Recent advances reveal novel strategies for the regulation of transport and the attachment of motors to cargoes. Current findings also illustrate the importance of directed transport in neuronal biology, including microtubule-motor-dependent transduction of neurotrophic signals and axonal damage signal complexes. Furthermore, recent data implicating the dysfunction of microtubule-dependent

Brian W Guzik; Lawrence SB Goldstein

2004-01-01

66

Three-Particle Azimuthal Correlations  

E-print Network

Two-particle azimuthal correlations reveal broadened and softened away-side correlations. Several different physics mechanisms are possible: large angle gluon radiation, deflected jets, and conical flow or Cerenkov radiation. Three-particle correlations are investigated to try to discriminate these mechanisms. We present results on 3-particle azimuthal correlations between a trigger particle of 3

Jason Glyndwr Ulery

2006-09-29

67

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

68

Kinesin-1/Hsc70-dependent mechanism of slow axonal transport and its relation to fast axonal transport.  

PubMed

Cytoplasmic protein transport in axons ('slow axonal transport') is essential for neuronal homeostasis, and involves Kinesin-1, the same motor for membranous organelle transport ('fast axonal transport'). However, both molecular mechanisms of slow axonal transport and difference in usage of Kinesin-1 between slow and fast axonal transport have been elusive. Here, we show that slow axonal transport depends on the interaction between the DnaJ-like domain of the kinesin light chain in the Kinesin-1 motor complex and Hsc70, scaffolding between cytoplasmic proteins and Kinesin-1. The domain is within the tetratricopeptide repeat, which can bind to membranous organelles, and competitive perturbation of the domain in squid giant axons disrupted cytoplasmic protein transport and reinforced membranous organelle transport, indicating that this domain might have a function as a switchover system between slow and fast transport by Hsc70. Transgenic mice overexpressing a dominant-negative form of the domain showed delayed slow transport, accelerated fast transport and optic axonopathy. These findings provide a basis for the regulatory mechanism of intracellular transport and its intriguing implication in neuronal dysfunction. PMID:20111006

Terada, Sumio; Kinjo, Masataka; Aihara, Makoto; Takei, Yosuke; Hirokawa, Nobutaka

2010-02-17

69

Kinesin-1/Hsc70-dependent mechanism of slow axonal transport and its relation to fast axonal transport  

PubMed Central

Cytoplasmic protein transport in axons (‘slow axonal transport') is essential for neuronal homeostasis, and involves Kinesin-1, the same motor for membranous organelle transport (‘fast axonal transport'). However, both molecular mechanisms of slow axonal transport and difference in usage of Kinesin-1 between slow and fast axonal transport have been elusive. Here, we show that slow axonal transport depends on the interaction between the DnaJ-like domain of the kinesin light chain in the Kinesin-1 motor complex and Hsc70, scaffolding between cytoplasmic proteins and Kinesin-1. The domain is within the tetratricopeptide repeat, which can bind to membranous organelles, and competitive perturbation of the domain in squid giant axons disrupted cytoplasmic protein transport and reinforced membranous organelle transport, indicating that this domain might have a function as a switchover system between slow and fast transport by Hsc70. Transgenic mice overexpressing a dominant-negative form of the domain showed delayed slow transport, accelerated fast transport and optic axonopathy. These findings provide a basis for the regulatory mechanism of intracellular transport and its intriguing implication in neuronal dysfunction. PMID:20111006

Terada, Sumio; Kinjo, Masataka; Aihara, Makoto; Takei, Yosuke; Hirokawa, Nobutaka

2010-01-01

70

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

71

Directional drilling azimuth control system  

Microsoft Academic Search

A downhole anchor assembly is described for absorbing reaction torque from a downhole mud motor in a directional drill string so as to minimize azimuthal deviation from such reaction torque, the anchor assembly comprising: an elongated, generally cylindrical housing having upper and lower ends with tool joints thereon for coupling the body into a directional drill string and having a

Cheek

1986-01-01

72

Analytical solution for one-dimensional advection-dispersion transport equation with distance-dependent coefficients  

Technology Transfer Automated Retrieval System (TEKTRAN)

Mathematical models describing contaminant transport in heterogeneous porous media are often formulated as an advection-dispersion transport equation with distance-dependent transport coefficients. In this work, a general analytical solution is presented for the linear, one-dimensional advection-di...

73

POTENTIAL TRANSPORTATION MEASURES TO REDUCE SOUTH AFRICA'S DEPENDENCY ON CRUDE OIL  

Microsoft Academic Search

Transportation, including the movement of people and freight, accounts for over 60% of all oil consumed globally, and the world's transportation systems are over 90% dependent on oil and oil by-products. Oil represents the single largest item on South Africa's import account. Gasoline and diesel fuels, which are almost exclusively used for transportation services, form a significant proportion of these

M Vanderschuren; R Jobanputra

74

pH-Dependent passive and active transport of acidic drugs across Caco-2 cell monolayers  

Microsoft Academic Search

The aim of this study was to investigate pH-dependent passive and active transport of acidic drugs across Caco-2 cells. Therefore, the bidirectional pH-dependent transport of two acidic drugs, indomethacin and salicylic acid, across Caco-2 cells was studied in the physiological pH range of the gastrointestinal tract. The transport of both drugs decreased with increased pH, as expected from the pH-partition

Sibylle Neuhoff; Anna-Lena Ungell; Ismael Zamora; Per Artursson

2005-01-01

75

Seismological Detection of Azimuthal Anisotropy in the Transition Zone  

NASA Astrophysics Data System (ADS)

The goal of this research is to determine whether azimuthal anisotropy is present in the transition zone. Mineral physics data demonstrate that wadsleyite, which is likely present in the upper transition zone, is intrinsically anisotropy. However, because the detection of seismic anisotropy at these depths is challenging, its existence in the transition zone is still a matter of debate. It is, nevertheless, an important issue since it can give us insight on the style of convection in the mantle. We apply a singular value decomposition inversion method to global azimuthally anisotropic Love wave phase velocity maps in order to constrain azimuthal anisotropy down to ~1000km depth. We use 70 different modes, fundamental and overtones up to order 5, at periods between 35s and ~175s. This gives us unprecedented sensitivity to elastic parameter G, which describes the azimuthal dependence of vertically polarized shear waves. Our preliminary results show that the best data fit is generally obtained for models that display a non-negligible amount of azimuthal anisotropy in the transition zone. Uncertainties remain regarding the amplitude and the fast direction of the anisotropy, but its presence under continents appears independent of the depth parameterization or the damping applied. Under oceans, the results are less stable with respect to damping and parametrization, and display large parameters trade-offs. This could be due to inconsistencies among the data due to a poorer azimuthal data coverage in those regions. We also tested the influence of the crustal model on the local sensitivity kernels and on the resulting models of azimuthal anisotropy. Our results show that the effect of the crust on parameter G is the strongest in the top 200km, but generally negligible at larger depths.

Yuan, K.; Beghein, C.

2010-12-01

76

Azimuthal anisotropy: The higher harmonics  

SciTech Connect

We report the first observations of the fourth harmonic (v{sub 4}) in the azimuthal distribution of particles at RHIC. The measurement was done taking advantage of the large elliptic flow generated at RHIC. The integrated v{sub 4} is about a factor of 10 smaller than v{sub 2}. For the sixth (v{sub 6}) and eighth (v{sub 8}) harmonics upper limits on the magnitudes are reported.

Poskanzer, Arthur M.; STAR Collaboration

2004-03-12

77

Improvement of Azimuthator Based on Particle Simulation  

NASA Astrophysics Data System (ADS)

The azimuthator is an important part of plasma optical mass separation. The existing design for an azimuthator is based on the single particle orbit theory and focused on the movement of ions. In this paper, the particle simulation method is adopted to study the behavior of plasma crossing an azimuthator. The results show that electrons are bounded at the entrance of the azimuthator and an axial electric field is produced due to the charge separation. In order to better achieve the function of the azimuthator, a cathode is designed to transmit the electrons and to obtain a quasi-neutral plasma beam.

Zhao, Hailong; Wang, Chunsheng; Yan, Yuming; Liu, Hongchen; Jiang, Binhao

2015-01-01

78

Angular dependent transport of auroral electrons in the upper atmosphere  

NASA Technical Reports Server (NTRS)

The transport of auroral electrons through the upper atmosphere is analyzed. The transport equation is solved using a discrete-ordinate method, including elastic and inelastic scattering of electrons (resulting in changes of pitch angle) and degradation in energy as the electrons penetrate into the atmosphere. The transport equation is solved numerically for the electron intensity as a function of altitude, pitch angle, and energy. In situ measurements of the pitch angle and energy distribution of precipitating electrons over an auroral arc provide boundary conditions for the calculation. Model calculations were carried out with various different phase functions for elastic and inelastic collisions to attempt changing the angular scattering, but the observed pitch angle distributions remain unexplained. It is suggested that mechanisms other than collisional scattering influence the angular distribution of auroral electrons at or below 300 km altitude in the low-energy domain.

Lummerzheim, D.; Rees, M. H.; Anderson, H. R.

1989-01-01

79

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. PMID:23585651

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

2013-01-01

80

Meteorological dependence of atmospheric transport of trace gases  

NASA Astrophysics Data System (ADS)

Atmospheric chemistry and transport models (CTMs) often use a single year's meteorological data to produce the constituent fields that are used in model intercomparison exercises. These fields are compared with observations and with fields produced by other CTMs that may use different meteorological data. The comparisons are often made without regard to any sensitivity of the calculated constituent fields to meteorological input. Here we investigate this sensitivity by comparing results for simulations of radon and CFC-12 using two years of meteorological data from each of two sources. These are the NASA Goddard Space Flight Center Finite Volume General Circulation Model (FVGCM) and a recent version of the Goddard Earth Observing System Data Assimilation System (GEOS DAS). The FVGCM uses a flux-form semi-Lagrangian transport scheme and a quasi-Lagrangian vertical coordinate system to ensure accurate representation of transport by the resolved-scale flow. The new DAS system uses the FVGCM at the core of the assimilation system, and is termed FVDAS. Winds, temperatures, and convective and diffusive coefficients from FVGCM and FVDAS are input to this off-line transport model along with emissions and loss frequencies of the tracers. This analysis will focus on the sensitivity of model-model and model-data comparisons to the input meteorology, emphasizing the sorts of comparisons that are commonly used in intercomparison exercises. These include flux exchange across the equator, interhemispheric mixing ratio gradients, vertical flux exchange and gradients, zonal and meridional tracer fields, and global lifetime of CFC-12. The analysis will identify minimal spatial and temporal scales for observational data sets that will be useful for robust characterization of the CTM transport.

Gupta, M.; Douglass, A.; Kawa, S.

2003-04-01

81

On time-dependent counting statistics of mesoscopic electron transport  

NASA Astrophysics Data System (ADS)

Full counting statistics (FCS) has emerged as a key concept to understand quantum transport in mesoscopic systems like heterostructures, quantum wires, and quantum dots. The knowlegde of the FCS not only enables to predict all measurable zero-frequency quantities accessible via charge detection, but also allows to identify the elementary transport events and the correlations between them. We demonstrate this concept for a standard quantum point contact between normal and/or superconducting leads under dc- and ac-bias. [M. Vanevic, Yu. V. Nazarov, W. Belzig, Phys. Rev. Lett. 99, 076601 (2007)] Finally we address the question, how these concepts can be applied to time-resolved current measurements. [A. Bednorz and W. Belzig, Phys. Rev. Lett. 101, 206803 (2008)

Belzig, Wolfgang

2009-03-01

82

View-dependent precomputed light transport using non-linear Gaussian function approximations  

E-print Network

We propose a real-time method for rendering rigid objects with complex view-dependent effects under distant all-frequency lighting. Existing precomputed light transport approaches can render rich global illumination effects, ...

Green, Paul Elijah

2006-01-01

83

TEMPERATURE DEPENDENCE OF POSTPHLOEM TRANSPORT REGULATED BY RESPIRATION IN TOMATO FRUITS  

Microsoft Academic Search

KITANO M., ARAKI T. and ECUCHI H. Temperature dependence of postphloem transport regulated by respiration in tomato fruit. BIOTRONICS 27. 33-39, 1998. Temperature effect on postphloem transport in tomato fruits was analyzed by measuring fruit growth rate, pedicel sugar flux and fruit respiratory CO, efflux under changes in air temperature around fruits. Dynamic responses of fruit growth rate and pedicel

M. KITANO; T. ARAKI; H. EGUCHI

84

Statistical description of slope-dependent soil transport and the diffusion-like coefficient  

E-print Network

. The analysis is consistent with published profiles of soil creep displacement and with published estimatesStatistical description of slope-dependent soil transport and the diffusion-like coefficient David ``diffusive'' soil transport, it is often assumed that the soil flux is proportional to the local land

Heimsath, Arjun M.

85

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

PubMed Central

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

2014-01-01

86

Frequency dependent magneto-transport in charge transfer Co(II) complex  

NASA Astrophysics Data System (ADS)

A charge transfer chelated system containing ferromagnetic metal centers is the ideal system to investigate the magneto-transport and magneto-dielectric effects due to the presence of both electronic as well as magnetic properties and their coupling. Magneto-transport properties in materials are usually studied through dc charge transport under magnetic field. As frequency dependent conductivity is an essential tool to understand the nature of carrier wave, its spatial extension and their mutual interaction, in the present work, we have investigated frequency dependent magneto-transport along with magnetization behavior in [Co2(II)-(5-(4-PhMe)-1,3,4-oxadiazole-H+-2-thiolate)5](OAc)4 metal complex to elucidate the nature of above quantities and their response under magnetic field in the transport property. We have used the existing model for ac conduction incorporating the field dependence to explain the frequency dependent magneto-transport. It is seen that the frequency dependent magneto-transport could be well explained using the existing model for ac conduction.

Shaw, Bikash Kumar; Saha, Shyamal K.

2014-09-01

87

Spin-dependent transport in II-VI magnetic semiconductor resonant tunneling diode  

Microsoft Academic Search

Spin-dependent transport through the CdTe\\/CdMgTe\\/CdMnTe\\/CdMgTe\\/CdTe heterostructure is investigated theoretically. Using the transfer matrix method and the effective-mass approximation, the effect of resonant states on spin transport is studied in a magnetic semiconductor resonant tunneling diode. The magnetic field dependences of the transmission coefficients, current densities, and tunnel magnetoresistance for the considered system have been studied. The doping and temperature effects

S. Mnasri; S. Abdi-Ben Nasrallah; A. Bouazra; N. Sfina; M. Said

2011-01-01

88

Stacking-order dependent transport properties of trilayer graphene  

NASA Astrophysics Data System (ADS)

We report markedly different transport properties of ABA- and ABC-stacked trilayer graphenes. Our experiments in double-gated trilayer devices provide evidence that a perpendicular electric field opens an energy gap in the ABC trilayer, while it causes the increase of a band overlap in the ABA trilayer. In a perpendicular magnetic field, the ABA trilayer develops quantum Hall plateaus at filling factors of ?=2,4,6,... with a step of ??=2, whereas the inversion-symmetric ABC trilayer exhibits plateaus at ?=6 and 10 with fourfold spin and valley degeneracy.

Jhang, S. H.; Craciun, M. F.; Schmidmeier, S.; Tokumitsu, S.; Russo, S.; Yamamoto, M.; Skourski, Y.; Wosnitza, J.; Tarucha, S.; Eroms, J.; Strunk, C.

2011-10-01

89

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

90

Comparative cation dependency of sugar transport by crustacean hepatopancreas and intestine.  

PubMed

Glucose is transported in crustacean hepatopancreas and intestine by Na(+)-dependent co-transport, while Na(+)-dependent D-fructose influx has only been described for the hepatopancreas. It is still unclear if the two sugars are independently transported by two distinct cation-dependent co-transporter carrier systems. In this study, lobster (Homarus americanus) hepatopancreas brush border membrane vesicles (BBMV) were used to characterize, in detail, the cation-dependency of both D-[(3)H]-glucose and D-[(3)H]-fructose influxes, while in vitro perfused intestines were employed to determine the nature of cation-dependent sugar transport across this organ. Over the sodium concentration range of 0-100?mM, both [(3)H]-glucose and [(3)H]-fructose influxes (0.1?mM; 1?min uptakes) by hepatopancreatic BBMV were hyperbolic functions of [Na(+)]. [(3)H]-glucose and [(3)H]-fructose influxes by hepatopancreatic BBMV over a potassium concentration range of 15-100?mM were hyperbolic functions of [K(+)]. Both sugars displayed significant (p<0.01) Na(+)/K(+)-dependent and cation-independent uptake processes. Transepithelial 25?µM [(3)H]-glucose and [(3)H]-fructose fluxes across lobster intestine over luminal sodium and potassium concentration ranges of 0-50?mM and 5-100?mM, respectively, were hyperbolic functions of luminal [Na(+)] and [K(+)]. As with hepatopancreatic sugar transport, transepithelial intestinal sugar transport exhibited both significant (p<0.01) Na(+)/K(+)-dependent and cation-independent processes. Results suggest that both D-glucose and D-fructose are transported by a single SGLT-type carrier in each organ with sodium being the "preferred", high affinity, cation for both sugars in the hepatopancreas, and potassium being the "preferred", high affinity, cation for both sugars in the intestine. PMID:24950971

Duka, Ada; Ahearn, Gregory A

2014-01-01

91

Comparative cation dependency of sugar transport by crustacean hepatopancreas and intestine  

PubMed Central

ABSTRACT Glucose is transported in crustacean hepatopancreas and intestine by Na+-dependent co-transport, while Na+-dependent D-fructose influx has only been described for the hepatopancreas. It is still unclear if the two sugars are independently transported by two distinct cation-dependent co-transporter carrier systems. In this study, lobster (Homarus americanus) hepatopancreas brush border membrane vesicles (BBMV) were used to characterize, in detail, the cation-dependency of both D-[3H]-glucose and D-[3H]-fructose influxes, while in vitro perfused intestines were employed to determine the nature of cation-dependent sugar transport across this organ. Over the sodium concentration range of 0–100?mM, both [3H]-glucose and [3H]-fructose influxes (0.1?mM; 1?min uptakes) by hepatopancreatic BBMV were hyperbolic functions of [Na+]. [3H]-glucose and [3H]-fructose influxes by hepatopancreatic BBMV over a potassium concentration range of 15–100?mM were hyperbolic functions of [K+]. Both sugars displayed significant (p<0.01) Na+/K+-dependent and cation-independent uptake processes. Transepithelial 25?µM [3H]-glucose and [3H]-fructose fluxes across lobster intestine over luminal sodium and potassium concentration ranges of 0–50?mM and 5–100?mM, respectively, were hyperbolic functions of luminal [Na+] and [K+]. As with hepatopancreatic sugar transport, transepithelial intestinal sugar transport exhibited both significant (p<0.01) Na+/K+-dependent and cation-independent processes. Results suggest that both D-glucose and D-fructose are transported by a single SGLT-type carrier in each organ with sodium being the “preferred”, high affinity, cation for both sugars in the hepatopancreas, and potassium being the “preferred”, high affinity, cation for both sugars in the intestine. PMID:24950971

Duka, Ada; Ahearn, Gregory A.

2014-01-01

92

Azimuthal Anisotropy of pi0 Production in Au+Au Collisions at sNN=200GeV: Path-Length Dependence of Jet Quenching and the Role of Initial Geometry  

Microsoft Academic Search

We have measured the azimuthal anisotropy of pi0 production for 1

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

2010-01-01

93

Fracture Spacing and Orientation Estimation from Spectral Analyses of Azimuth Stacks  

E-print Network

Discrete, vertically aligned fracture systems impart one or more notches in the spectral ratios of stacked reflected seismic traces. This apparent attenuation is due to the azimuth dependant scattering introduced by the ...

Vetri, Laura

2005-01-01

94

Structural insights into substrate recognition in proton-dependent oligopeptide transporters  

PubMed Central

Short-chain peptides are transported across membranes through promiscuous proton-dependent oligopeptide transporters (POTs)—a subfamily of the major facilitator superfamily (MFS). The human POTs, PEPT1 and PEPT2, are also involved in the absorption of various drugs in the gut as well as transport to target cells. Here, we present a structure of an oligomeric POT transporter from Shewanella oneidensis (PepTSo2), which was crystallized in the inward open conformation in complex with the peptidomimetic alafosfalin. All ligand-binding residues are highly conserved and the structural insights presented here are therefore likely to also apply to human POTs. PMID:23867627

Guettou, Fatma; Quistgaard, Esben M; Trésaugues, Lionel; Moberg, Per; Jegerschöld, Caroline; Zhu, Lin; Jong, Agnes Jin Oi; Nordlund, Pär; Löw, Christian

2013-01-01

95

Transport Simulation towards Understanding the Field-Dependent Ultracold Neutron Production in Solid Oxygen  

NASA Astrophysics Data System (ADS)

We will present a Monte-Carlo simulation on ultracold neutron (UCN) transport in the guide system used in the UCN production experiment in the summer of 2008. The simulation uses a UCN package [1] previously developed at Paul Scherrer Institute using the GEANT4 framework. The resulting transport efficiency is benchmarked by measurements on UCN transport through the same guide system. Furthermore, we simulate UCN transport through a non-uniform, solenoid magnetic field, results of which are used to extract the information of field-dependent UCN production in Solid Oxygen in low temperature alpha- and beta- phases. [1] F. Atchison et al., NIMA 552 (2005) 513

Feng, Yu; Liu, Chen-Yu; Lavelle, Christopher; Shin, Yunchang; Salvat, Daniel; McChesney, Patrick; Manus, Greg; Ribeill, Guilhem; Young, Albert; Morris, Chris; Makela, Mark; Saunders, Andy; Holley, Adam

2009-05-01

96

Structural insights into substrate recognition in proton-dependent oligopeptide transporters.  

PubMed

Short-chain peptides are transported across membranes through promiscuous proton-dependent oligopeptide transporters (POTs)--a subfamily of the major facilitator superfamily (MFS). The human POTs, PEPT1 and PEPT2, are also involved in the absorption of various drugs in the gut as well as transport to target cells. Here, we present a structure of an oligomeric POT transporter from Shewanella oneidensis (PepTSo2), which was crystallized in the inward open conformation in complex with the peptidomimetic alafosfalin. All ligand-binding residues are highly conserved and the structural insights presented here are therefore likely to also apply to human POTs. PMID:23867627

Guettou, Fatma; Quistgaard, Esben M; Trésaugues, Lionel; Moberg, Per; Jegerschöld, Caroline; Zhu, Lin; Jong, Agnes Jin Oi; Nordlund, Pär; Löw, Christian

2013-09-01

97

Azimuthal asymmetry in SIDIS off nuclei as probe for $\\hat q$  

E-print Network

The energy loss parameter $\\hat q$ is one of the fundamental transport parameters of hadronic matter. Using the twist-4 collinear approach, we show that the $\\cos \\phi$ azimuthal asymmetry in unpolarized semi-inclusive deeply inelastic scattering (SIDIS) off a large nucleus at intermediate transverse momentum is a sensitive observable for its determination. The effect is due to the suppression of the azimuthal asymmetry by final-state multiple scattering.

Jian-Hua Gao; Andreas Schäfer; Jian Zhou

2011-11-07

98

Length-Dependent Thermal Transport along Molecular Chains  

NASA Astrophysics Data System (ADS)

We present heat-transport measurements conducted with a vacuum-operated scanning thermal microscope to study the thermal conductance of monolayers of nine different alkane thiols self-assembled on Au(111) surfaces as a function of their length (2 to 18 methylene units). The molecular thermal conductance is probed in a confined area with a diameter below 10 nm in the contact between a silicon tip and the self-assembled monolayer. This yields a pWK-1 sensitivity per molecule at a tip temperature of 200-300 °C versus the gold at room temperature. We found a conductance variance of up to a factor of 3 as a function of alkane chain length, with maximum conductance for a chain length of four carbon atoms.

Meier, T.; Menges, F.; Nirmalraj, P.; Hölscher, H.; Riel, H.; Gotsmann, B.

2014-08-01

99

Nonparaxial propagation and focusing properties of azimuthal-variant vector fields diffracted by an annular aperture.  

PubMed

Based on the vectorial Rayleigh-Sommerfeld integrals, the analytical expressions for azimuthal-variant vector fields diffracted by an annular aperture are presented. This helps us to investigate the propagation behaviors and the focusing properties of apertured azimuthal-variant vector fields under nonparaxial and paraxial approximations. The diffraction by a circular aperture, a circular disk, or propagation in free space can be treated as special cases of this general result. Simulation results show that the transverse intensity, longitudinal intensity, and far-field divergence angle of nonparaxially apertured azimuthal-variant vector fields depend strongly on the azimuthal index, the outer truncation parameter and the inner truncation parameter of the annular aperture, as well as the ratio of the waist width to the wavelength. Moreover, the multiple-ring-structured intensity pattern of the focused azimuthal-variant vector field, which originates from the diffraction effect caused by an annular aperture, is experimentally demonstrated. PMID:25121455

Gu, Bing; Xu, Danfeng; Pan, Yang; Cui, Yiping

2014-07-01

100

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

Microsoft Academic Search

Summary The cambial Kþ content of poplar increases during the growth period in a Kþ supply dependent manner. Upon Kþ starvation or application of tetraethylammoniumchloride (TEAþ), a Kþ 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, Kþ 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

101

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

102

Diameter dependence of the transport properties of antimony telluride nanowires.  

PubMed

We report measurements of electronic, thermoelectric, and galvanomagnetic properties of individual single crystal antimony telluride (Sb(2)Te(3)) nanowires with diameters in the range of 20-100 nm. Temperature-dependent resistivity and thermoelectric power (TEP) measurements indicate hole dominant diffusive thermoelectric generation with an enhancement of the TEP for smaller diameter wires up to 110 microV/K at T = 300 K. We measure the magnetoresistance in magnetic fields both parallel and perpendicular to the nanowire [110] axis, where strong anisotropic positive magnetoresistance behavior was observed. PMID:20698617

Zuev, Yuri M; Lee, Jin Seok; Galloy, Clément; Park, Hongkun; Kim, Philip

2010-08-11

103

Subgridscale stabilization of time-dependent convection dominated diffusive transport  

NASA Astrophysics Data System (ADS)

In [W.J. Layton, A connection between subgrid scale eddy viscosity and mixed methods, Appl. Math. Comput. 133 (2002) 147-157], a variationally consistent eddy viscosity discretization is given for the stationary convection diffusion equation. We further develop this discretization to include the time-dependent problem. We give comprehensive stability and error analysis of the semi-discrete case. We also state the stability and error results for the fully discrete algorithm with a Crank-Nicholson time discretization. The error bound is near optimal and independent of the diffusion coefficient, [epsilon]. Finally, we give guidance on optimal parameter selection for some common finite element spaces.

Heitmann, N.

2007-07-01

104

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

105

Directional drilling azimuth control system  

SciTech Connect

A downhole anchor assembly is described for absorbing reaction torque from a downhole mud motor in a directional drill string so as to minimize azimuthal deviation from such reaction torque, the anchor assembly comprising: an elongated, generally cylindrical housing having upper and lower ends with tool joints thereon for coupling the body into a directional drill string and having a drilling fluid passage extending longitudinally through its length; at least one elongated chain support body longitudinally mounted in the housing; an elongated, endless anchor chain supported on the body, the chain having an elongated portion thereof longitudinally arranged and generally radially exposed externally of the body, the exposed chain portion being freely longitudinally movable along the body; the body being generally radially shiftable between a retracted position in which the exposed chain portion is substantially recessed in the housing; and actuating means in the housing engageable with the body for shifting the body from the retracted position to its extended position.

Cheek, A.E.

1986-09-23

106

Relative azimuth inversion by way of damped maximum correlation estimates  

NASA Astrophysics Data System (ADS)

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.

2012-06-01

107

A NEW MONTE CARLO METHOD FOR TIME-DEPENDENT NEUTRINO RADIATION TRANSPORT  

SciTech Connect

Monte Carlo approaches to radiation transport have several attractive properties such as simplicity of implementation, high accuracy, and good parallel scaling. Moreover, Monte Carlo methods can handle complicated geometries and are relatively easy to extend to multiple spatial dimensions, which makes them potentially interesting in modeling complex multi-dimensional astrophysical phenomena such as core-collapse supernovae. The aim of this paper is to explore Monte Carlo methods for modeling neutrino transport in core-collapse supernovae. We generalize the Implicit Monte Carlo photon transport scheme of Fleck and Cummings and gray discrete-diffusion scheme of Densmore et al. to energy-, time-, and velocity-dependent neutrino transport. Using our 1D spherically-symmetric implementation, we show that, similar to the photon transport case, the implicit scheme enables significantly larger timesteps compared with explicit time discretization, without sacrificing accuracy, while the discrete-diffusion method leads to significant speed-ups at high optical depth. Our results suggest that a combination of spectral, velocity-dependent, Implicit Monte Carlo and discrete-diffusion Monte Carlo methods represents a robust approach for use in neutrino transport calculations in core-collapse supernovae. Our velocity-dependent scheme can easily be adapted to photon transport.

Abdikamalov, Ernazar; Ott, Christian D.; O'Connor, Evan [TAPIR, California Institute of Technology, MC 350-17, 1200 E California Blvd., Pasadena, CA 91125 (United States); Burrows, Adam; Dolence, Joshua C. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States); Loeffler, Frank; Schnetter, Erik, E-mail: abdik@tapir.caltech.edu [Center for Computation and Technology, Louisiana State University, 216 Johnston Hall, Baton Rouge, LA 70803 (United States)

2012-08-20

108

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. PMID:20402791

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

2010-01-01

109

Temperature dependent electron transport studies for diffuse discharge switching applications  

NASA Astrophysics Data System (ADS)

A diffuse gas discharge switch must be capable of high speed, repetitive switching without significant degradation of its electron conduction and opening characteristics if it is to be useful in pulsed power switching applications. Whenever the switch is fired, the gas temperature T within the switch is expected to rise several degrees centigrade, and operating temperatures of several hundred degrees are likely for repetitively operated switches. The electron transport and rate coefficients, such as the electron drift velocity and the electron attachment coefficient for the most promising gas mixtures under study are expected to be funcions of T, and consequently, knowledge of these parameters as a function of T is desirable for modeling the operation of the diffuse discharge switch in practical application. Measurements of these parameters in C2F6/buffer gas (Ar, Ch4, N2) mixtures have been made and are reported. The electron attachment rate constant has also been measured for C2F6 and C3F8 as a function of the mean electron energy over the temperature range 300 less than or equal to T less than or equal to 750 K. For C2F6, the electron attachment rate constant has been found to increase by 30% over this temperature range, while for C3F6, the attachment rate constant first decreases when the temperature is increased to approximately 450 K and then significantly increases with increasing T. An interpretation of these measurements and their significance in repetitively operated diffuse discharge switching gas mixtures is outlined.

Hunter, S. R.; Carter, J. G.; Christophorou, L. G.; Spyrou, S. M.

110

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

111

Spin-dependent transport between magnetic nanopillars through a nano-granular metal matrix  

NASA Astrophysics Data System (ADS)

We investigate the influence of local magnetic field on the spin-dependent transport properties of magnetic granular metals. By means of electron-beam-induced-deposition we fabricate a complex granular system made of Co nanopillars embedded in a Pt-C nano-granular metal matrix. We identify two different spin-dependent tunnelling regimes. In the first one, transport occurs almost exclusively through the nano-granular Pt-C matrix and it is affected by the local stray field due to the Co nanopillars. In the second regime, the transport takes place through both the Pt-C matrix and the Co nanopillars. These two transport regimes are discriminated by the different sign of the magnetoresistance. In particular, a strong enhancement of the magnetoresistance is found at low temperatures in the second regime, which is caused by spin-flip scattering and higher order tunnelling processes.

Porrati, F.; Begun, E.; Sachser, R.; Huth, M.

2014-11-01

112

Statistical description of slope-dependent soil transport and the diffusion-like coefficient  

Microsoft Academic Search

For hillslopes undergoing ``diffusive'' soil transport, it is often assumed that the soil flux is proportional to the local land-surface gradient, where the coefficient of proportionality is like a diffusion coefficient. Inasmuch as transport involves quasi-random soil particle motions related to biomechanical mixing and similar dilational processes, a slope-dependent relation arises from a balance between particle fluxes that tend to

David Jon Furbish; Peter K. Haff; William E. Dietrich; Arjun M. Heimsath

2009-01-01

113

Statistical description of slope-dependent soil transport and the diffusion-like coefficient  

Microsoft Academic Search

For hillslopes undergoing “diffusive” soil transport, it is often assumed that the soil flux is proportional to the local land-surface gradient, where the coefficient of proportionality is like a diffusion coefficient. Inasmuch as transport involves quasi-random soil particle motions related to biomechanical mixing and similar dilational processes, a slope-dependent relation arises from a balance between particle fluxes that tend to

David Jon Furbish; Peter K. Haff; William E. Dietrich; Arjun M. Heimsath

2009-01-01

114

Dependence of Heat and Particle Transport on the Ratio of the Ion and Electron Temperatures  

SciTech Connect

Experiments in high confinement (H-mode) plasmas on the DIII-D tokamak show that the heat and particle transport are sensitive to the ratio of the ion and electron temperatures. Increasing the ion-to-electron temperature ratio decreases the electron and ion heat transport and the particle transport regardless of which temperature is being varied. A likely explanation of these results is the dependence of the ion-temperature-gradient instability on the ratio of the ion and electron temperatures. {copyright} {ital 1999} {ital The American Physical Society}

Petty, C.C.; Groebner, R.J.; Luce, T.C.; Staebler, G.M. [General Atomics, San Diego, California 92186-5608 (United States)] [General Atomics, San Diego, California 92186-5608 (United States); Wade, M.R. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-2009 (United States)] [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-2009 (United States); Kinsey, J.E. [Lehigh University, Bethlehem, Pennsylvania 18015 (United States)] [Lehigh University, Bethlehem, Pennsylvania 18015 (United States)

1999-11-01

115

First-principles study of spin-dependent transport through graphene/BNC/graphene structure.  

PubMed

: First-principles study on the electronic structure and transport property of the boron nitride sheet (BNC) structure, in which a triangular graphene flake surrounded by a hexagonal boron nitride sheet, is implemented. As the graphene flake becomes small and is more isolated by the boron nitride region, the magnetic ordering of the flake increases. When the BNC structure is connected to the graphene electrodes, the spin-polarized charge-density distribution appears only at the triangular graphene flake region, and the electronic structure of the graphene electrode is not spin polarized. First-principles transport calculation reveals that the transport property of the BNC structure is spin dependent. PMID:23634806

Ota, Tadashi; Ono, Tomoya

2013-01-01

116

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

117

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

SciTech Connect

As device miniaturization approaches nanoscale dimensions, interfaces begin to dominate electrical properties. Here the system archetype Au/SrTiO{sub 3} 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., E-mail: bonnell@lrsm.seas.upenn.edu [Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

2013-12-16

118

Characterization of the ATP-Dependent LTC 4Transporter in Cisplatin-Resistant Human KB Cells  

Microsoft Academic Search

An active efflux pump forcis-diamminedichloroplatinum(II) (cisplatin) has been identified in cisplatin-resistant KCP-4 cells isolated from human epidermoid carcinoma KB-3-1 cells. The adenosine triphosphate(ATP)-dependent transport of leukotriene C4(LTC4), an endogenous substrate for the glutathione S-conjugate export pump(GS-X pump), has been found in membrane vesicles prepared from KCP-4 cells. Multidrug resistance-associated protein (MRP) has also been identified as an ATP-dependent LTC4transporter. To

Yutaka Chuman; Zhe-Sheng Chen; Tomoyuki Sumizawa; Tatsuhiko Furukawa; Misako Haraguchi; Yuji Takebayashi; Kiyoshi Niwa; Kazutaka Yamada; Takashi Aikou; Shin-ichi Akiyama

1996-01-01

119

Characterization of a novel brain-specific chloride-dependent glutamic acid transport  

SciTech Connect

The apparent, chloride dependent binding of (/sup 3/H)-glutamate (CGB) to brain membranes has been proposed to label a physiological receptor. However, recent evaluation of the properties of (CBG) has led to the suggestion that it represents transport and sequestration. The purpose of the present work was to determine if CGB represents binding or transport. Our results indicate that CGB is sensitive to detergent and osmotic pertubations. Both association and dissociation of Glu are temperature dependent and the rate of dissociation is dependent on the amount of Glu in the incubation media. All these results indicate that CGB represents transport and sequestration. Synaptosomal chloride dependent Glu transport (CGT) was then characterized. This process has similar pharmacologic and ion stimulation profiles as CGB. It is concluded that these two phenomena represent the identical process. CGT is brain specific. Regional distribution, ontogenetic and lesion studies indicate that CGT is neuronal but is not associated with sodium dependent Glu uptake. These studies also indicate that CGT is either located post synaptically to Glu innervation or is not related to it. Finally, CGT is bidirectional and capable of homoexchange.

Zaczek, R.

1986-01-01

120

Rab9-dependent retrograde transport and endosomal sorting of the endopeptidase furin  

PubMed Central

The endopeptidase furin and the trans-Golgi network protein TGN38 are membrane proteins that recycle between the TGN and plasma membrane. TGN38 is transported by a retromer-dependent pathway from early endosomes to the TGN, whereas the intracellular transport of furin is poorly defined. Here we have identified the itinerary and transport requirements of furin. Using internalisation assays, we show that furin transits the early and late endosomes en route to the TGN. The GTPase Rab9 and the TGN golgin GCC185, components of the late endosome-to-TGN pathway, were required for efficient TGN retrieval of furin. By contrast, TGN38 trafficking was independent of Rab9 and GCC185. To identify the sorting signals for the early endosome-to-TGN pathway, the trafficking of furin–TGN38 chimeras was investigated. The diversion of furin from the Rab9-dependent late-endosome-to-TGN pathway to the retromer-dependent early-endosome-to-TGN pathway required both the transmembrane domain and cytoplasmic tail of TGN38. We present evidence to suggest that the length of the transmembrane domain is a contributing factor in endosomal sorting. Overall, these data show that furin uses the Rab9-dependent pathway from late endosomes and that retrograde transport directly from early endosomes is dependent on both the transmembrane domain and the cytoplasmic tail. PMID:21693586

Chia, Pei Zhi Cheryl; Gasnereau, Isabelle; Lieu, Zi Zhao; Gleeson, Paul A.

2011-01-01

121

Azimuthal anisotropy of the Pg-wave velocity in hypocentral volumes of NW Croatia  

Microsoft Academic Search

Based on a large set of arrival times of the Pg phase reported by local and regional stations, we estimate azimuthal anisotropy of the Pg-wave velocity in focal volumes of the upper crust in NW Croatia. The method is based on analyses of the azimuthal dependence\\u000a of ratios of cumulative differences of arrival times and travel paths between foci of

Marijan Herak; Davorka Herak; Josip Stipcevic

2009-01-01

122

Transverse spin azimuthal asymmetries in SIDIS at COMPASS: Multidimensional analysis  

E-print Network

COMPASS is a high-energy physics experiment operating at the SPS at CERN. Wide physics program of the experiment comprises study of hadron structure and spectroscopy with high energy muon and hadrons beams. As for the muon-program, one of the important objectives of the COMPASS experiment is the exploration of the transverse spin structure of the nucleon via spin (in)dependent azimuthal asymmetries in single-hadron production in deep inelastic scattering of polarized leptons off transversely polarized target. For this purpose a series of measurements were made in COMPASS, using 160 GeV/c longitudinally polarized muon beam and transversely polarized $^{6}LiD$ (in 2002, 2003 and 2004) and $NH_{3}$ (in 2007 and 2010) targets. The experimental results obtained by COMPASS for unpolarized target azimuthal asymmetries, Sivers and Collins effects and other azimuthal observables play an important role in the general understanding of the three-dimensional nature of the nucleon. Giving access to the entire "twsit-2" set of transverse momentum dependent parton distribution functions and fragmentation functions COMPASS data triggers constant theoretical interest and is being widely used in phenomenological analyses and global data fits. In this review main focus is given to the very recent results obtained by the COMPASS collaboration from first ever multi-dimensional extraction of transverse spin asymmetries.

Bakur Parsamyan

2015-04-08

123

CALCIUM-DEPENDENT INTERACTIONS OF THE HUMAN NOREPINEPHRINE TRANSPORTER WITH SYNTAXIN 1A  

PubMed Central

The norepinephrine (NE) transporter (NET) terminates noradrenergic signaling by clearing released NE at synapses. The activity of NET can be rapidly regulated by depolarization and receptor activation via Ca2+ and kinase/phosphatase linked pathways. The SNARE protein syntaxin 1A (SYN1A) interacts with NET and influences transporter surface trafficking and catalytic activity. In this study, we establish a link between changes in intracellular Ca2+ and SYN1A/NET interactions. SYN1A influenced NE transport only in the presence of Ca2+ in brain cortical synaptosomes. Although NET/SYN1A associations were sensitive to manipulations of Ca2+ in CHO cells, in vitro binding experiments using purified NET and SYN1A fusion proteins demonstrated a lack of direct Ca2+ sensitivity. Disruption of NET/SYN1A interaction abolished inhibition of NE transport by phorbol ester (PMA) to activate protein kinase C (PKC), but had no effect on transport inhibition by the Ca2+ calmodulin kinase (CaMK) inhibitor KN93. Furthermore, PMA enhanced Ca2+ dependent modulation of NE transport in synaptosomes. Our data reveal roles for SYN1A in the Ca2+-dependent regulation of NET, likely reliant on regulation by PKC signaling, but independent of CaMK. PMID:17188889

Sung, Uhna; Blakely, Randy D.

2007-01-01

124

Azimuthally sensitive femtoscopy in event-by-event hydrodynamics  

E-print Network

We analyze the pion femtoscopy correlations in noncentral Au-Au and Pb-Pb collisions. The azimuthally sensitive Hanbury Brown-Twiss (HBT) method is used to extract the interferometry radii depending on the azimuthal angle with respect to the second and third-order event plane. The results are in semiquantitative agreement with the STAR collaboration data on the HBT radii with respect to the second-order reaction plane, with the preliminary PHENIX collaboration data on the HBT radii with respect to the third-order reaction plane in Au-Au collisions at 200GeV, and with the preliminary ALICE collaboration data for the HBT radii with respect to the second-order event plane for Pb-Pb collisions at 2.76TeV.

Piotr Bozek

2014-01-20

125

Dependence of heat transport on the strength and shear rate of prescribed circulating flows  

E-print Network

We study numerically the dependence of heat transport on the maximum velocity and shear rate of physical circulating flows, which are prescribed to have the key characteristics of the large-scale mean flow observed in turbulent convection. When the side-boundary thermal layer is thinner than the viscous boundary layer, the Nusselt number (Nu), which measures the heat transport, scales with the normalized shear rate to an exponent 1/3. On the other hand, when the side-boundary thermal layer is thicker, the dependence of Nu on the Peclet number, which measures the maximum velocity, or the normalized shear rate when the viscous boundary layer thickness is fixed, is generally not a power law. Scaling behavior is obtained only in an asymptotic regime. The relevance of our results to the problem of heat transport in turbulent convection is also discussed.

Emily S. C. Ching; K. M. Pang

2001-11-28

126

A Modified Direct-Reading Azimuth Protractor  

ERIC Educational Resources Information Center

Describes the construction of a direct-reading azimuth protractor (DRAP) used for mapping fracture and joint-surface orientations in underground mines where magnetic disturbances affect typical geologic pocket transit. (SL)

Larson, William C.; Pugliese, Joseph M.

1977-01-01

127

Complex Imaging with wide azimuth data (Invited)  

NASA Astrophysics Data System (ADS)

The past couple of years have seen a tremendous increase in the acquisition of wide azimuth (WAZ) surveys that provide improved subsalt imaging. We have seen a step change improvement in image quality compared to conventional narrow azimuth (NAZ) surveys, even when using minimal processing and existing, conventional-survey velocity models. The improvement in image quality is taken to the next level when the wide azimuth data are combined with other seismic and non-seismic measurements to build ever more highly constrained models, and then more accurately migrated with two-way wave-equation methods. In this presentation we will show examples of WAZ data processed with the latest technology such as true azimuth 3D multiple attenuation using the general surface multiple prediction (GSMP), wave equation based multiple attenuation (WEM MOD) and reverse time migration (RTM). We will also discuss development of our next generation of velocity model building tools and techniques such as full waveform inversion (FWI).

Kapoor, J.; Moldoveanu, N.; Vigh, D.

2009-12-01

128

Evidence of spin-dependent quantum transport effects in CuO nanowires  

Microsoft Academic Search

We have observed strongly spin-dependent quantum transport in nanowires created by bringing macroscopic Cu wires into and out of contact under an applied magnetic field when exposed to air. A 70% increase in the strength of the first spin split conduction mode obtained from conductance histograms is observed for a field of 2 mT at room temperature, implying the existence

D. M. Gillingham; C. Müller; J. Hong; R. Q. Wu; J. A. C. Bland

2006-01-01

129

Time-dependent behaviour of electron transport in methane argon mixtures  

Microsoft Academic Search

The Boltzmann transport equation is solved to determine the time-dependent electron velocity distribution function in various mixtures of methane and argon subjected to an external electric field, E. In the solution of the equation no expansion of the distribution function is made. The concentration of methane in the mixture is varied systematically. The distribution function is used to calculate several

Alan A. Sebastian; J. M. Wadehra

2005-01-01

130

ATP-Dependent Silver Transport across the Basolateral Membrane of Rainbow Trout Gills  

E-print Network

ATP-Dependent Silver Transport across the Basolateral Membrane of Rainbow Trout Gills N. R. Bury- brane of Rainbow Trout Gills. Bury, N. R., Grosell, M., Grover, A. K., and Wood, C. M. (1999). Toxicol, the gills are also a route by which silver may enter the fish. Therefore, this study focuses

Grosell, Martin

131

Coherent Transport of Neutral Atoms in Spin-Dependent Optical Lattice Potentials  

Microsoft Academic Search

We demonstrate the controlled coherent transport and splitting of atomic wave packets in spin-dependent optical lattice potentials. Such experiments open intriguing possibilities for quantum state engineering of many body states. After first preparing localized atomic wave functions in an optical lattice through a Mott insulating phase, we place each atom in a superposition of two internal spin states. Then state

Olaf Mandel; Markus Greiner; Artur Widera; Tim Rom; Theodor W. Hänsch; Immanuel Bloch

2003-01-01

132

Azimuthal Resistivity Investigation of an Unconfined Aquifer at the Hanford Integrated Field Research Challenge Site  

NASA Astrophysics Data System (ADS)

Developing a robust large-scale groundwater contaminate transport model requires quantifying the effect of heterogeneity and anisotropy on solute transport. Here we investigated the feasibility of using surface azimuthal resistivity methods to characterize near-surface anisotropy and heterogeneity in order to improve the conceptual model for uranium transport through unconsolidated sediment at the Integrated Field Research Challenge Site (IFRC) which borders the Columbia River. A generalized azimuthal resistivity array was constructed with seven telescoping radii and 15° rotations between each electrode. Azimuthal array data were acquired by multiplexing with the MPT-DAS1 system connected to 172 surface electrodes. Array geometries included the square array, arrow array, offset wenner and equatorial dipole-dipole. Effective depths of exploration ranged between 5 and 57 m. Results from the upper 5m of exploration depth exhibit an isotropic resistivity which is consistent with the excavation and homogonous fill depth of the waste ponds at the IFRC. Exploration depths beyond 5 m are influenced by the Hanford and Ringold Formations. These formations exhibit a strong anisotropic resistivity which increases with depth. Assuming that the response is entirely controlled by hydrologic anisotropy, these azimuthal resistivity data suggest a preferential path with a mean azimuth between 150° and 170°. This azimuthal resistivity trend coincides with an incision feature in the Ringold formation measured in a suite of core logs and is consistent with the trajectory of a tracer plume from an injection test conducted in March 2009. Surface azimuthal resistivity methods may also have application in characterizing localized anisotropy and heterogeneity within shallow alluvial deposits at Hanford allowing for the optimal placement of tracer injections and borehole electrodes.

Greenwood, W. J.; Ward, A. L.; Versteeg, R. J.; Johnson, T. C.; Draper, K.

2009-12-01

133

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. PMID:22172222

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

2011-01-01

134

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. PMID:1599411

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

1992-01-01

135

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

136

K+-dependent Na+ transport driven by respiration in Escherichia coli cells and membrane vesicles.  

PubMed

Respiration-driven Na+ transport from Escherichia coli cells and right-side-out membrane vesicles is strictly dependent on K+. Cells from an E. colic mutant deficient in three major K+ transport systems were incapable of accumulating K+ or expelling Na+ unless valinomycin was added. Membrane vesicles from an E. coli mutant from which the genes encoding the two known electrogenic Na+/nH+ antiporters nhaA and nhaB were deleted transported Na+ as well as did vesicles from wild-type cells. Quantitative analysis of Delta psi and Delta pH showed a high driving force for electrogenic Na+/nH+ antiport whether K+ was present or not, although Na+ transport occurred only in its presence. These results suggest that an Na+/nH+ antiporter is not responsible for the Na+ transport. Respiration-driven efflux of Na+ from vesicles was found to be accompanied by primary uphill efflux of K+. Also, no respiration-dependent efflux of K+ was observed in the absence of Na+. Such coupling between Na+ and K+ fluxes may be explained by the operation of an Na+, K+/H+ antiporter previously described in E. coli membrane vesicles (Verkhovskay, M.L., Verkhovsky, M.I. and Wikström, M. (1995) FEBS Lett. 363, 46-48). Active Na+ transport is abolished when delta mu H+ is eliminated by a protonophore, but at low concentrations the protonophore actually accelerated Na+ transport. Such an effect may be expected if the Na+, K+/H+ antiporter normally operates in tight conjunction with respiratory chain complexes, thus exhibiting some phenomenological properties of a primary redox-linked sodium pump. PMID:8616158

Verkhovskaya, M L; Verkhovsky, M I; Wikström, M

1996-03-28

137

Temperature Dependence of the Charge Transport in a C60 based Organic Field Effect Transistor  

NASA Astrophysics Data System (ADS)

We studied the temperature dependence of the electron transport in C60 based Organic Field Effect Transistors (OFETs). On the spin-coated bottom gate dielectric, the semi-conducting C60 thin-film has been grown by standard evaporation technique. Device parameters as the threshold voltage, the field effect mobility and the activation energy of the electron transport were determined in the temperature range from 300 K to 77 K. The field effect mobility obeys the Meyer-Neldel Rule (MNR), which is an empirical relation between activation energy and the mobility prefactor.

Ullah, Mujeeb; Singh, Th. B.; Matt, G. J.; Simbruner, C.; Hernandz-Sosa, G.; Sariciftci, S. N.; Sitter, H.

138

Azimuthal-spin-wave-mode-driven vortex-core reversals  

NASA Astrophysics Data System (ADS)

We studied, by micromagnetic numerical calculations, asymmetric vortex-core reversals driven by the m = -1 and m = +1 azimuthal spin-wave modes' excitations in soft magnetic circular nano-disks. We addressed the similarities and differences between the asymmetric core reversals in terms of the temporal evolutions of the correlated core-motion speed, locally concentrated perpendicular gyrofield, and magnetization dip near the original vortex core. The criterion for the core reversals was found to be the magnetization dip that must reach the out-of-plane magnetization component, mz = -p, with the initial polarization p, where p = +1 (-1) for the upward (downward) core magnetization. The core-motion speed and the associated perpendicular gyrofield, variable and controllable with static perpendicular field, Hz, applied perpendicularly to the disk plane, must reach their threshold values to meet the ultimate core-reversal criterion. Also, we determined the Hz strength and direction dependence of the core-switching time and threshold exciting field strength required for the core reversals, whose parameters are essential in the application aspect. This work offers deeper insights into the azimuthal spin-wave-driven core-reversal dynamics as well as an efficient means of controlling the azimuthal-modes-driven core reversals.

Yoo, Myoung-Woo; Kim, Sang-Koog

2015-01-01

139

Sodium Dependent Multivitamin Transporter (SMVT): A Potential Target for Drug Delivery  

PubMed Central

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.

2015-01-01

140

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

NASA Astrophysics Data System (ADS)

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.; Mikkelsen, D. R.; White, A. E.; Reinke, M. L.; Ernst, D.; Podpaly, Y.; Candy, J.

2012-05-01

141

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

142

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. PMID:22641192

Razak, K.A.

2012-01-01

143

Multicomponent, multi-azimuth pre-stack seismic waveform inversion for azimuthally anisotropic media using a parallel and computationally efficient non-dominated sorting genetic algorithm  

NASA Astrophysics Data System (ADS)

Consideration of azimuthal anisotropy, at least to an orthorhombic symmetry is important in exploring the naturally fractured and unconventional hydrocarbon reservoirs. Full waveform inversion of multicomponent seismic data can, in principle, provide more robust estimates of subsurface elastic parameters and density than the inversion of single component (P wave) seismic data. In addition, azimuthally dependent anisotropy can only be resolved by carefully studying the multicomponent seismic displacement data acquired and processed along different azimuths. Such an analysis needs an inversion algorithm capable of simultaneously optimizing multiple objectives, one for each data component along each azimuth. These multicomponent and multi-azimuthal seismic inversions are non-linear with non-unique solutions; it is therefore appropriate to treat the objectives as a vector and simultaneously optimize each of its components such that the optimal set of solutions could be obtained. The fast non-dominated sorting genetic algorithm (NSGA II) is a robust stochastic global search method capable of handling multiple objectives, but its computational expense increases with increasing number of objectives and the number of model parameters to be inverted for. In addition, an accurate extraction of subsurface azimuthal anisotropy requires multicomponent seismic data acquired at a fine spatial resolution along many source-to-receiver azimuths. Because routine acquisition of such data is prohibitively expensive, they are typically available along two or at most three azimuthal orientations at a spatial resolution where such an inversion could be applied. This paper proposes a novel multi-objective methodology using a parallelized version of NSGA II for waveform inversion of multicomponent seismic displacement data along two azimuths. By scaling the objectives prior to ranking, redefining the crowding distance as functions of the scaled objective and the model spaces, and varying the crossover and mutation parameters over generations, the proposed methodology is also an improvement of the original NSGA II in overall computational efficiency, preservation of population diversity, and rapid sampling of the model space. By first inverting the near-offset pre-stack data for the background isotropic properties and obtaining constraints on the vertical velocities, followed by an inversion of the long-offset data, it is demonstrated that the proposed method can reliably estimate density and azimuthally anisotropic subsurface properties up to the complexity of an orthorhombic symmetry on noisy synthetic data computed from a model based on a real well log under an assumption of 1-D subsurface layers where the ambiguities between lateral heterogeneity and anisotropy could be ignored. In addition, a practical way to approximately compute the uncertainty values in the derived parameters using the method is also demonstrated.

Li, Tao; Mallick, Subhashis

2015-02-01

144

TIME-DEPENDENT PERPENDICULAR TRANSPORT OF FAST CHARGED PARTICLES IN A TURBULENT MAGNETIC FIELD  

SciTech Connect

We present an analytic derivation of the temporal dependence of the perpendicular transport coefficient of charged particles in magnetostatic turbulence, for times smaller than the time needed for charged particles to travel the turbulence correlation length. This time window is left unexplored in most transport models. In our analysis all magnetic scales are taken to be much larger than the particle gyroradius, so that perpendicular transport is assumed to be dominated by the guiding center motion. Particle drift from the local magnetic field lines (MFLs) and magnetic field line random walk are evaluated separately for slab and three-dimensional (3D) isotropic turbulence. Contributions of wavelength scales shorter and longer than the turbulence coherence length are compared. In contrast to the slab case, particles in 3D isotropic turbulence unexpectedly diffuse from local MFLs; this result questions the common assumption that particle magnetization is independent of turbulence geometry. Extensions of this model will allow for a study of solar wind anisotropies.

Fraschetti, F.; Jokipii, J. R. [Departments of Planetary Sciences and Astronomy, University of Arizona, Tucson, AZ 85721 (United States)

2011-06-20

145

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. PMID:21354396

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

2011-01-01

146

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. PMID:8381681

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

1993-01-01

147

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

148

Examination of temperature dependent subgroup formulations in direct whole core transport calculation for power reactors  

SciTech Connect

The traditional subgroup method which has been applied for lattice transport calculations has an inherent limitation for non-uniform temperature distributions. As a measure to incorporate temperature dependence into the subgroup formulation, the subgroup level and number density adjustment method have been proposed. In this paper, the temperature dependent subgroup formulations employed for reflecting the non-uniform temperature effects on the resonance spatial self-shielding are examined for the whole core transport calculation with the thermal feedback. For 2D pin-cell problem with non-uniform temperature profiles, the inherent limitation of conventional subgroup method is confirmed. And the improvement in terms of reactivity is observed with the proposed adjustment scheme. For the real PWR core calculation with thermal feedback in the hot-full-power condition, the noticeable correction for the fuel temperature coefficient by about 10% more negative is obtained with the correction schemes. (authors)

Jung, Y. S.; Lee, U. C.; Joo, H. G. [Dept. of Nuclear Engineering, Seoul National Univ., 599 Gwanak-ro, Gwanak-gu, Seoul (Korea, Republic of)

2012-07-01

149

Magnon excitation and temperature dependent transport properties in magnetic tunnel junctions with Heusler compound electrodes  

NASA Astrophysics Data System (ADS)

Magnetic tunnel junctions were prepared with the Heusler compounds Co2FeAl, Co2FeSi, and Co2MnSi as the soft magnetic electrode. The Co2MnSi electrodes had a multilayer design that used either the Co2FeAl or the Co2FeSi compound as a buffer material. Pinned Co-Fe was used as the hard reference electrode. The electronic transport characteristics were analyzed by tunneling spectroscopy. The dependence of sample properties on the buffer material was of interest, especially the gap in the minority density of states of the Heusler electrode. The temperature dependence of the transport properties was also investigated.

Drewello, Volker; Ebke, Daniel; Schäfers, Markus; Kugler, Zoë; Reiss, Günter; Thomas, Andy

2012-04-01

150

Time-dependent density functional theory quantum transport simulation in non-orthogonal basis  

SciTech Connect

Basing on the earlier works on the hierarchical equations of motion for quantum transport, we present in this paper a first principles scheme for time-dependent quantum transport by combining time-dependent density functional theory (TDDFT) and Keldysh's non-equilibrium Green's function formalism. This scheme is beyond the wide band limit approximation and is directly applicable to the case of non-orthogonal basis without the need of basis transformation. The overlap between the basis in the lead and the device region is treated properly by including it in the self-energy and it can be shown that this approach is equivalent to a lead-device orthogonalization. This scheme has been implemented at both TDDFT and density functional tight-binding level. Simulation results are presented to demonstrate our method and comparison with wide band limit approximation is made. Finally, the sparsity of the matrices and computational complexity of this method are analyzed.

Kwok, Yan Ho; Xie, Hang; Yam, Chi Yung; Chen, Guan Hua, E-mail: ghc@everest.hku.hk [Department of Chemistry, The University of Hong Kong, Pokfulam Road (Hong Kong); Zheng, Xiao [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2013-12-14

151

Structure and mechanism of a bacterial sodium-dependent dicarboxylate transporter  

PubMed Central

In human cells, cytosolic citrate is a major precursor for the synthesis of fatty acids, triacylglycerols, cholesterol and low-density lipoprotein. Cytosolic citrate further regulates the cell’s energy balance by activating the fatty acid synthesis pathway while down-regulating both the glycolysis and fatty acid ?-oxidation pathways (Supplementary Fig. 1) 1–4. The rate of fatty acid synthesis in liver and adipose cells, the two major tissue types for such synthesis, correlates directly with the concentration of citrate in the cytosol 2–5. The cytosolic citrate concentration partially depends on direct import across the plasma membrane via the Na+-dependent citrate transporter (NaCT) 6,7. Mutations of the homologous fly gene (INDY, I’m Not Dead Yet) result in reduced fat storage through calorie restriction 8. More recently, NaCT-knockout mice have been found to have increased hepatic mitochondrial biogenesis, higher lipid oxidation and energy expenditure, and reduced lipogenesis, which taken together protect the mice from obesity and insulin resistance 9. To understand the transport mechanism of NaCT/INDY proteins, here we report the 3.2 Å crystal structure of a bacterial INDY homolog. One citrate molecule and one sodium ion are bound per protein, and their binding sites are defined by conserved amino acid motifs, forming the structural basis for understanding the transporters’ specificity. Comparison of the structures of the two symmetrical halves of the transporter suggests conformational changes that propel substrate translocation. PMID:23086149

Mancusso, Romina; Gregorio, G. Glenn; Liu, Qun; Wang, Da-Neng

2013-01-01

152

Serum albumin promotes ATP-binding cassette transporter-dependent sterol uptake in yeast.  

PubMed

Sterol uptake in fungi is a multistep process that involves interaction between external sterols and the cell wall, incorporation of sterol molecules into the plasma membrane, and subsequent integration into intracellular membranes for turnover. ATP-binding cassette (ABC) transporters have been implicated in sterol uptake, but key features of their activity remain to be elucidated. Here, we apply fluorescent cholesterol (NBD-cholesterol) to monitor sterol uptake under anaerobic and aerobic conditions in two fungal species, Candida glabrata (Cg) and Saccharomyces cerevisiae (Sc). We found that in both fungal species, ABC transporter-dependent uptake of cholesterol under anaerobic conditions and in mutants lacking HEM1 gene is promoted in the presence of the serum protein albumin that is able to bind the sterol molecule. Furthermore, the C. glabrata ABC transporter CgAus1p expressed in S. cerevisiae requires the presence of serum or albumin for efficient cholesterol uptake. These results suggest that albumin can serve as sterol donor in ABC transporter-dependent sterol uptake, a process potentially important for growth of C. glabrata inside infected humans. PMID:25331273

Marek, Magdalena; Silvestro, Daniele; Fredslund, Maria D; Andersen, Tonni G; Pomorski, Thomas G

2014-12-01

153

Orbital-cooperative spin fluctuation and orbital-dependent transport in ruthenates  

NASA Astrophysics Data System (ADS)

Unusual transport properties deviating from the Fermi liquid are observed in ruthenates near a magnetic quantum-critical point (QCP). To understand the electronic properties of the ruthenates near and away from an antiferromagnetic (AF) QCP, I study the electronic structure and magnetic and transport properties for the t2 g-orbital Hubbard model on a square lattice in fluctuation-exchange approximation including Maki-Thompson (MT) current vertex correction (CVC). The results away from the AF QCP reproduce several experimental results of Sr2RuO4 qualitatively and provide new mechanisms about the enhancement of spin fluctuation at QIC -AF?(0.66 ? ,0.66 ? ) , larger mass enhancement of the dx y orbital than that of the dx z /y z orbital, and nonmonotonic temperature dependence of the Hall coefficient. Also, the results near the AF QCP explain the T -linear inplane resistivity in Sr2Ru0.075Ti0.025O4 and give an experimental test on the obtained temperature dependence of the Hall coefficient. I reveal spatial correlation including the self-energy of electrons beyond mean-field approximations is essential to determine the electronic properties of the ruthenates. I also show several ubiquitous transport properties near an AF QCP and characteristic transport properties of a multiorbital system by comparison with results of a single-orbital system near an AF QCP.

Arakawa, Naoya

2014-12-01

154

Structure and mechanism of a bacterial sodium-dependent dicarboxylate transporter.  

PubMed

In human cells, cytosolic citrate is a chief precursor for the synthesis of fatty acids, triacylglycerols, cholesterol and low-density lipoprotein. Cytosolic citrate further regulates the energy balance of the cell by activating the fatty-acid-synthesis pathway while downregulating both the glycolysis and fatty-acid ?-oxidation pathways. The rate of fatty-acid synthesis in liver and adipose cells, the two main tissue types for such synthesis, correlates directly with the concentration of citrate in the cytosol, with the cytosolic citrate concentration partially depending on direct import across the plasma membrane through the Na(+)-dependent citrate transporter (NaCT). Mutations of the homologous fly gene (Indy; I'm not dead yet) result in reduced fat storage through calorie restriction. More recently, Nact (also known as Slc13a5)-knockout mice have been found to have increased hepatic mitochondrial biogenesis, higher lipid oxidation and energy expenditure, and reduced lipogenesis, which taken together protect the mice from obesity and insulin resistance. To understand the transport mechanism of NaCT and INDY proteins, here we report the 3.2 Å crystal structure of a bacterial INDY homologue. One citrate molecule and one sodium ion are bound per protein, and their binding sites are defined by conserved amino acid motifs, forming the structural basis for understanding the specificity of the transporter. Comparison of the structures of the two symmetrical halves of the transporter suggests conformational changes that propel substrate translocation. PMID:23086149

Mancusso, Romina; Gregorio, G Glenn; Liu, Qun; Wang, Da-Neng

2012-11-22

155

Modeling Bacterial Detachment During Transport Through Porous Media as a Residence-Time-Dependent Process  

NASA Astrophysics Data System (ADS)

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.

Johnson, William P.; Blue, Karen A.; Logan, Bruce E.; Arnold, Robert G.

1995-01-01

156

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

SciTech Connect

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, E-mail: sibylle.meyer@wmi.badw-muenchen.de; Althammer, Matthias; Geprägs, Stephan; Opel, Matthias; Goennenwein, Sebastian T. B. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Gross, Rudolf [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany)

2014-06-16

157

Parametric dependence of turbulent particle transport in high density electron heated FTU plasmas  

Microsoft Academic Search

In this paper we present the result of a study carried out at the Frascati Tokamak Upgrade (FTU), on a set of full non-inductive current driven, electron heated, L-mode discharges aimed at investigating the parametric dependence of the electron density profile on the electron temperature and safety factor gradients as predicted by quasi-linear drift-turbulence transport theory. Experiments in FTU allow

M. Romanelli; G. T. Hoang; C. Bourdelle; C. Gormezano; E. Giovannozzi; M. Leigheb; M. Marinucci; D. Marocco; C. Mazzotta; L. Panaccione; V. Pericoli; G. Regnoli; O. Tudisco

2007-01-01

158

Aquaporin-4–dependent K+ and water transport modeled in brain extracellular space following neuroexcitation  

PubMed Central

Potassium (K+) ions released into brain extracellular space (ECS) during neuroexcitation are efficiently taken up by astrocytes. Deletion of astrocyte water channel aquaporin-4 (AQP4) in mice alters neuroexcitation by reducing ECS [K+] accumulation and slowing K+ reuptake. These effects could involve AQP4-dependent: (a) K+ permeability, (b) resting ECS volume, (c) ECS contraction during K+ reuptake, and (d) diffusion-limited water/K+ transport coupling. To investigate the role of these mechanisms, we compared experimental data to predictions of a model of K+ and water uptake into astrocytes after neuronal release of K+ into the ECS. The model computed the kinetics of ECS [K+] and volume, with input parameters including initial ECS volume, astrocyte K+ conductance and water permeability, and diffusion in astrocyte cytoplasm. Numerical methods were developed to compute transport and diffusion for a nonstationary astrocyte–ECS interface. The modeling showed that mechanisms b–d, together, can predict experimentally observed impairment in K+ reuptake from the ECS in AQP4 deficiency, as well as altered K+ accumulation in the ECS after neuroexcitation, provided that astrocyte water permeability is sufficiently reduced in AQP4 deficiency and that solute diffusion in astrocyte cytoplasm is sufficiently low. The modeling thus provides a potential explanation for AQP4-dependent K+/water coupling in the ECS without requiring AQP4-dependent astrocyte K+ permeability. Our model links the physical and ion/water transport properties of brain cells with the dynamics of neuroexcitation, and supports the conclusion that reduced AQP4-dependent water transport is responsible for defective neuroexcitation in AQP4 deficiency. PMID:23277478

Jin, Byung-Ju; Zhang, Hua; Binder, Devin K.

2013-01-01

159

Nanoscale spin-dependent transport of electrons and holes in Si-ferromagnet structures  

Microsoft Academic Search

Given the rapid development of magnetic data storage and spin-electronics into the realm of nanotechnology, the understanding of the spin-dependent electronic transport and switching behavior of magnetic structures at the nanoscale is an important issue. We have developed spin-sensitive techniques with nanoscale resolution, referred to as ballistic electron magnetic microscopy (BEMM) and ballistic hole magnetic microscopy (BHMM). The techniques are

E. Haq

2005-01-01

160

Short- and Long- Time Transport Structures in a Three Dimensional Time Dependent Flow  

E-print Network

Lagrangian transport structures for three-dimensional and time-dependent fluid flows are of great interest in numerous applications, particularly for geophysical or oceanic flows. In such flows, chaotic transport and mixing can play important environmental and ecological roles, for examples in pollution spills or plankton migration. In such flows, where simulations or observations are typically available only over a short time, understanding the difference between short-time and long-time transport structures is critical. In this paper, we use a set of classical (i.e. Poincar\\'e section, Lyapunov exponent) and alternative (i.e. finite time Lyapunov exponent, Lagrangian coherent structures) tools from dynamical systems theory that analyze chaotic transport both qualitatively and quantitatively. With this set of tools we are able to reveal, identify and highlight differences between short- and long-time transport structures inside a flow composed of a primary horizontal contra-rotating vortex chain, small lateral oscillations and a weak Ekman pumping. The difference is mainly the existence of regular or extremely slowly developing chaotic regions that are only present at short time.

Rodolphe Chabreyrie; Stefan G. Llewellyn Smith

2014-05-08

161

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

162

Mechanistic insights and functional determinants of the transport cycle of the ascorbic acid transporter SVCT2. Activation by sodium and absolute dependence on bivalent cations.  

PubMed

We characterized the human Na(+)-ascorbic acid transporter SVCT2 and developed a basic model for the transport cycle that challenges the current view that it functions as a Na(+)-dependent transporter. The properties of SVCT2 are modulated by Ca(2+)/Mg(2+) and a reciprocal functional interaction between Na(+) and ascorbic acid that defines the substrate binding order and the transport stoichiometry. Na(+) increased the ascorbic acid transport rate in a cooperative manner, decreasing the transport K(m) without affecting the V(max), thus converting a low affinity form of the transporter into a high affinity transporter. Inversely, ascorbic acid affected in a bimodal and concentration-dependent manner the Na(+) cooperativity, with absence of cooperativity at low and high ascorbic acid concentrations. Our data are consistent with a transport cycle characterized by a Na(+):ascorbic acid stoichiometry of 2:1 and a substrate binding order of the type Na(+):ascorbic acid:Na(+). However, SVCT2 is not electrogenic. SVCT2 showed an absolute requirement for Ca(2+)/Mg(2+) for function, with both cations switching the transporter from an inactive into an active conformation by increasing the transport V(max) without affecting the transport K(m) or the Na(+) cooperativity. Our data indicate that SVCT2 may switch between a number of states with characteristic properties, including an inactive conformation in the absence of Ca(2+)/Mg(2+). At least three active states can be envisioned, including a low affinity conformation at Na(+) concentrations below 20 mM and two high affinity conformations at elevated Na(+) concentrations whose Na(+) cooperativity is modulated by ascorbic acid. Thus, SVCT2 is a Ca(2+)/Mg(2+)-dependent transporter. PMID:17012227

Godoy, Alejandro; Ormazabal, Valeska; Moraga-Cid, Gustavo; Zúñiga, Felipe A; Sotomayor, Paula; Barra, Valeria; Vasquez, Osmán; Montecinos, Viviana; Mardones, Lorena; Guzmán, Catherine; Villagrán, Marcelo; Aguayo, Luis G; Oñate, Sergio A; Reyes, Alejandro M; Cárcamo, Juan G; Rivas, Coralia I; Vera, Juan Carlos

2007-01-01

163

Scale-Dependent Fracture-Matrix Interactions And Their Impact on Radionuclide Transport - Final Report  

SciTech Connect

Matrix diffusion and adsorption within a rock matrix are widely regarded as important mechanisms for retarding the transport of radionuclides and other solutes in fractured rock (e.g., Neretnieks, 1980; Tang et al., 1981; Maloszewski and Zuber, 1985; Novakowski and Lapcevic, 1994; Jardine et al., 1999; Zhou and Xie, 2003; Reimus et al., 2003a,b). When remediation options are being evaluated for old sources of contamination, where a large fraction of contaminants reside within the rock matrix, slow diffusion out of the matrix greatly increases the difficulty and timeframe of remediation. Estimating the rates of solute exchange between fractures and the adjacent rock matrix is a critical factor in quantifying immobilization and/or remobilization of DOE-relevant contaminants within the subsurface. In principle, the most rigorous approach to modeling solute transport with fracture-matrix interaction would be based on local-scale coupled advection-diffusion/dispersion equations for the rock matrix and in discrete fractures that comprise the fracture network (Discrete Fracture Network and Matrix approach, hereinafter referred to as DFNM approach), fully resolving aperture variability in fractures and matrix property heterogeneity. However, such approaches are computationally demanding, and thus, many predictive models rely upon simplified models. These models typically idealize fracture rock masses as a single fracture or system of parallel fractures interacting with slabs of porous matrix or as a mobile-immobile or multi-rate mass transfer system. These idealizations provide tractable approaches for interpreting tracer tests and predicting contaminant mobility, but rely upon a fitted effective matrix diffusivity or mass-transfer coefficients. However, because these fitted parameters are based upon simplified conceptual models, their effectiveness at predicting long-term transport processes remains uncertain. Evidence of scale dependence of effective matrix diffusion coefficients obtained from tracer tests highlights this point and suggests that the underlying mechanisms and relationship between rock and fracture properties are not fully understood in large complex fracture networks. In this project, we developed a high-resolution DFN model of solute transport in fracture networks to explore and quantify the mechanisms that control transport in complex fracture networks and how these may give rise to observed scale-dependent matrix diffusion coefficients. Results demonstrate that small scale heterogeneity in the flow field caused by local aperture variability within individual fractures can lead to long-tailed breakthrough curves indicative of matrix diffusion, even in the absence of interactions with the fracture matrix. Furthermore, the temporal and spatial scale dependence of these processes highlights the inability of short-term tracer tests to estimate transport parameters that will control long-term fate and transport of contaminants in fractured aquifers.

Detwiler, Russell

2014-06-30

164

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. PMID:23175668

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

165

Functional implications and ubiquitin-dependent degradation of the peptide transporter Ptr2 in Saccharomyces cerevisiae.  

PubMed

The peptide transporter Ptr2 plays a central role in di- or tripeptide import in Saccharomyces cerevisiae. Although PTR2 transcription has been extensively analyzed in terms of upregulation by the Ubr1-Cup9 circuit, the structural and functional information for this transporter is limited. Here we identified 14 amino acid residues required for peptide import through Ptr2 based on the crystallographic information of Streptococcus thermophilus peptide transporter PepTst and based on the conservation of primary sequences among the proton-dependent oligopeptide transporters (POTs). Expression of Ptr2 carrying one of the 14 mutations of which the corresponding residues of PepTst are involved in peptide recognition, salt bridge interaction, or peptide translocation failed to enable ptr2?trp1 cell growth in alanyl-tryptophan (Ala-Trp) medium. We observed that Ptr2 underwent rapid degradation after cycloheximide treatment (half-life, approximately 1 h), and this degradation depended on Rsp5 ubiquitin ligase. The ubiquitination of Ptr2 most likely occurs at the N-terminal lysines 16, 27, and 34. Simultaneous substitution of arginine for the three lysines fully prevented Ptr2 degradation. Ptr2 mutants of the presumed peptide-binding site (E92Q, R93K, K205R, W362L, and E480D) exhibited severe defects in peptide import and were subjected to Rsp5-dependent degradation when cells were moved to Ala-Trp medium, whereas, similar to what occurs in the wild-type Ptr2, mutant proteins of the intracellular gate were upregulated. These results suggest that Ptr2 undergoes quality control and the defects in peptide binding and the concomitant conformational change render Ptr2 subject to efficient ubiquitination and subsequent degradation. PMID:25172766

Kawai, Ken; Moriya, Atsuto; Uemura, Satoshi; Abe, Fumiyoshi

2014-11-01

166

Time-dependent 3-D dterministic transport on parallel architectures using Dantsys/MPI  

SciTech Connect

In addition to the ability to solve the static transport equation, we have also incorporated time dependence into our parallel 3-D S{sub {ital N}} code DANTSYS/MPI. Using a semi-implicit scheme, DANTSYS/MPI is capable of performing time-dependent calculations for both fissioning and pure source driven problems. We have applied this to various types of problems such as nuclear well logging and prompt fission experiments. This paper describes the form of the time- dependent equations implemented, their solution strategies in DANTSYS/MPI including iteration acceleration, and the strategies used for time-step control. Results are presented for a model nuclear well logging calculation.

Baker, R.S.; Alcouffe, R.E.

1996-12-31

167

System Design and Technology Development for an Azimuth Scanning Microwave Limb Sounder  

NASA Astrophysics Data System (ADS)

The NRC's Earth Science and Applications from Space decadal survey calls for a mission (GACM) to study global atmospheric composition, "with sufficient vertical resolution to detect the presence, transport, and chemical transformation of atmospheric layers from the surface to the lower stratosphere." Microwave limb sounding is particularly well suited for providing this information for the upper troposphere and above. The Microwave Limb Sounders on Aura and UARS have provided global measurements that have: quantified the evolution of the ozone layer; characterized the water vapor and cloud ice feedback mechanisms affecting climate change; documented the long range transport of pollution through tracers like CO; and improved the accuracy of global circulation models used for weather and climate forecasts. The Scanning Microwave Limb Sounder (SMLS) concept builds on the success of these instruments by adding an azimuth scan and increasing the antenna height to greatly improve horizontal and vertical resolution. The measurement swath is wide enough to provide, depending on orbit inclination, six or more daily measurements over midlatitudes. SMLS will incorporate a novel antenna design that enables rapid horizontal scanning, 4 Kelvin receiver front ends, advanced digital receiver back ends, and several lessons learned from previous missions. We will discuss the instrument design, technology development and readiness, and our approach to on-orbit calibration. We will also discuss plans and goals for a demonstration instrument that takes advantage of technologies developed through ESTO and other NASA and non-NASA programs. cameo.php

Stek, P. C.; Chattopadhyay, G.; Cofield, R.; Jarnot, R.; Kawamura, J.; Lee, K.; Livesey, N.; Ward, J.

2007-12-01

168

The Molecular Mechanism of Ion-Dependent Gating in Secondary Transporters  

PubMed Central

LeuT-like fold Na-dependent secondary active transporters form a large family of integral membrane proteins that transport various substrates against their concentration gradient across lipid membranes, using the free energy stored in the downhill concentration gradient of sodium ions. These transporters play an active role in synaptic transmission, the delivery of key nutrients, and the maintenance of osmotic pressure inside the cell. It is generally believed that binding of an ion and/or a substrate drives the conformational dynamics of the transporter. However, the exact mechanism for converting ion binding into useful work has yet to be established. Using a multi-dimensional path sampling (string-method) followed by all-atom free energy simulations, we established the principal thermodynamic and kinetic components governing the ion-dependent conformational dynamics of a LeuT-like fold transporter, the sodium/benzyl-hydantoin symporter Mhp1, for an entire conformational cycle. We found that inward-facing and outward-facing states of Mhp1 display nearly the same free energies with an ion absent from the Na2 site conserved across the LeuT-like fold transporters. The barrier separating an apo-state from inward-facing or outward-facing states of the transporter is very low, suggesting stochastic gating in the absence of ion/substrate bound. In contrast, the binding of a Na2 ion shifts the free energy stabilizing the outward-facing state and promoting substrate binding. Our results indicate that ion binding to the Na2 site may also play a key role in the intracellular thin gate dynamics modulation by altering its interactions with the transmembrane helix 5 (TM5). The Potential of Mean Force (PMF) computations for a substrate entrance displays two energy minima that correspond to the locations of the main binding site S1 and proposed allosteric S2 binding site. However, it was found that substrate's binds to the site S1 ?5 kcal/mol more favorable than that to the site S2 for all studied bound combinations of ions and a substrate. PMID:24204233

Zhao, Chunfeng; Noskov, Sergei Yu.

2013-01-01

169

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

NASA Technical Reports Server (NTRS)

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.

1992-01-01

170

Energy dependence of jet transport parameter and parton saturationin quark-gluon plasma  

SciTech Connect

We study the evolution and saturation of the gluondistribution function in the quark-gluon plasma as probed by apropagating parton and its effect on the computation of jet quenching ortransport parameter $\\hat q $. For thermal partons, the saturation scale$Q2_s$ is found to be proportional to the Debye screening mass $\\mu_D2$.For hard probes, evolution at small $x=Q2_s/6ET$ leads to jet energydependence of hat q. We study this dependence for both a conformal gaugetheory in weak and strong coupling limit and for (pure gluon) QCD. Theenergy dependence can be used to extract the shear viscosity $\\eta$ ofthe medium since $\\eta$ can be related to the transport parameter forthermal partons in a transport description. We also derive upper boundson the transport parameter for both energetic and thermal partons. Thelater leads to a lower bound on shear viscosity-to-entropy density ratiowhich is consistent with the conjectured lower bound $\\eta/s\\geq 1/4\\pi$.Implications on the study of jet quenching at RHIC and LHC and the bulkproperties of the dense matter are discussed.

Casalderrey-Solana, Jorge; Wang, Xin-Nian

2007-06-24

171

The orphan transporter v7-3 (slc6a15) is a Na+-dependent neutral amino acid transporter (B0AT2)  

PubMed Central

Transporters of the SLC6 (solute carrier 6) family play an important role in the removal of neurotransmitters in brain tissue and in amino acid transport in epithelial cells. In the present study, we demonstrate that mouse v7-3 (slc6a15) encodes a transporter for neutral amino acids. The transporter is functionally and sequence related to B0AT1 (slc6a19) and was hence named B0AT2. Leucine, isoleucine, valine, proline and methionine were recognized by the transporter, with values of K0.5 (half-saturation constant) ranging from 40 to 200 ?M. Alanine, glutamine and phenylalanine were low-affinity substrates of the transporter, with K0.5 values in the millimolar range. Transport of neutral amino acids via B0AT2 was Na+-dependent, Cl?-independent and electrogenic. Superfusion of mouse B0AT2-expressing oocytes with amino acid substrates generated robust inward currents. Na+-activation kinetics of proline transport and uptake under voltage clamp suggested a 1:1 Na+/amino acid co-transport stoichiometry. Susbtrate and co-substrate influenced each other's K0.5 values, suggesting that they share the same binding site. A mouse B0AT2-like transport activity was detected in synaptosomes and cultured neurons. A potential role of B0AT2 in transporting neurotransmitter precursors and neuromodulators is proposed. PMID:16185194

Bröer, Angelika; Tietze, Nadine; Kowalczuk, Sonja; Chubb, Sarah; Munzinger, Michael; Bak, Lasse K.; Bröer, Stefan

2005-01-01

172

Surface charge- and space-dependent transport of proteins in crowded environments of nanotailored posts.  

PubMed

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 photobleaching (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 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. PMID:20515056

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

2010-06-22

173

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. PMID:20515056

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

2010-01-01

174

Reflection seismology over azimuthally anisotropic media  

Microsoft Academic Search

Recent surveys have shown that azimuthal anisotropy (due most plausibly to aligned fractures) has an impor- tant effect on seismic shear waves. Previous work had discussed these effects on VSP data; the same effects are seen in surface recording of reflections at small to mod- erate angles of incidence. The anisotropic effects one dif- ferent polarization components of vertically traveling

Leon Thomsen

1988-01-01

175

Variable Azimuthal Anisotropy in Earth's Lowermost Mantle  

E-print Network

in the Dµ layer. The Dµ layer is located at the base of Earth_s silicate lower mantle, where it meets the liquid iron outer core. The Dµ layer plays a critical role in Earth_s dynamical evolution because it actsVariable Azimuthal Anisotropy in Earth's Lowermost Mantle Edward J. Garnero,1 * Vale´rie Maupin,2

Garnero, Ed

176

Polarization azimuth angle in daylight scenes  

Microsoft Academic Search

Lord Rayleigh derived the degree of polarization for singular molecular scattering phenomena in the atmosphere as a function of the relative angular orientations of the source, scattering center, and observer. This paper extends the Rayleigh model by giving the azimuth angle for the linearly polarized scattered radiation detected by the observer. Together these two parameters give a complete Stokes vector

Roy M. Matchko; Grant R. Gerhart

2005-01-01

177

Alcohol and the calcium-dependent potassium transport of human erythrocytes  

SciTech Connect

In vitro exposure of human red blood cells to ethanol (100 and 400 mM) was found to increase the initial rate of calcium-dependent potassium efflux through the red cell membrane. This effect of ethanol was apparently not due to an elevation of the intracellular free calcium but rather to a direct action of the drug on the transport process as, (1) intracellular calcium concentrations were tightly buffered with EGTA, (2) ethanol did not alter the efflux of UVCa from the cells, and (3) dantrolene, which has been proposed to counteract the effect of ethanol on intracellular calcium levels in the erythrocyte, did not inhibit the stimulatory action of ethanol. The efflux of potassium from erythrocytes obtained from chronic alcoholics was not different from that of erythrocytes from non-alcoholic individuals. The relationship of these findings to neuronal potassium transport is discussed.

Harris, R.A.; Caldwell, K.K.

1985-01-01

178

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

179

Numerical solution of the time dependent neutron transport equation by the method of the characteristics  

SciTech Connect

This study presents three numerical algorithms to solve the time dependent neutron transport equation by the method of the characteristics. The algorithms have been developed taking into account delayed neutrons and they have been implemented into the novel MCART code, which solves the neutron transport equation for two-dimensional geometry and an arbitrary number of energy groups. The MCART code uses regular mesh for the representation of the spatial domain, it models up-scattering, and takes advantage of OPENMP and OPENGL algorithms for parallel computing and plotting, respectively. The code has been benchmarked with the multiplication factor results of a Boiling Water Reactor, with the analytical results for a prompt jump transient in an infinite medium, and with PARTISN and TDTORT results for cross section and source transients. The numerical simulations have shown that only two numerical algorithms are stable for small time steps.

Talamo, Alberto, E-mail: alby@anl.gov [Nuclear Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States)] [Nuclear Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States)

2013-05-01

180

Spin-dependent transport in II-VI magnetic semiconductor resonant tunneling diode  

NASA Astrophysics Data System (ADS)

Spin-dependent transport through the CdTe/CdMgTe/CdMnTe/CdMgTe/CdTe heterostructure is investigated theoretically. Using the transfer matrix method and the effective-mass approximation, the effect of resonant states on spin transport is studied in a magnetic semiconductor resonant tunneling diode. The magnetic field dependences of the transmission coefficients, current densities, and tunnel magnetoresistance for the considered system have been studied. The doping and temperature effects on the current are also investigated theoretically. The numerical results show that the CdMnTe layers, which act as spin filters, polarize the electric currents. This spin splitting of the energy levels enables one to select the resonant condition for the desired spin by adjusting the magnetic field or the applied bias. The spin-up component of the current-density shows a strong suppression for increasing magnetic fields; the total current density is dominated by the spin-down component. It is also found that the tunnel magnetoresistance depends strongly on the magnetic field and the applied voltage.

Mnasri, S.; Nasrallah, S. Abdi-Ben; Bouazra, A.; Sfina, N.; Said, M.

2011-08-01

181

Multi-fluid transport code modeling of time-dependent recycling in ELMy H-mode  

SciTech Connect

Simulations of a high-confinement-mode (H-mode) tokamak discharge with infrequent giant type-I ELMs are performed by the multi-fluid, multi-species, two-dimensional transport code UEDGE-MB, which incorporates the Macro-Blob approach for intermittent non-diffusive transport due to filamentary coherent structures observed during the Edge Localized Modes (ELMs) and simple time-dependent multi-parametric models for cross-field plasma transport coefficients and working gas inventory in material surfaces. Temporal evolutions of pedestal plasma profiles, divertor recycling, and wall inventory in a sequence of ELMs are studied and compared to the experimental time-dependent data. Short- and long-time-scale variations of the pedestal and divertor plasmas where the ELM is described as a sequence of macro-blobs are discussed. It is shown that the ELM recovery includes the phase of relatively dense and cold post-ELM divertor plasma evolving on a several ms scale, which is set by the transport properties of H-mode barrier. The global gas balance in the discharge is also analyzed. The calculated rates of working gas deposition during each ELM and wall outgassing between ELMs are compared to the ELM particle losses from the pedestal and neutral-beam-injection fueling rate, correspondingly. A sensitivity study of the pedestal and divertor plasmas to model assumptions for gas deposition and release on material surfaces is presented. The performed simulations show that the dynamics of pedestal particle inventory is dominated by the transient intense gas deposition into the wall during each ELM followed by continuous gas release between ELMs at roughly a constant rate.

Pigarov, A. Yu.; Krasheninnikov, S. I.; Hollmann, E. M. [University of California at San Diego, La Jolla, California 92093 (United States); Rognlien, T. D.; Lasnier, C. J. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Unterberg, E. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

2014-06-15

182

Multi-fluid transport code modeling of time-dependent recycling in ELMy H-mode  

SciTech Connect

Simulations of a high-confinement-mode (H-mode) tokamak discharge with infrequent giant type-I ELMs are performed by the multi-fluid, multi-species, two-dimensional transport code UEDGE-MB, which incorporates the Macro-Blob approach for intermittent non-diffusive transport due to filamentary coherent structures observed during the Edge Localized Modes (ELMs) and simple time-dependent multi-parametric models for cross-field plasma transport coefficients and working gas inventory in material surfaces. Temporal evolutions of pedestal plasma profiles, divertor recycling, and wall inventory in a sequence of ELMs are studied and compared to the experimental time-dependent data. Short- and long-time-scale variations of the pedestal and divertor plasmas where the ELM is described as a sequence of macro-blobs are discussed. It is shown that the ELM recovery includes the phase of relatively dense and cold post-ELM divertor plasma evolving on a several ms scale, which is set by the transport properties of H-mode barrier. The global gas balance in the discharge is also analyzed. The calculated rates of working gas deposition during each ELM and wall outgassing between ELMs are compared to the ELM particle losses from the pedestal and neutral-beam-injection fueling rate, correspondingly. A sensitivity study of the pedestal and divertor plasmas to model assumptions for gas deposition and release on material surfaces is presented. The performed simulations show that the dynamics of pedestal particle inventory is dominated by the transient intense gas deposition into the wall during each ELM followed by continuous gas release between ELMs at roughly a constant rate.

Pigarov, A. Yu. [University of California, San Diego; Krasheninnikov, S. I. [University of California, La Jolla; Rognlien, T. D. [Lawrence Livermore National Laboratory (LLNL); Hollmann, E. M. [University of California, San Diego; Lasnier, C. J. [Lawrence Livermore National Laboratory (LLNL); Unterberg, Ezekial A [ORNL

2014-01-01

183

Spin Dependent Transport in Si/SiGe Few-Electron Quantum Dots  

NASA Astrophysics Data System (ADS)

Si/SiGe quantum dots are of interest for quantum information processing due in large part to the existence of spin zero isotopes of both Si and Ge. We present the results of transport measurements and integrated charge sensing in silicon double and single quantum dots.[1,2] We observe two effects arising from spin dependent transport in a double quantum dot. First, and as expected, for one direction of current flow we observe spin blockade -- the canonical example of spin-to-charge conversion in transport. In addition, when current flow is reversed, we observe a second effect: strong tails of current extend from the sharp triangular regions in which current conventionally is observed. The presence of these tails is explained by a combination of long spin relaxation times and preferential loading of an excited spin state. We also present charge-sensing measurements of single and double quantum dots using an integrated quantum point contact. The charge sensor signal from single electron tunneling is well correlated with conventional transport through the system. When the tunnel barriers are large and transport through the dot is not measurable, charge sensing remains a viable means to track charge transitions and is used to confirm individual-electron occupation in a single quantum dot. Work performed in collaboration with Nakul Shaji, Madhu Thalakulam, Levente J. Klein, H. Luo, Hua Qin, R. H. Blick, D. E. Savage, M. G. Lagally, A. J. Rimberg, R. Joynt, M. Friesen, S. N. Coppersmith, M. A. Eriksson. Work supported by ARO, LPS, NSF and DOE. (1) Shaji, N. et al. e-print arXiv:0708.0794 (2) Simmons, C. B. et al. Appl. Phys. Lett. 91, 213103 (2007).

Simmons, Christie

2008-03-01

184

Smith, E. R., and Kraus, N. C. 2007. Longshore and Sand Transport Calculated by Time-Dependent Shear Stress. Proceedings Coastal Sediments '07 Conference, ASCE Press, Reston,  

E-print Network

Smith, E. R., and Kraus, N. C. 2007. Longshore and Sand Transport Calculated by Time- Dependent SAND TRANSPORT CALCULATED BY TIME-DEPENDENT SHEAR STRESS Ernest R. Smith1 and Nicholas C. Kraus1 1. U.C.Kraus@erdc.usace.army.mil. Abstract: Based on longshore sand transport experiments performed in a large basin, measured sand transport

US Army Corps of Engineers

185

Fully predictive time-dependent transport simulations of ITB plasmas in JET, JT-60U and DIII-D  

Microsoft Academic Search

For the first time, the predictive capabilities of the mixed Bohm\\/GyroBohm, Weiland and 'retuned' GLF23 transport models are investigated with ITB discharges from the ITPA ITB database with fully predictive, time-dependent transport simulations. A range of plasma conditions is examined for JET, JT-60U and DIII-D discharges with internal transport barriers (ITBs). The simulations show that the Bohm\\/GyroBohm model is able

T. Tala; F. Imbeaux; V. V. Parail; C. Bourdelle; G. Corrigan; X. Garbet; D. J. Heading; X. Litaudon; P. I. Strand; J. Weiland; JET-EFDA contributors

2006-01-01

186

Wave-vector-dependent spin filtering and spin transport through magnetic barriers in graphene  

NASA Astrophysics Data System (ADS)

We study the spin-resolved transport through magnetic nanostructures in monolayer and bilayer graphene. We take into account both the orbital effect of the inhomogeneous perpendicular magnetic field as well as the in-plane spin splitting due to the Zeeman interaction and to the exchange coupling possibly induced by the proximity of a ferromagnetic insulator. We find that a single barrier exhibits a wave-vector-dependent spin filtering effect at energies close to the transmission threshold. This effect is significantly enhanced in a resonant double barrier configuration, where the spin polarization of the outgoing current can be increased up to 100% by increasing the distance between the barriers.

Dell'Anna, L.; de Martino, A.

2009-10-01

187

A time-dependent momentum-space density functional theoretical approach for electron transport dynamics in molecular devices  

E-print Network

We propose a time-dependent density functional theoretical (TDDFT) approach in momentum (\\mathcal{P} ) space for the study of electron transport in molecular devices under arbitrary biases. The basic equation of motion, ...

Chu, Shih-I; Zhou, Zhongyuan

2009-10-27

188

Transport by Populations of Fast and Slow Kinesins Uncovers Novel Family-Dependent Motor Characteristics Important for In Vivo Function  

E-print Network

Article Transport by Populations of Fast and Slow Kinesins Uncovers Novel Family-Dependent Motor Characteristics Important for In Vivo Function Go¨ker Arpag,1 Shankar Shastry,2 William O. Hancock,2,* and Erkan ABSTRACT Intracellular cargo transport frequently involves multiple motor types, either having opposite

Hancock, William O.

189

Hepatic adenosine triphosphate-dependent Ca2+ transport is mediated by distinct carriers on rat basolateral and canalicular membranes.  

PubMed Central

To characterize and localize hepatic plasma membrane ATP-dependent Ca2+ transport and Na+/Ca2+ exchange, studies were performed using highly purified rat basolateral and canalicular membrane vesicles. ATP-dependent Ca2+ transport activity was present in vesicles from both domains, insensitive to azide, oligomycin, oxalate, calmodulin, and calmidazolium, and virtually abolished at pH 6.8. However, basolateral and canalicular transport differed significantly. While basolateral transport was markedly stimulated by 1 mM Mg2+, canalicular transport was Mg2+ independent. Basolateral transport was similar at pH 7.4 and 8.0 but canalicular activity was stimulated fourfold at pH 8.0. Both Ca2+ Km [1.4 +/- 0.1 (SE).10(-8) vs. 4.8 +/- 0.7.10(-8) M] and Vmax (3.6 +/- 0.1 vs. 9.0 +/- 0.6 nmol mg-1 protein min-1) were lower in basolateral than in canalicular vesicles. Basolateral transport was somewhat more nucleotide specific (for ATP) and sensitive to vanadate (IC50 130 vs. 500 microM, respectively) than was canalicular transport. Na+/Ca2+ exchange activity was not detected in membranes from either domain. These studies suggest that hepatic ATP-dependent Ca2+ transport is mediated by domain-specific carriers on the basolateral and canalicular membranes. Images PMID:2703534

Blitzer, B L; Hostetler, B R; Scott, K A

1989-01-01

190

Spin-dependent electron transport in zinc- and manganese-doped adenine molecules  

SciTech Connect

The spin-dependent electron transport properties of zinc- and manganese-doped adenine molecules connected to zigzag graphene leads are studied in the zero bias regime using the non-equilibrium Green's function method. The conductance of the adenine molecule increased and became spin-dependent when a zinc or manganese atom was doped into the molecules. The effects of a transverse electric field on the spin-polarization of the transmitted electrons were investigated and the spin-polarization was controlled by changing the transverse electric field. Under the presence of a transverse electric field, both the zinc- and manganese-doped adenine molecules acted as spin-filters. The maximum spin-polarization of the manganese-doped adenine molecule was greater than the molecule doped with zinc.

Simchi, Hamidreza, E-mail: simchi@iust.ac.ir [Department of Physics, Iran University of Science and Technology, Narmak, Tehran 16844 (Iran, Islamic Republic of); Semiconductor Technology Center, Tehran 16844 (Iran, Islamic Republic of); Esmaeilzadeh, Mahdi, E-mail: mahdi@iust.ac.ir; Mazidabadi, Hossein [Department of Physics, Iran University of Science and Technology, Narmak, Tehran 16844 (Iran, Islamic Republic of)

2014-01-28

191

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

192

A hybrid transport-diffusion Monte Carlo method for frequency-dependent radiative-transfer simulations  

SciTech Connect

Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Implicit Monte Carlo radiative-transfer simulations in optically thick media. In DDMC, particles take discrete steps between spatial cells according to a discretized diffusion equation. Each discrete step replaces many smaller Monte Carlo steps, thus improving the efficiency of the simulation. In this paper, we present an extension of DDMC for frequency-dependent radiative transfer. We base our new DDMC method on a frequency-integrated diffusion equation for frequencies below a specified threshold, as optical thickness is typically a decreasing function of frequency. Above this threshold we employ standard Monte Carlo, which results in a hybrid transport-diffusion scheme. With a set of frequency-dependent test problems, we confirm the accuracy and increased efficiency of our new DDMC method.

Densmore, Jeffery D., E-mail: jdd@lanl.gov [Computational Physics and Methods Group, Los Alamos National Laboratory, P.O. Box 1663, MS D409, Los Alamos, NM 87545 (United States); Thompson, Kelly G., E-mail: kgt@lanl.gov [Computational Physics and Methods Group, Los Alamos National Laboratory, P.O. Box 1663, MS D409, Los Alamos, NM 87545 (United States); Urbatsch, Todd J., E-mail: tmonster@lanl.gov [Computational Physics and Methods Group, Los Alamos National Laboratory, P.O. Box 1663, MS D409, Los Alamos, NM 87545 (United States)

2012-08-15

193

Molecular cloning of the mouse IMINO system: an Na+- and Cl?-dependent proline transporter  

PubMed Central

Neurotransmitter transporters of the SLC6 family play an important role in the removal of neurotransmitters in brain tissue and in amino acid transport in epithelial cells. Here we demonstrate that the mouse homologue of slc6a20 has all properties of the long-sought IMINO system. The mouse has two homologues corresponding to the single human SLC6A20 gene: these have been named XT3 and XT3s1. Expression of mouse XT3s1, but not XT3, in Xenopus laevis oocytes induced an electrogenic Na+-and-Cl?-dependent transporter for proline, hydroxyproline, betaine, N-methylaminoisobutyric acid and pipecolic acid. Expression of XT3s1 was found in brain, kidney, small intestine, thymus, spleen and lung, whereas XT3 prevailed in kidney and lung. Accordingly we suggest that the two homologues be termed ‘XT3s1 IMINOB’ and ‘XT3 IMINOK’ to indicate the tissue expression of the two genes. PMID:15689184

2005-01-01

194

Charge-dependent transport switching of single molecular ions in a weak polyelectrolyte multilayer.  

PubMed

The tunable nature of weak polyelectrolyte multilayers makes them ideal candidates for drug loading and delivery, water filtration, and separations, yet the lateral transport of charged molecules in these systems remains largely unexplored at the single molecule level. We report the direct measurement of the charge-dependent, pH-tunable, multimodal interaction of single charged molecules with a weak polyelectrolyte multilayer thin film, a 10 bilayer film of poly(acrylic acid) and poly(allylamine hydrochloride) PAA/PAH. Using fluorescence microscopy and single-molecule tracking, two modes of interaction were detected: (1) adsorption, characterized by the molecule remaining immobilized in a subresolution region and (2) diffusion trajectories characteristic of hopping (D ? 10(-9) cm(2)/s). Radius of gyration evolution analysis and comparison with simulated trajectories confirmed the coexistence of the two transport modes in the same single molecule trajectories. A mechanistic explanation for the probe and condition mediated dynamics is proposed based on a combination of electrostatics and a reversible, pH-induced alteration of the nanoscopic structure of the film. Our results are in good agreement with ensemble studies conducted on similar films, confirm a previously-unobserved hopping mechanism for charged molecules in polyelectrolyte multilayers, and demonstrate that single molecule spectroscopy can offer mechanistic insight into the role of electrostatics and nanoscale tunability of transport in weak polyelectrolyte multilayers. PMID:24960617

Tauzin, Lawrence J; Shuang, Bo; Kisley, Lydia; Mansur, Andrea P; Chen, Jixin; de Leon, Al; Advincula, Rigoberto C; Landes, Christy F

2014-07-22

195

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

196

O+ transport in the dayside magnetosheath and its dependence on the IMF direction  

NASA Astrophysics Data System (ADS)

Recent studies have shown that the escape of oxygen ions (O+) into the magnetosheath along open magnetic field lines from the terrestrial cusp and mantle is significant. We present a study of how O+ transport in the dayside magnetosheath depends on the interplanetary magnetic field (IMF) direction. There are clear asymmetries in the O+ flows for southward and northward IMF. The asymmetries can be understood in terms of the different magnetic topologies that arise due to differences in the location of the reconnection site, which depends on the IMF direction. During southward IMF, most of the observed magnetosheath O+ is transported downstream. In contrast, for northward IMF we observe O+ flowing both downstream and equatorward towards the opposite hemisphere. We observe evidence of dual-lobe reconnection occasionally taking place during strong northward IMF conditions, a mechanism that may trap O+ and bring it back into the magnetosphere. Its effect on the overall escape is however small: we estimate the upper limit of trapped O+ to be 5%, a small number considering that ion flux calculations are rough estimates. The total O+ escape flux is higher by about a factor of 2 during times of southward IMF, in agreement with earlier studies of O+ cusp outflow.

Slapak, R.; Nilsson, H.; Westerberg, L. G.; Larsson, R.

2015-03-01

197

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. PMID:18962444

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

198

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

199

A nitrogen-dependent switch in the high affinity ammonium transport in Medicago truncatula.  

PubMed

Ammonium transporters (AMTs) are crucial for the high affinity primary uptake and translocation of ammonium in plants. In the model legume Medicago truncatula, the genomic set of AMT-type ammonium transporters comprises eight members. Only four genes were abundantly expressed in young seedlings, both in roots and shoots. While the expression of all AMTs in the shoot was not affected by the nitrogen availability, the dominating MtAMT1;1 gene was repressed by nitrogen in roots, despite that cellular nitrogen concentrations were far above deficiency levels. A contrasting de-repression by nitrogen was observed for MtAMT1;4 and MtAMT2;1, which were both expressed at intermediate level. Weak expression was found for MtAMT1;2 and MtAMT2;3, while the other AMTs were not detected in young seedlings. When expressed from their endogenous promoters, translational fusion proteins of MtAMT1;1 and MtAMT2;1 with green fluorescent protein were co-localized in the plasma membrane of rhizodermal cells, but also detected in cortical root layers. Both transporter proteins similarly functionally complemented a yeast strain that is deficient in high affinity ammonium transport, both at acidic and neutral pH. The uptake into yeast mediated by these transporters saturated with Km AMT1;1 = 89 µM and Km AMT2;1 = 123 µM, respectively. When expressed in oocytes, MtAMT1;1 mediated much larger (15)N-ammonium uptake than MtAMT2;1, but NH4 (+) currents were only recorded for MtAMT1;1. These currents saturated with a voltage-dependent Km = 90 µM at -80 mV. The cellular localization and regulation of the AMTs suggests that MtAMT1;1 encodes the major high affinity ammonium transporter gene in low nitrogen grown young M. truncatula roots and despite the similar localization and substrate affinity, MtAMT2;1 appears functionally distinct and more important at higher nitrogen supply. PMID:25164101

Straub, Daniel; Ludewig, Uwe; Neuhäuser, Benjamin

2014-11-01

200

Length dependence of electron transport through molecular wires--a first principles perspective.  

PubMed

One-dimensional wires constitute a fundamental building block in nanoscale electronics. However, truly one-dimensional metallic wires do not exist due to Peierls distortion. Molecular wires come close to being stable one-dimensional wires, but are typically semiconductors, with charge transport occurring via tunneling or thermally-activated hopping. In this review, we discuss electron transport through molecular wires, from a theoretical, quantum mechanical perspective based on first principles. We focus specifically on the off-resonant tunneling regime, applicable to shorter molecular wires (transport. Here, conductance decays exponentially with the wire length, with an exponential decay constant, beta, that is independent of temperature. Different levels of first principles theory are discussed, starting with the computational workhorse - density functional theory (DFT), and moving on to many-electron GW methods as well as GW-inspired DFT + Sigma calculations. These different levels of theory are applied in two major computational frameworks - complex band structure (CBS) calculations to estimate the tunneling decay constant, beta, and Landauer-Buttiker transport calculations that consider explicitly the effects of contact geometry, and compute the transmission spectra directly. In general, for the same level of theory, the Landauer-Buttiker calculations give more quantitative values of beta than the CBS calculations. However, the CBS calculations have a long history and are particularly useful for quick estimates of beta. Comparing different levels of theory, it is clear that GW and DFT + Sigma calculations give significantly improved agreement with experiment compared to DFT, especially for the conductance values. Quantitative agreement can also be obtained for the Seebeck coefficient - another independent probe of electron transport. This excellent agreement provides confirmative evidence of off-resonant tunneling in the systems under investigation. Calculations show that the tunneling decay constant beta is a robust quantity that does not depend on details of the contact geometry, provided that the same contact geometry is used for all molecular lengths considered. However, because conductance is sensitive to contact geometry, values of beta obtained by considering conductance values where the contact geometry is changing with the molecular junction length can be quite different. Experimentally measured values of beta in general compare well with beta obtained using DFT + Sigma and GW transport calculations, while discrepancies can be attributed to changes in the experimental contact geometries with molecular length. This review also summarizes experimental and theoretical efforts towards finding perfect molecular wires with high conductance and small beta values. PMID:25407785

Khoo, Khoong Hong; Chen, Yifeng; Li, Suchun; Quek, Su Ying

2015-01-01

201

Field dependent thermoelectric properties of organic semiconductors—A tool to determine the nature of charge transport in materials exhibiting thermally activated transport  

NASA Astrophysics Data System (ADS)

By implementing Monte Carlo simulations and employing the concept of effective temperature, we explore the effects of an applied field bias on the charge carrier statistics and Peltier coefficient in hopping systems subject to the parameter range applicable to disordered organic semiconductors. Distinct differences are found between the observed field dependences as obtained from systems in which energetic disorder is spatially correlated and those in which it is not. Considerable differences are also found between the charge carrier statistics and the Peltier coefficient's field dependence in systems in which charge is transported by bare charge carriers and systems in which it is propagated by polarons. Peltier coefficient field dependence investigations are, hence, proposed as a new tool for studying charge transport and thermoelectricity in disordered organic semiconductors and systems which exhibit thermally activated transport in general.

Mendels, Dan; Tessler, Nir

2015-03-01

202

Axial and azimuthal spin-wave eigenmodes in rolled-up permalloy stripes  

NASA Astrophysics Data System (ADS)

We experimentally realized rolled-up permalloy stripes to form three-dimensional ring-like ferromagnetic structures. By means of microwave absorption spectroscopy, we find multiple resonances occurring above a demagnetization field threshold which depends on the ring's axial width. Our experimental data can be well modeled by assuming both axial and azimuthal spin-wave confinement.

Balhorn, Felix; Jeni, Simon; Hansen, Wolfgang; Heitmann, Detlef; Mendach, Stefan

2012-05-01

203

Unveiling the nuclear structure at small x using azimuthal correlations in dA collisions  

E-print Network

We discuss azimuthal correlations in double inclusive hadron production in high energy $dA$ collisions at RHIC. We argue that the leading logarithmic approximation is inadequate for description of experimental data. Realistic shape of the azimuthal correlation function is obtain only if we keep terms that are finite in the rapidity difference between the produced hadrons. Likewise, transverse momentum dependence of parton distribution functions in both deuteron and nucleus must be retained. We observe depletion of the back-to-back correlations in central $dAu$ collisions in the forward direction consistent with the Color Glass Condensate predictions.

Tuchin, Kirill

2010-01-01

204

Infrared Observations Of Saturn's Rings : Azimuthal Variations And Thermal Modeling  

NASA Astrophysics Data System (ADS)

Saturn's rings represent a collection of icy centimeter to meter size particles with their local dynamic dictated by self gravity, mutual collisions, surface roughness and thickness of the rings themselves. The infrared observations obtained by the CIRS infrared spectrometer on board Cassini over the last 3.5 year contain informations on the local dynamic, as the thermal signature of planetary rings is influenced both by the ring structure and the particle properties. The ring temperature is very dependent on the solar phase angle (Spilker et al., this issue), and on the local hour angle around Saturn, depending on whether or not particles' visible hemispheres are heated by the Sun. The geometric filling factor, which can be estimated from CIRS spectra, is less dependent on the local hour angle, suggesting that the non isothermal behavior of particles' surfaces have low impact, but it is very dependent on the spacecraft elevation for the A and C rings. The ring small scale structure can be explored using CIRS data. Variations of the filling factor with the local hour angle relative to the spacecraft azimuth reveals self-gravity wakes. We derive morphological parameters of such wakes in both A and B rings assuming that wakes can be modeled either by regularly spaced bars with infinite or finite optical depth. Our results indicates that wakes in the A ring are almost flat, with a ratio height/width ? 0.44 ± 0.16 and with a pitch angle relative to the orbital motion direction of ? 27deg. This is consistent with UVIS (Colwell et al., 2006) and VIMS data (Hedman et al., 2007). Such models are more difficult to constrain in the B ring, but small variations of the filling factor indicate that the pitch angle decreases drastically in this ring. We also present a new thermal bar model to explain azimuthal variations of temperatures in the A ring. We compare results with previous ring thermal models of spherical particles. The Cassini/CIRS azimuthal scans data set is crucial input for any future modeling of Saturn's rings' thermal and dynamical properties.

Leyrat, C.; Spilker, L. J.; Altobelli, N.; Pilorz, S.; Ferrari, C.; Edgington, S. G.; Wallis, B. D.; Nugent, C.; Flasar, M.

2007-12-01

205

Glucose deprivation increases monocarboxylate transporter 1 (MCT1) expression and MCT1-dependent tumor cell migration.  

PubMed

The glycolytic end-product lactate is a pleiotropic tumor growth-promoting factor. Its activities primarily depend on its uptake, a process facilitated by the lactate-proton symporter monocarboxylate transporter 1 (MCT1). Therefore, targeting the transporter or its chaperon protein CD147/basigin, itself involved in the aggressive malignant phenotype, is an attractive therapeutic option for cancer, but basic information is still lacking regarding the regulation of the expression, interaction and activities of both proteins. In this study, we found that glucose deprivation dose-dependently upregulates MCT1 and CD147 protein expression and their interaction in oxidative tumor cells. While this posttranslational induction could be recapitulated using glycolysis inhibition, hypoxia, oxidative phosphorylation (OXPHOS) inhibitor rotenone or hydrogen peroxide, it was blocked with alternative oxidative substrates and specific antioxidants, pointing out at a mitochondrial control. Indeed, we found that the stabilization of MCT1 and CD147 proteins upon glucose removal depends on mitochondrial impairment and the associated generation of reactive oxygen species. When glucose was a limited resource (a situation occurring naturally or during the treatment of many tumors), MCT1-CD147 heterocomplexes accumulated, including in cell protrusions of the plasma membrane. It endowed oxidative tumor cells with increased migratory capacities towards glucose. Migration increased in cells overexpressing MCT1 and CD147, but it was inhibited in glucose-starved cells provided with an alternative oxidative fuel, treated with an antioxidant, lacking MCT1 expression, or submitted to pharmacological MCT1 inhibition. While our study identifies the mitochondrion as a glucose sensor promoting tumor cell migration, MCT1 is also revealed as a transducer of this response, providing a new rationale for the use of MCT1 inhibitors in cancer. PMID:24166504

De Saedeleer, C J; Porporato, P E; Copetti, T; Pérez-Escuredo, J; Payen, V L; Brisson, L; Feron, O; Sonveaux, P

2014-07-31

206

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

207

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

208

Hyperbolic theory for pH-dependent adsorption in reactive transport in porous media  

NASA Astrophysics Data System (ADS)

We use the hyperbolic theory of conservation laws to analyze the transport of strontium (Sr2+) through a porous medium with surface complexation. An hydrophilic iron-oxide surface was considered where Sr2+ and hydrogen (H+) compete for the same site leading to competitive adsorption described by an pH-dependent Langmuir isotherm. Despite the importance of pH-dependent adsorption in environmental applications, the basic structure of the displacement has received little attention. In reactive transport problems with pH-dependent adsorption, one of the conservation laws is for the total hydrogen (cHtot = cH+-cOH-) in the system, also called the acidity. The presence of this equation gives rise to additional nonlinearity in the problems that distinguishes them from other competitive sorption problems where hydrogen is not involved. We analyze a 1D reactive transport model with an incompressible fluid containing H+, Sr2+, sodium (Na+), and chlorine (Cl-) flowing through a reactive porous media made of goethite. Under the assumption of overall charge balance and of only advection for Na+ and Cl-, the mathematical problem reduces to a strictly hyperbolic 3x3 system of partial dierential equations (PDEs) for cHtot, Sr2+ (cSr2+), and effective anions (ca = cCl--cNa+) which are coupled by the adsorption isotherms for H+ and Sr2+ and have the non-linearity in the accumulation terms. One characteristic field is linearly degenerate while the other two are non-genuinely nonlinear due to inflection loci in both isotherms. We derived the complete set of analytical solutions to the Riemann problem (constant initial and injected states) and described the characteristic waves that may arise, concluding that only nine combinations of a contact discontinuity with rarefactions, shocks, shock-rarefactions are possible. The composite shock-rarefaction waves arise from the inflection loci in the isotherms and are absent in classic competitive Langmuir sorption. The inflection loci divide the composition space into two distinct high and low pH regions with distinct composition paths. The existence of a detached branch of the Hugoniot-locus is essential to the construction of composite waves that form when the left and right states are in distinct regions of the composition space. Highly resolved numerical solutions at large Peclet numbers show excellent agreement with the analytical solutions in the hyperbolic limit except under certain conditions when a pulse of Sr2+ and one of H+ arise ahead of the cor- responding retarded front and travel at the average fluid velocity. These conditions define the necessary conditions for the occurrence of the non-classical reactive transport which is not limited to only the Sr2+ front as observed in the earlier works [1,2] but it involves also the H+ front. These results raise important questions regarding the prediction of the migration of toxic compounds in the subsurface and pose also theoretical questions about the convergence of the vanishing diffusion solution to the hyperbolic limit, the stability of shock layers in reactive transport, and the role of the Riemann problem as an intermediate asymptotic solution for a wider range of problems. 1. Prigiobbe, V., Hesse, M., Bryant, S. L. (2012) Transport Porous Med 93 127-145. 2. Prigiobbe, V., Hesse, M., Bryant, S. L. (2012) accepted for publication in Geophys Res. Lett.

Prigiobbe, V.; Hesse, M. A.; Bryant, S. L.

2012-12-01

209

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

210

Effective grid-dependent dispersion coefficient for conservative and reactive transport simulations in heterogeneous porous media  

NASA Astrophysics Data System (ADS)

Because of the finite size of numerical grids, it is very difficult to correctly account for processes that occur at different spatial scales to accurately simulate the migration of conservative and reactive compounds dissolved in groundwater. In one hand, transport processes in heterogeneous porous media are controlled by local-scale dispersion associated to transport processes at the pore-scale. On the other hand, variations of velocity at the continuum- or Darcy-scale produce spreading of the contaminant plume, which is referred to as macro-dispersion. Furthermore, under some conditions both effects interact, so that spreading may enhance the action of local-scale dispersion resulting in higher mixing, dilution and reaction rates. Traditionally, transport processes at different spatial scales have been included in numerical simulations by using a single dispersion coefficient. This approach implicitly assumes that the separate effects of local-dispersion and macro-dispersion can be added and represented by a unique effective dispersion coefficient. Moreover, the selection of the effective dispersion coefficient for numerical simulations usually do not consider the filtering effect of the grid size over the small-scale flow features. We have developed a multi-scale Lagragian numerical method that allows using two different dispersion coefficients to represent local- and macro-scale dispersion. This technique considers fluid particles that carry solute mass and whose locations evolve according to a deterministic component given by the grid-scale velocity and a stochastic component that corresponds to a block-effective macro-dispersion coefficient. Mass transfer between particles due to local-scale dispersion is approximated by a meshless method. We use our model to test under which transport conditions the combined effect of local- and macro-dispersion are additive and can be represented by a single effective dispersion coefficient. We also demonstrate that for the situations where both processes are additive, an effective grid-dependent dispersion coefficient can be derived based on the concept of block-effective dispersion. We show that the proposed effective dispersion coefficient is able to reproduce dilution, mixing and reaction rates for a wide range of transport conditions similar to the ones found in many practical applications.

Cortinez, J. M.; Valocchi, A. J.; Herrera, P. A.

2013-12-01

211

Monte Carlo Assessment of Time Dependent Spectral Indexes for Benchmarking Neutron Transport in Iron  

NASA Astrophysics Data System (ADS)

Monte Carlo simulations (MCNP4C2) were performed to assess the ability to benchmark neutron transport calculations in iron using a pulsed-neutron slowing-down experiment. Specifically, calculations were performed to obtain the time dependent neutron energy spectra inside a 1 × 1 × 1 m natural iron moderator that is driven by a 14-MeV pulsed neutron source (simulating a pulsed D-T neutron generator). At various time intervals after the pulse, the energy spectrum was tallied and used to estimate the integral time-dependent reaction rates in 235U, 238U, 237Np, and 239Pu fission detectors that were located inside the moderator. The results show that within 0.05 ?s after the pulse, the average energy of the neutrons drops below 800 keV. Therefore, the threshold detectors (237Np, and 238U) can be useful at early times, while the fissile detectors (235U and 239Pu) can be utilized throughout the experiment. For these detectors, the time dependent reaction rates and spectral indexes (235U/239Pu, 237Np/239Pu, and 238U/239Pu) are developed and discussed.

Hawari, Ayman I.; Adams, James M.

2003-06-01

212

Pressure dependence of the large polaron transport in anatase TiO2 single crystals  

NASA Astrophysics Data System (ADS)

Anatase is a TiO2 polymorph which is a 3.2 eV gap semiconductor interesting for several applications, including catalysis, photocatalysis, and, especially, dye-sensitized solar cells. Surprisingly, transparent single crystals of anatase grown in our laboratory show a metallic resistivity above 60 K which origin is a shallow donor level created by oxygen vacancies. The high value of the resistivity and its T^3 temperature dependence are the result of the polaronic nature of the charge carriers which is supported by the Seebeck coefficient (S). The application of hydrostatic pressure fails to close the donor level and to extend the conducting state to the entire temperature range. Instead, we have found a non-monotonic variation of the low temperature activation energy with applied pressure which is ascribed to the change of polaron's mobility. Thermo-electric power exhibits an unconventional temperature and pressure dependence shedding an additional light on the conductivity mechanism in this compound. The pressure dependence of S is governed by the transport of the large entropy associated with the polaron formation.

Ja?imovi?, Ja?im; Vaju, Cristian; Berger, Helmuth; Magrez, Arnaud; Cerovski, Viktor; Žiki?, Radomir; Gaál, Richard; Forró, László

2012-02-01

213

The spin-dependent transport of Co-encapsulated Si nanotubes contacted with Cu electrodes  

SciTech Connect

Unlike carbon nanotubes, silicon ones are hard to form. However, they could be stabilized by metal-encapsulation. Using first-principles calculations, we investigate the spin-dependent electronic transport of Co-encapsulated Si nanotubes, which are contacted with Cu electrodes. For the finite tubes, as the tube-length increases, the transmission changes from spin-unpolarized to spin-polarized. Further analysis shows that, not only the screening of electrodes on Co's magnetism but also the spin-asymmetric Co-Co interactions are the physical mechanisms. As Cu and Si are the fundamental elements in semiconductor industry, our results may throw light on the development of silicon-based spintronic devices.

Guo, Yan-Dong; Yan, Xiao-Hong, E-mail: xhyan@nuaa.edu.cn [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210046 (China); Xiao, Yang [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

2014-02-10

214

The spin-dependent transport of Co-encapsulated Si nanotubes contacted with Cu electrodes  

NASA Astrophysics Data System (ADS)

Unlike carbon nanotubes, silicon ones are hard to form. However, they could be stabilized by metal-encapsulation. Using first-principles calculations, we investigate the spin-dependent electronic transport of Co-encapsulated Si nanotubes, which are contacted with Cu electrodes. For the finite tubes, as the tube-length increases, the transmission changes from spin-unpolarized to spin-polarized. Further analysis shows that, not only the screening of electrodes on Co's magnetism but also the spin-asymmetric Co-Co interactions are the physical mechanisms. As Cu and Si are the fundamental elements in semiconductor industry, our results may throw light on the development of silicon-based spintronic devices.

Guo, Yan-Dong; Yan, Xiao-Hong; Xiao, Yang

2014-02-01

215

Spin-dependent thermoelectronic transport of a single molecule magnet Mn(dmit){sub 2}  

SciTech Connect

We investigate spin-dependent thermoelectronic transport properties of a single molecule magnet Mn(dmit){sub 2} sandwiched between two Au electrodes using first-principles density functional theory combined with nonequilibrium Green's function method. By applying a temperature difference between the two Au electrodes, spin-up and spin-down currents flowing in opposite directions can be induced due to asymmetric distribution of the spin-up and spin-down transmission spectra around the Fermi level. A pure spin current and 100% spin polarization are achieved by tuning back-gate voltage to the system. The spin caloritronics of the molecule with a perpendicular conformation is also explored, where the spin-down current is blocked strongly. These results suggest that Mn(dmit){sub 2} is a promising material for spin caloritronic applications.

Su, Zhongbo; Wei, Xinyuan; Yang, Zhongqin, E-mail: zyang@fudan.edu.cn [State Key Laboratory of Surface Physics and Key Laboratory for Computational Physical Sciences (MOE) and Department of Physics, Fudan University, Shanghai 200433 (China); An, Yipeng [College of Physics and Electronic Engineering and Institute of Computational Materials Design, Henan Normal University, Xinxiang 453007 (China)

2014-05-28

216

Thickness dependence of electrical transport: A test for surface conduction in topological insulators  

NASA Astrophysics Data System (ADS)

Topological insulators have a conducting surface and an insulating bulk. Resistivity, as defined for a three dimensional conductor, should increase linearly with thickness in case of topological insulators. This is because resistivity is proportional to both resistance and thickness, and the surface conductance of a topological insulator should be independent of the thickness of the topological insulator. Thus, operationally, thickness dependence of resistivity could be one of the important tests in determining whether any material is a topological insulator or not. In this work, we have done a meta-analysis of the electrical transport data reported in the literature on topological insulators. However, many of the data do not follow any linear trend with thickness as is expected in the case of topological insulators. Thus we arrive at the conclusion from the existing data in the literature, that all of these materials cannot be considered as true topological insulators.

Barua, Sourabh; Rajeev, K. P.

2014-02-01

217

Cytoneme-mediated contact-dependent transport of the Drosophila Decapentaplegic signaling protein  

PubMed Central

Decapentaplegic (Dpp), a Drosophila morphogen signaling protein, transfers directly at synapes made at sites of contact between cells that produce Dpp and cytonemes that extend from recipient cells. The Dpp that cytonemes receive moves together with activated receptors toward the recipient cell body in motile puncta. Genetic loss-of-function conditions for diaphanous, shibire, neuroglian and capricious perturbed cytonemes by reducing their number or only the synapses they make with cells they target; and reduced cytoneme-mediated transport of Dpp and Dpp signaling. These experiments provide direct evidence that cells use cytonemes to exchange signaling proteins, that cytoneme-based exchange is essential for signaling and normal development, and that morphogen distribution and signaling can be contact-dependent, requiring cytoneme synapses. PMID:24385607

Roy, Sougata; Huang, Hai; Liu, Songmei; Kornberg, Thomas B.

2015-01-01

218

Environmental effects on temperature-dependent carrier transports in poly(3-hexylthiophene) films  

NASA Astrophysics Data System (ADS)

Applications of poly(3-hexylthiophene) (P3HT) to solar cells have been reported. The reliability of organic solar cells is a key factor of full-scale applications in commercial optoelectronics. In this study, the environmental effect on the carrier transport in P3HT is researched. Charge-trapping phenomena are studied through time-domain measurement for P3HT thin-film transistors. The time-domain data confirm the hole-trapping model, indicating that water vapor influences the response by producing additional hole traps that serve to increase the current time constant. To understand the P3HT degradation mechanisms, an analysis through the temperature-dependent transfer characteristics is presented. It is shown that the hopping conduction behavior can be affected by exposure to ambient humidity and ambient atmosphere, inducing fluctuations in the hopping distance and the barrier height for hopping that serve to influence the carrier mobility.

Lin, Yow-Jon; Chin, Yi-Min; Chang, Hsing-Cheng

2015-04-01

219

Chloride dependence of active sodium transport in frog skin: the role of intercellular spaces.  

PubMed Central

1. In agreement with previous observations the replacement of Cl by a nonpenetrating anion in the solution bathing either the outside or both sides of the frog skin causes a fall in the short-circuit current. 2. When Cl is replaced by a non-penetrating anion in the solution bathing the outside of the frog skin the Isc is still a correct measure of the net Na transport. 3. Under the same conditions both active and shunt paths seem to be affected since there is a decrease in Isc, Na influx, amiloride-dependent conductance, and initial Na uptake across the external barrier, together with a decrease in Cl-backfluxes and amiloride-independent conductance. There is also a decrease in water permeability and a reduction in size of the intercellular spaces. 4. The removal of Cl does not appear to affect the entry step of Na but may have an effect on the shunt path. This in turn may change the active Na transport. Images Plate 1 Plate 2 PMID:102765

Ferreira, K T; Hill, B S

1978-01-01

220

Temperature dependence of electrochemical DNA charge transport: influence of a mismatch.  

PubMed

Charge transfer through DNA is of interest as DNA is both the quintessential biomolecule of all living organisms and a self-organizing element in bioelectronic circuits and sensing applications. Here, we report the temperature-dependent properties of DNA charge transport in an electronically relevant arrangement of DNA monolayers on gold under biologically relevant conditions, and we track the effects of incorporating a CA single base pair mismatch. Charge transfer (CT) through double stranded, 17mer monolayers was monitored by following the yield of electrochemical reduction of a Nile blue redox probe conjugated to a modified thymine. Analysis with cyclic voltammetry and square wave voltammetry shows that DNA CT increases significantly with temperature, indicative of more DNA bridges becoming active for transport. The mismatch was found to attenuate DNA CT at lower temperatures, but the effect of the mismatch diminished as temperature was increased. Voltammograms were analyzed to extract the electron transfer rate k(0), the electron transfer coefficient ?, and the redox-active surface coverage ?*. Arrhenius behavior was observed, with activation energies of 100 meV for electron transfer through well-matched DNA. Single CA mismatches increased the activation energy by 60 meV. These results have clear implications for sensing applications and are evaluated with respect to the prominent models of DNA CT. PMID:23252597

Wohlgamuth, Chris H; McWilliams, Marc A; Slinker, Jason D

2013-02-01

221

Elevated copper ion levels as potential cause of impaired kinesin-dependent transport processes.  

PubMed

Copper is a trace element required to maintain essential life processes. In healthy organisms, copper metabolism is well balanced. If this balance is destroyed, the cellular level of free copper might increase and cause toxic effects. So far, the molecular mechanisms of copper intoxication are understood only partly. The present study revealed that the kinesin-dependent transport system is strongly affected by copper(II) ions. Both the microtubules, along which kinesin moves, and the kinesin itself were found to be the target structures of copper ions: Microtubule formation was suppressed by copper ions (IC50 26-70 µM) apparently chiefly by inhibition of binding of microtubule-associated proteins to tubulin. This inhibition could be widely compensated by the microtubule-stabilising agent paclitaxel. In addition, copper ions strongly inhibited the ATPase activity of neuron-specific kinesin KIF5A. At final KIF5A concentration of 112 nM, an IC50 of 1.3 µM was determined. Correspondingly, the motility activity of KIF5A, measured as velocity of microtubules gliding across a kinesin-covered surface, was blocked. The effects of copper ions on microtubules and on KIF5A are suggested to contribute to impaired transport processes within brain and other organs in cases of copper ion surplus. PMID:24853401

Böhm, Konrad J

2015-04-01

222

A new multidimensional, energy-dependent two-moment transport code for neutrino-hydrodynamics  

E-print Network

We present the new code ALCAR developed to model multidimensional, multi energy-group neutrino transport in the context of supernovae and neutron-star mergers. The algorithm solves the evolution equations of the 0th- and 1st-order angular moments of the specific intensity, supplemented by an algebraic relation for the 2nd-moment tensor to close the system. The scheme takes into account frame-dependent effects of order O(v/c) as well as the most important types of neutrino interactions. The transport scheme is significantly more efficient than a multidimensional solver of the Boltzmann equation, while it is more accurate and consistent than the flux-limited diffusion method. The finite-volume discretization of the essentially hyperbolic system of moment equations employs methods well-known from hydrodynamics. For the time integration of the potentially stiff moment equations we employ a scheme in which only the local source terms are treated implicitly, while the advection terms are kept explicit, thereby allo...

Just, Oliver; Janka, H -Thomas

2015-01-01

223

Na/sup +/-dependent transport of /sup 14/C-L-lysine across bullfrog alveolar epithelium  

SciTech Connect

Transepithelial transport of the basic amino acid L-lysine has been studied utilizing the isolated intact bullfrog lung mounted in the Ussing chamber. Lungs were excised from doubly pithed bullfrogs and sandwiched between two hemichambers. /sup 14/C-(U)-L-lysine was added to the upstream reservoir of amphibian Ringer solution, while the tissue was short-circuited. Two lungs from the same animal were used simultaneously to determine the two opposite unidirectional fluxes. Downstream and upstream radioactivities were assayed and used to estimate the apparent permeability (P) of the labeled lysine. Results indicate that the apparent P of /sup 14/C-L-lysine measured in the alveolar (M) to the pleural (S) direction is 19.06 (+- 2.84) x 10/sup -7/ cm/s and P in the S to M direction is 3.29 (+- 0.02) x 10/sup -7/ cm/s. When the 100 mM NaCl in the bath was replaced by 110 mM choline chloride, the flux of /sup 14/C-L-lysine from the alveolar to the pleural side decreased to the same value as that in the opposite direction. The flux from the pleural to the alveolar direction in the absence of Na/sup +/ did not change. These results suggest that the alveolar epithelium exhibits Na/sup +/-dependent amino acid (L-lysine) transport in the M->S, but not in the S->M, direction.

Kim, K.J.; Crandall, E.D.

1986-03-01

224

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.

225

Exactly Azimuthal Pixelizations of the Sky  

E-print Network

We investigate various pixelizations of the sky which allow for fast spherical transforms, for implementation in full sky CMB experiments such as Planck and MAP. We study the effect of varying pixel shape and area on the extraction of the CMB power spectrum. We argue for the benefits of having a truly azimuthal, or `igloo' pixelization. Such pixelizations are simple and allow for fast, exact simulations of pixelized skies. They also allow for precise correction to be made which accounts for the effects of pixel smoothing on extracted multipole moments.

Robert G. Crittenden; Neil G. Turok

1998-06-29

226

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

227

Demonstration of ATP dependent, transcellular transport of lipid across the lymphatic endothelium using an in vitro model of the lacteal  

PubMed Central

Purpose The lymphatic system plays crucial roles in tissue fluid balance, trafficking of immune cells, and the uptake of dietary lipid from the intestine. Given these roles there has been an interest in targeting lymphatics through oral lipid-based formulations or intradermal delivery of drug carrier systems. However the mechanisms regulating lipid uptake by lymphatics remain unknown. Thus we sought to modify a previously developed in vitro model to investigate the role of ATP in lipid uptake into the lymphatics. Methods Lymphatic endothelial cells were cultured on a transwell membrane and the effective permeability to free fatty acid and Caco-2 cell-secreted lipid was calculated in the presence or absence of the ATP-inhibitor sodium azide. Results: ATP inhibition reduced Caco-2 cell-secreted lipid transport, but not dextran transport. FFA transport was ATP-dependent primarily during early periods of ATP-inhibition, while Caco-2 cell-secreted lipid transport was lowered at all time points studied. Furthermore, the transcellular component of transport was highly ATP-dependent, a mechanism not observed in fibroblasts, suggesting these mechanisms are unique to lymphatics. Total transport of Caco-2 cell-secreted lipid was dose-dependently reduced by ATP inhibition, and transcellular lipoprotein transport was completely attenuated. Conclusion The transport of lipid across the lymphatic endothelium as demonstrated with this in vitro model occurs in part by an ATP-dependent, transcellular route independent of passive permeability. It remains to be determined the extent that this mechanism exists in vivo and future work should be directed in this area. PMID:24254195

Reed, Alana L.; Rowson, Sydney A.; Dixon, J. Brandon

2013-01-01

228

Binaural Sound Localizer for Azimuthal Movement Detection Based on Diffraction  

PubMed Central

Sound localization can be realized by utilizing the physics of acoustics in various methods. This paper investigates a novel detection architecture for the azimuthal movement of sound source based on the interaural level difference (ILD) between two receivers. One of the microphones in the system is surrounded by barriers of various heights in order to cast the direction dependent diffraction of the incoming signal. The gradient analysis of the ILD between the structured and unstructured microphone demonstrates the rotation directions as clockwise, counter clockwise, and no rotation of the sound source. Acoustic experiments with different types of sound source over a wide range of target movements show that the average true positive and false positive rates are 67% and 16%, respectively. Spectral analysis demonstrates that the low frequency delivers decreased true and false positive rates and the high frequency presents increases of both rates, overall. PMID:23112617

Kim, Keonwook; Choi, Anthony

2012-01-01

229

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

230

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

231

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

232

Triple-gluon and quadruple-gluon azimuthal correlations from glasma and higher-dimensional ridges  

NASA Astrophysics Data System (ADS)

We calculate the triple- and quadruple-gluon inclusive distributions with arbitrary rapidity and azimuthal angle dependence in the gluon saturation regime by using glasma diagrams. Also, we predict higher-dimensional ridges in triple- and quadruple-hadron correlations for p-p and p-Pb collisions at LHC, which have yet to be measured. In p-p and p-Pb collisions at the top LHC energies, gluon saturation is expected to occur since smaller Bjorken-x values are being probed. Glasma diagrams, which are enhanced at small-x , include gluon saturation effects, and they are used for calculating the long-range rapidity correlations ("ridges") and vn moments of the azimuthal distribution of detected hadrons. The glasma description reproduces the systematics of the data on both p-p and p-Pb ridges. As an alternative, relativistic hydrodynamics has also been applied to these small systems quite successfully. With the triple- and quadruple-gluon azimuthal correlations, this work aims to set the stage by going beyond the double-gluon azimuthal correlations in order to settle unambiguously the origin of "collectivity" in p-p and p-Pb collisions. We derive the triple- and quadruple-gluon azimuthal correlation functions in terms of unintegrated gluon distributions at arbitrary rapidities and azimuthal angles of produced gluons. Then, unintegrated gluon distributions from the running coupling Balitsky-Kovchegov evolution equation are used to calculate the triple- and quadruple-gluon correlations for various parameters of gluon momenta, initial scale for small-x evolution and beam energy.

Özönder, ?ener

2015-02-01

233

A Functional Role for Sodium-Dependent Glucose Transport across the Blood-Brain Barrier during Oxygen Glucose Deprivation  

PubMed Central

In the current study, we determined the functional significance of sodium-dependent/-independent glucose transporters at the neurovasculature during oxygen glucose deprivation (OGD). Confluent brain endothelial cells cocultured with astrocytes were exposed to varying degrees of in vitro stroke conditions. Glucose transporter (GLUT) 1 and sodium glucose cotransporter (SGLT) activity were investigated by luminal membrane uptake and transport studies using [3H]d-glucose and also by [14C]?-methyl d-glucopyranoside (AMG), a specific, nonmetabolized substrate of SGLT. In vivo middle cerebral artery occlusion experiments were tested to determine whether blood-brain barrier (BBB) SGLT activity was induced during ischemia. Increases in luminal d-glucose and AMG uptake and transport were observed with in vitro stroke conditions. Specific inhibitor experiments suggest a combined role for both SGLT and GLUT1 at the BBB during OGD. A time-dependent increase in the uptake of AMG was also seen in mice exposed to permanent focal ischemia, and this increase was sensitive to the SGLT inhibitor, phlorizin. Infarct and edema ratio during ischemia were significantly decreased by the inhibition of this transporter. These results show that both GLUT1 and SGLT play a role at the BBB in the blood-to-brain transport of glucose during ischemic conditions, and inhibition of SGLT during stroke has the potential to improve stroke outcome. Pharmacological modulation of this novel BBB transporter could prove to be a brain vascular target in stroke. PMID:18981287

Vemula, Sharanya; Roder, Karen E.; Yang, Tianzhi; Bhat, G. Jayarama; Thekkumkara, Thomas J.; Abbruscato, Thomas J.

2009-01-01

234

Azimuthal field instability in a confined ferrofluid  

NASA Astrophysics Data System (ADS)

We report the development of interfacial ferrohydrodynamic instabilities when an initially circular bubble of a nonmagnetic inviscid fluid is surrounded by a viscous ferrofluid in the confined geometry of a Hele-Shaw cell. The fluid-fluid interface becomes unstable due to the action of magnetic forces induced by an azimuthal field produced by a straight current-carrying wire that is normal to the cell plates. In this framework, a pattern formation process takes place through the interplay between magnetic and surface tension forces. By employing a perturbative mode-coupling approach we investigate analytically both linear and intermediate nonlinear regimes of the interface evolution. As a result, useful analytical information can be extracted regarding the destabilizing role of the azimuthal field at the linear level, as well as its influence on the interfacial pattern morphology at the onset of nonlinear effects. Finally, a vortex sheet formalism is used to access fully nonlinear stationary solutions for the two-fluid interface shapes.

Dias, Eduardo O.; Miranda, José A.

2015-02-01

235

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

NASA Astrophysics Data System (ADS)

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).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). Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04341j

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

2013-12-01

236

Phosphoenolpyruvate-dependent phosphotransferase system enzyme III and plasmid-encoded sucrose transport in Escherichia coli K-12.  

PubMed Central

The phosphoenolpyruvate-dependent carbohydrate:phosphotransferase system enzyme IISCR, specific for and regulated by sucrose, was analyzed in derivatives of Escherichia coli K-12 carrying the sucrose plasmid pUR404. Enzyme IIScr, coded for by gene scrA of the plasmid, depended for its transport and phosphorylation activity directly on the phosphotransferase system enzyme IIIGlc, Scr, coded for by the chromosomal gene crr. PMID:7045081

Lengeler, J W; Mayer, R J; Schmid, K

1982-01-01

237

INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES In air transport, the evolution of traffic depends  

E-print Network

27TH INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES 1 Abstract In air transport, the evolution to smaller airports. 1 Introduction During the last decade, the European air transport market saw role in the air transport industry, by improving their attractiveness and their competitiveness

Boyer, Edmond

238

Spin-dependent transport across Co/LaAlO{sub 3}/SrTiO{sub 3} heterojunctions  

SciTech Connect

The conducting interface formed between LaAlO{sub 3} and SrTiO{sub 3} exhibits high electron mobility, tunable carrier densities, and is theoretically predicted to have long spin lifetimes. Thus, the LaAlO{sub 3}/SrTiO{sub 3} heterostructure is a promising system for the transportation of spin information. We have investigated spin-dependent transport across Co/LaAlO{sub 3}/SrTiO{sub 3} heterostructures using an all electrical three terminal geometry and observed Lorentzian magnetoresistance typically associated with Hanle spin dephasing. However, such a picture fails to explain all the experimentally observed behavior. Further, experiments with spin-unpolarized Au/LaAlO{sub 3}/SrTiO{sub 3} heterojunctions support an alternative scenario involving current modulation by spin-dependent transport through defect states in the LaAlO{sub 3} barrier.

Swartz, Adrian G., E-mail: aswartz@stanford.edu [Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Harashima, Satoshi [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan); Xie, Yanwu; Kim, Bongju; Hwang, Harold Y. [Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Lu, Di [Department of Physics, Stanford University, Stanford, California 94305 (United States); Bell, Christopher [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Department of Physics, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Hikita, Yasuyuki [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States)

2014-07-21

239

Spin-dependent transport across Co/LaAlO3/SrTiO3 heterojunctions  

NASA Astrophysics Data System (ADS)

The conducting interface formed between LaAlO3 and SrTiO3 exhibits high electron mobility, tunable carrier densities, and is theoretically predicted to have long spin lifetimes. Thus, the LaAlO3/SrTiO3 heterostructure is a promising system for the transportation of spin information. We have investigated spin-dependent transport across Co/LaAlO3/SrTiO3 heterostructures using an all electrical three terminal geometry and observed Lorentzian magnetoresistance typically associated with Hanle spin dephasing. However, such a picture fails to explain all the experimentally observed behavior. Further, experiments with spin-unpolarized Au/LaAlO3/SrTiO3 heterojunctions support an alternative scenario involving current modulation by spin-dependent transport through defect states in the LaAlO3 barrier.

Swartz, Adrian G.; Harashima, Satoshi; Xie, Yanwu; Lu, Di; Kim, Bongju; Bell, Christopher; Hikita, Yasuyuki; Hwang, Harold Y.

2014-07-01

240

Time-dependent transport through quantum-impurity systems with Kondo resonance  

NASA Astrophysics Data System (ADS)

We investigate the time-dependent transport properties of single and double quantum-impurity systems based on the hierarchical equations of motion (HEOM) approach. In the Kondo regime, the dynamical current oscillates with time in both cases due to the temporal coherence of electrons tunneling through the device, which shares the same mechanism as the single-level resonance without e-e interactions, but shows some different characteristics. For single quantum-impurity systems, the temperature T has an inhibitory effect on the oscillations of dynamic current through its suppression of the Kondo effects. The amplitude of the current oscillations is attenuated by the e-e interaction U in the Kondo regime. The frequency of the current oscillations is found almost independent of T and U. For parallel-coupling double quantum-impurity systems, the oscillation of the current shows similar behavior to the single one, but with two-to-three times larger amplitudes. At the limit of small inter-impurity coupling the oscillation of the current exhibits enhanced characters, while it is weakened at the other limit.

Cheng, YongXi; Hou, WenJie; Wang, YuanDong; Li, ZhenHua; Wei, JianHua; Yan, YiJing

2015-03-01

241

Fast strontium transport induced by hydrodynamic dispersion and pH-dependent sorption  

NASA Astrophysics Data System (ADS)

As a fluid carries solutes through a porous material, species that sorb onto the surface of the material travel more slowly than the fluid. Stronger adsorption results in slower solute migration, or increased solute retardation. The adsorption of strontium (Sr2+) onto iron-oxides is strongly pH-dependent and becomes significant at high pH. Radioactive Sr2+ isotopes are, therefore, commonly stored in alkaline solutions to maximize their retardation. Field observations and numerical simulations of the leakage of such solutions into low-pH soils, however, show that even Sr2+ stored in alkaline solutions can migrate without retardation. Migration occurs because hydrodynamic dispersion allows mixing of Sr2+ with the low-pH fluid forming an acidic Sr2+-rich plume which can travel without retardation. Here we report the first experimental observations confirming this dispersion-induced fast Sr2+ transport. We report column-flood experiments where a high-pH solution containing Sr2+ was injected into a low-pH porous medium of iron-oxide-coated beads. We observe both a strongly retarded Sr2+ front and an isolated fast pulse of Sr2+ traveling at the average fluid velocity. This dispersion-induced fast pulse of strontium must be taken into account when considering the safety of radionuclide storage in alkaline solutions.

Prigiobbe, Valentina; Hesse, Marc A.; Bryant, Steven L.

2012-09-01

242

Thickness dependent quantum oscillations of transport properties in topological insulator Bi2Te3 thin films  

NASA Astrophysics Data System (ADS)

The dependences of the electrical conductivity, the Hall coefficient, and the Seebeck coefficient on the layer thickness d (d = 18-600 nm) of p-type topological insulator Bi2Te3 thin films grown by thermal evaporation in vacuum on glass substrates were obtained at room temperature. In the thickness range of d = 18-100 nm, sustained oscillations with a substantial amplitude were revealed. The observed oscillations are well approximated by a harmonic function with a period ?d = (9.5 ± 0.5) nm. At d > 100 nm, the transport coefficients practically do not change as d is increased. The oscillations of the kinetic properties are attributed to the quantum size effects due to the hole confinement in the Bi2Te3 quantum wells. The results of the theoretical calculations of ?d within the framework of a model of an infinitely deep potential well are in good agreement with the experimental results. It is suggested that the substantial amplitude of the oscillations and their sustained character as a function of d are connected with the topologically protected gapless surface states of Bi2Te3 and are inherent to topological insulators.

Rogacheva, E. I.; Budnik, A. V.; Sipatov, A. Yu.; Nashchekina, O. N.; Dresselhaus, M. S.

2015-02-01

243

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

244

MGS MAG/ER Data Analysis Using a Time and Magnetic Field Dependent Electron Transport Model  

NASA Technical Reports Server (NTRS)

The goal of that project was to examine certain details about the dayside electron environment at Mars as seen by the Mars Global Surveyor (MGS) magnetometer/electron reflectometer (MAG/ER) instrument. Specifically, we stated that we would use the Khazanov and Liemohn (K&L) kinetic electron transport model to analyze features in the observations. This code includes a non-uniform magnetic field and time-dependence in the result (different from most other models of this type). It was originally developed for electron motion along field lines in the Earth's magnetosphere (between conjugate ionospheres), and is thus quite appropriate for application to the Mars magnetic field scenario. Numerous code developments were implemented and the Mars version of the K&L model is fully operational. Initial results from this code have focused on the examination of MGS MAG/ER observations in the crustal field region when it is on the dayside. After several presentations at scientific meetings, this study culminated in a JGR publication last year.

Liemohn, Michael W.; Mitchell, David L.; Nagy, A. F.

2004-01-01

245

Stacking-order dependence in thermoelectric transport of biased trilayer graphene  

NASA Astrophysics Data System (ADS)

We numerically study the thermoelectric and thermal transport in trilayer graphene with different stacking orders in the presence of interlayer bias under a strong perpendicular magnetic field. In the biased ABA-stacked case, we find that the thermoelectric conductivity displays different asymptotic behaviors with the varying of the temperature, similar to that of monolayer graphene. In the high-temperature regime, the transverse thermoelectric conductivity ?xy saturates to a universal value 2.77kBe/h at the center of each Landau level, while it displays a linear temperature dependence at the low-temperature limit. The calculated transverse thermal conductivity ?xy exhibits two plateaus away from the band center. The transition between the two plateaus is continuous, which is accompanied by a pronounced peak in the longitudinal thermal conductivity ?xx. In the biased ABC-stacked case, it is found that both the thermoelectric conductivity and thermal conductivity have similar properties to the biased bilayer graphene, which is consistent with the behavior of a band insulator. The obtained results demonstrate the sensitivity of the thermoelectric conductivity to the band gap near the Dirac point. We also verify the validity of the Mott relation and the generalized Wiedemann-Franz law.

Ma, R.; Sheng, L.; Liu, M.; Sheng, D. N.

2012-09-01

246

Phospholamban-Dependent Effects of C12E8 on Calcium Transport and Molecular Dynamics in Cardiac Sarcoplasmic Reticulum  

E-print Network

the sarcoplasm into the SR lumen to allow relaxation of both skeletal and cardiac muscle. Previous studiesPhospholamban-Dependent Effects of C12E8 on Calcium Transport and Molecular Dynamics in Cardiac and cardiac sarcoplasmic reticulum (SR). In skeletal SR, C12E8 inhibits the Ca-ATPase, both at high

Thomas, David D.

247

A diffusion model for describing water transport in round squid mantle during drying with a moisture-dependent effective diffusivity  

Microsoft Academic Search

To date, only experimental drying studies have been published for the drying of squid mantle, neglecting the transport phenomenon of water in squid muscle. Added to this, the published studies of mass transfer phenomena during the drying of fish and other seafoods are always based on Fick's second law for evaluating constant effective diffusivity. Therefore, the dependence of the latter

Maurício B. F. Teixeira; Satoshi Tobinaga

1998-01-01

248

Resistin-like molecule-inhibits SGLT-1 activity and enhances GLUT2-dependent jejunal glucose transport  

E-print Network

not only be associated with inflammation but can also be a regulator of energy homeostasis. Glucose1 Resistin-like molecule- inhibits SGLT-1 activity and enhances GLUT2-dependent jejunal glucose transport Running title: RELM- increases glucose absorption Rim Belharbi Krimi, PhD, Philippe Letteron, Ph

Paris-Sud XI, Université de

249

The Role of Sodium-Dependent Glucose Transporter 1 and Glucose Transporter 2 in the Absorption of Cyanidin-3-O-?-Glucoside in Caco-2 Cells  

PubMed Central

Anthocyanins have multiple biological activities of benefit to human health. While a few studies have been conducted to evaluate the bioavailability of anthocyanins, the mechanisms of their absorption mechanism remain ill-defined. In the present study, we investigated the absorption mechanism of cyanidin-3-O-?-glucoside (Cy-3-G) in human intestinal epithelial (Caco-2) cells. Cy-3-G transport was assessed by measuring the absorptive and efflux direction. Inhibition studies were conducted using the pharmacological agents, phloridzin, an inhibitor of sodium-dependent glucose transporter 1 (SGLT1), or phloretin, an inhibitor of glucose transporter 2 (GLUT2). The results showed that phloridzin and phloretin significantly inhibited the absorption of Cy-3-G. In addition, Caco-2 cells transfected with small interfering RNA (siRNA) specific for SGLT1 or GLUT2 showed significantly decreased Cy-3-G absorption. These siRNA transfected cells also showed a significantly decreased rate of transport of Cy-3-G compared with the control group. These findings suggest that Cy-3-G absorption is dependent on the activities of SGLT1 and GLUT2 in the small intestine and that SGLT1 and GLUT2 could be a limiting step for the bioavailability of Cy-3-G. PMID:25314643

Zou, Tang-Bin; Feng, Dan; Song, Gang; Li, Hua-Wen; Tang, Huan-Wen; Ling, Wen-Hua

2014-01-01

250

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

NASA Astrophysics Data System (ADS)

We propose a semi-Lagrangian numerical algorithm for a time-dependent, anisotropic temperature transport equation in magnetized plasmas in regimes with negligible variation of the magnitude of the magnetic field B along field lines. The approach is based on a formal integral solution of the parallel (i.e., along the magnetic field) transport equation with sources. While this study focuses on a Braginskii (local) heat flux closure, the approach is able to accommodate nonlocal parallel heat flux closures as well. 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. Algorithmically, 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 algorithmically scalable). Accuracy-wise, the approach is free from the numerical pollution introduced by the discrete parallel transport term when the perpendicular to parallel transport coefficient ratio ??/?? becomes arbitrarily small, and is shown to capture the correct limiting solution when ?=??L?2/??L?2 ?0 (with L?, L? the parallel and perpendicular diffusion length scales, respectively). Therefore, the approach is asymptotic-preserving. We demonstrate the performance of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of heat transport across a magnetic island in cylindrical geometry in the presence of a large guide field.

Chacón, L.; del-Castillo-Negrete, D.; Hauck, C. D.

2014-09-01

251

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

252

Minimum audible movement angle as a function of the azimuth and elevation of the source.  

PubMed

In the future auditory directional cues may enhance situational awareness in cockpits with head-coupled displays. This benefit would depend, however, on the pilot's ability to detect the direction of moving sounds at different locations in space. The present investigation examined this ability. Auditory motion acuity was measured by the minimum audible movement angle (MAMA): the minimum angle of travel required for detection of the direction of sound movement. Five experienced listeners were instructed to indicate the direction of travel of a sound source (broadband noise at 50 dBA) that moved at a velocity of 20 deg/s. Nine azimuth positions were tested at 0 deg elevation. Five elevations were then tested at 0 deg azimuth. Finally two azimuth positions were tested at an elevation of 80 deg. The position of the source did not significantly affect the MAMA for azimuth locations between +40 and -40 deg and elevations below 80 deg. Within this area the MAMA ranged between 1 and 2 deg. Outside this area the MAMA increased to 3 to 10 deg. PMID:1634240

Strybel, T Z; Manligas, C L; Perrott, D R

1992-06-01

253

Azim: Direction Based Service Using Azimuth Based Position Estimation  

Microsoft Academic Search

In this paper, we propose a system named Azim that pro- vides service based on both location and direction, which uses potion estimation method based on azimuth data. In this system, a user's position is estimated by having the user point to and measure azimuths of several markers or ob- jects whose positions are already known. Because the mea- surements

Yohei Iwasaki; Nobuo Kawaguchi; Yasuyoshi Inagaki

2004-01-01

254

Azimuth estimation of mobile robot based on Federated Kalman Filter  

Microsoft Academic Search

Mobile robot is an important branch of robotics research, and the azimuth of mobile robot is a very important moving process parameter. In this paper, we adopted multi-sensor integrated, combining digital magnetic compass, fiber optic gyro and photoelectric encode to estimate the azimuth of mobile robot, and putting each measurement result into Federated filter. We use Unscented Kalman filter as

Qingxin Zhang; Xiaoyan Qiu; Guangyan Xu; Qinglong Di

2010-01-01

255

Cyclic AMP-dependent regulation of K+ transport in the rat distal colon.  

PubMed Central

1. The effect of agonists of the cyclic AMP pathway and of 293B, a chromanole-derived K+ channel blocker, on K+ transport in the rat distal colon was studied by measuring unidirectional fluxes, uptake, and efflux of Rb+ in mucosa-submucosa preparations and by patch-clamp of crypt epithelia from isolated crypts. 2. 293B concentration-dependently inhibited basal and forskolin-stimulated short-circuit current. In isolated crypts 293B blocked a basal K+ conductance but had no effect on cyclic AMP-evoked depolarization induced by the opening of apical Cl- channels. When the effect of cyclic AMP on Cl- conductance was prevented by substituting Cl- with gluconate, an inhibition of total cellular K+ conductance by forskolin and a membrane-permeable cyclic AMP analogue was unmasked. 3. Unidirectional ion flux measurements revealed that 293B suppressed the increase in JRbsm induced by forskolin. This, together with the inhibition of cyclic AMP-induced anion secretion indicates that the drug blocks K+ channels, presumably both in the apical and the basolateral membrane. Forskolin caused not only inhibition of K+ absorption, but also stimulation of K+ secretion. The inhibition was diminished, but not blocked, in the presence of inhibitors of the apical H(+)-K(+)-ATPase, vanadate and ouabain. Forskolin stimulated serosal, bumetanide-sensitive Rb+ uptake, whereas mucosal, ouabain/vanadate-sensitive uptake remained unaffected. 4. Efflux experiments revealed that forskolin caused a redistribution of cellular K+ efflux reducing the ratio of basolateral versus apical Rb+ efflux. 5. These results suggest that intracellular cyclic AMP exerts its effects on K+ transport by several mechanisms: an increase in the driving force for K+ efflux due to the depolarization induced by opening of Cl- channels, a stimulation of the basolateral uptake of K+ via the Na(+)-K(+)-Cl(-)-cotransporter, and a decrease of the ratio of basolateral versus apical K+ conductance leading to an enhanced efflux of K+ into the lumen and a reduced K+ efflux to the serosal compartment. PMID:8832075

Diener, M.; Hug, F.; Strabel, D.; Scharrer, E.

1996-01-01

256

Upper crustal azimuthal anisotropy across the contiguous U.S. determined by Rayleigh wave ellipticity  

NASA Astrophysics Data System (ADS)

Constraints on upper crustal seismic anisotropy provide insight into the local stress orientation and structural fabric, but such constraints are scarce except in areas with dense recordings of local seismicity. We investigate directionally dependent Rayleigh wave ellipticity, or Rayleigh wave H/V (horizontal to vertical) amplitude ratios, between 8 and 20 s period across USArray to infer azimuthal anisotropy in the upper crust across the contiguous U.S. To determine the H/V ratios, we use all available multicomponent ambient noise cross correlations between all USArray stations operating between 2007 and 2013. In many locations, the observed H/V ratios are clearly back azimuth dependent with a 180° periodicity, which allows the fast directions and amplitudes of upper crustal anisotropy to be determined. The observed patterns of anisotropy correlate well with both near-surface geological features (e.g., the Intermountain Seismic Belt and Appalachian-Ouachita collision belt) and a previous stress model.

Lin, Fan-Chi; Schmandt, Brandon

2014-12-01

257

Fluctuations of the azimuthal particle distribution in NA49 at the CERN SPS  

E-print Network

Event-by-event fluctuations and correlations in azimuthal angle are currently widely investigated in various experiments. In this paper the $\\Phi$ measure (earlier used in experiments to evaluate fluctuations in transverse momentum) is now applied to azimuthal angle $\\phi$. Properties of this $\\Phi_{\\phi}$ function are investigated through fast generators and with complex models such as Pythia, Hijing, and UrQMD. Preliminary results of NA49 on $\\Phi_{\\phi}$ are also presented. The system size dependence (p+p, C+C, Si+Si and 6 centralities of Pb+Pb) at the highest SPS energy (158$A$ GeV) is shown, as well as the energy dependence (20$A$ - 158$A$ GeV) for the 7.2\\% most central Pb+Pb interactions.

Tomasz Cetner; Katarzyna Grebieszkow for the NA49 Collaboration

2010-08-19

258

Cloning and molecular characterization of the ontogeny of a rat ileal sodium-dependent bile acid transporter.  

PubMed Central

Sodium-dependent bile acid transport in the rat ileum is abruptly expressed at weaning. Degenerate oligonucleotides, based on amino acid sequence identities between the rat liver and hamster ileal transporters, were used to amplify a rat ileal probe. A 1.2-kb cDNA clone, which contains the full coding region (348 amino acids, 38 kD), was isolated by hybridization screening. In vitro translation yielded a 38-kD protein which glycosylated to 48 kD. Sodium-dependent uptake of taurocholate was observed in oocytes injected with cRNA. Northern blot analysis revealed a 5.0-kb mRNA in ileum, kidney, and cecum. A 48-kD protein was detected in ileal brush border membranes and localized to the apical border of villus ileal enterocytes. mRNA and protein expression, which were negligible before weaning, increased dramatically at weaning. Nuclear transcription rates for the transporter increased 15-fold between postnatal days 7 and 28. The apparent molecular weight of the transporter also increased between days 19 and 28. In summary, the developmental regulation of the rat ileal sodium-dependent bile acid cotransporter is characterized by transcriptionally regulated increases in mRNA and protein levels at the time of weaning with changes in apparent molecular weight of the protein after weaning. Images PMID:7860756

Shneider, B L; Dawson, P A; Christie, D M; Hardikar, W; Wong, M H; Suchy, F J

1995-01-01

259

Plasma low density lipoprotein transport kinetics in noninsulin-dependent diabetes mellitus.  

PubMed Central

Plasma low density lipoprotein (LDL) transport kinetics were determined from the disappearance of 125I-LDL injected into age- and weight-matched groups of 13 normal subjects, 20 mild diabetics, and 8 moderately severe diabetic patients (fasting plasma glucose less than 150 and greater than 150 mg/100 ml, respectively). In mild diabetics, LDL apo-lipoprotein-B (apo-B) synthetic rate (SR) was significantly greater than normal. The fractional catabolic rate (FCR), however, was also increased so that plasma LDL concentration remained normal. In moderately severe diabetics, LDL SR was normal but FCR was reduced resulting in increased plasma LDL cholesterol and apo-B concentrations. In normal subjects, moderate obesity was associated with increased LDL secretion. In diabetic subjects, however, changes in LDL turnover were of equal magnitude in obese and nonobese patients. In normolipemic and hyperlipemic mild diabetic subjects with equal degrees of glucose intolerance, both LDL apo-B SR and FCR were greater than normal. The magnitude of these increases, however, was lower in the hyperlipemic individuals. Stepwise regression analysis revealed that both LDL SR and FCR correlated positively and linearly with insulin response to glucose loading, but negatively and curvilinearly with fasting plasma glucose and glucose response. We propose that in noninsulin-dependent diabetes, mild hyperglycemia is accompanied by increased LDL turnover, despite normal plasma LDL levels, whereas moderately severe hyperglycemia is associated with decreased LDL catabolism, resulting in increased plasma LDL levels. These changes cannot be attributed to the presence of obesity or hypertriglyceridemia, and may relate to varying degrees of insulin resistance and decreased insulin secretion affecting plasma very low density lipoprotein (VLDL) secretion, VLDL conversion to LDL, and LDL catabolism. Both increased LDL turnover in mild diabetes and delayed removal of LDL in moderately severe diabetes could increase cholesterol ester availability to peripheral tissues, and may result in an increased risk of atherosclerosis. PMID:6338042

Kissebah, A H; Alfarsi, S; Evans, D J; Adams, P W

1983-01-01

260

Computational models for drug inhibition of the human apical sodium-dependent bile acid transporter.  

PubMed

The human apical sodium-dependent bile acid transporter (ASBT; SLC10A2) is the primary mechanism for intestinal bile acid reabsorption. In the colon, secondary bile acids increase the risk of cancer. Therefore, drugs that inhibit ASBT have the potential to increase the risk of colon cancer. The objectives of this study were to identify FDA-approved drugs that inhibit ASBT and to derive computational models for ASBT inhibition. Inhibition was evaluated using ASBT-MDCK monolayers and taurocholate as the model substrate. Computational modeling employed a HipHop qualitative approach, a Hypogen quantitative approach, and a modified Laplacian Bayesian modeling method using 2D descriptors. Initially, 30 compounds were screened for ASBT inhibition. A qualitative pharmacophore was developed using the most potent 11 compounds and applied to search a drug database, yielding 58 hits. Additional compounds were tested, and their K(i) values were measured. A 3D-QSAR and a Bayesian model were developed using 38 molecules. The quantitative pharmacophore consisted of one hydrogen bond acceptor, three hydrophobic features, and five excluded volumes. Each model was further validated with two external test sets of 30 and 19 molecules. Validation analysis showed both models exhibited good predictability in determining whether a drug is a potent or nonpotent ASBT inhibitor. The Bayesian model correctly ranked the most active compounds. In summary, using a combined in vitro and computational approach, we found that many FDA-approved drugs from diverse classes, such as the dihydropyridine calcium channel blockers and HMG CoA-reductase inhibitors, are ASBT inhibitors. PMID:19673539

Zheng, Xiaowan; Ekins, Sean; Raufman, Jean-Pierre; Polli, James E

2009-01-01

261

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

262

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

263

A numerical method for solving a scalar advection-dominated transport equation with concentration-dependent sources  

Microsoft Academic Search

Abstract A numerical scheme, upstream biased Eulerian algorithm for transport equations with sources (UpBEATES), is developed for solving a scalar advective-dominated,transport equation,with concentration-independent,and -dependent source terms. A control- volume,method,is used for spatial discretization. Time integration is invoked to yield a discrete system of integrated-flux-integrated- source form,equations. The Bott’s upstream-biased,Eulerian advection scheme,[Moneatry and,Weakly Review 117 (1989a) 1006; Moneatry,and Weakly Review 117

Minghui Jin; Roseanne M. Ford; Peter T. Cummings

2003-01-01

264

Hydrodynamical analysis of azimuthal two-particle correlations in relativistic heavy-ion collisions  

NASA Astrophysics Data System (ADS)

Azimuthal two-particle correlations in heavy-ion collisions with the energy E(sub lab) is approximately 1 GeV/nucleon have been calculated in the three-dimensional hydrodynamic model. The results of calculation of the proton-proton correlation for a heavy target (C + Pb, E(sub lab) = 3.6 GeV/nucleon) reproduce the experimental data obtained at the Dubna synchrophasotron fairy well. The dependence of model results on nuclear compressibility is discussed.

Russkikh, V. N.

265

Soft Gluon Resummations in Dijet Azimuthal Angular Correlations at the Collider  

E-print Network

We derive all order soft gluon resummation in dijet azimuthal angular correlation in hadronic collisions at the next-to-leading logarithmic level. The relevant coefficients for the Sudakov resummation factor, the soft and hard factors, are calculated. The theory predictions agree well with the experimental data from D0 Collaboration at the Tevatron. This provides a benchmark calculation for the transverse momentum dependent QCD resummation for jet productions in hadron collisions and can be readily applied at the CERN LHC.

Peng Sun; C. -P. Yuan; Feng Yuan

2014-05-05

266

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

267

Soft gluon resummations in dijet azimuthal angular correlations in hadronic collisions.  

PubMed

We derive all order soft gluon resummation in dijet azimuthal angular correlation in hadronic collisions at the next-to-leading logarithmic level. The relevant coefficients for the Sudakov resummation factor, the soft and hard factors, are calculated. The theory predictions agree well with the experimental data from D0 Collaboration at the Tevatron. This provides a benchmark calculation for the transverse momentum dependent QCD resummation for jet productions in hadron collisions. PMID:25526118

Sun, Peng; Yuan, C-P; Yuan, Feng

2014-12-01

268

ATP-dependent cadmium transport by the cadA cadmium resistance determinant in everted membrane vesicles of Bacillus subtilis.  

PubMed

Resistance to cadmium conferred by the staphylococcal plasmid pI258 occurs by means of energy-dependent efflux, resulting in decreased intracellular accumulation of cadmium. Recent sequence information suggested that efflux is mediated by a P-type ATPase. The cadA gene was previously expressed in Bacillus subtilis, conferring resistance to cadmium. Everted membrane vesicles were prepared from B. subtilis cells harboring either a plasmid containing the cadA system or the vector plasmid alone. 109Cd2+ transport into the everted membranes was measured in the presence of various energy sources. Cadmium transport was detected only in the presence of ATP as an energy source. The production of an electrochemical proton gradient (delta mu H+) by using NADH or phenazine methosulfate plus ascorbate was not able to drive transport. Reagents which dissipate delta pH abolished calcium transport due to the Ca2+/H+ antiporter but only partially inhibited cadmium transport. Inhibition of transport by the antibiotic bafilomycin A1 occurred at concentrations comparable to those which inhibit P-type ATPases. A band corresponding to the cadA gene product was identified on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and antibodies to the protein were prepared. PMID:1530844

Tsai, K J; Yoon, K P; Lynn, A R

1992-01-01

269

Interactions of noncanonical motifs with hnRNP A2 promote activity-dependent RNA transport in neurons  

PubMed Central

A key determinant of neuronal functionality and plasticity is the targeted delivery of select ribonucleic acids (RNAs) to synaptodendritic sites of protein synthesis. In this paper, we ask how dendritic RNA transport can be regulated in a manner that is informed by the cell’s activity status. We describe a molecular mechanism in which inducible interactions of noncanonical RNA motif structures with targeting factor heterogeneous nuclear ribonucleoprotein (hnRNP) A2 form the basis for activity-dependent dendritic RNA targeting. High-affinity interactions between hnRNP A2 and conditional GA-type RNA targeting motifs are critically dependent on elevated Ca2+ levels in a narrow concentration range. Dendritic transport of messenger RNAs that carry such GA motifs is inducible by influx of Ca2+ through voltage-dependent calcium channels upon ?-adrenergic receptor activation. The combined data establish a functional correspondence between Ca2+-dependent RNA–protein interactions and activity-inducible RNA transport in dendrites. They also indicate a role of genomic retroposition in the phylogenetic development of RNA targeting competence. PMID:24841565

Muslimov, Ilham A.; Tuzhilin, Aliya; Tang, Thean Hock; Wong, Robert K.S.; Bianchi, Riccardo

2014-01-01

270

Azimuthal anisotropy in U+U collisions at STAR  

DOE PAGESBeta

The azimuthal anisotropy of particle production is commonly used in high-energy nuclear collisions to study the early evolution of the expanding system. The prolate shape of uranium nuclei makes it possible to study how the geometry of the colliding nuclei a#11;ffects #12;final state anisotropies. It also provides a unique opportunity to understand how entropy is produced in heavy ion collisions. In this paper, the two- and four- particle cumulant v2 (v2{2} and v2{4}) from U+U collisions at ?sNN = 193 GeV and Au+Au collisions at ?sNN = 200 GeV for inclusive charged hadrons will be presented. The STAR Zero Degree Calorimeters are used to select very central collisions. Diff#11;erences were observed between the multiplicity dependence of v2{2} for most central Au+Au and U+U collisions. The multiplicity dependence of v2{2} in central collisions were compared to Monte Carlo Glauber model predictions and it was seen that this model cannot explain the present results. (auth)

Wang, Hui; Sorensen, Paul

2014-12-01

271

Azimuthal anisotropy in U+U collisions at STAR  

SciTech Connect

The azimuthal anisotropy of particle production is commonly used in high-energy nuclear collisions to study the early evolution of the expanding system. The prolate shape of uranium nuclei makes it possible to study how the geometry of the colliding nuclei a#11;ffects #12;final state anisotropies. It also provides a unique opportunity to understand how entropy is produced in heavy ion collisions. In this paper, the two- and four- particle cumulant v2 (v2{2} and v2{4}) from U+U collisions at ?sNN = 193 GeV and Au+Au collisions at ?sNN = 200 GeV for inclusive charged hadrons will be presented. The STAR Zero Degree Calorimeters are used to select very central collisions. Diff#11;erences were observed between the multiplicity dependence of v2{2} for most central Au+Au and U+U collisions. The multiplicity dependence of v2{2} in central collisions were compared to Monte Carlo Glauber model predictions and it was seen that this model cannot explain the present results. (auth)

Wang, Hui; Sorensen, Paul

2014-12-01

272

Forward-backward correlations between multiplicities in windows separated in azimuth and rapidity  

E-print Network

The forward-backward (FB) charged particle multiplicity correlations between windows separated in rapidity and azimuth are analyzed using a model that treats strings as independent identical emitters. Both the short-range (SR) contribution, originating from the correlation between multiplicities produced from a single source, and the long-range (LR) contribution, originating from the fluctuation in the number of sources, are taken into account. The dependencies of the FB correlation coefficient, $b$, on the windows' rapidity and azimuthal acceptance and the gaps between these windows are studied and compared with the preliminary data of ALICE. The analysis of these dependencies effectively separates the contributions of two above mechanisms. It is also demonstrated that traditional definitions of FB correlation coefficient $b$ have a strong nonlinear dependence on the acceptance of windows. Suitable alternative observables for the future FB correlation studies are proposed. The connection between $b$ and the two-particle correlation function, $C_2$, is traced, as well as its connection to the untriggered di-hadron correlation analysis. Using a model independent analysis, it is shown that measurement of the FB multiplicity correlations between two small windows separated in rapidity and azimuth fully determine the two-particle correlation function $C_2$, even if the particle distribution in rapidity is not uniform.

Vladimir Vechernin

2014-10-24

273

ATP-dependent transport of statins by human and rat MRP2/Mrp2  

SciTech Connect

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 (logD{sub 7.0}) 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 IC{sub 50} 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. - Highlights: • We characterised MRP2 (human)/Mrp2 (rat)-mediated transport of statins. • We show statins were transported by human and rat MRP2/Mrp2. • Statins competed with a known substrate for transport by MRP2/Mrp2. • Competition involved more than one binding site on the MRP2/Mrp2 protein.

Ellis, Lucy C.J., E-mail: Luc_ellis@yahoo.co.uk [Section of Translational Medicine, Division of Applied Biology, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD (United Kingdom); Hawksworth, Gabrielle M. [Section of Translational Medicine, Division of Applied Biology, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD (United Kingdom); Weaver, Richard J. [Biologie Servier, Drug Safety Research Centre, 905 Route de Saran, 45520 Gidy (France)

2013-06-01

274

Strategies for optimization of mineral nutrient transport in plants: multilevel regulation of nutrient-dependent dynamics of root architecture and transporter activity.  

PubMed

How do sessile plants cope with irregularities in soil nutrient availability? The uptake of essential minerals from the soil influences plant growth and development. However, most environments do not provide sufficient nutrients; rather nutrient distribution in the soil can be uneven and change temporally according to environmental factors. To maintain mineral nutrient homeostasis in their tissues, plants have evolved sophisticated systems for coping with spatial and temporal variability in soil nutrient concentrations. Among these are mechanisms for modulating root system architecture in response to nutrient availability. This review discusses recent advances in knowledge of the two important strategies for optimizing nutrient uptake and translocation in plants: root architecture modification and transporter expression control in response to nutrient availability. Recent studies have determined (i) nutrient-specific root patterns; (ii) their physiological consequences; and (iii) the molecular mechanisms underlying these modulation systems that operate to facilitate efficient nutrient acquisition. Another mechanism employed by plants in nutrient-heterogeneous soils involves modification of nutrient transport activities in a nutrient concentration-dependent manner. In recent years, considerable progress has been made in characterizing the diverse functions of transporters for specific nutrients; it is now clear that the expression and activities of nutrient transporters are finely regulated in multiple steps at both the transcriptional and post-transcriptional levels for adaptation to a wide range of nutrient conditions. PMID:25378690

Aibara, Izumi; Miwa, Kyoko

2014-12-01

275

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

276

Thiol-dependent passive K\\/Cl transport in sheep red cells: VII. Volume-independent freezing by iodoacetamide, and sulfhydryl group heterogeneity  

Microsoft Academic Search

Summary The sulfhydryl (SH) reagent iodoacetamide (IAAM) inhibits stimulation of Cl-dependent K transport in low K (LK) sheep red cells by another SH reagent, N-ethylmaleimide (NEM), without itself activating this transport pathway (J. Membrane Biol., 1983,73:257–261). We now report that IAAM alone, acting with a kinetic slower than NEM, sharply reduced the capability of the Cl-dependent K transport system to

P. K. Lauf

1987-01-01

277

Regulation of energy partitioning and alternative electron transport pathways during cold acclimation of lodgepole pine is oxygen dependent.  

PubMed

Second year needles of Lodgepole pine (Pinus contorta L.) were exposed for 6 weeks to either simulated control summer ['summer'; 25 °C/250 photon flux denisty (PFD)], autumn ('autumn'; 15°C/250 PFD) or winter conditions ('winter'; 5 °C/250 PFD). We report that the proportion of linear electron transport utilized in carbon assimilation (ETR(CO2)) was 40% lower in both 'autumn' and 'winter' pine when compared with the 'summer' pine. In contrast, the proportion of excess photosynthetic linear electron transport (ETR(excess)) not used for carbon assimilation within the total ETR(Jf) increased by 30% in both 'autumn' and 'winter' pine. In 'autumn' pine acclimated to 15°C, the increased amounts of 'excess' electrons were directed equally to 21 ?kPa O2-dependent and 2 ?kPa O2-dependent alternative electron transport pathways and the fractions of excitation light energy utilized by PSII photochemistry (?(PSII)), thermally dissipated through ?(NPQ) and dissipated by additional quenching mechanism(s) (?(f,D)) were similar to those in 'summer' pine. In contrast, in 'winter' needles acclimated to 5 °C, 60% of photosynthetically generated 'excess' electrons were utilized through the 2 ?kPa O2-dependent electron sink and only 15% by the photorespiratory (21 ?kPa O2) electron pathway. Needles exposed to 'winter' conditions led to a 3-fold lower ?(PSII), only a marginal increase in ?(NPQ) and a 2-fold higher ?(f,D), which was O2 dependent compared with the 'summer' and 'autumn' pine. Our results demonstrate that the employment of a variety of alternative pathways for utilization of photosynthetically generated electrons by Lodgepole pine depends on the acclimation temperature. Furthermore, dissipation of excess light energy through constitutive non-photochemical quenching mechanisms is O2 dependent. PMID:20630988

Savitch, Leonid V; Ivanov, Alexander G; Krol, Marianna; Sprott, David P; Oquist, Gunnar; Huner, Norman P A

2010-09-01

278

Role of proton hopping in surface charge transport on tin dioxide as revealed by the thermal dependence of conductance.  

PubMed

The presence of water on an oxide surface can dramatically alter its electrical properties with important consequences for electrical measurements by scanning probe microscopy, and for the use of semiconducting oxides in sensing applications. Here, the thermal dependence of the conductance of tin dioxide is interpreted by combining semiconductor equilibrium carrier statistics with a proton hopping mechanism. First, the functional form of this charge transport model is fit to experimental conductance data for tin dioxide. Next, the important energy parameters in the model are computed with density functional theory. Comparing the values of the energy parameters obtained by fitting, to the values for the same parameters obtained from electronic structure calculations, yields new insight into the surface charge transport in tin dioxide. In particular, it is found that mobile protons, freed from the dissociative adsorption of water on the [110] surface, are an essential component of the observed thermal dependence of conductance in tin dioxide. PMID:25275726

Wexler, Robert B; Sohlberg, Karl

2014-12-26

279

Ca2+-dependent Calmodulin Binding to FcRn Affects Immunoglobulin G Transport in the Transcytotic Pathway  

PubMed Central

The Fc? receptor FcRn transports immunoglobulin G (IgG) so as to avoid lysosomal degradation and to carry it bidirectionally across epithelial barriers to affect mucosal immunity. Here, we identify a calmodulin-binding site within the FcRn cytoplasmic tail that affects FcRn trafficking. Calmodulin binding to the FcRn tail is direct, calcium-dependent, reversible, and specific to residues comprising a putative short amphipathic ?-helix immediately adjacent to the membrane. FcRn mutants with single residue substitutions in this motif, or FcRn mutants lacking the cytoplasmic tail completely, exhibit a shorter half-life and attenuated transcytosis. Chemical inhibitors of calmodulin phenocopy the mutant FcRn defect in transcytosis. These results suggest a novel mechanism for regulation of IgG transport by calmodulin-dependent sorting of FcRn and its cargo away from a degradative pathway and into a bidirectional transcytotic route. PMID:18003977

Dickinson, Bonny L.; Claypool, Steven M.; D'Angelo, June A.; Aiken, Martha L.; Venu, Nanda; Yen, Elizabeth H.; Wagner, Jessica S.; Borawski, Jason A.; Pierce, Amy T.; Hershberg, Robert; Blumberg, Richard S.

2008-01-01

280

Ca2+-dependent calmodulin binding to FcRn affects immunoglobulin G transport in the transcytotic pathway.  

PubMed

The Fcgamma receptor FcRn transports immunoglobulin G (IgG) so as to avoid lysosomal degradation and to carry it bidirectionally across epithelial barriers to affect mucosal immunity. Here, we identify a calmodulin-binding site within the FcRn cytoplasmic tail that affects FcRn trafficking. Calmodulin binding to the FcRn tail is direct, calcium-dependent, reversible, and specific to residues comprising a putative short amphipathic alpha-helix immediately adjacent to the membrane. FcRn mutants with single residue substitutions in this motif, or FcRn mutants lacking the cytoplasmic tail completely, exhibit a shorter half-life and attenuated transcytosis. Chemical inhibitors of calmodulin phenocopy the mutant FcRn defect in transcytosis. These results suggest a novel mechanism for regulation of IgG transport by calmodulin-dependent sorting of FcRn and its cargo away from a degradative pathway and into a bidirectional transcytotic route. PMID:18003977

Dickinson, Bonny L; Claypool, Steven M; D'Angelo, June A; Aiken, Martha L; Venu, Nanda; Yen, Elizabeth H; Wagner, Jessica S; Borawski, Jason A; Pierce, Amy T; Hershberg, Robert; Blumberg, Richard S; Lencer, Wayne I

2008-01-01

281

Gibberellin regulates PIN-FORMED abundance and is required for auxin transport-dependent growth and development in Arabidopsis thaliana.  

PubMed

Plants integrate different regulatory signals to control their growth and development. Although a number of physiological observations suggest that there is crosstalk between the phytohormone gibberellin (GA) and auxin, as well as with auxin transport, the molecular basis for this hormonal crosstalk remains largely unexplained. Here, we show that auxin transport is reduced in the inflorescences of Arabidopsis thaliana mutants deficient in GA biosynthesis and signaling. We further show that this reduced auxin transport correlates with a reduction in the abundance of PIN-FORMED (PIN) auxin efflux facilitators in GA-deficient plants and that PIN protein levels recover to wild-type levels following GA treatment. We also demonstrate that the regulation of PIN protein levels cannot be explained by a transcriptional regulation of the PIN genes but that GA deficiency promotes, at least in the case of PIN2, the targeting of PIN proteins for vacuolar degradation. In genetic studies, we reveal that the reduced auxin transport of GA mutants correlates with an impairment in two PIN-dependent growth processes, namely, cotyledon differentiation and root gravitropic responses. Our study thus presents evidence for a role of GA in these growth responses and for a GA-dependent modulation of PIN turnover that may be causative for these differential growth responses. PMID:21642547

Willige, Björn C; Isono, Erika; Richter, René; Zourelidou, Melina; Schwechheimer, Claus

2011-06-01

282

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

283

Presentation of viral antigen by MHC class I molecules is dependent on a putative peptide transporter heterodimer  

Microsoft Academic Search

MAJOR histocompatibility complex (MHC) class I molecules present peptides derived from the endogenous protein pool to cytotoxic T lymphocytes, which can thus recognize intracellular antigen1-3. This pathway may depend on a transporter (PSF1) (refs 4-6) to mediate entry of the cytosolic peptides into a pre-Golgi compartment where they hind to class I heavy chains and promote their stable assembly with

Thomas Spies; Vincenzo Cerundolo; Marco Colonna; Peter Cresswell; Alain Townsend; Robert Demars

1992-01-01

284

Monte Carlo Study of Thermal Transport of Frequency and Direction Dependent Reflecting  

E-print Network

Starr [1] found that copper/cuprous oxide systems showed thermal as well as electrical rectifi- cation the carbon and boron nitride nanotubes. Through phonon transport simulations we provide theoret- ical

Walker, D. Greg

285

*Iron accumulation in bronchial epithelial cells is dependent on concurrent sodium transport  

EPA Science Inventory

Airway epithelial cells prevent damaging effects of extracellular iron by taking up the metal and sequestering it within intracellular ferritin. Epithelial iron transport is associated with transcellular movement of other cations including changes in the expression or activity of...

286

Cloning and characterization of a novel human pH-dependent organic cation transporter, OCTN1  

Microsoft Academic Search

cDNA for a novel proton\\/organic cation transporter, OCTN1, was cloned from human fetal liver and its transport activity was investigated. OCTN1 encodes a 551-amino acid protein with 11 transmembrane domains and one nucleotide binding site motif. It is strongly expressed in kidney, trachea, bone marrow and fetal liver and in several human cancer cell lines, but not in adult liver.

Ikumi Tamai; Hikaru Yabuuchi; Jun-ichi Nezu; Yoshimichi Sai; Asuka Oku; Miyuki Shimane; Akira Tsuji

1997-01-01

287

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

288

Competitive inhibition of an energy-dependent nickel transport system by divalent cations in Bradyrhizobium japonicum JH.  

PubMed

Both nickel-specific transport and nickel transport by a magnesium transporter have been described previously for a variety of nickel-utilizing bacteria. The derepression of hydrogenase activity in Bradyzhizobium japonicum JH and in a gene-directed mutant of strain JH (in an intracellular Ni metabolism locus), strain JHK7, was inhibited by MgSO4. For both strains, Ni2+ uptake was also markedly inhibited by Mg2+, and the Mg(2+)-mediated inhibition could be overcome by high levels of Ni2+ provided in the assay buffer. The results indicate that both B. japonicum strains transport Ni2+ via a high-affinity magnesium transport system. Dixon plots (1/V versus inhibitor) showed that the divalent cations Co2+, Mn2+, and Zn2+, like Mg2+, were competitive inhibitors of Ni2+ uptake. The KiS for nickel uptake inhibition by Mg2+, Co2+, Mn2+, and Zn2+ were 48, 22, 12, and 8 microM, respectively. Cu2+ strongly inhibited Ni2+ uptake, and molybdate inhibited it slightly. Respiratory inhibitors cyanide and azide, the uncoupler carbonyl cyanide m-chlorophenylhydrazone, the ATPase inhibitor N,N'-dicyclohexylcarbodiimide, and ionophores nigericin and valinomycin significantly inhibited short-term (5 min) Ni2+ uptake, showing that Ni2+ uptake in strain JH is energy dependent. Most of these conclusions are quite different from those reported previously for a different B. japonicum strain belonging to a different serogroup. PMID:1785926

Fu, C L; Maier, R J

1991-12-01

289

Modulation of high affinity ATP-dependent cyclic nucleotide transporters by specific and non-specific cyclic nucleotide phosphodiesterase inhibitors.  

PubMed

Intracellular cyclic nucleotides are eliminated by phosphodiesterases (PDEs) and by ATP Binding cassette transporters such as ABCC4 and ABCC5. PDE5 and ABCC5 have similar affinity for cGMP whereas ABCC5 has much higher affinity for cGMP compared with cAMP. Since the substrate (cGMP) is identical for these two eliminatory processes it is conceivable that various PDE inhibitors also modulate ABCC5-transport. Cyclic GMP is also transported by ABBC4 but the affinity is much lower with a Km 50-100 times higher than for that of ABBCC5. The present study aimed to determine Ki-values for specific or relative specific PDE5 inhibitors (vardenafil, tadalafil, zaprinast and dipyridamole) and the non-specific PDE inhibitors (IBMX, caffeine and theophylline) for ABCC5 and ABCC4 transport. The transport of [(3)H]-cGMP (2 µM) was concentration-dependently inhibited with the following Ki-values: vardenafil (0.62 µM), tadalafil (14.1 µM), zaprinast (0.68 µM) and dipyridamole (1.2 µM), IBMX (10 µM), caffeine (48 µM) and theophylline (69 µM). The Ki-values for the inhibition of the [(3)H]-cAMP (2 µM) transport were: vardenafil (3.4 µM), tadalafil (194 µM), zaprinast (2.8 µM), dipyridamole (5.5 µM), IBMX (16 µM), caffeine (41 µM) and theophylline (85 µM). The specificity for ABCC5 we defined as ratio between Ki-values for inhibition of [(3)H]-cGMP and [(3)H]-cAMP transport. Tadalafil showed the highest specificity (Ki-ratio: 0.073) and caffeine the lowest (Ki-ratio: 1.2). PMID:25445042

Aronsen, Lena; Orvoll, Elin; Lysaa, Roy; Ravna, Aina W; Sager, Georg

2014-12-15

290

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

291

Characteristics of a ugp-encoded and phoB-dependent glycerophosphoryl diester phosphodiesterase which is physically dependent on the ugp transport system of Escherichia coli.  

PubMed Central

The ugp-encoded transport system of Escherichia coli accumulates sn-glycerol-3-phosphate with high affinity; it is binding protein mediated and part of the pho regulon. Here, we report that glycerophosphoryl diesters (deacylated phospholipids) are also high-affinity substrates for the ugp-encoded system. The diesters are not taken up in an unaltered form but are hydrolyzed during transport to sn-glycerol-3-phosphate plus the corresponding alcohols. The enzyme responsible for this reaction is not essential for the translocation of sn-glycerol-3-phosphate or for the glycerophosphoryl diesters but can only hydrolyze diesters that are in the process of being transported. Diesters in the periplasm or in the cytoplasm were not recognized, and no enzymatic activity could be detected in cellular extracts. The enzyme is encoded by the last gene in the ugp operon, termed ugpQ. The product of the ugpQ gene, expressed in minicells, has an apparent molecular weight of 17,500. We present evidence that only one major phoB-dependent promoter controls all ugp genes. Images PMID:2842304

Brzoska, P; Boos, W

1988-01-01

292

Thiol-dependent passive K\\/Cl transport in sheep red cells: III. Differential reactivity of membrane SH groups with N-ethylmaleimide and iodoacetamide  

Microsoft Academic Search

Summary Treatment with N-ethylmaleimide (NEM) is known to stimulate ouabain-insensitive, Cl--dependent K+ transport in low K+ (LK) but not in high K+ (HK) sheep red cells (Lauf, P.K., and Theg, B.E., 1980,Biophys. Biochem. Res. Commun.921422–1428). The dependence of this effect on the pH of pretreatment with NEM and\\/or iodoacetamide (IAA) was studied. Maximum stimulation of Cl--dependent K+ transport in LK

J. Bauer; P. K. Lauf

1983-01-01

293

14 CFR 171.313 - Azimuth performance requirements.  

Code of Federal Regulations, 2014 CFR

...runway centerline to the respective zero-degree guidance plane. Note 4...2) Be adjusted so that the zero degree azimuth plane will be a vertical plane which contains the centerline of the runway...

2014-01-01

294

14 CFR 171.313 - Azimuth performance requirements.  

Code of Federal Regulations, 2012 CFR

...runway centerline to the respective zero-degree guidance plane. Note 4...2) Be adjusted so that the zero degree azimuth plane will be a vertical plane which contains the centerline of the runway...

2012-01-01

295

14 CFR 171.313 - Azimuth performance requirements.  

Code of Federal Regulations, 2010 CFR

...runway centerline to the respective zero-degree guidance plane. Note 4...2) Be adjusted so that the zero degree azimuth plane will be a vertical plane which contains the centerline of the runway...

2010-01-01

296

14 CFR 171.313 - Azimuth performance requirements.  

Code of Federal Regulations, 2011 CFR

...runway centerline to the respective zero-degree guidance plane. Note 4...2) Be adjusted so that the zero degree azimuth plane will be a vertical plane which contains the centerline of the runway...

2011-01-01

297

14 CFR 171.313 - Azimuth performance requirements.  

Code of Federal Regulations, 2013 CFR

...runway centerline to the respective zero-degree guidance plane. Note 4...2) Be adjusted so that the zero degree azimuth plane will be a vertical plane which contains the centerline of the runway...

2013-01-01

298

Anomalous diameter dependence of thermal transport in ultra-narrow Si nanowires  

NASA Astrophysics Data System (ADS)

We present atomistic valence force field calculations of thermal transport in Si nanowires of diameters from 12 nm down to 1 nm. We show that as the diameter is reduced, the phonon density-of-states and transmission function acquire a finite value at low frequency, in contrast to approaching zero as in the bulk material. It turns out that this effect results in what Ziman described as the "problem of long longitudinal waves" [J. M. Ziman, Electrons and Phonons: The Theory of Transport Phenomena in Solids (Clarendon, Oxford, 1962)], which states that the thermal conductivity of a material increases as its length is increased due to the vanishing scattering for long-wavelength phonons. We show that this thermal transport improvement also appears in nanowires as their diameter is decreased below D = 5 nm (not only as the length increases), originating from the increase in the density of the long wavevector modes. The observation is present under ballistic transport conditions, and further enhanced with the introduction of phonon-phonon scattering. Because of this, in such ultra-narrow nanowires, as the diameter is reduced, phonon transport is dominated more and more by lower energy phonons with longer mean-free paths. We show that ˜80% of the heat is carried by phonons with energies less than 5 meV, most with mean-free paths of several hundreds of nanometers.

Karamitaheri, Hossein; Neophytou, Neophytos; Kosina, Hans

2014-01-01

299

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. PMID:24036509

Lim, Hyun-Ho; Stockbridge, Randy B.; Miller, Christopher

2013-01-01

300

Partial purification of (Ca2+ + Mg2+)-dependent ATPase from pig smooth muscle and reconstitution of an ATP-dependent Ca2+-transport system.  

PubMed Central

(CaMg)ATPase [(Ca2+ + Mg2+)-dependent ATPase] was partially purified from a microsomal fraction of the smooth muscle of the pig stomach (antrum). Membranes were solubilized with deoxycholate, followed by removal of the detergent by dialysis. The purified (CaMg)ATPase has a specific activity (at 37 degrees C) of 157 +/- 12.1 (7)nmol.min-1.mg-1 of protein, and it is stimulated by calmodulin to 255 +/- 20.9 (7)nmol.min.mg-1. This purification of the (CaMg)ATPase resulted in an increase of the specific activity by approx. 18-fold and in a recovery of the total enzyme activity of 55% compared with the microsomal fraction. The partially purified (CaMg)ATPase still contains some Mg2+-and (Na+ + K+)-dependent ATPase activities, but their specific activities are increased relatively less than that of the (CaMg)ATPase. The ratios of the (CaMg)ATPase to Mg2+- and (Na+ + K+)-dependent ATPase activities increase from respectively 0.14 and 0.81 in the crude microsomal fraction to 1.39 and 9.07 in the purified preparation. During removal of the deoxycholate by dialysis, vesicles were reconstituted which were capable of ATP-dependent Ca2+ transport. PMID:6119983

Wuytack, F; De Schutter, G; Casteels, R

1981-01-01

301

An ATP-dependent L-carnitine transporter in Listeria monocytogenes Scott A is involved in osmoprotection.  

PubMed Central

Listeria monocytogenes is a gram-positive, psychotrophic, food-borne pathogen which is able to grow in osmotically stressful environments. Carnitine (beta-hydroxy-L-tau-N-trimethyl aminobutyrate) can contribute significantly to growth of L. monocytogenes at high osmolarity (R. R. Beumer, M. C. te Giffel, L. J. Cox, F. M. Rombouts, and T. Abee, Appl. Environ. Microbiol. 60:1359-1363, 1994). Transport of L-[N-methyl-14C]carnitine in L. monocytogenes was shown to be energy dependent. Analysis of cell extracts revealed that L-carnitine was not further metabolized, which supplies evidence for its role as an osmoprotectant in L. monocytogenes. Uptake of L-carnitine proceeds in the absence of a proton motive force and is strongly inhibited in the presence of the phosphate analogs vanadate and arsenate. The L-carnitine permease is therefore most likely driven by ATP. Kinetic analysis of L-carnitine transport in glucose-energized cells revealed the presence of a high-affinity uptake system with a Km of 10 microM and a maximum rate of transport (Vmax) of 48 nmol min-1 mg of protein-1. L-[14C]carnitine transport in L. monocytogenes is significantly inhibited by a 10-fold excess of unlabelled L-carnitine, acetylcarnitine, and tau-butyrobetaine, whereas L-proline and betaine display, even at a 100-fold excess, only a weak inhibitory effect. In conclusion, an ATP-dependent L-carnitine transport system in L. monocytogenes is described, and its possible roles in cold adaptation and intracellular growth in mammalian cells are discussed. PMID:7768820

Verheul, A; Rombouts, F M; Beumer, R R; Abee, T

1995-01-01

302

Azimuthal doppler shift in light beams with orbital angular momentum  

Microsoft Academic Search

We show that an atom moving in a light beam with orbital angular momentum experiences an azimuthal shift in the resonant frequency in addition to the usual axial Doppler and recoil shifts. For a Laguerre-Gaussian beam characterised by an orbital angular momentum quantum number l, the shift is lVphi\\/r where r is the radial atomic position and Vphi the azimuthal

L. Allen; M. Babiker; W. L. Power

1994-01-01

303

Analysis of azimuthal mode dynamics of mesoscale eddies  

E-print Network

ANALYSIS OF AZIMUTHAL MODE DYNAMICS OF MESOSCALE EDDIES A Thesis by UOHN DAVID MCCALPIN Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 1984... Major Subject: Oceanography ANALYSIS OF AZIMUTHAL MODE DYNAMICS OF MESOSCALE EDDIES A Thesis by JOHN DAVID MCCALPIN Approved as to style and content by: rew . as ano (Chairman of Committee) o ert . ei (Member) uy . rancesc &ni (Member) Robert...

McCalpin, John David

1984-01-01

304

Commensurability-dependent transport of a Wigner crystal in a nanoconstriction.  

PubMed

We present the first transport measurements of a classical Wigner crystal through a constriction formed by a split-gate electrode. The Wigner crystal is formed on the surface of superfluid helium confined in a microchannel. At low temperatures, the current is periodically suppressed with increasing split-gate voltage, resulting in peaklike transport features. We also present the results of molecular dynamics simulations that reproduce this phenomenon. We demonstrate that, at the split-gate voltages for which the current is suppressed, the electron lattice is arranged such that the stability of particle positions against thermal fluctuations is enhanced. In these configurations, the suppression of transport due to interelectron Coulomb forces becomes important. PMID:22680890

Rees, D G; Totsuji, H; Kono, K

2012-04-27

305

Platelets as potential peripheral markers to study functioning of the high-affinity sodium-dependent glutamate transporters in the nerve terminals of the brain  

NASA Astrophysics Data System (ADS)

Activity of the high-affinity sodium-dependent glutamate transporters in the brain nerve terminals is demonstrated to alter under artificial gravity conditions. A comparison analysis is made for L-[14C] glutamate transport in platelets and isolated nerve terminals. The kinetic characteristics of the transporters, [Na+]-dependence and influence of the transpoter inhibitor DL-threo-beta-benzyloxyaspartate on the L-[14C] glutamate uptake process are determined. It is shown that glutamate uptake process is very similar for platelets and nerve terminals. Thus it is reasonable to use platelets as a potential peripheral model for glutamate transport.

Borisova, T. A.; Kasatkina, L. A.

306

Differential regulation of Na+ transporters along nephron during ANG II-dependent hypertension: distal stimulation counteracted by proximal inhibition.  

PubMed

During angiotensin II (ANG II)-dependent hypertension, ANG II stimulates, while hypertension inhibits, Na(+) transporter activity to balance Na(+) output to input. This study tests the hypothesis that ANG II infusion activates Na(+) transporters in the distal nephron while inhibiting transporters along the proximal nephron. Male Sprague-Dawley rats were infused with ANG II (400 ng·kg(-1)·min(-1)) or vehicle for 2 wk. Kidneys were dissected (cortex vs. medulla) or fixed for immunohistochemistry (IHC). ANG II increased mean arterial pressure by 40 mmHg, urine Na(+) by 1.67-fold, and urine volume by 3-fold, evidence for hypertension and pressure natriuresis. Na(+) transporters' abundance and activation [assessed by phosphorylation (-P) or proteolytic cleavage] were measured by immunoblot. During ANG II infusion Na(+)/H(+) exchanger 3 (NHE3) abundance decreased in both cortex and medulla; Na-K-2Cl cotransporter 2 (NKCC2) decreased in medullary thick ascending loop of Henle (TALH) and increased, along with NKCC2-P, in cortical TALH; Na-Cl cotransporter (NCC) and NCC-P increased in the distal convoluted tubule; and epithelial Na(+) channel subunits and their cleaved forms were increased in both cortex and medulla. Like NKCC2, STE20/SPS1-related proline alanine-rich kinase (SPAK) and SPAK-P were decreased in medulla and increased in cortex. By IHC, during ANG II NHE3 remained localized to proximal tubule microvilli at lower abundance, and the differential regulation of NKCC2 and NKCC2-P in cortex versus medulla was evident. In summary, ANG II infusion increases Na(+) transporter abundance and activation from cortical TALH to medullary collecting duct while the hypertension drives a natriuresis response evident as decreased Na(+) transporter abundance and activation from proximal tubule through medullary TALH. PMID:23720346

Nguyen, Mien T X; Lee, Donna H; Delpire, Eric; McDonough, Alicia A

2013-08-15

307

Na/sup +/-H/sup +/ exchange and Na/sup +/-dependent transport systems in streptozotocin diabetic rat kidneys  

SciTech Connect

The streptozotocin-induced diabetic rat was used to test the hypothesis that Na/sup +/-H/sup +/ exchange activity in the proximal tubule luminal membrane would be increased in association with renal hypertrophy, altered glomerular hemodynamics, enhanced filtered load and tubular reabsorption of /sup 22/Na/sup +/, and stimulated /sup 22/Na= pump activity in the basolateral membrane, previously reported characteristics of this experimental animal model. Amiloride-sensitive H/sup +/ gradient-dependent Na/sup +/ uptake and Na/sup +/ gradient-dependent H/sup +/ flux were increased in brush-border membrane vesicles from the streptozotocin-treated animals. Na/sup +/ gradient-dependent uptakes of phosphate, D-glucose, L-proline, and myoinositol were decreased in the drug-induced diabetic animals. These membrane transport alterations were not found when the streptozotocin-diabetic animals were treated with insulin.

El-Seifi, S.; Freiberg, J.M.; Kinsella, F.J.; Cheng, L.; Sacktor, B.

1987-01-01

308

Redundancy in Periplasmic Binding Protein-Dependent Transport Systems for Trehalose, Sucrose, and Maltose in Sinorhizobium meliloti  

PubMed Central

We have identified a cluster of six genes involved in trehalose transport and utilization (thu) in Sinorhizobium meliloti. Four of these genes, thuE, -F, -G, and -K, were found to encode components of a binding protein-dependent trehalose/maltose/sucrose ABC transporter. Their deduced gene products comprise a trehalose/maltose-binding protein (ThuE), two integral membrane proteins (ThuF and ThuG), and an ATP-binding protein (ThuK). In addition, a putative regulatory protein (ThuR) was found divergently transcribed from the thuEFGK operon. When the thuE locus was inactivated by gene replacement, the resulting S. meliloti strain was impaired in its ability to grow on trehalose, and a significant retardation in growth was seen on maltose as well. The wild type and the thuE mutant were indistinguishable for growth on glucose and sucrose. This suggested a possible overlap in function of the thuEFGK operon with the aglEFGAK operon, which was identified as a binding protein-dependent ATP-binding transport system for sucrose, maltose, and trehalose. The Kms for trehalose transport were 8 ± 1 nM and 55 ± 5 nM in the uninduced and induced cultures, respectively. Transport and growth experiments using mutants impaired in either or both of these transport systems show that these systems form the major transport systems for trehalose, maltose, and sucrose. By using a thuE?-lacZ fusion, we show that thuE is induced only by trehalose and not by cellobiose, glucose, maltopentaose, maltose, mannitol, or sucrose, suggesting that the thuEFGK system is primarily targeted toward trehalose. The aglEFGAK operon, on the other hand, is induced primarily by sucrose and to a lesser extent by trehalose. Tests for root colonization, nodulation, and nitrogen fixation suggest that uptake of disaccharides can be critical for colonization of alfalfa roots but is not important for nodulation and nitrogen fixation per se. PMID:12003938

Jensen, John Beck; Peters, N. Kent; Bhuvaneswari, T. V.

2002-01-01

309

Carboxypeptidase E cytoplasmic tail-driven vesicle transport is key for activity-dependent secretion of peptide hormones.  

PubMed

Vesicular transport of peptide hormones from the cell body to the plasma membrane for activity-dependent secretion is important for endocrine function, but how it is achieved is unclear. Here we uncover a mechanism in which the cytoplasmic tail of transmembrane carboxypeptidase E (CPE) found in proopiomelanocotin (POMC)/ACTH vesicles interacts with microtubule-based motors to control transport of these vesicles to the release site in pituitary cells. Overexpression of the CPE tail in live cells significantly reduced the velocity and distance of POMC/ACTH- and CPE-containing vesicle movement into the cell processes. Biochemical studies showed that the CPE tail interacted with dynactin, which, in turn, recruited microtubule plus-end motors kinesin 2 and kinesin 3. Overexpression of the CPE tail inhibited the stimulated secretion of ACTH from AtT20 cells. Thus, the CPE cytoplasmic tail interaction with dynactin-kinesin 2/kinesin 3 plays an important role in the transport of POMC vesicles for activity-dependent secretion. PMID:18202146

Park, Joshua J; Cawley, Niamh X; Loh, Y Peng

2008-04-01

310

Hydrogen sulfide modulates actin-dependent auxin transport via regulating ABPs results in changing of root development in Arabidopsis.  

PubMed

Hydrogen sulfide (H2S) signaling has been considered a key regulator of plant developmental processes and defenses. In this study, we demonstrate that high levels of H2S inhibit auxin transport and lead to alterations in root system development. H2S inhibits auxin transport by altering the polar subcellular distribution of PIN proteins. The vesicle trafficking and distribution of the PIN proteins are an actin-dependent process. H2S changes the expression of several actin-binding proteins (ABPs) and decreases the occupancy percentage of F-actin bundles in the Arabidopsis roots. We observed the effects of H2S on F-actin in T-DNA insertion mutants of cpa, cpb and prf3, indicating that the effects of H2S on F-actin are partially removed in the mutant plants. Thus, these data imply that the ABPs act as downstream effectors of the H2S signal and thereby regulate the assembly and depolymerization of F-actin in root cells. Taken together, our data suggest that the existence of a tightly regulated intertwined signaling network between auxin, H2S and actin that controls root system development. In the proposed process, H2S plays an important role in modulating auxin transport by an actin-dependent method, which results in alterations in root development in Arabidopsis. PMID:25652660

Jia, Honglei; Hu, Yanfeng; Fan, Tingting; Li, Jisheng

2015-01-01

311

Monosaccharide Absorption Activity of Arabidopsis Roots Depends on Expression Profiles of Transporter Genes under High Salinity Conditions*  

PubMed Central

Plant roots are able to absorb sugars from the rhizosphere but also release sugars and other metabolites that are critical for growth and environmental signaling. Reabsorption of released sugar molecules could help reduce the loss of photosynthetically fixed carbon through the roots. Although biochemical analyses have revealed monosaccharide uptake mechanisms in roots, the transporters that are involved in this process have not yet been fully characterized. In the present study we demonstrate that Arabidopsis STP1 and STP13 play important roles in roots during the absorption of monosaccharides from the rhizosphere. Among 14 STP transporter genes, we found that STP1 had the highest transcript level and that STP1 was a major contributor for monosaccharide uptake under normal conditions. In contrast, STP13 was found to be induced by abiotic stress, with low expression under normal conditions. We analyzed the role of STP13 in roots under high salinity conditions where membranes of the epidermal cells were damaged, and we detected an increase in the amount of STP13-dependent glucose uptake. Furthermore, the amount of glucose efflux from stp13 mutants was higher than that from wild type plants under high salinity conditions. These results indicate that STP13 can reabsorb the monosaccharides that are released by damaged cells under high salinity conditions. Overall, our data indicate that sugar uptake capacity in Arabidopsis roots changes in response to environmental stresses and that this activity is dependent on the expression pattern of sugar transporters. PMID:22041897

Yamada, Kohji; Kanai, Motoki; Osakabe, Yuriko; Ohiraki, Haruka; Shinozaki, Kazuo; Yamaguchi-Shinozaki, Kazuko

2011-01-01

312

Hydrogen sulfide modulates actin-dependent auxin transport via regulating ABPs results in changing of root development in Arabidopsis  

PubMed Central

Hydrogen sulfide (H2S) signaling has been considered a key regulator of plant developmental processes and defenses. In this study, we demonstrate that high levels of H2S inhibit auxin transport and lead to alterations in root system development. H2S inhibits auxin transport by altering the polar subcellular distribution of PIN proteins. The vesicle trafficking and distribution of the PIN proteins are an actin-dependent process. H2S changes the expression of several actin-binding proteins (ABPs) and decreases the occupancy percentage of F-actin bundles in the Arabidopsis roots. We observed the effects of H2S on F-actin in T-DNA insertion mutants of cpa, cpb and prf3, indicating that the effects of H2S on F-actin are partially removed in the mutant plants. Thus, these data imply that the ABPs act as downstream effectors of the H2S signal and thereby regulate the assembly and depolymerization of F-actin in root cells. Taken together, our data suggest that the existence of a tightly regulated intertwined signaling network between auxin, H2S and actin that controls root system development. In the proposed process, H2S plays an important role in modulating auxin transport by an actin-dependent method, which results in alterations in root development in Arabidopsis. PMID:25652660

Jia, Honglei; Hu, Yanfeng; Fan, Tingting; Li, Jisheng

2015-01-01

313

AtCCX3 is an Arabidopsis endomembrane H(+)-dependent K(+) transporter  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Arabidopsis ("Arabidopsis thaliana") cation calcium exchangers (CCXs) were recently identified as a subfamily of cation transporters; however, no plant "CCXs" have been functionally characterized. Here, we show that Arabidopsis AtCCX3 (At3g14070) and AtCCX4 (At1g54115) can suppress yeast mutants...

314

PHYSICAL REVIEW E 84, 041115 (2011) Heat generation and transport due to time-dependent forces  

E-print Network

to the temperature gradient or chemical potential gradient and, in the linear response regime, is governed by Fourier induce directed heat transport between the leads at the same temperature or even in the presence of a temperature gradient [16­18]. However, whether or not all energy driven by external forces can be transmitted

Li, Baowen

315

Modeling and analysis of time-dependent tritium transport in lithium oxide  

E-print Network

the tritium transport behavior in lithium-based ceramic materials. A computer code, named MISTRAL (Model *, M.A. Abdou Fusion Technology Group, 43-133 Engineering IV, Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, P.O. Box 951597, Los Angeles, CA 90095-1597, USA Received

Raffray, A. René

316

PI3-kinase-dependent electrogenic intestinal transport of glucose and amino acids.  

PubMed

Intestinal glucose and amino acid transport is stimulated by the serum- and glucocorticoid-inducible kinase isoforms SGK1, SGK2, and SGK3 and protein kinase B which are, in turn, stimulated following activation of the phosphoinositol-3 kinase (PI3 kinase). The present study has been performed to explore whether pharmacological inhibition of the PI3 kinase affects electrogenic jejunal transport of glucose and amino acids. In Ussing chamber experiments, glucose (20 mM), phenylalanine (20 mM), glutamine (20 mM), cysteine (20 mM), and proline (20 mM) generated lumen negative currents (I (glc), I (phe), I (gln), I (cys), and I (pro)), respectively, which gradually declined following application of the PI3 kinase inhibitor Wortmannin (1 muM). Within 40 min, Wortmannin treatment significantly decreased I (glc) by 39 +/- 10% (n = 5), I (phe) by 70 +/- 7% (n = 4), I (gln) by 69 +/- 8% (n = 4), I (cys) by 67 +/- 8% (n = 6), and I (prol) by 79 +/- 12% (n = 3). A similar decline of I (glc) was observed following application of the PI3 kinase inhibitor LY294002 (50 microM). Exposure to the inhibitors did not significantly alter transepithelial potential difference and resistance in the absence of substrates for electrogenic transport. The observations suggest that the electrogenic transport of glucose and several amino acids requires the continued activity of PI3 kinase. PMID:17051390

Rexhepaj, Rexhep; Artunc, Ferruh; Metzger, Marco; Skutella, Thomas; Lang, Florian

2007-03-01

317

Deformationally dependent fluid transport properties of porcine coronary arteries based on location in the coronary vasculature  

PubMed Central

Objective Understanding coronary artery mass transport allows researchers to better comprehend how drugs or proteins move through, and deposit into, the arterial wall. Characterizing how the convective component of transport changes based on arterial location could be useful to better understand how molecules distribute in different locations in the coronary vasculature. Methods and results We measured the mechanical properties and wall fluid flux transport properties of de-endothelialized (similar to post-stenting or angioplasty) left anterior descending (LADC) and right (RC) porcine coronary arteries along their arterial lengths. Multiphoton microscopy was used to determine microstructural differences. Proximal LADC regions had a higher circumferential stiffness than all other regions. Permeability decreased by 198% in the LADC distal region compared to other LADC regions. The RC artery showed a decrease of 46.9% from the proximal to middle region, and 51.7% from the middle to distal regions. The porosity increased in the intima between pressure states, without differences through the remainder of the arterial thickness. Conclusions We showed that the permeabilities and mechanical properties do vary in the coronary vasculature. With variations in mechanical properties, overexpansion of stents can occur more easily while variations in permeability may lead to altered transport based on location. PMID:23127633

Keyes, Joseph T.; Lockwood, Danielle R.; Simon, Bruce R.; Vande Geest, Jonathan P.

2013-01-01

318

Kinetic Approach to Quasi-Ballistic Field-Dependent Electron Transport  

E-print Network

] and inelastic- [1] scattering mechanisms. Application to regions in which there is an electric field. Pulfrey2 1 Nortel Networks, Nepean, Ontario K2H8E9, Canada 2 Department of Electrical and Computer transport. In this work, we present a kinetic approach based on the concept of path integrals which provides

Pulfrey, David L.

319

A KINETIC MODEL FOR CELL DENSITY DEPENDENT BACTERIAL TRANSPORT IN POROUS MEDIA  

EPA Science Inventory

A kinetic transport model with the ability to account for variations in cell density of the aqueous and solid phases was developed for bacteria in porous media. Sorption kinetics in the advective-dispersive-sorptive equation was described by assuming that adsorption was proportio...

320

Dimensionality-dependent charge transport in close-packed nanoparticle arrays: from 2D to 3D  

PubMed Central

Charge transport properties in close-packed nanoparticle arrays with thickness crossing over from two dimensions to three dimensions have been studied. The dimensionality transition of nanoparticle arrays was realized by continually printing spatially well-defined nanoparticle monolayers on top of the device in situ. The evolution of charge transport properties depending on the dimensionality has been investigated in both the Efros-Shaklovskii variable-range-hopping (ES-VRH) (low temperature) regime and the sequential hopping (SH) (medium temperature) regime. We find that the energy barriers to transport decrease when the thickness of nanoparticle arrays increases from monolayer to multilayers, but start to level off at the thickness of 4–5 monolayers. The energy barriers are characterized by the coefficient ?D at ES-VRH regime and the activation energy Ea at SH regime. Moreover, a turning point for the temperature coefficient of conductance was observed in multilayer nanoparticle arrays at high temperature, which is attributed to the increasing mobility with decreasing temperature of hopping transport in three dimensions. PMID:25523836

Wang, Ying; Duan, Chao; Peng, Lianmao; Liao, Jianhui

2014-01-01

321

Dimensionality-dependent charge transport in close-packed nanoparticle arrays: from 2D to 3D.  

PubMed

Charge transport properties in close-packed nanoparticle arrays with thickness crossing over from two dimensions to three dimensions have been studied. The dimensionality transition of nanoparticle arrays was realized by continually printing spatially well-defined nanoparticle monolayers on top of the device in situ. The evolution of charge transport properties depending on the dimensionality has been investigated in both the Efros-Shaklovskii variable-range-hopping (ES-VRH) (low temperature) regime and the sequential hopping (SH) (medium temperature) regime. We find that the energy barriers to transport decrease when the thickness of nanoparticle arrays increases from monolayer to multilayers, but start to level off at the thickness of 4-5 monolayers. The energy barriers are characterized by the coefficient ?D at ES-VRH regime and the activation energy Ea at SH regime. Moreover, a turning point for the temperature coefficient of conductance was observed in multilayer nanoparticle arrays at high temperature, which is attributed to the increasing mobility with decreasing temperature of hopping transport in three dimensions. PMID:25523836

Wang, Ying; Duan, Chao; Peng, Lianmao; Liao, Jianhui

2014-01-01

322

Dimensionality-dependent charge transport in close-packed nanoparticle arrays: from 2D to 3D  

NASA Astrophysics Data System (ADS)

Charge transport properties in close-packed nanoparticle arrays with thickness crossing over from two dimensions to three dimensions have been studied. The dimensionality transition of nanoparticle arrays was realized by continually printing spatially well-defined nanoparticle monolayers on top of the device in situ. The evolution of charge transport properties depending on the dimensionality has been investigated in both the Efros-Shaklovskii variable-range-hopping (ES-VRH) (low temperature) regime and the sequential hopping (SH) (medium temperature) regime. We find that the energy barriers to transport decrease when the thickness of nanoparticle arrays increases from monolayer to multilayers, but start to level off at the thickness of 4-5 monolayers. The energy barriers are characterized by the coefficient ?D at ES-VRH regime and the activation energy Ea at SH regime. Moreover, a turning point for the temperature coefficient of conductance was observed in multilayer nanoparticle arrays at high temperature, which is attributed to the increasing mobility with decreasing temperature of hopping transport in three dimensions.

Wang, Ying; Duan, Chao; Peng, Lianmao; Liao, Jianhui

2014-12-01

323

Analysis of mutations that uncouple transport from phosphorylation in enzyme IIGlc of the Escherichia coli phosphoenolpyruvate-dependent phosphotransferase system.  

PubMed Central

Mutations that uncouple glucose transport from phosphorylation were isolated in plasmid-encoded Escherichia coli enzyme IIGlc of the phosphoenolpyruvate-dependent phosphotransferase system (PTS). The uncoupled enzymes IIGlc were able to transport glucose in the absence of the general phosphoryl-carrying proteins of the PTS, enzyme I and HPr, although with relatively low affinity. Km values of the uncoupled enzymes IIGlc for glucose ranged from 0.5 to 2.5 mM, 2 orders of magnitude higher than the value of normal IIGlc. Most of the mutant proteins were still able to phosphorylate glucose and methyl alpha-glucoside (a non-metabolizable glucose analog specific for IIGlc), indicating that transport and phosphorylation are separable functions of the enzyme. Some of the uncoupled enzymes IIGlc transported glucose with a higher rate and lower apparent Km in a pts+ strain than in a delta ptsHI strain lacking the general proteins enzyme I and HPr. Since the properties of these uncoupled enzymes IIGlc in the presence of PTS-mediated phosphoryl transfer resembled those of wild-type IIGlc, these mutants appeared to be conditionally uncoupled. Sequencing of the mutated ptsG genes revealed that all amino acid substitutions occurred in a hydrophilic segment within the hydrophobic N-terminal part of IIGlc. These results suggest that this hydrophilic loop is involved in binding and translocation of the sugar substrate. Images PMID:1569016

Ruijter, G J; van Meurs, G; Verwey, M A; Postma, P W; van Dam, K

1992-01-01

324

Edge contact dependent spin transport for n-type doping zigzag-graphene with asymmetric edge hydrogenation  

PubMed Central

Spin transport features of the n-type doping zigzag graphene nanoribbons (ZGNRs) with an edge contact are investigated by first principle methods, where ZGNRs are C–H2 bonded at one edge while C–H bonded at the other to form an asymmetric edge hydrogenation. The results show that a perfect spin filtering effect (100%) in such ZGNR nanojunctions can be achieved in a very large bias region for the unchanged spin states regardless of bias polarities, and the nanojunction with a contact of two C–H2 bonded edges has larger spin polarized current than that with a contact of two C–H bonded edges. The transmission pathways and the projected density of states (PDOS) demonstrate that the edge of C-H2 bonds play a crucial role for the spin magnetism and spin-dependent transport properties. Moreover, the negative differential resistance (NDR) effect is also observed in the spin-polarized current. PMID:24509476

Deng, Xiaoqing; Zhang, Zhenhua; Tang, Guiping; Fan, Zhiqiang; Zhu, Huali; Yang, Changhu

2014-01-01

325

Spin-dependent transport behavior in C60 and Alq3 based spin valves with a magnetite electrode (invited)  

NASA Astrophysics Data System (ADS)

The spin-dependent transport behavior in organic semiconductors (OSs) is generally observed at low temperatures, which likely results from poor spin injection efficiency at room temperature from the ferromagnetic metal electrodes to the OS layer. Possible reasons for this are the low Curie temperature and/or the small spin polarization efficiency for the ferromagnetic electrodes used in these devices. Magnetite has potential as an advanced candidate for use as the electrode in spintronic devices, because it can achieve 100% spin polarization efficiency in theory, and has a high Curie temperature (850 K). Here, we fabricated two types of organic spin valves using magnetite as a high efficiency electrode. C60 and 8-hydroxyquinoline aluminum (Alq3) were employed as the OS layers. Magnetoresistance ratios of around 8% and over 6% were obtained in C60 and Alq3-based spin valves at room temperature, respectively, which are two of the highest magnetoresistance ratios in organic spin valves reported thus far. The magnetoresistance effect was systemically investigated by varying the thickness of the Alq3 layer. Moreover, the temperature dependence of the magnetoresistance ratios for C60 and Alq3-based spin valves were evaluated to gain insight into the spin-dependent transport behavior. This study provides a useful method in designing organic spin devices operated at room temperature.

Zhang, Xianmin; Mizukami, Shigemi; Ma, Qinli; Kubota, Takahide; Oogane, Mikihiko; Naganuma, Hiroshi; Ando, Yasuo; Miyazaki, Terunobu

2014-05-01

326

The hepatobiliary disposition of timosaponin b2 is highly dependent on influx/efflux transporters but not metabolism.  

PubMed

The purpose of this study was to characterize the hepatobiliary disposition of timosaponin B2 (TB-2), a natural saponin. Although TB-2 has multiple pharmacologic activities, the mechanism of its hepatobiliary disposition has not been explored. Because the metabolism of TB-2 is limited and the accumulation of TB-2 in primary hepatocytes is highly temperature dependent (93% of its accumulation is due to active uptake), the contribution of hepatic transporters was investigated. Organic anion-transporting polypeptide (OATP) 1B1- and OATP1B3-transfected human embryonic kidney 293 cells were employed. TB-2 serves as a substrate for OATP1B1 and OATP1B3, with the former playing a predominant role in the hepatic uptake of TB-2. An inhibition study in sandwich-cultured rat hepatocytes suggested that TB-2 is a substrate for both breast cancer resistance protein (Bcrp) and multidrug resistance-associated protein 2 (Mrp2), consistent with its high biliary excretion index (43.1-44.9%). This hypothesis was further verified in BCRP and MRP2 membrane vesicles. The cooperation of uptake and efflux transporters in TB-2 hepatic disposition could partially explain the double-peak phenomenon observed in rat plasma and liver and biliary clearance, which accounted for 70% of the total TB-2 clearance. Moreover, TB-2 significantly increased the rosuvastatin concentration in rat plasma in a concentration-dependent manner and decreased its biliary excretion, which corresponded to reductions in rosuvastatin accumulation in hepatocytes and the biliary excretion index in sandwich-cultured rat hepatocytes, representing a perfect example of a potential saponin-statin drug-drug interaction. These studies demonstrate that transporters (Oatp, Bcrp/Mrp2), but not metabolism, contribute significantly to rat TB-2 hepatobiliary disposition. PMID:25336752

Sheng, Jingjing; Tian, Xiaoting; Xu, Guanglin; Wu, Zhitao; Chen, Chen; Wang, Le; Pan, Lili; Huang, Chenggang; Pan, Guoyu

2015-01-01

327

Long-range azimuthal correlations in proton-proton and proton-nucleus collisions from the incoherent scattering of partons  

DOE PAGESBeta

We show that the incoherent elastic scattering of partons, as present in a multi-phase transport model (AMPT), with a modest parton–parton cross-section of ?=1.5–3 mb?=1.5–3 mb, naturally explains the long-range two-particle azimuthal correlation as observed in proton–proton and proton–nucleus collisions at the Large Hadron Collider.

Ma, Guo -Liang [Chinese Academy of Sciences, Shanghai (China).Shanghai Institute of Applied Physics; Bzdak, Adam [Brookhaven National Laboratory (BNL), Upton, NY (United States).Riken BNL Research Center

2014-12-01

328

SUMOylation-dependent LRH-1/PROX1 interaction promotes atherosclerosis by decreasing hepatic reverse cholesterol transport.  

PubMed

Reverse cholesterol transport (RCT) is an antiatherogenic process in which excessive cholesterol from peripheral tissues is transported to the liver and finally excreted from the body via the bile. The nuclear receptor liver receptor homolog 1 (LRH-1) drives expression of genes regulating RCT, and its activity can be modified by different posttranslational modifications. Here, we show that atherosclerosis-prone mice carrying a mutation that abolishes SUMOylation of LRH-1 on K289R develop less aortic plaques than control littermates when exposed to a high-cholesterol diet. The mechanism underlying this atheroprotection involves an increase in RCT and its associated hepatic genes and is secondary to a compromised interaction of LRH-1 K289R with the corepressor prospero homeobox protein 1 (PROX1). Our study reveals that the SUMOylation status of a single nuclear receptor lysine residue can impact the development of a complex metabolic disease such as atherosclerosis. PMID:25176150

Stein, Sokrates; Oosterveer, Maaike H; Mataki, Chikage; Xu, Pan; Lemos, Vera; Havinga, Rick; Dittner, Claudia; Ryu, Dongryeol; Menzies, Keir J; Wang, Xu; Perino, Alessia; Houten, Sander M; Melchior, Frauke; Schoonjans, Kristina

2014-10-01

329

Temperature-dependent gas transport performance of vertically aligned carbon nanotube/parylene composite membranes  

NASA Astrophysics Data System (ADS)

A novel composite membrane consisting of vertically aligned carbon nanotubes (CNTs) and parylene was successfully fabricated. Seamless filling of the spaces in CNT forests with parylene was achieved by a low-pressure chemical vapor deposition (CVD) technique and followed with the Ar/O2 plasma etching to expose CNT tips. Transport properties of various gases through the CNT/parylene membranes were explored. And gas permeances were independent on feed pressure in accordance with the Knudsen model, but the permeance values were over 60 times higher than that predicted by the Knudsen diffusion kinetics, which was attributed to specular momentum reflection inside smooth CNT pores. Gas permeances and enhancement factors over the Knudsen model firstly increased and then decreased with rising temperature, which confirmed the existence of non-Knudsen transport. And surface adsorption diffusion could affect the gas permeance at relatively low temperature. The gas permeance of the CNT/parylene composite membrane could be improved by optimizing operating temperature.

Zhang, Lei; Yang, Junhe; Wang, Xianying; Zhao, Bin; Zheng, Guangping

2014-08-01

330

Transport of bare and capped zinc oxide nanoparticles is dependent on porous medium composition  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nanoparticles are one of the most frequently used nanoparticles in industry and hence are likely to be introduced to the groundwater environment. The mobility of these nanoparticles in different aquifer materials has not been assessed. While some studies have been published on the transport of ZnO nanoparticles in individual porous media, these studies do not generally account for varying porous medium composition both within and between aquifers. As a first step towards understanding the impact of this variability, this paper compares the transport of bare ZnO nanoparticles (bZnO-NPs) and capped ZnO nanoparticles, coated with tri-aminopropyltriethoxysilane (cZnO-NPs), in saturated columns packed with glass beads, fine grained sand and fine grained calcite, at near-neutral pH and groundwater salinity levels. With the exception of cZnO-NPs in sand columns, ZnO nanoparticles are highly immobile in all three types of studied porous media, with most retention taking place near the column inlet. Results are in general agreement with DLVO theory, and the deviation in experiments with cZnO-NPs flowing through columns packed with sand is linked to variability in zeta potential of the capped nanoparticles and sand grains. Therefore, differences in surface charge of nanoparticles and porous media are demonstrated to be key drivers in nanoparticle transport.

Kurlanda-Witek, H.; Ngwenya, B. T.; Butler, I. B.

2014-07-01

331

Competitive inhibition of an energy-dependent nickel transport system by divalent cations in Bradyrhizobium japonicum JH  

SciTech Connect

Both nickel-specific transport and nickel transport by a magnesium transporter have been described previously for a variety of nickel-utilizing bacteria. The derepression of hydrogenase activity in Bradyrhizobium japonicum JH and in a gene-directed mutant of strain JH (in an intracellular Ni metabolism locus), strain JHK7, was inhibited by MgSO{sub 4}. For both strains, Ni{sup 2+} uptake was also markedly inhibited by Mg{sup 2+}, and the Mg{sup 2+}-mediated inhibition could be overcome by high levels of Ni{sup 2+} provided in the assay buffer. The results indicate that both B. japonicum strains transport Ni{sup 2+} via a high-affinity magnesium transport system. Dixon plots (1/V versus inhibitor) showed that the divalent cations Co{sup 2+}, Mn{sup 2+}, and Zn{sup 2+}, like Mg{sup 2+}, were competitive inhibitors of Ni{sup 2+} uptake, The K{sub i}s for nickel uptake inhibition by Mg{sup 2+}, Co{sup 2+}, Mn{sup 2+}, and Zn{sup 2+} were 48, 22, 12, and 8 {mu}M, respectively. Cu{sup 2+} strongly inhibited Ni{sup 2+} uptake, and molybdate inhibited it slightly. Respiratory inhibitors cyanide and azide, the uncoupler carbonyl cyanide m-chlorophenylhydrazone, the ATPase inhibitor N, N{prime}-dicyclohexylcarbodiimide, and ionospheres nigericin and valinomycin significantly inhibited short-term (5 min) Ni{sup 2+} uptake, showing that Ni{sup 2+} uptake in strain JH is energy dependent. Most of these conclusions are quite different from those reported previously for a different B. japonicum strain belonging to a different serogroup.

Changlin Fu; Maier, R.J. (John Hopkins Univ., Baltimore, MD (United States))

1991-12-01

332

Low Growth Temperature-Induced Increase in Light Saturated Photosystem I Electron Transport Is Cation Dependent 1  

PubMed Central

Thylakoid membranes isolated from cold tolerant, herbaceous monocots and dicots grown at 5°C exhibit a 1.5-fold to 2.7-fold increase in light saturated rates of photosystem I (PSI) electron transport compared to thylakoids isolated from the same plant species grown at 20°C. This was observed only when either water or reduced dichlorophenolindophenol was used as an electron donor. The apparent quantum yield for PSI electron transport was not affected by growth temperature. The higher light saturated rates of PSI electron transport in 5°C thylakoids had an absolute requirement for the presence of Na+ and Mg+2. The accessibility of reduced dichlorophenolindophenol to the donor site was not affected by growth temperature since 5°C and 20°C thylakoids exhibited no significant difference in the concentration of this electron donor required for half-maximal PSI activity. The cation dependent higher rates of light saturated PSI activity were also observed when rye thylakoids were developed under intermittent light conditions at 5°C. Thus, this cation effect on PSI activity appeared to be independent of light harvesting complex I and II. The extent of the in vitro reversibility of this cation effect appeared to be limited by an inherent decay process for PSI electron transport. The rate of decay for PSI activity was greatest when thylakoids were isolated in the absence of NaCl and MgCl2. We conclude that exposure of plants to low growth temperatures induces a reorganization of thylakoid membranes which increases the light saturated rates of PSI electron transport with no change in the apparent quantum efficiency for this reaction. Cations are required to stabilize this reorganization. Images Figure 4 Figure 5 PMID:16667181

Huner, Norman P. A.; Reynolds, Tracey L.

1989-01-01

333

Azimuthal velocity shear within an Earthward fast flow - further evidence for magnetotail untwisting?  

NASA Astrophysics Data System (ADS)

It is well known that nonzero interplanetary magnetic field By conditions lead to a twisted magnetotail configuration. The plasma sheet is rotated around its axis and tail magnetic field lines are twisted, which causes an azimuthal displacement of their ionospheric footprints. According to the untwisting hypothesis, the untwisting of twisted field lines is suggested to influence the azimuthal direction of convective fast flows in the nightside geospace. However, there is a lack of in situ magnetospheric observations, which show actual signatures of the possible untwisting process. In this paper, we report detailed Cluster observations of an azimuthal flow shear across the neutral sheet associated with an Earthward fast flow on 5 September 2001. The observations show a flow shear velocity pattern with a V⊥y sign change, near the neutral sheet (Bx~0) within a fast flow during the neutral sheet flapping motion over the spacecraft. Firstly, this implies that convective fast flows may not generally be unidirectional across the neutral sheet, but may have a more complex structure. Secondly, in this event tail By and the flow shear are as expected by the untwisting hypothesis. The analysis of the flow shear reveals a linear dependence between Bx and V⊥y close to the neutral sheet and suggests that Cluster crossed the neutral sheet in the dawnward part of the fast flow channel. The magnetospheric observations are supported by the semi-empirical T96 and TF04 models. Furthermore, the ionospheric SuperDARN convection maps support the satellite observations proposing that the azimuthal component of the magnetospheric flows is enforced by a magnetic field untwisting. In summary, the observations give strong supportive evidence to the tail untwisting hypothesis. However, the T96 ionospheric mapping demonstrates the limitations of the model in mapping from a twisted tail.

Pitkänen, T.; Hamrin, M.; Norqvist, P.; Karlsson, T.; Nilsson, H.; Kullen, A.; Imber, S. M.; Milan, S. E.

2015-03-01

334

Mapping Phase Velocities and Azimuthal Anisotropy of Rayleigh Waves in Iceland  

NASA Astrophysics Data System (ADS)

Using Rayleigh wave data recorded at both the HOTSPOT and the ICEMELT experiments in Iceland, we have applied the two-plane wave inversion technique and obtained phase velocities and azimuthal anisotropy from period 20 s to 100 s. The most striking feature is that the slow anomalies are generally confined beneath the Icelandic rift zones but not correlate with the plume center on the surface. Azimuthal anisotropy appears to be frequency dependent and also shows strong lateral variations especially between the western Iceland, the rift zones, and the eastern Iceland, as suggested by shear-wave splitting measurements. It is well known that tradeoffs exist between isotropic and anisotropic heterogeneity. We conducted resolution tests to estimate how robust the observed features of phase velocities and anisotropy are. Synthetic phase and amplitude data of Rayleigh waves were calculated from a typical phase velocity model that has low velocities beneath the Icelandic rift zones. Azimuthal anisotropy that uniformly distributes in the area or varies laterally by tectonic province was also included in the input models. The pattern of isotropic phase velocities with fast anomalies in the western and eastern Iceland and the slow in the rift zones is well recovered in both isotropic and anisotropic inversions. The azimuthal anisotropy larger than 1% in the input models can be largely retrieved. However, the amount of anisotropy when varying by tectonic province is not negligible in anisotropic solutions even for isotropic input models. Therefore, we suggest inverting synthetic data from the observed isotropic phase velocity models in order to detect whether the observed anisotropy reflects the real structure or the tradeoff with isotropic heterogeneity.

Li, A.; Detrick, R. S.

2002-05-01

335

Spin-dependent transport for a two-dimensional electron gas with magnetic barriers  

Microsoft Academic Search

The spin-dependent conductance and magnetoresistance ratio (MRR) for a semiconductor heterostructures consisting of two magnetic barriers with different height and space have been investigated by the transfer-matrix method. It is shown that the splitting of the conductance for parallel and antiparallel magnetization configurations results in tremendous spin-dependent MRR, and the maximal MRRs reach 5300% and 3800% for the magnetic barrier

Hai-Yan Wang; Zi-Gang Duan; Wen-Hu Liao; Guang-Hui Zhou

2010-01-01

336

Temperature dependent charge transport in organic field-effect transistors with the variation of both carrier concentration and electric field  

NASA Astrophysics Data System (ADS)

We present experimental evidence of combined effects of temperature, carrier concentration, electric field as well as disorder on charge transport in an organic field-effect transistor (OFET). Transfer characteristics of an OFET based on sexithiophene active layer were measured from 80 to 300 K. Thermally activated carrier mobility followed Arrhenius law with two activation energies. Carrier density variation led to finite extrapolated Meyer-Neldel (MN) temperature (780 K) at low fields. Negative electric field-dependent mobility was observed in available field range. MN temperature shifted towards higher temperature when the electric field increased, and did not retain its finite character above the field of 4 × 103 V cm-1.

Abbas, Mamatimin; Pivrikas, Almantas; Arici, Elif; Tekin, Nalan; Ullah, Mujeeb; Sitter, Helmut; Sariciftci, Niyazi Serdar

2013-12-01

337

Carrier generation, recombination, trapping, and transport in semiconductors with position-dependent composition. [in junction solar cells  

NASA Technical Reports Server (NTRS)

The spatial variation of the chemical composition of a semiconductor modifies the ideal one-electron energy band model as well as the Shockley equations for carrier recombination and transport in two important ways. The random component of the spatial variation introduces localized states in the energy gap by perturbing the band states. The nonrandom component gives rise to the position dependences of the conduction and valence band edges or the electron affinity and the energy gap. This paper gives the modifications of the Shockley equations from these two effects as well as an example of the steady-state recombination rate from distributed gap states in junction solar cells

Sah, C.-T.; Lindholm, F. A.

1977-01-01

338

EFFECT OF RESISTANCE TRAINING ON SKELETAL MUSCLE SODIUM-DEPENDENT GLUCOSE TRANSPORT (SGLT) GENE EXPRESSION IN OLDER ADULTS WITH TYPE 2 DIABETES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Muscle glucose uptake takes place by facilitated, insulin-stimulated glucose transport (GLUT4) or by active, sodium-dependent glucose transport (SGLT). Exercise regulates muscle GLUT4 expression. However, little is known about the role of exercise on SGLT. We examined the effect of resistance traini...

339

Transactivation of rat apical sodium-dependent bile acid transporter and increased bile acid transport by 1alpha,25-dihydroxyvitamin D3 via the vitamin D receptor.  

PubMed

Transactivation of the rat apical sodium-dependent bile acid transporter (ASBT; Slc10a2) by 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] via the vitamin D receptor (VDR), was studied. Levels of ASBT protein and mRNA were low in the duodenum and high in the ileum, and both were induced by 1,25(OH)(2)D(3). The nuclear receptor protein, VDR, was present uniformly in the duodenum, jejunum, and ileum of the rat small intestine. The physiological relevance of ASBT induction by 1,25(OH)(2)D(3) was assessed by measuring absorption of cholylsarcosine, a non-metabolized synthetic bile acid analog, from duodenal or ileal closed loops of the perfused rat small intestine preparation. Absorption of cholylsarcosine was much greater from the ileal segment (28-fold that of the duodenum under control conditions) and was enhanced with 1,25(OH)(2)D(3) treatment. Transient transfection analysis of the rat ASBT promoter in Caco-2 cells revealed concentration-dependent enhancement of luciferase reporter activity after treatment with 1,25(OH)(2)D(3). The activation by 1,25(OH)(2)D(3) was abrogated after site-directed mutagenesis or deletion of the vitamin D response element (VDRE) in the ASBT promoter. Gel-shift mobility assays of nuclear extracts from rat ileum showed that both rat retinoid X receptor and VDR were bound to the VDRE. The results indicate that rat ASBT gene expression is activated by 1,25(OH)(2)D(3) by specific binding to the VDRE and that such activation enhances ileal bile acid transport. Human ABST mRNA and promoter activity were also increased in Caco-2 cells treated with 1,25(OH)(2)D(3), suggesting a physiological role of VDR in human ileal bile acid homeostasis. PMID:16481392

Chen, Xianghai; Chen, Frank; Liu, Shanjun; Glaeser, Hartmut; Dawson, Paul A; Hofmann, Alan F; Kim, Richard B; Shneider, Benjamin L; Pang, K Sandy

2006-06-01

340

Fracture detection by using full azimuth P wave attributes  

NASA Astrophysics Data System (ADS)

A type of specific fractured hydrocarbon reservoir, a shale fractured reservoir, exists in the Shengli oilfield. Due to very small porosity of this type, low sensitivity to the variation of petrochemical property parameters, and strong anisotropy, it is very difficult to explore for them. So far, there is no set of mature methods for recognition of direction, distribution, and density of the fractures by an integrated analysis of geologic, geophysical, well log, drilling data, and etc. This paper presents a new method for acoustic impedance variation with azimuth (IPVA), based on existing fracture detection methods. Seismic acquisition, processing, and recognition techniques were developed for detecting directional vertical fractures using multi-azimuth P wave data in combination with the seismic and geological features of shale fractures in the Luojia area. The IPVA research is carried out for recognizing the distribution, strike, and density of fractures based on the study of velocity variation with azimuth (VVA) and amplitude variation with azimuth (AVA) for full azimuth P wave data at different CMP positions. Through practical application in the Luojia area, primary results have been obtained which verifies that the IPVA method provides good potential for quantitative detection of parallel, high angle, shale fractures.

Shouli, Qu; Yuxin, Ji; Xin, Wang; Xiuling, Wang; Xinrong, Chen; Guoqiang, Shen

2007-09-01

341

Reduced striatal dopamine transporter density associated with working memory deficits in opioid-dependent male subjects: a SPECT study.  

PubMed

Research on the effects of repeated opioid use on striatal dopamine transporters (DATs) has yielded inconsistent results, possibly confounded by a history of methamphetamine or methadone exposure in opioid-dependent individuals. Previous studies have shown that striatal DAT density is positively correlated with the cognitive performance of healthy volunteers. This study aimed to investigate changes in striatal DAT density and their functional significance in opioid-dependent individuals. Single-photon emission computed tomography (SPECT) with [(99m) Tc]TRODAT-1 as a ligand was used to measure striatal DAT levels in 20 opioid-dependent individuals and 20 age- and sex-matched healthy controls. Opioid-dependent individuals had no history of methamphetamine or methadone use. The Wisconsin Card Sorting Test (WCST) was performed to assess neurocognitive function. We found that compared with healthy controls, opioid-dependent individuals showed a significant reduction in striatal DAT density. They also showed poorer performance on the WCST in terms of the trials administered, total errors, perseverative responses, perseverative errors and non-perseverative errors. Striatal DAT levels negatively correlated with non-perseverative errors not only in opioid-dependent individuals but also in healthy controls. These findings suggest that in human, repeated opioid exposure reduces striatal DAT density, which can be associated with non-perseverative errors. Non-perseverative errors may be one of the more sensitive parameters in WCST to identify working memory deficits associated with striatal DAT reduction. Moreover, we suggest that whether opioid-associated neurotoxicity is reversible depends on the brain region. PMID:25439653

Liang, Chih-Sung; Ho, Pei-Shen; Yen, Che-Hung; Yeh, Yi-Wei; Kuo, Shin-Chang; Huang, Chang-Chih; Chen, Chun-Yen; Shih, Mei-Chen; Ma, Kuo-Hsing; Huang, San-Yuan

2014-12-01

342

Presynaptic Na+-dependent transport and exocytose of GABA and glutamate in brain in hypergravity.  

NASA Astrophysics Data System (ADS)

?-Aminobutyric acid (GABA) and L-glutamate are the most widespread neurotransmitter amino acids in the mammalian central nervous system. GABA is now widely recognized as the major inhibitory neurotransmitter. L-glutamate mediates the most of excitatory synaptic neurotransmission in the brain. They involved in the main aspects of normal brain function. The nerve terminals (synaptosomes) offer several advantages as a model system for the study of general mechanisms of neurosecretion. Our data allowed to conclude that exposure of animals to hypergravity (centrifugation of rats at 10G for 1 hour) had a profound effect on synaptic processes in brain. Comparative analysis of uptake and release of GABA and glutamate have demonstrated that hypergravity loading evokes oppositely directed alterations in inhibitory and excitatory signal transmission. We studied the maximal velocities of [^3H]GABA reuptake and revealed more than twofold enhancement of GABA transporter activity (Vmax rises from 1.4 |pm 0.3 nmol/min/mg of protein in the control group to 3.3 ± 0.59 nmol/min/mg of protein for animals exposed to hypergravity (P ? 0.05)). Recently we have also demonstrated the significant lowering of glutamate transporter activity (Vmax of glutamate reuptake decreased from 12.5 ± 3.2 nmol/min/mg of protein in the control group to 5.6 ± 0.9 nmol/min/mg of protein in the group of animals, exposed to the hypergravity stress (P ? 0.05)). Significant changes occurred in release of neurotransmitters induced by stimulating exocytosis with the agents, which depolarized nerve terminal plasma membrane. Depolarization-evoked Ca2+-stimulated release was more abundant for GABA (7.2 ± 0.54% and 11,74 ±1,2 % of total accumulated label for control and hypergravity, respectively (P?0.05)) and was essentially less for glutamate (14.4 ± 0.7% and 6.2 ± 1.9%) after exposure of animals to centrifuge induced artificial gravity. Changes observed in depolarization-evoked exocytotic release seem to be in a concert with alterations of plasma membrane transporters activity studied. Perhaps, lowering of glutamate transporter activity and increase of the velocity of GABA uptake correlated with diminution and augmentation of exocytotic release of these neurotransmitters, respectively. It is possible to suggest that observed changes in the activity of the processes responsible for the uptake and release of excitatory and inhibitory neurotransmitters are likely to be physiologically important and reflect making protective mechanisms more active for neutralization of harm influence of hypergravity stress.

Borisova, T.; Pozdnyakova, N.; Krisanova, N.; Himmelreich, N.

343

Haemophilus parainfluenzae expresses diverse lipopolysaccharide O-antigens using ABC transporter and Wzy polymerase-dependent mechanisms  

PubMed Central

Lipopolysaccharide O-antigens are the basis of serotyping schemes for Gram negative bacteria and help to determine the nature of host–bacterial interactions. Haemophilus parainfluenzae is a normal commensal of humans but is also an occasional pathogen. The prevalence, diversity and biosynthesis of O-antigens were investigated in this species for the first time. 18/18 commensal H. parainfluenzae isolates contain a O-antigen biosynthesis gene cluster flanked by glnA and pepB, the same position as the hmg locus for tetrasaccharide biosynthesis in Haemophilus influenzae. The O-antigen loci show diverse restriction digest patterns but fall into two main groups: (1) those encoding enzymes for the synthesis and transfer of FucNAc4N in addition to the Wzy-dependent mechanism of O-antigen synthesis and transport and (2) those encoding galactofuranose synthesis/transfer enzymes and an ABC transporter. The other glycosyltransferase genes differ between isolates. Three H. parainfluenzae isolates fell outside these groups and are predicted to synthesise O-antigens containing ribitol phosphate or deoxytalose. Isolates using the ABC transporter system encode a putative O-antigen ligase, required for the synthesis of O-antigen-containing LPS glycoforms, at a separate genomic location. The presence of an O-antigen contributes significantly to H. parainfluenzae resistance to the killing effect of human serum in vitro. The discovery of O-antigens in H. parainfluenzae is striking, as its close relative H. influenzae lacks this cell surface component. PMID:24035104

Young, Rosanna E.B.; Twelkmeyer, Brigitte; Vitiazeva, Varvara; Power, Peter M.; Schweda, Elke K.H.; Hood, Derek W.

2013-01-01

344

Time-dependent scenario modeling of the Tokamak Physics Experiment using a theory-based transport model  

SciTech Connect

Predictive transport and current drive simulations are presented for the time evolution of the temperature and density profiles in the Tokamak Physics Experiment (TPX). [W. M. Nevins {ital et} {ital al}., {ital Proceedings} {ital of} {ital the} {ital International} {ital Conference} {ital on} {ital Plasma} {ital Physics} {ital and} {ital Controlled} {ital Nuclear} {ital Fusion} {ital Research}, W{umlt u}rzburg, 1992 (International Atomic Energy Agency, Vienna, 1992), Vol. 3, p. 279]. A distinguishing feature of this study is that we use a theoretically derived transport model that has been empirically calibrated against Ohmic, low-confinement and high-confinement mode discharges from seven different tokamaks. Heating and deposition profiles predicted by the ACCOME current drive and magnetohydrodynamic equilibrium code [R. S. Devoto {ital et} {ital al}., Nucl. Fusion {bold 32}, 773 (1992)] are incorporated into the time-dependent BALDUR one-and-one-half dimensional transport code [C. E. Singer {ital et} {ital al}., Comput. Phys. Commun. {bold 49}, 275 (1988)]. We consider various scenarios of fast wave, lower hybrid, and neutral beam heating and current drive and evaluate the effects on the evolution of density and temperature profiles. {copyright} {ital 1996 American Institute of Physics.}

Kinsey, J.; Kritz, A. [Department of Physics, 16 Memorial Dr. East, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)] [Department of Physics, 16 Memorial Dr. East, Lehigh University, Bethlehem, Pennsylvania 18015 (United States); Bonoli, P.; Porkolab, M. [Massachusetts Institute of Technology Plasma Fusion Center, Cambridge, Massachusetts 02139 (United States)] [Massachusetts Institute of Technology Plasma Fusion Center, Cambridge, Massachusetts 02139 (United States)

1996-03-01

345

E-0702, a new cephalosporin, is incorporated into Escherichia coli cells via the tonB-dependent iron transport system.  

PubMed Central

E-0702, a new cephalosporin with a potent antipseudomonal action, was synthesized. In the study of the mode of action of this antibiotic in Escherichia coli, it was found that mutants which acquired resistance to E-0702 were isolated spontaneously and could be shown to be susceptible to its closely related derivatives, E-0702-060 and E-0702-061, and other representative beta-lactam antibiotics. In these mutants, no increased production of beta-lactamase was detectable. No apparent differences between the resistant mutants and the parental strains were observed in the affinity of E-0702 for penicillin-binding proteins. Furthermore, no significant reduction in or loss of both OmpF and OmpC porin proteins in the outer membrane was observed. The mutation was mapped to the tonB gene, which is known to be essential for the iron transport system of bacteria. The bactericidal action of E-0702 was rapidly expressed against iron-starved cells in which the iron transport system was induced, whereas the bactericidal action against iron-supplemented cells was ineffective. It is suggested that E-0702 is incorporated into bacterial cells as a chelator of iron via the tonB-dependent iron transport system, after which its strong and rapid bactericidal action is manifested. Images PMID:3037997

Watanabe, N A; Nagasu, T; Katsu, K; Kitoh, K

1987-01-01

346

Separation of Rashba and Dresselhaus spin-orbit interactions using crystal direction dependent transport measurements  

NASA Astrophysics Data System (ADS)

The Rashba spin-orbit interaction effective field is always in the plane of the two-dimensional electron gas and perpendicular to the carrier wavevector but the direction of the Dresselhaus field depends on the crystal orientation. These two spin-orbit interaction parameters can be determined separately by measuring and analyzing the Shubnikov-de Haas oscillations for various crystal directions. In the InAs quantum well system investigated, the Dresselhaus term is just 5% of the Rashba term. The gate dependence of the oscillation patterns clearly shows that only the Rashba term is modulated by an external electric field.

Ho Park, Youn; Kim, Hyung-jun; Chang, Joonyeon; Hee Han, Suk; Eom, Jonghwa; Choi, Heon-Jin; Cheol Koo, Hyun

2013-12-01

347

Separation of Rashba and Dresselhaus spin-orbit interactions using crystal direction dependent transport measurements  

SciTech Connect

The Rashba spin-orbit interaction effective field is always in the plane of the two-dimensional electron gas and perpendicular to the carrier wavevector but the direction of the Dresselhaus field depends on the crystal orientation. These two spin-orbit interaction parameters can be determined separately by measuring and analyzing the Shubnikov-de Haas oscillations for various crystal directions. In the InAs quantum well system investigated, the Dresselhaus term is just 5% of the Rashba term. The gate dependence of the oscillation patterns clearly shows that only the Rashba term is modulated by an external electric field.

Ho Park, Youn [Spin Convergence Research Center, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of) [Spin Convergence Research Center, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Hyung-jun; Chang, Joonyeon; Hee Han, Suk [Spin Convergence Research Center, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of)] [Spin Convergence Research Center, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Eom, Jonghwa [Department of Physics and Graphene Research Institute, Sejong University, Seoul 143-747 (Korea, Republic of)] [Department of Physics and Graphene Research Institute, Sejong University, Seoul 143-747 (Korea, Republic of); Choi, Heon-Jin [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)] [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Cheol Koo, Hyun, E-mail: hckoo@kist.re.kr [Spin Convergence Research Center, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-701 (Korea, Republic of)

2013-12-16

348

Fully predictive time-dependent transport simulations of ITB plasmas in JET, JT-60U and DIII-D  

NASA Astrophysics Data System (ADS)

For the first time, the predictive capabilities of the mixed Bohm/GyroBohm, Weiland and 'retuned' GLF23 transport models are investigated with ITB discharges from the ITPA ITB database with fully predictive, time-dependent transport simulations. A range of plasma conditions is examined for JET, JT-60U and DIII-D discharges with internal transport barriers (ITBs). The simulations show that the Bohm/GyroBohm model is able to follow the time evolution of the discharge from the preheating phase without an ITB through the ITB onset phase until the high performance phase with fair accuracy in most cases in JET and JT-60U. This indicates the importance of the interplay between the magnetic shear and ?E×B flow shear in ITB formation since these are the mechanisms that govern the ITB physics in the model. In order to achieve good agreement in DIII-D, the ?-stabilization had to be included in the model, emphasizing the role played by the ?-stabilization in the physics of the ITBs. The Weiland and GLF23 transport models show limited agreement between the model predictions and experimental time evolution of the ITB and kinetic plasma profiles. The Weiland model does not form a clear ITB in any of the three tokamaks despite varying plasma profiles, such as the q-profile. On the other hand, the average temperatures and density are often in fair agreement with experimental values. The GLF23 model often predicts an ITB, but its radial location is often too far inside the plasma, or shrinks as the simulations proceed in time. Consequently, the central temperatures at the end of the simulations during the high performance phase are usually underestimated. It is worth noting that GLF23 features in general better predictions of the Te and Ti profiles outside the ITB than the other models studied. Achieving the quantitative capability to predict the multi-channel ITB dynamics with fully predictive, time-dependent transport simulations has turned out to be extremely challenging.

Tala, T.; Imbeaux, F.; Parail, V. V.; Bourdelle, C.; Corrigan, G.; Garbet, X.; Heading, D. J.; Litaudon, X.; Strand, P. I.; Weiland, J.; contributors, JET-EFDA

2006-05-01

349

Cytokinin controls polarity of PIN1-dependent auxin transport during lateral root organogenesis.  

PubMed

The plant hormones auxin and cytokinin mutually coordinate their activities to control various aspects of development [1-9], and their crosstalk occurs at multiple levels [10, 11]. Cytokinin-mediated modulation of auxin transport provides an efficient means to regulate auxin distribution in plant organs. Here, we demonstrate that cytokinin does not merely control the overall auxin flow capacity, but might also act as a polarizing cue and control the auxin stream directionality during plant organogenesis. Cytokinin enhances the PIN-FORMED1 (PIN1) auxin transporter depletion at specific polar domains, thus rearranging the cellular PIN polarities and directly regulating the auxin flow direction. This selective cytokinin sensitivity correlates with the PIN protein phosphorylation degree. PIN1 phosphomimicking mutations, as well as enhanced phosphorylation in plants with modulated activities of PIN-specific kinases and phosphatases, desensitize PIN1 to cytokinin. Our results reveal conceptually novel, cytokinin-driven polarization mechanism that operates in developmental processes involving rapid auxin stream redirection, such as lateral root organogenesis, in which a gradual PIN polarity switch defines the growth axis of the newly formed organ. PMID:24768050

Marhavý, Peter; Duclercq, Jérôme; Weller, Benjamin; Feraru, Elena; Bielach, Agnieszka; Offringa, Remko; Friml, Ji?í; Schwechheimer, Claus; Murphy, Angus; Benková, Eva

2014-05-01

350

Heme Utilization by Nontypeable Haemophilus influenzae Is Essential and Dependent on Sap Transporter Function?†  

PubMed Central

Bacterial strategies of innate immune evasion and essential metabolic functions are critical for commensal-host homeostasis. Previously, we showed that Sap translocator function is necessary for nontypeable Haemophilus influenzae (NTHI) behaviors that mediate diseases of the human airway. Antimicrobial peptide (AP) lethality is limited by binding mediated by the Sap complex. SapA shares homology with the dipeptide-binding protein (DppA) and the heme-binding lipoprotein (HbpA), both of which have previously been shown to bind the iron-containing compound heme, whose acquisition is essential for Haemophilus survival. Computational modeling revealed conserved SapA residues, similarly modeled to mediate heme binding in HbpA. Here, we directly demonstrate that SapA bound heme and was essential for heme utilization by iron-starved NTHI. Further, the Sap translocator permease mediated heme transport into the bacterial cytoplasm, thus defining a heretofore unknown mechanism of intracytoplasmic membrane heme transport in Haemophilus. Since we demonstrate multiple ligand specificity for the SapA-binding protein, we tested whether APs would compete with heme for SapA binding. We showed that human ?-defensins 2 and 3, human cathelicidin LL-37, human neutrophil protein 1, and melittin displaced heme bound to SapA, thus supporting a hierarchy wherein immune evasion supercedes even the needed iron acquisition functions of the Sap system. PMID:21441512

Mason, Kevin M.; Raffel, Forrest K.; Ray, William C.; Bakaletz, Lauren O.

2011-01-01

351

Temperature-dependent gas transport performance of vertically aligned carbon nanotube/parylene composite membranes  

PubMed Central

A novel composite membrane consisting of vertically aligned carbon nanotubes (CNTs) and parylene was successfully fabricated. Seamless filling of the spaces in CNT forests with parylene was achieved by a low-pressure chemical vapor deposition (CVD) technique and followed with the Ar/O2 plasma etching to expose CNT tips. Transport properties of various gases through the CNT/parylene membranes were explored. And gas permeances were independent on feed pressure in accordance with the Knudsen model, but the permeance values were over 60 times higher than that predicted by the Knudsen diffusion kinetics, which was attributed to specular momentum reflection inside smooth CNT pores. Gas permeances and enhancement factors over the Knudsen model firstly increased and then decreased with rising temperature, which confirmed the existence of non-Knudsen transport. And surface adsorption diffusion could affect the gas permeance at relatively low temperature. The gas permeance of the CNT/parylene composite membrane could be improved by optimizing operating temperature. PMID:25246864

2014-01-01

352

Heme utilization by nontypeable Haemophilus influenzae is essential and dependent on Sap transporter function.  

PubMed

Bacterial strategies of innate immune evasion and essential metabolic functions are critical for commensal-host homeostasis. Previously, we showed that Sap translocator function is necessary for nontypeable Haemophilus influenzae (NTHI) behaviors that mediate diseases of the human airway. Antimicrobial peptide (AP) lethality is limited by binding mediated by the Sap complex. SapA shares homology with the dipeptide-binding protein (DppA) and the heme-binding lipoprotein (HbpA), both of which have previously been shown to bind the iron-containing compound heme, whose acquisition is essential for Haemophilus survival. Computational modeling revealed conserved SapA residues, similarly modeled to mediate heme binding in HbpA. Here, we directly demonstrate that SapA bound heme and was essential for heme utilization by iron-starved NTHI. Further, the Sap translocator permease mediated heme transport into the bacterial cytoplasm, thus defining a heretofore unknown mechanism of intracytoplasmic membrane heme transport in Haemophilus. Since we demonstrate multiple ligand specificity for the SapA-binding protein, we tested whether APs would compete with heme for SapA binding. We showed that human ?-defensins 2 and 3, human cathelicidin LL-37, human neutrophil protein 1, and melittin displaced heme bound to SapA, thus supporting a hierarchy wherein immune evasion supercedes even the needed iron acquisition functions of the Sap system. PMID:21441512

Mason, Kevin M; Raffel, Forrest K; Ray, William C; Bakaletz, Lauren O

2011-05-01

353

Pressure dependence of fluid transport properties of shallow fault systems in the Nankai subduction zone  

NASA Astrophysics Data System (ADS)

We measured fluid transport properties at an effective pressure of 40 MPa in core samples of sediments and fault rocks collected by the Integrated Ocean Drilling Program (IODP) NanTroSEIZE drilling project Expedition 316 from the megasplay fault system (site C0004) and the frontal thrust (site C0007) in the Nankai subduction zone. Permeability decreased with effective pressure as a power law function. Permeability values in the fault zones were 8 × 10-18 m2 at site C0004 and 9 × 10-18 m2 at site C0007. Stratigraphic variation in transport properties suggests that the megasplay fault zone may act as a barrier to fluid flow, but the frontal thrust fault zone might not. Depth variation in permeability at site C0007 is probably controlled by the mechanical compaction of sediment. Hydraulic diffusivity at shallow depths was approximately 1 × 10-6 m2 s-1 in both fault zones, which is small enough to lead to pore pressure generation that can cause dynamic fault weakening. However, absence of a very low permeable zone, which may have formed in the Japan Trench subduction zone, might prevent facilitation of huge shallow slips during Nankai subduction zone earthquakes. Porosity tests under dry conditions might have overestimated the porosity.

Tanikawa, Wataru; Mukoyoshi, Hideki; Lin, Weiren; Hirose, Takehiro; Tsutsumi, Akito

2014-12-01

354

Phase dependence of transport-aperture coordination variability reveals control strategy of reach-to-grasp movements.  

PubMed

Based on an assumption of movement control optimality in reach-to-grasp movements, we have recently developed a mathematical model of transport-aperture coordination (TAC), according to which the hand-target distance is a function of hand velocity and acceleration, aperture magnitude, and aperture velocity and acceleration (Rand et al. in Exp Brain Res 188:263-274, 2008). Reach-to-grasp movements were performed by young adults under four different reaching speeds and two different transport distances. The residual error magnitude of fitting the above model to data across different trials and subjects was minimal for the aperture-closure phase, but relatively much greater for the aperture-opening phase, indicating considerable difference in TAC variability between those phases. This study's goal is to identify the main reasons for that difference and obtain insights into the control strategy of reach-to-grasp movements. TAC variability within the aperture-opening phase of a single trial was found minimal, indicating that TAC variability between trials was not due to execution noise, but rather a result of inter-trial and inter-subject variability of motor plan. At the same time, the dependence of the extent of trial-to-trial variability of TAC in that phase on the speed of hand transport was sharply inconsistent with the concept of speed-accuracy trade-off: the lower the speed, the larger the variability. Conversely, the dependence of the extent of TAC variability in the aperture-closure phase on hand transport speed was consistent with that concept. Taking into account recent evidence that the cost of neural information processing is substantial for movement planning, the dependence of TAC variability in the aperture-opening phase on task performance conditions suggests that it is not the movement time that the CNS saves in that phase, but the cost of neuro-computational resources and metabolic energy required for TAC regulation in that phase. Thus, the CNS performs a trade-off between that cost and TAC regulation accuracy. It is further discussed that such trade-off is possible because, due to a special control law that governs optimal switching from aperture opening to aperture closure, the inter-trial variability of the end of aperture opening does not affect the high accuracy of TAC regulation in the subsequent aperture-closure phase. PMID:20931181

Rand, Miya K; Shimansky, Y P; Hossain, Abul B M I; Stelmach, George E

2010-11-01

355

Effects of symmetry and spin configuration on spin-dependent transport properties of iron-phthalocyanine-based devices  

SciTech Connect

Spin-dependent transport properties of nanodevices constructed by iron-phthalocyanine (FePc) molecule sandwiched between two zigzag graphene nanoribbon electrodes are studied using first-principles quantum transport calculations. The effects of the symmetry and spin configuration of electrodes have been taken into account. It is found that large magnetoresistance, large spin polarization, dual spin-filtering, and negative differential resistance (NDR) can coexist in these devices. Our results show that 5Z-FePc system presents well conductive ability in both parallel (P) and anti-parallel (AP) configurations. For 6Z-FePc-P system, spin filtering effect and large spin polarization can be found. A dual spin filtering and NDR can also be shown in 6Z-FePc-AP. Our studies indicate that the dual spin filtering effect depends on the orbitals symmetry of the energy bands and spin mismatching of the electrodes. And all the effects would open up possibilities for their applications in spin-valve, spin-filter as well as effective spin diode devices.

Cui, Li-Ling [Institute of Super Microstructure and Ultrafast Process in Advanced Materials, School of Physics and Electronics, Central South University, Changsha 410083 (China); School of Science, Hunan University of Technology, Zhuzhou 412007 (China); Yang, Bing-Chu, E-mail: bingchuyang@csu.edu.cn; Li, Xin-Mei; Cao, Can [Institute of Super Microstructure and Ultrafast Process in Advanced Materials, School of Physics and Electronics, Central South University, Changsha 410083 (China); Long, Meng-Qiu, E-mail: mqlong@csu.edu.cn [Institute of Super Microstructure and Ultrafast Process in Advanced Materials, School of Physics and Electronics, Central South University, Changsha 410083 (China); Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China)

2014-07-21

356

5-aminoimidazole-4-carboxamide riboside (AICAR) enhances GLUT2-dependent jejunal glucose transport: a possible role for AMPK.  

PubMed

AMPK (AMP-activated protein kinase) is a key sensor of energy status within the cell. Activated by an increase in the AMP/ATP ratio, AMPK acts to limit cellular energy depletion by down-regulating selective ATP-dependent processes. The purpose of the present study was to determine the role of AMPK in regulating intestinal glucose transport. [3H]3-O-methyl glucose fluxes were measured in murine jejunum in the presence and absence of the AMPK activators AICAR (5-aminoimidazole-4-carboxamide riboside) and metformin and the p38 inhibitor, SB203580. To differentiate between a sodium-coupled (SGLT1) and diffusive (GLUT2) route of entry, fluxes were measured in the presence of the SGLT1 and GLUT2 inhibitors phloridzin and phloretin. Glucose transporter mRNA levels were measured by reverse transcriptase-PCR, and localization by Western blotting. Surface-expressed GLUT2 was assessed by luminal biotinylation. Activation of p38 mitogen-activated protein kinase was analysed by Western blotting. We found that treatment of jejunal tissue with AICAR resulted in enhanced net glucose uptake and was associated with phosphorylation of p38 mitogen-activated protein kinase. Inhibition of p38 abrogated the stimulation of AICAR-stimulated glucose uptake. Phloretin abolished the AICAR-mediated increase in glucose flux, whereas phloridzin had no effect, suggesting the involvement of GLUT2. In addition, AICAR decreased total protein levels of SGLT1, concurrently increasing levels of GLUT2 in the brush-border membrane. The anti-diabetic drug metformin, a known activator of AMPK, also induced the localization of GLUT2 to the luminal surface. We conclude that the activation of AMPK results in an up-regulation of non-energy requiring glucose uptake by GLUT2 and a concurrent down-regulation of sodium-dependent glucose transport. PMID:15367103

Walker, John; Jijon, Humberto B; Diaz, Hugo; Salehi, Payam; Churchill, Thomas; Madsen, Karen L

2005-01-15

357

Advances in colloid and biocolloid transport in porous media: particle size-dependent dispersivity and gravity effects  

NASA Astrophysics Data System (ADS)

Accurate prediction of colloid and biocolloid transport in porous media relies heavily on usage of suitable dispersion coefficients. The widespread procedure for dispersion coefficient determination consists of conducting conservative tracer experiments and subsequently fitting the collected breakthrough data with a selected advection-dispersion transport model. The fitted dispersion coefficient is assumed to characterize the porous medium and is often used thereafter to analyze experimental results obtained from the same porous medium with other solutes, colloids, and biocolloids. The classical advection-dispersion equation implies that Fick's first law of diffusion adequately describes the dispersion process, or that the dispersive flux is proportional to the concentration gradient. Therefore, the above-described procedure inherently assumes that the dispersive flux of all solutes, colloids and biocolloids under the same flow field conditions is exactly the same. Furthermore, the available mathematical models for colloid and biocoloid transport in porous media do not adequately account for gravity effects. Here an extensive laboratory study was undertaken in order to assess whether the dispersivity, which traditionally has been considered to be a property of the porous medium, is dependent on colloid particle size, interstitial velocity and length scale. The breakthrough curves were successfully simulated with a mathematical model describing colloid and biocolloid transport in homogeneous, water saturated porous media. The results demonstrated that the dispersivity increases very slowly with increasing interstitial velocity, and increases with column length. Furthermore, contrary to earlier results, which were based either on just a few experimental observations or experimental conditions leading to low mass recoveries, dispersivity was positively correlated with colloid particle size. Also, transport experiments were performed with biocolloids (bacteriophages: ?X174, MS2) and colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b) in packed columns placed in various orientations (horizontal, vertical, and diagonal) under both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one dimensional, colloid and biocolloid transport model, accounting for gravity effects. The results revealed that flow direction has a significant influence on particle deposition. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for biocolloid and colloid deposition.

Chrysikopoulos, Constantinos V.; Manariotis, Ioannis D.; Syngouna, Vasiliki I.

2014-05-01

358

Decoherent time-dependent transport beyond the Landauer-Büttiker formulation: a quantum-drift alternative to quantum jumps  

E-print Network

We present a model for decoherence in time-dependent transport. It boils down into a form of wave function that undergoes a smooth stochastic drift of the phase in a local basis, the Quantum Drift (QD) model. This drift is nothing else but a local energy fluctuation. Unlike Quantum Jumps (QJ) models, no jumps are present in the density as the evolution is unitary. As a first application, we address the transport through a resonant state $\\left\\vert 0\\right\\rangle $ that undergoes decoherence. We show the equivalence with the decoherent steady state transport in presence of a B\\"{u}ttiker's voltage probe. In order to test the dynamics, we consider two many-spin systems whith a local energy fluctuation. A two-spin system is reduced to a two level system (TLS) that oscillates among $\\left\\vert 0\\right\\rangle $ $\\equiv $ $ \\left\\vert \\uparrow \\downarrow \\right\\rangle $ and $\\left\\vert 1\\right\\rangle \\equiv $ $\\left\\vert \\downarrow \\uparrow \\right\\rangle $. We show that QD model recovers not only the exponential damping of the oscillations in the low perturbation regime, but also the non-trivial bifurcation of the damping rates at a critical point, i.e. the quantum dynamical phase transition. We also address the spin-wave like dynamics of local polarization in a spin chain. The QD average solution has about half the dispersion respect to the mean dynamics than QJ. By evaluating the Loschmidt Echo (LE), we find that the pure states $\\left\\vert 0\\right\\rangle $ and $\\left\\vert 1\\right \\rangle $ are quite robust against the local decoherence. In contrast, the LE, and hence coherence, decays faster when the system is in a superposition state. Because its simple implementation, the method is well suited to assess decoherent transport problems as well as to include decoherence in both one-body and many-body dynamics.

Lucas J. Fernández-Alcázar; Horacio M. Pastawski

2015-02-27

359

Decoherent time-dependent transport beyond the Landauer-Büttiker formulation: A quantum-drift alternative to quantum jumps  

NASA Astrophysics Data System (ADS)

We develop and implement a model for decoherence in time-dependent transport. Inspired in a dynamical formulation of the Landauer-Büttiker equations, it boils down into a form of wave function that undergoes a smooth stochastic drift of the phase in a local basis, the quantum-drift (QD) model. This drift is nothing else but a local energy fluctuation. Unlike quantum-jumps (QJ) models, no jumps are present in the density as the evolution is unitary. As a first application, we address the transport through a resonant state |0 > that undergoes decoherence. Its numerical resolution shows the equivalence with the decoherent steady-state transport in presence of a Büttiker's voltage probe. In order to test the dynamics we consider two many-spin systems, which are cases of experimental interest, where a local energy fluctuation is a natural phenomenon. A two-spin system is reduced to a two-level system (TLS) that oscillates among |0 >?|??> and |1 >?|??> . We show that the QD model recovers not only the exponential damping of the oscillations in the low perturbation regime, but also the nontrivial bifurcation of the damping rates at a critical point, i.e., the quantum dynamical phase transition. We also address the spin-wave-like dynamics of local polarization in a spin chain. By averaging over Ns realizations, the QD solution has about half the dispersion respect to the mean dynamics than QJ. By evaluating the Loschmidt echo (LE), we find that the pure states |0 >?|??> and |1 >?|??> are quite robust against the local decoherence. In contrast, the LE, and hence coherence, decays faster when the system is in a superposition state (|??> ±|??>) /?{2 } , which is consistent with the general trend recently observed in spin systems through NMR. Because of its simple implementation, the method is well suited to assess decoherent transport problems as well as to include decoherence in both one-body and many-body dynamics.

Fernández-Alcázar, Lucas J.; Pastawski, Horacio M.

2015-02-01

360

Simulation of channel orientation dependent transport in ultra-scaled monolayer MoX2 (X = S, Se, Te) n-MOSFETs  

NASA Astrophysics Data System (ADS)

Transport properties of about 3?nm channel length monolayer MoX2 (X = S, Se, Te) n-channel metal-oxide-semiconductor field effect transistors (MOSFETs) are examined through ballistic full-band quantum transport simulations with atomistic tight-binding Hamiltonians. Our simulations reveal that single gate (SG) monolayer MoX2 MOSFETs with an approximately 2?nm gate underlap exhibit reasonable subthreshold characteristics. From these full-band simulations, we observe channel orientation dependent negative differential resistance (NDR) in the out characteristics in the ballistic transport regime. We discuss and compare NDR properties of monolayer MoX2 n-channel MOSFETs in different transport directions.

Chang, Jiwon

2015-04-01

361

Oxaliplatin-induced neurotoxicity is dependent on the organic cation transporter OCT2  

PubMed Central

Oxaliplatin is an integral component of colorectal cancer therapy, but its clinical use is associated with a dose-limiting peripheral neurotoxicity. We found that the organic cation transporter 2 (OCT2) is expressed on dorsal root ganglia cells within the nervous system where oxaliplatin is known to accumulate. Cellular uptake of oxaliplatin was increased by 16- to 35-fold in cells overexpressing mouse Oct2 or human OCT2, and this process was associated with increased DNA platination and oxaliplatin-induced cytotoxicity. Furthermore, genetic or pharmacologic knockout of Oct2 protected mice from hypersensitivity to cold or mechanical-induced allodynia, which are established tests to assess acute oxaliplatin-induced neurotoxicity. These findings provide a rationale for the development of targeted approaches to mitigate this debilitating toxicity. PMID:23776246

Sprowl, Jason A.; Ciarimboli, Giuliano; Lancaster, Cynthia S.; Giovinazzo, Hugh; Gibson, Alice A.; Du, Guoqing; Janke, Laura J.; Cavaletti, Guido; Shields, Anthony F.; Sparreboom, Alex

2013-01-01

362

Desketoneoenactin-siderophore conjugates for Candida: evidence of iron transport-dependent species selectivity.  

PubMed

We investigated the inhibitory activity of synthetic isocyanurate-based as well as linear mono- and trihydroxamate siderophore-drug conjugates against Candida spp. The conjugated drug was 13C-desketoneoenactin (DE). The MICs of siderophore-drug conjugates were determined in the absence and presence of 2,2'-dipyridyl to restrict iron availability. The ability of various siderophore types to promote growth in an iron-restricted medium was also assayed. Addition of a siderophore portion to the drug strongly impaired the inhibitory activity of DE. However, the activity of the drug conjugates was increased by up to 16-fold in iron-depleted medium for species having their growth strongly promoted by most hydroxamate-type siderophores (C. albicans, C. stellatoidea, and C. pseudotropicalis). The uptake of (55)Fe from ferrichrome and from two siderophore-drug conjugates was improved when C. albicans cells were grown in a low-iron medium. In the same assay, unlabeled ferrichrome was able to compete with the uptake of (55)Fe from both conjugates, indicating a common mechanism of uptake. A C. albicans strain lacking the siderophore transporter CaSit1/CaArn1 was not able to use ferrichrome or the synthetic ornithine-based trihydroxamate siderophore for growth promotion and was much less susceptible to the siderophore-drug conjugates than its isogenic parent strain. In summary, the ability of some Candida spp. to use ferrichrome-like siderophores for growth promotion explains the selective activity of hydroxamate-drug conjugates, and this activity seems to be related to the presence, in C. albicans, of the siderophore transporter CaSit1/CaArn1. New conjugate designs are necessary to fully restore or improve the initial DE activity. PMID:15616301

Bernier, Geneviève; Girijavallabhan, Vinay; Murray, Aaron; Niyaz, Noormohamed; Ding, Pingyu; Miller, Marvin J; Malouin, François

2005-01-01

363

Membrane potential dependence of the kinetics of cationic amino acid transport systems in human placenta.  

PubMed Central

1. Mediated influx of L-lysine into human placental brush-border membrane vesicles occurs through two systems, one of lower affinity but high capacity, the other of very high affinity but low capacity. These transporters have features characteristic of systems y+ (the classical system) and y+L (recently described in the erythrocyte), respectively. 2. In solutions containing sodium the entry of lysine through the high-affinity system (y+L) is inhibited by the neutral amino acids L-leucine, L-methionine and L-glutamine with comparable high affinity. The removal of sodium reduces the affinity but not the maximal extent of this inhibition. Leucine and methionine, but apparently not glutamine, inhibit lysine entry through system y+ with a much lower affinity. 3. The influx of lysine through system y+ changes markedly in response to alterations of membrane potential. In the presence of an inwardly directed negative diffusion potential created by an inwardly directed thiocyanate (SCN-) gradient, the influx of lysine through this route is accelerated; with an inwardly directed positive potassium diffusion potential, lysine influx through this route is reduced. The influx of lysine through system y+L is much less sensitive to such alterations of potential. 4. Analysis of the kinetic constants characterizing system y+ shows that with a change of potential from zero to negative (approximately -60 mV) the maximum velocity (Vmax) is roughly doubled and the half-saturation constant (Km) halved leading to a 4-fold increase in permeability. For system y+L smaller changes are seen and Km does not change; the resulting increase in y+L permeability is 1.5-fold. 5. These findings are discussed with respect both to the mechanism of membrane transport and placental epithelial function. PMID:7799228

Eleno, N; Devés, R; Boyd, C A

1994-01-01

364

Measurement of the anisotropy factor with azimuthal light backscattering  

NASA Astrophysics Data System (ADS)

The potential capability of low coherence backscattering (LBS) is explored to determine the anisotropy factor based on azimuthal light backscattering map. The scattering intensity signal measured at azimuthal angle ?=0° is extracted for analysis. By performing nonlinear regression fitting on the experimental signal to the Henyey-Greenstein phase function, the anisotropy factor is determined. The experiments with tissue phantom consisting of the aqueous suspension of polystyrene microspheres are carried out. The results show that the measured anisotropy factor is well described by Mie theory.

Wang, Pin; Li, Yong-ming; Chen, Bo-han

2014-11-01

365

Cooperative Effect of pH-Dependent Ion Transport within Two Symmetric-Structured Nanochannels.  

PubMed

A novel and simple design is introduced to construct bichannel nanofluid diodes by combining two poly(ethylene terephthalate) (PET) films with columnar nanochannel arrays varying in size or in surface charge. This type of bichannel device performs obvious ion current rectification, and the pH-dependent tunability and degree of rectification can be improved by histidine modification. The origin of the ion current rectification and its pH-dependent tunability are attributed to the cooperative effect of the two columnar half-channels and the applied bias on the mobile ions. As a result of surface groups on the bichannel being charged with different polarities or degrees at different pH values, the function of the bichannel device can be converted from a nanofluid diode to a normal nanochannel or to a reverse diode. PMID:25806828

Meng, Zheyi; Chen, Yang; Li, Xiulin; Xu, Yanglei; Zhai, Jin

2015-04-15

366

Systematic Azimuth Quadrupole and Minijet Trends from Two-Particle Correlations in Heavy-Ion Collisions  

NASA Astrophysics Data System (ADS)

Heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) produce a tremendous amount of data but new techniques are necessary for a comprehensive understanding of the physics behind these collisions. We present measurements from the STAR detector of both pt-integral and pt-differential azimuth two-particle correlations on azimuth (phi) and pseudorapidity (eta) for unidentified hadrons in Au-Au collisions at a center of mass energy = 62 and 200 GeV. The azimuth correlations can be fit to extract a quadrupole component--related to conventional v2 measures--and a same-side peak. The azimuth quadrupole component is distinguished from eta-localized same-side correlations by taking advantage of the full 2D eta and phi dependence. Both pt-integral and pt-differential results are presented as functions of Au-Au centrality. We observe simple universal energy and centrality trends for the pt-integral quadrupole component. pt-differential results can be transformed to reveal quadrupole pt spectra that are nearly independent of centrality. A parametrization of the pt-differential quadrupole shows a simple pt dependence that can be factorized from the centrality and collision energy dependence above 0.75 GeV/c. Angular correlations contain jet-like structure with most-probable hadron momentum 1 GeV/c. For better comparison to RHIC data we analyze the energy scale dependence of fragmentation functions from e+-e - collisions on rapidity y. We find that replotting fragmentation functions on a normalized rapidity variable results in a compact form precisely represented by the beta distribution, its two parameters varying slowly and simply with parton energy scale Q. The resulting parameterization enables extrapolation of fragmentation functions to low Q in order to describe fragment distributions at low transverse momentum ptin heavy ion collisions at RHIC. We convert minimum-bias jet-like angular correlations to single-particle hadron yields and compare them with parton fragment yields inferred from differential spectrum analysis (spectrum hard components). We find that jet-like correlations in central 200 GeV Au-Au collisions correspond quantitatively to pQCD predictions, and the jet-correlated hadron yield comprises one third of the Au-Au final state in central collisions.

Kettler, David

367

Lysine 27 Ubiquitination of the Mitochondrial Transport Protein Miro Is Dependent on Serine 65 of the Parkin Ubiquitin Ligase*  

PubMed Central

Mitochondrial transport plays an important role in matching mitochondrial distribution to localized energy production and calcium buffering requirements. Here, we demonstrate that Miro1, an outer mitochondrial membrane (OMM) protein crucial for the regulation of mitochondrial trafficking and distribution, is a substrate of the PINK1/Parkin mitochondrial quality control system in human dopaminergic neuroblastoma cells. Moreover, Miro1 turnover on damaged mitochondria is altered in Parkinson disease (PD) patient-derived fibroblasts containing a pathogenic mutation in the PARK2 gene (encoding Parkin). By analyzing the kinetics of Miro1 ubiquitination, we further demonstrate that mitochondrial damage triggers rapid (within minutes) and persistent Lys-27-type ubiquitination of Miro1 on the OMM, dependent on PINK1 and Parkin. Proteasomal degradation of Miro1 is then seen on a slower time scale, within 2–3 h of the onset of ubiquitination. We find Miro ubiquitination in dopaminergic neuroblastoma cells is independent of Miro1 phosphorylation at Ser-156 but is dependent on the recently identified Ser-65 residue within Parkin that is phosphorylated by PINK1. Interestingly, we find that Miro1 can stabilize phospho-mutant versions of Parkin on the OMM, suggesting that Miro is also part of a Parkin receptor complex. Moreover, we demonstrate that Ser-65 in Parkin is critical for regulating Miro levels upon mitochondrial damage in rodent cortical neurons. Our results provide new insights into the ubiquitination-dependent regulation of the Miro-mediated mitochondrial transport machinery by PINK1/Parkin and also suggest that disruption of this regulation may be implicated in Parkinson disease pathogenesis. PMID:24671417

Birsa, Nicol; Norkett, Rosalind; Wauer, Tobias; Mevissen, Tycho E. T.; Wu, Hsiu-Chuan; Foltynie, Thomas; Bhatia, Kailash; Hirst, Warren D.; Komander, David; Plun-Favreau, Helene; Kittler, Josef T.

2014-01-01

368

Transportation  

NSDL National Science Digital Library

A unit designed to increase students' knowledge and understanding of diesel and gasoline engines, providing an introduction for students interested in more specialized training in the automobile field and its scientific principles through math, science, and chemistry. It will also help students realize the importance of transportation, and will help them meet their needs in math through problem solving by dealing with materials in their world, letting them develop skills and techniques through hands-on experience. Includes more than 20 problems to solve.

Bryant, Joyce

369

Scale-Dependent Fracture-Matrix Interactions and Their Impact on Radionuclide Transport: Development of efficient particle-tracking methods  

SciTech Connect

Matrix Diffusion and Adsorption within a rock matrix are important mechanisms for retarding transport of radionuclides in fractured rock. Due to computational limitations and difficulties in characterizing complex subsurface systems, diffusive exchange between a fracture network and surrounding rock matrix is often modeled using simplified conceptual representations. There is significant uncertainty in “effective” parameters used in these models, such as the “effective matrix diffusivity”. Often, these parameters are estimated by fitting sparse breakthrough data, and estimated values fall outside meaningful ranges, because simplified interpretive models do not consider complex three-dimensional flow. There is limited understanding of the relationship between the effective parameters and rock mass characteristics including network structure and matrix properties. There is also evidence for an apparent scale-dependence in “effective matrix diffusion” coefficients. These observations raise questions on whether fracture-matrix interaction parameters estimated from small-scale tracer tests can be used for predicting radionuclide fate and transport at the scale of DOE field sites. High-resolution three-dimensional Discrete-Fracture-Network-Matrix (DFNM) models based on well-defined local scale transport equations can help to address some of these questions. Due to tremendous advances in computational technology over the last 10 years, DFNM modeling in relatively large domains is now feasible. The overarching objective of our research is to use DFNM modeling to improve fundamental understanding of how effective parameters in conceptual models are related to fracture network structure and matrix properties. An advanced three-dimensional DFNM model is being developed, which combines upscaled particle-tracking algorithms for fracture-matrix interaction and a parallel fracture-network flow simulator. The particle-tracking algorithms allow complexity in flow fields at different scales, and track transport across fracture-matrix interfaces based on rigorous local approximations to the transport equations. This modeling approach can incorporate aperture variability, multi-scale preferential flow and matrix heterogeneity. We developed efficient particle-tracking methods for handling matrix diffusion and adsorption on fracture walls and demonstrated their efficiency for use within the context of large-scale complex fracture network models with variability in apertures across a network of fractures and within individual fractures.

Rajaram, Harihar [University of Colorado, Boulder; Brutz, Michael [University of Colorado, Boulder; Klein, Dylan R [University of Colorado, Boulder; Mallikamas, Wasin [University of Colorado, Boulder

2014-09-18

370

Na+ dependent acid-base transporters in the choroid plexus; insights from slc4 and slc9 gene deletion studies  

PubMed Central

The choroid plexus epithelium (CPE) is located in the ventricular system of the brain, where it secretes the majority of the cerebrospinal fluid (CSF) that fills the ventricular system and surrounds the central nervous system. The CPE is a highly vascularized single layer of cuboidal cells with an unsurpassed transepithelial water and solute transport rate. Several members of the slc4a family of bicarbonate transporters are expressed in the CPE. In the basolateral membrane the electroneutral Na+ dependent Cl?/HCO3? exchanger, NCBE (slc4a10) is expressed. In the luminal membrane, the electrogenic Na+:HCO3? cotransporter, NBCe2 (slc4a5) is expressed. The electroneutral Na+:HCO3? cotransporter, NBCn1 (slc4a7), has been located in both membranes. In addition to the bicarbonate transporters, the Na+/H+ exchanger, NHE1 (slc9a1), is located in the luminal membrane of the CPE. Genetically modified mice targeting slc4a2, slc4a5, slc4a7, slc4a10, and slc9a1 have been generated. Deletion of slc4a5, 7 or 10, or slc9a1 has numerous impacts on CP function and structure in these mice. Removal of the transporters affects brain ventricle size (slc4a5 and slc4a10) and intracellular pH regulation (slc4a7 and slc4a10). In some instances, removal of the proteins from the CPE (slc4a5, 7, and 10) causes changes in abundance and localization of non-target transporters known to be involved in pH regulation and CSF secretion. The focus of this review is to combine the insights gathered from these knockout mice to highlight the impact of slc4 gene deletion on the CSF production and intracellular pH regulation resulting from the deletion of slc4a5, 7 and 10, and slc9a1. Furthermore, the review contains a comparison of the described human mutations of these genes to the findings in the knockout studies. Finally, the future perspective of utilizing these proteins as potential targets for the treatment of CSF disorders will be discussed. PMID:24155723

Christensen, Henriette L.; Nguyen, An T.; Pedersen, Fredrik D.; Damkier, Helle H.

2013-01-01

371

Stacking-dependent band gap and quantum transport in trilayer graphene  

NASA Astrophysics Data System (ADS)

Graphene is an extraordinary two-dimensional (2D) system with chiral charge carriers and fascinating electronic, mechanical and thermal properties. In multilayer graphene, stacking order provides an important yet rarely explored degree of freedom for tuning its electronic properties. For instance, Bernal-stacked trilayer graphene (B-TLG) is semi-metallic with a tunable band overlap, and rhombohedral-stacked trilayer graphene (r-TLG) is predicted to be semiconducting with a tunable band gap. These multilayer graphenes are also expected to exhibit rich novel phenomena at low charge densities owing to enhanced electronic interactions and competing symmetries. Here we demonstrate the dramatically different transport properties in TLG with different stacking orders, and the unexpected spontaneous gap opening in charge neutral r-TLG. At the Dirac point, B-TLG remains metallic, whereas r-TLG becomes insulating with an intrinsic interaction-driven gap ~6meV. In magnetic fields, well-developed quantum Hall (QH) plateaux in r-TLG split into three branches at higher fields. Such splitting is a signature of the Lifshitz transition, a topological change in the Fermi surface, that is found only in r-TLG. Our results underscore the rich interaction-induced phenomena in trilayer graphene with different stacking orders, and its potential towards electronic applications.

Bao, W.; Jing, L.; Velasco, J.; Lee, Y.; Liu, G.; Tran, D.; Standley, B.; Aykol, M.; Cronin, S. B.; Smirnov, D.; Koshino, M.; McCann, E.; Bockrath, M.; Lau, C. N.

2011-12-01

372

Study of thickness-dependent magnetic and transport properties of Fe/Al nanostructures  

NASA Astrophysics Data System (ADS)

The paper presents magnetic and transport properties of compositionally modulated Fe/Al multilayer structures (MLS), with an overall atomic concentration ratio of Fe:Al = 3:1, 2:1 and 1:1. All MLS show soft ferromagnetic behaviour at room temperature (RT) with an in-plane easy axis of magnetization. In each case, coercivity increases continuously and magnetization decreases with an increase in temperature due to enhancement in the anisotropy as a result of non-uniform and disordered formation of thin intermixed (dead) FeAl layer at the interfaces. The Curie temperature obtained for the MLS is much less than that of bcc Fe but is well above RT. The observed magnetic behaviour is mainly attributed to the formation of different FeAl phases and increase in anti-ferromagnetic interlayer coupling with addition of Al. The formation of these phases is also supported by resistivity results. The results of this research enabled us to understand that by controlling of layers thickness and temperature in multilayer systems, the nanogranular thin films with good resistive and soft magnetic properties can be obtained.

Vyas, Anupam; Rajan, Sandeep; Kumar, Anil; Brajpuriya, Ranjeet

2014-09-01

373

Temperature-Dependent Water and Ion Transport Properties of Barley and Sorghum Roots 1  

PubMed Central

Root temperature strongly affects shoot growth, possibly via “nonhydraulic messengers” from root to shoot. In short-term studies with barley (Hordeum vulgare L.) and sorghum (Sorghum bicolor L.) seedlings, the optimum root temperatures for leaf expansion were 25° and 35°C, respectively. Hydraulic conductance (Lp) of both intact plants and detached exuding roots of barley increased with increasing root temperature to a high value at 25°C, remaining high with further warming. In sorghum, the Lp of intact plants and of detached roots peaked at 35°C. In both species, root temperature did not affect water potentials of the expanded leaf blade or the growing region despite marked changes in Lp. Extreme temperatures greatly decreased ion flux, particularly K+ and NO3?, to the xylem of detached roots of both species. Removing external K+ did not alter short-term K+ flux to the xylem in sorghum but strongly inhibited flux at high temperature in barley, indicating differences in the sites of temperature effects. Leaf growth responses to root temperature, although apparently “uncoupled” from water transport properties, were correlated with ion fluxes. Studies of putative root messengers must take into account the possible role of ions. PMID:16668404

BassiriRad, Hormoz; Radin, John W.; Matsuda, Kaoru

1991-01-01

374

Effect of dopamine transporter genotype on intrinsic functional connectivity depends on cognitive state.  

PubMed

Functional connectivity between brain regions can define large-scale neural networks and provide information about relationships between those networks. We examined how relationships within and across intrinsic connectivity networks were 1) sensitive to individual differences in dopaminergic function, 2) modulated by cognitive state, and 3) associated with executive behavioral traits. We found that regardless of cognitive state, connections between frontal, parietal, and striatal nodes of Task-Positive networks (TPNs) and Task-Negative networks (TNNs) showed higher functional connectivity in 10/10 homozygotes of the dopamine transporter gene, a polymorphism influencing synaptic dopamine, than in 9/10 heterozygotes. However, performance of a working memory task (a state requiring dopamine release) modulated genotype differences selectively, such that cross-network connectivity between TPNs and TNNs was higher in 10/10 than 9/10 subjects during working memory but not during rest. This increased cross-network connectivity was associated with increased self-reported measures of impulsivity and inattention traits. By linking a gene regulating synaptic dopamine to a phenotype characterized by inefficient executive function, these findings validate cross-network connectivity as an endophenotype of executive dysfunction. PMID:22047966

Gordon, Evan M; Stollstorff, Melanie; Devaney, Joseph M; Bean, Stephanie; Vaidya, Chandan J

2012-09-01

375

Effect of Dopamine Transporter Genotype on Intrinsic Functional Connectivity Depends on Cognitive State  

PubMed Central

Functional connectivity between brain regions can define large-scale neural networks and provide information about relationships between those networks. We examined how relationships within and across intrinsic connectivity networks were 1) sensitive to individual differences in dopaminergic function, 2) modulated by cognitive state, and 3) associated with executive behavioral traits. We found that regardless of cognitive state, connections between frontal, parietal, and striatal nodes of Task-Positive networks (TPNs) and Task-Negative networks (TNNs) showed higher functional connectivity in 10/10 homozygotes of the dopamine transporter gene, a polymorphism influencing synaptic dopamine, than in 9/10 heterozygotes. However, performance of a working memory task (a state requiring dopamine release) modulated genotype differences selectively, such that cross-network connectivity between TPNs and TNNs was higher in 10/10 than 9/10 subjects during working memory but not during rest. This increased cross-network connectivity was associated with increased self-reported measures of impulsivity and inattention traits. By linking a gene regulating synaptic dopamine to a phenotype characterized by inefficient executive function, these findings validate cross-network connectivity as an endophenotype of executive dysfunction. PMID:22047966

Stollstorff, Melanie; Devaney, Joseph M.; Bean, Stephanie; Vaidya, Chandan J.

2012-01-01

376

Transport by populations of fast and slow kinesins uncovers novel family-dependent motor characteristics important for in vivo function.  

PubMed

Intracellular cargo transport frequently involves multiple motor types, either having opposite directionality or having the same directionality but different speeds. Although significant progress has been made in characterizing kinesin motors at the single-molecule level, predicting their ensemble behavior is challenging and requires tight coupling between experiments and modeling to uncover the underlying motor behavior. To understand how diverse kinesins attached to the same cargo coordinate their movement, we carried out microtubule gliding assays using pairwise mixtures of motors from the kinesin-1, -2, -3, -5, and -7 families engineered to have identical run lengths and surface attachments. Uniform motor densities were used and microtubule gliding speeds were measured for varying proportions of fast and slow motors. A coarse-grained computational model of gliding assays was developed and found to recapitulate the experiments. Simulations incorporated published force-dependent velocities and run lengths, along with mechanical interactions between motors bound to the same microtubule. The simulations show that the force-dependence of detachment is the key parameter that determines gliding speed in multimotor assays, while motor compliance, surface density, and stall force all play minimal roles. Simulations also provide estimates for force-dependent dissociation rates, suggesting that kinesin-1 and the mitotic motors kinesin-5 and -7 maintain microtubule association against loads, whereas kinesin-2 and -3 readily detach. This work uncovers unexpected motor behavior in multimotor ensembles and clarifies functional differences between kinesins that carry out distinct mechanical tasks in cells. PMID:25418170

Arpa?, Göker; Shastry, Shankar; Hancock, William O; Tüzel, Erkan

2014-10-21

377

Temperature Dependence of Electric Transport in Few-layer Graphene under Large Charge Doping Induced by Electrochemical Gating.  

PubMed

The temperature dependence of electric transport properties of single-layer and few-layer graphene at large charge doping is of great interest both for the study of the scattering processes dominating the conductivity at different temperatures and in view of the theoretically predicted possibility to reach the superconducting state in such extreme conditions. Here we present the results obtained in 3-, 4- and 5-layer graphene devices down to 3.5 K, where a large surface charge density up to about 6.8·10(14) cm(-2) has been reached by employing a novel polymer electrolyte solution for the electrochemical gating. In contrast with recent results obtained in single-layer graphene, the temperature dependence of the sheet resistance between 20 K and 280 K shows a low-temperature dominance of a T(2) component - that can be associated with electron-electron scattering - and, at about 100 K, a crossover to the classic electron-phonon regime. Unexpectedly, this crossover does not show any dependence on the induced charge density, i.e. on the large tuning of the Fermi energy. PMID:25906088

Gonnelli, R S; Paolucci, F; Piatti, E; Sharda, Kanudha; Sola, A; Tortello, M; Nair, Jijeesh R; Gerbaldi, C; Bruna, M; Borini, S

2015-01-01

378

STAT3 controls IL6-dependent regulation of serotonin transporter function and depression-like behavior.  

PubMed

Experimental evidence suggests a role for the immune system in the pathophysiology of depression. A specific involvement of the proinflammatory cytokine interleukin 6 (IL6) in both, patients suffering from the disease and pertinent animal models, has been proposed. However, it is not clear how IL6 impinges on neurotransmission and thus contributes to depression. Here we tested the hypothesis that IL6-induced modulation of serotonergic neurotransmission through the STAT3 signaling pathway contributes to the role of IL6 in depression. Addition of IL6 to JAR cells, endogenously expressing SERT, reduced SERT activity and downregulated SERT mRNA and protein levels. Similarly, SERT expression was reduced upon IL6 treatment in the mouse hippocampus. Conversely, hippocampal tissue of IL6-KO mice contained elevated levels of SERT and IL6-KO mice displayed a reduction in depression-like behavior and blunted response to acute antidepressant treatment. STAT3 IL6-dependently associated with the SERT promoter and inhibition of STAT3 blocked the effect of IL6 in-vitro and modulated depression-like behavior in-vivo. These observations demonstrate that IL6 directly controls SERT levels and consequently serotonin reuptake and identify STAT3-dependent regulation of SERT as conceivable neurobiological substrate for the involvement of IL6 in depression. PMID:25760924

Kong, Eryan; Sucic, Sonja; Monje, Francisco J; Savalli, Giorgia; Diao, Weifei; Khan, Deeba; Ronovsky, Marianne; Cabatic, Maureen; Koban, Florian; Freissmuth, Michael; Pollak, Daniela D

2015-01-01

379

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

380

Radial and Azimuthal Oscillations in Halo Coronal Mass Ejections  

NASA Astrophysics Data System (ADS)

We present the first observational detection of radial and azimuthal oscillations in full halo coronal mass ejections (HCMEs). We analyse nine HCMEs well-observed by the Large Angle and Spectrometric Coronagraph (LASCO) from February to June, 2011. Using the LASCO C3 running difference images, we estimated the instantaneous apparent speeds of the HCMEs in different radial directions from the solar disk centre. We find that the development of all these HCMEs is accompanied with quasi-periodic variations of the instantaneous radial velocity with the periods ranging from 24 to 48 minutes. The amplitudes of the instant speed variations reach about a half of the projected speeds. The amplitudes are found to anti-correlate with the periods and correlate with the HCME speed, indicating the nonlinear nature of the process. The oscillations have a clear azimuthal structure in the heliocentric polar coordinate system. The oscillations in seven events are found to be associated with distinct azimuthal wave modes with the azimuthal wave number m=1 for six events and m=2 for one event. The polarisation of the oscillations in these seven HCMEs is broadly consistent with those of their position angles with the mean difference of 42.5 degree. The oscillations may be connected with natural oscillations of the plasmoids around a dynamical equilibrium, or self-oscillatory processes, e.g. the periodic shedding of Alfvénic vortices. Our results indicate the need for advanced theory of oscillatory processes in CMEs.

Lee, Harim; Moon, Yong-Jae; Nakariakov, Valery

2015-04-01

381

Experiments with Podded Propulsors in Static Azimuthing Conditions  

Microsoft Academic Search

The paper presents a comprehensive experimental study of the variations of propulsive characteristics of puller and pusher podded propulsors in static azimuthing open water conditions. A custom designed six-component global dynamometer and a three-component pod dynamometer were used to measure the propulsive performance of a podded unit in pusher and puller configurations in a towing tank. The unit was tested

Islam M. F; Veitch B; Akinturk A; Bose N; Liu P

382

Vacuum Calculations in Azimuthally Symmetric Geometry \\Lambda M. S. Chance  

E-print Network

Vacuum Calculations in Azimuthally Symmetric Geometry \\Lambda M. S. Chance Princeton University the volume integrated perturbed magnetic energy in the vacuum region or through the continuity requirements plasma­vacuum boundary. The method is based upon using Green's second identity and the method

383

Vacuum Calculations in Azimuthally Symmetric Geometry M. S. Chance  

E-print Network

Vacuum Calculations in Azimuthally Symmetric Geometry M. S. Chance Princeton University Plasma energy in the vacuum region or through the continuity requirements for the normal component of the perturbed magnetic #12;eld and the total perturbed pressure across the unperturbed plasma-vacuum boundary

384

Computation of azimuthal combustion instabilities in an helicopter combustion chamber  

E-print Network

Computation of azimuthal combustion instabilities in an helicopter combustion chamber C. Sensiau of an annular helicopter combustor. First it is shown that the casing and geometrical details such as primary is commonly observed by turbine manufacturers.10 Moreover, since helicopter combustion chambers usually

Nicoud, Franck

385

Experimental and regional variations in Na+?dependent and Na+?independent phosphate transport along the rat small intestine and colon  

PubMed Central

Abstract Despite the importance of extracellular phosphate in many essential biological processes, the mechanisms of phosphate transport across the epithelium of different intestinal segments remain unclear. We have used an in vitro method to investigate phosphate transport at the brush border membrane (BBM) of intact intestinal segments and an in vivo method to study transepithelial phosphate absorption. We have used micromolar phosphate concentrations known to favor NaPi?IIb?mediated transport, and millimolar concentrations that are representative of the levels we have measured in luminal contents, to compare the extent of Na+?dependent and Na+?independent phosphate transport along the rat duodenum, jejunum, ileum, and proximal and distal colon. Our findings confirm that overall the jejunum is the main site of phosphate absorption; however, at millimolar concentrations, absorption shows ~30% Na+?dependency, suggesting that transport is unlikely to be mediated exclusively by the Na+?dependent NaPi?IIb co?transporter. In the ileum, studies in vitro confirmed that relatively low levels of phosphate transport occur at the BBM of this segment, although significant Na+?dependent transport was detected using millimolar levels of phosphate in vivo. Since NaPi?IIb protein is not detectable at the rat ileal BBM, our data suggest the presence of an as yet unidentified Na+?dependent uptake pathway in this intestinal segment in vivo. In addition, we have confirmed that the colon has a significant capacity for phosphate absorption. Overall, this study highlights the complexities of intestinal phosphate absorption that can be revealed using different phosphate concentrations and experimental techniques. PMID:25626876

Marks, Joanne; Lee, Grace J.; Nadaraja, Sobiya P.; Debnam, Edward S.; Unwin, Robert J.

2015-01-01

386

Experimental and regional variations in Na+-dependent and Na+-independent phosphate transport along the rat small intestine and colon.  

PubMed

Despite the importance of extracellular phosphate in many essential biological processes, the mechanisms of phosphate transport across the epithelium of different intestinal segments remain unclear. We have used an in vitro method to investigate phosphate transport at the brush border membrane (BBM) of intact intestinal segments and an in vivo method to study transepithelial phosphate absorption. We have used micromolar phosphate concentrations known to favor NaPi-IIb-mediated transport, and millimolar concentrations that are representative of the levels we have measured in luminal contents, to compare the extent of Na(+)-dependent and Na(+)-independent phosphate transport along the rat duodenum, jejunum, ileum, and proximal and distal colon. Our findings confirm that overall the jejunum is the main site of phosphate absorption; however, at millimolar concentrations, absorption shows ~30% Na(+)-dependency, suggesting that transport is unlikely to be mediated exclusively by the Na(+)-dependent NaPi-IIb co-transporter. In the ileum, studies in vitro confirmed that relatively low levels of phosphate transport occur at the BBM of this segment, although significant Na(+)-dependent transport was detected using millimolar levels of phosphate in vivo. Since NaPi-IIb protein is not detectable at the rat ileal BBM, our data suggest the presence of an as yet unidentified Na(+)-dependent uptake pathway in this intestinal segment in vivo. In addition, we have confirmed that the colon has a significant capacity for phosphate absorption. Overall, this study highlights the complexities of intestinal phosphate absorption that can be revealed using different phosphate concentrations and experimental techniques. PMID:25626876

Marks, Joanne; Lee, Grace J; Nadaraja, Sobiya P; Debnam, Edward S; Unwin, Robert J

2015-01-01

387

Sequence dependence of polymer dynamics in quenched disordered media: Weak attraction facilitates transport  

NASA Astrophysics Data System (ADS)

We study the dynamics of polymers in a random disordered medium of fixed obstacles using kinetic Monte Carlo methods. The polymers can have monomers which have attractive (A-type), repulsive (R-type) or neutral (H-type) interactions with the fixed obstacles that comprise the disordered medium. Several classes of homopolymers and heteropolymers with diverse sequences have been studied. Our most noteworthy result is that, above a threshold temperature, polymer bearing monomers that are attracted to the disordered medium translocate faster through the medium than those bearing neutral or repulsive monomers. We discuss how a delicate balance between energetic and entropic factors leads to this counterintuitive outcome. By examining heteropolymers with different sequences, we also find that the dependence of mobility on average composition is stronger than that on higher order correlations characterizing the sequence distribution. Connections between our results and experiments with synthetic and biological systems are noted.

Lee, Sung-Joo E.; Chakraborty, Arup K.

2002-12-01

388

Field and temperature dependent electron transport properties of random network single walled and multi walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Field and temperature dependent electron transport properties of random network single walled carbon nanotubes (SWCNTs) and multi walled carbon nanotubes (MWCNTs) were investigated and compared. The electrical characterizations of drop casted CNT samples were done by two probe measurements by varying temperatures from 80 K to 300 K in the field region 1-400 V cm-1. The charge transport mechanisms at low (<3.5 V) and high (>3.5 V) fields were analyzed from measured I-V characteristic curves at various temperatures (<300 K) with respect to applied field. At low field, the ohmic behavior was observed and at high field the charge transport appears to be Poole-Frenkel type in both types of CNTs network. Electron-electron and electron-phonon scatterings in the localized defect states dominate in SWCNTs, whereas in MWCNTs the delocalization of charge carriers as well as the scattering centers is responsible due to the presence of inner shells. Because of the different nature of chirality in random network, the SWCNTs displayed lower conduction when compared to MWCNTs. The variation in Poole-Frenkel co-efficient (?) (SWCNTs-0.193 × 10-22 MWCNTs-0.089 07 × 10-22 J V1/2 cm-1/2), activation energy (SWCNTs-90 meV; MWCNTs-60 meV for field of 7\\;{{V}^{1/2}}\\;c{{m}^{-1/2}}) and trap energy levels (SWCNTs-109 meV; MWCNTs-37 meV) are discussed for both SWCNTs and MWCNTs.

Rajavel, K.; Verma, S.; Asokan, K.; Rajendra Kumar, R. T.

2014-09-01

389

Inhibitors of the 5-lipoxygenase arachidonic acid pathway induce ATP release and ATP-dependent organic cation transport in macrophages.  

PubMed

We have previously described that arachidonic acid (AA)-5-lipoxygenase (5-LO) metabolism inhibitors such as NDGA and MK886, inhibit cell death by apoptosis, but not by necrosis, induced by extracellular ATP (ATPe) binding to P2X7 receptors in macrophages. ATPe binding to P2X7 also induces large cationic and anionic organic molecules uptake in these cells, a process that involves at least two distinct transport mechanisms: one for cations and another for anions. Here we show that inhibitors of the AA-5-LO pathway do not inhibit P2X7 receptors, as judged by the maintenance of the ATPe-induced uptake of fluorescent anionic dyes. In addition, we describe two new transport phenomena induced by these inhibitors in macrophages: a cation-selective uptake of fluorescent dyes and the release of ATP. The cation uptake requires secreted ATPe, but, differently from the P2X7/ATPe-induced phenomena, it is also present in macrophages derived from mice deficient in the P2X7 gene. Inhibitors of phospholipase A2 and of the AA-cyclooxygenase pathway did not induce the cation uptake. The uptake of non-organic cations was investigated by measuring the free intracellular Ca(2+) concentration ([Ca(2+)]i) by Fura-2 fluorescence. NDGA, but not MK886, induced an increase in [Ca(2+)]i. Chelating Ca(2+) ions in the extracellular medium suppressed the intracellular Ca(2+) signal without interfering in the uptake of cationic dyes. We conclude that inhibitors of the AA-5-LO pathway do not block P2X7 receptors, trigger the release of ATP, and induce an ATP-dependent uptake of organic cations by a Ca(2+)- and P2X7-independent transport mechanism in macrophages. PMID:24743022

da Silva-Souza, Hercules Antônio; Lira, Maria Nathalia de; Costa-Junior, Helio Miranda; da Cruz, Cristiane Monteiro; Vasconcellos, Jorge Silvio Silva; Mendes, Anderson Nogueira; Pimenta-Reis, Gabriela; Alvarez, Cora Lilia; Faccioli, Lucia Helena; Serezani, Carlos Henrique; Schachter, Julieta; Persechini, Pedro Muanis

2014-07-01

390

A role for cyclin-dependent kinase(s) in the modulation of fast anterograde axonal transport: effects defined by olomoucine and the APC tumor suppressor protein  

NASA Technical Reports Server (NTRS)

Proteins that interact with both cytoskeletal and membrane components are candidates to modulate membrane trafficking. The tumor suppressor proteins neurofibromin (NF1) and adenomatous polyposis coli (APC) both bind to microtubules and interact with membrane-associated proteins. The effects of recombinant NF1 and APC fragments on vesicle motility were evaluated by measuring fast axonal transport along microtubules in axoplasm from squid giant axons. APC4 (amino acids 1034-2844) reduced only anterograde movements, whereas APC2 (aa 1034-2130) or APC3 (aa 2130-2844) reduced both anterograde and retrograde transport. NF1 had no effect on organelle movement in either direction. Because APC contains multiple cyclin-dependent kinase (CDK) consensus phosphorylation motifs, the kinase inhibitor olomoucine was examined. At concentrations in which olomoucine is specific for cyclin-dependent kinases (5 microM), it reduced only anterograde transport, whereas anterograde and retrograde movement were both affected at concentrations at which other kinases are inhibited as well (50 microM). Both anterograde and retrograde transport also were inhibited by histone H1 and KSPXK peptides, substrates for proline-directed kinases, including CDKs. Our data suggest that CDK-like axonal kinases modulate fast anterograde transport and that other axonal kinases may be involved in modulating retrograde transport. The specific effect of APC4 on anterograde transport suggests a model in which the binding of APC to microtubules may limit the activity of axonal CDK kinase or kinases in restricted domains, thereby affecting organelle transport.

Ratner, N.; Bloom, G. S.; Brady, S. T.

1998-01-01