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  • Transport
  • Wind stress
  • American Meteorological Society  (31)
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  • 1
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    Seasonal variations in the circulation over the Middle Atlantic Bight continental shelf (2010)
    American Meteorological Society
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 1486–1500, doi:10.1175/2007JPO3767.1.
    Beschreibung: Fits of an annual harmonic to depth-average along-shelf current time series longer than 200 days from 27 sites over the Middle Atlantic Bight (MAB) continental shelf have amplitudes of a few centimeters per second. These seasonal variations are forced by seasonal variations in the wind stress and the cross-shelf density gradient. The component of wind stress that drives the along-shelf flow over most of the MAB mid- and outer shelf is oriented northeast–southwest, perpendicular to the major axis of the seasonal variation in the wind stress. Consequently, there is not a significant seasonal variation in the wind-driven along-shelf flow, except over the southern MAB shelf and the inner shelf of New England where the wind stress components forcing the along-shelf flow are north–south and east–west, respectively. The seasonal variation in the residual along-shelf flow, after removing the wind-driven component, has an amplitude of a few centimeters per second with maximum southwestward flow in spring onshore of the 60-m isobath and autumn offshore of the 60-m isobath. The spring maximum onshore of the 60-m isobath is consistent with the maximum river discharges in spring enhancing cross-shelf salinity gradients. The autumn maximum offshore of the 60-m isobath and a steady phase increase with water depth offshore of Cape Cod are both consistent with the seasonal variation in the cross-shelf temperature gradient associated with the development and destruction of a near-bottom pool of cold water over the mid and outer shelf (“cold pool”) due to seasonal variations in surface heat flux and wind stress.
    Beschreibung: This research was funded by the Ocean Sciences Division of the National Science Foundation under Grants OCE-820773, OCE-841292, and OCE- 848961.
    Schlagwort(e): Seasonal variability ; Ocean circulation ; Continental shelf ; Wind stress ; Density currents
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  • 2
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    North Pacific decadal variability in the Community Climate System Model version 2 (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 20 (2007): 2416-2433, doi:10.1175/JCLI4103.1.
    Beschreibung: North Pacific decadal oceanic and atmospheric variability is examined from a 650-yr control integration of the Community Climate System Model version 2. The dominant pattern of winter sea surface temperature (SST) variability is similar to the observed “Pacific decadal oscillation,” with maximum amplitude along the Kuroshio Extension. SST anomalies in this region exhibit significant spectral peaks at approximately 16 and 40 yr. Lateral geostrophic heat flux divergence, caused by a meridional shift of the Kuroshio Extension forced by basin-scale wind stress curl anomalies 3–5 yr earlier, is responsible for the decadal SST variability; local surface heat flux and Ekman heat flux divergence act as a damping and positive feedback, respectively. A simple linear Rossby wave model is invoked to explicitly demonstrate the link between the wind stress curl forcing and decadal variability in the Kuroshio Extension. The Rossby wave model not only successfully reproduces the two decadal spectral peaks, but also illustrates that only the low-frequency (〉10-yr period) portion of the approximately white noise wind stress curl forcing is relevant. This model also demonstrates that the weak and insignificant decadal spectral peaks in the wind stress curl forcing are necessary for producing the corresponding strong and significant oceanic peaks in the Kuroshio Extension. The wind stress curl response to decadal SST anomalies in the Kuroshio Extension is similar in structure but opposite in sign and somewhat weaker than the wind stress curl forcing pattern. These results suggest that the simulated North Pacific decadal variability owes its existence to two-way ocean–atmosphere coupling.
    Beschreibung: The first author gratefully acknowledges financial support from NOAA’s Office of Global Programs (grant to C. Deser) and the CCSM Project Office.
    Schlagwort(e): Decadal variability ; Fluxes ; Rossby waves ; Wind stress ; Coupled models
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  • 3
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    Midlatitude wind stress–sea surface temperature coupling in the vicinity of oceanic fronts (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 20 (2007): 3785–3801, doi:10.1175/JCLI4234.1
    Beschreibung: The influences of strong gradients in sea surface temperature on near-surface cross-front winds are explored in a series of idealized numerical modeling experiments. The atmospheric model is the Naval Research Laboratory Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) model, which is fully coupled to the Regional Ocean Modeling System (ROMS) ocean model. A series of idealized, two-dimensional model calculations is carried out in which the wind blows from the warm-to-cold side or the cold-to-warm side of an initially prescribed ocean front. The evolution of the near-surface winds, boundary layer, and thermal structure is described, and the balances in the momentum equation are diagnosed. The changes in surface winds across the front are consistent with previous models and observations, showing a strong positive correlation with the sea surface temperature and boundary layer thickness. The coupling arises mainly as a result of changes in the flux Richardson number across the front, and the strength of the coupling coefficient grows quadratically with the strength of the cross-front geostrophic wind. The acceleration of the winds over warm water results primarily from the rapid change in turbulent mixing and the resulting unbalanced Coriolis force in the vicinity of the front. Much of the loss/gain of momentum perpendicular to the front in the upper and lower boundary layer results from acceleration/deceleration of the flow parallel to the front via the Coriolis term. This mechanism is different from the previously suggested processes of downward mixing of momentum and adjustment to the horizontal pressure gradient, and is active for flows off the equator with sufficiently strong winds. Although the main focus of this work is on the midlatitude, strong wind regime, calculations at low latitudes and with weak winds show that the pressure gradient and turbulent mixing terms dominate the cross-front momentum budget, consistent with previous work.
    Beschreibung: This work was supported by the Office of Naval Research Grant N00014-05-1-0300.
    Schlagwort(e): Fronts ; Sea surface temperature ; Wind stress ; Coupled models ; Boundary layer
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  • 4
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    Can paleoceanographic tracers constrain meridional circulation rates? (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 37 (2007): 394-407, doi:10.1175/jpo3018.1.
    Beschreibung: The ability of paleoceanographic tracers to constrain rates of transport is examined using an inverse method to combine idealized observations with a geostrophic model. Considered are the spatial distribution, accuracy, and types of tracers required to constrain changes in meridional transport within an idealized single-hemisphere basin. Measurements of density and radioactive tracers each act to constrain rates of transport. Conservative tracers, while not of themselves able to inform regarding rates of transport, improve constraints when coupled with density or radioactive observations. It is found that the tracer data would require an accuracy one order of magnitude better than is presently available for paleo-observations to conclusively rule out factor-of-2 changes in meridional transport, even when assumed available over the entire model domain. When data are available only at the margins and bottom of the model, radiocarbon is unable to constrain transport while density remains effective only when a reference velocity level is assumed. The difficulty in constraining the circulation in this idealized model indicates that placing firm bounds on past meridional transport rates will prove challenging.
    Beschreibung: The first author is supported by the NOAA Postdoctoral Program in Climate and Global Change and GG by the National Ocean Partnership Program (ECCO). Author OM acknowledges support from the National Science Foundation.
    Schlagwort(e): Tracers ; Transport ; Paleoclimatology ; Ocean models
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  • 5
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    Shelf circulation and cross-shelf transport out of a bay driven by eddies from an open-ocean current. Part I : interaction between a barotropic vortex and a steplike topography (2011)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 41 (2011): 889–910, doi:10.1175/2010JPO4496.1.
    Beschreibung: This paper examines interaction between a barotropic point vortex and a steplike topography with a bay-shaped shelf. The interaction is governed by two mechanisms: propagation of topographic Rossby waves and advection by the forcing vortex. Topographic waves are supported by the potential vorticity (PV) jump across the topography and propagate along the step only in one direction, having higher PV on the right. Near one side boundary of the bay, which is in the wave propagation direction and has a narrow shelf, waves are blocked by the boundary, inducing strong out-of-bay transport in the form of detached crests. The wave–boundary interaction as well as out-of-bay transport is strengthened as the minimum shelf width is decreased. The two control mechanisms are related differently in anticyclone- and cyclone-induced interactions. In anticyclone-induced interactions, the PV front deformations are moved in opposite directions by the point vortex and topographic waves; a topographic cyclone forms out of the balance between the two opposing mechanisms and is advected by the forcing vortex into the deep ocean. In cyclone-induced interactions, the PV front deformations are moved in the same direction by the two mechanisms; a topographic cyclone forms out of the wave–boundary interaction but is confined to the coast. Therefore, anticyclonic vortices are more capable of driving water off the topography. The anticyclone-induced transport is enhanced for smaller vortex–step distance or smaller topography when the vortex advection is relatively strong compared to the wave propagation mechanism.
    Beschreibung: Y. Zhang acknowledges the support of theMIT-WHOI Joint Programin Physical Oceanography, NSF OCE-9901654 and OCE-0451086. J. Pedlosky acknowledges the support of NSF OCE- 9901654 and OCE-0451086.
    Schlagwort(e): Transport ; Eddies ; Barotropic flow ; Topographic effects ; Vortices ; Currents ; Potential vorticity ; Rossby waves
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  • 6
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    On the role of eddies and surface forcing in the heat transport and overturning circulation in marginal seas (2011)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 24 (2011): 4844–4858, doi:10.1175/2011JCLI4130.1.
    Beschreibung: The factors that determine the heat transport and overturning circulation in marginal seas subject to wind forcing and heat loss to the atmosphere are explored using a combination of a high-resolution ocean circulation model and a simple conceptual model. The study is motivated by the exchange between the subpolar North Atlantic Ocean and the Nordic Seas, a region that is of central importance to the oceanic thermohaline circulation. It is shown that mesoscale eddies formed in the marginal sea play a major role in determining the mean meridional heat transport and meridional overturning circulation across the sill. The balance between the oceanic eddy heat flux and atmospheric cooling, as characterized by a nondimensional number, is shown to be the primary factor in determining the properties of the exchange. Results from a series of eddy-resolving primitive equation model calculations for the meridional heat transport, overturning circulation, density of convective waters, and density of exported waters compare well with predictions from the conceptual model over a wide range of parameter space. Scaling and model results indicate that wind effects are small and the mean exchange is primarily buoyancy forced. These results imply that one must accurately resolve or parameterize eddy fluxes in order to properly represent the mean exchange between the North Atlantic and the Nordic Seas, and thus between the Nordic Seas and the atmosphere, in climate models.
    Beschreibung: This study was supported by the National Science Foundation under Grants OCE-0726339 and OCE-0850416.
    Schlagwort(e): Eddies ; Forcing ; Meridional overturning circulation ; Transport ; North Atlantic Ocean ; Seas/gulfs/bays
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  • 7
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    Wind-driven cross-equatorial flow in the Indian Ocean (2013)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 42 (2012): 2234–2253, doi:10.1175/JPO-D-12-033.1.
    Beschreibung: Meridional velocity, mass, and heat transport in the equatorial oceans are difficult to estimate because of the nonapplicability of the geostrophic balance. For this purpose a steady-state model is utilized in the equatorial Indian Ocean using NCEP wind stress and temperature and salinity data from the World Ocean Atlas 2005 (WOA05) and Argo. The results show a Somali Current flowing to the south during the winter monsoon carrying −11.5 ± 1.3 Sv (1 Sv ≡ 106 m3 s−1) and −12.3 ± 0.3 Sv from WOA05 and Argo, respectively. In the summer monsoon the Somali Current reverses to the north transporting 16.8 ± 1.2 Sv and 19.8 ± 0.6 Sv in the WOA05 and Argo results. Transitional periods are considered together and in consequence, there is not a clear Somali Current present in this period. Model results fit with in situ measurements made around the region, although Argo data results are quite more realistic than WOA05 data results.
    Beschreibung: This study has been partly funded by the MOC Project (CTM 2008- 06438) and the Spanish contribution to the Argo network (AC2009 ACI2009-0998), financed by the Spanish Government and Feder.
    Beschreibung: 2013-06-01
    Schlagwort(e): Indian Ocean ; Subtropics ; Currents ; Ocean circulation ; Transport ; Wind stress
    Repository-Name: Woods Hole Open Access Server
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  • 8
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    On the exchange of momentum over the open ocean (2013)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2013. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 43 (2013): 1589–1610, doi:10.1175/JPO-D-12-0173.1.
    Beschreibung: This study investigates the exchange of momentum between the atmosphere and ocean using data collected from four oceanic field experiments. Direct covariance estimates of momentum fluxes were collected in all four experiments and wind profiles were collected during three of them. The objective of the investigation is to improve parameterizations of the surface roughness and drag coefficient used to estimate the surface stress from bulk formulas. Specifically, the Coupled Ocean–Atmosphere Response Experiment (COARE) 3.0 bulk flux algorithm is refined to create COARE 3.5. Oversea measurements of dimensionless shear are used to investigate the stability function under stable and convective conditions. The behavior of surface roughness is then investigated over a wider range of wind speeds (up to 25 m s−1) and wave conditions than have been available from previous oversea field studies. The wind speed dependence of the Charnock coefficient α in the COARE algorithm is modified to , where m = 0.017 m−1 s and b = −0.005. When combined with a parameterization for smooth flow, this formulation gives better agreement with the stress estimates from all of the field programs at all winds speeds with significant improvement for wind speeds over 13 m s−1. Wave age– and wave slope–dependent parameterizations of the surface roughness are also investigated, but the COARE 3.5 wind speed–dependent formulation matches the observations well without any wave information. The available data provide a simple reason for why wind speed–, wave age–, and wave slope–dependent formulations give similar results—the inverse wave age varies nearly linearly with wind speed in long-fetch conditions for wind speeds up to 25 m s−1.
    Beschreibung: This work was funded by the National Science Foundation Grant OCE04-24536 as part of the CLIVAR Mode Water Dynamics Experiment (CLIMODE) and the Office of Naval Research Grant N00014-05-1-0139 as part of the CBLAST-LOW program.
    Beschreibung: 2014-02-01
    Schlagwort(e): Wind shear ; Wind stress ; Atmosphere-ocean interaction ; Fluxes ; Momentum ; Algorithms
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  • 9
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    Stommel’s box model of thermohaline circulation revisited - the role of mechanical energy supporting mixing and the wind-driven gyration (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 909–917, doi:10.1175/2007JPO3535.1.
    Beschreibung: The classical two-box model of Stommel is extended in two directions: replacing the buoyancy constraint with an energy constraint and including the wind-driven gyre. Stommel postulated a buoyancy constraint for the thermohaline circulation, and his basic idea has evolved into the dominating theory of thermohaline circulation; however, recently, it is argued that the thermohaline circulation is maintained by mechanical energy from wind stress and tides. The major difference between these two types of models is the bifurcation structure: the Stommel-like model has two thermal modes (one stable and another one unstable) and one stable haline mode, whereas the energy-constraint model has one stable thermal mode and two saline modes (one stable and another one unstable). Adding the wind-driven gyre changes the threshold value of thermohaline bifurcation greatly; thus, the inclusion of the wind-driven gyre is a vital step in completely modeling the physical processes related to thermohaline circulation.
    Beschreibung: YPG was supported by the National Science Foundation of China (NSFC, 40676022), the National Basic Research Program of China (2006CB403605), and the Guangdong Natural Science Foundation (5003672). RXH was supported by the National Oceanic and Atmospheric Administration through CICOR Cooperative Agreement NA17RJ1223 to the Woods Hole Oceanographic Institution.
    Schlagwort(e): Thermohaline circulation ; Mixing ; Wind stress ; Buoyancy ; Energy budget
    Repository-Name: Woods Hole Open Access Server
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  • 10
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    The effect of breaking waves on a coupled model of wind and ocean surface waves. Part II : growing seas (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 2164–2184, doi:10.1175/2008JPO3962.1.
    Beschreibung: This is the second part of a two-part investigation of a coupled wind and wave model that includes the enhanced form drag of breaking waves. The model is based on the wave energy balance and the conservation of air-side momentum and energy. In Part I, coupled nonlinear advance–delay differential equations were derived, which govern the wave height spectrum, the distribution of breaking waves, and vertical air side profiles of the turbulent stress and wind speed. Numeric solutions were determined for mature seas. Here, numeric solutions for a wide range of wind and wave conditions are obtained, including young, strongly forced wind waves. Furthermore, the “spatial sheltering effect” is introduced so that smaller waves in airflow separation regions of breaking longer waves cannot be forced by the wind. The solutions strongly depend on the wave height curvature spectrum at high wavenumbers (the “threshold saturation level”). As the threshold saturation level is reduced, the effect of breaking waves becomes stronger. For young strongly forced waves (laboratory conditions), breaking waves close to the spectral peak dominate the wind input and previous solutions of a model with only input to breaking waves are recovered. Model results of the normalized roughness length are generally consistent with previous laboratory and field measurements. For field conditions, the wind stress depends sensitively on the wave height spectrum. The spatial sheltering may modify the number of breaking shorter waves, in particular, for younger seas.
    Beschreibung: This work was supported by the U.S. National Science Foundation (Grant OCE- 0526177) and the U.S. Office of Naval Research (Grant N00014–06–10729).
    Schlagwort(e): Wave breaking ; Coupled models ; Wind stress ; Momentum ; Sea state
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  • 11
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    Observations and a model of undertow over the inner continental shelf (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 2341-2357, doi:10.1175/2008JPO3986.1.
    Beschreibung: Onshore volume transport (Stokes drift) due to surface gravity waves propagating toward the beach can result in a compensating Eulerian offshore flow in the surf zone referred to as undertow. Observed offshore flows indicate that wave-driven undertow extends well offshore of the surf zone, over the inner shelves of Martha’s Vineyard, Massachusetts, and North Carolina. Theoretical estimates of the wave-driven offshore transport from linear wave theory and observed wave characteristics account for 50% or more of the observed offshore transport variance in water depths between 5 and 12 m, and reproduce the observed dependence on wave height and water depth. During weak winds, wave-driven cross-shelf velocity profiles over the inner shelf have maximum offshore flow (1–6 cm s−1) and vertical shear near the surface and weak flow and shear in the lower half of the water column. The observed offshore flow profiles do not resemble the parabolic profiles with maximum flow at middepth observed within the surf zone. Instead, the vertical structure is similar to the Stokes drift velocity profile but with the opposite direction. This vertical structure is consistent with a dynamical balance between the Coriolis force associated with the offshore flow and an along-shelf “Hasselmann wave stress” due to the influence of the earth’s rotation on surface gravity waves. The close agreement between the observed and modeled profiles provides compelling evidence for the importance of the Hasselmann wave stress in forcing oceanic flows. Summer profiles are more vertically sheared than either winter profiles or model profiles, for reasons that remain unclear.
    Beschreibung: This research was funded by the Ocean Sciences Division of the National Science Foundation under Grants OCE-0241292 and OCE-0548961.
    Schlagwort(e): Continental shelf ; Transport ; Shear structure/flows ; Coastal flows ; Gravity waves
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  • 12
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    Western Arctic shelfbreak eddies : formation and transport (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 1644-1668, doi:10.1175/2007JPO3829.1.
    Beschreibung: The mean structure and time-dependent behavior of the shelfbreak jet along the southern Beaufort Sea, and its ability to transport properties into the basin interior via eddies are explored using high-resolution mooring data and an idealized numerical model. The analysis focuses on springtime, when weakly stratified winter-transformed Pacific water is being advected out of the Chukchi Sea. When winds are weak, the observed jet is bottom trapped with a low potential vorticity core and has maximum mean velocities of O(25 cm s−1) and an eastward transport of 0.42 Sv (1 Sv ≡ 106 m3 s−1). Despite the absence of winds, the current is highly time dependent, with relative vorticity and twisting vorticity often important components of the Ertel potential vorticity. An idealized primitive equation model forced by dense, weakly stratified waters flowing off a shelf produces a mean middepth boundary current similar in structure to that observed at the mooring site. The model boundary current is also highly variable, and produces numerous strong, small anticyclonic eddies that transport the shelf water into the basin interior. Analysis of the energy conversion terms in both the mooring data and the numerical model indicates that the eddies are formed via baroclinic instability of the boundary current. The structure of the eddies in the basin interior compares well with observations from drifting ice platforms. The results suggest that eddies shed from the shelfbreak jet contribute significantly to the offshore flux of heat, salt, and other properties, and are likely important for the ventilation of the halocline in the western Arctic Ocean. Interaction with an anticyclonic basin-scale circulation, meant to represent the Beaufort gyre, enhances the offshore transport of shelf water and results in a loss of mass transport from the shelfbreak jet.
    Beschreibung: This study was supported by the National Science Foundation Office of Polar Programs under Grants 0421904 and 035268 (MS), and by the Office of Naval Research Grant N00014-02-1-0317 (RP and PF). Analysis by AJP was supported by the Office of Naval Research under Grant N00014-97-1-0135 and by the National Science Foundation under Grant OPP-9815303.
    Schlagwort(e): Arctic ; Eddies ; Transport ; Currents ; Jets
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  • 13
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    Decadal changes of wind stress over the Southern Ocean associated with Antarctic ozone depletion (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 20 (2007): 3395-3410, doi:10.1175/JCLI4195.1
    Beschreibung: Using 40-yr ECMWF Re-Analysis (ERA-40) data and in situ observations, the positive trend of Southern Ocean surface wind stress during two recent decades is detected, and its close linkage with spring Antarctic ozone depletion is established. The spring Antarctic ozone depletion affects the Southern Hemisphere lower-stratospheric circulation in late spring/early summer. The positive feedback involves the strengthening and cooling of the polar vortex, the enhancement of meridional temperature gradients and the meridional and vertical potential vorticity gradients, the acceleration of the circumpolar westerlies, and the reduction of the upward wave flux. This feedback loop, together with the ozone-related photochemical interaction, leads to the upward tendency of lower-stratospheric zonal wind in austral summer. In addition, the stratosphere–troposphere coupling, facilitated by ozone-related dynamics and the Southern Annular Mode, cooperates to relay the zonal wind anomalies to the upper troposphere. The wave–mean flow interaction and the meridional circulation work together in the form of the Southern Annular Mode, which transfers anomalous wind signals downward to the surface, triggering a striking strengthening of surface wind stress over the Southern Ocean.
    Beschreibung: This study was supported by MOST of China (Grant 2006CB403604) and Chinese Academy of Sciences (Grant KZSW2-YW-214) (for YXY and DXW) and W. Alan Clark Chair from Woods Hole Oceanographic Institution (for RXH).
    Schlagwort(e): Wind stress ; Decadal variability ; Ozone ; Southern Ocean ; Stratospheric circulation
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  • 14
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    The western North Atlantic shelfbreak current system in summer (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography. 37 (2007): 2509-2533, doi:10.1175/JPO3123.1.
    Beschreibung: Twelve years of historical hydrographic data, spanning the period 1990–2001, are analyzed to examine the along-stream evolution of the western North Atlantic Ocean shelfbreak front and current, following its path between the west coast of Greenland and the Middle Atlantic Bight. Over 700 synoptic sections are used to construct a mean three-dimensional description of the summer shelfbreak front and to quantify the along-stream evolution in properties, including frontal strength and grounding position. Results show that there are actually two fronts in the northern part of the domain—a shallow front located near the shelf break and a deeper front centered in the core of Irminger Water over the upper slope. The properties of the deeper Irminger front erode gradually to the south, and the front disappears entirely near the Grand Banks of Newfoundland. The shallow shelfbreak front is identifiable throughout the domain, and its properties exhibit large variations from north to south, with the largest changes occurring near the Tail of the Grand Banks. Despite these structural changes, and large variations in topography, the foot of the shelfbreak front remains within 20 km of the shelf break. The hydrographic sections are also used to examine the evolution of the baroclinic velocity field and its associated volume transport. The baroclinic velocity structure consists of a single velocity core that is stronger and penetrates deeper where the Irminger front is present. The baroclinic volume transport decreases by equal amounts at the southern end of the Labrador Shelf and at the Tail of the Grand Banks. Overall, the results suggest that the Grand Banks is a geographically critical location in the North Atlantic shelfbreak system.
    Beschreibung: This work was supported by the National Science Foundation under Grants OCE00- 95261 (PF) and OCE-0450658 (RP).
    Schlagwort(e): Continental shelf ; Currents ; Atlantic Ocean ; Fronts ; Transport
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  • 15
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    Effect of sea surface temperature-wind stress coupling on baroclinic instability in the ocean (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 37 (2007): 1092–1097, doi:10.1175/JPO3045.1.
    Beschreibung: The impact of the observed relationship between sea surface temperature and surface wind stress on baroclinic instability in the ocean is explored using linear theory and a nonlinear model. A simple parameterization of the influence of sea surface temperature on wind stress is used to derive a surface boundary condition for the vertical velocity at the base of the oceanic Ekman layer. This boundary condition is applied to the classic linear, quasigeostrophic stability problem for a uniformly sheared flow originally studied by Eady in the 1940s. The results demonstrate that for a wind directed from warm water toward cold water, the coupling acts to enhance the growth rate, and increase the wavelength, of the most unstable wave. Winds in the opposite sense reduce the growth rate and decrease the wavelength of the most unstable wave. For representative coupling strengths, the change in growth rate can be as large as ±O(50%). This effect is largest for shallow, strongly stratified, low-latitude flows.
    Beschreibung: This work was supported by the Office of Naval Research Grant N00014-05-1-0300.
    Schlagwort(e): Wind stress ; Instability ; Sea surface temperature ; Baroclinic flows ; Ocean dynamics
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  • 16
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    Offshore transport of shelf waters through interaction of vortices with a shelfbreak current (2013)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2013. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 43 (2013): 905–919, doi:10.1175/JPO-D-12-0150.1.
    Beschreibung: Interactions between vortices and a shelfbreak current are investigated, with particular attention to the exchange of waters between the continental shelf and slope. The nonlinear, three-dimensional interaction between an anticyclonic vortex and the shelfbreak current is studied in the laboratory while varying the ratio ε of the maximum azimuthal velocity in the vortex to the maximum alongshelf velocity in the shelfbreak current. Strong interactions between the shelfbreak current and the vortex are observed when ε 〉 1; weak interactions are found when ε 〈 1. When the anticyclonic vortex comes in contact with the shelfbreak front during a strong interaction, a streamer of shelf water is drawn offshore and wraps anticyclonically around the vortex. Measurements of the offshore transport and identification of the particle trajectories in the shelfbreak current drawn offshore from the vortex allow quantification of the fraction of the shelfbreak current that is deflected onto the slope; this fraction increases for increasing values of ε. Experimental results in the laboratory are strikingly similar to results obtained from observations in the Middle Atlantic Bight (MAB); after proper scaling, measurements of offshore transport and offshore displacement of shelf water for vortices in the MAB that span a range of values of ε agree well with laboratory predictions.
    Beschreibung: Laboratory work was supported by the National Science Foundation through Grant OCE- 0081756. Glider observations in March–April 2006 were supported by the National Science Foundation through Grant OCE-0220769. Glider observations in July– October 2007 were supported by a grant from Raytheon. RET was supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Cooperative Institute for the North Atlantic Region. The REMUS observations were funded by the Office of Naval Research. GGG was supported by the National Science Foundation through Grant OCE-1129125 for analysis and writing.
    Beschreibung: 2013-11-01
    Schlagwort(e): Continental shelf/slope ; Eddies ; Fronts ; Transport ; Laboratory/physical models
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  • 17
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    The turbulent oscillator : a mechanism of low-frequency variability of the wind-driven ocean gyres (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography. 37 (2007): 2363-2386, doi:10.1175/jpo3118.1.
    Beschreibung: Intrinsic low-frequency variability is studied in the idealized, quasigeostrophic, midlatitude, wind-driven ocean gyres operating at large Reynolds number. A robust decadal variability mode driven by the transient mesoscale eddies is found and analyzed. The variability is a turbulent phenomenon, which is driven by the competition between the eddy rectification process and the potential vorticity anomalies induced by changes of the intergyre transport
    Beschreibung: Funding for Pavel Berloff was provided by NSF Grants OCE-0091836 and OCE- 0344094, by the U.K. Royal Society Fellowship, and by the Newton Trust Award, A. M. Hogg was supported by an Australian Research Council Postdoctoral Fellowship (DP0449851) during this work, and William K. Dewar was supported by NSF Grants OCE-0424227 and OCE-0550139.
    Schlagwort(e): Turbulence ; Gyres ; Transport ; Potential vorticity ; Mesoscale processes
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  • 18
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    Potential vorticity constraint on the flow between two basins (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography. 37 (2007): 2251-2266, doi:10.1175/jpo3116.1.
    Beschreibung: This paper examines the role of potential vorticity (PV) balance in source- and sink-driven flows between two basins. As shown in previous studies, PV advection into a basin, say a positive PV advection, requires a negative frictional torque to maintain a steady PV balance. This sense of torque may be provided by a cyclonic boundary current within the basin. The PV advection through a channel is due almost entirely to advection of planetary PV, f/H, where f is the Coriolis parameter and H is the column thickness. Therefore a localized change of depth, and thus H in the channel, directly affects the PV transport and will result in a basinwide change of the circulation pattern. For example, if the channel depth is made shallower while holding the transport fixed, the PV advection is then increased and the result may be a strong recirculation within the basin, as much as two orders of magnitude greater than the transport through the channel. When the basins are connected by two channels at different latitudes or with different sill depths, the throughflow is found to be divided between the two channels in a way that satisfies the integral constraint for flow around an island. The partition of the flow between two channels appears to be such as to minimize the net frictional torque. In still another set of experiments, the large-scale pressure difference (layer thickness) between the basins is specified and held fixed, while the throughflow is allowed to vary in response to changes in the frictional torque. The interbasin transport is strongly influenced by the length of the boundary or the magnitude of the viscosity in the sense that a greater PV frictional torque allows a greater PV transport and vice versa. This result is counterintuitive, if it is assumed that the throughflow is determined by viscous drag within the channel but is a straightforward consequence of the basin-scale PV balance. Thus, the important frictional effect in these experiments is on the basin-scale flow and not on the channel scale.
    Beschreibung: This study is supported by NSF Grants OCE-0611530 and OCE-0351055. Price was supported in part by the U.S. Office of Naval Research through Grant 13010900.
    Schlagwort(e): Potential vorticity ; Coriolis effect ; Boundary currents ; Advection ; Friction ; Transport
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  • 19
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    The role of advection, straining, and mixing on the tidal variability of estuarine stratification (2012)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 42 (2012): 855–868, doi:10.1175/JPO-D-10-05010.1.
    Beschreibung: Data from the Hudson River estuary demonstrate that the tidal variations in vertical salinity stratification are not consistent with the patterns associated with along-channel tidal straining. These observations result from three additional processes not accounted for in the traditional tidal straining model: 1) along-channel and 2) lateral advection of horizontal gradients in the vertical salinity gradient and 3) tidal asymmetries in the strength of vertical mixing. As a result, cross-sectionally averaged values of the vertical salinity gradient are shown to increase during the flood tide and decrease during the ebb. Only over a limited portion of the cross section does the observed stratification increase during the ebb and decrease during the flood. These observations highlight the three-dimensional nature of estuarine flows and demonstrate that lateral circulation provides an alternate mechanism that allows for the exchange of materials between surface and bottom waters, even when direct turbulent mixing through the pycnocline is prohibited by strong stratification.
    Beschreibung: The funding for this research was obtained from NSF Grant OCE-08-25226.
    Beschreibung: 2012-11-01
    Schlagwort(e): Mixing ; Ocean circulation ; Shear structure/flows ; Transport ; Turbulence
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  • 20
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    The Kuroshio Extension northern recirculation gyre : profiling float measurements and forcing mechanism (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 1764-1779, doi:10.1175/2008JPO3921.1.
    Beschreibung: Middepth, time-mean circulation in the western North Pacific Ocean (28°–45°N, 140°–165°E) is investigated using drift information from the profiling floats deployed in the Kuroshio Extension System Study (KESS) and the International Argo programs. A well-defined, cyclonic recirculation gyre (RG) is found to exist north of the Kuroshio Extension jet, confined zonally between the Japan Trench (145°E) and the Shatsky Rise (156°E), and bordered to the north by the subarctic boundary along 40°N. This northern RG, which is simulated favorably in the eddy-resolving OGCM for the Earth Simulator (OFES) hindcast run model, has a maximum volume transport at 26.4 Sv across 159°E and its presence persists on the interannual and longer time scales. An examination of the time-mean x-momentum balance from the OFES hindcast run output reveals that horizontal convergence of Reynolds stresses works to accelerate both the eastward-flowing Kuroshio Extension jet and a westward mean flow north of the meandering jet. The fact that the northern RG is eddy driven is further confirmed by examining the turbulent Sverdrup balance, in which convergent eddy potential vorticity fluxes are found to induce the cyclonic RG across the background potential vorticity gradient field. For the strength of the simulated northern RG, the authors find the eddy dissipation effect to be important as well.
    Beschreibung: This study was supported by NSF through Grant OCE-0220680 (UH) and OCE-0220161 (WHOI).
    Schlagwort(e): Gyres ; Ocean circulation ; Profilers ; Jets ; Transport
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  • 21
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    The mechanical energy input to the ocean induced by tropical cyclones (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 1253-1266, doi:10.1175/2007JPO3786.1.
    Beschreibung: Wind stress and tidal dissipation are the most important sources of mechanical energy for maintaining the oceanic general circulation. The contribution of mechanical energy due to tropical cyclones can be a vitally important factor in regulating the oceanic general circulation and its variability. However, previous estimates of wind stress energy input were based on low-resolution wind stress data in which strong nonlinear events, such as tropical cyclones, were smoothed out. Using a hurricane–ocean coupled model constructed from an axisymmetric hurricane model and a three-layer ocean model, the rate of energy input to the world’s oceans induced by tropical cyclones over the period from 1984 to 2003 was estimated. The energy input is estimated as follows: 1.62 TW to the surface waves and 0.10 TW to the surface currents (including 0.03 TW to the near-inertial motions). The rate of gravitational potential energy increase due to tropical cyclones is 0.05 TW. Both the energy input from tropical cyclones and the increase of gravitational potential energy of the ocean show strong interannual and decadal variability with an increasing rate of 16% over the past 20 years. The annual mean diapycnal upwelling induced by tropical cyclones over the past 20 years is estimated as 39 Sv (Sv ≡ 106 m3 s−1). Owing to tropical cyclones, diapycnal mixing in the upper ocean (below the mixed layer) is greatly enhanced. Within the regimes of strong activity of tropical cyclones, the increase of diapycnal diffusivity is on the order of (1 − 6) × 10−4 m2 s−1. The tropical cyclone–related energy input and diapycnal mixing may play an important role in climate variability, ecology, fishery, and environments.
    Beschreibung: LLL and WW were supported by the National Basic Research Priorities Programmer of China through Grant 2007CB816004 and National Outstanding Youth Natural Science Foundation of China FIG. 15. Annual-mean vertical diffusivity induced by tropical cyclones from 1984 to 2003 (units: 10 4 m2 s 1): (right) the horizontal distribution and (left) the zonally averaged vertical diffusivity. JUNE 2008 L IU ET AL . 1265 under Grant 40725017. RXH was supported by the W. Alan Clark Chair from Woods Hole Oceanographic Institution.
    Schlagwort(e): Tropical cyclones ; Ocean circulation ; Wind stress ; Mixing ; Interannual variability
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  • 22
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    Subtidal salinity and velocity in the Hudson River estuary : observations and modeling (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 753-770, doi:10.1175/2007JPO3808.1.
    Beschreibung: A tidally and cross-sectionally averaged model based on the temporal evolution of the quasi-steady Hansen and Rattray equations is applied to simulate the salinity distribution and vertical exchange flow along the Hudson River estuary. The model achieves high skill at hindcasting salinity and residual velocity variation during a 110-day period in 2004 covering a wide range of river discharges and tidal forcing. The approach is based on an existing model framework that has been modified to improve model skill relative to observations. The external forcing has been modified to capture meteorological time-scale variability in salinity, stratification, and residual velocity due to sea level fluctuations at the open boundary and along-estuary wind stress. To reflect changes in vertical mixing due to stratification, the vertical mixing coefficients have been modified to use the bottom boundary layer height rather than the water depth as an effective mixing length scale. The boundary layer parameterization depends on the tidal amplitude and the local baroclinic pressure gradient through the longitudinal Richardson number, and improves the model response to spring–neap variability in tidal amplitude during periods of high river discharge. Finally, steady-state model solutions are evaluated for both the Hudson River and northern San Francisco Bay over a range of forcing conditions. Agreement between the model and scaling of equilibrium salinity intrusions lends confidence that the approach is transferable to other estuaries, despite significant differences in bathymetry. Discrepancies between the model results and observations at high river discharge are indicative of limits at which the formulation begins to fail, and where an alternative approach that captures two-layer dynamics would be more appropriate.
    Beschreibung: This research was supported by the Hudson River Foundation Grant 005/03A, NSF Grant OCE-0452054, and by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the J. Seward Johnson Fund.
    Schlagwort(e): Estuaries ; Salinity ; Rivers ; Tides ; Wind stress
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  • 23
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    The effects of mesoscale ocean–atmosphere coupling on the large-scale ocean circulation (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 22 (2009): 4066–4082, doi:10.1175/2009JCLI2629.1.
    Beschreibung: Small-scale variation in wind stress due to ocean–atmosphere interaction within the atmospheric boundary layer alters the temporal and spatial scale of Ekman pumping driving the double-gyre circulation of the ocean. A high-resolution quasigeostrophic (QG) ocean model, coupled to a dynamic atmospheric mixed layer, is used to demonstrate that, despite the small spatial scale of the Ekman-pumping anomalies, this phenomenon significantly modifies the large-scale ocean circulation. The primary effect is to decrease the strength of the nonlinear component of the gyre circulation by approximately 30%–40%. This result is due to the highest transient Ekman-pumping anomalies destabilizing the flow in a dynamically sensitive region close to the western boundary current separation. The instability of the jet produces a flux of potential vorticity between the two gyres that acts to weaken both gyres.
    Beschreibung: AH and WD were supported by an ARC Linkage International Grant (LX0668781). WD was also supported by NSF Grants OCE 0424227 and OCE 0550139. Funding for PB was provided by NSF Grants OCE 0344094 and OCE 0725796 and by the research grant from the Newton Trust of the University of Cambridge. SK was supported by U.S. DOE Grant DE-FG02–02ER63413 and NASA Grant NNG-06- AG66G-1.
    Schlagwort(e): Airndashsea interaction ; Coupled models ; Mesoscale processes ; Wind stress ; Ekman pumping/transport
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  • 24
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    Anisotropic material transport by eddies and eddy-driven currents in a model of the North Atlantic (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 39 (2009): 3162-3175, doi:10.1175/2009JPO4239.1.
    Beschreibung: This study analyzes anisotropic properties of the material transport by eddies and eddy-driven zonal jets in a general circulation model of the North Atlantic through the analysis of Lagrangian particle trajectories. Spreading rates—defined here as half the rate of change in the particle dispersion—in the zonal direction systematically exceed the meridional rates by an order of magnitude. Area-averaged values for the upper-ocean zonal and meridional spreading rates are approximately 8100 and 1400 m2 s−1, respectively, and in the deep ocean they are 2400 and 200 m2 s−1. The results demonstrate that this anisotropy is mainly due to the action of the transient eddies and not to the shear dispersion associated with the time-mean jets. This property is consistent with the fact that eddies in this study have zonally elongated shapes. With the exception of the upper-ocean subpolar gyre, eddies also cause the superdiffusive zonal spreading, significant variations in the spreading rate in the vertical and meridional directions, and the difference between the westward and eastward spreading.
    Beschreibung: Funding for IK was provided by NSF Grants OCE 0346178, 0749722, and 0842834. Funding for PB was provided by NSF Grants OCE 0344094 and OCE 0725796 and by the research grant from the Newton Trust of the University of Cambridge. For JP the acknowledgement is to NSF OCE-0451086.
    Schlagwort(e): Eddies ; Transport ; Currents ; North Atlantic Ocean
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  • 25
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    Transport in an idealized three-gyre system with application to the Adriatic Sea (2010)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 39 (2009): 675-690, doi:10.1175/2008JPO3975.1.
    Beschreibung: Motivated by observations of surface drifters in the Adriatic Sea, transport in a three-gyre system is studied with the aid of dynamical systems techniques. Particular attention is paid to the issue of intergyre transport. The velocity field is assumed to be two-dimensional and incompressible and composed of a steady three-gyre background flow on which a time-dependent perturbation is superimposed. Two systems of this type are considered: 1) an observationally motivated, analytically prescribed model consisting of a steady background on which a multiperiodic time-dependent perturbation is superimposed, and 2) an observationally based model of the Adriatic Sea consisting of the mean surface circulation derived from surface drifter trajectories on which a time-dependent altimetry-based perturbation velocity field is superimposed. It is shown that for a small perturbation to the steady three-gyre background, two of the gyres exchange no fluid with the third gyre. When the perturbation strength exceeds a certain threshold, transport between all three gyres occurs. This behavior is described theoretically, illustrated using the analytic model and shown to be consistent with the observationally based model of the Adriatic. The relevance of the work presented to more complicated multiple-gyre problems is discussed.
    Beschreibung: This work was supported by the National Science Foundation Grants CMG0417425 and CMG0825547.
    Schlagwort(e): Transport ; Gyres ; Mediterranean region ; Ocean circulation ; Lagrangian circulation
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  • 26
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    Transport and dynamics of the Panay Sill overflow in the Philippine Seas (2011)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2010. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 40 (2010): 2679–2695, doi:10.1175/2010JPO4395.1.
    Beschreibung: Observations of stratification and currents between June 2007 and March 2009 reveal a strong overflow between 400- and 570-m depth from the Panay Strait into the Sulu Sea. The overflow water is derived from approximately 400 m deep in the South China Sea. Temporal mean velocity is greater than 0.75 m s−1 at 50 m above the 570-m Panay Sill. Empirical orthogonal function analysis of a mooring time series shows that the flow is dominated by the bottom overflow current with little seasonal variance. The overflow does not descend below 1250 m in the Sulu Sea but rather settles above high-salinity deep water derived from the Sulawesi Sea. The mean observed overflow transport at the sill is 0.32 × 106 m3 s−1. The observed transport was used to calculate a bulk diapycnal diffusivity of 4.4 × 10−4 m2 s−1 within the Sulu Sea slab (575–1250 m) ventilated from Panay Strait. Analysis of Froude number variation across the sill shows that the flow is hydraulically controlled. A suitable hydraulic control model shows overflow transport equivalent to the observed overflow. Thorpe-scale estimates show turbulent dissipation rates up to 5 × 10−7 W kg−1 just downstream of the supercritical to subcritical flow transition, suggesting a hydraulic jump downstream of the sill.
    Beschreibung: This work was supported by the Office of Naval Research Grant N00014-09-1-0582 to Lamont-Doherty Earth Observatory of Columbia University; Grants ONR-13759000 and N00014-09-1-0582 to the Woods Hole Oceanographic Institution; Grant ONR-N00014-06-1-0690 to Scripps Institute of Oceanography; and a National Defense Science and Engineering Graduate Fellowship.
    Schlagwort(e): Transport ; Dynamics ; Topographic effects ; Currents ; Empirical orthogonal functions
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  • 27
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    Near-surface transport pathways in the north Atlantic Ocean : looking for throughput from the subtropical to the subpolar gyre (2011)
    American Meteorological Society
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 41 (2011): 911–925, doi:10.1175/2011JPO4498.1.
    Beschreibung: Motivated by discrepancies between Eulerian transport estimates and the behavior of Lagrangian surface drifters, near-surface transport pathways and processes in the North Atlantic are studied using a combination of data, altimetric surface heights, statistical analysis of trajectories, and dynamical systems techniques. Particular attention is paid to the issue of the subtropical-to-subpolar intergyre fluid exchange. The velocity field used in this study is composed of a steady drifter-derived background flow, upon which a time-dependent altimeter-based perturbation is superimposed. This analysis suggests that most of the fluid entering the subpolar gyre from the subtropical gyre within two years comes from a narrow region lying inshore of the Gulf Stream core, whereas fluid on the offshore side of the Gulf Stream is largely prevented from doing so by the Gulf Stream core, which acts as a strong transport barrier, in agreement with past studies. The transport barrier near the Gulf Stream core is robust and persistent from 1992 until 2008. The qualitative behavior is found to be largely independent of the Ekman drift.
    Beschreibung: This work was supported by the National Science Foundation Grants CMG-82469600 and CMG-82579600 and by the Office of Naval Research Grant ONR-13108700.
    Schlagwort(e): Atlantic Ocean ; Transport ; Gyres ; Lagrangian circulation/transport ; Tracers ; Currents ; Meridional overturning circulation
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  • 28
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    An enhancement of low-frequency variability in the Kuroshio–Oyashio Extension in CCSM3 owing to ocean model biases (2011)
    American Meteorological Society
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Meteorological Society, 2010. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 23 (2010): 6221–6233, doi:10.1175/2010JCLI3402.1.
    Beschreibung: Enhanced decadal variability in sea surface temperature (SST) centered on the Kuroshio Extension (KE) has been found in the Community Climate System Model version 3 (CCSM3) as well as in other coupled climate models. This decadal peak has higher energy than is found in nature, almost twice as large in some cases. While previous analyses have concentrated on the mechanisms for such decadal variability in coupled models, an analysis of the causes of excessive SST response to changes in wind stress has been missing. Here, a detailed comparison of the relationships between interannual changes in SST and sea surface height (SSH) as a proxy for geostrophic surface currents in the region in both CCSM3 and observations, and how these relationships depend on the mean ocean circulation, temperature, and salinity, is made. We use observationally based climatological temperature and salinity fields as well as satellite-based SSH and SST fields for comparison. The primary cause for the excessive SST variability is the coincidence of the mean KE with the region of largest SST gradients in the model. In observations, these two regions are separated by almost 500 km. In addition, the too shallow surface oceanic mixed layer in March north of the KE in the subarctic Pacific contributes to the biases. These biases are not unique to CCSM3 and suggest that mean biases in current, temperature, and salinity structures in separated western boundary current regions can exert a large influence on the size of modeled decadal SST variability.
    Beschreibung: Support for L.T. was provided by the NASA sponsored Ocean Surface Topography Science Team, under Contract 1267196 with the University of Washington, administered by the Jet Propulsion Laboratory. Support for Y.-O. K. comes from the NOAA Office of Global Programs (grant to C. Deser and Y.-O. Kwon) and the WHOI Heyman fellowship.
    Schlagwort(e): Bias ; Coupled models ; Decadal variability ; Ocean models ; Sea surface temperature ; Wind stress
    Repository-Name: Woods Hole Open Access Server
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  • 29
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    Residual sediment fluxes in weakly-to-periodically stratified estuaries and tidal inlets (2013)
    American Meteorological Society
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Meteorological Society, 2013. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 43 (2013): 1841–1861, doi:10.1175/JPO-D-12-0231.1.
    Beschreibung: In this idealized numerical modeling study, the composition of residual sediment fluxes in energetic (e.g., weakly or periodically stratified) tidal estuaries is investigated by means of one-dimensional water column models, with some focus on the sediment availability. Scaling of the underlying dynamic equations shows dependence of the results on the Simpson number (relative strength of horizontal density gradient) and the Rouse number (relative settling velocity) as well as impacts of the Unsteadiness number (relative tidal frequency). Here, the parameter space given by the Simpson and Rouse numbers is mainly investigated. A simple analytical model based on the assumption of stationarity shows that for small Simpson and Rouse numbers sediment flux is down estuary and vice versa for large Simpson and Rouse numbers. A fully dynamic water column model coupled to a second-moment turbulence closure model allows to decompose the sediment flux profiles into contributions from the transport flux (product of subtidal velocity and sediment concentration profiles) and the fluctuation flux profiles (tidal covariance between current velocity and sediment concentration). Three different types of bottom sediment pools are distinguished to vary the sediment availability, by defining a time scale for complete sediment erosion. For short erosion times scales, the transport sediment flux may dominate, but for larger erosion time scales the fluctuation sediment flux largely dominates the tidal sediment flux. When quarter-diurnal components are added to the tidal forcing, up-estuary sediment fluxes are strongly increased for stronger and shorter flood tides and vice versa. The theoretical results are compared to field observations in a tidally energetic inlet.
    Beschreibung: Project funding was provided by the German Research Foundation (DFG) in the framework of the Project ECOWS (Role of Estuarine Circulation for Transport of Suspended Particulate Matter in the Wadden Sea, BU 1199/11) and by the German Federal Ministry of Research and Education in the framework of the Project PACE [The future of the Wadden Sea sediment fluxes: still keeping pace with sea level rise? (FKZ 03F0634A)].
    Beschreibung: 2014-03-01
    Schlagwort(e): Channel flows ; Coastal flows ; Mixing ; Transport ; Turbulence ; Single column models
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
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  • 30
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    Continuous, array-based estimates of Atlantic Ocean heat transport at 26.5°N (2011)
    American Meteorological Society
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 24 (2011): 2429–2449, doi:10.1175/2010JCLI3997.1.
    Beschreibung: Continuous estimates of the oceanic meridional heat transport in the Atlantic are derived from the Rapid Climate Change–Meridional Overturning Circulation (MOC) and Heatflux Array (RAPID–MOCHA) observing system deployed along 26.5°N, for the period from April 2004 to October 2007. The basinwide meridional heat transport (MHT) is derived by combining temperature transports (relative to a common reference) from 1) the Gulf Stream in the Straits of Florida; 2) the western boundary region offshore of Abaco, Bahamas; 3) the Ekman layer [derived from Quick Scatterometer (QuikSCAT) wind stresses]; and 4) the interior ocean monitored by “endpoint” dynamic height moorings. The interior eddy heat transport arising from spatial covariance of the velocity and temperature fields is estimated independently from repeat hydrographic and expendable bathythermograph (XBT) sections and can also be approximated by the array. The results for the 3.5 yr of data thus far available show a mean MHT of 1.33 ± 0.40 PW for 10-day-averaged estimates, on which time scale a basinwide mass balance can be reasonably assumed. The associated MOC strength and variability is 18.5 ± 4.9 Sv (1 Sv ≡ 106 m3 s−1). The continuous heat transport estimates range from a minimum of 0.2 to a maximum of 2.5 PW, with approximately half of the variance caused by Ekman transport changes and half caused by changes in the geostrophic circulation. The data suggest a seasonal cycle of the MHT with a maximum in summer (July–September) and minimum in late winter (March–April), with an annual range of 0.6 PW. A breakdown of the MHT into “overturning” and “gyre” components shows that the overturning component carries 88% of the total heat transport. The overall uncertainty of the annual mean MHT for the 3.5-yr record is 0.14 PW or about 10% of the mean value.
    Beschreibung: This research was supported by the U.S. National Science Foundation under Awards OCE0241438 and OCE0728108, by the U.K. RAPID Programme (RAPID Grant NER/T/S/2002/00481), and by the U.S. National Oceanic and Atmospheric Administration, as part of its Western Boundary Time Series Program.
    Schlagwort(e): Atlantic Ocean ; Meridonial overturning circulation ; Sea surface temperature ; Transport ; Anomalies
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 31
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    Aerial imaging of fluorescent dye in the near shore (2014)
    American Meteorological Society
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Meteorological Society, 2014. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 31 (2014): 1410–1421, doi:10.1175/JTECH-D-13-00230.1.
    Beschreibung: Aerial images are used to quantify the concentration of fluorescent Rhodamine water tracing (WT) dye in turbid and optically deep water. Tracer releases near the shoreline of an ocean beach and near a tidal inlet were observed with a two-band multispectral camera and a pushbroom hyperspectral imager, respectively. The aerial observations are compared with near-surface in situ measurements. The ratio of upwelling radiance near the Rhodamine WT excitation and emission peaks varies linearly with the in situ dye concentrations for concentrations 〈20 ppb (r2 = 0.70 and r2 = 0.85–0.88 at the beach and inlet, respectively). The linear relationship allows for relative tracer concentration estimates without in situ calibration. The O(1 m) image pixels resolve complex flow structures on the inner shelf that transport and mix tracer.
    Beschreibung: We thank ONR and NSF for funding this work.
    Beschreibung: 2014-12-01
    Schlagwort(e): Coastal flows ; Mixing ; Transport ; Aircraft observations ; Remote sensing ; Tracers
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
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  • 32
    Digitale Medien
    Digitale Medien
    Ein Tabu Search-Verfahren für Containerbeladeprobleme mit schwach heterogenem Kistenvorrat (1998)
    Springer
    OR spectrum 20 (1998), S. 237-250 
    Details
    ISSN: 1436-6304
    Schlagwort(e): Transport ; Container ; Containerbelade-problem ; Tabu Search ; Praxisrelevante Restriktionen ; Packing ; Container ; Container loading problem ; Tabu search ; Practical restrictions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Wirtschaftswissenschaften
    Beschreibung / Inhaltsverzeichnis: Abstract The paper presents a tabu search algorithm (TSA) for weakly heterogeneous container loading problems. The approach includes two integrated components: The generation of different stowage plans by means of a greedy algorithm and a tabu search using an appropriate representation of these plans. The TSA considers some restrictions of practical relevance. The overall algorithm has been applied to numerous benchmark problems and its performance is demonstrated by a numerical comparison with several loading procedures suggested by other authors.
    Notizen: Zusammenfassung Gegenstand des Beitrags ist die Entwicklung eines Tabu Search-Verfahrens (TSV) für Containerbeladeprobleme mit schwach heterogenem Kistenvorrat. Das TSV basiert auf einem zweistufigen Verfahrensansatz. Ein integrierter Greedy-Algorithmus dient unmittelbar der Erzeugung von Stauplänen. Vermittelt über eine geeignete Repräsentation zulässiger Problemlösungen wird in einer zweiten Verfahrensstufe eine Tabu-Suche durchgeführt. Das TSV berücksichtigt einige praxisrelevante Restriktionen. Die Performance des TSV wird anhand von Benchmarkproblemen aus der Literatur demonstriert, wobei Containerbeladeverfahren verschiedener Autoren zu Vergleichszwecken herangezogen werden.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01539742
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  • 33
    Digitale Medien
    Digitale Medien
    Survival of bacteria introduced into soil by means of transport by Lumbricus rubellus (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 63-69 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Lumbricus rubellus ; Introduced bacteria ; Transport ; Survival ; Casts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Four strains of bacteria, Rhizobium leguminosarum biovar trifolii, Pseudomonas fluorescens, Pseudomonas cepacia, and Flavobacterium sp., were introduced into loamy sand and then transported by earthworms of the species Lumbricus rubellus to uninoculated soil. Cell densities recovered from the earthworm gut and casts (both expressed per gram dry material) were significantly lower (up to 3 log units) than cell densities recovered from the inoculated soil. Total bacterial counts in casts were similar to those in the inoculated soil. In casts excreted into a sterile environment numbers of colony-forming units (CFU) increased, suggesting a favourable environment for growth. In casts excreted in a non-sterile environment, cell densities of introduced strains decreased. Casts therefore did not offer the introduced bacteria a protective micro-environment for survival in the bulk soil. Transport by worms of R. leguminosarum biovar trifolii and of P. fluorescens appeared to occur mostly by means of cast production; with the Flavobacterium sp. and P. cepacia a large proportion of the cells was possibly transported on the skin of earthworms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00307843
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  • 34
    Digitale Medien
    Digitale Medien
    The Rev axis of HIV-1 and its associated host cofactors: A viral window onto the workings of eukaryotic posttranscriptional RNA processing (1996)
    Springer
    Journal of biomedical science 3 (1996), S. 69-77 
    Details
    ISSN: 1423-0127
    Schlagwort(e): HIV ; Rev ; Nucleus ; Transport ; RNA ; Cofactors ; Processing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The Rev axis of HIV is one of two key autoregulatory pathways required for viral replication and pathogenesis. The viral Rev protein interacts with its RNA target sequence, the RRE, to overcome the inhibitory effects of constitutive repressor sequences and promote nucleocytoplasmic transport and expression of viral RNAs. The Rev axis is the subject of intense scrutiny not only because it plays a central role in the viral life cycle, but also because it offers a window onto the workings of key mechanisms of posttranscriptional regulation, including splicing, polyadenylation, degradation, transport, and translation. Recent reports have conclusively demonstrated a central role for transport in the Rev mechanism and have identified cellular factors that are good candidates for mediating the transport phenomena. Other potentially involved cellular factors are being investigated. Much of the apparent heterogeneity in the observed effects of Rev may actually derive from heterogeneity in the constitutive repressor sequences rather than from heterogeneity in the mechanism of action of Rev per se.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02255533
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  • 35
    Digitale Medien
    Digitale Medien
    Subseabed disposal of radioactive waste: effects of consolidational fluid flow (1996)
    Springer
    Environmental geology 27 (1996), S. 300-308 
    Details
    ISSN: 1432-0495
    Schlagwort(e): Subseabed disposal ; Consolidation ; Transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract Subseabed disposal of radioactive waste applies a multiple-barrier concept with the sediment being the most important barrier for preventing a release of nuclides into the biosphere. While many investigations have been carried out to analyze the risk potential in this type of disposal, the effects of sediment consolidation and associated fluid flow have not fully been taken into consideration. Here, possible effects of consolidational fluid flow in the penetrator disposal option and possible consequences to the transport of nuclides in the sediment are analyzed. Results of numerical experiments demonstrate that consolidation contributes to the transport of radioactive nuclides released from containers buried in the sediment and to the release of nuclides at the sediment-water interface. Both depend on geological conditions and to a large extent on possible alterations of hydraulic conductivity i of the sediment in the vicinity of the entry path of a penetrator.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00766699
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  • 36
    Digitale Medien
    Digitale Medien
    Effective porosity and longitudinal dispersivity of sedimentary rocks determined by laboratory and field tracer tests (1995)
    Springer
    Environmental geology 25 (1995), S. 71-85 
    Details
    ISSN: 1432-0495
    Schlagwort(e): Effective porosity ; Longitudinal dispersivity ; Tracer test ; Transport ; Groundwater flow ; Sedimentary rock ; Dispersion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract We performed two field tracer tests in Tertiary sedimentary rocks and laboratory tracer tests using core samples of the sedimentary rock and bentonite and quartz sand mixtures. We have estimated effective porosity and longitudinal dispersivity, which are essential to the evaluation of mass transport in groundwater. The results of these tests indicate that test scale should be considered in the evaluation of effective porosity and longitudinal dispersivity. As the test scale increases, effective porosity decreases and longitudinal dispersivity increases. The relationship may be useful for estimating mass transport in groundwater. From the laboratory scale to the field scale, the decrease in effective porosity and increase in longitudinal dispersivity may be due to the existence of cracks or fissures. At the laboratory scale, the decrease in effective porosity is probably due to a loss of connectivity of continuous pores.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00767863
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  • 37
    Digitale Medien
    Digitale Medien
    Subseabed disposal of radioactive waste: effects of consolidational fluid flow (1996)
    Springer
    Environmental geology 27 (1996), S. 300-308 
    Details
    ISSN: 1432-0495
    Schlagwort(e): Key words: Subseabed disposal ; Consolidation ; Transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract. Subseabed disposal of radioactive waste applies a multiple-barrier concept with the sediment being the most important barrier for preventing a release of nuclides into the biosphere. While many investigations have been carried out to analyze the risk potential in this type of disposal, the effects of sediment consolidation and associated fluid flow have not fully been taken into consideration. Here, possible effects of consolidational fluid flow in the penetrator disposal option and possible consequences to the transport of nuclides in the sediment are analyzed. Results of numerical experiments demonstrate that consolodation contributes to the transport of radioactive nuclides released from containers buried in the sediment and to the release of nuclides at the sediment-water interface. Both depend on geological conditions and to a large extent on possible alterations of hydraulic conductivity of the sediment in the vicinity of the entry path of a penetrator.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002540050063
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  • 38
    Digitale Medien
    Digitale Medien
    The charge state of an ion channel controls neutral polymer entry into its pore (1997)
    Springer
    European biophysics journal 26 (1997), S. 471-476 
    Details
    ISSN: 1432-1017
    Schlagwort(e): Key words Ion channel ; Transport ; Polymers ; Hydration ; Water structure ; Alpha hemolysin ; Poly(ethylene glycol)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract Electrostatic potentials created by fixed or induced charges regulate many cellular phenomena including the rate of ion transport through proteinaceous ion channels. Nanometer-scale pores of these channels also play a critical role in the transport of charged and neutral macromolecules. We demonstrate here that, surprisingly, changing the charge state of a channel markedly alters the ability of nonelectrolyte polymers to enter the channel's pore. Specifically, we show that the partitioning of differently-sized linear nonelectrolyte polymers of ethylene glycol into the Staphylococcus aureus α-hemolysin channel is altered by the solution pH. Protonating some of the channel side chains decreases the characteristic polymer size (molecular weight) that can enter the pore by ∼25% but increases the ionic current by ∼15%. Thus, the “steric” and “electric” size of the channel change in opposite directions. The results suggest that effects due to polymer and channel hydration are crucial for polymer transport through such pores.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002490050101
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  • 39
    Digitale Medien
    Digitale Medien
    Sec-dependent preprotein translocation in bacteria (1996)
    Springer
    Archives of microbiology 165 (1996), S. 1-8 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Key wordsEscherichia coli ; ATPase ; Energetics ; Membrane protein ; Protein folding ; Sec Proteins ; Transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Translocation of precursor proteins across the cytoplasmic membrane in bacteria is mediated by a multi-subunit protein complex termed translocase, which consists of the integral membrane heterotrimer SecYEG and the peripheral homodimeric ATPase SecA. Preproteins are bound by the cytosolic molecular chaperone SecB and targeted in a complex with SecA to the translocation site at the cytoplasmic membrane. This interaction with SecYEG allows the SecA/preprotein complex to insert into the membrane by binding of ATP to the high affinity nucleotide binding site of SecA. At that stage, presumably recognition and proofreading of the signal sequence occurs. Hydrolysis of ATP causes the release of the preprotein in the translocation channel and drives the withdrawal of SecA from the membrane-integrated state. Hydrolysis of ATP at the low-affinity nucleotide binding site of SecA converts the protein into a compact conformational state and releases it from the membrane. In the absence of the proton motive force, SecA is able to complete the translocation stepwise by multiple nucleotide modulated cycles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002030050289
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  • 40
    Digitale Medien
    Digitale Medien
    Thiamin biosynthesis in prokaryotes (1999)
    Springer
    Archives of microbiology 171 (1999), S. 293-300 
    Details
    ISSN: 1432-072X
    Schlagwort(e): Key words Thiamin ; Biosynthesis ; Prokaryotes ; Transport ; Kinase ; Mechanism ; Structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Twelve genes involved in thiamin biosynthesis in prokaryotes have been identified and overexpressed. Of these, six are required for the thiazole biosynthesis (thiFSGH, thiI, and dxs), one is involved in the pyrimidine biosynthesis (thiC), one is required for the linking of the thiazole and the pyrimidine (thiE), and four are kinase genes (thiD, thiM, thiL, and pdxK). The specific reactions catalyzed by ThiEF, Dxs, ThiDM, ThiL, and PdxK have been reconstituted in vitro and ThiS thiocarboxylate has been identified as the sulfur source. The X-ray structures of thiamin phosphate synthase and 5-hydroxyethyl-4-methylthiazole kinase have been completed. The genes coding for the thiamin transport system (thiBPQ) have also been identified. Remaining problems include the cloning and characterization of thiK (thiamin kinase) and the gene(s) involved in the regulation of thiamin biosynthesis. The specific reactions catalyzed by ThiC (pyrimidine formation), and ThiGH and ThiI (thiazole formation) have not yet been identified.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002030050713
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  • 41
    Digitale Medien
    Digitale Medien
    Magnesium transport in prokaryotes (1999)
    Springer
    JBIC 4 (1999), S. 523-527 
    Details
    ISSN: 1432-1327
    Schlagwort(e): Key words Magnesium ; Transport ; Prokaryotes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract  Possessing the largest hydrated radius, the smallest ionic radius, and the highest charge density among the biologically relevant cations, Mg2+ provides an interesting problem for transport into living cells. Transport systems for Mg2+ have been characterized primarily in Salmonella typhimurium because the well-developed genetics of Gram-negative bacteria make cloning and studying the transporters a viable proposition. The CorA transport system is expressed constitutively and is the major Mg2+ transporter in Eubacteria and Archaea. It has three transmembrane domains, a uniquely large periplasmic domain, and no sequence homology to other proteins. The MgtE Mg2+ transporter also lacks sequence homology to other proteins, and it is unclear if Mg2+ transport is its primary function. The MgtA and MgtB Mg2+ transporters have sequence homology to P-type ATPases. They are more closely related to the mammalian Ca2+–ATPases than to the prokaryotic P-type ATPases. MgtA and MgtB mediate Mg2+ influx with, rather than against, the Mg2+ electrochemical gradient. Unlike corA and mgtE, the mgtA and mgtC/mgtB loci are regulated, being induced by the two-component regulatory system PhoP/PhoQ. PhoQ is a Mg2+ membrane sensor kinase that phosphorylates the transcription factor PhoP under Mg2+–limiting conditions. This factor then induces transcription of mgtA and mgtCB. MgtC, which is encoded by the first gene in the mgtCB operon, has no sequence homology to any known protein and is essential for S. typhimurium virulence in mice and macrophages, but does appear to be a Mg2+ transporter. The physiological roles of these Mg2+ transporters and their mechanisms are not yet completely clear, but initial data indicate that Mg2+ transporters are unique transport systems with unusual mechanisms for mediating Mg2+ movement through the membrane.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s007750050374
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  • 42
    Digitale Medien
    Digitale Medien
    The transport kinetics of lanthanide species in a single erythrocyte probed by confocal laser scanning microscopy (1999)
    Springer
    JBIC 4 (1999), S. 447-456 
    Details
    ISSN: 1432-1327
    Schlagwort(e): Key words Lanthanide ; Erythrocyte ; Transport ; Confocal laser scanning microscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract  A novel method has been developed to visualize and follow the temporal course of lanthanide transport across the membrane into a single living erythrocyte. By means of confocal scanning microscopy and the optical section technique, the entry of lanthanide ions was followed by the fluorescence quenching of fluorescein isothiocyanate (FITC)-labeled membrane and cytosol. From the difference of the quenching kinetics of the whole section and the central area, the time for diffusion through the membrane and the diffusion in the extracellular and intracellular media can be deduced. To clarify the mechanism of lanthanide-induced fluorescence quenching of FITC-labeled erythrocytes and to ensure that this reaction can be used in this method, the reaction was investigated by steady-state fluorescence techniques. The results showed that the lanthanides strongly quenched the florescence emitted by FITC covalently bound to membrane proteins and cytosolic proteins. The static quenching mechanism is responsible for the fluorescence quenching of FITC-labeled proteins by Ln species. The quenching mechanism is discussed on the basis of complex formation. The dependence of fluorescence quenching on both ion size and the total orbital angular momentum L supports the complexation mechanism. The transport time across the membrane is strikingly correlated with Ln species and extracellular concentration. For a given concentration, the transport time of [Ln(cit)2]3– is much shorter than that of Ln3+, since they enter the cells via the anion channel. This is supported by the inhibition effect of 4,4′-diisothiocyanato-2,2′-stilbenendisulfonate on the transport of [Ln(cit)2]3–. On the other hand, the transport of free Ln3+ might be attributed to the enhanced permeability of erythrocytes owing to Ln3+ binding. These findings strongly demonstrate the existence of the non-internalization mechanism of Ln species uptake by erythrocytes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s007750050331
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  • 43
    Digitale Medien
    Digitale Medien
    Opportunities for materials modeling in microelectronics: Programmed rate chemical vapor deposition (1999)
    Springer
    Journal of computer-aided materials design 6 (1999), S. 283-309 
    Details
    ISSN: 1573-4900
    Schlagwort(e): Aluminum ; Growth ; Nucleation ; Predictive process engineering ; Reaction ; Semiconductor processing ; Thin films ; Transport ; Tungsten
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Two case studies are presented in order to highlight the status of materials modeling in semiconductor materials processing, as well as some opportunities in the area. Both case studies involve programmed rate chemical vapor deposition (PRCVD), which is a CVD process in which conditions are systematically changed during deposition in order to enhance either processing properties or resulting film properties. In the tungsten study, quantitative simulations, based on fundamental transport and reaction modeling and a continuum film representation, are used to guide experiments that demonstrate how PRCVD can provide significantly greater throughput than conventional, constant rate CVD (CRCVD). We start the deposition process at a much higher temperature, compared to a CRCVD process, then decrease the temperature during deposition. We achieve throughput increases of about a factor of three, with more improvement clearly obtainable. In addition to the increase in throughput, the properties of the PRCVD films are equal to, or superior to, CRCVD films. The aluminum PRCVD case study demonstrates some opportunities for materials modeling. The protocols used are based upon qualitative models of nucleation and film growth, as there are no simulators that predict microstructure and film properties. Nevertheless, we demonstrate that the PRCVD processes, designed using qualitative models, can yield films with better properties than CRCVD processes. PRCVD films can have higher nuclei densities, higher fractions of (111) orientated Al, lower surface roughnesses, higher reflectivities, and resistivities closer to that of bulk aluminum. In general, PRCVD protocols provide degrees of freedom that can be used to improve processing or film properties. PRCVD may become much more important as films get thinner and interfaces become more important.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008762530690
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  • 44
    Digitale Medien
    Digitale Medien
    Lithium ion transport in a model of amorphous polyethylene oxide (1996)
    Springer
    Journal of computer-aided materials design 3 (1996), S. 385-402 
    Details
    ISSN: 1573-4900
    Schlagwort(e): Lithium ; Polyethylene oxide ; Batteries ; Transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Summary We have made a molecular dynamics study of transport of a single lithium ion in a previously reported model of amorphous polyethylene oxide. New ab initio calculations of the interaction of the lithium ion with 1,2-dimethoxyethane and with dimethyl ether are reported which are used to determine force fields for the simulation. We report preliminary calculations of solvation energies and hopping barriers and a calculation of the ionic conductivity which is independent of any assumptions about the mechanism of ion transport. We also report some details of a study of transport of the trapped lithium ion on intermediate time and length scales.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01185677
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  • 45
    Digitale Medien
    Digitale Medien
    On momentum flux and velocity spectra over waves (1999)
    Springer
    Boundary layer meteorology 92 (1999), S. 489-515 
    Details
    ISSN: 1573-1472
    Schlagwort(e): Air-sea fluxes ; Wind stress ; Wind waves ; Swell ; Universal spectra ; Monin--Obukhov theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Data from a research tower in Lake Ontario are used to study the validity of Monin--Obukhov scaling in the marine atmospheric boundary layer under various wave conditions. It is found that over pure wind seas, the velocity spectra and cospectra follow established universal scaling laws. However, in the presence of swells outrunning weak winds, velocity spectra and cospectra no longer satisfy universal spectral shapes. Here, Monin–Obukhov similarity theory, and the classical logarithmic boundary layers, are no longer valid. It is further shown that, in the presence of such swells, the momentum flux can be significantly modified in comparison to pure wind sea values. The implications of these findings for bulk flux estimations and on the inertial dissipation method for calculating fluxes are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1002054820455
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  • 46
    Digitale Medien
    Digitale Medien
    Wind Stress Structure in the Unstable Marine Surface Layer Detected by Sar (1998)
    Springer
    Boundary layer meteorology 86 (1998), S. 1-28 
    Details
    ISSN: 1573-1472
    Schlagwort(e): Wind stress ; Synthetic Aperture Radar ; Marine surface layer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The wind stress in the marine surface layer under unstable conditions and low wind speed has been studied using a Synthetic Aperture Radar (SAR) image of the sea surface and time series of the horizontal and vertical wind velocities and of the wind stress recorded on board the C.N.R. research platform, in the northern Adriatic Sea, during a SAR overflight. A conditional sampling technique has been used on the wind stress time series and on the SAR image to detect downward (sweep) and upward (ejection) bursts of the momentum flux, as well as the two-dimensional structure of the radar backscatter. From the ensemble average of both the wind stress and the backscatter structures, it has been possible to estimate the mean duration of the upward (≈11 s) and the downward (≈15 s) wind stress bursts and the mean size of the bright patches of the SAR image (≈120 m). The front of the mean backscatter structure, associated with the downward wind stress bursts, has been related to the time length of the mean sweep stress structure to get, after accounting for a threshold of the wind stress for the generation of the sea surface wavelets, the translation velocity Ut of the mean wind stress of sweep, very close to the mean wind speed. The vertical coherence of the wind stress structures has permited to refer the translation velocity to a level very close to the sea surface, but above the viscous sublayer. The variability of Ut with height has been studied through comparison with the mean wind speed at different heights z calculated by a boundary-layer model. Accounting for the results reported in the literature, there is an indication that Ut is constant with height in the range 0.5 m ≤ z ≤ 15 m. The two-dimensional pattern of the wind stress structures has been derived from the SAR image. The structures appear elongated crosswind, as with microfronts, with an average cross- to down-wind ratio of ≈ 4. The area covered by the downward wind stress structures represents 13% of the total area.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1000522423136
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  • 47
    Digitale Medien
    Digitale Medien
    Aquaporin function, structure, and expression: are there more surprises to surface in water relations? (1998)
    Springer
    Planta 204 (1998), S. 131-139 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Key words: Aquaporin ; Plasma membrane intrinsic protein ; Tonoplast intrinsic protein ; Transport ; Water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004250050239
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  • 48
    Digitale Medien
    Digitale Medien
    Immunolocalization of a putative unconventional myosin on the surface of motile mitochondria in locust photoreceptors (1998)
    Springer
    Cell & tissue research 292 (1998), S. 219-227 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words Photoreceptor cells ; Transport ; intracellular ; Cytoskeleton ; Myosin ; Actin filaments ; Mitochondria ; Schistocerca gregaria (Insecta)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract  Light stimulation of locust (Schistocerca gregaria) photoreceptors results in an actin-dependent translocation of mitochondria towards the photoreceptive microvilli and an antagonistic movement of endoplasmic reticulum towards the cell body. Using immunocytochemical techniques, we have tried to identify myosin-like motors that may drive the light-induced organelle motility. A monoclonal antibody against the motor domain of Acanthamoeba myosin identifies a prominent 110-kDa protein on Western blots of locust retina. Cross-reactivity with two polyclonal anti-myosin antibodies and a monoclonal anti-myosin-I-antibody, together with ATP-dependent binding to actin filaments, provides evidence that the 110-kDa protein is an unconventional myosin. By indirect immunofluorescence, the 110-kDa protein has been localized to both photoreceptors and pigment cells within the retina. In the photoreceptor cells, the 110-kDa protein is bound to the surface of mitochondria. This putative unconventional myosin may thus be a motor protein involved in the light-induced translocation of mitochondria in photoreceptors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410051053
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  • 49
    Digitale Medien
    Digitale Medien
    Immunolocalization of kinesin and cytoplasmic dynein in the retina of the locust Schistocerca gregaria (1996)
    Springer
    Cell & tissue research 286 (1996), S. 547-549 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Compound eye ; Photoreceptor cells ; Cytoskeleton ; Transport ; intracellular ; Microtubules ; Membrane turnover ; Schistocerca gregaria (Insecta)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Light stimulation of locust photoreceptors causes a translocation of submicrovillar cisternae of the endoplasmic reticulum away from the rhabdome, and a movement of mitochondria towards the rhabdome. To examine whether the microtubule cytoskeleton could be involved in these organelle movements, we have analysed the distribution of the microtubule-dependent motor proteins kinesin and cytoplasmic dynein in the retina of the locust Schistocerca gregaria. Both kinesin and cytoplasmic dynein are associated with vesicular structures that are distinct from mitochondria and the submicrovillar endoplasmic reticulum. These results, together with the previous demonstration of a lack of microtubules in the cell area of light-dependent organelle movements, provide evidence that the microtubule cytoskeleton is not involved with light-induced organelle translocations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050725
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  • 50
    Digitale Medien
    Digitale Medien
    Influence of forskolin and carbachol on intestinal absorption of horseradish peroxidase in the goldfish (Carassius auratus) (1996)
    Springer
    Cell & tissue research 285 (1996), S. 51-56 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Intestine ; Endocytosis ; Tight junctions ; Carbachol ; Forskolin ; Transport ; Carassius auratus (Teleostei)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The transepithelial route for mucosa-to-serosa transport of the tracer macromolecule horseradish peroxidase (HRP; MW 40 kDa) and modulation of this transport by forskolin and carbachol have been studied in vi-tro in stripped goldfish intestinal epithelium mounted in Ussing-type chambers. Uptake and transport have been investigated by measuring the HRP flux from the muco-sal to serosal sides by an enzymatic method and by visualising HRP reaction products in the mucosa with electron-microscopical techniques. Both the cholinergic agonist carbachol (which is thought to increase intracellular Ca2+ and activate protein kinase C activity) and forskolin (a direct activator of adenylylcyclase) affect the amount of enzymatically active HRP in the tissue. In control tissue, HRP product is found only within the epithelial cells, the transepithelial flux reaching a constant value of about 1.5 pmoles/cm2 per h. Carbachol increases the amount of HRP product in the cells, but has no significant effect on the HRP flux compared with control values. Forskolin decreases the amount of HRP product in the cells; however, in the presence of forskolin, the lateral intercellular spaces become filled with HRP product. HRP is found in the lamina propria and the transepithelial protein flux increases more than 2.5-fold. In the presence of forskolin plus carbachol, the results are no different from the control. It is concluded that carbachol increases the endocytotic uptake of HRP, whereas forskolin inhibits the uptake but increases the paracellular permeability for HRP in goldfish intestine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050619
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  • 51
    Digitale Medien
    Digitale Medien
    Immunocytochemical analysis of the transport of arginine analogues into nitrergic neurons and other cells in the retina and pituitary (1997)
    Springer
    Cell & tissue research 290 (1997), S. 501-514 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Arginine ; Analogues ; Immunocytochemistry ; Nitric oxide ; Pituitary ; Retina ; Transport ; Rat (Wistar) ; Rabbit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Nitric oxide is formed by the action of nitric oxide synthase upon l-arginine. The efficacy of some exogenously applied arginine analogues in inhibiting nitric oxide synthase and thus nitrergic transmission indicates that neurons producing nitric oxide may possess an arginine transport system. To investigate whether arginine analogues are preferentially transported into nitric oxide-utilising cells or into cells making other neurochemicals, we have raised highly specific antisera against a number of arginine analogues including NG-methyl arginine, d-arginine, NGnitro-l-arginine, NG-nitro-l-arginine methyl ester and canavanine. Retinae were incubated in physiological media containing these analogues and rats were given intraperitoneal injections of the analogues to study the pituitary. Immunocytochemistry and NADPH-diaphorase histochemistry revealed that many of these analogues could be transported preferentially, but not exclusively, into nitric oxide-generating cells. However, some nitric oxide-producing cells apparently lacked the ability to take up some arginine analogues. We conclude that nitric oxide-generating cells in the retina and pituitary possess one or more arginine transporters. Other subsets of neurons that use GABA or glutamate as a neurotransmitter may also accumulate arginine analogues, possibly as a substrate for formation of these neurochemicals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050957
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  • 52
    Digitale Medien
    Digitale Medien
    Trafficking of glucose transporters-signals and mechanisms (1995)
    Springer
    Bioscience reports 15 (1995), S. 419-426 
    Details
    ISSN: 1573-4935
    Schlagwort(e): Transport ; glucose ; membrane trafficking ; interleukin-3 ; Abelson tyrosine kinase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The uptake of glucose into mammalian cells, catalysed by members of the GLUT family of glucose transporters, is regulated by a variety of hormones, growth factors and other agents. In adipocytes, skeletal muscle and heart the principal regulator is the hormone insulin, which rapidly stimulates glucose uptake by bringing about the translocation of the GLUT4 glucose transporter isoform from an intracellular vesicular compartment to the cell surface. Recent studies have implicated theC-terminal hydrophilic region of this protein as being primarily responsible for its insulin-regulated trafficking. In an attempt to identify the protein machinery involved in this trafficking, we have used glutathione S-transferase fusion proteins bearing hydrophilic domains of various GLUT transporters in affinity purification experiments on detergent-solubilized extracts of 3T3-L1 adipocyte intracellular membranes. TheC-terminal region of GLUT4 was found specifically to bind a number of polypeptides in these extracts, which are therefore candidates for components of the trafficking machinery. Although these proteins did not bind to the corresponding region of the more widely-distributed GLUT1 glucose transporter isoform, regulation of this transporter also appears to be of physiological importance in some cell types. To study such regulation we have used as a model system the interleukin-3 (IL-3)-dependent haemopoietic cell line IC.DP. These cells express a temperature-sensitive mutane of thev-abl tyrosine kinase, whose activation at the permissive temperature permits cell survival in the absence of IL-3 by suppression of apoptosis, although the growth factor is still required for proliferation. Both IL-3 and activation of the kinase were found to stimulate glucose transport by promoting the translocation of GLUT1 to the cell surface. Moreover, inhibition of glucose uptake by addition of transport inhibitors markedly increased the rate of apoptosis, an effect which could be reversed by the provision of alternative energy sources. These observations suggest that the trafficking of GLUT1, regulated by growth factors or oncogenes, may play an important role in the suppression of apoptosis in haemopoietic cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01204346
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  • 53
    Digitale Medien
    Digitale Medien
    Involvement of histidine permease (Hip1p) in manganese transport in Saccharomyces cerevisiae (1998)
    Springer
    Molecular genetics and genomics 259 (1998), S. 541-548 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Key words Manganese ; Divalent cations ; Transport ; HIP1 ; Saccharomyces cerevisiae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In a search for components involved in Mn2+ homeostasis in the budding yeast Saccharomyces cerevisiae, we isolated a mutant with modifications in Mn2+ transport. The mutation was found to be located in HIP1, a gene known to encode a high-affinity permease for histidine. The mutation, designated hip1–272, caused a frameshift that resulted in a stop codon at position 816 of the 1812-bp ORF. This mutation led to Mn2+ resistance, whereas the corresponding null mutation did not. Both hip1–272 cells and the null mutant exhibited low tolerance to divalent cations such as Co2+, Ni2+, Zn2+, and Cu2+. The Mn2+ phenotype was not influenced by supplementary histidine in either mutant, whereas the sensitivity to other divalent cations was alleviated by the addition of histidine. The cellular Mn2+ content of the hip1–272 mutant was lower than that of wild type or null mutant, due to increased rates of Mn2+ efflux. We propose that Hip1p is involved in Mn2+ transport, carrying out a function related to Mn2+ export.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004380050846
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  • 54
    Digitale Medien
    Digitale Medien
    Four Contemporary Issues Concerning Ionospheric Plasma Flow to the Magnetosphere (1997)
    Springer
    Space science reviews 80 (1997), S. 49-76 
    Details
    ISSN: 1572-9672
    Schlagwort(e): Magnetosphere ; Ionosphere ; Plasma ; Transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this review, we examine four specific questions/issues of contemporary interest within the overall topic of ionospheric plasma outflow into the magnetosphere. These four question areas are framed here as: (1) Are high-latitude F-region upflows predominantly driven by soft auroral electron precipitation?; (2) Is the O+ within the polar cap magnetosphere supplied primarily by the cleft ion fountain or a direct polar cap ionospheric source?; (3) Is centrifugal acceleration an important mechanism in the acceleration of ionospheric plasma outflows?; and (4) Are lobe ionospheric outflows captured by the plasma sheet?
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004973603955
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  • 55
    Digitale Medien
    Digitale Medien
    Observational Evidence for Transfer of Plasma Across the Magnetopause (1997)
    Springer
    Space science reviews 80 (1997), S. 217-234 
    Details
    ISSN: 1572-9672
    Schlagwort(e): Magnetopause ; Boundary Layer ; Magnetic Reconnection ; Diffusion ; Transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract There is a long history of particle measurements that have established that plasma is being transferred across Earth's magnetopause in both directions. The paper reviews the nature of the observational evidence as well as the implications regarding the transfer mechanisms and their efficiencies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004926004806
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  • 56
    Digitale Medien
    Digitale Medien
    A Description of Reverse Osmosis using Practical Kedem-Katchalsky Equations (1997)
    Springer
    Journal of biological physics 23 (1997), S. 111-120 
    Details
    ISSN: 1573-0689
    Schlagwort(e): Membrane ; Solution ; Transport ; Reverse osmosis ; Transport equations.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract The work is concerned with an analytical description of reverseosmosis using the Kedem-Katchalsky equations.The process has been considered for well-mixed solutions.We have obtained formulas describing the concentration of a solution(purified by reverse osmosis) as a function of the transportparameters of a membrane, concentration of the initial solution, andthe mechanical pressures on the membrane.The formulae are illustrated by numerical computations.Our results may be applicable to biophysical studies concerningreverse osmosis in biological membrane systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004928519666
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  • 57
    Digitale Medien
    Digitale Medien
    Correlation Relation for the Membrane Transport ParametersLp, σ, and ω (1997)
    Springer
    Journal of biological physics 23 (1997), S. 233-238 
    Details
    ISSN: 1573-0689
    Schlagwort(e): Membrane ; Transport ; Transport parameters ; Correlation ; Correlation constant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract We derive a formula for the correlation of the three practical transportparameters Lp, σ, and ω appearing in Kedem-Katchalskyequations. It has a form ω = KLp/vs(1-σ), where K = 0.0306 is a universal constant independent ofthe choice of a membrane and a solute. It can be used to calculate the valueof any of these parameters, provided the other two and the molar volume $$\overline {\upsilon _s } $$ of the solute are known. The formula couldbe very useful, in particular when measurements of the parameters aredifficult or even impossible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005013401487
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  • 58
    Digitale Medien
    Digitale Medien
    Transport of Neutral Arenes through an Aqueous Barrier by Resorcinol–Aldehyde Tetramers (1997)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 28 (1997), S. 105-116 
    Details
    ISSN: 1573-1111
    Schlagwort(e): Transport ; tetramers ; neutral arenes ; aqueous barrier
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The transportation of neutral arenes such as benzene, toluene, o,m,p-xylene, durene,biphenyl, anthracene and phenanthrene through an aqueous medium using the crownconformation of tetrameric cyclophane hosts 1 and 2 has been studied. In general,transportation of all arenes increases with time, exceptfor toluene, which showssaturation behaviour with both hosts 1 and 2.Among the larger arenes, transportationof biphenyl is a maximum with 1; with host 2,transportation of anthracene is a maximumdue to its larger association constant. In the case ofsmaller arenes, 1 transportsbenzene most effectively, and transportation decreases asthe number of methyl groups onbenzene increases, showing that stereoelectronic factors affecttransportation. With 2toluene is transported most effectively due tothe change in the shape of the binding cavitycaused by a change in bridging groups. A comparison oftransportation for 1 h with 1 and 2shows that for all arenes transportation is greater withhost 2 than with 1 due to thehydrophobic nature of 2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007950407337
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