Science.gov

Sample records for agulhas current transport

  1. The Agulhas Current

    NASA Astrophysics Data System (ADS)

    de Ruijter, Will P. M.

    2008-03-01

    Many people in the United States know about the Gulf Stream, the impressive boundary current along the eastern U.S. coast that carries large amounts of heat poleward and, after separation from the coast, across the North Atlantic. Its impact on warming the eastern United States and the North Atlantic region including western Europe is also well known to the general public. But who in the United States knows about the Agulhas Current? This warm, western boundary current of the southern Indian Ocean flows southward along the continental slope of the African continent and is about as large as the Gulf Stream. It brings heat and moisture to the coastal regions of southeastern Africa. Variations in its transport lead to significant rainfall anomalies over this region. On a larger scale, its influence may even extend as far as the North Atlantic.

  2. Measuring Agulhas Current strength and leakage from satellite altimetry

    NASA Astrophysics Data System (ADS)

    Le Bars, Dewi; De Ruijter, Wilhelmus P. M.; Dijkstra, Henk A.

    2013-04-01

    The Agulhas leakage is a flux of relatively warm and salty water from the Indian Ocean to the South Atlantic Ocean. It occurs south of the African continent where the Agulhas Current retroflects and sheds large anticyclonic eddies that quickly break up and mix with the surrounding water. This is one of the most energetic regions of the world ocean and the Agulhas leakage is therefore very difficult to quantify. In recent years two independent studies (Biastoch et al. 2009, Rouault et al. 2009) using different ocean models pointed out the possibility that the strength of the Agulhas leakage could have increased over the last decades. Unfortunately several discrepancies exist between these two studies on the magnitude and the causes of this increase showing the limitations of numerical modelling in this area. In this work we use a combination of along-track and mapped satellite geostrophic velocities to compute the strength of the Agulhas Current and to follow Lagrangian particles released in its core. The results confirm a positive trend of the volume of Agulhas leakage over the last two decades. This allows us to investigate the dependence of the leakage to upstream conditions like the Agulhas Current transport, the pattern and strength of the westerly winds and to test previous theories on the relations between these factors. Biastoch, A., Böning, C. W., Schwarzkopf, F. U. and Lutjeharms, J. R. E.: Increase in Agulhas leakage due to poleward shift of Southern Hemisphere westerlies, Nature, 462(7272), 495-498, doi:10.1038/nature08519, 2009. Rouault, M., Penven, P. and Pohl, B.: Warming in the Agulhas Current system since the 1980's, Geophys. Res. Lett, 36(L12602), doi:10.1029/2009GL037987, 2009.

  3. Satellite observations of the Agulhas Current system.

    PubMed

    Quartly, Graham D; Srokosz, Meric A

    2003-01-15

    The Agulhas Current system is a complex interplay of currents and eddies with the bathymetry. Components such as the East Madagascar Retroflection and the Agulhas Return Current evolve significantly over a month, and they are thus not adequately resolved by infrequent research-ship cruises. This paper contrasts the abilities of three different spaceborne sensors for monitoring these complex regimes. A key parameter is sea-surface temperature, measured by both infrared and microwave radiometers. Ocean colour observations of chlorophyll can also be used to distinguish between water masses. PMID:12626239

  4. Wind changes above warm Agulhas Current eddies

    NASA Astrophysics Data System (ADS)

    Rouault, M.; Verley, P.; Backeberg, B.

    2016-04-01

    Sea surface temperature (SST) estimated from the Advanced Microwave Scanning Radiometer E onboard the Aqua satellite and altimetry-derived sea level anomalies are used south of the Agulhas Current to identify warm-core mesoscale eddies presenting a distinct SST perturbation greater than to 1 °C to the surrounding ocean. The analysis of twice daily instantaneous charts of equivalent stability-neutral wind speed estimates from the SeaWinds scatterometer onboard the QuikScat satellite collocated with SST for six identified eddies shows stronger wind speed above the warm eddies than the surrounding water in all wind directions, if averaged over the lifespan of the eddies, as was found in previous studies. However, only half of the cases showed higher wind speeds above the eddies at the instantaneous scale; 20 % of cases had incomplete data due to partial global coverage by the scatterometer for one path. For cases where the wind is stronger above warm eddies, there is no relationship between the increase in surface wind speed and the SST perturbation, but we do find a linear relationship between the decrease in wind speed from the centre to the border of the eddy downstream and the SST perturbation. SST perturbations range from 1 to 6 °C for a mean eddy SST of 15.9 °C and mean SST perturbation of 2.65 °C. The diameter of the eddies range from 100 to 250 km. Mean background wind speed is about 12 m s-1 (mostly southwesterly to northwesterly) and ranging mainly from 4 to 16 m s-1. The mean wind increase is about 15 %, which corresponds to 1.8 m s-1. A wind speed increase of 4 to 7 m s-1 above warm eddies is not uncommon. Cases where the wind did not increase above the eddies or did not decrease downstream had higher wind speeds and occurred during a cold front associated with intense cyclonic low-pressure systems, suggesting certain synoptic conditions need to be met to allow for the development of wind speed anomalies over warm-core ocean eddies. In many cases

  5. Origins and impacts of mesoscale meanders in the Agulhas Current

    NASA Astrophysics Data System (ADS)

    Elipot, S.; Beal, L. M.

    2014-12-01

    The Agulhas Current (AC) is the western boundary current of the South Indian subtropical gyre and is also the pathway for the inter-basin exchange of water, heat and salt between the Indian Ocean and the Atlantic Ocean, and thus a crucial part of the global overturning circulation of the world ocean. The AC, which otherwise flows stably along the coast of South Africa, undergoes dramatic offshore excursions from its mean path, forming large mesoscale solitary meanders propagating downstream and potentially linked to the leakage of Indian Ocean waters to the South Atlantic. These irregular meander events have been referred to as Natal Pulses.Here we present new observations and analyses of Agulhas meanders using full-depth velocity mooring observations from the Agulhas Current Time series experiment (ACT). Detailed analyses of the in-situ velocity reveal important differences between the behavior of the flow during solitary meander events and during meander events of smaller amplitude. During solitary meanders, an onshore cyclonic circulation and an offshore anticyclonic circulation act in concert to displace the jet offshore, leading to sudden and strong positive conversion of kinetic energy of the mean flow to the meander. In contrast, smaller amplitude meanderings are principally represented by a single cyclonic circulation spanning the entire jet that acts to displace the jet without significantly extracting kinetic energy from the mean flow. Solitary meander events can be traced upstream using satellite altimetry and linked to either Mozambique Channel eddies or Madagascar dipoles, the latter possibly part of a basin-wide pattern of propagating sea level anomalies consistent with Rossby wave dynamics. However, only a small number of these anomalies lead to solitary meanders. Altimetric observations suggest 1.5 meanders per year and show that the two-year period during ACT when no events were observed is unprecedented in the 20-year satellite record.

  6. Ocean plankton. Environmental characteristics of Agulhas rings affect interocean plankton transport.

    PubMed

    Villar, Emilie; Farrant, Gregory K; Follows, Michael; Garczarek, Laurence; Speich, Sabrina; Audic, Stéphane; Bittner, Lucie; Blanke, Bruno; Brum, Jennifer R; Brunet, Christophe; Casotti, Raffaella; Chase, Alison; Dolan, John R; d'Ortenzio, Fabrizio; Gattuso, Jean-Pierre; Grima, Nicolas; Guidi, Lionel; Hill, Christopher N; Jahn, Oliver; Jamet, Jean-Louis; Le Goff, Hervé; Lepoivre, Cyrille; Malviya, Shruti; Pelletier, Eric; Romagnan, Jean-Baptiste; Roux, Simon; Santini, Sébastien; Scalco, Eleonora; Schwenck, Sarah M; Tanaka, Atsuko; Testor, Pierre; Vannier, Thomas; Vincent, Flora; Zingone, Adriana; Dimier, Céline; Picheral, Marc; Searson, Sarah; Kandels-Lewis, Stefanie; Acinas, Silvia G; Bork, Peer; Boss, Emmanuel; de Vargas, Colomban; Gorsky, Gabriel; Ogata, Hiroyuki; Pesant, Stéphane; Sullivan, Matthew B; Sunagawa, Shinichi; Wincker, Patrick; Karsenti, Eric; Bowler, Chris; Not, Fabrice; Hingamp, Pascal; Iudicone, Daniele

    2015-05-22

    Agulhas rings provide the principal route for ocean waters to circulate from the Indo-Pacific to the Atlantic basin. Their influence on global ocean circulation is well known, but their role in plankton transport is largely unexplored. We show that, although the coarse taxonomic structure of plankton communities is continuous across the Agulhas choke point, South Atlantic plankton diversity is altered compared with Indian Ocean source populations. Modeling and in situ sampling of a young Agulhas ring indicate that strong vertical mixing drives complex nitrogen cycling, shaping community metabolism and biogeochemical signatures as the ring and associated plankton transit westward. The peculiar local environment inside Agulhas rings may provide a selective mechanism contributing to the limited dispersal of Indian Ocean plankton populations into the Atlantic.

  7. Ocean plankton. Environmental characteristics of Agulhas rings affect interocean plankton transport.

    PubMed

    Villar, Emilie; Farrant, Gregory K; Follows, Michael; Garczarek, Laurence; Speich, Sabrina; Audic, Stéphane; Bittner, Lucie; Blanke, Bruno; Brum, Jennifer R; Brunet, Christophe; Casotti, Raffaella; Chase, Alison; Dolan, John R; d'Ortenzio, Fabrizio; Gattuso, Jean-Pierre; Grima, Nicolas; Guidi, Lionel; Hill, Christopher N; Jahn, Oliver; Jamet, Jean-Louis; Le Goff, Hervé; Lepoivre, Cyrille; Malviya, Shruti; Pelletier, Eric; Romagnan, Jean-Baptiste; Roux, Simon; Santini, Sébastien; Scalco, Eleonora; Schwenck, Sarah M; Tanaka, Atsuko; Testor, Pierre; Vannier, Thomas; Vincent, Flora; Zingone, Adriana; Dimier, Céline; Picheral, Marc; Searson, Sarah; Kandels-Lewis, Stefanie; Acinas, Silvia G; Bork, Peer; Boss, Emmanuel; de Vargas, Colomban; Gorsky, Gabriel; Ogata, Hiroyuki; Pesant, Stéphane; Sullivan, Matthew B; Sunagawa, Shinichi; Wincker, Patrick; Karsenti, Eric; Bowler, Chris; Not, Fabrice; Hingamp, Pascal; Iudicone, Daniele

    2015-05-22

    Agulhas rings provide the principal route for ocean waters to circulate from the Indo-Pacific to the Atlantic basin. Their influence on global ocean circulation is well known, but their role in plankton transport is largely unexplored. We show that, although the coarse taxonomic structure of plankton communities is continuous across the Agulhas choke point, South Atlantic plankton diversity is altered compared with Indian Ocean source populations. Modeling and in situ sampling of a young Agulhas ring indicate that strong vertical mixing drives complex nitrogen cycling, shaping community metabolism and biogeochemical signatures as the ring and associated plankton transit westward. The peculiar local environment inside Agulhas rings may provide a selective mechanism contributing to the limited dispersal of Indian Ocean plankton populations into the Atlantic. PMID:25999514

  8. Improving Understanding of the Agulhas Current and Its Global Climate Impacts

    NASA Astrophysics Data System (ADS)

    Beal, Lisa; Biastoch, Arne

    2010-05-01

    Working Group on the Climatic Importance of the Greater Agulhas System; Portland, Oregon, 20-21 February 2010; The first meeting of the new Scientific Committee on Oceanic Research (SCOR) Working Group 136 was held to discuss recent developments in understanding the greater Agulhas Current system and future research directions. The overarching goal of the working group is to improve understanding and awareness of the regional and global climate impacts of the Agulhas Current, a major western boundary current that flows along the east coast of Africa, and its interocean leakage. In addition to studying modern circulation, the working group is motivated by recent paleodata that suggest that through the currents' southern influence on the Atlantic meridional overturning circulation (AMOC), changes in the leakage of warm and salty Agulhas waters into the Atlantic may have triggered the end of ice ages. In terms of global climate, this arguably puts the importance of the greater Agulhas system on a par with Heinrich (land-ice release) events and high-latitude deepwater formation.

  9. Spatio-temporal characteristics of Agulhas leakage: a model inter-comparison study

    NASA Astrophysics Data System (ADS)

    Holton, L.; Deshayes, J.; Backeberg, B. C.; Loveday, B. R.; Hermes, J. C.; Reason, C. J. C.

    2016-05-01

    Investigating the variability of Agulhas leakage, the volume transport of water from the Indian Ocean to the South Atlantic Ocean, is highly relevant due to its potential contribution to the Atlantic Meridional Overturning Circulation as well as the global circulation of heat and salt and hence global climate. Quantifying Agulhas leakage is challenging due to the non-linear nature of this process; current observations are insufficient to estimate its variability and ocean models all have biases in this region, even at high resolution . An Eulerian threshold integration method is developed to examine the mechanisms of Agulhas leakage variability in six ocean model simulations of varying resolution. This intercomparison, based on the circulation and thermohaline structure at the Good Hope line, a transect to the south west of the southern tip of Africa , is used to identify features that are robust regardless of the model used and takes into account the thermohaline biases of each model. When determined by a passive tracer method, 60 % of the magnitude of Agulhas leakage is captured and more than 80 % of its temporal fluctuations, suggesting that the method is appropriate for investigating the variability of Agulhas leakage. In all simulations but one, the major driver of variability is associated with mesoscale features passing through the section. High resolution ({<} 1/10°) hindcast models agree on the temporal (2-4 cycles per year) and spatial (300-500 km) scales of these features corresponding to observed Agulhas Rings. Coarser resolution models ({<} 1/4°) reproduce similar time scale of variability of Agulhas leakage in spite of their difficulties in representing the Agulhas rings properties. A coarser resolution climate model (2°) does not resolve the spatio-temporal mechanism of variability of Agulhas leakage. Hence it is expected to underestimate the contribution of Agulhas Current System to climate variability.

  10. Observations of an early Agulhas current retroflection event in 2001: A temporary cessation of inter-ocean exchange south of Africa?

    NASA Astrophysics Data System (ADS)

    van Aken, H. M.; Lutjeharms, J. R. E.; Rouault, M.; Whittle, C.; de Ruijter, W. P. M.

    2013-02-01

    The exchange of heat and salt between the South Indian Ocean and South Atlantic Ocean, at the southern terminus of the Agulhas current, forms a crucial link in the global ocean circulation. It has been surmised that upstream retroflections in this current could produce temporary interruptions to the exchange, but that their impact would depend on the vertical extent of such retroflections and on their duration. The fortuitous presence at sea of a research vessel has now enabled us to investigate such an episode at subsurface levels in combination with remote sensing of the sea surface. We present here the first in situ evidence that an upstream or early retroflection can extend to a depth of well over 750 m and last for 5 months. This event was likely triggered upstream by the happenstance of two Natal Pulses, large cyclonic eddies inshore of the Agulhas current. These eddies short-circuited the Agulhas with its Return current, leading to the shedding of three large Agulhas rings in quick succession. The arrival of a third cyclonic eddy when the Retroflection was still quite retracted did not lead to another ring shedding event. The resulting early retroflection may have had the effect of stalling the shedding of Agulhas rings and their motion towards the Cape Basin. However, these early retroflections are too scarce to allow generic statements on their generation or consequences, and the relation with large-scale environmental factors. It is likely that the observed withdrawal of the retroflection into the Transkei Basin is a fortuitous result of a series of contingent interactions.

  11. Madagascar corals track sea surface temperature variability in the Agulhas Current core region over the past 334 years

    PubMed Central

    Zinke, J.; Loveday, B. R.; Reason, C. J. C.; Dullo, W.-C.; Kroon, D.

    2014-01-01

    The Agulhas Current (AC) is the strongest western boundary current in the Southern Hemisphere and is key for weather and climate patterns, both regionally and globally. Its heat transfer into both the midlatitude South Indian Ocean and South Atlantic is of global significance. A new composite coral record (Ifaty and Tulear massive Porites corals), is linked to historical AC sea surface temperature (SST) instrumental data, showing robust correlations. The composite coral SST data start in 1660 and comprise 200 years more than the AC instrumental record. Numerical modelling exhibits that this new coral derived SST record is representative for the wider core region of the AC. AC SSTs variabilities show distinct cooling through the Little Ice Age and warming during the late 18th, 19th and 20th century, with significant decadal variability superimposed. Furthermore, the AC SSTs are teleconnected with the broad southern Indian and Atlantic Oceans, showing that the AC system is pivotal for inter-ocean heat exchange south of Africa. PMID:24637665

  12. The spatial evolution of t he directional wave spectrum in the Southern Ocean: Its relation to extreme waves in Agulhas Current

    NASA Technical Reports Server (NTRS)

    Beal, R. C.; Goldfinger, A.; Irvine, D.; Monaldo, F.; Tilley, D.; Shuchman, R.; Lyzenga, D.; Lyden, J.; Deleonibus, P.; Rufenach, C.

    1984-01-01

    An experiment using the Shuttle Imaging Radar-B (SIR-B) to monitor certain properties of the ocean wave directional spectrum and to track the long swell systems as they propagate northward to encounter the Agulhas near the southeastern coast of Africa is discussed. The experiment is designed around the unique capability of SIR-B to overcome key limitations of the Seasat synthetic aperture radar data set, and to extend the existing Seasat results into new areas. Ocean wave systems will be tracked. The variable-incidence-angle capability to examine wave imaging quality will be utilized. Doppler current measurements will be attempted. An effort will be made to verify that the lower range-to-velocity ratio of SIR-B will lead to the improved response of azimuth-traveling wave systems.

  13. Sea surface temperatures from the southern Benguela region from the Pliocene and Pleistocene: tracking Agulhas Current input into the SE Atlantic

    NASA Astrophysics Data System (ADS)

    Petrick, B. F.; McClymont, E.; Felder, S.; Lloyd, J. M.; Leng, M. J.

    2011-12-01

    The Pliocene and-Pleistocene epochs provide a way to understand the effect of past climate changes on key ocean currents. Here, we show results from ODP Site1087 (31.28'S, 15.19'E, 1374m water depth) to investigate changes in ocean circulation over the period of the mid-Pliocene warm period 3.0-3.5 Ma and compare these to the time of the 100 kyr Pleistocene glacial cycles. ODP 1087 is located in the South-eastern Atlantic Ocean, outside of the Benguela upwelling region; reconstructing the temperature history of the site will therefore provide an important data set from a part of the ocean that has few orbital-scale and continuous Pliocene temperature reconstructions. ODP 1087 can be used to investigate the history of the heat and salt transfer to the Atlantic Ocean from the Indian Ocean via the Agulhas Retroflection, which plays an important part in the global thermohaline circulation (Lutjeharms, 2007). Climate models and reconstructions for the most recent glacial-interglacial cycles have shown that changes to the strength of the heat transfer may cause major climatic changes and may play a role in transitions from glacial to interglacial events (Knorr & Lohmann, 2003). It is unknown how this transfer reacted to generally warmer global temperatures during the mid-Pliocene. Because the mid-Pliocene is seen as a model for future climate change it might provide a model for ocean circulations in a warmer world. Our approach is to apply several organic geochemistry proxies and foraminiferal analyses to reconstruct the history of ODP 1087. The UK37' index records differences in the unsaturated bonds in the C37 alkenones to reconstruct sea surface temperatures (Brassell et al., 1986). We present SSTs generated for the mid-Pliocene Warm period with a resolution of 4000 years. We compare this data to the time of the 100 kyr glacial cycles during the late Pleistocene. Even though ODP 1087 is located outside the Benguela upwelling system, it has lower Pliocene temperatures

  14. Mechanisms of nearshore retention and offshore export of mussel larvae over the Agulhas Bank

    NASA Astrophysics Data System (ADS)

    Weidberg, Nicolás; Porri, Francesca; Von der Meden, Charles E. O.; Jackson, Jennifer M.; Goschen, Wayne; McQuaid, Christopher D.

    2015-04-01

    Ecological connectivity is critical for population dynamics but in many benthic species it is complicated by a planktonic larval phase, whose dispersal remains poorly understood. Using a plankton pump, we examine the distribution of intertidal mussel larvae along three axes: alongshore, cross-shelf and by depth during a large scale (600 km) cruise over the Agulhas Bank off southern Africa in August/September 2010. As a general pattern, higher veliger abundances were found close to the coast. Our analyses of the nearshore flow, estimated from ADCP data and the vertical distribution of larvae, show that onshore larval retention may be mediated by active vertical swimming through the water column guided by light and wind-induced turbulence. A massive offshore export of larvae off St Francis Bay was, however, observed during an Agulhas Current meander which influenced inner shelf waters. We hypothesize that, by increasing and homogenizing flow, the Agulhas Current may erase the effects of larval vertical positioning on onshore retention and transport larvae offshore. Our study highlights the need to integrate the effects of complex, region-specific physical dynamics with the swimming behaviour of larvae in order to explain their spatial distribution, population connectivity and the consequences for population dynamics.

  15. The arrest of Agulhas retroflection during glaciations

    NASA Astrophysics Data System (ADS)

    Zharkov, V.; Nof, D.; Ortiz, J. D.; Paldor, N.; Chassignet, E.

    2011-12-01

    Paleoceanographic proxy data indicate that the Agulhas leakage into the South Atlantic was dramatically reduced during glacial times, thus probably resulting in the collapse of the Atlantic Meridional Overturning Circulation. In our former papers, we hypothesized that this was due to a northward shift of the zero wind stress curl that, in turn, forced the retroflection to occur farther north, where the slant of the coastline relative to the north is steep. Here we propose that strong westerlies (0.4 Pa implying a wind speed of ~ 12 m/s at zero degrees centigrade), which were supposedly common during glaciations, also could have arrested the leakage. This arrest occurs because the wind stress opposes the momentum flux associated with the retroflection and, therefore, the retroflection does not shift in latitude. We use a simple, nonlinear, "reduced gravity" model to show analytically and numerically that, under the above conditions, the eastward wind stress compensates for the zonal westward flow-force associated with the retroflection, thus avoiding the development and shedding of rings. For a nearly zonal wall, westerly winds, and small upper layer thickness along the wall, the arresting wind stress is found, theoretically, to be, τx~0.042α3/2ρf[(2fQ)3/g']1/4 where α is twice the retroflection eddy vorticity, ρ the water density, and Q the Agulhas Current volume flux; the remaining notation is conventional. According to this formula, wind typical for the Agulhas region during glacial times (0.4Pa) significantly affects the moderately strong Agulhas rings of large PV (α=0.1) but, with increasing α, the influence of wind quickly decreases, and becomes negligible for α>0.2. This theoretical result is in agreement with the results of the numerical simulations that we conducted. The numerics show that the wind tends to destroy the detached rings by squeezing them onto the wall, a result that is valid in both the straight and the kinked coast cases. In the

  16. Inter-comparison studies between high-resolution HYCOM simulation and observational data: The South Atlantic and the Agulhas leakage system

    NASA Astrophysics Data System (ADS)

    Castellanos, P.; Campos, E. J. D.; Giddy, I.; Santis, W.

    2016-07-01

    Statistical analyses and model-data inter-comparisons are performed to evaluate the model's ability to reproduce the dynamics in the upper layers (< 2000 m) of the South Atlantic ocean. Outputs of an eddy-resolving Ocean General Circulation Model (OGCM) are analyzed and compared with observed data. The model, a 1/12-degree, 22-layer implementation of the Hybrid Coordinate Ocean Model (HYCOM) to the South Atlantic, was forced with monthly-mean products from the NCEP Reanalysis for the period 1960 to 2010. The numerical experiment was capable to reproduce the large scale and the mesoscale dynamic in the South Atlantic and in the Agulhas region. The vertical structure is in agreement with in situ data, the model has lower skill when compared with PIRATA lower temperatures, and is able to capture the seasonal and annual variability in the tropical Atlantic. Furthermore, sensitive change until 2007 is clear in the vertical structure, at 4°N-38°W; 0°-35°W and 10°S-10°W, suggesting an important change in the stratification. The primary results concern a significant change in the decadal anomalies of the temperatures and salinity, which exhibit a warmer and saltier water in the southeastern Atlantic. Furthermore, linear trends found in the transport time-series in the North Brazil Current, and the South Equatorial Current were seen to correspond with increasing trends of the warmer water from the Agulhas Current into South Atlantic. The integrated transport during the period 1960-2010, shows an increase in westward changes in the large-scale circulation south of Africa are show in the negative trends indicate a widening of the "Agulhas gap" and increase in westward volume transport since 1980. It is therefore suggested that variability in the Agulhas System on the last two decades is affecting the dynamic in the South Atlantic, namely the temperature and the volume transport, reach the tropical region of the Atlantic.

  17. Agulhas Plateau and Mozambique Ridge: Two LIPS of a Kind?

    NASA Astrophysics Data System (ADS)

    Uenzelmann-Neben, G.; Gohl, K.; Parsiegla, N.

    2008-12-01

    The seaway south of South Africa represents a critical gateway within the global ocean circulation. Here, warm surface and cold deep and bottom water masses meet and lead to a transfer of heat and salt between the Indian and Atlantic Oceans. This transfer maintains the global thermohaline circulation. The paths of the oceanic currents are strongly influenced by the seafloor topography observed in this region. Thus, the tectonic evolution of the South African continental margin and the gateway starting in Cretaceous times are of major importance in order to understand the evolution of the current system and the transition from the Greenhouse to the Icehouse world. The gateway itself is characterized by the Agulhas Plateau, which has been postulated to originate in the interaction of the Bouvet Hotspot and a triple junction and thus to fall within the world-wide suite of Large Igneous Provinces [Gohl and Uenzelmann-Neben, 2001; Parsiegla, et al., 2008; Uenzelmann-Neben, et al., 1999]. A similar structure has been identified for the crust of the southern Mozambique Ridge [Gohl, et al., submitted]. This raises the question whether those two LIP events were related, whether their emplacement happened at the same time and how they tie in with other LIP events observed in Late Cretaceous times such as the formation or the Kerguelen LIP. Furthermore, we may speculate on the effect those magmatic events had on the evolution of both oceanic currents and the climate. Similarities as well as differences in crustal structure and evolution and later sedimentary development will be presented for those two structures based on seismic refraction and reflection data. References: Gohl, K. and G. Uenzelmann-Neben (2001), The crustal role of the Agulhas Plateau, southwest Indian Ocean: Evidence from seismic profiling, Geophysical Journal International, 144, 632-646. Gohl, K., et al. (submitted), Is the Mozambique Ridge related to the Agulhas Plateau Large Igneous Province?, Geophysical

  18. Increase in Agulhas leakage due to poleward shift of Southern Hemisphere westerlies.

    PubMed

    Biastoch, A; Böning, C W; Schwarzkopf, F U; Lutjeharms, J R E

    2009-11-26

    The transport of warm and salty Indian Ocean waters into the Atlantic Ocean-the Agulhas leakage-has a crucial role in the global oceanic circulation and thus the evolution of future climate. At present these waters provide the main source of heat and salt for the surface branch of the Atlantic meridional overturning circulation (MOC). There is evidence from past glacial-to-interglacial variations in foraminiferal assemblages and model studies that the amount of Agulhas leakage and its corresponding effect on the MOC has been subject to substantial change, potentially linked to latitudinal shifts in the Southern Hemisphere westerlies. A progressive poleward migration of the westerlies has been observed during the past two to three decades and linked to anthropogenic forcing, but because of the sparse observational records it has not been possible to determine whether there has been a concomitant response of Agulhas leakage. Here we present the results of a high-resolution ocean general circulation model to show that the transport of Indian Ocean waters into the South Atlantic via the Agulhas leakage has increased during the past decades in response to the change in wind forcing. The increased leakage has contributed to the observed salinification of South Atlantic thermocline waters. Both model and historic measurements off South America suggest that the additional Indian Ocean waters have begun to invade the North Atlantic, with potential implications for the future evolution of the MOC. PMID:19940923

  19. The life cycle of a coherent Lagrangian Agulhas ring

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Beron-Vera, F. J.; Olascoaga, M. J.

    2016-06-01

    We document the long-term evolution of an Agulhas ring detected from satellite altimetry using a technique from nonlinear dynamical systems that enables objective (i.e., observer-independent) eddy framing. Such objectively detected eddies have Lagrangian (material) boundaries that remain coherent (unfilamented) over the detection period. The ring preserves a quite compact material entity for a period of about 2 years even after most initial coherence is lost within 5 months after detection. We attribute this to the successive development of short-term coherent material boundaries around the ring. These boundaries provide effective short-term shielding for the ring, which prevents a large fraction of the ring's interior from being mixed with the ambient turbulent flow. We show that such coherence regain events cannot be inferred from Eulerian analysis. This process is terminated by a ring-splitting event which marks the ring demise, near the South American coast. The genesis of the ring is characterized by a ring-merging event away from the Agulhas retroflection, followed by a 4 month-long partial coherence stage, scenario that is quite different than a current occlusion and subsequent eddy pinch off.

  20. Agulhas salt-leakage oscillations during abrupt climate changes of the Late Pleistocene

    NASA Astrophysics Data System (ADS)

    Marino, Gianluca; Zahn, Rainer; Ziegler, Martin; Purcell, Conor; Knorr, Gregor; Hall, Ian R.; Ziveri, Patrizia; Elderfield, Henry

    2013-09-01

    An ensemble of new, high-resolution records of surface ocean hydrography from the Indian-Atlantic oceanic gateway, south of Africa, demonstrates recurrent and high-amplitude salinity oscillations in the Agulhas Leakage area during the penultimate glacial-interglacial cycle. A series of millennial-scale salinification events, indicating strengthened salt leakage into the South Atlantic, appear to correlate with abrupt changes in the North Atlantic climate and Atlantic Meridional Overturning Circulation (AMOC). This interhemispheric coupling, which plausibly involved changes in the Hadley Cell and midlatitude westerlies that impacted the interocean transport at the tip of Africa, suggests that the Agulhas Leakage acted as a source of negative buoyancy for the perturbed AMOC, possibly aiding its return to full strength. Our finding points to the Indian-to-Atlantic salt transport as a potentially important modulator of the AMOC during the abrupt climate changes of the Late Pleistocene.

  1. On transport-driven currents

    SciTech Connect

    Ma, S.; Dawson, J.M. )

    1994-08-01

    An empirical electron viscosity is incorporated into Ohm's law to examine the effect of current diffusion on bootstrap currents. It is shown that for sufficiently large viscosity, no seed current is needed for steady state operation of tokamaks. This is expressed by the scaling law [Gamma][ital R][sup 2][sub [ital m

  2. Atlantic multi-decadal oscillation covaries with Agulhas leakage

    PubMed Central

    Biastoch, Arne; Durgadoo, Jonathan V.; Morrison, Adele K.; van Sebille, Erik; Weijer, Wilbert; Griffies, Stephen M.

    2015-01-01

    The interoceanic transfer of seawater between the Indian Ocean and the Atlantic, ‘Agulhas leakage', forms a choke point for the overturning circulation in the global ocean. Here, by combining output from a series of high-resolution ocean and climate models with in situ and satellite observations, we construct a time series of Agulhas leakage for the period 1870–2014. The time series demonstrates the impact of Southern Hemisphere westerlies on decadal timescales. Agulhas leakage shows a correlation with the Atlantic Multi-decadal Oscillation on multi-decadal timescales; the former leading by 15 years. This is relevant for climate in the North Atlantic. PMID:26656850

  3. Atlantic multi-decadal oscillation covaries with Agulhas leakage

    DOE PAGES

    Biastoch, Arne; Durgadoo, Jonathan V.; Morrison, Adele K.; van Sebille, Erik; Weijer, Wilbert; Griffies, Stephen M.

    2015-12-10

    The interoceanic transfer of seawater between the Indian Ocean and the Atlantic, ‘Agulhas leakage’, forms a choke point for the overturning circulation in the global ocean. Here, by combining output from a series of high-resolution ocean and climate models with in situ and satellite observations, we construct a time series of Agulhas leakage for the period 1870–2014. The time series demonstrates the impact of Southern Hemisphere westerlies on decadal timescales. Agulhas leakage shows a correlation with the Atlantic Multi-decadal Oscillation on multi-decadal timescales; the former leading by 15 years. Lastly, this is relevant for climate in the North Atlantic.

  4. A current view of serotonin transporters

    PubMed Central

    De Felice, Louis J.

    2016-01-01

    Serotonin transporters (SERTs) are largely recognized for one aspect of their function—to transport serotonin back into the presynaptic terminal after its release. Another aspect of their function, however, may be to generate currents large enough to have physiological consequences. The standard model for electrogenic transport is the alternating access model, in which serotonin is transported with a fixed ratio of co-transported ions resulting in net charge per cycle. The alternating access model, however, cannot account for all the observed currents through SERT or other monoamine transporters.  Furthermore, SERT agonists like ecstasy or antagonists like fluoxetine generate or suppress currents that the standard model cannot support.  Here we survey evidence for a channel mode of transport in which transmitters and ions move through a pore. Available structures for dopamine and serotonin transporters, however, provide no evidence for a pore conformation, raising questions of whether the proposed channel mode actually exists or whether the structural data are perhaps missing a transient open state. PMID:27540474

  5. A current view of serotonin transporters.

    PubMed

    De Felice, Louis J

    2016-01-01

    Serotonin transporters (SERTs) are largely recognized for one aspect of their function-to transport serotonin back into the presynaptic terminal after its release. Another aspect of their function, however, may be to generate currents large enough to have physiological consequences. The standard model for electrogenic transport is the alternating access model, in which serotonin is transported with a fixed ratio of co-transported ions resulting in net charge per cycle. The alternating access model, however, cannot account for all the observed currents through SERT or other monoamine transporters.  Furthermore, SERT agonists like ecstasy or antagonists like fluoxetine generate or suppress currents that the standard model cannot support.  Here we survey evidence for a channel mode of transport in which transmitters and ions move through a pore. Available structures for dopamine and serotonin transporters, however, provide no evidence for a pore conformation, raising questions of whether the proposed channel mode actually exists or whether the structural data are perhaps missing a transient open state. PMID:27540474

  6. Observations of A Young Agulhas Ring, During Mare

    NASA Astrophysics Data System (ADS)

    van Veldhoven, A. K.; van Aken, H. M.; Veth, C.

    The MARE (Mixing of Agulhas Rings Experiment) project studies the effects of inter- ocean exchange between the Indian and Atlantic Ocean, via Agulhas rings, on the Atlantic meridional overturning circulation. This presentation is about the field pro- gramme of MARE which concentrates on the study of the decay and modification of a single Agulhas ring named Astrid, formed in January 2000. The ring was first iden- tified by an analysis of satellite altimetry data. During a detailed survey of this two months old ring in March 2000 it appeared that the ring had a significant barotropic component, additional to the baroclinic flow around its warm centre. The influence of the present topography, the Agulhas Ridge, on this ring may therefore be important. The observed fine-structure near its boundary suggested that exchange of water with its surroundings already had started. During this presentation some highlights of the results will be presented.

  7. Revisiting Antarctic Circumpolar Current Transport Estimates

    NASA Astrophysics Data System (ADS)

    Sommers, L. A.; Donohue, K. A.; Rosburg, K.

    2014-12-01

    The Antarctic Circumpolar Current (ACC) is the world's strongest current, and acts as a conduit that transports water between Atlantic, Pacific, and Indian Oceans. ACC transport is a key metric used to evaluate the accuracy of ocean and climate models. The canonical transport of 134 Sv through Drake Passage, the narrowest choke point of the ACC, derives from a year-long experiment conducted in 1979 (DRAKE79). Recent studies suggest that this historical value may be biased low by as much as 20%. DRAKE79 transport estimates resulted from a complicated synthesis of historical data and in-situ measurements, and relied heavily on the outcome of referencing three hydrographic sections with directly measured currents. This study focuses on evaluating DRAKE79's geostrophic referencing technique. We hypothesized that the horizontal spacing and temporal averaging of current meters led to a bias in the historical estimate. Southern Ocean State Estimate (SOSE) was used as a test bed to evaluate DRAKE79 methods. A mean AAC transport of 181.5 ± 17.6 Sv was obtained by applying DRAKE79 methods to 2005 SOSE output. This value is greater than SOSE's "true" geostrophic transport (153.0 ± 5.7) by 29 Sv. This difference resulted primarily from linear interpolation between two lost moorings; however the horizontal spacing of the current meters did not resolve the narrow jets of the ACC regardless of mooring loss. Within SOSE, geostrophic transports referenced with velocities at all mooring locations resulted in a mean transport of 161.0 ± 10.2 Sv. Temporal smoothing of the reference velocities, using up to a 20-day running mean, had minimal impact on the mean transport estimate. A next step would evaluate whether the mooring positions should be modified within SOSE to capture the same circulation features as DRAKE79.

  8. Interannual forcing mechanisms of California Current transports I: Meridional Currents

    NASA Astrophysics Data System (ADS)

    Davis, Andrew; Di Lorenzo, Emanuele

    2015-02-01

    An ensemble of eddy-resolving ocean model hindcasts integrated from 1950 to 2008 is used to examine and quantify the interannual variability of large-scale (>200 km) alongshore equatorward flow in the California Current System (CCS). We also develop a single index of this transport in order to determine what fraction of variance is driven locally, by changes in wind stress curl, and remotely, by the arrival of coastally trapped waves of tropical origin. In agreement with previous studies, coastally trapped waves dominate large-scale interannual CCS sea surface height variability. In contrast, we find that large-scale alongshore currents (v) are driven predominantly by local wind stress curl variability rather than coastally trapped waves. A simple wind-driven diagnostic model of the time-dependent large-scale geostrophic meridional transport captures ~50% (R=0.7) of the total variance. The local wind-stress curl gradient that controls the largest fraction of meridional transport is not independent of the modulations in atmospheric circulation that drive the Pacific Decadal Oscillation (PDO), and a significant fraction of the monthly transport variability in the model ensembles is correlated to the PDO (R=0.4).

  9. High current ion beam transport using solenoids

    SciTech Connect

    Hollinger, R.; Spaedtke, P.

    2008-02-15

    In the framework of the future project FAIR several upgrade programs and construction of new facilities are in progress such as the U{sup 4+} upgrade for the existing high current injector and the new 70 MeV proton injector. For both injectors solenoids in the low energy beam transport section are foreseen to inject the beam into the following rf accelerator. The paper presents beam quality measurements of high current ion beams behind a solenoid using a slit-grid emittance measurement device, viewing targets, and a pepper pot measurement device at the high current test bench at GSI.

  10. Transport currents in Bose quantum liquids

    SciTech Connect

    Apaja, V.; Krotscheck, E.; Rimnac, A.; Zillich, R. E.

    2006-09-07

    Until now, most of what has been said about excitations in quantum liquids has concerned the dynamic structure function, which is observable by means of neutron scattering. The dynamic structure function can be calculated using standard linear response theory. However, at this level one needs only transition densities <0{rho}n> or transition currents <0jn>, which are oscillatory in time and hence do not describe mass transport. In this work we go a step further and study transport currents in excited states, , which requires the calculation of to second order. For that purpose, we take a well-tested microscopic theory of inhomogeneous quantum liquids and extend it to find the currents formed when helium atoms scatter off a helium slab or when excitations evaporate atoms (a setup experimented by A. F. G. Wyatt's group in Exeter). Current conservation was already a major theoretical problem encountered by R. Feynman and led him to introduce backflow corrections. We show that perfect current conservation is expected only for exact solutions of the time-dependent many-body Schroedinger equation. This is the first extensive theoretical study of transport phenomena in a quantum liquid based on an accurate microscopic theory.

  11. Agulhas ring injection into the South Atlantic during glacials and interglacials

    NASA Astrophysics Data System (ADS)

    Zharkov, V.; Nof, D.

    2008-03-01

    Recent proxies analysis suggest that, at the end of the last glacial, there was a significant increase in the injection of Agulhas rings into the South Atlantic (SA). This brought about a dramatic increase in the salt-influx (from the Indian Ocean) into the SA helping re-start the then-collapsed meridional overturning cell (MOC), leading to the termination of the Younger Dryas (YD). Here, we propose a mechanism through which large variations in ring production take place. Using nonlinear analytical solutions for eddy shedding we show that there are restricted possibilities for ring detachment when the coast is oriented in the north-south direction. We define a critical coastline angle below which there is rings shedding and above which there is almost no shedding. In the case of the Agulhas region, the particular shape of the African continent implies that rings can be produced only when the retroflection occurs beyond a specific latitude where the angle is critical. During glaciation, the wind stress curl (WSC) vanished at a latitude lower than that of the critical angle, which prohibited the retroflection from producing rings. When the latitude at which the WSC vanishes migrated poleward towards its present day position, the corresponding coastline angle decreased below the critical angle and allowed for a vigorous production of rings. Simple process-oriented numerical simulations (using the Bleck and Boudra model) are in very good agreement with our results and enable us to affirm that, during the glacials, the behavior of the Agulhas Current (AC) was similar to that of the modern East Australian Current (EAC), for which the coastline slant is supercritical.

  12. Agulhas ring injection into the South Atlantic during glacials and interglacials

    NASA Astrophysics Data System (ADS)

    Zharkov, V.; Nof, D.

    2008-09-01

    Recent proxies suggest that, at the end of the last glacial, there was a significant increase in the injection of Agulhas rings into the South Atlantic (SA). This brought about a dramatic increase in the salt-influx (from the Indian Ocean) into the SA helping re-start the then-collapsed meridional overturning cell (MOC), leading to the termination of the Younger Dryas (YD). Here, we propose a mechanism through which large variations in ring production take place. Using nonlinear analytical solutions for eddy shedding, we show that there are restricted possibilities for ring detachment when the coast is oriented in the north-south direction. We define a critical coastline angle below which there is rings shedding and above which there is almost no shedding. In the case of the Agulhas region, the particular shape of the African continent implies that rings can be produced only when the retroflection occurs beyond a specific latitude where the angle is critical. During glaciation, the wind stress curl (WSC) vanished at a latitude lower than that of the critical angle, which prohibited the retroflection from producing rings. When the latitude at which the WSC vanishes migrated poleward towards its present day position, the corresponding coastline angle decreased below the critical angle and allowed for a vigorous production of rings. Simple process-oriented numerical simulations (using the Bleck and Boudra model) are in satisfactory agreement with our results and enable us to affirm that, during the glacials, the behavior of the Agulhas Current (AC) was similar to that of the modern East Australian Current (EAC), for which the coastline slant is supercritical.

  13. Seismic Reflections Within the Water Column South of South Africa: Indications for the Agulhas Retroflection

    NASA Astrophysics Data System (ADS)

    Uenzelmann-Neben, G.; Klaeschen, D.; Krahmann, G.; Reston, T.; Visbeck, M.

    2006-12-01

    With the publication of Holbrook et al. (2003) the field of seismic oceanography experienced a major momentum. Several authors since then (Nandi et al., 2004; Holbrook and Fer, 2005; Paramo and Holbrook, 2005) could show that those reflections within the water column correspond to thin layers with strong vertical temperature gradients. Those reflections hence represent a chance to trace those temperature gradients over large distances. Weak seismic reflections within the water column south of South Africa gave rise to the question whether here traces of the Agulhas Current or Agulhas Retroflection can be observed. A careful reprocessing of the data led to the imaging of fields of reflections pointing towards a 135 km broad and about 1000 m deep reaching well stratified area with strong reflection amplitudes and several weaker reflections extending down to at least 1500 m water depth over the whole area of investigation. To image both the boundaries between the water masses as reflections and the different properties of the long wavelength velocity variations in depth special imaging technigues like prestack depth migration analysis were performed. Further, the temperature gradients from the short wavelength properties as velocity and density contrasts were determind by a two step inversion of acoustic amplitude versus angle analysis to better quantify the variations of the water masses of the Agulhas Current. References: Holbrook, W.S., and I. Fer, Ocean internal wave spectra inferred from seismic reflection transects, 2005, Geophys. Res. Lett., 32, L15604, doi:10.1029/2005GL023733. Nandi, P., W.S. Holbrook, S. Pearse, P. Paramo, and R.W. Schmitt, 2004, Seismic reflection imaging of Norwegian Sea water mass boundaries, Geophys. Res. Lett., 31, L23311, doi:10.1029/2004GL021325. Paramo, P., and W. S. Holbrook, 2005, Temperature contrasts in the water column inferred from amplitude-versus-offset analysis of acoustic reflections, Geophys. Res. Lett., v. 32, L24611, doi

  14. Achromatic beam transport of High Current Injector

    NASA Astrophysics Data System (ADS)

    Kumar, Sarvesh; Mandal, A.

    2016-02-01

    The high current injector (HCI) provides intense ion beams of high charge state using a high temperature superconducting ECR ion source. The ion beam is accelerated upto a final energy of 1.8 MeV/u due to an electrostatic potential, a radio frequency quadrupole (RFQ) and a drift tube linac (DTL). The ion beam has to be transported to superconducting LINAC which is around 50 m away from DTL. This section is termed as high energy beam transport section (HEBT) and is used to match the beam both in transverse and longitudinal phase space to the entrance of LINAC. The HEBT section is made up of four 90 deg. achromatic bends and interconnecting magnetic quadrupole triplets. Two RF bunchers have been used for longitudinal phase matching to the LINAC. The ion optical design of HEBT section has been simulated using different beam dynamics codes like TRACEWIN, GICOSY and TRACE 3D. The field computation code OPERA 3D has been utilized for hardware design of all the magnets. All the dipole and quadrupole magnets have been field mapped and their test results such as edge angles measurements, homogeneity and harmonic analysis etc. are reported. The whole design of HEBT section has been performed such that the most of the beam optical components share same hardware design and there is ample space for beam diagnostics as per geometry of the building. Many combination of achromatic bends have been simulated to transport the beam in HEBT section but finally the four 90 deg. achromatic bend configuration is found to be the best satisfying all the geometrical constraints with simplified beam tuning process in real time.

  15. Indian-atlantic transfer of thermocline water at the agulhas retroflection.

    PubMed

    Gordon, A L

    1985-03-01

    During November and December 1983, two anticyclonic eddies were observed west of the Agulhas Retroflection, apparently spawned at the retroflection. The western eddy, centered 300 kilometers southwest of Cape Town, has a winter cooled core encircled by warm Indian Ocean water. Between Cape Town and the "Cape Town Eddy" is a net geostrophic transport of Indian Ocean thermocline water (14 x 10(6) cubic meters per second) into the South Atlantic Ocean. This circulation configuration, similar to that observed by earlier researchers, suggests that Indian-Atlantic thermocline exchange is a common occurrence. Such a warmwater link between the Atlantic and Indian oceans would strongly influence global climate patterns. The Indian Ocean water is warmer than the adjacent South Atlantic water and thus represents a heat input of 2.3 x 10(13) to 47 x 10(13) watts into the Atlantic. The large uncertainty arises from the unknown partition between two possible routes for the return flow from the Atlantic to the Indian Ocean: cooler South Atlantic thermocline water or much colder North Atlantic Deep Water. In either case, interocean mass and heat exchange of thermocline water at the Agulhas Retroflection is a distinct likelihood.

  16. Studying an Agulhas ring's long-term pathway and decay with finite-time coherent sets

    NASA Astrophysics Data System (ADS)

    Froyland, Gary; Horenkamp, Christian; Rossi, Vincent; van Sebille, Erik

    2015-08-01

    Coherent sets in dynamical systems are regions in phase space that optimally "carry mass" with them under the system's evolution, so that these regions experience minimal leakage. The dominant tool for determining coherent sets is the transfer operator, which provides a complete description of Lagrangian mass transport. In this work, we combine existing transfer operator methods with a windowing scheme to study the spatial and temporal evolution of a so-called Agulhas ring: a large anticyclonic mesoscale eddy playing a key role in inter-ocean exchange of climate-relevant properties. Our focus is on ring decay over time and the windowing scheme enables us to study how the most coherent region (our estimate of the ring) varies in position and size over a period of more than two years. We compare the eddy-like structure and its spatio-temporal changes as revealed by our method and by a classical Eulerian approach.

  17. Continental crust beneath the Agulhas Plateau, Southwest Indian Ocean

    SciTech Connect

    Tucholke, B.E.; Houtz, R.E.; Barrett, D.M.

    1981-05-10

    The Agulhas Plateau lies 500 km off the Cape of Good Hope in the southwestern Indian Ocean. Acoustic basement beneath the northern one third of this large, aseismic structural high has rugged morphology, but basement in the south is anomalously smooth, excepting a 30- to 90-km-wide zone with irregular relief that trends south-southwest through the center of the plateau. Seismic refraction profiles across the southern plateau indicate that the zone of irregular acoustic basement overlies thickened oceanic crust and that continental crust, locally thinned and intruded by basalts, underlies several regions of smooth acoustic basement. Recovery of quartzo-feldspathic gneisses in dredge hauls confirms the presence of continental crust. The smoothness of acoustic basement probably results from erosion (perhaps initially subaerial) of topographic highs with depositions and cementation of debris in ponds to form high-velocity beds. Basalt flows and sills also may contribute locally to form smooth basement. The rugged basement of the northern plateau appears to be of oceanic origin. A plate reconstruction to the time of initial opening of the South Atlantic places the continental part of the southern plateau adjacent to the southern edge of the Falkland Plateau, and both abut the western Mozambique Ridge. Both the Agulhas and Falkland plateaus were displaced westward during initial rifting in the Early Cretaceous. Formation of an RRR triple junction at the northern edge of the Agulhas continental fragment during middle Cretaceous time may explain the origin of the rugged, thickened oceanic crust beneath plateau as well as the apparent extension of the continental crust and intrusion of basaltic magmas beneath the southern plateau.

  18. Current understanding of SEP acceleration and transport

    NASA Astrophysics Data System (ADS)

    Cohen, C. M. S.

    2016-03-01

    Through new missions and unusual solar conditions, solar cycle 24 has afforded the opportunity for expanding our understanding of solar energetic particle (SEP) acceleration and transport. With complementary SEP observations from multiple spacecraft separated significantly in longitude, it has been possible to examine the longitudinal distribution of energetic particles in individual events, rather than relying on statistical event studies. Unprecedented 360° views of the Sun, in multiple wavelengths and coronagraphs, has made it possible to identify solar source regions regardless of where they are located and to more accurately determine the properties of related coronal mass ejections. The unusually quiet conditions during the onset of cycle 24 allowed smaller SEP events to be examined and their source regions to be unambiguously identified. This paper reviews some of the unexpected results from multi-spacecraft SEP observations made over this solar cycle and discusses their implications for particle acceleration near the Sun and transport through the inner heliosphere.

  19. Superconducting fault current limiter for railway transport

    NASA Astrophysics Data System (ADS)

    Fisher, L. M.; Alferov, D. F.; Akhmetgareev, M. R.; Budovskii, A. I.; Evsin, D. V.; Voloshin, I. F.; Kalinov, A. V.

    2015-12-01

    A resistive switching superconducting fault current limiter (SFCL) for DC networks with voltage of 3.5 kV and nominal current of 2 kA is developed. The SFCL consists of two series-connected units: block of superconducting modules and high-speed vacuum breaker with total disconnection time not more than 8 ms. The results of laboratory tests of superconducting SFCL modules in current limiting mode are presented. The recovery time of superconductivity is experimentally determined. The possibility of application of SFCL on traction substations of Russian Railways is considered.

  20. Superconducting fault current limiter for railway transport

    SciTech Connect

    Fisher, L. M. Alferov, D. F.; Akhmetgareev, M. R.; Budovskii, A. I.; Evsin, D. V.; Voloshin, I. F.; Kalinov, A. V.

    2015-12-15

    A resistive switching superconducting fault current limiter (SFCL) for DC networks with voltage of 3.5 kV and nominal current of 2 kA is developed. The SFCL consists of two series-connected units: block of superconducting modules and high-speed vacuum breaker with total disconnection time not more than 8 ms. The results of laboratory tests of superconducting SFCL modules in current limiting mode are presented. The recovery time of superconductivity is experimentally determined. The possibility of application of SFCL on traction substations of Russian Railways is considered.

  1. Fuel consumption improvement in current transport engines

    NASA Technical Reports Server (NTRS)

    Hines, R. W.; Ziemianski, J. A.

    1978-01-01

    A review is conducted of improvements which can be made with respect to the fuel consumption of current engines and new production versions of current engines. A description is presented of an engine diagnostics program which has the objective to identify and quantify the causes and sources of performance deterioration in the JT9D turbofan engine and to develop basic data which will be applied to minimize performance degradation of current and future engines. General areas where performance losses occur are examined, taking into account seals, blades and vanes, and cases. Potential performance improvement concepts are related to improved component aerodynamics, improved flowpath sealing, blade tip clearance control, improved turbine cooling effectiveness, improved turbine materials and coatings, duct and nozzle aerodynamic refinements, nacelle aerodynamic refinements, forced exhaust mixers, advanced nacelle materials, and advanced fuel control.

  2. Magneto-optical imaging of transport current densities in superconductors

    SciTech Connect

    Crabtree, G.W.; Welp, U.; Gunter, D.O.; Zhong, W.; Balachandran, U.; Haldar, P.; Sokolowski, R.S.; Vlasko-Vlasov, V.K.; Nikitenko, V.I.

    1995-12-31

    Direct imaging of the paths of transport currents in superconductors creates many new possibilities for exploring the basic features of vortex pinning mechanisms and for improving the performance of superconducting materials. A technique for imaging the path and magnitude of the transport current density flowing in superconductors is described. Results are given for a 37-filament BSCCO 2223 powder-in-tube wire, showing a highly inhomogeneous current path within the filaments.

  3. MOMENTUM TRANSPORT FROM CURRENT-DRIVEN RECONNECTION IN ASTROPHYSICAL DISKS

    SciTech Connect

    Ebrahimi, F.; Prager, S. C.

    2011-12-20

    Current-driven reconnection is investigated as a possible mechanism for angular momentum transport in astrophysical disks. A theoretical and computational study of angular momentum transport from current-driven magnetohydrodynamic instabilities is performed. It is found that both a single resistive tearing instability and an ideal instability can transport momentum in the presence of azimuthal Keplerian flow. The structure of the Maxwell stress is examined for a single mode through analytic quasilinear theory and computation. Full nonlinear multiple-mode computation shows that a global Maxwell stress causes significant momentum transport.

  4. Current injection and transport in polyfluorene

    NASA Astrophysics Data System (ADS)

    Yang, Chieh-Kai; Yang, Chia-Ming; Liao, Hua-Hsien; Horng, Sheng-Fu; Meng, Hsin-Fei

    2007-08-01

    A comprehensive numerical model is established for the electrical processes in a sandwich organic semiconductor device with high carrier injection barrier. The charge injection at the anode interface with 0.8eV energy barrier is dominated by the hopping among the gap states of the semiconductor caused by disorders. The Ohmic behavior at low voltage is demonstrated to be not due to the background doping but the filaments formed by conductive clusters. In bipolar devices with low work function cathode it is shown that near the anode the electron traps significantly enhance hole injection through Fowler-Nordheim tunneling, resulting in rapid increases of the hole carrier and current in comparison with the hole-only devices.

  5. On the role of the Agulhas system in ocean circulation and climate.

    PubMed

    Beal, Lisa M; De Ruijter, Wilhelmus P M; Biastoch, Arne; Zahn, Rainer

    2011-04-28

    The Atlantic Ocean receives warm, saline water from the Indo-Pacific Ocean through Agulhas leakage around the southern tip of Africa. Recent findings suggest that Agulhas leakage is a crucial component of the climate system and that ongoing increases in leakage under anthropogenic warming could strengthen the Atlantic overturning circulation at a time when warming and accelerated meltwater input in the North Atlantic is predicted to weaken it. Yet in comparison with processes in the North Atlantic, the overall Agulhas system is largely overlooked as a potential climate trigger or feedback mechanism. Detailed modelling experiments--backed by palaeoceanographic and sustained modern observations--are required to establish firmly the role of the Agulhas system in a warming climate.

  6. Current patterns and orbital magnetism in mesoscopic dc transport.

    PubMed

    Walz, Michael; Wilhelm, Jan; Evers, Ferdinand

    2014-09-26

    We present ab initio calculations of the local current density j(r) as it arises in dc-transport measurements. We discover pronounced patterns in the local current density, ring currents ("eddies"), that go along with orbital magnetism. Importantly, the magnitude of the ring currents can exceed the (average) transport current by orders of magnitude. We find associated magnetic fields that exhibit drastic fluctuations with field gradients reaching 1  T nm⁻¹ V⁻¹. The relevance of our observations for spin relaxation in systems with very weak spin-orbit interaction, such as organic semiconductors, is discussed. In such systems, spin relaxation induced by bias driven orbital magnetism competes with relaxation induced by the hyperfine interaction and appears to be of similar strength. We propose a NMR-type experiment in the presence of dc-current flow to observe the spatial fluctuations of the induced magnetic fields.

  7. High current heavy ion beam transport experiment at LBL

    SciTech Connect

    Chupp, W.; Faltens, A.; Hartwig, E.C.; Keefe, D.; Kim, C.H.; Pike, C.; Rosenblum, S.S.; Tiefenback, M.; Vanecek, D.; Warwick, A.I.

    1984-01-01

    Information on the current limit in a long quadrupole transport channel is required in designing an accelerator driver for an inertial confinement fusion system. Although a current transport limit was proposed by Maschke, quantitative estimates require a detailed knowledge of the stability of the beam. Analytic calculations based on the Kapchinskij-Vladimirskij (K-V) distribution function have identified transversely unstable modes, but particle simulations have shown that some of the K-V instabilities are benign, i.e., particles redistribute themselves in the 4-D transverse phase space, but the rms emittances do not grow. Some preliminary results of beam transport experiments were reported in the 1983 Particle Accelerator Conference in Santa Fe.

  8. Transport and sedimentation in unconfined experimental dilute pyroclastic density currents

    NASA Astrophysics Data System (ADS)

    Ramirez, G.; Andrews, B. J.; Dennen, R. L.

    2013-12-01

    We present results from experiments conducted in a new facility that permits the study of large, unconfined particle laden density currents that are dynamically similar to natural dilute pyroclastic density currents (PDCs). Experiments were run in a sealed, air-filled tank measuring 8.5 m long by 6.1 m wide by 2.6 m tall. Currents were generated by feeding mixture of heated particles (5 μm aluminum oxide, 25 μm talc, 27 μm walnut shell, 76 μm glass beads) down a chute at controlled rates to produce dilute, turbulent gravity currents. Comparison of experimental currents with natural PDCs shows good agreement between Froude, densimetric and thermal Richardson, and particle Stokes and settling numbers; experimental currents have lower Reynolds numbers than natural PDCs, but are fully turbulent. Currents were illuminated with 3 orthogonal laser sheets (650, 532, and 450 nm wavelengths) and recorded with an array of HD video cameras and a high speed camera (up to 3000 fps). Deposits were mapped using a grid of sedimentation traps. We observe distinct differences between ambient temperature and warm currents: * warm currents have shorter run out distances, narrow map view distributions of currents and deposits, thicken with distance from the source, and lift off to form coignimbrite plumes; * ambient temperature currents typically travel farther, spread out radially, do not thicken greatly with transport distance, and do not form coignimbrite plumes. Long duration currents (600 s compared to 30-100 s) oscillate laterally with time (e.g. transport to the right, then the left, and back); this oscillation happens prior to any interaction with the tank walls. Isopach maps of the deposits show predictable trends in sedimentation versus distance in response to eruption parameters (eruption rate, duration, temperature, and initial current mass), but all sedimentation curves can be fit with 2nd order polynomials (R2>.9). Proximal sedimentation is similar in comparable warm

  9. AC and DC transport currents in melt-grown YBCO

    SciTech Connect

    Yi, Z.; Ashworth, S.; Becluz, C.; Scurlock, R.G. )

    1991-03-01

    It has been suggested that the transport J{sub c} in multi-grain samples of bulk YBCO are limited by the intergrain links. This paper reports on preliminary measurements of intergrain currents. The intergrain critical currents in melt grown YBCO do not appear to be as sensitive to the precise crystallographic alignment of adjacent grains a has been reported for thin films. The measured critical current of similar grain boundaries varies widely, between 15000 A/cm{sup 2} and 200A/Cm{sub 2} for adjacent boundaries in the same sample.

  10. Status of high transport current ROEBEL assembled coated conductor cables

    NASA Astrophysics Data System (ADS)

    Goldacker, Wilfried; Frank, Antje; Kudymow, Andrej; Heller, Reinhard; Kling, Andrea; Terzieva, Stanimira; Schmidt, Curt

    2009-03-01

    Assembling coated conductors (CC) into flat ROEBEL bars (RACC cable) was introduced in 2005 by the authors as a practicable method of reaching high transport currents in a low AC loss cable, which is a cable design suited for application in windings. The transport current of 1.02 kA in self-field at 77 K achieved so far, however, is still too low for several applications in electrical machinery such as larger transformers and generators/motors. A new cable concept for further increased currents was presented just recently. The goal of the new design was primarily to demonstrate the possibility of strongly increased transport currents without changing the important cable features for low AC losses. such as, for example, the transposition length of the strands. We present detailed investigations of the properties of this progressed cable design, which has threefold layered strands, an unchanged transposition pitch of 18.8 cm and finally the application of 45 coated conductors in the cable. A 1.1 m long sample (equivalent to six transposition lengths) was prepared from commercial Cu stabilized coated conductors purchased from Superpower. The measured new record DC transport current of the cable was 2628 A at 77 K in self-field (5 µV cm-1 criterion). The use of three slightly different current carrying batches of strand material (± 10%) was a special feature of the cable, which allowed for interesting investigations of current redistribution effects in the cable, by monitoring a representative strand of each batch during the critical current measurement. Although current redistribution effects showed a complex situation, the behaviour of the cable was found to be absolutely stable under all operational conditions, even above the critical current. The high self-field degradation of the critical current reached the order of 60% at 77 K, and could be modelled satisfactory with calculations based on a proven Biot-Savart-law approach, adapted to the specific boundary

  11. Universal scaling of optimal current distribution in transportation networks.

    PubMed

    Simini, Filippo; Rinaldo, Andrea; Maritan, Amos

    2009-04-01

    Transportation networks are inevitably selected with reference to their global cost which depends on the strengths and the distribution of the embedded currents. We prove that optimal current distributions for a uniformly injected d -dimensional network exhibit robust scale-invariance properties, independently of the particular cost function considered, as long as it is convex. We find that, in the limit of large currents, the distribution decays as a power law with an exponent equal to (2d-1)/(d-1). The current distribution can be exactly calculated in d=2 for all values of the current. Numerical simulations further suggest that the scaling properties remain unchanged for both random injections and by randomizing the convex cost functions. PMID:19518304

  12. Universal scaling of optimal current distribution in transportation networks.

    PubMed

    Simini, Filippo; Rinaldo, Andrea; Maritan, Amos

    2009-04-01

    Transportation networks are inevitably selected with reference to their global cost which depends on the strengths and the distribution of the embedded currents. We prove that optimal current distributions for a uniformly injected d -dimensional network exhibit robust scale-invariance properties, independently of the particular cost function considered, as long as it is convex. We find that, in the limit of large currents, the distribution decays as a power law with an exponent equal to (2d-1)/(d-1). The current distribution can be exactly calculated in d=2 for all values of the current. Numerical simulations further suggest that the scaling properties remain unchanged for both random injections and by randomizing the convex cost functions.

  13. Current-reinforced random walks for constructing transport networks.

    PubMed

    Ma, Qi; Johansson, Anders; Tero, Atsushi; Nakagaki, Toshiyuki; Sumpter, David J T

    2013-03-01

    Biological systems that build transport networks, such as trail-laying ants and the slime mould Physarum, can be described in terms of reinforced random walks. In a reinforced random walk, the route taken by 'walking' particles depends on the previous routes of other particles. Here, we present a novel form of random walk in which the flow of particles provides this reinforcement. Starting from an analogy between electrical networks and random walks, we show how to include current reinforcement. We demonstrate that current-reinforcement results in particles converging on the optimal solution of shortest path transport problems, and avoids the self-reinforcing loops seen in standard density-based reinforcement models. We further develop a variant of the model that is biologically realistic, in the sense that the particles can be identified as ants and their measured density corresponds to those observed in maze-solving experiments on Argentine ants. For network formation, we identify the importance of nonlinear current reinforcement in producing networks that optimize both network maintenance and travel times. Other than ant trail formation, these random walks are also closely related to other biological systems, such as blood vessels and neuronal networks, which involve the transport of materials or information. We argue that current reinforcement is likely to be a common mechanism in a range of systems where network construction is observed.

  14. Agulhas leakage as a key process in the modes of Quaternary climate changes

    PubMed Central

    Caley, Thibaut; Giraudeau, Jacques; Malaizé, Bruno; Rossignol, Linda; Pierre, Catherine

    2012-01-01

    Heat and salt transfer from the Indian Ocean to the Atlantic Ocean (Agulhas leakage) has an important effect on the global thermohaline circulation and climate. The lack of long transfer record prevents elucidation of its role on climate changes throughout the Quaternary. Here, we present a 1,350-ka accumulation rate record of the planktic foraminiferal species Globorotalia menardii. We demonstrate that, according to previous assumptions, the presence and reseeding of this fauna in the subtropical southeast Atlantic was driven by interocean exchange south of Africa. The Agulhas transfer strengthened at glacial ice-volume maxima for every glacial-interglacial transition, with maximum reinforcements organized according to a 400-ka periodicity. The long-term dynamics of Agulhas leakage may have played a crucial role in regulating meridional overturning circulation and global climate changes during the Mid-Brunhes event and the Mid-Pleistocene transition, and could also play an important role in the near future. PMID:22508999

  15. Agulhas leakage as a key process in the modes of Quaternary climate changes.

    PubMed

    Caley, Thibaut; Giraudeau, Jacques; Malaizé, Bruno; Rossignol, Linda; Pierre, Catherine

    2012-05-01

    Heat and salt transfer from the Indian Ocean to the Atlantic Ocean (Agulhas leakage) has an important effect on the global thermohaline circulation and climate. The lack of long transfer record prevents elucidation of its role on climate changes throughout the Quaternary. Here, we present a 1,350-ka accumulation rate record of the planktic foraminiferal species Globorotalia menardii. We demonstrate that, according to previous assumptions, the presence and reseeding of this fauna in the subtropical southeast Atlantic was driven by interocean exchange south of Africa. The Agulhas transfer strengthened at glacial ice-volume maxima for every glacial-interglacial transition, with maximum reinforcements organized according to a 400-ka periodicity. The long-term dynamics of Agulhas leakage may have played a crucial role in regulating meridional overturning circulation and global climate changes during the Mid-Brunhes event and the Mid-Pleistocene transition, and could also play an important role in the near future.

  16. Agulhas leakage as a key process in the modes of Quaternary climate changes.

    PubMed

    Caley, Thibaut; Giraudeau, Jacques; Malaizé, Bruno; Rossignol, Linda; Pierre, Catherine

    2012-05-01

    Heat and salt transfer from the Indian Ocean to the Atlantic Ocean (Agulhas leakage) has an important effect on the global thermohaline circulation and climate. The lack of long transfer record prevents elucidation of its role on climate changes throughout the Quaternary. Here, we present a 1,350-ka accumulation rate record of the planktic foraminiferal species Globorotalia menardii. We demonstrate that, according to previous assumptions, the presence and reseeding of this fauna in the subtropical southeast Atlantic was driven by interocean exchange south of Africa. The Agulhas transfer strengthened at glacial ice-volume maxima for every glacial-interglacial transition, with maximum reinforcements organized according to a 400-ka periodicity. The long-term dynamics of Agulhas leakage may have played a crucial role in regulating meridional overturning circulation and global climate changes during the Mid-Brunhes event and the Mid-Pleistocene transition, and could also play an important role in the near future. PMID:22508999

  17. Ocean Virtual Laboratory: A New Way to Explore Multi-Sensor Synergy Demonstrated over the Agulhas Region

    NASA Astrophysics Data System (ADS)

    Collard, F.; Quartly, G. D.; Konik, M.; Johannessen, J. A.; Korosov, A.; Chapron, B.; Piolle, J.-F.; Herledan, S.; Darecki, M.; Isar, A.; Nafornita, C.

    2015-12-01

    Ocean Virtual Laboratory is an ESA-funded project to prototype the concept of a single point of access for all satellite remote-sensing data with ancillary model output and in situ measurements for a given region. The idea is to provide easy access for the non-specialist to both data and state-of-the-art processing techniques and enable their easy analysis and display. The project, led by OceanDataLab, is being trialled in the region of the Agulhas Current, as it contains signals of strong contrast (due to very energetic upper ocean dynamics) and special SAR data acquisitions have been recorded there. The project also encourages the take up of Earth Observation data by developing training material to help those not in large scientific or governmental organizations make the best use of what data are available. The website for access is: http://ovlproject.oceandatalab.com/

  18. [alpha]-particle transport-driven current in tokamaks

    SciTech Connect

    Heikkinen, J.A. ); Sipilae, S.K. )

    1995-03-01

    It is shown that the radial transport of fusion-born energetic [alpha] particles, induced by electrostatic waves traveling in one poloidal direction, is directly connected to a net momentum of [alpha] particles in the toroidal direction in tokamaks. Because the momentum change is almost independent of toroidal velocity, the energy required for the momentum generation remains small on an [alpha]-particle population sustained by an isotropic time-independent source. By numerical toroidal Monte Carlo calculations it is shown that the current carried by [alpha] particles in the presence of intense well penetrated waves can reach several mega-amperes in reactor-sized tokamaks. The current obtained can greatly exceed the neoclassical bootstrap current of the [alpha] particles.

  19. The Euler current and relativistic parity odd transport

    NASA Astrophysics Data System (ADS)

    Golkar, Siavash; Roberts, Matthew M.; Son, Dam T.

    2015-04-01

    For a spacetime of odd dimensions endowed with a unit vector field, we introduce a new topological current that is identically conserved and whose charge is equal to the Euler character of the even dimensional spacelike foliations. The existence of this current allows us to introduce new Chern-Simons-type terms in the effective field theories describing relativistic quantum Hall states and (2 + 1) dimensional superfluids. Using effective field theory, we calculate various correlation functions and identify transport coefficients. In the quantum Hall case, this current provides the natural relativistic generalization of the Wen-Zee term, required to characterize the shift and Hall viscosity in quantum Hall systems. For the superfluid case this term is required to have nonzero Hall viscosity and to describe superfluids with non s-wave pairing.

  20. Global temperature responses to current emissions from the transport sectors

    PubMed Central

    Berntsen, Terje; Fuglestvedt, Jan

    2008-01-01

    Transport affects climate directly and indirectly through mechanisms that cause both warming and cooling of climate, and the effects operate on very different timescales. We calculate climate responses in terms of global mean temperature and find large differences between the transport sectors with respect to the size and mix of short- and long-lived effects, and even the sign of the temperature response. For year 2000 emissions, road transport has the largest effect on global mean temperature. After 20 and 100 years the response in net temperature is 7 and 6 times higher, respectively, than for aviation. Aviation and shipping have strong but quite uncertain short-lived warming and cooling effects, respectively, that dominate during the first decades after the emissions. For shipping the net cooling during the first 4 decades is due to emissions of SO2 and NOx. On a longer timescale, the current emissions from shipping cause net warming due to the persistence of the CO2 perturbation. If emissions stay constant at 2000 levels, the warming effect from road transport will continue to increase and will be almost 4 times larger than that of aviation by the end of the century. PMID:19047640

  1. Quantum quasi-steady states in current transport

    NASA Astrophysics Data System (ADS)

    D'Agosta, Roberto; Zwolak, Michael; di Ventra, Massimiliano

    2007-03-01

    We investigate quasi-steady state solutions to transport in quantum systems by finding states which at some time minimize the change in density throughout all space and have a given current density flowing from one part of the system to another [1]. Contrary to classical dynamics, in a quantum mechanical system there are many states with a given energy and particle number which satisfy this minimization criterion. Taking as an example spinless fermions on a one-dimensional lattice, we explicitly show the phase space of a class of quasi-steady states. We also discuss the possibility of coherent and incoherent mixing of these steady state solutions leading to a new type of noise in quantum transport. [1] M. Di Ventra and T.N. Todorov J. Phys. Cond. Matt. 16, 8025 (2004).

  2. Design of a proof of principle high current transport experiment

    SciTech Connect

    Lund, S.M.; Bangerter, R.O.; Barnard, J.J.; Celata, C.M.; Faltens, A.; Friedman, A.; Kwan, J.W.; Lee, E.P.; Seidl, P.A.

    2000-01-15

    Preliminary designs of an intense heavy-ion beam transport experiment to test issues for Heavy Ion Fusion (HIF) are presented. This transport channel will represent a single high current density beam at full driver scale and will evaluate practical issues such as aperture filling factors, electrons, halo, imperfect vacuum, etc., that cannot be fully tested using scaled experiments. Various machine configurations are evaluated in the context of the range of physics and technology issues that can be explored in a manner relevant to a full scale driver. it is anticipated that results from this experiment will allow confident construction of next generation ''Integrated Research Experiments'' leading to a full scale driver for energy production.

  3. On tide-induced lagrangian residual current and residual transport: 1. Lagrangian residual current

    USGS Publications Warehouse

    Feng, Shizuo; Cheng, Ralph T.; Pangen, Xi

    1986-01-01

    Residual currents in tidal estuaries and coastal embayments have been recognized as fundamental factors which affect the long-term transport processes. It has been pointed out by previous studies that it is more relevant to use a Lagrangian mean velocity than an Eulerian mean velocity to determine the movements of water masses. Under weakly nonlinear approximation, the parameter k, which is the ratio of the net displacement of a labeled water mass in one tidal cycle to the tidal excursion, is assumed to be small. Solutions for tides, tidal current, and residual current have been considered for two-dimensional, barotropic estuaries and coastal seas. Particular attention has been paid to the distinction between the Lagrangian and Eulerian residual currents. When k is small, the first-order Lagrangian residual is shown to be the sum of the Eulerian residual current and the Stokes drift. The Lagrangian residual drift velocity or the second-order Lagrangian residual current has been shown to be dependent on the phase of tidal current. The Lagrangian drift velocity is induced by nonlinear interactions between tides, tidal currents, and the first-order residual currents, and it takes the form of an ellipse on a hodograph plane. Several examples are given to further demonstrate the unique properties of the Lagrangian residual current.

  4. The high current transport experiment for heavy ion inertial fusion

    SciTech Connect

    Prost, L.R.; Baca, D.; Bieniosek, F.M.; Celata, C.M.; Faltens, A.; Henestroza, E.; Kwan, J.W.; Leitner, M.; Seidl, P.A.; Waldron, W.L.; Cohen, R.; Friedman, A.; Grote, D.; Lund, S.M.; Molvik, A.W.; Morse, E.

    2004-05-01

    The High Current Experiment (HCX) at Lawrence Berkeley National Laboratory is part of the US program to explore heavy-ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge-dominated heavy-ion beams at high intensity (line charge density {approx} 0.2 {micro}C/m) over long pulse durations (4 {micro}s) in alternating gradient focusing lattices of electrostatic or magnetic quadrupoles. This experiment is testing transport issues resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and steering, envelope matching, image charges and focusing field nonlinearities, halo and, electron and gas cloud effects. We present the results for a coasting 1 MeV K{sup +} ion beam transported through ten electrostatic quadrupoles. The measurements cover two different fill factor studies (60% and 80% of the clear aperture radius) for which the transverse phase-space of the beam was characterized in detail, along with beam energy measurements and the first halo measurements. Electrostatic quadrupole transport at high beam fill factor ({approx}80%) is achieved with acceptable emittance growth and beam loss, even though the initial beam distribution is not ideal (but the emittance is low) nor in thermal equilibrium. We achieved good envelope control, and rematching may only be needed every ten lattice periods (at 80% fill factor) in a longer lattice of similar design. We also show that understanding and controlling the time dependence of the envelope parameters is critical to achieving high fill factors, notably because of the injector and matching section dynamics.

  5. Current approaches to enhance glutamate transporter function and expression.

    PubMed

    Fontana, Andréia C K

    2015-09-01

    L-glutamate is the predominant excitatory neurotransmitter in the CNS and has a central role in a variety of brain functions. The termination of glutamate neurotransmission by excitatory amino acid transporters (EAATs) is essential to maintain glutamate concentration low in extracellular space and avoid excitotoxicity. EAAT2/GLT-1, being the most abundant subtype of glutamate transporter in the CNS, plays a key role in regulation of glutamate transmission. Dysfunction of EAAT2 has been correlated with various pathologies such as traumatic brain injury, stroke, amyotrophic lateral sclerosis, Alzheimer's disease, among others. Therefore, activators of the function or enhancers of the expression of EAAT2/GLT-1 could serve as a potential therapy for these conditions. Translational activators of EAAT2/GLT-1, such as ceftriaxone and LDN/OSU-0212320, have been described to have significant protective effects in animal models of amyotrophic lateral sclerosis and epilepsy. In addition, pharmacological activators of the activity of EAAT2/GLT-1 have been explored for decades and are currently emerging as promising tools for neuroprotection, having potential advantages over expression activators. This review describes the current status of the search for EAAT2/GLT-1 activators and addresses challenges and limitations that this approach might encounter. Termination of glutamate neurotransmission by glutamate transporter EAAT2 is essential to maintain homeostasis in the brain and to avoid excitotoxicity. Dysfunction of EAAT2 has been correlated with various neurological pathologies. Therefore, activators of the function or enhancers of the expression of EAAT2 (green arrows) could serve as a potential therapy for these conditions. This review describes the current status of the search for EAAT2 activators and addresses challenges and limitations of this approach. PMID:26096891

  6. Current status of the PSG Monte Carlo neutron transport code

    SciTech Connect

    Leppaenen, J.

    2006-07-01

    PSG is a new Monte Carlo neutron transport code, developed at the Technical Research Centre of Finland (VTT). The code is mainly intended for fuel assembly-level reactor physics calculations, such as group constant generation for deterministic reactor simulator codes. This paper presents the current status of the project and the essential capabilities of the code. Although the main application of PSG is in lattice calculations, the geometry is not restricted in two dimensions. This paper presents the validation of PSG against the experimental results of the three-dimensional MOX fuelled VENUS-2 reactor dosimetry benchmark. (authors)

  7. Bottom current and sediment transport on San Pedro Shelf, California

    USGS Publications Warehouse

    Drake, David E.; Cacchione, David A.; Karl, Herman A.

    1985-01-01

    GEOPROBE (Geological Processes Bottom Environmental) tripods were used to measure bottom currents, pressure, and light transmission and scattering and to obtain time-series photographs of the sea floor at depths of 23 m and 67 m on San Pedro shelf between 18 April and 6 June 1978. Winds were light (< 5 m/s) with a mean direction from the southwest throughout the measurement period. Hourly averaged currents 1 m above the bottom never exceeded 21 cm/s; average speeds were about 5 cm/s at the 23-m site and 6.8 cm/s at 67 m, and the strongest currents were produced by the tides. The mean flow of bottom water was less than 3 cm/s at both GEOPROBES and was rather persistently southward (offshelf). Wave-generated bottom currents and bottom-pressure variations were sampled at hourly intervals; average wave period and wave height were 12.8 s and 0.44 m, respectively, at the 23-m site. Wave orbital velocities ranged from about 5 to 30 cm/s at 23 m and from 2 to 8 cm/s at 67 m. Bottom photographs at 67 m show that the relatively sluggish tide-generated and mean currents were below threshold velocity for the silty, very fine sand throughout the observational period. Threshold depth for wave rippling of very fine sand averaged about 28 m with a range from about 12 m to 50 m. Wave-generated currents were the only currents that exceeded threshold levels. The wave currents maintained relatively high concentrations of sediment in suspension near the bottom over the inner shelf (< 25 m), and this material (principally silt and clay) was transported offshore by the weak mean flow. Approximately 50% of this material was deposited as the bottom orbital velocities decreased to subthreshold values ( nearly equal 10-15 cm/s). The observed movement of fine sediment across the inner shelf can account for a portion of the mud content of the modern silty sands on the central shelf and on the outer shelf. However, it is clear that the sand fractions, which constitute greater than 70% of the

  8. Persistent valley currents and topological transport in gapped graphene

    NASA Astrophysics Data System (ADS)

    Levitov, Leonid

    2015-03-01

    The anomalous Hall effect (AHE), arising due to Berry curvature in materials with broken inversion symmetry, results in topological currents flowing in system bulk transversely to the applied electric field. We will discuss recent work on AHE in materials with several valleys, such as e.g. graphene and transition metal dichalcogenide monolayers, where these currents have been observed [Mak et al., Science 344, 1489 (2014); Gorbachev et al., Science 346, 448 (2014)]. Interestingly, these materials do not fit the paradigm of topological materials with Chern bands and associated topologically protected edge modes dominating (quantized) Hall conductivity. Here, in contrast, gapless edge states may be absent since they are not enforced by topology or symmetry. Further, even when present, these states are not protected against backscattering due to roughness on the atomic scale. Naively, this would lead one to conclude that topological currents cease to exist. If true, this would imply that the key manifestations, such as the valley Hall conductivity and orbital magnetization, vanish in the gapped state. We will argue that the opposite is true: the absence of conducting edge modes does not present an obstacle since valley currents can be transmitted by the bulk states in the filled Fermi sea beneath the gap. This leads to an interesting behavior: rather than being vanishingly small, valley currents reach maximum value in the gapped state. Such undergap currents can also occur as persistent currents in the thermodynamic ground state and dominate orbital magnetization in valley-polarized gapped systems. We will conclude with discussing requirements for dissipationless valley transport and argue that they can be met under realistic conditions. Based on the work done in collaboration with Yuri Lensky, Polnop Samutpraphoot and Justin Song.

  9. Stormtime transport of ring current and radiation belt ions

    NASA Technical Reports Server (NTRS)

    Chen, Margaret W.; Schulz, Michael; Lyons, L. R.; Gorney, David J.

    1993-01-01

    This is an investigation of stormtime particle transport that leads to formation of the ring current. Our method is to trace the guiding-center motion of representative ions (having selected first adiabatic invariants mu) in response to model substorm-associated impulses in the convection electric field. We compare our simulation results qualitatively with existing analytically tractable idealizations of particle transport (direct convective access and radial diffusion) in order to assess the limits of validity of these approximations. For mu approximately less than 10 MeV/G (E approximately less than 10 keV at L equivalent to 3) the ion drift period on the final (ring-current) drift shell of interest (L equivalent to 3) exceeds the duration of the main phase of our model storm, and we find that the transport of ions to this drift shell is appropriately idealized as direct convective access, typically from open drift paths. Ion transport to a final closed drift path from an open (plasma-sheet) drift trajectory is possible for those portions of that drift path that lie outside the mean stormtime separatrix between closed and open drift trajectories, For mu approximately 10-25 MeV/G (110 keV approximately less than E approximately less than 280 keV at L equivalent to 3) the drift period at L equivalent to 3 is comparable to the postulated 3-hr duration of the storm, and the mode of transport is transitional between direct convective access and transport that resembles radial diffusion. (This particle population is transitional between the ring current and radiation belt). For mu approximately greater than 25 MeV/G (radiation-belt ions having E approximately greater than 280 keV at L equivalent to 3) the ion drift period is considerably shorter than the main phase of a typical storm, and ions gain access to the ring-current region essentially via radial diffusion. By computing the mean and mean-square cumulative changes in 1/L among (in this case) 12 representative

  10. Radial transport of storm time ring current ions

    NASA Technical Reports Server (NTRS)

    Lui, A. T. Y.

    1993-01-01

    Radial transport of energetic ions for the development of the main phase of geomagnetic storms is investigated with data from the medium energy particle analyzer (MEPA) on the Charge Composition Explorer spacecraft, which monitored protons, helium ions, and the carbon-nitrogen-oxygen group, which is mostly dominated by oxygen ions. From a study of four geomagnetic storms, we show that the flux increase of these ions in the inner ring current region can be accounted for by an inward displacement of the ring current population by 0.5 to 3.5 R(E). There is a general trend that a larger inward displacement occurs at higher L shells than at lower ones. These results are in agreement with previous findings. The radially injected population consists of the prestorm population modified by substorm injections which occur on a much shorter time scale than that for a storm main phase. It is also found that the inward displacement is relatively independent of ion mass and energy, suggesting that the radial transport of these energetic ions is effected primarily by convective motion from a large electric field or by diffusion resulting from magnetic field fluctuations.

  11. Agulhas Ridge, South Atlantic: the peculiar structure of a transform fault

    NASA Astrophysics Data System (ADS)

    Uenzelmann-Neben, G.; Gohl, K.

    2003-04-01

    Transform faults constitute conservative plate boundaries, where adjacent plates are in tangential contact. Transform faults in the ocean are marked by fracture zones, which are long, linear, bathymetric depressions. One of the largest transform offsets on Earth can be found in the South Atlantic. The 1200 km long Agulhas Falkland Fracture Zone (AFFZ), form by this, developed during the Early Cretaceous break-up of West Gondwana. Between approx. 41°S, 16°E and 43°S, 9°E the Agulhas Falkland Fracture Zone is characterised by a pronounced topographic anomaly, the Agulhas Ridge. The Agulhas Ridge rises more than 2 km above the surrounding seafloor. The only equivalent to this kind of topographic high, as part of the AFFZ, is found in form of marginal ridges along the continental parts of the fracture zone, namely the Falkland Escarpment at the South American continent and the Diaz Ridge adjacent to South Africa. But the Agulhas Ridge differs from both the Falkland Escarpment and the Diaz Ridge in the facts (1) that it was not formed during the early rift-drift phase, and (2) that it separates oceanic crust of different age and not continental from oceanic crust. A set of high-resolution seismic reflection data (total length 2000 km) and a seismic refraction line across the Agulhas Ridge give new information on the crustal and basement structure of this tectonic feature. We have observed that within the Cape Basin, to the North, the basement and sedimentary layers are in parts strongly deformed. We observe basement highs, which point towards intrusions. Both the basement and the sedimentary sequence show strong faulting. This points towards a combined tectono-magmatic activity, which led to the formation of basement ridges parallel to the Agulhas Ridge. Since at least the pre-Oligocene parts and, locally, the whole sedimentary column are affected we infer that the renewed activity began in the Middle Oligocene and may have lasted into the Quaternary. As an origin

  12. Pure spin current transport in Alq3 by spin pumping

    NASA Astrophysics Data System (ADS)

    Jiang, Shengwei; Wang, Peng; Luan, Zhongzhi; Tao, Xinde; Ding, Haifeng; Wu, Di

    2015-03-01

    The use of organic semiconductors (OSCs) in spintronics has aroused considerable interests, owing to their much longer spin-relaxation times of OSCs than those of inorganic counterparts. The most studied example is the organic spin valve (OSV), in which magnetoresistance (MR) effect is frequently reported. However, studies on pure spin current injection and transport in OSCs are scarce. Recently, the pioneering work by Watanabe et al. demonstrated that pure spin current can be pumped into and propagates in semiconducting polymers. In the present work we extend the study to small molecule OSCs, and demonstrate that pure spin current can be injected into Alq3 from the adjacent magnetic insulator Y3Fe5O12 (YIG) by spin pumping. The pure spin current is detected by inverse spin Hall effect (ISHE) in Pd after propagation through Alq3. From the ISHE voltage VISHE as a function of the Alq3 thickness, the spin diffusion length is determined to be ~ 50 nm and does not depend on temperature. This result indicates the MR decrease as increasing temperature in OSVs is not due to the reduced spin diffusion length.

  13. Currents and Transport across the eastern Sabrina Basin, East Antarctica

    NASA Astrophysics Data System (ADS)

    Zielinski, N. J.; Orsi, A. H.; Webb, C.

    2015-12-01

    Freshwater budgets of some Antarctic continental shelf sectors are key to the global Meridional Overturning Circulation. Poorly understood interactions of marginal currents with glaciers and ice-shelves are reported to have a sea level rise potential of about 50 m. The Moscow University Ice Shelf (MUIS) and Totten Glacier (TG) system alone accounts for one-eighth of East Antarctic Ice Sheet discharge, roughly the same as estimated for total Western Antarctic Ice Sheet drainage. Observational studies of the circulation, stratification, and exchange of oceanic, shelf and melt waters in the adjacent Sabrina Basin began in in the austral summer of 2014, with a unique set of shipboard measurements aboard the RVI Nathaniel B. Palmer. Among them are, for the first time over Antarctic margins, simultaneous underway profiling of ocean currents, temperature and salinity. Optimally averaged and quality controlled data from the Shipboard Acoustic Dopper Current Profiler (SADCP) and Underway Conductivity/Temperature/Depth (uCTD) system are analyzed to map flow patterns from the surface to the bottom. Unprecedented spatial (~1 km) and temporal (~30 min) profiling allowed the completion of multiple synoptic sections that effectively resolved the main characteristics of the slope (ASC) and Antarctic Coastal Current (ACoC). Adjusted geostrophic currents and volume transport across these sections were calculated for density layers spanning surface and thermocline waters with oceanic and shelf origin. After following the western flank of the Dalton Ice Tongue (DIT) to the south, the ACoC turns westward and continues alonog the MUIS front toward TG. Injection of meltwater to the ACoC at varying levels is revealed along this path. Highly contrasting bottom topography is also observed to differentially steer bottom waters. A smooth sedimentary dome found below the Dalton Polynya appears to drive an interior recirculation; whereas a relaitvely rough and narrow escarpment flank in front

  14. Hysteresis in Transport Critical-Current Measurements of Oxide Superconductors

    PubMed Central

    Goodrich, L. F.; Stauffer, T. C.

    2001-01-01

    We have investigated magnetic hysteresis in transport critical-current (Ic) measurements of Ag-matrix (Bi,Pb)2Sr2Ca2Cu3O10–x (Bi-2223) and AgMg-matrix Bi2Sr2CaCu2O8+x (Bi-2212) tapes. The effect of magnetic hysteresis on the measured critical current of high temperature superconductors is a very important consideration for every measurement procedure that involves more than one sweep of magnetic field, changes in field angle, or changes in temperature at a given field. The existence of this hysteresis is well known; however, the implications for a measurement standard or interlaboratory comparisons are often ignored and the measurements are often made in the most expedient way. A key finding is that Ic at a given angle, determined by sweeping the angles in a given magnetic field, can be 17 % different from the Ic determined after the angle was fixed in zero field and the magnet then ramped to the given field. Which value is correct is addressed in the context that the proper sequence of measurement conditions reflects the application conditions. The hysteresis in angle-sweep and temperature-sweep data is related to the hysteresis observed when the field is swept up and down at constant angle and temperature. The necessity of heating a specimen to near its transition temperature to reset it to an initial state between measurements at different angles and temperatures is discussed. PMID:27500042

  15. Deciphering ionic current signatures of DNA transport through a nanopore

    PubMed Central

    Aksimentiev, Aleksei

    2010-01-01

    Within just a decade from the pioneering work demonstrating the utility of nanopores for molecular sensing, nanopores have emerged as versatile systems for single molecule manipulation and analysis. In a typical setup, a gradient of the electrostatic potential captures charged solutes from the solution and forces them to move through a single nanopore, across otherwise impermeable membrane. The ionic current blockades resulting from the presence of a solute in a nanopore can reveal the type of the solute, for example, the nucleotide makeup of a DNA strand. Despite great successes, the microscopic mechanisms underlying the functionality of such stochastic sensors remain largely unknown, as it is not currently possible to characterize the microscopic conformations of single biomolecules directly in a nanopore and thereby unequivocally establish the causal relationship between the observables and the microscopic events. Such a relationship can be determined using molecular dynamics—a computational method that can accurately predicts the time evolution of a molecular system starting from a given microscopic state. This article describes recent applications of this method to the process of DNA transport through biological and synthetic nanopores. PMID:20644747

  16. Evaluating plasmonic transport in current-carrying silver nanowires.

    PubMed

    Song, Mingxia; Stolz, Arnaud; Zhang, Douguo; Arocas, Juan; Markey, Laurent; Colas des Francs, Gérard; Dujardin, Erik; Bouhelier, Alexandre

    2013-01-01

    Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support. In this context, metal nanowires are especially desirable for realizing dense routing networks. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires randomly distributed on a glass substrate. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry. PMID:24378340

  17. Evaluating plasmonic transport in current-carrying silver nanowires.

    PubMed

    Song, Mingxia; Stolz, Arnaud; Zhang, Douguo; Arocas, Juan; Markey, Laurent; Colas des Francs, Gérard; Dujardin, Erik; Bouhelier, Alexandre

    2013-12-11

    Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support. In this context, metal nanowires are especially desirable for realizing dense routing networks. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires randomly distributed on a glass substrate. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry.

  18. Electron Cyclotron Current Drive by Radial Transport of Particles in the Continuous Current Tokamak

    NASA Astrophysics Data System (ADS)

    Park, Sanghyun

    dependence of the current generated, and its independence of the wave launch angles indicate that the nature of the plasma current driven is due to the radial transport of particles acted upon by the poloidal field, and not by the Dopper-shifted resonance absorption of wave energy by fast particles. This is further evidenced by the effect of horizontal field on the radial current profile, where current profile can be reserved for null current or it can be unidirectional for maximum current.

  19. LDL–cholesterol transport to the endoplasmic reticulum: current concepts

    PubMed Central

    Pfisterer, Simon G.; Peränen, Johan; Ikonen, Elina

    2016-01-01

    Purpose of review In this article, we summarize the present information related to the export of LDL-derived cholesterol from late endosomes, with a focus on Nieman-Pick disease, type C1 (NPC1) cholesterol delivery toward the endoplasmic reticulum (ER). We review data suggesting that several pathways may operate in parallel, including membrane transport routes and membrane contact sites (MCSs). Recent findings There is increasing appreciation that MCSs provide an important mechanism for intermembrane lipid transfer. In late endosome–ER contacts, three protein bridges involving oxysterol binding protein related protein (ORP)1L-vesicle associated membrane protein-associated protein (VAP), steroidogenic acute regulatory protein (StAR)D3-VAP and ORP5-NPC1 proteins have been reported. How much they contribute to the flux of LDL–cholesterol to the ER is currently open. Studies for lipid transfer via MCSs have been most advanced in Saccharomyces cerevisiae. Recently, a new sterol-binding protein family conserved between yeast and man was identified. Its members localize at MCSs and were named lipid transfer protein anchored at membrane contact sites (Lam) proteins. In yeast, sterol transfer between the ER and the yeast lysosome may be facilitated by a Lam protein. Summary Increasing insights into the role of MCSs in directional sterol delivery between membranes propose that they might provide routes for LDL–cholesterol transfer to the ER. Future work should reveal which specific contacts may operate for this, and how they are controlled by cholesterol homeostatic machineries. PMID:27054443

  20. Clast comminution during pyroclastic density current transport: Mt St Helens

    NASA Astrophysics Data System (ADS)

    Dawson, B.; Brand, B. D.; Dufek, J.

    2011-12-01

    Volcanic clasts within pyroclastic density currents (PDCs) tend to be more rounded than those in fall deposits. This rounding reflects degrees of comminution during transport, which produces an increase in fine-grained ash with distance from source (Manga, M., Patel, A., Dufek., J. 2011. Bull Volcanol 73: 321-333). The amount of ash produced due to comminution can potentially affect runout distance, deposit sorting, the volume of ash lofted into the upper atmosphere, and increase internal pore pressure (e.g., Wohletz, K., Sheridan, M. F., Brown, W.K. 1989. J Geophy Res, 94, 15703-15721). For example, increased pore pressure has been shown to produce longer runout distances than non-comminuted PDC flows (e.g., Dufek, J., and M. Manga, 2008. J. Geophy Res, 113). We build on the work of Manga et al., (2011) by completing a pumice abrasion study for two well-exposed flow units from the May 18th, 1980 eruption of Mt St Helens (MSH). To quantify differences in comminution from source, sampling and the image analysis technique developed in Manga et al., 2010 was completed at distances proximal, medial, and distal from source. Within the units observed, data was taken from the base, middle, and pumice lobes within the outcrops. Our study is unique in that in addition to quantifying the degree of pumice rounding with distance from source, we also determine the possible range of ash sizes produced during comminution by analyzing bubble wall thickness of the pumice through petrographic and SEM analysis. The proportion of this ash size is then measured relative to the grain size of larger ash with distance from source. This allows us to correlate ash production with degree of rounding with distance from source, and determine the fraction of the fine ash produced due to comminution versus vent-fragmentation mechanisms. In addition we test the error in 2D analysis by completing a 3D image analysis of selected pumice samples using a Camsizer. We find that the roundness of PDC

  1. Mechanisms of the meridional heat transport in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Volkov, Denis L.; Fu, Lee-Lueng; Lee, Tong

    2010-08-01

    The Southern Ocean (SO) transports heat towards Antarctica and plays an important role in determining the heat budget of the Antarctic climate system. A global ocean data synthesis product at eddy-permitting resolution from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project is used to estimate the meridional heat transport (MHT) in the SO and to analyze its mechanisms. Despite the intense eddy activity, we demonstrate that most of the poleward MHT in the SO is due to the time-mean fields of the meridional velocity, V, and potential temperature, θ. This is because the mean circulation in the SO is not strictly zonal. The Antarctic Circumpolar Current carries warm waters from the region south of the Agulhas Retroflection to the lower latitudes of the Drake Passage and the Malvinas Current carries cold waters northward along the Argentinian shelf. Correlations between the time-varying fields of V and θ (defined as transient processes) significantly contribute to the horizontal-gyre heat transport, but not the overturning heat transport. In the highly energetic regions of the Agulhas Retroflection and the Brazil-Malvinas Confluence the contribution of the horizontal transient processes to the total MHT exceeds the contribution of the mean horizontal flow. We show that the southward total MHT is mainly maintained by the meridional excursion of the mean geostrophic horizontal shear flow (i.e., deviation from the zonal average) associated with the Antarctic Circumpolar Current that balances the equatorward MHT due to the Ekman transport and provides a net poleward MHT in the SO. The Indian sector of the SO serves as the main pathway for the poleward MHT.

  2. Multicentennial Agulhas leakage variability and links to North Atlantic climate during the past 80,000 years

    NASA Astrophysics Data System (ADS)

    Dyez, Kelsey A.; Zahn, Rainer; Hall, Ian R.

    2014-12-01

    New high-resolution sea surface temperature (SST) and sea surface salinity (SSS) estimates are presented from the Agulhas Bank slope in the Atlantic sector of the Agulhas Corridor using planktic foraminiferal (Globigerinoides ruber) δ18O and Mg/Ca-derived SST. By focusing on the last 80,000 years, this is the first fine-scale Agulhas leakage record that overlaps in time with much of the Greenland ice core record of abrupt climate changes in the North Atlantic region. The multicentennial profiles indicate instances of warm SST and/or increased SSS coincident with Northern Hemisphere cool periods, followed by Northern Hemisphere warming. These periods of enhanced SST and SSS in the Agulhas Corridor occur at the last glacial termination (T1) and during North Atlantic cold episodes associated with Heinrich (H) meltwater events. To a first-order approximation, the timing of maximal salinity events in relation to periods of North Atlantic freshwater perturbation is consistent with the concept suggested by climate models that enhanced Agulhas leakage provides for buoyancy compensation and can potentially trigger increased convective activity in the North Atlantic, thereby restoring Atlantic overturning circulation after relatively weak states.

  3. Theoretical monochromatic-wave-induced currents in intermediate water with viscosity and nonzero mass transport

    NASA Technical Reports Server (NTRS)

    Talay, T. A.

    1975-01-01

    Wave-induced mass-transport current theories with both zero and nonzero net mass (or volume) transport of the water column are reviewed. A relationship based on the Longuet-Higgens theory is derived for wave-induced, nonzero mass-transport currents in intermediate water depths for a viscous fluid. The relationship is in a form useful for experimental applications; therefore, some design criteria for experimental wave-tank tests are also presented. Sample parametric cases for typical wave-tank conditions and a typical ocean swell were assessed by using the relation in conjunction with an equation developed by Unluata and Mei for the maximum wave-induced volume transport. Calculations indicate that substantial changes in the wave-induced mass-transport current profiles may exist dependent upon the assumed net volume transport. A maximum volume transport, corresponding to an infinite channel or idealized ocean condition, produces the largest wave-induced mass-transport currents. These calculations suggest that wave-induced mass-transport currents may have considerable effects on pollution and suspended-sediments transport as well as buoy drift, the surface and midlayer water-column currents caused by waves increasing with increasing net volume transports. Some of these effects are discussed.

  4. Current transport mechanisms in mercury cadmium telluride diode

    NASA Astrophysics Data System (ADS)

    Gopal, Vishnu; Li, Qing; He, Jiale; He, Kai; Lin, Chun; Hu, Weida

    2016-08-01

    This paper reports the results of modelling of the current-voltage characteristics (I-V) of a planar mid-wave Mercury Cadmium Telluride photodiode in a gate controlled diode experiment. It is reported that the diode exhibits nearly ideal I-V characteristics under the optimum surface potential leading to the minimal surface leakage current. Deviations from the optimum surface potential lead to non ideal I-V characteristics, indicating a strong relationship between the ideality factor of the diode with its surface leakage current. Diode's I-V characteristics have been modelled over a range of gate voltages from -9 V to -2 V. This range of gate voltages includes accumulation, flat band, and depletion and inversion conditions below the gate structure of the diode. It is shown that the I-V characteristics of the diode can be very well described by (i) thermal diffusion current, (ii) ohmic shunt current, (iii) photo-current due to background illumination, and (iv) excess current that grows by the process of avalanche multiplication in the gate voltage range from -3 V to -5 V that corresponds to the optimum surface potential. Outside the optimum gate voltage range, the origin of the excess current of the diode is associated with its high surface leakage currents. It is reported that the ohmic shunt current model applies to small surface leakage currents. The higher surface leakage currents exhibit a nonlinear shunt behaviour. It is also shown that the observed zero-bias dynamic resistance of the diode over the entire gate voltage range is the sum of ohmic shunt resistance and estimated zero-bias dynamic resistance of the diode from its thermal saturation current.

  5. [Current views on oxygen transport from blood to tissues].

    PubMed

    Ivanov, K P

    2001-01-01

    During the recent 25-30 years, sophisticated experiments and mathematical simulation significantly changed the generally accepted theory of oxygen transport in tissue, which was based on two major postulates, namely: 1) Blood flows in capillaries continuously at uniform velocity, 2) Gas circulation between blood and tissue takes place exclusively in capillaries. As was shown by modern research techniques, blood flow in microvessels has irregular sharp velocity fluctuations in very short time intervals (seconds). In addition, mean velocity of blood flow in microvessels of the same caliber and the same micro-region of tissue may differ several times. Therefore, efficiency of microcirculation reactions may be assessed exclusively witH mean blood velocity in capillaries of the whole micro-region, and with complicated changes of the histogram of mean velocity distribution in capillaries. It was shown that arteriolas and venulas of inactive muscles and brain account for 30 to 50% of gas circulation between blood and tissue. This resulted in fundamental change of the previous postulates in the area of tissue gas circulation physiology, and, in effect, in replacement of oxygen transport paradigm created by A. Krog. This study is an attempt to present a new modern concept of oxygen transport in tissue, to show its research significance, and possible applications. PMID:11764645

  6. 40 CFR 93.114 - Criteria and procedures: Currently conforming transportation plan and TIP.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... conforming transportation plan and TIP. 93.114 Section 93.114 Protection of Environment ENVIRONMENTAL..., Programs, and Projects Developed, Funded or Approved Under Title 23 U.S.C. or the Federal Transit Laws § 93... currently conforming transportation plan and currently conforming TIP at the time of project approval, or...

  7. 40 CFR 93.114 - Criteria and procedures: Currently conforming transportation plan and TIP.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... conforming transportation plan and TIP. 93.114 Section 93.114 Protection of Environment ENVIRONMENTAL..., Programs, and Projects Developed, Funded or Approved Under Title 23 U.S.C. or the Federal Transit Laws § 93... currently conforming transportation plan and currently conforming TIP at the time of project approval, or...

  8. n value and Jc distribution dependence of AC transport current losses in HTS conductors

    NASA Astrophysics Data System (ADS)

    Ogawa, Jun; Sawai, Yusuke; Nakayama, Haruki; Tsukamoto, Osami; Miyagi, Daisuke

    2004-01-01

    Compared with LTS materials, HTS materials have some peculiarities affecting AC loss characteristics of the conductors. We measured the AC transport current losses in YBCO thin film coated conductors and a Bi2223/Ag sheathed tape. Comparing the measured data with analytical calculations, the dependence of the AC transport current losses on the n value and critical current density distributions are studied. It is shown that, considering the n values and Jc distributions, the peculiarities in the HTS materials can be taken into consideration and the transport current losses in HTS conductors can be calculated by the same analytical method used for LTS.

  9. Current problems in the study of colloidal transport in soil

    NASA Astrophysics Data System (ADS)

    Shein, E. V.; Devin, B. A.

    2007-04-01

    A review of recent literature on the transport of organic and mineral colloids in soils demonstrated the role of such factors as the extrema of water flow velocities, the anisotropy of physical properties, and the presence of preferential water flows in macropores and fissures. In unsaturated soils, the concentration of colloids at the gas-water interphace and the amphiphilicity of their surface are of great importance. The transfer of “living collids” (bacteria and viruses) is mainly due to the convection mechanism; however, of great importance are the entrapping of microorganisms in fine pores, their adsorption (adhesion), their concentration on the gas-water interphace, their sedimentation, and the affecting chemical factors, such as the ionic strength and the pH of the solution. The effect of biological factors is related to the size of cells, chemotaxic mobility, and the growth and reproduction of the microbial biomass. The focal points of recent studies on colloid transport are considered: the study of mechanisms of colloid mobilization under different conditions, the improvement of methods for the direct observation of colloid migration (micromodels, computer tomography, etc.), and the possibility of quantitative description of the entrapping of colloidal particles in soil pores.

  10. Secondary Flows and Sediment Transport due to Wave - Current Interaction

    NASA Astrophysics Data System (ADS)

    Ismail, Nabil; Wiegel, Robert

    2015-04-01

    Objectives: The main purpose of this study is to determine the modifications of coastal processes driven by wave-current interaction and thus to confirm hydrodynamic mechanisms associated with the interaction at river mouths and tidal inlets where anthropogenic impacts were introduced. Further, the aim of the work has been to characterize the effect of the relative strength of momentum action of waves to the opposing current on the nearshore circulation where river flow was previously effective to entrain sediments along the shoreline. Such analytical information are useful to provide guidelines for sustainable design of coastal defense structures. Methodology and Analysis: Use is made of an earlier study reported by the authors (1983) on the interaction of horizontal momentum jets and opposing shallow water waves at shorelines, and of an unpublished laboratory study (1980). The turbulent horizontal discharge was shore-normal, directed offshore, and the incident wave direction was shore-normal, travelling toward shore. Flow visualization at the smooth bottom and the water surface, velocity and water surface elevation measurements were made. Results were obtained for wave , current modifications as well as the flow pattern in the jet and the induced circulation on both sides of the jet, for a range of wave and jet characteristics. The experimental data, obtained from measurement in the 3-D laboratory basin, showed several distinct flow pattern regimes on the bottom and the water surface. The observed flow circulation regimes were found to depend on the ratio of the wave momentum action on the jet to the jet initial momentum. Based on the time and length scales of wave and current parameters and using the time average of the depth integrated conservation equations, it is found that the relative strength of the wave action on the jet could be represented by a dimensionless expression; Rsm ( ) 12ρSa20g-L0h-Cg- 2 Rsm ≈ (C0 - U) /ρ0U w (1) In the above dimensionless

  11. Currents, drag, and sediment transport induced by a tsunami

    USGS Publications Warehouse

    Lacy, Jessica R.; Rubin, David M.; Buscombe, Daniel

    2012-01-01

    We report observations of water surface elevation, currents, and suspended sediment concentration (SSC) from a 10-m deep site on the inner shelf in northern Monterey Bay during the arrival of the 2010 Chile tsunami. Velocity profiles were measured from 3.5 m above the bed (mab) to the surface at 2 min intervals, and from 0.1 to 0.7 mab at 1 Hz. SSC was determined from the acoustic backscatter of the near-bed profiler. The initial tsunami waves were directed cross shore and had a period of approximately 16 min. Maximum wave height was 1.1 m, and maximum current speed was 0.36 m/s. During the strongest onrush, near-bed velocities were clearly influenced by friction and a logarithmic boundary layer developed, extending more than 0.3 mab. We estimated friction velocity and bed shear stress from the logarithmic profiles. The logarithmic structure indicates that the flow can be characterized as quasi-steady at these times. At other phases of the tsunami waves, the magnitude of the acceleration term was significant in the near-bed momentum equation, indicating unsteady flow. The maximum tsunami-induced bed shear stress (0.4 N/m2) exceeded the critical shear stress for the medium-grained sand on the seafloor. Cross-shore sediment flux was enhanced by the tsunami. Oscillations of water surface elevation and currents continued for several days. The oscillations were dominated by resonant frequencies, the most energetic of which was the fundamental longitudinal frequency of Monterey Bay. The maximum current speed (hourly-timescale) in 18 months of observations occurred four hours after the tsunami arrived.

  12. RETURN CURRENTS AND ENERGY TRANSPORT IN THE SOLAR FLARING ATMOSPHERE

    SciTech Connect

    Codispoti, Anna; Torre, Gabriele; Piana, Michele; Pinamonti, Nicola

    2013-08-20

    According to the standard Ohmic perspective, the injection of accelerated electrons into the flaring region violates local charge equilibrium and therefore, in response, return currents are driven by an electric field to equilibrate such charge violation. In this framework, the energy loss rate associated with these local currents has an Ohmic nature and significantly shortens the accelerated electron path. In the present paper, we adopt a different viewpoint and, specifically, we study the impact of the background drift velocity on the energy loss rate of accelerated electrons in solar flares. We first utilize the Rutherford cross-section to derive the formula of the energy loss rate when the collisional target has a finite temperature and the background instantaneously and coherently moves up to equilibrate the electron injection. We then use the continuity equation for electrons and imaging spectroscopy data provided by RHESSI to validate this model. We show that this new formula for the energy loss rate provides a better fit of the experimental data with respect to the model based on the effects of standard Ohmic return currents.

  13. Potential of space-borne GNSS reflectometry to constrain simulations of the ocean circulation. A case study for the South African current system

    NASA Astrophysics Data System (ADS)

    Saynisch, Jan; Semmling, Maximilian; Wickert, Jens; Thomas, Maik

    2015-11-01

    The Agulhas current system transports warm and salty water masses from the Indian Ocean into the Southern Ocean and into the Atlantic. The transports impact past, present, and future climate on local and global scales. The size and variability, however, of the respective transports are still much debated. In this study, an idealized model based twin experiment is used to study whether sea surface height (SSH) anomalies estimated from reflected signals of the Global Navigation Satellite System reflectometry (GNSS-R) can be used to determine the internal water mass properties and transports of the Agulhas region. A space-borne GNSS-R detector on the International Space Station (ISS) is assumed and simulated. The detector is able to observe daily SSH fields with a spatial resolution of 1-5∘. Depending on reflection geometry, the precision of a single SSH observation is estimated to reach 3 cm (20 cm) when the carrier phase (code delay) information of the reflected GNSS signal is used. The average precision over the Agulhas region is 7 cm (42 cm). The proposed GNSS-R measurements surpass the radar-based satellite altimetry missions in temporal and spatial resolution but are less precise. Using the estimated GNSS-R characteristics, measurements of SSH are generated by sampling a regional nested general circulation model of the South African oceans. The artificial observations are subsequently assimilated with a 4DVAR adjoint data assimilation method into the same ocean model but with a different initial state and forcing. The assimilated and the original, i.e., the sampled model state, are compared to systematically identify improvements and degradations in the model variables that arise due to the assimilation of GNSS-R based SSH observations. We show that SSH and the independent, i.e., not assimilated model variables velocity, temperature, and salinity improve by the assimilation of GNSS-R based SSH observations. After the assimilation of 90 days of SSH observations

  14. Secondary Flows and Sediment Transport due to Wave - Current Interaction

    NASA Astrophysics Data System (ADS)

    Ismail, Nabil; Wiegel, Robert

    2015-04-01

    Objectives: The main purpose of this study is to determine the modifications of coastal processes driven by wave-current interaction and thus to confirm hydrodynamic mechanisms associated with the interaction at river mouths and tidal inlets where anthropogenic impacts were introduced. Further, the aim of the work has been to characterize the effect of the relative strength of momentum action of waves to the opposing current on the nearshore circulation where river flow was previously effective to entrain sediments along the shoreline. Such analytical information are useful to provide guidelines for sustainable design of coastal defense structures. Methodology and Analysis: Use is made of an earlier study reported by the authors (1983) on the interaction of horizontal momentum jets and opposing shallow water waves at shorelines, and of an unpublished laboratory study (1980). The turbulent horizontal discharge was shore-normal, directed offshore, and the incident wave direction was shore-normal, travelling toward shore. Flow visualization at the smooth bottom and the water surface, velocity and water surface elevation measurements were made. Results were obtained for wave , current modifications as well as the flow pattern in the jet and the induced circulation on both sides of the jet, for a range of wave and jet characteristics. The experimental data, obtained from measurement in the 3-D laboratory basin, showed several distinct flow pattern regimes on the bottom and the water surface. The observed flow circulation regimes were found to depend on the ratio of the wave momentum action on the jet to the jet initial momentum. Based on the time and length scales of wave and current parameters and using the time average of the depth integrated conservation equations, it is found that the relative strength of the wave action on the jet could be represented by a dimensionless expression; Rsm ( ) 12ρSa20g-L0h-Cg- 2 Rsm ≈ (C0 - U) /ρ0U w (1) In the above dimensionless

  15. Public transportation 1995: Current research in planning, management, technology, and ridesharing. Transportation research record

    SciTech Connect

    1995-12-31

    ;Partial Contents: Long-Range Planning Issues for Small Transit Agencies; Methods and Strategies for Transit Benefit Measurement; Relationships Between Public Transport Finance and National Economy in The Netherlands; Modifying Transit Mode Share in Household Survey Expansion; Measuring Impacts of Transit Financing Policy in Geopolitical Context: Montreal Case; Perspective on Maglev Transit and Introduction of Personal Rapid Transit Maglev; Profile of Employee Transportation Coordinators; Demographics of Carpooling; Carpooling with Co-workers in Los Angeles: Employer Involvement Does Make a Difference; Stated Choice-Based Performance Evaluation of Selected Transportation Control Measures and Their Transfer Across Sites; and Five-Year Results of Employee Commute Options in Southern California.

  16. Ac losses for the self field of an ac transport current with a dc transport current offset in high {Tc} superconducting magnet coils for MagLev application

    SciTech Connect

    Koosh, V.F.

    1993-10-01

    Although much research has been conducted concerning the losses of high-{Tc} superconductors, very little has concentrated on the self-field losses in an actual magnet arrangement. The coils studied in this work were designed for use as actual magnets in an industrial application. Self field loss measurements were made upon tape-wound 2223 superconducting helix coils. The self-field losses were produced by an AC transport current with a DC transport current offset. Losses were taken for single, double and triple tape windings, giving essentially monofilament, dual, and three filament cases. The losses measured here were varied over a range of AC current values for several different DC values, and over a range of frequencies. The currents were all AC sinusoids with a DC offset. All measurements were made at T = 77K.

  17. Effects of solution mass transport on the ECC ozonesonde background current. [Electrochemical Concentration Cell

    NASA Technical Reports Server (NTRS)

    Thornton, D. C.; Niazy, N.

    1983-01-01

    A technique is developed to measure the effective mass transport parameter for the electrochemical concentration cell (ECC) ozonesonde in order to determine the mass transport rate constant for the ECC as a function of pressure. It is shown that a pressure dependent factor in the background current originates in a convective mass transport parameter. It is determined that for atmospheric pressures greater than 100 mb the mass transport parameter is a constant, while at pressures less than 100 mb it decreases logarithmically with pressure. It is suggested that the background current correction is directly correlated to the mass transport parameter pressure dependence. The presently used background current correction, which is based on the partial pressure of oxygen, is found to lead to an overestimation of the integrated ozone value in the troposphere for the ECC ozonesonde data.

  18. Current-based detection of nonlocal spin transport in graphene for spin-based logic applications

    SciTech Connect

    Wen, Hua; Amamou, Walid; Zhu, Tiancong; Luo, Yunqiu; Kawakami, Roland K.

    2014-05-07

    Graphene has been proposed for novel spintronic devices due to its robust and efficient spin transport properties at room temperature. Some of the most promising proposals require current-based readout for integration purposes, but the current-based detection of spin accumulation has not yet been developed. In this work, we demonstrate current-based detection of spin transport in graphene using a modified nonlocal geometry. By adding a variable shunt resistor in parallel to the nonlocal voltmeter, we are able to systematically cross over from the conventional voltage-based detection to current-based detection. As the shunt resistor is reduced, the output current from the spin accumulation increases as the shunt resistance drops below a characteristic value R*. We analyze this behavior using a one-dimensional drift-diffusion model, which accounts well for the observed behavior. These results provide the experimental and theoretical foundation for current-based detection of nonlocal spin transport.

  19. Transportation for School-Age Child Care: Current Status in Westchester County.

    ERIC Educational Resources Information Center

    Child Care Council of Westchester, Inc., White Plains, NY.

    Based on countywide interviews with transportation and child care personnel in Westchester County, New York, this report describes current practices, legislation, and issues related to the transportation of elementary school children to and from child care providers. Following a brief introduction, the report discusses various regulated and…

  20. Spin polarized current injection and transportation in a double T-shaped organic spintronic device

    NASA Astrophysics Data System (ADS)

    Ren, JunFeng; Song, RuiRong; Yuan, XiaoBo; Hu, GuiChao

    2015-03-01

    A double T-shaped device model is constructed to investigate the spin polarized current injection and transportation properties in organic semiconductors. Based on the spin diffusion theory and Ohm's law and considering the different charge-spin relationship of the special carriers in organic semiconductors, the current spin polarization has been obtained. Effects of the branch current ratio and the polaron proportion on the spin polarized current injection efficiency are studied. From the calculation, it is found that the improvement of the spin polarized current injection efficiency can be obtained by adjusting the branch current ratio; moreover, high polaron proportion in organic semiconductors is beneficial for obtaining high current spin polarization.

  1. The freshwater transport and dynamics of the western Maine coastal current

    USGS Publications Warehouse

    Geyer, W.R.; Signell, R.P.; Fong, D.A.; Wang, Jingyuan; Anderson, D.M.; Keafer, B.A.

    2004-01-01

    Observations in the Gulf of Maine, USA, were used to characterize the freshwater transport, temporal variability and dynamics of the western Maine coastal current. These observations included moored measurements, multiple hydrographic surveys, and drifter releases during April-July of 1993 and 1994. There is a strong seasonal signal in salinity and along-shore velocity of the coastal current, caused by the freshwater inputs of the rivers entering the western Gulf. Surface salinity within the coastal current during the spring freshet is typically 2psu below ambient, and along-shore currents in the surface layer are directed southwestward at speeds of 0.10-0.20ms-1, occasionally reaching 0.50ms-1. The plume thickness is typically 10-20m in water depths of 50-100m, thus it is well isolated from the bottom over most of its areal extent. The along-coast freshwater transport within the plume varies considerably due to variations in wind stress, but on time scales of weeks to months it follows the variations of riverine input, with a time lag consistent with the advective velocity. Less than half of the transport of the coastal current is explained by the baroclinic gradient; the barotropic forcing associated with the larger-scale dynamics of the Gulf of Maine accounts for about 60% of the transport. The volume of freshwater transport in the coastal current exceeds the local riverine input of fresh water by 30%, suggesting a significant contribution of freshwater transport from the St. John River, 500km northeastward. The measurements within the western Maine coastal current, however, indicate a significant decrease in the baroclinic transport of fresh water along the coast, with an e-folding scale of approximately 200km. ?? 2004 Elsevier Ltd. All rights reserved.

  2. Method for determining transport critical current densities and flux penetration depth in bulk superconductors

    NASA Technical Reports Server (NTRS)

    Israelsson, Ulf E. (Inventor); Strayer, Donald M. (Inventor)

    1992-01-01

    A contact-less method for determining transport critical current density and flux penetration depth in bulk superconductor material. A compressor having a hollow interior and a plunger for selectively reducing the free space area for distribution of the magnetic flux therein are formed of superconductor material. Analytical relationships, based upon the critical state model, Maxwell's equations and geometrical relationships define transport critical current density and flux penetration depth in terms of the initial trapped magnetic flux density and the ratio between initial and final magnetic flux densities whereby data may be reliably determined by means of the simple test apparatus for evaluating the current density and flux penetration depth.

  3. A Semiconductor Device Noise Model: A Deterministic Approach to Semiconductor Device Current Noise for Semiclassical Transport

    SciTech Connect

    Noaman, B. A.; Korman, C. E.

    2009-04-23

    In this paper, we present a deterministic approach to calculate terminal current noise characteristics in semiconductor devices in the framework of semiclassical transport based on the spherical harmonics of the Boltzmann Transport Equation. The model relies on the solution of the Boltzmann equation in the frequency domain with special initial and boundary conditions. The terminal current fluctuation is directly related to scattering without the additional Langevin noise term added to the calculation. Simulation results are presented for the terminal current spectral density for a 1-D n{sup +}nn{sup +} structure due to elastic-acoustic and intervally scattering.

  4. Investigation of current transport normal and parallel to the tape plane in BSCCO/Ag tapes

    SciTech Connect

    Maley, M.P.; Cho, J.H.; Willis, J.O.; Bulaevskii, L.N.

    1995-07-01

    We have performed transport, resistivity and critical current measurements on Bi-2223/Ag and Bi-2212/Ag tapes with current directions both parallel and perpendicular to the tape plane in magnetic fields up to 7 T and 50current along the tape normal exhibits magnetic field and field orientation dependences similar to those for current flow along the tape plane. These results indicate that current flow along CuO{sub 2} planes dominates current transport even along the tape normal in highly textured tapes.

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

    SciTech Connect

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

    2012-05-15

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  7. Transport of volume, heat, and salt towards the Arctic in the Faroe Current 1993-2013

    NASA Astrophysics Data System (ADS)

    Hansen, B.; Larsen, K. M. H.; Hátún, H.; Kristiansen, R.; Mortensen, E.; Østerhus, S.

    2015-09-01

    The flow of warm and saline water from the Atlantic Ocean, across the Greenland-Scotland Ridge, into the Nordic Seas - the Atlantic inflow - is split into three separate branches. The most intense of these branches is the inflow between Iceland and the Faroe Islands (Faroes), which is focused into the Faroe Current, north of the Faroes. The Atlantic inflow is an integral part of the North Atlantic thermohaline circulation (THC), which is projected to weaken during the 21st century and might conceivably reduce the oceanic heat and salt transports towards the Arctic. Since the mid-1990s, hydrographic properties and current velocities of the Faroe Current have been monitored along a section extending north from the Faroe shelf. From these in situ observations, time series of volume, heat, and salt transport have previously been reported, but the high variability of the transport has made it difficult to establish whether there are trends. Here, we present results from a new analysis of the Faroe Current where the in situ observations have been combined with satellite altimetry. For the period 1993 to 2013, we find the average volume transport of Atlantic water in the Faroe Current to be 3.8 ± 0.5 Sv (1 Sv = 106 m3 s-1) with a heat transport relative to 0 °C of 124 ± 15 TW (1 TW = 1012 W). Consistent with other results for the Northeast Atlantic component of the THC, we find no indication of weakening. The transports of the Faroe Current, on the contrary, increased. The overall increase over the 2 decades of observation was 9 ± 8 % for volume transport and 18 ± 9 % for heat transport (95 % confidence intervals). During the same period, the salt transport relative to the salinity of the deep Faroe Bank Channel overflow (34.93) more than doubled, potentially strengthening the feedback on thermohaline intensity. The increased heat and salt transports are partly caused by the increased volume transport and partly by increased temperatures and salinities of the

  8. The N-terminus of the norepinephrine transporter regulates the magnitude and selectivity of the transporter-associated leak current.

    PubMed

    Binda, Francesca; Lute, Brandon J; Dipace, Concetta; Blakely, Randy D; Galli, Aurelio

    2006-03-01

    The norepinephrine (NE) transporter (NET) mediates the removal of NE from synaptic spaces and is a major target for antidepressants, amphetamine and cocaine. Previously, we have shown that syntaxin 1A (SYN 1A) supports human NET (hNET) cell surface expression, that hNET/SYN 1A interactions are direct and mediated by the hNET N-terminus, and that the hNET/SYN 1A association limits substrate-induced hNET-associated currents [Sung, U., Apparsundaram, S., Galli, A., Kahlig, K.M., Savchenko, V., Schroeter, S., Quick, M.W., Blakely, R.D., 2003. A regulated interaction of syntaxin 1A with the antidepressant-sensitive norepinephrine transporter establishes catecholamine clearance capacity. J. Neurosci. 23, 1697-1709]. These data raise the possibility that the hNET N-terminus, and potentially its interaction with SYN 1A, might regulate other hNET conductance states, including the hNET-mediated leak current. Importantly for monoamine transporters, the leak conductance has been shown to play a critical role in regulating cell membrane potential and possibly neuronal excitability [Quick, M.W., 2003. Regulating the conducting states of a mammalian serotonin transporter. Neuron 40, 537-549]. Here we demonstrate that deletion of the binding domain for SYN 1A in the NET N-terminus robustly enhances the NET-mediated leak current as well as its selectivity for Cl- permeation under particular intracellular ionic compositions. In addition, we show that the NET N-terminus coordinates the ability of intracellular Na+ and Cl- to regulate the leak conductance. These data suggest that the NET N-terminus regulates and defines the ionic specificity of the NET-mediated leak current.

  9. Ocean circulation in the southern Benguela region from the Pliocene to the Pleistocene: tracking Agulhas leakage into the SE Atlantic

    NASA Astrophysics Data System (ADS)

    Petrick, Benjamin; McClymont, Erin; Felder, Sojna; Leng, Melanie

    2013-04-01

    The transition from the warmth of the middle Pliocene to the large amplitude, 100 kyr glacial-interglacial cycles of the late Pleistocene provides a way to understand the forcings and impacts of regional and global climate change. Here, we investigate changes in ocean circulation over the period from 3.5 Ma to present using a marine sediment core, ODP Site 1087 (31o28'S, 15o19'E, 1374m water depth). ODP 1087 is located in the South-east Atlantic Ocean, outside the Benguela upwelling region. Its location allows investigation of the history of the heat and salt transfer to the Atlantic Ocean from the Indian Ocean ("Agulhas leakage"), which plays an important part in the global thermohaline circulation. It is not known how this transfer reacted to generally warmer global temperatures during the mid-Pliocene, nor to the transition to a globally cooler climate in the early Pleistocene. Our approach is to apply several organic geochemistry proxies and foraminiferal analyses to reconstruct the history of ODP 1087. These include the U37K' index to reconstruct sea surface temperatures, pigment analysis for understanding productivity changes, and foraminifera assemblage analysis to detect the presence of different water masses at the site. We have identified changes in SSTs and biological productivity that we argue to reflect shifts in the position of the Benguela upwelling cells, and a changing influence of Agulhas leakage. Our new data reveal a different organization in the Southeast Atlantic. It shows that during the Pliocene ODP 1087 was dominated by Benguela upwelling which had shifted south. We find no evidence for Agulhas leakage during the mid Pliocene, which could mean that Agulhas Leakage was severely reduced during the mid Pliocene. The implications of these results for understanding Plio-Pleistocene climate changes will be explored here.

  10. The Benguela Current: An ecosystem of four components

    NASA Astrophysics Data System (ADS)

    Hutchings, L.; van der Lingen, C. D.; Shannon, L. J.; Crawford, R. J. M.; Verheye, H. M. S.; Bartholomae, C. H.; van der Plas, A. K.; Louw, D.; Kreiner, A.; Ostrowski, M.; Fidel, Q.; Barlow, R. G.; Lamont, T.; Coetzee, J.; Shillington, F.; Veitch, J.; Currie, J. C.; Monteiro, P. M. S.

    2009-12-01

    sulphur eruptions result from local and remote forcing, restricting the habitat available for pelagic and demersal fish species. The Luderitz-Orange River Cone is an intensive perennial upwelling cell where strong winds, high turbulence and strong offshore transport constitute a partial barrier to epipelagic fish species. Upwelling source water alters in salinity and oxygen, across this boundary zone. A decline in upwelling-favourable winds occurred between 1990 and 2005. The southern Benguela region is characterised by a pulsed, seasonal, wind-driven upwelling at discrete centres and warm Agulhas water offshore. High primary productivity forms a belt of enrichment along the coast, constrained by a front. Low-oxygen water, which only occurs close inshore, may adversely affect some resources. The west coast is primarily a nursery ground for several fish species which spawn on the Agulhas Bank and are transported by alongshore jet currents to the west coast. The Agulhas Bank forms the southern boundary of the Benguela system and it displays characteristics of both an upwelling and a temperate shallow shelf system, with seasonal stratification and mixing, coastal, shelf-edge and dynamic upwelling, moderate productivity and a well oxygenated shelf. A large biomass of fish occupies the Bank during the summer season, with some evidence for tight coupling between trophic levels. A cool ridge of upwelled water, with links to coastal upwelling and to the Agulhas Current, appears to play an important but poorly understood role affecting the distribution and productivity of pelagic fish. A boom in sardine and anchovy populations was accompanied by an eastward shift, followed by 5 years of poor recruitment by sardine but successful recruitment of anchovy, indicating changes in the early life-history patterns of these two species.

  11. Solute transport mechanism during liquid phase epitaxial (LPE) growth with an applied current

    NASA Astrophysics Data System (ADS)

    Takenaka, Chisato; Kusunoki, Toshihiro; Nakajima, Kazuo

    1991-11-01

    The mechanism of the acceleration of solute transport is studied by passing an electric current through a solution during LPE. The amount of InP dissolved in the solution while a current was applied was measured. The current's magnitude and frequency were varied and the heater current's waveform was changed. It was found that the solute dissolved faster when the combination of the solution current and the heater coil current was either 50 Hz ac/50 Hz ac or dc/dc pulse. This indicates that the solute movement is affected by the Lorentz force generated by the current passing through the solution and the magnetic field produced in the heater coil. It is concluded that the accelerated dissolution of InP is attributed to the dynamic movement of solution by the Lorentz effect.

  12. Transport of electrons on liquid helium in a microchannel device near the current threshold

    NASA Astrophysics Data System (ADS)

    Beysengulov, N. R.; Rees, D. G.; Tayurskii, D. A.; Kono, K.

    2016-09-01

    We study the transport of strongly interacting electrons on the surface of liquid helium confined in a microchannel geometry, near the current threshold point. The current threshold depends on the electrostatic confinement, created by the microchannel electrodes, and on the electrostatic potential of electron system. Depending on the geometry of the microchannel, the current pinch-off can occur at the centre or move to the edges of the microchannel, as confirmed by Finite Element Model calculations. The confining potential dependence of electron conductivity above the current threshold point is consistent with a classical charge continuum model. However, we find that below the threshold point electron transport is suppressed due to charging energy effects.

  13. The potential of current- and wind-driven transport for environmental management of the Baltic Sea.

    PubMed

    Soomere, Tarmo; Döös, Kristofer; Lehmann, Andreas; Meier, H E Markus; Murawski, Jens; Myrberg, Kai; Stanev, Emil

    2014-02-01

    The ever increasing impact of the marine industry and transport on vulnerable sea areas puts the marine environment under exceptional pressure and calls for inspired methods for mitigating the impact of the related risks. We describe a method for preventive reduction of remote environmental risks caused by the shipping and maritime industry that are transported by surface currents and wind impact to the coasts. This method is based on characterizing systematically the damaging potential of the offshore areas in terms of potential transport to vulnerable regions of an oil spill or other pollution that has occurred in a particular area. The resulting maps of probabilities of pollution to be transported to the nearshore and the time it takes for the pollution to reach the nearshore are used to design environmentally optimized fairways for the Gulf of Finland, Baltic Proper, and south-western Baltic Sea. PMID:24414808

  14. Mean Flow Velocities and Mass Transport for Equatorially-Trapped Water Waves with an Underlying Current

    NASA Astrophysics Data System (ADS)

    Henry, David; Sastre-Gomez, Silvia

    2016-04-01

    In this paper we present an analysis of the mean flow velocities, and related mass transport, which are induced by certain equatorially-trapped water waves. In particular, we examine a recently-derived exact and explicit solution to the geophysical governing equations in the {β} -plane approximation at the equator which incorporates a constant underlying current.

  15. Controlling fluctuations and transport in the reversed field pinch with edge current drive and plasma biasing

    SciTech Connect

    Craig, D.J.G.

    1998-09-01

    Two techniques are employed in the Madison Symmetric Torus (MST) to test and control different aspects of fluctuation induced transport in the Reversed Field Pinch (RFP). Auxiliary edge currents are driven along the magnetic field to modify magnetic fluctuations, and the particle and energy transport associated with them. In addition, strong edge flows are produced by plasma biasing. Their effect on electrostatic fluctuations and the associated particle losses is studied. Both techniques are accomplished using miniature insertable plasma sources that are biased negatively to inject electrons. This type of emissive electrode is shown to reliably produce intense, directional current without significant contamination by impurities. The two most important conclusions derived from these studies are that the collective modes resonant at the reversal surface play a role in global plasma confinement, and that these modes can be controlled by modifying the parallel current profile outside of the reversal surface. This confirms predictions based on magnetohydrodynamic (MHD) simulations that auxiliary current drive in the sense to flatten the parallel current profile can be successful in controlling magnetic fluctuations in the RFP. However, these studies expand the group of magnetic modes believed to cause transport in MST and suggest that current profile control efforts need to address both the core resonant magnetic modes and those resonant at the reversal surface. The core resonant modes are not significantly altered in these experiments; however, the distribution and/or amplitude of the injected current is probably not optimal for affecting these modes. Plasma biasing generates strong edge flows with shear and particle confinement likely improves in these discharges. These experiments resemble biased H modes in other magnetic configurations in many ways. The similarities are likely due to the common role of electrostatic fluctuations in edge transport.

  16. Coastal currents and mass transport of surface sediments over the shelf regions of Monterey Bay, California

    USGS Publications Warehouse

    Wolf, S.C.

    1970-01-01

    In Monterey Bay, the highest concentrations of medium and fine sands occur nearshore between ten and thirty fathoms. Silt and clay accumulate in greater depths. Contours of median diameter roughly parallel the isobaths. Fine-grained materials are supplied to the bay region from erosion of cliffs which partly surround Monterey Bay, from sediment laden river discharge, and from continual reworking of widespread Pleistocene and Recent sea floor sediments. These sediments in turn are picked up by coastal currents and distributed over the shelf regions by present day current regimes. Studies of bottom currents over the shelf regions and in Monterey Canyon have revealed patterns which vary with seasonal changes. Current patterns during August and September exhibit remarkable symmetry about the axis of Monterey Submarine Canyon. Central Shelf currents north and south of Monterey Canyon flowed northwest at an average rate of 0.2 knots and south at 0.3 knots respectively. On the North Shelf between January and March currents flowed east to southeast at 0.3-0.5 knots with mirror image patterns above the South Shelf during the same period. Irregular current flow in the canyon indicates a complex current structure with frequent shifts in counterclockwise and clockwise direction over very short periods of time. Bottom topography of the canyon complex often causes localization of canyon currents. One particular observation at a depth of 51 fathoms indicated up-canyon flow at a rate of 0.2 knots. Most of the observed currents are related to seasonal variations, upwelling, ocean swell patterns, and to changes in the California and Davidson currents. Changes in current regimes are reflected in the patterns of sediment distribution and transport. Sediment transport is chiefly parallel to the isobaths, particularly on the North and South Shelf regions. Complex dispersal patterns are observed near Monterey Canyon and Moss Landing Harbor jetties. Longshore currents move sediments

  17. Revealing origin of quasi-one dimensional current transport in defect rich two dimensional materials

    SciTech Connect

    Lotz, Mikkel R.; Boll, Mads; Bøggild, Peter; Petersen, Dirch H.; Hansen, Ole; Kjær, Daniel

    2014-08-04

    The presence of defects in graphene have for a long time been recognized as a bottleneck for its utilization in electronic and mechanical devices. We recently showed that micro four-point probes may be used to evaluate if a graphene film is truly 2D or if defects in proximity of the probe will lead to a non-uniform current flow characteristic of lower dimensionality. In this work, simulations based on a finite element method together with a Monte Carlo approach are used to establish the transition from 2D to quasi-1D current transport, when applying a micro four-point probe to measure on 2D conductors with an increasing amount of line-shaped defects. Clear 2D and 1D signatures are observed at low and high defect densities, respectively, and current density plots reveal the presence of current channels or branches in defect configurations yielding 1D current transport. A strong correlation is found between the density filling factor and the simulation yield, the fraction of cases with 1D transport and the mean sheet conductance. The upper transition limit is shown to agree with the percolation threshold for sticks. Finally, the conductance of a square sample evaluated with macroscopic edge contacts is compared to the micro four-point probe conductance measurements and we find that the micro four-point probe tends to measure a slightly higher conductance in samples containing defects.

  18. Methods for stable recording of short-circuit current in a Na+-transporting epithelium

    PubMed Central

    Gondzik, Veronika

    2011-01-01

    Epithelial Na+ transport as measured by a variety of techniques, including the short-circuit current technique, has been described to exhibit a “rundown” phenomenon. This phenomenon manifests as time-dependent decrease of current and resistance and precludes the ability to carry out prolonged experiments aimed at examining the regulation of this transport. We developed methods for prolonged stable recordings of epithelial Na+ transport using modifications of the short-circuit current technique and commercial Ussing-type chambers. We utilize the polarized MDCK cell line expressing the epithelial Na+ channel (ENaC) to describe these methods. Briefly, existing commercial chambers were modified to allow continuous flow of Ringer solution and precise control of such flow. Chamber manifolds and associated plumbing were modified to allow precise temperature clamp preventing temperature oscillations. Recording electrodes were modified to eliminate the use of KCl and prevent membrane depolarization from KCl leakage. Solutions utilized standard bicarbonate-based buffers, but all gasses were prehydrated to clamp buffer osmolarity. We demonstrate that these modifications result in measurements of current and resistance that are stable for at least 2 h. We further demonstrate that drifts in osmolarity similar to those obtained before prior to our modifications can lead to a decrease of current and resistance similar to those attributed to rundown. PMID:21451104

  19. Forward current transport mechanisms in Ni/Au-AlGaN/GaN Schottky diodes

    NASA Astrophysics Data System (ADS)

    Yan, Dawei; Jiao, Jinping; Ren, Jian; Yang, Guofeng; Gu, Xiaofeng

    2013-10-01

    The forward current transport mechanisms in Ni/Au-AlGaN/GaN Schottky diodes are studied by temperature dependent current-voltage (T-I-V) measurements from 298 to 473 K. The zero-bias barrier height qϕBn and ideality factor values determined based on the conventional thermionic-emission (TE) model are strong functions of temperature, which cannot be explained by the standard TE theory. Various transport models are considered to analyze the experimental I-V data. The fitting results indicate that the increased current at low bias is due to the trap-assisted tunneling with an effective trap density of about 8.8 × 106 cm-2, while the high-bias current flow is dominated by the TE transport mechanism, accompanied by a significant series resistance effect. By fitting the high-forward-bias I-V characteristics, the effective qϕBn values with a small negative temperature coefficient are obtained. The temperature dependence of the saturation tunneling current and qϕBn is finally explained by considering the thermally induced band gap shrinkage effect.

  20. Neoclassical Transport Including Impurities and the Bootstrap Current in Advanced Helical Systems

    SciTech Connect

    Nishimura, Shin; Sugama, Hideo

    2004-07-15

    A recently developed method to calculate the neoclassical viscosity, diffusion, and current coefficients in general nonsymmetric toroidal plasmas by using the direct solution of the linearized drift kinetic equation with the pitch-angle-scattering collision operator is applied to impurity transport problems and bootstrap current calculations in stellarators. In this new method based on the basic idea of the so-called moment approach, the collisional momentum conservation is taken into account, and thus, it is applicable to the heat and particle diffusivity in advanced stellarators with quasi symmetry, and also to plasma flows currents, and viscosities in general nonsymmetric multispecies plasmas. In this paper, the impurity flow and the bootstrap current observed in the neoclassical internal transport barrier operation in the Compact Helical System are compared with theoretical calculations. Another topic is the benchmark test of existing analytical expressions for the bootstrap currents by comparing with numerically obtained current coefficients. The geometric factor, which is required for the current calculation based on the moment method, given by our new method is compared with these formulas.

  1. Exchange-Dominated Pure Spin Current Transport in Alq3 Molecules

    NASA Astrophysics Data System (ADS)

    Jiang, S. W.; Liu, S.; Wang, P.; Luan, Z. Z.; Tao, X. D.; Ding, H. F.; Wu, D.

    2015-08-01

    We address the controversy over the spin transport mechanism in Alq3 utilizing spin pumping in the Y3Fe5O12/Alq3/Pd system. An unusual angular dependence of the inverse spin Hall effect is found. It, however, disappears when the microwave magnetic field is fully in the sample plane, excluding the presence of the Hanle effect. Together with the quantitative temperature-dependent measurements, these results provide compelling evidence that the pure spin current transport in Alq3 is dominated by the exchange-mediated mechanism.

  2. Energy transport by energetic electrons released during solar flares. II - Current filamentation and plasma heating

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Dulk, G. A.; Pritchett, P. L.

    1988-01-01

    Two-dimensional electrostatic particle simulations are performed in order to investigate energy transport associated with the propagation of energetic electrons through a flaring flux tube. Results indicate that as the energetic electrons flow outward, a return current of ambient plasma electrons is drawn inward (to maintain quasi-neutrality) which can be spatially separate from the primary current carried by the energetic electrons. Return current electrons are shown to accumulate on either side of the acceleration region of the energetic electrons, and depletions of ambient plasma electrons develop in the return current regions. Plasma ions accelerate across the field lines to produce current closure or charge neutralization, achieving energies comparable to those of the energetic electrons.

  3. Extended estimations of neoclassical transport for the TJ-II stellarator: The bootstrap current

    SciTech Connect

    Tribaldos, V.; Beidler, C. D.; Turkin, Y.; Maassberg, H.

    2011-10-15

    This work extends previous Monte Carlo estimations of neoclassical transport for the TJ-II stellarator [V. Tribaldos, Phys. Plasmas 8, 1229 (2001)] to include, for the first time, the bootstrap current in low collisionality electron cyclotron resonance heated (ECRH) plasmas. The calculations are based on the mono-energetic coefficients calculated with DKES [W. I. van Rij and S. P. Hirshman, Phys. Fluids B 1, 563 (1989)] and MOCA codes. It is shown that despite the difficulties of calculating these coefficient in the long mean free path for TJ-II configurations, the bootstrap current can be accurately estimated based on the moderate temperatures measured in this device with and without enforcing momentum conservation [H. Maassberg et al., Phys. Plasmas 16, 072504 (2009)]. The computed bootstrap current is found to be in fair agreement with the currents being measured in ECRH regimes. Finally, the effect of the bootstrap current on the rotational transform profile is discussed.

  4. Bottom currents and sediment transport in Long Island Sound: A modeling study

    USGS Publications Warehouse

    Signell, R.P.; List, J.H.; Farris, A.S.

    2000-01-01

    A high resolution (300-400 m grid spacing), process oriented modeling study was undertaken to elucidate the physical processes affecting the characteristics and distribution of sea-floor sedimentary environments in Long Island Sound. Simulations using idealized forcing and high-resolution bathymetry were performed using a three-dimensional circulation model ECOM (Blumberg and Mellor, 1987) and a stationary shallow water wave model HISWA (Holthuijsen et al., 1989). The relative contributions of tide-, density-, wind- and wave-driven bottom currents are assessed and related to observed characteristics of the sea-floor environments, and simple bedload sediment transport simulations are performed. The fine grid spacing allows features with scales of several kilometers to be resolved. The simulations clearly show physical processes that affect the observed sea-floor characteristics at both regional and local scales. Simulations of near-bottom tidal currents reveal a strong gradient in the funnel-shaped eastern part of the Sound, which parallels an observed gradient in sedimentary environments from erosion or nondeposition, through bedload transport and sediment sorting, to fine-grained deposition. A simulation of estuarine flow driven by the along-axis gradient in salinity shows generally westward bottom currents of 2-4 cm/s that are locally enhanced to 6-8 cm/s along the axial depression of the Sound. Bottom wind-driven currents flow downwind along the shallow margins of the basin, but flow against the wind in the deeper regions. These bottom flows (in opposition to the wind) are strongest in the axial depression and add to the estuarine flow when winds are from the west. The combination of enhanced bottom currents due to both estuarine circulation and the prevailing westerly winds provide an explanation for the relatively coarse sediments found along parts of the axial depression. Climatological simulations of wave-driven bottom currents show that frequent high

  5. The spatial origin of current noise in semiconductor devices in the framework of semiclassical transport

    NASA Astrophysics Data System (ADS)

    Korman, C. E.; Noaman, B. A.

    2010-10-01

    A new model to semiconductor device electronic noise is presented in the framework of semiclassical transport theory. The salient feature of this model is that it connects the current noise characteristics directly to the physics of scattering of the semiclassical transport theory and makes no additional assumption regarding the nature of noise. Employing this approach, this work investigates the spatial origin of the current noise across two semiconductor structures. In this approach the terminal current noise is directly related to carrier scattering inside the device, which is accounted for in the Boltzmann transport equation (BTE), without the need to add Langevin noise terms to the calculations. Accordingly, it utilizes the well-established spherical harmonics expansion (SHE) technique to solve the BTE, and it combines analytical and numerical methods, in contrast with the Monte Carlo (MC) approach that employs ensemble averages of randomly generated events. The model leads to the solution of a time-dependent transient solution of the BTE with special initial and Ohmic boundary conditions that is solved in the frequency domain to directly compute the terminal current noise spectral density. It is also shown that with this approach the Nyquist theorem under thermal equilibrium conditions is recovered.

  6. The heliospheric current sheet and cosmic-ray transport in the heliosheath

    SciTech Connect

    Florinski, V.

    2012-05-21

    I propose a new mechanism of energetic particle transport in a heliosheath plasma that involves a tightly folded heliospheric current sheet. The distance between magnetic sectors of opposite polarity decreases with increasing heliocentric distance from the termination shock toward the heliopause, due to a slowdown of the flow of heliosheath plasma. If the sector width is comparable or smaller than the cyclotron radius of a galactic cosmic ray ion, the latter can efficiently traverse a stack of sectors via a drift-like or a diffusive mechanism. This mechanism could be responsible for record high intensities of galactic cosmic rays measured by Voyager 1 during 2010-2011. I also discuss the effects of the solar-cycle variations of the current sheet tilt for magnetic field topology in the vicinity of the heliopause and its implications for particle transport in that region.

  7. Transport and Measurements of High-Current Electron Beams from X pinches

    SciTech Connect

    Agafonov, Alexey V.; Mingaleev, Albert R.; Romanova, Vera M.; Tarakanov, Vladimir P.; Shelkovenko, Tatiana A.; Pikuz, Sergey A.; Blesener, Isaac C.; Kusse, Bruce R.; Hammer, David A.

    2009-01-21

    Generation of electron beams is an unavoidable property of X-pinches and other pulsed-power-driven pinches of different geometry. Some issues concerning high-current electron beam transport from the X pinch to the diagnostic system and measurements of the beam current by Faraday cups with different geometry's are discussed. Of particular interest is the partially neutralized nature of the beam propagating from the X-pinch to a diagnostic system. Two scenarios of electron beam propagation from X-pinch to Faraday cup are analyzed by means of computer simulation using the PIC-code KARAT. The first is longitudinal neutralization by ions extracted from plasma at an output window of the X-pinch diode; the second is the beam transport through a plasma background between the diode and a diagnostic system.

  8. Sea level variation as an indicator of Florida current volume transport: comparisons with direct measurements.

    PubMed

    Maul, G A; Chew, F; Bushnell, M; Mayer, D A

    1985-01-18

    Sea level measurements from tide gauges at Miami, Florida, and Cat Cay, Bahamas, and bottom pressure measurements from a water depth of 50 meters off Jupiter, Florida, and a water depth of 10 meters off Memory Rock, Bahamas, were correlated with 81 concurrent direct volume transport observations in the Straits of Florida. Daily-averaged sea level from either gauge on the Bahamian side of the Straits was poorly correlated with transport. Bottom pressure off Jupiter had a linear coefficient of determination ofr(2) = 0.93, and Miami sea level, when adjusted for weather effects, had r(2) = 0.74; the standard errors of estimating transports were +/- 1.2 x 10(6) and +/- 1.9 x 10(6) cubic meters per second, respectively. A linear multivariate regression, which combined bottom pressure, weather, and the submarine cable observations between Jupiter and the Bahamas, had r(2) = 0.94 with a standard error of estimating transport of +/- 1.1 x 10(6) cubic meters per second. These results suggest that a combination of easily obtained observations is sufficient to adequatelv monitor the daily volume transport fluctuations of the Florida Current. PMID:17742102

  9. Electrical transport properties and current density - voltage characteristic of PVA-Ag nanocomposite film

    NASA Astrophysics Data System (ADS)

    Das, A. K.; Dutta, B.; Sinha, S.; Mukherjee, A.; Basu, S.; Meikap, A. K.

    2016-05-01

    Silver (Ag) nanoparticle and Polyvinyl alcohol (PVA) - Silver (Ag) composite have been prepared and its dielectric constant, ac conductivity, and current density-voltage characteristics have been studied, at and above room temperature. Here correlated barrier hopping found to be the dominant charge transport mechanism with maximum barrier height of 0.11 eV. The sample, under ±5 V applied voltage, show back to back Schottky diode behaviour.

  10. Long-term trends in the East Australian Current separation latitude and eddy driven transport

    NASA Astrophysics Data System (ADS)

    Cetina-Heredia, P.; Roughan, M.; van Sebille, E.; Coleman, M. A.

    2014-07-01

    An observed warming of the Tasman Sea in recent decades has been linked to a poleward shift of the maximum wind stress curl, and a strengthening of the poleward flow along the coast of southeastern Australia. However, changes in the East Australian Current (EAC) separation latitude, as well as in the contribution of the EAC, the EAC extension and its eddy field to the total southward transport due to such a strengthening remain unknown. This study uses 30 years (1980-2010) of the Ocean Forecast for the Earth Simulator (OFES) sea surface height and velocity outputs to obtain a three decade long-time series of (i) the EAC separation latitude, (ii) the southward transport along the coast of southeastern Australia (28°S-39°S), and (iii) the southward transport across the EAC separation latitude. A Lagrangian approach is implemented and the spin parameter Ω is used to provide a quantitative distinction between the transports occurring outside and inside (cyclonic and anticyclonic) eddies. Significant positive trends of the low pass southward transports indicate that the intensification of the poleward flow has occurred both within the EAC and in the EAC extension. In addition, a significant increase in southward transport inside and outside eddies is found. Importantly, the contribution of eddy driven transport has a large temporal variability and shows a sharp increase from 2005 onward. Finally our results show that the EAC has not penetrated further south but it has separated more frequently at the southernmost latitudes within the region where it typically turns eastward.

  11. Current flow paths in deformed graphene: from quantum transport to classical trajectories in curved space

    NASA Astrophysics Data System (ADS)

    Stegmann, Thomas; Szpak, Nikodem

    2016-05-01

    In this work we compare two fundamentally different approaches to the electronic transport in deformed graphene: (a) the condensed matter approach in which current flow paths are obtained by applying the non-equilibrium Green’s function (NEGF) method to the tight-binding model with local strain, (b) the general relativistic approach in which classical trajectories of relativistic point particles moving in a curved surface with a pseudo-magnetic field are calculated. The connection between the two is established in the long-wave limit via an effective Dirac Hamiltonian in curved space. Geometrical optics approximation, applied to focused current beams, allows us to directly compare the wave and the particle pictures. We obtain very good numerical agreement between the quantum and the classical approaches for a fairly wide set of parameters, improving with the increasing size of the system. The presented method offers an enormous reduction of complexity from irregular tight-binding Hamiltonians defined on large lattices to geometric language for curved continuous surfaces. It facilitates a comfortable and efficient tool for predicting electronic transport properties in graphene nanostructures with complicated geometries. Combination of the curvature and the pseudo-magnetic field paves the way to new interesting transport phenomena such as bending or focusing (lensing) of currents depending on the shape of the deformation. It can be applied in designing ultrasensitive sensors or in nanoelectronics.

  12. Influence of electrolyte and voltage on the direct current enhanced transport of iron nanoparticles in clay.

    PubMed

    Gomes, Helena I; Dias-Ferreira, Celia; Ribeiro, Alexandra B; Pamukcu, Sibel

    2014-03-01

    Zero valent iron nanoparticles (nZVI) transport for soil and groundwater remediation is slowed down or halted by aggregation or fast depletion in the soil pores. Direct electric current can enhance the transport of nZVI in low permeability soils. However operational factors, including pH, oxidation-reduction potential (ORP), voltage and ionic strength of the electrolyte can play an important role in the treatment effectiveness. Experiments were conducted to enhance polymer coated nZVI mobility in a model low permeability soil medium (kaolin clay) using low direct current. Different electrolytes of varying ionic strengths and initial pH and high nZVI concentrations were applied. Results showed that the nZVI transport is enhanced by direct current, even considering concentrations typical of field application that favor nanoparticle aggregation. However, the factors considered (pH, ORP, voltage and electrolyte) failed to explain the iron concentration variation. The electrolyte and its ionic strength proved to be significant for pH and ORP measured during the experiments, and therefore will affect aggregation and fast oxidation of the particles.

  13. Transport, deposition, and liftoff in laboratory density currents composed of hot particles in air

    NASA Astrophysics Data System (ADS)

    Andrews, B. J.; Manga, M.

    2010-12-01

    Understanding the dynamics of transport, deposition, and air entrainment in pyroclastic density currents (PDCs) is required for accurate predictions of future current behaviors and interpretations of ancient deposits, but directly observing the interiors of natural PDCs is effectively impossible. We model PDCs with scaled, hot, particle-laden density currents generated in a 6 m long, 0.6 m wide, 1.8 m tall air-filled tank. Comparison of relevant scaling between our experiments and natural PDCs indicates that we are accurately capturing much of the dynamics of dilute PDCs: * Reynolds numbers of our experiments are lower than natural currents, 10^3 compared to 10^6, but still fully turbulent; * Densimetric and Thermal Richardson numbers are of O(1) in both natural and modeled currents; * Stokes and settling numbers for particles in the experiments fall within the expected range for natural PDCs. Conditions within the tank are monitored with temperature and humidity probes. Experiments are illuminated with sheet lighting, and recorded with high-definition video cameras. In general, currents have average velocities of 10-20 cm/s, initial thicknesses of 10-20 cm (although thickness greatly increases as currents entrain and expand air), and run out or lift off distances of 3-5 m. Large Kelvin-Helmholtz type eddies usually form along the top of the current immediately behind the head; these vortices are similar in size to the total current thickness. In currents that lift off, the distal current end typically retreats with time. Preliminary results suggest that lift off distance decreases with increasing thermal Richardson number. Analysis of turbulent structures indicates that the current heads are dominated by large coherent structures with length scales, L, comparable to the current thickness. Within 5-10 L of the current fronts, sequences of similar large eddies often occur. At greater distances behind the current fronts, turbulent structures become smaller and less

  14. Changing surface water conditions for the last 500 ka in the Southeast Atlantic: Implications for variable influences of Agulhas leakage and Benguela upwelling

    NASA Astrophysics Data System (ADS)

    Petrick, Benjamin F.; McClymont, Erin L.; Marret, Fabienne; Meer, Marcel T. J.

    2015-09-01

    The Southeast Atlantic Ocean is an important component of global ocean circulation, as it includes heat and salt transfer into the Atlantic through the Agulhas leakage as well as the highly productive Benguela upwelling system. Here we reconstruct sea surface temperatures (SSTs) from Ocean Drilling Program (ODP) Site 1087 in the Southeast Atlantic to investigate surface ocean circulation patterns during the late Pleistocene (0-500 ka). The UK'37 index and dinoflagellate cyst assemblages are used to reconstruct SSTs, δDalkenone is used to reconstruct changes in sea surface salinity, and mass accumulation rates of alkenones and chlorine pigments are quantified to detect changing marine export productivity. The greatest amplitude of SST warming precedes decreases in benthic δ18O and therefore occurs early in the transition from glacials to interglacials. The δDalkenone, as a salinity indicator, increases before SSTs, suggesting that the pattern of Agulhas leakage is more complex than suggested by SST proxies. Marine isotope stage (MIS) 10 shows an anomalous pattern: it is marked by a pronounced increase in chlorine concentration, which may be related to enhanced/expanded Benguela upwelling reaching the core site. We find no evidence of an absence of Agulhas leakage throughout the record, suggesting that there is no Agulhas cutoff even during MIS 10. Finally, the ODP Site 1087 record shows an increasing strength of Agulhas leakage towards the present day, which may have impacted the intensity of the Atlantic meridional overturning circulation. As a result, the new analyses from ODP Site 1087 demonstrate a complex interaction between influences of the Benguela upwelling and the Agulhas leakage through the late Pleistocene, which are inferred here to reflect changing circulation patterns in the Southern Ocean and in the atmosphere.

  15. Optimization of solenoid based low energy beam transport line for high current H+ beams

    NASA Astrophysics Data System (ADS)

    Pande, R.; Singh, P.; Rao, S. V. L. S.; Roy, S.; Krishnagopal, S.

    2015-02-01

    A 20 MeV, 30 mA CW proton linac is being developed at BARC, Mumbai. This linac will consist of an ECR ion source followed by a Radio Frequency Quadrupole (RFQ) and Drift tube Linac (DTL). The low energy beam transport (LEBT) line is used to match the beam from the ion source to the RFQ with minimum beam loss and increase in emittance. The LEBT is also used to eliminate the unwanted ions like H2+ and H3+ from entering the RFQ. In addition, space charge compensation is required for transportation of such high beam currents. All this requires careful design and optimization. Detailed beam dynamics simulations have been done to optimize the design of the LEBT using the Particle-in-cell code TRACEWIN. We find that with careful optimization it is possible to transport a 30 mA CW proton beam through the LEBT with 100% transmission and minimal emittance blow up, while at the same time suppressing unwanted species H2+ and H3+ to less than 3.3% of the total beam current.

  16. Numerical modeling of current-voltage characteristics to extract transport properties of organic semiconductors

    NASA Astrophysics Data System (ADS)

    Basile, A. F.; Fraboni, B.

    2014-11-01

    The current vs. voltage (I-V) characteristics of single crystal rubrene Organic Field-Effect Transistors (OFETs) and polycrystalline poly(p-phenylenevinylene) (PPV) films are modeled using the polaron transport theory presented in a previous work [A. F. Basile et al., J. Appl. Phys. 115, 244505 (2014)]. The model is first applied to rubrene OFETs, where transport is two-dimensional and is confined near the interface between the insulator and the organic semiconductor. By considering the effect of image charges in the insulator and by assuming a constant intrinsic mobility, we reproduce both the positive and the negative temperature dependences of the channel mobilities measured on OFETs having a gate dielectric and an air-gap insulator, respectively. In addition, we adapt this model to the three-dimensional transport in PPV films, characterized by effective mobilities which depend on temperature, charge density, and electric field. We show that the I-V characteristics of these materials can be matched by the numerical solution of the Poisson and drift-diffusion equations assuming a constant intrinsic mobility. The polaron binding energy can account for the thermally activated behavior of the I-V characteristics and for the increase of the effective mobility at high applied voltages. Therefore, this model enables to extract the intrinsic transport parameters of organic semiconductors, independent of the device structure, and of the measurement conditions.

  17. Current transport mechanisms in plasma-enhanced atomic layer deposited AlN thin films

    SciTech Connect

    Altuntas, Halit E-mail: biyikli@unam.bilkent.edu.tr; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi E-mail: biyikli@unam.bilkent.edu.tr

    2015-04-21

    Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200 °C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2–21.5 MV/m), Schottky emission (23.6–39.5 MV/m), Frenkel-Poole emission (63.8–211.8 MV/m), trap-assisted tunneling (226–280 MV/m), and Fowler-Nordheim tunneling (290–447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

  18. Development of a three-dimensional, regional, coupled wave, current, and sediment-transport model

    USGS Publications Warehouse

    Warner, J.C.; Sherwood, C.R.; Signell, R.P.; Harris, C.K.; Arango, H.G.

    2008-01-01

    We are developing a three-dimensional numerical model that implements algorithms for sediment transport and evolution of bottom morphology in the coastal-circulation model Regional Ocean Modeling System (ROMS v3.0), and provides a two-way link between ROMS and the wave model Simulating Waves in the Nearshore (SWAN) via the Model-Coupling Toolkit. The coupled model is applicable for fluvial, estuarine, shelf, and nearshore (surfzone) environments. Three-dimensional radiation-stress terms have been included in the momentum equations, along with effects of a surface wave roller model. The sediment-transport algorithms are implemented for an unlimited number of user-defined non-cohesive sediment classes. Each class has attributes of grain diameter, density, settling velocity, critical stress threshold for erosion, and erodibility constant. Suspended-sediment transport in the water column is computed with the same advection-diffusion algorithm used for all passive tracers and an additional algorithm for vertical settling that is not limited by the CFL criterion. Erosion and deposition are based on flux formulations. A multi-level bed framework tracks the distribution of every size class in each layer and stores bulk properties including layer thickness, porosity, and mass, allowing computation of bed morphology and stratigraphy. Also tracked are bed-surface properties including active-layer thickness, ripple geometry, and bed roughness. Bedload transport is calculated for mobile sediment classes in the top layer. Bottom-boundary layer submodels parameterize wave-current interactions that enhance bottom stresses and thereby facilitate sediment transport and increase bottom drag, creating a feedback to the circulation. The model is demonstrated in a series of simple test cases and a realistic application in Massachusetts Bay. ?? 2008 Elsevier Ltd. All rights reserved.

  19. Development of a three-dimensional, regional, coupled wave, current, and sediment-transport model

    NASA Astrophysics Data System (ADS)

    Warner, John C.; Sherwood, Christopher R.; Signell, Richard P.; Harris, Courtney K.; Arango, Hernan G.

    2008-10-01

    We are developing a three-dimensional numerical model that implements algorithms for sediment transport and evolution of bottom morphology in the coastal-circulation model Regional Ocean Modeling System (ROMS v3.0), and provides a two-way link between ROMS and the wave model Simulating Waves in the Nearshore (SWAN) via the Model-Coupling Toolkit. The coupled model is applicable for fluvial, estuarine, shelf, and nearshore (surfzone) environments. Three-dimensional radiation-stress terms have been included in the momentum equations, along with effects of a surface wave roller model. The sediment-transport algorithms are implemented for an unlimited number of user-defined non-cohesive sediment classes. Each class has attributes of grain diameter, density, settling velocity, critical stress threshold for erosion, and erodibility constant. Suspended-sediment transport in the water column is computed with the same advection-diffusion algorithm used for all passive tracers and an additional algorithm for vertical settling that is not limited by the CFL criterion. Erosion and deposition are based on flux formulations. A multi-level bed framework tracks the distribution of every size class in each layer and stores bulk properties including layer thickness, porosity, and mass, allowing computation of bed morphology and stratigraphy. Also tracked are bed-surface properties including active-layer thickness, ripple geometry, and bed roughness. Bedload transport is calculated for mobile sediment classes in the top layer. Bottom-boundary layer submodels parameterize wave-current interactions that enhance bottom stresses and thereby facilitate sediment transport and increase bottom drag, creating a feedback to the circulation. The model is demonstrated in a series of simple test cases and a realistic application in Massachusetts Bay.

  20. Anatomy of the Antarctic Circumpolar Current volume transports through Drake Passage

    NASA Astrophysics Data System (ADS)

    Koenig, Zoé; Provost, Christine; Park, Young-Hyang; Ferrari, Ramiro; Sennéchael, Nathalie

    2016-04-01

    The 20 year (October 1992 to August 2013) observation-based volume transport time series of the Antarctic Circumpolar Current (ACC) through Drake Passage (DP) across the Jason altimeter track #104 is analyzed to better understand the ACC transport variability and its potential causes. The time series of three transport components (total (TT), barotropic (BT), and baroclinic (BC)) referenced to 3000 m present energetic intraseasonal fluctuations, with a salient spectral peak at 50 and 36 days, with the largest (least) variance being associated with the BT (BC) component. Low-frequency variations are much less energetic with a significant variance limited to the annual and biannual timescales and show a nonstationary intermittent link with the Southern Annular Mode and the Nino 3.4 index for interannual timescales. The region around 57°S in the Yaghan Basin appears to be a strategic point for a practical monitoring of the ACC transport, as the whole-track TT is significantly correlated with the local TT (r = 0.53) and BT (r = 0.69) around 57°S. These local BT (and TT) variations are associated with a well-defined tripole pattern in altimetric sea level anomaly (SLA). There is evidence that the tripole pattern associated with BT is locally generated when the BC-associated mesoscale SLAs, which have propagated eastward from an upstream area of DP, cross the Shackleton Fracture Zone to penetrate into the Yaghan Basin. Barotropic basin modes excited within the Yaghan Basin are discussed as a plausible mechanism for the observed energy-containing intraseasonal spectral peaks found in the transport variability.

  1. Structure of Dilute Pyroclastic Density Currents During Transport, Buoyancy Reversal and Liftoff

    NASA Astrophysics Data System (ADS)

    Andrews, B. J.

    2014-12-01

    bypass region. Eddies that entrain air through the lateral margins grow in size with transport distance such that at the maximum runout distance, eddies have lengthscales comparable to the current width. The largest structures within the rising plumes have lengthscales comparable to the cross-stream plume width.

  2. 25 CFR 39.707 - Which student transportation expenses are currently not eligible for Student Transportation Funding?

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... (a)(4) of this section include: (1) Athletics; (2) Band; (3) Detention; (4) Tutoring, study hall and..., DEPARTMENT OF THE INTERIOR EDUCATION THE INDIAN SCHOOL EQUALIZATION PROGRAM Student Transportation... runs; (2) Transportation home for medical or other emergencies; (3) Transportation from school...

  3. 25 CFR 39.707 - Which student transportation expenses are currently not eligible for Student Transportation Funding?

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (a)(4) of this section include: (1) Athletics; (2) Band; (3) Detention; (4) Tutoring, study hall and..., DEPARTMENT OF THE INTERIOR EDUCATION THE INDIAN SCHOOL EQUALIZATION PROGRAM Student Transportation... runs; (2) Transportation home for medical or other emergencies; (3) Transportation from school...

  4. 25 CFR 39.707 - Which student transportation expenses are currently not eligible for Student Transportation Funding?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... (a)(4) of this section include: (1) Athletics; (2) Band; (3) Detention; (4) Tutoring, study hall and..., DEPARTMENT OF THE INTERIOR EDUCATION THE INDIAN SCHOOL EQUALIZATION PROGRAM Student Transportation... runs; (2) Transportation home for medical or other emergencies; (3) Transportation from school...

  5. 25 CFR 39.707 - Which student transportation expenses are currently not eligible for Student Transportation Funding?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (a)(4) of this section include: (1) Athletics; (2) Band; (3) Detention; (4) Tutoring, study hall and..., DEPARTMENT OF THE INTERIOR EDUCATION THE INDIAN SCHOOL EQUALIZATION PROGRAM Student Transportation... runs; (2) Transportation home for medical or other emergencies; (3) Transportation from school...

  6. 25 CFR 39.707 - Which student transportation expenses are currently not eligible for Student Transportation Funding?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... (a)(4) of this section include: (1) Athletics; (2) Band; (3) Detention; (4) Tutoring, study hall and..., DEPARTMENT OF THE INTERIOR EDUCATION THE INDIAN SCHOOL EQUALIZATION PROGRAM Student Transportation... runs; (2) Transportation home for medical or other emergencies; (3) Transportation from school...

  7. Charge transport in bacteriorhodopsin monolayers: The contribution of conformational change to current-voltage characteristics

    NASA Astrophysics Data System (ADS)

    Alfinito, E.; Reggiani, L.

    2009-03-01

    When moving from native to light-activated bacteriorhodospin, modification of charge transport consisting of an increase of conductance is correlated to the protein conformational change. A theoretical model based on a map of the protein tertiary structure into a resistor network is implemented to account for a sequential tunneling mechanism of charge transfer through neighbouring amino acids. The model is validated by comparison with current-voltage experiments. The predictability of the model is further tested on bovine rhodopsin, a G-protein coupled receptor (GPCR) also sensitive to light. In this case, results show an opposite behaviour with a decrease of conductance in the presence of light.

  8. Enhanced Transport Currents in Cu-Sheathed MgB2 Wires

    SciTech Connect

    Eisterer, M; Glowacki, B A.; Weber, H W.; Greenwood, Lawrence R. ); Majoros, M

    2002-01-01

    Copper sheathed MgB2 wires, prepared by an in-situ process, were exposed to neutron radiation in order to introduce defects into the superconductor. The high level of disorder (4.6 x 10{sup -2} dpa) leads to a decreases of the transition temperature by more than 4 K, but to an increase of the slope of the irreversibility line, thus resulting in higher irreversibility fields at low temperatures. The transport currents are significantly enhanced at 4.2 K for fields above 2 T.

  9. Modelling the potential transport of tropical fish larvae in the Leeuwin Current

    NASA Astrophysics Data System (ADS)

    Pearce, A.; Slawinski, D.; Feng, M.; Hutchins, B.; Fearns, P.

    2011-12-01

    Application of an individual-based particle tracking model to the migration of tropical fish larvae along the continental shelf between the Houtman Abrolhos Islands and Rottnest Island (Western Australia) has shown that there is potential for the southwards advection of passive particles/larvae in the Leeuwin Current system throughout the year. However, seasonal variations in the prevailing wind field result in corresponding seasonal changes in the surface current flow (both alongshore and cross-shelf) on the continental shelf, leading to a pulse of modelled particles arriving at Rottnest Island during the autumn months. This matches, within a month, the observed April/May peak in annual recruitment of 2 species of damselfish ( Abudefduf sexfasciatus and A. vaigiensis), at the time when the Leeuwin Current is strengthening. It is assumed that the larvae are in the uppermost 20 m of the water column and that there are no vertical diurnal movements. The model has a 10 km grid spacing, and so can resolve some of the current gradients across the continental shelf. Comparison of the modelled near-surface currents with ADCP measurements at 2 current mooring sites as well as with a broader range of historical current measurements off south-western Australia indicates that the alongshore net transport is reasonably well reproduced by the model, whereas agreement with the cross-shelf flow is not as good (this may be partly attributed to the paucity of high-quality near-surface current measurements in the area of study). Because of limitations in our knowledge of the swimming ability, choice of swimming direction and habitat selection of larval fish, as well as the inability of the model to reproduce the small-scale circulation around Rottnest Island, the swimming capacity of the late-stage larval fish is not specifically included; they are considered as potential settlers once they have reached within 20 km of the Island. The observed inter-annual variability in recruitment

  10. Reaction kinetic parameters for ion transport from steady-state current-voltage curves.

    PubMed Central

    Gradmann, D; Klieber, H G; Hansen, U P

    1987-01-01

    This study demonstrates possible ways to estimate the rate constants of reaction kinetic models for ion transport from steady-state current-voltage data as measured at various substrate concentrations. This issue is treated theoretically by algebraic reduction and extension of a reaction kinetic four-state model for uniport. Furthermore, an example for application is given; current-voltage data from an open K+ selective channel (Schroeder, J.I., R. Hedrich, and J.M. Fernandez, 1984, Nature (Lond.), 312:361-362) supplemented by some new data have been evaluated. The analysis yields absolute numerical estimates of the 14 rate constants of a six-state model, which is discussed in a wider context. PMID:2437973

  11. GABA transporter currents activated by protein kinase A excite midbrain neurons during opioid withdrawal.

    PubMed

    Bagley, Elena E; Gerke, Michelle B; Vaughan, Christopher W; Hack, Stephen P; Christie, MacDonald J

    2005-02-01

    Adaptations in neurons of the midbrain periaqueductal gray (PAG) induced by chronic morphine treatment mediate expression of many signs of opioid withdrawal. The abnormally elevated action potential rate of opioid-sensitive PAG neurons is a likely cellular mechanism for withdrawal expression. We report here that opioid withdrawal in vitro induced an opioid-sensitive cation current that was mediated by the GABA transporter-1 (GAT-1) and required activation of protein kinase A (PKA) for its expression. Inhibition of GAT-1 or PKA also prevented withdrawal-induced hyperexcitation of PAG neurons. Our findings indicate that GAT-1 currents can directly increase the action potential rates of neurons and that GAT-1 may be a target for therapy to alleviate opioid-withdrawal symptoms.

  12. LETTER: Elongation and current scalings of local and global energy transport

    NASA Astrophysics Data System (ADS)

    Becker, G.

    2002-04-01

    The scaling of local and global energy confinement with elongation κ and current in L- and H-mode plasmas is explored. It is shown that the elongation enters global confinement only through the geometrical quantities of plasma volume and surface area, while local transport does not contribute. The global scaling τEproptoκ0.8 is caused by WproptonT0V with the volume Vproptoκ and the surface area leading to T0proptoκ-0.2. Empirical scalings of the effective heat diffusivity χ with κ, the current inside a flux surface I(x), Bp and q are presented. Applying I(x) makes χ independent of κ, while a formulation with q yields strong implicit and explicit κ dependences.

  13. Generation and transport of valley-polarized current in transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Gong, Kui; Chen, Jingzhe; Liu, Lei; Zhu, Yu; Xiao, Di; Guo, Hong

    2014-11-01

    In two-dimensional crystals of transition-metal dichalcogenides (TMDC) having strong spin-orbit interaction such as monolayer WSe2, quantum states can be labeled by a valley index τ defined in the reciprocal space and the spin index s . We developed a first-principles theoretical formalism to both qualitatively and quantitatively predict nonequilibrium quantum transport of valley-polarized currents. We propose a WSe2 TMDC transistor to selectively deliver net valley- and spin-polarized current Iτ ,s to the source or drain by circularly polarized light under external bias. Due to the lack of translational symmetry of the real-space device, we predict a depolarization effect that increases with the decrease of the channel length of the transistor.

  14. A Computer Code for 2-D Transport Calculations in x-y Geometry Using the Interface Current Method.

    1990-12-01

    Version 00 RICANT performs 2-dimensional neutron transport calculations in x-y geometry using the interface current method. In the interface current method, the angular neutron currents crossing region surfaces are expanded in terms of the Legendre polynomials in the two half-spaces made by the region surfaces.

  15. Transport behavior of hairless mouse skin during constant current DC iontophoresis I: baseline studies.

    PubMed

    Liddell, Mark R; Li, S Kevin; Higuchi, William I

    2011-04-01

    The fluxes of charged and nonionic molecules across hairless mouse skin (HMS) were induced by direct current iontophoresis and used to characterize the transport pathways of the epidermal membrane. Experimental data were used to determine permeability coefficients from which the effective pore radii (Rp) of the transport pathways were calculated. Permeants used in these experiments were nonionic permeants (urea, mannitol, and raffinose), monovalent cationic permeants (sodium, tetraethylammonium, and tetraphenylphosphonium ions), and monovalent anionic permeants (chloride, salicylate, and taurocholate ions). The Rp estimates obtained by the anionic permeant pairs were 49, 22, and 20 Å for the chloride/salicylate (Cl:SA), chloride/taurocholate (Cl:TC), and salicylate/taurocholate (SA:TC) pairs, respectively; with the cationic permeant pairs, the Rp values obtained were 19, 30, and 24 Å for the sodium/tetraethylammonium (Na:TEA), sodium/tetraphenylphosphonium (Na:TPP), and the tetraethylammonium/tetraphenylphosphonium (TEA:TPP) pairs, respectively. Rp estimates for HMS obtained from nonionic permeant experiments ranged from 6.7 to 13.4 Å. When plotted versus their respective diffusion coefficients, all of the permeability coefficients for the cationic permeants were greater than those of the anionic permeants. Additionally, the magnitudes of permeability coefficients determined in the current study with HMS were of the same order of magnitude as those previously determined in our laboratory using human epidermal membrane under similar iontophoresis conditions. PMID:21259234

  16. Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current

    DOE PAGES

    Mollén, A.; Landreman, M.; Smith, H. M.; Braun, S.; Helander, P.

    2015-11-20

    Impurities cause radiation losses and plasma dilution, and in stellarator plasmas the neoclassical ambipolar radial electric field is often unfavorable for avoiding strong impurity peaking. In this work we use a new continuum drift-kinetic solver, the SFINCS code (the Stellarator Fokker-Planck Iterative Neoclassical Conservative Solver) [M. Landreman et al., Phys. Plasmas 21 (2014) 042503] which employs the full linearized Fokker-Planck-Landau operator, to calculate neoclassical impurity transport coefficients for a Wendelstein 7-X (W7-X) magnetic configuration. We compare SFINCS calculations with theoretical asymptotes in the high collisionality limit. We observe and explain a 1/nu-scaling of the inter-species radial transport coefficient at lowmore » collisionality, arising due to the field term in the inter-species collision operator, and which is not found with simplified collision models even when momentum correction is applied. However, this type of scaling disappears if a radial electric field is present. We use SFINCS to analyze how the impurity content affects the neoclassical impurity dynamics and the bootstrap current. We show that a change in plasma effective charge Zeff of order unity can affect the bootstrap current enough to cause a deviation in the divertor strike point locations.« less

  17. Investigation of nonthermal particle effects on ionization dynamics in high current density ion beam transport experiments

    NASA Astrophysics Data System (ADS)

    Chung, H. K.; MacFarlane, J. J.; Wang, P.; Moses, G. A.; Bailey, J. E.; Olson, C. L.; Welch, D. R.

    1997-01-01

    Light ion inertial fusion experiments require the presence of a moderate density background gas in the transport region to provide charge and current neutralization for a high current density ion beam. In this article, we investigate the effects of nonthermal particles such as beam ions or non-Maxwellian electron distributions on the ionization dynamics of the background gas. In particular, we focus on the case of Li beams being transported in an argon gas. Nonthermal particles as well as thermal electrons are included in time-dependent collisional-radiative calculations to determine time-dependent atomic level populations and charge state distributions in a beam-produced plasma. We also briefly discuss the effects of beam ions and energetic electrons on the visible and vacuum ultraviolet (VUV) spectral regions. It is found that the mean charge state of the gas, and hence the electron density, is significantly increased by collisions with energetic particles. This higher ionization significantly impacts the VUV spectral region, where numerous resonance lines occur. On the other hand, the visible spectrum tends to be less affected because the closely spaced excited states are populated by lower energy thermal electrons.

  18. Impurities in a non-axisymmetric plasma. Transport and effect on bootstrap current

    SciTech Connect

    Mollén, A.; Landreman, M.; Smith, H. M.; Braun, S.; Helander, P.

    2015-11-20

    Impurities cause radiation losses and plasma dilution, and in stellarator plasmas the neoclassical ambipolar radial electric field is often unfavorable for avoiding strong impurity peaking. In this work we use a new continuum drift-kinetic solver, the SFINCS code (the Stellarator Fokker-Planck Iterative Neoclassical Conservative Solver) [M. Landreman et al., Phys. Plasmas 21 (2014) 042503] which employs the full linearized Fokker-Planck-Landau operator, to calculate neoclassical impurity transport coefficients for a Wendelstein 7-X (W7-X) magnetic configuration. We compare SFINCS calculations with theoretical asymptotes in the high collisionality limit. We observe and explain a 1/nu-scaling of the inter-species radial transport coefficient at low collisionality, arising due to the field term in the inter-species collision operator, and which is not found with simplified collision models even when momentum correction is applied. However, this type of scaling disappears if a radial electric field is present. We use SFINCS to analyze how the impurity content affects the neoclassical impurity dynamics and the bootstrap current. We show that a change in plasma effective charge Zeff of order unity can affect the bootstrap current enough to cause a deviation in the divertor strike point locations.

  19. Impurities in a non-axisymmetric plasma: Transport and effect on bootstrap current

    SciTech Connect

    Mollén, A.; Landreman, M.; Smith, H. M.; Helander, P.; Braun, S.

    2015-11-15

    Impurities cause radiation losses and plasma dilution, and in stellarator plasmas the neoclassical ambipolar radial electric field is often unfavorable for avoiding strong impurity peaking. In this work we use a new continuum drift-kinetic solver, the SFINCS code (the Stellarator Fokker-Planck Iterative Neoclassical Conservative Solver) [M. Landreman et al., Phys. Plasmas 21, 042503 (2014)] which employs the full linearized Fokker-Planck-Landau operator, to calculate neoclassical impurity transport coefficients for a Wendelstein 7-X (W7-X) magnetic configuration. We compare SFINCS calculations with theoretical asymptotes in the high collisionality limit. We observe and explain a 1/ν-scaling of the inter-species radial transport coefficient at low collisionality, arising due to the field term in the inter-species collision operator, and which is not found with simplified collision models even when momentum correction is applied. However, this type of scaling disappears if a radial electric field is present. We also use SFINCS to analyze how the impurity content affects the neoclassical impurity dynamics and the bootstrap current. We show that a change in plasma effective charge Z{sub eff} of order unity can affect the bootstrap current enough to cause a deviation in the divertor strike point locations.

  20. Transport behavior of hairless mouse skin during constant current DC iontophoresis I: baseline studies.

    PubMed

    Liddell, Mark R; Li, S Kevin; Higuchi, William I

    2011-04-01

    The fluxes of charged and nonionic molecules across hairless mouse skin (HMS) were induced by direct current iontophoresis and used to characterize the transport pathways of the epidermal membrane. Experimental data were used to determine permeability coefficients from which the effective pore radii (Rp) of the transport pathways were calculated. Permeants used in these experiments were nonionic permeants (urea, mannitol, and raffinose), monovalent cationic permeants (sodium, tetraethylammonium, and tetraphenylphosphonium ions), and monovalent anionic permeants (chloride, salicylate, and taurocholate ions). The Rp estimates obtained by the anionic permeant pairs were 49, 22, and 20 Å for the chloride/salicylate (Cl:SA), chloride/taurocholate (Cl:TC), and salicylate/taurocholate (SA:TC) pairs, respectively; with the cationic permeant pairs, the Rp values obtained were 19, 30, and 24 Å for the sodium/tetraethylammonium (Na:TEA), sodium/tetraphenylphosphonium (Na:TPP), and the tetraethylammonium/tetraphenylphosphonium (TEA:TPP) pairs, respectively. Rp estimates for HMS obtained from nonionic permeant experiments ranged from 6.7 to 13.4 Å. When plotted versus their respective diffusion coefficients, all of the permeability coefficients for the cationic permeants were greater than those of the anionic permeants. Additionally, the magnitudes of permeability coefficients determined in the current study with HMS were of the same order of magnitude as those previously determined in our laboratory using human epidermal membrane under similar iontophoresis conditions.

  1. Transport mechanisms of leakage current in Al2O3/InAlAs MOS capacitors

    NASA Astrophysics Data System (ADS)

    Jin, Chengji; Lu, Hongliang; Zhang, Yimen; Zhang, Yuming; Guan, He; Wu, Lifan; Lu, Bin; Liu, Chen

    2016-09-01

    An Al2O3 layer is inserted between the InAlAs layer and the metal gate in InAs/AlSb HEMTs to suppress the leakage current. The transport mechanisms of leakage current in Al2O3/InAlAs metal-oxide-semiconductor (MOS) capacitors at both positive and negative biases at different temperatures ranging from 10 °C to 70 °C are investigated. For positive bias, the leakage current is dominated by Schottky emission. Based on the fitted straight lines, the relative dielectric constant of Al2O3 and the barrier height between Al2O3 and InAlAs are extracted. However, for negative bias, the leakage current is dominated by Frenkel-Poole (F-P) emission and the depth of the trap energy level from the conduction band (ϕt) is extracted. Furthermore, authors explain the reason why the dominating mechanisms at positive and negative biases are different.

  2. Stormtime ring current and radiation belt ion transport: Simulations and interpretations

    NASA Technical Reports Server (NTRS)

    Lyons, Larry R.; Gorney, David J.; Chen, Margaret W.; Schulz, Michael

    1995-01-01

    We use a dynamical guiding-center model to investigate the stormtime transport of ring current and radiation-belt ions. We trace the motion of representative ions' guiding centers in response to model substorm-associated impulses in the convection electric field for a range of ion energies. Our simple magnetospheric model allows us to compare our numerical results quantitatively with analytical descriptions of particle transport, (e.g., with the quasilinear theory of radial diffusion). We find that 10-145-keV ions gain access to L approximately 3, where they can form the stormtime ring current, mainly from outside the (trapping) region in which particles execute closed drift paths. Conversely, the transport of higher-energy ions (approximately greater than 145 keV at L approximately 3) turns out to resemble radial diffusion. The quasilinear diffusion coefficient calculated for our model storm does not vary smoothly with particle energy, since our impulses occur at specific (although randomly determined) times. Despite the spectral irregularity, quasilinear theory provides a surprisingly accurate description of the transport process for approximately greater than 145-keV ions, even for the case of an individual storm. For 4 different realizations of our model storm, the geometric mean discrepancies between diffusion coefficients D(sup sim, sub LL) obtained from the simulations and the quasilinear diffusion coefficient D(sup ql, sub LL) amount to factors of 2.3, 2.3, 1.5, and 3.0, respectively. We have found that these discrepancies between D(sup sim, sub LL) and D(sup ql, sub LL) can be reduced slightly by invoking drift-resonance broadening to smooth out the sharp minima and maxima in D(sup ql, sub LL). The mean of the remaining discrepancies between D(sup sim, sub LL) and D(sup ql, sub LL) for the 4 different storms then amount to factors of 1.9, 2.1, 1.5, and 2.7, respectively. We find even better agreement when we reduce the impulse amplitudes systematically in

  3. Exploiting multi-proxy analysis of marine sediments in the southeast Atlantic: Intensification of Agulhas leakage tied to the start of the 100ka cycles.

    NASA Astrophysics Data System (ADS)

    Petrick, Benjamin; McClymont, Erin; Marret, Fabienne

    2013-04-01

    The transition in orbital forcing from a 41 ka world to a 100 ka world was a major change in the climate regime over the last 1.5 Ma but its causes and its impacts are still being investigated. Here, we present reconstructions of sea-surface temperature (SST), salinity, and plankton assemblages obtained from a single core, ODP site 1087 (31°28'S, 15°19'E, 1374m water depth) spanning the last 1.5 Ma. Our hypothesis is that the response and position of the Agulhas leakage, which transfers heat and salt to the SE Atlantic region, has shifted as a result of changes in the dominant periodicity of orbital forcing. We draw on evidence from the alkenone (U37K') proxy for SST, dinoflagllate species analysis, and foraminifera oxygen isotopes for salinity and ice volume, to identify changes in the input of the Agulhas leakage to the SE Atlantic. We present the first continuous record of SE Atlantic SSTs reaching to 1.5 Ma which spans both the 41 kyr and 100 kyr glacial cycles. We identify large changes in SST and salinity on glacial-interglacial timescales, but show that there is a consistent pattern of SSTs leading salinity and then global ice volume change, so that deglaciation occurs some 5-10 kyr after the onset of rapid warming in the SE Atlantic during the recent glacials and interglacials. This early warming pattern, which characterizes the most recent cycles, began to develop as early at 900 ka, as the 100 kyr cycles became dominant. Before this time there is little evidence of Agulhas leakage in the ODP1087 record. We also show that over the last 600 ka there has been a strengthening of the Agulhas Leakage which has led to warmer interglacials over this time period. Overall the record shows that the strength and location of the Agulhas leakage is sensitive to changes in the dominant cycles in the climate.

  4. Changing surface water conditions for the last 500 ka in the Southeast Atlantic:Tracking Agulhas leakage using UK37' and δD

    NASA Astrophysics Data System (ADS)

    Petrick, Benjamin; McClymont, Erin; van der Meer, Marcel; Marret, Fabienne

    2015-04-01

    The Southeast Atlantic Ocean is an important component of global ocean circulation, as it includes heat and salt transfer into the Atlantic through Agulhas Leakage. Here, we reconstruct sea surface temperatures (SSTs) and sea surface salinity from Ocean Drilling Program (ODP) Site 1087 in the Southeast Atlantic to investigate surface ocean circulation patterns during the late Pleistocene (0-500 ka). The alkenone-derived U37K'index and assemblages of dinoflagellate cysts are used to reconstruct SSTs. The hydrogen isotope composition of the alkenones (δDalkenone) is used to reconstruct changes in sea-surface salinity. The greatest amplitude of SST warming precedes decreases in benthic δ18O and therefore occurs early in the transition from glacials to interglacials. The timing of the early warming is consistent with previously published foraminifera reconstructions from the same site (Caley et al., 2012). However, δDalkenone decreases at the start of interglacials, suggesting that sea surface salinity increased earlier than the deglacial warmings, and indicating that the pattern of Agulhas leakage is more complex than suggested by SST proxies alone. Furthermore, the δDalkenonevalues indicate a strong salinity increases occurred before both MIS 11 and MIS 1, which are both periods where there is evidence of connection between increased Agulhas Leakage and a stronger Atlantic meridional overturning circulation (AMOC). Finally, the ODP site 1087 record shows an overall trend of increasing SSTs and δDalkenone towards the present day, suggesting that Agulhas leakage has strengthened since 500 ka, which may have impacted the intensity of the AMOC. Caley, T., Giraudeau, J., Malaize, B., Rossignol, L., Pierre, C., 2012. Agulhas leakage as a key process in the modes of Quaternary climate changes. Proc. Natl. Acad. Sci. 109, 6835-6839. doi:10.1073/pnas.1115545109

  5. Stormtime ring current and radiation belt ion transport: Simulations and interpretations

    SciTech Connect

    Lyons, L.R.; Gorney, D.J.; Chen, M.W.; Schulz, M.

    1995-05-01

    The authors use a dynamical guiding-center model to investigate the stormtime transport of ring current and radiation-belt ions. They trace the motion of representative ions` guiding centers in response to model substorm-associated impulses in the convection electric field for a range of ion energies. Their simple magnetospheric model allows them to compare their numerical results quantitatively with analytical descriptions of particle transport, (e.g., with the quasilinear theory of radial diffusion). They find that 10-145-keV ions gain access to L approximately 3, where they can form the stormtime ring current, mainly from outside the (trapping) region in which particles execute closed drift paths. Conversely, the transport of higher-energy ions (approximately greater than 145 keV at L approximately 3) turns out to resemble radial diffusion. The quasilinear diffusion coefficient calculated for their model storm does not vary smoothly with particle energy, since their impulses occur at specific (although randomly determined) times. Despite the spectral irregularity, quasilinear theory provides a surprisingly accurate description of the transport process for approximately greater than 145-keV ions, even for the case of an individual storm. For 4 different realizations of their model storm, the geometric mean discrepancies between diffusion coefficients D(sup sim)(sub LL) obtained from the simulations and the quasilinear diffusion coefficient D(sup ql)(sub LL) amount to factors of 2.3, 2.3, 1.5, and 3.0, respectively. They have found that these discrepancies between D(sup sim)(sub LL) and D(sup ql)(sub LL) can be reduced slightly by invoking drift-resonance broadening to smooth out the sharp minima and maxima in D(sup ql)(sub LL). The mean of the remaining discrepancies between D(sup sim)(sub LL) and D(sup ql)(sub LL) for the 4 different storms then amount to factors of 1.9, 2.1, 1.5, and 2.7, respectively.

  6. Energy transportation via MITL by the linear current flow density up to 7 MA/cm

    NASA Astrophysics Data System (ADS)

    Korolev, V. D.; Bakshaev, Yu. L.; Bartov, A. V.; Blinov, P. I.; Bryzgunov, V. A.; Chernenko, A. S.; Dan'ko, S. A.; Kalinin, Yu. G.; Kingsep, A. S.; Kazakov, E. D.; Smirnov, V. P.; Smirnova, E. A.; Ustroev, G. I.

    2006-10-01

    The transmission properties of the magnetically self-insulated vacuum transporting line (MITL) were studied on the S-300 pulsed power machine (3 MA, 100 ns) at the high linear current flow density up to dI/db = 7 MA/cm. Experiments were carried out with the short line sections with 10 ÷ 15 mm length and 3 ÷ 5 mm vacuum gap. For measuring of the plasma parameters, the frame ICT photography with the nanosecond temporal resolution in the SXR range and ICT (Image Converter Tube) chronography in visible range were used. The X-ray radiation in various ranges was recorded by the XRD with thin filters (SXR) and by the semiconductor detectors (HXR). The information about current transmission efficiency was obtained by means of magnetic loops and low-inductance shunt. It was determined that dense plasma arose on both anode and cathode when the linear current flow density was low enough, dI/db ≤ 1 MA/cm. A dense plasma moves across the vacuum gap with the velocity (1 ÷ 2) × 106 cm/s. By recording the current and hard X-ray radiation it was found that electron losses in the current front did not exceed 10 ÷ 100 kA. Under strong magnetization of electrons r H = mvc/eB < d, these losses could be due to the motion of fast plasma component, which velocity exceeds 107 cm/s. Such a rare plasma sheath formed on the cathode by dI/db ≥ 1 MA/cm. Thereby the successful physical modeling of the recyclable MITL related to the Sandia Laboratories’ Conceptual Project of fusion reactor on the base of fast Z-pinch has been brought about.

  7. A survey of current ostrich handling and transport practices in North America with reference to ostrich welfare and transportation guidelines set up in other countries.

    PubMed

    Bejaei, M; Cheng, K M

    2014-02-01

    Appropriate management of an ostrich's exposure to stressors during preslaughter handling and transport practices can improve its well-being and product quality. Because of the lack of information about ostrich farming and transportation in North America and lack of developed Codes of Practice for ratite transport in Canada and the United States, the first objective of our research was to identify current preslaughter handling and transport practices of the ostrich industry in Canada and the United States, and to identify potential welfare issues based on the current practices. The second objective of this research was to review ostrich transport welfare standards and guidelines from Australia, European Union, New Zealand, and South Africa to investigate if those guidelines are applicable to Canadian and American ostrich production systems. Preliminary producer interviews, on-farm visits, and literature review information sources were used to design a producer questionnaire that was used to survey producers by Internet and mail surveying methods to identify existing ostrich transport norms in Canada and the United States. Based on the results of our producer survey and review of the transport standards and guidelines, we conclude that following factors are potential ostrich handling and transport welfare issues in Canada and the United States: lack of scientific information about welfare of ostriches during handling and transport; unfamiliarity of handlers and birds with handling and transport practices; not considering birds' social bounds, sex, behavior, and physical state in mixing them during handling and transport process; lack of an established specific maximum water and feed withdrawal duration for ostrich transport in Canada and the United States; lack of a specific vehicle designed for ratite transportation in Canada and the United States considering different physical body characteristics of ostriches compared with other species; exposure of birds to

  8. Junction formation and current transport mechanisms in hybrid n-Si/PEDOT:PSS solar cells

    NASA Astrophysics Data System (ADS)

    Jäckle, Sara; Mattiza, Matthias; Liebhaber, Martin; Brönstrup, Gerald; Rommel, Mathias; Lips, Klaus; Christiansen, Silke

    2015-08-01

    We investigated hybrid inorganic-organic solar cells combining monocrystalline n-type silicon (n-Si) and a highly conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The build-in potential, photo- and dark saturation current at this hybrid interface are monitored for varying n-Si doping concentrations. We corroborate that a high build-in potential forms at the hybrid junction leading to strong inversion of the n-Si surface. By extracting work function and valence band edge of the polymer from ultraviolet photoelectron spectroscopy, a band diagram of the hybrid n-Si/PEDOT:PSS heterojunction is presented. The current-voltage characteristics were analyzed using Schottky and abrupt pn-junction models. The magnitude as well as the dependence of dark saturation current on n-Si doping concentration proves that the transport is governed by diffusion of minority charge carriers in the n-Si and not by thermionic emission of majorities over a Schottky barrier. This leads to a comprehensive explanation of the high observed open-circuit voltages of up to 634 mV connected to high conversion efficiency of almost 14%, even for simple planar device structures without antireflection coating or optimized contacts. The presented work clearly shows that PEDOT:PSS forms a hybrid heterojunction with n-Si behaving similar to a conventional pn-junction and not, like commonly assumed, a Schottky junction.

  9. Dispersion and transport of hypersaline gravity currents in the presence of internal waves at a pycnocline

    NASA Astrophysics Data System (ADS)

    Hogg, C. A. R.; Pietrasz, V. B.; Ouellette, N. T.; Koseff, J. R.

    2015-12-01

    Desalination of seawater offers a source of potable water in arid regions and during drought. However, hypersaline discharge from desalination facilities presents environmental risks, particularly to benthic organisms. The risks posed by salt levels and chemical additives, which can be toxic to local ecosystems, are typically mitigated by ensuring high levels of dilution close to the source. We report on laboratory flume experiments examining how internal waves at the pycnocline of a layered ambient density stratification influence the transport of hypersaline effluent moving as a gravity current down the slope. We found that some of the hypersaline fluid from the gravity current was diverted away from the slope into an intrusion along the pycnocline. A parametric study investigated how varying the energy of the internal wave altered the amount of dense fluid that was diverted into the pycnocline intrusion. The results are compared to an analytical framework that compares the incident energy in the internal wave to potential energy used in diluting the gravity current. These results are significant for desalination effluents because fluid diverted into the intrusion avoids the ecologically sensitive benthic layer and disperses more quickly than if it had continued to propagate along the bed.

  10. Junction formation and current transport mechanisms in hybrid n-Si/PEDOT:PSS solar cells

    PubMed Central

    Jäckle, Sara; Mattiza, Matthias; Liebhaber, Martin; Brönstrup, Gerald; Rommel, Mathias; Lips, Klaus; Christiansen, Silke

    2015-01-01

    We investigated hybrid inorganic-organic solar cells combining monocrystalline n-type silicon (n-Si) and a highly conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The build-in potential, photo- and dark saturation current at this hybrid interface are monitored for varying n-Si doping concentrations. We corroborate that a high build-in potential forms at the hybrid junction leading to strong inversion of the n-Si surface. By extracting work function and valence band edge of the polymer from ultraviolet photoelectron spectroscopy, a band diagram of the hybrid n-Si/PEDOT:PSS heterojunction is presented. The current-voltage characteristics were analyzed using Schottky and abrupt pn-junction models. The magnitude as well as the dependence of dark saturation current on n-Si doping concentration proves that the transport is governed by diffusion of minority charge carriers in the n-Si and not by thermionic emission of majorities over a Schottky barrier. This leads to a comprehensive explanation of the high observed open-circuit voltages of up to 634 mV connected to high conversion efficiency of almost 14%, even for simple planar device structures without antireflection coating or optimized contacts. The presented work clearly shows that PEDOT:PSS forms a hybrid heterojunction with n-Si behaving similar to a conventional pn-junction and not, like commonly assumed, a Schottky junction. PMID:26278010

  11. Dynamical coupling between magnetic equilibrium and transport in tokamak scenario modelling, with application to current ramps

    NASA Astrophysics Data System (ADS)

    Fable, E.; Angioni, C.; Ivanov, A. A.; Lackner, K.; Maj, O.; Medvedev, S. Yu; Pautasso, G.; Pereverzev, G. V.; Treutterer, W.; the ASDEX Upgrade Team

    2013-07-01

    The modelling of tokamak scenarios requires the simultaneous solution of both the time evolution of the plasma kinetic profiles and of the magnetic equilibrium. Their dynamical coupling involves additional complications, which are not present when the two physical problems are solved separately. Difficulties arise in maintaining consistency in the time evolution among quantities which appear in both the transport and the Grad-Shafranov equations, specifically the poloidal and toroidal magnetic fluxes as a function of each other and of the geometry. The required consistency can be obtained by means of iteration cycles, which are performed outside the equilibrium code and which can have different convergence properties depending on the chosen numerical scheme. When these external iterations are performed, the stability of the coupled system becomes a concern. In contrast, if these iterations are not performed, the coupled system is numerically stable, but can become physically inconsistent. By employing a novel scheme (Fable E et al 2012 Nucl. Fusion submitted), which ensures stability and physical consistency among the same quantities that appear in both the transport and magnetic equilibrium equations, a newly developed version of the ASTRA transport code (Pereverzev G V et al 1991 IPP Report 5/42), which is coupled to the SPIDER equilibrium code (Ivanov A A et al 2005 32nd EPS Conf. on Plasma Physics (Tarragona, 27 June-1 July) vol 29C (ECA) P-5.063), in both prescribed- and free-boundary modes is presented here for the first time. The ASTRA-SPIDER coupled system is then applied to the specific study of the modelling of controlled current ramp-up in ASDEX Upgrade discharges.

  12. Simulation of System Error Tolerances of a High Current Transport Experiment for Heavy-Ion Fusion

    NASA Astrophysics Data System (ADS)

    Lund, Steven M.; Bangerter, Roger O.; Freidman, Alex; Grote, Dave P.; Seidl, Peter A.

    2000-10-01

    A driver-scale, intense ion beam transport experiment (HCX) is being designed to test issues for Heavy Ion Fusion (HIF) [1]. Here we present detailed, Particle in Cell simulations of HCX to parametrically explore how various system errors can impact machine performance. The simulations are transverse and include the full 3D fields of the quadrupole focusing magnets, spreads in axial momentum, conducting pipe boundary conditions, etc. System imperfections such as applied focusing field errors (magnet strength, field nonlinearities, etc.), alignment errors (magnet offsets and rotations), beam envelope mismatches to the focusing lattice, induced beam image charges, and beam distribution errors (beam nonuniformities, collective modes, and other distortions) are all analyzed in turn and in combination. The influence of these errors on the degradation of beam quality (emittance growth), halo production, and loss of beam control are evaluated. Evaluations of practical machine apertures and centroid steering corrections that can mitigate particle loss and degradation of beam quality are carried out. 1. P.A. Seidl, L.E. Ahle, R.O. Bangerter, V.P. Karpenko, S.M. Lund, A Faltens, R.M. Franks, D.B. Shuman, and H.K. Springer, Design of a Proof of Principal High Current Transport Experiment for Heavy-Ion Fusion, these proceedings.

  13. High-resolution modelling of waves, currents and sediment transport in the Catalan Sea.

    NASA Astrophysics Data System (ADS)

    Sánchez-Arcilla, Agustín; Grifoll, Manel; Pallares, Elena; Espino, Manuel

    2013-04-01

    In order to investigate coastal shelf dynamics, a sequence of high resolution multi-scale models have been implemented for the Catalan shelf (North-western Mediterranean Sea). The suite consists of a set of increasing-resolution nested models, based on the circulation model ROMS (Regional Ocean Modelling System), the wave model SWAN (Simulation Waves Nearshore) and the sediment transport model CSTM (Community Sediment Transport Model), covering different ranges of spatial (from ~1 km at shelf-slope regions to ~40 m around river mouth or local beaches) and temporal scales (from storms events to seasonal variability). Contributions in the understanding of local processes such as along-shelf dynamics in the inner-shelf, sediment dispersal from the river discharge or bi-directional wave-current interactions under different synoptic conditions and resolution have been obtained using the Catalan Coast as a pilot site. Numerical results have been compared with "ad-hoc" intensive field campaigns, data from observational models and remote sensing products. The results exhibit acceptable agreement with observations and the investigation has allowed developing generic knowledge and more efficient (process-based) strategies for the coastal and shelf management.

  14. Interconnections between magnetic state and transport currents in antiferromagnetic Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Tsoi, Maxim

    Interconnections between magnetic state and transport currents in ferromagnetic (F) heterostructures are the basis for spintronic applications, e.g. tunneling magnetoresistance and spin-transfer torque phenomena provide a means to read and write information in magnetic memory devices like STTRAM. Similar interconnections were proposed to occur in systems where F-components are replaced with antiferromagnets (AFM). We demonstrated experimentally the existence of such interconnections in antiferromagnetic Mott insulator Sr2IrO4: first, we found a very large anisotropic magnetoresistance (AMR) which can be used to monitor (read) the magnetic state of AFM; second, we demonstrated the feasibility of reversible resistive switching driven by high-density currents/high electric fields which can be used for writing in AFM memory applications. These results support the feasibility of AFM spintronics where antiferromagnets are used in place of ferromagnets. This work was supported in part by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA, and by NSF grants DMR-1207577, DMR-1265162 and DMR-1122603.

  15. On tide-induced Lagrangian residual current and residual transport: 2. Residual transport with application in south San Francisco Bay, California

    USGS Publications Warehouse

    Feng, Shizuo; Cheng, Ralph T.; Pangen, Xi

    1986-01-01

    The transports of solutes and other tracers are fundamental to estuarine processes. The apparent transport mechanisms are convection by tidal current and current-induced shear effect dispersion for processes which take place in a time period of the order of a tidal cycle. However, as emphasis is shifted toward the effects of intertidal processes, the net transport is mainly determined by tide-induced residual circulation and by residual circulation due to other processes. The commonly used intertidal conservation equation takes the form of a convection-dispersion equation in which the convective velocity is the Eulerian residual current, and the dispersion terms are often referred to as the phase effect dispersion or, sometimes, as the “tidal dispersion.” The presence of these dispersion terms is merely the result of a Fickian type hypothesis. Since the actual processes are not Fickian, thus a Fickian hypothesis obscures the physical significance of this equation. Recent research results on residual circulation have suggested that long-term transport phenomena are closely related to the Lagrangian residual current or the Lagrangian residual transport. In this paper a new formulation of an intertidal conservation equation is presented and examined in detail. In a weakly nonlinear tidal estuary the resultant intertidal transport equation also takes the form of a convection-dispersion equation without the ad hoc introduction of phase effect dispersion in a form of dispersion tensor. The convective velocity in the resultant equation is the first-order Lagrangian residual current (the sum of the Eulerian residual current and the Stokes drift). The remaining dispersion terms are important only in higher-order solutions; they are due to shear effect dispersion and turbulent mixing. There exists a dispersion boundary layer adjacent to shoreline boundaries. An order of magnitude estimate of the properties in the dispersion boundary layer is given. The present treatment

  16. Ion current rectification inversion in conic nanopores: nonequilibrium ion transport biased by ion selectivity and spatial asymmetry.

    PubMed

    Yan, Yu; Wang, Lin; Xue, Jianming; Chang, Hsueh-Chia

    2013-01-28

    We show both theoretically and experimentally that the ion-selectivity of a conic nanopore, as defined by a normalized density of the surface charge, significantly affects ion current rectification across the pore. For weakly selective negatively charged pores, intra-pore ion transport controls the current and internal ion enrichment/depletion at positive/reverse biased voltage (current enters/leaves through the tip, respectively), which is responsible for current rectification. For strongly selective negatively charged pores under positive bias, the current can be reduced by external field focusing and concentration depletion at the tip at low ionic strengths and high voltages, respectively. These external phenomena produce a rectification inversion for highly selective pores at high (low) voltage (ionic strength). With an asymptotic analysis of the intra-pore and external ion transport, we derive simple scaling laws to quantitatively capture empirical and numerical data for ion current rectification and rectification inversion of conic nanopores.

  17. Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

    SciTech Connect

    Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe

    2013-12-15

    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.

  18. Increasing transports of volume, heat, and salt towards the Arctic in the Faroe Current 1993-2013

    NASA Astrophysics Data System (ADS)

    Hansen, B.; Larsen, K. M. H.; Hátún, H.; Kristiansen, R.; Mortensen, E.; Østerhus, S.

    2015-06-01

    The flow of warm and saline water from the Atlantic Ocean, across the Greenland-Scotland Ridge, into the Nordic Seas - the Atlantic inflow - is split into three separate branches. The most intensive of these branches is the inflow between Iceland and the Faroe Islands (Faroes), which is focused into the Faroe Current, north of the Faroes. The Atlantic inflow is an integral part of the North Atlantic thermohaline circulation (THC), which is projected to weaken during the 21 century and might conceivably reduce the oceanic heat and salt transports towards the Arctic. Since the mid-1990s, hydrographic properties and current velocities of the Faroe Current have been monitored along a section extending north from the Faroe shelf. From these in situ observations, time series of volume, heat, and salt transport have previously been reported, but the high variability of the transport series has made it difficult to identify trends. Here, we present results from a new analysis of the Faroe Current where the in situ observations have been combined with satellite altimetry. For the period 1993 to 2013, we find the average volume transport of Atlantic water in the Faroe Current to be 3.8 ± 0.5 Sv (1 Sv =106 m3 s-1) with a heat transport relative to 0 °C of 124 ± 15 TW (1 TW =1012 W). Consistent with other results for the Northeast Atlantic component of the THC, we find no indication of weakening. The transports of the Faroe Current, on the contrary, increased. The overall trend over the two decades of observation was 9 ± 8% for volume transport and 18 ± 9% for heat transport (95% confidence intervals). During the same period, the salt transport relative to the salinity of the deep Faroe Bank Channel overflow (34.93) more than doubled, potentially strengthening the feedback on thermohaline intensity. The increased heat and salt transports are partly caused by the increased volume transport and partly by increased temperatures and salinities of the Atlantic inflow

  19. Absence of age-related dopamine transporter loss in current cocaine abusers

    SciTech Connect

    Wang, G.J.; Volkow, N.D.; Fischman, M.

    1997-05-01

    The brain dopamine (DA) system appears to play a crucial role in the reinforcing properties of cocaine. Using PET we had previously shown significant decreases in DA D2 receptors but no changes in DA transporters (DAT) in detoxified cocaine abusers (>1 month after last cocaine use). This study evaluates DAT availability in current cocaine abusers (15 male and 5 female; age = 36.2{+-}5.3 years old) using PET and [C-11]cocaine, as a DAT ligand, and compares it to that in 18 male and 2 female age matched normal controls. Cocaine abusers had a history of abusing 4.2{+-}2.8 gm /week of cocaine for an average of 11.0{+-}4.9 years and their last use of cocaine was 5.4{+-}8 days prior to PET study. DAT availability was obtained using the ratio of the distribution volume in the region of interest (caudate, pulamen) to that in cerebellum which is a function of Bmax./Kd.+1. DAT availability in cocaine abusers did not differ to that in normals (N) (C= 1.78{+-}0.14, N= 1.77{+-}0.13). In addition, there were no differences between the groups in the distribution volume or the Kl (plasma to brain transfer constant) measures for [C-11]cocaine. However, in the normals but not in the abusers striatal DAT availability decreased with age (C: r = -0.07, p = 0.76; N: r = -0.55, p < 0.01). Though this study fails to show group differences in DAT availability between normals and current cocaine abusers it indicates a blunting of the age-related decline in DAT availability in the cocaine abusers. Future studies in older cocaine abusers at different time after detoxification arc required in order to assess if cocaine slows the loss of DAT with age or whether these changes reflect compensation to increased DAT blockade and recover with detoxification.

  20. Thermally-restorable optical degradation and the mechanism of current transport in Cu2S-CdS photovoltaic cells

    NASA Technical Reports Server (NTRS)

    Fahrenbruch, A. L.; Bube, R. H.

    1974-01-01

    The photovoltaic properties of single-crystal Cu2S-CdS heterojunctions have been investigated as a function of heat treatment by detailed measurements of the dependence of short-circuit current on photon energy, temperature, and the state of optical degradation or enhancement. A coherent picture is formulated for the relationship between enhancement and optical degradation, and their effect on the transport of short-circuit photoexcited current and dark, forward-bias current in the cell. Optical degradation in the Cu2S-CdS cell is shown to be closely identical to optical degradation of lifetime in a homogeneous CdS:Cd:Cu crystal, indicating that the CdS:Cu layer near the junction interface controls carrier transport in the cell. It is proposed that both the photoexcited short-circuit current and the dark, forward-bias current are controlled by a tunneling-recombination process through interface states.

  1. Modeling alongshore propagating tides and currents around West Maui, Hawaii and implications for transport using Delft3D.

    NASA Astrophysics Data System (ADS)

    Vitousek, S.; Fletcher, C. H.; Storlazzi, C. D.

    2006-12-01

    Nearshore currents are driven by a number of components including tides, waves winds and even internal tides. To adequately simulate transport of sand and other constituents, the realistic behavior of the dominant current-generating phenomena should be resolved. This often requires sufficient observations and calibration/validation efforts to achieve realistic modeling results. The work explores the capabilities of modeling the currents along West Maui. The West Maui coast has a propagating tide where the observed peak tidal currents, which are directed parallel to the coast, occur very closely to the peak tidal water levels. In 2003, the USGS collected an extensive set of current observations along West Maui, Hawaii, with the goal of better understanding transport mechanisms of sediment, larvae, pollutants and other particles in coral reef settings. The observations included vessel mounted ADCP surveys and an array seafloor instruments at the 10m isobath along the coast. A simple 2DH model of West Maui using Delft3D shows good comparison of the modeled and observed currents. Nearshore currents driven by waves and winds are also considered. During the data collection period a significant erosion event occurred within the study domain at Kaanapali Beach. This event undermined several trees on the shoreline and threatened resort infrastructure. In modeling the nearshore currents of this region we hope to determine the potential for sand transport and shoreline change to hindcast this event.

  2. Regulating Current Rectification and Nanoparticle Transport Through a Salt Gradient in Bipolar Nanopores.

    PubMed

    Lin, Chih-Yuan; Yeh, Li-Hsien; Hsu, Jyh-Ping; Tseng, Shiojenn

    2015-09-16

    Tuning of ion and nanoparticle transport is validated through applying a salt gradient in two types of nanopores: the inner wall of a nanopore has bipolar charges and its outer wall neutral (type I), and both the inner and outer walls of a nanopore have bipolar charges (type II). The ion current rectification (ICR) behavior of these nanopores can be regulated by an applied salt gradient: if it is small, the degree of ICR in type II nanopore is more significant than that in type I nanopore; a reversed trend is observed at a sufficiently large salt gradient. If the applied salt gradient and electric field have the same direction, type I nanopore exhibits two significant features that are not observed in type II nanopore: (i) a cation-rich concentration polarization field and an enhanced funneling electric field are present near the cathode side of the nanopore, and (ii) the magnitude of the axial electric field inside the nanopore is reduced. These features imply that applying a salt gradient to type I nanopore is capable of simultaneously enhancing the nanoparticle capture into the nanopore and reducing its translocation velocity inside, so that high sensing performance and resolution can be achieved.

  3. Spallation neutron production and the current intra-nuclear cascade and transport codes

    NASA Astrophysics Data System (ADS)

    Filges, D.; Goldenbaum, F.; Enke, M.; Galin, J.; Herbach, C.-M.; Hilscher, D.; Jahnke, U.; Letourneau, A.; Lott, B.; Neef, R.-D.; Nünighoff, K.; Paul, N.; Péghaire, A.; Pienkowski, L.; Schaal, H.; Schröder, U.; Sterzenbach, G.; Tietze, A.; Tishchenko, V.; Toke, J.; Wohlmuther, M.

    A recent renascent interest in energetic proton-induced production of neutrons originates largely from the inception of projects for target stations of intense spallation neutron sources, like the planned European Spallation Source (ESS), accelerator-driven nuclear reactors, nuclear waste transmutation, and also from the application for radioactive beams. In the framework of such a neutron production, of major importance is the search for ways for the most efficient conversion of the primary beam energy into neutron production. Although the issue has been quite successfully addressed experimentally by varying the incident proton energy for various target materials and by covering a huge collection of different target geometries --providing an exhaustive matrix of benchmark data-- the ultimate challenge is to increase the predictive power of transport codes currently on the market. To scrutinize these codes, calculations of reaction cross-sections, hadronic interaction lengths, average neutron multiplicities, neutron multiplicity and energy distributions, and the development of hadronic showers are confronted with recent experimental data of the NESSI collaboration. Program packages like HERMES, LCS or MCNPX master the prevision of reaction cross-sections, hadronic interaction lengths, averaged neutron multiplicities and neutron multiplicity distributions in thick and thin targets for a wide spectrum of incident proton energies, geometrical shapes and materials of the target generally within less than 10% deviation, while production cross-section measurements for light charged particles on thin targets point out that appreciable distinctions exist within these models.

  4. Transient transport experiments in the current-drive experiment upgrade spherical torus

    NASA Astrophysics Data System (ADS)

    Munsat, T.; Efthimion, P. C.; Jones, B.; Kaita, R.; Majeski, R.; Stutman, D.; Taylor, G.

    2002-02-01

    Electron transport has been measured in the Current-Drive Experiment Upgrade (CDX-U) (T. Jones, Ph.D. thesis, Princeton University, 1995) using two separate perturbative techniques. Sawteeth at the q=1 radius (r/a˜0.15) induced outward-propagating heat pulses, providing time-of-flight information leading to a determination of χe as a function of radius. Gas modulation at the plasma edge introduced inward-propagating cold pulses, providing a complementary time-of-flight based χe profile measurement. This work represents the first localized measurement of χe in a spherical torus. Core (r/a<1/3) χe values from the sawtooth study are 1-2 m2/s, and from the gas modulation study are 1-6 m2/s, increasing by an order of magnitude or more outside of the core region. Furthermore, the χe profile exhibits a sharp transition near r/a=1/3. Spectral and profile analyses of the soft x-rays, scanning interferometer, and edge probe data show no evidence of a significant magnetic island causing the high χe region. Comparisons are performed to several theoretical models, with measured χe≈5-10× neoclassical estimates in the core.

  5. Polaronic transport and current blockades in epitaxial silicide nanowires and nanowire arrays.

    PubMed

    Iancu, Violeta; Zhang, X-G; Kim, Tae-Hwan; Menard, Laurent D; Kent, P R C; Woodson, Michael E; Ramsey, J Michael; Li, An-Ping; Weitering, Hanno H

    2013-08-14

    Crystalline micrometer-long YSi2 nanowires with cross sections as small as 1 × 0.5 nm(2) can be grown on the Si(001) surface. Their extreme aspect ratios make electron conduction within these nanowires almost ideally one-dimensional, while their compatibility with the silicon platform suggests application as metallic interconnect in Si-based nanoelectronic devices. Here we combine bottom-up epitaxial wire synthesis in ultrahigh vacuum with top-down miniaturization of the electrical measurement probes to elucidate the electronic conduction mechanism of both individual wires and arrays of nanowires. Temperature-dependent transport through individual nanowires is indicative of thermally assisted tunneling of small polarons between atomic-scale defect centers. In-depth analysis of complex wire networks emphasize significant electronic crosstalk between the nanowires due to the long-range Coulomb fields associated with polaronic charge fluctuations. This work establishes a semiquantitative correlation between the density and distributions of atomic-scale defects and resulting current-voltage characteristics of nanoscale network devices. PMID:23902411

  6. Polaronic transport and current blockades in epitaxial silicide nanowires and nanowire arrays.

    PubMed

    Iancu, Violeta; Zhang, X-G; Kim, Tae-Hwan; Menard, Laurent D; Kent, P R C; Woodson, Michael E; Ramsey, J Michael; Li, An-Ping; Weitering, Hanno H

    2013-08-14

    Crystalline micrometer-long YSi2 nanowires with cross sections as small as 1 × 0.5 nm(2) can be grown on the Si(001) surface. Their extreme aspect ratios make electron conduction within these nanowires almost ideally one-dimensional, while their compatibility with the silicon platform suggests application as metallic interconnect in Si-based nanoelectronic devices. Here we combine bottom-up epitaxial wire synthesis in ultrahigh vacuum with top-down miniaturization of the electrical measurement probes to elucidate the electronic conduction mechanism of both individual wires and arrays of nanowires. Temperature-dependent transport through individual nanowires is indicative of thermally assisted tunneling of small polarons between atomic-scale defect centers. In-depth analysis of complex wire networks emphasize significant electronic crosstalk between the nanowires due to the long-range Coulomb fields associated with polaronic charge fluctuations. This work establishes a semiquantitative correlation between the density and distributions of atomic-scale defects and resulting current-voltage characteristics of nanoscale network devices.

  7. California coast nearshore processes study. [nearshore currents, sediment transport, estuaries, and river discharge

    NASA Technical Reports Server (NTRS)

    Pirie, D. M.; Steller, D. D. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Large scale sediment plumes from intermittent streams and rivers form detectable seasonal patterns on ERTS-1 imagery. The ocean current systems, as plotted from three California coast ERTS mosaics, were identified. Offshore patterns of sediment in areas such as the Santa Barbara Channel are traceable. These patterns extend offshore to heretofore unanticipated ranges as shown on the ERTS-1 imagery. Flying spot scanner enhancements of NASA tapes resulted in details of subtle and often invisible (to the eye) nearshore features. The suspended sediments off San Francisco and in Monterey Bay are emphasized in detail. These are areas of extremely changeable offshore sediment transport patterns. Computer generated contouring of radiance levels resulted in maps that can be used in determining surface and nearsurface suspended sediment distribution. Tentative calibrations of ERTS-1 spectral brightness against sediment load have been made using shipboard measurements. Information from the combined enhancement and interpretation techniques is applicable to operational coastal engineering programs.

  8. Specific transport and storage solutions : waste management facing current and future stakes of the nuclear fuel cycle

    SciTech Connect

    Choho, T.; Blachet, L.; Deniau, H.; Gagner, L.; Gendreau, F.; Presta, A.

    2007-07-01

    With major projects ongoing or being planned, and also with the daily management of radioactive waste from nuclear facilities, the role of transport and/or storage packaging has been often overlooked. Indeed, the packaging development process and transport solutions implemented are a key part of the waste management challenge : protection of people and of the environment. During over four decades, the AREVA Group has developed a complete and coherent system for the transport of waste produced by nuclear industries. The transport solutions integrate the factors to consider, as industrial transportation needs, various waste forms, associated hazards and current regulations. Thus, TN International has designed, licensed and manufactured a large number of different transport, storage and dual purpose cask models for residues and all kinds of radioactive wastes. The present paper proposes to illustrate how a company acting both as a cask designer and a carrier is key to the waste management issue and how it can support the waste management policy of nuclear waste producers through their operational choices. We will focus on the TN International technical solutions implemented to guarantee safe and secure transportation and storage solutions. We will describe different aspects of the cask design process, insisting on how it enables to fulfil both customer needs and regulation requirements. We will also mention the associated services developed by the AREVA Business Unit Logistics (TN International, TRANSNUCLEAR, MAINCO, and LMC) in order to manage transportation of liquid and solid waste towards interim or final storage sites. (authors)

  9. Current-direction dependence of the transport properties in single-crystalline face-centered-cubic cobalt films

    SciTech Connect

    Xiao, X.; Liang, J. H.; Chen, B. L.; Li, J. X.; Ding, Z.; Wu, Y. Z.; Ma, D. H.

    2015-07-28

    Face-centered-cubic cobalt films are epitaxially grown on insulating LaAlO{sub 3}(001) substrates by molecular beam epitaxy. Transport measurements are conducted in different current directions relative to the crystal axes. We find that the temperature dependent anisotropic magnetoresistance ratio strongly depends on the current direction. However, the anomalous Hall effect shows isotropic behavior independent of the current direction. Our results demonstrate the interplay between the current direction and the crystalline lattice in single-crystalline ferromagnetic films. A phenomenological analysis is presented to interpret the experimental data.

  10. Effects of midlatitude westerlies on the paleoproductivity at the Agulhas Bank slope during the penultimate glacial cycle: Evidence from coccolith Sr/Ca ratios

    NASA Astrophysics Data System (ADS)

    Mejia, Luz Maria; Ziveri, Patrizia; Cagnetti, Marilisa; Bolton, Clara; Zahn, Rainer; Marino, Gianluca; Martinez Mendez, Gema; Stoll, Heather

    2015-04-01

    Because modern primary productivity on the Agulhas Bank, off South Africa, is linked to the mid-latitude westerlies, a paleoproductivity record from this area could be used to investigate past may changes in the westerlies dynamics. Coccolith Sr/Ca is a suitable productivity indicator to explore paleoproductivity from the penultimate glacial-interglacial cycle because it is independent of preservation changes that may accompany changes in deepwater circulation. In the Agulhas Bank slope core MD96-2080, the coccolith Sr/Ca record shows that phases of depressed productivity coincided with periods of stratification in the same core, indicated by high relative abundances of the coccolithophore Florisphaera profunda, and with low relative abundances of the upwelling indicator G. bulloides in the Cape Basin. This coherence suggests that upwelling regulated productivity throughout this region. As in the present, we infer that periods of low productivity result from northward positions of the westerlies which block the upwelling-promoting easterlies. Productivity minima also coincide with periods of increased ice-rafted detritus (IRD) deposition on the Agulhas Plateau, which also indicates extreme northward positions of the westerlies. The influence of the westerlies appears to be obliquity-conditioned, as productivity minima occur during low obliquity intervals. The dynamic connection between productivity and the westerlies is supported by coeval salinity changes in the South Indian Gyre that likewise respond sensitively to a poleward contraction of the westerlies.

  11. Current transport mechanism in graphene/AlGaN/GaN heterostructures with various Al mole fractions

    NASA Astrophysics Data System (ADS)

    Pandit, Bhishma; Seo, Tae Hoon; Ryu, Beo Deul; Cho, Jaehee

    2016-06-01

    The current transport mechanism of graphene formed on AlxGa1-xN/GaN heterostructures with various Al mole fractions (x = 0.15, 0.20, 0.30, and 0.40) is investigated. The current-voltage measurement from graphene to AlGaN/GaN shows an excellent rectifying property. The extracted Schottky barrier height of the graphene/AlGaN/GaN contacts increases with the Al mole fraction in AlGaN. However, the current transport mechanism deviates from the Schottky-Mott theory owing to the deterioration of AlGaN crystal quality at high Al mole fractions confirmed by reverse leakage current measurement.

  12. Effect of inhibitors of auxin transport and of calmodulin on a gravisensing-dependent current in maize roots

    NASA Technical Reports Server (NTRS)

    Bjorkman, T.; Leopold, A. C.

    1987-01-01

    Some characteristics of the gravity sensing mechanism in maize root caps were investigated using a bioelectric current as an indicator of gravity sensing. This technique involves the measurement of a change in the current density which arises at the columella region coincidently with the presentation time. Two inhibitors of auxin transport, triiodobenzoic acid and naphthylphthalamic acid, blocked gravitropic curvature but not the change in current density. Two inhibitors of calmodulin activity, compound 48/80 and calmidazolium, blocked both curvature and gravity-induced current. The results suggest that auxin transport is not a component of gravity sensing in the root cap. By contrast, the results suggest that calmodulin plays an intrinsic role in gravity sensing.

  13. Microstructural analysis of mass transport phenomena in gas diffusion media for high current density operation in PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Kotaka, Toshikazu; Tabuchi, Yuichiro; Mukherjee, Partha P.

    2015-04-01

    Cost reduction is a key issue for commercialization of fuel cell electric vehicles (FCEV). High current density operation is a solution pathway. In order to realize high current density operation, it is necessary to reduce mass transport resistance in the gas diffusion media commonly consisted of gas diffusion layer (GDL) and micro porous layer (MPL). However, fundamental understanding of the underlying mass transport phenomena in the porous components is not only critical but also not fully understood yet due to the inherent microstructural complexity. In this study, a comprehensive analysis of electron and oxygen transport in the GDL and MPL is conducted experimentally and numerically with three-dimensional (3D) microstructural data to reveal the structure-transport relationship. The results reveal that the mass transport in the GDL is strongly dependent on the local microstructural variations, such as local pore/solid volume fractions and connectivity. However, especially in the case of the electrical conductivity of MPL, the contact resistance between carbon particles is the dominant factor. This suggests that reducing the contact resistance between carbon particles and/or the number of contact points along the transport pathway can improve the electrical conductivity of MPL.

  14. Volume Transports from moored geostrophic and direct Measurements in the Deep Western Boundary Current east of Abaco, Bahamas

    NASA Astrophysics Data System (ADS)

    Kanzow, T.; Johns, W. E.; Zantopp, R.

    2003-04-01

    Moored geostrophic measurements are receiving increased attention in oceanic monitoring applications as they yield a horizontally integrated measure of the volume transport. Thus, they provide an inexpensive tool for climate research. Examples of ongoing or planned applications of this technique include the German MOVE experiment in the tropical Atlantic (operating since 2000) and a joint UK/US program designed to monitor the Atlantic meridional overturning circulation at 26.5 N (starting in 2004). This paper shows an earlier practical application of this approach in the Atlantic deep western boundary current at 26.5 N off Abaco, Bahamas, based on data collected within the framework of the ACCP (Atlantic Climate Change Program) between November 95 and June 97. We present the underlying methodology and describe the transport variability observed in the Deep Western Boundary Current by the moored geostrophic technique. Near-boundary transport fluctuations exceeding at times 40 Sv are found on a monthly scale, partly compensated by flow reversals further offshore. The signals are mainly barotropic but a significant baroclinic contribution on longer time scales is also observed. These geostrophic transports are compared to simultaneously acquired moored transports derived from current meter measurements, which proves the feasibility of the geostrophic approach. The array configuration also allows an extended error analysis of both methods (direct vs. geostrophic), which shows a comparable accuracy of both techniques and agreement within the estimated errors.

  15. Current-transport mechanism in Au/V-doped PVC+TCNQ/p-Si structures

    NASA Astrophysics Data System (ADS)

    Tecimer, H.; Vural, Ö.; Kaya, A.; Altındal, Ş.

    2015-03-01

    The forward and reverse bias current-voltage (I-V) characteristics of Au/V-doped polyvinyl chloride+Tetracyanoquino dimethane/porous silicon (PVC+TCNQ/p-Si) structures have been investigated in the temperature range of 160-340 K. The zero bias or apparent barrier height (BH) (Φap = ΦBo) and ideality factor (nap = n) were found strongly temperature dependent and the value of nap decreases, while the Φap increases with the increasing temperature. Also, the Φap versus T plot shows almost a straight line which has positive temperature coefficient and it is not in agreement with the negative temperature coefficient of ideal diode or forbidden bandgap of Si (αSi = -4.73×10-4eV/K). The high value of n cannot be explained only with respect to interfacial insulator layer and interface traps. In order to explain such behavior of Φap and nap with temperature, Φap Versus q/2kT plot was drawn and the mean value of (ΦBo) and standard deviation (σs) values found from the slope and intercept of this plot as 1.176 eV and 0.152 V, respectively. Thus, the modified (ln(Io/T2)-(qσs)2/2(kT)2 versus (q/kT) plot gives the ΦBo and effective Richardson constant A* as 1.115 eV and 31.94 Aṡ(cmṡK)-2, respectively. This value of A*( = 31.94 Aṡ(cmṡK)-2) is very close to the theoretical value of 32 Aṡ(cmṡK)-2 for p-Si. Therefore, the forward bias I-V-T characteristics confirmed that the current-transport mechanism (CTM) in Au/V-doped PVC+TCNQ/p-Si structures can be successfully explained in terms of the thermionic emission (TE) mechanism with a Gaussian distribution (GD) of BHs at around mean BH.

  16. Temperature dependence of critical current and transport current losses of 4 mm YBCO coated conductors manufactured using nonmagnetic substrate

    NASA Astrophysics Data System (ADS)

    Kvitkovic, J.; Hatwar, R.; Pamidi, S. V.; Fleshler, S.; Thieme, C.

    2015-12-01

    The temperature dependence of the critical current and AC losses were measured on American Superconductor Corporation's (AMSC) second generation high temperature superconducting (2G HTS) wire produced by Rolling Assisted Biaxially Textured Substrate (RABiTS) and Metal Organic Deposition (MOD) process. Wires manufactured with two types of substrates were characterized. The magnetic substrate with composition Ni5a%W exhibits a magnetic signature and has non-negligible AC losses in AC power applications. A new nonmagnetic substrate with an alloy composition Ni9a%W has been developed by AMSC to address the AC losses in 2G HTS. The data presented show that the performance of the new conductor is identical to the conductor with magnetic substrate in terms of critical current density. The data on AC losses demonstrate the absence of ferromagnetic loss component in the new conductor and significantly reduced AC losses at low to moderate values of I/Ic. The reduced losses will translate into reduced capital costs and lower operating costs of superconducting electrical devices for AC applications.

  17. Effect of the magnetic material on AC losses in HTS conductors in AC magnetic field carrying AC transport current

    NASA Astrophysics Data System (ADS)

    Wan, Xing-Xing; Huang, Chen-Guang; Yong, Hua-Dong; Zhou, You-He

    2015-11-01

    This paper presents an investigation on the AC losses in several typical superconducting composite conductors using the H-formulation model. A single superconducting strip with ferromagnetic substrate or cores and a stack of coated conductors with ferromagnetic substrates are studied. We consider all the coated conductors carrying AC transport currents and simultaneously exposed to perpendicular AC magnetic fields. The influences of the amplitude, frequency, phase difference and ferromagnetic materials on the AC losses are investigated. The results show that the magnetization losses of single strip and stacked strips have similar characteristics. The ferromagnetic substrate can increase the magnetization loss at low magnetic field, and decrease the loss at high magnetic field. The ferromagnetic substrate can obviously increase the transport loss in stacked strips. The trends of total AC losses of single strip and stacked strips are similar when they are carrying current or exposed to a perpendicular magnetic field. The effect of the frequency on the total AC losses of single strip is related to the amplitude of magnetic field. The AC losses decrease with increasing frequency in low magnetic field region while increase in high magnetic field region. As the phase difference changes, there is a periodic variation for the AC losses. Moreover, when the strip is under only the transport current and magnetic field, the ferromagnetic cores will increase the AC losses for large transport current or field.

  18. Current conceptual model of groundwater flow and contaminant transport at Sandia National Laboratories/New Mexico Technical Area V.

    SciTech Connect

    Orr, Brennon R.; Dettmers, Dana L.

    2004-04-01

    The New Mexico Environment Department (NMED) requires a Corrective Measures Evaluation to evaluate potential remedial alternatives for contaminants of concern (COCs) in groundwater at Sandia National Laboratories New Mexico (SNUNM) Technical Area (TA)-V. These COCs consist of trichloroethene, tetrachloroethene, and nitrate. This document presents the current conceptual model of groundwater flow and transport at TA-V that will provide the basis for a technically defensible evaluation. Characterization is defined by nine requirement areas that were identified in the NMED Compliance Order on Consent. These characterization requirement areas consist of geohydrologic characteristics that control the subsurface distribution and transport of contaminants. This conceptual model document summarizes the regional geohydrologic setting of SNUNM TA-V. The document also presents a summary of site-specific geohydrologic data and integrates these data into the current conceptual model of flow and contaminant transport. This summary includes characterization of the local geologic framework; characterization of hydrologic conditions at TA-V, including recharge, hydraulics of vadose-zone and aquifer flow, and the aquifer field of flow as it pertains to downgradient receptors. The summary also discusses characterization of contaminant transport in the subsurface, including discussion about source term inventory, release, and contaminant distribution and transport in the vadose zone and aquifer.

  19. Comparison between the magnetic and transport critical current densities in high critical current density melt-textured yttrium barium copper-oxide

    NASA Technical Reports Server (NTRS)

    Gao, L.; Meng, R. L.; Xue, Y. Y.; Hor, P. H.; Chu, C. W.

    1991-01-01

    Using a recently developed pulsed critical current density (Jc) measuring system, the Jc of the high-Jc melt-textured YBa2Cu3O(7-delta) (Y123) bulk samples has been determined. I-V curves with a voltage resolution of 0.5 microV were obtained, and transport Jc's along the a-b plane as high as 7.2 x 10 to the 4th A/sq cm were extracted. These results are comparable to the values obtained magnetically. On the other hand, transport Jc along the c axis were found to be two orders of magnitude smaller, even though the magnetic Jc along the c axis is only about five times smaller than Jc along the a-b plane. It is suggested that for the high-temperature superconducting materials which are highly anisotropic, caution should be taken when using the nontransport magnetic methods to determine Jc.

  20. Experimental evidence of direct contact formation for the current transport in silver thick film metallized silicon emitters

    NASA Astrophysics Data System (ADS)

    Cabrera, Enrique; Olibet, Sara; Glatz-Reichenbach, Joachim; Kopecek, Radovan; Reinke, Daniel; Schubert, Gunnar

    2011-12-01

    Great advances have been achieved in the development of silver pastes. The use of smaller silver particles, higher silver content, and, thus, less glass frit allow modern silver pastes to contact high resistive emitters without the necessity of a selective emitter or subsequent plating. To identify the microscopic key reasons behind the improvement of silver paste, it is essential to understand the current transport mechanism from the silicon emitter into the bulk of the silver finger. Two current transport theories predominate: i) The current flows through the Ag crystallites grown into the Si emitter, which are separated by a thin glass layer or possibly in direct contact with the silver finger. ii) The current is transported by means of multistep tunneling into the silver finger across nano-Ag colloids in the glass layer, which are formed at optimal firing conditions; the formation of Ag crystallites into the Si surface is synonymous with over-firing. In this study, we contact Si solar cell emitters with different silver pastes on textured and flat silicon surfaces. A sequential selective silver-glass etching process is employed to expose and isolate the different contact components for current transport. The surface configurations after the etching sequences are observed with scanning electron microscopy. Liquid conductive silver is then applied to each sample and the contact resistivity is measured to determine the dominant microscopic conduction path system. We observe glass-free emitter areas at the tops of the pyramidal-textured Si that lead to the formation of direct contacts between the Ag crystallites grown into the Si emitter and the bulk of the silver finger. We present experimental evidence that the major current flow into the silver finger is through these direct contacts.

  1. Airborne biological hazards and urban transport infrastructure: current challenges and future directions.

    PubMed

    Nasir, Zaheer Ahmad; Campos, Luiza Cintra; Christie, Nicola; Colbeck, Ian

    2016-08-01

    Exposure to airborne biological hazards in an ever expanding urban transport infrastructure and highly diverse mobile population is of growing concern, in terms of both public health and biosecurity. The existing policies and practices on design, construction and operation of these infrastructures may have severe implications for airborne disease transmission, particularly, in the event of a pandemic or intentional release of biological of agents. This paper reviews existing knowledge on airborne disease transmission in different modes of transport, highlights the factors enhancing the vulnerability of transport infrastructures to airborne disease transmission, discusses the potential protection measures and identifies the research gaps in order to build a bioresilient transport infrastructure. The unification of security and public health research, inclusion of public health security concepts at the design and planning phase, and a holistic system approach involving all the stakeholders over the life cycle of transport infrastructure hold the key to mitigate the challenges posed by biological hazards in the twenty-first century transport infrastructure.

  2. Airborne biological hazards and urban transport infrastructure: current challenges and future directions.

    PubMed

    Nasir, Zaheer Ahmad; Campos, Luiza Cintra; Christie, Nicola; Colbeck, Ian

    2016-08-01

    Exposure to airborne biological hazards in an ever expanding urban transport infrastructure and highly diverse mobile population is of growing concern, in terms of both public health and biosecurity. The existing policies and practices on design, construction and operation of these infrastructures may have severe implications for airborne disease transmission, particularly, in the event of a pandemic or intentional release of biological of agents. This paper reviews existing knowledge on airborne disease transmission in different modes of transport, highlights the factors enhancing the vulnerability of transport infrastructures to airborne disease transmission, discusses the potential protection measures and identifies the research gaps in order to build a bioresilient transport infrastructure. The unification of security and public health research, inclusion of public health security concepts at the design and planning phase, and a holistic system approach involving all the stakeholders over the life cycle of transport infrastructure hold the key to mitigate the challenges posed by biological hazards in the twenty-first century transport infrastructure. PMID:27318484

  3. Transporter-associated currents in the gamma-aminobutyric acid transporter GAT-1 are conditionally impaired by mutations of a conserved glycine residue.

    PubMed

    Zhou, Yonggang; Kanner, Baruch I

    2005-05-27

    To determine whether glycine residues play a role in the conformational changes during neurotransmitter transport, we have analyzed site-directed mutants of the gamma-aminobutyric acid (GABA) transporter GAT-1 in a domain containing three consecutive glycines conserved throughout the sodium- and chloride-dependent neurotransmitter transporter family. Only cysteine replacement of glycine 80 resulted in the complete loss of [(3)H]GABA uptake, but oocytes expressing this mutant exhibited the sodium-dependent transient currents thought to reflect a charge-moving conformational change. When sodium was removed and subsequently added back, the transients by G80C did not recover, as opposed to wild type, where recovery was almost complete. Remarkably, the transients by G80C could be restored after exposure of the oocytes to either GABA or a depolarizing pre-pulse. These treatments also resulted in a full recovery of the transients by the wild type. Whereas in wild type lithium leak currents are observed after prior sodium depletion, this was not the case for the glycine 80 mutants unless GABA was added or the oocytes were subjected to a depolarizing pre-pulse. Thus, glycine 80 appears essential for conformational transitions in GAT-1. When this residue is mutated, removal of sodium results in "freezing" the transporter in one conformation from which it can only exit by compensatory changes induced by GABA or depolarization. Our results can be explained by a model invoking two outward-facing states of the empty transporter and a defective transition between these states in the glycine 80 mutants.

  4. Current transport mechanisms in lattice-matched Pt/Au-InAlN/GaN Schottky diodes

    SciTech Connect

    Ren, Jian; Yan, Dawei Yang, Guofeng; Wang, Fuxue; Xiao, Shaoqing; Gu, Xiaofeng

    2015-04-21

    Lattice-matched Pt/Au-In{sub 0.17}Al{sub 0.83}N/GaN hetreojunction Schottky diodes with circular planar structure have been fabricated and investigated by temperature dependent electrical measurements. The forward and reverse current transport mechanisms are analyzed by fitting the experimental current-voltage characteristics of the devices with various models. The results show that (1) the forward-low-bias current is mainly due to the multiple trap-assisted tunneling, while the forward-high-bias current is governed by the thermionic emission mechanism with a significant series resistance effect; (2) the reverse leakage current under low electric fields (<6 MV/cm) is mainly carried by the Frenkel-Poole emission electrons, while at higher fields the Fowler-Nordheim tunneling mechanism dominates due to the formation of a triangular barrier.

  5. Transport studies in polymer electrolyte fuel cell with porous metallic flow field at ultra high current density

    NASA Astrophysics Data System (ADS)

    Srouji, Abdul-Kader

    Achieving cost reduction for polymer electrolyte fuel cells (PEFC) requires a simultaneous effort in increasing power density while reducing precious metal loading. In PEFCs, the cathode performance is often limiting due to both the slow oxygen reduction reaction (ORR), and mass transport limitation caused by limited oxygen diffusion and liquid water flooding at high current density. This study is motivated by the achievement of ultra-high current density through the elimination of the channel/land (C/L) paradigm in PEFC flow field design. An open metallic element (OME) flow field capable of operating at unprecedented ultra-high current density (3 A/cm2) introduces new advantages and limitations for PEFC operation. The first part of this study compares the OME with a conventional C/L flow field, through performance and electrochemical diagnostic tools such as electrochemical impedance spectroscopy (EIS). The results indicate the uniqueness of the OME's mass transport improvement. No sign of operation limitation due to flooding is noted. The second part specifically examines water management at high current density using the OME flow field. A unique experimental setup is developed to measure steady-state and transient net water drag across the membrane, in order to characterize the fundamental aspects of water transport at high current density with the OME. Instead of flooding, the new limitation is identified to be anode side dry-out of the membrane, caused by electroosmotic drag. The OME improves water removal from the cathode, which immediately improves oxygen transport and performance. However, the low water content in the cathode reduces back diffusion of water to the membrane, and electroosmotic drag dominates at high current density, leading to dry-out. The third part employs the OME flow field as a tool that avoids C/L effects endemic to a typical flow field, in order to study oxygen transport resistance at the catalyst layer of a PEFC. In open literature, a

  6. Hormone- and light-regulated nucleocytoplasmic transport in plants: current status.

    PubMed

    Lee, Yew; Lee, Hak-Soo; Lee, June-Seung; Kim, Seong-Ki; Kim, Soo-Hwan

    2008-01-01

    The gene regulation mechanisms underlying hormone- and light-induced signal transduction in plants rely not only on post-translational modification and protein degradation, but also on selective inclusion and exclusion of proteins from the nucleus. For example, plant cells treated with light or hormones actively transport many signalling regulatory proteins, transcription factors, and even photoreceptors and hormone receptors into the nucleus, while actively excluding other proteins. The nuclear envelope (NE) is the physical and functional barrier that mediates this selective partitioning, and nuclear transport regulators transduce hormone- or light-initiated signalling pathways across the membrane to mediate nuclear activities. Recent reports revealed that mutating the proteins regulating nuclear transport through the pores, such as nucleoporins, alters the plant's response to a stimulus. In this review, recent works are introduced that have revealed the importance of regulated nucleocytoplasmic partitioning. These important findings deepen our understanding about how co-ordinated plant hormone and light signal transduction pathways facilitate communication between the cytoplasm and the nucleus. The roles of nucleoporin components within the nuclear pore complex (NPC) are also emphasized, as well as nuclear transport cargo, such as Ran/TC4 and its binding proteins (RanBPs), in this process. Recent findings concerning these proteins may provide a possible direction by which to characterize the regulatory potential of hormone- or light-triggered nuclear transport.

  7. Ion transport and loss in the Earth`s quiet ring current: 2. Diffusion and magnetosphere-ionosphere coupling

    SciTech Connect

    Sheldon, R.B.

    1994-04-01

    The author has studied the transport and loss of H{sup +}, He{sup +}, and He{sup ++} ions in the Earth`s quite time ring current (1-300 keV/e, 3-7 R{sub E}, Kp<2+, {vert_bar}Dst{vert_bar}<11, 70{degrees}-110{degrees} pitchangles, all LT) comparing the standard radial diffusion model developed for the higher-energy radiation belt particles with measurements of the lower energy ring current ions in a previous paper. Large deviations of that model, which fit only 50% of the data to within a factor of 10, suggested that another transport mechanism is operating in the ring current. Here the author derives a modified diffusion coefficient corrected for electric field effects on ring current energy ions that fit nearly 80% of the data to within a factor of 2. Thus he infers that electric field fluctuations from the low-latitude to midlatitude ionosphere (ionosphere dynamo) dominate the ring current transport, rather than high-latitude or solar wind fluctuations. Much of the remaining deviation may arise from convective electric field transport of the E<30 keV particles. Since convection effects cannot be correctly treated with this azimuthally symmetric model, the author defers treatment of the lowest-energy ions to another paper. The author gives {Chi}{sup 2} contours for the best fit, showing the dependence of the fit upon the internal/external spectral power of the predicted electric and magnetic field fluctuations. 64 refs., 7 figs., 1 tab.

  8. The structure and stability of transport and mixing barriers in the Antarctic Circumpolar Current

    NASA Astrophysics Data System (ADS)

    Wilson, C.; Blundell, J. R.; Hughes, C. W.; Mazloff, M.; Shuckburgh, E.; Thompson, A. F.

    2012-04-01

    As well as transporting water large distances between ocean basins, the ACC also regulates transport and mixing across its flow. Understanding the spatial and temporal variations in transport behaviour is highly relevant for modelling and predicting the global Meridional Overturning Circulation, the spread of heat content anomalies to or from Antarctica and the transport of dissolved carbon dioxide by the ocean. Both the multiple jet structure of the ACC and its intermittent mixing inhibition are locally describable by a zonally-uniform model of potential vorticity dynamics, called the Potential Vorticity Staircase, used to explain temporally-intermittent mixing across the atmospheric ozone hole boundary and the persistence of jets on Jupiter. In a previous study, we found support for the zonally-inhomogeneous Southern Ocean analogue of the PV Staircase, and that the PV structure changes downstream of major features of seafloor topography. Here, we test the details of the PV Staircase model in the Southern Ocean using over 600 years of eddy-resolving experiments with the Q-GCM, OFES and SOSE models. We develop tools based on kernel density estimation to identify the staircase structure in the isopycnic potential vorticity. Under present-day and increased eastward wind stress experiments, we determine the relationship of the structure and its stability to mesoscale eddy intensity, measures of transport and mixing, mean flow and seafloor topography. From the multi-decadal ensemble of wind stress trend experiments we find evidence of 'eddy saturation': minimal response in the zonal transport with respect to increasing wind stress. There is a relationship between the strength of the wind stress and of the eddies, and hence substantial changes to the multiple jet structure, as expected from the PV Staircase. However, this relationship is complicated by regional variations in seafloor topography and by internal variability.

  9. Impact of charge transport on current-voltage characteristics and power-conversion efficiency of organic solar cells.

    PubMed

    Würfel, Uli; Neher, Dieter; Spies, Annika; Albrecht, Steve

    2015-04-24

    This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current-voltage curves of organic solar cells under illumination with the Shockley equation results in values for ideality factor, photocurrent and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells.

  10. Cross-shelf transport of pink shrimp larvae: Interactions of tidal currents, larval vertical migrations and internal tides

    USGS Publications Warehouse

    Criales, Maria M.; Browder, Joan A.; Mooers, C.N.K.; Robblee, M.B.; Cardenas, H.; Jackson, Thomas L.

    2007-01-01

    Transport and behavior of pink shrimp Farfantepenaeus duorarum larvae were investigated on the southwestern Florida (SWF) shelf of the Gulf of Mexico between the Dry Tortugas spawning grounds and Florida Bay nursery grounds. Stratified plankton samples and hydrographic data were collected at 2 h intervals at 3 stations located on a cross-shelf transect. At the Marquesas station, midway between Dry Tortugas and Florida Bay, internal tides were recognized by anomalously cool water, a shallow thermocline with strong density gradients, strong current shear, and a high concentration of pink shrimp larvae at the shallow thermocline. Low Richardson numbers occurred at the pycnocline depth, indicating vertical shear instability and possible turbulent transport from the lower to the upper layer where myses and postlarvae were concentrated. Analysis of vertically stratified plankton suggested that larvae perform vertical migrations and the specific behavior changes ontogenetically; protozoeae were found deeper than myses, and myses deeper than postlarvae. Relative concentrations of protozoea in the upper, middle and bottom layers were consistent with a diel vertical migration, whereas that of postlarvae and myses were consistent with the semidiurnal tides in phase with the flood tide. Postlarvae, the shallowest dwellers that migrate with a semidiurnal periodicity, experienced the largest net onshore flux and larval concentrations were highly correlated with the cross-shelf current. These results provide the first evidence of an onshore tidal transport (a type of selective tidal stream transport, STST), in decapod larvae migrating in continental shelf waters offshore, ca. 100 km from the coast and at a depth of 20 m, while approaching the coastal nursery grounds. Longer time series would be necessary to establish whether internal tides play any role in the larval onshore transport of this species and determine if the STST is the dominant onshore transport mechanism.

  11. Liquid freshwater transport and Polar Surface Water characteristics in the East Greenland Current during the AO-02 Oden expedition

    NASA Astrophysics Data System (ADS)

    Nilsson, Johan; Björk, Göran; Rudels, Bert; Winsor, Peter; Torres, Daniel

    2008-07-01

    Dynamical features of the East Greenland Current (EGC) are synthesized from a survey conducted by the Swedish icebreaker Oden during the International Arctic Ocean - 02 expedition (AO-02) in May 2002 with emphasis on the liquid freshwater transport and Polar Surface Water. The data include hydrography and lowered acoustic doppler current profiler (LADCP) velocities in eight transects along the EGC, from the Fram Strait in the north to the Denmark Strait in the south. The survey reveals a strong confinement of the low-salinity polar water in the EGC to the continental slope/shelf-a feature of relevance for the stability of the thermohaline circulation in the Arctic Mediterranean. The southward transport of liquid freshwater in the EGC was found to vary considerably between the sections, ranging between 0.01 and 0.1 Sverdrup. Computations based on geostrophic as well as LADCP velocities give a section-averaged southward freshwater transport of 0.06 Sverdrup in the EGC during May 2002. Furthermore, Oden data suggest that the liquid freshwater transport was as large north of the Fram Strait as it was south of the Denmark Strait.

  12. Levant jet system-effect of post LGM seafloor currents on Nile sediment transport in the eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Schattner, U.; Gurevich, M.; Kanari, M.; Lazar, M.

    2015-11-01

    Sedimentary development of a continental margin is directly related to seafloor current dynamics. Yet the linkage between the processes remains vague due to the different time scales they represent. To narrow this gap we focus on the thoroughly studied distribution system of Nile derived sediments across the Levant continental margin (eastern Mediterranean). These sediments dominate the Late Quaternary stratigraphy of the entire margin. Their mobilization has been explained exclusively by longshore transport, while oceanographic evidence from the basin and margin are not incorporated in the known mechanism. New data indicates that longshore mechanism is part of a much larger system. Based on integrated interpretation of multibeam bathymetry, high-resolution single-channel seismic reflection and oceanographic (temperature, salinity and chlorophyll) data we suggest a jet current system mobilizes the Levant Surface Water (LSW), Levant Intermediate Water (LIW) and Atlantic Water (AW) northwards along the margin, between 0 and 400 m water depths. On the seafloor, contourite currents form elongated along-strike morphologies. Below 400 m along-dip gravity flows dominate sediment transport to down the slope, below the Eastern Mediterranean Deep Water (EMDW). Initiation of this mechanism during the Pleistocene-Holocene transition and not at the end of the Last Glacial Maximum (LGM) indicates a gradual recovery of the thermo-haline circulation. Current intensification in the early Holocene may have also increased water stratification. This comprehensive mechanism explains sediment transport along the entire depth range of the continental margin, while integrating seafloor currents, morphology, as well as their relation to sea level rise and stratigraphy of water masses in the Levant basin since the LGM. Given the consistency of seafloor currents throughout the Holocene we propose to address them as the Levant Jet System.

  13. Transport of time-varying plasma currents by whistler wave packets

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.; Urrutia, J. M.; Rousculp, C.

    1992-01-01

    The relationship between pulsed currents and electromagnetic waves is examined in a regime characterized by electron MHD. Pulsed currents are generated by (1) collection/emission of charged particles by/from biased electrodes and (2) induction of currents by time-varying and moving magnetic fields. Pulsed currents are observed to propagate at the speed of whistler wave packets. Their field structure forms ropelike configurations which are electromagnetically force-free. Moving sources induce 'eddy' currents which excite waves and form Cerenkov-like whistler 'wings'. The radiation patterns of moving magnetic antennas and electrodynamic tethers are investigated. Nonlinear effects of large-amplitude, antenna-launched whistler pulses are observed. These involve a new modulational instability in which a channel of high conductivity which permits the wave/currents to penetrate deeply into a collisional plasma is formed.

  14. Measurements of the momentum and current transport from tearing instability in the Madison Symmetric Torus reversed-field pincha)

    NASA Astrophysics Data System (ADS)

    Kuritsyn, A.; Fiksel, G.; Almagri, A. F.; Brower, D. L.; Ding, W. X.; Miller, M. C.; Mirnov, V. V.; Prager, S. C.; Sarff, J. S.

    2009-05-01

    In this paper measurements of momentum and current transport caused by current driven tearing instability are reported. The measurements are done in the Madison Symmetric Torus reversed-field pinch [R. N. Dexter, D. W. Kerst, T. W. Lovell, S. C. Prager, and J. C. Sprott, Fusion Technol. 19, 131 (1991)] in a regime with repetitive bursts of tearing instability causing magnetic field reconnection. It is established that the plasma parallel momentum profile flattens during these reconnection events: The flow decreases in the core and increases at the edge. The momentum relaxation phenomenon is similar in nature to the well established relaxation of the parallel electrical current and could be a general feature of self-organized systems. The measured fluctuation-induced Maxwell and Reynolds stresses, which govern the dynamics of plasma flow, are large and almost balance each other such that their difference is approximately equal to the rate of change of plasma momentum. The Hall dynamo, which is directly related to the Maxwell stress, drives the parallel current profile relaxation at resonant surfaces at the reconnection events. These results qualitatively agree with analytical calculations and numerical simulations. It is plausible that current-driven instabilities can be responsible for momentum transport in other laboratory and astrophysical plasmas.

  15. Device for plasma confinement and heating by high currents and nonclassical plasma transport properties

    DOEpatents

    Coppi, B.; Montgomery, D.B.

    1973-12-11

    A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

  16. Development of microwave ion source and low energy beam transport system for high current cyclotron

    NASA Astrophysics Data System (ADS)

    Pandit, V. S.; Sing Babu, P.; Goswami, A.; Srivastava, S.; Misra, A.; Chatterjee, Mou; Nabhiraj, P. Y.; Yadav, R. C.; Bhattacharya, S.; Roy, S.; Nandi, C.; Pal, G.; Thakur, S. K.

    2013-12-01

    A 2.45 GHz microwave ion source and a low energy beam transport system have been developed to study the high intensity proton beam injection into a 10 MeV, 5 mA compact cyclotron. We have extracted proton beam more than 10 mA at 80 kV as measured by the DCCT after the extraction and a well collimated beam of 7 mA (through 1 cm × 1 cm slit) at the faraday cup 1.5 m away from the source. The transport of protons from the ion source in the presence of H2+, H3+ species has been studied using PIC simulations through our transport line which consists of two solenoids. We have also installed a small dipole magnet with similar field as that of the cyclotron along with vacuum chamber, spiral inflector and few diagnostic elements at the end of the beam line. In the preliminary testing of inflection, we achieved 1 mA beam on the faraday cup at the exit of inflector with ∼60% transmission efficiency.

  17. Effects of midlatitude westerlies on the paleoproductivity at the Agulhas Bank slope during the penultimate glacial cycle: Evidence from coccolith Sr/Ca ratios

    NASA Astrophysics Data System (ADS)

    Mejía, Luz María.; Ziveri, Patrizia; Cagnetti, Marilisa; Bolton, Clara; Zahn, Rainer; Marino, Gianluca; Martínez-Méndez, Gema; Stoll, Heather

    2014-07-01

    Modern primary productivity on the Agulhas Bank, off South Africa, has been proposed to be linked to the midlatitude westerlies. A paleoproductivity record from this area may therefore resolve temporal changes in the westerly dynamics. Accordingly, we produced a coccolith Sr/Ca-based paleoproductivity record from core MD96-2080 (Agulhas Bank slope) during the penultimate glacial-interglacial cycle. Deriving the productivity signal from Sr/Ca requires a correction for a temperature effect, here constrained using Mg/Ca sea surface temperatures from the foraminifer Globigerina bulloides from core MD96-2080. Phases of depressed productivity coincided with periods of stratification in the same core, indicated by high relative abundances of the coccolithophore Florisphaera profunda and with low relative abundances of the upwelling indicator G. bulloides in the nearby Cape Basin. These observations collectively suggest that productivity was regulated by upwelling throughout this region. We infer that, as in the present, periods of low productivity result from a more northerly position of the westerlies, potentially accompanied by subtropical front displacements, and blockage of upwelling promoting easterlies. Productivity minima also coincide with periods of increased ice-rafted detritus (IRD) deposition on the Agulhas Plateau, which also indicates extreme northward positions of the westerlies. The influence of the westerlies appears to be obliquity conditioned, as productivity minima (and IRD maxima) occur during low-obliquity intervals. The dynamic connection between productivity and the westerlies is supported by coeval salinity changes in the South Indian Gyre that likewise respond sensitively to a poleward contraction of the westerlies.

  18. Strontium isotope investigation of ungulate movement patterns on the Pleistocene Paleo-Agulhas Plain of the Greater Cape Floristic Region, South Africa

    NASA Astrophysics Data System (ADS)

    Copeland, Sandi R.; Cawthra, Hayley C.; Fisher, Erich C.; Lee-Thorp, Julia A.; Cowling, Richard M.; le Roux, Petrus J.; Hodgkins, Jamie; Marean, Curtis W.

    2016-06-01

    Middle Stone Age sites located within the Greater Cape Floristic Region on the South African southern coast have material culture with early evidence for key modern human behaviors such as projectile weaponry, large animal hunting, and symbolic behavior. In order to interpret how and why these changes evolved, it is necessary to understand their ecological context as it has direct relevance to foraging behavior. During periods of lowered sea level, a largely flat and vast expanse of land existed south of the modern coastline, but it is now submerged by higher sea levels. This exposed area, the Paleo-Agulhas Plain, likely created an ecological context unlike anything in the region today, as evidenced by fossil assemblages dominated by migratory ungulates. One hypothesis is that the Paleo-Agulhas Plain supported a migration ecosystem of large grazers driven by summer rainfall, producing palatable forage during summer in the east, and winter rainfall, producing palatable forage during winter in the west. Alternatively, ungulates may have been moving from the coastal plain in the south to the interior north of the Cape Fold Mountains, as observed for elephants in historic times. In this study, we assess ungulate movement patterns with inter- and intra-tooth enamel samples for strontium isotopes in fossil fauna from Pinnacle Point sites PP13B and PP30. To accomplish our goals we created a bioavailable 87Sr/86Sr isoscape for the region by collecting plants at 171 sampling sites and developing a geospatial model. The strontium isotope results indicate that ungulates spent most of their time on the Paleo-Agulhas Plain and avoided dissected plain, foothill, and mountain habitats located more than about 15 km north of the modern coastline. The results clearly exclude a north-south (coastal-interior) movement or migration pattern, and cannot falsify the east-west movements hypothesized in the south coast migration ecosystem hypothesis.

  19. Equatorial transport of Saturn's ionosphere as driven by a dust-ring current system

    SciTech Connect

    Ip, W.; Mendis, D.A.

    1983-03-01

    The diurnal modulation of the dust ring current of Saturn's D-ring causes field-aligned Birkeland currents ot flow near the dawn and dusk terminators and close across the mid-latitude ionosphere. One consequence of this current system is the establishment of a global convection pattern in the equatorial outer ionosphere. Outward motion of the dayside ionosheric plasma as well as the corresponding absorption effect of the inner ring system might be one physical cause of the depletion of the ionospheric content of Saturn.

  20. On the equatorial transport of Saturn's ionosphere as driven by a dust-ring current system

    NASA Astrophysics Data System (ADS)

    Ip, W.-H.; Mendis, D. A.

    1983-03-01

    The diurnal modulation of the dust ring current of Saturn's D-ring causes field-aligned Birkeland currents to flow near the dawn and dusk terminators and close across the mid-latitude ionosphere. One consequence of this current system is the establishment of a global convection pattern in the equatorial outer ionosphere. Outward motion of the dayside ionospheric plasma as well as the corresponding absorption effect of the inner ring system might be one physical cause of the depletion of the ionospheric content of Saturn.

  1. Lower hybrid current drive in experiments for transport barriers at high {beta}{sub N} of JET (Joint European Torus)

    SciTech Connect

    Cesario, R. C.; Castaldo, C.; De Angelis, R.; Smeulders, P.; Calabro, G.; Pericoli, V.; Ravera, G.

    2007-09-28

    LHCD has been used in JET experiments aimed at producing internal transport barriers (ITBs) in highly triangular plasmas ({delta}{approx_equal}0.4) at high {beta}{sub N} (up to 3) for steady-state application. The LHCD is a potentially valuable tool for (i) modifying the target q-profile, which can help avoid deleterious MHD modes and favour the formation of ITBs, and (ii) contributing to the non-inductive current drive required to prolong such plasma regimes. The q-profile evolution has been simulated during the current ramp-up phase for such a discharge (B{sub 0} = 2.3 T, I{sub P} = 1.5 MA) where 2 MW of LHCD has been coupled. The JETTO code was used taking measured plasma profiles, and the LHCD profile modeled by the LHstar code. The results are in agreement with MSE measurements and indicate the importance of the elevated electron temperature due to LHCD, as well as the driven current. During main heating with 18 MW of NBI and 3 MW of ICRH the bootstrap current density at the edge also becomes large, consistently with the observed reduction of the local turbulence and of the MHD activity. JETTO modelling suggests that the bootstrap current can reduce the magnetic shear (sh) at large radius, potentially affecting the MHD stability and turbulence behaviour in this region. Keywords: lower hybrid current drive (LHCD), bootstrap current, q (safety factor) and shear (sh) profile evolutions.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  3. Transportation.

    ERIC Educational Resources Information Center

    Crank, Ron

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

  4. Interannual variations of North Equatorial Current transport in the Pacific Ocean during two types of El Niño

    NASA Astrophysics Data System (ADS)

    Wu, Guoli; Zhai, Fangguo; Hu, Dunxin

    2016-05-01

    Interannual variations of Pacific North Equatorial Current (NEC) transport during eastern-Pacific El Niños (EP-El Niños) and central-Pacific El Niños (CP-El Niños) are investigated by composite analysis with European Centre for Medium-Range Weather Forecast Ocean Analysis/Reanalysis System 3. During EP-El Niño, NEC transport shows significant positive anomalies from the developing to decay phases, with the largest anomalies around the mature phase. During CP-El Niño, however, the NEC transport only shows positive anomalies before the mature phase, with much weaker anomalies than those during EP-El Niño. The NEC transport variations are strongly associated with variations of the tropical gyre and wind forcing in the tropical North Pacific. During EP-El Niño, strong westerly wind anomalies and positive wind stress curl anomalies in the tropical North Pacific induce local upward Ekman pumping and westward-propagating upwelling Rossby waves in the ocean, lowering the sea surface height and generating a cyclonic gyre anomaly in the western tropical Pacific. During CP-El Niño, however, strength of the wind and associated Ekman pumping velocity are very weak. Negative sea surface height and cyclonic flow anomalies are slightly north of those during EP El Niño.

  5. Charge transport in CdZnTe coplanar grid detectors examined by laser induced transient currents

    NASA Astrophysics Data System (ADS)

    Praus, P.; Kunc, J.; Belas, E.; Pekárek, J.; Grill, R.

    2016-09-01

    Laser-induced transient current technique was used for the visualization of charge transfer in the coplanar CdZnTe radiation detector including distinction to the collecting and noncollecting grids. Transient current waveforms measured at different intergrid biasing allowed us the identification of principal charge transit features and the final redistribution of collected charge between grids. We have demonstrated that while at the initial period of the charge passage through the detector bulk the current waveform shapes on the collection and non-collection electrodes are nearly the same, the intergrid biasing entails significant current deviation at the final part of the transients, where inverted current through the non-collecting grid induces markedly reduced/enhanced collected charge in the non-collecting/collecting electrode. An optimum ratio of cathode/intergrid biasing was found to be close to the ratio of detector/intergrid dimensions. Theoretical simulations demonstrating all charge-transfer characteristics were presented and proved the validity of the experimental data.

  6. Transport of the Norwegian Atlantic current as determined from satellite altimetry

    NASA Technical Reports Server (NTRS)

    Pistek, Pavel; Johnson, Donald R.

    1992-01-01

    Relatively warm and salty North Atlantic surface waters flow through the Faeroe-Shetland Channel into the higher latitudes of the Nordic Seas, preserving an ice-free winter environment for much of the exterior coast of northern Europe. This flow was monitored along the Norwegian coast using Geosat altimetry on two ascending arcs during the Exact Repeat Mission in 1987-1989. Concurrent undertrack CTD surveys were used to fix a reference surface for the altimeter-derived SSH anomalies, in effect creating time series of alongtrack surface dynamic height topographies. Climatologic CTD casts were then used, with empirical orthogonal function (EOF) analysis, to derive relationships between historical surface dynamic heights and vertical temperature and salinity profiles. Applying these EOF relationships to the altimeter signals, mean transports of volume, heat, and salt were calculated at approximately 2.9 Sverdrups, 8.1 x 10 exp 11 KCal/s and 1.0 x 10 exp 8 Kg/s, respectively. Maximum transports occurred in February/March and minimum in July/August.

  7. Sensitivity of transport and stability to the current profile in steady-state scenario plasmas in DIII-D

    SciTech Connect

    Turco, F.; Hanson, J. M.; Holcomb, C. T.; Ferron, J. R.; Luce, T. C.; Politzer, P. A.; Turnbull, A. D.; Park, J. M.; White, A. E.; Brennan, D. P.; Okabayashi, M.; In, Y.

    2012-12-15

    Recent experiments on DIII-D have provided the first systematic data on the impact of the current profile on the transport and stability properties of high-performance, steady-state scenario plasmas. In a future tokamak, to achieve 100% noninductive conditions and produce net power, the current profile J must be sustained by a large fraction of bootstrap current J{sub BS}, which is nonlinearly coupled with the kinetic profiles. Systematic scans of q{sub min} and q{sub 95} were performed to determine empirically the best alignment of the noninductive currents with J and the variation of the transport properties with q. Transport analysis indicates that {chi}{sub e} and {chi}{sub i} are sensitive to the details of J in a way that makes the pressure profile peaking and J{sub BS} scale nonlinearly with both q and {beta} in the experiment. Drift wave stability analysis yields linear growth rates that do not reproduce experimental trends in {chi} with q{sub min} and q{sub 95}. At high beta, necessary to maximize f{sub BS}, the plasma duration is often limited by n=1 tearing modes, whose stability also depends on the J profile. Broadly deposited electron cyclotron (EC) current at mid-radius was found to supply part of the required noninductive current and to positively affect the tearing stability. The modes appear when J{sub EC} is turned off for stable cases and always appear when the EC deposition is shifted outwards. The variation in the EC scan results is consistent with PEST3 calculations, showing that the tearing stability becomes extremely sensitive to small perturbations of the equilibrium in wall-stabilized plasmas run close to the ideal MHD limit. These modeling results are being used to design new experiments with higher ideal and tearing limits. A new capability for off-axis neutral beam injection system will be used to explore higher q{sub min} scenarios and different current alignments.

  8. Late-winter conditions and freshwater transport in the East Greenland Current: highlights from an icebreaker based survey.

    NASA Astrophysics Data System (ADS)

    Nilsson, J.; Björk, G.; Lake, I.; Nohr, C.; Rudels, B.; Winsor, P.

    2003-04-01

    General dynamical features of East Greenland Current (EGC) are synthesized from a survey conducted by the icebreaker Oden during the Swedish Arctic Ocean Expedition 2002. The data includes hydrography and ADCP observations in eight transects of the EGC, from the Fram Strait in the north to the Denmark Strait in the south. The survey reveals a strong confinement of the low-saline polar water in the EGC to the continental slope/shelf --- a feature of relevance for the overall stability of the thermohaline circulation in the Arctic Ocean. The southward transport of liquid freshwater in the EGC was found to vary dramatically between transects: from peak values on the order of 0.06 Sverdrup to virtually zero. The dynamical origin of the observed alongstream pulsations in freshwater transport is briefly discussed from a theoretical standpoint, emphasizing the potential for freshwater leakage into the deep-water producing areas in the Greenland Sea.

  9. Investigation of current transport parameters of Ti/4H-SiC MPS diode with inhomogeneous barrier

    NASA Astrophysics Data System (ADS)

    Song, Qing-Wen; Zhang, Yu-Ming; Zhang, Yi-Men; Chen, Feng-Ping; Tang, Xiao-Yan

    2011-05-01

    The current transport parameters of 4H-SiC merged PiN Schottky (MPS) diode are investigated in a temperature range of 300-520 K. Evaluation of the experimental current-voltage (I—V) data reveals the decrease in Schottky barrier height Φb but an increase in ideality factor n, with temperature decreasing, which suggests the presence of an inhomogeneous Schottky barrier. The current transport behaviours are analysed in detail using the Tung's model and the effective area of the low barrier patches is extracted. It is found that small low barrier patches, making only 4.3% of the total contact, may significantly influence the device electrical characteristics due to the fact that a barrier height of 0.968 eV is much lower than the average barrier height 1.39 eV. This shows that ion implantation in the Schottky contact region of MPS structure may result in a poor Ti/4H-SiC interface quality. In addition, the temperature dependence of the specific on-resistance (Ron—sp), T2.14, is determined between 300 K and 520 K, which is similar to that predicted by a reduction in electron mobility.

  10. USXR Based MHD, Transport, Equilibria and Current Profile Diagnostics for NSTX. Final Report

    SciTech Connect

    Finkenthal, Michael

    2009-06-01

    The present report resumes the research activities of the Plasma Spectroscopy/Diagnostics Group at Johns Hopkins University performed on the NSTX tokamak at PPPL during the period 1999-2009. During this period we have designed and implemented XUV based diagnostics for a large number of tasks: study of impurity content and particle transport, MHD activity, time-resolved electron temperature measeurements, ELM research, etc. Both line emission and continuum were used in the XUV range. New technics and novel methods have been devised within the framework of the present research. Graduate and post-graduate students have been involved at all times in addition to the senior research personnel. Several tens of papers have been published and lectures have been given based on the obtained results at conferences and various research institutions (lists of these activities were attached both in each proposal and in the annual reports submitted to our supervisors at OFES).

  11. Current Status of the Development of a Transportable and Compact VLBI System by NICT and GSI

    NASA Technical Reports Server (NTRS)

    Ishii, Atsutoshi; Ichikawa, Ryuichi; Takiguchi, Hiroshi; Takefuji, Kazuhiro; Ujihara, Hideki; Koyama, Yasuhiro; Kondo, Tetsuro; Kurihara, Shinobu; Miura, Yuji; Matsuzaka, Shigeru; Tanimoto, Daisuke

    2010-01-01

    MARBLE (Multiple Antenna Radio-interferometer for Baseline Length Evaluation) is under development by NICT and GSI. The main part of MARBLE is a transportable VLBI system with a compact antenna. The aim of this system is to provide precise baseline length over about 10 km for calibrating baselines. The calibration baselines are used to check and validate surveying instruments such as GPS receiver and EDM (Electro-optical Distance Meter). It is necessary to examine the calibration baselines regularly to keep the quality of the validation. The VLBI technique can examine and evaluate the calibration baselines. On the other hand, the following roles are expected of a compact VLBI antenna in the VLBI2010 project. In order to achieve the challenging measurement precision of VLBI2010, it is well known that it is necessary to deal with the problem of thermal and gravitational deformation of the antenna. One promising approach may be connected-element interferometry between a compact antenna and a VLBI2010 antenna. By measuring repeatedly the baseline between the small stable antenna and the VLBI2010 antenna, the deformation of the primary antenna can be measured and the thermal and gravitational models of the primary antenna will be able to be constructed. We made two prototypes of a transportable and compact VLBI system from 2007 to 2009. We performed VLBI experiments using theses prototypes and got a baseline length between the two prototypes. The formal error of the measured baseline length was 2.7 mm. We expect that the baseline length error will be reduced by using a high-speed A/D sampler.

  12. Multiple Transportable Carbohydrates During Exercise: Current Limitations and Directions for Future Research.

    PubMed

    Wilson, Patrick B

    2015-07-01

    The concept of multiple transportable carbohydrates (MTC) refers to a combination of saccharides that rely on distinct transporters for intestinal absorption. Ingestion of MTC during prolonged exercise has been purported to increase carbohydrate absorption efficiency, increase exogenous carbohydrate oxidation, reduce gastrointestinal (GI) distress, and improve athletic performance when carbohydrate intake is high (>50-60 g·h⁻¹). Although reviews of MTC research have been published previously, a comprehensive literature evaluation underscoring methodological limitations has not been conducted to guide future work. Accordingly, this review outlined the plausible mechanisms of MTC and subsequently evaluated MTC research based on several factors, including participant characteristics, exercise modality, exercise task, treatment formulation, treatment blinding, and pre-exercise nutrition status. A total of 27 articles examining MTC during exercise were identified and reviewed. Overall, ingestion of MTC led to increased exogenous carbohydrate oxidation, reduced GI distress, and improved performance during cycling lasting ≥2.5 hours, particularly when carbohydrate was ingested at ≥1.2 g·min⁻¹. Despite the apparent benefits, several limitations in the literature were apparent, including that only 3 studies used running, only 2 studies were conducted in the field, most participants were fasted, and women and adolescents were underrepresented. In addition, the majority of the studies fed carbohydrate at ≥1.2 g·min⁻¹, which may have inflated levels of GI distress and exaggerated performance decrements with single-saccharide feedings. Based on these limitations, future MTC investigations should consider focusing on running, examining team-based sports, including women and adolescents, conducting experiments under field conditions, examining the modifying effects of pre-exercise nutrition, and using modest feeding protocols (1.0-1.2 g·min⁻¹).

  13. Current transport of leatherback sea turtles (Dermochelys coriacea) in the ocean.

    PubMed Central

    Luschi, P; Sale, A; Mencacci, R; Hughes, G R; Lutjeharms, J R E; Papi, F

    2003-01-01

    While the long-distance movements of pelagic vertebrates are becoming known thanks to satellite telemetry, the factors determining their courses have hardly been investigated. We have analysed the effects of oceanographic factors on the post-nesting movements of three satellite-tracked leatherback turtles (Dermochelys coriacea) moving in the southwest Indian Ocean. By superimposing the turtle tracks on contemporaneous images of sea-surface temperatures and sea height anomalies, we show that currentrelated features dominate the shape of the reconstructed routes. After an initial offshore movement, turtles moved along straight routes when in the core of the current, or executed loops within eddies. Large parts of the routes were strikingly similar to those of surface drifters tracked in the same region. These findings document that long-lasting oceanic movements of marine turtles may be shaped by oceanic currents. PMID:14667360

  14. Strontium isotope investigation of ungulate movement patterns on the Pleistocene Paleo-Agulhas Plain of the Greater Cape Floristic Region, South Africa

    DOE PAGES

    Copeland, Sandi R.; Cawthra, Hayley C.; Fisher, Erich C.; Lee-Thorp, Julia A.; Cowling, Richard M.; le Roux, Petrus J.; Hodgkins, Jamie; Marean, Curtis W.

    2016-04-16

    Middle Stone Age sites located within the Greater Cape Floristic Region on the South African southern coast have material culture with early evidence for key modern human behaviors such as projectile weaponry, large animal hunting, and symbolic behavior. In order to interpret how and why these changes evolved, it is necessary to understand their ecological context as it has direct relevance to foraging behavior. During periods of lowered sea level, a largely flat and vast expanse of land existed south of the modern coastline, but it is now submerged by higher sea levels. This exposed area, the Paleo-Agulhas Plain, likelymore » created an ecological context unlike anything in the region today, as evidenced by fossil assemblages dominated by migratory ungulates. One hypothesis is that the Paleo-Agulhas Plain supported a migration ecosystem of large grazers driven by summer rainfall, producing palatable forage during summer in the east, and winter rainfall, producing palatable forage during winter in the west. Furthermore, ungulates may have been moving from the coastal plain in the south to the interior north of the Cape Fold Mountains, as observed for elephants in historic times.« less

  15. Quench behavior of Sr0.6K0.4Fe2As2/Ag tapes with AC and DC transport currents at different temperature

    NASA Astrophysics Data System (ADS)

    Liu, Qi; Zhang, Guomin; Yang, Hua; Li, Zhenming; Liu, Wei; Jing, Liwei; Yu, Hui; Liu, Guole

    2016-09-01

    In applications, superconducting wires may carry AC or DC transport current. Thus, it is important to understand the behavior of normal zone propagation in conductors and magnets under different current conditions in order to develop an effective quench protection system. In this paper, quench behavior of Ag sheathed Sr0.6K0.4Fe2As2 (Sr-122 in the family of iron-based superconductor) tapes with AC and DC transport current is reported. The measurements are performed as a function of different temperature (20 K-30 K), varying transport current and operating frequency (50 Hz-250 Hz). The focus of the research is the minimum quench energy (MQE), the normal zone propagation velocity (NZPV) and the comparison of the related results with AC and DC transport current.

  16. Current-use pesticide transport to Costa Rica's high-altitude tropical cloud forest.

    PubMed

    Shunthirasingham, Chubashini; Gouin, Todd; Lei, Ying D; Ruepert, Clemens; Castillo, Luisa E; Wania, Frank

    2011-12-01

    To gain insight into the atmospheric transport and deposition of organic contaminants in high-altitude forests in the humid tropics, pesticides were analyzed in air, water, and soil samples from Costa Rica. Passive samplers deployed across the country revealed annually averaged air concentrations of chlorothalonil, endosulfan, and pendimethalin that were higher in areas with intensive agricultural activities than in more remote areas. Atmospheric concentrations were particularly high in the intensively cultivated central valley. Only endosulfan and its degradation products were found in soils sampled along an altitudinal transect on the northern side of Volcano Turrialba, which is facing heavily cultivated coastal plains. Consistent with calculations of cold trapping in tropical mountains, concentrations of endosulfan sulfate increased with altitude. Pesticide levels in lake, creek, fog, and arboreal water samples from high-elevation cloud forests were generally below 10 ng · L(-1). Endosulfan sulfate was the most abundant pesticide in water, with concentrations ranging from 0.4 to 9.4 ng · L(-1). Its levels were highest in water sampled from bromeliads. Levels of total endosulfan in water are much lower than the reported median lethal concentration (LC50) value for acute toxicity of α-endosulfan to tadpoles. Although this suggests that the presence of pesticide might not have a direct impact on amphibian populations, the possibility of effects of chronic exposure to a mixture of substances cannot be excluded. Fog was relatively enriched in some of the analyzed pesticides, such as dacthal and chlorothalonil, and may constitute an important deposition pathway to high-altitude tropical cloud forest. PMID:21898568

  17. Shelfal sediment transport by undercurrents forces turbidity current activity during high sea level, Chile continental margin

    NASA Astrophysics Data System (ADS)

    Bernhardt, Anne; Hebbeln, Dierk; Regenberg, Marcus; Lückge, Andreas; Strecker, Manfred. R.

    2016-04-01

    Understanding the links between terrigenous sediment supply and marine transport and depositional processes along tectonically active margins is essential to decipher turbidite successions as potential archives of climatic and seismic forcings and to comprehend timing and quantity of marine clastic deposition. Sequence stratigraphic models predict coarse-grained terrigenous sediment delivery to deep-marine sites mainly during sea-level fall and lowstand. Marine clastic deposition during periods of transgression and highstand has been attributed to the continued geomorphic connectivity between terrestrial sediment sources and marine sinks (e.g., rivers connected to submarine canyons) often facilitated by narrow shelves, high sediment supply causing delta migration to the shelf edge, and/or abrupt increases in sediment supply due to climatic variability or catastrophic events. To decipher the controls on Holocene highstand turbidite deposition, we analyzed twelve sediment cores of spatially disparate, coeval Holocene turbidite systems along the Chile margin (29-40°S) with changing climatic and geomorphic characteristics but uniform changes of sea level. Intraslope basins in north-central Chile (29-33°S) offshore a narrow to absent shelf record a shut-off of turbidite activity during the Holocene. In contrast, core sites in south-central Chile (36-40°S) offshore a wide continental shelf have repeatedly experienced turbidite deposition during sea-level highstand conditions, even though most of the depocenters are not connected via canyons to sediment sources. The interplay of stable high sediment supply related to strong onshore precipitation in combination with a wide shelf, over which undercurrents move sediment towards the shelf edge, appears to control Holocene turbidite sedimentation and sediment export to the deep sea.

  18. Current-use pesticide transport to Costa Rica's high-altitude tropical cloud forest.

    PubMed

    Shunthirasingham, Chubashini; Gouin, Todd; Lei, Ying D; Ruepert, Clemens; Castillo, Luisa E; Wania, Frank

    2011-12-01

    To gain insight into the atmospheric transport and deposition of organic contaminants in high-altitude forests in the humid tropics, pesticides were analyzed in air, water, and soil samples from Costa Rica. Passive samplers deployed across the country revealed annually averaged air concentrations of chlorothalonil, endosulfan, and pendimethalin that were higher in areas with intensive agricultural activities than in more remote areas. Atmospheric concentrations were particularly high in the intensively cultivated central valley. Only endosulfan and its degradation products were found in soils sampled along an altitudinal transect on the northern side of Volcano Turrialba, which is facing heavily cultivated coastal plains. Consistent with calculations of cold trapping in tropical mountains, concentrations of endosulfan sulfate increased with altitude. Pesticide levels in lake, creek, fog, and arboreal water samples from high-elevation cloud forests were generally below 10 ng · L(-1). Endosulfan sulfate was the most abundant pesticide in water, with concentrations ranging from 0.4 to 9.4 ng · L(-1). Its levels were highest in water sampled from bromeliads. Levels of total endosulfan in water are much lower than the reported median lethal concentration (LC50) value for acute toxicity of α-endosulfan to tadpoles. Although this suggests that the presence of pesticide might not have a direct impact on amphibian populations, the possibility of effects of chronic exposure to a mixture of substances cannot be excluded. Fog was relatively enriched in some of the analyzed pesticides, such as dacthal and chlorothalonil, and may constitute an important deposition pathway to high-altitude tropical cloud forest.

  19. 10 to 25-fold increase in the transport superconducting critical current density of spark-plasma sintered Bi-2223 superconductors

    NASA Astrophysics Data System (ADS)

    Govea-Alcaide, E.; Machado, I. F.; Jardim, R. F.

    2015-01-01

    Pre-reacted powders of (Bi-Pb)2Sr2Ca2Cu3O10+δ (Bi-2223) were consolidated by using the spark plasma sintering (SPS) technique under vacuum and at two different temperatures TD: 750 and 830 °C. The results indicate the occurrence of grains with core-shell morphology, where the shell is oxygen deficient. A post-annealing heat treatment (PAHT), performed in air, at 750 °C, and for a brief time interval, is responsible for a 10 to 25-fold increase in the transport superconducting current density at 77 K. The role of the oxygen-deficient shell, before and after the PAHT, was investigated by means of magnetic and transport measurements. We argue that the PAHT is two folds: (i) it is responsible for the decrease of the width of the oxygen-deficient shell, then increasing the oxygen content along the grain boundaries; (ii) it promotes the formation of conduction current paths along the grain boundaries of the SPS material.

  20. Isothermal transient ionic current as a characterization technique for ion transport in Ta2O5

    NASA Astrophysics Data System (ADS)

    Mattsson, M. Strømme; Niklasson, G. A.

    1999-06-01

    The Isothermal Transient Ionic Current (ITIC) technique was applied to β-Ta2O5 samples made by chemical vapor deposition. The mobility, conductivity, and number of protons in the material could be extracted from the measurements. Li ions were intercalated electrochemically into the β-Ta2O5 and it was found that the ITIC method could separate the contribution from proton and Li ion conduction in such a way that the mobilities of both species could be extracted. Furthermore, the lattice-gas model [A. J. Berlinsky, W. G. Unruh, W. R. McKinnon, and R. R. Haering, Solid State Commun. 31, 135 (1979)] was employed to describe the Li interaction process. This model showed that the Li ions tended to distribute uniformly, rather then to attract each other and form clusters in the material.

  1. Transport phenomena in intrinsic semiconductors and insulators at high current densities: Suppression of the broken neutrality drift

    SciTech Connect

    Mnatsakanov, T. T.; Tandoev, A. G.; Yurkov, S. N.; Levinshtein, M. E.

    2013-08-14

    It is shown that, in addition to the diffusion and broken neutrality drift (BND) modes well-known for insulators and very lightly doped semiconductors, the quasineutral drift (QND) mode is possible. The transition from the BND to QND mode is accompanied by the appearance of a portion with a very sharp current rise in the current-voltage characteristic. This effect is observed in a new type of semiconductor detectors (CIDs, Current Injected Detectors) of high-intensity neutron and proton radiation, suggested, in particular, for Large Hadron Collider. The effect is unambiguously attributed now to the presence of radiation-induced deep centers in a semiconductor. It is shown, however, in this paper that the effect of a very sharp rise in current upon a slight increase in voltage is even possible when there are no deep centers. An equation adequately describing the possible transport modes in intrinsic semiconductors and insulators is derived. The results of an analytical study are confirmed by an adequate simulation.

  2. Intermodal Transportation: Current Fast Ship Designs Specify Propulsion Systems that Are about 20 Knots Faster than Ships in the Current Fleet

    ERIC Educational Resources Information Center

    Childress, Vincent W.

    2005-01-01

    Intermodal transportation is the moving of people or cargo using more than one mode of transportation. When a person drives to the airport, stands on a conveyor to move through the terminal, and flies to another city, then he or she is using intermodal transportation. Moving cargo in the first half of the twentieth century was a time-consuming and…

  3. Transport and fate of river waters under flood conditions and rim current influence: the Mississippi River test case

    NASA Astrophysics Data System (ADS)

    Kourafalou, Villy; Androulidakis, Yannis

    2013-04-01

    Large river plumes are a major supplier of freshwater, sediments and nutrients in coastal and shelf seas. Novel processes controlling the transport and fate of riverine waters (and associated materials) will be presented, under flood conditions and in the presence of complex topography, ambient shelf circulation and slope processes, controlled by the interaction with rim currents. The Mississippi River (MR) freshwater outflow is chosen as a test case, as a major circulation forcing mechanism for the Northern Gulf of Mexico and a unique river plume for the intense interactions with a large scale ocean current, namely the Loop Current branch of the Gulf Stream, and associated eddy field. The largest MR outflow in history (45,000 m3/sec in 2011) is compared with the second largest outflow in the last 8 years (41,000 m3/sec in 2008). Realistically forced simulations, based on the Hybrid Coordinate Ocean Model (HYCOM) with careful treatment of river plume dynamics and nested to a data assimilated, basin-wide model, reveal the synergistic effect of enhanced discharge, winds, stratification of ambient shelf waters and offshore circulation over the transport of plume waters. The investigation targets a broader understanding of the dynamics of large scale river plumes in general, and of the MR plume in particular. In addition, in situ observations from ship surveys and satellite chl-a data showed that the mathematical simulations with high temporal resolution river outflow input may reproduce adequately the buoyant waters spreading over the Northern Gulf of Mexico shelf and offshore areas. The fate of the river plume is strongly determined and affected by deep basin processes. The strong impacts of the Loop Current system (and its frontal eddies) on river plume evolution are of particular importance under conditions of increased offshore spreading, which is presumed under large discharge rates and can cause loss of riverine materials to the basin interior. Flood conditions

  4. Correcting acoustic Doppler current profiler discharge measurements biased by sediment transport

    USGS Publications Warehouse

    Mueller, D.S.; Wagner, C.R.

    2007-01-01

    A negative bias in discharge measurements made with an acoustic Doppler current profiler (ADCP) is attributed to the movement of sediment on or near the streambed, and is an issue widely acknowledged by the scientific community. The integration of a differentially corrected global positioning system (DGPS) to track the movement of the ADCP can be used to avoid the systematic bias associated with a moving bed. DGPS, however, cannot provide consistently accurate positions because of multipath errors and satellite signal reception problems on waterways with dense tree canopy along the banks, in deep valleys or canyons, and near bridges. An alternative method of correcting for the moving-bed bias, based on the closure error resulting from a two-way crossing of the river, is presented. The uncertainty in the mean moving-bed velocity measured by the loop method is shown to be approximately 0.6cm/s. For the 13 field measurements presented, the loop method resulted in corrected discharges that were within 5% of discharges measured utilizing DGPS to compensate for moving-bed conditions. ?? 2007 ASCE.

  5. ANALYTIC SOLUTIONS FOR CURRENT SHEET STRUCTURE DETERMINED BY SELF-CONSISTENT, ANISOTROPIC TRANSPORT PROCESSES IN A GRAVITATIONAL FIELD

    SciTech Connect

    Goodman, Michael L.

    2011-04-10

    A Harris sheet magnetic field with maximum magnitude B{sub 0} and length scale L is combined with the anisotropic electrical conductivity, viscosity, and thermoelectric tensors for an electron-proton plasma to define a magnetohydrodynamic model that determines the steady state of the plasma. The transport tensors are functions of temperature, density, and magnetic field strength, and are computed self-consistently as functions of position x normal to the current sheet. The flow velocity, magnetic field, and gravitational force lie along the z-axis. The plasma is supported against gravity by the viscous force. Analytic solutions are obtained for temperature, density, and velocity. They are valid over a broad range of temperature, density, and magnetic field strength, and so may be generally useful in astrophysical applications. Numerical examples of solutions in the parameter range of the solar atmosphere are presented. The objective is to compare Joule and viscous heating rates, determine the velocity shear that generates viscous forces that support the plasma and are self-consistent with a mean outward mass flux comparable to the solar wind mass flux, and compare the thermoelectric and conduction current contributions to the Joule heating rate. The ratio of the viscous to Joule heating rates per unit mass can exceed unity by orders of magnitude, and increases rapidly with L. The viscous heating rate can be concentrated outside the region where the current density is localized, corresponding to a resistively heated layer of plasma bounded by viscously heated plasma. The temperature gradient drives a thermoelectric current density that can have a magnitude greater than that of the electric-field-driven conduction current density, so thermoelectric effects are important in determining the Joule heating rate.

  6. Influence of electron-beam lithography exposure current level on the transport characteristics of graphene field effect transistors

    NASA Astrophysics Data System (ADS)

    Kang, Sangwoo; Movva, Hema C. P.; Sanne, Atresh; Rai, Amritesh; Banerjee, Sanjay K.

    2016-03-01

    Many factors have been identified to influence the electrical transport characteristics of graphene field-effect transistors. In this report, we examine the influence of the exposure current level used during electron beam lithography (EBL) for active region patterning. In the presence of a self-assembled hydrophobic residual layer generated by oxygen plasma etching covering the top surface of the graphene channel, we show that the use of low EBL current level results in higher mobility, lower residual carrier density, and charge neutrality point closer to 0 V, with reduced device-to-device variations. We show that this correlation originates from the resist heating dependent release of radicals from the resist material, near its interface with graphene, and its subsequent trapping by the hydrophobic polymer layer. Using a general model for resist heating, we calculate the difference in resist heating for different EBL current levels. We further corroborate our argument through control experiments, where radicals are either intentionally added or removed by other processes. We also utilize this finding to obtain mobilities in excess of 18 000 cm2/V s on silicon dioxide substrates. We believe these results are applicable to other 2D materials such as transition metal dichalcogenides and nanoscale devices in general.

  7. Spin-dependent transport and current-induced spin transfer torque in a disordered zigzag silicene nanoribbon

    NASA Astrophysics Data System (ADS)

    Zhou, Benliang; Zhou, Benhu; Liu, Guang; Guo, Dan; Zhou, Guanghui

    2016-11-01

    We study theoretically the spin-dependent transport and the current-induced spin transfer torque (STT) for a zigzag silicene nanoribbon (ZSiNR) with Anderson-type disorders between two ferromagnetic electrodes. By using the nonequilibrium Green's function method, it is predicted that the transport property and STT through the junction depend sensitively on the disorder, especially around the Dirac point. As a result, the conductance decreases and increases for two electrode in parallel and antiparallel configurations, respectively. Due to the disorder, the magnetoresistance (MR) decreases accordingly even within the energy regime for the perfect plateau without disorders. In addition, the conductance versus the relative angle of the magnetization shows a cosine-like behavior. The STT per unit of the bias voltage versus the angle of the magnetization exhibits a sine-like behavior, and versus the Fermi energy is antisymmetrical to the Dirac point and exhibits sharp peaks. Furthermore, the peaks of the STT are suppressed much as the disorder strength increases, especially around the Dirac point. The results obtained here may provide a valuable suggestion to experimentally design spin valve devices based on ZSiNR.

  8. Stable and null current hysteresis perovskite solar cells based nitrogen doped graphene oxide nanoribbons hole transport layer

    PubMed Central

    Kim, Jeongmo; Mat Teridi, Mohd Asri; Mohd Yusoff, Abd. Rashid bin; Jang, Jin

    2016-01-01

    Perovskite solar cells are becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequently used component poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has several shortcomings, such as an easily corroded indium-tin-oxide (ITO) interface at elevated temperatures and induced electrical inhomogeneity. Herein, we propose solution-processed nitrogen-doped graphene oxide nanoribbons (NGONRs) as a hole transport layer (HTL) in perovskite solar cells, replacing the conducting polymer PEDOT:PSS. The conversion efficiency of NGONR-based perovskite solar cells has outperformed a control device constructed using PEDOT:PSS. Moreover, our proposed NGONR-based devices also demonstrate a negligible current hysteresis along with improved stability. This work provides an effective route for substituting PEDOT:PSS as the effective HTL. PMID:27277388

  9. Sediment Transport Beyond the Surf Zone Under Waves and Currents of the Non-Tidal Sea: Lubiatowo (Poland) Case Study

    NASA Astrophysics Data System (ADS)

    Ostrowski, Rafał; Stella, Magdalena

    2016-06-01

    The paper deals with the sandy coastal zone at Lubiatowo in Poland (the south Baltic Sea). The study comprises experimental and theoretical investigations of hydrodynamic and lithodynamic processes in the coastal region located close to the seaward boundary of the surf zone and beyond the surf zone. The analysis is based on field data collected at the IBW PAN Coastal Research Station in Lubiatowo. The data consist of wind velocity reconstructed from the long-term wave climate, deep-water wave buoy records and sea bottom soil parameters. Nearbed flow velocities induced by waves and currents, as well as bed shear stresses are theoretically modelled for various conditions to determine sediment motion regimes in the considered area. The paper discusses the possibility of occasional intensive sediment transport and the occurrence of distinct sea bed changes at bigger water depths.

  10. Stable and null current hysteresis perovskite solar cells based nitrogen doped graphene oxide nanoribbons hole transport layer

    NASA Astrophysics Data System (ADS)

    Kim, Jeongmo; Mat Teridi, Mohd Asri; Mohd Yusoff, Abd. Rashid Bin; Jang, Jin

    2016-06-01

    Perovskite solar cells are becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequently used component poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has several shortcomings, such as an easily corroded indium-tin-oxide (ITO) interface at elevated temperatures and induced electrical inhomogeneity. Herein, we propose solution-processed nitrogen-doped graphene oxide nanoribbons (NGONRs) as a hole transport layer (HTL) in perovskite solar cells, replacing the conducting polymer PEDOT:PSS. The conversion efficiency of NGONR-based perovskite solar cells has outperformed a control device constructed using PEDOT:PSS. Moreover, our proposed NGONR-based devices also demonstrate a negligible current hysteresis along with improved stability. This work provides an effective route for substituting PEDOT:PSS as the effective HTL.

  11. Simultaneous resolution of the micromagnetic and spin transport equations applied to current-induced domain wall dynamics

    NASA Astrophysics Data System (ADS)

    Sturma, M.; Bellegarde, C.; Toussaint, J.-C.; Gusakova, D.

    2016-09-01

    In this paper, we use simulations to study current-induced domain wall dynamics by simultaneously resolving the spin transport and micromagnetic equations for a three-dimensional ferromagnetic strip. In contrast to local approaches, which neglect mutual interaction between spins and magnetic moments, our approach recalculates the spin distribution at each time step using the generalized drift diffusion model, which takes the transverse spin absorption phenomenon into account. We quantified the differences between a local approach and treatment based on a self-consistent method by plotting the domain wall velocity as a function of the domain wall width. We also characterized the domain wall velocity and the Walker breakdown condition as a function of the transverse spin absorption length l⊥, which plays a crucial role in domain wall dynamics.

  12. Impact of submerged aquatic macrophytes on 3-dim current systems and hydrodynamic transport processes in Lake Constance

    NASA Astrophysics Data System (ADS)

    Wolf, Thomas; Lüddeke, Frauke; Thiange, Christophe

    2015-04-01

    According to the assessment criteria of the European water framework directive Lake Constance is having a good water quality. Nevertheless upcoming criteria using environmental quality measures show that there are still problems with respect to micropollutants. In fact, we observe significantly enhanced concentrations of micropollutants close to river mouths and in the areas of shallow water zones within Lake Constance compared to deep water concentrations. These findings are caused by river water plumes which can flow over distances of kilometers in the lake without being diluted or mixed only weakly with the surrounding lake water body. Besides, in the area of interest exist large populations of submerged aquatic macrophytes (SAM). There is only little knowledge, how these influence the distribution and transport processes of micropollutants. In order to assess the impact and distribution of river water plumes in different areas of the lake we implemented a 3-dim hydrodynamic model using DELFT3D-FLOW on a locally refined numerical grid which enables to cover different process scales of the distribution of river water bodies ranging from a few meters up to basin wide scales in the order of a few kilometers. We used numerical tracers (conservative and non-conservative) in order to quantify the impact of different abstract substance classes which are distinguished by their decay rates. In order to asses the influence of SAM populations on current field and transport processes we used a special simulation technique - the trachytope concept. The results of our 3-dim hydrodynamic model showed significantly changed current velocities, residence times and age of water parameters within the SAM areas compared to the control simulation without SAM. By simulating the propagation of coliform bacteria using numerical tracers with spatially and temporarily variable decay rates, we found complex impact pattern of the SAM on the distribution of these potentially harmful

  13. Influence of Tailored Applied Magnetic Fields on High-Power MPD Thruster Current Transport and Onset-Related Phenomena

    NASA Technical Reports Server (NTRS)

    Moeller, Robert C.; Polk, James E.

    2013-01-01

    This work investigated the effects of tailored, externally-applied magnetic fields on current transport and near-anode processes in the plasma discharge of a magnetoplasmadynamic thruster (MPDT). Electrical and plasma diagnostics were used to investigate how localized applied magnetic fields could mitigate the effects of the "onset" phenomena, including large-amplitude terminal voltage fluctuations and high anode fall voltages associated with unstable operation and anode erosion. An MPDT with a multi-channel hollow cathode was developed and tested with quasi-steady pulses of 1 millisecond duration at power levels of 36 kilowatts (20 volts, 1800 amperes) to 3.3 milliwatts (255 volts, 13.1 kiloamperes) with argon propellant in three different magnetic configurations: self-field, applied B field tangential to the anode lip near the exit plane, and applied cusp B field. The current pattern and current densities redistributed to follow the applied poloidal magnetic field lines, which created increased conduction paths to the anode. Also, the anode fall voltage was substantially reduced with both applied B field topologies over a large range of currents. For example, at 10.7 kiloamperes, the cusp applied magnetic field decreased anode fall voltages from 45-83 volts down to 15 volts or lower along much of the anode. The amplitude and frequency of the voltage fluctuations were also reduced over a broad range of currents with the applied fields. E.g., the standard deviations of the fluctuations were lowered by 37-49 percent at 8-9 kiloamperes. In addition, decreases in the mean terminal voltages as large as 31 percent were measured with the applied magnetic fields. These effects are shown to be associated with the increased current conduction along the applied magnetic field lines in the near-anode region. These results also suggest a reduction in frequency and intensity of current-concentrating filaments and anode spots, which contribute to erosion. Overall, both applied

  14. Ion transport and loss in the Earth`s quiet ring current 1. Data and standard model

    SciTech Connect

    Sheldon, R.B.; Hamilton, D.C.

    1993-08-01

    The authors have studied the transport and loss of ions in the Earth`s quiet time ring current, comparing the standard radial diffusion model developed for the higher-energy radiation belt particles with measurements of the lower-energy ring current ions. They compiled a data set with full local time coverage from the quietest days seen by the AMPTE/CCE/CHEM instrument in near-equatorial orbit at L=2-9 R{sub E}. This data set provides, for the first time, ionic composition information in an energy range that includes the bulk of the ring current energy density, 1-300 keV/e. Protons were found to dominate the quiet time energy density at all altitudes, peaking near L{approximately}4 at 60 keV cm{sup {minus}3}, with much smaller contributions from O{sup +} (1-10%), He{sup +} (1-5%), and He{sup ++} (<1%). The authors improved on previously used model loss processes by incorporating the latest atomic physics cross sections from the literature, updating the last survey done 15 years ago. They also included the effects of finite electron temperature on Coulomb drag. A {chi}{sup 2} minimization procedure was used to fit the amplitudes of the standard electric radial diffusion coefficient, giving D{sub LL}{sup E} = 5.8 x 10{sup {minus}11} R{sub E}{sup 2}/s. Yet the model was unable to fit the data (to within a factor of 10) over 50% of the energy and radial ranges of the data set, particularly at L<4 or E<30 keV. Assuming that the loss terms in the model are correct, the data can be inverted to extract a radial diffusion coefficient that had nearly constant amplitude from 2-7 R{sub E}. This suggests that another transport mechanism is operating in the ring current region, which is strongest at smaller radial distances. The authors speculate that fluctuating ionospheric electric fields may be the source of this additional diffusion. 164 refs., 14 figs., 3 tabs.

  15. Paleo-Hydrography south of Africa: Assessing the role of the Subtropical Front in regulating Agulhas Leakage at the Last Glacial Termination

    NASA Astrophysics Data System (ADS)

    Skrivanek, A.; Franzese, A. M.

    2012-12-01

    While climate variability throughout the late Pleistocene and Holocene is linked to changes in insolation and atmospheric CO2, differences in the intensity of this variability indicate that other mechanisms are at work in the perturbation and stabilization of global climate. A proposed cause for glacial terminations - the rapid transition from glacial to warm interglacial climate - is the change in ocean circulation associated with a shift in westerly wind belts and corresponding oceanic fronts. Understanding the mechanisms behind such rapid events is critical to our prediction of future climate responses to anthropogenic global warming. This project reexamines the hypothesis that southward migrations of the Subtropical Front (STF) south of Africa allowed for increased Agulhas Leakage, which is recognized as a key component of the warm return route of Global Thermohaline Circulation, and is a possible prerequisite for North Atlantic overturning. We present new %CaCO3, Mg/Ca and stable oxygen isotope (δ18O) records using planktonic and benthic foraminifera for two sediment cores, VM34-158 (-41.25S) and VM34-155 (-42.17S), off the flank of the Agulhas Plateau. Benthic δ18O and %CaCO3 provide a framework for stratigraphy and the extent of dissolution throughout the cores. Planktonic Mg/Ca and δ18O of G.bulloides serve as proxies for sea surface temperature (SST) and salinity (SSS), and will be used to constrain the position of the STF with respect to changes in Agulhas Leakage. We observe a clear signal of the LGM and Holocene horizons and the Last Glacial termination ~18ka in all proxies. Higher δ18O and lower Mg/Ca ratios characterize the LGM, with the inverse situation for the early Holocene. Mg/Ca averages are 1.32±.21 and 1.04±.02 mmol/mol during the LGM, with δ18O averages of 3.17±.32‰ and 3.46±.28‰ for VM34-158 and VM34-155 respectively. The early Holocene features increased Mg/Ca averages of 1.52±.18 and 1.318±.12 mmol/mol, and reduced δ18O

  16. The SLC30 family of zinc transporters – a review of current understanding of their biological and pathophysiological roles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There are two families of zinc transporters involved in zinc homeostasis in the body, the SLC30 (ZnT, zinc transporter,) and SLC39 (ZIP, ZRT1 and IRT-like protein). The two zinc transporter family members function in opposite directions to maintain cellular zinc homeostasis. ZnT proteins are require...

  17. Across-Shelf Transport of Bivalve Larvae: Can the Interface between a Coastal Current and Inshore Waters Act as an Ecological Barrier to Larval Dispersal?

    PubMed Central

    Tilburg, Charles E.; McCartney, Michael A.; Yund, Philip O.

    2012-01-01

    Using an integrated physical and biological approach, we examined across-shelf advection and exchange and the associated transport of bivalve larvae in the presence of a strong coastal current separated from the coast by a stratified inshore environment. We tested the hypothesis that the interface of the coastal current and inshore waters can act as an ecological barrier to across-shelf transport of larvae but can be overcome by wind- or tidally-induced transport. Our study region in the Gulf of Maine encompasses a coastal current that diverges from the coast as it moves downshelf. The region inshore of this current is home to several species that exhibit limited recruitment in spite of extensive upshelf larval sources. Analysis of surface water temperatures and wind velocities revealed episodic decreases in temperature along the coast correlated with alongshelf (but not upwelling) winds, indicating wind-forced onshore movement of the cold coastal current. Such wind-driven onshore migrations are more common along the northern portion of the study region where the coastal current is near the coast, tidal currents are strong, and wind directions are more conducive to onshore migration, but rarer further south where the interface between inshore waters and the coastal current is further offshore and suitable wind events are less common. The distribution of bivalve larvae was consistent with the physical measurements. There was little across-shelf variation in larval abundance where the current abuts the coast, indicating strong across-shelf exchange of larvae, but strong across-shelf variation in larval density where the stratified inshore waters separate the current from the coast, indicating weak across-shelf transport of larvae. Our results suggest that the interface between the coastal current and inshore waters may constitute a major ecological barrier to larval dispersal in the southern part of the region that may only be overcome by rare, strong wind

  18. Chemical Transport and Reduced-Form Models for Assessing Air Quality Impacts of Current and Future Energy Scenarios

    NASA Astrophysics Data System (ADS)

    Adams, P. J.

    2015-12-01

    Though essential for informed decision-making, it is challenging to estimate the air quality and public health impacts associated with current and future energy generation scenarios because the analysis must address the complicated atmospheric processes that air pollutants undergo: emissions, dispersion, chemistry, and removal. Employing a chemical transport model (CTM) is the most rigorous way to address these atmospheric processes. However, CTMs are expensive from a computational standpoint and, therefore, beyond the reach of policy analysis for many types of problems. On the other hand, previously available reduced-form models used for policy analysis fall short of the rigor of CTMs and may lead to biased results. To address this gap, we developed the Estimating Air pollution Social Impacts Using Regression (EASIUR) method, which builds parameterizations that predict per-tonne social costs and intake fractions for pollutants emitted from any location in the United States. Derived from a large database of tagged CTM simulations, the EASIUR method predicts social costs almost indistinguishable from a full CTM but with negligible computational requirements. We found that the average mortality-related social costs from inorganic PM2.5 and its precursors in the United States are 150,000-180,000/t EC, 21,000-34,000/t SO2, 4,200-15,000/t NOx, and 29,000-85,000/t NH3. This talk will demonstrate examples of using both CTMs and reduced-form models for assessing air quality impacts associated with current energy production activities as well as a future deployment of carbon capture and sequestration.

  19. Irreversibility and entropy production in transport phenomena, IV: Symmetry, integrated intermediate processes and separated variational principles for multi-currents

    NASA Astrophysics Data System (ADS)

    Suzuki, Masuo

    2013-10-01

    The mechanism of entropy production in transport phenomena is discussed again by emphasizing the role of symmetry of non-equilibrium states and also by reformulating Einstein’s theory of Brownian motion to derive entropy production from it. This yields conceptual reviews of the previous papers [M. Suzuki, Physica A 390 (2011) 1904; 391 (2012) 1074; 392 (2013) 314]. Separated variational principles of steady states for multi external fields {Xi} and induced currents {Ji} are proposed by extending the principle of minimum integrated entropy production found by the present author for a single external field. The basic strategy of our theory on steady states is to take in all the intermediate processes from the equilibrium state to the final possible steady states in order to study the irreversible physics even in the steady states. As an application of this principle, Gransdorff-Prigogine’s evolution criterion inequality (or stability condition) dXP≡∫dr∑iJidXi≤0 is derived in the stronger form dQi≡∫drJidXi≤0 for individual force Xi and current Ji even in nonlinear responses which depend on all the external forces {Xk} nonlinearly. This is called “separated evolution criterion”. Some explicit demonstrations of the present general theory to simple electric circuits with multi external fields are given in order to clarify the physical essence of our new theory and to realize the condition of its validity concerning the existence of the solutions of the simultaneous equations obtained by the separated variational principles. It is also instructive to compare the two results obtained by the new variational theory and by the old scheme based on the instantaneous entropy production. This seems to be suggestive even to the energy problem in the world.

  20. Extending the Relaxed-State Principle to Allowing for Internal Transport Barriers: Implications of Electric Currents Networking in a Tokamak

    NASA Astrophysics Data System (ADS)

    Kukushkin, A. B.; Rantsev-Kartinov, V. A.

    1998-11-01

    An algorithm for calculating the equilibrium, "relaxed state" profiles in a tokamak is suggested which is based on a qualitative extension [1] of recently formulated concept [2] of a long-living filamentation of electric currents and their networking, from the case of dense Z-pinches (and other inertially confined plasmas) to the case of magnetically confined plasmas. The approach [1] allows to (i) give alternative explanation to the success of Taylor's principle [3] (relaxation to a minimum magnetic energy state under condition of the conserved magnetic helicity), (ii) indicate the most self-consistent extension, among several suggested approaches, of the concept [3] to the case of non-force-free equilibria (i.e. with finite pressure, plasma flows), and (iii) naturally include the presence of the strongest internal transport barriers (at low-order rational q surfaces) to minimization procedure. [1] Kukushkin A.B., Rantsev-Kartinov V.A., Preprint Kurchatov Institute, IAE-6095/6, 1998. [2] Kukushkin A.B., Rantsev-Kartinov V.A., Laser and Particle Beams, 16(3) 1998 (to be published). [3] Taylor J.B., Rev.Mod.Phys., 58 (1986) 741.

  1. Transport of ions in presence of induced electric field and electrostatic turbulence - Source of ions injected into ring current

    NASA Technical Reports Server (NTRS)

    Cladis, J. B.; Francis, W. E.

    1985-01-01

    The transport of ions from the polar ionosphere to the inner magnetosphere during stormtime conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the energization rate of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary, the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than 0.63 eV), the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4 to 8), with measurements made with the ISEE-1 satellite during a storm. This O(+) flux and a large part of the H(+) flux are consistent with the DE satellite measurements of the polar ionospheric outflow during disturbed times.

  2. The Serotonin Transporter 5-HTTPR Polymorphism is associated with Current and Lifetime Depression in Persons with Chronic Psychotic Disorders

    PubMed Central

    Contreras, Javier; Hare, Liz; Camarena, Beatriz; Glahn, David; Dassori, Albana; Medina, Rolando; Contrerasa, Salvador; Ramirez, Mercedes; Armas, Regina; Munoz, Rodrigo; Mendoza, Rick; Raventos, Henriette; Ontiveros, Alfonso; Nicolini, Humberto; Palmer, Raymond; Escamilla, Michael

    2013-01-01

    Objective Variation in the serotonin transporter gene (SLC6A4) promoter region has been shown to influence depression in persons who have been exposed to a number of stressful life events. Method We evaluated whether genetic variation in 5-HTTLPR, influences current depression, lifetime history of depression and quantitative measures of depression in persons with chronic psychotic disorders. This is an association study of a genetic variant with quantitative and categorical definitions of depression conducted in the Southwest United States, Mexico, and Costa Rica. We analyzed 260 subjects with a history of psychosis, from a sample of 129 families. Results We found that persons carrying at least one short allele had a statistically significant increased lifetime risk for depressive syndromes (p<.02, Odds Ratio=2.18, 95% CI=1.10–4.20). Conclusion The “ss” or “sl” genotype at the 5-HTTLPR promoter polymorphic locus increases the risk of psychotic individuals to develop major depression during the course of their illness. PMID:19016667

  3. Diagnosis of equilibrium magnetic profiles, current transport, and internal structures in a reversed-field pinch using electron temperature fluctuations

    NASA Astrophysics Data System (ADS)

    Parke, Eli

    Due to long fast ion confinement times, neutral beam injection (NBI) on the Madison Symmetric Torus (MST) yields large fast ion populations with substantial density gradients. Novel application of the unique high-rep-rate (>10 kHz) Thomson scattering diagnostic on MST has enabled characterization of a newly observed beam-driven instability, and detailed measurement of equilibrium changes caused by the fast ion population. While previous work has focused on high-frequency energetic particle modes (EPMs), recent observations indicate that fast ions drive a bursting instability near the plasma rotation frequency under appropriate conditions. The mode chirps strongly, with a frequency of approximately 7 kHz in the plasma reference frame at peak amplitude. Bursts are correlated with EPM activity and core neutral particle analyzer signals drop by 30% during a burst, suggesting that this mode participates in avalanches of the higher frequency EPMs and drives enhanced fast ion transport. Electron temperature fluctuations correlated with this low-frequency mode exhibit a core-peaked structure with a sensitive dependence on the safety factor q. Although this mode has not yet been positively identified, its characteristics and internal structure are suggestive of an internal kink (fishbone) or beta-induced Alfven eigenmode. In addition to driving EPMs, the large fast ion population also modifies the current profile. An increase in on-axis current density driven by NBI is offset by a reduction in the mid-radius, leading to net-zero current drive. This results in a slight flattening of the safety factor profile, observed by precise measurement of the rational surface locations of the dominant tearing modes; these are identified from the phase flip in correlated electron temperature fluctuations recorded by Thomson scattering. For the core n = 6 rational surface, an inward shift of 1.1 +/- 0.6 cm is observed, with an estimated reduction in q0 of 5%. This technique provides a

  4. Engineering America's Current and Future Space Transportation Systems: 50 Years of Systems Engineering Innovation for Sustainable Exploration

    NASA Technical Reports Server (NTRS)

    Dmbacher, Daniel L.; Lyles, Garry M.; McConnaughey, Paul

    2008-01-01

    Over the past 50 years, the National Aeronautics and Space Administration (NASA) has delivered space transportation solutions for America's complex missions, ranging from scientific payloads that expand knowledge, such as the Hubble Space Telescope, to astronauts and lunar rovers destined for voyages to the Moon. Currently, the venerable Space Shuttle, which has been in service since 1981, provides the United States' (U.S.) capability for both crew and heavy cargo to low-Earth orbit to' construct the International Space Station, before the Shuttle is retired in 2010. In the next decade, NASA will replace this system with a duo of launch vehicles: the Ares I Crew Launch Vehicle and the Ares V Cargo Launch Vehicle (Figure 1). The goals for this new system include increased safety and reliability coupled with lower operations costs that promote sustainable space exploration for decades to come. The Ares I will loft the Orion Crew Exploration Vehicle, while the heavy-lift Ares V will carry the Altair Lunar Lander and the equipment and supplies needed to construct a lunar outpost for a new generation of human and robotic space pioneers. This paper will provide details of the in-house systems engineering and vehicle integration work now being performed for the Ares I and planned for the Ares V. It will give an overview of the Ares I system-level test activities, such as the ground vibration testing that will be conducted in the Marshall Center's Dynamic Test Stand to verify the integrated vehicle stack's structural integrity and to validate computer modeling and simulation (Figure 2), as well as the main propulsion test article analysis to be conducted in the Static Test Stand. These activities also will help prove and refine mission concepts of operation, while supporting the spectrum of design and development work being performed by Marshall's Engineering Directorate, ranging from launch vehicles and lunar rovers to scientific spacecraft and associated experiments

  5. Nitrate fate and transport through current and former depressional wetlands in an agricultural landscape, Choptank Watershed, Maryland, United States

    USGS Publications Warehouse

    Denver, J.M.; Ator, S.W.; Lang, M.W.; Fisher, T.R.; Gustafson, A.B.; Fox, R.; Clune, J.W.; McCarty, G.W.

    2014-01-01

    Understanding local groundwater hydrology and geochemistry is critical for evaluating the effectiveness of wetlands at mitigating agricultural impacts on surface waters. The effectiveness of depressional wetlands at mitigating nitrate (NO3) transport from fertilized row crops, through groundwater, to local streams was examined in the watershed of the upper Choptank River, a tributary of Chesapeake Bay on the Atlantic Coastal Plain. Hydrologic, geochemical, and water quality data were collected from January of 2008 through December of 2009 from surface waters and networks of piezometers installed in and around current or former depressional wetlands of three major types along a gradient of anthropogenic alteration: (1) natural wetlands with native vegetation (i.e., forested); (2) prior-converted croplands, which are former wetlands located in cultivated fields; and (3) hydrologically restored wetlands, including one wetland restoration and one shallow water management area. These data were collected to estimate the orientation of groundwater flow paths and likely interactions of groundwater containing NO3 from agricultural sources with reducing conditions associated with wetlands of different types. Natural wetlands were found to have longer periods of soil saturation and reducing conditions conducive to denitrification compared to the other wetland types studied. Because natural wetlands are typically located in groundwater recharge areas along watershed divides, nitrogen (N) from nearby agriculture was not intercepted. However, these wetlands likely improve water quality in adjacent streams via dilution. Soil and geochemical conditions conducive to denitrification were also present in restored wetlands and prior-converted croplands, and substantial losses of agricultural NO3 were observed in groundwater flowing through these wetland sediments. However, delivery of NO3 from agricultural areas through groundwater to these wetlands resulting in opportunities for

  6. Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

    NASA Astrophysics Data System (ADS)

    Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

    2010-11-01

    AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean’s critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

  7. New direct estimates of Iceland-Scotland Overflow Water transport through the Charlie-Gibbs Fracture Zone and its relationship to the North Atlantic Current

    NASA Astrophysics Data System (ADS)

    Bower, Amy; Furey, Heather; Xu, Xiaobiao

    2015-04-01

    Detailed observations of the pathways, transports and water properties of dense overflows associated with the Atlantic Meridional Overturning Circulation (AMOC) provide critical benchmarks for climate models and mixing parameterizations. A recent two-year time series from eight moorings offers the first long-term simultaneous observations of the hydrographic properties and transport of Iceland-Scotland Overflow Water (ISOW) flowing westward through the Charlie-Gibbs Fracture Zone (CGFZ), a major deep gap in the Mid-Atlantic Ridge (MAR) connecting the eastern and western basins of the North Atlantic. In addition, current meters up to 500-m depth and satellite altimetry allow us to investigate the overlying North Atlantic Current (NAC) as a source of ISOW transport variability. Using the isohaline 34.94 to define the ISOW layer, the two year mean and standard deviation of ISOW transport was -1.7 ± 1.5 Sv, compared to -2.4 ± 3.0 Sv reported by Saunders for a 13-month period in 1988-1989 using the same isohaline. Differences in the two estimates are partly explained by limitations of the Saunders array, but more importantly reflect the strong low-frequency variability in ISOW transport through CGFZ (which includes complete reversals). Both the observations and output from a multi-decadal simulation of the North Atlantic using the Hybrid Coordinate Ocean Model (HYCOM) forced with interannually varying wind and buoyancy fields indicate a strong positive correlation between ISOW transport and the strength of the NAC through the CGFZ. This result raises new questions regarding the interaction of the upper and lower limbs of the AMOC, downstream propagation of ISOW transport variability in the Deep Western Boundary Current and alternative pathways of ISOW across the MAR.

  8. Observation of current variations off the New Guinea coast including the 1997-1998 El Niño period and their relationship with Sverdrup transport

    NASA Astrophysics Data System (ADS)

    Ueki, Iwao; Kashino, Yuji; Kuroda, Yoshifumi

    2003-07-01

    Seasonal and interannual variations of the New Guinea Coastal Current (NGCC) and New Guinea Coastal Undercurrent (NGCUC) were investigated by examining the 5 years' data from acoustic Doppler current profiler moorings at two sites (2°S 142°E, 2.5°S 142°E) off the New Guinea coast. The NGCC flowed northwestward as is usual and intensified during the boreal summer, then weakened or even reversed direction to southeastward during the boreal winter. This seasonal change correlated to the monsoonal wind variation. However, during the 1997-1998 El Niño, the southeastward NGCC during the boreal winter was not observed, and northwestward flow was dominant throughout the year. On the other hand, the NGCUC flowed steadily northwestward all year-round and intensified during the boreal summer. During the growing phase of the El Niño, the NGCUC intensified, and its northwestward flow reached from the surface to a depth of 250 m. Comparison between the volume transport of these currents and the Sverdrup transport along 2°S in the ocean interior indicated a mean difference of 13 × 106 m3 s-1 northward. The relationship between variations of these two transports showed a negative correlation on seasonal timescales except during the El Niño. During the mature phase of the El Niño, northward Sverdrup transport was enhanced significantly, furthermore the transport of these currents was also northward. The result demonstrates a process by which anomalous water volumes can flow into the equatorial region due to an imbalance between the volume transport in the ocean interior and the western boundary.

  9. Effect of boundary treatments on quantum transport current in the Green's function and Wigner distribution methods for a nano-scale DG-MOSFET

    SciTech Connect

    Jiang Haiyan; Cai Wei

    2010-06-20

    In this paper, we conduct a study of quantum transport models for a two-dimensional nano-size double gate (DG) MOSFET using two approaches: non-equilibrium Green's function (NEGF) and Wigner distribution. Both methods are implemented in the framework of the mode space methodology where the electron confinements below the gates are pre-calculated to produce subbands along the vertical direction of the device while the transport along the horizontal channel direction is described by either approach. Each approach handles the open quantum system along the transport direction in a different manner. The NEGF treats the open boundaries with boundary self-energy defined by a Dirichlet to Neumann mapping, which ensures non-reflection at the device boundaries for electron waves leaving the quantum device active region. On the other hand, the Wigner equation method imposes an inflow boundary treatment for the Wigner distribution, which in contrast ensures non-reflection at the boundaries for free electron waves entering the device active region. In both cases the space-charge effect is accounted for by a self-consistent coupling with a Poisson equation. Our goals are to study how the device boundaries are treated in both transport models affects the current calculations, and to investigate the performance of both approaches in modeling the DG-MOSFET. Numerical results show mostly consistent quantum transport characteristics of the DG-MOSFET using both methods, though with higher transport current for the Wigner equation method, and also provide the current-voltage (I-V) curve dependence on various physical parameters such as the gate voltage and the oxide thickness.

  10. Analysis for Heat Transfer in a High Current-Passing Carbon Nanosphere Using Nontraditional Thermal Transport Model.

    PubMed

    Hol C Y; Chen, B C; Tsai, Y H; Ma, C; Wen, M Y

    2015-11-01

    This paper investigates the thermal transport in hollow microscale and nanoscale spheres subject to electrical heat source using nontraditional thermal transport model. Working as supercapacitor electrodes, carbon hollow micrometer- and nanometer-sized spheres needs excellent heat transfer characteristics to maintain high specific capacitance, long cycle life, and high power density. In the nanoscale regime, the prediction of heat transfer from the traditional heat conduction equation based on Fourier's law deviates from the measured data. Consequently, the electrical heat source-induced heat transfer characteristics in hollow micrometer- and nanometer-sized spheres are studied using nontraditional thermal transport model. The effects of parameters on heat transfer in the hollow micrometer- and nanometer-sized spheres are discussed in this study. The results reveal that the heat transferred into the spherical interior, temperature and heat flux in the hollow sphere decrease with the increasing Knudsen number when the radius of sphere is comparable to the mean free path of heat carriers.

  11. Analysis for Heat Transfer in a High Current-Passing Carbon Nanosphere Using Nontraditional Thermal Transport Model.

    PubMed

    Hol C Y; Chen, B C; Tsai, Y H; Ma, C; Wen, M Y

    2015-11-01

    This paper investigates the thermal transport in hollow microscale and nanoscale spheres subject to electrical heat source using nontraditional thermal transport model. Working as supercapacitor electrodes, carbon hollow micrometer- and nanometer-sized spheres needs excellent heat transfer characteristics to maintain high specific capacitance, long cycle life, and high power density. In the nanoscale regime, the prediction of heat transfer from the traditional heat conduction equation based on Fourier's law deviates from the measured data. Consequently, the electrical heat source-induced heat transfer characteristics in hollow micrometer- and nanometer-sized spheres are studied using nontraditional thermal transport model. The effects of parameters on heat transfer in the hollow micrometer- and nanometer-sized spheres are discussed in this study. The results reveal that the heat transferred into the spherical interior, temperature and heat flux in the hollow sphere decrease with the increasing Knudsen number when the radius of sphere is comparable to the mean free path of heat carriers. PMID:26726687

  12. Processing, microstructure and transport currents of (100)/(100) and (110)/(110) domain boundaries in multi-seeded YBa2Cu3Oy fabrics

    NASA Astrophysics Data System (ADS)

    Sudhakar Reddy, E.; Noudem, J. G.; Tarka, M.; Noe, M.; Schmitz, G. J.

    2002-01-01

    Multi-domain YBa2Cu3Oy (123) superconducting fabrics with controlled domain orientations have been prepared from Y2O3 precursor cloths by multiple seeding during an infiltration and growth process. Long-length samples containing up to four domains with controlled orientations yielding the (110)/(110) and (100)/(100) junctions respectively have been produced by placing the seed crystals accordingly. The normal state resistivity and the transport currents along the domain boundaries are discussed and correlated with their microstructure. The (110)/(110) boundaries are observed to exhibit superior transport currents over the (100)/(100) boundaries due to the formation of relatively clean boundaries. The presence of boundary junctions is found to be effective in increasing the normal state resistivity of the samples. The coupling of domains rather than their crystallographic alignment is observed to be the dominant factor in deciding the final Jc of the multi-seeded samples.

  13. The interplay between diet, urate transporters and the risk for gout and hyperuricemia: current and future directions.

    PubMed

    Torralba, Karina D; De Jesus, Emerson; Rachabattula, Shylaja

    2012-12-01

    Diet plays a significant role in the development of gout and hyperuricemia. Gout and hyperuricemia have likewise been associated with the development of cardiovascular disease and metabolic syndrome. Epidemiological studies have shown that certain foods influence levels of serum uric acid and the risk for development of gout.This article reviews the influence of dietary factors on serum uric acid levels and risk of gout, as well as the role of urate transporters in the development of hyperuricemia and gout.Various epidemiological studies have shown the effects of certain foods on the risk of developing gout and hyperuricemia. Low-fat dairy products, purine-rich vegetables, whole grains, nuts and legumes, and less sugary fruits, coffee and vitamin C supplements decrease the risk, whereas intake of red meat, fructose-containing beverages and alcohol increase the risk of gout. There is also an increased although basic understanding of the effects of vitamin C, alcohol and fructose on urate transporters. Certain foods can lead to a decreased or increased risk of development of gout and hyperuricemia. Advances have established the interplay of certain foods on urate transporters and renal handling of urate. More studies, especially prospective ones, are needed to increase our understanding of the roles of foods and urate transporters and other molecular mechanisms on the risk of developing gout and hyperuricemia. PMID:23253231

  14. An overview of the current technology relevant to the design and development of the Space Transportation Main Engine (STME)

    NASA Technical Reports Server (NTRS)

    Das, Digendra K.

    1991-01-01

    The objective of this project was to review the latest literature relevant to the Space Transportation Main Engine (STME). The search was focused on the following engine components: (1) gas generator; (2) hydrostatic/fluid bearings; (3) seals/clearances; (4) heat exchanges; (5) nozzles; (6) nozzle/main combustion chamber joint; (7) main injector face plate; and (8) rocket engine.

  15. Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Current and advanced act control system definition study. Volume 2: Appendices

    NASA Technical Reports Server (NTRS)

    Hanks, G. W.; Shomber, H. A.; Dethman, H. A.; Gratzer, L. B.; Maeshiro, A.; Gangsaas, D.; Blight, J. D.; Buchan, S. M.; Crumb, C. B.; Dorwart, R. J.

    1981-01-01

    The current status of the Active Controls Technology (ACT) for the advanced subsonic transport project is investigated through analysis of the systems technical data. Control systems technologies under examination include computerized reliability analysis, pitch axis fly by wire actuator, flaperon actuation system design trade study, control law synthesis and analysis, flutter mode control and gust load alleviation analysis, and implementation of alternative ACT systems. Extensive analysis of the computer techniques involved in each system is included.

  16. Suppression of roll-off characteristics of organic light-emitting diodes by narrowing current injection/transport area to 50 nm

    SciTech Connect

    Hayashi, Kyohei Inoue, Munetomo; Yoshida, Kou; Nakanotani, Hajime; Mikhnenko, Oleksandr; Nguyen, Thuc-Quyen E-mail: adachi@cstf.kyushu-u.ac.jp; Adachi, Chihaya E-mail: adachi@cstf.kyushu-u.ac.jp

    2015-03-02

    Using e-beam nanolithography, the current injection/transport area in organic light-emitting diodes (OLEDs) was confined into a narrow linear structure with a minimum width of 50 nm. This caused suppression of Joule heating and partial separation of polarons and excitons, so the charge density where the electroluminescent efficiency decays to the half of the initial value (J{sub 0}) was significantly improved. A device with a narrow current injection width of 50 nm exhibited a J{sub 0} that was almost two orders of magnitude higher compared with that of the unpatterned OLED.

  17. Impact of slowdown of Atlantic overturning circulation on heat and freshwater transports

    NASA Astrophysics Data System (ADS)

    Kelly, Kathryn A.; Drushka, Kyla; Thompson, LuAnne; Le Bars, Dewi; McDonagh, Elaine L.

    2016-07-01

    Recent measurements of the strength of the Atlantic overturning circulation at 26°N show a 1 year drop and partial recovery amid a gradual weakening. To examine the extent and impact of the slowdown on basin wide heat and freshwater transports for 2004-2012, a box model that assimilates hydrographic and satellite observations is used to estimate heat transport and freshwater convergence as residuals of the heat and freshwater budgets. Using an independent transport estimate, convergences are converted to transports, which show a high level of spatial coherence. The similarity between Atlantic heat transport and the Agulhas Leakage suggests that it is the source of the surface heat transport anomalies. The freshwater budget in the North Atlantic is dominated by a decrease in freshwater flux. The increasing salinity during the slowdown supports modeling studies that show that heat, not freshwater, drives trends in the overturning circulation in a warming climate.

  18. Big-Ass Holes in the Surfzone: Waves, Currents, and Sediment Transport in a Seafloor Perturbation Experiment

    NASA Astrophysics Data System (ADS)

    Moulton, M. R.; Elgar, S.; Raubenheimer, B.

    2010-12-01

    The evolution of 2-m deep, 10-m diameter holes excavated in the inner surfzone on an energetic beach was monitored with a downward-looking current profiler at the center of each hole, a surfboard-mounted GPS-sonar survey system, and tall divers with graduated poles, tape measures, marked lines, and long arms. Waves and currents were measured with up to 14 current meters and profilers over a 1600-sq-m area. The mean water depth surrounding the holes was 1.5 m and the tidal range was 1 m. Significant wave heights ranged from 0.2 to 1.2 m, and mean current speeds ranged from 0.1 to 1.2 m/s. The surfzone holes filled with sand in 2 to 6 days, in contrast to a previous study in which holes of the same size in the swashzone filled in a few hours. Preliminary results suggest that the rate of change of the sand level in the holes was correlated more strongly with wave heights (and thus with wave-orbital velocities) than with mean current speeds. In a hole dug in the trough between a sandbar and the shoreline, the sand level rose relatively slowly (1 m in 4.5 days) when wave heights were small (0.4 m) and mean currents were increasing (from 0.15 to 0.8 m/s), then filled rapidly (0.8 m in 6 hours) as wave heights increased (to 1.1 m) and mean currents increased (to 1.2 m/s). For a second hole dug in the same location, wave heights were moderate and variable (0.3 to 0.8 m), mean flow speeds were moderate and increasing (from 0.3 to 0.7 m/s), and the hole filled steadily (1.7 m in 2.5 days). In some instances, horizontal flow patterns were consistent with rip current circulation, with converging alongshore currents feeding an offshore jet centered at the depression. Here, volume changes in the hole will be compared with the observed waves, wave-orbital velocities, mean currents, and surrounding bathymetry. These data were collected in August 2010 at the US Army Corps of Engineers Field Research Facility in Duck, North Carolina. Funded by a National Security Science and

  19. Electrostatic charging and charge transport by hydrated amorphous silica under a high voltage direct current electrical field

    NASA Astrophysics Data System (ADS)

    Perles, Carlos Eduardo; Volpe, Pedro Luiz Onófrio

    2011-06-01

    This work was initially based on the casual observation of an electrostatic phenomenon, in which particles of amorphous silica were attracted by a dc electrical field. The first observations were recently shown in a communication in this journal. To explain the electrical charge transport process observed in this work, all forces acting on silica particles were estimated and the significant ones were used to formulate a model made up of three elementary steps. Analyzing the experimental observations using this model, it was possible to suggest that electrons can be introduced into and removed from electronic bands of water.

  20. Electrostatic charging and charge transport by hydrated amorphous silica under a high voltage direct current electrical field.

    PubMed

    Perles, Carlos Eduardo; Volpe, Pedro Luiz Onófrio

    2011-06-01

    This work was initially based on the casual observation of an electrostatic phenomenon, in which particles of amorphous silica were attracted by a dc electrical field. The first observations were recently shown in a communication in this journal. To explain the electrical charge transport process observed in this work, all forces acting on silica particles were estimated and the significant ones were used to formulate a model made up of three elementary steps. Analyzing the experimental observations using this model, it was possible to suggest that electrons can be introduced into and removed from electronic bands of water.

  1. Discrimination between spin-dependent charge transport and spin-dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance

    NASA Astrophysics Data System (ADS)

    Kavand, Marzieh; Baird, Douglas; van Schooten, Kipp; Malissa, Hans; Lupton, John M.; Boehme, Christoph

    2016-08-01

    Spin-dependent processes play a crucial role in organic electronic devices. Spin coherence can give rise to spin mixing due to a number of processes such as hyperfine coupling, and leads to a range of magnetic field effects. However, it is not straightforward to differentiate between pure single-carrier spin-dependent transport processes which control the current and therefore the electroluminescence, and spin-dependent electron-hole recombination which determines the electroluminescence yield and in turn modulates the current. We therefore investigate the correlation between the dynamics of spin-dependent electric current and spin-dependent electroluminescence in two derivatives of the conjugated polymer poly(phenylene-vinylene) using simultaneously measured pulsed electrically detected (pEDMR) and optically detected (pODMR) magnetic resonance spectroscopy. This experimental approach requires careful analysis of the transient response functions under optical and electrical detection. At room temperature and under bipolar charge-carrier injection conditions, a correlation of the pEDMR and the pODMR signals is observed, consistent with the hypothesis that the recombination currents involve spin-dependent electronic transitions. This observation is inconsistent with the hypothesis that these signals are caused by spin-dependent charge-carrier transport. These results therefore provide no evidence that supports earlier claims that spin-dependent transport plays a role for room-temperature magnetoresistance effects. At low temperatures, however, the correlation between pEDMR and pODMR is weakened, demonstrating that more than one spin-dependent process influences the optoelectronic materials' properties. This conclusion is consistent with prior studies of half-field resonances that were attributed to spin-dependent triplet exciton recombination, which becomes significant at low temperatures when the triplet lifetime increases.

  2. Experimental and theoretical analysis of transport properties of core-shell wire light emitting diodes probed by electron beam induced current microscopy.

    PubMed

    Lavenus, P; Messanvi, A; Rigutti, L; De Luna Bugallo, A; Zhang, H; Bayle, F; Julien, F H; Eymery, J; Durand, C; Tchernycheva, M

    2014-06-27

    We report a systematic experimental and theoretical investigation of core-shell InGaN/GaN single wire light-emitting diodes (LEDs) using electron beam induced current (EBIC) microscopy. The wires were grown by catalyst-free MOVPE and processed into single wire LEDs using electron beam lithography on dispersed wires. The influence of the acceleration voltage and of the applied bias on the EBIC maps was investigated. We show that the EBIC maps provide information both on the minority carrier effects (i.e. on the local p-n junction collection efficiency) and on the majority carrier effects (i.e. the transport efficiency from the excited region toward the contacts). Because of a finite core and shell resistance a non-negligible current redistribution into the p-n junction takes place during the majority carrier transport. A theoretical model for transport in a core-shell wire is developed, allowing to explain the dependence of the EBIC profiles on the experimental parameters (the electron beam acceleration voltage and the bias applied on the device) and on the structural parameters of the wire (core and shell resistance, shunt resistance, etc). Comparison between simulated and experimental profiles provides valuable information concerning the structure inhomogeneities and gives insight into the wire electrical parameters.

  3. NON-LINEAR VISCO-RESISTIVE COLLISIONAL TRANSPORT IN TOROIDAL ELLIPTICAL PLASMAS WITH TRIANGULARITY AND HOLE CURRENTS: A REVIEW

    SciTech Connect

    Martin, Pablo; Castro, Enrique; Puerta, Julio

    2009-07-26

    Non-linear plasma diffusion effects due to hole currents in tokamaks is analyzed in this work. Since the recent discovery of hole currents in tokamaks, this matter has become very important in confinement and instabilities in tokamaks plasmas. The analysis here presented includes non-linear flows as well as hole currents. In the case of low vorticity plasmas our treatment is performed using MHD equations, an it is more suitable for plasmas with very low levels of turbulence, as in the H-mode. The present treatment follows the lines of previous works, and some of the equations and results look like those obtained on these papers. However, the form of the family of the magnetic surfaces is very different to previous treatment, since the hole current modifies those families in a very important way. Elliptic plasmas with triangularity are considered. Pfirsch-Schlueter type currents are obtained for these generalized cases. Diffusion with and without holes are calculated and compared for several values of ellipticity and triangularity. Negative and positive triangularities are considered. In most of the calculations triangularity improves confinement, but the results are different for the positive than for the negative case.

  4. Information needs for siting new, and evaluating current, nuclear facilities: ecology, fate and transport, and human health.

    PubMed

    Burger, Joanna; Clarke, James; Gochfeld, Michael

    2011-01-01

    The USA is entering an era of energy diversity, and increasing nuclear capacity and concerns focus on accidents, security, waste, and pollution. Physical buffers that separate outsiders from nuclear facilities often support important natural ecosystems but may contain contaminants. The US Nuclear Regulatory Commission (NRC) licenses nuclear reactors; the applicant provides environmental assessments that serve as the basis for Environmental Impact Statements developed by NRC. We provide a template for the types of information needed for safe siting of nuclear facilities with buffers in three categories: ecological, fate and transport, and human health information that can be used for risk evaluations. Each item on the lists is an indicator for evaluation, and individual indicators can be selected for specific region. Ecological information needs include biodiversity (species, populations, communities) and structure and functioning of ecosystems, habitats, and landscapes, in addition to common, abundant, and unique species and endangered and rare ones. The key variables of fate and transport are sources of release for radionuclides and other chemicals, nature of releases (atmospheric vapors, subsurface liquids), features, and properties of environmental media (wind speed, direction and atmospheric stability, hydraulic gradient, hydraulic conductivity, groundwater chemistry). Human health aspects include receptor populations (demography, density, dispersion, and distance), potential pathways (drinking water sources, gardening, fishing), and exposure opportunities (lifestyle activities). For each of the three types of information needs, we expect that only a few of the indicators will be applicable to a particular site and that stakeholders should agree on a site-specific suite. PMID:20140506

  5. Information needs for siting new, and evaluating current, nuclear facilities: ecology, fate and transport, and human health.

    PubMed

    Burger, Joanna; Clarke, James; Gochfeld, Michael

    2011-01-01

    The USA is entering an era of energy diversity, and increasing nuclear capacity and concerns focus on accidents, security, waste, and pollution. Physical buffers that separate outsiders from nuclear facilities often support important natural ecosystems but may contain contaminants. The US Nuclear Regulatory Commission (NRC) licenses nuclear reactors; the applicant provides environmental assessments that serve as the basis for Environmental Impact Statements developed by NRC. We provide a template for the types of information needed for safe siting of nuclear facilities with buffers in three categories: ecological, fate and transport, and human health information that can be used for risk evaluations. Each item on the lists is an indicator for evaluation, and individual indicators can be selected for specific region. Ecological information needs include biodiversity (species, populations, communities) and structure and functioning of ecosystems, habitats, and landscapes, in addition to common, abundant, and unique species and endangered and rare ones. The key variables of fate and transport are sources of release for radionuclides and other chemicals, nature of releases (atmospheric vapors, subsurface liquids), features, and properties of environmental media (wind speed, direction and atmospheric stability, hydraulic gradient, hydraulic conductivity, groundwater chemistry). Human health aspects include receptor populations (demography, density, dispersion, and distance), potential pathways (drinking water sources, gardening, fishing), and exposure opportunities (lifestyle activities). For each of the three types of information needs, we expect that only a few of the indicators will be applicable to a particular site and that stakeholders should agree on a site-specific suite.

  6. A review of new and current-use contaminants in the Arctic environment: evidence of long-range transport and indications of bioaccumulation.

    PubMed

    Vorkamp, Katrin; Rigét, Frank F

    2014-09-01

    Systematic monitoring of persistent organic pollutants (POPs) in the Arctic has been conducted for several years, in combination with assessments of POP levels in the Arctic, POP exposure and biological effects. Meanwhile, environmental research continues to detect new contaminants some of which could be potential new Arctic pollutants. This study summarizes the empirical evidence that is currently available of those compounds in the Arctic that are not commonly included in chemical monitoring programmes. The study has focused on novel flame retardants, e.g. alternatives to the banned polybrominated diphenyl ethers (PBDEs), current-use pesticides and various other compounds, i.e. synthetic musk compounds, siloxanes, phthalic acid esters and halogenated compounds like hexachlorobutadiene, octachlorostyrene, pentachlorobenzene and polychlorinated naphthalenes. For a number of novel brominated flame retardants, e.g. 2,3-bibromopropyl-2,4,6-tribromophenyl ether (DPTE), bis(2-ethylhexyl)tetrabromophthalate (TBPH), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), 1,2-bis(2,4,6-tribromophenoxy)-ethane (BTBPE), decabromodiphenyl ethane (DBDPE), pentabromoethylbenzene (PBEB) and hexabromobenzene (HBBz), transport to the Arctic has been documented, but evidence of bioaccumulation is sparse and ambiguous. For short-chain chlorinated paraffins and dechlorane plus, however, increasing evidence shows both long-range transport and bioaccumulation. Ice cores have documented increasing concentrations of some current-use pesticides, e.g. chlorpyrifos, endosulfan and trifluralin, and bioaccumulation has been observed for pentachloroanisole, chorpyrifos, endosulfan and metoxychlor, however, the question of biomagnification remains unanswered. PMID:24997943

  7. Survey of current state radiological emergency response capabilities for transportation related incidents. Final report, 1 October 1978-8 December 1980

    SciTech Connect

    Mitter, E.L.; Hume, R.D.; Vilardo, F.; Feigenbaum, E.; Briggs, H.

    1980-09-01

    The volume is the final report of a project to survey current state radiological emergency response capabilities for transportation related incidents. The survey was performed to provide the NRC with information useful in the development of guidelines for state organizations and planning for emergency response. The report includes the results of a mail and telephone survey of state emergency response officials; information gleaned from radiological emergency response plans and related official document; and some general conclusions and recommendations drawn in part from interviews conducted and site visits to selected states.

  8. Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Current and advanced act control system definition study

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The Current and Advanced Technology ACT control system definition tasks of the Integrated Application of Active Controls (IAAC) Technology project within the Energy Efficient Transport Program are summarized. The systems mechanize six active control functions: (1) pitch augmented stability; (2) angle of attack limiting; (3) lateral/directional augmented stability; (4) gust load alleviation; (5) maneuver load control; and (6) flutter mode control. The redundant digital control systems meet all function requirements with required reliability and declining weight and cost as advanced technology is introduced.

  9. Current status, research needs, and opportunities in applications of surface processing to transportation and utilities technologies. Proceedings of a December 1991 workshop

    SciTech Connect

    Czanderna, A.W.; Landgrebe, A.R.

    1992-09-01

    Goal of surface processing is to develop innovative methods of surface modification and characterization for optimum performance and environmental protection for cost-effective operational lifetimes of systems, materials, and components used in transportation and utilities. These proceedings document the principal discussions and conclusions reached at the workshop; they document chapters about the current status of surface characterization with focus on composition, structure, bonding, and atomic-scale topography of surfaces. Also documented are chapters on the current status of surface modification techniques: electrochemical, plasma-aided, reactive and nonreactive physical vapor deposition, sol-gel coatings, high-energy ion implantation, ion-assisted deposition, organized molecular assemblies, solar energy. Brief chapters in the appendices document basic research in surface science by NSF, Air Force, and DOE. Participants at the workshop were invited to serve on 10 working groups. Separate abstracts were prepared for the data base where appropriate.

  10. Application of acoustic-Doppler current profiler and expendable bathythermograph measurements to the study of the velocity structure and transport of the Gulf Stream

    NASA Technical Reports Server (NTRS)

    Joyce, T. M.; Dunworth, J. A.; Schubert, D. M.; Stalcup, M. C.; Barbour, R. L.

    1988-01-01

    The degree to which Acoustic-Doppler Current Profiler (ADCP) and expendable bathythermograph (XBT) data can provide quantitative measurements of the velocity structure and transport of the Gulf Stream is addressed. An algorithm is used to generate salinity from temperature and depth using an historical Temperature/Salinity relation for the NW Atlantic. Results have been simulated using CTD data and comparing real and pseudo salinity files. Errors are typically less than 2 dynamic cm for the upper 800 m out of a total signal of 80 cm (across the Gulf Stream). When combined with ADCP data for a near-surface reference velocity, transport errors in isopycnal layers are less than about 1 Sv (10 to the 6th power cu m/s), as is the difference in total transport for the upper 800 m between real and pseudo data. The method is capable of measuring the real variability of the Gulf Stream, and when combined with altimeter data, can provide estimates of the geoid slope with oceanic errors of a few parts in 10 to the 8th power over horizontal scales of 500 km.

  11. Interpretation of current-voltage relationships for "active" ion transport systems: I. Steady-state reaction-kinetic analysis of class-I mechanisms.

    PubMed

    Hansen, U P; Gradmann, D; Sanders, D; Slayman, C L

    1981-01-01

    This paper develops a simple reaction-kinetic model to describe electrogenic pumping and co- (or counter-) transport of ions. It uses the standard steady-state approach for cyclic enzyme- or carrier-mediated transport, but does not assume rate-limitation by any particular reaction step. Voltage-dependence is introduced, after the suggestion of Läuger and Stark (Biochim. Biophys. Acta 211:458-466, 1970), via a symmetric Eyring barrier, in which the charge-transit reaction constants are written as k12 = ko12 exp(zF delta psi/2RT) and k21 = ko21 exp(-zF delta psi/2RT). For interpretation of current-voltage relationships, all voltage-independent reaction steps are lumped together, so the model in its simplest form can be described as a pseudo-2-state model. It is characterized by the two voltage-dependent reaction constants, two lumped voltage-independent reaction constants (k12, k21), and two reserve factors (ri, ro) which formally take account of carrier states that are indistinguishable in the current-voltage (I-V) analysis. The model generates a wide range of I-V relationships, depending on the relative magnitudes of the four reaction constants, sufficient to describe essentially all I-V datas now available on "active" ion-transport systems. Algebraic and numerical analysis of the reserve factors, by means of expanded pseudo-3-, 4-, and 5-state models, shows them to be bounded and not large for most combinations of reaction constants in the lumped pathway. The most important exception to this rule occurs when carrier decharging immediately follows charge transit of the membrane and is very fast relative to other constituent voltage-independent reactions. Such a circumstance generates kinetic equivalence of chemical and electrical gradients, thus providing a consistent definition of ion-motive forces (e.g., proton-motive force, PMF). With appropriate restrictions, it also yields both linear and log-linear relationships between net transport velocity and either

  12. Imaging interfacial electrical transport in graphene-MoS2 heterostructures with electron-beam-induced-currents

    NASA Astrophysics Data System (ADS)

    White, E. R.; Kerelsky, Alexander; Hubbard, William A.; Dhall, Rohan; Cronin, Stephen B.; Mecklenburg, Matthew; Regan, B. C.

    2015-11-01

    Heterostructure devices with specific and extraordinary properties can be fabricated by stacking two-dimensional crystals. Cleanliness at the inter-crystal interfaces within a heterostructure is crucial for maximizing device performance. However, because these interfaces are buried, characterizing their impact on device function is challenging. Here, we show that electron-beam induced current (EBIC) mapping can be used to image interfacial contamination and to characterize the quality of buried heterostructure interfaces with nanometer-scale spatial resolution. We applied EBIC and photocurrent imaging to map photo-sensitive graphene-MoS2 heterostructures. The EBIC maps, together with concurrently acquired scanning transmission electron microscopy images, reveal how a device's photocurrent collection efficiency is adversely affected by nanoscale debris invisible to optical-resolution photocurrent mapping.

  13. Understanding the role of electron and hole trions on current transport in aluminium tris(8-hydroxyquinoline) using organic magnetoresistance

    SciTech Connect

    Zhang, Sijie; Gillin, W. P.; Willis, M.; Gotto, R.; Roy, K. A.; Kreouzis, T.; Rolfe, N. J.

    2014-01-27

    The change in current through an organic light emitting diode (OLED) when it is placed in a magnetic field has been dubbed organic magnetoresistance and provides a means to understand the spin interactions that are occurring in working devices. Whilst there are a wide range of interactions that have been proposed to be the cause of the measured effects, there is still a need to identify their individual roles and in particular how they respond to an applied magnetic field. In this work, we investigate the effect of changing the balance of electron and hole injection in a simple aluminium tris(8-hydroxyqinoline) based OLED and demonstrate that the triplet polaron interaction appears to be much stronger for electrons than for holes in this material.

  14. Application of the loop method for correcting acoustic doppler current profiler discharge measurements biased by sediment transport

    USGS Publications Warehouse

    Mueller, David S.; Wagner, Chad R.

    2006-01-01

    A systematic bias in discharge measurements made with an acoustic Doppler current profiler (ADCP) is attributed to the movement of sediment near the streambed-an issue widely acknowledged by the scientific community. This systematic bias leads to an underestimation of measured velocity and discharge. The integration of a differentially corrected Global Positioning System (DGPS) to track the movement of the ADCP can be used to avoid the systematic bias associated with a moving bed. DGPS systems, however, cannot provide consistently accurate positions because of multipath errors and satellite signal reception problems on waterways with dense tree canopy along the banks, in deep valleys or canyons, and near bridges. An alternative method of correcting for the moving-bed bias was investigated by the U.S. Geological Survey.

  15. Imaging interfacial electrical transport in graphene–MoS{sub 2} heterostructures with electron-beam-induced-currents

    SciTech Connect

    White, E. R. Kerelsky, Alexander; Hubbard, William A.; Regan, B. C.; Dhall, Rohan; Cronin, Stephen B.; Mecklenburg, Matthew

    2015-11-30

    Heterostructure devices with specific and extraordinary properties can be fabricated by stacking two-dimensional crystals. Cleanliness at the inter-crystal interfaces within a heterostructure is crucial for maximizing device performance. However, because these interfaces are buried, characterizing their impact on device function is challenging. Here, we show that electron-beam induced current (EBIC) mapping can be used to image interfacial contamination and to characterize the quality of buried heterostructure interfaces with nanometer-scale spatial resolution. We applied EBIC and photocurrent imaging to map photo-sensitive graphene-MoS{sub 2} heterostructures. The EBIC maps, together with concurrently acquired scanning transmission electron microscopy images, reveal how a device's photocurrent collection efficiency is adversely affected by nanoscale debris invisible to optical-resolution photocurrent mapping.

  16. Flow structure and transport characteristics of feeding and exchange currents generated by upside-down Cassiopea jellyfish.

    PubMed

    Santhanakrishnan, Arvind; Dollinger, Makani; Hamlet, Christina L; Colin, Sean P; Miller, Laura A

    2012-07-15

    Quantifying the flows generated by the pulsations of jellyfish bells is crucial for understanding the mechanics and efficiency of their swimming and feeding. Recent experimental and theoretical work has focused on the dynamics of vortices in the wakes of swimming jellyfish with relatively simple oral arms and tentacles. The significance of bell pulsations for generating feeding currents through elaborate oral arms and the consequences for particle capture are not as well understood. To isolate the generation of feeding currents from swimming, the pulsing kinematics and fluid flow around the benthic jellyfish Cassiopea spp. were investigated using a combination of videography, digital particle image velocimetry and direct numerical simulation. During the rapid contraction phase of the bell, fluid is pulled into a starting vortex ring that translates through the oral arms with peak velocities that can be of the order of 10 cm s(-1). Strong shear flows are also generated across the top of the oral arms throughout the entire pulse cycle. A coherent train of vortex rings is not observed, unlike in the case of swimming oblate medusae such as Aurelia aurita. The phase-averaged flow generated by bell pulsations is similar to a vertical jet, with induced flow velocities averaged over the cycle of the order of 1-10 mm s(-1). This introduces a strong near-horizontal entrainment of the fluid along the substrate and towards the oral arms. Continual flow along the substrate towards the jellyfish is reproduced by numerical simulations that model the oral arms as a porous Brinkman layer of finite thickness. This two-dimensional numerical model does not, however, capture the far-field flow above the medusa, suggesting that either the three-dimensionality or the complex structure of the oral arms helps to direct flow towards the central axis and up and away from the animal. PMID:22723475

  17. Flow structure and transport characteristics of feeding and exchange currents generated by upside-down Cassiopea jellyfish.

    PubMed

    Santhanakrishnan, Arvind; Dollinger, Makani; Hamlet, Christina L; Colin, Sean P; Miller, Laura A

    2012-07-15

    Quantifying the flows generated by the pulsations of jellyfish bells is crucial for understanding the mechanics and efficiency of their swimming and feeding. Recent experimental and theoretical work has focused on the dynamics of vortices in the wakes of swimming jellyfish with relatively simple oral arms and tentacles. The significance of bell pulsations for generating feeding currents through elaborate oral arms and the consequences for particle capture are not as well understood. To isolate the generation of feeding currents from swimming, the pulsing kinematics and fluid flow around the benthic jellyfish Cassiopea spp. were investigated using a combination of videography, digital particle image velocimetry and direct numerical simulation. During the rapid contraction phase of the bell, fluid is pulled into a starting vortex ring that translates through the oral arms with peak velocities that can be of the order of 10 cm s(-1). Strong shear flows are also generated across the top of the oral arms throughout the entire pulse cycle. A coherent train of vortex rings is not observed, unlike in the case of swimming oblate medusae such as Aurelia aurita. The phase-averaged flow generated by bell pulsations is similar to a vertical jet, with induced flow velocities averaged over the cycle of the order of 1-10 mm s(-1). This introduces a strong near-horizontal entrainment of the fluid along the substrate and towards the oral arms. Continual flow along the substrate towards the jellyfish is reproduced by numerical simulations that model the oral arms as a porous Brinkman layer of finite thickness. This two-dimensional numerical model does not, however, capture the far-field flow above the medusa, suggesting that either the three-dimensionality or the complex structure of the oral arms helps to direct flow towards the central axis and up and away from the animal.

  18. Dependence of Bootstrap Current, Stability, and Transport on the Safety Factor Profile in DIII-D Steady-State Scenario Discharges

    SciTech Connect

    Ferron, J; White, A; Luce, T; Politzer, P; Turco, F; DeBoo, J; Petrie, T; Petty, C; La Haye, R; Hyatt, A; Rhodes, T; Zeng, L; Doyle, E

    2009-10-14

    Conclusions of this report are: (1) In our scans of q{sub min} and q{sub 95}, the bootstrap current fraction increased with q{sub 95} but did not continue to increase with q{sub min} above about 1.5 as expected by f{sub BS} {approx} q{beta}{sub N}; (2) With existing control tools, q{sub min} {approx} 1.5 appears optimal for maximizing bootstrap current if the calculated ideal wall limit can be reached (only narrowly more so than q{sub min} {approx} 1.1); (3) q{sub min} {approx} 2 discharges achieved lower {beta}{sub N} and calculated n = 1 {beta}{sub N} limits, had increased transport, lower density, lower temperature gradients, and as a result did not produce as much bootstrap current; (4) Highest f{sub BS} achieved at highest q{sub 95} (=6.8), but scan suggests lower q{sub 95} is required for more reactor relevant fusion gain G {approx} {beta}{sub N}H{sub 89}/q{sub 95}{sup 2}; (5) New tools (off-axis NBI, more ECCD) may allow access to higher {beta}{sub N} limits and higher bootstrap fractions.

  19. Salinification and warming of the South Atlantic due to the Indonesian Throughflow

    NASA Astrophysics Data System (ADS)

    Le Bars, D.; Dijkstra, H. A.; de Ruijter, W. P. M.

    2012-04-01

    Experiments on the influence of the Indonesian Throughflow on the structure and water properties of the Southern Hemisphere supergyre is presented. In a strongly eddying global ocean model, we compare an upper ocean flow for a closed Indonesian Seaway experiment with that of a control simulation. Most of the volume transport from the Indonesian Throughflow flows through the Mozambique Channel into the Agulhas Current. Import of warm and fresh water from the Pacific leads to increasing temperature of the upper Indian Ocean and decreasing salinity of the Agulhas Current. Agulhas Leakage is strengthened and, even though its salinity decreases, brings extra salt and heat from the Indian into the Atlantic Ocean. This causes a warming and salinification of the South Atlantic. The dynamical relation between Indonesian Throughflow transport and Agulhas leakage is analyzed using a regional idealized model at high resolution. This allows us to derive a non-linear relation between these two quantities and to identify the important physical mechanisms involved.

  20. Application of acoustic doppler current profilers for measuring three-dimensional flow fields and as a surrogate measurement of bedload transport

    USGS Publications Warehouse

    Conaway, J.S.

    2005-01-01

    Acoustic Doppler current profilers (ADCPs) have been in use in the riverine environment for nearly 20 years. Their application primarily has been focused on the measurement of streamflow discharge. ADCPs emit high-frequency sound pulses and receive reflected sound echoes from sediment particles in the water column. The Doppler shift between transmitted and return signals is resolved into a velocity component that is measured in three dimensions by simultaneously transmitting four independent acoustical pulses. To measure the absolute velocity magnitude and direction in the water column, the velocity magnitude and direction of the instrument must also be computed. Typically this is accomplished by ensonifying the streambed with an acoustical pulse that also provides a depth measurement for each of the four acoustic beams. Sediment transport on or near the streambed will bias these measurements and requires external positioning such as a differentially corrected Global Positioning Systems (GPS). Although the influence of hydraulic structures such as spur dikes and bridge piers is typically only measured and described in one or two dimensions, the use of differentially corrected GPS with ADCPs provides a fully three-dimensional measurement of the magnitude and direction of the water column at such structures. The measurement of these flow disturbances in a field setting also captures the natural pulsations of river flow that cannot be easily quantified or modeled by numerical simulations or flumes. Several examples of measured three-dimensional flow conditions at bridge sites throughout Alaska are presented. The bias introduced to the bottom-track measurement is being investigated as a surrogate measurement of bedload transport. By fixing the position of the ADCP for a known period of time the apparent velocity of the streambed at that position can be determined. Initial results and comparison to traditionally measured bedload values are presented. These initial

  1. The Arctic Ocean Boundary Current along the Eurasian slope and the adjacent Lomonosov Ridge: Water mass properties, transports and transformations from moored instruments

    NASA Astrophysics Data System (ADS)

    Woodgate, Rebecca A.; Aagaard, Knut; Muench, Robin D.; Gunn, John; Björk, Göran; Rudels, Bert; Roach, A. T.; Schauer, Ursula

    2001-08-01

    Year-long (summer 1995 to 1996) time series of temperature, salinity and current velocity from three slope sites spanning the junction of the Lomonosov Ridge with the Eurasian continent are used to quantify the water properties, transformations and transport of the boundary current of the Arctic Ocean. The mean flow is cyclonic, weak (1 to 5 cm s -1), predominantly aligned along isobaths and has an equivalent barotropic structure in the vertical. We estimate the transport of the boundary current in the Eurasian Basin to be 5±1 Sv. About half of this flow is diverted north along the Eurasian Basin side of the Lomonosov Ridge. The warm waters (>1.4°C) of the Atlantic layer are also found on the Canadian Basin side of the ridge south of 86.5°N, but not north of this latitude. This suggests that the Atlantic layer crosses the ridge at various latitudes south of 86.5°N and flows southward along the Canadian Basin side of the ridge. Temperature and salinity records indicate a small (0.02 Sv), episodic flow of Canadian Basin deep water into the Eurasian Basin at ˜1700 m, providing a possible source for an anomalous eddy observed in the Amundsen Basin in 1996. There is also a similar flow of Eurasian Basin deep water into the Canadian Basin. Both flows probably pass through a gap in the Lomonosov Ridge at 80.4°N. A cooling and freshening of the Atlantic layer, observed at all three moorings, is attributed to changes (in temperature and salinity and/or volume) in the outflow from the Barents Sea the previous winter, possibly caused by an observed increased flow of ice from the Arctic Ocean into the Barents Sea. The change in water properties, which advects at ˜5 cm s -1 along the southern edge of the Eurasian Basin, also strengthens the cold halocline layer and increases the stability of the upper ocean. This suggests a feedback in which ice exported from the Arctic Ocean into the Barents Sea promotes ice growth elsewhere in the Arctic Ocean. The strongest currents

  2. Gravimorphism in current-year shoots of Abies balsamea: involvement of compensatory growth, indole-3-acetic acid transport and compression wood formation.

    PubMed

    Little, C H A; Lavigne, M B

    2002-04-01

    We investigated the cause of gravimorphic growth inhibition in current-year shoots of balsam fir (Abies balsamea (L.) Mill.) seedlings displaced from their normal orientation in the gravitational field. Tilting the main stem of seedlings decreased shoot elongation, cambial growth as measured by tracheid production, and leaf dry weight of the terminal shoot and the lateral shoots on the lower side of the tilted stem. Removing either the terminal shoot or all lateral shoots induced compensatory growth in the remaining shoots, but did not reduce the inhibitory effect of tilting on shoot growth. Bending the apical part of a tilted main stem to restore it to the vertical did not fully reverse the inhibition of terminal shoot growth caused by stem tilting. Stem tilting inhibited cambial activity at the base of decapitated terminal shoots treated apically with indole-3-acetic acid (IAA) and decreased the basipetal transport of a [1-(14)C]-IAA pulse. Stem tilting also induced compression wood formation on the lower side of the tilted stem. Compression wood formation was associated with increases in cambial activity and stem respiration. Stem tilting did not affect either the net photosynthetic rate in 1-year-old leaves or the xylem water potential in current-year lateral shoots. These results support the hypothesis that gravimorphic growth inhibition in a current-year shoot on a tilted stem involves reductions in (1) the shoot's capacity to export IAA, and hence to mobilize photoassimilates, and (2) the supply of photoassimilates available for import by the shoot, as a result of increased cambial sink activity associated with compression wood formation outside that shoot. PMID:11960755

  3. Bond length and electric current oscillation of long linear carbon chains: Density functional theory, MpB model, and quantum spin transport studies

    NASA Astrophysics Data System (ADS)

    Oeiras, R. Y.; da Silva, E. Z.

    2014-04-01

    Carbon linear atomic chains attached to graphene have experimentally been produced. Motivated by these results, we study the nature of the carbon bonds in these nanowires and how it affects their electrical properties. In the present study we investigate chains with different numbers of atoms and we observe that nanowires with odd number of atoms present a distinct behavior than the ones with even numbers. Using graphene nanoribbons as leads, we identify differences in the quantum transport of the chains with the consequence that even and odd numbered chains have low and high electrical conduction, respectively. We also noted a dependence of current with the wire size. We study this unexpected behavior using a combination of first principles calculations and simple models based on chemical bond theory. From our studies, the electrons of carbon nanowires present a quasi-free electron behavior and this explains qualitatively the high electrical conduction and the bond lengths with unexpected values for the case of odd nanowires. Our study also allows the understanding of the electric conduction dependence with the number of atoms and their parity in the chain. In the case of odd number chains a proposed π-bond (MpB) model describes unsaturated carbons that introduce a mobile π-bond that changes dramatically the structure and transport properties of these wires. Our results indicate that the nature of bonds plays the main role in the oscillation of quantum electrical conduction for chains with even and odd number of atoms and also that nanowires bonded to graphene nanoribbons behave as a quasi-free electron system, suggesting that this behavior is general and it could also remain if the chains are bonded to other materials.

  4. Bond length and electric current oscillation of long linear carbon chains: Density functional theory, MpB model, and quantum spin transport studies

    SciTech Connect

    Oeiras, R. Y.; Silva, E. Z. da

    2014-04-07

    Carbon linear atomic chains attached to graphene have experimentally been produced. Motivated by these results, we study the nature of the carbon bonds in these nanowires and how it affects their electrical properties. In the present study we investigate chains with different numbers of atoms and we observe that nanowires with odd number of atoms present a distinct behavior than the ones with even numbers. Using graphene nanoribbons as leads, we identify differences in the quantum transport of the chains with the consequence that even and odd numbered chains have low and high electrical conduction, respectively. We also noted a dependence of current with the wire size. We study this unexpected behavior using a combination of first principles calculations and simple models based on chemical bond theory. From our studies, the electrons of carbon nanowires present a quasi-free electron behavior and this explains qualitatively the high electrical conduction and the bond lengths with unexpected values for the case of odd nanowires. Our study also allows the understanding of the electric conduction dependence with the number of atoms and their parity in the chain. In the case of odd number chains a proposed π-bond (MpB) model describes unsaturated carbons that introduce a mobile π-bond that changes dramatically the structure and transport properties of these wires. Our results indicate that the nature of bonds plays the main role in the oscillation of quantum electrical conduction for chains with even and odd number of atoms and also that nanowires bonded to graphene nanoribbons behave as a quasi-free electron system, suggesting that this behavior is general and it could also remain if the chains are bonded to other materials.

  5. Multiple dating approach (14C, U/Th and 36Cl) of tsunami-transported reef-top megaclasts on Bonaire (Leeward Antilles) - potential and current limitations

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; May, Simon Matthias; Engel, Max; Mechernich, Silke; Keulertz, Rebecca; Schroeder-Ritzrau, Andrea; Fohlmeister, Jens; Frank, Norbert; Dunai, Tibor; Brueckner, Helmut

    2016-04-01

    Coastal hazard assessment depends on reliable information on the magnitude and frequency of past high-energy wave events (EWE: tsunamis, storms). For this purpose onshore sedimentary records represent promising geo-archives for the mid- and late-Holocene EWE history. In comparison to fine-grained sediments which have been extensively studied in the recent past, supralittoral megaclasts are less investigated, essentially due to the difficulties related to the dating of corresponding depositional events, and thus their limited value for inferring the timing of major events. On Bonaire (Leeward Antilles, Caribbean), supratidal coarse-clast deposits form prominent landforms all around the island. Fields of large boulders (up to 150 t) are among the best-studied reef-top megaclasts worldwide. Transport by Holocene tsunamis is assumed at least for the largest boulders (Engel and May, 2012). Although a large dataset of 14C and electron spin resonance (ESR) ages is available for major coral rubble ridges and ramparts, showing some age clusters during the Late Holocene, it is still debated whether these data reflect the timing of major depositional/transport event(s), and how these data sets are biased by reworking of coral fragments. In addition, different processes may be responsible for the deposition of the coral rubble ridges and ramparts (storm) and the solitary megaclasts (tsunami). As an attempt to overcome the current challenges for dating the dislocation of the megaclasts, three distinct dating methods were implemented: (i) 14C dating of boring bivalves (Lithophaga) attached to the boulders; (ii) uranium-series (U/Th) dating of post-depositional, secondary calcitic flowstone at the underside of the boulders; and (iii) surface exposure dating of overturned boulders via 36Cl concentration measurements in corals. The three 14C datings yield age estimates >37 ka, i.e. most probably beyond the applicability of the method, which sheds doubt on the usefulness of this

  6. Late Pleistocene temperature and productivity variations in the Benguela Current System (ODP Leg 175, Site 1082)

    NASA Astrophysics Data System (ADS)

    Wenzel, C.; Rullkötter, J.

    2003-04-01

    Site 1082 (Walvis Basin) is located close to the major upwelling cells along the Southwest African coast with a year-round upwelling activity. Sediment samples spanning the last 770 kyr were investigated to reconstruct the paleoclimatic and paleoceanographic conditions in the Benguela upwelling system off Namibia. Alkenone-derived paleo-sea surface temperatures (calculated from the Uk'37index) roughly follow the 18O variations of planktonic foraminifera. The core shows warmer SST values (18-20°C) during interglacial stages and colder SST values (14-16°C) during glacial stages. Two long-term trends were observed: a decrease in SST values by 1°C from 770 kyr to 450 kyr and an increase in SST values by 2°C for the last 450 kyr. SST values in the northern Benguela System confirm the onset of the dominant 100 ka cycles associated with Northern Hemisphere glaciation over the past 650 kyr. One important result is the observed warming trend in the Benguela Current region over the last 450 kyr. In this period, the trend to warmer sea surface temperatures is more evident during glacials, suggesting a southward migration of the polar and subpolar frontal systems and an intensification of the influence of the warm Agulhas Current on the Benguela Current System during glacial stages 10, 8, 6 and 4. Another possible mechanism that could be responsible for such a warming trend of the eastern South Atlantic is a weakening of the cross-equatorial heat transport from the South to the North Atlantic as a result of a weakening of the thermohaline circulation. The accumulation profile of the alkenones indicates an elevated marine surface productivity may have fluctuated over time due to the upwelling activity in the southeastern Atlantic Ocean. The fluctuations in marine productivity are not related to the glacial-interglacial cycles which exhibit increased productivity during glacials at other locations. The marine biomarker distributions indicate that periods of higher

  7. Marine radioactivity in the Arctic: a retrospect of environmental studies in Greenland waters with emphasis on transport of 90Sr and 137Cs with the East Greenland Current.

    PubMed

    Aarkrog, A; Dahlgaard, H; Nielsen, S P

    1999-09-30

    The waters around Greenland have received radioactive contamination from three major sources: Global fallout, discharges from the nuclear fuel reprocessing plant Sellafield in the UK, and the Chernobyl accident in the Former Soviet Union (FSU). The global fallout peaked in the early 1960s. The radiologically most important radionuclides from this source are 90Sr and 137Cs. The input of global fallout to arctic waters was direct deposition from the atmosphere and indirect delivery through river run off and advection from the Atlantic Ocean via the north-east Atlantic current system. The waterborne discharges from Sellafield which were at their peak between 1974 and 1981 contributed primarily 137Cs, although some 90Sr was also discharged. The Chernobyl accident in 1986 was characterised by its substantial atmospheric release of radiocaesium (134Cs and 137Cs). Other sources may, however, also have contributed to the radioactivity in the Greenland waters. Examples include La Hague, France, and radioactive discharges to the great Siberian rivers (Ob, Yenisey and Lena) from nuclear activities in the Former Soviet Union or the local fallout from the Novaya Zemlya nuclear weapons test site. Dumping of nuclear waste in the Kara and Barents Seas may be another, although minor source. From measurements in Greenland waters carried out since 1962 the transport of radionuclides with the East Greenland Current is calculated and compared with the estimated inputs of 90Sr and 137Cs to the Arctic Ocean. This study focus on 90Sr and 137Cs because the longest time series are available for these two radionuclides.

  8. Late Holocene distal mud deposits off the Nakdong delta, SE Korea: evidence for shore-parallel sediment transport in a current-dominated setting

    NASA Astrophysics Data System (ADS)

    Chun, Jong-Hwa; Kim, Yuri; Bahk, Jang-Jun; Kim, Young Jun; Kang, Dong-Hyo; Kim, Yong Hoon; Kim, Gil Young; Ryu, Byong-Jae

    2015-12-01

    The distal mud deposits (DMDs) off the Nakdong delta represent a subaqueous delta on the inner continental shelf aligned parallel to the southeast coast of Korea and displaying a clinoform geometry. Hydrographically, the coast is characterized by a micro-tidal regime, the strong Korean Coastal Current (KCC) and the East Korean Warm Current (EKWC). Age models and sedimentary facies related to the clinoform geometries are based on high-resolution chirp subbottom profile data and have provided information on shore-parallel sediment transport and accumulation during the late Holocene sea-level highstand. The highest sedimentation rates (6.19-9.17 cm/year) produced steep foresets in the central DMDs at water depths of 35-50 m. Here, vertical burrows are repeatedly truncated by laminated mud packages displaying erosional surfaces. This region represents the main depocenter of the Nakdong subaqueous delta. The topset sediments of the southern DMD at ~40 m water depth closer to the river mouth show relatively low sedimentation rates (0.01-0.12 cm/year). Here, the muds have a predominantly mottled character. Similarly, the foreset sediments of the northern DMD at ~71-80 m water depth with sedimentation rates of 0.10-2.03 cm/year are also predominantly characterized by mottled muds. The spatial dispersal pattern of the DMDs is consistent with the coast-parallel front between the KCC and EKWC along the southeast Korean coast. In addition, the depocenter of the Nakdong subaqueous delta clinoform is affected by the near-bed turbulence generated by episodic storm events.

  9. Reduction of the dark current in a P3HT-based organic photodiode with a ytterbium-fluoride buffer layer for electron transport

    NASA Astrophysics Data System (ADS)

    Lim, Seong Bin; Ji, Chan Hyuk; Kim, Kee Tae; Oh, Se Young

    2016-08-01

    Photodiodes are widely used to convert light into electrical signals. The conventional silicon (Si) based photodiodes boast high photoelectric conversion efficiency and detectivity. However, in general, inorganic-based photodiodes have low sensitivity at visible wavelengths due to their absorption of infrared wavelengths. Recently, electrical conducting polymer-based photodiodes have received significant attention due to their flexibility, low cost of production and high sensitivity at visible wavelength ranges. In the present work, we fabricated an organic photodiode (OPD) with a consisting of ITO/ NiO x / P3HT:PC60BM/ YbF3/Al structure. In the OPD, a yitterbium fluoride (YbF3) buffer layer was used as the electron transport layer. The OPD was analyzed by using optical-electrical measurements to determine its J-V, detectivity, and dynamic characteristics. We investigated the physical effects of the YbF3 buffer layer on the performance of OPD such as its carrier extraction, leakage current and ohmic characteristics.

  10. Meridional overturning transports at 30°S in the Indian and Pacific Oceans in 2002-2003 and 2009

    NASA Astrophysics Data System (ADS)

    Hernández-Guerra, Alonso; Talley, Lynne D.

    2016-08-01

    The meridional circulation and transports at 30°S in the Pacific and Indian Oceans for the years 2002-2003 and 2009 are compared, using GO-SHIP hydrographic section data with an inverse box model and several choices of constraints. Southward heat transport across the combined Indian-Pacific sections, reflecting net heating north of these sections, doubled from -0.7 ± 0.2 PW in 2002-2003 to -1.4 ± 0.1 PW in 2009 (negative sign is southward), with the increase concentrated in the Indian Ocean (∼0.6 PW compared with ∼0.2 PW in the Pacific), and was insensitive to model choices for the Indonesian Throughflow. Diagnosed net evaporation also more than doubled in the Indian Ocean, from 0.21-0.27 Sv in 2002-2003 to 0.51-0.58 in 2009, with a smaller but significant increase in net evaporation in the Pacific, from 0.06-0.08 Sv to 0.16-0.32 Sv. These increased heat and freshwater exports coincided with Indian Ocean warming, a shift in the Indian's shallow gyre overturning transport to lower densities, and an increase in southward Agulhas Current transport from 75 Sv in 2002 to 92 Sv in 2009. The Indian's deep overturn weakened from about 11 Sv in 2002 to 7 Sv in 2009. In contrast, the Pacific Ocean overturning circulation was nearly unchanged from 2003 to 2009, independent of model within the uncertainties. The East Australian Current transport decreased only slightly, from -52 Sv to -46 Sv. The southward Pacific Deep Water transport was at a higher density than the southward Indian Deep Water transport in both years and all models, similar to prior results. Estimated diapycnal diffusivity and velocity are strongly enhanced near the ocean bottom and are higher farther up in the water column in the Indian than in the Pacific, likely extending the reach of Indian Ocean overturning up to shallower depths than in the Pacific. The horizontal distribution of transports in the Pacific at all depths changed notably from 2003 to 2009, despite the stability of its meridional

  11. An H-formulation-based three-dimensional hysteresis loss modelling tool in a simulation including time varying applied field and transport current: the fundamental problem and its solution

    NASA Astrophysics Data System (ADS)

    Stenvall, A.; Lahtinen, V.; Lyly, M.

    2014-10-01

    When analytic solutions are not available, finite-element-based tools can be used to simulate hysteresis losses in superconductors with various shapes. A widely used tool for the corresponding magnetoquasistatic problem is based on the H-formulation, where H is the magnetic field intensity, eddy current model. In this paper, we study this type of tool in a three-dimensional simulation problem. We consider a case where we simultaneously apply both a time-varying external magnetic field and a transport current to a twisted wire. We show how the modelling decisions (air has high finite resistivity and applied field determines the boundary condition) affect the current density distribution along the wire. According to the results, the wire carries the imposed net current only on the boundary of the modelling domain, but not inside it. The current diffuses to the air and back to the boundary. To fix this problem, we present another formulation where air is treated as a region with 0 conductivity. Correspondingly, we express H in the air with a scalar potential and a cohomology basis function which considers the net current condition. As shown in this paper, this formulation does not fail in these so-called AC-AC (time varying transport current and applied magnetic field) simulations.

  12. Downslope Eulerian mean flow associated with high-frequency current fluctuations observed on the outer continental shelf and upper slope along the northeastern United States continental margin: implications for sediment transport

    USGS Publications Warehouse

    Butman, B.

    1988-01-01

    Eulerian current measurements made 5-7 m above bottom at six stations along the United States east coast continental margin show a net downslope flow of 1-5 cm s-1. Although the scalar current speed decreases with water depth and toward the bottom, fluctuations in the cross-isobath flow were stronger and increasingly asymmetric near the bottom. Maximum downslope flow exceeded maximum upslope flow by a factor of two to three. The strength of the low-passed downslope flow was proportional to the upslope Reynolds flux of density as well as to the amplitude of the current fluctuations that have periods shorter than 30 h. These flow characteristics may be caused by differential vertical mixing in the bottom boundary layer where a stratified fluid flows upslope (unstable) and downslope (stable). The asymmetry in current strength clearly favors net downslope transport of sediments that move as bedload. ?? 1988.

  13. Sequential fragmentation/transport theory, pyroclast size-density relationships, and the emplacement dynamics of pyroclastic density currents — A case study on the Mt. St. Helens (USA) 1980 eruption

    NASA Astrophysics Data System (ADS)

    Mackaman-Lofland, Chelsea; Brand, Brittany D.; Taddeucci, Jacopo; Wohletz, Kenneth

    2014-04-01

    Pyroclastic density currents (PDCs) are the most dangerous hazard associated with explosive volcanic eruptions. Despite recent advancements in the general understanding of PDC dynamics, limited direct observation and/or outcrop scarcity often hinder the interpretation of specific transport and depositional processes at many volcanoes. This study explores the potential of sequential fragmentation/transport theory (SFT; cf. Wohletz et al., 1989), a modeling method capable of predicting particle mass distributions based on the physical principles of fragmentation and transport, to retrieve the transport and depositional dynamics of well-characterized PDCs from the size and density distributions of individual components within the deposits. The extensive vertical and lateral exposures through the May 18th, 1980 PDC deposits at Mt. St. Helens (MSH) provide constraints on PDC regimes and flow boundary conditions at specific locations across the depositional area. Application to MSH deposits suggests that SFT parameter distributions can be effectively used to characterize flow boundary conditions and emplacement processes for a variety of PDC lithofacies and deposit locations. Results demonstrate that (1) the SFT approach reflects particle fragmentation and transport mechanisms regardless of variations in initial component distributions, consistent with results from previous studies; (2) SFT analysis reveals changes in particle characteristics that are not directly observable in grain size and fabric data; and (3) SFT parameters are more sensitive to regional transport conditions than local (outcrop-scale) depositional processes. The particle processing trends produced using SFT analysis are consistent with the degree of particle processing inferred from lithofacies architectures: for all lithofacies examined in this study, suspension sedimentation products exhibit much better processing than concentrated current deposits. Integrated field observations and SFT results

  14. Specific features of light current-voltage characteristics of p-i-n structures based on amorphous silicon in the case of the tunnel-drift mechanism of dark current transport

    SciTech Connect

    Andreev, A. A.

    2008-11-15

    Current-voltage (I-V) characteristics of p-i-n structures based on amorphous silicon ({alpha}-Si:H) with small hole diffusion lengths (shorter than the thickness of the i-layer of a p-i-n structure) have been experimentally studied with and without illumination. It is shown that forward I-V characteristics of structures of this kind can be described by a dependence inherent in diodes, with a diode ideality factor two-three times the maximum value of 2, theoretically predicted for generation-recombination currents in p-n junctions. The dark current is always substantially lower than the photocurrent in a cell biased with a voltage approximately equal to the opencircuit voltage of the photocell. Dark currents cannot contribute to the I-V characteristic under illumination. The photocurrent decreases with increasing photovoltage at a bias lower than the open-circuit voltage because of a decrease in the collection coefficient and the increasingly important role of back diffusion of electrons into the p-contact, rather than as a result of the dark injection. In the case of biases exceeding the open-circuit voltage, back diffusion becomes the predominant component of the current.

  15. Transport behavior of hairless mouse skin during constant current DC iontophoresis, part 2: iontophoresis of nonionic molecules with cotransport of polystyrene sulfonate oligomers.

    PubMed

    Liddell, Mark R; Li, S Kevin; Higuchi, William I

    2011-07-01

    The purpose of this study was to characterize changes that occur in the iontophoretic transport of nonionic probe permeants in hairless mouse skin epidermal membrane from the anode to cathode when polystyrene sulfonate (PSS) oligomers are cotransported from the cathode to anode. The experiments were conducted with trace levels of the nonionic probe permeants: urea, mannitol, and raffinose. In order to systematically assess changes that occur as a result of having PSS in the cathodal chamber, the steady-state transport parameters of the membrane and the experimental permeability coefficients of the probe permeants were determined and compared with results obtained from earlier baseline experiments where both the cathodal and anodal chamber media were phosphate buffered saline. In addition, the physicochemical properties of the PSS solutions were determined including the solution viscosity and conductance as well as the mobilities of individual PSS oligomers. The effective pore radii of the transport pathways were calculated using a theoretical expression based on simultaneous diffusion and electroosmosis. Compared with the baseline results, the calculated radii were found to have increased up to around twofold and the iontophoretic fluxes of the probe permeants increased by as much sixfold.

  16. A description of eddy-mean flow feedbacks in equatorial and boundary current systems of the South Indian Ocean

    NASA Astrophysics Data System (ADS)

    Aguiar-González, Borja; Ponsoni, Leandro; Maas, Leo R. M.; Ridderinkhof, Herman; van Aken, Hendrik

    2015-04-01

    While many observational and modeling efforts have addressed eddy-mean flow interactions acting over nearly idealized zonal jets, little is know about whether findings in those studies can be extended to current systems with different configurations in the real ocean. This topic is of special interest for ocean-climate models where eddy interactions with the mean flow may be unresolved, demanding further insight on the mechanism by which the eddy field and the mean circulation should feed back in a realistic representation of future climate change scenarios. Following this motivation, we investigate local exchange of momentum and kinetic energy operating in a variety of eddy-mean flow systems of the South Indian Ocean (SIO). To this aim we use 21 years (1993-2013) of newly processed satellite altimetry observations, and adopt a definition of the mean flow as a seasonally-dependent temporal mean where the eddy field encompasses the daily instantaneous deviation from the altimeter-derived velocities. This approach allows time-varying feedbacks to evolve throughout the year. We find that the eddy field feeds back on the mean circulation, contributing importantly to the overall seasonal strengthening and weakening of all current systems involved in the tropical and subtropical gyre of the SIO. Although significant contributions to the momentum and energy balances were also obtained along the Agulhas (Return) Current and the Antarctic Circumpolar Current (ACC), they exhibit a weak/absent seasonal cycle, suggesting that the strength of these dynamical processes is mostly persistent throughout the year. Spatial distribution of the eddy kinetic energy conversion rates and the convergence of horizontal eddy momentum fluxes indicate that over regions where the eddy field draws energy from the mean flow through barotropic instabilities, the current is importantly decelerated by alongstream eddy forces on its upstream side, while further downstream the situation reverses with

  17. Transportation of high-current ion and electron beams in the accelerator drift gap in the presence of an additional electron background

    NASA Astrophysics Data System (ADS)

    Karas', V. I.; Kornilov, E. A.; Manuilenko, O. V.; Tarakanov, V. P.; Fedorovskaya, O. V.

    2015-12-01

    The dynamics of a high-current ion beam propagating in the drift gap of a linear induction accelerator with collective focusing is studied using 3D numerical simulations in the framework of the full system of the Vlasov-Maxwell equations (code KARAT). The ion beam is neutralized by a comoving electron beam in the current density and, partially, in space charge, since the velocities of electrons and ions differ substantially. The dynamics of the high-current ion beam is investigated for different versions of additional neutralization of its space charge. It is established that, for a given configuration of the magnetic field and in the presence of a specially programmed injection of additional electrons from the boundary opposite to the ion injection boundary, the angular divergence of the ion beam almost vanishes, whereas the current of the ion beam at the exit from the accelerator drift gap changes insignificantly and the beam remains almost monoenergetic.

  18. Joint measurement of current-phase relations and transport properties of hybrid junctions using a three junctions superconducting quantum interference device

    SciTech Connect

    Basset, J.; Delagrange, R.; Weil, R.; Kasumov, A.; Bouchiat, H.; Deblock, R.

    2014-07-14

    We propose a scheme to measure both the current-phase relation and differential conductance dI/dV of a superconducting junction, in the normal and the superconducting states. This is done using a dc Superconducting Quantum Interference Device with two Josephson junctions in parallel with the device under investigation and three contacts. As a demonstration, we measure the current-phase relation and dI/dV of a small Josephson junction and a carbon nanotube junction. In this latter case, in a regime where the nanotube is well conducting, we show that the non-sinusoidal current phase relation we find is consistent with the theory for a weak link, using the transmission extracted from the differential conductance in the normal state. This method holds great promise for future investigations of the current-phase relation of more exotic junctions.

  19. Transportation of high-current ion and electron beams in the accelerator drift gap in the presence of an additional electron background

    SciTech Connect

    Karas’, V. I. Kornilov, E. A.; Manuilenko, O. V.; Tarakanov, V. P.; Fedorovskaya, O. V.

    2015-12-15

    The dynamics of a high-current ion beam propagating in the drift gap of a linear induction accelerator with collective focusing is studied using 3D numerical simulations in the framework of the full system of the Vlasov–Maxwell equations (code KARAT). The ion beam is neutralized by a comoving electron beam in the current density and, partially, in space charge, since the velocities of electrons and ions differ substantially. The dynamics of the high-current ion beam is investigated for different versions of additional neutralization of its space charge. It is established that, for a given configuration of the magnetic field and in the presence of a specially programmed injection of additional electrons from the boundary opposite to the ion injection boundary, the angular divergence of the ion beam almost vanishes, whereas the current of the ion beam at the exit from the accelerator drift gap changes insignificantly and the beam remains almost monoenergetic.

  20. Current transport mechanism of heterojunction diodes based on the reduced graphene oxide-based polymer composite and n-type Si

    NASA Astrophysics Data System (ADS)

    Lin, Jian-Huang; Zeng, Jian-Jhou; Su, Yu-Chao; Lin, Yow-Jon

    2012-04-01

    The present work reports the fabrication and detailed electrical properties of heterojunction diodes based on n-type Si and poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS) having the reduced graphene oxide (RGO). This heterojunction diode showed a good rectifying behavior with an ideality factor of 1.2. A photocurrent decay model is presented that addresses the charge trapping effect and doping mechanisms for composite PEDOT:PSS films having RGO sheets. The enhanced dark conductivity was observed by incorporating RGO into PEDOT:PSS. For heterojunction diodes, the high photocurrent density originates from efficient hole transport combined with electron trapping with long-second lifetime.

  1. Characterizing transport current defects in 1-cm-wide YBa[sub 2]Cu[sub 3]O[sub 7-delta] coated conductors.

    SciTech Connect

    Brown, G. W.; Hawley, M. E.; Peterson, E. J.; Coulter, J. Y.; Dowden, P. C.; Arendt, P. N.; Foltyn, S. R.; Mueller, F. M.

    2001-01-01

    We have used a low temperature magnetic imaging system to determine current pathways in 5 cm long 'good' and 'bad' regions of a 1-cm-wide YBa2Cu3O7-{delta} coated conductor. The good and bad regions were identified with 4 point probe measurements taken at 1 cm intervals along the tape length. The current density map from the good region showed the expected edge peaked structure, similar to that seen in previous work on high quality test samples grown on single crystal substrates. The structure was also consistent with theoretical understanding of thin film superconductors where demagnetizing effects are strong. The maps from the bad region showed that the current was primarily confined to the right half of the sample. The left half carried only a small current that reached saturation quickly. Effectively halving the sample width quantitatively explains the critical current measured in that section. Spatially resolved xray analysis with 1 mm resolution was used to further characterize the bad section and suggested an abnormally large amount of a-axis YBCO present. This may be the result of non-uniform heating leading to a low deposition temperature in that area.

  2. Effect of cold isostatic pressing on the transport current of filamentary MgB2 wire made by the IMD process

    NASA Astrophysics Data System (ADS)

    Kováč, P.; Hušek, I.; Pachla, W.; Melišek, T.; Kulich, M.; Rosová, A.; Kopera, L.

    2016-07-01

    This work describes the effect of cold isostatic pressing applied to as-drawn filamentary wires in a GlidCop and/or Cu sheath made by the internal magnesium diffusion process. Critical currents of as-drawn and isostatically pressed wires at high pressures up to 2.0 GPa followed by heat treatment at 640 °C for 40 min were measured. The obtained results show an improvement in boron powder density resulting in an increase of the critical current of MgB2 layers. The engineering current density increases by 4–13 times after the high-pressure treatment, and is influenced by the density of the boron powder and by the mechanical strength of the outer sheath.

  3. Effect of cold isostatic pressing on the transport current of filamentary MgB2 wire made by the IMD process

    NASA Astrophysics Data System (ADS)

    Kováč, P.; Hušek, I.; Pachla, W.; Melišek, T.; Kulich, M.; Rosová, A.; Kopera, L.

    2016-07-01

    This work describes the effect of cold isostatic pressing applied to as-drawn filamentary wires in a GlidCop and/or Cu sheath made by the internal magnesium diffusion process. Critical currents of as-drawn and isostatically pressed wires at high pressures up to 2.0 GPa followed by heat treatment at 640 °C for 40 min were measured. The obtained results show an improvement in boron powder density resulting in an increase of the critical current of MgB2 layers. The engineering current density increases by 4-13 times after the high-pressure treatment, and is influenced by the density of the boron powder and by the mechanical strength of the outer sheath.

  4. Assessing Current and Future Performance of the Alamitos Gap Seawater Intrusion Barrier with a New Flow and Transport Model, Los Angeles and Orange Counties, CA

    NASA Astrophysics Data System (ADS)

    Sigda, J. M.; Deeds, N.; Jordan, D. L.; Sengebush, R.

    2010-12-01

    Seawater intrusion has threatened aquifers that supply Los Angeles residents since the 1920s, but now millions depend on effective resource management, especially for the four injection barriers. Even with ~6,000 acre-ft/yr injected through the Alamitos Gap barrier, which straddles the San Gabriel River, chloride concentrations have continued to increase in several aquifers inland of the barrier. On behalf of the Orange County Water District, the Water Replenishment District of Southern California, and the Los Angeles Department of Public Works, INTERA created a new flow and solute transport model for permitting, management, and performance assessment of the injection barrier. We devised a new conceptual model, water balance, geologic model, and numerical flow and solute transport models in five months to meet a regulatory deadline. Quickly developing a hydrogeologic framework was challenging because erosion and deposition on the uplifted transgression-regression system of aquitards and aquifers created pathways within the Gap for seawater to travel inland. The pathways, called mergence zones, connect the seawater-intruded Recent Aquifer with several of the deeper aquifers used for water supply. Capturing their locations and geometries was critical to effectively simulating past and future seawater intrusion. We extended the new hydrogeologic framework beyond and below previous frameworks by combining traditional geologic interpretation, GIS analysis, and an innovative geologic modeling software tool. Using the new conceptual and geologic models as a foundation, INTERA constructed a three-dimensional transient groundwater flow model, the Alamitos Barrier Flow Model (ABFM), using the MODFLOW 2000 code. The ABFM was calibrated in three ways: (1) a steady-state calibration to average heads for the 1999-2009 period, (2) transient calibration to the heads observed from 1999 through 2009, and (3) final flow calibration adjustments based on the chloride transport

  5. Subsurface flow and transport of organic chemicals: an assessment of current modeling capability and priority directions for future research (1987-1995)

    SciTech Connect

    Streile, G.P.; Simmons, C.S.

    1986-09-01

    Theoretical and computer modeling capability for assessing the subsurface movement and fate of organic contaminants in groundwater was examined. Hence, this study is particularly concerned with energy-related, organic compounds that could enter a subsurface environment and move as components of a liquid phase separate from groundwater. The migration of organic chemicals that exist in an aqueous dissolved state is certainly a part of this more general scenario. However, modeling of the transport of chemicals in aqueous solution has already been the subject of several reviews. Hence, this study emphasizes the multiphase scenario. This study was initiated to focus on the important physicochemical processes that control the behavior of organic substances in groundwater systems, to evaluate the theory describing these processes, and to search for and evaluate computer codes that implement models that correctly conceptualize the problem situation. This study is not a code inventory, and no effort was made to identify every available code capable of representing a particular process.

  6. The magnitude and spatial range of current-use urban PCB and PBDE emissions estimated using a coupled multimedia and air transport model.

    PubMed

    Csiszar, Susan A; Diamond, Miriam L; Daggupaty, Sreerama M

    2014-01-21

    SO-MUM, a coupled atmospheric transport and multimedia urban model, was used to estimate spatially resolved (5 × 5 km(2)) air emissions and chemical fate based on measured air concentrations and chemical mass inventories within Toronto, Canada. Approximately 95% and 70% of Σ5PCBs (CB-28, -52, -101, -153, and -180) and Σ5PBDEs (BDE-28, -47, -100, -154, and -183) emissions of 17 (2-36) and 18 (3-42) kg y(-1), respectively, undergo atmospheric transport from the city, which is partly over Lake Ontario. The urban air plume was found to reach about 50 km for PCBs and PBDEs, in the direction of prevailing winds which is almost twice the distance of the wind-independent plume. The distance traveled by the plume is a function of prevailing wind velocity, the geographic distribution of the chemical inventory, and gas-particle partitioning. Soil wash-off of historically accumulated Σ5PCBs to surface water contributed ∼ 0.4 kg y(-1) (of mainly higher congeners) to near-shore Lake Ontario compared with volatilization of ∼ 6 kg y(-1) of mainly lighter congeners. Atmospheric emissions from primary sources followed by deposition to surface films and subsequent wash-off to surface water contributed ∼ 1 kg y(-1) and was the main route of Σ5PBDE loadings to near-shore Lake Ontario which acts as a net PBDE sink. Secondary emissions of PCBs and PBDEs from at least a ∼ 900,000 km(2) rural land area would be needed to produce the equivalent primary emissions as Toronto (∼ 640 km(2)). These results provide clear support for reducing inventories of these POPs.

  7. Late Pleistocene Variations in the Water Current and Ice Rafting Transportations of Organic Matter in the Central Arctic Ocean (ACEX Hole M0004C)

    NASA Astrophysics Data System (ADS)

    Yamamoto, M.; Sugisaki, S.; Sakamoto, T.

    2006-12-01

    Little is known about the source of organic matter and the response of sedimentary organic matter composition to glacial-interglacial changes in the central Arctic Ocean. Here we have generated late Pleistocene records of biomarkers and ice rafted debris (IRD) from IODP-Arctic Coring Expedition (ACEX) Hole M0004C to understand the glacial-interglacial changes of mass transportation in the Arctic Ocean. Major biomarkers detected in Hole M0004C were long-chain n-alkanes, n-fatty acids and n-alkan-1-ols, derived from fresh higher plants, and gem-alkanes (branched aliphatic alkanes with a quaternary substituted carbon atom), derived from unknown source. Minor biomarkers were oleanenes of angiosperm origin, unsaturated fatty acids, bacteria-derived anteiso- and iso-fatty acids, various hydroxy acids, formed by hydroxylation of n-fatty acids by aerobic bacteria, cholesterol and sitosterol, and hopanes, formed by diagenetic alteration of bacterial biohopanoids. There was no concrete evidence for in situ production of phytoplanktons. The concentrations of these biomarkers varied with IRD number variation. During periods of abundant IRD, diagenetic hopanes were abundant, suggesting that clastic materials were supplied by ice rafting. During periods of scarce IRD, the other biomarkers such as long-chain compounds were abundant, suggesting that the riverine discharge was enhanced. The IRD and biomarker variations were synchronized with the eastward expansion of the Fennoscandinavian Ice Sheet to northen Siberia, suggesting that the ice cover of northen Siberia is critical in switching mass transportation mechanisms in the Arctic Ocean.

  8. Large scale groundwater flow and hexavalent chromium transport modeling under current and future climatic conditions: the case of Asopos River Basin.

    PubMed

    Dokou, Zoi; Karagiorgi, Vasiliki; Karatzas, George P; Nikolaidis, Nikolaos P; Kalogerakis, Nicolas

    2016-03-01

    In recent years, high concentrations of hexavalent chromium, Cr(VI), have been observed in the groundwater system of the Asopos River Basin, raising public concern regarding the quality of drinking and irrigation water. The work described herein focuses on the development of a groundwater flow and Cr(VI) transport model using hydrologic, geologic, and water quality data collected from various sources. An important dataset for this goal comprised an extensive time series of Cr(VI) concentrations at various locations that provided an indication of areas of high concentration and also served as model calibration locations. Two main sources of Cr(VI) contamination were considered in the area: anthropogenic contamination originating from Cr-rich industrial wastes buried or injected into the aquifer and geogenic contamination from the leaching process of ophiolitic rocks. The aquifer's response under climatic change scenario A2 was also investigated for the next two decades. Under this scenario, it is expected that rainfall, and thus infiltration, will decrease by 7.7 % during the winter and 15 % during the summer periods. The results for two sub-scenarios (linear and variable precipitation reduction) that were implemented based on A2 show that the impact on the study aquifer is moderate, resulting in a mean level decrease less than 1 m in both cases. The drier climatic conditions resulted in higher Cr(VI) concentrations, especially around the industrial areas. PMID:26564185

  9. Case study of quasi-steady reconnection in Saturn's magnetotail, and update on our current understanding of mass transport and loss in Saturn's nightside magnetosphere

    NASA Astrophysics Data System (ADS)

    Jackman, C. M.; Thomsen, M. F.; Mitchell, D. G.; Sergis, N.; Arridge, C. S.; Felici, M.; Badman, S. V.; Paranicas, C.; Jia, X.; Hospodarsky, G. B.; Andriopoulou, M.; Khurana, K. K.; Smith, A. W.; Dougherty, M. K.

    2015-10-01

    We present a case study of an event from August20th (day 232) of 2006, as viewed by magnetic field, plasma, energetic particle and plasma wave sensors (MAG/CAPS/MIMI/RPWS) when the Cassini spacecraft was sampling the region near 32 Rs and 22 hours LT in Saturn's magnetotail. Cassini observed a strong northward-to-southward turning of the magnetic field, which is interpreted as the signature of dipolarization of the field as seen by the spacecraft planetward of the reconnection x-line. This event was accompanied by very rapid (up to ~1500 km s-1) thermal plasma flow toward the planet. At energies above 28 keV, energetic hydrogen and oxygen ion flow bursts were observed to stream planetward from a reconnection site downtail of the spacecraft. Meanwhile a strong field-aligned beam of energetic hydrogen was also observed to stream tailward, likely from an ionospheric source. Saturn Kilometric Radiation emissions were stimulated shortly after the observation of the dipolarization. We discuss the field, plasma, energetic particle and radio observations in the context of the impact this reconnection event had on global magnetospheric dynamics.We also discuss this event in terms of other recent studies of reconnection in Saturn's tail and update on the emerging picture concerning our understanding of how mass is transported and lost within Saturn's magnetosphere.

  10. Large scale groundwater flow and hexavalent chromium transport modeling under current and future climatic conditions: the case of Asopos River Basin.

    PubMed

    Dokou, Zoi; Karagiorgi, Vasiliki; Karatzas, George P; Nikolaidis, Nikolaos P; Kalogerakis, Nicolas

    2016-03-01

    In recent years, high concentrations of hexavalent chromium, Cr(VI), have been observed in the groundwater system of the Asopos River Basin, raising public concern regarding the quality of drinking and irrigation water. The work described herein focuses on the development of a groundwater flow and Cr(VI) transport model using hydrologic, geologic, and water quality data collected from various sources. An important dataset for this goal comprised an extensive time series of Cr(VI) concentrations at various locations that provided an indication of areas of high concentration and also served as model calibration locations. Two main sources of Cr(VI) contamination were considered in the area: anthropogenic contamination originating from Cr-rich industrial wastes buried or injected into the aquifer and geogenic contamination from the leaching process of ophiolitic rocks. The aquifer's response under climatic change scenario A2 was also investigated for the next two decades. Under this scenario, it is expected that rainfall, and thus infiltration, will decrease by 7.7 % during the winter and 15 % during the summer periods. The results for two sub-scenarios (linear and variable precipitation reduction) that were implemented based on A2 show that the impact on the study aquifer is moderate, resulting in a mean level decrease less than 1 m in both cases. The drier climatic conditions resulted in higher Cr(VI) concentrations, especially around the industrial areas.

  11. Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Current and advanced act control system definition study, volume 1

    NASA Technical Reports Server (NTRS)

    Hanks, G. W.; Shomber, H. A.; Dethman, H. A.; Gratzer, L. B.; Maeshiro, A.; Gangsaas, D.; Blight, J. D.; Buchan, S. M.; Crumb, C. B.; Dorwart, R. J.

    1981-01-01

    An active controls technology (ACT) system architecture was selected based on current technology system elements and optimal control theory was evaluated for use in analyzing and synthesizing ACT multiple control laws. The system selected employs three redundant computers to implement all of the ACT functions, four redundant smaller computers to implement the crucial pitch-augmented stability function, and a separate maintenance and display computer. The reliability objective of probability of crucial function failure of less than 1 x 10 to the -9th power per flight of 1 hr can be met with current technology system components, if the software is assumed fault free and coverage approaching 1.0 can be provided. The optimal control theory approach to ACT control law synthesis yielded comparable control law performance much more systematically and directly than the classical s-domain approach. The ACT control law performance, although somewhat degraded by the inclusion of representative nonlinearities, remained quite effective. Certain high-frequency gust-load alleviation functions may require increased surface rate capability.

  12. Sodium-glucose co-transporter-2 inhibitors and dipeptidyl peptidase-4 inhibitors combination therapy in type 2 diabetes: A systematic review of current evidence

    PubMed Central

    Singh, Awadhesh Kumar; Singh, Ritu

    2016-01-01

    As type 2 diabetes mellitus (T2DM) is a chronic and progressive disease with multiple pathophysiologic defects, no single anti-diabetic agent can tackle all these multi-factorial pathways. Consequently, multiple agents working through the different mechanisms will be required for the optimal glycemic control. Moreover, the combination therapies of different anti-diabetic agents may complement their actions and possibly act synergistic. Furthermore, these combinations could possess the additional properties to counter their undesired physiological compensatory response. Sodium-glucose co-transporter-2 inhibitors (SGLT-2I) are newly emerging class of drugs, with a great potential to reduce glucose effectively with an additional quality of lowering cardiovascular events as demonstrated very recently by one of the agents of this class. However, increase in endogenous glucose production (EGP) from the liver, either due to the increase in glucagon or compensatory response to glucosuria can offset the glucose-lowering potential of SGLT-2I. Interestingly, another class of drugs such as dipeptidyl peptidase-4 inhibitors (DPP-4I) effectively decrease glucagon and reduce EGP. In light of these findings, combination therapies with SGLT-2I and DPP-4I are particularly appealing and are expected to produce a synergistic effect. Preclinical studies of combination therapies with DPP-4I and SGLT-2I have already demonstrated a significant lowering of hemoglobin A1c potential and human studies also find no drug-drug interaction between these agents. This article aims to systematically review the efficacy and safety of combination therapy of SGLT-2I and DPP-4I in T2DM. PMID:27042423

  13. The Role of Benthic Currents and Sediment Transport On Deep-water Coral Mound Morphology and Growth: Examples From The Belgica and Moira Mounds, Eastern Porcupine Seabight, NE Atlantic

    NASA Astrophysics Data System (ADS)

    Wheeler, A.; Kozachenko, M.; Olu-Le Roy, K.

    Deep-water corals and associated carbonate mound build-ups are extensive along the European continental margin coincident with areas of strong benthic current activity and, often, regions of active sand transport. Although as yet unsubstantiated links to hydrocarbon seepage may play a defining role in the generation of carbonate mounds, the growth of mounds is strongly influenced by benthic current activity. Furthermore, the morphology of mounds, both in terms of their overall shape and surface morpho- logical features, is strongly dictated by the benthic-currents. Giant carbonate mounds, e.g. the Thérèse Mound, Belgica Mound province, eastern Porcupine Seabight, NE Atlantic, show upstream growth (through biological and sed- imentary accretion) with downstream scour and sediment starvation influencing their overall morphology. The surface morphological details of these giant mounds show distinct relationships to sediment waves that have become colonised and stabilised by coral and associated communities. Once colonised, the sandwave surface-morphology is mimic by biological growth with corals preferential growing on wave crests, taking advantage of stronger current and nutrient flux, to form coral banks. Furthermore, erosion of carbonate mounds by strong current activity exposes suitable hard substrates for further coral colonisation. Paradoxically therefore, mound erosion stimulates further coral growth illustrating another benthic-current control on mound growth. The Moira Mounds in the Belgica Mound Province, Porcupine Seabight are small coral-colonised mound features (tens of metres across and a few metres high) that represent an early stage of mound development and much younger then their giant carbonate mound counterparts. These features occur in areas of active sand transport, on rippled sand sheets and the upstream margins of sediment wave fields. Once coral colonies gained a SfootingT in these areas, coral colonies trap sand and build posi- & cedil; 1

  14. Fluctuation conductivity and pseudogap in HoBaCuO single crystals under pressure with transport current flowing under an angle 45° to the twin boundaries

    NASA Astrophysics Data System (ADS)

    Solovjov, A. L.; Tkachenko, M. A.; Vovk, R. V.; Chroneos, A.

    2014-06-01

    The influence of hydrostatic pressure up to 0.48 GPa on the fluctuation conductivity σ‧(T) and pseudogap (PG) Δ∗(T) of slightly doped HoBaCuO single crystals with Tc≈ 62 K and δ≈0.35 is studied with current passing under an angle 45° to the twin boundaries. It is shown that near Tc the conductivity σ‧(T) is well described by the Aslamasov-Larkin and Hikami-Larkin fluctuation theories demonstrating 3D-2D crossover with the increase of temperature. Δ∗(T) displays two representative maxima at T≈219 K and T≈241 K likely caused by the phase stratification of the single crystal. Pressure leads to disappearance of these maxima and linear Δ∗(T) with a positive gradient at high temperatures. Essentially, with the removal of pressure the maxima are restored. The comparison of our results with those obtained for YBaCu3O sheds more light on the role of magnetic subsystem in the high-Tc superconductors.

  15. The perfect ash-storm: large-scale Pyroclastic Density Current experiments reveal highly mobile, self-fluidising and air-cushioned flow transport regime

    NASA Astrophysics Data System (ADS)

    Lube, G.; Cronin, S. J.; Breard, E.; Valentine, G.; Bursik, M. I.; Hort, M. K.; Freundt, A.

    2013-12-01

    We report on the first systematic series of large-scale Pyroclastic Density Current (PDC) experiments using the New Zealand PDC Generator, a novel international research facility in Physical Volcanology recently commissioned at Massey University. Repeatable highly energetic and hot PDCs are synthesized by the controlled ';eruption column-collapse' of up to 3500 kg of homogenously aerated Taupo ignimbrite material from a 15 m-elevated hopper onto an instrumented inclined flume. At discharge rates between 250-1300 kg/s and low- to moderate gas injection rates (yielding initial solids concentration of 15-70 vol%) channelized gas-particle mixture flows life-scaled to dense PDCs can be generated. The flow fronts of the currents reach velocities of up to 9.5 m/s over their first 12 m of travel and rapidly develop strong vertical density stratification. The PDCs typically form a highly mobile, <60 cm-thick dense and channel-confined underflow, with an overriding dilute and turbulent ash cloud surge that also laterally escapes the flume boundaries. Depending on the PDC starting conditions underflows with 1-45 vol% solids concentration are formed, while the upper surge contains <<1 vol.% solids. A characteristic feature of the underflow is the occurrence of 'ignitive' front breakouts, producing jetted lobes that accelerate outward from the flow front, initially forming a lobe-cleft structure, followed by segregation downslope into multiple flow pulses. Depending on initial solids concentration and discharge rate, stratified, dune-bedded and inversely graded bedforms are created whose thicknesses are remarkably uniform along the medial to distal runout path characterising highly mobile flow runout. Along with high-speed video footage we present time-series data of basal arrays of load- and gas-pore pressure transducers to characterise the mobile dense underflows. Data shows that the PDCs are comprised of a turbulent coarse-grained and air-ingesting front with particle

  16. 49 CFR 236.733 - Current, foreign.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Current, foreign. A term applied to stray electric currents which may affect a signaling system, but which... 49 Transportation 4 2012-10-01 2012-10-01 false Current, foreign. 236.733 Section 236.733 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  17. 49 CFR 236.733 - Current, foreign.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Current, foreign. A term applied to stray electric currents which may affect a signaling system, but which... 49 Transportation 4 2010-10-01 2010-10-01 false Current, foreign. 236.733 Section 236.733 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  18. 49 CFR 236.735 - Current, leakage.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2010-10-01 2010-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  19. 49 CFR 236.733 - Current, foreign.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Current, foreign. A term applied to stray electric currents which may affect a signaling system, but which... 49 Transportation 4 2011-10-01 2011-10-01 false Current, foreign. 236.733 Section 236.733 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  20. 49 CFR 236.735 - Current, leakage.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2012-10-01 2012-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  1. 49 CFR 236.733 - Current, foreign.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Current, foreign. A term applied to stray electric currents which may affect a signaling system, but which... 49 Transportation 4 2014-10-01 2014-10-01 false Current, foreign. 236.733 Section 236.733 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  2. 49 CFR 236.733 - Current, foreign.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Current, foreign. A term applied to stray electric currents which may affect a signaling system, but which... 49 Transportation 4 2013-10-01 2013-10-01 false Current, foreign. 236.733 Section 236.733 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  3. 49 CFR 236.735 - Current, leakage.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2011-10-01 2011-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  4. 49 CFR 236.735 - Current, leakage.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2014-10-01 2014-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  5. 49 CFR 236.735 - Current, leakage.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Current, leakage. A stray electric current of relatively small value which flows through or across the... 49 Transportation 4 2013-10-01 2013-10-01 false Current, leakage. 236.735 Section 236.735 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD...

  6. Thermodynamics of nuclear transport

    NASA Astrophysics Data System (ADS)

    Wang, Ching-Hao; Mehta, Pankaj; Elbaum, Michael

    Molecular transport across the nuclear envelope is important for eukaryotes for gene expression and signaling. Experimental studies have revealed that nuclear transport is inherently a nonequilibrium process and actively consumes energy. In this work we present a thermodynamics theory of nuclear transport for a major class of nuclear transporters that are mediated by the small GTPase Ran. We identify the molecular elements responsible for powering nuclear transport, which we term the ``Ran battery'' and find that the efficiency of transport, measured by the cargo nuclear localization ratio, is limited by competition between cargo molecules and RanGTP to bind transport receptors, as well as the amount of NTF2 (i.e. RanGDP carrier) available to circulate the energy flow. This picture complements our current understanding of nuclear transport by providing a comprehensive thermodynamics framework to decipher the underlying biochemical machinery. Pm and CHW were supported by a Simons Investigator in the Mathematical Modeling in Living Systems grant (to PM).

  7. Determination of irreversibility field variations in mono- and multifilamentary (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} tapes by transport current methods

    SciTech Connect

    Anderson, J.W.; Parrell, J.A.; Polak, M.; Larbalestier, D.C.

    1997-12-01

    The irreversibility field, H{sup {asterisk}}, has been measured for a variety of mono- and multifilamentary (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (2223) tapes using two different transport current techniques. It is common to characterize the quality of 2223 tapes by their zero-field, 77 K critical current density [J{sub c}(0T, 77 K)], even though this ignores the fact that significant self-fields depress J{sub c}(0T,77K) and the possibility that the in-field J{sub c}(B) characteristics may be optimized independently of the J{sub c}(0T,77K) value. To provide more useful information, we propose a second characterization, that of the irreversibility field, H{sup {asterisk}}. Having both H{sup {asterisk}} and J{sub c}(0T,77K) information helps in separating the two independent contributions that better connectivity and stronger flux pinning can make to the J{sub c} of a tape. We illustrate this point with results from a variety of mono- and multifilamentary Bi-2223/Ag tapes in damaged and undamaged conditions, which show that H{sup {asterisk}} (77 K) can vary from {approximately}100 to {approximately}200mT and not directly correlate with J{sub c}(0T,77K). The two proposed protocols for H{sup {asterisk}} measurement are robust and compatible with common transport measurement procedures. {copyright} {ital 1997 American Institute of Physics.}

  8. Model equations for high current transport

    SciTech Connect

    Lee, E.P.

    1985-06-01

    The use of distribution functions to model transverse beam dynamics is discussed. Emphasis is placed on envelope equations, moments, the Vlasov equation, and the Kapchinski-Vladimirskij distribution. 10 refs.

  9. Residual currents and long-term transport

    USGS Publications Warehouse

    Cheng, R.T.

    1990-01-01

    Estuaries, bays, and contiguous coastal seas of the world are the most valuable and yet most vulnerable marine ecosystems. For centuries, society has placed enormous value on coastal areas for living, working, and recreation. In nearly all regions of the world, the largest population is distributed along the coastlines. The marine ecosystems provide food, shelter, and spawning grounds for fisheries, and refuge and sanctuary for wildlife. Dramatic increases in the population living in coastal regions have changed the pattern of land use and the movement of sediments. Obviously, these changes have not come without a price. Accompanying the coastal population increase is competition for the use of estuarine and coastal resources: the diversion of fresh water for irrigation and the discharge of waste water into these systems. The changing patterns of water use have resulted in deterioration of water quality, and in irreversible impacts on many marine ecosystems. All of these alterations directly affect the economic development and the quality of life in adjacent regions.

  10. Current topics in membranes and transport

    SciTech Connect

    Kleinzeller, A.

    1987-01-01

    This book contains 10 chapters. Some of the chapter titles are: Expression of the Oxytocin and Vasopressin Genes; Steroid Effects on Excitable Membranes: The Secretory Vesicle in Processing and Secretion of Neuropeptides: and Steroid Hormone Influences on Cyclic AMP-Generating Systems.

  11. Public transportation 1995: Current research in operations. Transportation research record

    SciTech Connect

    1995-12-31

    ;Contents: Metromover Extensions and Downtown Bus Service in Miami; Electric Bus Operation and Evaluation in California; Assessment of Alternative Structures for Privately Operated Bus Systems; Bus Priority at Traffic Signals in Portland: The Powell Boulevard Pilot Project; Transit Vehicle-Type Scheduling Problem; Optimal Mixed Bus Fleet for Urban Operations; Operational Characteristics of Paratransit in Developing Countries of Asia; Economics of Electric Trolley Coach Operation; Evaluation of Visual Impacts of Trolleybus Overhead Caternary System Intersections; Electric and Magnetic Fields and Electric Transit Systems; Diverting Automobile Users to Transit: Early Lessons from the Chicago Transit Authority`s Orange Line; Street-Running Rail Transit: A Historical Perspective; Diesel or Electric Power for Commuter Rail; It Depends; Generic Objectives for Evaluation of Intermodal Passenger Transfer Facilities; Airport Ground Access: Rail Transit Alternatives; Retrofit Techniques for Floating Slab Track; Calgary Light Rail Transit Surface Operations and Grade-Level Crossings; and Cost of Light Rail Collision Accidents.

  12. Enhancement in the transport critical current density Jc in YBa2Cu3O7-δ added with an insulating nano crystalline YBa2HfO5.5 perovskite

    NASA Astrophysics Data System (ADS)

    Rejith, P. P.; Vidya, S.; Solomon, Sam; Thomas, J. K.

    2014-01-01

    When a magnetic field is applied to type II superconductors, such as YBa2Cu307-δ (YBCO), the flux quanta penetrate the material as a regular array of vortices. However when transport currents are applied, they act to move these vortices, thus lowers the critical current density (Jc) as well as destroying superconductivity. The development of microstructures made of YBCO materials has enabled engineers to increase the critical current density, within Type II materials by introducing flux pinning centres into the material. The microstructure and flux pinning properties of YBa2Cu3O7-δ system with varying levels (0-5 wt. %) of a nano perovskite ceramic insulator; YBa2HfO5.5 addition was studied in detail. Orthorhombic YBa2Cu3O7-δ powder was prepared through conventional solid state route and a modified combustion method was used for synthesizing nanocrystalline YBa2HfO5.5. The structure and microstructure of the samples examined by X-ray diffraction and scanning electron microscopy showed that YBa2HfO5.5 and YBCO remained unreacted even at higher processing temperature without deteriorating the superconducting properties. The scanning electron microscope image shows that YBa2HfO5.5 forms an electrical-network between grains. These observations suggest that the YBa2HfO5.5 addition to the Y-123-compounds improve the electrical connection between superconducting grains and substantial improvements in the relative electrical transport properties of the composites. The variation of sintering temperature, density, critical transition temperature (Tc) and magnetic field dependence of critical current density (Jc) of YBa2Cu3O7-δ having different proportions of YBa2HfO5.5 in the matrix were also studied in detail. It is found that the addition of these elements considerably enhances the flux pinning strength of the system, and there is also an increase of critical temperature (Tc) and critical current density (Jc) up to an optimum value of 8.76 × 104 A/cm2 for a

  13. Current sensor

    DOEpatents

    Yakymyshyn, Christopher Paul; Brubaker, Michael Allen; Yakymyshyn, Pamela Jane

    2007-01-16

    A current sensor is described that uses a plurality of magnetic field sensors positioned around a current carrying conductor. The sensor can be hinged to allow clamping to a conductor. The current sensor provides high measurement accuracy for both DC and AC currents, and is substantially immune to the effects of temperature, conductor position, nearby current carrying conductors and aging.

  14. Radiation Transport

    SciTech Connect

    Urbatsch, Todd James

    2015-06-15

    We present an overview of radiation transport, covering terminology, blackbody raditation, opacities, Boltzmann transport theory, approximations to the transport equation. Next we introduce several transport methods. We present a section on Caseology, observing transport boundary layers. We briefly broach topics of software development, including verification and validation, and we close with a section on high energy-density experiments that highlight and support radiation transport.

  15. Space Transportation Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Liou, Meng-Sing; Stewart, Mark E.; Suresh, Ambady; Owen, A. Karl

    2001-01-01

    This report outlines the Space Transportation Propulsion Systems for the NPSS (Numerical Propulsion System Simulation) program. Topics include: 1) a review of Engine/Inlet Coupling Work; 2) Background/Organization of Space Transportation Initiative; 3) Synergy between High Performance Computing and Communications Program (HPCCP) and Advanced Space Transportation Program (ASTP); 4) Status of Space Transportation Effort, including planned deliverables for FY01-FY06, FY00 accomplishments (HPCCP Funded) and FY01 Major Milestones (HPCCP and ASTP); and 5) a review current technical efforts, including a review of the Rocket-Based Combined-Cycle (RBCC), Scope of Work, RBCC Concept Aerodynamic Analysis and RBCC Concept Multidisciplinary Analysis.

  16. Fluorine plasma treatment induced deep level traps and their effect on current transportation in Al0.83In0.17N/AlN/GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Xiang, Yong; Yu, Tongjun; Ji, Cheng; Cheng, Yutian; Yang, Xuelin; Kang, Xiangning; Shen, Bo; Zhang, Guoyi

    2016-08-01

    The deep level traps and the electrical properties of fluorine plasma treated (F-treated) and non-treated Al0.83In0.17N/AlN/GaN Schottky barrier diodes (SBDs) were investigated by the temperature-dependent current-voltage (I-V) and deep level transient spectroscopy (DLTS) measurements. Three deep level traps were detected in the SBD after F-treatment at ~E c  -  0.17 eV, ~E c  -  0.27 eV and ~E c  -  1.14 eV. One of the deep level traps at ~E c  -  1.14 eV is mainly located in the Al0.83In0.17N barrier layer with a captured cross section (σ) of ~6.50  ×  10-18 cm2. This F-related deep level trap has 3-4 orders of magnitude of the larger σ and ~0.46 eV greater active energy than that of the dislocation-related one at ~E c  -  0.68 eV with σ of ~1.92  ×  10-21 cm2. Meanwhile, the leakage current of F-treated SBD at  -5 V is reduced by ~2 orders of magnitude compared with that of the non-treated one. This leakage current reduction is mainly attributed to the increase of the Poole-Frenkel emission barrier height from ~0.09 eV in non-treated SBD to ~0.46 eV in the F-treated one. It is believed that the main reverse current transportation is the Poole-Frenkel emission from the F-related deep level trap states into the continuum states of the dislocations in F-treated Al0.83In0.17N/AlN/GaN SBD.

  17. 49 CFR 229.77 - Current collectors.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Current collectors. 229.77 Section 229.77 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....77 Current collectors. (a) Pantographs shall be so arranged that they can be operated from...

  18. 49 CFR 229.77 - Current collectors.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Current collectors. 229.77 Section 229.77 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....77 Current collectors. (a) Pantographs shall be so arranged that they can be operated from...

  19. 49 CFR 229.77 - Current collectors.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Current collectors. 229.77 Section 229.77 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....77 Current collectors. (a) Pantographs shall be so arranged that they can be operated from...

  20. 49 CFR 229.77 - Current collectors.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Current collectors. 229.77 Section 229.77 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....77 Current collectors. (a) Pantographs shall be so arranged that they can be operated from...

  1. 49 CFR 229.77 - Current collectors.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Current collectors. 229.77 Section 229.77 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION....77 Current collectors. (a) Pantographs shall be so arranged that they can be operated from...

  2. Chamber transport

    SciTech Connect

    OLSON,CRAIG L.

    2000-05-17

    Heavy ion beam transport through the containment chamber plays a crucial role in all heavy ion fusion (HIF) scenarios. Here, several parameters are used to characterize the operating space for HIF beams; transport modes are assessed in relation to evolving target/accelerator requirements; results of recent relevant experiments and simulations of HIF transport are summarized; and relevant instabilities are reviewed. All transport options still exist, including (1) vacuum ballistic transport, (2) neutralized ballistic transport, and (3) channel-like transport. Presently, the European HIF program favors vacuum ballistic transport, while the US HIF program favors neutralized ballistic transport with channel-like transport as an alternate approach. Further transport research is needed to clearly guide selection of the most attractive, integrated HIF system.

  3. Fluorine plasma treatment induced deep level traps and their effect on current transportation in Al0.83In0.17N/AlN/GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Xiang, Yong; Yu, Tongjun; Ji, Cheng; Cheng, Yutian; Yang, Xuelin; Kang, Xiangning; Shen, Bo; Zhang, Guoyi

    2016-08-01

    The deep level traps and the electrical properties of fluorine plasma treated (F-treated) and non-treated Al0.83In0.17N/AlN/GaN Schottky barrier diodes (SBDs) were investigated by the temperature-dependent current–voltage (I–V) and deep level transient spectroscopy (DLTS) measurements. Three deep level traps were detected in the SBD after F-treatment at ~E c  ‑  0.17 eV, ~E c  ‑  0.27 eV and ~E c  ‑  1.14 eV. One of the deep level traps at ~E c  ‑  1.14 eV is mainly located in the Al0.83In0.17N barrier layer with a captured cross section (σ) of ~6.50  ×  10‑18 cm2. This F-related deep level trap has 3–4 orders of magnitude of the larger σ and ~0.46 eV greater active energy than that of the dislocation-related one at ~E c  ‑  0.68 eV with σ of ~1.92  ×  10‑21 cm2. Meanwhile, the leakage current of F-treated SBD at  ‑5 V is reduced by ~2 orders of magnitude compared with that of the non-treated one. This leakage current reduction is mainly attributed to the increase of the Poole–Frenkel emission barrier height from ~0.09 eV in non-treated SBD to ~0.46 eV in the F-treated one. It is believed that the main reverse current transportation is the Poole–Frenkel emission from the F-related deep level trap states into the continuum states of the dislocations in F-treated Al0.83In0.17N/AlN/GaN SBD.

  4. Transport proteins.

    PubMed

    Thatcher, Jack D

    2013-04-16

    This Teaching Resource provides and describes two animated lessons that illustrate general properties of transport proteins. The lesson called "transport protein classes" depicts major classes and subclasses of transport proteins. The "transporters, mechanism of action" lesson explains how transporters and P class ATPase (adenosine triphosphatase) pumps function. These animations serve as valuable resources for any collegiate-level course that describes these important factors. Courses that might use them include introductory biology, biochemistry, cell biology, physiology, and biophysics.

  5. Structural diversity of ABC transporters

    PubMed Central

    ter Beek, Josy; Guskov, Albert

    2014-01-01

    ATP-binding cassette (ABC) transporters form a large superfamily of ATP-dependent protein complexes that mediate transport of a vast array of substrates across membranes. The 14 currently available structures of ABC transporters have greatly advanced insight into the transport mechanism and revealed a tremendous structural diversity. Whereas the domains that hydrolyze ATP are structurally related in all ABC transporters, the membrane-embedded domains, where the substrates are translocated, adopt four different unrelated folds. Here, we review the structural characteristics of ABC transporters and discuss the implications of this structural diversity for mechanistic diversity. PMID:24638992

  6. High current induction linacs

    NASA Astrophysics Data System (ADS)

    Barletta, W.; Faltens, A.; Henestroza, E.; Lee, E.

    1994-07-01

    Induction linacs are among the most powerful accelerators in existence. They have accelerated electron bunches of several kiloamperes, and are being investigated as drivers for heavy ion driven inertial confinement fusion (HIF), which requires peak beam currents of kiloamperes and average beam powers of some tens of megawatts. The requirement for waste transmutation with an 800 MeV proton or deuteron beam with an average current of 50 mA and an average power of 40 MW lies midway between the electron machines and the heavy ion machines in overall difficulty. Much of the technology and understanding of beam physics carries over from the previous machines to the new requirements. The induction linac allows use of a very large beam aperture, which may turn out to be crucial to reducing beam loss and machine activation from the beam halo. The major issues addressed here are transport of high intensity beams, availability of sources, efficiency of acceleration, and the state of the needed technology for the waste treatment application. Because of the transformer-like action of an induction core and the accompanying magnetizing current, induction linacs make the most economic sense and have the highest efficiencies with large beam currents. Based on present understanding of beam transport limits, induction core magnetizing current requirements, and pulse modulators, the efficiencies could be very high. The study of beam transport at high intensities has been the major activity of the HIF community. Beam transport and sources are limiting at low energies but are not significant constraints at the higher energies. As will be shown, the proton beams will be space-charge-dominated, for which the emittance has only a minor effect on the overall beam diameter but does determine the density falloff at the beam edge.

  7. School Transportation.

    ERIC Educational Resources Information Center

    Executive Educator, 1990

    1990-01-01

    This special section on student transportation offers a case study of a school system that recycles buses for safety drills; articles on fuel-saving strategies, the pros and cons of contracting for transportation services or operating a publicly owned bus fleet, and advice on full cost accounting for transportation costs; and a transportation…

  8. Transport Experiments

    NASA Technical Reports Server (NTRS)

    Hall, Timothy M.; Wuebbles, Donald J.; Boering, Kristie A.; Eckman, Richard S.; Lerner, Jean; Plumb, R. Alan; Rind, David H.; Rinsland, Curtis P.; Waugh, Darryn W.; Wei, Chu-Feng

    1999-01-01

    MM II defined a series of experiments to better understand and characterize model transport and to assess the realism of this transport by comparison to observations. Measurements from aircraft, balloon, and satellite, not yet available at the time of MM I [Prather and Remsberg, 1993], provide new and stringent constraints on model transport, and address the limits of our transport modeling abilities. Simulations of the idealized tracers the age spectrum, and propagating boundary conditions, and conserved HSCT-like emissions probe the relative roles of different model transport mechanisms, while simulations of SF6 and C02 make the connection to observations. Some of the tracers are related, and transport diagnostics such as the mean age can be derived from more than one of the experiments for comparison to observations. The goals of the transport experiments are: (1) To isolate the effects of transport in models from other processes; (2) To assess model transport for realistic tracers (such as SF6 and C02) for comparison to observations; (3) To use certain idealized tracers to isolate model mechanisms and relationships to atmospheric chemical perturbations; (4) To identify strengths and weaknesses of the treatment of transport processes in the models; (5) To relate evaluated shortcomings to aspects of model formulation. The following section are included:Executive Summary, Introduction, Age Spectrum, Observation, Tropical Transport in Models, Global Mean Age in Models, Source-Transport Covariance, HSCT "ANOY" Tracer Distributions, and Summary and Conclusions.

  9. Fault current limiter

    DOEpatents

    Darmann, Francis Anthony

    2013-10-08

    A fault current limiter (FCL) includes a series of high permeability posts for collectively define a core for the FCL. A DC coil, for the purposes of saturating a portion of the high permeability posts, surrounds the complete structure outside of an enclosure in the form of a vessel. The vessel contains a dielectric insulation medium. AC coils, for transporting AC current, are wound on insulating formers and electrically interconnected to each other in a manner such that the senses of the magnetic field produced by each AC coil in the corresponding high permeability core are opposing. There are insulation barriers between phases to improve dielectric withstand properties of the dielectric medium.

  10. Transporter taxonomy - a comparison of different transport protein classification schemes.

    PubMed

    Viereck, Michael; Gaulton, Anna; Digles, Daniela; Ecker, Gerhard F

    2014-06-01

    Currently, there are more than 800 well characterized human membrane transport proteins (including channels and transporters) and there are estimates that about 10% (approx. 2000) of all human genes are related to transport. Membrane transport proteins are of interest as potential drug targets, for drug delivery, and as a cause of side effects and drug–drug interactions. In light of the development of Open PHACTS, which provides an open pharmacological space, we analyzed selected membrane transport protein classification schemes (Transporter Classification Database, ChEMBL, IUPHAR/BPS Guide to Pharmacology, and Gene Ontology) for their ability to serve as a basis for pharmacology driven protein classification. A comparison of these membrane transport protein classification schemes by using a set of clinically relevant transporters as use-case reveals the strengths and weaknesses of the different taxonomy approaches.

  11. FAA Smoke Transport Code

    SciTech Connect

    Domino, Stefan; Luketa-Hanlin, Anay; Gallegos, Carlos

    2006-10-27

    FAA Smoke Transport Code, a physics-based Computational Fluid Dynamics tool, which couples heat, mass, and momentum transfer, has been developed to provide information on smoke transport in cargo compartments with various geometries and flight conditions. The software package contains a graphical user interface for specification of geometry and boundary conditions, analysis module for solving the governing equations, and a post-processing tool. The current code was produced by making substantial improvements and additions to a code obtained from a university. The original code was able to compute steady, uniform, isothermal turbulent pressurization. In addition, a preprocessor and postprocessor were added to arrive at the current software package.

  12. Current limiters

    SciTech Connect

    Loescher, D.H.; Noren, K.

    1996-09-01

    The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

  13. Current in wave driven plasmas

    SciTech Connect

    Karney, C.F.F.; Fisch, N.J.

    1985-06-01

    A theory for the generation of current in a toroidal plasma by radio-frequency waves is presented. The effect of an opposing electric field is included, allowing the case of time varying currents to be studied. The key quantities that characterize this regime are identified and numerically calculated. Circuit equations suitable for use in ray-tracing and transport codes are given.

  14. 49 CFR 192.473 - External corrosion control: Interference currents.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false External corrosion control: Interference currents. 192.473 Section 192.473 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER...

  15. 49 CFR 236.562 - Minimum rail current required.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Minimum rail current required. 236.562 Section 236.562 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... rail current required. The minimum rail current required to restore the locomotive equipment...

  16. 49 CFR 236.562 - Minimum rail current required.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Minimum rail current required. 236.562 Section 236.562 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... rail current required. The minimum rail current required to restore the locomotive equipment...

  17. 49 CFR 236.562 - Minimum rail current required.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Minimum rail current required. 236.562 Section 236.562 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... rail current required. The minimum rail current required to restore the locomotive equipment...

  18. 49 CFR 236.562 - Minimum rail current required.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Minimum rail current required. 236.562 Section 236.562 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... rail current required. The minimum rail current required to restore the locomotive equipment...

  19. 49 CFR 236.562 - Minimum rail current required.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Minimum rail current required. 236.562 Section 236.562 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD... rail current required. The minimum rail current required to restore the locomotive equipment...

  20. Transportation Baseline Report

    SciTech Connect

    Fawcett, Ricky Lee; Kramer, George Leroy Jr.

    1999-12-01

    The National Transportation Program 1999 Transportation Baseline Report presents data that form a baseline to enable analysis and planning for future Department of Energy (DOE) Environmental Management (EM) waste and materials transportation. In addition, this Report provides a summary overview of DOE’s projected quantities of waste and materials for transportation. Data presented in this report were gathered as a part of the IPABS Spring 1999 update of the EM Corporate Database and are current as of July 30, 1999. These data were input and compiled using the Analysis and Visualization System (AVS) which is used to update all stream-level components of the EM Corporate Database, as well as TSD System and programmatic risk (disposition barrier) information. Project (PBS) and site-level IPABS data are being collected through the Interim Data Management System (IDMS). The data are presented in appendices to this report.

  1. Transportation Network Topologies

    NASA Technical Reports Server (NTRS)

    Alexandrov, Natalia (Editor)

    2004-01-01

    The existing U.S. hub-and-spoke air transportation system is reaching saturation. Major aspects of the current system, such as capacity, safety, mobility, customer satisfaction, security, communications, and ecological effects, require improvements. The changing dynamics - increased presence of general aviation, unmanned autonomous vehicles, military aircraft in civil airspace as part of homeland defense - contributes to growing complexity of airspace. The system has proven remarkably resistant to change. NASA Langley Research Center and the National Institute of Aerospace conducted a workshop on Transportation Network Topologies on 9-10 December 2003 in Williamsburg, Virginia. The workshop aimed to examine the feasibility of traditional methods for complex system analysis and design as well as potential novel alternatives in application to transportation systems, identify state-of-the-art models and methods, conduct gap analysis, and thus to lay a foundation for establishing a focused research program in complex systems applied to air transportation.

  2. Nucleocytoplasmic transport of macromolecules.

    PubMed Central

    Corbett, A H; Silver, P A

    1997-01-01

    Nucleocytoplasmic transport is a complex process that consists of the movement of numerous macromolecules back and forth across the nuclear envelope. All macromolecules that move in and out of the nucleus do so via nuclear pore complexes that form large proteinaceous channels in the nuclear envelope. In addition to nuclear pores, nuclear transport of macromolecules requires a number of soluble factors that are found both in the cytoplasm and in the nucleus. A combination of biochemical, genetic, and cell biological approaches have been used to identify and characterize the various components of the nuclear transport machinery. Recent studies have shown that both import to and export from the nucleus are mediated by signals found within the transport substrates. Several studies have demonstrated that these signals are recognized by soluble factors that target these substrates to the nuclear pore. Once substrates have been directed to the pore, most transport events depend on a cycle of GTP hydrolysis mediated by the small Ras-like GTPase, Ran, as well as other proteins that regulate the guanine nucleotide-bound state of Ran. Many of the essential factors have been identified, and the challenge that remains is to determine the exact mechanism by which transport occurs. This review attempts to present an integrated view of our current understanding of nuclear transport while highlighting the contributions that have been made through studies with genetic organisms such as the budding yeast, Saccharomyces cerevisiae. PMID:9184010

  3. Bile acid transporters

    PubMed Central

    Dawson, Paul A.; Lan, Tian; Rao, Anuradha

    2009-01-01

    In liver and intestine, transporters play a critical role in maintaining the enterohepatic circulation and bile acid homeostasis. Over the past two decades, there has been significant progress toward identifying the individual membrane transporters and unraveling their complex regulation. In the liver, bile acids are efficiently transported across the sinusoidal membrane by the Na+ taurocholate cotransporting polypeptide with assistance by members of the organic anion transporting polypeptide family. The bile acids are then secreted in an ATP-dependent fashion across the canalicular membrane by the bile salt export pump. Following their movement with bile into the lumen of the small intestine, bile acids are almost quantitatively reclaimed in the ileum by the apical sodium-dependent bile acid transporter. The bile acids are shuttled across the enterocyte to the basolateral membrane and effluxed into the portal circulation by the recently indentified heteromeric organic solute transporter, OSTα-OSTβ. In addition to the hepatocyte and enterocyte, subgroups of these bile acid transporters are expressed by the biliary, renal, and colonic epithelium where they contribute to maintaining bile acid homeostasis and play important cytoprotective roles. This article will review our current understanding of the physiological role and regulation of these important carriers. PMID:19498215

  4. 75 FR 28100 - Agency Information Collection Activities: Notice of Request for Extension of Currently Approved...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-19

    ...: Eisenhower Transportation Fellowship Program. OMB Control #: 2125-0617. Background: The Eisenhower Transportation Fellowship Program is comprised of two programs, the Eisenhower Transportation Fellowship and the National Highway Institute (NHI). The Eisenhower Transportation Fellowship is currently authorized...

  5. Current Titles

    SciTech Connect

    Various

    2006-06-01

    This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Jane Cavlina, Administrator, at 510/486-6036.

  6. Microbial Transport in the Subsurface

    SciTech Connect

    Ginn, Timothy R.; Camesano, Terri; Scheibe, Timothy D.; Nelson, Kirk B.; Clement, T. P.; Wood, Brian D.

    2005-12-01

    In this article we focus on the physical, chemical, and biological processes involved in the transport of bacteria in the saturated subsurface. We will first review conceptual models of bacterial phases in the subsurface, and then the processes controlling fate and transport on short (e.g., bioremediation) time scales. Finally we briefly review field bacterial transport experiments and discuss a number of issues that impact the application of current process descriptions and models at the field scale.

  7. Transport Phenomena.

    ERIC Educational Resources Information Center

    McCready, Mark J.; Leighton, David T.

    1987-01-01

    Discusses the problems created in graduate chemical engineering programs when students enter with a wide diversity of understandings of transport phenomena. Describes a two-semester graduate transport course sequence at the University of Notre Dame which focuses on fluid mechanics and heat and mass transfer. (TW)

  8. Infants, Toddlers and Preschool Transportation.

    ERIC Educational Resources Information Center

    Illinois State Board of Education, Springfield.

    Providing transportation to children younger than kindergarten age has become more common for public school districts, and school personnel are unsure as to the rules, guidelines, and best practices that apply to the youngest school bus passengers. This document outlines the current Illinois requirements regarding the transportation of very young…

  9. Transport and magnetization current in a thin layer of Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2.0}Ca{sub 2.2}Cu{sub 3.0}O{sub y} adjacent to silver sheathing in BSCCO-2223 tapes

    SciTech Connect

    Lelovic, M.; Krishnaraj, P.; Deis, T.

    1995-07-01

    The thin superconducting region next to the silver sheath appears to be the region of high critical current density in BSCCO-2223 tapes. Transport current measurements on Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2.0}Ca{sub 2.2}Cu{sub 3.0}O{sub y} tape at 77 K in a low magnetic field applied parallel to the tape thickness indicate an exponential field dependence [J / J{sub c} {proportional_to} exp (- B / B{sub 0})] for transport currents. Magnetic hysteresis was measured in a 10-{mu}m-thick layer of superconductor near the silver sheath as a function of temperature, intensity, and orientation of applied field with respect to the tape. The characteristic field for full penetration depth, B*, for a superconducting slab was found to have a power law dependence on temperature. Magnetization currents as a function of temperature and applied field oriented parallel to the tape thickness, J{sub c,m}(B,T), were determined from the magnetization loop width with a Bean- model expression adapted for an orthorhombic sample. The critical-state model, adjusted for scaling and magnetic relaxation, correlates well with the magnetization current of the thin layer at 77 K.

  10. Panel 4 - applications to transportation

    SciTech Connect

    Nichols, F.; Au, J.; Bhattacharya, R.; Bhushan, B.; Blunier, D.; Boardman, B.; Brombolich, L.; Davidson, J.; Graham, M.; Hakim, N.; Harris, K.; Hay, R.; Herk, L.; Hojnacki, H.; Rourk, D.; Kamo, R.; Nieman, B.; O`Neill, D.; Peterson, M.B.; Pfaffenberger, G.; Pryor, R.W.; Russell, J.; Syniuta, W.; Tamor, M.; Vojnovich, T.; Yarbrough, W.; Yust, C.S.

    1993-01-01

    The aim of this group was to compile a listing of current and anticipated future problem areas in the transportation industry where the properties of diamond and DLC films make them especially attractive and where the panel could strongly endorse the establishment of DOE/Transportation Industry cooperative research efforts. This section identifies the problem areas for possible applications of diamond/DLC technology and presents indications of current approaches to these problems.

  11. ABC transporters: bacterial exporters.

    PubMed Central

    Fath, M J; Kolter, R

    1993-01-01

    The ABC transporters (also called traffic ATPases) make up a large superfamily of proteins which share a common function and a common ATP-binding domain. ABC transporters are classified into three major groups: bacterial importers (the periplasmic permeases), eukaryotic transporters, and bacterial exporters. We present a comprehensive review of the bacterial ABC exporter group, which currently includes over 40 systems. The bacterial ABC exporter systems are functionally subdivided on the basis of the type of substrate that each translocates. We describe three main groups: protein exporters, peptide exporters, and systems that transport nonprotein substrates. Prototype exporters from each group are described in detail to illustrate our current understanding of this protein family. The prototype systems include the alpha-hemolysin, colicin V, and capsular polysaccharide exporters from Escherichia coli, the protease exporter from Erwinia chrysanthemi, and the glucan exporters from Agrobacterium tumefaciens and Rhizobium meliloti. Phylogenetic analysis of the ATP-binding domains from 29 bacterial ABC exporters indicates that the bacterial ABC exporters can be divided into two primary branches. One branch contains the transport systems where the ATP-binding domain and the membrane-spanning domain are present on the same polypeptide, and the other branch contains the systems where these domains are found on separate polypeptides. Differences in substrate specificity do not correlate with evolutionary relatedness. A complete survey of the known and putative bacterial ABC exporters is included at the end of the review. PMID:8302219

  12. Current titles

    SciTech Connect

    1995-07-01

    This booklet is published for those interested in current research being conducted at the National Center for Electron Microscopy. The NCEM is a DOE-designated national user facility and is available at no charge to qualified researchers. Access is controlled by an external steering committee. Interested researchers may contact Gretchen Hermes at (510) 486-5006 or address below for a User`s Guide. Copies of available papers can be ordered from: Theda Crawford National Center for Electron Microscopy, Lawrence Berkeley Laboratory, One Cyclotron Rd., MS72, Berkeley, California, USA 94720.

  13. Eddy surface properties and propagation at Southern Hemisphere western boundary current systems

    NASA Astrophysics Data System (ADS)

    Pilo, G. S.; Mata, M. M.; Azevedo, J. L. L.

    2015-08-01

    Oceanic eddies exist throughout the world oceans, but are more energetic when associated with western boundary currents (WBC) systems. In these regions, eddies play an important role in mixing and energy exchange. Therefore, it is important to quantify and qualify eddies associated with these systems. This is particularly true for the Southern Hemisphere WBC system where only few eddy censuses have been performed to date. In these systems, important aspects of the local eddy population are still unknown, like their spatial distribution and propagation patterns. Moreover, the understanding of these patterns helps to establish monitoring programs and to gain insight in how eddies would affect local mixing. Here, we use a global eddy data set to qualify eddies based on their surface characteristics in the Agulhas Current (AC), the Brazil Current (BC) and the East Australian Current (EAC) systems. The analyses reveal that eddy propagation within each system is highly forced by the local mean flow and bathymetry. Large values of eddy amplitude and temporal variability are associated with the BC and EAC retroflections, while small values occur in the centre of the Argentine Basin and in the Tasman Sea. In the AC system, eddy polarity dictates the propagation distance. BC system eddies do not propagate beyond the Argentine Basin, and are advected by the local ocean circulation. EAC system eddies from both polarities cross south of Tasmania but only the anticyclonic ones reach the Great Australian Bight. For all three WBC systems, both cyclonic and anticyclonic eddies present a geographical segregation according to radius size and amplitude. Regions of high eddy kinetic energy are associated with the eddies' mean amplitudes, and not with their densities.

  14. Intercellular transport.

    PubMed

    Thatcher, Jack D

    2013-04-16

    These animations depict generalities of intercellular transport. The animation called "permeability and transport" demonstrates the permeability of four classes of molecules. The "gap junctions" animation shows how these intercellular complexes exclude large factors while they allow small factors to diffuse between cells. These animations serve as useful resources for any collegiate-level course that describes these processes. Courses that might use them include biochemistry, biophysics, cell biology, introductory biology, and physiology.

  15. A transportable optical lattice clock

    NASA Astrophysics Data System (ADS)

    Vogt, Stefan; Häfner, Sebastian; Grotti, Jacopo; Koller, Silvio; Al-Masoudi, Ali; Sterr, Uwe; Lisdat, Christian

    2016-06-01

    We present the experimental setup and first results of PTB's transportable 87Sr clock. It consists of a physics package, several compact laser breadboards, and a transportable high finesse cavity for the clock laser. A comparison of the transportable system with our stationary optical lattice clock yields an instability of 2.2 x 10-15 √s/τ for the transportable clock. The current fractional uncertainty of 1 × 10-15 is still limited by the not yet fully evaluated light shift from the free running optical lattice laser operated near the magic wavelength. We are currently improving our transportable system to reach an uncertainty at or below the 10-17 level, which will finaly be limited by the uncertainty in blackbody radiation shift correction.

  16. Development of the Neogene current system in the Cape Basin as recorded in the seismostratigraphy

    NASA Astrophysics Data System (ADS)

    Weigelt, E.; Uenzelmann-Neben, G.

    2003-04-01

    The sedimentary sequences of the continental margin off southwest Africa have been shaped by different currents. At the surface, the Benguela and Agulhas Currents are active, in greater depths the Antarctic Intermediate Water (AAIW), the North Atlantic Depth Water (NADW) and Antarctic Bottom Water (AABW) take effect. Our aim is to unravel the development and modifications of those current systems. Especially we want to concentrate on the onset of the Benguela Current Upwelling System, which represents one of the largest upwelling regions worldwide and is closely related to the developement of the climate in southern Africa. Significant events as incursions of warm or cold waters, terrigenous input, climate changes and slumpings are recorded in the deposited material. The sedimentary properties are expected to be reflected in the signal structure of the seismic data from this area. In this contribution we will present a seismic stratigraphy for the Neogene sedimentary layers in the entire Cape Basin on the base of results of the ODP Leg 175 Sites 1081-1087 which are correlated with seismic data. With a maximum depth of 610mbsf (Site 1085a) the sites span the time period between Holocene and late Miocene (0-15 Ma). Corelog parameters as for example velocity, density, lithostratigraphy, carbon and carbonate content are linked to the seismic sections via synthetic seismograms. This procedure enables an interpretation of the origin of reflectors and a spatial extrapolation of sites informations. The depositional enviroment in the Cape Basin can be divided roughly into three major areas and is reflected in a change in stratigraphy from north to south: Deposition in the northern regions is influenced by eroded sediments from the Walvis Ridge and by upwelling sediments. Sediments of the middle Cape Basin are dominated by the presumable most productive coastal upwelling cells. The depositions in the southern Cape Basin contain the most imprint of incursions from the south

  17. Ambipolar acoustic transport in silicon

    NASA Astrophysics Data System (ADS)

    Barros, A. D.; Batista, P. D.; Tahraoui, A.; Diniz, J. A.; Santos, P. V.

    2012-07-01

    We have investigated the ambipolar transport of electrons and holes by electrically generated surface acoustic waves (SAWs) on silicon wafers coated with a piezoelectric ZnO film. The transport experiments were carried out by using a focused laser beam to optically excite carriers. The carriers are then captured by the moving SAW piezoelectric field and then transported towards a lateral p-i-n junction, where they are electrically detected. The piezoelectric modulation modifies the current vs. voltage characteristics of the lateral p-i-n junction. This behavior is accounted for by a simple model for the change of the junction potential by the SAW fields. We demonstrate that electrons and holes can be acoustically transported over distances approaching 100 μm, the transport efficiency being limited by the low mobility of holes in the material. These results open the way for silicon-based acousto-electric devices using ambipolar transport such as photo-detectors and solar cells.

  18. 49 CFR 236.734 - Current of traffic.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Current of traffic. 236.734 Section 236.734 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Current of traffic. The movement of trains on a specified track in a designated direction....

  19. 49 CFR 236.734 - Current of traffic.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Current of traffic. 236.734 Section 236.734 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Current of traffic. The movement of trains on a specified track in a designated direction....

  20. 49 CFR 236.734 - Current of traffic.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Current of traffic. 236.734 Section 236.734 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Current of traffic. The movement of trains on a specified track in a designated direction....

  1. 49 CFR 192.473 - External corrosion control: Interference currents.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false External corrosion control: Interference currents. 192.473 Section 192.473 Transportation Other Regulations Relating to Transportation (Continued... for Corrosion Control § 192.473 External corrosion control: Interference currents. (a) Each...

  2. 49 CFR 192.473 - External corrosion control: Interference currents.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false External corrosion control: Interference currents. 192.473 Section 192.473 Transportation Other Regulations Relating to Transportation (Continued... for Corrosion Control § 192.473 External corrosion control: Interference currents. (a) Each...

  3. 49 CFR 192.473 - External corrosion control: Interference currents.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false External corrosion control: Interference currents. 192.473 Section 192.473 Transportation Other Regulations Relating to Transportation (Continued... for Corrosion Control § 192.473 External corrosion control: Interference currents. (a) Each...

  4. 49 CFR 192.473 - External corrosion control: Interference currents.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false External corrosion control: Interference currents. 192.473 Section 192.473 Transportation Other Regulations Relating to Transportation (Continued... for Corrosion Control § 192.473 External corrosion control: Interference currents. (a) Each...

  5. 49 CFR 236.734 - Current of traffic.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Current of traffic. 236.734 Section 236.734 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Current of traffic. The movement of trains on a specified track in a designated direction....

  6. 49 CFR 236.734 - Current of traffic.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Current of traffic. 236.734 Section 236.734 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Current of traffic. The movement of trains on a specified track in a designated direction....

  7. A study of current transport in superconductor-semiconductor-superconductor niobium/indium arsenide/niobium devices fabricated by passivated chlorine thermal etching of aluminum gallium antimonide/indium arsenide heterostructures

    NASA Astrophysics Data System (ADS)

    Bellomi, Giovanni L.

    2003-10-01

    The purpose of this project has been to investigate the application of an arsenic passivated Chlorine (Cl2) thermal etching of GaSb/AlGaSb/InAs heterostructure, in order to fabricate superconductor/semiconductor Nb/InAs/Nb structures. No temperature window exists in which the AlGaSb is completely removed from the InAs surface (barrier) and the InAs is not attacked by the Chlorine etch (damage). The Cl 2 etch process presents adequate selectivity to fabricate a standard InAs-base transistor, with higher mobility (˜x4) than wet etch fabricated devices. Conversely, due to the peculiarity of the two-particle coherent Andreev scattering, the presence of an AlGaSb barrier (30--50 A) or InAs damage (roughness ˜40--90 A) in the InAs strongly affects the coherent transport. As the Cl2 etching temperature increases, the SN system passes from a tunneling regime (T < 100°C) to a partially coherent diffusive regime (T > 100°C) showing coherent peak in the conductance. Our calculation shows that as coherence length L φ extends in the normal metal, disorder can increase conductance in SN junctions. The results coincide, for T = 0, zero voltage, and Lφ → infinity, with the Andreev conductance as calculated by Beenakker [1]. Coherent transport in Nb/InAs/Nb structures is primarily characterized by the diffusive nature of the single Nb/InAs interface.

  8. Using Cooperatives to Transport Rural Passengers.

    ERIC Educational Resources Information Center

    Stommes, Eileen S.; Byrne, Robert J.

    A study of two rural New York counties--Cortland and Otsego--was undertaken to identify innovative ways to provide public passenger transportation services in rural areas by using transportation cooperatives. Information about current transportation services was obtained from staff members of the human service agencies and county government…

  9. Electrofuels: Versatile Transportation Energy Solutions

    SciTech Connect

    2010-07-01

    Electrofuels Project: ARPA-E’s Electrofuels Project is using microorganisms to create liquid transportation fuels in a new and different way that could be up to 10 times more energy efficient than current biofuel production methods. ARPA-E is the only U.S. government agency currently funding research on Electrofuels.

  10. Transportation: Destination Mars

    NASA Technical Reports Server (NTRS)

    Eoff, Bill

    1998-01-01

    As the agency space transportation lead center, Marshall Space Flight Center has been conducting transportation assessments for future robotic and human Mars missions to identify critical technologies. Five human Mars options are currently under assessment with each option including all transportation requirements from Earth to Mars and return. The primary difference for each option is the propulsion source from Earth to Mars. In case any of the options require heavy launch capability that is not currently projected as available, an in-house study has been initiated to determine the most cost effective means of providing such launch capability. This assessment is only considering launch architectures that support the overall human Mars mission cost goal of $25B. The guidelines for the launch capability study included delivery of 80 metric ton (176 KLB) payloads, 25 feet diameter x 92 feet long, to 220 nmi orbits at 28.5 degrees. The launch vehicle concept of the study was designated "Magnum" to differentiate from prior heavy launch vehicle assessments. This assessment along with the assessment of options for all transportation phases of a Mars mission are on-going.

  11. High speed civil transport

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This report discusses the design and marketability of a next generation supersonic transport. Apogee Aeronautics Corporation has designated its High Speed Civil Transport (HSCT): Supercruiser HS-8. Since the beginning of the Concorde era, the general consensus has been that the proper time for the introduction of a next generation Supersonic Transport (SST) would depend upon the technical advances made in the areas of propulsion (reduction in emissions) and material composites (stronger, lighter materials). It is believed by many in the aerospace industry that these beforementioned technical advances lie on the horizon. With this being the case, this is the proper time to begin the design phase for the next generation HSCT. The design objective for a HSCT was to develop an aircraft that would be capable of transporting at least 250 passengers with baggage at a distance of 5500 nmi. The supersonic Mach number is currently unspecified. In addition, the design had to be marketable, cost effective, and certifiable. To achieve this goal, technical advances in the current SST's must be made, especially in the areas of aerodynamics and propulsion. As a result of these required aerodynamic advances, several different supersonic design concepts were reviewed.

  12. FAA Smoke Transport Code

    2006-10-27

    FAA Smoke Transport Code, a physics-based Computational Fluid Dynamics tool, which couples heat, mass, and momentum transfer, has been developed to provide information on smoke transport in cargo compartments with various geometries and flight conditions. The software package contains a graphical user interface for specification of geometry and boundary conditions, analysis module for solving the governing equations, and a post-processing tool. The current code was produced by making substantial improvements and additions to a codemore » obtained from a university. The original code was able to compute steady, uniform, isothermal turbulent pressurization. In addition, a preprocessor and postprocessor were added to arrive at the current software package.« less

  13. Nonlinear chiral transport phenomena

    NASA Astrophysics Data System (ADS)

    Chen, Jiunn-Wei; Ishii, Takeaki; Pu, Shi; Yamamoto, Naoki

    2016-06-01

    We study the nonlinear responses of relativistic chiral matter to the external fields such as the electric field E , gradients of temperature and chemical potential, ∇T and ∇μ . Using the kinetic theory with Berry curvature corrections under the relaxation time approximation, we compute the transport coefficients of possible new electric currents that are forbidden in usual chirally symmetric matter but are allowed in chirally asymmetric matter by parity. In particular, we find a new type of electric current proportional to ∇μ ×E due to the interplay between the effects of the Berry curvature and collisions. We also derive an analog of the "Wiedemann-Franz" law specific for anomalous nonlinear transport in relativistic chiral matter.

  14. 49 CFR 193.2633 - Interference currents.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...: FEDERAL SAFETY STANDARDS Maintenance § 193.2633 Interference currents. (a) Each component that is subject to electrical current interference must be protected by a continuing program to minimize the... 49 Transportation 3 2011-10-01 2011-10-01 false Interference currents. 193.2633 Section...

  15. 49 CFR 193.2633 - Interference currents.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...: FEDERAL SAFETY STANDARDS Maintenance § 193.2633 Interference currents. (a) Each component that is subject to electrical current interference must be protected by a continuing program to minimize the... 49 Transportation 3 2012-10-01 2012-10-01 false Interference currents. 193.2633 Section...

  16. 49 CFR 193.2633 - Interference currents.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...: FEDERAL SAFETY STANDARDS Maintenance § 193.2633 Interference currents. (a) Each component that is subject to electrical current interference must be protected by a continuing program to minimize the... 49 Transportation 3 2014-10-01 2014-10-01 false Interference currents. 193.2633 Section...

  17. 49 CFR 193.2633 - Interference currents.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...: FEDERAL SAFETY STANDARDS Maintenance § 193.2633 Interference currents. (a) Each component that is subject to electrical current interference must be protected by a continuing program to minimize the... 49 Transportation 3 2010-10-01 2010-10-01 false Interference currents. 193.2633 Section...

  18. 49 CFR 193.2633 - Interference currents.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...: FEDERAL SAFETY STANDARDS Maintenance § 193.2633 Interference currents. (a) Each component that is subject to electrical current interference must be protected by a continuing program to minimize the... 49 Transportation 3 2013-10-01 2013-10-01 false Interference currents. 193.2633 Section...

  19. In-line beam current monitor

    DOEpatents

    Ekdahl, C.A. Jr.; Frost, C.A.

    1984-11-13

    An intense relativistic electron beam current monitor for a gas neutralized beam transport line includes a first foil for conducting plasma current to the wall where it is measured as it traverses an inductive loop formed by a cavity in the wall. An insulator foil separates the first foil from a second conducting foil which returns the current to the plasma environment.

  20. In-line beam current monitor

    DOEpatents

    Ekdahl, Jr., Carl A.; Frost, Charles A.

    1986-01-01

    An intense relativistic electron beam current monitor for a gas neutralized beam transport line includes a first foil for conducting plasma current to the wall where it is measured as it traverses an inductive loop formed by a cavity in the wall. An insulator foil separates the first foil from a second conducting foil which returns the current to the plasma environment.

  1. Transportation Systems Center

    SciTech Connect

    Greer, G.S.

    1992-07-01

    The Transportation Systems Center at Sandia Laboratory performs research, development, and implementation of technologies that enhance the safe movement of people, goods, and information. Our focus is on systems engineering. However, we realize that to understand the puzzle, you must also understand the pieces. This brochure describes some of the activities currently underway at the Center and presents the breadth and depth of our capabilities. Please contact the noted, individuals for more, information.

  2. Inductance due to spin current

    SciTech Connect

    Chen, Wei

    2014-03-21

    The inductance of spintronic devices that transport charge neutral spin currents is discussed. It is known that in a media that contains charge neutral spins, a time-varying electric field induces a spin current. We show that since the spin current itself produces an electric field, this implies existence of inductance and electromotive force when the spin current changes with time. The relations between the electromotive force and the corresponding flux, which is a vector calculated by the cross product of electric field and the trajectory of the device, are clarified. The relativistic origin generally renders an extremely small inductance, which indicates the advantage of spin current in building low inductance devices. The same argument also explains the inductance due to electric dipole current and applies to physical dipoles consist of polarized bound charges.

  3. A National MagLev Transportation System

    NASA Technical Reports Server (NTRS)

    Wright, Michael R.

    2003-01-01

    The case for a national high-speed magnetic-levitation (MagLev) transportation system is presented. Focus is on current issues facing the country, such as national security, the economy, transportation, technology, and the environment. NASA s research into MagLev technology for launch assist is also highlighted. Further, current socio-cultural norms regarding motor-vehicle-based transportation systems are questioned in light of the problems currently facing the U.S. The multidisciplinary benefits of a long-distance MagLev system support the idea that such a system would be an important element of a truly multimodal U.S. transportation infrastructure.

  4. Pupil Transportation.

    ERIC Educational Resources Information Center

    Bete, Tim, Ed.

    1998-01-01

    Presents the opinions of four transportation experts on issues related to school buses. The experts respond to the following questions: will advertisements placed on buses be used to generate district revenue; will compressed natural gas or liquefied natural gas become standard fuel for school buses; and will school bus seat belts be mandatory and…

  5. Membrane Transport

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The selective movement and redistribution of ions and small organic molecules is essential for plant growth and cellular homeostasis. Because of this, plants have evolved numerous proteins that facilitate the transport of minerals, sugars, metabolites, and other compounds through the limiting membra...

  6. Functional insights of nucleocytoplasmic transport in plants

    PubMed Central

    Tamura, Kentaro; Hara-Nishimura, Ikuko

    2014-01-01

    Plant nucleocytoplasmic transport beyond the nuclear envelope is important not only for basic cellular functions but also for growth, development, hormonal signaling, and responses to environmental stimuli. Key components of this transport system include nuclear transport receptors and nucleoporins. The functional and physical interactions between receptors and the nuclear pore in the nuclear membrane are indispensable for nucleocytoplasmic transport. Recently, several groups have reported various plant mutants that are deficient in factors involved in nucleocytoplasmic transport. Here, we summarize the current state of knowledge about nucleocytoplasmic transport in plants, and we review the plant-specific regulation and roles of this process in plants. PMID:24765097

  7. Absolute geostrophic currents in global tropical oceans

    NASA Astrophysics Data System (ADS)

    Yang, Lina; Yuan, Dongliang

    2016-11-01

    A set of absolute geostrophic current (AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profiles in the world tropical oceans. The AGCs agree well with altimeter geostrophic currents, Ocean Surface Current Analysis-Real time currents, and moored current-meter measurements at 10-m depth, based on which the classical Sverdrup circulation theory is evaluated. Calculations have shown that errors of wind stress calculation, AGC transport, and depth ranges of vertical integration cannot explain non-Sverdrup transport, which is mainly in the subtropical western ocean basins and equatorial currents near the Equator in each ocean basin (except the North Indian Ocean, where the circulation is dominated by monsoons). The identified non-Sverdrup transport is thereby robust and attributed to the joint effect of baroclinicity and relief of the bottom (JEBAR) and mesoscale eddy nonlinearity.

  8. Sediment transport in the nearshore area of Phoenix Island

    NASA Astrophysics Data System (ADS)

    Hu, Rijun; Ma, Fang; Wu, Jianzheng; Zhang, Wei; Jiang, Shenghui; Xu, Yongchen; Zhu, Longhai; Wang, Nan; Liu, Aijiang

    2016-10-01

    Based on the measured data, suspended sediment concentration, surface sediment grain size, current and waves, the sediment transport mechanisms and pathways in the Phoenix Island area were analyzed using methods of flux decomposition and Grain Size Trend Analysis (GSTA). The results show that net suspended sediment is mainly transported by average current, Stokes drift, and gravitational circulation. The transport direction of suspended sediment is varying and basically following the direction of residual tidal currents. Surface sediment transport pathways are primarily parallel to the coastline along with two convergent centers. Waves and longshore currents have a significant influence on sediment transport, but the influence is limited due to a steep and deep underwater bank. Tidal current is the main controlling factor for sediment transport, especially in the deep water area. Neither suspended nor surface sediment is transported towards the southwest. The South Shandong Coastal Current (SSCC) has little effect on sediment transport processes in the nearshore area of Phoenix Island.

  9. Turbulent current drive

    NASA Astrophysics Data System (ADS)

    Garbet, X.; Esteve, D.; Sarazin, Y.; Dif-Pradalier, G.; Ghendrih, P.; Grandgirard, V.; Latu, G.; Smolyakov, A.

    2014-11-01

    The Ohm's law is modified when turbulent processes are accounted for. Besides an hyper-resistivity, already well known, pinch terms appear in the electron momentum flux. Moreover it appears that turbulence is responsible for a source term in the Ohm's law, called here turbulent current drive. Two terms contribute to this source. The first term is a residual stress in the momentum flux, while the second contribution is an electro-motive force. A non zero average parallel wave number is needed to get a finite source term. Hence a symmetry breaking mechanism must be invoked, as for ion momentum transport. E × B shear flows and turbulence intensity gradients are shown to provide similar contributions. Moreover this source term has to compete with the collision friction term (resistivity). The effect is found to be significant for a large scale turbulence in spite of an unfavorable scaling with the ratio of the electron to ion mass. Turbulent current drive appears to be a weak effect in the plasma core, but could be substantial in the plasma edge where it may produce up to 10 % of the local current density.

  10. LNG transportation

    SciTech Connect

    Picard, J.

    1988-01-01

    In the beginning of 1965, the participants to the starting up of first French LNG transportation system between ARZEW and LE HAVRE were indeed pioneers when they started the cool-down of the three tanks of LE HAVRE, with a LNG freight delivered by old liberty-ship ''BEAUVAIS''. Could they forecast the development of LNG industry in FRANCE and in the world and imagine that modest 'JULES VERNE' and his two english brothers would have, 25 years later, 80 successors - more than five times as big, for the main part of them, that 12 liquefaction plants would be running in the world, supplying about twenty LNG terminals. For the first time, a country - FRANCE - can draw the lessons from the exploitation of the 3 LNG transportation systems during a long period. That is the subject of the present paper.

  11. Copper transport.

    PubMed

    Linder, M C; Wooten, L; Cerveza, P; Cotton, S; Shulze, R; Lomeli, N

    1998-05-01

    In adult humans, the net absorption of dietary copper is approximately 1 mg/d. Dietary copper joins some 4-5 mg of endogenous copper flowing into the gastrointestinal tract through various digestive juices. Most of this copper returns to the circulation and to the tissues (including liver) that formed them. Much lower amounts of copper flow into and out of other major parts of the body (including heart, skeletal muscle, and brain). Newly absorbed copper is transported to body tissues in two phases, borne primarily by plasma protein carriers (albumin, transcuprein, and ceruloplasmin). In the first phase, copper goes from the intestine to the liver and kidney; in the second phase, copper usually goes from the liver (and perhaps also the kidney) to other organs. Ceruloplasmin plays a role in this second phase. Alternatively, liver copper can also exit via the bile, and in a form that is less easily reabsorbed. Copper is also present in and transported by other body fluids, including those bathing the brain and central nervous system and surrounding the fetus in the amniotic sac. Ceruloplasmin is present in these fluids and may also be involved in copper transport there. The concentrations of copper and ceruloplasmin in milk vary with lactational stage. Parallel changes occur in ceruloplasmin messenger RNA expression in the mammary gland (as determined in pigs). Copper in milk ceruloplasmin appears to be particularly available for absorption, at least in rats. PMID:9587137

  12. Copper transport.

    PubMed

    Linder, M C; Wooten, L; Cerveza, P; Cotton, S; Shulze, R; Lomeli, N

    1998-05-01

    In adult humans, the net absorption of dietary copper is approximately 1 mg/d. Dietary copper joins some 4-5 mg of endogenous copper flowing into the gastrointestinal tract through various digestive juices. Most of this copper returns to the circulation and to the tissues (including liver) that formed them. Much lower amounts of copper flow into and out of other major parts of the body (including heart, skeletal muscle, and brain). Newly absorbed copper is transported to body tissues in two phases, borne primarily by plasma protein carriers (albumin, transcuprein, and ceruloplasmin). In the first phase, copper goes from the intestine to the liver and kidney; in the second phase, copper usually goes from the liver (and perhaps also the kidney) to other organs. Ceruloplasmin plays a role in this second phase. Alternatively, liver copper can also exit via the bile, and in a form that is less easily reabsorbed. Copper is also present in and transported by other body fluids, including those bathing the brain and central nervous system and surrounding the fetus in the amniotic sac. Ceruloplasmin is present in these fluids and may also be involved in copper transport there. The concentrations of copper and ceruloplasmin in milk vary with lactational stage. Parallel changes occur in ceruloplasmin messenger RNA expression in the mammary gland (as determined in pigs). Copper in milk ceruloplasmin appears to be particularly available for absorption, at least in rats.

  13. Stratospheric dynamics and transport studies

    NASA Technical Reports Server (NTRS)

    Grose, William L.; Turner, R. E.; Blackshear, W. T.; Eckman, R. S.

    1990-01-01

    A three dimensional General Circulation Model/Transport Model is used to simulate stratospheric circulation and constituent distributions. Model simulations are analyzed to interpret radiative, chemical, and dynamical processes and their mutual interactions. Concurrent complementary studies are conducted using both global satellite data and other appropriate data. Comparisons of model simulations and data analysis studies are used to aid in understanding stratospheric dynamics and transport processes and to assess the validity of current theory and models.

  14. Direct-current transport properties of and microwave absorption in a bulk ceramic sample and a film of La0.5Sr0.5CoO3- δ: magnetic inhomogeneity effects

    NASA Astrophysics Data System (ADS)

    Belevtsev, B. I.; Cherpak, N. T.; Chukanova, I. N.; Gubin, A. I.; Krasovitsky, V. B.; Lavrinovich, A. A.

    2002-03-01

    The DC transport properties of and microwave absorption (at 41 GHz) in a bulk ceramic sample and a film (220 nm thick) of La0.5Sr0.5CoO3-δ are measured. The bulk sample was cut from a target from which the film was also produced, by pulsed-laser deposition. It is found that the temperature behaviours of the DC resistivity and magnetoresistance (MR) of the bulk sample are quite different from those of the film. This is attributed to oxygen depletion of the film as compared with the target. Below the Curie temperature TC, the film behaves like a highly inhomogeneous system of weakly connected ferromagnetic grains (or clusters). The microwave study provides further data on the inhomogeneity of the samples. It is found that the surface layer of the bulk sample has very low conductivity compared with the bulk. This can be explained by the oxygen depletion of the surface layer. The most important feature of doped cobaltates revealed in this study is the following: the microwave conductivity, which should be related mainly to the conductivity within the poorly connected grains, increases by an order of magnitude at the transition to the ferromagnetic state. The increase is much greater than that found in the reported DC measurements on doped cobaltates of the highest crystal perfection. The microwave effect found is attributed to an inherent magnetically inhomogeneous state of the doped cobaltates. On the basis of the results obtained, it can be suggested that the rather low MR in the doped cobaltates as compared with that of the manganites is attributable to their more inhomogeneous magnetic state.

  15. Transport numbers in transdermal iontophoresis.

    PubMed

    Mudry, Blaise; Guy, Richard H; Delgado-Charro, M Begoña

    2006-04-15

    Parameters determining ionic transport numbers in transdermal iontophoresis have been characterized. The transport number of an ion (its ability to carry charge) is key to its iontophoretic delivery or extraction across the skin. Using small inorganic ions, the roles of molar fraction and mobility of the co- and counterions present have been demonstrated. A direct, constant current was applied across mammalian skin in vitro. Cations were anodally delivered from either simple M(+)Cl(-) solutions (single-ion case, M(+) = sodium, lithium, ammonium, potassium), or binary and quaternary mixtures thereof. Transport numbers were deduced from ion fluxes. In the single-ion case, maximum cationic fluxes directly related to the corresponding ionic aqueous mobilities were found. Addition of co-ions decreased the transport numbers of all cations relative to the single-ion case, the degree of effect depending upon the molar fraction and mobility of the species involved. With chloride as the principal counterion competing to carry current across the skin (the in vivo situation), a maximum limit on the single or collective cation transport number was 0.6-0.8. Overall, these results demonstrate how current flowing across the skin during transdermal iontophoresis is distributed between competing ions, and establish simple rules with which to optimize transdermal iontophoretic transport.

  16. Quantum transport through aromatic molecules

    SciTech Connect

    Ojeda, J. H.; Rey-González, R. R.; Laroze, D.

    2013-12-07

    In this paper, we study the electronic transport properties through aromatic molecules connected to two semi-infinite leads. The molecules are in different geometrical configurations including arrays. Using a nearest neighbor tight-binding approach, the transport properties are analyzed into a Green's function technique within a real-space renormalization scheme. We calculate the transmission probability and the Current-Voltage characteristics as a function of a molecule-leads coupling parameter. Our results show different transport regimes for these systems, exhibiting metal-semiconductor-insulator transitions and the possibility to employ them in molecular devices.

  17. Cellular iron transport.

    PubMed

    Garrick, Michael D; Garrick, Laura M

    2009-05-01

    Iron has a split personality as an essential nutrient that also has the potential to generate reactive oxygen species. We discuss how different cell types within specific tissues manage this schizophrenia. The emphasis in enterocytes is on regulating the body's supply of iron by regulating transport into the blood stream. In developing red blood cells, adaptations in transport manage the body's highest flux of iron. Hepatocytes buffer the body's stock of iron. Macrophage recycle the iron from effete red cells among other iron management tasks. Pneumocytes provide a barrier to prevent illicit entry that, when at risk of breaching, leads to a need to handle the dangers in a fashion essentially shared with macrophage. We also discuss or introduce cell types including renal cells, neurons, other brain cells, and more where our ignorance, currently still vast, needs to be removed by future research. PMID:19344751

  18. Fuel cell water transport

    DOEpatents

    Vanderborgh, Nicholas E.; Hedstrom, James C.

    1990-01-01

    The moisture content and temperature of hydrogen and oxygen gases is regulated throughout traverse of the gases in a fuel cell incorporating a solid polymer membrane. At least one of the gases traverses a first flow field adjacent the solid polymer membrane, where chemical reactions occur to generate an electrical current. A second flow field is located sequential with the first flow field and incorporates a membrane for effective water transport. A control fluid is then circulated adjacent the second membrane on the face opposite the fuel cell gas wherein moisture is either transported from the control fluid to humidify a fuel gas, e.g., hydrogen, or to the control fluid to prevent excess water buildup in the oxidizer gas, e.g., oxygen. Evaporation of water into the control gas and the control gas temperature act to control the fuel cell gas temperatures throughout the traverse of the fuel cell by the gases.

  19. Transportation Statistics Annual Report 1997

    SciTech Connect

    Fenn, M.

    1997-01-01

    This document is the fourth Transportation Statistics Annual Report (TSAR) prepared by the Bureau of Transportation Statistics (BTS) for the President and Congress. As in previous years, it reports on the state of U.S. transportation system at two levels. First, in Part I, it provides a statistical and interpretive survey of the system—its physical characteristics, its economic attributes, aspects of its use and performance, and the scale and severity of unintended consequences of transportation, such as fatalities and injuries, oil import dependency, and environment impacts. Part I also explores the state of transportation statistics, and new needs of the rapidly changing world of transportation. Second, Part II of the report, as in prior years, explores in detail the performance of the U.S. transportation system from the perspective of desired social outcomes or strategic goals. This year, the performance aspect of transportation chosen for thematic treatment is “Mobility and Access,” which complements past TSAR theme sections on “The Economic Performance of Transportation” (1995) and “Transportation and the Environment” (1996). Mobility and access are at the heart of the transportation system’s performance from the user’s perspective. In what ways and to what extent does the geographic freedom provided by transportation enhance personal fulfillment of the nation’s residents and contribute to economic advancement of people and businesses? This broad question underlies many of the topics examined in Part II: What is the current level of personal mobility in the United States, and how does it vary by sex, age, income level, urban or rural location, and over time? What factors explain variations? Has transportation helped improve people’s access to work, shopping, recreational facilities, and medical services, and in what ways and in what locations? How have barriers, such as age, disabilities, or lack of an automobile, affected these

  20. Defense waste transportation: cost and logistics studies

    SciTech Connect

    Andrews, W.B.; Cole, B.M.; Engel, R.L.; Oylear, J.M.

    1982-08-01

    Transportation of nuclear wastes from defense programs is expected to significantly increase in the 1980s and 1990s as permanent waste disposal facilities come into operation. This report uses models of the defense waste transportation system to quantify potential transportation requirements for treated and untreated contact-handled transuranic (CH-TRU) wastes and high-level defense wastes (HLDW). Alternative waste management strategies in repository siting, waste retrieval and treatment, treatment facility siting, waste packaging and transportation system configurations were examined to determine their effect on transportation cost and hardware requirements. All cost estimates used 1980 costs. No adjustments were made for future changes in these costs relative to inflation. All costs are reported in 1980 dollars. If a single repository is used for defense wastes, transportation costs for CH-TRU waste currently in surface storage and similar wastes expected to be generated by the year 2000 were estimated to be 109 million dollars. Recovery and transport of the larger buried volumes of CH-TRU waste will increase CH-TRU waste transportation costs by a factor of 70. Emphasis of truck transportation and siting of multiple repositories would reduce CH-TRU transportation costs. Transportation of HLDW to repositories for 25 years beginning in 1997 is estimated to cost $229 M in 1980 costs and dollars. HLDW transportation costs could either increase or decrease with the selection of a final canister configuration. HLDW transportation costs are reduced when multiple repositories exist and emphasis is placed on truck transport.

  1. Mobile Transporter

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The Space Shuttle Atlantis, STS-110 mission, deployed this railcar, called the Mobile Transporter, and an initial 43-foot section of track, the S0 (S-zero) truss, preparing the International Space Station (ISS) for future spacewalks. The first railroad in space, the Mobile Transporter will allow the Station's robotic arm to travel up and down the finished truss for future assembly and maintenance. The 27,000-pound S0 truss is the first of 9 segments that will make up the Station's external framework that will eventually stretch 356 feet (109 meters), or approximately the length of a football field. The completed truss structure will hold solar arrays and radiators to provide power and cooling for additional international research laboratories from Japan and Europe that will be attached to the Station. The Space Shuttle Orbiter Atlantis, STS-110 mission, was launched April 8, 2002 and returned to Earth April 19, 2002. STS-110's Extravehicular Activity (EVA) marked the first use of the Station's robotic arm to maneuver spacewalkers around the Station.

  2. Proton Transport

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    The transport of protons across membranes is an essential process for both bioenergetics of modern cells and the origins of cellular life. All living systems make use of proton gradients across cell walls to convert environmental energy into a high-energy chemical compound, adenosine triphosphate (ATP), synthesized from adenosine diphosphate. ATP, in turn, is used as a source of energy to drive many cellular reactions. The ubiquity of this process in biology suggests that even the earliest cellular systems were relying on proton gradient for harvesting environmental energy needed to support their survival and growth. In contemporary cells, proton transfer is assisted by large, complex proteins embedded in membranes. The issue addressed in this Study was: how the same process can be accomplished with the aid of similar but much simpler molecules that could have existed in the protobiological milieu? The model system used in the study contained a bilayer membrane made of phospholipid, dimyristoylphosphatidylcholine (DMPC) which is a good model of the biological membranes forming cellular boundaries. Both sides of the bilayer were surrounded by water which simulated the environment inside and outside the cell. Embedded in the membrane was a fragment of the Influenza-A M$_2$ protein and enough sodium counterions to maintain system neutrality. This protein has been shown to exhibit remarkably high rates of proton transport and, therefore, is an excellent model to study the formation of proton gradients across membranes. The Influenza M$_2$ protein is 97 amino acids in length, but a fragment 25 amino acids long. which contains a transmembrane domain of 19 amino acids flanked by three amino acids on each side. is sufficient to transport protons. Four identical protein fragments, each folded into a helix, aggregate to form small channels spanning the membrane. Protons are conducted through a narrow pore in the middle of the channel in response to applied voltage. This

  3. SLC Transporters as Therapeutic Targets: Emerging Opportunities

    PubMed Central

    Lin, Lawrence; Yee, Sook Wah; Kim, Richard B.; Giacomini, Kathleen M.

    2015-01-01

    Solute carrier (SLC) transporters — a family of more than 300 membrane-bound proteins that facilitate the transport of a wide array of substrates across biological membranes — have important roles in physiological processes ranging from the cellular uptake of nutrients to the absorption of drugs and other xenobiotics. Several classes of marketed drugs target well-known SLC transporters, such as neurotransmitter transporters, and human genetic studies have provided powerful insight into the roles of more-recently characterized SLC transporters in both rare and common diseases, indicating a wealth of new therapeutic opportunities. This Review summarizes knowledge on the roles of SLC transporters in human disease, describes strategies to target such transporters, and highlights current and investigational drugs that modulate SLC transporters, as well as promising drug targets. PMID:26111766

  4. SLC transporters as therapeutic targets: emerging opportunities.

    PubMed

    Lin, Lawrence; Yee, Sook Wah; Kim, Richard B; Giacomini, Kathleen M

    2015-08-01

    Solute carrier (SLC) transporters - a family of more than 300 membrane-bound proteins that facilitate the transport of a wide array of substrates across biological membranes - have important roles in physiological processes ranging from the cellular uptake of nutrients to the absorption of drugs and other xenobiotics. Several classes of marketed drugs target well-known SLC transporters, such as neurotransmitter transporters, and human genetic studies have provided powerful insight into the roles of more-recently characterized SLC transporters in both rare and common diseases, indicating a wealth of new therapeutic opportunities. This Review summarizes knowledge on the roles of SLC transporters in human disease, describes strategies to target such transporters, and highlights current and investigational drugs that modulate SLC transporters, as well as promising drug targets.

  5. The Design of Transportation Equipment in Terms of Human Capabilities. The Role of Engineering Psychology in Transport Safety.

    ERIC Educational Resources Information Center

    McFarland, Ross A.

    Human factors engineering is considered with regard to the design of safety factors for aviation and highway transportation equipment. Current trends and problem areas are identified for jet air transportation and for highway transportation. Suggested solutions to transportation safety problems are developed by applying the techniques of human…

  6. Turbidity Current Head Mixing

    NASA Astrophysics Data System (ADS)

    Hernandez, David; Sanchez, Miguel Angel; Medina, Pablo

    2010-05-01

    A laboratory experimental set - up for studying the behaviour of sediment in presence of a turbulent field with zero mean flow is compared with the behaviour of turbidity currents [1] . Particular interest is shown on the initiation of sediment motion and in the sediment lift - off. The behaviour of the turbidity current in a flat ground is compared with the zero mean flow oscilating grid generated turbulence as when wave flow lifts off suspended sediments [2,3]. Some examples of the results obtained with this set-up relating the height of the head of the turbidity current to the equilibrium level of stirred lutoclines are shown. A turbulent velocity u' lower than that estimated by the Shield diagram is required to start sediment motion. The minimum u' required to start sediment lift - off, is a function of sediment size, cohesivity and resting time. The lutocline height depends on u', and the vorticity at the lutocline seems constant for a fixed sediment size [1,3]. Combining grid stirring and turbidty current head shapes analyzed by means of advanced image analysis, sediment vertical fluxes and settling speeds can be measured [4,5]. [1] D. Hernandez Turbulent structure of turbidity currents and sediment transport Ms Thesis ETSECCPB, UPC. Barcelona 2009. [2] A. Sánchez-Arcilla; A. Rodríguez; J.C. Santás; J.M. Redondo; V. Gracia; R. K'Osyan; S. Kuznetsov; C. Mösso. Delta'96 Surf-zone and nearshore measurements at the Ebro Delta. A: International Conference on Coastal Research through large Scale Experiments (Coastal Dynamics '97). University of Plymouth, 1997, p. 186-187. [3] P. Medina, M. A. Sánchez and J. M. Redondo. Grid stirred turbulence: applications to the initiation of sediment motion and lift-off studies Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere. 26, Issue 4, 2001, Pages 299-304 [4] M.O. Bezerra, M. Diez, C. Medeiros, A. Rodriguez, E. Bahia., A. Sanchez-Arcilla and J.M. Redondo. Study on the influence of waves on

  7. Mars Equipment Transport System

    NASA Technical Reports Server (NTRS)

    Sorrells, Cindy; Geiger, Michelle; Ohanlon, Sean; Pieloch, Stuart; Brogan, Nick

    1993-01-01

    Mechanical Engineering Senior Design Project 1 (ME4182) is a part of the NASA/University Advanced Design Program. Under this program, NASA allocates money and resources to students to be used in design work for a specified topic. The current topic is the exploration and colonization of Mars. The specific area in which we are to work is the transportation of the modules in which astronauts will live while on Mars. NASA is concerned about the weight of the module transferring system, as the shipping cost to Mars is quite expensive. NASA has specified that the weight of the system is to be minimized in order to reduce the shipping costs.

  8. Mars Equipment Transport System

    NASA Astrophysics Data System (ADS)

    Sorrells, Cindy; Geiger, Michelle; Ohanlon, Sean; Pieloch, Stuart; Brogan, Nick

    1993-12-01

    Mechanical Engineering Senior Design Project 1 (ME4182) is a part of the NASA/University Advanced Design Program. Under this program, NASA allocates money and resources to students to be used in design work for a specified topic. The current topic is the exploration and colonization of Mars. The specific area in which we are to work is the transportation of the modules in which astronauts will live while on Mars. NASA is concerned about the weight of the module transferring system, as the shipping cost to Mars is quite expensive. NASA has specified that the weight of the system is to be minimized in order to reduce the shipping costs.

  9. Combined tidal and wind driven flows and residual currents

    NASA Astrophysics Data System (ADS)

    Holmedal, Lars Erik; Wang, Hong

    2015-05-01

    The effect of a residual current on the combined tidal and wind driven flow and the resulting bedload sediment transport in the ocean has been investigated, using a simple one dimensional two-equation turbulence closure model. Predictions of the combined tidal and wind driven flow with given residual currents are presented, showing that the residual current has a substantial effect on both the depth averaged mass transport and the mean bedload transport directions; in some cases the effect of the residual current is to almost reverse the mean bedload transport direction. The residual current affects the rotation of the flow due to the Coriolis effect in the lower part of the water column (the near-surface flow is wind dominated), causing a larger or smaller clockwise rotation of the depth averaged mass transport, depending on the direction of the residual current.

  10. Functional Analysis of Arabidopsis Sucrose Transporters

    SciTech Connect

    John M. Ward

    2009-03-31

    Sucrose is the main photosynthetic product that is transported in the vasculature of plants. The long-distance transport of carbohydrates is required to support the growth and development of net-importing (sink) tissues such as fruit, seeds and roots. This project is focused on understanding the transport mechanism sucrose transporters (SUTs). These are proton-coupled sucrose uptake transporters (membrane proteins) that are required for transport of sucrose in the vasculature and uptake into sink tissues. The accomplishments of this project included: 1) the first analysis of substrate specificity for any SUT. This was accomplished using electrophysiology to analyze AtSUC2, a sucrose transporter from companion cells in Arabidopsis. 2) the first analysis of the transport activity for a monocot SUT. The transport kinetics and substrate specificity of HvSUT1 from barley were studied. 3) the first analysis of a sucrose transporter from sugarcane. and 4) the first analysis of transport activity of a sugar alcohol transporter homolog from plants, AtPLT5. During this period four primary research papers, funded directly by the project, were published in refereed journals. The characterization of several sucrose transporters was essential for the current effort in the analysis of structure/function for this gene family. In particular, the demonstration of strong differences in substrate specificity between type I and II SUTs was important to identify targets for site-directed mutagenesis.

  11. Superconducting fault current controller/current controller

    DOEpatents

    Cha, Yung S.

    2004-06-15

    A superconducting fault current controller/current controller employs a superconducting-shielded core reactor (SSCR) with a variable impedance in a secondary circuit to control current in a primary circuit such as an electrical distribution system. In a second embodiment, a variable current source is employed in a secondary circuit of an SSCR to control current in the primary circuit. In a third embodiment, both a variable impedance in one secondary circuit and a variable current source in a second circuit of an SSCR are employed for separate and independent control of current in the primary circuit.

  12. Currents in la jolla and scripps submarine canyons.

    PubMed

    Shepard, F P; Marshall, N F

    1969-07-11

    Velocities up to 34 centimeters per second have been recorded near the floors of submarine canyons off La Jolla, California. Currents move alternately down- and upcanyon with variable periods. All 3- to 6-day measurements show net current transport downcanyon. Many of the downcanyon currents of higher velocity correlate with ebbing tides, as measured at the nearby pier. Other factors producing the currents probably include internal waves. Velocities are sufficient to transport large quantities of fine sand. PMID:17834739

  13. Currents in la jolla and scripps submarine canyons.

    PubMed

    Shepard, F P; Marshall, N F

    1969-07-11

    Velocities up to 34 centimeters per second have been recorded near the floors of submarine canyons off La Jolla, California. Currents move alternately down- and upcanyon with variable periods. All 3- to 6-day measurements show net current transport downcanyon. Many of the downcanyon currents of higher velocity correlate with ebbing tides, as measured at the nearby pier. Other factors producing the currents probably include internal waves. Velocities are sufficient to transport large quantities of fine sand.

  14. Transporters in plant sulfur metabolism

    PubMed Central

    Gigolashvili, Tamara; Kopriva, Stanislav

    2014-01-01

    Sulfur is an essential nutrient, necessary for synthesis of many metabolites. The uptake of sulfate, primary and secondary assimilation, the biosynthesis, storage, and final utilization of sulfur (S) containing compounds requires a lot of movement between organs, cells, and organelles. Efficient transport systems of S-containing compounds across the internal barriers or the plasma membrane and organellar membranes are therefore required. Here, we review a current state of knowledge of the transport of a range of S-containing metabolites within and between the cells as well as of their long distance transport. An improved understanding of mechanisms and regulation of transport will facilitate successful engineering of the respective pathways, to improve the plant yield, biotic interaction and nutritional properties of crops. PMID:25250037

  15. Technology for Transportation Safety

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Boston Insulated Wire & Cable developed a new polyimide foam material, commercially known as Solimide, which resists ignition. It chars and decomposes when exposed to open flames. Used in the space shuttle, the material does not "outgas" until it begins to char making it safer than current materials with respect to toxic fumes. The polyimide can be made in two forms: a resilient foam and a rigid foam. Used in commercial transport interiors for such soft components as seat cushions to door, wall, floor, and ceiling panels. Material's flame resistance could lengthen from two minutes to five minutes, the time needed for passenger evacuation in a ground emergency. Could help reduce airline fuel consumption, since the foam is 50% lighter than current materials. Low-smoke cable assemblies used in rapid transit systems consists of an advanced wire and cable jacketing material with superior flame resistance and smoke retardation characteristics. Being supplied to mass transit systems in the U.S. and abroad.

  16. Surety applications in transportation

    SciTech Connect

    Matalucci, R.V.; Miyoshi, D.S.

    1998-01-01

    Infrastructure surety can make a valuable contribution to the transportation engineering industry. The lessons learned at Sandia National Laboratories in developing surety principles and technologies for the nuclear weapons complex and the nuclear power industry hold direct applications to the safety, security, and reliability of the critical infrastructure. This presentation introduces the concepts of infrastructure surety, including identification of the normal, abnormal, and malevolent threats to the transportation infrastructure. National problems are identified and examples of failures and successes in response to environmental loads and other structural and systemic vulnerabilities are presented. The infrastructure surety principles developed at Sandia National Laboratories are described. Currently available technologies including (a) three-dimensional computer-assisted drawing packages interactively combined with virtual reality systems, (b) the complex calculational and computational modeling and code-coupling capabilities associated with the new generation of supercomputers, and (c) risk-management methodologies with application to solving the national problems associated with threats to the critical transportation infrastructure are discussed.

  17. Experimental Tests Of Paleoclassical Transport

    SciTech Connect

    Callen, J D; Anderson, J K; Arlen, T C; Bateman, G; Budny, R V; Fujita, T; Greenfield, C M; Greenwald, M; Groebner, R J; Hill, D N; Hogeweij, G D; Kaye, S M; Kritz, A H; Lazarus, E A; Leonard, A C; Mahdavi, M A; McLean, H S; Osborne, T H; Pankin, A Y; Petty, C C; Sarff, J S; St. John, H E; Stacey, W M; Stutman, D; Synakowski, E J; Tritz, K

    2006-09-12

    Predictions of the recently developed paleoclassical transport model are compared with data from many toroidal plasma experiments: electron heat diffusivity in DIII-D, C-Mod and NSTX ohmic and near-ohmic plasmas; transport modeling of DIII-D ohmic-level discharges and of the RTP ECH 'stair-step' experiments with eITBs at low order rational surfaces; investigation of a strong eITB in JT-60U; H-mode Te edge pedestal properties in DIII-D; and electron heat diffusivities in non-tokamak experiments (NSTX/ST, MST/RFP, SSPX/spheromak). The radial electron heat transport predicted by the paleoclassical model is found to agree with a wide variety of ohmic-level experimental results and to set the lower limit (within a factor {approx} 2) for the radial electron heat transport in most resistive, current-carrying toroidal plasmas -- unless it is exceeded by fluctuation-induced transport, which often occurs in the edge of L-mode plasmas and when the electron temperature is high ({approx}>T{sub e}{sup crit} {approx}B{sup 2/3}{bar {alpha}}{sup 1/2} keV) because then paleoclassical transport becomes less than gyro-Bohm-level anomalous transport.

  18. Activated transport in AMTEC electrodes

    NASA Astrophysics Data System (ADS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; Oconnor, D.; Kikkert, S.

    1992-08-01

    Transport of alkali metal atoms through porous cathodes of alkali metal thermal-to-electric converter (AMTEC) cells is responsible for significant, reducible losses in the electrical performance of these cells. Experimental evidence for activated transport of metal atoms at grain surfaces and boundaries within some AMTEC electrodes has been derived from temperature dependent studies as well as from analysis of the detailed frequency dependence of ac impedance results for other electrodes, including thin, mature molybdenum electrodes which exhibit transport dominated by free molecular flow of sodium gas at low frequencies or dc conditions. Activated surface transport will almost always exist in parallel with free molecular flow transport, and the process of alkali atom adsorption/desorption from the electrode surface will invariably be part of the transport process, and possibly a dominant part in some cases. Little can be learned about the detailed mass transport process from the ac impedance or current voltage curves of an electrode at one set of operating parameters, because the transport process includes a number of important physical parameters that are not all uniquely determined by one experiment. The temperature dependence of the diffusion coefficient of the alkali metal through the electrode in several cases provides an activation energy and pre-exponential, but at least two activated processes may be operative, and the activation parameters should be expected to depend on the alkali metal activity gradient that the electrode experiences. In the case of Pt/W/Mn electrodes operated for 2500 hours, limiting currents varied with electrode thickness, and the activation parameters could be assigned primarily to the surface/grain boundary diffusion process.

  19. Effect of nanosized Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} on the transport critical current density of Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} superconductor

    SciTech Connect

    Hafiz, M.; Abd-Shukor, R.

    2014-09-03

    The effects of nano-sized Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} addition on the superconducting and transport properties of Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} (Bi-2223) in bulk form has been investigated. Bi-2223 superconductor was fabricated using co-precipitation method and 0.01 – 0.05 wt% of Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} nanoparticles with average size of 20 nm were added into the samples. The critical temperature (T{sub c}) and critical current density (J{sub c}) of the samples were measured by using the four-point probe method, while the phase formation and microstructure of the samples were examined using x-ray diffraction and SEM respectively. It was found that J{sub c} of all samples added with Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} were higher than non-added sample, with x = 0.01 wt. % sample showing the highest J{sub c}. This study showed that small addition of nano-Co{sub 0.5}Ni{sub 0.5}Fe{sub 2}O{sub 4} can effectively enhance the transport critical current density in Bi-2223 superconductor.

  20. ELECTROCHEMICAL POWER FOR TRANSPORTATION

    SciTech Connect

    Cairns, Elton J.; Hietbrink, Earl H.

    1981-01-01

    This section includes some historical background of the rise and fall and subsequent rebirth of the electric vehicle; and a brief discussion of current transportation needs, and environmental and energy utilization issues that resulted in the renewed interest in applying electrochemical energy conversion technology to electric vehicle applications. Although energy utilization has evolved to be the most significant and important issue, the environmental issue will be discussed first in this section only because of its chronological occurrence. The next part of the chapter is a review of passenger and commercial electric vehicle technology with emphasis on vehicle design and demonstrated performance of vehicles with candidate power sources being developed. This is followed by a discussion of electrochemical power source requirements associated with future electric vehicles that can play a role in meeting modern transportation needs. The last part of the chapter includes first a discussion of how to identify candidate electrochemical systems that might be of interest in meeting electric vehicle power source requirements. This is then followed by a review of the current technological status of these systems and a discussion of the most significant problems that must be resolved before each candidate system can be a viable power source.

  1. Robotic transportation.

    PubMed

    Lob, W S

    1990-09-01

    Mobile robots perform fetch-and-carry tasks autonomously. An intelligent, sensor-equipped mobile robot does not require dedicated pathways or extensive facility modification. In the hospital, mobile robots can be used to carry specimens, pharmaceuticals, meals, etc. between supply centers, patient areas, and laboratories. The HelpMate (Transitions Research Corp.) mobile robot was developed specifically for hospital environments. To reach a desired destination, Help-Mate navigates with an on-board computer that continuously polls a suite of sensors, matches the sensor data against a pre-programmed map of the environment, and issues drive commands and path corrections. A sender operates the robot with a user-friendly menu that prompts for payload insertion and desired destination(s). Upon arrival at its selected destination, the robot prompts the recipient for a security code or physical key and awaits acknowledgement of payload removal. In the future, the integration of HelpMate with robot manipulators, test equipment, and central institutional information systems will open new applications in more localized areas and should help overcome difficulties in filling transport staff positions.

  2. Robotic transportation.

    PubMed

    Lob, W S

    1990-09-01

    Mobile robots perform fetch-and-carry tasks autonomously. An intelligent, sensor-equipped mobile robot does not require dedicated pathways or extensive facility modification. In the hospital, mobile robots can be used to carry specimens, pharmaceuticals, meals, etc. between supply centers, patient areas, and laboratories. The HelpMate (Transitions Research Corp.) mobile robot was developed specifically for hospital environments. To reach a desired destination, Help-Mate navigates with an on-board computer that continuously polls a suite of sensors, matches the sensor data against a pre-programmed map of the environment, and issues drive commands and path corrections. A sender operates the robot with a user-friendly menu that prompts for payload insertion and desired destination(s). Upon arrival at its selected destination, the robot prompts the recipient for a security code or physical key and awaits acknowledgement of payload removal. In the future, the integration of HelpMate with robot manipulators, test equipment, and central institutional information systems will open new applications in more localized areas and should help overcome difficulties in filling transport staff positions. PMID:2208684

  3. ADVANCED CUTTINGS TRANSPORT STUDY

    SciTech Connect

    Ergun Kuru; Stefan Miska; Nicholas Takach; Kaveh Ashenayi; Gerald Kane; Mark Pickell; Len Volk; Mike Volk; Barkim Demirdal; Affonso Lourenco; Evren Ozbayoglu; Paco Vieira; Neelima Godugu

    2000-07-30

    ACTS flow loop is now operational under elevated pressure and temperature. Currently, experiments with synthetic based drilling fluids under pressure and temperature are being conducted. Based on the analysis of Fann 70 data, empirical correlations defining the shear stress as a function of temperature, pressure and the shear rate have been developed for Petrobras synthetic drilling fluids. PVT equipment has been modified for testing Synthetic oil base drilling fluids. PVT tests with Petrobras Synthetic base mud have been conducted and results are being analyzed Foam flow experiments have been conducted and the analysis of the data has been carried out to characterize the rheology of the foam. Comparison of pressure loss prediction from the available foam hydraulic models and the test results has been made. Cuttings transport experiments in horizontal annulus section have been conducted using air, water and cuttings. Currently, cuttings transport tests in inclined test section are being conducted. Foam PVT analysis tests have been conducted. Foam stability experiments have also been conducted. Effects of salt and oil concentration on the foam stability have been investigated. Design of ACTS flow loop modification for foam and aerated mud flow has been completed. A flow loop operation procedure for conducting foam flow experiments under EPET conditions has been prepared Design of the lab-scale flow loop for dynamic foam characterization and cuttings monitoring instrumentation tests has been completed. The construction of the test loop is underway. As part of the technology transport efforts, Advisory Board Meeting with ACTS-JIP industry members has been organized on May 13, 2000.

  4. Transporting particulate material

    DOEpatents

    Aldred, Derek Leslie; Rader, Jeffrey A.; Saunders, Timothy W.

    2011-08-30

    A material transporting system comprises a material transporting apparatus (100) including a material transporting apparatus hopper structure (200, 202), which comprises at least one rotary transporting apparatus; a stationary hub structure (900) constraining and assisting the at least one rotary transporting apparatus; an outlet duct configuration (700) configured to permit material to exit therefrom and comprising at least one diverging portion (702, 702'); an outlet abutment configuration (800) configured to direct material to the outlet duct configuration; an outlet valve assembly from the material transporting system venting the material transporting system; and a moving wall configuration in the material transporting apparatus capable of assisting the material transporting apparatus in transporting material in the material transporting system. Material can be moved from the material transporting apparatus hopper structure to the outlet duct configuration through the at least one rotary transporting apparatus, the outlet abutment configuration, and the outlet valve assembly.

  5. Auxin transport during root gravitropism: transporters and techniques.

    PubMed

    Geisler, M; Wang, B; Zhu, J

    2014-01-01

    Root gravitropism is a complex, plant-specific process allowing roots to grow downward into the soil. Polar auxin transport and redistribution are essential for root gravitropism. Here we summarise our current understanding of underlying molecular mechanisms and involved transporters that establish, maintain and redirect intercellular auxin gradients as the driving force for root gravitropism. We evaluate the genetic, biochemical and cell biological approaches presently used for the analysis of auxin redistribution and the quantification of auxin fluxes. Finally, we also discuss new tools that provide a higher spatial or temporal resolution and our technical needs for future gravitropism studies.

  6. Transport processes of the legume symbiosome membrane

    PubMed Central

    Clarke, Victoria C.; Loughlin, Patrick C.; Day, David A.; Smith, Penelope M. C.

    2014-01-01

    The symbiosome membrane (SM) is a physical barrier between the host plant and nitrogen-fixing bacteria in the legume:rhizobia symbiosis, and represents a regulated interface for the movement of solutes between the symbionts that is under plant control. The primary nutrient exchange across the SM is the transport of a carbon energy source from plant to bacteroid in exchange for fixed nitrogen. At a biochemical level two channels have been implicated in movement of fixed nitrogen across the SM and a uniporter that transports monovalent dicarboxylate ions has been characterized that would transport fixed carbon. The aquaporin NOD26 may provide a channel for ammonia, but the genes encoding the other transporters have not been identified. Transport of several other solutes, including calcium and potassium, have been demonstrated in isolated symbiosomes, and genes encoding transport systems for the movement of iron, nitrate, sulfate, and zinc in nodules have been identified. However, definitively matching transport activities with these genes has proved difficult and many further transport processes are expected on the SM to facilitate the movement of nutrients between the symbionts. Recently, work detailing the SM proteome in soybean has been completed, contributing significantly to the database of known SM proteins. This represents a valuable resource for the identification of transporter protein candidates, some of which may correspond to transport processes previously described, or to novel transport systems in the symbiosis. Putative transporters identified from the proteome include homologs of transporters of sulfate, calcium, peptides, and various metal ions. Here we review current knowledge of transport processes of the SM and discuss the requirements for additional transport routes of other nutrients exchanged in the symbiosis, with a focus on transport systems identified through the soybean SM proteome. PMID:25566274

  7. Overview of TFTR transport studies

    SciTech Connect

    Hawryluk, R.J.; Arunasalam, V.; Beer, M.; Bell, M.; Bell, R.; Biglari, H.; Bitter, M.; Boivin, R.; Bretz, N.L.; Budny, R.; Cheng, C.Z.; Chu, T.K.; Cohen, S.A.; Cowley, S.; Efthimion, P.C.; Fredrickson, E.; Furth, H.P.; Goldston, R.J.; Greene, G.; Grek, B.; Grisham, L.R.; Hammett, G.; Hill, K.W.; Hosea, J.; Hulse, R.A.; Hsuan, H.; Janos, A.; Jassby, D.; Jobes, F.C.; Johnson, D.W.; Johnson, L.C.; Kieras-Phillips, C.; Kilpatrick, S

    1991-10-01

    A review of TFTR plasma transport studies is presented. Parallel transport and the confinement of suprathermal ions are found to be relatively well described by theory. Cross-field transport of the thermal plasma, however, is anomalous with the momentum diffusivity being comparable to the ion thermal diffusivity and larger than the electron thermal diffusivity in neutral beam heated discharges. Perturbative experiments have studied non-linear dependencies in the transport coefficients and examined the role of possible non-local phenomena. The underlying turbulence has been studied using microwave scattering, beam emission spectroscopy and microwave reflectometry over a much broader range in k{perpendicular} than previously possible. Results indicate the existence of large-wavelength fluctuations correlated with enhanced transport. MHD instabilities set important operational constraints. However, by modifying the current profile using current ramp-down techniques, it has been possible to extend the operating regime to higher values of both {var epsilon}{beta}{sub p} and normalized {beta}{sub T}. In addition, the interaction of MHD fluctuations with fast ions, of potential relevance to {alpha}-particle confinement in D-T plasmas, has been investigated. The installation of carbon-carbon composite tiles and improvements in wall conditioning, in particular the use of Li pellet injection to reduce the carbon recycling, continue to be important in the improvement of plasma performance. 96 refs., 16 figs.

  8. Transporting Handicapped Students.

    ERIC Educational Resources Information Center

    Turner, Dayton Ray

    The book presents guidelines for adaptive transportation measures for handicapped students. Part 1 considers the transportation cycle as a means to evaluate individual student competencies at all logical points during the transportation experience. The transportation cycle is reviewed from deciding to transport the student to gaining access to…

  9. Spheromak Impedance and Current Amplification

    SciTech Connect

    Fowler, T K; Hua, D D; Stallard, B W

    2002-01-31

    It is shown that high current amplification can be achieved only by injecting helicity on the timescale for reconnection, {tau}{sub REC}, which determines the effective impedance of the spheromak. An approximate equation for current amplification is: dI{sub TOR}{sup 2}/dt {approx} I{sup 2}/{tau}{sub REC} - I{sub TOR}{sup 2}/{tau}{sub closed} where I is the gun current, I{sub TOR} is the spheromak toroidal current and {tau}{sub CLOSED} is the ohmic decay time of the spheromak. Achieving high current amplification, I{sub TOR} >> I, requires {tau}{sub REC} <<{tau}{sub CLOSED}. For resistive reconnection, this requires reconnection in a cold zone feeding helicity into a hot zone. Here we propose an impedance model based on these ideas in a form that can be implemented in the Corsica-based helicity transport code. The most important feature of the model is the possibility that {tau}{sub REC} actually increases as the spheromak temperature increases, perhaps accounting for the ''voltage sag'' observed in some experiments, and a tendency toward a constant ratio of field to current, B {proportional_to} I, or I{sub TOR} {approx} I. Program implications are discussed.

  10. Transport equations in tokamak plasmas

    SciTech Connect

    Callen, J. D.; Hegna, C. C.; Cole, A. J.

    2010-05-15

    Tokamak plasma transport equations are usually obtained by flux surface averaging the collisional Braginskii equations. However, tokamak plasmas are not in collisional regimes. Also, ad hoc terms are added for neoclassical effects on the parallel Ohm's law, fluctuation-induced transport, heating, current-drive and flow sources and sinks, small magnetic field nonaxisymmetries, magnetic field transients, etc. A set of self-consistent second order in gyroradius fluid-moment-based transport equations for nearly axisymmetric tokamak plasmas has been developed using a kinetic-based approach. The derivation uses neoclassical-based parallel viscous force closures, and includes all the effects noted above. Plasma processes on successive time scales and constraints they impose are considered sequentially: compressional Alfven waves (Grad-Shafranov equilibrium, ion radial force balance), sound waves (pressure constant along field lines, incompressible flows within a flux surface), and collisions (electrons, parallel Ohm's law; ions, damping of poloidal flow). Radial particle fluxes are driven by the many second order in gyroradius toroidal angular torques on a plasma species: seven ambipolar collision-based ones (classical, neoclassical, etc.) and eight nonambipolar ones (fluctuation-induced, polarization flows from toroidal rotation transients, etc.). The plasma toroidal rotation equation results from setting to zero the net radial current induced by the nonambipolar fluxes. The radial particle flux consists of the collision-based intrinsically ambipolar fluxes plus the nonambipolar fluxes evaluated at the ambipolarity-enforcing toroidal plasma rotation (radial electric field). The energy transport equations do not involve an ambipolar constraint and hence are more directly obtained. The 'mean field' effects of microturbulence on the parallel Ohm's law, poloidal ion flow, particle fluxes, and toroidal momentum and energy transport are all included self-consistently. The

  11. Transportation technology program: Strategic plan

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The purpose of this report is to define the technology program required to meet the transportation technology needs for current and future civil space missions. It is a part of an integrated plan, prepared by NASA in part in response to the Augustine Committee recommendations, to describe and advocate expanded and more aggressive efforts in the development of advanced space technologies. This expanded program will provide a technology basis for future space missions to which the U.S. aspires, and will help to regain technology leadership for the U.S. on a broader front. The six aspects of this integrated program/plan deal with focused technologies to support space sciences, exploration, transportation, platforms, and operations as well as provide a Research and Technology Base Program. This volume describes the technologies needed to support transportation systems, e.g., technologies needed for upgrades to current transportation systems and to provide reliable and efficient transportation for future space missions. The Office of Aeronautics, Exploration, and Technology (OAET) solicited technology needs from the major agency technology users and the aerospace industry community and formed a transportation technology team (appendix A) to develop a technology program to respond to those needs related to transportation technologies. This report addresses the results of that team activity. It is a strategic plan intended for use as a planning document rather than as a project management tool. It is anticipated that this document will be primarily utilized by research & technology (R&T) management at the various NASA Centers as well as by officials at NASA Headquarters and by industry in planning their corporate Independent Research and Development (IR&D) investments.

  12. Transport equations in tokamak plasmasa)

    NASA Astrophysics Data System (ADS)

    Callen, J. D.; Hegna, C. C.; Cole, A. J.

    2010-05-01

    Tokamak plasma transport equations are usually obtained by flux surface averaging the collisional Braginskii equations. However, tokamak plasmas are not in collisional regimes. Also, ad hoc terms are added for neoclassical effects on the parallel Ohm's law, fluctuation-induced transport, heating, current-drive and flow sources and sinks, small magnetic field nonaxisymmetries, magnetic field transients, etc. A set of self-consistent second order in gyroradius fluid-moment-based transport equations for nearly axisymmetric tokamak plasmas has been developed using a kinetic-based approach. The derivation uses neoclassical-based parallel viscous force closures, and includes all the effects noted above. Plasma processes on successive time scales and constraints they impose are considered sequentially: compressional Alfvén waves (Grad-Shafranov equilibrium, ion radial force balance), sound waves (pressure constant along field lines, incompressible flows within a flux surface), and collisions (electrons, parallel Ohm's law; ions, damping of poloidal flow). Radial particle fluxes are driven by the many second order in gyroradius toroidal angular torques on a plasma species: seven ambipolar collision-based ones (classical, neoclassical, etc.) and eight nonambipolar ones (fluctuation-induced, polarization flows from toroidal rotation transients, etc.). The plasma toroidal rotation equation results from setting to zero the net radial current induced by the nonambipolar fluxes. The radial particle flux consists of the collision-based intrinsically ambipolar fluxes plus the nonambipolar fluxes evaluated at the ambipolarity-enforcing toroidal plasma rotation (radial electric field). The energy transport equations do not involve an ambipolar constraint and hence are more directly obtained. The "mean field" effects of microturbulence on the parallel Ohm's law, poloidal ion flow, particle fluxes, and toroidal momentum and energy transport are all included self-consistently. The

  13. Enhancement in the transport critical current density J{sub c} in YBa{sub 2}Cu{sub 3}O{sub 7−δ} added with an insulating nano crystalline YBa{sub 2}HfO{sub 5.5} perovskite

    SciTech Connect

    Rejith, P. P.; Vidya, S.; Thomas, J. K.; Solomon, Sam

    2014-01-28

    When a magnetic field is applied to type II superconductors, such as YBa{sub 2}Cu{sub 3}0{sub 7−δ} (YBCO), the flux quanta penetrate the material as a regular array of vortices. However when transport currents are applied, they act to move these vortices, thus lowers the critical current density (J{sub c}) as well as destroying superconductivity. The development of microstructures made of YBCO materials has enabled engineers to increase the critical current density, within Type II materials by introducing flux pinning centres into the material. The microstructure and flux pinning properties of YBa{sub 2}Cu{sub 3}O{sub 7−δ} system with varying levels (0-5 wt. %) of a nano perovskite ceramic insulator; YBa{sub 2}HfO{sub 5.5} addition was studied in detail. Orthorhombic YBa{sub 2}Cu{sub 3}O{sub 7−δ} powder was prepared through conventional solid state route and a modified combustion method was used for synthesizing nanocrystalline YBa{sub 2}HfO{sub 5.5}. The structure and microstructure of the samples examined by X-ray diffraction and scanning electron microscopy showed that YBa{sub 2}HfO{sub 5.5} and YBCO remained unreacted even at higher processing temperature without deteriorating the superconducting properties. The scanning electron microscope image shows that YBa{sub 2}HfO{sub 5.5} forms an electrical-network between grains. These observations suggest that the YBa{sub 2}HfO{sub 5.5} addition to the Y-123-compounds improve the electrical connection between superconducting grains and substantial improvements in the relative electrical transport properties of the composites. The variation of sintering temperature, density, critical transition temperature (T{sub c}) and magnetic field dependence of critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}O{sub 7−δ} having different proportions of YBa{sub 2}HfO{sub 5.5} in the matrix were also studied in detail. It is found that the addition of these elements considerably enhances the flux pinning

  14. Polyamines alter intestinal glucose transport.

    PubMed

    Johnson, L R; Brockway, P D; Madsen, K; Hardin, J A; Gall, D G

    1995-03-01

    Polyamines are required for the growth of all eukaryotic cells. Enterocytes respond to luminal nutrients with large increases in polyamine synthesis, even though they are mature, nonproliferating cells. The role of polyamines in these cells is unknown. The current experiments examined whether polyamines affected intestinal transport of glucose, since absorption is the primary activity of enterocytes and since polyamines are known to affect membrane function and stability. Glucose transport was examined in rabbit brush-border membrane vesicles (BBMV). BBMV from rabbits given 5% alpha-difluoromethylornithine (DFMO) in their drinking water 24 h before they were killed transported significantly less glucose than control vesicles [38% decrease in maximal transport rate (Jmax)]. Orogastric administration of spermine, spermidine, or putrescine to DFMO-treated animals 24 h before they were killed prevented the decrease. In rabbits receiving only orogastric spermine, glucose transport was significantly increased (64% increase in Jmax), whereas in vivo spermidine and putrescine decreased Jmax. This increase in Jmax caused by in vivo administration of spermine was not dependent on protein synthesis. Addition of polyamines whether in vivo or in vitro decreased Michaelis constant in vesicles from control and DFMO-treated animals. The change in glucose transport induced by DFMO or polyamines was not related to altered membrane lipid composition or fluidity.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Membrane transporters in drug development

    PubMed Central

    2011-01-01

    Membrane transporters can be major determinants of the pharmacokinetic, safety and efficacy profiles of drugs. This presents several key questions for drug development, including which transporters are clinically important in drug absorption and disposition, and which in vitro methods are suitable for studying drug interactions with these transporters. In addition, what criteria should trigger follow-up clinical studies, and which clinical studies should be conducted if needed. In this article, we provide the recommendations of the International Transporter Consortium on these issues, and present decision trees that are intended to help guide clinical studies on the currently recognized most important drug transporter interactions. The recommendations are generally intended to support clinical development and filing of a new drug application. Overall, it is advised that the timing of transporter investigations should be driven by efficacy, safety and clinical trial enrolment questions (for example, exclusion and inclusion criteria), as well as a need for further understanding of the absorption, distribution, metabolism and excretion properties of the drug molecule, and information required for drug labeling. PMID:20190787

  16. Transportation of Hazardous Evidentiary Material.

    SciTech Connect

    Osborn, Douglas.

    2005-06-01

    This document describes the specimen and transportation containers currently available for use with hazardous and infectious materials. A detailed comparison of advantages, disadvantages, and costs of the different technologies is included. Short- and long-term recommendations are also provided.3 DraftDraftDraftExecutive SummaryThe Federal Bureau of Investigation's Hazardous Materials Response Unit currently has hazardous material transport containers for shipping 1-quart paint cans and small amounts of contaminated forensic evidence, but the containers may not be able to maintain their integrity under accident conditions or for some types of hazardous materials. This report provides guidance and recommendations on the availability of packages for the safe and secure transport of evidence consisting of or contaminated with hazardous chemicals or infectious materials. Only non-bulk containers were considered because these are appropriate for transport on small aircraft. This report will addresses packaging and transportation concerns for Hazardous Classes 3, 4, 5, 6, 8, and 9 materials. If the evidence is known or suspected of belonging to one of these Hazardous Classes, it must be packaged in accordance with the provisions of 49 CFR Part 173. The anthrax scare of several years ago, and less well publicized incidents involving unknown and uncharacterized substances, has required that suspicious substances be sent to appropriate analytical laboratories for analysis and characterization. Transportation of potentially hazardous or infectious material to an appropriate analytical laboratory requires transport containers that maintain both the biological and chemical integrity of the substance in question. As a rule, only relatively small quantities will be available for analysis. Appropriate transportation packaging is needed that will maintain the integrity of the substance, will not allow biological alteration, will not react chemically with the substance being

  17. Fluctuation of heat current in Josephson junctions

    SciTech Connect

    Virtanen, P.; Giazotto, F.

    2015-02-15

    We discuss the statistics of heat current between two superconductors at different temperatures connected by a generic weak link. As the electronic heat in superconductors is carried by Bogoliubov quasiparticles, the heat transport fluctuations follow the Levitov–Lesovik relation. We identify the energy-dependent quasiparticle transmission probabilities and discuss the resulting probability density and fluctuation relations of the heat current. We consider multichannel junctions, and find that heat transport in diffusive junctions is unique in that its statistics is independent of the phase difference between the superconductors.

  18. Transportation studies in progress by mode, 1992

    SciTech Connect

    Not Available

    1992-11-01

    The purpose of this document is to identify and summarize, in one document, current transportation studies in Washington State. It is focused primarily on studies of statewide significance, although regional model studies pertaining to current planning issues with statewide transferability are also included. In addition, the studies in this document are policy oriented. Numerous technical studies are ongoing and not identified here. An example would be the many high occupancy vehicle (HOV) regional studies which are a result of the emphasis on high capacity planning. To locate technical or regional studies, contact Washington State Department of Transportation (WSDOT) regional offices or the Washington Transportation Center (TRAC).

  19. Hypersonic transports - Economics and environmental effects.

    NASA Technical Reports Server (NTRS)

    Petersen, R. H.; Waters, M. H.

    1972-01-01

    An economic analysis of hypersonic transports is presented to show projected operating costs (direct and indirect) and return on investment. Important assumptions are varied to determine the probable range of values for operating costs and return on investment. The environmental effects of hypersonic transports are discussed and compared to current supersonic transports. Estimates of sideline and flyover noise are made for a typical hypersonic transport, and the sonic boom problem is analyzed and discussed. Since the exhaust products from liquid hydrogen-fueled engines differ from those of kerosene-fueled aircraft, a qualitative assessment of air pollution effects is made.

  20. Hypersonic transports - Economics and environmental effects.

    NASA Technical Reports Server (NTRS)

    Petersen, R. H.; Waters, M. H.

    1973-01-01

    An economic analysis of hypersonic transports is presented to show projected operating costs (direct and indirect) and return on investment. Important assumptions are varied to determine the probable range of values for operating costs and return on investment. The environmental effects of hypersonic transports are discussed and compared to current supersonic transports. Estimates of sideline and flyover noise are made for a typical hypersonic transport, and the sonic boom problem is analyzed and discussed. Since the exhaust products from liquid hydrogen-fueled engines differ from those of kerosene-fueled aircraft, a qualitative assessment of air pollution effects is made.

  1. Hypersonic transports: Economics and environmental effects

    NASA Technical Reports Server (NTRS)

    Petersen, R. H.; Waters, M. H.

    1972-01-01

    An economic analysis of hypersonic transports is presented to show projected operating costs (direct and indirect) and return on investment. Important assumptions are varied to determine the probable range of values for operating costs and return on investment. The environmental effects of hypersonic transports are discussed and compared to current supersonic transports. Estimates of sideline and fly-over noise are made for a typical hypersonic transport, and the sonic boom problem is analyzed and discussed. Since the exhaust products from liquid hydrogen-fueled engines differ from those of kerosene-fueled aircraft, a qualitative assessment of air pollution effects is made.

  2. Solenoid transport for heavy ion fusion

    SciTech Connect

    Lee, Edward

    2004-06-15

    Solenoid transport of high current, heavy ion beams is considered for several stages of a heavy ion fusion driver. In general this option is more efficient than magnetic quadrupole transport at sufficiently low kinetic energy and/or large e/m, and for this reason it has been employed in electron induction linacs. Ideally an ion beam would be transported in a state of Brillouin flow, i.e. cold in the transverse plane and spinning at one half the cyclotron frequency. The design of appropriate solenoids and the equilibrium and stability of transported ion beams are discussed. An outline of application to a fusion driver is also presented.

  3. Community rotorcraft air transportation benefits and opportunities

    NASA Technical Reports Server (NTRS)

    Gilbert, G. A.; Freund, D. J.; Winick, R. M.; Cafarelli, N. J.; Hodgkins, R. F.; Vickers, T. K.

    1981-01-01

    Information about rotorcraft that will assist community planners in assessing and planning for the use of rotorcraft transportation in their communities is provided. Information useful to helicopter researchers, manufacturers, and operators concerning helicopter opportunities and benefits is also given. Three primary topics are discussed: the current status and future projections of rotorcraft technology, and the comparison of that technology with other transportation vehicles; the community benefits of promising rotorcraft transportation opportunities; and the integration and interfacing considerations between rotorcraft and other transportation vehicles. Helicopter applications in a number of business and public service fields are examined in various geographical settings.

  4. Structural interaction with transportation and handling systems

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Problems involved in the handling and transportation of finished space vehicles from the factory to the launch site are presented, in addition to recommendations for properly accounting for in space vehicle structural design, adverse interactions during transportation. Emphasis is given to the protection of vehicle structures against those environments and loads encountered during transportation (including temporary storage) which would exceed the levels that the vehicle can safely withstand. Current practices for verifying vehicle safety are appraised, and some of the capabilities and limitations of transportation and handling systems are summarized.

  5. Asymptotic current-voltage relations for currents exceeding the diffusion limit

    NASA Astrophysics Data System (ADS)

    Yariv, Ehud

    2009-11-01

    We consider the one-dimensional transport of ions into a perm-selective solid. Direct attempts to evaluate the current-voltage characteristics for currents exceeding the diffusion limit are frustrated by the appearance of nonconverging integrals. We describe how to overcome this obstacle using a regularization scheme.

  6. Magnetic imaging of superconducting tapes to determine current flow

    SciTech Connect

    Brown, G. W.; Hawley, M. E.; Foltyn, S. R.; Mueller, F. M.

    2001-01-01

    We have developed a magnetic imaging system that uses magnetoresistive read heads from computer hard disk drives to map the transport-current-induced magnetic field at the surface of superconducting tapes at liquid nitrogen temperature. Transport current pathways are determined from the 2-dimensional magnetic field maps using established inversion schemes. We examined the current flow in pulsed-laser-deposited YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} a films patterned on single crystal SrTiO{sub 3} substrates and on a textured yttria-stabilized-zirconia layer deposited on an Inconel ribbon by ion beam assisted deposition. The transport current densities in all cases were consistent with the Critical State Model. For the Inconel-based sample, the transport current density maps have allowed us to observe defects and determine the region that limits the current carrying capacity of the structure.

  7. ADVANCED CUTTINGS TRANSPORT STUDY

    SciTech Connect

    Ergun Kuru; Stefan Miska; Nicholas Takach; Kaveh Ashenayi; Gerald Kane; Len Volk; Mark Pickell; Mike Volk; Barkim Demirdal; Affonso Lourenco; Evren Ozbayoglu; Paco Vieira; Neelima Godugu; Sri Suresh Kumar Thiroveedhula

    2000-04-30

    ACTS flow loop is now operational under elevated pressure and temperature. Currently, experiments with water under pressure and temperature are being conducted. Based on the analysis of Fann 70 data, empirical correlations defining the shear stress as a function of temperature, pressure and the shear rate have been developed for Petrobras synthetic drilling fluids. PVT equipment has been modified for testing Synthetic drilling fluids. Initial calibration tests have been conducted by using water. Currently, the base oil of the Petrobras synthetic drilling fluid is being tested. Foam flow experiments have been conducted. Currently, more experiments are being conducted while data are being analyzed to characterize the rheology of the foam. Cuttings transport experiments have been conducted using air, water and cuttings. Preliminary results have shown that it may not be possible to avoid cuttings bed deposition under any practical combination of air and water flow rates. Foam stability analyses have been conducted. Effects of salt and oil concentration on the foam stability have been investigated. A software for controlling the data sampling and data storage during cuttings monitoring process have been developed.

  8. Chamber transport for heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Olson, Craig L.

    2014-01-01

    A brief review is given of research on chamber transport for HIF (heavy ion fusion) dating from the first HIF Workshop in 1976 to the present. Chamber transport modes are categorized into ballistic transport modes and channel-like modes. Four major HIF reactor studies are summarized (HIBALL-II, HYLIFE-II, Prometheus-H, OSIRIS), with emphasis on the chamber transport environment. In general, many beams are used to provide the required symmetry and to permit focusing to the required small spots. Target parameters are then discussed, with a summary of the individual heavy ion beam parameters required for HIF. The beam parameters are then classified as to their line charge density and perveance, with special emphasis on the perveance limits for radial space charge spreading, for the space charge limiting current, and for the magnetic (Alfven) limiting current. The major experiments on ballistic transport (SFFE, Sabre beamlets, GAMBLE II, NTX, NDCX) are summarized, with specific reference to the axial electron trapping limit for charge neutralization. The major experiments on channel-like transport (GAMBLE II channel, GAMBLE II self-pinch, LBNL channels, GSI channels) are discussed. The status of current research on HIF chamber transport is summarized, and the value of future NDCX-II transport experiments for the future of HIF is noted.

  9. Overlimiting current in a microchannel.

    PubMed

    Dydek, E Victoria; Zaltzman, Boris; Rubinstein, Isaak; Deng, D S; Mani, Ali; Bazant, Martin Z

    2011-09-01

    We revisit the classical problem of diffusion-limited ion transport to a membrane (or electrode) by considering the effects of charged sidewalls. Using simple mathematical models and numerical simulations, we identify three basic mechanisms for overlimiting current in a microchannel: (i) surface conduction carried by excess counterions, which dominates for very thin channels, (ii) convection by electro-osmotic flow on the sidewalls, which dominates for thicker channels, and (iii) transitions to electro-osmotic instability on the membrane end in very thick channels. These intriguing electrokinetic phenomena may find applications in biological separations, water desalination, and electrochemical energy storage.

  10. TransportTP: A two-phase classification approach for membrane transporter prediction and characterization

    PubMed Central

    2009-01-01

    Background Membrane transporters play crucial roles in living cells. Experimental characterization of transporters is costly and time-consuming. Current computational methods for transporter characterization still require extensive curation efforts, especially for eukaryotic organisms. We developed a novel genome-scale transporter prediction and characterization system called TransportTP that combined homology-based and machine learning methods in a two-phase classification approach. First, traditional homology methods were employed to predict novel transporters based on sequence similarity to known classified proteins in the Transporter Classification Database (TCDB). Second, machine learning methods were used to integrate a variety of features to refine the initial predictions. A set of rules based on transporter features was developed by machine learning using well-curated proteomes as guides. Results In a cross-validation using the yeast proteome for training and the proteomes of ten other organisms for testing, TransportTP achieved an equivalent recall and precision of 81.8%, based on TransportDB, a manually annotated transporter database. In an independent test using the Arabidopsis proteome for training and four recently sequenced plant proteomes for testing, it achieved a recall of 74.6% and a precision of 73.4%, according to our manual curation. Conclusions TransportTP is the most effective tool for eukaryotic transporter characterization up to date. PMID:20003433

  11. The current catalog--how current?

    PubMed

    Sargent, C W

    1968-07-01

    NLM's Current Catalog has recently come in for some criticism. To be useful as a tool in acquisition and cataloging, currency in receipt of the Current Catalog is necessary. A survey of 263 titles with 1967 imprints, which were received by the Library of the Medical Sciences, University of New Mexico School of Medicine, was made to determine the correlation between the receipt of these books in the library and their appearance in the Current Catalog. PMID:5695111

  12. Spin-current noise from fluctuation relations

    SciTech Connect

    Lim, Jong Soo; Sánchez, David; López, Rosa

    2013-12-04

    We present fluctuation relations that connect spin-polarized current and noise in mesoscopic conductors. In linear response, these relations are equivalent to the fluctuation-dissipation theorem that relates equilibrium current-current correlations to the linear conductance. More interestingly, in the weakly nonlinear regime of transport, these relations establish a connection between the leading-order rectification spin conductance, the spin noise susceptibility and the third cumulant of spin current fluctuations at equilibrium. Our results are valid even for systems in the presence of magnetic fields and coupled to ferromagnetic electrodes.

  13. ADVANCED CUTTINGS TRANSPORT STUDY

    SciTech Connect

    Stefan Miska; Nicholas Takach; Kaveh Ashenayi; Mengjiao Yu; Ramadan Ahmed; Mark Pickell; Len Volk; Lei Zhou; Zhu Chen; Aimee Washington; Crystal Redden

    2003-09-30

    The Quarter began with installing the new drill pipe, hooking up the new hydraulic power unit, completing the pipe rotation system (Task 4 has been completed), and making the SWACO choke operational. Detailed design and procurement work is proceeding on a system to elevate the drill-string section. The prototype Foam Generator Cell has been completed by Temco and delivered. Work is currently underway to calibrate the system. Literature review and preliminary model development for cuttings transportation with polymer foam under EPET conditions are in progress. Preparations for preliminary cuttings transport experiments with polymer foam have been completed. Two nuclear densitometers were re-calibrated. Drill pipe rotation system was tested up to 250 RPM. Water flow tests were conducted while rotating the drill pipe up to 100 RPM. The accuracy of weight measurements for cuttings in the annulus was evaluated. Additional modifications of the cuttings collection system are being considered in order to obtain the desired accurate measurement of cuttings weight in the annular test section. Cutting transport experiments with aerated fluids are being conducted at EPET, and analyses of the collected data are in progress. The printed circuit board is functioning with acceptable noise level to measure cuttings concentration at static condition using ultrasonic method. We were able to conduct several tests using a standard low pass filter to eliminate high frequency noise. We tested to verify that we can distinguish between different depths of sand in a static bed of sand. We tested with water, air and a mix of the two mediums. Major modifications to the DTF have almost been completed. A stop-flow cell is being designed for the DTF, the ACTF and Foam Generator/Viscometer which will allow us to capture bubble images without the need for ultra fast shutter speeds or microsecond flash system.

  14. The Edge supersonic transport

    NASA Technical Reports Server (NTRS)

    Agosta, Roxana; Bilbija, Dushan; Deutsch, Marc; Gallant, David; Rose, Don; Shreve, Gene; Smario, David; Suffredini, Brian

    1992-01-01

    As intercontinental business and tourism volumes continue their rapid expansion, the need to reduce travel times becomes increasingly acute. The Edge Supersonic Transport Aircraft is designed to meet this demand by the year 2015. With a maximum range of 5750 nm, a payload of 294 passengers and a cruising speed of M = 2.4, The Edge will cut current international flight durations in half, while maintaining competitive first class, business class, and economy class comfort levels. Moreover, this transport will render a minimal impact upon the environment, and will meet all Federal Aviation Administration Part 36, Stage III noise requirements. The cornerstone of The Edge's superior flight performance is its aerodynamically efficient, dual-configuration design incorporating variable-geometry wingtips. This arrangement combines the benefits of a high aspect ratio wing at takeoff and low cruising speeds with the high performance of an arrow-wing in supersonic cruise. And while the structural weight concerns relating to swinging wingtips are substantial, The Edge looks to ever-advancing material technologies to further increase its viability. Heeding well the lessons of the past, The Edge design holds economic feasibility as its primary focus. Therefore, in addition to its inherently superior aerodynamic performance, The Edge uses a lightweight, largely windowless configuration, relying on a synthetic vision system for outside viewing by both pilot and passengers. Additionally, a fly-by-light flight control system is incorporated to address aircraft supersonic cruise instability. The Edge will be produced at an estimated volume of 400 aircraft and will be offered to airlines in 2015 at $167 million per transport (1992 dollars).

  15. Timescales and regions of the sensitivity of Atlantic meridional volume and heat transport: Toward observing system design

    NASA Astrophysics Data System (ADS)

    Heimbach, Patrick; Wunsch, Carl; Ponte, Rui M.; Forget, Gael; Hill, Chris; Utke, Jean

    2011-09-01

    A dual (adjoint) model is used to explore elements of the oceanic state influencing the meridional volume and heat transports (MVT and MHT) in the sub-tropical North Atlantic so as to understand their variability and to provide the elements of useful observational program design. Focus is on the effect of temperature (and salinity) perturbations. On short timescales (months), as expected, the greatest sensitivities are to local disturbances, but as the timescales extend back to a decade and longer, the region of influence expands to occupy much of the Atlantic basin and significant areas of the global ocean, although the influence of any specific point or small area tends to be quite weak. The propagation of information in the dual solution is a clear manifestation of oceanic teleconnections. It takes place through identifiable "dual" Kelvin, Rossby, and continental shelf-waves with an interpretable physics, in particular in terms of dual expressions of barotropic and baroclinic adjustment processes. Among the notable features are the relatively fast timescales of influence (albeit weak in amplitude) between 26°N and the tropical Pacific and Indian Ocean, the absence of dominance of the sub-polar North Atlantic, significant connections to the Agulhas leakage region in the southeast Atlantic on timescales of 5-10 years, and the marked sensitivity propagation of Doppler-shifted Rossby waves in the Southern Ocean on timescales of a decade and beyond. Regional, as well as time-dependent, differences between MVT and MHT sensitivities highlight the lack of a simple correspondence between their variability. Some implications for observing systems for the purpose of climate science are discussed.

  16. Intermodal transportation of spent fuel

    SciTech Connect

    Elder, H.K.

    1983-09-01

    Concepts for transportation of spent fuel in rail casks from nuclear power plant sites with no rail service are under consideration by the US Department of Energy in the Commercial Spent Fuel Management program at the Pacific Northwest Laboratory. This report identifies and evaluates three alternative systems for intermodal transfer of spent fuel: heavy-haul truck to rail, barge to rail, and barge to heavy-haul truck. This report concludes that, with some modifications and provisions for new equipment, existing rail and marine systems can provide a transportation base for the intermodal transfer of spent fuel to federal interim storage facilities. Some needed land transportation support and loading and unloading equipment does not currently exist. There are insufficient shipping casks available at this time, but the industrial capability to meet projected needs appears adequate.

  17. Consistent transport coefficients in astrophysics

    NASA Technical Reports Server (NTRS)

    Fontenla, Juan M.; Rovira, M.; Ferrofontan, C.

    1986-01-01

    A consistent theory for dealing with transport phenomena in stellar atmospheres starting with the kinetic equations and introducing three cases (LTE, partial LTE, and non-LTE) was developed. The consistent hydrodynamical equations were presented for partial-LTE, the transport coefficients defined, and a method shown to calculate them. The method is based on the numerical solution of kinetic equations considering Landau, Boltzmann, and Focker-Planck collision terms. Finally a set of results for the transport coefficients derived for a partially ionized hydrogen gas with radiation was shown, considering ionization and recombination as well as elastic collisions. The results obtained imply major changes is some types of theoretical model calculations and can resolve some important current problems concerning energy and mass balance in the solar atmosphere. It is shown that energy balance in the lower solar transition region can be fully explained by means of radiation losses and conductive flux.

  18. Affordable In-Space Transportation

    NASA Technical Reports Server (NTRS)

    Curtis, L. A.; VanDyke, M. K.; Lajoie, R. M.; Woodcock, G. R.

    1996-01-01

    Current and proposed launch systems will provide access to low-Earth orbit (LEO), and destinations beyond LEO, but the cost of delivering payloads will preclude the use of these services by many users. To develop and encourage revolutionary commercial utilization of geosynchronous orbit (GEO) and to provide an affordable means to continue NASA space science and exploration missions, the transportation costs to in-space destinations must be reduced. The principal objective of this study was to conceptually define three to four promising approaches to in-space transportation for delivery of satellites and other payloads, 3,000- to 10,000-lb class, to GEO destinations. This study established a methodology for evaluating in-space transportation systems based on life-cycle cost. The reusable concepts seemed to fare better in the evaluation than expendable, since a major driver in the life-cycle cost was the stage production cost.

  19. Glycine Transporters and Their Inhibitors

    NASA Astrophysics Data System (ADS)

    Gilfillan, Robert; Kerr, Jennifer; Walker, Glenn; Wishart, Grant

    Glycine plays a ubiquitous role in many biological processes. In the central nervous system it serves as an important neurotransmitter acting as an agonist at strychnine-sensitive glycine receptors and as an essential co-agonist with glutamate at the NMDA receptor complex. Control of glycine concentrations in the vicinity of these receptors is mediated by the specific glycine transporters, GlyT1 and GlyT2. Inhibition of these transporters has been postulated to be of potential benefit in several therapeutic indications including schizophrenia and pain. In this review we discuss our current knowledge of glycine transporters and focus on recent advances in the medicinal chemistry of GlyT1 and GlyT2 inhibitors.

  20. Skyrmions and Hall Transport.

    PubMed

    Kim, Bom Soo; Shapere, Alfred D

    2016-09-01

    We derive a generalized set of Ward identities that captures the effects of topological charge on Hall transport. The Ward identities follow from the (2+1)-dimensional momentum algebra, which includes a central extension proportional to the topological charge density. In the presence of topological objects like Skyrmions, we observe that the central term leads to a direct relation between the thermal Hall conductivity and the topological charge density. We extend this relation to incorporate the effects of a magnetic field and an electric current. The topological charge density produces a distinct signature in the electric Hall conductivity, which is identified in existing experimental data and yields further novel predictions. For insulating materials with translation invariance, the Hall viscosity can be directly determined from the Skyrmion density and the thermal Hall conductivity to be measured as a function of momentum. PMID:27661713