Flux

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Flux

  • acid flux
  • average flux
  • c flux
  • ca2+ flux
  • calcium flux
  • carbon dioxide flux
  • carbon flux
  • ch4 flux
  • co2 flux
  • constant flux
  • constant heat flux
  • critical heat flux
  • diffusion flux
  • diffusive flux
  • dioxide flux
  • downward flux
  • dust flux
  • electron flux
  • energy flux
  • fluid flux
  • gas flux
  • glycolytic flux
  • heat flux
  • high flux
  • hydrogen flux
  • increased flux
  • ion flux
  • ionic flux
  • k+ flux
  • latent heat flux
  • light flux
  • magnetic flux
  • mass flux
  • maximum heat flux
  • measured flux
  • membrane flux
  • metabolic flux
  • methane flux
  • moisture flux
  • n flux
  • n2o flux
  • net flux
  • nitrate flux
  • nitrous oxide flux
  • no flux
  • numerical flux
  • nutrient flux
  • oxide flux
  • particle flux
  • permeation flux
  • photon flux
  • proton flux
  • radiation flux
  • rotor flux
  • sediment flux
  • seepage flux
  • sensible heat flux
  • soil carbon flux
  • soil co2 flux
  • solid flux
  • solute flux
  • steady-state flux
  • substrate flux
  • surface flux
  • surface heat flux
  • total flux
  • transfer flux
  • turbulent flux
  • turbulent heat flux
  • uptake flux
  • vapour flux
  • vertical flux
  • volume flux
  • water flux
  • water vapour flux
  • x-ray flux

  • Terms modified by Flux

  • flux analysis
  • flux boundary condition
  • flux change
  • flux condition
  • flux control
  • flux convergence
  • flux data
  • flux decline
  • flux decreased
  • flux density
  • flux distribution
  • flux enhancement
  • flux estimation
  • flux function
  • flux limit
  • flux map
  • flux measurement
  • flux method
  • flux model
  • flux profile
  • flux rate
  • flux ratio
  • flux synthesis
  • flux value
  • flux variation

  • Selected Abstracts


    Wind effects on sediment transport by raindrop-impacted shallow flow: a wind-tunnel study

    EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2004
    G. Erpul
    Abstract In wind-driven rains, wind velocity and direction are expected to affect not only energy input of rains but also shallow ,ow hydraulics by changing roughness induced by raindrop impacts with an angle on ,ow and the unidirectional splashes in the wind direction. A wind-tunnel study under wind-driven rains was conducted to determine the effects of horizontal wind velocity and direction on sediment transport by the raindrop-impacted shallow ,ow. Windless rains and the rains driven by horizontal wind velocities of 6 m s,1, 10 m s,1, and 14 m s,1 were applied to three agricultural soils packed into a 20 by 55 cm soil pan placed on both windward and leeward slopes of 7 per cent, 15 per cent, and 20 per cent. During each rainfall application, sediment and runoff samples were collected at 5-min intervals at the bottom edge of the soil pan with wide-mouth bottles and were determined gravimetrically. Based on the interrill erosion mechanics, kinetic energy ,ux (Ern) as a rainfall parameter and product of unit discharge and slope in the form of qbSco as a ,ow parameter were used to explain the interactions between impact and ,ow parameters and sediment transport (qs). The differential sediment transport rates occurred depending on the variation in raindrop trajectory and rain intensity with the wind velocity and direction. Flux of rain energy computed by combining the effects of wind on the velocity, frequency, and angle of raindrop impact reasonably explained the characteristics of wind-driven rains and acceptably accounted for the differences in sediment delivery rates to the shallow ,ow transport (R2 , 0·78). Further analysis of the Pearson correlation coef,cients between Ern and qSo and qs also showed that wind velocity and direction signi,cantly affected the hydraulics of the shallow ,ow. Ern had a smaller correlation coef,cient with the qs in windward slopes where not only reverse splashes but also reverse lateral raindrop stress with respect to the shallow ,ow direction occurred. However, Ern was as much effective as qSo in the sediment transport in the leeward slopes where advance splashes and advance lateral raindrop stress on the ,ow occurred. Copyright © 2004 John Wiley & Sons, Ltd. [source]


    Flux and turnover of fixed carbon in soil microbial biomass of limed and unlimed plots of an upland grassland ecosystem

    ENVIRONMENTAL MICROBIOLOGY, Issue 4 2005
    J. Ignacio Rangel-Castro
    Summary The influence of liming on rhizosphere microbial biomass C and incorporation of root exudates was studied in the field by in situ pulse labelling of temperate grassland vegetation with 13CO2 for a 3-day period. In plots that had been limed (CaCO3 amended) annually for 3 years, incorporation into shoots and roots was, respectively, greater and lower than in unlimed plots. Analysis of chloroform-labile C demonstrated lower levels of 13C incorporation into microbial biomass in limed soils compared to unlimed soils. The turnover of the recently assimilated 13C compounds was faster in microbial biomass from limed than that from unlimed soils, suggesting that liming increases incorporation by microbial communities of root exudates. An exponential decay model of 13C in total microbial biomass in limed soils indicated that the half-life of the tracer within this carbon pool was 4.7 days. Results are presented and discussed in relation to the absolute values of 13C fixed and allocated within the plant,soil system. [source]


    Highly Crystalline, Idiomorphic Na2Ti6O13 Whiskers Grown from a NaCl Flux at a Relatively Low Temperature

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2010
    Katsuya Teshima
    Abstract Well-developed, highly crystalline Na2Ti6O13 whiskers were successfully grown by cooling a NaCl flux at a relatively low temperature of 700 °C. The obtained Na2Ti6O13 whiskers were colorless and transparent. The whiskers grown at 700 °C were single phase and exhibit the lowest sizes of up to about 3.5 ,m,×,0.1 ,m. From the results of SEM, XRD, and TEM, it was confirmed that the Na2Ti6O13 whiskers have very good crystallinity and elongated in the [lang]010[rang] directions. Furthermore, the whiskers exhibited good photocatalytic activity under ultraviolet light irradiation. It is reasonable to suppose that NaCl can be adequately used to synthesize high quality and well-developed titanate whiskers in an environmentally friendly process of crystal growth. [source]


    Spatial Analysis of the Factors Contributing to the Relationship between the Transient, Meridional Eddy Sensible, and Latent Heat Flux in the Southern Hemisphere

    GEOGRAPHICAL ANALYSIS, Issue 2 2000
    Marilyn Raphael
    In this paper principal component analysis (PCA) and singular value decomposition (SVD) are used to define the importance of the variables contributing to the relationship between the transient latent and sensible heat fluxes and to show their temporal and spatial variation. SVD is offered as an alternative means of isolating spatial and temporal structures in data with the advantage that it can depict simultaneous space-time variations that are aggregates of the results produced by PCA. Both methods of analysis produced two very important uncorrelated modes of variability in January and July, indicating that the transient heat fluxes are influenced by few controlling factors. We suggest that these modes of variability represent the influences of the meridional temperature gradient, atmospheric moisture, and activity within the source and sink regions of the transient heat fluxes. The physical relationships between the heat fluxes that appear to represented by the statistical modes of variability are discussed. [source]


    Net grassland carbon flux over a subambient to superambient CO2 gradient

    GLOBAL CHANGE BIOLOGY, Issue 7 2001
    P. C. Mielnick
    Abstract Increasing atmospheric CO2 concentrations may have a profound effect on the structure and function of plant communities. A previously grazed, central Texas grassland was exposed to a 200-µmol mol,1 to 550 µmol mol,1 CO2 gradient from March to mid-December in 1998 and 1999 using two, 60-m long, polyethylene- covered chambers built directly onto the site. One chamber was operated at subambient CO2 concentrations (200,360 µmol mol,1 daytime) and the other was regulated at superambient concentrations (360,550 µmol mol,1). Continuous CO2 gradients were maintained in each chamber by photosynthesis during the day and respiration at night. Net ecosystem CO2 flux and end-of-year biomass were measured in each of 10, 5-m long sections in each chamber. Net CO2 fluxes were maximal in late May (c. day 150) in 1998 and in late August in 1999 (c. day 240). In both years, fluxes were near zero and similar in both chambers at the beginning and end of the growing season. Average daily CO2 flux in 1998 was 13 g CO2 m,2 day,1 in the subambient chamber and 20 g CO2 m,2 day,1 in the superambient chamber; comparable averages were 15 and 26 g CO2 m,2 day,1 in 1999. Flux was positively and linearly correlated with end-of-year above-ground biomass but flux was not linearly correlated with CO2 concentration; a finding likely to be explained by inherent differences in vegetation. Because C3 plants were the dominant functional group, we adjusted average daily flux in each section by dividing the flux by the average percentage C3 cover. Adjusted fluxes were better correlated with CO2 concentration, although scatter remained. Our results indicate that after accounting for vegetation differences, CO2 flux increased linearly with CO2 concentration. This trend was more evident at subambient than superambient CO2 concentrations. [source]


    Ground Water Discharge and Nitrate Flux to the Gulf of Mexico

    GROUND WATER, Issue 3 2004
    Carolyn B. Dowling
    Ground water samples (37 to 186 m depth) from Baldwin County, Alabama, are used to define the hydrogeology of Gulf coastal aquifers and calculate the subsurface discharge of nutrients to the Gulf of Mexico. The ground water flow and nitrate flux have been determined by linking ground water concentrations to 3H/3He and 4He age dates. The middle aquifer (A2) is an active flow system characterized by postnuclear tritium levels, moderate vertical velocities, and high nitrate concentrations. Ground water discharge could be an unaccounted source for nutrients in the coastal oceans. The aquifers annually discharge 1.1 ± 0.01 × 108 moles of nitrate to the Gulf of Mexico, or 50% and 0.8% of the annual contributions from the Mobile-Alabama River System and the Mississippi River System, respectively. In southern Baldwin County, south of Loxley, increasing reliance on ground water in the deeper A3 aquifer requires accurate estimates of safe ground water withdrawal. This aquifer, partially confined by Pliocene clay above and Pensacola Clay below, is tritium dead and contains elevated 4He concentrations with no nitrate and estimated ground water ages from 100 to 7000 years. The isotopic composition and concentration of natural gas diffusing from the Pensacola Clay into the A3 aquifer aids in defining the deep ground water discharge. The highest 4He and CH4 concentrations are found only in the deepest sample (Gulf State Park), indicating that ground water flow into the Gulf of Mexico suppresses the natural gas plume. Using the shape of the CH4 -He plume and the accumulation of 4He rate (2.2 ± 0.8 ,cc/kg/1000 years), we estimate the natural submarine discharge and the replenishment rate for the A3 aquifer. [source]


    Analysis of Soil Vapor Extraction Data to Evaluate Mass-Transfer Constraints and Estimate Source-Zone Mass Flux

    GROUND WATER MONITORING & REMEDIATION, Issue 3 2010
    Mark L. Brusseau
    Methods are developed to use data collected during cyclic operation of soil vapor extraction (SVE) systems to help characterize the magnitudes and time scales of mass flux associated with vadose zone contaminant sources. Operational data collected at the Department of Energy's Hanford site are used to illustrate the use of such data. An analysis was conducted of carbon tetrachloride vapor concentrations collected during and between SVE operations. The objective of the analysis was to evaluate changes in concentrations measured during periods of operation and nonoperation of SVE, with a focus on quantifying temporal dynamics of the vadose zone contaminant mass flux, and associated source strength. Three mass flux terms, representing mass flux during the initial period of an SVE cycle, during the asymptotic period of a cycle, and during the rebound period, were calculated and compared. It was shown that it is possible to use the data to estimate time frames for effective operation of an SVE system if a sufficient set of historical cyclic operational data exists. This information could then be used to help evaluate changes in SVE operations, including system closure. The mass flux data would also be useful for risk assessments of the impact of vadose zone sources on groundwater contamination or vapor intrusion. [source]


    Estimating Persistent Mass Flux of Volatile Contaminants from the Vadose Zone to Ground Water

    GROUND WATER MONITORING & REMEDIATION, Issue 2 2009
    M.J. Truex
    Contaminants may persist for long time periods within low permeability portions of the vadose zone where they cannot be effectively treated and are a potential continuing source of contamination to ground water. Setting appropriate vadose zone remediation goals typically requires evaluating these persistent sources in terms of their impact on meeting ground water remediation goals. Estimating the impact on ground water can be challenging at sites with low aqueous recharge rates where vapor-phase movement is the dominant transport process in the vadose zone. Existing one-dimensional approaches for simulating transport of volatile contaminants in the vadose zone are considered and compared to a new flux-continuity-based assessment of vapor-phase contaminant movement from the vadose zone to the ground water. The flux-continuity-based assessment demonstrates that the ability of the ground water to move contaminant away from the water table controls the vapor-phase mass flux from the vadose zone across the water table. Limitations of these approaches are then discussed with respect to the required assumptions and the need to incorporate three-dimensional processes when evaluating vapor-phase transport from the vadose zone to the ground water. The carbon tetrachloride plume at the U.S. Department of Energy Hanford Site is used as the example site where persistent vadose zone contamination needs to be considered in the context of ground water remediation. [source]


    Hyporheic exchange flows induced by constructed riffles and steps in lowland streams in southern Ontario, Canada

    HYDROLOGICAL PROCESSES, Issue 20 2006
    Tamao Kasahara
    Abstract Stream,subsurface water interaction induced by natural riffles and constructed riffles/steps was examined in lowland streams in southern Ontario, Canada. The penetration of stream water into the subsurface was analysed using hydrometric data, and the zone of > 10% stream water was calculated from a chemical mixing equation using tracer injection of bromide and background chloride concentrations. The constructed riffles studied induced more extensive hyporheic exchange than the natural riffles because of their steeper longitudinal hydraulic head gradients and coarser streambed sediments. The depth of > 10% stream water zone in a small and a large constructed riffle extended to > 0·2 m and > 1·4 m depths respectively. Flux and residence time distribution of hyporheic exchange were simulated in constructed riffles using MODFLOW, a finite-difference groundwater flow model. Hyporheic flux and residence time distribution varied along the riffles, and the exchange occurring upstream from the riffle crest was small in flux and had a long residence time. In contrast, hyporheic exchange occurring downstream from the riffle crest had a relatively short residence time and accounted for 83% and 70% of total hyporheic exchange flow in a small and large riffle respectively. Although stream restoration projects have not considered the hyporheic zone, our data indicate that constructed riffles and steps can promote vertical hydrologic exchange and increase the groundwater,surface water linkage in degraded lowland streams. Copyright © 2006 John Wiley & Sons, Ltd. [source]


    Flux and source term discretization in two-dimensional shallow water models with porosity on unstructured grids

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2006
    Vincent Guinot
    Abstract Two-dimensional shallow water models with porosity appear as an interesting path for the large-scale modelling of floodplains with urbanized areas. The porosity accounts for the reduction in storage and in the exchange sections due to the presence of buildings and other structures in the floodplain. The introduction of a porosity into the two-dimensional shallow water equations leads to modified expressions for the fluxes and source terms. An extra source term appears in the momentum equation. This paper presents a discretization of the modified fluxes using a modified HLL Riemann solver on unstructured grids. The source term arising from the gradients in the topography and in the porosity is treated in an upwind fashion so as to enhance the stability of the solution. The Riemann solver is tested against new analytical solutions with variable porosity. A new formulation is proposed for the macroscopic head loss in urban areas. An application example is presented, where the large scale model with porosity is compared to a refined flow model containing obstacles that represent a schematic urban area. The quality of the results illustrates the potential usefulness of porosity-based shallow water models for large scale floodplain simulations. Copyright © 2005 John Wiley & Sons, Ltd. [source]


    Oxidation of small alkenes at high temperature

    INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2002
    Barbara Heyberger
    If the mechanism of formation of alkenes, the main primary products of the combustion of alkanes above 1000 K, is now well understood, their ways of degradation have been much less studied. Following a previous modeling of the oxidation of propene in a static and a jet-stirred reactors by using an automatically generated mechanism, the present paper shows new validations of the same mechanism for ignition delays in a shock tube. It also describes the extension of the rules used for the automatic generation to the case of 1-butene. The predictions of the mechanism produced for the oxidation of 1-butene are compared successfully with two sets of experimental results: the first obtained in a jet-stirred reactor between 900 and 1200 K; the second being new measurements of ignitions delays behind reflected shock waves for temperatures from 1200 up to 1670 K, pressures from 6.6 to 8.9 atm, equivalence ratios from 0.5 to 2, and with argon as bath gas. Flux and sensitivity analyses show that the role of termination reactions involving the very abundant allylic radicals is less important for 1-butene than for propene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 666,677, 2002 [source]


    Europe and Asia: Regions in Flux , Edited by P. Murray

    JCMS: JOURNAL OF COMMON MARKET STUDIES, Issue 5 2009
    FABIENNE BOSSUYT
    No abstract is available for this article. [source]


    Human skin permeation of ,8 -tetrahydrocannabinol, cannabidiol and cannabinol

    JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2004
    Audra L. Stinchcomb
    ABSTRACT The purpose of this study was to quantify the in-vitro human skin transdermal flux of ,8 -tetrahydrocannabinol (,8 -THC), cannabidiol (CBD) and cannabinol (CBN). These cannabinoids are of interest because they are likely candidates for transdermal combination therapy. Differential thermal analysis and in-vitro diffusion studies with human tissue were completed for the compounds. Heats of fusion, melting points and relative thermodynamic activities were determined for the crystalline compounds, CBD and CBN. Flux, permeability, tissue concentration and lag times were measured in the diffusion experiments. CBN had a lower heat of fusion and corresponding higher calculated relative thermodynamic activity than CBD. Ethanol concentrations of 30 to 33% significantly increased the transdermal flux of ,8 -THC and CBD. Tissue concentrations of ,8 -THC were significantly higher than for CBN. Lag times for CBD were significantly smaller than for CBN. The permeabilities of CBD and CBN were 10-fold higher than for ,8 -THC. Combinations of these cannabinoids with ethanol will be further studied in transdermal patch formulations in vitro and in vivo, as significant flux levels of all the drugs were obtained. CBD, the most polar of the three drugs, and other more polar cannabinoids will also be the focus of future drug design studies for improved transdermal delivery rates. [source]


    Quantitative Lipid Metabolomic Changes in Alcoholic Micropigs With Fatty Liver Disease

    ALCOHOLISM, Issue 4 2009
    Angela M. Zivkovic
    Background:, Chronic ethanol consumption coupled with folate deficiency leads to rapid liver fat accumulation and progression to alcoholic steatohepatitis (ASH). However, the specific effects of alcohol on key liver lipid metabolic pathways involved in fat accumulation are unknown. It is unclear whether lipid synthesis, lipid export, or a combination of both is contributing to hepatic steatosis in ASH. Methods:, In this study we estimated the flux of fatty acids (FA) through the stearoyl-CoA desaturase (SCD), phosphatidylethanolamine- N -methyltransferase (PEMT), and FA elongation pathways in relation to liver triacylglycerol (TG) content in Yucatan micropigs fed a 40% ethanol folate-deficient diet with or without supplementation with S -adenosyl methionine (SAM) compared with controls. Flux through the SCD and PEMT pathways was used to assess the contribution of lipid synthesis and lipid export respectively on the accumulation of fat in the liver. Liver FA composition within TG, cholesterol ester (CE), phosphatidylethanolamine, and phosphatidylcholine classes was quantified by gas chromatography. Results:, Alcoholic pigs had increased liver TG content relative to controls, accompanied by increased flux through the SCD pathway as indicated by increases in the ratios of 16:1n7 to 16:0 and 18:1n9 to 18:0. Conversely, flux through the elongation and PEMT pathways was suppressed by alcohol, as indicated by multiple metabolite ratios. SAM supplementation attenuated the TG accumulation associated with alcohol. Conclusions:, These data provide an in vivo examination of liver lipid metabolic pathways confirming that both increased de novo lipogenesis (e.g., lipid synthesis) and altered phospholipid metabolism (e.g., lipid export) contribute to the excessive accumulation of lipids in liver affected by ASH. [source]


    Optical spectra of Tm3+ -doped YAl3(BO3)4 single crystals

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007
    E. Cavalli
    Abstract Flux grown YAl3(BO3)4 (YAB) crystals doped with Tm3+ have been characterised by optical spectroscopy techniques. The absorption and emission spectra in the UV-VIS-NIR region have been measured at 10 and 298 K. The visible emission decay profiles have been measured at room temperature. The low temperature spectra have been used to obtain the energy level scheme of the optically active ion in YAB. The Judd-Ofelt parametrization scheme has been applied to the analysis of the room temperature absorption spectra in order to evaluate the intensity parameters, the branching ratios and the radiative lifetimes of the emitting states. These have been compared with the experimental values. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Correlation of Optical Emission and Ion Flux with GaN Etch Rate in Inductively Coupled Ar/Cl2 Plasma Etching

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003
    S.A. Rizvi
    Abstract The etching of GaN was investigated in an Ar/Cl2 inductively coupled plasma. Optical emission spectroscopy and an ion flux probe were used to obtain insight into the etch mechanisms during processing. Langmuir probe measurements were also used to determine the basic Ar/Cl2 plasma characteristics. Etch rates of ,500 nm/min were obtained at relatively low Cl2 fractions of ,50%. The dominant emission species observed were Ga (at 294 nm) and up to six GaCl peaks between 320 and 345 nm. Plasma characterisation and ion flux indicate etch mechanisms that depend strongly on atomic chlorine but with increasing power and at low Cl2, the significance of ion-based processes cannot be ruled out. [source]


    Flux of Positive Ions and Film Growth in Reactive Sputtering of Al-Doped ZnO Thin Films

    PLASMA PROCESSES AND POLYMERS, Issue S1 2007
    Florian Ruske
    Abstract The reactive magnetron sputtering deposition of Al-doped zinc oxide thin films using a dual magnetron has been studied for a flux of positive ions and the total thermal load onto the substrate. The spatial distribution of both quantities has been studied using a thermal probe and a retarding field analyzer mounted onto a moveable carrier system. The positive ions were found to mostly originate from the plasma sheath at the substrate, with the spatial distribution determined by the plasma density distribution in the coating chamber. The total energy flux to the substrate mainly originated from the plasma, with positive ions only contributing a small part of the total plasma irradiation. In the tested conditions and with the coater examined, the quality of the deposited films mainly depends on oxygen distribution on the substrate and is not a direct consequence of the total energy flux to the substrate. [source]


    Solids Circulation Flux and Gas Bypassing in a Pressurized Spout-fluid Bed with a Draft Tube

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2002
    Rui Xiao
    Abstract An experimental study on solids circulation flux and gas bypassing of a spout-fluid bed with a draft tube at elevated pressures up to 600 kPa was performed in a 200 mm diameter cylindrical steel column with a 608 conical distributor. Glass beads with mean diameter 2.067 mm were used as bed materials to investigate the effect of operating conditions and geometric configuration on the solids circulation flux and the gas distribution between the annulus and the draft tube. A novel technique has been developed to measure the solids fluxes under pressure, and gas (CO2) traces have been employed to investigate gas bypassing characteristics. The solids circulation flux is greatly enhanced when operating pressure and auxiliary gas flowrate are increased, and it is also strongly influenced by geometric configuration. Two experimental relations are proposed for predicting solids circulation flux enhancement factors. Une étude expérimentale sur le flux de circulation des solides et la dérivation du gaz d'un lit jaillissant muni d'un tube d'aspiration à des pressions élevées jusqu'à 600 kPa, a été réalisée dans une colonne d'acier cylindrique de 200 mm de diamètre avec un distributeur conique à 608. Des billes de verre d'un diamètre moyen de 2,067 mm ont été utilisées comme matériaux de lit pour étudier l'effet des conditions opératoires et de la configuration géométrique sur le flux de circulation des solides et la distribution du gaz entre l'espace annulaire et le tube d'aspiration. Une nouvelle technique a été élaborée pour mesurer les flux de solides sous pression et les caractéristiques de la dérivation du gaz ont été étudiées à l'aide de gaz traceurs (CO2). Le flux de circulation des solides est grandement amélioré lorsque la pression de fonctionnement et le débit de gaz auxiliaire sont augmentés, et il est également fortement influencé par la configuration géométrique. Deux relations expérimentales sont proposées pour la prédiction des facteurs d'amélioration du flux de circulation des solides. [source]


    France Luxuriates in a State of Flux

    THE POLITICAL QUARTERLY, Issue 3 2002
    Thierry Naudin
    No abstract is available for this article. [source]


    Global Gene Expression Differences Associated with Changes in Glycolytic Flux and Growth Rate in Escherichia coli during the Fermentation of Glucose and Xylose

    BIOTECHNOLOGY PROGRESS, Issue 1 2002
    Ramon Gonzalez
    The simplicity of the fermentation process (anaerobic with pH, temperature, and agitation control) in ethanologenic Escherichia coli KO11 and LY01 makes this an attractive system to investigate the utility of gene arrays for biotechnology applications. By using this system, gene expression, glycolytic flux, and growth rate have been compared in glucose-grown and xylose-grown cells. Although the initial metabolic steps differ, ethanol yields from both sugars were essentially identical on a weight basis, and little carbon was diverted to biosynthesis. Expression of only 27 genes changed by more than 2-fold in both strains. These included induction of xylose-specific operons ( xylE, xylFGHR, and xylAB) regulated by XylR and the cyclic AMP,CRP system and repression of Mlc-regulated genes encoding glucose uptake ( ptsHIcrr, ptsG) and mannose uptake ( manXYZ) during growth on xylose. However, expression of genes encoding central carbon metabolism and biosynthesis differed by less than 2-fold. Simple statistical methods were used to investigate these more subtle changes. The reproducibility (coefficient of variation of 12%) of expression measurements (mRNA as cDNA) was found to be similar to that typically observed for in vitro measurements of enzyme activities. Using Studentapos;s t test, many smaller but significant sugar-dependent changes were identified ( p < 0.05 in both strains). A total of 276 genes were more highly expressed during growth on xylose; 307 genes were more highly expressed with glucose. Slower growth (lower ATP yield) on xylose was accompanied by decreased expression of 62 genes concerned with the biosynthesis of small molecules (amino acids, nucleotides, cofactors, and lipids), transcription, and translation; 5 such genes were expressed at a higher level. In xylose-grown cells, 90 genes associated with the transport, catabolism, and regulation of pathways for alternative carbon sources were expressed at higher levels than in glucose-grown cells, consistent with a relaxation of control by the cyclic AMP,CRP regulatory system. Changes in expression of genes encoding the Embden,Meyerhof,Parnas (EMP) pathway were in excellent agreement with calculated changes in flux for individual metabolites. Flux through all but one step, pyruvate kinase, was predicted to be higher during glucose fermentation. Expression levels (glucose/xylose) were higher in glucose-grown cells for all EMP genes except the isoenzymes encoding pyruvate kinase ( pykA and pykF). Expression of both isoenzymes was generally higher during xylose fermentation but statistically higher in both strains only for pykF encoding the isoenzyme activated by fructose-6-phosphate, a key metabolite connecting pentose metabolism to the EMP pathway. The coordinated changes in expression of genes encoding the EMP pathway suggest the presence of a common regulatory system and that flux control within the EMP pathway may be broadly distributed. In contrast, expression levels for genes encoding the Pentose,Phosphate pathway did not differ significantly between glucose-grown and xylose-grown cells. [source]


    European Employment Models in Flux: A Comparison of Institutional Change in Nine European Countries , Edited by Gerhard Bosch, Steffen Lehndorff and Jill Rubery

    BRITISH JOURNAL OF INDUSTRIAL RELATIONS, Issue 1 2010
    Colin Crouch
    First page of article [source]


    Direct Measurements of Instantaneous Solid Flux in a CFB Riser using a Novel Multifunctional Optical Fiber Probe

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2009
    S. Ye
    Abstract With a novel optical fiber probe that can measure instantaneous local particle velocity and solid concentration simultaneously, extensive experiments were conducted to study transient flow structures in a 15.1-m long circulating fluidized bed (CFB) riser of 100,mm in diameter. This study analyzed the radial and axial distributions of solid concentration, particle velocity, and their variations with nine operating conditions and at six axial levels. Instantaneous local solid concentration and particle velocity were found to be well correlated at most of the radial positions. The detailed time evolution, axial and radial distribution of instantaneous solid flux, and the variation of solid flux with operating conditions were also investigated. The radial solid flux profile showed a flat shape with a maximum at near wall area under most operating conditions. The instantaneous solid flux was found to have a strong fluctuation at a radial position of r/R,=,0.8 ~ 0.9. [source]


    Influence of Growth Temperature and Carrier Flux on the Structure and Transport Properties of Highly Oriented CrO2 on Al2O3 (0001),

    CHEMICAL VAPOR DEPOSITION, Issue 10 2007
    M. Sousa
    Abstract In this work we report on the structure and magnetic and electrical transport properties of CrO2 films deposited onto (0001) sapphire by atmospheric pressure (AP)CVD from a CrO3 precursor. Films are grown within a broad range of deposition temperatures, from 320 to 410,°C, and oxygen carrier gas flow rates of 50,500,sccm, showing that it is viable to grow highly oriented a -axis CrO2 films at temperatures as low as 330,°C i.e., 60,70,°C lower than is reported in published data for the same chemical system. Depending on the experimental conditions, growth kinetic regimes dominated either by surface reaction or by mass-transport mechanisms are identified. The growth of a Cr2O3 interfacial layer as an intrinsic feature of the deposition process is studied and discussed. Films synthesized at 330,°C keep the same high quality magnetic and transport properties as those deposited at higher temperatures. [source]


    ChemInform Abstract: Europium Substitution into Intermetallic Phases Grown in Ca/Zn Flux.

    CHEMINFORM, Issue 45 2009
    Milorad Stojanovic
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    ChemInform Abstract: Subsolidus Phase Relationships in the System ZnO,V2O5,WO3 Research on Suitable Flux for ZnO Crystal Growth.

    CHEMINFORM, Issue 31 2009
    Xianzhi Chen
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    ChemInform Abstract: Synthesis, Magnetism and Electronic Structure of YbNi2-xFexAl8 (x = 0.91) Isolated from Al Flux.

    CHEMINFORM, Issue 11 2009
    Xiuni Wu
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    Ln2MAl6Si4 (Ln: Gd, Tb, Dy; M: Au, Pt): Layered Quaternary Intermetallics Featuring CaAl2Si2 -Type and YNiAl4Ge2 -Type Slabs Grown from Aluminum Flux.

    CHEMINFORM, Issue 6 2004
    Susan E. Latturner
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Synthesis of Rare Earth Polyborates Using Molten Boric Acid as a Flux.

    CHEMINFORM, Issue 10 2003
    Linyan Li
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Soft Mechanical Sensors Through Reverse Actuation in Polypyrrole,

    ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007
    Y. Wu
    Abstract The phenomenon of voltage generated from a soft sensor using polypyrrole in response to mechanical deformation is described and investigated. The sensor consists of two polypyrrole layers in contact with an electrolyte and operates in bending mode in air. The magnitude and sign of the induced voltage was found to depend on the type of dopant counter-ions and the nature of the surrounding electrolyte. The mechanical sensor response is shown to be a "reverse actuation", generating millivolt signals for millimeter sized deflections or ,,1000,C,m,3 charge for 1,% strain in the polypyrrole layer. A model based on ,Deformation Induced Ion Flux' has been proposed whereby the strain induced volume change in the polymer produces a shift in the Donnan equilibrium between mobile dopant ions inside the polymer and in the external electrolyte. A simple thermodynamic model provides reasonable estimates of the size of the voltage and charge produced. [source]


    Methane and nitrous oxide fluxes from a farmed Swedish Histosol

    EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2009
    Å. Kasimir Klemedtsson
    Summary Fluxes of the greenhouse gases methane (CH4) and nitrous oxide (N2O) from histosolic soils (which account for approximately 10% of Swedish agricultural soils) supporting grassley and barley production in Sweden were measured over 3 years using static chambers. Emissions varied both over area and time. Methane was both produced and oxidized in the soil: fluxes were small, with an average emission of 0.12 g CH4 m,2 year,1 at the grassley site and net uptake of ,0.01 g CH4 m,2 year,1 at the barley field. Methane emission was related to soil water, with more emission when wet. Nitrous oxide emissions varied, with peaks of emission after soil cultivation, ploughing and harrowing. On average, the grassley and barley field had emissions of 0.20 and 1.51 g N2O m,2 year,1, respectively. We found no correlation between N2O and soil factors, but the greatest N2O emission was associated with the driest areas, with < 60% average water-filled pore space. We suggest that the best management option to mitigate emissions is to keep the soil moderately wet with permanent grass production, which restricts N2O emissions whilst minimizing those of CH4. [source]