Journal articles on the topic 'Coupled transports'
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1
Grogan, Dustin F. P., and Terrence R. Nathan. "Passive versus Active Transport of Saharan Dust Aerosols by African Easterly Waves." Atmosphere 12, no. 11 (November 16, 2021): 1509. http://dx.doi.org/10.3390/atmos12111509.
Abstract:
Theory and modeling are combined to reveal the physical and dynamical processes that control Saharan dust transport by amplifying African easterly waves (AEWs). Two cases are examined: active transport, in which the dust is radiatively coupled to the circulation; passive transport, in which the dust is radiatively decoupled from the circulation. The theory is built around a dust conservation equation for dust-coupled AEWs in zonal-mean African easterly jets. The theory predicts that, for both the passive and active cases, the dust transports will be largest where the zonal-mean dust gradients are maximized on an AEW critical surface. Whether the dust transports are largest for the radiatively passive or radiatively active case depends on the growth rate of the AEWs, which is modulated by the dust heating. The theoretical predictions are confirmed via experiments carried out with the Weather Research and Forecasting model, which is coupled to a dust conservation equation. The experiments show that the meridional dust transports dominate in the passive case, while the vertical dust transports dominate in the active case.
2
Marino, S., M. Shapiro, and P. M. Adler. "Coupled Transports in Heterogeneous Media." Journal of Colloid and Interface Science 243, no. 2 (November 2001): 391–419. http://dx.doi.org/10.1006/jcis.2001.7826.
3
Nathan, Terrence R., Dustin F. P. Grogan, and Shu-Hua Chen. "Saharan Dust Transport during the Incipient Growth Phase of African Easterly Waves." Geosciences 9, no. 9 (September 5, 2019): 388. http://dx.doi.org/10.3390/geosciences9090388.
Abstract:
An analytical analysis is combined with numerical modeling simulations in order to expose the physical and dynamical processes that control the zonal-mean transport of Saharan mineral dust aerosols during the incipient growth phase of African easterly waves. The analytical analysis provides the theoretical basis for understanding and predicting how the waves and background flow combine to affect the zonal-mean eddy transports of dust. The analytically derived transport equations―which are valid for any wave field, irrespective of its spatial or temporal scale―predict that the eddy transports of dust are largest where the maximum in the background dust gradients coincide with a critical surface, i.e., where the Doppler-shifted frequency of the wave field vanishes. Linear simulations of the eddy dust transports are conducted using a mechanistic version of the Weather Research and Forecasting (WRF) model coupled to an interactive dust model. The simulations show that the eddy dust transports are directed down the background dust gradients and that the meridional transports of dust dominate over the vertical transports. The numerical simulations confirm the theoretical predictions. The predictions are used to explain recent statistical analyses of reanalysis data for dust-coupled African easterly waves.
4
Li, Shuang, Yihu Yang, and Weikai Li. "Human ferroportin mediates proton-coupled active transport of iron." Blood Advances 4, no. 19 (October 2, 2020): 4758–68. http://dx.doi.org/10.1182/bloodadvances.2020001864.
Abstract:
Abstract As the sole iron exporter in humans, ferroportin controls systemic iron homeostasis through exporting iron into the blood plasma. The molecular mechanism of how ferroportin exports iron under various physiological settings remains unclear. Here we found that purified ferroportin incorporated into liposomes preferentially transports Fe2+ and exhibits lower affinities of transporting other divalent metal ions. The iron transport by ferroportin is facilitated by downhill proton gradients at the same direction. Human ferroportin is also capable of transporting protons, and this activity is tightly coupled to the iron transport. Remarkably, ferroportin can conduct active transport uphill against the iron gradient, with favorable charge potential providing the driving force. Targeted mutagenesis suggests that the iron translocation site is located at the pore region of human ferroportin. Together, our studies enhance the mechanistic understanding by which human ferroportin transports iron and suggest that a combination of electrochemical gradients regulates iron export.
5
Merryfield, William J., and George J. Boer. "Variability of Upper Pacific Ocean Overturning in a Coupled Climate Model." Journal of Climate 18, no. 5 (March 1, 2005): 666–83. http://dx.doi.org/10.1175/jcli-3282.1.
Abstract:
Abstract Variability of subtropical cell (STC) overturning in the upper Pacific Ocean is examined in a coupled climate model in light of large observed changes in STC transport. In a 1000-yr control run, modeled STC variations are smaller than observed, but correlate in a similar way with low-frequency ENSO-like variability. In model runs that include anthropogenically forced climate change, STC pycnocline transports decrease progressively under the influence of global warming, attaining reductions of 8% by 2000 and 46% by 2100. Although the former reduction is insufficient to fully account for the apparent observed decline in STC transport over recent decades, it does suggest that global warming may have contributed to the observed changes. Analysis of coupled model results shows that STC transports play a significant role in modulating tropical Pacific Ocean heat content, and that such changes are dominated by anomalous currents advecting mean temperature, rather than by advection of temperature anomalies by mean currents.
6
Liu, Zhengyu, Chengfei He, and Feiyu Lu. "Local and Remote Responses of Atmospheric and Oceanic Heat Transports to Climate Forcing: Compensation versus Collaboration." Journal of Climate 31, no. 16 (August 2018): 6445–60. http://dx.doi.org/10.1175/jcli-d-17-0675.1.
Abstract:
We present a theoretical study on local and remote responses of atmosphere and ocean meridional heat transports (AHT and OHT, respectively) to climate forcing in a coupled energy balance model. We show that, in general, a surface heat flux forces opposite AHT and OHT responses in the so-called compensation response, while a net heat flux into the coupled system forces AHT and OHT responses of the same direction in the so-called collaboration response. Furthermore, unless the oceanic thermohaline circulation is significantly changed, a remote climate response far away from the forcing region tends to be dominated by the collaboration response, because of the effective propagation of a coupled ocean–atmosphere energy transport mode of collaboration structure. The relevance of our theory to previous CGCM experiments is also discussed. Our theoretical result provides a guideline for understanding of the response of heat transports and the associated climate changes.
7
Vellinga, Michael, and Peili Wu. "Relations between Northward Ocean and Atmosphere Energy Transports in a Coupled Climate Model." Journal of Climate 21, no. 3 (February 1, 2008): 561–75. http://dx.doi.org/10.1175/2007jcli1754.1.
Abstract:
Abstract The Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) is used to analyze the relation between northward energy transports in the ocean and atmosphere at centennial time scales. In a transient water-hosing experiment, where suppressing the Atlantic meridional overturning circulation (MOC) causes a reduction in northward ocean heat transport of up to 0.75 PW (i.e., 75%), the atmosphere compensates by increasing its northward transport of moist static energy. This compensation is very efficient at low latitudes and near complete at the equator throughout the experiment, but is incomplete farther north across the northern midlatitude storm tracks. The change in atmosphere energy transport enables the model to find a new global-mean radiative equilibrium after 240 yr. In a perturbed physics ensemble of HadCM3 it was found that time-averaged meridional energy transports in ocean and atmosphere can act opposingly. Where model formulation causes an unbalanced mean climate state, for example, an excessive top-of-the-atmosphere radiative surplus at low latitudes, the atmosphere increases its poleward energy transport to disperse this excess. MOC and ocean poleward heat transport tend to be reduced in such model versions, and this offsets the increased poleward atmospheric transport of the low-latitude energy surplus. Model versions that are close to net radiative equilibrium also have ocean heat transport and MOC close to observed values.
8
Juan, Wen-Tau, Ming-Hua Chang, Ying-Ju Lai, Ming-Heng Chen, and Lin I. "Laser Enhanced Transports in Strongly Coupled Dusty Plasmas." Physica Scripta T89, no. 1 (2001): 9. http://dx.doi.org/10.1238/physica.topical.089a00009.
9
Tsubaki, Shuji, Naoki Fujita, Fujio Wakaya, Yoshihiko Yuba, and Kenji Gamo. "Linear and nonlinear transports of coupled quantum dots." Superlattices and Microstructures 27, no. 5-6 (May 2000): 363–67. http://dx.doi.org/10.1006/spmi.2000.0842.
10
Yang, Qianzi, Yingying Zhao, Qin Wen, Jie Yao, and Haijun Yang. "Understanding Bjerknes Compensation in Meridional Heat Transports and the Role of Freshwater in a Warming Climate." Journal of Climate 31, no. 12 (June 2018): 4791–806. http://dx.doi.org/10.1175/jcli-d-17-0587.1.
Abstract:
The Bjerknes compensation (BJC) under global warming is studied using a simple box model and a coupled Earth system model. The BJC states the out-of-phase changes in the meridional atmosphere and ocean heat transports. Results suggest that the BJC can occur during the transient period of global warming. During the transient period, the sea ice melting in the high latitudes can cause a significant weakening of the Atlantic meridional overturning circulation (AMOC), resulting in a cooling in the North Atlantic. The meridional contrast of sea surface temperature would be enhanced, and this can eventually enhance the Hadley cell and storm-track activities in the Northern Hemisphere. Accompanied by changes in both ocean and atmosphere circulations, the northward ocean heat transport in the Atlantic is decreased while the northward atmosphere heat transport is increased, and the BJC occurs in the Northern Hemisphere. Once the freshwater influx into the North Atlantic Ocean stops, or the ocean even loses freshwater because of strong heating in the high latitudes, the AMOC would recover. Both the atmosphere and ocean heat transports would be enhanced, and they can eventually recover to the state of the control run, leading to the BJC to become invalid. The above processes are clearly demonstrated in the coupled model CO2 experiment. Since it is difficult to separate the freshwater effect from the heating effect in the coupled model, a simple box model is used to understand the BJC mechanism and freshwater’s role under global warming. In a warming climate, the freshwater flux into the ocean can cool the global surface temperature, mitigating the temperature rise. Box model experiments indicate clearly that it is the freshwater flux into the North Atlantic that causes out-of-phase changes in the atmosphere and ocean heat transports, which eventually plays a stabilizing role in global climate change.
11
Nathan, Terrence R., and Dustin F. P. Grogan. "Scale-Dependent Transport of Saharan Dust by African Easterly Waves." Geosciences 12, no. 9 (September 11, 2022): 337. http://dx.doi.org/10.3390/geosciences12090337.
Abstract:
The scale-dependent transport of Saharan dust aerosols by African easterly waves (AEWs) is examined analytically and numerically. The analytical analysis shows that the meridional and vertical wave transports of dust are modulated by the Doppler-shifted frequency, ωd, and the wave growth rate, ωi, both of which are functions of the zonal wave scale. The analytical analysis predicts that the AEW dust transports, which are driven by the Reynolds stresses acting on the mean dust gradients, are largest for the twin limits: ωd→0, which corresponds to flow near a critical surface, a local effect; and ωi→0, which corresponds to the slowest growing waves, a global effect. The numerical analysis is carried out with the Weather Research and Forecasting (WRF) model, which is radiatively coupled to the dust field. The model simulations are based on an AEW spectrum consistent with observations. The simulations agree with the theoretical predictions: the slowest growing waves have the strongest transports, which are as much as ~40% larger than the transports of the fastest growing wave. Although the transports are highly scale-dependent, largely due to the scale dependence of ωi, the location of the critical surface and thus the location of the maximum dust transports are not.
12
Treguier, Anne Marie, Pierre Mathiot, Tim Graham, Dan Copsey, Camille Lique, and Jean Sterlin. "Heat Balance in the Nordic Seas in a Global 1/12° Coupled Model." Journal of Climate 34, no. 1 (January 2021): 89–106. http://dx.doi.org/10.1175/jcli-d-20-0063.1.
Abstract:
AbstractThe Nordic seas are a gateway to the Arctic Ocean, where Atlantic water undergoes a strong cooling during its transit. Here we investigate the heat balance of these regions in the high-resolution Met Office Global Coupled Model GC3 with a 1/12° grid. The GC3 model reproduces the contrasted ice conditions and ocean heat loss between the eastern and western regions of the Nordic seas. In the west (Greenland and Iceland seas), the heat loss experienced by the ocean is stronger than the atmospheric heat gain, because of the cooling by ice melt. The latter is a major contribution to the heat loss over the path of the East Greenland Current and west of Svalbard. In the model, surface fluxes balance the convergence of heat in each of the eastern and western regions. The net east–west heat exchange, integrated from Fram Strait to Iceland, is relatively small: the westward heat transport of the Return Atlantic Current over Knipovich Ridge balances the eastward heat transport by the East Icelandic Current. Time fluctuations, including eddies, are a significant contribution to the net heat transports. The eddy flux represents about 20% of the total heat transport in Denmark Strait and across Knipovich Ridge. The coupled ocean–atmosphere–ice model may overestimate the heat imported from the Atlantic and exported to the Arctic by 10% or 15%. This confirms the tendency toward higher northward heat transports as model resolution is refined, which will impact scenarios of future climate.
13
Majda, Andrew J., and Samuel N. Stechmann. "Stochastic models for convective momentum transport." Proceedings of the National Academy of Sciences 105, no. 46 (November 17, 2008): 17614–19. http://dx.doi.org/10.1073/pnas.0806838105.
Abstract:
The improved parameterization of unresolved features of tropical convection is a central challenge in current computer models for long-range ensemble forecasting of weather and short-term climate change. Observations, theory, and detailed smaller-scale numerical simulations suggest that convective momentum transport (CMT) from the unresolved scales to the resolved scales is one of the major deficiencies in contemporary computer models. Here, a combination of mathematical and physical reasoning is utilized to build simple stochastic models that capture the significant intermittent upscale transports of CMT on the large scales due to organized unresolved convection from squall lines. Properties of the stochastic model for CMT are developed below in a test column model environment for the large-scale variables. The effects of CMT from the stochastic model on a large-scale convectively coupled wave in an idealized setting are presented below as a nontrivial test problem. Here, the upscale transports from stochastic effects are significant and even generate a large-scale mean flow which can interact with the convectively coupled wave.
14
Born, A., T. F. Stocker, and A. B. Sandø. "Coupling of eastern and western subpolar North Atlantic: salt transport in the Irminger Current." Ocean Science Discussions 10, no. 2 (March 15, 2013): 555–79. http://dx.doi.org/10.5194/osd-10-555-2013.
Abstract:
Abstract. Salt transport in the Irminger Current and thus the coupling between eastern and western subpolar North Atlantic plays an important role for climate variability across a wide range of time scales. High-resolution ocean modeling and observations indicate that salinities in the eastern subpolar North Atlantic decrease with enhanced circulation of the North Atlantic subpolar gyre (SPG). This has led to the perception that a stronger SPG also transports less salt westward. In this study, we analyze a regional ocean model and a comprehensive global coupled climate model, and show that a stronger SPG transports more salt in the Irminger Current irrespective of lower salinities in its source region. The additional salt converges in the Labrador Sea and the Irminger Basin by eddy transports, increases surface salinity in the western SPG, and favors more intense deep convection. This is part of a positive feedback mechanism with potentially large implications for climate variability and predictability.
15
Huang, Xu-Guang. "Phenomenology of anomalous chiral transports in heavy-ion collisions." EPJ Web of Conferences 172 (2018): 01003. http://dx.doi.org/10.1051/epjconf/201817201003.
Abstract:
High-energy Heavy-ion collisions can generate extremely hot quark-gluon matter and also extremely strong magnetic fields and fluid vorticity. Once coupled to chiral anomaly, the magnetic fields and fluid vorticity can induce a variety of novel transport phenomena, including the chiral magnetic effect, chiral vortical effect, etc. Some of them require the environmental violation of parity and thus provide a means to test the possible parity violation in hot strongly interacting matter. We will discuss the underlying mechanism and implications of these anomalous chiral transports in heavy-ion collisions.
16
Harrington, Gregory N., Katherine E. Dibley, Raymond J. Ritchie, Christina E. Offler, and John W. Patrick. "Hexose uptake by developing cotyledons of Vicia faba: physiological evidence for transporters of differing affinities and specificities." Functional Plant Biology 32, no. 11 (2005): 987. http://dx.doi.org/10.1071/fp05081.
Abstract:
Cotyledons of broad bean (Vicia faba L.) develop in an apoplasmic environment that shifts in composition from one dominated by hexoses to one dominated by sucrose. During the latter phase of development, sucrose / H+ symporter activity and expression is restricted to cotyledon epidermal transfer cell complexes that support sucrose fluxes that are 8.5-fold higher than those exhibited by the storage parenchyma. In contrast, the flux difference between these cotyledon tissues is only 1.7-fold for hexoses. Glucose and fructose uptake was shown to be sensitive to PCMBS and phloridzin, both of which slow H+-sugar transport. A low Km (or high affinity transporter, HAT) mechanism transports glucose and glucose-analogues exclusively. No HAT system for fructose could be found. A high Km (low affinity transporter, LAT) mechanism transports a broader range of hexoses, including glucose and fructose. Consistent with glucose and fructose transport being H+-coupled, their uptake was inhibited by dissipating the proton motive force (pmf) by treating cotyledons with carbonyl cyanide m-chlorophenol hydrazone, propionic acid or tetraphenylphosphonium ion. Erythrosin B inhibited hexose uptake, indicating a role for the P-type H+-ATPase in establishing the pmf. It is concluded that H+-coupled glucose and fructose transport mechanisms occur at plasma membranes of dermal transfer cell complexes and storage parenchyma cells. These transport mechanisms are active during pre- and storage phases of cotyledon development. However, hexose symport only makes a quantitative contribution to cotyledon biomass gain during the pre-storage stage of development.
17
Thomas, Matthew D., Agatha M. De Boer, Helen L. Johnson, and David P. Stevens. "Spatial and Temporal Scales of Sverdrup Balance*." Journal of Physical Oceanography 44, no. 10 (October 1, 2014): 2644–60. http://dx.doi.org/10.1175/jpo-d-13-0192.1.
Abstract:
Abstract Sverdrup balance underlies much of the theory of ocean circulation and provides a potential tool for describing the interior ocean transport from only the wind stress. Using both a model state estimate and an eddy-permitting coupled climate model, this study assesses to what extent and over what spatial and temporal scales Sverdrup balance describes the meridional transport. The authors find that Sverdrup balance holds to first order in the interior subtropical ocean when considered at spatial scales greater than approximately 5°. Outside the subtropics, in western boundary currents and at short spatial scales, significant departures occur due to failures in both the assumptions that there is a level of no motion at some depth and that the vorticity equation is linear. Despite the ocean transport adjustment occurring on time scales consistent with the basin-crossing times for Rossby waves, as predicted by theory, Sverdrup balance gives a useful measure of the subtropical circulation after only a few years. This is because the interannual transport variability is small compared to the mean transports. The vorticity input to the deep ocean by the interaction between deep currents and topography is found to be very large in both models. These deep transports, however, are separated from upper-layer transports that are in Sverdrup balance when considered over large scales.
18
de Saint-Jean, Maud, Vanessa Delfosse, Dominique Douguet, Gaëtan Chicanne, Bernard Payrastre, William Bourguet, Bruno Antonny, and Guillaume Drin. "Osh4p exchanges sterols for phosphatidylinositol 4-phosphate between lipid bilayers." Journal of Cell Biology 195, no. 6 (December 12, 2011): 965–78. http://dx.doi.org/10.1083/jcb.201104062.
Abstract:
Osh/Orp proteins transport sterols between organelles and are involved in phosphoinositide metabolism. The link between these two aspects remains elusive. Using novel assays, we address the influence of membrane composition on the ability of Osh4p/Kes1p to extract, deliver, or transport dehydroergosterol (DHE). Surprisingly, phosphatidylinositol 4-phosphate (PI(4)P) specifically inhibited DHE extraction because PI(4)P was itself efficiently extracted by Osh4p. We solve the structure of the Osh4p–PI(4)P complex and reveal how Osh4p selectively substitutes PI(4)P for sterol. Last, we show that Osh4p quickly exchanges DHE for PI(4)P and, thereby, can transport these two lipids between membranes along opposite routes. These results suggest a model in which Osh4p transports sterol from the ER to late compartments pinpointed by PI(4)P and, in turn, transports PI(4)P backward. Coupled to PI(4)P metabolism, this transport cycle would create sterol gradients. Because the residues that recognize PI(4)P are conserved in Osh4p homologues, other Osh/Orp are potential sterol/phosphoinositol phosphate exchangers.
19
Liu, Ye, H. E. Markus Meier, and Kari Eilola. "Nutrient transports in the Baltic Sea – results from a 30-year physical–biogeochemical reanalysis." Biogeosciences 14, no. 8 (April 25, 2017): 2113–31. http://dx.doi.org/10.5194/bg-14-2113-2017.
Abstract:
Abstract. Long-term oxygen and nutrient transports in the Baltic Sea are reconstructed using the Swedish Coastal and Ocean Biogeochemical model (SCOBI) coupled to the Rossby Centre Ocean model (RCO). Two simulations with and without data assimilation covering the period 1970–1999 are carried out. Here, the weakly coupled scheme with the Ensemble Optimal Interpolation (EnOI) method is adopted to assimilate observed profiles in the reanalysis system. The reanalysis shows considerable improvement in the simulation of both oxygen and nutrient concentrations relative to the free run. Further, the results suggest that the assimilation of biogeochemical observations has a significant effect on the simulation of the oxygen-dependent dynamics of biogeochemical cycles. From the reanalysis, nutrient transports between sub-basins, between the coastal zone and the open sea, and across latitudinal and longitudinal cross sections are calculated. Further, the spatial distributions of regions with nutrient import or export are examined. Our results emphasize the important role of the Baltic proper for the entire Baltic Sea, with large net transport (export minus import) of nutrients from the Baltic proper into the surrounding sub-basins (except the net phosphorus import from the Gulf of Riga and the net nitrogen import from the Gulf of Riga and Danish Straits). In agreement with previous studies, we found that the Bothnian Sea imports large amounts of phosphorus from the Baltic proper that are retained in this sub-basin. For the calculation of sub-basin budgets, the location of the lateral borders of the sub-basins is crucial, because net transports may change sign with the location of the border. Although the overall transport patterns resemble the results of previous studies, our calculated estimates differ in detail considerably.
20
Graffino, Giorgio, Riccardo Farneti, and Fred Kucharski. "Low-frequency variability of the Pacific Subtropical Cells as reproduced by coupled models and ocean reanalyses." Climate Dynamics 56, no. 9-10 (January 26, 2021): 3231–54. http://dx.doi.org/10.1007/s00382-021-05639-6.
Abstract:
AbstractLow-frequency variability of the Pacific Subtropical Cells (STCs) is investigated using outputs from several models included in the two latest phases of Coupled Model Intercomparison Project (CMIP), CMIP5 and CMIP6, as well as ocean reanalysis products. Our analysis focuses on historical simulations and an idealised future scenario integration. Mass and heat transport diagnostics are employed to assess how coupled models and ocean reanalyses reproduce Pacific STCs total and interior transport convergence at the equator and their relationship with equatorial Pacific sea surface temperature (SST). Trends of mass and heat transport are also evaluated, in order to study how the STCs are expected to change in a warming climate. A large spread is obtained across models in simulated mass transports, confirming that coupled models do not agree on reproducing observed Pacific STCs dynamics, with very limited improvement by CMIP6 models. Compared to ocean reanalysis products, coupled models tend to underestimate the STCs interior transport convergence, and are less efficient on propagating the signal generated by the subtropical wind stress towards the equator. Also, mass transport obtained from ocean reanalyses exhibit larger variability, and these products also better reproduce the STCs-SST relationship. Future scenario simulations suggest a weakening (strengthening) of the heat transport by the North (South) Pacific cell under warmer conditions, with a general agreement across models. Equatorward mass transport trends do not confirm this for total and interior components, but they do for the western boundary component.
21
Shaffrey, Len, and Rowan Sutton. "Bjerknes Compensation and the Decadal Variability of the Energy Transports in a Coupled Climate Model." Journal of Climate 19, no. 7 (April 1, 2006): 1167–81. http://dx.doi.org/10.1175/jcli3652.1.
Abstract:
Abstract In the 1960s, Jacob Bjerknes suggested that if the top-of-the-atmosphere (TOA) fluxes and the oceanic heat storage did not vary too much, then the total energy transport by the climate system would not vary too much either. This implies that any large anomalies of oceanic and atmospheric energy transport should be equal and opposite. This simple scenario has become known as Bjerknes compensation. A long control run of the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) has been investigated. It was found that northern extratropical decadal anomalies of atmospheric and oceanic energy transports are significantly anticorrelated and have similar magnitudes, which is consistent with the predictions of Bjerknes compensation. The degree of compensation in the northern extratropics was found to increase with increasing time scale. Bjerknes compensation did not occur in the Tropics, primarily as large changes in the surface fluxes were associated with large changes in the TOA fluxes. In the ocean, the decadal variability of the energy transport is associated with fluctuations in the meridional overturning circulation in the Atlantic Ocean. A stronger Atlantic Ocean energy transport leads to strong warming of surface temperatures in the Greenland–Iceland–Norwegian (GIN) Seas, which results in a reduced equator-to-pole surface temperature gradient and reduced atmospheric baroclinicity. It is argued that a stronger Atlantic Ocean energy transport leads to a weakened atmospheric transient energy transport.
22
Wang, Xiaoli, Peter H. Stone, and Jochem Marotzke. "Global Thermohaline Circulation. Part II: Sensitivity with Interactive Atmospheric Transports." Journal of Climate 12, no. 1 (January 1, 1999): 83–91. http://dx.doi.org/10.1175/1520-0442-12.1.83.
Abstract:
Abstract A hybrid coupled ocean–atmosphere model is used to investigate the stability of the thermohaline circulation (THC) to an increase in the surface freshwater forcing in the presence of interactive meridional transports in the atmosphere. The ocean component is the idealized global general circulation model used in Part I. The atmospheric model assumes fixed latitudinal structure of the heat and moisture transports, and the amplitudes are calculated separately for each hemisphere from the large-scale sea surface temperature (SST) and SST gradient, using parameterizations based on baroclinic stability theory. The ocean–atmosphere heat and freshwater exchanges are calculated as residuals of the steady-state atmospheric budgets. Owing to the ocean component’s weak heat transport, the model has too strong a meridional SST gradient when driven with observed atmospheric meridional transports. When the latter are made interactive, the conveyor belt circulation collapses. A flux adjustment is introduced in which the efficiency of the atmospheric transports is lowered to match the too low efficiency of the ocean component. The feedbacks between the THC and both the atmospheric heat and moisture transports are positive, whether atmospheric transports are interactive in the Northern Hemisphere, the Southern Hemisphere, or both. However, the feedbacks operate differently in the Northern and Southern Hemispheres, because the Pacific THC dominates in the Southern Hemisphere, and deep water formation in the two hemispheres is negatively correlated. The feedbacks in the two hemispheres do not necessarily reinforce each other because they have opposite effects on low-latitude temperatures. The model is qualitatively similar in stability to one with conventional “additive” flux adjustment, but quantitatively more stable.
23
Wang, Hong, You-Jun Fei, Vadivel Ganapathy, and Frederick H. Leibach. "Electrophysiological characteristics of the proton-coupled peptide transporter PEPT2 cloned from rat brain." American Journal of Physiology-Cell Physiology 275, no. 4 (October 1, 1998): C967—C975. http://dx.doi.org/10.1152/ajpcell.1998.275.4.c967.
Abstract:
We have cloned a peptide transporter from rat brain and found it to be identical to rat kidney PEPT2. In the present study we characterize the transport function of the rat brain PEPT2, with special emphasis on electrophysiological properties and interaction with N-acetyl-l-aspartyl-l-glutamate (NAAG). When heterologously expressed in HeLa cells and in SK-N-SH cells, PEPT2 transports several dipeptides but not free amino acids in the presence of a proton gradient. NAAG competes with other peptides for the PEPT2-mediated transport process. When PEPT2 is expressed in Xenopus laevis oocytes, substrate-induced inward currents are detectable with dipeptides of differing charge in the presence of a proton gradient. Proton activation kinetics are similar for differently charged peptides. NAAG is a transportable substrate for PEPT2, as evidenced by NAAG-induced currents. The Hill coefficient for protons for the activation of the transport of differently charged peptides, including NAAG, is 1. Although the peptide-to-proton stoichiometry for negatively charged peptides is 1, the transport nonetheless is associated with transfer of positive charge into the oocyte, as indicated by peptide-induced inward currents.
24
Hafter, G. H. "BOA—the RAPT's New Concept for its Urban System." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 206, no. 1 (January 1992): 75–78. http://dx.doi.org/10.1243/pime_proc_1992_206_218_02.
Abstract:
This mini-paper describes the background to the decision of the Régie Autonome des Transports Parisiens (RAPT), the Paris Transport Authority, to develop a new form of rolling stock for operation on the urban Métro network (as opposed to the RER), where car size is severely constrained by a tight loading gauge and extremely sharp curvature. The object was to provide for better passenger distribution throughout a train, coupled with a reduction in overall weight and a reduction of waste space between vehicles, with a consequent increase in the effective passenger capacity.
25
Mayer, Michael, Leopold Haimberger, John M. Edwards, and Patrick Hyder. "Toward Consistent Diagnostics of the Coupled Atmosphere and Ocean Energy Budgets." Journal of Climate 30, no. 22 (November 2017): 9225–46. http://dx.doi.org/10.1175/jcli-d-17-0137.1.
Abstract:
The widely used diagnostic vertically integrated total energy budget equations of atmosphere and ocean contain inconsistencies that should no longer be disregarded. The neglect of enthalpy fluxes associated with precipitation and evaporation leads to a spurious dependence on reference temperature. This seemingly small inconsistency is amplified because enthalpy of water vapor implicitly included in lateral atmospheric energy transports usually is computed on the Kelvin scale, leading to inconsistencies that, although zero when globally averaged, attain values on the order of 20 W m−2 in the tropics. A more consistent energy budget framework is presented, which is independent of reference temperature and which takes full account of enthalpy fluxes associated with mass transfer through the surface. The latter include effects of snowfall and additional nonlatent contributions, which have a net cooling effect on the earth’s surface (−1.3 W m−2). In addition to these diagnostic issues, comparatively small inconsistencies in the energetic formulations of current weather and climate models are highlighted. Using the energy budget formulation presented here, instead of that commonly used, yields enhanced self-consistency of diagnosed atmospheric energy budgets and substantially improved spatial agreement between fields of net surface energy flux inferred from the divergence of lateral atmospheric energy transports in conjunction with satellite-based radiative fluxes and independent surface flux products. Results imply that previous estimates of radiative plus turbulent surface fluxes over the ocean, balancing the observed ocean warming, are biased low by ~1.3 W m−2. Moreover, previous studies seriously underestimated cross-equatorial atmospheric and oceanic energy transports. Overall, the presented framework allows for unambiguous coupled energy budget diagnostics and yields more reliable benchmark values for validation purposes.
26
Zhou, Hui, Dongliang Yuan, Lina Yang, Xiang Li, and William Dewar. "Decadal Variability of the Meridional Geostrophic Transport in the Upper Tropical North Pacific Ocean." Journal of Climate 31, no. 15 (August 2018): 5891–910. http://dx.doi.org/10.1175/jcli-d-17-0639.1.
Abstract:
The meridional geostrophic transport (MGT) in the interior tropical North Pacific Ocean is estimated based on global ocean heat and salt content data. The decadal variations of the zonally and vertically integrated MGT in the tropical North Pacific Ocean are found to precede the Pacific decadal oscillation (PDO) by 1–3 years. The dynamics of the MGT are analyzed based on Sverdrup theory. It is found that the total meridional transport variability (MGT plus Ekman) is dominated by the MGT variability having positive correlations with the PDO index. The Sverdrup transports differ from the total meridional transport significantly and have insignificant correlations with PDO index, suggesting that the MGT variability is not controlled by the Sverdrup dynamics. In comparison, the simulated meridional transport variability in the models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and the Ocean General Circulation Model for the Earth Simulator are dominated by the Sverdrup transports, having insignificant correlations with the simulated PDO indices. The comparison suggests that the non-Sverdrup component in the MGT is important for the predictability of PDO and that significant deficiencies exist in these models in simulating a realistic structure of the tropical ocean gyre variability and predicting the decadal climate variations associated with it.
27
Downes, Stephanie M., and Andrew McC Hogg. "Southern Ocean Circulation and Eddy Compensation in CMIP5 Models." Journal of Climate 26, no. 18 (September 9, 2013): 7198–220. http://dx.doi.org/10.1175/jcli-d-12-00504.1.
Abstract:
Abstract Thirteen state-of-the-art climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are used to evaluate the response of the Antarctic Circumpolar Current (ACC) transport and Southern Ocean meridional overturning circulation to surface wind stress and buoyancy changes. Understanding how these flows—fundamental players in the global distribution of heat, gases, and nutrients—respond to climate change is currently a widely debated issue among oceanographers. Here, the authors analyze the circulation responses of these coarse-resolution coupled models to surface fluxes. Under a future CMIP5 climate pathway where the equivalent atmospheric CO2 reaches 1370 ppm by 2100, the models robustly project reduced Southern Ocean density in the upper 2000 m accompanied by strengthened stratification. Despite an overall increase in overlying wind stress (~20%), the projected ACC transports lie within ±15% of their historical state, and no significant relationship with changes in the magnitude or position of the wind stress is identified. The models indicate that a weakening of ACC transport at the end of the twenty-first century is correlated with a strong increase in the surface heat and freshwater fluxes in the ACC region. In contrast, the surface heat gain across the ACC region and the wind-driven surface transports are significantly correlated with an increased upper and decreased lower Eulerian-mean meridional overturning circulation. The change in the eddy-induced overturning in both the depth and density spaces is quantified, and it is found that the CMIP5 models project partial eddy compensation of the upper and lower overturning cells.
28
Baehr, J., S. Cunnningham, H. Haak, P. Heimbach, T. Kanzow, and J. Marotzke. "Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic." Ocean Science 5, no. 4 (November 16, 2009): 575–89. http://dx.doi.org/10.5194/os-5-575-2009.
Abstract:
Abstract. Daily timeseries of the meridional overturning circulation (MOC) estimated from the UK/US RAPID/MOCHA array at 26.5° N in the Atlantic are used to evaluate the MOC as simulated in two global circulation models: (I) an 8-member ensemble of the coupled climate model ECHAM5/MPI-OM, and (II) the ECCO-GODAE state estimate. In ECHAM5/MPI-OM, we find that the observed and simulated MOC have a similar variability and time-mean within the 99% confidence interval. In ECCO-GODAE, we find that the observed and simulated MOC show a significant correlation within the 99% confidence interval. To investigate the contribution of the different transport components, the MOC is decomposed into Florida Current, Ekman and mid-ocean transports. In both models, the mid-ocean transport is closely approximated by the residual of the MOC minus Florida Current and Ekman transports. As the models conserve volume by definition, future comparisons of the RAPID/MOCHA mid-ocean transport should be done against the residual transport in the models. The similarity in the variance and the correlation between the RAPID/MOCHA, and respectively ECHAM5/MPI-OM and ECCO-GODAE MOC estimates at 26.5° N is encouraging in the context of estimating (natural) variability in climate simulations and its use in climate change signal-to-noise detection analyses. Enhanced confidence in simulated hydrographic and transport variability will require longer observational time series.
29
Farneti, Riccardo, and Geoffrey K. Vallis. "Meridional Energy Transport in the Coupled Atmosphere–Ocean System: Compensation and Partitioning." Journal of Climate 26, no. 18 (September 9, 2013): 7151–66. http://dx.doi.org/10.1175/jcli-d-12-00133.1.
Abstract:
Abstract The variability and compensation of the meridional energy transport in the atmosphere and ocean are examined with the state-of-the-art GFDL Climate Model, version 2.1 (CM2.1), and the GFDL Intermediate Complexity Coupled Model (ICCM). On decadal time scales, a high degree of compensation between the energy transport in the atmosphere (AHT) and ocean (OHT) is found in the North Atlantic. The variability of the total or planetary heat transport (PHT) is much smaller than the variability in either AHT or OHT alone, a feature referred to as “Bjerknes compensation.” Natural decadal variability stems from the Atlantic meridional overturning circulation (AMOC), which leads OHT variability. The PHT is positively correlated with the OHT, implying that the atmosphere is compensating, but imperfectly, for variations in ocean transport. Because of the fundamental role of the AMOC in generating the decadal OHT anomalies, Bjerknes compensation is expected to be active only in coupled models with a low-frequency AMOC spectral peak. The AHT and the transport in the oceanic gyres are positively correlated because the gyre transport responds to the atmospheric winds, thereby militating against long-term variability involving the wind-driven flow. Moisture and sensible heat transports in the atmosphere are also positively correlated at decadal time scales. The authors further explore the mechanisms and degree of compensation with a simple, diffusive, two-layer energy balance model. Taken together, these results suggest that compensation can be interpreted as arising from the highly efficient nature of the meridional energy transport in the atmosphere responding to ocean variability rather than any a priori need for the top-of-atmosphere radiation budget to be fixed.
30
Outten, Stephen, Igor Esau, and Odd Helge Otterå. "Bjerknes Compensation in the CMIP5 Climate Models." Journal of Climate 31, no. 21 (November 2018): 8745–60. http://dx.doi.org/10.1175/jcli-d-18-0058.1.
Abstract:
This study examines the atmospheric and oceanic heat transports in preindustrial control and historical runs of 15 fully coupled global climate models from the CMIP5 project. The presence of Bjerknes compensation is confirmed in all models by the strong anticorrelation and approximately equal magnitude of the anomalies of these heat transports. Previous studies of Bjerknes compensation in the absence of external forcing have all shown the strongest compensation at high latitudes, where the warm ocean meets the cold Arctic atmosphere. In this study, however, it is found that many of the 15 models have a second and often dominant peak of compensation in the northern midlatitudes, where strong air–sea interaction is often associated with the midlatitude storm tracks. It has also been suggested that variations in heat transport in the ocean lead those in the atmosphere, but this work has found no clear and robust support for this, as only half the models show such a relationship. In the historical simulations where external forcings are applied, Bjerknes compensation continues to be present, but many models show pronounced trends in the heat transports. All of the models show multidecadal variability in heat transports in both preindustrial control and historical simulations. Any anthropogenic climate change signal could potentially be masked or amplified by the natural variability governed by Bjerknes compensation. Given its presence in the CMIP5 models, which are the basis of so much policy and adaptation planning, an improved understanding of Bjerknes compensation may have socioeconomic relevance for the future.
31
Yang, Haijun, Yingying Zhao, and Zhengyu Liu. "Understanding Bjerknes Compensation in Atmosphere and Ocean Heat Transports Using a Coupled Box Model." Journal of Climate 29, no. 6 (March 15, 2016): 2145–60. http://dx.doi.org/10.1175/jcli-d-15-0281.1.
Abstract:
Abstract A coupled box model is used to study the compensation between atmosphere and ocean heat transports. An analytical solution to the Bjerknes compensation (BJC) rate, defined as the ratio of anomalous atmosphere heat transport (AHT) to anomalous ocean heat transport (OHT), is obtained. The BJC rate is determined by local feedback between surface temperature and net heat flux at the top of atmosphere (TOA) and the AHT efficiency. In a stable climate that ensures global energy conservation, the changes between AHT and OHT tend to be always out of phase, and the BJC is always valid. This can be demonstrated when the climate is perturbed by freshwater flux. The BJC in this case exhibits three different behaviors: the anomalous AHT can undercompensate, overcompensate, or perfectly compensate the anomalous OHT, depending on the local feedback. Stronger negative local feedback will result in a lower BJC rate. Stronger positive local feedback will result in a larger overcompensation. If zero climate feedback occurs in the system, the AHT will compensate the OHT perfectly. However, the BJC will fail if the climate system is perturbed by heat flux. In this case, the changes in AHT and OHT will be in phase, and their ratio will be closely related to the mean AHT and OHT. In a more realistic situation when the climate is perturbed by both heat and freshwater fluxes, whether the BJC will occur depends largely on the interplay among meridional temperature and salinity gradients and the thermohaline circulation strength. This work explicitly shows that the energy conservation is the intrinsic mechanism of BJC and establishes a specific link between radiative feedback and the degree of compensation. It also implies a close relationship between the energy balance at the TOA and the ocean thermohaline dynamics.
32
Kunduri, Govind, Changqing Yuan, Velayoudame Parthibane, Katherine M. Nyswaner, Ritu Kanwar, Kunio Nagashima, Steven G. Britt, et al. "Phosphatidic acid phospholipase A1 mediates ER–Golgi transit of a family of G protein–coupled receptors." Journal of Cell Biology 206, no. 1 (July 7, 2014): 79–95. http://dx.doi.org/10.1083/jcb.201405020.
Abstract:
The coat protein II (COPII)–coated vesicular system transports newly synthesized secretory and membrane proteins from the endoplasmic reticulum (ER) to the Golgi complex. Recruitment of cargo into COPII vesicles requires an interaction of COPII proteins either with the cargo molecules directly or with cargo receptors for anterograde trafficking. We show that cytosolic phosphatidic acid phospholipase A1 (PAPLA1) interacts with COPII protein family members and is required for the transport of Rh1 (rhodopsin 1), an N-glycosylated G protein–coupled receptor (GPCR), from the ER to the Golgi complex. In papla1 mutants, in the absence of transport to the Golgi, Rh1 is aberrantly glycosylated and is mislocalized. These defects lead to decreased levels of the protein and decreased sensitivity of the photoreceptors to light. Several GPCRs, including other rhodopsins and Bride of sevenless, are similarly affected. Our findings show that a cytosolic protein is necessary for transit of selective transmembrane receptor cargo by the COPII coat for anterograde trafficking.
33
Ostfeld, A., and A. Pries. "Lake Kinneret watershed contamination transports - a GIS based hydrological model." Water Science and Technology 48, no. 10 (November 1, 2003): 63–70. http://dx.doi.org/10.2166/wst.2003.0540.
Abstract:
This paper describes the efforts and current achievements of developing a GIS based hydrological model for flow and contaminants transport within Lake Kinneret watershed. The proposed model is built of hydrological “input-output” physical response blocks for routing rainfall-runoff water quantity and quality in sub-watersheds, coupled further with a delineated GIS database. An illustrative example of the model capabilities is demonstrated.
34
Baehr, J., S. Cunnningham, H. Haak, P. Heimbach, T. Kanzow, and J. Marotzke. "Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic." Ocean Science Discussions 6, no. 2 (July 1, 2009): 1333–67. http://dx.doi.org/10.5194/osd-6-1333-2009.
Abstract:
Abstract. Daily timeseries of the meridional overturning circulation (MOC) estimated from the UK/US RAPID/MOCHA array at 26.5° N in the Atlantic are used to evaluate the MOC as simulated in two global circulation models: (i) an 8-member ensemble of the coupled climate model ECHAM5/MPI-OM, and (ii) the ECCO-GODAE state estimate. In ECHAM5/MPI-OM, we find that the observed and simulated MOC have a similar variability and time-mean within the 99 percent confidence interval. In ECCO-GODAE, we find that the observed and simulated MOC show a significant correlation within the 99 percent confidence interval. To investigate the contribution of the different transport components, the MOC is decomposed into Florida Current, Ekman and upper mid-ocean geostrophic transports. In both models, the mid-ocean transport is closely approximated by the residual of the MOC minus Florida Current and Ekman transports. As the models conserve volume by definition, future comparisons of the RAPID/MOCHA mid-ocean transport should be done against the residual transport in the models. The similarity in the variance and the correlation between the RAPID/MOCHA, and respectively ECHAM5/MPI-OM and ECCO-GODAE MOC estimates at 26.5° N is encouraging in the context of estimating (natural) variability in climate simulations and its use in climate change signal-to-noise detection analyses. Enhanced confidence in simulated hydrographic and transport variability will require longer observational time series.
35
Yang, Kaike, Jin Xiao, Zhihui Ren, Zhongming Wei, Jun-Wei Luo, Su-Huai Wei, and Hui-Xiong Deng. "Decoupling of the Electrical and Thermal Transports in Strongly Coupled Interlayer Materials." Journal of Physical Chemistry Letters 12, no. 32 (August 11, 2021): 7832–39. http://dx.doi.org/10.1021/acs.jpclett.1c01783.
36
Wang, Fei, and Jun-Min Wang. "Chaotic oscillations of one-dimensional coupled wave equations with mixed energy transports." Nonlinear Dynamics 99, no. 3 (January 1, 2020): 2277–90. http://dx.doi.org/10.1007/s11071-019-05431-6.
37
Li, Zhouhua, Liwei Wang, Thomas S. Hays, and Yu Cai. "Dynein-mediated apical localization of crumbs transcripts is required for Crumbs activity in epithelial polarity." Journal of Cell Biology 180, no. 1 (January 14, 2008): 31–38. http://dx.doi.org/10.1083/jcb.200707007.
Abstract:
Asymmetrical localization of transcripts coupled with localized translation constitutes an important mechanism widely deployed to regulate gene activity in a spatial manner. The conserved transmembrane protein Crumbs (Crb) is an important regulator of epithelial polarity. However, it remains unclear how Crb is targeted to the apical domain. Here, we show that the cytoplasmic dynein complex transports both Crb protein and transcripts to the apical domain of Drosophila melanogaster follicular cells (FCs). The crb 3′ untranslated region (UTR) is necessary and sufficient for the apical localization of its transcript and this apical transcript localization is crucial for crb function. In crb mutant FCs, Crb protein derived from transgenes lacking the 3′ UTR does not effectively localize to the apical domain and does not effectively restore normal epithelial polarity. We propose that dynein-mediated messenger RNA transport coupled with a localized translation mechanism is involved in localizing Crb to the apical domain to mediate epithelial apicobasal polarity and that this mechanism might be widely used to regulate cellular polarity.
38
Kehres, David G., Anuradha Janakiraman, James M. Slauch, and Michael E. Maguire. "SitABCD Is the Alkaline Mn2+ Transporter of Salmonella enterica Serovar Typhimurium." Journal of Bacteriology 184, no. 12 (June 15, 2002): 3159–66. http://dx.doi.org/10.1128/jb.184.12.3159-3166.2002.
Abstract:
ABSTRACT MntH, a bacterial homolog of the mammalian natural resistance-associated macrophage protein 1 (Nramp1), is a primary Mn2+ transporter of Salmonella enterica serovar Typhimurium and Escherichia coli. S. enterica serovar Typhimurium MntH expression is important for full virulence; however, strains carrying an mntH deletion are only partially attenuated and display no obvious signs of Mn2+ deficiency. We noted that promoter sequences for mntH and for the putative Fe2+ transporter sitABCD appeared to have the same regulatory element responsive to Mn2+ and so hypothesized that sitABCD could transport Mn2+ with high affinity. We have now characterized transport by SitABCD in S. enterica serovar Typhimurium using 54Mn2+ and 55Fe2+ and compared its properties to those of MntH. SitABCD mediates the influx of Mn2+ with an apparent affinity (Ka ) identical to that of MntH, 0.1 μM. It also transports Fe2+ but with a Ka 30 to 100 times lower, 3 to 10 μM. Inhibition of 54Mn2+ transport by Fe2+ and of 55Fe2+ transport by Mn2+ gave inhibition constants comparable to each cation's Ka for influx. Since micromolar concentrations of free Fe2+ are improbable in a biological system, we conclude that SitABCD functions physiologically as a Mn2+ transporter. The cation inhibition profiles of SitABCD and MntH are surprisingly similar for two structurally and energetically unrelated transporters, with a Cd2+ Ki of ≈1 μM and a Co2+ Ki of ≈20 μM and with Ni2+, Cu2+, and Fe3+ inhibiting both transporters only at concentrations of >0.1 mM. The one difference is that Zn2+ exhibits potent inhibition of SitABCD (Ki = 1 to 3 μM) but inhibits MntH weakly (Ki > 50 μM). We have previously shown that MntH transports Mn2+ most effectively under acidic conditions. In sharp contrast, SitABCD has almost no transport capacity at acid pHs and optimally transports Mn2+ at slightly alkaline pHs. Overall, coupled with evidence that each transporter is multiply but distinctly regulated at the transcriptional level, the distinct transport properties of MntH versus SitABCD suggest that each transporter may be specialized for Mn2+ uptake in different physiological environments.
39
Wu, Xiaodong, Falk Feddersen, Sarah N. Giddings, Nirnimesh Kumar, and Ganesh Gopalakrishnan. "Mechanisms of Mid- to Outer-Shelf Transport of Shoreline-Released Tracers." Journal of Physical Oceanography 50, no. 7 (July 1, 2020): 1813–37. http://dx.doi.org/10.1175/jpo-d-19-0225.1.
Abstract:
AbstractTransport of shoreline-released tracer from the surfzone across the shelf can be affected by a variety of physical processes from wind-driven to submesoscale, with implications for shoreline contaminant dilution and larval dispersion. Here, a high-resolution wave–current coupled model that resolves the surfzone and receives realistic oceanic and atmospheric forcing is used to simulate dye representing shoreline-released untreated wastewater in the San Diego–Tijuana region. Surfzone and shelf alongshore dye transports are primarily driven by obliquely incident wave breaking and alongshore pressure gradients, respectively. At the midshelf to outer-shelf (MS–OS) boundary (25-m depth), defined as a mean streamline, along-boundary density gradients are persistent, dye is surface enhanced and time and alongshelf patchy. Using baroclinic and along-boundary perturbation dye transports, two cross-shore dye exchange velocities are estimated and related to physical processes. Barotropic and baroclinic tides cannot explain the modeled cross-shore transport. The baroclinic exchange velocity is consistent with the wind-driven Ekman transport. The perturbation exchange velocity is elevated for alongshore dye and cross-shore velocity length scales < 1 km (within the submesoscale) and stronger alongshore density gradient ∂ρ/∂y variability, indicating that alongfront geostrophic flows induce offshore transport. This elevated ∂ρ/∂y is linked to convergent northward surface along-shelf currents (likely due to regional bathymetry), suggesting deformation frontogenesis. Both surfzone and shelf processes influence offshore transport of shoreline-released tracers with key parameters of surfzone and shelf alongcoast currents and alongshelf winds.
40
Jochum, M., and Carsten Eden. "The Connection between Southern Ocean Winds, the Atlantic Meridional Overturning Circulation, and Indo-Pacific Upwelling." Journal of Climate 28, no. 23 (December 1, 2015): 9250–57. http://dx.doi.org/10.1175/jcli-d-15-0263.1.
Abstract:
Abstract Coupled GCM simulations are analyzed to quantify the dynamic effect of Southern Ocean (SO) winds on transports in the ocean. It is found that the closure for skew diffusivity in the non-eddy-resolving ocean model does not allow for a realistic eddy saturation of the zonal transports in the SO in response to the wind changes and that eddy compensation of the meridional transports in the SO is underestimated too. Despite this underestimated eddy compensation in the SO, however, and in contrast to previous suggestions, the Atlantic meridional overturning circulation (AMOC) strength is almost insensitive to SO winds. In the limit of weak SO winds the AMOC waters upwell not in the SO but rather in the tropical Indo-Pacific. Through their effect on sea ice, weaker SO winds also lead to less production of Antarctic Bottom Water and therefore a deeper and stronger AMOC.
41
Saumon, G., and G. Basset. "Electrolyte and fluid transport across the mature alveolar epithelium." Journal of Applied Physiology 74, no. 1 (January 1, 1993): 1–15. http://dx.doi.org/10.1152/jappl.1993.74.1.1.
Abstract:
The lungs must be kept "dry" for efficient gas exchange. The mechanisms that contribute to clear alveoli from fetal lung fluid at birth are still present during adult life and allow recovery from alveolar flooding. It has recently been shown with the use of different approaches in vitro, as well as in vivo, that alveolar epithelium performs solute-coupled fluid transport. Fluid absorption from alveoli occurs chiefly as a result of active transepithelial Na+ transport. The mechanisms of Na+ transport have been partly elucidated; Na+ enters alveolar cells through apical Na+ channels and Na(+)-coupled solute transporters and is pumped out at the basolateral membrane by a Na(+)-K(+)-adenosinetriphosphatase (ATPase). Transepithelial Na+ transport and fluid absorption are stimulated by beta-adrenergic agonists, with adenosine 3',5'-cyclic monophosphate being the likely intracellular second messenger. K+ is probably secreted into alveoli because its concentration in the epithelial lining fluid is larger than expected for passive distribution. K+ channels have been described that, in conjunction with Na(+)-K(+)-ATP-ase, might provide pathways for active transport. Active proton secretion or bicarbonate absorption have been reported, which may explain the low pH of the alveolar epithelial lining fluid. It is probable that active solute transports are the main determinants of epithelial lining fluid depth and composition. A challenge for the future is to understand how this homeostasis is achieved.
42
FEI, You-Jun, Jin-Cai LIU, Katsuhisa INOUE, Lina ZHUANG, Katsuya MIYAKE, Seiji MIYAUCHI, and Vadivel GANAPATHY. "Relevance of NAC-2, an Na+-coupled citrate transporter, to life span, body size and fat content in Caenorhabditis elegans." Biochemical Journal 379, no. 1 (April 1, 2004): 191–98. http://dx.doi.org/10.1042/bj20031807.
Abstract:
We have cloned and functionally characterized an Na+-coupled citrate transporter from Caenorhabditis elegans (ceNAC-2). This transporter shows significant sequence homology to Drosophila Indy and the mammalian Na+-coupled citrate transporter NaCT (now known as NaC2). When heterologously expressed in a mammalian cell line or in Xenopus oocytes, the cloned ceNAC-2 mediates the Na+-coupled transport of various intermediates of the citric acid cycle. However, it transports the tricarboxylate citrate more efficiently than dicarboxylates such as succinate, a feature different from that of ceNAC-1 (formerly known as ceNaDC1) and ceNAC-3 (formerly known as ceNaDC2). The transport process is electrogenic, as evidenced from the substrate-induced inward currents in oocytes expressing the transporter under voltage-clamp conditions. Expression studies using a reporter-gene fusion method in transgenic C. elegans show that the gene is expressed in the intestinal tract, the organ responsible for not only the digestion and absorption of nutrients but also for the storage of energy in this organism. Functional knockdown of the transporter by RNAi (RNA interference) not only leads to a significant increase in life span, but also causes a significant decrease in body size and fat content. The substrates of ceNAC-2 play a critical role in metabolic energy production and in the biosynthesis of cholesterol and fatty acids. The present studies suggest that the knockdown of these metabolic functions by RNAi is linked to an extension of life span and a decrease in fat content and body size.
43
Marotzke, Jochem, and Peter H. Stone. "Atmospheric Transports, the Thermohaline Circulation, and Flux Adjustments in a Simple Coupled Model." Journal of Physical Oceanography 25, no. 6 (June 1995): 1350–64. http://dx.doi.org/10.1175/1520-0485(1995)025<1350:atttca>2.0.co;2.
44
Wang, An Mei. "The Electronic Transports Technology in a T-Shaped Double Quantum Dot." Advanced Materials Research 859 (December 2013): 542–46. http://dx.doi.org/10.4028/www.scientific.net/amr.859.542.
Abstract:
We study the phonon-assisted Fano interference of the linear conductance spectrum by taking into account the interdot-phonon exchange in a T-shaped double quantum dot (QD), where a central QD is coupled to a side QD and two nonmagnetic or ferromagnetic electrodes. Unlike the usual Fano interference between different elastic channels,this new-type Fano interference is shown to arise from electron waves tunneling coherently through phonon-assisted bonding and antibonding states.
45
Schmid, Claudia, and Sudip Majumder. "Transport variability of the Brazil Current from observations and a data assimilation model." Ocean Science 14, no. 3 (June 7, 2018): 417–36. http://dx.doi.org/10.5194/os-14-417-2018.
Abstract:
Abstract. The Brazil Current transports from observations and the Hybrid Coordinate Model (HYCOM) model are analyzed to improve our understanding of the current's structure and variability. A time series of the observed transport is derived from a three-dimensional field of the velocity in the South Atlantic covering the years 1993 to 2015 (hereinafter called Argo & SSH). The mean transports of the Brazil Current increases from 3.8 ± 2.2 Sv (1 Sv is 106 m3 s−1) at 25∘ S to 13.9 ± 2.6 Sv at 32∘ S, which corresponds to a mean slope of 1.4 ± 0.4 Sv per degree. Transport estimates derived from HYCOM fields are somewhat higher (5.2 ± 2.7 and 18.7 ± 7.1 Sv at 25 and 32∘ S, respectively) than those from Argo & SSH, but these differences are small when compared with the standard deviations. Overall, the observed latitude dependence of the transport of the Brazil Current is in agreement with the wind-driven circulation in the super gyre of the subtropical South Atlantic. A mean annual cycle with highest (lowest) transports in austral summer (winter) is found to exist at selected latitudes (24, 35, and 38∘ S). The significance of this signal shrinks with increasing latitude (both in Argo & SSH and HYCOM), mainly due to mesoscale and interannual variability. Both Argo & SSH, as well as HYCOM, reveal interannual variability at 24 and 35∘ S that results in relatively large power at periods of 2 years or more in wavelet spectra. It is found that the interannual variability at 24∘ S is correlated with the South Atlantic Subtropical Dipole Mode (SASD), the Southern Annular Mode (SAM), and the Niño 3.4 index. Similarly, correlations between SAM and the Brazil Current transport are also found at 35∘ S. Further investigation of the variability reveals that the first and second mode of a coupled empirical orthogonal function of the meridional transport and the sea level pressure explain 36 and 15 % of the covariance, respectively. Overall, the results indicate that SAM, SASD, and El Niño–Southern Oscillation have an influence on the transport of the Brazil Current.
46
Linton, S. M., and M. J. O'Donnell. "Novel aspects of the transport of organic anions by the malpighian tubules of Drosophila melanogaster." Journal of Experimental Biology 203, no. 23 (December 1, 2000): 3575–84. http://dx.doi.org/10.1242/jeb.203.23.3575.
Abstract:
Para-aminohippuric acid (PAH) is a negatively charged organic ion that can pass across the epithelium of Malpighian tubules. Its mode of transport was studied in Malpighian tubules of Drosophila melanogaster. PAH transport was an active process, with a K(m) of 2. 74 mmol l(−)(1) and a V(max) of 88.8 pmol min(−)(1). Tubules had a low passive permeability to PAH, but PAH transport rates (832 nmol min(−)(1)mm(2)) and concentrative ability ([PAH](secreted fluid):[PAH](bath)=81.2) were the highest measured to date for insects. Competition experiments indicated that there were two organic anion transporters, one that transports carboxylate compounds, such as PAH and fluorescein, and another that transports sulphonates, such as amaranth and Indigo Carmine. PAH transport appears to be maximal in vivo because the rate of transport by isolated tubules is not increased when these are challenged with cyclic AMP, cyclic GMP, leucokinin I or staurosporine. Basolateral PAH transport was inhibited by ouabain and dependent on the Na(+) gradient. The Malpighian tubules appeared not to possess an organic acid/ α -keto acid exchanger because PAH accumulation was not affected by low concentrations (100 μmol l(−)(1)) of α -keto acids (α -ketoglutarate, glutarate, citrate and succinate) or the activity of phosphokinase C. PAH transport may be directly coupled to the Na(+) gradient, perhaps via Na(+)/organic acid cotransport. Fluorescence microscopy showed that transport of the carboxylate fluorescein was confined to the principal cells of the main (secretory) segment and all the cells of the lower (reabsorptive) segment. Organic anions were transported across the cytoplasm of the principal cells both by diffusion and in vesicles. The accumulation of punctate fluorescence in the lumen is consistent with exocytosis of the cytoplasmic vesicles. Apical PAH transport was independent of the apical membrane potential and may not occur by an electrodiffusive mechanism.
47
Florindo-López, Cristian, Sheldon Bacon, Yevgeny Aksenov, Léon Chafik, Eugene Colbourne, and N. Penny Holliday. "Arctic Ocean and Hudson Bay Freshwater Exports: New Estimates from Seven Decades of Hydrographic Surveys on the Labrador Shelf." Journal of Climate 33, no. 20 (October 15, 2020): 8849–68. http://dx.doi.org/10.1175/jcli-d-19-0083.1.
Abstract:
AbstractWhile reasonable knowledge of multidecadal Arctic freshwater storage variability exists, we have little knowledge of Arctic freshwater exports on similar time scales. A hydrographic time series from the Labrador Shelf, spanning seven decades at annual resolution, is here used to quantify Arctic Ocean freshwater export variability west of Greenland. Output from a high-resolution coupled ice–ocean model is used to establish the representativeness of those hydrographic sections. Clear annual to decadal variability emerges, with high freshwater transports during the 1950s and 1970s–80s, and low transports in the 1960s and from the mid-1990s to 2016, with typical amplitudes of 30 mSv (1 Sv = 106 m3 s−1). The variability in both the transports and cumulative volumes correlates well both with Arctic and North Atlantic freshwater storage changes on the same time scale. We refer to the “inshore branch” of the Labrador Current as the Labrador Coastal Current, because it is a dynamically and geographically distinct feature. It originates as the Hudson Bay outflow, and preserves variability from river runoff into the Hudson Bay catchment. We find a need for parallel, long-term freshwater transport measurements from Fram and Davis Straits to better understand Arctic freshwater export control mechanisms and partitioning of variability between routes west and east of Greenland, and a need for better knowledge and understanding of year-round (solid and liquid) freshwater fluxes on the Labrador shelf. Our results have implications for wider, coherent atmospheric control on freshwater fluxes and content across the Arctic Ocean and northern North Atlantic Ocean.
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Leaist, Derek G. "Coupled diffusion of butanol solubilized in aqueous sodium dodecylsulfate micelles." Canadian Journal of Chemistry 68, no. 1 (January 1, 1990): 33–35. http://dx.doi.org/10.1139/v90-008.
Abstract:
Ternary interdiffusion coefficients have been measured for ten compositions of the system sodium dodecylsulfate (NaDS) + 1-butanol (BuOH) + water at 25 °C. The diffusivity of BuOH in this system is lower than in pure water because about one half of the alcohol is solubilized in the slowly-diffusing NaDS micelles. Yet, surprisingly, diffusion of the NaDS component transports only minor amounts of BuOH. Diffusion of the BuOH component, however, produces a substantial coupled flow of NaDS. Although added BuOH increases the solution viscosity and the size of the micelles, the diffusivity of the NaDS component does not change significantly. The Harned restricted diffusion method for the determination of electrolyte diffusivities is extended to electrolyte + nonelectrolyte solutes. Keywords: micelles, ionic; solubilization; diffusion, coupled.
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Bannon, Desmond I., Roger Abounader, Peter S. J. Lees, and Joseph P. Bressler. "Effect of DMT1 knockdown on iron, cadmium, and lead uptake in Caco-2 cells." American Journal of Physiology-Cell Physiology 284, no. 1 (January 1, 2003): C44—C50. http://dx.doi.org/10.1152/ajpcell.00184.2002.
Abstract:
DMT1 (divalent metal transporter 1) is a hydrogen-coupled divalent metal transporter with a substrate preference for iron, although the protein when expressed in frog oocytes transports a broad range of metals, including the toxic metals cadmium and lead. Wild-type Caco-2 cells displayed saturable transport of lead and iron that was stimulated by acid. Cadmium and manganese inhibited transport of iron, but zinc and lead did not. The involvement of DMT1 in the transport of toxic metals was examined by establishing clonal DMT1 knockdown and control Caco-2 cell lines. Knockdown cell lines displayed much lower levels of DMT1 mRNA and a smaller Vmaxfor iron uptake compared with control cell lines. One clone was further characterized and found to display an ∼50% reduction in uptake of iron across a pH range from 5.5 to 7.4. Uptake for cadmium also decreased 50% across the same pH range, but uptake for lead did not. These results show that DMT1 is important in iron and cadmium transport in Caco-2 cells but that lead enters these cells through an independent hydrogen-driven mechanism.
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Hewitt, Helene T., Malcolm J. Roberts, Pat Hyder, Tim Graham, Jamie Rae, Stephen E. Belcher, Romain Bourdallé-Badie, et al. "The impact of resolving the Rossby radius at mid-latitudes in the ocean: results from a high-resolution version of the Met Office GC2 coupled model." Geoscientific Model Development 9, no. 10 (October 13, 2016): 3655–70. http://dx.doi.org/10.5194/gmd-9-3655-2016.
Abstract:
Abstract. There is mounting evidence that resolving mesoscale eddies and western boundary currents as well as topographically controlled flows can play an important role in air–sea interaction associated with vertical and lateral transports of heat and salt. Here we describe the development of the Met Office Global Coupled Model version 2 (GC2) with increased resolution relative to the standard model: the ocean resolution is increased from 1/4 to 1/12° (28 to 9 km at the Equator), the atmosphere resolution increased from 60 km (N216) to 25 km (N512) and the coupling period reduced from 3 hourly to hourly. The technical developments that were required to build a version of the model at higher resolution are described as well as results from a 20-year simulation. The results demonstrate the key role played by the enhanced resolution of the ocean model: reduced sea surface temperature (SST) biases, improved ocean heat transports, deeper and stronger overturning circulation and a stronger Antarctic Circumpolar Current. Our results suggest that the improvements seen here require high resolution in both atmosphere and ocean components as well as high-frequency coupling. These results add to the body of evidence suggesting that ocean resolution is an important consideration when developing coupled models for weather and climate applications.