Structure and phase transitions of the multilamellar DMPC membranes in presence of the DMSO and DESO
Gorshkova, Yu E.; Ivankov, O. I.
2017-05-01
The structure and phase transitions of the prepared and formed spontaneously multilamellar vesicles (MLVs) of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in dimethyl sulfoxide (DMSO) and diethyl sulfoxide (DESO) were investigated using small angle neutron scattering (SANS). The both polar aprotic solvents increase the temperature of the main phase transition (Tm ). The pre-transition does not observed at sulfoxides mole fraction X = 0.2. The transition of the MLVs DMPC in the presence DMSO from gel to liquid-crystalline phase occurs at lower temperature. The method of the MLVs preparation has directly effects on the temperature of the main phase transition and its structure. The value of Tm is higher with ∼ 4.6 ºC in case of the spontaneous forming MLVs from extruded ULVs. The thickness of the solvent layer for prepared MLVs is less by 4.0 Å in gel phase and by 5.6 Å in liquid-crystalline phase than the thickness of the solvent layer for spontaneously formed MLVs.
Energy Technology Data Exchange (ETDEWEB)
Pentak, Danuta, E-mail: danuta.pentak@us.edu.pl
2014-05-01
Highlights: • New phase transition for DMPC was found. • FT-IR method is an important addition to the DSC studies. • The proposed method for determining the T{sub C} give very consistent results. - Abstract: In this work, alternatives to differential scanning calorimetry (DSC) as a method of determining the main phospholipid phase transition temperature are presented. The bilayer phase transitions from the ripple gel phase (P{sub β{sup ′}}) to the liquid-crystal phase (L{sub α}) of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were studied by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) methods. In this work, two correlations between the DSC and FT-IR methods, and NMR and EPR methods are shown. The proposed methods allow for determining the T{sub C} temperature with a high degree of accuracy. Furthermore, a comparison of results obtained using the DSC and FT-IR methods allowed for an observation of a new DMPC phase transition. The liposomes analyzed in this work were obtained by the modified reverse-phase evaporation method (mREV)
The effect of tail-length mismatch in binary DMPC/DSPC lipid bilayers
Ashkar, Rana; Nagao, Michihiro; Butler, Paul
2014-03-01
Bilayer heterogeneity has been long hypothesized to drive raft formation and promote complex functionality in lipid membranes. The highly dynamic nature of the membrane however is thought to play a critical role in this delicate balance between structure and performance. To probe the effect of lateral heterogeneity on membrane dynamics, we investigate the thermal response of unilamellar-vesicle systems of mixed dimyristoylphosphatidylcholine (DMPC) and distearoylphosphatidylcholine (DSPC) with DMPC/DSPC ratios of 50/50 and 70/30. Both lipids experience a transition from an ordered gel phase, with stiff stretched tails, to a melted fluid phase, with more coiled flexible tails, as they are heated through their melting temperature, Tm(DMPC) ~ 21 °C and Tm(DSPC) ~ 51 °C. The distinct Tm's of the two lipids provide a broad gel-fluid phase with a significant mismatch (~ 20 Å) between the tail-lengths of the DMPC and DSPC molecules. The structural properties of the vesicles were determined by small-angle neutron and x-ray scattering and the collective lipid dynamics in the bilayer were investigated by neutron spin-echo (NSE) spectroscopy on selectively deuterated samples. The NSE results indicate a slowdown of thickness fluctuations in the gel-fluid coexistence phase and an intriguingly strong enhancement in the thickness fluctuation amplitude for T >Tm(DSPC) compared to our previous work on single component vesicles.
Effects of Fatty Acid Inclusion in a DMPC Bilayer Membrane
DEFF Research Database (Denmark)
Peters, Günther H.J.; Hansen, Flemming Yssing; Møller, Martin S.
2009-01-01
Free fatty acids in biomembranes have been proposed to be a central component in several cellular control and regulatory mechanisms. To elucidate some fundamental elements underlying this, we have applied molecular dynamics simulations and experimental density measurements to study the molecular...... packing and structure of oleic acid (HOA) and stearic acid (HSA) in fluid bilayers of dimyristoylphosphatidylcholine (DMPC). The experimental data show a small but consistent positive excess volume for fatty acid concentrations below 10 mol %. At higher concentrations the fatty acids mix ideally...... with fluid DMPC. The simulations, which were benchmarked against the densitometric data, revealed interesting differences in the structure and location of the fatty acids depending on their protonation status. Thus, the protonated (uncharged) acid is located rather deeply in the membrane with an average...
Comprehensive examination of mesophases formed by DMPC and DHPC mixtures.
Harroun, Thad A; Koslowsky, Martin; Nieh, Mu-Ping; de Lannoy, Charles-François; Raghunathan, V A; Katsaras, John
2005-06-07
Mixtures of long- and short-chain phospholipids, specifically 14:0 and 6:0 phosphatidylcholines (DMPC and DHPC), have been used successfully in NMR studies as magnetically alignable substrates for membrane-associated proteins. However, recent publications have shown that the phase behavior of these mixtures is much more complex than originally thought. Using polarized light microscopy and small-angle neutron scattering, phase diagrams of DMPC/DHPC mixtures at molar ratios of 2, 3.2, and 5 have been determined. Generally, at temperatures below the main-chain melting transition of DMPC (T(M) = 23 degrees C), an isotropic phase of disk-like micelles is found. At high temperatures (T > 50 degrees C), a lamellar phase consisting of either multilamellar vesicles (MLV) or extended lamellae is formed, which at low lipid concentrations (e.g., MLV) coexists with an excess of water. At intermediate temperatures and lipid concentrations, a chiral nematic phase made up of worm-like micelles was observed.
Morphological effects of ceramide on DMPC/DHPC bicelles.
Barbosa-Barros, L; De la Maza, A; Walther, P; Estelrich, J; López, O
2008-04-01
Freeze fracture electron microscopy and dynamic light scattering were applied to characterize the morphological changes of DMPC/DHPC bicellar systems induced by the addition of ceramides. The results demonstrate a tendency of the DMPC/DHPC aggregates to evolve forming elongated or tubular structures with the increase of the temperature. At 20 degrees C, low concentrations of ceramide promote the appearance of elongated structures with twisted zones. Higher concentrations of this lipid lead to the formation of liposomes along the elongated structures. The increase of the temperature to 40 degrees C induces the growth of the structures containing low concentrations of ceramide forming branched aggregates. In samples with high amounts of ceramide, the increase of temperature causes phase separation and the formation of a mixed system composed by liposomes and multilamellar tubules. The morphological effects induced by ceramides in this new membrane model give new insights for the role played by this lipid in biological membranes.
Two-phase cooling fluids; Les fluides frigoporteurs diphasiques
Energy Technology Data Exchange (ETDEWEB)
Lallemand, A. [Institut National des Sciences Appliquees (INSA), 69 - Lyon (France)
1997-12-31
In the framework of the diminution of heat transfer fluid consumption, the concept of indirect refrigerating circuits, using cooling intermediate fluids, is reviewed and the fluids that are currently used in these systems are described. Two-phase cooling fluids advantages over single-phase fluids are presented with their thermophysical characteristics: solid fraction, two-phase mixture enthalpy, thermal and rheological properties, determination of heat and mass transfer characteristics, and cold storage through ice slurry
Hirshfeld, C.L.; Seul, M.
1990-01-01
The pressure-composition phase diagram of mixed monolayers of dimyristoyl phosphatidylcholine (DMPC) and cholesterol at a temperature of 23.5 °C is derived by numerical analysis of pressure-area isotherms and corroborated by direct fluorescence microscopic observations. We identify a fluid-fluid miscibility gap, terminated by an upper critical point which is accessible near room temperature. We propose that the coexisting mixed phases of cholesterol and DMPC contain the phospholipid in two di...
Phase transitions of quadrupolar fluids
O'Shea, Seamus F.; Dubey, Girija S.; Rasaiah, Jayendran C.
1997-07-01
Gibbs ensemble simulations are reported for Lennard-Jones particles with embedded quadrupoles of strength Q*=Q/(ɛσ5)1/2=2.0 where ɛ and σ are the Lennard-Jones parameters. Calculations revealing the effect of the dispersive forces on the liquid-vapor coexistence were carried out by scaling the attractive r-6 term in the Lennard-Jones pair potential by a factor λ ranging from 0 to 1. Liquid-vapor coexistence is observed for all values of λ including λ=0 for Q*=2.0, unlike the corresponding dipolar fluid studied by van Leeuwen and Smit et al. [Phys. Rev. Lett. 71, 3991 (1993)] which showed no phase transition below λ=0.35 when the reduced dipole moment μ*=2.0. The simulation data are analyzed to estimate the critical properties of the quadrupolar fluid and their dependence on the strength λ of the dispersive force. The critical temperature and pressure show a clear quadratic dependence on λ, while the density is less confidently identified as being linear in λ. The compressibility is roughly linear in λ.
Directory of Open Access Journals (Sweden)
Maciej Kozak
2013-04-01
Full Text Available Amphiphilic dicationic surfactants, known as gemini surfactants, are currently studied for gene delivery purposes. The gemini surfactant molecule is composed of two hydrophilic “head” groups attached to hydrophobic chains and connected via molecular linker between them. The influence of different concentrations of 1,5-bis (1-imidazolilo-3-decyloxymethyl pentane chloride (gemini surfactant on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC bilayers with and without the presence of DNA was investigated using Fourier transformed infrared (FTIR and circular dichroism (CD spectroscopies, small angle scattering of synchrotron radiation and differential scanning calorimetry. With increasing concentration of surfactant in DMPC/DNA systems, a disappearance of pretransition and a decrease in the main phase transition enthalpy and temperature were observed. The increasing intensity of diffraction peaks as a function of surfactant concentration also clearly shows the ability of the surfactant to promote the organisation of lipid bilayers in the multilayer lamellar phase.
Constant-pH MD Simulations of DMPA/DMPC Lipid Bilayers.
Santos, Hugo A F; Vila-Viçosa, Diogo; Teixeira, Vitor H; Baptista, António M; Machuqueiro, Miguel
2015-12-08
Current constant-pH molecular dynamics (CpHMD) simulations provide a proper treatment of pH effects on the structure and dynamics of soluble biomolecules like peptides and proteins. However, addressing such effects on lipid membrane assemblies has remained problematic until now, despite the important role played by lipid ionization at physiological pH in a plethora of biological processes. Modeling (de)protonation events in these systems requires a proper consideration of the physicochemical features of the membrane environment, including a sound treatment of solution ions. Here, we apply our recent CpHMD-L method to the study of pH effects on a 25% DMPA/DMPC bilayer membrane model, closely reproducing the correct lipid phases of this system, namely, gel-fluid coexistence at pH 4 and a fluid phase at pH 7. A significant transition is observed for the membrane ionization and mechanical properties at physiological pH, providing a molecular basis for the well-established role of phosphatidic acid (PA) as a key player in the regulation of many cellular events. Also, as reported experimentally, we observed pH-induced PA-PA lipid aggregation at acidic pH. By including the titration of anionic phospholipids, the current methodology makes possible to simulate lipid bilayers with increased realism. To the best of our knowledge, this is the first simulation study dealing with a continuous phospholipid bilayer with pH titration of all constituent lipids.
Motional Coherence in Fluid Phospholipid Membranes
Rheinstadter, Maikel C; Flenner, Elijah J; Bruening, Beate; Seydel, Tilo; Kosztin, Ioan
2008-01-01
We report a high energy-resolution neutron backscattering study, combined with in-situ diffraction, to investigate slow molecular motions on nanosecond time scales in the fluid phase of phospholipid bilayers of 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine (DMPC) and DMPC/40% cholesterol (wt/wt). A cooperative structural relaxation process was observed. From the in-plane scattering vector dependence of the relaxation rates in hydrogenated and deuterated samples, combined with results from a 0.1 microsecond long all atom molecular dynamics simulation, it is concluded that correlated dynamics in lipid membranes occurs over several lipid distances, spanning a time interval from pico- to nanoseconds.
Yang, Jing; Bonomi, Massimiliano; Calero, Carles; Martí, Jordi
2016-04-07
Exploring the free energy landscapes of metal cations on phospholipid membrane surfaces is important for the understanding of chemical and biological processes in cellular environments. Using metadynamics simulations we have performed systematic free energy calculations of sodium cations bound to DMPC phospholipid membranes with cholesterol concentration varying between 0% (cholesterol-free) and 50% (cholesterol-rich) at infinite dilution. The resulting free energy landscapes reveal the competition between binding of sodium to water and to lipid head groups. Moreover, the binding competitiveness of lipid head groups is diminished by cholesterol contents. As cholesterol concentration increases, the ionic affinity to membranes decreases. When cholesterol concentration is greater than 30%, the ionic binding is significantly reduced, which coincides with the phase transition point of DMPC-cholesterol membranes from a liquid-disordered phase to a liquid-ordered phase. We have also evaluated the contributions of different lipid head groups to the binding free energy separately. The DMPC's carbonyl group is the most favorable binding site for sodium, followed by DMPC's phosphate group and then the hydroxyl group of cholesterol.
Morphology of magnetically aligning DMPC/DHPC aggregates-perforated sheets, not disks.
van Dam, Lorens; Karlsson, Göran; Edwards, Katarina
2006-03-28
The morphology of DMPC/DHPC mixtures at total lipid concentration cL = 5% (w/w) and DMPC/DHPC ratio q approximately 3, doped with small amounts of DMPG or CTAB, was investigated. 31P NMR was used to identify the magnetically aligning phase, and cryo-transmission electron microscopy (cryo-TEM) was employed for structural characterization. Magnetic alignment was found to occur between approximately 30 and approximately 45 degrees C, and cryo-TEM showed that the magnetically aligning phase consisted of extended sheets with a lacelike structure. The aggregates are best described as intermediates between two-dimensional networks of flattened, highly branched, cylindrical micelles and lamellar sheets perforated by large irregular holes. DHPC most likely covers the edges of the holes, while DMPC makes up the bilayer bulk of the aggregates. However, 20-43% of the DHPC takes part in the bilayer, corresponding to 6-12% of the bilayer being made up of DHPC. This fraction increases with increasing temperature. At temperatures above 45 degrees C, the aligning phase collapses.
Thermodynamics phase changes of nanopore fluids
Islam, Akand W.
2015-07-01
The van der Waals (vdW) equation (Eq.) is modified to describe thermodynamic of phase behavior of fluids confined in nanopore. Our aim is to compute pressures exerted by the fluid molecules and to investigate how they change due to pore proximity by assuming the pore wall is inert. No additional scaling of model parameters is imposed and original volume and energy parameters are used in the calculations. Our results clearly show the phase changes due to confinement. The critical shifts of temperatures and pressures are in good agreement compared to the laboratory data and molecular simulation. Peng-Robinson (PR) equation-of-state (EOS) has resulted in different effect than the vdW. This work delivers insights into the nature of fluid behavior in extremely low-permeability nanoporous media, especially in the tight shale reservoirs, below the critical temperatures. © 2015 Elsevier B.V.
Interfacial behavior of Myristic acid in mixtures with DMPC and Cholesterol
Khattari, Z.; Sayyed, M. I.; Qashou, S. I.; Fasfous, I.; Al-Abdullah, T.; Maghrabi, M.
2017-06-01
Binary mixture monolayers of Myristic acid (MA) with the same length of saturated acyl chain lipid viz 1,2-myristoyl-sn-glycero-3-phosphocholine (DMPC) and Cholesterol (Chol), were investigated under different experimental conditions using Langmuir monolayers (LMs). The interfacial pressure-area (π-A) isotherms, excess molecular area, excess free energy and fluorescence microscopy (FM) images were recorded at the air/water interface. Monolayers of both systems (e.g. MA/DMPC, MA/Chol) reach the closest acyl hydrophobic chain packing in the range 0.20 air/water interface with negative deviation from the ideal behavior. Morphological features of MA/DMPC systems were found to depend strongly on MA mole fraction and pressures by showing two extreme minima in Gibbs free energy of mixing, while MA/Chol systems showed only an effective condensing effect at xMA = 0.90. In the whole range of compositions studied here, the liquid-expanded (LE) to liquid-condensed (LC) phase transition occurs at increasing xAM as it accomplished by a huge increase in the inverse compressibility modulus. FM observations confirmed the phase-transition and condensing effects of both mixture monolayers as evidenced by Gibbs free energy of mixing in a limited range of compositions.
Molecular Modeling of Solid Fluid Phase Behavior
Energy Technology Data Exchange (ETDEWEB)
Peter A. Monson
2007-12-20
This report gives a summary of the achievements under DOE contract No. DOE/ER/14150 during the period September 1, 1990 to December 31, 2007. This project was concerned with the molecular modeling of solid-fluid equilibrium. The focus was on understanding how solid-fluid and solid-solid phase behavior are related to molecular structure, and the research program made a seminal contribution in this area. The project led to 34 journal articles, including a comprehensive review article published in Advances in Chemical Physics. The DOE funding supported the work of 5 Ph.D. students, 2 M.S. students and 5 postdoctoral researchers.
Analysing DHPC/DMPC bicelles by diffusion NMR and multivariate decomposition.
Björnerås, Johannes; Nilsson, Mathias; Mäler, Lena
2015-11-01
Mixtures of lipids and detergents are known to form bicelles at certain parameter ranges, but many uncertainties remain concerning the details of the phase behaviour of these mixtures and the morphology of the formed lipid assemblies. Here we used nuclear magnetic resonance (NMR) diffusion data in combination with the multivariate processing method speedy component resolution (SCORE) to analyse mixtures of 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with the relative concentration q=[DMPC]/[DHPC]=0.5 at total lipid concentrations ranging from 15 to 300 mM. With this approach we were able to resolve the heavily overlapping mixture spectra into component spectra and obtained reliable diffusion coefficients for lipid concentrations in the range 15 to 300 mM, although at high concentrations (250-300 mM), non-negativity constraints or overfactoring was required to successfully decompose the data. At 50-300 mM total lipid concentration, the radii estimated from the diffusion coefficient of DMPC indicate assemblies of the appropriate bicelle size, although small size variations exist, while at lower concentrations the morphology appears to change to larger assemblies. Taken together, the results suggest that for q=0.5 DMPC/DHPC mixtures there is a relatively broad concentration range above 50 mM where bicelles may reliably be assumed to adopt the 'classical' bicelle morphology. The study clearly demonstrates the usefulness of our approach for accurately determining physical properties of complex mixtures such as bicelles. Both reliable diffusion coefficients and chemical shifts can be derived from overlapping data. This should prove useful for analysing the behaviour of other, more complex, lipid mixtures.
Phase behavior of an amphiphilic fluid.
Schoen, Martin; Giura, Stefano; Klapp, Sabine H L
2014-01-01
We invoke mean-field density functional theory (DFT) to investigate the phase behavior of an amphiphilic fluid composed of a hard-sphere core plus a superimposed anisometric Lennard-Jones perturbation. The orientation dependence of the interactions consists of a contribution analogous to the interaction potential between a pair of "spins" in the classical, three-dimensional Heisenberg fluid and another one reminiscent of the interaction between (electric or magnetic) point dipoles. At fixed orientation both contributions are short-range in nature decaying as r-6 (r being the separation between the centers of mass of a pair of amphiphiles). Based upon two mean-field-like approximations for the pair correlation function that differ in the degree of sophistication we derive expressions for the phase boundaries between various isotropic and polar phases that we solve numerically by the Newton-Raphson method. For sufficiently strong coupling between the Heisenberg "spins" both mean-field approximations generate three topologically different and generic types of phase diagrams that are observed in agreement with earlier work [see, for example, Tavares et al., Phys. Rev. E 52, 1915 (1995)]. Whereas the dipolar contribution alone is incapable of stabilizing polar phases on account of its short-range nature it is nevertheless important for details of the phase diagram such as location of the gas-isotropic liquid critical point, triple, and tricritical points. By tuning the dipolar coupling constant suitably one may, in fact, switch between topologically different phase diagrams. Employing also Monte Carlo simulations in the isothermal-isobaric ensemble the general topology of the DFT phase diagrams is confirmed.
Energy Technology Data Exchange (ETDEWEB)
Taha, Ziyad A., E-mail: tahaz33@just.edu.jo [Department of Applied Chemical Sciences, Faculty of Arts and Sciences, Jordan University of Science and Technology, Irbid 22110 (Jordan); Ajlouni, Abdulaziz M.; Hijazi, Ahmed K. [Department of Applied Chemical Sciences, Faculty of Arts and Sciences, Jordan University of Science and Technology, Irbid 22110 (Jordan); Al-Rawashdeh, Nathir A. [Department of Applied Chemical Sciences, Faculty of Arts and Sciences, Jordan University of Science and Technology, Irbid 22110 (Jordan); Department of Chemistry, United Arab Emirates University, Al Ain 15551 (United Arab Emirates); Al-Hassan, Khader A.; Al-Haj, Yaser A. [Department of Chemistry, Faculty of Science, Yarmouk University, 1163 Irbid (Jordan); Ebqa' ai, Mohammad A. [Al-Qunfudah Center For Scientific Research, Umm Al-Qura University, College in Al-Qunfudah, Makkah (Saudi Arabia); Altalafha, Ammar Y. [Department of Chemistry, Faculty of Science, Yarmouk University, 1163 Irbid (Jordan)
2015-05-15
A series of lanthanide complexes with the general formulae [Ln(dmpc)(NO{sub 3}){sub 2}(H{sub 2}O){sub 2}]NO{sub 3} (Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Er) and [La(dmpc)(NO{sub 3}){sub 2}(H{sub 2}O){sub 2}]NO{sub 3} were prepared by direct reaction between hydrated lanthanide(III) nitrate and dimethylpyridine-2,6-dicarboxylate (dmpc) in a 1:1 M ratio in ethylacetate–chloroform mixture. The luminescence properties of the dmpc and its Ln(III) complexes were investigated in solid state and in methanol, DMF and DMSO solutions. The Tb–dmpc, Eu–dmpc, Sm–dmpc and Dy–dmpc complexes exhibit characteristic luminescence of Tb(III), Eu(III), Sm(III) and Dy(III) ions indicating energy transfer from the dmpc to the Ln(III) ions. Scavenging activities of the dmpc and its Ln(III) complexes on DPPH{sup •} free radical were investigated in DMSO solution at a different concentrations ranges. - Highlights: • Nine new lanthanide complexes with dmpc ligand are prepared and characterized. • Ln–dmpc {Ln=Eu, Tb, Sm, Dy} complexes exhibit characteristic emissions of Ln ions. • The solvent effect on the luminescence intensity is investigated. • The antioxidant activity of the dmpc is enhanced upon complexation with lanthanide.
Thermal stabilization of DMPC/DHPC bicelles by addition of cholesterol sulfate.
Shapiro, Rebecca A; Brindley, Amanda J; Martin, Rachel W
2010-08-25
Doping DMPC/DHPC bicelles with cholesterol sulfate broadens the temperature range over which stable alignment occurs, forming an aligned phase at lower temperatures even with high lipid concentrations. Cholesterol sulfate appears to combine the advantages of cholesterol with those of charged amphiphiles, stabilizing the aligned phase and preventing precipitation. This allows NMR data for RDC and CSA protein structure constraints to be acquired at or below room temperature, an obvious advantage for solid-state and solution studies of heat-sensitive proteins.
Cholesterol orientation and tilt modulus in DMPC bilayers
Khelashvili, George; Pabst, Georg; Harries, Daniel
2010-01-01
We performed molecular dynamics (MD) simulations of hydrated bilayers containing mixtures of dimyristoylphosphatidylcholine (DMPC) and Cholesterol at various ratios, to study the effect of cholesterol concentration on its orientation, and to characterize the link between cholesterol tilt and overall phospholipid membrane organization. The simulations show a substantial probability for cholesterol molecules to transiently orient perpendicular to the bilayer normal, and suggest that cholesterol...
Effect of tetracaine on DMPC and DMPC+cholesterol biomembrane models: liposomes and monolayers.
Serro, A P; Galante, R; Kozica, A; Paradiso, P; da Silva, A M P S Gonçalves; Luzyanin, K V; Fernandes, A C; Saramago, B
2014-04-01
Different types of lipid bilayers/monolayers have been used to simulate the cellular membranes in the investigation of the interactions between drugs and cells. However, to our knowledge, very few studies focused on the influence of the chosen membrane model upon the obtained results. The main objective of this work is to understand how do the nature and immobilization state of the biomembrane models influence the action of the local anaesthetic tetracaine (TTC) upon the lipid membranes. The interaction of TTC with different biomembrane models of dimyristoylphosphatidylcholine (DMPC) with and without cholesterol (CHOL) was investigated through several techniques. A quartz crystal microbalance with dissipation (QCM-D) was used to study the effect on immobilized liposomes, while phosphorus nuclear magnetic resonance ((31)P-NMR) and differential scanning calorimetry (DSC) were applied to liposomes in suspension. The effect of TTC on Langmuir monolayers of lipids was also investigated through surface pressure-area measurements at the air-water interface. The general conclusion was that TTC has a fluidizing effect on the lipid membranes and, above certain concentrations, induces membrane swelling or even solubilization. However, different models led to variable responses to the TTC action. The intensity of the disordering effect caused by TTC increased in the following order: supported liposomes
High-pressure fluid phase equilibria phenomenology and computation
Deiters, Ulrich K
2012-01-01
The book begins with an overview of the phase diagrams of fluid mixtures (fluid = liquid, gas, or supercritical state), which can show an astonishing variety when elevated pressures are taken into account; phenomena like retrograde condensation (single and double) and azeotropy (normal and double) are discussed. It then gives an introduction into the relevant thermodynamic equations for fluid mixtures, including some that are rarely found in modern textbooks, and shows how they can they be used to compute phase diagrams and related properties. This chapter gives a consistent and axiomatic approach to fluid thermodynamics; it avoids using activity coefficients. Further chapters are dedicated to solid-fluid phase equilibria and global phase diagrams (systematic search for phase diagram classes). The appendix contains numerical algorithms needed for the computations. The book thus enables the reader to create or improve computer programs for the calculation of fluid phase diagrams. introduces phase diagram class...
The effect of selected surfactants on the structure of a bicellar system (DMPC/DHPC) studied by SAXS
Kozak, Maciej; Domka, Ludwik; Jurga, Stefan
2007-11-01
The stabilizing or disturbing effect of different surfactants on the bicellar phase of phospholipids significantly depends on their type. The effect of different surfactants on the bicellar structure made of a mixture of phospholipids 1,2-dimyristoyl-sn-glycero-3-phosphocholine and 1,2-dihexanoyl-sn-glycero-3-phospho-choline (DMPC/DHPC) has been studied by the small angle scattering of synchrotron radiation. The study has been performed for three surfactants: dodecyldimethyl-(hexyloxymethyl)ammonium chloride, n-undecylammonium chloride and t-octylphenoxypolyethoxyethanol (Triton X-100) introduced into a bicellar solution of DMPC/DHPC (2.8:1). The bicellar phase has been disturbed in the shortest time in the presence of dodecyldimethyl-(hexyloxymethyl)ammonium chloride in this system a transition from the bicellar to lamellar structure has been directly visible. The changes have been less pronounced in the presence of undecylammonium chloride and practically not noted in the presence of Triton X-100.
Phase transitions in fluids and biological systems
Sipos, Maksim
In this thesis, I consider systems from two seemingly different fields: fluid dynamics and microbial ecology. In these systems, the unifying features are the existences of global non-equilibrium steady states. I consider generic and statistical models for transitions between these global states, and I relate the model results with experimental data. A theme of this thesis is that these rather simple, minimal models are able to capture a lot of functional detail about complex dynamical systems. In Part I, I consider the transition between laminar and turbulent flow. I find that quantitative and qualitative features of pipe flow experiments, the superexponential lifetime and the splitting of turbulent puffs, and the growth rate of turbulent slugs, can all be explained by a coarse-grained, phenomenological model in the directed percolation universality class. To relate this critical phenomena approach closer to the fluid dynamics, I consider the transition to turbulence in the Burgers equation, a simplified model for Navier-Stokes equations. Via a transformation to a model of directed polymers in a random medium, I find that the transition to Burgers turbulence may also be in the directed percolation universality class. This evidence implies that the turbulent-to-laminar transition is statistical in nature and does not depend on details of the Navier-Stokes equations describing the fluid flow. In Part II, I consider the disparate subject of microbial ecology where the complex interactions within microbial ecosystems produce observable patterns in microbe abundance, diversity and genotype. In order to be able to study these patterns, I develop a bioinformatics pipeline to multiply align and quickly cluster large microbial metagenomics datasets. I also develop a novel metric that quantifies the degree of interactions underlying the assembly of a microbial ecosystem, particularly the transition between neutral (random) and niche (deterministic) assembly. I apply this
Optimization of crystal nucleation close to a metastable fluid-fluid phase transition.
Wedekind, Jan; Xu, Limei; Buldyrev, Sergey V; Stanley, H Eugene; Reguera, David; Franzese, Giancarlo
2015-06-22
The presence of a metastable fluid-fluid critical point is thought to dramatically influence the crystallization pathway, increasing the nucleation rate by many orders of magnitude over the predictions of classical nucleation theory. We use molecular dynamics simulations to study the kinetics of crystallization in the vicinity of this metastable critical point and throughout the metastable fluid-fluid phase diagram. To quantitatively understand how the fluid-fluid phase separation affects the crystal nucleation, we evaluate accurately the kinetics and reconstruct the thermodynamic free-energy landscape of crystal formation. Contrary to expectations, we find no special advantage of the proximity of the metastable critical point on the crystallization rates. However, we find that the ultrafast formation of a dense liquid phase causes the crystallization to accelerate both near the metastable critical point and almost everywhere below the fluid-fluid spinodal line. These results unveil three different scenarios for crystallization that could guide the optimization of the process in experiments.
Schmidt, Miranda L; Davis, James H
2016-04-01
Magnetically orienting bicelles are often made by combining the long chain phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with the short chain phospholipid 1,2-dicaproyl-sn-glycero-3-phosphocholine (DCPC) in buffer. These bicelles orient with their bilayer normals perpendicular to the external magnetic field. We have examined the phase behaviour of DMPC/DCPC bicelles and the effects of cholesterol and the unsaturated phospholipid 1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine (DPoPC) as a function of temperature using static solid state (2)H nuclear magnetic resonance spectroscopy. As expected, cholesterol has an ordering effect on the long phospholipid chains and this is reflected in the phase behaviour of the bicelle mixtures. Liquid disordered-liquid ordered, fluid-fluid phase coexistence is observed in DMPC/cholesterol/DCPC bicelles with cholesterol mole fractions of 0.13 and higher. DPoPC/DMPC/cholesterol/DCPC bicelles also exhibit two fluid phase coexistence over a broad range of temperatures and compositions. Bicelles can provide a useful medium in which to study membrane bound peptides and proteins. The orientation parallel to the magnetic field is favourable for studying membrane peptides/proteins because information about the orientation of relevant molecular bonds or internuclear vectors can be obtained directly from the resulting (2)H spectra. Lanthanide ions can be used to flip the bicelles to have their bilayer normals parallel to the external magnetic field. Yb(3+) was used to flip the DPoPC/DMPC/cholesterol/DCPC bicelles while Eu(3+) was found to be ineffective at flipping bicelles containing cholesterol in the present work.
Thermo-Fluid Dynamics of Two-Phase Flow
Ishii, Mamrou
2011-01-01
"Thermo-fluid Dynamics of Two-Phase Flow, Second Edition" is focused on the fundamental physics of two-phase flow. The authors present the detailed theoretical foundation of multi-phase flow thermo-fluid dynamics as they apply to: Nuclear reactor transient and accident analysis; Energy systems; Power generation systems; Chemical reactors and process systems; Space propulsion; Transport processes. This edition features updates on two-phase flow formulation and constitutive equations and CFD simulation codes such as FLUENT and CFX, new coverage of the lift force model, which is of part
Analysing DHPC/DMPC bicelles by diffusion NMR and multivariate decomposition
DEFF Research Database (Denmark)
Björnerås, Johannes; Nilsson, Lars Mathias; Mäler, Lena
2015-01-01
in combination with the multivariate processing method speedy component resolution (SCORE) to analyse mixtures of 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with the relative concentration q=[DMPC]/[DHPC]=0.5 at total lipid concentrations ranging from...
Pharmacological attenuation of Paramecium fluid-phase endocytosis.
Wiejak, Jolanta; Surmacz, Liliana; Wyroba, Elzbieta
2007-01-01
Spectrophotometric quantification of fluid phase endocytosis in the presence of different pharmacological compounds was performed in the model unicellular eukaryote Paramecium. The kinetics of Lucifer Yellow Carbohydrazide (LY) uptake in cells exposed to forskolin and isoproterenol--known to stimulate phagocytosis in this cell--was analyzed. Reduction in both the rate of endocytosis and total accumulation of fluid phase marker was observed following the treatment. Forskolin diminished total LY accumulation by 11% and 21% after 5 min and 25 min of incubation, respectively, whereas the rate of uptake was lowered by 21% in comparison to control cells. The inhibitory effect ofisoproterenol was less pronounced than that of forskolin. The total accumulation of LY was decreased by 11% in 5 min as compared to the untreated cells and this effect was persistent upon further exposition to this reagent up to 25 min. To better understand these observations, the effect of inhibitors of PKA and cAMP phosphodiesterase on fluid phase uptake was tested. 3-isobutyl-1-methyl xanthine (IBMX) caused 12% decrease in LY accumulation after 5 min of incubation. In combination with isoproterenol or forskolin, IBMX enhanced their inhibitory effect on fluid endocytosis, which was lowered by 25% and 29%, respectively. The strongest inhibitory effect on fluid endocytosis was exerted by the 10 microM PKA inhibitor, which diminished endocytosis by 35% in 5 min. These results suggest that Paramecium fluid phase uptake may be regulated through activation of PKA, although the precise mechanism of this process has not yet been elucidated.
Gyroid phase of fluids with spherically symmetric competing interactions.
Edelmann, Markus; Roth, Roland
2016-06-01
We study the phase diagram of a fluid with spherically symmetric competing pair interactions that consist of a short-ranged attraction and a longer-ranged repulsion in addition to a hard core. To this end we perform free minimizations of three-dimensional triple periodic structures within the framework of classical density functional theory. We compare our results to those from Landau theory. Our main finding is that the double gyroid phase can exist as a thermodynamically stable phase.
Dynamic changes of phase in a van der Waals fluid
Hagan, R.; Serrin, J.
1984-03-01
This paper gives sufficient conditions to guarantee the existence of a shock layer solution connecting two different equilibrium states in a van der Waals fluid. In particular, the equilibrium states can belong to two different phases of the fluid. The constitutive laws come from a modified Korteweg theory which is compatible with the Clausius Duhem inequality. The Clausius Duhem inequality in turn gives rise to a Liapunov function. The main mathematical tool is the LaSalle invariance principle.
Fluid-phase endocytosis in yeasts other than Saccharomyces cerevisiae.
Fernandez, N; Puente, P; Leal, F
1990-05-01
A FITC-dextran internalization assay with Saccharomyces cerevisiae as positive control was used to determine whether fluid-phase endocytosis is a general characteristic of yeasts. Schizosaccharomyces pombe, Pichia polymorpha, Kluyveromyces phaseolosporus, Yarrowia lipolytica and Candida albicans were clearly positive, whereas results obtained with Debaryomyces marama were inconclusive. In all cases internalized FITC-dextran was found to be localized in the vacuoles and the process was always time- and temperature-dependent. Lower eucaryotes, particularly yeasts, appear to have the ability to incorporate substances from the extracellular medium through fluid-phase endocytosis.
Stochastic analysis of particle-fluid two-phase flows
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
This paper is devoted to exploring approaches to understanding the stochastic characteristics of particle-fluid two-phase flow. By quantifying the forces dominating the particle motion and modelling the less important and/or unclear forces as random forces, a stochastic differential equation is proposed to describe the complex behavior of a particle motion. An exploratory simulation has shown satisfactory agreement with phase doppler particle analyzer (PDPA) measurements, which indicates that stochastic analysis is a potential approach for revealing the details of particle-fluid flow phenomena.
Acyl chain composition and coexisting fluid phases in lipid bilayers
Gu, Yongwen; Bradley, Miranda; Mitchell, Drake
2011-10-01
At room temperature phospholipid bilayers enriched in sphingolipids and cholesterol may form a solid phase as well as two coexisting fluid phases. These are the standard fluid phase, or the liquid-disordered phase, ld, and the liquid-ordered phase, lo, which is commonly associated with lipid rafts. Ternary mixtures of palmitoyl-oleoyl-phosphocholine (POPC; 16:0,18:1 PC), sphingomyelin (SPM), and cholesterol (Chol) form coexisting lo, ld and solid phases over a wide range of molar ratios. We are examining the ability of two fluorescent probes to detect these 2 phases: NBD linked to di-16:0 PE which partitions strongly into the lo phase and NBD linked to di-18:1 PE which partitions strongly into the ld phase. We are also examining the effect of the highly polyunsaturated phospholipid stearoyl-docosahexanoyl-phosphocholine (SDPC; 18:0, 22:6 PC) on the ternary phase diagram of POPC/SPM/Chol with particular focus on the functionally important lo/ld coexistence region. We report on the fluorescence lifetime and anisotropy decay dynamics of these two fluorescent probes.
Effect of divalent cations on DMPC/DHPC bicelle formation and alignment.
Brindley, Amanda J; Martin, Rachel W
2012-05-22
Many important classes of biomolecules require divalent cations for optimal activity, making these ions essential for biologically relevant structural studies. Bicelle mixtures composed of short-chain and long-chain lipids are often used in solution- and solid-state NMR structure determination; however, the phase diagrams of these useful orienting media and membrane mimetics are sensitive to other solution components. Therefore, we have investigated the effect of varying concentrations of four divalent cations, Ca(2+), Mg(2+), Zn(2+), and Cd(2+), on cholesterol sulfate-stabilized DMPC/DHPC bicelles. We found that low concentrations of all the divalent ions are tolerated with minimal perturbation. At higher concentrations Zn(2+) and Cd(2+) disrupt the magnetically aligned phase while Ca(2+) and Mg(2+) produce more strongly oriented phases. This result indicates that divalent cations are not only required to maintain the biological activity of proteins and nucleic acids; they may also be used to manipulate the behavior of the magnetically aligned phase.
Low-Density Fluid Phase of Dipolar Hard Spheres
Sear, Richard P.
1996-03-01
Unexpectedly, recent computer simulation studies [Weis and Levesque, Phys. Rev. Lett. 71, 2729 (1993); Leeuwen and Smit, ibid. 71, 3991 (1993)] failed to find a liquid phase for dipolar hard spheres. We argue that the liquid was not observed because the dipolar spheres form long chains which interact only weakly. To support this argument we derive a simple theory for noninteracting chains of dipolar spheres and show that it provides a reasonable description of the low-density fluid phase.
Modulated phases of graphene quantum Hall polariton fluids
Pellegrino, Francesco M. D.; Giovannetti, Vittorio; MacDonald, Allan H.; Polini, Marco
2016-11-01
There is a growing experimental interest in coupling cavity photons to the cyclotron resonance excitations of electron liquids in high-mobility semiconductor quantum wells or graphene sheets. These media offer unique platforms to carry out fundamental studies of exciton-polariton condensation and cavity quantum electrodynamics in a regime, in which electron-electron interactions are expected to play a pivotal role. Here, focusing on graphene, we present a theoretical study of the impact of electron-electron interactions on a quantum Hall polariton fluid, that is a fluid of magneto-excitons resonantly coupled to cavity photons. We show that electron-electron interactions are responsible for an instability of graphene integer quantum Hall polariton fluids towards a modulated phase. We demonstrate that this phase can be detected by measuring the collective excitation spectra, which is often at a characteristic wave vector of the order of the inverse magnetic length.
Rayleigh-Taylor instability of viscous fluids with phase change
Kim, Byoung Jae; Kim, Kyung Doo
2016-04-01
Film boiling on a horizontal surface is a typical example of the Rayleigh-Taylor instability. During the film boiling, phase changes take place at the interface, and thus heat and mass transfer must be taken into consideration in the stability analysis. Moreover, since the vapor layer is not quite thick, a viscous flow must be analyzed. Existing studies assumed equal kinematic viscosities of two fluids, and/or considered thin viscous fluids. The purpose of this study is to derive the analytical dispersion relation of the Rayleigh-Taylor instability for more general conditions. The two fluids have different properties. The thickness of the vapor layer is finite, but the liquid layer is thick enough to be nearly semi-infinite in view of perturbation. Initially, the vapor is in equilibrium with the liquid at the interface, and the direction of heat transfer is from the vapor side to the liquid side. In this case, the phase change has a stabilizing effect on the growth rate of the interface. When the vapor layer is thin, there is a coupled effect of the vapor viscosity, phase change, and vapor thickness on the critical wave number. For the other limit of a thick vapor, both the liquid and vapor viscosities influence the critical wave number. Finally, the most unstable wavelength is investigated. When the vapor layer is thin, the most unstable wavelength is not affected by phase change. When the vapor layer is thick, however, it increases with the increasing rate of phase change.
Cerroni, D.; Fancellu, L.; Manservisi, S.; Menghini, F.
2016-06-01
In this work we propose to study the behavior of a solid elastic object that interacts with a multiphase flow. Fluid structure interaction and multiphase problems are of great interest in engineering and science because of many potential applications. The study of this interaction by coupling a fluid structure interaction (FSI) solver with a multiphase problem could open a large range of possibilities in the investigation of realistic problems. We use a FSI solver based on a monolithic approach, while the two-phase interface advection and reconstruction is computed in the framework of a Volume of Fluid method which is one of the more popular algorithms for two-phase flow problems. The coupling between the FSI and VOF algorithm is efficiently handled with the use of MEDMEM libraries implemented in the computational platform Salome. The numerical results of a dam break problem over a deformable solid are reported in order to show the robustness and stability of this numerical approach.
Phase-separation models for swimming enhancement in complex fluids
Man, Yi
2015-01-01
Swimming cells often have to self-propel through fluids displaying non-Newtonian rheology. While past theoretical work seems to indicate that stresses arising from complex fluids should systematically hinder low-Reynolds number locomotion, experimental observations suggest that locomotion enhancement is possible. In this paper we propose a physical mechanism for locomotion enhancement of microscopic swimmers in a complex fluid. It is based on the fact that micro-structured fluids will generically phase-separate near surfaces, leading to the presence of low-viscosity layers which promote slip and decrease viscous friction near the surface of the swimmer. We use two models to address the consequence of this phase separation: a nonzero apparent slip length for the fluid and then an explicit modeling of the change of viscosity in a thin layer near the swimmer. Considering two canonical setups for low-Reynolds number locomotion, namely the waving locomotion of a two-dimensional sheet and that of a three-dimensiona...
Electrostatic interactions between particles through heterogeneous fluid phases.
Kang, Dong Woo; Lee, Mina; Kim, Kyung Hak; Xia, Ming; Im, Sang Hyuk; Park, Bum Jun
2017-09-27
We investigated the electrostatic interactions between particles acting through heterogeneous fluid phases. An oil lens system floating on the surface of water was used to trap particles at different fluid-fluid interfaces. The inner particles are located at the centrosymmetrically curved oil-water interface inside the oil lens while satellite particles are located at the curved air-water interface, separated by a particular distance from the triple phase boundary. The satellite particles are likely to be captured in an energy minimum state due to electrostatic repulsions by the inner particles balanced with the gravity-induced potential energy. As the size of the oil lens decreases upon evaporation, the satellite particles escape from the gravitational confinement at a critical moment. The self-potential values of the inner particles and the satellite particles were calculated by employing an energy balance and the experimentally obtained geometric parameter values. It was found that the self-potential values of the inner particles decrease as oil evaporates over time and that the magnitude of the self-potential of the satellite particles is a hundred times larger than that of the inner particles. These results demonstrate significant effects of the thickness and shape of the nonpolar superphase on the electrostatic interactions between the particles trapped at different fluid-fluid interfaces.
van Dam, Lorens; Karlsson, Göran; Edwards, Katarina
2004-08-30
We have used cryo-transmission electron microscopy (cryo-TEM) for inspection of aggregates formed by dimyristoylphosphatidylcholine (DMPC) and dihexanoylphosphatidylcholine (DHPC) in aqueous solution at total phospholipid concentrations cL DHPC ratios q < or = 4.0. In combination with ocular inspections, we are able to sketch out this part of phase-diagram at T = 14-80 degrees C. The temperature and the ratio q are the dominating variables for changing sample morphology, while cL to a lesser extent affects the aggregate structure. At q = 0.5, small, possibly disc-shaped, aggregates with a diameter of approximately 6 nm are formed. At higher q-values, distorted discoidal micelles that tend to short cylindrical micelles are observed. The more well-shaped discs have a diameter of around 20 nm. Upon increasing q or the temperature, long slightly flattened cylindrical micelles that eventually branch are formed. A holey lamellar phase finally appears upon further elevation of q or temperature. The implications for biological NMR work are two. First, discs prepared as membrane mimics are frequently much smaller than predicted by current "ideal bicelle" models. Second, the q approximately 3 preparations used for aligning water-soluble biomolecules in magnetic fields consist of perforated lamellar sheets. Furthermore, the discovered sequence of morphological transitions may have important implications for the development of bicelle-based membrane protein crystallization methods.
Coupling two-phase fluid flow with two-phase darcy flow in anisotropic porous media
Chen, J.
2014-06-03
This paper reports a numerical study of coupling two-phase fluid flow in a free fluid region with two-phase Darcy flow in a homogeneous and anisotropic porous medium region. The model consists of coupled Cahn-Hilliard and Navier-Stokes equations in the free fluid region and the two-phase Darcy law in the anisotropic porous medium region. A Robin-Robin domain decomposition method is used for the coupled Navier-Stokes and Darcy system with the generalized Beavers-Joseph-Saffman condition on the interface between the free flow and the porous media regions. Obtained results have shown the anisotropic properties effect on the velocity and pressure of the two-phase flow. 2014 Jie Chen et al.
Strong Static Magnetic Fields Increase the Gel Signal in Partially Hydrated DPPC/DMPC Membranes
Directory of Open Access Journals (Sweden)
Jennifer Tang
2015-09-01
Full Text Available NIt was recently reported that static magnetic fields increase lipid order in the hydrophobic membrane core of dehydrated native plant plasma membranes [Poinapen, Soft Matter 9:6804-6813, 2013]. As plasma membranes are multicomponent, highly complex structures, in order to elucidate the origin of this effect, we prepared model membranes consisting of a lipid species with low and high melting temperature. By controlling the temperature, bilayers coexisting of small gel and fluid domains were prepared as a basic model for the plasma membrane core. We studied molecular order in mixed lipid membranes made of dimyristoyl-sn-glycero-3-phosphocholine (DMPC and dipalmitoyl-sn-glycero-3-phosphocholine (DPPC using neutron diffraction in the presence of strong static magnetic fields up to 3.5 T. The contribution of the hydrophobic membrane core was highlighted through deuterium labeling the lipid acyl chains. There was no observable effect on lipid organization in fluid or gel domains at high hydration of the membranes. However, lipid order was found to be enhanced at a reduced relative humidity of 43%: a magnetic field of 3.5 T led to an increase of the gel signal in the diffraction patterns of 5%. While all biological materials have weak diamagnetic properties, the corresponding energy is too small to compete against thermal disorder or viscous effects in the case of lipid molecules. We tentatively propose that the interaction between the fatty acid chains’ electric moment and the external magnetic field is driving the lipid tails in the hydrophobic membrane core into a better ordered state.
Morphological Characterization of DMPC/CHAPSO Bicellar Mixtures: A Combined SANS and NMR Study
Energy Technology Data Exchange (ETDEWEB)
Li, Ming [University of Connecticut, Storrs; Morales, Hannah H [University of Toronto, Canada; Katsaras, John [ORNL; Kucerka, Norbert [Atomic Energy of Canada Limited (AECL), Canadian Neutron Beam Centre (CNBC) and Comenius University,; Yang, Yongkun [University of Connecticut, Storrs; Macdonald, P [University of Toronto, Canada; Nieh, Mu-Ping [University of Connecticut, Storrs
2013-01-01
Spontaneously forming structures of a system composed of dimyristoyl phosphatidylcholine (DMPC) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) were studied by small-angle neutron scattering (SANS), 31P NMR, and stimulated echo (STE) pulsed field gradient (PFG) 1H NMR diffusion measurements. Charged lipid dimyristoyl phosphatidylglycerol (DMPG) was used to induce different surface charge densities. The structures adopted were investigated as a function of temperature and lipid concentration for samples with a constant molar ratio of long-chain to short-chain lipids (=3). In the absence of DMPG, zwitterionic bicellar mixtures exhibited a phase transition from discoidal bicelles, or ribbons, to multilamellar vesicles either upon dilution or with increased temperature. CHAPSO-containing mixtures showed a higher thermal stability in morphology than DHPC-containing mixtures at the corresponding lipid concentrations. In the presence of DMPG, discoidal bicelles (or ribbons) were also found at low temperature and lower lipid concentration mixtures. At high temperature, perforated lamellae were observed in high concentration mixtures ( 7.5 wt %) whereas uniform unilamellar vesicles and bicelles formed in low-concentration mixtures ( 2.5 wt %), respectively, when the mixtures were moderately and highly charged. From the results, spontaneous structural diagrams of the zwitterionic and charged systems were constructed.
Bridelli, M. G.; Capelletti, R.; Mora, C.
2013-12-01
Thermally stimulated depolarization currents (TSDCs) and Fourier transform infrared (FTIR) spectroscopies were employed to investigate the state of water incorporated in a model DMPC (dimyristoyl-phosphatidylcholine) membrane. The lipid multilayers, highly inhomogeneous from the dielectric point of view, originate complex TSDC spectra critically dependent on the sample water content and thermal history. Different temperature ranges were chosen to polarize the sample, i.e. 100-300 K (type I) and 100-285 K (type II). The purpose of the latter choice was to avoid any sample heating above the DMPC phase transition temperature (295 K) along the sample polarization. According to the results, water in a fully hydrated system (aw = 0.92) (1) is ordered around the hydrophilic head molecular groups, (2) is layered in the interbilayer space and (3) penetrates among the hydrocarbon chains. It can assume different local structural configurations depending on the lipid packing. Irreversible conformational transitions in the lipid array system were monitored as a consequence of different dehydration treatments. FTIR absorption measurements were performed to study the water sorption kinetics into a DMPC thin film. The water related OH band was decomposed into three components, describing three water states, with different propensity to the H-bond formation. The changes of the lipid characteristic groups (CH2/CH3, PO_{2}^{-} and C=O) absorption bands as a function of increasing hydration level were monitored and discussed.
Lee, Pilhwa; Wolgemuth, Charles W.
2016-01-01
The swimming of microorganisms typically involves the undulation or rotation of thin, filamentary objects in a fluid or other medium. Swimming in Newtonian fluids has been examined extensively, and only recently have investigations into microorganism swimming through non-Newtonian fluids and gels been explored. The equations that govern these more complex media are often nonlinear and require computational algorithms to study moderate to large amplitude motions of the swimmer. Here, we develop an immersed boundary method for handling fluid-structure interactions in a general two-phase medium, where one phase is a Newtonian fluid and the other phase is viscoelastic (e.g., a polymer melt or network). We use this algorithm to investigate the swimming of an undulating, filamentary swimmer in 2D (i.e., a sheet). A novel aspect of our method is that it allows one to specify how forces produced by the swimmer are distributed between the two phases of the fluid. The algorithm is validated by comparing theoretical predictions for small amplitude swimming in gels and viscoelastic fluids. We show how the swimming velocity depends on material parameters of the fluid and the interaction between the fluid and swimmer. In addition, we simulate the swimming of Caenorhabditis elegans in viscoelastic fluids and find good agreement between the swimming speeds and fluid flows in our simulations and previous experimental measurements. These results suggest that our methodology provides an accurate means for exploring the physics of swimming through non-Newtonian fluids and gels.
A phase diagram for fluid-driven sediment trasport
Clark, Abe
When a fluid flows laterally over a granular bed, grains may be transported with the flow. This process shapes much of the natural world. The boundary between states with and without grain motion has been studied for decades. However, this boundary is not well understood, since the process whereby grains are transported involves the coupling of several complex phenomena: turbulent fluid flow near a rough boundary, Darcy flow through the pore structure of the granular bed, the yield strength of granular beds comprised of frictional grains with irregular shape, and inertial effects of grains that become entrained in the flow. In order to clarify the essential physics that governs the onset of granular motion, we study this process computationally by including only the minimal features and then adding complexities one by one. We start with a simple numerical model that includes only gravity, grain-grain interactions that are repulsive and frictionless, and a purely horizontal viscous fluid flow. By varying the fluid flow rate and the effective viscosity, we find behavior that is qualitatively consistent with a large collection of experimental data known as the Shields curve. Thus, our results suggest that the main features of this curve result from a competition between grain inertia and viscous damping. We find this phase diagram to be qualitatively insensitive to secondary effects, such as friction, irregular grain shape, and restitution losses. Funded by U.S. Army Research Office under Grant No. W911NF-14-1-0005.
Coupling fluid-structure interaction with phase-field fracture
Wick, Thomas
2016-12-01
In this work, a concept for coupling fluid-structure interaction with brittle fracture in elasticity is proposed. The fluid-structure interaction problem is modeled in terms of the arbitrary Lagrangian-Eulerian technique and couples the isothermal, incompressible Navier-Stokes equations with nonlinear elastodynamics using the Saint-Venant Kirchhoff solid model. The brittle fracture model is based on a phase-field approach for cracks in elasticity and pressurized elastic solids. In order to derive a common framework, the phase-field approach is re-formulated in Lagrangian coordinates to combine it with fluid-structure interaction. A crack irreversibility condition, that is mathematically characterized as an inequality constraint in time, is enforced with the help of an augmented Lagrangian iteration. The resulting problem is highly nonlinear and solved with a modified Newton method (e.g., error-oriented) that specifically allows for a temporary increase of the residuals. The proposed framework is substantiated with several numerical tests. In these examples, computational stability in space and time is shown for several goal functionals, which demonstrates reliability of numerical modeling and algorithmic techniques. But also current limitations such as the necessity of using solid damping are addressed.
Different effects of propofol and nitrosopropofol on DMPC multilamellar liposomes.
Momo, Federico; Fabris, Sabrina; Bindoli, Alberto; Scutari, Guido; Stevanato, Roberto
2002-02-19
The mechanisms of reaction of propofol with nitrosoglutathione lead to the formation of an active species which was identified, and then synthesised, as 2,6-diisopropyl-4-nitrosophenol. In the present work, we demonstrate the in vitro formation of 2,6-diisopropyl-4-nitrosophenol, then we discuss the interaction of propofol and 2,6-diisopropyl-4-nitrosophenol with dimyristoylphosphatidylcholine and egg yolk phosphatidylcholine multilamellar liposomes using differential scanning calorimetry and spin labelling techniques. It was demonstrated that both molecules are highly lipophylic and absorb almost entirely in the lipid phase. The thermotropic profiles showed that these molecules affect the temperature and the co-operativity of the gel-to-fluid state transition of the liposomes differently: the effects of 2,6-diisopropylphenol on the lipid organisation are quite similar to phenol and coherently interpretable in terms of the disorder produced in the membrane by a bulky group; 2,6-diisopropyl-4-nitrosophenol is a stronger perturbing agent, and ESR spectra suggest that this is due to a relative accumulation of the molecule into the interfacial region of the bilayer.
Transient thermohydraulic modeling of two-phase fluid systems
Blet, N.; Delalandre, N.; Ayel, V.; Bertin, Y.; Romestant, C.; Platel, V.
2012-11-01
This paper presents a transient thermohydraulic modeling, initially developed for a capillary pumped loop in gravitational applications, but also possibly suitable for all kinds of two-phase fluid systems. Using finite volumes method, it is based on Navier-Stokes equations for transcribing fluid mechanical aspects. The main feature of this 1D-model is based on a network representation by analogy with electrical. This paper also proposes a parametric study of a counterflow condenser following the sensitivity to inlet mass flow rate and cold source temperature. The comparison between modeling results and experimental data highlights a good numerical evaluation of temperatures. Furthermore, the model is able to represent a pretty good dynamic evolution of hydraulic variables.
Phase separation in fluids exposed to spatially periodic external fields.
Vink, R L C; Archer, A J
2012-03-01
When a fluid is confined within a spatially periodic external field, the liquid-vapor transition is replaced by a different transition called laser-induced condensation (LIC) [Götze et al., Mol. Phys. 101, 1651 (2003)]. In d=3 dimensions, the periodic field induces an additional phase, characterized by large density modulations along the field direction. At the triple point, all three phases (modulated, vapor, and liquid) coexist. At temperatures slightly above the triple point and for low (high) values of the chemical potential, two-phase coexistence between the modulated phase and the vapor (liquid) is observed; by increasing the temperature further, both coexistence regions terminate in critical points. In this paper, we reconsider LIC using the Ising model to resolve a number of open issues. To be specific, we (1) determine the universality class of the LIC critical points and elucidate the nature of the correlations along the field direction, (2) present a mean-field analysis to show how the LIC phase diagram changes as a function of the field wavelength and amplitude, (3) develop a simulation method by which the extremely low tension of the interface between modulated and vapor or liquid phase can be measured, (4) present a finite-size scaling analysis to accurately extract the LIC triple point from finite-size simulation data, and (5) consider the fate of LIC in d=2 dimensions.
Applications of the IAPWS-95 formulation in fluid inclusion and mineral-fluid phase equilibria
Directory of Open Access Journals (Sweden)
Lanlan Shi
2012-01-01
Full Text Available The IAPWS-95 formulation explicit in Helmholtz free energy proposed by Wagner and Pruβ (2002 is the best equation of state of water, from which all thermodynamic properties can be obtained over a wide T–p range from 273.16 to 1273 K and from 0 to 1000 MPa with experimental accuracy. This paper reports the applications of the IAPWS-95 formulation in fluid inclusion and mineral-water phase equilibria. A reliable and highly efficient calculation method is presented for the saturated properties of water so that the formulation can be conveniently applied in the study of fluid inclusion, such as calculating homogenization pressures, homogenization densities (or molar volumes, volume fractions and isochores. Meanwhile, the univariant curves of some mineral-dehydration reactions are calculated based on the IAPWS-95 formulation. The computer code of the IAPWS-95 formulation can be obtained from the corresponding author.
Lee, Pilhwa; Wolgemuth, Charles
2016-11-01
While swimming in Newtonian fluids has been examined extensively, only recently have investigations into microorganism swimming through non-Newtonian fluids and gels been explored. The equations that govern these more complex media are often nonlinear and require computational algorithms to study moderate to large amplitude motions of the swimmer. Here we develop an immersed boundary method for handling fluid-structure interactions in a general two-phase medium, where one phase is a Newtonian fluid and the other phase is viscoelastic. We use this algorithm to investigate the swimming of an undulating, filamentary swimmer in 2D. A novel aspect of our method is that it allows one to specify how forces produced by the swimmer are distributed between the two phases of the fluid. The algorithm is validated by comparison to theoretical predictions for small amplitude swimming in gels and viscoelastic fluids. We show how the swimming velocity depends on material parameters of the fluid and the interaction between the fluid and swimmer. In addition, we simulate the swimming of Caenorhabditis elegans in viscoelastic fluids and find good agreement between the swimming speeds and fluid flows in our simulations and previous experimental measurements. NIH R01 GM072004, NIH P50GM094503.
Density and Phase State of a Confined Nonpolar Fluid
Kienle, Daniel F.; Kuhl, Tonya L.
2016-07-01
Measurements of the mean refractive index of a spherelike nonpolar fluid, octamethytetracylclosiloxane (OMCTS), confined between mica sheets, demonstrate direct and conclusive experimental evidence of the absence of a first-order liquid-to-solid phase transition in the fluid when confined, which has been suggested to occur from previous experimental and simulation results. The results also show that the density remains constant throughout confinement, and that the fluid is incompressible. This, along with the observation of very large increases (many orders of magnitude) in viscosity during confinement from the literature, demonstrate that the molecular motion is limited by the confining wall and not the molecular packing. In addition, the recently developed refractive index profile correction method, which enables the structural perturbation inherent at a solid-liquid interface and that of a liquid in confinement to be determined independently, was used to show that there was no measurable excess or depleted mass of OMCTS near the mica surface in bulk films or confined films of only two molecular layers.
Phase segregation in a binary fluid confined inside a nanopore
Basu, Saikat; Majumder, Suman; Sutradhar, Sabyasachi; Das, Subir K.; Paul, Raja
2016-12-01
Using a hydrodynamics preserving thermostat, we present extensive molecular dynamics simulation results for the kinetics of phase separation in a model binary (A+B) fluid confined inside a cylindrical nanopore with neutral wall. We observe the formation of a striped pattern, where A-rich and B-rich domains appear alternately along the axis of the cylinder. For a wide range of diameters of the cylinders, the growth of the pattern freezes and does not lead to complete phase separation. Prior to freezing, the growth of these stripes passes through two power-law regimes. The early-time regime is related to the Lifshitz-Slyozov diffusive mechanism and the estimated value of the exponent for the later-time regime matches well with that for the inertial hydrodynamic growth in three-dimensional fluid systems. Appropriate arguments have been provided to justify the observations. Furthermore, our results show that the length of the cylinder does not seem to affect the average axial length of the frozen patterns. However, the latter exhibits a linear dependence on the diameter of the cylinder.
Thermodynamic Property Model of Wide-Fluid Phase Propane
Directory of Open Access Journals (Sweden)
I Made Astina
2007-05-01
Full Text Available A new thermodynamic property model for propane is expressed in form of the Helmholtz free energy function. It consists of eight terms of the ideal-gas part and eighteen terms of the residual part. Accurate experimental data of fluid properties and theoretical approach from the intermolecular potential were simultaneously considered in the development to insure accuracy and to improve reliability of the equation of state over wide range of pressures and temperatures. Based on the state range of experimental data used in the model development, the validity range is judged from the triple-point of 85.48 K to temperature of 450 K and pressure up to 60 MPa. The uncertainties with respect to different properties are estimated to be 0.03% in ideal-gas isobaric specific heat, 0.2% in liquid phase density, 0.3% in gaseous phase density 1% in specific heats, 0.1% in vapor-pressure except at very low temperatures, 0.05% in saturated-liquid density, 0.02% in speed of sound of the gaseous phase and 1% in speed of sound of the liquid phase.
DEFF Research Database (Denmark)
Enz, Stephanie; Thomsen, Jon Juel
2011-01-01
displacement and approximate axial shift in vibration phase. The analytical predictions are tested against pure numerical solution using representative examples, showing good agreement. Fluid pulsations are predicted not to influence CFM accuracy, since proper signal filtering is seen to allow......Knowing the influence of fluid flow perturbations on the dynamic behavior of fluid-conveying pipes is of relevance, e.g., when exploiting flow-induced oscillations of pipes to determine the fluids mass flow or density, as done with Coriolis flow meters (CFM). This could be used in the attempts...... the determination of the correct mean phase shift. Large amplitude motions, which could influence CFM robustness, do not appear to be induced by the investigated fluid pulsation. Pulsating fluid of the combination resonance type could, however, influence CFMs robustness, if induced pipe motions go unnoticed...
Indian Academy of Sciences (India)
Yousef Nademi; Sepideh Amjad Iranagh; Abbas Yousefpour; Seyedeh Zahra Mousavi; Hamid Modarress
2014-05-01
Molecular dynamics (MD) simulations and biased MD simulation were carried out for the neutral form of Paracetamol inserted in fully hydrated dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) lipid bilayers. For comparison, fully hydrated DMPC and DPPC lipid bilayers were also simulated separately without Paracetamol. The simulation time for each system was 50 ns. At two concentrations of Paracetamol, various properties of the lipid bilayer such as area per lipid, order parameter, diffusion coefficient, radial distribution function, electrostatic potential, mass density and hydrogen bonds have been calculated. Also, the convergence in time of the free energy profile of the Paracetamol along a DPPC bilayer normal was calculated by umbrella sampling method. From the obtained results, it can be concluded that neutral form of Paracetamol shows a generally similar behaviour in DPPC and DMPC lipid bilayers. It was shown that the addition of Paracetamol causes a decrease in tail order parameter of both DPPC and DMPC lipid bilayers and the tail of Paracetamol adopts an inward orientation in the lipid bilayers. Also from the free energy profile, the high penetration barrier in the bilayer centre was determined.
Numerical simulation of complex multi-phase fluid of casting process and its applications
Institute of Scientific and Technical Information of China (English)
CHEN Li-liang; LIU Rui-xiang; C. Beckermann
2006-01-01
The fluid of casting process is a typical kind of multi-phase flow. Actually, many casting phenomena have close relationship with the multi-phase flow, such as molten metal filling process, air entrapment, slag movement, venting process of die casting, gas escaping of lost foam casting and so on. Obviously, in order to analyze these phenomena accurately,numerical simulation of the multi-phase fluid is necessary. Unfortunately, so far, most of the commercial casting simulation systems do not have the ability of multi-phase flow modeling due to the difficulty in the multi-phase flow calculation. In the paper, Finite Different Method (FDM) technique was adopt to solve the multi-phase fluid model. And a simple object of the muiti-phase fluid was analyzed to obtain the fluid rates of the liquid phase and the entrapped air phase.
Numerical simulation of complex multi-phase fluid of casting process and its applications
Directory of Open Access Journals (Sweden)
CHEN Li-liang
2006-05-01
Full Text Available The fluid of casting process is a typical kind of multi-phase flow. Actually, many casting phenomena have close relationship with the multi-phase flow, such as molten metal filling process, air entrapment, slag movement, venting process of die casting, gas escaping of lost foam casting and so on. Obviously, in order to analyze these phenomena accurately, numerical simulation of the multi-phase fluid is necessary. Unfortunately, so far, most of the commercial casting simulation systems do not have the ability of multi-phase flow modeling due to the difficulty in the multi-phase flow calculation. In the paper, Finite Different Method (FDM technique was adopt to solve the multi-phase fluid model. And a simple object of the muiti-phase fluid was analyzed to obtain the fluid rates of the liquid phase and the entrapped air phase.
Novel phase behaviour of a confined fluid or Ising magnet
Parry, A. O.; Evans, R.
1992-02-01
The phase behaviour of a simple fluid or Ising magnet (at temperatures above its roughening transition) confined between parallel walls that exert opposing surface fields h2 = - h1 is found to be markedly different from that which arises for h2 = h1. Whereas critical wetting plays little role for confinement by identical walls, it is of crucial importance for opposing surface fields. Analysis of a Landau functional and other mean-field treatments show that if h1 is such that critical wetting occurs at a single wall ( L = ∞) at a transition temperature Tw, then phase coexistence, for finite wall separation L, is restricted to temperatures T T > Tw there is a single soft mode phase that is characterized, for zero bulk field and large L, by a +- interface located at the centre of the slit, a transverse correlation length ξ∼≈ eL and a solvation force that is repulsive. For large h1, Tw can lie arbitrarily far below the bulk critical temperature Tc, b. Scaling arguments, whose validity we have confirmed in two dimensions by comparison with exact solutions for interfacial Hamiltonians, predict that such behaviour persists beyond mean-field for systems with short-ranged forces. They also predict similar phase behaviour for long-ranged forces, but with ξ ξ ∼ increasing algebraically with L in the soft mode phase. The solvation force t˜f s changes from repulsive to attractive (at large L) as the temperature is reduced below Tw, i.e. the sign of t˜f s reflects wetting characteristics.
Fluid shifts during initial phase of immersion diuresis in man
Energy Technology Data Exchange (ETDEWEB)
Khosla, S.S.; Dubois, A.B.
1979-04-01
The object was to study shifts in man during the 1st hour of immersion diuresis. Control experiments were done on subjects lying down in air for 4 h with and without vasopressin. During immersion up to the neck, seven of nine subjects had significant diuresis and natriuresis. In the first 20 min of sitting in 33 C water, a hemodilution of 2% of blood volume was observed. As diuresis progressed, hemoconcentration began. When vasopressin was given just before immersion to prevent the diuresis, the hemodilution observed was greater and lasted longer. Thus the hematocrit fell by 1.7 U, plasma osmolality by 6.0 mosmol/kg, plasma proteins by 0.33 g/100 ml, and plasma sodium by 5.0 meq/l. It is concluded that a hemodilution of about 4% of blood volume occurs during the early phase of immersion and the degree of hyposmolality observed suggests that the fluid shifted was more hyposmotic than the interstitial fluid alone, possibly because some intracellular water may have shifted into the bloodstream during immersion.
Dynamic dielectrophoresis model of multi-phase ionic fluids.
Directory of Open Access Journals (Sweden)
Ying Yan
Full Text Available Ionic-based dielectrophoretic microchips have attracted significant attention due to their wide-ranging applications in electro kinetic and biological experiments. In this work, a numerical method is used to simulate the dynamic behaviors of ionic droplets in a microchannel under the effect of dielectrophoresis. When a discrete liquid dielectric is encompassed within a continuous fluid dielectric placed in an electric field, an electric force is produced due to the dielectrophoresis effect. If either or both of the fluids are ionic liquids, the magnitude and even the direction of the force will be changed because the net ionic charge induced by an electric field can affect the polarization degree of the dielectrics. However, using a dielectrophoresis model, assuming ideal dielectrics, results in significant errors. To avoid the inaccuracy caused by the model, this work incorporates the electrode kinetic equation and defines a relationship between the polarization charge and the net ionic charge. According to the simulation conditions presented herein, the electric force obtained in this work has an error exceeding 70% of the actual value if the false effect of net ionic charge is not accounted for, which would result in significant issues in the design and optimization of experimental parameters. Therefore, there is a clear motivation for developing a model adapted to ionic liquids to provide precise control for the dielectrophoresis of multi-phase ionic liquids.
Dynamic phase transitions in confined lubricant fluids under shear
Energy Technology Data Exchange (ETDEWEB)
Drummond, Carlos; Israelachvili, Jacob
2001-04-01
A surface force apparatus was used to measure the transient and steady-state friction forces between molecularly smooth mica surfaces confining thin films of squalane, C{sub 30}H{sub 62}, a saturated, branched hydrocarbon liquid. The dynamic friction ''phase diagram'' was determined under different shearing conditions, especially the transitions between stick-slip and smooth sliding ''states'' that exhibited a chaotic stick-slip regime. The apparently very different friction traces exhibited by simple spherical, linear, and branched hydrocarbon films under shear are shown to be due to the much longer relaxation times and characteristic length scales associated with transitions from rest to steady-state sliding, and vice versa, in the case of branched liquids. The physical reasons and tribological implications for the different types of transitions observed with spherical, linear, and branched fluids are discussed.
Khater, Syame; Lozac'h, Marie-Anne; Adam, Isabelle; Francotte, Eric; West, Caroline
2016-10-07
Analysis and production of enantiomerically pure compounds is a major topic of interest when active pharmaceutical ingredients are concerned. Enantioselective chromatography has become a favourite both at the analytical and preparative scales. High-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) are dominating the scene and are often seen as complementary techniques. Nowadays, for economic and ecologic reasons, SFC may be preferred over normal-phase HPLC (NPLC) as it allows significant reductions in solvent consumption. However, the transfer of NPLC methods to SFC is not always straightforward. In this study, we compare the retention of achiral molecules and separation of enantiomers under supercritical fluid (carbon dioxide with ethanol or isopropanol) and liquid normal-phase (heptane with ethanol or isopropanol) elution modes with polysaccharide stationary phases in order to explore the differences between the retention and enantioseparation properties between the two modes. Chemometric methods (namely quantitative structure-retention relationships and discriminant analysis) are employed to compare the results obtained on a large set of analytes (171 achiral probes and 97 racemates) and gain some understanding on the retention and separation mechanisms. The results indicate that, contrary to popular belief, carbon dioxide - solvent SFC mobile phases are often weaker eluents than liquid mobile phases. It appears that SFC and NPLC elution modes provide different retention mechanisms. While some enantioseparations are unaffected, facilitating the transfer between the two elution modes, other enantioseparations may be drastically different due to different types and strength of interactions contributing to enantioselectivity.
Lennard-Jones fluids in two-dimensional nano-pores. Multi-phase coexistence and fluid structure
Yatsyshin, Petr; Savva, Nikos; Kalliadasis, Serafim
2014-03-01
We present a number of fundamental findings on the wetting behaviour of nano-pores. A popular model for fluid confinement is a one-dimensional (1D) slit pore formed by two parallel planar walls and it exhibits capillary condensation (CC): a first-order phase transition from vapour to capillary-liquid (Kelvin shift). Capping such a pore at one end by a third orthogonal wall forms a prototypical two-dimensional (2D) pore. We show that 2D pores possess a wetting temperature such that below this temperature CC remains of first order, above it becomes a continuous phase transition manifested by a slab of capillary-liquid filling the pore from the capping wall. Continuous CC exhibits hysteresis and can be preceded by a first-order capillary prewetting transition. Additionally, liquid drops can form in the corners of the 2D pore (remnant of 2D wedge prewetting). The three fluid phases, vapour, capillary-liquid slab and corner drops, can coexist at the pore triple point. Our model is based on the statistical mechanics of fluids in the density functional formulation. The fluid-fluid and fluid-substrate interactions are dispersive. We analyze in detail the microscopic fluid structure, isotherms and full phase diagrams. Our findings also suggest novel ways to control wetting of nano-pores. We are grateful to the European Research Council via Advanced Grant No. 247031 for support.
Phase equilibria in fluid mixtures at high pressures: The He-CH4 system
Streett, W. B.; Erickson, A. L.; Hill, J. L. E.
1972-01-01
An experimental study of phase equilibria in the He-CH4 system was carried out over the temperature range 95 to 290 K and at pressures to 10,000 atm. The experimental results consist of equilibrium phase composition for twenty-eight isotherms in the region of coexistence of two fluid phases, together with the pressure-temperature trace of the three-phase boundary at which a CH4-rich solid phase is in equilibrium with the two fluid phases. The system exhibits a fluid-fluid phase separation which persists to temperatures and pressures beyond the range of this experiment. These results, together with those recently obtained for other binary systems, provide information about the form of phase diagrams for binary gas mixtures in the region of pressure induced phase transitions at high pressures. These findings are relevant to problems of deep atmosphere and interior structures in the outer planets.
Investigation of the Phase Equilibria and Interfacial Properties for Non-polar Fluids
Institute of Scientific and Technical Information of China (English)
付东; 赵毅
2005-01-01
A self-consistent density-functional theory (DFT) was applied to investigate the phase behavior and interfacial properties of non-polar fluids. For the bulk phases, the theory was reduced to the statistical associating fluid theory(SAFF) that provides accurate descriptions of vapor-liquid phase diagrams below the critical region. The phase diagrams in the critical region were corrected by the renormalization group theory (RGT). The density profile in the surface was obtained by minimizing the grand potential. With the same set of molecular parameters, both the phase equilibria and the interfacial properties of non-polar fluids were investigated satisfactorily.
Phase-controlled bistability of a dark soliton train in a polariton fluid
Goblot, Valentin; Carusotto, Iacopo; Galopin, Elisabeth; Lemaître, Aristide; Sagnes, Isabelle; Amo, Alberto; Bloch, Jacqueline
2016-01-01
We use a one-dimensional polariton fluid in a semiconductor microcavity to explore the rich nonlinear dynamics of counter-propagating interacting Bose fluids. The intrinsically driven-dissipative nature of the polariton fluid allows to use resonant pumping to impose a phase twist across the fluid. When the polariton-polariton interaction energy becomes comparable to their kinetic energy, linear interference fringes transform into a train of solitons. A novel type of bistable behavior controlled by the phase twist across the fluid is experimentally evidenced.
Complex phase behavior of a fluid in slits with semipermeable walls modified with tethered chains.
Borówko, M; Patrykiejew, A; Rżysko, W; Sokołowski, S; Ilnytskyi, J
2011-01-28
We study the phase behavior of a two-component fluid in a pore with the walls modified by tethered chains. The walls are completely permeable for one component of the fluid and completely impenetrable for the second component. The fluid is perfectly mixed in a bulk phase. We have found that depending on the details of the model the fluid undergoes capillary condensation inside the pore and wetting and layering transitions at the outer walls. Moreover, we have found transitions connected with the change of symmetry of the distribution of chains and fluid inside the pore.
Interactions between DMPC liposomes and the serum blood proteins HSA and IgG.
Sabín, Juan; Prieto, Gerardo; Ruso, Juan M; Messina, Paula V; Salgado, Francisco J; Nogueira, Montserrat; Costas, Miguel; Sarmiento, Félix
2009-02-12
The interaction between two serum blood proteins, namely human serum albumin (HSA) and human immunoglobulin G (IgG), with 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) liposomes has been studied in detail using dynamic light scattering, flow cytometry, enzyme-linked immunosorbent assay (ELISA), electrophoretic mobility, differential scanning calorimetry (DSC), and surface tension measurements. HSA and IgG interact with liposomes forming molecular aggregates that remain stable at protein concentrations beyond those of total liposome coverage. Both HSA and IgG penetrate into the liposome bilayer. An ELISA assay indicates that the Fc region of IgG is the one that is immersed in the DMPC membrane. The liposome-protein interaction is mainly of electrostatic nature, but an important hydrophobic contribution is also present.
Molecular packing in 1-hexanol-DMPC bilayers studied by molecular dynamics simulation
DEFF Research Database (Denmark)
Pedersen, U.R.; Peters, Günther H.j.; Westh, P.
2007-01-01
The structure and molecular packing density of a “mismatched” solute, 1-hexanol, in lipid membranes of dimyristoyl phosphatidylcholine (DMPC) was studied by molecular dynamics simulations. We found that the average location and orientation of the hexanol molecules matched earlier experimental data...... on comparable systems. The local density or molecular packing in DMPC–hexanol was elucidated through the average Voronoi volumes of all heavy (non-hydrogen) atoms. Analogous analysis was conducted on trajectories from simulations of pure 1-hexanol and pure (hydrated) DMPC bilayers. The results suggested...... of the alcohol upon partitioning and an even stronger loosening in the packing of the lipid. Furthermore, analysis of Voronoi volumes along the membrane normal identifies a distinctive depth dependence of the changes in molecular packing. The outer (interfacial) part of the lipid acyl chains (up to C8...
Phase equilibria in fluid mixtures at high pressures - The He-CH4 system.
Streett, W. B.; Erickson, A. L.; Hill, J. L. E.
1972-01-01
An experimental study of phase equilibria in the He-CH4 system has been carried out over the temperature range 95 to 290 K and at pressures to 10,000 atm. The experimental results consist of equilibrium phase composition for twenty-eight isotherms in the region of coexistence of two fluid phases, together with the pressure-temperature trace of the three-phase boundary at which a CH4-rich solid phase is in equilibrium with the two fluid phases. The system exhibits a fluid-fluid phase separation which persists to temperatures and pressures beyond the range of this experiment. These findings are relevant to problems of deep atmosphere and interior structures in the outer planets.-
Phase transitions of adsorbed fluids computed from multiplehistogram reweighting
Shi, Wei; Zhao, Xiongce; Johnson, J. Karl
This paper demonstrates the effectiveness of using multiple-histogram reweighting (MHR) to study phase transitions in confined fluids by examining capillary condensation, prewetting, and layering transitions for different systems. A comparison is made with previously published simulations, where available, to establish the accuracy of MHR as applied to inhomogeneous systems. Overlap between adjacent state points is assessed through single-histogram reweighting. Capillary condensation for methane adsorption in slit-like graphite pores exhibits 2D behaviour. Crossover of the effective exponent for the width of the coexistence curve from 2D Ising-like (1/8) further away from the critical point to mean-field (1/2) near the critical point is observed. The reduced critical temperature, the density and the effective value of the exponent for the model system are 0.77, 0.482, and 0.119, respectively, based on a fit to the simulation data. Prewetting transitions are observed for adsorption of Ar on solid CO 2 using model potentials. The wetting temperature is estimated based on the intersection of the prewetting and bulk vapour-liquid lines, and also by extrapolation to zero of the difference between the saturation and prewetting chemical potentials. The reduced wetting temperature is estimated to be around 0.69. The reduced prewetting critical temperature, calculated from the disappearance of the two peaks in the density probability distribution, is estimated to be 0.92. The monolayer to bilayer (1-2) transition for propane on graphite is computed over a range of temperatures. Results for the 1-2 layering transition computed from MHR from a small system are in good agreement with grand canonical Monte Carlo simulations for a much larger system.
Oyarzun, B.A.; Van Westen, T.; Vlugt, T.J.H.
2013-01-01
he liquid crystal phase behavior of linear and partially flexible hard-sphere chain fluids and the solubility of hard spheres in hard-sphere chain fluids are studied by constant pressure Monte Carlo simulations. An extensive study on the phase behavior of linear fluids with a length of 7, 8, 9, 10,
Phase equilibria, fluid structure, and diffusivity of a discotic liquid crystal.
Cienega-Cacerez, Octavio; Moreno-Razo, José Antonio; Díaz-Herrera, Enrique; Sambriski, Edward John
2014-05-14
Molecular Dynamics simulations were performed for the Gay-Berne discotic fluid parameterized by GB(0.345, 0.2, 1.0, 2.0). The volumetric phase diagram exhibits isotropic (IL), nematic (ND), and two columnar phases characterized by radial distribution functions: the transversal fluid structure varies between a hexagonal columnar (CD) phase (at higher temperatures and pressures) and a rectangular columnar (CO) phase (at lower temperatures and pressures). The slab-wise analysis of fluid dynamics suggests the formation of grain-boundary defects in the CO phase. Longitudinal fluid structure is highly periodic with narrow peaks for the CO phase, suggestive of a near-crystalline (yet diffusive) system, but is only short-ranged for the CD phase. The IL phase does not exhibit anisotropic diffusion. Transversal diffusion is more favorable in the ND phase at all times, but only favorable at short times for the columnar phases. In the columnar phases, a crossover occurs where longitudinal diffusion is favored over transversal diffusion at intermediate-to-long timescales. The anomalous diffusivity is pronounced in both columnar phases, with three identifiable contributions: (a) the rattling of discogens within a transient "interdigitation" cage, (b) the hopping of discogens across columns, and (c) the drifting motion of discogens along the orientation of the director.
Predicting phase shift of elastic waves in pipes due to fluid flow and imperfections
DEFF Research Database (Denmark)
Thomsen, Jon Juel; Dahl, Jonas; Fuglede, Niels
2009-01-01
Flexural vibrations of a fluid-conveying pipe is investigated, with special consideration to the spatial shift in phase caused by fluid flow and various imperfections, e.g., non-ideal supports, non-uniform stiffness or mass, non-proportional damping, weak nonlinearity, and flow pulsation. This is......Flexural vibrations of a fluid-conveying pipe is investigated, with special consideration to the spatial shift in phase caused by fluid flow and various imperfections, e.g., non-ideal supports, non-uniform stiffness or mass, non-proportional damping, weak nonlinearity, and flow pulsation....... This is relevant for understanding wave propagation in elastic media in general, and for the design and trouble-shooting of phase-shift measuring devices such as Coriolis mass flowmeters in particular. A multiple time scaling perturbation analysis is employed for a simple model of a fluid-conveying pipe...
McClure, James E.; Berrill, Mark A.; Gray, William G.; Miller, Cass T.
2016-09-01
Multiphase flows in porous medium systems are typically modeled at the macroscale by applying the principles of continuum mechanics to develop models that describe the behavior of averaged quantities, such as fluid pressure and saturation. These models require closure relations to produce solvable forms. One of these required closure relations is an expression relating the capillary pressure to fluid saturation and, in some cases, other topological invariants such as interfacial area and the Euler characteristic (or average Gaussian curvature). The forms that are used in traditional models, which typically consider only the relationship between capillary pressure and saturation, are hysteretic. An unresolved question is whether the inclusion of additional morphological and topological measures can lead to a nonhysteretic closure relation. Relying on the lattice Boltzmann (LB) method, we develop an approach to investigate equilibrium states for a two-fluid-phase porous medium system, which includes disconnected nonwetting phase features. A set of simulations are performed within a random close pack of 1964 spheres to produce a total of 42 908 distinct equilibrium configurations. This information is evaluated using generalized additive models to quantitatively assess the degree to which functional relationships can explain the behavior of the equilibrium data. The variance of various model estimates is computed, and we conclude that, except for the limiting behavior close to a single fluid regime, capillary pressure can be expressed as a deterministic and nonhysteretic function of fluid saturation, interfacial area between the fluid phases, and the Euler characteristic. To our knowledge, this work is unique in the methods employed, the size of the data set, the resolution in space and time, the true equilibrium nature of the data, the parametrizations investigated, and the broad set of functions examined. The conclusion of essentially nonhysteretic behavior provides
Stationary phase optimized selectivity supercritical fluid chromatography (SOS-SFC)
Delahaye, Sander; Lynen, Frederic
2013-01-01
In stationary phase optimized selectivity liquid chromatography (SOS-LC) the stationary phase becomes a tunable parameter by connecting column segments with variable lengths of different stationary phases. An optimization procedure and algorithm based on the PRISMA model for optimization of the mobile phase in LC was developed to apply this strategy for isocratic and gradient separations. An optimized column segment combination, giving the highest separation selectivity for all compounds in a...
Thermo-fluid dynamics of two-phase flow
Ishii, Mamoru; Ishii, Mamoru; Ishii, M
2006-01-01
Provides a very systematic treatment of two phase flow problems from a theoretical perspectiveProvides an easy to follow treatment of modeling and code devlopemnt of two phase flow related phenomenaCovers new results of two phase flow research such as coverage of fuel cells technology.
Two-phase dusty fluid flow along a cone with variable properties
Siddiqa, Sadia; Begum, Naheed; Hossain, Md. Anwar; Mustafa, Naeem; Gorla, Rama Subba Reddy
2016-09-01
In this paper numerical solutions of a two-phase natural convection dusty fluid flow are presented. The two-phase particulate suspension is investigated along a vertical cone by keeping variable viscosity and thermal conductivity of the carrier phase. Comprehensive flow formations of the gas and particle phases are given with the aim to predict the behavior of heat transport across the heated cone. The influence of (1) air with particles, (2) water with particles and (3) oil with particles are shown on shear stress coefficient and heat transfer coefficient. It is recorded that sufficient increment in heat transport rate can be achieved by loading the dust particles in the air. Further, distribution of velocity and temperature of both the carrier phase and the particle phase are shown graphically for the pure fluid (air, water) as well as for the fluid with particles (air-metal and water-metal particle mixture).
Diffusion of water and selected atoms in DMPC lipid bilayer membranes
DEFF Research Database (Denmark)
Hansen, Flemming Yssing; Peters, Günther H.J.; Taub, H.;
2012-01-01
with the diffusion rate of selected atoms in the lipid molecules shows that ∼6 water molecules per lipid molecule move on the same time scale as the lipids and may therefore be considered to be tightly bound to them. The quasielastic neutron scattering functions for water and selected atoms in the lipid molecule......Molecular dynamics simulations have been used to determine the diffusion of water molecules as a function of their position in a fully hydrated freestanding 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) bilayer membrane at 303 K and 1 atm. The diffusion rate of water in a ∼10 Å thick layer...
Retention Characteristics for Multiple-PhaseFluid Systems
Directory of Open Access Journals (Sweden)
Chia-Hsing Tsai and Gour-Tsyh Yeh
2012-01-01
Full Text Available The key objective of this paper is to point out that a widely used constitutive relationship between the degrees of saturation and capillary pressures for three-phasefluids over the past twenty five years has resulted in an undue constraint. To our knowledge, this constraint is neither physically justifiable nor is it theoretically supported. The discovery of the undue constraint leads this investigation to develop a viable parametric model to describe the constitutive relationship for a system of multiple fluids. Based on the physical consideration wherein fluid wettability follows a sequence, the proposed parametric model can be easily applied to any system of L arbitrary fluids. Three aspects are presented to confirm the plausibility and completeness of the model. First, the proposed closed-form expression of the saturation-capillary pressure head relationship is identical to van _ renowned model for two-phasefluid systems. Second, a constraint appearing in the widely used model is alleviated in the proposed model. Third, seven hypothetical examples are used to demonstrate that there is no need to impose the constraint on the sequence of capillary pressures. The results show the plausibility and completeness of the model for systems of multiple fluids. The proposed parametric model is a feasible analytic model which provides a generalized saturation-capillary pressure head relationship for any system with regard to multiple fluids. Hopefully, this study will pave a way for others to conduct experiments to validate the model further or develop other better non-constrained models based on experimental evidence.
Talanquer, V
2005-04-15
In this study, we explore the global phase behavior of a simple model for self-associating fluids where association reduces the strength of the dispersion interactions between bonded particles. Recent research shows that this type of behavior likely explains the thermodynamic properties of strongly polar fluids and certain micellar solutions. Based on Wertheim's theory of associating liquids [M. S. Wertheim, J. Stat. Phys. 42, 459 (1986); 42, 477 (1986)], our model takes into account the effect that dissimilar particle interactions have on the equilibrium constant for self-association in the system. We find that weaker interactions between bonded molecules tend to favor the dissociation of chains at any temperature and density. This effect stabilizes a monomeric liquid phase at high densities, enriching the global phase behavior of the system. In particular, for systems in which the energy of mixing between bonded and unbonded species is positive, we find a triple point involving a vapor, a dense phase of chain aggregates, and a monomeric liquid. Phase coexistence between the vapor and the monomeric fluid is always more stable at temperatures above the triple point, but a highly associated fluid may exist as a metastable phase under these conditions. The presence of this metastable phase may explain the characteristic nucleation behavior of the liquid phase in strongly dipolar fluids.
Marshall, Bennett D; Chapman, Walter G
2013-08-07
We develop a new theory for associating fluids with multiple association sites. The theory accounts for small bond angle effects such as steric hindrance, ring formation, and double bonding. The theory is validated against Monte Carlo simulations for the case of a fluid of patchy colloid particles with three patches and is found to be very accurate. Once validated, the theory is applied to study the phase diagram of a fluid composed of three patch colloids. It is found that bond angle has a significant effect on the phase diagram and the very existence of a liquid-vapor transition.
Numerical Analysis of Velocity Dispersion in Multi-Phase Fluid-Saturated Porous Rocks
Chen, Xuehua; Zhong, Wenli; Gao, Gang; Zou, Wen; He, Zhenhua
2017-03-01
Seismic waves are subject to velocity dispersion when they propagate in fluid-saturated porous media. In this work, we explore the velocity dispersion behavior of P- and SV-waves in multi-phase fluid-saturated porous reservoirs while taking into account the effects of multi-phase pore fluids on the effective viscosities that control the wave-induced fluid flow. The effective viscosities associated with the hydrocarbon saturation of a synthetic sandstone reservoir saturated with different pore fluid mixtures are calculated using the Refutas model. We then analyze the frequency-dependent velocity, dispersion variation rate and characteristic frequency for different fluid saturation cases by employing Chapman's dynamic equivalent-medium theory. The results demonstrate that the hydrocarbon proportions and types in multi-phase mixed pore fluids significantly affect the magnitude and characteristic frequencies of velocity dispersion features for both the P- and S-waves. The dispersion anomalies of SV-waves are in general larger than those of the P-waves. This indicates that the velocity dispersion anomalies of SV-waves are equally sensitive to fluid saturation as the P-waves and should not be neglected. The velocities at lower frequencies (e.g., 10 and 100 Hz) within the seismic frequency range show a more remarkable decrease with increasing hydrocarbon proportion than those at higher frequency (1000 Hz). The numerical examples help to improve the understanding of the frequency-dependent AVO inversion from seismic reflection data.
Numerical Analysis of Velocity Dispersion in Multi-Phase Fluid-Saturated Porous Rocks
Chen, Xuehua; Zhong, Wenli; Gao, Gang; Zou, Wen; He, Zhenhua
2016-12-01
Seismic waves are subject to velocity dispersion when they propagate in fluid-saturated porous media. In this work, we explore the velocity dispersion behavior of P- and SV-waves in multi-phase fluid-saturated porous reservoirs while taking into account the effects of multi-phase pore fluids on the effective viscosities that control the wave-induced fluid flow. The effective viscosities associated with the hydrocarbon saturation of a synthetic sandstone reservoir saturated with different pore fluid mixtures are calculated using the Refutas model. We then analyze the frequency-dependent velocity, dispersion variation rate and characteristic frequency for different fluid saturation cases by employing Chapman's dynamic equivalent-medium theory. The results demonstrate that the hydrocarbon proportions and types in multi-phase mixed pore fluids significantly affect the magnitude and characteristic frequencies of velocity dispersion features for both the P- and S-waves. The dispersion anomalies of SV-waves are in general larger than those of the P-waves. This indicates that the velocity dispersion anomalies of SV-waves are equally sensitive to fluid saturation as the P-waves and should not be neglected. The velocities at lower frequencies (e.g., 10 and 100 Hz) within the seismic frequency range show a more remarkable decrease with increasing hydrocarbon proportion than those at higher frequency (1000 Hz). The numerical examples help to improve the understanding of the frequency-dependent AVO inversion from seismic reflection data.
Establishment of a Cutting Fluid Control System (Phase III)
1982-09-01
usually takes two to five days. If a crystalline or extremely gummy residue is formed, this fluid should be discarded from further testing. After...REFERENCES 1. "Fishtail Defects in Bearing Races - Their Origin and Elimination," C. F. Barth, TRW TM-4713, December 1972. 2. "Elimination of...Fishtail Defects in Bearing Races Through Optimized Grinding Procedures," C. F. Barth, TRW TM-4768, November 1974. 3. "fhe Nature of Surface Finish
Solubility and Phase Behavior of CL20 in Supercritical Fluids
2006-09-01
supercritical state. The fugacity of the solute in the supercritical fluid can be evaluated using a cubic equation of state such as the Redlich - Kwong ...pro- gram was validated using available literature data for the solubility of naphthalene and of biphenyl in supercritical CO2. The applicability of...promising process using environmentally benign compressed gases as either solvents or anti-solvents is being investi- gated for applications in
Phase equilibrium data for development of correlations for coal fluids
Energy Technology Data Exchange (ETDEWEB)
Robinson, R.L. Jr.; Gasem, K.A.M.; Darwish, N.A.; Raff, A.M.
1991-02-01
The overall objective of the authors' work is to develop accurate predictive methods for representations of vapor-liquid equilibria in systems encountered in coal-conversion processes. The objectives pursued in the present project include: (1) Measurements of binary vapor-liquid phase behavior data for selected solute gases (e.g., C{sub 2}H{sub 6}, CH{sub 4}) in a series of paraffinic, naphthenic, and aromatic hydrocarbon solvents to permit evaluations of interaction parameters in models for phase behavior. Solubilities of the gases in the liquid phase have been determined. (2) Evaluation of existing equations of state and other models for representations of phase behavior in systems of the type studied experimentally; development of new correlation frameworks as needed. (3) Generalization of the interaction parameters for the solutes studied to a wide spectrum of heavy solvents; presentation of final results in formats useful in the design/optimization of coal liquefaction processes.
Khater, S; West, C; Lesellier, E
2013-12-06
Sub-2-microns particles employed as supporting phases are known to favor column efficiency. Recently a set of columns based on sub-2-microns particles for use with supercritical fluid mobile phases have been introduced by Waters. Five different stationary phase chemistries are available: BEH silica, BEHEthyl-pyridine, X Select CSH Fluorophenyl, HSS C18 SB and BEH Shield RP18. This paper describes the characterization of 15 stationary phases, the five different chemistries, and three particle sizes, 1.7 (or 1.8), 3.5 and 5 microns, with the same carbon dioxide–methanol mobile phase and a set of more than a hundred compounds. The interactions established in the 15 different chromatographic systems used in supercritical fluid chromatography (SFC) are assessed with linear solvation energy relationships (LSERs).The results show the good complementarity of the five column chemistries, and their comparative location inside a classification map containing today around 70 different commercial phases. Among the five different chemistries, the HSS C18 SB phase displays a rather unusual behavior in regards of classical C18 phases, as it displays significant hydrogen–bonding interactions. Besides, it appears, as expected, that the BEH Ethyl–pyridine phase has weak interactions with basic compounds. The effect of particle size was studied because smaller particles induce increased inlet and internal pressure. For compressible fluids,this pressure change modifies the fluid density, i.e. the apparent void volume and the eluting strength.These changes could modify the retention and the selectivity of compounds in the case of method trans-fer, by using different particle sizes, from 5 down to 1.7 m. A hierarchical cluster analysis shows that stationary phase clusters were based on the phase chemistry rather than on the particle size, meaning that method transfer from 5 to 1.7 microns can be achieved in the subcritical domain i.e. by using a weakly compressible fluid.
Phase shift effects for fluid conveying pipes with non-ideal supports
DEFF Research Database (Denmark)
Dahl, Jonas; Thomsen, Jon Juel
2008-01-01
Vibrations of a fluid-conveying pipe with non-ideal supports are investigated with respect to phase shift effects. A numerical Galerkin approach is developed for this general problem, and the use of it exemplified with a investigation of phase shift effects from rotational damping at supports...
Phase shift effects for fluid conveying pipes with non-ideal supports
DEFF Research Database (Denmark)
Dahl, Jonas; Thomsen, Jon Juel
2008-01-01
Vibrations of a fluid-conveying pipe with non-ideal supports are investigated with respect to phase shift effects. A numerical Galerkin approach is developed for this general problem, and the use of it exemplified with a investigation of phase shift effects from rotational damping at supports...
A model for wave propagation in a porous solid saturated by a three-phase fluid.
Santos, Juan E; Savioli, Gabriela B
2016-02-01
This paper presents a model to describe the propagation of waves in a poroelastic medium saturated by a three-phase viscous, compressible fluid. Two capillary relations between the three fluid phases are included in the model by introducing Lagrange multipliers in the principle of virtual complementary work. This approach generalizes that of Biot for single-phase fluids and allows to determine the strain energy density, identify the generalized strains and stresses, and derive the constitutive relations of the system. The kinetic and dissipative energy density functions are obtained assuming that the relative flow within the pore space is of laminar type and obeys Darcy's law for three-phase flow in porous media. After deriving the equations of motion, a plane wave analysis predicts the existence of four compressional waves, denoted as type I, II, III, and IV waves, and one shear wave. Numerical examples showing the behavior of all waves as function of saturation and frequency are presented.
Vapour-liquid phase diagram for an ionic fluid in a random porous medium.
Holovko, M F; Patsahan, O; Patsahan, T
2016-10-19
We study the vapour-liquid phase behaviour of an ionic fluid confined in a random porous matrix formed by uncharged hard sphere particles. The ionic fluid is modelled as an equimolar binary mixture of oppositely charged equisized hard spheres, the so-called restricted primitive model (RPM). Considering the matrix-fluid system as a partly-quenched model, we develop a theoretical approach which combines the method of collective variables with the extension of the scaled-particle theory (SPT) for a hard-sphere fluid confined in a disordered hard-sphere matrix. The approach allows us to formulate the perturbation theory using the SPT for the description of the thermodynamics of the reference system. The phase diagrams of the RPM in matrices of different porosities and for different size ratios of matrix and fluid particles are calculated in the random-phase approximation and also when the effects of higher-order correlations between ions are taken into account. Both approximations correctly reproduce the basic effects of porous media on the vapour-liquid phase diagram, i.e. with a decrease of porosity the critical point shifts towards lower fluid densities and lower temperatures and the coexistence region gets narrower. For the fixed matrix porosity, both the critical temperature and the critical density increase with an increase of size of matrix particles and tend to the critical values of the bulk RPM.
Vapour-liquid phase diagram for an ionic fluid in a random porous medium
Holovko, M. F.; Patsahan, O.; Patsahan, T.
2016-10-01
We study the vapour-liquid phase behaviour of an ionic fluid confined in a random porous matrix formed by uncharged hard sphere particles. The ionic fluid is modelled as an equimolar binary mixture of oppositely charged equisized hard spheres, the so-called restricted primitive model (RPM). Considering the matrix-fluid system as a partly-quenched model, we develop a theoretical approach which combines the method of collective variables with the extension of the scaled-particle theory (SPT) for a hard-sphere fluid confined in a disordered hard-sphere matrix. The approach allows us to formulate the perturbation theory using the SPT for the description of the thermodynamics of the reference system. The phase diagrams of the RPM in matrices of different porosities and for different size ratios of matrix and fluid particles are calculated in the random-phase approximation and also when the effects of higher-order correlations between ions are taken into account. Both approximations correctly reproduce the basic effects of porous media on the vapour-liquid phase diagram, i.e. with a decrease of porosity the critical point shifts towards lower fluid densities and lower temperatures and the coexistence region gets narrower. For the fixed matrix porosity, both the critical temperature and the critical density increase with an increase of size of matrix particles and tend to the critical values of the bulk RPM.
MOLECULAR SIMULATION OF PHASE EQUILIBRIA FOR COMPLEX FLUIDS
Energy Technology Data Exchange (ETDEWEB)
Athanassios Z. Panagiotopoulos
2009-09-09
The general area of this project was the development and application of novel molecular simulation methods for prediction of thermodynamic and structural properties of complex polymeric, surfactant and ionic fluids. Over this project period, we have made considerable progress in developing novel algorithms to meet the computational challenges presented by the strong or long-range interactions in these systems and have generated data for well-defined mod-els that can be used to test theories and compare to experimental data. Overall, 42 archival papers and many invited and contributed presentations and lectures have been based on work supported by this project. 6 PhD, 1 M.S. and 2 postdoctoral students have been associated with this work, as listed in the body of the report.
Tension induced phase transitions in biomimetic fluid membranes
Shapiro, Marc; Vlahovska, Petia
2012-11-01
Membranes in eukaryotic cells are mixtures of hundreds of lipid species. The lipid diversity enables membranes to phase separate and form domains, called rafts, which play a critical role in cell functions such as signaling and trafficking. The phase transitions underlying raft formation have been extensively studied as a function of temperature and composition. However, the third dimension of the phase diagram, i.e., the tension (2D pressure), is still unexplored because membrane tension is difficult to control and quantify. To overcome this challenge, we develop two approaches, capillary micromechanics and electrodeformation, in which the tension is regulated by the area dilation accompanying deformation of a vesicle (a closed membrane). The first technique consists of forcing an initially quasi-spherical vesicle through a tapered glass microcapillary, while the second method utilizes uniform electric fields to deform the vesicle into an ellipsoid. Domains are visualized using a fluorescent dye, which preferentially partitions in one of the phases. The experimental results suggest that the miscibility temperature (at which domains form in an initially homogeneous membrane) increases with applied tension. Domain motions and coarsening are also investigated.
Energy Technology Data Exchange (ETDEWEB)
Bordin, José Rafael, E-mail: josebordin@unipampa.edu.br [Campus Caçapava do Sul, Universidade Federal do Pampa, Caixa Postal 15051, CEP 96570-000, Caçapava do Sul, RS (Brazil); Krott, Leandro B., E-mail: leandro.krott@ufrgs.br; Barbosa, Marcia C., E-mail: marcia.barbosa@ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil)
2014-10-14
The behavior of a confined spherical symmetric anomalous fluid under high external pressure was studied with Molecular Dynamics simulations. The fluid is modeled by a core-softened potential with two characteristic length scales, which in bulk reproduces the dynamical, thermodynamical, and structural anomalous behavior observed for water and other anomalous fluids. Our findings show that this system has a superdiffusion regime for sufficient high pressure and low temperature. As well, our results indicate that this superdiffusive regime is strongly related with the fluid structural properties and the superdiffusion to diffusion transition is a first order phase transition. We show how the simulation time and statistics are important to obtain the correct dynamical behavior of the confined fluid. Our results are discussed on the basis of the two length scales.
The simplest model for non-congruent fluid-fluid phase transition in Coulomb system
Stroev, Nikita
2015-01-01
The simplest model for non-congruent phase transition of gas-liquid type was developed in frames of modified model with no associations of a binary ionic mixture (BIM) on a homogeneous compressible ideal background (or non-ideal) electron gas /BIM($\\sim$)/. The analytical approximation for equation of state equation of state of Potekhin and Chabrier of fully ionized electron-ionic plasma was used for description of the ion-ion correlations (Coulomb non-ideality) in combination with ``linear mixture'' (LM) approximation. Phase equilibrium for the charged species was calculated according to the Gibbs-Guggenheim conditions. The presently considered BIM($\\sim$) model allows to calculate full set of parameters for phase boundaries of non-congruent variant of phase equilibrium and to study all features for this non-congruent phase transition realization in Coulomb system in comparison with the simpler (standard) forced-congruent evaporation mode. In particular, in BIM($\\sim$) there were reproduced two-dimensional r...
Two-Phase Working Fluids for the Temperature Range 50 to 350 C
Saaski, E. W.; Owzarski, P. C.
1977-01-01
The decomposition and corrosion of two-phase heat transfer liquids and metal envelopes have been investigated on the basis of molecular bond strengths and chemical thermodynamics. Potentially stable heat transfer fluids for the temperature range 100 C to 350 C have been identified, and reflux heat pipes tests initiated with 10 fluids and carbon steel and aluminum envelopes to experimentally establish corrosion behavior and noncondensable gas generation rates.
Beyond Darcy's law: The role of phase topology and ganglion dynamics for two-fluid flow
Armstrong, Ryan T.; McClure, James E.; Berrill, Mark A.; Rücker, Maja; Schlüter, Steffen; Berg, Steffen
2016-10-01
In multiphase flow in porous media the consistent pore to Darcy scale description of two-fluid flow processes has been a long-standing challenge. Immiscible displacement processes occur at the scale of individual pores. However, the larger scale behavior is described by phenomenological relationships such as relative permeability, which typically uses only fluid saturation as a state variable. As a consequence pore scale properties such as contact angle cannot be directly related to Darcy scale flow parameters. Advanced imaging and computational technologies are closing the gap between the pore and Darcy scale, supporting the development of new theory. We utilize fast x-ray microtomography to observe pore-scale two-fluid configurations during immiscible flow and initialize lattice Boltzmann simulations that demonstrate that the mobilization of disconnected nonwetting phase clusters can account for a significant fraction of the total flux. We show that fluid topology can undergo substantial changes during flow at constant saturation, which is one of the underlying causes of hysteretic behavior. Traditional assumptions about fluid configurations are therefore an oversimplification. Our results suggest that the role of fluid connectivity cannot be ignored for multiphase flow. On the Darcy scale, fluid topology and phase connectivity are accounted for by interfacial area and Euler characteristic as parameters that are missing from our current models.
Beyond Darcy's law: The role of phase topology and ganglion dynamics for two-fluid flow.
Armstrong, Ryan T; McClure, James E; Berrill, Mark A; Rücker, Maja; Schlüter, Steffen; Berg, Steffen
2016-10-01
In multiphase flow in porous media the consistent pore to Darcy scale description of two-fluid flow processes has been a long-standing challenge. Immiscible displacement processes occur at the scale of individual pores. However, the larger scale behavior is described by phenomenological relationships such as relative permeability, which typically uses only fluid saturation as a state variable. As a consequence pore scale properties such as contact angle cannot be directly related to Darcy scale flow parameters. Advanced imaging and computational technologies are closing the gap between the pore and Darcy scale, supporting the development of new theory. We utilize fast x-ray microtomography to observe pore-scale two-fluid configurations during immiscible flow and initialize lattice Boltzmann simulations that demonstrate that the mobilization of disconnected nonwetting phase clusters can account for a significant fraction of the total flux. We show that fluid topology can undergo substantial changes during flow at constant saturation, which is one of the underlying causes of hysteretic behavior. Traditional assumptions about fluid configurations are therefore an oversimplification. Our results suggest that the role of fluid connectivity cannot be ignored for multiphase flow. On the Darcy scale, fluid topology and phase connectivity are accounted for by interfacial area and Euler characteristic as parameters that are missing from our current models.
Measurement of average density and relative volumes in a dispersed two-phase fluid
Sreepada, Sastry R.; Rippel, Robert R.
1992-01-01
An apparatus and a method are disclosed for measuring the average density and relative volumes in an essentially transparent, dispersed two-phase fluid. A laser beam with a diameter no greater than 1% of the diameter of the bubbles, droplets, or particles of the dispersed phase is directed onto a diffraction grating. A single-order component of the diffracted beam is directed through the two-phase fluid and its refraction is measured. Preferably, the refracted beam exiting the fluid is incident upon a optical filter with linearly varing optical density and the intensity of the filtered beam is measured. The invention can be combined with other laser-based measurement systems, e.g., laser doppler anemometry.
A two-phase solid/fluid model for dense granular flows including dilatancy effects
Mangeney, Anne; Bouchut, Francois; Fernandez-Nieto, Enrique; Koné, El-Hadj; Narbona-Reina, Gladys
2016-04-01
Describing grain/fluid interaction in debris flows models is still an open and challenging issue with key impact on hazard assessment [{Iverson et al.}, 2010]. We present here a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects. It describes the velocity of both the solid and the fluid phases, the compression/dilatation of the granular media and its interaction with the pore fluid pressure [{Bouchut et al.}, 2016]. The model is derived from a 3D two-phase model proposed by {Jackson} [2000] based on the 4 equations of mass and momentum conservation within the two phases. This system has 5 unknowns: the solid and fluid velocities, the solid and fluid pressures and the solid volume fraction. As a result, an additional equation inside the mixture is necessary to close the system. Surprisingly, this issue is inadequately accounted for in the models that have been developed on the basis of Jackson's work [{Bouchut et al.}, 2015]. In particular, {Pitman and Le} [2005] replaced this closure simply by imposing an extra boundary condition at the surface of the flow. When making a shallow expansion, this condition can be considered as a closure condition. However, the corresponding model cannot account for a dissipative energy balance. We propose here an approach to correctly deal with the thermodynamics of Jackson's model by closing the mixture equations by a weak compressibility relation following {Roux and Radjai} [1998]. This relation implies that the occurrence of dilation or contraction of the granular material in the model depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To
Phase Envelope Calculations for Reservoir Fluids in the Presence of Capillary Pressure
DEFF Research Database (Denmark)
Lemus, Diego; Yan, Wei; Michelsen, Michael L.
2015-01-01
Reservoir fluids are multicomponent mixtures in confined spaces, where the role of capillary force becomes important when the average pore size is on the order of tens of nanometers, such as in tight rocks and shale. We present an algorithm for calculating the phase envelope of multicomponent...... the bubble and dew point curves but also other quality lines with vapor fractions between 0 and 1. The algorithm has been used to calculate the phase envelopes of binary, multicomponent and reservoir fluid systems for pore radius from 10 to 50 nm. The presence of capillary pressure changes the saturation...
Conceptual design of two-phase fluid mechanics and heat transfer facility for spacelab
North, B. F.; Hill, M. E.
1980-01-01
Five specific experiments were analyzed to provide definition of experiments designed to evaluate two phase fluid behavior in low gravity. The conceptual design represents a fluid mechanics and heat transfer facility for a double rack in Spacelab. The five experiments are two phase flow patterns and pressure drop, flow boiling, liquid reorientation, and interface bubble dynamics. Hardware was sized, instrumentation and data recording requirements defined, and the five experiments were installed as an integrated experimental package. Applicable available hardware was selected in the experiment design and total experiment program costs were defined.
Hermanska, M.; Stefansson, A.
2014-12-01
Many active volcanic systems are associated with high-enthalpy geothermal systems. For systems characterized by shallow magmatic intrusions, liquid water often predominates at depth with two-phase fluids, vapor and liquid water, occurring at shallower depth due to depressurization boiling. Close to the intrusion, superheated or supercritical vapor may also occur. The Krafla high-enthalpy geothermal system provides an ideal opportunity to study such volcanic geothermal systems. Over forty wells have been drilled into the system with fluid discharge temperatures of 3200 kJ/kg. In this study, geochemical modelling of multicomponent fluid phases associated with shallow magmatic intrusions were conducted across variable temperature, pressure and enthalpy conditions and the results compared with the fluid geochemistry of the Krafla system. Within the reservoir at geothermal temperatures (250-300°C) liquid water predominates. Under these conditions, the concentrations of most major elements are controlled by equilibrium with secondary minerals. Geochemical modelling and observations at Krafla support these findings. Around the magma intrusions believed to be at shallow depth at Krafla, superheated vapor is formed. Such fluid was discharged by the IDDP-1 well at 450°C and 140 bar. According to the geochemical modelling, superheated vapor is produced upon heat addition by the intrusion to the surrounding geothermal water resulting in boiling to dryness, precipitation of non-volatiles (Si, Fe, Mg, Al, SO4, Na, K, Ca) whereas volatiles (CO2, H2S, Cl, F, B) are unaffected. By mass, quartz is the predominant secondary mineral around the intrusions. The chemical composition of the modelled and observed superheated vapor compared well. Upon ascent and depressurization of the liquid geothermal water and the superheated vapor various processes may occur, including superheated vapor condensation, mixing and depressurization boiling. This leads to formation of two-phase liquid and
Estimation of flow velocity for a debris flow via the two-phase fluid model
Directory of Open Access Journals (Sweden)
S. Guo
2014-06-01
Full Text Available The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate accurately the velocity for a debris flow.
Uddin, Md Nasir; Morrow, Michael R
2010-07-20
Variable-pressure deuterium nuclear magnetic resonance ((2)H NMR) has been used to study the pressure-temperature phase diagram of bicellar mixtures containing 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC). Spectra were obtained for DMPC-d(54)/DHPC (3:1), DMPC-d(54)/DHPC (4.4:1), DMPC/DHPC-d(22) (3:1), and DMPC/DHPC-d(22) (4.4:1) in the range 10-68 degrees C at ambient pressure, 66 MPa, 102 MPa, and 135 MPa. Isotropic-to-nematic and nematic-to-lamellar transition temperatures were found to rise with pressure at approximately 0.15 and approximately 0.14 degrees C/MPa, respectively, for DMPC-d(54)/DHPC (3:1) and at at approximately 0.19 and approximately 0.18 degrees C/MPa, respectively, for DMPC-d(54)/DHPC (4.4:1). Pressure had little effect on the range of DMPC-d(54) chain orientational order through the nematic phase temperature range, but the behavior of chain orientational order at the nematic-to-lamellar transition was found to vary slightly with pressure. Comparison of differential scanning calorimetry (DSC) observations with ambient-pressure (2)H NMR observations of DMPC-d(54) in the bicellar mixtures suggests that absorption of heat persists for a few degrees above the onset of axially symmetric DMPC-d(54) reorientation.
Phenomena at the QCD phase transition in nonequilibrium chiral fluid dynamics (NχFD)
Energy Technology Data Exchange (ETDEWEB)
Nahrgang, Marlene [Duke University, Department of Physics, Durham, NC (United States); Herold, Christoph [Suranaree University of Technology, School of Physics, Nakhon Ratchasima (Thailand)
2016-08-15
Heavy-ion collisions performed in the beam energy range accessible by the NICA collider facility are expected to produce systems of extreme net-baryon densities and can thus reach yet unexplored regions of the QCD phase diagram. Here, one expects the phase transition between the plasma of deconfined quarks and gluons and the hadronic matter to be of first order. A discovery of the first-order phase transition would as well prove the existence of the QCD critical point, a landmark in the phase diagram. In order to understand possible signals of the first-order phase transition in heavy-ion collision experiments it is very important to develop dynamical models of the phase transition. Here, we discuss the opportunities of studying dynamical effects at the QCD first-order phase transition within our model of nonequilibrium chiral fluid dynamics. (orig.)
DEFF Research Database (Denmark)
Kaasgaard, Thomas; Leidy, Chad; Crowe, J.H.
2003-01-01
ripples was seen. From height profiles of the AFM images, estimates of the amplitudes of the different ripple phases are reported. To elucidate the processes of ripple formation and disappearance, a ripple-phase DPPC lipid bilayer was taken through the pretransition in the cooling and the heating...... was heated from the ripple phase and into the ripple-phase/fluid-phase coexistence temperature region, the AFM images revealed that several dynamic properties of the ripple phase are important for the melting behavior of the lipid mixture. Onset of melting is observed at grain boundaries between different......Temperature-controlled atomic force microscopy (AFM) has been used to visualize and study the structure and kinetics of ripple phases in one-component dipalmitoylphosphaticlylcholine (DPPC) and two-component dimyristoylphosphatidylcholine-distearoylphosphatidylcholine (DMPC-DSPC) lipid bilayers...
Phase Behaviors of Reservoir Fluids with Capillary Eff ect Using Particle Swarm Optimization
Ma, Zhiwei
2013-05-06
The study of phase behavior is important for the oil and gas industry. Many approaches have been proposed and developed for phase behavior calculation. In this thesis, an alternative method is introduced to study the phase behavior by means of minimization of Helmholtz free energy. For a system at fixed volume, constant temperature and constant number of moles, the Helmholtz free energy reaches minimum at the equilibrium state. Based on this theory, a stochastic method called Particle Swarm Optimization (PSO) algorithm, is implemented to compute the phase diagrams for several pure component and mixture systems. After comparing with experimental and the classical PT-ash calculation, we found the phase diagrams obtained by minimization of the Helmholtz Free Energy approach match the experimental and theoretical diagrams very well. Capillary effect is also considered in this thesis because it has a significant influence on the phase behavior of reservoir fluids. In this part, we focus on computing the phase envelopes, which consists of bubble and dew point lines. Both fixed and calculated capillary pressure from the Young-Laplace equation cases are introduced to study their effects on phase envelopes. We found that the existence of capillary pressure will change the phase envelopes. Positive capillary pressure reduces the dew point and bubble point temperatures under the same pressure condition, while the negative capillary pressure increases the dew point and bubble point temperatures. In addition, the change of contact angle and pore radius will affect the phase envelope. The effect of the pore radius on the phase envelope is insignificant when the radius is very large. These results may become reference for future research and study. Keywords: Phase Behavior; Particle Swarm Optimization; Capillary Pressure; Reservoir Fluids; Phase Equilibrium; Phase Envelope.
Phase Behavior and Percolation Properties of the Patchy Colloidal Fluids in the Random Porous Media.
Kalyuzhnyi, Y V; Holovko, M; Patsahan, T; Cummings, P T
2014-12-18
The lack of a simple analytical description of the hard-sphere fluid in a matrix with hard-core obstacles is limiting progress in the development of thermodynamic perturbation theories for the fluid in random porous media. We propose a simple and highly accurate analytical scheme, which allows us to calculate thermodynamic and percolation properties of a network-forming fluid confined in the random porous media, represented by the hard-sphere fluid and overlapping hard-sphere matrices, respectively. Our scheme is based on the combination of scaled-particle theory, Wertheim's thermodynamic perturbation theory for associating fluids and extension of the Flory-Stockmayer theory for percolation. The liquid-gas phase diagram and percolation threshold line for several versions of the patchy colloidal fluid model confined in a random porous media are calculated and discussed. The method presented enables calculation of the thermodynamic and percolation properties of a large variety of polymerizing and network-forming fluids confined in random porous media.
Computer simulations on the gas-liquid phase diagram of Stockmayer fluids
Institute of Scientific and Technical Information of China (English)
L(U) Zhongyuan; OUYANG Wenze; SUN Zhaoyan; LI Zesheng; AN Lijia
2005-01-01
Particle exchange molecular dynamics (PEMD) simulation technique is proposed to study the gas-liquid phase diagram of fluids. In the simulations, the fluid particles can be transferred between the two coupled boxes, which possess constant total number of particles and volume. The particle transfer is controlled by the difference of chemical potential in the respective simulation box. After equilibrium the two boxes have the same pressure, temperature and chemical potential. The method is further used to study the gas-liquid phase diagram of Stockmayer fluid. Increasing the dipole strength will enhance the critical temperature. The predicted critical points are in agreement with those from Gibbs ensemble Monte Carlo simulations, while the small systematic difference is attributed to the system size effects and the thermostat methods.
The redox budget of crust-derived fluid phases at the slab-mantle interface
Malaspina, N.; Langenhorst, F.; Tumiati, S.; Campione, M.; Frezzotti, M. L.; Poli, S.
2017-07-01
The redox processes taking place in the portion of the mantle on top of the subducting slab are poorly investigated and the redox potential of crust-derived fluid phases is still poorly constrained. A case study of supra-subduction mantle affected by metasomatism from crust-derived fluid phases is represented by garnet orthopyroxenites from the Maowu Ultramafic Complex (China) deriving from harzburgite precursors metasomatised at ∼4 GPa, 750-800 °C by a silica- and incompatible trace element-rich fluid phase. This metasomatism produced poikilitic orthopyroxene and inclusion-rich garnet porphyroblasts. Solid multiphase primary micro-inclusions in garnet display negative crystal shapes and infilling minerals (spinel, ±orthopyroxene, amphiboles, chlorite, ±talc, ±mica) occur with constant modal proportions, indicating that they derive from trapped solute-rich aqueous fluids. FT-IR hyper spectral imaging analyses and Raman spectroscopy, together with X-ray microtomography performed on single inclusions indicate that liquid water is still preserved at least in some inclusions (±spinel). To investigate the redox budget of these fluid phases, we measured for the first time the Fe3+ concentration of the micron-sized precipitates of the multiphase inclusions using EELS on a TEM. Results indicate that spinel contains up to 12% of Fe3+ with respect to the total iron, amphibole about 30%, while the ratio in inclusion phases such as chlorite and phlogopite may reach 70%. The Fe3+ fraction of the host garnet is equal to that measured in spinel as also confirmed by Flank Method EPMA measurements. Forward modelling fO2 calculations indicate that the garnet orthopyroxenites record ΔFMQ = -1.8 ÷ -1.5, therefore resulting apparently more reduced with respect to metasomatised supra-subduction garnet-peridotites. On the other hand, oxygen mass balance, performed both on the Maowu hybrid orthopyroxenite and on metasomatised supra-subduction garnet peridotites, indicate that the
Exploring fluctuations and phase equilibria in fluid mixtures via Monte Carlo simulation
Denton, Alan R.; Schmidt, Michael P.
2013-03-01
Monte Carlo simulation provides a powerful tool for understanding and exploring thermodynamic phase equilibria in many-particle interacting systems. Among the most physically intuitive simulation methods is Gibbs ensemble Monte Carlo (GEMC), which allows direct computation of phase coexistence curves of model fluids by assigning each phase to its own simulation cell. When one or both of the phases can be modelled virtually via an analytic free energy function (Mehta and Kofke 1993 Mol. Phys. 79 39), the GEMC method takes on new pedagogical significance as an efficient means of analysing fluctuations and illuminating the statistical foundation of phase behaviour in finite systems. Here we extend this virtual GEMC method to binary fluid mixtures and demonstrate its implementation and instructional value with two applications: (1) a lattice model of simple mixtures and polymer blends and (2) a free-volume model of a complex mixture of colloids and polymers. We present algorithms for performing Monte Carlo trial moves in the virtual Gibbs ensemble, validate the method by computing fluid demixing phase diagrams, and analyse the dependence of fluctuations on system size. Our open-source simulation programs, coded in the platform-independent Java language, are suitable for use in classroom, tutorial, or computational laboratory settings.
Phase-Field and Korteweg-Type Models for the Time-Dependent Flow of Compressible Two-Phase Fluids
Freistühler, Heinrich; Kotschote, Matthias
2016-11-01
Various versions of the Navier-Stokes-Allen-Cahn (NSAC), the Navier-Stokes-Cahn-Hilliard (NSCH), and the Navier-Stokes-Korteweg (NSK) equations have been used in the literature to model the dynamics of two-phase fluids. One main purpose of this paper consists in (re-)deriving NSAC, NSCH and NSK from first principles, in the spirit of rational mechanics, for fluids of very general constitutive laws. For NSAC, this deduction confirms and extends a proposal of Blesgen. Regarding NSCH, it continues work of Lowengrub and Truskinovsky and provides the apparently first justified formulation in the non-isothermal case. For NSK, it yields a most natural correction to the formulation by Dunn and Serrin. The paper uniformly recovers as examples various classes of fluids, distinguished according to whether none, one, or both of the phases are compressible, and according to the nature of their co-existence. The latter is captured not only by the mixing energy, but also by a `mixing rule'—a constitutive law that characterizes the type of the mixing. A second main purpose of the paper is to communicate the apparently new observation that in the case of two immiscible incompressible phases of different temperature-independent specific volumes, NSAC reduces literally to NSK. This finding may be considered as an independent justification of NSK. An analogous fact is shown for NSCH, which under the same assumption reduces to a new non-local version of NSK.
A fluid biopsy as investigating technology for the fluid phase of solid tumors
Kuhn, Peter; Bethel, Kelly
2012-02-01
, which has shown predictive utility in several cancer types—the blurry outlines of things to come began to coalesce. The field of CTC research is in its adolescence; enumeration and characterization research effort is methodologically varied, vigorously individuated and rich in innovation. The high definition CTC (HD-CTC) assay described herein and applied to several currently relevant research questions about cancer spread represents a new measure of an internal biologic process that will hopefully lead to great advancements in cancer medicine. First, the paper entitled 'Fluid biopsy in patients with metastatic prostate, pancreatic and breast cancers' by Marrinucci et al, represents the initial technical and clinical validation of an enrichment-free assay and demonstrates our ability to identify significant numbers of HD-CTCs in a majority of patients with prostate, breast and pancreatic cancers. It demonstrates very high rates of detection (>50%) in breast, prostate and pancreatic cancer patients with no CTCs found in normal control subjects. The assay detects significantly higher numbers of CTCs than the FDA-approved Cellsearch® assay and shows the presence of clusters of CTCs in many patients. The nature of the clusters is further evaluated in 'Characterization of circulating tumor cell aggregates identified in patients with epithelial tumors' by Cho et al, wherein CTC aggregates are identified in 43% of 86 patient samples. The fraction of CTC aggregation was investigated in blood draws from 24 breast, 14 non-small cell lung (NSCLC), 18 pancreatic, 15 prostate stage IV cancer patients and 15 normal blood donors (NBD). Cells contained in CTC aggregates had less area and length, on average, than single CTCs. The nuclear to cytoplasmic (N/C) ratio between single CTCs and CTC aggregates was similar. To assist with translating into patients the substantial cell biology work done using cell line cells instead of human tumor tissue, the paper entitled 'Cytometric
Phase diagram of the two-fluid Lipkin model: a butterfly catastrophe
García-Ramos, J E; Arias, J M; Freire, E
2016-01-01
Background: In the last few decades quantum phase transitions have been of great interest in Nuclear Physics. In this context, two-fluid algebraic models are ideal systems to study how the concept of quantum phase transition evolves when moving into more complex systems, but the number of publications along this line has been scarce up to now. Purpose: We intend to determine the phase diagram of a two-fluid Lipkin model, that resembles the nuclear proton-neutron interacting boson model Hamiltonian, using both numerical results and analytic tools, i.e., catastrophe theory, and to compare the mean-field results with exact diagonalizations for large systems. Method: The mean-field energy surface of a consistent-Q-like two-fluid Lipkin Hamiltonian is studied and compared with exact results coming from a direct diagonalization. The mean-field results are analyzed using the framework of catastrophe theory. Results: The phase diagram of the model is obtained and the order of the different phase-transition lines and ...
Cold phase fluid model of the longitudinal dynamics ofspace-charged dominated beams
Energy Technology Data Exchange (ETDEWEB)
de Hoon, Michiel J.L.; Lee, Edward P.; Barnard, John J.; Friedman, Alex
2002-03-01
The dynamics of a longitudinally cold, charged-particle beam can be simulated by dividing the beam into slices and calculating the motion of the slice boundaries due to the longitudinal electric field generated by the beam. On each time step, the beam charge is deposited onto an (r, z) grid, and an existing (r, z) electrostatic field solver is used to find the longitudinal electric field. Transversely, the beam envelope equation is used for each slice boundary separately. In contrast to the g-factor model, it can be shown analytically that the repulsive electric field of a slice compressed to zero length is bounded. Consequently, this model allows slices to overtake their neighbors, effectively incorporating mixing. The model then effectively describes a cold fluid in longitudinal z, v{sub z} phase space. Longitudinal beam compression calculations based on this cold phase fluid model showed that slice overtaking reflects local mixing, while the global phase space structure is preserved.
DEFF Research Database (Denmark)
Thomsen, Jon Juel; Dahl, Jonas
2010-01-01
Resonant vibrations of a fluid-conveying pipe are investigated, with special consideration to axial shifts in vibration phase accompanying fluid flow and various imperfections. This is relevant for understanding elastic wave propagation in general, and for the design and trouble-shooting of phase...
Effects of confinement on anomalies and phase transitions of core-softened fluids
Energy Technology Data Exchange (ETDEWEB)
Krott, Leandro B., E-mail: leandro.krott@ufrgs.br; Barbosa, Marcia C., E-mail: marciabarbosa@ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil); Bordin, José Rafael, E-mail: josebordin@unipampa.edu.br [Campus Caçapava do Sul, Universidade Federal do Pampa, Av. Pedro Anunciação, s/n, CEP 96570-000, Caçapava do Sul, RS (Brazil); Barraz, Ney M., E-mail: ney.barraz@uffs.edu.br [Campus Cerro Largo, Universidade Federal da Fronteira Sul, Av. Jacob Reinaldo Haupenthal, 1580. CEP 97900-000, Cerro Largo, RS (Brazil)
2015-04-07
We use molecular dynamics simulations to study how the confinement affects the dynamic, thermodynamic, and structural properties of a confined anomalous fluid. The fluid is modeled using an effective pair potential derived from the ST4 atomistic model for water. This system exhibits density, structural, and dynamical anomalies, and the vapor-liquid and liquid-liquid critical points similar to the quantities observed in bulk water. The confinement is modeled both by smooth and structured walls. The temperatures of extreme density and diffusion for the confined fluid show a shift to lower values while the pressures move to higher amounts for both smooth and structured confinements. In the case of smooth walls, the critical points and the limit between fluid and amorphous phases show a non-monotonic change in the temperatures and pressures when the nanopore size is increase. In the case of structured walls, the pressures and temperatures of the critical points varies monotonically with the pore size. Our results are explained on basis of the competition between the different length scales of the fluid and the wall-fluid interaction.
Phase diagram of the two-fluid Lipkin model: A "butterfly" catastrophe
García-Ramos, J. E.; Pérez-Fernández, P.; Arias, J. M.; Freire, E.
2016-03-01
Background: In the past few decades quantum phase transitions have been of great interest in nuclear physics. In this context, two-fluid algebraic models are ideal systems to study how the concept of quantum phase transition evolves when moving into more complex systems, but the number of publications along this line has been scarce up to now. Purpose: We intend to determine the phase diagram of a two-fluid Lipkin model that resembles the nuclear proton-neutron interacting boson model Hamiltonian using both numerical results and analytic tools, i.e., catastrophe theory, and compare the mean-field results with exact diagonalizations for large systems. Method: The mean-field energy surface of a consistent-Q -like two-fluid Lipkin Hamiltonian is studied and compared with exact results coming from a direct diagonalization. The mean-field results are analyzed using the framework of catastrophe theory. Results: The phase diagram of the model is obtained and the order of the different phase-transition lines and surfaces is determined using a catastrophe theory analysis. Conclusions: There are two first-order surfaces in the phase diagram, one separating the spherical and the deformed shapes, while the other separates two different deformed phases. A second-order line, where the later surfaces merge, is found. This line finishes in a transition point with a divergence in the second-order derivative of the energy that corresponds to a tricritical point in the language of the Ginzburg-Landau theory for phase transitions.
A New Uniform Phase Bridge Functional: Test and Its Application to Non-uniform Phase Fluid
Institute of Scientific and Technical Information of China (English)
ZHOU Shi-Qi; CHEN Hong; ZHANG Xiao-Qi
2003-01-01
A new bridge functional as a function of indirect correlation function was proposed, which was basedon analysis on the asymptotic behavior of the Ornstein-Zernike (OZ) equation system and a series expansion whoserenormalization resulted in an adjustable parameter determined by the thermodynamics consistency condition. Theproposed bridge functional was tested by applying it to bulk hard sphere and hard core Yukawa fluid for the predictionof structure and thermodynamics properties based on the OZ equation. As an application, the present bridge functionalwas employed for non-uniform fluid of the above two kinds by means of the density functional theory methodology, theresulting density distribution profiles were in good agreement with the available computer simulation data.
Dahms, Rainer N.; Oefelein, Joseph C.
2013-09-01
A theory that explains the operating pressures where liquid injection processes transition from exhibiting classical two-phase spray atomization phenomena to single-phase diffusion-dominated mixing is presented. Imaging from a variety of experiments have long shown that under certain conditions, typically when the pressure of the working fluid exceeds the thermodynamic critical pressure of the liquid phase, the presence of discrete two-phase flow processes become diminished. Instead, the classical gas-liquid interface is replaced by diffusion-dominated mixing. When and how this transition occurs, however, is not well understood. Modern theory still lacks a physically based model to quantify this transition and the precise mechanisms that lead to it. In this paper, we derive a new model that explains how the transition occurs in multicomponent fluids and present a detailed analysis to quantify it. The model applies a detailed property evaluation scheme based on a modified 32-term Benedict-Webb-Rubin equation of state that accounts for the relevant real-fluid thermodynamic and transport properties of the multicomponent system. This framework is combined with Linear Gradient Theory, which describes the detailed molecular structure of the vapor-liquid interface region. Our analysis reveals that the two-phase interface breaks down not necessarily due to vanishing surface tension forces, but due to thickened interfaces at high subcritical temperatures coupled with an inherent reduction of the mean free molecular path. At a certain point, the combination of reduced surface tension, the thicker interface, and reduced mean free molecular path enter the continuum length scale regime. When this occurs, inter-molecular forces approach that of the multicomponent continuum where transport processes dominate across the interfacial region. This leads to a continuous phase transition from compressed liquid to supercritical mixture states. Based on this theory, a regime diagram for
Bulk fluid phase behaviour of colloidal platelet-sphere and platelet-polymer mixtures.
de las Heras, Daniel; Schmidt, Matthias
2013-04-13
Using a geometry-based fundamental measure density functional theory, we calculate bulk fluid phase diagrams of colloidal mixtures of vanishingly thin hard circular platelets and hard spheres. We find isotropic-nematic phase separation, with strong broadening of the biphasic region, upon increasing the pressure. In mixtures with large size ratio of platelet and sphere diameters, there is also demixing between two nematic phases with differing platelet concentrations. We formulate a fundamental measure density functional for mixtures of colloidal platelets and freely overlapping spheres, which represent ideal polymers, and use it to obtain phase diagrams. We find that, for low platelet-polymer size ratio, in addition to isotropic-nematic and nematic-nematic phase coexistence, platelet-polymer mixtures also display isotropic-isotropic demixing. By contrast, we do not find isotropic-isotropic demixing in hard-core platelet-sphere mixtures for the size ratios considered.
Equilibres de phases dans les systèmes fluides petroliers-eau Phase Equilibria in Oil-Water Systems
Directory of Open Access Journals (Sweden)
Peneloux A.
2006-11-01
Full Text Available Nous présentons quelques résultats obtenus à partir du logiciel FHYD qui permet le traitement des mélanges eau-fluides pétroliers, avec la détermination de la nature des phases (huile-gaz-eau-hydrate thermodynamiquement stables dans des conditions données de température et de pression, ainsi que de la quantité, de la composition de ces différentes phases et de leurs propriétés. Ce logiciel permet le tracé automatique des diagrammes de phases et nous présentons des exemples, depuis les systèmes binaires (eau-éthane, ternaires (eau-méthane-propane jusqu'aux fluides les plus complexes. La présence de sels (chlorure de sodium dissous est envisagée, ainsi que le calcul des conditions de dépôt du sel solide. Des exemples de problèmes pétroliers sont cités (gaz de séparateur saturé en eau, huile saturée en eau dans les conditions de gisement, huile en présence d'eau salée. Les estimations sur les quantités d'hydrate formées et leurs compositions sont comparées à des données expérimentales et aux résultats obtenus par d'autres logiciels. Le programme FHYD pourrait permettre une représentation plus réaliste de l'évolution des fluides pétroliers et des propriétés de transport de leurs différentes phases dans les modèles de simulation des conduites polyphasiques. This article presents a selection of results obtained with the FHYD program. This software allows simulation of mixtures composed of petroleum fluids and water, with determination of the nature of thermodynamically stable phases (oil-gas-water-hydrate under given conditions of temperature and pressure, along with the quantity, composition and properties of these different phases. Additionally, the program can automatically produce phase diagrams. Several examples of these have been included here, ranging from binary systems (water-ethane and ternary systems (water-methane-propane to the most complex petroleum fluids. The presence of dissolved salts
Numerical modeling of two-phase binary fluid mixing using mixed finite elements
Sun, Shuyu
2012-07-27
Diffusion coefficients of dense gases in liquids can be measured by considering two-phase binary nonequilibrium fluid mixing in a closed cell with a fixed volume. This process is based on convection and diffusion in each phase. Numerical simulation of the mixing often requires accurate algorithms. In this paper, we design two efficient numerical methods for simulating the mixing of two-phase binary fluids in one-dimensional, highly permeable media. Mathematical model for isothermal compositional two-phase flow in porous media is established based on Darcy\\'s law, material balance, local thermodynamic equilibrium for the phases, and diffusion across the phases. The time-lag and operator-splitting techniques are used to decompose each convection-diffusion equation into two steps: diffusion step and convection step. The Mixed finite element (MFE) method is used for diffusion equation because it can achieve a high-order and stable approximation of both the scalar variable and the diffusive fluxes across grid-cell interfaces. We employ the characteristic finite element method with moving mesh to track the liquid-gas interface. Based on the above schemes, we propose two methods: single-domain and two-domain methods. The main difference between two methods is that the two-domain method utilizes the assumption of sharp interface between two fluid phases, while the single-domain method allows fractional saturation level. Two-domain method treats the gas domain and the liquid domain separately. Because liquid-gas interface moves with time, the two-domain method needs work with a moving mesh. On the other hand, the single-domain method allows the use of a fixed mesh. We derive the formulas to compute the diffusive flux for MFE in both methods. The single-domain method is extended to multiple dimensions. Numerical results indicate that both methods can accurately describe the evolution of the pressure and liquid level. © 2012 Springer Science+Business Media B.V.
Simulation of horizontal pipe two-phase slug flows using the two-fluid model
Energy Technology Data Exchange (ETDEWEB)
Ortega Malca, Arturo J. [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Mecanica. Nucleo de Simulacao Termohidraulica de Dutos (SIMDUT); Nieckele, Angela O. [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Mecanica
2005-07-01
Slug flow occurs in many engineering applications, mainly in the transport of hydrocarbon fluids in pipelines. The intermittency of slug flow causes severe unsteady loading on the pipelines carrying the fluids, which gives rise to design problems. Therefore, it is important to be able to predict the onset and development of slug flow as well as slug characteristics. The present work consists in the simulation of two-phase flow in slug pattern through horizontal pipes using the two-fluid model in its transient and one-dimensional form. The advantage of this model is that the flow field is allowed to develop naturally from a given initial conditions as part of the transient calculation; the slug evolves automatically as a product of the computed flow development. Simulations are then carried out for a large number of flow conditions that lead a slug flow. (author)
Computational fluid dynamics simulations of blood flow regularized by 3D phase contrast MRI
DEFF Research Database (Denmark)
Rispoli, Vinicius C; Nielsen, Jon; Nayak, Krishna S
2015-01-01
approach in regularizing 3D flow fields is evaluated. METHODS: The proposed algorithm incorporates both a Newtonian fluid physics model and a linear PC-MRI signal model. The model equations are solved numerically using a modified CFD algorithm. The numerical solution corresponds to the optimal solution......BACKGROUND: Phase contrast magnetic resonance imaging (PC-MRI) is used clinically for quantitative assessment of cardiovascular flow and function, as it is capable of providing directly-measured 3D velocity maps. Alternatively, vascular flow can be estimated from model-based computation fluid...... dynamics (CFD) calculations. CFD provides arbitrarily high resolution, but its accuracy hinges on model assumptions, while velocity fields measured with PC-MRI generally do not satisfy the equations of fluid dynamics, provide limited resolution, and suffer from partial volume effects. The purpose...
Comparative study of Nusselt number for a single phase fluid flow using plate heat exchanger
Directory of Open Access Journals (Sweden)
Shanmugam Rajasekaran
2016-01-01
Full Text Available In this study, the plate heat exchangers are used for various applications in the industries for heat exchange process such as heating, cooling and condensation. The performance of plate heat exchanger depends on many factors such as flow arrangements, plate design, chevron angle, enlargement factor, type of fluid used, etc. The various Nusselt number correlations are developed by considering that the water as a working fluid. The main objective of the present work is to design the experimental set-up for a single phase fluid flow using plate heat exchanger and studied the heat transfer performance. The experiments are carried out for various Reynolds number between 500 and 2200, the heat transfer coefficients are estimated. Based on the experimental results the new correlation is developed for Nusselt number and compared with an existing correlation.
Suppression of turbulent energy cascade due to phase separation in homogenous binary mixture fluid
Takagi, Youhei; Okamoto, Sachiya
2015-11-01
When a multi-component fluid mixture becomes themophysically unstable state by quenching from well-melting condition, phase separation due to spinodal decomposition occurs, and a self-organized structure is formed. During phase separation, free energy is consumed for the structure formation. In our previous report, the phase separation in homogenous turbulence was numerically simulated and the coarsening process of phase separation was discussed. In this study, we extended our numerical model to a high Schmidt number fluid corresponding to actual polymer solution. The governing equations were continuity, Navier-Stokes, and Chan-Hiliard equations as same as our previous report. The flow filed was an isotropic homogenous turbulence, and the dimensionless parameters in the Chan-Hilliard equation were estimated based on the thermophysical condition of binary mixture. From the numerical results, it was found that turbulent energy cascade was drastically suppressed in the inertial subrange by phase separation for the high Schmidt number flow. By using the identification of turbulent and phase separation structure, we discussed the relation between total energy balance and the structures formation processes. This study is financially supported by the Grand-in-Aid for Young Scientists (B) (No. T26820045) from the Ministry of Education, Cul-ture, Sports, Science and Technology of Japan.
DEFF Research Database (Denmark)
Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri
2014-01-01
Accurate multi-phase flow solvers at low Reynolds number are of particular interest for the simulation of interface instabilities in the co-processing of multilayered material. We present a two-phase flow solver for incompressible viscous fluids which uses the streamfunction as the primary variab...
Directory of Open Access Journals (Sweden)
M.Premkumar
2013-03-01
Full Text Available Heat transfer plays an important role in the enhancement of thermal energy storage in phase change material (PCM. The effective utilization of solar thermal energy can be obtained by proper storage of that energy. There are various techniques for the enhancement solar thermal storage in phase change material such as introductionof wire brushes, honey comb structure, fins and packed bed storage. In this study the analysis of heat transfer between PCM and heat transfer fluids (HTF with Spherical and cylindrical finned encapsulations made of copper are done using computational fluid dynamic (CFD analysis software GAMBIT and Fluent 6.2. The analysis is done in two modes as charging and discharging. During the charging mode the input is given in terms of temperature to the heat transfer fluid and the amount of heat transfer inside the PCM encapsulation is taken as output. During the discharging process the output temperature in the PCM is given as input and the amount of heat transferred to the heat transfer fluid is noted. The results from CFD analysis conclude that the heat transfer is more in finned encapsulations than that of without finned encapsulations and the copper sphere with fins is considered to be the best out of all other encapsulations.
Simulation of non-equilibrium two-phase flow in single component fluid systems
Energy Technology Data Exchange (ETDEWEB)
Hoyer, Norbert [Scandpower A/S, Kjeller (Norway)
1996-12-31
Traditionally, two-phase flow has been modelled by separate correlations for void fraction, pressure drop and flow regimes. A more unified approach, which treats flow regimes as an integral part of the two-fluid model is described in this work. A general, transient simulator for steam-water/inert gas systems has been developed. MONA is based on a full two-fluid, three field, nonequilibrium, nonhomogeneous two-phase flow model. It includes further an extensive heat and mass transfer package. The major contribution for MONA validation comes from the FRIGG loop experiments, covering a wide range of parameters like geometry, flow, subcooling, pressure and heat flux. Both validation against steady state and dynamic experiments has been carried out, the former comprising void fractions, pressure drops as well as natural and forced circulation flow rates while the latter consists of boiling instability analysis. 69 refs., 41 figs., 5 tabs.
Zhitova, L.; Borisenko, A.; Morgunov, K.; Zhukova, I.
2007-12-01
Fluid inclusions in quartz of the Merensky Reef (Bushveld Complex, South Africa) and the Chineisky Pluton (Transbaikal Region, Russia) were studied using cryometry, microthermometry, Raman-spectroscopy, LA ICP- MS, scanning electronic microscopy, gas-chromatography and isotopic methods. This allowed us to document some examples of fluid phase separation resulting in formation of different types of PGE-sulfide mineralization for layered basic intrusions. The results obtained show at least three generations of fluid separated from boiling residual alumosilicate intercumulus liquid of the Merensky Reef. The earliest fluid phase composed of homogenous high-dense methane and nitrogen gas mixture was identified in primary gas and co-existing anomalous fluid inclusions from symplectitic quartz. The next generation, heterophase fluid, composed of brines containing a free low-dense (mostly of carbon dioxide) gas phase, was observed in primary multiphase and coexisting gas-rich inclusions of miarolitic quartz crystals. The latest generation was also a heterophase fluid (low salinity water-salt solution and free low-dense methane gas phase) found in primary water-salt and syngenetic gas inclusions from peripheral zones of miarolitic quartz crystals. For the Chineisky Pluton reduced endocontact magmatogene fluids changed to oxidized low salinity hydrothermal fluids in exocontact zone. This resulted in formation of sulfide-PGE enrichment marginal zones of intrusion. The results obtained give us a possibility to suggest that: 1) Fluid phase separation is a typical feature of magmatogene fluids for layered basic intrusions. 2) Reduced fluids can extract and transport substantial PGE and sulfide concentrations. 3) Oxidation of reduced fluids is one of the most important geochemical barriers causing abundant PGE minerals and sulfides precipitation. This in turn results in both formation of PGE reefs or enriched contact zones of layered basic intrusions. This work was supported by
Predicting the Fluid Phase Behaviour of Aqueous Solutions of ELP (VPGVG) Sequences Using SAFT-VR.
Zhao, Binwu; Lindeboom, Tom; Benner, Steven W; Jackson, George; Galindo, Amparo; Hall, Carol K
2017-08-08
The statistical associating fluid theory for potentials of variable range (SAFT-VR) is used in this paper to predict the fluid phase behaviour of elastin-like polypeptides (ELPs) sequences in aqueous solution.with special focus on the loci of lower critical solution temperature (LCST) points. A SAFT-VR model for these solutions is obtained following a coarse-graining approach combining information from atomistic simulations and from previous SAFT models for relevant systems available in the literature. Constant-pressure temperature-composition phase diagrams for (VPGVG)n sequences + water are calculated for n =1 to 300. The SAFT-VR equation of state lends itself to the easy calculation of phase boundaries, so that complete fluid-phase diagrams can be calculated efficiently. A broad range of thermodynamic conditions of temperature and pressure are considered, and regions of vapour-liquid and liquid-liquid coexistence, including LCSTs are found. The calculated phase boundaries at low concentrations match those measured in experiments. The temperature-composition phase diagrams of the ELP + water systems at low pressure (0.1 MPa) are similar to those of types V and VI phase behaviour in the classification of Scott and van Konynenburg. Study of the high-pressure phase behaviour confirms however that a closed-loop liquid-liquid immiscibility region, separate from the gas-liquid envelope, is present for the (VPGVG)30-water system; such a phase diagram is typical of type VI phase behavior. ELPs with shorter lengths exhibit both liquid-liquid and gas-liquid regions, both of which shrink as the chain length of ELPs decrease. The strength of the hydrogen-bonding interaction is also found to affect the phase diagram of (VPGVG)30-water system in that the liquid-liquid and gas-liquid region expand as the H-bonding strength decreases and shrink as the H-bonding strength increases. The LCSTs of the mixtures are seen to decrease as the ELP chain length increases.
Equation-of-State Modeling of Phase Equilibria in Petroleum Fluids
DEFF Research Database (Denmark)
Jørgensen, Marianne
1996-01-01
The Soave-Redlich-Kwong (SRK) equation of state was used to investigate and develop several aspects of the modeling of natural petroleum fluids.A new method was presented for numerical evaluation of PVT experiments. This method was used in the estimation of binary interaction parameters. A comphr...... that exists for mixtures of CO2 and crude oils. Good results are obtained, and a tuning procedure is proposed for improved representation of the three phase equilibria....
US-UK Phase 3 Task 1 Oxidation in Supercritical Fluids
Energy Technology Data Exchange (ETDEWEB)
Holcomb, Gordon R. [National Energy Technology Lab. (NETL), Albany, OR (United States)
2017-03-20
A presentation of the US-UK Phase 3 Task 1 Oxidation in Supercritical Fluids. Includes slides on Supercritical Steam, sCO_{2} Power Cycles – Indirect, sCO_{2} Power Cycles – Direct, Experimental Exposures, Alloys, Why Si, Results—Ni-xCr Alloys (5-24Cr), Fatigue Crack Growth$-$Experiment, and Alloys and Samples, Fatigue Crack Growth—Results (H282).
Kiefer, Johannes
2010-06-01
A novel Raman spectroscopy setup for the investigation of multiphase fluid mixtures is proposed. The total output of a frequency-doubled Nd:YAG laser is separated into a strong 532 nm beam for generating Raman signals in the vapor phase and the weak residual of the fundamental 1064 nm radiation to be utilized as laser source for Raman scattering in the liquid phase. This approach will provide sufficient signal intensity from the gas (despite low density) for determination of mixture composition and at the same time it facilitates recording high-resolution spectra from the liquid in order to allow studying molecular physics phenomena together with concentration measurements.
Substellar fragmentation in self-gravitating fluids with a major phase transition
Füglistaler, A.; Pfenniger, D.
2015-06-01
Context. The observation of various ices in cold molecular clouds, the existence of ubiquitous substellar, cold H2 globules in planetary nebulae and supernova remnants, or the mere existence of comets suggest that the physics of very cold interstellar gas might be much richer than usually envisioned. At the extreme of low temperatures (≲10 K), H2 itself is subject to a phase transition crossing the entire cosmic gas density scale. Aims: This well-known, laboratory-based fact motivates us to study the ideal case of a cold neutral gaseous medium in interstellar conditions for which the bulk of the mass, instead of trace elements, is subject to a gas-liquid or gas-solid phase transition. Methods: On the one hand, the equilibrium of general non-ideal fluids is studied using the virial theorem and linear stability analysis. On the other hand, the non-linear dynamics is studied using computer simulations to characterize the expected formation of solid bodies analogous to comets. The simulations are run with a state-of-the-art molecular dynamics code (LAMMPS) using the Lennard-Jones inter-molecular potential. The long-range gravitational forces can be taken into account together with short-range molecular forces with finite limited computational resources, using super-molecules, provided the right scaling is followed. Results: The concept of super-molecule, where the phase transition conditions are preserved by the proper choice of the particle parameters, is tested with computer simulations, allowing us to correctly satisfy the Jeans instability criterion for one-phase fluids. The simulations show that fluids presenting a phase transition are gravitationally unstable as well, independent of the strength of the gravitational potential, producing two distinct kinds of substellar bodies, those dominated by gravity (planetoids) and those dominated by molecular attractive force (comets). Conclusions: Observations, formal analysis, and computer simulations suggest the
Thermal Marangoni Convection of Two-phase Dusty Fluid Flow along a Vertical Wavy Surface
Directory of Open Access Journals (Sweden)
S. Siddiqa
2017-01-01
Full Text Available The paper considers the influence of thermal Marangoni convection on boundary layer flow of two-phase dusty fluid along a vertical wavy surface. The dimensionless boundary layer equations for two-phase problem are reduced to a convenient form by primitive variable transformations (PVF and then integrated numerically by employing the implicit finite difference method along with the Thomas Algorithm. The effect of thermal Marangoni convection, dusty water and sinusoidal waveform are discussed in detail in terms of local heat transfer rate, skin friction coefficient, velocity and temperature distributions. This investigation reveals the fact that the water-particle mixture reduces the rate of heat transfer, significantly.
Freund, Friedemann
1991-01-01
Substantial progress has been made towards a better understanding of the dissolution of common gas/fluid phase components, notably H2O and CO2, in minerals. It has been shown that the dissolution mechanisms are significantly more complex than currently believed. By judiciously combining various solid state analytical techniques, convincing evidence was obtained that traces of dissolved gas/fluid phase components undergo, at least in part, a redox conversion by which they split into reduced H2 and and reduced C on one hand and oxidized oxygen, O(-), on the other. Analysis for 2 and C as well as for any organic molecules which may form during the process of co-segregation are still impeded by the omnipresent danger of extraneous contamination. However, the presence of O(-), an unusual oxidized form of oxygen, has been proven beyond a reasonable doubt. The presence of O(-) testifies to the fact that a redox reaction must have taken place in the solid state involving the dissolved traces of gas/fluid phase components. Detailed information on the techniques used and the results obtained are given.
Murakami, Jillian N; Thurbide, Kevin B
2015-05-01
The coating properties of a novel water stationary phase used in capillary supercritical fluid chromatography were investigated. The findings confirm that increasing the length or internal diameter of the type 316 stainless-steel column used provides a linear increase in the volume of stationary phase present. Under normal operating conditions, results indicate that about 4.9 ± 0.5 μL/m of water phase is deposited uniformly inside of a typical 250 μm internal diameter 316 stainless-steel column, which translates to an area coverage of about 6.3 ± 0.5 nL/mm(2) regardless of dimension. Efforts to increase the stationary phase volume present showed that etching the stainless-steel capillary wall using hydrofluoric acid was very effective for this. For instance, after five etching cycles, this volume doubled inside of both the type 304 and the type 316 stainless-steel columns examined. This in turn doubled analyte retention, while maintaining good peak shape and column efficiency. Overall, 316 stainless-steel columns were more resistant to etching than 304 stainless-steel columns. Results indicate that this approach could be useful to employ as a means of controlling the volume of water stationary phase that can be established inside of the stainless-steel columns used with this supercritical fluid chromatography technique.
DEFF Research Database (Denmark)
Karakatsani, Eirini; Kontogeorgis, Georgios; Economou, Ioannis
2006-01-01
Perturbed chain-statistical associating fluid theory (PC-SAFT) was extended rigorously to polar fluids based on the theory of Stell and co-workers [Mol. Phys. 1977, 33, 987]. The new PC-PSAFT was simplified to truncated PC-PSAFT (tPC-PSAFT) so that it can be practical for real polar fluid thermod...
Institute of Scientific and Technical Information of China (English)
FU Dong; YAN Shu-Mei; WANG Xue-Min
2008-01-01
The excess Helmholtz free energy functional for four-site associating Lennard-Jones(LJ)fluid was formulated in terms of a modified fundamental measure theory for short-ranged interactions and a first-order mean-spherical approximation theory for long-ranged attraction.Within the framework of density functional theory,the thermodynamic properties including the average density isotherms,density profiles and fractions of not bonded monomers characterizing the coexistences between gas-like and liquid-like phases for capillary condensation,phase equilibria and equilibrium plate-fluid interfacial tensions were investigated.The influences of association energy,fluid-solid interaction and pore width on the inhomogeneous behavior of four-site associating LJ fluids confined in slit pores were discussed.
General model of phospholipid bilayers in fluid phase within the single chain mean field theory
Energy Technology Data Exchange (ETDEWEB)
Guo, Yachong; Baulin, Vladimir A. [Departament d’Enginyeria Química, Universitat Rovira i Virgili, Av. dels Paisos Catalans 26, 43007 Tarragona (Spain); Pogodin, Sergey [Institute of Chemical Research of Catalonia, ICIQ, Av. Paisos Catalans 16, 43007 Tarragona (Spain)
2014-05-07
Coarse-grained model for saturated phospholipids: 1,2-didecanoyl-sn-glycero-3-phosphocholine (DCPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and unsaturated phospholipids: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2- dioleoyl-sn-glycero-3-phosphocholine (DOPC) is introduced within the single chain mean field theory. A single set of parameters adjusted for DMPC bilayers gives an adequate description of equilibrium and mechanical properties of a range of saturated lipid molecules that differ only in length of their hydrophobic tails and unsaturated (POPC, DOPC) phospholipids which have double bonds in the tails. A double bond is modeled with a fixed angle of 120°, while the rest of the parameters are kept the same as saturated lipids. The thickness of the bilayer and its hydrophobic core, the compressibility, and the equilibrium area per lipid correspond to experimentally measured values for each lipid, changing linearly with the length of the tail. The model for unsaturated phospholipids also fetches main thermodynamical properties of the bilayers. This model is used for an accurate estimation of the free energies of the compressed or stretched bilayers in stacks or multilayers and gives reasonable estimates for free energies. The proposed model may further be used for studies of mixtures of lipids, small molecule inclusions, interactions of bilayers with embedded proteins.
Phase-field model for the Rayleigh--Taylor instability of immiscible fluids
Celani, Antonio; Muratore-Ginanneschi, Paolo; Vozella, Lara
2008-01-01
The Rayleigh--Taylor instability of two immiscible fluids in the limit of small Atwood numbers is studied by means of a phase-field description. In this method the sharp fluid interface is replaced by a thin, yet finite, transition layer where the interfacial forces vary smoothly. This is achieved by introducing an order parameter (the phase field) whose variation is continuous across the interfacial layers and is uniform in the bulk region. The phase field model obeys a Cahn--Hilliard equation and is two-way coupled to the standard Navier--Stokes equations. Starting from this system of equations we have first performed a linear analysis from which we have analytically rederived the known gravity-capillary dispersion relation in the limit of vanishing mixing energy density and capillary width. We have performed numerical simulations and identified a region of parameters in which the known properties of the linear phase (both stable and unstable) are reproduced in a very accurate way. This has been done both i...
Molecular modeling the microstructure and phase behavior of bulk and inhomogeneous complex fluids
Bymaster, Adam
Accurate prediction of the thermodynamics and microstructure of complex fluids is contingent upon a model's ability to capture the molecular architecture and the specific intermolecular and intramolecular interactions that govern fluid behavior. This dissertation makes key contributions to improving the understanding and molecular modeling of complex bulk and inhomogeneous fluids, with an emphasis on associating and macromolecular molecules (water, hydrocarbons, polymers, surfactants, and colloids). Such developments apply broadly to fields ranging from biology and medicine, to high performance soft materials and energy. In the bulk, the perturbed-chain statistical associating fluid theory (PC-SAFT), an equation of state based on Wertheim's thermodynamic perturbation theory (TPT1), is extended to include a crossover correction that significantly improves the predicted phase behavior in the critical region. In addition, PC-SAFT is used to investigate the vapor-liquid equilibrium of sour gas mixtures, to improve the understanding of mercaptan/sulfide removal via gas treating. For inhomogeneous fluids, a density functional theory (DFT) based on TPT1 is extended to problems that exhibit radially symmetric inhomogeneities. First, the influence of model solutes on the structure and interfacial properties of water are investigated. The DFT successfully describes the hydrophobic phenomena on microscopic and macroscopic length scales, capturing structural changes as a function of solute size and temperature. The DFT is used to investigate the structure and effective forces in nonadsorbing polymer-colloid mixtures. A comprehensive study is conducted characterizing the role of polymer concentration and particle/polymer size ratio on the structure, polymer induced depletion forces, and tendency towards colloidal aggregation. The inhomogeneous form of the association functional is used, for the first time, to extend the DFT to associating polymer systems, applicable to any
Phase-space analysis of the cosmological 3-fluid problem: Families of attractors and repellers
Azreg-Aïnou, Mustapha
2013-01-01
We perform a phase-space analysis of the cosmological 3-fluid problem consisting of a barotropic fluid with an equation-of-state parameter $\\gamma-1$, a pressureless dark matter fluid, plus a scalar field $\\phi$ (representing dark energy) coupled to exponential potential $V=V_0\\exp{(-\\kappa\\lambda\\phi)}$. Besides the potential-kinetic-scaling solutions, which are not the unique late-time attractors whenever they exist for $\\lambda^2\\geq 3\\ga$, we derive new attractors where both dark energy and dark matter coexist and the final density is shared in a way independent of the value of $\\ga >1$. The case of a pressureless barotropic fluid ($\\ga=1$) has a one-parameter family of attractors where all components coexist. New one-parameter families of matter-dark matter saddle points and kinetic-matter repellers exist. We investigate the stability of the ten critical points by linearization and/or Lyapunov's Theorems and a variant of the theorems formulated in this paper.
Institute of Scientific and Technical Information of China (English)
Guo-Qing Jiang; Ping Chen; Dou-Sheng Bai; Jing-Wang Tan; Hao Su; Min-Hao Peng
2012-01-01
AIM:To investigate the correlation between peri-operative fluid therapy and early-phase recovery after liver transplantation (LT) by retrospectively reviewing 102 consecutive recipients.METHODS:Based on whether or not the patients had pulmonary complications,the patients were categorized into non-pulmonary and pulmonary groups.Twentyeight peri-operative variables were analyzed in both groups to screen for the factors related to the occurrence of early pulmonary complications.RESULTS:The starting hemoglobin (Hb) value,an intra-operative transfusion ＞ 100 mL/kg,and a fluid balance ≤-14 mL/kg on the first day and the second or third day post-operatively were significant factors for early pulmonary complications.The extubation time,time to initial passage of flatus,or intensive care unit length of stay were significantly prolonged in patients who had not received an intra-operative transfusion ≤100 mL/kg or a fluid balance ≤-14 mL/kg on the first day and the second or the third day post-operatively.Moreover,these patients had poorer results in arterial blood gas analysis.CONCLUSION:It is important to offer a precise and individualized fluid therapy during the peri-operative period to the patients undergoing LT for cirrhosis-associated hepatocellular carcinoma.
Receptor-Mediated and Fluid-Phase Transcytosis of Horseradish Peroxidase across Rat Hepatocytes
Directory of Open Access Journals (Sweden)
Isabella Ellinger
2010-01-01
Full Text Available Horseradish peroxidase (HRP is often used as a fluid-phase marker to characterize endocytic and transcytotic processes. Likewise, it has been applied to investigate the mechanisms of biliary secretion of fluid in rat liver hepatocytes. However, HRP contains mannose residues and thus binds to mannose receptors (MRs on liver cells, including hepatocytes. To study the role of MR-mediated endocytosis of HRP transport in hepatocytes, we determined the influence of the oligosaccharid mannan on HRP biliary secretion in the isolated perfused rat liver. A 1-minute pulse of HRP was applied followed by marker-free perfusion. HRP appeared in bile with biphasic kinetics: a first peak at 7 minutes and a second peak at 15 minutes after labeling. Perfusion with 0.8 mg/mL HRP in the presence of a twofold excess of mannan reduced the first peak by 41% without effect on the second one. Together with recently published data on MR expression in rat hepatocytes this demonstrates two different mechanisms for HRP transcytosis: a rapid, receptor-mediated transport and a slower fluid-phase transport.
Microtomography and pore-scale modeling of two-phase Fluid Distribution
Energy Technology Data Exchange (ETDEWEB)
Silin, D.; Tomutsa, L.; Benson, S.; Patzek, T.
2010-10-19
Synchrotron-based X-ray microtomography (micro CT) at the Advanced Light Source (ALS) line 8.3.2 at the Lawrence Berkeley National Laboratory produces three-dimensional micron-scale-resolution digital images of the pore space of the reservoir rock along with the spacial distribution of the fluids. Pore-scale visualization of carbon dioxide flooding experiments performed at a reservoir pressure demonstrates that the injected gas fills some pores and pore clusters, and entirely bypasses the others. Using 3D digital images of the pore space as input data, the method of maximal inscribed spheres (MIS) predicts two-phase fluid distribution in capillary equilibrium. Verification against the tomography images shows a good agreement between the computed fluid distribution in the pores and the experimental data. The model-predicted capillary pressure curves and tomography-based porosimetry distributions compared favorably with the mercury injection data. Thus, micro CT in combination with modeling based on the MIS is a viable approach to study the pore-scale mechanisms of CO{sub 2} injection into an aquifer, as well as more general multi-phase flows.
Evidence of a Pre-eruptive Fluid Phase for the Millennium Eruption, Paektu Volcano, North Korea
Iacovino, K.; Sisson, T. W.; Lowenstern, J. B.
2014-12-01
We present initial results of a study of comenditic to trachytic melt inclusions from the Millennium Eruption (ME) of Paektu volcano (AD 946; VEI≥7; 25 km3 DRE). Paektu volcano (aka Changbaishan) is a remote and poorly studied intraplate stratovolcano whose 37 km2 caldera is bisected by the political border between North Korea and China, limiting studies of its proximal deposits. ME magmas are predominantly phenocryst-poor (≤3 vol%) comendites plus a volumetrically minor late-stage, more phenocryst-rich (10-20 vol%) trachyte. Sizeable (100-500 µm diameter) glassy but bubble-bearing melt inclusions are widespread in anorthoclase and hedenbergite phenocrysts, as well as in rarer quartz and fayalite phenocrysts. Comparing the relative enrichments of incompatible volatile and non-volatile elements in melt inclusions along a liquid line of descent shows decreasing volatile/Zr ratios suggesting the partitioning of volatiles into a fluid phase. This suggests that current gas-yield estimates (Horn & Schminke, 2000) for the ME, based on the petrologic method (difference in volatiles between melt inclusions and matrix glass), could be severe underestimates. Establishing the composition and quantity of a pre-eruptive fluid phase is the primary goal of this study and has implications for eruption triggering and for modeling the climatic effects of one of the largest eruptions in the last 10,000 years. Including results from Horne and Schminke (2000), melt inclusions from within a single pumice fall unit show a wide range in dissolved volatile contents and magma chemistries. Concentrations of H2O are moderate (2-3.5 wt% via FTIR), with Cl and F ranging from 500-4600 ppm and 1100-4700 ppm (via EPMA). CO2 is below the detection limit of 2 ppm (FTIR with N2 purge) in bubble-bearing melt inclusions, but is detectable (≤56 ppm) in melt inclusions homogenized at 100 MPa and 850-900 °C for ~30 min (conditions also leading to reduction of dissolved H2O to 0.6-2 wt
Solid-liquid phase equilibria of the Gaussian core model fluid.
Mausbach, Peter; Ahmed, Alauddin; Sadus, Richard J
2009-11-14
The solid-liquid phase equilibria of the Gaussian core model are determined using the GWTS [J. Ge, G.-W. Wu, B. D. Todd, and R. J. Sadus, J. Chem. Phys. 119, 11017 (2003)] algorithm, which combines equilibrium and nonequilibrium molecular dynamics simulations. This is the first reported use of the GWTS algorithm for a fluid system displaying a reentrant melting scenario. Using the GWTS algorithm, the phase envelope of the Gaussian core model can be calculated more precisely than previously possible. The results for the low-density and the high-density (reentrant melting) sides of the solid state are in good agreement with those obtained by Monte Carlo simulations in conjunction with calculations of the solid free energies. The common point on the Gaussian core envelope, where equal-density solid and liquid phases are in coexistence, could be determined with high precision.
Phase mixing induced by granular fluid pump during mantle strain localization
Précigout, Jacques; Prigent, Cécile; Palasse, Laurie; Pochon, Anthony
2014-05-01
Mantle viscous strain localization is often attributed to feedbacks between grain boundary sliding (GBS) and phase mixing, as GBS could promote mixing through grain switching, and phase mixing would enhance grain-size-sensitive granular flow through grain boundary pinning. However, although GBS and phase mixing are intimately related, recent data show that GBS alone cannot end-up with randomly mixed phases. Here we show natural observations of an ultramylonitic shear zone from the Ronda peridotite (Spain) where both GBS and phase mixing occur. Microprobe analyses and coupled EDX/EBSD data first document enrichment in pyroxenes and amphibole concomitant with both phase mixing and complete randomization of the olivine fabric in fine-grained layers (5-20 microns) where strain has been localized. Both the fabric randomization and some microstructural observations indicate that these layers mostly deformed by granular flow, i.e., by GBS. Based on petrological pseudo-sections, we also show that phase enrichment does not result from metamorphic reaction, but instead from dissolution-precipitation phenomena. Finally, we document in adjacent areas a change of olivine fabric geometry that highlights syn-tectonic water draining towards fine-grained layers. While olivine fabric switches from E-type (moderately hydrated fabric) to C-type (highly hydrated fabric) towards fine-grained layers, it changes from E-type to D-type (highly hydrated fabric) in coarse-grained bands between E/C-type layers. Altogether, our findings suggest that water converges as a result of GBS-induced creep cavitation and subsequent granular fluid pump in fine-grained layers. We propose that phase mixing originates here from such a creep cavitation through dissolution-precipitation of secondary phases in newly formed cavities, giving rise to a key process for the relationships between GBS and phase mixing, and hence, for the origin of viscous strain localization in the upper mantle.
Comparison of twin-fluid atomizers using a phase Doppler analyser
Energy Technology Data Exchange (ETDEWEB)
Zaremba, Matouš, E-mail: y116215@stud.fme.vutbr.cz, E-mail: y145527@stud.fme.vutbr.cz, E-mail: jedelsky@fme.vutbr.cz, E-mail: jicha@fme.vutbr.cz; Malý, Milan, E-mail: y116215@stud.fme.vutbr.cz, E-mail: y145527@stud.fme.vutbr.cz, E-mail: jedelsky@fme.vutbr.cz, E-mail: jicha@fme.vutbr.cz; Jedelský, Jan, E-mail: y116215@stud.fme.vutbr.cz, E-mail: y145527@stud.fme.vutbr.cz, E-mail: jedelsky@fme.vutbr.cz, E-mail: jicha@fme.vutbr.cz; Jícha, Miroslav, E-mail: y116215@stud.fme.vutbr.cz, E-mail: y145527@stud.fme.vutbr.cz, E-mail: jedelsky@fme.vutbr.cz, E-mail: jicha@fme.vutbr.cz [Brno University of technology, Technická 2896/2, 616 69 Brno (Czech Republic)
2014-08-06
The quality of atomization is crucial in combustion processes, especially in cases of highly viscous fuels. Twin-fluid atomizers have been developed for atomizing heavy and waste fuels and they have undergone significant development in the last decades. Nevertheless, in order to design an atomizer for a given industrial application, a comparison of different atomizers at similar operating conditions is required. This paper focuses on the description and comparison of two internally mixed twin-fluid atomizers at the same operating regime. The Y-jet and the Inverse-effervescent atomizers were examined. The phase-Doppler analyzer was used to measure the velocity and size of droplets in a radial profile in the spray. Data were sorted out into classes with respect to the droplet size and the motion analysis was done for both atomizers.
Phase transitions, interfacial fluctuations and hidden symmetries for fluids near structured walls
Indian Academy of Sciences (India)
A O Parry; J M Romero-Enrique
2005-05-01
Fluids adsorbed at micro-patterned and geometrically structured substrates can exhibit novel phase transitions and interfacial fluctuation effects distinct from those characteristic of wetting at planar, homogeneous walls. We review recent theoretical progress in this area paying particular attention to filling transitions pertinent to fluid adsorption near wedges, which have highlighted a deep connection between geometrical and contact angles. We show that filling transitions are not only characterized by large scale interfacial fluctuations leading to universal critical singularities but also reveal hidden symmetries with short-ranged critical wetting transitions and properties of dimensional reduction. We propose a non-local interfacial model which fulfills all these properties and throws light on long-standing problems regarding the order of the 3D short-range critical wetting transition.
Study of Phase Equilibria of Petrochemical Fluids using Gibbs Ensemble Monte Carlo Methods
Nath, Shyamal
2001-03-01
Knowledge of phase behavior of hydrocarbons and related compounds are highly of interest to chemical and petrochemical industries. For example, design of processes such as supercritical fluid extraction, petroleum refining, enhanced oil recovery, gas treatment, and fractionation of wax products. A precise knowledge of the phase equilibria of alkanes, alkenes and related compounds and their mixtures are required for efficient design of these processes. Experimental studies to understand the related phase equilibria often become unsuitable for various reasons. With the advancement of simulation technology, molecular simulations could provide a useful complement and alternative in the study and description of phase behavior of these systems. In this work we study vapor-liquid phase equilibria of pure hydrocarbons and their mixtures using Gibbs ensemble simulation. Insertion of long and articulated chain molecules are facilitated in our simulations by means of configurational bias and expanded ensemble methods. We use the newly developed NERD force field in our simulation. In this work NERD force field is extended to provide coverage for hydrocarbons with any arbitrary architecture. Our simulation results provide excellent quantitative agreement with available experimental phase equilibria data for both the pure components and mixtures.
Kumar, Sanyog
Sorption-based methodologies are proposed and developed to study rock-fluid interactions and properties of the fluid-phase in organic-rich shale reservoirs. Lack of appropriate methods to study these attributes of shale reservoirs affects the efficiency and economy of the shale-based exploration and production (E&P) efforts. A macroscopic conception of fluids still guides most existing methods for studying rock-fluid interaction and fluid phase properties. However, the modified regime of surface forces in fluids confined within nanometer and sub-nanometer sized pores typical of shales render such a macroscopic treatment fundamentally inconsistent. Apart from these theoretical limitations, shales are operationally challenging for the existing methods for rock-fluid interaction studies, primarily due to their ultra-low permeability, compositional heterogeneity, and the presence of organic matter and swelling clay minerals. Therefore, I propose using sorption-based methods that are sensitive to the modified regime of the surface forces in nano- and sub-nano-pores to study rock-fluid interaction and fluid-phase properties in shales. The Nitrogen adsorption method that is commonly used to study pore-structures was improvised in this thesis. In addition to nitrogen, water and hexane vapors were used to study rock-fluid interactions in organic-rich shales, which helped in quantifying the surface areas of the hydrophilic and hydrophobic pores of shales. In another study, the role of hydrophilic and hydrophobic pores in supercritical CO2 sorption was further investigated by measuring supercritical CO2 sorption isotherms for illite clay and organic-rich shale samples in dry and in water-imbibed conditions. In a separate study, ultrasonic p-wave measurements during sorption experiments allowed a determination of the phase properties of fluids confined in the nano- and sub-nanometer sized pores. BET specific surface areas (SSA) determined from the isotherms of water and hexane
Phase transitions of two-dimensional dipolar fluids in external fields.
Schmidle, Heiko; Klapp, Sabine H L
2011-03-21
In this work, we study condensation phase transitions of two-dimensional Stockmayer fluids under additional external fields using Monte-Carlo (MC) simulations in the grand-canonical ensemble. We employ two recently developed methods to determine phase transitions in fluids, namely Wang-Landau (WL) MC simulations and successive-umbrella (SU) sampling. Considering first systems in zero field (and dipolar coupling strengths μ(2)∕εσ(3) ≤ 6), we demonstrate that the two techniques yield essentially consistent results but display pronounced differences in terms of efficiency. Indeed, comparing the computation times for these systems on a qualitative level, the SU sampling turns out to be significantly faster. In the presence of homogeneous external fields, however, the SU method becomes plagued by pronounced sampling difficulties, yielding the calculation of coexistence lines essentially impossible. Employing the WL scheme, on the other hand, we find phase coexistence even for strongly field-aligned systems. The corresponding critical temperatures are significantly shifted relative to the zero-field case.
Phase transitions of two-dimensional dipolar fluids in external fields
Schmidle, Heiko; Klapp, Sabine H. L.
2011-03-01
In this work, we study condensation phase transitions of two-dimensional Stockmayer fluids under additional external fields using Monte-Carlo (MC) simulations in the grand-canonical ensemble. We employ two recently developed methods to determine phase transitions in fluids, namely Wang-Landau (WL) MC simulations and successive-umbrella (SU) sampling. Considering first systems in zero field (and dipolar coupling strengths μ2/ɛσ3 ⩽ 6), we demonstrate that the two techniques yield essentially consistent results but display pronounced differences in terms of efficiency. Indeed, comparing the computation times for these systems on a qualitative level, the SU sampling turns out to be significantly faster. In the presence of homogeneous external fields, however, the SU method becomes plagued by pronounced sampling difficulties, yielding the calculation of coexistence lines essentially impossible. Employing the WL scheme, on the other hand, we find phase coexistence even for strongly field-aligned systems. The corresponding critical temperatures are significantly shifted relative to the zero-field case.
Simulation of plasma discharge in liquids: A detailed two-phase fluid approach
Charchi Aghdam, Ali; Farouk, Tanvir; Reacting Systems; Advanced Energy Research Laboratory Team
2015-09-01
Plasma discharge in liquids has gained great attention recently due to its applications in biomedical engineering, fuel processing, and water treatment and so on. Despite the tremendous interest, a comprehensive understanding of the underlying physics still remains limited. In the current work, an attempt is made to present a mathematical multi-physics model to describe the discharge of plasma in liquids. An in-house modeling platform is developed for simulating plasma formation in multiphase fluids. The model resolves a detailed two-phase fluid including viscous effects, surface tension, gravitational forces and electrical body force. All the governing equations are solved for gas and liquid phases. Electric field and charged species equations along with the plasma reaction kinetics are solved to get the charge distribution in the different phases as well as at the gas-liquid interface to obtain the electric body force acting at the interface. By coupling the above sub-models, a comprehensive multi-physics model for plasma discharge in liquids is constructed which is able to capture several physical aspects of the phenomena especially the role of the bubble, its motion and distortion on plasma characteristics.
Mryglod, I M; Omelyan, I P; Folk, R
2001-04-02
The magnetic phase transition in a Heisenberg fluid is studied by means of the finite size scaling technique. We find that even for larger systems, considered in an ensemble with fixed density, the critical exponents show deviations from the expected lattice values similar to those obtained previously. This puzzle is clarified by proving the importance of the leading correction to the scaling that appears due to Fisher renormalization with the critical exponent equal to the absolute value of the specific heat exponent alpha. The appearance of such new corretions to scaling is a general feature of systems with constraints.
Measurements of viscosity and permeability of two phase miscible fluid flow in rock cores.
Williams, J L; Taylor, D G
1994-01-01
This paper describes the application of 1H magnetic resonance imaging (MRI) to the measurement of fluid viscosity and rock core plug permeability during two phase miscible displacements in certain rock types. The core plug permeability was determined by monitoring glycerol solutions displacing D2O. Simple physical principles were used to calculate the core permeability from the measured displacement angle for a set of Lochaline sandstone core plugs. In a further experiment the viscosity of polyacrylamide solution 1500 ppm was determined in the core plug. The permeability and viscosity results compared well to conventional core analysis methods.
Energy Technology Data Exchange (ETDEWEB)
Singh, Raman Deep, E-mail: Takhter.Ramandeep@mayo.edu; Schroeder, Andreas S.; Scheffer, Luana; Holicky, Eileen L.; Wheatley, Christine L.; Marks, David L., E-mail: Marks.david@mayo.edu; Pagano, Richard E.
2013-05-10
Highlights: •Prominin-2 expression induced protrusions that co-localized with lipid raft markers. •Prominin-2 expression decreased caveolae, caveolar endocytosis and increased pCav1. •Prominin-2 expression inhibited fluid phase endocytosis by inactivation of Cdc42. •These endocytic effects can be reversed by adding exogenous cholesterol. •Caveolin1 knockdown restored fluid phase endocytosis in Prominin2 expressing cells. -- Abstract: Background: Membrane protrusions play important roles in biological processes such as cell adhesion, wound healing, migration, and sensing of the external environment. Cell protrusions are a subtype of membrane microdomains composed of cholesterol and sphingolipids, and can be disrupted by cholesterol depletion. Prominins are pentaspan membrane proteins that bind cholesterol and localize to plasma membrane (PM) protrusions. Prominin-1 is of great interest as a marker for stem and cancer cells, while Prominin-2 (Prom2) is reportedly restricted to epithelial cells. Aim: To characterize the effects of Prom-2 expression on PM microdomain organization. Methods: Prom2-fluorescent protein was transfected in human skin fibroblasts (HSF) and Chinese hamster ovary (CHO) cells for PM raft and endocytic studies. Caveolae at PM were visualized using transmission electron microscopy. Cdc42 activation was measured and caveolin-1 knockdown was performed using siRNAs. Results: Prom2 expression in HSF and CHO cells caused extensive Prom2-positive protrusions that co-localized with lipid raft markers. Prom2 expression significantly decreased caveolae at the PM, reduced caveolar endocytosis and increased caveolin-1 phosphorylation. Prom2 expression also inhibited Cdc42-dependent fluid phase endocytosis via decreased Cdc42 activation. Effects on endocytosis were reversed by addition of cholesterol. Knockdown of caveolin-1 by siRNA restored Cdc42 dependent fluid phase endocytosis in Prom2-expressing cells. Conclusions: Prom2 protrusions primarily
Energy Technology Data Exchange (ETDEWEB)
Aksenova, A.E.; Chudanov, V.V.; Strizhov, V.F.; Vabishchevich, P.N. [Institute of Nuclear Safety Russian Academy Science, Moscow (Russian Federation)
1995-09-01
Unsteady natural convection of a heat-generating fluid with phase transitions in the enclosures of a square section with isothermal rigid walls is investigated numerically for a wide range of dimensionless parameters. The quasisteady state solutions of conjugate heat and mass transfer problem are compared with available experimental results. Correlation relations for heat flux distributions at the domain boundaries depending on Rayleigh and Ostrogradskii numbers are obtained. It is shown that generally heat transfer is governed both by natural circulation and crust formation phenomena. Results of this paper may be used for analysis of experiments with prototypic core materials.
Improving cooling devices for the hot face of Peltier pellets based on phase change fluids
Energy Technology Data Exchange (ETDEWEB)
Esarte, J. [Centros Tecnologicos de Navarra, Poligono Industrial Noain, 31009 Navarra (Spain); Blanco, J.M.; Mendia, F. [Depto. Maquinas y Motores Termicos, Universidad del Pais Vasco/EHU, Alameda de Urquijo s/n, 48013 Bilbao (Spain); Pena, F. [Iberdrola Generacion, Bahia de Santurce, 48009 Vizcaya (Spain)
2006-07-15
The thermoelectricity has not suffered any important progress for the last twenty years, owed mainly to the low efficiency of the heat sinks, because the Peltier pellet provides a high calorific power across a small surface. In this paper a deep study of the fin cooling for Peltier pellets, has been carried out, by means of both an experimental model and also through computational fluid dynamics. A phase change device called thermosyphon has also been designed and optimized, which allows to uniform the heat flow, decreasing in this way the pellet thermal resistance. The work focuses on its hot face and leaves for another study the cold face optimization. (author)
Ahyayauch, Hasna; Collado, M. Isabel; Alonso, Alicia; Goñi, Felix M.
2012-01-01
It has been repeatedly observed that lipid bilayers in the gel phase are solubilized by lower concentrations of Triton X-100, at least within certain temperature ranges, or other nonionic detergents than bilayers in the fluid phase. In a previous study, we showed that detergent partition coefficients into the lipid bilayer were the same for the gel and the fluid phases. In this contribution, turbidity, calorimetry, and 31P-NMR concur in showing that bilayers in the gel state (at least down to 13–20°C below the gel-fluid transition temperature) become saturated with detergent at lower detergent concentrations than those in the fluid state, irrespective of temperature. The different saturation may explain the observed differences in solubilization. PMID:22713566
A Well-Posed Two Phase Flow Model and its Numerical Solutions for Reactor Thermal-Fluids Analysis
Energy Technology Data Exchange (ETDEWEB)
Kadioglu, Samet Y. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Berry, Ray [Idaho National Lab. (INL), Idaho Falls, ID (United States); Martineau, Richard [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2016-08-01
A 7-equation two-phase flow model and its numerical implementation is presented for reactor thermal-fluids applications. The equation system is well-posed and treats both phases as compressible flows. The numerical discretization of the equation system is based on the finite element formalism. The numerical algorithm is implemented in the next generation RELAP-7 code (Idaho National Laboratory (INL)’s thermal-fluids code) built on top of an other INL’s product, the massively parallel multi-implicit multi-physics object oriented code environment (MOOSE). Some preliminary thermal-fluids computations are presented.
A parametric analysis of waves propagating in a porous solid saturated by a three-phase fluid.
Santos, Juan E; Savioli, Gabriela B
2015-11-01
This paper presents an analysis of a model for the propagation of waves in a poroelastic solid saturated by a three-phase viscous, compressible fluid. The constitutive relations and the equations of motion are stated first. Then a plane wave analysis determines the phase velocities and attenuation coefficients of the four compressional waves and one shear wave that propagate in this type of medium. A procedure to compute the elastic constants in the constitutive relations is defined next. Assuming the knowledge of the shear modulus of the dry matrix, the other elastic constants in the stress-strain relations are determined by employing ideal gedanken experiments generalizing those of Biot's theory for single-phase fluids. These experiments yield expressions for the elastic constants in terms of the properties of the individual solid and fluids phases. Finally the phase velocities and attenuation coefficients of all waves are computed for a sample of Berea sandstone saturated by oil, gas, and water.
Characterization of Phase Transition in Heisenberg Fluids from Density Functional Theory
Li, Liang-Sheng; Li, Li; Chen, Xiao-Song
2009-02-01
The phase transition of Heisenberg fluid has been investigated with the density functional theory in mean-field approximation (MF). The matrix of the second derivatives of the grand canonical potential Ω with respect to the particle density fluctuations and the magnetization fluctuations has been investigated and diagonalized. The smallest eigenvalue being 0 signalizes the phase instability and the related eigenvector characterizes this phase transition. We find a Curie line where the order parameter is pure magnetization and a spinodal where the order parameter is a mixture of particle density and magnetization. Along the spinodal, the character of phase instability changes continuously from predominant condensation to predominant ferromagnetic phase transition with the decrease of total density. The spinodal meets the Curie line at the critical endpoint with the reduced density ρ* = ρσ3 = 0.224 and the reduced temperature T* = kT/in = 1.87 (σ is the diameter of Heisenberg hard sphere and in is the coupling constant).
Characterization of Phase Transition in Heisenberg Fluids from Density Functional Theory
Institute of Scientific and Technical Information of China (English)
LI Liang-Sheng; LI Li; CHEN Xiao-Song
2009-01-01
The phase transition of Heisenberg fluid has been investigated with the density functional theory in mean-field approximation (MF).The matrix of the second derivatives of the grand canonical potential Ω with respect to the particle density fluctuations and the magnetization fluctuations has been investigated and diagonalized.The smallest eigenvalue being 0 signalizes the phase instability and the related eigenvector characterizes this phase transition.We find a Curie line where the order parameter is pure magnetization and a spinodM where the order parameter is a mixture of particle density and magnetization.Along the spinodal, the character of phase instability changes continuously from predominant condensation to predominant ferromagnetic phase transition with the decrease of total density.The spinodal meets the Curie line at the critical endpoint with the reduced density ρ*= ρσ3=0.224 and the reduced temperature T* = kT/ε = 1.87 (σ is the diameter of Heisenberg hard sphere and e is the coupling constant).
SECOND-ORDER MOMENT MODEL FOR DENSE TWO-PHASE TURBULENT FLOW OF BINGHAM FLUID WITH PARTICLES
Institute of Scientific and Technical Information of China (English)
ZENG Zhuo-xiong; ZHOU Li-xing; LIU Zhi-he
2006-01-01
The USM-θ model of Bingham fluid for dense two-phase turbulent flow was developed, which combines the second-order moment model for two-phase turbulence with the particle kinetic theory for the inter-particle collision. In this model, phases interaction and the extra term of Bingharn fluid yield stress are taken into account. An algorithm for USM-θ model in dense two-phase flow was proposed, in which the influence of particle volume fraction is accounted for. This model was used to simulate turbulent flow of Bingham fluid single-phase and dense liquid-particle two-phase in pipe. It is shown USM-θ model has better prediction result than the five-equation model, in which the particle-particle collision is modeled by the particle kinetic theory, while the turbulence of both phase is simulated by the two-equation turbulence model. The USM-θ model was then used to simulate the dense two-phase turbulent up flow of Bingham fluid with particles. With the increasing of the yield stress, the velocities of Bingham and particle decrease near the pipe centre. Comparing the two-phase flow of Bingham-particle with that of liquid-particle, it is found the source term of yield stress has significant effect on flow.
Liquid phase fluid dynamic (methanol) run in the LaPorte alternative fuels development unit
Energy Technology Data Exchange (ETDEWEB)
Bharat L. Bhatt
1997-05-01
A fluid dynamic study was successfully completed in a bubble column at DOE's Alternative Fuels Development Unit (AFDU) in LaPorte, Texas. Significant fluid dynamic information was gathered at pilot scale during three weeks of Liquid Phase Methanol (LPMEOJP) operations in June 1995. In addition to the usual nuclear density and temperature measurements, unique differential pressure data were collected using Sandia's high-speed data acquisition system to gain insight on flow regime characteristics and bubble size distribution. Statistical analysis of the fluctuations in the pressure data suggests that the column was being operated in the churn turbulent regime at most of the velocities considered. Dynamic gas disengagement experiments showed a different behavior than seen in low-pressure, cold-flow work. Operation with a superficial gas velocity of 1.2 ft/sec was achieved during this run, with stable fluid dynamics and catalyst performance. Improvements included for catalyst activation in the design of the Clean Coal III LPMEOH{trademark} plant at Kingsport, Tennessee, were also confirmed. In addition, an alternate catalyst was demonstrated for LPMEOH{trademark}.
CFD simulation of gas and non-Newtonian fluid two-phase flow in anaerobic digesters.
Wu, Binxin
2010-07-01
This paper presents an Eulerian multiphase flow model that characterizes gas mixing in anaerobic digesters. In the model development, liquid manure is assumed to be water or a non-Newtonian fluid that is dependent on total solids (TS) concentration. To establish the appropriate models for different TS levels, twelve turbulence models are evaluated by comparing the frictional pressure drops of gas and non-Newtonian fluid two-phase flow in a horizontal pipe obtained from computational fluid dynamics (CFD) with those from a correlation analysis. The commercial CFD software, Fluent12.0, is employed to simulate the multiphase flow in the digesters. The simulation results in a small-sized digester are validated against the experimental data from literature. Comparison of two gas mixing designs in a medium-sized digester demonstrates that mixing intensity is insensitive to the TS in confined gas mixing, whereas there are significant decreases with increases of TS in unconfined gas mixing. Moreover, comparison of three mixing methods indicates that gas mixing is more efficient than mixing by pumped circulation while it is less efficient than mechanical mixing.
Molecular dynamics study of phase separation in fluids with chemical reactions.
Krishnan, Raishma; Puri, Sanjay
2015-11-01
We present results from the first d=3 molecular dynamics (MD) study of phase-separating fluid mixtures (AB) with simple chemical reactions (A⇌B). We focus on the case where the rates of forward and backward reactions are equal. The chemical reactions compete with segregation, and the coarsening system settles into a steady-state mesoscale morphology. However, hydrodynamic effects destroy the lamellar morphology which characterizes the diffusive case. This has important consequences for the phase-separating structure, which we study in detail. In particular, the equilibrium length scale (ℓ(eq)) in the steady state suggests a power-law dependence on the reaction rate ε:ℓ(eq)∼ε(-θ) with θ≃1.0.
Connecting Pore Scale Dynamics to Macroscopic Models for Two-Fluid Phase Flow
McClure, J. E.; Dye, A. L.; Miller, C. T.; Gray, W. G.
2015-12-01
Imaging technologies such as computed micro-tomography (CMT) provide high resolution three-dimensional images of real porous medium systems that reveal the true geometric structure of fluid and solid phases. Simulation and analysis tools are essential to extract knowledge from this raw data, and can be applied in tandem to provide information that is otherwise inaccessible. Guidance from multi-scale averaging theory is used to develop a multi-scale analysis framework to determine phase connectivity and extract interfacial areas, curvatures, common line length, contact angle and the velocities of the interface and common curve. The approach is applied to analyze pore-scale dynamics based on a multiphase lattice Boltzmann method. Dense sets of simulations are performed to evaluate the equilibrium relationship between capillary pressure, saturation and interfacial area for several experimentally imaged porous media. The approach is also used study the evolution of macroscopic quantities under dynamic conditions, which is compared to the equilibrium data.
Reference Equations of State for the Thermodynamic Properties of Fluid Phase n-Butane and Isobutane
Bücker, D.; Wagner, W.
2006-06-01
New formulations for the thermodynamic properties of fluid phase n-butane and isobutane in the form of fundamental equations explicit in the Helmholtz energy are presented. The functional form of the correlation equations for the residual parts was developed simultaneously for both substances considering data for the thermodynamic properties of ethane, propane, n-butane, and isobutane. Each contains 25 coefficients which were fitted to selected data for the thermal and caloric properties of the respective fluid both in the single-phase region and on the vapor-liquid phase boundary. This work provides information on the available experimental data for the thermodynamic properties of n- and isobutane, and presents all details of the new formulations. The new equations of state describe the pρT surfaces with uncertainties in density of 0.02% (coverage factor k=2 corresponding to a confidence level of about 95%) from the melting line up to temperatures of 340 K and pressures of 12 MPa. The available reliable data sets in other regions are represented within their experimental uncertainties. The primary data, to which the equation for n-butane was fitted, cover the fluid region from the melting line to temperatures of 575 K and pressures of 69 MPa. The equation for isobutane was fitted to primary data that cover the fluid region from the melting line to temperatures of 575 K and pressures of 35 MPa. Beyond the range described by experimental data, the equations yield reasonable extrapolation behavior up to very high temperatures and pressures. In addition to the equations of state, independent equations for the vapor pressures, the saturated-liquid and saturated-vapor densities, and the melting pressures are given. Tables of thermodynamic properties calculated from the new formulations are listed in Appendix 2. Additionally, a preliminary equation of state for propane is presented that was developed in the course of the simultaneous optimization. This equation has the
Optical Measurement of Mass Flow of a Two-Phase Fluid
Wiley, John; Pedersen, Kevin; Koman, Valentin; Gregory, Don
2008-01-01
An optoelectronic system utilizes wavelength-dependent scattering of light for measuring the density and mass flow of a two-phase fluid in a pipe. The apparatus was invented for original use in measuring the mass flow of a two-phase cryogenic fluid (e.g., liquid hydrogen containing bubbles of hydrogen gas), but underlying principles of operation can readily be adapted to non-cryogenic two-phase fluids. The system (see figure) includes a laser module, which contains two or more laser diodes, each operating at a different wavelength. The laser module also contains beam splitters that combine the beams at the various wavelengths so as to produce two output beams, each containing all of the wavelengths. One of the multiwavelength output beams is sent, via a multimode fiberoptic cable, to a transmitting optical coupler. The other multiwavelength output beam is sent, via another multimode fiber-optic cable, to a reference detector module, wherein fiber-optic splitters split the light into several multiwavelength beams, each going to a photodiode having a spectral response that is known and that differs from the spectral responses of the other photodiodes. The outputs of these photodiodes are digitized and fed to a processor, which executes an algorithm that utilizes the known spectral responses to convert the photodiode outputs to obtain reference laser-power levels for the various wavelengths. The transmitting optical coupler is mounted in (and sealed to) a hole in the pipe and is oriented at a slant with respect to the axis of the pipe. The transmitting optical coupler contains a collimating lens and a cylindrical lens that form the light emerging from the end of the fiber-optic cable into a fan-shaped beam in a meridional plane of the pipe. Receiving optical couplers similar to the transmitting optical couplers are mounted in the same meridional plane at various longitudinal positions on the opposite side of the pipe, approximately facing the transmitting optical
Gustafsson, Jonathan; Sritharan, Sivaguru S.
2015-11-01
Equations of High Energy Laser propagation in a turbulent medium and the equations of quantum fluid dynamics are connected through a mathematical transformation. In this way the problem of adaptive phase compensation can be phrased as an initial velocity control problem for quantum fluid dynamics. The quantum hydrodynamics equation can be derived by applying the Madelung transformation to the time-dependent linear or nonlinear Schrödinger equation. The resulting equations are similar to incompressible Euler equations with an additional term denoted the quantum pressure term. The quantum hydrodynamics equation can thus be a good way to understand adaptive optics and laser propagation through the atmosphere. A Riemann solver within the Clawpack framework has been developed. An initial value optimization problem will be solved using adjoint methods. The initial phase can be controlled when the beam leaves the laser appartus. The control method can also be coupled to a Navier-Stokes solver in order to study thermal blooming where the laser heats the air and changes the index of refraction. The change in refractive index will in turn affect the propagation of the Laser beam. Using optimal control techniques, it is possible to adjust the beam in order to compensate for the heating.
Entropic Lattice Boltzmann Methods for Fluid Mechanics: Thermal, Multi-phase and Turbulence
Chikatamarla, Shyam; Boesch, F.; Frapolli, N.; Mazloomi, A.; Karlin, I.
2014-11-01
With its roots in statistical mechanics and kinetic theory, the lattice Boltzmann method (LBM) is a paradigm-changing innovation, offering for the first time an intrinsically parallel CFD algorithm. Over the past two decades, LBM has achieved numerous results in the field of CFD and is now in a position to challenge state-of-the art CFD techniques. Major restyling of LBM resulted in an unconditionally stable entropic LBM which restored Second Law (Boltzmann H theorem) in the LBM kinetics and thus enabled affordable direct simulations of fluid turbulence. In this talk, we shall review recent advances in ELBM as a practical, modeling-free tool for simulation of complex flow phenomenon. We shall present recent simulations of fluid turbulence including turbulent channel flow, flow past a circular cylinder, creation and dynamics of vortex tubes, and flow past a surface mounted cube. Apart from its achievements in turbulent flow simulations, ELBM has also presented us the opportunity to extend lattice Boltzmann method to higher order lattices which shall be employed for turbulent, multi-phase and thermal flow simulations. A new class of entropy functions are proposed to handle non-ideal equation of state and surface tension terms in multi-phase flows. It is shown the entropy principle brings unconditional stability and thermodynamic consistency to all the three flow regimes considered here. Acknowledgements: ERC Advanced Grant ``ELBM'' and CSCS grant s437 are deeply acknowledged. References:
Effect of phase ratio and column type on retention in SFC (supercritical fluid chromatography)
Energy Technology Data Exchange (ETDEWEB)
Yonker, C.R.; Smith, R.D.
1987-08-01
Extensive discussion continues regarding the relative merits of capillary and packed columns for supercritical fluid chromatography (SFC). Columns of interest typically include commercially available 50-..mu..m i.d. capillaries having an /approximately/0.25-..mu..m film thickness and packed columns containing 3-..mu..m or 5-..mu..m diameter developed for HPLC. It has been demonstrated that packed columns can offer advantages in terms of speed because the properties of fluids high linear velocities to be utilized, but the lower pressure drop with open tubular capillary columns allows a greater number of effective theoretical plates through the use of longer columns. Much discussion has centered about the comparison of columns under various operating conditions of practical interest (e.g., pressure programming for capillaries or isobaric operation for packed columns). It is the purpose of this report to show the importance of column phase ratio (i.e., the ratio of stationary to mobile phase volumes. V/sub s/ and V/sub m/, respectively in the selection of columns for specific SFC applications.
Sub-stellar fragmentation in self-gravitating fluids with a major phase transition
Füglistaler, Andreas
2015-01-01
The existence of sub-stellar cold H2 globules in planetary nebulae and the mere existence of comets suggest that the physics of cold interstellar gas might be much richer than usually envisioned. We study the case of a cold gaseous medium in ISM conditions which is subject to a gas-liquid/solid phase transition. First the equilibrium of such fluids is studied using the virial theorem and linear stability analysis. Then the non-linear dynamics is studied by using simulations in order to characterize the expected formation of solid bodies analogous to comets. The simulations are run with a state of the art molecular dynamics code (LAMMPS). The long-range gravitational forces can be taken into account together with short-range molecular forces with finite limited computational resources by using super-molecules, provided the right scaling is followed. The concept of super-molecule is tested with simulations, allowing to correctly satisfy the ideal gas Jeans instability criterion for one-phase fluids. The simulat...
An equivalent ground thermal test method for single-phase fluid loop space radiator
Directory of Open Access Journals (Sweden)
Ning Xianwen
2015-02-01
Full Text Available Thermal vacuum test is widely used for the ground validation of spacecraft thermal control system. However, the conduction and convection can be simulated in normal ground pressure environment completely. By the employment of pumped fluid loops’ thermal control technology on spacecraft, conduction and convection become the main heat transfer behavior between radiator and inside cabin. As long as the heat transfer behavior between radiator and outer space can be equivalently simulated in normal pressure, the thermal vacuum test can be substituted by the normal ground pressure thermal test. In this paper, an equivalent normal pressure thermal test method for the spacecraft single-phase fluid loop radiator is proposed. The heat radiation between radiator and outer space has been equivalently simulated by combination of a group of refrigerators and thermal electrical cooler (TEC array. By adjusting the heat rejection of each device, the relationship between heat flux and surface temperature of the radiator can be maintained. To verify this method, a validating system has been built up and the experiments have been carried out. The results indicate that the proposed equivalent ground thermal test method can simulate the heat rejection performance of radiator correctly and the temperature error between in-orbit theory value and experiment result of the radiator is less than 0.5 °C, except for the equipment startup period. This provides a potential method for the thermal test of space systems especially for extra-large spacecraft which employs single-phase fluid loop radiator as thermal control approach.
An equivalent ground thermal test method for single-phase fluid loop space radiator
Institute of Scientific and Technical Information of China (English)
Ning Xianwen; Wang Yuying; Zhang Jiaxun; Liu Dongxiao
2015-01-01
Thermal vacuum test is widely used for the ground validation of spacecraft thermal con-trol system. However, the conduction and convection can be simulated in normal ground pressure environment completely. By the employment of pumped fluid loops’ thermal control technology on spacecraft, conduction and convection become the main heat transfer behavior between radiator and inside cabin. As long as the heat transfer behavior between radiator and outer space can be equivalently simulated in normal pressure, the thermal vacuum test can be substituted by the nor-mal ground pressure thermal test. In this paper, an equivalent normal pressure thermal test method for the spacecraft single-phase fluid loop radiator is proposed. The heat radiation between radiator and outer space has been equivalently simulated by combination of a group of refrigerators and thermal electrical cooler (TEC) array. By adjusting the heat rejection of each device, the relationship between heat flux and surface temperature of the radiator can be maintained. To verify this method, a validating system has been built up and the experiments have been carried out. The results indi-cate that the proposed equivalent ground thermal test method can simulate the heat rejection per-formance of radiator correctly and the temperature error between in-orbit theory value and experiment result of the radiator is less than 0.5 ?C, except for the equipment startup period. This provides a potential method for the thermal test of space systems especially for extra-large space-craft which employs single-phase fluid loop radiator as thermal control approach.
Khajeh, Aboozar; Modarress, Hamid
2014-01-01
In this work, molecular dynamics (MD) simulations were performed to investigate the effects of cholesterol on the interaction between the hydrophilic anticancer drug, 5-FU, and fully hydrated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayer. Several structural and dynamical parameters of DMPC bilayers with varying amounts of cholesterol (0, 25, and 50mol%) in the presence and absence of drug molecules were calculated. Moreover, the free energy barriers for translocation of one 5-FU molecule from water to the lipid bilayer were determined by using the potential of mean force (PMF). PMF studies indicated that the location of the maximum free energy barrier was in the hydrophobic middle region of bilayer, while the minimums of the barrier were located at the hydrophilic part of bilayer at the interface with water. The minimum and maximum of the free energy profiles were independent of cholesterol concentration and suggested that the drug molecules 5-FU were accumulated in the vicinity of the polar head group of lipid bilayers. Moreover, the results showed that with increasing cholesterol concentration in the bilayer, the free energy barrier for translocation of 5-FU across the bilayer also increases which can be attributed to the condensing effect of the cholesterol on the bilayer.
Berendt, Artur; Domaszka, Magdalena; Mizeraczyk, Jerzy
2017-04-01
The electrical characteristics of a steady-state negative DC corona discharge in a two-phase fluid (air with suspended cigarette smoke particles) flowing along a chamber with a needle-to-plate electrode arrangement were experimentally investigated. The two-phase flow was transverse in respect to the needle-to-plate axis. The velocity of the transverse two-phase flow was limited to 0.8 m/s, typical of the electrostatic precipitators. We found that three discharge current modes of the negative corona exist in the two-phase (air + smoke particles) fluid: the Trichel pulses mode, the "Trichel pulses superimposed on DC component" mode and the DC component mode, similarly as in the corona discharge in air (a single-phase fluid). The shape of Trichel pulses in the air + suspended particles fluid is similar to that in air. However, the Trichel pulse amplitudes are higher than those in "pure" air while their repetition frequency is lower. As a net consequence of that the averaged corona discharge current in the two-phase fluid is lower than in "pure" air. It was also found that the average discharge current decreases with increasing suspended particle concentration. The calculations showed that the dependence of the average negative corona current (which is a macroscopic corona discharge parameter) on the particle concentration can be explained by the particle-concentration dependencies of the electric charge of Trichel pulse and the repetition frequency of Trichel pulses, both giving a microscopic insight into the electrical phenomena in the negative corona discharge. Our investigations showed also that the average corona discharge current in the two-phase fluid is almost unaffected by the transverse fluid flow up to a velocity of 0.8 m/s. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder
Numerical Simulation of Flow Field in the New Reactor with Two-Phase Fluid
Directory of Open Access Journals (Sweden)
Shu Xu
2013-03-01
Full Text Available On the basic of the PIV flows field measurement, mature commercial software to fit and test heat plate reactor momentum transfer mathematical model are used and the flow field in various operation conditions of heat plate reactor is simulated. The transfer process of two-phases flow is complicated, the ideal even bubbles model is used to simulate, analyze and calculate, the deviation values of temperature profile of two-phases flow and flow profile of H2O-Air are minor, but they are high than that of homogeneous phase flow. We use the mature business software (CFX of CFD not only to fit, prove the momentum and heat transfer model in reactor with the experiment data of flow profile and temperature profile, but also to simulate the whole flow profile and temperature profile of two-phase fluids, their deviation values between the calculated values and experiment value are lower than the values simulated by traditional empirical formula, these will provide analysis of the transfer process in reactor with reliable mechanism model and computing method.
Murakami, Jillian N; Thurbide, Kevin B
2015-09-15
Stainless steel (SS) particles were demonstrated as a novel useful support for a water stationary phase in packed column supercritical fluid chromatography using a CO2 mobile phase. Separations employed flame ionization detection, and the system was operated over a range of temperatures and pressures. Retention times reproduced well with RSD values of 2.6% or less. Compared to analogous separations employing a water stationary phase coated onto a SS capillary column, the packed column method provided separations that were about 10× faster, with nearly 8-fold larger analyte retention factors, while maintaining good peak shape and comparable column efficiency. Under normal operating conditions, the packed column contains about 131 ± 4 μL/m of water phase (around a 5% m/m coating), which is over 25× greater than the capillary column and also affords it a 20-fold larger sample capacity. Several applications of the packed column system are examined, and the results indicate that it is a useful alternative to the capillary column mode, particularly where analyte loads or sample matrix interference is a concern. Given its high sample capacity, this packed column method may also be useful to explore on a more preparative scale in the future.
West, Caroline; Khalikova, Maria A; Lesellier, Eric; Héberger, Károly
2015-08-28
The identification of a suitable stationary phase in supercritical fluid chromatography (SFC) is a major source of difficulty for those with little experience in this technique. Several protocols have been suggested for column classification in high-performance liquid chromatography (HPLC), gas chromatography (GC), and SFC. However, none of the proposed classification schemes received general acceptance. A fair way to compare columns was proposed with the sum of ranking differences (SRD). In this project, we used the retention data obtained for 86 test compounds with varied polarity and structure, analyzed on 71 different stationary phases encompassing the full range in polarity of commercial packed columns currently available to the SFC chromatographer, with a single set of mobile phase and operating conditions (carbon dioxide-methanol mobile phase, 25°C, 150bar outlet pressure, 3ml/min). First, a reference column was selected and the 70 remaining columns were ranked based on this reference column and the retention data obtained on the 86 analytes. As these analytes previously served for the calculation of linear solvation energy relationships (LSER) on the 71 columns, SRD ranks were compared to LSER methodology. Finally, an external comparison based on the analysis of 10 other analytes (UV filters) related the observed selectivity to SRD ranking. Comparison of elution orders of the UV filters to the SRD rankings is highly supportive of the adequacy of SRD methodology to select similar and dissimilar columns.
Numerical modelling of the impact of a liquid drop on the surface of a two-phase fluid system
Sochan, Agata; Lamorski, Krzysztof; Bieganowski, Andrzej; Ryżak, Magdalena
2014-05-01
The aim of the study was validation of a numerical model of the impact of a liquid drop on the surface of a two-phase system of immiscible fluids. The drop impact phenomenon was recorded using a high-speed camera (Vision Research MIRO M310) and the data were recorded at 2000 frames per second. The numerical calculations were performed with the Finite Volume Method (FVM) solving the three-dimensional Navier-Stokes equations for three phases: air and two selected immiscible fluids. The Volume of Fluid (VOF) technique was employed for modelling of the boundaries between the phases. Numerical modelling was done with the Finite Volume Method using an available OpenFOAM software. The experiment was based on three variables: • the height from which the drop of the selected fluids fell (the speed of the drop), • the thickness of the layers of the two selected immiscible fluids (a thin layer of the fluid with a lower density was spread over the higher-density fluid), • the size of the fluid droplet. The velocity and radius of the falling drop was calculated based on the recorded images. The used parameters allowed adequate projection of the impact of fluid droplets on a system of two immiscible liquids. Development of the numerical model of splash may further have practical applications in environmental protection (spraying of hazardous fluids, spread of fuels and other hazardous substances as a result of disasters, spraying (water cooling) of hot surfaces), and in agriculture (prevention of soil erosion). The study was partially funded from the National Science Centre (Poland) based on the decision no. DEC-2012/07/N/ST10/03280.
Shibuya, Ryoichi; Yonenobu, Kazuo; Koizumi, Toshiaki; Kato, Yasuji; Mitta, Motoharu; Yoshikawa, Hideki
2002-05-15
A technical report is presented. To investigate the relation between the severity of myelopathy and the degree of cerebrospinal fluid flow disturbance by using magnetic resonance imaging to measure the velocity of the cerebrospinal fluid flow in patients with cervical spondylotic myelopathy. Analyses of pulsatile cerebrospinal fluid flow measured by phase-contrast magnetic resonance imaging in healthy subjects and patients with Arnold-Chiari syndrome have been reported. Few studies have evaluated the change of pulsatile cerebrospinal fluid flow velocity and the waveform of the plotted velocity in patients with cervical spondylotic myelopathy. Study 1: Pulsatile cerebrospinal fluid flow was measured at C7, positioned with cervical spine flexion and extension, to investigate the influence of cervical alignment on the pulsatile cerebrospinal fluid flow in five patients with cervical spondylotic myelopathy. Study 2: In 31 patients with cervical spondylotic myelopathy, pulsatile cerebrospinal fluid flow was measured at C3 and C7, with the neck set centrally. The relevance of cerebrospinal fluid flow disturbance and the severity of myelopathy evaluated by the Japanese Orthopedic Association scoring system also were studied. Study 1: The waveform of plotted pulsatile cerebrospinal fluid flow velocity showed no change resulting from the position of the cervical spine. Study 2: A high correlation between the Japanese Orthopedic Association score and the cerebrospinal fluid pulsatile flow amplitude at C7 was demonstrated (r = 0.75; P < 0.0001). The average Japanese Orthopedic Association score of 14 patients whose cerebrospinal fluid flow velocity waveforms were absent was significantly lower (P < 0.0001) than that of 17 patients whose waveforms were present. The disturbance of pulsatile cerebrospinal fluid flow demonstrated high correlation with the severity of myelopathy. Measurement of cerebrospinal fluid flow disturbance can quantify the degree of dural sac and spinal
Energy Technology Data Exchange (ETDEWEB)
Ricoeur, A.
2000-07-01
The subject under consideration is the development and propagation of sound in two-phase flows. The investigations are focused on fluids, which are composed of liquid and gas. The gaseous phase may consist of both noncondensable gas and of vapour, originating from phase transitions of the liquid. Fields of application are, among others, flow noise, sonochemistry, the acoustical surveillance of industrial flow processes or ocean acoustics. A stochastic model, which describes spectral properties of noise sources, conditioned by imploding vapour bubbles, is connected to transfer functions. The latter are based on constitutive equations, accounting for the wave mechanics of the two-phase fluids. In combination with a numerical algorithm they permit for the calculation of noise spectra at any distance from the noise sources. The field problem is solved by implementing the constitutive equations into a hybrid boundary element method, which combines low discretization effort with fast evaluation of domain variables. The constitutive equations are based on models for the dynamics of gas- and vapour bubbles. Therefore, the nonlinear and linear bubble dynamics are extensively investigated. Furthermore, fundamental knowledge concerning wave dispersion in two-phase fluids is presented. The constitutive equation for pseudocavitation is experimentally verified by means of an acoustical wave guide. Additionally the experimental set-up serves for investigating fluid-structure-interaction. (orig.) [German] Die Arbeit befasst sich mit der Entstehung und Ausbreitung von Schall in Zweiphasenstroemungen. Betrachtet werden Fluide aus Fluessigkeit und Gas, deren Gasphase sowohl als nichtkondensierendes Gas, als auch in Gestalt des Dampfes der Fluessigkeit vorliegt. Anwendungen liegen beispielsweise in der Stroemungsakustik, der Sonochemie, der akustischen Ueberwachung verfahrenstechnischer Prozesse oder der Meeresakustik. Ein stochastisches Modell zur spektralen Beschreibung von
Directory of Open Access Journals (Sweden)
Boga Mwanamvua
2010-10-01
Full Text Available Abstract Background Children with severe malnutrition who develop shock have a high mortality. Contrary to contemporaneous paediatric practice, current guidelines recommend use of low dose hypotonic fluid resuscitation (half-strength Darrows/5% dextrose (HSD/5D. We evaluated the safety and efficacy of this guideline compared to resuscitation with a standard isotonic solution. Methods A Phase II randomised controlled, safety and efficacy trial in Kenyan children aged over 6 months with severe malnutrition and shock including children with severe dehydration/shock and presumptive septic shock (non-diarrhoeal shock. Eligible children were randomised to HSD/5D or Ringer's Lactate (RL. A maximum of two boluses of 15 ml/kg of HSD/5D were given over two hours (as recommended by guidelines while those randomised to RL received 10 ml/kg aliquots half hourly (maximum 40 ml/kg. Primary endpoint was resolution of shock at 8 and 24 hours. Secondary outcomes included resolution of acidosis, adverse events and mortality. Results 61 children were enrolled: 41 had shock and severe dehydrating diarrhoea, 20 had presumptive septic shock; 69% had decompensated shock. By 8 hours response to volume resuscitation was poor with shock persisting in most children:-HSD/5D 15/22 (68% and RL14/25 (52%, p = 0.39. Oliguria was more prevalent at 8 hours in the HSD/5D group, 9/22 (41%, compared to RL-3/25 (12%, p = 0.02. Mortality was high, HSD/5D-15/26(58% and RL 13/29(45%; p = 0.42. Most deaths occurred within 48 hours of admission. Neither pulmonary oedema nor cardiogenic failure was detected. Conclusions Outcome was universally poor characterised by persistence of shock, oliguria and high case fatality. Isotonic fluid was associated with modest improvement in shock and survival when compared to HSD/5D but inconclusive due to the limitations of design and effectiveness of either resuscitation strategy. Although isotonic fluid resuscitation did not result in cardiogenic heart
Desgranges, Caroline; Delhommelle, Jerome
2009-06-28
In recent years, powerful and accurate methods, based on a Wang-Landau sampling, have been developed to determine phase equilibria. However, while these methods have been extensively applied to study the phase behavior of model fluids, they have yet to be applied to molecular systems. In this work, we show how, by combining hybrid Monte Carlo simulations in the isothermal-isobaric ensemble with the Wang-Landau sampling method, we determine the vapor-liquid equilibria of various molecular fluids. More specifically, we present results obtained on rigid molecules, such as benzene, as well as on flexible chains of n-alkanes. The reliability of the method introduced in this work is assessed by demonstrating that our results are in excellent agreement with the results obtained in previous work on simple fluids, using either transition matrix or conventional Monte Carlo simulations with a Wang-Landau sampling, and on molecular fluids, using histogram reweighting or Gibbs ensemble Monte Carlo simulations.
Variant of a volume-of-fluid method for surface tension-dominant two-phase flows
Indian Academy of Sciences (India)
G Biswas
2013-12-01
The capabilities of the volume-of-fluid method for the calculation of surface tension-dominant two-phase flows are explained. The accurate calculation of the interface remains a problem for the volume-of-fluid method if the density ratios of the fluids in different phases are high. The simulations of bubble growth is performed in water at near critical pressure for different degrees of superheat using combined levelset and volume-of fluid (CLSVOF) method. The effect of superheat on the frequency of bubble formation was analyzed. A deviation from the periodic bubble release is observed in the case of superheat of 20 K in water. The vapor-jet-like columnar structure is observed. Effect of heat flux on the slender vapor column has also been explained.
A two-fluid model for reactive dilute solid-liquid mixtures with phase changes
Reis, Martina Costa; Wang, Yongqi
2016-12-01
Based on the Eulerian spatial averaging theory and the Müller-Liu entropy principle, a two-fluid model for reactive dilute solid-liquid mixtures is presented. Initially, some averaging theorems and properties of average quantities are discussed and, then, averaged balance equations including interfacial source terms are postulated. Moreover, constitutive equations are proposed for a reactive dilute solid-liquid mixture, where the formation of the solid phase is due to a precipitation chemical reaction that involves ions dissolved in the liquid phase. To this end, principles of constitutive theory are used to propose linearized constitutive equations that account for diffusion, heat conduction, viscous and drag effects, and interfacial deformations. A particularity of the model is that the mass interfacial source term is regarded as an independent constitutive variable. The obtained results show that the inclusion of the mass interfacial source term into the set of independent constitutive variables permits to easily describe the phase changes associated with precipitation chemical reactions.
Unsteady MHD two-phase Couette flow of fluid-particle suspension in an annulus
Directory of Open Access Journals (Sweden)
Basant K. Jha
2011-12-01
Full Text Available The problem of two-phase unsteady MHD flow between two concentric cylinders of infinite length has been analysed when the outer cylinder is impulsively started. The system of partial differential equations describing the flow problem is formulated taking the viscosity of the particle phase into consideration. Unified closed form expressions are obtained for the velocities and the skin frictions for both cases of the applied magnetic field being fixed to either the fluid or the moving outer cylinder. The problem is solved using a combination of the Laplace transform technique, D’Alemberts and the Riemann-sum approximation methods. The solution obtained is validated by comparisons with the closed form solutions obtained for the steady states which has been derived separately. The governing equations are also solved using the implicit finite difference method to verify the present proposed method. The variation of the velocity and the skin friction with the dimensionless parameters occuring in the problem are illustrated graphically and discussed for both phases.
A two-fluid model for reactive dilute solid-liquid mixtures with phase changes
Reis, Martina Costa; Wang, Yongqi
2017-03-01
Based on the Eulerian spatial averaging theory and the Müller-Liu entropy principle, a two-fluid model for reactive dilute solid-liquid mixtures is presented. Initially, some averaging theorems and properties of average quantities are discussed and, then, averaged balance equations including interfacial source terms are postulated. Moreover, constitutive equations are proposed for a reactive dilute solid-liquid mixture, where the formation of the solid phase is due to a precipitation chemical reaction that involves ions dissolved in the liquid phase. To this end, principles of constitutive theory are used to propose linearized constitutive equations that account for diffusion, heat conduction, viscous and drag effects, and interfacial deformations. A particularity of the model is that the mass interfacial source term is regarded as an independent constitutive variable. The obtained results show that the inclusion of the mass interfacial source term into the set of independent constitutive variables permits to easily describe the phase changes associated with precipitation chemical reactions.
Góźdź, W T
2017-08-30
We have calculated the values of the critical packing fractions for the mixtures of symmetric nonadditive hard spheres at high densities for small values of the nonadditivity parameter. Calculations have been performed for solid-solid and fluid-fluid demixing transitions. A cluster algorithm for Monte Carlo simulations in a semigrand ensemble was used, and the waste recycling method was applied to improve the accuracy of the calculations. The finite size scaling analysis was employed to compute the critical packing fractions for infinite systems with high accuracy.
Frezzotti, Maria Luce
1992-01-01
The Mount Genis granite is one of the post-tectonic intrusives emplaced late in the magmatic history of the Hercynian batholith in Sardinia. Devitrified silicate melt inclusions are present in some (magmatic) rock-forming and miarolitic quartz. These magmatic remnants show initial melting at 680- 720°C. High-temperature observations (700-800°C) revealed the presence in some of the inclusions of mixed hydrosaline melt (L1) and silicate melt (L2), with extremely variable L1/L2 ratios. Electron microprobe analyses indicate L1 to be K-Na dominated chlorides. Inclusions of mixed silicate and hydrosaline melts are interpreted to have been formed by heterogeneous trapping of two immiscible fluid phases (silicate-hydrosaline) after second boiling, most likely during the final crystallization stage. Magma-derived brines (63 eq wt% NaCl) circulated at subsolidus conditions from ≈600°C and were retained in the miarolitic cavities down to about 400°C. Fluid unmixing occurred locally in the miarolitic cavities from 550° to 412°C. At temperatures of ≈400° to 100°C the microgranite was invaded by diluted waters (≈4-5 eq wt% NaCl). A possible model for fluid evolution begins with a hydrosaline melt exsolving from the magma at the late-magmatic stage. The absence of boiling within the volatile (hydrosaline) system shows that brines can occur by direct magmatic immiscibility. The comprehensive hydrothermal evolution suggests a nearly isobaric cooling path, with local boiling episodes in the miaroles, probably in coincidence with invasion of external waters.
Two-phase working fluids for the temperature range 100-350 C. [in heat pipes for solar applications
Saaski, E. W.; Tower, L.
1977-01-01
The decomposition and corrosion of two-phase heat transfer liquids and metal envelopes have been investigated on the basis of molecular, bond strengths and chemical thermodynamics. Potentially stable heat transfer fluids for the temperature range 100 to 350 C have been identified, and reflux heat pipe tests initiated with 10 fluids and carbon steel and aluminum envelopes to experimentally establish corrosion behavior and noncondensable gas generation rates.
Acute phase proteins in serum and cerebrospinal fluid in the course of bacterial meningitis.
Paradowski, M; Lobos, M; Kuydowicz, J; Krakowiak, M; Kubasiewicz-Ujma, B
1995-08-01
We carried out estimations of the following acute phase proteins: C-reactive protein (CRP), alpha-1-antitrypsin (AAT), alpha-1-acid glycoprotein (AAG), alpha-2-ceruloplasmin (CER), and alpha-2-haptoglobin (HPT) in serum and in cerebrospinal fluid (CSF) in patients with bacterial meningitis (BM, n = 30) and viral meningitis (VM, n = 30). We have shown that determinations of concentrations of AAG and CRP in serum and CER in CSF are useful in differentiation between BM and VM. The diagnostic power of these three tests (the areas under their ROC curves equal 0.942, 0.929, and 0.931, respectively) is bigger, though statistically not significantly, than that of traditional parameters of BM in CSF, i.e., total protein concentration and white blood cell count. Determination of AAG, CRP, and AAT in serum is a valuable monitoring marker in the course of BM treatment. Convenience of serum sampling constitutes an advantage over traditional BM parameters in CSF.
Zhao, Xuemei; Li, Rui; Chen, Yu; Sia, Sheau Fung; Li, Donghai; Zhang, Yu; Liu, Aihua
2017-03-01
Additional hemodynamic parameters are highly desirable in the clinical management of intracranial aneurysm rupture as static medical images cannot demonstrate the blood flow within aneurysms. There are two ways of obtaining the hemodynamic information—by phase-contrast magnetic resonance imaging (PCMRI) and computational fluid dynamics (CFD). In this paper, we compared PCMRI and CFD in the analysis of a stable patient's specific aneurysm. The results showed that PCMRI and CFD are in good agreement with each other. An additional CFD study of two stable and two ruptured aneurysms revealed that ruptured aneurysms have a higher statistical average blood velocity, wall shear stress, and oscillatory shear index (OSI) within the aneurysm sac compared to those of stable aneurysms. Furthermore, for ruptured aneurysms, the OSI divides the positive and negative wall shear stress divergence at the aneurysm sac.
Phase Equilibrium Calculations for Multi-Component Polar Fluid Mixtures with tPC-PSAFT
DEFF Research Database (Denmark)
Karakatsani, Eirini; Economou, Ioannis
2007-01-01
The truncated Perturbed-Chain Polar Statistical Associating Fluid Theory (tPC-PSAFT) is applied to a number of different mixtures, including binary, ternary and quaternary mixtures of components that differ substantially in terms of intermolecular interactions and molecular size. In contrast...... to most other SAFT versions, tPC-PSAFT accounts explicitly for polar forces. Three pure-component parameters are required for non-polar and non-associating compounds, two additional parameters characterize the association contribution and one parameter is needed to account for polar interactions....... The experimental dipole and/or quadrupole moment and/or polarizability of the component are used to calculate polar interactions. Using a temperature-independent interaction parameter kij for each binary system, tPC-PSAFT provides accurate prediction of multi-component phase behavior over a wide range...
Cerebrospinal fluid production and dynamics in normal aging: a MRI phase-mapping study
DEFF Research Database (Denmark)
Gideon, P; Thomsen, C; Ståhlberg, F
1994-01-01
Magnetic resonance imaging (MRI) phase mapping was used for non-invasive evaluation of the to-and-fro motion of cerebrospinal fluid (CSF) in the cerebral aqueduct, and to measure the supratentorial CSF production in vivo, in 13 healthy volunteers to determine whether normal aging affects...... these parameters. Eight young healthy volunteers (mean age 29.8 years) and five elderly healthy volunteers (mean age 69.0 years) were examined, all were normal on conventional MRI. Slightly higher aqueductal CSF peak flow velocities and peak volume flow in both the caudal and rostral directions were found...... in fact occurs at this relatively high rate. Our study further suggests that the differences found in human CSF production rates are caused by interindividual factors other than age....
Trusler, J P Martin
2017-06-07
Phase behavior and thermophysical properties of mixtures of carbon dioxide with various other substances are very important for the design and operation of carbon capture and storage (CCS) processes. The available empirical data are reviewed, together with some models for the calculation of these properties. The systems considered in detail are, first, mixtures of carbon dioxide, water, and salts; second, carbon dioxide-rich nonelectrolyte mixtures; and third, mixtures of carbon dioxide with water and amines. The empirical data and the plethora of available models permit the estimation of key fluid properties required in the design and operation of CCS processes. The engineering community would benefit from the further development, and delivery in convenient form, of a small number of these models sufficient to encompass the component slate and operating conditions of CCS processes.
Evaluation of two-phase flow solvers using Level Set and Volume of Fluid methods
Bilger, C.; Aboukhedr, M.; Vogiatzaki, K.; Cant, R. S.
2017-09-01
Two principal methods have been used to simulate the evolution of two-phase immiscible flows of liquid and gas separated by an interface. These are the Level-Set (LS) method and the Volume of Fluid (VoF) method. Both methods attempt to represent the very sharp interface between the phases and to deal with the large jumps in physical properties associated with it. Both methods have their own strengths and weaknesses. For example, the VoF method is known to be prone to excessive numerical diffusion, while the basic LS method has some difficulty in conserving mass. Major progress has been made in remedying these deficiencies, and both methods have now reached a high level of physical accuracy. Nevertheless, there remains an issue, in that each of these methods has been developed by different research groups, using different codes and most importantly the implementations have been fine tuned to tackle different applications. Thus, it remains unclear what are the remaining advantages and drawbacks of each method relative to the other, and what might be the optimal way to unify them. In this paper, we address this gap by performing a direct comparison of two current state-of-the-art variations of these methods (LS: RCLSFoam and VoF: interPore) and implemented in the same code (OpenFoam). We subject both methods to a pair of benchmark test cases while using the same numerical meshes to examine a) the accuracy of curvature representation, b) the effect of tuning parameters, c) the ability to minimise spurious velocities and d) the ability to tackle fluids with very different densities. For each method, one of the test cases is chosen to be fairly benign while the other test case is expected to present a greater challenge. The results indicate that both methods can be made to work well on both test cases, while displaying different sensitivity to the relevant parameters.
Dependence of bicellar system phase behavior and dynamics on anionic lipid concentration.
MacEachern, Lauren; Sylvester, Alexander; Flynn, Alanna; Rahmani, Ashkan; Morrow, Michael R
2013-03-19
Bicellar dispersions of chain perdeuterated 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC-d54) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) were prepared with the molar fraction of DHPC held fixed at 20% and varying amounts of DMPC replaced by the anionic lipid 1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DMPG). (2)H NMR spectra were examined to assess the effect of added DMPG on mixture phase behavior and morphology. Quadrupole echo decay and quadrupole-Carr-Purcell-Mieboom-Gill echo train measurements provided information about slow motions contributing to echo decay in the high temperature phases. The spectra and quadrupole echo decay properties of DMPC-d54/DHPC (4:1) and DMPC-d54/DMPG/DHPC (3:1:1) were qualitatively similar. With increasing DMPG concentration, the transition between the magnetically orientable phase and the higher temperature phase became increasingly distinct, and the spectral shape and echo decay characteristics of the high temperature bicellar phase became increasingly similar to those of DMPC-d54 in the liquid crystalline phase. The observation that DMPG changes spectra in the orientable phase incrementally while increasing the distinction between the orientable and high temperature bicellar phases provides new insights into how DMPG influences bicellar mixture morphology.
Malaspina, Nadia; Alvaro, Matteo; Campione, Marcello; Wilhelm, Heribert; Nestola, Fabrizio
2015-03-01
Remnants of the fluid phase at ultrahigh pressure (UHP) in subduction environments may be preserved as primary multiphase inclusions in UHP minerals. The mode of crystallization of daughter minerals during precipitation within the inclusion and/or the mechanism of interaction between the fluid at supercritical conditions and the host mineral are still poorly understood from a crystallographic point of view. A case study is represented by garnet-orthopyroxenites from the Maowu Ultramafic Complex (China) deriving from harzburgite precursors metasomatized at ~4 GPa, 750 °C by a silica- and incompatible trace element-rich fluid phase. This metasomatism produced poikilitic orthopyroxene and inclusion-rich garnet porphyroblasts. Solid multiphase primary inclusions in garnet display a size within a few tens of micrometres and negative crystal shapes. Infilling minerals (spinel: 10-20 vol%; amphibole, chlorite, talc, mica: 80-90 vol%) occur with constant volume proportions and derive from trapped solute-rich aqueous fluids. To constrain the possible mode of precipitation of daughter minerals, we performed for the first time a single-crystal X-ray diffraction experiment by synchrotron radiation at Diamond Light Source. In combination with electron probe microanalyses, this measurement allowed the unique identification of each mineral phase and reciprocal orientations. We demonstrated the epitaxial relationship between spinel and garnet and between some hydrous minerals. Such information is discussed in relation to the physico-chemical aspects of nucleation and growth, shedding light on the mode of mineral crystallization from a fluid phase trapped at supercritical conditions.
A fundamental measure density functional for fluid and crystal phases of the Asakura-Oosawa model
Mortazavifar, Mostafa; Oettel, Martin
2016-06-01
We investigate a density functional for the Asakura-Oosawa model of colloid-polymer mixtures, describing both fluid and crystal phases. It is derived by linearizing the two-component fundamental-measure hard sphere tensor functional in the second (polymer) component. We discuss the formulation of an effective density functional for colloids only. For small polymer-colloid size ratios the effective, polymer-induced potential between colloids is short-range attractive and of two-body form but we show that the effective density functional is not equivalent to standard mean-field approaches where attractions are taken into account by terms second order in the colloid density. We calculate numerically free energies and phase diagrams in good agreement with available simulations, furthermore we discuss the colloid and polymer distributions in the crystal and determine equilibrium vacancy concentrations. Numerical results reveal a fairly strong sensitivity to the specific type of underlying fundamental measure hard sphere functional which could aid further development of fundamental measure theory.
Energy Technology Data Exchange (ETDEWEB)
Masella, J.M.
1997-05-29
This thesis is devoted to the numerical simulation of some two-fluid models describing gas-liquid two-phase flow in pipes. The numerical models developed here can be more generally used in the modelling of a wide class of physical models which can be put under an hyperbolic form. We introduce first two isothermal two-fluid models, composed of a mass balance equation and a momentum equation written in each phase, describing respectively a stratified two-phase flow and a dispersed two-phase flow. These models are hyperbolic under some physical assumptions and can be written under a nonconservative vectorial system. We define and analyse a new numerical finite volume scheme (v{integral}Roe) founded on a linearized Riemann solver. This scheme does not need any analytical calculation and gives good results in the tracking of shocks. We compare this new scheme with the classical Roe scheme. Then we propose and study some numerical models, with and without flux splitting method, which are adapted to the discretization of the two-fluid models. This numerical models are given by a finite volume integration of the equations, and lean on the v{integral} scheme. In order to reducing cpu time, due to the low Mach number of two-phase flows, acoustic waves are implicit. Afterwards we proposed a discretization of boundary conditions, which allows the generation of transient flows in pipe. Some numerical academic and more physical tests show the good behaviour of the numerical methods. (author) 77 refs.
Polanco, J D; Ujevic, M; Polanco, Jose D.; Letelier, Patricio S.; Ujevic, Maximiliano
2004-01-01
A numerical solution of Einstein field equations for a spherical symmetric and stationary system of identical and auto-gravitating particles in phase transition is presented. The fluid possess a perfect fluid energy momentum tensor, and the internal interactions of the system are represented by a van der Walls like equation of state able to describe a first order phase transition of the type gas-liquid. We find that the space-time curvature, the radial component of the metric, and the pressure and density show discontinuities in their radial derivatives in the phase coexistence region. This region is found to be a spherical surface concentric with the star and the system can be thought as a foliation of acronal, concentric and isobaric surfaces in which the coexistence of phases occurs in only one of these surfaces. This kind of system can be used to represent a star with a high energy density core and low energy density mantle in hydrodynamic equilibrium.
Moebius, F.; Or, D.
2012-04-01
Many natural and engineering processes involve motion of fluid fronts in porous media, from infiltration and drainage in hydrology to reservoir management in petroleum engineering. Macroscopically smooth and continuous motion of displacement fronts involves numerous rapid interfacial jumps and local reconfigurations. Detailed observations of displacement processes in micromodels illustrate the wide array of fluid interfacial dynamics ranging from irregular jumping-pinning motions to gradual pore scale invasions. The pressure fluctuations associated with interfacial motions reflect not only pore geometry (as traditionally hypothesized) but there is a strong influence of boundary conditions (e.g., mean drainage rate). The time scales associated with waiting time distribution of individual invasion events and decay time of inertial oscillations (following a rapid interfacial jump) provide a means for distinguishing between displacement regimes. Direct observations using high-speed camera combined with concurrent pressure signal measurements were instrumental in clarifying influences of flow rates, pore size, and gravity on burst size distribution and waiting times. We compared our results with the early experimental and theoretical study on burst size and waiting time distribution during slow drainage processes of Måløy et al. [Måløy et al., 1992]. Results provide insights on critical invasion events that exert strong influence on macroscopic phenomena such as front morphology and residual phase entrapment behind leading to hysteresis. Måløy, K. J., L. Furuberg, J. Feder, and T. Jossang (1992), Dynamics of Slow Drainage in Porous-Media, Phys Rev Lett, 68(14), 2161-2164.
National Research Council Canada - National Science Library
M.Premkumar; S.Ramachandran
2013-01-01
.... In this study the analysis of heat transfer between PCM and heat transfer fluids (HTF) with Spherical and cylindrical finned encapsulations made of copper are done using computational fluid dynamic (CFD...
Kvasniuk, D. I.; Vasyuk, V. L.
2012-01-01
A new method for differential diagnosis of pathological changes of the joints on the basis of synovial fluid was founded. Adduced description scheme and the principles of polarization filtering to determine the coordinate distributions of phase shifts.The optical model of polycrystalline networks of knee joint synovial fluid is suggested. The results of investigating the interrelation between the values of statistical (statistical moments of the 1st-4th order) parameters are presented. They characterize the coordinate distributions of phase shifts between the orthogonal components of the amplitude in the points of laser images of synovial fluid smears and the change in optical anisotropy of this biological object. The diagnostic criteria of knee joint inflammation processes are determined.
Vörtler, Horst L; Schäfer, Katja; Smith, William R
2008-04-17
We study the simulation cell size dependence of chemical potential isotherms in subcritical square-well fluids by means of series of canonical ensemble Monte Carlo simulations with increasing numbers of particles, for both three-dimensional bulk systems and two-dimensional planar layers, using Widom-like particle insertion methods. By estimating the corresponding vapor/liquid coexistence densities using a Maxwell-like equal area rule for the subcritical chemical potential isotherms, we are able to study the influence of system size not only on chemical potentials but also on the coexistence properties. The chemical potential versus density isotherms show van der Waals-like loops in the subcritical vapor/liquid coexistence range that exhibit distinct finite size effects for both two- and three-dimensional fluids. Generally, in agreement with recent findings for related studies of Lennard-Jones fluids, the loops shrink with increasing number of particles. In contrast to the subcritical isotherms themselves, the equilibrium vapor/liquid densities show only a weak system size dependence and agree quantitatively with the best-known literature values for three-dimensional fluids. This allows our approach to be used to accurately predict the phase coexistence properties. Our resulting phase equilibrium results for two-dimensional square-well fluids are new. Knowledge concerning finite size effects of square-well systems is important not only for the simulation of thermodynamic properties of simple fluids, but also for the simulation of models of more complex fluids (such as aqueous or polymer fluids) involving square-well interactions.
Doppler, Gerald; Bakker, Ronald J.
2014-06-01
The influence of the α-β quartz phase transition on the properties of fluid inclusions was investigated experimentally. The experiments were designed to have no gradients in pressure and fugacity between fluid inclusions and pore fluid. Deformation due to pressure differences were also excluded in this study. H2O-rich fluid inclusions with similar densities were synthesized in quartz at approximately 625 °C and 280 MPa in the α-quartz stability field, and at approximately 675 °C and 320 MPa in the β-quartz stability field. The experimental set-up prevented any pressure differences during loading and unloading of the experiments. These inclusions were re-equilibrated at the same temperature-pressure-fluid conditions, and changes in total homogenization temperature and ice melting temperature were recorded. Fluid inclusions are sensitive monitors of fluid conditions during entrapment, which record minor variation in temperature and pressure and display a corresponding distribution pattern in homogenization temperatures. Fluid inclusions re-equilibrated in the α-quartz stability field were not affected by changes in density. Fluid inclusions re-equilibrated in the β-quartz stability field revealed density loss of - 0.6% at 320 MPa to - 3.0% at 280 MPa, which was caused by the α-β quartz phase transition. Consequently, density loss, which is probably caused by the formation of micro-cracks at the transition from α- to β-quartz is more efficient at lower pressures. In addition, re-equilibration experiments were performed with a pure D2O pore fluid, to investigate diffusion processes at these experimental conditions. Diffusion of D2O is more efficient in β-quartz stability field, and may result in near total exchange of the original H2O content within only 19 days. Fluid inclusions re-equilibrated in the α-quartz stability field contain only half the amount of D2O within the same experimentation run time, up to 53 mol% D2O.
Bethel, Kelly; Luttgen, Madelyn S.; Damani, Samir; Kolatkar, Anand; Lamy, Rachelle; Sabouri-Ghomi, Mohsen; Topol, Sarah; Topol, Eric J.; Kuhn, Peter
2014-02-01
Elevated levels of circulating endothelial cells (CECs) occur in response to various pathological conditions including myocardial infarction (MI). Here, we adapted a fluid phase biopsy technology platform that successfully detects circulating tumor cells in the blood of cancer patients (HD-CTC assay), to create a high-definition circulating endothelial cell (HD-CEC) assay for the detection and characterization of CECs. Peripheral blood samples were collected from 79 MI patients, 25 healthy controls and six patients undergoing vascular surgery (VS). CECs were defined by positive staining for DAPI, CD146 and von Willebrand Factor and negative staining for CD45. In addition, CECs exhibited distinct morphological features that enable differentiation from surrounding white blood cells. CECs were found both as individual cells and as aggregates. CEC numbers were higher in MI patients compared with healthy controls. VS patients had lower CEC counts when compared with MI patients but were not different from healthy controls. Both HD-CEC and CellSearch® assays could discriminate MI patients from healthy controls with comparable accuracy but the HD-CEC assay exhibited higher specificity while maintaining high sensitivity. Our HD-CEC assay may be used as a robust diagnostic biomarker in MI patients.
Magnetohydrodynamic two-phase dusty fluid flow and heat model over deforming isothermal surfaces
Turkyilmazoglu, Mustafa
2017-01-01
This paper is devoted to the mathematical analysis of a magnetohydrodynamic viscous two-phase dusty fluid flow and heat transfer over permeable stretching or shrinking bodies. The wall boundary is subjected to a linear deformation as well as to a quadratic surface temperature. Such a highly nonlinear phenomenon, for the first time in the literature, is attacked to search for occurrence of exact solutions, whose numerical correspondences are already available for limited wall transpiration velocities. The obtained analytical solutions are found be in perfect line with the numerical computations. Besides this, exact solutions point to the existence of dual solutions for both permeable stretching and shrinking cases, which were not detected from the numerical studies up to date. The existence of such exact solutions and their parameter domain particularly depending on the wall suction or injection are successfully analyzed. The physical outcomes concerning the effects of suspended particles on the momentum and thermal boundary layers well-documented in the open literature can be best understood from the presented exact solutions.
An Overview of SBIR Phase 2 In-Space Propulsion and Cryogenic Fluids Management
Nguyen, Hung D.; Steele, Gynelle C.
2015-01-01
Technological innovation is the overall focus of NASA's Small Business Innovation Research (SBIR) program. The program invests in the development of innovative concepts and technologies to help NASA's mission directorates address critical research and development needs for agency projects. This report highlights innovative SBIR Phase II projects from 2007-2012 specifically addressing Areas in In-Space Propulsion and Cryogenic Fluids Management which is one of six core competencies at NASA Glenn Research Center. There are nineteen technologies featured with emphasis on a wide spectrum of applications such as high-performance Hall thruster support system, thruster discharge power converter, high-performance combustion chamber, ion thruster design tool, green liquid monopropellant thruster, and much more. Each article in this booklet describes an innovation, technical objective, and highlights NASA commercial and industrial applications. This report serves as an opportunity for NASA personnel including engineers, researchers, and program managers to learn of NASA SBIR's capabilities that might be crosscutting into this technology area. As the result, it would cause collaborations and partnerships between the small companies and NASA Programs and Projects resulting in benefit to both SBIR companies and NASA.
Goto, Hiroki; Aichi, Masaatsu; Tokunaga, Tomochika; Yamamoto, Hajime; Ogawa, Toyokazu; Aoki, Tomoyuki
2014-08-01
Coupled two-phase fluid flow and poroelastic deformation of Berea sandstone is studied through laboratory experiment and numerical simulation. In the experiment, compressed air was infiltrated from the bottom of a water-saturated cylindrical Berea sandstone sample under hydrostatic external stress condition. Both axial and circumferential strains at half the height of the sample showed sudden extension and monotonic and gradual extension afterward. Numerical simulation based on thermodynamically consistent constitutive equations was conducted in order to quantitatively analyze the experimental results. In a simulation assuming isotropy of material properties, the volumetric discharge rate of water at the outlet and one of the axial, circumferential, and volumetric strains at half the height of the sample were reproduced well by each parameter set, while the other two strains were not. When introducing transverse isotropy, all the experimental data were reproduced well. In addition, the effect of saturation dependency of Bishop's effective stress coefficient on the deformation behavior of porous media was discussed, and it was found that strains, both axial and circumferential, are sensitive to the coefficient.
Fluid-structure interaction of complex bodies in two-phase flows on locally refined grids
Angelidis, Dionysios; Shen, Lian; Sotiropoulos, Fotis
2016-11-01
Many real-life flow problems in engineering applications involve fluid-structure interaction (FSI) of arbitrarily complex geometries interacting with free surface flows. Despite the recent significant computational advances, conventional numerical methods are inefficient to resolve the prevailing complex dynamics due to the inherent large disparity of spatial and temporal scales that emerge in the air/water phases of the flow and around rigid bodies. To this end, the new generation 3D, unsteady, unstructured Cartesian incompressible flow solver, developed at the Saint Anthony Falls Laboratory (SAFL), is integrated with a FSI immersed boundary method and is coupled with the level-set formulation. The predictive capabilities of our method to simulate non-linear free surface phenomena, with low computational cost, are significantly improved by locally refining the computational grid in the vicinity of solid boundaries and around the free surface interface. We simulate three-dimensional complex flows involving complex rigid bodies interacting with a free surface both with prescribed body motion and coupled FSI and we investigate breaking wave events. In all the cases, very good agreement with benchmark data is found. This material is based upon work supported by the National Science Foundation (CBET-1509071).
de Strulle, Ronald; Rheinhart, Maximilian
2012-03-01
We report macroscale environmentally-neutral use of cryogenic fluids to induce phase transitions from crystalline water-ices to amorphous solid water (ASW). New IP and uses in remediation of oil-spills and hazardous immiscibles from aquatic environments. We display high-resolution images of the transitions from hexagonal to cubic crystalline water-ice, then to hydrophobic ASW. Accretion and encapsulation of viscous pollutants within crystalline water-ice, and sequestration of condensed volatiles (PAH, methane) and low viscosity fluids within the interstitial cavities of ASW are shown and differentiated for: crude oils, diesel (heating) and blended oils, petroleum byproducts, vegetable and mineral oils, lipids, and light immiscible fluids. The effects of PdV work and thermal energy transfers during phase changes are shown, along with the sequestration efficiencies for hexagonal and cubic ice lattices vs. non-crystalline ASW, for a range of pollutant substances. The viability of ASW as a medium for study of quantum criticality phases is also proposed. The process is environmentally-neutral in that only substantially condensed-phase air liquefaction products, e.g. nitrogen in >90% liquid phase are employed as an active agent. The applications are also presented in terms of the scale-up of experiments performed at the nanoscale.
Energy Technology Data Exchange (ETDEWEB)
Butto, C. [Universite Paul Sabatier, LESETH, 31 - Toulouse (France)
1996-12-31
Two-phase fluid loops with capillary pumping are particularly interesting silent devices which allow energy savings and do not create any noise pollution (no mechanical vibrations). In terrestrial environment, the gravity field, when judiciously used, allows to improve their performances and thus, their use in thermal regulation of big computers, power electronic components, transformers, etc, is particularly interesting. In this study, the main results concerning the functioning of such a loop in the gravity field are presented and used to highlight the conditions that allow to take advantage of this field and the improvements obtained. (J.S.) 5 refs.
Directory of Open Access Journals (Sweden)
Mathilde Blaise
2015-07-01
Full Text Available A Carnot type engine with a changing phase during the heating and the cooling is modeled with its thermal contact with the heat source. In a first optimization, the optimal high temperature of the cycle is determined to maximize the power output. The temperature and the mass flow rate of the heat source are given. This does not take into account the converter internal fluid and its mass flow rate. It is an exogenous optimization of the converter. In a second optimization, the endogenous optimization, the isothermal heating corresponds only to the vaporization of the selected fluid. The maximization of the power output gives the optimal vaporization temperature of the cycled fluid. Using these two optima allows connecting the temperature of the heat source to the working fluid used. For a given temperature level, mass flow rate and composition of the waste heat to recover, an optimal fluid and its temperature of vaporization are deduced. The optimal conditions size also the internal mass flow rate and the compression ratio (pump size. The optimum corresponds to the maximum of the power output and must be combined with the environmental fluid impact and the technological constraints.
DEFF Research Database (Denmark)
Coman, Paul Tiberiu; Veje, Christian
2014-01-01
This paper presents a dynamic model for simulating the heat generation and the impact of Phase Change Materials (PCMs) on the maximum temperature in LiFePO4 battery cells. The model is constructed by coupling a one-dimensional electro-chemical model with a two-dimensional thermal model and fluid...... flow model in a battery pack array. Two different physics are analysed and compared, one when the heat equation is considered for the PCM (no-flow case) and another one when fluid flow is considered. The results show that by using PCMs, the maximum temperature drops considerably for both physics...
Two-Phase Flow in Wire Coating with Heat Transfer Analysis of an Elastic-Viscous Fluid
Directory of Open Access Journals (Sweden)
Zeeshan Khan
2016-01-01
Full Text Available This work considers two-phase flow of an elastic-viscous fluid for double-layer coating of wire. The wet-on-wet (WOW coating process is used in this study. The analytical solution of the theoretical model is obtained by Optimal Homotopy Asymptotic Method (OHAM. The expression for the velocity field and temperature distribution for both layers is obtained. The convergence of the obtained series solution is established. The analytical results are verified by Adomian Decomposition Method (ADM. The obtained velocity field is compared with the existing exact solution of the same flow problem of second-grade fluid and with analytical solution of a third-grade fluid. Also, emerging parameters on the solutions are discussed and appropriate conclusions are drawn.
Lipoprotein accumulation in macrophages via TLR4-dependent fluid phase uptake
Choi, Soo-Ho; Harkewicz, Richard; Lee, Jee Hyun; Boullier, Agnès; Almazan, Felicidad; Li, Andrew C.; Witztum, Joseph L.; Bae, Yun Soo; Miller, Yury I.
2009-01-01
Toll-like receptor-4 (TLR4) recognizes microbial pathogens, such as lipopolysaccharide (LPS), and mediates LPS-induced proinflammatory cytokine secretion, as well as microbial uptake by macrophages. In addition to exogenous pathogens, TLR4 recognizes modified self, such as minimally oxidized low-density lipoprotein (mmLDL). Here we report that mmLDL and its active components, cholesteryl ester (CE) hydroperoxides, induce TLR4-dependent fluid phase uptake typical of macropinocytosis. We show that mmLDL induced recruitment of spleen tyrosine kinase (Syk) to a TLR4 signaling complex, TLR4 phosphorylation, activation of a Vav1-Ras-Raf-MEK-ERK1/2 signaling cascade, phosphorylation of paxillin, and activation of Rac, Cdc42 and Rho. These mmLDL-induced and TLR4- and Syk-dependent signaling events and cytoskeletal rearrangements lead to enhanced uptake of small molecules, dextran and, most importantly, of both native and oxidized LDL, resulting in intracellular lipid accumulation. An intravenous injection of fluorescently labeled mmLDL in wild type mice resulted in its rapid accumulation in circulating monocytes, which was significantly attenuated in TLR4-deficient mice. These data describe a novel mechanism leading to enhanced lipoprotein uptake in macrophages that would contribute to foam cell formation and atherosclerosis. These data also suggest that CE hydroperoxides are an endogenous ligand for TLR4. As TLR4 is highly expressed on the surface of circulating monocytes in patients with chronic inflammatory conditions, and CE hydroperoxides are present in plasma, lipid uptake by monocytes in circulation may contribute to monocytes' pathological roles in chronic inflammatory diseases. PMID:19461045
Sowers, Susanne Lynn
1997-11-01
Microporous sorbents such as carbons, silicas and aluminas are used commercially in a variety of separation, purification and selective reaction applications. A detailed study of the effects of the porous material characteristics on the adsorption equilibrium properties such as selectivity and phase equilibria of fluid mixtures can enhance our understanding of adsorption on a molecular level. Such knowledge will improve our utilization of such adsorbents and provide a tool for directing the future of tailoring sorbents for particular separation processes. The effect of pore size, shape and pressure on the selective adsorption of trace pollutants from an inert gas was studied using prototype mixtures of Lennard-Tones (LJ) N2/CCl4, CF4, and SO2. Both nonlocal density functional theory (DFT) and grand canonical Monte Carlo (GCMC) molecular simulations were used in order to investigate the validity of the theory, which is much quicker and easier to use. Our results indicate that there is an optimal pore size and shape for which the pollutant selectivity is greatly enhanced. In many industrial adsorption processes relative humidity can greatly affect the life of an adsorbent bed, as seen in breakthrough curves. Therefore, the influence of water vapor on the selective adsorption of CCl4 from a mixture of N2/CCl4/H20 in activated carbon was studied using GCMC simulations. The equilibrium adsorption properties are found to be dependent upon both the density of active sites on the pore walls and the relative humidity. Liquid-liquid transitions in porous materials are of interest in connection with oil recovery, lubrication, coating technology and pollution control. The results of a study on the effect of confinement on the liquid-liquid equilibrium of binary LJ mixtures using DFT are compared with those of molecular simulation and experiments. Our findings show that the phase coexistence for the confined mixture is in general decreased and shifted toward the component which
Georgiev, Georgi As; Sarker, Dipak K; Al-Hanbali, Othman; Georgiev, Georgi D; Lalchev, Zdravko
2007-10-01
Foam thin liquid films (TLF) and monolayers at the air-water interface formed by DMPC mixed with DMPE-bonded poly (ethylene glycol)s (DMPE-PEG(550), DMPE-PEG(2000) and DMPE-PEG(5000)) were obtained. The influence of both (i) PEG chain size (evaluated in terms of Mw) and mushroom-to-brush conformational transition and (ii) of the liposome/micelle ratio in the film-forming dispersions, on the interfacial properties of mixed DMPC/DMPE-PEG films was compared. Foam film studies demonstrated that DMPE-PEG addition to foam TLFs caused (i) delayed kinetics of film thinning and black spot expansion and (ii) film stabilization. At the mushroom-to-brush transition, due to steric repulsion increased DMPE-PEG films thickness reached 25 nm while pure DMPC films were only 8 nm thick Newton black films. It was possible to differentiate DMPE-PEG(2000/5000) from DMPE-PEG(550) by the ability to change foam TLF formation mechanism, which could be of great importance for "stealth" liposome design. Monolayer studies showed improved formation kinetics and equilibrium surface tension decrease for DMPE-PEG monolayers compared with DMPC pure films. SEM observations revealed "smoothing" and "sealing" of the defects in the solid-supported layer surface by DMPE-PEGs adsorption, which could explain DMPE-PEGs ability to stabilize TLFs and to decrease monolayer surface tension. All effects in monolayers, foam TLFs and solid-supported layers increased with the increase of PEG Mw and DMPE-PEG concentration. However, at the critical DMPE-PEG concentration (where mushroom-to-brush conformational transition occurred) maximal magnitude of the effects was reached, which only slightly changed at further DMPE-PEG content and micelle/liposome ratio increase.
Wiejak, J; Surmacz, L; Wyroba, E
2001-01-01
The kinetics of the uptake of the fluid phase marker Lucifer Yellow (LY), and its alteration by wortmannin, an inhibitor of phosphatidylinositol-3 kinase (PI-3K), and the PKC modulators: GF 109203 X, an inhibitor, and phorbol ester, an activator was studied in eukaryotic model Paramecium aurelia. Spectrophotometric quantification of LY accumulation was performed in the presence or absence of transferrin, a marker of receptor-mediated endocytosis. Internalization of LY showed a curvilinear kinetics: the high initial rate of LY uptake (575 ng LY/mg protein/hr) decreased almost 5-fold within 15 min, reaching plateau at 126 ng/mg protein/hr. Transferrin induced a small increase (7.5%) in the fluid phase uptake rate (after 5 min) followed by a small decrease at longer incubation times. Lucifer Yellow and transferrin (visualized by streptavidin-FITC) were localized in Paramecium by 3-D reconstruction by confocal microscopy. LY showed a scattered, diffuse fluorescence typical of fluid phase uptake whereas transferrin accumulated in membrane-surrounded endosomes. Wortmannin did not affect LY accumulation but decreased it when transferrin was present in the incubation medium. This suggests an effect on the transferrin uptake pathway, presumably on the stage of internalization in "mixing" endosomes to which transferrin and LY were targeted. Phorbol ester diminished LY accumulation by 22% and this effect persisted up to 25 min of incubation. PKC inhibitor did not affect LY uptake. However, in the presence of transferrin, the LY uptake increased within the first 15 minutes followed by a rapid 20% decrease in comparison to the control. Such an effect of PKC modulators suggests that PMA action on fluid phase uptake is not directly mediated by PKC.
Directory of Open Access Journals (Sweden)
J Wiejak
2009-12-01
Full Text Available The kinetics of the uptake of the fluid phase marker Lucifer Yellow (LY, and its alteration by wortmannin, an inhibitor of phosphatidylinositol-3 kinase (PI-3K, and the PKC modulators: GF 109203 X, an inhibitor, and phorbol ester, an activator was studied in eukaryotic model Paramecium aurelia. Spectrophotometric quantification of LY accumulation was performed in the presence or absence of transferrin, a marker of receptor-mediated endocytosis. Internalization of LY showed a curvilinear kinetics: the high initial rate of LYuptake (575 ng LY/ mg protein /hr decreased almost 5-fold within 15 min, reaching plateau at 126 ng/ mg protein /hr. Transferrin induced a small increase (7.5% in the fluid phase uptake rate (after 5 min followed by a small decrease at longer incubation times. Lucifer Yellow and transferrin (visualized by streptavidin– FITC were localized in Paramecium by 3-D reconstruction by confocal microscopy. LY showed a scattered, diffuse fluorescence typical of fluid phase uptake whereas transferrin accumulated in membrane-surrounded endosomes. Wortmannin did not affect LY accumulation but decreased it when transferrin was present in the incubation medium. This suggests an effect on the transferrin uptake pathway, presumably on the stage of internalization in “mixing” endosomes to which transferrin and LY were targeted. Phorbol ester diminished LY accumulation by 22% and this effect persisted up to 25 min of incubation. PKC inhibitor did not affect LY uptake. However, in the presence of transferrin, the LY uptake increased within the first 15 minutes followed by a rapid 20% decrease in comparison to the control. Such an effect of PKC modulators suggests that PMA action on fluid phase uptake is not directly mediated by PKC.
Turbulent mixing and a generalized phase transition in shear-thickening fluids
Baumert, Helmut Z
2016-01-01
This paper presents a new theory of turbulent mixing in stirred reactors. The degree of homogeneity of a mixed fluid may be characterized by the Kolmogorov micro-scale. The smaller its value, the better homogeneity. The micro-scale scales inversely with the fourth root of the energy dissipation rate in the stirring process. The higher this rate, the smaller lambda, and the better the homogeneity in the reactor. This is true for Newtonian fluids. In non-Newtonian fluids the situation is different. For instance, in shear-thickening fluids it is plausible that high shear rates thicken the fluid and might strangle the mixing. The internal interactions between different fluid-mechanical and colloidal variables are subtle, namely due to the (until recently) very limited understanding of turbulence. Starting from a qualitatively new turbulence theory for inviscid fluids [Baumert, 2013], giving e.g. the Karman constant as $(2\\pi)^{-1/2} = 0.40$ [the super-pipe in Princeton gave 0.40 p/m 0.02, Bailey et al., 2014], we...
Directory of Open Access Journals (Sweden)
Dali Hou
2016-01-01
Full Text Available Due to the special phase behavior of near-critical fluid, the development approaches of near-critical condensate gas and near-critical volatile oil reservoirs differ from conventional oil and gas reservoirs. In the near-critical region, slightly reduced pressure may result in considerable change in gas and liquid composition since a large amount of gas or retrograde condensate liquid is generated. It is of significance to gain insight into the composition variation of near-critical reservoir during the depletion development. In our study, we performed a series of PVT experiments on a real near-critical gas condensate reservoir fluid. In addition to the experimental studies, a commercial simulator combined with the PREOS model was utilized to study retrograde condensate characteristics and reevaporation mechanism of condensate oil with CO2 injection based on vapor-liquid phase equilibrium thermodynamic theory. The research shows that when reservoir pressure drops below a certain pressure, the variation of retrograde condensate liquid saturation of the residual reservoir fluid exhibits the phase behavior of volatile oil.
Goldstein, Raymond Ethan
The longstanding problem of the precise correspondence between critical phenomena in fluids and ferromagnets is resolved in Part I through a synthesis of mean field theory, exact results for lattice models, field-theoretic techniques, and by extensive quantitative comparison with experiment. Emphasis is placed on the origin of broken particle-hole symmetry in fluids as reflected in the form of the critical point scaling fields and in systematic variations in certain nonuniversal critical amplitudes with molecular polarizability. Those trends and the degree to which the scaling axes are linearly mixed versions of the bare "thermal" and "magnetic" fields in particle-hole symmetric systems are shown both for lattice models and real fluids to be intimately related to the presence of many-body interactions of the Axilrod-Teller type. A quantitatively accurate microscopic expression for the field-mixing operator of fluids is derived on the basis of an exact Hubbard-Stratonovich transformation relating the fluid Hamiltonian to that of a Landau-Ginzburg-Wilson model. A phenomenological theory of the phase behavior of multilamellar liquid crystals of hydrated phospholipid bilayers is developed in Part II, and its predictions tested by extensive comparison with experiment. A Ginzburg-Landau free energy functional based on the elastic properties of two coupled monolayers is proposed to describe intrabilayer ordering, and the phenomenon of structural phase transitions driven by membrane interactions is described by incorporating in addition the attractive dispersion interactions and repulsive "hydration" forces acting between membranes. The theory indicates and experiments support a connection between the pseudocriticality of the bilayer transitions and the large susceptibility of the in-plane order to membrane interactions. The pseudocriticality in turn is suggested to arise from the analog of a capillary critical point accessible by finite-size effects. Theoretical phase
Herring, Anna L.; Middleton, Jill; Walsh, Rick; Kingston, Andrew; Sheppard, Adrian
2017-09-01
We investigate capillary pressure-saturation (PC-S) relationships for drainage-imbibition experiments conducted with air (nonwetting phase) and brine (wetting phase) in Bentheimer sandstone cores. Three different flow rate conditions, ranging over three orders of magnitude, are investigated. X-ray micro-computed tomographic imaging is used to characterize the distribution and amount of fluids and their interfacial characteristics. Capillary pressure is measured via (1) bulk-phase pressure transducer measurements, and (2) image-based curvature measurements, calculated using a novel 3D curvature algorithm. We distinguish between connected (percolating) and disconnected air clusters: curvatures measured on the connected phase interfaces are used to validate the curvature algorithm and provide an indication of the equilibrium condition of the data; curvature and volume distributions of disconnected clusters provide insight to the snap-off processes occurring during drainage and imbibition under different flow rate conditions.
Institute of Scientific and Technical Information of China (English)
WANG Haijun; HONG Xiaozhong; GU Fang; BA Xinwu
2006-01-01
The influence of hydrogen bonds on the physical and chemical properties of hydrogen bonding fluid system of AaDd type is investigated from two viewpoints by the principle of statistical mechanics. In detail, we proposed two new ways that can be used to obtain the equilibrium size distribution of the hydrogen bonding clusters, and derived the analytical expression of a relationship between the hydrogen bonding free energy and hydrogen bonding degree. For the nonlinear hydrogen bonding systems, it is shown that the sol-gel phase transition can take place under proper conditions, which is further proven to be a kind of geometrical phase transition rather than a thermodynamic one. Moreover, several problems associated with the geometrical phase transition and liquid-solid phase transition in nonlinear hydrogen bonding systems are discussed.
Thermally responsive phospholipid preparations for fluid steering and separation in microfluidics.
Wu, Xingwei; Langan, Ted J; Durney, Brandon C; Holland, Lisa A
2012-09-01
Aqueous phospholipid preparations comprised of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) are prevalent materials for biological characterization and become gel-like near physiological temperature, but have a low viscosity below 24°C. The rheology of 20% phospholipid preparations of [DMPC]/[DHPC] = 2.5 reveals that, under conditions utilized for fluid steering, the materials are shear-thinning power-law fluids with a power-law index ranging from 0.30 through 0.90. Phospholipid preparations are utilized to steer fluids in microfluidic chips and support hydrodynamic delivery of sample across a double T injection region in a chip. The fact that the phospholipids are fully integrated as a valving material as well as a separation medium is demonstrated through the separation of linear oligosaccharides labeled with 1-aminopyrene-3,6,8-trisulfonic acid.
Saho, Tatsunori; Onishi, Hideo
2015-12-01
Detailed strategy for regional hemodynamics is significant for knowledge of plaque development on vascular diseases such as atherosclerosis. The aim of this study was to derive relation between atherosclerosis and hemodynamics at human carotid bifurcation by the use of computational fluid dynamics (CFD), and to provide more accurate hemodynamic information. Blood velocity datasets at common carotid artery were obtained by phase-contrast cine magnetic resonance imaging (PC cine MRI). Carotid bifurcation model was computed for systolic, mid-diastolic, and end-diastolic phase. Comparison of wall shear stress (WSS) was performed for each cardiac phase. PC cine MRI provided velocity measurement for common carotid artery with various cardiac phases. The blood velocity had acute variation from 0.21 m/s to 1.07 m/s at systolic phase. The variation of WSS during cardiac phase was presented at carotid bifurcation model. High shear stress area was observed at dividing wall for all cardiac phases. The systole-diastole WSS ratio was 10.15 at internal carotid side of bifurcation. And low shear stress (cine MRI was allowed to determine an accurate analysis condition. This led to the representation of hemodynamics in vivo.
Geiger, S.; Driesner, T.; Matthai, S.; Heinrich, C.
2002-12-01
Realistic modelling of multi-phase fluid flow, energy and component transport in magmatic-hydrothermal systems is very challenging because hydrological properties of fluids and rocks vary over many orders of magnitude and the geometric complexities of such systems. Furthermore, density dependent component transport and transient permeability variations due to P-T changes and fluid-rock interactions introduce additional difficulties. As a result, the governing equations for the hydrodynamics, energy and component transport, and thermodynamics in magmatic hydrothermal systems are highly non-linear and strongly coupled. Essential requirements of a numerical formulation for such a system are: (1) a treatment of the hydrodynamics that can accurately resolve complex geological structures and represent the highly variable fluid velocities herein, (2) a realistic thermodynamic representation of the fluid properties including the wide P-T-X range of liquid+vapour coexistence for the highly saline fluids, and (3) an accurate handling of the highly contrasting transport properties of the two fluids. We are combining higher order finite-element (FE) methods with total variation diminishing finite volume (TVDFV) methods to model the hydrodynamics and energy and component transport of magmatic hydrothermal systems. Combined FE and TVDFV methods are mass and shock preserving, yield great geometric flexibility in 2D and 3D [2]. Furthermore, efficient matrix solvers can be employed to model fluid flow in geologically realistic structures [5]. The governing equations are linearized by operator-splitting and solved sequentially using a Picard iteration scheme. We chose the system water-NaCl as a realistic proxy for natural fluids occurring in magmatic-hydrothermal systems. An in-depth evaluation of the available experimental and theoretical data led to a consistent and accurate set of formulations for the PVTXH relations that are valid from 0 to 800 C, 0 to 500 MPa, and 0 to 1 XNa
Bhandari, Pradeep; Dudik, Brenda; Birur, Gajanana; Karlmann, Paul; Bame, David; Mastropietro, A. J.
2012-01-01
For single phase mechanically pumped fluid loops used for thermal control of spacecraft, a gas charged accumulator is typically used to modulate pressures within the loop. This is needed to accommodate changes in the working fluid volume due to changes in the operating temperatures as the spacecraft encounters varying thermal environments during its mission. Overall, the three key requirements on the accumulator to maintain an appropriate pressure range throughout the mission are: accommodation of the volume change of the fluid due to temperature changes, avoidance of pump cavitation and prevention of boiling in the liquid. The sizing and design of such an accumulator requires very careful and accurate accounting of temperature distribution within each element of the working fluid for the entire range of conditions expected, accurate knowledge of volume of each fluid element, assessment of corresponding pressures needed to avoid boiling in the liquid, as well as the pressures needed to avoid cavitation in the pump. The appropriate liquid and accumulator strokes required to accommodate the liquid volume change, as well as the appropriate gas volumes, require proper sizing to ensure that the correct pressure range is maintained during the mission. Additionally, a very careful assessment of the process for charging both the gas side and the liquid side of the accumulator is required to properly position the bellows and pressurize the system to a level commensurate with requirements. To achieve the accurate sizing of the accumulator and the charging of the system, sophisticated EXCEL based spreadsheets were developed to rapidly come up with an accumulator design and the corresponding charging parameters. These spreadsheets have proven to be computationally fast and accurate tools for this purpose. This paper will describe the entire process of designing and charging the system, using a case study of the Mars Science Laboratory (MSL) fluid loops, which is en route to
Numerical simulation of an acoustic field generated by a phased arc array in a fluid-filled borehole
Institute of Scientific and Technical Information of China (English)
Che Xiaohua; Qiao Wenxiao
2009-01-01
The acoustic tools widely used in borehole well logging and being developed in borehole acoustic reflection imaging do not have the function of azimuthal measurement due to a symmetric source, so they can not be used to evaluate the azimuthal character of borehole formation. In this paper, a 3D finite difference method was used to simulate the acoustic fields in a fluid-filled borehole generated by a traditional monopole source and a phased arc array. Acoustic waveforms were presented for both cases. The analysis of the simulated waveforms showed that different from the monopole source, the acoustic energy generated by the phased arc array transmitter mainly radiated to the borehole in a narrow azimuthal range, which was the key technique to implement azimuthal acoustic well logging. Similar to the monopole source, the waveforms generated by the phased arc array in the fluid-filled borehole also contain compressional (P) waves and shear (S) waves refracted along the borehole, which is the theoretical foundation of phased arc array acoustic well logging.
Institute of Scientific and Technical Information of China (English)
张小斌; 姚蕾; 邱利民; 张学军
2013-01-01
Characterizing the complex two-phase hydrodynamics in structured packed columns requires a power-ful modeling tool. The traditional two-dimensional model exhibits limitations when one attempts to model the de-tailed two-phase flow inside the columns. The present paper presents a three-dimensional computational fluid dy-namics (CFD) model to simulate the two-phase flow in a representative unit of the column. The unit consists of an entire corrugation channel and describes well the real liquid flow conditions. The detailed unsteady two-phase 3D CFD calculations on column packed with Flexipak 1Y were implemented within the volume of fluid (VOF) mathe-matical framework. The CFD model was validated by comparing the calculated thickness of liquid film with the available experimental data. Special attention was given to quantitative analysis of the effects of gravity on the hy-drodynamics. Fluctuations in the liquid mass flow rate and the calculated pressure drop loss were found to be quali-tatively in agreement with the experimental observations.
Energy Technology Data Exchange (ETDEWEB)
Abu Saleem, Rabie A., E-mail: raabusaleem@just.edu.jo [Nuclear Engineering Department, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110 (Jordan); Kozlowski, Tomasz, E-mail: txk@illinois.edu [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, 216 Talbot Laboratory, 104 S. Wright St., Urbana, IL 61801 (United States); Shrestha, Rijan, E-mail: rijan.shrestha@intel.com [Portland Technology Development, Intel Corporation, 2501 NW 229th Ave Hillsboro OR 97124 (United States)
2016-05-15
Highlights: • The two-fluid model and the challenges associated with its numerical modeling are investigated. • A high-order solver based on flux limiter schemes and the theta method was developed. • The solver was compared to existing thermal hydraulics codes used in nuclear industry. • The solver was shown to handle fast transients with discontinuities and phase change. - Abstract: Finite volume techniques with staggered mesh are used to develop a new numerical solver for the one-dimensional two-phase two-fluid model using a high-resolution, Total Variation Diminishing (TVD) scheme. The solver is implemented to analyze numerical benchmark problems for verification and testing its abilities to handle discontinuities and fast transients with phase change. Convergence rates are investigated by comparing numerical results to analytical solutions available in literature for the case of the faucet flow problem. The solver based on a new TVD scheme is shown to exhibit higher-order of accuracy compared to other numerical schemes. Mass errors are also examined when phase change occurs for the shock tube problem, and compared to those of the 1st-order upwind scheme implemented in the nuclear thermal-hydraulics code TRACE. The solver is shown to exhibit numerical stability when applied to problems with discontinuous solutions and results of the new solver are free of spurious oscillations.
Energy Technology Data Exchange (ETDEWEB)
Serrato, M. G.
2013-09-27
located at the Florida International University Applied Research Center, Miami, FL (FIU-ARC). A follow-on fluid injection test was developed to detect fluid and ion migration in a cementitious material/grouted test cube using a limited number of existing embedded sensor systems. This In Situ Decommissioning Sensor Network, Meso-Scale Test Bed (ISDSN-MSTB) - Phase 3 Fluid Injection Test Summary Report summarizes the test implementation, acquired and processed data, and results from the activated embedded sensor systems used during the fluid injection test. The ISDSN-MSTB Phase 3 Fluid Injection Test was conducted from August 27 through September 6, 2013 at the FIU-ARC ISDSN-MSTB test cube. The fluid injection test activated a portion of the existing embedded sensor systems in the ISDSN-MSTB test cube: Electrical Resistivity Tomography-Thermocouple Sensor Arrays, Advance Tensiometer Sensors, and Fiber Loop Ringdown Optical Sensors. These embedded sensor systems were activated 15 months after initial placement. All sensor systems were remotely operated and data acquisition was completed through the established Sensor Remote Access System (SRAS) hosted on the DOE D&D Knowledge Management Information Tool (D&D DKM-IT) server. The ISDN Phase 3 Fluid Injection Test successfully demonstrated the feasibility of embedding sensor systems to assess moisture-fluid flow and resulting transport potential for contaminate mobility through a cementitious material/grout monolith. The ISDSN embedded sensor systems activated for the fluid injection test highlighted the robustness of the sensor systems and the importance of configuring systems in-depth (i.e., complementary sensors and measurements) to alleviate data acquisition gaps.
Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio
2016-04-21
We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.
May, Helge-Otmar; Mausbach, Peter
2012-03-01
The behavior of thermodynamic response functions and the thermodynamic scalar curvature in the supercritical region have been studied for a Lennard-Jones fluid based on a revised modified Benedict-Webb-Rubin equation of state. Response function extrema are sometimes used to estimate the Widom line, which is characterized by the maxima of the correlation lengths. We calculated the Widom line for the Lennard-Jones fluid without using any response function extrema. Since the volume of the correlation length is proportional to the Riemannian thermodynamic scalar curvature, the locus of the Widom line follows the slope of maximum curvature. We show that the slope of the Widom line follows the slope of the isobaric heat capacity maximum only in the close vicinity of the critical point and that, therefore, the use of response function extrema in this context is problematic. Furthermore, we constructed the vapor-liquid coexistence line for the Lennard-Jones fluid using the fact that the correlation length, and therefore the thermodynamic scalar curvature, must be equal in the two coexisting phases. We compared the resulting phase envelope with those from simulation data where multiple histogram reweighting was used and found striking agreement between the two methods.
Liu, Yu; Yu, Xiping
2016-09-01
A coupled phase-field and volume-of-fluid method is developed to study the sensitive behavior of water waves during breaking. The THINC model is employed to solve the volume-of-fluid function over the entire domain covered by a relatively coarse grid while the phase-field model based on Allen-Cahn equation is applied over the fine grid. A special algorithm that takes into account the sharpness of the diffuse-interface is introduced to correlate the order parameter obtained on the fine grid and the volume-of-fluid function obtained on the coarse grid. The coupled model is then applied to the study of water waves generated by moving pressures on the free surface. The deformation process of the wave crest during the initial stage of breaking is discussed in details. It is shown that there is a significant variation of the free nappe developed at the front side of the wave crest as the wave steepness differs. It is of a plunging type at large wave steepness while of a spilling type at small wave steepness. The numerical results also indicate that breaking occurs later and the duration of breaking is shorter for waves of smaller steepness and vice versa. Neglecting the capillary effect leads to wave breaking with a sharper nappe and a more dynamic plunging process. The surface tension also has an effect to prevent the formation of a free nappe at the front side of the wave crest in some cases.
Moebius, F.; Or, D.
2012-12-01
Dynamics of fluid fronts in porous media shape transport properties of the unsaturated zone and affect management of petroleum reservoirs and their storage properties. What appears macroscopically as smooth and continuous motion of a displacement fluid front may involve numerous rapid interfacial jumps often resembling avalanches of invasion events. Direct observations using high-speed camera and pressure sensors in sintered glass micro-models provide new insights on the influence of flow rates, pore size, and gravity on invasion events and on burst size distribution. Fundamental differences emerge between geometrically-defined pores and "functional" pores invaded during a single burst (invasion event). The waiting times distribution of individual invasion events and decay times of inertial oscillations (following a rapid interfacial jump) are characteristics of different displacement regimes. An invasion percolation model with gradients and including the role of inertia provide a framework for linking flow regimes with invasion sequences and phase entrapment. Model results were compared with measurements and with early studies on invasion burst sizes and waiting times distribution during slow drainage processes by Måløy et al. [1992]. The study provides new insights into the discrete invasion events and their weak links with geometrically-deduced pore geometry. Results highlight factors controlling pore invasion events that exert strong influence on macroscopic phenomena such as front morphology and residual phase entrapment shaping hydraulic properties after the passage of a fluid front.
Novitskiy, Alexander A; Ke, Jie; Comak, Gurbuz; Poliakoff, Martyn; George, Michael W
2011-08-01
A new continuous flow method using attenuated total reflection infrared (ATR-IR) spectroscopy has been developed for monitoring phase transitions in multicomponent fluids at high pressures and temperatures. Our approach uses Fourier transform infrared (FT-IR) and a modified Golden Gate attenuated total reflection (ATR) cell and exploits the fact that the absorbance of a vapor is much lower than that of the corresponding liquid to monitor the phase transition between vapor and liquid. We demonstrate that this method can provide quantitative measurements on both the dew point and the bubble point. We have validated our approach using three single-component systems (EtOH, MeOH, and H(2)O) and a binary system of EtOH + H(2)O, monitoring phase transitions at temperature up to 300 °C and pressure up to 10 MPa.
Modeling Two-Phase Flow and Vapor Cycles Using the Generalized Fluid System Simulation Program
Smith, Amanda D.; Majumdar, Alok K.
2017-01-01
This work presents three new applications for the general purpose fluid network solver code GFSSP developed at NASA's Marshall Space Flight Center: (1) cooling tower, (2) vapor-compression refrigeration system, and (3) vapor-expansion power generation system. These systems are widely used across engineering disciplines in a variety of energy systems, and these models expand the capabilities and the use of GFSSP to include fluids and features that are not part of its present set of provided examples. GFSSP provides pressure, temperature, and species concentrations at designated locations, or nodes, within a fluid network based on a finite volume formulation of thermodynamics and conservation laws. This paper describes the theoretical basis for the construction of the models, their implementation in the current GFSSP modeling system, and a brief evaluation of the usefulness of the model results, as well as their applicability toward a broader spectrum of analytical problems in both university teaching and engineering research.
Isotropic-nematic phase equilibria of hard-sphere chain fluids-Pure components and binary mixtures.
Oyarzún, Bernardo; van Westen, Thijs; Vlugt, Thijs J H
2015-02-14
The isotropic-nematic phase equilibria of linear hard-sphere chains and binary mixtures of them are obtained from Monte Carlo simulations. In addition, the infinite dilution solubility of hard spheres in the coexisting isotropic and nematic phases is determined. Phase equilibria calculations are performed in an expanded formulation of the Gibbs ensemble. This method allows us to carry out an extensive simulation study on the phase equilibria of pure linear chains with a length of 7 to 20 beads (7-mer to 20-mer), and binary mixtures of an 8-mer with a 14-, a 16-, and a 19-mer. The effect of molecular flexibility on the isotropic-nematic phase equilibria is assessed on the 8-mer+19-mer mixture by allowing one and two fully flexible beads at the end of the longest molecule. Results for binary mixtures are compared with the theoretical predictions of van Westen et al. [J. Chem. Phys. 140, 034504 (2014)]. Excellent agreement between theory and simulations is observed. The infinite dilution solubility of hard spheres in the hard-sphere fluids is obtained by the Widom test-particle insertion method. As in our previous work, on pure linear hard-sphere chains [B. Oyarzún, T. van Westen, and T. J. H. Vlugt, J. Chem. Phys. 138, 204905 (2013)], a linear relationship between relative infinite dilution solubility (relative to that of hard spheres in a hard-sphere fluid) and packing fraction is found. It is observed that binary mixtures greatly increase the solubility difference between coexisting isotropic and nematic phases compared to pure components.
Energy Technology Data Exchange (ETDEWEB)
Souza, Daniele Z., E-mail: daniele.dzs@dpf.gov.br [Setor Tecnico-Cientifico, Superintendencia Regional do Departamento de Policia Federal no Rio Grande do Sul, 1365 Ipiranga Avenue, Azenha, Zip Code 90160-093 Porto Alegre, Rio Grande do Sul (Brazil); Programa de Pos-Graduacao em Ciencias Farmaceuticas, Faculdade de Farmacia, Universidade Federal do Rio Grande do Sul, 2752 Ipiranga Avenue, Santana, Zip Code 90610-000 Porto Alegre, Rio Grande do Sul (Brazil); Boehl, Paula O.; Comiran, Eloisa; Mariotti, Kristiane C. [Programa de Pos-Graduacao em Ciencias Farmaceuticas, Faculdade de Farmacia, Universidade Federal do Rio Grande do Sul, 2752 Ipiranga Avenue, Santana, Zip Code 90610-000 Porto Alegre, Rio Grande do Sul (Brazil); Pechansky, Flavio [Centro de Pesquisa em Alcool e Drogas (CPAD), Hospital de Clinicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, 2350, Ramiro Barcelos Street, Zip Code 90035-903 Porto Alegre, Rio Grande do Sul (Brazil); Duarte, Paulina C.A.V. [Secretaria Nacional de Politicas sobre Drogas (SENAD), Esplanada dos Ministerios, Block ' A' , 5th floor, Zip Code 70050-907 Brasilia, Distrito Federal (Brazil); De Boni, Raquel [Centro de Pesquisa em Alcool e Drogas (CPAD), Hospital de Clinicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, 2350, Ramiro Barcelos Street, Zip Code 90035-903 Porto Alegre, Rio Grande do Sul (Brazil); Froehlich, Pedro E.; Limberger, Renata P. [Programa de Pos-Graduacao em Ciencias Farmaceuticas, Faculdade de Farmacia, Universidade Federal do Rio Grande do Sul, 2752 Ipiranga Avenue, Santana, Zip Code 90610-000 Porto Alegre, Rio Grande do Sul (Brazil)
2011-06-24
Graphical abstract: Highlights: > Propylchloroformate derivatization of amphetamine-type stimulants in oral fluid. > Direct immersion solid-phase microextraction/gas chromatography-mass spectrometry. > Linear range 2(4)-256 ng mL{sup -1}, detection limits 0.5-2 ng mL{sup -1}. > Accuracy 98-112%, precision <15% of RSD, recovery 77-112%. > Importance of residual evaluation in checking model goodness-of-fit. - Abstract: A method for the simultaneous identification and quantification of amphetamine (AMP), methamphetamine (MET), fenproporex (FEN), diethylpropion (DIE) and methylphenidate (MPH) in oral fluid collected with Quantisal{sup TM} device has been developed and validated. Thereunto, in-matrix propylchloroformate derivatization followed by direct immersion solid-phase microextraction and gas chromatography-mass spectrometry were employed. Deuterium labeled AMP was used as internal standard for all the stimulants and analysis was performed using the selected ion monitoring mode. The detector response was linear for the studied drugs in the concentration range of 2-256 ng mL{sup -1} (neat oral fluid), except for FEN, whereas the linear range was 4-256 ng mL{sup -1}. The detection limits were 0.5 ng mL{sup -1} (MET), 1 ng mL{sup -1} (MPH) and 2 ng mL{sup -1} (DIE, AMP, FEN), respectively. Accuracy of quality control samples remained within 98.2-111.9% of the target concentrations, while precision has not exceeded 15% of the relative standard deviation. Recoveries with Quantisal{sup TM} device ranged from 77.2% to 112.1%. Also, the goodness-of-fit concerning the ordinary least squares model in the statistical inference of data has been tested through residual plotting and ANOVA. The validated method can be easily automated and then used for screening and confirmation of amphetamine-type stimulants in drivers' oral fluid.
Note: Sound velocity of a soft sphere model near the fluid-solid phase transition.
Khrapak, Sergey A
2016-03-28
The quasilocalized charge approximation is applied to estimate the sound velocity of simple soft sphere fluid with the repulsive inverse-power-law interaction. The obtained results are discussed in the context of the sound velocity of the hard-sphere system and of liquid metals at the melting temperature.
Pelaez-Fernandez, M.; Souslov, Anton; Lyon, L. A.; Goldbart, P. M.; Fernandez-Nieves, A.
2015-03-01
We study ionic microgel suspensions composed of swollen particles for various single-particle stiffnesses. We measure the osmotic pressure π of these suspensions and show that it is dominated by the contribution of free ions in solution. As this ionic osmotic pressure depends on the volume fraction of the suspension ϕ , we can determine ϕ from π , even at volume fractions so high that the microgel particles are compressed. We find that the width of the fluid-solid phase coexistence, measured using ϕ , is larger than its hard-sphere value for the stiffer microgels that we study and progressively decreases for softer microgels. For sufficiently soft microgels, the suspensions are fluidlike, irrespective of volume fraction. By calculating the dependence on ϕ of the mean volume of a microgel particle, we show that the behavior of the phase-coexistence width correlates with whether or not the microgel particles are compressed at the volume fractions corresponding to fluid-solid phase coexistence.
DEFF Research Database (Denmark)
Gharnati, Loubna; Musko, Nikolai; Jensen, Anker Degn
2013-01-01
In the present study the influence of the amount of carbon dioxide on the catalytic performance during the propylene carbonate synthesis from propylene oxide and CO2 was investigated. The reaction was performed in high-pressure batch autoclaves using immobilized 1-hydroxyethyl-9-propyl......-cyclic guanidinium bromide on SBA-15 (HEPCGBr/SBA-15) as catalyst in the absence of any co-catalyst. It was found that the yield was strongly dependent on the amount of CO2 added to the system and that the phase behavior strongly changes along the reaction pathway. The Cubic-Plus-Association (CPA) equation of state......-phase region where a CO2-expanded reactant/product phase (larger volume due to the dissolution of carbon dioxide in the liquid phase) is present. Optimal conditions for performing the reaction have been derived which requires consideration not only of the phase behavior of the starting phase but also...
Shaw, Sachin; Murthy, P V S N
2010-09-01
The present investigation deals with finding the trajectories of the drug dosed magnetic carrier particle in a microvessel with two-phase fluid model which is subjected to the external magnetic field. The radius of the microvessel is divided into the endothelial glycocalyx layer in which the blood is assumed to obey Newtonian character and a core and plug regions where the blood obeys the non-Newtonian Herschel-Bulkley character which is suitable for the microvessel of radius 50 microm. The carrier particles, bound with nanoparticles and drug molecules are injected into the vascular system upstream from malignant tissue, and captured at the tumor site using a local applied magnetic field. The applied magnetic field is produced by a cylindrical magnet positioned outside the body and near the tumor position. The expressions for the fluidic force for the carrier particle traversing in the two-phase fluid in the microvessel and the magnetic force due to the external magnetic field are obtained. Several factors that influence the magnetic targeting of the carrier particles in the microvasculature, such as the size of the carrier particle, the volume fraction of embedded magnetic nanoparticles, and the distance of separation of the magnet from the axis of the microvessel are considered in the present problem. An algorithm is given to solve the system of coupled equations for trajectories of the carrier particle in the invasive case. The trajectories of the carrier particle are found for both invasive and noninvasive targeting systems. A comparison is made between the trajectories in these cases. Also, the present results are compared with the data available for the impermeable microvessel with single-phase fluid flow. Also, a prediction of the capture of therapeutic magnetic nanoparticle in the impermeable microvasculature is made for different radii, distances and volume fractions in both the invasive and noninvasive cases.
Thompson, Patricia A.; Hsu, Chiu-Hsieh; Green, Sylvan; Stopeck, Alison T.; Johnson, Karen; Alberts, David S.; Chow, H.-H. Sherry
2010-01-01
Regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) has been associated with reduced risk of breast cancer. Sulindac, a non-selective NSAID with both cyclooxygenase 2 (COX2) dependent and independent activities, is a candidate for breast chemoprevention. We conducted a Phase Ib trial in 30 women at increased risk for breast cancer to evaluate the breast tissue distribution of sulindac at two dose levels (150 mg q.d. and 150 mg b.i.d. for 6 weeks), using nipple aspirate fluid (NAF) as...
Wen, Jianping; Jia, Xiaoqiang; Cheng, Xianrui; Yang, Peng
2005-05-01
Hydrodynamic and gas-liquid mass transfer characteristics, such as liquid velocity, gas holdup, solid holdup and gas-liquid volumetric mass transfer coefficient, in the riser and downcomer of the gas-liquid-solid three-phase internal loop airlift bioreactors with complete gas recirculation for non-Newtonian fluids, were investigated. A mathematical model for the description of flow behavior and gas-liquid mass transfer of these bioreactors was developed. The predicted results of this model agreed well with the experimental data.
Lin, Jian-Yu; Shen, Yi; Ding, Hang; Liu, Nan-Sheng; Lu, Xi-Yun
2017-01-01
We develop a robust cut-cell method for numerical simulation of compressible two-phase flows with topology change of the fluid-fluid interface. In cut cell methods the flows can be solved in the finite volume framework and the jump conditions at the interface are resolved by solving a local Riemann problem. Therefore, cut cell methods can obtain interface evolution with high resolution, and at the same time satisfactorily maintain the conservation of flow quantities. However, it remains a challenge for the cut cell methods to handle interfaces with topology change or very high curvature, where the mesh is not sufficiently fine to resolve the interface. Inappropriate treatment could give rise to either distorted interface advection or unphysical oscillation of flow variables, especially when the regularization process (e.g. reinitialization in the level set methods) is implemented. A robust cut-cell method is proposed here, with the interface being tracked by a level set function. The local unphysical oscillation of flow variables in the presence of topology change is shown to be greatly suppressed by using a delayed reinitialization. The method can achieve second-order accuracy with respect to the interface position in the absence of topology changes of interface, while locally degrading to first-order at the interface region where topology change occurs. Its performance is examined through a variety of numerical tests, such as Rayleigh collapse, shock-bubble interaction, and shock-induced bubble collapse in water. Numerical results are compared against either benchmark solutions or experimental observations, and good agreement has been achieved qualitatively and/or quantitatively. Finally, we apply the method to investigating the collapse process of two tandem bubbles in water.
Phase autowaves in the near-electrode layer in the electrochemical cell with a magnetic fluid
Chekanov, V. V.; Kandaurova, N. V.; Chekanov, V. S.
2017-06-01
A change in color of the thin pellicle when light is reflected from the surface of the magnetic fluid at the interface with the transparent electrode in the electric field was observed. The formation of variable thickness near-electrode layer leads to a change in the spectrum of the reflected light depending on the applied voltage. Autowaves, that were observed in the layer are a unique object for the study of self-organization process.
Volume of Fluid (VOF) type advection methods in two-phase flow: a comparative study
Aniszewski, Wojciech; Marek, Maciej
2014-01-01
In this paper, four distinct approaches to Volume of Fluid (VOF) computational method are compared. Two of the methods are the 'simplified' VOF formulations, in that they do not require geometrical interface reconstruction. The assessment is made possible by implementing all four approaches into the same code as a switchable options. This allows to rule out possible influence of other parts of numerical scheme, be it the discretisation of Navier-Stokes equations or chosen approximation of curvature, so that we are left with conclusive arguments because only one factor differs the compared methods. The comparison is done in the framework of CLSVOF (Coupled Level Set Volume of Fluid), so that all four methods are coupled with Level Set interface, which is used to compute pressure jump via the GFM (Ghost-Fluid Method). Results presented include static advections, full N-S solutions in laminar and turbulent flows. The paper is aimed at research groups who are implementing VOF methods in their computations or inte...
Single-Phase Flow of Non-Newtonian Fluids in Porous Media
Sochi, Taha
2009-01-01
The study of flow of non-Newtonian fluids in porous media is very important and serves a wide variety of practical applications in processes such as enhanced oil recovery from underground reservoirs, filtration of polymer solutions and soil remediation through the removal of liquid pollutants. These fluids occur in diverse natural and synthetic forms and can be regarded as the rule rather than the exception. They show very complex strain and time dependent behavior and may have initial yield-stress. Their common feature is that they do not obey the simple Newtonian relation of proportionality between stress and rate of deformation. Non-Newtonian fluids are generally classified into three main categories: time-independent whose strain rate solely depends on the instantaneous stress, time-dependent whose strain rate is a function of both magnitude and duration of the applied stress and viscoelastic which shows partial elastic recovery on removal of the deforming stress and usually demonstrates both time and str...
Delzanno, G. L.; Finn, J. M.; Lapenta, G.
2002-12-01
The nonlinear dynamics of a Penning trap plasma, including the effect of the finite length and end curvature of the plasma column, is studied. A new cylindrical particle-in-cell code, called KANDINSKY, has been implemented by using a new interpolation scheme. The principal idea is to calculate the volume of each cell from a particle volume, in the same manner as is done for the cell charge. With this new method, the density is conserved along streamlines and artificial sources of compressibility are avoided. The code has been validated with a number of tests. The code is then used to compare the dynamics of three different models: the standard Euler or drift-Poisson model, the modified drift-Poisson model [J. Finn et al. Phys. Plasmas 6, 3744 (1999); Phys. Rev. Lett. 84, 2401 (2000)] with compressional effects, and the quasigeostrophic model of geophysical fluid dynamics in the limit of the γ-plane approximation. The results of this investigation show that Penning traps can be used to simulate geophysical fluids. Moreover, the results for the m=1 diocotron instability reproduce qualitatively the experiments [C. F. Driscoll, Phy. Rev. Lett. 64, 645 (1990); C. F. Driscoll et al. Phys. Fluids B 2, 1359 (1990)]: The instability turns the plasma "inside-out" resulting at the end in a stable, monotonic profile.
Yang, Xiao-Qiang; Li, Zi-Long; Yu, Sheng-Qiang
2016-08-01
Charnockites in the Datian region of the northeastern Cathaysia Block, South China have an assemblage of garnet, clinopyroxene, orthopyroxene, plagioclase, anti-perthite, K-feldspar, biotite, quartz and ilmenite. Phase equilibrium modeling indicates that the Datian charnockite was formed at T = 845-855 °C and P = 8.2-8.4 kbar with corresponding water activity lower than 0.50. Fluid inclusions in the Datian charnockite are dominated by N2 and CO2 with minor CH4. The fluids homogenized to liquid at -153.0 to -138.8 °C and 18.3-21.6 °C, respectively, showing a low-density nature. The low-density fluids could be attributed to selective leakage of water due to the affinity of water to melt and decompression-dominated retrograde process. Combined with previous studies, a two-stage formation model is proposed to interpret the petrogenesis of the Datian charnockite, viz emplaced at the Paleoproterozoic and underwent the granulite-facies metamorphism during the Phanerozoic tectonic event.
Zhou, J. X.; Shen, X.; Yin, Y. J.; Guo, Z.; Wang, H.
2015-06-01
In this paper, Gas-liquid two phase flow mathematic models of incompressible fluid were proposed to explore the feature of fluid under certain centrifugal force in vertical centrifugal casting (VCC). Modified projection-level-set method was introduced to solve the mathematic models. To validate the simulation results, two methods were used in this study. In the first method, the simulation result of basic VCC flow process was compared with its analytic solution. The relationship between the numerical solution and deterministic analytic solution was presented to verify the correctness of numerical algorithms. In the second method, systematic water simulation experiments were developed. In this initial experiment, special experimental vertical centrifugal device and casting shapes were designed to describe typical mold-filling processes in VCC. High speed camera system and data collection devices were used to capture flow shape during the mold-filling process. Moreover, fluid characteristic at different rotation speed (from 40rpm, 60rpmand 80rpm) was discussed to provide comparative resource for simulation results. As compared with the simulation results, the proposed mathematical models could be proven and the experimental design could help us advance the accuracy of simulation and further studies for VCC.
Energy Technology Data Exchange (ETDEWEB)
Doughty, C.; Pruess, K. [Lawrence Berkeley Lab., CA (United States)
1991-06-01
Over the past few years the authors have developed a semianalytical solution for transient two-phase water, air, and heat flow in a porous medium surrounding a constant-strength linear heat source, using a similarity variable {eta} = r/{radical}t. Although the similarity transformation approach requires a simplified geometry, all the complex physical mechanisms involved in coupled two-phase fluid and heat flow can be taken into account in a rigorous way, so that the solution may be applied to a variety of problems of current interest. The work was motivated by adverse to predict the thermohydrological response to the proposed geologic repository for heat-generating high-level nuclear wastes at Yucca Mountain, Nevada, in a partially saturated, highly fractured volcanic formation. The paper describes thermal and hydrologic conditions near the heat source; new features of the model; vapor pressure lowering; and the effective-continuum representation of a fractured/porous medium.
Desfontaine, Vincent; Veuthey, Jean-Luc; Guillarme, Davy
2016-03-18
Similar to reversed phase liquid chromatography, basic compounds can be highly challenging to analyze by supercritical fluid chromatography (SFC), as they tend to exhibit poor peak shape, especially those with high pKa values. In this study, three new stationary phase ligand chemistries available in sub -2 μm particle sizes, namely 2-picolylamine (2-PIC), 1-aminoanthracene (1-AA) and diethylamine (DEA), were tested in SFC conditions for the analysis of basic drugs. Due to the basic properties of these ligands, it is expected that the repulsive forces may improve peak shape of basic substances, similarly to the widely used 2-ethypyridine (2-EP) phase. However, among the 38 tested basic drugs, less of 10% displayed Gaussian peaks (asymmetry between 0.8 and 1.4) using pure CO2/methanol on these phases. The addition of 10mM ammonium formate as mobile phase additive, drastically improved peak shapes and increased this proportion to 67% on 2-PIC. Introducing the additive in the injection solvent rather than in the organic modifier, gave acceptable results for 2-PIC only, with 31% of Gaussian peaks with an average asymmetry of 1.89 for the 38 selected basic drugs. These columns were also compared to hybrid silica (BEH), DIOL and 2-EP stationary phases, commonly employed in SFC. These phases commonly exhibit alternative retention and selectivity. In the end, the two most interesting ligands used as complementary columns were 2-PIC and BEH, as they provided suitable peak shapes for the basic drugs and almost orthogonal selectivities.
Investigation on phase shifting for a 4 K Stirling pulse tube cryocooler with He-3 as working fluid
Qiu, L. M.; Han, L.; Zhi, X. Q.; Dietrich, M.; Gan, Z. H.; Thummes, G.
2015-07-01
He-3 is generally recognized for its ability to provide more excellent thermophysical performance than He-4, especially in the 4 K temperature range. However, this was not always the case in our preliminary experiments on a three-stage Stirling-type pulse tube cryocooler (SPTC). Our ongoing studies, as reported in this paper, demonstrate that the different working fluids also affect the performance through their phase shifting capability. This feature has been passed over in large part by researchers considering refrigerant substitution. Unlike previous theoretical analyses that focus primarily on regenerator losses, this report investigates the effects of the working fluid on the phase angle at the cold end in order to quantitatively reveal the relationship between the lowest attainable temperature and the cooling capacity. The analysis agrees well with our experimental results on a three-stage SPTC. While running with the operating parameters optimized for He-3, the lowest temperature of the SPTC decreased from 5.4 K down to 4.03 K. This is the lowest refrigeration temperature ever achieved with a three-stage SPTC.
Institute of Scientific and Technical Information of China (English)
邓英尔; 刘慈群
2003-01-01
A mathematical model of two-phase fluid nonlinear flow in the direction ofnormal of ellipse through low-permeability porous media was established according to anonlinear flow law expressed in a continuous function with three parameters, a massconservation law and a concept of turbulent ellipses. A solution to the model was obtainedby using a finite difference method and an extrapolation method. Formulas of calculatingdevelopment index not only before but also after water breaks through an oil well in thecondition of two-phase fluid nonlinear flow in the media were derived. An example wasdiscussed. Water saturation distribution was presented. The moving law of drainage frontwas found. Laws of change of pressure difference with time were recognized. Results showthat there is much difference of water saturation distribution between nonlinear flow andlinear flow; that drainage front by water moves faster, water breaks through sooner and theindex gets worse because of the nonlinear flow ; and that dimensionless pressure differencegets larger at the same dimensionless time and difficulty of oil development becomes biggerby the nonlinear flow . Thus, it is necessary that influence of nonlinear flow on developmentindexes of the oil fields be taken into account. The results provide water-floodingdevelopment of the oil fields with scientific basis.
Density-functional theory for fluid-solid and solid-solid phase transitions
Bharadwaj, Atul S.; Singh, Yashwant
2017-03-01
We develop a theory to describe solid-solid phase transitions. The density functional formalism of classical statistical mechanics is used to find an exact expression for the difference in the grand thermodynamic potentials of the two coexisting phases. The expression involves both the symmetry conserving and the symmetry broken parts of the direct pair correlation function. The theory is used to calculate phase diagram of systems of soft spheres interacting via inverse power potentials u (r ) =ɛ "close="1 /n )">σ /r n , where parameter n measures softness of the potential. We find that for 1 /n ≥0.154 the body-centred-cubic (bcc) structure is preferred. The bcc structure transforms into the fcc structure upon increasing the density. The calculated phase diagram is in good agreement with the one found from molecular simulations.
On The Dynamics And Kinematics Of Two Fluid Phase Flow In Porous Media
2015-06-16
surface. The microscale density, qab, has units of m/L 2; and vab includes all three components of the velocity of the fluid in the interface. The...constant then it follows that equation (22) can be written as @ab @t 1r ab vab 1 1 qab M ab!a 1 1 qab M ab!b 2 1 qab X j2J2cab M j!ab 50 : (24...the velocity in this equation, vab , is the velocity of the material in the interface rather than the velocity of the interface. A second special case
Fluid dynamics of the unsteady two phase processes leading to DDT in granular solid propellants
Krier, H.; Butler, P. B.; Lembeck, M. F.
1980-01-01
Deflagration to Detonation (DDT) was predicted to occur in porous beds of high-energy solid propellants by solving the unsteady fluid mechanical convective heat transfer from hot gas products, obtained from the rapid burning at high pressures, provides the impetus to develop a narrow combustion zone and a resulting strong shock. A parametric study clearly indicates that DDT occurs only when a combination of the solids loading fraction, the burning rate constants, the propellant chemical energy, and the particle size provide for critical energy and gas release to support a detonation wave. Predictions for the run-up length to detonation as a function of these parameters are presented.
Georgescu, Ionuţ; Brown, Sandra E; Mandelshtam, Vladimir A
2013-04-01
In order to address the issue of whether neon liquid in coexistence with its gas phase can be mapped to a quantum Lennard-Jones (LJ) fluid, we perform a series of simulations using Gibbs ensemble Monte Carlo for a range of de Boer quantum parameters Λ=ℏ/(σ√(mε)). The quantum effects are incorporated by implementing the variational gaussian wavepacket method, which provides an efficient numerical framework for estimating the quantum density at thermal equilibrium. The computed data for the LJ liquid is used to produce its phase diagram as a function of the quantum parameter, 0.065 ≤ Λ ≤ 0.11. These data are then used to fit the experimental phase diagram for neon liquid. The resulting parameters, ε = 35.68 ± 0.03 K and σ = 2.7616 ± 0.0005 Å (Λ = 0.0940), of the LJ pair potential are optimized to best represent liquid neon in coexistence with its gas phase for a range of physically relevant temperatures. This multi-temperature approach towards fitting and assessing a pair-potential is much more consistent than merely fitting a single data point, such as a melting temperature or a second virial coefficient.
Directory of Open Access Journals (Sweden)
Celný David
2016-01-01
Full Text Available Development of methods for accurate modeling of phase interfaces is important for understanding various natural processes and for applications in technology such as power production and carbon dioxide separation and storage. In particular, prediction of the course of the non-equilibrium phase transition processes requires knowledge of the properties of the strongly curved phase interfaces of microscopic droplets. In our work, we focus on the spherical vapor–liquid phase interfaces for binary mixtures. We developed a robust computational method to determine the density and concentration profiles. The fundamentals of our approach lie in the Cahn-Hilliard gradient theory, allowing to transcribe the functional formulation into a system of ordinary Euler-Langrange equations. This system is then split and modified into a shape suitable for iterative computation. For this task, we combine the Newton-Raphson and the shooting methods providing a good convergence speed. For the thermodynamic roperties, the PC–SAFT equation of state is used. We determine the density and concentration profiles for spherical phase interfaces at various saturation factors for the binary mixture of CO2 and C9H20. The computed concentration profiles allow to the determine the work of formation and other characteristics of the microscopic droplets.
Two-Phase Fluid Simulation Using a Diffuse Interface Model with Peng--Robinson Equation of State
Qiao, Zhonghua
2014-01-01
In this paper, two-phase fluid systems are simulated using a diffusive interface model with the Peng-Robinson equation of state (EOS), a widely used realistic EOS for hydrocarbon fluid in the petroleum industry. We first utilize the gradient theory of thermodynamics and variational calculus to derive a generalized chemical equilibrium equation, which is mathematically a second-order elliptic partial differential equation (PDE) in molar density with a strongly nonlinear source term. To solve this PDE, we convert it to a time-dependent parabolic PDE with the main interest in its final steady state solution. A Lagrange multiplier is used to enforce mass conservation. The parabolic PDE is then solved by mixed finite element methods with a semi-implicit time marching scheme. Convex splitting of the energy functional is proposed to construct this time marching scheme, where the volume exclusion effect of an EOS is treated implicitly while the pairwise attraction effect of EOS is calculated explicitly. This scheme is proved to be unconditionally energy stable. Our proposed algorithm is able to solve successfully the spatially heterogeneous two-phase systems with the Peng-Robinson EOS in multiple spatial dimensions, the first time in the literature. Numerical examples are provided with realistic hydrocarbon components to illustrate the theory. Furthermore, our computational results are compared with laboratory experimental data and verified with the Young-Laplace equation with good agreement. This work sets the stage for a broad extension of efficient convex-splitting semi-implicit schemes for numerical simulation of phase field models with a realistic EOS in complex geometries of multiple spatial dimensions.
On the late phase of relaxation of two-dimensional fluids: turbulence of unitons
Spineanu, F
2016-01-01
The two-dimensional ideal fluid and the plasma confined by a strong magnetic field exhibit an intrinsic tendency to organization due to the inverse spectral cascade. In the asymptotic states reached at relaxation the turbulence has vanished and there are only coherent vortical structures. We are interested in the regime that precedes these ordered flow patterns, in which there still is turbulence and imperfect but robust structures have emerged. To develop an analytical description we propose to start from the stationary coherent states and (in the direction opposite to relaxation) explore the space of configurations before the extremum of the functional that defines the structures has been reached. We find necessary to assemble different but related models: point-like vortices, its field theoretical formulation as interacting matter and gauge fields, chiral model and surfaces with constant mean curvature. These models are connected by the similar ability to describe randomly interacting coherent structures. ...
Institute of Scientific and Technical Information of China (English)
Ying Zhao; Hong Liu; Zhong-yuan Lu; Chia-chung Sun
2008-01-01
It was investigated that the domain growth processes of spinodal decomposition with different quenching depth in two and three dimensional binary immiscible fluids by using parallel dissipative particle dynamics simulations. In two dimensions, the dynamic scaling exponent 1/2 for coalescence and 2/3 for inertial regimes in the shallow quench and strong finite size effects in the cases of deep quenching were obtained. In three dimensions, it was used that the diffusive regime with exponent n=1/3 in the shallow quench and the inertial hydrodynamic regime with n=2/3 for different quenches. The viscous effects are not clearly reflected, showing n=l/2 in both shallow and deep quenches in this time period, due to the soft nature of interaction potential adopted in dissipative particle dynamics.
vanVlimmeren, BAC; Fraaije, JGEM
1996-01-01
We present a simple method for the numerical calculation of the noise distribution in multicomponent functional Langevin models. The topic is of considerable importance, in view of the increased interest in the application of mesoscopic dynamics simulation models to phase separation of complex
Formation of organic solid phases in hydrocarbon reservoir fluids. Final report
Energy Technology Data Exchange (ETDEWEB)
Andersen, S.I.; Lindeloff, N.; Stenby, E.H.
1998-12-31
The occurrence of solid phases during oil recovery is a potential problem. The present work has mainly been concerned with wax formation due to cooling of oils with a large paraffin content. 8 oils have been included in this project, although only a few of these have till now been subject to all the experimental techniques applied. The oils and wax fractions from these have been characterized using techniques such as GC-MS and Ftir. The goal has in part been to get a detailed description of the oil composition for use in model evaluation and development and in part to get a fundamental understanding of waxy oil properties and behaviour. A high pressure (200 bar) equipment has been developed for automatic detection of wax appearance using a filtration technique and laser light turbidimetry. The latter was found to be far superior to the filtration. The filtration was used to sample the incipient solid phase for characterization. However entrapment of liquid in the filters currently used have hampered this part. A number of model systems and one gas condensate have been investigated. The GC-MS procedure was found only to been able to detect molecules up to n-C45 and the group type analysis was not accurate enough for modelling purposes. Using Ftir it was obvious that incipient phases may contain very complex molecules (asphaltenes) which are not captured by GC-MS especially when fractionation is done using the acetone precipitation at elevated temperature. The latter fractionation procedure has been investigated thoroughly as a tool for understanding wax distribution etc. Within thermodynamic modelling a delta lattice parameter model has been developed which incorporates the non-ideality of the solid phases into the calculation of SLE. The non-ideality is estimated from pure component properties. A new algorithm for phase equilibria involving gas-liquid-solid has been developed. Currently both the model work and the experimental works are continued. (au)
Thermophysical Properties of Fluids and Fluid Mixtures
Energy Technology Data Exchange (ETDEWEB)
Sengers, Jan V.; Anisimov, Mikhail A.
2004-05-03
The major goal of the project was to study the effect of critical fluctuations on the thermophysical properties and phase behavior of fluids and fluid mixtures. Long-range fluctuations appear because of the presence of critical phase transitions. A global theory of critical fluctuations was developed and applied to represent thermodynamic properties and transport properties of molecular fluids and fluid mixtures. In the second phase of the project, the theory was extended to deal with critical fluctuations in complex fluids such as polymer solutions and electrolyte solutions. The theoretical predictions have been confirmed by computer simulations and by light-scattering experiments. Fluctuations in fluids in nonequilibrium states have also been investigated.
Franciò, Giancarlo; Hintermair, Ulrich; Leitner, Walter
2015-12-28
Solution-phase catalysis using molecular transition metal complexes is an extremely powerful tool for chemical synthesis and a key technology for sustainable manufacturing. However, as the reaction complexity and thermal sensitivity of the catalytic system increase, engineering challenges associated with product separation and catalyst recovery can override the value of the product. This persistent downstream issue often renders industrial exploitation of homogeneous catalysis uneconomical despite impressive batch performance of the catalyst. In this regard, continuous-flow systems that allow steady-state homogeneous turnover in a stationary liquid phase while at the same time effecting integrated product separation at mild process temperatures represent a particularly attractive scenario. While continuous-flow processing is a standard procedure for large volume manufacturing, capitalizing on its potential in the realm of the molecular complexity of organic synthesis is still an emerging area that requires innovative solutions. Here we highlight some recent developments which have succeeded in realizing such systems by the combination of near- and supercritical fluids with homogeneous catalysts in supported liquid phases. The cases discussed exemplify how all three levels of continuous-flow homogeneous catalysis (catalyst system, separation strategy, process scheme) must be matched to locate viable process conditions.
High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2005-2008)
DEFF Research Database (Denmark)
Fonseca, José; Dohrn, Ralf; Peper, Stephanie
2011-01-01
A review of systems is given, for which experimental high-pressure phase-equilibrium data were published in the period between 2005 and 2008, continuing a series of reviews. To find candidates for articles that are of interest for this survey a three-stage search strategy was used including...... a systematic search of the contents of the 17 most important journals of the field. Experimental methods for the investigation of high-pressure phase equilibria were classified, described and illustrated using examples from articles of the period between 2005 and 2008. For the systems investigated......, the reference, the temperature and pressure range of the data, and the experimental method used for the measurements is given in 54 tables. Vapor–liquid equilibria, liquid–liquid equilibria, vapor–liquid–liquid equilibria, solid–liquid equilibria, solid–vapor equilibria, solid–vapor–liquid equilibria, critical...
Coupled Hydromechanical Model of Two-Phase Fluid Flow in Deformable Porous Media
Directory of Open Access Journals (Sweden)
You-Seong Kim
2013-01-01
Full Text Available A model of solid-water-air coupling in triphasic mixtures is compared with solid-water coupling in biphasic mixtures with an application to partially saturated porous media. Based on thermodynamics, the mathematical framework governing the behavior of a partially saturated soil is derived using balance equations, and the numerical implementation and drainage tests of a soil column are carried out to validate the obtained formulations. The role of the air phase in the hydro-mechanical behavior of triphasic mixtures can be analyzed from the interactions among multiple phases for the constitutive behavior of a solid skeleton, and the triphasic mixture model can be applied in geotechnical engineering problems, such as CO2 sequestration and air storage in aquifers.
Long-range interactions and phase defects in chains of fluid-coupled oscillators
Brumley, Douglas R; Kotar, Jurij; Goldstein, Raymond E; Cicuta, Pietro; Polin, Marco
2016-01-01
Eukaryotic cilia and flagella are chemo-mechanical oscillators capable of generating long-range coordinated motions known as metachronal waves. Pair synchronization is a fundamental requirement for these collective dynamics, but it is generally not sufficient for collective phase-locking, chiefly due to the effect of long-range interactions. Here we explore experimentally and numerically a minimal model for a ciliated surface; hydrodynamically coupled oscillators rotating above a no-slip plane. Increasing their distance from the wall profoundly effects the global dynamics, due to variations in hydrodynamic interaction range. The array undergoes a transition from a traveling wave to either a steady chevron pattern or one punctuated by periodic phase defects. Within the transition between these regimes the system displays behavior reminiscent of chimera states.
Lesellier, E
2012-03-09
The chromatographic efficiency, in terms of plate number per second, was dramatically improved by the introduction of sub-two microns particles with ultra-high pressure liquid chromatography (UHPLC). On the other hand, the recent development of superficially porous particles, called core-shell or fused-core particles, appears to allow the achievement of the same efficiency performances at higher speed without high pressure drops. CO₂-based mobile phases exhibiting much lower viscosities than aqueous based mobile phases allow better theoretical efficiencies, even with 3-5 μm particles, but with relative low pressure drops. They also allow much higher flow rates or much longer columns while using conventional instruments capable to operate below 400 bar. Moreover, the use of superficially porous particles in SFC could enhance the chromatographic performances even more. The kinetic behavior of ODS phases bonded on these particles was studied, with varied flow rates, outlet (and obviously inlet) pressures, temperatures, by using a homologous series (alkylbenzenes) with 10% modifier (methanol or acetonitrile) in the carbon dioxide mobile phase. Results were also compared with classical fully porous particles, having different sizes, from 2.5 to 5 μm. Superior efficiency (N) and reduced h were obtained with these new ODS-bonded particles in regards to classical ones, showing their great interest for use in SFC. However, surprising behavior were noticed, i.e. the increase of the theoretical plate number vs. the increase of the chain length of the compounds. This behavior, opposite to the one classically reported vs. the retention factor, was not depending on the outlet pressure, but on the flow rate and the temperature changes. The lower radial trans-column diffusion on this particle types could explain these results. This diffusion reduction with these ODS-bonded superficially porous particles seems to decrease with the increase of the residence time of compounds.
Competition of percolation and phase separation in a fluid of adhesive hard spheres
Miller, M.A.; Frenkel, D.
2003-01-01
Using a combination of Monte Carlo techniques, we locate the liquid-vapor critical point of adhesive hard spheres. We find that the critical point lies deep inside the gel region of the phase diagram. The (reduced) critical temperature and density are τc = 0.1133±0.0005 and ρc = 0.508±0.01. We compa
Yan, Wenfei; Hall, Stephen B.
2006-01-01
To determine how coexistence of liquid-expanded (LE) and tilted-condensed (TC) phases in phospholipid monolayers affects collapse from the air/water interface, we studied binary films containing dioleoyl phosphatidylcholine–dipalmitoyl phosphatidylcholine (DPPC) mixtures between 10 and 100% DPPC. Previously published results established that this range of compositions represents the LE–TC coexistence region at the equilibrium spreading pressure of 47 mN/m. When held at 49.5 mN/m on a captive ...
Study of three-phase fluid dynamics in a surging production system
Energy Technology Data Exchange (ETDEWEB)
Oliveira, Rodolfo; Assuncao, Pablo Morelato; Ressel, Fabio de Assis [Universidade Federal do Espirito Santo, Sao Mateus, ES (Brazil)
2010-07-01
Among others factors, petroleum extraction is subordinate to the reservoir pressure and the required pressure to rise it to the surface production facilities. Reservoir deliverability equations tied production rate with reservoir driving force (Economides, 1994). The Inflow Performance Relationship (IPR) is obtained by measuring the production rates under various drawdown pressures, and is used to assess well performance by plotting the well production rate against the flowing bottonhole pressure. Others limiting rate of production factors are imposed by wellhead required pressure and the production tubing performance. The tubing performance is sensitive to several parameters among which we can highlight the production tubing geometry and the properties of the produced fluids (Guo, 2007). Therewith we can define the Tubing Performance Relationship (TPR) similarly to the IPR. Thus the present work aims the hydraulic performance analysis of a production system with a flowing well without artificial elevation methods. Furthermore the triphasic (water-oil-gas) flow studies, both in the production string and the production line, allowed the inspection of the main variables of the system, fluid properties, operation conditions and geometric parameters, on the head loss. In order obtain all these, several methods were developed, each one with specifics limitations to include all flow patterns. The most common biphasic horizontal flow patterns according to Brill and Beggs (1975) are: mist flow, bubble flow, plug flow, slug flow, stratified flow, wavy flow and annular flow. Yet according to Brill and Beggs (1975) the most common biphasic vertical flow patterns are: bubbly flow, slug flow, churn flow, and annular flow. Accordingly to these, another outbreak discussed is the pattern flow sensibility on the head loss. The methodology used in the present work is based on the discretization of the system in several discrete counterparts cells, in which was where it was applied
Directory of Open Access Journals (Sweden)
M. Kannan
2014-01-01
Full Text Available In the present investigation a two phase thermosyphon has been fabricated to investigate the effect of operating parameters on the heat transport capability. The system consists of evaporator section, adiabatic section and condenser section with thermocouples located on the wall of thermosyphon. Electric heater was fixed on the bottom of the evaporator section and water jacket for cooling the condenser was placed on the top of the condenser section of the thermosyphon. The experiments were conducted with three different thermosyphons with inner diameters of 6.7, 9.5 and 12 mm. The variation of heat transport capability of the thermosyphon was studied for the input heat transfer rate ranging from 0 to 1200 W for various filling ratios and with operating temperature from 30 to 70°C. Water, methanol, ethanol and acetone were used as working fluids. The maximum heat transport capability was found to be high for water compared to other fluids such as ethanol, methanol and acetone at the operating temperatures higher than 40°C.
Energy Technology Data Exchange (ETDEWEB)
Lesellier, E. [Institut Universitaire de Technologie, (LETIAM), 91 - Orsay (France)
1999-05-01
Solid phase micro-extraction (SPME) is a clean and simple pre-concentration method. Previously used for trace analysis of volatile compounds, the use of SPME was extended to non volatile molecules with the development of an SPME/HPLC interface. This new interface allows the extraction and the analysis of high molecular weight compounds found in aqueous samples. Since superficial fluid chromatography is particularly well suited for analysis of complex mixtures containing non volatile compounds, the feasibility of coupling SPME and SFC has been investigated and applied to PAHs. Several points have been studied: behavior of interface and of fiber to superficial fluid and high pressure required by the analytical method; kind of the compounds transfer from the fiber to the analytical column; relation between the nature of the fibers and the quantity of extracted compounds; effect of salt addition. The results show that the SPME/SFC technic may be used for extraction and analysis of PAHs, since the quantity of extracted compounds reach 30 %. (author) 17 refs.
Directory of Open Access Journals (Sweden)
Xiangwei Kong
2015-01-01
Full Text Available A dynamic pressure wave velocity model is presented based on momentum equation, mass-balance equation, equation of state, and small perturbation theory. Simultaneously, the drift model was used to analyze the flow characteristics of oil, gas, water, and drilling fluid multiphase flow. In addition, the dynamic model considers the gas dissolution, virtual mass force, drag force, and relative motion of the interphase as well. Finite difference and Newton-Raphson iterative are introduced to the numerical simulation of the dynamic model. The calculation results indicate that the wave velocity is more sensitive to the increase of gas influx rate than the increase of oil/water influx rate. Wave velocity decreases significantly with the increase of gas influx. Influenced by the pressure drop of four-phase fluid flowing along the annulus, wave velocity tends to increase with respect to well depth, contrary to the gradual reduction of gas void fraction at different depths with the increase of backpressure (BP. Analysis also found that the growth of angular frequency will lead to an increase of wave velocity at low range. Comparison with the calculation results without considering virtual mass force demonstrates that the calculated wave velocity is relatively bigger by using the presented model.
Jin, Shi; Shu, Ruiwen
2017-04-01
In this paper we consider a kinetic-fluid model for disperse two-phase flows with uncertainty. We propose a stochastic asymptotic-preserving (s-AP) scheme in the generalized polynomial chaos stochastic Galerkin (gPC-sG) framework, which allows the efficient computation of the problem in both kinetic and hydrodynamic regimes. The s-AP property is proved by deriving the equilibrium of the gPC version of the Fokker-Planck operator. The coefficient matrices that arise in a Helmholtz equation and a Poisson equation, essential ingredients of the algorithms, are proved to be positive definite under reasonable and mild assumptions. The computation of the gPC version of a translation operator that arises in the inversion of the Fokker-Planck operator is accelerated by a spectrally accurate splitting method. Numerical examples illustrate the s-AP property and the efficiency of the gPC-sG method in various asymptotic regimes.
Energy Technology Data Exchange (ETDEWEB)
Jin, Shi, E-mail: sjin@wisc.edu [Department of Mathematics, University of Wisconsin–Madison, Madison, WI 53706 (United States); Institute of Natural Sciences, School of Mathematical Science, MOELSEC and SHL-MAC, Shanghai Jiao Tong University, Shanghai 200240 (China); Shu, Ruiwen, E-mail: rshu2@math.wisc.edu [Department of Mathematics, University of Wisconsin–Madison, Madison, WI 53706 (United States)
2017-04-15
In this paper we consider a kinetic-fluid model for disperse two-phase flows with uncertainty. We propose a stochastic asymptotic-preserving (s-AP) scheme in the generalized polynomial chaos stochastic Galerkin (gPC-sG) framework, which allows the efficient computation of the problem in both kinetic and hydrodynamic regimes. The s-AP property is proved by deriving the equilibrium of the gPC version of the Fokker–Planck operator. The coefficient matrices that arise in a Helmholtz equation and a Poisson equation, essential ingredients of the algorithms, are proved to be positive definite under reasonable and mild assumptions. The computation of the gPC version of a translation operator that arises in the inversion of the Fokker–Planck operator is accelerated by a spectrally accurate splitting method. Numerical examples illustrate the s-AP property and the efficiency of the gPC-sG method in various asymptotic regimes.
Dharma-wardana, M W C
2016-01-01
Using data from recent laser-shock experiments and related density-functional molecular-dynamics simulations on carbon, we demonstrate that the ionic structures predicted within the neutral-pseudo-atom approach for a complex liquid in the warm-dense matter regime are in good agreement with available data, even where transient covalent bonding dominates ionic correlations. Evidence for an unusual phase transition of a liquid $\\to$ vapor with an abrupt decrease in ionization occurring simultaneously is presented. Here a covalently-bonded metallic-liquid, i.e., carbon of density 1.0 g/cm$^3$, transits to a disordered mono-atomic fluid at 7 eV. Other transitions where the mean ionization $Z$ drops abruptly are also uncovered
Roton Excitations and the Fluid-Solid Phase Transition in Superfluid 2D Yukawa Bosons
Molinelli, S.; Galli, D. E.; Reatto, L.; Motta, M.
2016-10-01
We compute several ground-state properties and the dynamical structure factor of a zero-temperature system of Bosons interacting with the 2D screened Coulomb (2D-SC) potential. We resort to the exact shadow path integral ground state (SPIGS) quantum Monte Carlo method to compute the imaginary-time correlation function of the model, and to the genetic algorithm via falsification of theories (GIFT) to retrieve the dynamical structure factor. We provide a detailed comparison of ground-state properties and collective excitations of 2D-SC and ^4He atoms. The roton energy of the 2D-SC system is an increasing function of density, and not a decreasing one as in ^4He. This result is in contrast with the view that the roton is the soft mode of the fluid-solid transition. We uncover a remarkable quasi-universality of backflow and of other properties when expressed in terms of the amount of short-range order as quantified by the height of the first peak of the static structure factor.
Design of Gas-phase Synthesis of Core-Shell Particles by Computational Fluid - Aerosol Dynamics.
Buesser, B; Pratsinis, S E
2011-11-01
Core-shell particles preserve the bulk properties (e.g. magnetic, optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO2 nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core-shell nanoparticles. The predicted extent of hermetic coating shells is compared to the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO2 shells prevent the photocatalytic activity of titania. Finally the performance of a simpler, plug-flow coating model is assessed by comparisons to the present detailed CFD model in terms of coating efficiency and silica average shell thickness and texture.
Energy Technology Data Exchange (ETDEWEB)
Ordaz-Flores, A. [Posgrado en Ingenieria (Energia), Univ. Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Garcia-Valladares, O.; Gomez, V.H. [Centro de Investigacion en Energia, Univ. Nacional Autonoma de Mexico, Temixco, Morelos (Mexico)
2008-07-01
A water heating closed two-phase thermosyphon solar system was designed and built. The system consists of a flat plate solar collector coupled to a thermotank by a continuous copper tubing in which the working fluid circulates. The working fluid evaporates in the collector and condensates in the thermotank transferring its latent heat to the water through a coil heat exchanger. The tested fluids are acetone and R134a. The thermal performance of the proposed systems is compared with a conventional solar water thermosyphon under the same operating conditions. Advantages of a two-phase system include the elimination of freezing, fouling, scaling and corrosion. Geometry and construction materials are the same except for the closed circuit presented in the two-phase system. Data were collected from temperature and pressure sensors throughout the two systems. Early results suggest that R134a may provide a better performance than acetone for this kind of systems. (orig.)
Pudasaini, Shiva P.; Kattel, Parameshwari; Kafle, Jeevan; Pokhrel, Puskar R.; Khattri, Khim B.
2014-05-01
We present a technique that simulates transport and flow of a real two-phase fluid (a mixture of fluid and sediment particles) down three-dimensional slopes and channels. This technique combines novel mechanics formulations and modeling into a unified high-resolution framework, providing a unique opportunity to simulate two-phase subearial landslides and debris flows with dynamically changing concentrations of solid particles. This mixture then impacts downslope with particle-laden fluid reservoirs, rivers, fjords, lakes, or oceans. This results in a super tsunami wave in the fluid body, while the submarine debris flow moves along the bathymetry. The same modelling technique can be applied to simulate rock-ice avalanches and turbidity currents with changing physical properties and mechanical responses of the phases that enhances the flow mobility. These results fundamentally advance our present knowledge associated with the complex mechanics and dynamics of multi-phase geophysical mass flows, including the subearial and submarine sediment transport and deposition processes. Our findings contribute significantly to our understanding of mixing and separation between phases, generation and propagation of special solid and fluid structures, and phase-transitions during the flow process. Finally, these results provide new insights into the evolution of morphodynamics of steep mountain slopes and channels. References Pudasaini, S. P. A general two-phase debris flow model. Journal of Geophysical Research, 117, F03010, 2012. doi: 10.1029/2011JF002186. Pudasaini, S. P. and Miller, S. A. A real two-phase submarine debris flow and tsunami. American Institute of Physics Proceedings, 1479, 197-200, 2012. doi: 10.1063/1.4756096.
High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2000-2004)
DEFF Research Database (Denmark)
Dohrn, Ralf; Peper, Stephanie; Fonseca, José
2010-01-01
, and the experimental method used for the measurements are given in 54 tables. Most of experimental data in the literature have been given for binary systems. Of the 1204 binary systems, 681 (57%) have carbon dioxide as one of the components. Information on 156 pure components, 451 ternary systems of which 267 (62......%) contain carbon dioxide, 150 multicomponent and complex systems, and 129 systems with hydrates is given. Experimental methods for the investigation of high-pressure phase equilibria are classified and described. Work on the continuation of the review series is under way, covering the period between 2005...
Focal junctions retard lateral movement and disrupt fluid phase connectivity in the plasma membrane
DEFF Research Database (Denmark)
Vind-Kezunovic, D.; Wojewodzka, U.; Gniadecki, R.
2008-01-01
containing liquid-ordered (L-o) lipids. Indeed, values of maximal fluorescence recovery after photobleaching revealed that the long-range mobility of cholera toxin B subunit (CTB, marker of L-o) was similar to 1.5-fold retarded within the focal junctions compared to the surrounding membrane. However, 1......,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI-C-18:0), which specifically partitions to the liquid-disordered (L-d), non-raft phase, was also enriched in focal junctions and its mobility was slightly retarded. Cross-linking of GM(1) by CTB or raft aggregation by methyl...
Directory of Open Access Journals (Sweden)
Naoki Takada
2014-09-01
Full Text Available Applicability of two kinds of computational-fluid-dynamics method adopting Cahn-Hilliard (CH and Allen-Cahn (AC-type diffuse-interface advection equations based on a phase-field model (PFM is examined to simulation of motions of microscopic incompressible two-phase fluid on solid surface. A capillarity-driven gas-liquid motion in rectangular channel is simulated by use of a PFM method for solving Navier-Stokes (NS equations and a CH equation, whereas an immiscible liquid-liquid flow in a microchannel with T-junction and square cross section is simulated by use of another PFM method proposed in this study, which adopts a lattice-Boltzmann method based on fictitious particles kinematics as numerical scheme for solving NS equations and an AC equation that is modified to improve volume-of-fluid conservation. The major findings are as follows: (1 effect of capillary force on the dynamic two-phase fluid system with a high density ratio is well predicted for cross-sectional aspect ratio of the channel = 1 and 2; (2 mono-dispersed slug flow pattern transition is reproduced in good agreement with experimental observations in terms of variation in length and interval of droplets as increasing their volumetric flow rates at a constant flow rate ratio = 1. These results prove that the PFM methods can be used for analyzing two-phase fluid motions in various microfluidic devices and micro fabrication processes.
Maximizing performance in supercritical fluid chromatography using low-density mobile phases.
Gritti, Fabrice; Fogwill, Michael; Gilar, Martin; Jarrell, Joseph A
2016-10-14
The performance of a 3.0mm×150mm column packed with 1.8μm fully porous HSS-SB-C18 particles was investigated in supercritical fluid chromatography (SFC) with low-density, highly expansible carbon dioxide. These conditions are selected for the analysis of semi-volatile compounds. Elevated temperatures (>100°C) were then combined with low column back pressures (temperature of pure carbon dioxide was set at 107°C, the active back pressure regulator (ABPR) pressure was fixed at 100bar, and the flow rate was set at 2.1mL/min at 12°C (liquefied carbon dioxide) and at an inlet column pressure close to 300bar. Nine n-alkylbenzenes (from benzene to octadecylbenzene) were injected under linear (no sample overload) conditions. The severe steepness of the temperature gradients across the column diameter were predicted from a simplified heat transfer model. Such conditions dramatically lower the column performance by affecting the symmetry of the peak shape. In order to cope with this problem, three different approaches were experimentally tested. They include (1) the decoupling and the proper selection of the inlet eluent temperature with respect to the oven temperature, (2) the partial thermal insulation of the column using polyethylene aerogel, and (3) the application of a high vacuum (10(-5)Torr provided by a turbo-molecular pump) in a housing chamber surrounding the whole column body. The results reveal that (1) the column efficiency can be maximized by properly selecting the difference between the eluent and the oven temperatures, (2) the mere wrapping of the column with an excellent insulating material is insufficient to fully eliminate heat exchanges by conduction and the undesirable radial density gradients across the column i.d., and (3) the complete thermal insulation of the SFC column under high vacuum allows to maximize the column efficiency by maintaining the integrity of the peak shape.
Directory of Open Access Journals (Sweden)
Peng-Fei Hou
2014-11-01
Full Text Available Two-dimensional Green's functions for a line heat source applied in the fluid and pyroelectric two-phase plane are presented in this paper. By virtue of the two-dimensional general solutions which are expressed in harmonic functions, six newly introduced harmonic functions with undetermined constants are constructed. Then, all the pyroelectric components in the fluid and pyroelectric two-phase plane can be derived by substituting these harmonic functions into the corresponding general solutions. And the undetermined constants can be obtained by the interface compatibility conditions and the mechanical, electric, and thermal equilibrium conditions. Numerical results are given graphically by contours.
流体-固体两相流的数值模拟%NUMERICAL SIMULATION OF FLUID-SOLID TWO-PHASE FLOWS
Institute of Scientific and Technical Information of China (English)
张政; 谢灼利
2001-01-01
Numerical simulation of fluid-solid two-phase flows is reviewed with 105 references. There are two approaches (Lagrangian approach and Eulerian approach) typically used for modeling fluid-solid flows. The former treats the fluid phase as continuous phase and the solid phase as dispersed phase and predicts the particle trajectories in the fluid phase as the results of forces acting on particles.The latter treats the solid as a certain kind of continuum and solves two continuum equations for both fluid and solid phase. At first, as the basis of fluid-solid two-phase flow, several turbulence models, such as Reynolds Association Numerical Simulation (RANS), Direct Numerical Simulation (DNS), Large Eddy Simulation (LES) and Discrete Vortex Simulation (DVS), for the continuous fluid phase are summarized,and the mechanisms of RANS are discussed in detail. In the Lagrangian approach, a particle kinetic equation is presented and the importance of each force acting on a particle is discussed. For a flow with dense particles, various interaction models between particles are discussed, among which the Distinct Element Method (DEM) newly developed from rock deformation study is particularly described, and the new method shows great predicting ability. In the Eulerian approach, the basis equations for the solid and fluid phases as well as their numerical treatments are presented. To close the turbulence and phase related equations, calculation of solid phase viscosity and pressure are discussed respectively. Finally, a k-ε-kp model and model derived from kinetic theory of granular flow are especially introduced. As a complement, a discussion of one-way coupling and two-way coupling between fluid and solid phase is included. Based on the review of the advantages and disadvantages of all models, the existing problems and the future development direction of fluid-solid two phase flow are given as conclusions.%鉴于流体－固体两相流及其数
Interacting cosmic fluids and phase transitions under a holographic modeling for dark energy
Lepe, Samuel; Peña, Francisco
2016-09-01
We discuss the consequences of possible sign changes of the Q-function which measures the transfer of energy between dark energy and dark matter. We investigate this scenario from a holographic perspective by modeling dark energy by a linear parametrization and CPL-parametrization of the equation of state (ω ). By imposing the strong constraint of the second law of thermodynamics, we show that the change of sign for Q, due to the cosmic evolution, imply changes in the temperatures of dark energy and dark matter. We also discuss the phase transitions, in the past and future, experienced by dark energy and dark matter (or, equivalently, the sign changes of their heat capacities).
Gas phase synthesis of core-shell Fe@FeO x magnetic nanoparticles into fluids
Aktas, Sitki; Thornton, Stuart C.; Binns, Chris; Denby, Phil
2016-12-01
Sorbitol, short chain molecules, have been used to stabilise of Fe@FeO x nanoparticles produced in the gas phase under the ultra-high vacuum (UHV) conditions. The sorbitol coated Fe@FeO x nanoparticles produced by our method have a narrow size distribution with a hydrodynamic diameter of 35 nm after NaOH is added to the solution. Magnetisation measurement shows that the magnetic nanoparticles are superparamagnetic at 100 K and demonstrate hysteresis at 5 K with an anisotropy constant of 5.31 × 104 J/m3 (similar to bulk iron). Also, it is shown that sorbitol is only suitable for stabilising the Fe@FeO x suspensions, and it does not prevent further oxidation of the metallic Fe core. According to MRI measurement, the nanoparticles have a high transverse relaxation rate of 425 mM-1 s-1.
Interacting cosmic fluids and phase transitions under a holographic modeling for dark energy
Energy Technology Data Exchange (ETDEWEB)
Lepe, Samuel [Pontificia Universidad Catolica de Valparaiso, Instituto de Fisica, Facultad de Ciencias, Valparaiso (Chile); Pena, Francisco [Universidad de La Frontera, Departamento de Ciencias Fisicas, Facultad de Ingenieria y Ciencias, Temuco (Chile)
2016-09-15
We discuss the consequences of possible sign changes of the Q-function which measures the transfer of energy between dark energy and dark matter. We investigate this scenario from a holographic perspective by modeling dark energy by a linear parametrization and CPL-parametrization of the equation of state (ω). By imposing the strong constraint of the second law of thermodynamics, we show that the change of sign for Q, due to the cosmic evolution, imply changes in the temperatures of dark energy and dark matter. We also discuss the phase transitions, in the past and future, experienced by dark energy and dark matter (or, equivalently, the sign changes of their heat capacities). (orig.)
Malaspina, Nadia; Alvaro, Matteo; Campione, Marcello; Nestola, Fabrizio
2015-04-01
Remnants of the fluid phase at ultrahigh pressure (UHP) in subduction environments may be preserved as primary multiphase inclusions in UHP minerals. These inclusions are frequently hosted by minerals stable at mantle depths, such as garnet, and show the same textural features as fluid inclusions. The mineral infillings of the solid multiphase inclusions are generally assumed to have crystallized by precipitation from the solute load of dense supercritical fluids equilibrating with the host rock. Notwithstanding the validity of this assumption, the mode of crystallization of daughter minerals during precipitation within the inclusion and/or the mechanism of interaction between the fluid at supercritical conditions and the host mineral are still poorly understood from a crystallographic point of view. A case study is represented by garnet orthopyroxenites from the Maowu Ultramafic Complex (China) deriving from harzburgite precursors metasomatised at ~ 4 GPa, 750 °C by a silica- and incompatible trace element-rich fluid phase. This metasomatism produced poikilitic orthopyroxene and inclusion-rich garnet porphyroblasts. Solid multiphase primary inclusions in garnet display a size within a few tens of micrometers and negative crystal shapes. Infilling minerals (spinel: 10-20 vol.%; amphibole, chlorite, talc, mica: 80- 90 vol.%) occur with constant volume ratios and derive from trapped solute-rich aqueous fluids. To constrain the possible mode of precipitation of daughter minerals, we performed for the first time a single-crystal X-ray diffraction experiment by means of Synchrotron Radiation at DLS-Diamond Light Source. In combination with electron probe microanalyses, this measurement allowed the unique identification of each mineral phase and their reciprocal orientations. We demonstrated the epitaxial relationship between spinel and garnet and between some hydrous minerals. Epitaxy drives a first-stage nucleation of spinel under near-to-equilibrium conditions
François, Isabelle; Pereira, Alberto dos Santos; Lynen, Frédéric; Sandra, Pat
2008-10-01
The design of a new interface to hyphen high efficiency supercritical fluid chromatography (SFC) and fast RPLC in a comprehensive configuration is described. SFC x RPLC is a viable alternative to normal phase (NP) LC x RPLC and is characterized by high orthogonality. Compared to NPLC x RPLC an additional advantage is the expansion of supercritical carbon dioxide (CO(2)) when exposed to atmospheric pressure leading to fractions consisting of solvents that are miscible with the second dimension RPLC mobile phase. The interface consists of a two-position/ten-port switching valve equipped with two packed octadecyl silica (C(18)) loops for effective trapping and focusing of the analytes after elution from the SFC dimension. The addition of a water make-up flow to the SFC effluent prior to entering the loops is of fundamental importance to efficiently focus the solutes on the C(18) material and to reduce interferences of expanded CO(2) gas on the second dimension separation. The features of the system are illustrated with the analysis of a lemon oil sample.
Duc, Linh Do; Horák, Vladimír; Kulish, Vladimir; Lukáč, Tomáš
2017-01-01
Carbon dioxide is widely used as the power gas in the gas guns community due to its ease of handling, storability at room temperature, and high vapor pressure depending only upon temperature, but not a tank size, as long as some liquid carbon dioxide remains in the tank. This high vapor pressure can be used as the pressurant, making it what is referred to as a self-pressurising propellant. However, as a two-phase substance, carbon dioxide does have its drawbacks: (1) vaporization of liquefied CO2 inside a tank when shooting rapidly or a lot causes the tank to get cool, resulting in pressure fluctuations that makes the gun's performance and accuracy worse, (2) solid carbon dioxide that is also known as dry ice can appear on the output valve of the tank while shooting and it can cause damage or slow the gun's performance down, if it works its way into some control components, including the barrel of the gun. Hence, it is crucial to obtain a scientific understanding of carbon dioxide behavior and further the discharge characteristics of a wide range of pressure-tank configurations. For the purpose of satisfying this goal, a comprehensive discharge mathematical model for carbon dioxide tank dynamics is required. In this paper, the possibility to develop an advanced non-equilibrium model of depressurization in two-phase fluids is discussed.
Klejdus, B; Kopecký, J; Benesová, L; Vacek, J
2009-01-30
In the present paper a new extraction technique based on the combination of solid-phase/supercritical-fluid extraction (SPE/SFE) with subsequent reversed-phase HPLC is described. The SPE/SFE extractor was originally constructed from SPE-cartridge incorporated into the SFE extraction cell. Selected groups of benzoic acid derivatives (p-hydroxybenzoic, protocatechuic, gallic, vanillic and syringic acid), hydroxybenzaldehydes (4-hydroxybenzaldehyde and 3,4-dihydroxybenzaldehyde) and cinnamic acid derivatives (o-coumaric, p-coumaric, caffeic, ferulic, sinapic and chlorogenic acid) were extracted. Cyclic addition of binary extraction solvent system based on methanol:water (1:1, v/v) and methanol/ammonia aqueous solution was used for extraction at 40MPa and 80 degrees C. The p-hydroxybenzoic, protocatechuic, vanillic, syringic, caffeic and chlorogenic acid; 4-hydroxybenzaldehyde and 3,4-dihydroxybenzaldehyde were identified by HPLC-electrospray mass spectrometry in SPE/SFE extracts of acid hydrolyzates of microalga (Spongiochloris spongiosa) and cyanobacterial strains (Spirulina platensis, Anabaena doliolum, Nostoc sp., and Cylindrospermum sp.). For the identification and quantification of the compounds the quasi-molecular ions [M-H](-) and specific fragments were analysed by quadrupole mass spectrometry analyzer. Our analysis showed that the microalgae and cyanobacteria usually contained phenolic acids or aldehydes at microg levels per gram of lyophilized sample. The proposed SPE/SFE extraction method would be useful for the analysis of different plant species containing trace amount of polar fraction of phenols.
Elbahjaoui, Radouane; El Qarnia, Hamid; El Ganaoui, Mohammed
2016-05-01
The proposed work presents a numerical investigation of the melting of a phase change material (PCM: Paraffin wax P116) dispersed with nanoparticles (Al2O3) in a latent heat storage unit (LHSU). The latter is composed of a number of vertical and identical slabs of nano-enhanced phase change material (NEPCM) separated by rectangular channels through which passes heat transfer fluid (HTF: water). A mathematical model based on the conservation equations of mass, momentum and energy has been developed. The resulting equations are discretized using the finite volume approach. The numerical model has been validated by experimental and numerical results published in literature. Numerical investigations have been conducted to evaluate the effects of the volumetric fraction of nanoparticles, HTF mass flow rate and inlet temperature on the latent heat storage unit's thermal behaviour and performance. Modelling results show that the volumetric fraction, HTF mass flow rate and inlet temperature need to be designed to achieve a significant improvement in thermal performance. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui
Energy Technology Data Exchange (ETDEWEB)
Alix, P.
1997-10-03
In the case of a confinement loss (breakage of a connection piece) on a pressurized liquefied gas tank, a critical two-phase (liquid-vapour) flow is generated. This thesis is aimed at the validation of models describing these flows with various fluids (water, R 11, methanol, ethyl acetate, pure butane, commercial butane), using a pilot experimental plant. Results show that reduced upstream pressure is the main parameter, thus indicating that a model can be validated using minimal fluids. The homogenous models DEM and HRM appear to be more precise
Computational Fluid Dynamics Simulation of Liquid-Phase FCC Diesel Hydrotreating in Tubular Reactor
Institute of Scientific and Technical Information of China (English)
Li Hua; Liu Ningqiang; Zeng Zhiyu; Zou Ying; Wang Jiming
2015-01-01
The computational lfuid dynamics (CFD) code, FLUENT, was used to simulate the liquid-phase FCC diesel hy-drotreating tubular reactor with a ceramic membrane tube dispenser. The chemical reaction and reaction heat were added to the model by user-deifned function (UDF), showing the distribution of temperature and content of sulifdes, nitrides, bicyclic aromatics and monocyclic aromatics in different parts of the reaction bed. When the pressure was 6.5 MPa, the amount of mixing hydrogen was 0.84% (m), the space velocity was 2 h-1 and the inlet temperature was 633K, the temperature reached a maximum at a height of 0.15 m, and the range of radial temperature reached its maximum (2.5 K) at a height of 0.15 m. It indicated that the proper ratio of height to diameter of catalyst bed in the tubular reactor was 5-6. The increase of inlet temperature, the mixing hydrogen and the decrease of space velocity led to the decrease in the content of bicyclic aromatics, sulifdes and nitrides, and the increase in monocyclic aromatics content, while the high temperature increased. The results were in good agreement with experimental data, indicating to the high accuracy of the model.
Hvozd, Taras V; Kalyuzhnyi, Yurij V
2017-02-15
We have studied the phase behavior of polydisperse Yukawa hard-sphere fluid confined in random porous media using extension and combination of high temperature approximation and scaled particle theory. The porous media are represented by the matrix of randomly placed hard-sphere obstacles. Due to the confinement, polydispersity effects are substantially enhanced. At an intermediate degree of fluid polydispersity and low density of the matrix, we observe two-phase coexistence with two critical points, and cloud and shadow curves forming closed loops of ellipsoidal shape. With the increase of the matrix density and the constant degree of polydispersity, these two critical points merge and disappear, and at lower temperatures the system fractionates into three coexisting phases. A similar phase behavior was observed in the absence of the porous media caused, however, by the increase of the polydispersity.
Giner, Beatriz; Bandrés, Isabel; Carmen López, M.; Lafuente, Carlos; Galindo, Amparo
2007-10-01
A study of the phase equilibrium (experimental and modeled) of mixtures formed by a cyclic ether and haloalkanes has been derived. Experimental data for the isothermal vapor liquid equilibrium of mixtures formed by tetrahydrofuran and tetrahydropyran and isomeric chlorobutanes at temperatures of 298.15, 313.15, and 328.15K are presented. Experimental results have been discussed in terms of both molecular characteristics of pure compounds and potential intermolecular interaction between them using thermodynamic information of the mixtures obtained earlier. The statistical associating fluid theory for potential of variable range (SAFT-VR) approach together with standard combining rules without adjustable parameters has been used to model the phase equilibrium. Good agreement between experiment and the prediction is found with such a model. Mean absolute deviations for pressures are of the order of 1kPa, while less than 0.013mole fraction for vapor phase compositions. In order to improve the results obtained, a new modeling has been carried out by introducing a unique transferable parameter kij, which modifies the strength of the dispersion interaction between unlike components in the mixtures, and is valid for all the studied mixtures being not temperature or pressure dependent. This parameter together with the SAFT-VR approach provides a description of the vapor-liquid equilibrium of the mixtures that is in excellent agreement with the experimental data for most cases. The absolute deviations are of the order of 0.005mole fraction for vapor phase compositions and less than 0.3kPa for pressure, excepting for mixtures containing 2-chloro-2-methylpropane which deviations for pressure are larger. Results obtained in this work in the modeling of the phase equilibrium with the SAFT-VR equation of state have been compared to the ones obtained in a previous study when the approach was used to model similar mixtures with clear differences in the thermodynamic behavior. We
Singh Dhillon, Navdeep; Pisano, Albert P.
2014-03-01
A novel two-port thermal-flux method has been proposed and demonstrated for degassing and charging two-phase microfluidic thermal transport systems with a degassed working fluid. In microscale heat pipes and loop heat pipes (mLHPs), small device volumes and large capillary forces associated with smaller feature sizes render conventional vacuum pump-based degassing methods quite impractical. Instead, we employ a thermally generated pressure differential to purge non-condensable gases from these devices before charging them with a degassed working fluid in a two-step process. Based on the results of preliminary experiments studying the effectiveness and reliability of three different high temperature-compatible device packaging approaches, an optimized compression packaging technique was developed to degas and charge a mLHP device using the thermal-flux method. An induction heating-based noninvasive hermetic sealing approach for permanently sealing the degassed and charged mLHP devices has also been proposed. To demonstrate the efficacy of this approach, induction heating experiments were performed to noninvasively seal 1 mm square silicon fill-hole samples with donut-shaped solder preforms. The results show that the minimum hole sealing induction heating time is heat flux limited and can be estimated using a lumped capacitance thermal model. However, further continued heating of the solder uncovers the hole due to surface tension-induced contact line dynamics of the molten solder. It was found that an optimum mass of the solder preform is required to ensure a wide enough induction-heating time window for successful sealing of a fill-hole.
Venkatachari, Anand K; Halliburton, Sandra S; Setser, Randolph M; White, Richard D; Chatzimavroudis, George P
2007-01-01
A major determinant of the success of surgical vascular modifications, such as the total cavopulmonary connection (TCPC), is the energetic efficiency that is assessed by calculating the mechanical energy loss of blood flow through the new connection. Currently, however, to determine the energy loss, invasive pressure measurements are necessary. Therefore, this study evaluated the feasibility of the viscous dissipation (VD) method, which has the potential to provide the energy loss without the need for invasive pressure measurements. Two experimental phantoms, a U-shaped tube and a glass TCPC, were scanned in a magnetic resonance (MR) imaging scanner and the images were used to construct computational models of both geometries. MR phase velocity mapping (PVM) acquisitions of all three spatial components of the fluid velocity were made in both phantoms and the VD was calculated. VD results from MR PVM experiments were compared with VD results from computational fluid dynamics (CFD) simulations on the image-based computational models. The results showed an overall agreement between MR PVM and CFD. There was a similar ascending tendency in the VD values as the image spatial resolution increased. The most accurate computations of the energy loss were achieved for a CFD grid density that was too high for MR to achieve under current MR system capabilities (in-plane pixel size of less than 0.4 mm). Nevertheless, the agreement between the MR PVM and the CFD VD results under the same resolution settings suggests that the VD method implemented with a clinical imaging modality such as MR has good potential to quantify the energy loss in vascular geometries such as the TCPC.
Bioaccessibility, solid phase distribution, and speciation of Sb in soils and in digestive fluids.
Denys, Sébastien; Tack, Karine; Caboche, Julien; Delalain, Patrice
2009-02-01
Antimony (Sb) is a pollutant found in lead-contaminated soils and occurs mainly in oxidation states Sb(III) or Sb(V), this latter being the less toxic forms to organisms. In human health risk assessment, soil ingestion is one of a major exposure route in which Human bioavailability is not considered. The objectives of this paper were to establish a link between Sb speciation in soils and its bioaccessibility considering the possible evolution of the speciation in the digestive tract. Four soils were sampled around a former lead-extraction site. Total Sb content on these soils ranged between 26mgkg(-1) and 1150mgkg(-1). Sb bioaccessibility in the soils was measured using an in vitro Bioaccessibility Group Research Europe (BARGE) digestion test. A sequential extraction procedure and physical analyses were carried out on these samples to estimate Sb speciation in soils. Differential pulse anodic stripping voltammetry (DPASV) was also used to study the evolution of Sb speciation during the digestion process. For the four samples, Sb bioaccessibility was low, ranging between 1.5% and 12% of total Sb content. Sequential extractions and physical analysis on the most contaminated soil showed that Sb was mostly occurring in the iron oxide and sulphide phases and in the pentavalent form. No change of this speciation was occurring during the digestion process. Determination of the Sb speciation in the soil matrix is thus an accurate way to demonstrate that this metalloïd can be considered as a non major issue in the overall risk characterisation if it occurs under the pentavalent form.
Dittmer, Jens; Thøgersen, Lea; Underhaug, Jarl; Bertelsen, Kresten; Vosegaard, Thomas; Pedersen, Jan M; Schiøtt, Birgit; Tajkhorshid, Emad; Skrydstrup, Troels; Nielsen, Niels Chr
2009-05-14
Detailed insight into the interplay between antimicrobial peptides and biological membranes is fundamental to our understanding of the mechanism of bacterial ion channels and the action of these in biological host-defense systems. To explore this interplay, we have studied the incorporation, membrane-bound structure, and conformation of the antimicrobial peptide alamethicin in lipid bilayers using a combination of 1H liquid-state NMR spectroscopy and molecular dynamics (MD) simulations. On the basis of experimental NMR data, we evaluate simple in-plane and transmembrane incorporation models as well as pore formation for alamethicin in DMPC/DHPC (1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine/1,2-dihexanoyl-sn-glycero-3-phosphatidylcholine) bicelles. Peptide-lipid nuclear Overhauser effect (NOE) and paramagnetic relaxation enhancement (PRE) data support a transmembrane configuration of the peptide in the bilayers, but they also reveal that the system cannot be described by a single simple conformational model because there is a very high degree of dynamics and heterogeneity in the three-component system. To explore the origin of this heterogeneity and dynamics, we have compared the NOE and PRE data with MD simulations of an ensemble of alamethicin peptides in a DMPC bilayer. From all-atom MD simulations, the contacts between peptide, lipid, and water protons are quantified over a time interval up to 95 ns. The MD simulations provide a statistical base that reflects our NMR data and even can explain some initially surprising NMR results concerning specific interactions between alamethicin and the lipids.
Selditz, U; Copinga, S; Grol, CJ; Franke, JP; de Zeeuw, RA; Wikstrom, H; Gyllenhaal, O
1999-01-01
The chromatographic behaviour of thirty structurally related racemic 2-amidotetralins on a cis-(3R, 4S)-Whelk-O 1 stationary phase was investigated at five different temperatures between 50 and -15 degrees C using super- or subscritical fluid chromatography (SFC/SubFC). Generally, low selectivity fa
Energy Technology Data Exchange (ETDEWEB)
Gassowski, G. de
1999-07-01
This study concerns the mechanical vibrations of tubular structures under the effect of an external flow and in particular the lower and upper parts of steam generators where the tubes are submitted to a transverse flow. Large amplitude vibrations can occur due to the transfer of part of the kinetic energy of the fluid into vibrational energy for the structure. This study focusses on the problems due to vibrations induced by a two-phase flow. Fluid-elastic strengths were measured for a tube submitted to a transverse flow with different levels of vacuum and for low velocities. The influence of frequency, diameter, level of vacuum, and flow rate of the mixture on the evolution of the fluid damping is analyzed experimentally. Then, the existing theoretical models are verified according to the results obtained. (J.S.)
van Ooij, P; Guédon, A; Poelma, C; Schneiders, J; Rutten, M C M; Marquering, H A; Majoie, C B; VanBavel, E; Nederveen, A J
2012-01-01
The aim of this study was to validate the flow patterns measured by high-resolution, time-resolved, three-dimensional phase contrast MRI in a real-size intracranial aneurysm phantom. Retrospectively gated three-dimensional phase contrast MRI was performed in an intracranial aneurysm phantom at a resolution of 0.2 × 0.2 × 0.3 mm(3) in a solenoid rat coil. Both steady and pulsatile flows were applied. The phase contrast MRI measurements were compared with particle image velocimetry measurements and computational fluid dynamics simulations. A quantitative comparison was performed by calculating the differences between the magnitude of the velocity vectors and angles between the velocity vectors in corresponding voxels. Qualitative analysis of the results was executed by visual inspection and comparison of the flow patterns. The root-mean-square errors of the velocity magnitude in the comparison between phase contrast MRI and computational fluid dynamics were 5% and 4% of the maximum phase contrast MRI velocity, and the medians of the angle distribution between corresponding velocity vectors were 16° and 14° for the steady and pulsatile measurements, respectively. In the phase contrast MRI and particle image velocimetry comparison, the root-mean-square errors were 12% and 10% of the maximum phase contrast MRI velocity, and the medians of the angle distribution between corresponding velocity vectors were 19° and 15° for the steady and pulsatile measurements, respectively. Good agreement was found in the qualitative comparison of flow patterns between the phase contrast MRI measurements and both particle image velocimetry measurements and computational fluid dynamics simulations. High-resolution, time-resolved, three-dimensional phase contrast MRI can accurately measure complex flow patterns in an intracranial aneurysm phantom. Copyright © 2011 John Wiley & Sons, Ltd.
Barrachina, Laura; Remacha, Ana Rosa; Soler, Lourdes; García, Natalia; Romero, Antonio; Vázquez, Francisco José; Vitoria, Arantza; Álava, María Ángeles; Lamprave, Fermín; Rodellar, Clementina
2016-12-01
Acute phase proteins are useful inflammatory markers in horses. Haptoglobin (Hp) serum level is increased in horses undergoing different inflammatory processes, including arthritis. However, Hp concentration has not been assessed in inflammatory synovial fluid (SF). The aim of the present study was to investigate the Hp response in serum and SF in horses undergoing experimentally induced arthritis. For this purpose, serum and SF samples were collected from 12 animals before amphotericin B-induced arthritis was created (T0, healthy) and 15days after the lesion induction (T1, joint inflammation) and Hp was determined by single radial immunodiffusion. The Hp increase between T0 and T1 was significant in both serum and SF, and serum Hp concentration at T0 was significantly higher than in SF, but significant differences were not found at T1, indicating a higher Hp increase in SF. A significant positive correlation for Hp concentration between serum and SF samples was found. These results highlight the potential usefulness of Hp as inflammatory marker in horses, showing for the first time the increase of Hp in SF from joint inflammation in the horse. Copyright © 2016 Elsevier B.V. All rights reserved.
Ibragimov, Ranis N.
2010-09-01
We study the linearized stability of a planar dynamical model describing two-phase perfect fluid circulating around a circle with a sufficiently large radius within a central gravitational field. The model is associated with the spatial and temporal structure of the zonally averaged global-scale atmospheric longitudinal circulation around the Earth. Two cases are studied separately; in the first one, the simulations were carried out using the rigid lid approximation at the upper boundary of the outer atmospheric layer. In the second one, the free boundary nonlinear conditions (kinematic and dynamic) were assumed on the outer atmospheric layer. For the both cases, a certain family of steady, explicit solutions which have circular streamlines was considered. The governing equations were linearized at these solutions to find the typical wave numbers of the interfacial wave perturbation to the basic state at which the destabilizing effect of shear, which overcomes the stabilizing effect of stratification, occurs. It is shown that for the both cases, the model always have the same two potentially unstable wave modes while there always exist two wave modes which are stable for any wavelengths. The behavior of the stable and unstable modes were compared for the both cases to investigate the effects of the free boundary on the mixing process at the interface.
Gu, Rui
Vapor compression cycles are widely used in heating, refrigerating and air-conditioning. A slight performance improvement in the components of a vapor compression cycle, such as the compressor, can play a significant role in saving energy use. However, the complexity and cost of these improvements can block their application in the market. Modifying the conventional cycle configuration can offer a less complex and less costly alternative approach. Economizing is a common modification for improving the performance of the refrigeration cycle, resulting in decreasing the work required to compress the gas per unit mass. Traditionally, economizing requires multi-stage compressors, the cost of which has restrained the scope for practical implementation. Compressors with injection ports, which can be used to inject economized refrigerant during the compression process, introduce new possibilities for economization with less cost. This work focuses on computationally investigating a refrigeration system performance with two-phase fluid injection, developing a better understanding of the impact of injected refrigerant quality on refrigeration system performance as well as evaluating the potential COP improvement that injection provides based on refrigeration system performance provided by Copeland.
Huang, Jun-Jie; Wang, Xinzhu
2013-01-01
We studied several wetting boundary conditions (WBCs) in the simulation of binary fluids based on phase-field theory. Five WBCs, three belonging to the surface energy (SE) formulation using the linear, cubic and sine functions (denoted as LinSE, CubSE and SinSE), the fourth using a geometric formulation (Geom), and the fifth using a characteristic interpolation (CI), were compared with each other through the study of several problems: (1) the static contact angle of a drop; (2) a Poiseuille flow-driven liquid column; (3) a wettability gradient (WG)-driven liquid column; (4) drop dewetting. It was found that while all WBCs can predict the static contact angle fairly accurately, they may affect the simulation outcomes of dynamic problems differently, depending on the driving mechanism. For the flow-driven problem, to use different WBCs had almost no effect on the flow characteristics over a large scale. But for other capillarity-driven problems, the WBC had some noticeable effects. For the WG-driven liquid colu...
Nguyen, Hung D.; Steele, Gynelle C.
2016-01-01
NASA's Small Business Innovation Research (SBIR) program focuses on technological innovation by investing in the development of innovative concepts and technologies to help NASA's mission directorates address critical research and development needs for Agency programs. This report highlights 11 of the innovative SBIR 2014 Phase I and II projects from 2010 to 2012 that focus on one of NASA Glenn Research Center's six core competencies-In-Space Propulsion and Cryogenic Fluids Management. The technologies cover a wide spectrum of applications such as divergent field annular ion engines, miniature nontoxic nitrous oxide-propane propulsion, noncatalytic ignition systems for high-performance advanced monopropellant thrusters, nontoxic storable liquid propulsion, and superconducting electric boost pumps for nuclear thermal propulsion. Each article describes an innovation and technical objective and highlights NASA commercial and industrial applications. This report provides an opportunity for NASA engineers, researchers, and program managers to learn how NASA SBIR technologies could help their programs and projects, and lead to collaborations and partnerships between the small SBIR companies and NASA that would benefit both.
Venkatramani, C J; Al-Sayah, Mohammad; Li, Guannan; Goel, Meenakshi; Girotti, James; Zang, Lisa; Wigman, Larry; Yehl, Peter; Chetwyn, Nik
2016-02-01
A new interface was designed to enable the coupling of reversed phase liquid chromatography (RPLC) and supercritical fluid chromatography (SFC). This online two-dimensional chromatographic system utilizing RPLC in the first dimension and SFC in the second was developed to achieve simultaneous achiral and chiral analysis of pharmaceutical compounds. The interface consists of an eight-port, dual-position switching valve with small volume C-18 trapping columns. The peaks of interest eluting from the first RPLC dimension column were effectively focused as sharp concentration pulses on small volume C-18 trapping column/s and then injected onto the second dimension SFC column. The first dimension RPLC separation provides the achiral purity result, and the second dimension SFC separation provides the chiral purity result (enantiomeric excess). The results are quantitative enabling simultaneous achiral, chiral analysis of compounds. The interface design and proof of concept demonstration are presented. Additionally, comparative studies to conventional SFC and case studies of the applications of 2D LC-SFC in pharmaceutical analysis is presented.
Directory of Open Access Journals (Sweden)
Ferenc Fenyvesi
Full Text Available Cyclodextrins are widely used excipients for increasing the bioavailability of poorly water-soluble drugs. Their effect on drug absorption in the gastrointestinal tract is explained by their solubility- and permeability-enhancement. The aims of this study were to investigate penetration properties of fluorescently labeled randomly methylated-beta-cyclodextrin (FITC-RAMEB on Caco-2 cell layer and examine the cellular entry of cyclodextrins on intestinal cells. The permeability of FITC-RAMEB through Caco-2 monolayers was very limited. Using this compound in 0.05 mM concentration the permeability coefficient was 3.35±1.29×10(-8 cm/s and its permeability did not change in the presence of 5 mM randomly methylated-beta-cyclodextrin. Despite of the low permeability, cellular accumulation of FITC-RAMEB in cytoplasmic vesicles was significant and showed strong time and concentration dependence, similar to the characteristics of the macropinocytosis marker Lucifer Yellow. The internalization process was fully inhibited at 0°C and it was drastically reduced at 37°C applying rottlerin, an inhibitor of macropinocytosis. Notably, FITC-RAMEB colocalized with the early endosome organizer Rab5a. These results have revealed that FITC-RAMEB is able to enter intestinal epithelial cells by fluid-phase endocytosis from the apical side. This mechanism can be an additional process which helps to overcome the intestinal barrier and contributes to the bioavailability enhancement of cyclodextrins.
Energy Technology Data Exchange (ETDEWEB)
Hirn, Gerhard
2012-07-01
When it comes to transporting heat from boilers to heating surfaces or supplying cooling energy to cooling ceilings, water has proved to be an excellent heat transfer medium. However, in some application areas it is now facing competition: various research groups are working on heat transfer fluids that have at least double the energy density. Phase change materials such as paraffin, which are finely distributed in water, store heat when they melt and release it again when they solidify.
Liu, H; Cooper, L M; Raynie, D E; Pinkston, J D; Wehmeyer, K R
1992-04-01
Supercritical fluid extraction was coupled with solid-phase extraction using octadecylsilane cartridges for the selective isolation of ultratrace levels of a drug metabolite, mebeverine alcohol, from plasma. Plasma was directly applied to the extraction cartridge, the cartridge was washed to remove protein and then extracted under supercritical conditions using CO2/5% methanol. The effluent from the extraction cell was bubbled through a small volume of 2-propanol to trap the extracted mebeverine alcohol. The effects of extraction pressure and temperature on analyte recovery were examined. The absolute recovery, selectivity, precision, and accuracy of the combined supercritical fluid extraction/solid-phase extraction approach were compared to those of conventional solid-phase extraction using gas chromatography/mass spectrometry in the selected-ion monitoring mode. Mebeverine alcohol was used as a model compound, and dog plasma was employed as the biological matrix for these studies.
Ricci, Francesco
This dissertation describes theoretical and computational studies of the origin of biological homochirality, and the existence of a liquid-liquid phase transition in pure-component network-forming fluids. A common theme throughout these studies is the use of sophisticated computer simulation and statistical mechanics techniques to study complex condensed-phase phenomena. In the first part of this dissertation, we use an elementary lattice model with molecular degrees of freedom, and satisfying microscopic reversibility, to investigate the effect of reaction reversibility on the evolution of stochastic symmetry breaking via autocatalysis and mutual inhibition in a closed system. We identify conditions under which the system's evolution towards racemic equilibrium becomes extremely slow, allowing for long-time persistence of a symmetry-broken state. We also identify a "monomer purification" mechanism, due to which a nearly homochiral state can persist for long times, even in the presence of significant reverse reaction rates. Order of magnitude estimates show that with reasonable physical parameters a symmetry broken state could persist over geologically-relevant time scales. In the second part of this dissertation, we study a chiral-symmetry breaking mechanism known as Viedma ripening. We develop a Monte Carlo model to gain further insights into the mechanisms capable of reproducing key experimental signatures associated with this phenomenon. We also provide a comprehensive investigation of how the model parameters impact the system's overall behavior. It is shown that size-dependent crystal solubility alone is insufficient to reproduce most experimental signatures, and that some form of a solid-phase chiral feedback mechanism (e.g., agglomeration) must be invoked in our model. In the third part of this dissertation, we perform rigorous free energy calculations to investigate the possibility of a liquid-liquid phase transition (LLPT) in the Stillinger-Weber (SW
Institute of Scientific and Technical Information of China (English)
付东
2004-01-01
An analytical equation of state (EOS) for hard core Asakura-Oosawa (AO) fluid is established by combining the AO potential, the first-order perturbation theory and the radial distribution function (RDF) for the hard sphere fluid. The phase equilibria are studied by using the renormalization-group (RG) theory. The obtained results agree well with the simulation data. Investigation shows that the attractive range parameter plays an important role in the phase equilibria for AO fluid.
Pester, Nicholas J.; Reeves, Eoghan P.; Rough, Mikaella E.; Ding, Kang; Seewald, Jeffrey S.; Seyfried, William E.
2012-08-01
As part of an integrated study conducted at the Lucky Strike Seamount (Mid-Atlantic Ridge, 37°17'N) in 2008, gas-tight sampling devices were used to collect high-temperature (˜300 °C) hydrothermal fluids issuing from sulfide structures distributed throughout the vent field located in the summit depression. Compared with previous observations from 1993 to 1997, the most substantial changes in vent fluid compositions are dramatically increased CO2 concentrations (˜5×, up to 133 mmol/L) and the observation of vent fluids enriched in dissolved chloride relative to seawater. Combined with an increase in δ13C values by ˜4‰ in 2008, the elevated CO2 indicates replenishment of the magmatic heat source and may be indicative of a recent magmatic event. The additional supporting fluid chemistry is, however, similar to that of the previous sampling intervals, necessitating a reassessment of the subseafloor controls on vent fluid chemistry at Lucky Strike in the context of recently obtained geophysical data that provides the depth/extent of a steady-state magma chamber. Two-phase behavior is indicated by the chloride variability in the vent fluids; and comparison with experimental data for the associated chloride-dependent partitioning of minor/trace elements suggests the possibility of a similar source fluid for all the vent structures, while limiting the likelihood of shallow phase separation and subseafloor mixing for the hydrothermal end-members. A recently calibrated Fe/Mn geothermometer indicates minimum subseafloor equilibration temperatures of 350-385 °C. However, constraints imposed by dissolved Si/Cl in conjunction with geophysical observations are consistent with peak reaction conditions at temperatures of 430-475 °C and pressures near the top of the axial magma chamber (˜410-480 bars), where magmatic CO2 becomes entrained in the circulating fluids. The distance between the magma chamber and the seafloor at Lucky Strike is substantially greater than at
Directory of Open Access Journals (Sweden)
Fuchs A.
2006-12-01
Full Text Available koWe briefly review the molecular simulation methods which can be used to predict thermophysical properties of fluids and fluid mixtures. It is shown in this paper, on the one hand, how the Gibbs Ensemble Monte Carlo Method allows phase behavior predictions for real fluids under conditions for which experimental data are difficult or impossible to obtain. On the other hand, the molecular dynamics methods used for predicting transport properties of molecular fluids are described. Finally we discuss possible future applications of these methods. Dans cet article, nous passons brièvement en revue les méthodes de simulation moléculaire applicables à la prédiction des propriétés thermophysiques des fluides et des mélanges. Nous montrons, d'une part, comment la méthode de Monte-Carlo dans l'ensemble de Gibbs permet de prédire le comportement de phase de fluides réels dans des conditions telles que l'acquisition de données expérimentales serait difficile, voire impossible. D'autre part, nous décrivons les méthodes de dynamique moléculaire utilisées pour prédire les propriétés de transport de fluides moléculaires. Enfin, nous discutons le potentiel de ces méthodes pour les applications futures.
Kondrakhov, S V; Zakharova, N E; Fadeeva, L M; Tanyashin, S V
Meningiomas of the foramen magnum (FMR) region account for 1.8 to 3.2% of all meningiomas. The international literature has insufficient data describing the state of cerebrospinal fluid (CSF) circulation in these patients. We studied 38 patients with FM meningiomas, aged from 35 to 79 years (mean age, 56.7 years). The mean meningioma size was 30 mm (10-60 mm). Meningiomas had the anterolateral localization in 29 patients, ventral localization in 5 patients, and dorsal localization in 4 patients. Twenty nine patients underwent surgery. All operated patients were examined before and after surgery. The CSF circulation was studied using phase contrast MRI (PC-MRI). The size and localization of FM meningiomas do not significantly affect the CFS circulation parameters. Pyramidal symptoms, sensory disorders, and XIth cranial nerve dysfunction are correlated with the CFS circulation parameters. According to the preoperative PC-MRI data, the CFS circulation parameters in all FM meningioma patients were significantly higher than their normal values. Surgery was followed by a reduction in the peak positive velocity, negative peak velocity, and range of the maximum linear velocity amplitude. Positive and negative volumes and the stroke volume did not change. Recovery dynamics of the CFS circulation parameters was similar, regardless of surgery completeness. According to the PC-MRI data, the CFS circulation parameters did not reach normal values in all groups of operated patients. The results of investigation of the CFS circulation in patients with FM meningiomas support the use of palliative surgery (partial resection, dural plasty, craniovertebral junction decompression) in the case of inoperable meningiomas.
Deli, M A; Abrahám, C S; Takahata, H; Katamine, S; Niwa, M
2000-12-01
1. Effects of pentosan polysulfate (PPS) and the structurally related sulfated polyanions dextran sulfate, fucoidan, and heparin on the scavenger receptor-mediated and fluidphase endocytosis in GP8 immortalized rat brain endothelial cells were investigated. 2. Using 1,1'-dioctadecyl-3,3,3,3'-tetramethylindocarboxyamine perchlorate-labeled acetylated low-density lipoprotein (DiI-AcLDL), we found a binding site with high affinity and low binding capacity, and another one with low affinity and high binding capacity. Increasing ligand concentrations could not saturate DiI-AcLDL uptake. DiI-AcLDL uptake, but not binding, was sensitive to pretreatment with filipin, an inhibitor of caveola formation. 3. PPS (20-200 microg/ml) significantly reduced the binding of DiI-AcLDL after coincubation for 3 hr, though this effect was less expressed after 18 hr. Among other polyanions, only fucoidan decreased the DiI-AcLDL binding after 3 hr, whereas dextran sulfate significantly increased it after 18 hr. PPS treatment induced an increase in DiI-AcLDL uptake, whereas other polysulfated compounds caused a significant reduction. 4. Fluid-phase endocytosis determined by the accumulation of Lucifer yellow was concentration and time dependent in GP8 cells. Coincubation with PPS or other sulfated polyanions could not significantly alter the rate of Lucifer yellow uptake. 5. In conclusion. PPS decreased the binding and increased the uptake of DiI-AcLDL in cerebral endothelial cells, an effect not mimicked by the other polyanions investigated.
Pihl, T H; Scheepers, E; Sanz, M; Goddard, A; Page, P; Toft, N; Andersen, P H; Jacobsen, S
2015-01-01
The acute phase proteins (APP) serum amyloid A (SAA), haptoglobin, and fibrinogen are valuable blood biomarkers in equine inflammatory diseases, but knowledge of factors influencing their concentrations in blood and peritoneal fluid (PF) of horses with colic is needed. The objective of this study was to investigate the influence of demographics (age, sex, breed), disease process (simple obstruction, strangulating obstruction, inflammatory), disease location, disease duration, hypovolemia, and admission hospital on concentrations of APP, lactate and white blood cell counts (WBC) in horses with colic admitted to 2 referral hospitals. The study included 367 horses with colic admitted at 2 referral hospitals. Prospective multicenter observational study of clinical data, as well as blood and PF biomarkers. Associations between biomarker concentrations and clinical variables were analyzed using multivariate linear regression analysis. Increasing pre-admission duration of colic was associated with increased concentrations of APP in blood and PF. Blood concentrations of SAA and fibrinogen were associated with disease process (inflammatory, strangulations, simple obstructions) in more colic duration groups (5-12 and >24 hours) than any of the other biomarkers. No relevant associations between demographic factors, hospital, or hydration status and the measured biomarkers were found. In horses with colic, concentrations of APP are associated mainly with disease process and duration of colic and may thus be used for assessment of disease independently of demographic or geographic factors. Serum amyloid A may be a diagnostic marker for use in colic differential diagnosis, but further evaluation is needed. Copyright © 2015 by the American College of Veterinary Internal Medicine.
Energy Technology Data Exchange (ETDEWEB)
Sharma, S.L., E-mail: sharma55@purdue.edu [School of Nuclear Engineering, Purdue University, West Lafayette, IN (United States); Hibiki, T.; Ishii, M. [School of Nuclear Engineering, Purdue University, West Lafayette, IN (United States); Schlegel, J.P. [Department of Mining and Nuclear Engineering, Missouri University of Science and Technology, Rolla, MO (United States); Buchanan, J.R.; Hogan, K.J. [Bettis Laboratory, Naval Nuclear Laboratory, West Mifflin, PA (United States); Guilbert, P.W. [ANSYS UK Ltd, Oxfordshire (United Kingdom)
2017-02-15
Highlights: • Closure form of the interfacial shear term in three-dimensional form is investigated. • Assessment against adiabatic upward bubbly air–water flow data using CFD. • Effect of addition of the interfacial shear term on the phase distribution. - Abstract: In commercially available Computational Fluid Dynamics (CFD) codes such as ANSYS CFX and Fluent, the interfacial shear term is missing in the field momentum equations. The derivation of the two-fluid model (Ishii and Hibiki, 2011) indicates the presence of this term as a momentum source in the right hand side of the field momentum equation. The inclusion of this term is considered important for proper modeling of the interfacial momentum coupling between phases. For separated flows, such as annular flow, the importance of the shear term is understood in the one-dimensional (1-D) form as the major mechanism by which the wall shear is transferred to the gas phase (Ishii and Mishima, 1984). For gas dispersed two-phase flow CFD simulations, it is important to assess the significance of this term in the prediction of phase distributions. In the first part of this work, the closure of this term in three-dimensional (3-D) form in a CFD code is investigated. For dispersed gas–liquid flow, such as bubbly or churn-turbulent flow, bubbles are dispersed in the shear layer of the continuous phase. The continuous phase shear stress is mainly due to the presence of the wall and the modeling of turbulence through the Boussinesq hypothesis. In a 3-D simulation, the continuous phase shear stress can be calculated from the continuous fluid velocity gradient, so that the interfacial shear term can be closed using the local values of the volume fraction and the total stress of liquid phase. This form also assures that the term acts as an action-reaction force for multiple phases. In the second part of this work, the effect of this term on the volume fraction distribution is investigated. For testing the model two-phase
Morini, M A; Sierra, M B; Pedroni, V I; Alarcon, L M; Appignanesi, G A; Disalvo, E A
2015-07-01
The purpose of the work is to compare the influence of the multilamellarity, phase state, lipid head groups and ionic media on the origin of the surface potential of lipid membranes. With this aim, we present a new analysis of the zeta potential of multilamellar and unilamellar vesicles composed by phosphatidylcholines (PC) and phosphatidylethanolamines (PE) dispersed in water and ionic solutions of polarizable anions, at temperatures below and above the phase transition. In general, the adsorption of anions seems to explain the origin of the zeta potential in vesicles only above the transition temperature (Tc). In this case, the sign of the surface potential is ascribed to a partial orientation of head group moiety toward the aqueous phase. This is noticeable in PC head groups but not in PEs, due to the strong lateral interaction between PO and NH group in PE.
Institute of Scientific and Technical Information of China (English)
闻建平; 贾晓强; 毛国柱
2004-01-01
A small scale isotropic mass transfer model was developed for the local liquid side mass transfer coefficients in gas-liquid-solid three-phase flow airlift loop reactor for Newtonian and non-Newtonian fluids. It is based on Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence with kl=3√2D∈11/3/π(η1-1/3-λf-1/3)where e1 is local rate of energy dissipation, Af is the local microscale, r/l is the local Kolmogoroff scale and D is the diffusion coefficient. The capability of the proposed model is discussed in the light of experimental data obtained from 12 L gas-liquid-solid three-phase flow airlift loop reactor using Newtonian and non-Newtonian fluids. Good agreement with the experimental data was obtained over a wide range of conditions suggesting a general applicability of the proposed model.
KORTI, Abdel Illah Nabil
2010-01-01
In this paper, two dimensional unsteady flow and energy equations are employed for simulating the fluid flow, heat transfer and solidification during direct chill continuous casting of Al-Mg alloy billet. In these processes, the formation of some macro defects such as thermal cracking, hot tearing, surface cracking, etc, has been found to initiate during the starting phase of the operation. International Journal of Computational Methods.
1994-12-01
Determining the Pure Component Parameters in the Redlich - Kwong -Soave Equation of State," Chemical Engineering Science, 35, 1725, 1980. 100 80. J.M...suitability for this application . Extensive literature reviews, thermophysical property surveys, and surveys of compound availability on the aromatic...and testing of novel two-phase working fluids for spacecraft thermal management applications between 300’C and 400"C. The main application of these
Directory of Open Access Journals (Sweden)
Eric A Legenzov
Full Text Available To avoid spectral interference with common fluorophores in multicolor fluorescence microscopy, a fluid-phase tracer with excitation and emission in the violet end of the visible spectrum is desirable. CM-pyranine is easily synthesized and purified. Its excitation and emission maxima at 401.5 nm and 428.5 nm, respectively, are well suited for excitation by 405-nm diode lasers now commonly available on laser-scanning microscopes. High fluorescence quantum efficiency (Q = 0.96 and strong light absorption (ε405 > 25,000 M-1cm-1 together make CM-pyranine the brightest violet aqueous tracer. The fluorescence spectrum of CM-pyranine is invariant above pH 4, which makes it a good fluid-phase marker in all cellular compartments. CM-pyranine is very photostable, is retained for long periods by cells, does not self-quench, and has negligible excimer emission. The sum of its properties make CM-pyranine an ideal fluorescent tracer. The use of CM-pyranine as a fluid-phase marker is demonstrated by multicolor confocal microscopy of cells that are also labeled with lipid and nuclear markers that have green and red fluorescence emission, respectively.
Artimenko, Margaret V.
2016-12-01
Phase equilibria in the system SiO2-TiO2-Al2O3-Fe2O3-MnO-MgO-CaO-Na2O-K2O-P2O5-H2O-CO2-N2 are calculated to illustrate phase relations in amphibolite facies metasediments over a wide range of X[H2O-CO2-N2] conditions at 600 °C and 4.4 kb. Calculations are performed using the Gibbs free energy minimization technique. Results are presented in plots showing stable mineral assemblages as a function of total carbon in the system at varying water (a_{{{{H}}2 {{O}}}} = 1) content in the presence/absence of N2 in the fluid. The calculations indicate that the typical assemblage plagioclase—quartz—biotite—ilmenite—garnet—apatite is restricted to the rocks with CO2 saturation and X_{{{{H}}_{ 2} {{O}}}} higher than 60% in the fluid. Significant decrease in X_{{{{CO}}2 }} favors the stability of muscovite rather than garnet, whereas the decrease in X_{{{{H}}_{ 2} {{O}}}} leads to the stability of microcline over all range of X_{{{{CO}}2 }}. This paper also presents the composition and parameters (pH, Eh) of the fluid equilibrated with mineral assemblage. It is shown that the presence of low concentrations of N2 causes the fluid to consist of two phases when an aqueous supercritical solution (AS) coexists with a supercritical fluid with gas-like properties (SF). At high concentration of N2, the fluid consists of SF alone; in the absence of nitrogen, the fluid consists of AS alone. The solubility of monomer SiO 2 0 and dimer Si2O 4 0 decreases with increasing CO2 and after CO2 saturation point is held constant. The magnitude of the silica solubility at CO2 saturation depends upon the water content in AS. The effect of nitrogen on quartz solubility has been demonstrated to be negligible.
Cao, M; Monson, P A
2009-10-22
We present a study of the phase behavior for models of n-alkanes with chain lengths up to C(21) based on hard sphere united atom models of methyl and methylene groups, with fixed bond lengths and C-C-C bond angles. We extend earlier work on such models of shorter alkanes by allowing for gauche conformations in the chains. We focus particularly on the orientational order about the chain axes in the solid phase near the melting point, and our model shows how the loss of this orientational order leads to the formation of rotator phases. We have made extensive calculations of the thermodynamic properties of the models as well as order parameters for tracking the degree of orientational order around the chain axis. Depending on the chain length and whether the carbon number is even or odd, the model exhibits both a rotator phase and a more orientationally ordered solid phase in addition to the fluid phase. Our results indicate that the transition between the two solid phases is first-order with a small density change. The results are qualitatively similar to those seen experimentally and show that rotator phases can appear in models of alkanes without explicit treatment of attractive forces or explicit treatment of the hydrogen atoms in the chains.
Directory of Open Access Journals (Sweden)
Yu.V. Kalyuzhnyi
2012-06-01
Full Text Available The liquid-gas phase diagram for polydisperse dipolar hard-sphere fluid with polydispersity in the hard-sphere size and dipolar moment is calculated using extension of the recently proposed thermodynamic perturbation theory for central force (TPT-CF associating potential. To establish the connection with the phase behavior of ferrocolloidal dispersions it is assumed that the dipole moment is proportional to the cube of the hard-sphere diameter. We present and discuss the full phase diagram, which includes cloud and shadow curves, binodals and distribution functions of the coexisting daughter phases at different degrees of the system polydispersity. In all cases studied polydispersity increases the region of the phase instability and shifts the critical point to the higher values of the temperature and density. The larger size particles always fractionate to the liquid phase and the smaller size particles tend to move to the gas phase. At relatively high values of the system polydispersity three-phase coexistence is observed.
Agangi, Andrea; Reddy, Steven M.
2016-11-01
The Sunda arc of Indonesia is an excellent example of how volcanic processes at convergent plate margins affect the distribution of metals and control the distribution of ore deposits. In this paper, we report microtextural observations and microanalytical data (SEM-EDS and LA-ICP-MS) of silicate and sulfide melt inclusions from fresh samples of volcanic rocks from the 2008 eruption of Mt. Krakatau and 1963 eruption of Mt. Batur, Sunda arc, Indonesia that bear implications on the concentration and transport of Cu and other chalcophile elements in mafic-intermediate magmas in arc settings. These multi-phase inclusions contain glass, amphibole and plagioclase, together with co-trapped apatite, magnetite, sulfides and lobed, drop-like Fe-oxide. We observed two stages of sulfide formation: 1) early-formed sulfide globules (pyrrhotite and intermediate solid solution), which derived from an immiscible sulfide melt and only occur as inclusions in phenocrysts; and 2) late-formed, irregular Cu-rich sulfides (intermediate solid solution to bornite), which were deposited in the presence of an aqueous fluid, and are contained as fluid phase precipitates in vapour bubbles of melt inclusions and in vesicles, as well as finely dispersed grains in the groundmass. Microtextural observations and X-ray elemental maps show that interaction between sulfide globules and aqueous fluid resulted in partial oxidation and transfer of Cu between the fluid and the sulfide phase. A compilation of whole-rock analyses from the Sunda arc indicates that Cu reaches 250-300 ppm in mafic samples (SiO2 ≤ 52 wt.%), and then suddenly drops with progressive fractionation to MS analyses of whole multi-phase melt inclusions hosted in olivine, pyroxene and plagioclase indicate variable Cu and S contents (Cu up to 6000 ppm), which do not correlate with fractionation indicators (e.g. SiO2, MgO, Rb), consistent with co-trapping of Cusbnd S phases with silicate melt. The highest Cu concentrations, Cu/S and
Lavison, Gwenaelle; Bertoncini, Fabrice; Thiébaut, Didier; Beziau, Jean-François; Carrazé, Bernadette; Valette, Pascale; Duteurtre, Xavier
2007-08-17
Car lubricant additives are added to mineral or synthetic base stocks to improve viscosity and resistance to oxidation of the lubricant and to limit wear of engines. Their total amount in the commercial lubricant varies from a few percents to 20-25%. As they belong to various chemical classes and are added to a very complex medium, the base stock, their detailed chromatographic analysis is very difficult and time consuming as it should involve sample treatment and preparative scale separations in order to simplify the sample. The aim of this work is to determine the feasibility of the separation of low molecular weight lubricant additives using various packed columns with pure CO(2) as a mobile phase to enable implementation of flame ionisation detection as universal detector. This is part of a hypernated system including more sophisticated specific detectors, such as AED, FTIR or MS to obtain detailed structural information of compounds. This paper is devoted to the comparison of some stationary phases supposed to provide hydrocarbon group type separation (silica and normal phase) or separations on alkyl-bonded silica in non-aqueous mode of some selected classes of additives in test mixtures or in base stocks. Adsorption chromatography allows partial separation of additives from the base stocks while the direct elution of test additives can only be obtained on reversed phase supports having a very efficient silanol group protection so the interaction of the more polar compounds is much reduced. A two-dimensional scheme of analysis is also described. It combines adsorption chromatography to separate most of the polar additives from the base stock and alkyl-bonded silica for more detailed separation of the additives. However, overlapping between groups of compounds and the lack of resolution between some additives and the base stock should be addressed by the implementing of selective detectors.
Institute of Scientific and Technical Information of China (English)
Hua Shang; Huaijun Liu; Leka Yan; Jianming Lei; Caixia Cui; Hui Li
2012-01-01
A total of 50 healthy volunteers aged between 18 and 54 years underwent phase-contrast cine MRI to assess cerebrospinal fluid flow characteristics in different regions of the vertebral canal. The results revealed that the cerebrospinal fluid peak flow velocity and peak flow rate in the systolic phase were significantly greater than those in the diastolic phase at the same level in the subarachnoid space of the cervical spinal canal. The ventral peak flow velocity and peak flow rate were significantly greater than the post-lateral peak flow velocity and flow rate, while there were no differences between left and right post-lateral subarachnoid peak velocity and flow rate. Moreover, there were no significant differences in peak flow velocity and peak flow rate between the systolic and diastolic phases, ventral, right post-lateral or left post-lateral peak flow velocity and peak flow rate at the same level in the subarachnoid space of the cervical spinal canal among different age groups (18-24, 25-34, 35-44, ≥ 45 years).
Huerta, Adrian; Pizio, Orest; Bryk, Pawel; Sokolowski, Stefan
A density functional approach is used to study the adsorption of the four-bonding-site model associating Lennard-Jones fluid in slit-like pores with energetically heterogeneous walls. The fluid-wall potential is qualitatively similar to that invoked by Röcken, P., Somoza, A., Tarazona, P., and Findenegg, G. H., 1999, J. chem. Phys., 108, 8089, i.e. it consists of a homogeneous part that varies in the direction perpendicular to the wall and a periodic part, varying also in one direction parallel to the wall. Both parts are modelled by Lennard-Jones 9,3-type functions. The structure of the adsorbed film is characterized by the local densities of all particles and the densities of the monomers. The phase diagrams are evaluated for several systems characterized by different corrugation of the adsorbing potential. The adsorbing field is strong enough to allow for the layering transition. As well as the formation of the so-called bridge phase that fills the pore space over the most energetic parts of the wall and of capillary condensation, the layering transition is observed within the first layer adjacent to the pore walls. If the adsorbing potential due to each pore wall is shifted in phase by pi/2, the bridge phase is not formed.
Gong, Yuezheng; Zhao, Jia; Wang, Qi
2017-10-01
A quasi-incompressible hydrodynamic phase field model for flows of fluid mixtures of two incompressible viscous fluids of distinct densities and viscosities is derived by using the generalized Onsager principle, which warrants the variational structure, the mass conservation and energy dissipation law. We recast the model in an equivalent form and discretize the equivalent system in space firstly to arrive at a time-dependent ordinary differential and algebraic equation (DAE) system, which preserves the mass conservation and energy dissipation law at the semi-discrete level. Then, we develop a temporal discretization scheme for the DAE system, where the mass conservation and the energy dissipation law are once again preserved at the fully discretized level. We prove that the fully discretized algorithm is unconditionally energy stable. Several numerical examples, including drop dynamics of viscous fluid drops immersed in another viscous fluid matrix and mixing dynamics of binary polymeric solutions, are presented to show the convergence property as well as the accuracy and efficiency of the new scheme.
Bird, R. Byron
1980-01-01
Problems in polymer fluid dynamics are described, including development of constitutive equations, rheometry, kinetic theory, flow visualization, heat transfer studies, flows with phase change, two-phase flow, polymer unit operations, and drag reduction. (JN)
Zhao, Jia; Yang, Xiaofeng; Shen, Jie; Wang, Qi
2016-01-01
We develop a linear, first-order, decoupled, energy-stable scheme for a binary hydrodynamic phase field model of mixtures of nematic liquid crystals and viscous fluids that satisfies an energy dissipation law. We show that the semi-discrete scheme in time satisfies an analogous, semi-discrete energy-dissipation law for any time-step and is therefore unconditionally stable. We then discretize the spatial operators in the scheme by a finite-difference method and implement the fully discrete scheme in a simplified version using CUDA on GPUs in 3 dimensions in space and time. Two numerical examples for rupture of nematic liquid crystal filaments immersed in a viscous fluid matrix are given, illustrating the effectiveness of this new scheme in resolving complex interfacial phenomena in free surface flows of nematic liquid crystals.
Directory of Open Access Journals (Sweden)
Algieri Angelo
2013-01-01
Full Text Available The purpose of the present work is the analysis of the fluid dynamic behavior of a high performance internal combustion engine during the intake phase. In particular, a four-valve spark-ignition engine has been characterized at the steady flow rig. Dimensionless discharge coefficients have been used to define the global fluid dynamic efficiency of the intake system, while the Laser Doppler Anemometry (LDA technique has been employed to evaluate the mean flow in the valve curtain area and to characterise the interference phenomena between the two intake valves. The investigation has shown the significant influence of the valve lift on the volumetric efficiency of the intake apparatus. Moreover, the experimental analysis has highlighted that the valve-valve interference phenomena have a relevant impact on the head breathability, on the flow development within the combustion chamber and on the velocity standard deviations.
DEFF Research Database (Denmark)
Qiu, Chen; Krüger, Yves; Wilke, Max;
2016-01-01
We present new experimental data of the low-temperature metastable region of liquid water derived from high-density synthetic fluid inclusions (996−916 kg/m3) in quartz. Microthermometric measurements include: i) Prograde (upon heating) and retrograde (upon cooling) liquid-vapour homogenisation. ...
DEFF Research Database (Denmark)
Brumm, T.; Jørgensen, Kent; Mouritsen, Ole G.
1996-01-01
The phase transition behavior of a lipid bilayer of dimyristoyl-sn-glycero-3-phosphalidylcholine/distearoyl-sn- glycero-3-phosphatidylcholine (DMPC-d54/DSPC) (1:1) on a solid support with varying curvatures was investigated with differential scanning calorimetry, infrared spectroscopy, and model...
Shrestha, Rebika; Cardenas, Alfredo E; Elber, Ron; Webb, Lauren J
2015-02-19
The magnitude of the membrane dipole field was measured using vibrational Stark effect (VSE) shifts of nitrile oscillators placed on the unnatural amino acid p-cyanophenylalanine (p-CN-Phe) added to a peptide sequence at four unique positions. These peptides, which were based on a repeating alanine-leucine motif, intercalated into small unilamellar DMPC vesicles which formed an α-helix as confirmed by circular dichroic (CD) spectroscopy. Molecular dynamics simulations of the membrane-intercalated helix containing two of the nitrile probes, one near the headgroup region of the lipid (αLAX(25)) and one buried in the interior of the bilayer (αLAX(16)), were used to examine the structure of the nitrile with respect to the membrane normal, the assumed direction of the dipole field, by quantifying both a small tilt of the helix in the bilayer and conformational rotation of the p-CN-Phe side chain at steady state. Vibrational absorption energies of the nitrile oscillator at each position showed a systematic blue shift as the nitrile was stepped toward the membrane interior; for several different concentrations of peptide, the absorption energy of the nitrile located in the middle of the bilayer was ∼3 cm(-1) greater than that of the nitrile closest to the surface of the membrane. Taken together, the measured VSE shifts and nitrile orientations within the membrane resulted in an absolute magnitude of 8-11 MV/cm for the dipole field, at the high end of the range of possible values that have been accumulated from a variety of indirect measurements. Implications for this are discussed.
Honda, H.; Mitani, Y.; Kitamura, K.; Ikemi, H.; Takaki, S.
2015-12-01
this study, we will discuss this mismatch by using fluid mechanical theory and numerical simulation of two-phase fluid flow in porous geological medium based on experimental results of two different types of sandstone.
Xu, Zhijie; Meakin, Paul
2009-06-21
Dissipative particle dynamics (DPD) is an effective mesoscopic particle model with a lower computational cost than molecular dynamics because of the soft potentials that it employs. However, the soft potential is not strong enough to prevent the DPD particles that are used to represent the fluid from penetrating solid boundaries represented by stationary DPD particles. A phase-field variable, phi(x,t), is used to indicate the phase at point x and time t, with a smooth transition from -1 (phase 1) to +1 (phase 2) across the interface. We describe an efficient implementation of no-slip boundary conditions in DPD models that combines solid-liquid particle-particle interactions with reflection at a sharp boundary located with subgrid scale accuracy using the phase field. This approach can be used for arbitrarily complex flow geometries and other similar particle models (such as smoothed particle hydrodynamics), and the validity of the model is demonstrated by DPD simulations of flow in confined systems with various geometries.
Patel, M A; Riley, F; Ashraf-Khorassani, M; Taylor, L T
2012-04-13
Both analytical scale and preparative scale packed column supercritical fluid chromatography (SFC) have found widespread applicability for chiral separations of multiple polar pharmaceutical candidates. However, SFC is rapidly becoming an achiral technique. More specifically, ion pair SFC is finding greater utility for separation of ionic analytes such as amine salts and organic sulfonates. The key to this success is, in part, the incorporation of additives such as trifluoroacetic acid and ammonium acetate into the mobile phase in association with a wide variety of both bonded silica stationary phases and high purity bare silica. Ion pairing SFC coupled with evaporative light scattering detection and mass spectrometric detection is presented here for the separation of water soluble, uncapped, isomeric peptide pairs that differ in amino acid arrangement. The separation is best achieved on either diol-bonded silica or bare silica with 1-5% (w/w) water as a significant ingredient in the mobile phase. Nitrogenous stationary phases such as 2-ethylpyridine, which had been very successful for the separation of capped peptides failed to yield the desired separation regardless of the mobile phase composition. A HILIC type retention mechanism is postulated for the separation of both isomeric uncapped peptide pairs.
Directory of Open Access Journals (Sweden)
S. Sugiharto
2014-08-01
Full Text Available Measurement of vapor flow in geothermal pipe faces great challenges due to fast fluids flow in high-temperature and high-pressure environment. In present study the flow rate measurement has been performed to characterization the geothermal vapor flow in a pipe. The experiment was carried out in a pipe which is connected to a geothermal production well, KMJ-14. The pipe has a 10” outside diameter and contains dry vapor at a pressure of 8 kg/cm2 and a temperature of 170 oC. Krypton-85 gas isotope (85Kr has been injected into the pipe. Three collimated radiation detectors positioned respectively at 127, 177 and 227m from injection point were used to obtain experimental data which represent radiotracer residence time distribution (RTD in the pipe. The last detector at the position of 227 m did not respond, which might be due to problems in cable connections. Flow properties calculated using mean residence time (MRT shows that the flow rate of the vapor in pipe is 10.98 m/s, much faster than fluid flow commonly found in various industrial process plants. Best fitting evaluated using dedicated software developed by IAEA expert obtained the Péclet number Pe as 223. This means that the flow of vapor of geothermal fluids in pipe is plug flow in character. The molecular diffusion coefficient is 0.45 m2/s, calculated from the axial dispersion model.
Ji, Xiang; Li, Dan; Li, Hua
2015-08-01
A novel molecularly imprinted polymer (MIP) monolith for highly selective extraction of cholecystokinin (CCK) neuropeptides was prepared in a micropipette tip. The MIPs were synthesized by epitope imprinting technique and the polymerization conditions were investigated and optimized. The synthesized MIPs were characterized by infrared spectroscopy, elemental analyzer and scanning electron microscope. A molecularly imprinted solid-phase microextraction (MI-μ-SPE) method was developed for the extraction of CCK neuropeptides in aqueous solutions. The parameters affecting MI-μ-SPE were optimized. The results indicated that this MIP monolith exhibited specific recognition capability and high enrichment efficiency for CCK neuropeptides. In addition, it showed excellent reusability. This MIP monolith was used for desalting and enrichment of CCK4, CCK5 and CCK8 from human cerebrospinal fluid prior to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis, and the results show that this MIP monolith can be a useful tool for effective purification and highly selective enrichment of multiple homologous CCK neuropeptides in cerebrospinal fluid simultaneously. By employing MI-μ-SPE combined with HPLC-ESI-MS/MS analysis, endogenous CCK4 in human cerebrospinal fluid was quantified.
Litasov, Konstantin D.; Shatskiy, Anton; Ohtani, Eiji
2014-04-01
Melting phase relations of peridotite and eclogite coexisting with reduced C-O-H fluid have been studied at 3-16 GPa and 1200-1600 °C. In order to perform these experiments the double-capsule technique with fO2 control by outer Mo-MoO2 or Fe-FeO buffer capsule was designed and developed for multianvil experiments at pressures 3-21 GPa. Silicate phase assemblages resemble those in volatile-free lithologies, i.e. olivine/wadsleyite-orthopyroxene-clinopyroxene-garnet in peridotite and garnet-omphacite in eclogite. Melting was detected by the appearance of quenched crystals of pyroxene, feldspar and glassy silica. Estimated solidus temperatures for peridotite + C-O-H fluid with fO2=Fe-FeO are 1200 °C at 3 GPa and 1700 °C at 16 GPa. The solidus of the system with fO2=Mo-MoO2 was about 100 °C lower. Estimated solidus temperatures for eclogite + C-O-H fluid with fO2=Fe-FeO are 1100 °C at 3 GPa and 1600 °C at 16 GPa, and for eclogite at fO2=Mo-MoO2 solidus temperatures were 20-50 °C lower. These solidus temperatures are much higher (300-500 °C) than those for peridotite and eclogite systems with H2O and/or CO2, but are still 300-400 °C lower than the solidi of volatile-free peridotite and eclogite at studied pressures. The compositions of partial melt were estimated from mass-balance calculations: partial melts of peridotite have CaO-poor (6-9 wt.%) basaltic compositions with 44-47 wt.% SiO2 and 1.1-1.6 wt.% Na2O. Melts of eclogite contain more SiO2 (47-49 wt.%) and are enriched in CaO (9-15 wt.%), Na2O (9-14 wt.%), and K2O (1.3-2.2 wt.%). All runs contained graphite or diamond crystals along with porous carbon aggregate with micro-inclusions of silicates indicating that reduced fluid may dissolve significant amounts of silicate components. Analyses of carbon aggregates using a defocused electron microprobe beam reveal compositions similar to estimated partial melts. The diamonds formed from reduced C-O-H fluid may have natural analogues as polycrystalline
Wan, Ye; Wang, Xiaolin; Hu, Wenxuan; Chou, I.-Ming; Wang, Xiaoyu; Chen, Ying; Xu, Zhimin
2017-08-01
This study presents the first description of liquid-liquid phase separation in a vapor-saturated CdSO4 solution at temperatures above 222.2 °C in fused silica capillary tubing, in which a sulfate-rich liquid (Srich) phase separates from an initially homogeneous aqueous solution and coexists with the remaining sulfate-poor liquid (Spoor) phase and a vapor phase. This phase behavior is characterized by a lower critical solution temperature (∼222.2 °C), which is a macroscale property of polymer mixtures. In situ Raman spectroscopy shows an increase in Cd2+-SO42- associations with increasing temperature, especially in the immiscible Srich phase. Phase behavior observations and in situ Raman spectroscopic analyses confirm our previous conclusion that strong ion associations are responsible for the liquid-liquid phase separation in inorganic solutions. The effects of pressure and the fluid composition on liquid-liquid phase separation are also investigated. The temperature of liquid-liquid phase separation increases almost linearly with pressure at a rate of ∼0.5 °C/MPa and decreases with the addition of methanol. Both decreases in pressure and increases in the methanol concentration decrease the dielectric constant of the solutions, favoring the Cd2+-SO42- interaction and thus liquid-liquid phase separation. The capillary size also exerts a strong influence on liquid-liquid phase separation because the immiscible Srich phase is more stable in fused silica capillary tubing with an inner diameter of ≤300 μm. Therefore, liquid-liquid phase separation can occur in hydrothermal fluids hosted in porous rocks/sediments, especially those that are rich in low-dielectric-constant components and/or at low pressures. Liquid-liquid phase separation may play an important role in the formation of Mississippi-valley-type ore deposits because the ore-forming fluids are enriched in low-dielectric-constant components. The occurrence of liquid-liquid phase separation can promote
Wang, Huili; Gao, Ming; Wang, Mei; Zhang, Rongbo; Wang, Wenwei; Dahlgren, Randy A; Wang, Xuedong
2015-03-15
Herein, we developed a novel integrated device to perform phase separation based on ultrasound-assisted salt-induced liquid-liquid microextraction for determination of five fluoroquinones (FQs) in human body fluids. The integrated device consisted of three simple HDPE components used to separate the extraction solvent from the aqueous phase prior to retrieving the extractant. A series of extraction parameters were optimized using the response surface method based on central composite design. Optimal conditions consisted of 945μL acetone extraction solvent, pH 2.1, 4.1min stir time, 5.9g Na2SO4, and 4.0min centrifugation. Under optimized conditions, the limits of detection (at S/N=3) were 0.12-0.66μgL(-1), the linear range was 0.5-500μgL(-1) and recoveries were 92.6-110.9% for the five FQs extracted from plasma and urine. The proposed method has several advantages, such as easy construction from inexpensive materials, high extraction efficiency, short extraction time, and compatibility with HPLC analysis. Thus, this method shows excellent prospects for sample pretreatment and analysis of FQs in human body fluids.
Kou, Jisheng
2016-02-25
In this paper, we propose an energy-stable evolution method for the calculation of the phase equilibria under given volume, temperature, and moles (VT-flash). An evolution model for describing the dynamics of two-phase fluid system is based on Fick’s law of diffusion for multi-component fluids and the Peng-Robinson equation of state. The mobility is obtained from diffusion coefficients by relating the gradient of chemical potential to the gradient of molar density. The evolution equation for moles of each component is derived using the discretization of diffusion equations, while the volume evolution equation is constructed based on the mechanical mechanism and the Peng-Robinson equation of state. It is proven that the proposed evolution system can well model the VT-flash problem, and moreover, it possesses the property of total energy decay. By using the Euler time scheme to discretize this evolution system, we develop an energy stable algorithm with an adaptive choice strategy of time steps, which allows us to calculate the suitable time step size to guarantee the physical properties of moles and volumes, including positivity, maximum limits, and correct definition of the Helmhotz free energy function. The proposed evolution method is also proven to be energy-stable under the proposed time step choice. Numerical examples are tested to demonstrate efficiency and robustness of the proposed method.
Lubeseder-Martellato, Clara; Alexandrow, Katharina; Hidalgo-Sastre, Ana; Heid, Irina; Boos, Sophie Luise; Briel, Thomas; Schmid, Roland M; Siveke, Jens T
2017-02-01
Fluid-phase endocytosis is a homeostatic process with an unknown role in tumor initiation. The driver mutation in pancreatic ductal adenocarcinoma (PDAC) is constitutively active KRas(G12D), which induces neoplastic transformation of acinar cells through acinar-to-ductal metaplasia (ADM). We have previously shown that KRas(G12D)-induced ADM is dependent on RAC1 and EGF receptor (EGFR) by a not fully clarified mechanism. Using three-dimensional mouse and human acinar tissue cultures and genetically engineered mouse models, we provide evidence that (i) KRas(G12D) leads to EGFR-dependent sustained fluid-phase endocytosis (FPE) during acinar metaplasia; (ii) variations in plasma membrane tension increase FPE and lead to ADM in vitro independently of EGFR; and (iii) that RAC1 regulates ADM formation partially through actin-dependent regulation of FPE. In addition, mice with a pancreas-specific deletion of the Neural-Wiskott-Aldrich syndrome protein (N-WASP), a regulator of F-actin, have reduced FPE and impaired ADM emphasizing the in vivo relevance of our findings. This work defines a new role of FPE as a tumor initiating mechanism.
Jumper, E. J.; Hugo, R. J.
1992-07-01
This paper discusses the small-aperture beam technique, a relatively new way of experimentally quantifying optically-active, turbulent-fluid-flow-induced optical degradation. The paper lays out the theoretical basis for the technique, and the relationship of the measured jitter of the beam to optical path difference. A numerical simulation of a two-dimensional heated jet is used to explore the validity of beam jitter to obtain optical path difference in a flow region where eddy production constitutes the major character of the 'turbulent' flow field.
Hu, Yuan; Sinha, Sudipta Kumar; Patel, Sandeep
2014-10-16
Using the translocation of short, charged cationic oligo-arginine peptides (mono-, di-, and triarginine) from bulk aqueous solution into model DMPC bilayers, we explore the question of the similarity of thermodynamic and structural predictions obtained from molecular dynamics simulations using all-atom and Martini coarse-grain force fields. Specifically, we estimate potentials of mean force associated with translocation using standard all-atom (CHARMM36 lipid) and polarizable and nonpolarizable Martini force fields, as well as a series of modified Martini-based parameter sets. We find that we are able to reproduce qualitative features of potentials of mean force of single amino acid side chain analogues into model bilayers. In particular, modifications of peptide-water and peptide-membrane interactions allow prediction of free energy minima at the bilayer-water interface as obtained with all-atom force fields. In the case of oligo-arginine peptides, the modified parameter sets predict interfacial free energy minima as well as free energy barriers in almost quantitative agreement with all-atom force field based simulations. Interfacial free energy minima predicted by a modified coarse-grained parameter set are -2.51, -4.28, and -5.42 for mono-, di-, and triarginine; corresponding values from all-atom simulations are -0.83, -3.33, and -3.29, respectively, all in units of kcal/mol. We found that a stronger interaction between oligo-arginine and the membrane components and a weaker interaction between oligo-arginine and water are crucial for producing such minima in PMFs using the polarizable CG model. The difference between bulk aqueous and bilayer center states predicted by the modified coarse-grain force field are 11.71, 14.14, and 16.53 kcal/mol, and those by the all-atom model are 6.94, 8.64, and 12.80 kcal/mol; those are of almost the same order of magnitude. Our simulations also demonstrate a remarkable similarity in the structural aspects of the ensemble of
Jiang, F.; Tsuji, T.
2017-01-01
Given the world's growing demand for energy, a combination of geological CO2 sequestration and enhanced oil recovery (EOR) technologies is currently regarded as a promising solution, as it would provide a means of reducing carbon emissions into the atmosphere while also leading to the economic benefit of simultaneously recovering oil. The optimization of injection strategies to maximize CO2 storage and increase the oil recovery factors requires complicated pore-scale flow information within a reservoir system consisting of coexisting oil, water, and CO2 phases. In this study, an immiscible three-phase lattice-Boltzmann (LB) model was developed to investigate the complicated flow state with interaction between water, oil, and CO2 systems in porous media. The two main mechanisms of oil remobilization, namely, double-drainage and film flow, can be captured by our model. The estimation of three-phase relative permeability is proposed using the digital rock physics (DRP) simulations. The results indicate that the relative permeability of CO2 as calculated using our steady state method is not sensitive to the initial oil fraction if the oil distribution is originally uniform. Baker's (1988) empirical model was tested and found to be able to provide a good prediction of the three-phase relative permeability data. Our numerical method provides a new tool for accurately predicting three-phase relative permeability data directly based on micro-CT rock images.
DEFF Research Database (Denmark)
Qiu, Chen; Krüger, Yves; Wilke, Max
2016-01-01
We present new experimental data of the low-temperature metastable region of liquid water derived from high-density synthetic fluid inclusions (996−916 kg/m3) in quartz. Microthermometric measurements include: i) Prograde (upon heating) and retrograde (upon cooling) liquid-vapour homogenisation. We...... used single ultrashort laser pulses to stimulate vapour bubble nucleation in initially monophase liquid inclusions. Water densities were calculated based on prograde homogenisation temperatures using the IAPWS-95 formulation. We found retrograde liquid-vapour homogenisation temperatures in excellent...... water with a density of 0.921 kg/m3 remains in a homogeneous state during cooling down to the temperaure of −30.5 °C, where it is transformed into ice whose density corresponds to zero pressure. iii) ice melting. Ice melting temperatures of up to 6.8 °C were measured in absence of the vapour bubble, i...
Schellen, A.; Ooms, B.; Lagemaat, D. van de; Vreeken, R.; Dongen, W.D. van
2003-01-01
A generic method was developed for the fast determination of a wide range of drugs in serum or plasma. The methodology comprises generic solid-phase extraction, on-line coupled to gradient HPLC with tandem mass spectrometric detection (SPE-LC-MS/MS). The individual components of the SPE-LC-MS/MS sys
Directory of Open Access Journals (Sweden)
F. Gharagheizi
2006-09-01
Full Text Available In order to model phase equilibria at all pressures, it is necessary to have an equation of state. We have chosen the Sako-Wu-Prausnitz cubic equation of state, which had shown some promising results. However, in order to satisfy our demands, we had to modify it slightly and fit new pure component parameters. New pure component parameters have been determined for ethylene and the n-alkane series, using vapor pressure data, saturated liquid volume and one-phase PVT-data. For higher n-alkanes, where vapor pressure data are poor or not available, determination of the pure component parameters was made in part by extrapolation and in part by fitting to one-phase PVT-data. Using one-fluid van der Waals mixing rules, with one adjustable interaction parameter, good correlation of binary hydrocarbon system was obtained, except for the critical region. The extension of the equation of state to polyethylene systems is covered in this work. Using the determined parameters, flash and cloud point calculations were performed, and treating the polymer as polydisperse. The results fit data well.
Yan, Tony Q; Orihuela, Carlos; Preston, Jay P; Xia, Fang
2010-11-01
The use of phase appropriate technologies is critical for efficiently moving drug candidates forward in the early stages of drug discovery and development. Phase appropriate purification technology develops the analytical method and subsequently scales up the method and turns the sample around quickly (Kennedy et al., J Chromatogr A 2004; 1046:55). In this article, separation results and conditions from supercritical fluid chromatography (SFC), high-performance liquid chromatography (HPLC), and steady-state recycling (SSR) for the resolutions of three pharmaceutical intermediates in the early stage of the drug development are discussed. The first study used SFC and SSR to separate an impurity for a Good Manufacturing Practice (GMP) campaign. The analytical method development and scale-up conditions are discussed. Productivity, solvent usage, and sample solubility under SFC and SSR conditions are also compared. The second study compared SFC to batch HPLC in separating a diastereomer. Due to higher separation efficiency, SFC was able to resolute multiple peaks. The third study involved the addition of dichloromethane as a co-solvent in SFC purification--improving sample selectivity and solubility. From the separation results of these purifications, SFC and SSR are clearly phase appropriate technologies in the early drug development stage.
Mirjalili, Shahab; Ivey, Christopher Blake; Mani, Ali
2016-11-01
The diffuse interface(DI) and volume of fluid(VOF) methods are mass conserving front capturing schemes which can handle large interfacial topology changes in realistic two phase flows. The DI method is a conservative phase field method that tracks an interface with finite thickness spread over a few cells and does not require reinitialization. In addition to having the desirable properties of level set methods for naturally capturing curvature and surface tension forces, the model conserves mass continuously and discretely. The VOF method, which tracks the fractional tagged volume in a cell, is discretely conservative by requiring costly geometric reconstructions of the interface and the fluxes. Both methods however, suffer from inaccuracies in calculation of curvature and surface tension forces. We present a quantitative comparison of these methods in terms of their accuracy, convergence rate, memory, and computational cost using canonical 2D two-phase test cases: damped surface wave, oscillating drop, equilibrium static drop, and dense moving drop. We further compared the models in their ability to handle thin films by looking at the impact of a water drop onto a deep water pool. Considering these results, we suggest qualitative guidelines for using the DI and VOF methods. Supported by ONR.
Drift flux model as approximation of two fluid model for two phase dispersed and slug flow in tube
Energy Technology Data Exchange (ETDEWEB)
Nigmatulin, R.I.
1995-09-01
The analysis of one-dimensional schematizing for non-steady two-phase dispersed and slug flow in tube is presented. Quasi-static approximation, when inertia forces because of the accelerations of the phases may be neglected, is considered. Gas-liquid bubbly and slug vertical upward flows are analyzed. Non-trivial theoretical equations for slip velocity for these flows are derived. Juxtaposition of the derived equations for slip velocity with the famous Zuber-Findlay correlation as cross correlation coefficients is criticized. The generalization of non-steady drift flux Wallis theory taking into account influence of wall friction on the bubbly or slug flows for kinematical waves is considered.
Zhang, Y.; Ye, S.; Wu, J.
2013-12-01
Immiscible two-phase flows in fractured media are encountered in many engineering processes such as recovery of oil and gas, exploitation of geothermal energy, and groundwater contamination by immiscible chemicals. A two-dimensional rough wall parallel plate fracture model was set up and light transmission method (LTM) was applied to study two-phase flow system in fractured media. The fracture model stood with up and bottom flow and no flow on other two sides. A charge-coupled device (CCD) camera was used to monitor the migration of DNAPL and gas bubbles in the fracture model. To simulate two-phase system in fracture media, air was injected into the water saturated cell (C1) through the middle of the bottom and NAPL was injected into another water saturated cell (C2) through the middle of the top of the cell. The results show LTM was an effective way in monitoring the migration of DNAPL and gas bubbles in the fracture models. Gas moved upwards quickly to the top of C1 in the way of air bubbles generated at the injection position and formed a continuous distribution. The migration of TCE was controlled by its own weight and fracture aperture. TCE migrated to large aperture firstly when moving downwards, and intruded into smaller one with accumulation of TCE. Light Intensity-Saturation Models (LISMs) were developed to estimate the gas or NAPL saturation in two-phase system. The volume amount of infiltration of gas bubbles or NAPL could be estimated from light intensities by LISMs. There were strong correlations between the added and calculated amounts of gas or TCE. It is feasible to use the light transmission method to characterize the movement and spatial distribution of gas or NAPL in fractured media.
Li, Jun
2013-09-01
We present a single-particle Lennard-Jones (L-J) model for CO2 and N2. Simplified L-J models for other small polyatomic molecules can be obtained following the methodology described herein. The phase-coexistence diagrams of single-component systems computed using the proposed single-particle models for CO2 and N2 agree well with experimental data over a wide range of temperatures. These diagrams are computed using the Markov Chain Monte Carlo method based on the Gibbs-NVT ensemble. This good agreement validates the proposed simplified models. That is, with properly selected parameters, the single-particle models have similar accuracy in predicting gas-phase properties as more complex, state-of-the-art molecular models. To further test these single-particle models, three binary mixtures of CH4, CO2 and N2 are studied using a Gibbs-NPT ensemble. These results are compared against experimental data over a wide range of pressures. The single-particle model has similar accuracy in the gas phase as traditional models although its deviation in the liquid phase is greater. Since the single-particle model reduces the particle number and avoids the time-consuming Ewald summation used to evaluate Coulomb interactions, the proposed model improves the computational efficiency significantly, particularly in the case of high liquid density where the acceptance rate of the particle-swap trial move increases. We compare, at constant temperature and pressure, the Gibbs-NPT and Gibbs-NVT ensembles to analyze their performance differences and results consistency. As theoretically predicted, the agreement between the simulations implies that Gibbs-NVT can be used to validate Gibbs-NPT predictions when experimental data is not available. © 2013 Elsevier Inc.
Pihl, Tina; Scheepers, E.; Sanz, M.; Goddard, A.; Page, P.; Toft, Nils; Andersen, Pia Haubro; Jacobsen, Stine
2015-01-01
Background: The acute phase proteins (APP) serum amyloid A (SAA), haptoglobin, and ﬁbrinogen are valuable blood bi-omarkers in equine inﬂammatory diseases, but knowledge of factors inﬂuencing their concentrations in blood and peritonealﬂuid (PF) of horses with colic is needed.Objectives: The objective of this study was to investigate the inﬂuence of demographics (age, sex, breed), disease process (sim-ple obstruction, strangulating obstruction, inﬂammatory), disease location, disease duration...
Universal phase and force diagrams for a microbubble or pendant drop in static fluid on a surface
Wei, P. S.; Hsiao, C. C.; Chen, K. Y.
2008-01-01
Dimensionless three-dimensional universal phase and lift force diagrams of a microbubble (or pendant drop) in static liquid on a solid surface (or orifice) are presented in this work. Microbubble dynamics has been found to play a vital role in mass, momentum, energy, and concentration transfer rates in contemporary micro- and nanosciences and technologies. In this study, dimensionless phase and force diagrams are introduced by utilizing the analytical solutions of the microbubble shape reported in the literature. It shows that phase and force diagrams can be universally specified by two dimensionless independent parameters, Bond number, and contact angle (or base radius). Based on the presence of an inflection point or neck on the microbubble surface, each diagram exhibits three regions. Growth, detachment, and entrapment of a microbubble can be described by path lines in three regions. The corresponding universal total lift forces include hydrostatic buoyancy, difference in gas, and hydrostatic pressures at the base, capillary pressure, as well as surface tension induced by the variation of circumference, which has not been treated in the literature so far. In the absence of viscous stress and Marangoni force, the total lift force equals surface tension induced by the variation of circumference. The latter can be an attaching or lifting force, depending on whether the state in the distinct regions and contact angle is less than or greater than a critical angle. The critical angle, which is slightly less than the inclination angle at the inflection point, is decreased with increasing Bond number.
Reiss, Howard; Manzanares, José A.
2016-09-01
Using several theoretical toolsldots (i) the nucleation theorem, (ii) an equivalent cavity, (iii) the reversible work of adding a cavity to an open hard sphere system, and (iv) the theory of "stability"... the authors estimated the density at which the hard sphere freezing transition occurs. No direct involvement of the equilibrium solid phase is involved. The reduced density \\uppi a^3ρ _f/6 (where a is the hard sphere diameter and ρ _f is the actual density at which freezing occurs) is found to be 0.4937 while the value obtained by computer simulation is 0.494. The agreement is good, but the new method still contains some approximation. However, the approximation is based on the idea that at a density just below ρ _f the fluid adopts a distorted structure resembling the solid, but different enough so that long-range order vanishes. Initial loss of stability may not be involved in every fluid-solid transition, but it may be an early step in the hard sphere and related systems.
Soják, Ladislav; Addová, Gabriela; Kubinec, Róbert; Kraus, Angelika; Hu, Gengyuan
2002-02-15
Published retention indices of acyclic alkenes C5-C7 on squalane and polydimethylsiloxane as stationary phases were investigated, and reliable retention indices of alkenes from various sources were converted to separation systems used in a laboratory. Retention indices measured on available authentic commercial alkenes and on alkenic fraction of gasoline, published retention indices as well as means of GC-MS were used for verification of calculated retention indices. Retention of some gas chromatographic unseparated isomer pairs was obtained by mass spectrometric deconvolution using a specific single-ion monitoring. On the basis of these retention data, C5-C7 alkenes were identified and analyzed in the gasoline from fluid catalytic cracking. In the gasoline all 59 acyclic C5-C7 isomeric alkenes were determined at significantly different concentration levels.
DEFF Research Database (Denmark)
Bundgaard, Louise; Bendixen, Emøke; Sørensen, Mette Aa
2016-01-01
In horses, pathological healing with formation of exuberant granulation tissue (EGT) is a particular problem in limb wounds, whereas body wounds tend to heal without complications. Chronic inflammation has been proposed to be central to the pathogenesis of EGT. This study aimed to investigate...... levels of inflammatory acute phase proteins (APPs) in interstitial fluid from wounds in horses. A novel approach for absolute quantification of proteins, selected reaction monitoring (SRM)-based mass spectrometry in combination with a quantification concatamer (QconCAT), was used for the quantification...... five horses at days 1, 2, 7, and 14 after wounding and healing without (body) and with (limb) the formation of EGT. The QconCAT included proteotypic peptides representing each of the protein targets and was used to direct the design of a gene, which was expressed in Escherichia coli in a media...
DEFF Research Database (Denmark)
Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens
2013-01-01
The complex fluid phase behaviour, of the binary system comprised of water and tetrahydrofuran (THF) is modelled by use of the cubic-plus-association (CPA) equation of state. A total of seven modelling approaches are analysed, differing only in their way of describing THF and its interactions...... are named Case 2 to Case 7. Case 2 treats THF as non self-associating, but applies a single association site on the THF oxygen atom, that allows for cross-linking with a single water molecule. Case 3 is identical to Case 2 but applies two association sites on THF, allowing for simultaneous cross...... accepting- and two electron donating sites.Cases 6 and 7 are similar to Cases 4 and 5, respectively, however the binary cross-association volume between electron accepting sites on water and electron donating sites on THF is adjusted to match the CPA descriptions with available experimental VLE data...
DEFF Research Database (Denmark)
Jiang, Fengli; Rao, Yulan; Wang, Rong;
2016-01-01
A novel and simple online solid-phase extraction liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous determination of diazepam and its five metabolites including nordazepam, oxazepam, temazepam, oxazepam glucuronide, and temazepam glucuronide...... in human oral fluid. Human oral fluid was obtained using the Salivette(®) collection device, and 100 μL of oral fluid samples were loaded onto HySphere Resin GP cartridge for extraction. Analytes were separated on a Waters Xterra C18 column and quantified by liquid chromatography with tandem mass...
Refrigerating fluids; Fluides frigorigenes
Energy Technology Data Exchange (ETDEWEB)
Anon.
1999-03-01
Refrigerating fluids are experiencing a real revolution since few years. CFCs with their destructive effect on the ozone layer are now prohibited while HCFCs will be progressively eliminated and replaced by HFCs. However, HFCs can contribute to the increase of the greenhouse effect. The solutions proposed by thermal engineering professionals consist in the confinement of air-conditioning installations (elimination of recurrent leaks) and in the improvement of installations efficiency. HCFC fluids like the R 22 are still widely used in air-conditioning but they are supposed to be replaced by HFC fluids like the R 134a, the R 407C or the R 410A. This short paper gives a brief presentation of these fluids and of their chemical characteristics. (J.S.)
Directory of Open Access Journals (Sweden)
Yuanhua Lin
2013-01-01
Full Text Available Investigation of propagation characteristics of a pressure wave is of great significance to the solution of the transient pressure problem caused by unsteady operations during management pressure drilling operations. With consideration of the important factors such as virtual mass force, drag force, angular frequency, gas influx rate, pressure, temperature, and well depth, a united wave velocity model has been proposed based on pressure gradient equations in drilling operations, gas-liquid two-fluid model, the gas-drilling mud equations of state, and small perturbation theory. Solved by adopting the Runge-Kutta method, calculation results indicate that the wave velocity and void fraction have different values with respect to well depth. In the annulus, the drop of pressure causes an increase in void fraction along the flow direction. The void fraction increases first slightly and then sharply; correspondingly the wave velocity first gradually decreases and then slightly increases. In general, the wave velocity tends to increase with the increase in back pressure and the decrease of gas influx rate and angular frequency, significantly in low range. Taking the virtual mass force into account, the dispersion characteristic of the pressure wave weakens obviously, especially at the position close to the wellhead.
Energy Technology Data Exchange (ETDEWEB)
Pruess, K.
2011-04-01
ECO2M is a fluid property module for the TOUGH2 simulator (Version 2.0) that was designed for applications to geologic storage of CO{sub 2} in saline aquifers. It includes a comprehensive description of the thermodynamics and thermophysical properties of H{sub 2}O - NaCl - CO{sub 2} mixtures, that reproduces fluid properties largely within experimental error for temperature, pressure and salinity conditions in the range of 10 C {le} T {le} 110 C, P {le} 600 bar, and salinity from zero up to full halite saturation. The fluid property correlations used in ECO2M are identical to the earlier ECO2N fluid property package, but whereas ECO2N could represent only a single CO{sub 2}-rich phase, ECO2M can describe all possible phase conditions for brine-CO{sub 2} mixtures, including transitions between super- and sub-critical conditions, and phase change between liquid and gaseous CO{sub 2}. This allows for seamless modeling of CO{sub 2} storage and leakage. Flow processes can be modeled isothermally or non-isothermally, and phase conditions represented may include a single (aqueous or CO{sub 2}-rich) phase, as well as two-and three-phase mixtures of aqueous, liquid CO{sub 2} and gaseous CO{sub 2} phases. Fluid phases may appear or disappear in the course of a simulation, and solid salt may precipitate or dissolve. TOUGH2/ECO2M is upwardly compatible with ECO2N and accepts ECO2N-style inputs. This report gives technical specifications of ECO2M and includes instructions for preparing input data. Code applications are illustrated by means of several sample problems, including problems that had been previously solved with TOUGH2/ECO2N.
Energy Technology Data Exchange (ETDEWEB)
Lallemand, A. [Institut National des Sciences Appliquees (INSA), Centre de Thermique de Lyon (CETHIL), UMR 5008, 69 - Villeurbanne (France); Mercier, P. [CEA Grenoble, Groupement pour la Recherche sur les Echangeurs Thermiques (GRETH), 38 (France); Royon, L. [Paris-1 Univ., Lab. de Biorheologie et d' Hydrodynamique Physico-Chimique, 75 (France); Dumas, J.P. [L' Ecole Nationale Superieure en Genie des Technologies Industrielles, Lab. de Thermique Energetique et Procedes, 64 - Pau (France); Guilpart, J. [URGPAN/CEMAGRE, 33 - Bordeaux (France)
2004-07-01
This PRI aims to participate to the development of alternate solutions for refrigerant fluids, for the cold transport and more specially a two phase refrigerant fluid: the stabilized ice slurry. The research program presented three main axis: design, realization and characterization of stabilized ice slurry, experimental studies of transport and transfer properties, study of online measurement process of the solid content. A simulation has been realized to evaluate the energy efficiency of this refrigerant use. (A.L.B.)
Bloch, C A; Watkins, J B
1978-05-01
A simple mehtod using reverse-phase liquid chromatography is presented for resolution and quantitation of the major conjugated bile acids of man, including the glycine and taurine conjugates of the dihydroxy bile acids, chenodeoxycholic and deoxycholic acid. Using modern, high-performance chromatographic equipment, analysis time is less than 30 minutes. The quantitative range of the method, with detection by refractive index, is 0.05 to 0.1 mumol of bile acid and the limit of detection for an injection sample is 0.01 mumol. This provides a sensitivity sufficient for analysis of dilute duodenal and gallbladder bile with minimal sample preparation.
Directory of Open Access Journals (Sweden)
Mr. Sanjay V. Barad,
2014-04-01
Full Text Available In this paper The Thermal behaviour of Micro channel heat sink were investigated used Al2o3-water base nanoluid. The model have been solved by ANSYS fluent 14.5 solver. The Dimension of each rectangular channel is 215m width, 821m depth and 4.48cm length. The Reynolds number range from 200 to 400 for power input 100 w. The high thermal conductivity of nanoparticles is shown to enhance the single phase heat transfer coefficient, especially for laminar flow. Higher heat transfer coefficient were achieved mostly in entrances region of micro channels. The enhancement was weaker in fully developed region.
Dahms, Rainer N
2015-05-01
The fidelity of Gradient Theory simulations depends on the accuracy of saturation properties and influence parameters, and require equations of state (EoS) which exhibit a fundamentally consistent behavior in the two-phase regime. Widely applied multi-parameter EoS, however, are generally invalid inside this region. Hence, they may not be fully suitable for application in concert with Gradient Theory despite their ability to accurately predict saturation properties. The commonly assumed temperature-dependence of pure component influence parameters usually restricts their validity to subcritical temperature regimes. This may distort predictions for general multi-component interfaces where temperatures often exceed the critical temperature of vapor phase components. Then, the calculation of influence parameters is not well defined. In this paper, one of the first studies is presented in which Gradient Theory is combined with a next-generation Helmholtz energy EoS which facilitates fundamentally consistent calculations over the entire two-phase regime. Illustrated on pentafluoroethane as an example, reference simulations using this method are performed. They demonstrate the significance of such high-accuracy and fundamentally consistent calculations for the computation of interfacial properties. These reference simulations are compared to corresponding results from cubic PR EoS, widely-applied in combination with Gradient Theory, and mBWR EoS. The analysis reveals that neither of those two methods succeeds to consistently capture the qualitative distribution of obtained key thermodynamic properties in Gradient Theory. Furthermore, a generalized expression of the pure component influence parameter is presented. This development is informed by its fundamental definition based on the direct correlation function of the homogeneous fluid and by presented high-fidelity simulations of interfacial density profiles. The new model preserves the accuracy of previous temperature
Geerts, Bart
2011-01-01
Patients in the intensive care unit (ICU) and in the peri-operative phase are dependent on physicians and nurses for their fluid intake. Volume status optimization is required to maximize oxygen delivery to vital organs. Unnecessary fluid administration can, however, lead to general and pulmonary
Geerts, Bart
2011-01-01
Patients in the intensive care unit (ICU) and in the peri-operative phase are dependent on physicians and nurses for their fluid intake. Volume status optimization is required to maximize oxygen delivery to vital organs. Unnecessary fluid administration can, however, lead to general and pulmonary oe
Geerts, Bart
2011-01-01
Patients in the intensive care unit (ICU) and in the peri-operative phase are dependent on physicians and nurses for their fluid intake. Volume status optimization is required to maximize oxygen delivery to vital organs. Unnecessary fluid administration can, however, lead to general and pulmonary oe
Supercritical fluid reverse micelle separation
Fulton, John L.; Smith, Richard D.
1993-01-01
A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W.sub.o that determines the maximum size of the reverse micelles. The maximum ratio W.sub.o of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions.
Supercritical fluid reverse micelle separation
Fulton, J.L.; Smith, R.D.
1993-11-30
A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W[sub o] that determines the maximum size of the reverse micelles. The maximum ratio W[sub o] of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions. 27 figures.
DEFF Research Database (Denmark)
Musko, Nikolai; Jensen, Anker Degn; Baiker, Alfons
2012-01-01
vapour–liquid or liquid–liquid equilibria data available in the literature. No experimental data for the CO2–2-butenal binary system were available in the literature; therefore, the bubble points of this mixture of varying composition at three different temperatures were measured in a high-pressure view...... cell. The results of the catalytic experiments showed that small amounts of carbon dioxide added to the system significantly decrease the conversion, whereas at higher loadings of CO2 the reaction rate gradually increases reaching a maximum. The CPA calculations revealed that this maximum is achieved...... in the so-called “expanded liquid” region, which is located near the critical point of the reacting mixture. It was also found that in this point the hydrogen concentration achieved its maximum in the CO2-expanded phase. Furthermore, the pressure – temperature regions where the multicomponent reaction...
Directory of Open Access Journals (Sweden)
Maher A.R. Sadiq Al-Baghdadi
2010-05-01
Full Text Available Damage mechanisms in a proton exchange membrane (PEM fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the damage mechanisms in the membrane and gas diffusion layers, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional. In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to simulate the hygro and thermal stresses in PEM fuel cell, which are occurring during the cell operation due to the changes of temperature and relative humidity. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. The mechanical behaviour of the membrane, catalyst layers, and gas diffusion layers during the operation of a unit cell has been studied and investigated. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and stresses distribution that have limited experimental data. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. These results may explain the occurrence of cracks and pinholes in the membrane during regular cell operation. This model is used to study the effect of operating, design, and material parameters on fuel cell hygro-thermal stresses in polymer membrane, catalyst layers, and gas diffusion layers. Detailed analyses of the fuel cell durability under various operating conditions have been
Li, Hua; Li, Dan
2015-11-10
In this study, a novel molecularly imprinted polymer (MIP) monolith for highly selective extraction of enkephalins was synthesized and prepared in a micropipette tip using epitope imprinting technique. The synthesized MIPs were characterized by scanning electron microscope (SEM) and infrared spectroscopy. A molecularly imprinted solid-phase microextraction (MISPME) method was developed for extraction of enkephalins in aqueous solutions. The parameters affecting MISPME were optimized. The results indicated that this MIP monolith exhibited specific recognition capability, high enrichment efficiency and excellent reusability for enkephalins. MALDI-TOF MS analysis demonstrated that this MIP monolith can act as a useful tool for highly selective purification and enrichment of enkephalin, a kind of low abundance protein, from high-abundance proteins in human cerebrospinal fluids (CSF). Employed this MIP monolith as solid-phase microextraction column, quantitative assay of enkephalins in human CSF was developed by HPLC-ultraviolet (UV) detection in this work. The detection limits were 0.05-0.08nM. This MISPME/HPLC-UV method was used to quantify Met-enkephalin and Leu-enkephalin levels in the CSF of patients with cancer pain.
Zehani, Yasmine; Lemaire, Lucas; Ghinet, Alina; Millet, Régis; Chavatte, Philippe; Vaccher, Claude; Lipka, Emmanuelle
2016-10-07
Four polysaccharide based chiral stationary phases were chosen, two chlorinated: Lux™ Amylose-2 (tris-5-chloro-2-methylphenylcarbamate of amylose) and Lux™ Cellulose-2 (tris-3-chloro-4-methylphenylcarbamate of cellulose) and two methylated: Chiralpak(®) AD-H (tris-3,5-dimethylphenylcarbamate of amylose) and Chiralcel(®) OD-H (tris-3,5-dimethylphenylcarbamate of cellulose) to separate four 3-carboxamido-5-aryl isoxazole derivatives by supercritical fluid chromatography. The effect of chiral stationary phase, co-solvent nature (MeOH, EtOH, 2-PrOH and ACN) and percentage (10-20%), temperature (20-45°C) and chemical structure of the compounds on retention, resolution and elution order were thoroughly studied. In addition, thermodynamic parameters were determined from the linear portion of the Van't Hoff plots. For all the derivatives, the Lux™ Cellulose-2 and Chiralpak(®) AD-H provided excellent resolutions (Rs=9.78) in short run time (under 6min). The preparation of about 10mg of each of the eight enantiomers was achieved successfully on a Chiralpak(®) AD-H with various percentages of ethanol as a co-solvent. Lastly, the enantiomeric purity of each of the eight individual enantiomer generated was determined and found higher than 98%.
Directory of Open Access Journals (Sweden)
Narimatsu C.P.
2001-01-01
Full Text Available In this work, the effects of particle size and density on the fluid dynamic behavior of vertical gas-solid transport of Group D particles in a 53.4 mm diameter transport tube were studied. For the conditions tested, the experimental curves of pressure gradient versus air velocity presented a minimum pressure gradient point, which is associated with a change in the flow regime from dense to dilute phase. The increases in particle size from 1.00 to 3.68 mm and in density from 935 to 2500 kg/m³ caused an increase in pressure gradient for the dense-phase transport region, but were not relevant in dilute transport. The transition velocity between dense and dilute flow (Umin also increased with increasing particle density and diameter. An empirical equation was fitted for predicting transition air velocity for the transport of glass spheres. Additional experiments, covering a wider range of conditions and particles properties, are still needed to allow the fitting of a generalized equation for prediction of Umin.
Sheth, Rubik B.; Ahlstrom, Thomas D.; Le, Hung V.
2016-01-01
NASA's Orion Multipurpose Crew Vehicle's Exploration Mission 2 is expected to loiter in Lunar orbit for a relatively long period of time. In low Lunar orbit (LLO) the thermal environment is cyclic - extremely cold in the eclipse and relatively hot near the subsolar point. Phase change material heat exchangers (PCM HXs) are the best option for long term missions in these environments. A PCM HX allows a vehicle to store excess waste energy by thawing a phase change material such as n-pentadecane wax. During portions of the orbit that are extremely cold, the excess energy is rejected, resolidifying the wax. Due to the inherent risk of compromising the heat exchanger during multiple freeze and thaw cycles, a unique payload was designed for the International Space Station to test and demonstration the functions of a PCM HX. The payload incorporates the use of a pumped fluid system and a thermoelectric heat exchanger to promote the freezing and thawing of the PCM HX. This paper shall review the design and development undertaken to build such a system.
Baudelet, Davy; Schifano-Faux, Nadège; Ghinet, Alina; Dezitter, Xavier; Barbotin, Florent; Gautret, Philippe; Rigo, Benoit; Chavatte, Philippe; Millet, Régis; Furman, Christophe; Vaccher, Claude; Lipka, Emmanuelle
2014-10-10
Analytical enantioseparation of three pyroglutamide derivatives with pharmacological activity against the purinergic receptor P2X7, was run in both high-performance liquid chromatography and supercritical fluid chromatography. Four polysaccharide based chiral stationary phases, namely amylose and cellulose tris (3,5-dimethylphenylcarbamate), amylose tris ((S)-α-methylbenzylcarbamate) and cellulose tris (4-methylbenzoate) with various mobile phases consisted of either heptane/alcohol (ethanol and 2-propanol) or carbon dioxide/alcohol (methanol or ethanol) mixtures, were investigated. After analytical screenings, the best conditions were transposed, for compound 1, to semi-preparative scale. Each approach was fully validated to meet the International Conference on Harmonisation requirements and compared. Whereas the limits of detection and quantification were near six-fold better in HPLC than in SFC (respectively 0.20 and 0.66 μM versus 1.11 and 3.53 μM for one of the enantiomers), in terms of low solvent consumption (7.2 mL of EtOH versus 3.2 mL of EtOH plus 28.8 mL of toxic and inflammable heptane per injection in SFC and HPLC, respectively), time effective cost (9 min versus 40 min per injection in SFC and HPLC, respectively) and yields (98% versus 71% in SFC and HPLC, respectively), the latter method proved its ecological superiority.
He, Lin; Li, Qing; Liu, Lihua; Wang, Yuanli; Xie, Jing; Yang, Hongdan; Wang, Qun
2015-01-01
The accessory gland (AG) is an important component of the male reproductive system of arthropods, its secretions enhance fertility, some AG proteins bind to the spermatozoa and affect its function and properties. Here we report the first comprehensive catalog of the AG secreted fluid during the mature phase of the Chinese mitten crab (Eriocheir sinensis). AG proteins were separated by one-dimensional gel electrophoresis and analyzed by reverse phase high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). Altogether, the mass spectra of 1173 peptides were detected (1067 without decoy and contaminants) which allowed for the identification of 486 different proteins annotated upon the NCBI database (http://www.ncbi.nlm.nih.gov/) and our transcritptome dataset. The mass spectrometry proteomics data have been deposited at the ProteomeXchange with identifier PXD000700. An extensive description of the AG proteome will help provide the basis for a better understanding of a number of reproductive mechanisms, including potentially spermatophore breakdown, dynamic functional and morphological changes in sperm cells and sperm acrosin enzyme vitality. Thus, the comprehensive catalog of proteins presented here can serve as a valuable reference for future studies of sperm maturation and regulatory mechanisms involved in crustacean reproduction.
Directory of Open Access Journals (Sweden)
Stamataki S. K.
2006-11-01
Full Text Available The capabilities of cubic Equations of State (EoS in the correlation and the prediction of phase equilibria at hyperbaric conditions is examined. PVT data of pure compounds as well as VLE and volumetric data of binary mixtures up to 2000 bar are used. Correlation and prediction results are presented with the translated and modified Peng-Robinson (t - mPR EoS and EoS/GE models. The performance of cubic EoS with a single interaction parameter (kij in describing VLE is remarkable considering the level of pressures involved. The same is valid for the PVT results including the relative liquid volumes of the C1/nC24 system. With typical errors of about 10% deviations in pressure of 100 - 200 bar are, of course, encountered which can be eliminated by the use of second interaction coefficient in the covolume combining rule. Predicted kij values obtained from generalized correlations developed from low pressure VLE data provide reasonable results for systems with hydrocarbons up to nC16 even at high pressures, but fail for higher asymmetric ones. Volume translation is essential for PVT predictions. The temperature independent translation of t - mPR and that of Jhaveri and Yougren give very satisfactory results. LCVM provides the best results of the EoS/GE models studied and gives very good predictions for rather symmetric systems which become poorer with asymmetric ones at very high pressures. La capacité des équations d'état (EoS cubiques pour corréler et prédire les équilibres de phases en conditions hyperbares est analysée. Les données PVT de corps purs ainsi que les données d'équilibres liquide-vapeur (VLE et volumétriques pour des mélanges binaires, jusqu'à 2000 bar sont utilisées. Les résultats des corrélations et des prédictions sont présentés pour l'équation de Peng-Robinson translatée et modifiée (t - mPR, ainsi que pour les modèles EoS/GE. Les performances des EoS cubiques avec un paramètre d'interaction unique (kij pour
Directory of Open Access Journals (Sweden)
Yadollah Yamini
2014-08-01
Full Text Available A simple, rapid and sensitive method termed as magnetic solid phase extraction (MSPE combined with high-performance liquid chromatography-ultraviolet detector (HPLC-UV has been proposed for the determination of trace amounts of chlorpromazine (CPZ in water, urine and plasma samples. The separation and determination was performed on a C18 column under the optimal chromatographic conditions. Several factors influencing the extraction efficiency of CPZ, such as pH, surfactant and adsorbent amounts, ionic strength, extraction time, sample volume and desorption conditions, were studied and optimized. Under the optimal MSPE conditions, the extraction percentage of CPZ was 74%, 27% and 16% in water, urine and plasma samples, respectively. The limits of detection (LODs of the proposed approach were 0.1, 5.0 and 10 ng/mL in water, urine and plasma samples, respectively. The relative standard deviations (RSDs based on five replicate determinations at 10 ng/mL level of CPZ was 1.2%. Good linear behaviors over the investigated concentration ranges (0.25–300 ng/mL with good coefficient of determination, R2>0.9998, were obtained. Good spike recoveries with relative errors less than 9.0% were obtained when applying the proposed method to water, urine and plasma samples.
... carefully. Removing a sample of the fluid through amniocentesis can provide information about the sex, health, and development of the fetus. Images Amniocentesis Amniotic fluid Polyhydramnios Amniotic fluid References Cunningham FG, ...
DEFF Research Database (Denmark)
Pedersen, Ulf Rørbæk; Peters, Günther H.; Schrøder, Thomas;
by Heimburg from experiments focusing on the phase transition between the fluid and the ordered gel phases. The correlations, which are reported here for three different membranes (DMPC, DMPS-Na, and DMPSH), have volume-energy correlation coefficients ranging from 0.81 to 0.89. The DMPC membrane was studied...... at two temperatures showing that the correlation coefficient increases as the phase transition is approached...
Bolze, Jörg; Fujisawa, Tetsuro; Nagao, Takashi; Norisada, Kazushi; Saitô, Hazime; Naito, Akira
2000-10-01
The phase behavior of lipid bilayered micelles (`bicelles') (dimyristoyl-phosphatidylcholine, DMPC/dihexanoyl-phosphatidyl-choline, DHPC 2.6/1) has been studied by small angle X-ray scattering and 31P NMR. Below 3% w/v the bilayers are arranged in tightly packed stacks. At intermediate concentrations single units are observed, whereas at 24% w/v and higher, weak stacking occurs again. The DMPC/DHPC ratio in the bicelles strongly increases at low concentration, which is correlated with an increase in the bicelle size and stacking. The increase of the order parameter in a magnetic field is related to the stack formation. Below 297 K there is no stacking at any concentration and no magnetic alignment.
Energy Technology Data Exchange (ETDEWEB)
Isoda, Haruo; Takeda, Hiroyasu; Yamashita, Shuhei; Takehara, Yasuo; Sakahara, Harumi [Hamamatsu University School of Medicine, Department of Radiology, Hamamatsu, Shizuoka (Japan); Ohkura, Yasuhide; Kosugi, Takashi [Renaissance of Technology Corporation, Hamamatsu, Shizuoka (Japan); Hirano, Masaya [GE Healthcare Japan, Tokyo (Japan); Hiramatsu, Hisaya; Namba, Hiroki [Hamamatsu University School of Medicine, Department of Neurosurgery, Hamamatsu, Shizuoka (Japan); Alley, Marcus T.; Bammer, Roland; Pelc, Norbert J. [Stanford University School of Medicine, Department of Radiology, Radiological Sciences Laboratory, Stanford, CA (United States)
2010-10-15
Hemodynamics is thought to play a very important role in the initiation, growth, and rupture of intracranial aneurysms. The purpose of our study was to perform in vivo hemodynamic analysis of unruptured intracranial aneurysms of magnetic resonance fluid dynamics using time-resolved three-dimensional phase-contrast MRI (4D-Flow) at 1.5 T and to analyze relationships between hemodynamics and wall shear stress (WSS) and oscillatory shear index (OSI). This study included nine subjects with 14 unruptured aneurysms. 4D-Flow was performed by a 1.5-T magnetic resonance scanner with a head coil. We calculated in vivo streamlines, WSS, and OSI of intracranial aneurysms based on 4D-Flow with our software. We evaluated the number of spiral flows in the aneurysms and compared the differences in WSS or OSI between the vessel and aneurysm and between whole aneurysm and the apex of the spiral flow. 3D streamlines, WSS, and OSI distribution maps in arbitrary direction during the cardiac phase were obtained for all intracranial aneurysms. Twelve aneurysms had one spiral flow each, and two aneurysms had two spiral flows each. The WSS was lower and the OSI was higher in the aneurysm compared to the vessel. The apex of the spiral flow had a lower WSS and higher OSI relative to the whole aneurysm. Each intracranial aneurysm in this study had at least one spiral flow. The WSS was lower and OSI was higher at the apex of the spiral flow than the whole aneurysmal wall. (orig.)
Analysis of the two-fluid model and the drift-flux model for numerical calculation of two-phase flow
Energy Technology Data Exchange (ETDEWEB)
Munkejord, Svend Tollak
2006-05-11
This thesis analyses models for two-phase flows and methods for the numerical resolution of these models. It is therefore one contribution to the development of reliable design tools for multiphase applications. Such tools are needed and expected by engineers in a range of fields, including in the oil and gas industry. The approximate Riemann solver of Roe has been studied. Roe schemes for three different two-phase flow models have been implemented in the framework of a standard numerical algorithm for the solution of hyperbolic conservation laws. The schemes have been analysed by calculation of benchmark tests from the literature, and by comparison with each other. A Roe scheme for the four-equation one-pressure two-fluid model has been implemented, and a second-order extension based on wave decomposition and flux-difference splitting was shown to work well and to give improved results compared to the first-order scheme. The convergence properties of the scheme were tested on smooth and discontinuous solutions. A Roe scheme has been proposed for a five-equation two-pressure two-fluid model with pressure relaxation. The use of analogous numerical methods for the five-equation and four-equation models allowed for a direct comparison of a method with and without pressure relaxation. Numerical experiments demonstrated that the two approaches converged to the same results, but that the five-equation pressure-relaxation method was significantly more dissipative, particularly for contact discontinuities. Furthermore, even though the five-equation model with instantaneous pressure relaxation has real eigenvalues, the calculations showed that it produced oscillations for cases where the four-equation model had complex eigenvalues. A Roe scheme has been constructed for the drift-flux model with general closure laws. For the case of the Zuber-Findlay slip law describing bubbly flows, the Roe matrix is completely analytical. Hence the present Roe scheme is more efficient than
Soso, Simone B; Koziel, Jacek A
2017-07-11
Lions (Panthera leo) use chemical signaling to indicate health, reproductive status, and territorial ownership. To date, no study has reported on both scent and composition of marking fluid (MF) from P. leo. The objectives of this study were to: 1) develop a novel method for simultaneous chemical and scent identification of lion MF in its totality (urine + MF), 2) identify characteristic odorants responsible for the overall scent of MF as perceived by human panelists, and 3) compare the existing library of known odorous compounds characterized as eliciting behaviors in animals in order to understand potential functionality in lion behavior. Solid-phase microextraction and simultaneous chemical-sensory analyses with multidimensional gas-chromatography-mass spectrometry-olfactometry improved separating, isolating, and identifying mixed (MF, urine) compounds versus solvent-based extraction and chemical analyses. 2,5-Dimethylpyrazine, 4-methylphenol, and 3-methylcyclopentanone were isolated and identified as the compounds responsible for the characteristic odor of lion MF. Twenty-eight volatile organic compounds (VOCs) emitted from MF were identified, adding a new list of compounds previously unidentified in lion urine. New chemicals were identified in nine compound groups: ketones, aldehydes, amines, alcohols, aromatics, sulfur-containing compounds, phenyls, phenols, and volatile fatty acids. Twenty-three VOCs are known semiochemicals that are implicated in attraction, reproduction, and alarm-signaling behaviors in other species.
Zhang, Cheng; Jin, Lixia; Zhou, Shanshan; Zhang, Yifan; Feng, Shuoli; Zhou, Qinyan
2011-03-01
The enantiomeric separations of three neonicotinoid insecticides (identified as compounds 1, 2, and 3) were performed on three polysaccharide-type chiral columns, that is, Chiralcel OD-H, Chiralpak AD-H, and Chiralpak IB, by high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). Effects of the modifier percentage and column temperature on chiral recognitions of chiral stationary phases were also studied. Both 1 and 2 could be resolved on all three columns selected, with the highest R(s) values obtained on Chiralpak AD-H and Chiralcel OD-H, respectively. However, satisfactory separation of the four stereoisomers of 3 was only achieved on Chiralcel OD-H. Considering the effects of ethanol on the values of k, α, and R(s), we concluded that hydrogen bonding, π-π, and/or dipole-dipole interactions might be all responsible for the chiral separation. In comparison to HPLC, a shorter run time was achieved for 1 and 2 by SFC. However, 3 could not be stereoselectively resolved using SFC. On the basis of the calculated thermodynamic parameters, we found that the separation processes of enantiomers of 1 and 2 were entropy controlled and enthalpy controlled, respectively.
Jumaah, Firas; Jędrkiewicz, Renata; Gromadzka, Justyna; Namieśnik, Jacek; Essén, Sofia; Turner, Charlotta; Sandahl, Margareta
2017-09-20
This study demonstrates the effect of column selectivity and density of supercritical carbon dioxide (SC-CO2) on the separation of monochloropropanediol (MCPD) esters, known as food toxicants, using SC-CO2 without addition of cosolvent in ultrahigh performance supercritical fluid chromatography-mass spectrometry (UHPSFC-MS). This study shows that over 20 2-monochloropropanediol (2-MCPD) and 3-monochloropropanediol (3-MCPD) mono- and diesters are separated on a 2-picolylamine column in less than 12 min. The presence and position of a hydroxyl group in the structure, the number of unsaturated bonds, and the acyl chain length play a significant role in the separation of MCPD esters. The flow rate, backpressure, and column oven temperature, which affect the density of the mobile phase, were shown to have a substantial impact on retention, efficiency, and selectivity. The developed method was successfully applied for the determination of MCPD esters in refined oils and showed a close to excellent green analysis score using the Analytical Eco-Scale.
Mohd Adib, Mohd Azrul Hisham; Ii, Satoshi; Watanabe, Yoshiyuki; Wada, Shigeo
2017-02-04
The integration of phase-contrast magnetic resonance images (PC-MRI) and computational fluid dynamics (CFD) is a way to obtain detailed information of patient-specific hemodynamics. This study proposes a novel strategy for imposing a pressure condition on the outlet boundary (called the outlet pressure) in CFD to minimize velocity differences between the PC-MRI measurement and the CFD simulation, and to investigate the effects of outlet pressure on the numerical solution. The investigation involved ten patient-specific aneurysms reconstructed from a digital subtraction angiography image, specifically on aneurysms located at the bifurcation region. To evaluate the effects of imposing the outlet pressure, three different approaches were used, namely: a pressure-fixed (P-fixed) approach; a flow rate control (Q-control) approach; and a velocity-field-optimized (V-optimized) approach. Numerical investigations show that the highest reduction in velocity difference always occurs in the V-optimized approach, where the mean of velocity difference (normalized by inlet velocity) is 19.3%. Additionally, the highest velocity differences appear near to the wall and vessel bifurcation for 60% of the patients, resulting in differences in wall shear stress. These findings provide a new methodology for PC-MRI integrated CFD simulation and are useful for understanding the evaluation of velocity difference between the PC-MRI and CFD.
Nold, Andreas; Sibley, David N.; Goddard, Benjamin D.; Kalliadasis, Serafim
2014-07-01
We examine the nanoscale behavior of an equilibrium three-phase contact line in the presence of long-ranged intermolecular forces by employing a statistical mechanics of fluids approach, namely, density functional theory (DFT) together with fundamental measure theory (FMT). This enables us to evaluate the predictive quality of effective Hamiltonian models in the vicinity of the contact line. In particular, we compare the results for mean field effective Hamiltonians with disjoining pressures defined through (i) the adsorption isotherm for a planar liquid film, and (ii) the normal force balance at the contact line. We find that the height profile obtained using (i) shows good agreement with the adsorption film thickness of the DFT-FMT equilibrium density profile in terms of maximal curvature and the behavior at large film heights. In contrast, we observe that while the height profile obtained by using (ii) satisfies basic sum rules, it shows little agreement with the adsorption film thickness of the DFT results. The results are verified for contact angles of 20°, 40°, and 60°.
Institute of Scientific and Technical Information of China (English)
刘春江; 袁希钢
2002-01-01
A computational fluid-dynamics model is presented for predicting the two-phase two-dimensional liquid phase flow on a distillation column tray based on the modification of Navier-Stokes Equation by considering both the resistance and the enhanced turbulence created by the uprising vapor. Experimental measurement of the local liquid phase velocity on an air-water simulator of 1.2 m in diameter by using the hot film anemometer is briefly described. Two of the conventional fluid-dynaxmic constants are readjusted for the case of liquid flow on a tray by fitting the experimental data. The predicted local liquid phase velocity and direction of flow by the present model are confirmed satisfactorily by the authors' experimental measurements and by the data from literature. By the aid of the present model, the concentration field on the tray can be computed for the evaluation of the enhancement of liquid phase concentration across a tray. The advantages of applying computational fluid-dynamics to tray column design are discussed.
Centrella, Stephen; Austrheim, Håkon; Putnis, Andrew
2015-11-01
The Precambrian granulite facies rocks of Lindås Nappe, Bergen Arcs, Caledonides of W. Norway are partially hydrated at amphibolite and eclogite facies conditions. The Lindås Nappe outcrops over an area of ca. 1000 km2 where relict granulite facies lenses make up only ca. 10%. At Hillandsvatnet, garnetite displays sharp hydration fronts across which the granulite facies assemblage composed of garnet (55%) and clinopyroxene (45%) is replaced by an amphibolite facies mineralogy defined by chlorite, epidote and amphibole. The major element bulk composition does not change significantly across the hydration front, apart from the volatile components (loss on ignition, LOI) that increases from 0.17 wt.% in the granulite to 2.43 wt.% in the amphibolite. However the replacements of garnet and of clinopyroxene are pseudomorphic so that the grain shapes of the garnet and clinopyroxene are preserved even when they are completely replaced. The textural evolution during the replacement of garnet by pargasite, epidote and chlorite and of pyroxene by hornblende and quartz in our rock sample conforms to that expected by a coupled dissolution-precipitation mechanism. SEM and electron microprobe analysis coupled with the software XMapTools V 1.06.1 were used to quantify the local mass transfer required during the replacement processes. The element losses and gains in replacing the garnet are approximately balanced by the opposite gains and losses associated with the replacement of clinopyroxene. The coupling between dissolution and precipitation on both the grain and whole rock spatial scale preserves the volume of the rock throughout the hydration process. However, the hydration involves reduction of rock density and mass balance calculations, together with volume preservation (isovolumetric reaction) require a significant loss of the mass of the rock to the fluid phase. This suggests a mechanism for coupling between the local stress generated by hydration reactions and mass
Valchev, Galin; Dantchev, Daniel
2015-07-01
We study, using general scaling arguments and mean-field type calculations, the behavior of the critical Casimir force and its interplay with the van der Waals force acting between two parallel slabs separated at a distance L from each other, confining some fluctuating fluid medium, say a nonpolar one-component fluid or a binary liquid mixture. The surfaces of the slabs are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials ensuring the so-called (+,+) boundary conditions. The slabs, on the other hand, influence the fluid by long-range competing dispersion potentials, which represent irrelevant interactions in renormalization-group sense. Under such conditions, one usually expects attractive Casimir force governed by universal scaling function, pertinent to the extraordinary surface universality class of Ising type systems, to which the dispersion potentials provide only corrections to scaling. We demonstrate, however, that below a given threshold thickness of the system Lcrit for a suitable set of slabs-fluid and fluid-fluid coupling parameters the competition between the effects due to the coatings and the slabs can result in sign change of the Casimir force acting between the surfaces confining the fluid when one changes the temperature T , the chemical potential of the fluid μ , or L . The last implies that by choosing specific materials for the slabs, coatings, and the fluid for L ≲Lcrit one can realize repulsive Casimir force with nonuniversal behavior which, upon increasing L , gradually turns into an attractive one described by a universal scaling function, depending only on the relevant scaling fields related to the temperature and the excess chemical potential, for L ≫Lcrit . We present arguments and relevant data for specific substances in support of the experimental feasibility of the predicted behavior of the force. It can
Energy Technology Data Exchange (ETDEWEB)
Demasles, H.
2002-05-15
The purpose of the work is to study two-phase mixture heat exchange composed of water particles suspended in silicone oil circulating in a closed loop. Water, contained in polymer porous matrix, is freezing by successive passages in plane plate heat exchanger. Thermo-hydraulic literature data analysis about these fluids in exchangers shows important blanks in exchange coefficient and pressure drop forecast methods and in experimental data. Experimental results, issued of global energy balance on a test section specifically conceived and made for this study, show doping effect on exchange coefficient. Before phase change, micro-convective effects of rotating particles improve exchange coefficient of 2,3 factor. Supplementary enhancement included between 2 and 16 appeared during phase change. Trial measured discrepancy are certainly induced by bed layer formation due to low flow speed. At the end of particle freezing, when latent heat is not involved anymore in exchange enhancement, important heat transfer reduction is observed. This is attributed to the cooling suspension rheological evolution and the change of flow particle distribution. Modelling results corroborate heat exchange improvement due to phase change: particles act as sources when discharging there latent heat. They stop fluid temperature dropping and enable to keep a high wall temperature gradient. A deepened suspension rheological study is necessary for a better understanding of observed phenomenon, nevertheless these first results show already an important energetic profit brings by particles in range temperature of 0 and -6 deg C. (author)
Directory of Open Access Journals (Sweden)
Selaković Vesna M.
2002-01-01
Full Text Available Background. Brain ischemia initiates series of biochemical reactions that could, directly or indirectly, induce and extend processes that damage numerous cellular and subcellular structures. One of the reactions of organism to ischemia is the increased release of glucocorticoid hormones, included in regulation of effects of numerous mediators/modulators that could be released in the acute phase of brain ischemia. Considering that brain infarction induced systemic response of organism to stress, we presumed that it reflected the contents of cortisol in the cerebrospinal fluid (CSF during the acute phase of the disease, and that cortisol influenced damaging processes of lipid peroxidation in CNS initiated by ischemia. The aim of our investigation was to define temporal dynamics and manner correlation of cortisol concentration and index of lipid peroxidation (ILP in the CSF patients in the acute phase of completed stroke. Methods. In this investigation we followed changes of cortisol concentration and ILP in the CSF of 53 patients in the acute phase of completed stroke. Control group included 14 age and sex matched patients, subjected to diagnostic lumbar radiculography because of the sudden motor deficiency onset, without disturbances in the CSF passage and without pain and the consequences of anti-pain and anti-inflammatory therapy. From the perspective of the duration of period after an ischemic episode patients were divided into four groups: group A: 0-6 hours (n=12, group B: 7-12 hours (n=14, group C: 13-24 hours (n=14, and group D: 24-48 hours of postischemic period (n=13. Concentration of cortisol in the CSF was measured by quantitative RIA method (Cortisol Bridge kit, Biodata. The ILP was determined according to the spectrophotometric method. Results. Concentration of cortisol in the CSF of patients with completed stroke was of amount 69 ± 6.7 pmol/ml CSF and was significantly increased (p<0.001 compared to the values of the control group
Seung, W P; Feldman, B F
1985-09-01
Acute hemorrhagic pancreatitis (AHP) was induced in 43 anesthetized rats by retrograde injection of sodium taurodeoxycholic acid into the common pancreatic biliary duct. At postinjection hours 1, 3, 6, 12, and 18, samples of plasma and hemorrhagic ascitic fluid (HAF) were obtained from rats in which AHP was induced and from rats that were sham operated. Early phase components of the kallikrein kinin system, including kallikrein-like (KK) activity and prekallikrein (PKK) and kallikrein inhibitor (KKI) concentrations, were measured in plasma and HAF samples. In the rats with induced AHP, PKK concentrations were decreased significantly in 18-hour plasma samples (P less than 0.05) and in all HAF samples (P less than 0.001) from 1 to 18 hours after induction of AHP. The KK activity was significantly increased (P less than 0.001) in the 6- and 12-hour plasma samples. In the 1-hour HAF samples, KK activity was increased greater than 10 times over that in the plasma pool of rats and remained increased for 18 hours. The KKI concentrations were markedly decreased in all HAF samples. In the sham-operated group, no significant change was observed. Histopathologic changes included edema, extensive hemorrhage, focal necrosis of many acinar cells around the head of the pancreas, slight inflammatory cell infiltration, vascular thrombosis, and partial lysis of pancreatic ducts. The extent of the changes of PKK, KK, and KKI values in HAF was greater than the extent of those in plasma. Increasing KK activity in plasma and HAF is indicative of bradykinin generation and the participation of this system in local and systemic pathologic change.(ABSTRACT TRUNCATED AT 250 WORDS)
Berg, Philipp; Stucht, Daniel; Janiga, Gábor; Beuing, Oliver; Speck, Oliver; Thévenin, Dominique
2014-04-01
Computational fluid dynamics (CFD) opens up multiple opportunities to investigate the hemodynamics of the human vascular system. However, due to numerous assumptions the acceptance of CFD among physicians is still limited in practice and validation through comparison is mandatory. Time-dependent quantitative phase-contrast magnetic resonance imaging PC-MRI measurements in a healthy volunteer and two intracranial aneurysms were carried out at 3 and 7 Tesla. Based on the acquired images, three-dimensional (3D) models of the aneurysms were reconstructed and used for the numerical simulations. Flow information from the MR measurements were applied as boundary conditions. The four-dimensional (4D) velocity fields obtained by CFD and MRI were qualitatively as well as quantitatively compared including cut planes and vector analyses. For all cases a high similarity of the velocity patterns was observed. Additionally, the quantitative analysis revealed a good agreement between CFD and MRI. Deviations were caused by minor differences between the reconstructed vessel models and the actual lumen. The comparisons between diastole and systole indicate that relative differences between MRI and CFD are intensified with increasing velocity. The findings of this study lead to the conclusion that CFD and MRI agree well in predicting intracranial velocities when realistic geometries and boundary conditions are provided. Due to the considerably higher temporal and spatial resolution of CFD compared to MRI, complex flow patterns can be further investigated in order to evaluate their role with respect to aneurysm formation or rupture. Nevertheless, special care is required regarding the vessel reconstruction since the geometry has a major impact on the subsequent numerical results.
Lim, Hyun-Hee; Shin, Ho-Sang
2017-02-01
An analytical method for the detection of 14 volatile organic compounds (VOCs) was developed to investigate VOCs in refill fluids and cartridges of electronic cigarettes (EC) using headspace solid-phase micro extraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). In total, 14 VOCs were identified and quantified in 283 flavored liquids, 21 nicotine liquids, and 12 disposable cartridges. The detected concentration ranges of the VOCs are as follows: benzene (0.008-2.28 mg L(-1)), toluene (0.006-0.687 mg L(-1)), ethylbenzene (0.01-1.21 mg L(-1)), m-xylene (0.002-1.13 mg L(-1)), p-xylene (0.007-2.8 mg L(-1)), o-xylene (0.004-2.27 mg L(-1)), styrene (0.011-0.339 mg L(-1)), ethyl acetate (0.3-669.9 mg L(-1)), ethanol (16-38,742 mg L(-1)), methanol (66-3375 mg L(-1)), pyridine (0.077-99.7 mg L(-1)), acetylpyrazine (0.077-147 mg L(-1)), 2,3,5-trimethylpyrazine (0.008-96.8 mg L(-1)), and octamethylcyclotetrasiloxane (0.1-57.2 mg L(-1)). Benzene, toluene, ethylbenzene, m-xylene, p-xylene, and o-xylene coexisted in samples, which may have originated from the use of petrogenic hydrocarbons as an extraction solvent for flavor and nicotine from natural plants. The maximum detected concentrations of benzene, methanol, and ethanol in liquid samples were found in quantities higher than their authorized maximum limits as residual solvents in pharmaceutical products.
Berger, Terry A
2014-10-17
A mis-match between the post-column mobile phase temperature and the UV detector flow cell temperature can cause significant UV noise in supercritical fluid chromatography (SFC). Deviations as little as 5 °C can increase noise as much as 5 times, making the detector unsuited for trace analysis. Two approaches were used to minimize this noise. When a flow cell was in direct thermal contact (metal on metal) with the detector optical bench, the mobile phase temperature was actively controlled to the measured flow cell temperature, by using one of the heat exchangers (HX) in the column compartment. However, with some older, but still widely used flow cell designs, this required repeated, hourly monitoring of the flow cell temperature and repeated manual adjustment of the heat exchanger temperature, due to thermal drift. Flow cell design had a strong influence on susceptibility to this thermally induced noise. Thermally insulating the flow cell from the optical bench made some cells much less susceptible to such thermally induced noise. Five different flow cells, some insulated, some un-insulated, were evaluated. Most had a truncated conical flow path, but one had a cylindrical flow path. Using either approach, the ASTM noise, with a 10mm, 13 μL conical flow cell, could be optimized to ≈0.007 mAU at 2.5 Hz, in SFC, which is very near the 0.006 mAU manufacturer's specification for HPLC. The insulated version of this flow cell required far less optimization, compared to the un-insulated version. At 150 bar, an experimental 3mm, 2 μL flow cell, with only one side insulated, yielded noise slightly too high (≈0.16-0.18 mAU) for trace analysis, at 80 Hz. However, at 200 bar, noise at 80 Hz was noise ratio (S/N) >10. Even partially un-insulated, this flow cell design was much less susceptible to thermally induced noise. Further insulating this flow cell design failed to improve performance.
Fluid-fluid versus fluid-solid demixing in mixtures of parallel hard hypercubes
Lafuente, Luis; Martínez-Ratón, Yuri
2011-02-01
It is well known that increase of the spatial dimensionality enhances the fluid-fluid demixing of a binary mixture of hard hyperspheres, i.e. the demixing occurs for lower mixture size asymmetry as compared to the three-dimensional case. However, according to simulations, in the latter dimension the fluid-fluid demixing is metastable with respect to the fluid-solid transition. According to the results obtained from approximations to the equation of state of hard hyperspheres in higher dimensions, the fluid-fluid demixing might become stable for high enough dimension. However, this conclusion is rather speculative since none of these works have taken into account the stability of the crystalline phase (by a minimization of a given density functional, by spinodal calculations or by MC simulations). Of course, the lack of results is justified by the difficulty of performing density functional calculations or simulations in high dimensions and, in particular, for highly asymmetric binary mixtures. In the present work, we will take advantage of a well tested theoretical tool, namely the fundamental measure density functional theory for parallel hard hypercubes (in the continuum and in the hypercubic lattice). With this, we have calculated the fluid-fluid and fluid-solid spinodals for different spatial dimensions. We have obtained, no matter what the dimensionality, the mixture size asymmetry or the polydispersity (included as a bimodal distribution function centered around the asymmetric edge lengths), that the fluid-fluid critical point is always located above the fluid-solid spinodal. In conclusion, these results point to the existence of demixing between at least one solid phase rich in large particles and one fluid phase rich in small ones, preempting a fluid-fluid demixing, independently of the spatial dimension or the polydispersity.
Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming
2007-01-01
A modified hydrothermal diamond anvil cell (HDAC) rail assembly has been constructed for making synchrotron x-ray absorption spectroscopy, x-ray fluorescence, and x-ray mapping measurements on fluids or solid phases in contact with hydrothermal fluids up to ???900??C and 700 MPa. The diamond anvils of the HDAC are modified by laser milling grooves or holes, for the reduction of attenuation of incident and fluorescent x rays and sample cavities. The modified HDAC rail assembly has flexibility in design for measurement of light elements at low concentrations or heavy elements at trace levels in the sample and the capability to probe minute individual phases of a multiphase fluid-based system using focused x-ray microbeam. The supporting rail allows for uniform translation of the HDAC, rotation and tilt stages, and a focusing mirror, which is used to illuminate the sample for visual observation using a microscope, relative to the direction of the incident x-ray beam. A structure study of Eu(III) aqua ion behavior in high-temperature aqueous solutions and a study of Nb partitioning and coordination in a silicate melt in contact with a hydrothermal fluid are described as applications utilizing the modified HDAC rail assembly. ?? 2007 American Institute of Physics.
Drazin, Philip
1987-01-01
Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)
DEFF Research Database (Denmark)
Hansen, Klaus Marius
2001-01-01
Fluid interaction, interaction by the user with the system that causes few breakdowns, is essential to many user interfaces. We present two concrete software systems that try to support fluid interaction for different work practices. Furthermore, we present specificity, generality, and minimality...... as design goals for fluid interfaces....
Drazin, Philip
1987-01-01
Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)
Kundu, Pijush K; Dowling, David R
2011-01-01
Fluid mechanics, the study of how fluids behave and interact under various forces and in various applied situations-whether in the liquid or gaseous state or both-is introduced and comprehensively covered in this widely adopted text. Revised and updated by Dr. David Dowling, Fluid Mechanics, 5e is suitable for both a first or second course in fluid mechanics at the graduate or advanced undergraduate level. Along with more than 100 new figures, the text has been reorganized and consolidated to provide a better flow and more cohesion of topics.Changes made to the
Salinity of oceanic hydrothermal fluids: a fluid inclusion study
Nehlig, Pierre
1991-03-01
An extensive microthermometric study of quartz, epidote, plagioclase, anhydrite and sphalerite-hosted fluid inclusions from ophiolitic [Semail (Oman) and Trinity (California) ophiolites] and oceanic (East Pacific Rise hydrothermal vents, Gorringe Bank, ODP Leg 111 Hole 504B) crust has been carried out in order to constrain a model accounting for wide salinity variations measured in the oceanic hydrothermal fluids. Recorded salinities in fluid inclusions vary between 0.3 and 52 wt% NaCl eq. However, more than 60% of the mean (± standard deviation) salinities of the samples are within the range 3.2 ± 0.3wt% NaCl eq (= microthermometric error) and the mean salinity of all fluid inclusions (without the brines) is 4.0 wt% NaCl eq with a standard deviation of 1.6 wt% NaCl eq. Whereas most samples display slightly higher salinities than seawater, several samples exhibit very high salinities (more than two times that of seawater). These high salinities are restricted to the plagiogranites (Semail and Trinity ophiolites) which mark the top of the fossil magma chamber, in the transition zone between the plutonic sequence and the sheeted dyke complex. The fluid inclusion population studied in the plagiogranites is characterized by the occurrence of four major fluid inclusion families: (1) low- to medium-salinity Liquid/Vapor fluid inclusions which homogenize into the liquid phase; (2) low-salinity Liquid/Vapor fluid inclusions with pseudocritical homogenization; (3) low- to medium-salinity Liquid/Vapor fluid inclusions which homogenize into the vapor phase; and (4) high-salinity Liquid/Vapor/Halite fluid inclusions which homogenize into the liquid phase by halite dissolution and exhibit salinities as high as 52 wt% NaCl eq. These fluid inclusion families are interpreted as resulting from phase separation occurring in hydrothermal or magmatic fluids within the transition zone between the hydrothermal system and the magma chamber at temperatures higher than 500°C. Very low
Volkov, N B
1993-01-01
A set of equations according to which the conducting medium consists of two fluids - laminar and vortex, has been obtained in the present paper by transforming MHD equations. In a similar way, an electronic fluid is assumed to consist of a laminar and a vortex fluid. This system allows one to study the formation and the dynamics of large-scale hydrodynamic fluctuations. From this model a model of a non-equilibrium phase transition belonging to a class of the Lorenz-type models has been developed [Lorenz E N 1963 J. Atmos. Sci. {\\bf 20} 130]. Vortex structures resulting in the increase in an effective resistance of the conducting medium and the interruption of current have been shown to appear even at constant transport coefficients in a laminar electronic fluid. Critical exponents of the parameters of an order (amplitudes), which for a direct current coincide with the critical exponents in the Lorenz model, have been found. A spatial scale of the structure described by the theory is in good agreement with exp...
DEFF Research Database (Denmark)
Wadsäter, Maria Helena; Barker, Robert; Mortensen, Kell;
2013-01-01
the ability to determine the average structure of the film along an axis perpendicular to the interface as measured by neutron reflectivity. The nanodisc film was optimized in terms of nanodisc coverage, reduced film roughness, and stability for time-consuming studies. This was achieved by a systematic...... variation of the lipid phase, charge, and length of lipid tails. Herein, we show that, although all studied nanodiscs align with their lipid bilayer parallel to the interface, gel-phase DMPC nanodiscs form the most suitable film for future membrane protein studies since they yield a dense irreversibly...
DEFF Research Database (Denmark)
Brorsen, Michael
These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University.......These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University....
M. Cibiş (Merih); W.V. Potters (Wouter); F.J.H. Gijsen (Frank); H. Marquering (Henk); E. VanBavel (Ed); A.F.W. van der Steen (Ton); A.J. Nederveen (Aart); J.J. Wentzel (Jolanda)
2014-01-01
textabstractWall shear stress (WSS) is involved in many pathophysiological processes related to cardiovascular diseases, and knowledge of WSS may provide vital information on disease progression. WSS is generally quantified with computational fluid dynamics (CFD), but can also be calculated using
Energy Technology Data Exchange (ETDEWEB)
Barragan-Reyes, Rosa Maria; Arellano-Gomez, Victor Manuel; Portugal-Marin, Enrique [Instituto de Investigaciones Electricas (Mexico); De Leon-Vivar, Jesus [Comision Federal de Electricidad, Residencia General de Cerro Prieto, B.C (Mexico)
2008-10-15
The gas composition of fluids produced by CP IV geothermal wells from the Cerro Prieto field was studied in order to identify different types of fluids entering the wells by estimating their temperature and excess steam. A method based on the Fischer Tropsch reaction and H2S equilibrium with pyrite-pyrrhotite as mineral buffer (FTHSH3) was used. The results for the reservoir natural state indicated the presence of fluids with heterogeneous reservoir temperature (between 275 and 310 degrees Celsius) and excess steam values, which were found from negative (boiled liquid that has lost steam when flowing to the well) to one (steam phase with zero liquid saturation). The study for individual wells in which boiling processes were identified, showed that through time, the feeding fluids consist of a two-phase mixture with different liquid/steam proportions. Also, the results suggested that a steam phase could occur at CP IV which is added to the feeding fluid, depending on the operation conditions of the wells. The origin of this steam could be the boiling of the deeper liquid due to a pressure drop. [Spanish] Se estudio la composicion gaseosa de los fluidos producidos por pozos geotermicos del sector CP IV del campo de Cerro Prieto para tratar de distinguir aportes de fluidos diferentes mediante la estimacion de su temperatura de yacimiento y del exceso de vapor. Se utilizo un metodo de equilibrio gaseoso basado en la reaccion de Fischer Tropsch y el equilibrio combinado pirita-pirrotita (FT-HSH3). Los resultados obtenidos indican que en el estado inicial del yacimiento existen fluidos que muestran heterogeneidad en los valores de temperatura de yacimiento (entre 275 y 310 grados Celsius), asi como en el exceso de vapor con valores desde negativos (liquido que despues de ebullir ha perdido vapor en su trayecto hacia el pozo) hasta uno (vapor con cero saturacion de liquido). El estudio individual de los pozos con fenomenos de ebullicion muestra que a traves del tiempo
Desgranges, Caroline; Delhommelle, Jerome
2016-03-28
We extend Expanded Wang-Landau (EWL) simulations beyond classical systems and develop the EWL method for systems modeled with a tight-binding Hamiltonian. We then apply the method to determine the partition function and thus all thermodynamic properties, including the Gibbs free energy and entropy, of the fluid phases of Si. We compare the results from quantum many-body (QMB) tight binding models, which explicitly calculate the overlap between the atomic orbitals of neighboring atoms, to those obtained with classical many-body (CMB) force fields, which allow to recover the tetrahedral organization in condensed phases of Si through, e.g., a repulsive 3-body term that favors the ideal tetrahedral angle. Along the vapor-liquid coexistence, between 3000 K and 6000 K, the densities for the two coexisting phases are found to vary significantly (by 5 orders of magnitude for the vapor and by up to 25% for the liquid) and to provide a stringent test of the models. Transitions from vapor to liquid are predicted to occur for chemical potentials that are 10%-15% higher for CMB models than for QMB models, and a ranking of the force fields is provided by comparing the predictions for the vapor pressure to the experimental data. QMB models also reveal the formation of a gap in the electronic density of states of the coexisting liquid at high temperatures. Subjecting Si to a nanoscopic confinement has a dramatic effect on the phase diagram with, e.g. at 6000 K, a decrease in liquid densities by about 50% for both CMB and QMB models and an increase in vapor densities between 90% (CMB) and 170% (QMB). The results presented here provide a full picture of the impact of the strategy (CMB or QMB) chosen to model many-body effects on the thermodynamic properties of the fluid phases of Si.
Fluid dynamics of dilatant fluid
DEFF Research Database (Denmark)
Nakanishi, Hiizu; Nagahiro, Shin-ichiro; Mitarai, Namiko
2012-01-01
A dense mixture of granules and liquid often shows a severe shear thickening and is called a dilatant fluid. We construct a fluid dynamics model for the dilatant fluid by introducing a phenomenological state variable for a local state of dispersed particles. With simple assumptions for an equation...... of the state variable, we demonstrate that the model can describe basic features of the dilatant fluid such as the stress-shear rate curve that represents discontinuous severe shear thickening, hysteresis upon changing shear rate, and instantaneous hardening upon external impact. An analysis of the model...... reveals that the shear thickening fluid shows an instability in a shear flow for some regime and exhibits the shear thickening oscillation (i.e., the oscillatory shear flow alternating between the thickened and the relaxed states). The results of numerical simulations are presented for one- and two...
Energy Technology Data Exchange (ETDEWEB)
Schaefer, B.; Lambert, S.M.; Song, Y.; Prausnitz, J.M.
1994-10-01
Goal of this work is the extension of a Perturbed-Hard-Sphere-Chain equation of state (PHSC EOS) to systems containing strong polar components. Three different types of association models (ten Brinke/Karasz, SAFI, modified Veytsman) were used to calculate the contribution of specific interactions like hydrogen bonding to thermodynamic quantities. Pure component parameters obtained from regression of temperature dependent density and vapor pressure data allow the prediction of VLE and LLE data. The results of simple fluids and polymer solutions were compared with experimental data. The SAFT and the modified Veytsman extension give similar results for pure fluids and mixtures with components of similar segment size. Differences increase with increasing difference of segment size.
Konn, Cecile; Magner, Jörgen; Charlou, Jean-luc; Holm, Nils G.; Alsberg, Tomas
2015-01-01
Investigation of amino acids in hydrothermal systems is of prime importance for the understanding of geochemistry and microbiology of hydrothermal vents and plumes, for carbon and metals global cycles, for metabolism of some hydrothermal microorganisms and for the origin of life issue. Extensive theoretical and experimental work on amino acids behaviour in hydrothermal fluids has been done, conversely only few data exist on natural samples. Because each hydrothermal vent is unique, the more d...
Bernard, Peter S
2015-01-01
This book presents a focused, readable account of the principal physical and mathematical ideas at the heart of fluid dynamics. Graduate students in engineering, applied math, and physics who are taking their first graduate course in fluids will find this book invaluable in providing the background in physics and mathematics necessary to pursue advanced study. The book includes a detailed derivation of the Navier-Stokes and energy equations, followed by many examples of their use in studying the dynamics of fluid flows. Modern tensor analysis is used to simplify the mathematical derivations, thus allowing a clearer view of the physics. Peter Bernard also covers the motivation behind many fundamental concepts such as Bernoulli's equation and the stream function. Many exercises are designed with a view toward using MATLAB or its equivalent to simplify and extend the analysis of fluid motion including developing flow simulations based on techniques described in the book.
Pedersen, Ulf R; Schrøder, Thomas B; Dyre, Jeppe C
2007-01-01
Constant-pressure molecular-dynamics simulations of phospholipid membranes in the fluid phase reveal strong correlations between equilibrium fluctuations of volume and energy on the nanosecond time-scale. The existence of strong volume-energy correlations was previously deduced indirectly by Heimburg from experiments focusing on the phase transition between the fluid and the ordered gel phases. The correlations, which are reported here for three different membranes (DMPC, DMPS-Na, and DMPSH), have volume-energy correlation coefficients ranging from 0.81 to 0.89. The DMPC membrane was studied at two temperatures showing that the correlation coefficient increases as the phase transition is approached.
Bogomyakova, Olga; Stankevich, Yu; Mesropyan, N; Shaybman, L; Tulupov, A
2016-12-01
To determine the difference in the velocity parameters of cerebrospinal fluid flow in patients with varying severity of communicating hydrocephalus compared to a group of healthy volunteers without hydrodynamic disorders. The study involved 35 subjects with communicating hydrocephalus (25 subjects with Evans index of 0.31; 10 subject with Evans index of 0.46) and 62 healthy volunteers. The mean, volume, and peak flow velocities were determined at the different intracranial levels. Also were made an assessment of gender and age differences. Analysis of the differences between the mean values showed the progressive inhibition of cerebrospinal fluid outflow from the cranial cavity [in moderate communicating hydrocephalus-at 1.5 times (p hydrocephalus at 2-2.5 times (p < 0.01)], depending on the severity of enlargement of the ventricular system and, most likely, related to inhibition of its reabsorption. These changes may explain the clinical symptoms of subjects and serve as diagnostic criteria. Also it was revealed a significant influence of the factor of age on speed characteristics of the cerebrospinal fluid flow (F = 5.3303, p = 0.0003, for mean velocity).
Multivariate Analysis of Mixed Lipid Aggregate Phase Transitions Monitored Using Raman Spectroscopy.
Neal, Sharon L
2017-01-01
The phase behavior of aqueous 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC)/1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) mixtures between 8.0 ℃ and 41.0 ℃ were monitored using Raman spectroscopy. Temperature-dependent Raman matrices were assembled from series of spectra and subjected to multivariate analysis. The consensus of pseudo-rank estimation results is that seven to eight components account for the temperature-dependent changes observed in the spectra. The spectra and temperature response profiles of the mixture components were resolved by applying a variant of the non-negative matrix factorization (NMF) algorithm described by Lee and Seung (1999). The rotational ambiguity of the data matrix was reduced by augmenting the original temperature-dependent spectral matrix with its cumulative counterpart, i.e., the matrix formed by successive integration of the spectra across the temperature index (columns). Successive rounds of constrained NMF were used to isolate component spectra from a significant fluorescence background. Five major components exhibiting varying degrees of gel and liquid crystalline lipid character were resolved. Hydrogen-bonded water networks exhibiting varying degrees of organization are associated with the lipid components. Spectral parameters were computed to compare the chain conformation, packing, and hydration indicated by the resolved spectra. Based on spectral features and relative amounts of the components observed, four components reflect long chain lipid response. The fifth component could reflect the response of the short chain lipid, DHPC, but there were no definitive spectral features confirming this assignment. A minor component of uncertain assignment that exhibits a striking response to the DMPC pre-transition and chain melting transition also was recovered. While none of the spectra resolved exhibit features unequivocally attributable to a specific aggregate morphology or step in the gelation process
Energy Technology Data Exchange (ETDEWEB)
Ambrose, William A.; Hamilton, Douglas S.; Zeng, Hongliu; Holtz, Mark H.; Light, Malcolm; Yeh, Joseph S. [University of Texas at Austin, TX (United States). Bureau of Economic Geology; Carvajal, Gladys de; Pinto, Jonny; Garibaldi, Luis; Azpiritxaga, Izaskun [Petroleos de Venezuela S.A., Caracas (Venezuela). Exploracion y Produccion
1999-07-01
Three-dimensional seismic data are increasingly being used in reservoir characterization studies as an aid in detecting and delineating structural and lithologic features as well as changes in fluid distribution that may not be resolvable with log data at wide well spacings. Amplitude maps, in addition to displaying distribution of lithology, can also be effective in inferring subtle faults associated with changes in reservoir fluid content. In a 12-month reservoir characterization study of tide-dominated deltaic and shelf reservoirs of the Lower Eocene Misoa Formation in a 4-m{sup 2} (10.4-km{sup 2}) rectangular are (Phase III Area) in the Bloque I Area, 3-D seismic data were used in conjunction with logs from approximately 50 wells to detect delineate faults and to infer interwell sand-body distribution. The goal of this reservoir analysis analysis was construct an improved geological model of oil-and gas-productive reservoirs in the Lower Eocene to better understand controls on reservoir compartmentalization and to identify areas of unswept hydrocarbons. This paper provides examples from the C4 Member and demonstrates how 3-D seismic data were used to infer the presence of faults not previously detected in earlier studies of these reservoirs with conventional log data and to illustrate their control on fluid distribution. (author)
Energy Technology Data Exchange (ETDEWEB)
Darbouret, M.
2005-12-15
Secondary two-phase fluids are suspensions of solid crystals. Thanks to the melting latent heat, they present a great interest for cold transportation. Moreover, they are a mean of reducing the amount of classical refrigerant. In the refrigeration field, ice slurries are already used. The goal is now to extend this technology to other temperature ranges suitable for other applications like freezing or air-conditioning. For an air-conditioning application, a TBAB (Tetra-Butyl-Ammonium Bromide) aqueous solution is studied. Under atmospheric pressure and for positive temperatures, this solution crystallizes into ice-like compounds named 'hydrates'. First, the physical properties of the aqueous solution and its crystallisation conditions were studied. Two different types of hydrates can appear. The goal of the experimental set-up is to study the rheological behaviour of two-phase fluids. Slurries are made in brushed-surface heat exchanger and pumped into pipes where flow rates and pressure drops are measured. The rheological behaviour of TBAB hydrates slurries can be described using a Bingham fluid model. We highlight that the two rheological parameters, which are the apparent viscosity and the yield shear stress, depend on the volume fraction of crystal of course, but also on the hydrate type, and on the initial concentration of the solution. The yield shear stress is interpreted as the consequence of the Van der Waals inter-particle interaction forces. Finally, possible stratification effects are modelled with a finite difference method. The principle is to calculate particle concentration and velocity profiles following the flow of the slurry. Calculations are validated with experimental velocity profiles published by P. Reghem (2002). This model underlines the influence of the particle distribution in the pipe on pressure drops. (author)
Energy Technology Data Exchange (ETDEWEB)
Zhou, Yijie [ORNL; Lim, Hyun-Kyung [ORNL; de Almeida, Valmor F [ORNL; Navamita, Ray [State University of New York, Stony Brook; Wang, Shuqiang [State University of New York, Stony Brook; Glimm, James G [ORNL; Li, Xiao-lin [State University of New York, Stony Brook; Jiao, Xiangmin [ORNL
2012-06-01
This progress report describes the development of a front tracking method for the solution of the governing equations of motion for two-phase micromixing of incompressible, viscous, liquid-liquid solvent extraction processes. The ability to compute the detailed local interfacial structure of the mixture allows characterization of the statistical properties of the two-phase mixture in terms of droplets, filaments, and other structures which emerge as a dispersed phase embedded into a continuous phase. Such a statistical picture provides the information needed for building a consistent coarsened model applicable to the entire mixing device. Coarsening is an undertaking for a future mathematical development and is outside the scope of the present work. We present here a method for accurate simulation of the micromixing dynamics of an aqueous and an organic phase exposed to intense centrifugal force and shearing stress. The onset of mixing is the result of the combination of the classical Rayleigh- Taylor and Kelvin-Helmholtz instabilities. A mixing environment that emulates a sector of the annular mixing zone of a centrifugal contactor is used for the mathematical domain. The domain is small enough to allow for resolution of the individual interfacial structures and large enough to allow for an analysis of their statistical distribution of sizes and shapes. A set of accurate algorithms for this application requires an advanced front tracking approach constrained by the incompressibility condition. This research is aimed at designing and implementing these algorithms. We demonstrate verification and convergence results for one-phase and unmixed, two-phase flows. In addition we report on preliminary results for mixed, two-phase flow for realistic operating flow parameters.
Oettel, M; Dorosz, S; Berghoff, M; Nestler, B; Schilling, T
2012-08-01
In materials science the phase-field crystal approach has become popular to model crystallization processes. Phase-field crystal models are in essence Landau-Ginzburg-type models, which should be derivable from the underlying microscopic description of the system in question. We present a study on classical density functional theory in three stages of approximation leading to a specific phase-field crystal model, and we discuss the limits of applicability of the models that result from these approximations. As a test system we have chosen the three-dimensional suspension of monodisperse hard spheres. The levels of density functional theory that we discuss are fundamental measure theory, a second-order Taylor expansion thereof, and a minimal phase-field crystal model. We have computed coexistence densities, vacancy concentrations in the crystalline phase, interfacial tensions, and interfacial order parameter profiles, and we compare these quantities to simulation results. We also suggest a procedure to fit the free parameters of the phase-field crystal model. Thereby it turns out that the order parameter of the phase-field crystal model is more consistent with a smeared density field (shifted and rescaled) than with the shifted and rescaled density itself. In brief, we conclude that fundamental measure theory is very accurate and can serve as a benchmark for the other theories. Taylor expansion strongly affects free energies, surface tensions, and vacancy concentrations. Furthermore it is phenomenologically misleading to interpret the phase-field crystal model as stemming directly from Taylor-expanded density functional theory.
Mac Dowell, N; Pereira, F E; Llovell, F; Blas, F J; Adjiman, C S; Jackson, G; Galindo, A
2011-06-30
The amine functional groups are fundamental building blocks of many molecules that are central to life, such as the amino acids, and to industrial processes, such as the alkanolamines, which are used extensively for gas absorption. The modeling of amines and of mixtures of amines with water (H(2)O) and carbon dioxide (CO(2)) is thus relevant to a number of applications. In this contribution, we use the statistical associating fluid theory for potentials of variable range (SAFT-VR) to describe the fluid phase behavior of ammonia + H(2)O + CO(2) and n-alkyl-1-amine + H(2)O + CO(2) mixtures. Models are developed for ammonia (NH(3)) and n-alkyl-1-amines up to n-hexyl-1-amine (CH(3)NH(2) to C(6)H(13)NH(2)). The amines are modeled as homonuclear chain molecules formed from spherical segments with additional association sites incorporated to mediate the effect of hydrogen-bonding interactions. The SAFT-VR approach provides a representation of the pure component fluid phase equilibria, on average, to within 1.48% of the experimental data in relative terms for the saturated liquid densities and vapor pressures. A simple empirical correlation is derived for the SAFT-VR parameters of the n -alkylamine series as a function of molecular weight. Aqueous mixtures of the amines are modeled using a model of water taken from previous work. The models developed for the mixtures are of high fidelity and can be used to calculate the binary fluid phase equilibrium of these systems to within 2.28% in relative terms for the temperature or pressure and 0.027 in absolute terms for the mole fraction. Regions of both vapor-liquid and liquid-liquid equilibria are considered. We also consider the reactive mixtures of amines and CO(2) in aqueous solution. To model the reaction of CO(2) with the amine, an additional site is included on the otherwise nonassociating CO(2) model. The unlike interaction parameters for the NH(3) + H(2)O + CO(2) ternary mixture are obtained by comparison to the
DEFF Research Database (Denmark)
Gromov, Pavel; Gromova, Irina; Olsen, Charlotta J.
2013-01-01
Tumor interstitial fluid (TIF) is a proximal fluid that, in addition to the set of blood soluble phase-borne proteins, holds a subset of aberrantly externalized components, mainly proteins, released by tumor cells and tumor microenvironment through various mechanisms, which include classical...... secretion, non-classical secretion, secretion via exosomes and membrane protein shedding. Consequently, the interstitial aqueous phase of solid tumors is a highly promising resource for the discovery of molecules associated with pathological changes in tissues. Firstly, it allows one to delve deeper...... into the regulatory mechanisms and functions of secretion-related processes in tumor development. Secondly, the anomalous secretion of molecules that is innate to tumors and the tumor microenvironment, being associated with cancer progression, offers a valuable source for biomarker discovery and possible targets...
Directory of Open Access Journals (Sweden)
Caimmi R.
2008-01-01
Full Text Available A theory of collisionless fluids is developed in a unified picture, where nonrotating (Ωf1 = Ωf2 = Ωf3 = 0 figures with some given random velocity component distributions, and rotating (Ωf1 = Ωf2 = Ωf3 figures with a different random velocity component distributions, make adjoint configurations to the same system. R fluids are defined as ideal, self-gravitating fluids satisfying the virial theorem assumptions, in presence of systematic rotation around each of the principal axes of inertia. To this aim, mean and rms angular velocities and mean and rms tangential velocity components are expressed, by weighting on the moment of inertia and the mass, respectively. The figure rotation is defined as the mean angular velocity, weighted on the moment of inertia, with respect to a selected axis. The generalized tensor virial equations (Caimmi and Marmo 2005 are formulated for R fluids and further attention is devoted to axisymmetric configurations where, for selected coordinate axes, a variation in figure rotation has to be counterbalanced by a variation in anisotropy excess and vice versa. A microscopical analysis of systematic and random motions is performed under a few general hypotheses, by reversing the sign of tangential or axial velocity components of an assigned fraction of particles, leaving the distribution function and other parameters unchanged (Meza 2002. The application of the reversion process to tangential velocity components is found to imply the conversion of random motion rotation kinetic energy into systematic motion rotation kinetic energy. The application of the reversion process to axial velocity components is found to imply the conversion of random motion translation kinetic energy into systematic motion translation kinetic energy, and the loss related to a change of reference frame is expressed in terms of systematic motion (imaginary rotation kinetic energy. A number of special situations are investigated in greater
Visualization of working fluid flow in gravity assisted heat pipe
Nemec Patrik; Malcho Milan
2015-01-01
Heat pipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapor and vice versa help heat pipe to transport high heat flux. The article deal about construction and processes casing in heat pipe during operation. Experiment visualization of working fluid flow is performed with glass heat pipe filed with ethanol. The visualization of working fluid flow explains the phenomena as working fl...
Or, D.; Ioannidis, M.
2010-12-01
Degassing and in situ development of a mobile gas bubbles occur when injecting supersaturated aqueous phase into water-saturated porous media. Supersaturated water injection (SWI) has potentially significant applications in remediation of soils contaminated by non-aqueous phase liquids and in enhanced oil recovery. Pore network simulations indicate the formation of a region near the injection boundary where gas phase nuclei are activated and grow by mass transfer from the flowing supersaturated aqueous phase. Ramified clusters of gas-filled pores develop which, owing to the low prevailing Bond number, grow laterally to a significant extent prior to the onset of mobilization, and are thus likely to coalesce. Gas cluster mobilization invariably results in fragmentation and stranding, such that a macroscopic region containing few tenuously connected large gas clusters is established. Beyond this region, gas phase nucleation and mass transfer from the aqueous phase are limited by diminishing supply of dissolved gas. New insights into SWI dynamics are obtained using rapid micro-visualization in transparent glass micromodels. Using high-speed imaging, we observe the nucleation, initial growth and subsequent fate (mobilization, fragmentation, collision, coalescence and stranding) of CO2 bubbles and clusters of gas-filled pores and analyze cluster population statistics. We find significant support for the development of invasion-percolation-like patterns, but also report on hitherto unaccounted for gas bubble behavior. Additionally, we report for the first time on the acoustic emission signature of SWI in porous media and relate it to the dynamics of bubble nucleation and growth. Finally, we identify the pore-scale mechanisms associated with the mobilization and subsequent recovery of a residual non-aqueous phase liquid due to gas bubble dynamics during SWI.
Ramirez, Daniela Andrea; Locatelli, Daniela Ana; Torres-Palazzolo, Carolina Andrea; Altamirano, Jorgelina Cecilia; Camargo, Alejandra Beatriz
2017-01-15
Organosulphur compounds (OSCs) present in garlic (Allium sativum L.) are responsible of several biological properties. Functional foods researches indicate the importance of quantifying these compounds in food matrices and biological fluids. For this purpose, this paper introduces a novel methodology based on dispersive liquid-liquid microextraction (DLLME) coupled to high performance liquid chromatography with ultraviolet detector (HPLC-UV) for the extraction and determination of organosulphur compounds in different matrices. The target analytes were allicin, (E)- and (Z)-ajoene, 2-vinyl-4H-1,2-dithiin (2-VD), diallyl sulphide (DAS) and diallyl disulphide (DADS). The microextraction technique was optimized using an experimental design, and the analytical performance was evaluated under optimum conditions. The desirability function presented an optimal value for 600μL of chloroform as extraction solvent using acetonitrile as dispersant. The method proved to be reliable, precise and accurate. It was successfully applied to determine OSCs in cooked garlic samples as well as blood plasma and digestive fluids. Copyright © 2016 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Caimmi, R.
2008-06-01
Full Text Available A theory of collisionless fluids is developed in a unified picture, where nonrotating $(widetilde{Omega_1}=widetilde{Omega_2}= widetilde{Omega_3}=0$ figures with some given random velocity component distributions, and rotating $(widetilde{Omega_1} ewidetilde{Omega_2} e widetilde{Omega_3} $ figures with a different random velocity component distributions, make adjoint configurations to the same system. R fluids are defined as ideal, self-gravitating fluids satisfying the virial theorem assumptions, in presence of systematic rotation around each of the principal axes of inertia. To this aim, mean and rms angular velocities and mean and rms tangential velocity components are expressed, by weighting on the moment of inertia and the mass, respectively. The figure rotation is defined as the mean angular velocity, weighted on the moment of inertia, with respectto a selected axis. The generalized tensor virial equations (Caimmi and Marmo 2005 are formulated for R fluidsand further attention is devoted to axisymmetric configurations where, for selected coordinateaxes, a variation in figure rotation has to be counterbalanced by a variation in anisotropy excess and viceversa. A microscopical analysis of systematic and random motions is performed under a fewgeneral hypotheses, by reversing the sign of tangential or axial velocity components of anassigned fraction of particles, leaving the distribution function and other parametersunchanged (Meza 2002. The application of the reversion process to tangential velocitycomponents is found to imply the conversion of random motion rotation kinetic energy intosystematic motion rotation kinetic energy. The application ofthe reversion process to axial velocity components is found to imply the conversionof random motion translation kinetic energy into systematic motion translation kinetic energy, and theloss related to a change of reference frame is expressed in terms of systematic motion (imaginary rotation kinetic
Oanh, Vuong Thi Kim; Lam, Tran Dai; Thu, Vu Thi; Lu, Le Trong; Nam, Pham Hong; Tam, Le The; Manh, Do Hung; Phuc, Nguyen Xuan
2016-08-01
Highly stable Fe3O4 liquid was synthesized by thermal decomposition using poly(acrylic acid) (PAA) as a phase transfer ligand. The crystalline structure, morphology, and magnetic properties of the as-prepared samples were thoroughly characterized. Results demonstrated that the magnetic Fe3O4 nanomaterial was formed in liquid phase with a spinel single-phase structure, average size of 8-13 nm, and high saturation magnetization (up to 75 emu/g). The PAA-capped Fe3O4 nanoparticles displayed high stability over a wide pH range (from 4 to 7) in 300 mM salt solution. More importantly, the heat-generating capacity of the nanoparticle systems was quantified at a specific absorption rate (SAR) of 70.22 W/g, which is 35% higher than magnetic nanoparticles coated with sodium dodecyl sulfate (SDS). These findings suggest the potential application of PAA-coated magnetic nanoparticles in magnetic hyperthermia.
Institute of Scientific and Technical Information of China (English)
惠丰; 张敏华; 马静
2012-01-01
Gibbs系综蒙特卡罗方法（简称GEMC）作为一种计算纯物质及混合物相平衡的模拟手段已经发展得较为成熟。本文描述了GEMC方法的基本原理和发展概况,介绍和评价了与GEMC方法紧密相关的力场,以第六届工业流体性质模拟挑战赛结果为例说明了GEMC模拟方法的有效性,并分类评述了国内外GEMC方法用于纯物质和混合物物系相平衡数据计算的发展情况。同时指出了GEMC方法的局限性,并展望了其未来的发展趋势。%Gibbs ensemble Monte Carlo（GEMC） is used to predict fluid phase equilibria.The basis of GEMC method is first introduced.Force fields are important to GEMC.Different kinds of force fields are reviewed.The effectiveness of GEMC prediction on fluid phase equilibria is discussed.And then,examples in which GEMC is used to provide pure component properties and phase behavior of mixtures are given.In addition,the developments of GEMC in China are specially addressed;the current limitations and possible improvements of Gibbs ensemble Monte Carlo methods are also discussed.
Scholl, M. A.; Ingebritsen, S. E.; Essaid, H. I.
1993-02-01
Fox (1990), in order to explain observations during the Axial Seamount Hydrothermal Emissions Study (ASHES), proposed a conceptual model for a two-phase subsea hydrothermal system in which steam controlled flow patterns by blocking liquid flow. An attempt is made here to demonstrate with a very general model that relative permeability contrasts by themselves do not cause spatial isolation of phases in steam/liquid water systems and that density segregation, independent of relative permeability effects, should not be ruled out as an explanation for the observations at the ASHES site. Fox replies that density segregation is probably not the only mechanism at work.
Institute of Scientific and Technical Information of China (English)
ZHAO Li-Yun; GUO Bo-Ling; HUANG Hai-Yang
2011-01-01
@@ The explicit solutions to both the Oldroyd-B model with an infinite Weissenberg number and the coupled Navier- Stokes/phase-field system are constructed by the method of separation of variables.It is found that the solutions blow up in finite time.%The explicit solutions to both the Oldroyd-B model with an infinite Weissenberg number and the coupled Navier- Stokes/phase-Beld system are constructed by the method of separation of variables. It is found that the solutions blow up in finite time.
Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; Liu, J.; Macias, B.; Martin, D. S.; Minkoff, L.; Ploutz-Snyder, R.; Ribeiro, L. C.; Sargsyan, A.; Smith, S. M.
2017-01-01
Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid
Institute of Scientific and Technical Information of China (English)
邵雄飞; 吴忠标
2004-01-01
The flow field of gas and liquid in a φ150mm rotating-stream-tray (RST) scrubber is simulated by using computational fluid dynamic (CFD) method. The simulation is based on the two-equation RNG κ-ε turbulence model, Eulerian multiphase model, mad a real-shape 3D model with a huge number of meshes. The simulation results include detailed information about velocity, pressure, volume fraction and so on. Some features of the flow field are obtained: liquid is atomized in a thin annular zone; a high velocity air zone prevents water drops at the bottom from flying towards the wall;the pressure varies sharply at the end of blades and so on. The results will be helpful for structure optimization and engineering design.
Directory of Open Access Journals (Sweden)
Knežević Milena M.
2014-01-01
Full Text Available Distribution of gas bubbles and volumetric mass transfer coefficient, Kla, in a three phase system, with different types of solid particles at different operation conditions were studied in this paper. The ranges of superficial gas and liquid velocities used in this study were 0,03-0,09 m/s and 0-0,1 m/s, respectively. The three different types of solid particles were used as a bed in the column (glass dp=3 mm, dp=6 mm; ceramic dp=6 mm. The experiments were carried out in a 2D plexiglas column, 278 x 20,4 x 500 mm and in a cylindrical plexiglas column, with a diameter of 64 mm and a hight of 2000 mm. The Kla coefficient increased with gas and liquid velocities. Results showed that the volumetric mass transfer coefficient has a higher values in three phase system, with solid particles, compared with two phase system. The particles properties (diameter and density have a major impact on oxygen mass transfer in three phase systems.
Çalapkorur, M Unlu; Alkan, B A; Tasdemir, Z; Akcali, Y; Saatçi, E
2017-06-01
Inflammation is a common feature of both peripheral arterial disease (PAD) and periodontal disease. The aim of this study was to evaluate the relationship between PAD and periodontal disease by examining the levels of inflammatory cytokines (pentraxin 3 and interleukin 1β) and high sensitive C-reactive protein from gingival crevicular fluid and serum. A total of 60 patients were included in this cross-sectional study. Patients were divided into two groups based on ankle-brachial index values: with PAD (test group) and non-PAD (control group). Demographic evaluations, clinical periodontal examinations and biochemical analysis for pentraxin 3, interleukin 1β and high sensitive C-reactive protein were performed to compare the two groups. There were no significant differences with respect to gender, age, body mass index, or smoking history (duration, amount) between the two groups (p > 0.05). There were no significant differences between the two groups in terms of clinical periodontal parameters (p > 0.05). Neither gingival crevicular fluid nor serum levels of the cytokines showed differences between the two groups. Logistic regression analysis revealed that, after adjusting for confounding factors (age, gender, diabetes, hypertension and body mass index), periodontitis raised the odds ratio for having PAD to 5.842 (95% confidence interval: 1.558-21.909). Although there were no significant differences with respect to clinical periodontal parameters and biochemical analyses between the study group and control, periodontitis did raise the odds ratio for having PAD. To clarify this possible relationship, future prospective studies are needed. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Dipolar fluids under external perturbations
Energy Technology Data Exchange (ETDEWEB)
Klapp, Sabine H L [Stranski-Laboratorium fuer Physikalische und Theoretische Chemie Sekretariat TC7, Technische Universitaet Berlin, Strasse des 17. Juni 124, D-10623 Berlin (Germany)
2005-04-20
We discuss recent developments and present new findings on the structural and phase properties of dipolar model fluids influenced by various external perturbations. We concentrate on systems of spherical particles with permanent (point) dipole moments. Starting from what is known about the three-dimensional systems, particular emphasis is given to dipolar fluids in different confining situations involving both simple and complex (disordered) pore geometries. Further topics concern the effect of quenched positional disorder, the influence of external (electric or magnetic) fields, and the fluid-fluid phase behaviour of various dipolar mixtures. It is demonstrated that due to the translational-orientational coupling and due to the long range of dipolar interactions even simple perturbations such as hard walls can have a profound impact on the systems. (topical review)
Energy Technology Data Exchange (ETDEWEB)
Guillemaud, V
2007-03-15
This thesis is devoted to the modelling and numerical simulation of liquid-vapor flows. In order to describe these phase transition flows, a two-fluid two-pressure approach is considered. This description of the liquid-vapor mixing is associated to the seven-equation model introduced by Baer and Nunziato. This work investigates the properties of this model in order to simulate the phase transition flows occurring in nuclear engineering. First, a theoretical thermodynamic framework is constructed to describe the liquid-vapor mixing. Provided with this framework, various modelling choices are suggested for the interaction terms between the phases. These closure laws comply with an entropy inequality. The mathematical properties of this model are thereafter examined. The convective part is associated to a nonconservative hyperbolic system. First, we focus on the definition of its weak solutions. Several flow regimes for the two-phase mixing derive from this analysis. Such regimes for the two-phase flows are analogous to the torrential and fluvial regimes for the shallow-water equations. Furthermore, we establish the linear and nonlinear stabilities of the liquid-vapor equilibrium. Finally, the implementation of a turbulence model and the introduction of a reconstruction process for the interfacial area are investigated in order to refine the description of the interfacial transfers. Using a fractional step approach, a Finite Volume method is at last constructed to simulate this model. First, various nonconservative adaptations of standard Riemann solvers are developed to approach the convective part. Unlike the classic nonconservative framework, these schemes converge towards the same solution. Furthermore, a new relaxation scheme is proposed to approach the interfacial transfers. Provided with these schemes, the whole numerical method preserves the liquid-vapor equilibria. Using this numerical method, a careful comparison between the one- and two-pressure two-fluid
Duan, Zhenhao; Mao, Shide
2006-07-01
A thermodynamic model is presented to calculate methane solubility, liquid phase density and gas phase composition of the H 2O-CH 4 and H 2O-CH 4-NaCl systems from 273 to 523 K (possibly up to 573 K), from 1 to 2000 bar and from 0 to 6 mol kg -1 of NaCl with experimental accuracy. By a more strict theoretical approach and using updated experimental data, this model made substantial improvements over previous models: (1) the accuracy of methane solubility in pure water in the temperature range between 273 and 283 K is increased from about 10% to about 5%, but confirms the accuracy of the Duan model [Duan Z., Moller N., Weare J.H., 1992a. Prediction of methane solubilities in natural waters to high ionic strength from 0 to 250 °C and from 0 to 1600 bar. Geochim. Cosmochim. Acta56, 1451-1460] above 283 K up to 2000 bar; (2) the accuracy of methane solubility in the NaCl aqueous solutions is increased from >12% to about 6% on average from 273 K and 1 bar to 523 K and 2000 bar; (3) this model is able to calculate water content in the gas phase and liquid phase density, which cannot be calculated by previous models; and (4) it covers a wider range of temperature and pressure space. With a simple approach, this model is extended to predict CH 4 solubility in other aqueous salt solutions containing Na +, K +, Mg 2+, Ca 2+, Cl - and SO42-, such as seawater and geothermal brines, with excellent accuracy. This model is also able to calculate homogenization pressure of fluid inclusions (CH 4-H 2O-NaCl) and CH 4 solubility in water at gas-liquid-hydrate phase equilibrium. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm.
Energy Technology Data Exchange (ETDEWEB)
Kock, Ingo; Frieling, Gerd; Navarro, Martin
2016-10-15
The aim of the project is the understanding of two-phase flow processes in a complex final repository system. The consideration of two-phase flow processes for calculations concerning the modeled final repository system induces processes and effects that influence the fluid and radionuclide transport significantly. Two-phase flow processes cover not only capillary pressures and the relative permeability but also a basic competition of phases for the pore volume with respect to storage and transport and density driven vertical phase separation.
Bagheri Sadeghi, Hayedeh; Panahi, Homayon Ahmad; Mahabadi, Mahsa; Moniri, Elham
2015-01-01
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-infammatory and antipyretic actions. It is used to relieve mild to moderate pains. Solid-phase extraction of mefenamic acid by a polymer grafted to silica gel is reported. Poly allyl glycidyl ether/iminodiacetic acid-co-N, N-dimethylacrylamide was synthesized and grafted to silica gel and was used as an adsorbent for extraction of trace mefenamic acid in pharmaceutical and biological samples. Different fa...
Margalho, Cláudia; Gallardo, Eugenia; Castanheira, Alice; Vieira, Duarte Nuno; López-Rivadulla, Manuel; Real, Francisco Corte
2013-08-23
The use of vitreous humor and pericardial fluid as alternative matrices to blood and plasma in the field of forensic toxicology is described to quantitate low levels of Salvinorin A using ethion as internal standard. The method was optimized and fully validated using international accepted guidelines. The developed methodology utilizes a solid phase extraction procedure coupled to gas chromatography mass spectrometry operated in the selected ion monitoring mode. The method was linear in the range of 5.0-100ng/mL with determination coefficients higher than 0.99 in 100μL of vitreous humor and in 250μL of each matrix pericardial fluid, whole blood and plasma. The limits of detection and quantitation were experimentally determined as 5.0ng/mL, intra-day precision, intermediate precision and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The sample cleanup step presented mean efficiencies between 80 and 106% in the different biological specimens analyzed. According to the low volumes of samples used, and the low limits achieved using a single quadrupole mass spectrometer, which is available in most laboratories, we can conclude that the validated methodology is sensitive and simple and is suitable for the application in forensic toxicology laboratories for the routine analysis of Salvinorin A in both conventional and unconventional biological samples.
Inter-domain dipolar repulsion in lipid monolayers with phase coexistence
Fiori, Elena Rufeil; Banchio, Adolfo J
2015-01-01
A great variety of biologically relevant monolayers present phase coexistence characterized by domains formed by lipids in a long-range ordered phase state dispersed in a continuous, disordered phase. Because of the difference in surface densities the domains possess an excess dipolar density with respect to the surrounding liquid phase. In this work we propose an alternative method to measure the dipolar repulsion for neutral lipid monolayers. The procedure is based on the comparison of the radial distribution function, g(r), from experiments and Brownian dynamic (BD) simulations. The domains were modeled as disks with surface dipolar density, whose strength was varied to best describe the experimentally determined monolayer structure. For comparison, the point dipole approximation was also studied. As an example, we applied the method for mixed monolayers with different proportions of distearoylphosphatidylcholine (DSPC) and dimyristoylphosphatidylcholine (DMPC) and obtained the excess dipolar density, whic...
Energy Technology Data Exchange (ETDEWEB)
Hansson, Roberta Concilio; Park, Hyun Sun; Dinh, Truc-Nam [Royal Institute of Technology, Division of Nuclear Power Safety, AlbaNova, Stockholm SE-106 91 (Sweden)
2009-04-15
As typical for the study of the vapor explosions, the qualitative and quantitative understanding of the phenomena requires visualization of both material and interface dynamics. A new approach to multi-fluid multiphase visualization is presented with the focus on the development of a synchronized high-speed visualization by digital cinematography and X-ray radiography. The developed system, named SHARP (simultaneous high-speed acquisition of X-ray radiography and photography), and its image processing methodology, directed to an image synchronization procedure and a separate quantification of vapor and molten material dynamics, is presented in this paper. Furthermore, we exploit an intrinsic property of the X-ray radiation, namely the differences in linear mass attenuation coefficients over the beam path through a multi-component system, to characterize the evolution of molten material distribution. Analysis of the data obtained by the SHARP system and image processing procedure developed granted new insights into the physics of the vapor explosion phenomena, as well as, quantitative information of the associated dynamic micro-interactions. (author)
Wang, Ding; Chen, Rui; Zhong, Xuan; Fan, Yong; Lai, Weiqiang; Sun, Xiaofang
2014-11-01
The present study aimed to improve the characterization of amniotic fluid cells (AFCs) in order to optimize their use in chromosomal prenatal diagnosis and as seed or stem cells for tissue engineering. The AFCs used in the current study were obtained from three females in their second trimester of pregnancy. The cells were cultured independently and characterized by cell morphology, cell markers, cell cycle distribution and chromosome Giemsa banding in an early- and late-passage. The AFCs remained homogeneous in culture and expressed mesenchymal markers, but not endothelial markers along the culture process. In addition, compared with the early-passage cells, the late-passage cells exhibit an increase in CD105 expression, a decrease in cell division and a delay in the cell cycle, and a number of cells underwent cell cycle arrest. However, the cells retained a normal karyotype. Therefore, the current study characterized AFCs in a clinical culture and confirmed that AFCs are mesenchymal precursors. The results obtained may be useful for the application of AFCs in prenatal diagnosis.
Ruban, Anatoly I
This is the first book in a four-part series designed to give a comprehensive and coherent description of Fluid Dynamics, starting with chapters on classical theory suitable for an introductory undergraduate lecture course, and then progressing through more advanced material up to the level of modern research in the field. The present Part 1 consists of four chapters. Chapter 1 begins with a discussion of Continuum Hypothesis, which is followed by an introduction to macroscopic functions, the velocity vector, pressure, density, and enthalpy. We then analyse the forces acting inside a fluid, and deduce the Navier-Stokes equations for incompressible and compressible fluids in Cartesian and curvilinear coordinates. In Chapter 2 we study the properties of a number of flows that are presented by the so-called exact solutions of the Navier-Stokes equations, including the Couette flow between two parallel plates, Hagen-Poiseuille flow through a pipe, and Karman flow above an infinite rotating disk. Chapter 3 is d...
Lemasson, Elise; Bertin, Sophie; Hennig, Philippe; Boiteux, Hélène; Lesellier, Eric; West, Caroline
2015-08-21
Impurity profiling of organic products that are synthesized as possible drug candidates requires complementary analytical methods to ensure that all impurities are identified. Supercritical fluid chromatography (SFC) is a very useful tool to achieve this objective, as an adequate selection of stationary phases can provide orthogonal separations so as to maximize the chances to see all impurities. In this series of papers, we have developed a method for achiral SFC-MS profiling of drug candidates, based on a selection of 160 analytes issued from Servier Research Laboratories. In the first part of this study, focusing on mobile phase selection, a gradient elution with carbon dioxide and methanol comprising 2% water and 20mM ammonium acetate proved to be the best in terms of chromatographic performance, while also providing good MS response [1]. The objective of this second part was the selection of an orthogonal set of ultra-high performance stationary phases, that was carried out in two steps. Firstly, a reduced set of analytes (20) was used to screen 23 columns. The columns selected were all 1.7-2.5μm fully porous or 2.6-2.7μm superficially porous particles, with a variety of stationary phase chemistries. Derringer desirability functions were used to rank the columns according to retention window, column efficiency evaluated with peak width of selected analytes, and the proportion of analytes successfully eluted with good peak shapes. The columns providing the worst performances were thus eliminated and a shorter selection of columns (11) was obtained. Secondly, based on 160 tested analytes, the 11 columns were ranked again. The retention data obtained on these columns were then compared to define a reduced set of the best columns providing the greatest orthogonality, to maximize the chances to see all impurities within a limited number of runs. Two high-performance columns were thus selected: ACQUITY UPC(2) HSS C18 SB and Nucleoshell HILIC.
Institute of Scientific and Technical Information of China (English)
王东升; 霍文婕; 朱伟云; 毛胜勇
2011-01-01
This study was conducted to establish a method of simultaneously detecting concentration of biogenic amine in rumen fluid by reverse phase-high performance liquid chromatography ( RP-HPLC). Samples were extracted by hydrochloric acid (0. 5 mol/L) , and then derived using dansyl chloride, the mobile phase was a gradient elution program with a binary mixture of acetonitrile and 0. 1 mol/L ammonium acetate and the flow rate was 1 mL/min; the wavelength of UV detector was 254 nm, and the column temperature was 30 t. The method was then used to investigate the effect of diet forage-to-concentrate ratio on concentrations of the five biogenic amines in rumen fluid of goats. The results showed that a good separation of tryptamine, putrescine, methylamine, histamine and tyramine was seen within 40 min, and the average recovery were ranged from 88. 46% to 98. 49% , and the relative standard deviations were less than 10% ; Compared with goats fed low concentrate diet, tryptamine and histamine concentrations in rumen fluid of goats fed high concentrate diet were significantly higher (P 0. 05). The results indicate that this method presented here can be used to determine biogenic amine concentrations in rumen fluid, and concentrations of biogenic amine in rumen fluid of goats can be affected by diet forage-to-concentrate ratio.%本文旨在应用反相高效液相色谱法建立瘤胃液中生物胺的测定方法.样品经0.5 mol/L盐酸提取后,用丹磺酰氯柱前衍生,流动相为乙腈和0.1 mol/L乙酸铵溶液；采用梯度洗脱,流速为1.0 mL/min；紫外检测器波长254 nm,柱温30℃.应用该方法,研究高精料和低精料饲粮条件下瘤胃液中5种生物胺浓度的差异.结果表明:采用该方法,色胺、腐胺、甲胺、组胺和酪胺5种生物胺能在40 min内得到良好地分离,回收率为88.46％～98.49％,相对标准偏差小于10％.在高精料饲粮条件下,饲喂前山羊瘤胃液中的酪胺和甲胺浓度
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-12-31
This conference day was organized by the `radiations` section of the French association of thermal engineers. This book of proceedings contains 8 papers entitled: `simultaneous temperature and NO concentration measurements in a hydrogen-air turbulent flame`; `application of iodine laser induced fluorescence to temperature, pressure and velocity measurements`; `Doppler phase measurement of refractive index and temperature`; `experimental and numerical study of temperature fields of particulates in plasma jets`; `measurement and determination of temperatures and concentrations of hot exhaust gases with FTIR emission spectroscopy`; `combustion control in gas turbines using CO{sub 2} emission spectroscopy`; `analysis of gases temperature fields and particulate jets. Application to hydrogen-air, kerosene stato-reactors and to solid propellant jets`; `restitution of temperature and species profiles in pre-mixing flames by inversion of transmission and IR emission data. (J.S.)
... Home Visit Global Sites Search Help? Pleural Fluid Analysis Share this page: Was this page helpful? Formal name: Pleural Fluid Analysis Related tests: Pericardial Fluid Analysis , Peritoneal Fluid Analysis , ...
DEFF Research Database (Denmark)
Kaasgaard, Thomas; Leidy, Chad; Crowe, J.H.
2003-01-01
ripples was seen. From height profiles of the AFM images, estimates of the amplitudes of the different ripple phases are reported. To elucidate the processes of ripple formation and disappearance, a ripple-phase DPPC lipid bilayer was taken through the pretransition in the cooling and the heating......Temperature-controlled atomic force microscopy (AFM) has been used to visualize and study the structure and kinetics of ripple phases in one-component dipalmitoylphosphaticlylcholine (DPPC) and two-component dimyristoylphosphatidylcholine-distearoylphosphatidylcholine (DMPC-DSPC) lipid bilayers....... The lipid bilayers are mica-supported double bilayers in which ripple-phase formation occurs in the top bilayer. In one-component DPPC lipid bilayers, the stable and metastable ripple phases were observed. In addition, a third ripple structure with approximately twice the wavelength of the metastable...
Barfi, Behruz; Asghari, Alireza; Rajabi, Maryam; Barfi, Azadeh; Saeidi, Iman
2013-10-11
In the present study, for the first time, a simplified miniaturized ultrasound-assisted matrix solid-phase dispersion (SM-USA-MSPD) method with a different application for liquid matrices was developed to extract different flavonoids (hesperidin, diosmin, eriocitrin, narirutin, naringin, hesperetin and naringenin) from citrus fruit juice and human fluid samples prior to their determination using high performance liquid chromatography (HPLC). Different effective parameters were studied and under the optimum conditions (including sample volume: 150μL; solid phase: silica-based C18, 200mg; eluting solvent: methanol, 500μL; pH: 4; and sonication: 6min; at room temperature), limits of detection and limits of quantification were ranged from 23.3 to 46.8ngmL(-1) and 74.8 to 141.5ngmL(-1), respectively. Once optimized, analytical performance of the method was studied in terms of linearity (0.074-198.5μgmL(-1), r(2)>0.991), accuracy (recovery=84.6-101.5%), and precision (repeatability: intra-day precisionjuices- and the obtained results confirmed that these compounds could be used as good biomarkers of citrus fruit juice intake.
Dynamics, Surface Electrostatics and Phase Properties of Nanoscale Curved Lipid Bilayers
Koolivand, Amir
Surface electrostatic potential of a lipid bilayer governs many vital functions of living cells. Several classes of proteins are known of exhibiting strong binding preferences to curved lipid bilayer surfaces. In this project we employed electron paramagnetic resonance (EPR) of a recently introduced phospholipid (IMTSL-PTE) bearing a pH-sensitive nitroxide covalently attached to the lipid head group to measure the surface electrostatics of the lipid membrane and nanopore-confined lipid bilayers as a function of the bilayer curvature. The pKa of the ionizable group of this lipid-based spin probe is reporting on the bilayer surface electrostatics potential by changes in the EPR spectra. Specifically, both rotational dynamics and magnetic parameters of the nitroxide are affected by the probe protonation. Effect of curvature on the surface electrostatic potential and dynamics of lipid bilayer was studied for POPG and DMPG unilamellar vesicles (ULVs). It was found that the magnitude of the negative surface electrostatic potential increased upon decrease in the vesicle diameter for the bilayers in the fluid phase; however, no significant changes were observed for DMPG ULVs in a gel phase. We speculate that biologically relevant fluid bilayer phase allows for a larger variability in the lipid packing density in the lipid polar head group region than a more ordered gel phase and it is likely that the lipid flip-flop is responsible for pH equilibration of IMTSL-PTE. The kinetic EPR study of nitroxide reduction showed that the rate of flip-flop is in the order of 10-5 s-1. The flip-flop rate constant increases when vesicle size deceases. Oxygen permeability measured by X-ban EPR decreases in higher curved vesicles---an observation that is consistent with a tighter packing in smaller vesicles. Partitioning of a small nitroxide molecule TEMPO into ULVs was measured by X-band (9 GHz) and W-band (95 GHz) EPR spectroscopy. The partitioning coefficient of this probe in the lipid
DEVELOPMENT OF NEW DRILLING FLUIDS
Energy Technology Data Exchange (ETDEWEB)
David B. Burnett
2003-08-01
The goal of the project has been to develop new types of drill-in fluids (DIFs) and completion fluids (CFs) for use in natural gas reservoirs. Phase 1 of the project was a 24-month study to develop the concept of advanced type of fluids usable in well completions. Phase 1 tested this concept and created a kinetic mathematical model to accurately track the fluid's behavior under downhole conditions. Phase 2 includes tests of the new materials and practices. Work includes the preparation of new materials and the deployment of the new fluids and new practices to the field. The project addresses the special problem of formation damage issues related to the use of CFs and DIFs in open hole horizontal well completions. The concept of a ''removable filtercake'' has, as its basis, a mechanism to initiate or trigger the removal process. Our approach to developing such a mechanism is to identify the components of the filtercake and measure the change in the characteristics of these components when certain cleanup (filtercake removal) techniques are employed.
Bagheri Sadeghi, Hayedeh; Panahi, Homayon Ahmad; Mahabadi, Mahsa; Moniri, Elham
2015-01-01
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-infammatory and antipyretic actions. It is used to relieve mild to moderate pains. Solid-phase extraction of mefenamic acid by a polymer grafted to silica gel is reported. Poly allyl glycidyl ether/iminodiacetic acid-co-N, N-dimethylacrylamide was synthesized and grafted to silica gel and was used as an adsorbent for extraction of trace mefenamic acid in pharmaceutical and biological samples. Different factors affecting the extraction method were investigated and optimum conditions were obtained. The optimum pH value for sorption of mefenamic acid was 4.0. The sorption capacity of grafted adsorbent was 7.0 mg/g. The best eluent solvent was found to be trifluoroacetic acid-acetic acid in methanol with a recovery of 99.6%. The equilibrium adsorption data of mefenamic acid by grafted silica gel was analyzed by Langmuir model. The conformation of obtained data to Langmuir isotherm model reveals the homogeneous binding sites of grafted silica gel surface. Kinetic study of the mefenamic acid sorption by grafted silica gel indicates the good accessibility of the active sites in the grafted polymer. The sorption rate of the investigated mefenamic acid on the grafted silica gel was less than 5 min. This novel synthesized adsorbent can be successfully applied for the extraction of trace mefenamic acid in human plasma, urine and pharmaceutical samples. PMID:26330865
Institute of Scientific and Technical Information of China (English)
徐新建; 朱涛; 王喜艳; 付靓; 杨乐; 魏德海
2008-01-01
Objective To study the characteristic and mechanism of fluid metabolism in acute re-action phase of the severe acute pancreatitis (SAP). Methods Twenty-three dogs were randomly divided into two groups:mild acute pancreatitis (MAP) group (n=8) and SAP group (n= 15).The model of a-cute pancreatitis was made by injecting bile into main pancreatic duct. All the dogs were subjected to infu-sion therapy 1-5 days after model establishment. The plasma concentra