Science.gov

Sample records for countercurrent flow limitation

  1. Counter-current flow limitation in thin rectangular channels

    NASA Astrophysics Data System (ADS)

    Cheng, Lap Y.

    The phenomenon of counter-current flow limitation (CCFL) in thin rectangular channels is important in determining the heat removal capability of research reactors which use plate-type fuel elements similar to the MTR design. An analytical expression for predicting CCFL in narrow rectangular channels was derived from the momentum equations for the liquid and gas phase. The model assumes that the liquid downflow is in the form of a film along the narrower side walls of the channel, while the gas flow occupies the wide span of the rectangular channel. The average thickness of liquid film is related to the rate of gas flow through a stability criterion for the liquid film. The CCFL correlation agrees with air/water data taken at relatively high gas velocities. Depending on the magnitude of the dimensionless channel width, the new CCFL correlation approaches zero liquid penetration either in the form of a Wallis correlation or in terms of a Kutateladze number. The new correlation indicates that for a thin rectangular channel, the constant C in the Wallis flooding correlation depends on the aspect ratio of the channel. The approach to the appropriate asymptotic solutions also justifies the use of twice the wide span as the correct length scale for thin rectangular channels.

  2. COUNTERCURRENT FLOW LIMITATION EXPERIMENTS AND MODELING FOR IMPROVED REACTOR SAFETY

    SciTech Connect

    Vierow, Karen

    2008-09-26

    This project is investigating countercurrent flow and “flooding” phenomena in light water reactor systems to improve reactor safety of current and future reactors. To better understand the occurrence of flooding in the surge line geometry of a PWR, two experimental programs were performed. In the first, a test facility with an acrylic test section provided visual data on flooding for air-water systems in large diameter tubes. This test section also allowed for development of techniques to form an annular liquid film along the inner surface of the “surge line” and other techniques which would be difficult to verify in an opaque test section. Based on experiences in the air-water testing and the improved understanding of flooding phenomena, two series of tests were conducted in a large-diameter, stainless steel test section. Air-water test results and steam-water test results were directly compared to note the effect of condensation. Results indicate that, as for smaller diameter tubes, the flooding phenomena is predominantly driven by the hydrodynamics. Tests with the test sections inclined were attempted but the annular film was easily disrupted. A theoretical model for steam venting from inclined tubes is proposed herein and validated against air-water data. Empirical correlations were proposed for air-water and steam-water data. Methods for developing analytical models of the air-water and steam-water systems are discussed, as is the applicability of the current data to the surge line conditions. This report documents the project results from July 1, 2005 through June 30, 2008.

  3. Countercurrent flow absorber and desorber

    DOEpatents

    Wilkinson, W.H.

    1984-10-16

    Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system. 9 figs.

  4. Countercurrent flow absorber and desorber

    DOEpatents

    Wilkinson, William H.

    1984-01-01

    Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system.

  5. Flooding in counter-current two-phase flow

    SciTech Connect

    Ragland, W.A.; Ganic, E.N.

    1982-01-01

    Flooding is a phenomenon which is best described as the transition from counter-current to co-current flow. Early notice was taken of this phenomenon in the chemical engineering industry. Flooding also plays an important role in the field of two-phase heat transfer since it is a limit for many systems involving counter-current flow. Practical applications of flooding limited processes include wickless thermosyphons and the emergency core cooling system (ECCS) of pressurized water nuclear reactors. The phenomenon of flooding also is involved in the behavior of nuclear reactor core materials during severe accident conditions where flooding is one of the mechanisms governing the motion of the molten fuel pin cladding.

  6. Stability of steam-water countercurrent stratified flow

    SciTech Connect

    Lee, S C

    1985-10-01

    Two flow instabilities which limit the normal condensation processes in countercurrent stratified steam-water flow have been identified experimentally: flooding and condensation-induced waterhammer. In order to initiate condensation-induced waterhammer in nearly horizontal or moderately-inclined steam/subcooled-water flow, two conditions, the appearance of a wavy interface and complete condensation of the incoming steam, are necessary. Analyses of these conditions are performed on a basis of flow stability and heat transfer considerations. Flooding data for several inclinations and channel heights are collected. Effects of condensation, inclination angle and channel height on the flooding characteristics are discussed. An envelope theory for the onset of flooding in inclined stratified flow is developed, which agrees well with the experimental data. Some empirical information on basic flow parameters, such as mean film thickness and interfacial friction factor required for this theory are measured. The previous viewpoints on flooding appear not to conflict with the present experimental data in nearly horizontal flow but the flooding phenomena in nearly vertical flow appear to be more complicated than those described by these viewpoints because of liquid droplet entrainment.

  7. Evaluation of dual flow counter-current chromatography and intermittent counter-current extraction.

    PubMed

    Ignatova, Svetlana; Hewitson, Peter; Mathews, Ben; Sutherland, Ian

    2011-09-09

    The aim of this research is to compare two continuous extraction technologies, intermittent counter-current extraction (ICcE) and dual flow counter-current chromatography (DFCCC), in terms of loading and throughput using the GUESSmix, and show the advantages and disadvantages of the two methods. A model sample containing caffeine, vanillin, naringenin and carvone, with a total load of 11.2 g, was employed with a hexane-ethyl acetate-methanol-water (2:3:2:3) phase system to evaluate an ICcE method on a preparative (912 ml coil volume) DE-Midi instrument. While DFCCC was carried out on a specially designed preparative (561 ml coil volume) bobbin installed in a similar Midi instrument case. While similar throughputs of 7.8 g/h and 6.9 g/h were achieved for the ICcE and DFCCC methods respectively, ICcE was demonstrated to have a number of advantages over DFCCC.

  8. A criterion for the onset of slugging in horizontal stratified air-water countercurrent flow

    SciTech Connect

    Chun, Moon-Hyun; Lee, Byung-Ryung; Kim, Yang-Seok

    1995-09-01

    This paper presents an experimental and theoretical investigation of wave height and transition criterion from wavy to slug flow in horizontal air-water countercurrent stratified flow conditions. A theoretical formula for the wave height in a stratified wavy flow regime has been developed using the concept of total energy balance over a wave crest to consider the shear stress acting on the interface of two fluids. From the limiting condition of the formula for the wave height, a necessary criterion for transition from a stratified wavy flow to a slug flow has been derived. A series of experiments have been conducted changing the non-dimensional water depth and the flow rates of air in a horizontal pipe and a duct. Comparisons between the measured data and the predictions of the present theory show that the agreement is within {plus_minus}8%.

  9. Counter-current flow in a vertical to horizontal tube with obstructions

    SciTech Connect

    Tye, P.; Matuszkiewicz, A.; Teyssedou, A.

    1995-09-01

    This paper presents experimental results on counter-current flow and flooding in an elbow between a vertical and a horizontal run. The experimental technique used allowed not only the flooding limit to be determined, but also the entire partial delivery region to be studied as well. The influence that various size orifices placed in the horizontal run have on both the delivered liquid flow rates and on the flooding limits is also examined. It is observed that both the flooding limits and the delivered liquid flow rates decrease with decreasing orifice size. Further, it is also observed that the mechanisms that govern the partial delivery of the liquid are significantly different when an orifice is present in the horizontal leg as compared to the case when no orifice is present.

  10. Ultraefficient reduced model for countercurrent two-layer flows

    NASA Astrophysics Data System (ADS)

    Lavalle, Gianluca; Vila, Jean-Paul; Lucquiaud, Mathieu; Valluri, Prashant

    2017-01-01

    We investigate the dynamics of two superposed layers with density contrast flowing countercurrent inside a channel, when the lower layer is much thinner than the wavelength of interfacial waves. We apply a low-dimensional film model to the bottom (heavier) layer and introduce a fast and efficient method to predict the onset of flow reversal in this phase. We study three vertical scenarios with different applied pressure gradients and compare the temporal growth rates of linear and weakly nonlinear waves to the Orr-Sommerfeld problem and to the weakly nonlinear theory, respectively. At the loading point, i.e., when a large wave hump stands at the interface, our spatiotemporal analysis shows that the system is absolutely unstable. We then present profiles of nonlinear saturated waves, pressure field, and streamline distribution in agreement with direct numerical simulation. The reduced model presented here allows us to explore the effect of the upper-layer speed on the wave pattern, showing that the wave profile is very sensitive when the mean film thickness, rather than the liquid flow rate, is maintained constant in the simulation. In addition, we show the strong effect of surface tension on both the maximum wave hump and the crest steepness before the loading point. Finally, we reveal how the nonlinear wave speed affects the vortex distribution within the lower layer by analyzing the stream function under different scenarios.

  11. Local properties of countercurrent stratified steam-water flow

    SciTech Connect

    Kim, H J

    1985-10-01

    A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel/flat plate geometry over a wide range of inclination angles (4/sup 0/-87/sup 0/) at several aspect ratios. Variables were inlet water and steam flow rates, and inlet water temperature. Local condensation rates and pressure gradients were measured, and local condensation heat transfer coefficients and interfacial shear stress were calculated. Contact probe traverses of the surface waves were made, which allowed a statistical analysis of the wave properties. The local condensation Nusselt number was correlated in terms of local water and steam Reynolds or Froude numbers, as well as the liquid Prandtl number. A turbulence-centered model developed by Theofanous, et al. principally for gas absorption in several geometries, was modified. A correlation for the interfacial shear stress and the pressure gradient agreed with measured values. Mean water layer thicknesses were calculated. Interfacial wave parameters, such as the mean water layer thickness, liquid fraction probability distribution, wave amplitude and wave frequency, are analyzed.

  12. Experimental Investigation of Micro Counter-Current Flow Using High-Speed Micro PIV

    NASA Astrophysics Data System (ADS)

    Shinohara, Kyosuke; Sugii, Yasuhiko; Aota, Arata; Hibara, Akihide; Kitamori, Takehiko; Okamoto, Koji

    2004-11-01

    Microfluidic devices have been developed for chemical analysis as micro total analysis systems (u-TAS). To utilize scale merits, continuous-flow chemical processing and micro unit operations had been proposed as microfluidic device including mixing, phase confluence, solvent extraction, and so on. Recently, as one of these integrated chemical processes, micro counter-current flow system had been developed for highly efficient solvent extraction. The system consisted of oil flow and water flow in inverse direction. Using the system, more efficient extraction of Co (II) complex than theoretical prediction was confirmed. In this paper, in order to investigate the fundamental characteristics of the micro counter-current flow, velocity fields of the micro counter-current flow were measured using high-speed micro PIV system. The system consisted of a high-speed CMOS camera with an image intensifier, an epi-fluorescent microscope with an objective lens and a color filter, and a CW laser. The velocity fields of water were visualized for a time resolution of 500 us and a spatial resolution of 2.2 x 2.2 um. Transient micro vortices at the water-butyl acetate interface were captured clearly.

  13. Cross-flow versus counter-current flow packed-bed scrubbers: a mathematical analysis

    SciTech Connect

    Fthenakis, V.M.

    1996-02-01

    Little is known about the mass transfer properties of packing media exposed to a crossflow of gas and liquid, whereas there is abundant information related to counter-current scrubbers. This paper presents a theoretical analysis of mass transfer and hydrodynamics in cross- flow packed bed scrubbers and compares those with information available for counter current towers, so that the first can be evaluated and/or designed based on data derived for the second. Mathematical models of mass transfer in cross-flow and counter- current packed bed scrubbers are presented. From those, one can predict the removal effectiveness of a crossflow scrubber from the number of transfer units (NTU) calculated for a similar counterflow operation; alternatively, when the removal effectiveness in counterflow is known, one can predict the corresponding NTU in crossflow.

  14. A PCM/forced convection conjugate transient analysis of energy storage systems with annular and countercurrent flows

    NASA Technical Reports Server (NTRS)

    Cao, Y.; Faghri, A.; Juhasz, A.

    1991-01-01

    Latent heat energy storage systems with both annular and countercurrent flows are modeled numerically. The change of phase of the phase-change material (PCM) and the transient forced convective heat transfer for the transfer fluid are solved simultaneously as a conjugate problem. A parametric study and a system optimization are conducted. It is found that the energy storage system with the countercurrent flow is an efficient way to absorb heat energy in a short period for pulsed power load space applications.

  15. Experimental study of heat and mass transfer in a buoyant countercurrent exchange flow

    NASA Astrophysics Data System (ADS)

    Conover, Timothy Allan

    Buoyant Countercurrent Exchange Flow occurs in a vertical vent through which two miscible fluids communicate, the higher-density fluid, residing above the lower-density fluid, separated by the vented partition. The buoyancy- driven zero net volumetric flow through the vent transports any passive scalars, such as heat and toxic fumes, between the two compartments as the fluids seek thermodynamic and gravitational equilibrium. The plume rising from the vent into the top compartment resembles a pool fire plume. In some circumstances both countercurrent flows and pool fires can ``puff'' periodically, with distinct frequencies. One experimental test section containing fresh water in the top compartment and brine (NaCl solution) in the bottom compartment provided a convenient, idealized flow for study. This brine flow decayed in time as the concentrations approached equilibrium. A second test section contained fresh water that was cooled by heat exchangers above and heated by electrical elements below and operated steadily, allowing more time for data acquisition. Brine transport was reduced to a buoyancy- scaled flow coefficient, Q*, and heat transfer was reduced to an analogous coefficient, H*. Results for vent diameter D = 5.08 cm were consistent between test sections and with the literature. Some results for D = 2.54 cm were inconsistent, suggesting viscosity and/or molecular diffusion of heat become important at smaller scales. Laser Doppler Velocimetry was used to measure velocity fields in both test sections, and in thermal flow a small thermocouple measured temperature simultaneously with velocity. Measurement fields were restricted to the plume base region, above the vent proper. In baseline periodic flow, instantaneous velocity and temperature were ensemble averaged, producing a movie of the average variation of each measure during a puffing flow cycle. The temperature movie revealed the previously unknown cold core of the puff during its early development. The

  16. Wall pressure measurements of flooding in vertical countercurrent annular air–water flow

    SciTech Connect

    Choutapalli, I., Vierow, K.

    2010-01-01

    An experimental study of flooding in countercurrent air-water annular flow in a large diameter vertical tube using wall pressure measurements is described in this paper. Axial pressure profiles along the length of the test section were measured up to and after flooding using fast response pressure transducers for three representative liquid flow rates representing a wide range of liquid Reynolds numbers (ReL = 4Γ/μ; Γ is the liquid mass flow rate per unit perimeter; μ is the dynamic viscosity) from 3341 to 19,048. The results show that flooding in large diameter tubes cannot be initiated near the air outlet and is only initiated near the air inlet. Fourier analysis of the wall pressure measurements shows that up to the point of flooding, there is no dominant wave frequency but rather a band of frequencies encompassing both the low frequency and the broad band that are responsible for flooding. The data indicates that flooding in large diameter vertical tubes may be caused by the constructive superposition of a plurality of waves rather than the action of a single large-amplitude wave.

  17. Co- and counter-current spontaneous imbibition into groups of capillary tubes with lateral connections permitting cross-flow.

    PubMed

    Unsal, E; Mason, G; Ruth, D W; Morrow, N R

    2007-11-01

    A model for co- and counter-current imbibition through independent capillaries has already been developed and experiments conducted to verify the theory [E. Unsal, G. Mason, N.R. Morrow, D.W. Ruth, J. Colloid Interface Sci. 306 (2007) 105]. In this paper, the work is extended to capillaries which are connected laterally and in which cross-flow can take place. The fundamental pore geometry is a rod in an angled round-bottomed slot with a gap between the rod and a capping glass plate. The surfaces of the slot, rod and plate form capillaries and interconnecting passages which have non-axisymmetric cross-sections. Depending on the gap size either (i) a large single meniscus, (ii) two menisci one on each side of the rod, or (iii) three menisci, one between the rod and the glass additional to the ones on each side can be formed. A viscous refined oil was applied to one end of the capillaries and co-current and counter-current spontaneous imbibition experiments were performed. The opposite end was left open to the atmosphere for co-current experiments. When the gap between the rod and the plate was large, the imbibing oil advanced into the tubes with the meniscus in the largest capillary always lagging behind the two menisci in the other two smaller capillaries. For counter-current imbibition experiments the open end was sealed and connected to a sensitive pressure transducer. In some experiments, the oil imbibed into the smaller capillaries and expelled air as a series of bubbles from the end of the largest capillary. In other experiments, the oil was allowed to imbibe part way into the tubes before counter-current imbibition was started. The meniscus curvatures of the capillaries have been calculated using the Mayer and Stowe-Princen method for different cell slot angles and gap sizes using a value of zero for the contact angle. These values have been compared with actual values by measuring the capillary rise in the tubes; agreement was very close. A model for co

  18. Linear and nonlinear instability in vertical counter-current laminar gas-liquid flows

    NASA Astrophysics Data System (ADS)

    Schmidt, Patrick; Ó Náraigh, Lennon; Lucquiaud, Mathieu; Valluri, Prashant

    2016-04-01

    We consider the genesis and dynamics of interfacial instability in vertical gas-liquid flows, using as a model the two-dimensional channel flow of a thin falling film sheared by counter-current gas. The methodology is linear stability theory (Orr-Sommerfeld analysis) together with direct numerical simulation of the two-phase flow in the case of nonlinear disturbances. We investigate the influence of two main flow parameters on the interfacial dynamics, namely the film thickness and pressure drop applied to drive the gas stream. To make contact with existing studies in the literature, the effect of various density contrasts is also examined. Energy budget analyses based on the Orr-Sommerfeld theory reveal various coexisting unstable modes (interfacial, shear, internal) in the case of high density contrasts, which results in mode coalescence and mode competition, but only one dynamically relevant unstable interfacial mode for low density contrast. A study of absolute and convective instability for low density contrast shows that the system is absolutely unstable for all but two narrow regions of the investigated parameter space. Direct numerical simulations of the same system (low density contrast) show that linear theory holds up remarkably well upon the onset of large-amplitude waves as well as the existence of weakly nonlinear waves. For high density contrasts, corresponding more closely to an air-water-type system, linear stability theory is also successful at determining the most-dominant features in the interfacial wave dynamics at early-to-intermediate times. Nevertheless, the short waves selected by the linear theory undergo secondary instability and the wave train is no longer regular but rather exhibits chaotic motion. The same linear stability theory predicts when the direction of travel of the waves changes — from downwards to upwards. We outline the practical implications of this change in terms of loading and flooding. The change in direction of the

  19. Interfacial instability in vertical counter-current gas-liquid film flow: theory, direct numerical simulation and experiment

    NASA Astrophysics Data System (ADS)

    Schmidt, Patrick; Ausner, Ilja; Ó Náraigh, Lennon; Lucquiaud, Mathieu; Valluri, Prashant

    2016-11-01

    The dynamics of vertical counter-current gas-liquid flows are largely determined by interfacial instability, which gives rise to a multitude of complex wave patterns and internal flows. To study the genesis and evolution of the instability in detail, we employ theoretical stability analysis, experiment and a newly developed level set method based in-house solver to carry out direct numerical simulations. Crucial results of these simulations, such as growth rate and phase velocity of interfacial waves, are rigorously compared against linear and weakly nonlinear theory; thereby showing remarkable agreement. The analysis also reveals the spatio-temporal character of the waves, depicting regimes of absolute and convective instability. Complementing the benchmark set by (non-)linear theory, we perform film thickness measurements of a real gas-liquid system (air-silicone oil) by means of a non-intrusive light-induced fluorescence technique to further validate the solver regarding its capability of capturing interfacial dynamics accurately. These measurements are in good agreement with the results of the nonlinear direct numerical simulations with respect to wavelength and wave shape of the most unstable mode.

  20. Wave-driven Countercurrent Plasma Centrifuge

    SciTech Connect

    A.J. Fetterman and N.J. Fisch

    2009-03-20

    A method for driving rotation and a countercurrent flow in a fully ionized plasma centrifuge is described. The rotation is produced by radiofrequency waves near the cyclotron resonance. The wave energy is transferred into potential energy in a manner similar to the α channeling effect. The countercurrent flow may also be driven by radiofrequency waves. By driving both the rotation and the flow pattern using waves instead of electrodes, physical and engineering issues may be avoided.

  1. Production of carbonaceous adsorbents from agricultural by-products and novolac resin under a continuous countercurrent flow type pyrolysis operation.

    PubMed

    Ioannou, Z; Simitzis, J

    2013-02-01

    Carbonaceous adsorbents based on novolac resin (N) and olive stone biomass (B) in a proportion of 20/80 and 40/60 w./w. N/O were produced. The specimens were cured (c) and pyrolyzed/carbonized (C) up to 1000 °C under a continuous countercurrent flow type pyrolysis operation (N20B-cC, N40B-cC). Commercial activated carbon (AC) was used for comparison reasons. Methylene blue adsorption from its aqueous solutions onto the adsorbents and kinetic analysis were investigated. The specific surface area of adsorbents and the gross calorific values (GCV) of cured materials were determined. The results show that N40B-cC presents lower weight loss and shrinkage but higher methylene blue adsorption than N20B-cC. Pseudo-second order mechanism describes better methylene blue adsorption onto all adsorbents. The specific surface area of carbonaceous and the gross calorific values of cured materials follow the order: AC>N20B-cC>N40B-cC and N100-c>N40B-c>N20B-c>B respectively. Olive stone biomass may constitute a suitable precursor for the production of carbonaceous materials.

  2. The Calculated Ratio of the Gas Flow in a Countercurrent Cyclone Dust Concentrator

    NASA Astrophysics Data System (ADS)

    Vasilevsky, Michail; Razva, Aleksandr; Pleschko, Alissa; Kadurkin, Ivan

    2016-02-01

    There are numerous studies of the structure of swirling flow in a variety of devices in which the peculiarities of the parameters associated with the twist flow. The values of the local parameters of the twist of the axial direction are experimentally and connect them with a constructive twist parameter, which is built from the idealized repose of the gas flow in vortex distribution and speed at the exit of the swirl. For counter flow chamber is the equation for the input pulse in the radial direction and the twist parameter is provided in the radial direction. It allows us to estimate the maximum radius of the circumferential velocity not only near the outlet, but also near the end surface of the chamber. On a cylindrical surface with a radius of outlet cyclone tangential turbulent friction in the radial direction depends on the product of a circle and radial speeds. Compiled equation changes the flow of angular momentum in the axial zone, depending on the force of friction tangential flow on the surface with the radius of the outlet pipe of the cyclone. This equation allowed assessing the circulation of gas in the axial zone.

  3. Local Heat and Mass Transfer in a Counter-current Slug Flow Absorber for Ammonia-water Absorption Heat Pump System

    NASA Astrophysics Data System (ADS)

    Koyama, Shigeru; B. Saha, Bidyut; Kim, Hyun-Young

    This study deals with experimental results and data reduction model for a counter-current slug flow absorber working with ammonia-water mixture for significantly low solution flow rate-condition that is required for operating as the GAX cycle. From visualization results of flow pattern, frost flow just after the gas inlet followed by slug flow with well-shaped Taylor bubble are observed, while dry patch on the tube wall are not observed. The local heat flow rate is measured by varying main parameters, namely, pressure, ammonia gas flow rate, solution flow rate, ammonia concentration of inlet solution and coolant inlet conditions. A data reduction model to obtain local heat and mass transfer coefficient on the liquid side is proposed by using the drift flux model to analyze the flow characteristics. Control volume method and heat and mass transfer analogy are employed to solve the combined heat and mass transfer problem. As a result, it is found that the local heat and mass transfer coefficient on the liquid side is greatly influenced by the flow pattern. The heat and mass transfer coefficient at the frost flow region is higher than that at the slug flow region due to flow disturbance and random fluctuation.

  4. Investigation of Countercurrent Helium-Air Flows in Air-ingress Accidents for VHTRs

    SciTech Connect

    Sun, Xiaodong; Christensen, Richard; Oh, Chang

    2013-10-03

    The primary objective of this research is to develop an extensive experimental database for the air- ingress phenomenon for the validation of computational fluid dynamics (CFD) analyses. This research is intended to be a separate-effects experimental study. However, the project team will perform a careful scaling analysis prior to designing a scaled-down test facility in order to closely tie this research with the real application. As a reference design in this study, the team will use the 600 MWth gas turbine modular helium reactor (GT-MHR) developed by General Atomic. In the test matrix of the experiments, researchers will vary the temperature and pressure of the helium— along with break size, location, shape, and orientation—to simulate deferent scenarios and to identify potential mitigation strategies. Under support of the Department of Energy, a high-temperature helium test facility has been designed and is currently being constructed at Ohio State University, primarily for high- temperature compact heat exchanger testing for the VHTR program. Once the facility is in operation (expected April 2009), this study will utilize high-temperature helium up to 900°C and 3 MPa for loss-of-coolant accident (LOCA) depressurization and air-ingress experiments. The project team will first conduct a scaling study and then design an air-ingress test facility. The major parameter to be measured in the experiments is oxygen (or nitrogen) concentration history at various locations following a LOCA scenario. The team will use two measurement techniques: 1) oxygen (or similar type) sensors employed in the flow field, which will introduce some undesirable intrusiveness, disturbing the flow, and 2) a planar laser-induced fluorescence (PLIF) imaging technique, which has no physical intrusiveness to the flow but requires a transparent window or test section that the laser beam can penetrate. The team will construct two test facilities, one for high-temperature helium tests with

  5. Experimental study of steam condensation on water in countercurrent flow in presence of inert gases

    NASA Astrophysics Data System (ADS)

    Bharathan, D.; Althof, J.

    1984-08-01

    Experimental results of investigating steam condensation on water in the presence of (noncondensable) inert gases at low temperatures and pressures relevant to open-cycle ocean thermal energy conversion (OTEC) systems are reported. Seven different condenser configurations were tested. The experimental data are correlated using a liquid flow fraction and a vent fraction to yield simple relationships of condenser performance over a wide range of test conditions. Performance maps and envelopes are provided for evaluating the relative merits of tested configurations. The height of transfer unit (HTU) for condensation ranges from 0.2 to 0.3 m among the various condenser geometries. Also reported are the pressure-loss coefficients for all the tested geometries.

  6. Countercurrent flow afterburner

    DOEpatents

    Leggett, Ronald L.; Presse, Donald E.; Smith, Carl J.; Teter, Alton R.

    1976-01-01

    Afterburner apparatus for receiving from an incinerator products of combustion and distributing them through a domed distributor in counterflow manner throughout a housing, in opposition to a stream of combustible gas.

  7. Counter-current motion in counter-current chromatography.

    PubMed

    Ito, Yoichiro

    2014-12-12

    After the CCC2012 meeting, I have received an e-mail regarding the terminology of "Countercurrent Chromatography". It stated that the term "Countercurrent" is a misnomer, because its stationary phase is motionless in the column and that the method should be renamed as liquid-liquid separations or centrifugal separations. However, it was found that these names are already used for various other techniques as found via Google search. The term "Countercurrent Chromatography" was originally made after two preparative methods of Countercurrent distribution and liquid Chromatography, both having no countercurrent motion in the column. However, it is surprising to find that this F1 hybrid method "Countercurrent Chromatography" can clearly exhibit countercurrent motion within the separation column in both hydrodynamic and hydrostatic equilibrium systems. This justifies that "Countercurrent Chromatography" is a proper term for this chromatographic method.

  8. Study of Co-Current and Counter-Current Gas-Liquid Two-Phase Flow Through Packed Bed in Microgravity

    NASA Astrophysics Data System (ADS)

    Revankar, Shripad T.

    2002-11-01

    The main goal of the project is to obtain new experimental data and development of models on the co-current and counter-current gas-liquid two-phase flow through a packed bed in microgravity and characterize the flow regime transition, pressure drop, void and interfacial area distribution, and liquid hold up. Experimental data will be obtained for earth gravity and microgravity conditions. Models will be developed for the prediction of flow regime transition, void fraction distribution and interfacial area concentration, which are key parameters to characterize the packed bed performance. Thus the specific objectives of the proposed research are to: (1) Develop experiments for the study of the gas liquid two-phase flow through the packed bed with three different flow combinations: co-current down flow, co-current upflow and counter current flow. (2) Develop pore scale and bed scale two-phase instrumentation for measurement of flow regime transition, void distribution and gas-liquid interfacial area concentration in the packed bed. (3) Obtain database on flow regime transition, pressure drop, void distribution, interfacial area concentration and liquid hold up as a function of bed characteristics such as bed particle size, porosity, and liquid properties such as viscosity and surface tension. (4) Develop mathematical model for flow regime transition, void fraction distribution and interfacial area concentration for co-current gas-liquid flow through the porous bed in gravity and micro gravity conditions.(4) Develop mathematical model for the flooding phenomena in counter-current gas-liquid flow through the porous bed in gravity and micro gravity conditions. The present proposal addresses the most important topic of HEDS-specific microgravity fluid physics research identified by NASA 's one of the strategic enterprises, OBPR Enterprise. The proposed project is well defined and makes efficient use of the ground-based parabolic flight research aircraft facility. The

  9. Exercise Ventilatory Limitation: The Role Of Expiratory Flow Limitation

    PubMed Central

    Babb, Tony G.

    2012-01-01

    Ventilatory limitation to exercise remains an important unresolved clinical issue; as a result, many individuals misinterpret the effects of expiratory flow limitation as an all-or-nothing phenomenon. Expiratory flow limitation is not all-or-none; approaching maximal expiratory flow can have important effects not only on ventilatory capacity but also on breathing mechanics, ventilatory control, and possibly exertional dyspnea and exercise intolerance. PMID:23038244

  10. Passive restriction of blood flow and counter-current heat exchange via lingual retia in the tongue of a neonatal gray whale Eschrichtius robustus (Cetacea, Mysticeti).

    PubMed

    Ekdale, Eric G; Kienle, Sarah S

    2015-04-01

    Retia mirabilia play broad roles in cetacean physiology, including thermoregulation during feeding and pressure regulations during diving. Vascular bundles of lingual retia are described within the base of the tongue of a neonatal female gray whale (Eschrichtius robustus). Each rete consists of a central artery surrounded by four to six smaller veins. The retia and constituent vessels decrease in diameter as they extend anteriorly within the hyoglossus muscle from a position anterior to the basihyal cartilage toward the apex of the tongue. The position of the retia embedded in the hyoglossus and the anterior constriction of the vessels differs from reports of similar vascular bundles that were previously identified in gray whales. The retia likely serve as a counter-current heat exchange system to control body temperature during feeding. Cold blood flowing toward the body center within the periarterial veins would accept heat from warm blood in the central artery flowing toward the anterior end of the tongue. Although thermoregulatory systems have been identified within the mouths of a few mysticete species, the distribution of such vascular structures likely is more widespread among baleen whales than has previously been described.

  11. A Laboratory Exercise Using a Physical Model for Demonstrating Countercurrent Heat Exchange

    ERIC Educational Resources Information Center

    Loudon, Catherine; Davis-Berg, Elizabeth C.; Botz, Jason T.

    2012-01-01

    A physical model was used in a laboratory exercise to teach students about countercurrent exchange mechanisms. Countercurrent exchange is the transport of heat or chemicals between fluids moving in opposite directions separated by a permeable barrier (such as blood within adjacent blood vessels flowing in opposite directions). Greater exchange of…

  12. Spiral Countercurrent Chromatography

    PubMed Central

    Ito, Yoichiro; Knight, Martha; Finn, Thomas M.

    2013-01-01

    For many years, high-speed countercurrent chromatography conducted in open tubing coils has been widely used for the separation of natural and synthetic compounds. In this method, the retention of the stationary phase is solely provided by the Archimedean screw effect by rotating the coiled column in the centrifugal force field. However, the system fails to retain enough of the stationary phase for polar solvent systems such as the aqueous–aqueous polymer phase systems. To address this problem, the geometry of the coiled channel was modified to a spiral configuration so that the system could utilize the radially acting centrifugal force. This successfully improved the retention of the stationary phase. Two different types of spiral columns were fabricated: the spiral disk assembly, made by stacking multiple plastic disks with single or four interwoven spiral channels connected in series, and the spiral tube assembly, made by inserting the tetrafluoroethylene tubing into a spiral frame (spiral tube support). The capabilities of these column assemblies were successfully demonstrated by separations of peptides and proteins with polar two-phase solvent systems whose stationary phases had not been well retained in the earlier multilayer coil separation column for high-speed countercurrent chromatography. PMID:23833207

  13. Holocinematographic velocimetry - Resolution limitation for flow measurement

    NASA Astrophysics Data System (ADS)

    Liburdy, James A.

    1987-10-01

    The goal of developing a holocinematographic velocimeter (HCV) is to provide a technique to study the evolution of instantaneous three-dimensional velocity profiles in turbulent flow fields. The method tracks individual seed particles that have been introduced into the flow. An imaging system using far-field holography is used to provide a full field of view tracking. Velocity information is determined from measured particle displacements of sequential hologram reconstruction. This study examines the resolution limits of far-field holography as applied to the HCV. The results aid in the determination of required seeding concentrations, establish the ability to resolve particle centers, and illustrate the use of a dual TV camera system to aid resolution. A straightforward enhancement technique provides a means to eliminate noise and reduce out of image plane ambiguity.

  14. Quantitation of countercurrent exchange during passive absorption from the dog small intestine: evidence for marked species differences in the efficiency of exchange.

    PubMed Central

    Bond, J H; Levitt, D G; Levitt, M D

    1977-01-01

    The present investigation was designed to quantitatively assess the possible influence of countercurrent exchange on passive absorption from the small intestine of the dog. Villus blood flow was measured with a modification of the microsphere method. Simultaneously, the absorption from the gut lumen of five diffusible gases (H2, He, CH4, 133Xe, and CO) was determined. Villus blood flow averaged 0.247 +/- 0.03 (SEM) ml/min per g. The observed absorption of H2, He, CH4, and 133Xe was only 16.2 +/- 1.8, 12.8 +/- 2.3, 12.0 +/- 1.8, and 15.8 +/- 1.4 %, respectively, of what this villus blood flow could carry away if it reached perfect equilibrium with the luminal gases. This low absorption rate could result from diffusion limitation to absorption or countercurrent exchange. The diffusive permeability of the barrier seperating the luminal gases and villus blood flow was assessed by measuring the absorption rate of CO. Because absorbed CO binds tightly to hemoglobin, it cannot exchange, and when present in low concentrations its uptake is entirely diffusion limited. Knowledge of the diffusion rate through tissue of the unbound gases relative to that of CO made it possible to calculate the degree to which each of the unbound gases should equilibrate with villus tip blood. The percentage equilibration between lumen and blood at the villus tip for H2, He, CH4, and 133Xe was 99.7, 99.9, 75.6, and 36.0% , respectively. Each of these values greatly exceeded the percentage equilibration of blood leaving the villus (calculated from the observed absorption rate and villus blood flow) and indicated an exchange of 83.8, 87.2, 84.1, and 56.1% of initially absorbed H2, He, CH4, and 133Xe. This result is in accord with theoretical calculations which suggest that countercurrent exchange should be exceedingly efficient in the dog. The striking effect of countercurrent exchange on passive absorption in the dog differs from our previous studies in the rabbit where no exchange was

  15. A laboratory exercise using a physical model for demonstrating countercurrent heat exchange.

    PubMed

    Loudon, Catherine; Davis-Berg, Elizabeth C; Botz, Jason T

    2012-03-01

    A physical model was used in a laboratory exercise to teach students about countercurrent exchange mechanisms. Countercurrent exchange is the transport of heat or chemicals between fluids moving in opposite directions separated by a permeable barrier (such as blood within adjacent blood vessels flowing in opposite directions). Greater exchange of heat or chemicals between the fluids occurs when the flows are in opposite directions (countercurrent) than in the same direction (concurrent). When a vessel loops back on itself, countercurrent exchange can occur between the two arms of the loop, minimizing loss or uptake at the bend of the loop. Comprehension of the physical principles underlying countercurrent exchange helps students to understand how kidneys work and how modifications of a circulatory system can influence the movement of heat or chemicals to promote or minimize exchange and reinforces the concept that heat and chemicals move down their temperature or concentration gradients, respectively. One example of a well-documented countercurrent exchanger is the close arrangement of veins and arteries inside bird legs; therefore, the setup was arranged to mimic blood vessels inside a bird leg, using water flowing inside tubing as a physical proxy for blood flow within blood vessels.

  16. Flow rate limitation in open capillary channel flows.

    PubMed

    Haake, Dennis; Rosendahl, Uwe; Ohlhoff, Antje; Dreyer, Michael E

    2006-09-01

    This paper reports the experimental and theoretical investigations of forced liquid flows through open capillary channels under reduced gravity conditions. An open capillary channel is a structure that establishes a liquid flow path at low Bond numbers, when the capillary pressure caused by the surface tension force dominates in comparison to the hydrostatic pressure induced by gravitational or residual accelerations. In case of steady flow through the channel, the capillary pressure of the free surface balances the pressure difference between the liquid and the surrounding constant-pressure gas phase. Because of convective and viscous momentum transport, the pressure along the flow path decreases and causes the free surface to bend inward. The maximum flow rate is achieved when the free surface collapses and gas ingestion occurs at the outlet. This critical flow rate depends on the geometry of the channel and the properties of the liquid. In this paper we present a comparison of the theoretical and experimental critical flow rates and surface profiles for convective dominated flows. For the prediction of the critical flow rate a one-dimensional theoretical model taking into account the entrance pressure loss and the frictional pressure loss in the channel is developed.

  17. Counter-current thermocapilllary migration of bubbles in microchannels using self-rewetting liquids

    NASA Astrophysics Data System (ADS)

    Nazareth, Robson; Saenz, Pedro; Valluri, Prashant; Sefiane, Khellil

    2015-11-01

    The study of bubble transport in microchannels is of great interest in evaporative cooling of microdevices technologies. This is because bubble transport under heat-transfer or phase-change causes several flow instabilities that are less understood and hinder informed design of microcooling devices. Bubble motion in microchannels under temperature gradients is highly influenced by thermocapillary forces due surface tension gradients. Most studies until now so far are mainly based on pure liquids which present a linear temperature (inverse) dependence of surface tension. In this work, we consider motion of a bubble (formed of inert gas) in the so-called self-rewetting fluid that presents a parabolic (quadratic) dependence of surface tension on temperature, in a temperature range that includes a surface tension minimum. We particularly investigate the counter-current thermocapillary migration of bubbles in these liquids, as experimentally depicted by Shanahan and Sefiane (2014), by means of direct numerical simulations. We present a model that solves the 3D governing equations of mass, momentum, interface and energy for the two-phase system composed by incompressible, Newtonian and immiscible fluids. We resolve the deformable interface by means of a Volume-of-Fluid method. Our results indicate that there exists a pressure drop limit beyond which there would be no counter-current migration of bubbles.

  18. Multifraction separation in countercurrent chromatography (MCSGP).

    PubMed

    Krättli, Martin; Müller-Späth, Thomas; Morbidelli, Massimo

    2013-09-01

    The multicolumn countercurrent solvent gradient purification (MCSGP) process is a continuous countercurrent multicolumn chromatography process capable of performing three fraction separations while applying a linear gradient of some modifier. This process can then be used either for the purification of a single species from a multicomponent mixture or to separate a three component mixture in one single operation. In this work, this process is extended to the separation of multifractions, in principle with no limitation. To achieve this goal the MCSGP standard process is extended by introducing one extra separation section per extra fraction to be isolated. Such an extra separation section is realized in this work through a single additional column, so that a n fraction MCSGP process can be realized using a minimum of n columns. Two separation processes were considered to experimentally demonstrate the possibility of realizing a four-fraction MCSGP unit able to purify two intermediate products in a given multicomponent mixture. The first one was a model mixture containing four different proteins. The two proteins eluting in the center of the chromatogram were purified with yields equal to 95% for the early eluting and 92% for the later eluting one. The corresponding purities were 94% and 97%, respectively. Such performance was well superior to that of the batch operation with the same modifier gradient which for the same purity values could not achieve yields larger than 67% and 81%, respectively. Similar performance improvements were found for the second separation where two out of seven charge variants which constitute the mAb Cetuximab currently available on the market have been purified in one single operation using a four-fraction MCSGP unit. In this case, yields of 81% and 65% were obtained with purities of 90% and 89%, respectively. These data compare well with the corresponding data from batch chromatography where with the same gradient and for the same

  19. Evaluation of a watershed model for estimating daily flow using limited flow measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Soil and Water Assessment Tool (SWAT) model was evaluated for estimation of continuous daily flow based on limited flow measurements in the Upper Oyster Creek (UOC) watershed. SWAT was calibrated against limited measured flow data and then validated. The Nash-Sutcliffe model Efficiency (NSE) and...

  20. An Activity Model to Demonstrate Countercurrent Exchange.

    ERIC Educational Resources Information Center

    Benner, D. B.

    1998-01-01

    Discusses the scant coverage in high school textbooks of countercurrent exchange for the efficient movement of molecules across biological membranes. Argues that this is one of the most intriguing of the physiological adaptive mechanisms. (DDR)

  1. Two-phase-flow models and their limitations

    SciTech Connect

    Ishii, M.; Kocamustafaogullari, G.

    1982-01-01

    An accurate prediction of transient two-phase flow is essential to safety analyses of nuclear reactors under accident conditions. The fluid flow and heat transfer encountered are often extremely complex due to the reactor geometry and occurrence of transient two-phase flow. Recently considerable progresses in understanding and predicting these phenomena have been made by a combination of rigorous model development, advanced computational techniques, and a number of small and large scale supporting experiments. In view of their essential importance, the foundation of various two-phase-flow models and their limitations are discussed in this paper.

  2. Interannual variability of the South Indian Countercurrent

    NASA Astrophysics Data System (ADS)

    Menezes, Viviane V.; Phillips, Helen E.; Vianna, Marcio L.; Bindoff, Nathaniel L.

    2016-05-01

    In the present work, we investigate the interannual variability of the South Indian Countercurrent (SICC), a major and still understudied current of the Indian Ocean circulation. To characterize the interannual variability of the SICC, four different data sets (altimetry, GLORYS, OFAM3, and SODA) are analyzed using multiple tools, which include Singular Spectrum Analysis and wavelet methods. The quasi-biennial band dominates the SICC low-frequency variance, with the main peak in the 1.5-1.8 year interval. A secondary peak (2.1-2.5 year) is only found in the western basin. Interannual and decadal-type modulations of the quasi-biennial signal are also identified. In addition, limitations of SODA before the 1960s in the SICC region are revealed. Within the quasi-biennial band, the SICC system presents two main patterns with a multiple jet structure. One pattern is characterized by a robust northern jet, while in the other the central jet is well developed and northern jet is weaker. In both patterns, the southern jet has always a strong signature. When the northern SICC jet is stronger, the northern cell of the subtropical gyre has a triangular shape, with its southern limb having a strong equatorward slant. The quasi-biennial variability of the SICC is probably related to the Indian Ocean tropical climate modes that are known to have a strong biennial characteristic.

  3. Estimating respiratory mechanics in the presence of flow limitation.

    PubMed

    Bijaoui, E; Tuck, S A; Remmers, J E; Bates, J H

    1999-01-01

    Dynamic collapse of the pulmonary airways, leading to flow limitation, is a significant event in a number of respiratory pathologies, including obstructive sleep apnea syndrome and chronic obstructive pulmonary disease. Quantitative evaluation of the mechanical status of the respiratory system in these conditions provides useful insights into airway caliber and tissue stiffness, which are hallmarks of such abnormalities. However, assessing respiratory mechanics in the presence of flow limitation is problematic because the single-compartment linear model on which most assessment methods are based is not valid over the entire breath. Indeed, even deciding which parts of a breath are flow limited from measurement of mouth flow and pleural pressure often proves to be difficult. In this study, we investigated the use of two approaches to assessing the overall mechanical properties of the respiratory system in the presence of inspiratory flow limitation. The first method is an adaptation of the classic Mead-Whittenberger method, and the second method is based on information-weighted histograms obtained from recursively estimated signals of respiratory resistance and elastance. We tested the methods on data simulated by using a computer model of the respiratory system and on data collected from obese sleeping pigs. We found that the information-weighted histograms provided the more robust overall estimates of respiratory mechanics.

  4. Purification of monoclonal antibodies from clarified cell culture fluid using Protein A capture continuous countercurrent tangential chromatography.

    PubMed

    Dutta, Amit K; Tran, Travis; Napadensky, Boris; Teella, Achyuta; Brookhart, Gary; Ropp, Philip A; Zhang, Ada W; Tustian, Andrew D; Zydney, Andrew L; Shinkazh, Oleg

    2015-11-10

    Recent studies using simple model systems have demonstrated that continuous countercurrent tangential chromatography (CCTC) has the potential to overcome many of the limitations of conventional Protein A chromatography using packed columns. The objective of this work was to optimize and implement a CCTC system for monoclonal antibody purification from clarified Chinese Hamster Ovary (CHO) cell culture fluid using a commercial Protein A resin. Several improvements were introduced to the previous CCTC system including the use of retentate pumps to maintain stable resin concentrations in the flowing slurry, the elimination of a slurry holding tank to improve productivity, and the introduction of an "after binder" to the binding step to increase antibody recovery. A kinetic binding model was developed to estimate the required residence times in the multi-stage binding step to optimize yield and productivity. Data were obtained by purifying two commercial antibodies from two different manufactures, one with low titer (∼ 0.67 g/L) and one with high titer (∼ 6.9 g/L), demonstrating the versatility of the CCTC system. Host cell protein removal, antibody yields and purities were similar to those obtained with conventional column chromatography; however, the CCTC system showed much higher productivity. These results clearly demonstrate the capabilities of continuous countercurrent tangential chromatography for the commercial purification of monoclonal antibody products.

  5. UV DRIVEN EVAPORATION OF CLOSE-IN PLANETS: ENERGY-LIMITED, RECOMBINATION-LIMITED, AND PHOTON-LIMITED FLOWS

    SciTech Connect

    Owen, James E.; Alvarez, Marcelo A.

    2016-01-01

    We have investigated the evaporation of close-in exoplanets irradiated by ionizing photons. We find that the properties of the flow are controlled by the ratio of the recombination time to the flow timescale. When the recombination timescale is short compared to the flow timescale, the flow is in approximate local ionization equilibrium with a thin ionization front where the photon mean free path is short compared to the flow scale. In this “recombination-limited” flow the mass-loss scales roughly with the square root of the incident flux. When the recombination time is long compared to the flow timescale the ionization front becomes thick and encompasses the entire flow with the mass-loss rate scaling linearly with flux. If the planet's potential is deep, then the flow is approximately “energy-limited”; however, if the planet's potential is shallow, then we identify a new limiting mass-loss regime, which we term “photon-limited.” In this scenario, the mass-loss rate is purely limited by the incoming flux of ionizing photons. We have developed a new numerical approach that takes into account the frequency dependence of the incoming ionizing spectrum and performed a large suite of 1D simulations to characterize UV driven mass-loss around low-mass planets. We find that the flow is “recombination-limited” at high fluxes but becomes “energy-limited” at low fluxes; however, the transition is broad occurring over several orders of magnitude in flux. Finally, we point out that the transitions between the different flow types do not occur at a single flux value but depend on the planet's properties, with higher-mass planets becoming “energy-limited” at lower fluxes.

  6. Scale invariance of subsurface flow patterns and its limitation

    NASA Astrophysics Data System (ADS)

    Hergarten, S.; Winkler, G.; Birk, S.

    2016-05-01

    Preferential flow patterns in the subsurface are of great importance for the availability and the quality of water resources. However, knowledge of their spatial structure is still behind their importance, so that understanding the nature of preferential flow patterns is a major issue in subsurface hydrology. Comparing the statistics of river catchment sizes and spring discharges, we found that the morphology of preferential subsurface flow patterns is probably scale invariant and similar to that of dendritic river networks. This result is not limited to karstic aquifers where the occurrence of dendritic structures has been known at least qualitatively for a long time. The scale invariance even seems to be independent of the lithology of the aquifer. However, scale invariance of river patterns seems to be only limited by the continental scale, while scale invariance of subsurface flow patterns breaks down at much smaller scales. The upper limit of scale invariance in subsurface flow patterns is highly variable. We found a range from thousands of square kilometers for limestone aquifers down to less than 1 km2 in the weathered zone and debris accumulations of crystalline rocks.

  7. Phase distribution visualisation in continuous counter-current extraction.

    PubMed

    van den Heuvel, Remco; Sutherland, Ian

    2009-05-08

    Flow visualisation is essential when trying to understand hydrodynamic equilibrium in continuous counter-current extraction (CCCE) (also known as dual-flow counter-current chromatography). The technique allows two immiscible liquid phases to be pumped through the spinning coil simultaneously in opposite directions. When this process was described previously it was assumed that the phases were evenly distributed throughout the coil. Visualisation studies by van den Heuvel and Sutherland in 2007 showed that this was not the case. A special centrifuge, where the coil is cantilevered so that the coil and the fluids inside the coil can be visualised, was used to study the distribution of the phases. Factorial experimental design was used to systematically study the effect of the starting conditions inside the coil on the phase distribution at equilibrium. For each experiment the eluted volumes and the volume of upper phase in the coil at the end of the experiment (at equilibrium) were recorded. In addition, two photographs were taken when the phases in the coil had reached equilibrium. One of these photographs was taken during the experiment when the phases were still being pumped through and one when the flow was stopped. The systematic experiments showed that the initial phase inside the coil has no effect on the phase distribution achieved at equilibrium. Statistical analysis also showed that the lower phase flow rate has double the effect on the phase distribution compared to the upper phase flow rate. From these visualisation studies, it can be concluded that the balance of the phases flowing through the coil at equilibrium is complex. The volumes of upper and lower phase and how they are distributed does influence the separation. It is important therefore to understand the relationship between respective flow rates and the phase distribution if peak elution is to be accurately predicted.

  8. Correlation of Normal Gravity Mixed Convection Blowoff Limits with Microgravity Forced Flow Blowoff Limits

    NASA Technical Reports Server (NTRS)

    Marcum, Jeremy W.; Olson, Sandra L.; Ferkul, Paul V.

    2016-01-01

    The axisymmetric rod geometry in upward axial stagnation flow provides a simple way to measure normal gravity blowoff limits to compare with microgravity Burning and Suppression of Solids - II (BASS-II) results recently obtained aboard the International Space Station. This testing utilized the same BASS-II concurrent rod geometry, but with the addition of normal gravity buoyant flow. Cast polymethylmethacrylate (PMMA) rods of diameters ranging from 0.635 cm to 3.81 cm were burned at oxygen concentrations ranging from 14 to 18% by volume. The forced flow velocity where blowoff occurred was determined for each rod size and oxygen concentration. These blowoff limits compare favorably with the BASS-II results when the buoyant stretch is included and the flow is corrected by considering the blockage factor of the fuel. From these results, the normal gravity blowoff boundary for this axisymmetric rod geometry is determined to be linear, with oxygen concentration directly proportional to flow speed. We describe a new normal gravity 'upward flame spread test' method which extrapolates the linear blowoff boundary to the zero stretch limit in order to resolve microgravity flammability limits-something current methods cannot do. This new test method can improve spacecraft fire safety for future exploration missions by providing a tractable way to obtain good estimates of material flammability in low gravity.

  9. On the Asymptotic Limit of Flows Past a Ribbed Boundary

    NASA Astrophysics Data System (ADS)

    Bucur, Dorin; Feireisl, Eduard; Nečasová, Šárka

    2008-11-01

    We consider a stationary Navier-Stokes flow in a bounded domain supplemented with the complete slip boundary conditions. Assuming the boundary of the domain is formed by a family of unidirectional asperities, whose amplitude as well as frequency is proportional to a small parameter ɛ, we shall show that in the asymptotic limit the motion of the fluid is governed by the same system of the Navier-Stokes equations, however, the limit boundary conditions are different. Specifically, the resulting boundary conditions prevent the fluid from slipping in the direction of asperities, while the motion in the orthogonal direction is allowed without any constraint.

  10. Physiological techniques for detecting expiratory flow limitation during tidal breathing.

    PubMed

    Koulouris, N G; Hardavella, G

    2011-09-01

    Patients with severe chronic obstructive pulmonary disease (COPD) often exhale along the same flow-volume curve during quiet breathing as they do during the forced expiratory vital capacity manoeuvre, and this has been taken as an indicator of expiratory flow limitation at rest (EFL(T)). Therefore, EFL(T), namely attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. EFL(T) leads to small airway injury and promotes dynamic pulmonary hyperinflation, with concurrent dyspnoea and exercise limitation. In fact, EFL(T) occurs commonly in COPD patients (mainly in Global Initiative for Chronic Obstructive Lung Disease III and IV stage), in whom the latter symptoms are common, but is not exclusive to COPD, since it can also be detected in other pulmonary and nonpulmonary diseases like asthma, acute respiratory distress syndrome, heart failure and obesity, etc. The existing up to date physiological techniques of assessing EFL(T) are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, noninvasive, practical and accurate new technique.

  11. Solvent System Selection Strategies in Countercurrent Separation

    PubMed Central

    Liu, Yang; Friesen, J. Brent; McAlpine, James B.; Pauli, Guido F.

    2015-01-01

    The majority of applications in countercurrent and centrifugal partition chromatography, collectively known as countercurrent separation, are dedicated to medicinal plant and natural product research. In countercurrent separation, the selection of the appropriate solvent system is of utmost importance as it is the equivalent to the simultaneous choice of column and eluent in liquid chromatography. However, solvent system selection is often laborious, involving extensive partition and/or analytical trials. Therefore, simplified solvent system selection strategies that predict the partition coefficients and, thus, analyte behavior are in high demand and may advance both the science of countercurrent separation and its applications. The last decade of solvent system selection theory and applications are critically reviewed, and strategies are classified according to their data input requirements. This offers the practitioner an up-to-date overview of rationales and methods for choosing an efficient solvent system, provides a perspective regarding their accuracy, reliability, and practicality, and discusses the possibility of combining multiple methods for enhanced prediction power. PMID:26393937

  12. Limiting photocurrent analysis of a wide channel photoelectrochemical flow reactor

    NASA Astrophysics Data System (ADS)

    Davis, Jonathan T.; Esposito, Daniel V.

    2017-03-01

    The development of efficient and scalable photoelectrochemical (PEC) reactors is of great importance for the eventual commercialization of solar fuels technology. In this study, we systematically explore the influence of convective mass transport and light intensity on the performance of a 3D-printed PEC flow cell reactor based on a wide channel, parallel plate geometry. Using this design, the limiting current density generated from the hydrogen evolution reaction at a p-Si metal–insulator–semiconductor (MIS) photocathode was investigated under varied reactant concentration, fluid velocity, and light intensity. Additionally, a simple model is introduced to predict the range of operating conditions (reactant concentration, light intensity, fluid velocity) for which the photocurrent generated in a parallel plate PEC flow cell is limited by light absorption or mass transport. This model can serve as a useful guide for the design and operation of wide-channel PEC flow reactors. The results of this study have important implications for PEC reactors operating in electrolytes with dilute reactant concentrations and/or under high light intensities where high fluid velocities are required in order to avoid operation in the mass transport-limited regime.

  13. Inert gas clearance from tissue by co-currently and counter-currently arranged microvessels.

    PubMed

    Lu, Y; Michel, C C; Wang, W

    2012-08-01

    To elucidate the clearance of dissolved inert gas from tissues, we have developed numerical models of gas transport in a cylindrical block of tissue supplied by one or two capillaries. With two capillaries, attention is given to the effects of co-current and counter-current flow on tissue gas clearance. Clearance by counter-current flow is compared with clearance by a single capillary or by two co-currently arranged capillaries. Effects of the blood velocity, solubility, and diffusivity of the gas in the tissue are investigated using parameters with physiological values. It is found that under the conditions investigated, almost identical clearances are achieved by a single capillary as by a co-current pair when the total flow per tissue volume in each unit is the same (i.e., flow velocity in the single capillary is twice that in each co-current vessel). For both co-current and counter-current arrangements, approximate linear relations exist between the tissue gas clearance rate and tissue blood perfusion rate. However, the counter-current arrangement of capillaries results in less-efficient clearance of the inert gas from tissues. Furthermore, this difference in efficiency increases at higher blood flow rates. At a given blood flow, the simple conduction-capacitance model, which has been used to estimate tissue blood perfusion rate from inert gas clearance, underestimates gas clearance rates predicted by the numerical models for single vessel or for two vessels with co-current flow. This difference is accounted for in discussion, which also considers the choice of parameters and possible effects of microvascular architecture on the interpretation of tissue inert gas clearance.

  14. Novel Design for Centrifugal Countercurrent Chromatography: I. Zigzag Toroidal Column

    PubMed Central

    Yang, Yi; Aisa, Haji Akber; Ito, Yoichiro

    2009-01-01

    The toroidal coil using an equilateral triangular core has improved both retention of the stationary phase and peak resolution of the conventional toroidal coil in centrifugal countercurrent chromatography. To further improve the retention of stationary phase and peak resolution, a novel zigzag toroidal coil was designed and the performance of the system was evaluated at various flow rates. The results indicated that both retention of stationary phase and peak resolution were improved as the flow rate was decreased. Modification of the tubing by pressing at given intervals with a pair of pliers improved the peak resolution without increasing the column pressure. All these separations were performed under low column pressure indicating the separation can be further improved by increasing the column length and/or revolution speed without damaging the separation column. PMID:20046954

  15. Efficient methods for isolating five phytochemicals from Gentiana macrophylla using high-performance countercurrent chromatography.

    PubMed

    Rho, Taewoong; Jung, Mila; Lee, Min Won; Chin, Young-Won; Yoon, Kee Dong

    2016-12-01

    Efficient high-performance countercurrent chromatography methods were developed to isolate five typical compounds from the extracts of Gentiana macrophylla. n-Butanol-soluble extract of G. macrophylla contained three hydrophilic iridoids, loganic acid (1), swertiamarin (2) and gentiopicroside (3), and a chromene derivative, macrophylloside D (4) which were successfully isolated by flow rate gradient (1.5 mL/min in 0-60 min, 5.0 mL/min in 60-120 min), and consecutive flow rate gradient HPCCC using n-butanol/0.1% aqueous trifluoroacetic acid (1:1, v/v, normal phase mode) system. The yields of 1-4 were 22, 16, 122, and 6 mg, respectively, with purities over 97% in a flow rate gradient high-performance countercurrent chromatography, and consecutive flow rate gradient high-performance countercurrent chromatography gave 1, 2, 3 (54, 41, 348 mg, respectively, purities over 97%) and 4 (13 mg, purity at 95%) from 750 mg of sample. The main compound in methylene chloride soluble extract, 2-methoxyanofinic acid, was successfully separated by n-hexane/ethyl acetate/methanol/water (4:6:4:6, v/v/v/v, flow-rate: 4 mL/min, reversed phase mode) condition. The structures of five isolates were elucidated by (1) H, (13) C NMR and ESI-Q-TOF-MS spectroscopic data which were compared with previously reported values.

  16. Flow Analysis on a Limited Volume Chilled Water System

    SciTech Connect

    Zheng, Lin

    2012-07-31

    LANL Currently has a limited volume chilled water system for use in a glove box, but the system needs to be updated. Before we start building our new system, a flow analysis is needed to ensure that there are no high flow rates, extreme pressures, or any other hazards involved in the system. In this project the piping system is extremely important to us because it directly affects the overall design of the entire system. The primary components necessary for the chilled water piping system are shown in the design. They include the pipes themselves (perhaps of more than one diameter), the various fitting used to connect the individual pipes to form the desired system, the flow rate control devices (valves), and the pumps that add energy to the fluid. Even the most simple pipe systems are actually quite complex when they are viewed in terms of rigorous analytical considerations. I used an 'exact' analysis and dimensional analysis considerations combined with experimental results for this project. When 'real-world' effects are important (such as viscous effects in pipe flows), it is often difficult or impossible to use only theoretical methods to obtain the desired results. A judicious combination of experimental data with theoretical considerations and dimensional analysis are needed in order to reduce risks to an acceptable level.

  17. Speed limit and ramp meter control for traffic flow networks

    NASA Astrophysics Data System (ADS)

    Goatin, Paola; Göttlich, Simone; Kolb, Oliver

    2016-07-01

    The control of traffic flow can be related to different applications. In this work, a method to manage variable speed limits combined with coordinated ramp metering within the framework of the Lighthill-Whitham-Richards (LWR) network model is introduced. Following a 'first-discretize-then-optimize' approach, the first order optimality system is derived and the switch of speeds at certain fixed points in time is explained, together with the boundary control for the ramp metering. Sequential quadratic programming methods are used to solve the control problem numerically. For application purposes, experimental setups are presented wherein variable speed limits are used as a traffic guidance system to avoid traffic jams on highway interchanges and on-ramps.

  18. Inspiratory duty cycle responses to flow limitation predict nocturnal hypoventilation.

    PubMed

    Schneider, H; Krishnan, V; Pichard, L E; Patil, S P; Smith, P L; Schwartz, A R

    2009-05-01

    Upper airway obstruction (UAO) can elicit neuromuscular responses that mitigate and/or compensate for the obstruction. It was hypothesised that flow-limited breathing elicits specific timing responses that can preserve ventilation due to increases in inspiratory duty cycle rather than respiratory rate. By altering nasal pressure during non-rapid eye movement (non-REM) sleep, similar degrees of UAO were induced in healthy males and females (n = 10 each). Inspiratory duty cycle, respiratory rate and minute ventilation were determined for each degree of UAO during non-REM sleep and compared with the baseline nonflow-limited condition. A dose-dependent increase in the inspiratory duty cycle and respiratory rate was observed in response to increasing severity of UAO. Increases in the inspiratory duty cycle, but not respiratory rate, helped to acutely maintain ventilation. Heterogeneity in these responses was associated with variable degrees of ventilatory compensation, allowing for the segregation of individuals at risk for hypoventilation during periods of inspiratory airflow limitation. Upper airway obstruction constitutes a unique load on the respiratory system. The inspiratory duty cycle, but not the respiratory rate, determine the individual's ability to compensate for inspiratory airflow limitation during sleep, and may represent a quantitative phenotype for obstructive sleep apnoea susceptibility.

  19. Countercurrent direct contact heat exchange process and system

    DOEpatents

    Wahl, III, Edward F.; Boucher, Frederic B.

    1979-01-01

    Recovery of energy from geothermal brines and other hot water sources by direct contact heat exchange with a working fluid, such as a hydrocarbon working fluid, e.g. isobutane. The process and system consists of a plurality of stages, each stage including mixing and settling units. In the first stage, hot brine and arm working fluid are intimately mixed and passed into a settler wherein the brine settles to the bottom of the settler and the hot working fluid rises to the top. The hot working fluid is passed to a heat engine or turbine to produce work and the working fluid is then recycled back into the system. The system is comprised of a series of stages each containing a settler and mixer, and wherein the working fluid and the brine flow in a countercurrent manner through the stages to recover the heat from the brine in increments and raise the temperature of the working fluid in increments.

  20. Expiratory flow limitation and obstruction in the elderly.

    PubMed

    de Bisschop, C; Marty, M L; Tessier, J F; Barberger-Gateau, P; Dartigues, J F; Guénard, H

    2005-10-01

    Elderly people commonly suffer from dyspnoea, which may stem from expiratory flow limitation (EFL). The relationship between EFL, as assessed by the negative expiratory pressure method and spirometric indices, was investigated in an elderly French population. Subjects, aged 66-88 yrs, filled in socio-demographic and standardised questionnaires, which dealt with: medical history, smoking status and respiratory symptoms. EFL measurements and forced expiratory manoeuvres were performed. Validated measurements were obtained in 750 out of 1,318 subjects: 47% were EFL+ (EFL >0), with a higher prevalence in females than in males. EFL and forced expiratory volume in one second (FEV1) were correlated with age. A total of 116, from the 750 subjects, with no medical history and no symptoms, served as a healthy group. The prevalence of EFL+ subjects increased with the grade of dyspnoea and was highest in respiratory and cardiac patients when compared with the healthy subjects. EFL did not correlate with FEV1/forced vital capacity (FVC), the usual index of obstruction. Some elderly subjects (15%) with dyspnoea but with no medical history, mainly females with small FVC and normal FEV1/FVC, had a greater EFL than the healthy subjects. In elderly people, expiratory flow limitation measurements, along with the usual forced expiratory volume in one second/ forced vital capacity ratio, may be of value for the interpretation of dyspnoea.

  1. Countercurrent Separation of Natural Products: An Update

    PubMed Central

    2015-01-01

    This work assesses the current instrumentation, method development, and applications in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CCS). The article provides a critical review of the CCS literature from 2007 since our last review (J. Nat. Prod.2008, 71, 1489–1508), with a special emphasis on the applications of CCS in natural products research. The current state of CCS is reviewed in regard to three continuing topics (instrumentation, solvent system development, theory) and three new topics (optimization of parameters, workflow, bioactivity applications). The goals of this review are to deliver the necessary background with references for an up-to-date perspective of CCS, to point out its potential for the natural product scientist, and thereby to induce new applications in natural product chemistry, metabolome, and drug discovery research involving organisms from terrestrial and marine sources. PMID:26177360

  2. Countercurrent Separation of Natural Products: An Update.

    PubMed

    Friesen, J Brent; McAlpine, James B; Chen, Shao-Nong; Pauli, Guido F

    2015-07-24

    This work assesses the current instrumentation, method development, and applications in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CCS). The article provides a critical review of the CCS literature from 2007 since our last review (J. Nat. Prod. 2008, 71, 1489-1508), with a special emphasis on the applications of CCS in natural products research. The current state of CCS is reviewed in regard to three continuing topics (instrumentation, solvent system development, theory) and three new topics (optimization of parameters, workflow, bioactivity applications). The goals of this review are to deliver the necessary background with references for an up-to-date perspective of CCS, to point out its potential for the natural product scientist, and thereby to induce new applications in natural product chemistry, metabolome, and drug discovery research involving organisms from terrestrial and marine sources.

  3. Dysanapsis ratio as a predictor for expiratory flow limitation.

    PubMed

    Smith, Joshua R; Rosenkranz, Sara K; Harms, Craig A

    2014-07-01

    To determine the efficacy of the dysanapsis ratio (DR) in predicting expiratory flow limitation during exercise, 146 subjects (73 men, 73 women) performed standard pulmonary function and maximal incremental exercise tests. Tidal flow-volume loops were recorded at maximal exercise with maximal flow-volume loops measured pre- and post-exercise. Men had larger (p<0.05) lung volumes, flow rates, and V˙O2max compared to women, but DR was similar (0.21±0.05 vs. 0.20±0.06, respectively, p>0.05). V˙O2max was not different (p>0.05) between the EFL subjects compared to the non-EFL subjects for both men and women. Men with EFL compared to non-EFL men had smaller FVC (5.16±0.89L vs. 5.67±0.86L, p<0.05) and DR (0.19±0.05 vs. 0.23±0.04, p<0.05). Similarly, women with EFL compared to non-EFL had significantly smaller DR (0.18±0.05 vs. 0.24±0.05), but similar FVC (3.88±0.52 vs. 4.12±0.64, p>0.05). A DR threshold was not determined; however, a DR continuum exists with increasing DR leading to decreased prevalence of EFL. In conclusion, DR is effective in determining the likelihood of EFL at maximal exercise.

  4. Peak-counts blood flow model-errors and limitations

    SciTech Connect

    Mullani, N.A.; Marani, S.K.; Ekas, R.D.; Gould, K.L.

    1984-01-01

    The peak-counts model has several advantages, but its use may be limited due to the condition that the venous egress may not be negligible at the time of peak-counts. Consequently, blood flow measurements by the peak-counts model will depend on the bolus size, bolus duration, and the minimum transit time of the bolus through the region of interest. The effect of bolus size on the measurement of extraction fraction and blood flow was evaluated by injecting 1 to 30ml of rubidium chloride in the femoral vein of a dog and measuring the myocardial activity with a beta probe over the heart. Regional blood flow measurements were not found to vary with bolus sizes up to 30ml. The effect of bolus duration was studied by injecting a 10cc bolus of tracer at different speeds in the femoral vein of a dog. All intravenous injections undergo a broadening of the bolus duration due to the transit time of the tracer through the lungs and the heart. This transit time was found to range from 4-6 second FWHM and dominates the duration of the bolus to the myocardium for up to 3 second injections. A computer simulation has been carried out in which the different parameters of delay time, extraction fraction, and bolus duration can be changed to assess the errors in the peak-counts model. The results of the simulations show that the error will be greatest for short transit time delays and for low extraction fractions.

  5. Space-charge-limited flow in quantum regime

    NASA Astrophysics Data System (ADS)

    Ang, Lay Kee

    2005-10-01

    Space-charge-limited (SCL) flow has been an area of active research in the development of non-neutral plasma physics, high current diodes, high power microwave sources, vacuum microelectronics and sheath physics. According to the classical Child-Langmuir (CL) law for the planar diodes, the current density scales as 3/2's power of gap voltage and to the inverse squared power of gap spacing. In the past decade, there have been renewed interests in extending the classical CL law to multi-dimensional models both numerically and analytically. The study of SCL flow in quantum regime has also attracted considerable interests in the past 3 years [1-3]. With the recent advances in nanotechnology, electron beam with very high current density may be transported in a nano-scale gap with a relatively low gap voltage. In this new operating regime, where the electron wavelength is comparable or larger than the gap spacing, the quantum effects become important. In this talk, the quantum theory of CL law will be introduced to reveal that the classical CL law is enhanced by a large factor due to electron tunneling and exchange-correlation effects, and there is a new quantum scaling for the current density, which is proportional to the 1/2's power of gap voltage, and to the inverse fourth-power of gap spacing [1-2]. Quasi-2D and 3D models with finite emission area will be shown [3]. We will also show that the classical properties of the SCL flow such as bipolar flow, beam-loaded capacitance, transit time and noise will require a complete revision in the quantum regime. The implications of the emission law of Fowler-Nordheim in the presence of intense space charge over the nanometer scale will be discussed.[1] L. K. Ang, T. J. T. Kwan, and Y. Y. Lau, ``New Scaling of Child-Langmuir Law in the Quantum Regime,'' Phys. Rev. Lett. 91, 208303 (2003). [2] L. K. Ang, Y. Y. Lau, and T. J. T. Kwan, ``Simple Derivation of Quantum Scaling in Child-Langmuir law,'' IEEE Trans Plasma Sci. 32, 410

  6. Two-zone countercurrent smelter system and process

    DOEpatents

    Cox, James H.; Fruehan, Richard J.; Elliott, deceased, John F.

    1995-01-01

    A process for continuously smelting iron ore by use of coal to yield molten iron or semi-steel is disclosed. The process comprises the steps of establishing a melt covered by slag; inducing the slag and the molten iron to flow countercurrently to one another, toward opposite ends of the smelter; maintaining iron oxide-reducing conditions in that zone of the smelter towards which the slag flows; maintaining carbon-oxidizing conditions in that zone of the smelter towards which the molten iron flows; continuously or semicontinuously tapping the slag from the reducing zone end of the smelter; continuously or semicontinuously tapping the molten iron from the oxidizing zone end of the smelter; and adding to both zones iron ore, coal, oxygen, and flux at addition rates sufficient to keep the molten iron in the reducing zone substantially saturated with carbon, maintain in the slag being tapped an FeO content of about 5 weight percent or less, and maintain in the molten iron being tapped a carbon content of about 0.5 to 5 weight percent. A slag dam preferably is included in the smelter, to impede the backflow of the slag from the reducing zone to the oxidizing zone. A metal bath dam with one or more flow-through portals also is preferably used, submerged below the slag dam, to impede the backflow of the hot metal.

  7. Two-zone countercurrent smelter system and process

    DOEpatents

    Cox, J.H.; Fruehan, R.J.; Elliott, J.F.

    1995-01-03

    A process for continuously smelting iron ore by use of coal to yield molten iron or semi-steel is disclosed. The process comprises the steps of establishing a melt covered by slag; inducing the slag and the molten iron to flow countercurrently to one another, toward opposite ends of the smelter; maintaining iron oxide-reducing conditions in that zone of the smelter towards which the slag flows; maintaining carbon-oxidizing conditions in that zone of the smelter towards which the molten iron flows; continuously or semicontinuously tapping the slag from the reducing zone end of the smelter; continuously or semicontinuously tapping the molten iron from the oxidizing zone end of the smelter; and adding to both zones iron ore, coal, oxygen, and flux at addition rates sufficient to keep the molten iron in the reducing zone substantially saturated with carbon, maintain in the slag being tapped an FeO content of about 5 weight percent or less, and maintain in the molten iron being tapped a carbon content of about 0.5 to 5 weight percent. A slag dam preferably is included in the smelter, to impede the backflow of the slag from the reducing zone to the oxidizing zone. A metal bath dam with one or more flow-through portals also is preferably used, submerged below the slag dam, to impede the backflow of the hot metal. 8 figures.

  8. Expiratory flow limitation in morbidly obese postoperative mechanically ventilated patients.

    PubMed

    Koutsoukou, A; Koulouris, N; Bekos, B; Sotiropoulou, C; Kosmas, E; Papadima, K; Roussos, C

    2004-10-01

    Although obesity promotes tidal expiratory flow limitation (EFL), with concurrent dynamic hyperinflation (DH), intrinsic PEEP (PEEPi) and risk of low lung volume injury, the prevalence and magnitude of EFL, DH and PEEPi have not yet been studied in mechanically ventilated morbidly obese subjects. In 15 postoperative mechanically ventilated morbidly obese subjects, we assessed the prevalence of EFL [using the negative expiratory pressure (NEP) technique], PEEPi, DH, respiratory mechanics, arterial oxygenation and PEEPi inequality index as well as the levels of PEEP required to abolish EFL. In supine position at zero PEEP, 10 patients exhibited EFL with a significantly higher PEEPi and DH and a significantly lower PEEPi inequality index than found in the five non-EFL (NEFL) subjects. Impaired gas exchange was found in all cases without significant differences between the EFL and NEFL subjects. Application of 7.5 +/- 2.5 cm H2O of PEEP (range: 4-16) abolished EFL with a reduction of PEEPi and DH and an increase in FRC and the PEEPi inequality index but no significant effect on gas exchange. The present study indicates that: (a) on zero PEEP, EFL is present in most postoperative mechanically ventilated morbidly obese subjects; (b) EFL (and concurrent risk of low lung volume injury) is abolished with appropriate levels of PEEP; and (c) impaired gas exchange is common in these patients, probably mainly due to atelectasis.

  9. Countercurrent distribution of biological cells

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.

    1979-01-01

    A neutral polymer phase system consisting of 7.5 percent dextran 40/4.5 percent PEG 6, 0.11 M Na phosphate, 5 percent fetal bovine serum (FBS), pH 7.5, was developed which has a high phase droplet electrophoretic mobility and retains cell viability over many hours. In this and related systems, the drop mobility was a linear function of drop size, at least in the range 4-30 micron diameter. Applications of and electric field of 4.5 v/cm to a system containing 10 percent v/v bottom phase cleared the system more than two orders of magnitude faster than in the absence of the field. At higher bottom phase concentrations a secondary phenomenon intervened in the field driven separations which resulted in an increase in turbidity after clearing had commenced. The increase was associated with a dilution of the phase system in the chamber. The effect depended on the presence of the electric field. It may be due to electroosmotic flow of buffer through the Amicon membranes into the sample chamber and flow of phase system out into the rinse stream. Strategies to eliminate this problem are proposed.

  10. Applications and limitations of a rheology for granular flows

    NASA Astrophysics Data System (ADS)

    Cawthorn, Chris; Hinch, John; Huppert, Herbert

    2007-11-01

    In order to assess the validity of the rheological law for granular flows proposed by Jop, Pouliquen and Forterre [Nature, vol. 441, pp.727-730], we present its application to a number of different problems. Whilst it works well for steady flow on a confined sandpile, or in an inclined channel, we will show that the law fails to qualitatively predict flow some simple geometries, such as annular Couette flow and vertical chute flow. In addition, we consider perturbations to 2D flow on an inclined plane and 3D flow in an inclined channel, where the effect of the confining vertical walls becomes important. Implications for the use of Jop's rheology for more complicated problems, particularly those involving dam-break or column collapse will also be addressed.

  11. Maximal oxygen uptake validation in children with expiratory flow limitation.

    PubMed

    Robben, Katherine E; Poole, David C; Harms, Craig A

    2013-02-01

    A two-test protocol (incremental/ramp (IWT) + supramaximal constant-load (CWR)) to affirm max and obviate reliance on secondary criteria has only been validated in highly fit children. In girls (n = 15) and boys (n = 12) with a wide range of VO2max (17-47 ml/kg/min), we hypothesized that this procedure would evince a VO2-WR plateau and unambiguous VO2max even in the presence of expiratory flow limitation (EFL). A plateau in the VO2-work rate relationship occurred in 75% of subjects irrespective of EFL There was a range in RER at max exercise for girls (0.97-1.14; mean 1.06 ± 0.04) and boys (0.98-1.09; mean 1.03 ± 0.03) such that 3/15 girls and 2/12 boys did not achieve the criterion RER. Moreover, in girls with RER > 1.0 it would have been possible to achieve this criterion at 78% VO2max. Boys achieved 92% VO2max at RER = 1.0. This was true also for HRmax where 8/15 girls' and 6/12 boys' VO2max would have been rejected based on HRmax being < 90% of age-predicted HRmax. In those who achieved the HRmax criterion, it represented a VO2 of 86% (girls) and 87% (boys) VO2max. We conclude that this two-test protocol confirms VO2max in children across a threefold range of VO2max irrespective of EFL and circumvents reliance on secondary criteria.

  12. Countercurrent distribution of biological cells

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.

    1982-01-01

    Detailed physiochemical studies of dextran/poly(ethylene glycol) (PEG) two phase systems were carried out to characterize and provide understanding of the properties of the systems which determine cell partition and the electrophoretic behavior of phase drops responsible for electric field driven phase separation. A detailed study of the electrostatic and electrokinetic potentials developed in these systems was carried out. The salt partition was examined both in phase systems and with pure polymer solutions via equilibrium dialysis and mechanism of sulfate, chloride and phosphate partition shown to be exclusion by PEG rather than binding by dextran. Salt partition was shown to have a strong effect on the polymer compositions of the phases as well, an effect which produces large changes in the interfacial tension between them. These effects were characterized and the interfacial tension shown to obey a power law with respect to its dependence on the length of the tie line describing the system composition on a phase diagram. The electrostatic potential differences measured via salt bridges were shown to obey thermodynamic predictions. The electrophoretic mobilities measured were utilized to provide a partial test of Levine's incomplete theory of phase drop electrophoresis. The data were consistent with Levine's expression over a limited range of the variables tested.

  13. Countercurrent fixed-bed gasification of biomass at laboratory scale

    SciTech Connect

    Di Blasi, C.; Signorelli, G.; Portoricco, G.

    1999-07-01

    A laboratory-scale countercurrent fixed-bed gasification plant has been designed and constructed to produce data for process modeling and to compare the gasification characteristics of several biomasses (beechwood, nutshells, olive husks, and grape residues). The composition of producer gas and spatial temperature profiles have been measured for biomass gasification at different air flow rates. The gas-heating value always attains a maximum as a function of this operating variable, associated with a decrease of the air-to-fuel ratio. Optical gasification conditions of wood and agricultural residues give rise to comparable gas-heating values, comprised in the range 5--5.5 MJ/Nm{sup 3} with 28--30% CO, 5--7% CO{sub 2}, 6--8% H{sub 2}, 1--2% CH{sub 4}, and small amounts of C{sub 2}- hydrocarbons (apart from nitrogen). However, gasification of agricultural residues is more difficult because of bed transport, partial ash sintering, nonuniform flow distribution, and the presence of a muddy phase in the effluents, so that proper pretreatments are needed for largescale applications.

  14. Capillarity-driven flows at the continuum limit.

    PubMed

    Vincent, Olivier; Szenicer, Alexandre; Stroock, Abraham D

    2016-08-21

    We experimentally investigate the dynamics of capillary-driven flows at the nanoscale, using an original platform that combines nanoscale pores (⋍3 nm in diameter) and microfluidic features. In particular, we show that drying involves a fine coupling between thermodynamics and fluid mechanics that can be used to generate precisely controlled nanoflows driven by extreme stresses - up to 100 MPa of tension. We exploit these tunable flows to provide quantitative tests of continuum theories (e.g. Kelvin-Laplace equation and Poiseuille flow) across an unprecedented range and we isolate the breakdown of continuum as a negative slip length of molecular dimension. Our results show a coherent picture across multiple experiments including drying-induced permeation flows, imbibition and poroelastic transients.

  15. Nonlocal rheological properties of granular flows near a jamming limit

    NASA Astrophysics Data System (ADS)

    Aranson, Igor S.; Tsimring, Lev S.; Malloggi, Florent; Clément, Eric

    2008-09-01

    We study the rheology of sheared granular flows close to a jamming transition. We use the approach of partially fluidized theory (PFT) with a full set of equations extending the thin layer approximation derived previously for the description of the granular avalanches phenomenology. This theory provides a picture compatible with a local rheology at large shear rates [G. D. R. Midi, Eur. Phys. J. E 14, 341 (2004)] and it works in the vicinity of the jamming transition, where a description in terms of a simple local rheology comes short. We investigate two situations displaying important deviations from local rheology. The first one is based on a set of numerical simulations of sheared soft two-dimensional circular grains. The next case describes previous experimental results obtained on avalanches of sandy material flowing down an incline. Both cases display, close to jamming, significant deviations from the now standard Pouliquen’s flow rule [O. Pouliquen, Phys. Fluids 11, 542 (1999); 11, 1956 (1999)]. This discrepancy is the hallmark of a strongly nonlocal rheology and in both cases, we relate the empirical results and the outcomes of PFT. The numerical simulations show a characteristic constitutive structure for the fluid part of the stress involving the confining pressure and the material stiffness that appear in the form of an additional dimensionless parameter. This constitutive relation is then used to describe the case of sandy flows. We show a quantitative agreement as far as the effective flow rules are concerned. A fundamental feature is identified in PFT as the existence of a jammed layer developing in the vicinity of the flow arrest that corroborates the experimental findings. Finally, we study the case of solitary erosive granular avalanches and relate the outcome with the PFT analysis.

  16. Capillarity-driven flows at the continuum limit

    NASA Astrophysics Data System (ADS)

    Vincent, Olivier; Szenicer, Alexandre; Stroock, Abraham D.

    We experimentally investigate the dynamics of capillary-driven flows at the nanoscale, using an original platform that combines nanoscale pores and microfluidic features. Our results show a coherent picture across multiple experiments including imbibition, poroelastic transient flows, and a drying-based method that we introduce. In particular, we exploit extreme drying stresses - up to 100 MPa of tension - to drive nanoflows and provide quantitative tests of continuum theories of fluid mechanics and thermodynamics (e.g. Kelvin-Laplace equation) across an unprecedented range. We isolate the breakdown of continuum as a negative slip length of molecular dimension.

  17. Robust design of binary countercurrent adsorption separation processes

    SciTech Connect

    Storti, G. ); Mazzotti, M.; Morbidelli, M.; Carra, S. )

    1993-03-01

    The separation of a binary mixture, using a third component having intermediate adsorptivity as desorbent, in a four section countercurrent adsorption separation unit is considered. A procedure for the optimal and robust design of the unit is developed in the frame of Equilibrium Theory, using a model where the adsorption equilibria are described through the constant selectivity stoichiometric model, while mass-transfer resistances and axial mixing are neglected. By requiring that the unit achieves complete separation, it is possible to identify a set of implicity constraints on the operating parameters, that is, the flow rate ratios in the four sections of the unit. From these constraints explicit bounds on the operating parameters are obtained, thus yielding a region in the operating parameters space, which can be drawn a priori in terms of the adsorption equilibrium constants and the feed composition. This result provides a very convenient tool to determine both optimal and robust operating conditions. The latter issue is addressed by first analyzing the various possible sources of disturbances, as well as their effect on the separation performance. Next, the criteria for the robust design of the unit are discussed. Finally, these theoretical findings are compared with a set of experimental results obtained in a six port simulated moving bed adsorption separation unit operated in the vapor phase.

  18. Reciprocal symmetry plots as a representation of countercurrent chromatograms.

    PubMed

    Friesen, J Brent; Pauli, Guido F

    2007-03-15

    Traditionally, chromatograms in countercurrent chromatography (CCC) have been plotted with retention volume or time on the x-axis. However, the distribution constant (K) is a more appropriate, reproducible value for the x-axis, because it is a physicochemical property of a particular analyte in a particular solvent system. Therefore, K is independent of both the total column volume and the stationary-phase volume ratio (SF) of the column. Going one step beyond simple K plots, the reciprocal symmetry (ReS) plot, with K and 1/K positioned on either side of a line of symmetry on the x-axis, represents all K values, zero to infinity. Based on experimental evidence, using a mixture of CCC reference standards, the ReS plot demonstrates both the invertible and "symmetric" nature of CCC, a consequence of the exchange of the mobile and stationary phases by reversing the direction of the flow and the symmetry of the liquid-liquid partitioning process between two immiscible phases, respectively. Moreover, the interval of optimal resolution can be centered on the ReS plot to focus on K values of interest, establishing the reciprocal shifted symmetry (ReSS) plots in CCC. Improved representation of peak shape across the whole CCC polarity range is an added advantage of ReSS plots over both K and classical retention volume plots.

  19. Scale invariance of subsurface flow patterns and its limitation

    NASA Astrophysics Data System (ADS)

    Hergarten, Stefan; Winkler, Gerfried; Birk, Steffen

    2015-04-01

    The morphology of river networks at the Earth's surface has been addressed in numerous studies. Numerical simulations of fluvial erosion processes and concepts of optimization have provided a rather comprehensive understanding about the scale invariance of river networks. Less is known about the structure of preferential flow patterns in the subsurface because these are only accessible by indirect measurements in most cases. As preferential flow patterns are crucial for all transport processes in the subsurface, unraveling their structure is a major challenge in subsurface hydrology. Transferring the idea of optimization from surface flow to subsurface flow it was recently suggested that preferential subsurface flow patterns should also have a dendritic, scale-invariant structure similar to that of river networks. In this study we analyzed the mean discharges of serval thousand springs with respect to scale invariance. For this purpose we reanalyzed a data set comprising about 17,000 springs from Spain already published in the literature and three new data sets from the Eastern Alps in Austria. We found that the probability density f(Q) of the discharge distribution can be described by a power law with an exponential cutoff, f(Q) ≈ Q-τe- QQc. The scaling exponent τ was found to be about 1.6, which is slightly larger than the exponent τ = 1.5 of river networks. In contrast to rivers, the distributions of the spring discharges are characterized by a significant cutoff at large discharges. This cutoff strongly depends on the lithology of the aquifers, while the scaling exponent τ ˜ 1.6 seems to be universal. The highest cutoff was found for limestones being one of the primary host rocks for karstic aquifers. We found Qc ˜ 6000 l/s for the limestones in the data set from Spain, suggesting a scale-invariant subsurface flow pattern up to catchment sizes of several thousand square kilometers. At the other edge, we found a cutoff at catchment sizes in the order of

  20. Ground Testing for Hypervelocity Flow, Capabilities and Limitations

    DTIC Science & Technology

    2010-03-29

    NOTES See also ADA569031. Aerothermodynamic Design, Review on Ground Testing and CFD (Conception aerothermodynamique, revue sur les essais au sol et...reservoir enthalpy corresponding to a flow speed of 6 km/s is 18 MJ/kg, which, at a reservoir pressure of 100 MPa, implies a temperature of nearly 9000 K...in air. The high pressure is necessary to ensure that the chemical reaction rates occur at the right speed for correct simulation of nonequilibrium

  1. Endocannabinoids Control Platelet Activation and Limit Aggregate Formation under Flow

    PubMed Central

    De Angelis, Valentina; Koekman, Arnold C.; Weeterings, Cees; Roest, Mark; de Groot, Philip G.; Herczenik, Eszter; Maas, Coen

    2014-01-01

    Background The endocannabinoid system has previously been implicated in the regulation of neurons and inflammatory cells. Additionally, it has been reported that endocannabinoid receptors are present on circulating platelets, but there has been conflicting evidence on their contribution to platelet function. Objectives Our aim was to examine the role of endocannabinoids in platelet function in vitro and in vivo. Methods and Results We studied the effects of the well-characterized endogenous endocannabinoid anandamide on platelet aggregation in suspension, α-granule release, calcium mobilization, Syk phosphorylation, as well as platelet spreading and aggregate formation under flow. Anandamide inhibits platelet aggregation and α-granule release by collagen, collagen-derived peptide CRP-XL, ADP, arachidonic acid and thromboxane A2 analogue U46619. However, activation via thrombin receptor PAR-1 stays largely unaffected. Calcium mobilization is significantly impaired when platelets are stimulated with collagen or CRP-XL, but remains normal in the presence of the other agonists. In line with this finding, we found that anandamide prevents collagen-induced Syk phosphorylation. Furthermore, anandamide-treated platelets exhibit reduced spreading on immobilized fibrinogen, have a decreased capacity for binding fibrinogen in solution and show perturbed platelet aggregate formation under flow over collagen. Finally, we investigated the influence of Cannabis sativa consumption by human volunteers on platelet activation. Similar to our in vitro findings with anandamide, ex vivo collagen-induced platelet aggregation and aggregate formation on immobilized collagen under flow were impaired in whole blood of donors that had consumed Cannabis sativa. Conclusions Endocannabinoid receptor agonists reduce platelet activation and aggregate formation both in vitro and ex vivo after Cannabis sativa consumption. Further elucidation of this novel regulatory mechanism for platelet function

  2. Preconditioning and the limit to the incompressible flow equations

    NASA Technical Reports Server (NTRS)

    Turkel, E.; Fiterman, A.; Vanleer, B.

    1993-01-01

    The use of preconditioning methods to accelerate the convergence to a steady state for both the incompressible and compressible fluid dynamic equations are considered. The relation between them for both the continuous problem and the finite difference approximation is also considered. The analysis relies on the inviscid equations. The preconditioning consists of a matrix multiplying the time derivatives. Hence, the steady state of the preconditioned system is the same as the steady state of the original system. For finite difference methods the preconditioning can change and improve the steady state solutions. An application to flow around an airfoil is presented.

  3. Pluto's Polygonal Terrain Places Lower Limit on Planetary Heat Flow

    NASA Astrophysics Data System (ADS)

    Trowbridge, A.; Steckloff, J. K.; Melosh, H., IV; Freed, A. M.

    2015-12-01

    During its recent flyby of Pluto, New Horizons imaged an icy plains region (Sputnik Planum) whose surface is divided into polygonal blocks, ca. 20-30 km across, bordered by what appear to be shallow troughs. The lack of craters within these plains suggests they are relatively young, implying that the underlying material is recently active. The scale of these features argues against an origin by cooling and contraction. Here we investigate the alternative scenario that they are the surface manifestation of shallow convection in a thick layer of nitrogen ice. Typical Rayleigh-Bernard convective cells are approximately three times wider than the depth of the convecting layer, implying a layer depth of ca. 7-10 km. Our convection hypothesis requires that the Rayleigh number exceed a minimum of about 1000 in the nitrogen ice layer. We coupled a parameterized convection model with a temperature dependent rheology of nitrogen ice (Yamashita, 2008), finding a Rayleigh number 1500 to 7500 times critical for a plausible range of heat flows for Pluto's interior. The computed range of heat flow (3.5-5.2 mW/m2) is consistent with the radiogenic heat generated by a carbonaceous chondrite (CC) core implied by Pluto's bulk density. The minimum heat flow at the critical Rayleigh number is 0.13 mW/m2. Our model implies a core temperature of 44 K in the interior of the convecting layer. This is very close to the exothermic β-α phase transition in nitrogen ice at 35.6 K (for pure N2 ice; dissolved CO can increase this, depending on its concentration), suggesting that the warm cores of the rising convective cells may be β phase, whereas the cooler sinking limbs may be α phase. This transition may thus be observable due to the large difference in their spectral signature. Further applying our model to Pluto's putative water ice mantle, the heat flow from CC is consistent with convection in Pluto's mantle and the activity observed on its surface.

  4. Mean flow stability wave models for coherent structures in open shear flows: experimental assessment of potentials and limitations

    NASA Astrophysics Data System (ADS)

    Oberleithner, Kilian; Rukes, Lothar; Paschereit, Oliver; Soria, Julio

    2014-11-01

    We report on a number of experimental and theoretical investigations of shear flow instabilities in jet flows. In these studies, linear stability analysis is employed to the time-averaged flow taken from experiments, contrasting the ``classic'' stability approach that is based on a stationary base flow. The eigenmodes of the time-averaged flow are considered as models for the nonlinearly saturated state of the instability waves. The accuracy of these models is validated through a detailed comparison with experiments. In this talk we outline the potential and limitation of these flow models for convectively and globally unstable jet flows. The first author was supported by a fellowship within the Postdoc-Program of the German Academic Exchange Service (DAAD). The support of the Australian Research Council (ARC) and the German Research Foundation (DFG) is greatfully acknowledged.

  5. Design and optimization of a back-flow limiter for the high performance light water reactor

    SciTech Connect

    Fischer, Kai; Laurien, Eckart; Claas, Andreas G.; Schulenberg, Thomas

    2007-07-01

    Design and Analysis of a back-flow limiter are presented, which is implemented as a safety device in the four inlet lines of the Reactor Pressure Vessel (RPV) of the High Performance Light Water Reactor (HPLWR). As a passive component, the back-flow limiter has no moving parts and belongs to the group of fluid diodes. It has low flow resistance for regular operation condition and a high flow resistance when the flow direction is reversed which is the case if a break of the feedwater line occurs. The increased flow resistance is due to a substantially increased swirl for reverse flow condition. The design is optimized employing 1D flow analyses in combination with 3D CFD analyses with respect to geometrical modifications, like the nozzle shape and swirler angles. (authors)

  6. The dynamic connection of the Indonesian Throughflow, South Indian Ocean Countercurrent and the Leeuwin Current

    NASA Astrophysics Data System (ADS)

    Lambert, E.; Le Bars, D.; de Ruijter, W. P. M.

    2015-09-01

    East of Madagascar, wind and surface buoyancy fluxes reinforce each other, leading to frontogenesis, outcrop and an eastward along-front flow: the South Indian Ocean Countercurrent (SICC). In the east the Leeuwin Current (LC) is a unique eastern boundary current which flows poleward along Australia. It is often described as a regional coastal current forced by an off-shore meridional density gradient or a sea surface slope, yet little is known of the forcing and dynamics that control these open ocean meridional gadients. To complete this understanding, we make use of both an ocean general circulation model and a conceptual two-layer model. The SICC impinges on west Australia and adds to a sea level slope and a southward geostrophic coastal jet: the Leeuwin Current. The SICC and the LC are thus dynamically connected. An observed transport maximum of the LC around 22° S is directly related to this impingement of the SICC. The circulation of the Indonesian Throughflow (ITF) through the Indian Ocean appears to be partly trapped in the upper layer north of the outcrop line and is redirected along this outcrop line to join the eastward flow of the SICC. Shutdown of the ITF in both models strongly decreases the Leeuwin Current transport and breaks the connection between the LC and SICC. In this case, most of the SICC was found to reconnect to the internal gyre circulation in the Indian Ocean. The Indonesian Throughflow, South Indian Ocean Countercurrent and the Leeuwin Current are thus dynamically coupled.

  7. Binary concepts and standardization in counter-current separation technology.

    PubMed

    Friesen, J B; Pauli, G F

    2009-05-08

    Counter-current separation (CS) technology is currently faced with the challenge of being fit for the purpose of omics analysis, which involves highly complex samples and digitized research environments. Resembling a network of binary decisions, CS requires standardization of operation parameters in order to be efficient. While recent CS engineering solutions uniformly involve centrifugal force designs to overcome the limitation of the earth's 1xg force, factors of instrument design, operation, and graphical representation of the outcome are equally important targets for standardization. For example, chromatograms that emphasize the unique K-based nature of CS, such as reciprocal symmetry (ReS) plots, foster the fundamental understanding of CS operation. Because significant differences exist in underlying mechanism (e.g., stationary phase volume), outcome (e.g., construction of chromatograms), and scale (e.g., factors affecting overall method sensitivity) of solid-liquid vs. liquid-liquid chromatography technologies, standardization will enable the systematic exploration of the differential properties of the two LC technologies, and will be key to making CS fit for the digital omics age.

  8. A model-based method for flow limitation analysis in the heterogeneous human lung.

    PubMed

    Polak, Adam G

    2008-02-01

    Flow limitation in the airways is a fundamental process constituting the maximal expiratory flow-volume curve. Its location is referred to as the choke point. In this work, expressions enabling the calculation of critical flows in the case of wave-speed, turbulent or viscous limitation were derived. Then a computational model for the forced expiration from the heterogeneous lung was used to analyse the regime and degree of flow limitation as well as movement and arrangement of the choke points. The conclusion is that flow limitation begins at similar time in every branch of the bronchial tree developing a parallel arrangement of the choke points. A serial configuration of flow-limiting sites is possible for short time periods in the case of increased airway heterogeneity. The most probable locations of choke points are the regions of airway junctions. The wave-speed mechanism is responsible for flow choking over most of vital capacity and viscous dissipation of pressure for the last part of the test. Turbulent dissipation, however, may play a significant role as a supporting factor in transition between wave-speed and viscous flow limitation.

  9. Singular Limits in a Model of Radiative Flow

    NASA Astrophysics Data System (ADS)

    Ducomet, Bernard; Nečasová, Šárka

    2015-06-01

    We consider a "semi-relativistic" model of radiative viscous compressible Navier-Stokes-Fourier system coupled to the radiative transfer equation extending the classical model introduced in Ducomet et al. (Ann Inst Henri Poincarè AN 28:797-812, 2011) and we study some of its singular limits (low Mach and diffusion) in the case of well-prepared initial data and Dirichlet boundary condition for the velocity field. In the low Mach number case we prove the convergence toward the incompressible Navier-Stokes system coupled to a system of two stationary transport equations. In the diffusion case we prove the convergence toward the compressible Navier-Stokes with modified state functions (equilibrium case) or toward the compressible Navier-Stokes coupled to a diffusion equation (non equilibrium case).

  10. Countercurrent soil washing system for remediation of viscous hydrocarbons, heavy metals, radionuclides

    SciTech Connect

    Kuhlman, M.I.; Karlsson, M.K.; Downie, C.A.

    1995-12-31

    Drying augers and multicell DAF tanks are excellent machines in which to countercurrently wash soil and remove hazardous hydrocarbons, metals or radionuclides. An auger works well because it preferentially moves soil along one side of its trough. Thus, when enough high pressure and temperature water jets are placed along that path, contaminants can be melted, or dissolved and scoured from the soil. Contaminants and fines flow down the opposite side of the auger and out for extraction in a series of flotation tanks. Countercurrent washing of the silt results when soil settles in tanks through rising water and air bubbles then is pumped through cyclones placed above the next DAF tank of the series. LNAPLs, DNAPLs, or metallic contaminants made hydrophobic by chemicals in the system are removed at the overflow of the cyclones or by flotation in the tanks. The overflow from the cyclones and DAF tanks flows into the previous tank of the series. Examples of contaminants remediated include; arsenic, cadmium, lead and mercury, Naturally Occurring Radioactive Materials (NORM), uranium, solid oils, polyaromatic hydrocarbons in creosote and coal tars, and polychlorinated hydrocarbons.

  11. Pleistocene dynamics of the Pacific South Equatorial Countercurrent

    NASA Astrophysics Data System (ADS)

    Nuernberg, D.; Raddatz, J.; Rippert, N.; Tiedemann, R.

    2014-12-01

    The Western Pacific Warm Pool (WPWP) with extremely high sea-surface-temperatures (SST) is a key area for global climate. It also acts as a crossroad for mode and intermediate water masses such as the South Equatorial Countercurrent (SECC) transporting water masses originating from higher latitudes. The SECC flows above the main thermocline and strongly interacts with the Intertropical Convergence Zone (ITCZ) and South Pacific Convergence Zone (SPCZ). To constrain changes in sea-surface and subsurface water mass dynamics affecting thermocline depth, we reconstruct SST, subSST and salinity conditions using combined δ18O and Mg/Ca signals of surface (Globigerinoides ruber, Globigerinoides sacculifer) and subsurface dwelling (Globorotalia tumida) planktonic foraminifera. Our study is based on RV SONNE SO-225 piston cores retrieved from Manihiki plateau, which is located at the southeastern margin of the WPWP (between ~ 5°S-15°S and 170-160°W). The proxy records cover the last ~ 3 Myr SSTMg/Ca remained nearly constant throughout the entire Pleistocene varying between ~30 to 32 (°C), while the subSSTMg/Ca reconstructions reveal pronounced variations from ~10 to 16 (°C). Our results imply that the WPWP thermocline depth has undergone significant vertical movements throughout the Pleistocene. Notably, thermocline depth is continuously decreasing from the early to the late Pleistocene, and coincides with the change from the 41 kyr to a dominant 100 kyr climate periodicity between 1 and 1.7 Ma. We hypothesize that the repeated change in thermocline depth is due to either 1) changes in mode or intermediate water masses advection from Southern Ocean sources via "ocean tunneling", 2) changes in the tropical Pacific wind regime, and/or 3) changes in the Western Pacific Monsoon sytem.

  12. Use of partition coefficients in flow-limited physiologically-based pharmacokinetic modeling.

    PubMed

    Thompson, Matthew D; Beard, Daniel A; Wu, Fan

    2012-08-01

    Permeability-limited two-subcompartment and flow-limited, well-stirred tank tissue compartment models are routinely used in physiologically-based pharmacokinetic modeling. Here, the permeability-limited two-subcompartment model is used to derive a general flow-limited case of a two-subcompartment model with the well-stirred tank being a specific case where tissue fractional blood volume approaches zero. The general flow-limited two-subcompartment model provides a clear distinction between two partition coefficients typically used in PBPK: a biophysical partition coefficient and a well-stirred partition coefficient. Case studies using diazepam and cotinine demonstrate that, when the well-stirred tank is used with a priori predicted biophysical partition coefficients, simulations overestimate or underestimate total organ drug concentration relative to flow-limited two-subcompartment model behavior in tissues with higher fractional blood volumes. However, whole-body simulations show predicted drug concentrations in plasma and lower fractional blood volume tissues are relatively unaffected. These findings point to the importance of accurately determining tissue fractional blood volume for flow-limited PBPK modeling. Simulations using biophysical and well-stirred partition coefficients optimized with flow-limited two-subcompartment and well-stirred models, respectively, lead to nearly identical fits to tissue drug distribution data. Therefore, results of whole-body PBPK modeling with diazepam and cotinine indicate both flow-limited models are appropriate PBPK tissue models as long as the correct partition coefficient is used: the biophysical partition coefficient is for use with two-subcompartment models and the well-stirred partition coefficient is for use with the well-stirred tank model.

  13. Euglossine bees mediate only limited long-distance gene flow in a tropical vine.

    PubMed

    Opedal, Øystein H; Falahati-Anbaran, Mohsen; Albertsen, Elena; Armbruster, W Scott; Pérez-Barrales, Rocío; Stenøien, Hans K; Pélabon, Christophe

    2017-03-01

    Euglossine bees (Apidae: Euglossini) have long been hypothesized to act as long-distance pollinators of many low-density tropical plants. We tested this hypothesis by the analysis of gene flow and genetic structure within and among populations of the euglossine bee-pollinated vine Dalechampia scandens. Using microsatellite markers, we assessed historical gene flow by the quantification of regional-scale genetic structure and isolation by distance among 18 populations, and contemporary gene flow by the estimation of recent migration rates among populations. To assess bee-mediated pollen dispersal on a smaller scale, we conducted paternity analyses within a focal population, and quantified within-population spatial genetic structure in four populations. Gene flow was limited to certain nearby populations within continuous forest blocks, whereas drift appeared to dominate on larger scales. Limited long-distance gene flow was supported by within-population patterns; gene flow was biased towards nearby plants, and significant small-scale spatial genetic structure was detected within populations. These findings suggest that, although female euglossine bees might be effective at moving pollen within populations, and perhaps within forest blocks, their contribution to gene flow on the regional scale seems too limited to counteract genetic drift in patchily distributed tropical plants. Among-population gene flow might have been reduced following habitat fragmentation.

  14. Bifurcations of limit cycles in open and closed loop reverse flow reactors

    NASA Astrophysics Data System (ADS)

    Russo, Lucia; Crescitelli, Silvestro; Brasiello, Antonio

    2013-10-01

    The present work analyses the bifurcations of limit cycles in open and loop reverse flow reactors. The open loop system consists of a reactor where the flow direction is periodically forced whereas in the closed loop system, the flow inversion is dictated by a control law which activates when the temperature at the edge of catalytic bed falls below the set-point value. We performed the bifurcation analysis of the open loop system as the switch time is varied and we constructed the solution diagram through the application of continuation technique. Many Naimark-Sacker bifurcations leading to quasi-periodic regimes have been found on the limit cycles branches. Finally, we compared these limit cycles with those of the closed loop system where the flow inversion is dictated by a control system which acts if the temperature measured at the edge of reactor falls below a set-point value.

  15. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Ren, J.; Zuo, G. Z.; Hu, J. S.; Sun, Z.; Yang, Q. X.; Li, J. G.; Zakharov, L. E.; Xie, H.; Chen, Z. X.

    2015-02-01

    A program involving the extensive and systematic use of lithium (Li) as a "first," or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak—both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST.

  16. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Ren, J.; Zuo, G. Z.; Hu, J. S.; Sun, Z.; Yang, Q. X.; Li, J. G.; Xie, H.; Chen, Z. X.; Zakharov, L. E.

    2015-02-15

    A program involving the extensive and systematic use of lithium (Li) as a “first,” or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak—both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST.

  17. A flowing liquid lithium limiter for the Experimental Advanced Superconducting Tokamak.

    PubMed

    Ren, J; Zuo, G Z; Hu, J S; Sun, Z; Yang, Q X; Li, J G; Zakharov, L E; Xie, H; Chen, Z X

    2015-02-01

    A program involving the extensive and systematic use of lithium (Li) as a "first," or plasma-facing, surface in Tokamak fusion research devices located at Institute of Plasma Physics, Chinese Academy of Sciences, was started in 2009. Many remarkable results have been obtained by the application of Li coatings in Experimental Advanced Superconducting Tokamak (EAST) and liquid Li limiters in the HT-7 Tokamak-both located at the institute. In furtherance of the lithium program, a flowing liquid lithium (FLiLi) limiter system has been designed and manufactured for EAST. The design of the FLiLi limiter is based on the concept of a thin flowing film which was previously tested in HT-7. Exploiting the capabilities of the existing material and plasma evaluation system on EAST, the limiter will be pre-wetted with Li and mechanically translated to the edge of EAST during plasma discharges. The limiter will employ a novel electro-magnetic pump which is designed to drive liquid Li flow from a collector at the bottom of limiter into a distributor at its top, and thus supply a continuously flowing liquid Li film to the wetted plasma-facing surface. This paper focuses on the major design elements of the FLiLi limiter. In addition, a simulation of incoming heat flux has shown that the distribution of heat flux on the limiter surface is acceptable for a future test of power extraction on EAST.

  18. Counter-current thermocapillary migration of bubbles in self-rewetting liquids

    NASA Astrophysics Data System (ADS)

    Nazareth, R.; Saenz, P.; Sefiane, K.; Kim, J.; Valluri, P.

    2016-11-01

    In this work, we study the counter-current thermocapillary propulsion of a suspended bubble in the fluid flowing inside a channel subject to an axial temperature gradient when the surface tension dependence on temperature is non-monotonic. We use direct numerical simulations to address the two-phase conservation of mass, momentum and energy with a volume-of-fluid method to resolve the deformable interface. Two distinct regimes of counter-current bubble migration are characterized: i) "exponential decay" where the bubble decelerates rapidly until it comes to a halt at the spatial position corresponding to the minimum surface tension and ii) "sustained oscillations" where the bubble oscillates about the point of minimum surface tension. We illustrate how these sustained oscillations arise at low capillary number O(10-5) and moderate Reynolds number O(10) and, they are dampened by viscosity at lower Reynolds number. These results are in agreement with the experiments by Shanahan and Sefiane (Sci. Rep. 4, 2014). The work was supported by the Science without Borders program from CAPES agency of Brazilian Ministry of Education and the European Commission's Thermapower Project (294905).

  19. Do Sverdrup transports account for the Pacific North Equatorial Countercurrent

    SciTech Connect

    Meyers, G.

    1980-02-20

    Poleward and equatorward geostrophic transports calculated from density are nearly equal to Sverdrup transports calculated from the curl of the wind stress in the North and South Pacific subtropical gyres. But the Sverdrup transports do not account for the Pacific North Equatorial Countercurrent.

  20. Counter-current carbon dioxide extraction of soy skim

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of carbon dioxide in a counter-current fractionation column was investigated as a means to remove residual fat from soy skim after enzyme-assisted aqueous extraction of soybeans. The stainless steel column was 1.2 meters long with an internal diameter of 1.75 cm and filled protruded stainles...

  1. Inspiratory Flow Limitation in a Normal Population of Adults in São Paulo, Brazil

    PubMed Central

    Palombini, Luciana O.; Tufik, Sergio; Rapoport, David M.; Ayappa, Indu A.; Guilleminault, Christian; de Godoy, Luciana B. M.; Castro, Laura S.; Bittencourt, Lia

    2013-01-01

    Study Objectives: Inspiratory flow limitation (IFL) during sleep occurs when airflow remains constant despite an increase in respiratory effort. This respiratory event has been recognized as an important parameter for identifying sleep breathing disorders. The purpose of this study was to investigate how much IFL normal individuals can present during sleep. Design: Cross-sectional study derived from a general population sample. Setting: A “normal” asymptomatic sample derived from the epidemiological cohort of São Paulo. Patients and Participants: This study was derived from a general population study involving questionnaires and nocturnal polysomnography of 1,042 individuals. A subgroup defined as a nonsymptomatic healthy group was used as the normal group. Interventions: N/A. Measurements and Results: All participants answered several questionnaires and underwent full nocturnal polysomnography. IFL was manually scored, and the percentage of IFL of total sleep time was considered for final analysis. The distribution of the percentage of IFL was analyzed, and associated factors (age, sex, and body mass index) were calculated. There were 95% of normal individuals who exhibited IFL during less than 30% of the total sleep time. Body mass index was positively associated with IFL. Conclusions: Inspiratory flow limitation can be observed in the polysomnography of normal individuals, with an influence of body weight on percentage of inspiratory flow limitation. However, only 5% of asymptomatic individuals will have more than 30% of total sleep time with inspiratory flow limitation. This suggests that only levels of inspiratory flow limitation > 30% be considered in the process of diagnosing obstructive sleep apnea in the absence of an apnea-hypopnea index > 5 and that < 30% of inspiratory flow limitation may be a normal finding in many patients. Citation: Palombini LO; Tufik S; Rapoport DM; Ayappa IA; Guilleminault C; de Godoy LBM; Castro LS; Bittencourt L

  2. Mixer-settler counter-current chromatography with multiple spiral disk assembly.

    PubMed

    Ito, Yoichiro; Clary, Robert; Sharpnak, Frank; Metger, Howard; Powell, Jimmie

    2007-11-23

    A novel system for performing high-speed counter-current chromatography has been developed for separation of biopolymers using polymer phase systems. The spiral disk assembly consisting of eight units, each equipped with over 300 mixer-settler sets, was constructed and performance evaluated in terms of retention of the stationary phase and separation efficiency. A series of experiments was performed with a polymer phase system composed of polyethylene glycol 1000 (12.5%, w/w) and dibasic potassium phosphate (12.5%, w/w) using two stable protein samples of myoglobin and lysozyme at various experimental conditions of flow rates and revolution speeds. The best results were obtained with revolution speeds of 800-1000rpm at flow rates of 0.25-0.5ml/min where the partition efficiency of several 100 theoretical plates was achieved with over 50% stationary phase retention.

  3. Flow motifs reveal limitations of the static framework to represent human interactions

    NASA Astrophysics Data System (ADS)

    Rocha, Luis E. C.; Blondel, Vincent D.

    2013-04-01

    Networks are commonly used to define underlying interaction structures where infections, information, or other quantities may spread. Although the standard approach has been to aggregate all links into a static structure, some studies have shown that the time order in which the links are established may alter the dynamics of spreading. In this paper, we study the impact of the time ordering in the limits of flow on various empirical temporal networks. By using a random walk dynamics, we estimate the flow on links and convert the original undirected network (temporal and static) into a directed flow network. We then introduce the concept of flow motifs and quantify the divergence in the representativity of motifs when using the temporal and static frameworks. We find that the regularity of contacts and persistence of vertices (common in email communication and face-to-face interactions) result on little differences in the limits of flow for both frameworks. On the other hand, in the case of communication within a dating site and of a sexual network, the flow between vertices changes significantly in the temporal framework such that the static approximation poorly represents the structure of contacts. We have also observed that cliques with 3 and 4 vertices containing only low-flow links are more represented than the same cliques with all high-flow links. The representativity of these low-flow cliques is higher in the temporal framework. Our results suggest that the flow between vertices connected in cliques depend on the topological context in which they are placed and in the time sequence in which the links are established. The structure of the clique alone does not completely characterize the potential of flow between the vertices.

  4. Mass transfer in thin films under counter-current gas: experiments and numerical study

    NASA Astrophysics Data System (ADS)

    Lucquiaud, Mathieu; Lavalle, Gianluca; Schmidt, Patrick; Ausner, Ilja; Wehrli, Marc; O Naraigh, Lennon; Valluri, Prashant

    2016-11-01

    Mass transfer in liquid-gas stratified flows is strongly affected by the waviness of the interface. For reactive flows, the chemical reactions occurring at the liquid-gas interface also influence the mass transfer rate. This is encountered in several technological applications, such as absorption units for carbon capture. We investigate the absorption rate of carbon dioxide in a liquid solution. The experimental set-up consists of a vertical channel where a falling film is sheared by a counter-current gas flow. We measure the absorption occurring at different flow conditions, by changing the liquid solution, the liquid flow rate and the gas composition. With the aim to support the experimental results with numerical simulations, we implement in our level-set flow solver a novel module for mass transfer taking into account a variant of the ghost-fluid formalism. We firstly validate the pure mass transfer case with and without hydrodynamics by comparing the species concentration in the bulk flow to the analytical solution. In a final stage, we analyse the absorption rate in reactive flows, and try to reproduce the experimental results by means of numerical simulations to explore the active role of the waves at the interface.

  5. An analysis of small target feature detection limits using optic flow

    NASA Astrophysics Data System (ADS)

    Conroy, Joseph; Gremillion, Gregory; Mathis, Allison; Nothwang, William

    2015-05-01

    The neurophysiology of insects suggests that they are able to track conspecifics, which manifest as small targets, against a variety of backgrounds with ease. This perception occurs at the same stage as motion perception suggesting a role for optic flow in target discrimination. Optic flow also is an attractive method of perception for visual system design due to the possibility of parallel processing that lends itself to implementation in hardware acceleration. This paper investigates some of the limits for reliable target discrimination solely from an optic flow field which are dependent on algorithm parameters, the nature of the target, and imager noise properties.

  6. Methods for Assessing Expiratory Flow Limitation during Tidal Breathing in COPD Patients.

    PubMed

    Koulouris, Nickolaos G; Kaltsakas, Georgios; Palamidas, Anastasios F; Gennimata, Sofia-Antiopi

    2012-01-01

    Patients with severe COPD often exhale along the same flow-volume curve during quite breathing as during forced expiratory vital capacity manoeuvre, and this has been taken as indicating expiratory flow limitation at rest (EFL(T)). Therefore, EFL(T), namely, attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. EFL(T) leads to small airway injury and promotes dynamic pulmonary hyperinflation with concurrent dyspnoea and exercise limitation. In fact, EFL(T) occurs commonly in COPD patients (mainly in GOLD III and IV stage) in whom the latter symptoms are common. The existing up-to-date physiological methods for assessing expiratory flow limitation (EFL(T)) are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure (NEP) has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, non invasive, most practical, and accurate new technique.

  7. New analytical spiral tube assembly for separation of proteins by counter-current chromatography

    PubMed Central

    Ma, Xiaofeng; Ito, Yoichiro

    2015-01-01

    A new spiral column assembly for analytical separation by counter-current chromatography is described. The column is made from a plastic spiral tube support which has 12 interwoven spiral grooves. The PTFE tubing of 1.6 mm ID was first flattened by extruding through a narrow slit and inserted into the grooves to make 5 spiral layers with about 60 ml capacity. The performance of the spiral column assembly was tested with separation of three stable protein samples including cytochrome C, myoglobin and lysozyme in a polymer phase system composed of polyethylene glycol 1000 and dibasic potassium phosphate each at 12.5 % (w/w) in water. At 2 ml/min, three protein samples were well resolved in one hour. The separation time may be further shortened by application of higher revolution speed and flow rate by improving the strength of the spiral tube support in the future. PMID:26074099

  8. Improved spiral tube assembly for high-speed counter-current chromatography

    PubMed Central

    Ito, Y.; Clary, R.; Powell, J.; Knight, M.; Finn, T. M.

    2009-01-01

    The original spiral tube support (STS) assembly is improved by changing the shape of the tubing, with 1-cm presses perpendicularly along the length. This modification interrupts the laminar flow of the mobile phase. The tubing in the 4 return grooves to the center of the rotor is flattened by a specially made pressing tool to decrease the dead volume and thus increase the column efficiency. The performance of this spiral tube assembly was tested in separations of dipeptides and proteins with suitable polar two-phase solvent systems. The results revealed that the present system yields high partition efficiency with a satisfactory level of stationary phase retention in a short elution time. The present high-speed counter-current chromatographic system will be efficiently applied to a broad spectrum of two-phase solvent systems including aqueous-aqueous polymer phase systems which are used for separation of biopolymers such as proteins and nucleic acids. . PMID:19062024

  9. One-step purification of proteins from chicken egg white using counter-current chromatography.

    PubMed

    Shibusawa, Y; Kihira, S; Ito, Y

    1998-05-29

    Proteins present in chicken egg white are separated by counter-current chromatography (CCC) in one step using a cross-axis coil planet centrifuge (X-axis CPC). The separation was performed with an aqueous polymer two-phase system composed of 16% (w/w) poly(ethylene glycol) 1000 and 12.5% (w/w) dibasic potassium phosphate by eluting the lower phase at a flow-rate of 1.0 ml/min. From about 20 g of the crude egg white solution, lysozyme, ovalbumin, and ovotransferrin were resolved within 5.5 h. Each component was identified by 12% SDS gel electrophoresis with Coomassie brilliant blue staining.

  10. GUESSmix-guided optimization of elution-extrusion counter-current separations.

    PubMed

    Friesen, J Brent; Pauli, Guido F

    2009-05-08

    Rational strategies for the optimization of separations are vital to any chromatographic technique. In counter-current separations (CS), once a suitable solvent system is selected for a given separation, the operator is faced with the task of optimizing the separation through the manipulation of those adjustable operation parameters allowed for by the current CS technology. This study employed a mixture of 21 natural products of varying polarity, molecular mass, and functionality, termed the GUESSmix, as a tool to assess the effectiveness of optimization strategies. The behavior of the GUESSmix was observed in the hexane/ethyl acetate/methanol/water 4:6:4:6 (HEMWat +3) solvent system. The effect of operation parameters on both the elution and extrusion stages of a recently introduced CS methodology, termed elution-extrusion counter-current chromatography (EECCC), was investigated. The resulting chromatograms were plotted with K-based reciprocal symmetry plots (ReS and ReSS), which allow comparison of the K values of significant peaks and assessment of resolution of eluting compounds in the interval 0< or =K< or =infinity. The operation parameters studied were: (1) the effect of temperature controlled water circulation around the centrifuge; (2) the combination of flow rate and revolution speed; (3) sample loading capacity; (4) the direction of rotation either agreeing with or opposing the direction of coil winding; (5) injection before equilibration, a practice that saves operator time and reduces solvent consumption. The GUESSmix was found to be a highly useful reference mixture to compare and contrast stationary phase retention volume ratios, resolution, K-values, peak shapes, and extrusion characteristics between CS experiments. EECCC is shown to be a robust technique that may be enhanced with appropriate temperature, rpm, flow rate, sample loading, direction of rotation, and injection timing. Plotting ReS[S] chromatograms enables systematic study of CS

  11. Countercurrent Process for Lignin Separation from Biomass Matrix

    SciTech Connect

    Kiran Kadam; Ed Lehrburger

    2006-03-31

    The overall goal of the project was to test the concept of using a twin-screw extruder to conduct autohydrolysis pretreatment of wheat straw in countercurrent fashion, demonstrate in situ solid/liquid separation, and produce a low-lignin cellulose product using ethanol as an extractant. The resultant solid product is suitable for sugar production through enzymatic hydrolysis and for pulp applications. Pilot-scale equipment was used to successfully demonstrate the process both for sugar and pulp applications.

  12. Cyclooxygenase blockade limits blood flow to collateral-dependent myocardium during exercise.

    PubMed

    Altman, J D; Klassen, C L; Bache, R J

    1995-11-01

    Cyclooxygenase blockade has been found to cause vasoconstriction of coronary collateral vessels in open-chest animals. This study was carried out to determine whether cyclooxygenase blockade can limit blood flow to collateral-dependent myocardium during exercise. Studies were performed in 8 adult mongrel dogs in which intermittent followed by permanent occlusion of the left anterior descending coronary artery produced an area of collateral-dependent myocardium. Myocardial blood flow was measured with radioactive microspheres at rest and during treadmill exercise to produce heart rates of 215 +/-0 7 beats/min. At rest collateral zone blood flow (1.00 +/- 0.10 ml/min per g) was significantly less than normal zone flow (1.23 +/- 0.14) (P < 0.05). During control exercise blood flow increased 91 +/- 22% in the collateral zone and 102 +/- 28% in the normal zone (each P < 0.05). Thirty minutes after cyclooxygenase blockade with indomethacin (5 mg/kg i.v.) blood flow in the normal zone and the collateral zone was not different from control during resting conditions. Indomethacin did not change heart rate or arterial pressure during exercise, but significantly increased the aortic-to-distal coronary pressure gradient from 33 +/- 3 to 40 +/- 5 mmHg (P < 0.05). Indomethacin increased transcollateral resistance during exercise by 42 +/- 10% (P < 0.05); this was associated with a 27 +/- 11% decrease in subendocardial flow in the collateral zone (P < 0.05) with no significant change in subepicardial flow, and no change in normal zone blood flow. These findings demonstrate that in the intact awake animal cyclooxygenase blockade causes coronary collateral vasoconstriction which can impair blood flow to the dependent myocardium during exercise.

  13. On the structural limitations of recursive digital filters for base flow estimation

    NASA Astrophysics Data System (ADS)

    Su, Chun-Hsu; Costelloe, Justin F.; Peterson, Tim J.; Western, Andrew W.

    2016-06-01

    Recursive digital filters (RDFs) are widely used for estimating base flow from streamflow hydrographs, and various forms of RDFs have been developed based on different physical models. Numerical experiments have been used to objectively evaluate their performance, but they have not been sufficiently comprehensive to assess a wide range of RDFs. This paper extends these studies to understand the limitations of a generalized RDF method as a pathway for future field calibration. Two formalisms are presented to generalize most existing RDFs, allowing systematic tuning of their complexity. The RDFs with variable complexity are evaluated collectively in a synthetic setting, using modeled daily base flow produced by Li et al. (2014) from a range of synthetic catchments simulated with HydroGeoSphere. Our evaluation reveals that there are optimal RDF complexities in reproducing base flow simulations but shows that there is an inherent physical inconsistency within the RDF construction. Even under the idealized setting where true base flow data are available to calibrate the RDFs, there is persistent disagreement between true and estimated base flow over catchments with small base flow components, low saturated hydraulic conductivity of the soil and larger surface runoff. The simplest explanation is that low base flow "signal" in the streamflow data is hard to distinguish, although more complex RDFs can improve upon the simpler Eckhardt filter at these catchments.

  14. Lung and chest wall mechanics during exercise: effects of expiratory flow limitation.

    PubMed

    Aliverti, Andrea

    2008-11-30

    This short review summarizes how lung and chest wall mechanics can be modelled and which are the mechanical constraints imposed on the ventilatory system and its components during exercise. In healthy humans the structural and functional characteristics of the ventilator pump are able to meet the increased demands of ventilation during exercise and it is rare that arterial blood gas is significantly altered up to maximal exercise. In contrast, exercise is frequently limited by the ventilator system in disease, especially when altered mechanical properties of the airway and lung make expiratory flow limitation (EFL) a common feature. EFL is a phenomenon that can be understood in terms of the viscous effects of gas flowing from the alveoli to the airway opening along a collapsible airway which leads during exercise to dynamic hyperflation and several abnormalities of the ventilatory pump. These, in turn, determine a series of secondary manifestations, namely dyspnoea, exercise limitation and hypercapnia that can cause serious morbidity.

  15. Mean Field Limit and Propagation of Chaos for a Pedestrian Flow Model

    NASA Astrophysics Data System (ADS)

    Chen, Li; Göttlich, Simone; Yin, Qitao

    2017-01-01

    In this paper a rigorous proof of the mean field limit for a pedestrian flow model in two dimensions is given by using a probabilistic method. The model under investigation is an interacting particle system coupled to the eikonal equation on the microscopic scale. For stochastic initial data, it is proved that the solution of the N-particle pedestrian flow system with properly chosen cut-off converges in the probability sense to the solution of the characteristics of the non-cut-off Vlasov equation. Furthermore, the result on propagation of chaos is also deduced in terms of bounded Lipschitz distance.

  16. Rapid separation of cyanidin-3-glucoside and cyanidin-3-rutinoside from crude mulberry extract using high-performance countercurrent chromatography and establishment of a volumetric scale-up process.

    PubMed

    Choi, Soo-Jung; Choi, Janggyoo; Lee, Chang Uk; Yoon, Shin Hee; Bae, Soo Kyung; Chin, Young-Won; Kim, Jinwoong; Yoon, Kee Dong

    2015-06-01

    This study describes the rapid separation of mulberry anthocyanins; namely, cyanidin-3-glucoside and cyanidin-3-rutinoside, using high-performance countercurrent chromatography, and the establishment of a volumetric scale-up process from semi-preparative to preparative-scale. To optimize the separation parameters, biphasic solvent systems composed of tert-butyl methyl ether/n-butanol/acetonitrile/0.01% trifluoroacetic acid, flow rate, sample amount and rotational speed were evaluated for the semi-preparative-scale high-performance countercurrent chromatography. The optimized semi-preparative-scale high-performance countercurrent chromatography parameters (tert-butyl methyl ether/n-butanol/acetonitrile/0.01% trifluoroacetic acid, 1:3:1:5, v/v; flow rate, 4.0 mL/min; sample amount, 200-1000 mg; rotational speed, 1600 rpm) were transferred directly to a preparative-scale (tert-butyl methyl ether/n-butanol/acetonitrile/0.01% trifluoroacetic acid, 1:3:1:5, v/v; flow rate, 28 mL/min; sample amount, 5.0-10.0 g; rotational speed, 1400 rpm) to achieve separation results identical to cyanidin-3-glucoside and cyanidin-3-rutinoside. The separation of mulberry anthocyanins using semi-preparative high-performance countercurrent chromatography and its volumetric scale-up to preparative-scale was addressed for the first time in this report.

  17. Recovering mean flow quantities from limited time-resolved PIV measurements through a data assimilation framework

    NASA Astrophysics Data System (ADS)

    Symon, Sean; Schmid, Peter; Sipp, Denis; McKeon, Beverley

    2016-11-01

    Data assimilation combines experimental and numerical realizations of the same flow to produce hybrid flow fields. These have the advantages of less noise contamination and higher resolution while simultaneously reproducing the main physical features of the measured flow. This study investigates data assimilation of the mean flow around an idealized airfoil (Re = 13500) obtained from time-averaged PIV data. The experimental data, which represents a low-dimensional representation of the full flow field due to resolution and field of view limitations, is incorporated into a simulation governed by the incompressible RANS equations with an unknown momentum forcing. This forcing, which corresponds to the divergence of the Reynolds stress tensor, is calculated from a direct-adjoint optimization procedure to match the experimental and numerical mean velocity fields. The simulation is projected to the low-dimensional subspace of the experiment to calculate the discrepancy and a smoothing procedure is used to recover adjoint solutions on the higher-dimensional subspace of the simulation. The study quantifies how well data assimilation can reconstruct the mean flow and the minimum experimental measurements needed by altering the resolution and domain size of the time-averaged PIV.

  18. The ecological limits of hydrologic alteration (ELOHA): A new framework for developing regional environmental flow standards

    USGS Publications Warehouse

    Poff, N.L.; Richter, B.D.; Arthington, A.H.; Bunn, S.E.; Naiman, R.J.; Kendy, E.; Acreman, M.; Apse, C.; Bledsoe, B.P.; Freeman, Mary C.; Henriksen, J.; Jacobson, R.B.; Kennen, J.G.; Merritt, D.M.; O'Keeffe, J. H.; Olden, J.D.; Rogers, K.; Tharme, R.E.; Warner, A.

    2010-01-01

    The flow regime is a primary determinant of the structure and function of aquatic and riparian ecosystems for streams and rivers. Hydrologic alteration has impaired riverine ecosystems on a global scale, and the pace and intensity of human development greatly exceeds the ability of scientists to assess the effects on a river-by-river basis. Current scientific understanding of hydrologic controls on riverine ecosystems and experience gained from individual river studies support development of environmental flow standards at the regional scale. 2. This paper presents a consensus view from a group of international scientists on a new framework for assessing environmental flow needs for many streams and rivers simultaneously to foster development and implementation of environmental flow standards at the regional scale. This framework, the ecological limits of hydrologic alteration (ELOHA), is a synthesis of a number of existing hydrologic techniques and environmental flow methods that are currently being used to various degrees and that can support comprehensive regional flow management. The flexible approach allows scientists, water-resource managers and stakeholders to analyse and synthesise available scientific information into ecologically based and socially acceptable goals and standards for management of environmental flows. 3. The ELOHA framework includes the synthesis of existing hydrologic and ecological databases from many rivers within a user-defined region to develop scientifically defensible and empirically testable relationships between flow alteration and ecological responses. These relationships serve as the basis for the societally driven process of developing regional flow standards. This is to be achieved by first using hydrologic modelling to build a 'hydrologic foundation' of baseline and current hydrographs for stream and river segments throughout the region. Second, using a set of ecologically relevant flow variables, river segments within the

  19. Limiter

    DOEpatents

    Cohen, S.A.; Hosea, J.C.; Timberlake, J.R.

    1984-10-19

    A limiter with a specially contoured front face is provided. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution. This limiter shape accommodates the various power scrape-off distances lambda p, which depend on the parallel velocity, V/sub parallel/, of the impacting particles.

  20. Sinks as limited resources? A new indicator for evaluating anthropogenic material flows

    PubMed Central

    Kral, Ulrich; Brunner, Paul H.; Chen, Pi-Cheng; Chen, Sih-Rong

    2014-01-01

    Besides recyclables, the use of materials inevitably yields non-recyclable materials such as emissions and wastes for disposal. These flows must be directed to sinks in a way that no adverse effects arise for humans and the environment. The objective of this paper is to present a new indicator for the assessment of substance flows to sinks on a regional scale. The indicator quantifies the environmentally acceptable mass share of a substance in actual waste and emission flows, ranging from 0% as worst case to 100% as best case. This paper consists of three parts: first, the indicator is defined. Second, a methodology to determine the indicator score is presented, including (i) substance flows analysis and (ii) a distant-to-target approach based on an adaptation of the Ecological Scarcity Method 2006. Third, the metric developed is applied in three case studies including copper (Cu) and lead (Pb) in the city of Vienna, and perfluorooctane sulfonate (PFOS) in Switzerland. The following results were obtained: in Vienna, 99% of Cu flows to geogenic and anthropogenic sinks are acceptable when evaluated by the distant-to-target approach. However, the 0.7% of Cu entering urban soils and the 0.3% entering receiving waters are beyond the acceptable level. In the case of Pb, 92% of all flows into sinks prove to be acceptable, and 8% are disposed of in local landfills with limited capacity. For PFOS, 96% of all flows into sinks are acceptable. 4% cannot be evaluated due to a lack of normative criteria, despite posing a risk for human health and the environment. The examples demonstrate the need (i) for appropriate data of good quality to calculate the sink indicator and (ii) for standards, needed for the assessment of substance flows to urban soils and receiving waters. This study corroborates that the new indicator is well suited as a base for decisions regarding the control of hazardous substances in waste and environmental management. PMID:25368543

  1. SPH modelling of depth‐limited turbulent open channel flows over rough boundaries

    PubMed Central

    Kazemi, Ehsan; Nichols, Andrew; Tait, Simon

    2016-01-01

    Summary A numerical model based on the smoothed particle hydrodynamics method is developed to simulate depth‐limited turbulent open channel flows over hydraulically rough beds. The 2D Lagrangian form of the Navier–Stokes equations is solved, in which a drag‐based formulation is used based on an effective roughness zone near the bed to account for the roughness effect of bed spheres and an improved sub‐particle‐scale model is applied to account for the effect of turbulence. The sub‐particle‐scale model is constructed based on the mixing‐length assumption rather than the standard Smagorinsky approach to compute the eddy‐viscosity. A robust in/out‐flow boundary technique is also proposed to achieve stable uniform flow conditions at the inlet and outlet boundaries where the flow characteristics are unknown. The model is applied to simulate uniform open channel flows over a rough bed composed of regular spheres and validated by experimental velocity data. To investigate the influence of the bed roughness on different flow conditions, data from 12 experimental tests with different bed slopes and uniform water depths are simulated, and a good agreement has been observed between the model and experimental results of the streamwise velocity and turbulent shear stress. This shows that both the roughness effect and flow turbulence should be addressed in order to simulate the correct mechanisms of turbulent flow over a rough bed boundary and that the presented smoothed particle hydrodynamics model accomplishes this successfully. © 2016 The Authors International Journal for Numerical Methods in Fluids Published by John Wiley & Sons Ltd PMID:28066121

  2. Sinks as limited resources? A new indicator for evaluating anthropogenic material flows.

    PubMed

    Kral, Ulrich; Brunner, Paul H; Chen, Pi-Cheng; Chen, Sih-Rong

    2014-11-01

    Besides recyclables, the use of materials inevitably yields non-recyclable materials such as emissions and wastes for disposal. These flows must be directed to sinks in a way that no adverse effects arise for humans and the environment. The objective of this paper is to present a new indicator for the assessment of substance flows to sinks on a regional scale. The indicator quantifies the environmentally acceptable mass share of a substance in actual waste and emission flows, ranging from 0% as worst case to 100% as best case. This paper consists of three parts: first, the indicator is defined. Second, a methodology to determine the indicator score is presented, including (i) substance flows analysis and (ii) a distant-to-target approach based on an adaptation of the Ecological Scarcity Method 2006. Third, the metric developed is applied in three case studies including copper (Cu) and lead (Pb) in the city of Vienna, and perfluorooctane sulfonate (PFOS) in Switzerland. The following results were obtained: in Vienna, 99% of Cu flows to geogenic and anthropogenic sinks are acceptable when evaluated by the distant-to-target approach. However, the 0.7% of Cu entering urban soils and the 0.3% entering receiving waters are beyond the acceptable level. In the case of Pb, 92% of all flows into sinks prove to be acceptable, and 8% are disposed of in local landfills with limited capacity. For PFOS, 96% of all flows into sinks are acceptable. 4% cannot be evaluated due to a lack of normative criteria, despite posing a risk for human health and the environment. The examples demonstrate the need (i) for appropriate data of good quality to calculate the sink indicator and (ii) for standards, needed for the assessment of substance flows to urban soils and receiving waters. This study corroborates that the new indicator is well suited as a base for decisions regarding the control of hazardous substances in waste and environmental management.

  3. Experimental verification of subcooled flow boiling for tokamak pump limiter designs

    SciTech Connect

    Koski, J.A.; Beattie, A.G.; Whitley, J.B.; Croessmann, C.D.

    1987-01-01

    In fusion energy research devices such as tokamaks, limiters are used to define the plasma boundary, and may serve the additional functions of plasma density and impurity control by removing neutralized particles from the plasma edge region. Because the devices must operate in the plasma edge, they are subject to high heat fluxes. In this paper, experimental studies conducted in support of a pump limiter design currently under development are discussed. Subcooled flow boiling of water and twisted tape flow enhancement are combined to enable heat removal of highly peaked local heat fluxes at the tube-water boundary in the 40 to 50 MW/m/sup 2/ range. Critical heat flux and heat removal experiments were conducted on copper tube targets with the use of a rastered 30 kV electron beam apparatus capable of producing the desired steady state heat flux levels.

  4. Characterizing the interaction between enantiomers of eight psychoactive drugs and highly sulfated-β-cyclodextrin by counter-current capillary electrophoresis.

    PubMed

    Asensi-Bernardi, Lucía; Escuder-Gilabert, Laura; Martín-Biosca, Yolanda; Sagrado, Salvador; Medina-Hernández, María José

    2014-01-01

    The estimation of apparent binding constants and limit mobilities of the complexes of the enantiomers that characterize the interaction of enantiomers with chiral selectors, in this case highly sulfated β-cyclodextrin, was approached using a simple and economic electrophoretic modality, the complete filling technique (CFT) in counter-current mode. The enantiomers of eight psychoactive drugs, four antihistamines (dimethindene, promethazine, orphenadrine and terfenadine) and four antidepressants (bupropion, fluoxetine, nomifensine and viloxazine) were separated for the first time for this cyclodextrin (CD). Estimations of thermodynamic and electrophoretic enantioselectivies were also performed. Results indicate that, in general, thermodynamic enantioselectivity is the main component explaining the high resolution found, but also one case suggests that electrophoretic enantioselectivity itself is enough to obtain a satisfactory resolution. CFT results advantageous compared with conventional capillary electrophoresis (CE) and partial filling technique (PFT) for the study of the interaction between drugs and chiral selectors. It combines the use of a simple fitting model (as in CE), when the enantiomers do not exit the chiral selector plug during the separation (i.e. mobility of electroosmotic flow larger than mobility of CD), and drastic reduction of the consumption (and cost; ~99.7%) of the CD reagent (as in PFT) compared with the conventional CE.

  5. [Purification of ovalbumin from hen egg white by high-speed counter-current aqueous two-phase chromatography].

    PubMed

    Zhi, Wen-Bo; Deng, Qiu-Yun; Song, Jiang-Nan; Ouyang, Fan

    2005-01-01

    High-speed counte-recurrent chromatography (HSCCC) is a continuous liquid-liquid partition chromatography without solid matrix, which has the significant features of high resolution and high recovery. The separation of bio-macromolecule in aqueous two-phase systems (ATPs) with HSCCC is still under research, and the establishment of high-speed counter-current aqueous two-phase chromatography (HSCCC-ATP) relies on the improvement of equipment structure and optimization of operation parameters. By using a multi-column high-speed counter-current chromatograph, the separation of protein mixture and the purification of ovalbumin from hen egg white were studied. The effects of pH and PEG concentration on the partition coefficients of proteins were tested in PEG1000-phosphate ATPs, and distinct differences among partition coefficients of proteins were found at pH 9.2 and 15.0% (W/W) PEG concentration in said system. The separation of protein mixture, consisting of cytochrome C, lysozyme and myoglobin was successfully performed in 15.0% (W/W) PEG1000-17.0% (W/W) potassium phosphate ATPs at pH 9.2 with high-speed counter-current chromatograph at rotation speed of 850r/min and flow rate of 0.8mL/min, using upper phase as stationary phase. pH and PEG concentration also had distinct effects on the partition coefficients of the major protein components in hen egg white, including ovaltransferrin, ovalbumin and lysozyme. The optimal pH value and PEG concentration for the purification of ovalbumin by HSCCC-ATP were found to be 9.2 and 16.0% (W/W) respectively. Ovalbumin was successfully purified to homogeneity from the hen egg white sample in 16.0% (W/W) PEG1000-17.0% (W/W) potassium phosphate ATPs at pH 9.2 with high-speed counter-current chromatograph at rotation speed of 850r/min and flow rate of 1.8mL/min, using upper phase as stationary phase. The purification recovery of ovalbumin was around 95%.

  6. Role of edge turbulence and shear flows in density limit on HL-2A tokamak

    NASA Astrophysics Data System (ADS)

    Hong, Rongjie; Tynan, George; Xu, Min; Nie, Lin; Guo, Dong; Ke, Rui; Long, Ting; Wu, Yifang; Yuan, Boda

    2016-10-01

    The tokamak density limit has long been suspected as a consequence of the enhanced turbulent transport in edge plasmas. In this study, evolutions of the turbulence and shear flows were investigated at different normalized density ne /nG in the plasma boundary region of HL-2A tokamak using Langmuir probes. As the density limit was approached, the equilibrium profile of density was flattened in the Scrape-Off Layer (SOL) and steepened inside the separatrix, while the edge cooling was observed from the electron temperature profile. The turbulent cross-field transport also increased substantially with the ne /nG and the collisionality. In addition, the amplitude of the poloidal phase velocity decreased at higher densities. This destruction of the shear layer was associated with the collapse of the Reynolds stress and thus the reduction in the nonlinear energy transfer from high-frequency fluctuations to low-frequency shear flows. These observations indicate an important role of the edge turbulence and the turbulence-driven shear flow in the underlying physics of tokamak density limit. Thank the HL-2A team for machine operation. Partly supported by DOE Grant No. DE-SC0008378.

  7. Limiter

    DOEpatents

    Cohen, Samuel A.; Hosea, Joel C.; Timberlake, John R.

    1986-01-01

    A limiter with a specially contoured front face accommodates the various power scrape-off distances .lambda..sub.p, which depend on the parallel velocity, V.sub..parallel., of the impacting particles. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution.

  8. Limits of the potential flow model for obstacle detection using a lateral line

    NASA Astrophysics Data System (ADS)

    Maertens, Audrey; Weymouth, Gabriel; Triantafyllou, Michael

    2012-11-01

    Fish have a particular sensory system called lateral line through which they measure flow velocity and pressure gradient. Behavioral studies have shown that fish can detect and identify obstacles while gliding using this sensory system alone. Despite a widespread interest of the community in understanding and reproducing this capability, a realistic approach is still missing. Indeed, due to computational constraints, most attempts to date have used potential flow models. The present work aims at revealing the limits of the potential flow model in the case of a vehicle gliding by a cylinder. The understanding thus gained can be used to account for viscous effects in a computationally-efficient fashion. An improvement of the boundary data immersion method provides accurate pressure predictions at the Reynolds numbers considered (500 < Re < 10000). It is shown how a potential flow-based obstacle detection algorithm fails at locating the cylinder at these Reynolds numbers. It is also shown that a panel method accounting for dynamically changing displacement thickness leads to accurate pressure prediction. This is a first step toward real-time pressure predictions for viscous flows which is needed for efficient obstacle detection and identification algorithms.

  9. Low blood flow at onset of moderate-intensity exercise does not limit muscle oxygen uptake.

    PubMed

    Nyberg, Michael; Mortensen, Stefan P; Saltin, Bengt; Hellsten, Ylva; Bangsbo, Jens

    2010-03-01

    The effect of low blood flow at onset of moderate-intensity exercise on the rate of rise in muscle oxygen uptake was examined. Seven male subjects performed a 3.5-min one-legged knee-extensor exercise bout (24 +/- 1 W, mean +/- SD) without (Con) and with (double blockade; DB) arterial infusion of inhibitors of nitric oxide synthase (N(G)-monomethyl-l-arginine) and cyclooxygenase (indomethacin) to inhibit the synthesis of nitric oxide and prostanoids, respectively. Leg blood flow and leg oxygen delivery throughout exercise was 25-50% lower (P < 0.05) in DB compared with Con. Leg oxygen extraction (arteriovenous O(2) difference) was higher (P < 0.05) in DB than in Con (5 s: 127 +/- 3 vs. 56 +/- 4 ml/l), and leg oxygen uptake was not different between Con and DB during exercise. The difference between leg oxygen delivery and leg oxygen uptake was smaller (P < 0.05) during exercise in DB than in Con (5 s: 59 +/- 12 vs. 262 +/- 39 ml/min). The present data demonstrate that muscle blood flow and oxygen delivery can be markedly reduced without affecting muscle oxygen uptake in the initial phase of moderate-intensity exercise, suggesting that blood flow does not limit muscle oxygen uptake at the onset of exercise. Additionally, prostanoids and/or nitric oxide appear to play important roles in elevating skeletal muscle blood flow in the initial phase of exercise.

  10. Using LAHARZ to Forecast Inundation from lahars, debris flows, and rock avalanches: Confidence Limits on Prediction

    NASA Astrophysics Data System (ADS)

    Schilling, S. P.; Griswold, J. P.; Iverson, R. M.

    2008-12-01

    LAHARZ is a computational model that uses statistical descriptions of areas inundated by past mass-flow events to forecast areas likely to be inundated by hypothetical future events. The forecasts are based on sets of physically motivated and statistically calibrated power-law equations that each have a form A = cV2/3, relating mass-flow volume (V) to planimetric or cross-sectional areas (A) inundated by an average flow as it descends a given drainage. Calibration of the equations utilizes logarithmic transformation and linear regression to determine the best-fit values of c. The LAHARZ software uses specified values of V, an algorithm for idenitifying mass-flow source areas, and digital elevation models of topography to portray forecast hazard zones on maps. In typical applications, a range of plausible V values results in a set of nested hazard zones showing areas likely to be inundated by a range of hypothetical flows. LAHARZ forecasts have not included explicit confidence limits for areas likely to be inundated by individual flows, however; here we describe work that remedies this shortcoming. The basic elements required to generate explict confidence limits in LAHARZ forecasts are the sets of data pairs relating values of V and A, the statistically calibrated prediction equations, a user-specified level of confidence, and t-distribution statistics. The prediction equations and data are used to calculate the standard error of regression, standard error of the mean, and standard error of prediction. Calculation of these standard errors closely parallels procedures described in many statistics books, but differs subtly because the LAHARZ prediction equations have only one calibrated parameter (c), not two as in typical linear regression. Standard errors do not fully determine prediction uncertainty, however, because it does not account for the fact that predictions are based on an incomplete sample of the population of V and A values. The effect of incomplete

  11. Fundamental uncertainty limit of optical flow velocimetry according to Heisenberg's uncertainty principle.

    PubMed

    Fischer, Andreas

    2016-11-01

    Optical flow velocity measurements are important for understanding the complex behavior of flows. Although a huge variety of methods exist, they are either based on a Doppler or a time-of-flight measurement principle. Doppler velocimetry evaluates the velocity-dependent frequency shift of light scattered at a moving particle, whereas time-of-flight velocimetry evaluates the traveled distance of a scattering particle per time interval. Regarding the aim of achieving a minimal measurement uncertainty, it is unclear if one principle allows to achieve lower uncertainties or if both principles can achieve equal uncertainties. For this reason, the natural, fundamental uncertainty limit according to Heisenberg's uncertainty principle is derived for Doppler and time-of-flight measurement principles, respectively. The obtained limits of the velocity uncertainty are qualitatively identical showing, e.g., a direct proportionality for the absolute value of the velocity to the power of 32 and an indirect proportionality to the square root of the scattered light power. Hence, both measurement principles have identical potentials regarding the fundamental uncertainty limit due to the quantum mechanical behavior of photons. This fundamental limit can be attained (at least asymptotically) in reality either with Doppler or time-of-flight methods, because the respective Cramér-Rao bounds for dominating photon shot noise, which is modeled as white Poissonian noise, are identical with the conclusions from Heisenberg's uncertainty principle.

  12. Lean-limit extinction of propane/air mixtures in the stagnation-point flow

    NASA Technical Reports Server (NTRS)

    Law, C. K.; Ishizuka, S.; Mizomoto, M.

    1981-01-01

    The extinction limits of lean propane/air mixtures in the stagnation-point flow of a flat surface were mapped as functions of the surface temperature and the mixture concentration, velocity, and temperature. The maximum flame temperatures and the flame locations were also measured. The results show that the extinction limits are extremely insensitive to the nature of the surface, which can be heated to 1000 C. On the other hand preheating the gas mixture increases the flame temperature by an almost equal amount and therefore significantly extends the extinction limits. It is also found that at extinction the maximum flame temperatures and the flame locations, which when scaled with the velocity gradient, assume almost constant values independent of the other system variables investigated.

  13. Qualitative and quantitative evaluation of solvent systems for countercurrent separation.

    PubMed

    Friesen, J Brent; Ahmed, Sana; Pauli, Guido F

    2015-01-16

    Rational solvent system selection for countercurrent chromatography and centrifugal partition chromatography technology (collectively known as countercurrent separation) studies continues to be a scientific challenge as the fundamental questions of comparing polarity range and selectivity within a solvent system family and between putative orthogonal solvent systems remain unanswered. The current emphasis on metabolomic investigations and analysis of complex mixtures necessitates the use of successive orthogonal countercurrent separation (CS) steps as part of complex fractionation protocols. Addressing the broad range of metabolite polarities demands development of new CS solvent systems with appropriate composition, polarity (π), selectivity (σ), and suitability. In this study, a mixture of twenty commercially available natural products, called the GUESSmix, was utilized to evaluate both solvent system polarity and selectively characteristics. Comparisons of GUESSmix analyte partition coefficient (K) values give rise to a measure of solvent system polarity range called the GUESSmix polarity index (GUPI). Solvatochromic dye and electrical permittivity measurements were also evaluated in quantitatively assessing solvent system polarity. The relative selectivity of solvent systems were evaluated with the GUESSmix by calculating the pairwise resolution (αip), the number of analytes found in the sweet spot (Nsw), and the pairwise resolution of those sweet spot analytes (αsw). The combination of these parameters allowed for both intra- and inter-family comparison of solvent system selectivity. Finally, 2-dimensional reciprocal shifted symmetry plots (ReSS(2)) were created to visually compare both the polarities and selectivities of solvent system pairs. This study helps to pave the way to the development of new solvent systems that are amenable to successive orthogonal CS protocols employed in metabolomic studies.

  14. The "limiting line" in mixed subsonic and supersonic flow of compressible fluids

    NASA Technical Reports Server (NTRS)

    Tsien, Hsue-Shen

    1944-01-01

    It is well known that the vorticity for any fluid element is constant if the fluid is non-viscous and the change of state of the fluid is isentropic. When a solid body is placed in a uniform stream, the flow far ahead of the body is irrotational. Then if the flow is further assumed to be isentropic, the vorticity will be zero over the whole filed of flow. In other words, the flow is irrotational. For such flow over a solid body, it is shown by Theodorsen that the solid body experiences no resistance. If the fluid has a small viscosity, its effect will be limited in the boundary layer over the solid body and the body will have a drag due to the skin friction. This type of essentially isentropic irrotational flow is generally observed for a streamlined body placed in a uniform stream, if the velocity of the stream is kept below the so-called "critical speed." At the critical speed or rather at a certain value of the ratio of the velocity of the undisturbed flow and the corresponding velocity of sound, shock waves appear. This phenomenon is called the "compressibility bubble." Along a shock wave, the change of state of the fluid is no longer isentropic, although still adiabatic. This results in an increase in entropy of the fluid and generally introduces vorticity in an originally irrotational flow. The increase in entropy of the fluid is, of course, the consequence of changing part of the mechanical energy into heat energy. In other words, the part of fluid affected by the shock wave has a reduced mechanical energy. Therefore, with the appearance of shock waves, the wake of the streamline body is very much widened, and the drag increases drastically. Furthermore, the accompanying change in the pressure distribution over the body changes the aerodynamic moment acting on it and in the case of an airfoil decreases the lift force. All these consequences of the breakdown of isentropic irrotational flow are generally undesirable in applied aerodynamics. Its occurrence

  15. Reduced hepatic blood flow does not limit gluconeogenesis in awake endotoxic minipigs.

    PubMed

    Hand, M S; Fettman, M J; Chandrasena, L G; Cleek, J L; Mason, R A; Phillips, R W

    1983-01-01

    Hypoglycemia associated with endotoxic shock is due to increased glucose utilization coupled with inadequate hepatic glucogenesis. Decreased hepatic blood flow is common in shock and could conceivably reduce hepatic gluconeogenic substrate and oxygen delivery, thereby limiting gluconeogenesis. A study was conducted to assess endotoxin-induced alteration of hepatic hemodynamics and its effect on glucose metabolism. Eight adult minipigs were fitted with jugular, portal, and hepatic vein and carotid artery catheters, and hepatic artery and portal vein flow cuffs for determination of transhepatic kinetics. Three days later they were infused with endotoxin at 15 micrograms/kg/hr. Hepatic blood flow and portal vein oxygen (O2) content became significantly (P less than or equal to 0.05) reduced thereby decreasing hepatic O2 input. Hepatic O2 extraction increased from 24 to 73% but never achieved the reported maximum of 97%. Therefore, reduction of O2 input did not seem to rate limit gluconeogenesis. Reductions in gluconeogenic substrate delivery were not involved since hepatic lactate and pyruvate input actually increased due to elevated blood lactate and pyruvate concentrations.

  16. A DGBGK scheme based on WENO limiters for viscous and inviscid flows

    SciTech Connect

    Ni Guoxi Jiang Song Xu Kun

    2008-05-10

    This paper presents a discontinuous Galerkin BGK (DGBGK) method for both viscous and inviscid flow simulations under a DG framework with a gas-kinetic flux and WENO limiters. In the DGBGK method, the construction of the flux in the DG method is based on the particle transport and collisional mechanism which not only couples the convective and dissipative terms together, but also includes both discontinuous and continuous terms in the flux formulation. Due to the connection between the gas-kinetic BGK model and the Euler as well as the Navier-Stokes equations, both viscous and inviscid flow equations can be simulated by a unified formulation. WENO limiters are used to obtain uniform high-order accuracy and sharp non-oscillatory shock transition. In the current method, the time accuracy is achieved by the direct integration of both time-dependent flux function at a cell interface and the flow variables inside each element. Numerical examples in one and two space dimensions are presented to illustrate the robustness and accuracy of the present scheme.

  17. Liquid cooled counter flow turbine bucket

    DOEpatents

    Dakin, James T.

    1982-09-21

    Means and a method are provided whereby liquid coolant flows radially outward through coolant passages in a liquid cooled turbine bucket under the influence of centrifugal force while in contact with countercurrently flowing coolant vapor such that liquid is entrained in the flow of vapor resulting in an increase in the wetted cooling area of the individual passages.

  18. CORONAL RAIN IN MAGNETIC ARCADES: REBOUND SHOCKS, LIMIT CYCLES, AND SHEAR FLOWS

    SciTech Connect

    Fang, X.; Xia, C.; Keppens, R.; Doorsselaere, T. Van

    2015-07-10

    We extend our earlier multidimensional, magnetohydrodynamic simulations of coronal rain occurring in magnetic arcades with higher resolution, grid-adaptive computations covering a much longer (>6 hr) time span. We quantify how blob-like condensations forming in situ grow along and across field lines and show that rain showers can occur in limit cycles, here demonstrated for the first time in 2.5D setups. We discuss dynamical, multi-dimensional aspects of the rebound shocks generated by the siphon inflows and quantify the thermodynamics of a prominence–corona transition-region-like structure surrounding the blobs. We point out the correlation between condensation rates and the cross-sectional size of loop systems where catastrophic cooling takes place. We also study the variations of the typical number density, kinetic energy, and temperature while blobs descend, impact, and sink into the transition region. In addition, we explain the mechanisms leading to concurrent upflows while the blobs descend. As a result, there are plenty of shear flows generated with relative velocity difference around 80 km s{sup −1} in our simulations. These shear flows are siphon flows set up by multiple blob dynamics and they in turn affect the deformation of the falling blobs. In particular, we show how shear flows can break apart blobs into smaller fragments, within minutes.

  19. Experimental verification of subcooled flow boiling for tokamak pump limiter designs

    SciTech Connect

    Koski, J.A.; Beattie, A.G.; Whitley, J.B.; Croessmann, C.D.

    1987-01-01

    In fusion energy research devices such as tokamaks, limiters are used to define the plasma boundary, and may serve the additional functions of plasma density and impurity control by removing neutralized particles from the plasma edge region. Because the devices must operate in the plasma edge or ''scrape-off-layer,'' they are subject to high heat fluxes. In this paper, experimental studies for a pump limiter design currently under development are discussed. Subcooled flow boiling of water and twisted tape flow enhancement are combined to enable heat removal of highly peaked local heat fluxes at the tube-water boundary in the 40 to 50 MW/m/sup 2/ range. Experiments were conducted with the use of a rastered 30 kV electron beam apparatus which is capable of producing the desired steady state heat flux levels. Objectives of the experiment were (1) to verify the heat removal model used for finite element thermal and stress analyses, (2) selection of appropriate critical heat flux (CHF) margins and criteria, and (3) development of acoustic techniques to monitor the onset of CHF during actual limiter operation.

  20. Marine heat flow measurements across subsea permafrost limit in the eastern Mackenzie Trough, Canadian Beaufort Sea

    NASA Astrophysics Data System (ADS)

    Kim, Y. G.; Hong, J. K.; Jin, Y. K.; Riedel, M.; Melling, H.; Kang, S. G.; Dallimore, S.

    2015-12-01

    Marine heat flow measurements using a 5 m-long Ewing-type heat probe were made during Korean icebreaker R/V Araon's Arctic expeditions (ARA04C in 2013 and ARA05B in 2014) to better know the shallow subsurface thermal structure in the eastern slope of Mackenzie Trough, the Canadian Beaufort Sea, in which associative geological processes of permafrost degradation and gas hydrate dissociation occur because of long-term warming since the Last Glacial Maximum. Heat flow in the continental slope was collected for the first time and is rather higher than those from deep boreholes (up to a few km below the seafloor) in the continental shelf. However, the smaller geothermal gradient and thermal conductivity were observed from sites along a transect line across permafrost limit on the eastern slope of the trough. It is noted that geothermal gradients are relatively constant in the vicinity of permafrost limit but are much smaller (even minus) only at deeper depths with positive bottom water temperature. Reason for such distribution is unclear yet. Based on observed geothermal gradient and bottom water temperature, permafrost table shown in subbottom profile seems to be controlled not by temperature. On the other hand, our finding of permafrost evidence on the other subbottom profile located landward may support that permafrost limit in the trough is along with ~100 m isobath.

  1. Improving Landslide Inventories by Limiting Land Classification to Drainage Areas of Debris Flow-Dominated Channels

    NASA Astrophysics Data System (ADS)

    Lyons, N. J.; Mitasova, H.; Wegmann, K. W.

    2011-12-01

    Landslide inventories, frequently created by aerial photograph interpretation (API), are often used in the production of hillslope hazard maps to characterize past landslides or to evaluate a hazard model. In the former application of inventories, potential landslides in hazard maps are delineated as areas that have similar morphometrics as past landslides at locations of modeled hillslope instability. Therefore, the accuracy of the inventory has a strong influence upon hazard extent. In the latter application, the partial inventories that sometimes result from API, due to the subjectivity of interpretation and revegetation of landslides, likely results in incorrect evaluations. A more complete, less subjective technique is needed to not only better characterize past landslides and improve evaluation of hazard models, but also to assess the extent of areas prone to significant mass wasting in mountainous regions due to the evolution of landscapes. Inventory accuracy continues to improve with new technology and automated techniques, though rarely is the form of a channel's topography incorporated into the inventory process despite the growing evidence of a topographic signature of debris flows. This signature demarcates the transition between the dominant channel erosional process: fluvial or debris flow. These process transitions are often observed at scaling breaks in log-log plots of a channel's drainage area versus slope (DS plot). The scaling breaks, above which the effects of fluvial power laws upon channel topography are not observed and below which debris flow scars are not found, may signify the lowest point in the watershed where debris flows occur. We present an inventory technique that limits a land classification algorithm to areas that are upstream from this scaling break determined from DS plots of five streams in the Great Smoky Mountains National Park (GSMNP) region of the southern Appalachians. Topographic data for the DS plots and the

  2. Stoichiometry, Metabolism and Nutrient Limitation Across the Periodic Table in Natural Flowing-Water Chemostats

    NASA Astrophysics Data System (ADS)

    Cohen, M. J.; Nifong, R. L.; Kurz, M. J.; Cropper, W. P.; Martin, J. B.

    2014-12-01

    Relative supplies of macro and micronutrients (C,N,P, various metals), along with light and water, controls ecosystem metabolism, trophic energy transfer and community structure. Here we test the hypothesis, using measurements from 41 spring-fed rivers in Florida, that tissue stoichiometry indicates autotroph nutrient limitation status. Low variation in discharge, temperature and chemical composition within springs, but large variation across springs creates an ideal setting to assess the relationship between limitation and resource supply. Molar N:P ranges from 0.4 to 90, subjecting autotrophs to dramatically different nutrient supply. Over this gradient, species-specific autotroph tissue C:N:P ratios are strictly homeostatic, and with no evidence that nutrient supply affects species composition. Expanding to include 19 metals and micronutrients revealed autotrophs are more plastic in response to micronutrient variation, particularly for iron and manganese whose supply fluxes are small compared to biotic demand. Using a Droop model modified to reflect springs conditions (benthic production, light limitation, high hydraulic turnover), we show that tissue stoichiometry transitions from homeostatic to plastic with the onset of nutrient limitation, providing a potentially powerful new tool for predicting nutrient limitation and thus eutrophication in flowing waters.

  3. The limitation of pulsatile flow through the aqueduct of Sylvius as a cause of hydrocephalus.

    PubMed

    White, D N; Wilson, K C; Curry, G R; Stevenson, R J

    1979-06-01

    The concept is advanced that hydrocephalus results from limitation in the pulsatile flow of CSF downwards through the aqueduct of Sylvius during systole which is necessary to accommodate for the pulsatile pressure and volume increase that accompanies the propagation of the arterial pulse through the brain. Evidence is given to show that flow through the fixed human aqueduct is disturbed and not laminar. Further, with the pressures availalbe, the aqueduct is only just large enough to pass the quantity of fluid which must be vented extracranially during systole. Should the capacity of this systolic venting mechanism be exceeded, physical strain will cause cellular damage in the periventricular and periaqueductal regions which, if prolonged, will lead to tissue destruction and hydrocephalus. There appear to be two main causes for hydrocephalus resulting from this mechanism. Firstly, structural lesions, restricting the lumina of the CSF-venting pathways, especially the aqueduct, will reduce the volume of CSF that can flow through these pathways during systole. The hydrocephalic process will then be continuous and only limited when tissue destruction reduces the systolic volume expansion of the brain such that it can be accomodated by the restricted CSF venting pathways. Secondly, conditions which may increase the amount of the systolic volume expansion of the brain beyond the capacity of the CSF venting pathways. Raised mean intracranial pressure is the most important of these conditions. In such cases the hydrocephalus will be limited by the duration of the causal process and possibly also by the enlargement of the venting pathways, as a result of tissue destruction. This hypothesis also accounts for hydrocephalus resulting from obliteration of the cortical subarachnoid space, obstruction to the cranial venous drainage, deformities in the region of the foramen magnum and arterial encroachment upon the ventricular system.

  4. Tidal expiratory flow limitation, dyspnoea and exercise capacity in patients with bilateral bronchiectasis.

    PubMed

    Koulouris, N G; Retsou, S; Kosmas, E; Dimakou, K; Malagari, K; Mantzikopoulos, G; Koutsoukou, A; Milic-Emili, J; Jordanoglou, J

    2003-05-01

    In this study the authors investigated whether expiratory flow limitation (FL) is present during tidal breathing in patients with bilateral bronchiectasis (BB) and whether it is related to the severity of chronic dyspnoea (Medical Research Council (MRC) dyspnoea scale), exercise capacity (maximal mechanical power output (WRmax)) and severity of the disease, as assessed by high-resolution computed tomography (HRCT) scoring. Lung function, MRC dyspnoea, HRCT score, WRmax and FL were assessed in 23 stable caucasian patients (six males) aged 56 +/- 17 yrs. FL was assessed at rest both in seated and supine positions. To detect FL, the negative expiratory pressure (NEP) technique was used. The degree of FL was rated using a five-point FL score. WRmax was measured using a cyclo-ergometer. According to the NEP technique, five patients were FL during resting breathing when supine but not seated, four were FL both seated and supine, and 14 were NFL both seated and supine. Furthermore, it was shown that: 1) in stable BB patients FL during resting breathing is common, especially in the supine position; 2) the degree of MRC dyspnoea is closely related to the five-point FL score; 3) WRmax (% pred) is more closely correlated with the MRC dyspnoea score than with the five-point FL score; and 4) HRCT score is closely related to forced expiratory volume in one second % pred but not five-point FL score. In conclusion, flow limitation is common at rest in sitting and supine positions in patients with bilateral bronchiectasis. Flow limitation and reduced exercise capacity are both associated with more severe dyspnoea. Finally, high-resolution computed tomography scoring correlates best with forced expiratory volume in one second.

  5. Subextensive Scaling in the Athermal, Quasistatic Limit of Amorphous Matter in Plastic Shear Flow

    SciTech Connect

    Maloney, C; Lemaitre, A

    2004-01-29

    We present the results of numerical simulations of an atomistic system undergoing plastic shear flow in the athermal, quasistatic limit. The system is shown to undergo cascades of local re-arrangements, associated with quadrupolar energy fluctuations, which induce system-spanning events organized into lines of slip oriented along the Bravais axes of the simulation cell. A finite size scaling analysis reveals subextensive scaling of the energy drops and participation numbers, linear in the length of the simulation cell, in good agreement with the real-space structure of plastic events

  6. Unique laminar-flow stability limit based shallow-water theory

    USGS Publications Warehouse

    Chen, Cheng-lung

    1993-01-01

    Two approaches are generally taken in deriving the stability limit for the Froude member (Fs) for laminar sheet flow. The first approach used the Orr-Sommerfeld equation, while the second uses the cross-section-averaged equations of continuity and motion. Because both approaches are based on shallow-water theory, the values of Fs obtained from both approaches should be identical, yet in the literature they are not. This suggests that a defect exists in at least one of the two approaches. After examining the governing equations used in both approaches, one finds that the existing cross-section -averaged equation of motion is dependent on the frame of reference.

  7. Extinction Limits of Nonadiabatic, Catalyst-Assisted Flames in Stagnation-Point Flow

    SciTech Connect

    Stephen B. Margolis; Timothy J. Gardner

    2001-02-01

    An idealized geometry corresponding to a premixed flame in stagnation-point flow is used to investigate the effects of catalysis on extending the extinction limits of on adiabatic stretched flames. Specifically, a surface catalytic reaction is assumed to occur on the stagnation plane, thereby augmenting combustion in the bulk gas with a exothermic surface reaction characterized by a reduced activation energy. Assuming the activation energies remain large, an asymptotic analysis of the resulting flame structure yields a formula for the extinction limit as a function of various parameters. In particular, it is demonstrated that the presence of a surface catalyst can extend the burning regime, thus counterbalancing the effects of heat loss and flame stretch that tend to shrink it. The analysis is relevant to small-volume combustors, where the increased surface-to-volume ratio can lead to extinction of the nonadiabatic flame in the absence of a catalyst.

  8. A simple tool for tubing modification to improve spiral high-speed counter-current chromatography for protein purification

    PubMed Central

    Ito, Yoichiro; Ma, Xiaofeng; Clary, Robert

    2016-01-01

    A simple tool is introduced which can modify the shape of tubing to enhance the partition efficiency in high-speed countercurrent chromatography. It consists of a pair of interlocking identical gears, each coaxially holding a pressing wheel to intermittently compress plastic tubing in 0 – 10 mm length at every 1 cm interval. The performance of the processed tubing is examined in protein separation with 1.6 mm ID PTFE tubing intermittently pressed in 3 mm and 10 mm width both at 10 mm intervals at various flow rates and revolution speeds. A series of experiments was performed with a polymer phase system composed of polyethylene glycol and dibasic potassium phosphate each at 12.5% (w/w) in deionized water using three protein samples. Overall results clearly demonstrate that the compressed tubing can yield substantially higher peak resolution than the non-processed tubing. The simple tubing modifier is very useful for separation of proteins with high-speed countercurrent chromatography. PMID:27818942

  9. A simple tool for tubing modification to improve spiral high-speed counter-current chromatography for protein purification.

    PubMed

    Ito, Yoichiro; Ma, Xiaofeng; Clary, Robert

    2016-01-01

    A simple tool is introduced which can modify the shape of tubing to enhance the partition efficiency in high-speed countercurrent chromatography. It consists of a pair of interlocking identical gears, each coaxially holding a pressing wheel to intermittently compress plastic tubing in 0 - 10 mm length at every 1 cm interval. The performance of the processed tubing is examined in protein separation with 1.6 mm ID PTFE tubing intermittently pressed in 3 mm and 10 mm width both at 10 mm intervals at various flow rates and revolution speeds. A series of experiments was performed with a polymer phase system composed of polyethylene glycol and dibasic potassium phosphate each at 12.5% (w/w) in deionized water using three protein samples. Overall results clearly demonstrate that the compressed tubing can yield substantially higher peak resolution than the non-processed tubing. The simple tubing modifier is very useful for separation of proteins with high-speed countercurrent chromatography.

  10. Nonlinear mechanisms determining expiratory flow limitation in mechanical ventilation: a model-based interpretation.

    PubMed

    Barbini, Paolo; Cevenini, Gabriele; Avanzolni, Guido

    2003-09-01

    A nonlinear model of breathing mechanics, in which the tracheobronchial airways are considered in three serial segments, is presented to obtain insights into the mechanisms underlying expiratory flow limitation (EFL) in mechanically ventilated patients. Chronic obstructive pulmonary disease (COPD) and normal conditions were simulated and EFL was detected by application of negative expiratory pressure at the mouth or resistance reduction of the expiratory circuit. Simulation results confirm that both techniques reveal remarkable differences in the flow-volume curves between normal subjects and COPD patients, the former showing absence of EFL and the latter exhibiting EFL over most of the expiration. To interpret the role of different nonlinear mechanisms in producing EFL, different flow-volume curves obtained by changing model parameter values were analyzed. An increase in lower-airway resistance did not give rise to EFL, whereas a change in the pressure-volume characteristic of the intermediate-airway segment, towards increased resistance and easier collapse, significantly modified system behavior. In particular, EFL was observed when this intermediate-segment change was combined with an increase in lower-airway resistance. This evidence suggests that modifications, producing loss of radial traction and consequent narrowing of the airways in the peribronchial region, may play a leading role in EFL in COPD patients.

  11. Expiratory flow limitation and operating lung volumes during exercise in older and younger adults.

    PubMed

    Smith, Joshua R; Kurti, Stephanie P; Meskimen, Kayla; Harms, Craig A

    2017-02-20

    We determined the effect of aging on expiratory flow limitation (EFL) and operating lung volumes when matched for lung size. We hypothesized that older adults will exhibit greater EFL and increases in EELV during exercise compared to younger controls. Ten older (5M/5W; >60years old) and nineteen height-matched young adults (10M/9W) were recruited. Young adults were matched for%predicted forced vital capacity (FVC) (Y-matched%Pred FVC; n=10) and absolute FVC (Y-matched FVC; n=10). Tidal flow-volume loops were recorded during the incremental exercise test with maximal flow-volume loops measured pre- and post-exercise. Compared to younger controls, older adults exhibited more EFL at ventilations of 26, 35, 51, and 80L/min. The older group had higher end-inspiratory lung volume compared to Y-matched%Pred FVC group during submaximal ventilations. The older group increased EELV during exercise, while EELV stayed below resting in the Y-matched%Pred FVC group. These data suggest older adults exhibit more EFL and increase EELV earlier during exercise compared to younger adults.

  12. Two-dimensional relativistic space charge limited current flow in the drift space

    SciTech Connect

    Liu, Y. L.; Chen, S. H.; Koh, W. S.; Ang, L. K.

    2014-04-15

    Relativistic two-dimensional (2D) electrostatic (ES) formulations have been derived for studying the steady-state space charge limited (SCL) current flow of a finite width W in a drift space with a gap distance D. The theoretical analyses show that the 2D SCL current density in terms of the 1D SCL current density monotonically increases with D/W, and the theory recovers the 1D classical Child-Langmuir law in the drift space under the approximation of uniform charge density in the transverse direction. A 2D static model has also been constructed to study the dynamical behaviors of the current flow with current density exceeding the SCL current density, and the static theory for evaluating the transmitted current fraction and minimum potential position have been verified by using 2D ES particle-in-cell simulation. The results show the 2D SCL current density is mainly determined by the geometrical effects, but the dynamical behaviors of the current flow are mainly determined by the relativistic effect at the current density exceeding the SCL current density.

  13. Fluid mechanics of osmotic pipe flows and limitations on the lengths of conifer needles

    NASA Astrophysics Data System (ADS)

    Bohr, Tomas; Rademaker, Hanna; Jensen, Kaare; Zwieniecki, Maciej

    2016-11-01

    Plant leaves produce sugars, which are exported osmotically through the sieve tubes of the leaf. Leaf sizes vary by more than 3 orders of magnitude, from a few millimeters to over one meter. Conifer leaves (needles), however, are relatively short and the majority of needles are no longer than 6 cm. The reason for this limitation is unknown, but we argue that it can be explained by the linear venation pattern and the narrow sieve tubes, combined with the osmotic flow mechanism. Thus sugars produced near the tip of long needles cannot be exported efficiently, because the pressure required to drive vascular flow would exceed the greatest available pressure (the osmotic pressure). This basic constraint leads to the formation of an inactive region of stagnant fluid near the needle tip, which does not contribute to sugar flow. The active region, emerging from the base of the needle, has the length Leff =r 3 / 2 16 ηLp 1 / 2 , where r is the conduit radius, η is the sap viscosity, and Lp is the cell membrane permeability. It is independent of the needle length and corresponds well with maximal needle lengths observed in nature.

  14. An efficient collision limiter Monte Carlo simulation for hypersonic near-continuum flows

    NASA Astrophysics Data System (ADS)

    Liang, Jie; Li, Zhihui; Li, Xuguo; Fang, Boqiang Du Ming

    2016-11-01

    The implementation of a collision limiter DSMC-based hybrid approach is presented to simulate hypersonic near-continuum flow. The continuum breakdown parameters based on gradient-length local Knudsen number are characterized different regions of the flowfield. The collision limiter is used in continuum inviscid regions with large time step and cell size. Local density gradient-based dynamic adaptation of collision and sampling cells refinement is employed in high gradient regions including strong shocks and boundary layer near surface. A variable time step scheme is adopted to make sure a more uniform distribution of model particles per collision cell throughout the computational domain, with a constant ratio of local time step interval to particle weights to avoid particles cloned or destroyed when crossing interface from cell to cell. The surface pressure and friction coefficients of hypersonic reentry flow for a blunt capsule are computed in different conditions and compared with benchmark case in transitional regime to examine the efficiency and accuracy. The aerodynamic characteristics of a wave rider shape with sharp leading edge are simulated in the test state for hypersonic near-continuum. The computed aerodynamic coefficients have good agreements with experimental data in low density wind tunnel of CARDC and have less computational expense.

  15. Implicit high-order discontinuous Galerkin method with HWENO type limiters for steady viscous flow simulations

    NASA Astrophysics Data System (ADS)

    Jiang, Zhen-Hua; Yan, Chao; Yu, Jian

    2013-08-01

    Two types of implicit algorithms have been improved for high order discontinuous Galerkin (DG) method to solve compressible Navier-Stokes (NS) equations on triangular grids. A block lower-upper symmetric Gauss-Seidel (BLU-SGS) approach is implemented as a nonlinear iterative scheme. And a modified LU-SGS (LLU-SGS) approach is suggested to reduce the memory requirements while retain the good convergence performance of the original LU-SGS approach. Both implicit schemes have the significant advantage that only the diagonal block matrix is stored. The resulting implicit high-order DG methods are applied, in combination with Hermite weighted essentially non-oscillatory (HWENO) limiters, to solve viscous flow problems. Numerical results demonstrate that the present implicit methods are able to achieve significant efficiency improvements over explicit counterparts and for viscous flows with shocks, and the HWENO limiters can be used to achieve the desired essentially non-oscillatory shock transition and the designed high-order accuracy simultaneously.

  16. Evidence for environmental and ecological selection in a microbe with no geographic limits to gene flow

    PubMed Central

    Whittaker, Kerry A.; Rynearson, Tatiana A.

    2017-01-01

    The ability for organisms to disperse throughout their environment is thought to strongly influence population structure and thus evolution of diversity within species. A decades-long debate surrounds processes that generate and support high microbial diversity, particularly in the ocean. The debate concerns whether diversification occurs primarily through geographic partitioning (where distance limits gene flow) or through environmental selection, and remains unresolved due to lack of empirical data. Here we show that gene flow in a diatom, an ecologically important eukaryotic microbe, is not limited by global-scale geographic distance. Instead, environmental and ecological selection likely play a more significant role than dispersal in generating and maintaining diversity. We detected significantly diverged populations (FST > 0.130) and discovered temporal genetic variability at a single site that was on par with spatial genetic variability observed over distances of 15,000 km. Relatedness among populations was decoupled from geographic distance across the global ocean and instead, correlated significantly with water temperature and whole-community chlorophyll a. Correlations with temperature point to the importance of environmental selection in structuring populations. Correlations with whole-community chlorophyll a, a proxy for autotrophic biomass, suggest that ecological selection via interactions with other plankton may generate and maintain population genetic structure in marine microbes despite global-scale dispersal. Here, we provide empirical evidence for global gene flow in a marine eukaryotic microbe, suggesting that everything holds the potential to be everywhere, with environmental and ecological selection rather than geography or dispersal dictating the structure and evolution of diversity over space and time. PMID:28209775

  17. Validation of a Mechanistic Model for Non-Invasive Study of Ecological Energetics in an Endangered Wading Bird with Counter-Current Heat Exchange in its Legs.

    PubMed

    Fitzpatrick, Megan J; Mathewson, Paul D; Porter, Warren P

    2015-01-01

    Mechanistic models provide a powerful, minimally invasive tool for gaining a deeper understanding of the ecology of animals across geographic space and time. In this paper, we modified and validated the accuracy of the mechanistic model Niche Mapper for simulating heat exchanges of animals with counter-current heat exchange mechanisms in their legs and animals that wade in water. We then used Niche Mapper to explore the effects of wading and counter-current heat exchange on the energy expenditures of Whooping Cranes, a long-legged wading bird. We validated model accuracy against the energy expenditure of two captive Whooping Cranes measured using the doubly-labeled water method and time energy budgets. Energy expenditure values modeled by Niche Mapper were similar to values measured by the doubly-labeled water method and values estimated from time-energy budgets. Future studies will be able to use Niche Mapper as a non-invasive tool to explore energy-based limits to the fundamental niche of Whooping Cranes and apply this knowledge to management decisions. Basic questions about the importance of counter-current exchange and wading to animal physiological tolerances can also now be explored with the model.

  18. Validation of a Mechanistic Model for Non-Invasive Study of Ecological Energetics in an Endangered Wading Bird with Counter-Current Heat Exchange in its Legs

    PubMed Central

    Fitzpatrick, Megan J.; Mathewson, Paul D.; Porter, Warren P.

    2015-01-01

    Mechanistic models provide a powerful, minimally invasive tool for gaining a deeper understanding of the ecology of animals across geographic space and time. In this paper, we modified and validated the accuracy of the mechanistic model Niche Mapper for simulating heat exchanges of animals with counter-current heat exchange mechanisms in their legs and animals that wade in water. We then used Niche Mapper to explore the effects of wading and counter-current heat exchange on the energy expenditures of Whooping Cranes, a long-legged wading bird. We validated model accuracy against the energy expenditure of two captive Whooping Cranes measured using the doubly-labeled water method and time energy budgets. Energy expenditure values modeled by Niche Mapper were similar to values measured by the doubly-labeled water method and values estimated from time-energy budgets. Future studies will be able to use Niche Mapper as a non-invasive tool to explore energy-based limits to the fundamental niche of Whooping Cranes and apply this knowledge to management decisions. Basic questions about the importance of counter-current exchange and wading to animal physiological tolerances can also now be explored with the model. PMID:26308207

  19. The South Indian Ocean Countercurrent: a return pathway of the Indonesian Throughflow?

    NASA Astrophysics Data System (ADS)

    Lambert, Erwin; leBars, Dewi; de Ruijter, Will

    2014-05-01

    The South Indian Ocean Counter Current (SICC) is associated with a thermal front embedded in a broad eastward flow across the subtropical Indian Ocean and feeds into the poleward Leeuwin Current (LC). Previous studies have shown that the LC and SICC are sensitive to variations of the inflow of Pacific water through the Indonesian Passages (ITF). These subtropical countercurrents, of which the SICC is an example, are characterized by high eddy activity and theoretical work has shown the non-linear nature of their dynamics. That has motivated us to investigate the inertial response to the ITF of the IO circulaion. Analysis of two global eddy resolving model runs with the Indonesian Passages open and closed showed that the full 15 Sv of the ITF flows through the Mozambique Channel but only 10 Sv ends up in the Agulhas Current. This suggests that the SICC-LC system forms part of the return pathway of the ITF to the Pacific. Using the Hallberg Isopycnal Model we have investigated the combined effect of ITF, wind- and buoyancy forcing on the Indian Ocean circulation in the inertial boundary layer regime.

  20. Sample injection strategy to increase throughput in counter-current chromatography: Case study of Honokiol purification.

    PubMed

    Peng, Aihua; Hewitson, Peter; Ye, Haoyu; Zu, Liansuo; Garrard, Ian; Sutherland, Ian; Chen, Lijuan; Ignatova, Svetlana

    2016-12-09

    Counter-current chromatography (CCC) has been widely used as a preparative separation method to purify natural products from plant extracts and fermentation broths. Traditionally, throughput optimization in CCC has focused on sample concentration and sample volume. In this paper sample injection was considered as consisting of three variables: injection flow rate, post-injection flow rate and sample solvent. The effects of these parameters were studied using a honokiol purification from a Magnolia officinalis bark extract as a case study aiming to achieve the highest throughput/yield ratio for greater than 99% purity of this potential anti-cancer drug obtained for submission to the Chinese FDA. An injection method was established that increased the throughput of honokiol by 46.5% (from 3.05g/h to 4.47g/h), and decreased the solvent consumption of mobile phase and stationary phase per gram of honokiol by 40.0% (from 0.68L/g to 0.41L/g) and 48.4% (from 0.40L/g to 0.21L/g) respectively. These results show the importance of understanding the whole injection process when optimizing a given CCC separation.

  1. Enhanced Dissipation, Hypoellipticity, and Anomalous Small Noise Inviscid Limits in Shear Flows

    NASA Astrophysics Data System (ADS)

    Bedrossian, Jacob; Coti Zelati, Michele

    2017-02-01

    We analyze the decay and instant regularization properties of the evolution semigroups generated by two-dimensional drift-diffusion equations in which the scalar is advected by a shear flow and dissipated by full or partial diffusion. We consider both the space-periodic {T^2} setting and the case of a bounded channel {T × [0,1]} with no-flux boundary conditions. In the infinite Péclet number limit (diffusivity {νto 0} ), our work quantifies the enhanced dissipation effect due to the shear. We also obtain hypoelliptic regularization, showing that solutions are instantly Gevrey regular even with only partial diffusion. The proofs rely on localized spectral gap inequalities and ideas from hypocoercivity with an augmented energy functional with weights replaced by pseudo-differential operators (of a rather simple form). As an application, we study small noise inviscid limits of invariant measures of stochastic perturbations of passive scalars, and show that the classical Freidlin scaling between noise and diffusion can be modified. In particular, although statistically stationary solutions blow up in {H^1} in the limit {ν to 0} , we show that viscous invariant measures still converge to a unique inviscid measure.

  2. Combined micro and macro geodynamic modelling of mantle flow: methods, potentialities and limits.

    NASA Astrophysics Data System (ADS)

    Faccenda, M.

    2015-12-01

    Over the last few years, geodynamic simulations aiming at reconstructing the Earth's internal dynamics have increasingly attempted to link processes occurring at the micro (i.e., strain-induced lattice preferred orientation (LPO) of crystal aggregates) and macro scale (2D/3D mantle convection). As a major outcome, such a combined approach results in the prediction of the modelled region's elastic properties that, in turn, can be used to perform seismological synthetic experiments. By comparison with observables, the geodynamic simulations can then be considered as a good numerical analogue of specific tectonic settings, constraining their deep structure and recent tectonic evolution. In this contribution, I will discuss the recent methodologies, potentialities and current limits of combined micro- and macro-flow simulations, with particular attention to convergent margins whose dynamics and deep structure is still the object of extensive studies.

  3. Oxygen kinetics and debt during recovery from expiratory flow-limited exercise in healthy humans.

    PubMed

    Vogiatzis, I; Zakynthinos, S; Georgiadou, O; Golemati, S; Pedotti, A; Macklem, P T; Roussos, C; Aliverti, A

    2007-02-01

    In healthy subjects expiratory flow limitation (EFL) during exercise can lower O(2) delivery to the working muscles. We hypothesized that if this affects exercise performance it should influence O(2) kinetics at the end of exercise when the O(2) debt is repaid. We performed an incremental exercise test on six healthy males with a Starling resistor in the expiratory line limiting expiratory flow to approximately 1 l s(-1) to determine maximal EFL exercise workload (W (max)). In two more square-wave exercise runs subjects exercised with and without EFL at W (max) for 6 min, while measuring arterial O(2) saturation (% SaO(2)), end-tidal pressure of CO(2) (P (ET)CO(2)) and breath-by-breath O(2) consumption VO2 taking into account changes in O(2) stored in the lungs. Over the last minute of EFL exercise, mean P (ET)CO(2) (54.7 +/- 9.9 mmHg) was significantly higher (P < 0.05) compared to control (41.4 +/- 3.9 mmHg). At the end of EFL exercise %SaO(2) fell significantly by 4 +/- 3%. When exercise stopped, EFL was removed, and we continued to measure VO2. During recovery, there was an immediate step increase in [Formula: see text] so that repayment of EFL O(2) debt started at a higher VO2 than control. Recovery VO2 kinetics after EFL exercise was best characterized by a double-exponential function with fundamental and slow time constants of 27 +/- 11 and 1,020 +/- 305 s, compared to control values of 41 +/- 10 and 1,358 +/- 320 s, respectively. EFL O(2) debt was 52 +/- 22% greater than control (2.19 +/- 0.58 vs. 1.49 +/- 0.38 l). We conclude that EFL exercise increases the O(2) debt and leads to hypoxemia in part due to hypercapnia.

  4. Fractional flow reserve: physiological basis, advantages and limitations, and potential gender differences.

    PubMed

    Crystal, George J; Klein, Lloyd W

    2015-01-01

    Fractional flow reserve (FFR) is a physiological index of the severity of a stenosis in an epicardial coronary artery, based on the pressure differential across the stenosis. Clinicians are increasingly relying on this method because it is independent of baseline flow, relatively simple, and cost effective. The accurate measurement of FFR is predicated on maximal hyperemia being achieved by pharmacological dilation of the downstream resistance vessels (arterioles). When the stenosis causes FFR to be impaired by > 20%, it is considered to be significant and to justify revascularization. A diminished hyperemic response due to microvascular dysfunction can lead to a false normal FFR value, and a misguided clinical decision. The blunted vasodilation could be the result of defects in the signaling pathways modulated (activated or inhibited) by the drug. This might involve a downregulation or reduced number of vascular receptors, endothelial impairment, or an increased activity of an opposing vasoconstricting mechanism, such as the coronary sympathetic nerves or endothelin. There are data to suggest that microvascular dysfunction is more prevalent in post-menopausal women, perhaps due to reduced estrogen levels. The current review discusses the historical background and physiological basis for FFR, its advantages and limitations, and the phenomenon of microvascular dysfunction and its impact on FFR measurements. The question of whether it is warranted to apply gender-specific guidelines in interpreting FFR measurements is addressed.

  5. Flow-Through Stream Modeling with MODFLOW and MT3D: Certainties and Limitations.

    PubMed

    Ben Simon, Rose; Bernard, Stéphane; Meurville, Charles; Rebour, Vincent

    2015-01-01

    This paper aims to assess MODFLOW and MT3D capabilities for simulating the spread of contaminants from a river exhibiting an unusual relationship with an alluvial aquifer, with the groundwater head higher than the river head on one side and lower on the other (flow-through stream). A series of simulation tests is conducted using a simple hypothetical model so as to characterize and quantify these limitations. Simulation results show that the expected contaminant spread could be achieved with a specific configuration composed of two sets of parameters: (1) modeled object parameters (hydraulic groundwater gradient, hydraulic conductivity values of aquifer and streambed), and (2) modeling parameters (vertical discretization of aquifer, horizontal refinement of stream modeled with River [RIV] package). The influence of these various parameters on simulation results is investigated, and potential complications and errors are identified. Contaminant spread from stream to aquifer is not always reproduced by MT3D due to the RIV package's inability to simulate lateral exchange fluxes between stream and aquifer. This paper identifies the need for a MODFLOW streamflow package allowing lateral stream-aquifer interactions and streamflow routine calculations. Such developments could be of particular interest for modeling contaminated flow-through streams.

  6. Threshold scaling limits of RO concentrates flowing in a long waste disposal pipeline.

    PubMed

    Semiat, R; Hasson, D; Zelmanov, G; Hemo, I

    2004-01-01

    Disposal of RO concentrates emanating from inland brackish water desalination plants presents a difficult environmental problem. The solution adopted by Mekorot--the National Water Company of Israel--is to construct a 30 km waste disposal pipeline for collecting concentrates emanating from several RO desalination plants and discharging them into the sea. The discharged concentrates are highly supersaturated with respect to CaCO3. Scale precipitation during concentrate flow through the RO module is inhibited by the presence of anti-scalants. The retention time of the concentrate solution in the discharge pipe will exceed 100 hours. This raises the issue of the risk of scale precipitation in the discharge pipe that could impair its proper functioning. The aim of the present study was to provide data for guiding the design and operation of the disposal pipeline. The extent of the induction period prior to the onset of precipitation was measured in a pilot plant simulating flow of concentrate solutions dosed with anti-scalants. The parameters investigated were the scaling potential, the anti-scalant concentration and the presence of a mixture of several anti-scalants. The results of this study provide threshold scaling limits under various conditions.

  7. Investigations of Internal Flow Fields of Constant-Area Mixing-Tubes under Starting-Limit Conditions

    NASA Astrophysics Data System (ADS)

    Kitamura, Eijiro; Tomioka, Sadatake; Sakuranaka, Noboru; Watanabe, Syuichi; Masuya, Goro

    Flow fields in the constant-area mixing tubes of ejector jets were investigated under the starting-limit conditions of an aerodynamic choking mode by performing numerical simulations and cold flow experiments. Pressure recovery was almost completed in the shock-train region. The length of the shock-train region (Lst) was measured under various conditions. Lst was proportional to the mass flow rate ratio of the secondary flow to the primary flow when this ratio was less than 0.15. On the other hand, Lst became almost constant when the mass flow rate ratio exceeded 0.15. Numerical studies showed that this change was caused by the difference in the mechanism of the flow fields. In the cases with low air mass flow rates, the primary and secondary flows almost mixed in a region between the inlets of the mixing tubes and the choking points. The pressure was recovered by a pseudo-shock-wave generated downstream of the choking point. On the other hand, when the mass flow rate ratio was higher than 0.15, the primary and secondary flows were clearly separated at the choking point. The pressure recovery was achieved by the mixing between the primary and secondary flows downstream of the choking point.

  8. The effect of water temperature and flow on respiration in barnacles: patterns of mass transfer versus kinetic limitation.

    PubMed

    Nishizaki, Michael T; Carrington, Emily

    2014-06-15

    In aquatic systems, physiological processes such as respiration, photosynthesis and calcification are potentially limited by the exchange of dissolved materials between organisms and their environment. The nature and extent of physiological limitation is, therefore, likely to be dependent on environmental conditions. Here, we assessed the metabolic sensitivity of barnacles under a range of water temperatures and velocities, two factors that influence their distribution. Respiration rates increased in response to changes in temperature and flow, with an interaction where flow had less influence on respiration at low temperatures, and a much larger effect at high temperatures. Model analysis suggested that respiration is mass transfer limited under conditions of low velocity (<7.5 cm (-1)) and high temperature (20-25°C). In contrast, limitation by uptake reaction kinetics, when the biotic capacity of barnacles to absorb and process oxygen is slower than its physical delivery by mass transport, prevailed at high flows (40-150 cm s(-1)) and low temperatures (5-15°C). Moreover, there are intermediate flow-temperature conditions where both mass transfer and kinetic limitation are important. Behavioral monitoring revealed that barnacles fully extend their cirral appendages at low flows and display abbreviated 'testing' behaviors at high flows, suggesting some form of mechanical limitation. In low flow-high temperature treatments, however, barnacles displayed distinct 'pumping' behaviors that may serve to increase ventilation. Our results suggest that in slow-moving waters, respiration may become mass transfer limited as temperatures rise, whereas faster flows may serve to ameliorate the effects of elevated temperatures. Moreover, these results underscore the necessity for approaches that evaluate the combined effects of multiple environmental factors when examining physiological and behavioral performance.

  9. Novel design for centrifugal counter-current chromatography: VI. Ellipsoid column.

    PubMed

    Gu, Dongyu; Yang, Yi; Xin, Xuelei; Aisa, Haji Akber; Ito, Yoichiro

    2015-01-01

    A novel ellipsoid column was designed for centrifugal counter-current chromatography. Performance of the ellipsoid column with a capacity of 3.4 mL was examined with three different solvent systems composed of 1-butanol-acetic acid-water (4:1:5, v/v) (BAW), hexane-ethyl acetate-methanol-0.1 M HCl (1:1:1:1, v/v) (HEMH), and 12.5% (w/w) PEG1000 and 12.5% (w/w) dibasic potassium phosphate in water (PEG-DPP) each with suitable test samples. In dipeptide separation with BAW system, both stationary phase retention (Sf) and peak resolution (Rs) of the ellipsoid column were much higher at 0° column angle (column axis parallel to the centrifugal force) than at 90° column angle (column axis perpendicular to the centrifugal force), where elution with the lower phase at a low flow rate produced the best separation yielding Rs at 2.02 with 27.8% Sf at a flow rate of 0.07 ml/min. In the DNP-amino acid separation with HEMW system, the best results were obtained at a flow rate of 0.05 ml/min with 31.6% Sf yielding high Rs values at 2.16 between DNP-DL-glu and DNP-β-ala peaks and 1.81 between DNP-β-ala and DNP-L-ala peaks. In protein separation with PEG-DPP system, lysozyme and myolobin were resolved at Rs of 1.08 at a flow rate of 0.03 ml/min with 38.9% Sf. Most of those Rs values exceed those obtained from the figure-8 column under similar experimental conditions previously reported.

  10. Temporal analysis of transonic flow field characteristics associated with limit cycle oscillations

    NASA Astrophysics Data System (ADS)

    Pasiliao, Crystal Lynn

    Limit Cycle Oscillation (LCO) is a sustained, non-divergent, periodic motion experienced by aircraft with certain external store configurations. Flutter, an instability caused by the aerodynamic forces coupling with the structural dynamics, and LCO are related as evidenced by the accuracy with which linear flutter models predict LCO frequencies and modal mechanisms. However, since the characteristics of LCO motion are a result of nonlinear effects, flutter models do not accurately predict LCO onset speed and amplitude. Current engineering knowledge and theories are not sufficient to provide an analytical means for direct prediction of LCO; instead engineers rely heavily on historical experience and interpretation of traditional flutter analyses and flight tests as they may correlate to the expected LCO characteristics for the configuration of concern. There exists a significant need for a detailed understanding of the physical mechanisms involved in LCO that can lead to a unified theory and analysis methodology. This dissertation aims for a more thorough comprehension of the nature of the nonlinear aerodynamic effects for transonic LCO mechanisms, providing a significant building block in the understanding of the overall aeroelastic effects in the LCO mechanism. Examination of a true fluid-structure interaction (FSI) LCO case (flexible structure coupled with CFD) is considered quasi-incrementally since this capability does not yet exist in the flutter community. The first step in this process is to perform fluid-structure reaction (FSR) simulations, examining the flow-field during rigid body pitch and roll oscillations, simulating the torsional and bending nature of an LCO mechanism. More complicated configurations and motions will be examined as the state of technology progresses. Through this build-up FSR approach, valuable insight is gained into the characteristics of the flow-field during transonic LCO conditions in order to assess any possible influences on

  11. The upper limit of cerebral blood flow autoregulation in acute intracranial hypertension.

    PubMed

    Hauerberg, J; Xiaodong, M; Willumsen, L; Pedersen, D B; Juhler, M

    1998-04-01

    The present series of experiments was performed to investigate the influence of acute intracranial hypertension on the upper limit (UL) of cerebral blood flow (CBF) autoregulation. Three groups of eight rats each--one with normal intracranial pressure (ICP) (2 mmHg), one with ICP = 30 mmHg, and one with ICP = 50 mmHg--were investigated. Intracranial hypertension was maintained by continuous infusion of lactated Ringer's solution into the cisterna magna, where the pressure was used as ICP. Cerebral perfusion pressure (CPP), calculated as mean arterial blood pressure (MABP)-ICP, was increased stepwise by continuous intravenous infusion of norepinephrine. CBF was calculated by the intracarotid 133Xe method. In all three groups the corresponding CBF/CPP curve included a plateau where CBF was independent of changes in CPP, showing intact autoregulation. At normal ICP the UL was found at a CPP of 141 +/-2 mmHg, at ICP = 30 mmHg the UL was 103+/-5 mmHg, and at ICP = 50 mmHg the UL was found at 88+/-7 mmHg. This shift of the UL was more pronounced than the shift of the lower limit (LL) of the CBF autoregulation found previously. We conclude that intracranial hypertension is followed by both a shift toward lower CPP values and a narrowing of the autoregulated interval between the LL and the UL.

  12. Limits to the evolution of assortative mating by female choice under restricted gene flow.

    PubMed

    Servedio, Maria R

    2011-01-22

    The evolution of assortative mating is a key component of the process of speciation with gene flow. Several recent theoretical studies have pointed out, however, that sexual selection which can result from assortative mating may cause it to plateau at an intermediate level; this is primarily owing to search costs of individuals with extreme phenotypes and to assortative preferences developed by individuals with intermediate phenotypes. I explore the limitations of assortative mating further by analysing a simple model in which these factors have been removed. Specifically, I use a haploid two-population model to ask whether the existence of assortative mating is sufficient to drive the further evolution of assortative mating. I find that a weakening in the effective strength of sexual selection with strong assortment leads to the existence of both a peak level of trait differentiation and the evolution of an intermediate level of assortative mating that will cause that peak. This result is robust to the inclusion of local adaptation and different genetic architecture of the trait. The results imply the existence of fundamental limits to the evolution of assortment via sexual selection in this situation, with which other factors, such as search costs, may interact.

  13. A conservative approximation to compressible two-phase flow models in the stiff mechanical relaxation limit

    SciTech Connect

    Deledicque, Vincent; Papalexandris, Miltiadis V.

    2008-11-10

    In this article, we present and analyze a conservative approximation to reduced one-pressure one-velocity models for compressible two-phase flows that contain non-conservative products. This approximation is valid when certain material properties of the two phases are considerably different from each other. Although it cannot be applied to arbitrary mixtures, it is applicable to many heterogeneous mixtures of technological interest. Herein, we derive the Rankine-Hugoniot relations and Riemann invariants for the homogeneous part of the proposed model and develop an exact Riemann solver for it. Further, we investigate the structure of the steady two-phase detonation waves, with inert or reactive solid particles, admitted by the proposed model. Comparisons with the corresponding gaseous detonations are also made. Moreover, we derive a lower limit for the propagation speed of steady two-phase detonations in the case of reactive particles. At the limiting case of very dilute mixtures, this minimum speed tends to the Chapman-Jouguet velocity of gaseous detonations. Finally, we report on numerical simulations of the transmission of a purely gaseous detonation to heterogeneous mixtures containing inert or reactive solid particles. The effect of the solid particles on the structure of the resulting two-phase detonation is discussed in detail.

  14. Turbulence, flows and edge localized mode (ELM) dynamics in limiter H-mode plasmas in TEXTOR

    NASA Astrophysics Data System (ADS)

    Soldatov, S.; Krämer-Flecken, A.; Kantor, M.; Unterberg, B.; Sun, Y.; Van Oost, G.; Reiter, D.; TEXTOR Team

    2010-08-01

    The turbulence, plasma flow and edge localized mode (ELM) dynamics in the limiter H-mode TEXTOR plasmas are investigated. Properties of both ambient turbulence within 0 < k⊥ < 4.2 cm-1 and coherent modes are studied on the ELM time scale in detail. The turbulence level near the pedestal is shown to evolve several times with the period of ELMs. Within the inter-ELM period the 'silent stage' is found which is characterized by an extremely low (below that for Ohmic plasmas) turbulence level and a phase growth in the reflectometry signal. The silent stage is associated with the quasi-steady state when the pedestal is formed and confinement is improved between two successive ELMs. Quasi-coherent density oscillations near the pedestal region with m ≈ 3, 5, 16 and 38 are measured with correlation reflectometry. Low-m modes are found to reveal the signatures of precursor mode. At first, the radial structure of the rotation shear and radial electric field Er in limiter H-mode in TEXTOR is presented. The characteristic negative electric field well with the sharp gradient ∇Er ≈ 250 V cm-2 at ≈2 cm inside separatrix is resolved. The Er × B rotation profile defines both the resulting plasma rotation in the electron diamagnetic drift direction and a significant rotation shear near the separatrix which exceeds the decorrelation rate of ambient turbulence by several times.

  15. Preparative separation of grape skin polyphenols by high-speed counter-current chromatography.

    PubMed

    Luo, Lanxin; Cui, Yan; Zhang, Shuting; Li, Lingxi; Li, Yuanyuan; Zhou, Peiyu; Sun, Baoshan

    2016-12-01

    To develop an efficient method for large preparation of various individual polyphenols from white grape skins (Fernão Pires; Vitis vinifera) by preparative high-speed counter-current chromatography (HSCCC) and preparative-HPLC, an optimized preparative HSCCC condition with two-phase solvent system composed of Hex-EtOAc-H2O (1:50:50, v/v) was used to separate grape skin polyphenols into various fractions. Both the tail-head and head-tail elution modes were used with a flow rate of 3.0ml/min and a rotary speed of 950rpm. Afterwards, a preparative-HPLC separation was applied to isolate individual polyphenols in each of the fractions from HSCCC. Total of 7 fractions (Fraction A to G) were obtained from grape skin extract by HSCCC. After preparative-HPLC isolation, fifteen individual compounds were obtained, most of which presented high yields and purity (all over 90%). The HSCCC method followed with preparative-HPLC appeared to be convenient and economical, constituting an efficient strategy for the isolation of grape skin polyphenols.

  16. Improved spiral tube assembly for high-speed counter-current chromatography.

    PubMed

    Ito, Y; Clary, R; Powell, J; Knight, M; Finn, T M

    2009-05-08

    The original spiral tube support (STS) assembly is improved by changing the shape of the tubing, with 1-cm presses perpendicularly along the length. This modification interrupts the laminar flow of the mobile phase. The tubing in the four return grooves to the center of the rotor is flattened by a specially made pressing tool to increase the number of spiral layers and decrease the dead space volume, thus increasing the column efficiency. The performance of this spiral tube assembly was tested in separations of dipeptides and proteins with suitable polar two-phase solvent systems. The results revealed that the present system yields high partition efficiency with a satisfactory level of stationary phase retention in a short elution time. The present high-speed counter-current chromatographic (HSCCC) system will be efficiently applied to a broad spectrum of two-phase solvent systems including aqueous-aqueous polymer phase systems (TPAS) which are used for separation of biopolymers such as proteins and nucleic acids.

  17. High-frequency limit of non-autonomous gradient flows of functionals with time-periodic forcing

    NASA Astrophysics Data System (ADS)

    Plazotta, Simon; Zinsl, Jonathan

    2016-12-01

    We study the high-frequency limit of non-autonomous gradient flows in metric spaces of energy functionals comprising an explicitly time-dependent perturbation term which might oscillate in a rapid way. On grounds of the existence results by Ferreira and Guevara (2015) on non-autonomous gradient flows (which we also extend to a broader range of energy functionals), we prove that the associated solution curves converge to a solution of the time-averaged evolution equation in the limit of infinite frequency. Under additional assumptions on the energy, we obtain an explicit rate of convergence. Furthermore, we specifically investigate nonlinear drift-diffusion equations with time-dependent drift which formally are gradient flows with respect to the L2-Wasserstein distance. We prove that a family of weak solutions obtained as a limit of the Minimizing Movements scheme exhibits the above-mentioned behavior in the high-frequency limit.

  18. Preparative separation of high-purity cordycepin from Cordyceps militaris(L.) Link by high-speed countercurrent chromatography

    PubMed Central

    Zhu, Licai; Liang, Yong; Lao, Deqiang; Zhang, Tianyou; Ito, Yoichiro

    2009-01-01

    A high-speed counter-current chromatography (HSCCC) technique in a preparative scale has been applied to separate and purify cordycepin from the extract of Cordyceps militaris(L.) Link by a one-step separation. A high efficiency of HSCCC separation was achieved on a two-phase solvent system of n-hexane–n-butanol–methanol–water (23:80:30:155, v/v/v/v) by eluting the lower mobile phase at a flow rate of 2 ml/min under a revolution speed of 850 rpm. HSCCC separation of 216.2 mg crude sample (contained cordycepin at 44.7% purity after 732 cation-exchange resin clean-up) yielded 64.8 mg cordycepin with purity of 98.9% and 91.7% recovery. Identification of the target compound was performed by UV, IR, MS, 1H NMR and 13C NMR. PMID:21643461

  19. Isolation of all-trans lycopene by high-speed counter-current chromatography using a temperature-controlled solvent system.

    PubMed

    Baldermann, Susanne; Ropeter, Katharina; Köhler, Nils; Fleischmann, Peter

    2008-05-23

    The effect of solvent system, partition coefficient, retention of stationary phase, column, revolution speed, and flow rate of mobile phase are well known parameters to effect HSCCC (high-speed counter-current chromatography) separations. Temperature effects on chromatographic techniques like HPLC and GC are well studied, but the influence of temperature on CCC solvent systems is hardly investigated. This paper presents the influence of temperature on several key parameters (partition coefficient, settling time, volume ratios) in the hydrophobic HSCCC solvent system hexane:dichloromethane:acetonitrile (30:11:18, v/v/v) used for the isolation of lycopene from tomato paste at 10, 15, 20 and 25 degrees C.

  20. First results of the use of a continuously flowing lithium limiter in high performance discharges in the EAST device

    NASA Astrophysics Data System (ADS)

    Hu, J. S.; Zuo, G. Z.; Ren, J.; Yang, Q. X.; Chen, Z. X.; Xu, H.; Zakharov, L. E.; Maingi, R.; Gentile, C.; Meng, X. C.; Sun, Z.; Xu, W.; Chen, Y.; Fan, D.; Yan, N.; Duan, Y. M.; Yang, Z. D.; Zhao, H. L.; Song, Y. T.; Zhang, X. D.; Wan, B. N.; Li, J. G.; EAST Team

    2016-04-01

    As an alternative choice of solid plasma facing components (PFCs), flowing liquid lithium can serve as a limiter or divertor PFC and offers a self-healing surface with acceptable heat removal and good impurity control. Such a system could improve plasma performance, and therefore be attractive for future fusion devices. Recently, a continuously flowing liquid lithium (FLiLi) limiter has been successfully designed and tested in the EAST superconducting tokamak. A circulating lithium layer with a thickness of  <0.1 mm and a flow rate ~2 cm3 s-1 was achieved. A novel in-vessel electro-magnetic pump, working with the toroidal magnetic field of the EAST device, was reliable to control the lithium flow speed. The flowing liquid limiter was found to be fully compatible with various plasma scenarios, including high confinement mode plasmas heated by lower hybrid waves or by neutral beam injection. It was also found that the controllable lithium emission from the limiter was beneficial for the reduction of recycling and impurities, for the reduction of divertor heat flux, and in certain cases, for the improvement of plasma stored energy, which bodes well application for the use of flowing liquid lithium PFCs in future fusion devices.

  1. Larval tolerance, gene flow, and the northern geographic range limit of fiddler crabs.

    PubMed

    Sanford, Eric; Holzman, Samuel B; Haney, Robert A; Rand, David M; Bertness, Mark D

    2006-11-01

    Despite growing interest in species' range shifts, little is known about the ecological and evolutionary factors that control geographic range boundaries. We investigated the processes that maintain the northern range limit of the mud fiddler crab (Uca pugnax) at North Scituate, Massachusetts, USA (42 degrees 14' N), located approximately 60 km north of Cape Cod. Larvae from five populations in Massachusetts were reared under controlled temperatures to test whether cooler water near the edge of this species' range inhibits planktonic development. Few larvae completed development at temperatures < 18 degrees C, a threshold that larvae would regularly encounter north of Cape Cod. Extensive salt marshes are present north of the current range boundary, and a transplant experiment using field enclosures confirmed that benthic fiddler crabs can survive severe winter conditions in this northern habitat. Taken with oceanographic data, these results suggest that the range boundary of fiddler crabs is likely maintained by the influence of cooler water temperatures on the larval phase. Analyses of mitochondrial DNA sequences from a neutral marker (COI) indicate high gene flow among U. pugnax populations in Massachusetts with little differentiation across Cape Cod. Consistent with predictions regarding the homogenizing influence of gene flow, larvae from source populations north and south of Cape Cod shared a common lower threshold for development. However, larvae produced near the range edge had faster growth rates than those from the south side of Cape Cod (typically reaching the final megalopal stage 1.0-5.5 d faster at 18 degrees C). Additional studies are needed to determine the mechanism underlying this counter-gradient variation in development time. We hypothesize that dispersal into cooler water on the north side of Cape Cod may act as a selection filter that sieves out slow developers from the larval pool by increasing planktonic duration and exposure to associated

  2. Seasonal variation of the surface North Equatorial Countercurrent (NECC) in the western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Zhao, Jun; Li, Yuanlong; Wang, Fan

    2016-11-01

    The North Equatorial Countercurrent (NECC) is an important zonal flow in the upper circulation of the tropical Pacific Ocean, which plays a vital role in the heat budget of the western Pacific warm pool. Using satellite-derived data of ocean surface currents and sea surface heights (SSHs) from 1992 to 2011, the seasonal variation of the surface NECC in the western tropical Pacific Ocean was investigated. It was found that the intensity (INT) and axis position (Y CM ) of the surface NECC exhibit strikingly different seasonal fluctuations in the upstream (128°-136°E) and downstream (145°-160°E) regions. Of the two regions, the seasonal cycle of the upstream NECC shows the greater interannual variability. Its INT and YCM are greatly influenced by variations of the Mindanao Eddy, Mindanao Dome (MD), and equatorial Rossby waves to its south. Both INT and Y CM also show semiannual signals induced by the combined effects of equatorial Rossby waves from the Central Pacific and local wind forcing in the western Pacific Ocean. In the downstream region, the variability of the NECC is affected by SSH anomalies in the MD and the central equatorial Pacific Ocean. Those in the MD region are especially important in modulating the YCM of the downstream NECC. In addition to the SSH-related geostrophic flow, zonal Ekman flow driven by meridional wind stress also plays a role, having considerable impact on INT variability of the surface NECC. The contrasting features of the variability of the NECC in the upstream and downstream regions reflect the high complexity of regional ocean dynamics.

  3. Determination of Alternaria mycotoxins in wine and juice using ionic liquid modified countercurrent chromatography as a pretreatment method followed by high-performance liquid chromatography.

    PubMed

    Fan, Chen; Cao, Xueli; Liu, Man; Wang, Wei

    2016-03-04

    Alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA) are some of the main Alternaria mycotoxins that can be found as contaminants in food materials. The objective of this study was to develop a pretreatment method with countercurrent chromatography (CCC) for enrichment and cleanup of trace Alternaria mycotoxins in food samples prior to high-performance liquid chromatography (HPLC) analysis. An Analytical CCC instrument with a column volume 22.5mL was used, and a two-phase solvent system composed of ethyl acetate and water modified with 6% [HOOMIM][Cl] in mass to volume ratio was selected. Under the optimized CCC operation conditions, trace amounts of AOH, AME, and TeA in large volume of liquid sample were efficiently extracted and enriched in the stationary phase, and then eluted out just by reversing the stationary phase as mobile phase in the opposite flowing direction tail-to-head. The enrichment and elution strategies are unique and can be fulfilled online with high enrichment factors (87-114) and high recoveries (81.14-110.94%). The method has been successively applied to the determination of Alternaria mycotoxins in real apple juice and wine samples with the limits of detection (LOD) in the range of 0.03-0.14μgL(-1). Totally 12 wine samples and 15 apple juice samples from the local market were analyzed. The detection rate of AOH and AME in both kinds of the samples were more than 50%, while TeA was found in relatively high level of 1.75-49.61μgL(-1) in some of the apple juice samples. The proposed method is simple, rapid, and sensitive and could also be used for the analysis and monitoring of Alternaria mycotoxin in other food samples.

  4. Fluid Dynamics Panel Working Group 10 on Calculation of 3D Separate Turbulent Flows in Boundary Layer Limit (Le Calcul des Ecoulements Turbulents, Decolles Tridimensionnels en Couche Limite)

    DTIC Science & Technology

    1990-05-01

    sufficient inspiration to appreciate the work performed by the various members of the Working Group and their co-workers. The participants’ names are given...Depuis la premiere reunion, organis&c vera la fin de l’annee 1985, un certain nombre de problimes d’ordre technique et logistique se sont poses et le...96503-0007 1. INTRODUCTION Flow separation plays a dominant role in the high lift performance of combat aircraft, invariably limiting takeoff and

  5. [Chronic cough in the elderly is associated with expiratory flow limitation].

    PubMed

    Frappé, E; Gautier-Guillot, M; Barthélémy, J-C; Maudoux, D; Roche, F; Costes, F

    2013-03-01

    As chronic respiratory symptoms and the presence of expiratory flow limitation (EFL) are commonly reported in the elderly, we investigated whether they were associated in a population of 75 years old volunteers. We analyzed the results of a prevalence survey of chronic respiratory symptoms and respiratory infections, and performed spirometry and measured EFL after application of a negative expiratory pressure at the mouth (NEP). EFL was present in 170 (46%) subjects, a chronic cough in 49 (13%), chronic sputum in 58 (29%) and a history of respiratory infection in 62 (17%). Chronic cough and the composite outcome "chronic cough or sputum" were significantly associated with the presence of EFL (respectively 60% vs. 43%, OR=2.04 [1.09 to 3.78], P=0.023, and 56% vs. 43%, OR=1.74 [1.05 to 2.87], P=0.04), after controlling for smoking or airway obstruction. History of respiratory infections were not associated with an increased prevalence of EFL. We concluded that the presence of a LED could be an interesting indicator of respiratory aging. Its detection could be advocated in elderly subjects presenting with respiratory symptoms.

  6. Is tidal expiratory flow limitation predictive of sleep-related disorders in the elderly?

    PubMed

    Guillot, M; Costes, F; Sforza, E; Maudoux, D; Bertoletti, L; Barthélémy, J C; Roche, F

    2010-10-01

    Sleep-related disorders represent an important health burden and their prevalence increases with age. In patients with snoring or sleepiness, the presence of expiratory flow limitation (EFL), determined via the negative expiratory pressure (NEP) method, is related to the apnoea/hypopnoea index (AHI). In this study, we examined whether EFL can be used to predict obstructive sleep apnoea syndrome (OSAS) in healthy asymptomatic older subjects. A group of 72-yr-old subjects (n = 448, 44% males) with a mean body mass index of 25.5±3.8 kg·m(-2) were examined. All subjects underwent spirometry, NEP (-5 cmH(2)O, sitting position) and ventilatory polygraphy (VP). Spirometry was within normal values in 88% of the group and EFL was present in 143 (32%) subjects with a higher prevalence in females (89 out of 249 versus 54 out of 199 in females and males, respectively). VP showed an AHI<15 h(-1) in 238 subjects (53%) and OSAS with an AHI ≥15 h(-1) in 47%. EFL was found in 15% of subjects with OSAS. Consequently, EFL had low sensitivity and specificity in the prediction of OSAS (31.4% and 67.7%, respectively). We conclude that the prevalence of EFL is elevated in healthy older subjects and cannot be used to predict the presence of sleep-related disorders in an older population.

  7. Respiratory muscle dynamics and control during exercise with externally imposed expiratory flow limitation.

    PubMed

    Aliverti, Andrea; Iandelli, Iacopo; Duranti, Roberto; Cala, Stephen J; Kayser, Bengt; Kelly, Susan; Misuri, Gianni; Pedotti, Antonio; Scano, Giorgio; Sliwinski, Pawel; Yan, Sheng; Macklem, Peter T

    2002-05-01

    To determine how decreasing velocity of shortening (U) of expiratory muscles affects breathing during exercise, six normal men performed incremental exercise with externally imposed expiratory flow limitation (EFLe) at approximately 1 l/s. We measured volumes of chest wall, lung- and diaphragm-apposed rib cage (Vrc,p and Vrc,a, respectively), and abdomen (Vab) by optoelectronic plethysmography; esophageal, gastric, and transdiaphragmatic pressures (Pdi); and end-tidal CO2 concentration. From these, we calculated velocity of shortening and power (W) of diaphragm, rib cage, and abdominal muscles (di, rcm, ab, respectively). EFLe forced a decrease in Uab, which increased Pab and which lasted well into inspiration. This imposed a load, overcome by preinspiratory diaphragm contraction. Udi and inspiratory Urcm increased, reducing their ability to generate pressure. Pdi, Prcm, and Wab increased, indicating an increased central drive to all muscle groups secondary to hypercapnia, which developed in all subjects. These results suggest a vicious cycle in which EFLe decreases Uab, increasing Pab and exacerbating the hypercapnia, which increases central drive increasing Pab even more, leading to further CO2 retention, and so forth.

  8. Explaining the subpulse drift velocity of pulsar magnetosphere within the space-charge limited flow model

    NASA Astrophysics Data System (ADS)

    Morozova, Viktoriya S.; Ahmedov, Bobomurat J.; Zanotti, Olindo

    2014-10-01

    We try to explain the subpulse drift phenomena adopting the space-charge limited flow model and comparing the plasma drift velocity in the inner region of pulsar magnetospheres with the observed velocity of drifting subpulses. We apply the approach described in a recent paper of van Leeuwen & Timokhin, where it was shown that the standard estimation of the subpulse drift velocity through the total value of the scalar potential drop in the inner gap gives inaccurate results, while the exact expression relating the drift velocity to the gradient of the scalar potential should be used instead. After considering a selected sample of sources taken from the catalogue of Weltevrede et al. with coherently drifting subpulses and reasonably known observing geometry, we show that their subpulse drift velocities would correspond to the drift of the plasma located very close or above the pair formation front. Moreover, a detailed analysis of PSR B0826-34 and PSR B0818-41 reveals that the variation of the subpulse separation with the pulse longitude can be successfully explained by the dependence of the plasma drift velocity on the angular coordinates.

  9. Accurate early-time and late-time modeling of countercurrent spontaneous imbibition

    NASA Astrophysics Data System (ADS)

    March, Rafael; Doster, Florian; Geiger, Sebastian

    2016-08-01

    Spontaneous countercurrent imbibition into a finite porous medium is an important physical mechanism for many applications, included but not limited to irrigation, CO2 storage, and oil recovery. Symmetry considerations that are often valid in fractured porous media allow us to study the process in a one-dimensional domain. In 1-D, for incompressible fluids and homogeneous rocks, the onset of imbibition can be captured by self-similar solutions and the imbibed volume scales with √t. At later times, the imbibition rate decreases and the finite size of the medium has to be taken into account. This requires numerical solutions. Here we present a new approach to approximate the whole imbibition process semianalytically. The onset is captured by a semianalytical solution. We also provide an a priori estimate of the time until which the imbibed volume scales with √t. This time is significantly longer than the time it takes until the imbibition front reaches the model boundary. The remainder of the imbibition process is obtained from a self-similarity solution. We test our approach against numerical solutions that employ parametrizations relevant for oil recovery and CO2 sequestration. We show that this concept improves common first-order approaches that heavily underestimate early-time behavior and note that it can be readily included into dual-porosity models.

  10. Channel Flow Model of Extrusion of the Higher Himalaya- Successes & Limitations

    NASA Astrophysics Data System (ADS)

    Mukherjee, S.

    2009-04-01

    During laminar ‘channel flow'/‘Plane Poiseuille flow' of an incompressible Newtonian viscous fluid through a very long parallel horizontal static walls of a channel due to a pressure gradient, a parabolic velocity profile is produced. The sense of ductile shearing across the middle of the channel is opposite. Grujic et al. (1996) and Beaumont et al. (2001) applied this flow mechanism to explain the extrusion of the Higher Himalaya (HH). In their sequel, the Dalhousie school of modelers kept enumerating this extrusion model. Successes of the channel flow extrusion model are that it explains (1) extensional top-to-NE sense of ductile shearing in the South Tibetan Detachment System (STDS) simultaneous to the top-to-SW sense of compressional shearing in the remainder of the HH; (2) fluid activity below the southern part of the Tibetan plateau; and (3) inverted metamorphism in the HH. However, limitations of this extrusion model are as follows. (1) A previous top-to-SW sense of compressional shearing in the STDS is not taken care by the model alone. (2) The thickness of the STDS in reality is thinner than the remainder of the HH. In the model, on the other hand, their thicknesses should be the same. (3) Presence of a second strand of the STDS inside the HH that is absent in some sections of the mountain chain remained unexplained in the model. (4) The ductile shear fabric of more commonly sigmoid-, and less commonly parallelogram- and lenticular geometries are found inside the HH. However, had the channel flow been the extrusion mechanism and rocks deformed as a Newtonian fluid, parabolic shear fabrics are expected. Additionally, can the genesis of the intrafolial folds inside the two strands of the STDS (e.g. Mukherjee, 2007) be explained by the channel flow mechanism? (5) Regions and their spatial extents with different senses of ductile shearing would change if the rocks deformed Non-Newtonically. The exact geometry of the velocity profile will depend on the

  11. On Postoperative Day Balloon Angioplasty for Salvage of Newly-Placed, Flow-Limiting Native Arteriovenous Fistula

    PubMed Central

    Park, Jae Young; Yoo, Chang Hyun

    2015-01-01

    Purpose: To report result and usefulness of immediate postoperative balloon angioplasty of de novo arteriovenous fistula (AVF) with limited flow just after creation. Materials and Methods: From January 1, 2012 to March 31, 2014, 1,270 patients received native AVF creations in a single vascular clinic. In twenty-four patients (1.9% of total AVF creation), immediate postoperative balloon angioplasty was performed because of limited flow on palpation (only pulsation or no thrill) just after AVF creation. Medical records were reviewed retrospectively; technical success (restoration of AVF flow)/clinical success (growing as functional AVF) rate, maturation time, primary patency rate and fistula survival outcome were analyzed during a mean 10.8 months of follow-up. Results: Technical/clinical success rate was 95.8% (23/24 cases); AVF flow was restored after balloon angioplasty, and all the flow-restorated AVFs grew as functional AVFs with mean±standard deviation, 4.5±1.5 weeks of maturation time. In seven (30.4%) patients, a secondary balloon angioplasty was needed to enhance maturation. The overall primary patency after immediate postoperative balloon angioplasty was 69.6% at 1 and 6 months and 59.0% at 12 months. There was 1 complication (operation site hematoma). Conclusion: Immediate postoperative balloon angioplasty for salvage of newly-placed, flow-limiting native AVF is a useful, effective and safe procedure. PMID:26217640

  12. Numerical model for swirl flow cooling in high-heat-flux particle beam targets and the design of a swirl-flow-based plasma limiter

    SciTech Connect

    Milora, S.L.; Combs, S.K.; Foster, C.A.

    1984-11-01

    An unsteady, two-dimensional heat conduction code has been used to study the performance of swirl-flow-based neutral particle beam targets. The model includes the effects of two-phase heat transfer and asymmetric heating of tubular elements. The calorimeter installed in the Medium Energy Test Facility, which has been subjected to 30-s neutral beam pulses with incident heat flux intensities of greater than or equal to 5 kW/cm/sup 2/, has been modeled. The numerical results indicate that local heat fluxes in excess of 7 kW/cm/sup 2/ occur at the water-cooled surface on the side exposed to the beam. This exceeds critical heat flux limits for uniformly heated tubes wih straight flow by approximately a factor of 5. The design of a plasma limiter based on swirl flow heat transfer is presented.

  13. Prediction of cavitation performance and choking flow limit of inducers for cold water and for fluids with thermodynamic effect

    NASA Astrophysics Data System (ADS)

    Sauvage-Boutar, E.; Desclaux, J.

    1990-07-01

    Two methods of prediction of partial cavitation in inducers of rocket engine turbopumps have been developed. The first one is an analytical method previously developed to predict minimum NPSH (inlet total head minus vapor pressure) and the choking flow limit which was modified to include the computation of blade and boundary layer blockage. The second one is a method based on the work of Moore and Ruggeri (1969). This method takes into account thermodynamic effect for the prediction of the cavitation parameter Ki. For the choking flow limit, the first method can be extended to cryogenic fluids. Comparisons with available experimental data obtained with VULCAIN inducer pumping water and liquid hydrogen are presented.

  14. Characterisation of coastal counter-currents on the inner shelf of the Gulf of Cadiz

    NASA Astrophysics Data System (ADS)

    Garel, E.; Laiz, I.; Drago, T.; Relvas, P.

    2016-03-01

    At the Gulf of Cadiz (GoC), poleward currents leaning along the coast alternate with coastal upwelling jets of opposite direction. Here the patterns of these coastal countercurrents (CCCs) are derived from ADCP data collected during 7 deployments at a single location on the inner shelf. The multiyear (2008-2014) time-series, constituting ~ 18 months of hourly records, are further analysed together with wind data from several sources representing local and basin-scale conditions. During one deployment, temperature sensors were also installed near the mooring site to examine the vertical thermal stratification associated with periods of poleward flow. These observations indicate that the coastal circulation is mainly alongshore and barotropic. However, a baroclinic flow is often observed shortly at the time of flow inversion to poleward. CCCs develop all year-round and exclusively control the occurrence of warm coastal water during the upwelling season. On average, one poleward flow lasting 3 days was observed every week, corresponding to CCCs during ~ 40% of the time without seasonal variability. Thus, the studied region is distinct from typical upwelling systems where equatorward coastal upwelling jets largely predominate. CCCs often start to develop near the bed and are frequently associated with 2-layer cross-shore flows characteristic of downwelling conditions (offshore near the bed). In general, the action of alongshore wind stress alone does not justify the development of CCCs. The coastal circulation is best correlated and shows the highest coherence with south-eastward wind in the basin that proceeds from the rotation of southward wind at the West coast of Portugal, hence suggesting a dominant control of large-scale wind conditions. In agreement, wavelet analyses indicate that CCCs are best correlated with alongshore wind occurring in a band period characteristic of the upwelling system (8-32 days). Furthermore, in the absence of wind coastal currents tend

  15. Influence of expiratory flow-limitation during exercise on systemic oxygen delivery in humans.

    PubMed

    Aliverti, A; Dellacà, R L; Lotti, P; Bertini, S; Duranti, R; Scano, G; Heyman, J; Lo Mauro, A; Pedotti, A; Macklem, P T

    2005-10-01

    To determine the effects of exercise with expiratory flow-limitation (EFL) on systemic O(2) delivery, seven normal subjects performed incremental exercise with and without EFL at approximately 0.8 l s(-1) (imposed by a Starling resistor in the expiratory line) to determine maximal power output under control (W'(max,c)) and EFL (W'(max,e)) conditions. W'(max,e) was 62.5% of W'(max,c), and EFL exercise caused a significant fall in the ventilatory threshold. In a third test, after exercising at W'(max,e) without EFL for 4 min, EFL was imposed; exercise continued for 4 more minutes or until exhaustion. O(2) consumption (V'(O)(2)) was measured breath-by-breath for the last 90 s of control, and for the first 90 s of EFL exercise. Assuming that the arterio-mixed venous O(2) content remained constant immediately after EFL imposition, we used V'(O)(2) as a measure of cardiac output (Q'(c)). Q'(c) was also calculated by the pulse contour method with blood pressure measured continuously by a photo-plethysmographic device. Both sets of data showed a decrease of Q'(c) due to a decrease in stroke volume by 10% (p < 0.001 for V'(O)(2)) with EFL and remained decreased for the full 90 s. Concurrently, arterial O(2) saturation decreased by 5%, abdominal, pleural and alveolar pressures increased, and duty cycle decreased by 43%. We conclude that this combination of events led to a decrease in venous return secondary to high expiratory pressures, and a decreased duty cycle which decreased O(2) delivery to working muscles by approximately 15%.

  16. Possibilities and limitations of modeling environmental exposure to engineered nanomaterials by probabilistic material flow analysis.

    PubMed

    Gottschalk, Fadri; Sonderer, Tobias; Scholz, Roland W; Nowack, Bernd

    2010-05-01

    Information on environmental concentrations is needed to assess the risks that engineered nanomaterials (ENM) may pose to the environment. In this study, predicted environmental concentrations (PEC) were modeled for nano-TiO2, carbon nanotubes (CNT) and nano-Ag for Switzerland. Based on a life-cycle perspective, the model considered as input parameters the production volumes of the ENMs, the manufacturing and consumption quantities of products containing those materials, and the fate and pathways of ENMs in natural and technical environments. Faced with a distinct scarcity of data, we used a probabilistic material flow analysis model, treating all parameters as probability distributions. The modeling included Monte Carlo and Markov Chain Monte Carlo simulations as well as a sensitivity and uncertainty analysis. The PEC values of the ENMs in the different environmental compartments vary widely due to different ENM production volumes and different life cycles of the nanoproducts. The use of ENM in products with high water relevance leads to higher water and sediment concentrations for nano-TiO2 and nano-Ag, compared to CNTs, where smaller amounts of ENM reach the aquatic compartments. This study also presents a sensitivity analysis and a comprehensive discussion of the uncertainties of the simulation results and the limitations of the used approach. To estimate potential risks, the PEC values were compared to the predicted-no-effect concentrations (PNEC) derived from published data. The risk quotients (PEC/PNEC) for nano-TiO2 and nano-Ag were larger than one for treated wastewater and much smaller for all other environmental compartments (e.g., water, sediments, soils). We conclude that probabilistic modeling is very useful for predicting environmental concentrations of ENMs given the current lack of substantiated data.

  17. High-speed counter-current chromatographic separation of phytosterols.

    PubMed

    Schröder, Markus; Vetter, Walter

    2011-07-01

    Phytosterols are bioactive compounds which occur in low concentrations in plant oils. Due to their beneficial effects on human health, phytosterols have already been supplemented to food. Commercial phytosterol standards show insufficient purity and/or are very expensive. In this study, we developed a high-speed counter-current chromatography (HSCCC) method for the fractionation and analysis of a commercial crude β-sitosterol standard (purity ∼60% according to supplier). Different solvent systems were tested in shake-flask experiments, and the system n-hexane/methanol/aqueous silver nitrate solution (34/24/1, v/v/v) was finally used for HSCCC fractionation. About 50 mg phytosterols was injected and distributed into 57 fractions. Selected fractions were condensed and re-injected into the HSCCC system. This measure provided pure sitostanol (>99%) and β-sitosterol (∼99%), as well as a mixture of campesterol and stigmasterol without further phytosterols. An enriched HSCCC fraction facilitated the mass spectrometric analysis of further 11 minor phytosterols (after trimethylsilylation). It was also shown that the commercial product contained about 0.3% carotinoids which eluted without delay into an early HSCCC fraction and which were separated from the phytosterols.

  18. Enantioselective Recognition in Solution: The Case of Countercurrent Chromatography

    NASA Astrophysics Data System (ADS)

    Rubio, Núria; Minguillón, Cristina

    Countercurrent chromatography (CCC) is a preparative separation technique that works with a liquid stationary phase. Biphasic liquid systems are needed to perform a separation. Since a chiral selector is required to perform enantiomer separations, special requirements are imposed in CCC. The chiral selector (CS) must be located in the stationary phase since partitioning with the mobile phase would cause losses of the valuable chiral selector in the mobile phase. Sulfated cyclodextrins and proteins were used as polar CS located in the polar stationary phase (reversed phase mode). Apolar CSs such as N-dodecyl-L-proline 3,5-dimethylanilide or Whelk-O selectors, quinine and quinidine derivatives, cellulose or amylose apolar derivatives were used located in the apolar stationary phase (normal phase mode). The special CCC displacement method called pH-zone refining was found useful in the increase of the loading capacity for cellulose, quinine, quinidine, and proline-derived selectors. Dual and multidual mode uses of CCC could produce an increase in peak separation thereby broadening the applicability of moderately enantioselective CSs.

  19. Annual and longitudinal variations of the Pacific North Equatorial Countercurrent

    NASA Technical Reports Server (NTRS)

    Lolk, Nina K.

    1992-01-01

    The climatological annual cycle of the Pacific North Equatorial Countercurrent (NECC) simulated by an ocean general circulation model (OGCM) was studied. The longitudinal variation of transports, degree of geostrophy, and the relationship between Ekman pumping and vertical displacement of the thermocline were emphasized. The longitudinal variation was explored using six sections along 150 deg E, 180 deg, 160 deg W, 140 deg W, 125 deg W, and 110 deg W. A primitive equation OGCM of the Pacific Ocean was run for three years and the fields used were from the third year. The fields consisted of zonal, meridional, and vertical current components and temperature and salinity averaged every three days. The model was forced with the Hellerman and Rosenstein climatological wind stress. The mean annual eastward transport (19.9 Sv) was largest at 160 deg W. The maximum-current boundaries along 160 deg W were 9.2 deg N (1.0 deg), 5.1 deg N (1.1 deg), and 187 m (90.6 m). The annual-cycle amplitude of the NECC was greatest between 160 deg W and 140 deg W. Although the NECC is geostrophic to the first order, deviations from geostrophy were found in the boreal spring and summer near the southern boundary and near the surface. Meridional local acceleration played a role between 3 deg N-5 deg N.

  20. MOLECULAR METHODS USED TO ASSESS THE RISKS OF TRANSGENE FLOW; BENEFITS AND LIMITATIONS

    EPA Science Inventory

    The US EPA WED has initiated a gene flow project to characterize ecological risks of gene flow from GM plants to native species. Development of molecular assays for risk characterization down to gene expression level is of high interest to the EPA. Phylogenetic analyses of ampl...

  1. Comparison of laser excited fluorescence and photoacoustic limits of detection for static and flow cells

    SciTech Connect

    Voigtman, E.; Jurgensen, A.; Winefordner, J.D.

    1981-10-01

    The fluorescence and photoacoustic characteristics of a windowless flow cell intended for liquid chromatographic applications are compared with respective characteristics of a static cuvette cell. In addition, a photoionization mode of operation for the flow cell is exhibited which utilizes the ionization products of two-photon excitation of polynuclear aromatic hydrocarbons in n-alkanes to effect a sensitive detection of those PAHs.

  2. Accuracy of 1D microvascular flow models in the limit of low Reynolds numbers.

    PubMed

    Pindera, Maciej Z; Ding, Hui; Athavale, Mahesh M; Chen, Zhijian

    2009-05-01

    We describe results of numerical simulations of steady flows in tubes with branch bifurcations using fully 3D and reduced 1D geometries. The intent is to delineate the range of validity of reduced models used for simulations of flows in microcapillary networks, as a function of the flow Reynolds number Re. Results from model problems indicate that for Re less than 1 and possibly as high as 10, vasculatures may be represented by strictly 1D Poiseuille flow geometries with flow variation in the axial dimensions only. In that range flow rate predictions in the different branches generated by 1D and 3D models differ by a constant factor, independent of Re. When the cross-sectional areas of the branches are constant these differences are generally small and appear to stem from an uncertainty of how the individual branch lengths are defined. This uncertainty can be accounted for by a simple geometrical correction. For non-constant cross-sections the differences can be much more significant. If additional corrections for the presence of branch junctions and flow area variations are not taken into account in 1D models of complex vasculatures, the resultant flow predictions should be interpreted with caution.

  3. Steady-state and non-steady state operation of counter-current chromatography devices.

    PubMed

    Kostanyan, Artak E; Ignatova, Svetlana N; Sutherland, Ian A; Hewitson, Peter; Zakhodjaeva, Yulya A; Erastov, Andrey A

    2013-11-01

    Different variants of separation processes based on steady-state (continuous sample loading) and non-steady state (batch) operating modes of CCC columns have been analyzed and compared. The analysis is carried out on the basis of the modified equilibrium cell model, which takes into account both mechanisms of band broadening - interphase mass transfer and axial mixing. A full theoretical treatment of the intermittent counter-current chromatography with short sample loading time is performed. Analytical expressions are presented allowing the simulation of the intermittent counter-current chromatography separations for various experimental conditions. Chromatographic and extraction separations have been compared and advantages and disadvantages of the two methods have been evaluated. Further technical development of the CCC machines to implement counter-current extraction separations is considered.

  4. Intermittent counter-current extraction-Equilibrium cell model, scaling and an improved bobbin design.

    PubMed

    Hewitson, Peter; Sutherland, Ian; Kostanyan, Artak E; Voshkin, Andrei A; Ignatova, Svetlana

    2013-08-16

    This paper describes an equilibrium cell model for intermittent counter-current extraction that is analytically solved for the first time for continuous sample injection between a pair of columns. The model is compared with practice for injections of a model mixture of compounds on a standard high-performance counter-current chromatography instrument giving good agreement for compound elution order and the times to maximum concentration for the eluted components. An improved design of end fittings for the counter-current chromatography bobbins is described which permits on-column switching of the mobile and stationary phases. This on-column switching successfully eliminates the displaced stationary phase seen in fractions when operating ICcE with standard flying leads and gives a 6% reduction in the retention time of compounds and improved resolution due to the elimination of the time delay required to pump the previous mobile phase from standard flying leads.

  5. 2D application of a friction-limited model for debris flow propagation

    NASA Astrophysics Data System (ADS)

    Jaboyedoff, M.; Demierre, J.; Rudaz, B.

    2012-04-01

    Debris flows are each year responsible of severe infrastructure damages and human losses. Accurate simulation of this phenomenon allows for prevention of risks related to such events and can help for a sustainable territorial planning. A simple and intuitive 2-D debris flow model is developed using MatLab. It is based on the coupling of a mass point motion along the slope and the flattening of a volume linked to this mass point. Three main parameters have to be tuned in order to obtain a realistic prediction: the basal friction angle, the flattening coefficient and the debris flow maximum velocity. The model enables to simulate the location of the debris as a function of time and thus predict an important parameter of debris flow events, the runout distance. This tool allows for rapid calculations and has the advantage to use parameters that are easily assessable, such as the thickness of the debris flow deposit. The model is applied and compared to a debris flow event that occurred in Switzerland (Fully, VS) in October 2000. Following heavy rainfall and a hydroelectric pipe failure, a morainic deposit failed and propagated as a debris flow, reaching human-occupied areas (vineyards and roads). The event is well documented, with the initiation point, the flow velocity and runout distance known. A good agreement is found between the model prediction and the data from the debris flow event described above. This shows that the developed simple model can be an efficient tool to predict important debris flow characteristics, such as the runout distance. A further development would be to implement a 3-D model based on this approach

  6. Compressive Sensing Based Machine Learning Strategy For Characterizing The Flow Around A Cylinder With Limited Pressure Measurements

    SciTech Connect

    Bright, Ido; Lin, Guang; Kutz, Nathan

    2013-12-05

    Compressive sensing is used to determine the flow characteristics around a cylinder (Reynolds number and pressure/flow field) from a sparse number of pressure measurements on the cylinder. Using a supervised machine learning strategy, library elements encoding the dimensionally reduced dynamics are computed for various Reynolds numbers. Convex L1 optimization is then used with a limited number of pressure measurements on the cylinder to reconstruct, or decode, the full pressure field and the resulting flow field around the cylinder. Aside from the highly turbulent regime (large Reynolds number) where only the Reynolds number can be identified, accurate reconstruction of the pressure field and Reynolds number is achieved. The proposed data-driven strategy thus achieves encoding of the fluid dynamics using the L2 norm, and robust decoding (flow field reconstruction) using the sparsity promoting L1 norm.

  7. Fractionation of wheat gliadins by counter-current distribution using an organic two-phase system.

    PubMed

    Truust, H; Johansson, G

    1998-06-26

    A liquid liquid two-phase system based on N,N-dimethylformamide and the two polymers, poly(ethyleneglycol) and Ficoll, useful for partitioning of hydrophobic proteins, has been developed. The system has been applied to a counter-current distribution process in 56 steps for analysing the heterogeneity of proteins extracted with N,N-dimethylformamide from wheat flour. The counter-current distribution patterns of proteins, extracted from eight kinds of wheat, have been analysed. The minimum number of hypothetical proteins necessary to describe the patterns was found to be seven. The relative amount of these hypothetical components varied among the wheats.

  8. Isolation of chlorophylls a and b from spinach by counter-current chromatography.

    PubMed

    Jubert, Carole; Bailey, George

    2007-01-26

    A method for the isolation of chlorophylls from spinach by counter-current chromatography was developed. An initial extraction protocol was devised to avoid the notorious sensitivity of chlorophylls to degradation by light, heat, oxygen, acids and bases. Further purification and separation of chlorophylls a and b were achieved using counter-current chromatography. Chlorophyll structures and purities were established by HPLC, fast atom bombardment mass spectrometry and nuclear magnetic resonance. Purity was estimated to be >95% (100% by HPLC). Typical yields from 30g of freeze-dried spinach were 300mg of chlorophyll a and 100mg of chlorophyll b.

  9. Transport-driven scrape-off layer flows and the x-point dependence of the L-H power threshold in Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    LaBombard, B.; Rice, J. E.; Hubbard, A. E.; Hughes, J. W.; Greenwald, M.; Granetz, R. S.; Irby, J. H.; Lin, Y.; Lipschultz, B.; Marmar, E. S.; Marr, K.; Mossessian, D.; Parker, R.; Rowan, W.; Smick, N.; Snipes, J. A.; Terry, J. L.; Wolfe, S. M.; Wukitch, S. J.

    2005-05-01

    Factor of ˜2 higher power thresholds for low- to high-confinement mode transitions (L-H) with unfavorable x-point topologies in Alcator C-Mod [Phys. Plasmas 1, 1511 (1994)] are linked to flow boundary conditions imposed by the scrape-off layer (SOL). Ballooning-like transport drives flow along magnetic field lines from low- to high-field regions with toroidal direction dependent on upper/lower x-point balance; the toroidal rotation of the confined plasma responds, exhibiting a strong counter-current rotation when B ×∇B points away from the x point. Increased auxiliary heating power (rf, no momentum input) leads to an L-H transition at approximately twice the edge electron pressure gradient when B ×∇B points away. As gradients rise prior to the transition, toroidal rotation ramps toward the co-current direction; the H mode is seen when the counter-current rotation imposed by the SOL flow becomes compensated. Remarkably, L-H thresholds in lower-limited discharges are identical to lower x-point discharges; SOL flows are also found similar, suggesting a connection.

  10. The limit of the film extraction technique for annular two-phase flow in a small tube

    SciTech Connect

    Helm, D.E.; Lopez de Bertodano, M.; Beus, S.G.

    1999-07-01

    The limit of the liquid film extraction technique was identified in air-water and Freon-113 annular two-phase flow loops. The purpose of this research is to find the limit of the entrainment rate correlation obtained by Lopez de Bertodano et. al. (1998). The film extraction technique involves the suction of the liquid film through a porous tube and has been widely used to obtain annular flow entrainment and entrainment rate data. In these experiments there are two extraction probes. After the first extraction the entrained droplets in the gas core deposit on the tube wall. A new liquid film develops entirely from liquid deposition and a second liquid film extraction is performed. While it is assumed that the entire liquid film is removed after the first extraction unit, this is not true for high liquid flow. At high liquid film flows the interfacial structure of the film becomes frothy. Then the entire liquid film cannot be removed at the first extraction unit, but continues on and is extracted at the second extraction unit. A simple model to characterize the limit of the extraction technique was obtained based on the hypothesis that the transition occurs due to a change in the wave structure. The resulting dimensionless correlation agrees with the data.

  11. Readdressing the issue of thermally significant blood vessels using a countercurrent vessel network.

    PubMed

    Shrivastava, Devashish; Roemer, Robert B

    2006-04-01

    A physiologically realistic arterio-venous countercurrent vessel network model consisting of ten branching vessel generations, where the diameter of each generation of vessels is smaller than the previous ones, has been created and used to determine the thermal significance of different vessel generations by investigating their ability to exchange thermal energy with the tissue. The temperature distribution in the 3D network (8178 vessels; diameters from 10 to 1000 microm) is obtained by solving the conduction equation in the tissue and the convective energy equation with a specified Nusselt number in the vessels. The sensitivity of the exchange of energy between the vessels and the tissue to changes in the network parameters is studied for two cases; a high temperature thermal therapy case when tissue is heated by a uniformly distributed source term and the network cools the tissue, and a hypothermia related case, when tissue is cooled from the surface and the blood heats the tissue. Results show that first, the relative roles of vessels of different diameters are strongly determined by the inlet temperatures to those vessels (e.g., as affected by changing mass flow rates), and the surrounding tissue temperature, but not by their diameter. Second, changes in the following do not significantly affect the heat transfer rates between tissue and vessels; (a) the ratio of arterial to venous vessel diameter, (b) the diameter reduction coefficient (the ratio of diameters of successive vessel generations), and (c) the Nusselt number. Third, both arteries and veins play significant roles in the exchange of energy between tissue and vessels, with arteries playing a more significant role. These results suggest that the determination of which diameter vessels are thermally important should be performed on a case-by-case, problem dependent basis. And, that in the development of site-specific vessel network models, reasonable predictions of the relative roles of different

  12. Countercurrent Gaseous Diffusion Model of Oxidation Through a Porous Coating

    SciTech Connect

    Holcomb, G.R.

    1996-07-01

    A countercurrent gaseous diffusion model was developed to describe oxidation through porous coatings and scales. The specific system modeled involved graphite oxidized through a porous alumina (Al{sub 2}O{sub 3}) overcoat between 570 C (1,058 F) and 975 C (1,787 F). The model separated the porous Al{sub 2}O{sub 3} coating into two gas diffusion regions separated by a flame front, where oxygen (O{sub 2}) and carbon monoxide (CO) react to form carbon dioxide (CO{sub 2}). In the outer region O{sub 2} and CO{sub 2} counterdiffused. In the inner region, CO{sub 2} and CO counterdiffused. Concentration gradients of each gaseous specie in the pores of the Al{sub 2}O{sub 3} were determined, and the oxidation rate was calculated. The model was verified by oxidation experiments using graphite through various porous Al{sub 2}O{sub 3} overcoats. The Al{sub 2}O{sub 3} overcoats ranged in fractional porosity and in average pore radius from 0.077 {micro}m (3.0 x 10{sup -6} in., Knudsen diffusion) to 10.0 {micro}m (3.9 x 10{sup -4} in., molecular diffusion). Predicted and measured oxidation rates were shown to have the same dependence upon porosity, pore radius, temperature, and oxygen partial pressure (P{sub O{sub 2}}). Use of the model was proposed for other oxidation systems and for chemical vapor infiltration (CVI). This work was part of the U.S. Bureau of Mines corrosion research program.

  13. Physical Limits on the Predictability of Erosion and Sediment Transport by Landslides and Debris Flows

    NASA Astrophysics Data System (ADS)

    Iverson, R. M.

    2015-12-01

    Episodic landslides and debris flows play a key role in sculpting many steep landscapes, and they also pose significant natural hazards. Field evidence, laboratory experiments, and theoretical analyses show that variations in the quantity, speed, and distance of sediment transport by landslides and debris flows can depend strongly on nuanced differences in initial conditions. Moreover, initial conditions themselves can be strongly dependent on the geological legacy of prior events. The scope of these dependencies is revealed by the results of landslide dynamics experiments [Iverson et al., Science, 2000], debris-flow erosion experiments [Iverson et al., Nature Geosci., 2011], and numerical simulations of the highly destructive 2014 Oso, Washington, landslide [Iverson et al., Earth Planet. Sci. Let., 2015]. In each of these cases, feedbacks between basal sediment deformation and pore-pressure generation cause the speed and distance of sediment transport to be very sensitive to subtle differences in the ambient sediment porosity and water content. On the other hand, the onset of most landslides and debris flows depends largely on pore-water pressure distributions and only indirectly on sediment porosity and water content. Thus, even if perfect predictions of the locations and timing of landslides and debris flows were available, the dynamics of the events - and their consequent hazards and sediment transport - would be difficult to predict. This difficulty is a manifestation of the nonlinear physics involved, rather than of poor understanding of those physics. Consequently, physically based models for assessing the hazards and sediment transport due to landslides and debris flows must take into account both evolving nonlinear dynamics and inherent uncertainties about initial conditions. By contrast, landscape evolution models that use prescribed algebraic formulas to represent sediment transport by landslides and debris flows lack a sound physical basis.

  14. A high performance cocurrent-flow heat pipe for heat recovery applications

    NASA Technical Reports Server (NTRS)

    Saaski, E. W.; Hartl, J. C.

    1980-01-01

    By the introduction of a plate-and-tube separator assembly into a heat pipe vapor core, it has been demonstrated that axial transport capacity in reflux mode can be improved by up to a factor of 10. This improvement is largely the result of eliminating the countercurrent shear that commonly limits reflux heat pipe axial capacity. With benzene, axial heat fluxes up to 1800 W/sq cm were obtained in the temperature range 40 to 80 C, while heat flux densities up to 3000 W/sq cm were obtained with R-11 over the temperature range 40 to 80 C. These very high axial capacities compare favorably with liquid metal limits; the sonic limit for liquid sodium, for example, is 3000 W/sq cm at 657 C. Computational models developed for these cocurrent flow heat pipes agreed with experimental data within + or - 25%.

  15. Combination of integrated expanded bed adsorption chromatography and countercurrent chromatography for the direct extraction and purification of pseudohypericin and hypericin from St. John's wort (Hypericum perforatum L.).

    PubMed

    Cai, Fanfan; Li, Yang; Zhang, Min; Zhang, Hongyang; Wang, Yuerong; Hu, Ping

    2015-08-01

    St. John's wort has attracted particular attention because of its beneficial effects as an antidepressant, antiviral, and anticancer agent. A method for the combination of integrated expanded bed adsorption chromatography and countercurrent chromatography for the simultaneous extraction and purification of pseudohypericin and hypericin from the herb is presented in this paper. Firstly, the constituents were extracted and directly adsorbed by expanded bed adsorption chromatography under optimal conditions. The stepwise elution was then performed by expanded bed adsorption chromatography that enriched the targets with higher purities and recoveries compared to other methods. Secondly, the eluent fractions from expanded bed adsorption chromatography were further separated by two-step high-speed countercurrent chromatography. A two-step high-speed countercurrent chromatography method with a biphasic solvent system composed of n-hexane/ethyl acetate/methanol/water with a volume ratio of 1:2:1:2 was performed by stepwise changing the flow rate of the mobile phase. Consequently, 5.6 mg of pseudohypericin and 2.2 mg of hypericin with purities of 95.5 and 95.0%, respectively, were successfully obtained from 40 mg of crude sample.

  16. Non-local rheological properties of granular flows near a jamming limit.

    SciTech Connect

    Aranson, I. S.; Tsimring, L. S.; Malloggi, F.; Clement, E.; Materials Science Division; Univ. of California at San Diego; CNRS-ESPCI Univ.

    2008-01-01

    We study the rheology of sheared granular flows close to a jamming transition. We use the approach of partially fluidized theory (PFT) with a full set of equations extending the thin layer approximation derived previously for the description of the granular avalanches phenomenology. This theory provides a picture compatible with a local rheology at large shear rates [G. D. R. Midi, Eur. Phys. J. E 14, 341 (2004)] and it works in the vicinity of the jamming transition, where a description in terms of a simple local rheology comes short. We investigate two situations displaying important deviations from local rheology. The first one is based on a set of numerical simulations of sheared soft two-dimensional circular grains. The next case describes previous experimental results obtained on avalanches of sandy material flowing down an incline. Both cases display, close to jamming, significant deviations from the now standard Pouliquen's flow rule [O. Pouliquen, Phys. Fluids 11, 542 (1999); 11, 1956 (1999)]. This discrepancy is the hallmark of a strongly nonlocal rheology and in both cases, we relate the empirical results and the outcomes of PFT. The numerical simulations show a characteristic constitutive structure for the fluid part of the stress involving the confining pressure and the material stiffness that appear in the form of an additional dimensionless parameter. This constitutive relation is then used to describe the case of sandy flows. We show a quantitative agreement as far as the effective flow rules are concerned. A fundamental feature is identified in PFT as the existence of a jammed layer developing in the vicinity of the flow arrest that corroborates the experimental findings. Finally, we study the case of solitary erosive granular avalanches and relate the outcome with the PFT analysis.

  17. Upper Limit of the Viscosity Parameter in Accretion Flows around a Black Hole with Shock Waves

    NASA Astrophysics Data System (ADS)

    Nagarkoti, Shreeram; Chakrabarti, Sandip K.

    2016-01-01

    Black hole accretion is necessarily transonic; thus, flows must become supersonic and, therefore, sub-Keplerian before they enter into the black hole. The viscous timescale is much longer than the infall timescale close to a black hole. Hence, the angular momentum remains almost constant and the centrifugal force ˜ {l}2/{r}3 becomes increasingly dominant over the gravitational force ˜ 1/{r}2. The slowed down matter piles creating an accretion shock. The flow between shock and inner sonic point is puffed up and behaves like a boundary layer. This so-called Comptonizing cloud/corona produces hard X-rays and jets/outflows and, therefore, is an important component of black hole astrophysics. In this paper, we study steady state viscous, axisymmetric, transonic accretion flows around a Schwarzschild black hole. We adopt a viscosity parameter α and compute the highest possible value of α (namely, {α }{cr}) for each pair of two inner boundary parameters (namely, specific angular momentum carried to horizon, lin and specific energy at inner sonic point, E({x}{in})) which is still capable of producing a standing or oscillating shock. We find that while such possibilities exist for α as high as {α }{cr}=0.3 in very small regions of the flow parameter space, typical {α }{cr} appears to be about ˜0.05-0.1. Coincidentally, this also happens to be the typical viscosity parameter achieved by simulations of magnetorotational instabilities in accretion flows. We therefore believe that all realistic accretion flows are likely to have centrifugal pressure supported shocks unless the viscosity parameter everywhere is higher than {α }{cr}.

  18. Streams of Content, Limited Attention: The Flow of Information through Social Media

    ERIC Educational Resources Information Center

    Boyd, Danah

    2010-01-01

    The future of Web 2.0 is about content streams or streams of information. The metaphor implied by "streams" is powerful. The idea is that individuals are living inside the stream: adding to it, consuming it, redirecting it. The goal today is to be attentively aligned--"in flow"--with these information streams, to be aware of information as it…

  19. Limitations of respiratory muscle and vastus lateralis blood flow during continuous exercise.

    PubMed

    Henderson, William R; Guenette, Jordan A; Dominelli, Paolo B; Griesdale, Donald E G; Querido, Jordan S; Boushel, Robert; Sheel, A William

    2012-05-31

    Measurement of regional blood flow to the respiratory muscles has traditionally been invasive. The blood flow index (BFI), a minimally invasive method using indocyanine green dye (ICG) and near infrared spectroscopy, allows assessment of within subject changes in regional blood flow. This study assessed regional BFI to the vastus lateralis muscle (QBFI) and the superficial respiratory muscles in the seventh intercostal space (RMBFI). Eight healthy subjects cycled continuously at incrementally more difficulty stages to exhaustion. In our subjects, QBFI declined between 83% and 100% of maximal exertion (p=0.002) and no statistically significant changes in RMBFI were seen despite steadily increasing ventilatory workloads. Post hoc pairwise comparisons demonstrated that QBFI at 83% work (0.015μmoless(-1)±0.005) was significantly higher than at maximum work output (0.011μmoless(-1)±0.004, p=0.007). There were no other significant differences of QBFI between maximum work output and different levels of work. The current study suggests that respiratory and locomotor muscle blood flow during sub-maximal and maximal exertion is unable to match increasing workloads.

  20. Limitations in the hydraulic pathway: Effects of xylem embolisms on sap velocity and flow

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sap flow in plants takes place in the xylem, a hydraulic system that is usually under negative pressure and in which gas and liquid phases are separated by nanoporous, fibrous pit membranes. It has long been known that this system is at risk of drawing gas nanobubbles through these membranes into th...

  1. Recognizing the importance of tropical forests in limiting rainfall-induced debris flows

    EPA Science Inventory

    Worldwide concern for continuing loss of montane forest cover in the tropics usually focuses on adverse ecological consequences. Less recognized, but equally important to inhabitants of these affected regions, is an increasing susceptibility to rainfall-induced debris flows and t...

  2. Design of Countercurrent Separation of Ginkgo biloba Terpene Lactones by Nuclear Magnetic Resonance

    PubMed Central

    Qiu, Feng; Friesen, Brent J.; McAlpine, James B.; Pauli, Guido F.

    2012-01-01

    Terpene lactones such as bilobalide, ginkgolides A, B, C, and J are major bioactive compounds of Ginkgo biloba L. Purification of these compounds is tedious due to their similar chemical properties. For the purpose of developing an effective and efficient method for both analytical and preparative separation of terpene lactones in G. biloba, an innovative orthogonality-enhanced high-speed countercurrent chromatography (HSCCC) method was established. Taking advantage of quantitative 1H NMR (qHNMR) methodology, partition coefficients (K) of individual terpene lactones were calculated directly from crude G. biloba leaf extract, using their H-12 signals as distinguishing feature. The partitioning experiment assisted the design of a two dimensional (2D) HSCCC procedure using a pair of orthogonal HSCCC solvent systems (SSs), ChMWat +4 and HEMSoWat +3/0.05%. It was surprising that the resolution of ginkgolides A and B was improved by 25% in the HEMWat +3 SS modified with 0.5% DMSO. Consequently, all five terpene lactones could be well separated with qHNMR purity > 95% from G. biloba leaf extract. The separation was further evaluated by offline qHNMR analysis of HSCCC fractions associated with Gaussian curve fitting. The results showed less than 2% error in HSCCC retention predicted from the partitioning experiment. This compelling consistency demonstrates that qHNMR-derived K determination (“K-by-NMR”) can be used to predict CCC fractionation and target purification of analytes from complex mixtures. Furthermore, Gaussian curve fitting enabled an accurate prediction of less than 2% impurity in the CCC fraction, which demonstrates its potential as a powerful tool to study the presence of minor constituents, especially when they are beyond the detection limit of conventional spectroscopic detectors. PMID:22579361

  3. Counter-current acid leaching process for copper azole treated wood waste.

    PubMed

    Janin, Amélie; Riche, Pauline; Blais, Jean-François; Mercier, Guy; Cooper, Paul; Morris, Paul

    2012-09-01

    This study explores the performance of a counter-current leaching process (CCLP) for copper extraction from copper azole treated wood waste for recycling of wood and copper. The leaching process uses three acid leaching steps with 0.1 M H2SO4 at 75degrees C and 15% slurry density followed by three rinses with water. Copper is recovered from the leachate using electrodeposition at 5 amperes (A) for 75 min. Ten counter-current remediation cycles were completed achieving > or = 94% copper extraction from the wood during the 10 cycles; 80-90% of the copper was recovered from the extract solution by electrodeposition. The counter-current leaching process reduced acid consumption by 86% and effluent discharge volume was 12 times lower compared with the same process without use of counter-current leaching. However, the reuse of leachates from one leaching step to another released dissolved organic carbon and caused its build-up in the early cycles.

  4. How-to-Do-It: Countercurrent Heat Exchange in Vertebrate Limbs.

    ERIC Educational Resources Information Center

    Franklin, George B.; Plakke, Ronald K.

    1988-01-01

    Describes principals of physics that are manifested in simple biological systems of heat conservation structures. Outlines materials needed, data collection, analysis, and discussion questions for construction and operation of two models, one that is a countercurrent heat exchange model and one that is not. (RT)

  5. The Countercurrent Extraction of Ink: A Demonstration of the Chromatographic Mechanism.

    ERIC Educational Resources Information Center

    Bricker, Clark E.; Sloop, Gregory T.

    1985-01-01

    Describes an experiment (carried out in less than two hours) in which the merits of countercurrent extraction are immediately evident by visible colors. The experiment requires eight 125-ml separatory funnels, 250ml of 1-butanol, 250ml of 0.1-0.5 molar hydrochloric acid, and a small amount of Sheaffer's Skrip blue-black soluble ink. (JN)

  6. Isolation of bitter acids from hops (Humulus lupulus L.) using countercurrent chromatography.

    PubMed

    Dahlberg, Clinton J; Harris, Guy; Urban, Jan; Tripp, Matthew L; Bland, Jeffrey S; Carroll, Brian J

    2012-05-01

    Commercially available hops (Humulus lupulus L.) bitter acid extracts contain a mixture of three major congeners (co-, n-, and ad-) in addition to cis/trans diastereomers for each congener. Individual isomerized α-acids were obtained by the consecutive application of two separate countercurrent chromatography methods. First, individual isomerized α-acid congeners as a mixture of cis/trans diastereomers were obtained using a solvent system consisting of hexane and aqueous buffer. The second purification, capable of separating cis/trans diastereomers, was accomplished using a quaternary solvent system; an alternative procedure using β-cyclodextrin followed by countercurrent chromatography was also investigated. The NaBH(4) reduction of the purified isomerized α-acid compounds followed by countercurrent chromatography purification resulted in individual ρ iso α-acids (>95%). Similarly, catalytic hydrogenation of the purified isomerized α-acid compounds followed by countercurrent chromatography purification produced individual tetrahydro isomerized α-acids (>95%). Reported herein is a widely applicable approach that focuses on three critical variables--solvent system composition, pH, and buffer-to-sample ratio--that enable the efficient purification of individual bitter acids (≥95%) from commercially available hops extracts.

  7. Purification of SoyScreen using critical carbon dioxide in a counter-current fractionation column

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This research evaluated the use of critical carbon dioxide (CO2) in a counter-current fractionation column for purifying SoyScreen, a mixture of feruloylated glycerides. The process concept was tested using a mixture consisting of triacylglycerides (TAGs), ethyl ferulate and fatty acid ethyl esters...

  8. The formation of perched lava ponds on basaltic volcanoes: the influence of flow geometry on cooling-limited lava flow lengths

    NASA Astrophysics Data System (ADS)

    Wilson, Lionel; Parfitt, Elisabeth A.

    1993-05-01

    Analysis of the formation of morphologically distinctive perched lava ponds produced in effusive basaltic eruptions focusses attention on the ways in which cooling and fluid dynamics interact to limit the distance a lava flow can travel. If a previously channelised flow spreads laterally on encountering a sudden decrease in the slope of the substrate or some other abrupt change in topography, its speed and thickness decrease progressively, in a way dictated by the requirements of mass and energy conservation. There is a consequent dramatic increase in heat loss from the lava as it thins. Where a flow spreads approximately radially in this way, it may form a perched lava pond. The high heat loss limits the size of any such pond to be at most a few hundred meters under almost all circumstances. Pond size depends much more strongly on lava volume flux than on any other physical parameter involved in the system, and the formation of these features provides a means of estimating eruption rates in paleo-eruptive episodes.

  9. Kinetic performance limits of constant pressure versus constant flow rate gradient elution separations. Part I: theory.

    PubMed

    Broeckhoven, K; Verstraeten, M; Choikhet, K; Dittmann, M; Witt, K; Desmet, G

    2011-02-25

    We report on a general theoretical assessment of the potential kinetic advantages of running LC gradient elution separations in the constant-pressure mode instead of in the customarily used constant-flow rate mode. Analytical calculations as well as numerical simulation results are presented. It is shown that, provided both modes are run with the same volume-based gradient program, the constant-pressure mode can potentially offer an identical separation selectivity (except from some small differences induced by the difference in pressure and viscous heating trajectory), but in a significantly shorter time. For a gradient running between 5 and 95% of organic modifier, the decrease in analysis time can be expected to be of the order of some 20% for both water-methanol and water-acetonitrile gradients, and only weakly depending on the value of V(G)/V₀ (or equivalently t(G)/t₀). Obviously, the gain will be smaller when the start and end composition lie closer to the viscosity maximum of the considered water-organic modifier system. The assumptions underlying the obtained results (no effects of pressure and temperature on the viscosity or retention coefficient) are critically reviewed, and can be inferred to only have a small effect on the general conclusions. It is also shown that, under the adopted assumptions, the kinetic plot theory also holds for operations where the flow rate varies with the time, as is the case for constant-pressure operation. Comparing both operation modes in a kinetic plot representing the maximal peak capacity versus time, it is theoretically predicted here that both modes can be expected to perform equally well in the fully C-term dominated regime (where H varies linearly with the flow rate), while the constant pressure mode is advantageous for all lower flow rates. Near the optimal flow rate, and for linear gradients running from 5 to 95% organic modifier, time gains of the order of some 20% can be expected (or 25-30% when accounting for

  10. Blood flow and vascular reactivity during attacks of classic migraine--limitations of the Xe-133 intraarterial technique

    SciTech Connect

    Skyhoj Olsen, T.; Lassen, N.A.

    1989-01-01

    The present study reports cerebral blood flow (CBF) measurements in 11 patients during attacks of classic migraine (CM)--migraine with aura. In 6 and 7 patients, respectively, cerebral vascular reactivity to increased blood pressure and to hypocapnia was also investigated during the CM attacks. The Xenon-133 intraarterial injection technique was used to measure CBF. In this study, based in part on previously published data, methodological limitations, in particular caused by scattered radiation (Compton scatter), are critically analysed. Based on this analysis and the results of the CBF studies it is concluded: During CM attacks CBF appears to decrease focally in the posterior part of the brain to a level around 20 ml/100 g/min which is consistent with a mild degree of ischemia. Changes of CBF in focal low flow areas are difficult to evaluate accurately with the Xe-133 technique. In most cases true CBF may change 50% or more in the low flow areas without giving rise to significantly measurable changes of CBF. This analysis suggests that the autoregulation response cannot be evaluated in the low flow areas with the technique used while the observations are compatible with the concept that a vasoconstrictive state, unresponsive to hypocapnia, prevails in the low flow areas during CM attacks. The gradual increase in size of the low flow area seen in several cases may be interpreted in two different ways. A spreading process may actually exist. However, due to Compton scatter, a gradual decrease of CBF in a territory that does not increase in size will also appear as a gradually spreading low flow area when studied with the Xe-133 intracarotid technique.

  11. Limitations of one-dimensional mesoscale PBL parameterizations in reproducing mountain-wave flows

    DOE PAGES

    Munoz-Esparza, Domingo; Sauer, Jeremy A.; Linn, Rodman R.; ...

    2015-12-08

    In this study, mesoscale models are considered to be the state of the art in modeling mountain-wave flows. Herein, we investigate the role and accuracy of planetary boundary layer (PBL) parameterizations in handling the interaction between large-scale mountain waves and the atmospheric boundary layer. To that end, we use recent large-eddy simulation (LES) results of mountain waves over a symmetric two-dimensional bell-shaped hill [Sauer et al., J. Atmos. Sci. (2015)], and compare them to four commonly used PBL schemes. We find that one-dimensional PBL parameterizations produce reasonable agreement with the LES results in terms of vertical wavelength, amplitude of velocitymore » and turbulent kinetic energy distribution in the downhill shooting flow region. However, the assumption of horizontal homogeneity in PBL parameterizations does not hold in the context of these complex flow configurations. This inappropriate modeling assumption results in a vertical wavelength shift producing errors of ≈ 10 m s–1 at downstream locations due to the presence of a coherent trapped lee wave that does not mix with the atmospheric boundary layer. In contrast, horizontally-integrated momentum flux derived from these PBL schemes displays a realistic pattern. Therefore results from mesoscale models using ensembles of one-dimensional PBL schemes can still potentially be used to parameterize drag effects in general circulation models. Nonetheless, three-dimensional PBL schemes must be developed in order for mesoscale models to accurately represent complex-terrain and other types of flows where one-dimensional PBL assumptions are violated.« less

  12. Limitations of one-dimensional mesoscale PBL parameterizations in reproducing mountain-wave flows

    SciTech Connect

    Munoz-Esparza, Domingo; Sauer, Jeremy A.; Linn, Rodman R.; Kosovic, Branko

    2015-12-08

    In this study, mesoscale models are considered to be the state of the art in modeling mountain-wave flows. Herein, we investigate the role and accuracy of planetary boundary layer (PBL) parameterizations in handling the interaction between large-scale mountain waves and the atmospheric boundary layer. To that end, we use recent large-eddy simulation (LES) results of mountain waves over a symmetric two-dimensional bell-shaped hill [Sauer et al., J. Atmos. Sci. (2015)], and compare them to four commonly used PBL schemes. We find that one-dimensional PBL parameterizations produce reasonable agreement with the LES results in terms of vertical wavelength, amplitude of velocity and turbulent kinetic energy distribution in the downhill shooting flow region. However, the assumption of horizontal homogeneity in PBL parameterizations does not hold in the context of these complex flow configurations. This inappropriate modeling assumption results in a vertical wavelength shift producing errors of ≈ 10 m s–1 at downstream locations due to the presence of a coherent trapped lee wave that does not mix with the atmospheric boundary layer. In contrast, horizontally-integrated momentum flux derived from these PBL schemes displays a realistic pattern. Therefore results from mesoscale models using ensembles of one-dimensional PBL schemes can still potentially be used to parameterize drag effects in general circulation models. Nonetheless, three-dimensional PBL schemes must be developed in order for mesoscale models to accurately represent complex-terrain and other types of flows where one-dimensional PBL assumptions are violated.

  13. Co-current and counter-current imbibition in independent tubes of non-axisymmetric geometry.

    PubMed

    Unsal, E; Mason, G; Morrow, N R; Ruth, D W

    2007-02-01

    Experiments that illustrate and quantify the basics of co- and counter-current spontaneous imbibition have been conducted in a series of simple model pore systems. The fundamental pore geometry is a rod in an angled round-bottomed slot with the rod touching a capping glass plate. The capillaries thus formed by the surfaces of the slot, rod and plate do not have circular cross-sections but more complicated geometric structures with angular corners. The tubes formed at each side of the rod connect at both ends. A viscous, refined oil was applied from one end. For co-current experiments, the opposite end was left open to the atmosphere and oil imbibed into both tubes. For counter-current experiments the opposite end was sealed and connected to a sensitive pressure transducer. Oil imbibed into the smaller capillary and expelled air as a series of bubbles from the end of the larger capillary. Bubble snap-off was observed to be rate-dependent and occurred at a lower curvature than that of the cylindrical meniscus that just fits inside the tube. Only the corners of the larger capillary filled with oil during counter-current imbibition. Meniscus curvatures were calculated using the Mayer and Stowe-Princen method and were compared with actual values by measuring the capillary rise in the tubes; agreement was close. A simple model for co-current and counter-current imbibition has also been developed and the predictions compared with the experimental results. The model results were in agreement with the experiments. The experiments demonstrate that the capillary back pressure generated by the interfaces and bubbles in counter-current imbibition can slow the process significantly.

  14. Balancing photosynthetic electron flow is critical for cyanobacterial acclimation to nitrogen limitation.

    PubMed

    Salomon, Eitan; Bar-Eyal, Leeat; Sharon, Shir; Keren, Nir

    2013-03-01

    Nitrogen limitation forces photosynthetic organisms to reallocate available nitrogen to essential functions. At the same time, it increases the probability of photo-damage by limiting the rate of energy-demanding metabolic processes, downstream of the photosynthetic apparatus. Non-diazotrophic cyanobacteria cope with this situation by decreasing the size of their phycobilisome antenna and by modifying their photosynthetic apparatus. These changes can serve two purposes: to provide extra amino-acids and to decrease excitation pressure. We examined the effects of nitrogen limitation on the form and function of the photosynthetic apparatus. Our aim was to study which of the two demands serve as the driving force for the remodeling of the photosynthetic apparatus, under different growth conditions. We found that a drastic reduction in light intensity allowed cells to maintain a more functional photosynthetic apparatus: the phycobilisome antenna was bigger, the activity of both photosystems was higher and the levels of photosystem (PS) proteins were higher. Pre-acclimating cells to Mn limitation, under which the activity of both PSI and PSII is diminished, results in a very similar response. The rate of PSII photoinhibition, in nitrogen limited cells, was found to be directly related to the activity of the photosynthetic apparatus. These data indicate that, under our experimental conditions, photo-damage avoidance was the more prominent determinant during the acclimation process. The combinations of limiting factors tested here is by no means artificial. Similar scenarios can take place under environmental conditions and should be taken into account when estimating nutrient limitations in nature.

  15. "Reagentless" flow injection determination of ammonia and urea using membrane separation and solid phase basification.

    PubMed

    Akse, J R; Thompson, J O; Sauer, R L; Atwater, J E

    1998-07-01

    Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media. the speciation of ammoniacal nitrogen is shifted toward the un-ionized form. which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 microgram/L and a dynamic concentration range spanning three orders of magnitude using a 315-microliters sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea.

  16. "Reagentless" flow injection determination of ammonia and urea using membrane separation and solid phase basification

    NASA Technical Reports Server (NTRS)

    Akse, J. R.; Thompson, J. O.; Sauer, R. L.; Atwater, J. E.

    1998-01-01

    Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media. the speciation of ammoniacal nitrogen is shifted toward the un-ionized form. which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 microgram/L and a dynamic concentration range spanning three orders of magnitude using a 315-microliters sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea.

  17. Semi-industrial isolation of salicin and amygdalin from plant extracts using slow rotary counter-current chromatography.

    PubMed

    Du, Qizhen; Jerz, Gerold; Ha, Yangchun; Li, Lei; Xu, Yuanjin; Zhang, Qi; Zheng, Qunxiong; Winterhalter, Peterb; Ito, Yoichiro

    2005-05-13

    Salicin in the bark extract of Salix alba and amygdalin in the fruit extract of Semen armeniacae were each separated by slow rotary counter-current chromatography (SRCCC). The apparatus was equipped with a 40-L column made of 17 mm i.d. convoluted Teflon tubing. A 500g amount of crude extract containing salicin at 13.5% was separated yielding 63.5 g of salicin at 95.3% purity in 20h using methyl tert-butyl ether-l-butanol (1:3) saturated by methanol-water (1:5) as a stationary phase and methanol-water (1:5) saturated by methyl tert-butyl ether-1-butanol (1:3) as a mobile phase. A 400g amount of crude extract containing amygdalin at 55.3% was isolated to yield 221.2g of amygdalin at 94.1% purity in 19h using ethyl acetate-1-butanol (1:2) saturated by water as a stationary phase and water saturated by ethyl acetate-1-butanol (1:2) as a mobile phase. The flow rate of the mobile phase was 50 ml/min. The results show that industrial SRCCC separation of salicin and amygdalin is feasible using a larger column at a higher flow rate of the mobile phase.

  18. Seasonal Shift in Climatic Limiting Factors on Tree Transpiration: Evidence from Sap Flow Observations at Alpine Treelines in Southeast Tibet

    PubMed Central

    Liu, Xinsheng; Nie, Yuqin; Luo, Tianxiang; Yu, Jiehui; Shen, Wei; Zhang, Lin

    2016-01-01

    Alpine and northern treelines are primarily controlled by low temperatures. However, little is known about the impact of low soil temperature on tree transpiration at treelines. We aim to test the hypothesis that in cold-limited forests, the main limiting factors for tree transpiration switch from low soil temperature before summer solstice to atmospheric evaporative demand after summer solstice, which generally results in low transpiration in the early growing season. Sap flow, meteorological factors and predawn needle water potential were continuously monitored throughout one growing season across Smith fir (Abies georgei var. smithii) and juniper (Juniperus saltuaria) treelines in southeast Tibet. Sap flow started in early May and corresponded to a threshold mean air-temperature of 0°C. Across tree species, transpiration was mainly limited by low soil temperature prior to the summer solstice but by vapor pressure deficit and solar radiation post-summer solstice, which was further confirmed on a daily scale. As a result, tree transpiration for both tree species was significantly reduced in the pre-summer solstice period as compared to post-summer solstice, resulting in a lower predawn needle water potential for Smith fir trees in the early growing season. Our data supported the hypothesis, suggesting that tree transpiration mainly responds to soil temperature variations in the early growing season. The results are important for understanding the hydrological response of cold-limited forest ecosystems to climate change. PMID:27468289

  19. Seasonal Shift in Climatic Limiting Factors on Tree Transpiration: Evidence from Sap Flow Observations at Alpine Treelines in Southeast Tibet.

    PubMed

    Liu, Xinsheng; Nie, Yuqin; Luo, Tianxiang; Yu, Jiehui; Shen, Wei; Zhang, Lin

    2016-01-01

    Alpine and northern treelines are primarily controlled by low temperatures. However, little is known about the impact of low soil temperature on tree transpiration at treelines. We aim to test the hypothesis that in cold-limited forests, the main limiting factors for tree transpiration switch from low soil temperature before summer solstice to atmospheric evaporative demand after summer solstice, which generally results in low transpiration in the early growing season. Sap flow, meteorological factors and predawn needle water potential were continuously monitored throughout one growing season across Smith fir (Abies georgei var. smithii) and juniper (Juniperus saltuaria) treelines in southeast Tibet. Sap flow started in early May and corresponded to a threshold mean air-temperature of 0°C. Across tree species, transpiration was mainly limited by low soil temperature prior to the summer solstice but by vapor pressure deficit and solar radiation post-summer solstice, which was further confirmed on a daily scale. As a result, tree transpiration for both tree species was significantly reduced in the pre-summer solstice period as compared to post-summer solstice, resulting in a lower predawn needle water potential for Smith fir trees in the early growing season. Our data supported the hypothesis, suggesting that tree transpiration mainly responds to soil temperature variations in the early growing season. The results are important for understanding the hydrological response of cold-limited forest ecosystems to climate change.

  20. Electrochemical flow injection analysis of hydrazine in an excess of an active pharmaceutical ingredient: achieving pharmaceutical detection limits electrochemically.

    PubMed

    Channon, Robert B; Joseph, Maxim B; Bitziou, Eleni; Bristow, Anthony W T; Ray, Andrew D; Macpherson, Julie V

    2015-10-06

    The quantification of genotoxic impurities (GIs) such as hydrazine (HZ) is of critical importance in the pharmaceutical industry in order to uphold drug safety. HZ is a particularly intractable GI and its detection represents a significant technical challenge. Here, we present, for the first time, the use of electrochemical analysis to achieve the required detection limits by the pharmaceutical industry for the detection of HZ in the presence of a large excess of a common active pharmaceutical ingredient (API), acetaminophen (ACM) which itself is redox active, typical of many APIs. A flow injection analysis approach with electrochemical detection (FIA-EC) is utilized, in conjunction with a coplanar boron doped diamond (BDD) microband electrode, insulated in an insulating diamond platform for durability and integrated into a two piece flow cell. In order to separate the electrochemical signature for HZ such that it is not obscured by that of the ACM (present in excess), the BDD electrode is functionalized with Pt nanoparticles (NPs) to significantly shift the half wave potential for HZ oxidation to less positive potentials. Microstereolithography was used to fabricate flow cells with defined hydrodynamics which minimize dispersion of the analyte and optimize detection sensitivity. Importantly, the Pt NPs were shown to be stable under flow, and a limit of detection of 64.5 nM or 0.274 ppm for HZ with respect to the ACM, present in excess, was achieved. This represents the first electrochemical approach which surpasses the required detection limits set by the pharmaceutical industry for HZ detection in the presence of an API and paves the wave for online analysis and application to other GI and API systems.

  1. Analytical Investigation of Icing Limit for Diamond-Shaped Airfoil in Transonic and Supersonic Flow

    NASA Technical Reports Server (NTRS)

    Callaghan, Edmund E.; Serafini, John S.

    1953-01-01

    Calculations have been made for the icing limit of a diamond airfoil at zero angle of attack in terms of the stream Mach number, stream temperature, and pressure altitude. The icing limit is defined as a wetted-surface temperature of 320 F and is related to the stream conditions by the method of Hardy. The results show that the point most likely to ice on the airfoil lies immediately behind the shoulder and is subject to possible icing at Mach numbers as high as 1.4.

  2. Limiting pumping from the Edwards Aquifer: An economic investigation of proposals, water markets, and spring flow guarantees

    NASA Astrophysics Data System (ADS)

    McCarl, Bruce A.; Dillon, Carl R.; Keplinger, Keith O.; Williams, R. Lynn

    1999-04-01

    The Edwards Aquifer, near San Antonio, Texas, is an important water source for both pumping and spring flow, which in turn provides water for recreation and habitat for several endangered species. A management authority is charged with aquifer management and is mandated to reduce pumping, facilitate water markets, protect agricultural rights, and protect the species habitat. This paper examines the economic dimensions of authority duties. A combined hydrologic-economic model is used in the investigation. The results indicate that proposed pumping limits are shown to have large consequences for agricultural usage and to decrease the welfare of current aquifer pumping users. However, the spring flow habitat is found to be protected, and the gains from that protection would have to exceed pumping user losses in order for the protection measures to increase regional economic welfare. Agricultural guarantees are shown to cause use value differences, indicating the opportunity for emergence of an active water market. Fixed quantity pumping limits are found to be an expensive way of insuring adequate spring flow.

  3. The Generally Useful Estimate of Solvent Systems (GUESS) method enables the rapid purification of methylpyridoxine regioisomers by countercurrent chromatography

    PubMed Central

    Liu, Yang; Friesen, J. Brent; Klein, Larry L.; McAlpine, James B.; Lankin, David C.; Pauli, Guido F.; Chen, Shao-Nong

    2016-01-01

    The TLC-based Generally Useful Estimate of Solvent Systems (GUESS) method was employed for countercurrent chromatography solvent system selection, in order to separate the three synthetic isomers: 3-O-methylpyridoxine, 4′-O-methylpyridoxine (ginkgotoxin) and 5′-O-methylpyridoxine. The Rf values of the three isomers indicated that ChMWat +2 (chloroformmethanol-water 10:5:5, v/v/v) was appropriate for the countercurrent chromatography. The isomer separation was highly selective and demonstrated that the TLC-based GUESS method can accelerate solvent system selection for countercurrent chromatography. Accordingly, the study re-emphasizes the practicality of TLC as a tool to facilitate the rapid development of new countercurrent and centrifugal partition chromatography methods for this solvent system. Purity and structure characterization of all samples was performed by quantitative 1H NMR. PMID:26680272

  4. The Generally Useful Estimate of Solvent Systems (GUESS) method enables the rapid purification of methylpyridoxine regioisomers by countercurrent chromatography.

    PubMed

    Liu, Yang; Friesen, J Brent; Klein, Larry L; McAlpine, James B; Lankin, David C; Pauli, Guido F; Chen, Shao-Nong

    2015-12-24

    The TLC-based Generally Useful Estimate of Solvent Systems (GUESS) method was employed for countercurrent chromatography solvent system selection, in order to separate the three synthetic isomers: 3-O-methylpyridoxine, 4'-O-methylpyridoxine (ginkgotoxin), and 5'-O-methylpyridoxine. The Rf values of the three isomers indicated that ChMWat+2 (chloroform-methanol-water 10:5:5, v/v/v) was appropriate for the countercurrent separation. The isomer separation was highly selective and demonstrated that the TLC-based GUESS method can accelerate solvent system selection for countercurrent separation. Accordingly, the study re-emphasizes the practicality of TLC as a tool to facilitate the rapid development of new countercurrent and centrifugal partition chromatography methods for this solvent system. Purity and structure characterization of all samples was performed by quantitative (1)H NMR.

  5. Radially dependent large-scale dynamos in global cylindrical shear flows and the local cartesian limit

    NASA Astrophysics Data System (ADS)

    Ebrahimi, F.; Blackman, E. G.

    2016-06-01

    For cylindrical differentially rotating plasmas, we study large-scale magnetic field generation from finite amplitude non-axisymmetric perturbations by comparing numerical simulations with quasi-linear analytic theory. When initiated with a vertical magnetic field of either zero or finite net flux, our global cylindrical simulations exhibit the magnetorotational instability (MRI) and large-scale dynamo growth of radially alternating mean fields, averaged over height and azimuth. This dynamo growth is explained by our analytic calculations of a non-axisymmetric fluctuation-induced electromotive force that is sustained by azimuthal shear of the fluctuating fields. The standard `Ω effect' (shear of the mean field by differential rotation) is unimportant. For the MRI case, we express the large-scale dynamo field as a function of differential rotation. The resulting radially alternating large-scale fields may have implications for angular momentum transport in discs and corona. To connect with previous work on large-scale dynamos with local linear shear and identify the minimum conditions needed for large-scale field growth, we also solve our equations in local Cartesian coordinates. We find that large-scale dynamo growth in a linear shear flow without rotation can be sustained by shear plus non-axisymmetric fluctuations - even if not helical, a seemingly previously unidentified distinction. The linear shear flow dynamo emerges as a more restricted version of our more general new global cylindrical calculations.

  6. Minimum current principle and variational method in theory of space charge limited flow

    SciTech Connect

    Rokhlenko, A.

    2015-10-21

    In spirit of the principle of least action, which means that when a perturbation is applied to a physical system, its reaction is such that it modifies its state to “agree” with the perturbation by “minimal” change of its initial state. In particular, the electron field emission should produce the minimum current consistent with boundary conditions. It can be found theoretically by solving corresponding equations using different techniques. We apply here the variational method for the current calculation, which can be quite effective even when involving a short set of trial functions. The approach to a better result can be monitored by the total current that should decrease when we on the right track. Here, we present only an illustration for simple geometries of devices with the electron flow. The development of these methods can be useful when the emitter and/or anode shapes make difficult the use of standard approaches. Though direct numerical calculations including particle-in-cell technique are very effective, but theoretical calculations can provide an important insight for understanding general features of flow formation and even sometimes be realized by simpler routines.

  7. Two-dimensional space-charge-limited flows in a crossed-field gap

    SciTech Connect

    Koh, W. S.; Ang, L. K.

    2007-04-02

    This letter presents a two-dimensional (2D) model of space-charge-limited current in a planar crossed-field gap with a magnetic strength of B/B{sub H}=0-3, where B{sub H} is the Hull cutoff magnetic field. The electrons are emitted from an infinite length strip of finite width W comparable to the gap spacing D. It is found that the 2D enhancement of the crossed-field limiting current is 1+Fx4D/({pi}W), where F (=0.05-0.5) is a normalized mean-position factor, and it is a function of B/B{sub H}. Good agreement has been obtained in comparisons with particle-in-cell simulation.

  8. Theory of Molecular Cloud Formation through Colliding Flows: Successes and Limits

    NASA Astrophysics Data System (ADS)

    Hennebelle, P.

    2013-10-01

    We discuss the recent efforts which have been made to understand the formation of molecular clouds through the accumulation of diffuse material, a scenario sometimes called “colliding flows”. We present a set of statistics which have been inferred from these simulations and which seem to agree reasonably with observations seemingly suggesting that this scenario could indeed be applied to understand molecular cloud formation. We also emphasize the limits of this highly idealized model.

  9. Solution of the Burnett equations for hypersonic flows near the continuum limit

    NASA Technical Reports Server (NTRS)

    Imlay, Scott T.

    1992-01-01

    The INCA code, a three-dimensional Navier-Stokes code for analysis of hypersonic flowfields, was modified to analyze the lower reaches of the continuum transition regime, where the Navier-Stokes equations become inaccurate and Monte Carlo methods become too computationally expensive. The two-dimensional Burnett equations and the three-dimensional rotational energy transport equation were added to the code and one- and two-dimensional calculations were performed. For the structure of normal shock waves, the Burnett equations give consistently better results than Navier-Stokes equations and compare reasonably well with Monte Carlo methods. For two-dimensional flow of Nitrogen past a circular cylinder the Burnett equations predict the total drag reasonably well. Care must be taken, however, not to exceed the range of validity of the Burnett equations.

  10. A new limiting procedure for discontinuous Galerkin methods applied to compressible multiphase flows with shocks and interfaces

    NASA Astrophysics Data System (ADS)

    Henry de Frahan, Marc T.; Varadan, Sreenivas; Johnsen, Eric

    2015-01-01

    Although the Discontinuous Galerkin (DG) method has seen widespread use for compressible flow problems in a single fluid with constant material properties, it has yet to be implemented in a consistent fashion for compressible multiphase flows with shocks and interfaces. Specifically, it is challenging to design a scheme that meets the following requirements: conservation, high-order accuracy in smooth regions and non-oscillatory behavior at discontinuities (in particular, material interfaces). Following the interface-capturing approach of Abgrall [1], we model flows of multiple fluid components or phases using a single equation of state with variable material properties; discontinuities in these properties correspond to interfaces. To represent compressible phenomena in solids, liquids, and gases, we present our analysis for equations of state belonging to the Mie-Grüneisen family. Within the DG framework, we propose a conservative, high-order accurate, and non-oscillatory limiting procedure, verified with simple multifluid and multiphase problems. We show analytically that two key elements are required to prevent spurious pressure oscillations at interfaces and maintain conservation: (i) the transport equation(s) describing the material properties must be solved in a non-conservative weak form, and (ii) the suitable variables must be limited (density, momentum, pressure, and appropriate properties entering the equation of state), coupled with a consistent reconstruction of the energy. Further, we introduce a physics-based discontinuity sensor to apply limiting in a solution-adaptive fashion. We verify this approach with one- and two-dimensional problems with shocks and interfaces, including high pressure and density ratios, for fluids obeying different equations of state to illustrate the robustness and versatility of the method. The algorithm is implemented on parallel graphics processing units (GPU) to achieve high speedup.

  11. A fully-online Neuro-Fuzzy model for flow forecasting in basins with limited data

    NASA Astrophysics Data System (ADS)

    Ashrafi, Mohammad; Chua, Lloyd Hock Chye; Quek, Chai; Qin, Xiaosheng

    2017-02-01

    Current state-of-the-art online neuro fuzzy models (NFMs) such as DENFIS (Dynamic Evolving Neural-Fuzzy Inference System) have been used for runoff forecasting. Online NFMs adopt a local learning approach and are able to adapt to changes continuously. The DENFIS model however requires upper/lower bound for normalization and also the number of rules increases monotonically. This requirement makes the model unsuitable for use in basins with limited data, since a priori data is required. In order to address this and other drawbacks of current online models, the Generic Self-Evolving Takagi-Sugeno-Kang (GSETSK) is adopted in this study for forecast applications in basins with limited data. GSETSK is a fully-online NFM which updates its structure and parameters based on the most recent data. The model does not require the need for historical data and adopts clustering and rule pruning techniques to generate a compact and up-to-date rule-base. GSETSK was used in two forecast applications, rainfall-runoff (a catchment in Sweden) and river routing (Lower Mekong River) forecasts. Each of these two applications was studied under two scenarios: (i) there is no prior data, and (ii) only limited data is available (1 year for the Swedish catchment and 1 season for the Mekong River). For the Swedish Basin, GSETSK model results were compared to available results from a calibrated HBV (Hydrologiska Byråns Vattenbalansavdelning) model. For the Mekong River, GSETSK results were compared against the URBS (Unified River Basin Simulator) model. Both comparisons showed that results from GSETSK are comparable with the physically based models, which were calibrated with historical data. Thus, even though GSETSK was trained with a very limited dataset in comparison with HBV or URBS, similar results were achieved. Similarly, further comparisons between GSETSK with DENFIS and the RBF (Radial Basis Function) models highlighted further advantages of GSETSK as having a rule-base (compared to

  12. Technical requirements and limitations of miniaturized axial flow pumps for circulatory support.

    PubMed

    Reul, H

    1994-01-01

    The engineering principles of rotary blood pumps are elucidated by means of a basic introduction into turbomachinery. Additionally, some important dimensionless quantities which relate to pumping characteristics and pump type are introduced. These theoretical fundamentals are applied to the design of high-speed microaxial pumps, especially the two Hemopump versions. The theoretical estimates clearly show that each pump version has its physical limits, especially at small impeller sizes. It is also demonstrated that not any clinically desirable working point of an axial pump can be achieved with an arbitrarily small pump size.

  13. Pressurized liquid extraction coupled with countercurrent chromatography for systematic isolation of chemical constituents by preprogrammed automatic control.

    PubMed

    Zhang, Yuchi; Guo, Liping; Liu, Chunming; Fu, Zi' ao; Cong, Lei; Qi, Yanjuan; Li, Dongping; Li, Sainan; Wang, Jing

    2013-09-15

    Pressurized liquid extraction (PLE) coupled with high-speed countercurrent chromatography (HSCCC) via an automated procedure was firstly developed to extract and isolate ginsenosides from Panax quinquefolium. The experiments were designed under the guidance of mathematical model. The partition coefficient (K) values of the target compounds and resolutions of peak profiles were employed as the research indicators, and exponential function and binomial formulas were used to optimizing the solvent systems and flow rates of the mobile phases in a three-stage separation. In the first stage, ethyl acetate, n-butanol, and water were simultaneously pumped into the solvent separator at the flow rates 11.0, 10.0, and 23.0mL/min, respectively. The upper phase of the solvent system in the solvent separator was used as both the PLE solvent and the HSCCC stationary phase, followed by elution with the lower phase of the corresponding solvent system to separate the common ginsenosides. In the second and third stages, rare ginsenosides were first separated by elution with ethyl acetate, n-butanol, methanol, and water (flow rates: 20.0, 3.0, 5.0, and 11.0mL/min, respectively), then with n-heptane, n-butanol, methanol, and water (flow rates: 17.5, 6.0, 5.0, and 22.5mL/min, respectively). Nine target compounds, with purities exceeding 95.0%, and three non-target compounds, with purities above 84.48%, were successfully separated at the semipreparative scale in 450min. The separation results prove that the PLE/HSCCC parameters calculated via mathematical model and formulas were accurately and scientifically. This research has opened up great prospects for industrial automation application.

  14. [Separation of proteins in aqueous two-phase systems with high-speed counter-current chromatography].

    PubMed

    Zhi, Wenbo; Deng, Qiuyun; Song, Jiangnan; Gu, Ming; Ouyang, Fan

    2005-01-01

    High-speed counter-current chromatography (HSCCC) is a continuous liquid-liquid partition chromatography, with remarkable advantages of high separation efficiency and no adsorption or denaturation by solid phase. The retention of stationary phase and the separation of proteins in polyethylene glycol 1000 (PEG1000)-phosphate aqueous two-phase system (ATPs) were studied with a multi-column high speed-counter-current chromatograph. The flow direction and speed of the mobile phase, and the rotation direction and speed of the apparatus showed different effects on the retention of the stationary phase, which reached the maximum at 33.3% with a flow rate of 0.6 mL/min and a rotation speed of 900 r/min in 14.0% PEG1000-16.0% phosphate ATPs. Distinct differences in partition coefficients among cytochrome C, lysozyme and hemoglobin were found at pH 9.2 and these three proteins were successfully separated in 14.0% PEG1000-16.0% phosphate ATPs at pH 9.2 by HSCCC with the apparatus rotating at 850 r/min and the mobile phase flow rate of 1.0 mL/min. The major protein components in hen egg white, including ovaltransferrin, ovalbumin and lysozyme also show distinct differences of partition coefficients in PEG1000-phosphate ATPs at pH 9.2. Ovalbumin and lysozyme were successfully purified to homogeneity and ovaltransferrin to ca 60% purity from the hen egg white sample with yields over 90% in 15.0% PEG1000-17.0% phosphate ATPs at pH 9.2 with the apparatus rotating at 850 r/min and mobile phase flow rate of 1.0 mL/min.

  15. Disk-to-disk transfer as the rate-limiting step for energy flow in phycobilisomes

    SciTech Connect

    Glazer, A.N.; Yeh, S.W.; Webb, S.P.; Clark, J.H.

    1985-01-25

    A broadly tunable picosecond laser source and an ultrafast streak camera were used to measure temporally and spectrally resolved emission from intact phycobilisomes and from individual phycobiliproteins as a function of excitation wavelength. Both wild-type and mutant phycobilisomes of the unicellular cyanobacterium Synechocystis 6701 were examined, as well as two biliproteins, R-phycoerythrin (240 kilodaltons, 34 bilins) and allophycocyanin (100 kilodaltons, 6 bilins). Measurements of intact phycobilisomes with known structural differences showed that the addition of an average of 1.6 phycoerythrin disks in the phycobilisome rod increased the overall energy transfer time by 30 +/- 5 picoseconds. In the isolated phycobiliproteins the onset of emission was as prompt as that of a solution of rhodamine B laser dye and was independent of excitation wavelength. This imposes an upper limit of 8 picoseconds (instrument-limited) on the transfer time from sensitizing to fluorescing chromophores in these biliproteins. These results indicate that disk-to-disk transfer is the slowest energy transfer process in phycobilisomes and, in combination with previous structural analyses, show that with respect to energy transfer the lattice of approximately 625 light-harvesting chromophores in the Synechocystis 6701 wild-type phycobilisome functions as a linear five-point array.

  16. Flow-through, viral co-infection assay for resource-limited settings.

    PubMed

    Cretich, Marina; Torrisi, Marcello; Daminelli, Serena; Gagni, Paola; Plavisch, Lauren; Chiari, Marcella

    2015-01-01

    Here we present a new and rapid immunofiltration assay for simultaneous detection of HIV p24 and hepatitis B virus antigens. The assay platform is composed of a 13 mm nitrocellulose filter spotted with capturing bioprobes and inserted in a Swinnex(®) syringe filter holder. Samples and reagents are flown through the nitrocellulose filter by manual pressure on the syringe. A colorimetric detection allows for naked eye results interpretation. The assay provides sensitivity in the picomolar range in just 5 min, even using low volumes of sample in complex matrix. Probe deposition by spotting allows for flexible combinations of different capturing agents and multiple diagnoses; furthermore, the very simple and inexpensive set-up makes the syringe-based immunoassay on paper microarray a suitable diagnostic system for resource-limited settings.

  17. Power flow analysis and optimal locations of resistive type superconducting fault current limiters.

    PubMed

    Zhang, Xiuchang; Ruiz, Harold S; Geng, Jianzhao; Shen, Boyang; Fu, Lin; Zhang, Heng; Coombs, Tim A

    2016-01-01

    Based on conventional approaches for the integration of resistive-type superconducting fault current limiters (SFCLs) on electric distribution networks, SFCL models largely rely on the insertion of a step or exponential resistance that is determined by a predefined quenching time. In this paper, we expand the scope of the aforementioned models by considering the actual behaviour of an SFCL in terms of the temperature dynamic power-law dependence between the electrical field and the current density, characteristic of high temperature superconductors. Our results are compared to the step-resistance models for the sake of discussion and clarity of the conclusions. Both SFCL models were integrated into a power system model built based on the UK power standard, to study the impact of these protection strategies on the performance of the overall electricity network. As a representative renewable energy source, a 90 MVA wind farm was considered for the simulations. Three fault conditions were simulated, and the figures for the fault current reduction predicted by both fault current limiting models have been compared in terms of multiple current measuring points and allocation strategies. Consequently, we have shown that the incorporation of the E-J characteristics and thermal properties of the superconductor at the simulation level of electric power systems, is crucial for estimations of reliability and determining the optimal locations of resistive type SFCLs in distributed power networks. Our results may help decision making by distribution network operators regarding investment and promotion of SFCL technologies, as it is possible to determine the maximum number of SFCLs necessary to protect against different fault conditions at multiple locations.

  18. pH-zone-refining counter-current chromatography: Origin, mechanism, procedure and applications✩

    PubMed Central

    Ito, Yoichiro

    2012-01-01

    Since 1980, high-speed counter-current chromatography (HSCCC) has been used for separation and purification of natural and synthetic products in a standard elution mode. In 1991, a novel elution mode called pH-zone refining CCC was introduced from an incidental discovery that an organic acid in the sample solution formed the sharp peak of an acid analyte. The cause of this sharp peak formation was found to be bromoacetic acid present in the sample solution which formed a sharp trailing border to trap the acidic analyte. Further studies on the separation of DNP-amino acids with three spacer acids in the stationary phase revealed that increased sample size resulted in the formation of fused rectangular peaks, each preserving high purity and zone pH with sharp boundaries. The mechanism of this phenomenon was found to be the formation of a sharp trailing border of an acid (retainer) in the column which moves at a lower rate than that of the mobile phase. In order to facilitate the application of the method, a new method was devised using a set of retainer and eluter to form a sharp retainer rear border which moves through the column at a desired rate regardless of the composition of the two-phase solvent system. This was achieved by adding the retainer in the stationary phase and the eluter in the mobile phase at a given molar ratio. Using this new method the hydrodynamics of pH-zone-refining CCC was diagrammatically illustrated by three acidic samples. In this review paper, typical pH-zone-refining CCC separations were presented, including affinity separations with a ligand and a separation of a racemic mixture using a chiral selector in the stationary phase. Major characteristics of pH-zone-refining CCC over conventional HSCCC are as follows: the sample loading capacity is increased over 10 times; fractions are highly concentrated near saturation level; yield is improved by increasing the sample size; minute charged compounds are concentrated and detected at the peak

  19. pH-zone-refining counter-current chromatography: origin, mechanism, procedure and applications.

    PubMed

    Ito, Yoichiro

    2013-01-04

    Since 1980, high-speed counter-current chromatography (HSCCC) has been used for separation and purification of natural and synthetic products in a standard elution mode. In 1991, a novel elution mode called pH-zone refining CCC was introduced from an incidental discovery that an organic acid in the sample solution formed the sharp peak of an acid analyte. The cause of this sharp peak formation was found to be bromoacetic acid present in the sample solution which formed a sharp trailing border to trap the acidic analyte. Further studies on the separation of DNP-amino acids with three spacer acids in the stationary phase revealed that increased sample size resulted in the formation of fused rectangular peaks, each preserving high purity and zone pH with sharp boundaries. The mechanism of this phenomenon was found to be the formation of a sharp trailing border of an acid (retainer) in the column which moves at a lower rate than that of the mobile phase. In order to facilitate the application of the method, a new method was devised using a set of retainer and eluter to form a sharp retainer rear border which moves through the column at a desired rate regardless of the composition of the two-phase solvent system. This was achieved by adding the retainer in the stationary phase and the eluter in the mobile phase at a given molar ratio. Using this new method the hydrodynamics of pH-zone-refining CCC was diagrammatically illustrated by three acidic samples. In this review paper, typical pH-zone-refining CCC separations were presented, including affinity separations with a ligand and a separation of a racemic mixture using a chiral selector in the stationary phase. Major characteristics of pH-zone-refining CCC over conventional HSCCC are as follows: the sample loading capacity is increased over 10 times; fractions are highly concentrated near saturation level; yield is improved by increasing the sample size; minute charged compounds are concentrated and detected at the peak

  20. Counter-current chromatographic separation of glycoprotein components from Morchella esculenta (L.) with a polymer phase system by a cross-axis coil planet centrifuge.

    PubMed

    Wei, Y; Zhang, T; Ito, Y

    2001-05-11

    Using a cross-axis coil planet centrifuge, glycoproteins were separated from fermentation media of Morchella esculenta (L.) by high-speed counter-current chromatography. The performance of the apparatus was optimized with four standard proteins including pepsin, lysozyme, ovalbumin and hemoglobin and a polymer phase system composed of 12.5% (w/w) polyethylene glycol 8000 and 25% (w/w) potassium phosphate in distilled water at various pH values. Separations were performed by eluting the lower phosphate-rich phase at a flow-rate of 1.0 ml/min. Under the optimized conditions three glycoprotein components in Morchella esculenta (L.) were resolved within 6 h.

  1. Factors influencing the detection limit of the lateral-flow sandwich immunoassay: a case study with potato virus X.

    PubMed

    Safenkova, Irina; Zherdev, Anatoly; Dzantiev, Boris

    2012-06-01

    Key factors influencing the analyte detection limit of the sandwich immunochromatographic assay (ICA), namely, the size of gold nanoparticles, the antibody concentration, the conjugation pH, and characteristics of membranes, are discussed. The impacts of these factors were quantitatively characterized and compared for the first time using the same antigen (potato virus X). The antibody-colloidal gold conjugates synthesized at pH 9.0-9.5 (the pH was examined in the range from 7.5 to 10.0) and at an antibody concentration of 15 μg/mL (the concentration was tested from 10 to 100 μg/mL) demonstrated maximum binding with the analyte. The relationship between the size of gold nanoparticles and the ICA detection limit was determined. The detection limit decreases from 80 to 3 ng/mL (for antibodies with K (D) = 1.0 × 10(-9) M, data were obtained using a BIAcore X instrument) for a series of particles with a diameter from 6.4 to 33.4 nm (electron microscopy and dynamic light scattering data). In the case of larger particles (52 nm in diameter), the detection limit increases and reaches 9 ng/mL. A 10 mM phosphate buffer, pH 8, and a 50 mM phosphate buffer, pH 7, were the conditions of choice for the deposition of reactants. Taking into account these facts, we developed a lateral-flow test system for the rapid (10 min) detection of potato virus X in plant leaves. The ICA provided a visual detection limit of 3 ng/mL. In the case of the instrumental processing, potato virus X can be determined in the concentration range from 3 to 300 ng/mL with a detection limit 2 ng/mL.

  2. Limited contemporary gene flow and high self-replenishment drives peripheral isolation in an endemic coral reef fish

    PubMed Central

    van der Meer, Martin H; Horne, John B; Gardner, Michael G; Hobbs, Jean-Paul A; Pratchett, Morgan; van Herwerden, Lynne

    2013-01-01

    Extensive ongoing degradation of coral reef habitats worldwide has lead to declines in abundance of coral reef fishes and local extinction of some species. Those most vulnerable are ecological specialists and endemic species. Determining connectivity between locations is vital to understanding recovery and long-term persistence of these species following local extinction. This study explored population connectivity in the ecologically-specialized endemic three-striped butterflyfish (Chaetodon tricinctus) using mt and msatDNA (nuclear microsatellites) to distinguish evolutionary versus contemporary gene flow, estimate self-replenishment and measure genetic diversity among locations at the remote Australian offshore coral reefs of Middleton Reef (MR), Elizabeth Reef (ER), Lord Howe Island (LHI), and Norfolk Island (NI). Mt and msatDNA suggested genetic differentiation of the most peripheral location (NI) from the remaining three locations (MR, ER, LHI). Despite high levels of mtDNA gene flow, there is limited msatDNA gene flow with evidence of high levels of self-replenishment (≥76%) at all four locations. Taken together, this suggests prolonged population recovery times following population declines. The peripheral population (NI) is most vulnerable to local extinction due to its relative isolation, extreme levels of self-replenishment (95%), and low contemporary abundance. PMID:23789075

  3. Rate-limited mass transfer of octane, decane, and dodecane into nonionic surfactants solutions under laminar flow conditions.

    PubMed

    Prak, Dianne J Luning

    2008-05-01

    A key component to predicting the success of utilizing surfactants to enhance the removal of organic liquids from soil system is quantifying micellar solubilization kinetics. In this study, a flow reactor was employed to investigate the influence of surfactant ethoxylate chain length on the rates of solubilization of octane, decane, and dodecane in micellar solutions of a homologous series of purified dodecyl alcohol ethoxylates. Effluent concentration data were fit using a finite element model utilizing a linear-driving-force model to represent mass transfer at the interface. For flow rates between 0.1 and 2 ml min(-1), mass transfer coefficients ranged from 5 x 10(-8) to 7 x 10(-7)m s(-1) and did not vary in a systematic way with either solute structure or surfactant ethoxylate chain length and were lower than those found in pure water. Correlations developed for the Sherwood number based on diffusion coefficients of surfactant micelles containing organic material (organic-laden micelle) exhibit a velocity dependence similar to that found for systems based on aqueous diffusion. These results suggest that under gentle flowing conditions, the mass transfer is limited by diffusion of the organic-laden micelle. Although these trends are specific for this experimental system, the results demonstrate the importance of selecting the proper diffusion coefficient when modeling surfactant solubilization processes.

  4. Limited contemporary gene flow and high self-replenishment drives peripheral isolation in an endemic coral reef fish.

    PubMed

    van der Meer, Martin H; Horne, John B; Gardner, Michael G; Hobbs, Jean-Paul A; Pratchett, Morgan; van Herwerden, Lynne

    2013-06-01

    Extensive ongoing degradation of coral reef habitats worldwide has lead to declines in abundance of coral reef fishes and local extinction of some species. Those most vulnerable are ecological specialists and endemic species. Determining connectivity between locations is vital to understanding recovery and long-term persistence of these species following local extinction. This study explored population connectivity in the ecologically-specialized endemic three-striped butterflyfish (Chaetodon tricinctus) using mt and msatDNA (nuclear microsatellites) to distinguish evolutionary versus contemporary gene flow, estimate self-replenishment and measure genetic diversity among locations at the remote Australian offshore coral reefs of Middleton Reef (MR), Elizabeth Reef (ER), Lord Howe Island (LHI), and Norfolk Island (NI). Mt and msatDNA suggested genetic differentiation of the most peripheral location (NI) from the remaining three locations (MR, ER, LHI). Despite high levels of mtDNA gene flow, there is limited msatDNA gene flow with evidence of high levels of self-replenishment (≥76%) at all four locations. Taken together, this suggests prolonged population recovery times following population declines. The peripheral population (NI) is most vulnerable to local extinction due to its relative isolation, extreme levels of self-replenishment (95%), and low contemporary abundance.

  5. Chronic air-flow limitation does not increase respiratory epithelial permeability assessed by aerosolized solute, but smoking does

    SciTech Connect

    Huchon, G.J.; Russell, J.A.; Barritault, L.G.; Lipavsky, A.; Murray, J.F.

    1984-09-01

    To determine the separate influences of smoking and severe air-flow limitation on aerosol deposition and respiratory epithelial permeability, we studied 26 normal nonsmokers, 12 smokers without airway obstruction, 12 nonsmokers with chronic obstructive pulmonary disease (COPD), and 11 smokers with COPD. We aerosolized 99mTc-labeled diethylene triamine pentaacetic acid to particles approximately 1 micron activity median aerodynamic diameter. Levels of radioactivity were plotted semilogarithmically against time to calculate clearance as percent per minute. The distribution of radioactivity was homogeneous in control subjects and in smokers, but patchy in both groups with COPD. No difference was found between clearances of the control group (1.18 +/- 0.31% min-1), and nonsmoker COPD group (1.37 +/- 0.82% min-1), whereas values in smokers without COPD (4.00 +/- 1.70% min-1) and smokers with COPD (3.62 +/- 2.88% min-1) were significantly greater than in both nonsmoking groups. We conclude that (1) small particles appear to deposit peripherally, even with severe COPD; (2) respiratory epithelial permeability is normal in nonsmokers with COPD; (3) smoking increases permeability by a mechanism unrelated to air-flow limitation.

  6. Chromatographic separation of three monoclonal antibody variants using multicolumn countercurrent solvent gradient purification (MCSGP).

    PubMed

    Müller-Späth, Thomas; Aumann, Lars; Melter, Lena; Ströhlein, Guido; Morbidelli, Massimo

    2008-08-15

    Multicolumn countercurrent solvent gradient purification (MCSGP) is a continuous chromatographic process developed in recent years (Aumann and Morbidelli, 2007a; Aumann et al., 2007) that is particularly suited for applications in the field of bioseparations. Like batch chromatography, MCSGP is suitable for three-fraction chromatographic separations and able to perform solvent gradients but it is superior in terms of solvent consumption, yield, purity, and productivity due to the countercurrent movement of the liquid and the solid phases. In this work, the MCSGP process is applied to the separation of three monoclonal antibody variants on a conventional preparative cation exchange resin. The experimental process performance was compared to simulations based on a lumped kinetic model. Yield and purity values of the target variant of 93%, respectively were obtained experimentally. The batch reference process was clearly outperformed by the MCSGP process.

  7. Separation of Catalpol from Rehmannia glutinosa Libosch. by High-Speed Countercurrent Chromatography

    PubMed Central

    Tong, Shengqiang; Chen, Lin; Zhang, Qing; Liu, Jian; Yan, Jizhong; Ito, Yoichiro

    2015-01-01

    The bioactive iridoid component catalpol was successfully separated by high-speed countercurrent chromatography with high purity from the partially purified crude extract of Rehmannia glutinosa. A polar two-phase solvent system composed of ethyl acetate–n-butanol–water (2:1:3, v/v/v) was selected by thin-layer chromatography and run on a preparative scale where the lower aqueous phase was used as the mobile phase with a head-to-tail elution mode. A 105 mg quantity of the partially purified sample containing 39.2% catalpol was loaded on a 270-mL capacity high-speed countercurrent separation column, yielding 35 mg of catalpol at 95.6% purity. The chemical structure of catalpol was determined by comparison with the high-performance liquid chromatography retention time of standard substance as well as the 1H NMR spectrum. PMID:25214499

  8. Mass transfer in countercurrent packed columns: Application to supercritical CO[sub 2] extraction of terpenes

    SciTech Connect

    Simoes, P.C.; Matos, H.A.; Carmelo, P.J.; Gomes de Azevedo, E.; Nunes da Ponte, M. . Faculdade de Ciencias e Tecnologia)

    1995-02-01

    Supercritical fluid extraction (SFE) is an alternative separation method to more conventional processes such as liquid extraction and distillation. However, up to now, few works have been devoted to the investigation of the efficiency of countercurrent packed columns under supercritical conditions from a mass transfer point of view. Mass transfer in a countercurrent column, filled with structured gauze packing, was measured for the separation of a mixture of terpenes (d-limonene/1,8-cineole) by supercritical carbon dioxide, at 313 and 318 K and pressures up to 9 MPa. The extraction efficiency was determined in terms of the overall mass transfer coefficient. Operating lines for this process had an appreciable curvature due to a high miscibility of the two contacting phases. The real slope of these lines had to be estimated. Available mass transfer models for packed columns predicted efficiencies diverging to a great extent from the experimental results.

  9. Current flow and pair creation at low altitude in rotation-powered pulsars' force-free magnetospheres: space charge limited flow

    NASA Astrophysics Data System (ADS)

    Timokhin, A. N.; Arons, J.

    2013-02-01

    We report the results of an investigation of particle acceleration and electron-positron plasma generation at low altitude in the polar magnetic flux tubes of rotation-powered pulsars, when the stellar surface is free to emit whatever charges and currents are demanded by the force-free magnetosphere. We apply a new 1D hybrid plasma simulation code to the dynamical problem, using Particle-in-Cell methods for the dynamics of the charged particles, including a determination of the collective electrostatic fluctuations in the plasma, combined with a Monte Carlo treatment of the high-energy gamma-rays that mediate the formation of the electron-positron pairs. We assume the electric current flowing through the pair creation zone is fixed by the much higher inductance magnetosphere, and adopt the results of force-free magnetosphere models to provide the currents which must be carried by the accelerator. The models are spatially one dimensional, and designed to explore the physics, although of practical relevance to young, high-voltage pulsars. We observe novel behaviour (a) When the current density j is less than the Goldreich-Julian value (0 < j/jGJ < 1), space charge limited acceleration of the current carrying beam is mild, with the full Goldreich-Julian charge density comprising the charge densities of the beam and a cloud of electrically trapped particles with the same sign of charge as the beam. The voltage drops are of the order of mc2/e, and pair creation is absent. (b) When the current density exceeds the Goldreich-Julian value (j/jGJ > 1), the system develops high voltage drops (TV or greater), causing emission of curvature gamma-rays and intense bursts of pair creation. The bursts exhibit limit cycle behaviour, with characteristic time-scales somewhat longer than the relativistic fly-by time over distances comparable to the polar cap diameter (microseconds). (c) In return current regions, where j/jGJ < 0, the system develops similar bursts of pair creation

  10. Expected climate change impacts on extreme flows in Vietnam: The limits of bias correction techniques

    NASA Astrophysics Data System (ADS)

    Laux, Patrick; Dang, Thinh; Kunstmann, Harald

    2016-04-01

    increase of 4%, 65%, and 94% HQ100 is estimated for 2011-2030, 2031-2050, and 2080-2099, respectively. Albeit there is a large spread of simulated peak magnitudes, a tendency towards positive future peak flows can be concluded. Due to the obtained large spread of simulated peak magnitudes, we stress the need for combined climate and hydrological ensemble simulations. This inherently large spread of future peak magnitudes is further increased by the inflated distributions obtained from the bias corrected meteorological input variables. The wide spread of future expected magnitudes remains a crucial problem for decision makers in climate change assessments, as demonstrated here for the VuGia-ThuBon river basin.

  11. Assessment of nitrogen and phosphorus flows in agricultural and urban systems in a small island under limited data availability.

    PubMed

    Firmansyah, I; Spiller, M; de Ruijter, F J; Carsjens, G J; Zeeman, G

    2017-01-01

    Nitrogen (N) and phosphorus (P) are two essential macronutrients required in agricultural production. The major share of this production relies on chemical fertilizer that requires energy and relies on limited resources (P). Since these nutrients are lost to the environment, there is a need to shift from this linear urban metabolism to a circular metabolism in which N and P from domestic waste and wastewater are reused in agriculture. A first step to facilitate a transition to more circular urban N and P management is to understand the flows of these resources in a coupled urban-agricultural system. For the first time this paper presents a Substance Flow Analysis (SFA) approach for the assessment of the coupled agricultural and urban systems under limited data availability in a small island. The developed SFA approach is used to identify intervention points that can provide N and P stocks for agricultural production. The island of St. Eustatius, a small island in the Caribbean, was used as a case study. The model developed in this study consists of eight sub-systems: agricultural and natural lands, urban lands, crop production, animal production, market, household consumption, soakage pit and open-dump landfill. A total of 26 flows were identified and quantified for a period of one year (2013). The results showed that the agricultural system is a significant source for N and P loss because of erosion/run-off and leaching. Moreover, urban sanitation systems contribute to deterioration of the island's ecosystem through N and P losses from domestic waste and wastewater by leaching and atmospheric emission. Proposed interventions are the treatment of blackwater and greywater for the recovery of N and P. In conclusion, this study allows for identification of potential N and P losses and proposes mitigation measures to improve nutrient management in a small island context.

  12. Counter-current carbon dioxide extraction of fat from soy skim

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This research aims to investigate the use of counter-current carbon dioxide extraction method as a means to reduce residual fat in soy skim after the enzyme-assisted aqueous extraction of soybeans. Extractions with liquid CO2 at 25°C and 10.34 MPa and supercritical CO2 at 50°C and 25.16 MPa are comp...

  13. Long-Term Observations of a Coastal Countercurrent on the Southeast Florida Shelf

    NASA Astrophysics Data System (ADS)

    Soloviev, A.

    2010-12-01

    Coastal circulation along the southeast Florida shelf is strongly related to the dynamics of the Florida Current as a part of the western boundary current system. We have conducted long-term observations with a mooring array deployed on the Ft. Lauderdale FL shelf. The array consists of a bottom ADCP mooring at 11 m isobath on the Dania Beach Shelf providing almost continuous observations since 1999 and a bottom ADCP mooring deployed on the Miami Terrace near Pompano Beach at 240 m isobath since 2007. There is a strong variability of the coastal current at this location on time scales ranging from hours to months, which is explained by the proximity to the Florida Current. An interesting feature revealed during these observations is an intermittent coastal countercurrent. This coastal countercurrent is seasonally modulated, reversing its direction during the summer season. The appearance of the countercurrent on the southeast Florida shelf and its relation to the Florida Current and undercurrent have not yet been completely understood. The possible physical mechanism behind this feature of the coastal circulation on the Southeast Florida shelf and practical applications are being discussed.

  14. Application of an asymmetric flow field flow fractionation multi-detector approach for metallic engineered nanoparticle characterization--prospects and limitations demonstrated on Au nanoparticles.

    PubMed

    Hagendorfer, Harald; Kaegi, Ralf; Traber, Jacqueline; Mertens, Stijn F L; Scherrers, Roger; Ludwig, Christian; Ulrich, Andrea

    2011-11-14

    In this work we discuss about the method development, applicability and limitations of an asymmetric flow field flow fractionation (A4F) system in combination with a multi-detector setup consisting of UV/vis, light scattering, and inductively coupled plasma mass spectrometry (ICPMS). The overall aim was to obtain a size dependent-, element specific-, and quantitative method appropriate for the characterization of metallic engineered nanoparticle (ENP) dispersions. Thus, systematic investigations of crucial method parameters were performed by employing well characterized Au nanoparticles (Au-NPs) as a defined model system. For good separation performance, the A4F flow-, membrane-, and carrier conditions were optimized. To obtain reliable size information, the use of laser light scattering based detectors was evaluated, where an online dynamic light scattering (DLS) detector showed good results for the investigated Au-NP up to a size of 80 nm in hydrodynamic diameter. To adapt large sensitivity differences of the various detectors, as well as to guarantee long term stability and minimum contamination of the mass spectrometer a split-flow concept for coupling ICPMS was evaluated. To test for reliable quantification, the ICPMS signal response of ionic Au standards was compared to that of Au-NP. Using proper stabilization with surfactants, no difference for concentrations of 1-50 μg Au L(-1) in the size range from 5 to 80 nm for citrate stabilized dispersions was observed. However, studies using different A4F channel membranes showed unspecific particle-membrane interaction resulting in retention time shifts and unspecific loss of nanoparticles, depending on the Au-NP system as well as membrane batch and type. Thus, reliable quantification and discrimination of ionic and particular species was performed using ICPMS in combination with ultracentrifugation instead of direct quantification with the A4F multi-detector setup. Figures of merit were obtained, by comparing the

  15. Phenolic profiling of rooibos using off-line comprehensive normal phase countercurrent chromatography×reversed phase liquid chromatography.

    PubMed

    Walters, Nico A; de Villiers, André; Joubert, Elizabeth; de Beer, Dalene

    2017-03-24

    Limited performance of one dimensional chromatographic methods provides the incentive for the development of multidimensional chromatographic techniques for the analysis of complex mixtures. Rooibos (Aspalathus linearis) represents such a complex sample, containing a range of phenolic compounds that cannot be separated and identified using a single chromatographic technique within a reasonable run time. By implementing NP high performance countercurrent chromatography (NP-HPCCC) in the first dimension ((1)D) and RP ultra-high pressure LC (RP-UHPLC) in the second dimension ((2)D), a highly orthogonal (∼80%) off-line comprehensive two-dimensional separation of rooibos phenolic compounds was achieved in a total analysis time of 17h. The use of a gradient for the (1)D HPCCC separation ensured a good spread of relatively polar flavonoid di-C-glycosides and less polar mono- and di-O-glycosides, while the highly efficient UHPLC method was able to separate compounds eluting in the same (1)D fraction. Analysis of green ("unfermented") and traditional "fermented" rooibos samples enabled tentative identification of 39 phenolic compounds based on UV-vis and MS characteristics, of which 18 have not previously been reported in rooibos. Scolymoside (a flavone), hesperidin (a flavanone) and phloretin-3',5'-di-C-β-d-glucopyranoside (a dihydrochalcone) were identified for the first time in rooibos by comparison with authentic reference standards.

  16. Diagnosis of acute bacterial pneumonia in Nigerian children. Value of needle aspiration of lung of countercurrent immunoelectrophoresis.

    PubMed Central

    Silverman, M; Stratton, D; Diallo, A; Egler, L J

    1977-01-01

    Eighty-eight Nigerian children with untreated, severe, acute pneumonia were investigated by standard bacteriological techniques (blood culture and culture of pharyngeal secretions) and by needle aspiration of the consolidated lung. Countercurrent immunoelectrophoresis (CIE) against grouped pneumococcal and Haemophilus influenzae type b antisera was carried out on serum samples from 45 patients. The aetiology of pneumonia was shown by examination of the needle aspirate in 70/88 patients (79%), by CIE in 9/45 patients (20%), and by blood culture in 4/36 patients (11%). Overall, a bacterial cause for pneumonia was shown in 73/88 patients (83%). The results of pharyngeal culture were misleading when compared with cultures of needle aspirates. The prediction of aetiology from the radiological appearance was alos inaccurate, even for labor pneumonia. Needle aspiration of the lung, with a low (5%) and minor complication rate, merits wider application in the diagnosis of acute pulmonary infections in children. Tradiational bacteriological techniques (blood culture and pharyngeal culture) are of very limited value. The place of CIE in the investigation of childhood pneumonia still needs thorough evaluation. PMID:343723

  17. Effects of an aging pulmonary system on expiratory flow limitation and dyspnoea during exercise in healthy women.

    PubMed

    Wilkie, Sabrina S; Guenette, Jordan A; Dominelli, Paolo B; Sheel, A William

    2012-06-01

    Aging related changes in pulmonary function may make older women (OW) more susceptible to expiratory flow limitation (EFL) and lead to higher dyspnoea ratings during exercise relative to young women (YW). Accordingly, the purpose of this study was to compare sensory responses and EFL susceptibility and magnitude in 8 YW (29 ± 7 years) and 8 healthy OW (64 ± 3 years) matched for percentage-predicted forced vital capacity (% predicted FVC) and % predicted forced expiratory volume in 1 s. EFL was calculated as the percent overlap between tidal flow-volume loops during maximal exercise and the maximal expiratory flow-volume (MEFV) curve. Peak oxygen consumption (V'O(2peak)) was lower in the OW compared to the YW (29.4 ± 3.6 vs. 49.1 ± 8.9 ml kg(-1) min(-1), P < 0.05) as was maximal ventilation (73.7 ± 18.4 vs. 108.7 ± 14.1 l min(-1), P < 0.05). EFL at maximal exercise was present in 2 of 8 YW and in 5 of 8 OW. There were no significant differences in the magnitude of EFL between OW (23 ± 24, range: 0-69 %EFL) and YW (9 ± 18, range: 0-46 %EFL, P = 0.21). The magnitude of EFL in OW was inversely related to % predicted FVC (r = -0.69, P = 0.06), but this relationships was not observed in the YW (r = -0.23, P = 0.59). The OW consistently reported greater dyspnoea and leg discomfort for any given absolute work rate, but not when work was expressed as a percentage of maximum. Reduced ventilatory and exercise capacities may cause OW to be more susceptible to EFL during exercise and experience greater dyspnoea relative to YW for a standardized physical task.

  18. Nonlinear dynamical behavior of the limited Explodator in a CSTR under square wave perturbation of the flow rate

    NASA Astrophysics Data System (ADS)

    Wu, Xiaomao; Schelly, Z. A.; Vastano, John A.

    1994-07-01

    Results of studies of the limited Explodator model in a continuous-flow stirred tank reactor (CSTR) under square wave perturbation of the flow rate are reported. The perturbation is applied in such a way that the system is alternately attracted to two different periodic attractors in the parameter region close the Hopf bifurcation point. The system is shown to display a variety of entrainment bands, birhythmicity, quasiperiodicity, resonance-like phenomenon, period doubling and intermittency routes to chaos, and a complicated window structure of the chaotic region. In addition, a novel phenomenon, “intermittent alternative laminar oscillations”, was observed in a chaotic regime sandwiched between two entrainment bands. Transient chaos occurs in one of the entrainment bands, which intimates chaos in the adjacent regime. Positive Lyapunov exponents were found to be associated with the chaotic behavior. The folding and stretching property of the chaotic attractors was analyzed through stroboscopic representations. The deterministic nature of the chaotic behavior was confirmed by the quadratic-like curve formed in the one-dimensional map.

  19. Current Flow and Pair Creation at Low Altitude in Rotation-Powered Pulsars' Force-Free Magnetospheres: Space Charge Limited Flow

    NASA Technical Reports Server (NTRS)

    Timokhin, A. N.; Arons, J.

    2013-01-01

    We report the results of an investigation of particle acceleration and electron-positron plasma generation at low altitude in the polar magnetic flux tubes of rotation-powered pulsars, when the stellar surface is free to emit whatever charges and currents are demanded by the force-free magnetosphere. We apply a new 1D hybrid plasma simulation code to the dynamical problem, using Particle-in-Cell methods for the dynamics of the charged particles, including a determination of the collective electrostatic fluctuations in the plasma, combined with a Monte Carlo treatment of the high-energy gamma-rays that mediate the formation of the electron-positron pairs.We assume the electric current flowing through the pair creation zone is fixed by the much higher inductance magnetosphere, and adopt the results of force-free magnetosphere models to provide the currents which must be carried by the accelerator. The models are spatially one dimensional, and designed to explore the physics, although of practical relevance to young, high-voltage pulsars. We observe novel behaviour (a) When the current density j is less than the Goldreich-Julian value (0 < j/j(sub GJ) < 1), space charge limited acceleration of the current carrying beam is mild, with the full Goldreich-Julian charge density comprising the charge densities of the beam and a cloud of electrically trapped particles with the same sign of charge as the beam. The voltage drops are of the order of mc(sup 2)/e, and pair creation is absent. (b) When the current density exceeds the Goldreich-Julian value (j/j(sub GJ) > 1), the system develops high voltage drops (TV or greater), causing emission of curvature gamma-rays and intense bursts of pair creation. The bursts exhibit limit cycle behaviour, with characteristic time-scales somewhat longer than the relativistic fly-by time over distances comparable to the polar cap diameter (microseconds). (c) In return current regions, where j/j(sub GJ) < 0, the system develops similar

  20. Isolation of dimeric, trimeric, tetrameric and pentameric procyanidins from unroasted cocoa beans (Theobroma cacao L.) using countercurrent chromatography.

    PubMed

    Esatbeyoglu, Tuba; Wray, Victor; Winterhalter, Peter

    2015-07-15

    The main procyanidins, including dimeric B2 and B5, trimeric C1, tetrameric and pentameric procyanidins, were isolated from unroasted cocoa beans (Theobroma cacao L.) using various techniques of countercurrent chromatography, such as high-speed countercurrent chromatography (HSCCC), low-speed rotary countercurrent chromatography (LSRCCC) and spiral-coil LSRCCC. Furthermore, dimeric procyanidins B1 and B7, which are not present naturally in the analysed cocoa beans, were obtained after semisynthesis of cocoa bean polymers with (+)-catechin as nucleophile and separated by countercurrent chromatography. In this way, the isolation of dimeric procyanidin B1 in considerable amounts (500mg, purity>97%) was possible in a single run. This is the first report concerning the isolation and semisynthesis of dimeric to pentameric procyanidins from T. cacao by countercurrent chromatography. Additionally, the chemical structures of tetrameric (cinnamtannin A2) and pentameric procyanidins (cinnamtannin A3) were elucidated on the basis of (1)H NMR spectroscopy. Interflavanoid linkage was determined by NOE-correlations, for the first time.

  1. [Application of spiral disk column in high-speed counter-current chromatography for peptide and protein separation].

    PubMed

    Hu, Guanghui; Cao, Xueli

    2009-04-01

    In order to improve the stationary phase retention of polar solvent systems and aqueous two-phase systems (ATPSs), we designed a multiple spiral disk assembly for type-J high-speed counter-current chromatography (HSCCC). The stationary phase retention was studied under different elution modes by using two solvent systems that contained 1-butanol-acetic acid-water (4:1:5, V/V/V) and polyethylene glycol (PEG) 1000-K2HPO4-water (12.5:12.5:75, W/W/W). The best retention was obtained in L-I-T, U-O-H, L-I-H three modes by pumping lower mobile phase from inner terminal (I) to outer terminal (O), and upper mobile phase from outer terminal (O) to inner terminal (I) at a relatively high flow rate. Meanwhile, the relationship between retention percentage of the stationary phase (Sf) and various parameters such as flow-rate (F), rotation speed (w) and column temperature (T) was also studied. Sf increased with the increase of w and decreased with the increase of F. Regression analysis showed a linear relationship between Sf and F1/2/w. The influence of T on Sf was not obvious between 20 degrees C and 40 degrees C, lower temperature than 20 degrees C was not suitable for viscous ATPSs. Acceptable resolutions were achieved when it was applied for the separation of dipeptides including Leu-Tyr and Val-Tyr by using 1-butanol-acetic acid-water (4:1:5, V/V/V) solvent system. The proteins including cytochrome C and myoglobin, lysozyme and myoglobin, and fresh chicken egg-white proteins were well separated by 12.5% PEG1000-12.5% K2HPO4-75% water (pH 9.0) and 16% PEG 1000-12.5% K2HPO4-71.5% water (pH 8.0) system.

  2. Path of carbon flow during NO/sub 3//sup -/-induced photosynthetic suppression in N-limited Selenastrum minutum

    SciTech Connect

    Elrifi, I.R.; Turpin, D.H.

    1987-01-01

    Nitrate addition to nitrate-limited cultures of Selenastrum minutum Naeg. Collins (Chlorophyta) resulted in a 70% suppression of photosynthetic carbon fixation. In /sup 14/CO/sub 2/ pulse/chase experiments nitrate resupply increased radiolabel incorporation into amino and organic acids and decreased radiolabel incorporation into insoluble material. Nitrate resupply increased the concentration of phosphoenolpyruvate and increased the radiolabeling of phosphoenolpyruvate, pyruvate and tricarboxylic acid cycle intermediates, notably citrate, fumarate, and malate. Furthermore, nitrate also increased the pool sizes and radiolabeling of most amino acids, with alanine, aspartate, glutamate, and glutamine showing the largest changes. Nitrate resupply increased the proportion of radiolabel in the C-4 position of malate and increased the ratios of radiolabel in aspartate to phosphoenolpyruvate and in pyruvate to phosphoenolpyruvate, indicative of increased phosphoenolpyruvate carboxylase and pyruvate kinase activities. Analysis of these data showed that the rate of carbon flow through glutamate (10.6 ..mu..moles glutamate per milligram chlorophyll per hour) and the rate of net glutamate production (7.9 ..mu..moles glutamate per milligram chlorophyll per hour) were both greater than the maximum rate of carbon export from the Calvin cycle which could be maintained during steady state photosynthesis. These results are consistent with the hypothesis that nitrogen resupply to nitrogen-limited microalgae results in a transient suppression of photosynthetic carbon fixation due, in part, to the severity of competition for carbon skeletons between the Calvin cycle and nitrogen assimilation.

  3. Separation and purification of two new and two known alkaloids from leaves of Nitraria sibirica by pH-zone-refining counter-current chromatography.

    PubMed

    Bakri, Mahinur; Chen, Qibin; Ma, Qingling; Yang, Yi; Abdukadir, Abdumijit; Aisa, Haji Akber

    2015-12-01

    The total alkaloids from Nitraria sibirica leaves have been confirmed to exhibit significant protective effects against inflammatory renal injury, hypertension and albuminuria in angiotensin II-salt hypertension. In the present study, a separation method of pH-zone-refining counter-current chromatography was established for separation of the alkaloids from N. sibirica. The separation was performed with a solvent system of MtBE-n-BuOH-H2O (2:2:5, v/v) at a flow rate of 2.0mL/min. And 15mM triethylamine (TEA) was added to the upper organic phase, while 10mM hydrochloric acid was added to the lower aqueous phase. As a result, a new alkaloid, schobemine (5.6mg), and a known alkaloid, nitraramine (5.0mg), together with fractions A and B were obtained from the total alkaloids of N. sibirica. The fractions A and B were further purified by means of pH-zone-refining counter-current chromatography with solvent systems of n-hexane-n-BuOH-H2O (1.5:3.5:5, v/v) and (2:3:5, v/v), respectively. TEA (10mM) was added to the upper phase, and 10mM of HCl was added to the lower phase in above two solvent systems, respectively. As a result, a known alkaloid, schoberidine (5.0mg), and a new alkaloid, schoberimine (3.0mg) were obtained from fractions A and B, respectively. The purities of the compounds were measured by HPLC-ELSD, and their structures were identified by ESI-MS, 1D and 2D NMR.

  4. Use of two-stage membrane countercurrent cascade for natural gas purification from carbon dioxide

    NASA Astrophysics Data System (ADS)

    Kurchatov, I. M.; Laguntsov, N. I.; Karaseva, M. D.

    2016-09-01

    Membrane technology scheme is offered and presented as a two-stage countercurrent recirculating cascade, in order to solve the problem of natural gas dehydration and purification from CO2. The first stage is a single divider, and the second stage is a recirculating two-module divider. This scheme allows natural gas to be cleaned from impurities, with any desired degree of methane extraction. In this paper, the optimal values of the basic parameters of the selected technological scheme are determined. An estimation of energy efficiency was carried out, taking into account the energy consumption of interstage compressor and methane losses in energy units.

  5. High-speed counter-current chromatographic isolation of ricinine, an insecticide from Ricinus communis.

    PubMed

    Cazal, Cristiane de Melo; Batalhão, Jaqueline Raquel; Domingues, Vanessa de Cássia; Bueno, Odair Corrêa; Filho, Edson Rodrigues; Forim, Moacir R; da Silva, Maria Fátima G Fernandes; Vieira, Paulo Cezar; Fernandes, João Batista

    2009-05-08

    The alkaloid ricinine, an insecticide for leaf-cutting ant (Atta sexdens rubropilosa), was obtained from Ricinus communis. A two-phase solvent system composed of CH(2)Cl(2)/EtOH/H(2)O (93:35:72, v/v/v) was used for high-speed counter-current chromatographic (HSCCC) isolation of ricinine in high yield and with over 96% purity, as determined by liquid and gas chromatography-mass spectrometry (LC-MS and GC-MS). Identification of ricinine was performed by comparison of (1)H NMR, (13)C NMR and LC-MS/MS data.

  6. Effect of pulmonary rehabilitation on tidal expiratory flow limitation at rest and during exercise in COPD patients.

    PubMed

    Theodorakopoulou, Elpida P; Gennimata, Sofia-Antiopi; Harikiopoulou, Maria; Kaltsakas, Georgios; Palamidas, Anastasios; Koutsoukou, Antonia; Roussos, Charis; Kosmas, Epameinondas N; Bakakos, Petros; Koulouris, Nickolaos G

    2017-04-01

    We hypothesized that severe COPD patients who present with the disadvantageous phenomenon of Expiratory Flow Limitation (EFL) may benefit as COPD patients without EFL do after implementation of a Pulmonary Rehabilitation (PR) program. Forty-two stable COPD patients were studied at rest and during exercise. EFL and dynamic hyperinflation (DH) were documented using the negative expiratory pressure (NEP) technique and inspiratory capacity (IC) maneuvers, respectively. Patient centered outcomes were evaluated by the Saint-George's Respiratory Questionnaire (SGRQ) and the mMRC dyspnea scale. Before PR, 16 patients presented with EFL at rest and/or during exercise. After PR, EFL was abolished in 15 out of those 16 EFL patients who exhibited a significant increase in IC values. These were mainly accomplished through a modification of the breathing pattern. In the 26 NFL patients no increase was noted in their IC or a modification of their breathing pattern. However, both NFL and EFL COPD patients improved exercise capacity and patients centered outcomes undergoing the same PR program.

  7. Angina pectoris in patients without flow-limiting coronary artery disease (cardiac syndrome X). A forest of a variety of trees.

    PubMed

    Cocco, Giuseppe; Jerie, Paul

    2015-01-01

    Coronary heart disease (CHD) represents an important problem worldwide. At present, more women than men are evaluated for CHD and it has been recognized that the prevalence of this pathology in women is at least the same as in men. We have learned that cardiac syndrome X (CSX) is frequent because worldwide each year millions of people (mostly women) with angina pectoris without flow-limiting epicardial pathology are identified. Data from large myocardial infarction registries suggest a 5% to 25% prevalence of cases without flow-limiting coronary pathology. It must, however, be considered that these people are said to have normal coronary arteries by visual analysis of biplane coronarography. On the other hand, as demonstrated from autopsy, and in vivo by ultrasound intravascular studies, it would be more appropriate to say that in the majority of these cases no obstructive or flow-limiting coronary pathology was detected by coronarography. In CSX, endothelial dysfunction and microvascular dysfunction, sometimes with coronary microvascular spasm and epicardial coronary artery spasm, have been recognized as pathophysiologic mechanisms. In CSX, symptoms and pathologic signs are the same in patients with flow-limiting coronary pathology. The difference lies in the fact that the mechanisms of myocardial ischemia are microvascular and flow-limiting epicardial coronary pathology is absent. By interplay, the pathologic entities at work in CSX are linked with poor long-term outcome. The prevalence of these outcomes is probably smaller than in patients with flow-limiting coronary pathology but we lack precise values. Nonetheless, severe cardiovascular complications are frequent in CSX and it is thus the pathology is not benign. Drugs used in coronary ischemic disease are empirically prescribed to treat CSX, but we lack data from specific trials. It seems that statins and ranolazine might exert positive effects. However, specific research to target interventions in CSX would

  8. Improving Efficiency of a Counter-Current Flow Moving Bed Granular Filter

    SciTech Connect

    Colver, G.M.; Brown, R.C.; Shi, H.; Soo, D.S-C.

    2002-09-18

    The goal of this research is to improve the performance of moving bed granular filters for gas cleaning at high temperatures and pressures. A second goal of the research is to optimize the performances of both solids and gas filtering processes through appropriate use of granular bed materials, particle sizes, feed rates etc. in a factorial study. These goals are directed toward applications of advanced coal-fired power cycles under development by the U.S. Department of Energy including pressurized fluidized bed combustion and integrated gasification/combined cycles based on gas turbines and fuel cells. Only results for particulate gas cleaning are reported here.

  9. Purification of semiconducting single-walled carbon nanotubes by spiral counter-current chromatography.

    PubMed

    Knight, Martha; Lazo-Portugal, Rodrigo; Ahn, Saeyoung Nate; Stefansson, Steingrimur

    2017-02-03

    Over the last decade man-made carbon nanostructures have shown great promise in electronic applications, but they are produced as very heterogeneous mixtures with different properties so the achievement of a significant commercial application has been elusive. The dimensions of single-wall carbon nanotubes are generally a nanometer wide, up to hundreds of microns long and the carbon nanotubes have anisotropic structures. They are processed to have shorter lengths but they need to be sorted by diameter and chirality. Thus counter-current chromatography methods developed for large molecules are applied to separate these compounds. A modified mixer-settler spiral CCC rotor made with 3 D printed disks was used with a polyethylene glycol-dextran 2-phase solvent system and a surfactant gradient to purify the major species in a commercial preparation. We isolated the semi-conducting single walled carbon nanotube chiral species identified by UV spectral analysis. The further development of spiral counter-current chromatography instrumentation and methods will enable the scalable purification of carbon nanotubes useful for the next generation electronics.

  10. Separation and purification of five alkaloids from Aconitum duclouxii by counter-current chromatography.

    PubMed

    Wang, Yarong; Cai, Shining; Chen, Yang; Deng, Liang; Zhou, Xumei; Liu, Jia; Xu, Xin; Xia, Qiang; Lin, Mao; Zhang, Jili; Huang, Weili; Wang, Wenjun; Xiang, Canhui; Cui, Guozhen; Du, Lianfeng; He, Huan; Qi, Baohui

    2015-07-01

    C19 -diterpenoid alkaloids are the main components of Aconitum duclouxii Levl. The process of separation and purification of these compounds in previous studies was tedious and time consuming, requiring multiple chromatographic steps, thus resulted in low recovery and high cost. In the present work, five C19 -diterpenoid alkaloids, namely, benzoylaconine (1), N-deethylaconitine (2), aconitine (3), deoxyaconitine (4), and ducloudine A (5), were efficiently prepared from A. duclouxii Levl (Aconitum L.) by ethyl acetate extraction followed with counter-current chromatography. In the process of separation, the critical conditions of counter-current chromatography were optimized. The two-phase solvent system composed of n-hexane/ethyl acetate/methanol/water/NH3 ·H2 O (25%) (1:1:1:1:0.1, v/v) was selected and 148.2 mg of 1, 24.1 mg of 2, 250.6 mg of 3, 73.9 mg of 4, and 31.4 mg of 5 were obtained from 1 g total Aconitum alkaloids extract, respectively, in a single run within 4 h. Their purities were found to be 98.4, 97.2, 98.2, 96.8, and 96.6%, respectively, by ultra-high performance liquid chromatography analysis. The presented separation and purification method was simple, fast, and efficient, and the obtained highly pure alkaloids are suitable for biochemical and toxicological investigation.

  11. Reverse osmosis concentrate treatment via a PAC-MF accumulative countercurrent adsorption process.

    PubMed

    Zhao, Chunxia; Gu, Ping; Cui, Hangyu; Zhang, Guanghui

    2012-01-01

    Organic pollutants in reverse osmosis (RO) concentrates from wastewater reclamation are mainly comprised of low molecular weight biorefractory compounds. Generally, advanced oxidation methods for oxidizing these organics require a relatively high level of energy consumption. In addition, conventional adsorption removal methods require a large dose of activated carbon. However, the dose can be reduced if its full adsorption capacity can be used. Therefore, the combined technology of powdered activated carbon (PAC) adsorption and microfiltration (MF) membrane filtration was studied to develop a countercurrent two-stage adsorption process. A PAC accumulative adsorption prediction method was proposed based on the verification of a PAC multi-stage adsorption capacity equation. Moreover, the prediction method was amended for a more accurate prediction of the effluent quality because adsorption isotherm constants were affected by the initial adsorbate concentration. The required PAC dose for the accumulative countercurrent two-stage adsorption system was 0.6 g/L, whereas that of the conventional adsorption process was 1.05 g/L when the dilution factor(F) was 0.1 and the COD and DOC removal rates were set to 70% and 68.1%, respectively. Organic pollutants were satisfactorily removed with less consumption of PAC. Effluent from this combined technology can be further reclaimed by an RO process to improve the overall recovery rate to between 91.0% and 93.8% with both economic and environmental benefits.

  12. Performance characteristics of countercurrent separation in analysis of natural products of agricultural significance.

    PubMed

    Friesen, J Brent; Pauli, Guido F

    2008-01-09

    A standard test mix consisting of 21 commercially available natural products of agricultural significance, termed the GUESSmix, was employed to measure the countercurrent chromatography performance characteristics of a very popular quaternary solvent system family made up of hexane-ethyl acetate-methanol-water (HEMWat). The polarity range of the GUESSmix combined with the elution-extrusion countercurrent chromatography (EECCC) technique and the newly developed reciprocal symmetry (ReS) and reciprocal shifted symmetry (ReSS) plots allow liquid-liquid distribution ratios ( K D) to be plotted for every compound eluted on a scale of zero to infinity. It was demonstrated that 16 of the 21 GUESSmix compounds are found in the optimal range of resolution (0.25 < K(D) < 16) of at least one HEMWat solvent system. The HEMWat solvent systems represented by the ratios 4:6:5:5, 4:6:4:6, and 3:7:4:6 possess the most densely populated optimal ranges of resolution for this standard mix. ReS plots have been shown to reveal the symmetrical reversibility of the EECCC method in reference to K(D) = 1. This study lays the groundwork for evaluation and comparison of solvent system families proposed in the literature, as well as the creation of new solvent system families with desired performance characteristics.

  13. Numerical Studies of Fluid Leakage from a Geologic DisposalReservoir for CO2 Show Self-Limiting Feedback between Fluid Flow and HeatTransfer

    SciTech Connect

    Pruess, Karsten

    2005-03-22

    Leakage of CO2 from a hypothetical geologic storage reservoir along an idealized fault zone has been simulated, including transitions between supercritical, liquid, and gaseous CO2. We find strong non-isothermal effects due to boiling and Joule-Thomson cooling of expanding CO2. Leakage fluxes are limited by limitations in conductive heat transfer to the fault zone. The interplay between multiphase flow and heat transfer effects produces non-monotonic leakage behavior.

  14. Online-storage recycling counter-current chromatography for preparative isolation of naphthaquinones from Arnebia euchroma (Royle) Johnst.

    PubMed

    He, Jian-Ming; Zhang, Shi-Yue; Mu, Qing

    2016-09-16

    Counter-current Chromatography (CCC) has gradually become a popular method for preparative separation, especially in natural product isolation. As an effective separation method, one-dimensional (1D) CCC often results in insufficiently resolved peaks, due to limitations in the separation efficiency and peak capacity in an equipment. Therefore, two dimensional (2D)/multi-dimensional (multi-D) CCC strategies with recycling elution mode were developed to achieve successful separation of target compounds. However, the reported 2D or multi-D CCC approaches lead to experimental costs, complicated procedures, higher requirements for equipment, and increased time consumption. In this study, an online-storage recycling (OSR) CCC strategy was designed to achieve sequential recycling elution for multi-fractions of effluent in non-stop separation with single instrument using three 6-port valves and two storage loops, which would be realized by introducing 2D or multi-D CCC method before. In this non-stop separation system, the fraction C of effluent was subjected to recycling separation while the other fractions (A and B) were storing online, following which these two fractions were subjected to subsequent recycling separations in order, after the completion of the previous recycling elution. Then, six natural occurring naphthaquinone analogues, namely, shikonin (1), propionylshikonin (2), deoxyshikonin (3), isobutyrylshikonin (4), β, β-dimethylacrylshikonin (5) and isovalerylshikonin (6), were isolated from the crude extract of Arnebia euchroma in single run. The purities of all compounds were > 95.0% as determined by HPLC, and their structures were determined by means of UV, MS, (1)H NMR, (13)C NMR, and optical rotatory dispersion (ORD).

  15. Recovery of butanol by counter-current carbon dioxide fractionation with its potential application to butanol fermentation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A counter-current CO2 fractionation method was studied as a means to recover butanol (also known as 1-butanol or n-butanol) and other compounds that are typically obtained from biobutanol fermentation broth from aqueous solutions. The influence of operating parameters, such as solvent-to-feed ratio,...

  16. Isolation of chavibetol from essential oil of Pimenta pseudocaryophyllus leaf by high-speed counter-current chromatography.

    PubMed

    dos Santos, Bruna C B; da Silva, Júlio César T; Guerrero, Palimécio G; Leitão, Gilda G; Barata, Lauro E S

    2009-05-08

    Counter-current chromatography (CCC) was used to isolate chavibetol from the essential oil of leaves of Pimenta pseudocaryophyllus (Gomes) Landrum. Chavibetol was obtained in high purity (98%) and mass recovery (94.4%). Methyleugenol was also isolated. The CCC biphasic solvent system used was composed of hexane:n-butanol:methanol:water (12:4:4:3, v/v/v/v).

  17. Elution-extrusion counter-current chromatography for the separation of two pairs of isomeric monoterpenes from Paeoniae Alba Radix.

    PubMed

    Chu, Chu; Zhang, Shidi; Tong, Shengqiang; Li, Xingnuo; Li, Qingyong; Yan, Jizhong

    2015-09-01

    In this work, a simple and efficient protocol for the rapid separation of two pairs of isomeric monoterpenes from Paeoniae Alba Radix was developed by combining macroporous resin and elution-extrusion counter-current chromatography. The crude extract was firstly subjected to a D101 macroporous resin column eluted with water and a series of different concentrations of ethanol. Then, effluents of 30 and 95% ethanol were collected as sample 1 and sample 2 for further counter-current chromatography purification. Finally, a pair of isomers, 96 mg of compound 1 and 48 mg of compound 2 with purities of 91.1 and 96.2%, respectively, was isolated from 200 mg of sample 1. The other pair of isomers, 14 mg of compound 3 and 8 mg of compound 4 with purities of 93.6 and 88.9%, respectively, was isolated from 48 mg of sample 2. Their purities were analyzed by high-performance liquid chromatography, and their chemical structures were identified by mass spectrometry and (1) H NMR spectroscopy. Compared to a normal counter-current chromatography separation, the separation time and solvent consumption of elution-extrusion counter-current chromatography were reduced while the resolutions were still good. The established protocol is promising for the separation of natural products with great disparity of content in herbal medicines.

  18. Synthesis of medronic acid monoesters and their purification by high-performance countercurrent chromatography or by hydroxyapatite

    PubMed Central

    Vepsäläinen, Jouko; Turhanen, Petri A

    2016-01-01

    Summary We achieved the synthesis of important medronic acid monoalkyl esters via the dealkylation of mixed trimethyl monoalkyl esters of medronic acid. Two methods were developed for the purification of medronic acid monoesters: 1) small scale (10–20 mg) purification by using hydroxyapatite and 2) large scale (tested up to 140 mg) purification by high-performance countercurrent chromatography (HPCCC). PMID:27829921

  19. Limitations and empirical extensions of the k-epsilon model as applied to turbulent confined swirling flows

    NASA Technical Reports Server (NTRS)

    Lilley, D. G.; Abujelala, M. T.

    1984-01-01

    Shortcomings and recommended corrections to the standard two-equation k-epsilon turbulence model suggested by previous investigators are presented. They are assessed regarding their applicability to turbulent swirling recirculating flow. Recent experimental data on swirling confined flows, obtained with a five-hole pitot probe and a six-orientation hot-wire probe, are used to obtain optimum values of the turbulence parameters C-mu, C2, and sigma-epsilon for swirling flows. General predictions of moderately and strongly swirling flows with these values are more accurate than predictions with the standard or previous simple extensions of the k-epsilon turbulence model.

  20. Numerical model for swirl cooling in high-heat-flux particle beam targets and the design of a swirl-flow-based plasma limiter

    NASA Astrophysics Data System (ADS)

    Milora, S. L.; Combs, S. K.; Foster, C. A.

    1984-11-01

    An unsteady, two-dimensional heat conduction code was used to study the performance of swirl-flow-based neutral particle beam targets. The model includes the effects of two-phase heat transfer and asymmetric heating of tubular elements. The calorimeter subjected to 30-s neutral beam pulses with incident heat flux intensities of greater than or equal to 5 kW/cu cm, is modeled. The numerical results indicate that local heat fluxes in excess of 7 kW/sq cm occur at the water cooled surface on the side exposed to the beam. This exceeds critical heat flux limits for uniformly heated tubes with straight flow by approximately a factor of 5. The design of a plasma limiter based on swirl flow heat transfer is presented.

  1. Determination and purification of sesamin and sesamolin in sesame seed oil unsaponified matter using reversed-phase liquid chromatography coupled with photodiode array and tandem mass spectrometry and high-speed countercurrent chromatography.

    PubMed

    Takahashi, Miki; Nishizaki, Yuzo; Sugimoto, Naoki; Takeuchi, Hiroaki; Nakagawa, Kazuya; Akiyama, Hiroshi; Sato, Kyoko; Inoue, Koichi

    2016-10-01

    In Asian countries, sesame seed oil unsaponified matter is used as a natural food additive due to its associated antioxidant effects. We determined and purified the primary lignans sesamin and sesamolin in sesame seed oil unsaponified matter using reversed-phase liquid chromatography coupled with photodiode array and tandem mass spectrometry and high-speed countercurrent chromatography. Calibration curves showed good correlation coefficients (r(2) > 0.999, range 0.08 and/or 0.15 to 5 μg/mL) with a limit of detection (at 290 nm) of 0.02 μg/mL for sesamin and 0.04 μg/mL for sesamolin. Sesame seed oil unsaponified matter contained 2.82% sesamin and 2.54% sesamolin, respectively. Direct qualitative analysis of sesamin and sesamolin was achieved using quadrupole mass spectrometry with positive-mode electrospray ionization. Pure (>99%) sesamin and sesamolin standards were obtained using high-speed countercurrent chromatographic purification (hexane/ethyl acetate/methanol/water; 7:3:7:3). An effective method for determining and purifying sesamin and sesamolin from sesame seed oil unsaponified matter was developed by combining these separation techniques for standardized food additives.

  2. Effect of pregnancy and nitric oxide on the myogenic vasodilation of posterior cerebral arteries and the lower limit of cerebral blood flow autoregulation.

    PubMed

    Chapman, Abbie C; Cipolla, Marilyn J; Chan, Siu-Lung

    2013-09-01

    Hemorrhage during parturition can lower blood pressure beyond the lower limit of cerebral blood flow (CBF) autoregulation that can cause ischemic brain injury. However, the impact of pregnancy on the lower limit of CBF autoregulation is unknown. We measured myogenic vasodilation, a major contributor of CBF autoregulation, in isolated posterior cerebral arteries (PCAs) from nonpregnant and late-pregnant rats (n = 10/group) while the effect of pregnancy on the lower limit of CBF autoregulation was studied in the posterior cerebral cortex during controlled hemorrhage (n = 8). Pregnancy enhanced myogenic vasodilation in PCA and shifted the lower limit of CBF autoregulation to lower pressures. Inhibition of nitric oxide synthase (NOS) prevented the enhanced myogenic vasodilation during pregnancy but did not affect the lower limit of CBF autoregulation. The shift in the autoregulatory curve to lower pressures during pregnancy is likely protective of ischemic injury during hemorrhage and appears to be independent of NOS.

  3. Chemical Safety Alert: Emergency Isolation for Hazardous Material Fluid Transfer Systems - Application and Limitations of Excess Flow Valves

    EPA Pesticide Factsheets

    While excess flow valves (EFV) are in extensive service and have prevented numerous pipe or hose breaks from becoming much more serious incidents, experience shows that in some cases the EFV did not perform as intended, usually because of misapplication.

  4. Limitations of Snow-Water Equivalent and Precipitation Data in Seasonal Flow Forecasting in the Upper Klamath River Basin of Oregon and California

    NASA Astrophysics Data System (ADS)

    Risley, J. C.; Roehl, E. A.

    2005-12-01

    Water managers in the upper Klamath Basin, located in south-central Oregon and northeastern California, rely on accurate forecasts of spring and summer streamflow to optimally allocate increasingly limited water supplies for various demands that include irrigation for agriculture, habitat for endangered fishes, and hydropower production. Federal agencies make forecasts on the 1st of each month, from January through May, of the total volume of water expected to pass a stream gage or flow into a reservoir during an entire summer irrigation season. Often the forecasts are based on output from flow forecast models that use real-time snow-water equivalent (SWE) and precipitation data as input. Because the January and February forecasts are significantly less accurate than those made in the spring, we were interested in quantifying the limitations of real-time SWE and precipitation data in forecasting future flows. Using over 20 years of daily SWE, precipitation, and flow time-series from five sites in the upper Klamath Basin, we first decomposed the flow records into annual periodic, long-term climatic, and chaotic traces. Being the component of the original flow records with their seasonality and long-term trends removed, the chaotic traces were then lag correlated with SWE and precipitation records. After a 120 day lag (approximately 4 months), all of the correlation coefficients between the chaotic flow traces and the SWE and precipitation records were less than 0.4. From this, we could infer that SWE and precipitation data older than 120 days provide forecast models only with information regarding the annual seasonal and long-term climate patterns and do not provide information that is unique and specific for the upcoming irrigation season. These results also support the need to find new climate variables, such as mid-oceanic indicators, to improve forecast model accuracy rather than using just real-time SWE and precipitation conditions.

  5. Separation of two major chalcones from Angelica keiskei by high-speed counter-current chromatography.

    PubMed

    Kil, Yun-Seo; Nam, Joo-Won; Lee, Jun; Seo, Eun Kyoung

    2015-08-01

    Angelica keiskei (Shin-sun cho) is an edible higher plant with the beneficial preventive effects on cancer, hypertension, and coronary heart disease. Two bioactive chalcones of Shin-sun cho, xanthoangelol (1) and 4-hydroxyderricin (2), were separated simultaneously by using high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane-EtOAc-MeOH-H2O (9:5:9:4). Only nonconsuming processes, solvent fractionations and Sephadex LH-20 column chromatography, were conducted as presteps. Xanthoangelol (1, 35.9 mg, 99.9 % purity at 254 and 365 nm) and 4-hydroxyderricin (2, 4.4 mg, 98.7 % purity at 254 nm and 98.8 % purity at 365 nm) were successfully purified from 70 mg of the processed extract from A. keiskei. The structures of two compounds were confirmed by (1)H- and (13)C-NMR analysis.

  6. Real-Time Volumetric Phase Monitoring: Advancing Chemical Analysis by Countercurrent Separation.

    PubMed

    Pauli, Guido F; Pro, Samuel M; Chadwick, Lucas R; Burdick, Thomas; Pro, Luke; Friedl, Warren; Novak, Nick; Maltby, John; Qiu, Feng; Friesen, J Brent

    2015-07-21

    Countercurrent separation (CCS) utilizes the differential partitioning behavior of analytes between two immiscible liquid phases. We introduce the first platform ("CherryOne") capable of real-time monitoring, metering, and control of the dynamic liquid-liquid CCS process. Automated phase monitoring and volumetrics are made possible with an array of sensors, including the new permittivity-based phase metering apparatus (PMA). Volumetric data for each liquid phase are converted into a dynamic real-time display of stationary phase retention (Sf) and eluent partition coefficients (K), which represent critical parameters of CCS reproducibility. When coupled with the elution-extrusion operational mode (EECCC), automated Sf and K determination empowers untargeted and targeted applications ranging from metabolomic analysis to preparative purifications.

  7. Experimental Evidence for Self-Limiting Reactive Flow through a Fractured Cement Core: Implications for Time-Dependent Wellbore Leakage

    SciTech Connect

    Huerta, Nicolas J; Hesse, Marc A; Bryant, Steven L; Strazisar, Brian R; Lopano, Christina L

    2013-01-01

    We present a set of reactive transport experiments in cement fractures. The experiments simulate coupling between flow and reaction when acidic, CO{sub 2}-rich fluids flow along a leaky wellbore. An analog dilute acid with a pH between 2.0 and 3.15 was injected at constant rate between 0.3 and 9.4 cm/s into a fractured cement core. Pressure differential across the core and effluent pH were measured to track flow path evolution, which was analyzed with electron microscopy after injection. In many experiments reaction was restricted within relatively narrow, tortuous channels along the fracture surface. The observations are consistent with coupling between flow and dissolution/precipitation. Injected acid reacts along the fracture surface to leach calcium from cement phases. Ahead of the reaction front, high pH pore fluid mixes with calcium-rich water and induces mineral precipitation. Increases in the pressure differential for most experiments indicate that precipitation can be sufficient to restrict flow. Experimental data from this study combined with published field evidence for mineral precipitation along cemented annuli suggests that leakage of CO{sub 2}-rich fluids along a wellbore may seal the leakage pathway if the initial aperture is small and residence time allows mobilization and precipitation of minerals along the fracture.

  8. Strictly hyperbolic models of co-current three-phase flow withgravity

    SciTech Connect

    Juanes, Ruben; Patzek, Tadeusz W.

    2002-11-18

    We study the character of the equations in the traditional formulation of one-dimensional immiscible three-phase flow with gravity, in the limit of negligible capillarity. We restrict our analysis to co-current flow required for a displacement process; in cases of mixed co-current and counter-current flow, capillarity effects cannot be dropped from the formulation. The model makes use of the classical multiphase extension of Darcy's equation. It is well known that, if relative permeabilities are taken as fixed functions of saturations, the model yields regions in the saturation space where the system of equations is locally elliptic. We regard elliptic behavior as a nonphysical artifact of an incomplete formulation, and derive conditions on the relative permeabilities that ensure strict hyperbolicity of the governing equations. The key point is to acknowledge that a Darcy-type formulation is insufficient to capture all the physics of three-phase flow and that, consequently, the relative permeabilities are functionals that depend on the fluid viscosity ratio and the gravity number. The derived conditions are consistent with the type of displacements that take place in porous media. By means of an illustrative example, we show how elliptic behavior can be removed, even when using simplistic relative permeability models.

  9. Isolation of aspalathin and nothofagin from rooibos (Aspalathus linearis) using high-performance countercurrent chromatography: sample loading and compound stability considerations.

    PubMed

    de Beer, Dalene; Malherbe, Christiaan J; Beelders, Theresa; Willenburg, Elize L; Brand, D Jacobus; Joubert, Elizabeth

    2015-02-13

    Aspalathin and nothofagin, the major dihydrochalcones in rooibos (Aspalathus linearis), are valuable bioactive compounds, but their bioactivity has not been fully elucidated. Isolation of these compounds using high-performance countercurrent chromatography (HPCCC), a gentle, support-free, up-scalable technique, offers an alternative to synthesis for obtaining sufficient amounts. An HPLC-DAD method was adapted to allow rapid (16 min from injection to injection) quantification of the four major compounds (aspalathin, nothofagin, isoorientin, orientin) during development of the isolation protocol. The traditional shake-flask method, used to determine distribution constants (K(D)) for target compounds, was also adapted to obtain higher repeatability. Green rooibos leaves with a high aspalathin and nothofagin content were selected as source material. Sample loading of the polyphenol-enriched extract was limited due to constituents with emulsifying properties, but could be increased by removing ethanol-insoluble matter. Furthermore, problems with degradation of aspalathin during HPCCC separation and further processing could be limited by acidifying the HPCCC solvent system. Aspalathin was shown to be fairly stable at pH 3 (91% remaining after 29 h) compared to pH 7 (45% remaining after 29 h). Aspalathin and nothofagin with high purities (99% and 100%, respectively) were obtained from HPCCC fractions after semi-preparative HPLC.

  10. Limitation of parallel flow in double diffusive convection: Two- and three-dimensional transitions in a horizontal porous domain

    SciTech Connect

    Mimouni, N.; Chikh, S.; Rahli, O.; Bennacer, R.

    2014-07-15

    Two-dimensional (2D) and three-dimensional (3D) numerical simulations of double diffusion natural convection in an elongated enclosure filled with a binary fluid saturating a porous medium are carried out in the present work. The Boussinesq approximation is made in the formulation of the problem, and Neumann boundary conditions for temperature and concentration are adopted, respectively, on vertical and horizontal walls of the cavity. The used numerical method is based on the control volume approach, with the third order quadratic upstream interpolation scheme in approximating the advection terms. A semi implicit method algorithm is used to handle the velocity-pressure coupling. To avoid the excessively high computer time inherent to the solution of 3D natural convection problems, full approximation storage with full multigrid method is used to solve the problem. A wide range of the controlling parameters (Rayleigh-Darcy number Ra, lateral aspect ratio Ay, Lewis number Le, and the buoyancy ration N) is investigated. We clearly show that increasing the depth of the cavity (i.e., the lateral aspect ratio) has an important effect on the flow patterns. The 2D perfect parallel flows obtained for small lateral aspect ratio are drastically destabilized by increasing the cavity lateral dimension. This yields a 3D fluid motion with a much more complex flow pattern and the usually considered 2D parallel flow model cannot be applied.

  11. Test Problems for Reactive Flow HE Model in the ALE3D Code and Limited Sensitivity Study

    SciTech Connect

    Gerassimenko, M.

    2000-03-01

    We document quick running test problems for a reactive flow model of HE initiation incorporated into ALE3D. A quarter percent change in projectile velocity changes the outcome from detonation to HE burn that dies down. We study the sensitivity of calculated HE behavior to several parameters of practical interest where modeling HE initiation with ALE3D.

  12. Fluid Dynamics of Contrast Dispersion in Coronary Arteries: Mechanism and Implications for Identification of Flow-Limiting Lesions

    NASA Astrophysics Data System (ADS)

    Eslami, Parastou; Seo, Jung-Hee; Lardo, Albert C.; Mittal, Rajat

    2013-11-01

    Recent coronary computed tomography angiography studies have noted the presence of axial contrast concentration gradients in stenosed coronary arteries, but the mechanism responsible for this phenomenon is not well understood. We use computational fluid dynamics to study intracoronary contrast dispersion and the correlation of concentration gradients with intracoronary blood flow and stenotic severity. Simulations of flow and contrast dispersion in both canonical and patient derived models of the left coronary artery (LCA) are carried out with a prescribed contrast bolus profile, and stenoses of varying severities (0% to 80%) considered. Data from our CFD simulations show the presence of measurable contrast gradients, the magnitude of which is found to decrease monotonically with stenotic severity and increase monotonically with the pressure drop across the stenosis. All simulated cases indicate a strong inverse correlation between contrast gradients and coronary flow rate. The study reveals that contrast gradients are generated by intracoronary advection effects, and therefore, encode coronary flow velocity. This research is supported by a grant from Coulter Foundation.

  13. Age-Associated Induction of Cell Membrane CD47 Limits Basal and Temperature-Induced Changes in Cutaneous Blood Flow

    PubMed Central

    Rogers, Natasha M.; Roberts, David D.; Isenberg, Jeffrey S.

    2012-01-01

    Objective We tested the hypothesis that the matricellular protein thrombospondin-1 (TSP1), through binding to and activation of the cell receptor CD47, inhibits basal and thermal-mediated cutaneous blood flow. Background Data Abnormal and decreased cutaneous blood flow in response to temperature changes or vasoactive agents is a feature of cardiovascular disease and aging. The reasons for decreased cutaneous blood flow remain incompletely understood. Further, a role for matricellular proteins in the regulation skin blood flow has never been proposed. Methods C57BL/6 wild type, TSP1- and CD47-null 12 and 72 week old male mice underwent analysis of skin blood flow (SkBF) via laser Doppler in response to thermal stress and vasoactive challenge. Results Young and aged TSP1- and CD47-null mice displayed enhanced basal and thermal sensitive SkFB changes compared to age matched wild type controls. Nitric oxide-mediated increases in SkBF were also greater in null mice. TSP1 and CD47 were expressed in skin from young wild type mice, and both were significantly upregulated in aged animals. Tissue 3',5'-cyclic guanosine monophosphate (cGMP), a potent vasodilator, was greater in skin samples from null mice compared to wild type regardless of age. Finally, treating wild type animals with a CD47 monoclonal antibody, that inhibits TSP1 activation of CD47, enhanced SkBF in both young and aged animals. Conclusions The above results suggest that secreted TSP1, via its cognate receptor CD47, acutely modulates SkBF. These data further support therapeutically targeting CD47 to mitigate age-associated loss of SkBF and maximize wound healing. PMID:23275312

  14. High-speed counter-current chromatography in separation of betacyanins from flowers of red Gomphrena globosa L. cultivars.

    PubMed

    Spórna-Kucab, Aneta; Hołda, Ewelina; Wybraniec, Sławomir

    2016-10-15

    Antioxidant and possible chemopreventive properties of betacyanins, natural plant pigments, contribute to a growing interest in their chemistry and separation. Mixtures of betacyanins from fresh red Gomphrena globosa L. cultivar flowers were separated in three highly polar solvent systems by high-speed counter-current chromatography (HSCCC) for a direct comparison of their separation effectiveness. Three samples of crude extract (600mg) were run on semi-preparative scale in solvent system (NH4)2SO4soln - EtOH (2.0:1.0, v/v) (system I) and the modified systems: EtOH - ACN - 1-PrOH - (NH4)2SO4satd.soln - H2O (0.5:0.5:0.5:1.2:1.0, v/v/v/v/v) (system II) and EtOH - ACN - (NH4)2SO4satd.soln - H2O (1.0:0.5:1.2:1.0, v/v/v/v) (system III). The systems were used in the head-to-tail (system I) or tail-to-head (systems II and III) mode. The flow rate of the mobile phase was 2.0ml/min and the column rotation speed was 860rpm. The retention of the stationary phase was 52.0% (system I), 80.2% (systems II) and 82.0% (system III). The betacyanins in the crude extract as well as HSCCC fractions were analyzed by LC-MS/MS. System I was applied for the first time in HSCCC for the separation of betacyanins and was quite effective in separation of amaranthine and 17-decarboxy-amaranthine (αI=1.19) and very effective for 17-decarboxy-amaranthine and betanin (αI=2.20). Modification of system I with acetonitrile (system III) as well as acetonitrile and propanol (system II) increased their separation effectiveness. Systems II-III enable complete separation of 17-decarboxy-amaranthine (KD(II)=2.94,KD(III)=2.42) and betanin (KD(II)=2.46,KD(III)=1.10) as well as betanin and gomphrenin I (KD(II)=1.62, KD(III)=0.74). In addition, separation of amaranthine and 17-decarboxy-amaranthine is the most effective in system II, therefore, this system proved to be the most suitable for the separation of all polar betacyanins.

  15. Separation of polyphenols and caffeine from the acetone extract of fermented tea leaves (Camellia sinensis) using high-performance countercurrent chromatography.

    PubMed

    Choi, Soo Jung; Hong, Yong Deog; Lee, Bumjin; Park, Jun Seong; Jeong, Hyun Woo; Kim, Wan Gi; Shin, Song Seok; Yoon, Kee Dong

    2015-07-21

    Leaves from Camellia sienensis are a popular natural source of various beverage worldwide, and contain caffeine and polyphenols derived from catechin analogues. In the current study, caffeine (CAF, 1) and three tea polyphenols including (-)-epigallocatechin 3-O-gallate (EGCg, 2), (-)-gallocatechin 3-O-gallate (GCg, 3), and (-)-epicatechin 3-O-gallate (ECg, 4) were isolated and purified by flow-rate gradient high-performance countercurrent chromatography (HPCCC) using a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:9:1:9, v/v). Two hundred milligrams of acetone-soluble extract from fermented C. sinensis leaves was separated by HPCCC to give 1 (25.4 mg), 2 (16.3 mg), 3 (11.1 mg) and 4 (4.4 mg) with purities over 98%. The structures of 1-4 were elucidated by QTOF-MS, as well as 1H- and 13C-NMR, and the obtained data were compared to the previously reported values.

  16. Predictable and linear scale-up of four phenolic alkaloids separation from the roots of Menispermum dauricum using high-performance counter-current chromatography.

    PubMed

    Luo, Houding; Peng, Ming; Ye, Haoyu; Chen, Lijuan; Peng, Aihua; Tang, Minghai; Zhang, Fan; Shi, Jie

    2010-07-15

    This paper describes how distribution ratios were used for prediction of peak elution in analytical high-performance counter-current chromatography (HPCCC) to explore the method for separation and purification of bioactive compounds from the roots of Menispermum dauricum. Then important parameters related to HPCCC separations including solvent systems, sample concentration, sample loading volume and flow rate were optimized on an analytical Mini-DE HPCCC and finally linearly scaled up to a preparative Midi-DE HPCCC with nearly the same resolutions and separation time. Four phenolic alkaloids were for the first time obtained by HPCCC separation with a two-phase solvent system composed of petroleum ether-ethyl acetate-ethanol-water (1:2:1:2, v/v). This process produced 131.3 mg daurisolin, 197.1 mg dauricine, 32.4 mg daurinoline and 14.7 mg dauricicoline with the purity of 97.6%, 96.4%, 97.2% and 98.3%, respectively from 500 mg crude extract of the roots of M. dauricum in a one-step separation. The purities of compounds were determined by high-performance liquid chromatography (HPLC). Their structures were identified by electrospray ionization mass spectrometer (ESI-MS) and nuclear magnetic resonance (NMR).

  17. [Isolation and preparation of an imidazole alkaloid from radix radix of Aconitum pendulum Busch by semi-preparative high-speed counter-current chromatography].

    PubMed

    Liu, Yongling; Chen, Tao; Chen, Chen; Zou, Denglang; Li, Yulin

    2014-05-01

    Aconitum pendulum Busch is rich C19 diterpenoid alkaloids, but there is no report of imidazole alkaloid in Aconitum pendulum Busch. In this study, an imidazole alkaloid named 1H-imidazole-2-carboxylic acid, butyl ester (ICABE) was successfully separated from Aconitum pendulum Busch with semi-preparative high-speed counter-current chromatography (HSCCC). The partition coefficient was measured by HPLC to select the solvent systems for ICABE separation by HSCCC. The separation was performed with a two-phase solvent system composed of n-hexane-chloroform-ethanol-water (10:1 : 13:2, v/v/v/v). The upper phase was used as the stationary phase and the lower phase as the mobile phase. It was operated at a flow rate of 1.8 mL/min. The apparatus was rotated at 850 r/min, and the detection wavelength was set at 230 nm. Under the selected conditions, a high efficiency separation of HSCCC was achieved, and 7.5 mg of ICABE was obtained from 100 mg of the crude sample of Aconitum pendulum in one-step separation within 350 min. The HPLC analysis showed that the purity of the compound was over 98%. The chemical structure was confirmed by UV, 1H-NMR and 13C-NMR. The established method is simple, highly efficient and suitable for large scale separation of ICABE from radix of Aconitum pendulum Busch.

  18. PREPARATIVE ISOLATION AND PURIFICATION OF THREE GLYCINE-CONJUGATED CHOLIC ACIDS FROM PULVIS FELLIS SUIS BY HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY COUPLED WITH ELSD DETECTION

    PubMed Central

    He, Jiao; Li, Jing; Sun, Wenji; Zhang, Tianyou; Ito, Yoichiro

    2011-01-01

    Coupled with evaporative light scattering detection, a high-speed counter-current chromatography (HSCCC) method was developed for preparative isolation and purification of three glycine-conjugated cholic acids, glycochenodeoxycholic acid (GCDCA), glycohyodeoxycholic acid (GHDCA) and glycohyocholic acid (GHCA) from Pulvis Fellis Suis (Pig gallbladder bile) for the first time. The separation was performed with a two-phase solvent system consisted of chloroform-methanol-water-acetic acid (65:30:10:1.5, v/v/v/v) by eluting the lower phase in the head-to-tail elution mode. The revolution speed of the separation column, flow rate of the mobile phase and separation temperature were 800 rpm, 2 ml/min and 25 °C, respectively. In a single operation, 33 mg of GCDCA, 38 mg of GHDCA and 23 mg of GHCA were obtained from 200 mg of crude extract with the purity of 95.65%, 96.72% and 96.63%, respectively, in one step separation. The HSCCC fractions were analyzed by high-performance liquid chromatography (HPLC) and the structures of the three glycine-conjugated cholic acids were identified by ESI-MS, 1H NMR and 13C NMR. PMID:23008527

  19. [Isolation and purification of solanesol from potato leaves by high-speed counter-current chromatography and identification by atmospheric pressure chemical ionization mass spectrometry].

    PubMed

    Hu, Jiangyong; Liang, Yong; Xie, Ya; Huang, Zhaofeng; Zhong, Hanzuo

    2007-07-01

    Preparative high-speed counter-current chromatography (HSCCC) was used for the isolation and purification of solanesol from potato leaves. Experimental conditions of the extraction of solanesol from potato leaves have been optimized. An ultrafine extraction method was applied in this study. The efficiency using an ultrafine extraction was found to be improved in the investigation, the yields of solanesol by different extraction methods were 0.083% by ultrafine extraction and 0.050% by ultrasonic extraction. Using n-hexane-methanol (10:7, v/v) as the two-phase solvent system, preparative HSCCC was successfully performed with the yield of 5 mg solanesol at 98.7% of purity from 60 mg of crude extract in the one-step separation. The mobile phase was the lower phase and operated at a flow rate of 1.5 mL/min, while the apparatus rotated at 800 r/min. The solanesol was identified by the atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The ionization and cleavage mechanisms of solanesol in APCI-MS and APCI-MS/MS are discussed.

  20. Online polar two phase countercurrent chromatography×high performance liquid chromatography for preparative isolation of polar polyphenols from tea extract in a single step.

    PubMed

    Chen, Wei-Bin; Li, Shu-Qi; Chen, Long-Jiang; Fang, Mei-Juan; Chen, Quan-Cheng; Wu, Zhen; Wu, Yun-Long; Qiu, Ying-Kun

    2015-08-01

    Herein, we report an on-line two-dimensional system constructed by counter-current chromatography (CCC) coupling with preparative high-performance liquid chromatography (prep-HPLC) for the separation and purification of polar natural products. The CCC was used as the first dimensional isolation column, where an environmental friendly polar two-phase solvent system of isopropanol and 16% sodium chloride aqueous solution (1:1.2, v/v) was introduced for low toxicity and favorable resolution. In addition, by applying the stop-and-go flow technique, effluents pre-fractionated by CCC was further purified by a preparative column packed with octadecyl silane (ODS) as the second dimension. The interface between the two dimensions was comprised of a 6-port switching valve and an electronically controlled 2-position 10-port switching valve connected with two equivalent holding columns. To be highlighted here, this rationally designed interface for the purpose of smooth desalination, absorption and desorption, successfully solved the solvent compatibility problem between the two dimensional separation systems. The present integrated system was successfully applied in a one-step preparative separation and identification of 10 pure compounds from the water extracts of Tieguanyin tea (Chinese oolong tea). In short, all the results demonstrated that the on-line 2D CCC×LC method is an efficient and green approach for harvesting polar targets in a single step, which showed great promise in drug discovery.

  1. Scale-up protein separation on stainless steel wide bore toroidal columns in the type-J counter-current chromatography.

    PubMed

    Guan, Yue Hugh; Hewitson, Peter; van den Heuvel, Remco N A M; Zhao, Yan; Siebers, Rick P G; Zhuang, Ying-Ping; Sutherland, Ian

    2015-12-11

    Manufacturing high-value added biotech biopharmaceutical products (e.g. therapeutic proteins) requires quick-to-develop, GMP-compliant, easy-to-scale and cost effective preparatory chromatography technologies. In this work, we describe the construction and testing of a set of 5-mm inner diameter stainless steel toroidal columns for use on commercially available preparatory scale synchronous J-type counter-current chromatography (CCC) machinery. We used a 20.2m long column with an aqueous two-phase system containing 14% (w/w) PEG1000 and 14% (w/w) potassium phosphate at pH 7, and tested a sample loading of 5% column volume and a mobile phase flow rate of 20ml/min. We then satisfactorily demonstrated the potential for a weekly protein separation and preparation throughput of ca. 11g based on a normal weekly routine for separating a pair of model proteins by making five stacked injections on a single portion of stationary phase with no stripping. Compared to our previous 1.6mm bore PTFE toroidal column, the present columns enlarged the nominal column processing throughput by nearly 10. For an ideal model protein injection modality, we observed a scaling up factor of at least 21. The 2 scales of protein separation and purification steps were realized on the same commercial CCC device.

  2. The contribution of nasal countercurrent heat exchange to water balance in the northern elephant seal, Mirounga angustirostris.

    PubMed

    Huntley, A C; Costa, D P; Rubin, R D

    1984-11-01

    Elephant seals fast completely from food and water for 1-3 months during terrestrial breeding. Temporal countercurrent heat exchange in the nasal passage reduces expired air temperature (Te) below body temperature (Tb). At a mean ambient temperature of 13.7 degrees C, Te is 20.9 degrees C. This results in the recovery of 71.5% of the water added to inspired air. The amount of cooling of the expired air (Tb - Te) and the percentage of water recovery varies inversely with ambient temperature. Total nasal surface area available for heat and water exchange, located in the highly convoluted nasal turbinates, is estimated to be 720 cm2 in weaned pups and 3140 cm2 in an adult male. Nasal temporal countercurrent heat exchange reduces total water loss sufficiently to allow maintenance of water balance using metabolic water production alone.

  3. Separation of epimeric aromatic acid (-)-menthol esters by countercurrent chromatography using hydroxypropyl-β-cyclodextrin as an additive.

    PubMed

    Wang, Xiaoping; Lv, Liqiong; Bu, Zhisi; Yan, Jizhong; Tong, Shengqiang

    2017-02-28

    The separation of ten epimeric aromatic acid (-)-menthol esters by countercurrent chromatography with hydroxypropyl-β-cyclodextrin as the mobile phase additive was investigated, and methods for the analysis of all the epimeric esters by reversed-phase high-performance liquid chromatography were established. A biphasic solvent system composed of n-hexane/20-70% methanol containing 50 mmol/L of hydroxypropyl-β-cyclodextrin (1:1, v/v) was selected, which provided high separation factors for five of the epimeric esters, and successful separations by countercurrent chromatography were achieved. The complete separation of five pairs of epimeric ester was obtained with the purity being over 98% for each peak fractions, as determined by high-performance liquid chromatography. The recovery of each analyte from the eluted fractions reached around 80-88%.

  4. Benefits and limitations of using the weather radar for the definition of rainfall thresholds for debris flows. Case study from Catalonia (Spain).

    NASA Astrophysics Data System (ADS)

    Abancó, C.; Hürlimann, M.; Sempere, D.; Berenguer, M.

    2012-04-01

    Torrential processes such as debris flows or hyperconcentrated flows are fast movements formed by a mix of water and different amounts of unsorted solid material. They occur in steep torrents and suppose a high risk for the human settlements. Rainfall is the most common triggering factor for debris flows. The rainfall threshold defines the rainfall conditions that, when reached or exceeded, are likely to provoke one or more events. Many different types of empirical rainfall thresholds for landslide triggering have been defined. Direct measurements of rainfall data are normally not available from a point next to or in the surroundings of the initiation area of the landslide. For this reason, most of the thresholds published for debris flows have been established by data measured at the nearest rain gauges (often located several km far from the landslide). Only in very few cases, the rainfall data to analyse the triggering conditions of the debris flows have been obtained by weather (Doppler) radar. Radar devices present certain limitations in mountainous regions due to undesired reboots, but their main advantage is that radar data can be obtained for any point of the territory. The objective of this work was to test the use of the weather radar data for the definition of rainfall thresholds for debris-flow triggering. Thus, rainfall data obtained from 3 to 5 rain gauges and from radar were compared for a dataset of events occurred in Catalonia (Spain). The goal was to determine in which cases the description of the rainfall episode (in particular the maximum intensity) had been more accurate. The analysed dataset consists of: 1) three events occurred in the Rebaixader debris-flow monitoring station (Axial Pyrenees) including two hyperconcentrated flows and one debris flow; 2) one debris-flow event occurred in the Port Ainé ski resort (Axial Pyrenees); 3) one debris-flow event in Montserrat (Mediterranean Coastal range). The comparison of the hyetographs from the

  5. Review of computational fluid dynamics in the assessment of nasal air flow and analysis of its limitations.

    PubMed

    Quadrio, Maurizio; Pipolo, Carlotta; Corti, Stefano; Lenzi, Riccardo; Messina, Francesco; Pesci, Chiara; Felisati, Giovanni

    2014-09-01

    Nasal breathing difficulties (NBD) are a widespread medical condition, yet decisions pertaining to the surgical treatment of chronic NBD still imply a significant degree of subjective judgement of the surgeon. The current standard objective examinations for nasal flow, e.g., rhinomanometry and acoustic rhinomanometry, do not suffice to reliably direct the surgeon on the extent of any necessary surgery. In the last two decades, several groups have therefore considered the numerical simulation of nasal airflow. Currently, these analyses take many hours of labor from the operator, and require a huge amount of computer time and the use of expensive commercial software. Most often, their results are insufficiently validated so that virtual surgery, which is the eventual application, is still absent in clinical practice. Very recently, however, attempts at considering the finest details of the flow are beginning to appear, for example unsteady turbulent simulations validated through laboratory measurements through particle image velocimetry. In this paper, we first discuss recent developments in how computational fluid dynamics (CFD) is helping surgeons improve their understanding of nasal physiology and the effect of surgical modifications on the airflow in the nasal cavity. In a second part, the procedural and modeling challenges that still prevent CFD from being routinely used in clinical practice are surveyed and critically discussed.

  6. Solvent systems with n-hexane and/or cyclohexane in countercurrent chromatography--Physico-chemical parameters and their impact on the separation of alkyl hydroxybenzoates.

    PubMed

    Englert, Michael; Vetter, Walter

    2014-05-16

    Countercurrent chromatography (CCC) is an efficient preparative separation technique based on the liquid-liquid distribution of compounds between two phases of a biphasic liquid system. The crucial parameter for the successful application is the selection of the solvent system. Especially for nonpolar analytes the selection options are limited. On the search for a suitable solvent system for the separation of an alkyl hydroxybenzoate homologous series, we noted that the substitution of cyclohexane with n-hexane was accompanied with unexpected differences in partitioning coefficients of the individual analytes. In this study, we investigated the influence of the subsequent substitution of n-hexane with cyclohexane in the n-hexane/cyclohexane/tert-butylmethylether/methanol/water solvent system family. Exact phase compositions and polarity, viscosity and density differences were determined to characterize the different mixtures containing n-hexane and/or cyclohexane. Findings were confirmed by performing CCC separations with different mixtures, which led to baseline resolution for positional isomers when increasing the amount of cyclohexane while the resolution between two pairs of structural isomers decreased. With the new methodology described, structurally similar compounds could be resolved by choosing a certain ratio of n-hexane to cyclohexane.

  7. At-line hyphenation of high-speed countercurrent chromatography with Sephadex LH-20 column chromatography for bioassay-guided separation of antioxidants from vine tea (Ampelopsis grossedentata).

    PubMed

    Ma, Ruyi; Zhou, Rongrong; Tong, Runna; Shi, Shuyun; Chen, Xiaoqing

    2017-01-01

    Vine tea (Ampelopsis grossedentata), a widely used healthy tea, beverage and herbal medicine, exhibited strong antioxidant activity. However, systematic purification of antioxidants, especially for those with similar structures or polarities, is a challenging work. Here, we present a novel at-line hyphenation of high-speed countercurrent chromatography with Sephadex LH-20 column chromatography (HSCCC-Sephadex LH-20 CC) for rapid and efficient separation of antioxidants from vine tea target-guided by 1,1-diphenyl-2-picryl-hydrazyl radical-high performance liquid chromatography (DPPH-HPLC) experiment. A makeup pump, a six-port switching valve and a trapping column were served as interface. The configuration had no operational time and mobile phase limitations between two dimensional chromatography and showed great flexibility without tedious sample-handling procedure. Seven targeted antioxidants were firstly separated by stepwise HSCCC using petroleum ether-ethyl acetate-methanol-water (4:9:4:9, v/v/v/v) and (4:9:5:8, v/v/v/v) as solvent systems, and then co-eluted antioxidants were on-line trapped, concentrated and desorbed to Sephadex LH-20 column for further off-line purification by methanol. It is noted that six elucidated antioxidants with purity over 95% exhibited stronger activity than ascorbic acid (VC). More importantly, this at-line hyphenated strategy could sever as a rapid and efficient pathway for systematic purification of bioactive components from complex matrix.

  8. Effectiveness of flow inflating device in providing Continuous Positive Airway Pressure for critically ill children in limited-resource settings: A prospective observational study

    PubMed Central

    Anitha, G. Fatima Shirly; Velmurugan, Lakshmi; Sangareddi, Shanthi; Nedunchelian, Krishnamurthy; Selvaraj, Vinoth

    2016-01-01

    Background and Aims: Noninvasive ventilation (NIV) is an emerging popular concept, which includes bi-level positive airway pressure or continuous positive airway pressure (CPAP). In settings with scarce resources for NIV machines, CPAP can be provided through various indigenous means and one such mode is flow inflating device - Jackson-Rees circuit (JR)/Bain circuit. The study analyses the epidemiology, various clinical indications, predictors of CPAP failure, and stresses the usefulness of flow inflating device as an indigenous way of providing CPAP. Methods: A prospective observational study was undertaken in the critical care unit of a Government Tertiary Care Hospital, from November 2013 to September 2014. All children who required CPAP in the age group 1 month to 12 years of both sexes were included in this study. They were started on indigenous CPAP through flow inflating device on clinical grounds based on the pediatric assessment triangle, and the duration and outcome were analyzed. Results: This study population included 214 children. CPAP through flow inflating device was successful in 89.7% of cases, of which bronchiolitis accounted for 98.3%. A prolonged duration of CPAP support of >96 h was required in pneumonia. CPAP failure was noted in 10.3% of cases, the major risk factors being children <1 year and pneumonia with septic shock. Conclusion: We conclude that flow inflating devices - JR/Bain circuit are effective as an indigenous CPAP in limited resource settings. Despite its benefits, CPAP is not a substitute for invasive ventilation, as when the need for intubation arises timely intervention is needed. PMID:27630454

  9. Sanitary landfill local-scale flow and transport modeling in support of alternative concentrations limit demonstrations, Savannah River Site

    SciTech Connect

    Kelly, V.A.; Beach, J.A.; Statham, W.H.; Pickens, J.F.

    1993-02-19

    The Savannah River Site (SRS) is a Department of Energy (DOE) facility located near Aiken, South Carolina which is currently operated and managed by Westinghouse Savannah River Company (WSRC). The Sanitary Landfill (Sanitary Landfill) at the SRS is located approximately 2,000 feet Northwest of Upper Three Runs Creek (UTRC) on an approximately 70 acre site located south of Road C between the SRS B-Area and UTRC. The Sanitary Landfill has been receiving wastes since 1974 and operates as an unlined trench and fill operation. The original landfill site was 32 acres. This area reached its capacity around 1987 and a Northern Expansion of 16 acres and a Southern Expansion of 22 acres were added in 1987. The Northern Expansion has not been used for waste disposal to date and the Southern Expansion is expected to reach capacity in 1992 or 1993. The waste received at the Sanitary Landfill is predominantly paper, plastics, rubber, wood, metal, cardboard, rags saturated with degreasing solvents, pesticide bags, empty cans, and asbestos in bags. The landfill is not supposed to receive any radioactive wastes. However, tritium has been detected in the groundwater at the site. Gross alpha and gross beta are also evaluated at the landfill. The objectives of this modeling study are twofold: (1) to create a local scale Sanitary Landfill flow model to study hydraulic effects resulting from capping the Sanitary Landfill; and (2) to create a Sanitary Landfill local scale transport model to support ACL Demonstrations for a RCRA Part B Permit Renewal.

  10. Rising of a single Taylor drop in a stagnant liquid—2D laminar flow and axisymmetry limits

    NASA Astrophysics Data System (ADS)

    Direito, F. J. N.; Campos, J. B. L. M.; Miranda, J. M.

    2016-05-01

    A numerical (computational fluid dynamics (CFD)) study concerning the rise of individual liquid Taylor drops through vertical columns of stagnant heavier liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier liquid was within the range 0.01-40 and Eötvös number was between 8 and 30. Morton number was within the interval of 2.32 × 10-6-100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.

  11. Continuous counter-current chromatography for capture and polishing steps in biopharmaceutical production.

    PubMed

    Steinebach, Fabian; Müller-Späth, Thomas; Morbidelli, Massimo

    2016-09-01

    The economic advantages of continuous processing of biopharmaceuticals, which include smaller equipment and faster, efficient processes, have increased interest in this technology over the past decade. Continuous processes can also improve quality assurance and enable greater controllability, consistent with the quality initiatives of the FDA. Here, we discuss different continuous multi-column chromatography processes. Differences in the capture and polishing steps result in two different types of continuous processes that employ counter-current column movement. Continuous-capture processes are associated with increased productivity per cycle and decreased buffer consumption, whereas the typical purity-yield trade-off of classical batch chromatography can be surmounted by continuous processes for polishing applications. In the context of continuous manufacturing, different but complementary chromatographic columns or devices are typically combined to improve overall process performance and avoid unnecessary product storage. In the following, these various processes, their performances compared with batch processing and resulting product quality are discussed based on a review of the literature. Based on various examples of applications, primarily monoclonal antibody production processes, conclusions are drawn about the future of these continuous-manufacturing technologies.

  12. Concentrical coils counter-current chromatography for natural products isolation: Salvia miltiorrhiza Bunge as example.

    PubMed

    Zhang, Lihong; Wang, Yanyan; Guo, Xiuyun; Wu, Shihua

    2017-02-22

    Countercurrent chromatography (CCC) is an efficient separation technique without the solid support matrix, largely depending on the partition of two-immiscible liquid phases in the separation column. Since the helical coil planet centrifuge was invented in early 1970s by Yoichiro Ito, a series of coils columns, including spiral coils and conical coils columns have been developed for CCC separation. In this work, we introduced a new simple and efficient concentrical coils column for CCC separation, which was prepared by winding the whole polytetrafluoroethylene (PTFE) tube into the circular grooves from the rotation axis in the same direction. Once the PTFE tube filled in all space of one round of the circular groove, it was jumped into the nearby outer circular groove through the gap and until the whole groove was filled. The three same concentrical coils distributed on three disc-shaped holders were connected by the same PTFE tube to form concentrical coils separation column. The separation capacity was further investigated using ten tanshinones of the extracts of a Traditional Chinese Medicine Salvia miltiorrhiza Bunge as a model natural product. All results indicated that the concentrical coils column could hold satisfactory retention of the stationary phase, higher theoretical plate number and better resolution for CCC separation of more than ten tanshinones. It may be an alternative CCC column for non-targeted and targeted isolation of bioactive natural products.

  13. Topsy-turvy: Turning the counter-current heat exchange of leatherback turtles upside down

    USGS Publications Warehouse

    Davenport, John; Jones, T. Todd; Work, Thierry M.; Balazs, George H.

    2015-01-01

    Counter-current heat exchangers associated with appendages of endotherms feature bundles of closely applied arteriovenous vessels. The accepted paradigm is that heat from warm arterial blood travelling into the appendage crosses into cool venous blood returning to the body. High core temperature is maintained, but the appendage functions at low temperature. Leatherback turtles have elevated core temperatures in cold seawater and arteriovenous plexuses at the roots of all four limbs. We demonstrate that plexuses of the hindlimbs are situated wholly within the hip musculature, and that, at the distal ends of the plexuses, most blood vessels supply or drain the hip muscles, with little distal vascular supply to, or drainage from the limb blades. Venous blood entering a plexus will therefore be drained from active locomotory muscles that are overlaid by thick blubber when the adults are foraging in cold temperate waters. Plexuses maintain high limb muscle temperature and avoid excessive loss of heat to the core, the reverse of the accepted paradigm. Plexuses protect the core from overheating generated by muscular thermogenesis during nesting.

  14. Countercurrent extraction of soluble sugars from almond hulls and assessment of the bioenergy potential.

    PubMed

    Holtman, Kevin M; Offeman, Richard D; Franqui-Villanueva, Diana; Bayati, Andre K; Orts, William J

    2015-03-11

    Almond hulls contain considerable proportions (37% by dry weight) of water-soluble, fermentable sugars (sucrose, glucose, and fructose), which can be extracted for industrial purposes. The maximum optimal solids loading was determined to be 20% for sugar extraction, and the addition of 0.5% (w/v) pectinase aided in maintaining a sufficient free water volume for sugar recovery. A laboratory countercurrent extraction experiment utilizing a 1 h steep followed by three extraction (wash) stages produced a high-concentration (131 g/L fermentable sugar) syrup. Overall, sugar recovery efficiency was 88%. The inner stage washing efficiencies were compatible with solution equilibrium calculations, indicating that efficiency was high. The concentrated sugar syrup was fermented to ethanol at high efficiency (86% conversion), and ethanol concentrations in the broth were 7.4% (v/v). Thin stillage contained 233 g SCOD/L, which was converted to biomethane at an efficiency of 90% with a biomethane potential of 297 mL/g SCODdestroyed. Overall, results suggested that a minima of 49 gal (185 L) ethanol and 75 m(3) methane/t hulls (dry whole hull basis) are achievable.

  15. Powerful leverages and counter-currents in the unborn child spiritual care: a qualitative study.

    PubMed

    Heidari, Tooba; Ziaei, Saeideh; Ahmadi, Fazlollah; Mohammadi, Eesa

    2014-08-22

    In different cultures, pregnancy, birth and motherhood are perceived as spiritual events through their miraculous processes and create an ideal context for spiritual enrichment. However, studies on spirituality and birth are at very early stages. The purpose of this study was to understand the facilitators and barriers of the unborn child spiritual care in Iranian women. Twenty-two mothers with live pregnancy experience who were willing and able to share their life stories were selected purposefully in Tehran (Iran) from May 2012 to April 2013. Qualitative content analysis was used to analyze 27 interviews. Active and passive acquisition of information, inner inspirational messages, receiving effective support from the people around as well as modeling of self and significant others created "powerful leverages" to accelerate mother for caring her unborn child. "Counter-currents" in the form of unsuitable physical conditions during pregnancy, poor economic and social conditions, unsuitable psychological and cognitive conditions and finally understanding unsuitable ideological conditions of the self and care giver were identified as barriers. Iranian cultural and religious perspective on the unborn child physical and mental influence from mother has an important role in mother's self-care behaviors during pregnancy. It seems that using interdisciplinary professionals' skills based on understanding facilitators and barriers of mother care of the unborn child can lead to providing comprehensive prenatal care according to mothers' cultural, religious and social context.

  16. Pulsed counter-current ultrasound-assisted extraction and characterization of polysaccharides from Boletus edulis.

    PubMed

    You, Qinghong; Yin, Xiulian; Ji, Chaowen

    2014-01-30

    Four methods for extracting polysaccharides from Boletus edulis, namely, hot-water extraction, ultrasonic clearer extraction, static probe ultrasonic extraction, and pulsed counter-current probe ultrasonic extraction (CCPUE), were studied. Results showed that CCPUE has the highest extraction efficiency among the methods studied. Under optimal CCPUE conditions, a B. edulis polysaccharide (BEP) yield of 8.21% was obtained. Three purified fractions, BEP-I, BEP-II, and BEP-III, were obtained through sequential purification by DEAE-52 and Sephadex G-75 chromatography. The average molecular weights of BEP-I, BEP-II, and BEP-III were 10,278, 23,761, and 42,736 Da, respectively. The polysaccharides were mainly composed of xylose, mannose, galactose, and glucose; of these, mannose contents were the highest. The antioxidant activities of the BEPs were further investigated by measurement of their ability to scavenge DPPH and hydroxyl radicals as well as their reducing power. The results indicated that the BEPs have good antioxidant activity.

  17. Preparative separation of five flavones from flowers of Polygonum cuspidatum by high-speed countercurrent chromatography.

    PubMed

    Sun, Yinshi; Gu, Shubo; Guo, Linlin; Xia, Xue; Zhang, Hong; Wang, Jianhua

    2014-07-01

    A preparative high-speed countercurrent chromatography method was successfully used for the isolation of five minor flavones from Polygonum cuspidatum flowers. Among them, three compounds were obtained from P. cuspidatum for the first time. A twin two-phase solvent system composed of n-hexane/ethyl acetate/ethanol/water (1:6:3:6, v/v/v/v) and petroleum ether/ethyl acetate/methanol/water (2:4:3:3, v/v/v/v) was developed. Compounds were obtained from the fraction B and fraction C prepurified by silica gel column chromatography. Five minor compositions, 6.8 mg of hesperidin, 11.2 mg of phloridzin, 4.9 mg of luteolin, 5.3 mg of hyperin, and 3.7 mg of luteoloside were obtained from 140 mg of the fraction B and 110 mg of fraction C with a purity of 95.3, 96.4, 98.0, 96.8, and 95.3%, respectively, as determined by high-performance liquid chromatography. The structures of these compounds were identified by (1) H and (13) C NMR spectroscopy.

  18. Purification of Active Myrosinase from Plants by Aqueous Two-Phase Counter-Current Chromatography

    PubMed Central

    Wade, Kristina L.; Ito, Yoichiro; Ramarathnam, Aarthi; Holtzclaw, W. David; Fahey, Jed W.

    2014-01-01

    Introduction Myrosinase (thioglucoside glucohydrolase; E.C. 3.2.1.147), is a plant enzyme of increasing interest and importance to the biomedical community. Myrosinase catalyses the formation of isothiocyanates such as sulforaphane (frombroccoli) and 4-(α-l-rhamnopyranosyloxy)benzyl isothiocyanate (from moringa), which are potent inducers of the cytoprotective phase-2 response in humans, by hydrolysis of their abundant glucosinolate (β-thioglucoside N-hydroxysulphate) precursors. Objective To develop an aqueous two-phase counter-current chromatography (CCC) system for the rapid, three-step purification of catalytically active myrosinase. Methods A high-concentration potassium phosphate and polyethylene glycol biphasic aqueous two-phase system (ATPS) is used with a newly developed CCC configuration that utilises spiral-wound, flat-twisted tubing (with an ovoid cross-section). Results Making the initial crude plant extract directly in the ATPS and injecting only the lower phase permitted highly selective partitioning of the myrosinase complex before a short chromatography on a spiral disk CCC. Optimum phase retention and separation of myrosinase from other plant proteins afforded a 60-fold purification. Conclusion Catalytically active myrosinase is purified from 3-day broccoli sprouts, 7-day daikon sprouts, mustard seeds and the leaves of field-grown moringa trees, in a CCC system that is predictably scalable. PMID:25130502

  19. Single-step total fractionation of single-wall carbon nanotubes by countercurrent chromatography

    PubMed Central

    Zhang, Min; Khripin, Constantine Y; Fagan, Jeffrey A.; McPhie, Peter; Ito, Yoichiro; Zheng, Ming

    2014-01-01

    Development of simple processes to fractionate synthetic mixtures of single-wall carbon nanotubes (SWCNTs) into individual species is crucial to many applications. Existing methods for single-chirality SWCNT purification are cumbersome, often requiring multiple steps and different conditions for different species. Here, we report a method to achieve total fractionation of a synthetic SWCNT mixture by countercurrent chromatography, resulting in purification of many single-chirality SWCNT species in a single run. This method is based on tunable partition of sodium deoxycholate dispersed SWCNTs in polyethylene glycol / dextran aqueous two-phase system. By running the mobile phase with 0.02% of sodium deoxycholate and a gradient of sodium dodecyl sulfate from 0.1% to 0.7% (w/w), we observe clear diameter-dependent elution, with ~ 90% total recovery. Among all the fractions collected, a number of them are enriched in single-chirality (9,4), (7,5), (7,6), (8,3), (6,5) species, while most of the remaining ones contain no more than 2-3 major species. We also observe strong (n,m)-dependent elution peak width due to enantiomer-resolved partition. These results demonstrate CCC as an effective way to obtain high purity (n, m) species, and suggest the potential of CCC as an analytical tool for chirality distribution mapping of synthetic SWCNT mixtures. PMID:24673411

  20. Topsy-turvy: turning the counter-current heat exchange of leatherback turtles upside down

    PubMed Central

    Davenport, John; Jones, T. Todd; Work, Thierry M.; Balazs, George H.

    2015-01-01

    Counter-current heat exchangers associated with appendages of endotherms feature bundles of closely applied arteriovenous vessels. The accepted paradigm is that heat from warm arterial blood travelling into the appendage crosses into cool venous blood returning to the body. High core temperature is maintained, but the appendage functions at low temperature. Leatherback turtles have elevated core temperatures in cold seawater and arteriovenous plexuses at the roots of all four limbs. We demonstrate that plexuses of the hindlimbs are situated wholly within the hip musculature, and that, at the distal ends of the plexuses, most blood vessels supply or drain the hip muscles, with little distal vascular supply to, or drainage from the limb blades. Venous blood entering a plexus will therefore be drained from active locomotory muscles that are overlaid by thick blubber when the adults are foraging in cold temperate waters. Plexuses maintain high limb muscle temperature and avoid excessive loss of heat to the core, the reverse of the accepted paradigm. Plexuses protect the core from overheating generated by muscular thermogenesis during nesting. PMID:26445982

  1. Countercurrent assisted quantitative recovery of metabolites from plant-associated natural deep eutectic solvents.

    PubMed

    Liu, Yang; Garzon, Jahir; Friesen, J Brent; Zhang, Yu; McAlpine, James B; Lankin, David C; Chen, Shao-Nong; Pauli, Guido F

    2016-07-01

    NAtural Deep Eutectic Solvents (NADES) are chemically simple but physiologically important plant constituents that exhibit unique solubilizing properties of other metabolites, including bioactive constituents. The high polarity of NADES introduces a challenge in the ability of conventional solid-support based chromatography to recover potential bioactive metabolites. This complicates the systematic explanation of the NADES' functions in botanical extracts. The present study utilizes countercurrent separation (CCS) methodology to overcome the recovery challenge. To demonstrate its feasibility, Glucose-Choline chloride-Water (GCWat, 2:5:5, mole/mole) served as a model NADES, and four widely used marker flavonoids with different polarities (rutin, quercetin, kaempferol, and daidzein) were chosen as model target analytes. In order to prepare GCWat with high consistency, a water drying study was performed. The unique capabilities of the recently introduced CherryOne system, offering volumetric phase metering, were used to monitor the CCS operations. The collected fractions were analyzed using UHPLC and NMR/quantitative NMR. CCS was able to recover the analytes from the NADES matrix with quantitative recoveries of 95.7%, 94.6%, 97.0%, and 96.7% for rutin, quercetin, kaempferol, and daidzein respectively. The CCS strategy enables recovery of target metabolites from NADES-containing crude extracts as well as from other chemical mixtures, and moreover offers a means of using NADES as environmentally friendly extraction solvents.

  2. Rational development of solvent system families in counter-current chromatography.

    PubMed

    Friesen, J Brent; Pauli, Guido F

    2007-06-01

    Application of a mixture of 21 commercially available natural products, termed the GUESSmix, established a standard test that allows for a systematic analysis and comparison of the properties of biphasic solvent systems in counter-current/partition chromatography. Because the GUESSmix is comprised of compounds with varying polarities, functional groups, and structural features, it proves to be a rational method for mapping the optimal resolution polarity range of a particular solvent system. The mapping of optimal resolution polarity ranges of solvent systems provided for the description of the overall optimal resolution polarity range of a solvent system family, comprised of the same solvents in different proportions. By comparing the GUESSmix performance in the individual members of a solvent system family, the solvent system that best functions as the representative of, or portal to, the solvent system families was determined. The GUESSmix also afforded a method to compare the overall optimal resolution polarity ranges of solvent system families. Based on performance of GUESSmix chromatograms, the counter-current chromatography (CCC) properties of a two ternary literature solvent systems, ethyl acetate/n-butanol/water (EBuWat) and t-butylmethylether/acetonitrile/water (terAcWat), were explored in order to contrast and compare their CCC potential. A quaternary solvent system, hexane/t-butylmethylether/acetonitrile/water (HterAcWat), was also formulated and studied. The results indicated that the GUESSmix is fit for the purpose of developing and evaluating CCC solvent system families with desired performance characteristics.

  3. Purification of betulinic acid from Eugenia florida (Myrtaceae) by high-speed counter-current chromatography.

    PubMed

    Frighetto, Nelson; Welendorf, Rodolfo Max; Pereira da Silva, Ana Maria; Nakamura, Marcos Jun; Siani, Antonio Carlos

    2005-01-01

    A high yield of betulinic acid (up to 17% from the ethanolic extract) was found in the leaves of Eugenia florida collected in south-eastern Brazil, making this species a potential commercial source of the title compound. Extracts of E. florida were subjected to solvent partition, and rapid high-speed counter-current chromatography (HSCCC) was applied to the semi-crude extracts to afford betulinic acid in high purity. The mobile and stationary phases were derived from the two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (10:5:2.5:1). The developing solvent system (stationary and mobile phases) for optimum HSCCC separation was chosen by dissolving the fraction to be chromatographed in the proposed solvent mixture and determining the amount of betulinic acid in each phase by densitometric TLC. Purified betulinic acid was characterized by 13C-NMR, GC-MS and co-injection of its methyl ester with standards in GC-FID. The HSCCC technique is commonly employed to isolate triterpene glycosides, but is applied in this study to an aglycone.

  4. Removal of cesium from simulated liquid waste with countercurrent two-stage adsorption followed by microfiltration.

    PubMed

    Han, Fei; Zhang, Guang-Hui; Gu, Ping

    2012-07-30

    Copper ferrocyanide (CuFC) was used as an adsorbent to remove cesium. Jar test results showed that the adsorption capacity of CuFC was better than that of potassium zinc hexacyanoferrate. Lab-scale tests were performed by an adsorption-microfiltration process, and the mean decontamination factor (DF) was 463 when the initial cesium concentration was 101.3μg/L, the dosage of CuFC was 40mg/L and the adsorption time was 20min. The cesium concentration in the effluent continuously decreased with the operation time, which indicated that the used adsorbent retained its adsorption capacity. To use this capacity, experiments on a countercurrent two-stage adsorption (CTA)-microfiltration (MF) process were carried out with CuFC adsorption combined with membrane separation. A calculation method for determining the cesium concentration in the effluent was given, and batch tests in a pressure cup were performed to verify the calculated method. The results showed that the experimental values fitted well with the calculated values in the CTA-MF process. The mean DF was 1123 when the dilution factor was 0.4, the initial cesium concentration was 98.75μg/L and the dosage of CuFC and adsorption time were the same as those used in the lab-scale test. The DF obtained by CTA-MF process was more than three times higher than the single-stage adsorption in the jar test.

  5. Rapid isolation and purification of phorbol esters from Jatropha curcas by high-speed countercurrent chromatography.

    PubMed

    Hua, Wan; Hu, Huiling; Chen, Fang; Tang, Lin; Peng, Tong; Wang, Zhanguo

    2015-03-18

    In this work, a high-speed countercurrent chromatography (HSCCC) method was established for the preparation of phorbol esters (PEs) from Jatropha curcas. n-Hexane-ethyl acetate-methanol-water (1.5:1.5:1.2:0.5, v/v) was selected as the optimum two-phase solvent system to separate and purify jatropha factor C1 (JC1) with a purity of 85.2%, as determined by HPLC, and to obtain a mixture containing four or five PEs. Subsequently, continuous semipreparative HPLC was applied to further purify JC1 (99.8% as determined by HPLC). In addition, UPLC-PDA and UPLC-MS were established and successfully used to evaluate the isolated JC1 and PE-rich crude extract. The purity of JC1 was only 87.8% by UPLC-UV. A peak (a compound highly similar to JC1) was indentified as the isomer of JC1 by comparing the characteristic UV absorption and MS spectra. Meanwhile, this strategy was also applied to analyze the PE-rich crude extract from J. curcas. It is interesting that there may be more than 15 PEs according to the same quasi-molecular ion peaks, highly similar sequence-specific fragment ions, and similar UV absorption spectrum.

  6. Isolation and purification of series bioactive components from Hypericum perforatum L. by counter-current chromatography.

    PubMed

    Cao, Xueli; Wang, Qiaoe; Li, Yan; Bai, Ge; Ren, Hong; Xu, Chunming; Ito, Yoichiro

    2011-03-01

    Counter-current chromatography (CCC) combined with pre-separation by ultrasonic solvent extraction was successively used for the separation of series bioactive compounds from the crude extract of Hypericum perforatum L. The petroleum ether extract was separated by the solvent system of n-heptane-methanol-acetonitrile (1.5:0.5:0.5, v/v) and n-heptane-methanol (1.5:1, v/v) in gradient elution, yielding a phloroglucinol compound, hyperforin with HPLC purity over 98%. The ethyl acetate extract was separated by using the solvent system composed of hexane-ethyl acetate-methanol-water (1:1:1:1 and 1:3:1:3, v/v) in gradient through both reverse phase and normal phase elution mode, yielding a naphthodianthrone compound, hypericin with HPLC purity about 95%. The n-butanol extract was separated with the solvent system composed of n-butanol-ethyl acetate-water (1:4:5 and 1.5:3.5:5, v/v) in elution and back-extrusion mode, yielding two of flavones, rutin and hyperoside, with HPLC purity over 95%. HPLC-MS, reference sample and UV spectrum were selectively used in separation to search for target compounds from HPLC-DAD profiles of different sub-extracts. The structures of isolated compounds were further identified by ESI-MS, ¹HNMR and ¹³CNMR.

  7. Interannual and interdecadal variability of the North Equatorial Countercurrent in the Western Pacific

    NASA Astrophysics Data System (ADS)

    Chen, Xiao; Qiu, Bo; Du, Yan; Chen, Shuiming; Qi, Yiquan

    2016-10-01

    Interannual and longer timescale variations of the North Equatorial Countercurrent (NECC) in the western Pacific are investigated using the multidecade (1960-2014) hindcast by the Ocean general circulation model for the Earth Simulator (OFES). The OFES-simulated sea level and upper ocean circulation changes show favorable comparisons with available tide gauge data and repeat hydrographic surveys along the 137°E meridian. An empirical orthogonal function (EOF) analysis reveals that the low-frequency NECC variability is dominated by two distinct modes. The first mode fluctuates interannually and shows strengthening and southward migration of the NECC concurrent with the development of El Niño events. Unlike the extratropical western Pacific Ocean circulation variability controlled by wind forcing west of the dateline, the interannual NECC variations are forced by equatorial wind forcing cumulative across the entire Pacific basin. The second mode of the NECC variability has an interdecadal timescale and is characterized by NECC's progressive weakening in strength, migrating poleward, and broadening in width over the past 50 years. These long-term changes in NECC are caused by the corresponding changes in the trade wind system that weakened and expanded poleward in the past half a century across the Pacific basin.

  8. Effect of Coriolis force on counter-current chromatographic separation by centrifugal partition chromatography.

    PubMed

    Ikehata, Jun-Ichi; Shinomiya, Kazufusa; Kobayashi, Koji; Ohshima, Hisashi; Kitanaka, Susumu; Ito, Yoichiro

    2004-02-06

    The effect of Coriolis force on the counter-current chromatographic separation was studied using centrifugal partition chromatography (CPC) with four different two-phase solvent systems including n-hexane-acetonitrile (ACN); tert-butyl methyl ether (MtBE)-aqueous 0.1% trifluoroacetic acid (TFA) (1:1); MtBE-ACN-aqueous 0.1% TFA (2:2:3); and 12.5% (w/w) polyethylene glycol (PEG) 1000-12.5% (w/w) dibasic potassium phosphate. Each separation was performed by eluting either the upper phase in the ascending mode or the lower phase in the descending mode, each in clockwise (CW) and counterclockwise column rotation. Better partition efficiencies were attained by the CW rotation in both mobile phases in all the two-phase solvent systems examined. The mathematical analysis also revealed the Coriolis force works favorably under the CW column rotation for both mobile phases. The overall results demonstrated that the Coriolis force produces substantial effects on CPC separation in both organic-aqueous and aqueous-aqueous two-phase systems.

  9. Experimental design of a twin-column countercurrent gradient purification process.

    PubMed

    Steinebach, Fabian; Ulmer, Nicole; Decker, Lara; Aumann, Lars; Morbidelli, Massimo

    2017-02-23

    As typical for separation processes, single unit batch chromatography exhibits a trade-off between purity and yield. The twin-column MCSGP (multi-column countercurrent solvent gradient purification) process allows alleviating such trade-offs, particularly in the case of difficult separations. In this work an efficient and reliable procedure for the design of the twin-column MCSGP process is developed. This is based on a single batch chromatogram, which is selected as the design chromatogram. The derived MCSGP operation is not intended to provide optimal performance, but it provides the target product in the selected fraction of the batch chromatogram, but with higher yield. The design procedure is illustrated for the isolation of the main charge isoform of a monoclonal antibody from Protein A eluate with ion-exchange chromatography. The main charge isoform was obtained at a purity and yield larger than 90%. At the same time process related impurities such as HCP and leached Protein A as well as aggregates were at least equally well removed. Additionally, the impact of several design parameters on the process performance in terms of purity, yield, productivity and buffer consumption is discussed. The obtained results can be used for further fine-tuning of the process parameters so as to improve its performance.

  10. Isolation of terpenoids from Pimpinella anisum essential oil by high-performance counter-current chromatography.

    PubMed

    Skalicka-Woźniak, Krystyna; Walasek, Magdalena; Ludwiczuk, Agnieszka; Głowniak, Kazimierz

    2013-08-01

    High-performance counter-current chromatography was successfully used for the isolation and purification of terpenoid compounds from the essential oil of Pimpinella anisum L. A two-phase solvent system composed of n-heptane/methanol/ethyl acetate/water (5:2:5:2, v/v/v/v) was suitable for the purification of linalool, terpinen-4-ol, α-terpineol, p-anisaldehyde, while n-heptane/methanol (1:1, v/v) was used for the isolation of anethole and foeniculin. A scale-up process from analytical to preparative was developed. Additionally, a stepwise gradient elution was applied and instead of two different runs, 40 min each, one 80 min separation was performed; although the time of separation remains the same, it was possible to repeat the efficiency even if the water-containing mobile phase was changed to a nonaqueous system. The obtained essential oil, as well as purified compounds, was analyzed by GC. A total of 0.64 mg of linalool, 0.52 mg of terpinen-4-ol, 0.10 mg of α-terpineol, 0.62 mg of p-anisaldehyde, 15 mg of anethole, and 2.12 mg of foeniculin were obtained from 210 mg of the essential oil of P. anisum L. in a short time with purities of 99, 98, 94, 93.54, 93, and 93.6%, respectively.

  11. [Droplet countercurrent chromatography to isolate ecdysteroids from the herb Silene tatarica (L>)].

    PubMed

    Báthori, M; Máthe, I

    1996-05-01

    Our research project was to isolate ecdysteroids from Silene tatarica (L.) Pers., which plant belongs to Caryophyllaceae family. This plant as a species of the Silence genus has been considered as a good potential source of ecdysteroids, including new, hitherto never identified natural product(s). The raw material of isolation was the herba of Silene tatarica (L.) Pers. that was cultivated in the fields of the Ecological and Botanical Research Institute of the Hungarian Academy of Sciences (Vácrátót, Hungary) and the plants were collected in June of 1994. The isolation procedure started with methanol extraction of the ground and milled herba. To improve the recovery, the extraction was done with boiling methanol under reflux for 20 minutes. The crude extract was purified using simple techniques, such as fractioned precipitation (with acetone), solvent-solvent partition (benzene-aqueous methanol). Further purification includes droplet counter-current chromatography (chloroform-methanol-water, 65:20:20, v/v/v) and straight-phase HPLC (silica stationary phase, dichloromethane-150 propanol-water. 125:25:2 v/v/v, mobile phase). Structural identification was done by using mass spectrometry and NMR spectroscopy. Three of the isolated ecdysteroids were identified as 20-hydroxyecdysone, 2-deoxy-20-hydroxyecdysone and 20-hydroxyecdysone-22-benzoate these compounds have never been detected in Silene tatarica (L.) Pers. Structural elucidation of the fourt isolated ecdysteroid resulted in a new natural product with the chemical structure of 2-deoxy-20-hydroxyecdysone 22-benzoate.

  12. Topsy-turvy: turning the counter-current heat exchange of leatherback turtles upside down.

    PubMed

    Davenport, John; Jones, T Todd; Work, Thierry M; Balazs, George H

    2015-10-01

    Counter-current heat exchangers associated with appendages of endotherms feature bundles of closely applied arteriovenous vessels. The accepted paradigm is that heat from warm arterial blood travelling into the appendage crosses into cool venous blood returning to the body. High core temperature is maintained, but the appendage functions at low temperature. Leatherback turtles have elevated core temperatures in cold seawater and arteriovenous plexuses at the roots of all four limbs. We demonstrate that plexuses of the hindlimbs are situated wholly within the hip musculature, and that, at the distal ends of the plexuses, most blood vessels supply or drain the hip muscles, with little distal vascular supply to, or drainage from the limb blades. Venous blood entering a plexus will therefore be drained from active locomotory muscles that are overlaid by thick blubber when the adults are foraging in cold temperate waters. Plexuses maintain high limb muscle temperature and avoid excessive loss of heat to the core, the reverse of the accepted paradigm. Plexuses protect the core from overheating generated by muscular thermogenesis during nesting.

  13. Improved flow cytometric method to enumerate residual cells: minimal linear detection limits for platelets, erythrocytes, and leukocytes.

    PubMed

    Pichler, J; Printz, D; Scharner, D; Trbojevic, D; Siekmann, J; Fritsch, G

    2002-08-15

    Increasing demand for quality control of blood products requires more sensitive methods to enumerate residual cells. Presently, the reported threshold (in cells per microliter) is 400 for red blood cells, 30-500 for platelets, and 1 for leukocytes. To examine precision and linearity in enumerating residual platelets and red blood cells, EDTA-anticoagulated blood from healthy donors was serially diluted with serum, stained in TruCount tubes using a no-lyse/no-wash procedure and a monoclonal antibody cocktail against the CD42a (FL1) and glycophorin-A (FL2) epitopes, and analyzed by flow cytometry. Leukocyte counts were determined in separate tubes. Cell preparation and analysis were performed once for 20 blood samples each and 20 times using the same specimen. Acquisition from the same tube was performed separately for platelets (threshold on FL1) and red blood cells (threshold on FL2). Multiparameter analysis was used for data evaluation. Linear results were obtained for platelets per microliter between 3,410 and 5 and for red blood cells per microliter between 54,000 and 3. For the lower cell concentrations, the coefficient of variation was 16.7% for platelets and 10.9% for red blood cells. The presented method allows the distinction between physiologically intact and ghost red blood cells. The method represents a reliable, sensitive, and accurate approach to quantify platelets and red blood cells in diluted blood. It can be applied to enumerate residual cells in plasma products and meets the increasing demand for quality control in blood components.

  14. Low reproductive isolation and highly variable levels of gene flow reveal limited progress towards speciation between European river and brook lampreys.

    PubMed

    Rougemont, Q; Gaigher, A; Lasne, E; Côte, J; Coke, M; Besnard, A-L; Launey, S; Evanno, G

    2015-12-01

    Ecologically based divergent selection is a factor that could drive reproductive isolation even in the presence of gene flow. Population pairs arrayed along a continuum of divergence provide a good opportunity to address this issue. Here, we used a combination of mating trials, experimental crosses and population genetic analyses to investigate the evolution of reproductive isolation between two closely related species of lampreys with distinct life histories. We used microsatellite markers to genotype over 1000 individuals of the migratory parasitic river lamprey (Lampetra fluviatilis) and freshwater-resident nonparasitic brook lamprey (Lampetra planeri) distributed in 10 sympatric and parapatric population pairs in France. Mating trials, parentage analyses and artificial fertilizations demonstrated a low level of reproductive isolation between species even though size-assortative mating may contribute to isolation. Most parapatric population pairs were strongly differentiated due to the joint effects of geographic distance and barriers to migration. In contrast, we found variable levels of gene flow between sympatric populations ranging from panmixia to moderate differentiation, which indicates a gradient of divergence with some population pairs that may correspond to alternative morphs or ecotypes of a single species and others that remain partially isolated. Ecologically based divergent selection may explain these variable levels of divergence among sympatric population pairs, but incomplete genome swamping following secondary contact could have also played a role. Overall, this study illustrates how highly differentiated phenotypes can be maintained despite high levels of gene flow that limit the progress towards speciation.

  15. Mitigation of plasma–material interactions via passive Li efflux from the surface of a flowing liquid lithium limiter in EAST

    NASA Astrophysics Data System (ADS)

    Zuo, G. Z.; Hu, J. S.; Maingi, R.; Ren, J.; Sun, Z.; Yang, Q. X.; Chen, Z. X.; Xu, H.; Tritz, K.; Zakharov, L. E.; Gentile, C.; Meng, X. C.; Huang, M.; Xu, W.; Chen, Y.; Wang, L.; Yan, N.; Mao, S. T.; Yang, Z. D.; Li, J. G.; EAST Team

    2017-04-01

    A new flowing liquid Li limiter (FLiLi) based on the concept of a thin flowing film has been successfully designed and tested in the EAST device in 2014. A bright Li radiative mantle at the plasma edge was observed during discharges using FLiLi, resulting from passive Li injection and transport in the scrape-off layer (SOL) plasma. Li particle efflux from the FLiLi surface into the plasma was estimated at  >5  ×  1020 atom s‑1, due to surface evaporation and sputtering, and accompanied with a few small Li droplets ~1 mm diameter that were ejected from FLiLi. The Li efflux from FLiLi was ionized by the SOL plasma and formed a Li radiation band that originated from the FLiLi surface, and then spread toroidally by SOL plasma flow. The Li radiative mantle appeared to partly isolate the plasma from the wall, reducing impurity release from the wall materials, and possibly leading to a modest improvement in confinement. In addition, strong Li radiation reduced the particle and heat fluxes impacting onto the divertor plate, with certain similarities to heat flux reduction and detachment onset via low-Z impurity injection.

  16. Limonene in Arizona liquid systems used in countercurrent chromatography. II Polarity and stationary-phase retention.

    PubMed

    Faure, K; Bouju, E; Doby, J; Berthod, A

    2014-09-01

    The previous article in this series described the physico-chemical properties and chemical compositions of the two phases of the limonene-ethyl acetate-ethanol-water biphasic liquid system. This system was designed to be a "green" version of the so-called Arizona (AZ) scale of heptane-ethyl acetate-methanol compositions in which the heptane-ethyl acetate volume ratio is exactly the same as the methanol-water ratio. The first major difference between the standard and "green" AZ systems is the difference in upper and lower phase densities. The higher density of limonene compared with heptane greatly reduces the density difference of the "green" system: half the compositions have a density difference lower than 0.06 g mL(-1), precluding their use in hydrodynamic CCC columns. The other major difference is the phase polarity. The better distribution of ethanol between the upper organic and lower aqueous phases of the "green" AZ scale renders them more polar than their counterparts in standard heptane-based compositions. The test solutes aspirin and coumarin have higher distribution constants in the "green" AZ compositions. It is revealed that a hydrostatic column is suitable for use with all "green" compositions, with very good phase retention and limited driving pressure at high flow rates. A hydrodynamic column only functioned at limited flow rates with polar compositions of sufficient phase-density difference. The CCC chromatograms obtained with different compositions and columns are shown, and their peak position and sharpness discussed.

  17. Influence of temporal noise on the skin blood flow measurements performed by cooled thermal imaging camera: limit possibilities within each physiological frequency range

    NASA Astrophysics Data System (ADS)

    Sagaidachnyi, A. A.; Volkov, I. U.; Fomin, A. V.

    2016-04-01

    This paper describes limit possibilities of modern cooled thermal imaging cameras as a tool for estimation of blood flow oscillations at the surface of living body. Skin temperature oscillations, as we assumed, are a consequence of the blood flow oscillations. We considered the temperature sensitivity 0.01-0.02 °C as a typical for the most of modern cooled long wave thermal imaging cameras. Fourier filter used to investigate the temperature signal separately within endothelial, neurogenic, myogenic, respiratory and cardiac frequency ranges. The level of temporal noise has been estimated during measurements of no living body with stabilized temperature ~ 24°C. The level of temperature oscillations has been calculated for the group of healthy subjects within each frequency range. Thus, we were able to determine signal-to-noise ratio within frequency band [0.001, 1] Hz. As a result, we determine that skin temperature oscillations measured by thermal imaging camera with sensitivity 0.02°C have the upper frequency limit ~ 0.2 Hz. In other words, within the respiratory and cardiac frequency ranges of blood flow oscillations the noise level exceeds signal one, and temperature measurements at the skin surface are practically useless. The endothelial, neurogenic and myogenic components of the temperature oscillations contain ~98% of the total spectral power of the signal. We have plot the empirical extrapolated curve of sensitivity of thermal imaging camera vs. frequency of the temperature oscillations. The data analysis shows that measurements of skin temperature oscillations within respiratory and cardiac ranges require the temperature sensitivity at least ~ 0.01°C and 0.001°C, respectively.

  18. Combinative application of pH-zone-refining and conventional high-speed counter-current chromatography for preparative separation of caged polyprenylated xanthones from gamboge.

    PubMed

    Xu, Min; Fu, Wenwei; Zhang, Baojun; Tan, Hongsheng; Xiu, Yanfeng; Xu, Hongxi

    2016-02-01

    An efficient method for the preparative separation of four structurally similar caged xanthones from the crude extracts of gamboge was established, which involves the combination of pH-zone-refining counter-current chromatography and conventional high-speed counter-current chromatography for the first time. pH-zone-refining counter-current chromatography was performed with the solvent system composed of n-hexane/ethyl acetate/methanol/water (7:3:8:2, v/v/v/v), where 0.1% trifluoroacetic acid was added to the upper organic stationary phase as a retainer and 0.03% triethylamine was added to the aqueous mobile phase as an eluter. From 3.157 g of the crude extract, 1.134 g of gambogic acid, 180.5 mg of gambogenic acid and 572.9 mg of a mixture of two other caged polyprenylated xanthones were obtained. The mixture was further separated by conventional high-speed counter-current chromatography with a solvent system composed of n-hexane/ethyl acetate/methanol/water (5:5:10:5, v/v/v/v) and n-hexane/methyl tert-butyl ether/acetonitrile/water (8:2:6:4,v/v/v/v), yielding 11.6 mg of isogambogenic acid and 10.4 mg of β-morellic acid from 218.0 mg of the mixture, respectively. The purities of all four of the compounds were over 95%, as determined by high-performance liquid chromatography, and the chemical structures of the four compounds were confirmed by electrospray ionization mass spectrometry and NMR spectroscopy. The combinative application of pH-zone-refining counter-current chromatography and conventional high-speed counter-current chromatography shows great advantages in isolating and enriching the caged polyprenylated xanthones.

  19. Exogenous and endogenous angiotensin‐II decrease renal cortical oxygen tension in conscious rats by limiting renal blood flow

    PubMed Central

    Emans, Tonja W.; Janssen, Ben J.; Pinkham, Maximilian I.; Ow, Connie P. C.; Evans, Roger G.; Joles, Jaap A.; Malpas, Simon C.; Krediet, C. T. Paul

    2016-01-01

    Key points Our understanding of the mechanisms underlying the role of hypoxia in the initiation and progression of renal disease remains rudimentary.We have developed a method that allows wireless measurement of renal tissue oxygen tension in unrestrained rats.This method provides stable and continuous measurements of cortical tissue oxygen tension (PO2) for more than 2 weeks and can reproducibly detect acute changes in cortical oxygenation.Exogenous angiotensin‐II reduced renal cortical tissue PO2 more than equi‐pressor doses of phenylephrine, probably because it reduced renal oxygen delivery more than did phenylephrine.Activation of the endogenous renin–angiotensin system in transgenic Cyp1a1Ren2 rats reduced cortical tissue PO2; in this model renal hypoxia precedes the development of structural pathology and can be reversed acutely by an angiotensin‐II receptor type 1 antagonist.Angiotensin‐II promotes renal hypoxia, which may in turn contribute to its pathological effects during development of chronic kidney disease. Abstract We hypothesised that both exogenous and endogenous angiotensin‐II (AngII) can decrease the partial pressure of oxygen (PO2) in the renal cortex of unrestrained rats, which might in turn contribute to the progression of chronic kidney disease. Rats were instrumented with telemeters equipped with a carbon paste electrode for continuous measurement of renal cortical tissue PO2. The method reproducibly detected acute changes in cortical oxygenation induced by systemic hyperoxia and hypoxia. In conscious rats, renal cortical PO2 was dose‐dependently reduced by intravenous AngII. Reductions in PO2 were significantly greater than those induced by equi‐pressor doses of phenylephrine. In anaesthetised rats, renal oxygen consumption was not affected, and filtration fraction was increased only in the AngII infused animals. Oxygen delivery decreased by 50% after infusion of AngII and renal blood flow (RBF) fell by 3.3 ml min−1

  20. Nitrite accumulation from simultaneous free-ammonia and free-nitrous-acid inhibition and oxygen limitation in a continuous-flow biofilm reactor.

    PubMed

    Park, Seongjun; Chung, Jinwook; Rittmann, Bruce E; Bae, Wookeun

    2015-01-01

    To achieve nitrite accumulation for shortcut biological nitrogen removal (SBNR) in a biofilm process, we explored the simultaneous effects of oxygen limitation and free ammonia (FA) and free nitrous acid (FNA) inhibition in the nitrifying biofilm. We used the multi-species nitrifying biofilm model (MSNBM) to identify conditions that should or should not lead to nitrite accumulation, and evaluated the effectiveness of those conditions with experiments in continuous flow biofilm reactors (CFBRs). CFBR experiments were organized into four sets with these expected outcomes based on the MSNBM as follows: (i) Control, giving full nitrification; (ii) oxygen limitation, giving modest long-term nitrite build up; (iii) FA inhibition, giving no long-term nitrite accumulation; and (iv) FA inhibition plus oxygen limitation, giving major long-term nitrite accumulation. Consistent with MSNBM predictions, the experimental results showed that nitrite accumulated in sets 2-4 in the short term, but long-term nitrite accumulation was maintained only in sets 2 and 4, which involved oxygen limitation. Furthermore, nitrite accumulation was substantially greater in set 4, which also included FA inhibition. However, FA inhibition (and accompanying FNA inhibition) alone in set 3 did not maintained long-term nitrite accumulation. Nitrite-oxidizing bacteria (NOB) activity batch tests confirmed that little NOB or only a small fraction of NOB were present in the biofilms for sets 4 and 2, respectively. The experimental data supported the previous modeling results that nitrite accumulation could be achieved with a lower ammonium concentration than had been required for a suspended-growth process. Additional findings were that the biofilm exposed to low dissolved oxygen (DO) limitation and FA inhibition was substantially denser and probably had a lower detachment rate.

  1. Scale-up of counter-current chromatography: demonstration of predictable isocratic and quasi-continuous operating modes from the test tube to pilot/process scale.

    PubMed

    Sutherland, Ian; Hewitson, Peter; Ignatova, Svetlana

    2009-12-11

    Predictable scale-up from test tube derived distribution ratios and analytical-scale sample loading optimisation is demonstrated using a model sample system of benzyl alcohol and p-cresol in a heptane:ethyl acetate:methanol:water phase system with the new 18 L Maxi counter-current chromatography centrifuge. The versatility of having a liquid stationary phase with its high loading capacity and flexible operating modes is demonstrated at two different scales by separating and concentrating target compounds using a mixture of caffeine, vanillin, naringenin and carvone using a quasi-continuous technique called intermittent counter-current extraction.

  2. Current limiters

    SciTech Connect

    Loescher, D.H.; Noren, K.

    1996-09-01

    The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

  3. High-performance countercurrent chromatography separation of Peucedanum cervaria fruit extract for the isolation of rare coumarin derivatives.

    PubMed

    Skalicka-Woźniak, Krystyna; Mroczek, Tomasz; Kozioł, Ewelina

    2015-01-01

    For the first time, rare major and minor compounds from fruits of Peucedanum cervaria were isolated. High-performance countercurrent chromatography with two different solvent systems, heptane/ethyl acetate/methanol/water (3:2:3:2 and 2:1:2:1, v/v), was successfully used in the reversed-phase mode. A scale-up process from analytical to semipreparative in a very short time was developed. The structures of isolated compounds were evaluated by high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry, gas chromatography with mass spectrometry, and one- and two-dimensional NMR spectroscopy. (8S,9R)-9-(3-Methylbutenoyloxy)-O-acetyl-8,9-dihydrooroselol (compound B), (8S,9R)-9-(2-methyl-Z-butenoyloxy)-O-acetyl-8,9-dihydrooroselol (edultin, compound C), and (8S,9R)-9-acetoxy-O-(2α-methylbutyryl)-8,9-dihydrooroselol (compound D) were obtained using heptane/ethyl acetate/methanol/water (2:1:2:1, v/v) in <40 min. The method yielded 4.6 mg of a mixture of compounds B and C (11:89) and 3.7 mg of compound D. These amounts were obtained from the crude extract (0.5 g) in a single run. Although the compounds are known, their isolation by countercurrent chromatography and the analysis of their relative stereochemistry by two-dimensional NMR spectroscopy have been performed for the first time. Additionally, heptane/ethyl acetate/methanol/water (3:2:3:2, v/v) led to the isolation of oxypeucedanin (1.2 mg; compound A). This is the first time that angular dihydrofuranocoumarin was isolated from plant extract by countercurrent chromatography.

  4. Preparative separation of flavonoid glycosides in leaves extract of Ampelopsis grossedentata using high-speed counter-current chromatography.

    PubMed

    Du, Qizhen; Chen, Ping; Jerz, Gerold; Winterhalter, Peter

    2004-06-18

    Preparative separation of flavonoid glycosides in leaves extract of Ampelopsis grossedentata was conducted using high-speed counter-current chromatograph (HSCCC) with a solvent system composed of n-hexane-ethyl acetate-methanol-water (1:6:1.5:7.5, v/v). In a single operation, 28 mg of 5,7-dihydroxy-3',4'-trihydroxyflavone-3-O-6''-rhamnose and 18 mg of 5,7-dihydroxy-3',4'-dihydroxyflavone-3-O-6''-rhamnose was obtained from 150 mg of the extract. The chemical structure of the two compounds was elucidated by electrospray ionization (EIS) MS and NMR.

  5. Preparative isolation and purification of harpagoside from Scrophularia ningpoensis hemsley by high-speed counter-current chromatography.

    PubMed

    Tong, Shengqiang; Yan, Jizhong; Lou, Jianzhong

    2006-01-01

    The bioactive component harpagoside was successfully separated from the crude extract of Scrophularia ningpoensis Hemsley by one-step purification using high-speed counter-current chromatography (HSCCC). A two-phase solvent system containing n-butanol:ethyl acetate:water (1:9:10) was selected following consideration of the partition coefficient of the target compound. A 276 mg quantity of the crude extract was loaded onto a 250 mL HSCCC column and yielded 11 mg harpagoside at over 97% purity. The chemical structure of harpagoside was determined by HPLC-ESI/MS and 1H-NMR.

  6. Preparative separation of cichoric acid from Echinacea purpurea by pH-zone-refining counter-current chromatography.

    PubMed

    Wang, Xiao; Geng, Yanling; Li, Fuwei; Gao, Qianshan; Shi, Xingang

    2006-01-20

    pH-zone-refining counter-current chromatography was successfully applied to the separation of cichoric acid from Echinacea Purpurea (L.) Moench. A 3.0 g quantity of sample was separated using the following two-phase solvent system: MtBE-CH3CN-water (4:1:5, v/v), 10 mM trifluoroacetic acid in organic stationary phase and 10 mM ammonia in aqueous mobile phase. The obtained fractions were analyzed by high-performance liquid chromatography and negative ion electrospray ionization mass spectrometry. Double separations were performed with the same solvent system yielding 563 mg cichoric acid at 95.6% purity.

  7. Isolation of xanthyletin, an inhibitor of ants' symbiotic fungus, by high-speed counter-current chromatography.

    PubMed

    Cazal, Cristiane de Melo; Domingues, Vanessa de Cássia; Batalhão, Jaqueline Raquel; Bueno, Odair Corrêa; Filho, Edson Rodrigues; da Silva, Maria Fátima G Fernandes; Vieira, Paulo Cezar; Fernandes, João Batista

    2009-05-08

    Xanthyletin, an inhibitor of symbiotic fungus (Leucoagaricus gongylophorus) of leaf-cutting ant (Atta sexdens rubropilosa), as well as suberosin, seselin and xanthoxyletin were isolated from Citrus sinensis grafted on Citrus limonia. A two-phase solvent system composed of hexane/ethanol/acetonitrile/water (10:8:1:1, v/v) was used for the high-speed counter-current chromatographic isolation of xanthyletin with high yield and over 99% purity as determined by liquid and gas chromatography with mass spectrometry detection. Identifications were performed by UV spectra, IR spectra, (1)H NMR and (13)C NMR.

  8. Influence of the gas-liquid flow configuration in the absorption column on photosynthetic biogas upgrading in algal-bacterial photobioreactors.

    PubMed

    Toledo-Cervantes, Alma; Madrid-Chirinos, Cindy; Cantera, Sara; Lebrero, Raquel; Muñoz, Raúl

    2017-02-01

    The potential of an algal-bacterial system consisting of a high rate algal pond (HRAP) interconnected to an absorption column (AC) via recirculation of the cultivation broth for the upgrading of biogas and digestate was investigated. The influence of the gas-liquid flow configuration in the AC on the photosynthetic biogas upgrading process was assessed. AC operation in a co-current configuration enabled to maintain a biomass productivity of 15gm(-2)d(-1), while during counter-current operation biomass productivity decreased to 8.7±0.5gm(-2)d(-1) as a result of trace metal limitation. A bio-methane composition complying with most international regulatory limits for injection into natural gas grids was obtained regardless of the gas-liquid flow configuration. Furthermore, the influence of the recycling liquid to biogas flowrate (L/G) ratio on bio-methane quality was assessed under both operational configurations obtaining the best composition at an L/G ratio of 0.5 and co-current flow operation.

  9. Direct-injection chemiluminescence detector. Properties and potential applications in flow analysis.

    PubMed

    Koronkiewicz, Stanislawa; Kalinowski, Slawomir

    2015-02-01

    We present a novel chemiluminescence detector, with a cone-shaped detection chamber where the analytical reaction takes place. The sample and appropriate reagents are injected directly into the chamber in countercurrent using solenoid-operated pulse micro-pumps. The proposed detector allows for fast measurement of the chemiluminescence signal in stop-flow conditions from the moment of reagents mixing. To evaluate potential applications of the detector the Fenton-like reaction with a luminol-H2O2 system and several transition metal ions (Co(2+), Cu(2+), Cr(3+), Fe(3+)) as a catalyst were investigated. The results demonstrate suitability of the proposed detector for quantitative analysis and for investigations of reaction kinetics, particularly rapid reactions. A multi-pumping flow system was designed and optimized. The developed methodology demonstrated that the shape of the analytical signals strongly depends on the type and concentration of the metal ions. The application of the detector in quantitative analysis was assessed for determination of Fe(III). The direct-injection chemiluminescence detector allows for a sensitive and repeatable (R.S.D. 2%) determination. The intensity of chemiluminescence increased linearly in the range from about 0.5 to 10 mg L(-1) Fe(III) with the detection limit of 0.025 mg L(-1). The time of analysis depended mainly on reaction kinetics. It is possible to achieve the high sampling rate of 144 samples per hour.

  10. [Preparative isolation and purification of five non-volatile compounds from Fructus caryophylli and Flos caryophylli by high-speed counter-current chromatography].

    PubMed

    Gao, Lu; Yu, Bo; Yang, Hong

    2011-11-01

    A high-speed counter-current chromatographic (HSCCC) method was successfully developed for the isolation of three non-volatile compounds from Fructus Caryophylli and two chromone compounds from Flos Caryophylli. The optimum separation solution systems included system A (n-hexane-ethyl acetate-methanol-water (5:8:6: 13, v/v/v/v) and system B (n-hexane-ethyl acetate-methanol-water (5: 8: 9: 10, v/v/v/v). The upper phase of the system A was used as the stationary phase, and the lower phases of the systems A and B as the mobile phases were operated at a flow of 1.2 mL/min, while the apparatus rotated at 880 r/min. The 12.3 mg of ellagic acid, 9.6 mg of rhamnetin, 17.2 mg of quercetin were successfully purified from 70 mg of the crude extract of Fructus Caryophylli by a two-step separation. In the same way, 10.2 mg of 5,7-dimethoxy-2-methylchromone, 8.6 mg of 5,7-dimethoxy-2,6-dimethyl-chromone were purified from 50 mg of the crude extract of Flos Caryophylli. The purities of the compounds were all over 96% as determined by high performance liquid chromatography (HPLC). The five compounds were indentified by mass spectrometry (MS), 1H-nuclear magnetic resonance (NMR) and 13C-NMR. The results indicate that HSCCC is a powerful technique for the purification of non-volatile compounds from different parts of Eugenia caryophylla Thunb.

  11. Distribution ratio, distribution constant and partition coefficient. Countercurrent chromatography retention of benzoic acid.

    PubMed

    Berthod, Alain; Mekaoui, Nazim

    2011-09-09

    There is some confusion in chromatography between terms such as solute distribution ratio, distribution constant and partition coefficient. These terms are very precisely defined in the field of liquid-liquid systems and liquid-liquid extraction as well as in the field of chromatography with sometimes conflicting definitions. Countercurrent chromatography (CCC) is a chromatographic technique in which the stationary phase is a support-free liquid. Since the mobile phase is also liquid, biphasic liquid systems are used. This work focuses on the exact meaning of the terms since there are consequences on experimental results. The retention volumes of solutes in CCC are linearly related to their distribution ratios. The partition coefficient that should be termed (IUPAC recommendation) distribution constant is linked to a single definite species. Using benzoic acid that can dimerize in heptane and ionize in aqueous phase and an 18 mL hydrodynamic CCC column, the role and relationships between parameters and the consequences on experimental peak position and shape are discussed. If the heptane/water distribution constant (marginally accepted to be called partition coefficient) of benzoic acid is 0.2 at 20 °C and can be tabulated in books, its CCC measured distribution ratio or distribution coefficient can change between zero (basic aqueous mobile phase) and more than 25 (acidic aqueous mobile phase and elevated concentration). Benzoic acid distribution ratio and partition coefficient coincide only when both dimerization and ionization are quenched, i.e. at very low concentration and pH 2. It is possible to quench dimerization adding butanol in the heptane/water system. However, butanol additions also affect the partition coefficient of benzoic acid greatly by increasing it.

  12. Seasonal eddy kinetic energy modulations along the North Equatorial Countercurrent in the western Pacific

    NASA Astrophysics Data System (ADS)

    Chen, Xiao; Qiu, Bo; Chen, Shuiming; Qi, Yiquan; Du, Yan

    2015-09-01

    Seasonal eddy kinetic energy (EKE) variability and its associated eddy energy conversion processes in the western tropical Pacific are investigated using satellite altimeter observations and a global, eddy-resolving, ocean general circulation model (OGCM). Both the altimeter-observed sea surface height anomalies and the OGCM simulation show an area with enhanced EKE east of the Mindanao Island centered around 133°E and 5°N. This enhanced EKE area corresponds to the location of the quasi-stationary meander of the North Equatorial Countercurrent (NECC) and is bordered to the south by the Halmahera Eddy. The mesoscale EKE in this area exhibits a clear seasonality, strong in summer (July-August) and weak in winter (November-January), and much of this seasonality is confined to the upper 200 m layer. An investigation into the upper ocean eddy energetics based on the OGCM simulation reveals that the areal barotropic eddy energy conversion rate has an annual cycle similar to the EKE variations, while the areal baroclinic eddy energy conversion is found to be much smaller that the barotropic conversion rate and exhibits no clear seasonal changes. This indicates that the EKE variations are largely controlled by barotropic conversion of the seasonally varying regional circulation. By examining the seasonal background circulation changes, we find that the amplification of the barotropic eddy energy conversion rate in July-August is related to the seasonal evolution of the Mindanao Current and the New Guinea Coastal Current that amplifies the curvature and amplitude of the quasi-stationary meander of the NECC and results in an elevated EKE level through increased regional barotropic conversion.

  13. The equivalence of quasistatic flow in fluid-saturated porous media and Biot's slow wave in the limit of zero frequency

    NASA Astrophysics Data System (ADS)

    Chandler, Richard N.; Johnson, David Linton

    1981-05-01

    We have established in a simple and straightforward fashion that the analysis of quasistatic flow in fluid-saturated porous media due to Rice and Cleary is derivable from the low-frequency limit of Biot's slow compressional/diffusive mode. The single material parameter of the problem, the diffusivity, is simply related to the bulk and shear moduli and permeability of the skeletal frame and to the viscous and elastic properties of the constitutive media. Since this common theory treats fluid and solid displacements on an equal footing, it is the most general linearized description of the problem; other treatments are special cases. These latter include the rigid frame approximation used in the petroleum industry and the weak frame approximation used by De Gennes to describe the motion of polymer gels.

  14. Limited gene flow among brown bear populations in far Northern Europe? Genetic analysis of the east-west border population in the Pasvik Valley.

    PubMed

    Schregel, Julia; Kopatz, Alexander; Hagen, Snorre B; Brøseth, Henrik; Smith, Martin E; Wikan, Steinar; Wartiainen, Ingvild; Aspholm, Paul E; Aspi, Jouni; Swenson, Jon E; Makarova, Olga; Polikarpova, Natalia; Schneider, Michael; Knappskog, Per M; Ruokonen, Minna; Kojola, Ilpo; Tirronen, Konstantin F; Danilov, Pjotr I; Eiken, Hans Geir

    2012-07-01

    Noninvasively collected genetic data can be used to analyse large-scale connectivity patterns among populations of large predators without disturbing them, which may contribute to unravel the species' roles in natural ecosystems and their requirements for long-term survival. The demographic history of brown bears (Ursus arctos) in Northern Europe indicates several extinction and recolonization events, but little is known about present gene flow between populations of the east and west. We used 12 validated microsatellite markers to analyse 1580 hair and faecal samples collected during six consecutive years (2005-2010) in the Pasvik Valley at 70°N on the border of Norway, Finland and Russia. Our results showed an overall high correlation between the annual estimates of population size (N(c) ), density (D), effective size (N(e) ) and N(e) /N(c) ratio. Furthermore, we observed a genetic heterogeneity of ∼0.8 and high N(e) /N(c) ratios of ∼0.6, which suggests gene flow from the east. Thus, we expanded the population genetic study to include Karelia (Russia, Finland), Västerbotten (Sweden) and Troms (Norway) (477 individuals in total) and detected four distinct genetic clusters with low migration rates among the regions. More specifically, we found that differentiation was relatively low from the Pasvik Valley towards the south and east, whereas, in contrast, moderately high pairwise F(ST) values (0.91-0.12) were detected between the east and the west. Our results indicate ongoing limits to gene flow towards the west, and the existence of barriers to migration between eastern and western brown bear populations in Northern Europe.

  15. Limited Flow of Continental Crust at UHP Depths: Coupled Age and Trace-Element Analyses of Titanite in the Western Gneiss Region, Norway

    NASA Astrophysics Data System (ADS)

    Garber, J. M.; Hacker, B. R.; Kylander-Clark, A. R.

    2015-12-01

    Coupled age and trace-element data from titanites in the Western Gneiss Region (WGR) of Norway suggest that continental crust underwent limited recrystallization and ductile flow through ~40 My of deep subduction and subsequent exhumation. Precambrian igneous titanites in granitic to tonalitic orthogneisses from the WGR were metastably preserved though Caledonian ultrahigh-pressure (UHP) metamorphism and variably recrystallized through subsequent amphibolite-facies metamorphism from ~420-385 Ma. The inherited Precambrian titanites are not present everywhere but rather cluster primarily in a cooler "southern domain" (peak T ~650oC) and a hotter "northern domain" (peak T ~750-800oC).Titanite data were collected using LASS (laser-ablation split stream inductively-coupled plasma mass spectrometry) at UCSB, and a principal component analysis (PCA) was used to define age and trace-element populations. These data indicate that inherited titanites are LREE-enriched, HFSE-enriched, and have higher Th/U, consistent with Precambrian neocrystallization from a granitic melt. In contrast, the recrystallized titanites have generally lower Th/U and flat, LREE-depleted, or hump-shaped trace-element patterns. These data suggest that (1) Caledonian titanite recrystallization occurred in the presence of LREE-depleted melts or fluids, or that (2) recrystallization was accompanied by a "typical" granitic melt, but that titanite/bulk-rock distribution coefficients are different for neo- and recrystallization; on-going whole-rock analyses will clarify these hypotheses. Critically, the geochemical signature of recrystallized titanite in felsic orthogneisses is comparable across the entire WGR - emphasizing that the petrologic process of titanite recrystallization was similar orogen-wide, but was less extensive in the domains where inherited titanite was preserved. In this case, large volumes of crust outside of the "old domains" may also have retained metastable titanite during subduction

  16. Amazonian mid- to high-latitude glaciation on Mars: Supply-limited ice sources, ice accumulation patterns, and concentric crater fill glacial flow and ice sequestration

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.

    2014-02-01

    Crater deposit thicknesses (~50 m) cannot fill the craters in a time period compatible with the interpreted formation times of the Pedestal Crater mantled ice layers. We use a representative obliquity solution to drive an ice flow model and show that a cyclical pattern of multiply recurring layers can both fill the craters with a significant volume of ice, as well as transport debris from the crater walls out into the central regions of the craters. The cyclical pattern of waxing and waning mantling layers results in a rippled pattern of surface debris extending out into the crater interiors that would manifest itself as an observable concentric pattern, comparable in appearance to concentric crater fill. In this scenario, the formation of mantling sublimation till layers seals the accumulating ice and sequesters it from significant temperature variations at diurnal, annual and spin-axis/orbital cycle time scales, to produce ancient ice records preserved today below CCF crater floors. Lack of meltwater features associated with concentric crater fill provides evidence that the Late Amazonian climate did not exceed the melting temperature in the mid- to high-latitudes for any significant period of time. Continued sequestration of ice with time in CCF and related deposits (lobate debris aprons and lineated valley fill) further reduces the already supply-limited polar ice sources, suggesting that there has been a declining reservoir of available ice with each ensuing glacial period. Together, these deposits represent a candidate library of climate chemistry and global change dating from the Late Amazonian, and a non-polar water resource for future exploration.

  17. Enzymolysis kinetics, thermodynamics and model of porcine cerebral protein with single-frequency countercurrent and pulsed ultrasound-assisted processing.

    PubMed

    Zou, Ye; Ding, Yangyang; Feng, Weiwei; Wang, Wei; Li, Qian; Chen, Yao; Wu, Huiyu; Wang, Xintong; Yang, Liuqing; Wu, Xiangyang

    2016-01-01

    The present work investigated the enzymolysis kinetics, thermodynamics and model of porcine cerebral protein (PCP) which was pretreated by single-frequency countercurrent and pulsed ultrasound. The kinetic constants for ultrasonic pretreated and traditional enzymolysis have been determined. Results showed that the value of KM in ultrasonic PCP (UPCP) enzymolysis decreased by 9% over that in the traditional enzymolysis. The values of reaction rate constant (k) for UPCP enzymolysis increased by 207%, 121%, 62%, and 45% at 293, 303, 313 and 323 K, respectively. For the thermodynamic parameters, ultrasound decreased activation energy (Ea), change in enthalpy (ΔH) and entropy (ΔS) by 76%, 82% and 31% in PCP, respectively. However, ultrasound had little change in Gibbs free energy (ΔG) value in the temperature range of 293-323 K. Therefore, a general kinetic equation for the enzymolysis model of UPCP by a simple empirical equation was suggested. The experimental values fits with the enzymolysis kinetic model with a low average relative error (4%) confirmed that the kinetic model was accurate to reflect the enzymolysis process. The positive effect of single-frequency countercurrent and pulsed ultrasound in this study and application of the kinetic model may be useful for the release of bioactive peptides from meat processing by-products.

  18. Purification of α-glucosidase from mouse intestine by countercurrent chromatography coupled with a reverse micelle solvent system.

    PubMed

    He, Kai; Zou, Zongyao; Hu, Yinran; Yang, Yong; Xiao, Yubo; Gao, Pincao; Li, Xuegang; Ye, Xiaoli

    2016-02-01

    Countercurrent chromatography coupled with a reverse micelle solvent was applied to separate α-glucosidase, which is stable at pH 6.0-8.8, 15-50°C. The separation conditions are as follows: stationary phase: pH 4.0 Tris-HCl buffer phase containing 50 mM Tris-HCl and 50 mM KCl; mobile phase A: isooctane containing 50 mM anionic surfactant sodium di(2-ethylhexyl)sulfosuccinate; mobile phase B: 50 mM Tris-HCl buffer containing 500 mM KCl (pH 8.0); In total, 25 mL (23.9 mg) crude enzyme was injected through the injection valve, the enzymatic reaction and sodium dodecylsulfate polyacrylamide gel electrophoresis results imply that the activity of purified α-glucosidase is 6.63-fold higher than that of the crude enzyme. Therefore, countercurrent chromatography coupled with a reverse micelle solvent is capable for protein separation and enrichment.

  19. Isolation and purification of two antioxidant isomers of resveratrol dimer from the wine grape by counter-current chromatography.

    PubMed

    Kong, Qingjun; Ren, Xueyan; Hu, Ruilin; Yin, Xuefeng; Jiang, Guoshan; Pan, Yuanjiang

    2016-06-01

    Resveratrol dimers belong to a group of compounds called stilbenes, which along with proanthocyanidins, anthocyanins, catechins, and flavonols are natural phenolic compounds found in grapes and red wine. Stilbenes have a variety of structural isomers, all of which exhibit various biological properties. Counter-current chromatography with a two-phase solvent system composed of n-hexane/ethyl acetate/methanol/water (2:5:4:5, v/v/v/v) was applied to isolate and purify stilbene from the stems of wine grape. Two isomers of resveratrol dimers trans-ε-viniferin and trans-δ-viniferin were obtained from the crude sample in a one-step separation, with purities of 93.2 and 97.5%, respectively, as determined by high-performance liquid chromatography. The structures of these two compounds were identified by (1) H and (13) C NMR spectroscopy. In addition, their antioxidant activities were assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The antioxidant activities of trans-δ-viniferin were higher than that of trans-ε-viniferin in this model. This work demonstrated that counter-current chromatography is a powerful and effective method for the isolation and purification of polyphenols from wine grape. Additionally, the DPPH radical assay showed that the isolated component trans-δ-viniferin exhibited stronger antioxidant activities than trans-ε-viniferin and a little bit weaker than vitamin E at the same concentration.

  20. Isolation and purification of arctigenin from Fructus Arctii by enzymatic hydrolysis combined with high-speed counter-current chromatography.

    PubMed

    Liu, Feng; Xi, Xingjun; Wang, Mei; Fan, Li; Geng, Yanling; Wang, Xiao

    2014-02-01

    Enzymatic hydrolysis pretreatment combined with high-speed counter-current chromatography for the transformation and isolation of arctigenin from Fructus Arctii was successfully developed. In the first step, the extract solution of Fructus Arctii was enzymatic hydrolyzed by β-glucosidase. The optimal hydrolysis conditions were 40°C, pH 5.0, 24 h of hydrolysis time, and 1.25 mg/mL β-glucosidase concentration. Under these conditions, the content of arctigenin was transformed from 2.60 to 12.59 mg/g. In the second step, arctigenin in the hydrolysis products was separated and purified by high-speed counter-current chromatography with a two-phase solvent system composed of petroleum ether/ethyl acetate/methanol/water (10:25:15:20, v/v), and the fraction was analyzed by HPLC, ESI-MS, and (1)H NMR spectroscopy. Finally, 102 mg of arctigenin with a purity of 98.9% was obtained in a one-step separation from 200 mg of hydrolyzed sample.

  1. Preparative isolation and purification of antioxidative diarylheptanoid derivatives from Alnus japonica by high-speed counter-current chromatography.

    PubMed

    Lim, Soon Sung; Lee, Min Young; Ahn, Hong Ryul; Choi, Soon Jung; Lee, Jae-Yong; Jung, Sang Hoon

    2011-12-01

    This study employed the online HPLC-2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS)(+) bioassay to rapidly determine the antioxidant compounds occurring in the crude extract of Alnus japonica. The negative peaks of the ABTS(+) radical scavenging detection system, which indicated the presence of antioxidant activity, were monitored by measuring the decrease in absorbance at 734 nm. The ABTS(+)-based antioxidant activity profile showed that three negative peaks exhibited antioxidant activity. High-speed counter-current chromatography (HSCCC) was used for preparative scale separation of the three active peaks from the extract. The purity of the isolated compounds was analyzed by HPLC and their structures were identified by (1)H- and (13)C-nuclear magnetic resonance spectrometry (NMR), heteronuclear multiple bond correlation (HMBC), and heteronuclear single quantum correlation (HSQC). Two solvent systems composed of n-hexane/ethylacetate/methanol/water (4:6:4:6, v/v) and of ethyl acetate/methanol/water (1:0.1:1, v/v) were performed in high-speed counter-current chromatography. Consequently, a total of 527 mg of hirsutanonol 5-O-β-D-glucopyranoside, 80.04 mg of 3-deoxohirsutenonol 5-O-β-D-glucopyranoside, and 91.0 mg of hirsutenone were obtained with purity of 94.7, 90.5, and 98.6%, respectively.

  2. Review and evaluation of recent developments in melic inlet dynamic flow distortion prediction and computer program documentation and user's manual estimating maximum instantaneous inlet flow distortion from steady-state total pressure measurements with full, limited, or no dynamic data

    NASA Technical Reports Server (NTRS)

    Schweikhard, W. G.; Dennon, S. R.

    1986-01-01

    A review of the Melick method of inlet flow dynamic distortion prediction by statistical means is provided. These developments include the general Melick approach with full dynamic measurements, a limited dynamic measurement approach, and a turbulence modelling approach which requires no dynamic rms pressure fluctuation measurements. These modifications are evaluated by comparing predicted and measured peak instantaneous distortion levels from provisional inlet data sets. A nonlinear mean-line following vortex model is proposed and evaluated as a potential criterion for improving the peak instantaneous distortion map generated from the conventional linear vortex of the Melick method. The model is simplified to a series of linear vortex segments which lay along the mean line. Maps generated with this new approach are compared with conventionally generated maps, as well as measured peak instantaneous maps. Inlet data sets include subsonic, transonic, and supersonic inlets under various flight conditions.

  3. Application and comparison of high-speed countercurrent chromatography and high performance liquid chromatography in preparative enantioseparation of α-substitution mandelic acids.

    PubMed

    Tong, Shengqiang; Zhang, Hu; Shen, Mangmang; Ito, Yoichiro; Yan, Jizhong

    2015-04-01

    Preparative enantioseparations of α-cyclopentylmandelic acid and α-methylmandelic acid by high-speed countercurrent chromatography (HSCCC) and high performance liquid chromatography (HPLC) were compared using hydroxypropy-β-cyclodextrin (HP-β-CD) and sulfobutyl ether-β-cyclodextrin (SBE-β-CD) as the chiral mobile phase additives. In preparative HPLC the enantioseparation was achieved on the ODS C18 reverse phase column with the mobile phase composed of a mixture of acetonitrile and 0.10 mol L(-1) phosphate buffer at pH 2.68 containing 20 mmol L(-1) HP-β-CD for α-cyclopentylmandelic acid and 20 mmol L(-1) SBE-β-CD for α-methylmandelic acid. The maximum sample size for α-cyclopentylmandelic acid and α-methylmandelic acid was only about 10 mg and 5 mg, respectively. In preparative HSCCC the enantioseparations of these two racemates were performed with the two-phase solvent system composed of n-hexane-methyl tert.-butyl ether-0.1 molL(-1) phosphate buffer solution at pH 2.67 containing 0.1 mol L(-1) HP-β-CD for α-cyclopentylmandelic acid (8.5:1.5:10, v/v/v) and 0.1 mol L(-1) SBE-β-CD for α-methylmandelic acid (3:7:10, v/v/v). Under the optimum separation conditions, total 250 mg of racemic α-cyclopentylmandelic acid could be completely enantioseparated by HSCCC with HP-β-CD as a chiral mobile phase additive in a single run, yielding 105-110 mg of enantiomers with 95-98% purity and 85-90% recovery. But, no complete enantioseparation of α-methylmandelic acid was achieved by preparative HSCCC with either of the chiral selectors due to their limited enantioselectivity. In this paper preparative enantioseparation by HSCCC and HPLC was compared from various aspects.

  4. Application and comparison of high-speed countercurrent chromatography and high performance liquid chromatography in preparative enantioseparation of α-substitution mandelic acids

    PubMed Central

    Tong, Shengqiang; Zhang, Hu; Shen, Mangmang; Ito, Yoichiro; Yan, Jizhong

    2014-01-01

    Preparative enantioseparations of α-cyclopentylmandelic acid and α-methylmandelic acid by high-speed countercurrent chromatography (HSCCC) and high performance liquid chromatography (HPLC) were compared using hydroxypropy-β-cyclodextrin (HP-β-CD) and sulfobutyl ether-β-cyclodextrin (SBE-β-CD) as the chiral mobile phase additives. In preparative HPLC the enantioseparation was achieved on the ODS C18 reverse phase column with the mobile phase composed of a mixture of acetonitrile and 0.10 mol L−1 phosphate buffer at pH 2.68 containing 20 mmol L−1 HP-β-CD for α-cyclopentylmandelic acid and 20 mmol L−1 SBE-β-CD for α-methylmandelic acid. The maximum sample size for α-cyclopentylmandelic acid and α-methylmandelic acid was only about 10 mg and 5 mg, respectively. In preparative HSCCC the enantioseparations of these two racemates were performed with the two-phase solvent system composed of n-hexane-methyl tert.-butyl ether-0.1 molL−1 phosphate buffer solution at pH 2.67 containing 0.1 mol L−1 HP-β-CD for α-cyclopentylmandelic acid (8.5:1.5:10, v/v/v) and 0.1 mol L−1 SBE-β-CD for α-methylmandelic acid (3:7:10, v/v/v). Under the optimum separation conditions, total 250 mg of racemic α-cyclopentylmandelic acid could be completely enantioseparated by HSCCC with HP-β-CD as a chiral mobile phase additive in a single run, yielding 105-110 mg of enantiomers with 95-98% purity and 85-90% recovery. But, no complete enantioseparation of α-methylmandelic acid was achieved by preparative HSCCC with either of the chiral selectors due to their limited enantioselectivity. In this paper preparative enantioseparation by HSCCC and HPLC was compared from various aspects. PMID:25983356

  5. SIMULATION OF NON-AZEOTROPIC REFRIGERANT MIXTURES FOR USE IN A DUAL-CIRCUIT REFRIGERATOR/FREEZER WITH COUNTERCURRENT HEAT EXCHANGES

    EPA Science Inventory

    The paper discusses a refrigerator/freezer (RF) system that has two complete and independent refrigeration cycles for the two compartments. It uses a non-azeotropic refrigerant mixture (NARM) in each cycle and countercurrent heat exchangers throughout. This RF is housed in a stan...

  6. Investigation of Multiscale and Multiphase Flow, Transport and Reaction in Heavy Oil Recovery Processes

    SciTech Connect

    Yortsos, Yanis C.

    2002-10-08

    In this report, the thrust areas include the following: Internal drives, vapor-liquid flows, combustion and reaction processes, fluid displacements and the effect of instabilities and heterogeneities and the flow of fluids with yield stress. These find respective applications in foamy oils, the evolution of dissolved gas, internal steam drives, the mechanics of concurrent and countercurrent vapor-liquid flows, associated with thermal methods and steam injection, such as SAGD, the in-situ combustion, the upscaling of displacements in heterogeneous media and the flow of foams, Bingham plastics and heavy oils in porous media and the development of wormholes during cold production.

  7. Quantification and correction of the error due to limited PIV resolution on the accuracy of non-intrusive spatial pressure measurement using a DNS channel flow database

    NASA Astrophysics Data System (ADS)

    Liu, Xiaofeng; Siddle-Mitchell, Seth

    2016-11-01

    The effect of the subgrid-scale (SGS) stress due to limited PIV resolution on pressure measurement accuracy is quantified using data from a direct numerical simulation database of turbulent channel flow (JHTDB). A series of 2000 consecutive realizations of sample block data with 512x512x49 grid nodal points were selected and spatially filtered with a coarse 17x17x17 and a fine 5x5x5 box averaging, respectively, giving rise to corresponding PIV resolutions of roughly 62.6 and 18.4 times of the viscous length scale. Comparison of the reconstructed pressure at different levels of pressure gradient approximation with the filtered pressure shows that the neglect of the viscous term leads to a small but noticeable change in the reconstructed pressure, especially in regions near the channel walls. As a contrast, the neglect of the SGS stress results in a more significant increase in both the bias and the random errors, indicating the SGS term must be accounted for in PIV pressure measurement. Correction using similarity SGS modeling reduces the random error due to the omission of SGS stress from 114.5% of the filtered pressure r.m.s. fluctuation to 89.1% for the coarse PIV resolution, and from 66.5% to 35.9% for the fine PIV resolution, respectively, confirming the benefit of the error compensation method and the positive influence of increasing PIV resolution on pressure measurement accuracy improvement.

  8. Mitochondrial population structure and post-glacial dispersal of longnose sucker Catostomus catostomus in Labrador, Canada: evidence for multiple refugial origins and limited ongoing gene flow.

    PubMed

    Langille, B L; Perry, R; Keefe, D; Barker, O; Marshall, H D

    2016-08-01

    Two hundred and eighty-seven longnose sucker Catostomus catostomus were collected from 14 lakes in Labrador, 52 from three lakes in Ontario, 43 from two lakes in British Columbia and 32 from a lake in Yukon; a total of 414 in all. The resulting 34 haplotypes (20 in Labrador) contained moderate haplotypic diversity (h = 0·657) and relatively low nucleotide diversity (π = 3·730 × 10(-3) . Mean ϕST (0·453, P < 0·05) over all populations revealed distinct genetic structuring among C. catostomus populations across Canada, based on province, which was validated by the analysis and spatial analysis of molecular variance (c. 80% variation between provinces). These results probably reflect the historical imprint of recolonization from different refugia and possibly indicate limited ongoing gene flow within provinces. A haplotype network revealed one major and two minor clades within Labrador that were assigned to the Atlantic, Beringian and Mississippian refugia, respectively, with tests of neutrality and mismatch distribution indicative of a recent population expansion in Labrador, dated between c. 3500 and 8300 years ago.

  9. Estimation of Blood Flow With Radioactive Tracers

    PubMed Central

    Bassingthwaighte, James B.; Holloway, G. Allen

    2010-01-01

    The techniques of tracer dilution in the circulation, and of tracer uptake by and washout from an organ, may be described using expressions that are general and are not dependent on specific models such as exponentials. The expressions have been applied to the measurement of cardiac output using impulse and constant rate injection techniques. Further expressions have been given for estimating organ blood flow from inflow/outflow concentration-time curves, washout curves, and from the distribution of deposited tracer. Some problems with respect to the use of deposition techniques as they are ordinarily applied to the estimation of regional blood flow must be considered, particularly where there are capillary beds in series or where there is countercurrent diffusional shunting of diffusible tracers between inflow and outflow. This review deals with these various aspects of tracer theory as they relate to the measurement of blood flow. PMID:775641

  10. Debris Flow Initiation and Fan Reworking in the Green River Canyons of the Eastern Uinta Mountains: The Limited Role of Wildfire and the Significance of Low-Magnitude Floods

    NASA Astrophysics Data System (ADS)

    Larsen, I. J.; Schmidt, J. C.; Pederson, J. L.; Martin, J. A.

    2003-12-01

    The primary determinant on channel organization of the Green River in the canyons of the eastern Uinta Mountains is the occurrence and frequency of debris flows in tributary watersheds. The frequency of these debris flows appears to be related to climatic factors, not factors related to wildfire. Debris flows in the eastern Uinta Mountains occur by a process known as the firehose effect, wherein overland flow generated on bedrock slopes cascades down steep cliffs and saturates and impacts colluvium stored in bedrock hollows. The colluvium fails, initiating debris flows that travel downslope to the Green River. The dry climate and high-strength bedrock cause hillslopes to be weathering-limited, prohibiting the formation of extensive regolith and vegetative cover. This reduces the degree vegetation regulates geomorphic processes and, in turn, causes wildfire to have little influence on debris flow initiation; slight increases in watershed runoff do not appear to alter the likelihood of this process occurring. A secondary determinant on channel organization in debris fan-dominated canyons are the magnitude of mainstem discharges and the degree to which they rework debris flow deposits; in this case flows are regulated by Flaming Gorge Dam. Substantial reworking of debris flow deposits can be accomplished by mainstem floods with discharges greater than 75%\\ of the pre-dam two year flood, whereas floods with magnitudes less than 40%\\ of the pre-dam 2-year flood do little reworking.

  11. Countercurrent Chromatographic Separation of Proteins Using an Eccentric Coiled Column with Synchronous and Nonsynchronous Type-J Planetary Motions

    PubMed Central

    SHINOMIYA, Kazufusa; YOSHIDA, Kazunori; TOKURA, Koji; TSUKIDATE, Etsuhiro; YANAGIDAIRA, Kazuhiro; ITO, Yoichiro

    2015-01-01

    Protein separation was performed using the high-speed counter-current chromatograph (HSCCC) at both synchronous and nonsynchronous type-J planetary motions. The partition efficiency was evaluated with two different column configurations, eccentric coil and toroidal coil, on the separation of a set of stable protein samples including cytochrome C, myoglobin and lysozyme with a polymer phase system composed of 12.5% (w/w) polyethylene glycol 1000 and 12.5% (w/w) dibasic potassium phosphate. Better peak resolution was obtained by the eccentric coil than by the toroidal coil using either lower or upper phase as the mobile phase. The peak resolution was further improved using the eccentric coil by the nonsynchronous type-J planetary motion with the combination of 1066 rpm of column rotation and 1000 rpm of revolution. PMID:25765276

  12. PREPARATIVE SEPARATION OF AXIFOLIN-3-GLUCOSIDE, HYPEROSIDE AND AMYGDALIN FROM PLANT EXTRACTS BY HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY.

    PubMed

    Wei, Yun; Xie, Qianqian; Ito, Yoichiro

    2009-01-01

    High-speed countercurrent chromatography (HSCCC) was successfully used to isolate three bioactive compounds, i.e., amygdalin from bitter almond and taxifolin-3-glucoside and quercetin-3-galactoside (hyperoside) from water extract of Agrimonia pilosa Ledeb, respectively. From 1 g of the crude extract 65 mg of amygdalin was isolated at 97% purity using a two-phase solvent system composed of ethyl acetate-n-butanol-water (5:2:5, v/v) by preparative HSCCC. From a 400 mg amount of crude extract of Agrimonia pilosa Ledeb, 11 mg of taxifolin-3-glucoside and 8 mg of hyperoside were isolated at 96% purity using a two-phase solvent system composed of ethyl acetate-methanol-water (25:1:25, v/v) similarly by preparative HSCCC. The final structural identification was performed by MS, (1)H-NMR and (13)C-NMR Spectra.

  13. Comparison of counter-current chromatography and preparative high performance liquid chromatography applied to separating minor impurities in drug preparations.

    PubMed

    Li, Shucai; Wang, Wenwen; Tang, Huan; Chen, Kai; Yang, Jianhong; He, Linhong; Ye, Haoyu; Peng, Aihua; Chen, Lijuan

    2014-05-30

    Drug impurity profiling and identification are carried out along with the drug discovery process. Due to its inherent low concentration in drug products, the isolation and purification of impurities present a challenge to drug development processes. In our development of honokiol and quercetin as anticancer drug candidates, counter-current chromatography (CCC) and preparative HPLC were used for the impurity profiling and identification of honokiol and quercetin. Several performance parameters such as separation column volume, maximum sample loading, separation time, solvent consumption and sample throughput were investigated in order to compare the separation efficiency. We found that the sample loading capacity and therefore the throughput of preparative HPLC were not satisfactory, while CCC provided larger sample loading (especially for a sample with poor solubility), consumed less solvent and produced higher throughput than preparative HPLC. Six impurities of honokiol including one new compound were isolated in the present work.

  14. A comprehensive classification of solvent systems used for natural product purifications in countercurrent and centrifugal partition chromatography.

    PubMed

    Skalicka-Woźniak, Krystyna; Garrard, Ian

    2015-11-01

    Using both library paper copies and modern electronic copies, every known, published, English-language journal paper that employs either countercurrent or centrifugal partition chromatography solvent systems for natural product purifications has been studied and the solvent systems classified in a comprehensive database. Papers were studied from the earliest found examples containing natural product separations in 1984 until the end of 2014. In total, 2594 solvent systems have been classified, of which 272 are gradient systems. To observe any trends or patterns in the data, the natural product solutes were divided into 21 classes and the solvent systems into 7 different types. The complete database, sorted according to natural product class, is available for download to assist separation scientists in future liquid-liquid chromatography purifications.

  15. Isolation of chlorogenic acid from Mutellina purpurea L. herb using high-performance counter-current chromatography.

    PubMed

    Sieniawska, Elwira; Skalicka-Woźniak, Krystyna

    2014-01-01

    The aim of the study was to explore proper isolation conditions of chlorogenic acid from the herb of Mutelina purpurea L. - a new source of this bioactive molecule. The accelerated solvent extraction (ASE) with 40% aqueous solution of methanol combined with high-performance counter-current chromatography (HPCCC) was utilised for the efficient extraction and the separation of chlorogenic acid from the M. purpurea herb in less than 30 min. The structure of the obtained compound was confirmed by mass spectrometry and NMR analysis. The preparative HPCCC was performed using the mixture of ethyl acetate, butanol and water (4:1:5, v/v/v) in the reverse-phase mode. The chlorogenic acid was isolated from this herb for the first time, yielding 96% purity. The ASE with 40% methanol combined with HPCCC separation was proven to be a useful tool for quick and efficient isolation of chlorogenic acid from M. purpurea.

  16. Comparison of preparative reversed phase liquid chromatography and countercurrent chromatography for the kilogram scale purification of crude spinetoram insecticide.

    PubMed

    DeAmicis, Carl; Edwards, Neil A; Giles, Michael B; Harris, Guy H; Hewitson, Peter; Janaway, Lee; Ignatova, Svetlana

    2011-09-09

    Reversed phase HPLC (RP-HPLC) and high performance countercurrent chromatography (HPCCC) were compared for the pilot scale purification of two semi-synthetic spinosyns, spinetoram-J and spinetoram-L, the major components of the commercial insecticide spinetoram. Two, independently performed, 1 kg, purification campaigns were compared. Each method resulted in the isolation of both components at a purity of >97% and yields for spinetoram-J and spinetoram-L of >93% and ≥ 63% of theoretical, respectively. The HPCCC process produced a 2-fold higher throughput and consumed approximately 70% less solvent than preparative scale RP-HPLC, the volume of product containing fractions from HPCCC amounted to 7% of that produced by HPLC and so required much less post-run processing.

  17. Facilitating the use of counter-current chromatography in pharmaceutical purification through use of organic solvent nanofiltration.

    PubMed

    Rundquist, Elin; Pink, Christopher; Vilminot, Elsa; Livingston, Andrew

    2012-03-16

    This paper demonstrates a combined approach for separating an active pharmaceutical ingredient (API) from a heavily contaminated waste stream. The approach uses organic solvent nanofiltration (OSN) to improve the application of counter-current chromatography (CCC) in an industrial process. OSN provides an efficient route for exchanging solutes from the process solvent into the desired mobile phase for CCC, generating a CCC feed containing less than 0.01% (area % by GC) of the original process solvents. The high solvent burden of CCC was additionally reduced through recovery of mobile phase using OSN, with the recovered solvent containing less than 1% (area % by HPLC) impurities. The recovered solvent was then successfully recycled into a subsequent CCC run with no indication of impurity build-up. Coupling OSN with CCC improved the mass-intensity of the CCC process, reducing the solvent use by 56%. OSN can be a useful tool in facilitating the application of CCC to pharmaceutical process streams.

  18. Two-stage fractionation of polar alkaloids from Rhizoma coptidis by countercurrent chromatography considering the strategy of reactive extraction.

    PubMed

    Li, Yang; Cai, Fanfan; Zhang, Min; Zhang, Hongyang; Wang, Yuerong; Hu, Ping

    2015-01-23

    Separation of polar alkaloids by countercurrent chromatography (CCC) is challengeable due to their close partition behaviors in solvent system. In this paper, a two-stage method for isolation of epiberberine, jatrorrhizine, palmatine, coptisine, and berberine from Rhizoma coptidis was presented. The first stage separation performed on CCC was based on the principle of reactive extraction. Trifluoroacetic acid was acted as a modulator to selectively react with alkaloids, which changed their partition coefficients in solvent system. Purified epiberberine and other partially separated targets were eluted by ammonium adjusted mobile phase. In the second stage, four alkaloids were purified in pH-zone-refining CCC mode. All the targets collected were over 97% pure determined by HPLC. The method developed demonstrates performing of reactive extraction on standard CCC as an option for separation of polar alkaloids from medicinal plants.

  19. Separation and purification of astaxanthin from Phaffia rhodozyma by preparative high-speed counter-current chromatography.

    PubMed

    Du, Xiping; Dong, Congcong; Wang, Kai; Jiang, Zedong; Chen, Yanhong; Yang, Yuanfan; Chen, Feng; Ni, Hui

    2016-09-01

    An effective high-speed counter-current chromatography (HSCCC) method was established for the preparative isolation and purification of astaxanthin from Phaffia rhodozyma. With a two-phase solvent system composed of n-hexane-acetone-ethanol-water (1:1:1:1, v/v/v/v), 100mg crude extract of P. rhodozyma was separated to yield 20.6mg of astaxanthin at 92.0% purity. By further one step silica gel column chromatography, the purity reached 99.0%. The chemical structure of astaxanthin was confirmed by thin layer chromatography (TLC), UV spectroscopy scanning, high performance liquid chromatography with a ZORBAX SB-C18 column and a Waters Nova-pak C18 column, and ESI/MS/MS.

  20. Preparative isolation and purification of xanthohumol from hops (Humulus lupulus L.) by high-speed counter-current chromatography.

    PubMed

    Chen, Qi-He; Fu, Ming-Liang; Chen, Miao-Miao; Liu, Jing; Liu, Xiao-Jie; He, Guo-Qing; Pu, Shou-Cheng

    2012-05-01

    Xanthohumol (XN) and related prenylflavonoids are the main bioactive components of hops (Humulus lupulus L.). The current work is to investigate the use of high-speed counter-current chromatography (HSCCC) in search for high isolation of xanthohumol from hops. A solvent system consisted of n-hexane-ethyl acetate-methanol-water at a volume ratio of 5:5:4:3 was employed. The results demonstrated that the constructed method could be well applied for the isolation of xanthohumol from hops extract. After HSCCC isolation procedure, the purity of xanthohumol was over 95% assayed by HPLC and the yield of extraction was 93.60%. The chemical structure identification of xanthohumol was carried out by UV, (1)H NMR and (13)C NMR. The present results demonstrated that xanthohumol could be efficiently obtained using a single HSCCC step from H. lupulus L. extract.

  1. Isolation and purification of orientin and vitexin from Trollius chinensis Bunge by high-speed counter-current chromatography.

    PubMed

    Yu, Xiao-Xue; Huang, Jie-Yun; Xu, Dan; Xie, Zhi-Yong; Xie, Zhi-Sheng; Xu, Xin-Jun

    2014-01-01

    Orientin and vitexin are the two main bioactive compounds in Trollius chinensis Bunge. In this study, a rapid method was established for the isolation and purification of orientin and vitexin from T. chinensis Bunge using high-speed counter-current chromatography in one step, with a solvent system of ethyl acetate-ethanol-water (4:1:5, v/v/v). A total of 9.8 mg orientin and 2.1 mg vitexin were obtained from 100 mg of the ethyl acetate extract, with purities of 99.2% and 96.0%, respectively. Their structures were identified by UV, MS and NMR. The method was efficient and convenient, which could be used for the preparative separation of orientin and vitexin from T. chinensis Bunge.

  2. Isolation and purification of oridonin from the whole plant of Isodon rubescens by high-speed counter-current chromatography.

    PubMed

    He, Fa; Bai, Yuhua; Wang, Jing; Wei, Jing; Yu, Chunyue; Li, Sen; Yang, Weili; Han, Chenghua

    2011-09-14

    Semi-preparative high-speed counter-current chromatography (HSCCC) was successfully used for isolation and purification of oridonin from Isodon rubescens by using a two-phase-solvent system composed of n-hexane-ethyl acetate-methanol-water (2.8:5:2.8:5, v/v/v/v). The targeted compound isolated, collected and purified by HSCCC was analyzed by high performance liquid chromatography (HPLC). A total of 40.6 mg of oridonin with the purity of 73.5% was obtained in less than 100 min from 100 mg of crude Isodon rubescens extract. The chemical structure of the compound was identified by IR, 1H-NMR and 13C-NMR.

  3. Preparative isolation and purification of three sesquiterpenoid lactones from Eupatorium lindleyanum DC. by high-speed counter-current chromatography.

    PubMed

    Yan, Guilong; Ji, Lilian; Luo, Yuming; Hu, Yonghong

    2012-07-27

    A high-speed counter-current chromatography (HSCCC) method was established for the preparative separation of three sesquiterpenoid lactones from Eupatorium lindleyanum DC. The two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:4:2:3, v/v/v/v) was selected. From 540 mg of the n-butanol fraction of Eupatorium lindleyanum DC., 10.8 mg of 3β-hydroxy-8β-[4'-hydroxytigloyloxy]-costunolide, 17.9 mg of eupalinolide A and 19.3 mg of eupalinolide B were obtained in a one-step HSCCC separation, with purities of 91.8%, 97.9% and 97.1%, respectively, as determined by HPLC. Their structures were further identified by ESI-MS and ¹H-NMR.

  4. Separation and purification of harmine and harmaline from Peganum harmala using pH-zone-refining counter-current chromatography.

    PubMed

    Wang, Xiao; Geng, Yanling; Wang, Daijie; Shi, Xingang; Liu, Jianhua

    2008-10-01

    pH-zone-refining counter-current chromatography was successfully applied to the separation of alkaloids from a crude extract of Peganum harmala L. using a multilayer coil planet centrifuge. The experiment was performed with a two-phase solvent system composed of methyl tert-butyl ether/THF/water (2:2:3 by volume) where triethylamine (10 mM) was added to the upper organic stationary phase as a retainer and hydrochloric acid (5 mM) to the aqueous mobile phase as an eluter. From 1.2 g of the crude extract, 554 mg harmine and 325 mg harmaline were obtained each with a purity of over 96% as determined by HPLC. The structures of the isolated compounds were identified by electron ionization MS (EI-MS), (1)H NMR, and (13)C NMR.

  5. Using an aqueous two-phase polymer-salt system to rapidly concentrate viruses for improving the detection limit of the lateral-flow immunoassay.

    PubMed

    Jue, Erik; Yamanishi, Cameron D; Chiu, Ricky Y T; Wu, Benjamin M; Kamei, Daniel T

    2014-12-01

    The development of point-of-need (PON) diagnostics for viruses has the potential to prevent pandemics and protects against biological warfare threats. Here we discuss the approach of using aqueous two-phase systems (ATPSs) to concentrate biomolecules prior to the lateral-flow immunoassay (LFA) for improved viral detection. In this paper, we developed a rapid PON detection assay as an extension to our previous proof-of-concept studies which used a micellar ATPS. We present our investigation of a more rapid polymer-salt ATPS that can drastically improve the assay time, and show that the phase containing the concentrated biomolecule can be extracted prior to macroscopic phase separation equilibrium without affecting the measured biomolecule concentration in that phase. We could therefore significantly decrease the time of the diagnostic assay with an early extraction time of just 30 min. Using this rapid ATPS, the model virus bacteriophage M13 was concentrated between approximately 2 and 10-fold by altering the volume ratio between the two phases. As the extracted virus-rich phase contained a high salt concentration which destabilized the colloidal gold indicator used in LFA, we decorated the gold nanoprobes with polyethylene glycol (PEG) to provide steric stabilization, and used these nanoprobes to demonstrate a 10-fold improvement in the LFA detection limit. Lastly, a MATLAB script was used to quantify the LFA results with and without the pre-concentration step. This approach of combining a rapid ATPS with LFA has great potential for PON applications, especially as greater concentration-fold improvements can be achieved by further varying the volume ratio. Biotechnol. Bioeng. 2014;111: 2499-2507. © 2014 Wiley Periodicals, Inc.

  6. Flow Curve Determination at Large Plastic Strain Levels: Limitations of the Membrane Theory in the Analysis of the Hydraulic Bulge Test

    NASA Astrophysics Data System (ADS)

    Lemoine, X.; Iancu, A.; Ferron, G.

    2011-05-01

    Nowadays, an accurate determination of the true stress-strain curve is a key-element for all finite element (FE) forming predictions. Since the introduction of Advanced High Strength Steels (AHSS) for the automotive market, the standard uniaxial tension test suffers the drawback of relatively low uniform elongations. The extrapolation of the uniaxial stress-strain curve up to large strains is not without consequence in forming predictions—especially formability and springback. One of the means to solve this problem is to use experimental tests where large plastic strain levels can be reached. The hydraulic bulge test is one of these tests. The effective plastic strain levels reached in the bulge test are of about 0.7. From an experimental standpoint, the biaxial flow stress is estimated using measurement of fluid pressure, and calculation of thickness and curvature at the pole, via appropriate measurements and assumptions. The biaxial stress at the pole is determined using the membrane equilibrium equation. The analysis proposed in this paper consists of performing "virtual experiments" where the results obtained by means of FE calculations are used as input data for determining the biaxial stress-strain law in agreement with the experimental procedure. In this way, a critical discussion of the experimental procedure can be made, by comparing the "experimental" stress-strain curve (Membrane theory curve) with the "reference" one introduced in the simulations. In particular, the influences of the "(die diameter)/thickness" ratio and of the plastic anisotropy are studied, and limitations of the hydraulic bulge test analysis are discussed.

  7. Combining Coronary Angiography and Myocardial Perfusion by Computed Tomography in the Identification of Flow-Limiting Stenosis – The CORE320 study

    PubMed Central

    Magalhães, Tiago A.; Kishi, Satoru; George, Richard; Arbab-Zadeh, Armin; Vavere, Andrea; Cox, Christopher; Matheson, Matthew B.; Miller, Julie; Brinker, Jeffrey; Di Carli, Marcelo; Rybicki, Frank J.; Rochitte, Carlos E.; Clouse, Melvin; Lima, João A.C.

    2015-01-01

    Background The combination of coronary computed tomography angiography (CTA) and myocardial CT perfusion (CTP) is gaining increasing acceptance, but a standardized approach to be implemented in the clinical setting is necessary. Objectives To investigate the accuracy of a combined coronary CTA and myocardial CTP comprehensive protocol compared to coronary CTA alone, using a combination of invasive coronary angiography (ICA) and Single-Photon Emission Computed Tomography (SPECT) as reference. Methods Three-hundred eighty-one patients included in CORE320 trial were analyzed in this study. Flow-limiting stenosis was defined as the presence of ≥50% stenosis by ICA with a related perfusion deficit by SPECT. The combined CTA+CTP definition of disease was the presence of a ≥50% stenosis with a related perfusion deficit. All data sets were analyzed by two experienced readers, aligning anatomical findings by CTA with perfusion deficits by CTP. Results Mean patient age was 62±6 years (66% male), 27% with prior history of myocardial infarction. In a per-patient analysis, sensitivity for CTA alone was 93% specificity was 54%, positive predictive value (PPV) was 55%; negative predictive value (NPV) 93% and overall accuracy was 69%. After combining CTA and CTP, sensitivity was 78%, specificity 73%, NPV 64%; PPV 0.85% and overall accuracy was 75%. In a per-vessel analysis, overall accuracy of CTA alone was 73%as compared to 79% for the combination of CTA and CTP (p<0.0001 for difference). Conclusions Combining coronary CTA and myocardial CTP findings through a comprehensive protocol is feasible. While sensitivity is lower, specificity and overall accuracy are higher than assessment by coronary CTA when compared against a reference standard of stenosis with an associated perfusion deficit. PMID:25977111

  8. Effect of gas-liquid flow pattern and microbial diversity analysis of a pilot-scale biotrickling filter for anoxic biogas desulfurization.

    PubMed

    Almenglo, Fernando; Bezerra, Tercia; Lafuente, Javier; Gabriel, David; Ramírez, Martín; Cantero, Domingo

    2016-08-01

    Hydrogen sulfide removal from biogas was studied under anoxic conditions in a pilot-scale biotrickling filter operated under counter- and co-current gas-liquid flow patterns. The best performance was found under counter-current conditions (maximum elimination capacity of 140 gS m(-3) h(-1)). Nevertheless, switching conditions between co- and counter-current flow lead to a favorable redistribution of biomass and elemental sulfur along the bed height. Moreover, elemental sulfur was oxidized to sulfate when the feeding biogas was disconnected and the supply of nitrate (electron acceptor) was maintained. Removal of elemental sulfur was important to prevent clogging in the packed bed and, thereby, to increase the lifespan of the packed bed between maintenance episodes. The larger elemental sulfur removal rate during shutdowns was 59.1 gS m(-3) h(-1). Tag-encoded FLX amplicon pyrosequencing was used to study the diversity of bacteria under co-current flow pattern with liquid recirculation and counter-current mode with a single-pass flow of the liquid phase. The main desulfurizing bacteria were Sedimenticola while significant role of heterotrophic, opportunistic species was envisaged. Remarkable differences between communities were found when a single-pass flow of industrial water was fed to the biotrickling filter.

  9. New solvent systems for gradient counter-current chromatography in separation of betanin and its derivatives from processed Beta vulgaris L. juice.

    PubMed

    Spórna-Kucab, Aneta; Garrard, Ian; Ignatova, Svetlana; Wybraniec, Sławomir

    2015-02-06

    Betalains, natural plant pigments, are beneficial compounds due to their antioxidant and possible chemoprotective properties. A mixture of betalains: betanin/isobetanin, decarboxybetanins and neobetanin from processed red beet roots (Beta vulgaris L.) juice was separated in food-grade, gradient solvent systems using high-performance counter-current chromatography (HPCCC). The decarboxylated and dehydrogenated betanins were obtained by thermal degradation of betanin/isobetanin from processed B. vulgaris L. juice under mild conditions. Two solvent systems (differing in their composition by phosphoric acid and ethanol volume gradient) consisting of BuOH-EtOH-NaClsolution-H2O-H3PO4 (v/v/v/v/v, 1300:200-1000:1300:700:2.5-10) in the 'tail-to-head' mode were run. The flow rate of the mobile phase (organic phase) was 1.0 or 2.0 ml/min and the column rotation speed was 1,600 rpm (20°C). The retention of the solvent system stationary phase (aqueous phase) was ca. 80%. The system with the acid and ethanol volume gradient consisting of BuOH-EtOH-NaClsolution-H2O-H3PO4 (v/v/v/v/v, 1300:200-240:1300:700:2.5-4.5) pumped at 2.0 ml/min was the most effective for a separation of betanin/isobetanin, 17-decarboxy-betanin/-isobetanin, 2-decarboxy-betanin/-isobetanin, 2,17-bidecarboxy-betanin/-isobetanin pairs as well as neobetanin. The pigments were detected by LC-DAD and LC-MS. The results are crucial in the application of completely food-grade solvent systems in separation of food-grade compounds as well, and the systems can possibly be extended to other ionizable and polar compounds with potential health benefits. In particular, the method is applicable for the isolation and purification of betalains present in such rich sources as B. vulgaris L. roots as well as cacti fruits and Amaranthaceae flowering plants due to modification possibilities of the solvent systems polarity.

  10. New small-scale cross-axis coil planet centrifuge. The design of the apparatus and its application to counter-current chromatographic separation of proteins with aqueous-aqueous polymer phase systems.

    PubMed

    Shinomiya, Kazufusa; Yanagidaira, Kazuhiro; Ito, Yoichiro

    2006-02-03

    The cross-axis coil planet centrifuge (X-axis CPC) is useful for partitioning macromolecules with aqueous-aqueous polymer phase systems. The floor model we have built with a pair of separation columns had some shortcomings such as requirement of large space, short life of the flow tubes, and difficulty in installing columns. In order to improve the partition efficiency and the utility of counter-current chromatography (CCC), a new small-scale X-axis CPC was designed and fabricated in our laboratory. The down-sizing of the apparatus was done by reducing the scale to about 1/2 of our original model of X-1.5L type with several improvements. Performance of the apparatus was evaluated on protein separation using an aqueous-aqueous polymer phase system composed of polyethylene glycol 1000 and dibasic potassium phosphate with four multilayer coiled columns. A series of experiments revealed that the combination of right- and left-handed coils produced the best partition efficiencies for both lower and upper mobile phases by selecting the revolution direction. The overall results indicate that the head-tail elution mode substantially affects to the peak resolution and stationary phase retention. This new X-axis CPC would be useful for the separation of various kinds of biologically active compounds.

  11. Advances in gas-liquid flows 1990

    SciTech Connect

    Kim, J.M. . Nuclear Reactor Lab.); Rohatgi, U.S. ); Hashemi, A. )

    1990-01-01

    Gas-liquid two-phase flows commonly occur in nature and industrial applications. Rain, clouds, geysers, and waterfalls are examples of natural gas-liquid flow phenomena, whereas industrial applications can be found in nuclear reactors, steam generators, boilers, condensers, evaporators, fuel atomization, heat pipes, electronic equipment cooling, petroleum engineering, chemical process engineering, and many others. The household-variety phenomena such as garden sprinklers, shower, whirlpool bath, dripping faucet, boiling tea pot, and bubbling beer provide daily experience of gas-liquid flows. The papers presented in this volume reflect the variety and richness of gas-liquid two-phase flow and the increasing role it plays in modern technology. This volume contains papers dealing with some recent development in gas-liquid flow science and technology, covering basic gas-liquid flows, measurements and instrumentation, cavitation and flashing flows, countercurrent flow and flooding, flow in various components and geometries liquid metals and thermocapillary effects, heat transfer, nonlinear phenomena, instability, and other special and general topics related to gas-liquid flows.

  12. Unilateral fetal-type circle of Willis anatomy causes right-left asymmetry in cerebral blood flow with pseudo-continuous arterial spin labeling: A limitation of arterial spin labeling-based cerebral blood flow measurements?

    PubMed

    Barkeij Wolf, Jurriaan Jh; Foster-Dingley, Jessica C; Moonen, Justine Ef; van Osch, Matthias Jp; de Craen, Anton Jm; de Ruijter, Wouter; van der Mast, Roos C; van der Grond, Jeroen

    2016-09-01

    The accuracy of cerebral blood flow measurements using pseudo-continuous arterial spin labeling can be affected by vascular factors other than cerebral blood flow, such as flow velocity and arterial transit time. We aimed to elucidate the effects of common variations in vascular anatomy of the circle of Willis on pseudo-continuous arterial spin labeling signal. In addition, we investigated whether possible differences in pseudo-continuous arterial spin labeling signal could be mediated by differences in flow velocities. Two hundred and three elderly participants underwent magnetic resonance angiography of the circle of Willis and pseudo-continuous arterial spin labeling scans. Mean pseudo-continuous arterial spin labeling-cerebral blood flow signal was calculated for the gray matter of the main cerebral flow territories. Mean cerebellar gray matter pseudo-continuous arterial spin labeling-cerebral blood flow was significantly lower in subjects having a posterior fetal circle of Willis variant with an absent P1 segment. The posterior fetal circle of Willis variants also showed a significantly higher pseudo-continuous arterial spin labeling-cerebral blood flow signal in the ipsilateral flow territory of the posterior cerebral artery. Flow velocity in the basilar artery was significantly lower in these posterior fetal circle of Willis variants. This study indicates that pseudo-continuous arterial spin labeling measurements underestimate cerebral blood flow in the posterior flow territories and cerebellum of subjects with a highly prevalent variation in circle of Willis morphology. Additionally, our data suggest that this effect is mediated by concomitant differences in flow velocity between the supplying arteries.

  13. Isolation of the new minor constituents dihydropyranochromone and furanocoumarin from fruits of Peucedanum alsaticum L. by high-speed counter-current chromatography.

    PubMed

    Skalicka-Woźniak, Krystyna; Mroczek, Tomasz; Garrard, Ian; Głowniak, Kazimierz

    2009-07-24

    A preparative high-speed counter-current chromatography (HSCCC) method was successfully used for isolation of two new minor compounds--alsaticol and alsaticocoumarin A. A two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:1:1:1) was developed. Compounds were obtained from the dichloromethane extract of Peucedanum alsaticum fruits and their identification was performed with NMR and MS methods. Optimized HSCCC offers a rapid method of obtaining new natural compounds.

  14. The 8th International Conference on Counter-current Chromatography held at Brunel University, London, UK, July 23-25, 2014.

    PubMed

    Ignatova, Svetlana; Sutherland, Ian

    2015-12-18

    The 8th International Conference on Counter-current Chromatography (CCC2014) was held at Brunel University London from July 23rd to 25th, 2014. It has been 14 years since Brunel hosted the first International Conference on CCC (CCC2000) at the beginning of the millennium and therefore, it was a good opportunity to review the progress of this emerging technology and particularly the impact it is having with industry today.

  15. Separation of caffeoylquinic acids and flavonoids from Asteris souliei by high-performance counter-current chromatography and their anti-inflammatory activity in vitro.

    PubMed

    Zhang, Qiang; Pei, He-Ying; Chen, Kai; Tang, Huan; Wu, Bo; Tang, Ming-Hai; Peng, Ai-Hua; Ye, Hao-Yu; Chen, Li-Juan

    2017-03-23

    Eleven compounds were successfully separated from Asteris souliei by using a two-step high-performance counter-current chromatography method. The first step involved a reversed phase isocratic counter-current chromatography separation using hexane/ethyl acetate/methanol/water (1:0.8:1:1 v/v), which produced three fractions, the first two of which were mixtures. The second step used step-gradient reversed-phase counter-current chromatography with hexane/butanol/ethyl acetate/methanol/water (1:0.5:3.5:1:4 v/v) initially followed by hexane/ethyl acetate/methanol/water (1:2:1:2 v/v) to separate Fraction 1 into seven compounds; and hexane/ethyl acetate/methanol/water (1:1:1:1.2 v/v) to separate Fraction 2 into three further compounds. The chemical structures of the separated compounds were identified by ESI-MS and NMR spectroscopy ((1) H and (13) C). Baicalin (5), eriodictyol (7), apigenin-7-glycoside (8), quercetin (9), luteolin (10), and apigenin (11) showed obvious inhibitory effects on lipopolysaccharide-induced nitric oxide production in RAW264.7 cells at a concentration of 10 μg/mL. This article is protected by copyright. All rights reserved.

  16. Preparative isolation and analysis of alcohol dehydrogenase inhibitors from Glycyrrhiza uralensis root using ultrafiltration combined with high-performance liquid chromatography and high-speed countercurrent chromatography.

    PubMed

    Chen, Miao; Liu, Liangliang; Chen, Xiaoqing

    2014-07-01

    A simple, rapid, and effective assay based on ultrafiltration combined with high-performance liquid chromatography and high-speed countercurrent chromatography was developed for screening and purifying alcohol dehydrogenase inhibitors from Glycyrrhiza uralensis root extract. Experiments were carried out to optimize binding conditions including alcohol dehydrogenase concentration, incubation time, temperature, and pH. By comparing the chromatograms, three compounds were found possessing alcohol dehydrogenase binding activity in Glycyrrhiza uralensis root. Under the target-guidance of ultrafiltration combined with the high-performance liquid chromatography experiment, liquiritin (1), isoliquiritin (2), and liquiritigenin (3) were separated by high-speed countercurrent chromatography using ethyl acetate/methanol/water (5:1:4) as the solvent system. The alcohol dehydrogenase inhibitory activities of these three isolated compounds were assessed; compound 2 showed strongest inhibitory activity with an IC50 of 8.95 μM. The results of the present study indicated that the combinative method using ultrafiltration, high-performance liquid chromatography and high-speed countercurrent chromatography could be widely applied for the rapid screening and isolation of enzyme inhibitors from complex mixtures.

  17. Preparative isolation of a cytotoxic principle of a forest mushroom Suillus luteus by sodium dodecyl sulfate based "salting-in" countercurrent chromatography.

    PubMed

    Yang, Zhi; Hu, Xueqian; Wu, Shihua

    2016-02-01

    In the course of screening new anticancer natural products, an edible forest mushroom Suillus luteus (L. Ex Franch). Gray was found to have potent cytotoxicity against several human cancer cells. However, the lipophilic sample made some countercurrent chromatography solvent systems emulsify, which caused difficulties in the separation of its cytotoxic components. Here, we found that the addition of an organic salt sodium dodecyl sulfate could efficiently shorten the settling time of the mushroom sample solutions by eliminating the emulsification of two-phase solvent systems. Moreover, we found that sodium dodecyl sulfate could play a new "salting-in" role and made the partition coefficients of the solutes decrease with the increased concentrations. Thus, a sodium dodecyl sulfate based salting-in countercurrent chromatography method has been successfully established for the first time for preparative isolation of a cytotoxic principle of the mushroom. The active component was identified as isosuillin. Whole results indicated that sodium dodecyl sulfate could be used as an efficient salting-in reagent for two-phase solvent system selection and targeted countercurrent chromatography isolation. It is very useful for current natural products isolation and drug discovery.

  18. Isolation of a furan fatty acid from Hevea brasiliensis latex employing the combined use of pH-zone-refining and conventional countercurrent chromatography.

    PubMed

    Englert, Michael; Ulms, Kerstin; Wendlinger, Christine; Vetter, Walter

    2016-02-01

    Furan fatty acids are valuable and bioactive minor fatty acids that usually contribute <0.1% to the fatty acid content of food samples. Their biological role still remains unclear as authentic furan fatty acid standards are not readily available and thorough experimental studies verifying the relevance of furan fatty acids are thus virtually impossible. An efficient protocol for the isolation of the furan fatty acid 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid from hydrolyzed and centrifuged latex of Hevea brasiliensis was developed using countercurrent chromatography. A first run using pH-zone-refining countercurrent chromatography provided 48.4 mg of 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid from 210 mg latex extract in a purity of 95%. The purity was increased to 99% by means of one second run in conventional countercurrent chromatography mode. The Structure and purity of 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid were determined by gas chromatography coupled to mass spectrometry and (1)H and (13)C NMR spectroscopy.

  19. Comparison of slide coagglutination test and countercurrent immunoelectrophoresis for detection of group B streptococcal antigen in cerebrospinal fluid from infants with meningitis.

    PubMed Central

    Webb, B J; Edwards, M S; Baker, C J

    1980-01-01

    The usefulness of Phadebact streptococcus reagents for the detection of group B streptococcal antigen in cerebrospinal fluid was evaluated in 54 infants with meningitis and in 22 normal infants. Antigens was detected by slide coagglutination in 19 (82.6%) and by countercurrent immunoelectrophoresis in 20 (87.0%) of 23 cerebrospinal fluid specimens from infants with group B streptococcal meningitis at admission. After initiation of antimicrobial therapy, antigen could be detected in 11 of 19 (by slide coagglutination) and 7 of 18 (by countercurrent immunoelectrophoresis) cerebrospinal fluids. False-positive reactions were noted by slide coagglutination in one infant with S. bovis meningitis and one with group B streptococcal bacteremia without meningitis; none occurred with countercurrent immunoelectrophoresis. The commercial availiability, simplicity, sensitivity (82.6%), and specificity (96.4%) of the Phadebact slide coaggluatination test for detecting group B streptococcal antigen in cerebrospinal fluid suggest that it may be useful for the early and rapid diagnosis of group B streptococcal meningitis. PMID:6991524

  20. Semisynthetic preparation and isolation of dimeric procyanidins B1-B8 from roasted hazelnut skins (Corylus avellana L.) on a large scale using countercurrent chromatography.

    PubMed

    Esatbeyoglu, Tuba; Juadjur, Andreas; Wray, Victor; Winterhalter, Peter

    2014-07-23

    Dimeric procyanidins B1-B8 were produced via semisynthesis from a polymeric proanthocyanidin fraction of hazelnut skins (Corylus avellana L.). This polymeric fraction was found to consist mostly of (+)-catechin and (-)-epicatechin as upper units. Therefore, according to the choice of nucleophile agent, it is possible to semisynthesize dimeric procyanidins B1, B3, B6, and B7 with (+)-catechin and B2, B4, B5, and B8 with (-)-epicatechin. The semisynthetic mixtures were separated on a preparative scale using high-speed countercurrent chromatography (HSCCC) and low-speed rotary countercurrent chromatography (LSRCCC). C4 → C8 linked dimeric procyanidins B1-B4 were isolated in amounts of 350-740 mg. To the best of the authors' knowledge this is the first study isolating dimeric procyanidins B1-B8 in large amounts with countercurrent chromatography. Moreover, the dimeric prodelphinidins B1, B2, and B3 and their structural elucidation by (1)H NMR spectroscopy without derivatization are described for hazelnuts as natural compounds for the first time.

  1. Preparative separation of two subsidiary colors of FD&C Yellow No. 5 (Tartrazine) using spiral high-speed counter-current chromatography.

    PubMed

    Weisz, Adrian; Ridge, Clark D; Roque, Jose A; Mazzola, Eugene P; Ito, Yoichiro

    2014-05-23

    Specifications in the U.S. Code of Federal Regulations for the color additive FD&C Yellow No. 5 (Color Index No. 19140) limit the level of the tetrasodium salt of 4-[(4',5-disulfo[1,1'-biphenyl]-2-yl)hydrazono]-4,5-dihydro-5-oxo-1-(4-sulfophenyl)-1H-pyrazole-3-carboxylic acid and that of the trisodium salt of 4,4'-[4,5-dihydro-5-oxo-4-[(4-sulfophenyl)hydrazono]-1H-pyrazol-1,3-diyl]bis[benzenesulfonic acid], which are subsidiary colors abbreviated as Pk5 and Pk7, respectively. Small amounts of Pk5 and Pk7 are needed by the U.S. Food and Drug Administration for confirmatory analyses and for development of analytical methods. The present study describes the use of spiral high-speed counter-current chromatography (HSCCC) to separate the closely related minor components Pk5 and Pk7 from a sample of FD&C Yellow No. 5 containing ∼3.5% Pk5 and ∼0.7% Pk7. The separations were performed with highly polar organic/high-ionic strength aqueous two-phase solvent systems that were chosen by applying the recently introduced method known as graphic optimization of partition coefficients (Zeng et al., 2013). Multiple ∼1.0g portions of FD&C Yellow No. 5 (totaling 6.4g dye) were separated, using the upper phase of the solvent system 1-butanol/abs. ethanol/saturated ammonium sulfate/water, 1.7:0.3:1:1, v/v/v/v, as the mobile phase. After removing the ammonium sulfate from the HSCCC-collected fractions, these separations resulted in an enriched dye mixture (∼160mg) of which Pk5 represented ∼46% and Pk7, ∼21%. Separation of the enriched mixture, this time using the lower phase of that solvent system as the mobile phase, resulted in ∼61mg of Pk5 collected in fractions whose purity ranged from 88.0% to 92.7%. Pk7 (20.7mg, ∼83% purity) was recovered from the upper phase of the column contents. Application of this procedure also resulted in purifying the major component of FD&C Yellow No. 5 to >99% purity. The separated compounds were characterized by high-resolution mass

  2. Role of limited hydrogen and flow interval on the growth of single crystal to continuous graphene by low-pressure chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Borah, Munu; Pathak, Abhishek K.; Singh, Dilip K.; Pal, Prabir; Dhakate, Sanjay R.

    2017-02-01

    A method for defect-free large crystallite graphene growth remains unknown despite much research effort. In this work, we discuss the role of flow duration of H2 gas for the production of graphene as per requirement and production at a minimum flow rate considering the safety issue of hydrogen utilization. The copper substrate used for growth was treated for different time intervals (0 to 35 min) in H2 flow prior to growth. Structural and chemical changes occurring in the copper substrate surface were probed by grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. The results were correlated with the Raman spectroscopy data, which can quantify the quality of graphene. With increasing H2 flow interval, secondary nucleation sites were observed and growth favored few-layer graphene structures. The surface-adsorbed oxygen molecules and its conversion to an OH terminated surface with increasing hydrogen flow interval was found to be a key factor in enhancing nucleation density. The Stranski-Krastanov type of nucleation was observed for samples grown with different time intervals of H2 treatment, except 5 min of H2 flow prior to growth for which the Volmer-Weber type of growth favored monolayer graphene crystallite growth.

  3. Role of limited hydrogen and flow interval on the growth of single crystal to continuous graphene by low-pressure chemical vapor deposition.

    PubMed

    Borah, Munu; Pathak, Abhishek K; Singh, Dilip K; Pal, Prabir; Dhakate, Sanjay R

    2017-02-17

    A method for defect-free large crystallite graphene growth remains unknown despite much research effort. In this work, we discuss the role of flow duration of H2 gas for the production of graphene as per requirement and production at a minimum flow rate considering the safety issue of hydrogen utilization. The copper substrate used for growth was treated for different time intervals (0 to 35 min) in H2 flow prior to growth. Structural and chemical changes occurring in the copper substrate surface were probed by grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. The results were correlated with the Raman spectroscopy data, which can quantify the quality of graphene. With increasing H2 flow interval, secondary nucleation sites were observed and growth favored few-layer graphene structures. The surface-adsorbed oxygen molecules and its conversion to an OH terminated surface with increasing hydrogen flow interval was found to be a key factor in enhancing nucleation density. The Stranski-Krastanov type of nucleation was observed for samples grown with different time intervals of H2 treatment, except 5 min of H2 flow prior to growth for which the Volmer-Weber type of growth favored monolayer graphene crystallite growth.

  4. Flow visualization

    NASA Technical Reports Server (NTRS)

    Weinstein, Leonard M.

    1991-01-01

    Flow visualization techniques are reviewed, with particular attention given to those applicable to liquid helium flows. Three techniques capable of obtaining qualitative and quantitative measurements of complex 3D flow fields are discussed including focusing schlieren, particle image volocimetry, and holocinematography (HCV). It is concluded that the HCV appears to be uniquely capable of obtaining full time-varying, 3D velocity field data, but is limited to the low speeds typical of liquid helium facilities.

  5. Flow visualization

    NASA Astrophysics Data System (ADS)

    Weinstein, Leonard M.

    Flow visualization techniques are reviewed, with particular attention given to those applicable to liquid helium flows. Three techniques capable of obtaining qualitative and quantitative measurements of complex 3D flow fields are discussed including focusing schlieren, particle image volocimetry, and holocinematography (HCV). It is concluded that the HCV appears to be uniquely capable of obtaining full time-varying, 3D velocity field data, but is limited to the low speeds typical of liquid helium facilities.

  6. Interfacial shear stress in stratified flow in a horizontal rectangular duct

    SciTech Connect

    Lorencez, C.; Kawaji, M.; Murao, Y.

    1995-09-01

    Interfacial shear stress has been experimentally examined for both cocurrent and countercurrent stratified wavy flows in a horizontal interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress from the measurements were examined and the results have been compared with existing correlations. Some differences were found in the estimated interfacial shear stress values at high gas flow rates which could be attributed to the assumptions and procedures involved in each method. The interfacial waves and secondary motions were also found to have significant effects on the accuracy of Reynolds stress and turbulence kinetic energy extrapolation methods.

  7. Abscisic acid signalling when soil moisture is heterogeneous: decreased photoperiod sap flow from drying roots limits abscisic acid export to the shoots.

    PubMed

    Dodd, Ian C; Egea, Gregorio; Davies, William J

    2008-09-01

    To investigate the contribution of different parts of the root system to total sap flow and leaf xylem abscisic acid (ABA) concentration ([X-ABA](leaf)), individual sunflower (Helianthus annuus L.) shoots were grafted onto the root systems of two plants grown in separate pots and sap flow through each hypocotyl measured below the graft union. During deficit irrigation (DI), both pots received the same irrigation volumes, while during partial root zone drying (PRD) one pot ('wet') was watered and another ('dry') was not. During PRD, once soil water content (theta) decreased below a threshold, the fraction of sap flow from drying roots declined. As theta declined, root xylem ABA concentration increased in both irrigation treatments, and [X-ABA](leaf) increased in DI plants, but [X-ABA](leaf) of PRD plants actually decreased within a certain theta range. A simple model that weighted ABA contributions of wet and dry root systems to [X-ABA](leaf) according to the sap flow from each, better predicted [X-ABA](leaf) of PRD plants than either [X-ABA](dry), [X-ABA](wet) or their mean. Model simulations revealed that [X-ABA](leaf) during PRD exceeded that of DI with moderate soil drying, but continued soil drying (such that sap flow from roots in drying soil ceased) resulted in the opposite effect.

  8. Design of a coil satellite centrifuge and its performance on counter-current chromatographic separation of 4-methylumbelliferyl sugar derivatives with polar organic-aqueous two-phase solvent systems.

    PubMed

    Shinomiya, Kazufusa; Tokura, Koji; Kimura, Emiru; Takai, Midori; Harikai, Naoki; Yoshida, Kazunori; Yanagidaira, Kazuhiro; Ito, Yoichiro

    2015-05-01

    A new high-speed counter-current chromatograph, named coil satellite centrifuge (CSC), was designed and fabricated in our laboratory. The CSC apparatus produces the satellite motion such that the coiled column simultaneously rotates around the sun axis (the angular velocity, ω1), the planet axis (ω2) and the satellite axis (the central axis of the column) (ω3). In order to achieve this triplicate rotary motion without twisting of the flow tube, the rotation of each axis was determined by the following formula: ω1=ω2+ω3. This relation enabled to lay out the flow tube without twisting by the simultaneous rotation of three axes. The flow tube was introduced from the bottom side of the apparatus into the sun axis of the first rotary frame reaching the upper side of the planet axis and connected to the column in the satellite axis. The performance of the apparatus was examined on separation of 4-methylumbelliferyl (MU) sugar derivatives as test samples with organic-aqueous two-phase solvent systems composed of ethyl acetate/1-butanol/water (3:2:5, v/v) for lower phase mobile and (1:4:5, v/v) for upper phase mobile. With lower phase mobile, five 4-MU sugar derivatives including β-D-cellobioside (Cel), β-D-glucopyranoside, α-D-mannopyranoside, β-D-fucopyranoside and α-L-fucopyranoside (α-L-Fuc) were separated with the combined rotation around each axis at counterclockwise (CCW) (ω1) - CCW (ω2) - CCW (ω3) by the flow tube distribution. With upper phase mobile, three 4-MU sugar derivatives including α-L-Fuc, β-D-galactopyranoside and Cel were separated with the combined rotation around each axis at clockwise (CW) (ω1) - CW (ω2) - CW (ω3) by the flow tube distribution. A series of experiments on peak resolution and stationary phase retention revealed that better partition efficiencies were obtained at the flow rate of 0.5 mL/min (column 1) and 0.8 mL/min (column 2) for lower phase mobile and 0.2 mL/min (column 1) and 0.4 mL/min (column 2) for upper phase

  9. ORGANIC-HIGH IONIC STRENGTH AQUEOUS SOLVENT SYSTEMS FOR SPIRAL COUNTER-CURRENT CHROMATOGRAPHY: GRAPHIC OPTIMIZATION OF PARTITION COEFFICIENT.

    PubMed

    Zeng, Yun; Liu, Gang; Ma, Ying; Chen, Xiaoyuan; Ito, Yoichiro

    2013-01-10

    A new series of organic-high ionic strength aqueous two-phase solvents systems was designed for separation of highly polar compounds by spiral high-speed counter-current chromatography. A total of 21 solvent systems composed of 1-butanol-ethanol-saturated ammonium sulfate-water at various volume ratios are arranged according to an increasing order of polarity. Selection of the two-phase solvent system for a single compound or a multiple sample mixture can be achieved by two steps of partition coefficient measurements using a graphic method. The capability of the method is demonstrated by optimization of partition coefficient for seven highly polar samples including tartrazine (K=0.77), tryptophan (K=1.00), methyl green (K= 0.93), tyrosine (0.81), metanephrine (K=0.89), tyramine (K=0.98), and normetanephrine (K=0.96). Three sulfonic acid components in D&C Green No. 8 were successfully separated by HSCCC using the graphic selection of the two-phase solvent system.

  10. Microwave-Assisted Extraction and Purification of Arctiin and Arctigenin from Fructus Arctii by High-Speed Countercurrent Chromatography.

    PubMed

    Lü, Haitao; Sun, Zhaoyun; Shan, Hu; Song, Jiying

    2016-03-01

    An efficient method for the rapid extraction, separation and purification of bioactive lignans, arctiin and arctigenin, from Fructus arctii by microwave-assisted extraction coupled with high-speed countercurrent chromatography was developed. The optimal extraction conditions of arctiin and arctigenin were evaluated by orthogonal array. Arctigenin could be converted from arctiin by hydrochloric acid hydrolysis. The separations were performed at a preparative scale with two-phase solvents composed of ethyl acetate-ethanol-water (5 : 1 : 5, v/v/v) for arctiin, and n-hexane-ethyl acetate-ethanol-water (4 : 4 : 3 : 4, v/v/v/v) for arctigenin. From 500 mg of crude extract sample, 122.3 mg of arctiin and 45.7 mg of arctigenin were obtained with the purity of 98.46 and 96.57%, and the recovery of 94.3 and 81.6%, respectively. Their structures were determined by comparison with the high-performance liquid chromatography retention time of standard substance as well as UV, FT-IR, electrospray ion source (ESI)-MS, (1)H-NMR and (13)C-NMR spectrum. According to the antioxidant activity assay, arctigenin had stronger 1,1-diphenyl-2-picrylhydrazyl free radicals scavenging activity.

  11. Purification of two triterpenoids from Schisandra chinensis by macroporous resin combined with high-speed counter-current chromatography.

    PubMed

    Zhu, Lijie; Li, Bin; Liu, Xiuying; Meng, Xianjun

    2014-10-01

    A method for preparative purification of corosolic acid and nigranoic acid from Schisandra chinensis (SC) was established using a combination of macroporous absorption resin column separation and high-speed counter-current chromatography (HSCCC). The crude extracts obtained from SC using 70% ethanol were separated on a macroporous resin column and then eluted with a graded ethanol series. The 70% ethanol fraction was used as the sample for separation of the two triterpenoids by HSCCC. The two-phase solvent system used for HSCCC separation was chloroform-n-butanol-methanol-water (10:0.5:7:4, v/v/v/v). The upper phase was used as the stationary phase of HSCCC. Corosolic acid (16.4 mg) of 96.3% purity and nigranoic acid (9.5 mg) of 98.9% purity were obtained in a one-step HSCCC separation from 100 mg of the sample. The structures of corosolic acid and nigranoic acid were identified by (1)H-nuclear magnetic resonance (NMR) and (13)C-NMR.

  12. Purification of coenzyme Q10 from fermentation extract: high-speed counter-current chromatography versus silica gel column chromatography.

    PubMed

    Cao, Xue-Li; Xu, Ya-Tao; Zhang, Guang-Ming; Xie, Sheng-Meng; Dong, Ying-Mao; Ito, Yoichiro

    2006-09-15

    High-speed counter-current chromatography (HSCCC) is applied to the purification of coenzyme Q(10) (CoQ(10)) for the first time. CoQ(10) was obtained from a fermentation broth extract. A non-aqueous two-phase solvent system composed of heptane-acetonitrile-dichloromethane (12:7:3.5, v/v/v) was selected by analytical HSCCC and used for purification of CoQ(10) from 500 mg of the crude extract. The separation yielded 130 mg of CoQ(10) at an HPLC purity of over 99%. The overall results of the present studies show the advantages of HSCCC over an alternative of silica gel chromatography followed by recrystallization. These advantages extend to higher purity (97.8% versus 93.3%), recovery (88% versus 74.3%) and yield (26.4% versus 23.4%). An effort to avoid the toxic, expensive solvent CH(2)Cl(2) was unsuccessful, but at least its percentage is low in the solvent system.

  13. Preparative isolation and purification of coumarins from Peucedanum praeruptorum Dunn by high-speed counter-current chromatography.

    PubMed

    Liu, Renmin; Feng, Lei; Sun, Ailing; Kong, Lingyi

    2004-11-19

    A preparative high-speed counter-current chromatography (HSCCC) method for isolation and purification of coumarins from Peucedanum praeruptorum Dunn (Baihuaqianhu in Chinese) was successfully established by using light petroleum-ethyl acetate-methanol-water as the two-phase solvent system in gradient elution mode. The upper phase of light petroleum-ethyl acetate-methanol-water (5:5:5:5, v/v) was used as the stationary phase of HSCCC. The mobile phase used in HSCCC was the lower phase of light petroleum-ethyl acetate-methanol-water (5:5:5:5, v/v) and light petroleum-ethyl acetate-methanol-water (5:5:6.5:3.5, v/v) that was changed in gradient. Four kinds of coumarins and another unknown compound were obtained and yielded 5.3 mg of qianhucoumarin D, 7.7 mg of Pd-Ib, 35.8 mg of (+)-praeruptorin A, 31.9 mg of (+)-praeruptorin B and 6.4 mg of unknown compound with the purity of 98.6%, 92.8%, 99.5%, 99.4% and 99.8% in one-step separation, respectively. The structures of the coumarins were identified by 1H NMR and 13C NMR.

  14. Comprehensive multi-channel multi-dimensional counter-current chromatography for separation of tanshinones from Salvia miltiorrhiza Bunge.

    PubMed

    Meng, Jie; Yang, Zhi; Liang, Junling; Zhou, Hui; Wu, Shihua

    2014-01-03

    Multi-dimensional chromatography offers the increased resolution and peak capacity by coupling of multiple columns with the same or different separation mechanisms. In this work, a novel multi-channel multi-dimensional counter-current chromatography (CCC) has been successfully constructed and used for several two-dimensional (2D) and three-dimensional (3D) CCC separations including 2D A×B/A×C, A×B-C and A-B×C, and 3D A×B×C systems. These 2D and 3D CCC systems were further applied to separate the bioactive tanshinones from the extract of Tanshen (or Danshen, Salvia miltiorrhiza Bunge), a famous Traditional Chinese Medicine (TCM). As a result, the developed 2D and 3D CCC methods were successful and efficient for resolving the tanshinones from complex extracts. Compared to the 1D multiple columns CCC separation, the 2D and 3D CCC decrease analysis time, reduce solvent consumption and increase sample throughput significantly. It may be widely used for current drug development, metabolomic analysis and natural product isolation.

  15. Separation of phenolic acids and flavonoids from Trollius chinensis Bunge by high speed counter-current chromatography.

    PubMed

    Qin, Yanhua; Liang, Yizeng; Ren, Dabing; Qiu, Ximin; Li, Xi

    2015-09-15

    In this work, eleven compounds were successfully separated from Trollius chinensis Bunge by using a two-step high-speed counter-current chromatography (HSCCC) method. NRTL-SAC (nonrandom two-liquid segment activity coefficient) method, a newly developed solvent system selection strategy, was applied to screening the suitable biphasic liquid systems. Hexane/ethyl acetate/ethanol/water (3:7:3:7, v/v) solvent system was used in the first step, while the hexane/ethyl acetate/methanol/water (1:2:1:2, 1:4:1:4, 1:9:1:9, v/v) systems were employed in the second step. The chemical structures of the separated compounds were identified by UV, high resolution ESI-MS and MS/MS data. The separated compounds are 3,4-dihydroxyphenylethanol (1), vanillic acid (2), orientin (3), vitexin (4), veratric acid (5), 2″-O-(3‴, 4‴-dimethoxybenzoyl) orientin (6), 2″-O-feruloylorientin (7), 2″-O-feruloylvitexin (8), 2″-O-(2‴-methylbutyryl) vitexin (9), 2″-O-(2‴-methylbutyryl) isoswertiajaponin (10), 2″-O-(2‴-methylbutyryl) isoswertisin (11). The results demonstrate that HSCCC is a powerful tool for the separation of compounds from extremely complex samples.

  16. Extraction and preparative purification of tanshinones from Salvia miltiorrhiza Bunge by high-speed counter-current chromatography.

    PubMed

    Sun, Ailing; Zhang, Yongqing; Li, Aifeng; Meng, Zhaoling; Liu, Renmin

    2011-07-01

    A method for extraction and preparative separation of tanshinones from Salvia miltiorrhiza Bunge was successfully established in this paper. Tanshinones from Salvia miltiorrhiza Bunge were extracted using ethyl acetate as the extractant under reflux. The extracts were then purified by high speed counter-current chromatography (HSCCC) with light petroleum-ethyl acetate-methanol-water (6:4:6.5:3.5, v/v) as the two phase solvent system. The upper phase was used as the stationary phase and the lower phase as the mobile phase. 8.2mg of dihydrotanshinone I, 5.8 mg of 1,2,15,16-tetrahydrotanshiquinone, 26.3mg of cryptotanshinone, 16.2mg of tanshinone I, 25.6 mg of neo-przewaquinone A, 68.8 mg of tanshinone IIA and 9.3mg of miltirone were obtained from 400mg of extracts from Salvia miltiorrhiza Bunge in one-step HSCCC separation, with the purity of 97. 6%, 95.1%, 99.0%, 99.1%, 93.2%, 99.3% and 98.7%, respectively, as determined by HPLC area normalization method. Their chemical structures were identified by ¹H NMR.

  17. Ethyl acetate-n-butanol gradient solvent system for high-speed countercurrent chromatography to screen bioactive substances in okra.

    PubMed

    Ying, Hao; Jiang, Heyuan; Liu, Huan; Chen, Fangjuan; Du, Qizhen

    2014-09-12

    High-speed countercurrent chromatographic separation (HSCCC) possesses the property of zero-loss of sample, which is very useful for the screening of bioactive components. In the present study, the ethyl acetate-n-butanol gradient HSCCC solvent system composed of n-hexane-ethyl acetate-n-butanol-water was investigated for the screening of bioactive substances. To screen the antiproliferative compounds in okra extract, we used the stationary phase ethyl acetate-n-butanol-water (1:1:10) as the stationary phase, and eluted the antiproliferative components by 6-steps of gradient using mobile phases n-hexane-ethyl acetate (1:2), n-hexane-ethyl acetate (1:4), n-hexane-ethyl acetate (0:4), n-butanol-ethyl acetate (1:4) n-butanol-ethyl acetate (1:2), n-butanol-ethyl acetate (2:2), and n-butanol-ethyl acetate (2:1). The fractions collected from HSCCC separation with the gradient solvent system were assayed for antiproliferative activity against cancer cells. Bioactive components were identified: a major anti-cancer compound, 4'-hydroxy phenethyl trans-ferulate, with middle activity, and a minor anti-cancer compound, carolignan, with strong activity. The result shows that the gradient solvent system is potential for the screening of bioactive compounds from natural products.

  18. Preparative isolation of anthocyanins from Japanese purple sweet potato (Ipomoea batatas L.) varieties by high-speed countercurrent chromatography.

    PubMed

    Montilla, Elyana Cuevas; Hillebrand, Silke; Butschbach, Daniela; Baldermann, Susanne; Watanabe, Naoharu; Winterhalter, Peter

    2010-09-22

    Purple-fleshed sweet potatoes (Ipomoea batatas L.) contain a very complex anthocyanin profile due to the presence of several non-, mono-, and diacylated glucosides of cyanidin and peonidin. In this study, the anthocyanin composition of four Japanese purple sweet potato cultivars (Chiran Murasaki, Tanegashima Murasaki, Naka Murasaki, and Purple Sweet) were investigated by HPLC-DAD and ESI-MSn analyses. The HPLC chromatograms of the different cultivars show a remarkable variation of the two major pigments, cyanidin-3-(6''-caffeoylsophoroside)-5-glucoside and peonidin-3-(6''-caffeoylsophoroside)-5-glucoside, respectively. According to this, they can be categorized into two groups on the basis of the peonidin/cyanidin ratio: the cultivars Chiran Murasaki and Purple Sweet showed a high content of peonidin derivatives (peonidin type), whereas the varieties Tanegashima Murasaki and Naka Murasaki were classified as cyanidin types. By means of high-speed countercurrent chromatography (HSCCC) the nonacylated 3-sophoroside-5-glucoside of cyanidin was isolated on a preparative scale. Furthermore, it was possible to isolate the monoacylated cyanidin-3-(6''-caffeoylsophoroside)-5-glucoside as well as three diacylated major pigments, cyanidin-3-(6'',6'''-dicaffeoylsophoroside)-5-glucoside, cyanidin-3-(6''-caffeoyl-6'''-p-hydroxy-benzoylsophoroside)-5-glucoside, and peonidin-3-(6''-caffeoyl-6'''-p-hydroxybenzoyl-sophoroside)-5-glucoside. The purity and identity of the so-obtained pigments were confirmed by NMR measurements.

  19. Schinus terebinthifolius countercurrent chromatography (Part II): Intra-apparatus scale-up and inter-apparatus method transfer.

    PubMed

    Costa, Fernanda das Neves; Vieira, Mariana Neves; Garrard, Ian; Hewitson, Peter; Jerz, Gerold; Leitão, Gilda Guimarães; Ignatova, Svetlana

    2016-09-30

    Countercurrent chromatography (CCC) is being widely used across the world for purification of various materials, especially in natural product research. The predictability of CCC scale-up has been successfully demonstrated using specially designed instruments of the same manufacturer. The reality is that the most of CCC users do not have access to such instruments and do not have enough experience to transfer methods from one CCC column to another. This unique study of three international teams is based on innovative approach to simplify the scale-up between different CCC machines using fractionation of Schinus terebinthifolius berries dichloromethane extract as a case study. The optimized separation methodology, recently developed by the authors (Part I), was repeatedly performed on CCC columns of different design available at most research laboratories across the world. Hexane - ethyl acetate - methanol - water (6:1:6:1, v/v/v/v) was used as solvent system with masticadienonic and 3β-masticadienolic acids as target compounds to monitor stationary phase retention and calculate peak resolution. It has been demonstrated that volumetric, linear and length scale-up transfer factors based on column characteristics can be directly applied to different i.d., volume and length columns independently on instrument make in an intra-apparatus scale-up and inter-apparatus method transfer.

  20. Isolation of secondary metabolites from Hortia oreadica (Rutaceae) leaves through high-speed counter-current chromatography.

    PubMed

    Severino, Vanessa Gisele Pasqualotto; Cazal, Cristiane de Melo; Forim, Moacir Rossi; da Silva, Maria Fátima das Graças Fernandes; Rodrigues-Filho, Edson; Fernandes, João Batista; Vieira, Paulo Cezar

    2009-05-08

    High-speed counter-current chromatography (HSCCC) with a two-phase solvent system (hexane-ethanol-acetonitrile-water 10:8:1:1, v/v) was applied to examine the leaves of Hortia oreadica, which afforded the known limonoid guyanin (1), the alkaloids rutaecarpin (2) and dictamnine (6), the dihydrocinnamic acid derivatives methyl 5,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran-6-propanoate (3), 5,8-dimethoxy-2,2-dimethyl-2H-1-benzopyran-6-propanoic acid (4), together with the new E-3,4-dimethoxy-alpha(3-hydroxy-4-carbomethoxyphenyl)cinnamic acid (5). The recovery of compounds 1-6 was determined by comparison with LC-atmospheric pressure chemical ionization MS/MS data: 66.2%, 93.1%, 102.5%, 101.2%, 99.0% and 84.9%, respectively. Compound 3 showed IC(50) of 23.6microM against Plasmodium falciparum and 15.6microM against Trypanosoma brucei rhodesienses and was not toxic to KB cells (IC(50)>100microM).

  1. Modeling of the simulated countercurrent moving-bed chromatographic reactor used for the oxidative coupling of methane

    SciTech Connect

    Tonkovich, A.L.Y.; Carr, R.W.

    1994-09-01

    The oxidative coupling reaction of methane (OCM) is a potential industrial reaction for the efficient production of ethylene. Replacement of current technologies requires significant product yield improvements. An experimental novel reactor design, the modified simulated countercurrent moving-bed chromatographic reactor (SCMCR), has reported improved ethane and ethylene product yields over other reported values. An understanding of the reactor operation is aided by concurrent mathematical modeling. The model mimics the exact experimental reactor configuration. Four sections are used; each section contains a reaction column and two separation columns connected in series. The feed is switched from section to section at discrete intervals. Reaction occurs in the first column and is followed by product and reactant separation in the ensuing section columns. Langmuir adsorption isotherms are used. The model does not incorporate the realistic and complex kinetics rising, from the OCM, rather a simplified reaction term is used to qualitatively gain insight into the operation of the modified SCMCR. A unimolecular reaction network is used in the model. The rate constants are set to permit a small fractional conversion, 5% per pass, at the concentrations during the first cycle. Similarly to the experimental reactor, the model adds a make-up feed (defined as percentage of the original feed, where excess methane is fed during the first cycle of the experimental reactor) to augment lost reactants.

  2. Preparative purification of five bioactive components from Agrimonia pilosa Ledeb by high-speed counter-current chromatography.

    PubMed

    Wang, Yan; Liu, Mozhen; Zheng, Lingli; Yin, Lianhong; Xu, Lina; Qi, Yan; Ma, Xiaochi; Liu, Kexin; Peng, Jinyong

    2012-08-01

    High-speed counter-current chromatography (HSCCC) coupled with ultraviolet (UV) detection or evaporative light-scattering detection was successfully applied for preparative separation of five bioactive compounds from Agrimonia pilosa Ledeb. In preliminary process, D101 macroporous resin was used to separate the crude extract of the plant and four fractions (20, 40, 50, and 60% aqueous ethanol elutions) were produced. Then, these fractions were directly subjected to HSCCC purification. Five chemicals including taxifolin-3-glucoside (6.4 mg), quercetin-3-rhamnoside (13.0 mg), tiliroside (14.7 mg), agrimonolide (21.4 mg), and tormentic acid (29.8 mg) with the purities of 94.24, 95.37, 97.42, 95.29, and 96.34% were separated from each 200 mg prepared fraction. The purities were analyzed by high-performance liquid chromatography, and the chemical structures of the products were identified by UV detection, mass spectrometry, nuclear magnetic resonance, and the standards. This paper used a simple method to separate five bioactive compounds from A. pilosa Ledeb, and it could provide a new idea for the purification of bioactive compounds from other medicinal plants.

  3. Isolation and purification of prenylated phenolics from Amorpha fruticosa by high-speed counter-current chromatography.

    PubMed

    Chen, Chu; Wu, Yan; Chen, Yang; Du, Leilei

    2015-08-01

    Prenylated phenolics such as amorfrutins are recently identified potent anti-inflammatory and antidiabetic natural products. In this work, high-speed counter-current chromatography was investigated for the isolation and purification of prenylated phenolics from the fruits of Amorpha fruticosa by using a two-phase solvent system composed of n-hexane/ethanol/water (5:4:1, v/v). As a result, 14.2 mg of 5,7-dihydroxy-8-geranylflavanone, 10.7 mg of amorfrutin A and 17.4 mg of amorfrutin B were obtained from 200 mg of n-hexane-soluble crude extract in one step within 250 min. The purities of 5,7-dihydroxy-8-geranylflavanone, amorfrutins A and B were 95.2, 96.7 and 97.1%, respectively, as determined by ultra high performance liquid chromatography. The structural identification was performed by mass spectrometry and (1) H and (13) C NMR spectroscopy. The results indicated that the established method is an efficient and convenient way to purified prenylated phenolics from A. fruticosa extract.

  4. Separation and purification of glucosinolates from crude plant homogenates by high-speed counter-current chromatography.

    PubMed

    Fahey, Jed W; Wade, Kristina L; Stephenson, Katherine K; Chou, F Edward

    2003-05-09

    Glucosinolates are anionic, hydrophilic plant secondary metabolites which are of particular interest due to their role in the prevention of cancer and other chronic and degenerative diseases. The separation and purification of glucosinolates from a variety of plant sources (e.g. seeds of broccoli, arugula and the horseradish tree), was achieved using high-speed counter-current chromatography (HSCCC). A high-salt, highly polar system containing 1-propanol-acetonitrile-saturated aqueous ammonium sulfate-water (1:0.5:1.2:1), was run on a semi-preparative scale and then transferred directly to preparative scale. Up to 7 g of a concentrated methanolic syrup containing about 10% glucosinolates was loaded on an 850-ml HSCCC column, and good separation and recovery were demonstrated for 4-methylsulfinylbutyl, 3-methylsulfinylpropyl, 4-methylthiobutyl, 2-propenyl and 4-(rhamnopyranosyloxy)benzyl glucosinolates. Multiple injections (5 to 6 times) were performed with well-preserved liquid stationary phase under centrifugal force. Pooled sequential runs with broccoli seed extract yielded about 20 g of its predominant glucosinolate, glucoraphanin, which was produced at > 95% purity and reduced to powdered form.

  5. Room temperature ionic liquids-based salting-in strategy for counter-current chromatography in the separation of arctiin.

    PubMed

    Wang, Yanyan; Zhang, Lihong; Wang, Dingding; Guo, Xiuyun; Wu, Shihua

    2016-12-23

    Counter-current chromatography (CCC) is a solid support-free liquid-liquid partition chromatography and has wide applications. However, CCC separation is still a challenging process and the selection of appropriate solvent system for separation of target compound(s) is still relatively time-consuming. In this work, we introduced a room temperature ionic liquids-based salting-in strategy for the rapid selection of suitable solvent systems for CCC separation. In the randomly selected solvent systems, such as ethyl acetate-water, n-butanol-water, n-pentanol-water, n-hexanol-water, and n-octanol-water, several ionic liquids such as [AMIM]Cl, [MAMIM]Cl, and [BMIM]Cl can increase the solubility of the solutes in the lower phase, which made a dose-dependent decreasing of partition coefficient of solute in the two-phase solvent system. Thus, it is possible to get a suitable solvent system with sweet K spot such as K=1 only by adding some ionic liquids into the systems. As an example, arctiin, a bioactive lignin component of the fruit of Arctium lappa. L. (Niubangzi in Chinese), was selected and successfully separated by CCC with room temperature ionic liquids-based n-butanol-water systems. It seems a very efficient alternative strategy for the optimization of solvent systems for CCC separation of natural products.

  6. Ecological limit functions relating fish community response to hydrologic departures of the ecological flow regime in the Tennessee River basin, United States

    USGS Publications Warehouse

    Knight, Rodney R.; Murphy, Jennifer C.; Wolfe, William J.; Saylor, Charles F.; Wales, Amy K.

    2014-01-01

    Ecological limit functions relating streamflow and aquatic ecosystems remain elusive despite decades of research. We investigated functional relationships between species richness and changes in streamflow characteristics at 662 fish sampling sites in the Tennessee River basin. Our approach included the following: (1) a brief summary of relevant literature on functional relations between fish and streamflow, (2) the development of ecological limit functions that describe the strongest discernible relationships between fish species richness and streamflow characteristics, (3) the evaluation of proposed definitions of hydrologic reference conditions, and (4) an investigation of the internal structures of wedge-shaped distributions underlying ecological limit functions.Twenty-one ecological limit functions were developed across three ecoregions that relate the species richness of 11 fish groups and departures from hydrologic reference conditions using multivariate and quantile regression methods. Each negatively sloped function is described using up to four streamflow characteristics expressed in terms of cumulative departure from hydrologic reference conditions. Negative slopes indicate increased departure results in decreased species richness.Sites with the highest measured fish species richness generally had near-reference hydrologic conditions for a given ecoregion. Hydrology did not generally differ between sites with the highest and lowest fish species richness, indicating that other environmental factors likely limit species richness at sites with reference hydrology.Use of ecological limit functions to make decisions regarding proposed hydrologic regime changes, although commonly presented as a management tool, is not as straightforward or informative as often assumed. We contend that statistical evaluation of the internal wedge structure below limit functions may provide a probabilistic understanding of how aquatic ecology is influenced by altered hydrology

  7. Hydrocarbon processing of gas containing feed in a countercurrent moving catalyst bed

    SciTech Connect

    Smith, D.S.

    1990-11-06

    This patent describes method of upgrading a hydrocarbon feedstream containing organo-metallic and/or metal components under catalytic hydrocarbon upgrading conditions in a reactor vessel. In it an upwardly flowing feed stream reacts with a downwardly moving catalyst bed, the vessel including feed inlet means at the lower end thereof and product recovery means and catalyst delivery means at the upper end thereof.

  8. Heat Transfer Correlations for compressible flow in Micro Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Coppola, M. A.; Croce, G.

    2016-09-01

    The paper discusses the definition of dimensionless parameters useful to define a local correlation for convective heat transfer in compressible, micro scale gaseous flows. A combination of static and stagnation temperatures is chosen, as it allows to weight the temperature change related to the heat transfer and that induced by conversion of internal energy into kinetic one. The correlation offers a purely convective local Nusselt number, i.e. correlating the heat flow rate with the local flow parameters and wall surface temperature. The correlation is validated through a series of numerical computations in both counter-current and co-current micro heat exchanger configurations. The numerical computations take into account rarefaction and conjugate heat transfer effects.

  9. Dynamic pH junction high-speed counter-current chromatography coupled with microwave-assisted extraction for online separation and purification of alkaloids from Stephania cepharantha.

    PubMed

    Yuan, Zhiquan; Xiao, Xiaohua; Li, Gongke

    2013-11-22

    A simple and efficient dynamic pH junction high-speed counter-current chromatography method was developed and further applied to the online extraction, separation and purification of alkaloids from Stephania cepharantha by coupling with microwave-assisted extraction. Mineral acid and organic base were added into the mobile phase and the sample solution, respectively, leading to the formation of a dynamic pH junction in the column and causing focus of alkaloids. Selective focus of analytes can be achieved on the basis of velocity changes of the pH junction through appropriate selection of solvent systems and optimization of additive concentrations. The extract can be directly introduced into the HSCCC for the online extraction, separation and purification of alkaloids from S. cepharantha. Continuous separation can be easily achieved with the same solvent system. Under the optimum conditions, 6.0 g original sample was extracted with 60 mL of the upper phase of hexane-ethyl acetate-methanol-water (1:1:1:1, v/v/v/v) containing 10% triethylamine under 50 °C and 400 W irradiation power for 10 min, the extracts were directly separated and purified by high-speed counter-current chromatography. A total of 5.7 mg sinomenine, 8.3mg 6,7-di-O-acetylsinococuline, 17.9 mg berbamine, 12.7 mg isotetrandrine and 14.6 mg cepharanthine were obtained with purities of 96.7%, 93.7%, 98.7%, 97.3% and 99.3%, respectively. The online method provides good selectivity to ionizable compounds and improves the separation and purification efficiency of the high-speed counter-current chromatography technique. It has good potential for separation and purification of effective compounds from natural products.

  10. The connection of the Indonesian Throughflow, South Indian Ocean Countercurrent and the Leeuwin Current

    NASA Astrophysics Data System (ADS)

    Lambert, Erwin; Le Bars, Dewi; de Ruijter, Wilhelmus P. M.

    2016-06-01

    East of Madagascar, the shallow "South Indian Ocean Counter Current (SICC)" flows from west to east across the Indian Ocean against the direction of the wind-driven circulation. The SICC impinges on west Australia and enhances the sea level slope, strengthening the alongshore coastal jet: the Leeuwin Current (LC), which flows poleward along Australia. An observed transport maximum of the LC around 22° S can likely be attributed to this impingement of the SICC. The LC is often described as a regional coastal current that is forced by an offshore meridional density gradient or sea surface slope. However, little is known about the controls of these open-ocean gradients. The regional circulation system is embedded in the subtropical "super gyre" that connects the Indo-Pacific via the Tasman Gateway and the Indonesian passages. The Indonesian Throughflow (ITF) circulates through the Indian Ocean back into the Pacific south of Australia. This return pathway appears to be partly trapped in the upper layer north of an outcrop line. It is redirected along this outcrop line and joins the eastward flow of the SICC. To study the connection of the basin-scale and the inter-ocean-scale dynamics, we apply both an ocean general circulation model and a conceptual two-layer model. Shutdown of the ITF in the models leads to a large decrease in Leeuwin Current transport. Most of the SICC was found to then reconnect to the internal gyre circulation in the Indian Ocean. ITF, SICC and LC thus appear to be dynamically connected.

  11. Limited genetic divergence among Australian alpine Poa tussock grasses coupled with regional structuring points to ongoing gene flow and taxonomic challenges

    PubMed Central

    Griffin, Philippa C.; Hoffmann, Ary A.

    2014-01-01

    Background and Aims While molecular approaches can often accurately reconstruct species relationships, taxa that are incompletely differentiated pose a challenge even with extensive data. Such taxa are functionally differentiated, but may be genetically differentiated only at small and/or patchy regions of the genome. This issue is considered here in Poa tussock grass species that dominate grassland and herbfields in the Australian alpine zone. Methods Previously reported tetraploidy was confirmed in all species by sequencing seven nuclear regions and five microsatellite markers. A Bayesian approach was used to co-estimate nuclear and chloroplast gene trees with an overall dated species tree. The resulting species tree was used to examine species structure and recent hybridization, and intertaxon fertility was tested by experimental crosses. Key Results Species tree estimation revealed Poa gunnii, a Tasmanian endemic species, as sister to the rest of the Australian alpine Poa. The taxa have radiated in the last 0·5–1·2 million years and the non-gunnii taxa are not supported as genetically distinct. Recent hybridization following past species divergence was also not supported. Ongoing gene flow is suggested, with some broad-scale geographic structure within the group. Conclusions The Australian alpine Poa species are not genetically distinct despite being distinguishable phenotypically, suggesting recent adaptive divergence with ongoing intertaxon gene flow. This highlights challenges in using conventional molecular taxonomy to infer species relationships in recent, rapid radiations. PMID:24607721

  12. Two-dimensional countercurrent chromatography×high performance liquid chromatography with heart-cutting and stop-and-go techniques for preparative isolation of coumarin derivatives from Peucedanum praeruptorum Dunn.

    PubMed

    Liu, Jing-Lan; Wang, Xin-Yuan; Zhang, Ling-Ling; Fang, Mei-Juan; Wu, Yun-Long; Wu, Zhen; Qiu, Ying-Kun

    2014-12-29

    Pure compounds isolated from complex natural plants are important for drug discovery. This study describes a novel two-dimensional hyphenation of counter-current chromatography and high-performance liquid chromatography (2D CCC×HPLC) with heart-cutting and stop-and-go techniques for preparative isolation of multiple targets components from Peucedanum praeruptorum Dunn (Umbelliferae) crude extracts in a single step. The CCC and HPLC were hyphenated via a 4-port valve equipped at the post-end of the CCC column, to heart cut the impure fractions to the 2nd dimensional HPLC for further separation. Furthermore, the stop-and-go flow scheme was applied in the 1st dimensional CCC to fit with the time constraints of the 2nd dimensional preparative HPLC. Last but not least, an optimal biphasic solvent system composed of n-heptane/acetone/water (31:50:19, v/v/v) with suitable Kd values and a higher retention of the stationary phase was chosen to separate target compounds, resulting in the improvement of the CCC column efficiency. By taking the advantages of this rationally designed system, sixteen coumarins were isolated from 1.0g of P. praeruptorum crude extract, with HPLC purity from 90.1% to 99.5%, in a single 2D separation run. More interestingly, two minor linear coumarins and one angular coumarin were isolated from P. praeruptorum Dunn for the first time. As far as we known, this is the first report on the combination of heart-cutting technique and stop-and-go protocol in 2D CCC×HPLC system, by which good separations on comprehensive matrix were achieved. We expect that this approach may have broad applications for simultaneous isolation and purification of multiple components from other complex plant-derived natural products.

  13. High-speed counter-current chromatography coupled online to high performance liquid chromatography-diode array detector-mass spectrometry for purification, analysis and identification of target compounds from natural products.

    PubMed

    Liang, Xuejuan; Zhang, Yuping; Chen, Wei; Cai, Ping; Zhang, Shuihan; Chen, Xiaoqin; Shi, Shuyun

    2015-03-13

    A challenge in coupling high-speed counter-current chromatography (HSCCC) online with high performance liquid chromatography (HPLC) for purity analysis was their time incompatibility. Consequently, HSCCC-HPLC was conducted by either controlling HPLC analysis time and HSCCC flow rate or using stop-and-go scheme. For natural products containing compounds with a wide range of polarities, the former would optimize experimental conditions, while the latter required more time. Here, a novel HSCCC-HPLC-diode array detector-mass spectrometry (HSCCC-HPLC-DAD-MS) was developed for undisrupted purification, analysis and identification of multi-compounds from natural products. Two six-port injection valves and a six-port switching valve were used as interface for collecting key HSCCC effluents alternatively for HPLC-DAD-MS analysis and identification. The ethyl acetate extract of Malus doumeri was performed on the hyphenated system to verify its efficacy. Five main flavonoids, 3-hydroxyphloridzin (1), phloridzin (2), 4',6'-dihydroxyhydrochalcone-2'-O-β-D-glucopyranoside (3, first found in M. doumeri), phloretin (4), and chrysin (5), were purified with purities over 99% by extrusion elution and/or stepwise elution mode in two-step HSCCC, and 25mM ammonium acetate solution was selected instead of water to depress emulsification in the first HSCCC. The online system shortened manipulation time largely compared with off-line analysis procedure and stop-and-go scheme. The results indicated that the present method could serve as a simple, rapid and effective way to achieve target compounds with high purity from natural products.

  14. Spiral column configuration for protein separation by high-speed countercurrent chromatography

    PubMed Central

    Ito, Yoichiro

    2009-01-01

    Retention of the stationary phase of aqueous-aqueous polymer phase systems is improved by a spiral column configuration which utilizes the radially acting centrifugal force along the spiral pitch to retain the heavier phase in the outer portion and the lighter phase in the inner portion of the spiral channel. For the separation of proteins which has low mass transfer rates, the system needs further modification of the separation channel to interrupt the laminar flow and enhance mixing of the two phases. Two spiral column assemblies were developed, one using a disk with spiral grooves and the other, the spiral tube support which accommodates the multiple spiral layers made from a single piece of fluorinated plastic tubing. In the spiral disk assembly, the best protein separation is achieved by the mixer-settler system which vigorously mixes two phases by vibrating glass beads placed in every other section of barricaded spiral channel, while in the spiral tube assembly the partition efficiency of proteins is enhanced by compressing the tubing to interrupt the laminar flow of the mobile phase. In both systems protein samples were well resolved by choosing the suitable elution modes. PMID:20823942

  15. Separation of betalains from berries of Phytolacca americana by ion-pair high-speed counter-current chromatography.

    PubMed

    Jerz, Gerold; Skotzki, Tanja; Fiege, Kathrin; Winterhalter, Peter; Wybraniec, Sławomir

    2008-05-09

    The first preparative fractionation of betalain pigments by means of ion-pair high-speed counter-current chromatography (IP-HSCCC) from berry extracts of Phytolacca americana (Phytolaccaceae) is presented. A novel HSCCC solvent system consisting of 1-butanol-acetonitrile-water (5:1:6, v/v/v) was applied using ion-pair forming trifluoroacetic acid at low concentration (0.7%, v/v). Affinity of polar betacyanins and betaxanthins to the organic stationary phase of the biphasic HSCCC solvent mixture was considerably improved. Partitioning coefficient values and influence of increasing trifluoroacetic acid additions to the biphasic solvent mixture were measured for all identified betacyanins and betaxanthins. Gentle separation by IP-HSCCC of the injected pigment extract (900 mg) yielded sufficient amounts of the principal pigments 15S-betanin/15R-isobetanin. The pure epimers separated by C18-HPLC were immediately studied by one- and two-dimensional NMR. In the recovered fractions, minor concentrated betacyanins and betaxanthins were significantly enriched by IP-HSCCC and were detected for the first time in the extracts of P. americana. IP-HSCCC and C18-HPLC were shown to be complementary techniques in the isolation procedure of recovering minor concentrated, highly polar and chemically instable betacyanins and betaxanthin from complex plant matrices. Altogether, identification of 17 betalains was achieved by HPLC-diode array detection-electrospray ionization MS/MS in the HSCCC fractions with their respective isomers, also resulting in the tentative elucidation of betacyanins with novel salicylic acid substitution pattern in the berry extracts of P. americana.

  16. Preparative Separation of Main Ustilaginoidins from Rice False Smut Balls by High-Speed Counter-Current Chromatography

    PubMed Central

    Sun, Weibo; Dong, Xuejiao; Xu, Dan; Meng, Jiajia; Fu, Xiaoxiang; Wang, Xiaohan; Lai, Daowan; Zhou, Ligang; Liu, Yang

    2016-01-01

    Ustilaginoidins are bis-naphtho-γ-pyrone mycotoxins isolated from the rice false smut balls (FSBs) infected by the pathogen Villosiclava virens in rice spikelets on panicles. In order to obtain large amounts of pure ustilaginoidins to further evaluate their biological activities and functions, phytotoxicity on rice, security to human and animals as well as to accelerate their applications as pharmaceuticals, preparative high-speed counter-current chromatography (HSCCC) was successfully applied to the isolation and purification of seven bis-naphtho-γ-pyrone mycotoxins, namely ustilaginoidins A (1), G (2), B (3), H (4), I (5), C (6), and J (7) from the ethyl acetate crude extract of rice FSBs. Both 1 and 2 were prepared by HSCCC from the low-polarity fraction of the crude extract using the two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water at the volume ratio of 6.5:3.5:5.0:5.0. Similarly, 3, 4 and 5 were prepared from the medium-polarity fraction using the system at the volume ratio of 4.0:5.0:5.0:6.0, and 6 and 7 were prepared from the higher-polarity fraction using the system at volume ratio of 3.0:5.0:4.0:6.7. A total of 6.2 mg of 1, 5.1 mg of 2, 3.9 mg of 3, 1.2 mg of 4, 5.7 mg of 5, 3.5 mg of 6, and 6.1 mg of 7 with purities of 88%, 82%, 91%, 80%, 92%, 81% and 83%, respectively, were yielded from total 62 mg fraction samples in three independent HSCCC runs. The structures of the purified ustilaginoidins were characterized by means of physicochemical and spectrometric analysis. PMID:26771638

  17. Conical coils counter-current chromatography for preparative isolation and purification of tanshinones from Salvia miltiorrhiza Bunge.

    PubMed

    Liang, Junling; Meng, Jie; Guo, Mengzhe; Yang, Zhi; Wu, Shihua

    2013-05-03

    Modern counter-current chromatography (CCC) originated from the helical coil planet centrifuge. Recently, spiral coils were found to possess higher separation efficiency in both the retention of stationary phase and solutes resolution than other CCC coils like the helical and toroidal coils used on type-J CCC and cross-axis CCC. In this work, we built a novel conical coil CCC for the preparative isolation and purification of tanshinones from Salvia miltiorrhiza Bunge. The conical coils were wound on three identical upright tapered holders in head-to-tail and left-handed direction and connected in series. Compared with helical and spiral coil CCC, conical coil CCC not only placed CCC column in a two-dimensional centrifugal field, but also provided a potential centrifugal force gradient both in axial and radial directions. The extra centrifugal gradient made mobile phase move faster and enabled CCC much higher retention of stationary phase and better resolution. As a result, higher efficiency has been obtained with the solvent system of hexane-ethyl acetate-methanol-water (HEMWat) with the volume ratio of 5:5:7:3 by using conical coil CCC apparatus. Four tanshinones, including cryptotanshinone (1), tanshinone I (2), 1,2-dihydrotanshinquinone (3) and tanshinone IIA (4), were well resolved from 500mg to 1g crude samples with high purity. Furthermore, the conical coil CCC can make a much higher solid phase retention, which makes it to be a powerful separation tool with high throughput. This is the first report about conical coil CCC for separation of tanshinones and it may also be an important advancement for natural products isolation.

  18. Separation of flavonoids from Millettia griffithii with high-performance counter-current chromatography guided by anti-inflammatory activity.

    PubMed

    Tang, Huan; Wu, Bo; Chen, Kai; Pei, Heying; Wu, Wenshuang; Ma, Liang; Peng, Aihua; Ye, Haoyu; Chen, Lijuan

    2015-02-01

    Millettia griffithii is a unique Chinese plant located in the southern part of Yunnan Province. Up to now, there is no report about its phytochemical or related bioactivity research. In our previous study, the n-hexane crude extract of Millettia griffithii revealed significant anti-inflammatory activity at 100 μg/mL, inspiring us to explore the anti-inflammatory constituents. Four fractions (I, II, III, and A) were fractionated from n-hexane crude extract by high-performance counter-current chromatography with solvent system composed of n-hexane/ethyl acetate/methanol/water (8:9:8:9, v/v) and then were investigated for the potent anti-inflammatory activity. Fraction A, with the most potent inhibitory activity was further separated to give another four fractions (IV, V, VI, and B) with solvent system composed of n-hexane/ethyl acetate/methanol/water (8:4:8:4, v/v). Compound V and fraction B exhibited remarkable anti-inflammatory activity with nitric oxide inhibitory rate of 80 and 65%, which was worth further fractionation. Then, three fractions (VII, VIII, and IX) were separated from fraction B with a solvent system composed of n-hexane/ethyl acetate/methanol/water (8:1:8:1, v/v), with compound VIII demonstrating the most potent inhibitory activity (80%). Finally, the IC50 values of compound V and VIII were tested as 38.2 and 14.9 μM. The structures were identified by electrospray ionization mass spectrometry and(1)H and (13)C NMR spectroscopy.

  19. Sap flow measurements combining sap-flux density radial profiles with punctual sap-flux density measurements in oak trees (Quercus ilex and Quercus pyrenaica) - water-use implications in a water-limited savanna-

    NASA Astrophysics Data System (ADS)

    Reyes, J. Leonardo; Lubczynski1, Maciek W.

    2010-05-01

    Sap flow measurement is a key aspect for understanding how plants use water and their impacts on the ecosystems. A variety of sensors have been developed to measure sap flow, each one with its unique characteristics. When the aim of a research is to have accurate tree water use calculations, with high temporal and spatial resolution (i.e. scaled), a sensor with high accuracy, high measurement efficiency, low signal-to-noise ratio and low price is ideal, but such has not been developed yet. Granier's thermal dissipation probes (TDP) have been widely used in many studies and various environmental conditions because of its simplicity, reliability, efficiency and low cost. However, it has two major flaws when is used in semi-arid environments and broad-stem tree species: it is often affected by high natural thermal gradients (NTG), which distorts the measurements, and it cannot measure the radial variability of sap-flux density in trees with sapwood thicker than two centimeters. The new, multi point heat field deformation sensor (HFD) is theoretically not affected by NTG, and it can measure the radial variability of the sap flow at different depths. However, its high cost is a serious limitation when simultaneous measurements are required in several trees (e.g. catchment-scale studies). The underlying challenge is to develop a monitoring schema in which HFD and TDP are combined to satisfy the needs of measurement efficiency and accuracy in water accounting. To assess the level of agreement between TDP and HFD methods in quantifying sap flow rates and temporal patterns on Quercus ilex (Q.i ) and Quercus pyrenaica trees (Q.p.), three measurement schemas: standard TDP, TDP-NTG-corrected and HFD were compared in dry season at the semi-arid Sardon area, near Salamanca in Spain in the period from June to September 2009. To correct TDP measurements with regard to radial sap flow variability, a radial sap flux density correction factor was applied and tested by adjusting TDP

  20. Low volume flow meter

    DOEpatents

    Meixler, Lewis D.

    1993-01-01

    The low flow monitor provides a means for determining if a fluid flow meets a minimum threshold level of flow. The low flow monitor operates with a minimum of intrusion by the flow detection device into the flow. The electrical portion of the monitor is externally located with respect to the fluid stream which allows for repairs to the monitor without disrupting the flow. The electronics provide for the adjustment of the threshold level to meet the required conditions. The apparatus can be modified to provide an upper limit to the flow monitor by providing for a parallel electronic circuit which provides for a bracketing of the desired flow rate.

  1. Flow behaviour and transitions in surfactant-laden gas-liquid vertical flows

    NASA Astrophysics Data System (ADS)

    Zadrazil, Ivan; Chakraborty, Sourojeet; Matar, Omar; Markides, Christos

    2016-11-01

    The aim of this work is to elucidate the effect of surfactant additives on vertical gas-liquid counter-current pipe flows. Two experimental campaigns were undertaken, one with water and one with a light oil (Exxsol D80) as the liquid phase; in both cases air was used as the gaseous phase. Suitable surfactants were added to the liquid phase up to the critical micelle concentration (CMC); measurements in the absence of additives were also taken, for benchmarking. The experiments were performed in a 32-mm bore and 5-m long vertical pipe, over a range of superficial velocities (liquid: 1 to 7 m/s, gas: 1 to 44 m/s). High-speed axial- and side-view imaging was performed at different lengths along the pipe, together with pressure drop measurements. Flow regime maps were then obtained describing the observed flow behaviour and related phenomena, i.e., downwards/upwards annular flow, flooding, bridging, gas/liquid entrainment, oscillatory film flow, standing waves, climbing films, churn flow and dryout. Comparisons of the air-water and oil-water results will be presented and discussed, along with the role of the surfactants in affecting overall and detailed flow behaviour and transitions; in particular, a possible mechanism underlying the phenomenon of flooding will be presented. EPSRC UK Programme Grant EP/K003976/1.

  2. Proton gradient regulation 5-mediated cyclic electron flow under ATP- or redox-limited conditions: a study of ΔATpase pgr5 and ΔrbcL pgr5 mutants in the green alga Chlamydomonas reinhardtii.

    PubMed

    Johnson, Xenie; Steinbeck, Janina; Dent, Rachel M; Takahashi, Hiroko; Richaud, Pierre; Ozawa, Shin-Ichiro; Houille-Vernes, Laura; Petroutsos, Dimitris; Rappaport, Fabrice; Grossman, Arthur R; Niyogi, Krishna K; Hippler, Michael; Alric, Jean

    2014-05-01

    The Chlamydomonas reinhardtii proton gradient regulation5 (Crpgr5) mutant shows phenotypic and functional traits similar to mutants in the Arabidopsis (Arabidopsis thaliana) ortholog, Atpgr5, providing strong evidence for conservation of PGR5-mediated cyclic electron flow (CEF). Comparing the Crpgr5 mutant with the wild type, we discriminate two pathways for CEF and determine their maximum electron flow rates. The PGR5/proton gradient regulation-like1 (PGRL1) ferredoxin (Fd) pathway, involved in recycling excess reductant to increase ATP synthesis, may be controlled by extreme photosystem I acceptor side limitation or ATP depletion. Here, we show that PGR5/PGRL1-Fd CEF functions in accordance with an ATP/redox control model. In the absence of Rubisco and PGR5, a sustained electron flow is maintained with molecular oxygen instead of carbon dioxide serving as the terminal electron acceptor. When photosynthetic control is decreased, compensatory alternative pathways can take the full load of linear electron flow. In the case of the ATP synthase pgr5 double mutant, a decrease in photosensitivity is observed compared with the single ATPase-less mutant that we assign to a decreased proton motive force. Altogether, our results suggest that PGR5/PGRL1-Fd CEF is most required under conditions when Fd becomes overreduced and photosystem I is subjected to photoinhibition. CEF is not a valve; it only recycles electrons, but in doing so, it generates a proton motive force that controls the rate of photosynthesis. The conditions where the PGR5 pathway is most required may vary in photosynthetic organisms like C. reinhardtii from anoxia to high light to limitations imposed at the level of carbon dioxide fixation.

  3. Online control of the twin-column countercurrent solvent gradient process for biochromatography.

    PubMed

    Krättli, M; Steinebach, F; Morbidelli, M

    2013-06-07

    A new control concept for the twin-column MCSGP process has been developed. The controller is based on two independent PID controllers each of which affects one side of the product collection window. Accordingly, the two controllers, although independent, can together shift the product collection along the elution chromatogram. The product stream collected during one entire process cycle is analyzed with an at-line HPLC allowing a direct feedback of the measured purity values to the controller. The two set points are given by the purity values with respect to weak and strong impurities in the product stream. The controller performance was tested with two systems: In the first one, a three component protein model mixture was considered. The controller stability and reliability was tested in conditions of both set point tracking and rejection of feed composition and pump flow rate disturbances. The complete experiment ran for 112h during which the desired purity values were always kept within the set points. A more realistic example was the purification of a monoclonal antibody supernatant from fragments and aggregates. In this case, the process reached specifications after five cycles, and kept them for 20h of operation in spite of ongoing disturbances in pump flow rates and feed composition. A new general start-up procedure was developed and tested in this particular purification process. The procedure starts from very simple initial conditions and let the controller to identify conditions, particularly for the recycle streams, which lead to yield and purity values significantly better than the corresponding values achieved in batch chromatography in specs.

  4. Gas holdup and flow regime transition in spider-sparger bubble column: effect of liquid phase properties

    NASA Astrophysics Data System (ADS)

    Besagni, G.; Inzoli, F.; De Guido, G.; Pellegrini, L. A.

    2017-01-01

    This paper discusses the effects of the liquid velocity and the liquid phase properties on the gas holdup and the flow regime transition in a large-diameter and large-scale counter-current two-phase bubble column. In particular, we compared and analysed the experimental data obtained in our previous experimental studies. The bubble column is 5.3 m in height, has an inner diameter of 0.24 m, it was operated with gas superficial velocities in the range of 0.004–0.20 m/s and, in the counter-current mode, the liquid was recirculated up to a superficial velocity of -0.09 m/s. Air was used as the dispersed phase and various fluids (tap water, aqueous solutions of sodium chloride, ethanol and monoethylene glycol) were employed as liquid phases. The experimental dataset consist in gas holdup measurements and was used to investigate the global fluid dynamics and the flow regime transition between the homogeneous flow regime and the transition flow regime. We found that the liquid velocity and the liquid phase properties significantly affect the gas holdup and the flow regime transition. In this respect, a possible relationship (based on the lift force) between the flow regime transition and the gas holdup was proposed.

  5. A limiter-based well-balanced discontinuous Galerkin method for shallow-water flows with wetting and drying: One-dimensional case

    NASA Astrophysics Data System (ADS)

    Vater, Stefan; Beisiegel, Nicole; Behrens, Jörn

    2015-11-01

    An important part in the numerical simulation of tsunami and storm surge events is the accurate modeling of flooding and the appearance of dry areas when the water recedes. This paper proposes a new algorithm to model inundation events with piecewise linear Runge-Kutta discontinuous Galerkin approximations applied to the shallow water equations. This study is restricted to the one-dimensional case and shows a detailed analysis and the corresponding numerical treatment of the inundation problem. The main feature is a velocity based "limiting" of the momentum distribution in each cell, which prevents instabilities in case of wetting or drying situations. Additional limiting of the fluid depth ensures its positivity while preserving local mass conservation. A special flux modification in cells located at the wet/dry interface leads to a well-balanced method, which maintains the steady state at rest. The discontinuous Galerkin scheme is formulated in a nodal form using a Lagrange basis. The proposed wetting and drying treatment is verified with several numerical simulations. These test cases demonstrate the well-balancing property of the method and its stability in case of rapid transition of the wet/dry interface. We also verify the conservation of mass and investigate the convergence characteristics of the scheme.

  6. Combined application of macroporous resin and high speed counter-current chromatography for preparative separation of three flavonoid triglycosides from the leaves of Actinidia valvata Dunn.

    PubMed

    Qu, Liping; Xin, Hailiang; Su, Yonghua; Zheng, Guoyin; Ling, Changquan

    2012-04-01

    In this paper, the combined techniques of macroporous resin column chromatography and high speed counter-current chromatography were applied for preparative separation of flavonoid triglycosides from the leaves of Actinidia valvata Dunn, a famous Chinese medicinal herb. Twelve kinds of macroporous resins were investigated by adsorption and desorption tests. HPD-300 resin showed the maximum effectiveness and thus was selected for the first cleaning-up, in which 20% ethanol was used to remove the undesired constituents and 60% ethanol to elute the targets. The crude extract was then purified by high speed counter-current chromatography with the solvent system composed of ethyl acetate-n-butanol-water (2:1:3 and 4:1:5, v/v). Three flavonoid triglycosides, namely, kaempferol 3-O-α-L-rhamnopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→6)-β-D-galactopyranoside, kaempferol 3-O-α-L-rhamnopyranosyl-(1→3)-(4-O-acetyl-α-L-rhamnopyranosyl)-(1→6)-β-D-galactopyranoside and kaempferol 3-O-α-L-rhamnopyranosyl-(1→3)-(2,4-di-O-acetyl-α-L-rhamnopyranosyl)-(1→6)-β-D-galactopyranoside, were obtained. The purities of the separated compounds were all over 95% as determined by HPLC area normalization method. Their chemical structures were confirmed by UV, MS, NMR, and the standards.

  7. Simultaneous separation of triterpenoid saponins and flavonoid glycosides from the roots of Glycyrrhiza uralensis Fisch by pH-zone-refining counter-current chromatography.

    PubMed

    Xu, Jinfang; Luo, Jianguang; Kong, Lingyi

    2013-10-01

    Glycosides including triterpenoid saponins and flavonoid glycosides are the main constituents of Glycyrrhiza uralensis Fisch (licorice) and exhibit prominent pharmacological activities. However, conventional methods for the separation of glycosides always cause irreversible adsorption and unavoidable loss of sample due to their high hydrophilicities. The present paper describes a convenient method for the simultaneous separation of triterpenoid saponins and flavonoid glycosides from licorice by pH-zone-refining counter-current chromatography. Ethyl acetate/n-butanol/water (2:3:5, v/v) with 10 mM TFA in the upper organic stationary phase and 10 mM ammonia in the lower aqueous mobile phase was used as the biphasic solvent system. Three triterpenoid saponins and two flavonoid glycosides including licorice-saponin A3 (63.3 mg), glycyrrhizic acid (342.2 mg), 3-O-[β-D-glucuronopyranosyl-(1 → 2)-β-D-galactopyranosyl]glycyrrhetic acid (56.0 mg), liquiritin apioside (232.6 mg), and liquiritin (386.5 mg) were successfully obtained from licorice ethanol extract (2 g) in one step. This method subtly takes advantage of the common acidic properties of triterpenoid saponins and flavonoid glycosides, and obviously is much more efficient and convenient than the previous methods. It is also the first time that the separation of acidic triterpenoid saponins by using pH-zone-refining counter-current chromatography has been reported.

  8. Three-phase solvent systems for the comprehensive separation of a wide variety of compounds from Dicranostigma leptopodum by high-speed counter-current chromatography.

    PubMed

    Liu, Yanjuan; Chen, Xiaofen; Liu, JunXi; Di, Duolong

    2015-06-01

    A three-phase solvent system was efficiently applied for high-speed counter-current chromatography to separate secondary metabolites with a wide range of hydrophobicity in Dicranostigma leptopodum. The three-phase solvent system of n-hexane/methyl tert-butyl ether/acetonitrile/0.5% triethylamine (2:2:3:2, v/v/v/v) was selected for high-speed counter-current chromatography separation. The separation was initiated by filling the column with a mixture of intermediate phase and lower phase as a stationary phase followed by elution with upper phase to separate the hydrophobic compounds. Then the mobile phase was switched to the intermediate phase to elute the moderately hydrophobic compounds, and finally the polar compounds still retained in the column were fractionated by eluting the column with the lower phase. In this research, 12 peaks were eluted out in one-step operation within 110 min, among them, eight compounds with acceptable purity were obtained and identified. The purities of β-sitosterol, protopine, allocryptopine, isocorydione, isocorydine, coptisine, berberrubine, and berberine were 94.7, 96.5, 97.9, 86.6, 98.9, 97.6, 95.7, and 92.8%, respectively.

  9. Separation and purification of four flavonol diglucosides from the flower of Meconopsis integrifolia by high-speed counter-current chromatography.

    PubMed

    Huang, Yanfei; Han, Yatao; Chen, Keli; Huang, Bisheng; Liu, Yuan

    2015-12-01

    Flavonoids are the main components of Meconopsis integrifolia (Maxim.) Franch, which is a traditional Tibetan medicine. However, traditional chromatography separation requires a large quantity of raw M. integrifolia and is very time consuming. Herein, we applied high-speed counter-current chromatography in the separation and purification of flavonoids from the ethanol extracts of M. integrifolia flower. Ethyl acetate/n-butanol/water (2:3:5, v/v/v) was selected as the optimum solvent system to purify the four components, namely quercetin-3-O-β-d-glucopyrannosy-(1→6)-β-d-glucopyranoside (compound 1, 60 mg), quercetin 3-O-[2'''-O-acetyl-β-d-glucopyranosyl-(1→6)-β-d-glucopyranoside (compound 2, 40 mg), quercetin 3-O-[3'''-O-acetyl-β-d-glucopyranosyl-(1→6)-β-d-glucopyranoside (compound 3, 11 mg), and quercetin 3-O-[6'''-O-acetyl-β-d-glucopyranosyl-(1→6)-β-d-glucopyranoside (compound 4, 16 mg). Among the four compounds, 3 and 4 were new acetylated flavonol diglucosides. After the high-speed counter-current chromatography separation, the purities of the four flavonol diglucosides were 98, 95, 90, and 92%, respectively. The structures of these compounds were identified by mass spectrometry and NMR spectroscopy.

  10. Bioassay-guided isolation of an active compound with protein tyrosine phosphatase 1B inhibitory activity from Sargassum fusiforme by high-speed counter-current chromatography.

    PubMed

    Wang, Miao; Gu, Dongyu; Guo, Xinfeng; Li, Haoquan; Wang, Yi; Guo, Hong; Yang, Yi; Tian, Jing

    2016-11-01

    A rapid and efficient method using high-speed counter-current chromatography was established for the bioassay-guided separation of an active compound with protein tyrosine phosphatase 1B inhibitory activity from Sargassum fusiforme. Under the bioassay guidance, the ethyl acetate extract with the best IC50 value of 0.37 ± 0.07 μg/mL exhibited a potential protein tyrosine phosphatase 1B inhibitory activity, which was further separated by high-speed counter-current chromatography. The separation was performed with a two-phase solvent system composed of n-hexane/methanol/water (5:4:1, v/v). As a result, dibutyl phthalate (19.7 mg) with the purity of 95.3% was obtained from 200 mg of the ethyl acetate extract. Its IC50 was 14.05 ± 0.06 μM, which was further explained by molecular docking. The result of molecular docking showed that dibutyl phthalate enfolded in the catalytic site of protein tyrosine phosphatase 1B. The main force between dibutyl phthalate and protein tyrosine phosphatase 1B was the hydrogen bond interaction with Gln266. In addition, hydrogen bond, van der Waals force and hydrophobic interaction with the amino acids (Ala217, Ile219, and Gly220) were also responsible for the stable protein-ligand complex.

  11. Preparative separation of bioactive compounds from essential oil of Flaveria bidentis (L.) Kuntze using steam distillation extraction and one step high-speed counter-current chromatography.

    PubMed

    Wei, Yun; Du, Jilin; Lu, Yuanyuan

    2012-10-01

    In order to utilize and control the invasive weed, bioactive compounds from essential oil of Flaveria bidentis (L.) Kuntze were studied. Steam distillation extraction and one step high-speed counter-current chromatography were applied to separate and purify the caryophyllene oxide, 7,11-dimethyl-3-methylene-1,6,10-dodecatriene, and caryophyllene from essential oil of Flaveria bidentis (L.) Kuntze. The two-phase solvent system containing n-hexane/acetonitrile/ethanol (5:4:3, v/v/v) was selected for the one step separation mode according to the partition coefficient values (K) of the target compounds and the separation factor (α). The purity of each isolated fraction after a single high-speed counter-current chromatography run was determined by high performance liquid chromatography. A 3.2 mg of caryophyllene oxide at a purity of 92.6%, 10.4 mg of 7,11-dimethyl-3-methylene-1,6,10-dodecatriene at a purity of 99.1% and 5.7 mg of caryophyllene at a purity of 98.8% were obtained from 200 mg essential oil of Flaveria bidentis (L.) Kuntze. The chemical structures of these components were identified by GC-MS, (1) H-NMR, and (13) C-NMR.

  12. Amide-I lifetime-limited vibrational energy flow in a one-dimensional lattice of hydrogen-bonded peptide units.

    PubMed

    Pouthier, Vincent

    2008-12-01

    A time-convolutionless master equation is established for describing the amide-I vibrational energy flow in a lattice of H-bonded peptide units. The dynamics is addressed within the small polaron formalism to account for the strong coupling between the amide-I vibron and the phonons describing the H-bond vibrations. Therefore, special attention is paid to characterize the influence of the amide-I relaxation on the polaron transport properties. This relaxation is modeled by assuming that each amide-I mode interacts with a bath of intramolecular normal modes whose displacements are strongly localized on the C=O groups. It has been shown that the energy relaxation occurs over a very short time scale which prevents any significant delocalization of the polaron. At biological temperature, the polaron explores a finite region around the excited site whose size is about one or two lattice parameters. However, two regimes occur depending on whether the vibron-phonon coupling is weak or strong. For a weak coupling, the energy propagates coherently along the lattice until the polaron disappears. By contrast, for a strong coupling, a diffusive regime occurs so that the polaron explores a finite size region incoherently. In both cases, the finite polaron lifetime favors the localization of the vibron density whose amplitude decreases exponentially.

  13. Landscape genomics of Populus trichocarpa: the role of hybridization, limited gene flow, and natural selection in shaping patterns of population structure.

    PubMed

    Geraldes, Armando; Farzaneh, Nima; Grassa, Christopher J; McKown, Athena D; Guy, Robert D; Mansfield, Shawn D; Douglas, Carl J; Cronk, Quentin C B

    2014-11-01

    Populus trichocarpa is an ecologically important tree across western North America. We used a large population sample of 498 accessions over a wide geographical area genotyped with a 34K Populus SNP array to quantify geographical patterns of genetic variation in this species (landscape genomics). We present evidence that three processes contribute to the observed patterns: (1) introgression from the sister species P. balsamifera, (2) isolation by distance (IBD), and (3) natural selection. Introgression was detected only at the margins of the species' distribution. IBD was significant across the sampled area as a whole, but no evidence of restricted gene flow was detected in a core of drainages from southern British Columbia (BC). We identified a large number of FST outliers. Gene Ontology analyses revealed that FST outliers are overrepresented in genes involved in circadian rhythm and response to red/far-red light when the entire dataset is considered, whereas in southern BC heat response genes are overrepresented. We also identified strong correlations between geoclimate variables and allele frequencies at FST outlier loci that provide clues regarding the selective pressures acting at these loci.

  14. Kinetics of /sup 13/N-ammonia uptake in myocardial single cells indicating potential limitations in its applicability as a marker of myocardial blood flow

    SciTech Connect

    Rauch, B.; Helus, F.; Grunze, M.; Braunwell, E.; Mall, G.; Hasselbach, W.; Kuebler, W.

    1985-02-01

    To study kinetics and principles of cellular uptake of /sup 13/N-ammonia, a marker of coronary perfusion in myocardial scintigraphy, heart muscle cells of adult rats were isolated by perfusion with collagenase and hyaluronidase. Net uptake of /sup 13/N, measured by flow dialysis, reached equilibrium within 20 sec in the presence of sodium bicarbonate and carbon dioxide (pH 7.4, 37 degrees C). Total extraction, 80 sec after the reaction start, was 786 +/- 159 mumol/ml cell volume. Cells destroyed by calcium overload were unable to extract /sup 13/N-ammonia. Omission of bicarbonate and carbon dioxide reduced total extraction to 36% of control. /sup 13/N-Ammonia uptake could also be reduced by 50 muM 4,4' diisothiocyanostilbene 2,2' disulfonic acid, by 100 micrograms/ml 1-methionine sulfoximine, and by preincubation with 5 muM free oleic acid. These results indicate that in addition to metabolic trapping by glutamine synthetase, the extraction of /sup 13/N-ammonia by myocardial cells is influenced by cell membrane integrity, intracellular-extracellular pH gradient, and possibly an anion exchange system for bicarbonate. For this reason, the uptake of /sup 13/N-ammonia may not always provide a valid measurement of myocardial perfusion.

  15. Computational studies of reacting flows with applications to zinc selenide nanoparticle synthesis and methane/hydrogen separation

    NASA Astrophysics Data System (ADS)

    Koutsona, Maria

    This work is a numerical study of the design and operation of two reacting flow systems, each with great potential in their fields. The design of reacting flow systems by computer simulations are successfully used in science and engineering to evaluate design geometries and operation, without resorting to experimental trial and error that is expensive, time consuming and, in some cases, dangerous. The models of the two systems described in this work are based on fundamental conservation equations for momentum and mass transfer coupled with chemical reaction kinetics and particle dynamics. The first part of this work is a study aiming to elucidate the transport phenomena and chemical reactions that control the size of ZnSe nanoparticles formed by a new vapor-phase synthesis route. The nanoparticles are synthesized by reacting vapors of (CH3)2Zn:N(C2H 5)3 adduct with H2Se gas (diluted in hydrogen) fed continuously from opposite sides into a counterflow jet reactor. The nuclei of the nanocrystals are formed by a direct condensation reaction near the stagnation point. The nuclei grow into nanoparticles by coalescence/coagulation and by surface growth reactions. A 2D model of an axially symmetric reactor was developed that includes descriptions of flow, mass transfer by convection and diffusion, chemical kinetics, particle nucleation, coagulation and surface growth. The coupled nonlinear partial differential equations of the model were solved using the Galerkin Finite Element Method. The model was used to study the relative importance of the underlying physical and chemical phenomena in controlling particle size and particle size distribution. Model predictions compared well with the limited experimental data available for this system. The model was also used for model-assisted design of the experimental counterflow jet reactor, where vapor-phase synthesis of ZnSe nanoparticles was demonstrated for the first time. The second part of this work involves the development of

  16. Adenovirus purification by two-column, size-exclusion, simulated countercurrent chromatography.

    PubMed

    Nestola, Piergiuseppe; Silva, Ricardo J S; Peixoto, Cristina; Alves, Paula M; Carrondo, Manuel J T; Mota, José P B

    2014-06-20

    Adenovirus serotype 5 (Ad5) was successfully separated by size-exclusion chromatography (SEC) using a simple, yet efficient, two-column, quasi-continuous, simulated moving-bed process operated in an open-loop configuration. The operating cycle is divided into two identical half-cycles, each of them consisting of the following sequence of sub-steps: (i) elution of the upstream column and direction of the effluent of the downstream column to waste; (ii) elution of the upstream column and redirection of its effluent to waste while the downstream column is fed with the clarified bioreaction bulk and its effluent collected as purified product; (iii) operation of the system as in step (i) but collecting the effluent of the downstream column as product; (iv) elution of the upstream column and direction of its effluent to waste while the flow through the downstream column is temporarily halted. Clearance of impurities, namely DNA and host cell protein (HCP), were experimentally assessed. The pilot-scale run yielded a virus recovery of 86%, and a clearance of 90% and 89% for DNA and HCP, respectively, without any fine tunning of the predetermined operating parameters. These figures compare very favorably against single-column batch chromatography for the same volume of size-exclusion resin. However, and most importantly, the virus yield was increased from 57% for the batch system to 86% for the two-column SEC process because of internal recycling of the mixed fractions of contaminated Ad5, even though the two-column process was operated strictly in an open-loop configuration. And last, but not least, the productivity was increased by 6-fold with the two-column process. In conclusion, the main drawbacks of size-exclusion chromatography, namely low productivity and low product titer, were overcome to a considerable extent by an innovative two-column configuration that keeps the mixed fractions inside the system at all times.

  17. Effects of pH, CO2, and flow pattern on the autotrophic degradation of hydrogen sulfide in a biotrickling filter.

    PubMed

    Jin, Yaomin; Veiga, María C; Kennes, Christian

    2005-11-20

    In this study, the effects of pH, CO(2), and flow pattern on the performance of a biotrickling filter (BTF) packed with plastic Pall rings and treating a H(2)S-polluted waste gas were investigated to establish the optimum operating conditions and design criteria. The CO(2) concentration had no effect on the biodegradation at H(2)S concentrations below 50 ppm. In the range of 50-127 ppm H(2)S, CO(2) concentrations between 865 and 1,087 ppm enhanced H(2)S removal, while higher concentrations of 1,309-4,009 ppm CO(2) slightly inhibited H(2)S removal. The co-current flow BTF presented the advantage of a more uniform H(2)S removal and biomass growth in each section than the counter-current flow BTF. Examination of the pH-effect in the range of pH 2.00-7.00 revealed optimal activity for autotrophs at pH 6.00. Under optimal conditions, the elimination capacity reached 31.12 g H(2)S/m(3)/h with a removal efficiency exceeding 97%. In the present research, autotrophic biomass was developed in the BTF, performing both a partial oxidization of H(2)S to elemental sulfur and a complete oxidization to sulfate, which is favorable from an environmental point of view. Results showed that around 60% of the sulfide concentration fed to the reactor was transformed into sulfate. Such autotrophic trickling filters may present other advantages, including the fact that they do not release any CO(2) to the atmosphere. Besides, the limited growth of autotrophs avoids potential clogging problems. Experimental performance data were compared with data from a mathematical model. Comparisons showed that the theoretical model was successful in predicting the performance of the biotrickling filter.

  18. Turbulence Considerations for Comparing Ecosystem Exchange over Old-Growth and Clear-Cut Stands For Limited Fetch and Complex Canopy Flow Conditions

    SciTech Connect

    Wharton, S; Schroeder, M; Paw U, K T; Falk, M; Bible, K

    2009-01-08

    Carbon dioxide, water vapor and energy fluxes were measured using eddy covariance (EC) methodology over three adjacent forests in southern Washington State to identify stand-level age-effects on ecosystem exchange. The sites represent Douglas-fir forest ecosystems at two contrasting successional stages: old-growth (OG) and early seral (ES). Here we present eddy flux and meteorological data from two early seral stands and the Wind River AmeriFlux old-growth forest during the growing season (March-October) in 2006 and 2007. We show an alternative approach to the usual friction velocity (u*) method for determining periods of adequate atmospheric boundary layer (ABL) mixing based on the ratio of mean horizontal ({bar u}) and vertical ({bar w}) wind flow to a modified turbulent kinetic energy scale (uTKE). This new parameter in addition to footprint modeling showed that daytime CO{sub 2} fluxes (F{sub NEE}) in small clear-cuts (< 10 hectares) can be measured accurately with EC if micrometeorological conditions are carefully evaluated. Peak midday CO{sub 2} fluxes (F{sub NEE} = -14.0 to -12.3 {micro}mol m{sup -2} s{sup -1}) at OG were measured in April in both 2006 and 2007 before bud break when air and soil temperatures and vapor pressure deficit were relatively low, and soil moisture and light levels were favorable for photosynthesis. At the early seral stands, peak midday CO{sub 2} fluxes (F{sub NEE} = -11.0 to -8.7 {micro}mol m{sup -2} s{sup -1}) were measured in June and July while spring-time CO{sub 2} fluxes were much smaller (F{sub NEE} = -3.8 to -3.6 {micro}mol m{sup -2} s{sup -1}). Overall, we measured lower evapotranspiration (OG = 230 mm; ES = 297 mm) higher midday F{sub NEE} (OG F{sub NEE} = -9.0 {micro}mol m{sup -2} s{sup -1}; ES F{sub NEE} = -7.3 {micro}mol m{sup -2} s{sup -1}) and higher Bowen ratios (OG {beta} = 2.0. ES {beta} = 1.2) at the old-growth forest than at the ES sites during the summer months (May-August). Eddy covariance studies such as ours

  19. Versatile solvent systems for the separation of betalains from processed Beta vulgaris L. juice using counter-current chromatography.

    PubMed

    Spórna-Kucab, Aneta; Ignatova, Svetlana; Garrard, Ian; Wybraniec, Sławomir

    2013-12-15

    Two mixtures of decarboxylated and dehydrogenated betacyanins from processed red beet roots (Beta vulgaris L.) juice were fractionated by high performance counter-current chromatography (HPCCC) producing a range of isolated components. Mixture 1 contained mainly betacyanins, 14,15-dehydro-betanin (neobetanin) and their decarboxylated derivatives while mixture 2 consisted of decarboxy- and dehydro-betacyanins. The products of mixture 1 arose during thermal degradation of betanin/isobetanin in mild conditions while the dehydro-betacyanins of mixture 2 appeared after longer heating of the juice from B. vulgaris L. Two solvent systems were found to be effective for the HPCCC. A highly polar, high salt concentration system of 1-PrOH-ACN-(NH4)2SO4 (satd. soln)-water (v/v/v/v, 1:0.5:1.2:1) (tail-to-head mode) enabled the purification of 2-decarboxy-betanin/-isobetanin, 2,17-bidecarboxy-betanin/-isobetanin and neobetanin (all from mixture 1) plus 17-decarboxy-neobetanin, 2,15,17-tridecarboxy-2,3-dehydro-neobetanin, 2-decarboxy-neobetanin and 2,15,17-tridecarboxy-neobetanin (from mixture 2). The other solvent system included heptafluorobutyric acid (HFBA) as ion-pair reagent and consisted of tert-butyl methyl ether (TBME)-1-BuOH-ACN-water (acidified with 0.7% HFBA) (2:2:1:5, v/v/v/v) (head-to-tail mode). This system enabled the HPCCC purification of 2,17-bidecarboxy-betanin/-isobetanin and neobetanin (from mixture 1) plus 2,15,17-tridecarboxy-2,3-dehydro-neobetanin, 2,17-bidecarboxy-2,3-dehydro-neobetanin and 2,15,17-tridecarboxy-neobetanin (mixture 2). The results of this research are crucial in finding effective isolation methods of betacyanins and their derivatives which are meaningful compounds due their colorant properties and potential health benefits regarding antioxidant and cancer prevention. The pigments were detected by LC-DAD and LC-MS/MS techniques.

  20. Separation of polar betalain pigments from cacti fruits of Hylocereus polyrhizus by ion-pair high-speed countercurrent chromatography.

    PubMed

    Wybraniec, Sławomir; Stalica, Paweł; Jerz, Gerold; Klose, Bettina; Gebers, Nadine; Winterhalter, Peter; Spórna, Aneta; Szaleniec, Maciej; Mizrahi, Yosef

    2009-10-09

    Polar betacyanin pigments together with betaxanthins from ripe cactus fruits of Hylocereus polyrhizus (Cactaceae) were fractionated by means of preparative ion-pair high-speed countercurrent chromatography (IP-HSCCC) also using the elution-extrusion (EE) approach for a complete pigment recovery. HSCCC separations were operated in the classical 'head-to-tail' mode with an aqueous mobile phase. Different CCC solvent systems were evaluated in respect of influence and effectiveness of fractionation capabilities to separate the occurring pigment profile of H. polyrhizus. For that reason, the additions of two different volatile ion-pair forming perfluorinated carboxylic acids (PFCA) were investigated. For a direct comparison, five samples of Hylocereus pigment extract were run on preparative scale (900 mg) in 1-butanol-acetonitrile-aqueous TFA 0.7% (5:1:6, v/v/v) and the modified systems tert.-butyl methyl ether-1-butanol-acetonitrile-aqueous PFCA (2:2:1:5, v/v/v/v) using 0.7% and 1.0% trifluoroacetic acid (TFA) or heptafluorobutyric acid (HFBA) in the aqueous phase, respectively. The chemical affinity to the organic stationary CCC solvent phases and in consequence the retention of these highly polar betalain pigments was significantly increased by the use of the more lipophilic fluorinated ion-pair reagent HFBA instead of TFA. The HFBA additions separated more effectively the typical cacti pigments phyllocactin and hylocerenin from betanin as well as their iso-forms. Unfortunately, similar K(D) ratios and selectivity factors alpha around 1.0-1.1 in all tested solvent systems proved that the corresponding diastereomers, 15S-type pigments cannot be resolved from the 15R-epimers (iso-forms). Surprisingly, additions of the stronger ion-pair reagent (HFBA) resulted in a partial separation of hylocerenin from phyllocactin which were not resolved in the other solvent systems. The pigments were detected by means of HPLC-DAD and HPLC-electrospray ionization-MS using also

  1. Observations of intra-wave suspended sediment transport under acceleration-skewed oscillatory flow

    NASA Astrophysics Data System (ADS)

    Ruessink, G.; Michallet, H.; Hurther, D.; Silva, P.

    2008-12-01

    In the nearshore, waves transform from skewed shoaling waves to asymmetric breaking waves. Velocity skewness, such as found beneath Stokes second-order waves, generally results in a net onshore sediment transport. Recent numerical studies and limited experimental laboratory data have demonstrated the potential importance of acceleration skewness to onshore sediment transport beneath asymmetric, 'saw- tooth' waves. Here, we investigate new full-scale laboratory tunnel experiments under sheetflow conditions in which regular oscillatory sawtooh flow with varying degrees of acceleration skewness and velocity skewness were generated over a mobile bed. In all experiments the velocity amplitude was 1.2 m/s, the wave period was 7 s, and the bed was composed of well-sorted, fine to medium sand (d50 = 200~μm). In several experiments a counter-current of 0.4 m/s was imposed to imitate undertow. We deployed (1) a 2-MHz Acoustical Doppler Velocimeter Profiler (ADVP) to obtain vertical profiles of (phase-averaged) horizontal and vertical oscillatory and turbulent flow with a temporal and vertical resolution of 50 Hz and 3 mm, respectively, and (2) a triple-frequency Acoustical Backscatter Sensor to obtain vertical profiles of (phase-averaged) suspended sediment concentration with a temporal and vertical resolution of 10 Hz and 5 mm, respectively. Under waves with acceleration skewness only, we observed two concentration peaks, which at the top of the sheetflow layer were approximately in phase with the free-stream velocity. As the concentration peak following the rapid acceleration towards maximum onshore flow was slightly larger than the concentration peak under maximum offshore flow, the depth-integrated and wave-averaged suspended transport was directed onshore. While most sediment stirred during the onshore flow phase had settled back to the bed before flow reversal, some sediment stirred during the offshore flow phase persisted into the onshore flow phase, thus providing

  2. Investigation of Multiscale and Multiphase Flow, Transport and Reaction in Heavy Oil Recovery Processes

    SciTech Connect

    Yortsos, Yanis C.

    2001-08-07

    This project is an investigation of various multi-phase and multiscale transport and reaction processes associated with heavy oil recovery. The thrust areas of the project include the following: Internal drives, vapor-liquid flows, combustion and reaction processes, fluid displacements and the effect of instabilities and heterogeneities and the flow of fluids with yield stress. These find respective applications in foamy oils, the evolution of dissolved gas, internal steam drives, the mechanics of concurrent and countercurrent vapor-liquid flows, associated with thermal methods and steam injection, such as SAGD, the in-situ combustion, the upscaling of displacements in heterogeneous media and the flow of foams, Bingham plastics and heavy oils in porous media and the development of wormholes during cold production.

  3. Investigation of Multiscale and Multiphase Flow, Transport and Reaction in Heavy Oil Recovery Processes

    SciTech Connect

    Yortsos, Y.C.

    2001-05-29

    This report is an investigation of various multi-phase and multiscale transport and reaction processes associated with heavy oil recovery. The thrust areas of the project include the following: Internal drives, vapor-liquid flows, combustion and reaction processes, fluid displacements and the effect of instabilities and heterogeneities and the flow of fluids with yield stress. These find respective applications in foamy oils, the evolution of dissolved gas, internal steam drives, the mechanics of concurrent and countercurrent vapor-liquid flows, associated with thermal methods and steam injection, such as SAGD, the in-situ combustion, the upscaling of displacements in heterogeneous media and the flow of foams, Bingham plastics and heavy oils in porous media and the development of wormholes during cold production.

  4. Design of a novel coil satellite centrifuge and its performance on counter-current chromatographic separation of 4-methylumbelliferyl sugar derivatives with organic-aqueous two-phase solvent systems

    PubMed Central

    Shinomiya, Kazufusa; Tokura, Koji; Kimura, Emiru; Takai, Midori; Harikai, Naoki; Yoshida, Kazunori; Yanagidaira, Kazuhiro; Ito, Yoichiro

    2015-01-01

    A new high-speed counter-current chromatograph, named coil satellite centrifuge (CSC), was designed and fabricated in our laboratory. The CSC apparatus produces the satellite motion such that the coiled column simultaneously rotates around the sun axis (the angular velocity, ω1), the planet axis (ω2) and the satellite axis (the central axis of the column) (ω3). In order to achieve this triplicate rotary motion without twisting of the flow tube, the rotation of each axis was determined by the following formula: ω1 = ω2 + ω3. This relation enabled to lay out the flow tube by two different ways, the SS type and the JS type. In the SS type, the flow tube was introduced from the upper side of the apparatus into the sun axis of the first rotary frame and connected to the planet axis of the second rotary frame like a double letter SS. In the JS type, the flow tube was introduced from the bottom of the apparatus into the sun axis reaching the upper side of the planet axis an inversed letter J, followed by distribution as in the SS type. The performance of the apparatus was examined on separation of 4-methylumbelliferyl (MU) sugar derivatives as test samples with organic-aqueous two-phase solvent systems composed of ethyl acetate/1-butanol/water (3 : 2 : 5, v/v) for lower phase mobile and (1 : 4 : 5, v/v) for upper phase mobile. With lower phase mobile, five 4-MU sugar derivatives including β-D-cellobioside (Cel), β-D-glucopyranoside, α-D-mannopyranoside, β-D-fucopyranoside and α-L-fucopyranoside (α-L-Fuc) were separated with the combined rotation around each axis at counterclockwise (CCW) (ω1) – CCW (ω2) – CCW (ω3) by the JS type flow tube distribution. With upper phase mobile, three 4-MU sugar derivatives including α-L-Fuc, β-D-galactopyranoside and Cel were separated with the combined rotation around each axis at clockwise (CW) (ω1) – CW (ω2) – CW (ω3) by the JS type flow tube distribution. A series of experiments on peak resolution and

  5. Hybrid upwind discretization of nonlinear two-phase flow with gravity

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Efendiev, Y.; Tchelepi, H. A.

    2015-08-01

    Multiphase flow in porous media is described by coupled nonlinear mass conservation laws. For immiscible Darcy flow of multiple fluid phases, whereby capillary effects are negligible, the transport equations in the presence of viscous and buoyancy forces are highly nonlinear and hyperbolic. Numerical simulation of multiphase flow processes in heterogeneous formations requires the development of discretization and solution schemes that are able to handle the complex nonlinear dynamics, especially of the saturation evolution, in a reliable and computationally efficient manner. In reservoir simulation practice, single-point upwinding of the flux across an interface between two control volumes (cells) is performed for each fluid phase, whereby the upstream direction is based on the gradient of the phase-potential (pressure plus gravity head). This upwinding scheme, which we refer to as Phase-Potential Upwinding (PPU), is combined with implicit (backward-Euler) time discretization to obtain a Fully Implicit Method (FIM). Even though FIM suffers from numerical dispersion effects, it is widely used in practice. This is because of its unconditional stability and because it yields conservative, monotone numerical solutions. However, FIM is not unconditionally convergent. The convergence difficulties are particularly pronounced when the different immiscible fluid phases switch between co-current and counter-current states as a function of time, or (Newton) iteration. Whether the multiphase flow across an interface (between two control-volumes) is co-current, or counter-current, depends on the local balance between the viscous and buoyancy forces, and how the balance evolves in time. The sensitivity of PPU to small changes in the (local) pressure distribution exacerbates the problem. The common strategy to deal with these difficulties is to cut the timestep and try again. Here, we propose a Hybrid-Upwinding (HU) scheme for the phase fluxes, then HU is combined with implicit

  6. Flow structure in continuous flow electrophoresis chambers

    NASA Technical Reports Server (NTRS)

    Deiber, J. A.; Saville, D. A.

    1982-01-01

    There are at least two ways that hydrodynamic processes can limit continiuous flow electrophoresis. One arises from the sensitivity of the flow to small temerature gradients, especially at low flow rates and power levels. This sensitivity can be suppressed, at least in principle, by providing a carefully tailored, stabilizing temperature gradient in the cooling system that surrounds the flow channel. At higher power levels another limitation arises due to a restructuring of the main flow. This restructuring is caused by buoyancy, which is in turn affected by the electro-osmotic crossflow. Approximate solutions to appropriate partial differential equations have been computed by finite difference methods. One set of results is described here to illustrate the strong coupling between the structure of the main (axial) flow and the electro-osmotic flow.

  7. Preparative Separation of N-Feruloyl Serotonin and N-(p-Coumaroyl) Serotonin from Safflower Seed Meal Using High-Speed Counter-Current Chromatography.

    PubMed

    Zhang, Qiulong; Hu, Na; Li, Wencong; Ding, Chenxi; Ma, Tao; Bai, Bo; Wang, Honglun; Suo, Yourui; Wang, Xiaoyan; Ding, Chenxu

    2015-09-01

    High-speed counter-current chromatography (HSCCC) was successfully applied for the preparative separation and purification of N-feruloyl serotonin (NF) and N-(p-coumaroyl) serotonin (NP) from safflower seed meal. After the measurement of partition coefficient of the two target compounds in the two-phase solvent systems, the HSCCC was performed well with a two-phase solvent system composed of CHCl3-methanol-0.1 M HCl at a volume ratio of 1 : 1 : 1, v/v. The upper phase was used as stationary phase and the lower phase was used as mobile phase. Under the optimized condition, 7.5 mg NF and 6.9 mg NP were separated from 40 mg crude sample with the purity of 98.8 and 97.3%, respectively. The structures of the isolated compounds were identified by (1)H NMR and (13)C NMR.

  8. Isolation and purification of three flavonoid glycosides from the leaves of Nelumbo nucifera (Lotus) by high-speed counter-current chromatography.

    PubMed

    Deng, Shengguo; Deng, Zeyuan; Fan, Yawei; Peng, You; Li, Jing; Xiong, Dongmei; Liu, Rong

    2009-08-15

    Semi-preparative high-speed counter-current chromatography (HSCCC) was successfully used for isolation and purification of flavonoid glycosides from the leaves of Nelumbo nucifera (Lotus) by using a two-phase-solvent system composed of n-hexane-ethyl acetate-methanol-water (1:5:1:5, v/v/v/v). The targeted compounds isolated, collected and purified by HSCCC were analyzed by high performance liquid chromatography (HPLC). A total of 4.6 mg of isoquercitrin, 9.1 mg of hyperoside and 3.0 mg of astragalin with the purity of 95.8%, 97.5% and 98.3%, respectively, were obtained in one-step separation and less than 6 h from 80 mg of crude extract from the leaves of N. nucifera. The chemical structures of all the three compounds were identified by MS, (1)H NMR, (13)C NMR. Astragalin was obtained from N. nucifera for the first time.

  9. Separation of five flavonoids from tartary buckwheat (Fagopyrum tataricum (L.) Gaertn) grains via off-line two dimensional high-speed counter-current chromatography.

    PubMed

    Jiang, Shujing; Liu, Qi; Xie, Yixi; Zeng, Hualiang; Zhang, Li; Jiang, Xinyu; Chen, Xiaoqing

    2015-11-01

    An off-line two dimensional (2D) high-speed counter-current chromatography (HSCCC) strategy was successfully used for preparative separation of five flavonoids from tartary buckwheat (Fagopyrum tataricum (L.) Gaertn) grains with different solvent systems for the first time in this paper. n-Hexane-ethyl acetate-methanol-water 3:5:3:5 (v/v) was selected as the first dimension solvent system to purify quercetin (4) and kaempferol (5). The second dimension solvent system, ethyl acetate-n-butanol-water 7:3:10 (v/v), was used to isolate quercetin 3-O-rutinoside-3'-O-β-glucopyranoside (1), rutin (2) and kaempferol 3-rutinoside (3). The purities of these compounds were all above 96.0% and their structures were identified through UV, MS and (1)H NMR. The results indicated that the off-line 2D HSCCC is an efficient technique to isolate flavonoids compounds from grains.

  10. Purification of six lignans from the stems of Schisandra chinensis by using high-speed counter-current chromatography combined with preparative high-performance liquid chromatography.

    PubMed

    Zhu, Lijie; Li, Bin; Liu, Xiuying; Huang, Guohui; Meng, Xianjun

    2015-11-01

    A method for the preparative purification of lignans from Schisandra chinensis was established using a combination of high-speed counter-current chromatography (HSCCC) and preparative high-performance liquid chromatography (HPLC). The crude extracts obtained from S. chinensis by using 70% ethanol were separated on a macroporous resin column and then eluted with a graded ethanol series. A two-phase solvent system consisting of n-hexane-ethyl acetate-methanol-water (1:1:1:1, v/v) was used for HSCCC, and a mobile phase of acetonitrile-water (50:50, v/v) was used for preparative HPLC. The results obtained using HSCCC were compared with those obtained using preparative HPLC, and their advantages were further integrated to improve the separation efficiency. Six known lignans were identified by electrospray ionisation mass spectrometry and (1)H nuclear magnetic resonance (NMR) and (13)C NMR analyses; the purities of all the compounds were more than 91%.

  11. Chiral counter-current chromatography of gemifloxacin guided by capillary electrophoresis using (+)-(18-crown-6)-tetracarboxylic acid as a chiral selector.

    PubMed

    Kim, Eunsook; Koob, Yoon-Mo; Chung, Doo Soo

    2004-08-06

    (+)-(18-crown-6)-tetracarboxylic acid (18C6H4) has been known as a highly efficient chiral selector for resolving primary amine enantiomers in capillary electrophoresis (CE). We investigated the chiral separation of gemifloxacin using 18C6H4 in analytical counter-current chromatography (CCC). The separation conditions for CE, including the binding constant, pH, and run buffer constituents, provided a helpful guideline for chiral CCC. A successful separation of gemifloxacin enantiomers could be achieved using a two-phase solvent system composed of 1-butanol-ethyl-acetate-bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane acetate buffer with a small amount of 18C6H4. The hydrophobicity of the solvent system and the 18C6H4 concentration were varied to optimize the chiral separation.

  12. An application of high-speed counter-current chromatography coupled with electrospray ionization mass spectrometry for separation and online identification of coumarins from Peucedanum praeruptorum Dunn.

    PubMed

    Hou, Zhiguo; Xu, Deran; Yao, Shun; Luo, Jianguang; Kong, Lingyi

    2009-08-15

    A new and systematic application for separation and online identification of coumarins from Peucedanum praeruptorum Dunn by preparative high-speed counter-current chromatography coupled with electrospray ionization multi-stage mass spectrometry (prep-HSCCC/ESI-MS(n)) was established. The procedure of separation was guided by the chromatogram of ion current. The structures of acquisitions were deduced by MS information. The hyphenation between prep-HSCCC/ESI-MS(n) was designed to keep the split ratio from 1:20 to 1:200 exactly. Seven compounds were obtained and two new compounds were detected. It was proved that prep-HSCCC/ESI-MS(n) was an effective method for sensitive detection, rapid identification and separation of natural products.