Science.gov

Sample records for dependent fluxes due

  1. Collisionality dependence of the quasilinear particle flux due to microinstabilities

    SciTech Connect

    Fueloep, T.; Pusztai, I.; Helander, P.

    2008-07-15

    The collisionality dependence of the quasilinear particle flux due to the ion temperature gradient (ITG) and trapped electron mode (TEM) instabilities is studied by including electron collisions modeled by a pitch-angle scattering collision operator in the gyrokinetic equation. The inward transport due to ITG modes is caused mainly by magnetic curvature and thermodiffusion and can be reversed as electron collisions are introduced, if the plasma is far from marginal stability. However, if the plasma is close to marginal stability, collisions may even enhance the inward transport. The sign and the magnitude of the transport are sensitive to the form of the collision operator, to the magnetic drift normalized to the real frequency of the mode, and to the density and temperature scale lengths. These analytical results are in agreement with previously published gyrokinetic simulations. Unlike the ITG-driven flux, the TEM-driven flux is expected to be outwards for conditions far from marginal stability and inwards otherwise.

  2. Temperature-dependent surface modification of Ta due to high-flux, low-energy He+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Novakowski, T. J.; Tripathi, J. K.; Hassanein, A.

    2015-12-01

    This work examines the response of Tantalum (Ta) as a potential candidate for plasma-facing components (PFCs) in future nuclear fusion reactors. Tantalum samples were exposed to high-flux, low-energy He+ ion irradiation at different temperatures in the range of 823-1223 K. The samples were irradiated at normal incidence with 100 eV He+ ions at constant flux of 1.2 × 1021 ions m-2 s-1 to a total fluence of 4.3 × 1024 ions m-2. An additional Ta sample was also irradiated at 1023 K using a higher ion fluence of 1.7 × 1025 ions m-2 (at the same flux of 1.2 × 1021 ions m-2 s-1), to confirm the possibility of fuzz formation at higher fluence. This higher fluence was chosen to roughly correspond to the lower fluence threshold of fuzz formation in Tungsten (W). Surface morphology was characterized with a combination of field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). These results demonstrate that the main mode of surface damage is pinholes with an average size of ∼70 nm2 for all temperatures. However, significantly larger pinholes are observed at elevated temperatures (1123 and 1223 K) resulting from the agglomeration of smaller pinholes. Ex situ X-ray photoelectron spectroscopy (XPS) provides information about the oxidation characteristics of irradiated surfaces, showing minimal exfoliation of the irradiated Ta surface. Additionally, optical reflectivity measurements are performed to further characterize radiation damage on Ta samples, showing gradual reductions in the optical reflectivity as a function of temperature.

  3. Plasma flux-dependent lipid A deactivation

    NASA Astrophysics Data System (ADS)

    Chang, Hung-Wen; Hsu, Cheng-Che; Ahmed, Musahid; Liu, Suet Yi; Fang, Yigang; Seog, Joonil; Oehrlein, Gottlieb S.; Graves, David B.

    2014-06-01

    This paper reports the influence of gas plasma flux on endotoxin lipid A film deactivation. To study the effect of the flux magnitude of reactive species, a modified low-pressure inductively coupled plasma (ICP) with O radical flux ˜1016 cm-2 s-1 was used. After ICP exposures, it was observed that while the Fourier transform infrared absorbance of fatty chains responsible for the toxicity drops by 80% through the film, no obvious film endotoxin deactivation is seen. This is in contrast to that previously observed under low flux exposure conducted in a vacuum beam system: near-surface only loss of fatty chains led to significant film deactivation. Secondary ion mass spectrometry characterization of changes at the film surface did not appear to correlate with the degree of deactivation. Lipid A films need to be nearly completely removed in order to detect significant deactivation under high flux conditions. Additional high reactive species flux experiments were conducted using an atmospheric pressure helium plasma jet and a UV/ozone device. Exposure of lipid A films to reactive species with these devices showed similar deactivation behaviour. The causes for the difference between low and high flux exposures may be due to the nature of near-surface structural modifications as a function of the rate of film removal.

  4. Flux concentrations on solar dynamic components due to mispointing

    NASA Technical Reports Server (NTRS)

    Rylicki, Daniel S.

    1992-01-01

    Mispointing of the solar dynamic (SD) concentrator designed for use on Space Station Freedom (SSF) causes the optical axis of the concentrator to be nonparallel to the incoming rays from the Sun. This causes solar flux not to be focused into the aperture hole of the receiver and may position the flux on other SSF components. A Rocketdyne analysis has determined the thermal impact of off-axis radiation due to mispointing on elements of the SD module and photovoltaic (PV) arrays. The conclusion was that flux distributions on some of the radiator components, the two-axis gimbal rings, the truss, and the PV arrays could present problems. The OFFSET computer code was used at Lewis Research Center to further investigate these flux distributions incident on components. The Lewis study included distributions for a greater range of mispoint angles than the Rocketdyne study.

  5. Outward Poynting flux due to electromagnetic fluctuations in an RFP

    NASA Astrophysics Data System (ADS)

    Thuecks, D. J.; McCollam, K. J.; Stone, D. R.

    2013-10-01

    In a reversed-field pinch (RFP) driven by a toroidal electric field, tearing modes not only generate the net EMF that sustains the equilibrium profile but are also expected to produce an outward flow of electromagnetic energy, or Poynting flux, to be dissipated at the plasma edge. In MST experiments, insertable edge probes measure both electrostatic Ẽ and magnetic B~ fluctuations, which are used to reconstruct the flux-surface average Poynting flux < Ẽ × B~ > as it varies with minor radius, time, and equilibrium parameters. Our initial results indicate that this outward flux is a significant fraction of the total input power on time average and increases to large values during the brief periods surrounding discrete magnetic relaxation events, or sawtooth crashes. The flux decreases with radius outside of the reversal surface, suggesting that the electromagnetic energy is deposited there and dissipated into the plasma. These results are qualitatively similar to expectation from a simple model of an incompressible fluid plasma with a solid, resistive boundary. DOE and NSF support this work.

  6. Uncertainties Associated with Flux Measurements Due to Heterogeneous Contaminant Distributions

    EPA Science Inventory

    Mass flux and mass discharge measurements at contaminated sites have been applied to assist with remedial management, and can be divided into two broad categories: point-scale measurement techniques and pumping methods. Extrapolation across un-sampled space is necessary when usi...

  7. g Dependent particle concentration due to sedimentation

    NASA Astrophysics Data System (ADS)

    Haranas, Ioannis; Gkigkitzis, Ioannis; Zouganelis, George D.

    2012-11-01

    Sedimentation of particles in a fluid has long been used to characterize particle size distribution. Stokes' law is used to determine an unknown distribution of spherical particle sizes by measuring the time required for the particles to settle a known distance in a fluid of known viscosity and density. In this paper, we study the effects of gravity on sedimentation by examining the resulting particle concentration distributed in an equilibrium profile of concentration C m, n above the bottom of a container. This is for an experiment on the surface of the Earth and therefore the acceleration of gravity had been corrected for the oblateness of the Earth and its rotation. Next, at the orbital altitude of the spacecraft in orbit around Earth the acceleration due to the central field is corrected for the oblateness of the Earth. Our results show that for experiments taking place in circular or elliptical orbits of various inclinations around the Earth the concentration ratio C m, n / C m, ave , the inclination seems to be the most ineffective in affecting the concentration among all the orbital elements. For orbital experiment that use particles of diameter d p =0.001 μm the concentration ratios for circular and slightly elliptical orbits in the range e=0-0.1 exhibit a 0.009 % difference. The concentration ratio increases with the increase of eccentricity, which increases more for particles of larger diameters. Finally, for particles of the same diameter concentration ratios between Earth and Mars surface experiments are related in the following way C_{(m,n)_{mathit{Earth}}} = 0.99962 C_{(m,n)_{mathit{Mars}}}.

  8. Eddy-covariance flux errors due to biases in gas concentration measurements: origins, quantification and correction

    NASA Astrophysics Data System (ADS)

    Fratini, G.; McDermitt, D. K.; Papale, D.

    2013-08-01

    Errors in gas concentration measurements by infrared gas analysers can occur during eddy-covariance campaigns, associated with actual or apparent instrumental drifts or to biases due to thermal expansion, dirt contamination, aging of components or errors in field operations. If occurring on long time scales (hours to days), these errors are normally ignored during flux computation, under the assumption that errors in mean gas concentrations do not affect the estimation of turbulent fluctuations and, hence, of covariances. By analysing instrument theory of operation, and using numerical simulations and field data, we show that this is not the case for instruments with curvilinear calibrations; we further show that if not appropriately accounted for, concentration biases can lead to roughly proportional systematic flux errors, where the fractional errors in fluxes are about 30-40% the fractional errors in concentrations. We quantify these errors and characterize their dependency on main determinants. We then propose a correction procedure that largely - potentially completely - eliminates these errors. The correction, to be applied during flux computation, is based on knowledge of instrument calibration curves and on field or laboratory calibration data. Finally, we demonstrate the occurrence of such errors and validate the correction procedure by means of a field experiment, and accordingly provide recommendations for in situ operations. The correction described in this paper will soon be available in the EddyPro software (www.licor.com/eddypro).

  9. Test particle Monte Carlo simulation of return flux due to ambient scatter of outgassing molecules

    NASA Astrophysics Data System (ADS)

    Jin, Xuhong; Huang, Fei; Cheng, Xiaoli

    2014-12-01

    The return flux on circular disk surface due to ambient scatter of outgassing molecules is simulated by using the test particle Monte Carlo (TPMC) method. The return flux ratio (RFR) obtained here for the return flux problem is in good agreement with existent results. Moreover, some factors affecting the return flux, such as the radius and temperature of the circular disk and the freestream molecular mass, velocity, temperature and molecular number density, have been analyzed and the mechanism how they affect RFR has been discussed, which provide theoretical explanations for the evaluation and control of the return flux contamination.

  10. Spatial pattern dynamics due to the fitness gradient flux in evolutionary games.

    PubMed

    deForest, Russ; Belmonte, Andrew

    2013-06-01

    We introduce a nondiffusive spatial coupling term into the replicator equation of evolutionary game theory. The spatial flux is based on motion due to local gradients in the relative fitness of each strategy, providing a game-dependent alternative to diffusive coupling. We study numerically the development of patterns in one dimension (1D) for two-strategy games including the coordination game and the prisoner's dilemma, and in two dimensions (2D) for the rock-paper-scissors game. In 1D we observe modified traveling wave solutions in the presence of diffusion, and asymptotic attracting states under a frozen-strategy assumption without diffusion. In 2D we observe spiral formation and breakup in the frozen-strategy rock-paper-scissors game without diffusion. A change of variables appropriate to replicator dynamics is shown to correctly capture the 1D asymptotic steady state via a nonlinear diffusion equation. PMID:23848658

  11. Suppression of weak localization due to magnetic flux in few-channel ballistic microstructures

    SciTech Connect

    Pluhar, Z.; Weidenmueller, H.A.; Zuk, J.A. ); Lewenkopf, C.H. )

    1994-10-10

    Using a random-matrix model for the Hamiltonian of a ballistic microstructure, which is chaotic in the classical limit, maximizing the coupling to the external leads, and employing Landauer's formula and Efetov's supersymmetry technique, we derive an expression for the magnetic-flux dependence of weak localization. This expression describes the crossover from orthogonal to unitary symmetry, depends only on the number of channels and on the magnetic flux through the structure, and is expected to apply universally.

  12. Validation of neutron flux redistribution factors in JSI TRIGA reactor due to control rod movements.

    PubMed

    Kaiba, Tanja; Žerovnik, Gašper; Jazbec, Anže; Štancar, Žiga; Barbot, Loïc; Fourmentel, Damien; Snoj, Luka

    2015-10-01

    For efficient utilization of research reactors, such as TRIGA Mark II reactor in Ljubljana, it is important to know neutron flux distribution in the reactor as accurately as possible. The focus of this study is on the neutron flux redistributions due to control rod movements. For analyzing neutron flux redistributions, Monte Carlo calculations of fission rate distributions with the JSI TRIGA reactor model at different control rod configurations have been performed. Sensitivity of the detector response due to control rod movement have been studied. Optimal radial and axial positions of the detector have been determined. Measurements of the axial neutron flux distribution using the CEA manufactured fission chambers have been performed. The experiments at different control rod positions were conducted and compared with the MCNP calculations for a fixed detector axial position. In the future, simultaneous on-line measurements with multiple fission chambers will be performed inside the reactor core for a more accurate on-line power monitoring system. PMID:26141293

  13. Heat flux due to poloidal electric field in the banana regime

    SciTech Connect

    Taguchi, M. )

    1992-02-01

    The heat flux due to poloidally varying electrostatic potential is calculated in the banana regime. This electrostatic potential determined self-consistently from charge neutrality is shown to increase the electron heat flux by a factor {radical}{ital m}{sub {ital i}}/{ital m}{sub {ital e}} compared with that when this potential is neglected, where {ital m}{sub {ital e}} and {ital m}{sub {ital i}} are the masses of electron and ion, respectively.

  14. Time-dependent modeling of solar wind acceleration from turbulent heating in open flux tubes

    NASA Astrophysics Data System (ADS)

    Woolsey, Lauren Nicole; Cranmer, Steven R.

    2015-04-01

    The acceleration of the solar wind, particularly from open flux tubes, remains an open question in solar physics. Countless physical processes have been suggested to explain all or parts of the coupled problem of coronal heating and wind acceleration, but the current generation of observations have been so far unable to distinguish which mechanism(s) dominates. In this project, we consider heating by Alfvén waves in a three-dimensional, time-dependent reduced magnetohydrodynamics model. This model solves for the heating rate as a function of time due to the twisting and braiding of magnetic field lines within a flux tube, which is caused by Alfvén waves generated at the single footpoint of the flux tube. We investigate three specific structures commonly found in the corona: 1) an open flux tube in a coronal hole, 2) an open flux tube on the edge of an equatorial streamer, and 3) an open flux tube directly neighboring an active region. We present the time-dependent heating rate, power spectra of fluctuations, and the time-averaged properties of the solar wind arising from each magnetic structure. We compare the time-averaged properties from the present modeling with previous results from a one-dimensional, time-steady code (Cranmer et al. 2007) to better calibrate the physics in the lower-dimensional code and get a better understanding of the intricate role that bursty, transient heating from Alfvén-wave-driven turbulence plays in the acceleration of the solar wind from different magnetic structures.

  15. Forest Thinning Dramatically Enhances Ozone Flux due to Reactions With Elevated Emissions of Biogenic Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Goldstein, A. H.; McKay, M.; Kurpius, M. R.; Schade, G. W.

    2003-12-01

    Forests are routinely managed for timber production and fire suppression by thinning and harvesting. The impact of these activities on biosphere-atmosphere exchange of reactive trace gases is profound, but has rarely been studied in the field. Here we present simultaneous observations of ozone and terpene fluxes before, during, and after pre-commercial thinning of a ponderosa pine plantation at Blodgett Forest (1300 m elevation on the western slope of the Sierra Nevada Mountains, CA). We previously reported that monoterpene emissions increased by an order of magnitude during and following forest thinning (Schade and Goldstein, GRL 2003). We also previously reported that half the daytime ozone flux to this ecosystem under normal summertime conditions (no disturbance) was due to gas-phase chemical loss, and we suggested that this ozone loss was occurring by reactions with biogenically emitted terpenes whose lifetime was short enough that they reacted before escaping the forest canopy (Kurpius and Goldstein, GRL 2003). Here we report that ozone loss was also dramatically enhanced during and following thinning, and we link these observations to confirm that the chemical ozone loss in the canopy was indeed due to reaction with biogenically emitted compounds whose emission was enhanced by disturbance. Based on the magnitudes of ozone flux due to chemical loss and the measured terpene fluxes, we infer that the emissions of previously undetected short-lived terpenes are approximately 15-20 times those of a-pinene during thinning, and 30-50 times those of a-pinene during summer and fall. Since a-pinene accounts for approximately 25% of the total monoterpenes we routinely measure with our automated in-situ GC instrumentation, we conclude that emissions of highly reactive terpenoid compounds could have been drastically under measured in previous field campaigns and that emissions of unidentified reactive terpenes could be 5-10 times larger than emissions of total terpenes

  16. The time dependence of reversed archeomagnetic flux patches

    NASA Astrophysics Data System (ADS)

    Terra-Nova, Filipe; Amit, Hagay; Hartmann, Gelvam A.; Trindade, Ricardo I. F.

    2015-02-01

    Archeomagnetic field models may provide important insights to the geodynamo. Here we investigate the existence and mobility of reversed flux patches (RFPs) in an archeomagnetic field model. We introduce topological algorithms to define, identify, and track RFPs. In addition, we explore the relations between RFPs and dipole changes and apply robustness tests to the RFPs. In contrast to previous definitions, patches that reside on the geographic equator are adequately identified based on our RFPs definition. Most RFPs exhibit a westward drift and migrate toward higher latitudes. Undulations of the magnetic equator and RFPs oppose the axial dipole moment (ADM). Filtered models show a tracking behavior similar to the nonfiltered model, and surprisingly new RFPs occasionally emerge. The advection and diffusion of RFPs have worked in unison to yield the decrease of the ADM at recent times. The absence of RFPs in the period 550-1440 A.D. is related to a low in intermediate degrees of the geomagnetic power spectrum. We thus hypothesize that the RFPs are strongly dependent on intermediate spherical harmonic degrees 4 and above.

  17. The time dependence of reversed archeomagnetic flux patches

    NASA Astrophysics Data System (ADS)

    Terra-Nova, Filipe; Amit, Hagay; Hartmann, Gelvam A.; Trindade, Ricardo I. F.

    2016-04-01

    Archeomagnetic field models may provide important insights to the geodynamo. Here we investigate the existence and mobility of reversed flux patches (RFPs) in archeomagnetic field model CALS3k.4b of Korte and Constable (2011; PEPI, 188, 247-259). We introduce topological algorithms to define, identify and track RPFs. In addition, we explore the relations between RFPs and dipole changes, and apply robustness tests to the RFPs. In contrast to previous definitions, patches that reside on the geographic equator are adequately identified based on our RFPs definition that takes the magnetic equator as a reference. Most RFPs exhibit a westward drift and migrate towards higher latitudes. Undulations of the magnetic equator and RFPs oppose the axial dipole moment (ADM). Filtered models show a tracking behaviour similar to the non-filtered model, and surprisingly new RFPs occasionally emerge. The advection and diffusion of RFPs have worked in unison to yield the decrease of the ADM at recent times. The absence of RFPs in the period 550-1440 AD is related to a low in intermediate degrees of the geomagnetic power spectrum. We thus hypothesize that the RFPs are strongly dependent on intermediate spherical harmonic degrees 4 and above. Comparison of tracking of RFPs among various archeomagnetic field models was also performed and gives more complex results.

  18. Kilometric radiation power flux dependence on area of discrete aurora

    NASA Technical Reports Server (NTRS)

    Saflekos, N. A.; Burch, J. L.; Gurnett, D. A.; Anderson, R. R.; Sheehan, R. E.

    1989-01-01

    Kilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.

  19. Net Fluorescein Flux Across Corneal Endothelium Strongly Suggests Fluid Transport is due to Electro-osmosis.

    PubMed

    Sanchez, J M; Cacace, V; Kusnier, C F; Nelson, R; Rubashkin, A A; Iserovich, P; Fischbarg, J

    2016-08-01

    We have presented prior evidence suggesting that fluid transport results from electro-osmosis at the intercellular junctions of the corneal endothelium. Such phenomenon ought to drag other extracellular solutes. We have investigated this using fluorescein-Na2 as an extracellular marker. We measured unidirectional fluxes across layers of cultured human corneal endothelial (HCE) cells. SV-40-transformed HCE layers were grown to confluence on permeable membrane inserts. The medium was DMEM with high glucose and no phenol red. Fluorescein-labeled medium was placed either on the basolateral or the apical side of the inserts; the other side carried unlabeled medium. The inserts were held in a CO2 incubator for 1 h (at 37 °C), after which the entire volume of the unlabeled side was collected. After that, label was placed on the opposite side, and the corresponding paired sample was collected after another hour. Fluorescein counts were determined with a (Photon Technology) DeltaScan fluorometer (excitation 380 nm; emission 550 nm; 2 nm bwth). Samples were read for 60 s. The cells utilized are known to transport fluid from the basolateral to the apical side, just as they do in vivo in several species. We used 4 inserts for influx and efflux (total: 20 1-h periods). We found a net flux of fluorescein from the basolateral to the apical side. The flux ratio was 1.104 ± 0.056. That difference was statistically significant (p = 0.00006, t test, paired samples). The endothelium has a definite restriction at the junctions. Hence, an asymmetry in unidirectional fluxes cannot arise from osmosis, and can only point instead to paracellular solvent drag. We suggest, once more, that such drag is due to electro-osmotic coupling at the paracellular junctions. PMID:26989056

  20. LYM2-dependent chitin perception limits molecular flux via plasmodesmata

    PubMed Central

    Faulkner, Christine; Petutschnig, Elena; Benitez-Alfonso, Yoselin; Beck, Martina; Robatzek, Silke; Lipka, Volker; Maule, Andrew J.

    2013-01-01

    Chitin acts as a pathogen-associated molecular pattern from fungal pathogens whose perception triggers a range of defense responses. We show that LYSIN MOTIF DOMAIN-CONTAINING GLYCOSYLPHOSPHATIDYLINOSITOL-ANCHORED PROTEIN 2 (LYM2), the Arabidopsis homolog of a rice chitin receptor-like protein, mediates a reduction in molecular flux via plasmodesmata in the presence of chitin. For this response, lym2-1 mutants are insensitive to the presence of chitin, but not to the flagellin derivative flg22. Surprisingly, the chitin-recognition receptor CHITIN ELCITOR RECEPTOR KINASE 1 (CERK1) is not required for chitin-induced changes to plasmodesmata flux, suggesting that there are at least two chitin-activated response pathways in Arabidopsis and that LYM2 is not required for CERK1-mediated chitin-triggered defense responses, indicating that these pathways are independent. In accordance with a role in the regulation of intercellular flux, LYM2 is resident at the plasma membrane and is enriched at plasmodesmata. Chitin-triggered regulation of molecular flux between cells is required for defense responses against the fungal pathogen Botrytis cinerea, and thus we conclude that the regulation of symplastic continuity and molecular flux between cells is a vital component of chitin-triggered immunity in Arabidopsis. PMID:23674687

  1. The evolution of future geogenic matter fluxes due Enhanced Weathering: Results from the Antwerp Experiment

    NASA Astrophysics Data System (ADS)

    Hartmann, Jens; Weiss, Andreas; Struyf, Eric; Schoelynck, Jonas; Meire, Patrick; Amann, Thorben

    2015-04-01

    Understanding the evolution of geogenic matter fluxes in soils due the application of rock products ontop of soils is relevant to evaluate alteration of soil solutions and saturation states of solutes. In the future the practice of applying rock products will continue and areas affected will likely spread (Hartmann et al., 2013). This trend will likely be fuelled by attempts to optimize carbon dioxide removal by increasing biomass production, soil organic carbon stocks, increase crop production or afforestation. All those efforts demand a certain amount of geogenic nutrients, which need to be replaced. To investigate the release patterns and the downward transport of an array of elements, and to study their fate as well as reaction processes, altered through this practice, a mesocosm experiment was established at Antwerp University. Extended results will be presented (c.f., Weiss et al., 2014) focusing on the release and transport of DIC (dissolved inorganic carbon) and Mg (magnesium) in the soil column downwards after the application of 22 kg m-2 olivine powder. Elevated DIC and Mg concentrations are detected in case of olivine is applied to mesocosms with wheat and barley, if compared to the mesocsoms without plants, and without olivine. The change patterns in concentrations and fluxes will be discussed. Hartmann, J., et al. (2013) Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, supply nutrients, and mitigate ocean acidification. Reviews of Geophysics; 51(2), 113-149. doi: 10.1002/rog.20004 Weiss, A., et al. (2014) The overlooked compartment of the critical-zone-complex, considering the evolution of future geogenic matter fluxes: Agricultural topsoils. Procedia Earth and Planetary Science, 10, 339-342. doi:10.1016/j.proeps.2014.08.032

  2. MEASUREMENT OF RF LOSSES DUE TO TRAPPED FLUX IN A LARGE-GRAIN NIOBIUM CAVITY

    SciTech Connect

    Gianluigi Ciovati; Alex Gurevich

    2008-01-23

    Trapped magnetic field in superconducting niobium is a well known cause of radio-frequency (RF) residual losses. In this contribution, we present the results of RF tests on a single-cell cavity made of high-purity large grain niobium before and after allowing a fraction of the Earth magnetic field to be trapped in the cavity during the cooldown below the critical temperature Tc. This experiment has been done on the cavity before and after a low temperature baking. Temperature mapping allowed us to determine the location of hot-spots with high losses and to measure their field dependence. The results show not only an increase of the low-field residual resistance, but also a larger increase of the surface resistance for intermediate RF field (higher “medium field Q-slope”), which depends on the amount of the trapped flux. These additional field-dependent losses can be described as losses of pinned vortices oscillating under the applied RF magnetic field.

  3. MEASUREMENT OF RF LOSSES DUE TO TRAPPED FLUX IN A LARGE-GRAIN NIOBIUM CAVITY

    SciTech Connect

    Gianluigi Ciovati; Alex Gurevich

    2008-01-23

    Trapped magnetic field in superconducting niobium is a well known cause of radio-frequency (RF) residual losses. In this contribution, we present the results of RF tests on a single-cell cavity made of high-purity large grain niobium before and after allowing a fraction of the Earth’s magnetic field to be trapped in the cavity during the cooldown below the critical temperature Tc. This experiment has been done on the cavity before and after a low temperature baking. Temperature mapping allowed us to determine the location of hot-spots with high losses and to measure their field dependence. The results show not only an increase of the low-field residual resistance, but also a larger increase of the surface resistance for intermediate RF field (higher "medium field Qslope"), which depends on the amount of the trapped flux. These additional field-dependent losses can be described as losses of pinned vortices oscillating under the applied RF magnetic field.

  4. Soil organic carbon stocks and fluxes due to land use conversions at the European scale

    NASA Astrophysics Data System (ADS)

    Gobin, A.; Campling, P.

    2012-04-01

    (HOC) assimilated depends on the yields, as these directly relate to potential residue production, and on the prevailing climate with cold temperatures and dry moisture regimes being less favourable. Incorporating all crop residues into the soil results in HOC fluxes that range from 1.36 tonnes HOC/ha for oilseed and 1.14 tonnes HOC/ha for cereal to 0.54 tonnes/ha for sugar beet. The HOC fluxes drop to 0.69, 0.58 and 0.05 tonnes HOC/ha respectively when all residues are removed, e.g. for bio-energy purposes. Taking into account the projected areas for cereals (65 Mha), oilseed (10 Mha) and sugarbeet (2 Mha) in 2030, shows that residue management of cereals has a much larger impact on carbon fluxes to the agricultural soil than oilseed and sugar beet. The removal of all crop residues result in a lowering of soil organic carbon stocks, a reduction of humified organic carbon fluxes into the soil and an increase of carbon dioxide concentrations in the atmosphere. A significant minimum percentage of crop residues should be retained in the soils. Land management, land use changes and climate change have a significant influence on soil organic carbon stocks and fluxes across the EU-27. Determining the soil sequestration potential necessitates soil monitoring to provide evidence on the state of, and change, in agricultural soils, allowing to evaluate its effectiveness.

  5. Direction dependence of cosmological parameters due to cosmic hemispherical asymmetry

    NASA Astrophysics Data System (ADS)

    Mukherjee, Suvodip; Aluri, Pavan K.; Das, Santanu; Shaikh, Shabbir; Souradeep, Tarun

    2016-06-01

    Persistent evidence for a cosmic hemispherical asymmetry in the temperature field of cosmic microwave background (CMB) as observed by both WMAP as well as PLANCK increases the possibility of its cosmological origin. Presence of this signal may lead to different values for the standard model cosmological parameters in different directions, and that can have significant implications for other studies where they are used. We investigate the effect of this cosmic hemispherical asymmetry on cosmological parameters using non-isotropic Gaussian random simulations injected with both scale dependent and scale independent modulation strengths. Our analysis shows that As and ns are the most susceptible parameters to acquire position dependence across the sky for the kind of isotropy breaking phenomena under study. As expected, we find maximum variation arises for the case of scale independent modulation of CMB anisotropies. We find that scale dependent modulation profile as seen in PLANCK data could lead to only 1.25σ deviation in As in comparison to its estimate from isotropic CMB sky.

  6. Scale dependent climate change due to deforestation in Amazonia

    NASA Astrophysics Data System (ADS)

    Rauscher, Sara A.

    Numerous experiments were conducted with a regional climate model (MM5) to determine its ability to simulate the climate of tropical South America and to investigate the modeled climate's response to deforestation. Six month-long test simulations were performed for the wet (January) and dry seasons (July). MM5 was able to simulate the differences in regional circulation between the two seasons, and also reproduced the regional climate features of each month quite well. An evaluation of MM5's land surface model (OSULSM) showed that OSULSM does not partition energy at the surface correctly. The modeled sensible heat flux was far too high in comparison with observations. In order to mitigate this effect, soil layer depth, rooting depth, leaf area index, and initial soil moisture were increased. This configuration compared more favorably with observed data. Three experiments with 100% (DEF), 50% (PD1), and 20% (PD2) deforestation were performed for January and July. The partial deforestation experiments were designed to present a realistic picture of deforestation. The experiments showed that the model climate was more sensitive to land cover changes during the dry season. In addition, the response of the model to the imposed land cover changes was of the same or lesser magnitude than the difference between the wet and dry months for each season. In the January experiments, the area-averaged precipitation response was small. The July simulations showed a stronger response to the land cover changes, as precipitation decreased in all three experiments. The reduction in precipitation for each experiment was not proportional to the amount of deforestation: the decrease in precipitation for PD1 and PD2 was less than amount of deforestation relative to DEF, indicating that the amount and distribution of deforestation does have an impact on the climate signal. These simulations are sensitivity studies, and should not be interpreted as a forecast of the climatic effects of

  7. Thermodynamics of deposition flux-dependent intrinsic film stress

    PubMed Central

    Saedi, Amirmehdi; Rost, Marcel J.

    2016-01-01

    Vapour deposition on polycrystalline films can lead to extremely high levels of compressive stress, exceeding even the yield strength of the films. A significant part of this stress has a reversible nature: it disappears when the deposition is stopped and re-emerges on resumption. Although the debate on the underlying mechanism still continues, insertion of atoms into grain boundaries seems to be the most likely one. However, the required driving force has not been identified. To address the problem we analyse, here, the entire film system using thermodynamic arguments. We find that the observed, tremendous stress levels can be explained by the flux-induced entropic effects in the extremely dilute adatom gas on the surface. Our analysis justifies any adatom incorporation model, as it delivers the underlying thermodynamic driving force. Counterintuitively, we also show that the stress levels decrease, if the barrier(s) for adatoms to reach the grain boundaries are decreased. PMID:26888311

  8. Thermodynamics of deposition flux-dependent intrinsic film stress

    NASA Astrophysics Data System (ADS)

    Saedi, Amirmehdi; Rost, Marcel J.

    2016-02-01

    Vapour deposition on polycrystalline films can lead to extremely high levels of compressive stress, exceeding even the yield strength of the films. A significant part of this stress has a reversible nature: it disappears when the deposition is stopped and re-emerges on resumption. Although the debate on the underlying mechanism still continues, insertion of atoms into grain boundaries seems to be the most likely one. However, the required driving force has not been identified. To address the problem we analyse, here, the entire film system using thermodynamic arguments. We find that the observed, tremendous stress levels can be explained by the flux-induced entropic effects in the extremely dilute adatom gas on the surface. Our analysis justifies any adatom incorporation model, as it delivers the underlying thermodynamic driving force. Counterintuitively, we also show that the stress levels decrease, if the barrier(s) for adatoms to reach the grain boundaries are decreased.

  9. EFT for vortices with dilaton-dependent localized flux

    NASA Astrophysics Data System (ADS)

    Burgess, C. P.; Diener, Ross; Williams, M.

    2015-11-01

    We study how codimension-two objects like vortices back-react gravitationally with their environment in theories (such as 4D or higher-dimensional supergravity) where the bulk is described by a dilaton-Maxwell-Einstein system. We do so both in the full theory, for which the vortex is an explicit classical `fat brane' solution, and in the effective theory of `point branes' appropriate when the vortices are much smaller than the scales of interest for their back-reaction (such as the transverse Kaluza-Klein scale). We extend the standard Nambu-Goto description to include the physics of flux-localization wherein the ambient flux of the external Maxwell field becomes partially localized to the vortex, generalizing the results of a companion paper [4] from N=2 supergravity as the end-point of a hierarchical limit in which the Planck mass first and then the supersymmetry breaking scale are sent to infinity. We define, in the parent supergravity model, a new symplectic frame in which, in the rigid limit, manifest symplectic invariance is preserved and the electric and magnetic Fayet-Iliopoulos terms are fully originated from the dyonic components of the embedding tensor. The supergravity origin of several features of the resulting rigid supersymmetric theory are then elucidated, such as the presence of a traceless SU(2)- Lie algebra term in the Ward identity and the existence of a central charge in the supersymmetry algebra which manifests itself as a harmless gauge transformation on the gauge vectors of the rigid theory; we show that this effect can be interpreted as a kind of "superspace non-locality" which does not affect the rigid theory on space-time. To set the stage of our analysis we take the opportunity in this paper to provide and prove the relevant identities of the most general dyonic gauging of Special-Kaehler and Quaternionic-Kaehler isometries in a generic N=2 model, which include the supersymmetry Ward identity, in a fully symplectic-covariant formalism.

  10. Quantitative flux analysis reveals folate-dependent NADPH production

    NASA Astrophysics Data System (ADS)

    Fan, Jing; Ye, Jiangbin; Kamphorst, Jurre J.; Shlomi, Tomer; Thompson, Craig B.; Rabinowitz, Joshua D.

    2014-06-01

    ATP is the dominant energy source in animals for mechanical and electrical work (for example, muscle contraction or neuronal firing). For chemical work, there is an equally important role for NADPH, which powers redox defence and reductive biosynthesis. The most direct route to produce NADPH from glucose is the oxidative pentose phosphate pathway, with malic enzyme sometimes also important. Although the relative contribution of glycolysis and oxidative phosphorylation to ATP production has been extensively analysed, similar analysis of NADPH metabolism has been lacking. Here we demonstrate the ability to directly track, by liquid chromatography-mass spectrometry, the passage of deuterium from labelled substrates into NADPH, and combine this approach with carbon labelling and mathematical modelling to measure NADPH fluxes. In proliferating cells, the largest contributor to cytosolic NADPH is the oxidative pentose phosphate pathway. Surprisingly, a nearly comparable contribution comes from serine-driven one-carbon metabolism, in which oxidation of methylene tetrahydrofolate to 10-formyl-tetrahydrofolate is coupled to reduction of NADP+ to NADPH. Moreover, tracing of mitochondrial one-carbon metabolism revealed complete oxidation of 10-formyl-tetrahydrofolate to make NADPH. As folate metabolism has not previously been considered an NADPH producer, confirmation of its functional significance was undertaken through knockdown of methylenetetrahydrofolate dehydrogenase (MTHFD) genes. Depletion of either the cytosolic or mitochondrial MTHFD isozyme resulted in decreased cellular NADPH/NADP+ and reduced/oxidized glutathione ratios (GSH/GSSG) and increased cell sensitivity to oxidative stress. Thus, although the importance of folate metabolism for proliferating cells has been long recognized and attributed to its function of producing one-carbon units for nucleic acid synthesis, another crucial function of this pathway is generating reducing power.

  11. Estimation of surface temperature variations due to changes in sky and solar flux with elevation.

    USGS Publications Warehouse

    Hummer-Miller, S.

    1981-01-01

    Sky and solar radiance are of major importance in determining the ground temperature. Knowledge of their behavior is a fundamental part of surface temperature models. These 2 fluxes vary with elevation and this variation produces temperature changes. Therefore, when using thermal-property differences to discriminate geologic materials, these flux variations with elevation need to be considered. -from Author

  12. Flux noise due to magnetic impurities in superconducting circuits: Optimal spin texture and role of phase transition

    NASA Astrophysics Data System (ADS)

    de Sousa, Rogério

    Superconducting quantum interference devices (SQUIDs) and other superconducting circuits are limited by intrinsic flux noise with spectral density 1 /fα with α < 1 whose origin is believed to be due to spin impurities. We present a theory of flux noise in the presence of phase transitions and arbitrary spin textures in the impurity spin system. At higher temperatures we find that the spin-spin correlation length scale (describing, e.g., the average size of ferromagnetic spin clusters) greatly impacts the scaling of flux noise with wire geometry. At lower temperatures we find that flux noise is quite sensitive to the particular spin texture realized by the spin system ground state. Remarkably, we show that flux-noise is exactly equal to zero when the spins form a poloidal texture. Flux noise is nonzero for other spin textures, but gets reduced in the presence of correlated ferromagnetic fluctuations between the top and bottom wire surfaces, where the flux vectors are antiparallel. This demonstrates the idea of engineering spin textures and/or intersurface correlation as a method to reduce flux noise in superconducting circuits. This research was supported by the Natural Sciences and Engineering Research Council of Canada (RGPIN/342982-2010, EGP/429649-2012) through its Discovery and Engage programs.

  13. Fast stratocumulus adjustment timescale due to entrainment-liquid flux feedback

    NASA Astrophysics Data System (ADS)

    Jones, C. R.; Bretherton, C. S.; Blossey, P. N.

    2013-12-01

    We use a mixed-layer model (MLM) and large eddy simulation (LES) to analyze the response timescales of a stratocumulus-topped boundary layer. From the MLM, we find three separate time scales: a slow adjustment timescale associated with boundary layer deepening (on the order of several days); an intermediate timescale associated with thermodynamic adjustment of the boundary layer (approximately one day); and a fast timescale (6-12 hours) associated with entrainment rate feedbacks. We show that the fast scale is due to entrainment-liquid flux (ELF) adjustment, an internal cloud-regulating feedback between entrainment rate and the cloud liquid water path (LWP). A thicker cloud generates more turbulent kinetic energy and an increased entrainment rate which tends to warm and dry the boundary layer, thereby decreasing the cloud thickness (a negative feedback). Through this mechanism, the cloud base quickly adjusts until the entrainment rate and LWP stabilize as entrainment warming balances boundary-layer radiative cooling. We use two cases based on past model intercomparison studies to investigate the fast time scale. The first (DYCOMS RF01) involves a nocturnal stratocumulus-capped mixed layer with idealized radiative forcing. A perturbation to the free tropospheric relative humidity is shown to induce fast adjustment of cloud thickness in the MLM and also in an LES. A second case with realistic radiation used in past for cloud feedback studies (CGILS S12) is used to show that an instantaneous CO2 increase does not elicit a fast response in cloud thickness. However, an instantaneous temperature increase to the whole atmosphere-ocean column induces a cloud thinning with a few hours in both MLM and LES that largely explains the equilibrium response of the cloud layer to this forcing. This fast ELF adjustment suggests that stratocumulus cloud changes likely have a positive feedback on greenhouse warming.

  14. Evidence for a possible calcium flux dependent cardiomyopathy in hyperthyroidism

    SciTech Connect

    Barat, J.L.; Wicker, P.; Manley, W.; Brendel, A.J.; Lefort, G.; San Galli, F.; Commenges-Ducos, M.; Latapie, J.L.; Riviere, J.; Ducassou, D.

    1985-05-01

    This study was designed to test the hypothesis that the impaired functional cardiac reserve to exercise in hyperthyroidism is related to alterations in the regulation of calcium transport. In 2l hyperthyroid patients, the left ventricular ejection fraction (LVEF) was measured using equilibrium gated radionuclide angiocardiography at rest and during supine dynamic exercise. After a recovery period, the patients performed a second exercise study after random administration of Verapamil, a calcium entry blocker (11 pts), or propanolol, a beta adrenergic antagonist (10 pts) for comparison. The results showed i) normal resting LVEF with no significant change during exercise before any medication, ii) resting LVEF significantly decreased after Propanolol, and no significantly changed after Verapamil, iii) during exercise, significant increase of LVEF after Verapamil, and no significant change after Propanolol. These results are consistent with previous studies showing that abnormal change in LVEF during exercise in hyperthyroidism seems independent of beta adrenergic activation, and suggest a reversible functional cardiomyopathy dependent of calcium transporting systems.

  15. Energy dependence of relativistic electron flux variations in the outer radiation belt during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Xiong, Ying; Xie, Lun; Li, Jinxing; Fu, Suiyan; Pu, Zuyin; Chen, Lunjin; Ni, Binbin; Li, Wen

    2015-04-01

    Geomagnetic storms can either increase or decrease relativistic electron fluxes in the outer radiation belt, depending on the delicate competition between electron energization and loss processes. Despite the well-known "energy independent" prototype in which electron fluxes enhance after geomagnetic storms at all energies, we present observations of "energy dependent" events, i.e., post-storm electron fluxes at lower energies (0.3-2.5 MeV, measured by MEPED/POES) recover or even exceed the pre-storm level, while electron fluxes at higher energies (2.5-14 MeV, measured by PET/SAMPEX) do not restore. The statistical survey of 84 isolated storms demonstrates that geomagnetic storms preferentially decrease relativistic electron fluxes at higher energies while flux enhancements are more common at lower energies: ~ 82% (3%) storm events produce increased (decreased) flux for 0.3-2.5 MeV electrons, while ~ 37% (45%) storms lead to enhancements (reductions) of 2.5-14 MeV electron flux. Superposed epoch analysis suggests that "energy dependent" events preferentially occur during periods of high solar wind density along with high dynamic pressure. Previous statistical studies have shown that this kind of solar wind conditions account for significant enhancements of EMIC waves, which cause efficient precipitation of > 2 MeV electrons into atmosphere via pitch angle scattering. Two cases of "energy dependent" events are investigated in detail with evident observations of EMIC waves that can resonate effectively with >2 MeV electrons. Besides, we do not capture much differences in the chorus wave activity between those "energy dependent" and "energy independent" events. Therefore, our results strongly suggest that EMIC waves play a crucial role in the occurrences of those "energy dependent" events in the outer zone during geomagnetic storms.

  16. Energy Dependent Responses of Relativistic Electron Fluxes in the Outer Radiation Belt to Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Xie, L.

    2015-12-01

    Geomagnetic storms can either increase 4 or decrease relativistic electron fluxes in the outer radiation belt. A statistical survey of 84 isolated storms demonstrates that geomagnetic storms preferentially decrease relativistic electron fluxes at higher energies while flux enhancements are more common at lower energies. In about 87% of the storms, 0.3-2.5 MeV electrons fluxes show increase, whereas 2.5-14 MeV electron fluxes increase in only 35% of the storms. Superposed epoch analyses suggest that such 'energy dependent' behavior of electrons preferably occurs during conditions of high solar wind density which is favorable to generate magnetospheric electromagnetic ion cyclotron (EMIC) waves and these 'energy dependent' events are associated with relatively weaker chorus activities. We have examined one of the cases where observed EMIC waves can resonate effectively with >2.5 MeV electrons and scatter them into the atmosphere. The correlation study further illustrates that electron flux drop-outs during storm main phases do not correlate well with the flux build-up during storm recovery phases. We suggest that a combination of efficient EMIC-induced scattering and weaker chorus-driven acceleration provide a viable candidate for the energy dependent responses of outer radiation belt relativistic electrons to geomagnetic storms. These results are of great interest to both understanding of the radiation belt dynamics and applications in space weather.

  17. Self-Regulated Plasma Heat Flux Mitigation Due to Liquid Sn Vapor Shielding.

    PubMed

    van Eden, G G; Morgan, T W; Aussems, D U B; van den Berg, M A; Bystrov, K; van de Sanden, M C M

    2016-04-01

    A steady-state high-flux H or He plasma beam was balanced against the pressure of a Sn vapor cloud for the first time, resulting in a self-regulated heat flux intensity near the liquid surface. A temperature response of the liquid surface characterized by a decoupling from the received heating power and significant cooling of the plasma in the neutral Sn cloud were observed. The plasma heat flux impinging on the target was found to be mitigated, as heat was partially dissipated by volumetric processes in the vapor cloud rather than wholly by surface effects. These results motivate further exploration of liquid metal solutions to the critical challenge of heat and particle flux handling in fusion power plants. PMID:27081983

  18. Self-Regulated Plasma Heat Flux Mitigation Due to Liquid Sn Vapor Shielding

    NASA Astrophysics Data System (ADS)

    van Eden, G. G.; Morgan, T. W.; Aussems, D. U. B.; van den Berg, M. A.; Bystrov, K.; van de Sanden, M. C. M.

    2016-04-01

    A steady-state high-flux H or He plasma beam was balanced against the pressure of a Sn vapor cloud for the first time, resulting in a self-regulated heat flux intensity near the liquid surface. A temperature response of the liquid surface characterized by a decoupling from the received heating power and significant cooling of the plasma in the neutral Sn cloud were observed. The plasma heat flux impinging on the target was found to be mitigated, as heat was partially dissipated by volumetric processes in the vapor cloud rather than wholly by surface effects. These results motivate further exploration of liquid metal solutions to the critical challenge of heat and particle flux handling in fusion power plants.

  19. A case study of electron precipitation fluxes due to plasmaspheric hiss

    NASA Astrophysics Data System (ADS)

    Hardman, Rachael; Clilverd, Mark A.; Rodger, Craig J.; Brundell, James B.; Duthie, Roger; Holzworth, Robert H.; Mann, Ian R.; Milling, David K.; Macusova, Eva

    2015-08-01

    We find that during a large geomagnetic storm in October 2011 the trapped fluxes of >30, >100, and >300 keV outer radiation belt electrons were enhanced at L = 3-4 during the storm main phase. A gradual decay of the trapped fluxes was observed over the following 5-7 days, even though no significant precipitation fluxes could be observed in the Polar Orbiting Environmental Satellite (POES) electron precipitation detectors. We use the Antarctic-Arctic Radiation-belt (Dynamic) Deposition-VLF Atmospheric Research Konsortium receiver network to investigate the characteristics of the electron precipitation throughout the storm period. Weak electron precipitation was observed on the dayside for 5-7 days, consistent with being driven by plasmaspheric hiss. Using a previously published plasmaspheric hiss-induced electron energy e-folding spectrum of E0 = 365 keV, the observed radio wave perturbation levels at L = 3-4 were found to be caused by >30 keV electron precipitation with flux ~100 el cm-2 s-1 sr-1. The low levels of precipitation explain the lack of response of the POES telescopes to the flux, because of the effect of the POES lower sensitivity limit and ability to measure weak diffusion-driven precipitation. The detection of dayside, inner plasmasphere electron precipitation during the recovery phase of the storm is consistent with plasmaspheric hiss wave-particle interactions and shows that the waves can be a significant influence on the evolution of the outer radiation belt trapped flux that resides inside the plasmapause.

  20. Artificial neural network prediction model for geosynchronous electron fluxes: Dependence on satellite position and particle energy

    NASA Astrophysics Data System (ADS)

    Shin, Dae-Kyu; Lee, Dae-Young; Kim, Kyung-Chan; Hwang, Junga; Kim, Jaehun

    2016-04-01

    Geosynchronous satellites are often exposed to energetic electrons, the flux of which varies often to a large extent. Since the electrons can cause irreparable damage to the satellites, efforts to develop electron flux prediction models have long been made until recently. In this study, we adopt a neural network scheme to construct a prediction model for the geosynchronous electron flux in a wide energy range (40 keV to >2 MeV) and at a high time resolution (as based on 5 min resolution data). As the model inputs, we take the solar wind variables, geomagnetic indices, and geosynchronous electron fluxes themselves. We also take into account the magnetic local time (MLT) dependence of the geosynchronous electron fluxes. We use the electron data from two geosynchronous satellites, GOES 13 and 15, and apply the same neural network scheme separately to each of the GOES satellite data. We focus on the dependence of prediction capability on satellite's magnetic latitude and MLT as well as particle energy. Our model prediction works less efficiently for magnetic latitudes more away from the equator (thus for GOES 13 than for GOES 15) and for MLTs nearer to midnight than noon. The magnetic latitude dependence is most significant for an intermediate energy range (a few hundreds of keV), and the MLT dependence is largest for the lowest energy (40 keV). We interpret this based on degree of variance in the electron fluxes, which depends on magnetic latitude and MLT at geosynchronous orbit as well as particle energy. We demonstrate how substorms affect the flux variance.

  1. Intensity of Upward Muon Flux Due to Cosmic-Ray Neutrinos Produced in the Atmosphere

    DOE R&D Accomplishments Database

    Lee, T. D.; Robinson, H.; Schwartz, M.; Cool, R.

    1963-06-01

    Calculations were performed to determine the upward going muon flux leaving the earth's surface after production by cosmic-ray neutrinos in the crust. Only neutrinos produced in the earth's atmosphere are considered. Rates of the order of one per 100 sq m/day might be expected if an intermediate boson exists and has a mass less than 2 Bev. (auth)

  2. The seasonal dependence of relativistic electron fluxes in the Earth's outer van Allen Belt

    NASA Astrophysics Data System (ADS)

    Kanekal, S. G.; Baker, D. N.; McPherron, R.

    2007-12-01

    It is well known that geomagnetic activity shows a marked seasonal dependence. This effect has been attributed to the seasonal variation of the Earth's dipole tilt angle exposing the magnetosphere to an increased southward component of the interplanetary field (the Russell-McPherron effect) or an increased solar wind velocity (the axial/equinoctial effect). We examine the seasonal dependence of relativistic electron fluxes in the Earth's outer Van Allen belt. An earlier investigation by Baker et. al., (1999) found that the relativistic electron fluxes do show a strong seasonal dependence with the equinoctial electron fluxes being almost three times higher than the solstitial fluxes. We extend this previous investigation using data obtained by sensors onboard SAMPEX. This study of the seasonal dependence is based on data with a higher time resolution as compared to the earlier study. The results of our analysis show that the peak electron fluxes are shifted in time from the nominal equinoctial times. We discuss some possible implications of our observations in the context of electron energization in the Earth's magnetosphere. Baker, D.N., S.G. Kanekal, T.I. Pulkkinen, and J.B. Blake, Equinoctial and solstitial averages of magnetospheric relativistic electrons: A strong semiannual modulation, Geophys. Res. Lett., 26, No. 20, 3193-3196, 1999.

  3. Temperature dependent surface modification of molybdenum due to low energy He+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Tripathi, J. K.; Novakowski, T. J.; Joseph, G.; Linke, J.; Hassanein, A.

    2015-09-01

    In this paper, we report on the temperature dependent surface modifications in molybdenum (Mo) samples due to 100 eV He+ ion irradiation in extreme conditions as a potential candidate to plasma-facing components in fusion devices alternative to tungsten. The Mo samples were irradiated at normal incidence, using an ion fluence of 2.6 × 1024 ions m-2 (with a flux of 7.2 × 1020 ions m-2 s-1). Surface modifications have been studied using high-resolution field emission scanning electron-(SEM) and atomic force (AFM) microscopy. At 773 K target temperature homogeneous evolution of molybdenum nanograins on the entire Mo surface were observed. However, at 823 K target temperature appearance of nano-pores and pin-holes nearby the grain boundaries, and Mo fuzz in patches were observed. The fuzz density increases significantly with target temperatures and continued until 973 K. However, at target temperatures beyond 973 K, counterintuitively, a sequential reduction in the fuzz density has been seen till 1073 K temperatures. At 1173 K and above temperatures, only molybdenum nano structures were observed. Our temperature dependent studies confirm a clear temperature widow, 823-1073 K, for Mo fuzz formation. Ex-situ high resolution X-ray photoelectron spectroscopy studies on Mo fuzzy samples show the evidence of MoO3 3d doublets. This elucidates that almost all the Mo fuzz were oxidized during open air exposure and are thick enough as well. Likewise the microscopy studies, the optical reflectivity measurements also show a sequential reduction in the reflectivity values (i.e., enhancement in the fuzz density) up to 973 K and after then a sequential enhancement in the reflectivity values (i.e., reduction in the fuzz density) with target temperatures. This is in well agreement with microscopy studies where we observed clear temperature window for Mo fuzz growth.

  4. The thermal dependence of Na+ flux in isolated liver cells from ectotherms and endotherms.

    PubMed

    Else, Paul L

    2016-07-15

    The thermal dependence (0-40°C) of Na(+) flux in isolated liver cells of three endotherms (mice, rat and rabbit) was compared with that of ectotherms in the form of a thermally tolerant amphibian (cane toad), a cold-water fish (rainbow trout) and a thermophilic reptile (lizard). Mammals were found to share similar high rates of Na(+) flux (3.0-3.7 nmol Na(+) mg(-1) protein min(-1)) at their normal body temperatures (36-39°C). These Na(+) flux rates were significantly greater (P<0.0004-0.0001) than those of the ectotherms, which shared similar low rates of Na(+) flux (0.7-1.3 nmol Na(+) mg(-1) protein min(-1)) at their very different normal acclimated body temperatures (15°C for trout, 25°C for toad and 37°C for the lizard species). Trout, which possess highly unsaturated membranes (similar to those of mammals), showed a Na(+) flux with high thermal sensitivity at low temperatures similar to that found in mammals at higher temperatures. The thermal sensitivity of toad Na(+) flux was significantly less (P<0.05-0.01) than that of rat and rabbit. Trout Na(+) flux did not increase with increasing temperature much above 20°C, whereas all other species measured increased their Na(+) flux with increasing temperature up to 40°C. In conclusion, at normal operating body temperatures, the rate of Na(+) flux is much lower in ectotherms. PMID:27207635

  5. Dependence of Large-Scale Global Poynting Flux on IMF By Polarity Change

    NASA Astrophysics Data System (ADS)

    Humberset, B. K.; Gjerloev, J. W.

    2014-12-01

    In this study we present the dependence of the global Poynting flux on the IMF By polarity change. The amount of energy that enters the magnetosphere from the solar wind is a function of the solar wind speed and pressure and the IMF orientation and magnitude. All the various published coupling models show that the polarity of the IMF By component does not change the energy input. In contrast the global convection patterns, and thus the ionospheric Pedersen currents, depend on IMF By polarity. This seems to imply that the ionospheric energy deposition is a function of IMF By polarity. Thus, there appear to be a fundamental difference between the input (from the solar wind) and the output (energy dissipating Pedersen currents). We, therefore, ask the question: To what extend is the global Poynting flux dependent on the IMF By polarity? We have performed a statistical study evaluating 59 abrupt transitions in the IMF By component (polarity changes) as measured by the ACE spacecraft. The effect of other solar wind coupling parameters, such as the IMF Bz component, are minimized by selecting events where these are nearly constant. We use electric field distributions from SuperDARN and field-aligned current distributions from AMPERE to calculate the global distribution of the Poynting Flux. To minimize the effect of magnetospheric energy unloading we focus on the 06-18 MLT region. We further investigate the dependence on solar induced conductivity. We find that the Poynting flux is slightly larger for positive IMF By compared to negative By conditions. For a low conductivity (not sunlit) ionosphere the Poynting flux is smaller than in the high conductivity (sunlit) ionosphere and we find a smaller dependence on IMF By polarity. The study emphasizes the global dynamic behavior of the ionosphere in its response to changes in the external driver (IMF).

  6. Apparent drifts of IRGA measurements due to optical path contamination and their effects on eddy-covariance fluxes

    NASA Astrophysics Data System (ADS)

    McDermitt, D. K.; Fratini, G.; Papale, D.

    2013-12-01

    Apparent instrumental biases can cause errors in gas concentration measurements by infrared gas analysers (IRGAs) used in eddy-covariance flux measurements. Such biases most often result from deposition of atmospheric pollutants, such as aerosols, pollen, or particulate matter on surfaces in the optical path, which in some cases, can cause differential signal attenuation in the sample and reference channels of the gas analyser. We refer to such biases as apparent, to stress that they are not the result of an intrinsic loss of instrumental metric performance, but rather of incidental and avoidable deployment artefacts. Nonetheless, due to the curvilinear nature of IRGAs calibration curves, they can cause errors in eddy-covariance fluxes, resulting from reduced accuracy of the gas concentration measurement. In this work we describe the phenomenological and mathematical foundations of these concentration biases, also showing how measurements from different IRGA typologies are affected as a result. By means of numerical simulations, we find that concentration biases can lead to roughly proportional systematic flux errors, where the fractional errors in fluxes are roughly 30-40% the fractional errors in concentrations. We also propose a correction procedure and provide recommendations for field deployment and operation, to minimize or completely eliminate such errors. The correction procedure will soon be available in the EddyPro software (www.licor.com/eddypro).

  7. Angular dependences of the motion of the anisotropic flux line lattice and the peak effect in MgB2

    NASA Astrophysics Data System (ADS)

    Jang, D.-J.; Lee, H.-S.; Kang, B.; Lee, H.-G.; Cho, M.-H.; Lee, S.-I.

    2008-12-01

    We have studied the angle-dependent motion of the anisotropic flux line lattice (FLL) and the peak effect (PE) in MgB2 single crystals. For arbitrary angles (θ), we measured the resistance (R(H)) and critical current (Ic(H)) with AC and DC currents, respectively. At low fields below the PE, R(H) and Ic(H) showed a weak angular dependence, regardless of the type of excitation current, because of the stable vortex state. At intermediate fields near the PE, R(H) and Ic(H) at the onset of the PE varied with θ, depending on the type of external current, due to the metastability of the disordered vortex lattice near the PE. At high fields above the PE and near the upper critical field Hc2, the R(H) curves showed a simple scaling behavior with θ.

  8. Excessive magnetic field flux density distribution from overhead isolated powerline conductors due to neutral line current.

    PubMed

    Netzer, Moshe

    2013-06-01

    Overhead isolated powerline conductors (hereinafter: "OIPLC") are the most compact form for distributing low voltage currents. From the known physics of magnetic field emission from 3-phase power lines, it is expected that excellent symmetry of the 120° shifted phase currents and where compact configuration of the 3-phase+neutral line exist, the phase current vectorial summation of the magnetic field flux density (MFFD) is expected to be extremely low. However, despite this estimation, an unexpectedly very high MFFD was found in at least three towns in Israel. This paper explains the reasons leading to high MFFD emissions from compact OIPLC and the proper technique to fix it. Analysis and measurement results had led to the failure hypothsis of neutral line poor connection design and poor grounding design of the HV-LV utility transformers. The paper elaborates on the low MFFD exposure level setup by the Israeli Environmental Protection Office which adopted a rather conservative precaution principal exposure level (2 mG averaged over 24 h). PMID:23675630

  9. Generation mechanism of L-value dependence of oxygen flux enhancements during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Kletzing, C.

    2015-12-01

    The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures charged particles with an energy range from ~eV to ~ tens of keV. The observation shows that the energy flux of the particles increases inside the geosynchronous orbit during substorms. For some night-side events around the apogee, the energy flux of O+ ion enhances below ~10 keV at lower L shell, whereas the flux below ~8 keV sharply decreases at higher L shells. This structure of L-energy spectrogram of flux is observed only for the O+ ions. The purpose of this study is to investigate the generation mechanism of the structure by using numerical simulations. We utilized the global MHD simulation developed by Tanaka et al (2010, JGR) to simulate the electric and magnetic fields during substorms. We performed test particle simulation under the electric and magnetic fields by applying the same model introduced by Nakayama et al. (2015, JGR). In the test particle simulation each test particle carries the real number of particles in accordance with the Liouville theorem. Using the real number of particles, we reconstructed 6-dimensional phase space density and differential flux of O+ ions in the inner magnetosphere. We obtained the following results. (1) Just after the substorm onset, the dawn-to-dusk electric field is enhanced to ~ 20 mV/m in the night side tail region at L > 7. (2) The O+ ions are accelerated and transported to the inner region (L > ~5.5) by the large-amplitude electric field. (3) The reconstructed L-energy spectrogram shows a similar structure to the Van Allen Probes observation. (4) The difference in the flux enhancement between at lower L shell and higher L shells is due to two distinct acceleration processes: adiabatic and non-adiabatic. We will discuss the relationship between the particle acceleration and the structure of L-energy spectrogram of flux enhancement in detail.

  10. Higher order treatment on temporal derivative of angular flux for time-dependent MOC

    SciTech Connect

    Tsujita, K.; Endo, T.; Yamamoto, A.; Kamiyama, Y.; Kirimura, K.

    2013-07-01

    A new kinetic analysis method, whose angular dependence of temporal derivative for angular flux is accurately treated within practical memory requirement, is proposed. The method of characteristics (MOC) is being widely used for reactor analysis thanks to the advances of numerical algorithms and computer hardware. However, the computational resources, i.e., the memory capacity, can be still a crucial problem for rigorous kinetic calculations using MOC. In the straightforward approach for kinetic calculation using MOC, the segment-averaged angular fluxes should be stored on the memory in order to explicitly calculate the temporal derivative of the angular flux, which would require huge memory. Thus, in the conventional kinetic calculation code using MOC, the temporal derivative of the angular flux has been approximated as angularly isotropic in order to reduce the memory requirement (isotropic assumption). However, the approximation error caused by the conventional isotropic assumption has not been thoroughly and quantitatively investigated so far and an accurate kinetic calculation method, which can quantitatively estimate the above approximation error within practical memory storage, has not been developed. The present study tries to address this issue with a newly developed approach. Effect of the approximate treatment for the temporal derivative of angular flux is evaluated through benchmark calculations. (authors)

  11. The uncertainty of UTCI due to uncertainties in the determination of radiation fluxes derived from measured and observed meteorological data

    NASA Astrophysics Data System (ADS)

    Weihs, Philipp; Staiger, Henning; Tinz, Birger; Batchvarova, Ekaterina; Rieder, Harald; Vuilleumier, Laurent; Maturilli, Marion; Jendritzky, Gerd

    2012-05-01

    In the present study, we investigate the determination accuracy of the Universal Thermal Climate Index (UTCI). We study especially the UTCI uncertainties due to uncertainties in radiation fluxes, whose impacts on UTCI are evaluated via the mean radiant temperature ( Tmrt). We assume "normal conditions", which means that usual meteorological information and data are available but no special additional measurements. First, the uncertainty arising only from the measurement uncertainties of the meteorological data is determined. Here, simulations show that uncertainties between 0.4 and 2 K due to the uncertainty of just one of the meteorological input parameters may be expected. We then analyse the determination accuracy when not all radiation data are available and modelling of the missing data is required. Since radiative transfer models require a lot of information that is usually not available, we concentrate only on the determination accuracy achievable with empirical models. The simulations show that uncertainties in the calculation of the diffuse irradiance may lead to Tmrt uncertainties of up to ±2.9 K. If long-wave radiation is missing, we may expect an uncertainty of ±2 K. If modelling of diffuse radiation and of longwave radiation is used for the calculation of Tmrt, we may then expect a determination uncertainty of ±3 K. If all radiative fluxes are modelled based on synoptic observation, the uncertainty in Tmrt is ±5.9 K. Because Tmrt is only one of the four input data required in the calculation of UTCI, the uncertainty in UTCI due to the uncertainty in radiation fluxes is less than ±2 K. The UTCI uncertainties due to uncertainties of the four meteorological input values are not larger than the 6 K reference intervals of the UTCI scale, which means that UTCI may only be wrong by one UTCI scale. This uncertainty may, however, be critical at the two temperature extremes, i.e. under extreme hot or extreme cold conditions.

  12. Magnetic Flux Concentrations in Stratified Turbulent Plasma Due to Negative Effective Magnetic Pressure Instability

    NASA Astrophysics Data System (ADS)

    Jabbari, S.; Brandenburg, A.

    2014-12-01

    al. 2013). When the field is vertical, the resulting magnetic flux concentrations lead to the magnetic spots and can be of equipartition field strength. DNS, MFS, and implicit large eddy simulations (ILES) confirm that in a proper parameter regime, vertical imposed fields lead to the formation of circular magnetic spots (Brandenburg et al. 2014).

  13. Calculations of increased solar UV fluxes and DUV doses due to stratospheric-ozone depletions

    SciTech Connect

    Zardecki, A.; Gerstl, S.A.W.

    1982-02-01

    Accurate radiative transfer calculations are performed in the middle ultraviolet spectral region for aerosol-loaded atmospheres with the goal of determining the solar irradiance at the ground and quantifying the irradiance perturbations due to the presence of aerosols and various ozone depletions. The extent of the increase of UV-B radiation as a function of wave-length and solar zenith angle is calculated for five model atmospheres. In addition, the damaging ultraviolet dose rates and radiation amplification factors are evaluated at different latitudes and seasons for erythemal and DNA action spectra.

  14. INCLINATION-DEPENDENT ACTIVE GALACTIC NUCLEUS FLUX PROFILES FROM STRONG LENSING OF THE KERR SPACETIME

    SciTech Connect

    Chen, Bin; Dai, Xinyu; Baron, E.

    2013-01-10

    Recent quasar microlensing observations have constrained the X-ray emission sizes of quasars to be about 10 gravitational radii, one order of magnitude smaller than the optical emission sizes. Using a new ray-tracing code for the Kerr spacetime, we find that the observed X-ray flux is strongly influenced by the gravity field of the central black hole, even for observers at moderate inclination angles. We calculate inclination-dependent flux profiles of active galactic nuclei in the optical and X-ray bands by combining the Kerr lensing and projection effects for future reference. We further study the dependence of the X-ray-to-optical flux ratio on the inclination angle caused by differential lensing distortion of the X-ray and optical emission, assuming several corona geometries. The strong lensing X-ray-to-optical magnification ratio can change by a factor of {approx}10 for normal quasars in some cases, and a further factor of {approx}10 for broad absorption line (BAL) quasars and obscured quasars. Comparing our results with the observed distributions in normal and BAL quasars, we find that the inclination angle dependence of the magnification ratios can significantly change the X-ray-to-optical flux ratio distributions. In particular, the mean value of the spectrum slope parameter {alpha}{sub ox}, 0.3838log F {sub 2keV}/F {sub 2500A}, can differ by {approx}0.1-0.2 between normal and BAL quasars, depending on corona geometries, suggesting larger intrinsic absorptions in BAL quasars.

  15. Changes in Carbon Flux at the Duke Forest Hardwood Ameriflux Site Due to Land Cover/Land Use Changes

    NASA Astrophysics Data System (ADS)

    McCombs, A. G.

    2014-12-01

    The Raleigh/Durham, North Carolina metropolitan area has been ranked by Forbes as the fastest growing cities in the United States. As a result of the rapid growth, there has been a significant amount of urban sprawl. The objective of this study was to determine if the changes in land use and land cover have caused a change in the carbon flux near the Duke Forest AmeriFlux station that was active from 2001 to 2008. The land cover and land use were assessed every two years to determine how land cover has changed at the Duke Forest Hardwoods (US-Dk2) AmeriFlux site from 2001 to 2008 using Landsat scenes. The change in land cover and land use was then compared to changes in the carbon footprint that is computed annually from 2001 to 2008. The footprint model for each wind direction determined that there are changes annually and that the research will determine if these changes are due to annual weather patterns or land use and land cover changes.

  16. Time dependent theory of gapless d-wave superconductors: Application to the flux flow

    SciTech Connect

    Kopnin, N.B. |

    1998-02-01

    Time-dependent equations for a d-wave superconductor are derived for temperatures close to T{sub c} under the gapless condition {tau}{Delta}(T) {much_lt} 1. They differ from the usual time-dependent Ginzburg-Landau (TDGL) theory by an additional term which describes as diffusive relaxation of nonequilibrium excitations. These equations are applied to the problem of flux flow. The longitudinal conductivity is found to differ considerably from the Bardeen and Stephen model; the implication of this result for resistive measurements of the upper critical field is discussed. The Hall conductivity, however, coincides with the usual TDGL expression.

  17. Origin of dc voltage in type II superconducting flux pumps: field, field rate of change, and current density dependence of resistivity

    NASA Astrophysics Data System (ADS)

    Geng, J.; Matsuda, K.; Fu, L.; Fagnard, J.-F.; Zhang, H.; Zhang, X.; Shen, B.; Dong, Q.; Baghdadi, M.; Coombs, T. A.

    2016-03-01

    Superconducting flux pumps are the kind of devices which can generate direct current into superconducting circuit using external magnetic field. The key point is how to induce a dc voltage across the superconducting load by ac fields. Giaever (1966 IEEE Spectr. 3 117) pointed out flux motion in superconductors will induce a dc voltage, and demonstrated a rectifier model which depended on breaking superconductivity. van de Klundert et al (1981 Cryogenics 21 195, 267) in their review(s) described various configurations for flux pumps all of which relied on inducing the normal state in at least part of the superconductor. In this letter, following their work, we reveal that a variation in the resistivity of type II superconductors is sufficient to induce a dc voltage in flux pumps and it is not necessary to break superconductivity. This variation in resistivity is due to the fact that flux flow is influenced by current density, field intensity, and field rate of change. We propose a general circuit analogy for travelling wave flux pumps, and provide a mathematical analysis to explain the dc voltage. Several existing superconducting flux pumps which rely on the use of a travelling magnetic wave can be explained using the analysis enclosed. This work can also throw light on the design and optimization of flux pumps.

  18. Transient Convection Due to Imposed Heat Flux: Application to Liquid-Acquisition Devices

    NASA Technical Reports Server (NTRS)

    Duval, Walter M. B.; Chato, David J.; Doherty, Michael P.

    2014-01-01

    A model problem is considered that addresses the effect of heat load from an ambient laboratory environment on the temperature rise of liquid nitrogen inside an enclosure. This model has applications to liquid acquisition devices inside the cryogenic storage tanks used to transport vapor-free propellant to the main engine. We show that heat loads from Q = 0.001 to 10 W, with corresponding Rayleigh numbers from Ra = 109 to 1013, yield a range of unsteady convective states and temperature rise in the liquid. The results show that Q = 1 to 10 W (Ra = 1012 to 1013) yield temperature distributions along the enclosure height that are similar in trend to experimental measurements. Unsteady convection, which shows selfsimilarity in its planforms, is predicted for the range of heat-load conditions. The onset of convection occurs from a free-convection-dominated base flow that becomes unstable against convective instability generated at the bottom of the enclosure while the top of the enclosure is convectively stable. A number of modes are generated with small-scale thermals at the bottom of the enclosure in which the flow selforganizes into two symmetric modes prior to the onset of the propagation of the instability. These symmetric vertical modes transition to asymmetric modes that propagate as a traveling-wave-type motion of convective modes and are representative of the asymptotic convective state of the flow field. Intense vorticity production is created in the core of the flow field due to the fact that there is shear instability between the vertical and horizontal modes. For the higher Rayleigh numbers, 1012 to 1013, there is a transition from a stationary to a nonstationary response time signal of the flow and temperature fields with a mean value that increases with time over various time bands and regions of the enclosure.

  19. Magnetic Flux Concentrations in Stratified Turbulent Plasma Due to Negative Effective Magnetic Pressure Instability

    NASA Astrophysics Data System (ADS)

    Jabbari, Sarah

    2015-08-01

    We study a system of a highly stratified turbulent plasma. In such a system, when the magnetic Reynolds number is large enough and there is a background field of suitable strength, a new effect will play role in con- centrating magnetic fields such that it leads to the formation of magnetic spots and bipolar regions. This effect is due to the fact that the turbu- lent pressure is suppressed by the large-scale magnetic field, which adds a negative term to the total mean-field (effective) pressure. This leads to an instability, which is known as the negative effective magnetic pressure instability (NEMPI). Direct numerical simulations (DNS) of isothermally forced turbulence have shown that NEMPI leads to the formation of spots in the presence of an imposed field. Our main aim now is to use NEMPI to explain the formation of active regions and sunspots. To achieve this goal, we need to move progressively to more realistic models. Here we extend our model by allowing the magnetic field to be generated by a dy- namo. A dynamo plays an important role in solar activity. Therefore, it is of interest to investigate NEMPI in the presence of dynamo-generated magnetic fields. Mean-field simulations (MFS) of such systems in spheri- cal geometry have shown how these two instabilities work in concert. In fact NEMPI will be activated as long as the strength of the magnetic field generated by the dynamo is in a proper range (for more detail see Jab- bari et al. 2013). In our new study, we use DNS to investigate a similar system. The turbulence is forced in the entire spherical shell, but the forc- ing is made helical in the lower 30% of the shell, similar to the model of Mitra et al. (2014). We perform simulations using the Pencil Code for different density contrasts and other input parameters. We applied ver- tical field boundary conditions in the r direction. The results show that, when the stratification is high enough, intense bipolar regions form and as time passes, they expand

  20. The field-dependent shock profiles of a magnetorhelogical damper due to high impact: an experimental investigation

    NASA Astrophysics Data System (ADS)

    Kim, Hwan-Choong; Oh, Jong-Seok; Choi, Seung-Bok

    2015-02-01

    This work proposes a new damper featuring magnetorheological fluid (MR damper) and presents its field-dependent damping forces due to high impact. To achieve this goal, a large MR damper, which can produce a damping force of 100 kN at 6 A, is designed and manufactured based on the analysis of the magnetic flux intensity of the damper. After identifying the field-dependent damping force levels of the manufactured MR damper, a hydraulic horizontal shock tester is established. This shock testing system consists of a velocity generator, impact mass, shock programmer, and test mass. The MR damper is installed at the end of the wall in the shock tester and tested under four different experimental conditions. The shock profile characteristics of the MR damper due to different impact velocities are investigated at various input current levels. In addition, the inner pressure of the MR damper during impact, which depends on the input’s current level, is evaluated at two positions that can represent the pressure drop that generates the damping force of the MR damper. It is demonstrated from this impact testing that the shock profiles can be changed by the magnitude of the input current applied to the MR damper. It directly indicates that a desired shock profile can be achieved by installing the MR damper associated with appropriate control logics to adjust the magnitude of the input current.

  1. Voltage-Dependent Regulation of Complex II Energized Mitochondrial Oxygen Flux.

    PubMed

    Bai, Fan; Fink, Brian D; Yu, Liping; Sivitz, William I

    2016-01-01

    Oxygen consumption by isolated mitochondria is generally measured during state 4 respiration (no ATP production) or state 3 (maximal ATP production at high ADP availability). However, mitochondria in vivo do not function at either extreme. Here we used ADP recycling methodology to assess muscle mitochondrial function over intermediate clamped ADP concentrations. In so doing, we uncovered a previously unrecognized biphasic respiratory pattern wherein O2 flux on the complex II substrate, succinate, initially increased and peaked over low clamped ADP concentrations then decreased markedly at higher clamped concentrations. Mechanistic studies revealed no evidence that the observed changes in O2 flux were due to altered opening or function of the mitochondrial permeability transition pore or to changes in reactive oxygen. Based on metabolite and functional metabolic data, we propose a multifactorial mechanism that consists of coordinate changes that follow from reduced membrane potential (as the ADP concentration in increased). These changes include altered directional electron flow, altered NADH/NAD+ redox cycling, metabolite exit, and OAA inhibition of succinate dehydrogenase. In summary, we report a previously unrecognized pattern for complex II energized O2 flux. Moreover, our findings suggest that the ADP recycling approach might be more widely adapted for mitochondrial studies. PMID:27153112

  2. Voltage-Dependent Regulation of Complex II Energized Mitochondrial Oxygen Flux

    PubMed Central

    Bai, Fan; Fink, Brian D.; Yu, Liping; Sivitz, William I.

    2016-01-01

    Oxygen consumption by isolated mitochondria is generally measured during state 4 respiration (no ATP production) or state 3 (maximal ATP production at high ADP availability). However, mitochondria in vivo do not function at either extreme. Here we used ADP recycling methodology to assess muscle mitochondrial function over intermediate clamped ADP concentrations. In so doing, we uncovered a previously unrecognized biphasic respiratory pattern wherein O2 flux on the complex II substrate, succinate, initially increased and peaked over low clamped ADP concentrations then decreased markedly at higher clamped concentrations. Mechanistic studies revealed no evidence that the observed changes in O2 flux were due to altered opening or function of the mitochondrial permeability transition pore or to changes in reactive oxygen. Based on metabolite and functional metabolic data, we propose a multifactorial mechanism that consists of coordinate changes that follow from reduced membrane potential (as the ADP concentration in increased). These changes include altered directional electron flow, altered NADH/NAD+ redox cycling, metabolite exit, and OAA inhibition of succinate dehydrogenase. In summary, we report a previously unrecognized pattern for complex II energized O2 flux. Moreover, our findings suggest that the ADP recycling approach might be more widely adapted for mitochondrial studies. PMID:27153112

  3. On the existence of motion-induced heat flux due to thermoelastic waves in a one-dimensional solid rod

    NASA Astrophysics Data System (ADS)

    Semperlotti, Fabio; Sen, Mihir

    2014-03-01

    In this Letter, we show the existence of motion-induced heat transfer in homogeneous isotropic solids due to the propagation of thermoelastic waves. In particular, using the linearized governing equations for thermoelastic waves, we show that heat transfer in a one-dimensional rod is not only due to conduction but also to the local particle displacement a phenomenon which, in principle, is similar to advective heat transfer in fluids. It is found that the time-averaged heat transfer is dependent on both the material properties and the external excitation parameters. This mechanism can potentially be useful in ultrasonic welding and in the development of solid state refrigerators or heat pumps.

  4. The Yeast Cyclin-Dependent Kinase Routes Carbon Fluxes to Fuel Cell Cycle Progression.

    PubMed

    Ewald, Jennifer C; Kuehne, Andreas; Zamboni, Nicola; Skotheim, Jan M

    2016-05-19

    Cell division entails a sequence of processes whose specific demands for biosynthetic precursors and energy place dynamic requirements on metabolism. However, little is known about how metabolic fluxes are coordinated with the cell division cycle. Here, we examine budding yeast to show that more than half of all measured metabolites change significantly through the cell division cycle. Cell cycle-dependent changes in central carbon metabolism are controlled by the cyclin-dependent kinase (Cdk1), a major cell cycle regulator, and the metabolic regulator protein kinase A. At the G1/S transition, Cdk1 phosphorylates and activates the enzyme Nth1, which funnels the storage carbohydrate trehalose into central carbon metabolism. Trehalose utilization fuels anabolic processes required to reliably complete cell division. Thus, the cell cycle entrains carbon metabolism to fuel biosynthesis. Because the oscillation of Cdk activity is a conserved feature of the eukaryotic cell cycle, we anticipate its frequent use in dynamically regulating metabolism for efficient proliferation. PMID:27203178

  5. Ion flux's pressure dependence in an asymmetric capacitively coupled rf discharge in NF3

    NASA Astrophysics Data System (ADS)

    Mateev, Emil; Zhelyazkov, Ivan

    2004-03-01

    Starting from an analytical macroscopic/phenomenological model yielding the self-bias voltage as a function of the absorbed radio-frequency (rf) power of an asymmetric capacitively coupled discharge in NF3 this paper studies the dependence of the ion flux onto the powered electrode on the gas pressure. An essential feature of the model is the assumption that the ions' drift velocity in the sheath near the powered electrode is proportional to E α, where E=-ΔU (U being the self-bias potential), and α is a coefficient depending on the gas pressure and cross section of elastic ion-neutral collisions. The model also considers the role of γ-electrons, stochastic heating as well as the contribution of the active electron current to the global discharge power balance. Numerically solving the model's basic equations one can extract the magnitude of the ion flux (at three different gas pressures) in a technological etching device (Alcatel GIR 220) by using easily measurable quantities, notably the self-bias voltage and absorbed rf power.

  6. Nonlinear thermoelectric response due to energy-dependent transport properties of a quantum dot

    NASA Astrophysics Data System (ADS)

    Svilans, Artis; Burke, Adam M.; Svensson, Sofia Fahlvik; Leijnse, Martin; Linke, Heiner

    2016-08-01

    Quantum dots are useful model systems for studying quantum thermoelectric behavior because of their highly energy-dependent electron transport properties, which are tunable by electrostatic gating. As a result of this strong energy dependence, the thermoelectric response of quantum dots is expected to be nonlinear with respect to an applied thermal bias. However, until now this effect has been challenging to observe because, first, it is experimentally difficult to apply a sufficiently large thermal bias at the nanoscale and, second, it is difficult to distinguish thermal bias effects from purely temperature-dependent effects due to overall heating of a device. Here we take advantage of a novel thermal biasing technique and demonstrate a nonlinear thermoelectric response in a quantum dot which is defined in a heterostructured semiconductor nanowire. We also show that a theoretical model based on the Master equations fully explains the observed nonlinear thermoelectric response given the energy-dependent transport properties of the quantum dot.

  7. Inter-element fractionation of highly siderophile elements in the Tonga Arc due to flux melting of a depleted source

    NASA Astrophysics Data System (ADS)

    Dale, Christopher W.; Macpherson, Colin G.; Pearson, D. Graham; Hammond, Samantha J.; Arculus, Richard J.

    2012-07-01

    Highly siderophile element concentrations (HSEs: Os, Ir, Ru, Pt, Pd, and Re) have been determined for a suite of fresh, submarine mafic lavas from the northern Tonga Arc front and the nascent backarc Fonualei Spreading Centre (FSC). Prior melt depletion of the Tongan mantle wedge combined with a high degree of fluid fluxed melting is thought to have produced boninitic magmas at several arc and FSC locations. As such, this arc system provides an opportunity to assess the fluid mobility of HSEs and to investigate the effects of fluid-induced melting and prior melt depletion on HSE behaviour during both mantle melting and magma evolution. Tongan lavas display extreme enrichment of Pt (2.5-32 ng/g) and Pd over Os (0.002-0.6 ng/g), Ir, and Ru, significantly greater than basalts from mid-ocean ridges. Magma evolution increases the degree of fractionation, resulting in the highest recorded Pt/Ru ratios (>300) in arc front samples with MgO <8 wt.%. This increasing fractionation is due to the mild incompatibility of Pt and Pd, and concurrent compatibility of Ru, during sulphide undersaturated magma evolution. However, the fractionation of Pt and Pd from Os, Ir, and Ru is observed in the highest MgO samples, indicating source inheritance. Prior melt depletion of the mantle and elevated oxygen fugacity both increase the likelihood of complete consumption of sulphide in the source during melting, which typically leads to melts with high concentrations of all the HSE. Indeed, modelling indicates that 25% aggregate partial melting of a depleted MORB-mantle source, proposed for the Tonga Arc, will lead to complete base-metal sulphide consumption unless there is considerable addition of S by the slab flux (at least 200 μg/g). Although source enrichment of Pt, Pd, and Re by slab fluids may take place, the fractionation of Pt and Pd from Os, Ir, and Ru can largely be explained by relatively low-temperature, yet high-degree, melting of fluid-fluxed melt-depleted mantle. The high Pt

  8. Seasonal to interannual depth-dependent changes in phosphorus flux in Cariaco Basin, Venezuela

    NASA Astrophysics Data System (ADS)

    Benitez-Nelson, C. R.; O'Neill, L.; Thunell, R.

    2004-12-01

    One of the major removal pathways of phosphorus (P) from the water column is through the formation, sinking, and burial of particles formed during marine biological production. Yet the flux of P containing particles to the seafloor remains one of the least studied components of the P cycle. In this study, particulate inorganic P (PIP) and particulate organic P (POP) fluxes were measured in a series of samples collected from sediment traps ranging in depth from 275 to 1255 m from November 1995 - November 2002 in Cariaco Basin, Venezuela. PIP concentrations averaged 40- 60 % (depending on depth) of the total particulate P (TPP) measured in the traps. PIP fluxes decreased by 75 % between the surface and deep waters, from a median of 28.6 to 6.3 \\mu mol m-2 d-1, whereas POP fluxes decreased by only 50 %, from 17.2 to 8.5 \\mu mol m-2 d-1. TPP, PIP and POP all vary seasonally and higher fluxes follow higher production during the upwelling season from late January to April. The relationship between particulate organic C (POC) and POP is relatively constant (POC:POP = 283) throughout the entire water column over the entire period (r2 = 0.58). However, there is a much tighter relationship between POP and POC in upwelling (January through April, r2 = 0.85) versus non upwelling (May through December, r2 = 0.40) seasons. Furthermore, upwelling, and hence higher production appears to be associated with higher POC:POP ratios (327 versus 258 in non upwelling periods). Higher than Redfield POC:POP ratios may indicate that preferential release of P containing organic matter is occurring, but if true, it is restricted to the upper 250 m of the water column above the shallowest sediment trap. An alternative explanation may be that the composition of plankton in the Cariaco Basin does not conform to the Redfield-ratio. Plankton tow samples collected over the upper 200 m with a > 200 um mesh had POC:POP ratios of 294 +/- 38. However, there is no other evidence that the euphotic zone

  9. An experimental measurement of metal multilayer x-ray reflectivity degradation due to intense x-ray flux

    SciTech Connect

    Hockaday, M.Y.P.

    1987-06-01

    The degradation of the x-ray reflection characteristics of metal multilayer Bragg diffractors due to intense x-ray flux was investigated. The Z-pinch plasma produced by PROTO II of Sandia National Laboratories, Albuquerque, New Mexico, was used as the source. The plasma generated total x-ray yields of as much as 40 kJ with up to 15 kJ in the neon hydrogen- and helium-like resonance lines in nominal 20-ns pulses. Molybdenum-carbon, palladium-carbon, and tungsten-carbon metal multilayers were placed at 15 and 150 cm from the plasma center. The multilayers were at nominal angles of 5/sup 0/ and 10/sup 0/ to diffract the neon resonance lines. The time-integrated x-ray reflection of the metal multilayers was monitored by x-ray film. A fluorescer-fiber optic-visible streak camera detector system was then used to monitor the time-resolved x-ray reflection characteristics of 135 A- 2d tungsten-carbon multilayers. A large specular component in the reflectivity prevented determination of the rocking curve of the multilayer. For a neon implosion onto a vanadium-doped polyacrylic acid foam target shot, detailed modeling was attempted. The spectral flux was determined with data from 5 XRD channels and deconvolved using the code SHAZAM. The observed decay in reflectivity was assumed to correspond to the melting of the first tungsten layer. A ''conduction factor'' of 82 was required to manipulate the heat loading of the first tungsten layer such that the time of melting corresponded to the observed decay. The power at destruction was 141 MW/cm/sup 2/ and the integrated energy at destruction was 2.0 J/cm/sup 2/. 82 refs., 66 figs., 10 tabs.

  10. Analytical Model for Estimating the Zenith Angle Dependence of Terrestrial Cosmic Ray Fluxes

    PubMed Central

    Sato, Tatsuhiko

    2016-01-01

    A new model called “PHITS-based Analytical Radiation Model in the Atmosphere (PARMA) version 4.0” was developed to facilitate instantaneous estimation of not only omnidirectional but also angular differential energy spectra of cosmic ray fluxes anywhere in Earth’s atmosphere at nearly any given time. It consists of its previous version, PARMA3.0, for calculating the omnidirectional fluxes and several mathematical functions proposed in this study for expressing their zenith-angle dependences. The numerical values of the parameters used in these functions were fitted to reproduce the results of the extensive air shower simulation performed by Particle and Heavy Ion Transport code System (PHITS). The angular distributions of ground-level muons at large zenith angles were specially determined by introducing an optional function developed on the basis of experimental data. The accuracy of PARMA4.0 was closely verified using multiple sets of experimental data obtained under various global conditions. This extension enlarges the model’s applicability to more areas of research, including design of cosmic-ray detectors, muon radiography, soil moisture monitoring, and cosmic-ray shielding calculation. PARMA4.0 is available freely and is easy to use, as implemented in the open-access EXcel-based Program for Calculating Atmospheric Cosmic-ray Spectrum (EXPACS). PMID:27490175

  11. Analytical Model for Estimating the Zenith Angle Dependence of Terrestrial Cosmic Ray Fluxes.

    PubMed

    Sato, Tatsuhiko

    2016-01-01

    A new model called "PHITS-based Analytical Radiation Model in the Atmosphere (PARMA) version 4.0" was developed to facilitate instantaneous estimation of not only omnidirectional but also angular differential energy spectra of cosmic ray fluxes anywhere in Earth's atmosphere at nearly any given time. It consists of its previous version, PARMA3.0, for calculating the omnidirectional fluxes and several mathematical functions proposed in this study for expressing their zenith-angle dependences. The numerical values of the parameters used in these functions were fitted to reproduce the results of the extensive air shower simulation performed by Particle and Heavy Ion Transport code System (PHITS). The angular distributions of ground-level muons at large zenith angles were specially determined by introducing an optional function developed on the basis of experimental data. The accuracy of PARMA4.0 was closely verified using multiple sets of experimental data obtained under various global conditions. This extension enlarges the model's applicability to more areas of research, including design of cosmic-ray detectors, muon radiography, soil moisture monitoring, and cosmic-ray shielding calculation. PARMA4.0 is available freely and is easy to use, as implemented in the open-access EXcel-based Program for Calculating Atmospheric Cosmic-ray Spectrum (EXPACS). PMID:27490175

  12. Scalings for unsteady natural convection boundary layers on an evenly heated plate with time-dependent heating flux

    NASA Astrophysics Data System (ADS)

    Lin, Wenxian; Armfield, S. W.

    2013-12-01

    It is of fundamental significance, especially with regard to application, to fully understand the flow behavior of unsteady natural convection boundary layers on a vertical plate heated by a time-dependent heat flux. Such an understanding is currently scarce. In this paper, the scaling analysis by Lin et al. [Phys. Rev. E 79, 066313 (2009), 10.1103/PhysRevE.79.066313] using a simple three-region structure for the unsteady natural convection boundary layer of a homogeneous Newtonian fluid with Pr >1 under isothermal heating was substantially extended for the case when the heating is due to a time-varying sinusoidal heat flux. A series of scalings was developed for the thermal boundary thickness, the plate temperature, the viscous boundary thicknesses, and the maximum vertical velocity within the boundary layer, which are the major parameters representing the flow behavior, in terms of the governing parameters of the flow, i.e., the Rayleigh number Ra, the Prandtl number Pr, and the dimensionless natural frequency fn of the time-varying sinusoidal heat flux, at the start-up stage, at the transition time scale which represents the ending of the start-up stage and the beginning of the transitional stage of the boundary-layer development, and at the quasi-steady stage. These scalings were validated by comparison to 10 full numerical solutions of the governing equations with Ra, Pr, and fn in the ranges 106≤Ra≤109, 3≤Pr≤100, and 0.01≤fn≤0.1 and were shown in general to provide an accurate description of the flow at different development stages, except for high-Pr runs in which a further, although weak, Pr dependence is present, which cannot be accurately predicted by the current scaling analysis using the simple three-region structure, attributed to the non-boundary-layer nature of the velocity field with high-Pr fluids. Some scalings at the transition time scale and at the quasi-steady stage also produce noticeable deviations from the numerical results when

  13. Latitudinal dependence of solar proton flux derived from interplanetary Lyman alpha emission

    NASA Astrophysics Data System (ADS)

    Nakagawa, H.; Fukunishi, H.; Watanabe, S.; Takahashi, Y.; Taguchi, M.; Bertaux, J.; Quemerais, E.; Lallement, R.

    2004-12-01

    There is a uniform flow of the interplanetary hydrogen in the solar system. The distribution of interplanetary neutral hydrogen is sensitive to solar wind proton flux, which has a latitudinal distribution, because interplanetary neutral hydrogen atoms are mainly ionized through a process of charge-exchange with solar wind protons (contributing to 80% of the total ionization rate). Rucinski et al. [1996] estimated the ionization rate of the interplanetary hydrogen in an average solar activity condition: 6.4±0.14 [10E-7/s] for charge exchange with protons. The most practical technique for determining the latitudinal dependence of the interplanetary hydrogen is observation of resonant backscatter of solar Lyman ƒ¿ emission at 121.6 nm. The interplanetary Lyman ƒ¿ emission has been measured by the ultraviolet imaging spectrometer (UVS) on board the Nozomi spacecraft crusing on its Mars transfer orbit with a periapsis of 1 AU and an apoapsis 1.5 AU from the Sun. The field-of-view of UVS is perpendicular to the spin axis of the spacecraft, which is controlled toward the Earth. The spatial resolution of UVS is 1.41 degrees in a plane perpendicular to the spin axis and 0.29 degrees in a plane including the spin axis. Spatial distributions are obtained from the full sky scanning of UVS with spin and orbital motions of the Nozomi spacecraft. One-year UVS data enable us to construct a full sky image of Lyman ƒ¿ emission. We present the results obtained from Nozomi/UVS data analysis for the period of 1999-2002. From a fitting of model calculations to the observed data, it is confirmed that a latitudinal anisotropy with the higher ionization region at the equator is reduced toward solar maximum. Finally, higher ionization region are found at the poles than at the equator near solar maximum. Basically, this change is produced by variations in the latitudinal dependence of persistent solar wind proton flux. However, proton flux from transient CMEs also affects the

  14. Characterization of time-dependent component reliability and availability effects due to aging

    NASA Astrophysics Data System (ADS)

    Hilsmeier, Todd Andrew

    The time-dependent effects of reliability and unavailability that occur due to the component first failure density and due to the maintenance policy are important since: (i) they may substantially deviate from static or average values, (ii) when these time-dependent effects are incorporated into a system, deviations can superimpose creating even greater deviations from static. Characterization of component reliability and unavailability effects due to aging is important for all engineering systems and has not been investigated. A general surveillance/repair policy including its constraints and limitations is defined. Potential dynamic variables under this surveillance/repair policy are identified, and a methodology for determining the most useful of these dynamic variables under this surveillance/repair policy are also developed. Under periodic surveillance and perfect detection/repair, expressions for time-dependent unavailability, failure frequency, and renewal frequency are developed from the general methodology. Under periodic surveillance, time-dependent failure frequency, w(t), unavailability, q(t), and probability of failure within test interval, Wsb{n}(T), are determined for Weibull and linear failure rates with aging threshold time, and normal failure density. These failure densities model component aging in nuclear power plants. The time-dependent variables are plotted and some important features that describe their time-dependent behavior (characteristics) are defined and determined directly from the plots. Using these characteristics, criteria are established to demonstrate the significance of dynamic modeling under periodic surveillance. It is observed that w(t) and q(t) may oscillate to values exceeding 5 times the static values during plant life. Also, dynamic periods may be on the order of years; therefore, dynamic modeling of q(t) and w(t) under periodic surveillance may be necessary. Under periodic surveillance, a simple non-recursive expression

  15. Uncertainties in wind speed dependent CO2 transfer velocities due to airflow distortion at anemometer sites on ships

    NASA Astrophysics Data System (ADS)

    Griessbaum, F.; Moat, B. I.; Narita, Y.; Yelland, M. J.; Klemm, O.; Uematsu, M.

    2009-09-01

    Data from research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterizations of the gas transfer velocity (k) and measurements of the difference between the concentration of CO2 in the ocean (pCO2sw) and atmosphere (pCO2atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error due to air flow distortion by the ship's hull and superstructure introducing biases into the measured wind speed. The effect of airflow distortion on estimates of the transfer velocity was examined by modelling the airflow around the three-dimensional geometries of the research vessels Hakuho Maru and Mirai, using the Large Eddy Simulation code GERRIS. For airflows within ±45° of the bow the maximum bias was +16%. For wind speed of 10 m s-1 to 15 m s-1, a +16% bias in wind speed would cause an overestimate in the calculated value of k of 30% to 50%, depending on which k parameterisation is used. This is due to the propagation of errors when using quadratic or cubic parameterizations. Recommendations for suitable anemometer locations on research vessels are given. The errors in transfer velocity may be much larger for typical merchant ships, as the anemometers are generally not as well-exposed as those on research vessels. Flow distortion may also introduce biases in the wind speed dependent k parameterizations themselves, since these are obtained by relating measurements of the CO2 flux to measurements of the wind speed and the CO2 concentration difference. To investigate this, flow distortion effects were estimated for three different platforms from which wind speed dependent parameterizations are published. The estimates ranged from -4% to +14% and showed that flow distortion may have a significant impact on wind speed dependent parameterizations. However, the wind biases are not large enough to explain the differences at high wind speeds in parameterizations which are based on eddy covariance and

  16. Uncertainties in wind speed dependent CO2 transfer velocities due to airflow distortion at anemometer sites on ships

    NASA Astrophysics Data System (ADS)

    Griessbaum, F.; Moat, B. I.; Narita, Y.; Yelland, M. J.; Klemm, O.; Uematsu, M.

    2010-06-01

    Data from platforms, research vessels and merchant ships are used to estimate ocean CO2 uptake via parameterisations of the gas transfer velocity (k) and measurements of the difference between the partial pressures of CO2 in the ocean (pCO2 sw) and atmosphere (pCO2 atm) and of wind speed. Gas transfer velocities estimated using wind speed dependent parameterisations may be in error due to air flow distortion by the ship's hull and superstructure introducing biases into the measured wind speed. The effect of airflow distortion on estimates of the transfer velocity was examined by modelling the airflow around the three-dimensional geometries of the research vessels Hakuho Maru and Mirai, using the Large Eddy Simulation code GERRIS. For airflows within ±45° of the bow the maximum bias was +16%. For wind speed of 10 m s-1 to 15 m s-1, a +16% bias in wind speed would cause an overestimate in the calculated value of k of 30% to 50%, depending on which k parameterisation is used. This is due to the propagation of errors when using quadratic or cubic parameterisations. Recommendations for suitable anemometer locations on research vessels are given. The errors in transfer velocity may be much larger for typical merchant ships, as the anemometers are generally not as well-exposed as those on research vessels. Flow distortion may also introduce biases in the wind speed dependent k parameterisations themselves, since these are obtained by relating measurements of the CO2 flux to measurements of the wind speed and the CO2 concentration difference. To investigate this, flow distortion effects were estimated for three different platforms from which wind speed dependent parameterisations are published. The estimates ranged from -4% to +14% and showed that flow distortion may have a significant impact on wind speed dependent parameterisations. However, the wind biases are not large enough to explain the differences at high wind speeds in parameterisations which are based on eddy

  17. LETM1-dependent mitochondrial Ca2+ flux modulates cellular bioenergetics and proliferation.

    PubMed

    Doonan, Patrick J; Chandramoorthy, Harish C; Hoffman, Nicholas E; Zhang, Xueqian; Cárdenas, César; Shanmughapriya, Santhanam; Rajan, Sudarsan; Vallem, Sandhya; Chen, Xiongwen; Foskett, J Kevin; Cheung, Joseph Y; Houser, Steven R; Madesh, Muniswamy

    2014-11-01

    Dysregulation of mitochondrial Ca(2+)-dependent bioenergetics has been implicated in various pathophysiological settings, including neurodegeneration and myocardial infarction. Although mitochondrial Ca(2+) transport has been characterized, and several molecules, including LETM1, have been identified, the functional role of LETM1-mediated Ca(2+) transport remains unresolved. This study examines LETM1-mediated mitochondrial Ca(2+) transport and bioenergetics in multiple cell types, including fibroblasts derived from patients with Wolf-Hirschhorn syndrome (WHS). The results show that both mitochondrial Ca(2+) influx and efflux rates are impaired in LETM1 knockdown, and similar phenotypes were observed in ΔEF hand, (D676A D688K)LETM1 mutant-overexpressed cells, and in cells derived from patients with WHS. Although LETM1 levels were lower in WHS-derived fibroblasts, the mitochondrial Ca(2+) uniporter components MCU, MCUR1, and MICU1 remain unaltered. In addition, the MCU mitoplast patch-clamp current (IMCU) was largely unaffected in LETM1-knockdown cells. Silencing of LETM1 also impaired basal mitochondrial oxygen consumption, possibly via complex IV inactivation and ATP production. Remarkably, LETM1 knockdown also resulted in increased reactive oxygen species production. Further, LETM1 silencing promoted AMPK activation, autophagy, and cell cycle arrest. Reconstitution of LETM1 or antioxidant overexpression rescued mitochondrial Ca(2+) transport and bioenergetics. These findings reveal the role of LETM1-dependent mitochondrial Ca(2+) flux in shaping cellular bioenergetics. PMID:25077561

  18. Beam test results of the dependence of signal size on incident particle flux in diamond pixel and pad detectors

    NASA Astrophysics Data System (ADS)

    Wallny, R.

    2015-07-01

    We present results of beam tests of charged particle detectors based on single-crystal and poly-crystalline Chemical Vapor Deposition (CVD) diamond. We measured the signal pulse height dependence on the particle flux. The detectors were tested over a range of particle fluxes from 2 kHz/cm2 to 20 MHz/cm2. The pulse height of the sensors was measured with pad and pixel readout electronics. The pulse height of the non-irradiated single-crystal CVD diamond pad sensors was stable with respect to flux, while the pulse height of irradiated single-crystal CVD diamond pad sensors decreased with increasing particle flux. The pulse height of the non-irradiated single-crystal CVD diamond pixel detectors decreased slightly with increasing particle flux while the pulse height of the irradiated single-crystal CVD diamond pixel detectors decreased significantly with increasing particle flux. The observed sensitivity to flux is similar in both the diamond pad sensors constructed using diamonds from the Pixel Luminosity Telescope (PLT) irradiated during its pilot run in the Compact Muon Solenoid (CMS) detector and in neutron irradiated diamond pad sensors from the same manufacturer irradiated to the same fluence of neutrons. The pulse height for irradiated poly-crystalline CVD diamond pad sensors proved to be stable with respect to particle flux.

  19. Isotopically nonstationary 13C flux analysis of changes in Arabidopsis thaliana leaf metabolism due to high light acclimation.

    PubMed

    Ma, Fangfang; Jazmin, Lara J; Young, Jamey D; Allen, Doug K

    2014-11-25

    Improving plant productivity is an important aim for metabolic engineering. There are few comprehensive methods that quantitatively describe leaf metabolism, although such information would be valuable for increasing photosynthetic capacity, enhancing biomass production, and rerouting carbon flux toward desirable end products. Isotopically nonstationary metabolic flux analysis (INST-MFA) has been previously applied to map carbon fluxes in photoautotrophic bacteria, which involves model-based regression of transient (13)C-labeling patterns of intracellular metabolites. However, experimental and computational difficulties have hindered its application to terrestrial plant systems. We performed in vivo isotopic labeling of Arabidopsis thaliana rosettes with (13)CO2 and estimated fluxes throughout leaf photosynthetic metabolism by INST-MFA. Plants grown at 200 µmol m(-2)s(-1) light were compared with plants acclimated for 9 d at an irradiance of 500 µmol⋅m(-2)⋅s(-1). Approximately 1,400 independent mass isotopomer measurements obtained from analysis of 37 metabolite fragment ions were regressed to estimate 136 total fluxes (54 free fluxes) under each condition. The results provide a comprehensive description of changes in carbon partitioning and overall photosynthetic flux after long-term developmental acclimation of leaves to high light. Despite a doubling in the carboxylation rate, the photorespiratory flux increased from 17 to 28% of net CO2 assimilation with high-light acclimation (Vc/Vo: 3.5:1 vs. 2.3:1, respectively). This study highlights the potential of (13)C INST-MFA to describe emergent flux phenotypes that respond to environmental conditions or plant physiology and cannot be obtained by other complementary approaches. PMID:25368168

  20. Methane fluxes show consistent temperature dependence across microbial to ecosystem scales.

    PubMed

    Yvon-Durocher, Gabriel; Allen, Andrew P; Bastviken, David; Conrad, Ralf; Gudasz, Cristian; St-Pierre, Annick; Thanh-Duc, Nguyen; del Giorgio, Paul A

    2014-03-27

    Methane (CH4) is an important greenhouse gas because it has 25 times the global warming potential of carbon dioxide (CO2) by mass over a century. Recent calculations suggest that atmospheric CH4 emissions have been responsible for approximately 20% of Earth's warming since pre-industrial times. Understanding how CH4 emissions from ecosystems will respond to expected increases in global temperature is therefore fundamental to predicting whether the carbon cycle will mitigate or accelerate climate change. Methanogenesis is the terminal step in the remineralization of organic matter and is carried out by strictly anaerobic Archaea. Like most other forms of metabolism, methanogenesis is temperature-dependent. However, it is not yet known how this physiological response combines with other biotic processes (for example, methanotrophy, substrate supply, microbial community composition) and abiotic processes (for example, water-table depth) to determine the temperature dependence of ecosystem-level CH4 emissions. It is also not known whether CH4 emissions at the ecosystem level have a fundamentally different temperature dependence than other key fluxes in the carbon cycle, such as photosynthesis and respiration. Here we use meta-analyses to show that seasonal variations in CH4 emissions from a wide range of ecosystems exhibit an average temperature dependence similar to that of CH4 production derived from pure cultures of methanogens and anaerobic microbial communities. This average temperature dependence (0.96 electron volts (eV)), which corresponds to a 57-fold increase between 0 and 30°C, is considerably higher than previously observed for respiration (approximately 0.65 eV) and photosynthesis (approximately 0.3 eV). As a result, we show that both the emission of CH4 and the ratio of CH4 to CO2 emissions increase markedly with seasonal increases in temperature. Our findings suggest that global warming may have a large impact on the relative contributions of CO2 and CH

  1. Energy dependent time delays of kHz oscillations due to thermal Comptonization

    NASA Astrophysics Data System (ADS)

    Kumar, Nagendra; Misra, Ranjeev

    2014-12-01

    We study the energy dependent photon variability from a thermal Comptonizing plasma that is oscillating at kHz frequencies. In particular, we solve the linearized time-dependent Kompaneets equation and consider the oscillatory perturbation to be either in the soft photon source or in the heating rate of the plasma. For each case, we self consistently consider the energy balance of the plasma and the soft photon source. The model incorporates the possibility of a fraction of the Comptonized photons impinging back into the soft photon source. We find that when the oscillation is due to the soft photon source, the variation of the fractional root mean sqaure (rms) is nearly constant with energy and the time-lags are hard. However, for the case when the oscillation is due to variation in the heating rate of the corona, and when a significant fraction of the photons impinge back into the soft photon source, the rms increases with energy and the time-lags are soft. As an example, we compare the results with the ˜850 Hz oscillation observed on 1996 March 3 for 4U 1608-52 and show that both the observed soft time-lags as well as the rms versus energy can be well described by such a model where the size of the Comptonizing plasma is ˜1 km. Thus, modelling of the time-lags as due to Comptonization delays, can provide tight constraints on the size and geometry of the system. Detailed analysis would require well-constrained spectral parameters.

  2. Food-dependent exercise-induced anaphylaxis due to wheat in a young woman.

    PubMed

    Ahanchian, Hamid; Farid, Reza; Ansari, Elham; Kianifar, Hamid Reza; Jabbari Azad, Farahzad; Jafari, Seyed Ali; Purreza, Reza; Noorizadeh, Shadi

    2013-03-01

    Food Dependent Exercise-Induced Allergy is a rare condition. However, the occurrence of anaphylaxis is increasing especially in young people. The diagnosis of anaphylaxis is based on clinical criteria and can be supported by laboratory tests such as serum tryptase and positive skin test results for specific IgE to potential triggering allergens. Anaphylaxis prevention needs strict avoidance of confirmed relevant allergen. Food-exercise challenge test may be an acceptable method for diagnosis of Food Dependent Exercise-Induced Allergy and dietary elimination of food is recommended to manage it. In this study, a 32 year-old woman visited the allergy clinic with a history of several episodes of hives since 11 years ago and 3 life-threatening attacks of anaphylaxis during the previous 6 months. The onsets of majority of these attacks were due to physical activity after breakfast. On Blood RAST test, the panel of common food Allergens was used and she had positive test only to wheat flour. On skin prick tests for common food allergens she showed a 6 millimeter wheal with 14 mm flare to Wheat Extract. The rest of allergens were negative.The patient was diagnosed as wheat-dependent exercise-induced, and all foods containing wheat were omitted from her diet. In this report we emphasized on the importance of careful history taking in anaphylaxis diagnosis. PMID:23454785

  3. Breaks of dose dependence of transient creep as result of competing influence of defects’ fluxes on climb of dislocations

    NASA Astrophysics Data System (ADS)

    Selyshchev, P.

    2015-04-01

    In the framework of climb-glide model a theoretical approach is developed to describe transient creep under irradiation. It is obtained the explicit expression for creep rate which describes experimentally observed breaks of dose dependence of creep. It is shown that the breaks arise as result of competition of radiation and thermal fluxes of defects to dislocation. When interstitial and vacancy fluxes become equal, the dislocation cannot overcome the obstacle via climbing and cannot continue glide. Climb-glide mechanism does not contribute to the creep. The creep rate drops. Numbers of breaks depend on initial state of material and conditions of irradiation. Dose (time) of break appearance are obtained.

  4. Multispecies Density and Temperature Gradient Dependence of Quasilinear Particle and Energy Fluxes

    SciTech Connect

    G. Rewoldt; R.V. Budny; W.M. Tang

    2004-08-09

    The variations of the normalized quasilinear particle and energy fluxes with artificial changes in the density and temperature gradients, as well as the variations of the linear growth rates and real frequencies, for ion temperature gradient and trapped-electron modes, are calculated. The quasilinear fluxes are normalized to the total energy flux, summed over all species. Here, realistic cases for tokamaks and spherical torii are considered which have two impurity species. For situations where there are substantial changes in the normalized fluxes, the ''diffusive approximation,'' in which the normalized fluxes are taken to be linear in the gradients, is seen to be inaccurate. Even in the case of small artificial changes in density or temperature gradients, changes in the fluxes of different species (''off-diagonal'') generally are significant, or even dominant, compared to those for the same species (''diagonal'').

  5. PLANETESIMAL FORMATION IN MAGNETOROTATIONALLY DEAD ZONES: CRITICAL DEPENDENCE ON THE NET VERTICAL MAGNETIC FLUX

    SciTech Connect

    Okuzumi, Satoshi; Hirose, Shigenobu

    2012-07-01

    Turbulence driven by magnetorotational instability (MRI) affects planetesimal formation by inducing diffusion and collisional fragmentation of dust particles. We examine conditions preferred for planetesimal formation in MRI-inactive 'dead zones' using an analytic dead-zone model based on our recent resistive MHD simulations. We argue that successful planetesimal formation requires not only a sufficiently large dead zone (which can be produced by tiny dust grains) but also a sufficiently small net vertical magnetic flux (NVF). Although often ignored, the latter condition is indeed important since the NVF strength determines the saturation level of turbulence in MRI-active layers. We show that direct collisional formation of icy planetesimal across the fragmentation barrier is possible when the NVF strength is lower than 10 mG (for the minimum-mass solar nebula model). Formation of rocky planetesimals via the secular gravitational instability is also possible within a similar range of the NVF strength. Our results indicate that the fate of planet formation largely depends on how the NVF is radially transported in the initial disk formation and subsequent disk accretion processes.

  6. Water and Carbon Fluxes in a Semi-Arid Region Floodplain: Multiple Approaches to Constrain Estimates of Seasonal- and Depth Dependent Fluxes at Rifle, Colorado

    NASA Astrophysics Data System (ADS)

    Tokunaga, T. K.; Wan, J.; Dong, W.; Kim, Y.; Williams, K. H.; Conrad, M. E.; Christensen, J. N.; Bill, M.; Faybishenko, B.; Hobson, C.; Dayvault, R.; Long, P. E.; Hubbard, S. S.

    2014-12-01

    at the soil surface are consistent with estimates based on season- and temperature-dependent diffusion and respiration within the vadose zone. Thus, fairly predictable seasonal variations in water table elevation, evapotranspiration, and temperature can help constrain estimates of water and carbon fluxes.

  7. Quantitative analysis of some mechanisms affecting the yield of oxidative phosphorylation: dependence upon both fluxes and forces.

    PubMed

    Rigoulet, M; Leverve, X; Fontaine, E; Ouhabi, R; Guérin, B

    1998-07-01

    The purpose of this work was to show how the quantitative definition of the different parameters involved in mitochondrial oxidative phosphorylation makes it possible to characterize the mechanisms by which the yield of ATP synthesis is affected. Three different factors have to be considered: (i) the size of the different forces involved (free energy of redox reactions and ATP synthesis, proton electrochemical difference); (ii) the physical properties of the inner mitochondrial membrane in terms of leaks (H+ and cations); and finally (iii) the properties of the different proton pumps involved in this system (kinetic properties, regulation, modification of intrinsic stoichiometry). The data presented different situations where one or more of these parameters are affected, leading to a different yield of oxidative phosphorylation. (1) By manipulating the actual flux through each of the respiratory chain units at constant protonmotive force in yeast mitochondria, we show that the ATP/O ratio decreases when the flux increases. Moreover, the highest efficiency was obtained when the respiratory rate was low and almost entirely controlled by the electron supply. (2) By using almitrine in different kinds of mitochondria, we show that this drug leads to a decrease in ATP synthesis efficiency by increasing the H+/ATP stoichiometry ofATP synthase (Rigoulet M et al. Biochim Biophys Acta 1018: 91-97, 1990). Since this enzyme is reversible, it was possible to test the effect of this drug on the reverse reaction of the enzyme i.e. extrusion of protons catalyzed by ATP hydrolysis. Hence, we are able to prove that, in this case, the decrease in efficiency of oxidative phosphorylation is due to a change in the mechanistic stoichiometry of this proton pump. To our knowledge, this is the first example of a modification in oxidative phosphorylation yield by a change in mechanistic stoichiometry of one of the proton pumps involved. (3) In a model of polyunsaturated fatty acid deficiency

  8. Pharmacological and genetic reversal of age dependent cognitive deficits due to decreased presenilin function

    PubMed Central

    McBride, Sean M. J.; Choi, Catherine H.; Schoenfeld, Brian P.; Bell, Aaron J.; Liebelt, David A.; Ferreiro, David; Choi, Richard J.; Hinchey, Paul; Kollaros, Maria; Terlizzi, Allison M.; Ferrick, Neal J.; Koenigsberg, Eric; Rudominer, Rebecca L.; Sumida, Ai; Chiorean, Stephanie; Siwicki, Kathleen K.; Nguyen, Hanh T.; Fortini, Mark E.; McDonald, Thomas V.; Jongens, Thomas A.

    2010-01-01

    Alzheimer's disease is the leading cause of cognitive loss and neurodegeneration in the developed world. Although its genetic and environmental causes are not generally known, familial forms of the disease (FAD) are due to mutations in a single copy of the Presenilin (PS) and Amyloid Precursor Protein (APP) genes. The dominant inheritance pattern of FAD indicates that it may be due to gain or change of function mutations. Studies of FAD-linked forms of presenilin in model organisms, however, indicate that they are loss of function, leading to the possibility that a reduction in PS activity might contribute to FAD and that proper psn levels are important for maintaining normal cognition throughout life. To explore this issue further, we have tested the effect of reducing psn activity during aging in Drosophila melanogaster males. We have found that flies in which the dosage of psn function is reduced by 50% display age-onset impairments in learning and memory. Treatment with metabotropic glutamate receptor (mGluR) antagonists or lithium during the aging process prevented the onset of these deficits, and treatment of aged flies reversed the age-dependent deficits. Genetic reduction of DmGluRA, the inositol trisphosphate receptor (InsP3R) or IPPase also prevented these age-onset cognitive deficits. These findings suggest that reduced psn activity may contribute to the age onset cognitive loss observed with FAD. They also indicate that enhanced mGluR signaling and calcium release regulated by InsP3R as underlying causes of the age-dependent cognitive phenotypes observed when psn activity is reduced. PMID:20631179

  9. Convective radial energy flux due to resonant magnetic perturbations and magnetic curvature at the tokamak plasma edge

    SciTech Connect

    Marcus, F. A.; Beyer, P.; Fuhr, G.; Monnier, A.; Benkadda, S.

    2014-08-15

    With the resonant magnetic perturbations (RMPs) consolidating as an important tool to control the transport barrier relaxation, the mechanism on how they work is still a subject to be clearly understood. In this work, we investigate the equilibrium states in the presence of RMPs for a reduced MHD model using 3D electromagnetic fluid numerical code with a single harmonic RMP (single magnetic island chain) and multiple harmonics RMPs in cylindrical and toroidal geometry. Two different equilibrium states were found in the presence of the RMPs with different characteristics for each of the geometries used. For the cylindrical geometry in the presence of a single RMP, the equilibrium state is characterized by a strong convective radial thermal flux and the generation of a mean poloidal velocity shear. In contrast, for toroidal geometry, the thermal flux is dominated by the magnetic flutter. For multiple RMPs, the high amplitude of the convective flux and poloidal rotation are basically the same in cylindrical geometry, but in toroidal geometry the convective thermal flux and the poloidal rotation appear only with the islands overlapping of the linear coupling between neighbouring poloidal wavenumbers m, m – 1, and m + 1.

  10. The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization

    NASA Astrophysics Data System (ADS)

    Sakamoto, Kimiko M.; Laing, James R.; Stevens, Robin G.; Jaffe, Daniel A.; Pierce, Jeffrey R.

    2016-06-01

    Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA) evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, accurately accounting for biomass-burning aerosol size in global models requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emission-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations and yields R2 values of 0.83 and 0.89 for Dpm and modal width, respectively. The

  11. Geoid Height Time Dependence Due to Global Glacial Isostatic Adjustment: The Critical Influence of Rotational Feedback

    NASA Astrophysics Data System (ADS)

    Peltier, W.

    2006-05-01

    It has recently been suggested in Mitrovica, Wahr et al.(2005. Geophys. J. Int. 161, 491-506) that the theory previously developed to predict the Earth's rotational response to the Late Quaternary glaciation-deglaciation cycle may require modification. This theory was initially described in Peltier (1982, Advances in Geophysics 24, 1-146) and in Wu and Peltier (1984, Geophys. J. R. astr. Soc. 76, 202-242). Its importance for understanding the GIA contribution to the modern rate of geoid height time dependence that is currently being measured by the GRACE satellite system lies in the fact that the polar wander induced by the ice-age cycle contributes to this field in an important way. It has proven possible to test the quality of the original form of the theory in a definitive way by employing Holocene inferences of relative sea level history based upon radio- carbon dated sea level index points. This test relies upon data from a wide range of sites on the Earth's surface, sites located in regions that are expcted to be most strongly influenced by the feedback of the polar wander component of the Earth's rotatonal response to the glaciation cycle onto sea level history itself. Application of the test demonstrates that the claims made in the Mitrovica, Wahr et al. paper concerning the existence of a flaw in the theory are incorrect. The previously published ICE-5G(VM2)prediction of the expected geoid height time dependence due to the GIA process is therefor secure (see Peltier, 2005. QSR 24, 1655- 1671).

  12. Solar flux-density distribution due to partially shaded/blocked mirrors using the separation of variables/superposition technique with polynomial and Gaussian sunshapes

    SciTech Connect

    Elsayed, M.; Fathalah, K.A.

    1996-05-01

    In a previous work, the separation of a variable/superposition technique was used to predict the flux density distribution on the receiver surfaces of solar central receiver plants. In this paper further developments of the technique are given. A numerical technique is derived to carry out the convolution of the sunshape and error density functions. Also, a simplified numerical procedure is presented to determine the basic flux density function on which the technique depends. The technique is used to predict the receiver solar flux distribution using two sunshapes, polynomial and Gaussian distributions. The results predicted with the technique are validated by comparison with experimental results from mirrors both with and without partial shading/blocking of their surfaces.

  13. ENERGY INJECTION VIA FLUX EMERGENCE ON THE SUN DEPENDING ON THE GEOMETRIC SHAPE OF MAGNETIC FIELD

    SciTech Connect

    Magara, T.

    2011-04-20

    Flux emergence is a complicated process involving flow and magnetic field, which provides a way of injecting magnetic energy into the solar atmosphere. We show that energy injection via this complicated process is characterized by a physical quantity called the emergence velocity, which is determined by the spatial relationship between the flow velocity and magnetic field vectors. By using this quantity, we demonstrate that the geometric shape of magnetic field might play an important role in the energy injection via flux emergence.

  14. Dynamic superconcentration at critical-point double-layer gates of conducting nanoporous granules due to asymmetric tangential fluxes

    PubMed Central

    Wang, Shau-Chun; Wei, Hsien-Hung; Chen, Hsiao-Ping; Tsai, Min-Hsuan; Yu, Chun-Ching; Chang, Hsueh-Chia

    2008-01-01

    A transient 106-fold concentration of double-layer counterions by a high-intensity electric field is demonstrated at the exit pole of a millimeter-sized conducting nanoporous granule that permits ion permeation. The phenomenon is attributed to a unique counterion screening dynamics that transforms half of the surface field into a converging one toward the ejecting pole. The resulting surface conduction flux then funnels a large upstream electro-osmotic convective counterion flux into the injecting hemisphere toward the zero-dimensional gate of the ejecting hemisphere to produce the superconcentration. As the concentrated counterion is ejected into the electroneutral bulk electrolyte, it attracts co-ions and produce a corresponding concentration of the co-ions. This mechanism is also shown to trap and concentrate co-ion microcolloids of micron sizes too (macroions) and hence has potential application in bead-based molecular assays. PMID:19693364

  15. Temperature dependence of bromine activation due to reaction with ozone in a proxy for organic aerosols

    NASA Astrophysics Data System (ADS)

    Edebeli, Jacinta; Ammann, Markus; Gilgen, Anina; Eichler, Anja; Schneebeli, Martin; Bartels-Rausch, Thorsten

    2016-04-01

    The discovery of boundary layer ozone depletion events in the Polar Regions [1] and in the mid-latitudes [2], two areas of very different temperature regimes, begs the question of temperature dependence of reactions responsible for these observations [3]. These ODEs have been attributed to ozone reacting with halides leading to reactive halogens (halogen activation) of which bromide is extensively studied, R1 - R3 [4, 5] (R1 is a multiphase reaction). O3 + Br‑→ O2 + OBr‑ (R1) OBr‑ + H+ ↔ HOBr (R2) HOBr + H+ + Br‑→ Br2 + H2O (R3) Despite extensive studies of ozone-bromide interactions, the temperature dependence of bromine activation is not clear [3]. This limits parameterization of the involved reactions and factors in atmospheric models [3, 6]. Viscosity changes in the matrix (such as organic aerosols) due to temperature have been shown to influence heterogeneous reaction rates and products beyond pure temperature effect [7]. With the application of coated wall flow-tubes, the aim of this study is therefore to investigate the temperature dependence of bromine activation by ozone interaction while attempting to characterize the contributions of the bulk and surface reactions to observed ozone uptake. Citric acid is used in this study as a hygroscopically characterized matrix whose viscosity changes with temperature and humidity. Here, we present reactive ozone uptake measured between 258 and 289 K. The data show high reproducibility. Comparison of measured uptake with modelled bulk uptake at different matrix compositions (and viscosities) indicate that bulk reactive uptake dominates, but there are other factors which still need further consideration in the model. References 1. Barrie, L.A., et al., Nature, 1988. 334: p. 138 - 141. 2. Hebestreit, K., et al., Science, 1999. 283: p. 55-57. 3. Simpson, W.R., et al., Atmospheric Chemistry and Physics, 2007. 7: p. 4375 - 4418. 4. Haag, R.W. and J. Hoigné, Environ Sci Technol, 1983. 17: p. 261-267. 5. Oum

  16. Verification and validation of the maximum entropy method of moment reconstruction of energy dependent neutron flux

    NASA Astrophysics Data System (ADS)

    Crawford, Douglas Spencer

    Verification and Validation of reconstructed neutron flux based on the maximum entropy method, is presented in this paper. The verification is carried out by comparing the neutron flux spectrum from the maximum entropy method with Monte Carlo N Particle 5 version 1.40 (MCNP5) and Attila-7.1.0-beta (Attila). A spherical 100% 235U critical assembly is modeled as the test case to compare the three methods. The verification error range for the maximum entropy method is 15% to 23% where MCNP5 is taken to be the comparison standard. Attila relative error for the critical assembly is 20% to 35%. Validation is accomplished by comparing a neutron flux spectrum that is back calculated from foil activation measurements performed in the GODIVA experiment (GODIVA). The error range of the reconstructed flux compared to GODIVA is 0%-10%. The error range of the neutron flux spectrum from MCNP5 compared to GODIVA is 0%-20% and the Attila error range compared to the GODIVA is 0%-35%. The maximum entropy method for reconstructing flux is shown to be a fast reliable method, compared to either Monte Carlo methods (MCNP5) or 30 multienergy group methods (Attila) and with respect to the GODIVA experiment.

  17. Measurement of Heat Flux and Heat Transfer Coefficient Due to Spray Application for the Die Casting Process

    SciTech Connect

    Sabau, Adrian S

    2007-01-01

    Lubricant spray application experiments were conducted for the die casting process. The heat flux was measured in situ using a differential thermopile sensor for three application techniques. First, the lubricant was applied under a constant flowrate while the nozzle was held in the same position. Second, the lubricant was applied in a pulsed, static manner, in which the nozzle was held over the same surface while it was turned on and off several times. Third, the lubricant was applied in a sweeping manner, in which the nozzle was moved along the die surface while it was held open. The experiments were conducted at several die temperatures and at sweep speeds of 20, 23, and 68 cm/s. The heat flux data, which were obtained with a sensor that was located in the centre of the test plate, were presented and discussed. The sensor can be used to evaluate lubricants, monitor the consistency of die lubrication process, and obtain useful process data, such as surface temperature, heat flux, and heat transfer coefficients. The heat removed from the die surface during lubricant application is necessary for (a) designing the cooling channels in the die, i.e. their size and placement, and (b) performing accurate numerical simulations of the die casting process.

  18. The Energy-Dependent Position of the IBEX Ribbon Due to the Solar Wind Structure

    NASA Astrophysics Data System (ADS)

    Swaczyna, Paweł; Bzowski, Maciej; Sokół, Justyna M.

    2016-08-01

    Observations of energetic neutral atoms (ENAs) allow for remote studies of the condition of plasma in the heliosphere and the neighboring local interstellar medium. The first results from the Interstellar Boundary Explorer (IBEX) revealed an arc-like enhancement of the ENA intensity in the sky, known as the ribbon. The ribbon was not expected from the heliospheric models prior to the launch of IBEX. One proposed explanation for the ribbon is the mechanism of secondary ENA emission. The ribbon reveals energy-dependent structure in the relative intensity along its circumference and in its position. That is, the geometric center of the ribbon varies systematically by about 10° in the energy range 0.7–4.3 keV. Here, we show by analytical modeling that this effect is a consequence of the helio-latitudinal structure of the solar wind reflected in the secondary ENAs. Along with a recently measured distance to the ribbon’s source just beyond the heliopause, our findings support the connection of the ribbon with the local interstellar magnetic field by the mechanism of secondary ENA emission. However, the magnitude of the center shift in the highest IBEX energy channel is much larger in the observations than expected from the modeling. This may be due to another, not currently recognized, process of ENA generation.

  19. Alteration of the oxygen-dependent reactivity of de novo Due Ferri proteins.

    PubMed

    Reig, Amanda J; Pires, Marcos M; Snyder, Rae Ana; Wu, Yibing; Jo, Hyunil; Kulp, Daniel W; Butch, Susan E; Calhoun, Jennifer R; Szyperski, Thomas; Szyperski, Thomas G; Solomon, Edward I; DeGrado, William F

    2012-11-01

    De novo proteins provide a unique opportunity to investigate the structure-function relationships of metalloproteins in a minimal, well-defined and controlled scaffold. Here, we describe the rational programming of function in a de novo designed di-iron carboxylate protein from the Due Ferri family. Originally created to catalyse the O(2)-dependent, two-electron oxidation of hydroquinones, the protein was reprogrammed to catalyse the selective N-hydroxylation of arylamines by remodelling the substrate access cavity and introducing a critical third His ligand to the metal-binding cavity. Additional second- and third-shell modifications were required to stabilize the His ligand in the core of the protein. These structural changes resulted in at least a 10(6)-fold increase in the relative rate between the arylamine N-hydroxylation and hydroquinone oxidation reactions. This result highlights the potential for using de novo proteins as scaffolds for future investigations of the geometric and electronic factors that influence the catalytic tuning of di-iron active sites. PMID:23089864

  20. Uncertainties in Eddy Covariance fluxes due to post-field data processing: a multi-site, full factorial analysis

    NASA Astrophysics Data System (ADS)

    Sabbatini, S.; Fratini, G.; Arriga, N.; Papale, D.

    2012-04-01

    Eddy Covariance (EC) is the only technologically available direct method to measure carbon and energy fluxes between ecosystems and atmosphere. However, uncertainties related to this method have not been exhaustively assessed yet, including those deriving from post-field data processing. The latter arise because there is no exact processing sequence established for any given situation, and the sequence itself is long and complex, with many processing steps and options available. However, the consistency and inter-comparability of flux estimates may be largely affected by the adoption of different processing sequences. The goal of our work is to quantify the uncertainty introduced in each processing step by the fact that different options are available, and to study how the overall uncertainty propagates throughout the processing sequence. We propose an easy-to-use methodology to assign a confidence level to the calculated fluxes of energy and mass, based on the adopted processing sequence, and on available information such as the EC system type (e.g. open vs. closed path), the climate and the ecosystem type. The proposed methodology synthesizes the results of a massive full-factorial experiment. We use one year of raw data from 15 European flux stations and process them so as to cover all possible combinations of the available options across a selection of the most relevant processing steps. The 15 sites have been selected to be representative of different ecosystems (forests, croplands and grasslands), climates (mediterranean, nordic, arid and humid) and instrumental setup (e.g. open vs. closed path). The software used for this analysis is EddyPro™ 3.0 (www.licor.com/eddypro). The critical processing steps, selected on the basis of the different options commonly used in the FLUXNET community, are: angle of attack correction; coordinate rotation; trend removal; time lag compensation; low- and high- frequency spectral correction; correction for air density

  1. Skyshine analysis using energy and angular dependent dose-contribution fluxes obtained from air-over-ground adjoint calculation.

    PubMed

    Uematsu, Mikio; Kurosawa, Masahiko

    2005-01-01

    A generalised and convenient skyshine dose analysis method has been developed based on forward-adjoint folding technique. In the method, the air penetration data were prepared by performing an adjoint DOT3.5 calculation with cylindrical air-over-ground geometry having an adjoint point source (importance of unit flux to dose rate at detection point) in the centre. The accuracy of the present method was certified by comparing with DOT3.5 forward calculation. The adjoint flux data can be used as generalised radiation skyshine data for all sorts of nuclear facilities. Moreover, the present method supplies plenty of energy-angular dependent contribution flux data, which will be useful for detailed shielding design of facilities. PMID:16604693

  2. Model-dependent high-energy neutrino flux from gamma-ray bursts.

    PubMed

    Zhang, Bing; Kumar, Pawan

    2013-03-22

    The IceCube Collaboration recently reported a stringent upper limit on the high energy neutrino flux from gamma-ray bursts (GRBs), which provides a meaningful constraint on the standard internal shock model. Recent broadband electromagnetic observations of GRBs also challenge the internal shock paradigm for GRBs, and some competing models for γ-ray prompt emission have been proposed. We describe a general scheme for calculating the GRB neutrino flux, and compare the predicted neutrino flux levels for different models. We point out that the current neutrino flux upper limit starts to constrain the standard internal shock model. The dissipative photosphere models are also challenged if the cosmic ray luminosity from GRBs is at least 10 times larger than the γ-ray luminosity. If the neutrino flux upper limit continues to go down in the next few years, then it would suggest the following possibilities: (i) the photon-to-proton luminosity ratio in GRBs is anomalously high for shocks, which may be achieved in some dissipative photosphere models and magnetic dissipation models; or (ii) the GRB emission site is at a larger radius than the internal shock radius, as expected in some magnetic dissipation models such as the internal collision-induced magnetic reconnection and turbulence model. PMID:25166786

  3. Mechanisms controlling the SST air-sea heat flux feedback and its dependence on spatial scale

    NASA Astrophysics Data System (ADS)

    Hausmann, Ute; Czaja, Arnaud; Marshall, John

    2016-05-01

    The turbulent air-sea heat flux feedback (α , in {W m}^{-2}{ K}^{-1} ) is a major contributor to setting the damping timescale of sea surface temperature (SST) anomalies. In this study we compare the spatial distribution and magnitude of α in the North Atlantic and the Southern Ocean, as estimated from the ERA-Interim reanalysis dataset. The comparison is rationalized in terms of an upper bound on the heat flux feedback, associated with "fast" atmospheric export of temperature and moisture anomalies away from the marine boundary layer, and a lower bound associated with "slow" export. It is found that regions of cold surface waters (≤ 10° C) are best described as approaching the slow export limit. This conclusion is not only valid at the synoptic scale resolved by the reanalysis data, but also on basin scales. In particular, it applies to the heat flux feedback acting as circumpolar SST anomaly scales are approached in the Southern Ocean, with feedbacks of ≤ 10 {W m}^{-2}{ K}^{-1} . In contrast, the magnitude of the heat flux feedback is close to that expected from the fast export limit over the Gulf Stream and its recirculation with values on the order of ≈40 {W m}^{-2}{ K}^{-1} . Further analysis suggests that this high value reflects a compensation between a moderate thermodynamic adjustment of the boundary layer, which tends to weaken the heat flux feedback, and an enhancement of the surface winds over warm SST anomalies, which tend to enhance the feedback.

  4. Relationships between cosmic ray neutron flux and rain flows in dependence on different latitudes and altitudes

    NASA Astrophysics Data System (ADS)

    Velinov, Peter; Velinov, Peter; Belov, Anatolii; Yanke, Viktor; Eroshenko, Evgenia; Mishev, Alexander; Tassev, Yordan

    A convenient tool for investigation of primary cosmic ray variations is the registration of secondary cosmic ray neutrons. A network of neutron monitors, aiming the studies of cosmic ray variations exists. At the same time cosmic ray variations may be related to some atmospheric processes. In this connection, using the data from Moskow neutron monitor (latitude 55 degree) and lead free neutron monitor at BEO Moussala (latitude 42 degree and latitude 2971 m above see level), we studied the correlations between rain flows and neutron flux. In this study we used daily averages on the basis of 10 min data for the neutron flux, corrected for barometric pressure and data for local meteo-stations. The measured data permitted to study such effect at different observation levels and latitudes. The preliminary studies permits to observe correlation between rain flows and neutron flux in several cases.

  5. Effect of high-flux H/He plasma exposure on tungsten damage due to transient heat loads

    NASA Astrophysics Data System (ADS)

    De Temmerman, G.; Morgan, T. W.; van Eden, G. G.; de Kruif, T.; Wirtz, M.; Matejicek, J.; Chraska, T.; Pitts, R. A.; Wright, G. M.

    2015-08-01

    The thermal shock behaviour of tungsten exposed to high-flux plasma is studied using a high-power laser. The cases of laser-only, sequential laser and hydrogen (H) plasma and simultaneous laser plus H plasma exposure are studied. H plasma exposure leads to an embrittlement of the material and the appearance of a crack network originating from the centre of the laser spot. Under simultaneous loading, significant surface melting is observed. In general, H plasma exposure lowers the heat flux parameter (FHF) for the onset of surface melting by ∼25%. In the case of He-modified (fuzzy) surfaces, strong surface deformations are observed already after 1000 laser pulses at moderate FHF = 19 MJ m-2 s-1/2, and a dense network of fine cracks is observed. These results indicate that high-fluence ITER-like plasma exposure influences the thermal shock properties of tungsten, lowering the permissible transient energy density beyond which macroscopic surface modifications begin to occur.

  6. Sputter roughening instability on the Ge(001) surface: Energy and flux dependence

    SciTech Connect

    Chason, E.; Mayer, T.M.; Kellerman, B.K.

    1995-12-31

    We have measured surface roughening kinetics during low energy Xe ion sputtering of Ge (001) surfaces. Results are interpreted in terms of an instability theory developed by Bradley and Harper. Although the calculated magnitude of the roughening rate does not agree with the measured value, the variation of the rate with ion flux and energy is on agreement with the theory.

  7. Development of a Detector to Measure the Angular Dependence of the Cosmic Ray Induced Neutron Background Flux at Ground Level

    SciTech Connect

    Morgan, J F; Gosnell, T B; Luke, S J; Archer, D E; Lochner, R T; Frank, I M; Prussin, S G; Quiter, B J; Chivers, D H

    2002-01-28

    The detection of low intensity sources of radiation in containers is of particular interest for arms control, non-proliferation and nuclear smuggling activities. Attempts to procure and smuggle nuclear materials that could be used in terrorist activities have been well documented in recent years. These incidents have included fissile materials such, as plutonium and uranium, as well as medical and industrial isotopes that could be used in a Radiation Dispersal Device. The vast majority of these incidents have been discovered through human intelligence work due to the difficulty of using radiation monitoring. The detection of radiation sources in well-shielded containers presents a difficult technological challenge. Few neutrons and gamma rays may escape from the container and these may be obscured by the naturally occurring background. The world in general is a radioactive environment. Many elements in the earth's crust, as well as in common plants and building materials, emit a constant stream of radiation. In fact the ultimate limit on the detection of hidden sources is often the background level at the location of interest. It has long been understood that knowledge of the directionality of this background can be used to improve the signal/noise ratio in detectors used for these measurements. Imaging detectors are one method of reducing the effect of the background, but this reduction comes at the expensive of a huge increase in detector complexity. Hence these systems, while important in some specific applications, are probably not suited for the deployment of many detectors over a large area. There may be another way of reducing the effect of backgrounds on monitoring measurements. This method consists of using knowledge of the directional dependence of the background flux to help reduce its effect on the detectors in question. An accurate knowledge of this angular distribution allows one to develop better shielding designs for the detectors.

  8. Photochemistry of solutes in/on ice: reaction rate dependence on sample orientation and photon flux

    NASA Astrophysics Data System (ADS)

    Hullar, T.; Anastasio, C.

    2015-12-01

    Particularly in polar regions, photochemical reactions in snowpacks can be an important mechanism for transforming organic and inorganic compounds. Chemicals within snow and ice are found in three different compartments: distributed in the bulk ice, concentrated in liquid-like regions (LLRs) within the ice matrix (such as at grain boundaries), or present in quasi-liquid layers (QLLs) at the air-ice interface. While some previous work suggested reaction rates may vary in these different compartments, our preliminary experiments found similar reaction rates in all three compartments, as well as in aqueous solution. Previous work also suggested reaction rate constants may be independent of photon flux under certain illumination conditions. Here, we extend our investigations to measure reaction rate constants in ice samples with different orientations to the illumination source, which our work thus far suggests may impact the measured rate constants. Polycyclic aromatic hydrocarbons (PAHs) are common pollutants in snow and ice. We first prepared aqueous solutions of a single PAH. We then froze these samples using various methods previously shown to segregate the solute into known locations in the ice matrix. With simulated polar sunlight, we illuminated these samples and measured photon flux (using 2-nitrobenzaldehyde as a chemical actinometer) and photodecay of the PAH. Using this information, we normalized the rate of PAH loss to the photon flux and calculated the rate constants for PAH photodegradation under various freezing conditions, photon fluxes, and sample orientations. We will report on the impact of these variables on PAH photodegradation as well as the effect of varying the photon flux.

  9. Numerical Study of Cattaneo-Christov Heat Flux Model for Viscoelastic Flow Due to an Exponentially Stretching Surface

    PubMed Central

    Ahmad Khan, Junaid; Mustafa, M.; Hayat, T.; Alsaedi, A.

    2015-01-01

    This work deals with the flow and heat transfer in upper-convected Maxwell fluid above an exponentially stretching surface. Cattaneo-Christov heat flux model is employed for the formulation of the energy equation. This model can predict the effects of thermal relaxation time on the boundary layer. Similarity approach is utilized to normalize the governing boundary layer equations. Local similarity solutions are achieved by shooting approach together with fourth-fifth-order Runge-Kutta integration technique and Newton’s method. Our computations reveal that fluid temperature has inverse relationship with the thermal relaxation time. Further the fluid velocity is a decreasing function of the fluid relaxation time. A comparison of Fourier’s law and the Cattaneo-Christov’s law is also presented. Present attempt even in the case of Newtonian fluid is not yet available in the literature. PMID:26325426

  10. Numerical Study of Cattaneo-Christov Heat Flux Model for Viscoelastic Flow Due to an Exponentially Stretching Surface.

    PubMed

    Ahmad Khan, Junaid; Mustafa, M; Hayat, T; Alsaedi, A

    2015-01-01

    This work deals with the flow and heat transfer in upper-convected Maxwell fluid above an exponentially stretching surface. Cattaneo-Christov heat flux model is employed for the formulation of the energy equation. This model can predict the effects of thermal relaxation time on the boundary layer. Similarity approach is utilized to normalize the governing boundary layer equations. Local similarity solutions are achieved by shooting approach together with fourth-fifth-order Runge-Kutta integration technique and Newton's method. Our computations reveal that fluid temperature has inverse relationship with the thermal relaxation time. Further the fluid velocity is a decreasing function of the fluid relaxation time. A comparison of Fourier's law and the Cattaneo-Christov's law is also presented. Present attempt even in the case of Newtonian fluid is not yet available in the literature. PMID:26325426

  11. Application of the 15N gas-flux method for measuring in situ N2 and N2O fluxes due to denitrification in natural and semi-natural terrestrial ecosystems and comparison with the acetylene inhibition technique

    NASA Astrophysics Data System (ADS)

    Sgouridis, Fotis; Stott, Andrew; Ullah, Sami

    2016-03-01

    Soil denitrification is considered the most un-constrained process in the global N cycle due to uncertain in situ N2 flux measurements, particularly in natural and semi-natural terrestrial ecosystems. 15N tracer approaches can provide in situ measurements of both N2 and N2O simultaneously, but their use has been limited to fertilized agro-ecosystems due to the need for large 15N additions in order to detect 15N2 production against the high atmospheric N2. For 15N-N2 analyses, we have used an "in-house" laboratory designed and manufactured N2 preparation instrument which can be interfaced to any commercial continuous flow isotope ratio mass spectrometer (CF-IRMS). The N2 prep unit has gas purification steps and a copper-based reduction furnace, and allows the analysis of small gas injection volumes (4 µL) for 15N-N2 analysis. For the analysis of N2O, an automated Tracegas Preconcentrator (Isoprime Ltd) coupled to an IRMS was used to measure the 15N-N2O (4 mL gas injection volume). Consequently, the coefficient of variation for the determination of isotope ratios for N2 in air and in standard N2O (0.5 ppm) was better than 0.5 %. The 15N gas-flux method was adapted for application in natural and semi-natural land use types (peatlands, forests, and grasslands) by lowering the 15N tracer application rate to 0.04-0.5 kg 15N ha-1. The minimum detectable flux rates were 4 µg N m-2 h-1 and 0.2 ng N m-2 h-1 for the N2 and N2O fluxes respectively. Total denitrification rates measured by the acetylene inhibition technique in the same land use types correlated (r = 0.58) with the denitrification rates measured under the 15N gas-flux method, but were underestimated by a factor of 4, and this was partially attributed to the incomplete inhibition of N2O reduction to N2, under a relatively high soil moisture content, and/or the catalytic NO decomposition in the presence of acetylene. Even though relatively robust for in situ denitrification measurements, methodological

  12. Generation of the cosmic rays flux variations due to surfatron acceleration of charges by electromagnetic waves in space plasma

    NASA Astrophysics Data System (ADS)

    Erokhin, Nikolay; Loznikov, Vladimir; Shkevov, Rumen; Zolnikova, Nadezhda; Mikhailovskaya, Ludmila

    2016-07-01

    The analysis of experimental data on the spectra of cosmic rays (CR) has shown their variability on time scales of a few years, in particular, CR variations observed in E / Z range from TeV to 10000 TeV, where E is the energy of the particle, Z is its charge number. Consequently, the source of these variations must be located at a distance of no more than 1 parsec from the sun in the closest local interstellar clouds. As a mechanism of such variations appearance it is considered the surfatron acceleration of CR particles by electromagnetic wave in a relatively quiet space plasma. On the basis of developed model the numerical calculations were performed for particle capture dynamics (electrons, protons, helium and iron nuclei) in the wave effective potential well with a following growth their energy by 3-6 orders of magnitude. Optimal conditions for the implementation of charged particles surfatron acceleration in space plasma, the rate of trapped particles energy growth, the dynamics of wave phase on the captured particle trajectory, a temporal dynamics of components for charge impulse momentum and speed were studied. It is indicated that the capture of a small fraction of particles by wave for energies about TeV and less followed by their surfatron acceleration to an energy of about 10000 TeV will lead to a significant increase in the CR flux at such high energies. Thus CL flow variations are conditioned by changes in the space weather parameters

  13. Application of the 15N-Gas Flux method for measuring in situ N2 and N2O fluxes due to denitrification in natural and semi-natural terrestrial ecosystems and comparison with the acetylene inhibition technique

    NASA Astrophysics Data System (ADS)

    Sgouridis, F.; Ullah, S.; Stott, A.

    2015-08-01

    Soil denitrification is considered the most un-constrained process in the global N cycle due to uncertain in situ N2 flux measurements, particularly in natural and semi-natural terrestrial ecosystems. 15N tracer approaches can provide in situ measurements of both N2 and N2O simultaneously, but their use has been limited to fertilised agro-ecosystems due to the need for large 15N additions in order to detect 15N2 production against the high atmospheric N2. For 15N-N2 analyses, we have used an "in house" laboratory designed and manufactured N2 preparation instrument which can be interfaced to any commercial continuous flow isotope ratio mass spectrometer (CF-IRMS). The N2 prep unit has gas purification steps, a copper based reduction furnace, and allows the analysis of small gas injection volumes (4 μL) for 15N-N2 analysis. For the analysis of N2O, an automated Tracegas Pre-concentrator (Isoprime Ltd) coupled to an IRMS was used to measure the 15N-N2O (4 mL gas injection volume). Consequently, the coefficient of variation for the determination of isotope ratios for N2 in air and in standard N2O (0.5 ppm) was better than 0.5 %. The 15N Gas-Flux method was adapted for application in natural and semi-natural land use types (peatlands, forests and grasslands) by lowering the 15N tracer application rate to 0.04-0.5 kg 15N ha-1. For our chamber design (volume / surface = 8:1) and a 20 h incubation period, the minimum detectable flux rates were 4 μg N m-2 h-1 and 0.2 ng N m-2 h-1 for the N2 and N2O fluxes respectively. The N2 flux ranged between 2.4 and 416.6 μg N m-2 h-1, and the grassland soils showed on average 3 and 14 times higher denitrification rates than the woodland and organic soils respectively. The N2O flux was on average 20 to 200 times lower than the N2 flux, while the denitrification product ratio (N2O/N2 + N2O) was low, ranging between 0.03 and 13 %. Total denitrification rates measured by the acetylene inhibition technique under the same field conditions

  14. Gravity wave activity in the thermosphere inferred from GOCE data, and its dependence on solar flux conditions.

    NASA Astrophysics Data System (ADS)

    Garcia, Raphael F.; Bruinsma, Sean; Doornbos, Eelco; Massarweh, Lotfi

    2016-04-01

    This study is focused on the effect of solar flux conditions on the dynamics of Gravity Waves (GW) in thermosphere. Air density and cross-wind in situ estimates from the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) accelerometers are analyzed for the whole mission duration. The analysis was performed in the Fourier spectral domain averaging spectral results over periods of 2 months close to solstices. First the Amplitude Spectral Density (ASD) and the Magnitude Squared Coherence (MSC) of physical parameters are linked to local gravity waves. Then, a new GW marker (called Cf3) was introduced here to constrain GWs activity under Low, Medium and High solar flux conditions, showing a clear solar dumping effect on GW activity. Most of GW signal has been found in a spectral range above 8 mHz in GOCE data, meaning a maximum horizontal wavelength around 1000 km. The level GW activity at GOCE altitude is strongly decreasing with increasing solar flux. Furthermore, a shift in the dominant frequency with solar flux conditions has been noted, leading to a larger horizontal wavelengths (from 200 to 500 km) during high solar flux conditions. The influence of correlated error sources, between air density and cross-winds, is discussed. Consistency of the spectral domain results has been verified in time-domain with a global mapping of high frequency perturbations along GOCE orbit. This analysis shows a clear dependence with geomagnetic latitude with strong perturbations at magnetic poles, and an extension to lower latitudes favoured by low solar activity conditions. Various possible causes of this spatial trend are discussed.

  15. Thermal ion upflow in the cusp ionosphere and its dependence on soft electron energy flux

    NASA Astrophysics Data System (ADS)

    Burchill, J. K.; Knudsen, D. J.; Clemmons, J. H.; Oksavik, K.; Pfaff, R. F.; Steigies, C. T.; Yau, A. W.; Yeoman, T. K.

    2010-05-01

    We investigate the origin of low-energy (Ek < 10 eV) ion upflows in Earth's low-altitude dayside cusp region. The Cusp-2002 sounding rocket flew from Ny Ålesund, Svalbard, on 14 December 2002, carrying plasma and field instrumentation to an altitude of 768 km. The Suprathermal Ion Imager, a two-dimensional energy/arrival angle spectrograph, observed large (>500 m s-1) ion upflows within the cusp at altitudes between 640 km and 768 km. We report a significant correlation between ion upflow and precipitating magnetosheath electron energy flux in this altitude range. There is only very weak correlation between upflow and wave power in the VLF band. We find a small negative correlation between upflow and the magnitude of the DC electric field for fields less than about 70 mV m-1. The apparent relation between upflow and electron energy flux suggests a mechanism whereby ions are accelerated by parallel electric fields that are established by the soft electrons. Significant ion upflows are not observed for electron energy fluxes less than about 1010 eV cm-2 s-1. The lack of correspondence between ∣$\\vec{E∣ and upflow on the one hand, and wave power and upflow on the other, does not rule out these processes but implies that, if operating, they are not local to the measurement region. We also observe narrow regions of large ion downflow that imply either a rebalancing of the ionosphere toward a low-Te equilibrium during which gravity dominates over the pressure gradients or a convection of the upflowing ions away from the precipitation region, outside of which the ions must fall back into equilibrium at lower altitudes.

  16. Ion Outflow in the Dayside Cusp Ionosphere and its Dependence on Soft Electron Energy Flux

    NASA Astrophysics Data System (ADS)

    Burchill, J. K.; Knudsen, D. J.; Clemmons, J. H.; Oksavik, K.; Pfaff, R. F.; Steigies, C. T.; Yau, A. W.; Yeoman, T. K.

    2009-12-01

    We investigate the origin of low energy (Ek<10 eV) ion upflows in Earth's low-altitude dayside cusp region. The Cusp-2002 sounding rocket flew from Ny Ålesund, Svalbard, on 14 December 2002, carrying plasma and field instrumentation to an altitude of 768 km. The Suprathermal Ion Imager, a two-dimensional energy/arrival-angle spectrograph, observed large (>500 m/s) O+ upflows within the cusp at altitudes between 640 km and 768 km. We report a significant association between ion upflow and precipitating magnetosheath electron energy flux in this altitude range, but no causal links between upflow and either wave power or the magnitude of the dc electric field. The correspondence between upflow and logarithm of the electron energy flux suggests a mechanism whereby ions are accelerated locally by ambipolar electric fields that are driven by the soft electrons. Significant ion upflows are not observed for electron energy fluxes below ˜1010 eV cm-2s-1, which suggests that any ambipolar fields present above 640 km must be in equilibrium with gravity and pressure gradients under this condition. The lack of correspondence between │E│ and upflow on the one hand, and wave power and upflow on the other, does not rule out these processes, but implies that, if operating, they are not local to the measurement region. We observe narrow regions of large downflow that imply either a re-balancing of the ionosphere toward a low-Te equilibrium during which gravity dominates the pressure gradients, or convection of the upflowing ions away from the precipitation region, outside of which the ions must fall back into equilibrium at lower altitudes.

  17. Linear MHD Wave Propagation in Time-Dependent Flux Tube. II. Finite Plasma Beta

    NASA Astrophysics Data System (ADS)

    Williamson, A.; Erdélyi, R.

    2014-04-01

    The propagation of magnetohydrodynamic (MHD) waves is an area that has been thoroughly studied for idealised static and steady state magnetised plasma systems applied to numerous solar structures. By applying the generalisation of a temporally varying background density to an open magnetic flux tube, mimicking the observed slow evolution of such waveguides in the solar atmosphere, further investigations into the propagation of both fast and slow MHD waves can take place. The assumption of a zero-beta plasma (no gas pressure) was applied in Williamson and Erdélyi ( Solar Phys. 2013, doi:10.1007/s11207-013-0366-9, Paper I) is now relaxed for further analysis here. Firstly, the introduction of a finite thermal pressure to the magnetic flux tube equilibrium modifies the existence of fast MHD waves which are directly comparable to their counterparts found in Paper I. Further, as a direct consequence of the non-zero kinetic plasma pressure, a slow MHD wave now exists, and is investigated. Analysis of the slow wave shows that, similar to the fast MHD wave, wave amplitude amplification takes place in time and height. The evolution of the wave amplitude is determined here analytically. We conclude that for a temporally slowly decreasing background density both propagating magnetosonic wave modes are amplified for over-dense magnetic flux tubes. This information can be very practical and useful for future solar magneto-seismology applications in the study of the amplitude and frequency properties of MHD waveguides, e.g. for diagnostic purposes, present in the solar atmosphere.

  18. The Modification of Time-Dependent Mechanical Properties of Polyamides due to Sterilization

    NASA Astrophysics Data System (ADS)

    Florjancic, Urska; Zupancic, Barbara; Sutton, Elizabeth; Sitar, Ksenija Rener; Marion, Ljubo; Batista, Urska; Groselj, Dusan; Emri, Igor

    2008-07-01

    We examine the effect of sterilization on functionality and durability of Polyamide 6. Nowadays there are several applications of this material in medicine in a form of surgical sewing material, vascular catheters and other implants. Understanding the time-dependent behavior of PA-6 is critical in predicting the durability of different medical products made from this polymer. We show that two PA-6 materials having different initial kinetics and processed with the same technology, when exposed to sterilization, change their time-dependent mechanical properties, and hence the durability in significantly different ways.

  19. Observation of sudden temperature jumps in optically levitated microdroplets due to morphology-dependent input resonances.

    PubMed

    Popp, J; Lankers, M; Schaschek, K; Kiefer, W; Hodges, J T

    1995-05-01

    During the slow evaporation of an optically levitated microdroplet of a glycerol-water mixture (3:1) (approximately 12.44 µm in radius) several morphology-dependent input resonances have been observed in its Raman spectrum. These resonances yield sudden temperature jumps of approximately 10 °C in the microdroplet as evidenced by sudden shifts in the output (Raman) resonance spectra. The latter effects could be explained by a simple energy balance calculation and the dependence of droplet refractive index and density on temperature. PMID:21037793

  20. Morphology-dependent water budgets and nutrient fluxes in arctic thaw ponds

    USGS Publications Warehouse

    Koch, Joshua C.; Gurney, Kirsty; Wipfli, Mark S.

    2014-01-01

    Thaw ponds on the Arctic Coastal Plain of Alaska are productive ecosystems, providing habitat and food resources for many fish and bird species. Permafrost in this region creates unique pond morphologies: deep troughs, shallow low-centred polygons (LCPs) and larger coalescent ponds. By monitoring seasonal trends in pond volume and chemistry, we evaluated whether pond morphology and size affect water temperature and desiccation, and nitrogen (N) and phosphorus (P) fluxes. Evaporation was the largest early-summer water flux in all pond types. LCPs dried quickly and displayed high early-summer nutrient concentrations and losses. Troughs consistently received solute-rich subsurface inflows, which accounted for 12 to 42 per cent of their volume and may explain higher P in the troughs. N to P ratios increased and ammonium concentrations decreased with pond volume, suggesting that P and inorganic N availability may limit ecosystem productivity in older, larger ponds. Arctic summer temperatures will likely increase in the future, which may accelerate mid-summer desiccation. Given their morphology, troughs may remain wet, become warmer and derive greater nutrient loads from their thawing banks. Overall, seasonal- to decadal-scale warming may increase ecosystem productivity in troughs relative to other Arctic Coastal Plain ponds. 

  1. Flux-Dependent Growth Kinetics and Diameter Selectivity in Single-Wall Carbon Nanotube Arrays

    SciTech Connect

    Geohegan, David B; Puretzky, Alexander A; Jackson, Jeremy Joseph; Rouleau, Christopher M; Eres, Gyula; More, Karren Leslie

    2011-01-01

    The nucleation and growth kinetics of single-wall carbon nanotubes in aligned arrays have been measured using fast pulses of acetylene and in situ optical diagnostics in conjunction with low pressure chemical vapor deposition (CVD). Increasing the acetylene partial pressure is shown to decrease nucleation times by three orders of magnitude, permitting aligned nanotube arrays to nucleate and grow to microns lengths within single gas pulses at high (up to 7 micron/s) peak growth rates and short ~ 0.5 s times.Low-frequency Raman scattering (> 10 cm-1) and transmission electron microscopy measurements show that increasing the feedstock flux in both continuous-CVD and pulsed-CVD shifts the product distribution to large single-wall carbon nanotube diameters > 2.5 nm. Sufficiently high acetylene partial pressures in pulsed-CVD appear to temporarily terminate the growth of the fastest- growing, small-diameter nanotubes by overcoating the more catalytically-active, smaller catalyst nanoparticles within the ensemble with non-nanotube carbon in agreement with a growth model. The results indicate that subsets of catalyst nanoparticle ensembles nucleate, grow, and terminate growth within different flux ranges according to their catalytic activity.

  2. Role of native defects in nitrogen flux dependent carrier concentration of InN films grown by molecular beam epitaxy

    SciTech Connect

    Tangi, Malleswararao; Kuyyalil, Jithesh; Shivaprasad, S. M.

    2012-10-01

    We address the carrier concentration, strain, and bandgap issue of InN films grown on c-sapphire at different N-flux by molecular beam epitaxy using x-ray diffraction and x-ray photoelectron spectroscopy. We demonstrate that the strain in InN films arises due to point defects like nitrogen interstitials and nitrogen antisites. We report minimal biaxial strain due to relaxed growth morphology and a minimal hydrostatic strain arising due to interstitial nitrogen atoms being partially compensated by nitrogen antisites. We find that the variation in absorption edge can be attributed to defect induced carrier concentration and that nitrogen interstitials and nitrogen antisites act as donors that yield the respective absorption edge and Moss-Burstein shift. Our studies are a step towards the ability to form low carrier concentration strain-relaxed films and to determine the intrinsic band gap value for this technologically important material.

  3. Self-healing slip pulses in dynamic rupture models due to velocity-dependent strength

    USGS Publications Warehouse

    Beeler, N.M.; Tullis, T.E.

    1996-01-01

    Seismological observations of short slip duration on faults (short rise time on seismograms) during earthquakes are not consistent with conventional crack models of dynamic rupture and fault slip. In these models, the leading edge of rupture stops only when a strong region is encountered, and slip at an interior point ceases only when waves from the stopped edge of slip propagate back to that point. In contrast, some seismological evidence suggests that the duration of slip is too short for waves to propagate from the nearest edge of the ruptured surface, perhaps even if the distance used is an asperity size instead of the entire rupture dimension. What controls slip duration, if not dimensions of the fault or of asperities? In this study, dynamic earthquake rupture and slip are represented by a propagating shear crack. For all propagating shear cracks, slip velocity is highest near the rupture front, and at a small distance behind the rupture front, the slip velocity decreases. As pointed out by Heaton (1990), if the crack obeys a negative slip-rate-dependent strength relation, the lower slip velocity behind the rupture front will lead to strengthening that further reduces the velocity, and under certain circumstances, healing of slip can occur. The boundary element method of Hamano (1974) is used in a program adapted from Andrews (1985) for numerical simulations of mode II rupture with two different velocity-dependent strength functions. For the first function, after a slip-weakening displacement, the crack follows an exponential velocity-weakening relation. The characteristic velocity V0 of the exponential determines the magnitude of the velocity-dependence at dynamic velocities. The velocity-dependence at high velocity is essentially zero when V0 is small and the resulting slip velocity distribution is similar to slip weakening. If V0 is larger, rupture propagation initially resembles slip-weakening, but spontaneous healing occurs behind the rupture front. The

  4. Simulating Damage Due to a Lightning Strike Event: Effects of Temperature Dependent Properties on Interlaminar Damage

    NASA Technical Reports Server (NTRS)

    Ghezeljeh, Paria Naghipour; Pineda, Evan Jorge

    2014-01-01

    A multidirectional, carbon fiber-epoxy, composite panel is subjected to a simulated lightning strike, within a finite element method framework, and the effect of material properties on the failure (delamination) response is investigated through a detailed numerical study. The numerical model of the composite panel consists of individual homogenized plies with user-defined, cohesive interface elements between them. Lightning strikes are simulated as an assumed combination of excessive heat and high pressure loadings. It is observed that the initiation and propagation of lightning-induced delamination is a significant function of the temperature dependency of interfacial fracture toughness. This dependency must be defined properly in order to achieve reliable predictions of the present lightning-induced delamination in the composite panel.

  5. Direct Evidence for Projectile Charge-State Dependent Crater Formation Due to Fast Ions

    SciTech Connect

    Papaleo, R. M.; Silva, M. R.; Leal, R.; Grande, P. L.; Roth, M.; Schattat, B.; Schiwietz, G.

    2008-10-17

    We report on craters formed by individual 3 MeV/u Au{sup q{sub i}{sub n}{sub i}{sup +}} ions of selected incident charge states q{sub ini} penetrating thin layers of poly(methyl methacrylate). Holes and raised regions are formed around the region of the impact, with sizes that depend strongly and differently on q{sub ini}. Variation of q{sub ini}, of the film thickness and of the angle of incidence allows us to extract information about the depth of origin contributing to different crater features.

  6. Hyperinsulinemic hypoglycemia due to adult nesidioblastosis in insulin-dependent diabetes

    PubMed Central

    Raffel, A; Anlauf, M; Hosch, SB; Krausch, M; Henopp, T; Bauersfeld, J; Klofat, R; Bach, D; Eisenberger, CF; Klöppel, G; Knoefel, WT

    2006-01-01

    In neonates, persistent hyperinsulinemic hypoglycemia (PHH) is associated with nesidioblastosis. In adults, PHH is usually caused by solitary benign insulinomas. We report on an adult patient who suffered from insulin-dependent diabetes mellitus, and subsequently developed PHH caused by diffuse nesidioblastosis. Mutations of the MEN1 and Mody 2/3 genes were ruled out. Preoperative diagnostic procedures, the histopathological criteria and the surgical treatment options of adult nesidioblastosis are discussed. So far only one similar case of adult nesidioblastosis subsequent to diabetes mellitus II has been reported in the literature. In case of conversion of diabetes into hyperinsulinemic hypoglycemia syndrome, nesidioblastosis in addition to insulinoma should be considered. PMID:17131493

  7. Observations of the scale-dependent turbulence and evaluation of the flux-gradient relationship for sensible heat for a closed Douglas-Fir canopy in very weak wind conditions

    DOE PAGESBeta

    Vickers, D.; Thomas, C.

    2014-05-13

    Observations of the scale-dependent turbulent fluxes and variances above, within and beneath a tall closed Douglas-Fir canopy in very weak winds are examined. The daytime subcanopy vertical velocity spectra exhibit a double-peak structure with peaks at time scales of 0.8 s and 51.2 s. A double-peak structure is also observed in the daytime subcanopy heat flux cospectra. The daytime momentum flux cospectra inside the canopy and in the subcanopy are characterized by a relatively large cross-wind component, likely due to the extremely light and variable winds, such that the definition of a mean wind direction, and subsequent partitioning of themore » momentum flux into along- and cross-wind components, has little physical meaning. Positive values of both momentum flux components in the subcanopy contribute to upward transfer of momentum, consistent with the observed mean wind speed profile. In the canopy at night at the smallest resolved scales, we find relatively large momentum fluxes (compared to at larger scales), and increasing vertical velocity variance with decreasing time scale, consistent with very small eddies likely generated by wake shedding from the canopy elements that transport momentum but not heat. We find unusually large values of the velocity aspect ratio within the canopy, consistent with enhanced suppression of the horizontal wind components compared to the vertical by the canopy. The flux-gradient approach for sensible heat flux is found to be valid for the subcanopy and above-canopy layers when considered separately; however, single source approaches that ignore the canopy fail because they make the heat flux appear to be counter-gradient when in fact it is aligned with the local temperature gradient in both the subcanopy and above-canopy layers. Modeled sensible heat fluxes above dark warm closed canopies are likely underestimated using typical values of the Stanton number.« less

  8. The neurophysiological index of visual working memory maintenance is not due to load dependent eye movements.

    PubMed

    Kang, Min-Suk; Woodman, Geoffrey F

    2014-04-01

    The Contralateral Delayed Activity (CDA) is slow negative potential found during a variety of tasks, providing an important measure of the representation of information in visual working memory. However, it is studied using stimulus arrays in which the to-be-remembered objects are shown in the periphery of the left or the right visual field. Our goal was to determine whether fixational eye movements in the direction of the memoranda might underlie the CDA. We found that subjects' gaze was shifted toward the visual field of the memoranda during the retention interval, with its magnitude increasing with the set size. However, the CDA was clearly observed even when the subjects' gaze shifts were absent. In addition, the magnitude of the subjects' gaze shifts was unrelated to their visual working memory capacity measured with behavioral data, unlike the CDA. Finally, the onset latency of the set size dependent eye movements followed the onset of the set size dependent CDA. Thus, our findings clearly show that the CDA does not represent a simple inability to maintain fixation during visual working memory maintenance, but that this neural index of representation in working memory appears to induce eye movements toward the locations of the objects being remembered. PMID:24440409

  9. Enhanced momentum delivery by electric force to an ion flux due to collisions of ions with neutrals

    NASA Astrophysics Data System (ADS)

    Fruchtman, Amnon

    2014-10-01

    A major figure of merit in propulsion in general and in electric propulsion in particular is the thrust per unit of deposited power, the ratio of thrust over power. We have recently demonstrated experimentally and theoretically [1--4] that for a fixed deposited power in the ions, the momentum delivered by the electric force is larger if the accelerated ions collide with neutrals during the acceleration. The higher thrust for given power is achieved for a collisional plasma at the expense of a lower thrust per unit mass flow rate, reflecting what is true in general, that the lower the flow velocity is, the higher the thrust for a given power. This is the usual trade-off between having a large specific impulse and a large thrust. Broadening the range of jet velocities and thrust levels is desirable since there are different propulsion requirements for different space missions. The mechanism of thrust enhancement by ion-neutral collisions has been investigated in the past in the case of electric pressure, what is called ionic wind. I will describe in the talk experimental results for an enhanced thrust due to ion-neutral collisions in a configuration where the thrust is a result of magnetic pressure [1,3]. The plasma is accelerated by J × B force, in a configuration similar to that of Hall thrusters. Our measurements for three different gases and for various gas flow rates and magnetic field intensities, confirmed that the thrust increase is proportional to the square-root of the number of ion-neutral collisions. Additional measurements of local discharge parameters will be shown to be consistent with the force measurements. Issues that are crucial for the use of this mechanism in an electric thruster will also be discussed. These are the possible increase of the electron transport across magnetic field lines by electron-neutral collisions, and the possible effect on various sources of inefficiency. Supported by Grant No. 765/11 from the Israel Science Foundation.

  10. The Goddard Satellite-based Surface Turbulent Fluxes (GSSTF) Datasets and the Uncertainties/Impact due to the SSM/I Brightness Temperature

    NASA Astrophysics Data System (ADS)

    Shie, C.; Hilburn, K. A.

    2011-12-01

    Accurate ocean surface turbulent flux measurements are crucial to understanding the global water and energy cycle changes. Remote sensing is a valuable tool for global monitoring of these flux measurements. The GSSTF algorithm was thus developed and applied to remote sensing research and applications. The early version GSSTF2 (a global 1°x1° daily dataset of July 1987-December 2000) was widely used by the scientific community for global energy and water cycle research, and regional and short period data analysis since its official release in 2001. In a recently funded project by the NASA/Making Earth System data records for Use in Research Environments (MEaSUREs) Program, a new version GSSTF2b (a global 1°x1° daily dataset of July 1987-December 2008) using the improved and upgraded input datasets that included the updated Special Sensor Microwave Imagers (SSM/I) V6 product (e.g., brightness temperature [TB]) and the NCEP-DOE Reanalysis II product (e.g., sea surface/skin temperature) was therefore produced and distributed in October 2010. GSSTF2b was found to generally agree better with the sounding observations than GSSTF2 did in all three components of fluxes, i.e., latent heat flux (LHF), sensible heat flux (SHF), and wind stress (WST). In a recent intercomparison study led by one of the GSSTF2b/GSSTF2 users, GSSTF2b was also found performed well, especially in LHF and SHF, among the eleven accessed global oceanic surface turbulent fluxes datasets that include six reanalysis, four satellite-derived, and one combined. Certain foremost climate and weather scenarios such as the ENSO and the Monsoon activities can also be genuinely demonstrated by the GSSTF2b fluxes. However, we recently realized that the gradually increasing temporal trend shown in the globally averaged LHF of GSSTF2b, especially post 2000~2001, was somewhat related to a trend found in the SSM/I TB that was used to retrieve the bottom layer precipitable water (WB), then the specific humidity (Qa

  11. Passive trapping of rigid rods due to conformation-dependent electrophoretic mobility.

    PubMed

    Pandey, Harsh; Szafran, Sylvia A; Underhill, Patrick T

    2016-03-16

    We present computer simulations of a rigid rod in a combination of an extensional fluid flow and extensional electric field. The electrophoretic mobility of the rod is different parallel or perpendicular to the rod. The dependence of the mobility on the conformation (orientation) leads to a new phenomenon where the rods can be passively trapped in all directions at the stagnation point. This contrasts with the behavior in either fluid flow or electric field alone, in which an object can be pushed towards the stagnation point along some directions but is pushed away in others. We have determined the state space where trapping occurs and have developed a model that describes the strength of trapping when it does occur. This new phenomenon could be used in the future to separate objects based on a coupling between their mobility and ability to be oriented. PMID:26892384

  12. Enhancement of microbial motility due to speed-dependent nutrient absorption.

    PubMed

    Di Salvo, Mario E; Condat, C A

    2014-02-01

    Marine microorganisms often reach high swimming speeds, either to take advantage of evanescent nutrient patches or to beat Brownian forces. Since this implies that a sizable part of their energetic budget must be allocated to motion, it is reasonable to assume that some fast-swimming microorganisms may increase their nutrient intake by increasing their speed v. We formulate a model to investigate this hypothesis and its consequences, finding the steady-state solutions and analyzing their stability. Surprisingly, we find that even modest increases in nutrient absorption may lead to a significant increase of the microbial speed. In fact, evaluations obtained using realistic parameter values for bacteria indicate that the speed increase due to the enhanced nutrient absorption may be quite large. PMID:24451235

  13. Model predictions of latitude-dependent ozone depletion due to aerospace vehicle operations

    NASA Technical Reports Server (NTRS)

    Borucki, W. J.; Whitten, R. C.; Watson, V. R.; Riegel, C. A.; Maples, A. L.; Capone, L. A.

    1976-01-01

    Results are presented from a two-dimensional model of the stratosphere that simulates the seasonal movement of ozone by both wind and eddy transport, and contains all the chemistry known to be important. The calculated reductions in ozone due to NO2 injection from a fleet of supersonic transports are compared with the zonally averaged results of a three-dimensional model for a similar episode of injection. The agreement is good in the northern hemisphere, but is not as good in the southern hemisphere. Both sets of calculations show a strong corridor effect in that the predicted ozone depletions are largest to the north of the flight corridor for aircraft operating in the northern hemisphere.

  14. Model predictions of latitude-dependent ozone depletion due to supersonic transport operations

    NASA Technical Reports Server (NTRS)

    Borucki, W. J.; Whitten, R. C.; Watson, V. R.; Woodward, H. T.; Riegel, C. A.; Capone, L. A.; Becker, T.

    1976-01-01

    Results are presented from a two-dimensional model of the stratosphere that simulates the seasonal movement of ozone by both wind and eddy transport, and contains all the chemistry known to be important. The calculated reductions in ozone due to NO2 injection from a fleet of supersonic transports are compared with the zonally averaged results of a three-dimensional model for a similar episode of injection. The agreement is good in the northern hemisphere, but is not as good in the southern hemisphere. Both sets of calculations show a strong corridor effect in that the predicted ozone depletions are largest to the north of the flight corridor for aircraft operating in the northern hemisphere.

  15. Underestimating extreme events in power-law behavior due to machine-dependent cutoffs

    NASA Astrophysics Data System (ADS)

    Radicchi, Filippo

    2014-11-01

    Power-law distributions are typical macroscopic features occurring in almost all complex systems observable in nature. As a result, researchers in quantitative analyses must often generate random synthetic variates obeying power-law distributions. The task is usually performed through standard methods that map uniform random variates into the desired probability space. Whereas all these algorithms are theoretically solid, in this paper we show that they are subject to severe machine-dependent limitations. As a result, two dramatic consequences arise: (i) the sampling in the tail of the distribution is not random but deterministic; (ii) the moments of the sample distribution, which are theoretically expected to diverge as functions of the sample sizes, converge instead to finite values. We provide quantitative indications for the range of distribution parameters that can be safely handled by standard libraries used in computational analyses. Whereas our findings indicate possible reinterpretations of numerical results obtained through flawed sampling methodologies, they also pave the way for the search for a concrete solution to this central issue shared by all quantitative sciences dealing with complexity.

  16. Mitigation of Angle Tracking Errors Due to Color Dependent Centroid Shifts in SIM-Lite

    NASA Technical Reports Server (NTRS)

    Nemati, Bijan; An, Xin; Goullioud, Renaud; Shao, Michael; Shen, Tsae-Pyng; Wehmeier, Udo J.; Weilert, Mark A.; Wang, Xu; Werne, Thomas A.; Wu, Janet P.; Zhai, Chengxing

    2010-01-01

    The SIM-Lite astrometric interferometer will search for Earth-size planets in the habitable zones of nearby stars. In this search the interferometer will monitor the astrometric position of candidate stars relative to nearby reference stars over the course of a 5 year mission. The elemental measurement is the angle between a target star and a reference star. This is a two-step process, in which the interferometer will each time need to use its controllable optics to align the starlight in the two arms with each other and with the metrology beams. The sensor for this alignment is an angle tracking CCD camera. Various constraints in the design of the camera subject it to systematic alignment errors when observing a star of one spectrum compared with a start of a different spectrum. This effect is called a Color Dependent Centroid Shift (CDCS) and has been studied extensively with SIM-Lite's SCDU testbed. Here we describe results from the simulation and testing of this error in the SCDU testbed, as well as effective ways that it can be reduced to acceptable levels.

  17. The velocity dependence of X-ray emission due to Charge Exchange in the Cygnus Loop

    NASA Astrophysics Data System (ADS)

    Cumbee, Renata; Lyons, David; Mullen, Patrick Dean; Shelton, Robin L.; Stancil, Phillip C.; Schultz, David R.

    2016-01-01

    The fundamental collisional process of charge exchange (CX) has been been established as a primary source of X-ray emission from the heliosphere [1], planetary exospheres [2], and supernova remnants [3,4]. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly-excited, high charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays.To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross-sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics for collisions of bare and H-like C to Al ions with H, He, and H2. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant will be shown as an example with ion velocity dependence.[1] Henley, D. B. & Shelton, R. L. 2010, ApJSS, 187, 388[2] Dennerl, K. et al. 2002, A&A 386, 319[3] Katsuda, S. et al. 2011, ApJ 730 24[4] Cumbee, R. S. et al. 2014, ApJ 787 L31This work was partially supported by NASA grant NNX09AC46G.

  18. Estimated Overturning of Internal Waves due to Time-Dependent Shear in the Ocean

    NASA Astrophysics Data System (ADS)

    Latorre, Leonardo; Vanderhoff, Julie

    2010-11-01

    The ocean and atmosphere have a particular characteristic that sustains propagation of internal gravity waves called a stable stratification. Internal waves are generated, with wavelengths which can vary from a few meters to kilometers. These waves propagate through the ocean and atmosphere exchanging energy and momentum as they interact with other fluid phenomena and break, which in turn affects circulation, heat transport, nutrient distribution and biological activity in the oceans and the atmosphere. However large scale circulation models lack the appropriate resolution to detect these motions, hence it is necessary to accurately parameterize internal wave breaking in order to establish a better relationship between wave energy dissipation and its effects on oceanic and atmospheric circulation patterns. In this research internal waves interact with a time dependent background in the form of a near-inertial wave, which are common in the ocean. Using a two dimensional, fully non-linear Navier-Stokes equation solver and ray theory, estimates of wave breaking parameters which predict breaking at the same location in both of these models are accomplished. A statistical analysis of waves observed during the Hawaiian Ocean Mixing Experiment will provide an estimate of the percentage of waves expected to break during propagation through an inertial wave.

  19. Flux-dependent percolation transition in immiscible two-phase flows in porous media.

    PubMed

    Ramstad, Thomas; Hansen, Alex; Oren, Pål-Eric

    2009-03-01

    Using numerical simulations, we study immiscible two-phase flow in a pore network reconstructed from Berea sandstone under flow conditions that are statistically invariant under translation. Under such conditions, the flow is a state function which is not dependent on initial conditions. We find a second-order phase transition resembling the phase inversion transition found in emulsions. The flow regimes under consideration are those of low surface tension-hence high capillary numbers Ca-where viscous forces dominate. Nevertheless, capillary forces are imminent, we observe a critical stage in saturation where the transition takes place. We determine polydispersity critical exponent tau=2.27+/-0.08 and find that the critical saturation depends on how fast the fluids flow. PMID:19392052

  20. Rubidium beam flux dependence of film properties of Ba1 - xRbxBiO3 deposited by molecular-beam epitaxy using distilled ozone

    NASA Astrophysics Data System (ADS)

    Ogihara, M.; Toda, F.; Makita, T.; Abe, H.

    1993-10-01

    We have focused our attention on the dependence of Ba1-xRbxBiO3 (BRBO) film composition ratio and film properties on rubidium-beam-flux intensity. BRBO films were deposited on MgO(100) substrates by molecular-beam epitaxy (MBE) using distilled ozone. Systematic measurements showed that the rubidium content was nearly independent of rubidium-beam-flux intensity in a wide beam-flux range. Therefore, it can be concluded that some degree of self-control of rubidium stoichiometry is actually possible in BRBO film growth by MBE. This study also revealed that the BRBO film properties had strong dependences on rubidium-beam-flux intensity even in the range for self-control of rubudium stoichiometry. Our study also clarified that rubidium-beam flux affects the barium content in the BRBO film.

  1. The directional dependence of apertures, limits and sensitivity of the lunar Cherenkov technique to a UHE neutrino flux

    NASA Astrophysics Data System (ADS)

    James, C. W.; Protheroe, R. J.

    2009-06-01

    We use computer simulations to obtain the directional-dependence of the lunar Cherenkov technique for ultra-high energy (UHE) neutrino detection. We calculate the instantaneous effective area of past lunar Cherenkov experiments at Parkes, Goldstone (Goldstone Lunar Ultra-high energy neutrino Experiment, GLUE), and Kalyazin, as a function of neutrino arrival direction, finding that the potential sensitivity to a point source of UHE neutrinos for these experiments was as much as thirty times that to an isotropic flux, depending on the beam-pointing position and incident neutrino energy. Convolving our results with the known lunar positions during the Parkes and Goldstone experiments allows us to calculate an exposure map, and hence the directional-dependence of the combined limit imposed by these experiments. In the 10 21-10 23 eV range, we find parts of the sky where the GLUE limit likely still dominates, and areas where none of the limits from either Parkes, GLUE, or experiments such as the Antarctic Impulsive Transient Antenna (ANITA) balloon experiment or FORTE (Fast On-orbit Recording of Transient Events) satellite experiment are likely to be significant. Hence a large anisotropic flux of UHE neutrinos from these regions is not yet excluded. We also determine the directional dependence of the aperture of future planned experiments with the Australia Telescope Compact Array (ATCA), Australian SKA Pathfinder (ASKAP) and the Square Kilometre Array (SKA) to a UHE neutrino flux, and calculate the potential annual exposure to astronomical objects as a function of angular distance from the lunar trajectory through celestial coordinates. We find that the potential exposure of all experiments at 10 20 eV and below, integrated over a calendar year, is flat out to ˜25° from the lunar trajectory and then drops off rapidly. The region of greater sensitivity includes much of the Supergalactic Plane, including M87 and Cen A, as well as the Galactic Centre. At higher energies

  2. Frequency dependence in seismoacoustic imaging of shallow free gas due to gas bubble resonance

    NASA Astrophysics Data System (ADS)

    Tóth, Zsuzsanna; Spiess, Volkhard; Keil, Hanno

    2015-12-01

    Shallow free gas is investigated in seismoacoustic data in 10 frequency bands covering a frequency range between 0.2 and 43 kHz. At the edge of a gassy patch in the Bornholm Basin (Baltic Sea), compressional wave attenuation caused by free gas is estimated from reflection amplitudes beneath the gassy sediment layer. Imaging of shallow free gas is considerably influenced by gas bubble resonance, because in the resonance frequency range attenuation is significantly increased. At the resonance frequency of the largest bubbles between 3 and 5 kHz, high scattering causes complete acoustic blanking beneath the top of the gassy sediment layer. In the wider resonance frequency range between 3 and 15 kHz, the effect of smaller bubbles becomes dominant and the attenuation slightly decreases. This allows acoustic waves to be transmitted and reflections can be observed beneath the gassy sediment layer for higher frequencies. Above resonance beginning at ˜19 kHz, attenuation is low and the presence of free gas can be inferred from the decreased reflection amplitudes beneath the gassy layer. Below the resonance frequency range (<1 kHz), attenuation is generally very low and not dependent on frequency. Using the geoacoustic model of Anderson and Hampton, the observed frequency boundaries suggest gas bubble sizes between 1 and 4-6 mm, and gas volume fractions up to 0.02% in a ˜2 m thick sediment layer, whose upper boundary is the gas front. With the multifrequency acoustic approach and the Anderson and Hampton model, quantification of free gas in shallow marine environments is possible if the measurement frequency range allows the identification of the resonance frequency peak. The method presented is limited to places with only moderate attenuation, where the amplitudes of a reflection can be analyzed beneath the gassy sediment layer.

  3. Theoretical basal Ca II and Mg II fluxes for late-type stars: results from acoustic wave spectra with time-dependent ionization and multilevel radiation treatments

    NASA Astrophysics Data System (ADS)

    Fawzy, Diaa E.

    2015-08-01

    Computations of chromospheric models and the resulting spectral line emission fluxes are presented for late-type stars exhibiting very low level of chromospheric activity, referred to as a basal flux stars or low activity stars. The computations are self-consistent, and consider the entire acoustic wave energy spectra generated in the stellar convection zones. We consider multilevel atomic models, take into account departures from local thermodynamic equilibrium and also consider the time-dependent ionization processes of hydrogen. We employ the new finding of the mixing-length parameter α = 1.8. The Ca II H+K and Mg II h+k line fluxes are computed assuming pseudo-partial redistribution. The results show the importance of time-dependent ionization in modelling the middle and high chromospheres. Models without considering time-dependent ionization overestimate the emitted Ca II fluxes by factors between 1.1 and 5.6 for F8V and M0V stars, respectively, while factors between 1.8 for G0V and 17.4 for M0V stars have been obtained for the Mg II fluxes. The theoretically computed basal fluxes in Ca II and Mg II, respectively, follow simple linear formulae depending on the effective temperature log Teff. The obtained results for Ca II fluxes show reasonable agreement with observations.

  4. Time-dependent excitation and ionization modelling of absorption-line variability due to GRB 080310

    NASA Astrophysics Data System (ADS)

    Vreeswijk, P. M.; Ledoux, C.; Raassen, A. J. J.; Smette, A.; De Cia, A.; Woźniak, P. R.; Fox, A. J.; Vestrand, W. T.; Jakobsson, P.

    2013-01-01

    We model the time-variable absorption of Fe II, Fe III, Si II, C II and Cr II detected in Ultraviolet and Visual Echelle Spectrograph (UVES) spectra of gamma-ray burst (GRB) 080310, with the afterglow radiation exciting and ionizing the interstellar medium in the host galaxy at a redshift of z = 2.42743. To estimate the rest-frame afterglow brightness as a function of time, we use a combination of the optical VRI photometry obtained by the RAPTOR-T telescope array, which is presented in this paper, and Swift's X-Ray Telescope (XRT) observations. Excitation alone, which has been successfully applied for a handful of other GRBs, fails to describe the observed column density evolution in the case of GRB 080310. Inclusion of ionization is required to explain the column density decrease of all observed Fe II levels (including the ground state 6D9/2) and increase of the Fe III 7S3 level. The large population of ions in this latter level (up to 10% of all Fe III) can only be explained through ionization of Fe II, as a large fraction of the ionized Fe II ions (we calculate 31% using the Flexible Atomic and Cowan codes) initially populate the 7S3 level of Fe III rather than the ground state. This channel for producing a significant Fe III 7S3 level population may be relevant for other objects in which absorption lines from this level, the UV34 triplet, are observed, such as broad absorption line (BAL) quasars and η Carinae. This provides conclusive evidence for time-variable ionization in the circumburst medium, which to date has not been convincingly detected. However, the best-fit distance of the neutral absorbing cloud to the GRB is 200-400 pc, i.e. similar to GRB-absorber distance estimates for GRBs without any evidence for ionization. We find that the presence of time-varying ionization in GRB 080310 is likely due to a combination of the super-solar iron abundance ([Fe/H] = +0.2) and the low H I column density (log N(H i) = 18.7) in the host of GRB 080310. Finally

  5. Linear MHD Wave Propagation in Time-Dependent Flux Tube. I. Zero Plasma-β

    NASA Astrophysics Data System (ADS)

    Williamson, A.; Erdélyi, R.

    2014-03-01

    MHD waves and oscillations in sharply structured magnetic plasmas have been studied for static and steady systems in the thin tube approximation over many years. This work will generalize these studies by introducing a slowly varying background density in time, in order to determine the changes to the wave parameters introduced by this temporally varying equilibrium, i.e. to investigate the amplitude, frequency, and wavenumber for the kink and higher order propagating fast magnetohydrodynamic wave in the leading order approximation to the WKB approach in a zero- β plasma representing the upper solar atmosphere. To progress, the thin tube and over-dense loop approximations are used, restricting the results found here to the duration of a number of multiples of the characteristic density change timescale. Using such approximations it is shown that the amplitude of the kink wave is enhanced in a manner proportional to the square of the Alfvén speed, . The frequency of the wave solution tends to the driving frequency of the system as time progresses; however, the wavenumber approaches zero after a large multiple of the characteristic density change timescale, indicating an ever increasing wavelength. For the higher order fluting modes the changes in amplitude are dependent upon the wave mode; for the m=2 mode the wave is amplified to a constant level; however, for all m≥3 the fast MHD wave is damped within a relatively small multiple of the characteristic density change timescale. Understanding MHD wave behavior in time-dependent plasmas is an important step towards a more complete model of the solar atmosphere and has a key role to play in solar magneto-seismological applications.

  6. Integration of transcription and flux data reveals molecular paths associated with differences in oxygen-dependent phenotypes of Saccharomyces cerevisiae

    PubMed Central

    2014-01-01

    Background Saccharomyces cerevisiae is able to adapt to a wide range of external oxygen conditions. Previously, oxygen-dependent phenotypes have been studied individually at the transcriptional, metabolite, and flux level. However, the regulation of cell phenotype occurs across the different levels of cell function. Integrative analysis of data from multiple levels of cell function in the context of a network of several known biochemical interaction types could enable identification of active regulatory paths not limited to a single level of cell function. Results The graph theoretical method called Enriched Molecular Path detection (EMPath) was extended to enable integrative utilization of transcription and flux data. The utility of the method was demonstrated by detecting paths associated with phenotype differences of S. cerevisiae under three different conditions of oxygen provision: 20.9%, 2.8% and 0.5%. The detection of molecular paths was performed in an integrated genome-scale metabolic and protein-protein interaction network. Conclusions The molecular paths associated with the phenotype differences of S. cerevisiae under conditions of different oxygen provisions revealed paths of molecular interactions that could potentially mediate information transfer between processes that respond to the particular oxygen availabilities. PMID:24528924

  7. The Hardening Hypothesis: Is the Ability to Quit Decreasing Due to Increasing Nicotine Dependence? A Review and Commentary

    PubMed Central

    Hughes, John R.

    2011-01-01

    The “hardening hypothesis” states tobacco control activities have mostly influenced those smokers who found it easier to quit and, thus, remaining smokers are those who are less likely to stop smoking. This paper first describes a conceptual model for hardening. Then the paper describes important methodological distinctions (quit attempts vs. ability to remain abstinent as indicators, measures of hardening per se vs. measures of causes of hardening, and dependence measures that do vs. do not include cigarettes per day (cigs/day).) After this commentary, the paper reviews data from prior reviews and new searches for studies on one type of hardening: the decreasing ability to quit due to increasing nicotine dependence. Overall, all four studies of the general population of smokers found no evidence of decreased ability to quit; however, both secondary analyses of treatment-seeking smokers found quit rates were decreasing over time. Cigs/day and time-to-first cigarette measures of dependence did not increase over time; however, two studies found that DSM-defined dependence appeared to be increasing over time. Although these data suggest hardening may be occurring in treatment seekers but perhaps not in the general population of smokers, this conclusion may be premature given the small number of data sets and indirect measures of quit success and dependence in the data sets. Future studies should include questions about quit attempts, ability to abstain, treatment use, and multi-item dependence measures. PMID:21411244

  8. Tear film dynamics with evaporation, wetting, and time-dependent flux boundary condition on an eye-shaped domain

    PubMed Central

    Li, Longfei; Braun, R. J.; Maki, K. L.; Henshaw, W. D.; King-Smith, P. E.

    2014-01-01

    We study tear film dynamics with evaporation on a wettable eye-shaped ocular surface using a lubrication model. The mathematical model has a time-dependent flux boundary condition that models the cycles of tear fluid supply and drainage; it mimics blinks on a stationary eye-shaped domain. We generate computational grids and solve the nonlinear governing equations using the OVERTURE computational framework. In vivo experimental results using fluorescent imaging are used to visualize the influx and redistribution of tears for an open eye. Results from the numerical simulations are compared with the experiment. The model captures the flow around the meniscus and other dynamic features of human tear film observed in vivo. PMID:24926191

  9. Tear film dynamics with evaporation, wetting, and time-dependent flux boundary condition on an eye-shaped domain

    NASA Astrophysics Data System (ADS)

    Li, Longfei; Braun, R. J.; Maki, K. L.; Henshaw, W. D.; King-Smith, P. E.

    2014-05-01

    We study tear film dynamics with evaporation on a wettable eye-shaped ocular surface using a lubrication model. The mathematical model has a time-dependent flux boundary condition that models the cycles of tear fluid supply and drainage; it mimics blinks on a stationary eye-shaped domain. We generate computational grids and solve the nonlinear governing equations using the OVERTURE computational framework. In vivo experimental results using fluorescent imaging are used to visualize the influx and redistribution of tears for an open eye. Results from the numerical simulations are compared with the experiment. The model captures the flow around the meniscus and other dynamic features of human tear film observed in vivo.

  10. A new approach to model oxygen dependent benthic phosphate fluxes in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Almroth-Rosell, Elin; Eilola, Kari; Kuznetsov, Ivan; Hall, Per O. J.; Meier, H. E. Markus

    2015-04-01

    The new approach to model the oxygen dependent phosphate release by implementing formulations of the oxygen penetration depths (OPD) and mineral bound inorganic phosphorus pools to the Swedish Coastal and Ocean Biogeochemical model (SCOBI) is described. The phosphorus dynamics and the oxygen concentrations in the Baltic proper sediment are studied during the period 1980-2008 using SCOBI coupled to the 3D-Rossby Centre Ocean model. Model data are compared to observations from monitoring stations and experiments. The impact from oxygen consumption on the determination of the OPD is found to be largest in the coastal zones where also the largest OPD are found. In the deep water the low oxygen concentrations mainly determine the OPD. Highest modelled release rate of phosphate from the sediment is about 59 × 103 t P year- 1 and is found on anoxic sediment at depths between 60-150 m, corresponding to 17% of the Baltic proper total area. The deposition of organic and inorganic phosphorus on sediments with oxic bottom water is larger than the release of phosphorus, about 43 × 103 t P year- 1. For anoxic bottoms the release of total phosphorus during the investigated period is larger than the deposition, about 19 × 103 t P year- 1. In total the net Baltic proper sediment sink is about 23.7 × 103 t P year- 1. The estimated phosphorus sink efficiency of the entire Baltic Sea is on average about 83% during the period.

  11. Activity-dependent branching ratios in stocks, solar x-ray flux, and the Bak-Tang-Wiesenfeld sandpile model

    NASA Astrophysics Data System (ADS)

    Martin, Elliot; Shreim, Amer; Paczuski, Maya

    2010-01-01

    We define an activity-dependent branching ratio that allows comparison of different time series Xt . The branching ratio bx is defined as bx=E[ξx/x] . The random variable ξx is the value of the next signal given that the previous one is equal to x , so ξx={Xt+1∣Xt=x} . If bx>1 , the process is on average supercritical when the signal is equal to x , while if bx<1 , it is subcritical. For stock prices we find bx=1 within statistical uncertainty, for all x , consistent with an “efficient market hypothesis.” For stock volumes, solar x-ray flux intensities, and the Bak-Tang-Wiesenfeld (BTW) sandpile model, bx is supercritical for small values of activity and subcritical for the largest ones, indicating a tendency to return to a typical value. For stock volumes this tendency has an approximate power-law behavior. For solar x-ray flux and the BTW model, there is a broad regime of activity where bx≃1 , which we interpret as an indicator of critical behavior. This is true despite different underlying probability distributions for Xt and for ξx . For the BTW model the distribution of ξx is Gaussian, for x sufficiently larger than 1, and its variance grows linearly with x . Hence, the activity in the BTW model obeys a central limit theorem when sampling over past histories. The broad region of activity where bx is close to one disappears once bulk dissipation is introduced in the BTW model—supporting our hypothesis that it is an indicator of criticality.

  12. Activity-dependent branching ratios in stocks, solar x-ray flux, and the Bak-Tang-Wiesenfeld sandpile model.

    PubMed

    Martin, Elliot; Shreim, Amer; Paczuski, Maya

    2010-01-01

    We define an activity-dependent branching ratio that allows comparison of different time series X(t). The branching ratio b(x) is defined as b(x)=E[xi(x)/x]. The random variable xi(x) is the value of the next signal given that the previous one is equal to x, so xi(x)=[X(t+1) | X(t)=x]. If b(x)>1, the process is on average supercritical when the signal is equal to x, while if b(x)<1, it is subcritical. For stock prices we find b(x)=1 within statistical uncertainty, for all x, consistent with an "efficient market hypothesis." For stock volumes, solar x-ray flux intensities, and the Bak-Tang-Wiesenfeld (BTW) sandpile model, b(x) is supercritical for small values of activity and subcritical for the largest ones, indicating a tendency to return to a typical value. For stock volumes this tendency has an approximate power-law behavior. For solar x-ray flux and the BTW model, there is a broad regime of activity where b(x) approximately equal 1, which we interpret as an indicator of critical behavior. This is true despite different underlying probability distributions for X(t) and for xi(x). For the BTW model the distribution of xi(x) is Gaussian, for x sufficiently larger than 1, and its variance grows linearly with x. Hence, the activity in the BTW model obeys a central limit theorem when sampling over past histories. The broad region of activity where b(x) is close to one disappears once bulk dissipation is introduced in the BTW model-supporting our hypothesis that it is an indicator of criticality. PMID:20365434

  13. The uncertainty of UTCI due to uncertainties in the determination of radiation fluxes derived from numerical weather prediction and regional climate model simulations

    NASA Astrophysics Data System (ADS)

    Schreier, Stefan F.; Suomi, Irene; Bröde, Peter; Formayer, Herbert; Rieder, Harald E.; Nadeem, Imram; Jendritzky, Gerd; Batchvarova, Ekaterina; Weihs, Philipp

    2013-03-01

    In this study we examine the determination accuracy of both the mean radiant temperature (Tmrt) and the Universal Thermal Climate Index (UTCI) within the scope of numerical weather prediction (NWP), and global (GCM) and regional (RCM) climate model simulations. First, Tmrt is determined and the so-called UTCI-Fiala model is then used for the calculation of UTCI. Taking into account the uncertainties of NWP model (among others the HIgh Resolution Limited Area Model HIRLAM) output (temperature, downwelling short-wave and long-wave radiation) stated in the literature, we simulate and discuss the uncertainties of Tmrt and UTCI at three stations in different climatic regions of Europe. The results show that highest negative (positive) differences to reference cases (under assumed clear-sky conditions) of up to -21°C (9°C) for Tmrt and up to -6°C (3.5°C) for UTCI occur in summer (winter) due to cloudiness. In a second step, the uncertainties of RCM simulations are analyzed: three RCMs, namely ALADIN (Aire Limitée Adaptation dynamique Développement InterNational), RegCM (REGional Climate Model) and REMO (REgional MOdel) are nested into GCMs and used for the prediction of temperature and radiation fluxes in order to estimate Tmrt and UTCI. The inter-comparison of RCM output for the three selected locations shows that biases between 0.0 and ±17.7°C (between 0.0 and ±13.3°C) for Tmrt (UTCI), and RMSE between ±0.5 and ±17.8°C (between ±0.8 and ±13.4°C) for Tmrt (UTCI) may be expected. In general the study shows that uncertainties of UTCI, due to uncertainties arising from calculations of radiation fluxes (based on NWP models) required for the prediction of Tmrt, are well below ±2°C for clear-sky cases. However, significant higher uncertainties in UTCI of up to ±6°C are found, especially when prediction of cloudiness is wrong.

  14. Preliminary Assessment of the Impact on Reactor Vessel dpa Rates Due to Installation of a Proposed Low Enriched Uranium (LEU) Core in the High Flux Isotope Reactor (HFIR)

    SciTech Connect

    Daily, Charles R.

    2015-10-01

    An assessment of the impact on the High Flux Isotope Reactor (HFIR) reactor vessel (RV) displacements-per-atom (dpa) rates due to operations with the proposed low enriched uranium (LEU) core described by Ilas and Primm has been performed and is presented herein. The analyses documented herein support the conclusion that conversion of HFIR to low-enriched uranium (LEU) core operations using the LEU core design of Ilas and Primm will have no negative impact on HFIR RV dpa rates. Since its inception, HFIR has been operated with highly enriched uranium (HEU) cores. As part of an effort sponsored by the National Nuclear Security Administration (NNSA), conversion to LEU cores is being considered for future HFIR operations. The HFIR LEU configurations analyzed are consistent with the LEU core models used by Ilas and Primm and the HEU balance-of-plant models used by Risner and Blakeman in the latest analyses performed to support the HFIR materials surveillance program. The Risner and Blakeman analyses, as well as the studies documented herein, are the first to apply the hybrid transport methods available in the Automated Variance reduction Generator (ADVANTG) code to HFIR RV dpa rate calculations. These calculations have been performed on the Oak Ridge National Laboratory (ORNL) Institutional Cluster (OIC) with version 1.60 of the Monte Carlo N-Particle 5 (MCNP5) computer code.

  15. Length-dependent changes in contractile dynamics are blunted due to cardiac myosin binding protein-C ablation

    PubMed Central

    Mamidi, Ranganath; Gresham, Kenneth S.; Stelzer, Julian E.

    2014-01-01

    Enhanced cardiac contractile function with increased sarcomere length (SL) is, in part, mediated by a decrease in the radial distance between myosin heads and actin. The radial disposition of myosin heads relative to actin is modulated by cardiac myosin binding protein-C (cMyBP-C), suggesting that cMyBP-C contributes to the length-dependent activation (LDA) in the myocardium. However, the precise roles of cMyBP-C in modulating cardiac LDA are unclear. To determine the impact of cMyBP-C on LDA, we measured isometric force, myofilament Ca2+-sensitivity (pCa50) and length-dependent changes in kinetic parameters of cross-bridge (XB) relaxation (krel), and recruitment (kdf) due to rapid stretch, as well as the rate of force redevelopment (ktr) in response to a large slack-restretch maneuver in skinned ventricular multicellular preparations isolated from the hearts of wild-type (WT) and cMyBP-C knockout (KO) mice, at SL's 1.9 μm or 2.1 μm. Our results show that maximal force was not significantly different between KO and WT preparations but length-dependent increase in pCa50 was attenuated in the KO preparations. pCa50 was not significantly different between WT and KO preparations at long SL (5.82 ± 0.02 in WT vs. 5.87 ± 0.02 in KO), whereas pCa50 was significantly different between WT and KO preparations at short SL (5.71 ± 0.02 in WT vs. 5.80 ± 0.01 in KO; p < 0.05). The ktr, measured at half-maximal Ca2+-activation, was significantly accelerated at short SL in WT preparations (8.74 ± 0.56 s−1 at 1.9 μm vs. 5.71 ± 0.40 s−1 at 2.1 μm, p < 0.05). Furthermore, krel and kdf were accelerated by 32% and 50%, respectively at short SL in WT preparations. In contrast, ktr was not altered by changes in SL in KO preparations (8.03 ± 0.54 s−1 at 1.9 μm vs. 8.90 ± 0.37 s−1 at 2.1 μm). Similarly, KO preparations did not exhibit length-dependent changes in krel and kdf. Collectively, our data implicate cMyBP-C as an important regulator of LDA via its impact on

  16. Parallel machine scheduling problem with ready times, due times and sequence-dependent setup times using meta-heuristic algorithms

    NASA Astrophysics Data System (ADS)

    Joo, Cheol Min; Kim, Byung Soo

    2012-09-01

    This article considers a parallel machine scheduling problem with ready times, due times and sequence-dependent setup times. The objective of this problem is to determine the allocation policy of jobs and the scheduling policy of machines to minimize the weighted sum of setup times, delay times and tardy times. A mathematical model for optimal solution is derived. An in-depth analysis of the model shows that it is very complicated and difficult to obtain optimal solutions as the problem size becomes large. Therefore, two meta-heuristics, genetic algorithm (GA) and a new population-based evolutionary meta-heuristic called self-evolution algorithm (SEA), are proposed. The performances of the meta-heuristic algorithms are evaluated through comparison with optimal solutions using several randomly generated examples.

  17. The Cystic Fibrosis Transmembrane Conductance Regulator and Chloride-Dependent Ion Fluxes of Ovine Vocal Fold Epithelium

    ERIC Educational Resources Information Center

    Leydon, Ciara; Fisher, Kimberly V.; Lodewyck-Falciglia, Danielle

    2009-01-01

    Purpose: Ion-driven transepithelial water fluxes participate in maintaining superficial vocal fold hydration, which is necessary for normal voice production. The authors hypothesized that Cl[superscript -] channels are present in vocal fold epithelial cells and that transepithelial Cl[superscript -] fluxes can be manipulated pharmacologically.…

  18. Theoretical limits on the threshold for the response of long cells to weak extremely low frequency electric fields due to ionic and molecular flux rectification.

    PubMed Central

    Weaver, J C; Vaughan, T E; Adair, R K; Astumian, R D

    1998-01-01

    Understanding exposure thresholds for the response of biological systems to extremely low frequency (ELF) electric and magnetic fields is a fundamental problem of long-standing interest. We consider a two-state model for voltage-gated channels in the membrane of an isolated elongated cell (Lcell = 1 mm; rcell = 25 micron) and use a previously described process of ionic and molecular flux rectification to set lower bounds for a threshold exposure. A key assumption is that it is the ability of weak physical fields to alter biochemistry that is limiting, not the ability of a small number of molecules to alter biological systems. Moreover, molecular shot noise, not thermal voltage noise, is the basis of threshold estimates. Models with and without stochastic resonance are used, with a long exposure time, texp = 10(4) s. We also determined the dependence of the threshold on the basal transport rate. By considering both spherical and elongated cells, we find that the lowest bound for the threshold is Emin approximately 9 x 10(-3) V m-1 (9 x 10(-5) V cm-1). Using a conservative value for the loop radius rloop = 0.3 m for induced current, the corresponding lower bound in the human body for a magnetic field exposure is Bmin approximately 6 x 10(-4) T (6 G). Unless large, organized, and electrically amplifying multicellular systems such as the ampullae of Lorenzini of elasmobranch fish are involved, these results strongly suggest that the biophysical mechanism of voltage-gated macromolecules in the membranes of cells can be ruled out as a basis of possible effects of weak ELF electric and magnetic fields in humans. PMID:9788920

  19. Hybrid-like 2/1 flux-pumping and magnetic island evolution due to edge localized mode-neoclassical tearing mode coupling in DIII-D

    NASA Astrophysics Data System (ADS)

    King, J. D.; La Haye, R. J.; Petty, C. C.; Osborne, T. H.; Lasnier, C. J.; Groebner, R. J.; Volpe, F. A.; Lanctot, M. J.; Makowski, M. A.; Holcomb, C. T.; Solomon, W. M.; Allen, S. L.; Luce, T. C.; Austin, M. E.; Meyer, W. H.; Morse, E. C.

    2012-02-01

    Direct analysis of internal magnetic field pitch angles measured using the motional Stark effect diagnostic shows m /n=2/1 neoclassical tearing modes exhibit stronger poloidal magnetic flux-pumping than typical hybrids containing m /n=3/2 modes. This flux-pumping causes the avoidance of sawteeth, and is present during partial electron cyclotron current drive suppression of the tearing mode. This finding could lead to hybrid discharges with higher normalized fusion performance at lower q95. The degree of edge localized mode-neoclassical tearing mode (ELM-NTM) coupling and the strength of flux-pumping increase with beta and the proximity of the modes to the ELMing pedestal. Flux-pumping appears independent of magnetic island width. Individual ELM-NTM coupling events show a rapid timescale drop in the island width followed by a resistive recovery that is successfully modeled using the modified Rutherford equation. The fast transient drop in island width increases with ELM size.

  20. Critical film thickness dependence on As flux in In{sub 0.27}Ga{sub 0.73}As/GaAs(001) films

    SciTech Connect

    Riposan, A.; Mirecki Millunchick, J.; Pearson, Chris

    2007-02-26

    The transition between planar and nonplanar growth is examined for compressively strained In{sub 0.27}Ga{sub 0.73}As/GaAs(001) films using reflection high energy electron diffraction, atomic force microscopy, and scanning tunneling microscopy (STM). For a narrow range of temperature and composition, the critical thickness (t{sub SK}) is strongly dependent on As flux. For high values of As flux, t{sub SK} increases by more than a factor of 2. The morphology of three-dimensional islands formed during the initial stages of nonplanar growth is also characterized by high resolution STM.

  1. Mode- and Direction-Dependent Mechanical Energy Dissipation in Single-Crystal Resonators due to Anharmonic Phonon-Phonon Scattering

    NASA Astrophysics Data System (ADS)

    Iyer, Srikanth S.; Candler, Robert N.

    2016-03-01

    In this work, we determine the intrinsic mechanical energy dissipation limit for single-crystal resonators due to anharmonic phonon-phonon scattering in the Akhiezer (Ω τ ≪1 ) regime. The energy loss is derived using perturbation theory and the linearized Boltzmann transport equation for phonons, and includes the direction- and polarization-dependent mode-Grüneisen parameters in order to capture the strain-induced anharmonicity among phonon branches. This expression reveals the fundamental differences among the internal friction limits for different types of bulk-mode elastic waves. For cubic crystals, 2D-extensional modes have increased dissipation compared to width-extensional modes because the biaxial deformation opposes the natural Poisson contraction of the solid. Additionally, we show that shear-mode vibrations, which preserve volume, have significantly reduced energy loss because dissipative phonon-phonon scattering is restricted to pure-shear phonon branches, indicating that Lamé- or wineglass-mode resonators will have the highest upper limit on mechanical efficiency. Finally, we employ key simplifications to evaluate the quality factor limits for common mode shapes in single-crystal silicon devices, explicitly including the correct effective elastic storage moduli for different vibration modes and crystal orientations. Our expression satisfies the pressing need for a reliable analytical model that can predict the phonon-phonon dissipation limits for modern resonant microelectromechanical systems, where precise manufacturing techniques and accurate finite-element methods can be used to select particular vibrational mode shapes and crystal orientations.

  2. The Net Carbon Flux due to Deforestation and Forest Re-Growth in the Brazilian Amazon: Analysis using a Process-Based Model

    NASA Technical Reports Server (NTRS)

    Hirsch, A. I.; Little, W. S.; Houghton, R. A.; Scott, N. A.; White, J. D.

    2004-01-01

    We developed a process-based model of forest growth, carbon cycling, and land cover dynamics named CARLUC (for CARbon and Land Use Change) to estimate the size of terrestrial carbon pools in terra firme (non-flooded) forests across the Brazilian Legal Amazon and the net flux of carbon resulting from forest disturbance and forest recovery from disturbance. Our goal in building the model was to construct a relatively simple ecosystem model that would respond to soil and climatic heterogeneity that allows us to study of the impact of Amazonian deforestation, selective logging, and accidental fire on the global carbon cycle. This paper focuses on the net flux caused by deforestation and forest re-growth over the period from 1970-1998. We calculate that the net flux to the atmosphere during this period reached a maximum of approx. 0.35 PgC/yr (1PgC = 1 x 10(exp I5) gC) in 1990, with a cumulative release of approx. 7 PgC from 1970- 1998. The net flux is higher than predicted by an earlier study by a total of 1 PgC over the period 1989-1 998 mainly because CARLUC predicts relatively high mature forest carbon storage compared to the datasets used in the earlier study. Incorporating the dynamics of litter and soil carbon pools into the model increases the cumulative net flux by approx. 1 PgC from 1970-1998, while different assumptions about land cover dynamics only caused small changes. The uncertainty of the net flux, calculated with a Monte-Carlo approach, is roughly 35% of the mean value (1 SD).

  3. Hybrid-Like Discharges With 2/1 Flux-Pumping Due to ELM-NTM Coupling in DIII-D

    NASA Astrophysics Data System (ADS)

    King, J. D.; Lasnier, C. J.; Lanctot, M. J.; Makowski, M. A.; Holcomb, C. T.; Allen, S. L.; Meyer, W. H.; La Haye, R. J.; Petty, C. C.; Osborne, T. H.; Groebner, R. J.; Luce, T. C.; Volpe, F.; Austin, M. E.; Morse, E. C.

    2011-10-01

    Edge localized mode (ELM)-neoclassical tearing mode (NTM) coupling pumps poloidal flux from the core to the edge in hybrid discharges, contributing to flattening of the safety factor profile and avoidance of sawteeth. Direct motional Stark effect diagnostic analysis of internal magnetic field pitch angles show 2/1 NTMs exhibit stronger magnetic flux-pumping than typical hybrids, albeit at lower beta. This 2/1 flux-pumping is present during partial electron cyclotron current drive NTM suppression. This finding may lead to an alternative discharge with normalized fusion performance exceeding that required for Qfus = 10 operation in ITER. The strength of flux-pumping increases with beta and proximity of the NTM to the ELMing pedestal. Individual ELM-NTM coupling events are successfully modeled using the modified Rutherford equation (MRE). Work supported by US DOE under DE-AC52-07NA27344, DE-FC02-04ER54698, DE-FG03-97ER54415, and DE-FG03-89ER51116.

  4. Compartmental flux and in situ methods underestimate total feed nitrogen as judged by the omasal sampling method due to ignoring soluble feed nitrogen flow.

    PubMed

    Huhtanen, Pekka; Bayat, Alireza; Krizsan, Sophie J; Vanhatalo, Aila

    2014-02-01

    The objective of the present study was to estimate ruminal feed N outflow in lactating cows using the omasal sampling, compartmental flux or in situ method. A total of five ruminally fistulated Finnish Ayrshire dairy cows were used in a 5 × 5 Latin square study with 21 d periods. Experimental silages of grass or red clover harvested at two stages of maturity in addition to a supplement of 9·0 kg concentrate/d were fed to the cows. In vivo omasal N flow was determined using the omasal sampling technique. Ruminal in situ N flow was calculated from N intake and degradability (38 μm nylon bags). The samples of ruminal contents and faeces were divided into seven particle-size fractions by wet sieving; the concentrations of indigestible neutral-detergent fibre and N were used to calculate N flow in the compartmental flux method. In vivo omasal N flow was greater for the red clover silage diets than for the grass silage diets. The N flow calculated using the compartmental flux technique and that calculated using the in situ technique were highly correlated, but both were less than and poorly correlated with the in vivo N flow. In both in situ and compartmental flux techniques, forage maturity increased the particle-associated N flow, with the increase being significantly greater for the red clover diets than for the grass silage diets. In conclusion, the compartmental flux and in situ methods described the N flow associated with the particle fractions rather than the total ruminal outflow of feed N. PMID:23962678

  5. Dynamic two-axis model of a linear synchronous reluctance motor based on current and position-dependent characteristics of flux linkages

    NASA Astrophysics Data System (ADS)

    Štumberger, Gorazd; Štumberger, Bojan; Dolinar, Drago

    2006-09-01

    This paper analyses the impact of armature slotting and magnetically nonlinear and anisotropic iron core on the trajectories of a kinematically controlled linear synchronous reluctance motor (LSRM). A new magnetically nonlinear dynamic two-axis LSRM model is introduced in order to perform the analysis. The magnetic nonlinearities and slotting effects are accounted for by the current and position-dependent characteristics of flux linkages.

  6. Radial Transport Characteristics of Fast Ions Due to Energetic-Particle Modes inside the Last Closed-Flux Surface in the Compact Helical System

    SciTech Connect

    Nagaoka, Kenichi; Isobe, Mitsutaka; Toi, Kazuo; Shimizu, Akihiro; Fujisawa, Akihide; Ohshima, Shunsuke; Nakano, Haruhisa; Osakabe, Masaki; Todo, Yasushi; Akiyama, Tsuyoshi; Suzuki, Chihiro; Nishimura, Shin; Yoshimura, Yasuo; Matsuoka, Keisuke; Okamura, Shoichi; Nagashima, Yoshihiko

    2008-02-15

    The internal behavior of fast ions interacting with magnetohydrodynamic bursts excited by energetic ions has been experimentally investigated in the compact helical system. The resonant convective oscillation of fast ions was identified inside the last closed-flux surface during an energetic-particle mode (EPM) burst. The phase difference between the fast-ion oscillation and the EPM, indicating the coupling strength between them, remains a certain value during the EPM burst and drives an anomalous transport of fast ions.

  7. Orientation-dependent critical currents in Y sub 1 Ba sub 2 Cu sub 3 O sub 7-x epitaxial thin films: Evidence for intrinsic flux pinning

    SciTech Connect

    Christen, D.K.; Klabunde, C.E.; Feenstra, R.; Lowndes, D.H.; Norton, D.P.; Budai, J.D.; Kerchner, H.R.; Thompson, J.R.; Zhu, S. ); Marwick, A.D. )

    1990-01-01

    For YBCO epitaxial thin films the basal plane transport critical current density J{sub c}, flowing perpendicular to an applied magnetic field H, depends sensitively on the orientation of the crystal with respect to H. In particular, J{sub c} is sharply peaked and greatly enhanced when H is precisely parallel to the copper-oxygen planes. Experiments on a series of epitaxial monolithic and superconductor-insulator multilayer thin films provide clear evidence that the enhancement is a bulk, rather than surface or thin sample, phenomenon. Measurements of the orientation dependence are presented and compared with a model of intrinsic flux pinning'' by the layered crystal structure.

  8. Spatial Dependence of Heat Flux Transients and Wetting Behavior During Immersion Quenching of Inconel 600 Probe in Brine and Polymer Media

    NASA Astrophysics Data System (ADS)

    Ramesh, G.; Narayan Prabhu, K.

    2014-08-01

    Cooling curve analysis of Inconel 600 probe during immersion quenching in brine and polymer quench media was carried out. Thermal histories at various axial and radial locations were recorded using a high-speed data acquisition system and were input to an inverse heat-conduction model for estimating the metal/quenchant heat flux transients. A high performance smart camera was used for online video imaging of the immersion quenching process. Solution to two-dimensional inverse heat-conduction problem clearly brings out the spatial dependence of boundary heat flux transients for a Inconel 600 probe with a simple cylindrical geometry. The estimated heat flux transients show large variation on axial as well as radial directions of quench probe surface for brine quenching. Polymer quenching showed less variation in metal/quenchant heat flux transients. Shorter durations of vapor film, higher rewetting temperatures, and faster movement of wetting front on quench probe surface were observed with brine quenching. Measurement of dynamic contact angle showed better spreading and good wettability for polymer medium as compared to brine quenchant. The solid-liquid interfacial tension between polymer medium and Inconel substrate was lower compared with that of solution. Rewetting and boiling processes were nonuniform and faster on quench probe surface during immersion quenching in brine solution. For the polymer quench medium, slow rewetting, uniform boiling and repeated wetting were observed.

  9. Flow and Heat Transfer of Powell-Eyring Fluid due to an Exponential Stretching Sheet with Heat Flux and Variable Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Megahed, Ahmed M.

    2015-03-01

    An analysis was carried out to describe the problem of flow and heat transfer of Powell-Eyring fluid in boundary layers on an exponentially stretching continuous permeable surface with an exponential temperature distribution in the presence of heat flux and variable thermal conductivity. The governing partial differential equations describing the problem were transformed into a set of coupled non-linear ordinary differential equations and then solved with a numerical technique using appropriate boundary conditions for various physical parameters. The numerical solution for the governing non-linear boundary value problem is based on applying the shooting method over the entire range of physical parameters. The effects of various parameters like the thermal conductivity parameter, suction parameter, dimensionless Powell-Eyring parameters and the Prandtl number on the flow and temperature profiles as well as on the local skin-friction coefficient and the local Nusselt number are presented and discussed. In this work, special attention was given to investigate the effect of the thermal conductivity parameter on the velocity and temperature fields above the sheet in the presence of heat flux. The numerical results were also validated with results from a previously published work on various special cases of the problem, and good agreements were seen.

  10. Large increase in dissolved inorganic carbon flux from the Mississippi River to Gulf of Mexico due to climatic and anthropogenic changes over the 21st century

    NASA Astrophysics Data System (ADS)

    Ren, Wei; Tian, Hanqin; Tao, Bo; Yang, Jia; Pan, Shufen; Cai, Wei-Jun; Lohrenz, Steven E.; He, Ruoying; Hopkinson, Charles S.

    2015-04-01

    It is recognized that anthropogenic factors have had a major impact on carbon fluxes from land to the ocean during the past two centuries. However, little is known about how future changes in climate, atmospheric CO2, and land use may affect riverine carbon fluxes over the 21st century. Using a coupled hydrological-biogeochemical model, the Dynamic Land Ecosystem Model, this study examines potential changes in dissolved inorganic carbon (DIC) export from the Mississippi River basin to the Gulf of Mexico during 2010-2099 attributable to climate-related conditions (temperature and precipitation), atmospheric CO2, and land use change. Rates of annual DIC export are projected to increase by 65% under the high emission scenario (A2) and 35% under the low emission scenario (B1) between the 2000s and the 2090s. Climate-related changes along with rising atmospheric CO2 together would account for over 90% of the total increase in DIC export throughout the 21st century. The predicted increase in DIC export from the Mississippi River basin would alter chemistry of the coastal ocean unless appropriate climate mitigation actions are taken in the near future.

  11. Relative Magnitude and Controls of in Situ N2 and N2O Fluxes due to Denitrification in Natural and Seminatural Terrestrial Ecosystems Using (15)N Tracers.

    PubMed

    Sgouridis, Fotis; Ullah, Sami

    2015-12-15

    Denitrification is the most uncertain component of the nitrogen (N) cycle, hampering our ability to assess its contribution to reactive N (Nr) removal. This uncertainty emanates from the difficulty in measuring in situ soil N2 production and from the high spatiotemporal variability of the process itself. In situ denitrification was measured monthly between April 2013 and October 2014 in natural (organic and forest) and seminatural ecosystems (semi-improved and improved grasslands) in two UK catchments. Using the (15)N-gas flux method with low additions of (15)NO3(-) tracer, a minimum detectable flux rate of 4 μg N m(-2) h(-1) and 0.2 ng N m(-2) h(-1) for N2 and N2O, respectively, was achieved. Denitrification rates were lower in organic and forest (8 and 10 kg N ha(-1) y(-1), respectively) than in semi-improved and improved grassland soils (13 and 25 kg N ha(-1) y(-1), respectively). The ratio of N2O/N2 + N2O was low and ranged from <1% to 7% across the sites. Variation in denitrification was driven by differences in soil respiration, nitrate, C:N ratio, bulk density, moisture, and pH across the sites. Overall, the contribution of denitrification to Nr removal in natural ecosystems was ~50% of the annual atmospheric Nr deposition, making these ecosystems vulnerable to chronic N saturation. PMID:26509488

  12. Modified structural and frequency dependent impedance formalism of nanoscale BaTiO3 due to Tb inclusion

    NASA Astrophysics Data System (ADS)

    Borah, Manjit; Mohanta, Dambarudhar

    2016-05-01

    We report the effect of Tb-doping on the structural and high frequency impedance response of the nanoscale BaTiO3 (BT) systems. While exhibiting a mixed phase crystal structure, the nano-BT systems are found to evolve with edges, and facets. The interplanar spacing of crystal lattice fringes is ~0.25 nm. The Cole-Cole plots, in the impedance formalism, have demonstrated semicircles which are the characteristic feature of grain boundary resistance of several MΩ. A lowering of ac conductivity with doping was believed to be due to the manifestation of oxygen vacancies and vacancy ordering.

  13. Ultrasmall gold nanoparticles as carriers for nucleus-based gene therapy due to size-dependent nuclear entry.

    PubMed

    Huo, Shuaidong; Jin, Shubin; Ma, Xiaowei; Xue, Xiangdong; Yang, Keni; Kumar, Anil; Wang, Paul C; Zhang, Jinchao; Hu, Zhongbo; Liang, Xing-Jie

    2014-06-24

    The aim of this study was to determine the size-dependent penetration ability of gold nanoparticles and the potential application of ultrasmall gold nanoparticles for intranucleus delivery and therapy. We synthesized gold nanoparticles with diameters of 2, 6, 10, and 16 nm and compared their intracellular distribution in MCF-7 breast cancer cells. Nanoparticles smaller than 10 nm (2 and 6 nm) could enter the nucleus, whereas larger ones (10 and 16 nm) were found only in the cytoplasm. We then investigated the possibility of using ultrasmall 2 nm nanoparticles as carriers for nuclear delivery of a triplex-forming oligonucleotide (TFO) that binds to the c-myc promoter. Compared to free TFO, the nanoparticle-conjugated TFO was more effective at reducing c-myc RNA and c-myc protein, which resulted in reduced cell viability. Our result demonstrated that the entry of gold nanoparticles into the cell nucleus is critically dependent on the size of the nanoparticles. We developed a strategy for regulating gene expression, by directly delivering TFOs into the nucleus using ultrasmall gold nanoparticles. More importantly, guidelines were provided to choose appropriate nanocarriers for different biomedical purposes. PMID:24824865

  14. Spin-Dependent Emission from Arrays of Planar Chiral Nanoantennas Due to Lattice and Localized Plasmon Resonances.

    PubMed

    Cotrufo, Michele; Osorio, Clara I; Koenderink, A Femius

    2016-03-22

    Chiral plasmonic nanoantennas manifest a strong asymmetric response to circularly polarized light. Particularly, the geometric handedness of a plasmonic structure can alter the circular polarization state of light emitted from nearby sources, leading to a spin-dependent emission direction. In past experiments, these effects have been attributed entirely to the localized plasmonic resonances of single antennas. In this work, we demonstrate that, when chiral nanoparticles are arranged in diffractive arrays, lattice resonances play a primary role in determining the spin-dependent emission of light. We fabricate 2D diffractive arrays of planar chiral metallic nanoparticles embedded in a light-emitting dye-doped slab. By measuring the polarized photoluminescence enhancement, we show that the geometric chirality of the array's unit cell induces a preferential circular polarization, and that both the localized surface plasmon resonance and the delocalized hybrid plasmonic-photonic mode contribute to this phenomenon. By further mapping the angle-resolved degree of circular polarization, we demonstrate that strong chiral dissymmetries are mainly localized at the narrow emission directions of the surface lattice resonances. We validate these results against a coupled dipole model calculation, which correctly reproduces the main features. Our findings demonstrate that, in diffractive arrays, lattice resonances play a primary role into the light spin-orbit effect, introducing a highly nontrivial behavior in the angular spectra. PMID:26854880

  15. Deficiency in DGCR8-dependent canonical microRNAs causes infertility due to multiple abnormalities during uterine development in mice

    PubMed Central

    Kim, Yeon Sun; Kim, Hye-Ryun; Kim, Hyongbum; Yang, Seung Chel; Park, Mira; Yoon, Jung Ah; Lim, Hyunjung J.; Hong, Seok-Ho; DeMayo, Francesco J.; Lydon, John P.; Choi, Youngsok; Lee, Dong Ryul; Song, Haengseok

    2016-01-01

    DGCR8 is an RNA-binding protein that interacts with DROSHA to produce pre-microRNA in the nucleus, while DICER generates not only mature microRNA, but also endogenous small interfering RNAs in the cytoplasm. Here, we produced Dgcr8 conditional knock-out mice using progesterone receptor (PR)-Cre (Dgcr8d/d) and demonstrated that canonical microRNAs dependent on the DROSHA-DGCR8 complex are required for uterine development as well as female fertility in mice. Adult Dgcr8d/d females neither underwent regular reproductive cycles nor produced pups, whereas administration of exogenous gonadotropins induced normal ovulation in these mice. Interestingly, immune cells associated with acute inflammation aberrantly infiltrated into reproductive organs of pregnant Dgcr8d/d mice. Regarding uterine development, multiple uterine abnormalities were noticeable at 4 weeks of age when PR is significantly increased, and the severity of these deformities increased over time. Gland formation and myometrial layers were significantly reduced, and the stromal cell compartment did not expand and became atrophic during uterine development in these mice. These results were consistent with aberrantly reduced stromal cell proliferation and completely failed decidualization. Collectively, we suggest that DGCR8-dependent canonical microRNAs are essential for uterine development and physiological processes such as proper immune modulation, reproductive cycle, and steroid hormone responsiveness in mice. PMID:26833131

  16. Ultrasmall Gold Nanoparticles as Carriers for Nucleus-Based Gene Therapy Due to Size-Dependent Nuclear Entry

    PubMed Central

    2015-01-01

    The aim of this study was to determine the size-dependent penetration ability of gold nanoparticles and the potential application of ultrasmall gold nanoparticles for intranucleus delivery and therapy. We synthesized gold nanoparticles with diameters of 2, 6, 10, and 16 nm and compared their intracellular distribution in MCF-7 breast cancer cells. Nanoparticles smaller than 10 nm (2 and 6 nm) could enter the nucleus, whereas larger ones (10 and 16 nm) were found only in the cytoplasm. We then investigated the possibility of using ultrasmall 2 nm nanoparticles as carriers for nuclear delivery of a triplex-forming oligonucleotide (TFO) that binds to the c-myc promoter. Compared to free TFO, the nanoparticle-conjugated TFO was more effective at reducing c-myc RNA and c-myc protein, which resulted in reduced cell viability. Our result demonstrated that the entry of gold nanoparticles into the cell nucleus is critically dependent on the size of the nanoparticles. We developed a strategy for regulating gene expression, by directly delivering TFOs into the nucleus using ultrasmall gold nanoparticles. More importantly, guidelines were provided to choose appropriate nanocarriers for different biomedical purposes. PMID:24824865

  17. Early, H+-V-ATPase-dependent proton flux is necessary for consistent left-right patterning of non-mammalian vertebrates

    PubMed Central

    Adams, Dany S.; Robinson, Kenneth R.; Fukumoto, Takahiro; Yuan, Shipeng; Albertson, R. Craig; Yelick, Pamela; Kuo, Lindsay; McSweeney, Megan; Levin, Michael

    2011-01-01

    Biased left-right asymmetry is a fascinating and medically important phenomenon. We provide molecular genetic and physiological characterization of a novel, conserved, early, biophysical event that is crucial for correct asymmetry: H+ flux. A pharmacological screen implicated the H+-pump H+-V-ATPase in Xenopus asymmetry, where it acts upstream of early asymmetric markers. Immunohistochemistry revealed an actin-dependent asymmetry of H+-V-ATPase subunits during the first three cleavages. H+-flux across plasma membranes is also asymmetric at the four- and eight-cell stages, and this asymmetry requires H+-V-ATPase activity. Abolishing the asymmetry in H+ flux, using a dominant-negative subunit of the H+-V-ATPase or an ectopic H+ pump, randomized embryonic situs without causing any other defects. To understand the mechanism of action of H+-V-ATPase, we isolated its two physiological functions, cytoplasmic pH and membrane voltage (Vmem) regulation. Varying either pH or Vmem, independently of direct manipulation of H+-V-ATPase, caused disruptions of normal asymmetry, suggesting roles for both functions. V-ATPase inhibition also abolished the normal early localization of serotonin, functionally linking these two early asymmetry pathways. The involvement of H+-V-ATPase in asymmetry is conserved to chick and zebrafish. Inhibition of the H+-V-ATPase induces heterotaxia in both species; in chick, H+-V-ATPase activity is upstream of Shh; in fish, it is upstream of Kupffer's vesicle and Spaw expression. Our data implicate H+-V-ATPase activity in patterning the LR axis of vertebrates and reveal mechanisms upstream and downstream of its activity. We propose a pH- and Vmem-dependent model of the early physiology of LR patterning. PMID:16554361

  18. ENERGY-DEPENDENT GAMMA-RAY BURST PULSE WIDTH DUE TO THE CURVATURE EFFECT AND INTRINSIC BAND SPECTRUM

    SciTech Connect

    Peng, Z. Y.; Ma, L.; Zhao, X. H.; Yin, Y.; Bao, Y. Y.

    2012-06-20

    Previous studies have found that the width of the gamma-ray burst (GRB) pulse is energy dependent and that it decreases as a power-law function with increasing photon energy. In this work we have investigated the relation between the energy dependence of the pulse and the so-called Band spectrum by using a sample including 51 well-separated fast rise and exponential decay long-duration GRB pulses observed by BATSE (Burst and Transient Source Experiment on the Compton Gamma Ray Observatory). We first decompose these pulses into rise and decay phases and find that the rise widths and the decay widths also behave as a power-law function with photon energy. Then we investigate statistically the relations between the three power-law indices of the rise, decay, and total width of the pulse (denoted as {delta}{sub r}, {delta}{sub d}, and {delta}{sub w}, respectively) and the three Band spectral parameters, high-energy index ({alpha}), low-energy index ({beta}), and peak energy (E{sub p} ). It is found that (1) {alpha} is strongly correlated with {delta}{sub w} and {delta}{sub d} but seems uncorrelated with {delta}{sub r}; (2) {beta} is weakly correlated with the three power-law indices, and (3) E{sub p} does not show evident correlations with the three power-law indices. We further investigate the origin of {delta}{sub d}-{alpha} and {delta}{sub w}-{alpha}. We show that the curvature effect and the intrinsic Band spectrum could naturally lead to the energy dependence of the GRB pulse width and also the {delta}{sub d}-{alpha} and {delta}{sub w}-{alpha} correlations. Our results hold so long as the shell emitting gamma rays has a curved surface and the intrinsic spectrum is a Band spectrum or broken power law. The strong {delta}{sub d}-{alpha} correlation and inapparent correlations between {delta}{sub r} and the three Band spectral parameters also suggest that the rise and decay phases of the GRB pulses have different origins.

  19. RF heating due to conductive wires during MRI depends on the phase distribution of the transmit field.

    PubMed

    Yeung, Christopher J; Susil, Robert C; Atalar, Ergin

    2002-12-01

    In many studies concerning wire heating during MR imaging, a "resonant wire length" that maximizes RF heating is determined. This may lead to the nonintuitive conclusion that adding more wire, so as to avoid this resonant length, will actually improve heating safety. Through a theoretical analysis using the method of moments, we show that this behavior depends on the phase distribution of the RF transmit field. If the RF transmit field has linear phase, with slope equal to the real part of the wavenumber in the tissue, long wires always heat more than short wires. In order to characterize the intrinsic safety of a device without reference to a specific body coil design, this maximum-tip heating phase distribution must be considered. Finally, adjusting the phase distribution of the electric field generated by an RF transmit coil may lead to an "implant-friendly" coil design. PMID:12465125

  20. Statistical model of the range-dependent error in radar-rainfall estimates due to the vertical profile of reflectivity

    NASA Astrophysics Data System (ADS)

    Krajewski, Witold F.; Vignal, Bertrand; Seo, Bong-Chul; Villarini, Gabriele

    2011-05-01

    SummaryThe authors developed an approach for deriving a statistical model of range-dependent error (RDE) in radar-rainfall estimates by parameterizing the structure of the non-uniform vertical profile of radar reflectivity (VPR). The proposed parameterization of the mean VPR and its expected variations are characterized by several climatological parameters that describe dominant atmospheric conditions related to vertical reflectivity variation. We have used four years of radar volume scan data from the Tulsa weather radar WSR-88D (Oklahoma) to illustrate this approach and have estimated the model parameters by minimizing the sum of the squared differences between the modeled and observed VPR influences that were computed using radar data. We evaluated the mean and standard deviation of the modeled RDE against rain gauge data from the Oklahoma Mesonet network. No rain gauge data were used in the model development. The authors used the three lowest antenna elevation angles to demonstrate the model performance for cold (November-April) and warm (May-October) seasons. The RDE derived from the parameterized models shows very good agreement with the observed differences between radar and rain gauge estimates of rainfall. For the third elevation angle and cold season, there are 82% and 42% improvements for the RDE and its standard deviation with respect to the no-VPR case. The results of this study indicate that VPR is a key factor in the characterization of the radar range-dependent bias, and the proposed models can be used to represent the radar RDE in the absence of rain gauge data.

  1. Impairment of Atg5-Dependent Autophagic Flux Promotes Paraquat- and MPP+-Induced Apoptosis But Not Rotenone or 6-Hydroxydopamine Toxicity

    PubMed Central

    Franco, Rodrigo

    2013-01-01

    Controversial reports on the role of autophagy as a survival or cell death mechanism in dopaminergic cell death induced by parkinsonian toxins exist. We investigated the alterations in autophagic flux and the role of autophagy protein 5 (Atg5)-dependent autophagy in dopaminergic cell death induced by parkinsonian toxins. Dopaminergic cell death induced by the mitochondrial complex I inhibitors 1-methyl-4-phenylpyridinium (MPP+) and rotenone, the pesticide paraquat, and the dopamine analog 6-hydroxydopamine (6-OHDA) was paralleled by increased autophagosome accumulation. However, when compared with basal autophagy levels using chloroquine, autophagosome accumulation was a result of impaired autophagic flux. Only 6-OHDA induced an increase in autophagosome formation. Overexpression of a dominant negative form of Atg5 increased paraquat- and MPP+-induced cell death. Stimulation of mammalian target of rapamycin (mTOR)-dependent signaling protected against cell death induced by paraquat, whereas MPP+-induced toxicity was enhanced by wortmannin, a phosphoinositide 3-kinase class III inhibitor, rapamycin, and trehalose, an mTOR-independent autophagy activator. Modulation of autophagy by either pharmacological or genetic approaches had no effect on rotenone or 6-OHDA toxicity. Cell death induced by parkinsonian neurotoxins was inhibited by the pan caspase inhibitor (Z-VAD), but only caspase-3 inhibition was able to decrease MPP+-induced cell death. Finally, inhibition of the lysosomal hydrolases, cathepsins, increased the toxicity by paraquat and MPP+, supporting a protective role of Atg5-dependent autophagy and lysosomes degradation pathways on dopaminegic cell death. These results demonstrate that in dopaminergic cells, Atg5-dependent autophagy acts as a protective mechanism during apoptotic cell death induced by paraquat and MPP+ but not during rotenone or 6-OHDA toxicity. PMID:23997112

  2. Diagnostic differentiation of mild cognitive impairment due to Alzheimer's disease using a hippocampus-dependent test of spatial memory.

    PubMed

    Moodley, Kuven; Minati, Ludovico; Contarino, Valeria; Prioni, Sara; Wood, Ruth; Cooper, Rebecca; D'Incerti, Ludovico; Tagliavini, Fabrizio; Chan, Dennis

    2015-08-01

    The hippocampus is one of the earliest brain regions affected in Alzheimer's disease (AD) and tests of hippocampal function have the potential to detect AD in its earliest stages. Given that the hippocampus is critically involved in allocentric spatial memory, this study applied a short test of spatial memory, the 4 Mountains Test (4MT), to determine whether test performance can differentiate mild cognitive impairment (MCI) patients with and without CSF biomarker evidence of underlying AD and whether the test can distinguish patients with MCI and mild AD dementia when applied in different cultural settings. Healthy controls (HC), patients with MCI, and mild AD dementia were recruited from study sites in UK and Italy. Study numbers were: HC (UK 20, Italy 10), MCI (UK 21, Italy 14), and AD (UK 11, Italy 9). Nineteen UK MCI patients were grouped into CSF biomarker-positive (MCI+, n = 10) and biomarker-negative (MCI-, n = 9) subgroups. Behavioral data were correlated with hippocampal volume and cortical thickness of the precuneus and posterior cingulate gyrus. Spatial memory was impaired in both UK and Italy MCI and AD patients. Test performance additionally differentiated between MCI+ and MCI- subgroups (P = 0.001). A 4MT score of ≤8/15 was associated with 100% sensitivity and 90% specificity for detection of early AD (MCI+ and mild AD dementia) in the UK population, and with 100% sensitivity and 50% specificity for detection of MCI and AD in the Italy sample. 4MT performance correlated with hippocampal volume in the UK population and cortical thickness of the precuneus in both study populations. In conclusion, performance on a hippocampus-sensitive test of spatial memory differentiates MCI due to AD with high diagnostic sensitivity and specificity. The observation that similar diagnostic sensitivity was obtained in two separate study populations, allied to the scalability and usability of the test in community memory clinics, supports future application of the 4MT

  3. Ultrasonic Measurement of Change in Elasticity due to Endothelium Dependent Relaxation Response by Accurate Detection of Artery-Wall Boundary

    NASA Astrophysics Data System (ADS)

    Kaneko, Takuya; Hasegawa, Hideyuki; Kanai, Hiroshi

    2007-07-01

    Ross hypothesized that an endothelial dysfunction is considered to be an initial step in atherosclerosis. Endothelial cells, which release nitric oxide (NO) in response to shear stress from blood flow, have a function of relaxing smooth muscle in the media of the arterial wall. For the assessment of the endothelial function, there is a conventional method in which the change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) is measured with ultrasound. However, despite the fact that the collagen-rich hard adventitia does not respond to NO, the conventional method measures the change in diameter depending on the mechanical property of the entire wall including the adventitia. Therefore, we developed a method of measuring the change in the thickness and the elasticity of the brachial artery during a cardiac cycle using the phased tracking method for the evaluation of the mechanical property of only the intima-media region. In this study, the initial positions of echoes from the lumen-intima and media-adventitia boundaries are determined using complex template matching to accurately estimate the minute change in the thickness and the elasticity of the brachial and radial arteries. The ambiguity in the determination of such boundaries was eliminated using complex template matching, and the change in elasticity measured by the proposed method was larger than the change in inner diameter obtained by the conventional method.

  4. The velocity dependence of X-ray emission due to Charge Exchange: Applications in the Cygnus Loop

    NASA Astrophysics Data System (ADS)

    Cumbee, Renata; Lyons, David; Mullen, Patrick; Shelton, Robin L.; Stancil, Phillip C.; Schultz, David R.

    2016-04-01

    The fundamental collisional process of charge exchange (CX) has been been established as a primary source of X-ray emission from the heliosphere [1], planetary exospheres [2], and supernova remnants [3,4]. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly-excited, high charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays.To provide reliable CX-induced X-ray spectral models to realistically simulate high-energy astrophysical environments, line ratios and spectra are computed using theoretical CX cross-sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for various collisional velocities. Collisions of bare and H-like C to Al ions with H, He, and H2 are considered. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant will be shown as an example with ion velocity dependence.[1] Henley, D. B. & Shelton, R. L. 2010, ApJSS, 187, 388[2] Dennerl, K. et al. 2002, A&A 386, 319[3] Katsuda, S. et al. 2011, ApJ 730 24[4] Cumbee, R. S. et al. 2014, ApJ 787 L31

  5. Dependence of implantation sequence on surface blistering characteristics due to H and He ions co-implanted in silicon

    NASA Astrophysics Data System (ADS)

    Liang, J. H.; Hsieh, H. Y.; Wu, C. W.; Lin, C. M.

    2015-12-01

    This study investigated surface blistering characteristics due to H and He ions co-implanted in silicon at room temperature. The H and He ion energies were 40 and 50 keV, respectively, so that their depth profiles were similar. The total implantation fluence for the H and He ions was 5 × 1016 cm-2 under various fluence fractions in the H ions. The implantation sequences under investigation were He + H and H + He. Dynamic optical microscopy (DOM) was employed in order to dynamically analyze surface blistering characteristics. This study used DOM data to construct so-called time-temperature-transformation (T-T-T) curves to easily predict blistering and crater transformation at specific annealing times and temperatures. The results revealed that the curves of blister initialization, crater initialization, and crater completion in the He + H implant occurred at a lower annealing temperature but with a longer annealing time compared to those in the H + He implant. Furthermore, the threshold annealing temperatures for blister and crater formation in the He + H implant were lower than they were in the H + He implant. The size distributions of the blisters and craters in the He + H implant extended wider than those in the H + He implant. In addition, the He + H implant exhibited larger blisters and craters compared to the ones in the H + He implant. Since the former has a higher percentage of exfoliation area than the latter, it is regarded as the more optimal implantation sequence.

  6. The genotypic and phenotypic spectrum of pyridoxine-dependent epilepsy due to mutations in ALDH7A1

    PubMed Central

    Scharer, Gunter; Brocker, Chad; Vasiliou, Vasilis; Creadon-Swindell, Geralyn; Gallagher, Renata C.; Spector, Elaine

    2011-01-01

    Pyridoxine-dependent epilepsy is a disorder associated with severe seizures that may be caused by deficient activity of α-aminoadipic semialdehyde dehydrogenase, encoded by the ALDH7A1 gene, with accumulation of α-aminoadipic semialdehyde and piperideine-6-carboxylic acid. The latter reacts with pyridoxal-phosphate, explaining the effective treatment with pyridoxine. We report the clinical phenotype of three patients, their mutations and those of 12 additional patients identified in our clinical molecular laboratory. There were six missense, one nonsense, and five splice-site mutations, and two small deletions. Mutations c.1217_1218delAT, I431F, IVS-1(+2)T>G, IVS-2(+1)G>A, and IVS-12(+1)G>A are novel. Some disease alleles were recurring: E399Q (eight times), G477R (six times), R82X (two times), and c.1217_1218delAT (two times). A systematic review of mutations from the literature indicates that missense mutations cluster around exons 14, 15, and 16. Nine mutations represent 61% of alleles. Molecular modeling of missense mutations allows classification into three groups: those that affect NAD+binding or catalysis, those that affect the substrate binding site, and those that affect multimerization. There are three clinical phenotypes: patients with complete seizure control with pyridoxine and normal developmental outcome (group 1) including our first patient; patients with complete seizure control with pyridoxine but with developmental delay (group 2), including our other two patients; and patients with persistent seizures despite pyridoxine treatment and with developmental delay (group 3). There is preliminary evidence for a genotype-phenotype correlation with patients from group 1 having mutations with residual activity. There is evidence from patients with similar genotypes for nongenetic factors contributing to the phenotypic spectrum. PMID:20814824

  7. Light and Nutrient Dependent Responses in Secondary Metabolites of Plantago lanceolata Offspring Are Due to Phenotypic Plasticity in Experimental Grasslands

    PubMed Central

    Miehe-Steier, Annegret; Roscher, Christiane; Reichelt, Michael; Gershenzon, Jonathan; Unsicker, Sybille B.

    2015-01-01

    A few studies in the past have shown that plant diversity in terms of species richness and functional composition can modify plant defense chemistry. However, it is not yet clear to what extent genetic differentiation of plant chemotypes or phenotypic plasticity in response to diversity-induced variation in growth conditions or a combination of both is responsible for this pattern. We collected seed families of ribwort plantain (Plantago lanceolata) from six-year old experimental grasslands of varying plant diversity (Jena Experiment). The offspring of these seed families was grown under standardized conditions with two levels of light and nutrients. The iridoid glycosides, catalpol and aucubin, and verbascoside, a caffeoyl phenylethanoid glycoside, were measured in roots and shoots. Although offspring of different seed families differed in the tissue concentrations of defensive metabolites, plant diversity in the mothers' environment did not explain the variation in the measured defensive metabolites of P. lanceolata offspring. However secondary metabolite levels in roots and shoots were strongly affected by light and nutrient availability. Highest concentrations of iridoid glycosides and verbascoside were found under high light conditions, and nutrient availability had positive effects on iridoid glycoside concentrations in plants grown under high light conditions. However, verbascoside concentrations decreased under high levels of nutrients irrespective of light. The data from our greenhouse study show that phenotypic plasticity in response to environmental variation rather than genetic differentiation in response to plant community diversity is responsible for variation in secondary metabolite concentrations of P. lanceolata in the six-year old communities of the grassland biodiversity experiment. Due to its large phenotypic plasticity P. lanceolata has the potential for a fast and efficient adjustment to varying environmental conditions in plant communities of

  8. Linear MHD Wave Propagation in Time-Dependent Flux Tube. III. Leaky Waves in Zero-Beta Plasma

    NASA Astrophysics Data System (ADS)

    Williamson, A.; Erdélyi, R.

    2016-01-01

    In this article, we evaluate the time-dependent wave properties and the damping rate of propagating fast magneto-hydrodynamic (MHD) waves when energy leakage into a magnetised atmosphere is considered. By considering a cold plasma, initial investigations into the evolution of MHD wave damping through this energy leakage will take place. The time-dependent governing equations have been derived previously in Williamson and Erdélyi (2014a, Solar Phys. 289, 899 - 909) and are now solved when the assumption of evanescent wave propagation in the outside of the waveguide is relaxed. The dispersion relation for leaky waves applicable to a straight magnetic field is determined in both an arbitrary tube and a thin-tube approximation. By analytically solving the dispersion relation in the thin-tube approximation, the explicit expressions for the temporal evolution of the dynamic frequency and wavenumber are determined. The damping rate is, then, obtained from the dispersion relation and is shown to decrease as the density ratio increases. By comparing the decrease in damping rate to the increase in damping for a stationary system, as shown, we aim to point out that energy leakage may not be as efficient a damping mechanism as previously thought.

  9. Fermentation of Xylose Causes Inefficient Metabolic State Due to Carbon/Energy Starvation and Reduced Glycolytic Flux in Recombinant Industrial Saccharomyces cerevisiae

    PubMed Central

    Matsushika, Akinori; Nagashima, Atsushi; Goshima, Tetsuya; Hoshino, Tamotsu

    2013-01-01

    In the present study, comprehensive, quantitative metabolome analysis was carried out on the recombinant glucose/xylose-cofermenting S. cerevisiae strain MA-R4 during fermentation with different carbon sources, including glucose, xylose, or glucose/xylose mixtures. Capillary electrophoresis time-of-flight mass spectrometry was used to determine the intracellular pools of metabolites from the central carbon pathways, energy metabolism pathways, and the levels of twenty amino acids. When xylose instead of glucose was metabolized by MA-R4, glycolytic metabolites including 3- phosphoglycerate, 2- phosphoglycerate, phosphoenolpyruvate, and pyruvate were dramatically reduced, while conversely, most pentose phosphate pathway metabolites such as sedoheptulose 7- phosphate and ribulose 5-phosphate were greatly increased. These results suggest that the low metabolic activity of glycolysis and the pool of pentose phosphate pathway intermediates are potential limiting factors in xylose utilization. It was further demonstrated that during xylose fermentation, about half of the twenty amino acids declined, and the adenylate/guanylate energy charge was impacted due to markedly decreased adenosine triphosphate/adenosine monophosphate and guanosine triphosphate/guanosine monophosphate ratios, implying that the fermentation of xylose leads to an inefficient metabolic state where the biosynthetic capabilities and energy balance are severely impaired. In addition, fermentation with xylose alone drastically increased the level of citrate in the tricarboxylic acid cycle and increased the aromatic amino acids tryptophan and tyrosine, strongly supporting the view that carbon starvation was induced. Interestingly, fermentation with xylose alone also increased the synthesis of the polyamine spermidine and its precursor S-adenosylmethionine. Thus, differences in carbon substrates, including glucose and xylose in the fermentation medium, strongly influenced the dynamic metabolism of MA-R4

  10. Fermentation of xylose causes inefficient metabolic state due to carbon/energy starvation and reduced glycolytic flux in recombinant industrial Saccharomyces cerevisiae.

    PubMed

    Matsushika, Akinori; Nagashima, Atsushi; Goshima, Tetsuya; Hoshino, Tamotsu

    2013-01-01

    In the present study, comprehensive, quantitative metabolome analysis was carried out on the recombinant glucose/xylose-cofermenting S. cerevisiae strain MA-R4 during fermentation with different carbon sources, including glucose, xylose, or glucose/xylose mixtures. Capillary electrophoresis time-of-flight mass spectrometry was used to determine the intracellular pools of metabolites from the central carbon pathways, energy metabolism pathways, and the levels of twenty amino acids. When xylose instead of glucose was metabolized by MA-R4, glycolytic metabolites including 3- phosphoglycerate, 2- phosphoglycerate, phosphoenolpyruvate, and pyruvate were dramatically reduced, while conversely, most pentose phosphate pathway metabolites such as sedoheptulose 7- phosphate and ribulose 5-phosphate were greatly increased. These results suggest that the low metabolic activity of glycolysis and the pool of pentose phosphate pathway intermediates are potential limiting factors in xylose utilization. It was further demonstrated that during xylose fermentation, about half of the twenty amino acids declined, and the adenylate/guanylate energy charge was impacted due to markedly decreased adenosine triphosphate/adenosine monophosphate and guanosine triphosphate/guanosine monophosphate ratios, implying that the fermentation of xylose leads to an inefficient metabolic state where the biosynthetic capabilities and energy balance are severely impaired. In addition, fermentation with xylose alone drastically increased the level of citrate in the tricarboxylic acid cycle and increased the aromatic amino acids tryptophan and tyrosine, strongly supporting the view that carbon starvation was induced. Interestingly, fermentation with xylose alone also increased the synthesis of the polyamine spermidine and its precursor S-adenosylmethionine. Thus, differences in carbon substrates, including glucose and xylose in the fermentation medium, strongly influenced the dynamic metabolism of MA-R4

  11. Estimates of net infiltration in arid basins and potential impacts on recharge and solute flux due to land use and vegetation change

    NASA Astrophysics Data System (ADS)

    Robertson, Wendy Marie; Sharp, John M.

    2015-03-01

    Human impacts on land use and vegetation in arid basins have, in some regions, altered infiltration, recharge, and groundwater chemistry. However, some modeling approaches currently used do not account for these effects. In the Trans-Pecos region of Texas the presence of modern water, increasing groundwater NO3- concentrations, and vadose zone cores flushed of naturally accumulated solutes belie the notion that basin groundwater is unaffected by overlying land use and vegetation change. Recharge to the Trans-Pecos basins is spatially and temporally variable, and due to human impacts it has likely changed since pre-western settlement time (circa 1850s). By using the INFIL 3.0.1 model, a spatially distributed model of net infiltration, the volume and spatial distribution of net infiltration was examined for two basins, Wild Horse/Michigan Flats and Lobo/Ryan Flats, with model simulations designed to examine the effects of irrigated agriculture and human impacts on vegetation. Model results indicate that recharge to the basins is not limited to mountain-front zones and discrete features (i.e., alluvial channels), rather, irrigation return flow contributes an estimated 6.3 × 107 m3 (408 mm) of net infiltration over 40 yrs and net infiltration on the basin floors could contribute between 7% and 11.5% of annual basin recharge. Model results also indicate that net infiltration may be higher under current vegetation regimes than in pre-western settlement conditions; the removal of thick dense grasslands in INFIL model simulations enhanced net infiltration by 48% or more. Results from distributed models (like INFIL) improve upon scientific understanding of the links between vegetation regime and hydrological processes; this is important for the sustainable management of arid basin aquifers in Texas and elsewhere.

  12. Limits to solar cycle predictability: Cross-equatorial flux plumes

    NASA Astrophysics Data System (ADS)

    Cameron, R. H.; Dasi-Espuig, M.; Jiang, J.; Işık, E.; Schmitt, D.; Schüssler, M.

    2013-09-01

    Context. Within the Babcock-Leighton framework for the solar dynamo, the strength of a cycle is expected to depend on the strength of the dipole moment or net hemispheric flux during the preceding minimum, which depends on how much flux was present in each hemisphere at the start of the previous cycle and how much net magnetic flux was transported across the equator during the cycle. Some of this transport is associated with the random walk of magnetic flux tubes subject to granular and supergranular buffeting, some of it is due to the advection caused by systematic cross-equatorial flows such as those associated with the inflows into active regions, and some crosses the equator during the emergence process. Aims: We aim to determine how much of the cross-equatorial transport is due to small-scale disorganized motions (treated as diffusion) compared with other processes such as emergence flux across the equator. Methods: We measure the cross-equatorial flux transport using Kitt Peak synoptic magnetograms, estimating both the total and diffusive fluxes. Results: Occasionally a large sunspot group, with a large tilt angle emerges crossing the equator, with flux from the two polarities in opposite hemispheres. The largest of these events carry a substantial amount of flux across the equator (compared to the magnetic flux near the poles). We call such events cross-equatorial flux plumes. There are very few such large events during a cycle, which introduces an uncertainty into the determination of the amount of magnetic flux transported across the equator in any particular cycle. As the amount of flux which crosses the equator determines the amount of net flux in each hemisphere, it follows that the cross-equatorial plumes introduce an uncertainty in the prediction of the net flux in each hemisphere. This leads to an uncertainty in predictions of the strength of the following cycle.

  13. Pancreatic islet function in omega-3 fatty acid-depleted rats: alteration of calcium fluxes and calcium-dependent insulin release.

    PubMed

    Zhang, Y; Oguzhan, B; Louchami, K; Chardigny, J-M; Portois, L; Carpentier, Y A; Malaisse, W J; Herchuelz, A; Sener, A

    2006-09-01

    Considering the insufficient supply of long-chain polyunsaturated omega-3 fatty acids often prevailing in Western populations, this report deals mainly with alterations of Ca(2+) fluxes and Ca(2+)-dependent insulin secretory events in isolated pancreatic islets from omega-3-depleted rats. In terms of (45)Ca(2+) handling, the islets from omega-3-depleted rats, compared with those from normal animals, displayed an unaltered responsiveness to an increase in extracellular K(+) concentration, a lower inflow rate and lower fractional outflow rate of the divalent cation, and higher (45)Ca(2+)-labeled cellular pool(s) at isotopic equilibrium. The latter anomaly was corrected 120 min after intravenous injection of a novel medium-chain triglyceride-fish oil (MCT:FO) emulsion, distinct from a control omega-3-poor MCT-olive oil (MCT:OO) emulsion. At 8.3 mM D-glucose, insulin release was higher in islets from omega-3-depleted rats vs. control animals, coinciding with a higher cytosolic Ca(2+) concentration. The relative magnitude of the increase in insulin output attributable to a rise in D-glucose as well as extracellular Ca(2+) or K(+) concentration, to the absence vs. presence of verapamil and to the presence vs. absence of extracellular Ca(2+), theophylline, phorbol 12-myristate 13-acetate, or Ba(2+), was always more pronounced in islets from omega-3-depleted rats injected with the MCT:OO compared with the MCT:FO emulsion. A comparable situation prevailed when comparing islets from noninjected omega-3-depleted and normal rats. In light of these and previous findings, we propose that an impairment of Na(+),K(+)-ATPase activity plays a major, although not an exclusive, role in the perturbation of Ca(2+) fluxes and Ca(2+)-dependent secretory events in the islets from omega-3-depleted rats. PMID:16912059

  14. Reconnecting Flux Ropes

    NASA Astrophysics Data System (ADS)

    Gekelman, Walter; van Compernolle, Bart

    2012-10-01

    Magnetic flux ropes are due to helical currents and form a dense carpet of arches on the surface of the sun. Occasionally one tears loose as a coronal mass ejection and its rope structure is detected by satellites close to the earth. Current sheets can tear into filaments and these are nothing other than flux ropes. Ropes are not static, they exert mutual JxB forces causing them to twist about each other and merge. Kink instabilities cause them to violently smash into each other and reconnect at the point of contact. We report on experiments done in the large plasma device (LAPD) at UCLA (L=17m,dia=60cm,0.3<=B0z<=2.5kG,n˜2x10^12cm-3)on three dimensional flux ropes. Two, three or more magnetic flux ropes are generated from initially adjacent pulsed current channels in a background magnetized plasma. The currents and magnetic fields form exotic shapes with no ignorable direction and no magnetic nulls. Volumetric space-time data show multiple reconnection sites with time-dependent locations. The concept of a quasi-separatrix layer (QSL), a tool to understand 3D reconnection without null points. In our experiment the QSL is a narrow ribbon-like region(s) that twists between field lines. Within the QSL(s) field lines that start close to one another rapidly diverge as they pass through one or more reconnection regions. When the field lines are tracked they are observed to slip along the QSL when reconnection occurs. The Heating and other co-existing waves will be presented.

  15. RETRACTION: Unsteady flow and heat transfer of viscous incompressible fluid with temperature-dependent viscosity due to a rotating disc in a porous medium

    NASA Astrophysics Data System (ADS)

    Attia, H. A.

    2007-04-01

    It has come to the attention of the Institute of Physics that this article should not have been submitted for publication owing to its plagiarism of an earlier paper (Hossain A, Hossain M A and Wilson M 2001 Unsteady flow of viscous incompressible fluid with temperature-dependent viscosity due to a rotating disc in presence of transverse magnetic field and heat transfer Int. J. Therm. Sci. 40 11-20). Therefore this article has been retracted by the Institute of Physics and by the author, Hazem Ali Attia.

  16. Heat flux viscosity in collisional magnetized plasmas

    SciTech Connect

    Liu, C.; Fox, W.; Bhattacharjee, A.

    2015-05-15

    Momentum transport in collisional magnetized plasmas due to gradients in the heat flux, a “heat flux viscosity,” is demonstrated. Even though no net particle flux is associated with a heat flux, in a plasma there can still be momentum transport owing to the velocity dependence of the Coulomb collision frequency, analogous to the thermal force. This heat-flux viscosity may play an important role in numerous plasma environments, in particular, in strongly driven high-energy-density plasma, where strong heat flux can dominate over ordinary plasma flows. The heat flux viscosity can influence the dynamics of the magnetic field in plasmas through the generalized Ohm's law and may therefore play an important role as a dissipation mechanism allowing magnetic field line reconnection. The heat flux viscosity is calculated directly using the finite-difference method of Epperlein and Haines [Phys. Fluids 29, 1029 (1986)], which is shown to be more accurate than Braginskii's method [S. I. Braginskii, Rev. Plasma Phys. 1, 205 (1965)], and confirmed with one-dimensional collisional particle-in-cell simulations. The resulting transport coefficients are tabulated for ease of application.

  17. Heat flux viscosity in collisional magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Liu, C.; Fox, W.; Bhattacharjee, A.

    2015-05-01

    Momentum transport in collisional magnetized plasmas due to gradients in the heat flux, a "heat flux viscosity," is demonstrated. Even though no net particle flux is associated with a heat flux, in a plasma there can still be momentum transport owing to the velocity dependence of the Coulomb collision frequency, analogous to the thermal force. This heat-flux viscosity may play an important role in numerous plasma environments, in particular, in strongly driven high-energy-density plasma, where strong heat flux can dominate over ordinary plasma flows. The heat flux viscosity can influence the dynamics of the magnetic field in plasmas through the generalized Ohm's law and may therefore play an important role as a dissipation mechanism allowing magnetic field line reconnection. The heat flux viscosity is calculated directly using the finite-difference method of Epperlein and Haines [Phys. Fluids 29, 1029 (1986)], which is shown to be more accurate than Braginskii's method [S. I. Braginskii, Rev. Plasma Phys. 1, 205 (1965)], and confirmed with one-dimensional collisional particle-in-cell simulations. The resulting transport coefficients are tabulated for ease of application.

  18. Analysis of the uncertainties associated with the age-dependent thyroid doses and risk of thyroid cancer due to exposure to {sup 131}I

    SciTech Connect

    Hoffman, F.O.; Apostoaei, A.I.; Nair, S.K.

    1996-06-01

    Effects on the thyroid gland due to exposure to {sup 131}I are currently of interest for ongoing retrospective studies of historical releases in Oak Ridge, Tennessee, and Hanford, Washington. Most of the work to date has been limited to dose estimation. This work focuses on estimating both dose and risk of thyroid cancer to an exposed individual. The age-dependent thyroid dose is calculated using a standard metabolic model for iodine. Updated information on thyroid mass from measurements using modem ultrasound techniques was used. The age-dependent risk is calculated using a linear excess relative risk model. An analysis of uncertainties in dose and risk estimates was performed for an individual in a population characterized by the mass of thyroid, by the iodine metabolic parameters, by the background incidence of thyroid cancer and by the excess relative risk per Gy of absorbed dose. The uncertainty analysis was performed using Monte-Carlo simulation, by considering the age-dependent parameters as random functions. The correlation between the metabolic age-dependent parameters was considered explicitly. Special attention is given to a modifying factor that accounts for the effectiveness of {sup 131}I in inducing thyroid cancer as compared to gamma irradiation, for which most of the excess risk factors are derived. This factor is based on review of recent literature and on informal interviews with outside experts, and thus, the expressed uncertainty is subjective in nature. The paper summarizes the age-dependent dose conversion factors (Sv Bq{sup -1}) and slope factors (risk Bq{sup -1}) as well as the uncertainty associated with them. An analysis that identifies the parameters of dominant importance by their contributions to the overall uncertainty is also included.

  19. Time-dependent convection models of mantle thermal structure constrained by seismic tomography and geodynamics: implications for mantle plume dynamics and CMB heat flux

    NASA Astrophysics Data System (ADS)

    Glišović, P.; Forte, A. M.; Moucha, R.

    2012-08-01

    surface plates and a rigid surface. The thermal interpretation of seismic tomography models does not provide a radial profile of the horizontally averaged temperature (i.e. the geotherm) in the mantle. One important goal of this study is to obtain a steady-state geotherm with boundary layers which satisfies energy balance of the system and provides the starting point for more realistic numerical simulations of the Earth's evolution. We obtain surface heat flux in the range of Earth-like values : 37 TW for a rigid surface and 44 TW for a surface with tectonic plates coupled to the mantle flow. Also, our convection simulations deliver CMB heat flux that is on the high end of previously estimated values, namely 13 TW and 20 TW, for rigid and plate-like surface boundary conditions, respectively. We finally employ these two end-member surface boundary conditions to explore the very-long-time scale evolution of convection over billion-year time windows. These billion-year-scale simulations will allow us to determine the extent to which a 'memory' of the starting tomography-based thermal structure is preserved and hence to explore the longevity of the structures in the present-day mantle. The two surface boundary conditions, along with the geodynamically inferred radial viscosity profiles, yield steady-state convective flows that are dominated by long wavelengths throughout the lower mantle. The rigid-surface condition yields a spectrum of mantle heterogeneity dominated by spherical harmonic degree 3 and 4, and the plate-like surface condition yields a pattern dominated by degree 1. Our exploration of the time-dependence of the spatial heterogeneity shows that, for both types of surface boundary condition, deep-mantle hot upwellings resolved in the present-day tomography model are durable and stable features. These deeply rooted mantle plumes show remarkable longevity over very long geological time spans, mainly owing to the geodynamically inferred high viscosity in the lower

  20. Kinetics of olfactory responses might largely depend on the odorant-receptor interaction and the odorant deactivation postulated for flux detectors.

    PubMed

    Kaissling, Karl-Ernst

    2013-11-01

    Experimental data together with modeling of pheromone perireceptor and receptor events in moths (Bombyx mori, Antheraea polyphemus) suggest that the kinetics of olfactory receptor potentials largely depend on the association of the odorant with the neuronal receptor molecules and the deactivation of the odorant accumulated around the receptor neuron. The first process could be responsible for the reaction times (mean about 400 ms) of the nerve impulses at threshold. The second process has been postulated for flux detectors such as olfactory sensilla of moths. The odorant deactivation could involve a modification of the pheromone-binding protein (PBP) that "locks" the pheromone inside the inner binding cavity of the protein. The model combines seemingly contradictory functions of the PBP such as pheromone transport, protection of the pheromone from enzymatic degradation, pheromone deactivation, and pheromone-receptor interaction. Model calculations reveal a density of at least 6,000 receptor molecules per µm(2) of neuronal membrane. The volatile decanoyl-thio-1,1,1-trifluoropropanone specifically blocks pheromone receptor neurons, probably when bound to the PBP and by competitive binding to the receptor molecules. The shallow dose-response curve of the receptor potential and altered response properties observed with pheromone derivatives or after adaptation may indicate shortened opening of ion channels. PMID:23563709

  1. Flux attenuation at NREL's High-Flux Solar Furnace

    NASA Astrophysics Data System (ADS)

    Bingham, Carl E.; Scholl, Kent L.; Lewandowski, Allan A.

    1994-10-01

    The High-Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory (NREL) has a faceted primary concentrator and a long focal-length-to-diameter ratio (due to its off-axis design). Each primary facet can be aimed individually to produce different flux distributions at the target plane. Two different types of attenuators are used depending on the flux distribution. A sliding-plate attenuator is used primarily when the facets are aimed at the same target point. The alternate attenuator resembles a venetian blind. Both attenuators are located between the concentrator and the focal point. The venetian-blind attenuator is primarily used to control the levels of sunlight failing on a target when the primary concentrators are not focused to a single point. This paper will demonstrate the problem of using the sliding-plate attenuator with a faceted concentrator when the facets are not aimed at the same target point. We will show that although the alternate attenuator necessarily blocks a certain amount of incoming sunlight, even when fully open, it provides a more even attenuation of the flux for alternate aiming strategies.

  2. Possible involvement of CD10 in the development of endometriosis due to its inhibitory effects on CD44-dependent cell adhesion.

    PubMed

    Iwase, Akira; Kotani, Tomomi; Goto, Maki; Kobayashi, Hiroharu; Takikawa, Sachiko; Nakahara, Tatsuo; Nakamura, Tomoko; Kondo, Mika; Bayasula; Nagatomo, Yoshinari; Kikkawa, Fumitaka

    2014-01-01

    A reduced response to progesterone in the eutopic endometrium with endometriosis and in endometriotic tissues is considered to be the underlying factor for endometriosis. CD10 is known to be expressed by endometrial and endometriotic stromal cells and may be induced by progestins, although the function of CD10 is not fully revealed in endometrial or endometriotic tissues. In the current study, the expression of CD10 was significantly increased by treatment of the cells with progesterone, 17β-estradiol, and dibutyryl cyclic adenosine monophosphate (cAMP) in the endometrial stromal cells. On the other hand, the expression of CD10 following treatment with progesterone, 17β-estradiol, and dibutyryl cAMP was not significantly increased in endometriotic stromal cells. The adhesion assay for endometrial and endometriotic stromal cells to hyaluronan using 5- or 6-(N-succinimidyloxycarbonyl)-fluorescein 3', 6'-diacetate-labeled cells demonstrated that the CD44-dependent adhesion of stromal cells was inhibited by CD10. As far as the induction of CD10 is concerned, the effect of progesterone was different between endometrial stromal cells and endometriotic stromal cells. CD10 might be involved in the development of endometriosis due to its influence on CD44-dependent cell adhesion. PMID:23653392

  3. PIP2-dependent coupling is prominent in Kv7.1 due to weakened interactions between S4-S5 and S6

    NASA Astrophysics Data System (ADS)

    Kasimova, Marina A.; Zaydman, Mark A.; Cui, Jianmin; Tarek, Mounir

    2015-01-01

    Among critical aspects of voltage-gated potassium (Kv) channels' functioning is the effective communication between their two composing domains, the voltage sensor (VSD) and the pore. This communication, called coupling, might be transmitted directly through interactions between these domains and, as recently proposed, indirectly through interactions with phosphatidylinositol-4,5-bisphosphate (PIP2), a minor lipid of the inner plasma membrane leaflet. Here, we show how the two components of coupling, mediated by protein-protein or protein-lipid interactions, both contribute in the Kv7.1 functioning. On the one hand, using molecular dynamics simulations, we identified a Kv7.1 PIP2 binding site that involves residues playing a key role in PIP2-dependent coupling. On the other hand, combined theoretical and experimental approaches have shown that the direct interaction between the segments of the VSD (S4-S5) and the pore (S6) is weakened by electrostatic repulsion. Finally, we conclude that due to weakened protein-protein interactions, the PIP2-dependent coupling is especially prominent in Kv7.1.

  4. PIP₂-dependent coupling is prominent in Kv7.1 due to weakened interactions between S4-S5 and S6.

    PubMed

    Kasimova, Marina A; Zaydman, Mark A; Cui, Jianmin; Tarek, Mounir

    2015-01-01

    Among critical aspects of voltage-gated potassium (Kv) channels' functioning is the effective communication between their two composing domains, the voltage sensor (VSD) and the pore. This communication, called coupling, might be transmitted directly through interactions between these domains and, as recently proposed, indirectly through interactions with phosphatidylinositol-4,5-bisphosphate (PIP₂), a minor lipid of the inner plasma membrane leaflet. Here, we show how the two components of coupling, mediated by protein-protein or protein-lipid interactions, both contribute in the Kv7.1 functioning. On the one hand, using molecular dynamics simulations, we identified a Kv7.1 PIP₂ binding site that involves residues playing a key role in PIP₂-dependent coupling. On the other hand, combined theoretical and experimental approaches have shown that the direct interaction between the segments of the VSD (S4-S5) and the pore (S6) is weakened by electrostatic repulsion. Finally, we conclude that due to weakened protein-protein interactions, the PIP2-dependent coupling is especially prominent in Kv7.1. PMID:25559286

  5. PIP2-dependent coupling is prominent in Kv7.1 due to weakened interactions between S4-S5 and S6

    PubMed Central

    Kasimova, Marina A.; Zaydman, Mark A.; Cui, Jianmin; Tarek, Mounir

    2015-01-01

    Among critical aspects of voltage-gated potassium (Kv) channels' functioning is the effective communication between their two composing domains, the voltage sensor (VSD) and the pore. This communication, called coupling, might be transmitted directly through interactions between these domains and, as recently proposed, indirectly through interactions with phosphatidylinositol-4,5-bisphosphate (PIP2), a minor lipid of the inner plasma membrane leaflet. Here, we show how the two components of coupling, mediated by protein-protein or protein-lipid interactions, both contribute in the Kv7.1 functioning. On the one hand, using molecular dynamics simulations, we identified a Kv7.1 PIP2 binding site that involves residues playing a key role in PIP2-dependent coupling. On the other hand, combined theoretical and experimental approaches have shown that the direct interaction between the segments of the VSD (S4–S5) and the pore (S6) is weakened by electrostatic repulsion. Finally, we conclude that due to weakened protein-protein interactions, the PIP2-dependent coupling is especially prominent in Kv7.1. PMID:25559286

  6. Osteopetrorickets due to Snx10 Deficiency in Mice Results from Both Failed Osteoclast Activity and Loss of Gastric Acid-Dependent Calcium Absorption

    PubMed Central

    Ye, Liang; Morse, Leslie R.; Zhang, Li; Sasaki, Hajime; Mills, Jason C.; Odgren, Paul R.; Sibbel, Greg; Stanley, James R. L.; Wong, Gee; Zamarioli, Ariane; Battaglino, Ricardo A.

    2015-01-01

    Mutations in sorting nexin 10 (Snx10) have recently been found to account for roughly 4% of all human malignant osteopetrosis, some of them fatal. To study the disease pathogenesis, we investigated the expression of Snx10 and created mouse models in which Snx10 was knocked down globally or knocked out in osteoclasts. Endocytosis is severely defective in Snx10-deficent osteoclasts, as is extracellular acidification, ruffled border formation, and bone resorption. We also discovered that Snx10 is highly expressed in stomach epithelium, with mutations leading to high stomach pH and low calcium solubilization. Global Snx10-deficiency in mice results in a combined phenotype: osteopetrosis (due to osteoclast defect) and rickets (due to high stomach pH and low calcium availability, resulting in impaired bone mineralization). Osteopetrorickets, the paradoxical association of insufficient mineralization in the context of a positive total body calcium balance, is thought to occur due to the inability of the osteoclasts to maintain normal calcium–phosphorus homeostasis. However, osteoclast-specific Snx10 knockout had no effect on calcium balance, and therefore led to severe osteopetrosis without rickets. Moreover, supplementation with calcium gluconate rescued mice from the rachitic phenotype and dramatically extended life span in global Snx10-deficient mice, suggesting that this may be a life-saving component of the clinical approach to Snx10-dependent human osteopetrosis that has previously gone unrecognized. We conclude that tissue-specific effects of Snx10 mutation need to be considered in clinical approaches to this disease entity. Reliance solely on hematopoietic stem cell transplantation can leave hypocalcemia uncorrected with sometimes fatal consequences. These studies established an essential role for Snx10 in bone homeostasis and underscore the importance of gastric acidification in calcium uptake. PMID:25811986

  7. The energy dependence of the cosmic-ray neutron leakage flux in the range 0.01-10 MeV.

    NASA Technical Reports Server (NTRS)

    Jenkins, R. W.; Ifedili, S. O.; Lockwood, J. A.; Razdan, H.

    1971-01-01

    Measurement of the cosmic-ray neutron leakage flux and energy spectrum in the range 1 to 10 MeV by a neutron detector on the Ogo 6 satellite from June 7 to Sept. 30, 1969. The same detector simultaneously measured the total leakage flux, having 75% of its response to the leakage flux in the interval from 1 keV to 1 MeV. For a neutron energy spectrum of the form AE to the minus gamma in the range from 1 to 10 MeV, the upper limit to gamma for polar regions was found to be 1.0 and for the equatorial regions was 1.2. For the polar regions, the lower limit to gamma was found to be 0.8. This energy spectrum at 1 to 10 MeV is slightly flatter than Newkirk (1963) predicted.

  8. O2-dependent K+ fluxes in trout red blood cells: the nature of O2 sensing revealed by the O2 affinity, cooperativity and pH dependence of transport

    PubMed Central

    Berenbrink, Michael; Völkel, Susanne; Heisler, Norbert; Nikinmaa, Mikko

    2000-01-01

    The effects of pH and O2 tension on the isotonic ouabain-resistant K+ (Rb+) flux pathway and on haemoglobin O2 binding were studied in trout red blood cells (RBCs) in order to test for a direct effect of haemoglobin O2 saturation on K+ transport across the RBC membrane. At pH values corresponding to in vivo control arterial plasma pH and higher, elevation of the O2 partial pressure (PO2) from 7.8 to 157 mmHg increased unidirectional K+ influx across the RBC membrane several-fold. At lower extracellular pH values, stimulation of K+ influx by O2 was depressed, exhibiting an apparent pKa (pK′a) for the process of 8.0. Under similar conditions the pK′a for acid-induced deoxygenation of haemoglobin (Hb) was 7.3. When trout RBCs were exposed to PO2 values between 0 and 747 mmHg, O2 equilibrium curves typical of Hb O2 saturation were also obtained for K+ influx and efflux. However, at pH 7.9, the PO2 for half-maximal K+ efflux and K+ influx (P50) was about 8- to 12-fold higher than the P50 for Hb-O2 binding. While K+ influx and efflux stimulation by O2 was essentially non-cooperative, Hb-O2 equilibrium curves were distinctly sigmoidal (Hill parameters close to 1 and 3, respectively). O2-stimulated K+ influx and efflux were strongly pH dependent. When the definition of the Bohr factor for respiratory pigments (Φ =ΔlogP50×ΔpH−1) was extended to the effect of pH on O2-dependent K+ influx and efflux, extracellular Bohr factors (Φo) of -2.00 and -2.06 were obtained, values much higher than that for Hb (Φo = -0.49). The results of this study are consistent with an O2 sensing mechanism differing markedly in affinity and cooperativity of O2 binding, as well as in pH sensitivity, from bulk Hb. PMID:10878100

  9. Video Meteor Fluxes

    NASA Technical Reports Server (NTRS)

    Campbell-Brown, M. D.; Braid, D.

    2011-01-01

    estimate the flux (Love & Brownlee, 1993); here the physical area of the detector is well known, but the masses depend strongly on the unknown velocity distribution. In the same size range, Thomas & Netherway (1989) used the narrow-beam radar at Jindalee to calculate the flux of sporadics. In between these very large and very small sizes, a number of video and photographic observations were reduced by Ceplecha (2001). These fluxes were calculated (details are given in Ceplecha, 1988) taking the Halliday et al. (1984) MORP fireball fluxes, slightly corrected in mass, as a calibration, and adjusting the flux of small cameras to overlap with the number/mass relation from that work.

  10. EFFECTS OF ULTRAVIOLET-B IRRADIANCE ON SOYBEAN. V. THE DEPENDENCE OF PLANT SENSITIVITY ON THE PHOTOSYNTHETIC PHOTON FLUX DENSITY DURING AND AFTER LEAF EXPANSION

    EPA Science Inventory

    Soybeans (Glycine max (L.) Merr. cv Essex) were grown in a green house, and the first trifoliate leaf was either allowed to expand under a high photosynthetic photon flux density (PPFD) (1.4 millimoled per square meter per second) or a low PPFD (0.8 Millimoles per square meter pe...

  11. Fluxes of Ultrafine Particles Over and In a Deciduous Forest

    NASA Astrophysics Data System (ADS)

    Pryor, S. C.; Hornsby, K. E.

    2013-12-01

    Given the importance of forests to land surface cover and particle removal (due to the very high deposition velocities and well-developed turbulence) there is a specific need to understand removal to, and in, forests. Fluxes of size-resolved and total particle number fluxes over (at 46 m) and in (at 7 m) a deciduous forest over a 14 month period are presented based on data from two Gill 3-D WindMaster Pro sonic anemometers, an Ultrafine Condensation Particle Counter (UCPC) operated at 10 Hz and a Fast Mobility Particle Sizer (FMPS) operated at 1 Hz. Size-resolved particle profiles during the same period are measured using a separate FMPS scanning at three measurement heights across the canopy (top, middle and bottom). Three methods are being applied to derive the total number and size-resolved fluxes from the UCPC and FMPS respectively; eddy covariance, inertial dissipation and the co-spectral approach. The results are integrated with fluxes of sensible heat, momentum and carbon dioxide derived using a Licor LI-7200. Results for the total number flux concentrations and the size-resolved concentrations derived using the three different approaches applied to the above canopy sampling level show a high degree of accord, but that the eddy-covariance fluxes are generally of smaller magnitude than those derived using the spectral methods. In keeping with prior research our results show a considerable number of fluxes are characterized by upward fluxes. Further our results show distinctly different flux diurnal profiles for the nucleation versus Aitken mode particles indicating some differential control on fluxes of particles of different sizes (including a role for aerosol dynamics). This presentation will provide details regarding the experimental approach, flux and gradient estimation methodologies, diagnose the size dependence of the fluxes, and compare and contrast the canopy and ground partitioning of the particle fluxes during leaf-on and leaf-off periods.

  12. Study of the rotational-level and temperature dependence of the quenching rate of OH fluorescence due to collisions with water molecules

    NASA Technical Reports Server (NTRS)

    Koker, Edmond B.

    1995-01-01

    The importance of the OH radical as an intermediate in many combustion reactions and in atmospheric photochemistry has led many researchers to use it as a diagnostic tool in these processes. The amount of data that has been acquired over the years for this radical is quite considerable. However, the quenching rate of OH with water molecules as a function of temperature and the rotational level of the excited state is not very well understood. The motivation of the studies undertaken is to bridge the gap between the low temperature measurements and the high temperature ones reported in the literature. The technique generally employed in these diagnostics is laser-induced fluorescence (LIF), through which rotational state selective excitation of the radical is possible. Furthermore, in a combustion medium, water is produced in abundance so that knowledge of the quenching rate of OH due to water molecules plays a crucial role in interpreting the data. In general, the precursor to an understanding of the collisional quenching rates of OH involves a characterization of the mode in which the radical is produced; the resulting rotational and translational distribution, followed by a measurement of the OH temperature; and ultimately obtaining the rate constants from the pressure dependence of the fluorescence signal. The experimental implementation of these measurements therefore involved, as a first step, the production of the OH radicals in a microwave discharge cell using water vapor as the source, wherein a hydrogen atom is abstracted from H2O. The second step involved the absorption of photons from the frequency-doubled output of a pulsed amplified, single-frequency cw ring dye laser. By tuning the laser to the peak of the transition and observing the fluorescence decay after the laser pulse, the lifetime of the OH in a particular rotational electronic state was determined (tau = 1.4 microseconds for Q(sub 1)(3)). Knowledge of this parameter led to a determination of

  13. Loss of E-cadherin-dependent cell-cell adhesion due to mutation of the beta-catenin gene in a human cancer cell line, HSC-39.

    PubMed Central

    Kawanishi, J; Kato, J; Sasaki, K; Fujii, S; Watanabe, N; Niitsu, Y

    1995-01-01

    Detachment of cell-cell adhesion is indispensable for the first step of invasion and metastasis of cancer. This mechanism is frequently associated with the impairment of either E-cadherin expression or function. However, mechanisms of such abnormalities have not been fully elucidated. In this study, we demonstrated that the function of E-cadherin was completely abolished in the human gastric cancer cell line HSC-39, despite the high expression of E-cadherin, because of mutations in one of the E-cadherin-associated cytoplasmic proteins, beta-catenin. Although immunofluorescence staining of HSC-39 cells by using an anti-E-cadherin antibody (HECD-1) revealed the strong and uniform expression of E-cadherin on the cell surface, cell compaction and cell aggregation were not observed in this cell. Western blotting (immunoblotting) using HECD-1 exhibited a 120-kDa band which is equivalent to normal E-cadherin. Northern (RNA) blotting demonstrated a 4.7-kb band, the same as mature E-cadherin mRNA. Immunoprecipitation of metabolically labeled proteins with HECD-1 revealed three bands corresponding to E-cadherin, alpha-catenin, and gamma-catenin and a 79-kDa band which was apparently smaller than that of normal beta-catenin, indicating truncated beta-catenin. The 79-kDa band was immunologically identified as beta-catenin by using immunoblotting with anti-beta-catenin antibodies. Examination of beta-catenin mRNA by the reverse transcriptase-PCR method revealed a transcript which was shorter than that of normal beta-catenin. The sequencing of PCR product for beta-catenin confirmed deletion in 321 bases from nucleotides +82 to +402. Southern blotting of beta-catenin DNA disclosed mutation at the genomic level. Expression vectors of Beta-catenin were introduced into HSC-39 cells by transfection. In the obtained transfectants, E-cadherin-dependent cell-cell adhesiveness was recovered, as revealed by cell compaction, cell aggregation, and immunoflourescence staining. From these

  14. Temperature Dependence of Behavior of Interface Between Molten Sn and LiCl-KCl Eutectic Melt Due to Rising Gas Bubble

    NASA Astrophysics Data System (ADS)

    Natsui, Shungo; Nashimoto, Ryota; Takai, Hifumi; Kumagai, Takehiko; Kikuchi, Tatsuya; Suzuki, Ryosuke O.

    2016-06-01

    The behavior of the interface between molten Sn and the LiCl-KCl eutectic melt system was observed directly. We found that the transient behavior of the interface exhibits considerable temperature dependence through a change in its physical properties. The "metal film" generated in the upper molten salt phase significantly influences the shape of the interface. Although the lifetime of the metal film depends on the gas flow rate, it is not affected by the buoyancy if the interfacial tension is dominant.

  15. Muon and neutrino fluxes

    NASA Technical Reports Server (NTRS)

    Edwards, P. G.; Protheroe, R. J.

    1985-01-01

    The result of a new calculation of the atmospheric muon and neutrino fluxes and the energy spectrum of muon-neutrinos produced in individual extensive air showers (EAS) initiated by proton and gamma-ray primaries is reported. Also explained is the possibility of detecting atmospheric nu sub mu's due to gamma-rays from these sources.

  16. Topological A-type models with flux

    NASA Astrophysics Data System (ADS)

    Stojevic, Vid

    2008-05-01

    We study deformations of the A-model in the presence of fluxes, by which we mean rank-three tensors with antisymmetrized upper/lower indices, using the AKSZ construction. There are two natural deformations of the A-model in the AKSZ language: 1) the Zucchini model, which can be defined on a generalized complex manifold and reduces to the A-model when the generalized complex structure comes from a symplectic structure, and 2) a topological membrane model, which naturally accommodates fluxes, and reduces to the Zucchini model on the boundary of the membrane when the fluxes are turned off. We show that the fluxes are related to deformations of the Courant bracket which generalize the twist by a closed 3-from H, in the sense that satisfying the AKSZ master equation implies precisely the integrability conditions for an almost generalized complex structure with respect to the deformed Courant bracket. In addition, the master equation imposes conditions on the fluxes that generalize dH = 0. The membrane model can be defined on a large class of U(m)- and U(m) × U(m)-structure manifolds relevant for string theory, including geometries inspired by (1, 1) supersymmetric σ-models with additional supersymmetries due to almost complex (but not necessarily complex) structures in the target space. In addition we show that the model can be defined on three particular half-flat manifolds related to the Iwasawa manifold. When only the closed 3-form flux is turned on it is possible to obtain a topological string model, which we do for the case of a Calabi-Yau. We argue that deformations from the standard A-model are due to the choice of gauge fixing fermion, rather than a flux deformation of the AKSZ action. The particularly interesting cases arise when the fermion depends on auxiliary fields, the simplest possibility being due to the (2, 0)+(0, 2) component of a non-trivial b-field. The model is generically no longer evaluated on holomorphic maps and defines new topological

  17. Dependence of the flux-creep activation energy on current density and magnetic field for a Ca10(Pt3As8)[(Fe1-xPtx)2As2]5 single crystal

    NASA Astrophysics Data System (ADS)

    Ge, J.; Gutierrez, J.; Li, J.; Yuan, J.; Wang, H.-B.; Yamaura, K.; Takayama-Muromachi, E.; Moshchalkov, V. V.

    2014-03-01

    We have performed detailed ac susceptibility measurements to investigate the vortex dynamics in a Ca10(Pt3As8)[(Fe1-xPtx)2As2]5 single crystal as a function of temperature, frequency, ac amplitude, and dc field. The field dependence of the activation energy U is derived in the framework of thermally activated flux creep theory, yielding a power law dependence of U ˜ Hα with α ≈ -1.0 for H above 0.30 T, while below 0.3 T U is independent of the field. The activation energy reaches 104 K at low fields, suggesting strong pinning in the material. The nonlinear function of the activation energy vs. the current density is determined, which shows logarithmic dependence U(J)∝lnJ.

  18. Retinoic Acid Induced-Autophagic Flux Inhibits ER-Stress Dependent Apoptosis and Prevents Disruption of Blood-Spinal Cord Barrier after Spinal Cord Injury

    PubMed Central

    Zhou, Yulong; Zhang, Hongyu; Zheng, Binbin; Ye, Libing; Zhu, Sipin; Johnson, Noah R; Wang, Zhouguang; Wei, Xiaojie; Chen, Daqing; Cao, Guodong; Fu, Xiaobing; Li, Xiaokun; Xu, Hua-Zi; Xiao, Jian

    2016-01-01

    Spinal cord injury (SCI) induces the disruption of the blood-spinal cord barrier (BSCB) which leads to infiltration of blood cells, an inflammatory response, and neuronal cell death, resulting spinal cord secondary damage. Retinoic acid (RA) has a neuroprotective effect in both ischemic brain injury and SCI, however the relationship between BSCB disruption and RA in SCI is still unclear. In this study, we demonstrated that autophagy and ER stress are involved in the protective effect of RA on the BSCB. RA attenuated BSCB permeability and decreased the loss of tight junction (TJ) molecules such as P120, β-catenin, Occludin and Claudin5 after injury in vivo as well as in Brain Microvascular Endothelial Cells (BMECs). Moreover, RA administration improved functional recovery in the rat model of SCI. RA inhibited the expression of CHOP and caspase-12 by induction of autophagic flux. However, RA had no significant effect on protein expression of GRP78 and PDI. Furthermore, combining RA with the autophagy inhibitor chloroquine (CQ) partially abolished its protective effect on the BSCB via exacerbated ER stress and subsequent loss of tight junctions. Taken together, the neuroprotective role of RA in recovery from SCI is related to prevention of of BSCB disruption via the activation of autophagic flux and the inhibition of ER stress-induced cell apoptosis. These findings lay the groundwork for future translational studies of RA for CNS diseases, especially those related to BSCB disruption. PMID:26722220

  19. Angular dependence of the flux pinning for YBa{sub 2}Cu{sub 3}O{sub y}/PrBa{sub 2}Cu{sub 3}O{sub y} superlattice

    SciTech Connect

    Horng, H.E.; Wu, J.M.; Yang, H.C.

    1997-06-01

    The angular dependence of the magnetic relaxation for YBa{sub 2}Cu{sub 3}O{sub y}/PrBa{sub 2}Cu{sub 3}O{sub y} (YBCO/PBCO) superlattice was measured under magnetic field to investigate the flux pinning. The applied magnetic field was 0.1 Tesla. The direction of the applied magnetic field makes an angle of 10{degrees}, 20{degrees}, 30{degrees}, 45{degrees}... with the c-axis of YBCO/PBCO superlattice. Based on the Anderson-Kim model the authors derive the pinning energy of this film. The pinning energy is angular independent. The results are discussed.

  20. Hysteretic Dependence of Magnetic Flux Density on Primary AC Current in Flat-Type Inductive Fault Current Limiter with YBCO Thin Film Discs

    NASA Astrophysics Data System (ADS)

    Harada, Masayuki; Yokomizu, Yasunobu; Matsumura, Toshiro

    2014-05-01

    This paper focuses on a flat-type inductive superconducting FCL (FIS-FCL) consisting of a pancake coil and a YBCO thin layer disc. AC current injection experiments and magnetic field analysis were carried out for two kinds of FIS-FCL, single-disc model and double-discs model. In the former, the pancake coil was putted on the YBCO disc. In the latter, the pancake coil was sandwiched with two YBCO discs. The double-discs model cancels out the magnetic flux density more effectively than the single-disc model. In the double-discs model, the superconducting state period is longer than in the single-disc model. Thus, it may be concluded that the double-discs model is considered to be suitable for FIS-FCL.

  1. Rotation dependence of a phase delay between plasma edge electron density and temperature fields due to a fast rotating, resonant magnetic perturbation field

    SciTech Connect

    Stoschus, H.; Schmitz, O.; Frerichs, H.; Unterberg, B.; Abdullaev, S. S.; Clever, M.; Coenen, J. W.; Kruezi, U.; Schega, D.; Samm, U.; Jakubowski, M. W.

    2010-06-15

    Measurements of the plasma edge electron density n{sub e} and temperature T{sub e} fields during application of a fast rotating, resonant magnetic perturbation (RMP) field show a characteristic modulation of both, n{sub e} and T{sub e} coherent to the rotation frequency of the RMP field. A phase delay PHI between the n{sub e}(t) and T{sub e}(t) waveforms is observed and it is demonstrated that this phase delay PHI is a function of the radius with PHI(r) depending on the relative rotation of the RMP field and the toroidal plasma rotation. This provides for the first time direct experimental evidence for a rotation dependent damping of the external RMP field in the edge layer of a resistive high-temperature plasma which breaks down at low rotation and high resonant field amplitudes.

  2. Ocean Winds and Turbulent Air-Sea Fluxes Inferred From Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bourassa, Mark A.; Gille, Sarah T.; Jackson, Daren L.; Roberts, J. Brent; Wick, Gary A.

    2010-01-01

    Air-sea turbulent fluxes determine the exchange of momentum, heat, freshwater, and gas between the atmosphere and ocean. These exchange processes are critical to a broad range of research questions spanning length scales from meters to thousands of kilometers and time scales from hours to decades. Examples are discussed (section 2). The estimation of surface turbulent fluxes from satellite is challenging and fraught with considerable errors (section 3); however, recent developments in retrievals (section 3) will greatly reduce these errors. Goals for the future observing system are summarized in section 4. Surface fluxes are defined as the rate per unit area at which something (e.g., momentum, energy, moisture, or CO Z ) is transferred across the air/sea interface. Wind- and buoyancy-driven surface fluxes are called surface turbulent fluxes because the mixing and transport are due to turbulence. Examples of nonturbulent processes are radiative fluxes (e.g., solar radiation) and precipitation (Schmitt et al., 2010). Turbulent fluxes are strongly dependent on wind speed; therefore, observations of wind speed are critical for the calculation of all turbulent surface fluxes. Wind stress, the vertical transport of horizontal momentum, also depends on wind direction. Stress is very important for many ocean processes, including upper ocean currents (Dohan and Maximenko, 2010) and deep ocean currents (Lee et al., 2010). On short time scales, this horizontal transport is usually small compared to surface fluxes. For long-term processes, transport can be very important but again is usually small compared to surface fluxes.

  3. Magnetic flux tube tunneling

    SciTech Connect

    Dahlburg, R.B.; Antiochos, S.K.; Norton, D.

    1997-08-01

    We present numerical simulations of the collision and subsequent interaction of {ital orthogonal} magnetic flux tubes. The simulations were carried out using a parallelized spectral algorithm for compressible magnetohydrodynamics. It is found that, under a wide range of conditions, the flux tubes can {open_quotes}tunnel{close_quotes} through each other, a behavior not previously seen in studies of either vortex tube or magnetic flux tube interactions. Two conditions must be satisfied for tunneling to occur: the magnetic field must be highly twisted with a field line pitch {gt}1, and the Lundquist number must be somewhat large, {ge}2880. An examination of magnetic field lines suggests that tunneling is due to a double-reconnection mechanism. Initially orthogonal field lines reconnect at two specific locations, exchange interacting sections, and {open_quotes}pass{close_quotes} through each other. The implications of these results for solar and space plasmas are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  4. Superradiance and flux conservation

    NASA Astrophysics Data System (ADS)

    Boonserm, Petarpa; Ngampitipan, Tritos; Visser, Matt

    2014-09-01

    The theoretical foundations of the phenomenon known as superradiance still continue to attract considerable attention. Despite many valiant attempts at pedagogically clear presentations, the effect nevertheless still continues to generate some significant confusion. Part of the confusion arises from the fact that superradiance in a quantum field theory context is not the same as superradiance (superfluorescence) in some condensed matter contexts; part of the confusion arises from traditional but sometimes awkward normalization conventions, and part is due to sometimes unnecessary confusion between fluxes and probabilities. We shall argue that the key point underlying the effect is flux conservation (and, in the presence of dissipation, a controlled amount of flux nonconservation), and that attempting to phrase things in terms of reflection and transmission probabilities only works in the absence of superradiance. To help clarify the situation we present a simple exactly solvable toy model exhibiting both superradiance and damping.

  5. Magnetic flux tube tunneling

    NASA Astrophysics Data System (ADS)

    Dahlburg, R. B.; Antiochos, S. K.; Norton, D.

    1997-08-01

    We present numerical simulations of the collision and subsequent interaction of orthogonal magnetic flux tubes. The simulations were carried out using a parallelized spectral algorithm for compressible magnetohydrodynamics. It is found that, under a wide range of conditions, the flux tubes can ``tunnel'' through each other, a behavior not previously seen in studies of either vortex tube or magnetic flux tube interactions. Two conditions must be satisfied for tunneling to occur: the magnetic field must be highly twisted with a field line pitch >>1, and the Lundquist number must be somewhat large, >=2880. An examination of magnetic field lines suggests that tunneling is due to a double-reconnection mechanism. Initially orthogonal field lines reconnect at two specific locations, exchange interacting sections, and ``pass'' through each other. The implications of these results for solar and space plasmas are discussed.

  6. Nerve growth factor-mediated inhibition of apoptosis post-caspase activation is due to removal of active caspase-3 in a lysosome-dependent manner

    PubMed Central

    Mnich, K; Carleton, L A; Kavanagh, E T; Doyle, K M; Samali, A; Gorman, A M

    2014-01-01

    Nerve growth factor (NGF) is well characterised as an important pro-survival factor in neuronal cells that can inhibit apoptotic cell death upstream of mitochondrial outer membrane permeabilisation. Here we addressed the question of whether NGF can also protect against apoptosis downstream of caspase activation. NGF treatment promoted a rapid reduction in the level of the p17 subunit of active caspase-3 in PC12 cells that had been induced to undergo apoptosis by various cytotoxins. The mechanism involved TrkA-dependent activation of extracellular signal-regulated kinase (ERK1/2) but not phosphatidylinositol 3-kinase (PI3K)/Akt, and de novo protein synthesis. Involvement of inhibitor of apoptosis proteins (IAPs) and proteasomal degradation were ruled out. In contrast, inhibition of lysosome function using chloroquine and concanamycin A reversed NGF-induced removal of p17. Moreover, in NGF-treated cells, active caspases were found to be localised to lysosomes. The involvement of macroautophagy and chaperone-mediated autophagy were ruled out. Taken together, these findings suggest an anti-apoptotic mechanism by which NGF induces removal of active caspase-3 in a lysosome-dependent manner. PMID:24787014

  7. Increased furfural tolerance due to overexpression of NADH-dependent oxidoreductase FucO in Escherichia coli strains engineered for the production of ethanol and lactate.

    PubMed

    Wang, X; Miller, E N; Yomano, L P; Zhang, X; Shanmugam, K T; Ingram, L O

    2011-08-01

    Furfural is an important fermentation inhibitor in hemicellulose sugar syrups derived from woody biomass. The metabolism of furfural by NADPH-dependent oxidoreductases, such as YqhD (low K(m) for NADPH), is proposed to inhibit the growth and fermentation of xylose in Escherichia coli by competing with biosynthesis for NADPH. The discovery that the NADH-dependent propanediol oxidoreductase (FucO) can reduce furfural provided a new approach to improve furfural tolerance. Strains that produced ethanol or lactate efficiently as primary products from xylose were developed. These strains included chromosomal mutations in yqhD expression that permitted the fermentation of xylose broths containing up to 10 mM furfural. Expression of fucO from plasmids was shown to increase furfural tolerance by 50% and to permit the fermentation of 15 mM furfural. Product yields with 15 mM furfural were equivalent to those of control strains without added furfural (85% to 90% of the theoretical maximum). These two defined genetic traits can be readily transferred to enteric biocatalysts designed to produce other products. A similar strategy that minimizes the depletion of NADPH pools by native detoxification enzymes may be generally useful for other inhibitory compounds in lignocellulosic sugar streams and with other organisms. PMID:21685167

  8. Vorticity flux from active dimples

    NASA Astrophysics Data System (ADS)

    McKeon, Beverley; Sherwin, Spencer; Morrison, Jonathan

    2004-11-01

    The effect of surface depressions, or dimples, in reducing drag on golf balls is well-known. Here this concept is extended to using ``active" dimples to manipulate vorticity flux at the wall. Surface vorticity flux is governed by surface accelerations, pressure and shear stress gradients, and surface curvature. ``Active" (or vibrating) dimples may generate vorticity flux by each of these terms, making them an excellent candidate for a basic study of flux manipulation, by which flow control may be achieved. Flow over an active dimple in fully-developed laminar channel flow is simulated with velocity boundary conditions developed from a linearized perturbation method imposed at the wall. This simple model cannot capture flow separation, but gives insight into the most straightforward means of flux generation from the concave surface. Vorticity flux due to dimple geometry and motion is quantified, and enhancements of two to three orders of magnitude in peak vorticity over the static dimple case are observed.

  9. The epithelial polarity regulator LGALS9/galectin-9 induces fatal frustrated autophagy in KRAS mutant colon carcinoma that depends on elevated basal autophagic flux

    PubMed Central

    Wiersma, Valerie R; de Bruyn, Marco; Wei, Yunwei; van Ginkel, Robert J; Hirashima, Mitsuomi; Niki, Toshiro; Nishi, Nozomu; Zhou, Jin; Pouwels, Simon D; Samplonius, Douwe F; Nijman, Hans W; Eggleton, Paul; Helfrich, Wijnand; Bremer, Edwin

    2015-01-01

    Oncogenic mutation of KRAS (Kirsten rat sarcoma viral oncogene homolog) in colorectal cancer (CRC) confers resistance to both chemotherapy and EGFR (epidermal growth factor receptor)-targeted therapy. We uncovered that KRAS mutant (KRASmut) CRC is uniquely sensitive to treatment with recombinant LGALS9/Galectin-9 (rLGALS9), a recently established regulator of epithelial polarity. Upon treatment of CRC cells, rLGALS9 rapidly internalizes via early- and late-endosomes and accumulates in the lysosomal compartment. Treatment with rLGALS9 is accompanied by induction of frustrated autophagy in KRASmut CRC, but not in CRC with BRAF (B-Raf proto-oncogene, serine/threonine kinase) mutations (BRAFmut). In KRASmut CRC, rLGALS9 acts as a lysosomal inhibitor that inhibits autophagosome-lysosome fusion, leading to autophagosome accumulation, excessive lysosomal swelling and cell death. This antitumor activity of rLGALS9 directly correlates with elevated basal autophagic flux in KRASmut cancer cells. Thus, rLGALS9 has potent antitumor activity toward refractory KRASmut CRC cells that may be exploitable for therapeutic use. PMID:26086204

  10. Photosynthetic acclimation to drought stress in Agave salmiana Otto ex Salm-Dyck seedlings is largely dependent on thermal dissipation and enhanced electron flux to photosystem I.

    PubMed

    Campos, Huitziméngari; Trejo, Carlos; Peña-Valdivia, Cecilia B; García-Nava, Rodolfo; Conde-Martínez, F Víctor; Cruz-Ortega, Ma Del Rocío

    2014-10-01

    Agave salmiana Otto ex Salm-Dyck, a crassulacean acid metabolism plant that is adapted to water-limited environments, has great potential for bioenergy production. However, drought stress decreases the requirement for light energy, and if the amount of incident light exceeds energy consumption, the photosynthetic apparatus can be injured, thereby limiting plant growth. The objective of this study was to evaluate the effects of drought and re-watering on the photosynthetic efficiency of A. salmiana seedlings. The leaf relative water content and leaf water potential decreased to 39.6 % and -1.1 MPa, respectively, over 115 days of water withholding and recovered after re-watering. Drought caused a direct effect on photosystem II (PSII) photochemistry in light-acclimated leaves, as indicated by a decrease in the photosynthetic electron transport rate. Additionally, down-regulation of photochemical activity occurred mainly through the inactivation of PSII reaction centres and an increased thermal dissipation capacity of the leaves. Prompt fluorescence kinetics also showed a larger pool of terminal electron acceptors in photosystem I (PSI) as well as an increase in some JIP-test parameters compared to controls, reflecting an enhanced efficiency and specific fluxes for electron transport from the plastoquinone pool to the PSI terminal acceptors. All the above parameters showed similar levels after re-watering. These results suggest that the thermal dissipation of excess energy and the increased energy conservation from photons absorbed by PSII to the reduction of PSI end acceptors may be an important acclimation mechanism to protect the photosynthetic apparatus from over-excitation in Agave plants. PMID:24798124

  11. Surface Turbulent Fluxes Over Pack Ice Inferred from TOVS Observations

    NASA Technical Reports Server (NTRS)

    Lindsay, R. W.; Francis, J. A.; Persson, P. O. G.; Rothrock, D. A.; Schweiger, A. J.

    1996-01-01

    A one-dimensional, atmospheric boundary layer model is coupled to a thermodynamic ice model to estimate the surface turbulent fluxes over thick sea ice. The principal forcing parameters in this time-dependent model are the air temperature, humidity, and wind speed at a specified level (either at 2 m or at 850 mb) and the downwelling surface radiative fluxes. The free parameters. are the air temperature, humidity, and wind speed profiles below the specified level, the surface skin temperature, the ice temperature profile, and the surface turbulent fluxes. The goal is to determine how well we can estimate the turbulent surface heat and momentum fluxes using forcing parameters from atmospheric temperatures and radiative fluxes retrieved from the TIROS-N Operational Vertical Sounder (TOVS) data. Meteorological observations from the Lead Experiment (LeadEx, April 1992) ice camp are used to validate turbulent fluxes computed with the surface observations and the results are used to compare with estimates based on radio-sonde observations or with estimates based on TOVS data. We find that the TOVS-based estimates of the stress are significantly more accurate than those found with a constant geostrophic drag coefficient, with a root-mean-square error about half as large. This improvement is due to stratification effects included in the boundary layer model. The errors in the sensible heat flux estimates, however, are large compared to the small mean values observed during the field experiment.

  12. Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages

    PubMed Central

    Caughlin, T. Trevor; Ferguson, Jake M.; Lichstein, Jeremy W.; Zuidema, Pieter A.; Bunyavejchewin, Sarayudh; Levey, Douglas J.

    2015-01-01

    Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now. PMID:25392471

  13. Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages.

    PubMed

    Caughlin, T Trevor; Ferguson, Jake M; Lichstein, Jeremy W; Zuidema, Pieter A; Bunyavejchewin, Sarayudh; Levey, Douglas J

    2015-01-01

    Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now. PMID:25392471

  14. The analgesic and anti-inflammatory effects of shark cartilage are due to a peptide molecule and are nitric oxide (NO) system dependent.

    PubMed

    Fontenele, J B; Araújo, G B; de Alencar, J W; Viana, G S

    1997-11-01

    The present work shows an antinociceptive and dose-dependent effect of shark cartilage hydrosoluble fraction (HF) on writhing and formalin tests in mice. The effect was not altered by thalidomide, a known inhibitor of tumor necrosis factor-alfa (TNF-alfa) synthesis. Similarly, the antinociceptive effect did not change in the presence of naloxone, indicating that the opioid system is not involved. However, the effect observed was blocked by L-arginine, a NO synthesis substrate, and it was potentiated by L-NAME, suggesting a role of the NO system in the shark cartilage antinociceptive effect. Effects similar to those seen with the HF were detected with peak II from gel filtration chromatography. The increase in vascular permeability induced by serotonin in rats was significantly abolished by the HF at the dose of 2 mg/kg, p.o., and again it was not potentiated by thalidomide. The observed blockade in the vascular permeability increase induced by histamine was detected only with a higher dose (10 mg/kg, p.o.). PMID:9401722

  15. On the optimization, and the intensity dependence, of the excitation rate for the absorption of two-photons due to the direct permanent dipole moment excitation mechanism

    NASA Astrophysics Data System (ADS)

    Meath, William J.

    2016-07-01

    A model two-level dipolar molecule, and the rotating wave approximation and perturbation theory, are used to investigate the optimization and the laser intensity dependence of the two-photon excitation rate via the direct permanent dipole mechanism. The rate is proportional to the square of the laser intensity I only for small intensities and times when perturbation theory is applicable. An improvement on perturbation theory is provided by a small time RWA result for the rate which is not proportional to I2; rather it is proportional to the square of an effective intensity Ieff. For each laser intensity the optimum RWA excitation rate as a function of time, for low intensities, is proportional to I, not I2, and for high intensities it is proportional to Ieff. For a given two-photon transition the laser-molecule coupling optimizes for an intensity Imax which, for example, leads to a maximum possible excitation rate as a function of time. The validity of the RWA results of this paper, and the importance of including the effects of virtual excited states, are also discussed briefly.

  16. Ion fluence dependence of the total sputtering yield and differential angular sputtering yield of bismuth due to 50 keV argon ion irradiation

    NASA Astrophysics Data System (ADS)

    Deoli, Naresh T.; Phinney, Lucas C.; Weathers, Duncan L.

    2014-08-01

    The dependences of the total sputtering yield of Bi and the differential angular distribution of these sputtered Bi atoms on the fluence of 50 keV Ar+ ions at normal incidence have been experimentally measured. Polycrystalline Bi targets were used for these purposes. The collector technique and accurate current integration methods were adopted for the determination of angular distributions of sputtered Bi atoms. The ion fluence was varied from 1.9 × 1019 to 3.1 × 1020 ions/cm2. The sputtered atoms were collected on high purity aluminum foils under ultra-high vacuum (∼5 × 10-9 Torr). The collector foils were subsequently analyzed using heavy ion Rutherford backscattering spectroscopy. The shape of the angular distribution of sputtered atoms was found not to change significantly with the fluence, but the sputtering yield increased significantly from 2.2 ± 0.2 to 9.6 ± 0.6 atoms/ion over the fluence range studied.

  17. Spatial decoupling of agricultural production and consumption: quantifying dependences of countries on food imports due to domestic land and water constraints

    NASA Astrophysics Data System (ADS)

    Fader, Marianela; Gerten, Dieter; Krause, Michael; Lucht, Wolfgang; Cramer, Wolfgang

    2013-03-01

    In our globalizing world, the geographical locations of food production and consumption are becoming increasingly disconnected, which increases reliance on external resources and their trade. We quantified to what extent water and land constraints limit countries’ capacities, at present and by 2050, to produce on their own territory the crop products that they currently import from other countries. Scenarios of increased crop productivity and water use, cropland expansion (excluding areas prioritized for other uses) and population change are accounted for. We found that currently 16% of the world population use the opportunities of international trade to cover their demand for agricultural products. Population change may strongly increase the number of people depending on ex situ land and water resources up to about 5.2 billion (51% of world population) in the SRES A2r scenario. International trade will thus have to intensify if population growth is not accompanied by dietary change towards less resource-intensive products, by cropland expansion, or by productivity improvements, mainly in Africa and the Middle East. Up to 1.3 billion people may be at risk of food insecurity in 2050 in present low-income economies (mainly in Africa), if their economic development does not allow them to afford productivity increases, cropland expansion and/or imports from other countries.

  18. NEUTRON FLUX INTENSITY DETECTION

    DOEpatents

    Russell, J.T.

    1964-04-21

    A method of measuring the instantaneous intensity of neutron flux in the core of a nuclear reactor is described. A target gas capable of being transmuted by neutron bombardment to a product having a resonance absorption line nt a particular microwave frequency is passed through the core of the reactor. Frequency-modulated microwave energy is passed through the target gas and the attenuation of the energy due to the formation of the transmuted product is measured. (AEC)

  19. Heterotic Calabi-Yau compactifications with flux

    NASA Astrophysics Data System (ADS)

    Klaput, Michael; Lukas, Andre; Svanes, Eirik E.

    2013-09-01

    Compactifications of the heterotic string with NS flux normally require non Calabi-Yau internal spaces which are complex but no longer Kähler. We point out that this conclusion rests on the assumption of a maximally symmetric four-dimensional space-time and can be avoided if this assumption is relaxed. Specifically, it is shown that an internal Calabi-Yau manifold is consistent with the presence of NS flux provided four-dimensional space-time is taken to be a domain wall. These Calabi-Yau domain wall solutions can still be associated with a covariant four-dimensional N = 1 supergravity. In this four-dimensional context, the domain wall arises as the "simplest" solution to the effective supergravity due to the presence of a flux potential with a runaway direction. Our main message is that NS flux is a legitimate ingredient for moduli stabilisation in heterotic Calabi-Yau models. Ultimately, the success of such models depends on the ability to stabilise the runaway direction and thereby "lift" the domain wall to a maximally supersymmetric vacuum.

  20. Protein kinase C is increased in the liver of humans and rats with non-insulin-dependent diabetes mellitus: an alteration not due to hyperglycemia.

    PubMed Central

    Considine, R V; Nyce, M R; Allen, L E; Morales, L M; Triester, S; Serrano, J; Colberg, J; Lanza-Jacoby, S; Caro, J F

    1995-01-01

    We tested the hypothesis that liver protein kinase C (PKC) is increased in non-insulin-dependent diabetes mellitus (NIDDM). To this end we examined the distribution of PKC isozymes in liver biopsies from obese individuals with and without NIDDM and in lean controls. PKC isozymes alpha, beta, epsilon and zeta were detected by immunoblotting in both the cytosol and membrane fractions. Isozymes gamma and delta were not detected. There was a significant increase in immunodetectable PKC-alpha (twofold), -epsilon (threefold), and -zeta (twofold) in the membrane fraction isolated from obese subjects with NIDDM compared with the lean controls. In obese subjects without NIDDM, the amount of membrane PKC isozymes was not different from the other two groups. We next sought an animal model where this observation could be studied further. The Zucker diabetic fatty rat offered such a model system. Immunodetectable membrane PKC-alpha, -beta, -epsilon, and -zeta were significantly increased when compared with both the lean and obese controls. The increase in immunodetectable PKC protein correlated with a 40% elevation in the activity of PKC at the membrane. Normalization of circulating glucose in the rat model by either insulin or phlorizin treatment did not result in a reduction in membrane PKC isozyme protein or kinase activity. Further, phlorizin treatment did not improve insulin receptor autophosphorylation nor did the treatment lower liver diacylglycerol. We conclude that liver PKC is increased in NIDDM, a change that is not secondary to hyperglycemia. It is possible that PKC-mediated phosphorylation of some component in the insulin signaling cascade contributes to the insulin resistance observed in NIDDM. Images PMID:7769136

  1. HEME-DEPENDENT ACTIVATION OF NEURONAL NITRIC-OXIDE SYNTHASE BY CYTOSOL IS DUE TO AN HSP70-DEPENDENT, THIOREDOXIN-MEDIATED THIOL-DISULFIDE INTERCHANGE IN THE HEME/SUBSTRATE BINDING CLEFT†

    PubMed Central

    Morishima, Yoshihiro; Lau, Miranda; Peng, Hwei-Ming; Miyata, Yoshinari; Gestwicki, Jason E.; Pratt, William B.; Osawa, Yoichi

    2011-01-01

    We have reported that heme-dependent activation of apo-neuronal nitric oxide synthase (apo-nNOS) to the active holo-enzyme dimer is dependent upon factors present in reticulocyte lysate and other cytosols. Here, we find that both Hsp70 and thioredoxin are components of the activation system. The apo-nNOS activating activity of reticulocyte lysate is retained in a pool of fractions containing Hsp70 that elute from DE52 prior to Hsp90. All of the activating activity and 20–30% of the Hsp70 elute in the flow-through fraction upon subsequent ATP-agarose chromatography. Apo-nNOS activation by this flow-through fraction is inhibited by pifithrin-μ, a small molecule inhibitor of Hsp70, suggesting that a non-ATP-binding form of Hsp70 is involved in heme-dependent apo-nNOS activation. Previous work has shown that apo-nNOS can be activated by thiol-disulfide exchange, and we show substantial activation with a small molecule dithiol modeled on the active motifs of thioredoxin and protein disulfide isomerase. Further fractionation of the ATP-agarose flow-through on Sephacryl S-300 separates free thioredoxin from apo-nNOS activating activity, Hsp70, and a small amount of thioredoxin, all of which are eluted throughout the macromolecular peak. Incubation of apo-nNOS with the macromolecular fraction in combination with either the thioredoxin-containing fraction or with purified recombinant human thioredoxin restores full heme-dependent activating activity. This supports a model in which Hsp70 binding to apo-nNOS stabilizes an open state of the heme/substrate binding cleft to facilitate thioredoxin access to the active site cysteine that coordinates with heme iron, permitting heme binding and dimerization to the active enzyme. PMID:21755988

  2. Heme-dependent activation of neuronal nitric oxide synthase by cytosol is due to an Hsp70-dependent, thioredoxin-mediated thiol-disulfide interchange in the heme/substrate binding cleft.

    PubMed

    Morishima, Yoshihiro; Lau, Miranda; Peng, Hwei-Ming; Miyata, Yoshinari; Gestwicki, Jason E; Pratt, William B; Osawa, Yoichi

    2011-08-23

    We have reported that heme-dependent activation of apo-neuronal nitric oxide synthase (apo-nNOS) to the active holo-enzyme dimer is dependent upon factors present in reticulocyte lysate and other cytosols. Here, we find that both Hsp70 and thioredoxin are components of the activation system. The apo-nNOS activating activity of reticulocyte lysate is retained in a pool of fractions containing Hsp70 that elute from DE52 prior to Hsp90. All of the activating activity and 20-30% of the Hsp70 elute in the flow-through fraction upon subsequent ATP-agarose chromatography. Apo-nNOS activation by this flow-through fraction is inhibited by pifithrin-μ, a small molecule inhibitor of Hsp70, suggesting that a non-ATP-binding form of Hsp70 is involved in heme-dependent apo-nNOS activation. Previous work has shown that apo-nNOS can be activated by thiol-disulfide exchange, and we show substantial activation with a small molecule dithiol modeled on the active motifs of thioredoxin and protein disulfide isomerase. Further fractionation of the ATP-agarose flow-through on Sephacryl S-300 separates free thioredoxin from apo-nNOS activating activity, Hsp70, and a small amount of thioredoxin, all of which are eluted throughout the macromolecular peak. Incubation of apo-nNOS with the macromolecular fraction in combination either with the thioredoxin-containing fraction or with purified recombinant human thioredoxin restores full heme-dependent activating activity. This supports a model in which Hsp70 binding to apo-nNOS stabilizes an open state of the heme/substrate binding cleft to facilitate thioredoxin access to the active site cysteine that coordinates with heme iron, permitting heme binding and dimerization to the active enzyme. PMID:21755988

  3. Neoclassical Angular Momentum Flux Revisited

    NASA Astrophysics Data System (ADS)

    Wong, S. K.; Chan, V. S.

    2004-11-01

    The toroidal angular momentum flux in neoclassical transport theory of small rotations depends on the second order (in ion poloidal gyroradius over plasma scale length) ion distribution function. Owing to the complexity of the calculation, the result obtained a long time ago for circular cross-section tokamak plasmas in the banana regime [M.N. Rosenbluth, et al., Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1971), Vol. 1, p. 495] has never been reproduced. Using a representation of the angular momentum flux based on the solution of an adjoint equation to the usual linearized drift kinetic equation, and performing systematically a large-aspect-ratio expansion, we have obtained the flux for flux surfaces of arbitrary shape. We have found the same analytic form for the temperature gradient driven part of the flux, but the overall numerical multiplier is different and has the opposite sign. Implications for rotations in discharges with no apparent momentum input will be discussed.

  4. Methane Fluxes from Subtropical Wetlands

    NASA Astrophysics Data System (ADS)

    DeLucia, N.; Gomez-Casanovas, N.; Bernacchi, C.

    2013-12-01

    It is well documented that green house gas concentrations have risen at unequivocal rates since the industrial revolution but the disparity between anthropogenic sources and natural sources is uncertain. Wetlands are one example of a natural ecosystem that can be a substantial source or sink for methane (CH4) depending on climate conditions. Due to strict anaerobic conditions required for CH4-generating microorganisms, natural wetlands are one of the main sources for biogenic CH4. Although wetlands occupy less than 5% of total land surface area, they contribute approximately 20% of total CH4 emissions to the atmosphere. The processes regulating CH4 emissions are sensitive to land use and management practices of areas surrounding wetlands. Variation in adjacent vegetation or grazing intensity by livestock can, for example, alter CH4 fluxes from wetland soils by altering nutrient balance, carbon inputs and hydrology. Therefore, understanding how these changes will affect wetland source strength is essential to understand the impact of wetland management practices on the global climate system. In this study we quantify wetland methane fluxes from subtropical wetlands on a working cattle ranch in central Florida near Okeechobee Lake (27o10'52.04'N, 81o21'8.56'W). To determine differences in CH4 fluxes associated with land use and management, a replicated (n = 4) full factorial experiment was designed for wetlands where the surrounding vegetation was (1) grazed or un-grazed and (2) composed of native vegetation or improved pasture. Net exchange of CH4 and CO2 between the land surface and the atmosphere were sampled with a LICOR Li-7700 open path CH4 analyzer and Li-7500A open path CO2/H20 analyzer mounted in a 1-m3 static gas-exchange chamber. Our results showed and verified that CH4 emissions from subtropical wetlands were larger when high soil moisture was coupled with high temperatures. The presence of cattle only amplified these results. These results help quantify

  5. Atmospheric lepton fluxes

    NASA Astrophysics Data System (ADS)

    Gaisser, Thomas K.

    2015-08-01

    This review of atmospheric muons and neutrinos emphasizes the high energy range relevant for backgrounds to high-energy neutrinos of astrophysical origin. After a brief historical introduction, the main distinguishing features of atmospheric νμ and νe are discussed, along with the implications of the muon charge ratio for the νµ / ν̅µ ratio. Methods to account for effects of the knee in the primary cosmic-ray spectrum and the energy-dependence of hadronic interactions on the neutrino fluxes are discussed and illustrated in the context of recent results from IceCube. A simple numerical/analytic method is proposed for systematic investigation of uncertainties in neutrino fluxes arising from uncertainties in the primary cosmic-ray spectrum/composition and hadronic interactions.

  6. Asymptotic domination of cold relativistic MHD winds by kinetic energy flux

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.; Li, Zhi-Yun

    1994-01-01

    We study the conditions which lead to the conversion of most Poynting flux into kinetic energy flux in cold, relativistic hydromagnetic winds. It is shown that plasma acceleration along a precisely radial flow is extremely inefficient due to the near cancellation of the toroidal magnetic pressure and tension forces. However, if the flux tubes in a flow diverge even slightly faster than radially, the fast magnetosonic point moves inward from infinity to a few times the light cylinder radius. Once the flow becomes supermagnetosonic, further divergence of the flux tubes beyond the fast point can accelerate the flow via the 'magnetic nozzle' effect, thereby further converting Poynting flux to kinetic energy flux. We show that the Grad-Shafranov equation admits a generic family of kinetic energy-dominated asymptotic wind solutions with finite total magnetic flux. The Poynting flux in these solutions vanishes logarithmically with distance. The way in which the flux surfaces are nested within the flow depends only on the ratio of angular velocity to poliodal 4-velocity as a function of magnetic flux. Radial variations in flow structure can be expressed in terms of a pressure boundary condition on the outermost flux surface, provided that no external toriodal field surrounds the flow. For a special case, we show explicitly how the flux surfaces merge gradually to their asymptotes. For flows confined by an external medium of pressure decreasing to zero at infinity we show that, depending on how fast the ambient pressure declines, the final flow state could be either a collimated jet or a wind that fills the entire space. We discuss the astrophysical implications of our results for jets from active galactic nuclei and for free pulsar winds such as that believed to power the Crab Nebula.

  7. Heat flux boundary anomalies and thermal winds

    NASA Astrophysics Data System (ADS)

    Dietrich, Wieland; Wicht, Johannes

    2013-04-01

    Several studies have shown strong effects of outer boundary heat flux patterns on the dynamo mechanism in planets. For example, the hemispherical field of the ancient Martian dynamo can be explained by a large scale sinusoidal anomaly of the core mantle boundary heat flux triggered by large scale mantle convection or giant impacts. The magnetic fields show typically the desired effect - though dynamo action is locally stronger where the underneath heat flux is higher. However, it remains an open question if these effects still apply for more realistic planetary parameters, such as vigor of the convection (Rayleigh number) or the rotation rate (Ekman). The sinusoidal variation of the CMB heat flux along the colatitude with larger heat flux in the southern and smaller in the northern hemisphere as used for Mars can lead to a concentration of magnetic field in the south. The shape of such a hemispherical dynamo matches the crustal magnetization pattern at the surface and seems therefore an admissible mode for the ancient Martian dynamo. As the consequence of the emerging latitudinal temperature gradients convection and induction are dominated by thermal winds. These zonal flows were found to be equatorial antisymmetric, axisymmetric, ageostrophic, of strong amplitude and have therefore a severe effect on core convection and especially the induction process. We measure the underlying thermal anomalies as a function of Rayleigh and Ekman number and show that they are responsible for the thermal winds. Our results suggest that temperature anomalies decrease clearly with the supercriticality of the convection due to faster stirring and mixing, but show no additional dependence on the Ekman number. Interestingly, the decline of the latitudinal temperature anomaly follows a recently suggested scaling law for the thickness of thermal boundary layers. Even though the convective supercriticality of planetary cores is rather large and therefore only a minor effect of thermal

  8. Flux Sampling Errors for Aircraft and Towers

    NASA Technical Reports Server (NTRS)

    Mahrt, Larry

    1998-01-01

    Various errors and influences leading to differences between tower- and aircraft-measured fluxes are surveyed. This survey is motivated by reports in the literature that aircraft fluxes are sometimes smaller than tower-measured fluxes. Both tower and aircraft flux errors are larger with surface heterogeneity due to several independent effects. Surface heterogeneity may cause tower flux errors to increase with decreasing wind speed. Techniques to assess flux sampling error are reviewed. Such error estimates suffer various degrees of inapplicability in real geophysical time series due to nonstationarity of tower time series (or inhomogeneity of aircraft data). A new measure for nonstationarity is developed that eliminates assumptions on the form of the nonstationarity inherent in previous methods. When this nonstationarity measure becomes large, the surface energy imbalance increases sharply. Finally, strategies for obtaining adequate flux sampling using repeated aircraft passes and grid patterns are outlined.

  9. Effects of Surface Sensible Heat Fluxes on the Tropical Cyclone Intensity

    NASA Astrophysics Data System (ADS)

    Ma, Zhanhong; Fei, Jianfang

    2016-04-01

    The contributions of surface sensible heat fluxes (SHX) to the evolution of tropical cyclone (TC) intensity and structure are examined in this study by conducting cloud-resolving simulations. Results suggest that although the peak values of SHX could account for nearly 30% of those of the total surface latent and sensible heat fluxes, the impact of SHX on TC intensification is nonetheless not distinct. However, the TC size shows great sensitivity to the SHX that the storm is shrunk by over 20% after removing the SHX. The reduced total surface enthalpy fluxes due to the removal of SHX do not necessarily result in weakened TCs, while the larger surface latent heat fluxes (LHX) basically correspond to stronger TCs. This suggests that the TC intensity is largely dependent on the LHX rather than the total surface enthalpy fluxes, although the latter is generally dominated by the former.

  10. Demonstration of HNO3 Eddy Flux Measurements at the Boulder Atmospheric Observatory Using Active Passivation

    NASA Astrophysics Data System (ADS)

    Roscioli, J. R.; Herndon, S. C.; Zahniser, M. S.; Nelson, D. D.; Zaragoza, J.; Pollack, I. B.; Fischer, E. V.

    2015-12-01

    Eddy flux measurements of "sticky" molecules have historically proven difficult due to strong interactions with instrument surfaces. A novel approach has been developed to improve these response times, enabling flux measurements of nitric acid (HNO3) and and ammonia (NH3). Deliberate addition of the vapor of perfluorinated acids and bases into a sample stream serves to eject existing surface-bound sample molecules and passivate instrument surfaces. HNO3 response times for an Aerodyne quantum cascade laser absorption spectrometer (QCLAS) improve by a factor of 60-fold when actively passivating. This approach was used during field measurements of HNO3 fluxes at the Boulder Atmospheric Observatory, where an actively passivated inertial inlet at 8 m height yielded HNO3 deposition fluxes of 0.5 - 2 nmol/m2/sec. The dependence of the deposition flux upon urban vs rural outflow is discussed.

  11. Modeled ground magnetic signatures of flux transfer events

    NASA Technical Reports Server (NTRS)

    Mchenry, Mark A.; Clauer, C. Robert

    1987-01-01

    The magnetic field on the ground due to a small (not greater than 200 km scale size) localized field-aligned current (FAC) system interacting with the ionosphere is calculated in terms of an integral over the ionospheric distribution of FAC. Two different candidate current systems for flux transfer events (FTEs) are considered: (1) a system which has current flowing down the center of a cylindrical flux tube with a return current uniformly distributed along the outside edge; and (2) a system which has upward current on one half of the perimeter of a cylindrical flux tube with downward current on the opposite half. The peak magnetic field on the ground is found to differ by a factor of 2 between the two systems, and the magnetic perturbations are in different directions depending on the observer's position.

  12. A microscale thermophoretic turbine driven by external diffusive heat flux

    NASA Astrophysics Data System (ADS)

    Yang, Mingcheng; Liu, Rui; Ripoll, Marisol; Chen, Ke

    2014-10-01

    We propose a theoretical prototype of a micro-scale turbine externally driven by diffusive heat flux without the need for macroscopic particle flux, which is in sharp contrast to conventional turbines. The prototypes are described analytically and validated by computer simulations. Our results indicate that a micro-scale turbine composed of anisotropic blades can rotate unidirectionally in an external temperature gradient due to the anisotropic thermophoresis effect. The rotational direction and speed depend on the temperature gradient, the geometry and the thermophoretic properties of the turbine. The proposed thermophoretic turbines can be experimentally realized and implemented on micro-devices such as computer-chips to recover waste heat or to facilitate cooling.We propose a theoretical prototype of a micro-scale turbine externally driven by diffusive heat flux without the need for macroscopic particle flux, which is in sharp contrast to conventional turbines. The prototypes are described analytically and validated by computer simulations. Our results indicate that a micro-scale turbine composed of anisotropic blades can rotate unidirectionally in an external temperature gradient due to the anisotropic thermophoresis effect. The rotational direction and speed depend on the temperature gradient, the geometry and the thermophoretic properties of the turbine. The proposed thermophoretic turbines can be experimentally realized and implemented on micro-devices such as computer-chips to recover waste heat or to facilitate cooling. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03990d

  13. Flux attenuation at NREL`s High-Flux Solar Furnace

    SciTech Connect

    Bingham, C E; Scholl, K L; Lewandowski, A A

    1994-10-01

    The High-Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory (NREL) has a faceted primary concentrator and a long focal-length-to-diameter ratio (due to its off-axis design). Each primary facet can be aimed individually to produce different flux distributions at the target plane. Two different types of attenuators are used depending on the flux distribution. A sliding-plate attenuator is used primarily when the facets are aimed at the same target point. The alternate attenuator resembles a venetian blind. Both attenuators are located between the concentrator and the focal point. The venetian-blind attenuator is primarily used to control the levels of sunlight failing on a target when the primary concentrators are not focused to a single point. This paper will demonstrate the problem of using the sliding-plate attenuator with a faceted concentrator when the facets are not aimed at the same target point. We will show that although the alternate attenuator necessarily blocks a certain amount of incoming sunlight, even when fully open, it provides a more even attenuation of the flux for alternate aiming strategies.

  14. Airborne flux measurements of biogenic volatile organic compounds over California

    NASA Astrophysics Data System (ADS)

    Misztal, P. K.; Karl, T.; Weber, R.; Jonsson, H. H.; Guenther, A. B.; Goldstein, A. H.

    2014-03-01

    Biogenic Volatile Organic Compound (BVOC) fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne BVOC Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a PTR-MS and a wind radome probe to directly determine fluxes of isoprene, MVK + MAC, methanol, monoterpenes, and MBO over ∼10 000 km of flight paths focusing on areas of California predicted to have the largest emissions of isoprene. The Fast Fourier Transform (FFT) approach was used to calculate fluxes over long transects of more than 15 km, most commonly between 50 and 150 km. The Continuous Wavelet Transformation (CWT) approach was used over the same transects to also calculate "instantaneous" fluxes with localization of both frequency and time independent of non-stationarities. Vertical flux divergence of isoprene is expected due to its relatively short lifetime and was measured directly using "racetrack" profiles at multiple altitudes. It was found to be linear and in the range 5% to 30% depending on the ratio of aircraft altitude to PBL height (z / zi). Fluxes were generally measured by flying consistently at 400 ± 50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to Basal Emission Factor (BEF) landcover datasets used to drive biogenic VOC (BVOC) emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. While isoprene emissions from agricultural crop regions, shrublands, and

  15. Theoretical models of flux pinning and flux motion in high-{Tc} superconducting oxides

    SciTech Connect

    Welch, D.O.

    1991-12-31

    Various issues involved in the development of phenomenological models of flux pinning and motion in high-{Tc} oxides are discussed. A simplified model is presented for the critical current density and is used to examine the question of whether flux flow results from an instability due to plasticity of the flux-line array or from pin breaking.

  16. Theoretical models of flux pinning and flux motion in high- Tc superconducting oxides

    SciTech Connect

    Welch, D.O.

    1991-01-01

    Various issues involved in the development of phenomenological models of flux pinning and motion in high-{Tc} oxides are discussed. A simplified model is presented for the critical current density and is used to examine the question of whether flux flow results from an instability due to plasticity of the flux-line array or from pin breaking.

  17. The potential and flux landscape theory of evolution

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Xu, Li; Zhang, Kun; Wang, Erkang; Wang, Jin

    2012-08-01

    We established the potential and flux landscape theory for evolution. We found explicitly the conventional Wright's gradient adaptive landscape based on the mean fitness is inadequate to describe the general evolutionary dynamics. We show the intrinsic potential as being Lyapunov function(monotonically decreasing in time) does exist and can define the adaptive landscape for general evolution dynamics for studying global stability. The driving force determining the dynamics can be decomposed into gradient of potential landscape and curl probability flux. Non-zero flux causes detailed balance breaking and measures how far the evolution from equilibrium state. The gradient of intrinsic potential and curl flux are perpendicular to each other in zero fluctuation limit resembling electric and magnetic forces on electrons. We quantified intrinsic energy, entropy and free energy of evolution and constructed non-equilibrium thermodynamics. The intrinsic non-equilibrium free energy is a Lyapunov function. Both intrinsic potential and free energy can be used to quantify the global stability and robustness of evolution. We investigated an example of three allele evolutionary dynamics with frequency dependent selection (detailed balance broken). We uncovered the underlying single, triple, and limit cycle attractor landscapes. We found quantitative criterions for stability through landscape topography. We also quantified evolution pathways and found paths do not follow potential gradient and are irreversible due to non-zero flux. We generalized the original Fisher's fundamental theorem to the general (i.e., frequency dependent selection) regime of evolution by linking the adaptive rate with not only genetic variance related to the potential but also the flux. We show there is an optimum potential where curl flux resulting from biotic interactions of individuals within a species or between species can sustain an endless evolution even if the physical environment is unchanged. We

  18. Unresolved Magnetic Flux Removal Process in the Photosphere

    NASA Astrophysics Data System (ADS)

    Kubo, Masahito; Chye Low, Boon; Lites, Bruce

    The mutual loss of magnetic flux due to the apparent collision of opposite-polarity magnetic elements is called "magnetic flux cancellation" as a descriptive term. The flux cancellation is essential to understand the dissipation of magnetic flux from the solar surface. An Ω-loop submerging below the surface or a U-loop rising through the photosphere is the usual idea to explain the magnetic flux cancellation. Magnetic reconnection may be crucial for the forma-tion of these loops, especially for the submerging -loop. In fact, chromospheric and coronal activities are often observed at the cancellation sites. We investigate the evolution of 5 cancel-lation events of the opposite-polarity magnetic elements at granular scales by using accurate spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode. We find that the horizontal magnetic field, which is expected in both submerging Ω-loop model and emerging U-loop model, does not appear between the canceling magnetic elements in 4 of the 5 events. The approaching magnetic elements in these events are more concentrated rather than gradually diffused, and they have nearly vertical fields even while they are in contact each other. We thus imply that the actual flux cancellation is highly time dependent event near the solar surface at scales less than a pixel of Hinode/SOT (about 200 km). At the polarity inversion line formed by the canceling magnetic elements, highly asymmetric Stokes-V profiles are observed. We confirm that such asymmetric profile can be made by the sum of the profiles at the opposite-polarity magnetic elements next to the polarity inversion line. This means that the approaching bipolar flux tubes still keep their nature within the pixel where they come in contact with each other, and thus supports the unresolved flux removal process within the pixel at the polarity inversion line.

  19. Solar flux and its variations

    NASA Technical Reports Server (NTRS)

    Smith, E. V. P.; Gottlieb, D. M.

    1975-01-01

    Data are presented on the solar irradiance as derived from a number of sources. An attempt was made to bring these data onto a uniform scale. Summation of fluxes at all wavelengths yields a figure of 1357.826 for the solar constant. Estimates are made of the solar flux variations due to flares, active regions (slowly varying component), 27-day period, and the 11-yr cycle. Solar activity does not produce a significant variation in the value of the solar constant. Variations in the X-ray and EUV portions of the solar flux may be several orders of magnitude during solar activity, especially at times of major flares. It is established that these short wavelength flux enhancements cause significant changes in the terrestrial ionosphere.

  20. Fast flux locked loop

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-09-10

    A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

  1. Seasonal trends in concentrations and fluxes of volatile organic compounds above central London

    NASA Astrophysics Data System (ADS)

    Valach, A. C.; Langford, B.; Nemitz, E.; MacKenzie, A. R.; Hewitt, C. N.

    2015-03-01

    Concentrations and fluxes of seven volatile organic compounds (VOCs) were measured between August and December 2012 at a roof-top site in central London as part of the ClearfLo project (Clean Air for London). VOC concentrations were quantified using a proton transfer reaction-mass spectrometer and fluxes were calculated using a virtual disjunct eddy covariance technique. The median VOC fluxes, including aromatics, oxygenated compounds and isoprene, ranged from 0.07 to 0.33 mg m-2 h-1 and mixing ratios were 7.27 ppb for methanol (m / z 33) and <1 ppb for the remaining compounds. Strong relationships were observed between most VOC fluxes and concentrations with traffic density, but also with photosynthetically active radiation (PAR) and temperature for the oxygenated compounds and isoprene. An estimated 50-90 % of aromatic fluxes were attributable to traffic activity, which showed little seasonal variation, suggesting boundary layer effects or possibly advected pollution may be the primary causes of increased concentrations of aromatics in winter. PAR and temperature-dependent processes accounted for the majority of isoprene, methanol and acetaldehyde fluxes and concentrations in August and September, when fluxes and concentrations were largest. Modelled biogenic isoprene fluxes using the G95 algorithm agreed well with measured fluxes in August and September, due to urban vegetation. Comparisons of estimated annual benzene emissions from the London and National Atmospheric Emissions Inventory agreed well with measured benzene fluxes. Flux footprint analysis indicated emission sources were localized and that boundary layer dynamics and source strengths were responsible for temporal and spatial VOC flux and concentration variability during the measurement period.

  2. Seasonal and diurnal cycles of 0.25-2.5 μm aerosol fluxes over urban Stockholm, Sweden

    NASA Astrophysics Data System (ADS)

    Vogt, M.; Nilsson, E. D.; Ahlm, L.; Mártensson, E. M.; Johansson, C.

    2011-11-01

    Size resolved aerosol and gas fluxes were measured in Stockholm from 1 April 2008 to 15 April 2009 over both urban and green sectors. CO2 and H2O fluxes peaked in daytime for all seasons. CO2 concentrations peaked in winter. Due to vegetation influence the CO2 fluxes had different diurnal cycles and magnitude in the two sectors. In the urban sector, CO2 fluxes indicated a net source. The sector dominated by residential areas and green spaces had its highest aerosol fluxes in winter. In spring, super micrometer concentrations for both sectors were significantly higher, as were the urban sector rush hour fluxes. The submicrometer aerosol fluxes had a similar diurnal pattern with daytime maxima for all seasons. This suggests that only the super micrometer aerosol emissions are dependent on season. During spring there was a clear difference in super micrometer fluxes between wet and dry streets. Our direct flux measurements have improved the understanding of the processes behind these aerosol emissions. They support the hypothesis that the spring peak in aerosol emissions are due to road dust, produced during the winter, but not released in large quantities until the roads dry up during spring, and explain why Stockholm has problems meeting the EU directive for aerosol mass (PM10).

  3. Magnetic-flux pump

    NASA Technical Reports Server (NTRS)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

  4. Plasmoids as magnetic flux ropes

    SciTech Connect

    Moldwin, M.B.; Hughes, W.J. )

    1991-08-01

    Observational constraints on the magnetic topology and orientation of plasmoids is examined using a magnetic field model. The authors develop a magnetic flux rope model to examine whether principal axis analysis (PAA) of magnetometer signatures from a single satellite pass is sufficient to determine the magnetic topology of plasmoids and if plasmoid observations are best explained by the flux rope, closed loop, or large-amplitude wave picture. Satellite data are simulated by extracting the magnetic field along a path through the model of a magnetic flux rope. They then examine the results using PAA. They find that the principal axis directions (and therefore the interpretation of structure orientation) is highly dependent on several parameters including the satellite trajectory through the structure. Because of this they conclude that PAA of magnetometer data from a single satellite pass is insufficient to differentiate between magnetic closed loop and flux rope models. They also compare the model results to ISEE 3 magnetometer data of plasmoid events in various coordinate frames including principal axis and geocentric solar magnetospheric. They find that previously identified plasmoid events that have been explained as closed loop structures can also be modeled as flux ropes. They also searched the literature for previously reported flux rope and closed loop plasmoid events to examine if these structures had any similarities and/or differences. The results of the modeling efforts and examination of both flux rope and plasmoid events lead them to favor the flux rope model of plasmoid formation, as it is better able to unify the observations of various magnetic structures observed by ISEE 3.

  5. Increase of mycorrhizal C flux in Siberian temperate forests during the extreme drought of 2012

    NASA Astrophysics Data System (ADS)

    Menyailo, Oleg; Matvienko, Anastasia; Cheng, Chih-Hsin

    2015-04-01

    Extreme climatic events have strong effect on the terrestrial carbon cycle. The soil C flux is the major uncertainty in the global C budget. Autotrophic (roots and mycorrhizae) component and heterotrophic microorganisms respond differently to altered precipitation and temperature, however their responses might vary in different ecosystems. We studied mycorrhizal, heterotrohic and total soil CO2 fluxes using in-growth mesh collars in forest soils under different tree species. The fluxes were measured between May and October of 2010-2012. The summer of 2012 was extremely hot and dry in Siberia, breaking records for the past 70 years of meteorological monitoring. The drought reduced soil surface CO2 flux for 20-30 % depending on the tree species. It is very surprising that the mycorrhizal flux in 2012 was under most species similar to the flux in a wetter years (2010-2011), under birch the mycorrhizal flux was even 1.5 times higher during the drought. Thus, decline in overall soil surface CO2 flux was mainly due to reduction of heterotrophic activities. Since the proportion of heterotrophic and autrophic activities is related to soil C sequestration, we conclude that under the most tree species in Siberia soil C will be accumulated during the drought. The most positive effect of the drought for soil carbon accrual is to be expected under birch.

  6. Surface heat flux variability of a large lake: Lake Geneva, Switzerland

    NASA Astrophysics Data System (ADS)

    Irani Rahaghi, A.; Lemmin, U.; Bouffard, D.; Riffler, M.; Wunderle, S.; Barry, D. A.

    2014-12-01

    The heat budget of a lake is a fundamental component of physical limnology, and is strongly dependent on the surface heat flux. However, the surface energy exchange depends on several factors, making it difficult to estimate. In this study we employed several bulk formulas to estimate Lake Geneva's surface heat flux. Combination of different surface heat flux terms leads to a surface heat exchange model which requires various data. Different data sources were used in the heat flux estimates. Meteorological data were taken from an operational numerical weather prediction model, namely COSMO-2 (run by the Swiss meteorological service), while satellite imagery was used for the lake surface water temperature (LSWT). In order to find the best combination of the bulk formulas and to calibrate the model, the temporal evolution of the heat budget was estimated using long-term time series of vertical temperature profiles. Vertical temperature profiles at two points (one in the Lake Geneva's large basin and one in its small basin) were used. A sensitivity analysis was performed to find the key parameters, and more significantly the optimal combination of different heat flux terms. Finally, the spatio-temporal surface heat flux variation was calculated according to the proposed model. In addition, the relationship between variability of the surface heat flux and meteorological forcing was assessed. The different models, which are of differing complexity, gave reasonably consistent results, with differences attributed to simplifications inherent in them. The modeling results revealed that the LSWT and wind forcing are dominant factors underlying Lake Geneva surface heat flux spatial variation, while its temporal variability is mainly due to the global radiation and air temperature changes. In conclusion, the bulk heat balance approach is a useful tool to estimate various heat flux terms as well as their monthly or seasonally contributions. But, in large lakes where the LSWT is

  7. Enhanced Climatic Warming in the Tibetan Plateau Due to Double CO2: A Model Study

    NASA Technical Reports Server (NTRS)

    Chen, Baode; Chao, Winston C.; Liu, Xiao-Dong; Lau, William K. M. (Technical Monitor)

    2001-01-01

    The NCAR (National Center for Atmospheric Research) regional climate model (RegCM2) with time-dependent lateral meteorological fields provided by a 130-year transient increasing CO2 simulation of the NCAR Climate System Model (CSM) has been used to investigate the mechanism of enhanced ground temperature warming over the TP (Tibetan Plateau). From our model results, a remarkable tendency of warming increasing with elevation is found for the winter season, and elevation dependency of warming is not clearly recognized in the summer season. This simulated feature of elevation dependency of ground temperature is consistent with observations. Based on an analysis of surface energy budget, the short wave solar radiation absorbed at the surface plus downward long wave flux reaching the surface shows a strong elevation dependency, and is mostly responsible for enhanced surface warming over the TP. At lower elevations, the precipitation forced by topography is enhanced due to an increase in water vapor supply resulted from a warming in the atmosphere induced by doubling CO2. This precipitation enhancement must be associated with an increase in clouds, which results in a decline in solar flux reaching surface. At higher elevations, large snow depletion is detected in the 2xCO2run. It leads to a decrease in albedo, therefore more solar flux is absorbed at the surface. On the other hand, much more uniform increase in downward long wave flux reaching the surface is found. The combination of these effects (i.e. decrease in solar flux at lower elevations, increase in solar flux at higher elevation and more uniform increase in downward long wave flux) results in elevation dependency of enhanced ground temperature warming over the TP.

  8. MARIE Dose and Flux Measurements in Mars Orbit

    NASA Technical Reports Server (NTRS)

    Zeitlin, C.; Cleghorn, T.; Cucinotta, F. A.; Saganti, P.; Andersen, V.; Lee, K. T.; Pinsky, L. S.; Turner, R.; Atwell, W.

    2004-01-01

    We present results from the Martian Radiation Environment Experiment (MARIE), aboard the 2001 Mars Odyssey spacecraft in orbit around Mars. MARIE operated successfully from March 2002 through October 2003. At the time of this writing, the instrument is off due to a loss of communications during an extremely intense Solar Particle Event. Efforts to revive MARIE are planned for Spring 2004, when Odyssey's role as a communications relay for the MER rovers is completed. During the period of successful operation, MARIE returned the first detailed energetic charged particle data from Mars. Due to limitations of the instrument, normalizing MARIE data to flux or dose is not straightforward - several large corrections are needed. Thus normalized results (like dose or flux) have large uncertainties and/or significant model-dependence. The problems in normalization are mainly due to inefficiency in detecting high-energy protons (signal-to-noise problems force the trigger threshold to be higher than optimal), to the excessively high gains employed in the signal processing electronics (many ions deposit energy sufficient to saturate the electronics, and dE/dx information is lost), and to artifacts associated with the two trigger detectors (incomplete registration of dE/dx). Despite these problems, MARIE is efficient for detecting helium ions with kinetic energies above about 30 MeV/nucleon, and for detecting high-energy ions (energies above about 400 MeV/nucleon) with charges from 5 to 10. Fluxes of these heavier ions can be compared to fluxes obtained from the ACE/CRIS instrument, providing at least one area of direct comparison between data obtained at Earth and at Mars; this analysis will be presented as a work in progress. We will also present dose-rate data, with a detailed explanation of the many sources of uncertainty in normalization. The results for both flux and dose will be compared to predictions of the HZETRN model of the GCR.

  9. Solar irradiance variations due to active regions

    SciTech Connect

    Oster, L.; Schatten, K.H.; Sofia, S.

    1982-05-15

    We have been able to reproduce the variations of the solar irradiance observed by ACRIM to an accuracy of better than +- 0.4 W m/sup -2/, assuming that during the 6 month observation period in 1980 the solar luminosity was constant. The improvement over previous attempts is primarily due to the inclusion of faculae. The reproduction scheme uses simple geometrical data on spot and facula areas, and conventional parameters for the respective fluxes and angular dependencies. The quality of reproduction is not very sensitive to most of the details of these parameters; nevertheless, there conventional parameters cannot be very different from their actual values in the solar atmosphere. It is interesting that the time average of the integrated excess emission (over directions) of the faculae cancels out the integrated deficit produced by the spots, within an accuracy of about 10%. If this behavior were maintained over longer periods of time, say, on the order of an activity cycle, active regions could be viewed as a kind of lighthouse where the energy deficit near the normal direction, associated with the spots, is primarily reemitted close to the tangential directions by the faculae. The currently available data suggest that energy ''storage'' associated with the redirection of flux near active regions on the Sun is comparable to the lifetime of the faculae.

  10. Parity-time symmetry under magnetic flux

    NASA Astrophysics Data System (ADS)

    Jin, L.; Song, Z.

    2016-06-01

    We study a parity-time-(PT -) symmetric ring lattice, with one pair of balanced gain and loss located at opposite positions. The system remains PT -symmetric when threaded by a magnetic flux; however, the PT symmetry is sensitive to the magnetic flux in the presence of a large balanced gain and loss, or in a large system. We find a threshold gain or loss above which any nontrivial magnetic flux breaks the PT symmetry. We obtain the maximally tolerable magnetic flux for the exact PT -symmetric phase, which is approximately linearly dependent on a weak gain or loss.

  11. Robust nonlinear position-flux zero-bias control for uncertain AMB system

    NASA Astrophysics Data System (ADS)

    Mystkowski, Arkadiusz; Pawluszewicz, Ewa; Dragašius, Egidijus

    2015-08-01

    This paper presents a robust nonlinear control law that combines a parametric uncertainty of the single one-degree-of-freedom active magnetic bearing (AMB) system with disturbance. The robust nonlinear feedback tool such as control Lyapunov function (CLF) and robust stability techniques are developed. The control objective is to globally stabilise the mass position of an AMB with flux feedback. The flux-based control model for an AMB system is derived due to voltage switching strategy with voltage saturation. This strategy enables the flux control under a zero-bias or low-bias flux operation. In the zero-bias control, only one electromagnet in each axis of the AMB is active at any given time, depending on the rotor displacement. The proposed robust nonlinear CLF with a zero-bias for an uncertain AMB system can achieve a dynamic performance superior to that of a linear controller with the zero-bias or with the classical bias operations.

  12. Flux Compression in HTS Films

    NASA Astrophysics Data System (ADS)

    Mikheenko, P.; Colclough, M. S.; Chakalov, R.; Kawano, K.; Muirhead, C. M.

    We report on experimental investigation of the effect of flux compression in superconducting YBa2Cu3Ox (YBCO) films and YBCO/CMR (Colossal Magnetoresistive) multilayers. The flux compression produces positive magnetic moment (m) upon the cooling in a field from above to below the critical temperature. We found effect of compression in all measured films and multilayers. In accordance with theoretical calculations, m is proportional to applied magnetic field. The amplitude of the effect depends on the cooling rate, which suggests the inhomogeneous cooling as its origin. The positive moment is always very small, a fraction of a percent of the ideal diamagnetic response. A CMR layer in contact with HTS decreases the amplitude of the effect. The flux compression weakly depends on sample size, but sensitive to its form and topology. The positive magnetic moment does not appear in bulk samples at low rates of the cooling. Our results show that the main features of the flux compression are very different from those in Paramagnetic Meissner effect observed in bulk high temperature superconductors and Nb disks.

  13. Long-term CH3Br and CH3Cl flux measurements in temperate salt marshes

    NASA Astrophysics Data System (ADS)

    Blei, E.; Heal, M. R.; Heal, K. V.

    2010-08-01

    Fluxes of CH3Br and CH3Cl and their relationship with potential drivers such as sunlight, temperature and soil moisture, were monitored at fortnightly to monthly intervals for more than two years at two contrasting temperate salt marsh sites in Scotland. Manipulation experiments were conducted to further investigate possible links between drivers and fluxes. Mean (± 1 sd) annually and diurnally-weighted net emissions from the two sites were found to be 300 ± 44 ng m-2 h-1 for CH3Br and 662 ± 266 ng m-2 h-1 for CH3Cl. A tentative scale-up indicates that salt marshes account for 0.5-3.2% and 0.05-0.33%, respectively, of currently-estimated total global production of these two gases, in line with previous findings from this and other research groups, but consistently lower than past global scale-up estimates from Southern Californian salt marshes. Fluxes followed both seasonal and diurnal trends with highest fluxes during summer days and lowest (negative) fluxes during winter nights. Statistical analysis generally did not demonstrate a strong link between temperature or sunlight levels and methyl halide fluxes, although it is likely that temperatures have a weak direct influence on emissions, and both certainly have indirect influence via the annual and daily cycles of the vegetation. CH3Cl flux magnitudes from different measurement locations depended on the plant species enclosed whereas such dependency was not discernible for CH3Br fluxes. In 14 out of 19 collars CH3Br and CH3Cl net fluxes were significantly correlated. The CH3Cl/CH3Br net-emission mass ratio was 2.2, a magnitude lower than mass ratios of global methyl halide budgets (~22) or emissions from tropical rainforests (~60). This is likely due to preference for CH3Br production by the relatively high bromine content in the salt marsh plant material.

  14. The role and detectability of the charm contribution to ultra high energy neutrino fluxes

    SciTech Connect

    Gandhi, Raj; Samanta, Abhijit; Watanabe, Atsushi E-mail: abhijit@hri.res.in

    2009-09-01

    It is widely believed that charm meson production and decay may play an important role in high energy astrophysical sources of neutrinos, especially those that are baryon-rich, providing an environment conducive to pp interactions. Using slow-jet supernovae (SJS) as an example of such a source, we study the detectability of high-energy neutrinos, paying particular attention to those produced from charmed-mesons. We highlight important distinguishing features in the ultra-high energy neutrino flux which would act as markers for the role of charm in the source. In particular, charm leads to significant event rates at higher energies, after the conventional (π,K) neutrino fluxes fall off. We calculate event rates both for a nearby single source and for diffuse SJS fluxes for an IceCube-like detector. By comparing muon event rates for the conventional and prompt fluxes in different energy bins, we demonstrate the striking energy dependence in the rates induced by the presence of charm. We also show that it leads to an energy dependant flux ratio of shower to muon events, providing an additional important diagnostic tool for the presence of prompt neutrinos. Motivated by the infusion of high energy anti-electron neutrinos into the flux by charm decay, we also study the detectability of the Glashow resonance due to these sources.

  15. Response of High Latitude Wetland Fluxes of Methane to Changes in Temperature and Water

    NASA Astrophysics Data System (ADS)

    Worden, J.; Bloom, A. A.; Bowman, K. W.; Lee, M.; Frankenberg, C.; Schimel, D.

    2014-12-01

    High latitude methane fluxes represent between 5 - 20% of the total methane budget. This large range in methane emissions estimates are due to poor knowledge of wetland extent, dependency of emissions to temperature and water, the seasonal cycle of freezing and thawing, and a poor measurement network. In turn, these uncertainties limit our ability to predict future methane fluxes in response to a warming climate. Temperature and rainfall at high-latitudes changed dramatically between 2009 and 2010, likely in response to variations in ENSO and the Arctic Anomaly. We might therefore expect that high-latitude methane fluxes significantly changed between 2009 and 2010 because these methane fluxes primarily depend on these environmental parameters. In this study, we implement several wetland models and their corresponding methane fluxes for 2009 and 2010 into the GEOS-Chem global chemistry model. We evaluate whether satellite measurements such as total column measurement from GOSAT or TROP-OMI can distinguish between these models, allowing for better estimates of the magnitude and timing of wetland fluxes and improved process understanding of high-latitude methane emissions.

  16. Flux flow and flux dynamics in high-Tc superconductors

    NASA Technical Reports Server (NTRS)

    Bennett, L. H.; Turchinskaya, M.; Swartzendruber, L. J.; Roitburd, A.; Lundy, D.; Ritter, J.; Kaiser, D. L.

    1991-01-01

    Because high temperature superconductors, including BYCO and BSSCO, are type 2 superconductors with relatively low H(sub c 1) values and high H(sub c 2) values, they will be in a critical state for many of their applications. In the critical state, with the applied field between H(sub c 1) and H(sub c 2), flux lines have penetrated the material and can form a flux lattice and can be pinned by structural defects, chemical inhomogeneities, and impurities. A detailed knowledge of how flux penetrates the material and its behavior under the influence of applied fields and current flow, and the effect of material processing on these properties, is required in order to apply, and to improve the properties of these superconductors. When the applied field is changed rapidly, the time dependence of flux change can be divided into three regions, an initial region which occurs very rapidly, a second region in which the magnetization has a 1n(t) behavior, and a saturation region at very long times. A critical field is defined for depinning, H(sub c,p) as that field at which the hysteresis loop changes from irreversible to reversible. As a function of temperature, it is found that H(sub c,p) is well described by a power law with an exponent between 1.5 and 2.5. The behavior of H(sub c,p) for various materials and its relationship to flux flow and flux dynamics are discussed.

  17. How the Saturnian Magnetosphere Conserves Magnetic Flux

    NASA Astrophysics Data System (ADS)

    Powell, R. L.; Wei, H.; Russell, C. T.; Arridge, C. S.; Dougherty, M. K.

    2012-12-01

    The magnetospheric dynamics at Saturn are driven by the centrifugal force of near co-rotating water group ions released at a rate of hundreds of kilograms per second by Saturn's moon Enceladus. The plasma is accelerated up to co-rotation speed by the magnetospheric magnetic field coupled to the Saturnian ionosphere. The plasma is lost ultimately through the process of magnetic reconnection in the tail. Conservation of magnetic flux requires that plasma-depleted, "empty" flux tubes return magnetic flux to the inner magnetosphere. After completion of the initial inrush of the reconnected and largely emptied flux tubes inward of the reconnection point, the flux tubes face the outflowing plasma and must move inward against the flow. Observations of such flux tubes have been identified in the eight years of Cassini magnetometer data. The occurrence of these tubes is observed at all local times indicating slow inward transport of the tubes relative to the co-rotation speed. Depleted flux tubes observed in the equatorial region appear as an enhancement in the magnitude of the magnetic field, whereas the same flux tubes observed at higher latitudes appear as decreased field strength. The difference in appearance of the low latitude and the high latitude tubes is due to the plasma environment just outside the tube. Warm low-density plasma fills the inside of the flux tube at all latitudes. This flux tube thus will expand in the less dense regions away from the magnetic equator and will be observed as a decrease in the magnitude of the magnetic field from the background. These flux tubes near the equator, where the plasma density outside of the flux tube is much greater, will be observed as an enhancement in the magnitude of the magnetic field. Cassini magnetometer and CAPS data are examined to understand the properties of these flux tubes and their radial and latitudinal evolution throughout the Saturnian magnetospheric environment.

  18. Variability of CO2 concentrations and fluxes in and above an urban street canyon

    NASA Astrophysics Data System (ADS)

    Lietzke, Björn; Vogt, Roland

    2013-08-01

    The variability of CO2 concentrations and fluxes in dense urban environments is high due to the inherent heterogeneity of these complex areas and their spatio-temporally variable anthropogenic sources. With a focus on micro- to local-scale CO2-exchange processes, measurements were conducted in a street canyon in the city of Basel, Switzerland in 2010. CO2 fluxes were sampled at the top of the canyon (19 m) and at 39 m while vertical CO2 concentration profiles were measured in the center and at a wall of the canyon. CO2 concentration distributions in the street canyon and exchange processes with the layers above show, apart from expected general diurnal patterns due mixing layer heights, a strong dependence on wind direction relative to the canyon. As a consequence of the resulting corkscrew-like canyon vortex, accumulation of CO2 inside the canyon is modulated with distinct distribution patterns. The evaluation of diurnal traffic data provides good explanations for the vertical and horizontal differences in CO2-distribution inside the canyon. Diurnal flux characteristics at the top of the canyon can almost solely be explained with traffic density expressed by the strong linear dependence. Even the diurnal course of the flux at 39 m shows a remarkable relationship to traffic density for east wind conditions while, for west wind situations, a change toward source areas with lower emissions leads to a reduced flux.

  19. Simulation study of solar plasma eruptions caused by interactions between emerging flux and coronal arcade fields

    SciTech Connect

    Kaneko, Takafumi; Yokoyama, Takaaki

    2014-11-20

    We investigate the triggering mechanisms of plasma eruptions in the solar atmosphere due to interactions between emerging flux and coronal arcade fields by using two-dimensional MHD simulations. We perform parameter surveys with respect to arcade field height, magnetic field strength, and emerging flux location. Our results show that two possible mechanisms exist, and which mechanism is dominant depends mostly on emerging flux location. One mechanism appears when the location of emerging flux is close to the polarity inversion line (PIL) of an arcade field. This mechanism requires reconnection between the emerging flux and the arcade field, as pointed out by previous studies. The other mechanism appears when the location of emerging flux is around the edge of an arcade field. This mechanism does not require reconnection between the emerging flux and the arcade field but does demand reconnection in the arcade field above the PIL. Furthermore, we found that the eruptive condition for this mechanism can be represented by a simple formula.

  20. Experimental evidence for turbulent sediment flux constituting a large portion of the total sediment flux along migrating sand dunes

    NASA Astrophysics Data System (ADS)

    Naqshband, S.; Ribberink, J. S.; Hurther, D.; Barraud, P. A.; Hulscher, S. J. M. H.

    2014-12-01

    Accurate estimation of sediment transport is critical for many fluvial processes but remains challenging due to high-frequency dynamics. Using novel acoustic flow instrumentation, we quantified the contribution of turbulent bed and suspended sediment fluxes to the total sediment fluxes along an entire dune profile and over the full flow depth. We found that over the dune stoss side and in the bed load layer, the turbulent mean streamwise flux is negative and reaches up to 40% of the total mean streamwise flux. Over the lee side, where turbulent intensities are highest, the contribution of the turbulent mean streamwise flux to the total mean streamwise flux is larger and reaches up to 50%. The mean vertical turbulent flux along the entire dune bed and in the bed load layer reaches nearly 30% of the total mean vertical flux. Turbulent sediment flux may thus constitute a large component of the total flux.

  1. A microscale thermophoretic turbine driven by external diffusive heat flux.

    PubMed

    Yang, Mingcheng; Liu, Rui; Ripoll, Marisol; Chen, Ke

    2014-11-21

    We propose a theoretical prototype of a micro-scale turbine externally driven by diffusive heat flux without the need for macroscopic particle flux, which is in sharp contrast to conventional turbines. The prototypes are described analytically and validated by computer simulations. Our results indicate that a micro-scale turbine composed of anisotropic blades can rotate unidirectionally in an external temperature gradient due to the anisotropic thermophoresis effect. The rotational direction and speed depend on the temperature gradient, the geometry and the thermophoretic properties of the turbine. The proposed thermophoretic turbines can be experimentally realized and implemented on micro-devices such as computer-chips to recover waste heat or to facilitate cooling. PMID:25268245

  2. Turbulent energy flux generated by shock/homogeneous-turbulence interaction

    NASA Astrophysics Data System (ADS)

    Sinha, Krishnendu; Quadros, Russell; Larsson, Johan

    2015-11-01

    High-speed turbulent flows with shock waves are characterized by high localized surface heat transfer rates. Computational predictions are often inaccurate due to the limitations in modeling of the unclosed turbulent energy flux in the highly non-equilibrium regions of shock interaction. In this paper, we investigate the turbulent energy flux generated when homogeneous isotropic turbulence passes through a nominally normal shock wave. We use linear interaction analysis where the incoming turbulence is idealized as being composed of a collection of two-dimensional planar vorticity waves, and the shock wave is taken to be a discontinuity. The nature of the post-shock turbulent energy flux is predicted to be strongly dependent on the incidence angle of the incoming waves. The energy flux correlation is also decomposed into its vortical, entropy and acoustic contributions to understand its rapid non-monotonic variation behind the shock. Three-dimensional statistics, calculated by integrating two-dimensional results over a prescribed upstream energy spectrum, are compared with available direct numerical simulation data. A detailed budget of the governing equation is also considered in order to gain insight into the underlying physics.

  3. Observations of Near-Surface Heat-Flux and Temperature Profiles Through the Early Evening Transition over Contrasting Surfaces

    NASA Astrophysics Data System (ADS)

    Jensen, Derek D.; Nadeau, Daniel F.; Hoch, Sebastian W.; Pardyjak, Eric R.

    2016-06-01

    Near-surface turbulence data from the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program are used to study countergradient heat fluxes through the early evening transition. Two sites, subjected to similar large-scale forcing, but with vastly different surface and sub-surface characteristics, are considered. The Playa site is situated at the interior of a large dry lakebed desert with high sub-surface soil moisture, shallow water table, and devoid of vegetation. The Sagebrush site is located in a desert steppe region with sparse vegetation and little soil moisture. Countergradient sensible heat fluxes are observed during the transition at both sites. The transition process is both site and height dependent. At the Sagebrush site, the countergradient flux at 5 m and below occurs when the sign change of the sensible heat flux precedes the local temperature gradient sign change. For 10 m and above, the countergradient flux occurs when the sign change of the sensible heat flux follows the local temperature gradient sign change. At the Playa site, the countergradient flux at all tower levels occurs when the sign change of the sensible heat flux follows the local temperature gradient sign change. The phenomenon is explained in terms of the mean temperature and heat-flux evolution. The temperature gradient sign reversal is a top-down process while the flux reversal occurs nearly simultaneously at all heights. The differing countergradient behaviour is primarily due to the different subsurface thermal characteristics at the two sites. The combined high volumetric heat capacity and high thermal conductivity at the Playa site lead to small vertical temperature gradients that affect the relative magnitude of terms in the heat-flux tendency equation. A critical ratio of the gradient production to buoyant production of sensible heat flux is suggested so as to predict the countergradient behaviour.

  4. Comparison of the high temperature heat flux sensor to traditional heat flux gages under high heat flux conditions.

    SciTech Connect

    Blanchat, Thomas K.; Hanks, Charles R.

    2013-04-01

    Four types of heat flux gages (Gardon, Schmidt-Boelter, Directional Flame Temperature, and High Temperature Heat Flux Sensor) were assessed and compared under flux conditions ranging between 100-1000 kW/m2, such as those seen in hydrocarbon fire or propellant fire conditions. Short duration step and pulse boundary conditions were imposed using a six-panel cylindrical array of high-temperature tungsten lamps. Overall, agreement between all gages was acceptable for the pulse tests and also for the step tests. However, repeated tests with the HTHFS with relatively long durations at temperatures approaching 1000%C2%B0C showed a substantial decrease (10-25%) in heat flux subsequent to the initial test, likely due to the mounting technique. New HTHFS gages have been ordered to allow additional tests to determine the cause of the flux reduction.

  5. Spacecraft-produced neutron fluxes on Skylab

    NASA Technical Reports Server (NTRS)

    Quist, T. C.; Furst, M.; Burnett, D. S.; Baum, J. H.; Peacock, C. L., Jr.; Perry, D. G.

    1977-01-01

    Estimates of neutron fluxes in different energy ranges are reported for the Skylab spacecraft. Detectors composed of uranium, thorium, and bismuth foils with mica as a fission track recorder, as well as boron foils with cellulose acetate as an alpha-particle recorder, were deployed at different positions in the Orbital Workshop. It was found that the Skylab neutron flux was dominated by high energy (greater than 1 MeV) contributions and that there was no significant time variation in the fluxes. Firm upper limits of 7-15 neutrons/sq cm-sec, depending on the detector location in the spacecraft, were established for fluxes above 1 MeV. Below 1 MeV, the neutron fluxes were about an order of magnitude lower. The neutrons are interpreted as originating from the interactions of leakage protons from the radiation belt with the spacecraft.

  6. Return flux experiment

    NASA Technical Reports Server (NTRS)

    Tveekrem, June L.

    1992-01-01

    All spacecraft emit molecules via outgassing, thruster plumes, vents, etc. The return flux is the portion of those molecules that scatter from the ambient atmosphere and return to the spacecraft. Return flux allows critical spacecraft surfaces to become contaminated even when there is no direct line of sight between the contamination source and the critical surface. Data from the Long Duration Exposure Facility (LDEF) show that contamination of LDEF surfaces could not have come entirely from direct flux. The data suggest significant return flux. Several computer models have been developed to simulate return flux, but the predictions have never been verified in orbit. Large uncertainties in predictions lead to overly conservative spacecraft designs. The purpose of the REturn FLux EXperiment (REFLEX) is to fly a controlled experiment that can be directly compared with predictions from several models.

  7. Aquatic eddy correlation: quantifying the artificial flux caused by stirring-sensitive O2 sensors.

    PubMed

    Holtappels, Moritz; Noss, Christian; Hancke, Kasper; Cathalot, Cecile; McGinnis, Daniel F; Lorke, Andreas; Glud, Ronnie N

    2015-01-01

    In the last decade, the aquatic eddy correlation (EC) technique has proven to be a powerful approach for non-invasive measurements of oxygen fluxes across the sediment water interface. Fundamental to the EC approach is the correlation of turbulent velocity and oxygen concentration fluctuations measured with high frequencies in the same sampling volume. Oxygen concentrations are commonly measured with fast responding electrochemical microsensors. However, due to their own oxygen consumption, electrochemical microsensors are sensitive to changes of the diffusive boundary layer surrounding the probe and thus to changes in the ambient flow velocity. The so-called stirring sensitivity of microsensors constitutes an inherent correlation of flow velocity and oxygen sensing and thus an artificial flux which can confound the benthic flux determination. To assess the artificial flux we measured the correlation between the turbulent flow velocity and the signal of oxygen microsensors in a sealed annular flume without any oxygen sinks and sources. Experiments revealed significant correlations, even for sensors designed to have low stirring sensitivities of ~0.7%. The artificial fluxes depended on ambient flow conditions and, counter intuitively, increased at higher velocities because of the nonlinear contribution of turbulent velocity fluctuations. The measured artificial fluxes ranged from 2-70 mmol m(-2) d(-1) for weak and very strong turbulent flow, respectively. Further, the stirring sensitivity depended on the sensor orientation towards the flow. For a sensor orientation typically used in field studies, the artificial flux could be predicted using a simplified mathematical model. Optical microsensors (optodes) that should not exhibit a stirring sensitivity were tested in parallel and did not show any significant correlation between O2 signals and turbulent flow. In conclusion, EC data obtained with electrochemical sensors can be affected by artificial flux and we

  8. Aquatic Eddy Correlation: Quantifying the Artificial Flux Caused by Stirring-Sensitive O2 Sensors

    PubMed Central

    Holtappels, Moritz; Noss, Christian; Hancke, Kasper; Cathalot, Cecile; McGinnis, Daniel F.; Lorke, Andreas; Glud, Ronnie N.

    2015-01-01

    In the last decade, the aquatic eddy correlation (EC) technique has proven to be a powerful approach for non-invasive measurements of oxygen fluxes across the sediment water interface. Fundamental to the EC approach is the correlation of turbulent velocity and oxygen concentration fluctuations measured with high frequencies in the same sampling volume. Oxygen concentrations are commonly measured with fast responding electrochemical microsensors. However, due to their own oxygen consumption, electrochemical microsensors are sensitive to changes of the diffusive boundary layer surrounding the probe and thus to changes in the ambient flow velocity. The so-called stirring sensitivity of microsensors constitutes an inherent correlation of flow velocity and oxygen sensing and thus an artificial flux which can confound the benthic flux determination. To assess the artificial flux we measured the correlation between the turbulent flow velocity and the signal of oxygen microsensors in a sealed annular flume without any oxygen sinks and sources. Experiments revealed significant correlations, even for sensors designed to have low stirring sensitivities of ~0.7%. The artificial fluxes depended on ambient flow conditions and, counter intuitively, increased at higher velocities because of the nonlinear contribution of turbulent velocity fluctuations. The measured artificial fluxes ranged from 2 - 70 mmol m-2 d-1 for weak and very strong turbulent flow, respectively. Further, the stirring sensitivity depended on the sensor orientation towards the flow. For a sensor orientation typically used in field studies, the artificial flux could be predicted using a simplified mathematical model. Optical microsensors (optodes) that should not exhibit a stirring sensitivity were tested in parallel and did not show any significant correlation between O2 signals and turbulent flow. In conclusion, EC data obtained with electrochemical sensors can be affected by artificial flux and we recommend

  9. Production flux of sea spray aerosol

    SciTech Connect

    de Leeuw, G.; Lewis, E.; Andreas, E. L.; Anguelova, M. D.; Fairall, C. W.; O’Dowd, C.; Schulz, M.; Schwartz, S. E.

    2011-05-07

    Knowledge of the size- and composition-dependent production flux of primary sea spray aerosol (SSA) particles and its dependence on environmental variables is required for modeling cloud microphysical properties and aerosol radiative influences, interpreting measurements of particulate matter in coastal areas and its relation to air quality, and evaluating rates of uptake and reactions of gases in sea spray drops. This review examines recent research pertinent to SSA production flux, which deals mainly with production of particles with r{sub 80} (equilibrium radius at 80% relative humidity) less than 1 {micro}m and as small as 0.01 {micro}m. Production of sea spray particles and its dependence on controlling factors has been investigated in laboratory studies that have examined the dependences on water temperature, salinity, and the presence of organics and in field measurements with micrometeorological techniques that use newly developed fast optical particle sizers. Extensive measurements show that water-insoluble organic matter contributes substantially to the composition of SSA particles with r{sub 80} < 0.25 {micro}m and, in locations with high biological activity, can be the dominant constituent. Order-of-magnitude variation remains in estimates of the size-dependent production flux per white area, the quantity central to formulations of the production flux based on the whitecap method. This variation indicates that the production flux may depend on quantities such as the volume flux of air bubbles to the surface that are not accounted for in current models. Variation in estimates of the whitecap fraction as a function of wind speed contributes additional, comparable uncertainty to production flux estimates.

  10. Flux Compression Magnetic Nozzle

    NASA Technical Reports Server (NTRS)

    Thio, Y. C. Francis; Schafer, Charles (Technical Monitor)

    2001-01-01

    In pulsed fusion propulsion schemes in which the fusion energy creates a radially expanding plasma, a magnetic nozzle is required to redirect the radially diverging flow of the expanding fusion plasma into a rearward axial flow, thereby producing a forward axial impulse to the vehicle. In a highly electrically conducting plasma, the presence of a magnetic field B in the plasma creates a pressure B(exp 2)/2(mu) in the plasma, the magnetic pressure. A gradient in the magnetic pressure can be used to decelerate the plasma traveling in the direction of increasing magnetic field, or to accelerate a plasma from rest in the direction of decreasing magnetic pressure. In principle, ignoring dissipative processes, it is possible to design magnetic configurations to produce an 'elastic' deflection of a plasma beam. In particular, it is conceivable that, by an appropriate arrangement of a set of coils, a good approximation to a parabolic 'magnetic mirror' may be formed, such that a beam of charged particles emanating from the focal point of the parabolic mirror would be reflected by the mirror to travel axially away from the mirror. The degree to which this may be accomplished depends on the degree of control one has over the flux surface of the magnetic field, which changes as a result of its interaction with a moving plasma.

  11. Heat flux measurements

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1989-01-01

    A new automated, computer controlled heat flux measurement facility is described. Continuous transient and steady-state surface heat flux values varying from about 0.3 to 6 MW/sq m over a temperature range of 100 to 1200 K can be obtained in the facility. An application of this facility is the development of heat flux gauges for continuous fast transient surface heat flux measurement on turbine blades operating in space shuttle main engine turbopumps. The facility is useful for durability testing at fast temperature transients.

  12. Aspects of flux compactification

    NASA Astrophysics Data System (ADS)

    Liu, Tao

    In this thesis, we study three main aspects of flux compactifications: (1) classify supergravity solutions from flux compactification; (2) construct flux-deformed geometry and 4D low-energy theory to describe these flux vacua; and (3) study 4D particle phenomenology and cosmology of flux vacua. In the first part, we review G-structure, the basic tool to study supersymmetric flux solutions, and some typical solutions obtained in heterotic, type IIA and type IIB string theories. Then we present a comprehensive classification of supersymmetric vacua of M-theory compactification on 7D manifolds with general four-form fluxes. We analyze the cases where the resulting four-dimensional vacua have N = 1, 2, 3, 4 supersymmetry and the internal space allows for SU(2)-, SU(3)- or G 2-structures. In particular, we find for N = 2 supersymmetry, that the external space-time is Minkowski and the base manifold of the internal space is conformally Kahler for SU(2) structures, while for SU(3) structures the internal space has to be Einstein-Sasaki and no internal fluxes are allowed. Moreover, we provide a new vacuum with N = 1 supersymmetry and SU(3) structure, where all fluxes are non-zero and the first order differential equations are solved. In the second part, we simply review the methods used to construct one subclass of fluxed-deformed geometry or the so-called "twisted manifold", and the associated 4D effective theory describing these flux vacua. Then by employing (generalized) Scherk-Schwarz reduction, we construct the geometric twisting for Calabi-Yau manifolds of Voisin-Borcea type (K 3 x T2)/ Z2 and study the superpotential in a type IIA orientifold based on this geometry. The twists modify the direct product by fibering the K 3 over T2 while preserving the Z2 involution. As an important application, the Voisin-Borcea class contains T6/( Z2 x Z2 ), the usual setting for intersecting D6 brane model building. Past work in this context considered only those twists inherited

  13. Identification of the monitoring point density needed to reliably estimate contaminant mass fluxes

    NASA Astrophysics Data System (ADS)

    Liedl, R.; Liu, S.; Fraser, M.; Barker, J.

    2005-12-01

    Plume monitoring frequently relies on the evaluation of point-scale measurements of concentration at observation wells which are located at control planes or `fences' perpendicular to groundwater flow. Depth-specific concentration values are used to estimate the total mass flux of individual contaminants through the fence. Results of this approach, which is based on spatial interpolation, obviously depend on the density of the measurement points. Our contribution relates the accurracy of mass flux estimation to the point density and, in particular, allows to identify a minimum point density needed to achieve a specified accurracy. In order to establish this relationship, concentration data from fences installed in the coal tar creosote plume at the Borden site are used. These fences are characterized by a rather high density of about 7 points/m2 and it is reasonable to assume that the true mass flux is obtained with this point density. This mass flux is then compared with results for less dense grids down to about 0.1points/m2. Mass flux estimates obtained for this range of point densities are analyzed by the moving window method in order to reduce purely random fluctuations. For each position of the moving window the mass flux is estimated and the coefficient of variation (CV) is calculated to quantify variablity of the results. Thus, the CV provides a relative measure of accurracy in the estimated fluxes. By applying this approach to the Borden naphthalene plume at different times, it is found that the point density changes from sufficient to insufficient due to the temporally decreasing mass flux. By comparing the results of naphthalene and phenol at the same fence and at the same time, we can see that the same grid density might be sufficient for one compound but not for another. If a rather strict CV criterion of 5% is used, a grid of 7 points/m2 is shown to allow for reliable estimates of the true mass fluxes only in the beginning of plume development when

  14. How does sampling frequency control accuracy of fluvial suspended particulate matter flux estimates?

    NASA Astrophysics Data System (ADS)

    Coynel, A.; Hurtrez, J. E.; Schäfer, J.; Etcheber, H.; Blanc, G.

    2003-04-01

    Climatic change and anthropogenic actions greatly affect the environment: impacts of these factors on erosion and Suspended Particulate Matter (SPM) transport have been studied in different watersheds of southwest France with heterogeneous flood characteristics, vegetal cover and land use. The influence of sampling frequency on annual SPM flux estimates was analysed in two contrasted watersheds: the Garonne basin, a large plain river system (55 000 km^2), and the Nivelle basin, a small Pyrenean mountainous river system (238 km^2). Data banks derived from long-term high resolution sampling in both basins allowed to determine seasonal variations of the relation between water discharge and SPM concentrations during individual floods. High resolution diagrams of SPM concentrations versus discharge show clockwise and anti-clockwise hysteresis loops that were attributed to different sediment sources. Annual SPM fluxes were calculated for the Garonne River (La Réole) in 1994-1998, and for the Nivelle River (Saint Pée-sur-Nivelle) in 1996 by addition of daily fluxes and 30-minute fluxes, respectively. The annual SPM fluxes derived from the most complete dataset derived are considered as reference fluxes. Then, different fixed period strategies (e.g. monthly, semi-monthly, weekly, daily) corresponding to lower sampling frequencies were simulated by randomly extracting individual SPM. and water discharge data from the data base. For each simulation, the reduced dataset was used to estimate maximum and minimum annual SPM fluxes in order to determine the confidence level generated for a given sampling strategy. To obtain a reliable estimate of the SPM flux with less than 20 % error, the minimum sampling frequency is every three days for the Garonne River, whereas for the Nivelle River the minimum sampling frequency for reliable SPM flux estimation is every six hours. This difference in minimum sampling frequency between the two watersheds appears to depend rather on flow

  15. Diamagnetic flux measurement in Aditya tokamak

    SciTech Connect

    Kumar, Sameer; Jha, Ratneshwar; Lal, Praveen; Hansaliya, Chandresh; Gopalkrishna, M. V.; Kulkarni, Sanjay; Mishra, Kishore

    2010-12-15

    Measurements of diamagnetic flux in Aditya tokamak for different discharge conditions are reported for the first time. The measured diamagnetic flux in a typical discharge is less than 0.6 mWb and therefore it has required careful compensation for various kinds of pick-ups. The hardware and software compensations employed in this measurement are described. We introduce compensation of a pick-up due to plasma current of less than 20 kA in short duration discharges, in which plasma pressure gradient is supposed to be negligible. The flux measurement during radio frequency heating is also presented in order to validate compensation.

  16. Fast flux module detection using matroid theory.

    PubMed

    Reimers, Arne C; Bruggeman, Frank J; Olivier, Brett G; Stougie, Leen

    2015-05-01

    Flux balance analysis (FBA) is one of the most often applied methods on genome-scale metabolic networks. Although FBA uniquely determines the optimal yield, the pathway that achieves this is usually not unique. The analysis of the optimal-yield flux space has been an open challenge. Flux variability analysis is only capturing some properties of the flux space, while elementary mode analysis is intractable due to the enormous number of elementary modes. However, it has been found by Kelk et al. (2012) that the space of optimal-yield fluxes decomposes into flux modules. These decompositions allow a much easier but still comprehensive analysis of the optimal-yield flux space. Using the mathematical definition of module introduced by Müller and Bockmayr (2013b), we discovered useful connections to matroid theory, through which efficient algorithms enable us to compute the decomposition into modules in a few seconds for genome-scale networks. Using that every module can be represented by one reaction that represents its function, in this article, we also present a method that uses this decomposition to visualize the interplay of modules. We expect the new method to replace flux variability analysis in the pipelines for metabolic networks. PMID:25565150

  17. Flux Based Surface Boundary Conditions for Navier-Stokes Simulations

    NASA Astrophysics Data System (ADS)

    Fertig, M.; Auweter-Kurtz, M.

    2005-02-01

    During re-entry high thermal combined with mechanical loads arise at the TPS surface of a re-entry vehicle. Due to low gas density, high Knudsen Numbers arise, which indicate rarefaction effects such as thermo-chemical non-equilibrium as well as temperature and velocity slip. With increasing altitude, local Knudsen Numbers predict the failure of continuum equations starting in the bow shock and at the surface. While local failure of the equations in the shock can be neglected for the determination of surface loads, local failure at the surface is not negligible. The validity of continuum models can be extended by emploing surface boundary equations accounting for temperature and velocity slip. A new flux based model has been developed originating on the Boltzmann Equation. Making use of the Enskog Method perturbed partition functions for a multi-component gas are determined from the Boltzmann Equation. By introduction of the moments of Boltzmann's Equation, Maxwell's Transport Equation can be obtained. Particles approaching the surface are distinguished from particles leaving the surface depending on their molecular velocities. Hence, mass, momentum and energy fluxes to the surface can be determined employing the collisional invariants. Reactive as well as scattering models can be easily introduced in order to compute the fluxes from the surface. Finally, flux differences are balanced with the continuum fluxes from the Navier-Stokes equations. Hence, the model is able to predict temperature and velocity slip at the surface of a re-entry vehicle under rarefied conditions. Moreover, it is valid in the continuum regime as well. The boundary equations are solved fully implicit and fully coupled with the non-equilibrium Navier-Stokes Code URANUS. Results are compared to DSMC simulations for the re-entry of the US Space Shuttle orbiter at high altitudes. Key words: Navier-Stokes; re-entry; slip; non-equilibrium.

  18. Updated Absolute Flux Calibration of the COS FUV Modes

    NASA Astrophysics Data System (ADS)

    Massa, D.; Ely, J.; Osten, R.; Penton, S.; Aloisi, A.; Bostroem, A.; Roman-Duval, J.; Proffitt, C.

    2014-03-01

    We present newly derived point source absolute flux calibrations for the COS FUV modes at both the original and second lifetime positions. The analysis includes observa- tions through the Primary Science Aperture (PSA) of the standard stars WD0308-565, GD71, WD1057+729 and WD0947+857 obtained as part of two calibration programs. Data were were obtained for all of the gratings at all of the original CENWAVE settings at both the original and second lifetime positions and for the G130M CENWAVE = 1222 at the second lifetime position. Data were also obtained with the FUVB segment for the G130M CENWAVE = 1055 and 1096 setting at the second lifetime position. We also present the derivation of L-flats that were used in processing the data and show that the internal consistency of the primary standards is 1%. The accuracy of the absolute flux calibrations over the UV are estimated to be 1-2% for the medium resolution gratings, and 2-3% over most of the wavelength range of the G140L grating, although the uncertainty can be as large as 5% or more at some G140L wavelengths. We note that these errors are all relative to the optical flux near the V band and small additional errors may be present due to inaccuracies in the V band calibration. In addition, these error estimates are for the time at which the flux calibration data were obtained; the accuracy of the flux calibration at other times can be affected by errors in the time dependent sensitivity (TDS) correction.

  19. LCLS Spectral Flux Viewer

    Energy Science and Technology Software Center (ESTSC)

    2005-10-25

    This application (FluxViewer) is a tool for displaying spectral flux data for the Linac Coherent Light Source (LCLS). This tool allows the user to view sliced spatial and energy distributions of the photons selected for specific energies and positions transverse to the beam axis.

  20. Airborne flux measurements of Biogenic Isoprene over California

    SciTech Connect

    Misztal, P.; Karl, Thomas G.; Weber, Robin; Jonsson, H. H.; Guenther, Alex B.; Goldstein, Allen H.

    2014-10-10

    Biogenic Volatile Organic Compound (BVOC) fluxes were measured onboard the CIRPAS Twin Otter aircraft as part of the California Airborne BVOC Emission Research in Natural Ecosystem Transects (CABERNET) campaign during June 2011. The airborne virtual disjunct eddy covariance (AvDEC) approach used measurements from a PTR-MS and a wind radome probe to directly determine fluxes of isoprene, MVK+MAC, methanol, monoterpenes, and MBO over ~10,000-km of flight paths focusing on areas of California predicted to have the largest emissions of isoprene. The Fast Fourier Transform (FFT) approach was used to calculate fluxes over long transects of more than 15 km, most commonly between 50 and 150 km. The Continuous Wavelet Transformation (CWT) approach was used over the same transects to also calculate "instantaneous" fluxes with localization of both frequency and time independent of non-stationarities. Vertical flux divergence of isoprene is expected due to its relatively short lifetime and was measured directly using "racetrack" profiles at multiple altitudes. It was found to be linear and in the range 5% to 30% depending on the ratio of aircraft altitude to PBL height (z/zi). Fluxes were generally measured by flying consistently 1 at 400 m ±50 m (a.g.l.) altitude, and extrapolated to the surface according to the determined flux divergence. The wavelet-derived surface fluxes of isoprene averaged to 2 km spatial resolution showed good correspondence to Basal Emission Factor (BEF) landcover datasets used to drive biogenic VOC (BVOC) emission models. The surface flux of isoprene was close to zero over Central Valley crops and desert shrublands, but was very high (up to 15 mg m-2 h-1) above oak woodlands, with clear dependence of emissions on temperature and oak density. Isoprene concentrations of up to 8 ppb were observed at aircraft height on the hottest days and over the dominant source regions. While isoprene emissions from agricultural crop regions, shrublands, and

  1. Stabilization of flux during dead-end ultra-low pressure ultrafiltration.

    PubMed

    Peter-Varbanets, Maryna; Hammes, Frederik; Vital, Marius; Pronk, Wouter

    2010-06-01

    Gravity driven ultrafiltration was operated in dead-end mode without any flushing or cleaning. In contrary to general expectations, the flux value stabilized after about one week of operation and remained constant during an extended period of time (several months). Different surface water types and diluted wastewater were used as feed water and, depending on the feed water composition, stable flux values were in the range of 4-10 L h(-1) m(-2). When sodium azide was added to the feed water to diminish the biological activity, no stabilization of flux occurred, indicating that biological processes play an important role in the flux stabilization process. Confocal laser scanning microscopy revealed the presence of a biofouling layer, of which the structure changed over time, leading to relatively heterogeneous structures. It is assumed that the stabilization of flux is related to the development of heterogeneous structures in the fouling layer, due to biological processes in the layer. The phenomenon of flux stabilization opens interesting possibilities for application, for instance in simple and low-cost ultrafiltration systems for decentralized drinking water treatment in developing and transition countries, independent of energy supply, chemicals, or complex process control. PMID:20488503

  2. The Effects of Flux Spectrum Perturbation on Transmutation of Actinides: Optimizing the Production of Transcurium Isotopes

    SciTech Connect

    Hogle, Susan L; Maldonado, G Ivan; Alexander, Charles W

    2012-01-01

    This research presented herein involves the optimization of transcurium production in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Due to the dependence of isotope cross sections on incoming neutron energy, the efficiency with which an isotope is transmuted is highly dependent upon the flux spectrum. There are certain energy bands in which the rate of fission of transcurium production feedstock materials is minimized, relative to the rate of non-fission absorptions. It is proposed that by perturbing the flux spectrum, it is possible to increase the amount of key isotopes, such as 249Bk and 252Cf, that are produced during a transmutation cycle, relative to the consumption of feedstock material. This optimization process is carried out by developing an iterative objective framework involving problem definition, flux spectrum and cross section analysis, simulated transmutation, and analysis of final yields and transmutation parameters. It is shown that it is possible to perturb the local flux spectrum in the transcurium target by perturbing the composition of the target. It is further shown that these perturbations are able to alter the target yields in a non-negligible way. Future work is necessary to develop the optimization framework, and identify the necessary algorithms to update the problem definition based upon progress towards the optimization goals.

  3. Sensitivity of Vadose Zone Water Fluxes to Climate Shifts in Arid Settings

    SciTech Connect

    Pfletschinger, H.; Prömmel, K.; Schüth, C.; Herbst, M.; Engelhardt, I.

    2014-01-01

    Vadose zone water fluxes in arid settings are investigated regarding their sensitivity to hydraulic soil parameters and meteorological data. The study is based on the inverse modeling of highly defined soil column experiments and subsequent scenario modeling comparing different climate projections for a defined arid region. In arid regions, groundwater resources are prone to depletion due to excessive water use and little recharge potential. Especially in sand dune areas, groundwater recharge is highly dependent on vadose zone properties and corresponding water fluxes. Nevertheless, vadose zone water fluxes under arid conditions are hard to determine owing to, among other reasons, deep vadose zones with generally low fluxes and only sporadic high infiltration events. In this study, we present an inverse model of infiltration experiments accounting for variable saturated nonisothermal water fluxes to estimate effective hydraulic and thermal parameters of dune sands. A subsequent scenario modeling links the results of the inverse model with projections of a global climate model until 2100. The scenario modeling clearly showed the high dependency of groundwater recharge on precipitation amounts and intensities, whereas temperature increases are only of minor importance for deep infiltration. However, simulated precipitation rates are still affected by high uncertainties in the response to the hydrological input data of the climate model. Thus, higher certainty in the prediction of precipitation pattern is a major future goal for climate modeling to constrain future groundwater management strategies in arid regions.

  4. Solar flux variation of the electron temperature morning overshoot in the equatorial F region

    NASA Astrophysics Data System (ADS)

    Stolle, C.; Liu, H.; Truhlík, V.; Lühr, H.; Richards, P. G.

    2011-04-01

    Using 8 years of CHAMP satellite observations of the equatorial electron temperature, Te, we investigate its behavior during the morning overshoot and at ionospheric altitudes below 450 km including its variation with solar activity. The morning Te has a maximum at the dip equator and decreases gradually with increasing latitude, which is due to the increasing importance of heat conduction as the dip angle becomes larger. The amplitude of the equatorial morning overshoot Te decreases with increasing solar flux by about -10°K/solar flux unit depending on season and longitude. Trends of similar magnitude are predicted by the FLIP model. The model calculations confirm that the electron cooling due to enhanced electron-ion collisions increases faster than the heating of thermal electrons through collision with photoelectrons for increasing solar EUV. Both data and model showed that elevated electron temperatures persist to later local times during low solar activity. Obviously, the decreased background plasma density, together with the slower rise of electron density after sunrise under such conditions are responsible for the longer persistence. First investigations of longitudinal aspects revealed that the strength of the anticorrelation between morning Te and solar flux and the seasonal difference of the Te amplitude varies with longitude. The positive correlation between the morning overshoot and solar flux at 600 km as was shown earlier in Hinotori data is consistent with FLIP predictions and radar observations. The solar flux variation of the morning Te reverses sign between 400 and 600 km.

  5. Comparison of the PSD radial profiles between before and after geosynchronous flux dropout: THEMIS observations

    NASA Astrophysics Data System (ADS)

    Hwang, J.; Lee, D.; Kim, K.; Choi, E.; Shin, D.; Kim, J.; Cho, J.

    2012-12-01

    Geosynchronous electron flux dropouts are most likely due to fast drift loss of the particles to the magnetopause (or equivalently, the "magnetopause shadowing effect"). A possible effect related to the drift loss is the radial diffusion of PSD due to gradient of PSD set by the drift loss effect at an outer L region. This possibly implies that the drift loss can affect the flux levels even inside the trapping boundary. We recently investigated the details of such diffusion process by solving the diffusion equation with a set of initial and boundary conditions set by the drift loss. Motivated by the simulation work, we have examined observationally the energy spectrum and pitch angle distribution near trapping boundary during the geosynchronous flux dropouts. For this work, we have first identified a list of geosynchronous flux dropout events for 2007-2010 from GOES satellite electron measurements and solar wind pressures observed by ACE satellite. We have then used the electron data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft measurements to investigate the particle fluxes. The five THEMIS spacecraft sufficiently cover the inner magnetospheric regions near the equatorial plane and thus provide us with data of much higher spatial resolution. In this paper, we report some case studies showing energy dependence during magnetopause shadowing effect.

  6. Systematics of flux tubes in the dual Ginzburg-Landau theory and Casimir scaling hypothesis: folklore and lattice facts

    NASA Astrophysics Data System (ADS)

    Koma, Y.; Koma (Takayama), M.

    2003-01-01

    The ratios between the string tensions σ_D of color-electric flux tubes in higher and fundamental SU(3) representations, dD equiv σD/σ3, are systematically studied in a Weyl symmetric formulation of the DGL theory. The ratio is found to depend on the Ginzburg-Landau (GL) parameter, kappa equiv m_{χ}/mB, the mass ratio between the monopoles (m_{χ}) and the masses of the dual gauge bosons (mB). While the ratios dD follow a simple flux counting rule in the Bogomol'nyi limit, kappa=1.0, systematic deviations appear with increasing kappa due to interactions between the fundamental flux inside a higher representation flux tube. We find that in a type-II dual superconducting vacuum near kappa = 3.0 this leads to a consistent description of the ratios dD as observed in lattice QCD simulations.

  7. Self-organization in magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Lukin, Vyacheslav S.

    2014-06-01

    This cross-disciplinary special issue on 'Self-organization in magnetic flux ropes' follows in the footsteps of another collection of manuscripts dedicated to the subject of magnetic flux ropes, a volume on 'Physics of magnetic flux ropes' published in the American Geophysical Union's Geophysical Monograph Series in 1990 [1]. Twenty-four years later, this special issue, composed of invited original contributions highlighting ongoing research on the physics of magnetic flux ropes in astrophysical, space and laboratory plasmas, can be considered an update on our state of understanding of this fundamental constituent of any magnetized plasma. Furthermore, by inviting contributions from research groups focused on the study of the origins and properties of magnetic flux ropes in a variety of different environments, we have attempted to underline both the diversity of and the commonalities among magnetic flux ropes throughout the solar system and, indeed, the universe. So, what is a magnetic flux rope? The answer will undoubtedly depend on whom you ask. A flux rope can be as narrow as a few Larmor radii and as wide as the Sun (see, e.g., the contributions by Heli Hietala et al and by Angelous Vourlidas). As described below by Ward Manchester IV et al , they can stretch from the Sun to the Earth in the form of interplanetary coronal mass ejections. Or, as in the Swarthmore Spheromak Experiment described by David Schaffner et al , they can fit into a meter-long laboratory device tended by college students. They can be helical and line-tied (see, e.g., Walter Gekelman et al or J Sears et al ), or toroidal and periodic (see, e.g., John O'Bryan et al or Philippa Browning et al ). They can form in the low plasma beta environment of the solar corona (Tibor Török et al ), the order unity beta plasmas of the solar wind (Stefan Eriksson et al ) and the plasma pressure dominated stellar convection zones (Nicholas Nelson and Mark Miesch). In this special issue, Setthivoine You

  8. The Effects of High-Flux Broadband Photoirradiation on Metallic Surfaces: Nickel and Stainless Steels

    NASA Astrophysics Data System (ADS)

    Mesarwi, Abdul-Wahab Khaled

    The effects of high flux (>=q1 MW/m^2) broad band (hnu ~ 0.5-6.2 eV) radiation on metallic surfaces were studied for nickel and a variety of stainless steels. This was done by exposing samples of these materials in air to a concentrated photon beam at sample temperatures 350-500^circ C. Analysis and characterization were done by Auger electron spectroscopy (AES) combined with ion sputter depth profiling, x-ray photoelectron spectroscopy (XPS), mass spectrometry (MS), thermal desorption spectroscopy (TDS), low energy electron diffraction (LEED) and scanning electron microscopy (SEM). The results were compared with reference samples of similar materials heated under the same conditions of temperatures and times but using infrared radiation. Oxidation under high flux photo-irradiation was found to be significantly enhanced for all samples. For nickel, the oxide thickness was found to be up to 320% greater under 3.3 MW/m^2 flux irradiation than under infrared heating. Also, the oxide thickness was found to increase linearly with increasing flux. The wavelength dependence of the photo-enhanced oxidation was studied using lasers and it has shown increasing oxidation with decreasing wavelength with a threshold wavelength around lambda = 720 nm. Stainless steels, depending on their composition, have shown varying amounts of photo-enhanced oxidation, with oxide thickness increases of up to 874% under high flux irradiation for type 304. The oxide thickness was found to increase with increasing flux but the dependence, however, was found to be quadratic in flux. Also, the oxide thickness was found to increase with decreasing wavelength and a threshold wavelength around lambda~ 413 nm was observed. The microstructure and morphology of the oxides produced under photo-irradiation and infrared heating were also studied and were found different. Finally, the surface temperature under high flux photo-irradiation was measured for Ni(100) using LEED. A maximum increase of 63^circC in

  9. Directed flux motor

    NASA Technical Reports Server (NTRS)

    Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

    2011-01-01

    A directed flux motor described utilizes the directed magnetic flux of at least one magnet through ferrous material to drive different planetary gear sets to achieve capabilities in six actuated shafts that are grouped three to a side of the motor. The flux motor also utilizes an interwoven magnet configuration which reduces the overall size of the motor. The motor allows for simple changes to modify the torque to speed ratio of the gearing contained within the motor as well as simple configurations for any number of output shafts up to six. The changes allow for improved manufacturability and reliability within the design.

  10. Heat Flux Sensor

    NASA Technical Reports Server (NTRS)

    1994-01-01

    A heat flux microsensor developed under a NASP Small Business Innovation Research (SBIR) has a wide range of potential commercial applications. Vatell Corporation originally designed microsensors for use in very high temperatures. The company then used the technology to develop heat flux sensors to measure the rate of heat energy flowing in and out of a surface as well as readings on the surface temperature. Additional major advantages include response to heat flux in less than 10 microseconds and the ability to withstand temperatures up to 1,200 degrees centigrade. Commercial applications are used in high speed aerodynamics, supersonic combustion, blade cooling, and mass flow measurements, etc.

  11. Terminology as a key uncertainty in net land use flux estimates (Invited)

    NASA Astrophysics Data System (ADS)

    Pongratz, J.; Reick, C. H.; Houghton, R. A.; House, J.

    2013-12-01

    Land use and land cover change (LULCC) constitutes the second largest source of anthropogenic CO2 emissions today. LULCC will play an important role for the global carbon cycle also in the future: depending on the socioeconomic scenario, substantial carbon sinks are expected for afforestation and by substitution effects of biofuel use, and substantial sources due to continuing clearing. However, LULCC is also the largest uncertainty in the global carbon cycle, affecting in turn the quality of our estimates of the residual land sink. Recent studies have identified various reasons for the large discrepancy between studies of land use emission estimates (the 'net land use flux'). These include differences with respect to the assumed rates of deforestation, the carbon densities for vegetation cleared, and the inclusiveness of management activities. However, the large range across published LULCC emission estimates is also fundamentally related to the exact definition of the net land use flux with respect to the way it is calculated by models. We introduce a conceptual framework that allows us to compare the different types of models and simulation setups used to derive land use fluxes. We find that published studies are based on at least 9 different definitions of the net land use flux. Our analysis reveals three key processes that are accounted for in different ways: the land use feedback, the loss of additional sink capacity, and legacy (regrowth and decomposition) fluxes. We show that these terminological differences, alone, explain a difference by a factor 2 between published net land use flux estimates for the historical period, and even larger differences for estimates of future land use emissions. While the decision to use a specific definition will depend on the scientific application and potential political considerations, our analysis shows that the uncertainty of the net land use flux can be substantially reduced by resolving the existing terminological

  12. Observations of intense trapped electron fluxes at synchronous altitudes

    NASA Technical Reports Server (NTRS)

    Davidson, G. T.; Filbert, P. C.; Nightingale, R. W.; Imhof, W. L.; Reagan, J. B.

    1988-01-01

    The concept of flux limiting in the outer radiation belt proposed by Kennel and Petschek (1966) has been tested in a dynamic situation by using data acquired with instruments aboard the SCATHA satellite. A case-by-case analysis of 12 events for evidence of flux limiting under various magnetospheric conditions is made. The reuslts indicate qualitative agreement with the flux limiting theory for all the events studied. Even the quiescent events and hard-spectrum events are consistent with flux limiting. The limiting flux level at any instant appears to depend strongly on the recent history of the trapped electrons and plasma in the outer magnetosphere.

  13. Implicit Flux Feedback Control for Magnetic Bearings

    NASA Astrophysics Data System (ADS)

    Keith, Frederick Joseph

    Design and implementation of a dynamic system that includes magnetic bearings is dependent on knowledge of the relationship between the command input to the magnetic actuator and the force that the bearing actually applies to the rotor (or other structure) being controlled. Traditional designs relate the bearing coil current to the developed bearing force; unfortunately, the current-to-force relationship is not invariant to magnetic hysteresis, magnetic saturation, eddy current effects, or changes in the bearing air gap length. To overcome these limitations, an approach known as implicit flux feedback is explored. Since the gap force in a magnetic circuit is directly related to the flux in that gap, measuring the gap flux and employing it as a feedback state results in a bearing with an improved command -to-force relation which is less subject to the error sources mentioned above. Confirmation of the flux-to-force relationship is accomplished via experiments on a test apparatus specifically designed to allow simultaneous force and flux measurements on a single-axis magnetic bearing (using both laminated and solid magnetic components). Successful implementation of the flux feedback algorithm simplifies the control system design of magnetic bearing systems by providing a more accurate, well characterized actuator model, and, by overcoming such effects as hysteresis, saturation, eddy currents and gap dependence, this approach provides magnetic bearings which exhibit significantly improved dynamic performance.

  14. Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system

    DOEpatents

    Kosc, Tanya Z.; Marshall, Kenneth L.; Jacobs, Stephen D.

    2006-05-09

    Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.

  15. Fluxes across a thermohaline interface

    NASA Astrophysics Data System (ADS)

    Fleury, M.; Lueck, R. G.

    1991-07-01

    Measurements of velocity and temperature microstructure and hydrography were made with a towed vehicle moving in and around a single interface in a double-diffusive staircase. The interface was traversed 222 times in a saw-tooth pattern over a track 35 km long. The salinity and potential temperature and density in the mixed layers adjacent to the interface were spatially uniform except for one 8 km long anomaly. The rate of dissipation of kinetic energy was uniformly low in the interface and in the mixed layers, except for one section 600 m long where a Kelvin-Helmholtz instability generated turbulence. For the non-turbulent section of the interface, the mean rate of dissipation was 30.2 × 10 -10 W kg -1 in the mixed layers and 9.5 × 10 -10 W kg -1 in the interface. The non-dimensional dissipation rate, ɛ/vN 2, was almost always less than 16 in the interface and therfore, there was no turblent buoyancy flux according to ROHRet al. (1988, Journal of Fluid Mechanics, 195, 77-111). The average double-diffusive flux of buoyancy by heat was 3.6 × 10 -10 W kg -1. Under certain assumptions the ratio of the flux of buoyancy by heat and salt can be estimated to be 0.53 ± 0.10, in good agreement with laboratory and theoretical estimates for salt fingers. The average Cox number was about 8 in the interface, consistent with the theories of STERN (1975, Ocean circulation physics, Academic Press) and KUNZE (1987, Journal of Marine Research, 45 533-556), but displayed an inverse dependence on the vertical temperature gradient which was not predicted. As a result, the flux of buoyancy, as well as the individual contributions by heat and salt, were independent of the local mean vertical temperature gradient and the buoyancy frequency. The length of the turbulent section of the interface was only 1.7% of the total length observed. However, the turbulence was intense—the mean rate of dissipation was 2.5 × 10 -8 W kg -1—and may have sufficiently enhanced the flux of heat to

  16. Flux change in viscous laminar flow under oscillating boundary condition

    NASA Astrophysics Data System (ADS)

    Ueda, R.; Mikada, H.; Goto, T.; Takekawa, J.

    2012-12-01

    The behavior of interstitial fluid is one of major interest in earth sciences in terms of the exploitation of water resources, the initiation of earthquakes, enhanced oil recovery (EOR), etc. Seismic waves are often known to increase the flux of interstitial fluid but the relationship between the flux and propagating seismic waves have not been well investigated in the past, although seismic stimulation has been applied in the oil industry for enhanced oil recovery (EOR). Many observations indicated that seismic waves could stimulate the oil production due to lowering of apparent viscosity coefficient, to the coalescence and/or the dispersion of droplets of a phase in multiphase fluids. However, the detailed mechanism of seismic stimulation has not been fully understood, either. In this study, We attempt to understand the mechanism of the flux change in viscous laminar flow under oscillating boundary condition for the simulation of interstitial flow. Here, we analyze a monophase flow in a pore throat. We first assume a Hagen-Poiseuille flow of incompressible fluid through a pore-throat in a porous medium. We adopt the Lattice Boltzmann method (LBM) in which the motion of fluid is simulated through the variation of velocity distribution function representing the distribution of discrete particle velocities. We use an improved incompressible LBKG model (d2q9i) proposed in Zou et. al. (1995) to accurately accommodate the boundary conditions of pressure and velocity in the Hagen-Poiseuille flow. We also use an half-way bounce back boundary condition as the velocity boundary condition. Also, we assume a uniform pressure (density) difference between inlet and outlet flow, and the density difference could initiate the flow in our simulation. The oscillating boundary condition is given by the body force acting on fluid particles. In this simulation, we found that the flux change is negligible under small amplitude of oscillation in both horizontal and vertical directions

  17. A Comparison Between Gravity Wave Momentum Fluxes in Observations and Climate Models

    NASA Technical Reports Server (NTRS)

    Geller, Marvin A.; Alexadner, M. Joan; Love, Peter T.; Bacmeister, Julio; Ern, Manfred; Hertzog, Albert; Manzini, Elisa; Preusse, Peter; Sato, Kaoru; Scaife, Adam A.; Zhou, Tiehan

    2013-01-01

    For the first time, a formal comparison is made between gravity wave momentum fluxes in models and those derived from observations. Although gravity waves occur over a wide range of spatial and temporal scales, the focus of this paper is on scales that are being parameterized in present climate models, sub-1000-km scales. Only observational methods that permit derivation of gravity wave momentum fluxes over large geographical areas are discussed, and these are from satellite temperature measurements, constant-density long-duration balloons, and high-vertical-resolution radiosonde data. The models discussed include two high-resolution models in which gravity waves are explicitly modeled, Kanto and the Community Atmosphere Model, version 5 (CAM5), and three climate models containing gravity wave parameterizations,MAECHAM5, Hadley Centre Global Environmental Model 3 (HadGEM3), and the Goddard Institute for Space Studies (GISS) model. Measurements generally show similar flux magnitudes as in models, except that the fluxes derived from satellite measurements fall off more rapidly with height. This is likely due to limitations on the observable range of wavelengths, although other factors may contribute. When one accounts for this more rapid fall off, the geographical distribution of the fluxes from observations and models compare reasonably well, except for certain features that depend on the specification of the nonorographic gravity wave source functions in the climate models. For instance, both the observed fluxes and those in the high-resolution models are very small at summer high latitudes, but this is not the case for some of the climate models. This comparison between gravity wave fluxes from climate models, high-resolution models, and fluxes derived from observations indicates that such efforts offer a promising path toward improving specifications of gravity wave sources in climate models.

  18. Acid soldering flux poisoning

    MedlinePlus

    The harmful substances in soldering fluxes are called hydrocarbons. They include: Ammonium chloride Rosin Hydrochloric acid Zinc ... Lee DC. Hydrocarbons. In: Marx JA, Hockberger RS, Walls RM, et ... Rosen's Emergency Medicine: Concepts and Clinical Practice . 8th ...

  19. Cryogenic flux-concentrator

    NASA Technical Reports Server (NTRS)

    Bailey, B. M.; Brechna, H.; Hill, D. A.

    1969-01-01

    Flux concentrator has high primary to secondary coupling efficiency enabling it to produce high magnetic fields. The device provides versatility in pulse duration, magnetic field strengths and power sources.

  20. On the Taxonomy of Flux Vacua

    SciTech Connect

    Giryavets, Alexander

    2004-04-25

    We investigate several predictions about the properties of IIB flux vacua on Calabi-Yau orientifolds, by constructing and characterizing a very large set of vacua in a specific example, an orientifold of the Calabi-Yau hypersurface in WP{sub 1,1,1,1,4}{sup 4}. We find support for the prediction of Ashok and Douglas that the density of vacua on moduli space is governed by det(-R-{omega}) where R and {omega} are curvature and Kaehler forms on the moduli space. The conifold point {psi} = 1 on moduli space therefore serves as an attractor, with a significant fraction of the flux vacua contained in a small neighborhood surrounding {psi} = 1. We also study the functional dependence of the number of flux vacua on the D3 charge in the fluxes, finding simple power law growth.

  1. Experimental flux measurements on a network scale

    SciTech Connect

    Schwender, J.

    2011-10-11

    Metabolic flux is a fundamental property of living organisms. In recent years, methods for measuring metabolic flux in plants on a network scale have evolved further. One major challenge in studying flux in plants is the complexity of the plant's metabolism. In particular, in the presence of parallel pathways in multiple cellular compartments, the core of plant central metabolism constitutes a complex network. Hence, a common problem with the reliability of the contemporary results of {sup 13}C-Metabolic Flux Analysis in plants is the substantial reduction in complexity that must be included in the simulated networks; this omission partly is due to limitations in computational simulations. Here, I discuss recent emerging strategies that will better address these shortcomings.

  2. Flux modulation scheme for direct current SQUID readout revisited

    NASA Astrophysics Data System (ADS)

    Hong, Tao; Wang, Hai; Zhang, Yi; Krause, Hans-Joachim; Braginski, Alex I.; Xie, Xiaoming; Offenhäusser, Andreas; Jiang, Mianheng

    2016-02-01

    The flux modulation scheme (FMS) is the standard readout technique of dc SQUIDs, where a step-up transformer links the SQUID to the preamplifier. The transformer's primary winding shunts the SQUID via a large capacitor while the secondary winding connects it to the preamplifier. A modulation flux having a frequency of typically 100 kHz generates an ac voltage across the SQUID, stepped up by the transformer. The SQUID with FMS is customarily operated in the current bias mode, because a constant dc bias current flows only through the SQUID due to the capacitor isolation. With FMS, however, the transformer ac shunts the SQUID so that in reality the operating mode is neither purely current-biased nor voltage-biased but rather nominal current-biased or "mixed biased." Our objective is to experimentally investigate the consequences of ac shunting of the dc SQUID in FMS and the transformer's transfer characteristics. For different shunt values we measure the change in the SQUID bias current due to the ac shunt using another SQUID in the two-stage readout scheme, and simultaneously monitor the SQUID output voltage signal. We then explain our measurements by a simplified graphic analysis of SQUID intrinsic current-voltage (I-V) characteristics. Since the total current flowing through the SQUID is not constant due to the shunting effect of the transformer, the amplitude of SQUID flux-to-voltage characteristics V(Φ) is less as compared to the direct readout scheme (DRS). Furthermore, we analyze and compare V(Φ) obtained by DRS and FMS. We show that in FMS, the transfer characteristics of the SQUID circuit also depend on the isolation capacitance and the dynamic resistance of the SQUID.

  3. Influence of random point defects introduced by proton irradiation on the flux creep rates and magnetic field dependence of the critical current density J c of co-evaporated GdBa2Cu3O7-δ coated conductors

    NASA Astrophysics Data System (ADS)

    Haberkorn, N.; Kim, Jeehoon; Suárez, S.; Lee, Jae-Hun; Moon, S. H.

    2015-12-01

    We report the influence of random point defects introduced by 3 MeV proton irradiation (doses of 0.5 × 1016, 1 × 1016, 2 × 1016 and 6 × 1016 cm-2) on the vortex dynamics of co-evaporated 1.3 μm thick, GdBa2Cu3O7-δ coated conductors. Our results indicate that the inclusion of additional random point defects reduces the low field and enhances the in-field critical current densities J c. The main in-field J c enhancement takes place below 40 K, which is in agreement with the expectations for pinning by random point defects. In addition, our data show a slight though clear increase in flux creep rates as a function of irradiation fluence. Maley analysis indicates that this increment can be associated with a reduction in the exponent μ characterizing the glassy behavior.

  4. Dynamical Evolution of a Coronal Streamer-Flux Rope System: 2. A Self-Consistent Non-Planar Magnetohydrodynamic Simulation

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Guo, W. P.; Dryer, Murray

    1996-01-01

    The dynamical response of a helmet streamer to a flux rope escape from the sub-photosphere is examined in a physically self-consistent manner within the approximation of axisymmetric three-dimensional magnetohydrodynamics (i.e., so-called '2 1/2 D'). In contrast to the previous planar analyses of Paper 1 (Wu, Guo, and Wang), the present study shows, with the inclusion of out-of-plane components of magnetic and velocity fields, that the magnetic configuration represents a helical flux rope instead of a planar bubble as shown in Paper 1. Because of this more physically-realistic configuration, we are able to examine the dynamical evolution of the helical flux rope's interaction with the helmet streamer. This process leads to the formation of two parts of the solar mass ejection: (i) the expulsion of the helmet dome due to eruption of this flux rope, and (ii) the flux rope's eruption itself. When this two-part feature propagates out to the interplanetary space, it exhibits all the physical characteristics of observed interplanetary magnetic clouds. These numerical simulations also show that the dynamical behavior of the streamer-flux rope system has three distinct states: (i) quasi-equilibrium, (ii) non-equilibrium, and (iii) eruptive state depending on the energy level of the flux rope.

  5. Benthic fluxes in San Francisco Bay

    USGS Publications Warehouse

    Hammond, Douglas E.; Fuller, C.; Harmon, D.; Hartman, Blayne; Korosec, M.; Miller, L.G.; Rea, R.; Warren, S.; Berelson, W.; Hager, S.W.

    1985-01-01

    Measurements of benthic fluxes have been made on four occasions between February 1980 and February 1981 at a channel station and a shoal station in South San Francisco Bay, using in situ flux chambers. On each occasion replicate measurements of easily measured substances such as radon, oxygen, ammonia, and silica showed a variability (??1??) of 30% or more over distances of a few meters to tens of meters, presumably due to spatial heterogeneity in the benthic community. Fluxes of radon were greater at the shoal station than at the channel station because of greater macrofaunal irrigation at the former, but showed little seasonal variability at either station. At both stations fluxes of oxygen, carbon dioxide, ammonia, and silica were largest following the spring bloom. Fluxes measured during different seasons ranged over factors of 2-3, 3, 4-5, and 3-10 (respectively), due to variations in phytoplankton productivity and temperature. Fluxes of oxygen and carbon dioxide were greater at the shoal station than at the channel station because the net phytoplankton productivity is greater there and the organic matter produced must be rapidly incorporated in the sediment column. Fluxes of silica were greater at the shoal station, probably because of the greater irrigation rates there. N + N (nitrate + nitrite) fluxes were variable in magnitude and in sign. Phosphate fluxes were too small to measure accurately. Alkalinity fluxes were similar at the two stations and are attributed primarily to carbonate dissolution at the shoal station and to sulfate reduction at the channel station. The estimated average fluxes into South Bay, based on results from these two stations over the course of a year, are (in mmol m-2 d-1): O2 = -27 ?? 6; TCO2 = 23 ?? 6; Alkalinity = 9 ?? 2; N + N = -0.3 ?? 0.5; NH3 = 1.4 ?? 0.2; PO4 = 0.1 ?? 0.4; Si = 5.6 ?? 1.1. These fluxes are comparable in magnitude to those in other temperate estuaries with similar productivity, although the seasonal

  6. NONLINEAR THREE-DIMENSIONAL MAGNETOCONVECTION AROUND MAGNETIC FLUX TUBES

    SciTech Connect

    Botha, G. J. J.; Rucklidge, A. M.; Hurlburt, N. E. E-mail: A.M.Rucklidge@leeds.ac.uk

    2011-04-20

    Magnetic flux in the solar photosphere forms concentrations from small scales, such as flux elements, to large scales, such as sunspots. This paper presents a study of the decay process of large magnetic flux tubes, such as sunspots, on a supergranular scale. Three-dimensional nonlinear resistive magnetohydrodynamic numerical simulations are performed in a cylindrical domain, initialized with axisymmetric solutions that consist of a well-defined central flux tube and an annular convection cell surrounding it. As the nonlinear convection evolves, the annular cell breaks up into many cells in the azimuthal direction, allowing magnetic flux to slip between cells away from the central flux tube (turbulent erosion). This lowers magnetic pressure in the central tube, and convection grows inside the tube, possibly becoming strong enough to push the tube apart. A remnant of the central flux tube persists with nonsymmetric perturbations caused by the convection surrounding it. Secondary flux concentrations form between convection cells away from the central tube. Tube decay is dependent on the convection around the tube. Convection cells forming inside the tube as time-dependent outflows will remove magnetic flux. (This is most pronounced for small tubes.) Flux is added to the tube when flux caught in the surrounding convection is pushed toward it. The tube persists when convection inside the tube is sufficiently suppressed by the remaining magnetic field. All examples of persistent tubes have the same effective magnetic field strength, consistent with the observation that pores and sunspot umbrae all have roughly the same magnetic field strength.

  7. Slip Running Reconnection in Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Gekelman, W. N.; Van Compernolle, B.; Vincena, S. T.; De Hass, T.

    2012-12-01

    Magnetic flux ropes are due to helical currents and form a dense carpet of arches on the surface of the sun. Occasionally one tears loose as a coronal mass ejection and its rope structure can be detected by satellites close to the earth. Current sheets can tear into filaments and these are nothing other than flux ropes. Ropes are not static, they exert mutual ěc{J}×ěc{B} forces causing them to twist about each other and eventually merge. Kink instabilities cause them to violently smash into each other and reconnect at the point of contact. We report on experiments on two adjacent ropes done in the large plasma device (LAPD) at UCLA ( ne ˜ 1012, Te ˜ 6 eV, B0z=330G, Brope}\\cong{10G,trep=1 Hz). The currents and magnetic fields form exotic shapes with no ignorable direction and no magnetic nulls. Volumetric space-time data (70,600 spatial locations) show multiple reconnection sites with time-dependent locations. The concept of a quasi-separatrix layer (QSL), a tool to understand and visualize 3D magnetic field lines reconnection without null points is introduced. Three-dimensional measurements of the QSL derived from magnetic field data are presented. Within the QSL field lines that start close to one another rapidly diverge as they pass through one or more reconnection regions. The motion of magnetic field lines are traced as reconnection proceeds and they are observed to slip through the regions of space where the QSL is largest. As the interaction proceeds we double the current in the ropes. This accompanied by intense heating as observed in uv light and plasma flows measured by Mach probes. The interaction of the ropes is clearly seen by vislaulizng magnetic field data , as well as in images from a fast framing camera. Work supported by the Dept. of Energy and The National Science Foundation, done at the Basic Plasma Science Facility at UCLA.Magnetic Field lines (measured) of three flux ropes and the plasma currents associated with them

  8. Magnetic Flux Cancellation and Formation of Prominence

    NASA Astrophysics Data System (ADS)

    Miley, George; Kim, Mun Song; Chon Nam, Sok; Kim, Kyong Chol

    2015-08-01

    Magnetic flux cancellation appears to be closely related to various kinds of solar activities such as flares, microflares/surges/jets, X-ray bright points, erupting mini-filaments, transition region explosive events, filament formation, filament activation and eruption, and coronal mass ejections. It is commonly believed that magnetic reconnections in the low atmosphere are responsible for canceling magnetic features, and magnetic fragments are observed to originate as bipoles. According to the Sweet-Parker type reconnection model, the inflow speed closely corresponds to the converging speed of each pole in a canceling magnetic feature and the rate of flux cancellation must be explained by the observed converging speed. As distinct from the corona, the efficiency of photospheric magnetic reconnection may be due to the small Cowling conductivity, instead of the Spitzer, of weakly ionized and magnetized plasma in the low atmosphere of the sun. Using the VAL-C atmospheric model and Cowling conductivity, we have computed the parameters describing Sweet-Parker type reconnecting current sheets in the plasma of the solar photosphere and chromosphere, and particularly for the phenomena of magnetic flux cancellation and dark filament formation which occurred on July 2, 1994 we have estimated the rate of flux cancellation, the inflow speed(the converging speed) and the upward mass flux to compare with the observation. The results show that when taking account of the Cowling conductivity in the low atmosphere, large flux cancellation rates(>1019Mxhr-1) in solar active regions are better explained than by the Spitzer conductivity-considered reconnection model. Particularly for the flux cancellation event on July 2, 1994, the inflow speed(0.26kms-1)is almost similar to the converging speed(0.22kms-1)and the upward mass flux(3.3X1012gs-1) in the model is sufficient for the large dark filament formation in a time of several hours through magnetic flux cancellation process.

  9. Eclipse and noneclipse differential photoelectron flux.

    NASA Technical Reports Server (NTRS)

    Knudsen, W. C.; Sharp, G. W.

    1972-01-01

    Differential photoelectron flux in the energy range of 3 to 50 eV has been measured in the lower ionosphere both during the March 7, 1970, solar eclipse and during a period 24 hours earlier. The two measurements were made with identical retarding potential analyzers carried on Nike-Apache rocket flights to a peak altitude of approximately 180 km. The differential electron flux spectrum within totality on the eclipse flight had the same shape but was a factor of 10 smaller in magnitude than that measured on the control day at altitudes between 120 and 180 km, an expected result for an eclipse function decreasing to 1/10 at totality. The differential flux spectrum measured in full sun has the same general energy dependence as that reported by Doering et al. (1970) but is larger by a factor of 2 to 10, depending on altitude.

  10. Siphon flows in isolated magnetic flux tubes. 3: The equilibrium path of the flux tube arch

    NASA Technical Reports Server (NTRS)

    Thomas, John H.; Montesinis, Benjamin

    1989-01-01

    The arched equilibrium path of a thin magnetic flux tube in a plane-stratified, nonmagnetic atmosphere is calculated for cases in which the flux tube contains a steady siphon flow. The large scale mechanical equilibrium of the flux tube involves a balance among the magnetic buoyancy force, the net magnetic tension force due to the curvature of the flux tube axis, and the inertial (centrifugal) force due to the siphon flow along curved streamlines. The ends of the flux tube are assumed to be pinned down by some other external force. Both isothermal and adiabatic siphon flows are considered for flux tubes in an isothermal external atmosphere. For the isothermal case, in the absence of a siphon flow the equilibrium path reduces to the static arch calculated by Parker (1975, 1979). The presence of a siphon flow causes the flux tube arch to bend more sharply, so that magnetic tension can overcome the additional straightening effect of the inertial force, and reduces the maximum width of the arch. The curvature of the arch increases as the siphon flow speed increases. For a critical siphon flow, with supercritical flow in the downstream leg, the arch is asymmetric, with greater curvature in the downstream leg of the arch. Adiabatic flow have qualitatively similar effects, except that adiabatic cooling reduces the buoyancy of the flux tube and thus leads to significantly wider arches. In some cases the cooling is strong enough to create negative buoyancy along sections of the flux tube, requiring upward curvature of the flux tube path along these sections and sometimes leading to unusual equilibrium paths of periodic, sinusoidal form.

  11. Long-term CH3Br and CH3Cl flux measurements in temperate salt marshes

    NASA Astrophysics Data System (ADS)

    Blei, E.; Heal, M. R.; Heal, K. V.

    2010-11-01

    Fluxes of CH3Br and CH3Cl and their relationship with potential drivers such as sunlight, temperature and soil moisture, were monitored at fortnightly to monthly intervals for more than two years at two contrasting temperate salt marsh sites in Scotland. Manipulation experiments were conducted to further investigate possible links between drivers and fluxes. Fluxes followed both seasonal and diurnal trends with highest fluxes during summer days and lowest (negative) fluxes during winter nights. Mean (± 1 sd) annually and diurnally-weighted net emissions from the two sites were found to be 300 ± 44 ng m-2 h-1 for CH3Br and 662 ± 266 ng m-2 h-1 for CH3Cl. The fluxes from this work are similar to findings from this and other research groups for salt marshes in cooler, higher latitude climates, but lower than values from salt marshes in the Mediterranean climate of southern California. Statistical analysis generally did not demonstrate a strong link between temperature or sunlight levels and methyl halide fluxes, although it is likely that temperatures have a weak direct influence on emissions, and both certainly have indirect influence via the annual and daily cycles of the vegetation. CH3Cl flux magnitudes from different measurement locations depended on the plant species enclosed whereas such dependency was not discernible for CH3Br fluxes. In 14 out of 18 collars with vegetation CH3Br and CH3Cl net fluxes were significantly positively correlated. The CH3Cl/CH3Br net-emission mass ratio was 2.2, a magnitude lower than mass ratios of global methyl halide budgets (~22) or emissions from tropical rainforests (~60). This is likely due to preference for CH3Br production by the relatively high bromine content in the salt marsh plant material. Extrapolation based solely on data from this study yields salt marsh contributions of 0.5-3.2% and 0.05-0.33%, respectively, of currently-estimated total global production of CH3Br and CH3Cl, but actual global contributions likely

  12. Relationship of High-Altitude Photoelectron Fluxes and Solar Zenith Angle

    NASA Astrophysics Data System (ADS)

    Xu, Shaosui; Liemohn, Michael; Bougher, Stephen W.; Mitchell, David L.

    2015-04-01

    Numerous studies have shown the ionosphere quantities' dependence on solar zenith angle (SZA), following Chapman theory. One would assume that photoelectron fluxes are also SZA dependent. However, high-altitude (~400 km) electron observations from magnetometer/electron reflectometer (MAG/ER) on board Mars Global Surveyor (MGS) show that the high energy (>100 eV) photoelectron fluxes are better correlated with the solar irradiance solely, without SZA factored in, while the low energy is somehow insensitive to SZA. Such counterintuitive results are due to the existence of a photoelectron exobase, only above which the photoelectrons are able to transport and escape to high altitudes. Through our SuperThermal Electron Transport (STET) model, we have determined that this exobase is around an altitude of 150-160 km, above which the production rate is rather independent of SZA.

  13. Cigarette smoke extract increases albumin flux across pulmonary endothelium in vitro

    SciTech Connect

    Holden, W.E.; Maier, J.M.; Malinow, M.R.

    1989-01-01

    Cigarette smoking causes lung inflammation, and a characteristic of inflammation is an increase in vascular permeability. To determine if cigarette smoke could alter endothelial permeability, we studied flux of radiolabeled albumin across monolayers of porcine pulmonary artery endothelium grown in culture on microporous membranes. Extracts (in either dimethylsulfoxide or phosphate-buffered saline) of cigarette smoke in a range estimate of concentrations simulating cigarette smoke exposure to the lungs in vivo caused a dose-dependent increase in albumin flux that was dependent on extracellular divalent cations and associated with polymerization of cellular actin. The effect was reversible, independent of the surface of endothelial cells exposed (either luminal or abluminal), and due primarily to components of the vapor phase of smoke. The effects occurred without evidence of cell damage, but subtle morphological changes were produced by exposure to the smoke extracts. These findings suggest that cigarette smoke can alter permeability of the lung endothelium through effects on cytoskeletal elements.

  14. Investigation of radiation flux in certain band via the preheat of aluminum sample

    SciTech Connect

    Zhang, Chen; Wang, Zhebin; Wang, Feng; Peng, Xiaoshi; Jiang, Shaoen; Ding, Yongkun; Zhao, Bin; Hu, Guangyue; Zheng, Jian

    2013-12-15

    Quantitative evaluation of the fractions of high energy x-rays in a hohlraum is crucial to the indirect driven-drive scheme of inertial confinement fusion and many other applications in high energy density physics. Preheat of a sample due to x-rays sensitively depends on optical thin photons. Analyzing the motion of a sample due to preheat can thus provide valuable information of those x-rays. In this article, we propose a method to infer the temporal evolution of the x-ray fluxes in the bands of our interest. By matching the simulation results to the motions of an aluminum sample, we can infer the time-resolved x-ray fluxes around the aluminum K-edge and the gold M-band inside the hohlraum.

  15. Tunable magnetic flux sensor using a metallic Rashba ring with half-metal electrodes

    SciTech Connect

    Chen, J.; Jalil, M. B. A.; Tan, S. G.

    2011-04-01

    We propose a magnetic field sensor consisting of a square ring made of metal with a strong Rashba spin-orbital coupling (RSOC) and contacted to half-metal electrodes. Due to the Aharonov-Casher effect, the presence of the RSOC imparts a spin-dependent geometric phase to conduction electrons in the ring. The combination of the magnetic flux emanating from the magnetic sample placed below the ring, and the Aharonov-Casher effect due to RSOC results in spin interference, which modulates the spin transport in the ring nanostructure. By using the tight-binding nonequilibrium Green's function formalism to model the transport across the nanoring detector, we theoretically show that with proper optimization, the Rashba ring can function as a sensitive and tunable magnetic probe to detect magnetic flux.

  16. SAMOS Surface Fluxes

    NASA Astrophysics Data System (ADS)

    Smith, Shawn; Bourassa, Mark

    2014-05-01

    The development of a new surface flux dataset based on underway meteorological observations from research vessels will be presented. The research vessel data center at the Florida State University routinely acquires, quality controls, and distributes underway surface meteorological and oceanographic observations from over 30 oceanographic vessels. These activities are coordinated by the Shipboard Automated Meteorological and Oceanographic System (SAMOS) initiative in partnership with the Rolling Deck to Repository (R2R) project. Recently, the SAMOS data center has used these underway observations to produce bulk flux estimates for each vessel along individual cruise tracks. A description of this new flux product, along with the underlying data quality control procedures applied to SAMOS observations, will be provided. Research vessels provide underway observations at high-temporal frequency (1 min. sampling interval) that include navigational (position, course, heading, and speed), meteorological (air temperature, humidity, wind, surface pressure, radiation, rainfall), and oceanographic (surface sea temperature and salinity) samples. Vessels recruited to the SAMOS initiative collect a high concentration of data within the U.S. continental shelf and also frequently operate well outside routine shipping lanes, capturing observations in extreme ocean environments (Southern, Arctic, South Atlantic, and South Pacific oceans). These observations are atypical for their spatial and temporal sampling, making them very useful for many applications including validation of numerical models and satellite retrievals, as well as local assessments of natural variability. Individual SAMOS observations undergo routine automated quality control and select vessels receive detailed visual data quality inspection. The result is a quality-flagged data set that is ideal for calculating turbulent flux estimates. We will describe the bulk flux algorithms that have been applied to the

  17. Algebraic Flux Correction II

    NASA Astrophysics Data System (ADS)

    Kuzmin, Dmitri; Möller, Matthias; Gurris, Marcel

    Flux limiting for hyperbolic systems requires a careful generalization of the design principles and algorithms introduced in the context of scalar conservation laws. In this chapter, we develop FCT-like algebraic flux correction schemes for the Euler equations of gas dynamics. In particular, we discuss the construction of artificial viscosity operators, the choice of variables to be limited, and the transformation of antidiffusive fluxes. An a posteriori control mechanism is implemented to make the limiter failsafe. The numerical treatment of initial and boundary conditions is discussed in some detail. The initialization is performed using an FCT-constrained L 2 projection. The characteristic boundary conditions are imposed in a weak sense, and an approximate Riemann solver is used to evaluate the fluxes on the boundary. We also present an unconditionally stable semi-implicit time-stepping scheme and an iterative solver for the fully discrete problem. The results of a numerical study indicate that the nonlinearity and non-differentiability of the flux limiter do not inhibit steady state convergence even in the case of strongly varying Mach numbers. Moreover, the convergence rates improve as the pseudo-time step is increased.

  18. Inductance due to spin current

    SciTech Connect

    Chen, Wei

    2014-03-21

    The inductance of spintronic devices that transport charge neutral spin currents is discussed. It is known that in a media that contains charge neutral spins, a time-varying electric field induces a spin current. We show that since the spin current itself produces an electric field, this implies existence of inductance and electromotive force when the spin current changes with time. The relations between the electromotive force and the corresponding flux, which is a vector calculated by the cross product of electric field and the trajectory of the device, are clarified. The relativistic origin generally renders an extremely small inductance, which indicates the advantage of spin current in building low inductance devices. The same argument also explains the inductance due to electric dipole current and applies to physical dipoles consist of polarized bound charges.

  19. Comparison of debris flux models

    NASA Astrophysics Data System (ADS)

    Sdunnus, H.; Beltrami, P.; Klinkrad, H.; Matney, M.; Nazarenko, A.; Wegener, P.

    The availability of models to estimate the impact risk from the man-made space debris and the natural meteoroid environment is essential for both, manned and unmanned satellite missions. Various independent tools based on different approaches have been developed in the past years. Due to an increased knowledge of the debris environment and its sources e.g. from improved measurement capabilities, these models could be updated regularly, providing more detailed and more reliable simulations. This paper addresses an in-depth, quantitative comparison of widely distributed debris flux models which were recently updated, namely ESA's MASTER 2001 model, NASA's ORDEM 2000 and the Russian SDPA 2000 model. The comparison was performed in the frame of the work of the 20t h Interagency Debris Coordination (IADC) meeting held in Surrey, UK. ORDEM 2000ORDEM 2000 uses careful empirical estimates of the orbit populations based onthree primary data sources - the US Space Command Catalog, the H ystackaRadar, and the Long Duration Exposure Facility spacecraft returned surfaces.Further data (e.g. HAX and Goldstone radars, impacts on Shuttle windows andradiators, and others) were used to adjust these populations for regions in time,size, and space not covered by the primary data sets. Some interpolation andextrapolation to regions with no data (such as projections into the future) wasprovided by the EVOLVE model. MASTER 2001The ESA MASTER model offers a full three dimensional description of theterrestrial debris distribution reaching from LEO up to the GEO region. Fluxresults relative to an orbiting target or to an inertial volume can be resolved intosource terms, impactor characteristics and orbit, as well as impact velocity anddirection. All relevant debris source terms are considered by the MASTERmodel. For each simulated source, a corresponding debris generation model interms of mass/diameter distribution, additional velocities, and directionalspreading has been developed. A

  20. Hawking fluxes, back reaction and covariant anomalies

    NASA Astrophysics Data System (ADS)

    Kulkarni, Shailesh

    2008-11-01

    Starting from the chiral covariant effective action approach of Banerjee and Kulkarni (2008 Phys. Lett. B 659 827), we provide a derivation of the Hawking radiation from a charged black hole in the presence of gravitational back reaction. The modified expressions for charge and energy flux, due to the effect of one-loop back reaction are obtained.

  1. Computation of time-dependent subsurface pore pressure variations and stresses due to time varying water loads at the Itoiz reservoir (Northern Spain), and their relation with near seismicity

    NASA Astrophysics Data System (ADS)

    Luzón, F.; García-Jerez, A.; Santoyo, M. A.

    2009-04-01

    In this work we study the seismicity produced near the newly constructed Itoiz reservoir in the western Pyrenees (northern Spain). We computed the evolution of the stress changes in the subsoil due to the time water load distribution and relate it with the main seismicity occurred after the beginning of impoundment in 2004. We also computed the pore pressure variations produced around Itoiz dam using a hybrid technique which take into account the time varying water loads in the reservoir. In this methodology, two different techniques are joined to calculate each one of the partial solutions evolved: the pore pressure diffusion term is obtained by using the Green functions of the problem, whereas the second term due to stress time changes is computed with a Finite Difference Method (FDM). We pay special attention to the pore pressure changes at the hypocenter location of the mainshock (with magnitude mb = 4.6) occurred on September 2004, 8 months after the beginning of its impounding. After this, we compute the coseismic and postseismic stress changes produced by the main events of the seismic series and study its influence on the triggering of the aftershocks by means of the Coulomb Failure Stress criterion (ΔCFS). Results show that at the time of occurrence of the main earthquake the pore pressure change was of about 1000 Pa at the hypocenter. However, the pore pressure variation exceeded 1000 Pa at other earlier times and at many different positions near Itoiz dam without the occurrence of earlier earthquakes. Thus, the origin of the September 18, 2004 earthquake (mb = 4.6) can be explained when considering the pore pressure perturbation at a pre-existent fault in the hypocenter location with more aptitude to fail than other sites, together with the assumption of regional pre-existing stress field. At last we found, a large positive influence over most of the aftershocks of the seismic series due to the stress changes produced by the largest events.

  2. Natural elemental fluxes as licensing criteria: A methodology

    SciTech Connect

    Miller, B.; Smith, G.; Wingefors, S.

    1995-12-01

    A study has been performed to assess the viability of using fluxes of natural elements and radionuclides from the geosphere into the biosphere as a basis for defining allowable releases from a radioactive waste repository into the biosphere. The mass and radioactive fluxes of elements and radionuclides due to groundwater transport, glacial erosion and non-glacial weathering in the vicinity of the Aespoe Hard Rock Laboratory, Sweden, were quantified and compared to proposed Swedish limits for biosphere releases from a high-level waste repository. This work demonstrates that it is possible to calculate fluxes of naturally-occurring radionuclides that are directly comparable to performance assessment predictions of repository fluxes to the biosphere. Since the radiological impact of natural fluxes of radionuclides is broadly understood and since natural and repository fluxes can be assessed on a comparable basis, this suggests that natural fluxes can be used as a basis for defining indicators of repository safety.

  3. Airway Surface Dehydration by Transforming Growth Factor β (TGF-β) in Cystic Fibrosis Is Due to Decreased Function of a Voltage-dependent Potassium Channel and Can Be Rescued by the Drug Pirfenidone.

    PubMed

    Manzanares, Dahis; Krick, Stefanie; Baumlin, Nathalie; Dennis, John S; Tyrrell, Jean; Tarran, Robert; Salathe, Matthias

    2015-10-16

    Transforming growth factor β1 (TGF-β1) is not only elevated in airways of cystic fibrosis (CF) patients, whose airways are characterized by abnormal ion transport and mucociliary clearance, but TGF-β1 is also associated with worse clinical outcomes. Effective mucociliary clearance depends on adequate airway hydration, governed by ion transport. Apically expressed, large-conductance, Ca(2+)- and voltage-dependent K(+) (BK) channels play an important role in this process. In this study, TGF-β1 decreased airway surface liquid volume, ciliary beat frequency, and BK activity in fully differentiated CF bronchial epithelial cells by reducing mRNA expression of the BK γ subunit leucine-rich repeat-containing protein 26 (LRRC26) and its function. Although LRRC26 knockdown itself reduced BK activity, LRRC26 overexpression partially reversed TGF-β1-induced BK dysfunction. TGF-β1-induced airway surface liquid volume hyper-absorption was reversed by the BK opener mallotoxin and the clinically useful TGF-β signaling inhibitor pirfenidone. The latter increased BK activity via rescue of LRRC26. Therefore, we propose that TGF-β1-induced mucociliary dysfunction in CF airways is associated with BK inactivation related to a LRRC26 decrease and is amenable to treatment with clinically useful TGF-β1 inhibitors. PMID:26338706

  4. Protected Flux Pairing Qubit

    NASA Astrophysics Data System (ADS)

    Bell, Matthew; Zhang, Wenyuan; Ioffe, Lev; Gershenson, Michael

    2014-03-01

    We have studied the coherent flux tunneling in a qubit containing two submicron Josephson junctions shunted by a superinductor (a dissipationless inductor with an impedance much greater than the resistance quantum). The two low energy quantum states of this device, 0 and 1, are represented by even and odd number of fluxes in the loop, respectively. This device is dual to the charge pairing Josephson rhombi qubit. The spectrum of the device, studied by microwave spectroscopy, reflects the interference between coherent quantum phase slips in the two junctions (the Aharonov-Casher effect). The time domain measurements demonstrate the suppression of the qubit's energy relaxation in the protected regime, which illustrates the potential of this flux pairing device as a protected quantum circuit. Templeton Foundation, NSF, and ARO.

  5. Can abundance of methanogen be a good indicator for CH4 flux in soil ecosystems?

    PubMed

    Kim, Jinhyun; Lee, Seung-Hoon; Jang, Inyoung; Jeong, Sangseom; Kang, Hojeong

    2015-12-01

    Methane, which is produced by methanogenic archaea, is the second most abundant carbon compound in the atmosphere. Due to its strong radiative forcing, many studies have been conducted to determine its sources, budget, and dynamics. However, a mechanistic model of methane flux has not been developed thus far. In this study, we attempt to examine the relevance of the abundance of methanogen as a biological indicator of methane flux in three different types of soil ecosystems: permafrost, rice paddy, and mountainous wetland. We measured the annual average methane flux and abundance of methanogen in the soil ecosystems in situ. The correlation between methane flux and the abundance of methanogen exists only under a specific biogeochemical conditions such as SOM of higher than 60%, pH of 5.6-6.4, and water-saturated. Except for these conditions, significant correlations were absent. Therefore, microbial abundance information can be applied to a methane flux model selectively depending on the biogeochemical properties of the soil ecosystem. PMID:26123992

  6. Prevention of ion flux inhomogeneities in large area capacitively coupled discharges via the Electrical Asymmetry Effect

    NASA Astrophysics Data System (ADS)

    Schuengel, Edmund; Schulze, Julian; Mohr, Sebastian; Czarnetzki, Uwe

    2014-10-01

    For large area processing applications of capacitively coupled radio frequency (CCRF) discharges, the lateral uniformity of the plasma surface interaction is crucially important. The benefit of an increase in the plasma density and, therefore, in the overall deposition rate by driving the discharge at higher frequencies is accompanied with inhomogeneities caused by the presence of electromagnetic effects. Here, we propose a method based on the Electrical Asymmetry Effect (EAE) to prevent such inhomogeneities. Spatially resolved measurements of the ion flux onto the grounded electrode of a CCRF discharge operated in hydrogen show a standing wave pattern in a 81.36 MHz single-frequency discharge, strongly reducing the ion flux uniformity. However, applying a dual-frequency voltage waveform consisting of 40.68 MHz + 81.36 MHz, the lateral distribution of the ion flux can be controlled via the phase angle between the two applied harmonics. Using the EAE, a phase angle dependent DC self-bias develops in the geometrically symmetric discharge. Tuning the phase angle allows for the compensation of ion flux inhomogeneities due to the standing wave effect. Thus, a high and laterally uniform ion flux can be generated in electrically asymmetric high frequency plasmas. Funding by the German Federal Ministry for the Environment, Nature conservation, and Nuclear Safety (0325210B) is gratefully acknowledged.

  7. Measurements and modelling of turbulent fluxes at two glaciers in British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Radic, V.; Fitzpatrick, N.; Tessema, M.; Menounos, B.; Shea, J. M.; Dery, S. J.

    2015-12-01

    The most physically-based method to simulate surface glacier melting is by surface energy balance models since they account for radiative and turbulent heat exchanges occurring at the snow or ice surface. Direct measurements of turbulent fluxes, however, are uncommon given the complexity of making reliable measurements of turbulent energy exchange on alpine glaciers. Most studies thus rely on the bulk aerodynamic method used to parametrize turbulent fluxes; an approach that may be inaccurate due to poorly specified empirical coefficients, such as the transfer coefficient and roughness lengths. Here we present direct measurements of turbulent energy fluxes for two alpine glaciers in British Columbia: Castle Glacier in the Interior Mountains for ablation seasons 2010 and 2012, and Nordic Glacier in Canadian Rockies for ablation season 2014. On both glaciers the turbulent heat fluxes may account for up to 35% of energy available for daily melt. Using eddy-covariance method we derive the roughness lengths for momentum, temperature and humidity, and evaluate the performance of bulk method with different parametrizations for transfer coefficient in simulating the turbulent fluxes. Finally, we estimate the transfer coefficient directly from our measurements, and investigate its dependence on meteorological variables measured at the glaciers.

  8. Performance of Peltier elements as a cryogenic heat flux sensor at temperatures down to 60 K

    NASA Astrophysics Data System (ADS)

    Haruyama, T.

    2001-05-01

    An in situ heat flux measuring technique could be a good tool to investigate the mechanism of radiation heat leak and optimize the performance of multi-layer insulation. There are several types of commercially available heat flux sensors, however, most of these sensors are mainly developed for much higher heat flux measurements, e.g., radiation from an iron furnace, heat leak from LNG tanks to the ground and so on. In cryogenic systems, the typical amount of heat flux from 300 K to the first-stage radiation shield of cryogenic system is around several W/m 2, which is three or four orders of magnitude smaller than that of an iron furnace. A conventional thermoelectric element, known as a Peltier element, has been evaluated as a heat flux sensor at cryogenic temperatures and found to be suitable due to its high output voltage. In this study, the temperature dependence of the sensitivity and thermal resistance of the Peltier elements were investigated at temperatures from 200 down to 60 K for possible practical applications.

  9. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W.; Borella, Henry M.; Cates, Michael R.; Turley, W. Dale; MacArthur, Charles D.; Cala, Gregory C.

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator, wherein each thermographic layer comprises a plurality of respective thermographic sensors in a juxtaposed relationship with respect to each other. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  10. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W.; Borella, Henry M.; Cates, Michael R.; Turley, W. Dale; MacArthur, Charles D.; Cala, Gregory C.

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator wherein each thermographic layer comprises a plurality of respective thermographic phosphors. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  11. Optical heat flux gauge

    DOEpatents

    Noel, Bruce W.; Borella, Henry M.; Cates, Michael R.; Turley, W. Dale; MaCarthur, Charles D.; Cala, Gregory C.

    1991-01-01

    A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable.

  12. Impurity transport due to electromagnetic drift wave turbulence

    NASA Astrophysics Data System (ADS)

    Moradi, Sara; Pusztai, Istvan; Mollén, Albert; Fülöp, Tünde

    2012-10-01

    In the view of an increasing interest in high β operation scenarios, such as hybrid scenarios for ITER the question of finite β effects on the impurity transport is a critical issue due to possible fuel dilution and radiative cooling in the core. Here, electromagnetic effects at finite β on impurity transport are studied through local linear gyro-kinetic simulations with gyro [J. Candy and E. Belli, General Atomics Report GA-A26818 (2011)]; in particular we investigate the parametric dependences of the impurity peaking factor (zero-flux density gradient) and the onset of the kinetic ballooning modes (KBM) and micro-tearing modes (MTM) in spherical (NSTX) and standard tokamaks (AUG and JET).

  13. Power Law Regression Analysis of Heat Flux Width in Type I ELMs

    NASA Astrophysics Data System (ADS)

    Stephens, C. D.; Makowski, M. A.; Leonard, A. W.; Osborne, T. H.

    2014-10-01

    In this project, a database of Type I ELM characteristics has been assembled and will be used to investigate possible dependencies of the heat flux width on physics and engineering parameters. At the edge near the divertor, high impulsive heat loads are imparted onto the surface. The impact of these ELMs can cause a reduction in divertor lifetime if the heat flux is great enough due to material erosion. A program will be used to analyze data, extract relevant, measurable quantities, and record the quantities in the table. Care is taken to accurately capture the complex space/time structure of the ELM. Then correlations between discharge and equilibrium parameters will be investigated. Power law regression analysis will be used to help determine the dependence of the heat flux width on these various measurable quantities and parameters. This will enable us to better understand the physics of heat flux at the edge. Work supported in part by the National Undergraduate Fellowship Program in Plasma Physics and Fusion Energy Sciences and the US DOE under DE-FG02-04ER54761, DE-AC52-07NA27344, DE-FC02-04ER54698.

  14. Land use effects on green water fluxes from agricultural production in Mato Grosso, Brazil

    NASA Astrophysics Data System (ADS)

    Lathuilliere, M. J.; Johnson, M. S.; Donner, S. D.

    2010-12-01

    The blue water/green water paradigm is increasingly used to differentiate between subsequent routing of precipitation once it reaches the soil. “Blue” water is that which infiltrates deep in the soil to become streams and aquifers, while “green” water is that which remains in the soil and is either evaporated (non-productive green water) or transpired by plants (productive green water). This differentiation in the fate of precipitation has provided a new way of thinking about water resources, especially in agriculture for which better use of productive green water may help to relieve stresses from irrigation (blue water). The state of Mato Grosso, Brazil, presents a unique case for the study of green water fluxes due to an expanding agricultural land base planted primarily to soybean, maize, sugar cane, and cotton. These products are highly dependent on green water resources in Mato Grosso where crops are almost entirely rain-fed. We estimate the change in green water fluxes from agricultural expansion for the 2000-2008 period in the state of Mato Grosso based on agricultural production data from the Instituto Brasileiro de Geografia e Estatísticas and a modified Penman-Monteith equation. Initial results for seven municipalities suggest an increase in agricultural green water fluxes, ranging from 1-10% per year, due primarily to increases in cropped areas. Further research is underway to elucidate the role of green water flux variations from land use practices on the regional water cycle.

  15. Large Wind Farms and the Scalar Flux over an Heterogeneously Rough Land Surface

    NASA Astrophysics Data System (ADS)

    Calaf, Marc; Higgins, Chad; Parlange, Marc B.

    2014-12-01

    The influence of surface heterogeneities extends vertically within the atmospheric surface layer to the so-called blending height, causing changes in the fluxes of momentum and scalars. Inside this region the turbulence structure cannot be treated as horizontally homogeneous; it is highly dependent on the local surface roughness, the buoyancy and the horizontal scale of heterogeneity. The present study analyzes the change in scalar flux induced by the presence of a large wind farm installed across a heterogeneously rough surface. The change in the internal atmospheric boundary-layer structure due to the large wind farm is decomposed and the change in the overall surface scalar flux is assessed. The equilibrium length scale characteristic of surface roughness transitions is found to be determined by the relative position of the smooth-to-rough transition and the wind turbines. It is shown that the change induced by large wind farms on the scalar flux is of the same order of magnitude as the adjustment they naturally undergo due to surface patchiness.

  16. Temporal variability of CO₂ fluxes at the sediment-air interface in mangroves (New Caledonia).

    PubMed

    Leopold, Audrey; Marchand, Cyril; Deborde, Jonathan; Allenbach, Michel

    2015-01-01

    Carbon budgets in mangrove forests are uncertain mainly due to the lack of data concerning carbon export in dissolved and gaseous forms. Temporal variability of in situ CO2 fluxes was investigated at the sediment-air interface in different seasons in different mangrove stands in a semi-arid climate. Fluxes were measured using dynamic closed incubation chambers (transparent and opaque) connected to an infra-red gas analyzer. Microclimatic conditions and chl-a contents of surface sediments were determined. Over all mangrove stands, CO2 fluxes on intact sediments were relatively low, ranging from -3.93 to 8.85 mmolCO₂·m(-2)·h(-1) in the light and in the dark, respectively. Changes in the fluxes over time appeared to depend to a great extent on the development of the biofilm at the sediment surface. We suggest that in intact sediments and in the dark, CO2 fluxes measured at the sediment-air interface rather reflect the metabolism of benthic organisms than sediment respiration (heterotrophic and autotrophic). However, without the biofilm, sediment water content and air temperature were main drivers of seasonal differences in CO2 fluxes, and their influence differed depending on the intertidal location of the stand. After removal of the biofilm, Q10 values in the Avicennia and the Rhizophora stands were 1.84 and 2.1, respectively, revealing the sensitivity of mangrove sediments to an increase in temperature. This study provides evidence that, if the influence of the biofilm is not taken into account, the in situ CO2 emission data currently used to calculate the budget will lead to underestimation of CO2 production linked to heterotrophic respiration fueled by organic matter detritus from the mangrove. PMID:25302449

  17. Interactive momentum flux forcing over sea ice in a global ocean GCM

    NASA Astrophysics Data System (ADS)

    StöSsel, Achim; Cheon, Woo-Geun; Vihma, Timo

    2008-05-01

    The sensitivity of Southern Ocean sea ice to the strength of the atmospheric momentum forcing is investigated in the framework of a global ocean general circulation model. In contrast to the usual approach of having the momentum flux just depend on the wind speed and a constant drag coefficient, the newly introduced momentum flux driving sea ice considers the local stratification and roughness over ice in one case, and the flux-aggregated stratification and roughness using the blending-height concept in the other case. While both cases thus allow for an interactive feedback, only the latter case accounts for the subgrid-scale heterogeneity of the sea-ice pack. In particular, the sea-ice feedback is in the former case only provided by the simulated ice thickness, affecting the surface temperature and local stratification, while in the latter case it is also determined by the ice concentration. Both parameterizations yield predominantly statically stable, but dynamically unstable conditions at any instant over the wintertime sea-ice pack. In the winter mean, statically and dynamically unstable conditions prevail over coastal polynyas, and lead to a positive feedback with increased momentum flux. The larger momentum flux enhances the along and offshore ice drift, leading to corresponding changes in the winter-mean ice-thickness distribution, a reduction in coastal ice concentration, and an increase of heat loss due to sensible heat flux. In the case where surface heterogeneity is accounted for, the impact of the lower coastal ice concentration leads to a larger momentum flux than in the homogeneous case. The long-term deep-ocean properties are only affected when in the heterogeneous case the form drag is raised by increasing the ice freeboard and decreasing the maximum ice concentration. Only the combination of both yields a significant increase of Antarctic Bottom Water formation, as reflected by a long-term cooling and freshening of the global deep-ocean properties.

  18. Flux-induced Isometry Gauging in Heterotic Strings

    SciTech Connect

    Chuang, Wu-yen; Gao, Peng

    2007-01-05

    We study the effect of flux-induced isometry gauging of the scalar manifold in N = 2 heterotic string compactification with gauge fluxes. We show that a vanishing theorem by Witten provides the protection mechanism. The other ungauged isometries in hyper moduli space could also be protected, depending on the gauge bundle structure. We also discuss the related issue in IIB setting.

  19. Dependence of red edge on eddy viscosity model parameters

    NASA Technical Reports Server (NTRS)

    Deupree, R. G.; Cole, P. W.

    1980-01-01

    The dependence of the red edge location on the two fundamental free parameters in the eddy viscosity treatment was extensively studied. It is found that the convective flux is rather insensitive to any reasonable or allowed value of the two free parameters of the treatment. This must be due in part to the fact that the convective flux is determined more by the properties of the hydrogen ionization region than by differences in convective structure. The changes in the effective temperature of the red edge of the RR Lyrae gap resulting from these parameter variations is quite small (approximately 150 K). This is true both because the parameter variation causes only small changes and because large changes in the convective flux are required to produce any significant change in red edge location. The possible changes found are substantially less than the approximately 600 K required to change the predicted helium abundance mass fraction from 0.3 to 0.2.

  20. Estimates of absolute flux and radiance factor of localized regions on Mars in the 2-4 micron wavelength region

    NASA Technical Reports Server (NTRS)

    Roush, Ted L.; Roush, Eileen A.; Singer, Robert B.; Lucey, Paul G.

    1992-01-01

    IRTF spectrophotometric observations of Mars obtained during the 1986 opposition are the bases for the present estimates of 2.0-4.15 micron absolute flux and radiance factor values. The bright/dark ratios obtained show a wavelength dependence similar to that observed by Bell and Crisp (1991) in 1990, but the spectral contrast for 1986 is lower than in those observations; this difference could be due to changes in the location, sample are size, and/or suspended atmospheric dust.

  1. Electrostatic heat flux instabilities

    NASA Technical Reports Server (NTRS)

    Morrison, P. J.; Ionson, J. A.

    1980-01-01

    The electrostatic cyclotron and ion acoustic instabilities in a plasma driven by a combined heat flux and current were investigated. The minimum critical heat conduction speed (above which the plasma is unstable) is given as a function of the ratio of electron to ion temperatures.

  2. Radiative Flux Analysis

    DOE Data Explorer

    Long, Chuck [NOAA

    2008-05-14

    The Radiative Flux Analysis is a technique for using surface broadband radiation measurements for detecting periods of clear (i.e. cloudless) skies, and using the detected clear-sky data to fit functions which are then used to produce continuous clear-sky estimates. The clear-sky estimates and measurements are then used in various ways to infer cloud macrophysical properties.

  3. Factors regulating soil surface CO2 and NOx flux in response to high temperature, pulse water events, and nutrient fertilization

    NASA Astrophysics Data System (ADS)

    Oikawa, P. Y.; Grantz, D. A.; Chatterjee, A.; Eberwein, J. R.; Allsman, L. A.; Jenerette, D.

    2012-12-01

    Trace gas emissions from the soil surface are often underestimated due to poor understanding of the factors regulating fluxes under extreme conditions when moisture can be highly variable. In particular, dynamics of soil surface trace gas emissions from hot agricultural regions can be difficult to predict due to the sporadic use of flood irrigation and nitrogen fertilization. Soil surface CO2 and NOx fluxes are especially difficult to predict due to nonlinear responses to pulse water and fertilization events. Additionally, models such as Lloyd and Taylor (1994) and Yienger and Levy II (1995) are not well parameterized for soil surface CO2 and NOx flux, respectively, under excessively high temperatures. We measured soil surface CO2 and NOx flux in an agricultural field transitioning from fallow to biofuel crop production (Sorghum bicolor). Soil surface CO2 flux was measured using CO2 probes coupled with the flux-gradient method. NOx measurements were made using chambers coupled with a NOx monitor. Our field site is located at the University of California Desert Research and Extension Center in the Imperial Valley of CA. Air temperatures regularly exceed 42°C in the summer. Flood irrigation is used at the site as well as nitrogen fertilizers. Soil respiration ranged from 0-15 μmoles CO2 m-2 s-1, with strong hysteresis observed both with and without plants. Soil CO2 fluxes measured in the fallow field before the biofuel crop was planted were temperature independent and mainly regulated by soil moisture. When plants were introduced, temperature became an important predictor for soil respiration as well as canopy height. NOx fluxes were highest at intermediate soil moisture and varied significantly across an irrigation cycle. NOx emissions were temperature dependent, ranging from 3-113 ng N cm-2 hr-1. Neither CO2 nor NOx emissions showed inhibition at soil temperatures up to 55°C. Models may underestimate fluxes of CO2 and NOx from hot agricultural regions due to

  4. On LBNE neutrino flux systematic uncertainties

    NASA Astrophysics Data System (ADS)

    Lebrun, Paul L. G.; Hylen, James; Marchionni, Alberto; Fields, Laura; Bashyal, Amit; Park, Seongtae; Watson, Blake

    2015-10-01

    The systematic uncertainties in the neutrino flux of the Long-Baseline Neutrino Experiment, due to alignment uncertanties and tolerances of the neutrino beamline components, are estimated. In particular residual systematics are evaluated in the determination of the neutrino flux at the far detector, assuming that the experiment will be equipped with a near detector with the same target material of the far detector, thereby canceling most of the uncertainties from hadroproduction and neutrino cross sections. This calculation is based on a detailed Geant4-based model of the neutrino beam line that includes the target, two focusing horns, the decay pipe and ancillary items, such as shielding.

  5. On LBNE neutrino flux systematic uncertainties

    SciTech Connect

    Lebrun, Paul L. G.; Hylen, James; Marchionni, Alberto; Fields, Laura; Bashyal, Amit; Park, Seongtae; Watson, Blake

    2015-10-15

    The systematic uncertainties in the neutrino flux of the Long-Baseline Neutrino Experiment, due to alignment uncertanties and tolerances of the neutrino beamline components, are estimated. In particular residual systematics are evaluated in the determination of the neutrino flux at the far detector, assuming that the experiment will be equipped with a near detector with the same target material of the far detector, thereby canceling most of the uncertainties from hadroproduction and neutrino cross sections. This calculation is based on a detailed Geant4-based model of the neutrino beam line that includes the target, two focusing horns, the decay pipe and ancillary items, such as shielding.

  6. Mismatch-induced lethality due to a defect in Escherichia coli RecQ helicase in exonuclease-deficient background: Dependence on MutS and UvrD functions.

    PubMed

    Yamana, Yoshimasa; Sonezaki, Shuji; Ogawa, Hiroaki I; Kusano, Kohji

    2010-05-01

    Escherichia coli DNA-unwinding protein RecQ has roles in the regulation of general recombination and the processing of stalled replication forks. In this study, we found that knockout of the recQ gene in combination with xonA xseA recJ mutations, which inhibit methyl-directed mismatch repair (MMR), caused about 100-fold increase in sensitivity to a purine analog 2-aminopurine (2AP). Intriguingly, inactivation of a MMR initiator due to the either mutation mutS or uvrD completely suppressed the 2AP sensitivity caused by recQ xonA xseA recJ mutations, suggesting that RecQ helicase might act on the DNA structures that are generated by the processing of DNA by the MutSLH complex and UvrD helicase. Moreover, the recQ gene knockout in combination with xonA xseA recJ mutations enhanced 2AP-induced filament formation, and increased by twofold the rate of spontaneous forward mutations in the thyA locus but did not increase the rate of rifampicin-resistant mutations. We discuss about the possible interplay between E. coli RecQ helicase and mismatch recognition factors. PMID:20018207

  7. Flux focusing eddy current probe

    NASA Technical Reports Server (NTRS)

    Simpson, John W. (Inventor); Clendenin, C. Gerald (Inventor); Fulton, James P. (Inventor); Wincheski, Russell A. (Inventor); Todhunter, Ronald G. (Inventor); Namkung, Min (Inventor); Nath, Shridhar C. (Inventor)

    1997-01-01

    A flux-focusing electromagnetic sensor which uses a ferromagnetic flux-focusing lens simplifies inspections and increases detectability of fatigue cracks and material loss in high conductivity material. The unique feature of the device is the ferrous shield isolating a high-turn pick-up coil from an excitation coil. The use of the magnetic shield is shown to produce a null voltage output across the receiving coil in the presence of an unflawed sample. A redistribution of the current flow in the sample caused by the presence of flaws, however, eliminates the shielding condition and a large output voltage is produced, yielding a clear unambiguous flaw signal. The maximum sensor output is obtained when positioned symmetrically above the crack. Hence, by obtaining the position of the maximum sensor output, it is possible to track the fault and locate the area surrounding its tip. The accuracy of tip location is enhanced by two unique features of the sensor; a very high signal-to-noise ratio of the probe's output which results in an extremely smooth signal peak across the fault, and a rapidly decaying sensor output outside a small area surrounding the crack tip which enables the region for searching to be clearly defined. Under low frequency operation, material thinning due to corrosion damage causes an incomplete shielding of the pick-up coil. The low frequency output voltage of the probe is therefore a direct indicator of the thickness of the test sample.

  8. Urban Carbon Dioxide Concentration and Flux Measurements from a Building Rooftop in Boston, Massachusetts

    NASA Astrophysics Data System (ADS)

    Potosnak, M. J.; Friedl, M. A.; Phillips, N.; Hutyra, L.; Sibley, A.

    2009-12-01

    Carbon dioxide concentrations and fluxes have been measured with an open path infrared gas analyzer (IRGA, Licor LI-7500) and sonic anemometer (Campbell CSAT) installed on a 1.8 m tower on top of a building (675 Commonwealth Ave) at Boston University since October, 2007. The flux data was transformed with a double rotation scheme that sets the vertical wind to zero. The resulting vertical rotation angle shows a clear dependence on the building geometry when plotted against wind direction. In addition, gaps in wind direction are observed due to wind shadowing from nearby taller buildings (the BU residential dorm towers on Commonwealth Ave). Although there are limitations on the dataset imposed by the non-ideal flux conditions, the fluxes do respond to the weekend effect. Considering data until the end of August, 2009, the carbon dioxide emissions are over twice as great on weekdays compared to weekends (0.131 mg m-2 s-1 verses 0.056 mg m-2 s-1). The weekend effect is also apparent in diurnal concentration data, which does not depend on meeting eddy flux criteria and corresponds to a much larger footprint. Considering monthly averages of diurnal cycles of carbon dioxide concentration, hourly bins on weekdays range from no increase to 30 ppm higher than weekend days. The diurnal weekend effect is typically largest during the early morning hours before the breakup of the nocturnal boundary layer. The weekend effect depends strongly on meteorological conditions and boundary layer mixing. Throughout the year, some months show differences of less than 10 ppm throughout the diurnal cycle. Carbon dioxide concentrations and the weekend effect are also impacted by wind direction. During the summer months, there is evidence for a land-sea breeze diurnal cycle in the wind data, and this impacts observed carbon dioxide concentrations.

  9. Evolution of the magnetic helicity flux during the formation and eruption of flux ropes

    SciTech Connect

    Romano, P.; Zuccarello, F. P.; Guglielmino, S. L.; Zuccarello, F.

    2014-10-20

    We describe the evolution and the magnetic helicity flux for two active regions (ARs) since their appearance on the solar disk: NOAA 11318 and NOAA 11675. Both ARs hosted the formation and destabilization of magnetic flux ropes. In the former AR, the formation of the flux rope culminated in a flare of C2.3 GOES class and a coronal mass ejection (CME) observed by Large Angle and Spectrometric Coronagraph Experiment. In the latter AR, the region hosting the flux rope was involved in several flares, but only a partial eruption with signatures of a minor plasma outflow was observed. We found a different behavior in the accumulation of the magnetic helicity flux in the corona, depending on the magnetic configuration and on the location of the flux ropes in the ARs. Our results suggest that the complexity and strength of the photospheric magnetic field is only a partial indicator of the real likelihood of an AR producing the eruption of a flux rope and a subsequent CME.

  10. Spatial Representativeness of Flux Tower Sites: A Comparison Between Tower and Aircraft Eddy-Covariance Fluxes

    NASA Astrophysics Data System (ADS)

    Caulton, D.; Shepson, P. B.; Munger, J. W.; Hollinger, D. Y.; Saatchi, S. S.; Moghaddam, M.; Stirm, B. H.

    2013-12-01

    Development and testing of regional and global scale ecosystem models rely on analysis of data from flux towers that have footprint scales (~1 km2) that are much smaller and contain relatively homogeneous land use types. This approach tends to assume that the patchwork approach appropriately represents regions that are, especially on larger scale, much more heterogeneous in terms of land cover, soil moisture, topography and climatology, etc. While aircraft platforms provide snapshot views of NEE, they have access to essentially any environment and can access difficult and heterogeneous environments. We used an instrumented aircraft platform equipped with a 50 Hz wind probe and GPS/INS and a 10 Hz Picarro CO2/H2O analyzer to measure eddy covariance fluxes over larger spatial scales (~20 km2) over and near Howland Forest, ME, Harvard Forest, MA and Duke Forest, NC, as part of the Airborne Observatory of Subcanopy and Subsurface (AirMOSS) mission campaigns. Flux measurements were conducted for varying land cover types in these forests in July, 2012 and June-August, 2013. Measured fluxes will be compared with tower fluxes from each of the three sites to investigate the quality of the aircraft data, and the ability to assess local-regional scale variability and the spatial representativeness of these towers, with respect to the larger scale fluxes. In addition, soil moisture data from a NASA G-III aircraft will be used to investigate spatial representativeness and the soil moisture dependence of the fluxes.

  11. Forces in Erupting Flux Ropes: CMEs and Failed Eruptions

    NASA Astrophysics Data System (ADS)

    Chen, James

    2016-05-01

    A range of dynamical behaviors that can be exhibited by a quasi-statically evolving flux rope is studied. Starting with a CME-like flux rope in equilibrium balanced by the ambient coronal pressure (non-force-free) and an overlying coronal magnetic field (Bc), the poloidal flux is slowly increased, on a timescale much longer than the eruptive timescale of several to tens of minutes. In this configuration, the overlying field Bc provides an external downward restraining force, constituting an effective potential barrier. Slowly increasing poloidal flux causes the flux rope to gradually rise, following a sequence of quasi-static equilibria. As the apex of the flux rope rises past a critical height Z*, slightly higher than the peak of the potential barrier Bc(Z), it expands on a faster, dynamical (Alfvenic) timescale determined by the magnetic field and geometry of the flux rope. The expanding flux rope may reach a new equilibrium at height Z1. Observationally, this behavior would be recognized as a ``failed eruption.'' The new equilibrium flux rope is established if the magnetic tension force due to the toroidal magnetic field component Bt can balance the outward hoop force due to the poloidal component Bp. The flux rope may also expand without reaching a new equilibrium, provided a sufficiennt amount of poloidal flux is injected on a dynamical timescale so that the tension force cannot balance the hoop force. This scenario would result in a CME eruption. The influence of the poloidal flux injection, the Bc(Z) profile, and boundary conditions on the quantitative balance of the forces in an expanding flux rope is elucidated. Potentially observable consequences of the difference scenarios/models are discussed.Work supported by the Naval Research Laboratory Base Research Program

  12. Temporal and spatial variations of CO2, CH4 and N2O fluxes at three differently managed grasslands

    NASA Astrophysics Data System (ADS)

    Imer, D.; Merbold, L.; Eugster, W.; Buchmann, N.

    2013-02-01

    A profound understanding of temporal and spatial variabilities of CO2, CH4 and N2O fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three greenhouse gas (GHG) fluxes are due to environmental drivers as well as to fertilizer applications, grazing and cutting events. To assess how these affect GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400 m a.s.l. (intensively managed) to 1000 m a.s.l. (moderately intensive managed) to 2000 m a.s.l. (extensively managed). Temporal and spatial variabilities of GHG fluxes were quantified along small-scale transects of 16 static soil chambers at each site. We then established functional relationships between drivers and the observed fluxes on diel and annual time scales. Furthermore, spatial variabilities and their effect on representative site-specific mean chamber GHG fluxes were assessed using geostatistical semivariogram approaches. All three grasslands were N2O sources, with mean annual fluxes ranging from 0.15 to 1.28 nmol m-2 s-1. Contrastingly, all sites were net CH4 sinks, with uptake rates ranging from -0.56 to -0.15 nmol m-2 s-1. Mean annual respiration losses of CO2, as measured with opaque chambers, ranged from 5.2 to 6.5 μmol m-2 s-1. While the environmental drivers and their respective explanatory power for N2O emissions differed considerably among the three grasslands (adjusted r2 ranging from 0.19 to 0.42), CH4 and CO2 fluxes were much better constrained (adjusted r2 ranging from 0.41 to 0.83), in particular by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for N2O and CH4 fluxes. We found permanent hot spots for N2O emissions and CH4 uptake at the extensively managed site

  13. Hypercharge flux in heterotic compactifications

    NASA Astrophysics Data System (ADS)

    Anderson, Lara B.; Constantin, Andrei; Lee, Seung-Joo; Lukas, Andre

    2015-02-01

    We study heterotic Calabi-Yau models with hypercharge flux breaking, where the visible E8 gauge group is directly broken to the standard model group by a nonflat gauge bundle, rather than by a two-step process involving an intermediate grand unified theory and a Wilson line. It is shown that the required alternative E8 embeddings of hypercharge, normalized as required for gauge unification, can be found and we classify these possibilities. However, for all but one of these embeddings we prove a general no-go theorem which asserts that no suitable geometry and vector bundle leading to a standard model spectrum can be found. Intuitively, this happens due to the large number of index conditions which have to be imposed in order to obtain a correct physical spectrum in the absence of an underlying grand unified theory.

  14. Flux Creep and Giant Flux Creep in High Tc Hg,Pb-based Superconductors

    NASA Astrophysics Data System (ADS)

    Kirven, Douglas; Owens, Frank; Iqbal, Z.; Bleiweiss, M.; Lungu, A.; Datta, T.

    1996-03-01

    Dynamic behavior of the trapped flux in fields of up to 17.5 T was studied in a set of Hg-Pb based superconductors with a Tc in excess of 130 K. Depending on the experimental conditions, both creep and giant flux creep dynamics were observed. Results were analyzed using to standard models such as Anderson-Kim and giant-flux creep models (GFC). The plots of relaxation rate of remnant magnetization versus temperature show a peak below Tc. These results were compared with other Cu-O compounds. A distribution of activation energies was found from the magnetization rate. The activation energy distribution shows a peak around 50 K. The peak determines the temperature where the flux flow rate is a maximum. A universal relation of the resistive behavior was also found as a function of temperature and field. The zero-field/field-cooled results gave a reversibility curve that also obeyed a universal power relation.

  15. Effects of dynamic heat fluxes on model climate sensitivity Meridional sensible and latent heat fluxes

    NASA Technical Reports Server (NTRS)

    Gutowski, W. J., Jr.; Wang, W.-C.; Stone, P. H.

    1985-01-01

    The high- and low-latitude radiative-dynamic (HLRD) climatic model of Wang et al. (1984) was used to study the effect of meridional heat (MH) fluxes on climate changes caused by increases of CO2 abundance and solar constant variations. However, the empirical MH parameterization of the HLRD model was replaced by physically based parameterization, which gives separate meridional sensible and latent heat fluxes and provides a complete representation of the dependence of the flux on the mean temperature field. Both parameterization methods yielded about the same changes in global mean surface temperature and ice line, and both produced only small changes in meridional temperature gradient, although the latter were even smaller with the physically based parameterizations. At any latitude, the hemispheric mean surface temperature, rather than MH fluxes, dominates the surface temperature changes.

  16. Stellar coronae - What can be predicted with minimum flux models?

    NASA Technical Reports Server (NTRS)

    Hammer, R.; Endler, F.; Ulmschneider, P.

    1983-01-01

    In order to determine the possible errors of various minimum flux corona (MFC) predictions, MFC models are compared with a grid of detailed coronal models covering a range of two orders of magnitude in coronal heating and damping length values. The MFC concept is totally unreliable in the prediction of mass loss and the relative importance of various kinds of energy losses, and MFC predictions for the mass loss rate and energy losses due to stellar wind can be wrong by many orders of magnitude. It is suggested that for future applications, the unreliable MFC formulas should be replaced by a grid of related models accounting for the coronal dependence on damping length, such as the models underlying the present study.

  17. Transient pool boiling heat transfer due to increasing heat inputs in subcooled water at high pressures

    SciTech Connect

    Fukuda, K.; Shiotsu, M.; Sakurai, A.

    1995-09-01

    Understanding of transient boiling phenomenon caused by increasing heat inputs in subcooled water at high pressures is necessary to predict correctly a severe accident due to a power burst in a water-cooled nuclear reactor. Transient maximum heat fluxes, q{sub max}, on a 1.2 mm diameter horizontal cylinder in a pool of saturated and subcooled water for exponential heat inputs, q{sub o}e{sup t/T}, with periods, {tau}, ranging from about 2 ms to 20 s at pressures from atmospheric up to 2063 kPa for water subcoolings from 0 to about 80 K were measured to obtain the extended data base to investigate the effect of high subcoolings on steady-state and transient maximum heat fluxes, q{sub max}. Two main mechanisms of q{sub max} exist depending on the exponential periods at low subcoolings. One is due to the time lag of the hydrodynamic instability which starts at steady-state maximum heat flux on fully developed nucleate boiling (FDNB), and the other is due to the heterogenous spontaneous nucleations (HSN) in flooded cavities which coexist with vapor bubbles growing up from active cavities. The shortest period corresponding to the maximum q{sub max} for long period range belonging to the former mechanism becomes longer and the q{sub max}mechanism for long period range shifts to that due the HSN on FDNB with the increase of subcooling and pressure. The longest period corresponding to the minimum q{sub max} for the short period range belonging to the latter mechanism becomes shorter with the increase in saturated pressure. On the contrary, the longest period becomes longer with the increase in subcooling at high pressures. Correlations for steady-state and transient maximum heat fluxes were presented for a wide range of pressure and subcooling.

  18. Fundamentals of heat measurement. [heat flux transducers

    NASA Technical Reports Server (NTRS)

    Gerashchenko, O. A.

    1979-01-01

    Various methods and devices for obtaining experimental data on heat flux density over wide ranges of temperature and pressure are examined. Laboratory tests and device fabrication details are supplemented by theoretical analyses of heat-conduction and thermoelectric effects, providing design guidelines and information relevant to further research and development. A theory defining the measure of correspondence between transducer signal and the measured heat flux is established for individual (isolated) heat flux transducers subject to space and time-dependent loading. An analysis of the properties of stacked (series-connected) transducers of various types (sandwich-type, plane, and spiral) is used to derive a similarity theory providing general governing relationships. The transducers examined are used in 36 types of derivative devices involving direct heat loss measurements, heat conduction studies, radiation pyrometry, calorimetry in medicine and industry and nuclear reactor dosimetry.

  19. Weibel instability due to inverse bremsstrahlung absorption

    SciTech Connect

    Bendib, A.; Bendib, K.,; Bendib, A.; Bendib, K.; Sid, A.,; Bendib, K.,

    1997-06-01

    A new Weibel source due to the inverse bremsstrahlung absorption is presented. It has been shown that in homogeneous plasmas, this mechanism may drive strong collisionless Weibel modes with growth rates of order of {gamma}{approximately}10{sup 11}s{sup {minus}1} and negligible group velocities. In the laser-produced plasmas, for short laser wavelengths ({lambda}{sub L}{lt}1{mu}m) and high laser fluxes (I{gt}10{sup 14}W/cm{sup 2}), this Weibel source is most efficient as the ones due to the heat flux and the plasma expansion. The useful scaling law of the convective e-foldings, with respect to the laser and the plasma parameters, is also derived. {copyright} {ital 1997} {ital The American Physical Society}

  20. Heat flux and crustal radio-activity near the Sudbury neutrino observatory, Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Mareschal, J.; Perry, C.; Jaupart, C.

    2009-05-01

    During its next phase, the Sudbury neutrino observatory (SNO) will detect geoneutrinos, antineutrinos produced by the decay of U and Th in the Earth. These observations will provide direct constraints on the contribution of radiogenic heat production in the crust and mantle to the energy budget of the Earth. The geoneutrino flux at SNO depends on the local level of crustal radio-activity. Surface heat flux data record average crustal radio-activity unaffected by small scale heterogeneities. We review all available heat flux data measurements in the Sudbury structure as well as measurements of U, Th, and K concentrations in the main geological units of the area. With all available data, the average heat flux in the Sudbury basin is ~53mW m-2, higher than the mean value of 42mW m-2 for the entire Canadian Shield. The elevated heat flux is due to high heat production in the shallow crust. We estimate that the average heat production of the upper crust near Sudbury is >1.5μ W m-3 compared to an average of 0.95μ W m-3 for the Superior Province. The high crustal radio-activity near Sudbury results in an about 50% increase of the local crustal component of the geoneutrino flux. Crustal radio-activity is highest in the southern part of the structure, near the Creighton mine where SNO is located. High heat flux and heat production values are also found in the Southern Province, on the margin of the Superior Province. An azimuthal variation in the geoneutrino flux with a higher flux from the south than from the north is expected on the basis on the present information. However, we shall need better estimates of the contribution of the rocks in the Superior Province to the North to assess the extent of azimuthal effects. The many available exploration drill holes and core samples provide an opportunity to determine the spatial variations in crustal radioactivity near SNO and improve the interpretation of future measurements of the geoneutrino flux.

  1. Time-Dependent Photodissociation Regions

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Natta, Antonella

    1995-01-01

    We present theoretical models of the time-dependent thermal and chemical structure of molecular gas suddenly exposed to far-ultraviolet (FUV) (6 eV less than hv less than 13.6 eV) radiation fields and the consequent time- dependent infrared emission of the gas. We focus on the response of molecular hydrogen for cloud densities ranging from n = 10(exp 3) to 10(exp 6)/cu cm and FUV fluxes G(sub 0) = 10(exp 3)-10(exp 6) times the local FUV interstellar flux. For G(sub 0)/n greater than 10(exp -2) cu cm, the emergent H(sub 2) vibrational line intensities are initially larger than the final equilibrium values. The H(sub 2) lines are excited by FUV fluorescence and by collisional excitation in warm gas. Most of the H(sub 2) intensity is generated at a characteristic hydrogen column density of N approximately 10(exp 21)/sq cm, which corresponds to an FUV optical depth of unity caused by dust opacity. The time dependence of the H(sub 2) intensities arises because the initial abundances of H(sub 2) at these depths is much higher than the equilibrium values, so that H(sub 2) initially competes more effectively with dust in absorbing FUV photons. Considerable column densities of warm (T approximately 1000) K H(sub 2) gas can be produced by the FUV pumping of H(sub 2) vibrational levels followed by collisional de-excitation, which transfers the energy to heat. In dense (n greater than or approximately 10(exp 5)/cu cm) gas exposed to high (G(sub 0) greater than or approximately 10(exp 4)) fluxes, this warm gas produces a 2-1 S(1)/1-0 S(l) H(sub 2) line ratio of approximately 0.1, which mimics the ratio found in shocked gas. In lower density regions, the FUV pumping produces a pure-fluorescent ratio of approximately 0.5. We also present calculations of the time dependence of the atomic hydrogen column densities and of the intensities of 0 I 6300 A, S II 6730 A, Fe II 1.64 microns, and rotational OH and H20 emission. Potential applications include star-forming regions, clouds

  2. Effect of chamber enclosure time on soil respiration flux: A comparison of linear and non-linear flux calculation methods

    NASA Astrophysics Data System (ADS)

    Kandel, Tanka P.; Lærke, Poul Erik; Elsgaard, Lars

    2016-09-01

    One of the shortcomings of closed chamber methods for soil respiration (SR) measurements is the decreased CO2 diffusion rate from soil to chamber headspace that may occur due to increased chamber CO2 concentrations. This feedback on diffusion rate may lead to underestimation of pre-deployment fluxes by linear regression techniques. Thus, usually the cumulative flux curve becomes downward concave due to the decreased gas diffusion rate. Non-linear models based on biophysical theory usually fit to such curvatures and may reduce the underestimation of fluxes. In this study, we examined the effect of increasing chamber enclosure time on SR flux rates calculated using a linear, an exponential and a revised Hutchinson and Mosier model (HMR). Soil respiration rates were measured with a closed chamber in combination with an infrared gas analyzer. During SR flux measurements the chamber was placed on fixed collars, and CO2 concentration in the chamber headspace were recorded at 1-s intervals for 45 min. Fluxes were measured in different soil types (sandy, sandy loam and organic soils), and for various manipulations (tillage, rain and drought) and soil conditions (temperature and moisture) to obtain a range of fluxes with different shapes of flux curves. The linear method provided more stable flux results during short enclosure times (few min) but underestimated initial fluxes by 15-300% after 45 min deployment time. Non-linear models reduced the underestimation as average underestimation was only about 10% after 45 min for regular flux curves. For irregular flux curves with a rapid increase in CO2 concentration immediately after chamber deployment it was shown that short enclosure times were prone to overestimation of pre-deployment fluxes, but this was mitigated by longer enclosure times (>10-15 min).

  3. Optical heat flux gauge

    DOEpatents

    Noel, B.W.; Borella, H.M.; Cates, M.R.; Turley, W.D.; MacArthur, C.D.; Cala, G.C.

    1991-04-09

    A heat flux gauge is disclosed comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator, wherein each thermographic layer comprises a plurality of respective thermographic sensors in a juxtaposed relationship with respect to each other. The gauge may be mounted on a surface with the first thermographic phosphor in contact with the surface. A light source is directed at the gauge, causing the phosphors to luminesce. The luminescence produced by the phosphors is collected and its spectra analyzed in order to determine the heat flux on the surface. First and second phosphor layers must be different materials to assure that the spectral lines collected will be distinguishable. 9 figures.

  4. Collapse of flux tubes

    NASA Astrophysics Data System (ADS)

    Wilets, L.; Puff, R. D.

    1995-01-01

    The dynamics of an idealized, infinite, MIT-type flux tube is followed in time as the interior evolves from a pure gluon field to a q¯q plasma. We work in color U(1). q¯q pair formation is evaluated according to the Schwinger mechanism using the results of Brink and Pavel. The motion of the quarks toward the tube end caps is calculated by a Boltzmann equation including collisions. The tube undergoes damped radial oscillations until the electric field settles down to zero. The electric field stabilizes the tube against pinch instabilities; when the field vanishes, the tube disintegrates into mesons. There is only one free parameter in the problem, namely the initial flux tube radius, to which the results are very sensitive. Among various quantities calculated is the mean energy of the emitted pions.

  5. Plasma-depleted Flux Tubes in the Saturnian Magnetosphere

    NASA Astrophysics Data System (ADS)

    Lai, H.; Russell, C. T.; Wei, H.; Jia, Y. D.; Dougherty, M. K.

    2015-12-01

    Similar to Io's mass loading in the jovian magnetosphere, Saturn's moon, Enceladus, provides 100s of kilograms of water group neutrals and plasma to the planet's magnetosphere every second. The newly added plasma, being accelerated and convecting outward due to the centrifugal force, is then lost through magnetic reconnection in the tail. To conserve the total magnetic flux established by the internal dynamo, the 'empty' reconnected magnetic flux must return from the tail back to the inner magnetosphere. At both Jupiter and Saturn, flux tubes with enhanced field strength relative to their surroundings have been detected and are believed to be taking the role of returning the magnetic flux. However, at Saturn, flux tubes with depressed field strength are also reported. To reveal the relationship between the two kinds of flux tubes, we have systematically surveyed all the available 1-sec magnetic field data measured by Cassini and studied their statistical properties. The spatial distributions show that enhanced-field flux tubes are concentrated near the equator and closer to the planet while depressed-field flux tubes are distributed in a larger latitudinal region and can be detected at larger distances. In addition, we find that for both types of flux tubes, their occurrence rates vary with the local time in the same pattern and their magnetic flux is in the same magnitude. Therefore, the two types of flux tubes are just different manifestations of the same phenomenon: near the equator with high ambient plasma density, the flux tubes convecting in from the tail are compressed, resulting in increased field strength; off the equator, these flux tubes expand slightly, resulting in decreased field strength. Here we also present the lifecycle of the enhanced-field flux tubes: they gradually break into smaller ones when convecting inward and become indistinguishable from the background inside an L-value of about 4.

  6. Heat Flux Sensor Testing

    NASA Technical Reports Server (NTRS)

    Clark, D. W.

    2002-01-01

    This viewgraph presentation provides information on the following objectives: Developing secondary calibration capabilities for MSFC's (Marshall Space Flight Center) Hot Gas Facility (HGF), a Mach 4 Aerothermal Wind Tunnel; Evaluating ASTM (American Society for Testing and Materials) slug/ thinskin calorimeters against current HGF heat flux sensors; Providing verification of baselined AEDC (Arnold Engineering Development Center) / Medtherm gage calibrations; Addressing future calibration issues involving NIST (National Institute of Standards and Technology) certified radiant gages.

  7. Defining Top-of-Atmosphere Flux Reference Level for Earth Radiation Budget Studies

    NASA Technical Reports Server (NTRS)

    Loeb, N. G.; Kato, S.; Wielicki, B. A.

    2002-01-01

    To estimate the earth's radiation budget at the top of the atmosphere (TOA) from satellite-measured radiances, it is necessary to account for the finite geometry of the earth and recognize that the earth is a solid body surrounded by a translucent atmosphere of finite thickness that attenuates solar radiation differently at different heights. As a result, in order to account for all of the reflected solar and emitted thermal radiation from the planet by direct integration of satellite-measured radiances, the measurement viewing geometry must be defined at a reference level well above the earth s surface (e.g., 100 km). This ensures that all radiation contributions, including radiation escaping the planet along slant paths above the earth s tangent point, are accounted for. By using a field-of- view (FOV) reference level that is too low (such as the surface reference level), TOA fluxes for most scene types are systematically underestimated by 1-2 W/sq m. In addition, since TOA flux represents a flow of radiant energy per unit area, and varies with distance from the earth according to the inverse-square law, a reference level is also needed to define satellite-based TOA fluxes. From theoretical radiative transfer calculations using a model that accounts for spherical geometry, the optimal reference level for defining TOA fluxes in radiation budget studies for the earth is estimated to be approximately 20 km. At this reference level, there is no need to explicitly account for horizontal transmission of solar radiation through the atmosphere in the earth radiation budget calculation. In this context, therefore, the 20-km reference level corresponds to the effective radiative top of atmosphere for the planet. Although the optimal flux reference level depends slightly on scene type due to differences in effective transmission of solar radiation with cloud height, the difference in flux caused by neglecting the scene-type dependence is less than 0.1%. If an inappropriate

  8. The neutrino signal at HALO: learning about the primary supernova neutrino fluxes and neutrino properties

    SciTech Connect

    Väänänen, Daavid; Volpe, Cristina E-mail: volpe@ipno.in2p3.fr

    2011-10-01

    Core-collapse supernova neutrinos undergo a variety of phenomena when they travel from the high neutrino density region and large matter densities to the Earth. We perform analytical calculations of the supernova neutrino fluxes including collective effects due to the neutrino-neutrino interactions, the Mikheev-Smirnov-Wolfenstein (MSW) effect due to the neutrino interactions with the background matter and decoherence of the wave packets as they propagate in space. We predict the numbers of one- and two-neutron charged and neutral-current electron-neutrino scattering on lead events. We show that, due to the energy thresholds, the ratios of one- to two-neutron events are sensitive to the pinching parameters of neutrino fluxes at the neutrinosphere, almost independently of the presently unknown neutrino properties. Besides, such events have an interesting sensitivity to the spectral split features that depend upon the presence/absence of energy equipartition among neutrino flavors. Our calculations show that a lead-based observatory like the Helium And Lead Observatory (HALO) has the potential to pin down important characteristics of the neutrino fluxes at the neutrinosphere, and provide us with information on the neutrino transport in the supernova core.

  9. Transmantle flux tectonics

    NASA Technical Reports Server (NTRS)

    Finn, V. J.; Dolginov, A. Z.; Baker, V. R.

    1993-01-01

    Venus, Earth, and Mars have surfaces that display topographic domes and depressions with quasi-circular planimetric shapes, relief of 0 to several km, and large spatial scales (10(exp 2) to 10(exp 4) km). Our morphostructural mapping reveals hierarchical arrangements of these features. They are explained by a model of long-acting mantle convection, as a particular case of convection in a stratified and random inhomogeneous medium, which develops the form of a hierarchy of different convective pattern scales, each arising from different levels in the mantle. The hypothesis of transmantle flux tectonics parsimoniously explains a diversity of seemingly unrelated terrestrial planetary phenomena, including Earth megaplumes, global resurfacing epochs on Venus, and cyclic ocean formation and global climate change for Mars. All these phenomenon are hypothesized to be parsimoniously explained by a process of transmantle flux tectonics in which long-acting mantle convection generates stresses in blocks of planetary lithosphere to produce distinctive quasi-circular global-hierarchical morphostructure (QGM) patterns. Transmantle flux tectonics differs from plume tectonics in that individual plumes are not considered in isolation. Rather, a wholly interactive process is envisioned in which various spatial and temporal scales of convection operate contemporaneously and hierarchically within other scales. This process of continual change by hierarchical convective cells affects the surface at varying temporal and spatial scales, and its effects are discernable through their relic geological manifestations, the QGM patterns.

  10. Universality of flux-fluctuation law in complex dynamical systems

    NASA Astrophysics Data System (ADS)

    Zhou, Zhao; Huang, Zi-Gang; Huang, Liang; Lai, Ying-Cheng; Yang, Lei; Xue, De-Sheng

    2013-01-01

    Recent work has revealed a law governing flux fluctuation and the average flux in complex dynamical systems. We establish the universality of this flux-fluctuation law through the following steps: (i) We derive the law in a more general setting, showing that it depends on a single parameter characterizing the external driving; (ii) we conduct extensive numerical computations using distinct external driving, different network topologies, and multiple traffic routing strategies; and (iii) we analyze data from an actual vehicle traffic system in a major city in China to lend more credence to the universality of the flux-fluctuation law. Additional factors considered include flux fluctuation on links, window size effect, and hidden topological structures such as nodal degree correlation. Besides its fundamental importance in complex systems, the flux-fluctuation law can be used to infer certain intrinsic property of the system for potential applications such as control of complex systems for improved performance.

  11. Metabolic fluxes in an illuminated Arabidopsis rosette.

    PubMed

    Szecowka, Marek; Heise, Robert; Tohge, Takayuki; Nunes-Nesi, Adriano; Vosloh, Daniel; Huege, Jan; Feil, Regina; Lunn, John; Nikoloski, Zoran; Stitt, Mark; Fernie, Alisdair R; Arrivault, Stéphanie

    2013-02-01

    Photosynthesis is the basis for life, and its optimization is a key biotechnological aim given the problems of population explosion and environmental deterioration. We describe a method to resolve intracellular fluxes in intact Arabidopsis thaliana rosettes based on time-dependent labeling patterns in the metabolome. Plants photosynthesizing under limiting irradiance and ambient CO2 in a custom-built chamber were transferred into a (13)CO2-enriched environment. The isotope labeling patterns of 40 metabolites were obtained using liquid or gas chromatography coupled to mass spectrometry. Labeling kinetics revealed striking differences between metabolites. At a qualitative level, they matched expectations in terms of pathway topology and stoichiometry, but some unexpected features point to the complexity of subcellular and cellular compartmentation. To achieve quantitative insights, the data set was used for estimating fluxes in the framework of kinetic flux profiling. We benchmarked flux estimates to four classically determined flux signatures of photosynthesis and assessed the robustness of the estimates with respect to different features of the underlying metabolic model and the time-resolved data set. PMID:23444331

  12. Curl flux, coherence, and population landscape of molecular systems: Nonequilibrium quantum steady state, energy (charge) transport, and thermodynamics

    SciTech Connect

    Zhang, Z. D.; Wang, J.

    2014-06-28

    We established a theoretical framework in terms of the curl flux, population landscape, and coherence for non-equilibrium quantum systems at steady state, through exploring the energy and charge transport in molecular processes. The curl quantum flux plays the key role in determining transport properties and the system reaches equilibrium when flux vanishes. The novel curl quantum flux reflects the degree of non-equilibriumness and the time-irreversibility. We found an analytical expression for the quantum flux and its relationship to the environmental pumping (non-equilibriumness quantified by the voltage away from the equilibrium) and the quantum tunneling. Furthermore, we investigated another quantum signature, the coherence, quantitatively measured by the non-zero off diagonal element of the density matrix. Populations of states give the probabilities of individual states and therefore quantify the population landscape. Both curl flux and coherence depend on steady state population landscape. Besides the environment-assistance which can give dramatic enhancement of coherence and quantum flux with high voltage at a fixed tunneling strength, the quantum flux is promoted by the coherence in the regime of small tunneling while reduced by the coherence in the regime of large tunneling, due to the non-monotonic relationship between the coherence and tunneling. This is in contrast to the previously found linear relationship. For the systems coupled to bosonic (photonic and phononic) reservoirs the flux is significantly promoted at large voltage while for fermionic (electronic) reservoirs the flux reaches a saturation after a significant enhancement at large voltage due to the Pauli exclusion principle. In view of the system as a quantum heat engine, we studied the non-equilibrium thermodynamics and established the analytical connections of curl quantum flux to the transport quantities such as energy (charge) transfer efficiency, chemical reaction efficiency, energy

  13. Papilledema Due to Mirtazapine

    PubMed Central

    Ceylan, Mehmet Emin; Evrensel, Alper; Cömert, Gökçe

    2016-01-01

    Background: Mirtazapine is a tetracyclic antidepressant that enhances both noradrenergic and serotonergic transmission. The most common cause of papilledema is increased intracranial pressure due to brain tumor. Also it may occur as a result of idiopathic intracranial hypertension (IIH, pseudo tumor cerebri). Moreover, papilledema may also develop due to retinitis, vasculitis, Graves’ disease, hypertension, leukemia, lymphoma, diabetes mellitus and radiation. Case Report: In this article, a patient who developed papilledema while under treatment with mirtazapine (30 mg/day) for two years and recovered with termination of mirtazapine treatment was discussed to draw the attention of clinicians to this side effect of mirtazapine. Conclusion: Idiopathic intracranial hypertension and papilledema due to psychotropic drugs has been reported in the literature. Mirtazapine may rarely cause peripheral edema. However, papilledema due to mirtazapine has not been previously reported. Although papilledema is a very rare side effect of an antidepressant treatment, fundoscopic examinations of patients must be performed regularly. PMID:27308085

  14. Annual Cycles of Surface Shortwave Radiative Fluxes

    NASA Technical Reports Server (NTRS)

    Wilber, Anne C.; Smith, G. Louis; Gupta, Shashi K.; Stackhouse, Paul W.

    2006-01-01

    The annual cycles of surface shortwave flux are investigated using the 8-yr dataset of the surface radiation budget (SRB) components for the period July 1983-June 1991. These components include the downward, upward, and net shortwave radiant fluxes at the earth's surface. The seasonal cycles are quantified in terms of principal components that describe the temporal variations and empirical orthogonal functions (EOFs) that describe the spatial patterns. The major part of the variation is simply due to the variation of the insolation at the top of the atmosphere, especially for the first term, which describes 92.4% of the variance for the downward shortwave flux. However, for the second term, which describes 4.1% of the variance, the effect of clouds is quite important and the effect of clouds dominates the third term, which describes 2.4% of the variance. To a large degree the second and third terms are due to the response of clouds to the annual cycle of solar forcing. For net shortwave flux at the surface, similar variances are described by each term. The regional values of the EOFs are related to climate classes, thereby defining the range of annual cycles of shortwave radiation for each climate class.

  15. Cross correlation of thermal flux noise in layered superconductors

    SciTech Connect

    Ashkenazy, V.D.; Jung, G. |; Shapiro, B.Y. |

    1996-10-01

    Cross correlation in the magnetic flux noise due to thermally activated movements of pancake vortices in strongly anisotropic layered superconductors has been investigated theoretically. It has been shown that there exists a crossover frequency, inversely proportional to the sample thickness, below which vortices behave as rigid rods and their ends move coherently on the opposite sides of the sample. At low frequencies, the cross-correlation spectrum is identical to the spectrum measured at each side of the sample. The cross-correlation spectrum demonstrates two regimes of behavior, separated by a characteristic frequency which depends on the geometry of the flux measuring loop. At high frequencies above the crossover frequency, the excitations of the elastic lattice modes lead to exponentially vanishing oscillations of the cross-correlation spectra. Pancake movements became incoherent and the correlation function decays, accompanied by the oscillations. The oscillations are most pronounced for the separation between pickup loops smaller than the sample thickness. In a typical experimental configuration with pickup loops located on the sample surface, the oscillations constitute only small perturbations to the dominating powerlike decay of the correlation function. {copyright} {ital 1996 The American Physical Society.}

  16. Stabilization of moduli by fluxes

    SciTech Connect

    Behrndt, Klaus

    2004-12-10

    In order to fix the moduli, non-trivial fluxes might the essential input. We summarize different aspects of compactifications in the presence of fluxes, as there is the relation to generalized Scherk-Schwarz reductions and gauged supergravity but also the description of flux-deformed geometries in terms of G-structures and intrinsic torsion.

  17. Climate-driven uncertainties in modeling terrestrial energy and water fluxes: a site-level to global-scale analysis.

    PubMed

    Barman, Rahul; Jain, Atul K; Liang, Miaoling

    2014-06-01

    We used a land surface model constrained using data from flux tower sites, to analyze the biases in ecosystem energy and water fluxes arising due to the use of meteorological reanalysis datasets. Following site-level model calibration encompassing major vegetation types from the tropics to the northern high-latitudes, we repeated the site and global simulations using two reanalysis datasets: the NCEP/NCAR and the CRUNCEP. In comparison with the model simulations using observed meteorology from sites, the reanalysis-driven simulations produced several systematic biases in net radiation (Rn ), latent heat (LE), and sensible heat (H) fluxes. These include: (i) persistently positive tropical/subtropical biases in Rn using the NCEP/NCAR, and gradually transitioning to negative Rn biases in the higher latitudes; (ii) large positive H biases in the tropics/subtropics using the NCEP/NCAR; (iii) negative LE biases using the NCEP/NCAR above 40°N; (iv) high tropical LE using the CRUNCEP in comparison with observationally derived global estimates; and (v) flux-partitioning biases from canopy and ground components. Across vegetation types, we investigated the role of the meteorological drivers (shortwave and longwave radiation, atmospheric humidity, temperature, precipitation) and their seasonal biases in controlling these reanalysis-driven uncertainties. At the global scale, our site-level analysis explains several model-data differences in the LE and H fluxes when compared with observationally derived global estimates of these fluxes. Using our results, we discuss the implications of site-level model calibration on subsequent regional/global applications to study energy and hydrological processes. The flux-partitioning biases presented in this study have potential implications on the couplings among terrestrial carbon, energy, and water fluxes, and for the calibration of land-atmosphere parameterizations that are dependent on LE/H partitioning. PMID:24273011

  18. Fluvial filtering of land-to-ocean fluxes: from natural Holocene variations to Anthropocene

    NASA Astrophysics Data System (ADS)

    Meybeck, Michel; Vörösmarty, Charles

    2005-02-01

    The evolution of river systems and their related fluxes is considered at various time scales: ( i) over the last 18 000 years, under climatic variability control, ( ii) over the last 50 to 200 years (Anthropocene) due to direct human impacts. Natural Holocene variations in time and space depend on ( i) land-to-ocean connections (endorheism, glacial cover, exposure of continental shelf); ( ii) types of natural fluvial filters (e.g., wetlands, lakes, floodplains, estuaries). Anthropocene changes concern ( i) land-ocean connection (e.g., partial to total runoff reduction resulting from water management), ( ii) modification and removal of natural filters, ( iii) creation of new filters, particularly irrigated fields and reservoirs, ( iv) acceleration and/or development of material sources from human activities. The total river basin area directly affected by human activities is of the same order of magnitude ( >40 Mkm) as the total area affected over the last 18 000 years. A tentative analysis of 38 major river systems totaling 55 Mkm is proposed for several criteria: ( i) trajectories of Holocene evolution, ( ii) occurrence of natural fluvial filters, ( iii) present-day fluvial filters: most river basins are unique. Riverine fluxes per unit area are characterized by hot spots that exceed the world average by one order of magnitude. At the Anthropocene (i.e., since 1950), many riverine fluxes have globally increased (sodium, chloride, sulfate, nitrogen, phosphorous, heavy metals), others are stable (calcium, bicarbonate, sediments) or likely to decrease (dissolved silica). Future trajectories of river fluxes will depend on the balance between increased sources of material (e.g., soil erosion, pollution, fertilization), water abstraction for irrigation and the modification of fluvial filters, particularly the occurrence of reservoirs that already intercept half of the water and store at least 30% of river sediment fluxes. In some river systems, retention actually

  19. Mapping AmeriFlux footprints: Towards knowing the flux source area across a network of towers

    NASA Astrophysics Data System (ADS)

    Menzer, O.; Pastorello, G.; Metzger, S.; Poindexter, C.; Agarwal, D.; Papale, D.

    2014-12-01

    The AmeriFlux network collects long-term carbon, water and energy flux measurements obtained with the eddy covariance method. In order to attribute fluxes to specific areas of the land surface, flux source calculations are essential. Consequently, footprint models can support flux up-scaling exercises to larger regions, often based on remote sensing data. However, flux footprints are not currently being routinely calculated; different approaches exist but have not been standardized. In part, this is due to varying instrumentation and data processing methods at the site level. The goal of this work is to map tower footprints for a future standardized AmeriFlux product to be generated at the network level. These footprints can be estimated by analytical models, Lagrangian simulations, and large-eddy simulations. However, for many sites, the datasets currently submitted to central databases generally do not include all variables required. The AmeriFlux network is moving to collection of raw data and expansion of the variables requested from sites, giving the possibility to calculate all parameters and variables needed to run most of the available footprint models. In this pilot study, we are applying state of the art footprint models across a subset of AmeriFlux sites, to evaluate the feasibility and merit of developing standardized footprint results. In addition to comparing outcomes from several footprint models, we will attempt to verify and validate the results in two ways: (i) Verification of our footprint calculations at sites where footprints have been experimentally estimated. (ii) Validation at towers situated in heterogeneous landscapes: here, variations in the observed fluxes are expected to correlate with spatiotemporal variations of the source area composition. Once implemented, the footprint results can be used as additional information within the AmeriFlux database that can support data interpretation and data assimilation. Lastly, we will explore the

  20. Impact of mountain pine beetle induced mortality on forest carbon and water fluxes

    NASA Astrophysics Data System (ADS)

    Reed, David E.; Ewers, Brent E.; Pendall, Elise

    2014-10-01

    Quantifying impacts of ecological disturbance on ecosystem carbon and water fluxes will improve predictive understanding of biosphere—atmosphere feedbacks. Tree mortality caused by mountain pine bark beetles (Dendroctonus ponderosae) is hypothesized to decrease photosynthesis and water flux to the atmosphere while increasing respiration at a rate proportional to mortality. This work uses data from an eddy-covariance flux tower in a bark beetle infested lodgepole pine (Pinus contorta) forest to test ecosystem responses during the outbreak. Analyses were conducted on components of carbon (C) and water fluxes in response to disturbance and environmental factors (solar radiation, soil water content and vapor pressure deficit). Maximum CO2 uptake did not change as tree basal area mortality increased from 30 to 78% over three years of beetle disturbance. Growing season evapotranspiration varied among years while ecosystem water use efficiency (the ratio of net CO2 uptake to water vapor loss) did not change. Between 2009 and 2011, canopy water conductance increased from 98.6 to 151.7 mmol H2O m-2 s-1. Ecosystem light use efficiency of photosynthesis increased, with quantum yield increasing by 16% during the outbreak as light increased below the mature tree canopy and illuminated remaining vegetation more. Overall net ecosystem productivity was correlated with water flux and hence water availability. Average weekly ecosystem respiration, derived from light response curves and standard Ameriflux protocols for CO2 flux partitioning into respiration and gross ecosystem productivity, did not change as mortality increased. Separate effects of increased respiration and photosynthesis efficiency largely canceled one another out, presumably due to increased diffuse light in the canopy and soil organic matter decomposition resulting in no change in net CO2 exchange. These results agree with an emerging consensus in the literature demonstrating CO2 and H2O dynamics following large

  1. Impact of land cover uncertainties on estimates of biospheric carbon fluxes

    NASA Astrophysics Data System (ADS)

    Quaife, T.; Quegan, S.; Disney, M.; Lewis, P.; Lomas, M.; Woodward, F. I.

    2008-12-01

    Large-scale bottom-up estimates of terrestrial carbon fluxes, whether based on models or inventory, are highly dependent on the assumed land cover. Most current land cover and land cover change maps are based on satellite data and are likely to be so for the foreseeable future. However, these maps show large differences, both at the class level and when transformed into Plant Functional Types (PFTs), and these can lead to large differences in terrestrial CO2 fluxes estimated by Dynamic Vegetation Models. In this study the Sheffield Dynamic Global Vegetation Model is used. We compare PFT maps and the resulting fluxes arising from the use of widely available moderate (1 km) resolution satellite-derived land cover maps (the Global Land Cover 2000 and several MODIS classification schemes), with fluxes calculated using a reference high (25 m) resolution land cover map specific to Great Britain (the Land Cover Map 2000). We demonstrate that uncertainty is introduced into carbon flux calculations by (1) incorrect or uncertain assignment of land cover classes to PFTs; (2) information loss at coarser resolutions; (3) difficulty in discriminating some vegetation types from satellite data. When averaged over Great Britain, modeled CO2 fluxes derived using the different 1 km resolution maps differ from estimates made using the reference map. The ranges of these differences are 254 gC m-2 a-1 in Gross Primary Production (GPP); 133 gC m-2 a-1 in Net Primary Production (NPP); and 43 gC m-2 a-1 in Net Ecosystem Production (NEP). In GPP this accounts for differences of -15.8% to 8.8%. Results for living biomass exhibit a range of 1109 gC m-2. The types of uncertainties due to land cover confusion are likely to be representative of many parts of the world, especially heterogeneous landscapes such as those found in western Europe.

  2. Flux noise resulting from vortex avalanches using a simple kinetic model

    SciTech Connect

    Mohler, G.; Stroud, D.

    1999-10-01

    We have carried out a model calculation of the flux noise produced by vortex avalanches in a type-II superconductor, using a simple kinetic model proposed by Bassler and Paczuski. Over a broad range of frequencies, we find that the flux noise S{sub {Phi}}({omega}) has a power-law dependence on frequency, S{sub {Phi}}({omega}){approximately}{omega}{sup {minus}s}, with s{approximately}1.4 in reasonable agreement with experiment. In addition, for small lattices, the calculated S{sub {Phi}}({omega}) has a high-frequency knee, which is seen in some experiments, and which is due to the finite lattice size. Deviations between calculation and experiment are attributed mostly to uncertainties in the measured critical current densities and pinning strengths of the experimental samples. {copyright} {ital 1999} {ital The American Physical Society}

  3. Long-term flux density variations of pulsars: Theoretical structure functions and comparisons with observations

    NASA Astrophysics Data System (ADS)

    Zhou, A. Z.; Wu, X. J.; Esamdin, A.

    2003-06-01

    By means of the refractive interstellar scintillation theory (RISS), the flux density structure functions of PSRs B1642-03, B0736-40, B0740-28 and B0329+54 are calculated and compared with the observations at 610 MHz by Stinebring et al. (\\cite{Stinebring00}, hereafter S2000). The theoretical results are in good agreement with observations and the spectra of the electron density fluctuation are all consistent with the Kolmogorov spectra. The theoretical modulation indices m are comparatively less sensitive to the distance H from the observer to the scattering screen but critically depend on the scattering strength line CN2. The structure function does not change remarkably with the variation of H if the scattering screen is closer to the pulsar than to the observer. The results in this paper indicate that the flux density variations observed for these four pulsars are due to a propagation effect (refractive scintillation), not to the intrinsic variability.

  4. Flux pinning mechanism and Hc2-anisotropy in melanin doped bulk MgB2

    NASA Astrophysics Data System (ADS)

    Shahabuddin Shah, M.; Shahabuddin, Mohammed; Alzayed, Nasser S.; Parakkandy, Jafar M.

    2014-06-01

    Flux pinning mechanism in melanin doped MgB2 superconductor has been studied using a scaling law proposed by Dew-Hughes and another method proposed by Eisterer. Our experimental data could be fitted very closely by the aforementioned scaling law. The fitting parameters, the positions of peaks bpeak and k = bpeak/bn confirm a grain-boundary pinning in the 10% melanin doped sample, while the undoped sample consists of mixed pinning. Furthermore, percolation theory was utilized under grain-boundary approximation to investigate the role of Hc2-anisotropy in the critical current density, and its dependence on applied field as well as temperature. The Hc2-anisotropy decreases with melanin doping resulting in the increase of Jc in high field. There is suppression of flux pinning maximum due to melanin doping, which is found to be the main reason for the degradation of low-field Jc.

  5. Nonlinear effects at high flux-flow electric fields.

    PubMed

    Huebener, R P

    2009-06-24

    Ohm's law with the linear relation between resistive voltage and electric current is strictly valid only in the limit of infinitesimally small voltages. On the other hand, at finite electric voltages nonlinearities in the electric resistance can develop due to the energy picked up by the charge carriers in the electric field. This can lead to important effects both in the case of semiconductors and of superconductors, where the energy rise of the charge carriers or the quasiparticles can become relatively large. In this paper we limit our discussion to the flux-flow voltage in the mixed state of a type-II superconductor. At sufficiently low temperatures the energy dependence of the quasiparticle density of states and, hence, of the quasiparticle scattering rate can cause distinct nonlinear effects in the flux-flow resistance. The recent advances in thin-film sample preparation provided new opportunities for observing nonlinear effects of the latter kind. PMID:21828432

  6. Flux line lattice form factor and paramagnetic effects in type II superconductors

    NASA Astrophysics Data System (ADS)

    Ichioka, Masanori; Machida, Kazushige

    2009-03-01

    Based on the quasiclassical Eilenberger theory, we investigate the vortex structure in type II superconductors with strong Pauli-paramagnetic contributions due to the Zeeman effect. We quantitatively study how the paramagnetic effect suppresses the superconductivity, and evaluate the flux line lattice (FLL) form factor from the calculated internal field distribution both in the s-wave and d-wave pairings. When the paramagnetic effects are strong, the intensity of the FLL form factor increases toward Hc2 as a function of an applied field, instead of exponential decay. This anomalous field dependence is due to the induced paramagnetic moments around the vortex core. We discuss the anomalous field-dependence of the FLL form factor observed by the small angle neutron scattering in CeCoIn5.

  7. Thermal flux transfer system

    NASA Technical Reports Server (NTRS)

    Freggens, R. A. (Inventor)

    1973-01-01

    A thermal flux transfer system for use in maintaining the thrust chamber of an operative reaction motor at given temperatures is described. The system is characterized by an hermetically sealed chamber surrounding a thrust chamber to be cooled, with a plurality of parallel, longitudinally spaced, disk-shaped wick members formed of a metallic mesh and employed in delivering a working fluid, in its liquid state, radially toward the thrust chamber and delivering the working fluid, in its vapor state, away from the nozzle for effecting a cooling of the nozzle, in accordance with known principles of an operating heat pipe.

  8. High flux reactor

    DOEpatents

    Lake, James A.; Heath, Russell L.; Liebenthal, John L.; DeBoisblanc, Deslonde R.; Leyse, Carl F.; Parsons, Kent; Ryskamp, John M.; Wadkins, Robert P.; Harker, Yale D.; Fillmore, Gary N.; Oh, Chang H.

    1988-01-01

    A high flux reactor is comprised of a core which is divided into two symetric segments housed in a pressure vessel. The core segments include at least one radial fuel plate. The spacing between the plates functions as a coolant flow channel. The core segments are spaced axially apart such that a coolant mixing plenum is formed between them. A channel is provided such that a portion of the coolant bypasses the first core section and goes directly into the mixing plenum. The outlet coolant from the first core segment is mixed with the bypass coolant resulting in a lower inlet temperature to the lower core segment.

  9. Seven-Year SSM/I-Derived Global Ocean Surface Turbulent Fluxes

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Hsien; Shie, Chung-Lin; Atlas, Robert M.; Ardizzone, Joe

    2000-01-01

    A 7.5-year (July 1987-December 1994) dataset of daily surface specific humidity and turbulent fluxes (momentum, latent heat, and sensible heat) over global oceans has been retrieved from the Special Sensor Microwave/Imager (SSM/I) data and other data. It has a spatial resolution of 2.0 deg.x 2.5 deg. latitude-longitude. The retrieved surface specific humidity is generally accurate over global oceans as validated against the collocated radiosonde observations. The retrieved daily wind stresses and latent heat fluxes show useful accuracy as verified by those measured by the RV Moana Wave and IMET buoy in the western equatorial Pacific. The derived turbulent fluxes and input variables are also found to agree generally with the global distributions of annual-and seasonal-means of those based on 4-year (1990-93) comprehensive ocean-atmosphere data set (COADS) with adjustment in wind speeds and other climatological studies. The COADS has collected the most complete surface marine observations, mainly from merchant ships. However, ship measurements generally have poor accuracy, and variable spatial coverages. Significant differences between the retrieved and COADS-based are found in some areas of the tropical and southern extratropical oceans, reflecting the paucity of ship observations outside the northern extratropical oceans. Averaged over the global oceans, the retrieved wind stress is smaller but the latent heat flux is larger than those based on COADS. The former is suggested to be mainly due to overestimation of the adjusted ship-estimated wind speeds (depending on sea states), while the latter is suggested to be mainly due to overestimation of ship-measured dew point temperatures. The study suggests that the SSM/I-derived turbulent fluxes can be used for climate studies and coupled model validations.

  10. Parameterization of biogeochemical sediment-water fluxes using in situ measurements and a diagenetic model

    NASA Astrophysics Data System (ADS)

    Laurent, A.; Fennel, K.; Wilson, R.; Lehrter, J.; Devereux, R.

    2016-01-01

    Diagenetic processes are important drivers of water column biogeochemistry in coastal areas. For example, sediment oxygen consumption can be a significant contributor to oxygen depletion in hypoxic systems, and sediment-water nutrient fluxes support primary productivity in the overlying water column. Moreover, nonlinearities develop between bottom water conditions and sediment-water fluxes due to loss of oxygen-dependent processes in the sediment as oxygen becomes depleted in bottom waters. Yet, sediment-water fluxes of chemical species are often parameterized crudely in coupled physical-biogeochemical models, using simple linear parameterizations that are only poorly constrained by observations. Diagenetic models that represent sediment biogeochemistry are available, but rarely are coupled to water column biogeochemical models because they are computationally expensive. Here, we apply a method that efficiently parameterizes sediment-water fluxes of oxygen, nitrate and ammonium by combining in situ measurements, a diagenetic model and a parameter optimization method. As a proof of concept, we apply this method to the Louisiana Shelf where high primary production, stimulated by excessive nutrient loads from the Mississippi-Atchafalaya River system, promotes the development of hypoxic bottom waters in summer. The parameterized sediment-water fluxes represent nonlinear feedbacks between water column and sediment processes at low bottom water oxygen concentrations, which may persist for long periods (weeks to months) in hypoxic systems such as the Louisiana Shelf. This method can be applied to other systems and is particularly relevant for shallow coastal and estuarine waters where the interaction between sediment and water column is strong and hypoxia is prone to occur due to land-based nutrient loads.

  11. Flux-flow voltages during guided flux collapse from hollow superconducting cylinders

    NASA Technical Reports Server (NTRS)

    Khanna, S. M.; Leblanc, M. A. R.; Clem, J. R.

    1976-01-01

    Voltages across diametrically opposite contact pairs on the outer surface of superconducting Nb tubes are found to depend dramatically upon the spatial configuration of the voltage-measuring leads relative to the positions of the moving magnetic flux lines. Experiments have been conducted to study these voltages for different wall thicknesses and for a variety of arrangements of the leads when flux in the hole and the wall of the Nb tube is made to exit or enter, completely or partially, by applying heat at a narrow strip along its length. Using the critical-state concept, a model for the change of flux and the resulting electric fields in the Nb tube on application of a heat pulse is presented. The resulting time-dependent and time-integrated voltages are calculated in excellent quantitative agreement with the experimental results. These results show that the flux-flow voltages across two contact points on a superconductor arise from the generation of an induced electric field over a chosen path in the superconductor between the contact points and from a change of magnetic flux through the surface bounded by the measuring leads and the chosen path in the superconductor.

  12. Eddy fluxes in baroclinic turbulence

    NASA Astrophysics Data System (ADS)

    Thompson, Andrew F.

    The eddy heat flux generated by the statistically equilibrated baroclinic instability of a uniform, horizontal temperature gradient is studied using a two-mode quasigeostrophic model. An overview of the dependence of the eddy diffusivity of heat Dtau on the planetary potential vorticity gradient beta, the bottom friction kappa, the deformation radius lambda, the vertical shear of the large-scale flow 2U and the domain size L is provided at 70 numerical simulations with beta = 0 (f-plane) and 110 simulations with beta ≠ 0 (beta-plane). Strong, axisymmetric, well-separated baroclinic vortices dominate the equilibrated barotropic vorticity and temperature fields of f-plane turbulence. The heat flux arises from a systematic northward (southward) migration of anti-cyclonic (cyclonic) eddies with warm (cold) fluid trapped in the cores. Zonal jets form spontaneously on the beta-plane, and stationary, isotropic, jet-scale eddies align within the strong eastward-flowing regions of the jets. In both studies, the vortices and jets give rise to a strong anti-correlation between the barotropic vorticity zeta and the temperature field tau. The baroclinic mode is also an important contributor to dissipation by bottom friction and energizes the barotropic mode at scales larger than lambda. This in part explains why previous parameterizations for the eddy heat flux based on Kolmogorovian cascade theories are found to be unreliable. In a separate study, temperature and salinity profiles obtained with expendable conductivity, temperature and depth (XCTD) probes within Drake Passage, Southern Ocean are used to analyze the turbulent diapycnal eddy diffusivity kappa rho to a depth of 1000 meters. The Polar Front separates two dynamically different regions with strong, surface-intensified mixing north of the Front. South of the Polar Front mixing is weaker and peaks at a depth of approximately 500 m, near the local temperature maximum. Peak values of kapparho are found to exceed 10-3 m

  13. Prediction of critical heat flux in water-cooled plasma facing components using computational fluid dynamics.

    SciTech Connect

    Bullock, James H.; Youchison, Dennis Lee; Ulrickson, Michael Andrew

    2010-11-01

    Several commercial computational fluid dynamics (CFD) codes now have the capability to analyze Eulerian two-phase flow using the Rohsenow nucleate boiling model. Analysis of boiling due to one-sided heating in plasma facing components (pfcs) is now receiving attention during the design of water-cooled first wall panels for ITER that may encounter heat fluxes as high as 5 MW/m2. Empirical thermalhydraulic design correlations developed for long fission reactor channels are not reliable when applied to pfcs because fully developed flow conditions seldom exist. Star-CCM+ is one of the commercial CFD codes that can model two-phase flows. Like others, it implements the RPI model for nucleate boiling, but it also seamlessly transitions to a volume-of-fluid model for film boiling. By benchmarking the results of our 3d models against recent experiments on critical heat flux for both smooth rectangular channels and hypervapotrons, we determined the six unique input parameters that accurately characterize the boiling physics for ITER flow conditions under a wide range of absorbed heat flux. We can now exploit this capability to predict the onset of critical heat flux in these components. In addition, the results clearly illustrate the production and transport of vapor and its effect on heat transfer in pfcs from nucleate boiling through transition to film boiling. This article describes the boiling physics implemented in CCM+ and compares the computational results to the benchmark experiments carried out independently in the United States and Russia. Temperature distributions agreed to within 10 C for a wide range of heat fluxes from 3 MW/m2 to 10 MW/m2 and flow velocities from 1 m/s to 10 m/s in these devices. Although the analysis is incapable of capturing the stochastic nature of critical heat flux (i.e., time and location may depend on a local materials defect or turbulence phenomenon), it is highly reliable in determining the heat flux where boiling instabilities begin

  14. Capture from random flux to channeling for protons transmitted through a Si foil

    NASA Astrophysics Data System (ADS)

    Karamian, S. A.; Assmann, W.; Ertl, K.; Frischke, D.; Mieskes, H. D.; Schmidt, B.; Tretyakova, S. P.

    2000-04-01

    Flux redistribution and formation of channeling peaks have been observed in the geometry of initially wide-angle incidence for protons transmitted through monocrystalline Si membranes. The channeling peaks are generated by the crystalline medium as a result of multiple charge-exchange events due to the impact-parameter dependence of the electron capture and loss cross-sections. This explains successfully the detection of channeling peaks only at a low enough residual proton energy: Epf⩽0.6 MeV, after the transmission.

  15. Experimental evidence of the effect of heat flux on thomson scattering off ion acoustic waves

    PubMed

    Amiranoff; Baton; Huller; Malka; Modena; Mounaix; Galloudec; Rousseaux; Salvati

    2000-02-01

    Thomson self-scattering measurements are performed in a preionized helium gas jet plasma at different locations along the laser propagation direction. A systematic and important variation of the intensity ratio between the blue and the red ion spectral components is observed, depending on whether the location of the probed region is in front of or behind the focal plane. A simple theoretical calculation of Thomson scattering shows that this behavior can be qualitatively understood in terms of a deformation of the electron distribution function due to the return current correlated with the classical thermal heat flux. PMID:11046481

  16. Electroslag remelting with used fluxes

    SciTech Connect

    Yakovlev, N.F.; Sokha, Yu.S.; Oleinik, Yu.S.; Prokhorov, A.N.; Ol'shanskaya, T.V.

    1988-05-01

    The Ukranian Scientific-Research Institute of Specialty Steel collaborated with plants engaged in the production of quality metals to introduce a low-waste electroslag remelting (ESR) technology employing used fluxes. It was established that the fluoride (type ANF-1) and fluoride-oxide (type ANF-6) fluxes which are widely used in ESR still have a high content of calcium fluoride and alumina and a low impurity content after 8-10 h of ESR. In the ESR of steels with used fluxes, the content of monitored components in the final slags changes negligibly, while the content of most impurities decreases. The used flux is also characterized by a low concentration of phosphorus and sulfur. It was found that flux can be used 3-5 times when it makes up 50% of the flux mixture in the charge. The savings realized from the use of spent flux in ESR amounts to 4-9 rubles/ton steel.

  17. Ising-Glauber Spin Cluster Model for Temperature-Dependent Magnetization Noise in SQUIDs

    NASA Astrophysics Data System (ADS)

    De, Amrit

    2014-11-01

    Clusters of interacting two-level-systems, likely due to Farbe+(F+) centers at the metal-insulator interface, are shown to self-consistently lead to 1 /fα magnetization noise [with α (T )≲1 ] in SQUIDs. Model calculations, based on a new method of obtaining correlation functions, explains various puzzling experimental features. It is shown why the inductance noise is inherently temperature dependent while the flux noise is not, despite the same underlying microscopics. Magnetic ordering in these systems, established by three-point correlation functions, explains the observed flux- inductance-noise cross correlations. Since long-range ferromagnetic interactions are shown to lead to a more weakly temperature dependent flux noise when compared to short-range interactions, the time reversal symmetry of the clusters is also not likely broken by the same mechanism which mediates surface ferromagnetism in nanoparticles and thin films of the same insulator materials.

  18. New method for black-hole spin measurement based on flux variation from an infalling gas ring

    NASA Astrophysics Data System (ADS)

    Moriyama, Kotaro; Mineshige, Shin

    2015-12-01

    We propose a new method for black hole spin measurement. In this method, we consider a gas blob or ring falling onto a black hole from the marginally stable orbit, keeping its initial orbital angular momentum. We calculate the gas motion and photon trajectories in the Kerr space-time and, assuming that the gas blob or ring emits monochromatic radiation, carefully examine how it is observed by a distant observer. The light curve of the orbiting gas blob is composed of many peaks because of periodic enhancement of the flux due to the gravitational lensing and beaming effects. Further, the intensity of each peak first gradually increases with time due to the focusing effect around the photon circular orbit and then rapidly decreases due to the gravitational redshift, as the gas blob approaches the event horizon. The light curve of the gas ring is equivalent to a superposition of those of the blobs with various initial orbital phases, and so it is continuous and with no peaks. The flux first gradually increases and then rapidly decays, as in the blob model. The flux variation timescale depends on the black hole spin and is independent of the inclination angle, while time-averaged frequency shift has dependence on both effects. We can thus, in principle, determine spin and inclination angle from observations. The observational implications and future issues are briefly discussed.

  19. Computing the Flux Footprint

    NASA Astrophysics Data System (ADS)

    Wilson, J. D.

    2015-07-01

    We address the flux footprint for measurement heights in the atmospheric surface layer, comparing eddy diffusion solutions with those furnished by the first-order Lagrangian stochastic (or "generalized Langevin") paradigm. The footprint given by Langevin models differs distinctly from that given by the random displacement model (i.e. zeroth-order Lagrangian stochastic model) corresponding to its "diffusion limit," which implies that a well-founded theory of the flux footprint must incorporate the turbulent velocity autocovariance. But irrespective of the choice of the eddy diffusion or Langevin class of model as basis for the footprint, tuning relative to observations is ultimately necessary. Some earlier treatments assume Monin-Obukhov profiles for the mean wind and eddy diffusivity and that the effective Schmidt number (ratio of eddy viscosity to the tracer eddy diffusivity) in the neutral limit , while others calibrate the model to the Project Prairie Grass dispersion trials. Because there remains uncertainty as to the optimal specification of (or a related parameter in alternative theories, e.g. the Kolmogorov coefficient in Langevin models) it is recommended that footprint models should be explicit in this regard.

  20. [Dynamic response of riverine nitrate flux to net anthropogenic nitrogen inputs in a typical river in Zhejiang Province over the 1980-2010 period].

    PubMed

    Zhang, Bai-Fa; Chen, Ding-Jiang

    2014-08-01

    derived from anthropogenic nitrogen sources. Although observed long-term interannual change of riverine NO3(-) -N flux was dependent on the combined influences of NANI and hydroclimate, a more immediate reduction of riverine NO3(-) -N flux may result from interception strategies than from cutting nitrogen source inputs due to the contribution of retained nitrogen pools. PMID:25338360

  1. Providers get their due.

    PubMed

    Morrissey, J

    1994-11-01

    Providers are getting their due, but only after employing computer software programs to help sort through the complex managed-care contracts they've negotiated. More and more accounting departments are relying on contract management systems to ensure accurate billing. PMID:10138187

  2. Paying Their Dues.

    ERIC Educational Resources Information Center

    Scalzo, Teresa

    1995-01-01

    Some colleges and universities have found that alumni prefer to have ownership of their alumni association, and such a membership program can raise revenues for the institution while providing a valuable communication tool. A strong dues program can work well with an annual giving campaign. A variety of membership structures is possible. Details…

  3. Diffusive flux of methane from warm wetlands

    SciTech Connect

    Barber, T.R.; Burke, R.A.; Sackett, W.M. )

    1988-12-01

    Diffusion of methane across the air-water interface from several wetland environments in south Florida was estimated from measured surface water concentrations using an empirically derived gas exchange model. The flux from the Everglades sawgrass marsh system varied widely, ranging from 0.18 + or{minus}0.21 mol CH{sub 4}/sq m/yr for densely vegetated regions to 2.01 + or{minus}0.88 for sparsely vegetated, calcitic mud areas. Despite brackish salinities, a strong methane flux, 1.87 + or{minus}0.63 mol CH{sub 4}/sq m/yr, was estimated for an organic-rich mangrove pond near Florida Bay. The diffusive flux accounted for 23, 36, and 13% of the total amount of CH{sub 4} emitted to the atmosphere from these environments, respectively. The average dissolved methane concentration for an organic-rich forested swamp was the highest of any site at 12.6 microM; however, the calculated diffusive flux from this location, 2.57 + or{minus}1.88 mol CH{sub 4}/sq m/yr, was diminished by an extensive plant canopy that sheltered the air-water interface from the wind. The mean diffusive flux from four freshwater lakes, 0.77 + or{minus}0.73 mol CH{sub 4}/sq m/yr, demonstrated little temperature dependence. The mean diffusive flux for an urbanized, subtropical estuary was 0.06 + or{minus}0.05 mol CH{sub 4}/sq m/yr.

  4. A Summary of Mass Flux Measurements in Solid 4He

    NASA Astrophysics Data System (ADS)

    Hallock, R. B.; Ray, M. W.; Vekhov, Y.

    2012-11-01

    Here we provide a summary and brief review of some of the work done with solid 4He at the University of Massachusetts Amherst below a sample pressure of 28 bar. The motivation for the work has been to attempt to pass 4He atoms through solid 4He without directly applying mechanical pressure to the solid itself. The specific technique chosen is limited to pressures near the melting curve and was initially designed to provide a yes/no answer to the question of whether or not it might be possible to observe such a mass flux. The thermo-mechanical effect and direct mass injection have been separately used to create chemical potential differences between two reservoirs of superfluid 4He connected to each other through superfluid-filled Vycor rods in series with solid 4He, which is in the hcp region of the phase diagram. The thermo-mechanical effect is a more versatile approach. And, in a particular symmetric application it is designed to provide a mass flux with little or no net increase in the density of the solid. Our observations, off but near the melting curve, have included: (1) the presence of an increasing DC flux of atoms through the solid-filled cell with decreasing temperature below ≈650 mK and no flux above this temperature; (2) the presence of a flux minimum and flux instability in the vicinity of 75-80 mK, with a flux increase at lower temperatures; (3) the temperature dependence of the flux above 100 mK and the dependence of the flux on the net driving chemical potential difference provide interesting insights on the possible mechanism that leads to the flux above 100 mK. The most recent data suggest that whatever is responsible for the flux in solid 4He, at least for T>100 mK, may be an example of a Bosonic Luttinger liquid.

  5. Clouds and Shortwave Fluxes at Nauru. Part II: Shortwave Flux Closure

    SciTech Connect

    McFarlane, Sally A.; Evans, K. F.

    2004-11-01

    The datasets currently being collected at the Atmospheric Radiation Measurement (ARM) Program's sites on the islands of Nauru and Manus represent the longest time series of ground based cloud measurements available in the tropical western Pacific region. In this series of papers, we present a shortwave flux closure study using observations collected at the Nauru site between June 1999 and May 2000. The previous paper presented frequency of occurrence of non-precipitating liquid and ice clouds detected by the millimeter wavelength cloud radar (MMCR) at Nauru and statistics of the retrieved microphysical properties. This paper presents estimates of the cloud radiative effect over the study period and results from a closure study in which the retrieved cloud properties are input to a radiative transfer model and the modeled surface fluxes are compared to observations. The average shortwave cloud radiative forcing at the surface is 48.2 W/m{sup 2}, which is significantly smaller than the cloud radiative forcing estimates found during the TOGA-COARE field project. The difference in the cloud radiative forcing estimates during the two periods are due to the variability in cloud amount over Nauru during the convective and suppressed phases of the El Nino-Southern Oscillation (ENSO). In the closure study, the modeled and observed surface fluxes show large differences at short time scales, due to the temporal and spatial variability of the clouds observed at Nauru. Averaging over 60 minutes reduces the average root-mean-square error in total flux to 10% of the observed flux. The modeled total downwelling fluxes are unbiased with respect to the observed fluxes while the direct fluxes are underestimated and the diffuse fluxes are overestimated. Examination of the errors over the dataset indicates that the cloud amount derived from the ground based measurements is an overestimate of the radiatively important cloud amount due to the anisotropy of the cloud field at Nauru, the

  6. Characterization of seismic hazard and structural response by energy flux

    USGS Publications Warehouse

    Afak, E.

    2000-01-01

    Seismic safety of structures depends on the structure's ability to absorb the seismic energy that is transmitted from ground to structure. One parameter that can be used to characterize seismic energy is the energy flux. Energy flux is defined as the amount of energy transmitted per unit time through a cross-section of a medium, and is equal to kinetic energy multiplied by the propagation velocity of seismic waves. The peak or the integral of energy flux can be used to characterize ground motions. By definition, energy flux automatically accounts for site amplification. Energy flux in a structure can be studied by formulating the problem as a wave propagation problem. For buildings founded on layered soil media and subjected to vertically incident plane shear waves, energy flux equations are derived by modeling the buildings as an extension of the layered soil medium, and considering each story as another layer. The propagation of energy flux in the layers is described in terms of the upgoing and downgoing energy flux in each layer, and the energy reflection and transmission coefficients at each interface. The formulation results in a pair of simple finite-difference equations for each layer, which can be solved recursively starting from the bedrock. The upgoing and downgoing energy flux in the layers allows calculation of the energy demand and energy dissipation in each layer. The methodology is applicable to linear, as well as nonlinear structures. ?? 2000 Published by Elsevier Science Ltd.

  7. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sikora, Marek; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2013-02-20

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  8. Herbicide and degradate flux in the Yazoo River Basin

    USGS Publications Warehouse

    Coupe, R.H.; Welch, H.L.; Pell, A.B.; Thurman, E.M.

    2005-01-01

    During 1996-1997, water samples were collected from five sites in the Yazoo River Basin and analysed for 14 herbicides and nine degradates. These included acetochlor, alachlor, atrazine, cyanazine, fluometuron, metolachlor, metribuzin, molinate, norflurazon, prometryn, propanil, propazine, simazine, trifluralin, three degradates of fluometuron, two degradates of atrazine, one degradate of cyanazine, norflurazon, prometryn, and propanil. Fluxes generally were higher in 1997 than in 1996 due to a greater rainfall in 1997 than 1996. Fluxes were much larger from streams in the alluvial plain (an area of very productive farmland) than from the Skuna River in the bluff hills (an area of small farms, pasture, and forest). Adding the flux of the atrazine degradates to the atrazine flux increased the total atrazine flux by an average of 14.5%. The fluometuron degradates added about 10% to the total fluometuron flux, and adding the norflurazon degradate flux to the norflurazon flux increased the flux by 82% in 1996 and by 171% in 1997. ?? 2005 Taylor & Francis.

  9. Measurement of Flux Density of Cas A at Low Frequencies

    NASA Astrophysics Data System (ADS)

    Patil, Ajinkya; Fisher, R.

    2012-01-01

    Cas A is used as a flux calibrator throughout the radio spectrum. Therefore it is important to know the spectral and secular variations in its flux density. Earlier observations by Scott et. al. (1969) and Baars et. al. (1972) suggested a secular decrease in flux density of Cas A at a rate of about 1% per year at all frequencies. However later observations by Erickson & Perley (1975) and Read (1977) indicated anomalously high flux from Cas A at 38 MHz. Also, these observations suggested that the original idea of faster decay of the flux density rate at low frequencies may be in error or that something more complex than simple decay is affecting the flux density at low frequencies. The source changes at 38 MHz still remains a mystery. We intend to present the results of follow up observations made from 1995 to 1998 with a three element interferometer in Green Bank operating in frequency range 30 to 120 MHz. We will discuss the problems at such low frequencies due to large beamwidth and unstable ionosphere. We will also discuss the strategies we have used so far to to find the flux density of Cas A by calculating the ratio of flux density of Cas A to that of Cyg A, assuming flux density of Cyg A to be constant. Above mentioned work was performed in summer student program sponsored by National Radio Astronomy Observatory.

  10. Particle transport due to magnetic fluctuations

    SciTech Connect

    Stoneking, M.R.; Hokin, S.A.; Prager, S.C.; Fiksel, G.; Ji, H.; Den Hartog, D.J.

    1994-01-01

    Electron current fluctuations are measured with an electrostatic energy analyzer at the edge of the MST reversed-field pinch plasma. The radial flux of fast electrons (E>T{sub e}) due to parallel streaming along a fluctuating magnetic field is determined locally by measuring the correlated product <{tilde J}{sub e}{tilde B}{sub r}>. Particle transport is small just inside the last closed flux surface ({Gamma}{sub e,mag} < 0.1 {Gamma}{sub e,total}), but can account for all observed particle losses inside r/a=0.8. Electron diffusion is found to increase with parallel velocity, as expected for diffusion in a region of field stochasticity.

  11. BVOC and tropospheric ozone fluxes from an orange orchard in the California Central Valley

    NASA Astrophysics Data System (ADS)

    Fares, S.; Gentner, D. R.; Park, J.; Weber, R.; Karlik, J. F.; Goldstein, A. H.

    2010-12-01

    Citrus plants, especially oranges, are widely cultivated in the Central Valley of California and in many other countries experiencing Mediterranean climates. In many of these areas, orchards are often exposed to high levels of tropospheric ozone (O3) due to their location in polluted airsheds. Citrus take up O3 through their stomata and emit biogenic volatile organic compounds (BVOC), which can contribute to non-stomatal O3 removal through fast gas-phase reactions with O3. The study was performed in a navel orange orchard in Exeter, California. The CO2 & water fluxes, together with O3 uptake and BVOC emissions were measured continuously using eddy covariance techniques. Vertical concentration gradients of these compounds were also measured at 4 heights from the orchard floor to above the canopy. We observed high levels (up to 40 ppb) of volatile organic compounds including methanol, isoprene, monoterpenes, sesquiterpenes, and some additional oxygenated BVOC. Methanol dominated BVOC emissions (up to 5 nmol m-2 s-1) followed by acetone. Monoterpenes fluxes were also recorded during the all vegetative period, with the highest emissions taking place during flowering periods. The orchard represented a sink for ozone, with uptake rates on the order of 10 nmol m-2 s-1 during the central hours of the day. BVOC fluxes were highly temperature dependent, while ozone fluxes were more dependent on the physiology of the orchard, consistent with dominant removal occurring through the stomatal opening. The current research is aimed at: 1. Quantifying the uptake of O3 by citrus and partitioning it into stomatal and non-stomatal processes; 2. Quantifying the BVOC emissions and their dependence on physical and ecophysiological parameters.

  12. PromptNuFlux: Prompt atmospheric neutrino flux calculator

    NASA Astrophysics Data System (ADS)

    Rottoli, Luca

    2015-11-01

    PromptNuFlux computes the prompt atmospheric neutrino flux E3Φ(GeV2/(cm2ssr)), including the total associated theory uncertainty, for a range of energies between E=103 GeV and E=107.5 GeV. Results are available for five different parametrizations of the input cosmic ray flux: BPL, H3P, H3A, H14a, H14b.

  13. Human due diligence.

    PubMed

    Harding, David; Rouse, Ted

    2007-04-01

    Most companies do a thorough job of financial due diligence when they acquire other companies. But all too often, deal makers simply ignore or underestimate the significance of people issues in mergers and acquisitions. The consequences are severe. Most obviously, there's a high degree of talent loss after a deal's announcement. To make matters worse, differences in decision-making styles lead to infighting; integration stalls; and productivity declines. The good news is that human due diligence can help companies avoid these problems. Done early enough, it helps acquirers decide whether to embrace or kill a deal and determine the price they are willing to pay. It also lays the groundwork for smooth integration. When acquirers have done their homework, they can uncover capability gaps, points of friction, and differences in decision making. Even more important, they can make the critical "people" decisions-who stays, who goes, who runs the combined business, what to do with the rank and file-at the time the deal is announced or shortly thereafter. Making such decisions within the first 30 days is critical to the success of a deal. Hostile situations clearly make things more difficult, but companies can and must still do a certain amount of human due diligence to reduce the inevitable fallout from the acquisition process and smooth the integration. This article details the steps involved in conducting human due diligence. The approach is structured around answering five basic questions: Who is the cultural acquirer? What kind of organization do you want? Will the two cultures mesh? Who are the people you most want to retain? And how will rank-and-file employees react to the deal? Unless an acquiring company has answered these questions to its satisfaction, the acquisition it is making will be very likely to end badly. PMID:17432159

  14. Real space visualization of thermal fluctuations in a triangular flux-line lattice

    NASA Astrophysics Data System (ADS)

    Schwarz, A.; Liebmann, M.; Pi, U. H.; Wiesendanger, R.

    2010-03-01

    The temperature-dependent properties of a triangular flux-line lattice (FLL) in the low-flux density regime were investigated by evaluating the imaged flux-line (FL) size and the lattice regularity observed in real space utilizing magnetic force microscopy (MFM). At low temperatures, pinning by randomly distributed point defects in the anisotropic type-II superconductor Bi2Sr2CaCu2O8+δ results in curved FLs and lateral disorder within the FLL (Bragg glass). Above 30 K, depinning of pancake vortices (PVs) leads to straightening of FLs and a better-ordered lattice. Evaluation of the temperature-dependent imaged FL size allows us to determine the stiffness of the potential, in which FLs in the lattice are caged due to mutual repulsion between them. At 54.1 K, far below melting temperatures reported so far, thermal fluctuations plus the lateral force exerted by the scanning tip facilitate decoupling of PVs near the surface and the image contrast exhibit a liquid-like behavior. Our analysis demonstrates the ability of MFM to obtain three-dimensional information on the arrangement of PVs.

  15. Variability of surface fluxes over a heterogeneous semi-arid grassland

    SciTech Connect

    Barnes, F.J.; Porch, W.; Cooper, D. ); Kunkel, K.E. ); Hipps, L.; Swiatek, E. )

    1991-01-01

    Efforts are increasing throughout the research community to improve the predictive capabilities of general circulation models (GCMs). The US Department of Energy's Atmospheric Radiation Measurement (ARM) program has stated its goals as improving the representation and parameterization of cloud radiative forcing and feedbacks in GCMs by a combined modeling and experimental approach. Along with ambient atmospheric conditions, including advection of water vapor and cloud nuclei from other regions, cloud dynamics depend on surface fluxes of heat and water vapor. The lower boundary of the GCM modeling domain, the earth's surface, exerts a strong influence on regional dynamics of heat and water vapor, and the heterogeneity in the surface features can be responsible for generating regional mesoscale circulation patterns. Changes in the surface vegetation due to anthropogenic activity can cause substantial changes in the ratio of sensible to latent heat flux and result in climate changes that may be irreversible. A broad variety of models for representing energy fluxes are in use, from individual leaf and canopy models to mesoscale atmospheric models and GCMs. Scaling-up a model is likely to result in significant errors, since biophysical responses often have nonlinear dependence on the abiotic environment. Thus, accurate and defensible methods for selecting measurement scales and modeling strategies are needed in the effort to improve GCMs. 7 refs., 4 figs., 1 tab.

  16. Resolving hyporheic and groundwater components of streambed water flux

    USGS Publications Warehouse

    Bhaskar, Aditi S.; Harvey, Judson W.; Henry, Eric J.

    2012-01-01

    Hyporheic and groundwater fluxes typically occur together in permeable sediments beneath flowing stream water. However, streambed water fluxes quantified using the thermal method are usually interpreted as representing either groundwater or hyporheic fluxes. Our purpose was to improve understanding of co-occurring groundwater and hyporheic fluxes using streambed temperature measurements and analysis of one-dimensional heat transport in shallow streambeds. First, we examined how changes in hyporheic and groundwater fluxes affect their relative magnitudes by reevaluating previously published simulations. These indicated that flux magnitudes are largely independent until a threshold is crossed, past which hyporheic fluxes are diminished by much larger (1000-fold) groundwater fluxes. We tested accurate quantification of co-occurring fluxes using one-dimensional approaches that are appropriate for analyzing streambed temperature data collected at field sites. The thermal analytical method, which uses an analytical solution to the one-dimensional heat transport equation, was used to analyze results from a numerical heat transport model, in which hyporheic flow was represented as increased thermal dispersion at shallow depths. We found that co-occurring groundwater and hyporheic fluxes can be quantified in streambeds, although not always accurately. For example, using a temperature time series collected in a sandy streambed, we found that hyporheic and groundwater flow could both be detected when thermal dispersion due to hyporheic flow was significant compared to thermal conduction. We provide guidance for when thermal data can be used to quantify both hyporheic and groundwater fluxes, and we show that neglecting thermal dispersion may affect accuracy and interpretation of estimated streambed water fluxes.

  17. California's Future Carbon Flux

    NASA Astrophysics Data System (ADS)

    Xu, L.; Pyles, R. D.; Paw U, K.; Gertz, M.

    2008-12-01

    The diversity of the climate and vegetation systems in the state of California provides a unique opportunity to study carton dioxide exchange between the terrestrial biosphere and the atmosphere. In order to accurately calculate the carbon flux, this study couples the sophisticated analytical surface layer model ACASA (Advance Canopy-Atmosphere-Soil Algorithm, developed in the University of California, Davis) with the newest version of mesoscale model WRF (the Weather Research & Forecasting Model, developed by NCAR and several other agencies). As a multilayer, steady state model, ACASA incorporates higher-order representations of vertical temperature variations, CO2 concentration, radiation, wind speed, turbulent statistics, and plant physiology. The WRF-ACASA coupling is designed to identify how multiple environmental factors, in particularly climate variability, population density, and vegetation distribution, impact on future carbon cycle prediction across a wide geographical range such as in California.

  18. Quantitative Flux Ecoregions for AmeriFlux Using MODIS

    NASA Astrophysics Data System (ADS)

    Hoffman, F. M.; Hargrove, W. W.

    2004-12-01

    Multivariate Geographic Clustering was used with maps of climate, soils, and physiography and MODIS remotely sensed data products to statistically produce a series of the 90 most-different homogeneous flux-relevant ecoregions in the conterminous United States using a parallel supercomputer. Nine separate sets of flux ecoregions were produced; only two will be discussed here. Both the IB and IIIB maps were quantitatively constructed from subsets of the input data integrated during the local growing season (frost-free period) in every 1 km cell. Each map is shown two ways --- once with the 90 flux ecoregions colored randomly, and once using color combinations derived statistically from the first three Principal Component Axes. Although the underlying flux ecoregion polygons are the same in both cases, the statistically derived colors show the similarity of conditions within each flux ecoregion. Coloring the same map in this way shows the continuous gradient of changing flux environments across the US. The IB map, since it considers only abiotic environmental factors, represents flux-ecoregions based on potential vegetation. The IIIB map, since it contains remotely sensed MODIS information about existing vegetation, includes the effects of natural and anthropogenic disturbance, and represents actual or realized flux ecoregions. Thus, differences between the maps are attributable to human activity and natural disturbances. The addition of information on existing vegetation exerts a unifying effect on abiotic-only flux ecoregions. The Mississippi Valley and Corn Belt areas show large differences between the two maps. Map IIIB shows a mosaic of ``speckles'' in areas of intense human land use, ostensibly from disturbances like agriculture, irrigation, fertilization, and clearing. Such ``speckles'' are absent from areas devoid of intense human land use. Major cities are also evident in the IIIB map. We will use the quantitative similarity of the suite of flux

  19. Methane flux in the Great Dismal Swamp

    NASA Technical Reports Server (NTRS)

    Harriss, R. C.; Sebacher, D. I.; Day, F. P., Jr.

    1982-01-01

    The paper reports measurements made over a 17-month period of the methane flux in the Great Dismal Swamp of Virginia in light of the potential implications of variations in atmospheric methane concentrations. Gas flux measurements were made by a technique combining a gas filter correlation IR absorption analyzer with improved sampling chambers that enclose a soil area under conditions ranging from totally flooded soils to dry soils resulting from drought conditions. Methane emissions are found to range from 0.0013 g CH4/sq m per day to 0.019 g CH4/sq m per day, depending on temperature and season, when the soil is in a waterlogged state. During drought conditions, the peat soils in the swamp were a sink for atmospheric methane, with fluxes from less than 0.001 to 0.005 g CH4/sq m per day and decreasing with decreasing temperature. Results illustrate the potential complexity of the processes which regulate the net flux of methane between wetland soils and the atmosphere.

  20. Insects, infestations and nutrient fluxes

    NASA Astrophysics Data System (ADS)

    Michalzik, B.

    2012-04-01

    Forest ecosystems are characterized by a high temporal and spatial variability in the vertical transfer of energy and matter within the canopy and the soil compartment. The mechanisms and controlling factors behind canopy processes and system-internal transfer dynamics are imperfectly understood at the moment. Seasonal flux diversities and inhomogeneities in throughfall composition have been reported from coniferous and deciduous forests, and in most cases leaf leaching has been considered as principle driver for differences in the amount and quality of nutrients and organic compounds (Tukey and Morgan 1963). Since herbivorous insects and the processes they initiate received less attention in past times, ecologists now emphasize the need for linking biological processes occurring in different ecosystem strata to explain rates and variability of nutrient cycling (Bardgett et al. 1998, Wardle et al. 2004). Consequently, herbivore insects in the canopies of forests are increasingly identified to play an important role for the (re)cycling and availability of nutrients, or, more generally, for the functioning of ecosystems not only in outbreak situations but also at endemic (non-outbreak) density levels (Stadler et al. 2001, Hunter et al. 2003). Before, little attention was paid to insect herbivores when quantifying element and energy fluxes through ecosystems, although the numerous and different functions insects fulfill in ecosystems (e.g. as pollinators, herbivores or detritivores) were unanimously recognized (Schowalter 2000). Amongst the reasons for this restraint was the argument that the total biomass of insects tends to be relatively low compared to the biomass of trees or the pool of soil organic matter (Ohmart et al. 1983). A second argument which was put forward to justify the inferior role of insects in nutrient cycling were the supposed low defoliation losses between 5-10% of the annual leaf biomass, or net primary production, due to insect herbivory under

  1. Geometry Dependence of Stellarator Turbulence

    SciTech Connect

    H.E. Mynick, P. Xanthopoulos and A.H. Boozer

    2009-08-10

    Using the nonlinear gyrokinetic code package GENE/GIST, we study the turbulent transport in a broad family of stellarator designs, to understand the geometry-dependence of the microturbulence. By using a set of flux tubes on a given flux surface, we construct a picture of the 2D structure of the microturbulence over that surface, and relate this to relevant geometric quantities, such as the curvature, local shear, and effective potential in the Schrodinger-like equation governing linear drift modes.

  2. Temporal and spatial variations of soil CO2, CH4 and N2O fluxes at three differently managed grasslands

    NASA Astrophysics Data System (ADS)

    Imer, D.; Merbold, L.; Eugster, W.; Buchmann, N.

    2013-09-01

    A profound understanding of temporal and spatial variabilities of soil carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three soil greenhouse gas (GHG) fluxes occur due to changes in environmental drivers as well as fertilizer applications, harvests and grazing. To assess how such changes affect soil GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400 m a.s.l. (intensively managed) to 1000 m a.s.l. (moderately intensive managed) to 2000 m a.s.l. (extensively managed). The alpine grassland was included to study both effects of extensive management on CH4 and N2O fluxes and the different climate regime occurring at this altitude. Temporal and spatial variabilities of soil GHG fluxes and environmental drivers on various timescales were determined along transects of 16 static soil chambers at each site. All three grasslands were N2O sources, with mean annual soil fluxes ranging from 0.15 to 1.28 nmol m-2 s-1. Contrastingly, all sites were weak CH4 sinks, with soil uptake rates ranging from -0.56 to -0.15 nmol m-2 s-1. Mean annual soil and plant respiration losses of CO2, measured with opaque chambers, ranged from 5.2 to 6.5 μmol m-2 s-1. While the environmental drivers and their respective explanatory power for soil N2O emissions differed considerably among the three grasslands (adjusted r2 ranging from 0.19 to 0.42), CH4 and CO2 soil fluxes were much better constrained (adjusted r2 ranging from 0.46 to 0.80) by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for soil N2O and CH4 fluxes. We found permanent hot spots for soil N2O emissions as well as locations of permanently lower

  3. Fluxes of nonequilibrium photo-excited phonons along surfaces of crystals without an inversion center

    SciTech Connect

    Blokh, M.D.

    1988-01-01

    The flux of nonequilibrium phonons excited by light in the near-surface domain of a crystal or a thin plate is investigated. An exact expression is obtained for the phonon energy flux for a crystal with a polar direction and its polarization dependence is analyzed. The magnitude of the energy flux can reach the incident light intensity. The temperature difference produced by the flux of nonequilibrium photo-excited phonons is found.

  4. Radiation-induced swelling and softening in magnesium aluminate spinel irradiated with high-flux Cu - ions

    NASA Astrophysics Data System (ADS)

    Lee, C. G.; Ohmura, T.; Takeda, Y.; Matsuoka, S.; Kishimoto, N.

    2004-03-01

    Magnesium aluminate spinel of single crystal was irradiated with 60 keV Cu - at a flux up to 6.2 × 10 18 ions/m 2 s, to a total fluence of 3 × 10 20 ions/m 2, in order to study changes in hardness and step-height swelling by high-flux implantation. Hardness determined by nano-indentation measurements steeply decreased with implantation. There is a strong negative correlation between flux dependences of the hardness and the step-height swelling: the former decreases as the latter increases. The Rutherford backscattering spectrometry (RBS)/channeling measurements showed that the spinel is not completely amorphized over the flux range in this study, and the radiation-induced softening observed is not due to amorphization. Results of optical absorbance suggested that radiation-induced point defects and their clusters on the anion sublattices of the spinel played an important role in the radiation-induced swelling under high-flux ion implantation.

  5. Magnetic Flux Cancellation in Ellerman Bombs

    NASA Astrophysics Data System (ADS)

    Reid, A.; Mathioudakis, M.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Henriques, V.; Ray, T.

    2016-06-01

    Ellerman Bombs (EBs) are often found to be co-spatial with bipolar photospheric magnetic fields. We use Hα imaging spectroscopy along with Fe i 6302.5 Å spectropolarimetry from the Swedish 1 m Solar Telescope (SST), combined with data from the Solar Dynamic Observatory, to study EBs and the evolution of the local magnetic fields at EB locations. EBs are found via an EB detection and tracking algorithm. Using NICOLE inversions of the spectropolarimetric data, we find that, on average, (3.43 ± 0.49) × 1024 erg of stored magnetic energy disappears from the bipolar region during EB burning. The inversions also show flux cancellation rates of 1014–1015 Mx s‑1 and temperature enhancements of 200 K at the detection footpoints. We investigate the near-simultaneous flaring of EBs due to co-temporal flux emergence from a sunspot, which shows a decrease in transverse velocity when interacting with an existing, stationary area of opposite polarity magnetic flux, resulting in the formation of the EBs. We also show that these EBs can be fueled further by additional, faster moving, negative magnetic flux regions.

  6. SYNOPTIC MAPPING OF CHROMOSPHERIC MAGNETIC FLUX

    SciTech Connect

    Jin, C. L.; Harvey, J. W.; Pietarila, A. E-mail: jharvey@nso.edu

    2013-03-10

    We used daily full-disk Ca II 854.2 nm magnetograms from the Synoptic Optical Long Term Investigations of the Sun (SOLIS) facility to study the chromospheric magnetic field from 2006 April through 2009 November. We determined and corrected previously unidentified zero offsets in the SOLIS magnetograms. By tracking the disk passages of stable unipolar regions, the measured net flux densities were found to systematically decrease from the disk center to the limb by a factor of about two. This decrease was modeled using a thin flux tube model with a difference in signal formation height between the center and limb sides. Comparison of photospheric and chromospheric observations shows that their differences are largely due to horizontal spreading of magnetic flux with increasing height. The north polar magnetic field decreased nearly linearly with time during our study period while the south polar field was nearly constant. We used the annual change in the viewing angle of the polar regions to estimate the radial and meridional components of the polar fields and found that the south polar fields were tilted away from the pole. Synoptic maps of the chromospheric radial flux density distribution were used as boundary conditions for extrapolation of the field from the chromosphere into the corona. A comparison of modeled and observed coronal hole boundaries and coronal streamer positions showed better agreement when using the chromospheric rather than the photospheric synoptic maps.

  7. Implosion Robustness, Time-Dependent Flux Asymmetries and Big Data

    NASA Astrophysics Data System (ADS)

    Peterson, J. L.; Field, J. E.; Spears, B. K.; Brandon, S. T.; Gaffney, J. A.; Hammer, J.; Kritcher, A.; Nora, R. C.; Springer, P. T.

    2015-11-01

    Both direct and indirect drive inertial confinement fusion rely on the formation of spherical implosions, which can be a challenge under temporal and spatial drive variations (either from discrete laser beams, a complex hohlraum radiation environment, or both). To that end, we examine the use of large simulation databases of 2D capsule implosions to determine the sensitivity of indirectly driven NIF designs to time-varying low-mode radiation drive asymmetries at varying convergence ratios. In particular, we define and calculate a large number of extensive quantities for the simulations within the database and compare with the equivalent quantities extracted from fully 3D simulations and those used in 1D hydrodynamic models. Additionally, we discuss some of the practical challenges of searching for physical insight in multi-petabyte datasets. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, Lawrence Livermore National Security, LLC. LLNL-ABS-674884.

  8. Regulation of GLUT4 and Insulin-Dependent Glucose Flux

    PubMed Central

    Olson, Ann Louise

    2012-01-01

    GLUT4 has long been known to be an insulin responsive glucose transporter. Regulation of GLUT4 has been a major focus of research on the cause and prevention of type 2 diabetes. Understanding how insulin signaling alters the intracellular trafficking of GLUT4 as well as understanding the fate of glucose transported into the cell by GLUT4 will be critically important for seeking solutions to the current rise in diabetes and metabolic disease.

  9. Flux growth and characterization of cuprorivaite: the influence of temperature, flux, and silica source

    NASA Astrophysics Data System (ADS)

    Bloise, A.; Abd El Salam, S.; De Luca, R.; Crisci, G. M.; Miriello, D.

    2016-07-01

    Single crystals of cuprorivaite (CaCuSi4O10), one of the oldest synthetic color pigments of Egyptian history, have been synthesized by slow-cooling flux method. Several runs were carried out at temperatures between 800 and 960 °C and with reaction times ranging from 10 to 72 h. The starting materials and run products were characterized by binocular microscope, X-ray powder diffraction, scanning electron microscopy with annexed energy-dispersive spectrometry, and μ-Raman spectroscopy. The effects of growth parameters (temperature, flux, silica source) on yield and size of crystals were studied. The growth of cuprorivaite depends greatly on the starting materials: they are observed as run products only using natron as flux. Furthermore, colorimetric analysis performed on the synthesizing pigment was compared with the archeological samples present in the literature in order to value similarities and differences.

  10. Acoustic emission from magnetic flux tubes in the solar network

    NASA Astrophysics Data System (ADS)

    Vigeesh, G.; Hasan, S. S.

    2013-06-01

    We present the results of three-dimensional numerical simulations to investigate the excitation of waves in the magnetic network of the Sun due to footpoint motions of a magnetic flux tube. We consider motions that typically mimic granular buffeting and vortex flows and implement them as driving motions at the base of the flux tube. The driving motions generates various MHD modes within the flux tube and acoustic waves in the ambient medium. The response of the upper atmosphere to the underlying photospheric motion and the role of the flux tube in channeling the waves is investigated. We compute the acoustic energy flux in the various wave modes across different boundary layers defined by the plasma and magnetic field parameters and examine the observational implications for chromospheric and coronal heating.

  11. Effect of spatial sampling from European flux towers for estimating carbon and water fluxes with artificial neural networks

    NASA Astrophysics Data System (ADS)

    Papale, Dario; Black, T. Andrew; Carvalhais, Nuno; Cescatti, Alessandro; Chen, Jiquan; Jung, Martin; Kiely, Gerard; Lasslop, Gitta; Mahecha, Miguel D.; Margolis, Hank; Merbold, Lutz; Montagnani, Leonardo; Moors, Eddy; Olesen, Jørgen E.; Reichstein, Markus; Tramontana, Gianluca; Gorsel, Eva; Wohlfahrt, Georg; Ráduly, Botond

    2015-10-01

    Empirical modeling approaches are frequently used to upscale local eddy covariance observations of carbon, water, and energy fluxes to regional and global scales. The predictive capacity of such models largely depends on the data used for parameterization and identification of input-output relationships, while prediction for conditions outside the training domain is generally uncertain. In this work, artificial neural networks (ANNs) were used for the prediction of gross primary production (GPP) and latent heat flux (LE) on local and European scales with the aim to assess the portion of uncertainties in extrapolation due to sample selection. ANNs were found to be a useful tool for GPP and LE prediction, in particular for extrapolation in time (mean absolute error MAE for GPP between 0.53 and 1.56 gC m-2 d-1). Extrapolation in space in similar climatic and vegetation conditions also gave good results (GPP MAE 0.7-1.41 gC m-2 d-1), while extrapolation in areas with different seasonal cycles and controlling factors (e.g., the tropical regions) showed noticeably higher errors (GPP MAE 0.8-2.09 gC m-2 d-1). The distribution and the number of sites used for ANN training had a remarkable effect on prediction uncertainty in both, regional GPP and LE budgets and their interannual variability. Results obtained show that for ANN upscaling for continents with relatively small networks of sites, the error due to the sampling can be large and needs to be considered and quantified. The analysis of the spatial variability of the uncertainty helped to identify the meteorological drivers driving the uncertainty.

  12. Sulfur-based denitrification: Effect of biofilm development on denitrification fluxes.

    PubMed

    Wang, Yue; Bott, Charles; Nerenberg, Robert

    2016-09-01

    Elemental sulfur (S(o)) can serve as an electron donor for denitrification. However, the mechanisms and rates of S(o)-based denitrification, which depend on a biofilm development on a solid S(o) surface, are not well understood. We used completely-mixed reactors packed with S(o) chips to systematically explore the behavior of S(o)-based denitrification as a function of the bulk nitrate (NO3(-)) concentration and biofilm development. High-purity (99.5%) and agricultural-grade (90% purity) S(o) chips were tested to explore differences in performance. NO3(-) fluxes followed a Monod-type relationship with the bulk NO3(-) concentration. For high-purity S(o), the maximum NO3(-) flux increased from 0.4 gN/m(2)-d at 21 days to 0.9 g N/m(2)-d at around 100 days, but then decreased to 0.65 gN/m(2)-d at 161 days. The apparent (extant) half-saturation constant for NO3(-) KSapp, based on the bulk NO3(-) concentration and NO3(-) fluxes into the biofilm, increased from 0.1 mgN/L at 21 days to 0.8 mgN/L at 161 days, reflecting the increasing mass transfer resistance as the biofilm thickness increased. Nitrite (NO2(-)) accumulation became significant at bulk NO3(-) concentration above 0.2 mgN/L. The behavior of the agricultural-grade S(o) was very similar to the high-purity S(o). The kinetic behavior of S(o)-based denitrification was consistent with substrate counter-diffusion, where the soluble sulfur species diffuse from the S(o) particle into the base of the biofilm, while NO3(-) diffuses into the biofilm from the bulk. Initially, the fluxes were low due to biomass limitation (thin biofilms). As the biofilm thickness increased with time, the fluxes first increased, stabilized, and then decreased. The decrease was probably due to increasing diffusional resistance in the thick biofilm. Results suggest that fluxes comparable to heterotrophic biofilm processes can be achieved, but careful management of biofilm accumulation is important to maintain high fluxes. PMID:27187050

  13. Heterogeneity of CH4 and net CO2 Fluxes Using Nested Chamber, Tower, Aircraft, Remote Sensing, and Modeling Approaches in Arctic Alaska for Regional Flux Estimation

    NASA Astrophysics Data System (ADS)

    Oechel, W. C.; Moreaux, V.; Kalhori, A. A. M.; Murphy, P.; Wilkman, E.; Sturtevant, C. S.; Zhuang, Q.; Miller, C. E.; Dinardo, S. J.; Fisher, J. B.; Gioli, B.; Zona, D.

    2014-12-01

    The topographic, environmental, biotic, and metabolic heterogeneity of terrestrial ecosystems and landscapes can be large even despite a seemingly homogeneous landscape. The error of estimating and simulating fluxes due to extant heterogeneity is commonly overlooked in regional and global estimates. Here we evaluate the pattern and controls on spatial heterogeneity on CH4 and CO2 fluxes over varying spatial scales. Data from the north slope of Alaska from chambers, up to a 16 year CO2 flux record from up to 7 permanent towers, over 20 portable tower locations, eddy covariance CH4 fluxes over several years and sites, new year-around CO2 and CH4 flux installations, hundreds of hours of aircraft concentration and fluxes, and terrestrial biosphere and flux inverse modeling, are used to evaluate the spatial variability of fluxes and to better estimate regional fluxes. Significant heterogeneity of fluxes is identified at varying scales from sub-meter scale to >100km. A careful consideration of the effect that heterogeneity causes when estimating ecosystem fluxes is critical to reliable regional and global estimates. The combination of eddy covariance tower flux, aircraft, remote sensing, and modeling can be used to provide reliable, accurate, regional assessments of CH4 and CO2 fluxes from large areas of heterogeneous landscape.

  14. Heat-Flux-Measuring Facility

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1990-01-01

    Apparatus simulates conditions in turbine engines. Automated facility generates and measures transient and steady-state heat fluxes at flux densities from 0.3 to 6 MW/m(Sup2) and temperatures from 100 to 1,200 K. Positioning arm holds heat-flux gauge at focal point of arc lamp. Arm previously chilled gauge in liquid nitrogen in Dewar flask. Cooling water flows through lamp to heat exchanger. Used to develop heat-flux gauges for turbine blades and to test materials for durability under rapidly changing temperatures.

  15. Measuring surface fluxes in CAPE

    NASA Technical Reports Server (NTRS)

    Kanemasu, E. T.; D-Shah, T.; Nie, Dalin

    1992-01-01

    Two stations (site 1612 and site 2008) were operated by the University of Georgia group from 6 July 1991 to 18 August 1991. The following data were collected continuously: surface energy fluxes (i.e., net radiation, soil heat fluxes, sensible heat flux and latent heat flux), air temperature, vapor pressure, soil temperature (at 1 cm depth), and precipitation. Canopy reflectance and light interception data were taken three times at each site between 6 July and 18 August. Soil moisture content was measured twice at each site.

  16. Fine resolution soil water fluxes measured with a small Smart Field Lysimeter: The noise removal and further interpretation

    NASA Astrophysics Data System (ADS)

    Dolezal, Frantisek; Bekere Mekonnen, Getu; Matula, Svatopluk; Mihalikova, Marketa; Fisak, Jaroslav; Teressa Chala, Ayele; Hrkalova, Marketa; Moreira Barradas, Joao Manuel

    2014-05-01

    A weighable Smart Field Lysimeter (30 cm diameter, 30 cm depth) with an adaptively regulated suction at its bottom was used to measure soil water fluxes at the surface and at the 30 cm depth of a short grass stand. No overland flow or accumulation of water at the surface were observed and there was no groundwater table within the soil profile. Appropriate distinction between the fluxes of different directions made it possible to separately estimate actual evapotranspiration (upward surface flux), precipitation and condensation (downward surface flux and dew on grass leaves), percolation (downward flux at 30 cm) and capillary rise (upward flux at 30 cm). The primary data were collected at 1 minute intervals but required digital filtering to remove the information noise. Various methods of filtering were tested, with a special regard to intensive rain events. The resulting data have a 10-minute resolution. The lysimeter is capable of self-recovery after a period of drought but the noise of percolation and capillary rise estimates is enhanced for some time during, before and after this period. In these situations, it is important that a porous matrix sensor measures the suction in parallel to the reference tensiometer. Both the precipitation and the actual evapotranspiration derived from the lysimeter data alone are in absolute values higher than the analogous quantities obtained with the help of the directly measured tipping bucket precipitation. These discrepancies are probably due to the rain gauge underestimating true precipitation, but partly also due to numerical noise, however smoothed. If the rain gauge data are used only to distinguish the periods of rain from the rainless periods, than the condensation of water in the soil and on the grass leaves can be estimated. The actual evapotranspiration measured by the lysimeter has a diurnal patterns depending on actual weather. The maximum occurs, on average, shortly after the noon. The percolation curves after rain

  17. Variability of particulate flux over the Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Abell, Richard E.; Brand, Tim; Dale, Andrew C.; Tilstone, Gavin H.; Beveridge, Christine

    2013-12-01

    The magnitude and composition of the sinking-particle flux were studied over the northern Mid-Atlantic Ridge (MAR) from June 2007 to July 2010. Four moorings equipped with dual sediment traps, 100 m and 1000 m above the sea floor, sampled regions north and south of the Charlie Gibbs Fracture Zone (between 49°N and 54°N) and east and west of the MAR. Biogenic data were coupled with satellite estimates of primary production and modelled particle source to assess the variability in export flux. Large variations were found in the seasonality, chemical composition, magnitude and source of sinking particulate material between mooring sites. The northern moorings recorded both greater mean primary production and greater particle mass flux than the southern moorings, although, the large inter-annual variability within the sites exceeded inter-site differences. While estimates of primary production and organic carbon fluxes are comparable to other investigations of this type, they are notably lower than previous estimates for the abyssal plain of the North Atlantic. The deeper traps consistently recorded a higher mass flux compared to the shallower traps. However, we suggest that the overall flux recorded by the shallower traps was reduced by trapping inefficiency, which in the light of the low current velocities, may largely be due to the physical nature of the sinking material. Although deep-trap flux estimates may be more susceptible to errors due to re-suspended and advected material from nearby topography, mass flux and current velocity are not linked. In addition, the relatively low aluminium concentration of the deep-trap material indicates that this contribution is relatively small. The organic carbon flux to the NE, NW, SE and SW station was 0.8, 1.2, 1.1 and 1.1 g m-2 y-1 respectively, corresponding to an export flux of 0.6% over this region of the MAR.

  18. Prediction of Metabolic Flux Distribution from Gene Expression Data Based on the Flux Minimization Principle

    PubMed Central

    Song, Hyun-Seob; Reifman, Jaques; Wallqvist, Anders

    2014-01-01

    Prediction of possible flux distributions in a metabolic network provides detailed phenotypic information that links metabolism to cellular physiology. To estimate metabolic steady-state fluxes, the most common approach is to solve a set of macroscopic mass balance equations subjected to stoichiometric constraints while attempting to optimize an assumed optimal objective function. This assumption is justifiable in specific cases but may be invalid when tested across different conditions, cell populations, or other organisms. With an aim to providing a more consistent and reliable prediction of flux distributions over a wide range of conditions, in this article we propose a framework that uses the flux minimization principle to predict active metabolic pathways from mRNA expression data. The proposed algorithm minimizes a weighted sum of flux magnitudes, while biomass production can be bounded to fit an ample range from very low to very high values according to the analyzed context. We have formulated the flux weights as a function of the corresponding enzyme reaction's gene expression value, enabling the creation of context-specific fluxes based on a generic metabolic network. In case studies of wild-type Saccharomyces cerevisiae, and wild-type and mutant Escherichia coli strains, our method achieved high prediction accuracy, as gauged by correlation coefficients and sums of squared error, with respect to the experimentally measured values. In contrast to other approaches, our method was able to provide quantitative predictions for both model organisms under a variety of conditions. Our approach requires no prior knowledge or assumption of a context-specific metabolic functionality and does not require trial-and-error parameter adjustments. Thus, our framework is of general applicability for modeling the transcription-dependent metabolism of bacteria and yeasts. PMID:25397773

  19. Calibration of the Galactic Cosmic Ray Flux

    NASA Technical Reports Server (NTRS)

    Mathew, K. J.; Marti, K.

    2004-01-01

    We report first Xe data on the cross-calibration of I-129-Xe-129(sub n) ages with conventional CRE ages, a method which is expected to provide information on the long-term constancy of the galactic cosmic ray (GCR) flux. We studied isotopic signatures of Xe released in stepwise heating, decomposition and melting of troilites in the Cape York iron meteorite to identify isotopic shifts in Xe-129 and Xe-131 due to neutron capture in Te-128 and Te-130. We also resolve components due to extinct 129I, spallation and fission Xe. There has recently been much speculation on the constancy of GCR over long time scales, as may be inferred from iron meteorites. If GCRs originate from supernova events, this provides the basis for postulating increased fluxes at locations with higher than average densities of supernovae, specifically in OB-associations. The solar system at present appears to be inside a local bubble between spiral arms and may experience an increased GCR flux.

  20. Direct measurements of CO2 flux in the Greenland Sea

    NASA Astrophysics Data System (ADS)

    Lauvset, Siv K.; McGillis, Wade R.; Bariteau, Ludovic; Fairall, C. W.; Johannessen, Truls; Olsen, Are; Zappa, Christopher J.

    2011-06-01

    During summer 2006 eddy correlation CO2 fluxes were measured in the Greenland Sea using a novel system set-up with two shrouded LICOR-7500 detectors. One detector was used exclusively to determine, and allow the removal of, the bias on CO2 fluxes due to sensor motion. A recently published correction method for the CO2-H2O cross-correlation was applied to the data set. We show that even with shrouded sensors the data require significant correction due to this cross-correlation. This correction adjusts the average CO2 flux by an order of magnitude from -6.7 × 10-2 mol m-2 day-1 to -0.61 × 10-2 mol m-2 day-1, making the corrected fluxes comparable to those calculated using established parameterizations for transfer velocity.

  1. South Atlantic meridional fluxes

    NASA Astrophysics Data System (ADS)

    Garzoli, Silvia L.; Baringer, Molly O.; Dong, Shenfu; Perez, Renellys C.; Yao, Qi

    2013-01-01

    The properties of the meridional overturning circulation (MOC) and associated meridional heat transport (MHT) and salt fluxes are analyzed in the South Atlantic. The oceanographic data used for the study consist of Expendable bathythermograph (XBT) data collected along 27 sections at nominally 35°S for the period of time 2002-2011, and Argo profile data collected in the region. Previous estimates obtained with a shorter record are improved and extended, using new oceanographic sections and wind fields. Different wind products are analyzed to determine the uncertainty in the Ekman component of the MHT derived from their use. Results of the analysis provide a 9-year time series of MHT, and volume transport in the upper layer of the MOC. Salt fluxes at 35°S are estimated using a parameter introduced by numerical studies, the Mov that represents the salt flux and helps determine the basin scale salt feedback associated with the MOC. Volume and heat transport by the western and eastern boundary currents are estimated, and their covariablity is examined. Analysis of the data shows that the South Atlantic is responsible for a northward MHT with a mean value of 0.54±0.14 PW. The MHT exhibits no significant trend from 2002 to 2011. The MOC varies from 14.4 to 22.7 Sv with a mean value of 18.1±2.3 Sv and the maximum overturning transport is found at a mean depth of 1250 m. Statistical analysis suggests that an increase of 1 Sv in the MOC leads to an increase of the MHT of 0.04±0.02 PW. Estimates of the Mov from data collected from three different kinds of observations, contrary to those obtained from models, feature a positive salt advection feedback (Mov<0) suggesting that freshwater perturbations will be amplified and that the MOC is bistable. In other words, the MOC might collapse with a large enough freshwater perturbation. Observations indicate that the mean value of the Brazil Current is -8.6±4.1 Sv at 24°S and -19.4±4.3 Sv at 35°S, increasing towards the

  2. Spatial and Temporal Trends in Greenhouse Gas Fluxes from a Temperate Floodplain Along a Stream-Riparian-Upland Gradient

    NASA Astrophysics Data System (ADS)

    Ensor, B. L.; Scott, D.; Strahm, B. D.; Thomas, R. Q.; Hester, E. T.

    2015-12-01

    Increasing floodplain and wetland restoration activity has raised concerns about potential impacts on the release of greenhouse gases (GHG) to the atmosphere due to restored connectivity between aquatic and terrestrial ecosystems. Research has shown GHG fluxes from hydrologically active landscapes such as floodplains and wetlands vary spatially and temporally in response to primary controls including soil moisture, soil temperature, and available nutrients. In this ongoing study, we are measuring GHG fluxes at six locations 24 times over a year within an Appalachian floodplain. Site locations are based on dominant landscape positions and hydrologic activity along a topographic gradient including the stream margin, an active slough, and the upland area. GHG fluxes are measured using a Picarro G2508 Cavity Ring Down Spectrometry GHG Analyzer employing the static chamber method. We are also conducting large synoptic sampling of GHG fluxes across the floodplain surface during the wet and dry seasons to explore spatial heterogeneity trends between extreme soil moisture conditions. Data collected thus far has shown correlations between CO2 and soil temperature and soil moisture. CH4 and N2O fluxes have shown to largely depend on degree of saturation in the soil. By the conclusion of our project, we predict temporal patterns in GHG fluxes and soil nutrient content that reflect an increase in microbial function and the release of CO2, CH4, and N2O during warmer and wetter seasons. Spatially, we hypothesize differences in GHG fluxes based on the frequency and duration of the floodpulse at the various locations similar to patterns we have seen thus far of increased production in CH4 and N2O at the intermittently flooded versus dry locations.

  3. KoFlux: Korean Regional Flux Network in AsiaFlux

    NASA Astrophysics Data System (ADS)

    Kim, J.

    2002-12-01

    AsiaFlux, the Asian arm of FLUXNET, held the Second International Workshop on Advanced Flux Network and Flux Evaluation in Jeju Island, Korea on 9-11 January 2002. In order to facilitate comprehensive Asia-wide studies of ecosystem fluxes, the meeting launched KoFlux, a new Korean regional network of long-term micrometeorological flux sites. For a successful assessment of carbon exchange between terrestrial ecosystems and the atmosphere, an accurate measurement of surface fluxes of energy and water is one of the prerequisites. During the 7th Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment (GAME) held in Nagoya, Japan on 1-2 October 2001, the Implementation Committee of the Coordinated Enhanced Observing Period (CEOP) was established. One of the immediate tasks of CEOP was and is to identify the reference sites to monitor energy and water fluxes over the Asian continent. Subsequently, to advance the regional and global network of these reference sites in the context of both FLUXNET and CEOP, the Korean flux community has re-organized the available resources to establish a new regional network, KoFlux. We have built up domestic network sites (equipped with wind profiler and radiosonde measurements) over deciduous and coniferous forests, urban and rural rice paddies and coastal farmland. As an outreach through collaborations with research groups in Japan, China and Thailand, we also proposed international flux sites at ecologically and climatologically important locations such as a prairie on the Tibetan plateau, tropical forest with mixed and rapid land use change in northern Thailand. Several sites in KoFlux already begun to accumulate interesting data and some highlights are presented at the meeting. The sciences generated by flux networks in other continents have proven the worthiness of a global array of micrometeorological flux towers. It is our intent that the launch of KoFlux would encourage other scientists to initiate and

  4. One year of continuous measurements of soil CH4 and CO2 fluxes in a Japanese cypress forest: Temporal and spatial variations associated with Asian monsoon rainfall

    NASA Astrophysics Data System (ADS)

    Sakabe, Ayaka; Kosugi, Yoshiko; Takahashi, Kenshi; Itoh, Masayuki; Kanazawa, Akito; Makita, Naoki; Ataka, Mioko

    2015-04-01

    We examined the effects of Asian monsoon rainfall on CH4 absorption of water-unsaturated forest soil. We conducted a 1 year continuous measurement of soil CH4 and CO2 fluxes with automated chamber systems in three plots with different soil characteristics and water content to investigate how temporal variations in CH4 fluxes vary with the soil environment. CH4 absorption was reduced by the "Baiu" summer rainfall event and peaked during the subsequent hot, dry period. Although CH4 absorption and CO2 emission typically increased as soil temperature increased, the temperature dependence of CH4 varied more than that of CO2, possibly due to the changing balance of activities between methanotrophs and methanogens occurring over a wide temperature range, which was strongly affected by soil water content. In short time intervals (30 min), the responses of CH4 and CO2 fluxes to rainfall were different for each plot. In a dry soil plot with a thick humus layer, both fluxes decreased abruptly at the peak of rainfall intensity. After rainfall, CO2 emission increased quickly, while CH4 absorption increased gradually. Release of accumulated CO2 underground and restriction and recovery of CH4 and CO2 exchange between soil and air determined flux responses to rainfall. In a wet soil plot and a dry soil plot with a thinner humus layer, abrupt decreases in CH4 fluxes were not observed. Consequently, the Asian monsoon rainfall strongly influenced temporal variations in CH4 fluxes, and the differences in flux responses to environmental factors among plots caused large variability in annual budgets of CH4 fluxes.

  5. A comparison of methane flux in a boreal landscape between a dry and a wet year

    NASA Astrophysics Data System (ADS)

    Bubier, Jill; Moore, Tim; Savage, Kathleen; Crill, Patrick

    2005-03-01

    We used field measurements of methane (CH4) flux from upland and wetland soils in the Northern Study Area (NSA) of BOREAS (BOReal Ecosystem-Atmosphere Study), near Thompson, Manitoba, during the summers of 1994 and 1996 to estimate the overall CH4 emission from a 1350 km2 landscape. June-September 1994 and 1996 were both drier and warmer than normal, but summer 1996 received 68 mm more precipitation than 1994, a 40% increase, and had a mean daily air temperature 0.6°C warmer than 1994. Upland soils consumed CH4 at rates from 0 to 1.0 mg m-2 d-1, with small spatial and temporal variations between years, and a weak dependence on soil temperature. In contrast, wetlands emitted CH4 at seasonal average rates ranging from 10 to 350 mg CH4 m-2 d-1, with high spatial and temporal variability, and increased an average of 60% during the wetter and warmer 1996. We used Landsat imagery, supervised classification, and ground truthing to scale point CH4 fluxes (<1 m2) to the landscape (>1000 km2). We performed a sensitivity analysis for error terms in both areal coverage and CH4 flux, showing that the small areas of high CH4 emission (e.g., small ponds, graminoid fens, and permafrost collapse margins) contribute the largest uncertainty in both flux measurements and mapping. Although wetlands cover less than 30% of the landscape, areally extrapolated CH4 flux for the NSA increased by 61% from 10 to16 mg CH4 m-2 d-1 between years, entirely attributed to the increase in wetland CH4 emission. We conclude that CH4 fluxes will tend to be underestimated in areas where much of the landscape is covered by wetlands. This is due to the large spatial and temporal variability encountered in chamber-based measurements of wetland CH4 fluxes, strong sensitivity of wetland CH4 emission to small changes in climate, and because most remote sensing images do not adequately identify small areas of high CH4 flux.

  6. Development of a laser remote sensing instrument to measure sub-aerial volcanic CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Queisser, Manuel; Burton, Mike

    2016-04-01

    A thorough quantification of volcanic CO2 fluxes would lead to an enhanced understanding of the role of volcanoes in the geological carbon cycle. This would enable a more subtle understanding of human impact on that cycle. Furthermore, variations in volcanic CO2 emissions are a key to understanding volcanic processes such as eruption phenomenology. However, measuring fluxes of volcanic CO2 is challenging as volcanic CO2 concentrations are modest compared with the ambient CO2 concentration (~400 ppm) . Volcanic CO2 quickly dilutes with the background air. For Mt. Etna (Italy), for instance, 1000 m downwind from the crater, dispersion modelling yields a signal of ~4 ppm only. It is for this reason that many magmatic CO2 concentration measurements focus on in situ techniques, such as direct sampling Giggenbach bottles, chemical sensors, IR absorption spectrometers or mass spectrometers. However, emission rates are highly variable in time and space. Point measurements fail to account for this variability. Inferring 1-D or 2-D gas concentration profiles, necessary to estimate gas fluxes, from point measurements may thus lead to erroneous flux estimations. Moreover, in situ probing is time consuming and, since many volcanoes emit toxic gases and are dangerous as mountains, may raise safety concerns. In addition, degassing is often diffuse and spatially extended, which makes a measurement approach with spatial coverage desirable. There are techniques that allow to indirectly retrieve CO2 fluxes from correlated SO2 concentrations and fluxes. However, they still rely on point measurements of CO2 and are prone to errors of SO2 fluxes due to light dilution and depend on blue sky conditions. Here, we present a new remote sensing instrument, developed with the ERC project CO2Volc, which measures 1-D column amounts of CO2 in the atmosphere with sufficient sensitivity to reveal the contribution of magmatic CO2. Based on differential absorption LIDAR (DIAL) the instrument measures

  7. Dermal absorption of benzene in occupational settings: estimating flux and applications for risk assessment.

    PubMed

    Williams, Pamela R D; Sahmel, Jennifer; Knutsen, Jeffrey; Spencer, John; Bunge, Annette L

    2011-02-01

    There is growing emphasis in the United States and Europe regarding the quantification of dermal exposures to chemical mixtures and other substances. In this paper, we determine the dermal flux of benzene in neat form, in organic solvents, and in aqueous solutions based on a critical review and analysis of the published literature, and discuss appropriate applications for using benzene dermal absorption data in occupational risk assessment. As part of this effort, we synthesize and analyze data for 77 experimental results taken from 16 studies of benzene skin absorption. We also assess the chemical activity of benzene in simple hydrocarbon solvent mixtures using a thermodynamic modeling software tool. Based on the collective human in vivo, human in vitro, and animal in vitro data sets, we find that the steady-state dermal flux for neat benzene (and benzene-saturated aqueous solutions) ranges from 0.2 to 0.4 mg/(cm²·h). Observed outlier values for some of the animal in vivo data sets are possibly due to the use of test species that have more permeable skin than humans or study conditions that resulted in damage to the skin barrier. Because relatively few dermal absorption studies have been conducted on benzene-containing organic solvents, and available test results may be influenced by study design or vehicle effects, it is not possible to use these data to quantify the dermal flux of benzene for other types of solvent mixtures. However, depending on the application, we describe several potential approaches that can be used to derive a rough approximation of the steady-state benzene dermal flux for these mixtures. Important limitations with respect to quantifying and evaluating the significance of dermal exposures to benzene in occupational settings include a lack of data on (1) factors that affect the dermal uptake of benzene, (2) the dermal flux of benzene for different organic solvent mixtures, (3) meaningful metrics for evaluating the dermal uptake of benzene

  8. Gaseous mercury fluxes from the forest floor of the Adirondacks.

    PubMed

    Choi, Hyun-Deok; Holsen, Thomas M

    2009-02-01

    The flux of gaseous elemental mercury (Hg(0)) from the forest floor of the Adirondack Mountains in New York (USA) was measured numerous times throughout 2005 and 2006 using a polycarbonate dynamic flux chamber (DFC). The Hg flux ranged between -2.5 and 27.2 ng m(-2) h(-1) and was positively correlated with temperature and solar radiation. The measured Hg emission flux was highest in spring, and summer, and lowest in winter. During leaf-off periods, the Hg emission flux was highly dependent on solar radiation and less dependent on temperature. During leaf-on periods, the Hg emission flux was fairly constant because the forest canopy was shading the forest floor. Two empirical models were developed to estimate yearly Hg(0) emissions, one for the leaf-off period and one for the leaf-on period. Using the U.S. EPA's CASTNET meteorological data, the cumulative estimated emission flux was approx. 7.0 microg Hg(0) m(-2) year(-1). PMID:18922608

  9. Theory of collective flux creep. [in high temperature superconductors

    NASA Technical Reports Server (NTRS)

    Feigel'man, M. V.; Geshkenbein, V. B.; Larkin, A. I.; Vinokur, V. M.

    1989-01-01

    The nature of flux-creep phenomena in the case of collective pinning by weak disorder is discussed. The Anderson concept of flux bundle is explored and developed. The dependence of the bundle activation barrier U on current j is studied and is shown to be of power-law type: U(j) is proportional to j exp -alpha. The values of exponent alpha for the different regimes of collective creep are found.

  10. Quantum depinning of flux lines from columnar defects

    SciTech Connect

    Chudnovsky, E.M. ); Ferrera, A.; Vilenkin, A. )

    1995-01-01

    The depinning of a flux line from a columnar defect is studied within the path-integral approach. Instantons of the quantum field theory in 1+1 dimensions are computed for the flux line whose dynamics is dominated by the Magnus force. The universal temperature dependence of the decay rate in the proximity of the critical current is obtained. This problem provides an example of macroscopic quantum tunneling, which is accessible to the direct comparison between theory and experiment.

  11. Direct control of air gap flux in permanent magnet machines

    DOEpatents

    Hsu, John S.

    2000-01-01

    A method and apparatus for field weakening in PM machines uses field weakening coils (35, 44, 45, 71, 72) to produce flux in one or more stators (34, 49, 63, 64), including a flux which counters flux normally produced in air gaps between the stator(s) (34, 49, 63, 64) and the rotor (20, 21, 41, 61) which carries the PM poles. Several modes of operation are introduced depending on the magnitude and polarity of current in the field weakening coils (35, 44, 45, 71, 72). The invention is particularly useful for, but not limited to, the electric vehicle drives and PM generators.

  12. Carbon Dioxide Flux Measurement Systems (CO2Flux) Handbook

    SciTech Connect

    Fischer, M

    2005-01-01

    The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The fluxes are obtained by the eddy covariance technique, which computes the flux as the mean product of the vertical wind component with CO2 and H2O densities, or estimated virtual temperature. A three-dimensional sonic anemometer is used to obtain the orthogonal wind components and the virtual (sonic) temperature. An infrared gas analyzer is used to obtain the CO2 and H2O densities. A separate sub-system also collects half-hour average measures of meteorological and soil variables from separate 4-m towers.

  13. Noncommutativity due to spin

    NASA Astrophysics Data System (ADS)

    Gomes, M.; Kupriyanov, V. G.; da Silva, A. J.

    2010-04-01

    Using the Berezin-Marinov pseudoclassical formulation of the spin particle we propose a classical model of spin noncommutativity. In the nonrelativistic case, the Poisson brackets between the coordinates are proportional to the spin angular momentum. The quantization of the model leads to the noncommutativity with mixed spatial and spin degrees of freedom. A modified Pauli equation, describing a spin half particle in an external electromagnetic field is obtained. We show that nonlocality caused by the spin noncommutativity depends on the spin of the particle; for spin zero, nonlocality does not appear, for spin half, ΔxΔy≥θ2/2, etc. In the relativistic case the noncommutative Dirac equation was derived. For that we introduce a new star product. The advantage of our model is that in spite of the presence of noncommutativity and nonlocality, it is Lorentz invariant. Also, in the quasiclassical approximation it gives noncommutativity with a nilpotent parameter.

  14. STRATIFIED COMPOSITION EFFECTS ON PLANETARY NEUTRON FLUX

    SciTech Connect

    O. GASNAULT; ET AL

    2001-01-01

    All the bodies of the solar system that are directly irradiated by the galactic cosmic rays, emit enough neutrons to allow a measurement from space. These leakage neutron fluxes are indexes of the surface composition, depending on the energy of the neutrons [1]. Recent work propose geochemical interpretations of these fluxes: the thermal energy range is sensitive to iron, titanium, rare earth elements and thorium [2, 3], the epithermal energy range is sensitive to hydrogen, samarium and gadolinium [2] and the fast energy range is representative of the average soil atomic mass [4]. Nevertheless these studies make the hypothesis of a composition uniform within the footprint of the spectrometer and independent of depth. We show in this abstract that a stratified composition could change significantly the flux intensity and complicate the interpretation of the measurements. The neutron leakage flux is a competition between production effects (sensitive at high energy) and diffusion-capture effects (mostly sensitive at low energy). On one hand, it happens to be that the elements which produce the higher number of neutrons in typical lunar compositions are iron and titanium, which have also large cross section of absorption with the neutrons. On the other hand, the maximum of neutron intensity does not occur at the surface but at about 180 g cm{sup {minus}2} in depth. Therefore, if we have an iron- and/or titanium-rich soil (important production of neutrons) with a top layer having less iron and/or titanium (i.e. more transparent to the neutrons), we can expect an enhancement of the flux compared to a uniform composition.

  15. A model of heat transfer in sapwood and implications for sap flux density measurements using thermal dissipation probes

    SciTech Connect

    Wullschleger, Stan D; Childs, Kenneth W; King, Anthony Wayne; Hanson, Paul J

    2011-01-01

    A variety of thermal approaches are used to estimate sap flux density in stems of woody plants. Models have proven valuable tools for interpreting the behavior of heat pulse, heat balance, and heat field deformation techniques, but have seldom been used to describe heat transfer dynamics for the heat dissipation method. Therefore, to better understand the behavior of heat dissipation probes, a model was developed that takes into account the thermal properties of wood, the physical dimensions and thermal characteristics of the probes, and the conductive and convective heat transfer that occurs due to water flow in the sapwood. Probes were simulated as aluminum tubes 20 mm in length and 2 mm in diameter, whereas sapwood, heartwood, and bark each had a density and water fraction that determined their thermal properties. Base simulations assumed a constant sap flux density with sapwood depth and no wounding or physical disruption of xylem beyond the 2 mm diameter hole drilled for probe installation. Simulations across a range of sap flux densities showed that the dimensionless quantity k defined as ( Tm T)/ T where Tm is the temperature differential ( T) between the heated and unheated probe under zero flow conditions was dependent on the thermal conductivity of the sapwood. The relationship between sap flux density and k was also sensitive to radial gradients in sap flux density and to xylem disruption near the probe. Monte Carlo analysis in which 1000 simulations were conducted while simultaneously varying thermal conductivity and wound diameter revealed that sap flux density and k showed considerable departure from the original calibration equation used with this technique. The departure was greatest for abrupt patterns of radial variation typical of ring-porous species. Depending on the specific combination of thermal conductivity and wound diameter, use of the original calibration equation resulted in an 81% under- to 48% over-estimation of sap flux density at

  16. The turbulent heat flux in low Mach number flows with large density variations

    NASA Technical Reports Server (NTRS)

    Orourke, Peter J.; Collins, Lance R.

    1988-01-01

    A transport equation has been derived which is the difference between the volume- and mass-averaged velocities and is simply related to the turbulent heat flux phi sup h. Using this equation and an assumption analogous to the drift flux approximation of two-phase flow modeling, an algebraic closure relation for phi sup h that exibits fluxes due to directed transport proportional to -del anti p and due to gradient transport proportional to -del tau has been obtained.

  17. Spatial-temporal variability in GHG fluxes and their functional interpretation in RusFluxNet

    NASA Astrophysics Data System (ADS)

    Vasenev, Ivan; Meshalkina, Julia; Sarzhanov, Dmitriy; Mazirov, Ilia; Yaroslavtsev, Alex; Komarova, Tatiana; Tikhonova, Maria

    2016-04-01

    High spatial and temporal variability is mutual feature for most modern boreal landscapes in the European Territory of Russia. This variability is result of their relatively young natural and land-use age with very complicated development stories. RusFluxNet includes a functionally-zonal set of representative natural, agricultural and urban ecosystems from the Central Forest Reserve in the north till the Central Chernozemic Reserve in the south (more than 1000 km distance). Especial attention has been traditionally given to their soil cover and land-use detailed variability, morphogenetic and functional dynamics. Central Forest Biosphere Reserve (360 km to North-West from Moscow) is the principal southern-taiga one in the European territory of Russia with long history of mature spruce ecosystem structure and dynamics investigation. Our studies (in frame of RF Governmental projects #11.G34.31.0079 and #14.120.14.4266) have been concentrated on the soil carbon stocks and GHG fluxes spatial variability and dynamics due to dominated there windthrow and fallow-forest successions. In Moscow RTSAU campus gives a good possibility to develop the ecosystem and soil monitoring of GHG fluxes in the comparable sites of urban forest, field crops and lawn ecosystems taking especial attention on their meso- and micro-relief, soil cover patterns and subsoil, vegetation and land-use technologies, temperature and moisture spatial and temporal variability. In the Central Chernozemic Biosphere Reserve and adjacent areas we do the comparative analysis of GHG fluxes and balances in the virgin and mowed meadow-steppe, forest, pasture, cropland and three types of urban ecosystems with similar subsoil and relief conditions. The carried out researches have shown not only sharp (in 2-5 times) changes in GHG ecosystem and soil fluxes and balances due to seasonal and daily microclimate variation, vegetation and crop development but their essential (in 2-4 times) spatial variability due to

  18. Flux-driven algebraic damping of diocotron modes

    SciTech Connect

    Chim, Chi Yung; O’Neil, Thomas M.

    2015-06-29

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 1 and m = 2 diocotron modes. Transport due to small field asymmetries produces a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius R{sub m}, where there is a matching of ω{sub m} = mω{sub E} (R{sub m}) for the mode frequency ω{sub m} and E × B-drift rotation frequency ω{sub E}. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from, spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This new mechanism of damping is due to transfer of canonical angular momentum from the mode to halo particles, as they are swept around the “cat’s eye” orbits of the resonant wave-particle interaction. This paper provides a simple derivation of the time dependence of the mode amplitudes.

  19. Flux-driven algebraic damping of diocotron modes

    NASA Astrophysics Data System (ADS)

    Chim, Chi Yung; O'Neil, Thomas M.

    2015-06-01

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 1 and m = 2 diocotron modes. Transport due to small field asymmetries produces a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius Rm, where there is a matching of ωm = mωE (Rm) for the mode frequency ωm and E × B-drift rotation frequency ωE. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from, spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This new mechanism of damping is due to transfer of canonical angular momentum from the mode to halo particles, as they are swept around the "cat's eye" orbits of the resonant wave-particle interaction. This paper provides a simple derivation of the time dependence of the mode amplitudes.

  20. Rifting, heat flux, and water availability beneath the catchment of Pine Island Glacier

    NASA Astrophysics Data System (ADS)

    Jordan, T. A.; Ferraccioli, F.; Hindmarsh, R. C.

    2012-04-01

    The West Antarctic Rift System (WARS) is a major rift system that developed in the Cretaceous and Cenozoic. It forms the lithsopheric cradle for the marine-based, and potentially unstable West Antarctic Ice Sheet (WAIS). Determining the geological boundary conditions beneath the WAIS and in particular geothermal heat flux may help model its response to external climatic forcing. However, in the Amundsen Sea Embayment sector of WAIS, where major glaciers such as Pine Island and Thwaites are rapidly changing today, fundamental properties such as geothermal heat flux to the base of the ice sheet have remained poorly constrained due to sparse geophysical data coverage and the lack of drilling sites. New crustal thickness estimates derived from airborne gravity data (Jordan et al., 2010, GSA Bul.), are interpreted to show a continuation of the WARS beneath Pine Island Glacier, and suggest two phases of continental rifting affected this region. Here we explore the impact of continental rifting on geothermal heat flux variations and basal water availability beneath Pine Island Glacier. Using 1D thermal models of rift evolution, we assess geothermal heat flux configurations resulting from either single or two-phase rifting and explore the dependency on the age of rifting and pre-rift setting. Additionally, 1D glaciological models were implemented to predict the changes in subglacial water distribution created by different rifting models. Our modelling reveals that geothermal heat-flux beneath the WAIS is critically sensitive to rift age and evolution and has the potential to significantly alter basal conditions if it continued to be active in the Neogene as some recent geological interpretations suggest.

  1. Surface flux patterns on planets in circumbinary systems and potential for photosynthesis

    NASA Astrophysics Data System (ADS)

    Forgan, Duncan H.; Mead, Alexander; Cockell, Charles S.; Raven, John A.

    2015-07-01

    Recently, the Kepler Space Telescope has detected several planets in orbit around a close binary star system. These so-called circumbinary planets will experience non-trivial spatial and temporal distributions of radiative flux on their surfaces, with features not seen in their single-star orbiting counterparts. Earth-like circumbinary planets inhabited by photosynthetic organisms will be forced to adapt to these unusual flux patterns. We map the flux received by putative Earth-like planets (as a function of surface latitude/longitude and time) orbiting the binary star systems Kepler-16 and Kepler-47, two star systems which already boast circumbinary exoplanet detections. The longitudinal and latitudinal distribution of flux is sensitive to the centre-of-mass motion of the binary, and the relative orbital phases of the binary and planet. Total eclipses of the secondary by the primary, as well as partial eclipses of the primary by the secondary add an extra forcing term to the system. We also find that the patterns of darkness on the surface are equally unique. Beyond the planet's polar circles, the surface spends a significantly longer time in darkness than latitudes around the equator, due to the stars' motions delaying the first sunrise of spring (or hastening the last sunset of autumn). In the case of Kepler-47, we also find a weak longitudinal dependence for darkness, but this effect tends to average out if considered over many orbits. In the light of these flux and darkness patterns, we consider and discuss the prospects and challenges for photosynthetic organisms, using terrestrial analogues as a guide.

  2. Poynting flux in the neighbourhood of a point charge in arbitrary motion and radiative power losses

    NASA Astrophysics Data System (ADS)

    Singal, Ashok K.

    2016-07-01

    We examine the electromagnetic fields in the neighbourhood of a ‘point charge’ in arbitrary motion and thereby determine the Poynting flux across a spherical surface of vanishingly small radius surrounding the charge. We show that the radiative power losses from a point charge turn out to be proportional to the scalar product of the instantaneous velocity and the first time-derivative of the acceleration of the charge. This may seem to be discordant with the familiar Larmor formula where the instantaneous power radiated from a charge is proportional to the square of acceleration. However, it seems that the root cause of the discrepancy actually lies in Larmor’s formula, which is derived using the acceleration fields but without due consideration for the Poynting flux associated with the velocity-dependent self-fields ‘co-moving’ with the charge. Further, while deriving Larmor’s formula, one equates the Poynting flux through a surface at some later time to the radiation loss by the enclosed charge at the retarded time. Poynting’s theorem, on the other hand, relates the outgoing radiation flux from a closed surface to the rate of energy decrease within the enclosed volume, all calculated for the same given instant only. Here we explicitly show the absence of any Poynting flux in the neighbourhood of an instantly stationary point charge, implying no radiative losses from such a charge, which is in complete conformity with energy conservation. We further show how Larmor’s formula is still able to serve our purpose in the vast majority of cases. It is further shown that Larmor’s formula in general violates momentum conservation and, in the case of synchrotron radiation, leads to a potentially incorrect conclusion about the pitch angle changes of the radiating charges, and that only the radiation reaction formula yields a correct result, consistent with special relativity.

  3. Measurement of the total boron-8 solar neutrino flux at the Sudbury Neutrino Observatory

    NASA Astrophysics Data System (ADS)

    Rusu, Vadim Liviu

    This work presents experimental measurements obtained by analyzing the first 254 live days of data from the SNO NaCl run. The electron neutrino flux was measured to be 1.66 +/- 0.10 stat.+0.07 -0.07 (syst.) x 106cm-2s-l and the non-electron neutrino flux was measured to be 3.32 +/- 0.38 stat.+0.26 -0.25 (syst.) x 106cm-2s-1. Using the above results we determined the integrated electron neutrino survival probability to be 0.33 +/- 0.04 stat.+0.02 -0.02 (syst.). This rejects maximum mixing in the solar neutrino sector at more than 3sigma using SNO data only under the assumption that the flavor changing mechanism is due to the MSW effect in the solar interior. The capability of the Sudbury Neutrino Observatory (SNO) to distinguish between the Charged-Current (CC) and Neutral-Current(NC) neutrino interactions made possible the first simultaneous measurements of the electron and non-electron solar neutrino flux, providing a direct test of the hypothesis that neutrinos change flavor as they propagate from the Sun to the Earth. Two tonnes of purified NaCl were added to the one kilotonne of heavy water target of SNO to enhance the neutron capture efficiency and detection of capture gamma-rays. Neutron capture on 35Cl often produces multiple gamma-rays, which permits a statistical separation of neutron capture and electron events based on the event isotropy, the increased statistical separation between event categories, using the degree of event isotropy, made possible a significant improvement on the measured fluxes. Moreover, the flux analysis does not require any assumption regarding the energy dependence of the flavor changing mechanism.

  4. Flux agreement above a Scots pine plantation

    NASA Astrophysics Data System (ADS)

    Gay, L. W.; Vogt, R.; Bernhofer, Ch.; Blanford, J. H.

    1996-03-01

    The surface energy exchange of 12m high Scots pine plantation at Hartheim, Germany, was measured with a variety of methods during a 11-day period of fine weather in mid-May 1992. Net radiation and rate of thermal storage were measured with conventional net radiometers, soil heat flux discs and temperature-based storage models. The turbulent fluxes discussed in this report were obtained with an interchanging Bowen ratio energy budget system (BREB, at 14 m), two one-propeller eddy correlation systems (OPEC systems 1 and 2 at 17m), a 1-dimensional sonic eddy correlation system (SEC system 3) at 15 m, all on one “low” tower, and a 3-dimensional sonic eddy correlation system (SEC system 22) at 22 m on the “high” tower that was about 46 m distant. All systems measured sensible and latent heat (H and LE) directly, except for OPEC systems 1 and 2 which estimated LE as a residual term in the surface energy balance. Closure of turbulent fluxes from the two SEC systems was around 80% for daytime and 30% for night, with closure of 1-dimensional SEC system 3 exceeding that of 3-dimensional SEC system 22. The night measurements of turbulent fluxes contained considerable uncertainty, especially with the BREB system where measured gradients often yielded erroneous fluxes due to problems inherent in the method (i.e., computational instability as Bowen's ratio approaches -1). Also, both eddy correlation system designs (OPEC and SEC) appeared to underestimate |H| during stable conditions at night. In addition, both sonic systems (1- and 3-dimension